ScienceDirect The influence of hydrothermal activity on the Li isotopic signature of rivers draining volcanic areas

International audienceWe explore the geochemistry and the isotopic composition of lithium (δ 7 Li) of rivers draining volcanic islands (Guadeloupe, Iceland, Java, Martinique and Sao Miguel) with a specific focus on continental hydrothermal activity. Our preliminary results reveal a global-scale trend between δ 7 Li and the elemental ratio Li/Na in rivers draining volcanic islands. We suggest that this trend results from a mixture between waters with low δ 7 Li and high Li/Na, inherited from high-temperature water rock interactions, and waters with low Li/Na and high δ 7 Li, in which Li is controlled by the neoformation of clays during low-temperature chemical weathering in basaltic soils. This latter process can be described by a simple isotope fractionation model, consistent with reported values for isotopic fractionation factors between secondary weathering products and water. These data highlight the important potential role of continental high-temperature weathering processes on the oceanic budget of lithium