Relation between Cretaceous arc magmatism and subduction and accretion

2015 Fiscal Year Final Research Report

• Project/Area Number: 24540490
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Geology
• Research Institution: Yamaguchi University
• Principal Investigator: Imaoka Teruyoshi 山口大学, 理工学研究科, 教授 (30193668)
• Co-Investigator(Kenkyū-buntansha): KIMINAMI KAZUO 山口大学, 名誉教授 (20127757) ; NAGASHIMA MARIKO 山口大学, 大学院理工学研究科, 准教授 (80580274)
• Co-Investigator(Renkei-kenkyūsha): ITAYA TETSUMARU 岡山理科大学, 自然科学研究所, 教授 (60148682) ; KAMEI ATSUSHI 島根大学, 理工学部, 教授 (60379691)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: 花崗岩 / 流紋岩 / 太平洋プレート / 白亜紀 / 古第三紀 / バソリス

Outline of Final Research Achievements

Ｗe examine spatiotemporal variations of Jurassic to Cretaceous magmatism along a c. 1000 km transect across eastern Asia, including SW Japan. Integration of tectonic regime data with age data from igneous rocks in eastern Asia (from the Tan-Lu Fault to SW Japan) suggests a shallowing of the subduction angle and subsequent flat-slab subduction during the Jurassic, and slab rollback during the Early Cretaceous. The combination of a subducting plateau and root-enhanced suction provides the best explanation for the flat-slab subduction. In the final stage (Albian) of slab rollback, the geotectonic setting changed from subduction-accretion to a continental arc in the area close to the ancient trench (i.e., the Inner Zone of SW Japan).
We advocated that the Cretaceous episodic magmatism at c. 100 Ma produced lamprophyres and adakitic granitoids in SW Japan was produced during the rollback of the plate. We also revealed 3D geometry of a batholith and a zoned pluton.

Free Research Field

岩石学