Hostname: page-component-586b7cd67f-rcrh6 Total loading time: 0 Render date: 2024-11-26T17:07:36.871Z Has data issue: false hasContentIssue false
  • English
  • Français

Nature and longevity of hydrothermal fluid flow and mineralisation in granites of the Bushveld Complex, South Africa

Published online by Cambridge University Press:  03 November 2011

L. J. Robb ,
L. A. Freeman  and
R. A. Armstrong
L. J. Robb
Affiliation:
Department of Geology, University of the Witwatersrand, Johannesburg, South Africa
L. A. Freeman
Affiliation:
Department of Geology, University of the Witwatersrand, Johannesburg, South Africa
R. A. Armstrong
Affiliation:
Research School of Earth Sciences, The Australian National University, Canberra, Australia
Get access Rights & Permissions [Opens in a new window]

Abstract

The Lebowa Granite Suite of the Bushveld Complex is a large, 2054 Ma old, A-type batholith, characterised by numerous relatively small magmato-hydrothermal, polymetallic ore deposits. The mineralisation is represented by a three-stage paragenetic sequence: early magmatic Sn-W-Mo-F ores (600°C > T > 400°C), followed by a Cu-Pb-Zn-As-Ag-Au paragenesis (400°C > T > 200°C) and then late-stage Fe-F-U mineralisation (< 200°C). The first stage of mineralisation (typified by the endogranitic Zaaiplaats tin deposit) is related to incompatible trace element concentration during crystal fractionation and subsequent fluid saturation of the magma. Evolution of the late magmatic fluids as they were channelled along fractures, as well as mingling with externally derived connate or meteoric fluids, resulted in the deposition of the second stage of mineralisation (typified by the fracture-related, endogranitic Spoedwel and Albert deposits and the exogranitic, sediment-hosted Rooiberg mine) which is dominated by polymetallic sulphide ores. As the externally derived fluid component became progressively more dominant, oxidation of the polymetallic sulphide assemblage and precipitation of hematite, pitchblende and fluorite occurred generally along the same fracture systems that hosted the earlier sulphide paragenesis.

Small hydrothermal zircons trapped along quartz growth zones from the Spoedwel deposit yield a U-Pb concordia age of 1957 ± 15 Ma. Whole-rock Rb-Sr age determinations from the Lebowa Granite Suite fall in the range 1790 ± 114 Ma to 1604 ± 70 Ma and are interpreted to reflect alkali element mobility and isotopic resetting during exhumation of the Bushveld granite. In contrast to thermal modelling which indicates that hydrothermal activity should have ceased within 4 my of emplacement, isotopic evidence suggests that mineralisation was long-lived, but episodic, and that fluid flow events were linked to major periods of Palaeo- and Mesoproterozoic orogenic activity along the margins of the Kaapvaal Craton. During these orogenic episodes, fluid flow was enhanced by tectonically induced fluid over-pressuring and/or exhumation of the Bushveld Complex.

Keywords

A-type graniteepisodic fluid flowfluid mixingmagmato-hydrothermal depositsU-Pb zircon ages
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 91 , Issue 1-2: Fourth Hutton Symposium: The Origin of Granites and Related Rocks , 2000 , pp. 269 - 281
Copyright
Copyright © Royal Society of Edinburgh 2000

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

Absolom, S. S. 1986. The Buffalo fluorspar deposit, Naboomspruit district. In Anhaeusser, C. R.& Maske, S. (eds) Mineral Deposits of Southern Africa vol. II, 1337–41. Johannesburg: Geological Society of South Africa.Google Scholar
Borrok, D. M., Kesler, S. E., Boer, R. H.& Essene, E. J. 1998. The Vergenoeg magnetite-fluorite deposit, South Africa: support for a hydrothermal model for massive iron oxide deposits. Economic Geology 93(5), 564–86.Google Scholar
Burger, A. J., Oosthuizen, E. J.& Van, Niekerk C. B. 1967. New Pb isotopic ages from minerals from granitic rocks in the northern and central Transvaal. Annals of the Geological Survey of South Africa 6, 85–9.Google Scholar
Cathles, L. M., Erendi, A. H. J.& Barrie, T. 1997. How long can a hydrothermal system be sustained by a single intrusive event? Economic Geology 92(7/8), 766–71.10.2113/gsecongeo.92.7-8.766Google Scholar
Cawthorn, R. G.& Walraven, F. 1998. Emplacement and crystallisation time for the Bushveld Complex. Journal of Petrology 39, 1669–87.10.1093/petroj/39.9.1669Google Scholar
Coertze, F., Burger, A. J., Walraven, F., Marlow, A. G.& MacCaskie, D. R. 1978. Field relations and age determinations in the Bushveld Complex. Transactions of the Geological Society of South Africa 81, 1–11.Google Scholar
Crocker, I. 1979. Metallogenic aspects of the Bushveld granites: fluorite, tin and associated rare-metal carbonate mineralisation. Special Publication Geological Society of South Africa 5, 275–95.Google Scholar
Crocker, I. 1986. The Zaaiplaats tinfield, Potgietersrus district. In Anhaeusser, C. R.& Maske, S. (eds) Mineral Deposits of southern Africa vol. II, 1287–99. Johannesburg: Geological Society of South Africa.Google Scholar
Davies, R. D., Allsopp, H. L., Erlank, A. J.& Manton, W. T. 1970. Sr-isotopic studies on various layered mafic intrusions in southern Africa. Special Publication, Geological Society of South Africa 1, 576–93.Google Scholar
Duane, M. J.& Kruger, F. J. 1991. Geochronological evidence for tectonically driven brine migration during the early Proterozoic Kheis orogeny of southern Africa. Geophysical Research Letters 18(5), 975–8.Google Scholar
Freeman, L. A. 1998. The nature of hydrothermal fluids associated with granite-hosted polymetallic mineralisation in the eastern lobe of the Bushveld Complex. (Unpublished PhD. Thesis, University of the Witwatersrand, Johannesburg).Google Scholar
Ge, S.& Garven, G. 1992. Hydrochemical modeling of tectonically driven groundwater flow with application to the Arkoma foreland basin. Journal of Geophysical Research 97, 9119–24.10.1029/92JB00677Google Scholar
Graney, J. R.& Kesler, S. E. 1995. Factors affecting gas analysis of inclusion fluid by quadrupole mass spectrometry. Geochimica et Cosmochimica Acta 59, 3977–86.10.1016/0016-7037(95)00238-UGoogle Scholar
Groves, D. I.& McCarthy, T. S. 1978. Fractional crystallisation and the origin of tin mineralisation in granitoids. Mineralium Deposita 13, 11–26.10.1007/BF00202905Google Scholar
Gulson, B. L.& Jones, M. T. 1992. Cassiterite: potential for direct dating of mineral deposits and a precise age for the Bushveld Complex granites. Geology 20, 355–8.10.1130/0091-7613(1992)020<0355:CPFDDO>2.3.CO;22.3.CO;2>Google Scholar
Hamilton, P. J. 1977. Sr isotope and trace element studies of the Great Dyke and Bushveld mafic phase and their relation to Proterozoic magma genesis in southern Africa. Journal of Petrology 18, 24–52.10.1093/petrology/18.1.24Google Scholar
Harmer, R. E.& Farrow, D. 1995. An isotope study on the volcanics of the Rooiberg Group: age implications and a potential exploration tool. Mineralium Deposita 30, 188–95.10.1007/BF00189348Google Scholar
Hartnady, C, Joubert, P.& Stowe, C. 1985. Proterozoic crustal evolution in southwestern Africa. Episodes 8(4), 236–44.Google Scholar
Jacobs, J., Thomas, R. J.& Weber, K. 1993. Accretion and indentation tectonics at the southern edge of the Kaapvaal Craton during the Kibaran (Grenville) orogeny. Geology 21, 203–6.Google Scholar
Jones, H. D.& Kesler, S. E. 1992. Fluid inclusion gas chemistry in east Tennessee Mississippi Valley-type districts: evidence for immiscibility and implications for depositional mechanisms. Geochimica et Cosmochimica Acta 56, 137–54.10.1016/0016-7037(92)90122-YGoogle Scholar
Koons, P. O.& Craw, D. 1991. Evolution of fluid driving forces and composition within collisional orogens. Geophysical Research Letters 18(5), 935–8.10.1029/91GL00910Google Scholar
Kruger, F. J., Duane, M. J.& Whitelaw, H. T. 1999. The c. 2 Ga Kheis tectonism in southern Africa and associated MVT mineralisation. In Stanley, C. et al. (eds) Mineral Deposits: Processes to Processing, 1263–6. Rotterdam: Balkema.Google Scholar
Leube, A.& Stumpfl, E. F. 1963. The Rooiberg and Leeuwpoort Tin Mines, Transvaal, South Africa. Economic Geology 58, 391–418.Google Scholar
McNaughton, N. J., Pollard, P. J., Groves, D. I.& Taylor, R. G. 1993. A long-lived hydrothermal system in Bushveld granites at the Zaaiplaats tin mine: lead isotope evidence. Economic Geology 88(1), 27–43.Google Scholar
Nicolaysen, L. O., De Villiers, J. W. L. Burger, A. J.& Strelow, F. W. E. 1958. New measurements relating to the absolute age of the Transvaal System and the Bushveld Igneous Complex. Transactions of the Geological Society of South Africa 61, 137–63.Google Scholar
Oliver, J. 1986. Fluids expelled tectonically from orogenic belts: their role in hydrocarbon migration and other geological phenomena. Geology 14, 99–102.10.1130/0091-7613(1986)14<99:FETFOB>2.0.CO;22.0.CO;2>Google Scholar
Oliver, N. H. S. 1996. Review and classification of structural controls on fluid flow during regional metamorphism. Journal of Metamorphic Geology 14, 477–92.Google Scholar
Ollila, J. T. 1981. A fluid inclusion and mineralogical study of tin deposits on rocks associated with the Bushveld Complex at the Zaaiplaats, Union and Rooiberg tin mines in the central Transvaal, South Africa. (Unpublished Ph.D. thesis, Rand Afrikaans University, Johannesburg).Google Scholar
Pollard, P. J., Andrew, A. S.& Taylor, R. G. 1991. Fluid inclusion and stable isotope evidence for interaction between granites and magmatic hydrothermal fluids during formation of disseminated and pipe-style mineralisation at the Zaaiplaats tin mine. Economic Geology 86(1), 121–41.10.2113/gsecongeo.86.1.121Google Scholar
Pringle, I. 1986a. The Union tin mine, Naboomspruit district. In Anhaeusser, C. R.& Maske, S. (eds) Mineral Deposits of southern Africa vol. II, 1301–5. Johannesburg: Geological Society of South Africa.Google Scholar
Pringle, I. 1986b. The Zwartkloof fluorite deposits, Warmbaths district. In Anhaeusser, C. R.& Maske, S. (eds) Mineral Deposits of southern Africa vol. II, 1343–9. Johannesburg: Geological Society of South Africa.Google Scholar
Robb, L. J., Robb, V. M.& Walraven, F. 1994. The Albert Silver Mine revisited: toward a model for polymetallic mineralisation in granites of the Bushveld Complex, South Africa. Exploration and Mining Geology 3, 219–30.Google Scholar
Robb, L. J., Armstrong, R. A.& Waters, D. J. 1999. The history of granulite facies metamorphism and crust forming events from single zircon U-Pb isotopic analyses; Namaqualand, South Africa. Journal of Petrology 78, 1747–70.10.1093/petroj/40.12.1747Google Scholar
Rozendaal, A., Toros, M. S.& Anderson, J. R. 1986. The Rooiberg tin deposits, west-central Transvaal. In Anhaeusser, C. R.& Maske, S. (eds) Mineral Deposits of southern Africa vol. II, 1307–27. Johannesburg: Geological Society of South Africa.Google Scholar
Smits, G. 1980. A mineralogical study of the Rooibokkop-Boschhoek copper deposit in the Marble Hall area. National Institute for Metallurgy Report 2057.Google Scholar
South African Committee for Stratigraphy (SACS) 1980. Stratigraphy of South Africa, Part 1 (compiled L. E. Kent). Lithostratigraphy of the Republic of South Africa, South West Africa/Namibia and the Republics of Bophuthatswana, Transkei and Venda. Handbook Geological Survey of South Africa 8.Google Scholar
Thomas, R. J., Agenbacht, A. L. D. Cornell, D. H.& Moore, J. M. 1994. The Kibaran of southern Africa: tectonic evolution and metallogeny. Ore Geology Reviews 9, 131–60.10.1016/0169-1368(94)90025-6Google Scholar
Vennemann, T. W.& O'Neil, J. R. 1993. A simple and inexpensive method of hydrogen isotope and water analyses of minerals and rocks based on zinc reagent. Chemical Geology (Isotope Geoscience section) 103, 227–34.Google Scholar
Wagner, P. A. 1921. The Mutue Fides-Stavoren Tin Fields. Memoir of the Geological Survey of South Africa 16.Google Scholar
Walraven, F. 1987. Geochronological and isotopic studies of Bushveld Complex rocks from the Fairfield borehole at Moloto, northwest of Pretoria. South African Journal of Geology 90, 352–60.Google Scholar
Walraven, F. 1997. Geochronology of the Rooiberg Group, Transvaal Supergroup, South Africa. Information Circular Economic Geology Research Unit, University of the Witwatersrand, Johannesburg 316.Google Scholar
Walraven, F., Burger, A. J.& Allsopp, H. L. 1981. Summary of age determinations carried out during the period April 1979 to March 1980. Annals of the Geological Survey of South Africa 15, 89–94.Google Scholar
Walraven, F., Burger, A. J.& Allsopp, H. L. 1982. Summary of age determinations carried out during the period April 1980 to March 1981. Annals of the Geological Survey of South Africa 16, 107–14.Google Scholar
Walraven, F., Burger, A. J.& Allsopp, H.L. 1983. Summary of age determinations carried out during the period April 1981 to March 1982. Annals of the Geological Survey of South Africa 17, 87–93.Google Scholar
Walraven, F., Kleeman, G. J.& Allsopp, H. L. 1985. Disturbance of trace element and isotope systems and its bearing on mineralisation in acid rocks of the Bushveld Complex, South Africa. In High Heat Production (HHP) Granites, Hydrothermal Circulation and Ore Genesis. London: The Institution of Mining and Metallurgy.Google Scholar
Walraven, F., Armstrong, R. A.& Kruger, F. J. 1990. A chronostratigraphic framework for the north-central Kaapvaal Craton, the Bushveld Complex and the Vredefort structure. Tectonophysics 171, 23–48.10.1016/0040-1951(90)90088-PGoogle Scholar
Walraven, F., Strydom, J. H.& Strydom, N. 1990. Rb-Sr open system behaviour and its application as a pathfinder for Sn mineralisation in granites of the Bushveld Complex, South Africa. Journal of Geochemical Exploration 37, 333–50.Google Scholar
Walraven, F.& Hattingh, E. 1993. Geochronology of the Nebo granite, Bushveld Complex. South African Journal of Geology 96, 31–41.Google Scholar