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2018 Fiscal Year Final Research Report

Geotectonic analyses of the Hidaka Collision Zone, northern Japan, based on zircon U-Pb ages

Research Project

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Project/Area Number 16K05585
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeMulti-year Fund
Section一般
Research Field Geology
Research InstitutionNational Institute of Advanced Industrial Science and Technology

Principal Investigator

TAKAHASHI Yutaka  国立研究開発法人産業技術総合研究所, 地質調査総合センター, 契約職員 (50357373)

Co-Investigator(Kenkyū-buntansha) 山崎 徹  国立研究開発法人産業技術総合研究所, 地質調査総合センター, 主任研究員 (00396285)
七山 太  国立研究開発法人産業技術総合研究所, 地質調査総合センター, 上級主任研究員 (20357685)
御子柴 真澄  国立研究開発法人産業技術総合研究所, 地質調査総合センター, 主任研究員 (50358082)
志村 俊昭  山口大学, 大学院創成科学研究科, 教授 (70242451)
Research Collaborator Kemp A.I.S  
Project Period (FY) 2016-04-01 – 2019-03-31
Keywords北海道中軸帯 / 日髙帯 / 常呂帯 / 日髙変成帯 / 中の川層群 / U-Pb年代 / ジルコン
Outline of Final Research Achievements

Zircon U-Pb age datings for the metamorphic rocks in the upper sequence of the Hidaka metamorphic belt were carried out. The zircon U-Pb ages of biotite gneiss in the Satsunai River were 39.6 +/- 0.9 Ma for overgrowth rims (weighted average of a youngest age group) and 53.1 +/- 0.9 Ma for detrital cores (weighted average of a youngest age group).
Zircon U-Pb ages of cordierite-biotite gneiss in the Saruru River were 35.9 +/- 0.7 Ma for overgrowth rims (weighted average of a youngest age group) and 46.5 +/- 2.8 Ma for detrital cores (weighted average of a youngest age group). Based on the U-Pb ages, the upper sequence of the Hidaka metamorphic belt was metamorphosed at around 40-36 Ma. Also, the protolith of the biotite gneiss and cordierite-biotite gneiss (sedimentary rock) should be formed after ca. 53-47 Ma.
Therefore, the upper sequence of the Hidaka metamorphic belt has different history from the lower sequence, in which main metamorphism had taken place at around 20ー19 Ma.

Free Research Field

地質学,岩石学,構造地質学,地球年代学

Academic Significance and Societal Importance of the Research Achievements

日高変成帯は島弧地殻の衝上断片と考えられており,グラニュライトから非変成堆積岩類までが連続して観察できる世界的に見ても貴重な地質帯である.
日高変成帯は下部層(グラニュライトー角閃岩相)及び上部層(角閃岩相ー緑色片岩相)に区分され,50 Ma前後の変成作用で形成されたと考えられていた.しかし,近年,下部層の深成・変成岩類から20ー19 Ma前後のジルコンUーPb年代が相次いで報告され,年代の再検討が求められている.そこで,日高変成帯上部層の変成岩類のジルコンUーPb年代を測定し,上部層の変成年代(40ー36 Ma前後)を確定するとともに原岩の堆積年代(53ー47 Ma以降)を明らかにした.

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Published: 2020-03-30  

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