中文摘要：

川黔湘构造带可划分为4个不同的构造带,其中雪峰山构造带地理位置特殊,恰位于华南块体南北向重力梯度带上,两侧岩石圈厚度差异显著,其成因机制历来是争论的焦点。雪峰山构造带基底是一个花状结构,与川黔隔槽式褶皱带构成一个整体,为一个厚皮结构。雪峰山基底在沅麻盆地隆升最高,表现为压扭性构造特点。参考深反射剖面,绘制了研究区浅层与深部结构地质剖面。板块受挤压,中、上地壳与下地壳存在不同的耦合方式,对此分析了研究区下地壳的变形过程。雪峰山下地壳向下存在对冲,形成山根,但并没有俯冲至地幔。随地壳加厚,岩石圈发生弯曲,下地壳与上地幔存在瑞利泰勒不稳定性,并下沉至软流圈地幔。晚中生代,伸展背景下的软流圈上涌使雪峰山以东岩石圈发生拆沉,致使两侧岩石圈厚度出现差异。

英文摘要：

The Sichuan（Chuan）-Guizhou（Qian）-Hunan（Xiang）tectonic belt（CQXTB）can be divided into four different sub-belts.The Xuefengshan tectonic belt（XTB）,one of the four sub-belts,is the most particular and hotly debated on its genetic mechanism,because it＇s just located in the gravity gradient belt of South China block,and the thickness of lithosphere changes greatly along the both sides of the XTB.The structural styles of CQCTB are analyzed.The geological basement of XTB shows a flower style and constitutes a thick-skinned structure together with Chuan-Qian fold belt,as a whole. The XTB is characterized by compressive-twisting features and its basement uplifts to the maximumheight in the Yuanma basin.The lithosphere thickness of South China is also transformed with time. Referring to the deep seismic reflection profile,the authors draw the deep and shallow structure profile maps of the QXTB.Based on the different coupling styles between middle-upper crust and lower crust, the authors discussed the deformation process of the lower crust.The lower crust＇s downward bidirectional subduction under the XTB forms a root without subduction into the mantle.Meanwhile, the lithosphere is bended due to the thickening of crust.After then,the lower crust and upper mantle probably depressed due to Rayleigh-Taylor instability of dense subcrustal lithosphere,where the lower crust and upper mantle sank into the asthenosphere mantle.Finally,under the extensional tectonic background,the asthenosphere rose,which resulted in the delamination of lithosphere at the east of XTB during the Late Mesozoic Era.