Petrographic Study and Geochemical Analysis of Basement Rocks in Federal University Gusau and Its Environs, Zamfara State, Northwestern Nigeria

Abstract

Petrographic and geochemical analysis of basement rocks in Federal University Gusau and its environs, Zamfara State, Northwestern Nigeria were carried out in order to unveil the major rock forming minerals as well as the textural relationships composition within the rock. The identified rock unit is granite and they are mainly whitishgrey in colour, with the majority of them having porphyritic-coarse-grained texture and minor with fine-grained texture. The light coloured crystals in hand specimens are the felsic minerals mainly quartz, and feldspars while the grey-dark crystals are the mafic minerals like the biotite-mica. The result of the thin section analysis depicts that the minerals present within the rock samples in the area: quartz (40%), orthoclase (40%) and biotite (20%). These identified minerals are classified as the major rock forming silicate minerals. The geochemical analysis result shows that the rocks are characterized by high percentage of quartz (SiO2) in the range of 77.4-98.2 wt% with an average of 84.87 wt%; subordinate amounts of hematite (Fe2O3) with an average concentration of 4.08 wt% as well as low concentration of K2O, CaO, TiO2, V2O5, MnO, NiO, CuO, ZnO, RuO2, In2O3 and other minor constituent oxides. The variation diagram of SiO2 and other oxides within the study area reveals a very strong negative correlation of SiO2 against CaO, TiO2, V2O5, MnO, Fe2O3, CUO, PbO, and Eu2O3 respectively, with the average correlation value of -0.91. The geochemical analysis results also reveal minor alteration of modal composition amongst the samples analysed which suggest the similarities in composition of all the samples within the study area.