The Formation and Preservation of the Witwatersrand Goldfields, the World’s Largest Gold Province

Frimmel, Hartwig E.; Groves, David; Kirk, J. Andrew; Ruiz, José Antonio Fernández; Chesley, John T.; Minter, W. E. L.

doi:10.5382/av100.23

Cited by 57 publications

(32 citation statements)

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“…[21,25]. In the detrital gold model [34] the pyrite rims on detrital pyrite cores are considered to be diagenetic in origin, and therefore do not support a major hydrothermal event that has introduced gold into the reefs. However, we argue that the uniform thickness and geochemistry of the rims, the high Co concentration and the presence of free gold micro-grains on the most As-rich rims throughout all samples studied from the CLR, supports a uniform hydrothermal event that introduced a significant amount of Au into the CLR.…”

Section: Gold Predominantly In the Core Of Pyrite (Py1)mentioning

confidence: 99%

“…A second example of invisible gold-bearing rims on pyrite is present in the giant Witwatersrand Carbon Leader Reef (CLR) deposit in South Africa [21]. A major controversary has existed for more than 100 years over the origin of the Witwatersrand gold deposits, with the two major competing theories claiming either a detrital origin [34] or a hydrothermal origin [32] for the gold. However, recent studies of the pyrite in the conglomerate lenses of the CLR have confirmed that both theories are likely to be correct with syn-sedimentary gold deposition being followed much later by a hydrothermal (syn-orogenic) gold event [21].…”

Section: Gold Concentrated On the Rim Of Pyritementioning

confidence: 99%

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Invisible Gold Paragenesis and Geochemistry in Pyrite from Orogenic and Sediment-Hosted Gold Deposits

Large

Масленников

2020

Minerals

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LA-ICPMS analysis of pyrite in ten gold deposits is used to determine the precise siting of invisible gold within pyrite, and thus the timing of gold introduction relative to the growth of pyrite and related orogenic events. A spectrum of invisible gold relationships in pyrite has been observed which suggests that, relative to orogenic pyrite growth, gold introduction in some deposits is early at the start of pyrite growth; in other deposits, it is late toward the end of pyrite growth and in a third case, it may be introduced at the intermediate stage of orogenic pyrite growth. In addition, we report a distinct chemical association of invisible gold in pyrite in the deposits studied. For example, in the Gold Quarry (Carlin type), Mt Olympus, Macraes and Konkera, the invisible gold is principally related to the arsenic content of pyrite. In contrast, in Kumtor and Geita Hill, the invisible gold is principally related to the tellurium content of pyrite. Other deposits (Golden Mile, Bendigo, Spanish Mountain, Witwatersrand Carbon Leader Reef (CLR)) exhibit both the Au-As and Au-Te association in pyrite. Some deposits of the Au-As association have late orogenic Au-As-rich rims on pyrite, which substantially increase the value of the ore. In contrast, deposits of the Au-Te association are not known to have Au-rich rims on pyrite but contain nano-to micro-inclusions of Au-Ag-(Pb-Bi) tellurides.solution As, known as arsenian pyrite [9,10]. Arsenic can substitute into either the Fe site or the S site in pyrite and a maximum of 8%-11% As has been reported [11][12][13]. The position of ionic gold in the structure of pyrite is still not clear, although it is assumed that ionic gold Au + substitutes for iron, entering distorted octahedral sites, whereas As substitutes for S in the tetrahedral sites [8]. Both surface speciation, and distortion-expansion of the pyrite lattice by incorporation of As are considered to be key processes in Au accumulation by arsenian pyrite [8,14].A landmark publication [4] defined a relationship between the amount of invisible solid solution gold in pyrite and its arsenic content, using a database of analyses of pyrite from several Carlin and epithermal deposits. This maximum limit of invisible gold, from pyrite formed in the temperature range of 150 to 250 • C, is approximately 100 ppm Au for 2000 ppm As, and 1000 ppm Au for 2% As, and has become known as the saturation line for Au in arsenian pyrite (Figure 1; [4]). Gold analyses of pyrite that plot above the saturation line indicate free gold as nano-to micro-inclusions in pyrite. More recent research [5] has shown that the gold saturation line is most probably controlled by a number of factors, possibly including the crystal chemistry of pyrite and fluid/rock interactions and therefore different positions of the gold saturation line may need to be defined for each gold deposit type.Minerals 2020, 10, x FOR PEER REVIEW 2 of 21 solution As, known as arsenian pyrite [9,10]. Arsenic can substitute into either the Fe site or the S site in pyrite a...

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Section: Gold Predominantly In the Core Of Pyrite (Py1)mentioning

confidence: 99%

Section: Gold Concentrated On the Rim Of Pyritementioning

confidence: 99%

Invisible Gold Paragenesis and Geochemistry in Pyrite from Orogenic and Sediment-Hosted Gold Deposits

Large

Масленников

2020

Minerals

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“…The sediment deposition of the Central Rand Group is thought to be controlled by fault‐related uplift to the east (Frimmel et al . ). The CLR is located at the base of the Central Rand Group (Figs.…”

Section: Mponeng Gold Minementioning

confidence: 97%

“…The F/W to the CLR consists of a package of conglomerates, known as the “Footwall bands of the CLR.” The multiple‐band CLR facies is defined as a gold‐bearing reef containing more than one conglomerate band separated by internal quartzite bands (Frimmel et al . ). These F/W bands are characterized by lenses of conglomerates, separated by grey argillaceous quartzites, referred to as Blyvooruitzicht Quartzite (Figs.…”

Section: Mponeng Gold Minementioning

confidence: 97%

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Integrated interpretation of 3D seismic data to enhance the detection of the gold‐bearing reef: Mponeng Gold mine, Witwatersrand Basin (South Africa)

Manzi

Cooper

Malehmir

et al. 2015

Geophysical Prospecting

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A B S T R A C TWe present an integrated approach to the seismic interpretation of one of the world's deepest gold ore body (Carbon Leader Reef) using three-dimensional seismic data, ultrasonic velocity measurements at elevated stresses, and modified instantaneous attribute analysis. Seismic wave velocities of the drill-core samples (quartzite, shale, and conglomeratic reef) from the mine are sensitive to uniaxial stress changes, i.e., they slowly increase with increasing pressure until they reach maximum value at ß25 MPa. For all the samples, seismic velocities are constant above 25 MPa, indicating a possible closure of microcracks at stress corresponding to 1.0 km-1.5 km. A reflection coefficient of 0.02 computed between hanging wall and footwall quartzites of the Carbon Leader Reef ore body suggests that it may be difficult to obtain a strong seismic reflection at their interface. Our modified seismic attribute algorithm, on the other hand, shows that the detection of the lateral continuity of the Carbon Leader Reef reflector can significantly be improved by sharpening the seismic traces. Three-dimensional seismic data reveal that faults with throws greater than 25 m that offset the Carbon Leader Reef can clearly be seen. Faults with throws less than 25 m but greater than 2-m throw were identified through horizon-based attribute analysis, while most dykes and sills with thickness less than 25 m were invisible. The detection of the lateral continuity of the Carbon Leader Reef reflector and its depth position is greatly improved by integrating the modified instantaneous attributes with controls from borehole observations. The three-dimensional visualization and effective interpretation of the Carbon Leader Reef horizon shows a host of structurally complex ore body blocks that may impact future shaft positioning and reduce its associated risks.

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3D Reflection Seismic Imaging for Gold and Platinum Exploration, Mine Development, and Safety

2019

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The Formation and Preservation of the Witwatersrand Goldfields, the World’s Largest Gold Province

Cited by 57 publications

References 0 publications

Invisible Gold Paragenesis and Geochemistry in Pyrite from Orogenic and Sediment-Hosted Gold Deposits

Invisible Gold Paragenesis and Geochemistry in Pyrite from Orogenic and Sediment-Hosted Gold Deposits

Integrated interpretation of 3D seismic data to enhance the detection of the gold‐bearing reef: Mponeng Gold mine, Witwatersrand Basin (South Africa)

3D Reflection Seismic Imaging for Gold and Platinum Exploration, Mine Development, and Safety

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