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 The Alligator Ridge district hosts disseminated gold deposits (Alligator Ridge, Yankee deposits) in Mississippian and Devonian clastic and carbonate rocks. The deposits are about 70 miles (113 km) northwest of Ely, Nevada, along the southern projection of the Carlin trend (Fig. 1), and east of the Roberts Mountain thrust. The area is underlain by lower-plate Paleozoic miogeoclinal carbonate and clastic rocks, Eocene(?) sedimentary rocks; and Oligocene and younger volcanic rocks. Jurassic plutonic rocks are exposed to the north at Bald Mountain (Hitchbom et a/., 1996) (Fig. 2). Hitchbom eta/. (1996) propose that at Bald Mountain tungsten, molybdenum, zinc, and precious metal deposits, including disseminated gold, are associated with the Jurassic pluton and are Jurassic in age, and that Alligator Ridge and Yankee are related distal deposits. The well-exposed Alligator Ridge area is ideal for unraveling the geologic history of ea.stem-facies rocks, and, in particular, documenting Mesozoic and Tertiary deformation and their controls on ore. An improved understanding of the tectonic history in the Alligator Ridge district may also help to identify Mesozoic and Tertiary structures in the Carlin trend which is underlain by eastern- and western-facies rocks that were deformed during the late Devonian-early Mississippian Antler and late Permian Sonoma orogenies, as well as during the Mesozoic and Tertiary tectonic events. Previously published geologic maps have depicted the Alligator Ridge-Bald Mountain area as a relatively undeformed uplift between the isoclinally folded and thrusted Diamond Mountains on the west side of Newark Valley and the broad syncline comprising the Butte Mountains