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Phase relations of aenigmatite minerals in a syenitic ejectum, wonchi volcano, Ethiopia

Published online by Cambridge University Press:  05 July 2018

Mario Gaeta  and
Annibale Mottana
Mario Gaeta
Affiliation:
Dipartimento di Scienze della Terra, Università, di Roma ‘La Sapienza’, Piazzale A. Moro, 5, I-00185 Roma RM, Italy
Annibale Mottana
Affiliation:
Dipartimento di Scienze della Terra, Università, di Roma ‘La Sapienza’, Piazzale A. Moro, 5, I-00185 Roma RM, Italy
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Abstract

Wonchi volcano (Ethiopia) is the second locality for wilkinsonite, the new mineral related to aenigmatite via the coupled substitution 2Fe3+ = TiFe2+. Wilkinsonite occurs as relics surrounded by rims of riebeckite and biotite in a syenitic ejectum which also contains microphenocrysts of aenigmatite. The two minerals do not represent an equilibrium pair. They both formed in the magma chamber under plutonic to hypabyssal conditions, but during two following stages of crystallisation separated by a major drop in ƒO2 conditions.

Keywords

aenigmatitewilkinsonitesyenitic ejectumWonchi volcanoEthiopia

Information

Type
Mineralogy
Information
Mineralogical Magazine , Volume 55 , Issue 381 , December 1991 , pp. 529 - 534
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1991

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References

Abbate, E. and Sagri, M. (1980) In Geodynamic evolution of the Afro-Arabic rift system. Atti Convegni Lincei 47, 219-27.Google Scholar
Baker, P. E. (1982) In Andesites (R. S. Thorpe, ed.), Wiley, New York pp. 11–23.Google Scholar
Barberi, F., Santacroce, R., and Varet, J. (1982) In Continental and Oceanic Rift. Trans. Amer. Geo-phys. Union, Geodyn. Sci. 8, 223-58.Google Scholar
Bonaccorsi, E., Merlino, S., and Pasero, M. (1990) Ear. J. Mineral, 20, 203–18.CrossRefGoogle Scholar
Cannillo, E., Mazzi, F., Fang, J. H., Robinson, P. D., and Ohya, Y. (1971) Am. Mineral, 56, 427–6.Google Scholar
Carmichael, I. S. E. (1962) Mineral. Mag., 33, 86–113.Google Scholar
Cosca, M. A., Rouse, R. C., and Essene, E. J. (1988) Am. Mineral, 73, 1440–8.Google Scholar
Deer, W. A., Howie, R. A., and Zussman, J. (1978) Rock-forming minerals. vol. 2A: Single chain silicates. John Wiley and Sons, New York, 668 pp.Google Scholar
Droop, G. T. R. (1987) Mineral Mag., 51, 431–5.CrossRefGoogle Scholar
Duggan, M. B. (1988) Ibid., 52, 491-6.Google Scholar
Duggan, M. B. (1990) Am. Mineral, 75, 694–701.Google Scholar
Grapes, R., Yagi, K., and Okamura, K. (1979) Contrib. Mineral. Petrol, 69, 97–103.CrossRefGoogle Scholar
Grunhagen, H. and Seek, H. A. (1972) Tscherm. Min. Petr. Mitt., 18, 17–38.CrossRefGoogle Scholar
Hodges, F. N. and Barker, D. S. (1973) In Carnegie Inst. Year Book, 72, 578–81.Google Scholar
Larsen, L. M. (1977) Lithos, 10, 257–70.CrossRefGoogle Scholar
Leake, B. E. (1978) Am. Mineral, 63, 1023–53.Google Scholar
Marsh, J. S. (1975) Contrib. Mineral. Petrol, 50, 135–4.CrossRefGoogle Scholar
Morimoto, N., Fabries, J., Ferguson, A. K., Ginzburg, I. V., Ross, M., Seifert, F. A., Zussman, J., Aoki, K., and Gottardi, G. (1988) Am. Mineral, 73, 1123–33.Google Scholar
Yagi, K. (1953) Geol. Soc. Amer. Bull, 64, 769–810.CrossRefGoogle Scholar
Yagi, K. and Souther, J. G. (1974) Am. Mineral, 59, 820–9.Google Scholar
Zanettin, B. and Justin-Visentin, E. (1974) Mem. 1st. Geol Miner. Univ. Padova, 31, 1–19.Google Scholar
Zanettin, B., Justin-Visentin, E., Nicoletti, M., and Piccirillo, E. M. (1980) In Geodynamic evolution of the Afro-Arabic rift system. Atti Convegni Lincei, 47, 231-52.Google Scholar