Three-Dimensional Modeling of Continental Subduction and the Evolution of Ultra High Pressure Metamorphism

该项目通过大陆俯冲的数值模拟和碰撞中物质的构造/岩石学演化的整合，研究与大陆俯冲和超高压变质作用有关的驱动力和物质行为。挪威西部片麻岩的自然超高压和高压组合为建模提供了流变学、几何学和年代学信息，而新西兰中部活动的斜向会聚的板块边界则是碰撞-俯冲转变的现代模拟。大陆俯冲带代表壳幔相互作用从近水平转变为以垂直为主的区域，突出了物体和粘性力在大陆演化中的相互竞争影响。因此，这些带包含了大量关于控制大陆构造的基本驱动力和物质行为的信息。挪威西部的超高压推覆体是为数不多的穿越大陆俯冲内脏并逃脱了后来事件的完全矿物叠加和构造解体的地形之一。因此，它们可以提供关于碰撞过程中获得的深度和温度、地壳物质在地幔中运动传递到地壳的瞬时流变行为以及物质通过碰撞造山带的空间轨迹的基本信息。这些特征确定了碰撞过程的连贯机械建模所需的基本约束。斜向收敛的地球动力学模型，以这些观测为条件，提供了造山带范围内的速度和应变率，并确定了斜向俯冲中应变分配的特征长度尺度。正在开发与现场结构观测重叠的比例尺运动学描述，将大尺度动态模型与露头级别的观测联系起来。该研究小组正在将这些数据集整合到大陆俯冲的三维动力学和运动学模型中，该模型能够描述作为机械、变质和热演化函数的颗粒历史。由于研究人员同时求解了热模式和物质流动模式，因此可以跟踪整个俯冲过程中物质的压力-温度和时间历史。这将提供模型颗粒历史，以便与自然岩石学进行比较。

This project investigates driving forces and material behavior associated with continental subduction and ultra high-pressure metamorphism through an integration of numerical modeling of continental subduction and structural/petrological evolution of the material caught in the collision. The natural ultra high-pressure and high-pressure assemblages of the Western Gneiss of Norway provide rheological, geometric and geochronological information for the modeling, while the active obliquely convergent plate boundary of central New Zealand serves as a modern analog of a collision-subduction transition. Continental subduction zones represent regions where the crust-mantle interaction changes from nearly horizontal to dominantly vertical, accentuating the competing influences of body and viscous forces in the evolution of continents. Consequently, these zones contain a wealth of information on the basic driving forces and material behavior that control continental tectonics. The ultra high-pressure nappes of western Norway represent one of the few terrains that have traversed the viscera of continental subduction and escaped complete mineralogical overprinting and structural dismemberment of later events. Consequently, they can provide fundamental information on depth and temperature attained during collision, transient rheological behavior of crustal material where the motion in the mantle is transmitted to the crust, and on the spatial trajectories of material through a collisional orogen. These features identify the basic constraints required for coherent mechanical modeling of the collisional process. The geodynamic models of oblique convergence, conditioned by these observations, provide orogen-wide velocity and strain rates and identify the characteristic length scales of strain partitioning within oblique subduction. Kinematic descriptions at a scale that overlap with field structural observations are being developed that relate the large scale dynamic model to observations made at the level of an outcrop. The research group is integrating these data sets into a three-dimensional dynamic and kinematic model of continental subduction capable of describing particle histories as a function of mechanical, metamorphic and thermal evolution. Because the researchers solve simultaneously for thermal as well as material flow patterns, pressure- temperature and time history of material throughout the subduction process can be tracked. This will provide model particle histories for comparison with the natural petrology.