Petrology of kaersutite-bearing ultramafic and mafic inclusions in Iki Island,Japan

Kaersutite-bearing peridotite, clinopyroxenite, gabbro and hornblendite inclusions up to 5 cm in size and megacrysts of kaersutite, andesine and titanomagnetite occur in alkali basalt scoria at Takenotsuji, Iki Island, Japan. New analyses are presented for seven kaersutite-bearing basaltic rocks, three inclusions, three clinopyroxenes and six kaersutites.From the petrography and chemistry of the inclusions and recent experimental work at high pressures and temperatures on natural rock systems, it is suggested that kaersutite-bearing inclusions have been produced from alkali basalt magmas under hydrous conditions at a depth of about 25 to 30 km in the lowest part of the crust.