Hostname: page-component-586b7cd67f-2brh9 Total loading time: 0 Render date: 2024-11-26T10:07:44.375Z Has data issue: false hasContentIssue false
  • English
  • Français

Formation of chlor- and fluor-apatite in layered intrusions

Published online by Cambridge University Press:  05 July 2018

R. Grant Cawthorn
R. Grant Cawthorn*
Affiliation:
Department of Geology, University of the Witwatersrand, Private Bag 3, PO Wits 2050, Republic of South Africa
Get access Rights & Permissions [Opens in a new window]

Abstract

Apatite in most igneous intrusions has a high Cl/F ratio. However, chlor-apatite has been reported in the lower portions of the Bushveld and Stillwater Complexes. This has been used as evidence supporting the early separation of a Cl-rich discrete hydrous fluid in these intrusions. Mineralogical evidence is presented here to demonstrate that the Bushveld Complex, at least, formed from a nearly anhydrous magma, and did not release a hydrous fluid before apatite began to crystallize. It is suggested that apatite in the earliest cumulates equilibrated with trapped interstitial liquid, which converted it from the typical F-rich composition of cumulus apatite to a Cl-rich composition. This is an analogous process to that in which cumulus mafic minerals may become more Fe-rich on cooling and reaction with interstitial liquid.

Keywords

apatitelayered intrusionsCl/F ratioBushveld Complex
Type
Mineralogy
Information
Mineralogical Magazine , Volume 58 , Issue 391 , June 1994 , pp. 299 - 306
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1994

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

Atkins, F. B. (1969) Pyroxenes of the Bushveld Intrusion, South Africa. J. Petrol, 10, 222–249.CrossRefGoogle Scholar
Barnes, S. J. (1986) The effect of trapped liquid crystallization on cumulus mineral compositions in layered intrusions. Contrib. Mineral. Petrol., 93, 524–531.CrossRefGoogle Scholar
Barnes, S. J. (1989) Are Bushveld U-type parent magmas boninites or contaminated komatiites. Contrib. Mineral. Petrol., 101, 447–457.CrossRefGoogle Scholar
Best, M. G. (1963) Petrology of the Guadalupe igneous complex, Southwestern Sierra Nevada foothills, California. J. Petrol, 4, 223–259.CrossRefGoogle Scholar
Biggar, G. M. (1974) Phase equilibria studies of the chilled margins of some layered intrusions. Contrib. Mineral. Petrol, 46, 159–167.CrossRefGoogle Scholar
Bird, D. K., Brooks, C. K., Gannicott, R. A. and Turner, P. A. (1991) A gold-bearing horizon in the Skaergaard Intrusion, East Greenland. Econ. Geoi, 86, 1083–1092.CrossRefGoogle Scholar
Boudreau, A. E. (1992) Volatile fluid overpressure in layered intrusions and the formation of potholes. Austral. J. Earth Sci., 39, 277–287.CrossRefGoogle Scholar
Boudreau, A. E. (in press) Chlorine as an exploration guide for the platinum-group elements in layered intrusions. J. Geochem. Explor. Google Scholar
Boudreau, A. E. and Kruger, F. J. (1990) Variation in the composition of apatite through the Merensky Cyclic Unit in the western Bushveld Complex. Econ. GeoL, 85, 737–745.CrossRefGoogle Scholar
Boudreau, A. E. and McCallum, I. S. (1989) Investigations of the Stillwater Complex: Part V. Apatites as indicators of evolving fluid composi-tion. Contrib. Mineral. Petrol, 102, 138–153.CrossRefGoogle Scholar
Boudreau, A. E. and McCallum, I. S. (1989) Concentration of platinum-group elements by magmatic fluids in layered intrusions. Econ. GeoL, 87, 1830–1848.CrossRefGoogle Scholar
Boudreau, A. E., Mathez, E. A. and McCallum, I. S. (1986) Halogen geochemistry of the Stillwater and Bushveld Complexes: evidence for transport of the platinum-group elements by Cl-rich fluids. J. Petrol., 27, 967–986.CrossRefGoogle Scholar
Brown, G. M. and Peckett, A. (1977) Fluorapatites from the Skaergaard intrusion, east Greenland. Mineral. Mag., 41, 227–232.CrossRefGoogle Scholar
Cameron, E. N. (1978) The Lower Zone of the Eastern Bushveld Complex in the Olifants River Trough. J. Petrol., 19, 437–462.CrossRefGoogle Scholar
Cawthorn, R. G. and Davies, G. (1983) Experimental data at 3 kbars pressure on parental magma to the Bushveld Complex. Contrib. Mineral. Petrol., 83, 128–135.CrossRefGoogle Scholar
Cawthorn, R. G. and McCarthy, T. S. (1985) Incompatible trace element behaviour in the Bushveld Complex. Econ. GeoL, 80, 1016–1026.CrossRefGoogle Scholar
Cawthorn, R. G. and Walsh, K. L. (1988) The use of phosphorus contents in yielding estimates of the proportion of trapped liquid in cumulates of the Upper Zone of the Bushveld Complex. Mineral. Mag., 52, 81–89.CrossRefGoogle Scholar
Cawthorn, R. G., Davies, G., Clubley-Armstrong, A. and McCarthy, T. S. (1981) Sills associated with the Bushveld Complex, South Africa: an estimate of the parental magma composition. Lithos, 14, 1–15.CrossRefGoogle Scholar
Cawthorn, R. G., Meyer, P. S. and Kruger, F. J. (1991). Major addition of magma at the Pyrox-enite Marker in the western Bushveld Complex. J. Petrol., 32, 739–763.CrossRefGoogle Scholar
Faure, G. (1992) Principles and applications of inorganic geochemistry. Macmillan Publishing Co., New York.Google Scholar
Green, T. H. and Watson, E. B. (1982) Crystallization of apatite in natural magmas under high pressure, hydrous conditions with particular reference to ‘orogenic’ rock series. Contrib. Mineral. Petrol., 79, 96–105.CrossRefGoogle Scholar
Hamilton, P. J. (1977) Sr isotope and trace element studies of the Great Dyke and Bushveld mafic phase and their relation to early Proterozoic magma genesis in Southern Africa. J. Petrol., 18, 24–52.CrossRefGoogle Scholar
Higgins, M. D. (1991) The origin of laminated and massive anorthosite, Sept lies layered intrusion, Quebec, Canada. Contrib. Mineral. Petrol., 106, 340–354.CrossRefGoogle Scholar
Hoatson, D. M. and Keays, R. R. (1989). Formation of platiniferous sulfide horizons by crystal fractionation and magma mixing in the Munni Munni Intrusion, west Pilbara Block, Western Australia. Econ. GeoL, 84, 1775–1804.CrossRefGoogle Scholar
Hunter, R. H. and Sparks, R. S. J. (1987) The differentiation of the Skaergaard Intrusion. Contrib. Mineral. Petrol., 95, 451–461.CrossRefGoogle Scholar
Huntington, H. D. (1979) Kiglapait mineralogy I: apatite, biotite and volatiles. J. Petrol., 20, 625–652.CrossRefGoogle Scholar
Irvine, T. N., Keith, D. W. and Todd, S. G. (1983) The J-M platinum-palladium reef of the Stillwater Complex, Montana. II. Origin by double diffusive convective magma mixing and implications for the Bushveld Complex. Econ. GeoL, 78, 1287–1334.CrossRefGoogle Scholar
Kruger, F. J. and Marsh, J. S. (1982) Significance of 87Sr/86Sr ratios in the Merensky cyclic Unit of the Bushveld Complex. Nature, 298, 53–55.CrossRefGoogle Scholar
Lindsley, D. H. (1983) Pyroxene thermometry. Amer. Mineral, 65, 477–493.Google Scholar
Love, C, Boudreau, A. E. and Prendergast, M. D. (1992) Halogen geochemistry of the Great Dyke, Zimbabwe: some preliminary results. Eos, 72 (suppl.), 305.Google Scholar
Mathez, E. A. (1989) Interactions involving fluids in the Stillwater and Bushveld Complexes: observa-tions from the rocks. Rev. Econ. GeoL, 4, 167–179.Google Scholar
McBirney, A. R. (1989) The Skaergaard Layered Series: I. Structure and average compositions. J. Petrol, 30, 363–397.CrossRefGoogle Scholar
McKenzie, D. P. (1984) The generation and compac-tion of partially molten rock. J. Petrol, 25, 713–765.CrossRefGoogle Scholar
McKenzie, D. P. (1987) The compaction of igneous and sedimentary rocks. J. GeoL Soc. London, 144, 299–307.CrossRefGoogle Scholar
Molyneux, T. G. (1974) A geological investigation of the Bushveld Complex in Sekhukhuneland and part of the Steelpoort valley. Trans. Geol. Soc. S. Afr., 77, 329–338.Google Scholar
Spulber, S. D. and Rutherford, M. J. (1983) The origin of rhyolite and plagiogranite in oceanic crust: an experimental study. J. Petrol, 24, 1—25.Google Scholar
Wager, L. R. and Brown, G. M. (1968) Layered igneous rocks. Oliver and Boyd, Edinburgh, 588 pp.Google Scholar
Wilson, J. R., Esbensen, K. H. and Thy, P. (1981) A new pyroxene fractionation trend from a layered basic intrusion. Nature, 290, 325–326.CrossRefGoogle Scholar