The Cenozoic Qaidam Basin on the northern Tibetan Plateau is bounded by the foreland thrust belts of the East Kunlun Mountains to the south and Qilian Mountains to the north. In this basin, the maximum thickness of the accumulated sedimentary strata is ∼17 km near the geographic center of the basin. Such a basin architecture challenges the classic foreland-basin deformation model, wherein substantial sediments should be localized near the basin margins owing to thrust loads on a bending plate. Based on the available geological and geophysical constraints, we built a two-dimensional viscoelastoplastic finite element model to investigate whether the unique pattern of the Qaidam Basin was mechanically related to the rheological structure of the crust and frictional strength of the basin-bounding thrust fault. By testing reasonable bounds on the viscosity of the ductile crust and effective frictional coefficient of the thrust faults, we modeled a basin framework that fits well with that of Qaidam Basin. The model parameters include a layered rheological structure, with the viscosity of the ductile crust of the basin being two orders of magnitude greater than that of the adjacent mountain belts and an effective frictional coefficient of >0.2. Furthermore, the initial width of the basin significantly affected its deformation style. Therefore, the layered rheological structure of the crust and frictional strength of the basin-bounding thrust faults played important roles in the formation of the Qaidam Basin. Our findings suggest that the inelastic behavior of the crust affects foreland deformation, highlighting that the classic foreland basin model must be revised for some tectonic settings.

中文翻译：

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地壳流变和断层强度对柴达木盆地形成的影响：二维力学模拟结果

青藏高原北部新生代柴达木盆地，南以东昆仑山、北至祁连山前陆冲断带为界。该盆地在盆地地理中心附近沉积地层的最大厚度约为17公里。这种盆地结构挑战了经典的前陆盆地变形模型，其中由于弯曲板上的推力载荷，大量沉积物应位于盆地边缘附近。基于现有的地质和地球物理约束，我们建立了二维粘弹塑性有限元模型，以研究柴达木盆地的独特格局是否与地壳流变结构和盆地逆冲断层的摩擦强度存在机械关系。通过测试韧性地壳粘度和逆冲断层有效摩擦系数的合理界限，我们模拟了与柴达木盆地相吻合的盆地格局。模型参数包括层状流变结构，盆地韧性地壳粘度比邻近山地带大两个数量级，有效摩擦系数>0.2。此外，盆地的初始宽度对其变形方式也有显着影响。因此，地壳层状流变结构和盆地逆冲断裂的摩擦强度对柴达木盆地的形成具有重要作用。我们的研究结果表明，地壳的非弹性行为影响前陆变形，强调经典的前陆盆地模型必须针对某些构造环境进行修正。