Abstracts for Annual Meeting of Japan Association of Mineralogical Sciences
2013 Annual Meeting of Japan Association of Mineralogical Sciences
Showing 1-50 articles out of 212 articles from the selected issue
J2: Chemistry and Mineralogy of the earth's interior at high pressure (Joint session with GSJ)
J4: Water-Rock Interaction (Joint session with GSJ)
S1: Igneous processes and fluids
  • Hitomi Nakamura, Teruki Oikawa, Nobuo Geshi, Akikazu Matsumoto
    Session ID: S1-01
    Published: 2013
    Released: June 07, 2018
    CONFERENCE PROCEEDINGS FREE ACCESS
    K-Ar ages have been determined for 14 volcanic rocks from the late Miocene to Pliocene periods in the north of Kanto Mountains. These volcanic rocks have been collected from volcanoes located behind the TTT triple junction with two subducting slabs of the Pacific and the Philippine Sea plates which are thought to have influenced the magmatism in the region. Based on the stratigraphy and K-Ar ages, three welded tuffs and the
    associated volcanic products are classified, which suggests that the volcanism in the studied area had continued during the late Miocene to the Pliocene and ceased before the Pleistocene.
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  • Morihisa Hamada
    Session ID: S1-02
    Published: 2013
    Released: June 07, 2018
    CONFERENCE PROCEEDINGS FREE ACCESS
    Differentiation condition of island arc low-K tholeiite magma was reviewed by comparing data of chemical composition of volcanic rocks from Izu-Oshima volcano during past 40,000 years and data of hydrous melting experiments to simulate crystallization differentiation of arc basalts. Chemical variation of volcanic rocks from Izu-Oshima volcano can be explained by internal mixing of H2O-rich magma crystallizing at higher pressure and H2O-poor magma crystallizing at lower pressure, suggesting low-K island arc tholeiite magma is H2O-saturated and undergoing polybaric degassing.
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  • Hidemi Ishibashi, Hiroyuki Kagi, Natsue Abe, Naoto Hirano
    Session ID: S1-03
    Published: 2013
    Released: June 07, 2018
    CONFERENCE PROCEEDINGS FREE ACCESS
    In this study, Fe-K edge XANES analyses were done for quenched basaltic glasses in six scoria samples dredged from the petit-spot, site B, located on the Pacific Plate ca. 800km from the Sanriku, Japan, to estimate fO2 conditions of the magma. The analyzed glasses revealed similar Fe3+/Fetotal ratios of ca. 0.37. The ratios are consisted with that estimated from the apparent Fe-Mg partition coefficient between olivine and melt. From the ratios, the fO2 condition of the magma was estimated to be QMF+2.3, which is more oxidized than MORB and similar to arc magmas.
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  • Kenta Ueki, Hikaru Iwamori
    Session ID: S1-04
    Published: 2013
    Released: June 07, 2018
    CONFERENCE PROCEEDINGS FREE ACCESS
    We present a new thermodynamic calculation for multi pressure melting phase relation of spinel lherzolite. The thermodynamic model for the calculation, which has been developed based on Ueki and Iwamori (2013), well reproduces the experimentally determined melting phase relation and its pressure dependence.
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  • Xianyu Xue, Masami Kanzaki
    Session ID: S1-05
    Published: 2013
    Released: June 07, 2018
    CONFERENCE PROCEEDINGS FREE ACCESS
    Knowledge of the dissolution mechanisms of CO2 in silicate melts/glasses is indispensible for understanding how it affects physical and thermodynamic properties. CO2 is generally known to dissolve in silicate melts/glasses as molecular CO2 and CO32- species, but how the latter groups are incorporated in the melt and its effect on the silicate structure have been less certain. Here we report ab initio calculation (vibrational frequencies, 13C chemical shift tensors) and multinuclear NMR study on 13CO2-bearing glasses of diverse silicate compositions. Our calculation suggests that both vibrational frequencies and 13C chemical shift tensor are sensitive to the local environments of carbonates. The experimental data indicate that carbonates are present dominantly as free carbonates (not bonded to tetrahedral Si/Al) in depolymerized melts, and as network carbonates (bonded to two tetrahedral Si/Al via two oxygens) in polymerized glasses. The formation of free carbonates would lead to polymerization of the silicate structure.   
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  • Mayumi Mujin, Michihiko Nakamura
    Session ID: S1-06
    Published: 2013
    Released: June 07, 2018
    CONFERENCE PROCEEDINGS FREE ACCESS
    We present detailed petrography of
    nanometer scale crystals (nanolites) in the quenched products of the
    sub-plinian and vulcanian eruptions from the Shinmoedake, Kirishma volcanic
    group in 2011. The nanolites were distinguished from microlites by a steeper
    slope of the CSD plots. The vulcanian eruption products (pumice and juvenile
    lithic fragments) contain both plagioclase and pyroxene nanolites, while sub-plinian
    pumices contain only pyroxene nanolites. The nanolite crystallization
    condition may reflect magma dehydration and residence time in a very shallow
    conduit, which are not recorded by microlites.
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  • Satoshi Okumura, Shanaka de Silva, Michihiko Nakamura, Osamu Sasaki
    Session ID: S1-07
    Published: 2013
    Released: June 07, 2018
    CONFERENCE PROCEEDINGS FREE ACCESS
    We investigate crystal microstructure in crystal-rich pumice and lava samples (six eruptions in the Central Andes) using X-ray CT. Slopes in the CSDs, which are obtained for phenocrysts, are independent of crystallinity. Phenocryst fragmentation in lavas is limited; this is inconsistent with experimental and theoretical predictions that interaction between crystals in shear flow should result in extensive crystal breakage in crystal-rich magma. This disconnection between natural samples and theoretical studies can be explained by considering that the crystal framework may be collapsed by gas bubbles, resulting in the shear-reduction of crystal-rich magma. 
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  • Shumpei Yoshimura, Shin-ichi Kagashima
    Session ID: S1-P01
    Published: 2013
    Released: June 07, 2018
    CONFERENCE PROCEEDINGS FREE ACCESS
    We have developed a new analytical method for H2O and CO2 in silicate glasses by using micro-Raman spectrometry. We analysed H2O- and CO2-bearing basaltic glasses using a Raman spectrometer and an FT-IR, and confirmed linear relationships between peak heights of H2O and CO32- in IR spectra and those in Raman spectra. Therefore, the Raman spectrometry has a potential for quantitative analysis of both H2O and CO2 in glass samples.
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S2: Water Rock Interaction
R1: Characterization and description of minerals
  • Toshiro Nagase, Koichi Momma, Takahiro Kuribayashi, Ryo-ichi Yamada
    Session ID: R1-01
    Published: 2013
    Released: June 07, 2018
    CONFERENCE PROCEEDINGS FREE ACCESS
    Chalcedony and agate are aggregates of cryptocrystalline crystals, and composed of quartz and moganite.  Numerous optical and transmission electron microscopies observations were carried out, and these results have revealed the characteristic features, e.g., development of Brazil twin lamellae, intergrowth with moganite, optically length-fast form. However, textural data from 1µm to 10 nm sized are not enough to clarify the relation between TEM and optical microscopy observations. We carried out to observation the fine textures of chalcedony and agate by using a field emission type scanning electron microscopy. The results suggest that the textures are grouped mainly to three types and that the optical textures are related with the secondary particle composed of aggregate of nanometer-sized crystals.    
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