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Evidence for phase transitions in mineral inclusions in superdeep diamonds of alluvial placers in the Sao Luiz River deposits (Brazil) is obtained by the electron backscatter diffraction technique. It has been shown that the crystal structure of superdeep diamonds is significantly deformed around inclusions of MgSi-, CaSi-, and CaTiSi-perovskites, SiO2 (stishovite?), and Mg2SiO4 (ringwoodite?). On the contrary, significant deformations around inclusions of olivine, ferropericlase, and majoritic garnet are not detected. The absence of deformation near these minerals reveals the lack of phase transitions with dramatic volume changes. The present study suggests that the formation of superdeep diamonds proceeds at different levels of the sublithospheric mantle, transition zone, and lower mantle. © 2015, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

We developed a new high pressure cell which allows us to perform accurate dielectric measurements above 3 GPa. The developed cell is based on Bridgman type opposed anvil cells with electrodes immersed into holes in the anvils in order to make the electrode area constant under compression. As a feasibility experiment, dielectric measurements for H2O were conducted up to 6.6 GPa and obtained dielectric constants are well consistent with previous studies.

Frictional heat generated during earthquakes provides insight into the coseismic fault strength. To detect increased heating associated with faulting at seismic slip rates, we analyzed the Raman spectra of carbonaceous material in natural and experimental pseudotachylytes derived from argillite. The results indicate that the increased carbonization in pseudotachylytes relative to the host rocks could be detected when the ambient temperature is lower than 280°C. This increased carbonization can occur in ~4–16 s and is preserved even after alteration of pseudotachylytes. The comparison between experiment and Raman data demonstrated that there is a correlation between the average shear stress and the Raman spectra in pseudotachylytes. The average coseismic shear stress estimated from the correlation was 1.8 MPa. The resulting apparent friction coefficient under hydrostatic conditions at depths of 4–6 km was ~0.03–0.05. Raman analysis of carbonaceous material-bearing pseudotachylytes will be useful for estimation of coseismic fault strength.

Young basaltic knolls have been discovered on the old oceanic lithosphere, namely petit-spot volcanoes. Based on their geochemical signatures, they have presumably originated from partial melts in the asthenosphere. However, there is no direct information on the depth provenance of petit-spot formation. Here we report new geothermobarometric data of rare mantle xenoliths discovered from petit-spot lavas exhibiting a geotherm much hotter than expected for the ca. 140 Ma seafloor on which petit-spots were formed. Such an anomalously hot geotherm indicates that melt porosity around the lithosphere-asthenosphere boundary (LAB) must be as high as a few percent. Such high melt porosity would be possible by continuous melt replenishment. Excess pressure induced by the outer-rise topography enables horizontal melt migration along the LAB and sustains a continuous melt supply to petit-spot magmatism. Given the general age-depth relationship of ocean basins, a melt-rich boundary region could also be a global feature.

Doping large amounts of a incompatible element into calcite, a polymorph of CaCO3, was achieved by pressurizing amorphous calcium carbonate (ACC) containing a dopant. Strontium-doped ACC samples were prepared from supersaturated solutions. ACC was transformed to calcite at 0.8 GPa and 25 °C. The lattice volume of calcite obtained by pressurizing ACC increased monotonically up to 372.5 A3 (1.3% increase from a Sr-free sample) with increasing Sr content in ACC up to 0.15 in Sr/(Sr + Ca). For comparison, the lattice volumes of calcite samples precipitated from supersaturated CaCO3 solution containing Sr were obtained, but the lattice volume of calcite precipitated from supersaturated solutions showed no noteworthy increase. Results of this study indicate that pressure-induced crystallization is an efficient pathway to dope incompatible elements into crystals.

In situ neutron diffraction measurements combined with the pulsed neutron source at the Japan Proton Accelerator Research Complex (J-PARC) were conducted on high-pressure polymorphs of deuterated portlandite (Ca(OD) 2 ) using a Paris–Edinburgh cell and a multi-anvil press. The atomic positions including hydrogen for the unquenchable high-pressure phase at room temperature (phase II′) were first clarified. The bent hydrogen bonds under high pressure were consistent with results from Raman spectroscopy. The structure of the high-pressure and high-temperature phase (Phase II) was concordant with that observed previously by another group for a recovered sample. The observations elucidate the phase transition mechanism among the polymorphs, which involves the sliding of CaO polyhedral layers, position modulations of Ca atoms, and recombination of Ca–O bonds accompanied by the reorientation of hydrogen to form more stable hydrogen bonds.

Species dissolved in H 2 fluid were investigated in a SiO 2 –H 2 system. Raman and infrared (IR) spectra were measured at high pressure and room temperature after heating experiments were conducted at two pressure and temperature conditions: 2.0 GPa, 1700 K and 3.0 GPa, 1500 K. With the dissolution of quartz, a SiH vibration mode assignable to SiH 4 was detected from Raman spectra of the fluid phase. Furthermore, an OH vibration mode was observed at 3260 cm −1 from the IR spectra at 3.0 GPa. With decreasing pressure, the OH vibration frequencies observed between 3.0 and 2.1 GPa correspond to that of ice VII, and those observed at 1.4 and 1.1 GPa correspond to that of ice VI. These results indicate that the chemical reaction between dissolved SiO 2 components and H 2 fluid caused the formation of H 2 O and SiH 4 , which was contrastive to that observed in SiO 2 –H 2 O fluid. Results imply that a part of H 2 is oxidized to form H 2 O when SiO 2 components of mantle minerals dissolve in H 2 fluid, even in an iron-free system.

861 The Udachnaya kimberlite pipe in the Daldyn kimberlite field (Daldyn–Alakit region) of the central part of the Yakutian diamond province is the largest diamond deposit in Russia and one of the largest in the world. The pipe consists of two conjugate bodies: Udachnaya East and Udachnaya West. As is evident from the U–Pb dating of perovskites from kimberlites, the ages of the Udachnaya pipe formation are 367 ± 3 and 367 ± 5 Ma (Udachnaya East); 361 ± 4 and 353 ± 5 Ma (Udachnaya West) [1]. Deep seated xenoliths of mantle rocks in kimber lite pipes are represented by a wide spectrum of ultra basic rocks, as well as pyroxenites and eclogites. Eclogites are coarse granular rocks mostly composed of garnet and clinopyroxene with accessory rutile. In addition to bimineral eclogites, the most abundant among xenoliths of the basic composition, there are corundum and kyanite eclogites [2]. Numerous stud ies of eclogite xenoliths from the Udachnaya kimber lite pipe have provided evidence for the influence of mantle metasomatism on the upper mantle rocks and have distinguished some signs of metasomatic origin of diamonds [3, 4]. However, the age of these processes has been not determined to date. Because of this, we have performed the dating of rutiles from the eclogite xenolith (Sample UD 208 05) entering the composi tion of the secondary mineral association. Eclogite xenolith from the Udachnaya pipe (Sam ple UD 208 05) is bimineral eclogite composed of dark green xenomorphic clinopyroxene (3–6 mm) and round garnet (2–5 mm) grains reaching ~55 and ~44 vol %, respectively. The xenolith contains the areas of partial melting including veins crossing rock forming omphacite and garnet, which consist of amor phous material (silicate glass) and products of its replacement (chlorite and quartz). These areas are surrounded by replaced omphacite with the typical “sponged textures” (symplectites) [3]. Among the accessory minerals are rutile, ilmenite, and pyrrhotite. The chemical composition of minerals was analyzed by energy dispersive spectrometry on a Tescan MYRA 3 LMU electron microscope with an EDS detector (Oxford Instruments) and using a JEOL JXA 8100 X ray microanalyzer at the Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences.

Diamonds from Juina province, Brazil, and some others localities reveal the existence of a deep, Ca-rich carbonate-silicate source different from ultramafic and eclogite compositions. In this study, we describe the first observation of merwinite (Ca 2.85 Mg 0.96 Fe 0.11 Si 2.04 O 8 ) in a diamond; it occurs as an inclusion in the central growth domain of a diamond from the Sao Luiz river alluvial deposits (Juina, Brazil). In addition, the diamond contains inclusions of walstromite-structured CaSiO 3 in the core and (Mg 0.86 Fe 0.14 ) 2 SiO 4 olivine in the rim. According to available experimental data, under mantle conditions, merwinite can only be formed in a specific Ca-rich and Mg- and Si-depleted enviroment that differs from any known mantle lithology (peridotitic or eclogitic). We suggest that such chemical conditions can occur during the interaction of subduction-derived calcium carbonatite melt with peridotitic mantle. The partial reduction of the melt could cause the simultaneous crystallization of Ca-rich silicates (CaSiO 3 and merwinite) and diamond at an early stage, and (Mg 0.86 Fe 0.14 ) 2 SiO 4 olivine and diamond at a later stage, after the Ca-Mg exchange between carbonatite melt and peridotite has ceased. This scenario is supported by the presence of calcite microinclusions within merwinite.

Taking advantage of the common occurrence of superdeep mineral inclusion assemblages, we examined core-to-rim primary zonation in 69 diamonds from the alluvial deposits of the Sao-Luis River (Juina, Brazil). Syngenetic inclusions were represented by phases of superdeep paragenesis. The dominant inclusions are majoritic garnets, ferropericlases and CaSi- and CaSiTi-perovskites. Rare inclusions of MgSi-perovskites, olivines, clinopyroxenes, TAPP, phases of SiO2, kyanites, AlSi-phases, KFsp (K-hollandite?), CF, NAL, grossular, merwinite, native iron, Fe-sulphides, magnesite and CaCO3 + CaMgSi2O6 (composite inclusions) were also found. The diamonds from Sao-Luis display wide variations in carbon isotopic compositions (δ13C), from +2.7 to −25.3‰. The diamonds with inclusions of ferropericlase have a very narrow range of δ13C values, from −2.1 to −7.7‰, which are close to the “normal” mantle values. In many cases, diamonds with inclusions of calcic majoritic garnet and CaSi- and CaSiTi-perovskites display marked differences from this range. Low δ13C values (−10 to −25 ‰) were observed exclusively in a series of diamonds with majorite garnets, Ca-silicates, aluminous silicates and SiO2. The δ13C values from the cores to rims in certain individual crystals varied substantially, indicating multiple stages of growth. The highly negative δ13C values in the cores (−20 to −25 ‰) potentially represent organic matter in metasediments of altered oceanic crust, and the lower δ13C values may represent mixing trends towards “normal” mantle compositions. In this study, we also found a set of diamonds that display an opposite trend of change of the carbon source, from primordial mantle to subducted/crust (either biotic or abiotic carbon).

Pressure-induced crystallization from amorphous calcium carbonate (ACC) was observed with X-ray diffraction at room temperature. Time-resolved diffraction patterns revealed that calcite and vaterit...

We developed a new device involving an individual P–T controlling system for neutron-scattering experiments available at 0–10 GPa and at 77–473 K. Thanks to the thermal insulators made of zirconia and glass-fiber-reinforced plastic under the anvils, temperature only around anvils can be controllable with fast heating/cooling rate of

It has been known for decades that certain aqueous salt solutions of LiCl and LiBr readily form glasses when cooled to below ≈160 K. This fact has recently been exploited to produce a « salty » high-pressure ice form: When the glass is compressed at low temperatures to pressures higher than 4 GPa and subsequently warmed, it crystallizes into ice VII with the ionic species trapped inside the ice lattice. Here we report the extreme limit of salt incorporation into ice VII, using high pressure neutron diffraction and molecular dynamics simulations. We show that high-pressure crystallisation of aqueous solutions of LiCl∙RH2O and LiBr∙RH2O with R = 5.6 leads to solids with strongly expanded volume, a destruction of the hydrogen-bond network with an isotropic distribution of water-dipole moments, as well as a crystal-to-amorphous transition on decompression. This highly unusual behaviour constitutes an interesting pathway from a glass to a crystal where translational periodicity is restored but the rotational degrees of freedom remaining completely random.

Most ice polymorphs have order–disorder “pairs” in terms of hydrogen positions, which contributes to the rich variety of ice polymorphs; in fact, three recently discovered polymorphs— ices XIII, XIV, and XV—are ordered counter forms to already identified disordered phases. Despite the considerable effort to understand order–disorder transition in ice crystals, there is an inconsistency among the various experiments and calculations for ice XV, the ordered counter form of ice VI, i.e., neutron diffraction observations suggest antiferroelectrically ordered structures, which disagree with dielectric measurement and theoretical studies, implying ferroelectrically ordered structures. Here we investigate in-situ neutron diffraction measurements and density functional theory calculations to revisit the structure and stability of ice XV. We find that none of the completely ordered configurations are particular favored; instead, partially ordered states are established as a mixture of ordered domains in disordered ice VI. This scenario in which several kinds of ordered configuration coexist dispels the contradictions in previous studies. It means that the order–disorder pairs in ice polymorphs are not one-to-one correspondent pairs but rather have one-to-n correspondence, where there are n possible configurations at finite temperature.

Most ice polymorphs have order–disorder “pairs” in terms of hydrogen positions, which contributes to the rich variety of ice polymorphs; in fact, three recently discovered polymorphs— ices XIII, XIV, and XV—are ordered counter forms to already identified disordered phases. Despite the considerable effort to understand order–disorder transition in ice crystals, there is an inconsistency among the various experiments and calculations for ice XV, the ordered counter form of ice VI, i.e., neutron diffraction observations suggest antiferroelectrically ordered structures, which disagree with dielectric measurement and theoretical studies, implying ferroelectrically ordered structures. Here we investigate in-situ neutron diffraction measurements and density functional theory calculations to revisit the structure and stability of ice XV. We find that none of the completely ordered configurations are particular favored; instead, partially ordered states are established as a mixture of ordered domains in disordered ice VI. This scenario in which several kinds of ordered configuration coexist dispels the contradictions in previous studies. It means that the order–disorder pairs in ice polymorphs are not one-to-one correspondent pairs but rather have one-to-n correspondence, where there are n possible configurations at finite temperature.

Wear resistance of nano-polycrystalline diamond (NPD) rods containing various amounts of hexagonal diamond has been tested with a new method for practical evaluation of the wear–resistance rate of superhard ceramics, in addition to the measurements of their Knoop hardness. The wear resistance of NPD has been found to increase with increasing synthesis temperature and accordingly decreasing proportion of hexagonal diamond. A slight increase in Knoop hardness with the synthesis temperature also has been observed for these samples, consistent with the results of the wear–resistance measurements. These results suggest that the presence of hexagonal diamond would not yield any observable increase in both hardness and wear resistance of NPD, contradictory to a recent prediction suggesting that hexagonal diamond is harder than cubic diamond. It is also demonstrated that NPD is superior to single crystal diamond in terms of relatively homogeneous wearing without any significant chipping/cracking. Зносостійкість нано-полікристалічних алмазних (НПА) стрижнів, з різним вмістом гексагонального алмазу, була протестована новим методом практичної оцінки швидкості зносу надтвердої кераміки, додатково до вимірюваня їх твердості по Кнупу. Було виявлено, що зносостійкість НПА збільшується зі зростанням температури синтезу і, відповідно, зі зменшенням частки гексагональних алмазів. Також, відповідно до результатів вимірювань зносостійкості, для цих зразків спостерігалося невелике збільшення твердості по Кнупу з температурою синтезу. Ці результати дозволяють припустити, що присутність гексагональних алмазів не приводить до будь-якого помітного збільшення як твердості, так і зносостійкості НПА, що суперечить недавньому припущенню про те, що гексагональний алмаз твердіший, ніж кубічний. Також показано, що НПА перевершує монокристал алмазу з точки зору відносно однорідного зношування без значних відколів/тріщин. Износостойкость нано-поликристаллических алмазных (НПА) стержней, с различным содержанием гексагонального алмаза, была протестирована новым методом практической оценки скорости износа сверхтвердой керамики, в дополнение к измерениям их твердости по Кнупу. Было обнаружено, что износостойкость НПА увеличивается с ростом температуры синтеза и, соответственно, с уменьшением доли гексагональных алмазов. Также, в соответствии с результатами измерений износостойкости, для этих образцов наблюдалось небольшое увеличение твердости по Кнупу с температурой синтеза. Эти результаты позволяют предположить, что присутствие гексагональных алмазов не приводит к какому-либо заметному увеличению как твердости, так и износостойкости НПА, что противоречит недавнему предположению о том, что гексагональный алмаз тверже, чем кубический. Также показано, что НПА превосходит монокристалл алмаза с точки зрения относительно однородного изнашивания без значительных сколов/трещин.

We developed a micro-Raman and photoluminescence imaging technique for visualizing the internal stress fields in a sapphire crystal. The technique was applied to an Australian sapphire gemstone with a zircon inclusion. Considering piezospectroscopic effects on Raman and photoluminescence spectra, the Raman shifts of sapphire around the zircon inclusion were converted to hydrostatic pressure and deviatoric components of stress tensor. The internal stress was highly concentrated at the tips of the zircon crystal, where the deviatoric stress and the hydrostatic pressure component reached 700 and 470 MPa, respectively. Generation of compressive stress on the crystal surface of zircon can be explained by the difference in thermal expansion coefficients and elastic constants between sapphire and zircon. In general, internal stress fields induced by mineral inclusions reflect the pressure and temperature conditions at which the host sapphire gemstones were crystallized. Thus, the present technique can be utilized to identify the origin of gemstones. Copyright © 2012 John Wiley & Sons, Ltd.

We designed new anvil assemblies for acquiring high-quality neutron diffraction data and ruby fluorescence spectra inside a sample chamber. The conical aperture of Ni-binded WC anvils was expanded by a factor of two. A hybrid gasket made of TiZr- and Al-alloy was developed to prevent outward extrusion. A small and optically transparent window of moissanite was introduced to allow for the determination of pressure and hydrostaticity by measurement of ruby fluorescence spectra. High pressure-generation tests that make use of Bi electrical conductivity and ruby pressure markers revealed that pressure could be determined over 10 GPa. In situ synchrotron X-ray diffraction experiments were also carried out using NaCl as the pressure calibrants. The maximum pressure achieved was approximately 13 GPa. The neutron diffraction intensity from the newly generated anvil assemblies was 2.5–3.0 times greater than that using the standard toroidal anvil assemblies used previously.

Carbonado, a variety of natural polycrystalline diamond whose origin remains unknown, differs notably in the properties from common diamonds of mantle origin. In this study, infrared spectroscopic and microscopic analyses were conducted on carbonado from the Central African Republic. Stepwise heating followed by infrared spectroscopic measurements indicated that liquid H 2 O is enclosed within diamond single crystals in carbonado. Transmission electron microscope observation revealed a negative crystal that is interpreted as a primary fluid inclusion in a diamond single crystal. Observations by field-emission scanning electron microscope and electron backscatter diffraction analysis show an absence of lattice preferred orientation of diamond crystals, {111} growth steps along grain boundaries, and the crystal-size distribution of diamond similar to those of crystals formed in liquid media. In addition, the redox conditions of carbonado formation is inferred to be ~3 log units below the quartz-magnetite-fayalite buffer, which is the prevailing condition in cratonic upper mantle. These lines of evidence suggest that the carbonado crystallized in C-O-H fluid, supporting the hypothesis of a mantle-depth origin of carbonado.

Based on pressure and temperature (P–T) information of mantle-derived xenoliths, this report describes a geotherm in Far Eastern Russia, which is situated in the backarc of volcanic chains in eastern Asia. The mantle xenoliths have abundant CO 2 fluid inclusions. Accurate determination of the internal pressure of the CO 2 fluid inclusions enables estimation of the depth provenance of the mantle xenoliths. The depth provenances obtained from five mantle xenoliths are correlated with equilibrium temperatures estimated using a geothermometer. Assuming that the correlation reflects the geotherm in this region, it corresponds to heat flow of around 100 mW/m 2 , which is comparable to the surface heat flow in the volcanic arc. Such high heat flow implies a thin lithosphere and high temperature of the shallower upper mantle. Backarc areas are universally characterized by both high surface heat flow and the occurrence of recent volcanic activities. Furthermore low seismic velocity anomaly is widely observed in the shallower upper mantle in the backarc, especially in eastern Asia. The present xenolith geotherm suggests that the seismic anomaly arises from high temperature of the shallower upper mantle. It would be direct evidence for warming of the lithospheric mantle and subsequent lithospheric thinning, which is likely attributable to asthenospheric upwelling.

This report describes a newly observed phenomenon: pressure-induced crystallization from amorphous calcium carbonate (ACC). Synthetic ACC samples were pressurized up to 800 MPa at room temperature. Then crystallization of vaterite and calcite was observed from X-ray diffraction patterns. The crystallization pressure depends on the H2O contents of ACCs. The ACC samples with high-H2O content (21 wt %), middle-H2O content (17 wt %), and low-H2O content (10 wt %) underwent crystallization at pressures higher than 240 MPa, 400 MPa, and 640 MPa, respectively. These results indicate that H2O in the ACC serves an important role in the crystallization process and that we should treat ACC carefully in preparation for analyses such as infrared spectroscopy to obtain the intrinsic information related to amorphous materials.

Effects of L-Aspartic acid (L-Asp) on step retreat kinetics in the dissolution of calcite were investigated. The step retreat velocities under surface-controlled kinetics were determined from in-situ atomic force microscopic observations using an improved flow-through system. Comparison of the present results with those obtained under a mixed kinetics condition revealed that the addition of L-Asp promotes the transport process in the calcite dissolution through acid–base and/or complex forming reactions in the diffusion boundary layer. Additionally, promotion of the acute and obtuse step retreats by the L-Asp additive was observed under surface-controlled kinetics. This report is the first to clarify that L-Asp promotes surface processes in the dissolution of calcite.

Congruent evaporation of a crystalline material in vacuum is an extreme reaction in that backward reactions and transport processes in the reactant can be neglected. The evaporation is strongly governed by surface processes and intrinsic nature of the substance. A thorough knowledge of the atomistic evaporation mechanism is fundamental for better understanding reaction kinetics between gas and condensed materials in general. We have conducted a series of evaporation experiments of forsterite in vacuum for crystallographically oriented surfaces at 1500 to 1810 °C. The (100), (010), and (001) surfaces developed their own morphology characterized by evaporation pits and grooves originated from dislocation outcrops. Nominal overall evaporation rate (average retreat rate of a surface) shows significant anisotropy with the maximum difference by a factor of five below 1740 °C. The overall evaporation rates for individual surfaces are fitted with respective Arrhenius relationships, giving the highest activation energy for (100), intermediate for (001), and the lowest for (010). The anisotropy decreases to within 50% at ~1800 °C, which is caused by enhancement of evaporation from (010) owing to preferential evaporation around dislocation outcrops. “Intrinsic evaporation rates” estimated by subtracting contributions of initial roughness and the preferential evaporation around dislocations from the nominal overall evaporation rates show substantial anisotropy even at ~1800 °C. The “intrinsic evaporation rate” for (010) is adequately fitted by an Arrhenius relationship over the examined temperature range giving a single activation energy of 655 kJ/mol. The prevalence of steps with submicrometer to nanometer-scale height shows that forsterite evaporates mostly by layer-by-layer mechanism. The only exception is the (001) surface above ~1650 °C, on which such steps are absent except for surface-parallel minor facets which are rapidly diminishing with time. The (001) surface is inferred to evaporate by direct detachment mechanism at high temperatures. The change of evaporation mechanisms for (001) at around 1650 °C corresponds to a rough-smooth transition kinetically induced by an atomistic evaporation process.

Copyright © 2012 by The Geochemical Society of Japan. phenomenon presenting important implications for environmental problems (Wittbrodt and Palmer, 1996, 1997; Kožuh et al., 2000). Reduction-oxidation studies of Cr in soils have mainly targeted estimation of the reduction kinetics and stability constants (complexation capacities), or have addressed the presence of Cr(VI) (Fukushima et al., 1995; Wittbrodt and Palmer, 1995, 1996, 1997; Nakayasu et al., 1999; Kožuh et al., 2000). Information about the detailed chemical structure of Cr in nature is also necessary for complete understanding of toxicity and stability. However, determining a chemical state of Cr during or after a reaction process of Cr(VI) and soils is challenging because the soil system is too complex for speciation studies of Cr. Analysis using X-ray absorption fine structure (XAFS) spectroscopy is effective for determination of a valence state and a chemical form of metals in heterogeneous materials because it yields information with elemental selectivity obtained through Speciation study of Cr(VI/III) reacting with humic substances and determination of local structure of Cr binding humic substances using XAFS spectroscopy

To assess the capacity of fluid inclusions in mantle minerals for CO 2 retention, annealing experiments were conducted for two mantle xenoliths with CO 2 inclusions for 8 days at 1000 °C under atmospheric pressure and f O 2 of 10 −11 MPa. The results show no marked decrease in the CO 2 density of the CO 2 inclusions for any examined minerals – olivine, orthopyroxene, clinopyroxene, or spinel. The CO 2 density of CO 2 inclusions in olivine in the present mantle xenoliths is lower than that in pyroxenes or spinel. Results of previous studies indicate that the low CO 2 density in olivine is attributable to plastic deformation of olivine around CO 2 inclusions during annealing in ascending magma. Results of this study present fundamental implications for deformation mechanisms that arise from internal pressure of fluid inclusions in silicate minerals. We calculated the stress field in minerals having a CO 2 inclusion. Results show a steep stress gradient in the host around the inclusion. Such local stress in the mineral induces a local rise in the density of dislocations around the CO 2 inclusions. The orthopyroxene used for this study showed a sparse distribution of dislocations around a CO 2 inclusion, whereas olivine showed dense dislocations around CO 2 inclusions, implying that the low CO 2 density of the CO 2 inclusions in olivine results from volume expansion of the CO 2 inclusions through plastic deformation of the host mineral during annealing of the xenoliths in ascending magma. In this respect, constancy of CO 2 density during the annealing experiments for all minerals is an interesting finding. Regarding olivines, the reduction of internal pressure of the CO 2 inclusions or interaction of the dense dislocations possibly inhibits decrepitation or further volume expansion of the CO 2 inclusions during annealing experiments. However, pyroxenes and spinel show higher and similar CO 2 density, which reflects the resistance to plastic deformation and which indicates the effectiveness of CO 2 inclusions in these minerals as a depth probe for mantle xenoliths.

High pressure and temperature reactions of a mixture of forsterite and hydrogen molecules have been carried out using a laser heated diamond anvil cell at 9.8–13.2 GPa and ~1,000 K. In situ X-ray diffraction measurements showed no sign of decomposition or phase transitions of the forsterite under these experimental conditions, indicating that the olivine structure was maintained throughout all runs. However, a substantial expansion of the unit cell volume of the forsterite was observed for samples down to ~3 GPa upon quenching to ambient pressure at room temperature. The Raman spectroscopy measurements under pressure showed significant shifts of the Raman peaks of the Si–O vibration modes for forsterite and of the intramolecular vibration mode for H2 molecules toward a lower frequency after heating. Additionally, no OH vibration modes were observed by Raman and FT-IR spectroscopic measurements. These lines of evidence show that the observed volume expansion in forsterite is not explained by the incorporation of hydrogen atoms as hydroxyl, but suggest the presence of hydrogen as molecules in the forsterite structure under these high pressure and temperature conditions.

The pressure responses of portlandite and the isotope effect on the phase transition were investigated at room temperature from single-crystal Raman and IR spectra and from powder X-ray diffraction using diamond anvil cells under quasi-hydrostatic conditions in a helium pressure-transmitting medium. Phase transformation and subsequent peak broadening (partial amorphization) observed from the Raman and IR spectra of Ca(OH)2 occurred at lower pressures than those of Ca(OD)2. In contrast, no isotope effect was found on the volume and axial compressions observed from powder X-ray diffraction patterns. X-ray diffraction lines attributable to the high-pressure phase remained up to 28.5 GPa, suggesting no total amorphization in a helium pressure medium within the examined pressure region. These results suggest that the H–D isotope effect is engendered in the local environment surrounding H(D) atoms. Moreover, the ratio of sample-to-methanol–ethanol pressure medium (i.e., packing density) in the sample chamber had a significant effect on the increase in the half widths of the diffraction lines, even at pressures below the hydrostatic limit of the pressure medium.

The relationship between Mg# [ = 100 Mg/(Mg + Fe) in mol] and the Raman shift was analyzed precisely for olivine [(Mg, Fe)2SiO4] samples with Mg# between 100 and 62.8. Two prominent peaks at 826–820 cm−1 (peak 1) and 858–849 cm−1 (peak 2) and three subordinate peaks at 883–881 cm−1 (peak 3), 920–914 cm−1 (peak 4), and 967–951 cm−1 (peak 5) were observed to shift monotonously to lower wavenumbers with decreasing Mg#. The ΔMg#( = Mg#ref − Mg#) versus Δν(= νref − ν) can be linearly regressed for each peak as ΔMg# = A Δν, where ν is a peak wavenumber of olivine with Mg# ranging from 100 to 62.8, and νref is that of olivine with a reference value of Mg#, namely, Mg#ref. We set Mg#ref as 100 (i.e.pure forsterite Mg2SiO4) whereas A is a regression parameter (5.789, 4.294, 12.34, 6.348, and 2.09, respectively,for peaks 1, 2, 3, 4, and 5). This equation enables us to avoid small inter-laboratory differences of wavenumber calibration. The equation for peak 2 yields estimations of Mg# in geologically satisfactory precision, ± 1 Mg# (1σ) in the Mg# range of 100–62.8. Copyright © 2011 John Wiley & Sons, Ltd.

Metamorphic diamonds from the Kokchetav massif in northern Kazakhstan are considered to have crystallized from a C–O–H fluid during ultra-high-pressure metamorphism of metasedimentary rocks subducted to 190–280 km depth. Noble gases contained in the diamonds offer great potential to constrain the noble gas state of deep mantle reservoirs. Previous studies have revealed that secondary processes during the diamond residence in the host rock drastically modified the original noble gas signature of the diamonds. However, nanometer-sized solid/fluid inclusions in the microdiamonds, which represent the former diamond-forming fluid, might preserve the noble-gas signature trapped at the time of diamond formation. We performed noble-gas analyses of the Kokchetav microdiamonds applying two gas extraction techniques: in vacuo crushing and stepwise heating. The former selectively extracts noble gases from inclusions with less noble gas extraction from the diamond lattice. Diamond crushing extracted most of the 3He, indicating that 3He occurs within inclusions trapped during diamond formation. The inclusion-hosted 3He/4He of (3.3–6.5) × 10−5 is significantly higher than that of the MORB-source mantle (1.1 × 10−5), but close to the maximum value observed in OIBs (ca. 7 × 10−5) containing noble gases enriched in a primordial component and delivered from the deep mantle by plumes. Neon isotope ratios obtained using stepwise heating also support the presence of a plume-like component. Results show that plume-like, primordial-enriched noble gases were involved in the Kokchetav microdiamond formation, implying metasomatism of the continental lithosphere by a plume prior to its subduction, or interaction of the continental slab and a fragment of the very deep mantle. The deep-mantle-derived fragment might have been delivered to the mantle wedge of the subduction channel by large-scale mantle convection originating from a deeper lower mantle source.

We conducted powder neutron diffraction for δ-AlOOH samples with and without Mg and Si ions under ambient conditions in order to investigate the long-standing problem of the symmetry of this phase. The observed reflection conditions clearly show that the space group of pure δ-AlOOH is P21 nm with ordered hydrogen bonds, whereas that of δ-(Al0.86Mg0.07Si0.07)OOH is Pnnm or Pnn2 with disordered hydrogen bonds. It is more likely that the space group of δ-(Al0.86Mg0.07Si0.07)OOH is Pnnm, because cation or hydrogen ordering that breaks the mirror plane perpendicular to c axis in the Pnnm structure would not occur. The previously reported inconsistency for the space group of this phase was caused by the substitution of Mg and Si ions to Al site, i.e., the disordered cations with different valences may fluctuate hydrogen positions, and the disordered hydrogen causes the symmetry change.

We examined dpp expression patterns in the pulmonate snail Lymnaea stagnalis and analyzed the functions of dpp using the Dpp signal inhibitor dorsomorphin in order to understand developmental mechanisms and evolution of shell formation in gastropods. The dpp gene is expressed in the right half of the circular area around the shell gland at the trochophore stage and at the right-hand side of the mantle at the veliger stage in the dextral snails. Two types of shell malformations were observed when the Dpp signals were inhibited by dorsomorphin. When the embryos were treated with dorsomorphin at the 2-cell and blastula stages before the shell gland is formed, the juvenile shells grew imperfectly and were not mineralized. On the other hand, when treated at the trochophore and veliger stage after the shell gland formation, juvenile shells grew to show a cone-like form rather than a normal coiled form. These results indicated that dpp plays important roles in the formation and coiling of the shell in this gastropod species.

This study reports the first application of dynamic light scattering to observations of crystal growth of calcium carbonate from a supersaturated solution. Crystal size distributions around the cri...

To elucidate processes of Cr(VI) reduction by humic acids in soils, humic acids reacting with Cr(VI) were characterized using IR and X-ray absorption near edge structure (XANES) spectroscopy. It is expected that oxidation of humic acid by Cr(VI) gives rise to the formation of aldehyde, ketone, and carboxyl species. However, no significant increase of IR-bands assignable to these functional groups has been reported. Instead, IR absorption spectra of humic acid oxidized by Cr(VI) show similar features to those of humic acid reacting with Cr(III). Consequently, the types and proportions of functional groups of HA substances did not differ significantly among experimental conditions. The IR spectra of humic acid reacting with Cr(III) and Cr(VI) show increased intensity of IR bands at 3400 cm, 1608 cm, and 1384 cm, with decreased intensity of peaks at 1707 cm and 1236–1250 cm. Those changes suggest the existence of bonding structures of two kinds: hydrated Cr forming an outer-sphere complex with humic acid, and Cr forming an inner-sphere complex with the carboxylate ligand of humic acid. The Cr-K edge XANES spectra of humic acid reacting with Cr(VI) suggest that Cr(III), reduced from Cr(VI), binds with humic acid. No systematic difference of XANES spectra was found with increased amounts of Cr(VI) in experimental solutions. These features are consistent with IR absorption spectra. The fractions of two kinds of binding forms suggested by IR spectra were determined from linear combination fitting using XANES spectra of reference compounds: 50% hydrated Cr(III) adsorbed onto HA electrostatically and the remainder of Cr(III) binding to carboxylic acid of HA. However, with increasing pH of experimental solutions, some Cr precipitates as Cr(OH)3•nH2O in the solid phase. The pH level or Cr concentration must be reduced to prevent production of a Cr(OH)3•nH2O precipitate.

Garnet clinopyroxenites occur within foliated dunite in the Higashi-akaishi peridotite mass, located within the subduction-type high-pressure/low-temperature Sanbagawa metamorphic belt. The garnet clinopyroxenites contain 3–80% garnet, and garnet and clinopyroxene are homogeneously distributed. Garnet crystals contain extensive, regular dislocation arrays and dislocation networks, suggesting that dislocation creep was the dominant deformation mechanism. Analyses of crystallographic orientation maps indicate similar grain sizes and aspect ratios for garnet and clinopyroxene, regardless of modal composition, indicating that these minerals deformed with similar degree of plasticity. Moreover, indexes of crystallographic fabric intensity (i.e., J-index and M-index) for both garnet and clinopyroxene tend to increase with increasing modal composition of garnet. Fourier-transform infrared spectroscopy analysis revealed that water content in garnet is ∼60 ppm, whereas that in clinopyroxene is ∼70 ppm. Olivine crystal-preferred orientations in the Higashi-akaishi peridotite mass, characterized by [0 0 1] (0 1 0), are thought to have developed during deformation under wet conditions. Consequently, we argue that the presence of water could act to enhance garnet plasticity during deformation. The results reveal contrasting influences of water on the deformation of garnet and diopside: under wet conditions compared with dry, the strain rate increases by two orders of magnitude for garnet but by an order of magnitude for diopside. Given the influence of water on the creep strength of garnet, garnet within the Higashi-akaishi mass may have become significantly as weak as clinopyroxene during deformation.

Micrometer- to nanometer-scale structures of the cut surfaces of single- and polycrystalline diamonds by a pulsed ultraviolet laser have been thoroughly investigated by scanning and transmission electron microscopy. Within the laser-cut grooves, the processed diamond surfaces are extensively covered with laser-modified debris which consists of complex layered units of graphite with various crystallinities. The units consist of 1) highly oriented graphite, 2) corrugated graphite, and 3) nanocrystalline graphite, which are sequentially located from the surface of the underlying diamond substrate to the center of the grooves. Detailed textural examinations revealed that the highly oriented graphite unit is a product of the initial graphitization of diamond by a solid-state diffusion process, whereas the latter two units are deposition products from the liquid and/or vapor phases of carbon in the later stage. The present study demonstrates that the laser-cutting of diamonds proceeds in a two-step process: 1) extensive graphitization of laser-scanning path and 2) subsequent sublimation of the pre-formed graphite. These processes are basically identical among the three different types of diamonds (single crystal type Ib, single crystal type IIa and nano-polycrystalline aggregate) tested in this study.

Five apatite crystal scintillators, which have chemical compositions of Ce 0.5%: Gd9.33(SiO4)6O2, Ce 0.5%: (Gd8Sr2)(SiO4)6O2, Ce 5%:(Gd8Sr2) (SiO4)6O2, Yb 0.5%:(Gd8Sr2) (SiO4)6 O2 and Yb 3%:(Gd8Sr2) (SiO4)6 O2 were grown by the micro-pulling down method. After cut and polishing processes, optical and radiation properties were evaluated. In a transmittance measurement, Ce doped crystals showed an absorption feature at approximately 300 nm and Yb doped ones 220 nm, respectively. When Ce-doped ones were excited by 340 nm photons, the emission peak appeared at approximately 400 and 440 nm, due to Ce3+ 5d-4f transitions. In Yb-doped series, 270 nm excitation caused emission peaking around 300 nm. The photoluminescence decay time kinetics of Ce-doped series were investigated. The Ce 0.5% doped (Gd8Sr2) (SiO4)6 O2 showed about 23 ns decay constants, and the 5% doped one showed 14 ns. When coupled with Si-APD and irradiated by 241Am α-ray, Ce doped scintillators showed 300-500 photons/5.5 MeV as α light yield.

We measured the neutron powder diffraction of 0.013 M KOD-doped D 2 O ice to investigate the formation process of ice XI, a hydrogen-ordered phase of ice Ih. The doped ice Ih transformed to ice XI after annealing at 57 and subsequently at 68 K. The mass fraction of ice XI to that of the doped ice ( f ) was estimated using Rietveld analysis for each sample. The f value of the doped ice, which had once experienced being ice XI ( f = 0.23), was larger than that of the doped ice, which had never experienced being ice XI ( f = 0.14). Results indicate that small hydrogen-ordered domains remained in the ice Ih, which had once transformed to ice XI, and accelerated the phase transition from ice Ih to ice XI. Results further suggest that large amounts of ice on icy bodies in our solar system can transform to ice XI, which might be detectable using infrared telescopes or planetary exploration in the near future.

Effects of l -aspartic acid ( l -Asp) on dissolution of calcite were investigated. The step retreat velocity and dissolution rate of calcite were measured simultaneously using an AFM flow-through system. The etch-pit morphology of calcite was observed using confocal laser scanning microscopy. Results show that the etch-pit morphologies changed drastically depending on the l -Asp concentration ([ l -Asp]) in the order of rhomboidal, pentagonal, and triangular (not perfectly, but retaining an extra step). The change in obtuse step directions and appearance of the [0 1 0] step triggered these morphological changes. Addition of l -Asp accelerated all step retreats at [ l -Asp] l -Asp on the diffusive barrier. In contrast, at [ l -Asp]>0.01 M, l -Asp inhibited the retreats of obtuse steps and [0 1 0] step, although the retreat velocities of acute steps were constant irrespective of [ l -Asp]. These results suggest that the directional changes and the inhibition of retreat velocities of obtuse steps were attributed to the generation of [ 4 1 1] and [4 5 1 ] steps caused by l -Asp. Moreover, we confirmed the preferential effects of l -Asp on the [4 8 1 ]+ to [ 4 4 1]± step edge, and proposed the preferential effects of l -Asp on the [ 4 1 1] to [4 5 1 ] step edge.

Graphite inclusions in diamond, K-bearing clinopyroxene, garnet and kyanite and graphite coatings around microdiamonds from the ultrahigh-pressure Kokchetav Massif, northern Kazakhstan were investigated by means of scanning electron microscopy, laser Raman spectroscopy and X-ray diffraction. Important observations include the increasing size of the graphite crystals from the diamond-graphite interface to the external part of the graphite coatings, the high volume fraction of graphite in the graphite coatings, the presence of composite crystals of successively formed diamond core-graphite mantle zone-diamond rim-external graphite coating, the spherulitic texture of the graphite coatings, the formation of both ordered and disordered graphite and the absence of any fluid associated with the graphite inclusions in diamond and other ultrahigh-pressure metamorphic (UHPM) minerals. These features combined with the presence of oriented graphite flakes in K-bearing clinopyroxene and in diamond-bearing garnet and kyanite and the presence of intergranular diamonds without graphite coatings in the quartzo-feldspathic matrix require reconsideration of the generally accepted diamond graphitization model for interpreting the formation of graphite in UHPM rocks. Metastable growth of graphite within the diamond stability field is suggested and the following crystallization scheme for the C-polymorph is proposed: graphite was the first C-polymorph formed in the diamond stability field, followed by diamond; the graphite coatings around diamond formed during the final stage of UHPM conditions.

We have recently carried out a neutron powder diffraction experiment at high pressure using nano-polycrystalline diamond as opposed anvils. Although spurious diffraction peaks from these anvils are rather large, a few peaks from Pb sample with 0.7 mm3 volume were clearly observed. Future potential and problem of the current scheme toward neutron diffraction at the highest pressure regime have been demonstrated.

Residual pressure around mineral inclusions in diamond can provide useful information on the depth of diamond origin. Differential stress between an inclusion and host diamond arises from differences in thermal expansion and compressibility between host diamond and minerals. We determined residual pressure around mineral inclusions in a diamond from the Internationalnaya pipe, Yakutia, Russia, using the three-dimensional Raman mapping system developed recently by our group. The maximum residual pressures around the olivine and chromite inclusions were determined to be 0.69 GPa and 0.75 GPa, respectively. We proposed an advanced method for determining simultaneously pressure and temperature conditions where the mineral inclusions were trapped in the host diamond. The obtained values were 3.0 GPa and 447 °C, but these values are lower than typical P-T conditions in the mantle. Several technical possibilities for the discrepancy are discussed.

Characterization of fluid inclusions in graphite-bearing charnockites from the southwestern part of the Madurai Granulite Block in southern India reveals a probable relation with the formation and break down of graphite during the high-grade metamorphism. The first-generation monophase pure CO(2) inclusions, the composition of which is confirmed by laser Raman spectroscopy, recorded moderate density (0.77-0.87 g/cc) corresponding to low tapping pressure (around 2 kb) than that of the peak granulite-facies metamorphism. The precipitation of graphite, as inferred from graphite inclusions and delta(13)C values of the graphite from the outcrops, is interpreted as the cause of this lowering of fluid density. An intermediate generation of pseudosecondary inclusions resulted from the re-equilibration or modification of the first-generation fluids and the CO(2). formed is interpreted to be the oxidation product from graphite. The youngest generation of fluids which caused widespread retrogression of the granulites is a low-temperature (similar to 350 degrees C) high-saline (32.4-52.0 wt% NaCl equivalent) brine. Carbon isotope data on the graphite from the charnockites show delta(13)C values ranging from -11.3 to -19.9 parts per thousand, suggesting a possibility of mixing of carbon sources, relating to earlier biogenic and later CO(2) fluid influx. Combining the information gathered from petrologic, fluid inclusion and carbon stable isotope data, we model the fluid evolution in the massive charnockites of the southwestern Madurai Granulite Block. (c) 2009

Infrared absorption spectra of ice were obtained at 4, 60, 100, 140, 160, and 240 K to make spectroscopic observations of hydrogen ordering at low temperatures. A broad peak observed at around 850 cm–1 (11.7 μm) was derived from libration of water molecules. The peak width was notably narrower at temperatures less than 140 K. A decrease in the peak width occurring in accordance with the formation of ice with ordered arrangements of hydrogen atoms was suggested from incoherent inelastic neutron-scattering studies. These results are consistent with ordering of hydrogen atoms. The existence of hydrogen-ordered ice in space is the subject of continuing astronomical debate. Our results demonstrate that ordered ice in space is detectable using infrared telescopes and planetary exploration.

The compression behaviors of δ-AlOOH and δ-AlOOD were investigated under quasi-hydrostatic conditions at pressures up to 63.5 and 34.9 GPa, respectively, using results from synchrotron X-ray diffraction experiments conducted at ambient temperature. Because of the geometric isotope effect, at ambient pressure, the a and b axes of δ-AlOOD, which define the plane in which the hydrogen bond lies, are longer than those of δ-AOOH. Under increasing pressure, the a and b axes of δ-AlOOH stiffen at 10 GPa, although the c axis shows no marked change. Identical behavior was found in δ-AlOOD, but the change in compressibility was observed at a slightly higher pressure of 12 GPa. Axial ratios a / c and b / c first decrease rapidly with increasing pressure, then begin to increase at pressures >10 GPa in δ-AlOOH and >12 GPa in δ-AlOOD. At these pressures, the pressure dependence of a / b also changes from increasing to decreasing. The unit-cell volumes of δ-AlOOH and δ-AlOOD become slightly less compressible at high pressures. Assuming K ′ = 4, the calculated bulk moduli of δ-AlOOH below and above 10 GPa are 152(2) and 219(3) GPa, respectively. Those of δ-AlOOD below and above 12 GPa are 151(1) and 207(2) GPa, respectively.