物相之间氧同位素分馏的高温高压实验研究

EXPERIMENTAL STUDIES OF EQUILIBRIUM OXYGEN ISOTOPE FRACTIONATION FACTORS BETWEEN PHASES AT HIGH TEMPERATURES AND PRESSURES

应用理论计算、实验测定和经验估计三种方法均能获取含固体矿物体系的氧同位素分馏系数，其中高温高压实验研究不仅能够得到物相之间的同位素平衡分馏系数，而且能够提供与同位素交换动力学和机理有关的信息。同位素分馏系数的实验校准方法已经由原来的两相体系（矿物Ｈ２Ｏ、矿物ＣＯ２和矿物ＣａＣＯ３）交换发展为三相体系（ＣａＣＯ３矿物流体）交换，化学合成、重结晶和矿物反应技术得到了进一步应用。本文评述了近十年来这一领域的研究进展，着重介绍了Ｈ２Ｏ、ＣＯ２和ＣａＣＯ３作为交换介质进行氧同位素分馏系数校准的技术原理和结果，探讨了热液和碳酸盐交换实验结果不一致的原因。

Equilibrium stable isotope fractionation factors between phases can be calibrated by theoretical calculations, experimental determinations and empirical estimates. Isotopic exchange experiments at high temperatures and pressures have been one of the most important methods for this purpose. They can also provide information on the kinetic processes and exchange mechanism between phases. The experimental calibrations have been developed from oxygen isotopic exchange in a two phase system (e.g., mineral H 2O, mineral CO 2 and mineral CaCO 3) to that in a three phase system (e.g., CaCO 3 mineral fluid). Techniques involving the chemical synthesis, recrystallization and mineral reaction have been applied to obtain equilibrium oxygen isotope fractionation factors between phases. This paper reviews the procedures and results of the experimental studies that have been undertaken to determine oxygen isotope fractionations between mineral mineral, mineral fluid, glass fluid and melt fluid pairs at high temperatures and pressures.