13:45 〜 14:00
[SMP25-06] Archaean crustal evolution of the Napier Complex, East Antarctica – Review
キーワード：太古代、南極、ナピア岩体
The Archaean Napier Complex in East Antarctica consists of felsic-intermediate orthogneisses, mafic granulite and a variety of paragneisses metamorphosed under granulite-facies and UHT conditions at around ~2550-2480 Ma. The oldest protolith of the complex is dated as >3850-3770 Ma at Mt. Sones and Gage Ridge (Williams et al., 1984; Black et al., 1986; Harley and Black, 1997; Kelly and Harley, 2005; Guitreau et al., 2019), followed by long-lived magmatic and detrital zircon age populations from various localities in the age range of 3700-2630 Ma (e.g., Carson et al., 2002; Kelly and Harley, 2005; and references therein). From Mt. Riiser-Larsen, the largest and well-studied outcrop in the Napier Complex, c.3300 Ma tonalitic orthogneiss and c.3000-2700 Ma granitic and sedimentary protoliths are reported (Hokada et al., 2003, 2004, 2008; Suzuki et al., 2006). There have been several new U-Pb ages reported for the Napier Complex (Horie et al., 2012; Osanai et al., 2017; Takehara et al., 2020, 2023; Krol et al., 2020, 2022; Guitrean et al., 2019). From eastern Tula Mountains, >3700 Ma protoliths are discovered from several localities (Krol et al., 2020; Kusiak et al., 2021). Even though, protolith ages of most of the other areas are younger than 3500 Ma, and early Archaean domains are still restricted in eastern Tula Mountains (and further east). In tuern, the youngest ~2530 Ma magmatic protoliths are recognized from southwestern part (Scott Mountains and Ragatt Mountains area) of the Napier Complex (Takehara et al., 2020; Krol et al., 2022). These youngest protolith ages (~2530 Ma), restricted in the southwestern part of the complex, overlap with the timing of major UHT metamorphic event (~2550-2480 Ma). These updated geochronological information makes it necessary to re-examine the formation (and UHT metamorphic) processes of the Napier Complex.