1991 年 86 巻 8 号 p. 333-345
The original igneous rocks of weakly metamorphosed greenstones are basalt-dolerite and limburgite in Mikabu Green Rocks of the Ogose area, and basalt-dolerite-bostonite and limburgite in the Chichibu melange zone of the Agano area, both of Kanto Mountains. Relict phenocrystic clinopyroxenes of basaltic and limburgitic rocks of both areas are chromian augite (Cr2O3 0.4-0.8 wt.%) to chrome augite (Cr2O3 more than 0.8 wt.%), but, in general, comparatively poor in TiO2 (less than 0.1 wt.%). However, limburgitic pyroxenes of the Chichibu melange zone are slightly richer in TiO2 and Cr2O3 and higher in Mg/(Fe+Mg) than those of the Mikabu rocks. The phenocrystic clinopyroxenes are generally similar in Cr2O3/TiO2 ratios to clinopyroxenes of ocean-floor basalts and of peridotite xenoliths derived from the mantle.