Jornal de Geologia e Geofísica
Acesso livre

Abstrato

Geology and Petrography of Granitoid Rocks of Anger Gute Area, an Implication of Dimension Stone, East Wollega, Western Ethiopia

Faye Abule*, Dereje Kenea, Firawalin Desalegn

The Anger Gute area is located in the metamorphic terrains of Western Ethiopian Basement within the Nekemte map sheet. It occupies kilometres of metamorphic outcrops with a felsic granitoid intrusion. These granitoid intrusion cut across in the form of lineament that emplaced along with the lithological contact of low and high-grade rocks with decreasing of metamorphic grade from the lower to the upper complex. There are different microstructures and textures such as; perthites, mrymekite, quartz-vein, and joints with minimum space which indicates the tectonic evolution and metamorphic processes of granitoid rocks of the Anger Gute area. Anger Gute granite has been emplaced pre, syn/late-to post tectonically associated with the major deformation events. The deposits from massive boulders, big hills, mountain chains with minimum discontinuities afford the wide possibility for the extraction of large volumes of commercial valuable-sized dimension stone. Petrographically, this granite is characterized by coarse grain to medium grains and dominantly consists of alkali feldspar (K-feldspar) phenocrysts, quartz, plagioclase, and biotite as major components. Epidote, Muscovite Fe-Ti oxide (Opaque) as minor components and also Sphene and hornblende as trace minerals. The mineralogical composition is the main property controlling the rock strength. The Anger Gute Granitoid rocks compositionally contain Quartz, orthoclase, and garnet that indicate good strength and less strength depending on the percentage of Plagioclase, biotite, and muscovite minerals. The strength increases as the mean grain size decreases and the strength increase as the quartz and orthoclase content increases.