LITHIUM CLAYS IN SEDIMENTS FROM CLOSED-BASIN, EVAPORATIVE LAKES IN THE SOUTHWESTERN UNITED STATES

There is a renewed interest in Li clays due to their potential as a resource for Li, needed for Li batteries and renewable, mobile power. The southwestern US has several deposits of Li clay in Miocene to Pliocene-aged sediments/claystones from saline lakes formed in evaporative, closed basins. Li clays have also been identified in deposits from a caldera lake. We have conducted geochemical and mineralogical analysis of samples from evaporative, closed-basin lakes from Lyles AZ, Franklin Mills CA, Hector CA, Fish Lake Valley and Clayton Valley NV, and from the caldera lake at McDermitt NV. Data are analyzed for a link between Li concentration, clay mineralogy, and the environments of deposition and subsequent alteration.

Geochemical analyses were conducted by X-Ray Fluorescence (XRF) for major elements and a combination of Inductively Coupled Plasma Atomic Emission/Mass Spectrometry (ICP-AES/MS) for Li and trace elements. Mineralogical analysis consisted of powder X-Ray Diffraction (XRD) using random-packed and oriented (air-dried and glycolated) samples.

All samples are Mg- and F-rich. Most are smectite (hectorite), although illite (tainiolite) is also found at McDermitt and smectite-illite mixtures were identified in the Esmeralda Fm of Clayton Valley NV. Li content ranges from 0.05 – 0.71% in bulk sediments, and 0.12 – 1.24% in clay separates. The illites at McDermitt have the highest Li content and may be economical for mining. The clay from Lyles AZ is notable for a high bulk Sr concentration of 8%.

Sediments of the closed-basin lake environments share similar characteristics whereby clays are found interbedded with carbonates, silica, and volcanic ash, and there is evidence of hot-spring activity along nearby faults. The Li, F, and Sr components of the clay result from interaction with hydrothermal fluids. Clays appear to form both through alteration of volcanic ash and by direct precipitation from hydrothermal fluids, depending upon location.