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应用水热金刚石压腔结合拉曼光谱技术来进行石膏和重水间稳定同位素分馏的实验研究。氢同位素D与H的质量差百分比是所有稳定同位素里最大的,由质量引起的分馏更容易发生,更容易在实验中观测;石膏是浅部地壳重要的含水矿物,它与重水之间的同位素分馏效应对矿物-水体系的同位素平衡分馏研究具有重要意义。常用分馏系数是指两矿物或两物相间的同位素比值之商αA-B=RA/RB。拉曼光谱中,物质特征峰的峰强度比值与相应的物质的量的比值呈很好的线性相关,应用石膏和重水的拉曼特征峰强度比值来表征同位素分馏系数α=I(D-O)/I(H-O)石膏/I(D-O)I(H-O)重水两物相间要达到完全的同位素交换是测定稳定同位素分馏系数的前提。此研究应用化学合成法,增加体系的压力使矿物溶解,然后在不同的温度条件下降压使矿物重新结晶。重新结晶的晶体与流体间达到了完全的同位素分馏平衡,得出不同温度下的同位素分馏系数。相对于前人的研究,此方法的原位测量不破坏样品,避免了污染;同时避免了传统的淬火过程中同位素退化交换作用,达到了完全的同位素分馏平衡。金刚石压腔结合拉曼光谱法进行稳定同位素分馏的实验研究是完全可行的。
The experimental study of stable isotope fractionation between gypsum and heavy water was carried out by using hydrothermal diamond pressure chamber combined with Raman spectroscopy. The mass percentage difference between hydrogen isotopes D and H is the largest among all stable isotopes. Mass-induced fractionation is more likely to occur and is easier to observe experimentally. Gypsum is an important hydrous mineral in the shallow crust, and its isotope between heavy water Fractionation effect on mineral-water system isotope equilibrium fractionation is of great significance. The usual fractionation factor is the quotient of αA-B = RA / RB for the ratio of isotopes between two minerals or phases. In Raman spectrum, the peak intensity ratio of material characteristic peak is linearly correlated with the ratio of corresponding substance amount. The Raman peak intensity ratio of gypsum and heavy water is used to characterize the isotopic fractionation coefficient α = I (DO) / I (HO) gypsum / I (DO) I (HO) heavy water two isotopes to achieve complete isotope exchange is the determination of stable isotope fractionation factor premise. In this study, chemical synthesis was used to increase the pressure of the system to dissolve the minerals and then depressurize the minerals to recrystallize under different temperature conditions. The complete isotopic fractionation equilibrium between the recrystallized crystals and the fluid gives the isotopic fractionation coefficients at different temperatures. Compared with the previous studies, the in situ measurement of this method does not destroy the sample and avoids the pollution. At the same time, it avoids the traditional exchange process of isotope degeneration during quenching and achieves a complete isotopic fractionation equilibrium. It is feasible that diamond pressure chamber combined with Raman spectroscopy for stable isotope fractionation experiments.