Composition and structural metamorphism-deformation features of the central Jiangxi metamorphic zone

The central Jiangxi metamorphic zone is not a simple suite of Sinian strata but composed of a Mesoproterozoic medium and high grade metamorphic series (the whole rock Sm Nd isochron age of amphibolite is 1 113±49 Ma) as the crystalline basement and the low grade metamorphic Sinian as the folded basement. Between them is a dynamo thermal contact metamorphic zone composed of migmatization, ductile shear zone and progressive metamorphism, which occurred in the presence of hydrothermal fluids. The crystalline basement underwent four phases of reworking by structural metamorphism deformation. The structural deformation of each phase left various deformation markings. The metamorphism is manifested by an evolutionary series which was progressive in time and overprinted in space and is marked by a mineral assemblage with many disequilibrium textures and many coexisting minerals. The thermal metamorphic zone is a zone of dynamo thermal metamorphism plastic deformation, and in space there appear successively the sericite chloride zone, biotite zone, garnet zone, staurolite zone and sillimanite zone.