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Title: Geothermal Study in Northwest Lake Abaya Area (Southern Ethiopian Rift)
???metadata.dc.contributor.*???: Dr. G. M. DI Paola
Yirgu, Gezahegne
Issue Date: Jul-1980
Publisher: Addis Ababa University
Abstract: Geothermal energy, the cheapest among the different sources of power, is thought to provide a solution for the rising demand" of electricity in Ethiopia, because the Ethiopian Rift Valley and Afar area have been identified to have one of the greatest geo-thermal potential in the world. The NW Lake Abaya geothermal province, situated in the southern part of the Ethiopian Rift Valley near to its western maroin, is one of the target areas singled out for detailed exploration purposes. The area is characterized by high heat flow indicated by the presence of a number of hot_springs fumaroles and a geyser. The volcano-tectonic evolution which started in early Miocene, has been in progress throughout Plio—Pleistocene and Quaternary activity has been evidenced in the most active part of the Rift. The volcanic products, represented by basalts and rhyolitic products, vary from alkaline to mildly alkaline and the recent fissural basaltic volcanism shows a transitional nature. The final silicic products are represented by per alkaline royalties, probably commendites. The hydro geological evidence suggests that quite abundant amount I of water is recharged from the surrounding highland areas in the north and NW into the reservoir system and that the hot springs are all of meteoric origin. Important circulation of water at depth is evidenced from isotopic data. The chemical characteristics of the thermal manifestations suggest the presence of two groups of thermal waters with different geochemical histories, A high temperature reservoir is represented by the first group while different degrees of mixing and dilution of the original hot water with a cold subsurface groundwater is rethought; rise to the second group of thermal springs., Preliminary geoelectrical survey indicates the presence of two low—res1stivity zones separated by a layer of higher resistivity. The deeper low—resistivity structure has been tentatively interpreted to represent the geothermal reservoir of this area. All the available data show that the studied area has all the necessary characteristics for the existence of an exploitable geo-thermal field of high enthalpy. A hydrothermal system with an estimated temperature of ZOGOC is considered to exist at depth between 700 and 1300 m within an area of about 45 km2 extending for about 8 km north of the Nw Lake Abeya shore. This system, present in Tertiary ignimbrite-basalt series, is dominantly a hot water system. An effective cover formation is thought to be provided by an impermeable layer of some 200 m thick. It is considered that both the magmatic heat source and the groundwater circulation Supplying the reservoir are of regional importance.
Description: A Thesis Presented The School of Graduate Studies Addis Ababa University In Partial Fulfillment A of the Requirements for the Degree Master of Science in Geology.
Appears in Collections:Thesis - Earth Sciences

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