剪切带的流体－岩石相互作用

作为大陆岩石圈中的应变局部化带，剪切带中一般都渗透着大量流体。流体的来源与剪切带所处的构造背景、流变域和水文条件有关，而剪切带中流体的流动则受岩石的渗透率、孔隙度、孔隙性质、流体的扩散和渗透能力、环境的温压条件、应力或载荷的梯度等因素所制约。剪切带中流体的成分、通量及赋存状态或流动方式，直接影响着岩石的流变。由应变局部化及力学失稳所引起的化学不平衡和由流体与岩石的相互作用，使剪切带岩石的矿物成分和化学成分发生调整，其变异程度取决于原岩的性质、剪切的温压条件和流体的成分及通量等。由于流体的渗透流动和流体与岩石的相互作用使剪切带的体积有所变化，体积变化过程是一种自组织行为。较大的体积亏损，意味着剪切带中渗透过大量的流体，这对剪切带的流变行为、化学行为和成矿作用都有深刻的影响。

FLUID ROCK INTERACTION IN SHEAR ZONE

Being the strain localization zones in continental lithosphere, there is evidence that shear zones are infiltrated by a large volume of fluid. The sources of the fluid are related to the tectonic setting, rheological regime and hydrologic enviroment of the shear zone. The flow of fluid is controlled by the porosity and porous character of rocks, the diffusivity and permebility of the fluid, the p T conditions and the stress or loading gradient in the shear zone. The fluid compositon, fluid flux and fluid flow fashion directly accounte for the rock rheology in the zone. The fluid rock interaction and the chemical disequilibrium caused by strain localization and mechanical instablility induce the readjustment of mineral and chemical compositions within a shear zone, and the variation degree of the compositions depends on the protolith character, p T conditions of the shear zone and the consititution and flux of the fluid. The fluid infiltration and fluid flow, as well as the fluid rock interactin promote volume loss of the shear zone. The process of volume loss is an example of self organization. The critical volume loss of shear zone in nature is about 65%, impying a large amount of percolating fluid which greatly affect the rheological behavior, chemeical behavior and metallogenesis of the shear zone.