Practical use of the zircon chronology by rock thin section and its application to the Yaeyama metamorphic rocks

2016 Fiscal Year Final Research Report

• Project/Area Number: 26610164
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Geology
• Research Institution: Kochi University
• Principal Investigator: Ishizuka Hideo 高知大学, 教育研究部自然科学系理学部門, 教授 (00142349)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: 変成堆積岩 / 砕屑性ジルコン / U-Pb年代測定 / 八重山変成岩 / 三郡周防帯 / 南・北中国地塊 / 東アジア縁辺部 / 沈み込み変成作用

Outline of Final Research Achievements

This study was aimed at revealing provenance of sediments by using the LA-ICP-MS analyses of U-Pb ages of detritus zircons on thin section and separated grain. The samples are collected from the Ishigaki-jima Island (Okinawa Pref.), Nomo Peninsula (Nagasaki Pref.) and Nishiki-cho (Yamaguchi Pref.) areas, all of which belong to the high-pressure type of metamorphic belts. The results show that the meta-sediments contain detritus zircons with ages ranging from Ca. 3000 Ma to 200 Ma. The older ages represent the precursor derived from the North China Craton. The younger ages mean the final deposition ages of samples, and then, these younger zircon-bearing rocks were suffered the metamorphism. It is, therefore, emphasized that these metamorphic rocks are products formed by the E-W subduction of oceanic crust beneath the continental crust composed of both the collided North and South China Cratons, just after the N-S collision between the North and South China Cratons.

Free Research Field

変成岩地質学