| Title | A Review of Geological and Geophysical Exploration of Corbetti Geothermal Prospect, Ethiopia |
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| Authors | Altaye, E., Oluma, B., Hunegnaw, A., Tadesse, K. and Abdulkadir, M. |
| Year | 1986 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | |
| Abstract | Corbetti geothermal prospect is in the main Ethiopian rift with extensive surfacethenml manifestations. Hydrothermal activity took place in a setting of alternatinghydrolqical changes, denudation, sedimentations and periodic volcanism within the caldera floor. Hydrothermal features are controlled by volcanological and tectonic structures such as caldera rim fractures, fissures, fault s and eruption centers. The main surface alteration minerals are clays. Caldera and post caldera lavas are peralkaline rhyolite (pantelleriticrhyolite) as confirmed by petrochemistry. There is a change in chemistry between post caldera and caldera rocks. The movement of sub-surface hot geothermal fluid is from Corbetti caldera to Lake Shalla which is supported by local hydrological gradient and electrical resistivity results where an elonqated low resistivity structure along the Wonji fault belt is opening to Lake Shalla from the caldera. Thelow resistivity anomaly is associated with northern caldera rim structure and craters. The eastern component is related to inferred caldera rim and E-W fissures with hydrothermal features. Southern half of the caldera is characterized by high resistivity property that may not mean the absence of geothermal reservoir underneath but could be the e f f e c t of topography, coupling effect and inhomogeneity of the caldera complex. Two dimensional denser intrusive body is assumed due to the presence of >10 mgals that could not be compensated by topographic effect between Lake Shalla and Lake Awassa. The inferred caldera rim is supported by the Bouguer anomaly map of the prospect area and geological evidence. |