Browsing by Author "Ridwan, Munir"

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    Geology and Genesis of Gold Mineralization in Burikaro and Ejersa Areas, Guji Zone, Oromia National Regional State, Southern Ethiopia
    (Addis Ababa University, 2014-05-30) Ridwan, Munir; Getaneh, Worash (PhD)
    This study deals about geology and genesis of gold mineralization in Burikaro and Ejersa areas, which are located in the Neoproterozoic Adola gold field of southern Ethiopia. The area is not well explored and almost no research work has been done so far. Detailed review of the geodynamic evolution and mineralization history of the region, field description and geological mapping, rock and ore petrography, and surface sample chemical analysis were conducted. Secondary data from trench sample chemical analysis were also utilized in the study. The area comprises highly weathered and variably deformed upper greenschist to epidote-amphibolite facies metamorphic rocks like amphibolite, talc-tremolite-actinolite schist, graphite-quartz-mica schist, meta-conglomerate, and meta-sandstone. Intermediate to mafic meta-plutons such as meta-dolerite and meta-gabbro are also present intruding the amphibolite rock. A major N-S and two minor NW-SE and E-W trending shear zones; early- and late-tectonic quartz (± calcite) veins; and hydrothermal alterations like silicification, carbonatiztion, tourmalinization, and chloritization were observed. Besides its occurrence as a free gold, the gold mineralization of the study area is mainly associated with the hydrothermally altered major N-S trending shear zones containing late-tectonic quartz (± calcite) veins with associated sulfides and present mainly in the graphite-quartz-mica schist and meta-conglomerate/meta-sandstone. The ore minerals associated with gold are dominantly pyrite, magnetite, and ilmenite; minor amounts of hematite and chalcopyrite, and accessory mounts of sphalerite, covellite, and limonite chiefly occurring as open-space filling and replacement type mineralization. Based on texture, mineral association, and alteration a paragenetic sequence is suggested. The presence of not mineralized higher grade mafic metamorphic rocks at the base, the association of the gold mineralization with the lower grade meta-sediments, and the negative correlation between gold and metals like cobalt and nickel suggest that the possible source rocks of the gold are the underlying mafic rocks and metamorphic dehydration is the probable source for the hydrothermal fluids and leaching of gold from the mafic rocks. The association of gold mineralization with sulfides suggest that HS--or H2S-complexes were responsible for gold transport in the area.