Petrography and Geochemistry of Bada’u and its Environ, Katsina State Northwestern Nigeria

Abstract

The systematic studies of petrography and geochemistry of Bada’u revealed that the area are underlain by crystalline rocks of the Basement Complex, which is categorized as the low grade schist belt. The mapped area is situated within Malumfashi Local Government area of Katsina State, part of Malumfashi sheet 79 NW, which lies between latitudes 11051ʹ0.00˝N to 110 55ʹ00˝N and longitude of 70 32ʹ0.00˝E to 7035ʹ0.00˝E. The rock units were mapped in the sub-area on a scale of 1:25,000, covering an area of about 40km2. The major lithological units mapped in the study area comprises basically of mica schist intercalated with quartzites, porphyritic granites, and minor lithology which includes granite-gneiss, gneiss. The study area shows the evidence of post and syn-Tectonic (Primary and Secondary) structures such as joints, fracture, zenolith, and quartz veins. The dominant joint trend and Quartz veins of the study area are N-S E-W directions respectively which follows the general trend of structures resulting from Pan-African Orogeny. Seven rock samples were collected for both petrography and geochemical studies (2 samples of granites, two samples of gneiss and three samples of mica schist). The major minerals observed under plane polarized and cross polarized light microscope of the granite-gneiss, mica schist and granites are Quartz, feldspar (orthoclase), and micaceous minerals (Biotite and Muscovite) respectively. The geochemical result shows that the rock units within the study area have high percentage of SiO2 and Al2O3 concentration in wt%. This suggest that the rocks within the study were formed from a silica rich source. The granite within the area are peraluminous and shows calc-alkaline characteristics, and occur in syn collision environment as revealed under various geochemical classification plots. The gneiss in the area also have high percentage of SiO2 and Al2O3, suggesting a calc-alkaline affinity. The lesser amount of Na2O against K2O reflect an abundance of K-feldspars rock forming silicate. The mica schist also has high percentage of SiO2 and Al2O3, the high aluminium enrichment in mica shcist reflects the control of their composition by aluminum clay minerals, the mica schist specifically has high Barium contents which indicate K – feldspar rich source rock. The chemical concentration of Rb is similar to their derivation from shales or metapelites, which is a reflection of their origin.