大别山碧溪岭石榴橄榄岩-榴辉岩体的原岩性质及同位素年代学的启示

The Nature of Protolith of Bixiling Garnet Peridotite-Eclogite Massif in Dabie Mountains and the Implication of Its Isotopic Geochronology

碧溪岭橄榄岩一榴辉岩体的原岩为形成於岛弧环境并经受结晶分离作用的镁铁－超镁铁质侵入体。它们形成于２２１０±３９Ｍａ或更早，于８００～１０００Ｍａ时经受超高压变质之后上升于壳幔边界附近，并经受多期次高压退变质作用及韧性变形（６６０～４１０Ｍａ），于２１０～２５０Ｍａ时折返上升至地壳并伴随发生石榴石的重结晶以及随后在地壳条件下榴辉岩的角闪岩化。

The protolith of Bixiling garnet peridotite-eclogite massif in Dabie Mountains, China is a mafic-ultramafic intrusive body, which was formed in an island-arc environment and subjected to crystallizationfractionation. The intrusive body was formed in 2210±39 Ma or earlier and rised up to the vicinity of crustmantle boundary after UHP-metamorphism in 800~1000Ma. It has experinced mult-period high-pressure retrogressive metamorphism and ductile deformation (during the period of 660~410Ma), and exhumation to the middle crust associated with the recrystallization of garnet (during the period of 210~250 Ma), followed by the amphibolization of eclogite under crustal conditions.