島根大学総合理工学部地球資源環境学教室
ISSN:1343-9774
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Use this link to cite this item : https://ir.lib.shimane-u.ac.jp/6098
Geoscience reports of Shimane University 20
2001-12-28 発行
広島県吉舎地域・高田期の「双三火山―深成複合岩体」 : 斜長石Sr同位体比組成からのアプローチ
Futami Volcano−plutonic complex,Cretaceous Takada period,Kisa area,Hiroshima prefecture,Southwest Japan : Evidence from Sr isotopic ratios of plagioclase in Takada Rhyolites
Matsumoto, Ichiro
Faculty of Education, Shimane University
Sawada, Yoshihiro
Interdisciplinary Faculty of Science and Engineering, Department of Geoscience, Shimane University
Kagami, Hiroo
Graduate School of Science and Technology, Niigata University
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Description
Cretaceous volcanic and plutonic rocks are widely distributed in the central part of Chugoku district，southwest Japan．The Cretaceous igneous rocks in and around Kisa-cho in northern Hiroshima Prefecture，are divided into the Kisa Volcanics，the Takada Rhyolites and granitoids．Takada Rholites，which erupted immediately following the Kisa Volcanics，is composed mainly of rhyolitic pyroclastic flow deposits．We called this volcano-plutonic complex in Kisacho，Futami Volcano-plutonic complex．
Two samples of plagioclase from the lapilli tuff of the Takada Rhyolites have Sr isotopic ratios of 0.70648 ± 2 and 0.70672 ± 1． Sr isotopic ratios of the host rocks of the plagioclases are not available．Initial Sr isotopic ratios of the
plagioclases differ from the andesite-dacite group，but are similar to those of granitoids of the Futami Volcano-plutonic complex．
Two samples of plagioclase from the lapilli tuff of the Takada Rhyolites have Sr isotopic ratios of 0.70648 ± 2 and 0.70672 ± 1． Sr isotopic ratios of the host rocks of the plagioclases are not available．Initial Sr isotopic ratios of the
plagioclases differ from the andesite-dacite group，but are similar to those of granitoids of the Futami Volcano-plutonic complex．
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