Geological mapping, petrological characterisation and geochemistry of rocks in the Aus area, Southern Namibia: Implications for potential Copper mineralization
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Date
2020
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Publisher
University of Namibia
Abstract
The study area is located in the southern part of Namibia within the Aus Domain which forms part of the Mesoproterozoic Namaqua Sector of the Namaqua-Natal Metamorphic Province. The sector hosts some significant base metal sulphide deposits that have been mined for the past century. In this study, detailed field mapping, petrography, geochemistry and U-Pb zircon dating were conducted to evaluate the chemical characteristics and tectonic setting of the area with the intent to assess the feasibility and potential of known copper occurrences around Aus area. The Garub Group represents the oldest rocks in the area and comprises marble, calc-silicates, metapelites, garnet biotite quartz gneisses, amphibolites, mafic granulites and serpentinites, which have been intruded by several, variably deformed granites. The Aus, Tsirub and Kubub orthogneisses are the main intrusives in the area. However, field mapping identified a highly fractured
and metasomatized K-feldspar plagioclase epidote rock which requires further
investigation. Petrographic studies confirm the compositional and deformational
variability observed in the field. Geochemistry reveals that all granitoids within the study area are acidic, strongly peraluminous and products of shoshonitic and high-K calcalkaline magma derived from an A-type source. The A-type granites formed as a result of crustal contamination during the continental extensional phase and have been subjected to compressional deformation. Chondrite-normalised spider diagrams show negative Ta, Nb, P and Ti anomalies, with enrichments in Th and LREE, which suggest that the rocks are derived from an arc environment. Plots of K2O vs SiO2 show a considerably greater degree of scatter, which may be attributed to the effects of crustal contamination. Three geotectonic settings are established, i. e. the syn-collisional-Granite (syn-COLG), Volcanic Arc Granites (VAG) and Within Plate Granites (WPG). These inconsistent plots of samples may be attributed to hydrothermal alteration and/or sharing of varying degrees
of fractionation within multiple flows, and support a collision of crustal fragments model. Granitoid plutonism for Tsirub augen gneiss and Aus granite gneiss occurred at 1110 ± 7 Ma and 1085 ± 36 Ma respectively. Several granites, which could be responsible for hydrothermal activity, quartz veins, fault structures and occurrence of malachite may bear evidence for copper mineralization in the study area.
Description
A mini thesis submitted in partial fulfillment of the requirements for the Degree of Master of Science (Applied Geology)
Keywords
Geological mapping, Rocks, Copper