Hostname: page-component-586b7cd67f-t8hqh Total loading time: 0 Render date: 2024-11-26T11:18:44.407Z Has data issue: false hasContentIssue false
  • English
  • Français

The Wedza–Mimosa platinum deposit, Great Dyke, Zimbabwe: layering and stratiform PGE mineralization in a narrow mafic magma chamber

Published online by Cambridge University Press:  01 May 2009

M. D. Prendergast
M. D. Prendergast
Affiliation:
Cluff Resources Zimbabwe Limited, P.O. Box 1795, Harare, Zimbabwe
Get access Rights & Permissions [Opens in a new window]

Abstract

The Wedza–Mimosa platinum deposit is a loosely stratiform PGE-rich sulphide zone (MSZ) set within a complexly layered, shallow synclinal sequence of pyroxenites and gabbros. Both the MSZ and its host rocks display systematic stratigraphic, lithological and compositional variations between the margins and the axis of the deposit. A well preserved marginal facies is characterized by discordant layering, stratigraphic complexity, evidence of non-equilibrium crystallization, magmatic erosion and extensive pegmatoids, as well as by irregular MSZ development and metal contents. The principal transverse variations and marginal phenomena are interpreted in terms of the high transverse heat flux and heat gradient caused by the narrow trumpet-like cross-sectional structure of the original magma chamber, the magma replenishment process, the angular relationship between the chamber floor and the stratified magma, and the increase in magma density caused by the onset of plagioclase crystallization.

Type
Articles
Information
Geological Magazine , Volume 128 , Issue 3 , May 1991 , pp. 235 - 249
Copyright
Copyright © Cambridge University Press 1991

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

Campbell, I. H. 1987. Distribution of orthocumulate textures in the Jimberlana Intrusion. Journal of Geology 95, 35–54.CrossRefGoogle Scholar
Campbell, I. H. & Naldrett, A. J. 1979. The influence of silicate: sulfide ratios on the geochemistry of magmatic sulphides. Economic Geology 76, 1503–6.CrossRefGoogle Scholar
Campbell, I. H., Naldrett, A. J. & Barnes, S. J. 1983. A model for the origin of the platinum-rich sulphide horizons in the Bushveld and Stillwater Complexes. Journal of Petrology 24, 133–65.CrossRefGoogle Scholar
Campbell, I. H. & Turner, J. S. 1986. The influence of viscosity on fountains in magma chambers. Journal of Petrology 27, 1–30.CrossRefGoogle Scholar
Campbell, I. H. & Turner, J. S. 1991. Fountains in magma chambers. Journal of Petrology. In press.Google Scholar
Casey, J. F. & Karson, J. A. 1981. Magma chamber profiles from the Bay of Islands ophiolite complex. Nature 292, 295–301.CrossRefGoogle Scholar
Irvine, T. N. 1980 a. Magmatic infiltration metasomatism, double-diffusion fractional crystallisation, and ad-cumulus growth in the Muskox Intrusion and other layered intrusions. In Physics of Magmatic Processes (ed. Hargraves, R. B.), pp. 325–83. Princeton University Press.CrossRefGoogle Scholar
Irvine, T. N. 1980 b. Magmatic density currents and cumulus processes. American Journal of Science 280-A (1), 1–58.Google Scholar
Keays, R. R. & Campbell, I. H. 1981. Precious metals in the Jimberlana Intrusion, Western Australia: implications for the genesis of platiniferous ores in layered intrusions. Economic Geology 76, 1118–41.CrossRefGoogle Scholar
Klemm, D. D., Ketterer, S., Reichhardt, F., Steindl, J. & Weber-Diefenbach, K. 1985. Implication of vertical and lateral compositional variations across the Pyroxenite Marker and its associated rocks in the upper part of the Main Zone in the Eastern Bushveld Complex. Economic Geology 80, 1007–15.CrossRefGoogle Scholar
Martin, A. 1978. The geology of the Belingwe–Shabani schist belt. Bulletin of the Geological Survey of Rhodesia 83, 1–220.Google Scholar
McBirney, A. R. & Noyes, R. M. 1979. Crystallisation and layering of the Skaergaard Intrusion. Journal of Petrology 20, 487–554.CrossRefGoogle Scholar
Podmore, F. & Wilson, A. H. 1987. A reappraisal of the structure, geology and emplacement of the Great Dyke, Zimbabwe. In Mafic Dyke Swarms (eds Halls, H. C. and Fahrig, W. F.), pp. 317–30. Geological Association of Canada Special paper no. 34.Google Scholar
Prendergast, M. D. 1987. The chromite ore fields of the Great Dyke, Zimbabwe. In Evolution of Chromium Ore Fields (ed. Stowe, C. W.), pp. 89–108. Van Nostrand Reinhold.Google Scholar
Prendergast, M. D. 1988. The geology and economic potential of the PGE-rich Main Sulphide Zone of the Great Dyke, Zimbabwe. In Geo-Platinum ′87 (eds. Prichard, H. M. et al. ), pp. 281–302. Elsevier.CrossRefGoogle Scholar
Prendergast, M. D. 1990. Platinum group minerals and hydrosilicate ‘alteration’ in Wedza–Mimosa platinum deposit, Great Dyke, Zimbabwe – genetic and metallurgical implications. Transactions of the Institution of Mining and Metallurgy (Section B: Applied Earth Science) 99, May–August, 91–105.Google Scholar
Prendergast, M. D. & Keays, R. R. 1989. Controls of platinum-group element mineralisation and the origin of the PGE-rich Main Sulphide Zone in the Wedza Subchamber of the Great Dyke, Zimbabwe: implications for the genesis of, and exploration for, stratiform PGE mineralisation in layered intrusions. In Magmatic sulphides – The Zimbabwe Volume (eds Prendergast, M. D. and Jones, M. J.), pp. 43–70. The Institution of Mining and Metallurgy.Google Scholar
Prendergast, M. D. & Wilson, A. H. 1989. The Great Dyke of Zimbabwe: II – Mineralisation and mineral deposits. In Magmatic Sulphides – The Zimbabwe Volume (eds Prendergast, M. D. and Jones, M. J.), pp. 21–42. The Institution of Mining and Metallurgy.Google Scholar
Sparks, R. S. J. & Huppert, H. E. 1984. Density changes during the fractional crystallisation of basaltic magmas: fluid dynamic implications. Contributions to Mineralogy and Petrology 85, 300–9.CrossRefGoogle Scholar
Sparks, R. S. J., Huppert, H. E., Kerr, R. C., McKenzie, D. P. & Tait, S. A. 1985. Postcumulus processes in layered intrusions. Geological Magazine 122, 555–68.CrossRefGoogle Scholar
Turner, J. S. & Campbell, I. H. 1986. Convection and mixing in magma chambers. Earth Science Reviews 23, 255–352.CrossRefGoogle Scholar
Wilson, A. H. & Prendergast, M. D. 1987. The Great Dyke of Zimbabwe – an overview. In Abstracts and Field Guide for 5 th Magmatic Sulphides Field Conference (ed. Campbell, A.), pp. 23–55. Geological Society of Zimbabwe.Google Scholar
Wilson, A. H. & Prendergast, M. D. 1989. The Great Dyke of Zimbabwe: I – Tectonic setting, stratigraphy, petrology, structure, emplacement and crystallisation. In Magmatic Sulphides – The Zimbabwe Volume (eds Prendergast, M. D. & Jones, M. J.), pp. 1–20. The Institution of Mining and Metallurgy.Google Scholar
Wilson, J. R. & Larsen, B. S. 1985. Two-dimensional study of a layered intrusion – the Hyllingen Series, Norway. Geological Magazine 122, 97–124.CrossRefGoogle Scholar
Worst, B. G. 1960. The Great Dyke of Southern Rhodesia. Bulletin of the Geological Survey of Southern Rhodesia 47, 1–234.Google Scholar