Skip to Main Content

E-mail: munteanj@unr.edu

Abstract

Mining of Carlin-type gold deposits in Nevada has made the United States one of the leading gold producers in the world for almost four decades. These deposits constitute an endowment of ~255 Moz (7,931 tonnes) of gold, of which 89% occurs in four main clusters of deposits: the Carlin trend, Getchell, Cortez, and Jerritt Canyon. These four clusters share many characteristics, including (1) formation during a narrow time interval (42–34 Ma), (2) lithologic and structural controls to fluid flow and ore deposition, (3) geochemical signature of the ores, (4) hydrothermal alteration and ore paragenesis, (5) relatively low temperatures and salinities of ore fluids, (6) fairly shallow depths of formation, and (7) lack of mineral and elemental zoning.

A mineral systems approach to exploring for Carlin-type gold deposits in Nevada and elsewhere is presented, in which critical processes are laid out: (1) development of source(s) for gold and other critical components of the ore fluid, (2) formation of fluid pathways, (3) water-rock interaction and gold deposition, and (4) a tectonic trigger. The critical processes are then converted into a practical targeting system for Carlin-type gold deposits within and outside of Nevada, ranging from regional to district to drill target (<~20 km2) scales. The critical processes of the Carlin mineral system are translated into targeting elements and mappable targeting criteria.

At the regional scale, targeting elements for magmatic sources of gold and ore fluid components include (1) intrusive centers with a mantle component to the magmas, (2) processes that could result in metasomatized subcontinental lithospheric mantle, (3) high-K, H2O-rich calc-alkaline magmas, and (4) evidence for fluid release. For crustal sources of gold, targeting elements include (1) carbonaceous sedimentary rocks with diagenetic/syngenetic sulfides enriched in Au-As-Hg-Tl-Sb-(Te) and sulfates and (2) a heat source to drive convection of meteoric and/or formation of metamorphic fluids. Targeting elements for fluid pathways at the regional scale include (1) basement suture zones and rifted continental margins, (2) long-lived upper crustal faults that may be linked to basement faults, and (3) a reduced crustal section to ensure long transport of gold by sulfide-rich fluids. Targeting elements at the regional scale for water-rock interaction and gold deposition include (1) passive margin dominated by carbonate rocks, (2) contractional deformation and formation of regional thrust faults and fold belts, and (3) a regional Au-As-Hg-Tl-Sb-(Te) geochemical signature. Targeting elements for tectonic triggers include (1) changes from contraction to extension, (2) periods of intense magmatism, especially related to slab rollback, and (3) plate reorganization.

At the district scale, targeting elements for fluid pathways include (1) old reactivated high-angle fault zones, (2) zones of abundant low-displacement, high-angle extensional faults, (3) fault intersections, and (4) lithologic rheology contrasts, such as preore intrusions and contact aureoles. For water-rock interaction and gold deposition, targeting elements include (1) carbonate-bearing stratigraphy, (2) low-angle features that could divert upwelling fluids out of high-angle faults and into reactive wall rocks, (3) hydrothermal system of targeted age, (4) alteration consistent with wall-rock reaction with acidic, sulfide-rich hydrothermal fluids, and (5) Fe-rich rocks in the stratigraphic section, which will drive sulfidation. At the drill target scale, the targeting elements for fluid pathways are zones of increased fault/fracture permeability. The targeting elements for water-rock interaction and gold deposition include (1) zones of increased low-angle permeability in carbonate rocks proximal to high-angle faults, (2) favorable alteration, especially hydrothermal carbonate dissolution and silicification, (3) Fe-rich rocks including ferroan carbonates and mafic volcanic rocks and intrusions, (4) favorable Au-As-Hg-Tl-Sb-(Te) geochemical signature with low base metals and Ag/Au ratios, and (5) favorable mineralization, especially arsenian pyrite with textures and chemistry consistent with Carlin-type deposits.

Introduction

Since the discovery of the Carlin gold deposit in Nevada by Newmont Mining Corp. in 1961, Nevada and the United States have experienced their greatest gold mining boom. The boom has been primarily driven by the discovery and mining of numerous deposits with characteristics very similar to the original Carlin deposit. These deposits, commonly known as Carlin-type gold deposits, were missed by the hundreds of thousands of people that traveled over Nevada beginning in 1849 to join the California gold rush, as well as by the thousands of prospectors that explored Nevada after the discovery of the Comstock Lode in 1859. Carlin-type deposits went undetected because the gold in these deposits is too fine grained to pan. The gold occurs in the crystal structure of pyrite or as submicron inclusions of native gold in pyrite. Even when weathered, gold is rarely greater than a micron in size. Carlin-type ore is characterized by disseminations of this gold-bearing pyrite in hydrothermal replacement bodies, primarily in carbonate-bearing rocks.

Approximately 147.1 Moz (4,575 tonnes [t]) of gold have been produced from Carlin-type deposits in Nevada through 2016, with over 90% of it produced since 1986. Approximately 107.8 Moz (3,353 t) remains in reserves and resources (Davis and Muntean, 2017). The estimated total endowment of 255 Moz (7,931 t) in these Carlin-type deposits is focused in north-central and northeastern Nevada in a 300- × 300-km area, making it arguably the second largest concentration of gold in the world after the Witwatersrand in South Africa (Fig. 1). Remarkably, 95% of the production and 89% of the endowment comes from four clusters of deposits: the Carlin trend (88.2 Moz [2,743 t] produced; 117.5 Moz [3,655 t] endowment), Cortez (20.1 Moz [625 t] produced; 50.1 Moz [1,558 t] endowment), Getchell (22.6 Moz [703 t] produced; 45.6 Moz [1,418 t] endowment), and Jerritt Canyon (9.1 Moz [283 t] produced; 12.8 Moz [398 t] endowment). These deposits are of late Eocene age (Hofstra et al., 1999; Arehart et al., 2003), which corresponds to a transition from shallow subduction and compressional tectonics to renewed magmatism coincident with extension.

Fig. 1.

Maps of the gold fields within the Witswatersrand basin in the Union of South Africa (left) and Carlin-type gold deposits in north-central and northeastern Nevada (right). The maps are at the same scale for comparison. The Witswatersrand map is modified from Kirk et al. (2004). Insets show map locations in South Africa (left) and Nevada (right).

Fig. 1.

Maps of the gold fields within the Witswatersrand basin in the Union of South Africa (left) and Carlin-type gold deposits in north-central and northeastern Nevada (right). The maps are at the same scale for comparison. The Witswatersrand map is modified from Kirk et al. (2004). Insets show map locations in South Africa (left) and Nevada (right).

Gold production in Nevada, which increased significantly in the mid-1980s due mainly to rapid discovery and development of Carlin-type deposits, peaked at 8.9 Moz (277 t Au) in 1998 but had dropped to 5.47 Moz (170 t) in 2016. There are several reasons for this decline, including production that is increasingly coming from underground refractory ore as the large oxide pits are mined out. Another reason is a drop in the discovery rate. The peak in production in 1998 came after an incredible 20-year run of discoveries of giant (>5 Moz, 155 t) deposits, including Gold Quarry, Betze-Post, Twin Creeks, Meikle, Pipeline, Turquoise Ridge, and Leeville. Only two such deposits have been discovered since 1998—Cortez Hills and Goldrush, which are both over 10 Moz (310.51 t). Exploration has increased significantly in eastern Nevada where Long Canyon was discovered in 2005; however, no new deposits with reserves have been discovered since Long Canyon. Most of the giant deposits mentioned above were covered by preore bedrock, postore bedrock, and/or postore transported alluvium. Known districts where mineralization is exposed are still being explored, with some success by applying good field geology, examination of large data sets, and new ideas. However, future discoveries of giant deposits will likely continue to be under cover.

In this paper a minerals system approach is put forward for Carlin-type systems in Nevada. The development of the concept of the petroleum system in the oil and gas industry, along with 3-D seismic surveys, greatly helped increase drill success rates from 25% in the 1970s and 1980s to 50% for exploration wells and 88% for development wells in 2005 (Alfaro et al., 2007). The petroleum system involves identification of the essential elements of source, reservoir, seal, and overburden and the critical processes of trap formation and generation, migration, and accumulation of petroleum (cf. Magoon and Dow, 1994). Similar to the petroleum system, the Carlin mineral system is broken down in this paper into a series of critical processes that are essential for the formation of Carlin-type deposits. The critical processes are then translated into tangible exploration criteria from regional to deposit scales, with which one can address the two main questions facing exploration: where to look, and, once in the right place, how to find ore. Thus, rather than relying solely on empirical exploration criteria, this paper encourages explorers to consider critical processes that can be expressed in slightly different ways depending upon the local geologic setting. Such an approach allows for better prediction in different geologic settings. As detailed below, the mineral systems approach requires application of multiple disciplines at multiple scales ranging from nanometers to the entire planet. Though the paper is aimed primarily at exploration for Carlin-type gold deposits in Nevada, the process and targeting criteria can be modified and applied to exploration for deposits with similar characteristics outside Nevada.

Carlin Mineral System

Not only do the Carlin trend, Getchell, Cortez, and Jerritt Canyon clusters contain almost all the gold in the Carlin-type deposits in Nevada (and the world) but the characteristics of the deposits in these four clusters are also very similar, despite differences in local geologic settings. Shared characteristics include formation during a narrow time interval (42–34 Ma), lithologic and structural controls to fluid flow and ore deposition, the geochemical signature of the ores, hydrothermal alteration and ore paragenesis, relatively low temperatures and salinities of ore fluids, fairly shallow depths of formation (<~2–3 km), and lack of mineral and elemental zoning at scales of ~5 to 10 km laterally and <2 km vertically (Table 1). These shared characteristics led Hofstra and Cline (2000) to be the first to formally classify them as a distinct deposit type—Carlin-type gold deposits.

Table 1.

Shared Characteristics of Carlin-Type Gold Deposits in the Carlin Trend, Getchell, Cortez, and Jerritt Canyon Camps in Nevada

  1. The deposits occur along the rifted cratonic margin of western North America within a variably carbonaceous miogeoclinal sequence comprised of basal Neoproterozoic-early Cambrian siliciclastic and volcanic rocks and overlain predominantly by carbonate rocks of Cambrian to Devonian age

  2. Ore is hosted by rocks with significant carbonate content

  3. The carbonate-hosted deposits occur below siliciclastic and volcanic rocks, commonly in the lower plate of a preore regional thrust fault

  4. Ore is commonly associated with extensional faults and a variety of contractional structures (e.g., thrusts, folds), which are commonly reactivated preore structures

  5. A geochemical signature of Au-Tl-As-Hg-Sb-(Te) in ore that is low in Ag in base metals

  6. Hydrothermal alteration caused by acid-leaching and deposition of silica, resulting decarbonatization and silicification of carbonate minerals, and argillization of silicate minerals to illite and/or kaolinite/dickite

  7. Main ore stage is characterized by disseminated, auriferous pyrite rich in other trace elements, including As, Tl, Hg, Sb, as well as commonly Te and Cu; gold occurs as Au+1 in the structure of pyrite or, more rarely, nanoparticles of native gold in pyrite; the ore-stage pyrite typically occurs as <10- to 20-μm grains or as <10- to 20-μm rims on preore pyrite cores

  8. Open space filling mineralization is restricted to paragenetically late stages after main gold ore stage and is characterized by drusy quartz, very minor auriferous, trace element-rich pyrite, much more abundant realgar, orpiment, stibnite, calcite, as well as local barite and wide variety of sulfosalts and sulfides in small amounts

  9. Main ore-stage fluids that ranged mainly from ~180° to ~240°C, are of low salinity (mostly ≤6 wt % NaCl equiv), and show no recognizable evidence for boiling

  10. Formation depths of <3 km, based on geologic reconstructions and/or fluid inclusions

  11. Lack of demonstrable ore-stage mineral or elemental zoning at scales of <5 to 10 km laterally and <2 km vertically

  12. Formation during a narrow time interval between 42 and 34 Ma, corresponding to a change from compression to extension and renewal of magmatism

  1. The deposits occur along the rifted cratonic margin of western North America within a variably carbonaceous miogeoclinal sequence comprised of basal Neoproterozoic-early Cambrian siliciclastic and volcanic rocks and overlain predominantly by carbonate rocks of Cambrian to Devonian age

  2. Ore is hosted by rocks with significant carbonate content

  3. The carbonate-hosted deposits occur below siliciclastic and volcanic rocks, commonly in the lower plate of a preore regional thrust fault

  4. Ore is commonly associated with extensional faults and a variety of contractional structures (e.g., thrusts, folds), which are commonly reactivated preore structures

  5. A geochemical signature of Au-Tl-As-Hg-Sb-(Te) in ore that is low in Ag in base metals

  6. Hydrothermal alteration caused by acid-leaching and deposition of silica, resulting decarbonatization and silicification of carbonate minerals, and argillization of silicate minerals to illite and/or kaolinite/dickite

  7. Main ore stage is characterized by disseminated, auriferous pyrite rich in other trace elements, including As, Tl, Hg, Sb, as well as commonly Te and Cu; gold occurs as Au+1 in the structure of pyrite or, more rarely, nanoparticles of native gold in pyrite; the ore-stage pyrite typically occurs as <10- to 20-μm grains or as <10- to 20-μm rims on preore pyrite cores

  8. Open space filling mineralization is restricted to paragenetically late stages after main gold ore stage and is characterized by drusy quartz, very minor auriferous, trace element-rich pyrite, much more abundant realgar, orpiment, stibnite, calcite, as well as local barite and wide variety of sulfosalts and sulfides in small amounts

  9. Main ore-stage fluids that ranged mainly from ~180° to ~240°C, are of low salinity (mostly ≤6 wt % NaCl equiv), and show no recognizable evidence for boiling

  10. Formation depths of <3 km, based on geologic reconstructions and/or fluid inclusions

  11. Lack of demonstrable ore-stage mineral or elemental zoning at scales of <5 to 10 km laterally and <2 km vertically

  12. Formation during a narrow time interval between 42 and 34 Ma, corresponding to a change from compression to extension and renewal of magmatism

The similarities between the deposits suggest shared processes of ore formation at all scales. Nevertheless, there has been a lack of consensus for a genetic model for Carlin-type deposits. Hofstra and Cline (2000) pointed out that the development of a genetic model has been hampered by exceedingly fine grained alteration and ore minerals that make analyses of ore-stage minerals (e.g., geochemistry, isotopes, fluid inclusions) very difficult. The controversy mainly surrounds the source of the ore fluid and its constituents. Most models have vacillated between crustal sources and magmatic sources for gold, sulfur, and water (Hofstra and Cline, 2000; Cline et al., 2005). Crustal models include mixtures of metamorphic and meteoric fluids (Seedorff, 1991; Hofstra and Cline, 2000; Seedorff and Barton, 2005; Large et al., 2011), large meteoric convection cells that leach components from upper crust (Ilchik and Barton, 1997; Seedorff and Barton, 2005), and lateral secretion models, where gold from local auriferous sedimentary rocks is remobilized and concentrated in nearby deposits (Emsbo et al., 2003; Large et al., 2011). Magmatichydrothermal models invoke mixtures of exsolved magmatichydrothermal fluids and meteoric fluids, mostly in the context of distal products of upper crustal porphyry systems (Sillitoe and Bonham, 1990; Johnston and Ressel, 2004; Johnston et al., 2008). Though authors have discussed various models, Hofstra and Cline (2000) were the first to consider all available data and all the potential fluid sources in the crust, and they favored a model that was dominantly meteoric with input from fluid derived from deeper metamorphic devolatilization. Muntean et al. (2011) later put forward a magmatic-hydrothermal model that called upon release of magmatic-hydrothermal fluids from intrusions at depths greater than typical porphyry copper systems that evolved and mixed with meteoric fluids to form Au-rich liquids that were relatively poor in silver and base metals. An objective of Muntean et al. (2011) was to present the Carlin-type deposits as a mineral system with a series of viable hypotheses for ore fluid and ore-forming processes at all scales, ranging from partial melting of the lithospheric mantle to deposition of gold in pyrite at the site of the deposits. Their intent was to generate interest in testing those hypotheses.

Though knowing the source of gold and ore fluids is critical in understanding the genesis of Carlin-type gold deposits, emphasis on source has overshadowed other important processes in the formation of Carlin-type deposits. These include the nature of hydrothermal fluid pathways and fluid chemistry inboard, within, and outboard of the replacement bodies that constitute ore, the nature of fluid-rock interaction that led to dissolution and silicification of carbonates and deposition of gold and trace elements in pyrite, and the nature of what drove and focused the immense mass and energy flux that formed these four large clusters of Carlin-type gold deposits.

Critical processes

Critical processes are the foundation of a mineral system. If any one of the critical processes fails to occur, an ore deposit will not form (McCuaig et al., 2010). Within a given mineral system, each critical process may result from a combination of several processes, which McCuaig et al. (2010) refer to as constituent processes. Constituent processes represent the specific causes that might lead to a critical process. For the Carlin gold system, four critical processes are proposed: (1) development of source(s) for gold and other critical components of the ore fluid, (2) formation of fluid pathways, (3) water-rock interaction and gold deposition, and (4) a tectonic trigger. Next, potential constituent processes that constitute each of these four critical processes are explained.

Sources of ore fluid components: Sources of gold, fluids (e.g., water, magma), acid for carbonate dissolution, and sulfur to transport gold are necessary to form a Carlin ore fluid. There is general consensus, based on mineral equilibria and fluid inclusion studies of ore zones, that hydrothermal fluids at the site of gold deposition in Carlin-type deposits were ~160° to 240°C, reduced and rich in aqueous sulfide (10−1–10−2 m H2S), were low in salinity (<~6 wt % NaCl equiv, mostly ~2–3 wt % NaCl equiv), contained CO2 (~2–4 mol %), and were acidic (illite stability to near the illite-kaolinite buffer) (Hofstra and Cline, 2000; Cline et al., 2005).

The magmatic source, as put forward by Muntean et al. (2011), proposes the subcontinental lithospheric mantle (SCLM) underlying Nevada and the Great Basin was meta-somatized during nearly 200 m.y. of subduction that culminated in ~20 m.y. of flat subduction just prior to formation of the Carlin-type ore deposits. During subduction, the SCLM beneath the Great Basin was likely continually hydrated and metasomatized with metal-bearing sulfides and gold. This fertile SCLM was then exposed to asthenospheric mantle during slab rollback or removal of the Farallon slab, resulting in partial melting of lithospheric mantle and renewed high-potassium, calc-alkaline magmatism that swept south-westward across Nevada in the Eocene. The Carlin trend, Cortez, and Jerritt Canyon clusters of deposits have Eocene magmatic centers associated with them that are temporally associated with ore formation, as exhibited by synore dikes in the Carlin trend (Heitt et al., 2003) and Cortez (Henry et al., 2012). Magmas are interpreted to have exsolved gold-bearing magmatic-hydrothermal fluids that evolved into the ore fluids responsible for gold deposition (Sillitoe, 2008; Muntean et al., 2011).

Models for crustal sources invoke meteoric water convection cells with or without input from metamorphic fluids, as summarized by Hofstra and Cline (2000), Seedorff and Barton (2005), and Cline et al. (2005). Deep convection of meteoric water, down to the base of the brittle upper crust (~10–12 km), is interpreted to be driven by magmatism and increased permeability due to onset of extension in the Eocene. Gold is interpreted to have been leached from variably carbonaceous rocks of the miogeocline that began to form during rifting of Laurentia in the Neoproterozoic. Possible source rocks include (1) Neoproterozoic clastic and volcanic rocks that formed during rifting (Seedorff, 1991; Ilchik and Barton, 1997), (2) gold-bearing pyrites in silty carbonaceous carbonates that formed during passive-margin sedimentation (Large et al., 2011), (3) gold-bearing sedimentary exhalative (sedex) deposits (Emsbo et al., 1998), (4) shales (~20–30 ppb Au) associated with barite sedex deposits of the Roberts Mountain allochthon (Emsbo, 1993), and (5) Mesozoic intrusion-related gold deposits (Hofstra and Cline, 2000). In situ Pb isotope analyses of ore-stage arsenian pyrite by Tosdal et al. (2003) using a SHRIMP indicated Pb isotope ratios similar to that in average Neoproterozoic and Cambrian clastic rocks and concluded the values were not similar to potential magmatic sources.

Oxygen and hydrogen isotope data from ore-stage kaolinite, quartz, and fluid inclusions suggest the water in the ore fluid at the site of gold deposition was primarily highly exchanged meteoric water with low δD values (~–130 to –150‰) mixed with varying amounts of water with higher δD to produce waters as heavy as –33‰, with most data ranging in δD from –140 to –80‰ (Fig. 2). The waters contributing higher δD could have been exsolved magmatic water, water derived by metamorphic dehydration reactions in the crust, or connate waters in marine sedimentary rocks. The data are inconclusive in constraining the source of gold but indicate water is not solely of meteoric origin. These data led Hofstra and Cline (2000) to favor a model of deeply derived metamorphic fluids mixing with meteoric water, whereas Muntean et al. (2011) used these data to argue for mixing of magmatic-hydrothermal fluids with meteoric water.

Fig. 2.

Hydrogen and oxygen isotope compositions of ore-stage hydrothermal fluids in Carlin-type gold deposits, calculated for 200°C, relative to meteoric water (MWL), ocean water (SMOW), vapor-saturated felsic magmas (Dobson et al., 1989; Taylor, 1992; Hedenquist and Richards, 1998), and high-temperature vapors released from magmas (Giggenbach, 1992; Taylor, 1992). Fluid inclusion (δD) and host quartz (δ18O) analyses are from the Turquoise Ridge (Shigehiro, 1999), Getchell (Cline and Hofstra, 2000), and Betze-Post deposits (Lubben, 2004). Waters calculated from kaolinite analyses (either δD or δD and δ18O) are from the Cortez (Rye et al., 1974), Getchell (Cline et al., 2005), Twin Creeks (Cline et al., 2005), Deep Star (bars, Heitt, et al., 2003; squares, Cline et al., 2005), Gold Quarry (Cline et al., 2005), and Carlin deposits (Kuehn, 1989). The Deep Star analyses marked by the bars reflect quartz impurities. The bars are tie lines that reflect water in equilibrium with 100% kaolinite (right end of the bar) to 50% quartz-50% kaolinite (left end of the bar). The blue regions and outlines represent ranges of values calculated from analyses of coexisting clay (δD) and quartz (δ18O) from the Jerritt Canyon (J.C.) (Hofstra, 1994; Hofstra et al., 1999; Cline et al., 2005), Alligator Ridge (A.R.) (Ilchik, 1990; Nutt and Hofstra, 2003), Meikle, and Betze-Post (Meikle & B.P.) deposits (Arehart et al., 1992; Emsbo et al., 2003). The dashed line represents the trend of meteoric water evolution during water-rock interaction at progressively lower water-rock (W/R) ratios (calculated for 200°C). The heavy black line along the meteoric water line shows the interpreted range of values for Eocene meteoric water. See text for discussion. Abbreviations: jasp = jasperoid, qtz = quartz.

Fig. 2.

Hydrogen and oxygen isotope compositions of ore-stage hydrothermal fluids in Carlin-type gold deposits, calculated for 200°C, relative to meteoric water (MWL), ocean water (SMOW), vapor-saturated felsic magmas (Dobson et al., 1989; Taylor, 1992; Hedenquist and Richards, 1998), and high-temperature vapors released from magmas (Giggenbach, 1992; Taylor, 1992). Fluid inclusion (δD) and host quartz (δ18O) analyses are from the Turquoise Ridge (Shigehiro, 1999), Getchell (Cline and Hofstra, 2000), and Betze-Post deposits (Lubben, 2004). Waters calculated from kaolinite analyses (either δD or δD and δ18O) are from the Cortez (Rye et al., 1974), Getchell (Cline et al., 2005), Twin Creeks (Cline et al., 2005), Deep Star (bars, Heitt, et al., 2003; squares, Cline et al., 2005), Gold Quarry (Cline et al., 2005), and Carlin deposits (Kuehn, 1989). The Deep Star analyses marked by the bars reflect quartz impurities. The bars are tie lines that reflect water in equilibrium with 100% kaolinite (right end of the bar) to 50% quartz-50% kaolinite (left end of the bar). The blue regions and outlines represent ranges of values calculated from analyses of coexisting clay (δD) and quartz (δ18O) from the Jerritt Canyon (J.C.) (Hofstra, 1994; Hofstra et al., 1999; Cline et al., 2005), Alligator Ridge (A.R.) (Ilchik, 1990; Nutt and Hofstra, 2003), Meikle, and Betze-Post (Meikle & B.P.) deposits (Arehart et al., 1992; Emsbo et al., 2003). The dashed line represents the trend of meteoric water evolution during water-rock interaction at progressively lower water-rock (W/R) ratios (calculated for 200°C). The heavy black line along the meteoric water line shows the interpreted range of values for Eocene meteoric water. See text for discussion. Abbreviations: jasp = jasperoid, qtz = quartz.

As fluids rose to within ~3 to 4 km of the surface, the aqueous gold complex was likely Au(HS)2 and possibly AuHS°. Most conventional data from ore-stage pyrite indicate δ34S values ranging from 0 to 17‰ (Hofstra and Cline, 2000) (Fig. 2). These data do not identify a single, unambiguous sulfur source, but the heavy values (>5–10‰) require some sourcing from diagenetic pyrite by breakdown or leaching of organic sulfur compounds or from deeper levels by metamorphic desulfidation of pyrite. Higher δ34S values (>15–20‰) likely require that some H2S was generated by thermochemical reduction of sulfate, likely sourced from bedded barite deposits, which are common in northeastern Nevada.

Most of the early conventional data were generated by analyses of pyrite separates. However, ore-stage pyrite typically occurs as <10- to 20-μm grains or as <10- to 20-μm rims on preore pyrite cores. Therefore, conventional analyses can include preore and ore-stage pyrite. Figure 3 shows the few in situ δ34S analyses of ore-stage pyrite that have been done using an ion probe, as well as conventional analyses of pyrite and arsenopyrite separated from Eocene dikes, where the pyrite is similar in age to ore. The in situ analyses range in value between –4 and 8‰. Most of the values cluster between –1 and 3‰, consistent with sulfur that is magmatic and sourced from the mantle. Conversely, δ34S values near 0‰ could be the result of interaction between the hydrothermal fluid and rock containing diagenetic pyrite with values near 0‰, without any magmatic contribution. Thus, like the oxygen and hydrogen isotope data, the sulfur data are inconclusive, although there was certainly a component of crustal sedimentary sulfur in the ore fluid.

Fig. 3.

Histogram δ34S of ore-stage pyrite based on in situ ion probe analyses and conventional analyses of pyrite in Eocene dikes. The ion probe analyses are from Getchell (Cline et al., 2003, 2005), Betze-Post (Henkelman, 2004), and Screamer (Kesler et al., 2003). The analyses of the Eocene dikes are from Jerritt Canyon (Hofstra, 1994) and Betze-Post (Emsbo, 1999). Arsenopyrite was analyzed from Jerritt Canyon and likely formed during the late ore stage after most of the gold had been deposited. Summary of conventional data is from Cline et al. (2005). See text for discussion.

Fig. 3.

Histogram δ34S of ore-stage pyrite based on in situ ion probe analyses and conventional analyses of pyrite in Eocene dikes. The ion probe analyses are from Getchell (Cline et al., 2003, 2005), Betze-Post (Henkelman, 2004), and Screamer (Kesler et al., 2003). The analyses of the Eocene dikes are from Jerritt Canyon (Hofstra, 1994) and Betze-Post (Emsbo, 1999). Arsenopyrite was analyzed from Jerritt Canyon and likely formed during the late ore stage after most of the gold had been deposited. Summary of conventional data is from Cline et al. (2005). See text for discussion.

The main acid volatiles in the ore fluid were likely CO2 and possibly HCl, as pointed out by Hofstra and Cline (2000). HCl would likely be sourced from a magma, whereas CO2 can have multiple sources. Magmatic SO2 was likely not significant. Hypogene alunite that is intergrown with pyrite has only been documented in the Beast deposit on the Carlin trend, which is mainly hosted by an Eocene rhyolite dike (Ressel et al., 2000). If SO2 was exsolved from Eocene magmas, it may have been reduced by interaction with carbonaceous rocks, consistent with H2S as the dominant sulfur species in gas analyses of fluid inclusions (Cline and Hofstra, 2000; Cline et al., 2005). Hofstra et al. (1991) calculated a pH of 5.2 for calcite saturation for a 225°C ore fluid with 4 mol % CO2, based on gas analyses of fluid inclusions.

In summary, the oxygen and hydrogen isotope data indicate the water in the ore fluids was of predominantly meteoric origin that mixed with magmatic, metamorphic, and/or connate waters. Likewise, aqueous sulfide complexes, which complexed with gold in the ore fluids, require a component of crustal sedimentary sulfur, likely diagenetic pyrite or bedded barite. However, data permit a magmatic source for some of the sulfur in the ore fluid. Viable sources of gold occur in the mantle or in the variably carbonaceous and pyritic upper crustal rocks of the miogeocline.

Formation of fluid pathways for upwelling fluids: Another critical process is the formation of pathways that serve as collecting points for upwelling hydrothermal fluids, including meteoric water-dominant fluids, metamorphic fluids, and/or magmatic-hydrothermal fluids. Carlin-type gold deposits have a spatial association with high-angle faults at all scales (Hofstra and Cline, 2000). At the regional scale, all the Carlin-type deposits in Nevada lie on the rifted western cratonic margin of Laurentia (Fig. 4). Many workers have suggested that the lithospheric-scale faults, which formed during rifting in the Neoproterozoic, remained as zones of weaknesses that influenced subsequent deformation and sedimentation in the upper crust (Tosdal et al., 2000; Crafford and Grauch, 2002; Cline et el., 2005; Emsbo et al., 2006; Muntean et al., 2007). These reactivated basement structures have been interpreted to control the linear alignments of Carlin-type deposits by serving as fluid pathways for deeply sourced ore fluids and magmas (Tosdal et al., 2000; Cline et al., 2005; Muntean et al., 2007, 2011). Evidence for these basement faults comes from isotopic data (Kistler and Peterman, 1978; Tosdal et al., 2000; Grauch et al., 2003), magnetotelluric and gravity data (Grauch et al., 2003), patterns of sedimentation that suggest deposition in second-order basins formed by synsedimentary extension during formation of the early Paleozoic passive-margin sequence (Crafford and Grauch, 2002; Emsbo et al., 2006; Muntean et al., 2007), and upper crustal structures that are consistent with inversion of basement structures that formed during subsequent contractional events (Cline et al., 2005; Muntean et al., 2007; Lund, 2008). Most of the inverted structures interpreted by Muntean et al. (2007) strike west-northwest (N50°–70°W) and north-northwest (N0°–30°W). They point out that the two trends are parallel to Proterozoic normal faults throughout the western half of the United States. Studies of rift strata and dike swarms in the Rocky Mountains, the Colorado Plateau, and Mid-Continent indicate WNW-trending faults originally formed during a rifting event between 1.3 and 1.1 Ga, and formation of N-trending faults and reactivation of WNW-trending faults occurred between 0.9 and 0.7 Ga (Marshak et al., 2000; Timmons et al., 2001). The rifted margin of Laurentia is interpreted to be a network of northwest extensional segments and NE-striking transform segments (Tosdal et al., 2000; Grauch et al., 2003; Lund, 2008).

Fig. 4.

Map of the Great Basin and surrounding regions show key lithospheric, structural, volcanic, and stratigraphic features in relationship to Carlin-type gold deposits (red dots), distal disseminated Au-Ag deposits (green dots), and other large deposits of Eocene age (orange dots). Note that most large Eocene ore deposits are within 75 km of the interpreted Archean-Proterozoic suture zone. Archean and Paleoproterozoic terranes (blue lines), the Neoproterozoic cratonic margin based on 0.706 initial 87Sr/86Sr isopleth, are taken from summaries by Whitmeyer and Karlstrom (2007) and Yonkee et al. (2014). The eastern edge of thick Neoproterozoic rift sediments (green line) is from Stewart (1991). The 208Pb/204Pb isopleths (purple dashed lines) delineate underlying Archean from Proterozoic terranes (from Tosdal et al., 2000). Note the southern margin of the Grouse Creek block and Farmington zone is not a sharp boundary. The Pb isotope data of Tosdal et al. (2000) indicate there is a transitional zone with isotopic characteristics of both Archean and Paleoproterozoic crust extending up to nearly 100 km south of the boundary. The eastern extent of the Roberts Mountains thrust (RMT) and Golconda thrust (GT) (blue lines) are from Ludington et al. (1996). Contours of age of initial, locally sourced Tertiary magmatism, showing southwesterly migration of magmatism in Nevada due to slab rollback/removal (from Henry and John, 2013). The gray line axis of the middle Miocene northern Nevada rift (NNR) is from John (2001).

Fig. 4.

Map of the Great Basin and surrounding regions show key lithospheric, structural, volcanic, and stratigraphic features in relationship to Carlin-type gold deposits (red dots), distal disseminated Au-Ag deposits (green dots), and other large deposits of Eocene age (orange dots). Note that most large Eocene ore deposits are within 75 km of the interpreted Archean-Proterozoic suture zone. Archean and Paleoproterozoic terranes (blue lines), the Neoproterozoic cratonic margin based on 0.706 initial 87Sr/86Sr isopleth, are taken from summaries by Whitmeyer and Karlstrom (2007) and Yonkee et al. (2014). The eastern edge of thick Neoproterozoic rift sediments (green line) is from Stewart (1991). The 208Pb/204Pb isopleths (purple dashed lines) delineate underlying Archean from Proterozoic terranes (from Tosdal et al., 2000). Note the southern margin of the Grouse Creek block and Farmington zone is not a sharp boundary. The Pb isotope data of Tosdal et al. (2000) indicate there is a transitional zone with isotopic characteristics of both Archean and Paleoproterozoic crust extending up to nearly 100 km south of the boundary. The eastern extent of the Roberts Mountains thrust (RMT) and Golconda thrust (GT) (blue lines) are from Ludington et al. (1996). Contours of age of initial, locally sourced Tertiary magmatism, showing southwesterly migration of magmatism in Nevada due to slab rollback/removal (from Henry and John, 2013). The gray line axis of the middle Miocene northern Nevada rift (NNR) is from John (2001).

In addition, an older lithospheric boundary projects westward through northeastern Nevada at approximately 40° latitude, based on isotopic data (Tosdal et al., 2000) and existence of rocks interpreted to be Archean in the East Humboldt Range 115 km east of the Carlin trend (Lush et al., 1988, Premo et al., 2008, 2010; McGrew and Snoke, 2010). It separates the Archean Grouse Creek block to the north (>2.5 Ga) from the Paleoproterozoic Mojave Province to the south (Foster et al., 2006). The boundary appears to lie along the western projection of the Cheyenne belt, the suture that separates the Archean Wyoming craton to the north from Paleoproterozoic terranes to the south (Duebendorfer and Houston, 1986; Whitmeyer and Karlstrom, 2007). If one plots the amount of gold endowment in northeastern Nevada vs. latitude, most of the gold occurs at latitudes near the southern boundary of the Grouse Creek block (Fig. 5). Notably, the giant Bingham Canyon porphyry Cu-Au-Mo deposit also occurs to the east along the projection of the Cheyenne belt, east of the Grouse Creek block. Microanalyses of Pb isotopes in fluid inclusions in ore-stage quartz-sulfide veinlets from the Eocene Bingham porphyry Cu-Au-Mo deposit indicates the Pb, and presumably the Cu, Au, and Mo, were sourced from Archean lithospheric mantle that was metasomatized at ~1.8 Ga during subduction and accretion of arc terranes in the Paleoproterozoic (Pettke et al., 2010). All these observations and data support Hronsky et al.’s (2012) and Griffin et al.’s (2013) assertions that metasomatized SCLM and boundaries between lithospheric blocks are primary controls on gold deposits. Based on seismic tomography, Griffin et al. (2013) proposed that gold deposits related to magmatism, including possibly Carlin-type deposits in Nevada, are commonly coincident with medium- and lower-velocity SCLM near margins with higher-velocity SCLM. The lower-velocity zones are interpreted to represent magma pathways.

Fig. 5.

Schematic diagram illustration. A. the sulfidation process affecting the Roberts Mountains Formation, consisting of calcite (Cc), quartz silt (Q), detrital K-feldspar (Kspar), diagenetic dolomite (Dol), and diagenetic pyrite. For simplicity, sedimentary white mica that commonly occurs is not shown. B. Reaction with acid (H+), which preferentially dissolves calcite relative to the dolomite, whose rhombs are rounded (i.e., sanding). Note increase in porosity. K-feldspar is argillized to illite (or kaolinite). C. Sulfidation resulting from Fe2+ released from carbonates reacts with reduced sulfur in the ore fluid, which destabilizes reduced gold sulfide complexes (e.g., Au(HS)2), resulting in the formation of auriferous pyrite, either as micron grains (red squares) or as rims on diagenetic pyrite. Carbonate dissolution and sulfidation are essentially contemporaneous, along with deposition of hydrothermal quartz. See text for discussion.

Fig. 5.

Schematic diagram illustration. A. the sulfidation process affecting the Roberts Mountains Formation, consisting of calcite (Cc), quartz silt (Q), detrital K-feldspar (Kspar), diagenetic dolomite (Dol), and diagenetic pyrite. For simplicity, sedimentary white mica that commonly occurs is not shown. B. Reaction with acid (H+), which preferentially dissolves calcite relative to the dolomite, whose rhombs are rounded (i.e., sanding). Note increase in porosity. K-feldspar is argillized to illite (or kaolinite). C. Sulfidation resulting from Fe2+ released from carbonates reacts with reduced sulfur in the ore fluid, which destabilizes reduced gold sulfide complexes (e.g., Au(HS)2), resulting in the formation of auriferous pyrite, either as micron grains (red squares) or as rims on diagenetic pyrite. Carbonate dissolution and sulfidation are essentially contemporaneous, along with deposition of hydrothermal quartz. See text for discussion.

Within the four main clusters and in other Carlin-type deposits of Nevada, ore and hydrothermal alteration are commonly associated with high-angle fault zones—either reactivated older faults or faults that formed during onset of extension in the Eocene (Hofstra and Cline, 2000; Cline et al., 2005; Rhys et al., 2015). Ore is primarily hosted in second-order faults with minimal displacement rather than first-order faults with significant displacement.

Gold deposition by water-rock interaction: Gold deposition in Carlin-type deposits is a direct result of water-rock reaction. Numerous studies have established dissolution of carbonate and sulfidation of iron in the rock as the primary depositional mechanism for gold in Carlin-type deposits (Hofstra et al., 1991; Stenger et al., 1998). Figure 5 illustrates the process by which a typical slope-facies carbonate host rock, consisting of calcite, detrital quartz silt, fine-grained white mica, and K-feldspar along with diagenetic pyrite, reacts with an acidic ore fluid. Calcite dissolves preferentially over dolomite. The dolomite, which is more resistant to the acid, tends to have its rhombohedra rounded, resulting in an alteration texture commonly referred to as “sanding.” Quartz precipitates to varying degrees. The K-feldspar alters to illite, whereas the white mica partially dissolves and recrystallizes, forming a mixture of preore mica and ore-stage illite. If fluids are sufficiently acidic, kaolinite or dickite will form instead of illite. Reactive iron as Fe2+, which was freed from carbonate during dissolution, reacts with aqueous sulfide in the fluid to form pyrite. Some of the sulfide in the fluid was complexed with gold as Au(HS)2, or as Au(HS)° in more acidic fluids. The decrease in aqueous sulfide in the fluid due to pyrite formation destabilized the aqueous gold complexes. Gold-bearing pyrite deposited as micron-sized grains and rims on diagenetic pyrite. Along with gold, abundant arsenic (up to ~20 wt %), as well as Tl, Hg, Sb, Cu, Te, and other trace elements, deposited with the pyrite (Cline et al., 2005; Muntean et al., 2011).

Importantly, most of the gold is deposited as Au+ in the crystal structure of pyrite (Simon et al., 1999; Reich et al., 2005). Therefore, as pointed out by Simon et al. (1999), fluids did not have to be saturated with respect to native gold for gold deposition to occur. The implication is that Carlin ore fluids did not necessarily have high gold concentrations, compared to ore fluids that deposit native gold. Also, reduction is not necessary for gold deposition; therefore, reductants, such as carbonaceous materials, are not necessary, though carbonaceous rocks were important in keeping fluids reduced, which enhanced gold transport by sulfide complexes. Compilation of published gold concentrations in arsenian pyrite indicates the solubility limit of Au in arsenian pyrite is defined by an Au/As molar ratio of 0.02, which is independent of the geochemical environment of pyrite formation and depends rather on the crystal-chemical properties of pyrite (Reich et al., 2005; Deditus et al., 2014). At higher Au/As molar ratios, gold occurs as nanoparticles of native gold (Reich et al., 2005). The main driver of gold deposition, either as Au+ or native gold, is decrease in the activity of reduced sulfur in the ore fluid. In addition, gold deposition was likely facilitated by efficient scavenging as Au+ by adsorption onto negatively charged pyrite surfaces or other surficial mineral controls. Experiments by Widler and Seward (2002) at 25°C showed adsorption of gold by pyrite from solutions undersaturated with respect to native gold at pH values <5.5 was 100%.

Given that fluid-rock reaction is essential for gold deposition in Carlin deposits, it is critical that upwelling fluids left high-angle faults and fractures and infiltrated reactive carbonate rocks. In most deposits, the fluids infiltrated the wall rocks along features that dip at relatively low angles, compared to the high-angle faults along which they rose. The low-angle features formed mainly by contractional deformation. After Neoproterozoic-Early Cambrian rifting and early Paleozoic sedimentation of predominantly carbonates along the passive margin of western North America, a series of contractional orogenies began in the Late Devonian and occurred intermittently into the early Tertiary. The first of these, the Antler orogeny, thrusted deep oceanic siliciclastic and mafic volcanic rocks eastward over the carbonate rocks of the continental slope and platform margin along the Roberts Mountain thrust fault. The four main camps of Carlin-type deposits all occur in the lower plate of the thrust. Moreover, the four clusters are associated with antiformal culminations that in some cases formed by multiple contractional events (Rhys et al., 2015). During later uplift and erosion, these structural highs were preferentially exposed as windows through the upper plate of the Roberts Mountain thrust. Figure 6 is a cross section of the original Carlin deposit showing the typical tree-like geometry of Carlin-type gold deposits, the high-angle fault—the trunk—acted as a fluid pathway for upwelling fluids, and lower angle favorable stratigraphy—the branches—acted as the main zone of water-rock interaction. Note the highest grades were not in the high-angle fault but rather in the favorable stratigraphy, underscoring the importance of water-rock interaction. Also note that the deposit lies within 100 m of the projection of the Roberts Mountain thrust fault, as do most of the deposits in the four main clusters.

Fig. 6.

Schematic cross section showing spatial relationships of geologic and hydrothermal features at the Carlin mine. Note the high-angle structural and lower-angle stratigraphic controls to hydrothermal alteration and mineralization, as well as the proximity to the Roberts Mountains thrust. Modified from Kuehn and Rose (1992). Abbreviations: DSrm = Devonian Silurian Roberts Mountain Formation.

Fig. 6.

Schematic cross section showing spatial relationships of geologic and hydrothermal features at the Carlin mine. Note the high-angle structural and lower-angle stratigraphic controls to hydrothermal alteration and mineralization, as well as the proximity to the Roberts Mountains thrust. Modified from Kuehn and Rose (1992). Abbreviations: DSrm = Devonian Silurian Roberts Mountain Formation.

Furthermore, to form ore the fluids need to infiltrate the carbonate wall rocks when the fluids are reactive, meaning at sufficiently low pH to dissolve significant amounts of carbonate. As indicated above, the main acid was likely carbonic acid. If carbonic acid predominated, the ore fluid would not become acidic until it cooled below 350°C and would become increasingly acidic as the fluid cooled further and carbonic acid dissociated (Heinrich, 1990). As pointed out by Hofstra and Cline (2000), the vertical extent of ore in Carlin-type deposit is up to 1.5 km in the northern Carlin trend. A longitudinal section of the northern Carlin trend by Peters et al. (1998) demonstrated a rather flat boundary to the bottom of the lower extent of this large vertical extent of ore (Fig. 7). The lower boundary also transects stratigraphy. Such an elevation control is typically attributed to boiling in an epithermal system; however, boiling has not been documented in studies of Carlin-type deposits (Cline et al., 2005). Rather, the elevation control is likely the point at which acid in the fluid was sufficiently dissociated and acidic to cause extensive carbonate dissolution, sulfidation, and gold deposition.

Fig. 7.

Simplified long section of the northern Carlin trend emphasizing apparent elevation control and lack of deep structural roots to the orebodies (black). Preferred interpretation is that the apparent elevation control reflects the temperature at which acid molecules disassociated, resulting in a marked decrease in the pH of the ore fluid allowing significant carbonate dissolution. See text for discussion. From Hofstra and Cline (2000). Abbreviations: Dp = Devonian Popovich Formation, Dr = Devonian Rodeo Creek Formation, Jd = Jurassic diorite stock, Os = Ordovician sedimentary rocks, undifferentiated, OShc = Ordovician-Silurian Hanson Creek Formation, Ov = Ordovician Vinini Formation (Roberts Mountain allochthon), SDrm = Devonian-Silurian Roberts Mountain Formation.

Fig. 7.

Simplified long section of the northern Carlin trend emphasizing apparent elevation control and lack of deep structural roots to the orebodies (black). Preferred interpretation is that the apparent elevation control reflects the temperature at which acid molecules disassociated, resulting in a marked decrease in the pH of the ore fluid allowing significant carbonate dissolution. See text for discussion. From Hofstra and Cline (2000). Abbreviations: Dp = Devonian Popovich Formation, Dr = Devonian Rodeo Creek Formation, Jd = Jurassic diorite stock, Os = Ordovician sedimentary rocks, undifferentiated, OShc = Ordovician-Silurian Hanson Creek Formation, Ov = Ordovician Vinini Formation (Roberts Mountain allochthon), SDrm = Devonian-Silurian Roberts Mountain Formation.

Once fluids were sufficiently acidic, infiltrated the carbonate wall rocks, and began to dissolve carbonate, porosity and permeability increased, which led to ingress of more acidic fluids. The process was one of positive feedback, whereby permeability and the amount of water-rock interaction increased until the source acid was exhausted. The result was replacement orebodies with complex geometries, particularly at higher cutoff grades of gold. Nevertheless, the resulting overall geometry in cross-sectional view of many deposits is tree-like, whereby the higher-angle structures that focus upwelling fluids are the trunks and the lower-angle features that bring about extensive fluid-rock interaction in wall rocks are the branches.

Tectonic trigger: Analogous to the critical moment in the petroleum system, formation of Carlin-type deposits appears to have been triggered by a change in tectonics that interacted on an ideal architecture of structures and favorable rock types. Not only did Carlin-type deposits form during the late Eocene, but most of the Great Basin’s largest ore deposits also formed during this time. Examples include the Mount Hope porphyry molybdenum deposit (~38 Ma; Westra and Reidell, 1996) and the Phoenix/Fortitude copper-gold skarn deposits associated with the Copper Canyon porphyry system (~41–38 Ma; King, 2017) in the same region in Nevada as the four main clusters of Carlin-type gold deposits. At the eastern end of the Great Basin at the same latitude as the Carlin-type deposits, Bingham Canyon, North America’s most productive porphyry copper deposit and a major gold producer, also formed during the same time (~38 Ma; Parry et al., 2001). The Carlin-type deposits along with the other deposits clearly reflect a major thermal and mass transfer event in the Great Basin.

The critical trigger that caused this event was the rollback of the Farallon slab. A long-lived E-dipping subduction zone was established along western North America by the Middle Triassic. Intermittent back-arc magmatism in Nevada began in the Middle to Late Jurassic and ended by ~65 Ma due to flattening of the Farallon slab (Coney and Reynolds, 1977). Rollback or removal of the shallow-dipping slab led to renewed magmatism in Nevada, beginning at ~45 Ma (Humphreys, 1995). The magmatism swept southwestward across northeastern Nevada at a high angle to the continental margin. Muntean et al. (2011) pointed out that formation of Carlin-type deposits tracked the southwestern sweep of magmatism in time and space across Nevada. Moreover, the giant 20 Moz (622 t) Round Mountain epithermal gold deposit also formed during the rollback, at 26 Ma, farther southwestward in central Nevada. A change from contraction to extension coincided with rollback of the slab. The magnitude of Eocene extension is controversial, with studies supporting low magnitudes (Henry, 2008) and locally high magnitudes (Gans et al., 2001).

Nevada is a major metallogenic province for gold in that gold deposits formed at numerous times. Emsbo et al. (1998) made the case that gold was deposited as early as the Devonian in carbonate-hosted sedex deposits. However, most of the gold deposits in Nevada are spatially and temporally associated with magmatism. Gold deposits certainly formed as early as the Middle to Late Jurassic, during the first pulse of back-arc magmatism in Nevada. The largest example is the Jurassic intrusion-related Bald Mountain deposit in eastern Nevada (Nutt and Hofstra, 2007). Intrusion-related gold deposits also formed in the Late Cretaceous, examples including the Robinson porphyry copper system (James, 1976; Smith et al., 1988) and the Eureka polymetallic manto/vein district (Nolan and Hunt, 1968; Vikre, 1998). In addition to the Eocene and Oligocene deposits related to the southwestern sweep of magmatism, a significant number of epithermal gold-silver deposits formed during the Miocene and into the Quaternary. These epithermal deposits are related to subduction and the Miocene proto-Cascades in western Nevada (e.g., Comstock Lode, Goldfield) or to bimodal volcanism associated with the impingement of the Yellowstone hot spot and formation northern Nevada rift in north-central Nevada in the middle Miocene (John, 2001). Most of these gold deposits of multiple ages, like the Carlin-type deposits, occur along the rifted craton and thus share the same lithospheric architecture. Thus, the ideal arrangement of fluid pathways and potential gold sources was important in forming the metallogenic province. However, the late Eocene, during which the vast majority of the gold resource in Nevada formed, represents the combination of an ideal lithospheric architecture with a tectonic trigger that led to a world-class metallogenic epoch.

Summary of the Carlin gold system in Nevada

As stressed by Muntean et al. (2011), formation of the huge gold endowment within the late Eocene Carlin-type gold deposits represents convergence between the development of an ideal geologic setting and a major thermal event. The ideal architecture was a rifted continental margin with a passive-margin sequence dominated by carbonates. Contractional deformation led to the formation of antiformal culminations with features consistent with structural inversion of underlying basement faults, leading to an ideal architecture in which structural culminations of highly fractured reactive carbonate rocks were overlain by less reactive siliciclastic rocks above basement faults that served as fluid pathways for deeply sourced magmas and ore fluids (Fig. 8).

Fig. 8.

Schematic east-west cross sections across northeast Nevada showing A. interpreted lithospheric architecture just prior to late Eocene mineralization and B. tectonic trigger that resulted in slab rollback/removal, renewed magmatism, extension, fluid flow, and formation of Carlin-type gold deposits in the late Eocene. The premineral architecture section shows the rifted continental margin reactivated by late Paleozoic and Mesozoic contractional deformation, forming structural culminations over lithospheric-scale fault zones. Faults in the upper crust were soft linked to underlying basement faults, as suggested by Muntean et al., (2007). It is uncertain how far Sevier detachments in the basement extend westward and whether they displace crustal faults from their basement roots. Flat subduction from ~65 to ~45 Ma resulted in cessation of magmatism but continued metasomatism of the subcontinental lithospheric mantle (SCLM), interpreted to be a Paleoproterozoic arc terrane that was subducted northward underneath and metasomatized the Archean Grouse Creek block, similar to what Pettke et al. (2010) demonstrated for Bingham Canyon farther east in Utah. During slab rollback, asthenosphere impinged on highly metasomatized SCLM, forming rising partial melts, ponded first at the Moho, forming melting assimilation storage and homogenization (MASH) zones. More felsic magmas preferentially rose along reactivated fault zones, forming upper crustal magma chambers at ~5 to 10 km. The magmatism drove formation of metamorphic fluids, convection of meteoric water, and exsolution of magmatic-hydrothermal fluids, all of which were likely involved in formation of the Carlin-type gold deposits.

Fig. 8.

Schematic east-west cross sections across northeast Nevada showing A. interpreted lithospheric architecture just prior to late Eocene mineralization and B. tectonic trigger that resulted in slab rollback/removal, renewed magmatism, extension, fluid flow, and formation of Carlin-type gold deposits in the late Eocene. The premineral architecture section shows the rifted continental margin reactivated by late Paleozoic and Mesozoic contractional deformation, forming structural culminations over lithospheric-scale fault zones. Faults in the upper crust were soft linked to underlying basement faults, as suggested by Muntean et al., (2007). It is uncertain how far Sevier detachments in the basement extend westward and whether they displace crustal faults from their basement roots. Flat subduction from ~65 to ~45 Ma resulted in cessation of magmatism but continued metasomatism of the subcontinental lithospheric mantle (SCLM), interpreted to be a Paleoproterozoic arc terrane that was subducted northward underneath and metasomatized the Archean Grouse Creek block, similar to what Pettke et al. (2010) demonstrated for Bingham Canyon farther east in Utah. During slab rollback, asthenosphere impinged on highly metasomatized SCLM, forming rising partial melts, ponded first at the Moho, forming melting assimilation storage and homogenization (MASH) zones. More felsic magmas preferentially rose along reactivated fault zones, forming upper crustal magma chambers at ~5 to 10 km. The magmatism drove formation of metamorphic fluids, convection of meteoric water, and exsolution of magmatic-hydrothermal fluids, all of which were likely involved in formation of the Carlin-type gold deposits.

This ideal architecture set the stage for the major magmatic event during slab rollback in the late Eocene that served as the energy source that drove the formation and circulation of ore fluids and that coincided with a shift from contraction to extension. The shift to extension reactivated earlier formed structures. This was especially important for opening up and increasing the permeability of previously formed contractional structures, given they were essential in diverting upwelling ore fluids out of high-angle fault zones and into reactive carbonate rocks. This fluid-rock interaction was critical to extremely efficient gold deposition by incorporation of Au+ into the crystal structure of pyrite during dissolution and of carbonate and sulfidation by fluids that were likely undersaturated with respect to native gold.

Targeting System for Carlin-Type Gold Deposits

As emphasized by McCuaig et al. (2010), a mineral system, as is laid out above for Carlin-type gold deposits in Nevada, is not an exploration targeting system. Such a targeting system requires criteria, which are mappable data sets that are readily available or obtainable. In this section the critical processes for the Carlin mineral system are translated into a practical targeting system for Carlin-type gold deposits in Nevada that is applicable ranging from regional (>~5,000 km2) to district (~20–~5,000 km2) to drill target (<~20 km2) scales. This is accomplished by using parts of the framework proposed by McCuaig et al. (2010) that translates the targeting elements (geologic expressions of the critical processes) into targeting criteria that can be used to map the targeting elements either directly or by proxy. Targeting elements and criteria are presented for the four critical processes at the regional, district, and drill target scales.

Regional targeting (>5,000 km2)

Given the exploration maturity of Nevada, one might consider regional targeting elements and criteria are irrelevant in Nevada; nevertheless, they are detailed below to better understand why the deposits occur preferentially in certain parts of the Great Basin. Moreover, the targeting elements and criteria are important in identifying areas outside the Great Basin where there could be Carlin-type deposits comparable to those in Nevada in numbers, size, and grade. The targeting elements and targeting criteria, presented below and summarized in Table 2, are meant to identify prospective district-scale zones for further work and potential land acquisition.

Table 2.

Regional-Scale (>~5,000 km2) Targeting Elements and Criteria

Magmatic sources for ore fluid components: For magmatic sources, one needs to consider sources of magma, metals, and other ore fluid components such as sulfur and acid. In addition, one has to consider magmatic-hydrothermal processes that result in extraction of gold and other ore fluid components by exsolving magmatic aqueous fluids. Potential sources of magma for the Carlin mineral system in the Great Basin include the asthenosphere, metasomatized SCLM, mafic cumulates at the base of the crust, and potentially assimilation of crust. Loucks (2012), based on compilations of hundreds of whole-rock analyses of relatively primitive arc basalt from Cenozoic gold-mineralized and unmineralized segments of arcs worldwide, concluded that parental magmas of goldproductive differentiation series represent low-degree partial melts of the subarc mantle. The parental magmas were either unusually low degrees of partial melting in the asthenosphere or melting of SCLM that had been metasomatized with incompatible elements by trapping of earlier low-degree partial melts from the asthenosphere. Given the SCLM can remain attached to the crust for hundreds of millions to billions of years, Loucks (2012) concluded melting of SCLM was the primary source of ore-related magmas, as Muntean et al. (2011) did for Nevada, to explain metallogenic provinces that had gold deposits of multiple ages.

Work by Loucks and coworkers (e.g., Hronsky et al., 2012; Loucks, 2012, 2014; Lu et al., 2015), based on compilation of hundreds of whole-rock analyses of relatively primitive arc basalts from gold-mineralized and unmineralized segments of arcs, indicate magmas associated with mineralized settings were water rich and are characterized by elevated values of Nb, Th, and other highly incompatible water-soluble elements. Loucks (2012) demonstrated fresh or least altered samples of intrusions or flow domes representing magmas parental to epithermal, porphyry, and skarn gold or gold-copper deposits had higher Nb/Y, Th/Yb, and Ba/Zr ratios than volcanic and hypabyssal rocks of basaltic to rhyolitic composition, unmineralized segments of Neogene circum-Pacific island arcs, and continental-margin volcanic belts. For example, Nb/Y ratios are typically greater than 0.1 to 0.8, increasing with SiO2 content. The Nb/Y threshold ratio also depends upon whether the arc is oceanic or continental and, if continental, the age of the basement (Loucks, 2012). Where fresh igneous rocks are unavailable, zircon chemistry shows promise as a discriminator between fertile and infertile magmas. Dilles et al. (2015) compared the compositions of zircons in ore-forming and barren granitic plutons and demonstrated ore-forming granites related with porphyry copper and high-sulfidation epithermal gold deposits have relatively small negative europium anomalies (mostly Eu/Eu ≥0.4), compared to nonmineralized intrusions. They interpreted the anomalies to indicate magmas with high water content, as well as late magmatic oxidation attending loss of SO2-rich magmatic-hydrothermal ore fluids during crystallization. C. Johnson et al. (2015) showed that Eu/Eu values of zircons in dacite dikes, coeval with gold mineralization on the Carlin trend, were also greater than 0.4 and overlapped with Dilles et al.’s (2015) data on ore-forming granites. Similarly, Lu et al. (2016) presented zircon trace element data that indicated the best fertility indicators were elevated Eu/Eu (>0.3), 10,000(Eu/Eu)/Y (>1), (Ce/Nd)/Y (>0.01), and lower Dy/Yb (<0.3) ratios than infertile suites.

Another critical process if a magmatic source is invoked is exsolution of gold-rich aqueous fluids from the magmas. Based on experimental data, Zajacz et al. (2012) calculated partitioning coefficients of Au and Cu between melts and volatiles. Their coefficients for Au were 100 to 400 times higher than for Cu in pyrrhotite-saturated high-K calc-alkaline andesite melt at fairly reducing conditions at NNO + 0.5. Thus magmas with magmatic pyrrhotite have the potential to sequester more Cu than Au, thus allowing exsolving magmatic vapors to have higher Au/Cu ratios than a vapor exsolving from an oxidized magma (>NNO + 1). For Nevada, Muntean et al. (2011) argued transitory magma chambers in the middle crust may have fractionated monosulfide solid solution (close in composition to pyrrhotite), which would have removed more Cu from the melt relative to Au. The thick section of carbonaceous passive-margin sedimentary rocks may have played a role in the reduction of the Eocene high-K calc-alkaline magmas in Nevada, prior to exsolution of metalliferous magmatic fluids.

To summarize, if a magmatic source is invoked, one should look around the world for arcs of calc-alkaline magmatism that are largely coeval with the age of the targeted mineralization, preferably with high-K contents and with favorable fertility indicators. Belts dominated by dome fields and composite stratovolcanoes should be targeted rather than calderas and ignimbrites. Evidence for intrusions should be sought either in the form of mapped stocks and dikes or from geophysical signatures, namely from magnetic and gravity data that indicate subsurface intrusive centers. One should seek evidence in the regional magmatism for fluid release from intrusions that are coeval with the targeted mineralization, including miarolitic cavities, roof zones with abundant dikes, aplitic groundmass, pegmatites, potassic alteration, quartz veins, and/or skarn.

Crustal sources for ore fluid components: Targeting criteria at the regional scale include thick sections of pyritic carbonaceous carbonate and siliciclastic rocks. These rocks serve as potential sources of metals and reduced sulfide for the ore fluid. Reconnaissance laser ablation-inductively coupled plasma-mass spectroscopy (LA-ICP-MS) analyses of diagenetic sulfides and carbonaceous matter to test for elevated Au-As-Hg-Tl-Sb-(Te) concentrations is a potential tool to screen sedimentary sections for their fertility. In addition, carbonaceous sections with gold-bearing sedex occurrences would be favorable. Another criterion is the presence of bedded barite deposits in the section, which can serve as source of reduced sulfide by thermochemical sulfate reduction.

In addition to a fertile sedimentary section, potential for extraction of sulfide and metals from the sedimentary section and into meteoric and/or metamorphic fluids needs to be assessed. A carbonaceous sulfur-bearing section is important in that it keeps fluids reduced and enriched in aqueous sulfide to permit dissolution of gold by diffuse downwelling zones of convecting meteoric fluids at low water/rock ratios and long transport of gold. Widespread Eocene magmatism is likely the source of heat that drove the convection of meteoric water.

If metamorphic waters are invoked as a source of ore fluids, then there needs to be evidence of metamorphism that is the same age as the targeted mineralization. Metals could be leached from crustal sulfides by rising metamorphic aqueous reduced fluids similar to downwelling meteoric fluids. In addition, as argued by Large et al. (2011), desulfidation of pyrite to form pyrrhotite during lower greenschist to higher-grade metamorphism is an effective means to extract Au-As-Hg-Tl-Sb-(Te) from pyrite in the sedimentary section. Conversion to pyrrhotite is facilitated if carbonaceous material is present (Ferry, 1981). Regional metamorphism would be preferable, given the large volume of fluid it could generate. However, with regard to Nevada, peak regional metamorphic conditions in the area of Carlin-type deposits typically show Late Cretaceous ages (Miller and Gans, 1989; McGrew et al., 2000). Studies of diagenetic pyrite in Neoproterozoic rift sediments in deep oil wells (~2–4 km) show no evidence for conversion to pyrrhotite (Vikre et al., 2011). Furthermore, the Carlin trend and the Cortez and Jerritt Canyon clusters of Carlin-type deposits have evidence for large composite Eocene plutons underneath them, based on distribution of Eocene rhyolite dikes that could have resulted in desulfidation of pyrite. Therefore, contact metamorphism of the lower Paleozoic and Neoproterozoic section, associated with the emplacement of large Eocene plutons beneath Carlin-type deposits, could have been a source of fluids, metals, and sulfur.

Fluid pathways: At the regional scale, one is evaluating whether the targeted terrain has fluid pathways with sufficient vertical extent and connectivity to link the source of gold and other components of the ore fluid with the site of gold deposition, which for Carlin-type deposits was within ~2 to 3 km of the paleosurface.

These pathways may range down to the SCLM, to the amphibolite-greenschist transition, or to the base of the brittle crust. Thus, lithospheric-scale fault zones should be targeted. Such zones include suture zones between terranes and rifted continental margins, as in Nevada. A likely suture zone underlying Nevada is the western extension of the Cheyenne belt that separates from accreted Paleoproterozoic terranes and reworked Archean crust of Paleoproterozoic age to the south. In northeastern Nevada and northwestern Utah, the Archean crust is represented by the Grouse Creek block (Fig. 4).

Targeting criteria for rifted margins and suture zones include evidence from regional geologic maps and studies, such as passive-margin sedimentary sequences, juxtaposition of geologic terranes of different ages, and patterns of mantle-derived magmatism that is older than, coeval with, or younger than the targeted mineralization. Targeting criteria also include isotopic and geophysical data, including magnetic, gravity, and magnetotelluric (MT) data, all of which have been instrumental in helping map out basement structure in Nevada, as summarized by Grauch et al. (2003). Initial 87Sr/86Sr isotope ratios of Mesozoic and Tertiary granitoids of different ages were originally used to map the margin of the rifted Precambrian craton based on the 0.706 isopleth; however, the margin is likely a zone of westward-thinning continental crust along the eastern margin of the North American craton (Kistler and Peterman, 1978) (Fig. 4). The 38.8 and 39 isopleths of 208Pb/204Pb ratios from the granitoids correspond closely with the 0.706 isopleth (Tosdal et al., 2000). Tosdal et al. (2000) also demonstrated a distinct increase in 208Pb/204Pb ratios, defined by the 39.7 isopleth (Fig. 4). The isopleth trends northwest and is coincident with the eastern margin of the NNW-trending northern Nevada rift, clearly defined by gravity and magnetic data, and the northwest Carlin trend. The western margin of the northern Nevada rift is marked by narrow (~10 km), subvertical MT conductors that penetrate from 1 to 5 km below the sources to midcrustal depths (20 km) (Grauch et al., 2003). These conductors line up with what is known as the Battle Mountain-Eureka trend—northwest alignment of Eocene gold deposits including the Cortez and Getchell clusters of Carlin-type deposits. The Pb isotope data in eastern Nevada also reveal a pattern of decreasing 206Pb/204Pb ratios southward (Tosdal et al., 2000). 206Pb/204Pb ratios that are mostly >19.6 north of 40° latitude indicate intact Archean crust, likely the Grouse Creek block. To the south is a transition zone with values mainly between 19.1 and 19.3 that corresponds to the inferred southern margin of the Grouse Creek block. Further south, values of <18.7 indicate Proterozoic crust.

Besides lithospheric-scale faults, another targeting element is long-lived upper crustal fault zones that may be soft linked to underlying basement faults. At the regional scale, there are several targeting criteria that can be applied by compiling structural and stratigraphic data from published geologic maps. Regarding structural data, one should look for evidence of reactivated faults or underlying reactivated basement faults. Evidence includes narrow zones of anomalously trending folding axes within fold-and-thrust belts in the passive-margin sequence. For example, Evans and Theodore (1978) first pointed out that outside the Carlin trend fold axes trend mainly north-northeast, typical of folds associated with the late Paleozoic Antler orogeny and subsequent orogenies. However, within the Carlin trend, in a zone <10 km wide, fold axes trend northwest, parallel to the alignment of Carlin-type gold deposits (Fig. 9). Similarly, abrupt bends in stratigraphic form lines that bend back to their regional trend can be related to underlying basement structures. Other targeting criteria include dike swarms that are older than or the same age as the targeted mineralization.

Fig. 9.

Map defining Carlin trend using fold axes domains. Note the Carlin trend is largely defined by a ~5-km-wide zone of anomalous NW- to NNW-striking fold axes. Outside the Carlin trend, the fold axes strike predominantly north to northeast, which is the typical strike of fold axes associated with the Antler orogeny (Evans and Theodore, 1978). See text for discussion. Fold data are from Peters (1996), Moore (2002), and Harlan et al. (2002).

Fig. 9.

Map defining Carlin trend using fold axes domains. Note the Carlin trend is largely defined by a ~5-km-wide zone of anomalous NW- to NNW-striking fold axes. Outside the Carlin trend, the fold axes strike predominantly north to northeast, which is the typical strike of fold axes associated with the Antler orogeny (Evans and Theodore, 1978). See text for discussion. Fold data are from Peters (1996), Moore (2002), and Harlan et al. (2002).

Another regional targeting criterion, especially for extended regions like Nevada, is transverse tilt domain boundaries. Typically, the north-south ranges in Nevada are bounded by a major normal fault on one side of the range with kilometers of offset. Stewart (1996) produced a map of Nevada showing all the major basin and range faults, tilts of major structural blocks in the ranges, and attitudes of Tertiary rocks that define the tilt. Locally, the tilt of a given range can reverse abruptly, the boundaries of which Stewart (1996) defined as transverse boundaries. Faulds and Varga (1996) suggested preexisting structures are a major control on the locations of transverse accommodation zones that bound oppositely dipping fault blocks, citing examples from Rio Grande, Gulf of Suez, and East African rift.

Besides structural data, stratigraphic data can be used to infer pre-Eocene high-angle faults that may be linked to underlying basement faults. At the regional scale in Nevada, targeting criteria come from linear patterns in regional isopach maps of stratigraphy and identification of Paleozoic unconformities based on local absences of widespread stratigraphic units. Emsbo et al. (2006), pointed out that the Middle Devonian isopach map shows distinct narrow NW-trending zones of thick and thin sections, suggestive of horst and grabens, which Emsbo et al. (2006) suggested were caused by rifting in the Devonian (Fig. 10). The Carlin and Battle Mountain-Eureka trends occur along the margins of Devonian depocenters. Along the western margin of the Devonian depocenter, in the area of the Cortez mine, there is a major Middle Ordovician unconformity, in which ~750 m of stratigraphy is missing. The unconformity was associated with Middle Ordovician uplift and erosion, possibly a rifting event similar to what Emsbo et al. (2006) suggested for NW-trending Middle Devonian depocenters. Finally, an upper crustal section rich in carbonaceous rocks is important in helping keep fluids reduced and gold in solution. Thus, the faults described above will serve as much more efficient fluid pathways to transport gold if they cut carbonaceous rocks.

Fig. 10.

Map showing isopach contours of Middle Devonian strata in northeast Nevada. Note the strong northwest contour patterns that parallel gold deposits along the Carlin trend, the Battle Mountain-Eureka trend and Jerritt Canyon areas, which all are along the margins of thick sections of Devonian strata. See text for discussion. Modified slightly from Emsbo et al. (2006).

Fig. 10.

Map showing isopach contours of Middle Devonian strata in northeast Nevada. Note the strong northwest contour patterns that parallel gold deposits along the Carlin trend, the Battle Mountain-Eureka trend and Jerritt Canyon areas, which all are along the margins of thick sections of Devonian strata. See text for discussion. Modified slightly from Emsbo et al. (2006).

Water-rock interaction and gold deposition: At the regional scale, one is looking for lithologic packages and structures that would enable ascending fluids to leave high-angle faults and infiltrate reactive carbonate rocks. Also at this scale, one is looking for evidence of Carlin-type mineralization by identifying the characteristic Carlin geochemical signature in regional data sets like stream sediments and compilation of data and sampling of known deposits.

First at the regional scale, it is critical one is targeting a thick package of carbonate-bearing stratigraphy, preferably a passive-margin sequence, with rock types and structural zones within that carbonate-dominated sequence that promote water-rock interaction. Most passive-margin sequences are dominated by siliciclastic mudstone. To be carbonate dominated, passive-margin sequences had to form at low latitudes with sufficiently high ocean temperature for carbonate deposition. The Lower Cambrian to Upper Devonian portion of the passive margin in Nevada that is dominated by carbonate is about 4,575 to 6,000 m thick.

The favorable rock types that host ore in the four main clusters and several other Carlin-type deposits are typically thin bedded (<~10 cm) carbonates and carbonate debris flows that were deposited along the slope between the shallow platform and deep marine basin. These slope carbonates are typically dominated by carbonate mud with significant amounts of quartz silt and clay. Thus, knowing the location of the platform-slope boundary over time during passive-margin sedimentation is very important. As shown in Figure 11, the shelf slope boundary in Nevada moved east and west several times within a ~100-km-wide zone during the early Paleozoic, as mapped out by Cook (2015). After the shelf-slope boundaries are established, the next step is applying sequence stratigraphy to establish where lowstand system tracts occur in the stratigraphic section. As summarized by Cook and Corboy (2004) and Cook (2015), lowstands develop during the latter parts of lowering of relative sea level. Carbonate production decreases, and the shelf can become subaerially exposed and subject to karsting. Carbonate platform margins during lowstands can become gravitationally unstable and can collapse, forming turbidites, debris flow breccias, and slide blocks (Cook and Taylor, 1977). Cook (2015) presented comprehensive depositional facies profiles for the Lower Cambrian-Upper Devonian passive-margin section for northern Nevada extending from central Nevada to the border with Utah, in which he convincingly demonstrated that most carbonate strata that host Carlin-type deposits were deposited during lowstands, on both the slope and the shelf. Figure 12 summarizes the stratigraphic setting of Carlin-type deposits, based on Cook’s (2015) facies profiles.

Fig. 11.

Map showing the changing locations of the carbonate platform margin from Early Ordovician to Mississippian. See text for discussion. Modified from Cook (2015).

Fig. 11.

Map showing the changing locations of the carbonate platform margin from Early Ordovician to Mississippian. See text for discussion. Modified from Cook (2015).

Fig. 12.

Pre-Antler, Lower Cambrian to Upper Devonian west-east depositional facies profile for north-central and northeastern Nevada, from the Getchell area to the state line with Utah (~260 km). The stratigraphic thickness ranges from 4,575 to 6,000 m. Relative thicknesses of stratigraphic units have been altered for diagrammatic purposes. Red vertical bars show the positions of Carlin-type gold deposits within the profile. Note most deposits are on the slope. Modified from Cook (2015).

Fig. 12.

Pre-Antler, Lower Cambrian to Upper Devonian west-east depositional facies profile for north-central and northeastern Nevada, from the Getchell area to the state line with Utah (~260 km). The stratigraphic thickness ranges from 4,575 to 6,000 m. Relative thicknesses of stratigraphic units have been altered for diagrammatic purposes. Red vertical bars show the positions of Carlin-type gold deposits within the profile. Note most deposits are on the slope. Modified from Cook (2015).

Water-rock interaction is enhanced by structural features that enable upwelling fluids to leave high-angle faults and infiltrate the carbonate wall rocks. In addition to a carbonate-dominated passive-margin sequence, passive margins that have experienced contractional deformation and formation of fold-and-thrust belts should be targeted at the regional scale. Targeting criteria include deformed carbonate rocks, especially those in the lower plate of regional thrust faults. In Nevada, the oldest and lowest known regional thrust fault, the Roberts Mountain thrust, is a primary control on the location of many Carlin-type deposits in Nevada, in that many deposits are within 250 m of the thrust or the projection of it. The upper plate rocks are highly deformed silica-clastic rocks with little to no carbonate. Furthermore, as the Roberts Mountain thrust is approached from the footwall, contractional deformation in the lower plate carbonates increases, including a variety of folds and thrusts, including imbrication of the lower plate and upper plates in the Carlin trend (Rhys et al., 2015) as well as at Cortez (Leonardson, 2011) and Jerritt Canyon (Dewitt, 2001; T. Johnson et al., 2015). Folding and thrusting of the lower plate carbonates, especially the thin-bedded slope carbonates, resulted in bedding plane slip that developed fracture permeability along the numerous bedding planes.

Also, one should look for antiformal culminations, manifested as domes or regionally extensive unconformities. Over much of northeastern Nevada, there is a regional unconformity defined by Tertiary rocks overlying Triassic and older rocks. Typically in north-central and northeastern Nevada, Tertiary volcanic rocks overlie rocks of the Roberts Mountain and Golconda allochthons, emplaced in the late Paleozoic, or rocks younger than Silurian east of these allochthons (Long, 2012). However, there are places where Tertiary volcanic rocks overlie rocks as old as Cambrian, such as in the Eureka mining district (Long et al., 2014a). Mapping out the age of the rocks underlying the Tertiary unconformity using regional geologic maps is an effective way of identifying these culminations.

At the regional scale, identification of the characteristic Carlin-type geochemical signature is an important targeting element. Key targeting criteria are regional Au-As-Hg-Tl-Sb-(Te) signatures in regional stream sediment, soil, and/or groundwater data sets. The targeted signature might not have all of these elements and may have additional elements. For example, regional stream sediment and soil data for northern Nevada, summarized by Luddington et al. (2006), demonstrated that areas of >10 ppm As and high scores for a Sb-Ag-As-Pb-Au-Zn signature based on principal component analysis highlighted the Carlin and the Battle Mountain-Eureka trends (Fig. 13). As Ludington et al. (2006) pointed out, arsenic is an extremely mobile element and can be used to delineate structures that served as pathways for hydrothermal fluids. The stream sediment anomalies can be derived from multiples types and ages of mineralization, which can be superimposed in northern Nevada. Thus, the geochemistry is not solely indicating Carlin-type mineralization. Nevertheless, the strong arsenic signature highlighted by Ludington et al. (2006) is permissive for Carlin-type mineralization. Another targeting criterion is whether historical mining districts reported gold production from replacement deposits with low Ag/Au ratios (<2:1) with low silver and base metal production and whether reported trace element data were consistent with the Au-As-Hg-Tl-Sb-(Te) signature.

Fig. 13.

Regional stream sediment data for north-central and northeastern Nevada. A. Arsenic. B. Gold factor based on Sb-Ag-As-Pb-Au-Zn factor (elements listed in decreasing factor loading), which accounted for nearly 22% of the variance of the data sets. Figures are from Ludington et al. (2006).

Fig. 13.

Regional stream sediment data for north-central and northeastern Nevada. A. Arsenic. B. Gold factor based on Sb-Ag-As-Pb-Au-Zn factor (elements listed in decreasing factor loading), which accounted for nearly 22% of the variance of the data sets. Figures are from Ludington et al. (2006).

Tectonic trigger: The key targeting elements for Nevada that point to a tectonic trigger, which could apply to selection of terranes with potential to host Carlin-type deposits outside Nevada, include (1) a change from contraction to extension, (2) a major thermal event, (3) slab rollback or removal after a period of flat subduction, and (4) global plate reorganization. Targeting criteria include terranes along cratonic margins with fold-and-thrust belts with clear evidence for postorogenic extension, including normal faults, extensionally reactivated or collapsed contractional structures, and metamorphic core complexes. In Nevada, the major Eocene thermal event was driven mainly by magmatism. Periods of flat subduction in segments of arcs or abnormal spatial patterns of arc magmatism developed along continental margins may identify potential periods of slab rollback or removal. Major thermal events with accompanying magmatism and metamorphism could also result from crustal thickening, plume impact during subduction, subduction of oceanic ridges, erosion or delamination of SCLM, or postcollisional extension (e.g., Goldfarb et al., 2001; Richards, 2011). In addition, major plate reorganizations should be compiled to target specific time periods along continental margins (cf. Goldfarb et al., 2007). For example, the bend in the Hawaiian-Emperor seamount chain corresponds to a shift in plate in motion at 43 Ma (cf. Engebretson et al., 1985).

District targeting (~20–5,000 km2)

At the scale of ~20 to 5,000 km2, targeting elements and criteria detailed below are meant to target lands for acquisition or reevaluate existing land holdings for new targets. At this scale more detailed evaluation of existing data sets, collection of new data sets, and field work are necessary. Also at this scale, recognition of targeting elements or mapping targeting criteria for sources of ore fluid components and tectonic triggers is likely unnecessary. Table 3 lists the targeting elements at the district scale for fluid pathways and water-rock interaction and gold deposition.

Table 3.

District-Scale (~20–5,000 km2) Targeting Elements and Criteria

Fluid pathwaysWater-rock interaction and gold deposition
Targeting elementsTargeting criteriaTargeting elementsTargeting criteria
Old reactivated high-angle fault zones, especially those linked to underlying basement faultsStructural criteria for old reactivated faults, including narrow anomalies in form lines in stratigraphy, fault propagation folds, monoclines, flower structures, footwall shortcut thrust and floating islands, folded thrust faults, local zones of upright to inclined tight folds, folds with anomalous vergence, high-angle faults overlapped by preore sedimentary or volcanic rocksCarbonate-bearing stratigraphyCarbonate section with low-angle dips (<~30°) Thin-bedded carbonates susceptible to bedding plane slip
Low-angle features that divert fluids from high-angle faults and into reactive wall rocksDeformed carbonates in lower plates of regional thrust faults that have upper plate basinal siliciclastic rocks
 Stratigraphic criteria for old reactivated faults, including thickening, thinning, or abrupt facies changes, growth fault sequences, packages of sedimentary breccias with linear boundaries, reef and other shallow carbonate facies formation on tops of tilted fault blocks, and syngenetic barite Anticlines
High-angle extensional faults broadly synchronous with targeted mineralizationExtensional faults that control targeted alteration and mineralizationHydrothermal system of targeted ageEvidence of intrusive centers of the same age as target mineralization
Discordant zones of apatite fission trace cooling dates that are similar to age of targeted mineralization
Discordant zones of overmature carbonaceous matter in areas where hydrocarbons haven not matured to pyrobitumen prior to age of targeted mineralization
Discordant zones of high conodont indices
Fault intersectionsIntersections between old reactivated high-angle faults and synore normal faultsAlteration consistent with wall-rock reaction with acidic, sulfide-rich hydrothermal fluidsJasperoid outcrops
Rheology contrastContacts between hornfels aureoles and metamorphosed sediments, as mapped in the field or interpreted from geophysicsZones of limonite staining
Au-As-Hg-Tl-Sb geochemical signature with low Ag and base metals in rock chips, soils, or drilling
Zones of abundant low-displacement high-angle faultsFaulted relay ramps between overlapping high-angle normal faults  
 Tips of high-angle normal faults  
Fluid pathwaysWater-rock interaction and gold deposition
Targeting elementsTargeting criteriaTargeting elementsTargeting criteria
Old reactivated high-angle fault zones, especially those linked to underlying basement faultsStructural criteria for old reactivated faults, including narrow anomalies in form lines in stratigraphy, fault propagation folds, monoclines, flower structures, footwall shortcut thrust and floating islands, folded thrust faults, local zones of upright to inclined tight folds, folds with anomalous vergence, high-angle faults overlapped by preore sedimentary or volcanic rocksCarbonate-bearing stratigraphyCarbonate section with low-angle dips (<~30°) Thin-bedded carbonates susceptible to bedding plane slip
Low-angle features that divert fluids from high-angle faults and into reactive wall rocksDeformed carbonates in lower plates of regional thrust faults that have upper plate basinal siliciclastic rocks
 Stratigraphic criteria for old reactivated faults, including thickening, thinning, or abrupt facies changes, growth fault sequences, packages of sedimentary breccias with linear boundaries, reef and other shallow carbonate facies formation on tops of tilted fault blocks, and syngenetic barite Anticlines
High-angle extensional faults broadly synchronous with targeted mineralizationExtensional faults that control targeted alteration and mineralizationHydrothermal system of targeted ageEvidence of intrusive centers of the same age as target mineralization
Discordant zones of apatite fission trace cooling dates that are similar to age of targeted mineralization
Discordant zones of overmature carbonaceous matter in areas where hydrocarbons haven not matured to pyrobitumen prior to age of targeted mineralization
Discordant zones of high conodont indices
Fault intersectionsIntersections between old reactivated high-angle faults and synore normal faultsAlteration consistent with wall-rock reaction with acidic, sulfide-rich hydrothermal fluidsJasperoid outcrops
Rheology contrastContacts between hornfels aureoles and metamorphosed sediments, as mapped in the field or interpreted from geophysicsZones of limonite staining
Au-As-Hg-Tl-Sb geochemical signature with low Ag and base metals in rock chips, soils, or drilling
Zones of abundant low-displacement high-angle faultsFaulted relay ramps between overlapping high-angle normal faults  
 Tips of high-angle normal faults  

Note: Sources of ore fluid components and tectonic triggers are not considered at this scale

Fluid pathways: At the district scale, one is looking for structural settings that focused upwelling ore fluids. Compilation of overall orientation of Carlin-type deposits in Nevada, based on azimuths of open pits, blast hole patterns, grade times thickness maps, and information on controlling structures, shows high-angle north-northwest faults (~330°–360° azimuth) are the primary control in most deposits, followed by northwest (~290°–315° azimuth) and northeast faults (30°– 65° azimuth) (Fig. 14). Old, reactivated high-angle faults, especially those that appear to be linked to underlying basement faults, are important targeting elements. Both structural and stratigraphic targeting criteria can be used to identify and map these old reactivated fault zones.

Fig. 14.

Rose diagrams of the trends of the dominant ore-controlling structures or of the trend of pits of 110 Carlin-type gold deposits in Nevada. Dominant trends are north-south (355°–10°), north-northwest (330°–345°), and west-northwest (285°–315°).

Fig. 14.

Rose diagrams of the trends of the dominant ore-controlling structures or of the trend of pits of 110 Carlin-type gold deposits in Nevada. Dominant trends are north-south (355°–10°), north-northwest (330°–345°), and west-northwest (285°–315°).

Stratigraphic targeting criteria for such reactivated faults include thickening, thinning, or abrupt facies changes in sedimentary units, growth fault sequences, marine sedimentary breccias with linear boundaries, reefs and other shallow-water carbonate sequences with sharp boundaries, and syngenetic barite or sulfide occurrences. Stratigraphic studies in the northern Carlin trend and Getchell area demonstrated abrupt facies changes that suggest synsedimentary faulting and formation of second-order basins mainly along the platform margin. In the northern Carlin trend, Paleozoic normal faulting is suggested by a rapid facies change over a distance of <800 m across a WNW-trending boundary (Bettles, 2002) (Fig. 15). Massive oolitic fossiliferous limestones of the Devonian Bootstrap limestone, indicative of shallow, high-energy conditions, occur to the northeast (Armstrong et al., 1998). To the southwest of the Bootstrap margin, laminated muddy limestones and debris-flow breccias of the time-equivalent Popovich Formation indicate a transition to deeper water (Furley, 2001). Emsbo et al. (1998, 2003) suggested Devonian extension was responsible for this margin. In the Getchell area (Fig. 16), a sequence of pillow basalt and underlying sedimentary debris-flow breccias of Cambrian-Ordovician age pinch out to the south along a sharp N70°W southern margin that is an important ore control to the Turquoise Ridge deposit. The margin occurs along the northern limb of a monocline that is interpreted to have formed by an underlying N-dipping, WNW-trending Cambrian-Ordovician syndepositional normal fault (Muntean et al., 2007; Cassinerio and Muntean, 2011).

Fig. 15.

A. Map of the northern Carlin trend showing locations of Carlin-type gold deposits, open pits, and surface projections of underground deposits. Note the clustering of deposits around the Jurassic Goldstrike stock. The map also shows the major faults and the predicted slip pattern during Eocene extension. B. Interpreted paleoenvironment of the host rocks in the northern Carlin trend, showing distribution of carbonate facies and their formations. The Devonian rocks in the northern Carlin trend represent the reef foreslope facies and the progressive drowning of the Bootstrap reef by the Rodeo Creek unit. The map in A shows the interpreted location of the Bootstrap shelf margin. From Cline et al. (2005).

Fig. 15.

A. Map of the northern Carlin trend showing locations of Carlin-type gold deposits, open pits, and surface projections of underground deposits. Note the clustering of deposits around the Jurassic Goldstrike stock. The map also shows the major faults and the predicted slip pattern during Eocene extension. B. Interpreted paleoenvironment of the host rocks in the northern Carlin trend, showing distribution of carbonate facies and their formations. The Devonian rocks in the northern Carlin trend represent the reef foreslope facies and the progressive drowning of the Bootstrap reef by the Rodeo Creek unit. The map in A shows the interpreted location of the Bootstrap shelf margin. From Cline et al. (2005).

Fig. 16.

Simplified geologic map of the Getchell-Twin Creeks area, based mostly on mapping by Hotz and Willden (1964) and unpublished mapping by Placer Dome geologists. The oval outlines a proposed faulted relay ramp, composed of a mesh of north-south and northeast faults that is transferring extension from the Getchell fault zone to the Rabbit Creek fault on the east side of the Twin Creeks deposit. Note how the Turquoise Ridge deposit straddles the edge of the metamorphic contact aureole associated with the Cretaceous Osgood stock (pink body). See text for discussion. Modified from Muntean et al. (2007).

Fig. 16.

Simplified geologic map of the Getchell-Twin Creeks area, based mostly on mapping by Hotz and Willden (1964) and unpublished mapping by Placer Dome geologists. The oval outlines a proposed faulted relay ramp, composed of a mesh of north-south and northeast faults that is transferring extension from the Getchell fault zone to the Rabbit Creek fault on the east side of the Twin Creeks deposit. Note how the Turquoise Ridge deposit straddles the edge of the metamorphic contact aureole associated with the Cretaceous Osgood stock (pink body). See text for discussion. Modified from Muntean et al. (2007).

Fault and fold geometries are present in districts of Carlin-type deposits that are consistent with structural inversion of pre-Eocene normal faults interpreted to be soft linked to underlying basement faults. Fault propagation folds—fold geometries that involve long, gently dipping backlimbs and short, steep forelimbs—are common in north-central and northeastern Nevada. Typically, such hanging-wall anticlines in Nevada are attributed to ramps in a fold-thrust belt related to thin-skinned tectonics, but as argued by Cline et al. (2005) and Muntean et al. (2007), many could be related to thickskinned tectonics in which underlying basement faults were reactivated as reverse faults. When high-angle faults are reactivated to form reverse faults, lower-angle shortcut thrusts can form in the footwall as a series of splays that result in a flower structure (Williams et al., 1989; Coward, 1994). Radiating arrays of faults in the steep forelimb that root to a master fault (wedge shaped in section) and are subparallel in trend to the axial plane of the associated anticline can be formed by contractional deformation of preexisting high-angle faults. Subsequent extensional reactivation can result in a floating island geometry, where a wedge of older rocks is preserved between younger rocks.

At Turquoise Ridge, Cassinerio and Muntean (2011) showed the basin margin that bounded the pillow basalt was subsequently inverted, resulting in folds and thrust faults parallel to the margin. The deformed margin is an important ore control at the Turquoise Ridge deposit. At Jerrritt Canyon, high-angle N50°–70°W extensional faults commonly intruded by Pennsylvanian basalt-andesite dikes were reactivated as reverse faults and then subsequently extensionally reactivated during mineralization. The latest extensional event preserved floating island geometries in their footwalls. They are important ore controls at Jerritt Canyon (Fig. 17A).

Fig. 17.

A. Cross section by author, looking west, across the underground Murray Carlin-type gold deposit in the Jerritt Canyon district. Ore is controlled by the WNWstriking New Deep fault, which was intruded by ~320 Ma basaltic dikes after the emplacement of the Roberts Mountain thrust. Ore is also controlled by the contact of the Silurian-Ordovician Hanson Creek and Devonian-Silurian Roberts Mountains Formations. Note the floating island in the footwall of the New Deep fault, where a thrusted wedge of Hanson Creek Formation is preserved. The geometry is interpreted to have formed by reverse reactivation of an original normal fault during the Antler orogeny, resulting in an asymmetric hanging-wall anticline, which forms where hanging-wall rocks are displaced from the original normal fault onto a new higher level along a more gently dipping thrust. The normal fault then underwent extensional reactivation during emplacement of the basalt dikes, leaving the floating island in the footwall. Cross section is modified from Kantor et al. (1998). B. Cross section of the West Bazza pit in the northern Carlin trend, looking east, modified from Lauha (1998). The radiating array of shortcut thrusts (bold lines) shows net contraction. The normal fault, to the right, shows net extension. The thrusts and the normal fault have west-northwest strikes. All of the faults have hanging-wall anticlines. Note one of the shortcut thrusts is intruded by a Jurassic dike, suggesting thrusts are Jurassic or older. Both cross sections show no vertical exaggeration.

Fig. 17.

A. Cross section by author, looking west, across the underground Murray Carlin-type gold deposit in the Jerritt Canyon district. Ore is controlled by the WNWstriking New Deep fault, which was intruded by ~320 Ma basaltic dikes after the emplacement of the Roberts Mountain thrust. Ore is also controlled by the contact of the Silurian-Ordovician Hanson Creek and Devonian-Silurian Roberts Mountains Formations. Note the floating island in the footwall of the New Deep fault, where a thrusted wedge of Hanson Creek Formation is preserved. The geometry is interpreted to have formed by reverse reactivation of an original normal fault during the Antler orogeny, resulting in an asymmetric hanging-wall anticline, which forms where hanging-wall rocks are displaced from the original normal fault onto a new higher level along a more gently dipping thrust. The normal fault then underwent extensional reactivation during emplacement of the basalt dikes, leaving the floating island in the footwall. Cross section is modified from Kantor et al. (1998). B. Cross section of the West Bazza pit in the northern Carlin trend, looking east, modified from Lauha (1998). The radiating array of shortcut thrusts (bold lines) shows net contraction. The normal fault, to the right, shows net extension. The thrusts and the normal fault have west-northwest strikes. All of the faults have hanging-wall anticlines. Note one of the shortcut thrusts is intruded by a Jurassic dike, suggesting thrusts are Jurassic or older. Both cross sections show no vertical exaggeration.

In the Eureka district, Long et al. (2014a, 2015) interpreted the antiformal culmination that exposes Lower Cambrian rocks to be a fault propagation fold related to a ramp structure in the hinterland of the Cretaceous Sevier fold-and-thrust belt (Fig. 18). Alternatively, rather than a ramp, a more deeply rooted, high-angle reverse fault cannot be ruled out. Importantly, Long et al. (2014a) demonstrated Eocene volcanic rocks, likely coeval with Carlin-type gold deposits in the Eureka district, overlapped normal faults that down-dropped Devonian rocks against Cambrian rocks during Late Cretaceous to Paleocene (75–60 Ma) extensional collapse of the culmination (Long et al., 2014a, 2015). These pre-Eocene normal faults localized the Carlin-type gold deposits (Di Fiori et al., 2015). Such collapsed fold belts typically have normal faults with low cut-off angles with stratigraphy. Steep fold limbs collapse as high-angle faults, and shallow fold limbs collapse as low-angle faults commonly referred to as detachments. A similar relationship exists at the antiformal culmination associated with Carlin-style gold deposits at Kinsley Mountain (Hannink et al., 2015; Muntean et al., 2017b).

Fig. 18.

Pre-Eocene extensional collapse of structural culmination in the Eureka district. A. Simplified geologic map of the Eureka district. B. Enlargement of the southern Eureka district showing locations of Windfall and Lookout Mountain deposits along north-south normal faults that formed between ~80 and ~38 Ma. C. West-east cross section and restored (prior to extension) cross section, located at the bottom of the map in B. See text for discussion. From Long et al. (2014b).

Fig. 18.

Pre-Eocene extensional collapse of structural culmination in the Eureka district. A. Simplified geologic map of the Eureka district. B. Enlargement of the southern Eureka district showing locations of Windfall and Lookout Mountain deposits along north-south normal faults that formed between ~80 and ~38 Ma. C. West-east cross section and restored (prior to extension) cross section, located at the bottom of the map in B. See text for discussion. From Long et al. (2014b).

As previously pointed out, Carlin-type deposits in Nevada formed during the onset of extension in the late Eocene. Therefore, an important criterion is normal faults that are broadly synchronous with targeted mineralization. In addition to pre-Eocene extensional and reactivated contractional structures, upwelling fluids were also controlled by Eocene extensional faults. The Eocene normal faults typically have steep dips. Eocene extension (and most post-Eocene extension) in northern Nevada was oriented broadly northwesterly to westerly (280°–330°), as indicated by the strike of Eocene-age fault blocks, by the general orientation of Eocene dikes (Ressel et al., 2000; Theodore, 2000; Cline et al., 2005; Henry, 2008; Rhys et al., 2015), and by the direction of midcrustal flow of demonstrably Eocene age in the Ruby Mountains-East Humboldt Range metamorphic core complexes (Howard, 2003, and references therein). Eocene dikes commonly strike northeast in the Carlin trend (Ressel et al., 2000; Ressel and Henry, 2006) and Jerritt Canyon (Phinisey et al., 1996; Hofstra et al., 1999), in addition to occupying older reactivated faults. Given WNW-directed extension in the Eocene, predictions can be made about the kinematics of the meshes of Eocene and pre-Eocene faults during late Eocene ore formation. Northeast faults would be predominantly dip slip, north-northwest faults would have a mixture of dextral and dip slip, and west-northwest faults would be predominantly dextral with a minor component of dip slip (Cline et al., 2005; Rhys et al., 2015) (Fig. 15).

An important targeting element is fault intersections. In Nevada, the targeted intersections are between NE-striking Eocene faults and older, reactivated NNW-striking and WNW-striking faults. For example, the giant Gold Quarry deposit on the Carlin trend lies at the intersection of the N40°W Good Hope reverse fault and the later N30°E Gold Quarry fault zone (Harlan et al., 2002), also known as the Chukar-Alunite fault zone (Rhys et al., 2015). The Gold Quarry fault zone formed in the Eocene and is the principal control on mineralization at Gold Quarry (Rhys et al., 2015). At Jerritt Canyon, several deposits, including SSX, Steer/Saval, Smith/Dash, California Mountain, Starvation Canyon, and Burns Basin, occur at the intersection of reactivated, WNW-striking Pennsylvanian faults described above and northeast faults of likely Eocene age (Eliason and Wilton, 2005; Muntean and Henry, 2007). The Getchell fault is at least Cretaceous in age, given abundant parallel Cretaceous granite dikes along the fault zone (Berger and Taylor, 1980).

Strong lithologic rheology contrast is also an important targeting element in focusing upwelling fluids. In Nevada, this is expressed by preore intrusions and their metamorphic contact aureoles. Five giant deposits—Betze-Post (Fig 15), Gold Quarry, Turquoise Ridge (Fig. 16), Pipeline, and Cortez Hills, with a combined endowment of ~150 Moz (467 t)—occur along the margins of metamorphic contact aureoles associated with Mesozoic stocks. Rising Mesozoic magmas likely utilized the same basement-linked fault systems postulated above. Once stocks crystallized at upper crustal levels along these faults systems, they essentially acted as rigid bodies that pinned and controlled postintrusion deformation. The stock and contact metamorphic aureole consisting of hornfels and local skarn forms a major rheologic contrast with the surrounding unmetamorphosed sedimentary rocks. During ore Eocene formation, extension reactivated favorably oriented faults, which were largely the NNE- to NNW-striking faults. However, because of the low magnitudes of strain, slip on these faults near the older Mesozoic intrusions was forced around the rigid stocks and contact aureoles along a complex fracture mesh, typically adjacent to skarn-hornfels contact aureoles (Fig. 19). Geophysical data, particularly air magnetics and gravity, can be used to map covered intrusions and aureoles.

Fig. 19.

Schematic explanation of how accommodating faults form around granites that pin deformation on earlier formed faults in areas of low mean stress and rheological contrast between hornfels and nonmetamorphosed rocks.

Fig. 19.

Schematic explanation of how accommodating faults form around granites that pin deformation on earlier formed faults in areas of low mean stress and rheological contrast between hornfels and nonmetamorphosed rocks.

Water-rock interaction and gold deposition: At the district scale, four targeting elements for water-rock interaction and gold deposition stand out: (1) carbonate-bearing rock types, especially thin-bedded units with low-angle dips (<~35°), (2) low-angle features in the carbonate host rocks that will divert fluids from high-angle faults and into the wall rocks, (3) a hydrothermal system of the targeted age, and (4) alteration consistent with wall-rock reaction with acidic, sulfide-rich hydrothermal fluids.

At the district scale much more attention than at the regional scale should be paid to identifying low-angle features that facilitate ingress of ore fluids into reactive carbonate wall rocks. As recently documented in the Carlin trend by Rhys et al. (2015), the Roberts Mountain thrust varies from a ductile to semibrittle zone that ranges from a discrete shear to a broad high-strain zone that locally exceeds 50 m in thickness. They documented similar high-strain zones within the lower plate carbonates, which are manifested as low-angle reverse faults that commonly show evidence for extensional reactivation. These zones are important local controls on ore, indicating they diverted upwelling fluids into reactive carbonate wall rocks. The Roberts Mountain thrust forms a cap to the reactive carbonate rocks, both in permeability and reactivity. As the thrust is approached from below, permeability changes from predominantly steep fault/fracture controls to low-angle fault/fracture controls. Fluids that dissolve carbonate and create porosity in the lower plate during water-rock interaction decrease porosity in the upper plate siliciclastic and volcanic rocks by argillization and deposition of silica.

A key observation regarding water-rock interaction is that the vast majority of Carlin-type deposits have carbonate hosts rocks that dip ≤35°. Like the low-angle deformation zones in the lower place carbonates proximal to the Roberts Mountains thrust, low-angle bedding dips divert fluid out of the high-angle faults and fractures into rocks. These low dips, apparently present during ore formation, are important for both practical mining and ore-forming processes. The low angles for the host stratigraphy and resulting low-angle tabular nature to the orebodies decrease the amount of stripping necessary for open-pit mining. If the stratigraphy dipped steeply at similar angles to the high-angle faults, fluids would have continued to rise and not form large replacement zones. Rather, narrower zones would have formed along the high-angle faults, and ore fluids would have likely flowed across the thrust and continued to rise and disperse metals in the nonreactive siliciclastic rocks of the upper plate.

The porosity and permeability formed during bedding slip associated with folding are best developed in the hinge zones of folds; thus, folds are important controls on Carlin-type deposits, especially anticlines. The best example is the N-trending Conelea anticline, which is the main control at the giant Twin Creeks deposit (Fig. 20). Gold grade is highest in the hinge zone. Other deposits that have anticlines as important controls include the WNW-trending Betze anticline and the NNW-trending Post anticline in the Betze Post open-pit deposit, the largest Carlin-type gold deposit in the world. Folds are also important at Getchell, Turquoise Ridge, Pipeline, and several deposits at Jerritt Canyon.

Fig. 20.

Southwest-northeast cross section across the Conelea anticline in the Megapit deposit (also known as Rabbit Creek) at Twin Creeks. Fold is defined by several mafic sills and volcanic units. Note how the higher gold grades are focused in the hinge zone of the fold. Modified from Stenger et al. (1998). See Figure 16 for the location of the section.

Fig. 20.

Southwest-northeast cross section across the Conelea anticline in the Megapit deposit (also known as Rabbit Creek) at Twin Creeks. Fold is defined by several mafic sills and volcanic units. Note how the higher gold grades are focused in the hinge zone of the fold. Modified from Stenger et al. (1998). See Figure 16 for the location of the section.

As highlighted by Smith and Cook (2018), shallow platform carbonates on the shelf in eastern Nevada and western Utah host Carlin-style gold deposits. Most of the occurrences are associated with karsts that form in typically shallow water, massive carbonate during lowstands. Cook (2015) shows lowstands forming at the Cambrian-Ordovician boundary—several between the end of the Early Ordovician and Early Silurian and throughout the Devonian (Fig. 12). Long Canyon, the largest Carlin-type gold deposit discovered to date on the shelf, is focused along the Cambrian-Ordovician boundary. Besides karst, the boundary is a significant rheology boundary between underlying, more brittle dolomite of the Cambrian Notch Peak Formation and limestone of the Ordovician Goodwin Formation. During contractional deformation, the dolomite deformed in a brittle fashion, forming boudins, whereas the limestone underwent ductile deformation. The margins of the boudins control the higher grades at Long Canyon (Smith et al., 2013). In addition to karst, the succeeding transgressive sequence that places deeper-water thin-bedded carbonates over massive carbonates (Cook, 2015) creates a rheological contrast. Such rheological contrasts can occur throughout the early Paleozoic section, especially contacts between calcareous shale/siltstone and massive carbonate units. During contractional deformation, the shale/siltstone units take up most of the strain, which greatly enhances porosity and permeability near the contact with the less deformed massive limestone or dolomite.

Lamprophyre dikes, typically of Jurassic age (~160 Ma), occur on the Carlin trend (Ressel and Henry, 2006) and at other Carlin-type deposits. They indicate extension along deep-seated fault systems that tapped mantle-sourced magmas. In the northern Carlin trend, they typically have north-south to N30°W strikes, parallel to the Post-Gen fault system, an important ore-controlling structure. In the northern Carlin trend, the N60°W SSW-dipping Bazza fault at the west end of the Betze-Post deposit is parallel to the Bootstrap margin described above (Fig. 17B). The Bazza fault now shows apparent normal motion (Lauha, 1998) and has a floating island in its footwall. The floating island is floored by a shortcut thrust that is intruded by a Jurassic dike.

At the district scale, documentation of the presence of a hydrothermal system of the same age as the targeted mineralization is an important targeting element. In Nevada, a targeting criterion is evidence for Eocene intrusive centers, which at the very least provided heat to drive the Carlin hydrothermal systems. However, as pointed out by Hofstra and Cline (2000) and Cline et al. (2005), none of the four main clusters of Carlin-type deposits have a documented epizonal Eocene stock. Moreover, no mineral or geochemical zoning that is characteristic of hydrothermal systems associated with epizonal stocks has been documented in the four clusters. Rather than epizonal stocks, targeting criteria include the presence of dikes and geophysical evidence for underlying batholiths. Ressel and Henry (2006) noted the spatial and temporal distribution of rhyolite dikes in the northern Carlin trend required the presence of silicic plutons underlying the northern Carlin trend. Rhyolite is simply too viscous to have flowed laterally for significant distances from its underlying source pluton. Ressel and Henry (2006), presented aeromagnetic data that were upward continued to better define potential deep plutons. Based on geology, geochronology, and the aeromagnetic data, they interpreted an Eocene batholith composed of at least six plutons that formed over a 4-m.y. period (Fig. 21A). The estimated depths of the roofs of the pluton increased from ~3 km at the south end of the batholith to ~9 km at the north end, underneath the Betze-Post deposit.

Fig. 21.

Apatite fission track (AFT) data as indicators of Carlin-type systems. A. AFT data from pre-Cenozoic samples from the region around the Carlin trend. A zone of pervasive ~50 to 20 Ma thermal annealing of apatite spatially associated with the Carlin trend is outlined in green. The northern Carlin trend, also outlined in green, is characterized by partially annealed mixed apatite with dates ranging mainly from ~120 to 20 Ma. These Cenozoic age clusters that are centered on the Carlin trend resulted from hydrothermal fluid flow related to the formation of the Carlin trend. Annealing was more complete in lower plate carbonates and less so in the upper plate rocks to the north and south. AFT data in the Tuscarora Mountains to the north range, outlined in orange, are mainly from ~120 to 70 Ma. These dates constrain the age of exhumation. Also shown are Eocene plutons (dashed red lines labeled by age) inferred from the age, petrography, and distribution of Eocene dikes, as well as aeromagnetic data. Summarized from Cline et al. (2005) and Ressel and Henry (2006). B. AFT data from around the Pipeline and Gold Acres deposits that are part of the Cortez cluster of Carlin-type gold deposits. The zone of pervasive Eocene annealing in the Pipeline area is more narrow (~4–5 km) compared to that in the Carlin trend (~10–15 km). Summarized from Arehart and Donelick (2006).

Fig. 21.

Apatite fission track (AFT) data as indicators of Carlin-type systems. A. AFT data from pre-Cenozoic samples from the region around the Carlin trend. A zone of pervasive ~50 to 20 Ma thermal annealing of apatite spatially associated with the Carlin trend is outlined in green. The northern Carlin trend, also outlined in green, is characterized by partially annealed mixed apatite with dates ranging mainly from ~120 to 20 Ma. These Cenozoic age clusters that are centered on the Carlin trend resulted from hydrothermal fluid flow related to the formation of the Carlin trend. Annealing was more complete in lower plate carbonates and less so in the upper plate rocks to the north and south. AFT data in the Tuscarora Mountains to the north range, outlined in orange, are mainly from ~120 to 70 Ma. These dates constrain the age of exhumation. Also shown are Eocene plutons (dashed red lines labeled by age) inferred from the age, petrography, and distribution of Eocene dikes, as well as aeromagnetic data. Summarized from Cline et al. (2005) and Ressel and Henry (2006). B. AFT data from around the Pipeline and Gold Acres deposits that are part of the Cortez cluster of Carlin-type gold deposits. The zone of pervasive Eocene annealing in the Pipeline area is more narrow (~4–5 km) compared to that in the Carlin trend (~10–15 km). Summarized from Arehart and Donelick (2006).

In areas where organic carbonaceous material has not been regionally cooked to pyrobitumen, discordant zones of overmature organic carbonaceous material can be targeted. As pointed out by Hofstra and Cline (2000), most organic carbonaceous material is overmature in deposits that formed below the Roberts Mountain allochthon, including the four main clusters of Carlin-type deposits. Modeling of organic maturation (Gize et al., 2000) suggests that petroleum generation and migration occurred during and soon after the Antler orogeny. However, at the Alligator Ridge Carlin-type deposit, which occurs east of the Roberts Mountain thrust, Eocene hydrothermal fluids appear to have thermally matured a preexisting hydrocarbon reservoir based on Rock-Eval analyses that showed a bull’s-eye pattern of decreasing hydrogen indices centered on the Vantage orebody (Ilchik et al., 1986). Vitrinite reflectance or bitumen reflectance, as summarized by Kelley et al. (2006), increase in value with increasing temperature. Similarly, Raman spectroscopy on carbonaceous material can be used to map gradients in temperature (Beyssac et al., 2002). Conodont alteration indices (CAI) provide another potential tool to identify thermal anomalies. Conodonts are an index microfossil that are typically used to date carbonates of Late Cambrian to Late Triassic age. Conodonts undergo sequential color changes with increasing temperature (Epstein et al., 1977). Long periods at a given temperature may result in the same CAI that is caused by higher temperatures for a shorter period of time. Harris and Crafford (2007) published a database of conodont ages and CAI values for the entire state of Nevada.

The only age constraint on thermal anomalies mapped from temperature indicators in organic carbonaceous material or CAI values is that they are younger than the youngest rocks in which they occur. Apatite fission track (AFT) dating presents an opportunity to both detect and date a thermal anomaly. Fission tracks formed by spontaneous fission decay of 238U. The particles emitted by this fission process leave trails of damage, or tracks, in the apatite crystal. The fission tracks are preserved when the rock cools below an annealing temperature, which is typically around 90° to 120°C for apatite (Ketcham et al., 1999). Similar tracks are formed in zircon, which has an annealing temperature of 230° to 250°C (Brandon et al., 1998). Cline et al. (2005) and Arehart and Donelick (2006) used AFT dating of predominantly Paleozoic rocks to map Eocene thermal anomalies in the northern Carlin trend and at the Pipeline deposit in the Cortez cluster of Carlin-type gold deposits, respectively. AFT data from the northern Carlin trend showed two populations. The data in one set fell mainly between 110 and 70 Ma. These dates were from samples that were mostly more than 5 km from the Carlin-type gold deposits. These data represent cooling related to regional uplift in the Late Cretaceous. Data from the other set, from samples along the Carlin trend within 5 km of deposits, fell mainly between 80 and 20 Ma. Spatially within that set, there was a NW-trending zone 20 km long and up to 10 km wide that extended from the Gold Quarry deposit on the south to the Jurassic Goldstrike stock (Fig. 21A). Within that zone, all the AFT dates were <57 Ma, with most between 40 and 30 Ma. AFT dates between this zone and the Late Cretaceous populations are variable, suggesting temperatures were not hot enough for sufficient amounts of time in the Eocene to completely anneal the fission tracks and reset the AFT dates. The anomaly at Pipeline of AFT dates <50 Ma is 5 km wide and at least 7 km long (Fig. 21B).

Another targeting element at the district scale is documentation of hydrothermal alteration and geochemistry consistent with formation by Carlin-type deposits. At the district scale, targeting criteria for alteration include jasperoid outcrops and discordant zones of limonite that appear to be related to weathering of sulfide. The targeting criteria for geochemistry are documentation of the Au-As-Hg-Tl-Sb-(Te) geochemical signature with low Ag and base metals based on rock chip sampling of altered rocks, soil surveys, or previous drilling. Note the targeting criteria for favorable alteration and geochemistry at the district scale are only permissive for Carlin-type deposits, given jasperoid, limonite, and the Au-As-Hg-Tl-Sb-(Te) geochemical signature are not unique to Carlin-type deposits.

Drill targeting (<~20 km2)

At the scale of <~20 km2, one is typically generating drill targets on an existing district-scale land position. At this scale, it is important not only to intercept gold mineralization but also to document the presence of a Carlin-type gold system, particularly if the target is a large deposit like those that occur in the four main clusters in Nevada. At this scale, the focus shifts more to the critical processes of water-rock interaction and gold deposition rather than pathways of upwelling fluids. Table 4 lists the targeting elements at the deposit scale for fluid pathways and water-rock interaction and gold deposition.

Table 4.

Drill Target-Scale (<~20 km2) Targeting Elements and Criteria

Fluid pathwaysWater-rock interaction and gold deposition
Targeting elementsTargeting criteriaTargeting elementsTargeting criteria
Zones of increased paleopermeabilityDamage zones of high-angle faultsZones of increase low-angle permeability in wall rocks proximal to high-angle faultsLow-angle thrust zones, especially if extensionally reactivated
High densities of minimal displacement faultsHinge zones of folds
Stepover zones between high-angle faults (e.g., faulted relay ramps)Margins of dikes, sills, and volcanic rocks interlayered with favorable carbonate stratigraphy
Intersection zones between high-angle faultsZones of rheology contrast, especially contacts between thin-bedded and massive carbonate units
Dikes, both pre- and synoreSedimentary debris flow breccias
Karst breccias
  Favorable alterationZones of decarbonatization and/or silicification in carbonate strata
Structural jasperoids
Collapse breccias formed by dissolution of carbonate
Zones of low rock quality designation (RQD)
Illite and/or kaolinite/dickite-bearing alteration of igneous rocks, siliciclastic rocks, or silty/argillaceous carbonates
Discordant zones of depleted δ18O in carbonates
Favorable geochemistryStrong Au anomalies with As, Hg, Sb, and Tl but with low Ag (Ag/Au <~5) and low base metals (Cu + Pb + Zn <~500–1,000 ppm)
Iron-rich host rocksZones of ferroan carbonate, especially at boundaries with nonferroan carbonates
Mafic dikes and volcanic rocks
Favorable mineralizationArsenian pyrite, commonly as anhedral, micron-sized grains or micron-sized rims on preore pyrite
As-Sb-Hg-Tl sulfides including realgar, orpiment, and stibnite
Fluid pathwaysWater-rock interaction and gold deposition
Targeting elementsTargeting criteriaTargeting elementsTargeting criteria
Zones of increased paleopermeabilityDamage zones of high-angle faultsZones of increase low-angle permeability in wall rocks proximal to high-angle faultsLow-angle thrust zones, especially if extensionally reactivated
High densities of minimal displacement faultsHinge zones of folds
Stepover zones between high-angle faults (e.g., faulted relay ramps)Margins of dikes, sills, and volcanic rocks interlayered with favorable carbonate stratigraphy
Intersection zones between high-angle faultsZones of rheology contrast, especially contacts between thin-bedded and massive carbonate units
Dikes, both pre- and synoreSedimentary debris flow breccias
Karst breccias
  Favorable alterationZones of decarbonatization and/or silicification in carbonate strata
Structural jasperoids
Collapse breccias formed by dissolution of carbonate
Zones of low rock quality designation (RQD)
Illite and/or kaolinite/dickite-bearing alteration of igneous rocks, siliciclastic rocks, or silty/argillaceous carbonates
Discordant zones of depleted δ18O in carbonates
Favorable geochemistryStrong Au anomalies with As, Hg, Sb, and Tl but with low Ag (Ag/Au <~5) and low base metals (Cu + Pb + Zn <~500–1,000 ppm)
Iron-rich host rocksZones of ferroan carbonate, especially at boundaries with nonferroan carbonates
Mafic dikes and volcanic rocks
Favorable mineralizationArsenian pyrite, commonly as anhedral, micron-sized grains or micron-sized rims on preore pyrite
As-Sb-Hg-Tl sulfides including realgar, orpiment, and stibnite

Note: Sources of ore fluid components and tectonic triggers are not considered at this scale

Fluid pathways: The targeting element at the drill target for upwelling fluids is simply zones of increased fracture paleopermeability. Rhys et al. (2015) summarized the structural feeders to gold mineralization for deposits along the Carlin trend. These include (1) reactivated NW-striking faults (e.g., Castle Reef, Good Hope, Rain), (2) major en echelon extensional fault strands that typically have north-northwest strikes (e.g., Post and Gen faults), (3) faults localized along steeply dipping fold limbs, (4) low-angle reverse faults with large damage zones, linking zones at steps, or deflections along major strands (e.g., Deep Star at step between Gen and Post faults), (5) fault-fracture networks associated with fault deflection around rheological contrast (deposits around Gold-strike stock and its hornfels aureole), (6) intersecting networks of low-displacement, NE- and NW-trending, steeply dipping normal faults, and (7) duplex zones associated with reverse faults. Rhys et al. (2015) demonstrated convincingly that fluid rose along numerous high-angle faults and spread laterally into strata, which commonly coalesced into locally extensive, laterally continuous zones. There are no convincing data of extensive lateral flow along strata on the scale of kilometers.

At Getchell and Turquoise Ridge, the NW-striking Getchell fault is the first-order fault and was likely the main pathway for rising ore fluids (Fig. 16). Muntean et al. (2009) suggested that hydrothermal fluids rose along the Getchell fault and migrated up NNW-striking, steeply W-dipping fault fracture zones in the hanging wall (Fig. 22). These zones appear to have fed the overlying HGB ore zone. On the eastern end of Turquoise Ridge, there appears to be a steeply dipping, NE-striking fault/fracture zone that tapped fluids from the Getchell fault at greater depth (Deep East feeder; Fig. 22). The upwelling fluids either punched through a Cretaceous dacite dike and continued flowing upward along steeply dipping fracture zones (148 zone; Fig. 22), or they travelled westward updip along the margins of the dike and escaped upward along high-angle fracture zones. Fluid flow was passive and opportunistic and took advantage of local fractures and lithologic contacts. In most cases, fluid flow was discordant to stratigraphy.

Fig. 22.

Cross section through the Turquoise Ridge deposit, looking north. The top and bottom of the cross section are ~500 and ~1,000 m, respectively, below the surface. See Figure 16 for the location of the section. Late Cambrian-Early Ordovician stratigraphy going upward are lithologic packages dominated by carbonaceous mudstone and limestone with interlayers of calcarenite turbidites (purple), limestone debris flow breccias (white with black circles), slumped limestone (blue) and mudstone (brown), and pillow basalt (green with black “v”s). Preore Cretaceous dacite dikes (pink with black crosses) cut the deposits. Section shows moderate to strong decalcification/silicification/argillization (yellow overlay), gold grades (red overlay), and inferred hydrothermal fluid flow paths (blue arrows). Also shown are zones of abundant late ore-stage realgar (black stippled overlay), as well as the boundary between nonferroan calcite and overlying ferroan calcite, as determined by carbonate staining. Black thin lines are drill control, both surface and underground diamond drill holes. See discussion in text.

Fig. 22.

Cross section through the Turquoise Ridge deposit, looking north. The top and bottom of the cross section are ~500 and ~1,000 m, respectively, below the surface. See Figure 16 for the location of the section. Late Cambrian-Early Ordovician stratigraphy going upward are lithologic packages dominated by carbonaceous mudstone and limestone with interlayers of calcarenite turbidites (purple), limestone debris flow breccias (white with black circles), slumped limestone (blue) and mudstone (brown), and pillow basalt (green with black “v”s). Preore Cretaceous dacite dikes (pink with black crosses) cut the deposits. Section shows moderate to strong decalcification/silicification/argillization (yellow overlay), gold grades (red overlay), and inferred hydrothermal fluid flow paths (blue arrows). Also shown are zones of abundant late ore-stage realgar (black stippled overlay), as well as the boundary between nonferroan calcite and overlying ferroan calcite, as determined by carbonate staining. Black thin lines are drill control, both surface and underground diamond drill holes. See discussion in text.

These studies on the Carlin trend and Turquoise Ridge indicate Carlin-type orebodies are more closely associated with minimal displacement faults rather than with faults with significant displacement. Ore fluids preferentially traveled along second-order faults, which are common in the damage zones of first-order faults or in accommodation of stepover zones between first-order faults, because they contain much less gouge and are more permeable that first-order faults. Stress transfer modeling of faults on the Carlin trend and other localities (Micklethwaite et al., 2010; Micklethwaite, 2011) demonstrates aftershocks preferentially occur on second-order faults after major slip events on first-order faults. The damage associated with these aftershocks typically creates permeability rather than destroying permeability.

At the district scale, one could target such zones of abundant low-displacement high-angle faults in extensional terrains by looking for geometries consistent with accommodation zones between overlapping sets of high-angle faults. Normal faults commonly horsetail into a series of low-displacement faults at their tips. In the Basin and Range, such zones might occur nears the ends of the north-south ranges. Such accommodation zones have been demonstrated to focus upwelling hydrothermal fluids in a variety of ore deposits, including Carlin-type deposits (Micklethwaite, 2011) and active geothermal systems (Faulds and Hinz, 2015) (Fig. 23).

Fig. 23.

Favorable structural settings for active geothermal systems in the Great Basin, based on nearly 250 categorized geothermal fields (from Faulds and Hinz, 2015). Stepovers or relay ramps (D) in normal fault zones are the most favorable setting, hosting ~32% of the systems. Such areas are characterized by multiple, commonly overlapping fault strands, increased fracture density, and thus enhanced permeability as illustrated in the 3-D diagrams (I) from Faulds and Varga (1996). Normal fault terminations (C) host 25% of the systems, where horsetailing generates closely spaced faults and thus increased permeability. Fault intersections between two normal faults or between normal faults and transverse oblique-slip faults (E) host 22%, where multiple minor faults typically connect major structures, and fluids can flow readily through highly fractured, dilational quadrants. Less common settings include accommodation zones between fault dip domains (F, 9%), displacement transfer zones (G, 5%), transtensional pull-aparts in strike-slip faults (H, 3%), bends in normal faults (B, 2%), and major range-front normal faults (A, 1%).

Fig. 23.

Favorable structural settings for active geothermal systems in the Great Basin, based on nearly 250 categorized geothermal fields (from Faulds and Hinz, 2015). Stepovers or relay ramps (D) in normal fault zones are the most favorable setting, hosting ~32% of the systems. Such areas are characterized by multiple, commonly overlapping fault strands, increased fracture density, and thus enhanced permeability as illustrated in the 3-D diagrams (I) from Faulds and Varga (1996). Normal fault terminations (C) host 25% of the systems, where horsetailing generates closely spaced faults and thus increased permeability. Fault intersections between two normal faults or between normal faults and transverse oblique-slip faults (E) host 22%, where multiple minor faults typically connect major structures, and fluids can flow readily through highly fractured, dilational quadrants. Less common settings include accommodation zones between fault dip domains (F, 9%), displacement transfer zones (G, 5%), transtensional pull-aparts in strike-slip faults (H, 3%), bends in normal faults (B, 2%), and major range-front normal faults (A, 1%).

For example, the Post-Gen fault system in the northern Carlin trend has a pronounced stepover as the two faults approach the Jurassic Goldstrike stock (Fig. 15) (Cline et al., 2005; Micklethwaite, 2011). In the southern part of the Eureka district, Di Fiori et al. (2015) interpreted a kilometerscale, faulted relay ramp of second-order faults that transfer slip between first-order Late Cretaceous-Paleocene normal faults that formed during collapse of the antiformal culmination at Eureka. Within the relay ramp, damage zones of the second-order minimal displacement faults localized mineralization at the Lookout Mountain Carlin-type gold deposit (Fig. 24).

Fig. 24.

A. Geologic map of Lookout Mountain area in the southern portion of the Eureka district, showing distribution of gold resources and jasperoid and zones of carbonate dissolution (modified from Di Fiori et al., 2015). Map shows major firstorder faults (thick blue lines) and second-order faults (thin blue lines). The faults define a breached relay ramp between the Lookout Mountain fault and the Dugout Tunnel fault, which is outlined by the oval. Note how Eocene volcanic rocks at the south end of the map cover the Lookout Mountain fault that places Devonian strata against Cambrian strata, constraining movement to pre-Eocene. B. Cross section across the Lookout Mountain Carlin-type gold deposit. Note the large amount of dissolution breccia controlled by the Lookout Mountain fault and antithetic faults in its footwall, particularly the large amount of Hamburg dolomite (Ch) that was dissolved in the footwall of the antithetic faults.

Fig. 24.

A. Geologic map of Lookout Mountain area in the southern portion of the Eureka district, showing distribution of gold resources and jasperoid and zones of carbonate dissolution (modified from Di Fiori et al., 2015). Map shows major firstorder faults (thick blue lines) and second-order faults (thin blue lines). The faults define a breached relay ramp between the Lookout Mountain fault and the Dugout Tunnel fault, which is outlined by the oval. Note how Eocene volcanic rocks at the south end of the map cover the Lookout Mountain fault that places Devonian strata against Cambrian strata, constraining movement to pre-Eocene. B. Cross section across the Lookout Mountain Carlin-type gold deposit. Note the large amount of dissolution breccia controlled by the Lookout Mountain fault and antithetic faults in its footwall, particularly the large amount of Hamburg dolomite (Ch) that was dissolved in the footwall of the antithetic faults.

The Getchell fault controlled much of the original Getchell deposit. Low-angle mullions along Getchell fault surface exposed in the open pit led many to interpret the fault to be a major strike-slip structure (e.g., Boskie and Schweikert, 2001). However, the Getchell fault appears to decrease in displacement and terminate ~2 km north of the northernmost pit that constitutes the Getchell deposit (Fig. 16). The much larger Turquoise Ridge deposit is in the hanging wall of the Getchell fault in a zone of abundant minimum displacement faults with mainly north-south and northeast strikes. The multiple NE-striking normal faults that are Eocene or possibly older in age, which splay off the Getchell fault, cut across the WNW-trending Cambrian-Ordovician basin margin at Turquoise Ridge described above. This system of northeast faults with typically minor displacements extends to the giant Twin Creeks Carlin-type gold deposit ~7 km to the northeast (Fig. 16). East of the Twin Creeks deposit, the Rabbit Creek fault is another major down-to-the-east normal fault. Between Getchell and Twin Creeks there is a NE-trending mesh of north-south and northeast faults with minor displacements, which is interpreted here to be a faulted relay ramp between the Getchell fault and the normal fault east of Twin Creeks. Giant deposits occur on opposite sides of the relay ramp, and much of the intervening area has not been explored as carefully as around Getchell and Twin Creeks.

Water-rock interaction and gold deposition: At the drill target scale, targeting elements include zones of increased low-angle permeability in carbonate wall rocks that are cut by zones of increased fracture permeability that focused upwelling fluids. Other targeting elements, which relate more directly to gold mineralization, include favorable alteration, mineralization, and geochemistry characteristic of Carlin-type deposits and iron-rich host rocks to drive sulfidation.

There are several examples of stratabound ore zones in Carlin-type deposits, which suggests that the rock types in those zones had inherently high porosity and permeability. The best example is the Wispy Member of the Popovich Formation, a thin-bedded limy to dolomitic mudstone with wispy laminations due to bioturbation. This unit hosts much of the gold mineralization in the northern Carlin trend (Bettles, 2002). However, there have been no systematic studies of porosity of Cambrian to Devonian carbonate rocks in northeastern Nevada. Studies of thin section transects from unmineralized to mineralized rocks, where blue epoxy was utilized to highlight porosity, show nil porosity in unmineralized rocks (e.g., Cassinerio and Muntean, 2011; Maroun et al., 2017). Porosities typically vary from 0 to 10% in ancient carbonates, ~3 to 30% in carbonate oil reservoirs, and ~40 to 80% in recent carbonate sediment (Cook and Corboy, 2004). Shelf carbonates typically have higher porosities due to shallower water and periodic subaerial exposure that lead to dissolution of carbonate, which creates moldic porosity. Higher porosities are in rocks that have been dolomitized. Karsting creates even more porosity and, as stressed above, represent targets in shelf facies carbonates.

Rather than inherent rock porosity and permeability, the main targeting criteria at the deposit scale include low-angle thrust zones, hinge zones of folds, stratigraphic packages with zones of pronounced rheology contrast, especially if they have experienced slip during folding, and faulting associated with contractional deformation (Fig. 25). Features include thrust faults, hinge zones of anticlines, volcanic rocks interlayered within the carbonate-bearing rocks, pre- or synore sills and low-angle dikes, and zones of rheological contrast, especially between thin-bedded and massive carbonates.

Fig. 25.

Examples from the Jerritt Canyon district of bedding plane slip and its control on fluid flow. A. Unaltered member 3 of the Hanson Creek Formation, which hosts most of the ore in the district, shows interlayered micritic limestone (dark-gray beds, ~3–10 cm thick) interbedded with thinly bedded argillaceous, silty limestone (light gray, <~2.5 cm thick). Note the foliation in the silty limestone is oblique to the bedding of the micrite, indicating decoupled deformation and bedding plane slip. The micrite beds dip 12° with a dip direction of 298°, whereas the foliation of the argillaceous silty limestone dips 44° with a dip direction of 280°. Exposure in Mill Creek open pit. B. Member 3 of the Hanson Creek at the edge of an ore zone in the Marlborough Canyon open pit. Note the preferential alteration of the argillaceous silty limestone beds. Both micrite and silty limestone are altered in ore zones. C. Faulted contact between members 3 and 4 of the Hanson Creek Formation in the Stump Creek area. Note member 3 took up preferentially more strain, given it is relatively thin bedded compared to the more massive member 4. D. Strong WNW-directed deformation in the Roberts Mountain Formation, which overlies Hanson Creek Formation in the Stump Creek area. The thin-bedded calcareous siltstone of the Roberts Mountain Formation took up much more strain than the underlying Hanson Creek. There is slip along the contact almost everywhere in the district. The faulted contact is referred to in the district as the Saval discontinuity. E. Geologic map of the Stump Creek area (Muntean and Henry, 2007), which is one of the best exposures of the Roberts Mountains and Hanson Creek Formations at Jerritt Canyon, yet the contacts between the two formations and the members of the Hanson Creek are commonly faulted. Note the stratigraphy is striking east-northeast and dipping north-northwest, yet individual beds are locally striking perpendicular to the overall section, especially in the Roberts Mountains Formation. The coordinates are UTM NAD83 zone 11. Abbreviations: D = down (side that moved down along the fault), DSrm = Devonian-Silurian Roberts Mountain Formation, Qty = Quarternary sediments, SOhc = Silurian-Ordovician Hanson Creek Formation, U = up (side that moved up along the fault).

Fig. 25.

Examples from the Jerritt Canyon district of bedding plane slip and its control on fluid flow. A. Unaltered member 3 of the Hanson Creek Formation, which hosts most of the ore in the district, shows interlayered micritic limestone (dark-gray beds, ~3–10 cm thick) interbedded with thinly bedded argillaceous, silty limestone (light gray, <~2.5 cm thick). Note the foliation in the silty limestone is oblique to the bedding of the micrite, indicating decoupled deformation and bedding plane slip. The micrite beds dip 12° with a dip direction of 298°, whereas the foliation of the argillaceous silty limestone dips 44° with a dip direction of 280°. Exposure in Mill Creek open pit. B. Member 3 of the Hanson Creek at the edge of an ore zone in the Marlborough Canyon open pit. Note the preferential alteration of the argillaceous silty limestone beds. Both micrite and silty limestone are altered in ore zones. C. Faulted contact between members 3 and 4 of the Hanson Creek Formation in the Stump Creek area. Note member 3 took up preferentially more strain, given it is relatively thin bedded compared to the more massive member 4. D. Strong WNW-directed deformation in the Roberts Mountain Formation, which overlies Hanson Creek Formation in the Stump Creek area. The thin-bedded calcareous siltstone of the Roberts Mountain Formation took up much more strain than the underlying Hanson Creek. There is slip along the contact almost everywhere in the district. The faulted contact is referred to in the district as the Saval discontinuity. E. Geologic map of the Stump Creek area (Muntean and Henry, 2007), which is one of the best exposures of the Roberts Mountains and Hanson Creek Formations at Jerritt Canyon, yet the contacts between the two formations and the members of the Hanson Creek are commonly faulted. Note the stratigraphy is striking east-northeast and dipping north-northwest, yet individual beds are locally striking perpendicular to the overall section, especially in the Roberts Mountains Formation. The coordinates are UTM NAD83 zone 11. Abbreviations: D = down (side that moved down along the fault), DSrm = Devonian-Silurian Roberts Mountain Formation, Qty = Quarternary sediments, SOhc = Silurian-Ordovician Hanson Creek Formation, U = up (side that moved up along the fault).

Dikes and especially low angle sills or volcanic flows within the carbonate-bearing section are important in that when they are argillized, either by pre-Eocene hydrothermal fluids or by the Eocene ore fluids, they form aquitards. Examples include Twin Creeks (Stenger et al., 1998) and Turquoise Ridge (Cassinerio and Muntean, 2011) in the Getchell camp and the Meikle deposit on the Carlin trend (Bettles, 2002). Commonly, pre-Eocene hydrothermal fluids sericitized and/or Eocene hydrothermal fluids argillized the margins of flows, sills, and dikes (Hall et al., 2000; Emsbo et al., 2003; Cassinerio and Muntean, 2011). Subsequent fluid flow was then channeled along the margins of the flows and dikes. Such preore sills and dikes are important at several deposits on the Carlin trend (e.g., Emsbo et al., 2003) as well as in the Turquoise Ridge deposit (e.g., Cassinerio and Muntean, 2011).

As stressed in the description of critical processes, dissolution and sulfidation of carbonate is the primary ore depositional process. Secondary porosity and permeability formed during hydrothermal dissolution of carbonate during ore formation allowed greater ingress of ore fluids into the wall rocks. Thus, decarbonatization is a critical targeting element and is usually accompanied by varying amounts of silicification. As pointed out by Bakken (1990), carbonate dissolution and quartz precipitation are competing reactions. If carbonate is replaced directly by quartz, rock volume is conserved, and original rock textures are preserved. Once quartz precipitates, porosity and permeability typically decrease. If carbonate dissolves and quartz does not simultaneously precipitate, the rock volume is lost, porosity and permeability increase, rock can collapse due to the overlying load, and rock textures are typically destroyed. There are gradations between these two end-member scenarios. Figure 26 shows a comparison between unaltered, unmineralized finely laminated micritic limestone and mudstone and its highly altered, mineralized equivalent from the Turquoise Ridge deposit. Note the lack of blue epoxy marking porosity in the thin section of the unaltered sample (Fig. 26B) compared to the altered sample (Fig. 26D) formed by dissolution of carbonate. Note the completely decalcified limestone retained much its original rock fabric, despite significant creation of porosity. In strongly decalcified/silicified samples of similar interlayered limestone and mudstone, euhedral hydrothermal quartz grains (<0.01 mm) have completely replaced calcite grains, leaving a delicate spongelike texture of predominantly quartz with about 20 to 40% pore space (Fig. 26E). The surface of this type of rock instantaneously dries upon wetting and scratches easily, despite the abundance of quartz. Such alteration rarely crops out. Nevertheless, it is technically a jasperoid.

Fig. 26.

Examples of decalcification/silicification/argillization from the Turquoise Ridge deposit. A. Unaltered interbedded limestone and mudstone (blue and brown unit in Fig. 25). B. Thin section of sample in A. Dark layers are predominantly biotite formed during Cretaceous intrusive activity. Note lack of blue epoxy indicating nil porosity. C. Same lithology but strongly decalcified/silicified/argillized sample from ore zone. D. Thin section of the ore sample. Note the abundant blue epoxy reflecting the porosity creating during the alteration process. E. Scanning electron microscopy image of a chip of the sample shown in C and D. Note the abundant doubly terminated hydrothermal quartz formed during carbonate dissolution at the resulting high porosity. The platelets are kaolinite, formed by the replacement of biotite. The bright grain is ore-stage arsenian pyrite. See discussion in text. From Cassinerio and Muntean (2011) and Muntean et al. (2011).

Fig. 26.

Examples of decalcification/silicification/argillization from the Turquoise Ridge deposit. A. Unaltered interbedded limestone and mudstone (blue and brown unit in Fig. 25). B. Thin section of sample in A. Dark layers are predominantly biotite formed during Cretaceous intrusive activity. Note lack of blue epoxy indicating nil porosity. C. Same lithology but strongly decalcified/silicified/argillized sample from ore zone. D. Thin section of the ore sample. Note the abundant blue epoxy reflecting the porosity creating during the alteration process. E. Scanning electron microscopy image of a chip of the sample shown in C and D. Note the abundant doubly terminated hydrothermal quartz formed during carbonate dissolution at the resulting high porosity. The platelets are kaolinite, formed by the replacement of biotite. The bright grain is ore-stage arsenian pyrite. See discussion in text. From Cassinerio and Muntean (2011) and Muntean et al. (2011).

Most field geologists, on the other hand, would not describe the rock as a jasperoid. The term jasperoid is typically used by field geologists for dense rocks that leave steel upon scratching. If quartz directly replaced carbonate, then a dense jasperoid can form, and such rocks typically crop out. However, acidic ore fluids are not necessary for formation of jasperoid. Jasperoid can form simply by cooling of quartz-saturated fluids interacting with calcite, due to the retrograde nature of calcite solubility (Fig. 27). Though such jasperoids can host significant ore, they typically host much less ore than the decarbonatized rock (Bakken, 1990; Hofstra et al., 1991; Kuehn and Rose, 1992), as exemplified at the original Carlin deposit (Fig. 7).

Fig. 27.

Solubilities of quartz and calcite as a function of pressure and temperature, showing multiple paths for the generation of jasperoid. Note the retrograde solubility of calcite in contrast to the typical prograde solubility of quartz. Modified from Barton et al. (1997). CP = critical point of water.

Fig. 27.

Solubilities of quartz and calcite as a function of pressure and temperature, showing multiple paths for the generation of jasperoid. Note the retrograde solubility of calcite in contrast to the typical prograde solubility of quartz. Modified from Barton et al. (1997). CP = critical point of water.

Hydrothermal collapse breccias, where silicification did not keep up with carbonate dissolution, commonly host ore. Examples of such collapse breccias include the underground high-grade Meikle deposit at the north end of the Carlin trend (Evans, 2000; Bettles, 2002; Emsbo et al., 2003), the underground high-grade 194 orebody in the footwall of the Getchell fault (Tretbar, 2004), the large Cortez Hills open-pit deposit (Maroun et al., 2017), and the Lookout Mountain deposit in the Eureka district (Di Fiori et al., 2015). Rock quality designation (RQD) data from core holes can be used to map the footprint of such volume loss and collapse of carbonate dissolution. Cassinerio and Muntean (2011) showed that RQD values of <25% extended up to 30 m beyond the zones of >0.34 ppm Au and visible decarbonatization along a cross section through the Turquoise Ridge deposit.

The same ore fluids that dissolve carbonates argillize silicates. The common clays associated with ore are illite (1M or 2M1), kaolinite, and dickite (Hofstra and Cline, 2000; Cline et al., 2005). Argillization commonly occurs and focuses subsequent fluid along the margins of dikes, sills, and interlayered volcanic rocks. In Nevada, kaolinite and dickite are more diagnostic of Carlin-type ores, given the possibility that illite can be sedimentary (Hofstra et al., 1999) or related to pre-Eocene hydrothermal activity, especially for deposits proximal to Mesozoic intrusions. In the interpretive stage, argillization and decarbonatization should be combined to map out the pathways and water-rock interaction by acidic ore fluids.

Another way to map and potentially quantitatively map the intensity of alteration is to analyze both visually altered and unaltered carbonates for their oxygen isotope ratios. Numerous studies have demonstrated that halos of depleted δ18O in carbonate rocks surround ore zones in Carlin-type gold deposits (Cline et al., 2005; Arehart and Donelick, 2006; Hickey et al., 2014). Unaltered marine Paleozoic carbonates typically have δ18O values ≥22‰, whereas values of altered rocks can have negative values in the depleted halos surrounding ore. In a comprehensive, detailed study on the northern Carlin trend, Vaughan et al. (2016) documented marked depletion in visually unaltered limestones proximal to Au mineralization, indicating isotopic exchange between calcite in wall-rock limestone and hydrothermal fluids. The mechanism for the isotopic alteration is coupled dissolution-precipitation leading to pseudomorphous replacement of calcite during hydrothermal fluid-rock interaction. However, one needs to consider the possibility of preore hydrothermal circulation or metamorphic recrystallization forming δ18O depletion zones in carbonates prior to Carlin-type mineralization (Muntean et al., 2009), especially when one considers the common proximity of Carlin-type deposits to Mesozoic stocks in Nevada. Analyses of δ18O in carbonate can now be done relatively quickly and inexpensively using laser spectroscopy (Barker et al., 2013).

The characteristic Carlin geochemical signature, Au-As-Hg-Tl-Sb-(Te), needs to be recognized at the drill target scale from rock-chip sampling and drilling. An approach is to identify strong Au anomalies with anomalous As, Hg, Sb, and Tl with low Ag (Ag/Au <1–~5) and <~500 ppm combined Cu + Pb + Zn. An excellent example of this simple approach was the discovery of Carlin-type gold deposits in the Eureka district. Carbonate replacement deposits of Late Cretaceous age were originally mined in the Eureka district for their Ag, Au, and Pb, along with minor Zn and Cu (Nolan, 1962; Nolan and Hunt, 1968). Nolan (1962) noted one historic mine, Windfall, which produced Au with very little Ag and base metals. The Windfall mine was rediscovered and mined in the 1970s by Idaho Mining, which recognized it as a Carlin-type gold deposit (Wilson and Wilson, 1986). In the early 1990s, Home-stake Mining Company started an exploration program in the main part of the Eureka district, where most of the past Ag-Au-Pb production had taken place. The initial drill program was largely negative except for an intercept of 9.1 m grading 1.58 g/t that was underneath a prospect pit with anomalous Au-As-Hg and low base metals and Ag. Follow-up drilling led to the discovery of the Archimedes Carlin-type deposit underneath pediment gravels to the east of the prospect pit (Dilles et al., 1996). Though the prospect pit did not have the highest gold assays in the surface geochemical program, the focus on the Carlin signature was critical to the discovery of Archimedes.

Another approach would be to carry out factor analysis on geochemical data, identify a gold factor, and map gold factor scores. Patterson and Muntean (2011) demonstrated this for a large data set in the Jerritt Canyon district, which had a Hg-Tl-Au-As-Te-Sb factor, in order of decreasing loadings (Fig. 28A). The factor also had negative Ca, Mg, and Sr loadings, reflecting carbonate dissolution associated with gold mineralization. Patterson and Muntean (2011) plotted Ca/Au, which showed nice donut-shaped patterns surrounding the ore deposits (Fig. 28B), but one needs to be careful about data sets that sampled numerous rock types with variable original Ca. No studies have demonstrated zoning of the Au-As-Hg-Tl-Sb-(Te) signature around Carlin-type deposits. The concentrations appear to simply attenuate gradually from ore zones at about the same rate, in that ratios between various combinations of these elements do not show patterns.

Fig. 28.

District-scale multielement geochemistry of the base of the Roberts Mountain Formation in Jerritt Canyon based on intercepts from 6,416 drill holes, shown as the black dots. Red lines in each map outline orebodies—either open pit deposits or surface projections of underground deposits. A. Gridded image of the “gold factor” based on Hg-Tl-Au-As-Te-Sb factor (elements listed in decreasing factor loading), which accounted for nearly 11% of the variance of the data sets. The black thick lines are the 300-ppb contours and the black thin lines are the 50-ppb contours from the data set. B. Gridded image of Ca/Au ratios (using ppm), low values of which outline decalcification. C. Geologic map of the area from Muntean and Henry (2007). Figures A and B are from Patterson and Muntean (2011). Abbreviations: CTGD = Carlin-type gold deposit, Std Dev = standard deviation.

Fig. 28.

District-scale multielement geochemistry of the base of the Roberts Mountain Formation in Jerritt Canyon based on intercepts from 6,416 drill holes, shown as the black dots. Red lines in each map outline orebodies—either open pit deposits or surface projections of underground deposits. A. Gridded image of the “gold factor” based on Hg-Tl-Au-As-Te-Sb factor (elements listed in decreasing factor loading), which accounted for nearly 11% of the variance of the data sets. The black thick lines are the 300-ppb contours and the black thin lines are the 50-ppb contours from the data set. B. Gridded image of Ca/Au ratios (using ppm), low values of which outline decalcification. C. Geologic map of the area from Muntean and Henry (2007). Figures A and B are from Patterson and Muntean (2011). Abbreviations: CTGD = Carlin-type gold deposit, Std Dev = standard deviation.

Another important targeting element at the drill target scale is the identification of iron-rich rocks that can drive sulfidation and deposition of gold-bearing pyrite. Geochemical modeling by Hofstra et al. (1991) indicated that high amounts of reactive Fe are not necessary to form mineralization. High amounts (≥2 wt % Fe) produce small high-grade zones, whereas lower amounts (0.25 wt % Fe) can produce larger but lower-grade deposits. The targeted iron-rich rocks are zones of ferroan carbonate within the local carbonate-bearing sedimentary section and intermediate to mafic interlayered volcanic rocks, sills, and dikes. Most available evidence indicates ferroan carbonates associated with Carlin-type deposits in Nevada are epigenetic and formed prior to Eocene ore formation.

At the Meikle deposit, high-grade ore is commonly associated with epigenetic zones of hydrothermal ferroan dolomite in the Bootstrap limestone member of the Roberts Mountain Formation. Emsbo et al. (1998, 2003) interpreted ferroan dolomite to be Devonian in age and related to synsedimentary exhalative Zn-Au mineralization. Evans (2000) interpreted the ferroan dolomite to be related to postdiagenetic, weak Mississippi Valley-type Zn mineralization in the late Paleozoic.

At the Twin Creeks deposit in the Getchell area, Stenger et al. (1998) and Fortuna et al. (2003) documented a spatial relationship between ferroan dolomite and gold mineralization. Fortuna et al. (2003) interpreted the ferroan dolomite to have formed from sericitization of margins of basalt flows interbedded with carbonate-bearing sedimentary rocks, which mobilized iron, resulting in formation of ferroan dolomites, which later served as a source of iron for sulfidation to take place during gold mineralization in the Eocene. As previously pointed out, much of the ore at Twin Creeks occurs in the carbonatebearing rocks that are interlayered with the mafic volcanic rocks in the hinge of an anticline. The sericitization of the margins of the basalt flows took place in the Cretaceous, mainly between 109 and 103 Ma, based on 40Ar/39Ar dating on illite (Hall et al., 2000). Muntean et al. (2009) showed high-grade ore at nearby Turquoise Ridge occurred at a boundary between nonferroan calcite and overlying ferroan calcite (Fig. 22). The boundary is discordant to stratigraphy. The ferroan calcite is interpreted to be pre-Eocene. The zone of ferroan calcite underlies and appears to be spatially associated with the pillow basalt that is within the lower Paleozoic section at Turquoise Ridge. Ferroan carbonate can be easily detected by staining with potassium ferricyanide, which stains blue. Staining is inexpensive and provides real-time data if done effectively, as outlined by Hitzman (1999). Stained samples need to be inspected carefully to determine what carbonate phases are activating the stain and to ensure Fe-bearing sulfides and Fe-bearing silicates, including illite, are not causing the stain to activate.

Argillization and sulfidation of mafic dikes and sills can form high-grade ore zones, albeit much smaller in size than zones associated with sulfidation of more reactive ferroan carbonate. The Pennsylvanian dikes at Jerritt Canyon, described above, commonly host high-grade ore zones. Many have highlighted the importance of Jurassic lamprophyre dikes along the Carlin trend in localizing high-grade ore (Bettles, 2002; Emsbo et al., 2003).

The presence of arsenian pyrite should be documented as early as possible in the exploration program. This requires petrography on polished thin sections of suspected mineralization. Samples of unoxidized mineralization are preferable, though oxidized samples can yield worthwhile information. Textures of ore-stage arsenian pyrite in Carlin-type deposits typically include (1) spheroidal grains (≤~10 μm) of arsenian pyrite with fuzzy, ragged grain boundaries, (2) irregular masses of arsenian pyrite, and (3) rims of arsenian pyrite on preore pyrite cores (Fig. 29A-C) (Wells and Mullens, 1973; Cline and Hofstra, 2000; Cline, 2001; Longo et al., 2009; Maroun et al., 2017). The core-rim pyrites vary widely, from multistage rims from 1 to 30 μm wide to single-stage rims that are typically ≤5 μm wide. In reflected light, properties such as hardness, reflectance, and color of rims and small grains of arsenian pyrite are typically distinct from preore pyrite. Arsenian pyrite is normally softer than preore pyrite, producing differences in polished surfaces. In oxidized samples core-rim textures can still be recognizable in goethite or hematite pseudomorphs (Fig. 29D, E). Preferably, optical microscopy should be supplemented by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses to confirm arsenian pyrite. Confirming whether the pyrite contains gold requires analyses by electron microprobe (~100 ppm Au detection limit, beam size ~2 μm) or by LA-ICP-MS (~2 ppm beam, ~5–10 μm beam size). Arsenian pyrite, however, is not diagnostic of Carlin-type deposits. It occurs in some low-sulfidation epithermal deposits (John et al., 2003) and high-sulfidation epithermal deposits (Deditus et al., 2009).

Fig. 29.

Examples of ore-stage pyrite from Carlin-type deposits. See text for discussion. A. Reflected-light photograph of ore from the Getchell deposit, showing preore pyrite cores and ore-stage arsenian pyrite rims. Note the much better polish taken by preore pyrite relative to the trace element-rich arsenian pyrite. Also take note the ragged nature of the outer boundaries of the rims. Photo courtesy of Jean Cline. B. Backscattered scanning electron microscopy (SEM) image of preore pyrite cores (relatively dark) and ore-stage arsenian pyrite rims (relatively bright). The very bright material is late ore-stage realgar. The darkest material is quartz. Shown to the right are electron microprobe analyses (EMPA), highlighting the differences between the preore cores and the ore-stage rims. Image and data courtesy of Jean Cline. C. Backscattered SEM image showing various types of ore-stage pyrite from the Turquoise Ridge deposit, including (1) spheroidal fuzzy pyrites that have trace element concentrations ranging from 2,000 to 3,000 ppm Au, 2,500 to 3,500 ppm Cu, 1,000 to 1,600 ppm Te, 500 to 1,600 ppm Sb, 3,000 to 7,000 ppm Hg, 5,000 to 10,000 ppm Tl, and >10 wt % As, as determined by EMPA; (2) resorbed core-rim pyrites with multiple ore-stage rims. Trace element concentrations range from 10 to 2,400 ppm Au, 50 to 3,300 ppm Cu, 230 to 1,800 ppm Te, 90 to 750 ppm Sb, 45 to 7,500 ppm Hg, 18 to 11,000 ppm Tl, and 0.3 to 12.0 wt % As, (3) corroded and resorbed preore pyrite core with later multiple stage rims, and (4) spheroidal ore-stage pyrite encased by later realgar. From Muntean et al. (2011). D. Reflected-light photograph of preore pyrite core and ore-stage pyrite rims oxidized to limonite from Long Canyon, an oxidized Carlin-type deposit in eastern Nevada. Note one can still make out the poorly polished ore-stage limonite rims that locally contain native gold that likely formed during supergene oxidation. From Jarvie (2009). E. Backscattered electron image of the same field of view in D. From Jarvie (2009). Abbreviations: bdl = below detection limit.

Fig. 29.

Examples of ore-stage pyrite from Carlin-type deposits. See text for discussion. A. Reflected-light photograph of ore from the Getchell deposit, showing preore pyrite cores and ore-stage arsenian pyrite rims. Note the much better polish taken by preore pyrite relative to the trace element-rich arsenian pyrite. Also take note the ragged nature of the outer boundaries of the rims. Photo courtesy of Jean Cline. B. Backscattered scanning electron microscopy (SEM) image of preore pyrite cores (relatively dark) and ore-stage arsenian pyrite rims (relatively bright). The very bright material is late ore-stage realgar. The darkest material is quartz. Shown to the right are electron microprobe analyses (EMPA), highlighting the differences between the preore cores and the ore-stage rims. Image and data courtesy of Jean Cline. C. Backscattered SEM image showing various types of ore-stage pyrite from the Turquoise Ridge deposit, including (1) spheroidal fuzzy pyrites that have trace element concentrations ranging from 2,000 to 3,000 ppm Au, 2,500 to 3,500 ppm Cu, 1,000 to 1,600 ppm Te, 500 to 1,600 ppm Sb, 3,000 to 7,000 ppm Hg, 5,000 to 10,000 ppm Tl, and >10 wt % As, as determined by EMPA; (2) resorbed core-rim pyrites with multiple ore-stage rims. Trace element concentrations range from 10 to 2,400 ppm Au, 50 to 3,300 ppm Cu, 230 to 1,800 ppm Te, 90 to 750 ppm Sb, 45 to 7,500 ppm Hg, 18 to 11,000 ppm Tl, and 0.3 to 12.0 wt % As, (3) corroded and resorbed preore pyrite core with later multiple stage rims, and (4) spheroidal ore-stage pyrite encased by later realgar. From Muntean et al. (2011). D. Reflected-light photograph of preore pyrite core and ore-stage pyrite rims oxidized to limonite from Long Canyon, an oxidized Carlin-type deposit in eastern Nevada. Note one can still make out the poorly polished ore-stage limonite rims that locally contain native gold that likely formed during supergene oxidation. From Jarvie (2009). E. Backscattered electron image of the same field of view in D. From Jarvie (2009). Abbreviations: bdl = below detection limit.

Given the importance of ore-stage arsenian pyrite, the difficulty in systematically mapping its distribution, and the likelihood that it is the result of sulfur addition to the host rocks, multielement data can be used on unoxidized, unweathered drill samples to map the degree of sulfidation (DOS) to see whether it forms systematic patterns that may vector to ore:

 

DOS=wt % S / ([1 .15] [wt % Fe]).
(1)

The coefficient 1.15 is the Fe/S mass ratio in pyrite; thus, in the DOS notations, S contents are normalized to the amount of S necessary to convert all Fe in the rock to pyrite. Cassinerio and Muntean (2011) calculated and mapped DOS values for drill holes across an ore zone at Turquoise Ridge. DOS values of ≥1.2 were almost entirely restricted to zones of ≥3.4 ppm Au, whereas values of ≥0.8 showed little to no halo beyond the 0.34-ppm Au contour and visibly altered wall rock. They demonstrated excellent correlation between Leco total S analyses and S analyses by ICP-MS-atomic emission spectrometry of the same drill sample intervals, lending confidence to using S data from standard ICP analytical packages.

Typically the zone of decalcification and argillization extends outward from ore grades of gold, but not necessarily. In some deposits high gold grades locally occur in zones with very little decalcification (cf. Peters, 1996). At Turquoise Ridge, moderate to strong decalcification and argillization correlate closely with gold grades of >0.34 ppm (Fig. 22). The zoning patterns are a function of the amount of acid in the fluid, the amount of reactive iron in the host rock, the amount of reduced sulfur in the ore fluid, and the amount of gold in the ore fluid.

Realgar, orpiment, and stibnite are the most common ore-related sulfides besides arsenian pyrite. However, these conspicuous sulfides form late in the Carlin-type hydrothermal system, forming after most of the gold-bearing arsenian pyrite is deposited. Thus, these minerals show no systematic spatial zonation to ore. Nevertheless, the presence of realgar, orpiment, and stibnite can indicate proximity to Carlin-type mineralization. Like arsenian pyrite, these minerals are not diagnostic of Carlin-type deposits and can occur in other deposit types.

Exploration under cover

There are other exploration considerations to take into account in exploring for Carlin-type deposits, specifically in Nevada. As deposits that crop out become increasingly rare, discovery of covered deposits entails exploration under preore and/or postore cover. Typically, companies have generated targets under cover by projecting features exposed in bedrock underneath cover, such as geochemical anomalies in rock chips or residual soils, alteration zones, structures (mainly high-angle faults), and favorable host rocks.

The covered targets are commonly further refined with geophysics, which help identify high-angle faults and zones of shallow carbonate bedrock, and then they are drilled. Carbonate rocks are normally more dense and resistive than the cover rocks; thus, gravity and various electrical and electromagnetic methods are employed. Unfortunately, the physical rock properties of Carlin-type ore do not differ greatly from the surrounding rocks. For example, the amount of pyrite added to the rock during Carlin ore formation is insufficient to produce a significant induced polarization anomaly that differs much from the response produced from diagenetic pyrite in the host rocks (Wright and Lide, 1998). Likewise, the locally elevated content of carbonaceous matter in ore is insufficient to produce a reliable conductive response in a magnetotelluric or controlled source audio magnetotelluric survey, because the surrounding host rocks are commonly carbonaceous. Decarbonatization significantly decreases the density of carbonate, thus ore zones should be gravity lows. However, the decrease can result in values similar to siliciclastic rocks or postore volcanic rocks and alluvium. Thus, geophysics is mainly used to help map subsurface geology, rather than to directly detect ore or hydrothermal alteration.

Most potential under preore cover lies underneath the silici-clastic and volcanic rocks of the Roberts Mountain allochthon in the upper plate of the Roberts Mountain thrust. In addition, potential lies underneath carbonate-poor rocks in the lower plate of the thrust. There are few published studies on the hydrothermal expression in the carbonate-poor rocks overlying carbonate-hosted ores. The giant Betze-Post deposit in the northern Carlin trend was covered by >200 m of cover (Bettles, 2002). Prior to its discovery, small, low-grade oxide open-pit deposits were mined from carbonate-poor siliciclastic rocks of the lower plate Rodeo Creek unit as well as in the Jurassic Goldstrike stock. The original surface expression of these shallow deposits was marked by outcrops of jasperoid, which were typically anomalous in gold, arsenic, antimony, and mercury (Bettles, 2002). Surface soil anomalies of >20 ppb Au and >10 ppm As covered much of the Betze-Post deposit.

Heitt et al. (2003) demonstrated a plume of anomalous Au + As + Hg + Sb + Tl + W extending ~375 m upward into siliciclastic rocks of the Roberts Mountains allochthon and to the surface above the high-grade lower plate carbonate-hosted high-grade underground Deep Star deposit in the northern Carlin trend. Similarly, small low-grade open-pit gold deposits were mined above the high-grade underground Turquoise Ridge deposit, which mainly occurs at depths of >500 m (Cassinerio and Muntean, 2011). The deposits occur along faults and are associated with zones of silicification and/or argillization in noncalcareous greenstones and siliciclastic rocks. At Jerritt Canyon, a hole drilled below a 15-ppb Au surface sample of a Pennsylvanian dike encountered gold mineralization grading >3 ppm at a depth of ~170 m, which eventually led to the discovery of high-grade, underground SSX deposits (1.4 Moz [43.5 t] 9.12 ppm Au) (Eliason and Kantor, 1998).

Postore cover in Nevada can be Oligocene and younger volcanic rocks, but it is typically transported Neogene and Quaternary alluvial gravels. Many of the large deposits discovered in the last 30 years have been found under transported alluvial cover, including Twin Creeks, Pipeline, Cortez Hills, and Goldrush. Half of Nevada is covered by alluvial sediments that fill basins between north-south mountain ranges. Muntean and Taufen (2011) presented results of geochemical surveys around the alluvium-covered Gap-Pipeline deposit in the Cortez cluster of Carlin-type deposits and summarized the results of other published surveys over Carlin-type deposits covered by alluvium in Nevada. They recommended the following at increasingly smaller areas: hydrogeochemistry, stream sediment sampling, geochemistry of the base of gravels, and careful sampling of soil and or vegetation, guided by soil gas surveys.

Postore volcanic cover presents its own challenges in that there are many Oligocene and younger epithermal deposits that are very close in age to their host volcanic rocks. An example in Nevada is the low-sulfidation epithermal deposits of middle Miocene age in the northern Nevada rift. The rift and associated deposits are in close proximity to the northern Carlin trend and the Cortez and Getchell clusters of Carlin-type deposits. The gold in some of these epithermal deposits, such as at Mule Canyon (John et al., 2003), can predominantly occur in arsenian pyrite, and their ore can be characterized by an Au-As-Hg-Tl-Sb geochemical signature, though concentrations of Ag, Se, Cu, Pb, and Zn are typically higher than in Carlin-type gold deposits. If drilling intercepted the roots of these epithermal systems in Paleozoic carbonate rocks, distinguishing it from a potential Eocene Carlin-type system would be challenging.

The challenge is not necessarily finding a hydrothermal system under cover but rather determining whether the intercepted hydrothermal system represents a Carlin-type system and how to vector into ore within a Carlin-type system. As pointed out above, many targeting elements and criteria of Eocene Carlin-type deposits are not truly diagnostic, and they can occur in other types of auriferous mineral systems. For example, jasperoid, decarbonatization, arsenian pyrite, and Au-As-Hg-Tl-Sb geochemical signatures can occur in carbonate-hosted epithermal and intrusion-related systems. Epithermal systems are mostly Neogene in age in Nevada, while systems associated with upper crustal to hypabyssal intrusions in Nevada can be older (Jurassic-Cretaceous) and or the same age (Eocene) as the Carlin-type gold deposits. Even if one can discriminate between hydrothermal and geochemical features of a Carlin system and features of older or younger hydrothermal systems, vectoring to locate successive drill holes is exceedingly challenging because of the lack of zonation in geochemistry and hydrothermal mineralogy. More studies of the halos around Carlin-type gold deposits are needed.

Postore exploration considerations in Nevada

Significant postore extensional faulting and dismemberment of Carlin-type gold deposits is a possibility, but it has yet to be conclusively demonstrated. A possible candidate for dismemberment are deposits in the Cortez area. Colgan et al. (2008) documented the middle Miocene dismemberment of the Caetano caldera, which occurs adjacent to the south of the Cortez cluster of Carlin-type gold deposits. The caldera is 33.8 Ma and postdates the Carlin-type gold deposits at Cortez (John et al., 2008). Colgan et al. (2008) argue that the middle Miocene faults that extended the caldera 110% project northward into the area of the Gold Acres, Gap, and Pipeline deposits at Cortez. Subsequently, Colgan et al. (2014) demonstrated similar magnitudes of post-Eocene extension in the northern Shoshone Range north of the Cortez area.

Another important postore consideration is supergene oxidation, which greatly affects gold recovery, cut-off grade, and initial capital investment (e.g., heap leach vs. autoclave). Depth of oxidation can vary widely among deposits, including among deposits in the ranges and among deposits on the pediments at the margins of the basins. The few dates on supergene alunite on the Carlin trend indicate ages of ~10 to 8 Ma at Betze Post, ~26 Ma at Gold Quarry, and ~20 to 19 Ma at Rain as the south end of the trend. More dating and work on the timing of exhumation, oxidation, and preservation is necessary to work out the supergene history.

Carlin-Type vs. Carlin-Style Deposits

As previously discussed, Hofstra and Cline (2000) were the first to formally break out Carlin-type gold deposits as a distinct deposit type. They argued they should be distinguished from other sedimentary rock-hosted gold deposits, such as sedex, distal disseminated, and epithermal deposits, for which they pointed out key similarities and differences. In the literature, these other deposits have traditionally been called Carlin-like deposits, whereas Carlin-style deposits as used in this volume is meant to encompass both Carlin-type and Carlin-like deposits (Muntean and Cline, 2018). Here, the distinction and relationship between Carlin-type deposits and distal disseminated deposits and epithermal deposits are briefly examined.

Distal disseminated deposits

The term “distal disseminated” was first coined by the U.S. Geological Survey (Cox, 1992; Cox and Singer, 1992). Distal disseminated gold ± silver deposits in Nevada are of many ages and include the carbonate-hosted gold deposits at Bald Mountain (Jurassic; Nutt and Hofstra, 2007), the Robinson porphyry copper deposit (Cretaceous; James, 1976; Smith et al., 1988), Taylor silver deposit (Eocene; Graybeal, 1981), and several Eocene gold ± silver deposits near the town of Battle Mountain, including Lone Tree (Bloomstein et al., 2000; Theodore, 2000), Cove (Johnston et al., 2008), and Hilltop (Lisle and Derochers, 1988; Kelson et al., 2008). The deposits are similar to Carlin-type gold deposits in that they are disseminated replacement bodies in typically carbonates. The gold occurs both as free gold or in solid solution in pyrite, arsenopyrite, and other sulfides and sulfosalts. In contrast, acanthite is the main ore mineral in the Taylor distal disseminated silver deposit, which has very little gold (Graybeal, 1981). Distal disseminated deposits have a clear spatial and temporal relationship with epizonal granitic intrusive complexes, are commonly spatially and temporally associated with different types of ore deposits, including intrusion-hosted gold deposits and porphyry copper ± gold ± molybdenum deposits, and, zoning outward from the intrusions, are polymetallic skarns, veins, and carbonate replacement massive sulfide bodies. The distal disseminated deposits are typically the farthest from the intrusion (~2–10 km). Thus, alteration, ore mineralogy, and metals are strongly zoned, vectoring outward toward distal disseminated deposits. Most distal disseminated deposits differ significantly from Carlin-type gold deposits in many ways. Notably, a significant amount of ore can occur in noncarbonate rocks and can be associated with quartz-sulfide veinlets, which are essentially absent in Carlin-type gold deposits. Ore-stage sulfides are typically coarser grained than the micronsize grains and rims in Carlin-type gold deposits.

The distal disseminated deposit in Nevada with ore that looks most like Carlin-type gold deposits is the Cove deposit. Cove is one of the few Eocene distal disseminated deposits that has been studied in detail (Johnston et al., 2008). Past production at Cove amounted to 3.3 Moz (103 t) of gold and 108 Moz (3,359 t) of silver. As summarized from Johnston et al. (2008), the Cove deposit comprises two distinct ore types: a central core of polymetallic vein-type ore and an outer aureole of Ag-bearing Carlin-style ore. Both types of ore are associated with decarbonatized, silicified, and illitized rocks. Polymetallic veins consist of gold- and silver-bearing pyritesphalerite-galena veins, stockworks, and disseminations in mainly clastic and carbonate rocks of Triassic age. Carlin-style ore is characterized mainly by gold that occurs in solid solution in arsenian pyrite, just like Carlin-type deposits. However, silver also occurs in solid solution in pyrite (Johnston et al., 2008; Muntean et al., 2017a). Silver is commonly very low or undetectable in microanalyses of ore-stage pyrite in Carlin-type deposits (Cline et al., 2005). Polymetallic vein-type ore has Ag/Au ratios of typically >50:1, whereas Carlin-style ore has Ag/Au ratios that vary widely from ~1,000:1 to ~1:1. The overall production Ag/Au ratio of ~33:1 reflects the mining of the two ore types, which are locally juxtaposed. Where crosscutting relationships occur, the Carlin-style ore overprints the polymetallic mineralization (Muntean et al., 2017a).

Distal disseminated deposits with Carlin-style mineralization occur throughout the world; most are associated with porphyry copper-gold systems. Three localities are described in detail in this volume: Bau in Malaysia (Percival et al., 2018), the Agdarreh and Zarshouran deposits in northwestern Iran (Daliran et al., 2018), and Alshar in Macedonia (Strmić Palinkas et al., 2018). Examples in the Andes include Jeronimo in Chile (Thompson et al., 2004) and Purisima Concepcion in Peru (Alvarez and Noble, 1988). In southeast Asia examples include deposits in the Sepon district in Laos (Smith et al., 2005) and the Mesel deposit in Indonesia (Turner et al., 1994). In the Yukon, Brewery Creek is an example related to a reduced intrusion gold system (Poulsen, 1996; Flanigan et al., 2000). Examples in the United States outside Nevada include the Melco and Barney’s Canyon deposits associated with the Bingham porphyry copper-gold-molybdenum system in Utah (Presnell and Parry, 1996; Babcock et al., 1997; Cunningham et al., 2004).

At the regional scale, portions of arcs that have intrusive centers with known associated gold mineralization (e.g., porphyry systems, skarns, polymetallic veins, and replacement bodies) are prospective for distal disseminated deposits around their margins. Emplacement of the intrusive sedimentary rocks with carbonate-bearing rock types is important for development of Carlin-style mineralization. Rifted continental margins are not necessarily important. At the district and drill target scales, many of the targeting elements and criteria for Carlin-type gold deposits apply to the Carlin-style portions of distal disseminated deposits, including high-angle faults and zones of low-displacement high-angle faults that are broadly synchronous with targeted mineralization, an older contractional deformation, and the formation of folds and associated bedding plane slip. Reactivated basement structures do not appear to be as important as for Carlin-type gold deposits in Nevada. Low-angle features that divert fluids into reactive carbonate rocks are important. Jasperoids and zones of decarbonatization, like those in Carlin-type deposits, are targeting criteria. Sericitization is more common in distal disseminated deposits and typically predominates over argillization. The Carlin-type geochemical signature of Au-As-Hg-Sb-Tl-(Te) need not be applied as strictly in that there can be Ag, Cu, Bi, Pb, Zn, and Mn as well, especially if Carlin-like mineralization is juxtaposed on polymetallic sulfide mineralization.

Importantly, the strong zonation mentioned above can be used in exploration. Distal disseminated deposits, especially their Carlin-like portions, typically are the farthest from the intrusive center. For example, the Melco and Barney’s Canyon Carlin-style deposits are located 7 and 9 km north, respectively, of the Last Chance stock that hosts the Bingham Canyon porphyry copper deposit, near the limit of geochemically anomalous arsenic and gold in surface soil and rock-chip samples (Babcock et al., 1997). In contrast, the Cove distal disseminated deposit lies only 2.5 km northeast of coeval Brown stock and associated McCoy gold skarn. Notably, the Carlin-style mineralization at Cove is zoned in its Ag/Au ratio (Johnston et al., 2008; Muntean et al., 2017a).

Sillitoe and Bonham (1990) were the first to propose that Carlin-type gold deposits were distal products of hydrothermal systems associated with upper crustal intrusion systems and that magmatic-hydrothermal fluids contributed gold in the formation of Carlin-type gold deposits. Johnston and Ressel (2005) recognized the differences between distal disseminated and Carlin-type deposits and suggested there was a continuum between the two, with Carlin-type gold deposits being the most distal. Carlin-style ore at Cove may be the missing link (Johnston et al., 2008; Muntean et al., 2017a).

Epithermal deposits

As pointed out by Hofstra and Cline (2000), many low-sulfidation epithermal deposits of late Eocene to Pliocene age occur in Nevada and can share features of Carlin-type gold deposits, especially if they are hosted by carbonates and calcareous siliciclastic rocks. Examples of such deposits in Nevada include Florida Canyon (Hastings et al., 1988; Samal, 2007), Standard (Ronkos, 1986), Willard (Muto, 1980; Conelea and Howald, 2009), Relief Canyon (Wallace, 1989; Fifarek et al., 2015), Gold Point (Castor and Hulen, 1996), and Atlanta (LaBerge, 1995). Like Carlin-type gold deposits and distal disseminated deposits, ore is controlled by the same fracture permeability, including high-angle faults, thrusts, folds, and associated bedding plane slip, along with local karst. These deposits are commonly associated with jasperoid, decarbonatization, and argillization.

Jasperoid is much more common in the epithermal deposits. The jasperoids are commonly veined and/or hydrothermally brecciated, with open space filled by quartz, calcite, and/or adularia with textures indicative of boiling. As stressed above, Carlin-type gold deposits in the four main clusters in Nevada lack veins, hydrothermal breccias, and evidence for boiling. The epithermal deposits commonly have a Au-As-Hg-Sb-Tl geochemical signature but, in addition, commonly contain strongly anomalous Se, Cu, Pb, Zn, and Mn. In turn, ore is commonly associated with a variety of base metal sulfides and sulfosalts as well as arsenopyrite and ubiquitous pyrite. Gold typically occurs as free electrum but can occur in solid solution in arsenian pyrite or arsenopyrite.

Evidence for shallow Carlin-type gold deposits appears to occur at the Alligator Ridge deposit in eastern Nevada (≤300–800 m; Nutt and Hofstra, 2003). At Alligator Ridge, preore Eocene fluvial conglomerates and lacustrine sediments proximal to the deposit are silicified and have the same Carlin-type geochemical signature as ore at Alligator Ridge, containing up to 32 ppb Au, 447 ppm As, and 24 ppm Hg. Quartz in jasperoid locally has textures indicative of forming by recrystallization of amorphous silica. Jasperoid breccias locally have textures consistent with hydrothermal breccias, including rounded clasts, upward transported clasts, and rock-flour matrix (Tapper, 1986); however, most breccias are consistent with collapse (Ilchik, 1990). Breccia fragments are locally coated with drusy quartz ± stibnite ± barite. No veins, textures, or fluid inclusion data indicative of boiling have been reported. Similarly, proximal to the Emigrant deposit at the south end of the Carlin trend, Eocene conglomerates are silicified and anomalous in As and Hg (Ressel et al., 2015). Based on structural reconstruction, these mineralized Eocene sediments were about ~100 to 150 m above the Carlin-type ore at Emigrant. Ressel et al. (2015) stressed shallower ore had higher Ag/Au ratios than deeper ore and argued that this represented hypogene zonation suggestive of epithermal mineralization.

High-sulfidation epithermal deposits that form in carbonates and calcareous siliciclastic rocks can also resemble Carlin-type gold deposits. As pointed out by Einaudi (1982), sericitic and advanced argillic alteration in quartzofeldspathic rocks are typically expressed as silica-pyrite bodies in carbonates. Silica-pyrite bodies resemble jasperoid but contain much more pyrite (commonly >~10 vol %) than jasperoid associated with Carlin-type deposits (typically <~3 vol %). Similar to Carlin-type deposits, advanced argillic zones and silica-pyrite bodies narrow and pinch out with depth. Like Carlin-type deposits, this is due to increasing acidity of rising fluids because of increasing disassociation of acid molecules and, in the case of high-sulfidation epithermal deposits, the result of disproportionation of SO2.

The Santa Fe gold deposit in west-central Nevada (Albino and Boyer, 1992) is an example of a carbonate-hosted Carlin-style deposit related to a Miocene high-sulfidation epithermal system. The Santa Fe deposit occurs within highly fractured, steeply dipping carbonates of the Triassic Luning Formation. Mineralization associated with silicification and quartz-alunite alteration also occurs in Tertiary volcanic rocks. The two main styles of mineralization are fault-controlled antimony-rich jasperoid bodies and pyrite-rich siliceous breccias containing elevated As-Pb-Zn-Bi-Te-Mo. Locally, in the pyritic siliceous bodies, high-grade, sulfide-rich (up to 60 vol %) material that consists of arsenian pyrite and marcasite occurs at depth. Other carbonate-hosted high-sulfidation epithermal mineralization in the district is associated with jasperoids flanked by the decalcified and brecciated Luning Formation.

Whether Carlin-type gold deposits, distal disseminated deposits, and epithermal deposits have completely different origins or represent continua with a shared origin is more than simply an academic question. Comparisons of gold endowments between Carlin-type gold deposits, distal disseminated deposits, and Carlin-style low-sulfidation epithermal deposits are different. For example in Nevada, the Lone Tree deposit near Battle Mountain, the largest distal disseminated deposit, produced 4.6 Moz (143 t) of gold, and Florida Canyon, the largest Carlin-style low-sulfidation epithermal deposit, contains 3.3 Moz (103 t) of gold (production and resource) in very low grade ore. In contrast, the endowment of the Betze-Post deposit at the end of 2016 was 39.7 Moz (1,235 t) of gold.

Carlin-Type Deposits Outside Nevada?

An outstanding question for gold explorers is whether there are other places in the world that host clusters of Carlin-type deposits in the numbers, size, and grade like the four main clusters in Nevada. Thus far, the two candidates are southwestern China and the emerging Rackla belt in the Yukon. The deposits in southwestern China are covered by Su et al. (2018) and Xia et al. (2018) and the ones in the Rackla belt are by Tucker et al. (2018).

Southwestern China

The Golden Triangle in southwestern China occurs at the junction of the Yunnan, Guizhou, and Guangxi provinces. Thirty deposits in the Golden Triangle have a total gold endowment of 27.2 Moz (846 t; Berger et al., 2014). They are smaller on average than the Nevada deposits. For example, Nevada has at least nine Carlin-type gold deposits greater than 10 Moz (Davis and Muntean, 2017), whereas the largest deposit in the Golden Triangle, Jingfeng (Lannigou), contains 4.5 Moz (Berger et al., 2014). As pointed out by Cline et al. (2013), the deposits in the Golden Triangle exhibit both similarities to and differences from Carlin-type deposits in Nevada.

Both regions have similar geologic histories. Both occur along a deformed rifted cratonic margin, marked by passive-margin sequences containing significant carbonates. Deposits in both regions are commonly hosted by contractional structures adjacent to high-angle faults. A key difference is the presence of felsic magmatism in Nevada, both preore granitic plutons and synore dikes and volcanic rocks. Except for pre-ore basalts, igneous rocks in the Golden Triangle are limited Late Cretaceous alkaline ultramafic dikes.

Like in Nevada, the deposits in the Golden Triangle lack zoning in alteration, ore minerals, and geochemistry. In both regions gold occurs in arsenian pyrite associated with decarbonatization, silicification, and argillization. The arsenian pyrite in the Golden Triangle also occurs as rims to arsenic-poor pyrite cores; however, the rims are larger. Significant amounts of gold also occur in arsenopyrite in China. Both regions have abundant late ore-stage realgar, orpiment, and stibnite. In addition, the deposits in the Golden Triangle formed at greater depths than the Nevada deposits from overpressured fluids, as is evident from significant amounts of ore-stage quartz ± pyrite ± arsenopyrite veins in many of the Golden Triangle deposits. Fluid inclusions in vein quartz include both two-phase liquid-rich and two- to three-phase liquid-rich inclusions with vapor ± liquid CO2 (Su et al., 2009). Locally, two-phase aqueous-carbonic inclusions and monophase carbonic inclusions are present. Microthermometry indicates minimum temperatures of 190° to 245°C and pressures from 450 to 1,150 bar, corresponding to depths of 1.7 to 4.3 km under lithostatic load and 4.5 to 11.5 km assuming hydrostatic load. Calculated δ18O(H2O) and δD(H2O) values of water in equilibrium with minerals in ore zones from a few deposits range from 4 to 16‰ and –35 to –60‰ (Hofstra et al., 2005). Based largely on the fluid inclusion and isotopic data, Su et al. (2009) argued that ore fluids were of predominantly metamorphic origin.

Yukon

The cluster of Carlin-type gold occurrences in the Rackla belt in east-central Yukon was discovered in 2010. Thus far, no resource estimates have been reported. As pointed out by Arehart et al. (2013), the deposits in the Rackla belt exhibit both similarities to and differences from Carlin-type gold deposits in Nevada. The geologic history of the Rackla belt is even more similar to Nevada. The same rifted margin of Laurentia and carbonate-bearing passive-margin sequence occurs in east-central Yukon. The late Paleozoic compressional tectonism that affected Nevada deformed rocks in western Yukon. The Rackla belt experienced contractional deformation in the Mesozoic. Unlike the deposits in Nevada, the deposits in the Rackla belt have not been pinned to a period of major magmatism or extension. The descriptions of mineralization in the Rackla belt are very similar to descriptions of Carlin-type gold deposits (Arehart et al., 2013; Tucker et al., 2018) in terms of ore controls, geochemical signature (Au-Ag-As-Hg-Tl-[Sb]-[Ba] and ≤1:1 Ag/Au ratio), alteration (decarbonization, silicification, and argillization), occurrence of gold in arsenian pyrite rims, textures of ore-stage arsenian pyrite, and late ore-stage mineralogy (realgar, orpiment).

Need for higher precision age control

Similar to the situation in Nevada prior to the late 1990s, understanding of Carlin-type deposits in both the Golden Triangle in China and especially the Rackla belt in the Yukon is currently hampered by uncertainty of the ages of Carlin-type mineralization in these regions. In the late 1990s, a consensus of a late Eocene age for Carlin type deposits in Nevada finally formed (e.g., Hofstra et al., 1999; Arehart et al., 2003). This led to greater attention on the geologic and tectonic setting of Nevada leading up to and during formation of the deposits in the Eocene, which, in turn, constrained exploration and genetic models. Ages for the deposits in the Rackla belt are currently constrained between 74 and 42 Ma (Tucker et al., 2018). Ages for the deposits in the Golden Triangle are geologically constrained between Jurassic folds, which locally host ore, and Late Cretaceous dikes that locally cut ore (Su et al., 2018). Sm-Nd dates on calcite and fluorite in veins containing realgar, orpiment, and/or stibnite are between ~150 and ~130 Ma.

Concluding Remarks

As stressed by Seedorff and Barton (2005), shared deposit characteristics do not necessarily mean shared deposit origins. As they pointed out, dissolution of carbonate and replacement by quartz requires no more than a cooling, mildly acidic hydrothermal fluid. As Figure 27 shows, meteoric fluids, metamorphic fluids, or magmatic-hydrothermal fluids start rising and cooling at very different pressures and temperatures, yet at the conditions of ore formation of Carlin-like mineralization (<300°C and <500 bar) they converge. Thus, similarlooking deposits can have very different origins. Progress on determining whether Carlin-style deposits and Carlin-type deposits form a continuum and have shared origins or have distinct origins will be made by continued research on Carlin-type deposits in Nevada as key relationships are exposed by future drilling and mining and as microanalytical techniques continue to improve. More importantly, progress will be made by more studies on Carlin-style deposits, focusing on key similarities and differences through geochronology, regional geology, ore and alteration paragenetic studies, and microanalytical geochemical and isotopic studies.

The hope going forward in exploration is that geologists will embrace an approach that relies on understanding the critical processes of ore formation rather than simply on empiricism. Utilizing the mineral system approach involves looking for targeting elements, which are the geologic expressions of the critical processes, from the regional to deposit scale, then with careful field observations coupled with the latest geophysical, geochemical, and mineralogical technology, applying targeting criteria to detect and map those targeting elements. Is there another >100 Moz region of Carlin-type gold deposits outside Nevada? If there is, it may have significant differences from Nevada. One may embrace the differences that are encountered rather than be discouraged by them only if one understands how the critical processes of ore formation are expressed in different geologic settings in different parts of the world.

Acknowledgments

Acknowledgments

This paper represents the culmination of nearly 20 years of work by the author aimed at developing a mineral systems approach, based on geologic and physiochemical processes, to improve exploration for Carlin-type gold deposits. The author is eternally indebted to Andrew Jackson, Eliseo Gonzales Urien, and Antonio Arribas at Placer Dome Exploration for developing the idea for this project and giving him the opportunity to pursue it. Others at Placer Dome who were critical to the pursuit of this project were Mike Coward, Greg Hall, Charles Tarnocai, Radu Conelea, Paul Taufen, Jon Thorson, Paul Klipfel, and many others in the exploration and mine staffs at Placer Dome. The author thanks Barrick Gold Corp. for allowing the work to continue after its acquisition of Placer Dome in 2006. Such a project would not be possible without decades of geologic work and research done by many workers, as reflected by the long list of references. The author particularly values the contributions of and his interactions with Al Hofstra, Poul Emsbo, Chris Henry, Greg Arehart, Mike Ressel, Sean Long, David John, Chuck Thorman, Gary Edmondo, Harry Cook, Steve Kesler, Eric Seedorff, Mark Barton, Dick Tosdal, John Dilles, Adam Simon, Tony Longo, Ken Hickey, Shaun Barker, Chris Heinrich, and the mine and exploration staffs of Barrick Gold Corp. and Newmont Mining Corp., as well as the staffs of many junior exploration companies. The author acknowledges the many graduate students he has supervised since moving to the Nevada Bureau of Mines and Geology at the University of Nevada Reno, including Lucia Patterson, Mike Cassinerio, Tyler Hill, and Wilson Bonner, whose work was incorporated into this paper. Finally, the pursuit of this project would not have been successful without author’s long-term collaborator, Jean Cline, whose insight and friendship have been invaluable over the years. The author thanks Dick Tosdal, Jeremy Vaughan, Jon Hronsky, and Patrick Mercier-Langevin for their reviews.

This paper represents the culmination of nearly 20 years of work by the author aimed at developing a mineral systems approach, based on geologic and physiochemical processes, to improve exploration for Carlin-type gold deposits. The author is eternally indebted to Andrew Jackson, Eliseo Gonzales Urien, and Antonio Arribas at Placer Dome Exploration for developing the idea for this project and giving him the opportunity to pursue it. Others at Placer Dome who were critical to the pursuit of this project were Mike Coward, Greg Hall, Charles Tarnocai, Radu Conelea, Paul Taufen, Jon Thorson, Paul Klipfel, and many others in the exploration and mine staffs at Placer Dome. The author thanks Barrick Gold Corp. for allowing the work to continue after its acquisition of Placer Dome in 2006. Such a project would not be possible without decades of geologic work and research done by many workers, as reflected by the long list of references. The author particularly values the contributions of and his interactions with Al Hofstra, Poul Emsbo, Chris Henry, Greg Arehart, Mike Ressel, Sean Long, David John, Chuck Thorman, Gary Edmondo, Harry Cook, Steve Kesler, Eric Seedorff, Mark Barton, Dick Tosdal, John Dilles, Adam Simon, Tony Longo, Ken Hickey, Shaun Barker, Chris Heinrich, and the mine and exploration staffs of Barrick Gold Corp. and Newmont Mining Corp., as well as the staffs of many junior exploration companies. The author acknowledges the many graduate students he has supervised since moving to the Nevada Bureau of Mines and Geology at the University of Nevada Reno, including Lucia Patterson, Mike Cassinerio, Tyler Hill, and Wilson Bonner, whose work was incorporated into this paper. Finally, the pursuit of this project would not have been successful without author’s long-term collaborator, Jean Cline, whose insight and friendship have been invaluable over the years. The author thanks Dick Tosdal, Jeremy Vaughan, Jon Hronsky, and Patrick Mercier-Langevin for their reviews.

REFERENCES

Albino
,
G.V.
, and
Boyer
,
C.I.
,
1992
,
Lithologic and structural controls of gold deposits of the Santa Fe district, Mineral County, Nevada
, in
Craig
,
S.D.
, ed.,
Structure, tectonics, and mineralization of the Walker Lane, Geological Society of Nevada Walker Lane Symposium proceedings volume
:
Reno, Nevada
,
Geological Society of Nevada
, p.
187
211
.
Alfaro
,
J.C.
,
Corcoran
,
C.
,
Davies
,
K.
,
Pineda
,
F.G.
,
Hampson
,
G.
,
Hill
,
D.
, and
Kragh
,
E.
,
2007
,
Reducing exploration risk: Oilfield Review, v
.
19
, p.
26
43
.
Alvarez
,
A.
, and
Noble
,
D.C.
,
1988
,
Sedimentary rock-hosted disseminated precious metal mineralization at Purisima Concepcion
,
Yaricocha district, central Peru: Economic Geology
 , v.
83
, p.
1368
1378
.
Arehart
,
G.B.
, and
Donelick
,
R.A.
,
2006
,
Thermal and isotopic profiling of the Pipeline hydrothermal system: Application to exploration for Carlin-type gold deposits
:
Journal of Geochemical Exploration
 , p.
27
40
.
Arehart
,
G.B.
,
Kesler
,
S.E.
,
O’Neil
,
J.R.
, and
Foland
,
K.A.
,
1992
,
Evidence for the supergene origin of alunite in sediment-hosted micron gold deposits
,
Nevada: Economic Geology
 , v.
87
, p.
263
270
.
Arehart
,
G.B.
,
Chakurian
,
A.M.
,
Tretbar
,
D.R.
,
Christensen
,
J.N.
,
McInnes
,
B.A.
, and
Donelick
,
R.A.
,
2003
,
Evaluation of radioisotope dating of Carlin-type deposits in the Great Basin, western North America, and implications for deposit genesis
:
Economic Geology
 , v.
98
, p.
235
248
.
Arehart
,
G.B.
,
Ressel
,
M.
,
Carne
,
R.
, and
Muntean
,
J.
,
2013
,
A comparison of Carlin-type deposits in Nevada and Yukon: Society of Economic Geologists
,
Special Publication
 
17
, p.
389
401
.
Armstrong
,
A.K.
,
Theodore
,
T.G.
,
Oscarson
,
R.L.
,
Kotlyar
,
B.B.
,
Harris
,
A.G.
,
Bettles
,
K.H.
,
Lauha
,
E.A.
,
Hipsley
,
R.A.
,
Griffin
,
G.L.
,
Abbott
,
E.W.
, and
Cluer
,
J.K.
,
1998
,
Preliminary facies analysis of Silurian and Devonian autochthonous rocks that host gold along the Carlin trend, Nevada
:
U.S. Geological Survey Open-File Report 98–338
 , p.
38
68
.
Babcock
,
R.S.
, Jr.,
Ballantyne
,
G.H.
, and
Phillips
,
C.H.
,
1997
,
Summary of the geology of the Bingham district
,
Utah: Society of Economic Geologists Guidebook Series
 , v.
29
, p.
113
132
.
Bakken
,
B.M.
,
1990
,
Gold mineralization, wall-rock alteration, and the geochemical evolution of the hydrothermal system in the main orebody, Carlin Mine, Nevada
: Unpublished Ph.D. thesis,
Stanford, California
,
Stanford University
,
236
p.
Barker
,
S.L.L.
,
Dipple
,
G.M.
,
Hickey
,
K.A.
,
Lepore
,
W.A.
, and
Vaughan
,
J.R.
,
2013
,
Applying stable isotopes to mineral exploration: Teaching an old dog new tricks
:
Economic Geology
 , v.
108
, p.
1
9
.
Barton
,
M.D.
,
Seedorff
,
E.
,
Ilchik
,
R.P.
, and
Ghidotti
,
G.
,
1997
,
Contrasting siliceous replacement mineralization, east-central Nevada
:
Society of Economic Geologists Guidebook Series
 , v.
28
. p.
131
135
.
Berger
,
B.R.
, and
Taylor
,
B.E.
,
1980
,
Pre-Cenozoic normal faulting in the Osgood Mountains
,
Humboldt County, Nevada: Geology
 , v.
8
, p.
594
598
.
Berger
,
V.I.
,
Mosier
,
D.L.
,
Bliss
,
J.D.
, and
Moring
,
B.C.
,
2014
,
Sediment-hosted gold deposits of the world—database and grade and tonnage models
:
U.S. Geological Survey Open-File Report 2014–1074
 ,
51
p.
Bettles
,
K.
,
2002
,
Exploration and geology, 1962 to 2002, at the Goldstrike property
,
Carlin trend, Nevada: Society of Economic Geologists, Special Publication
 
9
, p.
275
298
.
Beyssac
,
O.
,
Goffe
,
B.
,
Chopin
,
C.
, and
Rouzaud
,
J.N.
,
2002
,
Raman spectra of carbonaceous material in metasediments: A new geothermometer
:
Journal of Metamorphic Petrology
 , v.
20
, p.
859
871
.
Bloomstein
,
E.I.
,
Braginton
,
B.L.
,
Owen
,
R.W.
,
Parratt
,
R.L.
,
Raabe
,
K.C.
, and
Thompson
,
W.F.
,
2000
,
Lone Tree gold deposit
, in
Theodore
,
T.G.
,
Geology of pluton-related gold mineralization at Battle Mountain, Nevada: Monographs in mineral resource science, no. 2: Tucson, Arizona, Center for Mineral Resources
 ,
271
p.
Boskie
,
R.M.
, and
Schweikert
,
R.A.
,
2001
,
Structure and stratigraphy of lower Paleozoic rocks of the Getchell trend
,
Osgood Mountains, Humboldt County, Nevada: Geological Society of Nevada, Special Publication
 
33
, p.
263
293
.
Brandon
,
M.T.
,
Roden-Tice
,
M.K.
, and
Garver
,
J.I.
,
1998
,
Late Cenozoic exhumation of the Cascadia accretionary wedge in the Olympic Mountains, northwest Washington State
:
Geological Society of America Bulletin
 , v.
110
, p.
985
1009
.
Cassinerio
,
M.D.
, and
Muntean
,
J.L.
,
2011
,
Patterns of lithology, structure, alteration, and trace elements around high-grade ore zones at the Turquoise Ridge gold deposit, Getchell district, Nevada
, in
Steininger
,
R.C.
, and
Pennell
,
W.M.
, eds.,
Great Basin evolution and metallogeny: 2010 symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
949
978
.
Cline
,
J.S.
,
2018
,
Nevada’s Carlin-type gold deposits: What we’ve learned during the past 10 to 15 years
:
Reviews in Economic Geology
 , v.
20
, p.
7
37
.
Castor
,
S.B.
, and
Hulen
,
J.B
,
1996
,
Electrum and organic matter at the Gold Point mine, Currant mining district, Nevada
, in
Coyner
,
A.R.
, and
Fahey
,
P.L.
, eds.,
Geology and ore deposits of the American Cordillera: Symposium proceedings
 :
Reno, Nevada
,
Geological Society of Nevada
, p.
547
565
.
Cline
,
J.S.
,
2001
,
Timing of gold and arsenic sulfide mineral deposition at the Getchell Carlin-type gold deposit, north-central Nevada
:
Economic Geology
 , v.
96
, p.
75
89
.
Cline
,
J.S.
, and
Hofstra
,
A.H.
,
2000
,
Ore fluid evolution at the Getchell Carlin-type gold deposit
,
Nevada, USA: European Journal of Mineralogy
 , v.
12
, p.
195
212
.
Cline
,
J.S.
,
Stuart
,
F.M.
,
Hofstra
,
A.H.
,
Premo
,
W.
,
Riciputi
,
L.
,
Tosdal
,
R.M.
, and
Tretbar
,
D.R.
,
2003
,
Multiple sources of ore fluid components at the Getchell Carlin-type gold deposit, Nevada, USA
, in
Eliopoulos
,
D.
, et al
, eds.,
Mineral exploration and sustainable development
 , v.
2
:
Rotterdam
,
Millpress
, p.
965
968
.
Cline
,
J.S.
,
Hofstra
,
A.H.
,
Muntean
,
J.L.
,
Tosdal
,
R.M.
, and
Hickey
,
K.A.
,
2005
,
Carlin-type gold deposits in Nevada, USA
:
Economic Geology 100th Anniversary Volume
 , p.
451
484
.
Cline
,
J.S.
,
Muntean
,
J.L.
,
Gu
,
X.
, and
Xia
,
Y.
,
2013
,
A comparison of Carlin-type gold deposits: Guizhou Province, Golden Triangle, southwest China, and northern Nevada, USA
:
Earth Science Frontiers
 , v.
20
, p.
1
18
.
Colgan
,
J.P
,
John
,
D.A.
,
Henry
,
C.D.
, and
Fleck
,
R.J.
,
2008
,
Large-magnitude Miocene extension of the Eocene Caetano caldera, Shoshone and Toiyabe Ranges, Nevada
:
Geosphere
 , v.
4
, p.
107
130
.
Colgan
,
J.P
,
Henry
,
C.D.
, and
John
,
D.A.
,
2014
,
Evidence for large-magnitude, post-Eocene extension in the northern Shoshone Range, Nevada, and its implications for the structural setting of Carlin-type gold deposits in the lower plate of the Roberts Mountains allochthon
:
Economic Geology
 , v.
109
, p.
1843
1862
.
Conelea
,
R.
, and
Howald
,
W.C.
,
2009
,
The geology and gold-silver mineralization of the Wilco project, Willard mining district, Pershing County, Nevada
:
Geological Society of Nevada, Special Publication 49
 , p.
92
108
.
Coney
,
P.J.
, and
Reynolds
,
S.J.
,
1977
,
Cordilleran Benioff zones
:
Nature
 , v.
270
, p.
403
406
.
Cook
,
H.E.
,
2015
,
The evolution and relationship of the western North America Paleozoic carbonate platform and basinal depositional environments to Carlin-type gold deposits in the context of the carbonate sequence stratigraphy
, in
Pennell
,
W.M.
and
Garside
,
L.J.
, eds.,
New concepts and discoveries: Geological Society of Nevada 2015 Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
1
80
.
Cook
,
H.E.
, and
Corboy
,
J.C.
,
2004
,
Great Basin Paleozoic carbonate platform: Facies, facies transitions, depositional models, platform architecture, sequence stratigraphy, and predictive mineral host models
:
U.S. Geological Survey Open-File Report 2004–1078
 ,
129
p.
Cook
,
H.E.
, and
Taylor
,
M.E.
,
1977
,
Comparison of continental slope and shelf environments in the Upper Cambrian and lowest Ordovician of Nevada
:
Society of Sedimentary Geologists (SEPM), Special Publication 25
 , p.
51
81
.
Coward
,
M.
,
1994
,
Inversion tectonics
, in
Hancock
,
P.L.
, ed.,
Continental deformation
 ,
Oxford
,
Permagon Press
, p.
289
304
.
Cox
,
D.P
,
1992
,
Descriptive model of distal disseminated Ag-Au deposits
:
U.S. Geological Survey Bulletin
 
2004
, p.
19
.
Cox
,
D.P.
, and
Singer
,
D.A.
,
1992
,
Grade and tonnage model of distal disseminated Ag-Au
:
U.S. Geological Survey Bulletin
 
2004
, p.
20
22
.
Crafford
,
A.E.J.
, and
Grauch
,
V.J.S.
,
2002
,
Geologic and geophysical evidence for the influence of deep crustal structures on Paleozoic tectonics and the alignment of world-class gold deposits, north central Nevada, USA
:
Ore Geology Reviews
 , v.
21
, p.
157
184
.
Cunningham
,
C.G.
,
Austin
,
G.W.
,
Naeser
,
C.W.
,
Rye
,
R.O.
,
Ballantyne
,
G.H.
,
Stamm
,
R.G.
, and
Barker
,
C.E.
,
2004
,
Formation of paleothermal anomaly and disseminated gold deposits associated with the Bingham Canyon porphyry Cu-Au-Mo system, Utah
:
Economic Geology
 , v.
99
, p.
789
806
.
Daliran
,
F.
,
Hofstra
,
A.
,
Walther
,
J.
, and
Topa
,
D.
,
2018
,
Ore genesis constraints on the Agdarreh and Zarshouran Carlin-style gold deposits in the Takab region of northwestern Iran
:
Reviews in Economic Geology
 , v.
20
, p.
299
333
.
Davis
,
D.A.
, and
Muntean
,
J.L.
,
2017
,
Metals
:
Nevada Bureau of Mines and Geology, Special Publication MI-2015
 , p.
14
109
.
Deditius
,
A.P.
,
Utsunomiya
,
S.
,
Ewing
,
R.C.
,
Chryssoulis
,
S.L.
,
Venter
,
D.
, and
Kesler
,
S.E.
,
2009
,
Decoupled geochemical behavior of As and Cu in hydrothermal systems
:
Geology
 , v.
37
, p.
707
710
.
Deditus
,
A.P.
,
Reich
,
M.
,
Kesler
,
S.E.
,
Utsonomiya
,
S.
,
Chryssoulis
,
S.L.
,
Walshe
,
J.
, and
Ewing
,
R.C.
,
2014
,
The coupled geochemistry of Au and As in pyrite from hydrothermal ore deposits
:
Geochimica et Cosmochimica Acta
 , v.
140
, p.
644
670
.
Dewitt
,
A.B.
,
2001
,
Structural architecture of the Jerritt Canyon district and gold deposits
:
Geological Society of Nevada, Special Publication 33
 , p.
135
145
.
Di Fiori
,
R.V.
,
Long
,
S.P.
,
Muntean
,
J.L.
, and
Edmondo
,
G.P.
,
2015
,
Structural analysis of gold mineralization in the southern Eureka mining district, Eureka County, Nevada: A predictive structural setting for Carlin-type mineralization
, in
Pennell
,
W.M.
, and
Garside
,
L.J.
, eds.,
New concepts and discoveries: Geological Society of Nevada 2015 Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
885
903
.
Dilles
,
J.H.
,
Kent
,
A.J.R.
,
Wooden
,
J.L.
,
Tosdal
,
R.M.
,
Koleszar
,
A.
,
Lee
,
R.G.
, and
Farmer
,
L.P.
,
2015
,
Zircon compositional evidence for sulfur-degassing from ore-forming arc magmas
:
Economic Geology
 , v.
110
, p.
241
251
.
Dilles
,
P.A.
,
Wright
,
W.A.
,
Monteleone
,
S.A.
,
Russell
,
K.D.
,
Marlowe
,
K.E.
,
Wood
,
R.A.
, and
Margolis
,
J.
,
1996
,
The geology of the West Archimedes deposit: A new gold discovery in the Eureka mining district, Eureka County, Nevada
, in
Coyner
,
A.R.
, and
Fahey
,
P.L.
, eds.,
Geology and ore deposits of the American Cordillera: Geological Society of Nevada Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
159
171
.
Dobson
,
P.F.
,
Epstein
,
S.
, and
Stolper
,
E.M.
,
1989
,
Hydrogen isotope fractionation between coexisting vapor and silicate glasses and melts at low pressure
:
Geochimica et Cosmochimica Acta
 , v.
53
, p.
2723
2730
.
Duebendorfer
,
E.M.
, and
Houston
,
R.S.
,
1986
,
Kinematic history of the Cheyenne belt
,
Medicine Bow Mountains, southeastern Wyoming (USA)
 :
Geology
 , v.
14
, p.
171
174
.
Einaudi
,
M.T.
,
1982
,
Description of skarns associated with porphyry copper plutons, southwestern North America
, in
Titley
,
S.R.
, ed.,
Advances in the geology of porphyry copper deposits in southwestern North America
:
Tucson, Arizona
,
University of Arizona Press
, p.
139
184
.
Eliason
,
R.
, and
Kantor
,
J.A.
,
1998
,
Geology of the SSX deposit
:
Geological Society of Nevada
 , Special Publication
28
, p.
170
.
Eliason
,
R.
, and
Wilton
,
D.T.
,
2005
,
Relation of gold mineralization to structure in the Jerritt Canyon mining district: Nevada
, in
Rhoden
,
H.N.
,
Steininger
,
R.C.
, and
Vikre
,
P.G.
, eds.,
Window to the world: 2005 symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
335
356
.
Emsbo
,
P.
,
1993
,
Geology and geochemistry of the Ordovician Vinini Formation, Roberts Mountains, Nevada
: Unpublished M.S. thesis,
Golden, Colorado
,
Colorado School of Mines
,
290
p.
Emsbo
,
P.
,
1999
,
Origin of the Meikle high-grade gold deposit from the superposition of Late Devonian Sedex and mid-Tertiary Carlin-type gold mineralization
: Unpublished Ph.D. thesis,
Golden, Colorado
,
Colorado School of Mines
,
394
p.
Emsbo
,
P.
,
Hutchinson
,
R.W.
,
Hofstra
,
A.H.
,
Volk
,
J.A.
,
Bettles
,
K.H.
,
Baschuk
,
G.J.
,
Collins
,
T.M.
,
Lauha
,
E.A.
, and
Borhauer
,
J.L.
,
1998
,
Syngenetic Au on the Carlin trend: Implications for Carlin-type gold deposits
:
Geology
 , v.
27
, p.
59
62
.
Emsbo
,
P.
,
Hofstra
,
A.H.
,
Lauha
,
E.A.
,
Griffin
,
G.L.
, and
Hutchinson
,
R.W.
,
2003
,
Origin of high-grade gold ore, source of ore fluid components, and genesis of the Meikle and neighboring Carlin-type deposits, northern Carlin trend, Nevada
:
Economic Geology
 , v.
98
, p.
1069
1105
.
Emsbo
,
P.
,
Groves
,
D.I.
,
Hofstra
,
A.H.
, and
Bierlein
,
F.P.
,
2006
,
The giant Carlin gold province: A protracted interplay of orogenic, basinal, and hydrothermal processes above a lithospheric boundary
:
Mineralium Deposita
 , v.
41
, p.
517
525
.
Engebretson
,
D.C.
,
Cox
,
A.
, and
Gordon
,
R.G.
,
1985
,
Relative motions between oceanic and continental plates in the Pacific basin
:
Geological Society of America, Special Paper 206
 ,
59
p.
Epstein
,
A.G.
,
Epstein
,
J.B.
, and
Harris
,
L.D.
,
1977
,
Conodont color alteration: An index to organic metamorphism
:
U.S. Geological Survey Professional Paper 995
 ,
27
p.
Evans
,
D.C.
,
2000
,
Carbonate-hosted breccias in the Meikle mine, Nevada, and their relationship with gold mineralization
: Unpublished M.S. thesis,
Golden, Colorado
,
Colorado School of Mines
,
266
p.
Evans
,
J.G.
, and
Theodore
,
T.G.
,
1978
,
Deformation of the Roberts Mountains allochthon in north-central Nevada
:
U.S. Geological Survey Professional Paper 1060
 ,
18
p.
Faulds
,
J.E.
, and
Hinz
,
N.H.
,
2015
,
Favorable tectonic and structural settings of geothermal systems in the Great Basin region, western USA
:
Proxies for discovering blind geothermal systems
 :
World Geothermal Congress, Melbourne, Australia, April 19–25, 2015, Proceedings
,
6
p.
Faulds
,
J.E.
, and
Varga
,
R.J.
,
1996
,
The role of accommodation zones and transfer zones in the regional segmentation of extended terranes: Geological Society of America
,
Special Paper 323
 , p.
1
46
.
Ferry
,
J.M.
,
1981
,
Petrology of graphitic sulfide-rich schist from south-central Maine: An example of desulfidation during prograde regional metamorphism
:
American Mineralogist
 , v.
66
, p.
908
931
.
Fifarek
,
R.H.
,
Prihar
,
D.W.
,
Hillesland
,
L.L.
,
Casaceli
,
R.J.
,
Dilles
,
P.A.
, and
Miggins
,
D.O.
,
2015
,
Tectonostratigraphic framework and timing of mineralization at the Relief Canyon mine, Pershing County, Nevada
, in
Pennell
,
W.M.
, and
Garside
,
L.J.
, eds.:
New concepts and discoveries: Geological Society of Nevada 2015 Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
453
482
.
Flanigan
,
B.
,
Freeman
,
C.
,
Newberry
,
R.
,
McCoy
,
D.
, and
Hart
,
C.
,
2000
,
Exploration models for mid and Late Cretaceous intrusion-related gold deposits in Alaska and the Yukon Territory, Canada
, in
Cluer
,
J.K.
,
Price
,
J.G.
,
Struhsacker
,
E.M.
, et al
, eds.,
Geology and ore deposits 2000: The Great Basin and beyond symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
591
614
.
Fortuna
,
J.
,
Kesler
,
S.E.
, and
Stenger
,
D.P.
,
2003
,
Source of iron for sulfidation and gold deposition, Twin Creeks Carlin-type deposit, Nevada
:
Economic Geology
 , v.
98
, p.
1213
1224
.
Foster
,
D.A.
,
Mueller
,
P.A.
,
Mogk
,
D.W.
,
Wooden
,
J.L.
, and
Vogl
,
J.J.
,
2006
,
Proterozoic evolution of the western margin of the Wyoming craton
:
Implications for the tectonic and magmatic evolution of the northern Rocky Mountains: Canadian Journal of Earth Sciences
 , v.
43
, p.
1601
1619
.
Furley
,
R.A.
,
2001
,
Sequence stratigraphic framework for the Silurian-Devonian Bootstrap Limestone, Roberts Mountains, and Devonian Popovich Formations, northern Carlin trend, Elko and Eureka Counties, Nevada
: Unpublished M.Sc. thesis,
Golden, Colorado
,
Colorado School of Mines
,
197
p.
Gans
,
P.B.
,
Seedorff
,
E.
,
Fahey
,
P.L.
,
Hasler
,
R.W.
,
Maher
,
D.J.
,
Jeanne
,
R.A.
, and
Shaver
,
S.A.
,
2001
,
Rapid Eocene extension in the Robinson district, White Pine County, Nevada: Constraints from 40Ar/39Ar dating
:
Geology
 , v.
29
, p.
475
478
.
Giggenbach
,
W.F.
,
1992
,
Magma degassing and mineral deposition in hydrothermal systems along convergent plate boundaries
:
Economic Geology
 , v.
87
, p.
1927
1944
.
Gize
,
A.P.
,
Kuehn
,
C.A.
,
Furlong
,
K.P.
, and
Gaunt
,
J.M.
,
2000
,
Organic maturation modeling applied to ore genesis and exploration
:
Reviews in Economic Geology
 , v.
9
, p.
87
104
.
Goldfarb
,
R.J.
,
Groves
,
D.I.
, and
Gardoll
,
S.
,
2001
,
Orogenic gold and geologic time: A global synthesis
:
Ore Geology Reviews
 , v.
18
, p.
1
75
.
Goldfarb
,
R.J.
,
Hart
,
C.J.R.
,
Davis
,
G.
, and
Groves
,
D.I.
,
2007
,
East Asian gold: Deciphering the anomaly of Phanerozoic gold in Precambrian cratons
:
Economic Geology
 , v.
102
, p.
341
346
.
Grauch
,
V.J.S.
,
Rodriguez
,
B.D.
, and
Wooden
,
J.L.
,
2003
,
Geophysical and isotopic constraints on crustal structure related to mineral trends in north-central Nevada and implications for tectonic history
:
Economic Geology
 , v.
98
, p.
269
286
.
Graybeal
,
F.T.
,
1981
,
Characteristics of disseminated silver deposits in the western United States
:
Arizona Geological Society Digest
 , v.
14
, p.
271
282
.
Griffin
,
W.L.
,
Begg
,
G.C.
, and
O’Reilly
,
Y.
,
2013
,
Continental-root control on the genesis of magmatic ore deposits
:
Nature Geoscience
 , v.
6
, p.
905
910
.
Hall
,
C.M.
,
Kesler
,
S.E.
,
Simon
,
G.
, and
Fortuna
,
J.
,
2000
,
Overlapping Cretaceous and Eocene alteration, Twin Creeks Carlin-type deposit, Nevada
:
Economic Geology
 , v.
95
, p.
1739
1752
.
Hannink
,
R.
Smith
,
M.
,
Shabestari
,
P.
,
Raabe
,
K.
,
Spalding
,
V.
, and
Hill
,
T.
,
2015
,
The discovery and geology of the Western Flank zone at the Kinsley Mountain project, Elko County, Nevada
, in
Pennell
,
W.M.
, and
Garside
,
L.J.
, eds.,
New concepts and discoveries: Geological Society of Nevada 2015 Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
295
312
.
Harlan
,
J.B.
,
Harris
,
D.A.
,
Mallette
,
P.M.
,
Norby
,
J.W.
,
Rota
,
J.C.
, and
Sagar
,
J.J.
,
2002
,
Geology and mineralization of the Maggie Creek district
:
Nevada Bureau of Mines and Geology Bulletin
 , v.
111
, p.
115
142
.
Harris
,
A.G.
, and
Crafford
,
A.E.J.
,
2007
,
A conodont database of Nevada
:
U.S. Geological Survey Data Series DS-249, scale 1:250,000
 .
Hastings
,
J.S.
,
Burkhart
,
T.H.
, and
Richardson
,
R.E.
,
1988
,
Geology of the Florida Canyon gold deposit, Pershing County, Nevada
, in
Schafer
,
R.W.
,
Cooper
,
J.J.
, and
Vikre
,
P.G.
, eds.,
Bulk mineable precious metal deposits of the western United States: Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
433
452
.
Hedenquist
,
J.W.
, and
Richards
,
J.P.
,
1998
,
The influence of geochemical techniques on the development of genetic models for porphyry copper deposits
:
Reviews in Economic Geology
 , v.
10
, p.
235
256
.
Henkelman
,
C.
,
2004
,
Variations in pyrite chemistry as clues to gold deposition at the Goldstrike system, Carlin trend, Nevada USA
: Unpublished M. Sc. thesis,
Las Vegas, Nevada
,
University of Nevada Las Vegas
,
150
p.
Heinrich
,
C.A.
,
1990
,
The chemistry of hydrothermal tin(-tungsten) ore deposition
:
Economic Geology
 , v.
85
, p.
457
481
.
Heitt
,
D.G.
,
Dunbar
,
W.W.
,
Thompson
,
T.B.
, and
Jackson
,
R.G.
,
2003
,
Geology and geochemistry of the Deep Star gold deposit
,
Carlin trend, Nevada: Economic Geology
 , v.
98
p.
1107
1135
.
Henry
,
C.
,
Muntean
,
J.
,
John
,
D.
, and
Colgan
,
J.
,
2012
,
Mesozoic-Cenozoic magmatism and mineralization in the greater Cortez area: An example of NBMG framework studies [abs.]
:
Geological Society of Nevada Newsletter
 , March
2012
, p.
3
.
Henry
,
C.D.
,
2008
,
Ash-flow tuffs and paleovalleys in northeastern Nevada: Implications for Eocene paleogeography and extension in the Sevier hinterland, northern Great Basin
:
Geosphere
  v.
4
, p.
1
35
.
Henry
,
C.D.
, and
John
,
D.
,
2013
,
Magmatism, ash-flow tuffs, and calderas of the ignimbrite flareup in the western Nevada volcanic field, Great Basin, USA
:
Geosphere
 , v.
9
, p.
951
1008
.
Hickey
,
K.A.
,
Barker
,
S.L.L.
,
Dipple
,
G.M.
,
Arehart
,
G.B.
, and
Donelick
,
R.A.
,
2014
,
The brevity of hydrothermal fluid flow revealed by thermal halos around giant gold deposits: Implications for Carlin-type gold systems
:
Economic Geology
 , v.
109
, p.
1461
1487
.
Hitzman
,
M.W.
,
1999
,
Routine staining of drill core to determine carbonate mineralogy and distinguish carbonate alteration textures
:
Mineralium Deposita
 , v.
34
, no.
8
, p.
794
798
.
Hofstra
,
A.H.
,
1994
,
Geology and genesis of the Carlin-type gold deposits in the Jerritt Canyon district, Nevada
: Unpublished Ph.D. dissertation,
Golden, Colorado
,
Colorado School of Mines
,
1287
p.
Hofstra
,
A.H.
, and
Cline
,
J.S.
,
2000
,
Characteristics and models for Carlin-type gold deposits
:
Reviews in Economic Geology
 , v.
13
, p.
163
220
.
Hofstra
,
A.H.
,
Leventhal
,
J.S.
, and
Northrop
,
G.P.
,
1991
,
Genesis of sediment-hosted disseminated-gold deposits by fluid mixing and sulfidization: Chemical-reaction-path modeling of ore-depositional processes documented in the Jerritt Canyon district, Nevada
:
Geology
 , v.
19
, p.
36
40
.
Hofstra
,
A.H.
,
Snee
,
L.W.
,
Rye
,
R.O.
,
Folger
,
H.W.
,
Phinisey
,
J.D.
,
Loranger
,
R.J.
,
Dahl
,
A.R.
,
Naeser
,
C.W.
,
Stein
,
H.J.
, and
Lewchuk
,
M.T.
,
1999
,
Age constraints on Jerritt Canyon and other Carlin-type gold deposits in the western United States; relationship to mid-Tertiary extension and magmatism
:
Economic Geology
 , v.
94
, p.
769
802
.
Hofstra
,
A.H.
,
Emsbo
,
P.
,
Christiansen
,
W.D.
,
Theodorakos
,
P.
,
Zhang
,
X.C.
,
Hu
,
R.Z.
,
Su
,
W.C.
, and
Fu
,
S.H.
,
2005
,
Source of ore fluids in Carlin-type gold deposits in China: Implications for genetic models
, in
Mao
,
J.W.
, and
Bierlein
,
F.P.
, eds.,
Mineral deposit research: Meeting the global challenge
, v.
1
:
Heidelberg
,
Springer-Verlag
, p.
533
536
.
Hotz
,
P.E.
, and
Willden
,
R.
,
1964
,
Geology and mineral deposits of the Osgood Mountains quadrangle, Humboldt County, Nevada
:
U.S. Geological Survey Professional Paper 431
 ,
128
p.
Howard
,
K.A.
,
2003
,
Crustal structure of the Elko-Carlin region, Nevada, during Eocene gold mineralization
:
Ruby Mountains-East Humboldt metamorphic core complex as a guide to the deep crust: Economic Geology
 , v.
98
, p.
249
268
.
Hronsky
,
J.M.A
,
Groves
,
D.L.
,
Loucks
,
R.R.
, and
Begg
,
G.C.
,
2012
,
A unified model for gold mineralization in accretionary orogens and implications for regional-scale exploration targeting methods
:
Mineralium Deposita
 , v.
47
, p.
339
358
.
Humphreys
,
E.D.
,
1995
,
Post-Laramide removal of the Farallon slab, western United States
:
Geology
 , v.
23
, p.
987
990
.
Ilchik
,
R.P.
,
1990
,
Geology and geochemistry of the Vantage gold deposits
,
Alligator Ridge-Bald Mountain mining district, Nevada
 :
Economic Geology
 , v.
85
, p.
50
75
.
Ilchik
,
R.P.
, and
Barton
,
M.D.
,
1997
,
An amagmatic origin of Carlin-type gold deposits
,
Economic Geology
 , v.
92
, p.
269
288
.
Ilchik
,
R.P.
,
Brimhall
,
G.H.
, and
Schull
,
H.W.
,
1986
,
Hydrothermal maturation of indigenous organic matter at the Alligator Ridge gold deposits
,
Nevada: Economic Geology
 , v.
81
, p.
113
130
.
James
,
L.P.
,
1976
,
Zoned alteration in limestone at porphyry copper deposits
,
Ely, Nevada: Economic Geology
 , v.
71
, p.
488
512
.
Jarvie
,
Z.J.
,
2009
,
Carlin-type mineralization and alteration of late Cambrian and Ordovician carbonate rocks at Long Canyon, Pequop Mountains, Nevada
: Unpublished M.S. thesis,
Reno, Nevada
,
University of Nevada Reno
,
62
p.
John
,
D.A.
,
2001
,
Miocene and early Pliocene epithermal gold-silver deposits in the northern Great Basin, western United States: Characteristics, distribution, and relationship to magmatism
:
Economic Geology
 , v.
96
, p.
1827
1853
.
John
,
D.A.
,
Hofstra
,
A.H.
,
Fleck
,
R.J.
,
Brummer
,
J.E.
, and
Saderholm
,
E.C.
,
2003
,
Geologic setting and genesis of the Mule Canyon low-sulfidation epithermal gold-silver deposit, north-central Nevada
:
Economic Geology
 , v.
98
, p.
425
463
.
John
,
D.A.
,
Henry
,
C.D.
, and
Colgan
,
J.P.
,
2008
,
Magmatic and tectonic evolution of the Caetano caldera, north-central Nevada: A tilted mid-Tertiary eruptive center and source of the Caetano tuff
:
Geosphere
 , v.
4
, p.
75
106
.
Johnson
,
C.L.
,
Dilles
,
J.H.
,
Kent
,
A.J.R.
, and
Farmer
,
L.P.
,
2015
,
Petrology and geochemistry of the Emigrant Pass volcanics, Nevada: Implications of a magmatic-hydrothermal origin of the Carlin gold deposits
, in
Pennell
,
W.M.
, and
Garside
,
L.J.
, eds.,
New concepts and discoveries: Geological Society of Nevada Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
391
408
.
Johnson
,
T.W.
,
Hofer
,
W.B.
,
Mendez
,
M.A.
,
Fletcher
,
C.M.
, and
Owusu
,
S.
,
2015
,
Carlin-type gold deposits and current mining activities at Jerritt Canyon, Elko County, Nevada
, in
Pennell
,
W.M.
, and
Garside
,
L.J.
, eds.,
New concepts and discoveries: Geological Society of Nevada Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
483
513
.
Johnston
,
M.K.
, and
Ressel
,
M.W.
,
2004
,
Controversies on the origin of world-class gold deposits, part II: Carlin-type and distal disseminated Au-Ag deposits: Related distal expressions of Eocene intrusive centers in north-central Nevada
:
Society of Economic Geologists Newsletter
 , v.
59
, p.
12
14
.
Johnston
,
M.K.
,
Thompson
,
T.B.
,
Emmons
,
D.L.
, and
Jones
,
K.
,
2008
,
Geology of the Cove Mine, Lander County, Nevada, and a genetic model for the McCoy-Cove hydrothermal system
:
Economic Geology
 , v.
103
, p.
759
782
.
Kantor
,
J.A
,
Colli
,
D.
, and
Eliason
,
R.
,
1998
,
Geology of the Murray and SSX underground mines, Jerritt Canyon mining district, Elko County, Nevada
:
Exploring New Opportunities, 104th Annual Northwest Mining Association Meeting
,
Spokane, Washington
,
1998
, Convention Paper.
Kelley
,
D.L.
,
Kelley
,
K.D.
,
Coker
,
W.B.
,
Caughlin
,
B.
, and
Doherty
,
M.E.
,
2006
,
Beyond the obvious limits of ore deposits: The use of mineralogical, geochemical, and biological features for the remote detection of mineralization
:
Economic Geology
 , v.
101
, p.
729
752
.
Kelson
,
C.R.
,
Crowe
,
D.E.
, and
Stein
,
H.J.
,
2008
,
Geochemical and geochronological constraints on mineralization within the Hilltop, Lewis, and Bullion mining districts, Battle Mountain-Eureka trend, Nevada
:
Economic Geology
 , v.
103
, p.
1483
1506
.
Kesler
,
S.E.
,
Fortuna
,
J.
,
Ye
,
Z.
,
Alt
,
J.C.
,
Core
,
D.P.
,
Zohar
,
P.
,
Borhauer
,
J.
, and
Chryssoulis
,
S.L.
,
2003
,
Evaluation of the role of sulfidation in deposition of gold, Screamer section of the Betze-Post Carlin-type deposit, Nevada
:
Economic Geology
 , v.
98
, p.
1137
1157
.
Ketcham
,
R.A.
,
Donelick
,
R.A.
, and
Carlson
,
W.D.
,
1999
,
Variability of apatite fission-track annealing kinetics III: Extrapolation to geological time scales
:
American Mineralogist
 ,
84
,
1235
1255
.
King
,
C.A.
,
2017
,
Igneous petrology, geochronology, alteration, and mineralization associated with hydrothermal systems in the Battle Mountain district, Nevada
: Unpublished Ph.D. thesis,
Tucson, Arizona
,
University of Arizona
,
707
p.
Kirk
,
J.
,
Ruiz
,
J.
,
Chesley
,
J.
, and
Titley
,
S.
,
2004
,
The origin of gold in South Africa
:
American Scientist
 , v.
91
, p.
534
541
.
Kistler
,
R.W.
, and
Peterman
,
Z.E.
,
1978
,
Reconstruction of crustal blocks of California on the basis of initial strontium isotopic compositions of Mesozoic granitic rocks
:
U.S. Geological Survey Professional Paper 1071
 ,
17
p.
Kuehn
,
C.A.
,
1989
,
Studies of disseminated gold deposits near Carlin, Nevada: Evidence for a deep geologic setting of ore formation
: Unpublished Ph.D. thesis,
University Park, Pennsylvania
,
Pennsylvania State University
,
396
p.
Kuehn
,
C.A.
, and
Rose
,
A.R.
,
1992
,
Geology and geochemistry of wall-rock alteration at the Carlin gold deposit, Nevada
:
Economic Geology
 , v.
87
, p.
1697
1721
.
LaBerge
,
R.D.
,
1995
,
Epithermal gold mineralization related to caldera volcanism at the Atlanta district, east-central Nevada
, in
Coyner
,
A.R.
, and
Fahey
,
P.L.
, eds.,
Geology and ore deposits of the American Cordillera: Geological Society of Nevada Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
309
328
.
Large
,
R.R.
,
Bull
,
S.W.
, and
Maslennikov
,
V.V.
,
2011
,
A carbonaceous sedimentary source-rock model for Carlin-type and orogenic gold deposits
:
Economic Geology
 , v.
106
, p.
331
358
.
Lauha
,
E.A.
,
1998
,
The West Bazza pit and its relationship to the Screamer deposit: Shallow expressions of deep, high-grade gold deposits
:
Geological Society of Nevada, Special Publication 28
 , p.
133
145
.
Leonardson
,
R.W.
,
2011
,
Barrick Cortez Gold Acres structure
, in
Steininger
,
R.C.
, and
Pennell
,
B.
, eds.,
Great Basin evolution and metallogeny: Geological Society of Nevada Symposium 2010
:
Reno, Nevada
,
Geological Society of Nevada
, p.
17
29
.
Lisle
,
R.E.
, and
Desrochers
,
G.J.
,
1988
,
Geology of the Hilltop gold deposit, Lander County, Nevada
, in
Schafer
,
R.W.
,
Cooper
,
J.J.
, and
Vikre
,
P.G.
, eds.,
Bulk mineable precious metal deposits of the western United States: Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
101
117
.
Long
,
S.P.
,
2012
,
Magnitudes and spatial patterns of erosional exhumation in the Sevier hinterland, eastern Nevada and western Utah, USA
:
Insights from a Paleogene paleogeologic map: Geosphere
 , v.
8
, p.
881
901
.
Long
,
S.P.
,
Henry
,
C.D.
,
Muntean
,
J.L.
,
Edmondo
,
G.P.
, and
Cassel
,
E.J.
,
2014a
,
Early Cretaceous construction of a structural culmination, Eureka, Nevada, USA
:
Implications for out-of-sequence deformation in the Sevier hinterland: Geosphere
 , v.
10
, p.
564
584
.
Long
,
S.P.
,
Henry
,
C.D.
,
Muntean
,
J.L.
,
Edmondo
,
G.P.
, and
Thomas
,
R.D.
,
2014b
,
Geologic map of the southern part of the Eureka mining district and surrounding areas of the Fish Creek Range, Mountain Boy Range, and Diamond Mountains, Eureka and White Pine Counties, Nevada
:
Nevada Bureau of Mines and Geology Map 183, scale 1:24,000, 2 plates
 ,
36
p.
Long
,
S.P.
,
Thomson
S.N.
,
Reiners
,
P.W.
, and
Di Fiori
,
R.V.
,
2015
,
Synorogenic extension localized by upper-crustal thickening: An example from the Late Cretaceouus Nevadaplano
:
Geology
 , v.
43
, p.
351
354
.
Longo
,
A.A.
,
Cline
,
J.S.
, and
Muntean
,
J.L.
,
2009
,
Using pyrite to track evolving fluid pathways and chemistry in Carlin-type deposits
, in
Williams
,
P.J.
, ed.,
Smart science for exploration and mining: Proceedings of the 10th biennial meeting of the Society for Geology Applied to Mineral Deposits
:
Townsville, Australia
, p.
242
244
.
Loucks
,
R.
,
2012
,
Chemical characteristics, geodynamic settings, and petrogenesis of gold-ore-forming arc magmas
:
Centre of Exploration Targeting Quarterly Newsletter
 , June
2012
, v.
20
, p. 1,
4
12
.
Loucks
,
R.R.
,
2014
,
Distinctive composition of copper-ore-forming arc magmas
:
Australian Journal of Earth Sciences
 , v.
61
, p.
5
16
.
Lu
,
Y.
,
Loucks
,
R.R.
,
Florentini
,
M.L.
,
Yang
,
Z.
, and
Hou
,
Z.
,
2015
,
Fluid flux melting generated postcollisional high Sr/Y copper ore-forming water-rich magmas in Tibet
:
Geology
 , v.
43
, p.
583
586
.
Lu
,
Y.J.
,
Loucks
,
R.R.
,
Fiorentini
,
M.L.
,
McCuaig
,
T.C.
,
Evans
,
N.J.
,
Yang
,
Z.M.
,
Hou
,
Z.Q.
,
Kirkland
,
C.L.
,
Parra-Avila
,
L.A.
, and
Kobussen
,
A.
,
2016
,
Zircon compositions as a pathfinder for porphyry Cu ± Mo ± Au mineral deposits
:
Society of Economic Geologists, Special Publication 19
 , p.
329
348
.
Lubben
,
J.D.
,
2004
,
Silicification across the Betze-Post Carlin-type Au deposit: Clues to ore fluid properties and sources, northern Carlin trend, Nevada
: Unpublished M.S. thesis,
Las Vegas, Nevada
,
University of Nevada Las Vegas
,
156
p.
Ludington
,
S.
,
McKee
,
E.H.
,
Cox
,
D.P.
,
Moring
,
B.C.
, and
Leonard
,
K.W.
,
1996
,
Pre-Tertiary geology of Nevada
:
Nevada Bureau of Mines and Geology Open-File Report 96–2
 , p.
4.1
4.17
Ludington
,
S.
,
Folger
,
H.
,
Kotlyar
,
B.
,
Mossotti
,
V.G.
,
Coombs
,
M.J.
, and
Hildenbrand
,
T.G.
,
2006
,
Regional surface geochemistry of the northern Great Basin
:
Economic Geology
 , v.
101
, p.
33
57
.
Lund
,
K.
,
2008
,
Geometry of the Neoproterozoic and Paleozoic rift margin of western Laurentia
:
Implications for mineral deposit settings: Geosphere
 , v.
4
, p.
429
444
.
Lush
,
A.P.
,
McGrew
,
A.J.
,
Snoke
,
A.W.
, and
Wright
,
J.E.
,
1988
,
Allochthonous Archean basement in the northern East Humboldt Range, Nevada
:
Geology
 , v.
16
, p.
349
353
.
Magoon
,
L.B.
, and
Dow
,
W.G.
1994
,
The petroleum system
:
American Association of Petroleum Geologists (AAPG) Memoir
 
60
, p.
3
24
.
Maroun
,
L.R.C.
,
Cline
,
J.S.
,
Simon
,
A.
,
Anderson
,
P.
, and
Muntean
J.L.
,
2017
,
High-grade gold deposition and collapse brecciation, Cortez Hills Carlin-type gold deposit, Nevada, USA
:
Economic Geology
 , v.
112
, p.
707
740
.
Marshak
,
S.
,
Karlstrom
,
K.
, and
Timmons
,
J.M.
,
2000
,
Inversion of Proterozoic extensional faults: An explanation for the pattern of Laramide and Ancestral Rockies intracratonic deformation, United States
:
Geology
 , v.
28
, p.
735
738
.
McCuaig
,
T.C.
,
Beresford
,
S.
, and
Hronsky
,
J.
,
2010
,
Translating the mineral systems approach into an effective exploration targeting system
:
Ore Geology Reviews
 , v.
38
, p.
128
138
.
McGrew
,
A.J.
, and
Snoke
,
A.W.
,
2010
,
SHRIMP-RG U-Pb isotopic systematics of zircon from the Angel Lake orthogneiss, East Humboldt Range, Nevada
:
Is this really Archean crust?: Comment: Geosphere
 , v.
6
, p.
962
965
.
McGrew
,
A.J.
,
Peters
,
M.T.
, and
Wright
,
J.E.
,
2000
,
Thermobarometric constraints on the tectonothermal evolution of the East Humboldt Range metamorphic core complex, Nevada
:
Geological Society of America Bulletin
 , v.
112
,
45
60
.
Micklethwaite
,
S.
,
2011
,
Fault-induced damage controlling the formation of Carlin-type ore deposits
, in
Steininger
,
R.
, and
Pennell
,
B.
, eds.,
Great Basin evolution and metallogeny: Geological Society of Nevada Symposium volume
:
Reno, Nevada
,
Geological Society of Nevada
, p.
221
231
.
Micklethwaite
,
S.
,
Sheldon
,
H.A.
, and
Baker
,
T.
,
2010
,
Active fault and shear processes and their implications for mineral deposit formation and discovery
:
Journal of Structural Geology
 , v.
32
, p.
151
165
.
Miller
,
E.L.
, and
Gans
,
P.B.
,
1989
,
Cretaceous crustal structure and metamorphism in the hinterland of the Sevier thrust belt, western U.S. Cordillera
:
Geology
 , v.
17
, p.
59
62
.
Moore
,
S.
,
2002
,
Geology of the northern Carlin trend (map)
:
Nevada Bureau of Mines, Bulletin 111, plate 1, scale 1:24,000
 .
Muntean
,
J.L.
, and
Cline
,
J.S.
,
2018
,
Diversity of Carlin-style gold deposits
:
Reviews in Economic Geology
 , v.
20
, p.
1
5
.
Muntean
,
J.L.
, and
Henry
,
C.D.
,
2007
,
Preliminary geologic map of the Jerritt Canyon mining district
:
Nevada Bureau of Mines and Geology Open File Report 07–03, scale 1:24,000
 .
Muntean
,
J.L.
, and
Taufen
,
P.M.
,
2011
,
Geochemical exploration for gold through transported alluvial cover in Nevada: Examples from the Cortez mine
:
Economic Geology
 , v.
106
, p.
809
833
.
Muntean
,
J.L.
,
Coward
,
M.P.
, and
Tarnocai
,
C.A.
,
2007
,
Reactivated Palaeozoic normal faults: Controls on the formation of Carlin-type gold deposits in north-central Nevada
:
Geological Society, London
 , Special Publications, v.
272
, p.
573
589
.
Muntean
,
J.L.
,
Cassinerio
,
M.D.
,
Arehart
,
G.B.
Cline
,
J.S.
, and
Longo
,
A.A.
,
2009
,
Fluid pathways at the Turquoise Ridge Carlin-type gold deposit, Getchell district, Nevada
, in
Williams
,
P.J.
, ed.,
Smart science for exploration and mining: Proceedings of the 10th biennial meeting of the Society for Geology Applied to Mineral Deposits
:
Townsville, Australia
, p.
251
253
.
Muntean
,
J.L.
,
Cline
,
J.S.
,
Simon
,
A.C.
, and
Longo
,
A.A.
,
2011
,
Magmatichydrothermal origin of Nevada’s Carlin-type gold deposits
:
Nature Geoscience
 , v.
4
, p.
122
127
.
Muntean
,
J.L.
,
Bonner
,
W.
, and
Hill
,
T.
,
2017a
,
Carlin-style gold-silver mineralization at the Cove deposit in Nevada, USA: Possible missing link between Carlin-type gold deposits and magmatic-hydrothermal systems
, in
Mercier-Langevin
,
P.
, et al
, eds.,
Mineral resources to discover: Proceedings of the 14th biennial meeting of the Society for Geology Applied to Mineral Deposits
:
Quebec City, Canada
, p.
71
74
.
Muntean
,
J.L.
,
Dee
,
S.
,
Hill
,
T.J.
,
Hannink
,
R.L.
,
Smith
,
M.
,
Urie
,
G.
, and
Raabe
,
K.
,
2017b
,
Preliminary geologic map of the Kinsley Mountains, Elko and White Pine Counties, Nevada
:
Nevada Bureau of Mines and Geology Open-File Report 17, scale 1:12,000
 .
Muto
,
P.
,
1980
,
Geology and mineralization of the Willard mining district, Pershing County, Nevada
: Unpublished M.S. thesis,
Reno, Nevada
,
University of Nevada Reno
,
62
p.
Nolan
,
T.B.
,
1962
,
The Eureka mining district, Nevada
:
U.S. Geological Survey Professional Paper 406
 ,
78
p.
Nolan
,
T.B.
, and
Hunt
,
R.N.
,
1968
,
The Eureka mining district, Nevada
, in
Ridge
,
J.D.
, ed.,
Ore deposits of the United States
 :
New York
,
Society of Mining Engineers of the American Institute of Mining, Metallurgy, and Petroleum Engineers, Inc.
, p.
966
991
.
Nutt
,
C.J.
, and
Hofstra
,
A.H.
,
2003
,
Alligator Ridge district, east-central Nevada: Carlin-type gold mineralization at shallow depths
:
Economic Geology
 , v.
98
, p.
1225
1241
.
Nutt
,
C.J.
, and
Hofstra
,
A.H.
,
2007
,
Bald Mountain gold mining district
,
Nevada: A Jurassic reduced intrusion-related gold system
 :
Economic Geology
 , v.
102
, p.
1129
1155
.
Parry
,
W.T.
,
Wilson
,
P.N.
,
Moser
,
D.
, and
Heizler
,
M.T.
,
2001
,
U-Pb dating of zircon and 40Ar/39Ar dating of biotite at Bingham, Utah
:
Economic Geology
 , v.
96
, p.
1671
1683
.
Patterson
,
L.M.
, and
Muntean
,
J.L.
,
2011
,
Multielement geochemistry across a Carlin-type gold district: Jerritt Canyon
, Nevada, in
Steininger
,
R.C.
, and
Pennell
,
W.M.
, eds.,
Great Basin evolution and metallogeny: Geological Society of Nevada 2010 Symposium proceedings
,
Reno, Nevada
,
Geological Society of Nevada
, p.
1119
1152
.
Percival
,
T.J.
,
Hofstra
,
A.H.
,
Gibson
,
P.C.
,
Noble
,
D.C.
,
Radtke
,
A.S.
,
Bagby
,
W.C.
,
Pickthorn
,
W.J.
, and
McKee
,
E.H.
,
2018
,
Sedimentary rock-hosted gold deposits related to epizonal intrusions, Bau district, Island of Borneo, Sarawak, East Malaysia
:
Reviews in Economic Geology
 , v.
20
, p.
259
297
.
Peters
,
S.G.
,
1996
,
Definition of the Carlin trend using orientation of fold axes and application to ore control and zoning in the Central Betze ore-body, Betze-Post mine
, in
Green
,
S.M.
, and
Struhsacker
,
E.
, eds.,
Geology and ore deposits of the American Cordillera: Field trip guidebook compendium
:
Reno, Nevada
,
Geological Society of Nevada
, p.
203
240
.
Peters
,
S.G.
,
Ferdock
,
G.C.
,
Woitsekhowskaya
,
M.B.
,
Leonardson
,
R.
, and
Rahn
,
J.
,
1998
,
Oreshoot zoning in the Carlin-type Betze orebody, Gold-strike mine, Eureka County, Nevada
:
U.S. Geological Survey Open-File Report 98–620
 ,
49
p.
Pettke
,
T.
,
Oberli
,
F.
, and
Heinrich
,
C.A.
,
2010
,
The magma and metal source of giant porphyry-type ore deposits, based on lead isotope microanalyses of individual fluid inclusion
:
Earth and Planetary Science Letters
 , v.
296
, p.
267
277
.
Phinisey
,
J.D.
,
Hofstra
,
A.H.
,
Snee
,
L.W.
,
Roberts
,
T.T.
,
Dahl
,
A.R.
, and
Loranger
,
R.J.
,
1996
,
Evidence for multiple episodes of igneous and hydrothermal activity and constraints on the timing of gold mineralization, Jerritt Canyon district, Elko County, Nevada
, in
Coyner
,
A.R.
, and
Fahey
,
P.L.
, eds.,
Geology and ore deposits of the American Cordillera: Geological Society of Nevada Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
15
39
.
Poulsen
,
K.H.
,
1996
,
Carlin-type gold deposits and their potential occurrence in the Canadian Cordillera
:
Geological Survey of Canada, Current Research, Report 1996-A
 , p.
1
9
.
Premo
,
W.R.
,
Castiñeiras
,
P.
, and
Wooden
,
J.L.
,
2008
,
SHRIMP-RG U-Pb isotopic systematics of zircon from the Angel Lake orthogneiss, East Humboldt Range, Nevada: Is this really Archean crust?
:
Geosphere
 , v.
4
, p.
963
975
.
Premo
,
W.R.
,
Castiñeiras
,
P
, and
Wooden
,
J.L.
,
2010
,
SHRIMP-RG U-Pb isotopic systematics of zircon from the Angel Lake orthogneiss, East Humboldt Range, Nevada: Is this really Archean crust?
:
Reply: Geosphere
 , v.
6
, p.
966
972
.
Presnell
,
R.D.
, and
Parry
,
W.T.
,
1996
,
Geology and geochemistry of the Barneys Canyon gold deposit, Utah
:
Economic Geology
 , v.
91
, p.
273
288
.
Reich
,
M.
,
Kesler
,
S.E.
,
Utsunoyiya
,
S.
,
Palenik
,
C.S.
,
Chryssoulis
,
S.
, and
Ewing
,
R.C.
,
2005
,
Solubility of gold in arsenian pyrite
:
Geochimica et Cosmochimica Acta
 , v.
69
, p.
2781
2796
.
Ressel
,
M.W.
, and
Henry
,
C.D.
,
2006
,
Igneous geology of the Carlin trend, Nevada: Development of the Eocene plutonic complex and significance for Carlin-type gold deposits
:
Economic Geology
 , v.
101
, p.
347
383
.
Ressel
,
M.W.
,
Noble
,
D.C.
,
Henry
,
C.D.
, and
Trudel
,
W.S.
,
2000
,
Dike-hosted ores of the Beast deposit and the importance of Eocene magmatism in gold mineralization of the Carlin trend, Nevada
:
Economic Geology
 , v.
95
, p.
1417
1444
.
Ressel
,
M.W.
,
Dendas
,
M.
,
Lujan
,
R.
,
Essman
,
J.
, and
Shumway
,
P.J.
,
2015
,
Shallow expressions of Carlin-type hydrothermal systems: An example from the Emigrant mine, Carlin trend, Nevada
, in
Pennell
,
W.M.
, and
Garside
,
L.J.
, eds.,
New concepts and discoveries: Geological Society of Nevada 2015 Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
409
433
.
Rhys
,
D.
,
Valli
,
F.
,
Burgess
,
R.
,
Heitt
,
D.
,
Griesel
,
G.
, and
Hart
,
K.
,
2015
,
Controls on fault and fold geometry on the distribution of gold mineralization on the Carlin trend
, in
Pennell
,
W.M.
, and
Garside
,
L.J.
, eds.,
New concepts and discoveries: Geological Society of Nevada 2015 Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
333
389
.
Richards
,
J.P.
,
2011
,
Magmatic to hydrothermal metal fluxes in convergent and collided margins
:
Ore Geology Reviews
 , v.
40
, p.
1
26
.
Ronkos
,
C.J.
,
1986
,
Geology and interpretation of the geochemistry at the Standard mine, Humboldt County, Nevada
:
Journal of Geochemical Exploration
 , v.
25
, p.
129
137
.
Rye
,
R.O.
,
Doe
,
B.R.
, and
Well
,
J.D.
,
1974
,
Stable isotope and lead isotope study of the Cortez, Nevada, gold deposit and surrounding area
:
U.S. Geological Survey Journal of Geological Research
 , v.
2
, p.
13
23
.
Samal
,
A.R.
,
2007
,
Genetic and exploration models for the Florida Canyon gold deposit, Nevada: Integrating geological, geochemical, GIS, remote sensing, geostatistical, and statistical data analysis
: Unpublished Ph.D. thesis,
Fairchild Air Force Base
 ,
Washington
,
Southern Illinois University
,
137
p.
Seedorff
,
E.
,
1991
,
Magmatism, extension, and ore deposits of Eocene to Holocene age in the Great Basin—mutual effects and preliminary proposed genetic relationships
, in
Raines
,
G.L.
,
Lisle
,
R.E.
,
Schafer
,
R.W.
, and
Wilkinson
,
W.H.
, eds.,
Geology and ore deposits of the Great Basin; Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
133
178
.
Seedorff
,
E.
, and
Barton
,
M.D.
,
2005
,
Controversies on the origin of world-class gold deposits, part III: Enigmatic origin of Carlin-type deposits: An amagmatic solution?
:
Society of Economic Geologists Newsletter
 , v.
59
, p.
14
16
.
Shigehiro
,
M.
,
1999
,
Mineral paragenesis and ore fluids at the Turquoise Ridge gold deposit, Nevada
: Unpublished M.Sc. thesis,
Las Vegas, Nevada
,
University of Nevada
,
152
p.
Sillitoe
,
R.H.
,
2008
,
Major gold deposits and belts of the North and South American Cordillera: Distribution, tectonomagmatic settings, and metallogenic considerations
:
Economic Geology
 , v.
103
, p.
663
687
.
Sillitoe
,
R.H.
, and
Bonham
,
H.F.
,
1990
,
Sediment-hosted gold deposits
:
Distal products of magmatic-hydrothermal systems, Geology
 , v.
18
, p.
157
161
.
Simon
,
G.
,
Kesler
,
S.E.
, and
Chrysoulis
,
S.
,
1999
,
Geochemistry and textures of gold-bearing arsenian pyrite, Twin Creeks, Nevada; implications for deposition of gold in Carlin-type deposits
:
Economic Geology
 , v.
94
, p.
405
422
.
Smith
,
M.R.
,
Wilson
,
W.R.
,
Benham
,
J.A.
,
Pescio
,
C.A.
, and
Valenti
,
P.
,
1988
,
The Star Pointer gold deposit, Robinson mining district, White Pine County, Nevada
, in
Schafer
,
R.W.
,
Cooper
,
J.J.
, and
Vikre
,
P.G.
, eds.,
Bulk mineable precious metal deposits of the western United States: Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
221
231
.
Smith
,
M.T.
, and
Cook
,
H.E.
,
2018
,
Carlin on the shelf? A review of sedimentary rock-hosted gold deposits and their settings in the eastern Great Basin, USA
:
Reviews in Economic Geology
 , v.
20
, p.
89
120
.
Smith
,
M.T.
,
Rhys
,
D.
,
Ross
,
K.
,
Lee
,
C.
, and
Gray
,
J.N.
,
2013
,
The Long Canyon deposit: Anatomy of a new off-trend sedimentary rock-hosted gold discovery in northeastern Nevada
:
Economic Geology
 , v.
108
, p.
1119
1145
.
Smith
,
S.G.
,
Olberg
,
D.
, and
Manini
,
A.J.
,
2005
,
The Sepon gold deposits, Laos: Exploration, geology, and comparison to Carlin-type gold deposits
, in
Rhoden
,
H.N.
,
Steininger
,
R.C.
, and
Vikre
,
P.G.
, eds.,
Window to the world: Geological Society of Nevada Symposium 2005
:
Reno, Nevada
,
Geological Society of Nevada
, p.
899
915
.
Stenger
,
D.P.
,
Kesler
,
S.E.
,
Peltonen
,
D.R.
, and
Tapper
,
C.J.
,
1998
,
Deposition of gold in Carlin-type deposits; the role of sulfidation and decarbonation at Twin Creeks, Nevada
:
Economic Geology
  v.
93
, p.
201
215
.
Stewart
,
J.H.
,
1991
,
Latest Proterozoic and Cambrian rocks of the western United States—an overview
:
Pacific Section Society for Sedimentary Geology (SEPM)
 , v.
67
, p.
13
38
.
Stewart
,
J.H.
,
1996
,
Regional characteristics, tilt domains, and extensional history of the late Cenozoic Basin and Range province, western North America
:
Geological Society of America, Special Paper 323
 , p.
47
74
.
Strmić Palinkaš
,
S.
,
Hofstra
,
A.H.
,
Percival
,
T.J.
,
Borojević Šoštarić
,
S.
,
Palinkaš
,
L.
Bermanec
,
V.
,
Pecskay
,
Z.
, and
Boev
,
B.
,
2018
,
Comparison of the Allchar Au-As-Sb-Tl deposit, Republic of Macedonia, with Carlin-type gold deposits
:
Reviews in Economic Geology
 , v.
20
, p.
335
363
.
Su
,
W.
,
Heinrich
,
C.A.
,
Pettke
,
T.
,
Zhang
,
X.
,
Hu
,
R.
, and
Xia
,
B.
,
2009
,
Sediment-hosted gold deposits in Guizhou, China: Products of wall-rock sulfidation by deep crustal fluids
:
Economic Geology
 , v.
104
, p.
73
93
.
Su
,
W.C.
,
Dong
,
W.D.
,
Zhang
,
X.C.
,
Shen
,
N.P.
,
Hu
,
R.Z.
,
Hofstra
,
A.H.
,
Cheng
,
L.Z.
,
Xia
,
Y.
, and
Yong
,
K.Y.
,
2018
,
Carlin-type gold deposits in the Dian-Qian-Gui “Golden Triangle” of southwest China
:
Reviews in Economic Geology
 , v.
20
, p.
157
185
.
Tapper
,
C.J.
,
1986
,
Geology and genesis of the Alligator Ridge mine, White Pine County, Nevada
:
Nevada Bureau of Mines and Geology
 , Report 40, p
85
103
.
Taylor
,
B.E.
,
1992
,
Degassing of H2O from rhyolite magma during eruption and shallow intrusion, and the isotopic composition of magmatic water in hydrothermal systems
:
Geological Survey of Japan
 , Report
279
, p.
190
194
.
Theodore
,
T.G.
,
2000
,
Geology of pluton-related gold mineralization at Battle Mountain, Nevada: Monographs in mineral resource science
, no.
2
:
Tucson, Arizona
,
Center for Mineral Resources
,
271
p.
Thompson
,
J.F.H.
,
Gale
,
V.G.
,
Tosdal
,
R.M.
, and
Wright
,
W.A.
,
2004
,
Characteristics and formation of the Jerónimo carbonate-replacement gold deposit, Potrerillos district, Chile
:
Society of Economic Geologists, Special Publication 11
 , p.
75
97
.
Timmons
,
J.M.
,
Karlstrom
,
K.E.
,
Dehler
,
C.M.
,
Geissman
,
J.W.
, and
Heizler
,
M.T.
,
2001
,
Proterozoic multistage (ca. 1.1 and 0.8 Ga) extension recorded in the Grand Canyon Supergroup and establishment of northwest- and north-trending tectonic grains in the southwestern United States
:
Geological Society of America Bulletin
 , v.
113
, p.
163
190
.
Tosdal
,
R.M.
,
Wooden
,
J.L.
, and
Kistler
,
R.W.
,
2000
,
Inheritance of Nevadan mineral belts from Neoproterozoic continental breakup
, in
Cluer
,
J.K.
,
Price
,
J.G.
,
Struhsacker
,
E.M.
,
Hardyman
,
R.F.
, and
Morris
,
C.L.
, eds.,
Geology and ore deposits 2000: The Great Basin and beyond: Geological Society of Nevada Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
451
466
.
Tosdal
,
R.M.
,
Cline
,
J.S.
,
Fanning
,
C.M.
, and
Wooden
,
J.L.
,
2003
,
Lead in the Getchell-Turquoise Ridge Carlin-type gold deposits from the perspective of potential igneous and sedimentary rock sources in northern Nevada: Implications for fluid and metal sources
:
Economic Geology
 , v.
98
, p.
1189
1211
.
Tretbar
,
D.R.
,
2004
,
The geology and geochemistry of the 194 orebody, Getchell mine, Humboldt County, Nevada
: Unpublished M.Sc. thesis,
Reno, Nevada
,
University of Nevada
,
216
p.
Tucker
,
M.J.
,
Lane
,
J.C.
, and
Hart
,
C.J.R.
,
2018
,
Overview of Carlin-type prospects of the Nadaleen trend: A Yukon analogue to Carlin-type gold mineralization of the Great Basin
:
Reviews in Economic Geology
 , v.
20
, p.
235
258
.
Turner
,
S.J.
,
Flindell
,
P.A.
,
Hendri
,
D.
,
Hardjana
,
I.
,
Lauricella
,
P.F.
,
Lindsay
,
R.P.
,
Marpaung
,
B.
, and
White
,
G.P.
,
1994
,
Sediment-hosted gold mineralization in the Ratatotok district, north Sulawesi, Indonesia
:
Journal of Geochemical Exploration
 , v.
50
, p.
317
336
.
Vaughan
,
J.R.
,
Hickey
,
K.A.
, and
Barker
,
S.L.L.
,
2016
,
Isotopic, chemical, and textural evidence for pervasive calcite dissolution and precipitation accompanying hydrothermal fluid flow in low-temperature, carbonate-hosted gold systems
:
Economic Geology
 , v.
111
, p.
1127
1157
.
Vikre
,
P.G.
,
1998
,
Intrusion-related, polymetallic carbonate replacement deposits in the Eureka district, Eureka County, Nevada
:
Nevada Bureau of Mines and Geology Bulletin
 , v.
110
,
52
p.
Vikre
,
P.G.
,
Poulson
,
S.R.
, and
Koenig
,
A.E.
,
2011
,
Derivation of S and Pb in Phanerozoic intrusion-related metal deposits from Neoproterozoic sedimentary pyrite, Great Basin, United States
:
Economic Geology
 , v.
106
, p.
883
912
.
Wallace
,
A.R.
,
1989
,
The Relief Canyon gold deposit
,
Nevada; a mineralized solution breccia
 :
Economic Geology
 , v.
84
, p.
279
290
.
Wells
,
J.D.
, and
Mullens
,
T.E.
,
1973
,
Gold-bearing arsenian pyrite determined by microprobe analysis, Cortez and Carlin gold mines, Nevada
:
Economic Geology
 , v.
68
, p.
187
201
.
Westra
,
G.
, and
Reidell
,
K.B.
,
1996
,
Geology of the Mount Hope stockwork molybdenum deposit, Eureka County, Nevada
, in
Coyner
,
A.R.
, and
Fahey
,
P.L.
, eds.,
Geology and ore deposits of the American Cordillera: Geological Society of Nevada Symposium
:
Reno, Nevada
,
Geological Society of Nevada
, p.
1639
1666
.
Whitmeyer
,
S.J.
, and
Karlstrom
,
K.E.
,
2007
,
Tectonic model for the Proterozoic growth of North America
:
Geosphere
 , v.
3
, p.
220
259
.
Widler
,
A.M.
, and
Seward
,
T.M.
,
2002
,
The adsorption of gold(I) hydrosulphide complexes by iron sulphide surfaces
:
Geochimica et Cosmochimica Acta
 , v.
66
, p.
383
402
.
Williams
,
G.D.
,
Powell
,
C.M.
, and
Cooper
,
M.A.
,
1989
,
Geometry and kinematics of inversion tectonics
:
Geological Society, London
 , Special Publications, v.
44
, p.
3
15
.
Wilson
,
W.L.
, and
Wilson
,
W.B.
,
1986
,
Geology of the Eureka-Windfall and Rustler gold deposits, Eureka County, Nevada
:
Nevada Bureau of Mines and Geology, Report 40
 , p.
81
83
.
Wright
,
J.L.
, and
Lide
,
C.S.
,
1998
,
Geophysical exploration for gold in northern Nevada
, in
Practical geophysical short course: 104th Northwest Miners Association Meeting
:
Spokane, Washington
,
85
p.
Yonkee
,
W.A.
,
Dehler
,
C.D.
,
Link
,
P.K.
,
Balgord
,
E.A.
,
Keely
,
J.A.
,
Hayes
,
D.S.
,
Wells
,
M.L.
,
Fanning
,
C.M.
, and
Johnston
,
S.M.
,
2014
,
Tectono-stratigraphic framework of Neoproterozoic to Cambrian strata, west-central U.S.: Protracted rifting, glaciation, and evolution of the North American Cordilleran margin
:
Earth-Science Reviews
 , v.
136
, p.
59
95
.
Zajacz
,
A.
,
Candela
,
P.A.
,
Piccoli
,
P.M.
,
Walle
,
M.
, and
Sanchez-Valle
,
C.
,
2012
,
Gold and copper in volatile saturated mafic to intermediate magmas: Solubilities, partitioning, and implications for ore deposit formation
:
Geochimica et Cosmochimica Acta
 , v.
91
, p.
140
159
.

REFERENCES

Albino
,
G.V.
, and
Boyer
,
C.I.
,
1992
,
Lithologic and structural controls of gold deposits of the Santa Fe district, Mineral County, Nevada
, in
Craig
,
S.D.
, ed.,
Structure, tectonics, and mineralization of the Walker Lane, Geological Society of Nevada Walker Lane Symposium proceedings volume
:
Reno, Nevada
,
Geological Society of Nevada
, p.
187
211
.
Alfaro
,
J.C.
,
Corcoran
,
C.
,
Davies
,
K.
,
Pineda
,
F.G.
,
Hampson
,
G.
,
Hill
,
D.
, and
Kragh
,
E.
,
2007
,
Reducing exploration risk: Oilfield Review, v
.
19
, p.
26
43
.
Alvarez
,
A.
, and
Noble
,
D.C.
,
1988
,
Sedimentary rock-hosted disseminated precious metal mineralization at Purisima Concepcion
,
Yaricocha district, central Peru: Economic Geology
 , v.
83
, p.
1368
1378
.
Arehart
,
G.B.
, and
Donelick
,
R.A.
,
2006
,
Thermal and isotopic profiling of the Pipeline hydrothermal system: Application to exploration for Carlin-type gold deposits
:
Journal of Geochemical Exploration
 , p.
27
40
.
Arehart
,
G.B.
,
Kesler
,
S.E.
,
O’Neil
,
J.R.
, and
Foland
,
K.A.
,
1992
,
Evidence for the supergene origin of alunite in sediment-hosted micron gold deposits
,
Nevada: Economic Geology
 , v.
87
, p.
263
270
.
Arehart
,
G.B.
,
Chakurian
,
A.M.
,
Tretbar
,
D.R.
,
Christensen
,
J.N.
,
McInnes
,
B.A.
, and
Donelick
,
R.A.
,
2003
,
Evaluation of radioisotope dating of Carlin-type deposits in the Great Basin, western North America, and implications for deposit genesis
:
Economic Geology
 , v.
98
, p.
235
248
.
Arehart
,
G.B.
,
Ressel
,
M.
,
Carne
,
R.
, and
Muntean
,
J.
,
2013
,
A comparison of Carlin-type deposits in Nevada and Yukon: Society of Economic Geologists
,
Special Publication
 
17
, p.
389
401
.
Armstrong
,
A.K.
,
Theodore
,
T.G.
,
Oscarson
,
R.L.
,
Kotlyar
,
B.B.
,
Harris
,
A.G.
,
Bettles
,
K.H.
,
Lauha
,
E.A.
,
Hipsley
,
R.A.
,
Griffin
,
G.L.
,
Abbott
,
E.W.
, and
Cluer
,
J.K.
,
1998
,
Preliminary facies analysis of Silurian and Devonian autochthonous rocks that host gold along the Carlin trend, Nevada
:
U.S. Geological Survey Open-File Report 98–338
 , p.
38
68
.
Babcock
,
R.S.
, Jr.,
Ballantyne
,
G.H.
, and
Phillips
,
C.H.
,
1997
,
Summary of the geology of the Bingham district
,
Utah: Society of Economic Geologists Guidebook Series
 , v.
29
, p.
113
132
.
Bakken
,
B.M.
,
1990
,
Gold mineralization, wall-rock alteration, and the geochemical evolution of the hydrothermal system in the main orebody, Carlin Mine, Nevada
: Unpublished Ph.D. thesis,
Stanford, California
,
Stanford University
,
236
p.
Barker
,
S.L.L.
,
Dipple
,
G.M.
,
Hickey
,
K.A.
,
Lepore
,
W.A.
, and
Vaughan
,
J.R.
,
2013
,
Applying stable isotopes to mineral exploration: Teaching an old dog new tricks
:
Economic Geology
 , v.
108
, p.
1
9
.
Barton
,
M.D.
,
Seedorff
,
E.
,
Ilchik
,
R.P.
, and
Ghidotti
,
G.
,
1997
,
Contrasting siliceous replacement mineralization, east-central Nevada
:
Society of Economic Geologists Guidebook Series
 , v.
28
. p.
131
135
.
Berger
,
B.R.
, and
Taylor
,
B.E.
,
1980
,
Pre-Cenozoic normal faulting in the Osgood Mountains
,
Humboldt County, Nevada: Geology
 , v.
8
, p.
594
598
.
Berger
,
V.I.
,
Mosier
,
D.L.
,
Bliss
,
J.D.
, and
Moring
,
B.C.
,
2014
,
Sediment-hosted gold deposits of the world—database and grade and tonnage models
:
U.S. Geological Survey Open-File Report 2014–1074
 ,
51
p.
Bettles
,
K.
,
2002
,
Exploration and geology, 1962 to 2002, at the Goldstrike property
,
Carlin trend, Nevada: Society of Economic Geologists, Special Publication
 
9
, p.
275
298
.
Beyssac
,
O.
,
Goffe
,
B.
,
Chopin
,
C.
, and
Rouzaud
,
J.N.
,
2002
,
Raman spectra of carbonaceous material in metasediments: A new geothermometer
:
Journal of Metamorphic Petrology
 , v.
20
, p.
859
871
.
Bloomstein
,
E.I.
,
Braginton
,
B.L.
,
Owen
,
R.W.
,
Parratt
,
R.L.
,
Raabe
,
K.C.
, and
Thompson
,
W.F.
,
2000
,
Lone Tree gold deposit
, in
Theodore
,
T.G.
,
Geology of pluton-related gold mineralization at Battle Mountain, Nevada: Monographs in mineral resource science, no. 2: Tucson, Arizona, Center for Mineral Resources
 ,
271
p.
Boskie
,
R.M.
, and
Schweikert
,
R.A.
,
2001
,
Structure and stratigraphy of lower Paleozoic rocks of the Getchell trend
,
Osgood Mountains, Humboldt County, Nevada: Geological Society of Nevada, Special Publication
 
33
, p.
263
293
.
Brandon
,
M.T.
,
Roden-Tice
,
M.K.
, and
Garver
,
J.I.
,
1998
,
Late Cenozoic exhumation of the Cascadia accretionary wedge in the Olympic Mountains, northwest Washington State
:
Geological Society of America Bulletin
 , v.
110
, p.
985
1009
.
Cassinerio
,
M.D.
, and
Muntean
,
J.L.
,
2011
,
Patterns of lithology, structure, alteration, and trace elements around high-grade ore zones at the Turquoise Ridge gold deposit, Getchell district, Nevada
, in
Steininger
,
R.C.
, and
Pennell
,
W.M.
, eds.,
Great Basin evolution and metallogeny: 2010 symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
949
978
.
Cline
,
J.S.
,
2018
,
Nevada’s Carlin-type gold deposits: What we’ve learned during the past 10 to 15 years
:
Reviews in Economic Geology
 , v.
20
, p.
7
37
.
Castor
,
S.B.
, and
Hulen
,
J.B
,
1996
,
Electrum and organic matter at the Gold Point mine, Currant mining district, Nevada
, in
Coyner
,
A.R.
, and
Fahey
,
P.L.
, eds.,
Geology and ore deposits of the American Cordillera: Symposium proceedings
 :
Reno, Nevada
,
Geological Society of Nevada
, p.
547
565
.
Cline
,
J.S.
,
2001
,
Timing of gold and arsenic sulfide mineral deposition at the Getchell Carlin-type gold deposit, north-central Nevada
:
Economic Geology
 , v.
96
, p.
75
89
.
Cline
,
J.S.
, and
Hofstra
,
A.H.
,
2000
,
Ore fluid evolution at the Getchell Carlin-type gold deposit
,
Nevada, USA: European Journal of Mineralogy
 , v.
12
, p.
195
212
.
Cline
,
J.S.
,
Stuart
,
F.M.
,
Hofstra
,
A.H.
,
Premo
,
W.
,
Riciputi
,
L.
,
Tosdal
,
R.M.
, and
Tretbar
,
D.R.
,
2003
,
Multiple sources of ore fluid components at the Getchell Carlin-type gold deposit, Nevada, USA
, in
Eliopoulos
,
D.
, et al
, eds.,
Mineral exploration and sustainable development
 , v.
2
:
Rotterdam
,
Millpress
, p.
965
968
.
Cline
,
J.S.
,
Hofstra
,
A.H.
,
Muntean
,
J.L.
,
Tosdal
,
R.M.
, and
Hickey
,
K.A.
,
2005
,
Carlin-type gold deposits in Nevada, USA
:
Economic Geology 100th Anniversary Volume
 , p.
451
484
.
Cline
,
J.S.
,
Muntean
,
J.L.
,
Gu
,
X.
, and
Xia
,
Y.
,
2013
,
A comparison of Carlin-type gold deposits: Guizhou Province, Golden Triangle, southwest China, and northern Nevada, USA
:
Earth Science Frontiers
 , v.
20
, p.
1
18
.
Colgan
,
J.P
,
John
,
D.A.
,
Henry
,
C.D.
, and
Fleck
,
R.J.
,
2008
,
Large-magnitude Miocene extension of the Eocene Caetano caldera, Shoshone and Toiyabe Ranges, Nevada
:
Geosphere
 , v.
4
, p.
107
130
.
Colgan
,
J.P
,
Henry
,
C.D.
, and
John
,
D.A.
,
2014
,
Evidence for large-magnitude, post-Eocene extension in the northern Shoshone Range, Nevada, and its implications for the structural setting of Carlin-type gold deposits in the lower plate of the Roberts Mountains allochthon
:
Economic Geology
 , v.
109
, p.
1843
1862
.
Conelea
,
R.
, and
Howald
,
W.C.
,
2009
,
The geology and gold-silver mineralization of the Wilco project, Willard mining district, Pershing County, Nevada
:
Geological Society of Nevada, Special Publication 49
 , p.
92
108
.
Coney
,
P.J.
, and
Reynolds
,
S.J.
,
1977
,
Cordilleran Benioff zones
:
Nature
 , v.
270
, p.
403
406
.
Cook
,
H.E.
,
2015
,
The evolution and relationship of the western North America Paleozoic carbonate platform and basinal depositional environments to Carlin-type gold deposits in the context of the carbonate sequence stratigraphy
, in
Pennell
,
W.M.
and
Garside
,
L.J.
, eds.,
New concepts and discoveries: Geological Society of Nevada 2015 Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
1
80
.
Cook
,
H.E.
, and
Corboy
,
J.C.
,
2004
,
Great Basin Paleozoic carbonate platform: Facies, facies transitions, depositional models, platform architecture, sequence stratigraphy, and predictive mineral host models
:
U.S. Geological Survey Open-File Report 2004–1078
 ,
129
p.
Cook
,
H.E.
, and
Taylor
,
M.E.
,
1977
,
Comparison of continental slope and shelf environments in the Upper Cambrian and lowest Ordovician of Nevada
:
Society of Sedimentary Geologists (SEPM), Special Publication 25
 , p.
51
81
.
Coward
,
M.
,
1994
,
Inversion tectonics
, in
Hancock
,
P.L.
, ed.,
Continental deformation
 ,
Oxford
,
Permagon Press
, p.
289
304
.
Cox
,
D.P
,
1992
,
Descriptive model of distal disseminated Ag-Au deposits
:
U.S. Geological Survey Bulletin
 
2004
, p.
19
.
Cox
,
D.P.
, and
Singer
,
D.A.
,
1992
,
Grade and tonnage model of distal disseminated Ag-Au
:
U.S. Geological Survey Bulletin
 
2004
, p.
20
22
.
Crafford
,
A.E.J.
, and
Grauch
,
V.J.S.
,
2002
,
Geologic and geophysical evidence for the influence of deep crustal structures on Paleozoic tectonics and the alignment of world-class gold deposits, north central Nevada, USA
:
Ore Geology Reviews
 , v.
21
, p.
157
184
.
Cunningham
,
C.G.
,
Austin
,
G.W.
,
Naeser
,
C.W.
,
Rye
,
R.O.
,
Ballantyne
,
G.H.
,
Stamm
,
R.G.
, and
Barker
,
C.E.
,
2004
,
Formation of paleothermal anomaly and disseminated gold deposits associated with the Bingham Canyon porphyry Cu-Au-Mo system, Utah
:
Economic Geology
 , v.
99
, p.
789
806
.
Daliran
,
F.
,
Hofstra
,
A.
,
Walther
,
J.
, and
Topa
,
D.
,
2018
,
Ore genesis constraints on the Agdarreh and Zarshouran Carlin-style gold deposits in the Takab region of northwestern Iran
:
Reviews in Economic Geology
 , v.
20
, p.
299
333
.
Davis
,
D.A.
, and
Muntean
,
J.L.
,
2017
,
Metals
:
Nevada Bureau of Mines and Geology, Special Publication MI-2015
 , p.
14
109
.
Deditius
,
A.P.
,
Utsunomiya
,
S.
,
Ewing
,
R.C.
,
Chryssoulis
,
S.L.
,
Venter
,
D.
, and
Kesler
,
S.E.
,
2009
,
Decoupled geochemical behavior of As and Cu in hydrothermal systems
:
Geology
 , v.
37
, p.
707
710
.
Deditus
,
A.P.
,
Reich
,
M.
,
Kesler
,
S.E.
,
Utsonomiya
,
S.
,
Chryssoulis
,
S.L.
,
Walshe
,
J.
, and
Ewing
,
R.C.
,
2014
,
The coupled geochemistry of Au and As in pyrite from hydrothermal ore deposits
:
Geochimica et Cosmochimica Acta
 , v.
140
, p.
644
670
.
Dewitt
,
A.B.
,
2001
,
Structural architecture of the Jerritt Canyon district and gold deposits
:
Geological Society of Nevada, Special Publication 33
 , p.
135
145
.
Di Fiori
,
R.V.
,
Long
,
S.P.
,
Muntean
,
J.L.
, and
Edmondo
,
G.P.
,
2015
,
Structural analysis of gold mineralization in the southern Eureka mining district, Eureka County, Nevada: A predictive structural setting for Carlin-type mineralization
, in
Pennell
,
W.M.
, and
Garside
,
L.J.
, eds.,
New concepts and discoveries: Geological Society of Nevada 2015 Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
885
903
.
Dilles
,
J.H.
,
Kent
,
A.J.R.
,
Wooden
,
J.L.
,
Tosdal
,
R.M.
,
Koleszar
,
A.
,
Lee
,
R.G.
, and
Farmer
,
L.P.
,
2015
,
Zircon compositional evidence for sulfur-degassing from ore-forming arc magmas
:
Economic Geology
 , v.
110
, p.
241
251
.
Dilles
,
P.A.
,
Wright
,
W.A.
,
Monteleone
,
S.A.
,
Russell
,
K.D.
,
Marlowe
,
K.E.
,
Wood
,
R.A.
, and
Margolis
,
J.
,
1996
,
The geology of the West Archimedes deposit: A new gold discovery in the Eureka mining district, Eureka County, Nevada
, in
Coyner
,
A.R.
, and
Fahey
,
P.L.
, eds.,
Geology and ore deposits of the American Cordillera: Geological Society of Nevada Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
159
171
.
Dobson
,
P.F.
,
Epstein
,
S.
, and
Stolper
,
E.M.
,
1989
,
Hydrogen isotope fractionation between coexisting vapor and silicate glasses and melts at low pressure
:
Geochimica et Cosmochimica Acta
 , v.
53
, p.
2723
2730
.
Duebendorfer
,
E.M.
, and
Houston
,
R.S.
,
1986
,
Kinematic history of the Cheyenne belt
,
Medicine Bow Mountains, southeastern Wyoming (USA)
 :
Geology
 , v.
14
, p.
171
174
.
Einaudi
,
M.T.
,
1982
,
Description of skarns associated with porphyry copper plutons, southwestern North America
, in
Titley
,
S.R.
, ed.,
Advances in the geology of porphyry copper deposits in southwestern North America
:
Tucson, Arizona
,
University of Arizona Press
, p.
139
184
.
Eliason
,
R.
, and
Kantor
,
J.A.
,
1998
,
Geology of the SSX deposit
:
Geological Society of Nevada
 , Special Publication
28
, p.
170
.
Eliason
,
R.
, and
Wilton
,
D.T.
,
2005
,
Relation of gold mineralization to structure in the Jerritt Canyon mining district: Nevada
, in
Rhoden
,
H.N.
,
Steininger
,
R.C.
, and
Vikre
,
P.G.
, eds.,
Window to the world: 2005 symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
335
356
.
Emsbo
,
P.
,
1993
,
Geology and geochemistry of the Ordovician Vinini Formation, Roberts Mountains, Nevada
: Unpublished M.S. thesis,
Golden, Colorado
,
Colorado School of Mines
,
290
p.
Emsbo
,
P.
,
1999
,
Origin of the Meikle high-grade gold deposit from the superposition of Late Devonian Sedex and mid-Tertiary Carlin-type gold mineralization
: Unpublished Ph.D. thesis,
Golden, Colorado
,
Colorado School of Mines
,
394
p.
Emsbo
,
P.
,
Hutchinson
,
R.W.
,
Hofstra
,
A.H.
,
Volk
,
J.A.
,
Bettles
,
K.H.
,
Baschuk
,
G.J.
,
Collins
,
T.M.
,
Lauha
,
E.A.
, and
Borhauer
,
J.L.
,
1998
,
Syngenetic Au on the Carlin trend: Implications for Carlin-type gold deposits
:
Geology
 , v.
27
, p.
59
62
.
Emsbo
,
P.
,
Hofstra
,
A.H.
,
Lauha
,
E.A.
,
Griffin
,
G.L.
, and
Hutchinson
,
R.W.
,
2003
,
Origin of high-grade gold ore, source of ore fluid components, and genesis of the Meikle and neighboring Carlin-type deposits, northern Carlin trend, Nevada
:
Economic Geology
 , v.
98
, p.
1069
1105
.
Emsbo
,
P.
,
Groves
,
D.I.
,
Hofstra
,
A.H.
, and
Bierlein
,
F.P.
,
2006
,
The giant Carlin gold province: A protracted interplay of orogenic, basinal, and hydrothermal processes above a lithospheric boundary
:
Mineralium Deposita
 , v.
41
, p.
517
525
.
Engebretson
,
D.C.
,
Cox
,
A.
, and
Gordon
,
R.G.
,
1985
,
Relative motions between oceanic and continental plates in the Pacific basin
:
Geological Society of America, Special Paper 206
 ,
59
p.
Epstein
,
A.G.
,
Epstein
,
J.B.
, and
Harris
,
L.D.
,
1977
,
Conodont color alteration: An index to organic metamorphism
:
U.S. Geological Survey Professional Paper 995
 ,
27
p.
Evans
,
D.C.
,
2000
,
Carbonate-hosted breccias in the Meikle mine, Nevada, and their relationship with gold mineralization
: Unpublished M.S. thesis,
Golden, Colorado
,
Colorado School of Mines
,
266
p.
Evans
,
J.G.
, and
Theodore
,
T.G.
,
1978
,
Deformation of the Roberts Mountains allochthon in north-central Nevada
:
U.S. Geological Survey Professional Paper 1060
 ,
18
p.
Faulds
,
J.E.
, and
Hinz
,
N.H.
,
2015
,
Favorable tectonic and structural settings of geothermal systems in the Great Basin region, western USA
:
Proxies for discovering blind geothermal systems
 :
World Geothermal Congress, Melbourne, Australia, April 19–25, 2015, Proceedings
,
6
p.
Faulds
,
J.E.
, and
Varga
,
R.J.
,
1996
,
The role of accommodation zones and transfer zones in the regional segmentation of extended terranes: Geological Society of America
,
Special Paper 323
 , p.
1
46
.
Ferry
,
J.M.
,
1981
,
Petrology of graphitic sulfide-rich schist from south-central Maine: An example of desulfidation during prograde regional metamorphism
:
American Mineralogist
 , v.
66
, p.
908
931
.
Fifarek
,
R.H.
,
Prihar
,
D.W.
,
Hillesland
,
L.L.
,
Casaceli
,
R.J.
,
Dilles
,
P.A.
, and
Miggins
,
D.O.
,
2015
,
Tectonostratigraphic framework and timing of mineralization at the Relief Canyon mine, Pershing County, Nevada
, in
Pennell
,
W.M.
, and
Garside
,
L.J.
, eds.:
New concepts and discoveries: Geological Society of Nevada 2015 Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
453
482
.
Flanigan
,
B.
,
Freeman
,
C.
,
Newberry
,
R.
,
McCoy
,
D.
, and
Hart
,
C.
,
2000
,
Exploration models for mid and Late Cretaceous intrusion-related gold deposits in Alaska and the Yukon Territory, Canada
, in
Cluer
,
J.K.
,
Price
,
J.G.
,
Struhsacker
,
E.M.
, et al
, eds.,
Geology and ore deposits 2000: The Great Basin and beyond symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
591
614
.
Fortuna
,
J.
,
Kesler
,
S.E.
, and
Stenger
,
D.P.
,
2003
,
Source of iron for sulfidation and gold deposition, Twin Creeks Carlin-type deposit, Nevada
:
Economic Geology
 , v.
98
, p.
1213
1224
.
Foster
,
D.A.
,
Mueller
,
P.A.
,
Mogk
,
D.W.
,
Wooden
,
J.L.
, and
Vogl
,
J.J.
,
2006
,
Proterozoic evolution of the western margin of the Wyoming craton
:
Implications for the tectonic and magmatic evolution of the northern Rocky Mountains: Canadian Journal of Earth Sciences
 , v.
43
, p.
1601
1619
.
Furley
,
R.A.
,
2001
,
Sequence stratigraphic framework for the Silurian-Devonian Bootstrap Limestone, Roberts Mountains, and Devonian Popovich Formations, northern Carlin trend, Elko and Eureka Counties, Nevada
: Unpublished M.Sc. thesis,
Golden, Colorado
,
Colorado School of Mines
,
197
p.
Gans
,
P.B.
,
Seedorff
,
E.
,
Fahey
,
P.L.
,
Hasler
,
R.W.
,
Maher
,
D.J.
,
Jeanne
,
R.A.
, and
Shaver
,
S.A.
,
2001
,
Rapid Eocene extension in the Robinson district, White Pine County, Nevada: Constraints from 40Ar/39Ar dating
:
Geology
 , v.
29
, p.
475
478
.
Giggenbach
,
W.F.
,
1992
,
Magma degassing and mineral deposition in hydrothermal systems along convergent plate boundaries
:
Economic Geology
 , v.
87
, p.
1927
1944
.
Gize
,
A.P.
,
Kuehn
,
C.A.
,
Furlong
,
K.P.
, and
Gaunt
,
J.M.
,
2000
,
Organic maturation modeling applied to ore genesis and exploration
:
Reviews in Economic Geology
 , v.
9
, p.
87
104
.
Goldfarb
,
R.J.
,
Groves
,
D.I.
, and
Gardoll
,
S.
,
2001
,
Orogenic gold and geologic time: A global synthesis
:
Ore Geology Reviews
 , v.
18
, p.
1
75
.
Goldfarb
,
R.J.
,
Hart
,
C.J.R.
,
Davis
,
G.
, and
Groves
,
D.I.
,
2007
,
East Asian gold: Deciphering the anomaly of Phanerozoic gold in Precambrian cratons
:
Economic Geology
 , v.
102
, p.
341
346
.
Grauch
,
V.J.S.
,
Rodriguez
,
B.D.
, and
Wooden
,
J.L.
,
2003
,
Geophysical and isotopic constraints on crustal structure related to mineral trends in north-central Nevada and implications for tectonic history
:
Economic Geology
 , v.
98
, p.
269
286
.
Graybeal
,
F.T.
,
1981
,
Characteristics of disseminated silver deposits in the western United States
:
Arizona Geological Society Digest
 , v.
14
, p.
271
282
.
Griffin
,
W.L.
,
Begg
,
G.C.
, and
O’Reilly
,
Y.
,
2013
,
Continental-root control on the genesis of magmatic ore deposits
:
Nature Geoscience
 , v.
6
, p.
905
910
.
Hall
,
C.M.
,
Kesler
,
S.E.
,
Simon
,
G.
, and
Fortuna
,
J.
,
2000
,
Overlapping Cretaceous and Eocene alteration, Twin Creeks Carlin-type deposit, Nevada
:
Economic Geology
 , v.
95
, p.
1739
1752
.
Hannink
,
R.
Smith
,
M.
,
Shabestari
,
P.
,
Raabe
,
K.
,
Spalding
,
V.
, and
Hill
,
T.
,
2015
,
The discovery and geology of the Western Flank zone at the Kinsley Mountain project, Elko County, Nevada
, in
Pennell
,
W.M.
, and
Garside
,
L.J.
, eds.,
New concepts and discoveries: Geological Society of Nevada 2015 Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
295
312
.
Harlan
,
J.B.
,
Harris
,
D.A.
,
Mallette
,
P.M.
,
Norby
,
J.W.
,
Rota
,
J.C.
, and
Sagar
,
J.J.
,
2002
,
Geology and mineralization of the Maggie Creek district
:
Nevada Bureau of Mines and Geology Bulletin
 , v.
111
, p.
115
142
.
Harris
,
A.G.
, and
Crafford
,
A.E.J.
,
2007
,
A conodont database of Nevada
:
U.S. Geological Survey Data Series DS-249, scale 1:250,000
 .
Hastings
,
J.S.
,
Burkhart
,
T.H.
, and
Richardson
,
R.E.
,
1988
,
Geology of the Florida Canyon gold deposit, Pershing County, Nevada
, in
Schafer
,
R.W.
,
Cooper
,
J.J.
, and
Vikre
,
P.G.
, eds.,
Bulk mineable precious metal deposits of the western United States: Symposium proceedings
:
Reno, Nevada
,
Geological Society of Nevada
, p.
433
452
.
Hedenquist
,
J.W.
, and
Richards
,
J.P.
,
1998
,
The influence of geochemical techniques on the development of genetic models for porphyry copper deposits
:
Reviews in Economic Geology
 , v.
10
, p.
235
256
.
Henkelman
,
C.
,
2004
,
Variations in pyrite chemistry as clues to gold deposition at the Goldstrike system, Carlin trend, Nevada USA
: Unpublished M. Sc. thesis,
Las Vegas, Nevada
,
University of Nevada Las Vegas
,
150
p.
Heinrich
,
C.A.
,
1990
,
The chemistry of hydrothermal tin(-tungsten) ore deposition
:
Economic Geology
 , v.
85
, p.
457
481
.
Heitt
,
D.G.
,
Dunbar
,
W.W.
,
Thompson
,
T.B.
, and
Jackson
,
R.G.
,
2003
,
Geology and geochemistry of the Deep Star gold deposit
,
Carlin trend, Nevada: Economic Geology
 , v.
98
p.
1107
1135
.
Henry
,
C.
,
Muntean
,
J.
,
John
,
D.
, and
Colgan
,
J.
,
2012
,
Mesozoic-Cenozoic magmatism and mineralization in the greater Cortez area: An example of NBMG framework studies [abs.]
:
Geological Society of Nevada Newsletter
 , March
2012
, p.
3
.
Henry
,
C.D.
,
2008
,
Ash-flow tuffs and paleovalleys in northeastern Nevada: Implications for Eocene paleogeography and extension in the Sevier hinterland, northern Great Basin
:
Geosphere
  v.
4
, p.
1
35
.
Henry
,
C.D.
, and
John
,
D.
,
2013
,
Magmatism, ash-flow tuffs, and calderas of the ignimbrite flareup in the western Nevada volcanic field, Great Basin, USA
:
Geosphere
 , v.
9
, p.
951
1008
.
Hickey
,
K.A.
,
Barker
,
S.L.L.
,
Dipple
,
G.M.
,
Arehart
,
G.B.
, and
Donelick
,
R.A.
,
2014
,
The brevity of hydrothermal fluid flow revealed by thermal halos around giant gold deposits: Implications for Carlin-type gold systems
:
Economic Geology
 , v.
109
, p.
1461
1487
.
Hitzman
,
M.W.
,
1999
,
Routine staining of drill core to determine carbonate mineralogy and distinguish carbonate alteration textures
:
Mineralium Deposita
 , v.
34
, no.
8
, p.
794
798
.
Hofstra
,
A.H.
,
1994
,
Geology and genesis of the Carlin-type gold deposits in the Jerritt Canyon district, Nevada
: Unpublished Ph.D. dissertation,
Golden, Colorado
,
Colorado School of Mines
,
1287
p.
Hofstra
,
A.H.
, and
Cline
,
J.S.
,
2000
,
Characteristics and models for Carlin-type gold deposits
:
Reviews in Economic Geology
 , v.
13
, p.
163
220
.