Characteristics of the Early Cretaceous Igneous Activity in the Korean Peninsula and Tectonic Implications

Abstract

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 ϵNd(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.