Assessing trace-element mobility during alteration of rhyolite tephra from the Dinaride Lake System using glass phase and clay separate LA-ICP-MS geochemistry

Present research reports on a novel approach in the study of trace element mobility during argillitization of volcanic glass which is based on in-situ LA-ICP-MS glass analyses and that of spatially related illite-smectite collected in the form of fraction separates. Studied material stems from lacustrine sediments of the Dinaride Lake System (DLS) which bear evidence of intensive weathering of distal tephra during the Miocene climatic optimum. Yttrium and HREE were likely mobilized from decomposing glass in the form of carbonate complexes and were, consequently, significantly depleted in studied clays. On the other hand, Mg-rich illite-smectite depicts an elevated adsorption potential of solvated LREE complexes. This may be explained by clay surface geochemistry largely controlled by Mg for Al octahedral substitution. Present research highlights the role of eogenetic 2:1 clay aluminosilicates which, under favorable geological conditions, may be conductive to secondary REE enrichment and formation of potential ion-adsorption type deposits.