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

Arch M. Reid, Anton P. le Roex
1988 Mineralogical magazine  
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
more » ... uent. 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.
doi:10.1180/minmag.1988.052.366.07 fatcat:bmcklvol4nae5btfy3msdmdyou