Role of plutonic and metamorphic block exhumation in a forearc ophiolite mélange belt: An example from the Mineoka belt, Japan

Ryota Mori, Yujiro Ogawa, Naoto Hirano, Toshiaki Tsunogae, Masanori Kurosawa, Tae Chiba

研究成果: Chapter

8 被引用数 (Scopus)

抄録

We investigated the field relations, metamorphic and deformation conditions, age, and chemistry of basaltic, plutonic, and metamorphic blocks in the Mineoka ophiolite mélange belt, Boso Peninsula, central Japan, to clarify their emplacement mechanisms. We considered internal and external deformation of the blocks in the context of the complicated processes by which the ophiolite mélange belt was formed in a forearc setting. A two-stage history leading to the present-day forearc sliver fault zone was revealed: an early stage of deep ductile deformation followed by an episode of brittle deformation at shallower levels. Both stages were the result of transpressional stress conditions. The first stage produced subduction-related schistosity with microfolding and mylonitization and then brecciation during exhumation in the intraoceanic subduction zone, from a maximum depth of garnet-amphibolite facies or eclogitic facies. The second stage was characterized by strong, brittle shear deformation as the rocks were incorporated into the present-day fault zone. The first incorporation of the oceanic plate to the side of the Honshu arc might have occurred during the Miocene, and was followed by right-lateral oblique subduction that has continued ever since the Boso triple junction arrived at its present-day position, thus forming the paleo-Sagami trough plate boundary.

本文言語English
ホスト出版物のタイトルMelanges
ホスト出版物のサブタイトルProcesses of Formation and Societal Significance
出版社Geological Society of America
ページ95-115
ページ数21
ISBN(印刷版)9780813724805
DOI
出版ステータスPublished - 2011

出版物シリーズ

名前Special Paper of the Geological Society of America
480
ISSN(印刷版)0072-1077

ASJC Scopus subject areas

  • Geology

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