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Mineral chemistry of a peralkaline combeite-lamprophyllite nephelinite from Oldoinyo Lengai, Tanzania

Published online by Cambridge University Press:  05 July 2018

J. B. Dawson  and
P. G. Hill
J. B. Dawson
Affiliation:
Department of Geology and Geophysics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK
P. G. Hill
Affiliation:
Department of Geology and Geophysics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK
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Abstract

A peralkaline nephelinite lava ([Na+K]/Al 2.15) from the active carbonatite volcano Oldoinyo Lengai, contains combeite, Ba lamprophyllite, a phase with affinities to delhayelite, CeSrNb perovskite, a CaNa phosphate high in Sr, Ba and K, and peralkaline glass; in addition to Fe-rich nepheline, aegirine-rich clinopyroxene and FeK-rich sodalite. The high alkali concentrations relative to alumina in the bulk rock could not have been achieved by fractionational crystallisation of the known Al-rich phenocryst phases (nepheline and sodalite) and some other process must be invoked.

Keywords

Oldoinyo LengaiTanzanianephelinitenatrocarbonatitecombeiteBa lamprophyllitedelhayeliteCaNa phosphateperalkaline glasses
Type
Research Article
Information
Mineralogical Magazine , Volume 62 , Issue 2 , April 1998 , pp. 179 - 196
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1998

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References

Chao, G.Y. (1971) Carletonite KNa4Ca4Si8O18(CO3)4 (F,OH).H2O, a new mineral from Mount St.Hilaire, Quebec. Amer. Mineral., 56, 1855–66.Google Scholar
Dawson, J.B. (1962) The geology of Oldoinyo Lengai. Bull. Volcanol., 24, 349–87.CrossRefGoogle Scholar
Dawson, J.B., Smith, J.V. and Steele, I.M. (1989) Combeite (Na2.33 Ca1.74others0.12)Si3O9 from Oldoinyo Lengai, Tanzania. J. Geol., 97, 365–72.CrossRefGoogle Scholar
Dawson, J.B., Smith, J.V. and Steele, I.M. (1995 a) Petrology and mineral chemistry of plutonic igneous xenoliths from the carbonatite volcano, Oldoinyo Lengai, Tanzania. J. Petrol., 36, 797–26.CrossRefGoogle Scholar
Dawson, J.B., Pinkerton, H., Norton, G.E., Pyle, D.M., Browning, P., Jackson, D.and Fallick, A.E. (1995 b) Petrology and geochemistry of the Oldoinyo Lengai lavas extruded in November, 1988; magma source, ascent and crystallisation. In: Carbonatite Volcanism (Bell, K. and Keller, J., eds). IAVCEI Proceedings in Volcanology, 4, Springer, Berlin, 47–69.CrossRefGoogle Scholar
Deer, W.A., Howie, R.A. and Zussman, J. (1971) Rockforming Minerals.Vol. 4, Framework Silicates. London, Longmans.Google Scholar
Donaldson, C.H., Dawson, J.B., Kanaris-Sotiriou, R., Batchelor, R.A. and Walsh, J.N. (1987) The silicate lavas of Oldoinyo Lengai, Tanzania. Neues Jahrb. Mineral. Abh., 156, 247–79.Google Scholar
Fersman, A.E. and Bonshtedt, E.M. (1937) Minerals of the Khibina and Lovozero Tundras.Lomonossov Inst. Acad Sci. U.S.S.R. (In Russian).Google Scholar
Gard, J.A. and Taylor, H.F.W. (1957) An investigation of two new minerals: rhodesite and mountainite. Mineral. Mag., 31, 611–23.Google Scholar
Haggerty, S.E. and Mariano, A.N. (1983) Strontian loparite and strontio-chevkinite: Two new minerals in rheomorphic fenites in the Parana Basin carbonatites, Brazil. Contrib. Mineral. Petrol. 84, 365–81.CrossRefGoogle Scholar
Hogarth, D.D. (1989) Pyrochlore, apatite and amphibole: distinctive minerals in carbonatite. In: Carbonatites: Genesis, and Evolution (Bell, K., ed.). London, Unwin Hyman, 106–48.Google Scholar
Johnsen, O., Nielsen, T.F.D. and Rønsbo, J.G. (1994) Lamprophyllite and barytolamprophyllite from the Tertiary Gardiner Complex, East Greenland. Neues Jahrb. Mineral. Mh., 328–36.Google Scholar
Khomyakov, A.P. (1995) Mineralogy of the Hyperagpaitic Rocks, Oxford, Clarendon Press.Google Scholar
Mitchell, R.H. (1996) Perovskites: a revised classification scheme for an important rare earth element host in alkaline rocks. In: Rare Earth Minerals: Chemistry, Origin and Ore Deposits (Jones, A.P. Wall, F. and Williams, C.T., eds), Chapman and Hall, London. 41–76.Google Scholar
Pecora, W.T. (1942) Nepheline syenite pegmatites, Rocky Boy Stock, Bearpaw Mountains, Montana. Amer. Mineral., 27, 397–424.Google Scholar
Peterson, T.D. (1989) Peralkaline nephelinites: I. Comparative petrology of Shombole and Oldoinyo L'engai, East Africa. Contrib. Mineral. Petrol., 101, 458–78.CrossRefGoogle Scholar
Platt, R.G. (1994) Perovskite, loparite and Ba-Fe hollandite from the Schryburt Lake carbonatite complex, northwestern Ontario, Canada. Mineral. Mag., 58, 49–57.CrossRefGoogle Scholar
Pochou, J.-L. and Pichoir, F. (1991) Quantitative analysis of homogeneous or stratified microvolumes applying the model “PAP”. In: Electron Probe Quantitation (Heinrich, K.F.J. and Newbury, D.E., eds). Plenum Press, New York, 31–75.CrossRefGoogle Scholar
Sahama, Th.G. and Hytönen, K. (1957) Götzenite and combeite, two new silicates from the Belgian Congo. Mineral. Mag., 31, 31–503.Google Scholar
Sahama, Th.G. and Hytönen, K. (1959) Delhayelite, a new silicate from the Belgian Congo. Mineral. Mag., 32, 32–6.Google Scholar
Stoppa, F., Sharygin, V.V. and Cundari, A. (1997) New mineral data from the kamafugite-carbonatite association: The melilitolite from Pian di Celle, Italy. Mineralogy and Petrology, 61 (in press).CrossRefGoogle Scholar
Vlasov, K.A. (1964) Geochemistry, mineralogy and economic deposits of the rare elements:Vol. 2, Mineralogy of the rare elements, Nauka, Moscow (In Russian).Google Scholar