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ABSTRACT
Akoko-Edo and environs is of the Basement Complex of Nigeria and consist of several types of metamorphic , sedimentary and igneous rocks, having its own unique characteristics. The case study entails a brief analysis of three types of metamorphic rocks namely, schist, quartzite and metaconglomerate which fall under the Igarra schist belt. The location of study of area lies between latitude N7 10’ 0‖ and N7 17’ 30‖ and longitude E6 2’ 30‖ and E6 15’ 0‖. Fifteen (15) rock samples were obtained randomly from the field and were analyzed under thin section to obtain their mineralogical characteristics. Modal composition of every rock sample obtained and analyzed shows presence of minerals like quartz, plagioclase, micas, hornblende in association with one another. The schist and metaconglomerate are observed to be medium grade metamorphic rocks while the quartzite formed under a much higher temperature and pressure, but still they all belong to the green schist facies. The structures found include folds, fractures (joints) and veins. The structural trends shows fracture trending in NW-SE direction for the metaconglomerate, NW-SE and N-S for the schist and NE-SW direction for the schistose quartzite. The foliation planes of each rock shows NWSE, a minor NE-SW and N-S direction for the Schist, while NW-SE direction for the Metaconglomerate and Schistose quartzite, all these were thus represented in rose plots. The petrographical analysis reveals that the three types of rock have similarity in their modal composition. The rose plots reflects that the rocks have undergone series of deformation and has been acted upon by heterogeneous stress. The similarity in the composition between the schist and metaconglomerate may be the reason why the fracture planes trends in the same direction and the more competent rock quartzite trending in an opposite direction.
