赣中变质岩带的组成及构造变质变形特征

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

赣中变质岩带不是简单的一套震旦纪地层 ,而是由结晶基底中元古界中深变质岩系 (斜长角闪岩的Sm Nd全岩等时线年龄为 1113± 4 9Ma)和褶皱基底变质较浅的震旦系组成。两者之间以具热流体参与的混合岩化、韧性剪切带和递进变质三位一体组成的动热变质带接触。结晶基底经历了4期构造变质变形的叠加改造 ,每期构造变形都在变质岩石构造单元内留下各种变形形迹 ,变质作用表现为时间上的递进和空间上的叠加演化系列 ,是一套以众多的不平衡结构和多相共生混存的矿物组合 ,热变质带为一套动热变质塑性变形带 ,空间上依次形成绢云母—绿泥石带、黑云母带、石榴石带。

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.