Evolution of the Cretaceous Orogenic belt: high-pressure metamorphic rocks response to tectonic erosion

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K21531
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Geology; Petrology/Mineralogy/Economic geology
• Research Institution: Okayama University of Science
• Principal Investigator: Aoki Kazumasa 岡山理科大学, 理学部, 准教授 (70586677)
• Research Collaborator: Komiya Tsuyoshi ; Aoki Shogo ; Tsuchiya Yuta ; Sawaki Yusuke ; Hirata Takafumi ; Nishido Hirotsugu ; Kato Daichi ; Seo Yoshiki ; Yamamoto Shinji
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: ジルコン / 造山帯 / U-Pb年代 / 沈み込み帯 / 構造浸食

Outline of Final Research Achievements

As a result of this research project, the exhumation mechanism of the high-pressure metamorphic rocks formed at the Cretaceous subduction zone in Japan was caused by not only shallowing subduction angle by application and subduction of ridge but also other multiple factors. They are considered to be reduction of sliding frictional force by fluid infiltration along the exhumation route, erosion in fore-arc materials by the tectonic erosion, and area expansion of back-flow in wedge mantle. This means that 'tectonic erosion' is one of the necessary conditions for the exhumation of the high-pressure-type metamorphic rocks in subduction zones.

Free Research Field

地質学

Academic Significance and Societal Importance of the Research Achievements

本研究の学術的意義は、古典的地質学・岩石学にジルコン年代学／地球化学という分析手法を組み合わせ、造山帯形成プロセスの核の１つである「高圧型変成岩上昇」に「構造浸食作用」が深く関わっていたことを示したことである。また、「日本列島を構成する基盤岩がその形成から現在に至る過程でどのように壊変・進化・成長してきたのか？」に対する新たな知見ももたらした。したがって、「火山・地震大国日本の形成・進化」に関する自然科学的教養の深化という意味でも本研究が果たした社会的意義は大きいだろう。