Hostname: page-component-78c5997874-mlc7c Total loading time: 0 Render date: 2024-11-14T17:23:52.719Z Has data issue: false hasContentIssue false
  • English
  • Français

First occurrence of the rare ‘corundum + quartz’ assemblage in the high-grade zone from the Namaqualand Metamorphic Complex, South Africa: evidence for higher-P, T metamorphism?

Published online by Cambridge University Press:  05 July 2018

H. Mouri ,
M. A. G. Andreoli ,
J. R. Kienast ,
M. Guiraud  and
S. A. De Waal
H. Mouri*
Affiliation:
Department of Geology, University of Pretoria, South Africa
M. A. G. Andreoli
Affiliation:
South African Nuclear Energy Corporation, P.O. Box 582, Pretoria 0001, South Africa
J. R. Kienast
Affiliation:
Laboratoire des Geosciences Marine, Université Paris 7, France
M. Guiraud
Affiliation:
USM 201 Minéralogie, FRE CNRS 2456, Dpt Histoire de la Terre, MNHN Paris, France
S. A. De Waal
Affiliation:
Department of Geology, University of Pretoria, South Africa
*
* E-mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

We report in this paper the first occurrence of the rare assemblage corundum + quartz in the high-grade metamorphic zone in the core of the Namaqualand Metamorphic Complex (NMC) (South Africa). The magnetite-bearing rocks hosting the corundum-quartz assemblage are very rare, and occur discontinuous bands a few cm wide, associated with diorite, tonalite and anorthosite within quartzfeldspar ± sillimanite ± biotite ± spinel supracrustal rocks extensively intruded by a foliated granite gneiss. The magnetite-bearing rocks are characterized by the presence of abundant crystals of magnetite together with ilmenite, spinel and large (∽1 cm in diameter) euhedral crystals of corundum both displaying a sharp contact with magnetite and quartz. However, in some micro-domains, spinel and quartz, as well as corundum and quartz, are separated by a thin corona of sillimanite with or without magnetite. These textural features suggest that the following reactions have taken place: quartz + corundum → sillimanite, and quartz + spinel + O2 → sillimanite + magnetite. These reactions are interpreted as occurring at higher, as yet unknown, P-T conditions than previously estimated for the NMC. Whether corundum and quartz were once in equilibrium is worth investigating, as it could constitute a geothermobarometric assemblage for ultra-high T granulites.

Keywords

corundumquartzNamaqualand Metamorphic ComplexSouth Africa.
Type
Research Article
Information
Mineralogical Magazine , Volume 67 , Issue 5 , October 2003 , pp. 1015 - 1021
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2003

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.)

Footnotes

†

Present address: Schonland Research Centre for Nuclear Science, University of the Witwatersrand, P.O. Box 3, Wits 2050, South Africa

References

Anderson, A.T. (1966 Mineralogy of the Labrieville anorthosite, Quebec. American Mineralogist, 51, 1671—1711.Google Scholar
Andreoli, M.A.G., Smith, C.B., Watkeys, M., Moore, J.M., Ashwal, L.D. and Hart, R.J., (1994 The geology of the Steenkampskraal monazite deposit, South Africa: Implications for REE-Th-Cu mineralization in charnockite-granulite terranes. Economic Geology, 89, 994—1016.CrossRefGoogle Scholar
Anovitz, L.M., Essen, E.J., Metz, G.W., Bohlen, S.R., Wesrrum, E.F. Jr. and Hemingway, B.S. (1993 Heat capacity and phase equilibria of almandine, Fe3Al2Si2012 . Geochimica et Cosmochimica Ada, 57, 4191—4204.CrossRefGoogle Scholar
Aramaki, S. and Roy, R. (1963 A new polymorph of Al2SiO5 and further studies in the system A12O3-SiO2-H2O. American Mineralogist, 48, 1322—1347.Google Scholar
Ashwal, L.D., Andreoli, M.A.G., Page, T., Armstrong, R.A. and Tucker, R.D. (1997 Geology and geochronology of high temperature granulites, Vaalputs area, central Namaqualand, South Africa. 13* Anniversary Conference of the Tectonic Division of the Geological Society of South Africa, University Of the Witwatersrand, Johannesburg (Abstract only), 2 pp.Google Scholar
Bohlen, S.R., Boettcher, A.L., WaU, V.J. and Clemens, J.D. (1983 Stability of phlogopite-quartz and sanidine-quartz: a model for melting in the lower crust. Contributions to Mineralogy and Petrology, 83, 270—277.CrossRefGoogle Scholar
Clifford, T.N, Gronow, J., Rex, D.C. and Burger, A.J. (1975 Geochronological and petrologic studies of high-grade metamorphic rocks and intrusives in Namaqualand, South Africa. Journal of Petrology, 16, 154—188.CrossRefGoogle Scholar
Gross, G.A., Gower, C.F. and Lefebure, D.V. (1997 Magmatic Ti-Fe±V oxide deposits. Pp. 24J-1 to 24J-3 in: Geological Fieldwork 1997. British Columbia Ministry of Employment and Investment.Google Scholar
Guiraud, M., Kienast, J.R. and Ouzegane, K. (1996 Corundum-quartz bearing assemblage in the Ihouhaouene area (In Ouzzal, Algeria). Journal of Metamorphic Geology, 14, 754—762.CrossRefGoogle Scholar
Harley, S.L. (1989 The origin of granulites: a metamorphic perspective. Geological Magazine, 126,215—247.CrossRefGoogle Scholar
Harlov, D.E. and Milke, R. (2002 Stability of corundum + quartz relative to kyanite and sillimanite at high temperature and pressure. American Mineralogist, 87, 424—432.CrossRefGoogle Scholar
Holland, T.J.B. and Powell, R. (1990 An enlarged and updated internally consistent thermodynamic dataset with uncertainties and correlations; the system K2O-Na2O-CaO-MgO-MnO-FeO-Fe2O3-Al2O3-TiO2-SiO2-C-H2-O2. Journal of Metamorphic Geology, 8, 89—124.CrossRefGoogle Scholar
Holland, T.J.B. and Powell, R. (1998 An internally consistent thermodynamic data set for phases of petrological interest. Journal of Metamorphic Geology, 16, 309—343.CrossRefGoogle Scholar
Knoper, M., Andreoli, M.A.G., Armstrong, R., Tucker, R.D. and Ashwal, L.D. (2001 Dextral transpression and lateral extrusion of Namaqualand during intra-continental convergence, from ca. 1150 to 1020 Ma. 4th International Field meeting IGCP 418, University of Durban-Westville, South Africa, Programme with Abstracts.Google Scholar
Kretz, R. (1983 Symbols for rock-forming minerals. American Mineralogist, 68, 277—279.Google Scholar
Motoyoshi, Y. and Hensen, G.J., (1990 Metastable growth of corundum adjacent to quartz in a spinel-bearing quartzite from the Archean Napier Complex, Antarctica. Journal of Metamorphic Geology, 8, 125—130.CrossRefGoogle Scholar
Nowicki, T.E., Frimmel, H.E. and Waters, D.J. (1995 The occurrence of osumilite in pelitic granulites of the Namaqualand Metamorphic Complex, South Africa. South African Journal of Geology, 98, 191—201.Google Scholar
Raith, J.G. and Harley, S.L. (1998 Low-P/high-T metamorphism in the Okiep Copper district, western Namaqualand, South Africa. Journal of Metamorphic Geology, 16, 281—305.CrossRefGoogle Scholar
Robb, L.J., Armstrong, R.A. and Waters, D.J. (1999 The history of granulite-facies metamorphism and crustal growth from single zircon U-Pb geochronol-ogy: Namaqualand, South Africa. Journal of Petrology, 40, 1747—1770.CrossRefGoogle Scholar
Shaw, R.K. and Arima, M. (1998 A corundum-quartz assemblage from the Eastern Ghats Belt, India: evidence for high P-T metamorphism? Journal of Metamorphic Geology, 16, 189—196.CrossRefGoogle Scholar
Waters, D.J. (1989 Metamorphic evidence for the heating and cooling path of Namaqualand granulites. Pp. 357—363 in: Evolution of Metamorphic Belts (Daly, J.S., Cliff, R.A. and Yardley, B.W.D., editors). Special Publication, 43. Geological Society, London.Google Scholar
Waters, D.J. (1991 Hercynite-quartz granulites: phase relations and implications for crustal processes. European Journal of Mineralogy, 3, 367—386.CrossRefGoogle Scholar
Windley, B.F. and Smith, J.V. (1976 Archaean high grade complexes and modern continental margins. Nature, 260, 671—675.CrossRefGoogle Scholar