Petrogenesis of the Palaeoproterozoic (1.87 Ga) Damyang amphibolites in the northewestern margin of the Yeongnam Massif and tectonic implications of the Korean Peninsula

The Yeongnam Massif is located in the southern part of the Korean Peninsula and holds key elements in understanding the Palaeoproterozoic tectonic evolution of north-east Asia during the amalgamation of the Columbia supercontinent. In this study, we have conducted geochronological and geochemical studies on the mafic intrusive along the northern margin of the Yeongnam Massif. Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon dating on two amphibolite and one gabbro samples in the Damyang area show that the amphibolites crystallized at similar to 1.87 Ga and the gabbro crystallized at similar to 87.6 Ma. The 1.87 Ga Damyang amphibolites are simultaneous with the Muju and Okbang amphibolites along the northern margin of the Yeongnam Massif. They also show similar geochemical characteristics, including tholeiitic basalt composition, enriched Light Rare Earth Elements (LREE) and large ion lithosphile elements (LILEs), depleted high field strength elements (HFSEs), and slightly enriched but various Hf isotopes, indicating that they originated from an enriched but heterogeneous mantle source with fluid addition. Thus, the 1.87 Ga amphibolites along the northern margin of the Yeongnam Massif were probably emplaced in an arc-related setting. Combined with the 2.02-1.96 Ga magmatism, it is proposed that the subduction might have lasted during the 2.02-1.85 Ga interval and mantle-derived magma rose up due to the roll-back process between 1.88-1.85 Ga.