Refinement of metamorphic facies-H2O content diagram for subducting oceanic crust by use of greenstones in accretionary complexes

2017 Fiscal Year Final Research Report

• Project/Area Number: 16K17823
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Geology
• Research Institution: Shimane University
• Principal Investigator: Endo Shunsuke 島根大学, 総合理工学研究科, 特任講師 (60738326)
• Project Period (FY): 2016-04-01 – 2018-03-31
• Keywords: 低温変成作用 / 付加体 / 秩父帯 / 緑色岩 / 玄武岩 / アルカリ輝石 / ローソン石

Outline of Final Research Achievements

Structural and metamorphic architectures of the Mikabu-Northern Chichibu belt have been revealed as an example of deep accretionary wedge. Metabasalts (greenstones) in each unit of the belt have been examined to understand mineral reactions in shallow subduction zones as well as low-temperature thermodynamic mixing properties of key metamorphic minerals. Structural evolution of the belts can be explained by thickening of accretionary wedge by underplating and subsequent tectonic thinning and exhumation of deep seated rocks in the wedge. Alkali pyroxene is an important metamorphic mineral in low-grade metabasalt and its low-temperature mixing behavior in the diopside-aegirine-jadeite system is preliminary established by the natural data. Common occurrence of lawsonite veins formed via dehydration of pre-existed zeolite veins is discovered from the unmetamorphosed N. Chichibu accretionary complex, and this can be important source of fluid in seismogenic plate boundaries.

Free Research Field

地質学