Punctuated release of Lithium from past ignimbrite eruptions: key to present Lithium-brine resources in the Western US & Central Andes

Lacustrine evaporite basins with significant Li resources in the western U.S and central Andes were filled over millions of years concurrent with volcanism. Since felsic ignimbrites are voluminous and contain more Li than andesites, their pre- and post-eruptive concentrations of Li were determined to evaluate Li mobility. Comparisons of the Li content of melt inclusions to those of pumice or whole rock show that Li-enriched ignimbrites release up to 98% of their Li into soluble salts that are removed by meteoric water whereas Li-poor ignimbrites release as little as 36%. Calderas trap about 1/3 of the Li released from such eruptions, with the remainder deposited in adjacent basins. Small volume eruptions of Li-enriched tuff can release tens of megatonnes into one basin whereas large volume eruptions of ordinary tuff spread a similar amount over many basins. Large volume eruptions of Li-enriched tuff can spread gigatonnes of Li over many basins. The punctuated release of large amounts (tens to thousands Mt) of Li from successive ignimbrite eruptions into closed drainage basins increases resource potential, is more than enough to form world-class Li-brine and clay resources (tenths to several Mt) and should be included in mass-balance, exploration, and assessment models.