[S-MP35] Antarctica and surrounds in Supercontinent Evolution

[SMP35-01] Re-examination of metamorphic and geochronologic events in eastern Dronning Maud Land and Enderby Land, East Antarctica: current status and future perspectives

*外田 智千^1,2、馬場 壮太郞³、亀井 淳志⁴、北野 一平⁵、Nantasin Prayath⁶、Setiawan Nugroho⁷、Dashbaatar Davaa-ochir⁸、本吉 洋一^1,2、廣井 美邦¹、小山内 康人⁵、Dunkley Daniel、堀江 憲路^1,2、竹原 真美¹、白石 和行¹ (1.国立極地研究所、2.総合研究大学院大学、3.琉球大学、4.島根大学、5.九州大学、6.Kasetsart University、7.Gadjah Mada University、8.Mongolian University of Science and Technology)

キーワード：南極、ゴンドワナ、超大陸、変成作用、地質年代学

Eastern part of Dronning Maud Land in East Antarctica comprises of the multiple high-grade metamorphic terranes as major constituents of Gondwana supercontinent. The Lützow-Holm Complex in eastern Dronning Maud Land has been belived to be typical of continental collision metamorphic belt of which amphibolite to granulite (partly UHT) facies regional metamorphism and clockwise P-T trajectory supported by the widespread occurrence of sillimanite with prograde kyanite and retrograde andalusite (e.g., Hiroi et al., 1983). However, it requires re-evaluation of the metamrophic processes by recent finding of nanogranite/felsite inclusions (Hiroi et al., 2014) and unusual occurrence of kyanite and andalusite. Major 550-520 Ma metamorphic age episode was indicated by SHRIMP zircon geochronology (e.g., Shiraishi et al., 1992; 1994; 2003) and was recently refined the early metamorphic events at >600 Ma (Hokada and Motoyoshi, 2006; Dunkley et al., 2014).

Archaean and Proterozoic pre-Gondwana history is preserved in the Napier Complex and the Rayner Complex in Enderby Land with the earliest geologic history traced back to >3.8 Ga (e.g., Harley and Kelly, 2007). Western Rayner Complex located between Lützow-Holm Complex and Napier-Rayner Complexes is key for the linkage between Gondwana and pre-Gondwana areas. All these areas were experienced granulite-facies partly UHT metamorphism.

This study will present our current understainding of the metamorphic and geochronologic evolution of these areas and the recent geologic field survey at Lützow-Holm, Western Rayner, Rayner and Napier Complexes during 2016-2017, and also future perspectives.