山东省平度地区下元古界荆山群变质作用特征

METAMORPHIC CHARACTERISTICS OF JINGSHAN GROUP OF THE LOWER PROTEROZOIC IN PINGDU AREA, SHANDONG

摘要:

胶北隆起新建荆山群,处于胶东群之上,暂置于粉子山群之下;为一套不稳定至半稳定型浅海相陆源碎屑(底部有少量火山碎屑)夹碳酸盐岩的类复理石建造,经过多期变质作用达到角闪麻粒岩相的变质沉积岩系。变质矿物共生组合和各世代矿物的相互关系显示该套岩系经历了四期变质作用。单矿物化学成分及地质温压计等定量估算出各期变质作用的P—T条件: 第一期变质作用相当于角闪麻粒岩相条件,t=780～817℃,p=0.5GPa±,fo_2=10~(-15.5) 第二期变质作用相当于高角闪岩相条件,t=630～690℃,p=0.4GPa±。第三期变质大致为低角闪岩相,t=525℃±。第四期变质相当于绿片岩相条件,t<400℃。

Abstract:

The newly defined Jingshan Group in Jiaobei Uplift, overlying the Jiaodong Group and underlying the Fenzishan Group unconclusively, is a flysch—like formation consisting of unstable to semi—stable terrigenous debris (with a minor quantity of pyroclastics at the bottom)of neritic facies with banded carbonate rocks, and has become a metamorphic sedimentary rock sequence of amphibolite—granulite facies after experiencing multi—stage metamorphism. The paragenetic association of the metamorphic minerals and th...