Lithium isotopes in waters of the tropical volcanic island of Guadeloupe: A proxy of high and low-temperature water-rock interactions

We report the first measurements of Lithium isotopic ratio (δ7Li) for eleven of the main rivers in Guadeloupe and four thermal springs on the slopes of La Soufrière volcano. We also report the chemical composition of these waters (concentrations of dissolved Li, Na, K, Ca, Mg, Cl, S, SiO2). We show that the large range of δ7Li values (3.0 to 31.6 ‰) is explained by several water-rock interaction processes at the scale of this small island. These results have important implications for characterizing the mean riverine flux of lithium coming from the weathering of continental volcanic rocks, understanding the global oceanic budget of lithium, and finally, for interpreting the δ7Li of past seawater.