Characteristics of the early cretaceous igneous activity in the Korean Peninsula and tectonic implications

This study presents sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon ages, K-Ar ages, and whole-rock chemical and isotopic (Sr-Nd) compositions of the Early Cretaceous igneous activity in western South Korea. The volcanics and plutons yield zircon U-Pb ages of ca. 110 Ma, in the Albian of the late Early Cretaceous. K-Ar biotite and plagioclase ages are slightly younger, ca. 103 Ma. The geochemical signatures of the rocks are characterized by negative Nb, Ta, and Ti anomalies, relatively low ε _Nd(T) values (between -15.91 and -9.36), and enrichment in light rare earth elements, suggesting the effects of subduction-related magmatism. Together with the Sr and Nd isotopic compositions of the intermediate to acid volcanics, geochemical characteristics reflect a lower-crustal magma source. This Albian event over the Korean Peninsula is related to Early Jurassic subduction and subsequent lithospheric delamination and/or slab rollback after the Early Cretaceous amalgamation between the North China Block (e.g., China, Korea, and Japan) and the paleo-Eurasia continent. This postorogenic event was accompanied by the initial formation of voluminous igneous activity and subsequent basin formation at about 130-110 Ma. Crustal relaxation during this stage should be related to this postorogenic event and is attributed to paleo-Pacific Plate subduction. This result provides important clues for the Cretaceous tectonic evolution of Northeast Asia in the context of plate convergence.