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Comparative study on the exhumation processes of high-pressure metamorphic belts, western Pacific

Research Project

Project/Area Number 10640464
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Petrology/Mineralogy/Science of ore deposit
Research InstitutionOsaka Prefecture University

Principal Investigator

MAEKAWA Hirokazu  College of Integrated Arts and Sciences, Professor, 総合科学部, 教授 (50173696)

Project Period (FY) 1998 – 1999
Project Status Completed (Fiscal Year 1999)
Budget Amount *help
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 1999: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1998: ¥2,700,000 (Direct Cost: ¥2,700,000)
KeywordsSnabagawa / high-pressure metamorphic belt / Haast Schists / stretching lineation / melange / Franciscan / 三波川変成帯 / 高圧変成作用 / ストレッチングリニエーション
Research Abstract

To understand the tectonic processes of the high-pressure metamorphic belts in the western margins of Pacific Ocean. I studied the metamorphism and deformation of the rocks in the Sanbagawa metamorphic belt and the Haast schists of New Zealand, and compared them with those in the Kamuikotan and Franciscan belts. Predominant direction of stretching lineation is E-W in the Sanbagawa metamorphic belt at Nushima. An analysis of microfabrics of stretching lineation indicates that the pull-apart fabrics have been formed with increase of temperature at the final stage of metamorhism. I studies the Haast schists in term of the rock samples taken in 1997. The Haast schists along the Lake Hawea route can be divided into two zones ; the southern chlorite zone and the northern garnet zone. Plagioclase is albite (<AnィイD25ィエD2) in the chlorite zone, whereas that show two phases (AnィイD20-5ィエD2 and AnィイD220-30ィエD2) near the garnet isograd in the garner zone, and is AnィイD25-35ィエD2 in the further north … More higher-grade regions. Sudden decrease of modal compositions of epidote at the region where Ca-rich plagioclase appears suggests that the decomposition of epidote related to the Ca-rich plagioclase froming reaciton. The lack of biotite zone in the study area suggests that the metamorphic P-T trends of the Haast schist terrane is situated at the intermediate pressure condition between the Sanbagawa and the Scotich Highland just below the intersection of biotite- and garnet-forming curves.
A large number of serpentinite seamounts in the western Pacific Izu-Ogasawara-Mariana forearcs indicate the serpentinite diapirism under the tensional stress field in the forearc regions. The presence of blueschist-facies rocks in the serpentinite seamounts provides evidence that the serpentinites generated from the hanging-wall peridotites have penetrated the high-pressure metamorphic region at depth in the accretionary prism. The high-pressure metamorphic terranes in the circum-Pacific regions, the Franciscan Complex, California, and the Kamuikotan metamorphic belt, Japan, are accompanied with serpentinite melange with deeper high-grade metamorphic rocks, whereas the Sanbagawa metamorphic belt, Japan, does not contain any serpentinite melange. It is highly probable that the former were formed under tensional stress regime, and the latter under compressional one. The rare occurrence of serpentinites and lack of serpentinite melange in the Sanbagawa belt may have been caused by the compressional stress environment in the trench-arc region during the metamorphism. Under such compressional stress environments, scraping off hanging-wall peridotites seems to be only a possibility to incorporate mantle materials into the accretionary prism which develops along the trench. The model can explain the limited occurrence of serpentinites to the high-grade pelitic schists in the Sanbagawa belt. Less

Report

(3 results)
  • 1999 Annual Research Report   Final Research Report Summary
  • 1998 Annual Research Report
  • Research Products

    (7 results)

All Other

All Publications (7 results)

  • [Publications] Maekawa, H.: "Comparison of genesis and tectonic setting of Jurassic-Cretaceous high-ressure metamorphic beltsin the circum-Pacfic regions"In H. Okada(ed) : Cretaceous Environments of Asia-synthesis-, The final volume of IGCP-350, Elsevier. (in press).

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] 前川寛和: "伊豆-小笠原、マリアナ前弧域における高圧型変成帯の形成とマントル物質の付加"月刊 地球 号外(海洋出版株式会社). No. 23. 99-106 (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] Maekawa H.: "Comparison of genesis and tectonic setting of Jurassic - Cretaceous high-pressure metamorphic belts in the circum-Pacific regious."In H. Okada (ed.) : Cretaceous Environments of Asia -Synthesis-. The final volume of IGCP-350, Elsevier (in press)..

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1999 Final Research Report Summary
  • [Publications] Maekawa, H.: "Comparison of genesis and tectonic setting of Jurassic - Cretaceous high-pressure metamorphic belts in the circum-Pacific regions"In H. Okada (ed.): Cretaceous Environments of Asia - Synthesis-,The final volume of IGCP-350,Elsevier. (in press).

    • Related Report
      1999 Annual Research Report
  • [Publications] 前川寛和: "伊豆-小笠原、マリアナ前弧域における高圧型変成帯の形成とマントル物質の付加"月刊 地球 号外(海洋出版株式会社). No.23. 99-106 (1999)

    • Related Report
      1999 Annual Research Report
  • [Publications] 前川 寛和: "伊豆・小笠原、マリアナ前弧域における高圧型変成帯の形式とマントル物質の付加" 月刊 地球(海洋出版株式会社). 号外23. 99-106 (1999)

    • Related Report
      1998 Annual Research Report
  • [Publications] 上野友子・前川寛和: "四国三波川変成帯貞光地域における東西性に先立つ南北性の引き伸ばし線構造" 構造地質研究会 1998冬の例会 講演要旨集. 41-42 (1998)

    • Related Report
      1998 Annual Research Report

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Published: 1998-04-01   Modified: 2016-04-21  

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