Geology and Petrology of Rocks around Rijiyar Malan, Bauchi, Northeast Nigeria

Abstract

he study area is part of Bauchi sheet 149SW which falls within the Basement Complex
of Nigeria. The study addressed the geology and petrography of Migmatite in the study
area. In this study, the area was mapped on a scale of 1:25,000. Samples were collected
at the flanks of the outcrops, railway cuts, road cuts as well as blasting sites within the
area. Samples were collected based on morphological variations at each sample point.
The first and second order morphological classifications of migmatites as being
metatexite or diatexite such as their physical criteria were used as the guiding
principle. This technique was repeated for the rest of the sampling points in the area
covering about sixteen (16) different locations. A total of 12 representative samples
were petrographically studied, which showed the presence of the various
metamorphic and rock-forming minerals which include orthopyroxene, biotite,
plagioclase, quartz, microcline, and graphite as observed within the field of view under
the plane- and crossed-polarized light field. Field mapping together with the
morphological features, it was observed that the area indicates various migmatite
morphological units, viz: Banded orthogneiss, melanocratic diatexite, mesocratic
diatexite and leucocratic diatexite. The microstructures in the form of intergrowth/
boundary migration of quartz, undulose extinction, and interstitial filling of micro
fractures reveal that the rocks of the area are subjected to metamorphism