Geology and Isotope Systematics of Gold Deposits in the Abansuoso Area of the Sefwi Belt, Southwestern Ghana

Abstract

This study utilised lithogeochemistry and stable isotope geochemistry to assess the gold mineralisation in the host rocks of the Abansuoso area. It also studied the isotopic signature of hydrothermally altered and unaltered rocks as a tool for the preliminary prospecting of gold in Ghana’s Birimian belt. The research identified a close association between Au and As, Mo, and W, which is characteristic of orogenic gold deposits. The mineralised and unmineralised rocks show similar content of major and trace elements which suggests that the mineralisation did not significantly affect the primary composition of the mineralised rocks. The concentrations of δ18O (8.9‰ to 17.4‰, n = 22, mean = +13.7‰) and δD (−117 to −33‰, n = 22, mean = −57.9‰) in the rocks are comparable to those from other Birimian regions in Ghana and West Africa. The lack of variation in δ18O suggests a system buffered by rocks, with metamorphic fluid originating from rocks with identical δ18O values. However, the effect of mineralisation on the δD values of rocks is substantially more apparent than its effect on the δ18O values of the rocks.

Keywords

• Stable isotopes
• mineral exploration
• geochemistry
• gold
• Birimian
• Ghana