The Geology of Nyangwena River South, A Confluency of the Chongwe River, Chongwe District Lusaka Province, Lusaka

Abstract

The Nyangwena River and its adjacent areas lies in Chongwe district in the Lusaka Province of Zambia. It is part of the Southern extension of the Irumide Belt. The study area is underlain by Mesoproterozoic Basement Complex which includes gneiss, amphibolites, quartzites and schist. The Neoproterozoic Katanga Supergroup uncomfortably overlies the Basement is mainly composed of schist. The tectonic history falls into three broad episode. The first deformation (DO resulted in recumbent folding and development of planar foliation (Si) which is defined in the gneisses and amphibolites.The first deformation was accompanied by a regional prograde metamorphism(Mi) defined by the mineral assemblage being hornblende-plagioclase-biotite-quartz-gamet-sphene. The second deformation phase (D2) resulted in steep, upright folds and thrusting in a North-West direction. In addition, the second deformatiom was accompanied by a prograde metamorphism followed by a retrograde metamorphism (M2) due to cooling and fluid circulation. The mineral assemblage associated with (M2) is typical of greenschist facies defined by chlorite-quartz-biotite-epidote-sphene-actinolite-iron oxide (opaque) as observed in the chlorite schist unit. The third deformation (D3) resulted in the development of open folds and thrusting in the North-East direcfion.