Overview of Regional Geology and Tectonic Setting of the Osgood Mountains Region, Humboldt County, Nevada
Elizabeth Jones Crafford, 2000. "Overview of Regional Geology and Tectonic Setting of the Osgood Mountains Region, Humboldt County, Nevada", Part I. Contrasting Styles of Intrusion-Associated Hydrothermal Systems: Part II. Geology & Gold Deposits of the Getchell Region, John H. Dilles, Mark D. Barton, David A. Johnson, John M. Proffett, Marco T. Einaudi, Elizabeth Jones Crafford
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Paleozoic and Mesozoic rocks in the Osgood Mountains region can be grouped into five terranes based on distinct lithologic, age, and structural characteristics. These terranes are: the Lower Paleozoic Osgood block, the Lower Paleozoic Roberts terrane, the Cambrian and Devonian Dutch Flat terrane, the Mississippian to Permian Golconda terrane, and the Triassic to Jurassic Jungo terrane. Each of these terranes is structurally bounded by moderately to steeply dipping fault zones or melange belts and has a distinct internal structural fabric.
Geologic evidence exposed in the Osgood Mountains provides support for a revised model for the Paleozoic tectonic history of the region. Paleozoic tectonic events in Nevada can be reinterpreted in a new framework that portrays the traditional Antler and Sonoma orogenies as complex, transpressive episodes of tectonism along the Paleo-Pacific North American plate margin. Recognizing the accreted Paleozoic terranes of Nevada as tectonic blocks that have experienced significant translational displacement and deformation relative to each other and to the continental margin explains many of the geologic observations that have not been accounted for in other models of the tectonic history of Nevada.
Several world-class gold deposits in Nevada, notably the Carlin area deposits, the Getchell region, and Pipeline, among others, are located close to inferred high-angle fault boundaries that can be related to these accreted and dislocated terranes. It is proposed that these terrane boundaries are a first-order control for subsequent gold mineralization in these regions. During younger (Tertiary) mineralizing events, these boundaries served as the preexisting deep crust/upper mantle deep-sourcing conduits, circulating large quantities of auriferous fluids through prospective host rocks.