电气石—水体系中D/H交换动力学研究

D/H Exchange Kinetics in the Tourmaline—Water System

本文对电气石－水体系氢同位素动力分馏进行了实验研究。研究表明，电气石－水体系氢同位素交换以扩散交换为主。在温度为８００－４５０℃范围内，该体系的氢扩散动力学方程为：ｌｏｇＤ＝－５．９６－６．６８×１０＾３／Ｔ，ｌｏｇＤ＝－５．６４－６．４２×１０＾３Ｔ，扩散活化能为１２８．０ｋＪ／ｍｏｌ和１２３．１ｋｇ／ｍｏｌ。

Hydrogen isotope kinetic fractionation in the tourmaline-water system has been studied experimentally. The results indicate that the exchange mechanism of hydrogen isotopes between tourmaline and water was dominated by hydrogen diffusion. Hydrogen diffusion coefficents (S) as related to temperature (t) for the system tourmaline-water for the temperature range 800-450℃ are experessed by the following equations: cylinder model logDcyl = -5. 96 - 6. 68 × 103/ T,E. = 128. 0 kJ/mol;plate model logDplate=-5. 64-6. 42 ×103/T,Ea = 123. 1 kJ/rnol. In the tourmaline-water system the closure temperature for the cessation of hydrogen isotope exchange is higher than that in amphibole, ilvaite and epidote, and close to that in muscovite, suggesting that in the processes of petrogenesis and minerogenesis the hydrogen isotopic composition of tourmaline is not liable to be influenced by low-temperatrue hydrothermal solutions of the late stage.