Paleoproterozoic (2.0-1.97 Ga) subduction-related magmatism on the north-central margin of the Yeongnam Massif, Korean Peninsula, and its tectonic implications for reconstruction of the Columbia supercontinent

摘要

The Muju area, located on the north-central margin of the Yeongnam Massif, mainly consists of Precambrian orthogneisses (granitic, leucogranitic, augen and dioritic gneisses) with minor migmatite. Zircon U-Pb dating indicates that the protoliths of the orthogneisses intruded at ca. 2.00-1.97 Ga and were metamorphosed at ca. 1.87-1.86 Ga. Magmatic zircon grains within the orthogneisses have positive to negative epsilon Hf(t) values (-7.63 to +3.3) and a Neoarchean two-stage model age (T-DM2 - 2.78 Ga), indicating that the protoliths of most of the orthogneisses may have been derived from Archean crustal material. The results of geochemical analysis indicate that the protoliths of the orthogneisses formed by partial melting of metagraywarice and mak igneous rocks in an arc-related tectonic setting. The intrusion ages and geochemical data of the Paleoproterozoic orthogneisses in the study area match well with those of Paleoproterozoic (ca. 2.00-1.97 Ga) orthogneisses in the northeastern Yeongnam Massif, indicating the presence of regional Paleoproterozoic subduction zones along the northern margin of the Yeongnam Massif at ca. 2.00-1.97 Ga. Meanwhile, ca. 2.00-1.97 Ga subduction-related magmatism has not been reported from the northern Gyeonggi and Nangrim Massifs in the Korean Peninsula or the Jiao-Liao-Ji belt in the eastern North China Craton, indicating that the Yeongnam Massif may not be correlatable with the northern Gyeonggi and Nangrim Massifs or the Jiao-Liao-Ji belt. The Yeongnam Massif may be correlated with the Cathaysia Block in the South China Craton and may have been located near Laurentia and the Siberian Craton within the Columbia supercontinent. (C) 2019 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.