Neoproterozoic plutonic rocks from the western Gyeonggi massif, South Korea: Implications for the amalgamation and break-up of the Rodinia supercontinent

We report sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon ages, and whole-rock chemical and isotopic (Sr-Nd) compositions from tonalite-trondhjemite-granodiorite (TTG) and alkaline plutons in and around the " Hongseong-Imjingang suture" along the western margin of the Gyeonggi massif, South Korea. The Neoproterozoic TTG and the alkali plutons from the Hongseong area of the Gyeonggi massif yield zircon U-Pb ages of ca. 841-822 Ma and ca. 751-746 Ma, respectively. Based on the geochemical and Nd-Sr isotope data on these plutons, together with the previously reported SHRIMP age of ca. 900 Ma from a tonalite, TTG plutons of ca. 900-820 Ma are interpreted as the products of arc-related magmatism. Their geochemical signatures include enrichment in LREE, negative Nb, Ta and Ti anomalies and relatively low e{open}_Nd(T) values between -0.5 and +5.0. The TTG plutons are coeval with those recently identified in and around the Yangtze block in China. In contrast, the alkali plutons from the Hongseong area, together with the previously reported ones around the Imjingang belt, represent anorogenic-type magmas that can be attributed to the disruption of Rodinia. They display significant negative Eu anomalies, and are strongly depleted in Sr, P and Ti. This transition from arc setting at ca. 900-820 Ma to continental rift setting at ca. 750-740 Ma suggests a regional tectonic link for the amalgamation and disruption of Rodinia in Northeast Asia.