高压超高压变质作用中流体-熔体-岩石相互作用

FLUID MELT ROCK INTERACTION IN THE HIGH PRE SSURE AND ULTRAHIGH PRESSURE METAMORPHISM

在高压超高压变质作用过程中所释放的流体对俯冲板块的演化起着重要作用，与岛弧岩浆活动有着直接联系。随着温度和压力的增加，俯冲板片将发生高压到超高压榴辉岩相转变，大量的水将通过含水矿物的消失反应释放出来。这些流体可引起上覆岩石圈大规模水化，并促进地幔楔状体的部分熔融。同时，通过流体的向上迁移可将某些组分带入上覆岩石圈板块，并改变其总体组成。许多含水矿物、同变质脉体、高压自形晶体组成的布丁、原生液态包裹体和熔融包裹体的发现，均表明在高压超高压变质作用过程中有含水流体相参与。流体—熔体—岩石相互作用的详细研究将为流体成分和演化过程的确定、超高压变质岩形成与折返动力学模型的建立提供重要限定条件。

Fluid released during the high pressure and ultrahigh pressure metamorphism plays an important role in the evolution of subducted slab and may connect directly with igneous activity in island arcs.With increasing p T conditions,the subducting slab passes through the high pressure to ultrahigh pressure eclogite facies transition where large amount of H 2O are released by the breakdown of hydrous minerals.These fluids can cause large scale hydration of the overriding lithosphere and trigger partial melting of the mantle wedge.Upward migration of slab derived fluids can add some elements to the overlying lithospheric plate,and alter the bulk composition in the overlying mantle wedge.Many H 2O and CO 2 bearing minerals,syn metamorphic veins,patches consisting of euhedral crystals of high pressure,primary fluid inclusion and melt inclusion have been found in the coesite and/or diamond bearing metamorphic rocks.These show the presence of aqueous fluid phase during high pressure and ultrahigh pressure metamorphism.The detailed studies of fluid melt rock interaction may provide important conditions for determining of the composition and evolution of fluid,and constructing of the dynamic model of formation and uplift of the high pressure and ultrahigh pressure metamorphic rocks.