质量传输和同位素交换:流动几何学和交换机制

COUPLED MASS TRANSPORT AND KINETICALLY LIMITED ISOTOPE EXCHANGE: FLOW GEOMETRY AND EXCHANGE MECHANISMS

耦合的质量传输和动力学限制的同位素交换模型综合考虑了平流、扩散、热液弥散 ,以及岩石与水之间的不平衡同位素交换等项因素。把耦合模型应用于 2个构造环境下的古热液系统 ,进而解释稳定同位素数据。对于造成环绕浅成侵入岩体分布的18O亏损环带的流体的流动几何学 ,以及浅部正断层流体流动的几何学 ,耦合模型提供了不同于单一同位素交换模型的解释。耦合模型也提供了关于同位素相对交换速率和同位素交换机制的信息。结果表明 ,断层带的动态重结晶促进了表面反应 ,进而便利了同位素交换 ;在化学不反应性和未变形的矿物中 ,同位素交换可能受制于固态条件下的扩散。

The model of coupled mass transport and kinetically limited isotope exchange synthetically considers the mechanisms of advection, diffusion, hydrothermal dispersion, and non-equilibrium exchange between water and rock. The complex model is applied to two fossil hydrothermal systems under different tectonic settings in order to interpret stable isotope data. This complex model provides alternative interpretations for the geometry of flow responsible for the development of 18O depletion annuli surrounding epizonal intrusions and for the geometry of flow in shallow -level normal faults. Valuable information is also extracted by using this complex model about the relative exchange rates and hence the mechanisms of isotope exchange. Dynamic recrystallization in fault zones enhances the exchange by surface reaction, whereas the exchange in chemically non-reactive and underformed minerals may be limited by solid-state diffusion.