桜島大正噴火の軽石と火砕成溶岩中に，はしご状（ladder type）の組織をもった磁硫鉄鉱（Po）の酸化分解生成物（magnetite，Mt；hematite，Hm）を見出した．この組織はPoの加熱実験でも観察され（Thornhill and Pidgeon, 1957），Po-気体間の反応を示唆する．先行研究(e.g., Dunn and Chamberlain 1991)からladder type酸化組織の形成メカニズムを推定した：(1)Poが気体O2と反応しMtと気体SO2を生成(2) SO2はPoの結晶構造に沿って空隙を形成(2’)MtはO2と反応しHm生成．(2)において，大気のような気体O2存在環境下では，空隙を通してSO2排出と気体O2の供給が瞬時に行えるので，Po-Mt境界の表面反応律速過程となり，反応開始点から瞬時にMtが生成する．これは，大気接触を経験している両噴出物にladder typeの酸化組織が見られたことと整合的である．Poのladder type酸化組織は噴出物の大気接触の有無を判定する指標となるため，破砕マグマへの大気の混合過程の理解に繋がる．
To understand the controls on the fluid compositional distribution in the crust, a thermodynamic model, which simulates the most stable distribution under pressure and temperature gradients, was established. NaCl solution was used as the representative of the crustal fluid. The model showed that the salinity increases with depth, and the salinity gradient is positively dependent on the temperature gradient. The calculation result was compared with natural salinity distribution of sedimentary fluids, and the calculated profiles are roughly consistent with natural data.
Quartz dissolution-precipitation could control spatial and temporal change of permeability in the Earth’s crust. However, the relationship between the Water-Rock Interaction and the seismic cycle is still unclear. In this study, our “CRACK model” reveal that the timescales of the formation of a quartz vein and the recovery of permeability correlate to the extensional stress period and the recurrence interval of mega-earthquakes in the Nankai Trough, respectively.
Hydrothermal experiments were carried out in olivine–quartz–H2O system. By using unique tube-in-tube type hydrothermal experiments vessel, spatial and temporal data were obtained. The observed mineral distribution was modeled by reaction-diffusion equation. To model our experiments, we set eight unknowns. However, this optimization problem on such many parameters would have several local minimums or broad minimum. Here, to overcome this problems, we use an optimization algorithm of the exchange Monte Carlo method rate law during serpentinization will be discussed.
History and activities relevant to high-pressure mineralogical sciences of the LVP beamline (BL04B1), one of the 10 preceding beamlines constructed over 20 years ago at SPring-8, will be reviewed with some future perspectives.
We observed fibrous alumino silicate in xenolith from Asama Volcano by transmission electron microscope (TEM), in order to identify their phase. In observation using scanning electron microscope (SEM), this mineral is similar to sillimanite, but slightly and significantly more Al-rich than stoichiometric sillimanite. As the result of TEM observation, mullite surrounded by sillimanite was found in sub-micrometric scale.
Stunning, bright blue crystals are common in members of the lavendulan group, which are prized by micromineral collectors for their beauty. But it is the structural complexity of the lavendulan family which is now proving to be as intriguing as its looks. Recently, a number of new finds from Russia and our own studies have expanded considerably the range of possibilities known for this structure family including new mineral species.