Abstract The Post deposit is located in Eureka County, Nevada, Section 19, T36N, R50E, approximately 40 km (26 miles) northwest of the town of Carlin and 7 km (4.5 miles) northwest of the Carlin #1 mill (Figure 1). The Post deposit is located along a spur of the Tuscarora Mountains that also hosts the Blue Star/Genesis and Deep Star deposits. Host rocks for the Post orebody are the sandstones, siltstones, calcareous mudstones, and limestones of the Siluro-Devonian Roberts Mountains and Popovich Formations, and the siliceous mudstones and siltstones of the Devonian Rodeo Creek unit. The Goldstrike diorite intrusion irregularly penetrates the sedimentary rocks as dikes, sills, and stocks producing local hornfels, skarn, and marble. Gold mineralization occurs along the northern margin of the Goldstrike intrusion in a structural domain dominated by a NW-striking antiform. The eastern limb of this antiform is truncated by the N20W high-angle Post Fault (Figure 2). Gold mineralization, occurring west of the Post Fault, is structurally-controlled along high-angle NE and NW-striking faults, and is stratigraphically-controlled within arenaceous lenses of the Rodeo Creek unit, and within breccias of the lower Popovich and the upper Roberts Mountains Formations. Mineralization is limited within argillized diorite sills and metamorphic rocks to zones that have been structurally-prepared. Gold mineralization is subdivided into three zones based on geology, morphology, grade, and metallurgical character: Upper Post, Lower Post, and Deep Post. Upper Post represents oxide ore (averaging 0.040 to 0.050 oz/st) hosted in argillized and silicified mudstones, siltstones, and sandstones of the Rodeo Creek

Abstract The Goldstrike property, located in the Carlin Trend in Nevada, contains a diverse group of Carlin deposits, including some of the largest and highest grade examples known. The largest deposit, Betze-Post, has a gold endowment of approximately 1,250 metric tons (t) Au, and the Meikle deposit, which contains 220 t Au, has a grade of 24.7 g/t Au. Goldstrike is part of the larger Blue Star-Goldstrike subdistrict, which has an areal extent of 58.5 by 2 km and a total gold endowment of 1,970 t. The first discovery of gold at Goldstrike was in 1962. Subsequent exploration culminated in the discovery in 1986 of large high-grade orebodies beneath smaller, lower grade orebodies. Exploration over a 40-yr period has relied on the evolution in understanding of geology and ore controls, supported by the application of geochemical and geophysical exploration techniques. The Goldstrike property is located close to the rifted margin of the North American craton, along an inferred deep crustal structure. Stratigraphy at Goldstrike consists of lower Paleozoic sedimentary rocks, including an autochthonous, miogeoclinal carbonate sequence and an allochthonous eugeoclinal siliciclastic sequence, separated by the early Mississippian Roberts Mountains thrust. Multiple periods of deformation are evident, dominated by contraction in the upper Paleozoic to Mesozoic, followed by extension beginning in the Eocene. This has resulted in a complex structural architecture that is a major control on the location, geometry, and size of the orebodies. Intrusive rocks at Goldstrike include a Late Jurassic calcalkaline suite of diorite, rhyodacite, and lamprophyre and late Eocene calc-alkaline dacite dikes. These dikes, dated at approximately 39 Ma, are coeval with the Carlin gold mineralization and the onset of regional extension. Gold in unoxidized ore is mainly found within arsenian pyrite and is associated with Hg, Sb, and Tl. The ore fluids were low salinity (<10 wt % NaCl equiv), had homogenization temperatures of 200° to 225°C, and are of meteoric origin. Alteration varies considerably between deposits and includes decarbonatization, argillization, and silicification. Dissolution of carbonate has produced collapse breccias, which often host high-grade ore. Supergene alteration has produced oxide ores, at depths up to 200 m. Mineralization at Goldstrike occurs in a variety of settings, reflecting an interplay of both structural and lithological controls. Structural controls include folds, low- and high-angle faults, particularly where faults intersect, and zones of fracturing and brecciation. Fracturing is enhanced in areas of rheological contrast, such as the contact of the Jurassic dioritic Goldstrike intrusion, which is the first-order control of the large Betze-Post deposit. The north-northwest-striking Post fault system is associated with the highest grade orebodies, such as the Meikle deposit and the Deep Post subdeposit. The majority of economic gold mineralization is hosted by the autochthonous rocks, mainly the limy to dolomitic mudstones of the Devonian Popovich Formation and brecciated limestones and dolomites of the Silurian-Devonian Bootstrap limestone. Lesser amounts are hosted in other autochthonous units and intrusive rocks. Characteristics of the host rocks that are believed to enhance their favorability to gold deposition are the presence of reactive carbonate, porosity, permeability, and the presence of iron, which can be sulfidized to form auriferous pyrite.

Abstract The West Leeville deposit is a deep, high-grade refractory gold deposit located on the Carlin Trend, 1.5 miles north of the Carlin Mine, Eureka County, Nevada. The deposit is part of a large gold system, extending northwest from the Carlin deposit. At a cutoff of0.200 oz/st, the deposit contains a drill-indicated resource of 7,287,984 tons at an average grade of 0.436 oz/st gold (3,177,561 ounces gold). The majority of the resource is located on the Newmont/Barrick HD Venture, where Newmont, as operator with a majority interest of 60%, has conducted deep exploration since 1992. The West Leeville deposit occurs at depths of 1,500 to 2,000 feet and is hosted by flat-lying, silty limestone of the upper Silurian-Devonian Roberts Mountains Formation. The Roberts Mountains Formation is subdivided into four informal subunits (SDrm 1-4). West Leeville ore occurs in two strata-bound zones near transitional contacts between these lithologic units. The upper zone contains the bulk of the mineralization and occurs within wispy-laminated (bioturbated), silty limestone (SDrm2) and bioclastic-rich silty limestone along the SDrm2/SDrm3 contact. Lower zone mineralization occurs at the contact between wispy-laminated, bioclastic-rich limestone (SDrm3) and planar-laminated silty limestone (Sdrm4). West Leeville is located along the western margin of the Leeville Corridor, a broad (Y2 x 1 mile), northwesttrending horst, containing extensive decalcification and local 0.100 to 0.200 oz/st gold mineralization. The deposit occurs in the footwall of the West Bounding Fault, a north-northeast-striking, 60 degrees west-dipping fault zone with 150 feet of apparent normal displacement. The thickest and highest -grade portion of the deposit is located where the northwest-striking Rodeo Creek Fault intersects the footwall of the West Bounding Fault. West Leeville ore occurs in grey to black, decalcified (calcite removed) and weakly to moderately silicified rocks composed of 60 to 70% quartz, 10 to 30% dolomite, 5 to 12% kaolinite, 2 to 4% illite and 2 to 4% pyrite. Ore can only be distinguished from waste by assay, as decalcification is far more extensive than mineralization. Bioclastic interbeds are preferentially silicified. Zones of strong silicification or strong decarbonatization (calcite and dolomite removed) are generally barren of +0.200 oz/st gold mineralization. Veins and breccias are rare within the deposit. Overlying micrite of the Popovich formation is generally silicified and largely barren of gold. The micrite or silicification may have acted as an impermeable and/or unreactive cap to the system during gold deposition. Quartz monzonite and lamprophyre dikes occupy fault zones within and marginal to the deposit. The dikes are altered but rarely contain +0.200 oz/st gold mineralization and more commonly bound gold zones within silty limestone of the Roberts Mountains Formation. In summary, the West Leeville deposit is representative of the more strata-bound end members of Carlin Trend deposits, similar in style to the Carlin deposit. The West Leeville and Carlin deposits occur within a large (nearly 2 square miles), strata-bound gold system in the upper Roberts Mountains Formation with + 0.010 oz/st gold mineralization continuous between the deposits. Both West Leeville and Carlin occur in horsts between northeaststriking faults and the northwest -striking Leeville fault, with mineralization located in the immediate footwall of the northeast-striking fault. Like Carlin, the deposit is largely strata-bound, but high angle faults acted as feeders and boundaries to the gold system and played a critical role in localizing the deposit.

Abstract Mike is a subhorizontal, sedimentary rock-hosted gold and copper deposit located in the Maggie Creek subdistrict within the greater southern Carlin trend, approximately two miles north of Newmont Mining's Gold Quarry mine, Eureka County Nevada (Fig. 1). Mike forms the northernmost of a belt of deposits including Gold Quarry and Tusc, that occur alongthe southwestern margin of the Carlin tectonic window and are controlled by the northwest trending Good Hope fault. On a district scale, the Carlin tectonic window forms a fault -bounded, anticlinorium of autochthonous lower Paleozoic sedimentary carbonate rocks, flanked by siliciclastic and carbonate-clastic rocks of the Roberts Mountains allochthon (Fig. 2). The Good Hope fault is a N45 o- 55 ow striking, high-angle reverse fault that bounds the southwestern margin of the window (Rota, 1987,1991,1993,1995~ Cole, 1995). The vast majority of gold mineralization within the Maggie Creek subdistrict occurs at intersections of the Good Hope fault with a series of northeast striking, high angle eros~ faults (Fig. 3). Mike is a buried deposit, covered by 450 to 800 feet of post-mineral, Tertiary Carlin Formation. The geology of the deposit is interpreted from 57 drill holes that range from 150 to 1000 foot spacings. Within the deposit, the Good Hope fault juxtaposes upper Silurian Roberts Mountains Formation in the hanging wall against parallochthonous, late Devonian siliciclastic rocks of the Rodeo Creek unit. While drilling indicates that disseminated gold and oxide copper mineralization straddles the fault zone, the bulk of mill-grade oxidized gold mineralization

Abstract This paper describes outcrop- and hand specimen-scale breccias in the Betze orebody, which is the largest gold deposit on the Carlin trend (Bettles and Lauha, 1991; Leonardson and Rahn, 1996). The Betze orebody lies in the north-central part of the Carlin trend in the Goldstrike Mine (Fig. 1), and it is part of the Betze-Post deposits (Arehart et al. , 1993; Lauha and Bettles, 1993; Smith and Sharon, 1994; Leonardson and Rahn, 1996). The orebody and much of the internal breccia bodies have a general WNW strike, with a sub-horizontal attitude (Peters, 1996; 1997). The open pit Goldstrike Mine exposes the Betze and Post orebodies, the Post anticline (Fig. 2), contacts between the Silurian and Devonian Roberts Mountains Formation, Devonian Popovich limestone and Devonian Rodeo Creek unit, and the northern contact of the Jurassic Goldstrike stock (Volk and Zimmerman (1991). Breccia bodies host much of the Betze ore body. Breccias are common rock types in most Carlin-type deposits (Williams, 1992, 1993), and they are particularly common in ore bodies of the north-central Carlin trend (Clode, 1993; Griffin et al., 1993; Leach, 1993). The host rocks in the Betze orebody are altered and deformed. The complex descriptive geology of the Goldstrike Mine is detailed by Volk et al. (1996), Peters et al.(1996), and Leonardson and Rahn (1996). The WNW-striking Dillon deformation zone (DDZ) hosts the upper central Betze orebody (Fig. 2) and contains several ore types associated with breccia (Peters, 1996, 1997). Rock types that host the orebody include phyllonitic black to