Tectonic evolution of Precambrian basement massifs and an adjoining fold-and-thrust belt (Gyeonggi Marginal Belt), Korea: An overview.

This contribution provides an overview on geology, geochronology, and tectonics of Precambrian basement massifs and adjoining Gyeonggi Marginal Belt (GMB), Korea. The three massifs (Gyeonggi, Yeongnam, and Nangrim) record tectonothermal events represented by ∼2.0-1.85 Ga arc-related magmatism and collisional orogenesis, culminating at ∼1.88-1.85 Ga. The oldest (∼2.51 Ga) migmatitic gneisses limitedly occur in the Nangrim and Gyeonggi massifs, suggesting the North China Craton (NCC) affinity of both massifs. The Yeongnam Massif is characterized by the occurrence of ∼1.87-1.86 Ga anorthosite-mangerite-charnockite-granite suite. This anorthositic suite is a late-orogenic product linked to the amalgamation of 'Paleoproterozoic Korean arc' with the North China Craton, forming the Columbia/Nuna supercontinent. The majority of Hf and Nd model ages of basement gneisses are in the range of ∼3.5-2.5 Ga, attesting to the crustal evolution since the Paleoarchean. P-T paths of the Paleoproterozoic basement gneisses are apparently variable, and the Gyeonggi and Yeongnam massifs are characterized by the kyanite-sillimanite and andalusite-sillimanite facies types, respectively. The GMB comprises three fold-and-thrust sub-belts (Imjingang Belt, Taean-Hongseong Complex, and Ogcheon Metamorphic Belt) which are correlative with each other in terms of tectonostratigraphy and detrital zircon geochronology. Two (meta)sedimentary units are diagnostic of this belt: (1) the Neoproterozoic Sangwon Supergroup sharing the provenance with younger rocks in the Ogcheon Belt; and (2) the Devonian turbiditic sequences present in all the three sub-belts. The latter are most distinctive in their detrital zircon age distribution characterized by two major populations at ∼1000-950 Ma and 450-430 Ma. This age pattern as well as the turbiditic lithology is critical for the correlation between the GMB and the Qinling Belt. Taken together, we suggest that the South China Craton-like GMB units are built upon the NCC-like basement (Gyeonggi Massif); this feature is the key to the Qinling-Gyeonggi microcontinent model which accounts for the assembly of a variety of tectonic slivers in the GMB. [ABSTRACT FROM AUTHOR]