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

• Published in: Geothermics 1999-04, Vol.28 (2), p.161-187
• Main Authors: LOWENSTERN, J. B, JANIK, C. J, FOURNIER, R. O, TESFAI, T, DUFFIELD, W. A, CLYNNE, M. A, SMITH, J. G, WOLDEGIORGIS, L, WELDEMARIAM, K, KAHSAI, G
• Format: Article
• Language: English
• Subjects: Deformation; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Geology; Geothermal fields; Geothermal prospecting; Geothermics; Isotopes; Temperature; Volcanic rocks
• ISSN: 0375-6505; 1879-3576
• DOI: 10.1016/S0375-6505(99)00002-4

Geological and geochemical studies indicate that a high-temperature geothermal system underlies the Alid volcanic center in the northern Danakil depression of Eritrea. Alid is a very 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 widely over an area of approx. 10 km super(2) on the northern half of Alid suggest that an active hydrothermal system underlies much of that part of the mountain. Geothermometers indicate that the fumarolic gases are derived from a geothermal system with temperatures >225 degree C. The isotopic composition of condensed fumarolic steam is consistent with these temperatures and implies that the source water is derived primarily from either lowland meteoric waters or fossil Red Sea water, or both. Some gases vented from the system (CO sub(2), H sub(2)S and 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 the Danakil depression.