Multiple metamorphic episodes recorded in the Paleozoic Pyeongan Supergroup on the northeastern margin of the Yeongnam massif, South Korea: Implications for the Songrim (Indosinian) orogeny

摘要: Abstract Metasedimentary rocks of the Pyeongan Supergroup, which occur as roof pendants on northeastern margin Yeongnam massif, South Korea, preserve a record impact Late Permian–Triassic Songrim (Indosinian) orogeny in eastern Eurasia margin. Metamorphic results this paper have revealed that metasedimentary were affected by three metamorphic events during Middle Permian to Mesozoic. Representative mineral assemblages from zones I, II and III are Cld + And ± Ky ± St, Grt + St + Ky + Bt ± And, And + Sill + Bt ± Grt ± St, respectively. Kyanite sillimanite paramorphs after andalusite I III, P–T conditions paths determined conventional geothermobarometers compositional isopleths chloritoid, staurolite, garnet pseudosections MnO–Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O (MnNCKFMASH) KFMASH–T (TiO2)–O (Fe2O3) systems. In study area, Supergroup experienced medium pressure regional metamorphism (M1 M2) belonging greenschist amphibolite facies followed thermal (M3). The M1 occurred at 450–500 °C 2–4 kbar produced kyanite paramorph andalusite. M2 520–600 °C 4–6 kbar, was associated with growth garnet, kyanite. later ca. 580 °C 4 kbar, caused intrusion Jurassic granitoids. around 270 Ma based SHRIMP U–Pb zircon ages.