牡丹江地区蓝片岩中脉状青铝闪石^（40）Ar—^（39）Ar年龄及其地质意义

￣(40)Ar ￣(39)Ar AGE AND ITS GEOLOGIC SIGNIFICANCE OF VEIN CROSSITE IN GLAUCOPHANE SCHIST,MUDANJIANG AREA

对穆棱县的磨刀石、椅子圈地区的蓝片岩研究，确定其经受过三期叠加变质作用：第一期为蓝片岩相变质作用；第二期为蓝闪绿片岩相变质作用；第三期为受断裂构造控制的动力变质作用，形成脉状青铝闪石、钠长石等变质矿物。通过对脉状产出的青铝闪石￣（４０）Ａｒ—￣（３９）Ａｒ年龄测定，获得较好的年龄谱，坪年龄为１５４．７±０．７Ｍａ。此年龄表明了该期变质作用与敦—密断裂发生大规模左行走滑有关，由于大型走滑断裂造成局部构造超高压，诱发了原有的蓝片岩中流体活化，而形成青铝闪石、钠长石、绿帘石等矿物组成的脉体沿剪切面分布。

On the basis of the study of glaucophane schist in Modaoshi and Yiziquan areas,Muling county,east of Mudanjiang city,it is determined that the rocksexperienced three phases of superposed metamorphism. The first metamorphism ischaracterized by blueschist facies metamorphism in the early stage of Late palaeozoic,the second by glaucophane green schist facies metamorphism in the late stage of Late Palaeozoic,the third by the dynamic metamorphism controlled by fracturing,with veincrossite formed in the third phase. An excellent age spectrum is obtained from ￣(40)Ar ￣(39)Ar ages of vein crossites,The mean age is l54.7±0. 7 Ma;it is verified because thethird metamorphism has a close relationship with Dunhua Mishan Fracture in whichoccurs a large scaled l efthanded strike slip.As a result of the large scaled strike slip fracture,local structural excess pressure formed and resulted in fluid activation inglaucophane. This formed the veins consisting of crossites albite,epidote chlorite,muscovite and quartz etc.,which aredistributed along the surfaces of shearing joints. The study also shows that mineral groups,such as glaucophane,occur not only insubduction zones,but also in fracture zones,However,the distribution of these groups isrestricted and most of them occur in veins.