Origin and evolution of alkali basaltic magma in the Okinawa Trough

摘要

The contents of major element composition of the phenocrysts and the matrix glass as well as the spinel inclusions and the melt inclusion in the phenocrysts of the basalt dredged from Station 133 of the Okinawa Trough are determined by electron microprobe. The results show that the basalt is a dor- galite consisting of phenocrysts of bytownite, chrysolite, clinopyroxene and magnetite as well as labradorite microcrystal, matrix glass and a few bits of broken vein quartz. Glassy melt inclusion and chromohercynite or chrompleonaste exist in bytownite and chrysolite. The formation of the spinels is re- lated to partial melting of mantle.