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

• The Obuom Gold Prospect belongs to the Central Ashanti Belt of Ghana.
• The underlain rocks are metabasalts, phyllites (graphitic and chlorite) and granite.
• The area is affected by two deformational episodes denoted as DO1 and DO2.
• DO1 and DO2 resulted from NW-SE and N-S compressional deformations respectively.
• The terrane is a dextral tectonised type with a presumed earlier sinistral movement.

The Obuom Gold Prospect is located in the central part of the Paleoproterozoic Birimian Ashanti belt of southwest Ghana. The prospect is approximately 45 km2 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, Do1 is characterized by NW-SE compression which resulted in subvertical NE-SW trending S1 axial plane metamorphic foliation in tight to isoclinal F1 folds with NW-SE trending L1 lineations. The second episode, Do2 indicates continuous shortening which produced nearly upright F2 folds with east-west striking axial planes, slight plunging hinges and associated subparallel crenulation cleavages. The first deformational event Do1 which represent NW-SE compression is observed affecting only the Sefwi Group. The Do2 resulting from N-S compression affected both the Sefwi and Kumasi Groups.