Pan-African deformations in the basement of the Negele area, southern Ethiopia

Abstract

Polydeformed and metamorphosed Neoproterozoic rocks of the East African Orogen in the Negele area constituted three lithostructurally distinct and thrustbounded terranes. These are, from west to east, the Kenticha, Alghe and Bulbul terranes. The Kenticha and Bulbul terranes are metavolcano-sedimentary and ultramafic sequences, representing parts of the Arabian-Nubian Shield (ANS), which are welded to the central Alghe gneissic terrane of the Mozambique Belt affinity along N-S-trending sheared thrust contacts. Structural data suggest that the Negele basement had evolved through three phases of deformation. During D1 (folding) deformation, north-south upright and inclined folds with north-trending axes were developed. East and west-verging thrusts, right-lateral shearing along the north-oriented Kenticha and Bulbul thrust contacts and related structural elements were developed during D2 (thrusting) deformation. The pervasive D1 event is interpreted to have occurred at 620-610 Ma and the D2 event ended prior to 554 Ma. Right-lateral strikeslips along thrust contacts are interpreted to have been initiated during late D2. During D3, left-lateral strike-slip along the Wadera Shear Zone and respective strike-slip movements along conjugate set of shear zones were developed in the Alghe terrane, and are interpreted to have occurred later than 557 Ma. The structural data suggest that eastward thrusting of the Kenticha and westward tectonic transport of the Bulbul sequences over the Alghe gneissic terrane of the Mozambique Belt, during D2, were accompanied by right-lateral strike-slip displacements along thrust contacts. Right-lateral strike-slip movements along the Kenticha thrust contact, further suggest northward movement of the Kenticha sequence during the Pan-African orogeny in the Neoproterozoic. Left-lateral strike-slip along the orogen-parallel NNE-SSW Wadera Shear Zone and strike-slip movements along a conjugate set of shear zones completed final terrane amalgamation between the Arabian-Nubian Shield and the Mozambique Belt in Neoproterozoic southern Ethiopia.

Evaluation of mining and mineral processing methods’ impact on tantalite concentrate in Kenticha open pit mine, southern Ethiopia

“…Both together form a coherent block mainly of juvenile crust formed in the oceanic arc setting. The age of subduction and syncollision related granitoid magmatism, metamorphism, thrusting, and strike-slip shearing is reported to have taken place between 680 and 550 Ma (Beraki et al 1989; Worku and Schandelmeier 1996; Yibas et al 2002; Yihunie 2002; Tsige and Abdelsalam 2005). Thus, the basement in southern Ethiopia has experienced a sustained period of compressional tectonics between 660 and 550 Ma (Worku and Schandelmeier 1996).…”