Experimental Study on the Chemical Processes Associated with Formation of Volcanic Gas

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It is well-known that volcanic volatiles control the condition of magma and are related to eruptive activities. A lot of observational studies on the chemical composition of volcanic volatiles have been already conducted, and degassing phenomena has been studied in view of theoretical point. However, experimental approach to understand the origin and evolution of volcanic volatiles has not been carried out yet. In this research project, we tried to make sure the chemical processes during the formation of volcanic gas according the following 3 steps. 1: Formation of minute bubbles under chemically-controlled environment using a high pressure apparatus. 2 : Establishment of micro-spectroscopy to, determine chemical cpmposition of fluid inclusions of synthesized or natural minerals. 3 : Improvement of in-situ chemical analyzes of volcanic gas. As to 1, we repeated bubble formation experiments under various chemical conditions As to 2, we developed a system of micro-raman spectroscopy with extremely high sensitivity. Among the many results using this system, it must be mentioned that fossil pressure of fluid inclusions, could be estimated based on pressure-dependence of raman shift of C0_2. As to 3 we developed a in-situ system of determination of volcanic gas using a micro gas chromatograph. We also obtained good results on chemical information of volcanic gas of diffuse emission.