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

Research output: Chapter in Book/Report/Conference proceedingChapter

8 Citations (Scopus)

Abstract

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.

Original languageEnglish
Title of host publicationMelanges
Subtitle of host publicationProcesses of Formation and Societal Significance
PublisherGeological Society of America
Pages95-115
Number of pages21
ISBN (Print)9780813724805
DOIs
Publication statusPublished - 2011

Publication series

NameSpecial Paper of the Geological Society of America
Volume480
ISSN (Print)0072-1077

ASJC Scopus subject areas

  • Geology

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