【摘要】 发采用“附晶生长法”分别在50℃和70℃下合成文五型碳酸钙矿物，获得了两种不同的文石与水之间的氧同位素分馏关系。结果证明，文石与水之间氧同位素分馆的化学动力学机理分为两步：（1）碳酸根与水之间进行氧同位素交换和平衡，即：［C16O3］2-＋2H218O［C18O216O］2＋2H216O；（2）与水平衡以后的［CO3］2-离子与Ca2+”结合生成文石，即：Ca2＋+［C18O216O］2－＋H218OCaC18O3（s）＋H216O，这一过程体现了矿物形成过程中氧同位素分馏的结构效应。其中［CO3］2-与H2O之间的氧同位素交换和平衡过程是控制文正与水之间氧同位素平衡分馏的速率限制步骤。在此基础上，采用不同方法合成文五和碳钡矿，测定了文石-水和碳钡矿-水体系的氧同位素分馏系数。实验结果不仅与增量方法理论计算结果相一致，而且也获得了内部一致的碳酸盐矿物与水之间的氧同位素分馏关系。更多还原

【Abstract】 Mineral aragonites were synthesized at 50℃ and 70℃ by "one-step" and "two-step"overgrowth techniques respectively, in order to determine oxygen isotope fractionation betweenaragonite and water. The results show two kinds of different oxygen isotope fractionationrelationships, pointing to the kinetic mechanism of oxygen isotope fractionation in thearagonite-water system as follows: (1) Oxygen isotope exchange and equilibrium between[CO3]2- and H2O: (2) Combination of Ca2+ with the [CO3]2 - that was equilibrated with water to form aragonite: The second step bears oxygen isotope fractionation due to structural effect when formingaragonite crystal. Oxygen isotope exchange and equilibrium between [CO3] 2- and H2O, i. e.the reaction (1), is the rate-limiting step for oxygen isotope equilibrium fractionation betweenaragonite and water. on the basis of the kinetic mechanism of oxygen isotope fractionationabove, aragonite and witherite were synthesized by different synthesis methods and oxygenisotope fractionations in the systems of aragonite-water and witherite-water were measured at50℃ and 70℃, respectively. The obtained results are in excellent agreement with not onlytheoretical calculations by the increment method, but also with internally fractionation relationsfor the systems carbonate-water.更多还原