胶北地体中的深层次拆离构造:扬子板片折返的板上响应  

Deep-level ductile detachment system in the Jiaobei terrain,eastern China:Deformation response of the overlying plate during the exhumation of Yangtze plate

作　　者：梁凤华[1] 许志琴[1] 李忠海[1] 陈方远[1] 

机构地区：[1]中国地质科学院地质研究所国土资源部大陆动力学重点实验室,北京100037

出　　处：《岩石学报》2011年第4期969-979,共11页Acta Petrologica Sinica

基　　金：地质调查项目(1210823218;1212010711816);中国地质科学院地质研究所基本科研业务费(J0919)联合资助

摘　　要：通过对胶北地体基底中的韧性变形构造的研究,厘定了位于太古宙胶东群和古元古界粉子山群之间及粉子山群与晚元古界蓬莱群之间的2条深层次韧性拆离断层。显微构造和石英组构研究表明它们的剪切指向自SE向NW,并经历了高温(>650℃)到低温(350℃)的组构演化过程。对剪切带中的长英质糜棱岩进行SHRIMPU-Pb测年,获得153±2Ma和128.5±1.5Ma两组重结晶变形年龄,代表韧性拆离断裂形成及活化的时限。结合地体中岩浆作用、莱阳白垩纪盆地沉积以及制约盆地的韧性拆离断裂(148Ma)等相关伸展构造特征,认为胶北深层次拆离构造是扬子深俯冲板块折返后期的板上伸展的响应。Two large-scale deep-level ductile detachments are identified in the Precambrian basement of Jiaobei block,at the southeast end of North China Craton and nearing the northern Sulu ultrahigh pressure metamorphic belt,eastern China.They are respectively DF1 locating between Archean Jiaodong Group （JD） and Paleo-proterozoic Fenzishan Group （FZS） and DF2 between FZS or JD and Neo-proterozoic Penglai Group （PL）.Microstructures and fabrics show the top-to-northwest shear sense and the fabric evolution of quartzite with temperature decreasing.The recrystallized deformation ages are restricted at 153±2Ma and 128.5±1.5Ma by SHRIMP U-Pb dating for mylonitic orthogneiss from DF1,which behalf respectively the forming age and reactive age of detachment.Combining with other extension structures,such as magmatism,sediments of Cretaceous Jiaolai basin and the ductile detachment confining Jiaolai basin （148Ma）,we suggest that the large-scale deep-level ductile detachments with top-to-NW shear sense formed during the uplift （late exhumation） extension stage of UHP metamorphic rocks and is kind of intraplate deformed effect of overlying plate during continental deep-subduction of Yangtze plate.

关 键 词：胶北陆块 板上拆离构造 后造山伸展作用 扬子/华北碰撞造山带 

分 类 号：P542.2[天文地球—构造地质学]