The basement of the Korean Peninsula consists of the Nanagrim, Gyeonggi and Yeongnam Massifs and underwent multiple magmatic and metamorphic events during the Precambrian. Although these basements have been correlated to the North and/or South China Cratons in many studies, relevant studies have been poorly carried out causing a difficulty in understanding of tectonic evolution for Northeast Asia. Thus, in this study, the petrogenesis for the Precambrian gneisses in the southeastern Gyeonggi and Yeongnam Massifs is investigated and the tectonic evolution of Northeast Asia including the Korean Peninsula is interpreted on the basis of the correlation between the Paleoproterozoic magmatic and metamorphic events occurred in the Korean Peninsula and those in China.
The emplacement age of ca. 2.50 Ga, 2.44 Ga, 1.95?1.92 Ga and 1.80 Ga were obtained from the granitic, migmatitic, two?mica granitic and porphyritic gneisses in the Wonju?Jechon area, the southeastern Gyeonggi Massif. The magmatic events at ca. 2.50 Ga, 2.44 Ga and 1.95?1.92 Ga occurred in arc?related tectonic setting and the metasedimentary rocks in the study area underwent regional metamorphism at ca. 1.95?1.92 Ga together with the intrusion of the two?mica granitic gneiss. The magmatic events of ca. 1.80 Ga also occurred in the post?collisional tectonic setting. According to the result of geochemical and zircon Hf isotopic analysis, protolith of granitic, migmatitic, two?mica granitic and porphyritic gneisses was formed by partial melting of ancient crust. The arc? (ca. 1.95?1.92 Ga) and post?collisional (ca. 1.80 Ga) magmatic events in the southeastern Gyeonggi Massif shows that they have different geochemical and geochronological feature compared to the Paleoproterozoic orthogneisses in the northern Gyeonggi and Nangrim Massifs and Jiao?Liao?Ji belt in the eastern North China Craton. It indicates that the southeastern Gyeonggi Massif may not be correlated to the northern Gyeonggi and Nangrim Massifs and Jiao?Liao?Ji belt.
The granitic, leucogranitic, augen and dioritic gneisses are widely distributed in the Muju area, the central?northern Yeongnam Massif. They formed during ca. 2.00?1.97 Ga and were metamorphosed at ca. 1.86 Ga. According to the result of geochemical and zircon Hf isotopic analysis, the protolith of the granitic, leucogranitic, augen and dioritic gneisses were formed by partial melting of ancient crustal rock and emplaced in the volcanic arc setting. The result of metamorphic P?T estimation shows that the metasedimentary rocks in the Muju area underwent lower granulite facies metamorphism with a moderate geothermal gradient (about 32°C/km) which is similar to the geothermal gradient in the island arc region. Together with arc related igneous rocks with ages of ca. 2.00?1.86 Ga in the Uljin area, the northeastern Yeongnam Massif, the result of this study indicates that the northern margin of the Yeongnam Massif including the Muju was located in the continental margin during ca. 2.00?1.86 Ga and cannot be correlated to the North China Craton.
In the Sancheong area, the central?southern Yeongnam Massif, the quartz?feldspathic, garnet and porphyritic gneisses and anorthosite are widely distributed. The quartz?feldspathic and garnet gneiss underwent the intermediate? and low?P/T metamorphism at ca. 1.92?1.88 Ga and 1.86 Ga, respectively. Meanwhile, the porphyritic gneiss formed in the post?collisional tectonic setting at ca. 1.88?1.87 Ga and was metamorphosed at ca. 1.86 Ga together with the intrusion of anorthosite. These magmatic and metamorphic events indicate that the continental collision event occurred in the Sancheong area during ca. 1.92?1.86 Ga. Considering arc?related setting (ca. 2.00?1.86 Ga) in the Muju area that is located to the north of the Sancheong area, the collision events in the Sancheong area may not be correlated to the collision event in the northern Gyeonggi and Nangrim Massifs and Jiao?Liao?Ji Belt. Meanwhile, similar continental collision event (ca. 1.93?1.87 Ga) is recently reported from the eastern Cathaysia Block indicating that the Sancheong area may have a close affinity to the eastern Cathaysia Block.
This and previous studies indicate that the Nargrim and the northern Gyeonggi Massifs had undergone same tectonic history and can be correlated to the North China Craton while the southern Gyeonggi and Yeongnam Massifs had experienced different tectonic history compared to the Nangrim and northern Gyeonggi Massifs implying they cannot be correlated to the North China Craton.