著者

Yuki MORI Tomokazu HOKADA Tomoharu MIYAMOTO Takeshi IKEDA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

pp.221124, (Released:2023-05-15)

被引用文献数

2

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We determined the metamorphic age and pressure–temperature conditions recorded in a sillimanite-garnet-bearing pelitic gneiss from Niban-nishi Rock, which is part of Niban Rock, on the Prince Olav Coast, eastern Dronning Maud Land, East Antarctica. Niban-nishi Rock is recognized as a component of the Lützow-Holm Complex (LHC), which is characterized by metamorphic age of 600–520 Ma and metamorphic grade of amphibolite to granulite facies. Electron microprobe U–Th–Pb monazite dating of the examined gneiss revealed that, unlike the typical exposures of the LHC, Niban-nishi Rock experienced Tonian metamorphism at 940.1 ± 9.8 Ma (2σ level), and is thus more similar to the neighboring exposures of Cape Hinode and Akebono Rock. Small numbers of younger monazite ages of 827–531 Ma were also detected, and some of which might relate to the metamorphism of the LHC. Phase equilibrium modeling and geothermobarometry indicate metamorphic conditions of 690–730 °C/0.38–0.68 GPa and 620–670 °C/0.42–0.60 GPa for peak and retrograde stages, respectively. The obtained peak temperature is lower than that of typical exposures in transitional- and granulite-facies zones of the LHC, such as Akarui Point and Skallen. Metamorphic features of Niban-nishi Rock, such as the upper amphibolite-facies condition and occurrences of garnet with retrograde zoning and sillimanite in the matrix, differ from those of Cape Hinode and Akebono Rock, with the former belonging to granulite facies and the latter showing kyanite in the matrix and garnet with growth zoning. Investigating Niban-nishi Rock is key in revealing the tectonic relation between the LHC and Cape Hinode (the Hinode Block). Further field surveys are required to reveal the metamorphic variations and the relations among exposures on the Prince Olav Coast.

著者

Yoshikuni Hiroi Tomokazu Hokada Tatsuro Adachi Kazuyuki Shiraishi Yoichi Motoyoshi Edward S. Grew

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

pp.221209, (Released:2023-03-28)

被引用文献数

3

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Grandidierite, (Mg,Fe)Al3O2(BO3)SiO4, was found in a garnet-clinopyroxene-ilmenite-rich mafic granulite from Austhovde in the Late Neoproterozoic to Early Cambrian Lützow-Holm Complex (LHC), East Antarctica, the first reported occurrence of this borosilicate in a mafic granulite. It occurs in one of the many nanogranitoid inclusions (NIs) in garnet. Quartz, sodic plagioclase, myrmekite, K-feldspar, epidote and biotite are also found only as inclusions in garnet. Garnet porphyroblasts show marked compositional zoning: Ca increases and Mg decreases from the core to rim with little change in Fe and Mn contents except for the outermost rim. Anorthite content of inclusion plagioclase increases from core to rim of host garnet in parallel with increase in garnet Ca towards the rim. This together with the distinctly different mineral assemblages within and exterior to garnet porphyroblasts suggests that partial melting took place and produced melts were extracted leaving a mafic and calcic restite. Partial melting also occurred locally in garnet porphyroblasts consuming different hydrous mineral inclusions to produce various NIs ranging from K-feldspar-rich to K-feldspar-free. Subsequent decompression at high temperatures resulted breakdown of garnet to orthopyroxene + calcic plagioclase with further consumption of quartz, such that none remained in the matrix of the granulite. Grandidierite may have formed by a reaction between a trapped boron-bearing aluminous granitic melt and host garnet upon cooling.

著者

Tadashi YOKOYAMA Satoki SHINTAKU Naoki NISHIYAMA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

pp.221107, (Released:2023-03-11)

被引用文献数

1

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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 µm 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.

著者

Kei-ichiro Murai Koyumi Yamashita Ginga Kitahara Makoto Tokuda Akira Yoshiasa

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

pp.220901, (Released:2023-03-11)

被引用文献数

2

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Single crystals of CaW1-xMoxO4 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 CaW1-xMoxO4 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 CaW1-xMoxO4 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 ∡Ocloser-Ca-Ocloser was directly related to the expansion of the c-axis. The Debye temperature ΘD for Ca, W and O atoms in CaWO4 were 381, 198 and 534 K, respectively. The obtained ΘD 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 ΘD values.

著者

Yasuyuki BANNO Koichi MOMMA Ritsuro MIYAWAKI Michiaki BUNNO

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

pp.220724, (Released:2023-02-04)

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Katoite, ideally denoted as {Ca3}[Al2](□xSi3-x)(OH)4xO12-4x, 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}[(Al1.614Fe3+0.208Mg0.063Ti0.019)Σ1.90S4+0.096]Σ2.00(□1.867Si1.120S6+0.013)Σ3.00[(OH)7.192O4.612F0.147Cl0.048]Σ12.00.

著者

Massimo NESPOLO Tohru OZAWA Yusuke KAWASAKI Kazumasa SUGIYAMA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.107, no.6, pp.226-243, 2012 (Released:2012-12-29)

参考文献数

32

被引用文献数

7 10

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The structure of quatrandorite is reported for the first time from an untwinned sample from Oura mine, San Jose, Bolivia. The mineral crystallizes in P21/c, a = 19.1686 (19) Å, b = 17.160 (3) Å, c = 13.042 (2) Å, β = 90.008 (12)°, V = 4289.9 (11) Å3, Z = 4. Refinement to Robs = 5.66% was obtained with Jana2006. Quatrandorite belongs to the andorite series, whose members share two cell parameters while the third can be expressed as n × 4.3 Å, with n = 2, 4 and 6 for ramdohrite (uchucchacuaite, fizelyite), quatrandorite and senandorite, respectively. Both quatrandorite and senandorite are strongly pseudosymmetric up to Cmcm with one parameter corresponding to n = 1 (∼ 4.3 Å). The hypothetical structure corresponding to Cmcm is also the aristotype common to both minerals. The strong structural similarity of quatrandorite and senandorite may explain their co-existence in some samples, which has in the past led to hypothesize the existence of a further member of the series, nakaséite, which was however later shown to consist of a random stacking of the two minerals. The Cmcm aristotype is not common to the n = 2 minerals (uchucchacuaite, ramdohrite, fizelyite), which are thus structurally less closely related to the two other members. A common aristotype to all three minerals can nevertheless be obtained via a different path, which leads to Cmme with the same cell parameters as Cmcm; the degree of pseudo-symmetry in this supergroup is however lower and there remain a difference in one sulfur position in this aristotype. It nevertheless confirms previous reports in the literature stating that the bulk of the structure of the minerals of this series can be reduced to a common principle, essentially a distorted galena; the departures from it are however crucial for the realization of the individual structures.

著者

Daiki FUKUYAMA Keiji SHINODA Daigo TAKAGI Yasuhiro KOBAYASHI

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.117, no.1, pp.220506, 2022 (Released:2022-10-18)

参考文献数

21

被引用文献数

2

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The compositional dependence of the intensity and electric field gradient (EFG) tensors for Fe2+ at the M1 sites, Fe2+ at the M2 sites, and Fe3+ at the M1 sites in Ca–rich pyroxene were obtained from Mössbauer spectra of crystallographically oriented single–crystal thin sections of four Ca–rich natural pyroxenes. Components of the intensity tensor (IXX, IYY, IXY, and IZZ) for Fe2+ at the M1 sites in Wo50 Ca–rich pyroxene were almost the same; the averages of the IXX, IYY, IXY, and IZZ components were 0.342, 0.477, 0.039, and 0.681, respectively. Intensity tensor for Fe2+ at the M1 sites of Wo40 Ca–rich pyroxene was different from the Wo50. Whereas principal axes of EFG tensors for Fe2+ at the M1 sites of Wo50 pyroxenes had the same direction, principal axes of VXX and VYY of EFG of Wo40 had different directions from that from Wo50. The difference of intensity and EFG tensors between Wo50 and Wo40 suggests that the intensity and EFG tensors for Fe2+ at M1 sites are dependent on the Ca contents and are independent of Fe contents. Some intensity and EFG tensors for Fe2+ at the M2 sites and Fe3+ at the M1 sites in Ca–rich pyroxene were also obtained. However, the compositional dependence of the intensity and EFG tensors has yet to be clarified, because the number of examples is insufficient.

著者

Fumiko HIGASHINO Tetsuo KAWAKAMI

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.117, no.1, pp.220325, 2022 (Released:2022-10-08)

参考文献数

59

被引用文献数

6

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This paper reports the first outcrop occurrence of an ultrahigh–temperature (UHT) metamorphic rock from the Sør Rondane Mountains (SRM), East Antarctica. A pelitic gneiss from Balchenfjella, eastern SRM, contains mesoperthite that gave UHT condition (>900 °C) by ternary feldspar thermometry. The UHT mesoperthite is present both in the matrix and as an inclusion in garnet. The garnet also has nanogranitoid inclusions next to the mesoperthite, which are interpreted to be an UHT melt. The re–integrated nanogranitoid composition is plotted in the primary phase region of quartz and classified as granite. Even crystallized nanogranitoids can provide appropriate original melt composition in the An–Ab–Or and Qz–Ab–Or spaces, whereas Mg concentration is enriched due to local retrograde Fe–Mg exchange reaction between the nanogranitoid inclusions and the host garnet. Although metamorphic rocks in the SRM are highly retrogressed, this study revealed that the microstructural evidence of UHT condition is partially preserved. Further investigation of timing and areal extent of UHT metamorphism helps us to understand the tectonic model of the SRM.

著者

Takashi YUGUCHI Hideki IWANO Takenori KATO Shuhei SAKATA Kentaro HATTORI Takafumi HIRATA Shigeru SUEOKA Tohru DANHARA Masayuki ISHIBASHI Eiji SASAO Tadao NISHIYAMA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.111, no.1, pp.9-34, 2016 (Released:2016-03-07)

参考文献数

86

被引用文献数

17 21

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Zircons collected from a granitic pluton provide evidence of serial growth events with specific mechanisms, crystallization temperatures and U–Pb ages, revealing details of the sequential formation process from intrusion through emplacement to crystallization/solidification. The events have been identified by: 1) the study of the internal structure of zircon using cathodoluminescence, 2) deriving crystallization temperatures using Ti–in–zircon thermometry of the internal structure and 3) U–Pb age dating of the internal structure. The magmatic zircons from the Toki granite, central Japan, show two kinds in their internal structure: a low luminescence core (LLC) and oscillatory zonation (OZ). The LLC was produced by interfacial reaction–controlled growth in the granitic magma with cooling from about 910 to 760 °C. The formation of OZ occurred by diffusion–controlled growth in a cooling magma chamber from about 850 to 690 °C. The U–Pb ages derived from the LLC ranges from 74.7 ± 4.2 to 70.5 ± 1.3 Ma, indicating the incipient intrusion timing of the magma into the shallow crust. The OZ ages distribute from 72.7 ± 0.6 to 70.4 ± 1.7 Ma, which mean the timing from emplacement to crystallization/solidification of the granite pluton. Thus, the serial processes from intrusion through emplacement to crystallization/solidification occurred within a few million years. The old LLC and OZ ages are recognized in the western margins of the Toki granite, implying that the magma forming the western margins was the first to intrude, emplace and crystallize/solidify. The western margins with initial intrusion may accompany the crustal assimilation in order to create sufficient magma reservoir space, which is consistent with larger SrI and ASI values found in the western margins of the granite.

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.117, no.1, pp.220525, 2022 (Released:2022-06-28)

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Editorial Message

著者

Tomokazu HOKADA Tatsuro ADACHI Yasuhito OSANAI Nobuhiko NAKANO Sotaro BABA Tsuyoshi TOYOSHIMA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.117, no.1, pp.220317, 2022 (Released:2022-08-20)

参考文献数

38

被引用文献数

3

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We have found corundum in direct contact with quartz and biotite and as inclusions in garnet in the pelitic gneisses of northern Austkampane in the Northeastern (NE) Terrane of the Sør Rondane Mountains (SRM), East Antarctica. Our samples, which include corundum–bearing gneisses, show petrographic features such as staurolite inclusions in garnet, compositional zoning of orthoamphibole with Al decreasing toward the rims, and late–stage cordierite formation, and these features are characteristic of a clockwise P–T trajectory. The observations are consistent with the proposed regional clockwise P–T evolution of the NE Terrane in the SRM. The corundum and other inclusions observed in the garnet porphyroblasts are interpreted to have formed owing to either staurolite breakdown or metastable crystallization relative to kyanite prior to the peak metamorphism. The close association of biotite and quartz surrounding corundum inclusions suggests fluid– or melt–related processes. These petrographic features imply that the corundum and quartz (rarely observed in high–grade metamorphic rocks) formed as a result of metastable crystallization during the prograde stage of the clockwise P–T evolution of a continental collision zone.

著者

Shoji ARAI Hisatoshi HIRAI Kozo UTO

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.95, no.4, pp.9-23, 2000 (Released:2005-12-15)

参考文献数

73

被引用文献数

56 58

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There are a number of Cenozoic ultramafic xenolith localities on the Southwest Japan arc, which enable us to deduce a petrological model of the upper mantle of the island arc or active continental margin on a regional scale. On the basis of mineral chemistry and petrology the mantle peridotites (harzburgite and lherzolite) from the Southwest Japan arc can be divided into two types, unmetasomatized and metasomatized types. The former type of peridotites, which are less predominant than the latter, have characteristics of mantle restite (olivine of Fo88−91) and are not accompanied with Fe-rich black pyroxene-bearing xenoliths and related pyroxene megacrysts. They are found exclusively in isolated monogenetic volcanoes not forming volcano clusters. In contrast, the latter type of peridotites, which are always accompanied with large amounts of Fe-rich black pyroxenite xenoliths and related black pyroxene megacrysts, have less magnesian minerals (e.g., olivine of Fo78−90) depending on the degree of metasomatism. They have textural and modal characteristics as mantle restites but also have chemical characteristics as metasomatites. They are mainly found in monogenetic volcanoes constituting volcano clusters.    The Fe-rich pyroxenites and related rocks are young precipitates of possibly Tertiary ages from alkali basaltic melts, genetically related with the xenolith-carrying basalts. A large scale asthenospheric upwelling in the Miocene time may have been responsible both for the intra-plate alkali basalt magmatism, namely the formation of xenolith-bearing basalts, metasomatism and precipitation of Fe-rich pyroxenites and megacrysts, and for the Japan Sea opening. The formation of Fe-rich pyroxenites and related rocks strongly modified the pre-existing mantle-crust both in chemistry and structure, leaving a chemically and geophysically intermediate Moho transition zone. This may be one of the characteristics of the upper mantle of active continental margin or island arc in the Western Pacific.

著者

Yoshihiro NAKAMURA Koji U. TAKAHASHI Jun HOSOI Hidetoshi HARA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.117, no.1, pp.220316, 2022 (Released:2022-08-09)

参考文献数

32

被引用文献数

1

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A new type of compact deep–UV micro–Raman spectroscopy system was developed with a single monochromator, front–illuminated cooled charge–coupled device, and 266 nm nanosecond pulsed laser to overcome laser–induced fluorescence from surrounding minerals and organic material. Deep–UV micro–Raman spectroscopy is particularly useful in analyzing the fluorescence–free Raman spectra of dispersed low–maturity carbonaceous material and coal, although deep–UV excitation lasers may cause serious degradation and laser–induced heating of the sample surface, especially in microanalysis. The laser–induced damage threshold for fully ordered graphite and coal (VRr = ~ 0.5%) was assessed to facilitate the acquisition of accurate Raman spectra with a spot size of ~ 1 µm. For fully ordered graphite, there was no serious degradation of the sample surface with an energy fluence of 0.10–2.50 J cm−2. Some sample surfaces became black at higher fluences of 1.96–2.50 J cm−2, suggesting irreversible damage by deep–UV lasers. The Raman shift of the G band after measurement involves a downshift of 1.7–7.4 cm−1 relative to other spectra obtained at low laser fluences of <0.34 J cm−2. The G band full width at half maximum (FWHM) also increased with increasing laser fluence. Serious degradation of polished coal surfaces occurs at even lower laser fluences of 0.34–2.50 J cm−2. The degree of change in Raman parameters such as the D and G band FWHM depends on the laser fluence during measurements. Heating and damage by a deep–UV laser is greater than that by visible lasers. Laser fluences of <0.16 and 0.34 J cm−2 are required for accurate Raman analyses of dispersed carbonaceous material in sedimentary rocks and fully ordered graphite in metasediment, respectively.

著者

Yuichiro MORI Hiroyuki KAGI Sho KAKIZAWA Kazuki KOMATSU Chikara SHITO Riko IIZUKA–OKU Katsutoshi AOKI Takanori HATTORI Asami SANO–FURUKAWA Ken–ichi FUNAKOSHI Hirouyki SAITOH

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

pp.210825, (Released:2022-03-02)

被引用文献数

1

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The Earth’s core is believed to contain some light elements because it is 10% less dense than pure Fe under the corresponding pressure and temperature conditions. Hydrogen, a promising candidate among light elements, has phase relations and physical properties that have been investigated mainly for the Fe–H system. This study specifically examined an Fe–Si–H system using in–situ neutron diffraction experiments to investigate the site occupancy of deuterium of hcp–Fe0.95Si0.05 hydride at 14.7 GPa and 800 K. To date, this pressure condition is the highest for neutron diffraction experiments conducted at high pressure and high temperature, where crystal structure analysis has been conducted. Results of Rietveld refinement indicate hcp–Fe0.95Si0.05 hydride as having deuterium (D) occupancy of 0.24(2) exclusively at the interstitial octahedral site in the hcp lattice. The effect on the site occupancy of D by addition of 2.6 wt% Si into Fe (Fe0.95Si0.05) was negligible compared to results obtained from an earlier study of an Fe–D system (Machida et al., 2019).

著者

Akio SUZUKI

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.117, no.1, pp.211215, 2022 (Released:2022-05-20)

参考文献数

21

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To determine the phase boundary between diaspore (α–AlOOH) and δ–AlOOH, in situ X–ray diffraction experiments were carried out using a multi–anvil high–pressure apparatus and synchrotron X–ray. The stability of each phase was determined by observing the change in powder X–ray diffraction patterns. The equilibrium phase boundary is described by the formula P (GPa) = 12.2 (±4.9) + 0.0027 (±0.0044) × T (K). The boundary determined in this study is located at a lower pressure than that estimated by previous quenching experimental studies.

著者

Toshio NOZAKA Daisuke MIYAMOTO

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.116, no.6, pp.314-319, 2021 (Released:2022-03-24)

参考文献数

25

被引用文献数

1

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Compositional variations of talc in peridotites and serpentinites could have significant implications for modeling of geochemical cycles involving the upper mantle but have been scarcely studied. We analyzed chemical compositions of prograde and retrograde talc and associated minerals in thermally metamorphosed serpentinites from Southwest Japan. The analyzed talc has variations of Si, Al, Mg, Fe, and Na contents. Most of the Si, Al, Mg, and Fe variations indicate mechanical mixing with serpentine and chlorite at a submicroscopic scale. Spatial distribution of talc–chlorite mixtures suggests their prograde metamorphic origin. Talc–serpentine mixtures could be formed by retrograde decomposition of talc–olivine assemblage and orthopyroxene at conditions of higher temperature and/or higher Si activity than serpentine–brucite mixtures, which are the typical products of serpentinization of olivine. Talc itself, regardless of prograde or retrograde origin, has compositional variations with Na enrichment as a likely result of solid solution or Na–mica mixing. The Na enrichment suggests that talc could be the most capable reservoir of Na in metamorphosed peridotites and serpentinites.

著者

Daisuke NISHIO–HAMANE Katsuyuki SAITO

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.116, no.5, pp.263-271, 2021 (Released:2022-02-03)

参考文献数

35

被引用文献数

2

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Au(Ag)–Sn–Sb–Pb minerals occurring in association with gold, rumoiite (AuSn2), shosanbetsuite (Ag3Sn), yuanjiangite (AuSn), aurostibite (AuSb2), and anyuiite (AuPb2), were found from the Shosanbetsu River (the former three), Shosanbetsu village and the Ainusawa River (the latter two), Haboro town, Rumoi province, Hokkaido, Japan. Rumoiite (IMA No. 2018–161) and shosanbetsuite (IMA No. 2018–162) have been approved as new minerals by the International Mineralogical Association, the Commission on New Minerals, Nomenclature and Classification (IMA–CNMNC) and named after the locality. Both minerals show anhedral shape at less than 5 µm and occur in close association with one another, yuanjiangite, and native lead in spherical aggregates in placer gold. The densities of rumoiite and shosanbetsuite based on their empirical formulae and powder diffraction data were calculated to be 10.1 and 11.1 g/cm3, respectively. The empirical formulae of rumoiite and shosanbetsuite were (Au0.95Ag<0.01)Σ0.96(Sn1.93Sb0.08Pb0.02Bi0.01)Σ2.04 (basis of 3 apfu) and (Ag2.46Au0.54)Σ2.99(Sn0.97Sb0.01Pb0.01Bi0.01)Σ1.01 (basis of 4 apfu), respectively. Rumoiite is orthorhombic, Pbca, with lattice parameters a = 6.9088(7) Å, b = 7.0135(17) Å, c = 11.7979(19) Å and V = 571.6(2) Å3 (Z = 8). Shosanbetsuite is orthorhombic, Pmmn, with lattice parameters a = 5.986(8) Å, b = 4.779(3) Å, c = 5.156(6) Å and V = 147.5(3) Å3 (Z = 2). Rumoiite and shosanbetsuite correspond to the synthetic AuSn2 and Ag3Sn phases, respectively. The chemical compositions for aurostibite, anyuiite, yuanjiangite, and native lead, and the unit cell parameters for yuanjiangite and native lead are also reported in this paper. Hydrothermal activity in ultramafic rocks after the formation of gold (electrum) grains may have been involved in the occurrence of Au(Ag)–Sn–Sb–Pb minerals.

著者

Keitaro OKAMOTO Takahiro KURIBAYASHI Toshiro NAGASE

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.116, no.5, pp.251-262, 2021 (Released:2022-02-03)

参考文献数

23

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In situ high–pressure single–crystal X–ray diffraction experiments on natural hemimorphite, ideally Zn4[Si2O7](OH)2·H2O, up to 4.7 GPa were conducted to investigate its pressure response property associated with pressure–induced phase transition. After the phase transition confirmed between 2.46 and 3.01 GPa, pairs of satellite reflections were newly found at certain Bragg reflections. The modulation vector q of the satellites was approximately [0, 1/8.4, 0]. The results of the refinements on the averaged structure indicated that the modulation arose from displacements of atomic sites associated with the mechanism of the phase transition, i.e., the rotation of the secondary building unit (SBU). The lower rotation angle of the SBU (Φ) than the value estimated from the non–modulated structure meant that the high–pressure phase contained anti–phase boundaries (APBs) resulting from the opposite direction of the SBU rotation and that the coherency was held across the APBs. Within the coherent domain, the APB’s intervals were distributed along the b–axis with a mean value of 8.4b ≈ 90 Å, where the displacement of each site η (y ) was approximated as the first–harmonic. The distribution of the direction of SBU rotation was initially considered to be inhomogeneous, but the elimination of the APBs had proceeded anisotropically and had been aborted below 3.01 GPa.

著者

Ibuki KINEBUCHI Atsushi KYONO

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.116, no.4, pp.211-219, 2021 (Released:2021-10-14)

参考文献数

47

被引用文献数

5

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The oxidation process from magnetite to hematite through maghemite was investigated by X–ray diffraction (XRD) and X–ray absorption spectroscopic techniques. The XRD pattern of magnetite heated at 100 °C for 3 h showed small reflections of maghemite with partially ordered distribution of vacancy (space group P4132 or P4332). Thereafter, the XRD pattern of magnetite heated at 250 °C for 3 h exhibited extra reflections corresponding to the tetragonal maghemite with fully ordered distribution of vacancy (space group P41212 or P43212). Diffraction peaks of hematite occurred from the magnetite heated at 250 °C, in which maghemite and hematite coexisted with magnetite. Diffraction peaks of magnetite subsequently disappeared at 300 °C. Instead, maghemite and hematite dominated the XRD pattern, but the amount of maghemite reduced from 300 °C. The maghemite completely disappeared at 500 °C, and hematite finally dominated the XRD pattern. Rietveld fitting results clearly showed that the a lattice parameter and site occupancy factor of Fe at the octahedral site continuously decreased at the temperatures from 25 to 300 °C. The X–ray absorption near edge structure (XANES) result showed that the Fe3+/ΣFe increased up to 300 °C and remained constant until 500 °C, indicating that Fe2+ in oxidized magnetite was completely oxidized to Fe3+ at 300 °C. Furthermore, the intensities of radial structure function (RSF) peaks at 1.7 and 3.1 Å corresponding to the Fe–O bonds in octahedral site and the Fe–Fe interaction between the octahedral sites reduced continuously from 25 to 300 °C. The fitting results of the first shells indicated that the coordination number and site occupancy factor at the octahedral site continuously decreased at the temperature range from 25 to 300 °C, which were approximately consistent with those of Rietveld fitting analysis. The a lattice parameter of the oxidized magnetite displayed a linear trend between stoichiometric magnetite and stoichiometric maghemite with a relationship of a = 0.0985x + 8.3397 (x = Fe2+/Fe3+). It was clearly confirmed that during the magnetite oxidation, Fe was continuously removed from the octahedral sites, which resulted in the formation of maghemite with partially ordered distribution of vacancy. Just after magnetite oxidation was completed, the vacancy ordering further progressed by the diffusion of Fe3+ within the structure, leading to the formation of maghemite with fully ordered distribution of vacancy.

著者

Tatsuki TSUJIMORI Hiroshi MIYAJIMA Ritsuro MIYAWAKI

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.112, no.5, pp.181-183, 2017 (Released:2017-11-15)

参考文献数

17

被引用文献数

1

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Gem sparkles deep: Preface of the special issue on ‘Jadeite and jadeitite’