PETROGRAPHY AND GEOCHEMISTRY OF NEOPROTEROZOIC GRANITES FROM GOZAMIN AREA, NORTH WESTERN ETHIOPIA

TELELU ABEBE

dc.contributor.author	TELELU ABEBE
dc.date.accessioned	2021-02-24T09:30:51Z
dc.date.available	2021-02-24T09:30:51Z
dc.date.issued	2021-02-24
dc.identifier.uri	http://ir.bdu.edu.et/handle/123456789/11954
dc.description.abstract	Gozamin area exposes granitic rocks belonging to eastern corner of the western Ethiopian Precambrian shield. The aim of this thesis work is to understand the petrography and the geochemical composition of Gozamin granites and finally to assess their petrogenesis. To achieve the objectives various methodologies were employed, such as field work for sampling and mapping, petrographic investigation and geochemical analysis. The major rock types identified in the studied area represented by medium to coarse grained pink and gray granite. Petrographically, Gozamin granites range from alkali feldspar to syenogranite and are predominantly composed of alkali feldspar and quartz with subordinate minerals of plagioclase, biotite, hornblende and opaque. Geochemically, they are characterized by high silica content, exhibit ranges of SiO2 (70.5-79.5) and are similar to high k-calc alkaline granites with higher total alkali content (7.52 - 8.81 wt.%) and show an overall predominance of K2O over N2O. The negative correlation of SiO2 with Al2O3, FeOt, CaO, TiO2, and P2O5 indicate fractionation nature of these granites during magmatic differentiation. They have distinctive geochemical features typical of I-type granitoid, metaluminious feature (A/CNK< 1.3), low P2O5 content, enriched in light rare earth elements relative to heavy rare earth elements and have fractionated rare earth element patterns (La/Yb) N=1.77–63.18). In primitive normalized mantle multi element diagram, the patterns of the samples show enrichment in large ion lithophile elements and depletion in high field strength elements (e.g., Nb, Ta, and Ti) and enrichment in Pb relative to Ce are typical of continental crustal magmatism. Additionally, the diagram shows high concentrations of Th, U, and Pb in the granites point to additional involvement of crustal components in their generation. Tectonically, the analyzed samples have characteristics of syn-collision and volcanic arc granitoid or subduction related granitoid rock formation which suggests that they are formed in syn-collisional and volcanic arc environment. This indicates the Gozamin granites are one of EAO features. The observed geochemical features (major element and trace element variation) suggest that the studied granites were generated by crustal melting and followed by fractional crystallization. Keywords Petrography, Geochemistry, Neo-Proterozoic granites, tectonic setting, Gozamin	en_US
dc.language.iso	en	en_US
dc.subject	Petrology	en_US
dc.title	PETROGRAPHY AND GEOCHEMISTRY OF NEOPROTEROZOIC GRANITES FROM GOZAMIN AREA, NORTH WESTERN ETHIOPIA	en_US
dc.type	Thesis	en_US