大别—苏鲁超高压变质带P-T-t轨迹的动力学模拟

THERMO-DYNAMIC MODELING OF P-T-t PATHSOF DABIE-SULU ULTRA-HIGH PRESSURE METAMORPISM

综合现有的地质、地球化学资料以及同位素年龄等研究成果 ,同时结合新西兰南岛北端陆壳俯冲的最新发现 ,提出了超高压变质岩的形成四阶段演化模式 :板片俯冲形成增生楔、板片俯冲驱动角落流、板片拆离浮力抬升至Moho深度和后期上地壳伸展阶段 .以此为定量模拟的出发点 ,利用二维有限元对大别—苏鲁超高压变质带的形成演化进行了动力学和热演化模拟 ,追踪超高压变质岩形成演化过程中的质点路径以及对应的P T t轨迹 .计算的P T t轨迹及其空间分布特征均能与实测结果较好吻合 .

HTBased on integrated study of geology, geochemistry, isotopic dating, and latest findings of continent subduction at northern South Island in New Zealand, we propose an evolution model on the ultra-high pressure metamorphic (UHPM) rocks. This model which includes four stages: plate subduction with wedge accretion, plate subduction with corner-flow driven by the slab, break-off of the slab and buoyant uplifting of the wedge to the normal Moho depth, and final exhumation with upper crust extension. Based on this model, we make 2-D finite element numerical modeling to simulate the dynamics and thermo-tectonics of UHPM belts of Dabie-Sulu, and trace trajectories of rocks at different locations and their corresponding P-T-t paths. The calculated P-T-t paths and the UHPM spatial distribution are in good agreement with the observations. HTH