We investigated the phase transition between coesite and stishovite in SiO2 at high pressures and high temperatures using the multi-anvil press and the synchrotron X-ray diffraction technique. The transition pressure determined in our study was in general agreement with that observed in previous high-pressure experiments and heat capacity measurements.
Phase relations of MgCr2O4.Mg2SiO4 were examined at 10-27 GPa and 1600 oC. Olivine and Mg-chromite are satble up to 12.5 GPa. Garnet, Mg2Cr2O5 phase with modified-ludwigite structure and anhydrous phase B become stable at 15-18 GPa. Ringwoodite coexists with calcium-ferrite type MgCr2O4 at 20-22 GPa. Bridgmanite, periclase and calcium-ferrite phase are stable above 24 GPa. The results suggest that origin of ultra-high pressure chromitites is restricted in the upper mantle conditions.
To re-examine the MgSiO3 akimotoite-bridgmanite phase boundary by thermodynamic approach, we re-determined drop-solution enthalpy of MgSiO3 akimotoite by performing drop-solution calorimetry using the lead borate solvent at 705 C. Drop solution enthalpy of MgSiO3 akimotoite was determined to be 57.67 +/- 2.16 kJ/mol from the average of four data. This value gives a consistent phase transition enthalpy between akimotoite and bridgmanite with those used in previous thermodynamic calculations.
Optical transparency and hardness of nano-polycrystalline garnet (NPG) with grain sizes less than 100 nm synthesized in multianvil apparatus have been measured. The NPGs are found to be as transparent as the corresponding single crystals and harder than the single crystals.
Hydrogarnet, katoite, was investigated with HP single-crystal XRD and HP and HT neutron diffraction analyses. Consequently, with the phase transformation, the space group of katoite is changed from Ia-3d to I-43d at about 5 GPa. in addition, katoite is decomposed into corundum and portlandite at 8 GPa and 900 oC.
We observed the decomposition of bridgmanite (MgSiO3) to periclase (MgO) and stishovite (SiO2) in the presence of methane-rich C-H-O fluid under high pressure and temperature corresponding to the mantle transition to lower mantle conditions. This suggests that the stability of silicate mantle minerals is largely influenced by the coexisting reducing fluids and the simple thermodynamic phase equilibrium in dry system make no sense in such environments.
Bridgmanite is a major constituent mineral in the lower mantle, and it is important to clarify the sound velocity to elucidate the mineral assembly (composition) of the lower mantle. In this study, as one of the physical property measurements of various Al-bearing bridgmanites, the sound velocity measurement under high temperature and high pressure was carried out by attempting a high-quality sintered sample synthesis. The results will be reported.
In this study, we try to determine stability field and substitution mechanism of Al-bearing superhydrous phaseB (SuB), which is stable in the upper part of lower mantle pressure. Water content and stability field of SuB is increased and expanded to higher temperature along with the incorporation of Al. Therefore, there is a possibility that Al-bearing SuB in the subducted slab is a host of water in the upper part of lower mantle.
To investigate the relation of change in compression behavious at high-pressure and hydrogen-bond symmetrization in δ-AlOOH, we conducted high-pressure neutron diffraction experiment. The results indicate the phase transitions occur at around 8 GPa in δ-AlOOH and at 12.1 GPa in δ-AlOOD.
Recently, we have reported the existence of new DHMS in lower mantle pressure conditions above about 45 GPa. This phase has MgSiO4H2 chemical composition and named as phase H. In this study, we further extends our exploration of this hydrous phase, such as the spin transition of Fe and the possibility of further phase transition of FeOOH using first principles calculation techniques and discuss the possible effects of this hydrous phase at the bottom of lower mantle.
We made in situ-Xray diffraction experiments of the stability of 10Å phase and 3.65 Å phase. 3.65 Å phase can be a water carrier in the cold slabs.Hydrous ringwoodite and phase Egg as inclusions in diamond strongly suggeststhe wet transition zone. Water may be transported as far as the bottom of the lower mantle by phase H-δ solid solution. The dehydration and separation of fluids or hydrous magmas at the base of the lower mantle can produced the hydration zone at the base of the lower mantle.
We determined the densities of FeS sulfide melts at 3.5 GPa and 1373-1773 K by means of X-ray absorption technique. Densities of liquid FeS is 8-10% lower than those determined by previous studies (Nishida et al., 2011; Chen et al., 2014). Our new data can be connected to 1 atm density data without the assumption that the structural change of FeS associated with rapid increase of its density occurs up to 0.5 GPa. We will discuss the structure of liquid FeS at high pressures.
Earth’s inner core consists of mainly iron-nickel alloy. Therefore, the physical properties of Fe-Ni alloy can provide significant knowledge about the core. Here, we report the compressional sound velocity (VP) of Fe-Ni alloy up to 162 GPa and 2300 K based on a combination of the laser-heated diamond anvil cell and inelastic X-ray scattering measurements. The pressure and temperature dependence suggest both the density and VP of Fe-Ni alloy are higher than PREM.
Self-diffusion of ice VII at the pressure-temperature range of 5.5 – 17 GPa and 400 – 425 K has been studied using micro Raman spectroscopy, diamond anvil cell (DAC) and isotope tracers: D2O and H218O. The pressure dependence of the diffusion coefficient of hydrogen has a peak at 11 GPa following increasing by over 2 orders of magnitude from the value at 6 GPa. The oxygen diffusion experiment revealed that the hydrogen diffusion is much faster than the oxygen diffusion.
Finite element method (FEM) is a useful technique to solve anisotropic or complicated shape system. I would introduce several examples of FEM analysis. Further, I would propose several idea how to utilize FEM in Mineral Physics.
A new cooling system using Peltier device is presented for low-temperature diamond anvil cell (DAC) instrument. It consists of Peltier devices and heat sinks where a cooled ethylene glycol-water flows by a chiller. Current are applied to the Peltier devices by a programmable DC power supply. The temperature of a sample can be controlled with a PID method. Using this system, we succeeded to cool the sample up to −60 ºC with very low-temperature fluctuation within 0.1ºC.
We conducted shock recovery experiment of silica gel for model of comet and investigated structural changes by solid 1H→29SiNMR(CP/MAS), TG-DTA and Raman spectroscopy. The shock experiments were performed at 20 GPa under cryogenic condition (100 K) and ambient condition (293 K). As a result, it was revealed that silica gel began to has variety of bonding state at 20 GPa and the structural change under cryogenic condition is a little smaller than ambient condition.
We developed an AE monitoring system for high-pressure reaction-deformation processes combined with Deformation-DIA apparatus and synchrotron monochromatic X-ray. We applied this technique to investigate shear instability during antigorite dehydration in pure shear up to ~8 GPa and ~780°C. Almost no AEs were detected within the antigorite samples during deformation and syndeformational dehydration although localized deformation textures were observed in recovered samples.
Mica and clay minerals can control the frictional strength and sliding behavior of faults. Here we aimed to understand the frictional properties of these minerals based on their crystal structures and interatomic interaction. In this study, we try to explain the results of experimental shear test by the first-principles calculations based on the density functional theory.
The present study elucidates the physico-chemical properties of REPO4 and the initial processes of mineralization at room temperature. REPO4 was classified to three groups, and the structure of stable phase can vary depending on the experimental parameter. Light RE3+ were preferentially distributed with tetrad effects into nano-crystalline with some heterogeneity in composition. Consequently, nano-scale mineralization of REPO4 can constrain the behavior of RE3+ in sub-surface environment.
Phosphate in EPS inhibits CeNPs aggregation by changing their surface charge. Saccharides in EPS possibility have an influence of inhibiting aggregation by increasing phosphate adsorption. Amino acids in EPS can neutralized the negative charges by their dipolar property. As a consequence, each inorganic and organic molecules in EPS has its specific effect on the mechanisms of inhibiting nanoparticles aggregation.
It is necessary to investigate the fate and the dynamic state of Cs released from the Fukushima Daiichi nuclear power plant. We conducted Cs-adsorption/desorption experiments for weathered biotite, zeolite and the other various clay minerals. The desorption experiments with low-concentrated Cs indicated that the weathered biotite fixed Cs very rigidly, whereas Cs sorbed in zeolite was easily eluted by ion-exchange.
Recently existence of radiocesium (Cs)-containing microparticles has been reported in the field (aerosols, soils, plants, and so on) of Kanto area, which were definitely released from Fukushima nuclear plants. These microparticles are 0.5 - 2 mm in diameter and substantially silicate glass containing Fe, Zn, Cs, Rb, K, Cl and Sn as major elements. We tried synthesis of bulk glass with similar compositions using a conventional glass synthetic technique.
Magnetic enhancement in Chinese loess is thought to be caused by formations of magnetic grains during pedogenesis. However, there is no mineralogical study confirming it. Here we show the results of XRD and SEM/TEM study of magnetic grains in Chinese loess. Magnetic grains (hematite and magnetite) exist mainly as nano inclusions in muscovite and occupy < 1% of the total loess volume. The magnetic grains were probably formed in situ during pedogenesis and responsible for the magnetic enhancement.
The present study aimed to clarify the behavior of heavy metals on lichen-slag interactions. The slag are weathered by hypha penetration and acids of lichens in addition to inorganic weathering and releases heavy metals. The dissolved Cu and Zn are contained in the hypha cells, while Fe is concentrated on the hyphae as Fe-hydroxides with As in the lichen thallus. The Fe-hydroxides also contain positively charged metals such as Zn, and therefore they could be a mixture with organic matters.
Change characteristics of Earth materials (minerals) are discussed by carbon- and mercury-bearing materials with the FE-ASEM observation. It is obtained in this study that cinnabar and calcite in composition are gradually replaced between heavy ions (Hg, Ca) and volatiles (S, C).
We observed the interface between cyanobacterial cell and olivine using transmission electron microscopy (TEM) and scanning transmission X-ray microscopy (STXM) to verify the hypothesis about mechanism proposed by Bundeleva et al. (2014). The results obtained by TEM and STXM mearsurements imply that the EPS is undersaturated with respect to carbonate minerals.
Degradation of concrete has not been studied until the latest. We began to investigate the basic characteristics of concrete and cement. One of reasons about the degradation is that calcium carbonate is created from calcium materials and carbon dioxide. We investigate the reaction of calcium hydroxide and carbon dioxide at around room temperature. Calcium carbonate was created from calcium hydroxide and carbon dioxide.
We have recently started an attempt to visualize the distribution of pH and Ca concentration around CaCO3 crystals which inorganically grows or dissolves, by applying the method used for the research on the biogenic calcification of foraminifers.The pH change near a dissolved calcite and aragonite surface has been succeeded, which may provide new insights into both inorganic and biogenic formation mechanism of CaCO3.
Monohydrocalcite (MHC) is hydrous calcium carbonate of which composition is CaCO3. H2O. Based on the crystal structure of MHC, Mg is incompatible to structure of MHC. However, it is well recognized that the significant amount of Mg is associated with MHC. This study examines the chemical states of Mg associated with MHC by means of synchrotron based XANES analyses of synthesized MHC with different Mg contents.
Flank-method Lβ/Lα by field-emission electron microanalyzer and averaged Fe3+/ΣFe for fresh or weathered biotites in Abukuma granite was well correlated. This promote an understanding from small area analysis of iron valence at this region.
Iron-reducing bacteria can reduce iron in ferrihydrite, and cause secondary mineralization. Bacterial iron reduction may affect remobilization of contaminant, whereas newly formed minerals may retain it. We investigated the fate of arsenic adsorbed on two-line ferrifydrite during bacterial-iron reduction. Mineralization processes varied depending on whether ferrihydrite initially adsorbs arsenate or arsenite.
To understand the kinetic aspect of cesium (Cs) sorption behavior, the diffusion property of Cs at interlayer spaces of hydrobiotite was examined using single crystal grains, 137Cs tracer and imaging-plate autoradiography. Based on Cs distribution inside grains, apparent diffusion coefficients of Cs at 25, 44 ºC were estimated 0.5, 2.0×10-13 m2s-1, respectively.
Extraterrestrial materials reveal solids mixed with injected ions which can be formed secondary water molecule after heating process, where author can be obtained after heating of Allende carbonaceous meteorite. Life body with two systems of starting and ending sites is required beyond Earth world.
Cr, Mn, Fe and Ni K-edge XANES and EXAFS spectra were measured on K-T boundary clays from Stevns Klint in Denmark. According to XANES spectra and EXAFS analyses, the local structures of Cr, Fe and Ni in K-T boundary clays is similar to Cr2O3, FeOOH and Ni(OH)2, respectively. On the other hands, Mn has a local structure like MnCO3 with divalent state.
This study performed micro X-ray absorption near edge stducture (μ-XANES) analysis on V and Fe in both inclusion and groundmass glasses of a Martian meteorite (Yamato 980459) to estimate the fO2 condition of Martian magma.
Nakhlites and chassignites are cumulate rocks formed near the Martian surface. The mesostasis abundance of NWA 10153 nakhlite is high, but olivine gives 100 deg./yr slow cooling. This implies that nakhlites might have been originated from multiple sills or lava flows. Chassignites are cumulate dunites with distinct olivine compositions, but all show similar cooling rates (30-100 deg./yr). These cooling rates are overlapped with those of nakhlites, suggesting origins from distinct igneous bodies.
Reddish olivine similar to brown olivine in Martian meteorites is reported in lunar meteorite. Our observation of such reddish olivine reveals that they formed by a similar way to that of brown olivine in Martian meteorites because of the presence of similar areas with low crystallinity including iron nano-particles (hematite). Since such nano-particles change reflectance spectra of olivine, we may not notice its presence and need to pay attention to this possibility on any large bodies.
We have carried out heating experiments of Tagish Lake and Murchison carbonaceous chondrites at temperatures of 400, 600, and 900C for 50 hours in vacuum and at IW buffer. Reflectance spectra of the Mars moons are relatively similar to those of Tagish Lake and Murchison samples that were heated at 400 or 600C in visible and near infrared range, but the experimental products fail to reproduce 0.65 micron absorption observed in Phobos and Deimos spectra.
Oxidation states of Fe in olivine from two pallasites were determined using Mössbauer spectroscopy. The Fo contents of olivine from Quijingue and Brahin were 87 and 89 mol%, respectively. The carefully separated olivine samples were subsidized to the analysis of oxidation states. To evaluate possible contamination of Fe, both XRD and the morphological observation using FE-EPMA were made. Our experiments demonstrated the presence of ferric iron in two olivine samples analyzed in this study.
Most ureilites are thought to be partial melt residues but some of augite-bearing ureilites can be interpreted as cumulates. In this study, we studied new Hughes 009 type ureilite NWA 3222 and found that it shares many mineralogical characteristics with other these types. In addition, augites in NWA 3222 show remarkable chemical zoning and we detected similar subtle zonation in FRO 90054. These compositional similarity suggest that they were derived from the same lithologic unit on UPB.
We report petrology and geochemistry of eucrite-like achondrites, Dho 007 and EET 92023. These achondrites contain significant amount of siderophile elements. These rocks experienced relatively rapid cooling at high temperature and slow cooling at low temperatures. The geochemical and petrologic evidence indicates that these achondrites experienced a large impact event shortly after crust formation.
We studied silica polymorphs in Y-75011 eucrite and discuss their formation conditions. There are 2 types of silica polymorphs in basaltic clast, aggregate of quartz and cristobalite and single quartz. Aggregates were formed either by hydrothermal activity or crystallization from Si-rich magma with water or Na. Single quartz is likely to have crystallized from Si-rich melt. If water was involved in the formation of this basaltic clast, it suggests a wide occurrence of water in the Vesta crust.
We have been investigating silica minerals in eucrites to understand their petrogenetic history. We found quartz in the four eucrite using cathodoluminescence (CL) technique. We carried out petrologic chemical, Raman and CL analysis to clarify the origin of quartz in four eucrite. The results imply that the quartz grains in the eucrites formed by hydrothermal alteration.
Lodranite meteorites are one group of primitive achondrite. We examined a fabric of Y-791491 lodranite. Results show that Y-791491 have olivine fabric with concentration of b-axis and girdle of other axes. Equilibration temperature of Y-791491 obtained by two-pyroxene thermometry is about 1050°C. On the basis of olivine shock feature, Y-791491 suffered shock event. All these lines of mineralogical indicate that fabric of Y-791491 formed by solid-state deformation process with partial melt.
We observed and analyzed four meteorites (Reid 013, Miller Range 090206/090340/090405). Reid 013 is a brachinite and MILs are brachinite-like meteorites. We found b axis concentration of crystallographic preferred orientation (CPO) in olivine from the four meteorites. This indicates that these meteorites were formed as cumulate rocks. On the other hand, other brachinites (EET 99407 and ALH 84025) shows c axis concentration of CPO. We continue to study what makes this difference in brachinite.
Almahata Sitta is a polymict breccia, consisting of many kinds of clasts. Here we present our mineralogical and petrological results on an EL3 clast, MS-177-1. We compare the results with an EL3 chondrite, Asuka (A) 881314, and discuss the unusual thermal history of this clast.
Four CB type carbonaceous chondrites, Gujba, Bencubbin, NWA 4025 and NWA 1814 were investigated to describe high-pressure polymorphs formed in their melting textures. Many kinds of high-pressure polymorphs were identified from all samples, implying that the parent-body of CB type carbonaceous chondrite was heavily shocked.
We performed irradiation experimenets to simulate irradiation on the asteroid Itokawa. The fluences correspond to 10, 100, and 1000-year irradiation durations. The surface modification observed has a two-layer structure: amorphous surface layer (20-40 nm thick) and underlain partially amorphized layer (20-40 nm thick). This stucture is common to the Itokawa grains. Blistering is more conspicuous in the simulants than that in the Itokawa grains.
Temperatures of CPxs obtained by the revised Lindsley's method agree well with temperatures obtained from OPxs. Ca-partitioning between clino- and orthopyroxenes is then thought to be equilibrated in types 5 to 7 ordinary chondrites. The temperatures for Tuxtuac (LL5), Dhurmsala (LL6), NWA 2029 (LL6/7) and Dho 011 (LL7) are 767-793, 818-835, 872-892 and 917-936 °C, rspectively, suggesting that chondrites of higher petrographic types show higher equilibrium temperatures of pyroxenes.