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Geologic map of Rhyolite Ridge and the northern Silver Peak Range, Esmeralda County, Nevada [MAP AND TEXT]
Geol Rhyolite Ridge

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Title: Geologic map of Rhyolite Ridge and the northern Silver Peak Range, Esmeralda County, Nevada

Author: Izabella Ogilvie, Michael H. Darin, John T. Reynolds, Daniel A. Chafetz, and Matthieu Harlaux
Year: 2023
Series: Open-File Report 2023-11
Format: map sheet with cross sections: 41 x 29.5 inches, color; text: 35 pages, color
Scale: 1:24,000

Rhyolite Ridge is located in the northern Silver Peak Range of southwestern Nevada and contains significant sediment-hosted lithium and boron deposits that are nearing development. Despite the economic importance of these resources, the primary source of lithium, deformation history, and the relative influences of structural, stratigraphic, and magmatic controls on lithium enrichment are uncertain. This report presents new 1:24,000-scale geologic mapping, whole-rock geochemistry, and a sub-regional compilation of Cenozoic geochronologic data to support the evaluation and assessment of these critical minerals through the U.S. Geological Survey (USGS) Earth Mapping Resources Initiative (Earth MRI). Most of the economic lithium and boron mineralization occurs in the upper Miocene to lower Pliocene Cave Spring formation, which is composed of interbedded lacustrine claystone, marl, limestone, volcaniclastic rocks, and tuffs. Anomalously high concentrations of lithium (up to 2,620 ppm; Reynolds and Chafetz, 2020) are bound in marl, smectite, and mixed illite-smectite clays, while boron is primarily associated with searlesite. The Cave Spring formation is mostly contained within a single structural basin in the study area and was deposited in an alluvial-lacustrine environment on top of ~6.1–5.8 Ma rhyolitic tuffs and lavas of the Rhyolite Ridge and Argentite Canyon formations. Geochemical data from these pre-basin volcanic rocks contain exceptionally high whole-rock lithium concentrations up to 451 ppm, though with notable spatial heterogeneity. The high lithium (and boron) concentrations and considerable spatial extent and volume of these rhyolites implicate them as a probable source for the mineralization in the Cave Spring formation. The White Hill and Cave Spring faults are a pair of conjugate normal faults that controlled deposition of the Cave Spring formation in an internally drained, alluvial-lacustrine basin that experienced WNW-directed extension since latest Miocene time (Ogilvie, 2023). Field relations, subsurface well data, airborne electromagnetic surveys, and our synthesis of geochronologic constraints indicate a similar style of extension across the study area associated with both NW- and SE-dipping normal faults. Active faulting and basin subsidence continues today near the western map boundary along the Emigrant Peak fault zone that bounds northern Fish Lake Valley.

This research and field work was supported by the U.S. Geological Survey, Earth Mapping Resources Initiative (Earth MRI) Program and National Cooperative Geologic Mapping Program, under USGS award number G21AC10365, and by a graduate student research grant to I. Ogilvie from the Geological Society of America.

Suggested citation:
Ogilvie, I., Darin, M.H., Reynolds, J.T., Chafetz, D.A., and Harlaux, M., 2023, Geologic map of Rhyolite Ridge and the northern Silver Peak Range, Esmeralda County, Nevada: Nevada Bureau of Mines and Geology Open-File Report 2023-11, scale 1:24,000, 35 p.

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