Source-to-Sink Evolution of Volcano-Sedimentary Li-B Deposits at Rhyolite Ridge, Southwestern Nevada

Volcano-sedimentary lithium (Li) and boron (B) deposits at Rhyolite Ridge, Nevada (USA), are poised for development and represent a critical opportunity to secure domestic supplies of these strategic mineral resources. Despite their significance, the sources of Li and B, the geochemical processes responsible for mineralization, and their connection to a proposed caldera in the central Silver Peak Range remain poorly understood. This study integrates detailed geologic mapping with new petrographic, geochemical, and geochronologic data from mineralized lacustrine strata of the Cave Spring formation and underlying volcanic rocks to assess the source-to-sink evolution of Li-B enrichment at Rhyolite Ridge. The Rhyolite Ridge and Argentite Canyon formations (ca. 6.1–5.8 Ma) consist of peraluminous to metaluminous rhyolitic and trachytic tuffs and lavas that include the distinctive Rhyolite Ridge tuff (ca. 6.0 Ma). These rocks exhibit unusually high Li (mean = 73 ppm; maximum = 352 ppm) and B (mean = 160 ppm; maximum = 817 ppm) concentrations, substantially higher than typical upper continental crust, with no clear correlation between Li and B; mild and spatially variable hydrothermal alteration is characterized by sericite, K-feldspar, or disseminated carbonate, along with depleted rare earth element patterns in more altered samples. Drill hole geochemical data from the overlying Cave Spring formation (ca. 5.8–4.7 Ma) indicate that mineralization occurs in stratiform claystone and marl, characterized by a depletion in transition metals and notable enrichment in Li, B, and other incompatible trace elements at concentrations 6 to 30 times higher than typical upper continental crust. Li and B were likely supplied by supergene weathering of surrounding volcanic rocks, possibly with additional input from early hydrothermal fluid circulation in the basin. We propose a regional stratigraphic correlation of the Rhyolite Ridge tuff supported by a new U-Pb date of 6.05 ± 0.08 Ma for an Li-enriched rhyolite tuff in the nearby Montezuma Range and strong compositional similarities in mineralogy and geochemistry from both outcrop and subsurface data across Clayton Valley, the Silver Peak Range, and northern Fish Lake Valley. This correlation suggests that the Rhyolite Ridge tuff erupted from a source in the Montezuma Range and was emplaced in an ~80-km-long, NW-SE–oriented paleovalley and that it is the probable source of Li in brine and volcano-sedimentary deposits throughout the greater Clayton Valley region.