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Trace-element content and partitioning in calcite, dolomite and apatite in carbonatite, Phalaborwa, South Africa

Published online by Cambridge University Press:  05 July 2018

J. B. Dawson  and
R. W. Hinton
J. B. Dawson*
Affiliation:
Department of Geology and Geophysics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK
R. W. Hinton
Affiliation:
Department of Geology and Geophysics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK
*
* E-mail: [email protected]
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Abstract

A carbonatite sample from Phalaborwa, South Africa, consists of apatite, magnetite and a calcitedolomite ‘perthite’ which is interpreted as being due to exsolution of dolomite from a high-Mg calcite precursor. Carbon and oxygen isotope data indicate that the carbonates are equilibrated. In situ ionmicroprobe analyses for Fe, Mn, Na, Si, Y, the REEs, Pb, Th and U give the following average concentrations (in ppm) in the sequence apatite, calcite, dolomite: Fe 98, 1680, 8190; Mn 61, 510, 615; Na 1171, 627, 125; Si 368; 1.6, 0.2; Sr 4447, 5418, 2393; Ba 37, 2189, 75; La 1245, 300, 67; Y 121, 50, 5.8; Pb 16, 5.4, 1.4; Th 20, 0.02, 0; U 2.4, 0, 0.01. The concentrations are reasonably uniform in both apatite and dolomite, but in calcite are more variable. Na, Si, Y, the REEs, Pb, Th and U partition into apatite relative to both carbonates (and, hence, the precursor carbonate); KD ap/cc for REE decreases from ∽4 for La to ∽2 for Tm. There is almost equal partitioning of Sr between apatite and calcite. During separation of dolomite from calcite, Sr and Ba partition strongly into calcite and all the other analysed elements, except Fe and Mn, also preferentially enter calcite. The REEs prefer calcite relative to dolomite, and the KD dol/cc is reasonably constant, only varying from 0.23 to 0.17. Sr, Ba and Pb in the carbonates, and their partitioning between the calcite and dolomite, differ from other carbonatite carbonates reported in the literature.

Keywords

carbonatitecalcitedolomiteapatitetrace elementsSouth Africa.
Type
Research Article
Information
Mineralogical Magazine , Volume 67 , Issue 5 , October 2003 , pp. 921 - 930
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2003

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References

Anovitz, L.M. and Essene, E.J. (1987) Phase equilibria in the system CaCO3-MgCO3-FeCO3. Journal of Petrology, 28, 389—414.CrossRefGoogle Scholar
Bizzarro, M., Simonetti, A., Stevenson, R.K. and David, J. (2002) Hf isotope evidence for a hidden isotope reservoir. Geology, 30, 771—774.2.0.CO;2>CrossRefGoogle Scholar
Bu¨hn, B., Wall, F. and Le Bas, M.J. (2001) Rare-earth element systematics of carbonatitic fluorapatites, and their significance for carbonatite magma evolution. Contributions to Mineralogy and Petrology, 141, 572—591.CrossRefGoogle Scholar
Cherniak, D.J. (2000) Rare earth element diffusion in apatite. Geochimica et Cosmochimica Acta, 64, 3871—3885.CrossRefGoogle Scholar
Dawson, J.B., Steele, I.M., Smith, J.V. and Rivers, M.L. (1996) Minor and trace element chemistry of carbonate s, apatites and magnetite s in some African carbonatites. Mineralogical Magazine, 60, 415—425.CrossRefGoogle Scholar
Deines, P. (1989) Stable isotope variations in carbonatites. Pp. 301—359 in: Carbonatites – Genesis and Evolution (K., Bell, editor). Unwin Hyman, London.Google Scholar
Eriksson, S.C. (1989) Phalaborwa: a saga of magmatism, metasomatism and miscibility. Pp. 221—254 in: Carbonatites – Genesis and Evolution (K.Bell, editor). Unwin Hyman, London.Google Scholar
Fleet, M.E. and Pan, Y. (1995) Site preference of rare earth elements in fluor apatite. Ame rican Mineralogist, 80, 329—335.CrossRefGoogle Scholar
Fleet, M.E., Liu, X. and Pan, Y. (2000) Rare earth elements in chlorapatite {Ca10(PO4)6Cl2}: uptake, site preference and degradation of monoclinic structure. American Mineralogist, 85, 1437—1446.CrossRefGoogle Scholar
Goldsmith, J.R. (1960) Exsolution of dolomite from calcite. Journal of Geology, 68, 103—9.CrossRefGoogle Scholar
Goldsmith, J.R. and Newton, R.C. (1969) P-T-X relations in the system CaCO3-MgCO3 at high temperatures and pressures. American Journal of Science, 267A, 160—190.Google Scholar
Golyshev, S.I., Padalko, N.L. and Pechenkin, S.A. (1981) Fractionation of stable oxygen and carbon isotopes in carbonate systems. Geochemistry International, 18, 85—99.Google Scholar
Heinrich, E.W. (1966) The Geology of Carbonatites. Rand McNally, Chicago.Google Scholar
Hogarth, D.D. (1989) Pyrochlore, apatite and amphibole: distinctive minerals in carbonatites. Pp. 105—48 in: Carbonatites – Genesis and Evolution (Bell, K., editor). Unwin Hyman, London.Google Scholar
Hornig-Kjaarsgaard, I. (1998) Rare earth elements in sövitic carbonatites and their mineral phases. Journal of Petrology, 39, 2105—2121.CrossRefGoogle Scholar
Ionov, D. and Harmer, R.E. (2002) Trace element distribution in calcite-dolomite carbonatites from Spitskop: inferences for differentiation of carbonatite magmas and the origin of carbonates in mantle xenoliths. Earth and Planetary Science Letters, 198, 495—510.CrossRefGoogle Scholar
Le Bas, M.J. and Srivastava , R.K. (1989) The mineralogy and geochemistry of the Mundwara carbonatite dykes, Sirohi district, Rajasthan, India. Neues Jahrbuch fu¨r Mineralogie Abhandlungen, 160, 207—227.Google Scholar
Le Bas, M.J., Keller, J., Keije, Tao, Wall, F., Williams, C.T. and Zhang Peishan (1992) Carbonatite dykes at Bayan Obo, Inner Mongolia, China. Mineralogy and Petrology, 46, 198—228.CrossRefGoogle Scholar
McDonough, W.F. and Sun, S.S. (1995) The composition of the Earth. Chemical Geology, 120, 223—253.CrossRefGoogle Scholar
Morbidelli, L., Beccaluva, L., Brotzu, P., Conte, A., Garbarino, C., Gomes, C.B., Macciotta, G., Ruberti, E., Scheibe, L.F. and Traversa, G. (1986) Petrological and geochemical studies of alkaline rocks from continental Brazil. 3. Fenitsation of jacupirangite by carbonatite magmas in the Jacupiranga Complex S.P. Perio dico di Mineralogia, 55, 261—285.Google Scholar
O’Neill, J.R. and Epstein, S. (1966) Oxygen isotope fractionation in the system dolomite-calcite-carbon dioxide. Science, 152, 188—201.Google Scholar
Quon, S.H. and Heinrich, E.W. (1966) Abundance and significance of some minor elements in carbonatitic calcites and dolomites. Mineralogical Society of India, International Mineralogical Association Volume, (Papers of the 4th General Meeting), 29–36.Google Scholar
Sheppard, S.M.F. and Dawson, J.B. (1973) 13C/12C and D/H isotope variations in "primary" igneous carbonatites. Fortschritte der Mineralogie, 50, 128—129.Google Scholar
Taylor, H.P, Frechen, J. and Degens, E.T. (1967) Oxygen and carbon isotope studies of carbonatites from the Laacher See district, West Germany, and the Alnödist rict, Sweden. Geochimica et Cosmochimica Acta, 31, 407—430.CrossRefGoogle Scholar
Veen, A.H. (1965) Calcite-dolomite intergrowths in high-temper ature carbonate rocks. American Mineralogist, 50, 2070—2077.Google Scholar
Veizer, J. (1983)) Trace elements and isotopes in sedimentary carbonates. Pp. 265—299 in: Carbonates : Mineralogy and Chemistry (Reeder, R.J., editor). Reviews in Mineralogy , 11. Mineralogical Society of America, Washington, D.C.CrossRefGoogle Scholar
Verwoerd, W.J. (1967) The Carbonatites of South Africa and South West Africa. Geological Survey of South Africa, Handbook 6, 452. pp.Google Scholar
Woolley, A.R. (1989) The spatial and temporal distribution of carbonatites. Pp. 15—37 in: Carbonatites – Genesis and Evolution (Bell, K., editor). Unwin Hyman, London.Google Scholar