Garnet clinopyroxenites were found in Mama Valley of Cona area, southeastern Tibet. They are enclosed as lenses in the garnet sillimanite gneisses of the Greater Himalayan Crystallines and consist of Fe-rich anhedral garnet, diopside with high Fe2+/(Fe2+ + Mg) ratio, quartz, Ti-poor ferrohornblende and magnetite, together with such accessory minerals as zircon and apatite. The garnet grains somewhat exhibit zoning patterns formed in the prograde metamorphism. Whole-rock compositions of the garnet clinopyroxenites are characterized by high SiO2 (59%~61%), Fe2O3 (18%~19%, total iron), CaO (12%~13%) and Al2O3 (5.3%~5.4%). Solid-phase thermobarometry reveals recrystallization of the garnet and diopside at temperature of 650~700 ℃ and pressure of 0.8~1.0 GPa. Texture, .mineral paragenesis and compositions, therefore, indicate probable derivation of the garnet clinopyroxenites from dehydration-driven partial melting of Fe-rich amphibolites in the middle crustal levels. Thus an example of amphibolite fades garnet clinopyroxenites is presented in this study.
