Deciphering structures and deformation of the Obuom Gold Prospect, Central Ashanti Belt of Ghana: A lithostructural approach

摘要

The Obuom Gold Prospect is located in the central part of the Paleoproterozoic Birimian Ashanti belt of southwest Ghana. The prospect is approximately 45 km(2) and is underlain by basalt, andesite and dacite volcanic beds, graphitic and chlorite phyllites of sedimentary origin and granites. Published works on the Obuom geological terrane, using gravity models, showed that, the structures are more complex than previously thought and may involve multiple thrust slices. This research identified two deformational episodes; the first has a remarkable sinistral sense probably synchronous with an Eoeburnean event with the second, an overprint of dextral shearing during the Eburnean event. The first episode, Do(1) is characterized by NW-SE compression which resulted in subvertical NE-SW trending S-1 axial plane metamorphic foliation in tight to isoclinal F-1 folds with NW-SE trending L-1 lineations. The second episode, Do(2) indicates continuous shortening which produced nearly upright F-2 folds with east-west striking axial planes, slight plunging hinges and associated subparallel crenulation cleavages. The first deformational event Do(1) which represent NW-SE compression is observed affecting only the Sefwi Group. The Do(2) resulting from N-S compression affected both the Sefwi and Kumasi Groups. (C) 2016 Elsevier Ltd. All rights reserved.