Integrated geological and geochemical studies of the Barneys Canyon gold deposit in the Oquirrh Mountains of north-central Utah suggest that compressional tectonism and metamorphism are Jurassic in age. Detailed geologic mapping, clay mineralogy, and fluid-inclusion analyses together with Jurassic K/Ar age determinations indicate that deformation at Barneys Canyon was contemporaneous with regional Jurassic metamorphism recognized in the southern Oquirrh Mountains by Wilson and Parry (1990b). The Barneys Canyon gold deposit occurs on the crestal region of the Copperton anticline which is interpreted as a fault-bend fold. Bedding-plane gouges formed within the Barneys Canyon sedimentary sequence during flexural slip folding. Clay minerals formed in the gouges and in the Barneys Canyon gold deposit are kaolinite, illite, and some minor interstratified illite-smectite. The distribution of illite and kaolinite shows that the orebody is associated with illite alteration surrounded by a halo of more kaolinitic material. Illite crystallinity suggests that a lower-temperature (retrograde) zone is associated with the orebody. Fluid-inclusion analyses from quartz and barite show a range of homogenization temperatures from 130–400 °C with two weak modes at 225 °C and 345 °C. Kaolinite and quartz are unstable with respect to pyrophyllite at the higher temperatures. No pyrophyllite has been observed at Barneys Canyon restricting the kaolinitic alteration to the lower-temperature range. The formation temperature of illite is not constrained. The bedding-plane gouges contain illite, kaolinite (minor), quartz, carbonate, and as much as 1.5 ppm Au. The illites yielded K/Ar ages of 147 Ma and 159 Ma consistent with K/Ar ages of heavy metal bearing illite veins in the southern Oquirrh Mountains described by Wilson and Parry (1990b). This interpretation extends Jurassic deformation to north-central Utah from areas to the west where Jurassic magmatism and tectonics have previously been described.

Abstract Today's field trip examines “Carlin-style” gold deposits hosted within Permian-aged sediments of the Copperton anticline. We will visit two gold mines: the now exhausted Barneys Canyon deposit and the active Melco mine. Representative core will be available at the respective sites. The excursion will focus on the structural controls and alteration related to gold mineralization in this group of deposits. Weather permitting, a traverse will be made along the axis of the Copperton anticline from the Melco haul road south to Bingham Canyon. The traverse will pass down section through a sequence of unmineralized Permian to Pennsylvanian siliceous clastic rocks and end in the Bingham pyrite halo. This road log begins at the intersection of the new Bingham Highway with Highway U-111, approximately two miles east of the town of Copperton. The route from downtown Salt Lake City to this junction may be followed on the Day Two Road Log for the Bingham Canyon field trip. The route heads southwest toward Copperton, northwest on a private road toward the Kennecott Utah Copper concentrator, and then continues northwest to the Barneys Canyon and Melco gold mines. 0.0 Begin at the junction of the new Bingham Highway and U-111. Head southwest, toward Copperton, on the new Bingham Highway. 0.5 Dead ahead are the waste-rock piles from the Bingham Canyon mine. 1.5 Turn right, onto a private road, through the entrance gate to the Copperton concentrator. 2.6 Turn right at the fork in the road. Bingham's Copperton concentrator is to the left. The

Abstract The Melco deposit is the largest of five gold mines that constitute the 1.5 million ounces Barneys Canyon project. The deposits form an arc along the nose of the north-trending Copperton anticline. Gold mineralization formed in structurally prepared zones near Theologically contrasting formational contacts. Bedding plane slip during Mesozoic folding caused some deformation. The Melco deposit, located on the NW flank of the Copperton anticline, was localized in a structurally complex zone at the intersection of a N 55° E-trending strain corridor and N 30° E-striking high-angle faults. The latter faults provided conduits for Tertiary-age gold-bearing fluids and late stage carbon-pyrite-orpiment-realgar introduction. In cross section, gold distributions resemble an upright goblet with a stem but no base. These sediment-hosted deposits contain micron-sized gold as native metal and as inclusions within the arsenic-rich rims of zoned pyrite grains. The deposits are anomalous in As-Sb-Tl-Hg, and contain low silver and base metal values. Bleaching and decalcification are the most pronounced alteration effects. Silicification is present but subtle. The deposits lie at the outer edge of an asymmetrical pyrite-Au-As halo developed around the Bingham Canyon porphyry system. There is a growing body of evidence that these sediment-hosted gold deposits represent a distal precious metal event genetically related to late stage mineralization at Bingham Canyon, which lies 5 miles to the south.

Abstract For the last several decades, gold exploration in Nevada has been strongly focused on sedimentary rock-hosted gold deposits in the Carlin, Cortez, Independence, and Getchell trends in north-central Nevada. Accordingly, less exploration activity has been directed toward the search for similar gold deposits in the eastern Great Basin, south and east of the major trends. Deposits in the central and northern Carlin and Cortez trends are hosted primarily in Upper Devonian middle slope soft-sediment slumps and slides and base-of-slope carbonate debris flows, turbidites, and enclosing in situ fractured lime mudstones. This is in marked contrast to gold deposits in the eastern Great Basin that are hosted primarily in three chronostratigraphic horizons: (1) shallow-water, Cambrian and Ordovician carbonate platform interior, supratidal karsted horizons and shelf lagoon strata, associated with eustatic sea-level lowstands and superjacent, transgressive calcareous shale and siltstone horizons that are deposited as sea level begins to rise, (2) Early Mississippian foreland basin turbidites and debris flows overlying karsted Late Devonian platform strata, and (3) Pennsylvanian and Permian shallow marine basin strata. Stratigraphic architecture in these three horizons was influenced in part by Mesozoic (Elko and Sevier) contractional deformation, including low-angle thrust and attenuation faults, boudinage, and large-scale folds, which in turn affected the orientation and localization of synmineral brittle normal faults. A compilation of past production, reserves, and resources (including historic and inferred) suggests an overall endowment of over 41 Moz of gold (1,275 tonnes) discovered to date in the eastern Great Basin, some in relatively large deposits. Significant clusters of deposits include the Rain-Emigrant-Railroad and Bald Mountain-Alligator Ridge areas on the southern extension of the Carlin trend, the Ruby Hill-Windfall-South Lookout-Pan on the southern extension of the Cortez trend, and the Long Canyon-West Pequop-Kinsley Mountain area near Wells, Nevada. Sedimentary rock-hosted gold deposits extend to the eastern edge of the Great Basin in Utah and Idaho and include the past-producing Black Pine, Barney’s Canyon, Mercur, and Goldstrike mines. The recognition of widespread, favorable host rocks and depositional environments on the Paleozoic platform-interior shelf in the eastern Great Basin opens up vast areas that have been relatively underexplored in the past. A basic premise throughout this paper is that the better we understand the origin of rocks and the depositional and postdepositional processes under which they formed, the more accurately we can make well-founded stratigraphic, sedimentological, structural, geochemical, and diagenetic interpretations. Without this understanding, as well as the rigorous application of multiple working hypotheses to explain our observations, the advance of science and the discovery of gold deposits is problematic.

Abstract Sediment-hosted, disseminated gold deposits in the Mercur district and Bameys Canyon in the Bingham district are infolded and thrust-faulted Paleozoic sediments of the Oquirrh Mountains, Utah. Folding and thrust faulting occurred in a Jurassic event and the Cretaceous Sevier Orogeny (Armstrong, 1968; Almendinger and Jordan, 1981; Almendinger et al.,1984; Snoke and Miller, 1988). The Oquirrh Mountain range is allocthonous and is underlain by the east-vergent Oquirrh thrust (Presnell, 1992; Presnell and Parry, 1995) not te Charleston thrust. Mercur is located . in the southern Oquirrh Mountains dominated by a series of northwest trending anticline-syncline pairs. Barneys Canyon and Bingham are in the central Oquirrh mountains where structural complexity results from the east -vergent thrust belt interacting with the Uinta arch.

ABSTRACT The Bingham District is a large polymetallic mining district centered on an Eocene porphyry copper deposit 20 miles southwest of Salt Lake City, Utah. Since its discovery in 1863 the district has at various times been a silver-lead, gold, lead-zinc-silver, and copper-gold-molybdenum district. The Bingham District is located in a zone of overlap between the Basin and Range extensional terrain and the Cordilleran fold and thrust belt. Permian quartzites and limestones were folded and thrust-faulted during several Mesozoic orogenies and then intruded by 39.8 to 37.5 Ma calcalkaline monzonite, quartz monzonite, and quartz latite. Volcanic breccias and flows petrochemically similar to the intrusions were erupted from centers close to the deposit from 39 to 33 Ma. The Bingham Porphyry Copper Deposit exhibits the concentric alteration and mineralization zoning characteristic of many porphyry deposits. However, the deposit is notable for the magnitude and intensity of the various kinds of mineralization present: It is one of the largest copper deposits in the world with pre-mining reserves of almost 3 billion tons of 0.67 percent copper ore. Nested within the copper orebody are overlapping zones of molybdenum, gold, and silver mineralization that mimic the shape of the copper deposit and contain greater than 0.1 percent MoS 2 , 0.01 ounces per ton gold, and 0.5 ounces per ton silver respectively. Major copper-gold skarn deposits flank the copper orebody on two sides. They include the Carr Fork Deposit (61 million tons of 1.90 percent copper, 0.01 ounces per ton gold, and 0.31 ounces per ton silver) and the North Ore Shoot Deposit (82 million tons of 2.81 percent copper, 0.05 ounces per ton gold, and 1.57 ounces per ton silver). Vein and replacement lead-zinc-silver deposits located in a halo around the porphyry and skarn deposits have produced 28 million tons at an average grade of 8.6 percent lead, 6.6 percent zinc, 5.0 ounces per ton silver, and 0.039 ounces per ton gold. The Barneys Canyon and Melco Deposits located five miles north of the porphyry copper deposit have combined pre-mining reserves of 19 million tons at a grade of 0.05 ounces per ton gold. They are sediment-hosted gold deposits characterized by sub-micron sized disseminated gold mineralization, an arsenic-antimony-barium-mercury-thallium geochemical signature, low silver and base metal contents, and an almost complete absence of quartz veining. The deposits lie at the outer edge of an extensive arsenic-gold geochemical halo about the Bingham Porphyry Copper Deposit, but chronological and genetic relationships to the porphyry deposit have not been clearly established.