The tectonic setting of the eastern margin of the Sino-Korean Block inferred from detrital zircon U–Pb age and Nd isotope composition of the Pyeongan Supergroup (upper Palaeozoic – Lower Triassic), Korea

Abstract

The upper Palaeozoic succession (Pyeongan Supergroup) in central eastern Korea is well correlated with the equivalent successions distributed in North China, suggestive of the Korean upper Palaeozoic being part of the Sino-Korean Block. Detrital zircon U–Pb ages and Sm–Nd isotope compositions of the Pyeongan Supergroup in the Samcheok coalfield of the Taebaeksan Basin were analysed. A single predominant zircon age peak at c. 1.9 Ga (> 70%) is marked in all sedimentary units, followed by varying amounts of minor late Palaeozoic grains (up to 30%). The rarity of Meso- to Neoproterozoic- and Silurian-aged zircons confirms that sediment influx from the South China and Qinling blocks was insignificant. The 2.0–1.8 Ga-dominated zircon age pattern and the Nd isotope composition (average εNd(0) = −15.5±4.0) of the Pyeongan Supergroup most closely reflect the signature of the Yeongnam Massif basements, which supports a previous hypothesis that the Pyeongan Supergroup was mostly derived from a palaeo-orogen located to the east–southeast. Relatively higher εNd(0) values (> −10.1) in the lowermost and the upper parts of the succession are closely matched by the increased occurrence of syn-depositional-aged zircons, which indicates considerable mixing of juvenile materials at c. 320 Ma and 260 Ma. Both arc-related magmatic events are interpreted to have been related to oceanic subduction, suggesting that the eastern margin of the Sino-Korean Block was an active continental margin during late Palaeozoic times.

Upper Permian paleoclimate of the Sino-Korean block: an example from the Gohan Formation (Korea) in the eastern margin and a synthesis

“…The Pyeongan Supergroup was deposited in a foreland basin setting (Lee and Sheen, 1998;Kim et al, 2012) and paleocur-rents flowed from east-southeast to west-northwest (Kim, 1976;Lee and Lim, 1995). The detritus for the Pyeongan Supergroup was mostly derived from convergent orogen and arc terranes located to the east and southeast of the Korean Peninsula (Yu et al, 1997;Lee and Sheen, 1998;Kim and Lee, 2017;Kim et al, 2019). The Gohan Formation in this study is from the Danyang coalfield (Figs.…”

“…The abundance of kaolinite (+ pyrophyllite) in the early stage of the Gohan Formation deposition indicates that the upland region had received sustained high precipitation over a prolonged period in stable landscape conditions. The source tectonic setting of the Gohan Formation was interpreted as the active continental margin where arc-related magmatism occurred (Yi et al, 2012;Kim and Lee, 2018;Kim et al, 2019Kim et al, , 2020, and thus the elevation of the source terrain was likely enough to have had much precipitation on highlands of the coastal mountain range. Considering the paleolatitude of the Taebaeksan Basin during the Permian, the precipitation of the eastern margin of the SKB may also have been influenced by the Intertropical Convergence Zone, although seasonal.…”

“…Given that there are significant regional variations in the Permian drying trends within North China, the Upper Permian climate record reported in this study can provide interesting new information. The physiographic setting of the North China craton may not have affected sedimentation and paleoclimate in the eastern margin of the SKB; it was interpreted that the sediment routing system of the Korean Peninsula was different from that of the North China craton (Kim and Lee, 2018;Kim et al, 2019Kim et al, , 2020. Based on the geochemistry and clay mineralogy, we investigate paleoclimatic trends recorded in the Gohan Formation and discuss the factors controlling the paleoclimate of the SKB during Middle-Late Permian time before the extreme climatic change at the end of the Permian.…”

Mercury evidence from the Sino-Korean block for Emeishan volcanism during the Capitanian mass extinction

“…1). The detritus for the Pyeongan Supergroup was mostly derived from recycled orogens located to the east and SE of the Korean Peninsula (Yu, Lee & Boggs, 1997;Lee & Sheen, 1998;Kim, Lee & Choi, 2017). The Gohan Formation in this study is from the Danyang coalfield (Fig.…”