Mineralogy and Hydrothermal Alteration of Rocks Associated With Gold Mineralization in Akobo Greenstone Belt, Southwestern Ethiopia

ABSTRACT

The Akobo Greenstone Belt gold mineralization in the Western Ethiopian Greenstone Terrain is hosted by the Surma shear zone. Talc‐chlorite schist, chlorite schist, actinolite bearing rocks, granite, meta ultramafic rocks, felsic metavolcanic rocks, and Banded Iron Formation are the dominant rock types found in the Gindibab‐Wolleta and Chamo‐Segele areas. This study describes the geology, mineralogy, and mineral chemistry/alteration of host rocks associated to the gold mineralization. We conducted outcrop and hand specemen, petrography, and mineral chemistry analyses. The host rocks of the auriferous quartz vein in the Gindibab‐Wolleta area is felsic metavolcanics and banded iron formation. The metamorphosed felsic‐mafic igneous rocks of greenschist facies hosts the mineralization. Chloritization, carbonatization, sericitization, and biotitization are the common hydrothermal alteration associated with the host rocks. The hydrothermal alteration is characterized by the chlorite + plagioclase + ankerite + biotite + calcite + sericite assemblages. The chlorite geothermometery suggests that the temperatures of hydrothermal fluids associated to the gold mineralization in the Chamo‐Segele and Gindibab‐Wolleta areas ranges from 180°C to 350°C.