威海地区榴辉岩及其变质作用

ECLOGITE AND ITS METAMORPHISM IN WEIHAI AREA

威海地区榴辉岩位于秦岭大别苏北胶南巨型榴辉岩带的北东段。榴辉岩体大小悬殊，呈透镜状、不规则状、脉状及似层状等赋存在早元古代荆山岩群变质层状岩系、尖晶石橄榄透闪片岩及晚元古代片麻状花岗闪长岩、片麻状二长花岗岩中，并与围岩一起经受了后期的构造变形改造。榴辉岩退变分带的核部为榴辉岩，次外边为榴闪岩，最外边为斜长角闪岩或石榴斜长角闪岩。三个变质作用阶段的特征是：前榴辉相阶段为中压相系绿帘角闪岩相；榴辉岩相阶段为高压相系；榴辉岩退变质阶段相当于中压相系的角闪麻粒岩相—角闪岩相。变质作用ＰＴｔ轨迹呈顺时针方向。榴辉岩形成于９００Ｍａ左右。

? Eclogites in Weihai area distributes in the northeast section of Dabie-Subei-Jiaonan huge eclogite belt, and its bodies varies from small size to large one. It occurred spinel olivine tremolite schist of Jingshan group (Paleoproterozoic) which is metamorphic layered rocks and gneissoid granodiroite and gneissoid monzonitic granite with len,irregular, vein and stratoid shapes. Eclogite bodies and its country rocks were together deformed by tectonization. The regressive metamorphism zoning of eclogite can be divided into three parts:the core part is eclogite,the one around it is the eclogite amphibolite, and the outer part is plagioclase amphibolite or garnet plagioclase amphibolite by the study of petrology. The characteristics of three metamorphic stages are as follows: before the eclogite-facies stage which is middle-pressure epidote amphibolite facies; the eclogite facies stage which is high-pressure facies;and the retrograde metamorphism stage which is equal to middle-pressure hornblende granulite facies-granulite facies. The trend of PTt is clockwise and the eclogite was formed in about 900Ma