Hostname: page-component-cd9895bd7-gvvz8 Total loading time: 0 Render date: 2024-12-24T03:06:41.009Z Has data issue: false hasContentIssue false
  • English
  • Français

A supposed sövite from Oldoinyo Lengai, Tanzania: result of extreme alteration of alkali carbonatite lava

Published online by Cambridge University Press:  05 July 2018

J. B. Dawson
J. B. Dawson*
Affiliation:
Department of Geology and Gcophysics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, U.K.
Get access Rights & Permissions [Opens in a new window]

Abstract

A calcite-rich block in nephelinitic agglomerate at Oldoinyo Lengai comprises Sr-calcite, apatite, fluorite, a Ba-Mn oxide akin to romanrchite, and a distinctive Mn-Fe spinel. Formerly reported as sövite, on textural, mineralogical and stable isotope grounds it is now re-interpreted as a highly-altered natrocarbonatite lava. An implication of this study is that natrocarbonatite is not just a modern phenomenon, but has been extruded from Oldoinyo Lengai for at least around 1250 years.

Keywords

sövitealtered natrocarbonatiteOldoinyo LengaiTanzania
Type
Petrology and Geochemistry
Information
Mineralogical Magazine , Volume 57 , Issue 386 , March 1993 , pp. 93 - 101
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1993

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

Barker, D. S. and Nixon, P. H. (1989) High-Ca, low-alkali carbonatite volcanism at Fort Portal, Uganda. Contrib. Mineral. Petrol., 103, 166–77.Google Scholar
Clarke, M. G. C. and Roberts, B. (1986) Carbonated melilitites and calcitized alkalicarbonatites from Homa Bay, western Kenya: a reinterpretation. Geol. Mag., 123, 683–92.Google Scholar
Dawson, J. B. (1962) The geology of Oldoinyo Lengai. Bull. Volcanol., 24, 349–87.Google Scholar
Dawson, J. B. (1989) Sodium carbonate extrusions from Oldoinyo Lengai, Tanzania; implications for carbonatite complex genesis. In Carbonatites: genesis and evlolution (Bell, K., ed.), 255-277, Unwin Hyman, London.Google Scholar
Dawson, J. B. Garson, M. S., and Roberts, B. (1987) Altered former alkalic carbonatite lave from Oldoinyo Len-gai, Tanzania: inferences for calcite carbonatite lavas. Geology, 15, 765–68.Google Scholar
Dawson, J. B. Pinkerton, H., Norton, G. E., Pyle, D. M., Browning, P., Jackson, D. and Fallick, A. E. in press Petrology and geochemistry of alkali carbonate lavas extruded from Oldoinyo Lengai, October 1988: inferences for magma sources, ascent and crystallis-ation. In Carbonatite volcanism of Oldoinyo Lengai: petrogenesis of natrocarbonatites (Bell, K. and Keller, J., eds.), IAVCEI Proceedings in Volcanology.Google Scholar
Deans, T. and Roberts, B. (1984) Carbonatite tufts and lava clasts of the Trinderet foothills, western Kenya; A study of calcified natrocarbonatites. J. Geol. Soc. London, 141, 563–80.Google Scholar
Gittins, J. (1989) The origin and evolution of carbonatite magmas. In Carbonatites: genesis and evolution (Bell, K., ed.), 580-600, Unwin Hyman, London.Google Scholar
Hay, R. L. (1983) Natrocarbonatite tephra of Kerimasi volcano, Tanzania. Geology, 11, 213–15.Google Scholar
Hay, R. L. (1989) Holocene carbonatite-nephelinite tephra depostis of Oldoinyo. Lengai, Tanzania. J. Volcanol. Geotherm. Res., 37, 77–91.Google Scholar
Hughson, M. R. and Sen Gupta, J. G. (1964) A thorian intermediate member of the britholite-apatite series. Amer. MineraL, 49, 937–51.Google Scholar
Javoy, M., Pineau, F., Cheminóe, J. L. and Krafft, M. (1988) The gas magma relationship in the 1988 eruption of Oldoinyo Lengai (Tanzania). EOS 69, 1466.Google Scholar
Kapustin, Y. L. (1973) Mineralogy of weathered crusts of carbonatites. Nedra Press, Moscow, 128 pp (in Russian).Google Scholar
Keller, J. (1981) Carbonatitic volcanism in the Kaiser-stuhl alkaline complex; Evidence for highly fluid carbonatite melts at the earth's surface. J. Volcanol. Geotherm. Res., 9, 423–31.Google Scholar
Keller, J. (1989) Extrusive carbonatites and their significance. In Carbonatites: genesis and evolution (Bell, K., ed.), 70–88, Unwin Hyman, London.Google Scholar
Mariano, A. N. and Roeder, P. L. (1983) Kerimasi; a neglected carbonatite volcano. J. Geol., 9L 449-55.Google Scholar
Ngwenya, B. T. and Bailey, D. K. (1990) Kaluwe carbonatite, Zambia: an alternative to natrocarbona-tite. J. Geol. Soc. London, 147, 213–16.Google Scholar
O'Neil, J. R. and Hay, R. L. (1973) L80/160 ratios in cherts associated with the saline lake depostis of East Africa. Earth Planet. Sci. Letts., 19, 257–66.Google Scholar
Perseil, E. A. and Pinet, M. (1976). Contribution ∼ la connaissance des romanrchites et des cryptomrlanes-coronadites-hollandites. Traits essentiels et para-genrses. Contrib. Mineral. Petrol., 55, 191–204.Google Scholar
Sheppard, S. M. F. and Dawson, J. B. (1973) 13C/12C and D/H isotope variations in primary igneous carbonatites. Fortschr. Mineral., 50, 128–9.Google Scholar
Taylor, S. R. and McLellan, S. M. (1985) The continental crust: its compostion and evolution. Black-wells, Oxford, 312 pp.Google Scholar
Turner, D. C. (1988) Volcanic carbonatites of the Kaluwe complex, Zambia. J. Geol. Soc. London, 145, 95–106.Google Scholar
Turner, S. and Buseck, P. R. (1979) Manganese oxide tunnel structures and their intergrowths. Science, 203, 456–8.Google Scholar
Turner, S. and Buseck, P. R. (1981) Todorokites: a new family of natural occurring manganese oxides. Ibid., 212, 1024-7.Google Scholar
Vance, E. R., and Agrawal, D. K. (1982). Incorpora-tion of radionuclides in crystalline titanates. Nuclear and Chemical Waste Management, 3, 229–34.Google Scholar
Winther, C. and Böggild, O. B. (1899) On some minerals from the nepheline syenite at Julianehaab, Greenland (Epistolite, britholite, schizolite and steenstrupine), Medd. Grønland, 24, 190–6.Google Scholar