Introduction to the Geology of Ethiopia
The Orogenic belts of the Arabian Nubian Shield (ANS) and the Mozambique Belt (MB) are believed to be more prominent in outcrop in Ethiopia than in any other country of the Horn of Africa (Kazmin, 1972; Berhe, 1990). However, the rocks belonging to these orogenic belts are only exposed in a few areas, which have not been affected by Cenozoic volcanism and rifting, and where the Phanerozoic cover rocks have been eroded away (Tefera et al., 1996)
Generally, little work was done on the geology of Ethiopia until the early 1970s. Some more generalized ideas about the Geology of Ethiopia were derived from limited mapping and prospecting in various regions of the country (eg., Blanford, 1870; Dainelli, 1943). Dainelli (1943) translated this work from the Italian in to the English language and compiled the Geology of Ethiopia with limited modification, specifically for the rift valley volcanics and tectonics. Subsequently, the work by Kazmin (1972), Kazmin et al. (1978) and Merla et al. (1973) extended the previous studies of the geology of Ethiopia and East Africa.
Gilboy (1970) and Chater (1971) were first to propose a three-fold classification of the Precambrian basement rocks of southern Ethiopiain to Lower, Middle and Upper Groups. Each of these groups is characterized by different lithology and structure, with an overall decrease in metamorphic grade from the Lower to the Upper Group. Kazmin (1972) redefined these groups as the Lower, Middle and Upper Complexes, comprising Archean, Early Proterozoic, and Late Proterozoic lithostratigraphic sequences, respectively. The same author compiled the Geology of Ethiopia in the form of a 1:2,000,000 scale map, with an accompanying report (Kazmin, 1972).
In 1968, the Ethiopian Institute of Geological Surveys (EIGS) was established with the aim to conduct systematic and integrated geological mapping and mineral exploration. Since then, a large amount of mapping and exploration activities has been carried out in different parts of the country (e.g., Omo River Project, 1975; Kozyrev et al., 1985; Moore et al., 1987; Woldegebriel et al., 1994; Hambissa et al., 1997; Tadesse, 1997; Tadesse and Melaku, 1998). At present, about 30 % of the country has been mapped at the 1:250,000 scale. The cumulative regional mapping shows that the country is covered by about 18% Proterozoic
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