2022 Fiscal Year Final Research Report

Study on supercontinent evolution based on Proterozoic magmatism recorded in East Antarctica

Research Project

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Project/Area Number	18H01313
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Review Section	Basic Section 17040:Solid earth sciences-related
Research Institution	Shimane University
Principal Investigator	Kamei Atsushi 島根大学, 学術研究院環境システム科学系, 教授 (60379691)
Co-Investigator(Kenkyū-buntansha)	堀江憲路国立極地研究所, 研究教育系, 助教 (00571093) 馬場壮太郎琉球大学, 教育学部, 教授 (10347122) 中野伸彦九州大学, 比較社会文化研究院, 准教授 (20452790) 大和田正明山口大学, 大学院創成科学研究科, 教授 (50213905) 外田智千国立極地研究所, 研究教育系, 教授 (60370095) 遠藤俊祐島根大学, 学術研究院環境システム科学系, 准教授 (60738326) 小山内康人九州大学, 比較社会文化研究院, 特任研究者 (80183771)
Project Period (FY)	2018-04-01 – 2022-03-31
Keywords	超大陸 / 変花崗岩 / リュツォ・ホルム岩体 / 南極 / 原生代
Outline of Final Research Achievements	During the Proterozoic, the supercontinents of Sclavia/Superia, Nuna/Columbia, Rodinia, and Pan-African formed. The Lutzow-Holm Complex in Antarctica was constructed in the Pan-African period, but contains several meta-granitoids with isotopic ages comparable to the earlier supercontinents. In the eastern part of the complex, the meta-granitoids exhibit chemical compositions characteristic of juvenile arcs: low-K granites, slab-derived adakites, and ocean ridge granites. These meta-granitoids are distinct from the component of the earlier Proterozoic supercontinents because the emplacement ages are concentrated within the range of 1.1-0.6 Ga. Conversely, in the western part of the complex, the meta-granitoids show geochemical similarities to the granites of mature continental arcs or continental interiors, such as high-K granites and within-plate granites. These meta-granitoids, ranging from 2.5 to 1.0 Ga in age, likely represent components of the Sclavia/Superia to Rodinia fragments.
Free Research Field	地質学・岩石学・地球化学
Academic Significance and Societal Importance of the Research Achievements	原生代に繰り返し出現した超大陸の復元には，当時のテクトニクス背景に関わる情報が不可欠である．東南極のリュツォ・ホルム複合岩体（延長約450 km）には2.5～0.6Gaの変花崗岩類が多産するが，その成因と地質学的位置づけの議論は僅かであった．本研究では岩体全域を対象として，これら変花崗岩類の化学組成と年代値に基づく花崗岩マグマ形成時のテクトニクス背景を検討した．この情報は原生代の超大陸形成の議論に大きく貢献すると考えられる．