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Kaersutite-Bearing Xenoliths and Megacrysts in Volcanic Rocks from the Funk Seamount in the Southwest Indian Ocean

Published online by Cambridge University Press:  05 July 2018

Arch M. Reid  and
Anton P. le Roex
Arch M. Reid
Affiliation:
Department of Geology, University of Cape Town, Rondebosch 7700, South Africa
Anton P. le Roex
Affiliation:
Department of Geology, University of Cape Town, Rondebosch 7700, South Africa
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Abstract

Eight samples (seven volcanic rocks and one quartz sandstone) have been dredged from the Funk Seamount, 60 km NW of Marion Island in the southwest Indian Ocean (lat. 46° 15′S, long. 37° 20′ E). The volcanic rocks are fine-grained vesicular basanitoids and glass-rich volcanic breccias geochemically similar to the Marion Island lavas. Lavas and breccias contain a suite of megacryst minerals and of small polymineralic xenoliths, in both of which kaersutite is a prominent constituent.

The megacryst suite comprises large unzoned single grains of kaersutite, plagioclase, pyroxene, magnetite and ilmenite, all showing textural evidence of resorption/reaction with the basanitoid host. The megacrysts have a limited range of compositions except for the plagioclase which ranges from oligoclase to labradorite.

The small (2 mm to ∼ 3 cm) xenoliths are mostly two-pyroxene amphibole assemblages with or without olivine, magnetite, ilmenite, plagioclase and apatite. The xenoliths show some evidence of reaction with the basanitoid host and most have undergone recrystallization and/or localised decompression melting.

Xenolith and megacryst assemblages are interpreted as being associated with the formation and partial crystallization of a hydrous basanitoid melt at depth.

Keywords

kaersutiteamphibolexenolithFunk SeamountIndian Ocean
Type
Mineralogy and Crystal Structures
Information
Mineralogical Magazine , Volume 52 , Issue 366 , June 1988 , pp. 359 - 370
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1988

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Footnotes

*

Present address: Department of Geosciences, University of Houston, Houston, Texas 77004, USA.

References

Aoki, K. (1970) Andesine megacrysts in alkaline basalts from Japan. Contrib. Mineral. Petrol. 25, 284-8CrossRefGoogle Scholar
Binns, R.A. (1969) High pressure megacrysts in basanitic lavas from Armidale, New South Wales. Am. J. Sei. 267, 33-49.Google Scholar
Buddington, A.F., and Lindsley, D.M. (1964) Iron titanium oxide minerals and synthetic equivalents. J. Petrol. 5, 310-57Google Scholar
Deer, W.A., Howie, R.A., and Zussman, J. (1966) An introduction to the rock forming minerals. 528 pp. (Longman).Google Scholar
Kable, E.J. D., Erlank, A.J., and Cherry, R.D. (1971) Geochemical features of lavas. Chapter 6 in Marion and Prince Edward Islands (van Zinderen, E. M. Bakker, J.M. Winterbottom, and R. A. Dyer, eds.). Balkema, Cape Town.Google Scholar
Laughlin, A.W., Manzer, G.K., and Carden, J.R. (1974) Feldspar megacrysts in alkali basalts. Geol. Soc. Am. Bull. 85, 413-162.0.CO;2>CrossRefGoogle Scholar
Leake, B.E. (1978) Nomenclature of amphiboles. Am. Mineral. 63, 1023-62.Google Scholar
le Roex, A.P., and Dick, H. J. B. (1981) Petrography and geochemistry of basaltic rocks from the Conrad fracture zone on the America-Antarctica Ridge. Earth Planet. Sci. Lett. 54, 117-38Google Scholar
Merrill, R.B., and Wyllie, P.J. (1975) Kaersutite and kaersutite eclogite from Kakanui, New Zealand— water excess and water deficient melting to 30 kilobars. Geol. Soc. Am. Bull. 86, 555-70.Google Scholar
Nash, W.P. (1973) Plagioclase resorption phenomena and geobarometry in basic lavas. Am. Geophys. Union. E.O.S. 54, 507Google Scholar
Roeder, P.L. and Emslie, R.F. (1970) Olivine-liquid equilibrium. Contrib. Mineral. Petrol. 29, 275-89.CrossRefGoogle Scholar
Wilkinson, J.F.G. and le Maitre, R.W. (1987) Upper mantle amphiboles and micas and TiO2, K2 0 and P2O5 abundances and 100Mg/(Mg + Fe2+) ratios of common basalts and andesites: implications for modal mantle metasomatism and undepleted mantle compositions. J. Petrol. 28, 377-3Google Scholar