Abstract
The Kimberley Reef is a Proterozoic gold-uranium-placer which was deposited during the Kimberley stage of the Upper Witwatersrand System, approximately 2.7 × 109 years ago. The investigated site at Marievale GMC. is located towards the fanbase of the East Rand Goldfield. Geological, sedimentological, and geochemical parameters show that the placer formed in a fluviatil depositional environment (ca. 40 cm water depth) with a small-scale meandering stream pattern. Gold anomalies are elongated and frequently arcuate-shaped with sinuosities of ±1.5; their orientation reveals a high degree of variability on the scale of a few metres to tens of metres. They formed at the inside of meandering channel curves next to and alongside elongated conglomerate bodies which correspond to point bars. Concentrations of other heavy minerals formed according to their decreasing specific gravity at the outer, convex side and the downstream part of gold anomalies roughly in the order uraninite — pyrite and chromite — zircon. This sedimentary-controlled gold and heavy mineral distribution pattern was complicated by lateral channel migrations and frequent bed changes of streams, as well as subsequent faulting which had a depletioning effect on gold.
Published Version
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