华南陆块及邻区岩石圈热结构特征与构造指示

    The characteristic of lithospheric thermal structure and its tectonic implications in the South China Block and adjacent areas

    • 摘要: 华南陆块既是全球构造的重要组成部分,又是地质构造演化极为复杂区域。目前华南陆块与青藏高原东缘的耦合关系存在较大争议。岩石圈热结构中蕴含着丰富的构造变形、地质演化过程及地球动力学信息,可为深入认识华南陆块与青藏高原东缘的耦合关系提供有效约束。本文基于居里面深度和大地热流数据之间的函数关系,融合得到高空间分辨率的综合大地热流数据。并通过稳态热传导方程和综合大地热流数据,以及地震横波速度与温度之间的关系,构建出华南陆块及邻区岩石圈热结构。通过分析岩石圈热结构中的壳幔热流分配、莫霍面温度与热岩石圈厚度结果发现华夏地块、华北板块、江南造山带东北部和扬子地块东部属于“冷壳热幔”结构,而四川盆地和松潘-甘孜地块属于“热壳冷幔”结构;古太平洋板块向华南陆块的北西向俯冲和后撤作用可能是导致莫霍面温度与热岩石圈厚度变化趋势均由北西向南东方向升高/增厚的原因。华南陆块与青藏高原东缘呈现相向运动,在地壳浅部,松潘-甘孜地块残留的刚性块体与扬子地块碰撞形成龙门山断裂带;而在地壳深部,扬子地块西缘受松潘-甘孜地块地壳熔融流体和深部热物质上涌引起的高温热侵蚀作用影响,逐步散失低温稳定性质。

       

      Abstract: The South China block (SCB) west of the eastern edge of the Tibetan Plateau (ETP) is both an important part of global tectonics and an area of extremely complex geological and tectonic evolution. The coupling relationship between the SCB and the ETP is currently highly controversial. The lithospheric thermal structure contains rich information on tectonic deformation, geological evolutionary processes and geodynamics, which can provide effective constraints for an in-depth understanding of the coupling relationship between the SCB and the ETP. The functional relationship between the depth of the Curie depth and the terrestrial heat flow data is used to obtain integrated terrestrial heat flow data and improve the spatial resolution of terrestrial heat flow data in the SCB. Then, the SCB’s reliable lithospheric thermal structure by the thermal steady-state conduction equation, integrated geodetic heat flow data, and the relationship between seismic S wave velocity and temperature. Analyses of crust-mantle heat flow distribution, Moho surface temperature and thermal lithospheric thickness in the lithospheric thermal structure show that the Cathaysia Block, the North China Plate, the northeastern part of the Jiangnan Orogenic Belt and the eastern part of the Yangtze Block belong to the ‘cold crust-hot mantle’ structure, whereas the Sichuan Basin and the Songpan-Ganzi Block belong to the ‘hot crust-cold mantle’ structure. The northwesterly subduction and retreat of the Palaeo-Pacific Plate to the SCB may be responsible for the northwesterly to southeasterly rise/thickening of both the temperature and thermal lithosphere thickness trends at the Moho surface. The SCB and the ETP show opposite movement. In the shallow part of the crust, rigid blocks of the upper crust of the SGB collide with the YB to form the Longmenshan Fault Zone. In the deep part of the crust, the Western YB is affected by thermal erosion (The SGB high-temperature indicated the partial melting fluids and the upwelling of deep thermal material), resulting in the progressive dissipation of low-temperature stable craton properties.

       

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