The tectonic evolution from the Archean to Triassic in the north central Gyeonggi Massif (Hongcheon-Chuncheon areas) in the Korean Peninsula, and its application to the tectonic evolution of the North China Craton

Abstract

The Hongcheon-Chuncheon areas located in the northern Gyeonggi Massif on the Korean Peninsula consist of Neoarchean (ca. 2.61–2.49 Ga) and middle Paleoproterozoic (ca. 2.09 Ga) metagranitoids, the Euiam Gneiss Complex (ca. 1.89–1.87 Ga), and metasedimentary units, including the Yongduri Gneiss Complex and Euiam Group. The Neoarchean metagranitoids intruded at ca. 2.61–2.49 Ga and underwent polymetamorphism at ca. 1.92–1.87 Ga and 229 Ma. Whole-rock geochemical data indicate that they were formed by partial melting of low-K mafic rock in the lower crust due to heat supplied from the underplated mafic magma chamber in the arc tectonic setting. The Paleoproterozoic metagranitoids are classified into three types based on geochronology and whole rock chemistry: ca. 2.09 Ga, ca. 1.90 Ga, and ca. 1.89–1.87 Ga metagranitoids that formed in an arc tectonic setting, a syn-collisional tectonic setting, and a post-collision tectonic setting, respectively. The Paleoproterozoic 1st stage metasedimentary rocks (paragneisses) deposited in the Yongduri Gneiss Complex experienced Paleoproterozoic metamorphism, whereas the 2nd stage metasedimentary rocks deposited in the Euiam Group did not experience Paleoproterozoic metamorphism. The 1st stage metasedimentary rocks (paragneisses) were deposited after 2.05–1.95 Ga in an arc tectonic setting; they experienced intermediate-P/T metamorphism (780–860 °C/8.7–11.0 kbar) at ca. 1.91 Ga and then low-P/T metamorphism (710–750 °C/6.0–6.5 kbar) at ca. 1.86 Ga. The 2nd metasedimentary rocks were deposited after ca. 1.88–1.83 Ga and metamorphosed at ca. 234–230 Ma. Together with previous data, these data indicate that the Hongcheon-Chuncheon areas have Archean remnants and experienced similar Paleoproterozoic tectonothermal events recognized from the Jiao-Liao-Ji Belt formed by the collision between the Longgang Block of the North China Craton and the Nangrim Massif of the Korean Peninsula, suggesting that the northern Gyeonggi Massif can be correlated to the North China Craton.