The petrography, metamorphism and deformation history of Neoproterozoic rock from Gida Ayana, Western Ethiopia: implication of Tectonometamorphic evolution

Bishaw Mihret^1*Ajebush Wuletaw²

• ¹Mekdela Amba University, Dessie, Ethiopia
• ²Debre Markos University, Debre Marqos, Ethiopia

The geological study of Ethiopia's basement rocks from the Gida Ayana area of western Ethiopia has revealed significant findings regarding petrography, metamorphism, and deformation history. The geological evolution of the rocks has been thoroughly analyzed through detailed field investigations, overprinting and cross-cutting relationships, and petrographic studies of metamorphic rocks. The findings reveal that the study area experienced poly-phased deformation, with at least three ductile deformation phases (D1 to D3) associated with two metamorphic events (M1 and M2) and the development of brittle structures such as irregular fractures, joints, and veins. Each type of structure observed in the study area has been discussed in detail, highlighting the formation of F2 folds, S2 foliation, L2 lineations, S3 foliations, F3 folds, and joints. The development of steep northeast- to southwestern striking foliation S2 gneissic banding, the mineral assemblage (Or + Pl + Qtz + Bt +- Sp indicates that the prograde metamorphism (M1) is synchronous with D2. The alteration products, sericite, chlorite, and biotite indicate retrograde metamorphism (M2) which may have taken place during uplift or D3 shear zone-related fluid migrations. Regional tectonic setting of Gida Ayana within the East African Orogen. The relationship between the Gida Ayana metamorphism and deformation with larger tectonic processes, like continental collisions during the Pan-African Orogeny, was discovered. The study analyzed the orientation and features of deformation structures and their associated metamorphic events, offering important insights into the tectonic and metamorphic history of the East African Orogen.