Geology, Petrography and Microtectonic Studies of Rocks in Lallangi and Environs, Part of Bauchi Sheet 149 NE, Bauchi, North East Nigeria

Abstract

The study addressed the geology, petrography and associated microstructures of the study area. The geological mapping indicated three to four (3-4) including various migmatite morphological units, granitoid and leucosome bands occurring in and around Lallangi in the Northern Nigerian Basement complex of Nigeria. Petrographic studies 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 plane and crossed polarized light Field. Field geology and petrographic analyses of structures carried out from outcrop to microscopic scale in the area reveal that the rocks were affected by multiple phases of deformations; the syn-tectonic deformation that includes regional metamorphism and post-tectonic typified by prograde metamorphism and shearing. The grade of metamorphism varies from low grade in the metatexites to medium grade that increases progressively from the mesocratic diatexites through to the granulitic granitoids manifested by foliation in biotites of the metatexites, coarsening of quartz grains and development of porphyroblastic microcline in the diatexite migmatite. The microstructures in the form of interlobing/ grain boundary migration of quartz, undulose extinction and interstitial filling of micro fractures, reveal that the rocks of the area are generally deformed.