The crust-mantle interaction in the Qiangtang terrane is significant to study continental rheology and evolution. Its mechanism remains a subject of considerable debate for the reason of lack of sufficient geophysical evidence. The effective elastic thickness (Te) of the lithosphere can provide important constraints on this issue because it is sensitive to the state of mechanical coupling between the crust and the lithospheric mantle. We present new high-resolution Te of the Qiangtang terrane by using the multitaper admittance method with fusion of different window, based on satellite gravity and topographical data. Thus, a detailed study of the lithosphere is conducted, for the first time to utilize the spatial variations of Te and associated parameters, including thermal structures of the lithosphere, uppermost mantle seismic Pn-velocity, and crustal deformation. The results indicate that crust-mantle interaction in the Qiangtang terrane primarily occurs in the middle Qiangtang terrane (87°E ∼ 95°E, 32°N ∼ 34°N), where Te values are lower. In the eastern and western Qiangtang terrane, Te values are higher, implying weaker late-stage modification. Due to Rayleigh-Taylor instability, lithospheric delamination occurred beneath the south Qiangtang terrane. Based on the extent of these low Te values (Te < 50 km), we conclude that the delaminated lithospheric slab sinking into the mantle is ∼400 km in length and elongated in shape. The delamination induces the upwelling of mantle material, upward stress, volcanic activity, extensional faults, and hot springs in the Qiangtang terrane.

中文翻译：

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羌塘地体壳幔相互作用：来自岩石圈有效弹性厚度的新证据


羌塘地体壳幔相互作用对于研究大陆流变和演化具有重要意义。由于缺乏足够的地球物理证据，其机制仍然是一个备受争议的话题。岩石圈的有效弹性厚度（Te）可以为这个问题提供重要的约束，因为它对地壳和岩石圈地幔之间的机械耦合状态敏感。基于卫星重力和地形数据，采用不同窗口融合的多锥导纳方法，提出了新的羌塘地体高分辨率Te。因此，首次利用 Te 和相关参数的空间变化对岩石圈进行了详细研究，包括岩石圈的热结构、上地幔地震 Pn 速度和地壳变形。结果表明，羌塘地体壳幔相互作用主要发生在羌塘地体中部（87°E ∼ 95°E，32°N ∼ 34°N），Te值较低。东、西羌塘地体Te值较高，表明后期改造较弱。由于瑞利-泰勒不稳定性，南羌塘地体下方发生了岩石圈拆沉。根据这些低 Te 值的范围（Te < 50 km），我们得出结论，沉入地幔中的脱层岩石圈板片长度约为 400 km，且形状拉长。拆沉作用导致羌塘地体地幔物质上涌、向上应力、火山活动、伸展断层和温泉。