Cryogenic Raman Spectroscopic Studies in the System of NaCl-MgCl2-H2O
YANG Dan1，2, XU Wen-yi2
1. School of Earth Sciences and Resoures, University of Geosciences, Beijing 100083, China 2. The Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China
Abstract：In the present paper, the best experimental conditions for producing hydrates in the NaCl-H2O and MgCl2-H2O systems were found through the cryogenic Raman spectroscopy. This experimental condition is rapidly cooling to -180 ℃ and slowly warming to observe hydrate formation process (that is manifested as a darkening of the vision in the microscope), and finally, rapidly cooling down to -180 ℃. Moreover, a qualitative or semiquantitative analytical method for NaCl-MgCl2-H2O system was established. This method is that 3 537 cm-1 may instruct the existence of NaCl hydrates, 3 514 cm-1 may instruct the existence of MgCl2 hydrates, and comparison of the intensity of 3 537 and 3 514 cm-1 peaks can be used to estimate the ratio of NaCl and MgCl2 in the system. All these are the foundations for quantifying the components of natural fluid inclusions. The author supports Samson’s idea through observing the phenomenon of experiments in the controversy of the meta-stable eutectics formation model, that is ice forms on initial cooling, leaving a residual, interstitial, hypersaline liquid. On warming, the salt hydrates crystallize from this liquid.
Key words：Composition of fluid inclusions;Dual and multi-component salt-water systems;Low temperature;Raman spectroscopy
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