Sapphirine-bearing high pressure mafic granu- lites are recognized in the Bashiwake area of the south Altyn Tagh. Mafic granulites and associated peridotites occur as lenses within kyanite-bearing high pressure felsic...Sapphirine-bearing high pressure mafic granu- lites are recognized in the Bashiwake area of the south Altyn Tagh. Mafic granulites and associated peridotites occur as lenses within kyanite-bearing high pressure felsic granulites. Sapphirine occurs as intergrowths with corundum, spinel and Ca-rich plagioclase in symplectite in between garnet and clinopyroxene. Reaction textures and mineral compositions indicate that sapphirine-bearing symplectites formed by re- actions consuming kyanite, garnet and clinopyroxene. Therefore, both petrographic observations and the mineral compositions suggest that these quartz-free mafic granulites had an eclogite origin with an assemblage of garnet + clino- pyroxene + kyanite, which is estimated to be stable at T = 1000℃ and P≥2.1 GPa. The sapphirine-bearing symplec- tites are resulted from isothermal decompression or decom- pression with slight cooling during exhumation of the host rock.展开更多
文摘Sapphirine-bearing high pressure mafic granu- lites are recognized in the Bashiwake area of the south Altyn Tagh. Mafic granulites and associated peridotites occur as lenses within kyanite-bearing high pressure felsic granulites. Sapphirine occurs as intergrowths with corundum, spinel and Ca-rich plagioclase in symplectite in between garnet and clinopyroxene. Reaction textures and mineral compositions indicate that sapphirine-bearing symplectites formed by re- actions consuming kyanite, garnet and clinopyroxene. Therefore, both petrographic observations and the mineral compositions suggest that these quartz-free mafic granulites had an eclogite origin with an assemblage of garnet + clino- pyroxene + kyanite, which is estimated to be stable at T = 1000℃ and P≥2.1 GPa. The sapphirine-bearing symplec- tites are resulted from isothermal decompression or decom- pression with slight cooling during exhumation of the host rock.
