Hostname: page-component-78c5997874-94fs2 Total loading time: 0 Render date: 2024-11-19T10:40:26.746Z Has data issue: false hasContentIssue false
  • English
  • Français

Cuspidine-sodalite natrocarbonatite from Oldoinyo Lengai, Tanzania: a novel hybrid carbonatite formed by assimilation of ijolite

Published online by Cambridge University Press:  05 July 2018

R. H. Mitchell  and
F. A. Belton
R. H. Mitchell*
Affiliation:
Department of Geology, Lakehead University, Thunder Bay, Ontario, Canada P7B 5E1
F. A. Belton
Affiliation:
Academic Enrichment Department, Middle Tennessee State University, Murfreesboro, TN 37132, USA
*
*E-mail: roger.mitchell@lakeheadu.ca
Get access Rights & Permissions [Opens in a new window]

Abstract

A unique hybrid natrocarbonatite, collected from the new ash cone of the volcano Oldoinyo Lengai. Tanzania in July 2008, consists of phenocrysts of nyerereite and gregoryite together with xenocrysts of clinopyroxene, nepheline and Ti-andradite set in a groundmass of cuspidine, sodalite, ferroan manganoan monticellite, K-Fe sulphide and manganoan titanian magnetite and gregoryite. The xenocrysts were not in equilibrium with the melt which formed their current host, as clinopyroxenes and Ti-andradite are mantled by cuspidine, and nepheline by sodalite and phlogopite—potassian kinoshitalite solid solutions. A microxenolith of ijolite exhibits similar reaction phenomena. The minerals of the xenocryst suite have similar compositions to plutonic ijolites found at Oldoinyo Lengai, and are thus considered to be derived by the fragmentation of such material in a previously contaminated natrocarbonatite melt. The latter, which has cuspidine, sodalite and monticellite as primary liquidus phases, is considered to have been formed by the complete assimilation of ijolitic material in a natrocarbonatite magma at depth in the volcano conduit. The occurrence of trace amounts of cuspidine, Fe-Mn-monticellite, K-Fe sulphide and Mn-Ti-spinel in recently erupted natrocarbonatites is ascribed to similar, but less extensive, assimilation of silicate material prior to their eruption.

Keywords

natrocarbonatiteassimilationcuspidinesodalitemonticellitekinoshitaliteOldoinyo LengaiTanzania
Type
Research Article
Information
Mineralogical Magazine , Volume 72 , Issue 6 , December 2008 , pp. 1261 - 1277
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2008

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

Bowen, NX. (1928) Evolution of the Igneous Rocks. Princeton University Press, New Jersey, USA.Google Scholar
Church, A. A. and Jones, A.P. (1995) Silicate-carbonatite immiscibility at Oldoinyo Lengai. Journal of Petrology, 36, 869–889.CrossRefGoogle Scholar
Dawson, J.B. (1998) Peralkaline nephelinite-natro-carbonatite relationships at Oldoinyo Lengai, Tanzania. Journal of Petrology, 39, 2077–2094.CrossRefGoogle Scholar
Dawson, J.B. and Hill, P.G. (1998) Mineral chemistry of a peralkaline combeite-lamprophyllite nephelinite from Oldoinyo Lengai, Tanzania. Mineralogical Magazine, 62, 179–196.CrossRefGoogle Scholar
Dawson, J.B., Smith, J.V. and Steele, I.M. (1992) 1966 ash eruption of the carbonatite volcano Oldoinyo Lengai: mineralogy of lapilli and mixing of silicate and carbonate magmas. Mineralogical Magazine, 56, 1–16.CrossRefGoogle Scholar
Dawson, J.B., Pinkerton, H., Norton, G.E., Pyle, D.M., Browning, P., Jackson, D. and Fallick, A.E. (1995a) Petrology and geochemistry of Oldoinyo Lengai lavas extruded in November 1988: magma source, ascent and crystallization. Pp. 47–69 in: Carbonatite Volcanism (Bell, K. and Keller, J., editors). Springer-Verlag, Berlin.Google Scholar
Dawson, J.B., Smith, J.V. and Steele, I.M. (19956) Petrology and mineral chemistry of plutonic igneous xenoliths from the carbonatite volcano, Oldoinyo Lengai, Tanzania. Journal of Petrology, 36, 797–826.CrossRefGoogle Scholar
Dawson, J.B., Pyle, D.M. and Pinkerton, H. (1996) Evolution of natrocarbonatite from a wollastonite nephelinite parent: evidence from the June 1993 eruption of Oldoinyo Lengai, Tanzania. Journal of Geology, 104, 41–54.CrossRefGoogle Scholar
Droop, G.T.R. (1987) A general equation for estimating Fe3+ concentrations in ferromagnesian silicates and oxides from microprobe analyses using stoichio-metric criteria. Mineralogical Magazine, 51, 431–435.CrossRefGoogle Scholar
Eichorn, B.W. (1994) Ternary transition metal sulfides. Progress in Inorganic Chemistry, 42, 139–240.Google Scholar
Hamilton, D.L. (1961) Nephelines as crystallization temperature indicators. Journal of Geology, 69, 321–329.CrossRefGoogle Scholar
Keller, J. and Krafft, M. (1990) Effusive natrocarbonatite activity at Oldoinyo Lengai, June 1988. Bulletin Volcanologie, 52, 629–645.CrossRefGoogle Scholar
Kervyn, M., Ernst, G.G., Klaudius, J., Keller, J., Kervyn, F., Mattson, H.B., Belton, F., Mbede, E. and Jacobs, P. (2008) Voluminous lava flows at Oldoinyo Lengai in 2006: chronology of events and insights into the shallow magmatic system. Bulletin of Volcanology, 70, 1069–1096.CrossRefGoogle Scholar
Kjarsgaard, B.A., Hamilton, D.L. and Peterson, T.D. (1995) Peralkaline nephelinite/carbonatite liquid immiscibility: comparison of phase compositions in experiments and natural lavas from Oldoinyo Lengai. Pp. 163–190 in: Carbonatite Volcanism (Bell, K. and Keller, J., editors). Springer-Verlag, Berlin.Google Scholar
Merlino, S. and Perchiazzi, N. (1998) Modular mineralogy in the cuspidine group of minerals. The Canadian Mineralogist, 26, 933–943.Google Scholar
Mitchell, R.H. (1995) Kimberlites, Orangeites and Related Rocks. Plenum Press Inc. New York.CrossRefGoogle Scholar
Mitchell, R.H. (1997) Carbonate-carbonate immiscibility, neighborite and potassium iron sulphide in Oldoinyo Lengai natrocarbonatite. Mineralogical Magazine, 61, 779–789.CrossRefGoogle Scholar
Mitchell, R.H. (2002) Perovskites: Modern and Ancient. Almaz Press, Thunder Bay, Ontario, Canada (http://www.almazpress.com)Google Scholar
Mitchell, R.H. (2006) Sylvite and fluorite microcrysts, and fluorite-nyerereite intergrowths from natrocarbonatite, Oldoinyo Lengai, Tanzania. Mineralogical Magazine, 70, 103–114.CrossRefGoogle Scholar
Mitchell, R.H. and Belton, F. (2004) Niocalite-cuspidine solid solution and manganoan monticellite from natrocarbonatite, Oldoinyo Lengai, Tanzania. Mineralogical Magazine, 68, 787–799.CrossRefGoogle Scholar
Mitchell, R.H. and Dawson, J.B. (2007) The 24th September 2007 ash eruption of the carbonatite volcano Oldoinyo Lengai, Tanzania: mineralogy of the ash and implications for the formation of a new hybrid magma type. Mineralogical Magazine, 71, 483–492.CrossRefGoogle Scholar
Mitchell, R.H. and Kamenetsky, V.S. (2008) Trace element geochemistry of nyerereite and gregoryite phenocrysts from Oldoinyo Lengai, natrocarbonatite lavas. Goldschmidt Conference 2008, Vancouver, abstract A637.Google Scholar
Peterson, T.D. (1990) Petrology and genesis of natrocarbonatite. Contributions to Mineralogy and Petrology, 105, 143–155.CrossRefGoogle Scholar
Reguir, E., Chakhmouradian, A.R., Halden, N.M., Yang, P. and Zaitsev, A.N. (2008) Early magmatic and reaction-induced trends in magnetite from the carbonatites of Kerimasi, Tanzania. The Canadian Mineralogist, 46, 879–900.CrossRefGoogle Scholar
Zaitsev, A.N. and Keller, J. (2006) Mineralogical and chemical transformation of Oldoinyo Lengai natro-carbonatites, Tanzania. Lithos, 91, 191–207.CrossRefGoogle Scholar
Zaitsev, A.N., Keller, A.N., Spratt, I, Perova, E.N, and Kearsl, A. (2008) Nyerereite-pirssonite-calcite shortite relationships in altered natrocarbonatites Oldoinyo Lengai, Tanzania. The Canadian Mineralogist, 46, 843–860.CrossRefGoogle Scholar