西秦岭断裂走滑与盆地的耦合——西秦岭—松甘块体新生代向东走滑挤出的证据  

COUPLING BETWEEN STRIKE-SLIP FAULTS AND BASINS:THE EVIDENCE FOR CENOZOIC EASTWARD EXTRUSION OF THE WEST QINLING-SONGGAN BLOCK

作　　者：姜晓玮[1] 王江海[1] 张会化[1] 

机构地区：[1]中国科学院广州地球化学研究所,广东广州510640

出　　处：《地学前缘》2003年第3期201-208,共8页Earth Science Frontiers

基　　金：国家重点基础研究发展规划项目 (G19980 40 80 7) ;广东省自然科学基金项目 (990 5 3 1) ;中国科学院知识创新项目(KZCX2 SW 117) ;国家自然科学基金资助项目 (4 9972 0 2 6) ;美国自然科学基金资助项目

摘　　要：新生代西秦岭—松甘块体向东挤出是印度—欧亚大陆碰撞后青藏东北部一种主要应变响应形式 ,它构成青藏高原东部走滑调节带的北支 ,并与南部印支挤出构造一起共同调节和吸收大陆碰撞后青藏东部的变形。西秦岭岷县—宕昌断裂的走滑与新生代盆地在时空上的耦合 ,明显展示出西秦岭—松甘块体向东走滑挤出历程并提供了走滑作用的定量标尺。古近纪岷县—宕昌断裂的走滑位移量为 36km ,而新近纪则为 76km ,相应的平均走滑速率分别为 0 .0 86mm/a和 0 .37mm/a ,表明新生代西秦岭—松甘块体向东挤出的幅度至少为 112km。西秦岭新生代幔源岩浆活动是在块体挤出背景下 ,块体旋转停止、断裂面弯曲和走滑加速等诸事件耦合的结果 ,同时也是断裂走滑的物质和时间记录器 ,表明岷县—宕昌断裂新生代的走滑波及到了岩石圈底部 ,记录了青藏东北部变形响应的动力学机制从以块体旋转为主向快速走滑为转变的时间 ,即西秦岭—松甘块体向东快速挤出的可能时间为 2 1.1～ 2 5 .4Ma。The Cenozoic eastward extrusion of the West Qinling-Songgan(Songpan-Garze) block is a major response in strain pattern, in NE Tibet induced by the Indion-Eurasian Continental collision. This extrusion belt is a northern branch of the strike-slip extrusion zone of the east Tibet. This branch, together with the southern branch, i.e., the Indochina extrusion belt may mutually regulated and absorbed the strain in east Tibet from the continental collision. The temporal-spatial coupling between the Minxian-Dangchang strike-slip fault with Cenozoic basins in West Qinling indicates that the existence of the eastward strike-slip and extrusion processes, which may provide a ruler for quantitative measuring of the extent of extrusion. The quantities of strike-slip displacement of the Minxian-Dangchang fault are 36 km in Paleogene and 76 km in Neogene respectively, and their corresponding strike-slip rates are 0.086 mm/a and 0.37 mm/a. This result suggests that the West Qinling-Songgan block was eastwards extruded at least up to 112 km in the Cenozoic. The Cenozoic mantle-derived magmatism in West Qinling was induced by the coupling among the ceasing of the block's rotation, the deformation of the fault planes and the accelerated strike-slip in the overall extrusion setting, and was also a recorder that records the status of the material and time of the strike-slip. Our studies suggest that the Minxian-Dangchang strike-slip fault affected the basal part of the lithosphere, recording the time of the dynamic change in NE Tibet from block rotation to rapid strike-slipping , i.e. the eastward extrusion of the West Qinling-Songgan block took place in the period of 21.1～25.4 Ma.

关 键 词：挤出构造 走滑盆地 幔源岩浆活动 西秦岭 青藏东部 

分 类 号：P546[天文地球—构造地质学] P544[天文地球—地质学]