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| dc.contributor.author | KIDIST TESFA | |
| dc.date.accessioned | 2021-01-11T09:04:10Z | |
| dc.date.available | 2021-01-11T09:04:10Z | |
| dc.date.issued | 2021-01-11 | |
| dc.identifier.uri | http://ir.bdu.edu.et/handle/123456789/11845 | |
| dc.description.abstract | This study is conducted in the Birsheleko area, NW Ethiopian plateau. The main aim is to determine the Petrogenesis of volcanic rocks and associated mafic dykes. To accomplish the research objective field investigation, petrographic and major and trace element geochemical analysis using a combination of ICP-MS and ICP-AES methods was applied. The lithological units identified in the study area are basalt, scoria cones, dolerite, and basaltic andesite. Basaltic andesite and dolerite are exposed as a dyke, besides; basaltic units cover most of the study area. The studied samples are characterized by aphyric to porphyritic texture with a variable proportion of plagioclase, olivine, and pyroxene as phenocryst. The groundmass is composed of plagioclase, olivine iron-titanium oxides (opaque minerals), clinopyroxene, and orthopyroxene. Based on the modal analysis the rocks are divided into pyroxene phyric basalt, Olivine phyric basalt, plagioclase phyric basalt, plagioclase phyric dolerite, and aphyric trachy flow basalt and basaltic andesite. Most of the studied samples fall into the tholeiitic group, however; two samples were grouped into transitional and alkaline groups. From the Harker variation diagram, most of the major and trace elements did not show a clear trend instead they are scattered suggesting the compositional variation of the studied rocks cannot be explained in terms of fractional crystalization. In the primitive mantle normalized multi-element diagram the tholeiitic samples show depletions in Rb, Th, Ce Pr, P, and Nb and prominent peaks at Ba, K, Pb, U, and Sr. However, the transitional and alkaline basaltic rocks show enrichment in Pb, Sr, Nb, Ba, depletion in Sm, Pr, without and the positive anomaly at U and K. This indicates that the tholeiites might experienced crustal contamination and the alkaline and transitional basalts are not From (Gd/Sm) N vs. (La/Sm)N diagram, it is determined that all the studied tholeiitic samples are formed by the melting of the spinel peridotite mantle source at a high degree of partial melting and shallow depth. In the contrast, the transitional and alkaline basalts are formed by the melting of the garnet peridotite mantle source by a low degree of partial melting at a greater depth than the tholeiites. Keywords: Crustal contamination, Degree of partial melting, Geochemistry, Northwestern Ethiopian plateau, Petrography | en_US |
| dc.language.iso | en | en_US |
| dc.subject | Seed Science and Technology Program | en_US |
| dc.title | PETROLOGY AND GEOCHEMISTRY OF VOLCANIC ROCKS AND ASSOCIATED MAFIC DYKES IN THE BIRSHELEKO AREA, NORTHWESTERN ETHIOPIAN PLATEAU | en_US |
| dc.type | Thesis | en_US |
