苏鲁高压-超高压变质带深俯冲阶段陆表面、Moho和构造应力场的时空变化

俯冲作用作为高压—超高压变质岩带形成的重要机制之一,俯冲块体的运动速度和强度将是制约其形成和演化的重要构造因素,借助于板块俯冲作用的研究探讨高压—超高压变质岩带的形成过程,对研究苏鲁高压—超高压变质岩带的形成机制和动力学建模,是一种有益的尝试。俯冲作用最显观的构造效应是俯冲地块前缘陆表面和Moho的强烈下插,导致山前坳陷带的形成和陆壳的加积、增厚。数值模拟的初步研究表明,俯冲地块的平移速度与山前坳陷带的坳陷量和坳陷速度及Moho的下弯量和下弯速度大致呈正相关关系,表明两者是俯冲过程中重要的壳内活动性构造界面。俯冲块体作为高压—超高压变质带深俯冲作用的运动载体,俯冲块体内部构造界面的运移,间接反映了高压—超高压变质带的形成过程和运动速度的变化,数值模拟结果似乎表明陆表面和Moho有可能成为探讨高压—超高压变质岩带形成过程和深俯冲作用的重要标志。俯冲块体内部的构造应力场也是制约和影响高压—超高压变质带形成过程的重要构造因素之一,模拟计算表明,俯冲过程中俯冲地块的壳内应力场较为稳定,始终以挤压应力为主导,俯冲作用强度仅影响应力大小,而不改变壳内应力场的应力分布。可见,高压—超高压变质岩带基本形成于挤压构造应力场环境...

Temporal-Spatial Changes of the Land Surface, Moho and Tectonic Stress Field during Subduction of the Sulu HP-UHP Metamorphic Belt

Subduction is one of the important mechanisms for the formation of the high-pressure (HP)-ultrahigh-pressure (UHP) metamorphic belt. The movement rate and strength of a subducted block are important tectonic constraints on its formation and evolution. Studying the formation process of a HP-UHP metamorphic belt by using plate subduction is a useful attempt to study the formation mechanism of the Sulu HP-UHP metamorphic belt and construction of a dynamic model. The most conspicuous tectonic effect of subduction is strong underthrusting of the land surface at the front of a subducted block and the Moho, which results in the formation of a piedmont depression and accretion and thickening of continental crust. Preliminary numerical modeling suggests that the translational rate of a subducted block is broadly positively correlated with the amount and rate of downwarping of a piedmont depression and the amount and rate of downward flexure of the Moho, indicating that they are boundaries of important intracrustal active tectonics. The migration of the tectonic boundary in the interior of a subducted block, as the movement carrier of deep subduction of a HP-UHP metamorphic belt, indirectly reflects the changes in formation process and movement rate of a HP-UHP metamorphic belt. The results of the numerical modeling seem to show that the land surface and Moho is likely to be boundaries of important active tectonics for the study of the formation process of a HP-UHP metamorphic belt and deep subduction. The tectonic stress field in the interior of a subducted block is also an important tectonic factor for constraining and influencing the formation process of a HP-UHP metamorphic belt. Modeling calculation indicates that the intracrustal stress field of a subducted block during subduction is relatively stable and always dominated by compressional stress, while the strength of subduction only affects the magnitude of stress rather than the distribution of stress in the intracrustal stress field.