方解石沉积速率控制的物理化学机制及其古环境重建意义

PHYSICOCHEMICAL MECHANISMS OF RATE-DETERMINING OF CALCITE DEPOSITION AND THEIR IMPLICATIONS FOR PALEO-ENVIRONMENTAL RECONSTRUCTION

本文总结了作者有关方解石沉积动力学研究的结果,发现方解石沉积速率受环境温度、CO2分压、水动力条件、水层厚度和溶液中钙浓度等多因素的控制。总的规律是温度愈高、CO2分压愈低、流速愈快、水层厚度愈大、溶液中钙浓度愈高,方解石沉积速率愈大。而且,方解石沉积速率随水中钙浓度的增加呈近似线性增加。文中对自然界类似环境条件下的速率系数和我国南北气候环境条件下的方解石沉积速率进行了总结和分析。文章最后对利用钙华和石笋的沉积速率进行古环境重建的复杂性进行了简要的讨论。

The paper summarized the research result on the kinetics of calcite deposition. It is found that the deposition rate of calcite is determined by temperature, CO2 partial pressure, hydrodynamic condition, water layer thickness and calcium concentration in the solution. The general law is that higher temperature, lower CO2 partial pressure, faster water flow, thicker water layer and higher calcium concentration contribute to higher calcite deposition rate. Moreover, the calcite deposition rate increases with the calcium concentration approximately linearly as the following form:F=α(-eq) where F is the calcite deposition rate in mmol·cm-2s-1; α is rate coefficient in cm·s-1 depending on temperature, CO2 partial pressure, hydrodynamic condition and water layer thickness; eq and are calcium concentrations in mmol·cm-3 at equilibrium and in the solution, respectively. The α values under conditions similar to nature and calcite deposition rates under climates similar to the North and South of China are summarized and analysed in this paper. We conclude with a brief discussion on the complexity of paleoenvironmental reconstruction with deposition rates of stalagmite and tufa. 