Hostname: page-component-586b7cd67f-r5fsc Total loading time: 0 Render date: 2024-11-22T17:43:38.459Z Has data issue: false hasContentIssue false
  • English
  • Français

Sulphidation in the Witwatersrand Goldfields: evidence from the Middelvlei Reef

Published online by Cambridge University Press:  05 July 2018

Russell E. Myers ,
Taihe Zhou  and
G. Neil Phillips
Russell E. Myers
Affiliation:
National Key Centre in Economic Geology, Geology Department, James Cook University, Townsville, Australia Q4811
Taihe Zhou
Affiliation:
National Key Centre in Economic Geology, Geology Department, James Cook University, Townsville, Australia Q4811
G. Neil Phillips
Affiliation:
National Key Centre in Economic Geology, Geology Department, James Cook University, Townsville, Australia Q4811
Get access Rights & Permissions [Opens in a new window]

Abstract

There is extensive textural evidence for sulphidation in the Middelvlei Reef of the Carletonville Goldfield, South Africa. Secondary iron sulphides have replaced sand- and pebble-sized elasts in conglomerate, as well as matrix material in both conglomerate and quartzite. Within the Middelvlei Reef there is a close correspondence between the intensity of sulphidation and areas of greater modal muscovite, and there is less sulphidation where chloritoid dominates. Both pyrite and minor pyrrhotite are widespread. The timing of the sulphidation appears to be post-depositional but the relative importance of diagenetic and syn-metamorphic processes cannot be determined using textural criteria. The absence of retrograde effects suggests that sulphidation occurred prior to or during peak metamorphism. The distribution and intensity of sulphidation and phyllosilicate alteration indicate that these processes may be more significant in the Witwatersrand than has generally been thought. These processes should be considered in all future genetic models.

Keywords

sulphidationgoldfieldsWitwatersrandSouth Africa
Type
Research Article
Information
Mineralogical Magazine , Volume 57 , Issue 388 , September 1993 , pp. 395 - 405
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1993

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Dimanche, F. and Bartholome, P. (1976) The alteration of ilmenite in sediments. Mineral Sci. Engineering, 8, 187–201.Google Scholar
Els, B. G. (1987) The auriferous Middelvlei Reef depositional system, West Wits Line, Witwatersrand Supergroup. PhD Thesis, Rand Afrikaans University, Johannesburg.Google Scholar
Els, B. G. (1991) Placer formation during progradational fluvial degradation: the late Archean Middelvlei gold placer, Witwatersrand South Africa. Econ. Geol., 86, 261-77.Google Scholar
Englebrecht, C. J., Baumbach, G. W. S., Matthysen, J. L., and Fletcher, P. (1986) The West Wits Line. In Mineral Deposits of Southern Africa, Volume H (C. R. Anhaeusser and S. Maske, eds.), Geol. Soc. S. Afr., 599–648.Google Scholar
Hesske, S. (1989) The sedimentology of the auriferous Middelvlei Reef in the 4 Shaft area of West Driefontein Gold Mine. Gold Fields of South Africa, internal report, 37 pp.Google Scholar
Hirdes, W. and Saager, R. (1983) The Proterozoic Kimberley Reef Placer in the Evander Goldfield, Witwatersrand, South Africa., Monograph Series on Mineral Deposits, GeBruder Borntraeger, Berlin, 20, 100 pp.Google Scholar
Holland, T. J. B. and Powell, R. (1990) An enlarged and updated internally consistent thermodynamic dataset with uncertainties and correlations: the system KzO-Na2O-CaO-MgO-MnO-FeO-Fe2O3-Al2O3-TiO2-SiO2-C-H2-O2. J. Metamorphic Geol., 8, 89–124.Google Scholar
Johnson, J. W., Oelkers, E. H., and Helgeson, H. L. (1992) A software package for calculating the standard molal thermodynamic properties of miner-als, gases, aqueous species, and reactions from 1 to 5000 bars and 0° to 1000 °C Computers Geosci., 18, 899–914.Google Scholar
Jolly, M. K. (1984) The sedimentology and economic potential of the auriferous Middelvlei Reef on West Driefontein Consolidated Limited. MSc Thesis, Rand Afrikaans University, Johannesburg.Google Scholar
Phillips, G. N. (1987) Metamorphism of the Witwatersrand goldfields: conditions during peak metamorphism. Z Metamorphic Geol., 5, 307–22.Google Scholar
Phillips, G. N. and Myers, R. E. (1989) The Witwatersrand Gold Fields Part II: An origin for Witwatersrand gold during metamorphism and associated alteration. Econ. Geol. Monograph, 6, 598–608.Google Scholar
Ramdohr, P. (1958) New Observations on the Ores of the Witwatersrand in South Africa and their Genetic Significance. Trans. Geol. Soc. S. Afr., Annex. to vol. 61, 111 pp.Google Scholar
Reimer, T. O. and Mossman, D. J. (1990a) Sulphidiza-tion of Witwatersrand black sands: from enigma to myth. Geology, 18, 426–9.Google Scholar
Reimer, T. O. and Mossman, D. J. (1990b) The Witwatersrand controversy revisited. Econ. Geol., 85, 337-43.Google Scholar
Robb, L. J. and Meyer, F. M. (1991) A contribution to recent debate concerning epigenetic versus syngene-tic mineralization processes in the Witwatersrand Basin. Econ. Geol., 86, 396–401.Google Scholar
Robert, F., Phillips, G. N., and Kesler, S. E. (1991) Greenstone gold and crustal evolution: scope and results of the conference. In Greenstone Gold and Crutal Evolution, Geol. Soc. Can., 2-7.Google Scholar
Saager, R. (1970) Structures in Pyrite from the Basal Reef in the Orange Free State. Trans. Geol. Soc. S. Afr., 73, 29–48.Google Scholar
Sutton, S. J., Ritger, S. D., and Maynard, J. B. (1990) Stratigraphic control of chemistry and mineralization in metamorphosed Witwatersrand quartzites. J. Geol., 98, 329–41.Google Scholar
Wallmach, T. and Meyer, F. M. (1990) A petrogenetic grid for metamorphosed aluminous Witwatersrand shales. S. Afr. J. Geol., 93, 93–102.Google Scholar
Walshe, J. L. (1986) A six component chlorite solid solution model and the conditions of chlorite formation in hydrothermal and geothermal systems. Econ Geol., 81, 681–703.Google Scholar