Abstract The Qilian Shan is located along the northeastern margin of the Tibetan Plateau, which is a key area for studying the growth and expansion of the Tibetan Plateau. There have been several geodynamic models developed to explain the deformation pattern of the Tibetan Plateau extending to the northeast, but they remain controversial. The magnetotelluric (MT) method can study subsurface electrical conductivity and rheological properties. A dense broadband and long period magnetotelluric (MT) profile across the middle Qilian Shan has been completed. The MT profile starts from the northeastern margin of the Qaidam Basin, crosses the Qilian Shan and Hexi Corridor, and finally reaches the southwestern margin of the Alashan Block. Based on data analysis results, a three-dimensional (3-D) resistivity model of the crust and upper mantle has finally been obtained. The MT results show that a relatively low resistivity zone exists at the bottom of the upper crust of the Qilian Shan, features as an intracrustal decollement, which indicates the decoupling deformation between the upper and lower crust. The isolated conductive bodies in the middle-lower crust of the Qilian Shan may have formed during the primary stage of plateau growth, suggesting that there may be no existence of the middle-lower crustal flow beneath the Qilian Shan. The Alashan Block lithospheric mantle may have partly underthrust southward the Northeastern Tibetan Plateau. The Tibetan Plateau may have grown and expanded northeastward across the Hexi Corridor to the Heli Shan Fault.

中文翻译：

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大地电磁数据3D反演揭示中祁连山电性结构：青藏高原东北部生长变形的新认识

摘要 祁连山位于青藏高原东北缘，是研究青藏高原生长扩张的重点地区。已经开发了几种地球动力学模型来解释青藏高原向东北延伸的变形模式，但它们仍然存在争议。大地电磁 (MT) 方法可以研究地下电导率和流变特性。完成了横跨中祁连山的密集宽带长周期大地电磁 (MT) 剖面。MT剖面起始于柴达木盆地东北缘，穿过祁连山和河西走廊，最终到达阿拉善地块西南缘。根据数据分析结果，最终获得了地壳和上地幔的三维（3-D）电阻率模型。MT结果表明，祁连山上地壳底部存在一个相对较低的电阻率带，具有地壳内脱滑特征，表明上地壳与下地壳发生脱钩变形。祁连山中下地壳孤立的导电体可能形成于高原生长的初级阶段，表明祁连山下方可能不存在中下地壳流动。阿拉善地块岩石圈地幔可能在青藏高原东北部向南发生部分逆冲。青藏高原可能已经生长并向东北扩展，穿过河西走廊到达河里山断裂。MT结果表明，祁连山上地壳底部存在一个相对较低的电阻率带，具有地壳内脱滑特征，表明上地壳和下地壳之间存在脱钩变形。祁连山中下地壳孤立的导电体可能形成于高原生长的初级阶段，表明祁连山下方可能不存在中下地壳流动。阿拉善地块岩石圈地幔可能在青藏高原东北部向南发生部分逆冲。青藏高原可能已经生长并向东北扩展，穿过河西走廊到达河里山断裂。MT结果表明，祁连山上地壳底部存在一个相对较低的电阻率带，具有地壳内脱滑特征，表明上地壳和下地壳之间存在脱钩变形。祁连山中下地壳孤立的导电体可能形成于高原生长的初级阶段，表明祁连山下方可能不存在中下地壳流动。阿拉善地块岩石圈地幔可能在青藏高原东北部向南发生部分逆冲。青藏高原可能已经生长并向东北扩展，穿过河西走廊到达河里山断裂。这表明上地壳和下地壳之间的解耦变形。祁连山中下地壳孤立的导电体可能形成于高原生长的初级阶段，表明祁连山下方可能不存在中下地壳流动。阿拉善地块岩石圈地幔可能在青藏高原东北部向南发生部分逆冲。青藏高原可能已经生长并向东北扩展，穿过河西走廊到达合力山断裂。这表明上地壳和下地壳之间的解耦变形。祁连山中下地壳孤立的导电体可能形成于高原生长的初级阶段，表明祁连山下方可能不存在中下地壳流动。阿拉善地块岩石圈地幔可能在青藏高原东北部向南发生部分逆冲。青藏高原可能已经生长并向东北扩展，穿过河西走廊到达河里山断裂。阿拉善地块岩石圈地幔可能在青藏高原东北部向南发生部分逆冲。青藏高原可能已经生长并向东北扩展，穿过河西走廊到达河里山断裂。阿拉善地块岩石圈地幔可能在青藏高原东北部向南发生部分逆冲。青藏高原可能已经生长并向东北扩展，穿过河西走廊到达河里山断裂。