LASER ABLATION U-PB FLUORITE AGES FROM THE DAISY AND DIAMOND QUEEN MINES, NYE COUNTY, NEVADA

Fluorite mineralization along with other important critical minerals is found in Cambrian carbonates of the Daisy and Diamond Queen mines in Nye County, Nevada (Castor and Weiss, 1992). We obtained laser ablation U-Pb fluorite ages for two samples from the Daisy Mine, and one sample from the Diamond Queen Mine. All samples have favorable U-Pb systematics, with elevated U concentrations (50-200 ppm) and ²³⁸U/²⁰⁶Pb ( ~50-600). From the Daisy mine, clear purple coarse crystalline vein fluorite gives an age of 9.75±0.26 Ma while black fine grained replacement fluorite gives an age of 9.2±1.1 Ma. The replacement fluorite shows complexity that may signal complex genesis. Banded black fluorite from the Diamond Queen Mine gives an age of 12.4±0.6 Ma. The Diamond Queen mine lies along the Bare Mountain fault near the Goldpass and Sterling mines. These mines have been grouped together with the Daisy mine as ‘Bare Mountain mineralization’ with a range of 13-11.2 (to perhaps younger) Ma (Castor and Weiss, 1992). Thus, our results extend the age of mineralization and show potential for U-Pb fluorite dating to constrain critical mineral enrichment.

We hypothesize that tectonic stress regimes involving transtension allows deep fluorine-bearing fluids to penetrate and interact with the crust, extracting important critical minerals along the path. This builds on our observation that modern hydrothermal systems across the Great Basin have elevated fluorine concentration where transtensional deformation is the greatest. The relationship between transtension and core complex formation has not been established here. However, thermochronology from the footwall of the associated Bullfrog detachment shows rapid exhumation between 12.6±1.6 to 11.1±1.9 Ma (Hoisch et al., 1997), overlapping the timing of mineralization and the U-Pb ages of the fluorite deposits. Geodynamic modeling and continued efforts to date fluorite in this region will test models of tectonics and mineralization.