GEOLOGICAL SETTING AND TECTONIC EVOLUTION OF ZUNGERU AND ITS ENVIRONS, PART OF SHEET 163 (ZUNGERU NW), NORTH CENTRAL NIGERIA
GEOLOGICAL SETTING AND TECTONIC EVOLUTION OF ZUNGERU AND ITS ENVIRONS, PART OF SHEET 163 (ZUNGERU NW), NORTH CENTRAL NIGERIA
No Thumbnail Available
Date
2016-10
Authors
ALIYU, ABUBAKAR ENEYE
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Fold and Thrust (FAT) Belts are regions that have been documented in environments resulting from plate convergence, such as those formed at plate boundaries. The Nigerian Basement Complex has been described by previous workers to have evolved by plate tectonic processes involving continental collisions. The present study, therefore seeks to investigate the presence of a thrust belt within the NW segment of the Nigerian Basement Complex. The geological investigations of Zungeru and its environs was undertaken in orderinterpret its structural and tectonic evolution. Remote sensing analysis usingsatellite data (Landsat ETM imageries
7
anddigital elevation models)and field investigations which include thecollection of rock samples as well as structural data show that the study area comprise of gneiss, migmatite, quartzite, phyllite, schist, amphibolite and mylonite. The Kalangai-Zungeru-Ifewara (KZI) transcurrent fault observed, cut through the study area producing fault rocks like cataclasites, sheared gneisses and mylonites. Structural relationships wereinvestigated through: microstructural, strain and fracture analyses and also evaluation of fold interference patterns. These analyses show that themain planar structures encountered in the study area are foliations and cleavages, bedding surfaces, fold axial planes, fault planes, joints and veins. Linear features measured in the field include bedding-cleavage intersection lineations, mineral stretching lineations, and minor fold axes (hinge lines). Rose diagram plots and circle inventory analysis of joints show that the fractures have a dominant NNE-SSW, NE-SW and NW-SE trends with the highest density in granite gneiss outcrops and lowest in migmatites. En echelon veins found in the area are thought to be evidence of shearing as a result of displacement across faults or shear zones. Microscale deformation at the scale of individual grains was determined through microstructural analysis of photomicrographs of rocks that deformed through a range of ductile grain scale deformation mechanisms such as recrystalization, intra-crystalline deformation and twining. Oriented thin-sections of deformed rocks from the study area were examined in the laboratory in order to determine the degree of deformation, the stress direction and sense of shearing. At this scale, the sense of shear indicators include porphyroclasts, mica fish and asymmetric microfolds, defining a predominant dextral strike-slip movement. The dominant stress direction is E-W, consistent with the Pan-African crustal shortening. This research reveals that the rocks in the area were affected by two successive deformational phases (D1 and D2), indicated by the presence cataclastic S1 cleavages and NNE-SSW trending open to isoclinal F2 folds. The alignment of lineaments and other major structures into NE-SW, NW-SE and N-S orientations imply that the D2 deformation was a late stage Pan-African event that affected the basement rocks of the study area. Processing of satellite images, structural analysis,microtectonics, and petrographic studies reveals that the area evolved through a transpressional deformation, which involves a component of strike-slip movement and a component of shortening. Thrust tectonics as an evidence of crustal shortening was observed within mylonites at the bank of River Kaduna.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF A MASTERS DEGREE IN GEOLOGY
Keywords
GEOLOGICAL SETTING,, TECTONIC EVOLUTION,, ZUNGERU,, ZUNGERU NW,, NORTH CENTRAL NIGERIA,