Journal of Mineralogical and Petrological Sciences
Online ISSN : 1349-3825
Print ISSN : 1345-6296
ISSN-L : 1345-6296
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Displaying 1-15 of 15 articles from this issue
LETTER
  • Nozomi M. KONDO, Yoshio KONO, Steeve GRÉAUX, Yuji HIGO
    2024 Volume 119 Issue 1 Article ID: 240220
    Published: 2024
    Released on J-STAGE: June 28, 2024
    Advance online publication: May 22, 2024
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    Knowledge of the viscosity of melts and liquids at high pressure conditions is essential to understand the mobility of magmas and other liquids in the Earth’s interior. The falling sphere viscosity measurement in large volume press using synchrotron X-ray imaging is one of the most powerful techniques for investigating the viscosities of melts and liquids at high pressure and high temperature conditions. Despite capability of the in-situ X-ray radiography falling sphere viscosity measurement strongly depends on the speed of X-ray imaging, common imaging setups are limited to speed of ∼ 30-60 frames/second (fps), which hamper proper viscosity measurements on low viscous melts and liquids. In this study, we developed a new high-speed X-ray imaging setup up to 5000 fps combined with 1500-ton multi-anvil press at the BL04B1 beamline in the SPring-8. By using the high-speed X-ray imaging with the frame rate of 1000 fps, we succeeded to determine low viscosity value of 0.0081 (±0.0011) Pa s in calcite (CaCO3) liquid at ∼ 4.7 GPa and ∼ 1925 °C. The high-speed X-ray imaging combined with 1500-ton multi-anvil press at the BL04B1 beamline would expand capability of falling sphere viscosity measurement of low viscous liquids at high pressure conditions of deep mantle.

ORIGINAL ARTICLE
  • Masako YOSHIKAWA, Mohamed Zaki KHEDR, Akihiro TAMURA, Shoji ARAI
    2024 Volume 119 Issue 1 Article ID: 231025
    Published: 2024
    Released on J-STAGE: June 24, 2024
    Advance online publication: May 27, 2024
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    Clinopyroxene (Cpx)-rich peridotites have been observed at the base of mantle section from northern to southern massifs in the Oman ophiolite. We present Nd isotopic ratios of Cpx grains separated from the Cpx-rich peridotites of the central Sarami massif and compared them with published Nd isotopic ratios of Cpx grains from the northern Fizh and the southern Wadi Tayin Cpx-rich peridotites. The Nd isotopic data combined with spinel Cr# suggest that fertile Cpx-rich peridotites (spinel Cr# < 0.3) from the northern and the central massifs preserved a simple melt extraction event, whereas relatively refractory Cpx-rich peridotite (spinel Cr# = 0.33) from the southern massif and harzburgite (spinel Cr# = 0.55) from the northern Hilti massif recorded a further melt extraction event with an influx of a mid-ocean ridge basalt like melt.

ORIGINAL ARTICLE
  • Masahiro TAKANO, Hiroyuki KAGI, Yuichiro MORI, Katsutoshi AOKI, Sho KA ...
    2024 Volume 119 Issue 1 Article ID: 240122
    Published: 2024
    Released on J-STAGE: June 17, 2024
    Advance online publication: May 10, 2024
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    Hydrogenation of iron sulfide (FeS) under high-pressure and high-temperature conditions has attracted attention because hydrogen and sulfur are promising candidates as light elements in the cores of the Earth and other terrestrial planets. In earlier reports describing the hydrogenation of FeS, the chemical compositions of starting materials were not fully clarified. This study reports in-situ neutron and X-ray diffraction measurements under high-pressure and high-temperature conditions of an Fe-S-H system using a stochiometric Fe1.000S (troilite) as a starting material. The site occupancies of hydrogen atoms in FeS, estimated by Rietveld refinement of neutron diffraction patterns collected at about 5 GPa, were 0.014(2) at 700 K and 0.024(2) at 1000 K. The hydrogen occupancy at 900 K and 18.2 GPa was estimated as 0.067(6) from the unit-cell volume determined by X-ray diffraction using the hydrogen-induced volume expansion calculated from first-principles calculations. These occupancies were significantly lower than those reported from earlier studies, indicating that the hydrogenation of FeS can be affected strongly by the stoichiometry of iron sulfide.

ORIGINAL ARTICLE
  • Rei KANEMARU, Akira YAMAGUCHI, Toshimori SEKINE, Naoya IMAE, Hirotsugu ...
    2024 Volume 119 Issue 1 Article ID: 231223
    Published: 2024
    Released on J-STAGE: June 13, 2024
    Advance online publication: May 23, 2024
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    We performed a cathodoluminescence (CL) study of Ca-rich plagioclase (An85-86Ab14Or<1) in Stillwater gabbronorite experimentally shocked at 20.1, 29.8, and ∼ 41 GPa, for characterization of the shock effects. Chroma CL image of unshocked plagioclase showed the homogeneous red CL emission. In contrast, experimentally shocked plagioclase showed the heterogeneous CL emission colors in red and blue. The Raman spectra analysis identified that the red and blue portions correspond to plagioclase and maskelynite, respectively. In our observation, plagioclase experimentally shocked at 20 GPa was partially converted into maskelynite. At 30 GPa, most of plagioclase were converted into maskelynite. At 40 GPa, plagioclase was fully converted into maskelynite. Our observations of Ca-rich plagioclase indicated that the maskelynization starts at a slightly lower pressure and completes at a higher pressure than those in the previous studies (∼ 24 and ∼ 28 GPa, respectively). These pressure differences may be due to the high sensitivity of CL, which allows for the detection of small (a few µm in size) and rare phases that may have been overlooked in the traditional methods. The CL spectra of plagioclase showed a continuous change with increasing shock pressure. Hence, the CL imaging method using plagioclase and maskelynite is found to be very effective to estimate precisely shock pressure. In particular, there was a marked decrease in the CL intensity of Mn2+ and Fe3+ centers. Furthermore, the shock-induced center around the UV region was observed in experimentally shocked plagioclase and maskelynite. These CL features reflect the destruction of the framework structure to varying extents depending upon shock pressure. Combined with the Fourier transform infrared spectroscopy (FTIR) analysis in the present study, the transition of plagioclase to maskelynite was clearly illustrated in spectra. The reflectivity decreased continuously with increasing shock pressures during maskelynization. Additionally, the absorption at ∼ 8.6 µm observed in plagioclase was absent in maskelynite. This feature can be used as a diagnostic feature to characterize plagioclase and maskelynite by FTIR. The combination of detailed petrology using CL and FTIR spectra provides valuable insights into the shock scale for achondrites and planetary materials rich in shock-experienced plagioclase.

ORIGINAL ARTICLE
  • Asha P. Anu-Sha, Kalthilparambil R. Baiju, Kandathil A. Justine
    2024 Volume 119 Issue 1 Article ID: 221212
    Published: 2024
    Released on J-STAGE: June 12, 2024
    Advance online publication: March 26, 2024
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    Supplementary material

    The Southern Granulite Terrain of peninsular India consists of a wide range of metamorphic rocks with formation ages that span the late Archean Era to the Cambrian Period. It consists of numerous tectonic blocks dissected by deep crustal-scale shear zones. The Madurai Block is the largest crustal block, comprising Neoarchean to Ediacaran-Cambrian gneisses that include charnockite, hornblende-biotite gneiss, mafic granulite and metapelite, amongst other lesser rock types. This study focuses on the geochemistry of granulite-facies rocks from the western part of the Madurai Block, how these rocks correlate with similar types in other tectonic blocks of the Southern Granulite Terrain, and the implication of such correlations for East Gondwana tectonics. The geochemistry of the various granulite-facies rocks from the western Madurai Block reveals metaluminous to slightly peraluminous, calcic to alkalic, and ferroan to magnesian signatures. Geochemical tectonic discrimination diagrams indicate both A-type granitoid and Cordilleran affinities, consistent with petrogenesis in active continental margin and extensional tectonic settings, with chemical variation also generated through magmatic differentiation. Similar lithological, geochronological and geochemical features have been reported from granulites of the Antananarivo Block of Madagascar, based on which a correlation can be made with the western Madurai Block that predates Gondwana assembly.

ORIGINAL ARTICLE
  • Junichi FUKUDA
    2024 Volume 119 Issue 1 Article ID: 240229
    Published: 2024
    Released on J-STAGE: May 30, 2024
    Advance online publication: May 09, 2024
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    Supplementary material

    Grain growth experiments were performed on rhombohedral camphor as a rock analogue at 24 °C [i.e., room temperature (RT)] and higher temperatures of 31, 35, 43, and 50 °C. The experiments were very simple compared with those on rocks, which require special apparatuses. The ground sample of camphor was pressed on a glass slide, and a thermometer was set next to the sample. The two-dimensional see-through experiment was performed at RT under a polarizing microscope. The evolving microstructures were clearly observable and showed real-time grain boundary migration by grain growth and the consumption of smaller grains by neighboring larger grains. The result was a consistent increase in grain size from ∼ 10 to ∼ 40 µm in 2 h. The higher-temperature experiments were performed on a hot plate. A glass slide and a weight that had been preheated on the hot plate were placed on top of the glass slide that contained the pressed sample and thermometer. The increase in grain size was controlled by increasing the temperature, with the temperature being held for the same durations. The grain size data in the case of grain growth were analyzed with the grain growth law of dnd0n = k0 exp(−Q/RT)t, where d (µm) is the grain size at time t (s), d0 (µm) is the initial grain size, n is the grain growth exponent, k0 (µmn/s) is a constant, Q (kJ/mol) is the activation energy, R is the gas constant, and T is the temperature in Kelvin. The determined parameters were n = 3.7 ± 0.2, k0 = 10−12.7±0.1, and Q = 60.4 ± 6.1.

ORIGINAL ARTICLE
  • Tomoharu MIYAMOTO, Katsuyuki YAMASHITA, Daniel J. DUNKLEY, Toshiaki TS ...
    2024 Volume 119 Issue 1 Article ID: 231207
    Published: 2024
    Released on J-STAGE: May 24, 2024
    Advance online publication: April 22, 2024
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    Supplementary material

    A WNW-ESE-trending mafic dyke intruding across major structures in high-grade metamorphic rocks was found at Niban Iwa (translated as ‘Number Two Rock’) in the Proterozoic Lützow-Holm Complex of East Antarctica. It is holocrystalline and aphyric, and comprises biotite, hornblende, plagioclase, orthoclase, quartz, apatite, and titanite. Chemically the dyke rock is alkali basalt with high K2O/Na2O and total Fe contents, and low Cr and Ni contents, indicating that it was formed by the differentiation of olivine from a primary alkali basaltic magma derived from the subcontinental mantle. The Rb-Sr mineral isochron age was obtained of 487 ± 15 Ma with SrIR = 0.70486 ± 0.00007. Considering that the metamorphic age of the gneisses at Niban Iwa was estimated to be 532 Ma, the dyke probably intruded after metamorphism as part of the post-orogenic igneous activity following the collision of East and West Gondwana.

ORIGINAL ARTICLE
  • Daisuke NISHIO-HAMANE, Katsuyuki SAITO
    2024 Volume 119 Issue 1 Article ID: 240304
    Published: 2024
    Released on J-STAGE: May 16, 2024
    Advance online publication: April 23, 2024
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    Ezochiite, a newly-discovered platinum-group mineral in the thiospinel group having the ideal formula Cu+(Rh3+Pt4+)S4, was discovered in samples from the Tomamae coast near Tomamae town, Hokkaido, Japan. Additional specimens were later found in the Shosanbetsu river, Ainusawa river and Obira coast, Hokkaido. Ezochiite crystallized in melt pockets trapped in isoferroplatinum grains, occurring in the form of anhedral grains less than 5 µm in length. Ezochiite is associated with sulfide minerals such as braggite, cooperite, torryweiserite, and chalcopyrite. It is opaque and has a metallic luster with a bluish gray color in reflected light. The Mohs hardness of this mineral was estimated to be 5 by analogy with related thiospinel group minerals and a density of 6.66 g·cm−3 was calculated from the empirical formula and powder X-ray diffraction data. The empirical formula, on the basis of 7 apfu was (Cu+0.85Fe3+0.15)Σ1.00(Rh3+1.09Pt4+0.78Ir3+0.08Pt2+0.05)Σ2.00S4.00 for a specimen obtained from the Tomamae coast. The powder X-ray diffraction study indicated that the mineral exhibits the spinel structure, space group Fd3m, with lattice parameters a = 9.8559(14) Å and V = 957.4(4) Å3 (Z = 8). Evidence for a spinel structure was also provided by Raman spectra. Data from samples of ezochiite and cuprorhodsite from samples sourced in Hokkaido showed a compositional relationship based on coupled Fe3+0.5Rh3+-Cu+0.5Pt4+ substitution. Ezochiite is not rare. It is also found various other geological environments, including in ophiolites, Ural-Alaskan intrusions and mafic-ultramafic intrusions.

LETTER
  • Kenta K. YOSHIDA, Hikaru SAWADA, Yu MARUYA, Wataru MATSUDA
    2024 Volume 119 Issue 1 Article ID: 231218
    Published: 2024
    Released on J-STAGE: May 16, 2024
    Advance online publication: April 19, 2024
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    Supplementary material

    The 2021 eruption of Fukutoku-Oka-no-Ba (FOB), which is a submarine volcano located at the southern end of the Izu-Ogasawara arc, produced a large number of pumice clasts that drifted to many places in the islands of Japan and eastern Asia. Amongst the typical gray pumice clasts, several peculiar clasts have been discovered, such as those with a black coloration and containing mafic enclaves. This study found a mostly bimineralic enclave consisting of plagioclase phenocrysts and an alkali feldspar matrix, with minor cristobalite, TiO2 minerals (anatase and rutile), and Fe sulfide. The chemical composition of the plagioclase phenocrysts is similar to that reported from the FOB pumice, and the tie line of the alkali feldspar and plagioclase in a Ca-Na-K ternary diagram indicates that they originated from melt extracted from the crystal mush of the FOB magma reservoir. The cristobalite occurs in the voids in the matrix, in which surrounding alkali feldspar compositions changed gradually along the ternary feldspar solvus of ∼ 850 °C. The formation of a cristobalite-bearing bimineralic enclave can be explained by (1) the melt was extracted and accumulated at the shallow part of the magma reservoir, which crystallized as syenitic rocks; (2) subsequent degassing-related alteration within the volcanic conduit that caused plagioclase breakdown and cristobalite crystallization; and (3) entrainment of the syenitic rock fragment by the nanolite-bearing magma being erupted from the conduit.

LETTER
  • Yasuyuki BANNO
    2024 Volume 119 Issue 1 Article ID: 231218b
    Published: 2024
    Released on J-STAGE: March 29, 2024
    Advance online publication: March 07, 2024
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    Wollastonite of variable cathodoluminescence (CL) intensity was found in a skarn xenolith from Tadano, Fukushima Prefecture, Japan. Electron microprobe analysis revealed bright-blue and faint-blue CL spots in crystals. Panchromatic CL images revealed that individual wollastonite grains often include bright and dark CL regions of bright- and faint-blue CL, respectively. The TiO2 contents of bright CL regions (0.055-0.110 wt%) were higher than those of dark CL regions (<0.008-0.013 wt%). The blue CL intensity gradually increased from <0.008 to 0.102 wt% TiO2, and that with 0.102 and 0.110 wt% TiO2 was almost the same. The results indicated a positive correlation of Ti content with blue CL intensity.

ORIGINAL ARTICLE
  • Sara AL-BUSAIDI, Atsushi KAMEI, Sasidharan A. SILPA
    2024 Volume 119 Issue 1 Article ID: 230908
    Published: 2024
    Released on J-STAGE: March 27, 2024
    Advance online publication: February 20, 2024
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    Supplementary material

    Shimane Peninsula in the San’in region, SW Japan, has preserved a wide distribution of igneous rocks related to back-arc rifting in the Miocene. We investigated the petrography, geochemistry, and Sr-Nd isotope systematics of rhyolite lavas (Josoji rhyolite: 18-15 Ma) and basaltic to dacitic intrusions of Stage I (∼ 14 Ma) and II (∼ 13 Ma) intrusive rocks. They are classified as medium-K magma series. The Josoji rhyolite and Stage I rocks show chemical compositions of arc-type signatures, whereas the Stage II rocks show elevated Nb and Ta abundances suggesting weaker arc signatures. The geochemical characteristics indicate that the Josoji rhyolite was produced by partial melting of arc-type basalt under lower to middle crustal conditions. The arc signatures of the Stage I rocks were inherited from a remnant metasomatized lithosphere formed by the subduction of the Pacific Plate before the opening of the Japan Sea. The Stage II rocks were formed from a fertile magma that might be produced by the melting of upwelling asthenospheric mantle. We conclude that various magmatic processes took place during and just after the back-arc rifting development in the San’in region.

ORIGINAL ARTICLE
  • Satoshi NAKANO
    2024 Volume 119 Issue 1 Article ID: 230630
    Published: 2024
    Released on J-STAGE: March 22, 2024
    Advance online publication: January 30, 2024
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    Feldspar internal textures in a pyroclastic trachyte from Oki-Dogo, Sea of Japan, were examined to expand the understanding of feldspar reactions during the cooling through magmatic to hydrothermal stages, beyond the previous information of feldspars in Oki-Dogo alkaline lava and sheet rocks, using the methods of an electron microprobe and cathodoluminescence. Two types of micron-size internal microtextures were found to coexist in individual feldspar phenocrysts: clear domain textures, formed during a high-temperature magmatic stage, and turbid microperthitic textures, formed during a low-temperature subsolidus stage. The both microtextures are products of metasomatic replacement reactions. In addition, nano-size fluorite grains are aligned across the microtextures. The fluorite occurrence records the behavior of fluorine related to feldspar reactions. The first account of metasomatic microtextures crosscut by fluorite alignments in volcanic alkali feldspars expands our knowledge of feldspar reactions during the cooling and fluorine behaviors related to them in igneous rocks and shows the significance of the careful analysis of feldspar internal microtextures.

ORIGINAL ARTICLE
  • Gen TAKAHASHI, Taiga OKUMURA, Takayoshi NAGAYA, Michio SUZUKI, Toshihi ...
    2024 Volume 119 Issue 1 Article ID: 231206
    Published: 2024
    Released on J-STAGE: March 08, 2024
    Advance online publication: February 09, 2024
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    The fine structure of goldfish (Carassius auratus) asterisci, which consists of vaterite—a metastable polymorph of anhydrous calcium carbonate—has been investigated and compared with inorganically synthesized vaterites, using electron microscopy. This is as a first step in elucidating the mechanism of polymorph selection of calcium carbonate in the biomineralization of otoliths. X-ray and electron diffraction analyses suggested that there was no marked difference in the unit cell parameters, supercell structure, or stacking disorder features between the asteriscus vaterite and the synthesized vaterites. Although the sizes of the vaterite single crystals in the asteriscus are considerably larger than those in the synthesized ones, both show mosaicity, or crystal aggregates with small misorientations, implying that this character is an intrinsic property of the vaterite structure. The asteriscus consists of slender elements radiating from the central region of the asteriscus, with the elements extending normal to the c-axis, suggesting that the polymorph was selected at the asteriscus initial growth stage.

ORIGINAL ARTICLE
  • Satoshi SUZUKI, Takashi YUGUCHI, Keito ISHIGURO, Kyoka ENDO, Asuka KAT ...
    2024 Volume 119 Issue 1 Article ID: 230807
    Published: 2024
    Released on J-STAGE: February 22, 2024
    Advance online publication: January 19, 2024
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    Supplementary material

    Understanding the crustal evolutionary dynamics of island arc-trench systems requires a thorough evaluation of magma chamber processes, and especially of shallow crustal granitic magma intrusion and emplacement processes. To address this, we studied the petrography and geochronology of the Kuki granite, Kitakami Mountains, northeast Japan, as an example of a non-adakitic granite at the magmatic flare-up stage. Analysis of paired crystallization temperatures and pressures of hornblende grains reveals the temperature-pressure (i.e., depth) history of the granitic magma. The pressure and temperature history of the Kuki granite indicates no change in the magma depth with cooling from 800 to 730 °C, and geobarometric calculations indicate the emplacement of magma at a depth of approximately 9-10 km. Simultaneous determination of the zircon U-Pb age, Ti concentration, and Th/U yields 1) the time-temperature history of granitic magma before its solidification, and 2) the correlation between temperature and Th/U in the magma. The magma chamber cooled from ∼ 900 to 700 °C at approximately 125 Ma. The change in Th/U with temperature indicates the progression of fractional crystallization in the cooling magma chamber, and greater fractional crystallization in the magma chamber at temperatures above 800 °C than below 800 °C.

ORIGINAL ARTICLE
  • Yuhei UMEDA, Yuma NAGAI, Naotaka TOMIOKA, Toshimori SEKINE, Masashi MI ...
    2024 Volume 119 Issue 1 Article ID: 230706
    Published: 2024
    Released on J-STAGE: February 06, 2024
    Advance online publication: January 10, 2024
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    Shock recovery experiments on the single crystal rutile and the powdered rutile were performed using a single-stage propellant gun to investigate the effects of porosity (i.e., temperature effect) on the formation of shock-induced deformation microstructures. X-ray diffraction and transmission electron microscopy analyses of the shocked single crystal rutile revealed the occurrence of a high-density stacking fault in the {101} plane of rutile. This defect suggests that the dominant slip system causing the plastic deformation of the crystal was {101}<101> at lower temperatures, forming stacking faults. Additionally, part of the crystal exhibited intergrowth with the α-PbO2 structure in a topotaxial relationship: <100>Rutile // <001>α-PbO2. Topological analysis suggests that the single crystal rutile transforms into the α-PbO2 structure concomitantly with the shear deformation via the fluorite structure. In contrast, the shocked powdered rutile primarily comprises particles with pervasive entangled dislocations and recrystallized particles, where the α-PbO2 structure was not observed at all. Considering the absence of stacking faults, the dominant slip system in the shocked powdered rutile should have been {110}<001>, which is expected to work more actively at higher temperatures. These contrasting results on shocked rutile indicate that the shock heating effect and the initial porosity significantly influenced the deformation microstructures and high-pressure phase transformations of rutile in shocked meteorites as well as in impact crater rocks.

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