PETROGENESIS OF GRANITOIDS OF GABA SANBATA AREA, EASTERN GIMBI, WESTERN ETHIOPIA

Degefa Temesgen

dc.contributor.author	Degefa Temesgen
dc.date.accessioned	2021-02-24T08:54:34Z
dc.date.available	2021-02-24T08:54:34Z
dc.date.issued	2021-02-24
dc.identifier.uri	http://ir.bdu.edu.et/handle/123456789/11950
dc.description.abstract	The study area is situated within Eastern Gimbi, western Ethiopian Precambrian basement terrain which can be classified into Didesa Domain group. It covers about 170 km2. This study generally considered the petrogenesis of granitoids of Gaba Sanbata area, Eastern Gimbi, Western Ethiopia. Field investigation, petrographic interpretation and geochemical data analyses have been applied to meet the objectives. The study area is dominated by migmatites gneiss, gabbro, quartz vein and granitoids. On the basis of modal analysis the studied samples are classified as syenogranite and alkali-feldspar granite. The petrographic interpretation suggested that the studied samples are characterized by phaneritic texture with dominance of K- feldspars, quartz, polysynthetic twining plagioclase and minor amount of biotite and opaque. Petrography and geochemical compositions of granitoids indicates that they are shoshonitic to high-K calc-alkaline affinities and characterized by high SiO2, high total alkali (Na2O+k2O) concentrations (8.42–10.32 wt. %). The negative correlation between SiO2 with other oxide such as Al2O3, MgO, CaO, Fe2O3total, TiO2 and P2O5 and positive correlation with other alkali K2O and Na2O indicate fractional crystallization process controls the evolution of magma. The enrichment of large ion lithophile elements (LILE), depletion of high field strength elements (HFSE) indicates a partial melting and crustal contamination of magma and were formed in the post-collisional tectonic setting. The negative Eu anomaly and depletion in Sr, Nb, Ba, and Ti are imply that fractionation of plagioclase. The studied samples are A-type, metaluminous granitoids and display slightly enriched in light rare earth elements relative to heavy rare earth elements. Thus, we concluded that the granitoids rocks are A-type and likely derived from mantle–crust (magma mixing) source of juvenile crust. The negative anomalies of Nb, Ti and P might indicate a source and contamination origin. Therefore, studied samples of Atype granitoids were formed by assisted of fractional crystallization from a crustal contamination of mantle derived magmas and partial melting of crustal materials within plate granite tectonic setting. Key words: Granitoids, petrogenesis, partial melting, fractionational crystallizations, crustal contamination, and tectonic setting	en_US
dc.language.iso	en	en_US
dc.subject	Petrology	en_US
dc.title	PETROGENESIS OF GRANITOIDS OF GABA SANBATA AREA, EASTERN GIMBI, WESTERN ETHIOPIA	en_US
dc.type	Thesis	en_US