【作者】 张进江； 丁林；

【Author】 Zhang Jinjiang~1 Ding Lin~2 (1.School of Earth and Space Science,Peking University,Beijing 100871; 2.Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029)

【机构】 北京大学地球与空间科学学院； 中国科学院地质与地球物理研究所；

【摘要】 东西和南北向伸展是青藏高原最显著的地质特征之一。南北向伸展形成的东西走向伸展构造,主要包括藏南拆离系(STDS),和沿喀喇昆仑—嘉黎断裂带(KJFZ)发育的正断层体系。东西向伸展形成数目众多的南北走向伸展构造,它们切割青藏高原几乎所有的东西走向构造单元,包括羌塘地块、KJFZ和STDS等,说明东西向伸展以整体形式发生并同时波及整个青藏高原,而不是由以KJFZ和STDS为边界的不同地块的不均匀挤出所致。南北走向伸展构造在地表呈之字形,为南北向挤压形成的追踪张断裂;剖面上表现为被后期高角度正断层叠加的拆离断层,拆离断层形成于中-晚中新世而高角度正断层形成于上新世及以后。导致拆离断层的东西向伸展可能是南北向挤压的变形分解,后期高角度正断层作用可能是高原隆升后的垮塌所致。东西向伸展是控制青藏高原新生代浅色花岗岩和盆地形成的主要因素。更多还原

【Abstract】 One of the most striking geological features in Tibet was widespread distribution extensional structures formed by north-south and east-west extension.Besides the southern Tibetan detachment system(STDS),another large-scale E-W-trending structure formed by north-south extension was the normal faults along the Karakorum-Jiali Fault zone(KJFZ).East-west extension resulted in a great quantity of north-south-trending structures.These N-S-trending extensional structures cut most of the east-west-trending tectonic units of Tibet including Qiangtang block,KJFZ and STDS,indicating that the east-west extension took place as a uniform tectonics involving almost the whole plateau simultaneously,which was unlike the supposition that the extension was caused by the heterogeneous extrusion of different blocks along KJFZ and STDS.The N-S-trending extensional faults took the zigzag shapes on earth surface,expressing the characters of tensional faults tracing conjugate faults formed by N-S contraction.In sections,these structures showed features of detachment faults superposed by later high-angle normal faulting.The detachment faults formed in Mid-Late Miocene whereas the high-angle faulting took place during and after Pliocene.The east-west extension resulting in the detachment faults was probably caused by the deformation partition of the north-south compression while the late high-angle faulting was possibly caused by the collapse of the Plateau after its uplift.The east-west extension was one of most important tectonic factors controlling the formation of Cenozoic leucogranite and basins in Tibet.更多还原