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Mineralogy of volcanic calciocarbonatites from the Trig Point Hill debris flow, Kerimasi volcano, Tanzania: implications for the altered natrocarbonatite hypothesis

Part of: Alkaline rocks - Gregory Yu. Ivanyuk memorial issue

Published online by Cambridge University Press:  27 November 2020

Roger H. Mitchell Open the ORCID record for Roger H. Mitchell [Opens in a new window]  and
J. Barry Dawson
Roger H. Mitchell*
Affiliation:
Department of Geology, Lakehead University, Thunder Bay, Ontario, CanadaP7B 5E1
J. Barry Dawson
Affiliation:
School of Geosciences, Grant Institute, University of Edinburgh, King's Buildings, Edinburgh, Scotland, UKEH9 3FE
*
*Author for correspondence: Roger H. Mitchell, Email: [email protected]
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Abstract

A major debris flow, the Trig Point Hill flow, originating from Kerimasi volcano (Tanzania) contains numerous blocks of extrusive/pyroclastic carbonatites similar to those exposed at the rim of the currently inactive crater. The blocks of calcite carbonatite consist of: (1) large clasts of corroded and altered coarse grained calcite; (2) primary prismatic inclusion bearing phenocrystal calcite; and (3) a matrix consisting primarily of fine-grained prismatic calcite. The large clasts are inclusion free and exhibit a ‘corduroy-like’ texture resulting from solution along cleavage planes. The resulting voids are filled by brown Fe–Mn hydroxides/oxides and secondary calcite. The prismatic or lath-shaped phenocrystal calcite is not altered and contains melt inclusions consisting principally of primary Na–Ca carbonates which contain earlier-formed crystals of monticellite, periclase, apatite, Mn–Mg-magnetite, Mn–Fe-sphalerite and Nb-perovskite. Individual Na–Ca carbonate inclusions are of uniform composition, and the overall range of all inclusions analysed (wt.%) is from 28.7 to 35.9 CaO; 16.7–23.6 Na2O; 0.5–2.8 K2O, with minor SO3 (1.1–2.2) and SrO (0.34–1.0). The Na–Ca carbonate compositions are similar to that of shortite, although this phase is not present. The Na–Ca carbonates are considered to be primary deuteric phases and not secondary minerals formed after nyerereite. Monticellite shows limited compositional variation and contains 2–4 wt.% MnO and 12 wt.% FeO and is Mn-poor relative to monticellite in Oldoinyo Lengai natrocarbonatite. Periclase is Fe-bearing with up to 13 wt.% FeO. Spinels are Cr-free, Mn-poor and belong to the magnetite–magnesioferrite series in contrast to Mn-rich spinels of the magnetite–jacobsite series occurring in Oldoinyo Lengai natrocarbonatite. The matrix in which the ‘corduroy’ clasts and phenocrystal calcite are set consists of closely packed small prisms of calcite lacking melt inclusions, with interstitial fine-grained apatite, baryte, strontianite and minor fluorite. Pore spaces are filled with secondary Mn–Fe hydroxides/oxides, anhydrite and gypsum. The hypothesis that flow-aligned calcite in volcanic calciocarbonatites from Kerimasi, Tinderet, Homa and Catanda is altered nyerereite is discussed and it is considered that these calcite are either primary phases or altered melilite. The nyerereite alteration hypothesis is discussed with respect to the volumetric and compositional aspects of pseudomorphism by dissolution–precipitation replacement mechanisms. This study concludes that none of the volcanic calciocarbonatites containing flow-aligned calcite phenocrysts are altered natrocarbonatite.

Keywords

carbonatitenatrocarbonatitenyerereitealkali carbonatemonticellitejacobsitemagnesioferriteKerimasiTinderetOldoinyo Lengai
Type
Article – Gregory Yu. Ivanyuk memorial issue
Information
Mineralogical Magazine , Volume 85 , Issue 4 , August 2021 , pp. 484 - 495
Copyright
Copyright © The Author(s), 2020. Published by Cambridge University Press on behalf of The Mineralogical Society of Great Britain and Ireland.

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Footnotes

†

Deceased, 1932–2013

This paper is part of a thematic set ‘Alkaline Rocks’ in memory of Dr Gregory Yu. Ivanyuk

Guest Editor: Anatoly Zaitsev

References

Bailey, D.K. (1993) Carbonatite magmas. Journal of the Geological Society, London, 150, 637–651.CrossRefGoogle Scholar
Campeny, M., Kamenetsky, V.S., Melgarejo, J.C., Mangas, J., Manuel, J., Alfonso, P., Kamenetsky, M.B., Bambi, A.C.J.M. and Gonçalves, A.O. (2015) Carbonatitic lavas in Catanda (Kwanza Sul, Angola): Mineralogical and geochemical constraints on the parental melt. Lithos, 232, 1–11.CrossRefGoogle Scholar
Church, A.A. (1995) The Petrology of the Kerimasi Carbonatite Volcano and the Carbonatites of Oldoinyo Lengai with a Review of Other Occurrences of Extrusive Carbonatites. Unpublished PhD thesis, University of London, London, UK, 384 pp.Google Scholar
Clarke, M.G.C. and Roberts, B. (1986) Carbonated melilitites and calcitized alkali carbonatites from Homa Mountain, western Kenya: a reinterpretation. Geological Magazine, 123, 683–692.CrossRefGoogle Scholar
Dawson, J.B. (2008) The Gregory Rift Valley and Neogene-Recent Volcanoes of Northern Tanzania. Memoir of the Geological Society of London, 33. The Geological Society, London (UK), 102 pp.Google Scholar
Dawson, J.B., Garson, M.S. and Roberts, D. (1987) Altered former alkalic carbonatite lava from Oldoinyo Lengai, Tanzania inferences for calcite carbonatite lavas. Geology, 15, 765–768.2.0.CO;2>CrossRefGoogle Scholar
Deans, T.D. and Roberts, B. (1984) Carbonatite tuffs and lava clasts of the Tinderet foothills, western Kenya: a study of calcified natrocarbonatites. Journal of the Geological Society, London, 141, 563–580.CrossRefGoogle Scholar
Delcamp, A., Delvaux, D., Kwela, G., Mocheyek, A. and Kervyn, M. (2016) Sector collapse events at volcanoes in the North Tanzanian divergence zone and their implications for regional tectonics. Geological Society of America Bulletin, 128, 169–186.Google Scholar
de Wit, J.J. (1975) Carbonatites and related rocks at Saltpetre Kop, Sutherland, Cape Province. Annals of the University of Stellenbosch Series A1 (Geology), 1, 193–232.Google Scholar
Droop, G.T.R. (1987) A general equation for estimating Fe3+ concentrations in ferromagnesian silicates and oxides from microprobe analyses, using stoichiometric criteria. Mineralogical Magazine, 51, 431–435.CrossRefGoogle Scholar
Gittins, J. and Harmer, R.E. (1997) Dawson's Oldoinyo Lengai calciocarbonatite: a magmatic sövite or an extremely altered natrocarbonatite? Mineralogical Magazine, 61, 351–355.CrossRefGoogle Scholar
Gittins, J. and Jago, B.C. (1991) Extrusive carbonatites: their origins reappraised in the light of new experimental data. Geological Magazine, 128, 301–305.CrossRefGoogle Scholar
Guest, N.J. (1953) The Geology of Part of Northern Tanganyika Territory. Unpublished PhD Thesis, University of Sheffield, UK.Google Scholar
Guzmics, T., Mitchell, R.H, Szabo, C., Berkesi, M., Milke, R. and Abart, R. (2011) Carbonatite melt inclusions in coexisting magnetite apatite and monticellite in Kerimasi calciocarbonatite, Tanzania: melt evolution and petrogenesis. Contributions to Mineralogy and Petrology, 161, 177–196.CrossRefGoogle Scholar
Guzmics, T., Mitchell, R.H., Szabo, C., Berkesi, M., Milke, R. and Ratter, K. (2012) Liquid immiscibility between silicate, carbonate and sulfide melts in melt inclusions hosted in co-precipitated minerals from Kerimasi volcano (Tanzania) evolution of carbonated nephelinitic magma. Contributions to Mineralogy and Petrology, 164, 101–122.CrossRefGoogle Scholar
Hay, R.L. (1978) Melilitite-carbonatite tuffs in the Laetolil beds of Tanzania. Contributions to Mineralogy and Petrology, 67, 357–367.CrossRefGoogle Scholar
Hay, R.L. (1983) Natrocarbonatite tephra of Kerimasi volcano, Tanzania. Geology, 11, 599–602.2.0.CO;2>CrossRefGoogle Scholar
Guzmics T., Káldos, Dawson J.B., Mitchell, Milke, R. and Szabo, C. (2015) A melt evolution model for Kerimasi volcano, Tanzania: Evidence from carbonate melt inclusions in jacupirangite, Lithos, 238, 101–119.Google Scholar
Keller, J. (1989) Extrusive carbonatites and their significance: Pp. 70–88 in: Carbonatites – Genesis and Evolution (Bell, K., editor). Unwin Hyman, London, UK.Google Scholar
Keller, J. and Krafft, M. (1990) Effusive natrocarbonatite activity of Oldoinyo Lengai, June 1988. Bulletin of Volcanology, 52, 629–645.CrossRefGoogle Scholar
Keller, J. and Zaitsev, A.N. (2006) Calciocarbonatite dykes at Oldoinyo Lengai, Tanzania: the fate of natrocarbonatite. The Canadian Mineralogist, 44, 857–876.CrossRefGoogle Scholar
Kervyn, M., Ernst, G.G., Klaudius, J., Keller, J., Mbedes, E. and Jacobs, P. (2008) Remote sensing study of sector collapse and debris avalanche deposits at Oldoinyo Lengai and Kerimasi volcanoes, Tanzania. Journal of Remote Sensing, 29, 6565–6595.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.CrossRefGoogle Scholar
Kogarko, L.N., Plant, D.A., Henderson, C.M.B. and Kjarsgaard, B.A. (1991) Na-rich carbonate inclusions in perovskite and calzirtite from the Guli intrusive carbonatite, polar Siberia. Contributions to Mineralogy and Petrology, 109, 124–129.CrossRefGoogle Scholar
Le Bas, M.J. (1984) Discussion of Deans and Roberts, vide supra. Journal of the Geological Society, 141, 580.Google Scholar
Larsen, E.S. and Goransen, E.A. (1932) The deuteric and later alteration of the uncomphagrite of Iron Hill, Colorado. American Mineralogist, 17, 343–356.Google Scholar
Mariano, A.N. and Roeder, P.L (1983) Kerimasi: a neglected carbonatite volcano. Journal of Geology, 91, 449–455.CrossRefGoogle Scholar
Mattson, H.B. (2012) Rapid magma ascent and short eruption durations in the Lake Natron-Engaruka monogenetic volcanic field (Tanzania): a case study of the olivine melilititic Pello Hill scoria cone. Journal of Volcanology and Geothermal Research, 247–248, 16–25.CrossRefGoogle Scholar
Mitchell, R.H. (1997a) Carbonate-carbonate immiscibility, neighborite, and potassium iron sulphide in Oldoinyo Lengai natrocarbonatite. Mineralogical Magazine, 61, 779–789.CrossRefGoogle Scholar
Mitchell, R.H. (1997b) Kimberlites, Orangeites, Lamproites, Melilitites, and Minettes: A Petrographic Atlas. Almaz Press, Thunder Bay, Ontario, Canada (www.almazpress.com)Google Scholar
Mitchell, R.H. (2005) Carbonatites and carbonatites and carbonatites. The Canadian Mineralogist, 43, 2049–2068.CrossRefGoogle Scholar
Mitchell, R.H. (2006) Sylvite and fluorite microcrysts, and fluorite-nyerereite intergrowths from natrocarbonatite, Oldoinyo Lengai, Tanzania. Mineralogical Magazine, 70, 101–114.CrossRefGoogle Scholar
Mitchell, R.H. and Belton, F.A. (2004) Niocalite–cuspidine solid solution and manganoan monticellite from natrocarbonatite, Oldoinyo Lengai, Tanzania. Mineralogical Magazine, 68, 787–799.CrossRefGoogle Scholar
Mitchell, R.H. and Belton, F.A. (2008) Cuspidine-sodalite natrocarbonatite from Oldoinyo Lengai, Tanzania: a novel hybrid natrocarbonatite formed by the assimilation of ijolite. Mineralogical Magazine, 72, 1147–1162.CrossRefGoogle Scholar
Mitchell, R.H. and Dawson, J.B. (2012) Carbonate-silicate immiscibility and extremely peralkaline glasses from Nasira cone and recent eruptions at Oldoinyo Lengai Volcano, Tanzania. Lithos, 152, 40–46.CrossRefGoogle Scholar
Peterson, T.D. (1990) Petrology and genesis of natrocarbonatite. Contributions to Mineralogy and Petrology, 105, 143–155.CrossRefGoogle Scholar
Putnis, A. and Austrheim, H. (2010) Fluid-induced processes: metasomatism and metamorphism. Geofluids, 10, 254–269.Google Scholar
Putnis, C. and Mezger, K. (2004) A mechanism of mineral replacement: Isotope tracing in the model system KCl–KBr–H2O. Geochimica et Cosmochimica Acta, 68, 2839–2848.CrossRefGoogle Scholar
Reguir, E.P., 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
Stansfield, J. (1923) Extensions of the Monteregian petrographical province to the west and northwest. Geological Magazine, 60, 433–453CrossRefGoogle Scholar
Stoppa, F., Schiazza, M., Rosatelli, G., Castorina, F., Sharygin, V.V., Ambrosioa, F.A. and Vicentinia, N. (2019) Italian carbonatite system: From mantle to ore-deposit. Ore Geology Reviews, 114, 103141.CrossRefGoogle Scholar
Treiman, AH. and Essene, E.J. (1984) A periclase-dolomite-calcite carbonatite from the Oka complex, Quebec and its calculated volatile composition. Contributions to Mineralogy and Petrology, 85, 149–157.CrossRefGoogle Scholar
Veksler, I.V., Nielsen, T.F.D. and Sokolov, S.V. (1998) Mineralogy of crystallized melt inclusions from Gardiner and Kovdor ultramafic alkaline complexes: implications for carbonatite genesis. Journal of Petrology, 39, 2015–2031.CrossRefGoogle Scholar
Woolley, A.R. and Church, A.A. (2005) Extrusive carbonatites: a brief review. Lithos, 85, 1–14.CrossRefGoogle Scholar
Zaitsev, A.N. (2010) Nyerereite from calcite carbonatite at the Kerimasi volcano, northern Tanzania. Geology of Ore Deposits, 52, 630–640.CrossRefGoogle Scholar
Zaitsev, A.N. and Keller, J. (2006) Mineralogical and chemical transformation of Oldoinyo Lengai natrocarbonatites, Tanzania. Lithos, 91, 191–207.CrossRefGoogle Scholar
Zaitsev, A.N, Keller, J. and Billström, K. (2009) Isotopic composition of Sr, Nd, and Pb in pirssonite, shortite and calcite carbonatites from Oldoinyo Lengai volcano, Tanzania. Doklady Earth Sciences, 425, 302–306.CrossRefGoogle Scholar
Zaitsev, A.N, Keller, J., Sprat, J., Perova, E.N. and Kearsley, A. (2008) Nyerereite - pirssonite - calcite -shortite relationships in altered natrocarbonatites. Oldoinyo Lengai, Tanzania. The Canadian Mineralogist, 46, 843–860.CrossRefGoogle Scholar
Zaitsev, A.N., Keller, J., Spratt, J., Jeffries, T.E. and Sharykin, V.V. (2009) Chemical composition of nyerereite and gregoryite from natrocarbonatites of Oldoinyo Lengai volcano, Tanzania. Geology of Ore Deposits, 51, 608–616CrossRefGoogle Scholar
Zaitsev, A.N., Wenzl, T., Venneman, T. and Markl, G. (2013) Tinderet volcano, Kenya: an altered natrocarbonatite locality? Mineralogical Magazine, 77, 213–226.CrossRefGoogle Scholar
Zaitsev, A.N., McHenry, L., Savchenok, A.I., Strekopytov, S., Spratt, J., Humphreys-Williams, E., Sharygin, V.V., Bogomolov, E.S., Chakhmouradian, A.R., Zaitseva, O.A., Arzamastsev, A.A., Reguir, E.P., Leach, L., Leach, M. and Mwankunda, J. (2019) Stratigraphy, mineralogy and geochemistry of the Upper Laetolil tuffs including a new tuff 7 site with footprints of Australopithecus afarensis, Laetolil, Tanzania. Journal of African Earth Sciences, 158, 103561.CrossRefGoogle Scholar
Zhabin, A.G. (1971) Primary textural-structural features of carbonatites and their metamorphic evolution. International Geology Review, 13, 1087–1096.CrossRefGoogle Scholar
Zhabin, A.G. and Cherepivskaya, G.Y. (1965) Carbonatite dikes as related to ultrabasic-alkalic extrusive activity. Doklady Akademiya Nauk SSSR, Earth Sciences Section, 160, 135–138.Google Scholar