Prospectivity mapping using stream sediment geochemistry along the Orange River Catchment for base metal, Prieska, Northern Cape, South Africa

Mashale, Hilda Nthabiseng
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The Areachap Terrane which is part of the Namaqua Sector of the Namaqua-Natal Belt in the Northern Cape Province host volcanic-hosted Zn-Cu deposits at volcanic centres. Major deposits that were mined till early 1990’s include Copperton (at Prieska) and Areachap deposits. Currently, Orion mining/exploration Company is further exploring some of the best target areas including Copperton, Areachap and Kantienpan base metal occurrences. The primary objective was to map base metal mineralisation, determine the heavy metal contents of sediments, locate the source of anomalies and delineate targets for follow-up studies. A total of 9314 stream sediments samples were collected and analysed using XRF at the Council for Geoscience laboratory. Spatial joint analysis tool was used to calculate the element associated with their respective lithostratigraphy. Fuzzy OR Overlay operation wa sapplied to combine maps of relevant indicator elements associated with the geology. The results for elements associated with the known base metals occurring in Prieska area as well as relevant multi-element groups were plotted on distribution maps using ArcGIS. The mineralisation target M1, M2, and M3 are delineated as potential VMS mineralisation zone and considered for further follow-up study. The M13 and M14 anomalies are delineated for Co_Ni (±Cu) mineralisation. M13 and M14 anomalies are sourced from ultramafic debris transported from the Ghaap Group, however this potential target will require follow-up studiesforverification.ThecorrelationoftheCu-Pb-Znanomalywithalkalielements(Nb, Zr, Th, and U) and REEs (in Table 3.3) suggests there is a possibility that the M26–M29 anomaly are alkali-granitic genetic origin. The As, Ba, Ce, Cr, Cu, Hf, Nd, Ni, Rb, Sr, S, V, Zr and Zn contents showed a heterogeneous spatial distribution, reflected by high coefficient of variation and large standard deviation; these elements concentrations are extremely elevated in stream sediments. There is a very high Cu-Zn correlation coefficient calculated for samples near the Copperton deposit. Normal Q-Q plots for S, Zn, Pb, and Ba have similar trends with outliers of the high coefficient of variations which might be sourced from the mine wastes. The high Cu, Zn and Pb are derived from the ore minerals related VMS deposits. The Fe elevated concentration are derived from both primary minerals which are not directly related to the VMS or Co_Ni (±Cu) mineralisation
A research report submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirement for the degree of Masters of Science, 2020