What does this research mean for the field?

Lithium enrichment in the McDermitt deposit is primarily controlled by the formation of Mg-Li smectites (hectorite) via devitrification of volcanic glass by heated meteoric waters, without the illitization of smectite observed in nearby deposits. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

The study aims to understand the processes responsible for lithium enrichment in the McDermitt caldera's clay-type mineralization.

May 16, 2026Mineralium Deposita3 citationsOpen Access

Lithium clay mineralization in the McDermitt volcano-sedimentary deposit, Oregon, USA

FPF. PutzoluNatural History Museum RAR. N. ArmstrongNatural History Museum LHL. E. HepburnScottish Universities Environmental Research Centre

Key Points

The study aims to understand the processes responsible for lithium enrichment in the McDermitt caldera's clay-type mineralization.
Conducted geological, mineralogical, and isotopic investigations of the McDermitt deposit.
Analyzed stratiform lacustrine units and their composition, including hectorite-bearing claystones and siliceous–carbonate beds.
Collected geochemical and isotopic data to evaluate mineralization conditions.
Lithium mineralization predominantly occurs in hectorite-rich claystones under geothermal conditions at 133 °C.
Mineralization was influenced by Mg–Li smectite formation and hydrous silica, with minimal illitization compared to nearby deposits.
Differences in lithium availability and pH of deeper fluids were noted compared to the Thacker Pass deposit.

Abstract

Abstract The McDermitt caldera (Oregon–Nevada, USA) hosts the largest volcano-sedimentary (VS) Li resource globally. This study presents an integrated geological, mineralogical, and isotopic investigation of the McDermitt deposit in Oregon, with the aim of constraining the processes responsible for Li enrichment in clay-type VS Li mineralization. Our study reveals that Li mineralization occurs in stratiform lacustrine units composed of hectorite-bearing claystones interbedded with siliceous–carbonate beds and altered ash fall units. Lithium enrichment is mainly controlled by the formation of Mg–Li smectites (hectorite) associated with hydrous silica, and locally by zeolitization of tuffaceous precursors – a pathway that can be explained by devitrification of volcanic glass under near-neutral to slightly alkaline conditions. Geochemical and isotopic data indicate that mineralization formed through fluids at average temperatures of 133 °C and δD values of − 107‰, consistent with heated meteoric waters in a geothermal setting. Unlike the nearby Thacker Pass deposit, illitization of smectite did not occur, reflecting differences in the total amount of Li available and in the pH chemistry of deeper fluids circulating on a caldera-scale.

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