A geochemical reconnaissance of the Alid volcaniccenter and geothermal system, Danakil depression, Eritrea

Abstract

Geological and geochemical studies indicate that a high-temperature geothermalsystem underlies the Alid volcanic center in the northern Danakil depression of Eritrea Alid is avery late-Pleistocene structural dome formed by shallow intrusion of rhyolitic magma some of which vented as lavas and pyroclastic flows Fumaroles and boiling pools distributed widelyover an area of ∼10 km2 on the northern half of Alid suggest that an activehydrothermal system underlies much of that part of the mountain Geothermometers indicate thatthe fumarolic gases are derived from a geothermal system with temperatures >225°C Theisotopic composition of condensed fumarolic steam is consistent with these temperatures andimplies that the source water is derived primarily from either lowland meteoric waters or fossilRed Sea water or both Some gases vented from the system (CO2 H2Sand He) are largely magmatic in origin Permeability beneath the volcanic center may be high given the amount of intrusion-related deformation and the active normal faulting within theDanakil depression