板块俯冲带水流体活动及其效应的定量化数值模拟

Aqueous Fluid Activity and Its Effects in the Subduction Zones:A Systematic

为探讨水流体活动对板块俯冲隧道过程及大陆碰撞造山的制约作用,采用热力学和动力学耦合的数值模拟方法,建立了系统的数值模型.结果显示俯冲隧道内的混杂岩存在两种不同的折返路径:(1)平行于俯冲隧道斜向上折返,形成靠近缝合带的高压-超高压变质岩;(2)近垂直穿过上覆地幔楔侵入地壳深度.这两种差异性的模式主要受控于俯冲带热结构.俯冲带的温度结构控制俯冲隧道内水流体和熔体活动,从而影响上覆地幔楔的弱化程度,最终导致俯冲带内物质的不同运移过程和折返路径.同时,大陆俯冲碰撞带的岩石圈变形和拆沉作用均与俯冲带的流体-熔体活动所导致的岩石圈弱化息息相关.数值模拟结果极大促进了对于板块俯冲带流体-熔体活动及其动力学过程的理解.

In order to study the effects of aqueous fluid activity on the subduction channel processes and continental collision dynamics,systematic numerical models were constructed with integrated thermodynamic and thermomechanical methods.The model results indicate that the subducted crustal materials may either exhume along the subduction channel to the surface near the suture zone,or extrude sub-vertically upward through the mantle wedge to the crust of the overriding plate.The contrasting modes are strongly dependent on the thermal structure of subduction zones.The temperature field controls the aqueous fluid and melt activities,which further regulates the weakening of overriding mantle wedge and finally dominates the material transportation in the subduction channel.Meanwhile,the lithospheric deformation during continental subduction and collision is also strongly dependent on the fluid-melt activity and the induced lithospheric weakening.The numerical models contribute significantly to the better understanding of subduction-zone fluid-melt activity and the geodynamic processes.