Geology and petrographic studies of basement complex rocks in Damaga and environs, northwestern Nigeria

Abstract

The geology and petrography of basement complex rocks in Damaga and environs were studied to identify the underlying rock types and determine their spatial coverage and mineralogical characteristics. Geological field mapping was conducted, fresh representative rock samples were collected during the field exercise, and petrographic analysis was performed on selected samples using a polarizing microscope. The major mapped rock units are granodiorite, phyllite, and amphibolite schist. Granodiorite accounts for about 38% of the total lithology and is divided into two textural groups: medium- to coarse-grained and porphyritic. It generally occurs as low-lying exposures and boulders. Phyllite is characterized by the alignment of light and dark minerals and constitutes about 34% of the total lithology, occurring mainly as low-lying outcrops exposed along river channels. Amphibolite schist covers about 20% of the total lithology and occurs largely as flat-lying outcrops. Petrographic investigations revealed that the mapped rocks are composed chiefly of felsic minerals, such as quartz, muscovite and feldspars (plagioclase and orthoclase), mafic minerals (biotite and amphibole), and minor opaque minerals. The minor lithologies, which account for 8%, consist of xenolith, aplite, and quartz veins. Structural readings revealed a dominant NE--SW trend that is consistent with Pan-African deformation.