The Geology and Structural Evolution of the Aningeje Metasediment in the Lower Part of Oban Massif, South-Eastern Nigeria

Abstract

The field mapping carried out in the study area was aimed at establishing the local geology of the area, which include the identification of rocks and minerals, and the reconstruction of the petrogenesis and structural evolution of the rocks in the area. Six representative rock samples from twenty two sample locations were selected for thin section petrographic analysis. The results revealed that the area is underlain dominantly by schist with pockets of granite gneiss, quartz-biotite gneiss, quartzite, pegmatite and amphibolite emplaced within the country rock (schist). The schist exhibits alternation of dark and white bands with foliation planes, and trending in the NE-SW direction. The quartz veins are leucocratic, whereas pegmatite contains porphyroblastic texture with the presence of leucocratic minerals (plagioclase). Certain index minerals revealed from the petrographic studies are; quartz, biotite, hornblende, microcline, muscovite, garnet, zircon, sphene, plagioclase and other accessories. These minerals suggested that the area was subjected to Barrovian sequence metamorphism of the amphibolite facies. Structural elements such as joints, fractures, foliations and veins show series of deformational episodes that affected the area, and the major NE-SW trend of the structures suggested Pan African event (600±150 Ma). Aningeje is endowed economically with valuable minerals such as quartz, mica, feldspar and other accessories. The rocks in the area are highly weathered, fractured and jointed. This provides a greater potential for ground water in the area.