Hostname: page-component-cd9895bd7-mkpzs Total loading time: 0 Render date: 2024-12-23T10:41:42.225Z Has data issue: false hasContentIssue false
  • English
  • Français

Caveats in defining the magmas parental to the mafic rocks of the Bushveld Complex, and the manner of their emplacement: review and commentary

Published online by Cambridge University Press:  05 July 2018

H. V. Eales
H. V. Eales*
Affiliation:
Department of Geology, Rhodes University, Grahamstown, South Africa
*
*E-mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

The composition of magmas proposed as parental to the layered suite of the Bushveld Complex, and some models for the manner of their emplacement, are reviewed briefly. Included are some contributions published in South Africa, with which overseas readers might be less familiar. Emphasis is given to the broader features of the cumulates, and the contradictions raised by whole-rock compositional, Sr-isotopic, and trace-element data that cloud their correlation with proposed parental magmas. It is concluded that the Lower, Critical and Main Zones are the derivatives of only two primary magmatic lineages, while a third was added to residual liquids from which the layered rocks above the Pyroxenite Marker were formed. Excessive amounts of olivine and chromium in the cumulates of the Lower and Lower Critical Zones in the northern sector of the Western Limb can seemingly not be accounted for by the composition and volume of the putative magmas. This is attributed to (1) this sector being a proximal facies located close to the original feeder, and/or (2) crystal-charged magma batches, expelled from a lower magma chamber, being periodically injected into and dispersed within the liquids already in place in the Bushveld chamber. Thus, ongoing changes in the bulk composition of the liquids within the chamber would not be reflected in the rinds of earlier, chilled-facies rocks. The expulsion of significant volumes of liquid residua from the chamber during cumulate deposition is not ruled out.

Keywords

magmaBushveld ComplexSouth Africachromiumolivine
Type
Research Article
Information
Mineralogical Magazine , Volume 66 , Issue 6 , December 2002 , pp. 815 - 832
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2002

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

Barnes, S.J. (1986) The distribution of chromium among orthopyroxene, spinel and silicate liquid at atmospheric pressure. Geochimica et Cosmochimica Acta, 50, 1889-909.CrossRefGoogle Scholar
Botha, M.J. (1987) Petrology and geochemistry of the Lower Group chromitites and host rocks on the farm Zandspruit 168JP, Western Bushveld Complex. Unpublished MSc thesis, Rhodes University, Grahamstown, South Africa, 152 pp.Google Scholar
Cameron, E.N. (1978) The Lower Zone of the Eastern Bushveld Complex in the Olifants River trough. Economic Geology, 73, 845-71.Google Scholar
Cameron, E.N. (1980) Evolution of the lower Critical Zone, Central Sector, Eastern Bushveld Complex. Economic Geology, 75, 845–871.CrossRefGoogle Scholar
Cameron, E.N. (1982) The upper Critical Zone of the eastern Bushveld Complex. Economic Geology, 77, 1307–1327.CrossRefGoogle Scholar
Campbell, I.H., Naldrett, A.J. and Barnes, S.J. (1983) A model for the origin of the platinum-rich sulfide horizons in the Bushveld and Stillwater complexes. Journal of Petrology, 24, 133–165.CrossRefGoogle Scholar
Cawthorn, R.G. and Davies, G. (1983) Experimental data at 3 kbars pressure on parental magma to the Bushveld Complex. Contributions to Mineralogy and Petrology, 83, 128–135.CrossRefGoogle Scholar
Cawthorn, R.G. and Walraven, F. (1998) Emplacement and crystallization time for the Bushveld Complex. Journal of Petrology, 39, 1669–1687.CrossRefGoogle Scholar
Cawthorn, R.G., Davies, G., Clubley-Armstrong, A. and McCarthy, T.S. (1981) Sills associated with the Bushveld Complex, South Africa. Lithos, 14, 1–15.CrossRefGoogle Scholar
Cawthorn, R.G., Cooper, G.R.J. and Webb, S.J. (1998) Connectivity between the western and eastern limbs of the Bushveld Complex. South African Journal of Geology, 101, 291–298.Google Scholar
Cawthorn, R.G., Meyer, P.S. and Kruger, F.J. (1991) Major addition of magma at the Pyroxenite Marker in the Western Bushveld Complex. Journal of Petrology, 32, 739–763.CrossRefGoogle Scholar
Clarke, B.B., Uken, R. and Watkeys, M.K. (2000) Intrusion mechanisms of the southwestern Rustenburg Layered Suite as deduced from the Spruitfontein inlier. South African Journal of Geology, 103, 120–127.CrossRefGoogle Scholar
Cousins, C.A. (1959) The structure of the mafic portion of the Bushveld Igneous Complex. Transactions of the Geological Society of South Africa, 62, 179–189.Google Scholar
Crawford, A.J., Falloon, T.J. and Green, D.H. (1989) Classification, petrogenesis and tectonic setting of boninites. Pp. 1–49 in: Boninites and Related Rocks (Crawford, A.J., editor). Unwin Hyman, London.Google Scholar
Davies, G. and Cawthorn, R.G. (1984) Mineralogical data on a multiple intrusion in the Rustenburg Layered Suite of the Bushv eld Complex. Mineralogical Magazine, 48, 469–480.CrossRefGoogle Scholar
Davies, G. and Tredoux, M. (1985) Platinum-group element and gold contents of the marginal rocks and sills of the Bushveld Complex. Economic Geology, 80, 838–848.CrossRefGoogle Scholar
Davies, G., Cawthorn, R.G., Barton, J.M. and Morton, M. (1980) Parental magma to the Bushveld Complex. Nature, 287, 33–35.CrossRefGoogle Scholar
De Klerk, W.J. (1991) Petrogenesis of the Upper Critical Zone in the Western Bushveld Complex. PhD thesis, Rhodes University, Grahamstown, South Africa, 294 pp.Google Scholar
De Waal, S.A. and Armstrong, R.A. (2000) The age of the Marble Hall diorite, its relationship to the Uitkomst Complex, and evidence for a new magma type associated with the Bushveld igneous event. South African Journal of Geology, 103, 128–140.CrossRefGoogle Scholar
De Waal, S.A. and Gauert, C.D.K. (1997) The Basal Gabbro Unit and the identity of the parental magma of the Uitkomst Complex, Badplaas, South Africa. South African Journal of Geology, 100, 349–362.Google Scholar
Du Toit, A.L. (1954) The geology of South Africa. Oliver and Boyd, London, 611 pp.Google Scholar
Eales, H.V. (2000) Implications of the chromium budget of the Western Limb of the Bushveld Complex. South African Journal of Geology, 103, 141–150.CrossRefGoogle Scholar
Eales, H.V. and Cawthorn, R.G. (1996) The Bushveld Complex. Pp. 181–229 in: Layered Intrusions (Cawthorn, R.G., editor). Elsevier Science, Amsterdam.CrossRefGoogle Scholar
Eales, H.V., Marsh, J.S., Mitchell, A.A., De Klerk, W.J., Kruger, F.J. and Field, M. (1986) Some geochemical constraints upon models for the crystallization of the upper critical zone-main zone interval, northwestern Bushveld complex. Mineralogical Magazine, 50, 567–582.CrossRefGoogle Scholar
Eales, H.V., Field, M., De Klerk, W.J. and Scoon, R.N. (1988) Regional trends of chemical variation and thermal erosion in the Upper Critical Zone, Western Bushveld Complex. Mineralogical Magazine, 52, 63–79.CrossRefGoogle Scholar
Eales, H.V., De Klerk, W.J. and Butcher, A.R. (1990) The cyclic unit beneath the UG1 Chromitite (UG1FW Unit) at RPM Union Section Platinum Mine – Rosetta stone of the Bushveld Upper Critical Zone. Mineralogical Magazine, 54, 23–43.CrossRefGoogle Scholar
Eales, H.V., Maier, W.D. and Teigler, B. (1991) Corroded plagioclase feldspar inclusions in orthopyroxene and olivine of the Lower and Critical Zones, western Bushveld Complex. Mineralogical Magazine, 55, 479–486.CrossRefGoogle Scholar
Eales, H.V., Botha, W.J., Hattingh, P.J., De Klerk, W.J., Maier, W.D. and Odgers, A.T.R. (1993) The mafic rocks of the Bushveld Complex. Journal of African Earth Sciences, 16, 121–142.CrossRefGoogle Scholar
Engelbrecht, J.P. (1990) The Marico Hypabyssal Suite and the Marginal Zone of the Bushveld Complex in the Marico district, western Transvaal, South Africa. South African Journal of Geology, 93, 318–328.Google Scholar
Frick, C. (1973) The sill phase and the chill zone of the Bushveld igneous complex. Transactions of the Geological Society of South Africa, 76, 7–14.Google Scholar
Ghiorso, M.S. and Sack, R.O. (1995) Chemical mass transfer in magmatic processes. IV A revised and internally consistent thermodynamic model. Contributions to Mineralogy and Petrology, 119, 197–212.CrossRefGoogle Scholar
Gough, D.J. and van Niekerk, C.B. (1959) A study of the palaeomagnetism of the Bushveld Complex. Philosophical Magazine, 14, 126–134.CrossRefGoogle Scholar
Harmer, R.E. and Sharpe, M.R. (1985) Field relations and strontium isotope systematics of the marginal rocks of the eastern Bushveld Complex. Economic Geology, 80, 813–837.CrossRefGoogle Scholar
Hattingh, P.J. (1991) The magnetic susceptibility of the mafic rocks of the Bushveld Complex. South African Journal of Geology, 94, 132–136.Google Scholar
Hatton, C.J. (1988) Densities and liquidus temperatures of Bushveld parental magmas as constraints on the formation of the Merensky Reef in the Bushveld Complex, South Africa. Pp. 87–93 in: Magmatic Sulphides: the Zimbabwe Volume (Prendergast, M.D. and Jones, M.J., editors). Institution of Mining and Metallurgy London.Google Scholar
Hatton, C.J. and Sharpe, M.R. (1989) Significance and origin of boninite-like rocks associated with the Bushveld Complex. Pp. 1–49 in: Boninites and Related Rocks (Crawford, A.J., editor). Unwin Hyman, London.Google Scholar
Hatton, C.J. and von Gruenewaldt, G. (1987) Geological setting and petrogenesis of the Bushveld chromitite layers. Pp. 109–143 in: Evolution of Chromium Ore Fields (Stowe, C.W., editor). Van Nostrand Reinhold Company, New York.Google Scholar
Hoyle, P. (2000) The Upper Zone of the Northwestern Bushveld Complex. Un. nished PhD thesis, Rhodes University, Grahamstown, South Africa.Google Scholar
Hughes, C.J. (1982) Igneous Petrology. Elsevier Publishing Co., Amsterdam, 551pp.Google Scholar
Irvine, T.N., Keith, D.W. and Todd, S.G. (1983) The J-M platinum-palladium reef of the Stillwater Complex, Montana. Economic Geology, 78, 1287–1334.CrossRefGoogle Scholar
Kleywegt, R.J. and Du Plessis, A. (1986) On the structure of the Bushveld Complex and the central Transvaal Basin. Extended Abstracts Geocongress ’86, University of the Witwatersrand, Johannesburg, South Africa.Google Scholar
Kruger, F.J. (1990) The stratigraphy of the Bushveld Complex: a reappraisal and the relocation of the Main Zone boundaries. South African Journal of Geology, 93, 376–381.Google Scholar
Kruger, F.J. (1991) Author's reply to discussion on ‘The stratigraphy of the Bushveld Complex’. South African Journal of Geology, 94, 187–190.Google Scholar
Kruger, F.J. (1992) The origin of the Merensky Cyclic Unit. Australian Journal of Earth Sciences, 39, 255–261.CrossRefGoogle Scholar
Kruger, F.J. (1994) The Sr-isotopic stratigraphy of the western Bushveld Complex. South African Journal of Geology, 97, 393–398.Google Scholar
Kruger, F.J. and Marsh, J.S. (1982) The Significance of 87Sr/86Sr ratios in the Merensky cyclic unit. Nature, 298, 53–55.CrossRefGoogle Scholar
Kruger, F.J., Cawthorn, R.G. and Walsh, K.L. (1987) Strontium isotopic evidence against magma addition in the Upper Zone of the Bushveld Complex. Earth and Planetary Science Letters, 84, 51–58.CrossRefGoogle Scholar
Lee, C.A. (1981) Post-deposition structures in the Bushveld Complex mafic sequence. Journal of Geological Society of London, 138, 327–341.CrossRefGoogle Scholar
Lee, C.A. and Butcher, A.R. (1990) Cyclicity in the Sr isotope stratigraphy through the Merensky and Bastard Reef Units, Atok Section, Eastern Bushveld Complex. Economic Geology, 85, 877–883.CrossRefGoogle Scholar
Lombaard, B.V. (1934) On the differentiation and relationships of the rocks of the Bushveld Complex. Transactions of the Geological Society of South Africa, 55, 175–198.Google Scholar
Maier, W.D. and Barnes, S.-J. (1998) Concentrations of rare earth elements in silicate rocks of the Lower, Critical and Main Zones of the Bushveld Complex. Chemical Geology, 150, 85–103.CrossRefGoogle Scholar
Maier, W.D. and Eales, H.V. (1994 a) Plagioclase inclusions in orthopyroxene and olivine of the UG2-Merensky Reef interval: regional trends in the western Bushveld Complex. South African Journal of Geology, 97, 408–414.Google Scholar
Maier, W.D. and Eales, H.V. (1994 b) A facies model for the interval between the UG2 and Merensky Reef, Western Bushveld Complex. Transactions of the Institution of Mining and Metallurgy, 103, B22–B30.Google Scholar
Maier, W.D. and Walters, B.M. (1994) The UG2 – Merensky Reef interval at Amandelbult Section, Rustenburg Platinum Mines: patterns of lateral variation in lithology. South African Journal of Geology, 97, 45–51.Google Scholar
Merkle, R.K.W. and von Gruenewaldt, G. (1986) Compositional variation of Co-rich pentlandite: relation to the evolution of the Upper Zone of the Western Bushveld Complex. The Canadian Mineralogist, 24, 529–546.Google Scholar
Meyer, R. and De Beer, J.H. (1987) Structure of the Bushveld Complex from resistivity measurements. Nature, 325, 610–612.CrossRefGoogle Scholar
Mitchell, A.A. (1986) The petrology, mineralogy and geochemistry of the Main Zone of the Bushveld Complex at Rustenburg Platinum Mine, Union Section. PhD thesis, Rhodes University, Grahamstown, South Africa, 157 pp.Google Scholar
Mitchell, A.A. (1990) The stratigraphy, petrography and mineralogy of the Main Zone of the northwestern Bushveld Complex. South African Journal of Geology, 93, 818–831.Google Scholar
Mitchell, A.A. and Scoon, R.N. (1991) Discussion on ‘The stratigraphy of the Bushveld Complex’. South African Journal of Geology, 94, 183–187.Google Scholar
Murck, B.W. (1985) Factors influencing the formation of chromite seams. PhD thesis, University of Toronto, Canada, 141 pp.Google Scholar
Murck, B.W. and Campbell, I.H. (1986) The effects of temperature, oxygen fugacity and melt composition on the behaviour of chromium in basic and ultrabasic melts. Geochimica et Cosmochimica Acta, 50, 1871–1887.CrossRefGoogle Scholar
Nathan, H.D. and Van Kirk, C.K. (1978) A model of magmatic crystallization. Journal of Petrology, 19, 66–94.CrossRefGoogle Scholar
Roeder, P.L. and Emslie, R.F. (1970) Olivine:liquid equilibrium. Contributions to Mineralogy and Petrology, 29, 275–289.CrossRefGoogle Scholar
SACS (South African Committee for Stratigraphy) (1980) Stratigraphy of South Africa (Kent, L.E., compiler). Geological Survey of South Africa, Pretoria, Handbook 8, 690 pp.Google Scholar
Scoon, R.N. (1985) Discordant bodies of postcumulus ultramafic rock in the Upper Critical Zone of the Bushveld Complex. PhD thesis, Rhodes University, Grahamstown, South Africa, 265 pp.Google Scholar
Scoon, R.N. and Mitchell, A.A. (1994) Discordant iron-rich ultramafic pegmatites in the Bushveld Complex and their relationship to iron-rich intercumulus and residual liquids. Journal of Petrology, 35, 881–917.CrossRefGoogle Scholar
Scoon, R.N. and Teigler, B. (1994) Platinum-Group element mineralization in the Critical Zone of the Western Bushveld Complex. Economic Geology, 89, 1094–1121.CrossRefGoogle Scholar
Scoon, R.N. and Teigler, B. (1995) A new chromite reserve at Eerste Geluk in the boundary zone between the central and southern sectors of the Eastern Bushveld Complex. Economic Geology, 90, 969–982.CrossRefGoogle Scholar
Sharpe, M.R. (1984) Petrography, Classification and chronology of mafic sill intrusions beneath the Eastern Bushveld Complex. Geological Survey of South Africa, Bulletin, 77, 40 pp.Google Scholar
Sharpe, M.R. (1985) Strontium isotope evidence for preserved density stratification in the Main Zone of the Bushveld Complex. Nature, 316, 119–126.CrossRefGoogle Scholar
Sharpe, M.R. and Hulbert, L.J. (1985) Ultramafic sills beneath the Eastern Bushveld Complex. Economic Geology, 80, 849-71.CrossRefGoogle Scholar
Smit, P.J., Hales, A.L. and Gough, D.I. (1962) The Gravity Survey of the Republic of South Africa. Government Printer, Pretoria, South Africa, Handbook 3, 484 pp.Google Scholar
Sparks, R.S.J. and Huppert, H.E. (1984) Density changes during the fractional crystallization of basaltic magmas: fluid dynamic implications. Contributions to Mineralogy and Petrology, 85, 300–309.CrossRefGoogle Scholar
Teigler, B. (1990) Mineralogy, petrology and geochemistry of the Lower and Lower Critical Zones, Northwestern Bushveld Complex. PhD thesis, Rhodes University, Grahamstown, South Africa, 247 pp.Google Scholar
Teigler, B. and Eales, H.V. (1996) The Lower and Critical Zones of the Western Limb of the Bushveld Complex as intersected by the Nooitgedacht boreholes. Bulleting of the Geological Survey of South Africa, 111, 126 pp.Google Scholar
Teigler, B., Eales, H.V. and Scoon, R.N. (1992) The cumulate succession of the Critical Zone of the Rustenburg Layered Suite at Brits, western Bushveld Complex. South African Journal of Geology, 95, 17–28.Google Scholar
Wager, L.R. and Brown, G.M. (1968) Layered Igneous Rocks. Oliver and Boyd, London, 588 pp.Google Scholar
Willemse, J. (1959) The ‘floor’ of the Bushveld Igneous Complex. Proceedings of the Geological Society of South Africa, LXII, xxi–lxxx.Google Scholar
Willemse, J. (1964) A brief outline of the geology of the Bushveld Igneous Complex. Pp. 91–131 in: The Geology of some Ore Deposits in Southern Africa (Haughton, S.H., editor). Geological Society of South Africa, Johannesburg.Google Scholar
Willemse, J. (1969) The geology of the Bushveld Complex, the largest repository of magmatic ore deposits in the World. Pp. 1–22 in: Magmatic Ore Deposits: A Symposium (Wilson, H.D.B., editor). Economic Geology Monograph 4. Economic Geology Publishing Co., Lancaster, PA, USA.Google Scholar
Wilson, J.R., Cawthorn, R.G., Kruger, F.J. and Grundvig, S. (1994) Intrusive origin for the Upper Zone in the Northwestern Gap, Western Bushveld Complex. South African Journal of Geology, 97, 462–472.Google Scholar