大别—苏鲁超高压变质带内变形分解作用对榴辉岩透镜体群发育的影响——以碧溪岭地区为例  

INFLUENCE OF DEFORMATION PARTITIONING ON THE DEVELOPMENT OF ECLOGITE LENSES IN DABIE-SULU UHP METAMORPHIC BELT,CHINA∶AN EXAMPLE FROM THE BIXILING AREA

作　　者：索书田[1] 钟增球[1] 周汉文[1] 游振东[1] 

机构地区：[1]中国地质大学地球科学学院

出　　处：《地质科技情报》2001年第2期15-22,共8页Geological Science and Technology Information

基　　金：国家重大基础发展项目 ( G19990 75 5 0 6) ;国家自然科学基金资助项目 ( 4 9972 0 67;497940 41)

摘　　要：确定超高压变质岩体的大小、分布、构造关系及变质演化 ,是理解超高压变质岩形成和折返动力学过程的关键。在大别—苏鲁超高压变质带内 ,榴辉岩及变质的镁铁质—超镁铁质岩石 ,一般成厘米至公里尺度的布丁或透镜体 ,散布于片麻岩及面理化含榴花岗岩内。区域系统性的岩石学及构造学观察 ,尤其是在安徽省碧溪岭区 1∶ 1万比例尺的精细制图中证实 ,榴辉岩及其它超高压变质岩透镜体群的形成 ,主要是多期及递进变形分解作用的结果 ,造成了网络状线形强应变带与透镜状弱应变域流变学组合型式。榴辉岩与围岩片麻岩的过渡关系也证实 ,超高压变质的榴辉岩体是“原地”形成的。榴辉岩体的形态、大小及空间分布规律特征 ,不支持超高压变质带岩石属构造混杂岩的推论 ,而是反映了超高压及角闪岩相条件下不均匀韧性流动的应变图像。The determination of the size,shape,distribution,structural relationship,and metamorphic evolution of coesite bearing eclogites is critical to understanding the geodynamical processes responsible for the creation and exhumation of UHP metamorphic rocks.In the Dabie Sulu UHP metamorphic belt,eclogites and meta mafic and ultramafic rocks are characterized by a boudin or lenticular style on all scales from a few centimetres to kilometres,and are enveloped in a regional amphibolite facies gneiss matrix and foliated garnet bearing granitic rocks.The systematic regional petrological and structural observations,in particular,detailed mapping on a scale of 1∶10 000 in the Bixiling area,Anhui Province,have demonstrated that the distribution of eclogite and other UHP metamorphic bodies,in the form of lenses,was mainly formed by polyphase and progressive deformation or strain partitioning.The structural features resulted are an anastomosing rheological pattern with a lens shaped domains of low strain separated by shear zones of high strain.The transition relationship between the eclogite and gneiss matrix also clearly shows that the eclogites were metamorphosed in situ.The shape,size and three dimensional array of the eclogite bodies which do not support the idea that the UHP metamophic rocks in the Dabie Sulu collisional orogenic belt are explained as a tectonic mélange.In fact,this reflects an overall ductile flow strain picture under UHP eclogite and amphibolite facies conditions,respectively.

关 键 词：榴辉岩透镜体 超高压变质岩 变形分解作用 流变学型式 大别-苏鲁区 碧溪岭地区 空间分布 

分 类 号：P588.34[天文地球—岩石学]