Genesis and evolutional processes of the Paleozoic oceanic island arc crust, Asago body of the Yakuno Ophiolite, Southwest Japan

DOI IR Web Site Web Site 5 Citations 68 References Open Access
  • Suda Yoshimitsu
    Center for Chronological Research, Nagoya University Present address: Department of Geosciences, Osaka City University
  • Hayasaka Yasutaka
    Graduate School of Science, Hiroshima University

Bibliographic Information

Other Title
  • 夜久野オフィオライト朝来岩体における古生代海洋内島弧地殻の形成と進化過程
  • 夜久野オフィオライト朝来岩体における古生代海洋内島弧地殻の形成と進化
  • ヤクノ オフィオライト アサゴガンタイ ニ オケル コセイダイ カイヨウナイ トウコ チカク ノ ケイセイ ト シンカ
  • Genesis and evolution processes of the Paleozoic oceanic island arc crust, Asago body of the Yakuno ophiolite, Southwest Japan

Search this article

Description

A middle to lower crustal section of Paleozoic oceanic island arc is exposed in the Asago body of the Yakuno ophiolite. Based on field occurrence, petrography, and geochemical modeling, we investigated the evolution of the Asago body and relevant magmatic processes. The Asago body consists of two stages of rocks. The first-stage rocks consist of metagabbro and schistose amphibolite that represent the basement to the Permian Yakuno paleo-island arc. The second-stage rocks are mainly arc granitoids that intrude the first-stage rocks. Mafic migmatites occur in the lower crustal section of the Asago body. Field occurrences and petrographic data suggest that the migmatites formed by the anatexis of first-stage rocks, and that segregation and accumulation of the anatectic melt resulted in morphological changes in the migmatites toward the middle crustal section. Geochemical data indicate that the first-stage rocks were derived from a basaltic magma of back-arc affinity, suggesting in turn that the Yakuno paleo-island arc was developed within a back-arc basin. Moreover, a low-K series (hornblende gabbro, quartz diorite, and tonalite) and high-K series (quartz monzodiorite and granodiorite) within the second-stage rocks were generated by high and low degrees of partial melting of first-stage rocks, respectively. We conclude that the Asago body is an example of the transition from oceanic to continental crust, related to the anatexis of mafic lower crust in an oceanic island arc setting.

Journal

Citations (5)*help

See more

References(68)*help

See more

Related Projects

See more

Keywords

Details 詳細情報について

Report a problem

Back to top