Seasonal variations of residence time and upper atmospheric contribution of aerosols studied with Pb-210, Bi-210, Po-210 and Be-7     

TAKAYUKI TOKIEDA  KENJI YAMANAKA  KOH HARADA  SHIZUO TSUNOGAI 《Tellus. Series B, Chemical and physical meteorology》1996,48(5):690-702

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Boron isotope variations in the atmosphere   总被引：2，自引：0，他引：2  

YOSHIKI MIYATA  TAKAYUKI TOKIEDA  HIROSHI AMAKAWA  MITSUO UEMATSU  YOSHIYUKI NOZAKI 《Tellus. Series B, Chemical and physical meteorology》2000,52(4):1057-1065

We report here the first measurements of boron isotope ratios in the maritime atmosphere together with those of precipitation. The δ¹¹B values of atmospheric condensates in the western North Pacific and Japanese coast and snow in Tokyo range from −12.8 to +5.1‰ and from −0.4 to +0.4‰, respectively, which are significantly lower than those of rainwater (+18.9 to +34.7‰) collected mostly over the North Pacific. Since the ¹¹B/¹⁰B ratios of the atmosphere are lower than those of volcanic emissions (δ¹¹B=+2.3 to +21.4‰), we must seek sources for atmospheric boron other than volcanism. We postulate that the sea may be an important supplier for atmospheric boron under some dynamic conditions and that boron isotope fractionation during evaporation from seawater and removal from the atmosphere may account for the large variations of ¹¹B/¹⁰B ratios observed in the atmosphere and precipitation.  相似文献   

Large amount of fluid migration around shallow seismogenic depth preserved in tectonic mélange: Yokonami mélange,the Cretaceous Shimanto Belt,Kochi, Southwest Japan     

YOSHITAKA HASHIMOTO  MIO EIDA  TAKAYUKI KIRIKAWA  RYOKO IIDA  MIE TAKAGI  NORIKO FURUYA  AKIRA NIKAIZO  TAKETO KIKUCHI  TOSHIO YOSHIMITSU 《Island Arc》2012,21(1):53-64

Studying subduction zone fluid at shallow seismogenic depths is important to understand the nature of fault rocks at the updip limit of the seismogenic zone because fluid–rock interactions affect heat and mass transfer, and fault strength. In this study, we conducted detailed analyses of distribution of shear veins, and estimation of pressure–temperature conditions for shear vein formation for the Yokonami mélange, Shikoku, Southwest Japan, which is tectonic mélange zone in an on‐land accretionary complex. We found a seismogenic fault at the upper boundary of the Yokonami mélange, indicating that the Yokonami mélange was active at seismogenic depth. The field‐transect distribution of shear veins was examined. The frequency, the total and mean thicknesses of the shear veins were about 3.7 per meter, about 10 mm per meter, and about 3 mm per shear vein, respectively. Quartz within the shear veins shows elongate‐blocky textures, suggesting precipitation from advective flow. The pressure and temperature conditions for shear vein formation were examined by fluid inclusion analysis, ranging 175–225°C and 143–215 MPa, respectively. The temperature is almost consistent with the paleotemperature determined from vitrinite reflectance, suggesting that the shear veins were formed at up to the maximum depth. The depth might be consistent with that where the seismogenic fault was formed. On the basis of the pressure and temperature conditions and the distribution of shear veins, we estimated the minimum volumetric ratio of fluid to host rocks, assuming that the shear veins had precipitated from advective flow. The estimated amount of fluid is about 106 m³ per cubic meter of host rocks. The results suggest that a large amount of fluid migrates through mélange zones at shallow seismogenic depths. This fluid possibly originates from the dehydration of clay minerals from underthrusted sediments and an altered subducting slab.  相似文献