中─高级变质相中水热流体的形成与作用

MECHANISM OF EVOLUTION OF HYDROTHERMAL FLUID IN MEDIUM-HIGH METAMORPHIC FACIES

固体地壳中流体是普遍存在的，中—高级变质相中的矿物并非只发生晶体塑性变形，溶解和溶移作用在非糜棱岩化岩石中占主导地位，因为高温高压环境下存在的水热流体，在变质变形作用中起着至关重要的作用。在周围分布有网络状进进剪切带的递进缩短带中，与应交梯度有直接关系的单个矿物的位错密度梯度在其晶体边缘形成，产生了化学位梯度，从而使矿物边缘发生溶解。变形分解作用是产生这一过程的动力，并为流体汇聚形成水热循环系统提供了空间。

Fluid is a foundamntal component of the earth's crust. dissolution and solution transfer other than crytal plasic deformaion are thought to dominate in medium-high metamorphic facies, especially in non-mylonitic rocks. Hydrothermal fluid Plays an imeportant role in deformation and metamorphism at higher temperatures and pressures. Where an individual mneral grain lies in a are of progressive shortening with a zone of progressive shearing anastomosing around its rim, a gradient in dislocation density, directly related to the strain gradient, is formed across its boundary . This change in dislocaion density would generate a chemical gradient that can make the grain rim dissolve. This process is controlled by deformation-decomoposition, which provides space for the hydrothermal fluid circu lation system.