THE STRUCTURAL FRAMEWORK UNDERLYING THE METAMORPHIC EVOLUTION OF THE KAZAURE SCHIST BELT, NW NIGERIA

Abstract

The structural framework underlying the metamorphic aspect of the various rocks in Kazaure schist belt (KZSB) was studied. The KZSB consists of metasediments and metavolcanics that are bounded by Older Granites and gneisses. Detailed structural analysis of the Kazaure schist belt revealed the occurrence of structures that resulted from ductile as well as brittle failure. On outcrop scale, isoclinal, open to tight, overturned and upright folds are observed in the study area. The rocks of the Kazaure schist belt have experienced a minimum of two major ductile deformational events. The first of which involved the development of a NNE-SSW trending S1 schistosity and recumbent isoclinal folds (F1). The second event formed nearly upright isoclinal folds with gently to moderately North plunging fold hinges. Evidence for brittle deformation is also recognized within the Kazaure rocks, throughout the area there are numerous fractures, joints and faults characterised by steepply dipping NE-SW and NW- SE trends. The study of microscopic texture domains of the rocks has allowed the identification of two periods of apparently prograde metamorphic recrystallisation (M1 and M2) and one retrograde period (M3). The metamorphic mineral assemblages show evidence of being either syn-D1, and syn or post-D2 related to some plastic style of folding. Keywords: Schist belt, deformation, metamorphism, texture, recrystallisation [Global Jnl Geol. Sci. Vol.1(1) 2003: 73-84]