Geology and Geochemistry of Aberma and Its Environ Sheet 54se Gusau, Zamfara State, Nigeria

Abstract

The study area falls within the northwestern part of Nigeria and is underlain by crystalline rocks of the Basement Complex. Field mapping in Aberma and its environs were carried out using topographical map sheet of 54 SE Gusau on a scale 1: 25,000 with an area extends of about 30.8052km2. This field work was carried out using traverse method in conjunction with field equipment such as compass/clinometers, geologic hammer, sample bag and global positioning system. This study however, aims at producing a detail geological map, including the various rock geochemistry and petrography of the study area. The area is underlain by two major lithological rock type which is mica schist and granite gneiss. The granite gneiss is strongly foliated, caused by high temperature and pressure and the minerals observed in plane polarized light include quartz, orthoclase, plagioclase, muscovite, opaque mineral and biotite. The mica schists in the study area are mostly weathered in ditches below the ground surface, the rock is moderately weathered and show schistocyte. The minerals observed in plane polarized light include quartz and muscovite. The dominant structures observed include; joints, Quartz veins, foliation and pegmatite dyke. Structural analysis shows that the rocks have been affected by the Pan African orogeny with the joint’s orientation trending dominantly NNE-SSW and Quartz vein trending in somewhat E-W direction. The microscopic studies revealed that the mineralogical composition of the rocks types of the study area contain varying percentages of quartz, muscovite, plagioclase, orthoclase, opaque mineral and biotite as the major minerals. The geochemical analysis revealed the major and minor elemental distribution of the rock types of the study area. The chemical assay revealed that the granite gneiss and mica schist rock type of the study area are super-saturated with respect to silica, silica (SiO<sub>2</sub>) is the most abundant oxide with an average value of 78.12% in the rock sample. This implies that the rock analyzed is acidic in nature and must have formed from crystallization of an acidic magma because the silica content being greater than 65%.