Tadesse, Solomon (Professor)Kebede, Ayele (PhD)Bedassa, Abebe2020-11-062023-11-092020-11-062023-11-092014-05-30http://10.90.10.223:4000/handle/123456789/23061The study area, Ashashire prospect, is located, in Benishangul-Gumz region western Ethiopia, about 741 km west of Addis Ababa. Field observation and petrographic study shows that the prospect comprises various units that include granite, plagioclase-muscovite (sericite)-quartz schist, quartz vein, actinolite-quartzchlorite schist, carbonitized chlorite-sericite-quartz schist and metasediments. Based on the critical mineral assemblages, the majority of the units are metamorphosed to green schist facies. Field observation and thin section analysis also revealed that the study area experienced at least three phase of deformations that are manifested by various structures. Fourteen samples are analyzed for major and trace elements using XRF method. Among the variation diagrams, only the graphs of K2O vs. Al2O3 and K2O vs. CaO show positive correlation. On the other hand, K2O is negatively correlated with MgO, Na2O and SiO2. Chondrite normalized (wood et al.1979b) spider diagram shows the pattern of the trace elements, particularly the pattern of high field strength elements (HFSE) Zr, Ti & Y, are generally similar, that implies the rocks are genetically related i.e. they have similar source rock. The discrimination diagram (Ti vs. Zr) shows the majority of the rocks of Ashashire area have similar tectonic environment as rocks formed in island arc tholeiites, calc-alkali basalt and mid oceanic ridge basalt (MORB) zone. Statistical analysis of AAS results of gold from forty samples showed a range of gold concentration from < 0.02-48.5 ppm and mean value of 2.88ppm. The histogram indicates about 49 percent of the samples have shown anomalous Au value i.e greater than 0.5ppm. Correlation value and the scatter diagrams of Au with the multi elements (Ag, Cu, Pb, Zn, Ni, Co and Mn) showed that gold has stronger positive association with silver (Ag) only. Based on field observation and textural relationship of ore minerals the gangue minerals that constitute the host rock are formed in the earliest phase and followed by magnetite hematite, ilmenite, pyrite; chalcopyrite and gold are crystallized respectively. The geological and structural setting, host rock alteration and gangue mineralogy are suggestive for a shear-zone hosted orogenic-gold type deposit at Ashashire.enGeologyGeochemistry & GenesisGold MineralizationAshashire ProspectBenishangul-Gumz RegionWestern EthiopianThesis