Pyrrhotite (Po) in the erupted materials from the Sakurajima Taisho eruption is sometimes oxidized to form magnetite (Mt) and hematite of ladder structure. The formation mechanisms were estimated based on previous Po oxidation experiments in air. Oxidation reaction of Po produces Mt and SO2 gas that forms pores, resulting in the easy escape of SO2 gas and easy access of O2 gas to the Po-Mt interface, leading to the formation of a Mt column. Therefore, the ladder type products indicate the oxidation in the air.
Hydrogen isotopes can be a tracer of magmatism and eruption. We performed hydrogen isotope exchange experiment of water in silica glass for fundamental understanding of the hydrogen isotope exchange in silicate glass. The obtained profiles of H and D can be fitted with an error function, suggesting the diffusion-controlled hydrogen isotope exchange reaction. The isotopic exchange rate of D with H in silica glass is 1.5-2 times larger than that of H with D in the glass, implying a large isotope fractionation effect.
X-ray absorption near edge structure (XANES) analyses on Fe in single plagioclase grain was performed to discuss the relationship between Fe valence state and the exsolution of magnetite in plagioclase. The current study found that averaged Fe valence state of plagioclase collected from three different gabbro body decreased with increasing the amount of exsolution of magnetite.
We report preliminary analytical results of 206Pb-based lead isotope ratios of olivine-hosted melt inclusions in basalt lavas from Rarotonga Island, Cook-Austral Islands in Southern Pacific, using femtosecond laser ablation-multiple Faraday collector-inductively coupled plasma-mass spectrometry. This method enables high-precision analysis of Pb isotopes from low-Pb (<10 ppm) melt inclusions with a crater size of ~30 μm diameter and depth. The small crater size allows for further analysis of major and trace elements from the same melt inclusions.
The V/Sc and Zn/Fe ratios of the harzburgite in the mantle section of the Oman ophiolite show a good negative and positive correlation with delta logfO2 (FMQ) of each peridotite. The amount of REE in these peridotite rocks tends to be higher as the amount of La is higher and the amount of Yb is lower in the more oxidative sample. This relationship may reflect the result of flux melting in the mantle wedge. H2O-rich fluid originally flowed into the reductive mantle wedge from the subducted slab, causing flux melting and recording the oxidative state in the residual harzburgite.
Structural state of plagioclase within volcanic ash erupted from Sakurajima volcano was preliminary investigated for monitoring the volcanic activity. Samples were collected for about 2 years and 2 months from May 2013 at the Higashi-Sakurajima junior high school located about 4 km southwest of Showa crater of Sakurajima volcano. Powder XRD data for the plagioclase suggests gradual change in degree of order in the crystal structure during this period.
Ca-rich plagioclase (An > 90 %) larger than 10 mm, which is called anorthite megacryst, occurs commonly from basalt - andesite in Japanese Island arc. We investigated anorthite megacrysts from Ogi Peninsula, Sado island and found melt inclusions rich in volatile components such as Cl and S. Electron microprobe analysis show that SiO2 and Cl in these melt inclusions range 48 - 56% and 0.01 - 0.12%, respectively. Our results indicate that anorthite megacrysts from Ogi Peninsula grew in volatile-rich environment caused by release of Cl and S from subducting slab.
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.
The mineral composition of mantle peridotite was evaluated in Wadi Tayin mantle section of southern Oman ophiolite. We revel the spatial distribution of spinel Cr# [=Cr/(Cr+Al) atomic ratio] of harzburgite and dunite. The Ce/Yb ratio of Cpx trace element suggests that flux-melting of the mantle peridotite. The dunite with high Cr# (=0.68) spinel shows the negative anomaly in the HFS elements such as Nb and Ta in the C1 chondrite-normalized pattern. This may indicate that a dehydrated fluid from the subducted slab reacted with harzburgite to produce the dunite described above.
In Akarui Point, Lützow-Holm Complex, East Antarctica, rare kornerupine-plagioclase-corundum (Krn-Pl-Crn) lens is developed in a Hb-gneiss or between an amphibolite lens and the Hb-gneiss. Boron isotope composition of Krn, prograde and secondary tourmalines are determined by SIMS. The d11B values of the prograde tourmaline support that fluids related to the oceanic plate subduction may have been responsible for the introduction of B into the Krn-Pl-Crn lens.
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.
A granite–porphyry system, associated with hydrothermal activity and mineralization, provides a suitable natural analog for studying a deep-seated geothermal reservoir where stockwork fracture systems are created in the presence of supercritical geothermal fluids.
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.
Oxygen isotopic ratios are examined for metapelitic rocks in the Tanohata contact metamorphic aureole. The whole rock oxygen isotopic ratios of metapelitic rocks suggest the absence of external fluid infiltration in the side wall of the Tanohata pluton. Those in the roof pendant area are generally low, suggesting a possible involvement of external fluid from the pluton in contact metamorphism of this part of the aureole.
Hydrogen site geometry in hydrous minerals is important for understanding their water storage mechanism. Diffusion dynamics of hydrogen in these minerals is important for understanding their hydration processes. Here we summarize our recent neutron diffraction and quasielastic scattering results obtained at J-PARC MLF and also at another neutron source, where high-resolution crystallography of hydrogen and its diffusion dynamics were successfully analyzed for various types of hydrous minerals.
Decompression of crustal fluid associated with formation of ore veins. However, there is no study on silica precipitation under high-supersaturated condition. We conducted silica-precipitation experiments by flashing of silica supersaturated conditions. Silica precipitates occurred in amorphous silica. Silica concentration of the solution after flashing from liquid to vapor phase decreased to solubility of saturated vapor pressure, but flashing from SCF does not decrease significantly. These results indicate that phase change is important for silica precipitation.
Consistency limits in clay-water system are important parameters in soil mechanics. Montmorillonite has higher liquid limit value comparing to the other clay minerals and can keep plastic state under higher water contents. Rheological analysis and pulverization experiments on montmorillonite-water system are conducted. Close relationships among water contents, viscosity, and degree of amorphization during pulverization are clarified and its significance on geological phenomena is discussed.
Microstructural observation of Pinatubo peridotite xenoliths erupted from Pinatubo volcano in 1991. The deformation conditions in the upper mantle beneath Pinatubo volcano were estimated. The results were hydrous condition.
Hydrothermal alteration experiments in sulfuric acid solution with graphite and CO2 atmosphere were carried out. Fayalite particles were dissolved to the fluid, and leached layers were formed on the particle surface. In the reaction layer, a fibrous structure was observed depending on crystal orientation of fayalite. With pH1 sulfuric acid solution, goethite occurs regardless of presence of graphite. Graphite can inhibit ferric iron oxides in moderate sulfuric acid solution.
Detailed outcrop observation of the Hirao limestone located in Kitakyushu city was conducted. There is clear trend that the grain size of the calcite coarsened by the contact metamorphism becomes larger as it is closer to the Hirao granodiorite which is considered as the heat source. In the northern part of surveyed area, there is a local grain growth region that does not match the surrounding grain size distribution and many veins consisting of coarse calcite are present. In this area, it is thought that local coarsening occurred due to the influence of crustal fluid.
Although chemical reactions between basalt and seawater might influence the elemental distribution around the globe, it remains unknown whether or not porous fractions filled with secondary minerals. In this study, clay characterizations were conducted for two basaltic core samples. X-ray diffraction pattern analysis of clay fractions collected from powdered core samples revealed the present of Fe-rich smectite, nontronite, in both samples. By transmission electron microscopy, it was revealed that nontronite was likely formed by weathering.
EBSD measurements using talc schists collected from the boundary between pelitic schist and antigorite serpentinite show talc CPO show the strong concentration of the normal direction of the (001) plane that is normal to the foliation. The strongest concentrations of the  and  directions of talc show the direction parallel to the lineation, and the direction parallel to the foliation and normal to the lineation, respectively.
We report paregenesis and chemical compositions of Mg-Fe mica (biotite/aspidolite) and associated minerals in gabbroic rocks recovered from Atlantis Bank during IODP Expedition 360. Many Mg-Fe mica are deficient in Na and K, showing a mixing trend with chlorite. In addition, they show an interference color lower than that of typical biotite, suggesting submicroscopic interlayering with chlorite. A close association of the Mg-Fe mica with felsic veins suggests that metasomatism by siliceous fluids pervasively took place in the lower crustal gabbroic rocks of Atlantis Bank.
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.
Photon Factory (PF) has been used in various fields of mineralogical science for 35 years after the first photon came out. At high-pressure beamlines, new measurement systems have been developed for both static- and shock-compression experiments. Other beamlines have been widely used for the analyses of natural and artificial minerals and PF is now planning to construct a new beamline for the scanning transmission X-ray microscopy.
Neutron is a unique particle that interacts with materials in a different way than X-rays. Therefore, it is widely used to investigate properties of materials that are not observable with X-rays, such as position and amount of hydrogen in hydrous minerals and its vibration/diffusion properties. In this talk, we introduce results obtained in Materials and Life Science Experimental Facility in J-PARC.
Strucuture variation of boehmite with increasing pressure was observed by in-situ x-ray and neutron diffraction. We found peculiar features that only specific diffraction peaks broadened or splitted. These phenomena could be explained by pressure-induced stacking disorder of layer displacement of AlO6layer.
High-pressure and temperature neutron diffraction on the albite (NaAlSi3O8) melt has been performed up to 2 GPa. The structure factors from neutron diffraction were successfully derived over 25 Å-1, which is much wider Q-region comparing with the one from X-ray diffraction. The first peak in the total radial distribution function, which corresponds to Si-O and Al-O correlation, appeared as single peak at 1.64 Å, suggesting that the coordination number of Al is almost 4 at least in this pressure interval.
We conducted the high pressure experiments up to 6 GPa, using X-ray and neutron to analyze the structural changes of basaltic glass with increasing pressure. We obtained structure factor and radial distribution function, which indicate that the shrinkage of T-O-T bond angle causes the intermediate range structure arrangement (T = Si4+, Al3+). Moreover, structure factor of neutron diffraction suggests that compression induces intermediate range disordering and short range ordering.
High-temperature and high-pressure experiments were performed to investigate the formation conditions of diamond in the C-H-O system under the mantle conditions of giant icy planets such as Neptune and Uranus. The results show that diamond formation through the dissociation of methane occurs above 1500 K between 2 and 90 GPa. This suggests that diamond potentially forms from methane in the icy mantle of Neptune and Uranus.
X-ray tomography is the nondestructive method for obtaining 3D structures of objects. By using monochromatized synchrotron radiation beams with high flux densities and coherence enable us to obtain images with quantitative absorption and phase contrasts. This method has applied to meteorites and cosmic dust and samples returned by space crafts. Recent results particularly on carbonaceous chondrites and development of new techniques for Hayabusa-2 and OSIRIS-REx samples will be presented.
We studied the application of discrimination analysis and logistic regression for the identification of synthetic or natural amethyst and ruby, and Paraiba-type tourmaline. We found logistic regression shows better error rate than discriminant analysis for identification of natural or synthetic amethyst and ruby. Discriminant analysis cannot identify the origin of Paraiba-type tourmaline among Brazil, Mozambique and Nigeria but logistic regression can identify 2-localities among them.
The 0.066 ct Fancy Vivid Yellow HPHT synthetic diamond tested our Laboratory showed B centre and B2 centre (platelets) in addition to C and A centres in FTIR analysis. The nitrogen concentration reached to 700 ppm in total, and a C-H related peak was detected at 3107 cm-1. We concluded This stone is a HPHT synthetic diamond produced using a Co solvent and then irradiated and HPHT treated after the growth, i.e., a HIH (HPHT growth/ Irradiation/ HPHT treatment) synthetic diamond.
Moganite is main constituent mineral of chalcedony, and is intergrowth with quartz crystals at the nanometer scale. Textures of chalcedony samples from several localities in Japan were observed by electron and optical microscopies, and measured its moganite contents by Raman spectroscopy. We present the results about variety of Raman spectra with texture.
Zeta-factor method was applied for (S)TEM-EDXS quantitative analysis of variou materials; oxides, sulfides and silicate minerals. The quantitative results wre in good agreement for all specimns including oxgen and light elements comosition. Zeta-factor method is the effective method for the quantitative analysis using (S)TEM-EDS, although it require attention to influence of heavy elements L-line on Oxygen K-line.
An improved pseudo-fixed dead time system is developed and implemented for long-term stage accurate X-ray counting in electron probe microanalysis (EPMA). Designed system is composed of three one-shot pulse generators. This system provides approximately 2 us non-extendable dead time when the original dead time is between 0.8 - 2.0 us and the X-ray intensity is <200kcps.
To reliable peak separation of Mössbauer quadrupole doublet peaks of single crystal, crystallographic orientation of electric field gradient vector of Fe site should be known. In this study, Mössbauer spectra of crystallographically oriented thin sections of aegirine were measured to determine the electric field gradient vector of M1 site in aegirine.
The precipitates within olivine phenocrysts in scorias from Kasayama volcano, Kami-Kometsuka scoria cone and Otsukayama scoria cones were investigated to clarify high temperature oxidation process of olivine phenocrysts in scoria. Electron microprobe analysis and Raman spectroscopy were used for mineral identification and electron back scattered diffraction to determine the crystallographic orientation of the precipitate minerals and host olivine phenocrysts. Oxidation process of olivine in scoria is generalized.
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.
The lamellae textures in the iridescent garnet from Tenkawa village, Nara prefecture, Japan were observed by means of a field emission scanning electron microprobe. Wavy lamellae are a moire texture caused by periodic thickness change of fine lamellae, as predicted by Hirai and Nakazawa (1986). The features of fine lamellae are suggested that fine lamellae texture is growth band, and reflect a shape of the growth surface when the garnet crystal was growing.
Microprobe analyses were carried out on wadalites in a skarn from Tadano, Fukushima Prefecture, Japan. The wadalite has slightly heterogeneous compositions. The compositional variations suggest the substitutions (Al,Fe3+) + vacancy = Si + Cl and 2(Al,Fe3+) = Mg + (Si,Ti).
In this study, we researched the mineralogical properties of ortho-type PS at Shimotake. Shimotake is the most ortho-type polygonal serpentine rich locality in Kyushu Kurosegawa belt. Ortho-type polygonal serpentine occurs as yellowish green vein between foliate serpentinites. The vein was chemically homogeneous, with minor Al (0.03-0.05 apfu) and Fe (0.05-0.12 apfu) components. The host serpentinite was more Al rich than the vein, which had bastite textures. The diameter of ortho-type PS was 200-300 nm, with 15 sectors.
Clays composed of fraipontite, allophane, and halloysite occur from the oxidized zone in the Kitabira mine, Yamaguchi Prefecture. In XRD experiments, the values of reflection of clay containing coarse fraipontite are 001 = 7.13 Å, and 060 = 1.54 Å, and the unit cell parameters are a = 5.34 (1) Å, b = 9.24 (1) Å, c = 14.32 (2) Å, ß = 93.7 (1) °, V = 705 (1) Å3. The chemical composition of fraipontite by EPMA is Ca0.05(Zn0.65Cu0.11Al1.59)(Si1.51Al0.49)As0.01P0.01O5(OH)4, and a correction for halloysite and allophane impurities leads to ideal fomula (Zn2Al)(SiAl)O5(OH)4.
Gadolinite supergroup was newly defined and approved by the CNMNC IMA. It consists of mineral species having the monoclinic P21/c crystal structure with the general chemical formula A2MQ2T2O8j2. The gadolinite supergroup is divided into two groups; gadolinite group (silicates) and herderite group (phosphates and arsenates). In the gadolinite group there are 2 subgroups; gadolinite and datolite subgroups. The herderite group is divided into 2 subgroups; the herderite drugmanite subgroups. “Bakerite” is discredited as mineral species.
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.
An unknown mineral has been discovered from the specimens obtained from the Fudotaki-deposit in Hitachi Mine, Ibaraki Prefecture, Japan. Synchrotron Single-crystal X-ray diffraction experiments were conducted to determine its crystal structure. The results of chemical and structure analyses indicate that this unknown mineral belongs to the tetradymite group.
Slickenside is the microstructure which is caused by faulting and has glossy. The slickenside is often found on the fault plane. The formation process of the slickenside is important to understand the faulting with the slickenside. This investigation reports the detail of the formation of the slickenside based on the characterization of the slickensides collected from the fields and the experiments for reproducing the slickensides, the characterization of the microstructure of the recovery samples.