Experimental measurements of seismic velocities on core samples and their dependence on mineralogy and stress; Witwatersrand Basin (South Africa)

2016 ◽  
Vol 61 (1) ◽  
pp. 115-144 ◽  
Author(s):  
Nomqhele Z. Nkosi ◽  
Musa S. D. Manzi ◽  
Gillian R. Drennan ◽  
Halil Yilmaz
Keyword(s):  
South Africa ◽  
Experimental Measurements ◽  
Seismic Velocities ◽  
Witwatersrand Basin ◽  
Core Samples

Delineation of Sandstone Reservoir Flow Zones in the Central Bredasdorp Basin, South Africa, Using Core Samples

2021 ◽  
Author(s):  
Mimonitu Opuwari ◽  
Moses Magoba ◽  
Nehemiah Dominick ◽  
Nicolas Waldmann
Keyword(s):  
South Africa ◽  
Core Samples ◽  
Reservoir Flow ◽  
Sandstone Reservoir

Tectono‐metamorphic setting and paragenetic sequence of Au‐U mineralisation in the Archaean Witwatersrand Basin, South Africa

1997 ◽  
Vol 44 (3) ◽  
pp. 353-371 ◽  
Author(s):  
L. J. Robb ◽  
E. G. Charlesworth ◽  
G. R. Drennan ◽  
R. L. Gibson ◽  
E. L. Tongu
Keyword(s):  
South Africa ◽  
Witwatersrand Basin ◽  
Paragenetic Sequence

scholarly journals Palaeoclimates: the first two billion years

2006 ◽  
Vol 361 (1470) ◽  
pp. 917-929 ◽  
Author(s):  
James F Kasting ◽  
Shuhei Ono
Keyword(s):  
South Africa ◽  
Oxygen Isotopes ◽  
Natural Explanation ◽  
Witwatersrand Basin ◽  
Late Archaean ◽  
Bacterial Sulphate Reduction ◽  
Climatic Constraints ◽  
The Mean ◽  
High Concentrations ◽  
Earth’S Climate

Earth's climate during the Archaean remains highly uncertain, as the relevant geologic evidence is sparse and occasionally contradictory. Oxygen isotopes in cherts suggest that between 3.5 and 3.2 Gyr ago (Ga) the Archaean climate was hot (55–85 °C); however, the fact that these cherts have experienced only a modest amount of weathering suggests that the climate was temperate, as today. The presence of diamictites in the Pongola Supergroup and the Witwatersrand Basin of South Africa suggests that by 2.9 Ga the climate was glacial. The Late Archaean was relatively warm; then glaciation (possibly of global extent) reappeared in the Early Palaeoproterozoic, around 2.3–2.4 Ga. Fitting these climatic constraints with a model requires high concentrations of atmospheric CO 2 or CH 4 , or both. Solar luminosity was 20–25% lower than today, so elevated greenhouse gas concentrations were needed just to keep the mean surface temperature above freezing. A rise in O 2 at approximately 2.4 Ga, and a concomitant decrease in CH 4 , provides a natural explanation for the Palaeoproterozoic glaciations. The Mid-Archaean glaciations may have been caused by a drawdown in H 2 and CH 4 caused by the origin of bacterial sulphate reduction. More work is needed to test this latter hypothesis.

The Significance of Erosion Channels on Gold Metallogeny in the Witwatersrand Basin (South Africa): Evidence from the Carbon Leader Reef in the Carletonville Gold Field

2020 ◽  
Author(s):  
G. T. Nwaila ◽  
J. E. Bourdeau ◽  
Z. Jinnah ◽  
H. E. Frimmel ◽  
G. M. Bybee ◽  
...  
Keyword(s):  
South Africa ◽  
High Resolution ◽  
Mass Balance ◽  
Closed System ◽  
Seismic Data ◽  
Crucial Role ◽  
Sediment Load ◽  
Witwatersrand Basin ◽  
Petrographic Analyses ◽  
Group A

Abstract Within the eastern portion of the Carletonville gold field, the gold- and uranium-rich Carbon Leader reef of the Central Rand Group (Witwatersrand Supergroup) is truncated by an erosion channel. This channel is asymmetrical and lenticular in shape, measuring 150 to 180 m in width and up to 100 m in depth. High-resolution seismic data show that the erosion channel cuts from the Carbon Leader reef into all older units of the Central Rand Group down to the Roodepoort Formation of the underlying West Rand Group. A total of seven bore-holes were drilled into the channel, revealing that it is composed of quartzite at its base (9 m thick), overlain by deformed (lower) and laminated (upper) chloritoid-bearing shale (21 m thick) and quartzite (18 m thick). The Carbon Leader reef is highly enriched in gold (5–40 g/t Au), whereas the gold tenor of the erosion channel fill is in general much lower (<1 g/t Au), although locally grades of as much as 3.8 g/t Au are reached. Detailed seismic, sedimentological, and petrographic analyses revealed that the channel was filled with locally sourced sediments from the Main Formation. A closed-system mass balance further demonstrates that gold in the erosion channel could have been entirely sourced from the Carbon Leader reef. Sediment load played a crucial role in the distribution of gold in the channel, thus supporting a stratigraphically controlled modified placer model for the origin of gold in the Carbon Leader reef.

scholarly journals Modern weathering in outcrop samples versus ancient paleoredox information in drill core samples from a Mesoarchaean marine oxygen oasis in Pongola Supergroup, South Africa

2019 ◽  
Vol 265 ◽  
pp. 330-353 ◽  
Author(s):  
Gülüm Albut ◽  
Balz S. Kamber ◽  
Annika Brüske ◽  
Nicolas J. Beukes ◽  
Albertus J.B. Smith ◽  
...  
Keyword(s):  
South Africa ◽  
Drill Core ◽  
Core Samples

Bushveld-aged fluid flow, peak metamorphism, and gold mobilization in the Witwatersrand basin, South Africa: Constraints from in situ SHRIMP U-Pb dating of monazite and xenotime

Geology ◽  
2007 ◽  
Vol 35 (10) ◽  
pp. 931 ◽  
Author(s):  
Birger Rasmussen ◽  
Ian R. Fletcher ◽  
Janet R. Muhling ◽  
Andreas G. Mueller ◽  
Greg C. Hall
Keyword(s):  
South Africa ◽  
Fluid Flow ◽  
Witwatersrand Basin ◽  
Peak Metamorphism

Textural and geochemical discrimination between xenotime of different origin in the Archaean Witwatersrand Basin, South Africa

2003 ◽  
Vol 67 (4) ◽  
pp. 709-731 ◽  
Author(s):  
Natalie Kositcin ◽  
Neal J. McNaughton ◽  
Brendan J. Griffin ◽  
Ian R. Fletcher ◽  
David I. Groves ◽  
...  
Keyword(s):  
South Africa ◽  
Witwatersrand Basin ◽  
Different Origin

The Origin and Age of Biogeochemical Trends in Deep Fracture Water of the Witwatersrand Basin, South Africa

2006 ◽  
Vol 23 (6) ◽  
pp. 369-414 ◽  
Author(s):  
T. C. Onstott ◽  
L.-H. Lin ◽  
M. Davidson ◽  
B. Mislowack ◽  
M. Borcsik ◽  
...  
Keyword(s):  
South Africa ◽  
Witwatersrand Basin ◽  
Deep Fracture
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