青藏高原东北缘祁连山与酒西盆地结合部深部地壳结构及其构造意义

青藏高原地壳变形加厚机制一直是地学界研究争论的热点问题.青藏高原目前仍然处在持续向外扩张之中，因此青藏高原的边界地带作为高原向外扩张的最前缘地区代表了高原最新的变形状态，是研究青藏高原地壳变形加厚的关键地区.本文以一条穿过青藏高原东北缘祁连山与酒西盆地结合部的深地震反射剖面为基础，结合前人地质、地球物理资料，通过细致的地质构造解译，获得青藏高原东北缘祁连山与酒西盆地结合部位地壳变形以壳内滑脱带为界上、下解耦.滑脱带位于壳内低速层的顶部，深度14~24 km.滑脱带之上的地壳部分以一系列南倾、北冲，并向下终止于滑脱带的逆冲断裂变形为主，指示了青藏高原向北的扩张方式；滑脱带之下的地壳以Moho面作为变形标志，指示了复杂的挤压缩短变形.据此我们推测上、下地壳的解耦缩短变形对青藏高原东北缘地壳的变形加厚起到了决定性的作用，甚至在整个青藏高原地壳的变形加厚过程中都起到了重要作用.

Deep crustal structure beneath the junction of the Qilian Shan and Jiuxi Basin in the northeastern margin of the Tibetan Plateau and its tectonic implications

The mechanism of crustal thickening in the Tibetan Plateau has long been a highly debated issue. The Tibetan Plateau continues to expanse outward at present, so the border areas as the leading edges of the plateau represent the latest deformation of the plateau, and are the critical places to study on crustal deformation and thickening of the plateau. Based on a deep seismic reflection profile across the junction of the Qilian Shan and the Jiuxi Basin in the northeastern margin of the Tibetan Plateau, combined with previous geological and geophysical data, this work obtained a clearly crustal deformation style beneath the junction of the Qilian Shan and the Jiuxi Basin by detailed geological interpretation of the seismic profile. The crustal deformation is bounded by a decollement layer at a depth of 14~24 km which is consistent with the upper boundary of the low velocity layer within crust. Crustal deformation above the decollement layer is featured by south-dipping, north thrusting faults which downwards ended at the decollement layer, implying the northward out-growth of the plateau. While the crust below the decollement layer experienced complicated shortening marked by a complex Moho geometry. We deduced that the decoupled upper crust and lower crust shortening played a critical role in the formation of the northeastern Tibetan Plateau, even in the formation of entire plateau.