Newly observed ore-minerals from the Basal Reef in the Orange Free State goldfield in South Africa

Saager, R.

doi:10.2113/gsecongeo.63.2.116

Cited by 19 publications

(26 citation statements)

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“…The investigated samples contain pyrite of three main types (Table 1): rounded massive pyrite, rounded porous pyrite, and authigenic pyrite, in accordance with previous observations from the same reef horizons (Ramdohr, 1958;Saager, 1970;Feather and Koen, 1975;Utter, 1978;Hallbauer, 1986;England et al, 2002). Rounded grains are spherical to discoidal, up to 1 cm in diameter and include massive and, less commonly, porous varieties, the latter with inclusions of various silicate minerals, such as quartz and phyllosilicates ( Fig.…”

Section: Sample Localities and Mineralogysupporting

confidence: 89%

“…Barnicoat et al, 1997). Our data add to the long list of arguments in favour of a detrital origin for rounded pyrite, such as the presence of abrasion features, sedimentological control on pyrite distribution, geochemical heterogeneity, and UPb and Re-Os ages greater than the depositional age (Ramdohr, 1958;Saager, 1970;Hallbauer, 1986;Barton and Hallbauer, 1996;Kirk et al, 2001;England et al, 2002;Minter, 2006). (Canfield et al, 2000), while a larger range of δ 34 S values in sedimentary sulphides is generally attributed to bacterial sulphate reduction in localized sulphate-rich environments (e.g.…”

Section: Discussionmentioning

confidence: 52%

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Multiple sulphur and iron isotope composition of detrital pyrite in Archaean sedimentary rocks: A new tool for provenance analysis

Hofmann

Bekker

Rouxel

et al. 2009

Earth and Planetary Science Letters

114

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Multiple S (δ 34 S and δ 33 S) and Fe (δ 56 Fe) isotope analyses of rounded pyrite grains from 3.1 to 2.6 Ga conglomerates of southern Africa indicate their detrital origin, which supports anoxic surface conditions in the Archaean. Rounded pyrites from Meso-to Neoarchaean gold and uranium-bearing strata of South Africa are derived from both crustal and sedimentary sources, the latter being characterised by non-mass dependent fractionation of S isotopes

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Section: Sample Localities and Mineralogysupporting

confidence: 89%

Section: Discussionmentioning

confidence: 52%

Multiple sulphur and iron isotope composition of detrital pyrite in Archaean sedimentary rocks: A new tool for provenance analysis

Hofmann

Bekker

Rouxel

et al. 2009

Earth and Planetary Science Letters

114

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“…Pyrite is the most conspicuous ore Ontario, London, Ontario, Canada N6A 5B 7 mineral in the Witwatersrand deposits, being present at 3 to 5 modal percent and often accounting for more than 90 percent of the ore minerals. Numerous varieties ofpyrite have been recognized (e.g., Ramdohr, 1958;Saager, 1970;Hallbauer, 1986) but three basic texturally distinct ones prevail: compact rounded, concretionary, and idioblastic--corresponding, respectively, to the allogenic detrital, synsedimentary, and authigenic varieties of Hallbauer (1986). Pyrite pseudomorphs, which represent a fourth distinct variety of pyrite (Ramdohr, 1958;Saager, 1970), were not encountered in the present study.…”

Section: Pyrite In Witwatersrand Depositsmentioning

confidence: 99%

“…Hydrothermalists point to the inferred secondary characteristics of the ore mineral suite, the virtual absence of detrital grains of iron oxides and ilmenite, greenschist facies metamorphism, and the two basinwide geochemical associations (Au-S-Fe-As in conglomerates and C-U-Au in carbon seams) that elsewhere are associated with hydrothermal processes. The interpretation of compact rounded pyrite grains associated with the gold ores as allogenic detrital (e.g., Ramdohr, 1958;Saager, 1970;Koppel and Saager, 1974;Hallbauer, 1986) has always been important (perhaps essential) evidence favoring a placer model. However, Phillips et al (1988a, p. 322) note that chemical rounding and pseudomorphous replacement of iron oxides and ilmenite have been invoked as explanations for some of this rounded pyrite (e.g., Ramdohr, 1958;Ramdohr, 1969, fig.…”

Section: Introductionmentioning

confidence: 99%

Detrital pyrite in the Witwatersrand gold fields of South Africa; evidence from truncated growth banding

MacLean¹,

Fleet²

1989

Economic Geology

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“…9D). Pyrite: Pyrite nodules that are massive, porous or contain concentric structures (Saager, 1970) abundant in the Vaal Reef orebody (Fig. 9E) an( comprise the bulk of the total pyrite content.…”

Section: Traces Of Granular Hydrocarbon Also Occur With Dark Concentrmentioning

confidence: 99%

Detrital gold, uranium, and pyrite concentrations related to sedimentology in the Precambrian Vaal Reef placer, Witwatersrand, South Africa

Minter¹

1976

Economic Geology

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The Vaal Reef placer was deposited during the Vaal Stage of the Upper Witwatersrand System, approximately 2,500 million years ago. The stratiform deposit is up to 5 feet thick and covers an area of over 100 square miles. It was discovered in 1934 and today is exploited at eight adjacent gold mines which produce approximately 16 percent of South Africa's total gold output.This study integrates stratigraphical, structural, petrological, and mineralogical data with a comprehensive set of sedimentological data to synthezise a model that describes the genesis of the Vaal Reef placer. Results show that the Vaal Reef placer was a shoreline feature of the Upper Witwatersrand Basin and that its deposition was controlled, firstly, by the major structure of the basin and, secondly, by a minor transverse synclinal structure that induced an entry point. The sediments in the footwall of the Vaal Reef placer regressed into the depository down a southeastern paleoslope in a shallow water fluviodeltaic environment. Lateral depositional limits are evident. A reduced supply of sediment to the tectonically subsiding shoreline resulted in a transgression, which truncated the consolidated deltaic plain to a very regular erosion surface with the remnants of a shallow braided drainage pattern incised upon it. The braided channels, up to 5 feet but generally less than 2 feet deep and 500 feet wide, meandered down a southeastern paleoslope. Protracted deposition of the Vaal Reef placer, marked by a mature pebbly quartz-arenite and basal algal growth, filled the irregularities of the erosion surface and spread between channels to form a dendroidal belt of sediment containing allogenic gold, uranium, and pyrite. Continuing transgression deepened the aqueous environment and a longshore, northeasterly current buried the Vaal Reef placer under a wedge of sediments that prograded from the southwest.New geological aspects that have emerged are, firstly, that the tectonic framework during Vaal Reef Stage deposition was very much simpler than previously envisaged. There is no evidence of subsidiary incipient basining. Secondly, modifications of previous conceptual models are made which emphasize the importance that detailed dispersal patterns and subtle paleosurface forms had on heavy mineral distribution in the distal fluviodeltaic environment of carbon-seam placers. Thirdly, sedimentary responses involving unconformities, disconformities, and accumulation are evidently related to particular entry points and may not be specifically correlated beyond their local tectonic framework. Fourthly, tectonic instability and basining is dated between Lower and Upper Ventersdorp System time and certainly before deposition of the Transvaal System.

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Newly observed ore-minerals from the Basal Reef in the Orange Free State goldfield in South Africa

Cited by 19 publications

References 0 publications

Multiple sulphur and iron isotope composition of detrital pyrite in Archaean sedimentary rocks: A new tool for provenance analysis

Multiple sulphur and iron isotope composition of detrital pyrite in Archaean sedimentary rocks: A new tool for provenance analysis

Detrital pyrite in the Witwatersrand gold fields of South Africa; evidence from truncated growth banding

Detrital gold, uranium, and pyrite concentrations related to sedimentology in the Precambrian Vaal Reef placer, Witwatersrand, South Africa

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