Strontium isotope composition in volcanic rocks from the Northeast Japan arc     

Kenji Notsu 《Journal of Volcanology and Geothermal Research》1983,18(1-4)

In the Northeast Japan arc, a number of Quaternary volcanoes form a long, narrow belt, parallel to the Japan Trench. ⁸⁷Sr/⁸⁶Sr ratios were determined in 52 specimens of volcanic rocks from 27 volcanoes in the Northeast Japan arc area. The results reveal that the ratios change systematically in space. Decreasing ⁸⁷Sr/⁸⁶Sr ratios across the arc were confirmed over a wide area of Northeast Japan. In the same direction, increases in both Rb and Sr contents were also found. The regular trends are considered to be a strong constraint for elucidation of subduction-originated magma genesis at the Eurasia plate vs. Pacific plate boundary. In the northern region of the Northeast Japan arc, ⁸⁷Sr/⁸⁶Sr ratios in volcanic rocks along the volcanic front were almost constant (0.7038–0.7045) and slightly higher than those from the Izu-Ogasawara arc (0.7032–0.7038). This suggests that “interactions” between the Eurasia plate and the Pacific plate, and those between the Philippine Sea plate and the Pacific plate are slightly different. The southern region of the Northeast Japan arc, where the direction of the volcanic front bends from southward to westward, showed anomalously high ⁸⁷Sr/⁸⁶Sr ratios, reaching to 0.7077. This region coincides with the triple junction of the Eurasia, Pacific and Philippine Sea plates, suggesting “anomalous interaction” at the triple junction.  相似文献   

Diffuse volcanic degassing and thermal energy release from Hengill volcanic system, Iceland     

Pedro A. Hernández  Nemesio M. Pérez  Thráinn Fridriksson  Jolie Egbert  Evgenia Ilyinskaya  Andri Thárhallsson  Gretar ívarsson  Gestur Gíslason  Ingvi Gunnarsson  Birgir Jónsson  Eleazar Padrón  Gladys Melián  Toshiya Mori  Kenji Notsu 《Bulletin of Volcanology》2012,74(10):2435-2448

We report the first detailed study of spatial variations on the diffuse emission of carbon dioxide (CO₂) and hydrogen sulfide (H₂S) from Hengill volcanic system, Iceland. Soil CO₂ and H₂S efflux measurements were performed at 752 sampling sites and ranged from nondetectable to 17,666 and 722?g?m^?2?day^?1, respectively. The soil temperature was measured at each sampling site and used to evaluate the heat flow. The chemical composition of soil gases sampled at selected sampling sites during this study shows they result from a mixing process between deep volcanic/hydrothermal component and air. Most of the diffuse CO₂ degassing is observed close to areas where active thermal manifestations occur, northeast flank of the Hengill central volcano close to the Nesjavellir power plant, suggesting a diffuse degassing structure with a SSW?CNNE trend, overlapping main fissure zone and indicating a structural control of the degassing process. On the other hand, H₂S efflux values are in general very low or negligible along the study area, except those observed at the northeast flank of the Hengill central volcano, where anomalously high CO₂ efflux and soil temperatures were also measured. The total diffuse CO₂ emission estimated for this volcanic system was about 1,526?±?160?t?day^?1 of which 453?t?day^?1 (29.7?%) are of volcanic/hydrothermal origin. To calculate the steam discharge associated with the volcanic/hydrothermal CO₂ output, we used the average H₂O/CO₂ mass ratio from 12 fumarole samples equal to 88.6 (range, 9.4?C240.2) as a representative value of the H₂O/CO₂ mass ratios for Hengill fumarole steam. The resulting estimate of the steam flow associated with the gas flux is equal to 40,154?t?day^?1. The condensation of this steam results in thermal energy release for Helgill volcanic system of 1.07?×?10¹⁴?J?day^?1 or to a total heat flow of 1,237?MW_t.  相似文献   

Forward     

O. Oshima  T. Tiba  S. Aramaki  H. Okada  K. Notsu 《Bulletin of Volcanology》1995,57(1):1-6

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