Hostname: page-component-cd9895bd7-q99xh Total loading time: 0 Render date: 2024-12-27T22:58:35.617Z Has data issue: false hasContentIssue false
  • English
  • Français

Carbonate-carbonate immiscibility, neighborite and potassium iron sulphide in Oldoinyo Lengai natrocarbonatite

Published online by Cambridge University Press:  05 July 2018

Roger H. Mitchell
Roger H. Mitchell*
Affiliation:
Department of Geology, Lakehead University, Thunder Bay, Ontario, Canada P7B 5El
Get access Rights & Permissions [Opens in a new window]

Abstract

Porphyritic natrocarbonatite lavas erupted from the Oldoinyo Lengai volcano (Tanzania) on 17 October 1995 and 15–19 December 1995 differ from previously studied lavas in that they preserve textures indicative of groundmass carbonate-carbonate immiscibility. The immiscible fractions are considered to involve: a Na-K-Ca-CO2-Cl-rich, F-bearing fluid crystallizing gregoryite, sodian sylvite, potassium neighborite as well as a complex Ba-rich carbonate; and a Na-rich, Cl-poor carbonate liquid approximating to a nyerereite-gregoryite cotectic composition. Compositional data are given for potassium neighborite, this mineral being the first recognized occurrence of a fluorine-based perovskite group mineral in a magmatic environment. New compositional data are also given for a previously recognized potassium iron sulphide which indicate that this phase is probably a solid solution between the ternary sulphides, KFe3S4, K2Fe3S4, and KFe2S3. Textural and paragenetic data are interpreted to suggest that these recent lavas are more evolved than previously investigated Oldoinyo Lengai lavas and that natrocarbonatite is a highly evolved rather than a primitive magma.

Keywords

carbonatiteliquid immiscibilityneighboritepotassium iron sulphidesylviteOldoinyo LengaiTanzania
Type
Petrology
Information
Mineralogical Magazine , Volume 61 , Issue 409 , December 1997 , pp. 779 - 789
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1997

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

Burns, P.C., Hawthorne, F.H., Hofmeister, A.M. and Moret, S.L. (1996) A structural phase transition in perovskite. Phys. Chem. Minerals, 23, 141-50.CrossRefGoogle Scholar
Chao, E.C.T., Evans, H.T. and Skinner, B.J. (1961) Neighborite NaMgF3, a new mineral from the Green River Formation, South Ouray, Utah. Amer. Mineral., 46, 379-93.Google Scholar
Church, A.A. and Jones, A.P. (1995) Silicate-carbonate immiscibility at Oldoinyo Lengai. or. Petrol., 36, 869-89.CrossRefGoogle Scholar
Clarke, J.R. and Brown, G.E. (1980) Crystal structure of rasvumite KFe2S3 . Amer. Mineral. 65, 477-82.Google Scholar
Dawson, J.B., Pinkerton, H., Norton, G.E., Pyle, D.M., Browning, P., Jackson, D. and Fallick, A.E. (1995) Petrology and geochemistry of Oldoinyo Lengai lavas extruded in November 1988: magma source, ascent and crystallization. In Carbonatite Volcanism (Bell, K. and Keller, J., eds.) Springer-Verlag, Berlin, 47–69.CrossRefGoogle Scholar
Dawson, J.B., Pyle, D.M. and Pinkerton, H. (1996) Evolution of natroearbnnatite from a wollastonite nephelinite parent: evidence from the June, 1993 eruption of Oldoinyo Lengai, Tanzania. J. Geol. 104, 41-54.CrossRefGoogle Scholar
Eichhorn, B. W. (1994) Ternary transition metal sulfides. Prog. in Inorganic Chem. 42, 139-240.Google Scholar
Gittins, J. (1989) The origin and evolution of carbonatite magmas. In Carbonatites: Genesis and Evolution (Bell, K., ed.), Unwin Hyman, London, 580–600.Google Scholar
Gittins, J. and Jago, C. (1991) Extrusive carbonatites: their origins reappraised in the light of new experimental data. Geol. Mag., 128, 301-5.CrossRefGoogle Scholar
Goldschmidt, V.M. (1926) Geochemische Verteilungsgesetze der Element VII. Skrifter Norske Videnskaps Akademie Klasse 1 Matematisk Naturvidenskaplig Klasse, Oslo.Google Scholar
Jago, B.C. (1991) The role of fluorine in the evolution of alkali-bearing carbonatite magma and the formation of carbonatite hosted apatite and pyrochlore deposits. Ph.D. Thesis, University of Toronto, Ontario, Canada, 374 pp.Google Scholar
Jago, B.C. and Gittins, J. (1991) The role of fluorine in carbonatite magma evolution. Nature, 349, 56—8.CrossRefGoogle Scholar
Keller, J. and Krafft, M. (1990) Effusive natrocarbonarite activity at Oldoinyo Lengai, June 1988. Bull. Volcanol., 52, 629-45.CrossRefGoogle Scholar
Keller, J. and Spettel, B. (1995) Trace element composition and petrogenesis of natrocarbonatite. In Carbonatite Volcanism (Bell, K. and Keller, J., eds.) Springer-Verlag, Berlin, 70–86.CrossRefGoogle Scholar
Konyev, A.A., Vorobyev, E.I., Piskunova, L.F., Ushchalovskaya, Z.F. and Tokhonova, G.A. (1991) Olekminskite (Sr,Ca,Ba)(CO3)2, a new mineral and the new isomorphous series olekminskite-paralsto-nite. Zap. Vses. Mineral. Obshch., 120, 89-96.Google Scholar
LeBas, M.J. (1989) Diversification of carbonatite. In Carbonatites: Genesis and Evolution (Bell, K., ed.), Unwin Hyman, London, 428—47.Google Scholar
Ludekens, W.L.W. and Welch, A.J.E. (1952) Reactions between metal oxides and fluorides: some new double-fluoride structures of type ABF3 . Acta Cryst., 5, 841.CrossRefGoogle Scholar
Peterson, T.D. (1990) Petrology and genesis of natrocarbonatite. Contrib. Mineral. Petrol, 105, 143-55.CrossRefGoogle Scholar
Portier, J., Tressaud, A., Dupin, J. and Pape, de (1969) Structures et proprietes magnetiques de quelques composes de fomulae MFeF3 (M = K, Rb, Cs, NH4, Tl). Materials Res. Bull., 4, 45-50.CrossRefGoogle Scholar
Twyman, J.D. and Gittins, J. (1987) Alkalic carbonatite magmas: parental or derivative? In Alkaline Igneous Rocks (Fitton, J. G. and Upton, B.J.G. eds.), Blackwell, London, 85–94.Google Scholar
Vetsch, P. (1995) Volcanic activity of Oldoinyo Lengai (Tanzania) in December 1995. Société de volcano-logie Genève. (Video cassette)Google Scholar
Vorobyev, E.I. and Piskunova, L.F. (1985) A new form of exsolution in natural calcite. Doklady Akadem. Sci. Earth Sci. Sect., 282, 160-3.Google Scholar
Vorobyev, E.I. and Piskunova, L.F. (1987) Subsolidus transformations of strontium- and barium-beating carbonatite calcite. Doklady Akadem. Sci. Earth Sci. Sect., 296, 141-6.Google Scholar
Waldbaum, D.R. (1969) Thermodynamic mixing properties of NaC1-KC1 liquids. Geochim. Cosmochim. Acta, 52, 2351-6.Google Scholar
Zhao, Y., Weidner, D.J., Ko, J., Leinenweber, K., Liu, X., Li, B., Meng, Y., Paealo, R.E.G., Vaughan, M.T., Wang, Y. and Yeganeh-Haeri, A. (1994) Perovskite at high P—T conditions: an in-situ synchrotron X-ray diffraction study of NaMgF3 perovskite. J. Geophys. Res., 99, 2871-85.CrossRefGoogle Scholar