地壳流体－岩石氧同位素交换反应动力学研究现状

CURRENT STATE OF RESEARCH ON OXYGEN ISOTOPE EXCHANGE KINETICS OF FLUID-ROCK SYSTEM WITHIN THE CRUST

矿物－流体体系氧同位素交换反应动力学模型主要分为５种：封闭、＂封闭＂、一般开放、流体缓冲体系以及岩石缓冲体系。交换机制主要为扩散控制和表面控制。层状辉长岩上部、下部岩系辉石往往表现出不同的交换速率和交换程度，流体的初始δ１８Ｏ值也显示出较大的不均一性。花岗岩－流体氧同位素交换反应绝大多数为开放体系不平衡类型。中深成岩基与浅成岩体在有效反应时限、流体标准化渗透率方面不同。前寒武纪条带状硅质铁建造分为低级变质地带（Ⅰ组）和高级变质地带（Ⅱ组），前者多为典型的开放体系不平衡类型，石英反应程度低；后者则接近平衡，石英反应程度高。造山带低级变质地体流体－岩石１８Ｏ交换主要是在岩石缓冲体系下进行的。流体循环与质量传输机制主要有：平流、扩散、扩散－平流复合机制。

Oxygen isotope exchange reactions in the mineral-fluid system fall into 5 kinetic models: closed, ' closed,' open,fluid-buffered and rock-buffered systems. Exchange mechanisms are chiefly diffusion-control and surface-control.Pyroxenes from upper and lower zones in layered gabbros show remarkable differences in their exchange rates and exchange extents,with a fairly heterogeneous fluid in its initial oxygen isotopic composition.The mineral-fluid oxygen isotope exchange in granitic rocks is mainly a non-equilibrium one in an open system. Mesozonal and epizonal plutons differ from each other in both the effective reaction time duration and the normalized fluid permeabillity rate.Two general patterns of exchange reaction are recognized in Precambrian banded siliceous iron formations:a nonequilibrium open system type in low-grade terrain of group Ⅰ with relatively inert quartz,and a quasi-equilibrium one in high-grade terrain of group Ⅱ,with a higher quartz-water reaction extent.Fluid-rock18 O exchange in the low-grade metamorphic terrain of an orogen can be best explained with a rock-buffered system.Three mechanisms-advection,diffusion and diffusion-advection-can be recognized for fluid migration and mass transport.