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Lithium in volcano-sedimentary deposits: an overview

^^ Francesco Putzolu^^ 1, Robin Armstrong1, Richard Herrington1

Abstract

The increase of the lithium (Li) demand, driven by its importance to develop low-CO2 emission technologies, makes the discovery of new esources and of new deposit types pivotal to securing a sufficient future supply of this critical commodity. Volcano-sedimentary (VS) deposits represent a relatively poorly studied and still underdeveloped type of Li resource. These deposits consist of mixed volcanic-sedimentary successions deposited in closed basins developed in felsic magmatic provinces. The Li ore in VS systems includes complex mineralogical assemblages dominated by phyllosilicates and borosilicates formed from the alteration of Li-fertile felsic volcaniclastic/pyroclastic suites. In this contribution we present an overview of the geological features of VS Li deposits with the goal of providing a generalized and updated deposit model. We focus on several key characteristics of VS deposits, including: 1) the relationship between specific tecto-magmatic environments and the generation of Li-rich melts; 2) the mechanisms of transfer of Li from the igneous to the volcano-sedimentary environment; 3)  the main alteration mechanisms linked to the Li upgrade in the critical zone and the formation of secondary ore-bearing assemblages.  These aspects are discussed based on published available data, but also by presenting new observations on representative VS deposits from western US,  eastern Europe and elsewhere.