日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 S (固体地球科学) » S-MP 岩石学・鉱物学

[S-MP31] Supercontinents and Crustal Evolution

2019年5月28日(火) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:Satish-Kumar Madhusoodhan(Department of Geology, Faculty of Science, Niigata University)、外田 智千(国立極地研究所)、Sajeev Krishnan(Centre for Earth Sciences, Indian Institute of Science)、小山内 康人(九州大学大学院比較社会文化研究院地球変動講座)

[SMP31-P04] Rapid UHT metamorphism and exhumation of the Lützow-Holm Complex in Antarctica

*Yoshikuni Hiroi1Tomokazu Hokada2Tatsuro Adachi3Yasuhito Osanai3Yoichi Motoyoshi2Kazuyuki Shiraishi2 (1.Chiba Univ、2.National Institute of Polar Research、3.Kyushu University)

キーワード:Antarctica, Gondwana, Supercontinent, UHT metamorphism

The Lützow-Holm Complex in Antarctica is a part of Neoproterozoic-Cambrian (c.650-500 Ma) collisional orogen to form Gondwana supercontinent. It is characterized by progressive metamorphism from upper amphibolite facies in the eastern part of the Prince Olav Coast to upper granulite facies in the southern Sôya Coast (e.g., Hiroi et al., 1991). UHT metamorphism is evidenced by such diagnostic mineral assemblages as Opx + Sil + Grt + Rt + Qz and Spr + Qz in Mg-Al-rich pelitic granulites in Rundvågshetta. Intimate intergrowths of Ky + Spr + Grt and Sil + Spr + Grt as well as andalusite-bearing falsite-nanogranite inclusions are included in the same porphyroblastic garnet, which is compositionally zoned, with Mg-rich core, Fe–Mn-rich rim, and core-to-rim oscillation of Ca. Integration of these new data with those previously documented leads to the inference of a rapid change in pressure–temperature conditions during regional UHT metamorphism in this part of the late Neoproterozoic to early Paleozoic ‘large and hot orogen’. Several lines of evidence indicate that partial melting and melt extraction took place even in mafic granulites of fragmented gabbro origin.