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

众所周知，火山挥发物控制着岩浆的条件，并与喷发活动有关。人们已经对火山挥发分的化学成分进行了大量的观测研究，并从理论上对脱气现象进行了研究。然而，了解火山挥发分起源和演化的实验方法尚未开展。在本研究项目中，我们试图通过以下三个步骤来确定火山气形成过程中的化学过程。1：使用高压设备在化学控制的环境下形成微小气泡。2：建立显微光谱分析方法，测定人造矿物或天然矿物流体包裹体的化学成分。3.改进火山气现场化学分析方法。对于1，我们重复了不同化学条件下的气泡形成实验。2，我们建立了一套灵敏度极高的微拉曼光谱系统。在使用该系统的众多结果中，必须指出的是，可以根据CO_2拉曼位移的压力依赖关系来估计流体包裹体的化石压力。关于3，我们开发了一套利用微型气相色谱仪现场测定火山气的系统。对扩散排放的火山气化学信息也取得了较好的结果。

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.