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The distribution of platinum group elements in the Insizwa Lobe, Mount Ayliff Complex, South Africa; implications for Ni-Cu-PGE sulfide exploration in the Karoo igneous province

W. D. Maier, J. S. Marsh, Sarah-Jane Barnes and D. C. Dodd
The distribution of platinum group elements in the Insizwa Lobe, Mount Ayliff Complex, South Africa; implications for Ni-Cu-PGE sulfide exploration in the Karoo igneous province
Economic Geology and the Bulletin of the Society of Economic Geologists (October 2002) 97 (6): 1293-1306

Abstract

The Mount Ayliff Complex of the Eastern Cape province of South Africa is a layered intrusion of some 800 km (super 2) surface area and up to 1,200 m thickness. On the basis of compositional similarities and spatial association, it is generally interpreted to form part of the Karoo igneous province. Similarities between the Mount Ayliff Complex and the staging chambers and feeder conduits to flood basalts that host magmatic sulfide ores elsewhere in the world suggest that the Mount Ayliff Complex may have an enhanced potential for Noril'sk-Talnakh-type massive Ni-Cu sulfide ores, an idea that is supported by the well-known sulfide occurrence at Waterfall Gorge. Here, we present major-, trace-, and noble-element data for 30 samples of cumulate rocks from a continuous 1,200 m drill core through the Insizwa lobe of the complex, as well as six samples of a footwall sill, the Taylor's Koppie dike, that was considered a possible feeder zone to the lobe, and through a massive sulfide lens in the footwall of the lobe at Ndzongiseni. We show that most of the Insizwa cumulate rocks contain small amounts of cumulus sulfides. The sulfides, including those at Waterfall Gorge, can be explained by a model in which the sulfides were segregated from magma having chilled-margin composition. On the basis of the composition of the chilled margins, the Insizwa magma contained no entrained sulfides and was depleted in platinum group elements (PGE), although not in Cu and Ni, before emplacement. These compositional characteristics are also observed in lavas of the central Karoo igneous province and suggest only limited sulfide segregation from these magmas at depth. Our findings thus indicate relatively little potential for economic magmatic Ni-Cu-PGE sulfide deposits in the Insizwa lobe.


ISSN: 0361-0128
EISSN: 1554-0774
Coden: ECGLAL
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: 97
Serial Issue: 6
Title: The distribution of platinum group elements in the Insizwa Lobe, Mount Ayliff Complex, South Africa; implications for Ni-Cu-PGE sulfide exploration in the Karoo igneous province
Affiliation: Rhodes University, Department of Geology, Grahamstown, South Africa
Pages: 1293-1306
Published: 200210
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
References: 38
Accession Number: 2003-005674
Categories: Economic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables, sketch maps
S34°10'00" - S30°04'60", E22°45'00" - E30°15'00"
Secondary Affiliation: Universite du Quebec a Chicoutimi, CAN, CanadaFalconbridge Ventures of Africa, ZAF, South Africa
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200302
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