Local-to micro-scale structural controls on shear-zone-hosted gold mineralisation, Ngubevu area, Natal Thrust Front, Tugela Terrane, South Africa.
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Date
2021
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Abstract
The research described in this dissertation focused on shear-zone-hosted precious and base metal
mineralisation in the Ngubevu area, in the Natal Thrust Front of the Tugela Terrane in the Natal
Metamorphic Province of South Africa. This province forms part of a 400-km-wide metamorphic
belt referred to as the Namaqua-Natal Metamorphic Province, which stretches from the Northern
Cape on the west coast to KwaZulu-Natal on the east coast of the country. Unlike the western
Namaqualand Metamorphic Province, which is well-explored and well-exploited for several mineral
deposits, the Natal Metamorphic Province is relatively poorly explored. One reason for this is that
the nature of structural controls on mineralisation in the Natal Metamorphic Province is poorly
understood. In the research described in this dissertation, known occurrences of shear-zonehosted
precious and base metal deposits in the Golden Eagle and Champion Mines in the Ngubevu
area, which have been described in the literature, were studied in the micro-scale, and the findings
obtained were integrated with existing knowledge of regional- to local-scale deformation in the
Tugela Terrane, in order to deduce the structural controls of such mineralisation in the area. The
micro-scale data, studied by spatial analytical methods (i.e., point pattern analysis, Fry analysis,
fractal analysis and shape analysis) show that the mineralisation in the area operated in at least
two spatial scales, within each thin section sample, of at most 0.005 μm and at least 0.002 μm and
that, within each thin section sample, the occurrence of shear-zone-hosted precious and base
metal deposits is non-random as they exhibit clustered and/or regular spatial distributions. Microfractures
in the area generally show major northerly trends in their alignments. Likewise, microscale
mineral distributions show NNE–SSW and NNW–SSE trends in their orientations. These
findings suggest that N–NE-directed compression controlled the occurrence and distribution of
shear-zone-hosted precious and base metal mineralisation in the Ngubevu area. This N–NEdirected
compression and thrusting during deformation (D1) controlled the circulation and
concentration of mineralising hydrothermal fluids in the Natal Thrust Front. These hydrothermal
fluids formed quartz veins along nearly E–W-trending foliations resulting in mineralisation in the
clustered and regular spatial patterns observed in the micro-scale.
Description
Masters Degree. University of KwaZulu-Natal, Durban.