Oligocene to Miocene volcanic rocks from the Toyama basin of the SW Japan arc, that were formed during back-arc spreading in the Japan Sea, were examined to reveal their petrogenesis and temporal change of arc volcanism during the Japan Sea opening. The arc volcanism in the Toyama basin initiated with rhyolitic pyroclastic flows (Tori Formation) containing hecatolite (moonstone) in 23-22 Ma. Enriched Sr-Nd isotope (SrI = 0.70769-0.70944; NdI = 0.51203-0.51224) suggests that contemporaneous andesitic magma (Kamiwazumi and Matsunagi Formations) mixed or assimilated basement granitoids and gneisses of the Hida belt to generate rhyolitic magma. Subsequently, andesitic volcanism (Iwaine Formation) occurred in 18-17 Ma after magmatic hiatus. Andesitic lavas of the Iwaine Formation are composed of high magnesian andesite (HMA), high-Sr andesite and tholeiitic andesite. HMA has Mg# > 64, high Cr and Ni concentrations, not so high Th/Yb and (La/Sm)_N ratios, and slightly enriched Sr-Nd isotope (SrI = 0.70482; NdI = 0.51279). High-Sr andesite has relatively low SiO₂ content (<60 wt%), high Sr (>2000 ppm) and K₂O contents (3.98 wt% in the maximum), indicating that it is low-SiO₂ adakite. These geochemical characteristics suggest that HMA and high-Sr andesite were produced by partial melting of the mantle wedge saturated by H₂O derived from slab fluid and metasomatized by slab melt, respectively. Although chemical variation diagrams suggest tholeiitic andesite seems to have been generated from basaltic magma, it has enriched Sr-Nd isotope (SrI = 0.70713-0.70756; NdI = 0.51237-0.51241). Thus, tholeiitic andesite is considered to have been produced by AFC (assimilation and fractional crystallization) after generation of basaltic parental magma. Andesitic magmatism of the Iwaine Formation was followed by rhyolitic magmatism of the Iozen Formation in 17-16 Ma. The petrogenesis of the rhyolite from the Iozen Formation can be explained by low-rate mixing between andesitic magma (Iwaine Formation) and the Hida belt. The petrogeneses of the andesites, especially HMA and high-Sr andesite, are related to slab melting. Because the old and cold Pacific plate was subducting beneath the Toyama basin during the Japan Sea opening, additional heat source such as upwelling of the asthenospheric mantle into the mantle wedge is required. Moreover, back-arc spreading in the Japan Sea was driven by upwelling of the asthenospheric mantle into the mantle wedge.

In this study, we investigated the origin and formation process of zeolitized gastropod fossils in Neogene sediments (Shiote Formation) in Minamisoma, Fukushima, Japan using powder X-ray diffraction, SEM-EDS and micro-Raman spectroscopic analysis. The formation of zeolites was particularly pronounced in the upper chamber, which was not filled with detrital particles, of the gastropod fossils, where tabular crystals of heulandite were observed growing directly from the shell wall. The heulandite crystals are often covered by large euhedral crystals of calcite and occasionally by acicular crystals of mordenite. The formation of zeolite (heulandite) was also observed in the matrix of the host sandstone together with clay minerals (mostly montmorillonite), suggesting that the Shiote Formation experienced moderate metamorphism equivalent to zeolite facies during burial diagenesis. The Si/Al ratio of heulandite was found to decrease gradually from the bottom (∼ 4.5) to the top (∼ 3.1) within single crystals across the threshold (4.0) for clinoptilolite/heulandite classification boundary. This may reflect the increase in temperature of the surrounding environment with increase in the burial depth. The extensive growth of zeolites and calcite inside the gastropod fossils indicates that the shell provided semi-closed spaces in which pore fluid could be retained and condensed during diagenesis, thus promoting the crystal growth from the supersaturated solution.

Asagiite, a newly-discovered mineral having the ideal formula NiCu₄(SO₄)₂(OH)₆·6H₂O, is a member of the ktenasite group, representing a Ni analogue. It occurs as a secondary mineral on smithsonite aggregates that overlie fractures in a serpentinite found in the Nakauri mine within Aichi Prefecture, Japan. Asagiite exhibits a unique pale blue-green coloration and so is named after the traditional Japanese color ‘asagi-iro’. Asagiite occurs as thin plate-like crystals with perfect cleavage along {001} planes. The crystal size of this mineral is typically 0.1-0.2 mm, although in rare cases crystals may range up to 0.5 mm in length. These crystals are vitreous, transparent and non-fluorescent and have also been shown to be brittle with a Mohs hardness of 2½. The measured and calculated densities of asagiite are 2.90(3) and 2.92 g·cm⁻³, respectively. This mineral is optically biaxial (−) with α = 1.577(2), β = 1.620(2), and γ = 1.631(2) together with a 2V_calc value of 52.4°. Electron microprobe analyses determined an empirical formula (based on 2S) of (Cu_3.44Ni_0.76Zn_0.59Co_0.18Fe_0.01)_Σ4.98S₂O_7.95(OH)_6.05·6H₂O. Based on single crystal X-ray diffraction data, the structure is monoclinic with space group P2₁/c and unit cell parameters a = 5.6095(8), b = 6.1259(7), c = 23.758(3) Å, β = 95.288(4)°, V = 812.92(17) ų, and Z = 2. Single-crystal structural determination also gives an R₁ value of 0.0303. The seven most intense peaks in the powder X-ray diffraction pattern [d in Å (I/I₀) hkl] were found to be 11.830 (100) 002, 5.912 (64) 004, 4.845 (55) 013, 3.920 (45) 006, 2.953 (33) 008, 2.668 (57) 202, and 2.571 (36) 123, with unit cell parameters of a = 5.614(5), b = 6.108(8), c = 23.758(18) Å, β = 95.62(7)°, and V = 810.8(14) ų.

H₂O-CO₂-dominated fluids play a crucial role in most geological phenomena involving fluid-mineral-melt interactions. The equation of state is an essential tool for understanding the phenomena because it predicts the thermodynamic properties of the fluids. The modified Lee-Kesler equation of state for H₂O-CO₂ mixture fluid developed by Duan and Zhang (2006) is the most accurate at present and is applicable to a wide pressure-temperature range (∼ 2573 K and ∼ 10 GPa). Because of its high accuracy and wide applicable range, the equation has been used for constructing solubility laws in silicate melts. In this paper I review the Duan and Zhang (2006) equation of state and present the calculation procedure. Because the equation for calculating the partial fugacity coefficient is erroneously presented in the original paper, the correct equation is provided here. A C-language code and a Windows executable program for computing thermodynamic properties are provided for the convenience of users. The influence of the nonideal behaviour of the H₂O-CO₂ mixture fluid on some geological situations is discussed.

The solubility of H₂O and CO₂ in silicate melts is crucial in understanding the geological phenomena occurring in a fluid-melt system. Although several recent solubility models are used in petrological studies, the model of Duan (2014) has rarely been used and has been evaluated less thoroughly, despite its potentially high applicability, mainly because calculation software is unavailable. This paper reviews the Duan (2014) solubility model and its calculation procedure for H₂O-CO₂ solubility. It was found that the Duan (2014) model uses a special protocol to calculate the fluid partial fugacity coefficient, for which no explanation is given in the original paper, thereby limiting the general use of the model. Therefore, I present an appropriate calculation procedure and provide a C-language code for convenience. The predictability of the model was evaluated by comparison with experimental solubility data. It was shown that the Duan (2014) model reproduces well the data for rhyolitic melts, whereas predictability is somewhat weak for other melts, including dacitic, andesitic, and basaltic melts. Caution is thus required when applying the Duan (2014) model to SiO₂-poor melts.

The intensity tensor for Fe²⁺ doublets at the M2 sites and electric field gradient tensor for Fe²⁺ at the M2 sites in two enstatites (En) with the orthorhombic system were determined by single crystal Mössbauer spectroscopy to examine the ferrosilite (Fs) component dependence of the intensity tensor of enstatite. The components of the intensity tensor for Fe²⁺ doublets at the M2 sites in the En_65.5Fs_31.7Wo_2.7-enstatite and En_90.7Fs_8.7Wo_0.6-enstatite are I_XX = 0.577(6), I_YY = 0.454(6), and I_ZZ = 0.470(12), and 0.616(2), 0.458(4), and 0.426(6), respectively. Thus, those three components have a weak dependence on the contents of Fs component. The components, I_XY, I_YZ, and I_XZ, of the intensity tensor due to Mössbauer nuclei that occupy general positions in the space group Pbca pyroxene structure are derived as I_XY = I_YZ = I_XZ = 0 by the symmetric summation of equivalent Mössbauer nuclei in the structural site. Three components, I_XX, I_YY, and I_ZZ, were determined by applying constraint of I_XY = I_YZ = I_XZ = 0. The intensity tensors by Mössbauer nuclei at general positions obtained without any constraints (I_XY ≠ I_YZ ≠ I_XZ ≠ 0) are consistent with those derived by applying the symmetrical constraint (I_XY = I_YZ = I_XZ = 0). This indicates that the intensity tensor due to Mössbauer nuclei that occupy general positions can be simplified by the symmetrical constraint.

Albite porphyroblasts occur in schists in higher-grade zones of the Sanbagawa metamorphic belt, Japan. In this study of pelitic schists from the Nagatoro area of the belt, various microstructures in albite porphyroblasts were identified and indicate that grain size reduction of the albite porphyroblasts occurred after their formation. Schists with recognizable porphyroblasts contain fine grains of albite aligned in the matrix. In comparison, schists without recognizable albite porphyroblasts contain lenticular aggregations of albite grains in quartz-rich layers that suggest grain size reduction of the original porphyroblasts. These observations suggest that the absence of albite porphyroblasts does not necessarily indicate different pressure, temperature, or chemical conditions but can instead be explained by grain size reduction of albite porphyroblasts during deformation.

Kiryuite and gunmaite were found as new minerals from Tsukubara, Kiryu City, Gunma Prefecture, Japan. Kiryuite is a Mn-rich analogue of viitaniemiite with an ideal formula of NaMnAl(PO₄)F₃ that mainly occurs as a white powder in cracks in triplite aggregate and occasionally forms porous plate-like aggregates up to 5 mm in size, while the grains are several micrometers in size. In most cases, the aggregates are also accompanied by small amounts of other minerals such as goyazite, gorceixite, and fluorite. Kiryuite shows white streaks with a vitreous luster, and its Mohs hardness is estimated to be 5 by analogy with viitaniemiite. The calculated density is 3.32 g·cm⁻³ based on the empirical formula and unit cell volume refined from powder X-ray diffraction (XRD) data. The empirical formula for kiryuite calculated on the basis of O = 4 and F + OH = 3 is Na_0.97(Mn_0.56Ca_0.38Fe_0.04Mg_0.02)_Σ1.00Al_0.98P_1.02O₄(F_2.29OH_0.71)_Σ3. Kiryuite is monoclinic (P2₁/m) with a = 5.425(4) Å, b = 7.128(4) Å, c = 6.817(6) Å, β = 109.41(7)°, and V = 248.7(3) ų (Z = 2). The parameters [d in Å (I/I₀) hkl] for the six strongest lines associated with kiryuite in the powder XRD pattern are 3.123 (57) 002, 2.923 (53) 012 and 120, 2.877 (100) 121, 2.560 (27) 200, 2.263 (43) 103, and 2.155 (76) 221. Gunmaite is a new alunite-related mineral with a new structure type that has an ideal formula of (Na₂Sr)Sr₂Al₁₀(PO₄)₄F₁₄(OH)₁₂. Gunmaite mainly occurs as a core in hexagonal tablet crystals that coexist with gorceixite and goyazite-like minerals. Gunmaite is colorless and transparent with a greasy to resinous luster and is non-fluorescent. As a bulk crystal including gunmaite, the Mohs hardness is 5, cleavage is perfect on {001} planes, and the tenacity is brittle. The calculated density based on the empirical formula is 3.38 g·cm⁻³ using the empirical formula and single-crystal XRD data. The empirical formula for gunmaite calculated on the basis of O = 16 and F + OH = 26 is (Na_1.72Sr_0.70Mg_0.56Ca_0.01)_Σ2.99(Sr_1.32Ba_0.68)_Σ2(Al_9.82Mg_0.18)_Σ10P_3.99O₁₆F_16.21(OH)_9.79. Gunmaite is trigonal (R3m) with a = 6.9972(2) Å, c = 50.270(2) Å, and V = 2131.51(13) ų (Z = 3). The structure consists of two PO₄, AlO₂(OH)₄, AlF₆, AlOF₃(OH)₂, SrO₆(OH)₆, and NaF₈ polyhedra. Kiryuite and gunmaite are products of the final stage of hydrothermal activity in association with greisenization.

We examined an alkaline ring complex in the Eastern Desert of Egypt, Wadi Dib ring complex (WDRC), to understand formation mechanisms of the intimately related ring structure and chemical diversity. The WDRC consists of multiple circular rings of the oldest volcanic units, the middle-stage plutonic unit, and the youngest dike unit, and these units show overlapping whole-rock major element compositions. The compositional variation of the volcanic and plutonic units can be accounted for by a stepwise fractional crystallization starting with a trachytic magma without significant magma replenishment or crustal contamination. From the margin to the center and oldest to youngest, the plutonic unit consists of an outer ring (syenite), inner rings 1 (quartz-bearing syenite) and 2 (quartz syenite), and a granitic core (syenogranite). The whole-rock chemical composition of the plutonic unit is progressively more fractionated inwards from the outer ring to the granitic core through the inner rings. Syenites from the innermost outer ring show high degree of deformation, which gradually decreases outwards in the outer ring and abruptly decreases inwards in the outermost inner ring 1. The deformed syenites show microstructures suggesting reactive melt transportation. The country rocks neighboring the ring complex and equivalent blocks present in the periphery of the outer ring, the overlying volcanic unit and equivalent blocks present in the inner rings all show microstructures indicative of pyrometamorphism. Spatial variations in the microstructures in the plutonic unit indicate an increase in cooling rate from the outer ring to the granitic core and thus with time. These geological, chemical, and microstructural features of the WDRC suggest that the ring complex represents an evolving roof zone of a subvolcanic magma body located at a depth of a few km. Intimate coupling of growing roof and sidewall mushy boundary layers and later collapse of the roof boundary layer with occasional involvement of the overlying volcanic piles induced segregation of interstitial fractionated melt from the wall boundary layer to the collapse space driven by a pressure gradient induced by the collapse. The ascended fractionated melt started to crystallize to form a roof boundary layer of the next generation by increasing cooling efficiency, which thickened until the next collapse on a smaller horizontal scale inducing melt segregation from the wall boundary layer towards the roof zone. Repetition of the sequence with shallowing and decreasing the horizontal scale produced the ring structure and chemical diversity of the WDRC.

To clarify the effect of oxygen defects on the perovskite structure under high pressure, structural changes in srebrodolskite Ca₂Fe₂O₅ were investigated by using high-pressure Raman spectroscopy and synchrotron powder X-ray diffraction analyses. The result of the high-pressure Raman spectroscopic study showed that with compression, a new Raman band appeared at 12.0 GPa. Furthermore, an additional new Raman band appeared at 16.0 GPa. The phase-transition pressure was approximately consistent with the previous research, and the intensities of these new bands became much stronger with increasing pressure. At least nine Raman bands were observable at 23.0 GPa. A high-pressure synchrotron powder X-ray diffraction study was performed up to 20.2 GPa. The obtained pressure-volume compression curve apparently deviated from the equation-of-state of srebrodolskite determined by the previous study above 9.1 GPa, at which point srebrodolskite began to transform into its high-pressure phase. The Rietveld refinement of the X-ray diffraction data at 12.6 GPa fitted with space group Pn2₁a yielded agreement factors of R_p = 1.46% and wR_p = 2.01%. The second high-pressure phase transition occurred at 14.2 GPa with the emergence of new reflections at d-spacing values of 3.938 and 1.953 Å. The powder X-ray diffraction patterns of the second high-pressure phase were characterized by three reflections appearing at approximately d-spacing values of 3.938, 2.609, and 1.953 Å. Consequently, the second high-pressure phase is likely to be composed of a new structure that is not included in the known brownmillerite-type structures. The results provide clues for understanding the physical properties of the chemically heterogeneous Earth’s mantle.

Needle-shaped rutile inclusions occur in garnet within the quartz-eclogite at Mt. Gongen in the Sanbagawa belt, central Shikoku. They are approximately 5-25 µm along the long axis and are typically oriented along three directions, each intersecting at 120°. This indicates that the needle-shaped rutile is a lamella exsolved from the garnet. Garnet with needle-rutile inclusions is restricted to the quartz-poor domain of the quartz eclogite sample, which consist of quartz, garnet, omphacite, phengite, epidote, kyanite, and hornblende. Garnet grains with rutile lamellae show a composition of the almandine-pyrope series with 14-21 mol% grossular content. Rutile exsolution lamellae were concentrated in the range of 27-34 mol% pyrope of garnet crystals. The garnet host with rutile lamellae has a higher TiO₂ content (TiO₂ = 0.06-0.19 wt%) than those in rutile-free areas. These chemical compositional characteristics suggest that Ti was incorporated into the crystal structure during garnet growth and subsequently partially exsolved as rutile lamellae during the retrograde stage. Rutile lamellae in garnet have generally been regarded as indicators of ultrahigh-pressure metamorphism, but the present report from quartz-eclogite of the Sanbagawa belt, where no coesite has been found, provides evidence in a natural sample that the appearance of rutile exsolution lamellae is not necessarily under ultrahigh-pressure conditions.

We carried out zircon U-Pb dating of the Cretaceous gabbroic and granitic rocks exposed in the Kajishima to determine their magmatic ages. The plutonic rocks in the Kajishima are classified into seven lithologies: Hbl-bearing olivine norite, Type-1 Hbl-bearing troctolite, Type-2 Hbl-bearing troctolite, Type-1 pyroxene hornblende gabbronorite, and Type-2 pyroxene hornblende gabbronorite, massive granodiorite, and deformed granodiorite. The new zircon U-Pb ages are: 90.77 ± 0.99 Ma for the Type-2 Hbl-bearing troctolite, 92.35 ± 0.74 Ma for the Type-1 pyroxene hornblende gabbronorite, 91.33 ± 1.03 Ma for the massive granodiorite, and 84.11 ± 1.12 Ma for the deformed granodiorite. The new zircon U-Pb ages suggest multiple episodes of magmatic intrusion in Kajishima during ∼ 92 and 84 Ma. Although two gabbroic rocks and a massive granodiorite show similar zircon U-Pb ages, subsequent granitic magmatism is unraveled in Kajishima, which is contrary to previous geological studies that postulated an evolution of all plutonic rocks from a single gabbroic parent magma.

Several investigations have demonstrated that olivine may be used to simulate geochemical and cosmochemical reactions. Since olivine in extra-terrestrial samples has varying forsterite numbers and natural olivine contains inevitable impurities, synthetic olivine with the requisite forsterite number has been prepared for various experimental research. This study aimed to synthesize Fe-bearing olivine via synthetic experiments conducted at near-solidus temperatures and elucidate the formation and decomposition mechanisms of the obtained Fe-bearing olivine. Specifically, we attempted to synthesize Fo₆₀ [Forsterite number = 100 × Mg/(Mg + Fe) = 60] olivine using a mixture of analytical-grade SiO₂, MgO, and Fe₂O₃. To clarify the stability of the obtained olivine, the temperature range (1350-1500 °C) and heating durations (1.5 or 15 h) were controlled under a constant oxygen fugacity of QFM-1 log units.

The target olivine (Fo₆₀) was obtained via heating for 1.5 h at 1500 °C, corresponding to the solidus line temperature. However, maintaining the olivine obtained at this temperature for 15 h resulted in a much higher forsterite number owing to the formation of oxidized minerals of olivine (magnetite and pyroxene). Similar oxidation products were also obtained following heating at 1450 °C for 15 h. These results indicated the primary formation of Fe-bearing olivine during 1.5 h of heating and its subsequent decomposition to magnetite and pyroxene owing to the high-temperature oxidation at near-solidus temperatures during heating for 1.5-15 h. These findings highlight a strategy for synthesizing Fe-bearing olivine and the associated mechanism and provide experimental insights into the decomposition of olivine in natural igneous rocks.

Analytical transmission electron microscopy (ATEM) is a powerful tool to obtain the chemical compositions of minerals at very small areas of minerals down to the nanometer scale. Most ATEM analytical systems are capable of performing quantitative calculations of chemical compositions by absorption correction. However, an appropriate procedure of obtaining the correct chemical compositions by absorption correction has not yet been established. In this study, we analyzed thin foils of garnet and olivine with known compositions and thicknesses using two different analytical systems to evaluate the certainty of the absorption correction based on the Cliff-Lorimer equation. The results show that the absorption correction using the real sample thicknesses at the analyzed spots did not yield the correct chemical compositions. The correct quantification data were obtained when using the sample thickness t corrected to minimize the value of the function SSR(t) (sum of squared residuals) = ∑_i[n_i⁰ − ∑_j n_ij(t)]², where n_i⁰ is the ideal atomic percentage of the i site, n_ij(t) is the atomic percentage of the j ion at the i site calculated by the software, and the sum holds all the ionic sites. Also, it was confirmed that the minimum value of the SSR obtained by calculating all existing elements as oxides (oxygen is not quantified) is in most cases smaller than that obtained by quantifying all elements, including oxygen, independently. This method of using the SSR without knowing the real thickness at the analyzed spot can be applied to the analytical results with absorption correction by any software. Therefore, this SSR has the potential of becoming a universal indicator to assess the results of quantitative chemical analyses by absorption correction in ATEM.

A previous high-pressure Raman spectroscopic study of phase A [Mg₇Si₂O₈(OH)₆] by Liu et al. (1997) showed that two O-H stretching bands gradually approach each other up to 18 GPa but do not intersect and move apart thereafter. In this study, vibrational calculations of phase A were performed to elucidate the origin of this behavior. The calculations with and without deuterium substitution show that pressure-tuned correlation field splitting of O-H stretching vibration is responsible for this curious behavior. The observed pressure changes in the O-H stretching frequencies were qualitatively reproduced. In phase C (= superhydrous phase B), the two O-H bands observed about 60 cm⁻¹ apart at 1 atm were found to be the result of correlated field splitting. The effect of correlation field splitting on the O-H stretching vibration modes is easily overlooked but can be clarified by vibrational calculations that mimic the isotope dilution method, as demonstrated in this study.

We estimated the protolith age and peak metamorphic temperature of the Yokokawagawa metamorphic rocks (YMR) east of the Itoigawa-Shizuoka Tectonic Line using detrital zircon U-Pb dating and Raman carbonaceous material geothermometry, respectively. U-Pb dating of a psammitic rock yielded a youngest age of ∼ 100 Ma, which corresponds to the protolith age. Raman carbonaceous material geothermometry results for five pelitic rock samples give metamorphic temperatures of ∼ 350-380 °C. The protolith age is consistent with those of the Sanbagawa metamorphic rocks (SMR), strongly indicating that the YMR are an extension of the SMR. The increase in peak temperature toward intrusive rocks along the eastern margin of the YMR may indicate that the relatively young ages yielded by previous K-Ar dating of the YMR reflect thermal resetting due to contact metamorphism.

The crystal structures of α-Na₂B₄O₇ and γ-Na₂B₄O₇ formed during the heating of borax were investigated by single-crystal X-ray diffraction. In addition, the structural stability of the fundamental building blocks (FBBs) was examined using ab initio quantum chemical calculations. α-Na₂B₄O₇ crystallized into the triclinic space group P1 with unit cell dimensions of a = 6.5489(7) Å, b = 8.6261(9) Å, c = 10.4909(11) Å, α = 93.2540(10)°, β = 94.8660(10)°, γ = 90.8380(10)°, V = 589.45(11) ų. γ-Na₂B₄O₇ crystallized into the triclinic space group P1 with unit cell dimensions of a = 6.7123(11) Å, b = 9.6052(17) Å, c = 13.270(2) Å, α = 104.183(4)°, β = 91.560(4)°, γ = 106.501(4)°, and V = 791.0(2) ų. In both α-Na₂B₄O₇ and γ-Na₂B₄O₇, Na coordination polyhedra with the same coordination numbers have similar coordination volumes; however, the Na polyhedra in γ-Na₂B₄O₇ possess more distortable environments than those in α-Na₂B₄O₇. The flexibility of the Na coordination environment allows these materials to adopt favorable oxygen positions, leading to an α-γ phase transition. The structural stability of the FBBs in α-Na₂B₄O₇ and γ-Na₂B₄O₇ was lowered by dehydration and recrystallization. Consequently, α-Na₂B₄O₇ and γ-Na₂B₄O₇ possess FBBs with readily changeable connection geometries, which causes a phase transformation between α-Na₂B₄O₇ and γ-Na₂B₄O₇ without requiring a significant amount of energy.

Single crystals of CaW_1−xMo_xO₄ scheelite-powellite solid solutions (x = 0.0, 0.03, 0.08, 0.2, 0.3, 0.5, 0.8, and 1.0) were synthesized using a melting method. The light emission spectra of the solid solutions were measured using a JASCO FP-8300 fluorescence spectrometer. The maximum fluorescence peak at 419 nm in the CaWO₄ scheelite end-member greatly decreases in intensity and shifts its peak position to 451 nm with only 3% Mo substitution. The change in near-ultraviolet light emission intensity at 292 and 301 nm are more moderate than those in the strong peak at 419 nm. The tendency of change in intensity and wavelength shift due to the Mo substitution differs among these fluorescence peaks. Single crystal X-ray diffraction experiments for the CaW_1−xMo_xO₄ solid solutions (x = 0.0, 0.2, 0.3, 0.5, 0.8, and 1.0) were carried out using a Rigaku Super-Nova Single source at offset/far HyPix3000 diffractometer. The R₁ index for CaW_1−xMo_xO₄ solid solutions were convergent to 1.22-1.71% using anisotropic temperature factors. The expansion of the c-axis and shrinkage of the unit cell volume were induced with an increase in Mo content. The significant increase in the angle ∡O_closer-Ca-O_closer was directly related to the expansion of the c-axis. The Debye temperature Θ_D for Ca, W, and O atoms in CaWO₄ were 381, 198, and 534 K, respectively. The obtained Θ_D for Ca, Mo, and O atoms in CaMoO₄ were 363, 257, and 503 K, respectively. The phonon density of states estimated from the lattice dynamics calculations coincided with the observed Θ_D values.

Rocks have pores of various sizes. We investigated which pore sizes filled with water and in what order with the progression of water infiltration. The pore radii of the sandstone mainly ranges from a few µm to several tens of µm. Water was passed through the sandstone core at 25 °C, and water saturation, S, was adjusted to 63, 67, 71, 87, and 100%. At each S, the porewater radius distribution was measured using the water expulsion method, in which water in pores of a given pore radius was expelled by gas pressure. The results showed that the porewater radius distribution was approximately the same for S = 63-71%. As S increased from 71 to 100%, the pores with 4-10 and 10-20 µm radii were filled with water first, followed by pores with 20-52 µm radius. For S = 63-71%, water was considered to have entered via adsorption on the pore walls and capillary action at the corners of the pore. Because this water cannot be expelled by gas pressure, an increased amount of water was not detected by the water expulsion method. As for the results at S > 71%, a theoretical model of the dissolution of entrapped air, assuming a cylindrical shape, showed that the length of the trapped air decreases faster in pores with small radii than in those with large radii. This may be a major explanation for the experimental result, which showed that pores with small radii fill with water more quickly than those with large radii.

The frequency characteristics of acoustic emission (AE) during triaxial compression of thermally cracked and unheated (‘fresh’) granite samples were investigated with the aim of understanding the influence of pre-existing cracks on precursor information regarding macroscopic failure. The peak frequency during the damage process was the same for thermally cracked and fresh granites. Analysis of AE signals showed that signals with low peak frequency appeared before failure of the sample, implying the initiation of macrocracks with progressive growth of cracks. The peak amplitude of the frequency spectrum recorded in the thermally cracked samples was much lower than that in the fresh samples. This result suggests two reasons for the difference in peak amplitude: reduction in shear modulus and the attenuation filtering phenomenon caused by thermal cracks (i.e., the differences in overall bulk properties). In particular, the maximum value of peak amplitude in the low-frequency band for the thermally cracked samples was smaller than that for fresh samples. This characteristic can be related to the properties of source of AE signals, such as the stress drop and crack size. Assuming that pre-existing thermal cracks grow during the pre-failure stage, the events with low peak frequency and low peak amplitude in the heat-treated samples are interpreted as exhibiting a low stress drop for individual events. Therefore, although AE signals with low frequency can be considered as precursors to rock failure, cracking behavior suggested by events with low frequency depends on the initial damage condition of the rock sample.

Microbial organic molecules are widely involved in the formation of calcium carbonate (CaCO₃) minerals in various environments on the earth’s surface including hot springs. To evaluate the effect of acidic microbial polysaccharides on the CaCO₃ polymorph formation in hot water environments, batch experiments on the CaCO₃ formation were performed in the systems containing alginic acid (A system) or gellan gum (G system) at 40, 60, and 80 °C for 24 h. Each system contained 5.0 mmol/L Ca²⁺ and 20.0 mmol/L total carbonate ions with 0.0, 1.0, 5.0, 10, 50, and 100 mg/L alginic acid or gellan gum. Results showed that needle- or rod-like shaped aragonite crystals were formed as the predominant polymorph in the absence of polysaccharides at 40-80 °C. In the presence of polysaccharides, alginic acid greatly inhibited the aragonite formation and favored the rhombohedral calcite formation as the predominant polymorph with increasing alginic acid concentration at 40 °C. The effect of alginic acid on the polymorphs slightly decreased as temperature increased but was maintained up to 80 °C. Gellan gum also exhibited a similar effect to a lesser extent than alginic acid at the same concentrations and temperatures. Thus, acidic microbial polysaccharides exhibited a significant inhibitory effect on the aragonite formation and favored the calcite formation depending on their molecular structures in hot water environments. This effect of polysaccharides on the CaCO₃ polymorphs is attributed to the high adsorption affinity of the polymer molecules for the aragonite surface.

Hydrocarbon fluid inclusions in authigenic quartz from the Jurassic Torinosu Limestone and associated sediment at Sakawa town, Japan, were studied by microthermometry, ultraviolet (UV) fluorescence, and Raman spectroscopy. The quartz contained abundant liquid hydrocarbon and subordinate vapor hydrocarbon fluid inclusions, and tiny solid inclusions of bitumen, calcite, and rarely pyrite. Aqueous fluid inclusions and aqueous components in hydrocarbon inclusions were absent. Under UV irradiation, most of the liquid inclusions from the limestone and associated sediment displayed intense whitish-blue and deep-blue luminescence, respectively. Further, these liquid inclusions were homogenized at around 24 °C and 53 °C, respectively. Small numbers of liquid inclusions from the associated sediments contained a liquefied gas-condensate. Raman measurements indicated the presence of aromatic compounds and the absence of H₂O or CO₂ molecules in the liquid and vapor inclusions.

Katoite, ideally denoted as {Ca₃}[Al₂](□_xSi_3−x)(OH)_4xO_12−4x, where 1.5 < x ≤ 3, was found in skarn xenoliths from Tadano, Fukushima Prefecture, Japan, and investigated by electron microprobe analyses, X-ray single crystal structure refinement, and infrared (IR) spectroscopy. Katoite characteristically contains up to 0.18 atoms per formula unit (apfu) of S and has a range of compositions, wherein Si = 0.96-1.25 apfu, Al = 1.47-1.74 apfu, Fe = 0.13-0.28 apfu, and Mg = 0.01-0.10 apfu. A difference Fourier map revealed the residual electron density near the octahedral Y site (Wyckoff position = 16a), and we interpreted that S with three-fold coordination occurs at the position of the residual electron density, which is represented as the Y’ site (Wyckoff position = 32e). The final refinement introduced the Y’ site to yield R1 [F² > 2σ(F²)] = 0.0353 with space group Ia3d and unit cell parameter a = 12.24095(8) Å. The IR spectrum in the range of 800-1200 cm⁻¹ shows a band at 1124 cm⁻¹ due to ν₃(SO₄) and doublet bands at 879 and 931 cm⁻¹ with different absorbances interpreted as ν₃(SiO₄) overlapping with ν₃(SO₃). The combined results of IR spectroscopy and structure refinement imply that in the Tadano katoite, S⁴⁺ and S⁶⁺, forming (SO₃)²⁻ and (SO₄)²⁻ coordinations, are placed at the Y’ and tetrahedral Z sites, respectively. Assuming that S is preferentially allotted to the Y’ site as S⁴⁺ to compensate for the deficiency of the octahedral cations Al, Fe, Mg, Mn, and Ti at the Y site, chemical formulae, including possible S⁴⁺ and S⁶⁺ contents, may be calculated. The average chemical formula for 14 different spots is as follows: {Ca₃}[(Al_1.614Fe³⁺_0.208Mg_0.063Ti_0.019)_Σ1.90S⁴⁺_0.096]_Σ2.00(□_1.867Si_1.120S⁶⁺_0.013)_Σ3.00[(OH)_7.192O_4.612F_0.147Cl_0.048]_Σ12.00.

We conducted single-crystal X-ray diffraction experiments on kulanite [Ba(Fe²⁺, Mn²⁺, Mg)₂(Al, Fe³⁺)₂(PO₄)₃(OH)₃] to investigate the potential orientational ordering of its hydroxy groups. Structural refinements showed no sign of a phase transition between 120 and 353 K. Additionally, the orientation of the hydroxy group was determined uniquely along the c-axis for the measured temperature range of 120-353 K.

The metamorphic and plutonic rocks within a serpentinite mélange in the Nagato Tectonic Zone, Yamaguchi prefecture, southwest Japan have been known as a part of the early Paleozoic rock record in Japan. Thus, they play an important role in deciphering the tectonic evolution of proto-Japan. This study determined their U-Pb zircon ages to deduce the origin and geological significance of the Nagato Tectonic Zone. The results of the petrographic observation and LA-ICP-MS U-Pb zircon dating revealed the occurrences of the massive amphibolite originated from the 460 Ma mafic igneous rock, two-mica tonalites formed at 470-460 Ma in association with some xenocrystic zircon grains, and low-grade metasedimentary rocks including detrital zircon grains of 2460-400 Ma. The lithology, petrographic characteristics, and U-Pb zircon ages of these constituent rocks in the Nagato Tectonic Zone are well comparable with the blocks within serpentinite mélange in the Kurosegawa Tectonic Belt, rather than the Hida Gaien Belt which has been considered to form a single geological unit with the Nagato Tectonic Zone as the Sangun-Renge metamorphic belt or Nagato-Renge belt. It implies the Nagato Tectonic Zone could be regarded as an isolated fragment of the Kurosegawa Tectonic Belt. The features of detrital age spectra and Ordovician magmatism in the Nagato Tectonic Zone and Kurosegawa Tectonic Belt provide the possibility of the development of their granitoids and protoliths of metamorphic rocks at the active continental margin of the South China craton.

Serpentinization is a widely observed hydration process in the earth’s crust. In this study, hydrothermal experiments were performed at different temperatures, times, and pH values to explore the geochemical processes of serpentinization in forsterite. The results indicated that forsterite converts to serpentine after reacting with SiO₂ at 200 °C and a pH of 13 for 20 days in a hydrothermal system. X-ray diffraction patterns showed that the serpentine is lizardite, with lamellar and leaf-like micro-morphology. Furthermore, hydroxyl absorption peaks, which represent the formation of lizardite, were observed in the Fourier-infrared spectroscopy spectra. The newly formed serpentine showed high crystallinity and a relatively perfect crystal form. High-resolution electron microscopy indicated that the serpentine crystal layer only appeared on the forsterite surface. The transformation was a process of the coupling of dissolution and precipitation where the forsterite was replaced from the surface; [SiO₄]⁴⁻ and [MgO₆]¹⁰⁻ units were attached in situ to the forsterite surface, reacted, and formed a serpentine structure. These results are of fundamental significance for exploring the transformation and controllable synthesis between olivine group and serpentine group minerals as well as understanding the genesis, geochemical behavior, and geological environment of ultrabafic rock alteration deposits.