Volcanic gases and sublimates from Showashinzan |
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Authors: | Shinya Oana |
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Institution: | 1. Institute of Earth Sciences, Nagoya University, Japan
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Abstract: | Volcanic gases from Showashinzan are qualitatively the same as those liberated from igneous rocks when they are heated in vacuum. Their main components are H2O, CO2, and H2. Then follow HCl, HF, N2, SO2, H2S, S, CH4, CO, Ar, Si, B, Mg, Na, K, Ca, Al, Fe, P, Br, NH3, As, Zn, Sr, Ba, Cu, Pb, Sn, Sb, Bi, Ge, Ag, Cr, Ni, Mo, Rn, Ra, etc. They come through fumaroles of high temperature (~750°C.). Metallic compounds deposit as sublimates around the outlet of fumaroles. They are fractionated there according to their thermodynamic properties. When the temperature of gases falls, heavy metal elements deposit before reaching the surface of the earth. Ra is among them. Owing to the contribution of Ra thus depositted, Rn content of vapor is larger in low temperature fumaroles than in high temperature ones. Chemical compounds of H, C, N, O, and S vary their composition according to the condition of temperature and pressure. Sulfur exists as SO2 more than H2S. As the temperature of gases falls, SO2 and H2 decrease and H2S increases. Mutual relation among them is ruled by the chemical equilibrium: SO2+3H2=H2S+2H2O. The structure of Showashinzan is not simple. Some deviations from the general rule are explained in connection with ground water. |
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