俯冲带深海-岩石圈流体交换及其效应

Deep sea-lithosphere fluid exchange in subduction zones and its effects:A critical review

俯冲带是地球上构造活动最复杂、最强烈的区域,也是地球物质循环系统的重要组成部分,对俯冲带的深入研究有助于加深我们对地球系统科学的认识。通过系统地梳理分析国内外相关文献,大洋岩石圈通过在汇聚板块边界的俯冲将大量水带入到地幔中,并对俯冲带地震的发生、地幔的熔融、岩浆的产生、陆壳的形成乃至矿产资源富集都起到了重要的控制作用。弧前隆起区的岩石圈地幔在顺断层渗透的深海水作用下发生强烈水化作用并形成水化地幔,是水富集在岩石圈的主要方式之一。随着俯冲板片深度的增加,在一定的温压条件下,水化地幔(蛇纹岩)发生脱水相变,引发俯冲带中源地震。脱出的水则由于运移的差异,既可以产生板内的水压致裂,也会影响俯冲界面的耦合,进而导致慢滑移地震区的形成。由此可见,俯冲带地区深海-岩石圈流体交换及其在深部的效应是一个包含化学反应-温度-流体流动-应力变形/破坏的多物理场耦合的复杂动力学系统。然而,目前的相关研究工作主要侧重于对其中某个因素、现象或者某个特定条件下具体过程的探索性观测分析研究。因此,我们需要从地球系统科学的角度出发,将流体运移、化学反应与传统的固体地球研究相结合,着眼于多学科交叉的多场耦合动力学综合研究,对俯冲带地区深海-岩石圈流体交换及其效应进行多时空尺度定量化表征和分析。

The subduction zone has the most complex and intense tectonic activities on Earth and is also an important part of the Earth’s material circulation system.In-depth study of subduction zones will help deepen our understanding of the earth system.According to published results,it is believed that the oceanic lithosphere brings large amounts of water into the mantle through subduction at the boundary of the convergent plate,and this phenomenon is responsible for the control of subduction earthquakes,mantle melting,magma production,continental crust formation,and even mineral enrichment.The lithospheric mantle of the fore-arc uplift area is intensively hydrated by deep seawater infiltration along faults,and mantle hydration is one of the main ways of water accumulation in the lithosphere.With the increase of subduction depth,the hydrous serpentinized mantle dehydrates under certain temperature and pressure conditions,leading to intermediate earthquakes in the subduction zone.Moreover,due to differences in water migration,the separated water not only can cause hydrofracturing in the plate,but also can affect subduction interface coupling to form slow slip zones.Hence,fluid exchange between the deep sea and lithosphere in the subduction zone and its effect in the deep earth are complex dynamic processes with multiphysics couplings between chemical reaction,temperature,fluid migration and stress deformation.However,current researches mainly focus on exploratory observation and analysis of specific factors,phenomena or processes under certain conditions.Future research,therefore,needs to focus on the comprehensive,multidisciplinary study of multiphysics coupling dynamics from the perspective of earth system science,integrating fluid migration and chemical reaction into conventional solid earth research to quantitatively characterize/analyze the deep sea-lithosphere fluid exchange and its effects on the subduction dynamics at multiple spatiotemporal scales.