Petrography, Field Relationship and Morpholgical Classification of Migmatites Around Gada Biyu- Maiturare, Northeastern Nigeria Part of Sheet 148 Toro S.E

Abstract

The study area is located within the Pan African Older Granite and is located in Rimin zayam East of Toro L.G.A in Bauchi state and is accessible through Bauchi-Jos Road. Using Sawyers classification of migmatites, the study area has various morphological units of migmatites, that are mainly metatexite (Banded Orthogneisses and Stromatic), diatexite (Schlieren and Nebulitic diatexite) and rhyolites occurring as dyke. Petrographically, the presence of metamorphic mineral garnet, sillimanite, hornblende, orthopyroxene and cordierite minerals in the rock’s morphologies suggest a high metamorphic grade. The change in morphologies is due to change in partial melting rate. Extinction observed on quartz grains in all slides suggests an intra-crystalline deformation and the polycrystalline nature of the quartz grains suggest a high temperature deformation as a result of grain boundary migration. The presence of structures like the ptygmatic folds, crenulation cleavage, Gneissic foliation are all evidence of complex shearing episode has affected the study area. The grade of metamorphism increases from metatexites, which is indicated by preferred elongation of biotite and abundance of biotite + muscovite + hornblende, through to the diatexites, which is indicated by the general coarsening of quartz grain size and depletion of the paleo-structure of the schist. 160 foliation planes were measured and plotted on a rose diagram to know the trend and stereographic projection to determine the beta and s-pole of the planes which gave a NW-SE Trend.

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