恒山绿岩带的构造特征──晚太古代大陆裂谷作用证据  

Continental Rifting at the End of Archaean:Structural Evidence From Hengshan Greenstone Belt,North China Craton

作　　者：李江海[1] 钱祥麟[1] 

机构地区：[1]北京大学地质学系

出　　处：《华北地质矿产杂志》1995年第2期181-189,共9页

基　　金：国家自然科学基金及中国博士后科学基金

摘　　要：恒山太古宙绿岩带呈断片或复式向形穿插于片麻岩基底内，绿岩带地层连续性较好，可以恢复出完整的沉积－火山地层序列。主要经历二期变形，早期逆冲褶皱变形和晚期右旋走滑变形。为绿帘角闪岩相－角闪岩相变质。构造恢复表明，绿岩带的形成明显晚于基底，并整合其上，且在其演化过程中对基底产生叠加影响，最合适的构造环境为大陆裂谷，在大陆裂谷闭合过程中。绿岩带及克拉通基底曾发生双向的逆冲作用，基底发生重新活动，并且受到开裂时形成的正断层的控制。当裂谷闭合到一定程度，由于受北部刚性基底的制约，横向挤压不再能调节压应力时，发生了右旋走滑变形，并使早先构造线向ＮＥＥ－ＥＷ向偏转。恒山绿岩带对应于五台山区、太行山北段、灵丘南山等地的五台群，有力地证明绿岩带形成于太古代末期－早元古代陆内裂谷环境，代表华北克技通演化过程中的重要事件，标志着晚太古代华北克拉通已达到相当大的规模，并发生ＮＥ向的刚性破裂。Hengshan greenstone belt(GRB)occured as slice or composite synform within gneissbasement(GNB).AIthough GRB underwent two phases of deformation,early thrusting-fold-ing and late dextral strike sliding,associated with epidote-amphibolite facies metamorphism,its stratigraphy was well preserved and sedimentary-volcanic sequence could be recog-nized.Through large-scale mapping and structural analysis,it was suggested that GRB wasgenerated after GNB had developed,and unconformed upon the latter, which are reworkid byGRB during deformation,Therefore,it was suggested that the most suitable tectonic settingfor GRB was continental rift,which was closed by symmetrical thrusting-folding,controledby movement of GNB along inverted normal fault of the rifting. After rift was closed signifi-cantly,strain within GRB could not be adjusted by shorting,and dextral strike sliding tookplaced as contraint from northern rigid basement. As a result, NE treding structural line wasdeflected to NEE-EW, Hengshan GRB correlated with Wutai Group in the Wutai Mts.,northern Taihang Mts.and Nanshan Mts.,1Jingqiu county, recorded an important event ofreworking during early Precambrian evolution of North China Craton(NCC),indicating thatat least in late Archaean NCC was large and rigid enongh to be fractured in NE strike.

关 键 词：晚太古代 绿岩带 大陆 裂谷作用 克拉通改造 

分 类 号：P534.2[天文地球—古生物学与地层学]