The tectonic evolution of the Gogunsan Islands in the southwestern margin of the Gyeonggi Massif and its implication for the Neoproterozoic tectonic evolution relating to the Rodinia in the Northeast Asia

Abstract

The Neoproterozoic rocks recognized in several locations on the Korean Peninsula provide important insight into the geological correlation between the Korean Peninsula and China and for understanding the tectonic processes occurring in northeastern Asia. The Gogunsan Islands, located on the southwestern margin of the Gyeonggi Massif of the Korean Peninsula, consist of Neoproterozoic igneous and sedimentary rocks. The sedimentary rocks in the Gogunsan Islands are divided into the Maldo and Bangchukdo Formations. The Maldo Formation was deposited sometime between 950 and 894 Ma and intruded by or tectonically contacted Neoproterozoic igneous rocks 930–894 Ma in an arc tectonic setting. The εHf(t) values of metabasites (3.63 to −5.09) and metagranitoids (3.29 to −5.76) indicate that the metabasites were formed from 1.67–1.32 Ga depleted mantle and the metagranitoids were formed by the reworking of ancient crust, which formed from 2.14–1.57 Ga depleted mantle. The metabasites in the Maldo Formation underwent intermediate-P/T amphibolite-facies metamorphism (4.35 ± 1.15 kbar and 465 ± 15 °C) with strong deformation before the deposition of the Bangchukdo Formation, indicating a collision event. The Bangchukdo Formation was deposited after 792–763 Ma in the rifting tectonic setting. The data in this and previous studies suggest that the Neoproterozoic igneous rocks in the Gogunsan Islands can be correlated to arc-related Neoproterozoic rocks formed during the Jiangnan orogeny on the southern margin of the Yangtze Block in the South China Craton. Along the Jiangnan orogenic belt, the arc stage was followed by the collision between the Yangtze and Cathaysia Blocks. The collision may have started in the Korean Peninsula and propagated westwards into South China.