Tropospheric ozone depletion in polar regions A comparison of observations in the Arctic and Antarctic   总被引：1，自引：0，他引：1  

S. WESSEL  S. AOKI  P. WINKLER  R. WELLER  A. HERBER  H. GERNANDT  O. SCHREMS 《Tellus. Series B, Chemical and physical meteorology》1998,50(1):34-50

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Mg-Fe partitioning between olivine and ultramafic melts at high pressures     

Kenji Mibe  Toshitsugu Fujii  Shigeaki Ono 《Geochimica et cosmochimica acta》2006,70(3):757-766

Precise determination of the partitioning of Mg and Fe²⁺ between olivine and ultramafic melt has been made at pressures from 5 to 13 GPa using a MA-8 type multi-anvil high-pressure apparatus (PREM) installed at Earthquake Research Institute, University of Tokyo. A very short rhenium capsule (<100 μm sample thickness) was adopted to minimize temperature variation within the sample container. Synthetic gels with the composition of the upper mantle peridotite were used as starting materials to promote the homogeneity. Analyses of quenched melts and coexisting olivines were made with an electron probe microanalyzer. The obtained partition coefficient, K_D [=(FeO/MgO)^ol/(FeO/MgO)^melt], decreases from 0.35 to 0.25 with increasing pressure from 5 to 13 GPa, suggesting a negative correlation between pressure and K_D above 5 GPa. Our result is consistent with a parabolic relationship between K_D and degree of polymerization (NBO/T) of melts reported by previous studies at lower pressures. The negative correlation between pressure and K_D suggests that olivine crystallizing in a magma ocean becomes more Mg-rich with depth and that primary magmas generated in the upper mantle become more Fe-rich with depth than previously estimated.  相似文献   

Hydrothermal alteration and K–Ar ages of Neogene‐Quaternary magmatic‐hydrothermal systems at Toyoha‐Muine area in southwest Hokkaido,Japan     

Toru SHIMIZU  Masahiro AOKI 《Resource Geology》2011,61(2):192-209

This paper presents a review of hydrothermal alteration and K–Ar age data from the Toyoha‐Muine area (TMA), where the Toyoha polymetallic (Ag–Pb–Zn–Cu–In) deposit is located near the Pliocene andesitic volcano that formed Mt Muine. Systematic prospect‐scale mapping, sampling, X‐ray analysis and microscopic observation show that hydrothermal alteration is divided into two groups: acid‐pH and neutral‐pH alteration types. The former is further divided into mineral assemblages I, II and III, while the latter into mineral assemblages IV and V. Different mineralogical features in five mineral assemblages are summarized as follows: (I) Quartz (silicified rock); (II) Pyrophyllite or dickite; (III) Kaolinite or halloysite ± alunite; (IV) Sericite or K‐feldspar; and (V) Interstratified minerals (illite/smectite and chlorite/smectite) and/or smectite. K–Ar radiometric ages determined on twenty‐eight K‐bearing samples (whole volcanic rocks and separated hydrothermal minerals) mainly fall into one of three periods: Early Miocene (24.6–21.4 Ma), Middle–Late Miocene (12.5–8.4 Ma) and Pliocene–Pleistocene (3.2–0 Ma). These three periods are characterized as follows. Early Miocene: A minor hydrothermal activity, which might be genetically related to the intermediate or felsic magmatic activities, formed mineral assemblage IV at 24.6 Ma in the northern part of the TMA. Middle to Late Miocene: The basaltic intrusion, andesitic eruption, and granodiorite intrusions induced hydrothermal activities between 12.5 and 8.4 Ma, resulting in the formation of a mineral assemblage IV with some base metal mineralization. Pliocene–Pleistocene: An andesitic eruption formed Mt Muine between 3.2 and 2.9 Ma. The andesitic activity was associated with acid‐pH mineral assemblages I, II and III locally around the volcano. Latent magmatic intrusions subsequent to the andesitic eruption generated hydrothermal activities that formed mineral assemblages IV and V between 1.9 and 0 Ma in the southern and southeastern parts of Toyoha deposit at depth, overprinting the Middle to Late Miocene alteration. The hydrothermal activities also formed mineral assemblages I, II and III along the Yunosawa fault (east of the Toyoha deposit) and assemblage III in the south and southeast of the Toyoha deposit near the surface.  相似文献   

Variations of tropospheric ozone concentration over Syowa Station, Antarctica     

SHOHEI MURAYAMA  TAKAKIYO NAKAZAWA  MASAYUKI TANAKA  SHUHJI AOKI  SADAO KAWAGUCHI 《Tellus. Series B, Chemical and physical meteorology》1992,44(4):262-272

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New high-pressure phases in BaCO<Subscript>3</Subscript>     

Shigeaki Ono 《Physics and Chemistry of Minerals》2007,34(4):215-221

Barium carbonate (BaCO₃) was examined in a diamond anvil cell up to a pressure of 73 GPa using an in situ angle-dispersive X-ray diffraction technique. Three new phases of BaCO₃ were observed at pressures >10 GPa. From 10 to 24 GPa, BaCO₃-IV had a post-aragonite structure with space group Pmmn. There are two molecules in a single unit cell (Z = 2) of the orthorhombic phase, which is same as the high-pressure phases of CaCO₃ and SrCO₃. The isothermal bulk modulus of BaCO₃-IV is K ₀ = 84(4) GPa, with V ₀ = 129.0(7) Å³ when K ₀′ = 4. The c axis of the unit cell parameter is less compressible than the a and b axes. The relative change in volume that accompanies the transformation between BaCO₃-III and BaCO₃-IV is ～6%. BaCO₃-V, which has an orthorhombic symmetry, was synthesized at 50 GPa. As the pressure increases, BaCO₃-V is transformed into tetragonal BaCO₃-VI. This transformation is likely to be second order, because the diffraction pattern of BaCO₃-V is similar to that of BaCO₃-VI, and some single peaks in BaCO₃-VI become doublets in BaCO₃-V. After decompression, the new high-pressure phases transform into BaCO₃-II. Our findings resolve a dispute regarding the stable high-pressure phases of BaCO₃.  相似文献   

Crustal strain observation for nine years with a laser strainmeter in Kobe, Japan     

Shuzo Takemoto  Takeyasu Yamamoto  Atsushi Mukai  Shigeaki Otsuka  Kunio Fujimori 《Journal of Geodynamics》2003,35(4-5):483-498

We carried out precise crustal strain observation using a laser strainmeter system at the Rokko-Takao station in Kobe, Japan from 1989 to 1997. The long-term strain record is characterized by remarkable annual changes of the order of 2–3×10⁻⁶ and linear strain accumulation of −4.4×10⁻⁷/year (in contraction). The annual strain changes are inversely proportional to temperature changes that precede the strain changes by about 1 month. The apparent annual strain changes were mainly caused by refractive-index changes in the light path due to the ambient temperature changes. After eliminating the annual temperature effect, linear strain accumulation is corrected to be −6.3−6.7×10⁻⁷/year. Residual strains show the oscillating behavior, in which the oscillating cycle seems to become shorter and shorter as time goes by. During the period, a destructive earthquake of M=7.2 occurred near the Kobe City on 17 January 1995. We investigated the oscillating behavior in secular variations of ground-strains by introducing the deterministic approach of earthquake prediction to search for the “critical point” of the occurrence of an earthquake in the extended power law equation. However, we could not obtain a unique solution to determine eight unknown parameters including the “critical point”. This may be mainly due to lack of data for 4 months from August to November in 1994 by the failure of the laser source before the occurrence of earthquake on 17 January 1995. After removing environmental effects and tidal components, we carefully re-examined strain changes in 7 days and 1 day before the occurrence of the earthquake, but we could not detect anomalous strain changes exceeding 1×10⁻⁸ before the earthquake.  相似文献   

In situ observation of a phase transition in Fe2SiO4 at high pressure and high temperature     

Shigeaki Ono  Takumi Kikegawa  Yuji Higo 《Physics and Chemistry of Minerals》2013,40(10):811-816

We used an in situ measurement method to investigate the phase transition of Fe₂SiO₄ polymorphs under high pressures and temperatures. A multi-anvil high-pressure apparatus combined with synchrotron X-ray radiation was used. The stability of each polymorph was identified by observing the X-ray diffraction data from the sample. In most experiments, the diffraction patterns were collected 10–30 min after reaching the desired pressure and temperature conditions. The transition boundary between the olivine and spinel phase at T = 1,000–1,500 K and P = 2–8 GPa was determined to occur at P (GPa) = 0.5 + 0.0034 × T (K). The transition pressure determined in this study was in general agreement with that observed in previous high-pressure experiments. However, the slope of the transition, dP/dT, determined in our study was significantly higher than that estimated by the previous study combined with the in situ X-ray method.  相似文献   

Temporal and spatial variations of upper tropospheric and lower stratospheric carbon dioxide     

TAKAKIYO NAKAZAWA  KOHJI MIYASHITA  SHUHJI AOKI  MASAYUKI TANAKA 《Tellus. Series B, Chemical and physical meteorology》1991,43(2):106-117

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A new high-pressure phase of strontium carbonate     

Shigeaki Ono  Miki Shirasaka  Takumi Kikegawa  Yasuo Ohishi 《Physics and Chemistry of Minerals》2005,32(1):8-12

High-pressure and high-temperature experiments conducted in a laser-heated diamond-anvil cell with a synchrotron X-ray diffraction method have revealed a phase transformation in the aragonite-type SrCO₃ at pressures above 10 GPa. The new phase has an orthorhombic symmetry and was confirmed to remain stable to 32 GPa. The Birch-Murnaghan equation of state for new phase was determined from the experimental unit cell parameters, with K₀ = 101 (± 16) GPa, K₀ = 4 (constrained value), and V₀ = 111.9 (± 2.2). This transformation in SrCO₃ is different from that in BaCO₃ as reported in previous studies. After decompression at ambient pressure, the high-pressure phase transforms to a metastable structure, which has an orthorhombic symmetry. This result should also resolve a dispute regarding the stable high-pressure phases in BaCO₃, which is an analog material of CaCO₃ and SrCO₃.This revised version was published in February 2005 with corrections to the Introduction and to the References.  相似文献   

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Shigeaki Kojima  Suguru Ohta 《Journal of Oceanography》1989,45(6):A103-A117

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