IEG 환경지질연구정보센터

광물학│암석학

2011 추계지질과학연합학술발표회 초록집 227

U-Pb zircon geochronology, geochemistry and Nd isotopes of Neoproterozoic plutons from the

western Gyeonggi massif, Korea

Sung Won Kim

․Weon-Seo Kee

․Sanghoon Kwon

1

Geological Research Division, Korea Institute of Geoscience and Mineral Resources, [email protected]

2

Department of Earth System Sciences, Yonsei University

We report sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon ages, and whole-rock chemical and isotopic (Sr-Nd) compositions from tonalite-trondhjemite-gran- odiorite (TTG) and alkaline plutons in and around the “Hongseong-Imjingang suture” along the western margin of the Gyeonggi massif, 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. 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, the ca. 900–

820 Ma TTG plutons are interpreted as the products of arc-related magmatism. Their geo- chemical signatures include enrichment in LREE, negative Nb, Ta and Ti anomalies and rela- tively low εNd(T) values between -0.5 and +5.0. The alkali plutons represent typical rifted-re- lated anorogenic-type magmas. They display significant negative Eu anomalies, and are strongly depleted in Sr, P and Ti. The subduction-related TTG plutons are coeval with those recently identified in and around the Yangtze block in China, and can be correlated with the Sibao orogenic event in China. In contrast, the alkali plutons from the Hongseong area, together with the previously reported ones around the Imjingang belt, might relate to the mantle super- plume event proposed for the disruption of Rodinia. Their geochemical data are similar to those from the Neoproterozoic metavolcanic rocks in the Okcheon belt of South Korea and the Nanhua and Kangdian rifts within South China. The 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. Furthermore, the western Gyeonggi massif in South Korea correlates with the northern and southern margins of the Yangtze block, including the northern Cathaysia block of South China.

41