Geochemistry and Mineralization of Some Selected Pegmatite Deposits in Panda North Central, Nigeria

Abstract

Pegmatite constitutes an important lithologic unit in the Precambrian Basement Complex of Panda north central Nigeria. The primary aim of this study is to present a geochemical data of various rock types in the area especially pegmatite in order to determine their geochemical classification and mineralization potential of some selected pegmatite deposits in the area. Geochemical analysis reveals that the pegmatite samples have high SiO2 content; 73.8-94.8 wt%, low Na2O/K2O ratio suggesting they are strongly peralkaline and peraluminous, indicating that the pegmatite may have formed from mixed plutonic sources. The discrimination diagram of TiO2 versus SiO2 shows that the samples plotted on both igneous and sedimentary field, but majorly on the igneous field which is an implication that substantial material may have been generated from igneous sources. Also the plotting of the pegmatite samples in both the tholeiitic and calc-alkaline fields shows that the magma from which the rock was formed was not totally restricted in occurrence only to subduction related environment but also from the oceanic crust of calc-alkaline environments. This is further confirmed by discrimination diagrams plot of TiO2-K2O-P2O which indicates that substantial samples plotted fall within the continental crust. High potash content alkalies with relative Fe-enrichment and silica suggest the plutonic generation of magma and the development of the rocks in both the oceanic and continental crust. Major elements analysis of both the granitic rock aplite and biotite gneiss shows moderately high silica values. These values reflect the geochemical characteristic of crystalline rocks. The pegmatite of the study area exhibits low contents of Nb, Ta, Ga, Rb and Sn which are the major mineralization indices for pegmatite bodies. In classifying the pegmatites, rare metal indicative elements were used to discriminate the barren ones from the mineralized. A plot of Ta-Ga reveals that all the samples plotted are below the boundary of mineralization line, suggesting all the pegmatite samples in the study area to be barren in term of rare earth metals and can be compared to other pegmatite bodies in Nigeria and around the world.