Subduction and Hydrogen Release: The Case of Bolivian Altiplano

Natural hydrogen is known to be generated in the crust by water/rock interactions, especially oxidation of iron-rich rock or radiolysis. However, other sources, deeper ones, exist. In context subduction, dehydration slab, destabilization NH4, and hydration mantle wedge above subducting lithosphere may generate H2. We present here a compilation gases central part Pacific subduction results first field acquisition dedicated H2 measurements Bolivia between La Paz South Lipez. Various zones have been studied: emerging thrust faults western borders Eastern Cordillera, Sajama area that corresponds volcanic zone near Chile border northward from Uyuni Salar, finally, Altiplano-Puna Volcanic Complex Soil gas measurement within around Salar itself was not fully conclusive. North are very rich CO2, enriched N2 poor On opposite, southward, all samples contain some H2; major nitrogen, which overpass 90% after air correction, CO2 content limited. δC13 isotope varies −5 −13‰, it surprisingly compatible with gas, as well asthenospheric CO2. The methane close 0, only few points reach 1%. isotopes (−1‰) indicate an abiotic origin, thus related deep presence. high steam flow geothermal Lipez combined water at least 1 ton currently released per day each deserve evaluation its economic value. nitrogen content, paleo-subduction areas, questions slab alteration.