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  2. 糀谷 浩

糀谷 浩

コウジタニ ヒロシ  (Hiroshi Kojitani)

基本情報

所属
学習院大学 理学部 化学科 教授
学位
博士(理学)(学習院大学)
Ph.D(Gakushuin University)
研究者番号
60291522
J-GLOBAL ID
200901050139239240
researchmap会員ID
5000032247

研究キーワード

 6

研究分野

 1

経歴

 13
もっとみる

委員歴

 4

受賞

 1

論文

 36
  • Hiroshi Kojitani, Mei Gonai, Yoshiyuki Inaguma, Masaki Akaogi
    Physics and Chemistry of Minerals 51(1) 2024年2月9日  査読有り筆頭著者
  • Hiroaki Hayashi, Yuichi Shirako, Lei Xing, Alexei A. Belik, Masao Arai, Masanori Kohno, Taichi Terashima, Hiroshi Kojitani, Masaki Akaogi, Kazunari Yamaura
    Physical Review B 108(7) 2023年8月17日  査読有り
  • Masaki Akaogi, Natsuki Miyazaki, Taisuke Tajima, Hiroshi Kojitani
    Physics and Chemistry of Minerals 50(3) 2023年7月14日  
  • Hiroshi Kojitani, Monami Yamazaki, Yuki Tsunekawa, Shiho Katsuragi, Masamichi Noda, Toru Inoue, Yoshiyuki Inaguma, Masaki Akaogi
    Physics of the Earth and Planetary Interiors 333 106937-106937 2022年12月  査読有り筆頭著者
  • Takayuki Ishii, Giacomo Criniti, Elena Bykova, Leonid Dubrovinsky, Tomoo Katsura, Hidekazu Arii, Hiroshi Kojitani, Masaki Akaogi
    American Mineralogist 106(7) 1105-1112 2021年7月1日  査読有り
    Abstract Three single crystals of CaTi2O4 (CT)-type, CaFe2O4 (CF)-type, and new low-density CaFe2O4 (LD-CF) related MgAl2O4 were synthesized at 27 GPa and 2500 °C and also CT-type MgAl2O4 at 45 GPa and 1727 °C using conventional and advanced multi-anvil technologies, respectively. The structures of CT-type and LD-CF related MgAl2O4 were analyzed by single-crystal X-ray diffraction. The lattice parameters of the CT-type phases synthesized at 27 and 45 GPa were a = 2.7903(4), b = 9.2132(10), and c = 9.3968(12) Å, and a = 2.7982(6), b = 9.2532(15), and c = 9.4461(16) Å, respectively, (Z = 4, space group: Cmcm) at ambient conditions. This phase has an AlO6 octahedral site and an MgO8 bicapped trigonal prism with two longer cation-oxygen bonds. The LD-CF related phase has a novel structure with orthorhombic symmetry (space group: Pnma), and lattice parameters of a = 9.207(2), b = 3.0118(6), and c = 9.739(2) Å (Z = 4). The structural framework comprises tunnel-shaped spaces constructed by edge- and corner-sharing of AlO6 and a 4+1 AlO5 trigonal bipyramid, in which MgO5 trigonal bipyramids are accommodated. The CF-type MgAl2O4 also has the same space group of Pnma but a slightly different atomic arrangement, with Mg and Al coordination numbers of 8 and 6, respectively. The LD-CF related phase has the lowest density of 3.50 g/cm3 among MgAl2O4 polymorphs, despite its high-pressure synthesis from the spinel-type phase (3.58 g/cm3), indicating that the LD-CF related phase formed via back-transformation from a high-pressure phase during the recovery. Combined with the previously determined phase relations, the phase transition between CF-and CT-type MgAl2O4 is expected to have a steep Clapeyron slope. Therefore, CT-type phase may be stable in basaltic- and continental-crust compositions at higher temperatures than the average mantle geotherm in the wide pressure range of the lower mantle. The LD-CF related phase could be found in shocked meteorites and used for estimating shock conditions.
もっとみる

MISC

 125
  • M Akaogi, N Kamii, A Kishi, H Kojitani
    PHYSICS AND CHEMISTRY OF MINERALS 31(2) 85-91 2004年3月  
    KAlSi3O8 sanidine dissociates into a mixture of K2Si4O9 wadeite, Al2SiO5 kyanite and SiO2 coesite, which further recombine into KAlSi3O8 hollandite with increasing pressure. Enthalpies of KAlSi3O8 sanidine and hollandite, K2Si4O9 wadeite and Al2SiO5 kyanite were measured by high-temperature solution calorimetry. Using the data, enthalpies of transitions at 298 K were obtained as 65.1 +/- 7.4 kJ mol(-1) for sanidine --> wadeite + kyanite + coesite and 99.3 +/- 3.6 kJ mol(-1) for wadeite + kyanite + coesite --> hollandite. The isobaric heat capacity of KAlSi3O8 hollandite was measured at 160-700 K by differential scanning calorimetry, and was also calculated using the Kieffer model. Combination of both the results yielded a heat-capacity equation of KAlSi3O8 hollandite above 298 K as C-p=3.896 x 10(2)-1.823 x 10(3)T(-0.5)-1.293 x 10(7)T(-2)+1.631 x 10(9)T(-3) (C-p in J mol(-1) K-1, T in K). The equilibrium transition boundaries were calculated using these new data on the transition enthalpies and heat capacity. The calculated transition boundaries are in general agreement with the phase relations experimentally determined previously. The calculated boundary for wadeite + kyanite + coesite --> hollandite intersects with the coesite-stishovite transition boundary, resulting in a stability field of the assemblage of wadeite + kyanite + stishovite below about 1273 K at about 8 GPa. Some phase-equilibrium experiments in the present study confirmed that sanidine transforms directly to wadeite + kyanite + coesite at 1373 K at about 6.3 GPa, without an intervening stability field of KAlSiO4 kalsilite + coesite which was previously suggested. The transition boundaries in KAlSi3O8 determined in this study put some constraints on the stability range of KAlSi3O8 hollandite in the mantle and that of sanidine inclusions in kimberlitic diamonds.
  • M Akaogi, N Kamii, A Kishi, H Kojitani
    PHYSICS AND CHEMISTRY OF MINERALS 31(2) 85-91 2004年3月  
    KAlSi3O8 sanidine dissociates into a mixture of K2Si4O9 wadeite, Al2SiO5 kyanite and SiO2 coesite, which further recombine into KAlSi3O8 hollandite with increasing pressure. Enthalpies of KAlSi3O8 sanidine and hollandite, K2Si4O9 wadeite and Al2SiO5 kyanite were measured by high-temperature solution calorimetry. Using the data, enthalpies of transitions at 298 K were obtained as 65.1 +/- 7.4 kJ mol(-1) for sanidine --> wadeite + kyanite + coesite and 99.3 +/- 3.6 kJ mol(-1) for wadeite + kyanite + coesite --> hollandite. The isobaric heat capacity of KAlSi3O8 hollandite was measured at 160-700 K by differential scanning calorimetry, and was also calculated using the Kieffer model. Combination of both the results yielded a heat-capacity equation of KAlSi3O8 hollandite above 298 K as C-p=3.896 x 10(2)-1.823 x 10(3)T(-0.5)-1.293 x 10(7)T(-2)+1.631 x 10(9)T(-3) (C-p in J mol(-1) K-1, T in K). The equilibrium transition boundaries were calculated using these new data on the transition enthalpies and heat capacity. The calculated transition boundaries are in general agreement with the phase relations experimentally determined previously. The calculated boundary for wadeite + kyanite + coesite --> hollandite intersects with the coesite-stishovite transition boundary, resulting in a stability field of the assemblage of wadeite + kyanite + stishovite below about 1273 K at about 8 GPa. Some phase-equilibrium experiments in the present study confirmed that sanidine transforms directly to wadeite + kyanite + coesite at 1373 K at about 6.3 GPa, without an intervening stability field of KAlSiO4 kalsilite + coesite which was previously suggested. The transition boundaries in KAlSi3O8 determined in this study put some constraints on the stability range of KAlSi3O8 hollandite in the mantle and that of sanidine inclusions in kimberlitic diamonds.
  • H Kojitani, K Nishimura, A Kubo, M Akaogi
    GEOCHIMICA ET COSMOCHIMICA ACTA 67(18) A228-A228 2003年9月  
  • H Kojitani, K Nishimura, A Kubo, M Sakashita, K Aoki, M Akaogi
    PHYSICS AND CHEMISTRY OF MINERALS 30(7) 409-415 2003年8月  
    Raman spectroscopy of calcium ferrite type MgAl2O4 and CaAl2O4 and heat capacity measurement of CaAl2O4 calcium ferrite were performed. The heat-capacity of CaAl2O4 calcium ferrite measured by a differential scanning calorimeter (DSC) was represented as C-P(T) = 190.6-1.116 x 10(7) T-2 + 1.491 x 10(9) T-3 above 250 K (T in K). The obtained Raman spectra were applied to lattice dynamics calculation of heat capacity using the Kieffer model. The calculated heat capacity for CaAl2O4 calcium ferrite showed good agreement with that by the DSC measurement. A Kieffer model calculation for MgAl2O4 calcium ferrite similar to that for CaAl2O4 calcium ferrite was made to estimate the heat capacity of the former. The heat capacity of MgAl2O4 calcium ferrite was represented as C-P(T) = 223.4-1352T(-0.5) - 4.181 x 10(6) T-2 + 4.300 x 10(8) T-3 above 250 K. The calculation also gave approximated vibrational entropies at 298 K of calcium ferrite type MgAl2O4 and CaAl2O4 as 97.6 and 114.9 J mol(-1) K-1, respectively.
  • H Kojitani, K Nishimura, A Kubo, M Sakashita, K Aoki, M Akaogi
    PHYSICS AND CHEMISTRY OF MINERALS 30(7) 409-415 2003年8月  
    Raman spectroscopy of calcium ferrite type MgAl2O4 and CaAl2O4 and heat capacity measurement of CaAl2O4 calcium ferrite were performed. The heat-capacity of CaAl2O4 calcium ferrite measured by a differential scanning calorimeter (DSC) was represented as C-P(T) = 190.6-1.116 x 10(7) T-2 + 1.491 x 10(9) T-3 above 250 K (T in K). The obtained Raman spectra were applied to lattice dynamics calculation of heat capacity using the Kieffer model. The calculated heat capacity for CaAl2O4 calcium ferrite showed good agreement with that by the DSC measurement. A Kieffer model calculation for MgAl2O4 calcium ferrite similar to that for CaAl2O4 calcium ferrite was made to estimate the heat capacity of the former. The heat capacity of MgAl2O4 calcium ferrite was represented as C-P(T) = 223.4-1352T(-0.5) - 4.181 x 10(6) T-2 + 4.300 x 10(8) T-3 above 250 K. The calculation also gave approximated vibrational entropies at 298 K of calcium ferrite type MgAl2O4 and CaAl2O4 as 97.6 and 114.9 J mol(-1) K-1, respectively.
  • A Navrotsky, M Schoenitz, H Kojitani, HW Xu, JZ Zhang, DJ Weidner, R Jeanloz
    JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 108(B7) 2330 2003年7月  
    [1] MgSiO3-rich perovskite is expected to dominate Earth's lower mantle (pressures >25 GPa) with iron and aluminum as significant substituents. The incorporation of trivalent ions, M3+, may occur by two competing mechanisms: Mg-A + Si-B = M-A + M-B and Si-B = Al-B + 0.5 (vacancy)(O). Phase synthesis studies show that both substitutions do occur and the nonstoichiometric or defect substitution is prevalent along the MgSiO3-MgAlO2.5 join. Lattice parameters associated with the first substitution ( stoichiometric) show more rapid increases with increasing Al content than those for the second substitution ( nonstoichiometric), consistent with the differences in size of substituting ions. Oxide melt solution calorimetry has been used to compare the energetics of both substitutions. The stoichiometric substitution, represented by the reaction 0.95 MgSiO3 (perovskite) + 0.05 Al2O3 (corundum) = Mg0.95Al0.10Si0.95O3 (perovskite), has an enthalpy of - 0.8 +/- 2.2 kJ/mol. The nonstoichiometric reaction, 0.90 MgSiO3 (perovskite) + 0.10 MgO (rocksalt) + 0.05 Al2O3 (corundum) = MgSi0.9Al0.1O2.95 (perovskite) has a small positive enthalpy of 8.5 +/- 4.6 kJ/mol. Configurational T DeltaS terms play a role in both substitutions. The defect substitution is not prohibitive in enthalpy, entropy, or volume, is favored in perovskite coexisting with magnesiowustite and may significantly affect the elasticity, rheology, and water retention of silicate perovskite in Earth.
  • JF Stebbins, H Kojitani, M Akaogi, A Navrotsky
    AMERICAN MINERALOGIST 88(7) 1161-1164 2003年7月  
    In the Earth's mantle, the mechanism(s) of solid solution of Al in MgSiO3 perovskite strongly impacts its thermodynamic and transport properties. We present Al-27 NMR data for perovskite samples of nominal composition Mg(Si0.9Al0.1)O-2.95, to test a mechanism by which Al3+ substitutes at the octahedral Si4+ sites, leaving a corresponding number of O-site vacancies. We find evidence for this process in a significantly greater peak area for Al at B (Si) sites vs. A (Mg) sites in the structure, and the possible identification of a small concentration of five-coordinated Al adjacent to such vacancies. However, substitution of Al3+ at the A sites remains significant. As in perovskite-type technological ceramics, O-atom vacancies may play an important role in enhancing ion mobility and the dissolution of water.
  • A Navrotsky, M Schoenitz, H Kojitani, HW Xu, JZ Zhang, DJ Weidner, R Jeanloz
    JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 108(B7) 2330 2003年7月  
    [1] MgSiO3-rich perovskite is expected to dominate Earth's lower mantle (pressures >25 GPa) with iron and aluminum as significant substituents. The incorporation of trivalent ions, M3+, may occur by two competing mechanisms: Mg-A + Si-B = M-A + M-B and Si-B = Al-B + 0.5 (vacancy)(O). Phase synthesis studies show that both substitutions do occur and the nonstoichiometric or defect substitution is prevalent along the MgSiO3-MgAlO2.5 join. Lattice parameters associated with the first substitution ( stoichiometric) show more rapid increases with increasing Al content than those for the second substitution ( nonstoichiometric), consistent with the differences in size of substituting ions. Oxide melt solution calorimetry has been used to compare the energetics of both substitutions. The stoichiometric substitution, represented by the reaction 0.95 MgSiO3 (perovskite) + 0.05 Al2O3 (corundum) = Mg0.95Al0.10Si0.95O3 (perovskite), has an enthalpy of - 0.8 +/- 2.2 kJ/mol. The nonstoichiometric reaction, 0.90 MgSiO3 (perovskite) + 0.10 MgO (rocksalt) + 0.05 Al2O3 (corundum) = MgSi0.9Al0.1O2.95 (perovskite) has a small positive enthalpy of 8.5 +/- 4.6 kJ/mol. Configurational T DeltaS terms play a role in both substitutions. The defect substitution is not prohibitive in enthalpy, entropy, or volume, is favored in perovskite coexisting with magnesiowustite and may significantly affect the elasticity, rheology, and water retention of silicate perovskite in Earth.
  • JF Stebbins, H Kojitani, M Akaogi, A Navrotsky
    AMERICAN MINERALOGIST 88(7) 1161-1164 2003年7月  
    In the Earth's mantle, the mechanism(s) of solid solution of Al in MgSiO3 perovskite strongly impacts its thermodynamic and transport properties. We present Al-27 NMR data for perovskite samples of nominal composition Mg(Si0.9Al0.1)O-2.95, to test a mechanism by which Al3+ substitutes at the octahedral Si4+ sites, leaving a corresponding number of O-site vacancies. We find evidence for this process in a significantly greater peak area for Al at B (Si) sites vs. A (Mg) sites in the structure, and the possible identification of a small concentration of five-coordinated Al adjacent to such vacancies. However, substitution of Al3+ at the A sites remains significant. As in perovskite-type technological ceramics, O-atom vacancies may play an important role in enhancing ion mobility and the dissolution of water.
  • 糀谷 浩, 糀谷浩, 宮島延吉
    高圧力の科学と技術 12 126-137 2002年  
  • A Navrotsky, M Schoenitz, H Kojitani, HW Xu, JZ Zhang, DJ Weidner, M Akaogi, R Jeanloz
    PEROVSKITE MATERIALS 718 103-108 2002年  
    MgSiO3 - rich perovskite is expected to dominate the Earth's lower mantle (pressures > 25 GPa), with iron and aluminum as significant substituents. The incorporation of trivalent ions, M3+, may occur by two competing mechanisms: Mg-A + Si-B = M-A + M-B and Si-B = Al-B + 0.5 V-O. Phase synthesis studies show that both substitutions do occur, and the nonstoichiometric or defect substitution is prevalent along the MgSiO3 - MgAlO2.5 join. Oxide melt solution calorimetry has been used to compare the energetics of both substitutions. The stoichiometric substitution, represented by the reaction 0.95 MgSiO3 (perovskite) + 0.05 Al2O3 (corundum) = Mg0.95Al0.10Si0.95O3 (perovskite), has an enthalpy of -0.8+/-2.2 kJ/mol. The nonstoichiometric reaction, 0.90 MgSiO3 (perovskite) + 0.10 MgO (rocksalt) + 0.05 Al2O3 (corundum) = MgSi0.9Al0.1O2.95 (perovskite) has a small positive enthalpy of 8.5+/-4.6 kJ/mol. The defect substitution is not prohibitive in enthalpy, entropy, or volume, is favored in perovskite coexisting with magnesiowustite, and may significantly affect the elasticity, rheology and water retention of silicate perovskite in the Earth.
  • KOJITANI HIROSHI, H. Kojitani, N. Miyajima
    The Review of High pressure Science and Technology 12 126-137 2002年  
  • A Navrotsky, M Schoenitz, H Kojitani, HW Xu, JZ Zhang, DJ Weidner, M Akaogi, R Jeanloz
    PEROVSKITE MATERIALS 718 103-108 2002年  
    MgSiO3 - rich perovskite is expected to dominate the Earth's lower mantle (pressures > 25 GPa), with iron and aluminum as significant substituents. The incorporation of trivalent ions, M3+, may occur by two competing mechanisms: Mg-A + Si-B = M-A + M-B and Si-B = Al-B + 0.5 V-O. Phase synthesis studies show that both substitutions do occur, and the nonstoichiometric or defect substitution is prevalent along the MgSiO3 - MgAlO2.5 join. Oxide melt solution calorimetry has been used to compare the energetics of both substitutions. The stoichiometric substitution, represented by the reaction 0.95 MgSiO3 (perovskite) + 0.05 Al2O3 (corundum) = Mg0.95Al0.10Si0.95O3 (perovskite), has an enthalpy of -0.8+/-2.2 kJ/mol. The nonstoichiometric reaction, 0.90 MgSiO3 (perovskite) + 0.10 MgO (rocksalt) + 0.05 Al2O3 (corundum) = MgSi0.9Al0.1O2.95 (perovskite) has a small positive enthalpy of 8.5+/-4.6 kJ/mol. The defect substitution is not prohibitive in enthalpy, entropy, or volume, is favored in perovskite coexisting with magnesiowustite, and may significantly affect the elasticity, rheology and water retention of silicate perovskite in the Earth.
  • H Kojitani, A Navrotsky, M Akaogi
    PHYSICS AND CHEMISTRY OF MINERALS 28(6) 413-420 2001年7月  
    Enthalpies of drop solution (DeltaH(drop-sol)) of CaGeO3, Ca(Si0.1Ge0.9)O-3, Ca(Si0.2Ge0.8)O-3, Ca(Si0.3-Ge0.7)O-3 perovskite solid solutions and CaSiO3 wollastonite were measured by high-temperature calorimetry using molten 2PbO .B2O3 solvent at 974 K. The obtained values were extrapolated linearly to the CaSiO3 end member to give DeltaH(drop-sol) of CaSiO3 perovskite of 0.2 +/-4.4 kJ mol(-1). The difference in DeltaH(drop-sol) between CaSiO3, wollastonite, and perovskite gives a transformation enthalpy (wo --> pv) of 104.4 +/-4.4 kJ mol(-1). The formation enthalpy of CaSiO3 perovskite was determined as 14.8 +/-4.4 kJ mol(-1) from lime + quartz or -22.2 +/-4.5 kJ mol(-1) from lime + stishovite. A comparison of lattice energies among A(2+)B(4+)O(3) perovskites suggests that amorphization during decompression may be due to the destabilizing effect on CaSiO3 perovskite from a large nonelectrostatic energy (repulsion energy) at atmospheric pressure. By using the formation enthalpy for CaSiO3 perovskite, phase boundaries between beta -Ca2SiO4 + CaSi2O5 and CaSiO3 perovskite were calculated thermodynamically utilizing two different reference points [where DeltaG(P, T) = 0] as the measured phase boundary. The calculations suggest that the phase equilibrium boundary occurs between 11.5 and 12.5 GPa around 1500 K. Its slope is still not well constrained.
  • H Kojitani, A Navrotsky, M Akaogi
    PHYSICS AND CHEMISTRY OF MINERALS 28(6) 413-420 2001年7月  
    Enthalpies of drop solution (DeltaH(drop-sol)) of CaGeO3, Ca(Si0.1Ge0.9)O-3, Ca(Si0.2Ge0.8)O-3, Ca(Si0.3-Ge0.7)O-3 perovskite solid solutions and CaSiO3 wollastonite were measured by high-temperature calorimetry using molten 2PbO .B2O3 solvent at 974 K. The obtained values were extrapolated linearly to the CaSiO3 end member to give DeltaH(drop-sol) of CaSiO3 perovskite of 0.2 +/-4.4 kJ mol(-1). The difference in DeltaH(drop-sol) between CaSiO3, wollastonite, and perovskite gives a transformation enthalpy (wo --> pv) of 104.4 +/-4.4 kJ mol(-1). The formation enthalpy of CaSiO3 perovskite was determined as 14.8 +/-4.4 kJ mol(-1) from lime + quartz or -22.2 +/-4.5 kJ mol(-1) from lime + stishovite. A comparison of lattice energies among A(2+)B(4+)O(3) perovskites suggests that amorphization during decompression may be due to the destabilizing effect on CaSiO3 perovskite from a large nonelectrostatic energy (repulsion energy) at atmospheric pressure. By using the formation enthalpy for CaSiO3 perovskite, phase boundaries between beta -Ca2SiO4 + CaSi2O5 and CaSiO3 perovskite were calculated thermodynamically utilizing two different reference points [where DeltaG(P, T) = 0] as the measured phase boundary. The calculations suggest that the phase equilibrium boundary occurs between 11.5 and 12.5 GPa around 1500 K. Its slope is still not well constrained.
  • H Kojitani, M Akaogi
    EARTH AND PLANETARY SCIENCE LETTERS 153(3-4) 209-222 1997年12月  
    High-temperature drop calorimetry in the temperature range of 1398-1785 K was performed for the samples of mixtures of synthetic anorthite (An), diopside (Di), enstatite (En) and forsterite (Fo) with the same compositions as those of primary melts generated at 1.1, 3 and 4 GPa at most 10 degrees above the solidus of anhydrous mantle peridotite in the CaO-MgO-Al2O3-SiO2 system. From the differences between the heat contents (H-T-H-298) of liquid and that of crystal mixture at the liquidus temperature, melting enthalpies of the samples of 1.1, 3 and 3 GPa-primary melt compositions were determined at 1 arm to be 531 +/- 39 J.g(-1) at 1583 K, 604 +/- 21 J.g(-1) at 1703 K, 646 +/- 21 J.g(-1) at 1753 K, respectively. These heat of fusion values suggest that mixing enthalpy of the melt in the An-Di-En-Fo system is approximately zero within the experimental errors when we use the heat of fusion of Fo by Richet et al. (P. Richet, F. Leclerc, L. Benoist, Melting of forsterite and spinel, with implications for the glass transition of Mg2SiO4 liquid, Geophys. Res. Lett. 20 (1993) 1675-1678). The measured enthalpies of melting at 1 atm were converted into those for melting reactions which occur under high pressures by correcting enthalpy changes associated with solid-state mineral reactions. Correcting the effects of pressure, temperature and FeO and Na2O components on the melting enthalpies at 1 atm, heat of fusion values of a representative mantle peridotite just above the solidus under high pressure were estimated to be 590 J at 1.1 GPa and 1523 K, 692 J at 3 GPa and 1773 K, and 807 J at 4 GPa and 1923 K for melting reactions producing liquid of 1 g, with uncertainties of 50 J. By applying these melting enthalpies to a mantle diapir model which generates present MORBs, a potential mantle temperature of 1533 K has been estimated, assuming an eruption temperature of magma of 1473 K. (C) 1997 Elsevier Science B.V.
  • 糀谷 浩, 赤荻正樹, 糀谷浩, 鈴木敏弘, 森棟朋子
    火山 42 S29-S34 1997年  
  • KOJITANI HIROSHI, H. Kojitani, M. Akaogi
    Earth Planet. Sci. Lett. 153 209-222 1997年  
  • 糀谷 浩, 糀谷浩, 赤荻正樹
    熱測定 23(4) 187-196 1996年  
    Calorimetric data on heats of fusion of rocks have been very limited. In our investigation, high-temperature drop calorimetry was performed to measure heats of fusion of mantle rocks in the system CaO-MgO-Al2O3-SiO2. Heats of fusion of natural mantle rocks under high pressure were estimated by correcting effects of FeO and Na2O components, pressure and temperature on melting enthalpies to the observed heats of fusion. It is suggested that mixing enthalpy of silicate melt in the system CaO-MgO-Al2O3-SiO2 is nearly zero by comparing the heats of fusion determined calorimetrically with those calculated by summing melting enthalpies of CaAl2Si2O8, CaMgSi2O6, MgSiO3 and Mg2SiO4.
  • H KOJITANI, M AKAOGI
    GEOPHYSICAL RESEARCH LETTERS 22(17) 2329-2332 1995年9月  
    Compositions of natural olivine tholeiites were simplified in the system CaO-Mgo-Al2O3-SiO2, and approximately eutectic composition in the system diopside(Di)- forsterite(Fo)- anorthite(An) (Di:Fo:An =49.0:7.5:43.5 wt%) was chosen as the model basalt composition. High-temperature drop calorimetry was performed at 1405 -1676K for the samples with the model basalt composition consisting of the mixture of synthetic diopside, forsterite and anorthite. The heat of fusion of the model basalt was obtained to be 506 +/- 38 J/g from the difference between the heat content of liquid and that of the mineral mixture at 1543K, which was the approximated eutectic temperature. This heat of fusion shows almost zero enthalpy of mixing in this system. Taking account of the pressure, temperature and composition effects on enthalpy, the heat of fusion of 490-560 J/g is estimated for generation of MORE (mid-ocean ridge basalt) in the upper mantle.
  • 糀谷 浩, 赤荻正樹, 糀谷浩, 石坂登, 鈴木敏弘
    月刊地球 17 19-22 1995年  
  • Hiroshi Kojitani, Masaki Akaogi
    Geophysical Research Letters 22(17) 2329-2332 1995年  
    Compositions of natural olivine tholeiites were simplified in the system CaO‐MgO‐Al2O3‐SiO2, and approximately eutectic composition in the system diopside(Di)‐ forsterite(Fo) ‐ anorthite(An) (Di:Fo:An = 49.0:7.5:43.5 wt%) was chosen as the model basalt composition. High‐temperature drop calorimetry was performed at 1405–1676K for the samples with the model basalt composition consisting of the mixture of synthetic diopside, forsterite and anorthite. The heat of fusion of the model basalt was obtained to be 506±38 J/g from the difference between the heat content of liquid and that of the mineral mixture at 1543K, which was the approximated eutectic temperature. This heat of fusion shows almost zero enthalpy of mixing in this system. Taking account of the pressure, temperature and composition effects on enthalpy, the heat of fusion of 490–560 J/g is estimated for generation of MORB (mid‐ocean ridge basalt) in the upper mantle. Copyright 1995 by the American Geophysical Union.
  • H KOJITANI, M AKAOGI
    PHYSICS AND CHEMISTRY OF MINERALS 20(8) 536-540 1994年  
    Solution enthalpies of synthetic olivine solid solutions in the system Mg2SiO4 - Fe2SiO4 have been measured in molten 2 PbO . B2O3 at 979 K. The enthalpy data show that olivine solid solutions have a positive enthalpy of mixing and the deviation from ideality is approximated as symmetric with respect to composition, in contrast to the previous study. Applying the symmetric regular solution model to the present enthalpy data, the interaction parameter of ethalpy (W(H)) is estimated to be 5.3 +/- 1.7 kJ/mol (one cation site basis). Using this W(H) and the published data on excess free energy of mixing, the nonideal parameter of entropy (W(S)) of olivine solid solutions is estimated as 0.6 +/- 1.5 J/mol . K.
  • 糀谷 浩, 糀谷浩, 赤荻正樹, 鈴木敏弘
    熱測定 20(3) 118-124 1994年  
    珪酸塩鉱物の熱力学的データは,地球のマントルにおける相平衡関係を計算するために不可欠なものである。本研究では,いくつかの珪酸塩鉱物の溶解,転移,及び融解のエンタルピーを測定するための高温熱量測定法を開発した。Mg2SiO4-Fe2SiO4オリビン固溶体の溶解エンタルピーは,ホウ酸鉛溶媒による溶解熱測定法で測定された。その結果は,オリビン固溶体が正の混合エンタルピーを持つことを示した。MgSiO3オルソパイロキシン-ペロブスカイト転移のエンタルピーは,示差落下溶解熱測定法で得られた。CaMgSi2O6ディオプサイドの融解エンタルピーは,DSC法により測定された。これらの熱力学的データは,高圧力,高温下での相平衡境界を計算するためや,マグマの成因を議論するために用いられる。
  • KOJITANI HIROSHI, H. Kojitani, M. Akaogi
    Phys. Chem. Miner. 20 536-540 1994年  

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