H2 generation versus H2 consumption in volcanic gas systems: A case study in the Afar hot spot in Djibouti

摘要: The Djibouti area is located in the Afar depression which corresponds to the core of a major hot spot at the junction of three rifts: The Red Sea oceanic rift, the Gulf of Aden oceanic rift and the East African continental rift. In the extension of the Gulf of Aden, the opening of the Gulf of Tadjourah in the last 30 million years was followed by the establishment of parallel NW-SE oriented depressions (Gobaad, Hanle, Gaggade, Assal-Ghoubbet). This region is characterised by high heat flow, complex volcanic and tectonic activity, and a dense network of faults favorable to the development of hydrothermal activities. A field survey was conducted to study the gas composition and origin in thermal springs and fumaroles along a transect running from the Lake Abbhé to Djibouti. Hydrogen traces were detected at fumaroles and hot springs associated with hydrothermal systems at the edges of the Gobaad, Hanlé, Gaggade, Assal …