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Regional trends of chemical variation and thermal erosion in the Upper Critical Zone, Western Bushveld Complex

Published online by Cambridge University Press:  05 July 2018

H. V. Eales ,
M. Field ,
W. J. de Klerk  and
R. N. Scoon
H. V. Eales
Affiliation:
Department of Geology, Rhodes University, Grahamstown, South Africa
M. Field
Affiliation:
Department of Geology, Rhodes University, Grahamstown, South Africa
W. J. de Klerk
Affiliation:
Department of Geology, Rhodes University, Grahamstown, South Africa
R. N. Scoon
Affiliation:
Department of Geology, Rhodes University, Grahamstown, South Africa
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Abstract

A comparison of R.P.M. Union and Amandelbult Sections reveals close geochemical and stratigraphic correlations, but the sequence at the latter is more complex. Mafic members at Union Section are consistently more magnesian than their equivalents at Amandelbult Section and (where available data allow comparisons) than at Rustenburg Section. This, taken together with regional patterns of progressive attenuation and elimination of leucocratic rocks beneath harzburgitic layers, identifies Union Section as proximally located with reference to an irruptive centre from which primitive liquids were injected along the floor/supernatant liquid interface. Successive injections led to thermal erosion of the floor, causing ‘dimpling’ and ‘potholing’ on a local scale, and elimination of noritic-anorthositic layers on a regional scale. Such erosion of the floors beneath new inputs of magmatic liquid is likely to be initiated by only partial remelting, mainly of lower-temperature phases (sodic rims to zoned plagioclase grains, and Fe-enriched pyroxenes) within intercumulus space. It is argued that resultant contamination of the primitive liquids may have led to direct superposition of anorthosites (accompanied by rare troctolite) upon harzburgite, without intervening pyroxenite members, as in the Pseudoreef Multicyclic Unit.

Keywords

Bushveld complexCritical ZonegeochemistrySouth Africa
Type
Geochemistry
Information
Mineralogical Magazine , Volume 52 , Issue 364 , March 1988 , pp. 63 - 79
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1988

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References

Campbell, I.H., Naldrett, A.J., and Barnes, S.J. (1983) J. Petrol. 24, 133–65.CrossRefGoogle Scholar
de Klerk, W.J. (1982) M.Sc. thesis, Rhodes University.Google Scholar
Donaldson, C.H. (1985) Mineral. Mag. 49, 683–94.CrossRefGoogle Scholar
Eales, H.V., and Reynolds, I.M. (1986) Econ. Geol. 81, 105-66.CrossRefGoogle Scholar
Marsh, J.S., Mitchell, A.A., de Klerk, W.J., Kruger, F.J., and Field, M. (1986) Mineral. Mag. 50, 567–82.Google Scholar
Farquhar, J. (1986) In Mineral Deposits of Southern Africa (C. R. Anhaeusser and S. Maske, eds.) Geol. Soc. S. Africa, 113-54.Google Scholar
Feringa, G. (1959) Geol. Soc. S. Africa Trans. 62, 219–38.Google Scholar
Field, M. (1986) M.Sc. thesis, Rhodes University.Google Scholar
French, W.J., and Cameron, E.P. (1981) Mineral. Ma9. 44, 19–26.CrossRefGoogle Scholar
Harmer, R.E., and Sharpe, M.R. (1985) Econ. Geol. 80, 813–37.CrossRefGoogle Scholar
Hiemstra, S.A. (1985) Ibid. 80, 944-67.Google Scholar
Huppert, H.E., and Sparks, R.S. J. (1980) Contrib. Mineral. Petrol. 75, 279-89.CrossRefGoogle Scholar
Huppert, H.E., and Sparks, R.S. J. (1985) J. Petrol. 26, 694–725.CrossRefGoogle Scholar
Irvine, T.N., Keith, D.W., and Todd, S.G. (1983) Econ. Geol. 78, 1287–334.CrossRefGoogle Scholar
Kruger, F.J. (1983) Ph.D. thesis, Rhodes University.Google Scholar
Kruger, F.J. and Marsh, J.S. (1982) Nature, 298, 53–5.CrossRefGoogle Scholar
Lee, C.A. (1981) J. Geol. Soc. London, 138, 327-41.CrossRefGoogle Scholar
Lee, C.A. (1983) Mineralium Deposita, 18, 173–90.CrossRefGoogle Scholar
Leeb-du Toit, A. (1986) In Mineral Deposits of Southern Africa (C. R. Anhaeusser and S. Maske, eds.) Geol. Soc. S. Africa, 1091-106.Google Scholar
Mitchell, A.A. (1986) Ph.D. thesis, Rhodes University.Google Scholar
Scoon, R.N. (1985) Ph.D, thesis, Rhodes University.Google Scholar
Scoon, R.N. and de Klerk, W.J. (1987) Can. Mineral. 25, 5178.Google Scholar
Sharpe, M.R., and Irvine, T.N. (1983) Carnegie Inst. Washington Yearb. 82, 295-30.Google Scholar
Streckeisen, A.L. (1973) Geotimes, Oct. 1973, 26–30.Google Scholar
van Zyl, J.P. (1969) Geol. Soc. S. Africa Spec. Publ. 1, 801-07.Google Scholar
Viljoen, M.J., and Hieber, R. (1986) In Mineral Deposits of Southern Africa (C. R. Anhaeusser and S. Maske, eds.) Geol. Soc. S. Africa, 110-73.Google Scholar
Viljoen, M.J., and Hieber, R. de Klerk, W.J. Coetzer, P.M., Hatch, N.P., Kinloch, E., and Peyerl, W. (1986a) Ibid. 1061-90.Google Scholar
Theron, J., Underwood, B., Walters, B.M., Weaver, J., and Peyerl, W. (1986b) Ibid. 104160.Google Scholar