216 Geochronology of Critical Mineral Deposits with Special Reference to U-Th-Pb Dating of Common-Pb-Rich Minerals

Radiometric dating of ore deposits containing critical minerals. Studies discussing analytical aspects of methods such as U-Th-Pb, Ar-Ar, Rb-Sr, Sm-Nd, Re-Os and/or using radiometric ages for ore genesis research or critical mineral resource evaluation.

Tuesday, 21 October 2025
1:30 PM - 5:30 PM
HBGCC, 304C

Age and Temperature of Authigenic Carbonates Associated with Lithium-Bearing Illite Claystones at Thacker Pass, Nevada, USA

Paper number: 216-8
Program: Technical Sessions
Time: 3:30 PM – 3:45 PM

Authors

Abstract

Lithium (Li) resources have become key obstacles for the green energy transition due to the proliferation of Li-ion batteries electric vehicles and energy storage technologies. The Thacker Pass volcano-sedimentary deposit, located in the McDermitt Caldera of Southeast Oregon and Northern Nevada, is the world’s largest known Li resource and is poised to supply much of the world’s Li. The processes that formed the illite clays this deposit have not been fully constrained, but the main competing models involve either a hydrothermal system during caldera resurgence or lower-temperature diagenesis. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for the uranium–lead (U-Pb) dating of calcite and fluorite, both secondary minerals with displacive fabrics within the Li rich claystones, provide direct dating of the fluids related to the genesis of the deposit. Calcite nodules in the smectite/illite clays formed at 16.37 ± 0.29 Ma and fluorite, which is recognized as a replacement mineral, are consistent with the calcite ages. Because these ages overlap with the McDermitt tuff which erupted to form the caldera, these minerals are interpreted to have formed during caldera resurgence. Fluorine is directly linked to the alteration of clays into the high-grade Li-illite making the age of fluorite an important constrain on the mineralization. The carbonates were further analyzed for carbon, oxygen, and clumped isotopes to reconstruct the conditions of mineralization. Based on the carbonates’ ∆47, their formation temperature ranged from 129 ± 15°C to 155 ± 30°C. Our findings suggest that syn- or immediately-post depositional hydrothermal alteration is the primary mechanism of Li enrichment in illite at Thacker Pass.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-414654

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