Statistical features of foreshocks in comparison with other earthquake clusters   总被引：2，自引：0，他引：2  

Yosihiko Ogata  Tokuji Utsu  Koichi Katsura 《Geophysical Journal International》1995,121(1):233-254

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Production of the Blood Pressure Lowing Peptides from Brown Alga ( Undaria pinnatifida )     

Sato Minoru  Oba Takashi  Hosokawa Takao  Yamaguchi Toshiyasu  Nakano Toshiki  Saito Tadao  Muramoto Koji  Kahara Takashi  Funayama Katsura  Kobayashi Akio  Nakano Takahisa 《中国海洋大学学报(英文版)》2005,4(3)

1 IntroductionIncreased blood pressure appears to be one of theprimary risk factors of circulatory organ diseases suchas encepharo-apoplexy, encepharo-infarction and cardi-ac infraction. Angiotensin-I-converting enzyme (ACE)plays an important role in the rennin-angiotensin sys-tem by regulating blood pressure. Antihypertensivedrugs such as captopril and enalapril are potent ACEinhibitors (Ondetti et al., 1977). Recently, severalinhibitory peptides derived from food proteins havebeen isolat…  相似文献   

Oxygen, carbon, and strontium isotope geochemistry of diamond-bearing carbonate rocks from Kumdy-Kol, Kokchetav Massif, Kazakhstan     

M Ohta  T Mock  Y Ogasawara  D Rumble   《Lithos》2003,70(3-4):77-90

Diamond-bearing carbonate rocks from Kumdy-Kol, Kokchetav massif, Kazakhstan, were strongly altered by fluids flowing through fractures and infiltrating along grain boundaries during exhumation. Alteration includes retrogradation of high-grade silicate assemblages by hydrous minerals, replacement of diamond by graphite and of dolomite by calcite. Diamond-bearing carbonate rocks are among the most intensely altered isotopically with δ¹⁸O_VSMOW values as low as +9‰, δ¹³C_VPDB=−9‰, and ⁸⁷Sr/⁸⁶Sr as high as 0.8050. Evidence of isotopic equilibration between coexisting dolomite and high-Mg calcite during ultrahigh-pressure metamorphism (UHPM) is preserved only rarely in samples isolated from infiltrating fluids by distance from fractures. Isotopic heterogeneity and isotopic disequilibrium are widespread on a hand-specimen scale. Because of this lack of homogeneity, bulk analyses cannot provide definitive measurements of ¹³C/¹²C fractionation between coexisting diamond and carbonate. Our study adequately documents alteration on a scale commensurate with observed vein structures. But, testing the hypothesis of metamorphic origin of microdiamonds has not fully succeeded because our analytical spatial resolution, limited to 0.5 mm, is not small enough to measure individual dolomite inclusions or individual diamond crystals.  相似文献   

Degassing, crystallization and eruption dynamics at Stromboli: trace element and lithium isotopic evidence from 2003 ashes     

Federica Schiavi  Katsura Kobayashi  Takuya Moriguti  Eizo Nakamura  Massimo Pompilio  Massimo Tiepolo  Riccardo Vannucci 《Contributions to Mineralogy and Petrology》2010,159(4):541-561

During its 1800-year-long persistent activity the Stromboli volcano has erupted a highly porphyritic (HP) volatile-poor scoriaceous magma and a low porphyritic (LP) volatile-rich pumiceous magma. The HP magma is erupted during normal Strombolian explosions and lava effusions, while the LP one is related to more energetic paroxysms. During the March–April 2003 explosive activity, Stromboli ejected two typologies of juvenile glassy ashes, namely highly vesicular LP shards and volatile-poor HP shards. Their textural and in situ chemical characteristics are used to unravel mutual relationships between HP and LP magmas, as well as magma dynamics within the shallow plumbing system. The mantle-normalized trace element patterns of both ash types show the typical arc-lava pattern; however, HP glasses possess incompatible element concentrations higher than LP glasses, along with Sr and Eu negative anomalies. HP shards are generally characterized by higher Li contents (to ~20 ppm) and lower δ⁷Li values (+1.2 to −3.8‰) with respect to LP shards (Li contents of 7–14 ppm and δ⁷Li ranging between +4.6 and +0.9‰). Fractional crystallization models based on major and trace element compositions, combined with a degassing model based on open-system Rayleigh distillation and on the assumption that ^melt/fluidD_Li > 1, show that abundant (~30%) plagioclase precipitation and variable degrees of degassing can lead the more primitive LP magma to evolve toward a differentiated (isotopically lighter) HP magma ponding in the upper conduit and undergoing slow continuous degassing-induced crystallization. This study also evidences that in March 2003 Stromboli volcano poured out a small early volume of LP magma that traveled slower within the conduit with respect to later and larger volumes of fast ascending LP magma erupted during the April 5 paroxysm. The different ascent rates and cooling rates of the two LP magma batches (i.e., pre- and post-paroxysm) resulted in small, but detectable, differences in their chemical signatures. Finally, this study highlights the high potential of in situ investigations of juvenile glassy ashes in petrologic and geochemical monitoring the volcanic activity and of Li isotopes as tracers of degassing processes within the shallow plumbing system.  相似文献   

The effect of oxygen fugacity on ionic conductivity in olivine     

Hongzhan Fei  Tomoo Katsura 《地学前缘(英文版)》2022,(1):76-84

The oxygen fugacity(f_O2) may affect the ionic conductivity of olivine under upper mantle conditions because Mg vacancies can be produced in the crystal structure by the oxidization of iron from Fe²⁺ to Fe3+. Here we investigated olivine ionic conductivity at 4 GPa, as a function of temperature, crystallographic orientation, and oxygen fugacity, corresponding to the topmost asthenospheric conditions. The results demonstrate that the ionic conductivity is insensitive to f_O2 under relatively reduced conditions(f_O2 below Re-ReO₂ buffer), whereas it has a clear f_O2-dependence under relatively oxidized conditions(f_O2 around the magnetite-hematite buffer). The ionic conduction in olivine may contribute significantly to the conductivity anomaly in the topmost asthenosphere especially at relatively oxidized conditions.  相似文献   

Decay of a post-depositional remanent magnetization in wet sediments due to the effect of drying     

Yo-ichiro Otofuji  Ikuo Katsura  Sadao Sasajima 《Geophysical Journal International》1982,70(1):191-203

Summary. The decay of the post-depositional remanent magnetization (post-DRM) during desiccation in magnetic field free space is measured as a function of the loss of water. The decay is ascribed to the drying effect and the time decay of viscous remanent magnetization (VRM). The VRM forms only 10 per cent of the total of loss of remanent magnetization. The decay due to the drying effects depends both on the loss of water and on either the evaporation rate or the period of storage. The percentage of loss of magnetization is independent of its intensity.
A critical drying stage appears (about 60 per cent in water content on a dry basis) which is characterized as a vanishing point of mobile particles or particle units. The mobile particles or units play an important role both in acquisition and demagnetization through physical rotational motion within wet sediments before the critical drying stage. More than 80 per cent of the total loss of the post-DRM is destroyed before the desiccation proceeds to the critical drying stage. The decay of post-DRh4 is concluded to be mainly due to the physically random rotation of the magnetic particles trapped in shallow energy wells which are overcome by the torques caused by the application of the alternating magnetic field less than 200 Oe.  相似文献   

Solubility of sulfur in some magmas at 1 atmosphere     

Takashi Katsura  Shigeru Nagashima 《Geochimica et cosmochimica acta》1974,38(4):517-531

In order to understand the distribution of sulfur in igneous rooks, we determined the solubility of sulfur in volcanic rock melts (tholeiite basalt, hawaiite and rhyodacite from Hawaii) at various gas compositions and at 1250° and 1300°C and 1 atm total pressure. The solubility of sulfur in the melt passes through a minimum with change in oxygen partial pressure, if other factors are held constant. For the basaltic liquid at 1200°C, most sulfur in the melt is as dissolved sulfide (S^?2) at oxygen partial pressures below 10^?8 atm and as dissolved sulfate at oxygen partial pressures above 10^?8 atm. Based on the present solubility data, 5 per cent is inferred for volcanic gas at 1 atm total pressure in equilibrium with subaerially extruded Hawaiian tholeiite basalt (Pele's hair with 180 ppm S) at 1200°C and 10^?8 atm P_O2.  相似文献   

Geomorphology and tectonic movement of the sea floor,northwest off Kyushu,Japan     

Tadahiko Katsura  Manao Nagano 《Journal of Oceanography》1976,32(3):139-150

As a result of the sea bottom survey of continental shelf northwest off Kyushu including Tsushima, Iki and Goto Islands which has been carried out by the Hydrographic Department of Japan, the following features of the area are revealed. Topographically, three groups of shelf channels, trending NE-SW, N-S and NW-SE respectively, are discovered and several small banks are found. Sand wave-like shapes are also seen in a seafloor about 200 m deep in the vicinity of Tsushima Straits. Geologically, remarkable tectonic lines characterized by faults and folding axes are confirmed and named Tsushima, Iki, Hirato and Goto Tectonic Lines. Several tectonic provinces can be defined by these tectonic lines. Each province consists of small geological blocks formed by indivisual tectonic movement such as tilting, uplifting and sinking. Such differential tectonic movement is often seen on the continental shelves around active island arc. In this area, these tectonics might be caused by activity of the Ryukyu Arc. This area may thus be a metastable portion existing between the northwestern Kyushu and the Asiatic continental block. The present submarine topography is probably closely related to these tectonics in addition to the eustatic sea-level changes in Quaternary age.  相似文献   

Clinopyroxene phenocrysts (with green salite cores) in trachybasalts: implications for two magma chambers under the Kokchetav UHP massif, North Kazakhstan     

Yongfeng Zhu  Yoshihide Ogasawara 《Journal of Asian Earth Sciences》2004,22(5):517

Clinopyroxene phenocrysts in the Kokchetav trachybasalts are variable in composition and textures. Two distinctive cores are recognized: diopside cores and green salite cores. The diopside cores with Mg# of 80–90 are mantled by colorless salite rims with Mg# of 70–80. The green salite cores have especially low Mg# (<70) but high Al and Ti contents. A Mg-rich band (Mg#=82–90) usually occurs between a green salite core and its rim, and/or between a colorless salite mantle and its rim. Dissolution surfaces are observed on all textural variants. Two magma chambers are needed to explain the observed clinopyroxene phenocrysts. A deep chamber at about 120 km in the upper mantle in which diopside cores crystallized, and a shallow chamber at depths of less than 40 km in which diopside cores were resorbed and overgrown by salite rims or mantles. Magma mixing in the shallow chamber is responsible for the formation of dissolution surfaces between the diopside bands and the colorless salite mantles. The dissolution surfaces on the diopside cores formed in the shallow chamber as a result of pressure decrease. This magma evolution scenario is complicated by the occurrence of the crustal-origin green salite cores in diopsides. These green cores likely represent the relics of continental materials, which were captured in the deep chamber and partially re-melted. Our observations indicate that subducted continental materials were returned to the Earth's surface as a result of magmatism. This study therefore provides direct evidence of a link between subducted continental materials (slab) and magmatism in this orogenic belt.  相似文献   

Chemical analysis of volcanic gases     

I. Iwasaki  T. Ozawa  M. Yoshida  T. Katsura  M. Kamada 《Bulletin of Volcanology》1965,28(1):3-16

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