FIELD GEOLOGY AND PETROGRAPHY AROUND NABARDO-TORO ENVIRONS, NORTH EASTERN, NIGERIA

Abstract

Background: The mapping exercise within the study ar ea on a scale of 1:25,000 was carried out to study the rocks, determine their distribution, composition, structures and assess the economic potential of the area. Objectives: The geology mapping aim to identify and understand the various geological structures present in the area to gain insights into the tectonic history and deformation processes that have shaped the area and to identify the minerals present in the rock, to understand the rock formation, composition and potential geologic processes involved. Method: Method of mapping involved road, footpath, rivers and stream traverses. Representative rock samples were collected for petrographic studies and geochemical analysis to establish the geology of the study area. Result: The study area which is part of Sheet 148, Toro SE is entirely typical of the Nigerian Basement Complex and is underlain by the following rock units: Migmatitic Gneiss, Granite gneiss, mica schist and porphyritic granite. The Migmatitic Gneiss constitutes the largest group of the rock units covering more than 45% of the mapped area and trending mainly NW/SE with few exceptions in an almost N/S to NE/SW direction. It is pertinent to know that almost E-W structures were also observed which forms relics of the older structure believed to have been affected by the eburnean (possibly) orogenic event. The granite gneiss shares boundary mainly with the migmatitic gneiss showing a weak foliation of light and dark materials. The mica schist is exposed at the western end, highly weathered with a general trend of NW/SE. The porphyritic granite intruded both the migmatite and granite gneiss occurring prominently as hilly and bouldery outcrops. However, flat lying low lying was also observed in some other localities. With respect to field observation and petrographical study the lithologies encountered were grouped into nine (9) categories- homogeneous, inhomogeneous, stromatic, banded orthogneiss, nebulitic, apo granite, pegmatite, intermediate and schist.Conclusion: Field evidence suggests that the study area has undergone an episode of metamorphism and deformations as depicted by the structural features like preferred orientation of the mineralogical and lithological units. It was also observed from the field measurements, that the main structural trend within the study area is from NNE/SSW.