Petrographic Studies of Rocks around Arum and Its Environs, North Central Nigeria
M. M. Iliya *
Department of Geology and Mining, Nasarawa State University, Nigeria.
U. M. Ma’aji
Department of Geology and Mining, Nasarawa State University, Nigeria.
Isah Umar
Department of Geology and Mining, Nasarawa State University, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
A detailed geological mapping of the area around Arum and environs part of Kurra sheet 189 SW was carried out on the scale of 1: 12, 500. Geologic field mapping and petrographic study (both megascopic and microscopic) were the methodology used. The geologic mapping of the area identified four rock units which are; granite, porphyritic granite, granitic gneiss and Porphyroblastic gneiss. These rock types were distributed such that the granite at the north-eastern part covered about 25%, the north –western portion was occupied by the porphyritic granite which occupied the largest portion of about 30% of the area. The third rock unit is the granitic gneiss which covered only about 20%. The fourth (last) and the oldest rock unit is the Porphyroblastic gneiss covering about 25% of the total area at the south-eastern corner. Megascopic and microscopic study revealed that the rocks in the area comprised of minerals such as; quartz, biotite, muscovite, microcline, feldspar, hornblende, garnet, etc. Structures that were clearly evident in the area included fault, foliation, joints, and veins. Structural analysis showed that their rose diagrams proved a NW-SE, NNE-SSW and NE-SW trends to be dominant.
Keywords: Petrography, structures, mapping, arum