The Permo-Triassic Songrim (Indosinian) orogeny in South Korea was a major tectonic event involving complicated continental collisions at the eastern margin of Eurasia. Previous studies have examined the structural and metamorphic features of the Songrim orogeny in each of the Paleozoic terranes of the orogenic belt (i.e., the Taebaeksan Basin, the Okcheon Basin, and the Imjingang Belt), but correlations of these features among the terranes remain uncertain. The aim of this paper is to reveal deformation history including bulk crustal shortening directions in the Taebaeksan Basin, and to correlate the tectono-metamorphic evolution of the Taebaeksan Basin with other Phanerozoic mobile belts in eastern Asia based on a combined analysis of foliation intersection/inflection axes (FIA) trends and metamorphic P-T and T-t (time) paths. The orientations and relative timing of FIA preserved as inclusion trails within porphyroblasts of andalusite, chloritoid, garnet, and staurolite reveal two age groups of inclusion trails in the Pyeongan Supergroup at the northeastern margin of the Taebaeksan Basin. These microstructures indicate the development of early NNW-NNE-trending structures and fabrics, followed by later E-W-trending ones. These observations suggest a change in the orientation of bulk crustal shortening from E-W to N-S during the Songrim orogeny. Based on the similar microstructures and temperature-time paths of the three Paleozoic terranes, we interpret that the E-W bulk crustal shortening influenced the eastern part of the Korean Peninsula during the early stages of the Songrim orogeny, presumably related to amalgamation between the proto-Japan terrane and the eastern margin of Eurasia, whereas the N-S bulk crustal shortening was stronger in the western part of the peninsula during the later stages of the orogeny, related to collision between the South and North China blocks.
Bibliographical noteFunding Information:
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) , funded by the Ministry of Education, Science and Technology ( 2010-0009429 ) and partly by Kyungpook National University Research Fund 2012 to H.S. Kim and partly by NRF 2010-0024206 to J.-H. Ree. We are pleased to have the opportunity to contribute this paper to celebrate an international conference in honor of Prof. Tim Bell. We are grateful for helpful and constructive reviews by Koen de Jong and anonymous reviewer, and thank Domingo Aerden for valuable comments as well as editorial handling.
- Bulk crustal shortening
- East Asia
- Foliation intersection/inflection axes (FIA)
- Permo-Triassic Songrim (Indosinian) orogeny
- Taebaeksan Basin
- Terrane collision
ASJC Scopus subject areas
- Earth-Surface Processes