Possible source rocks of Mesozoic granites in South Korea: implications for crustal evolution in NE Asia

Abstract

The exposed Precambrian cratonic crust in South Korea is divided into two massifs -the Gyeonggi massif to the north and the Yeongnam massif to the south. Mesozoic granites intruded into both massifs and are mostly I-types. The Jurassic granites form extensive deep-seated batholiths, the Triassic granites are deep-seated stocks and the Cretaceous granites occur as volcanic-plutonic complexes.The systematic variation of Nd and SrI in the Korean Mesozoic granites could result from the mixing of two components in different proportions to produce the source of the granites. Although most Mesozoic I-type granites were apparently derived from more juvenile crust, the old evolved crustal components seem to have been incorporated in the magmas in various proportions. Mantlecrust mixing can account for the generation of the source of the Triassic and Cretaceous granites in the Gyeongsang basin. On the other hand, crust-crust mixing can feasibly produce the source of the Triassic and Jurassic granites in the Yeongnam massif, the Jurassic granites in the Gyeonggi massif, and the Cretaceous granites in the Yeongdong-Gwangju basin and the Okcheon belt. However, some Jurassic granites in the Yeongnam massif and Cretaceous granites in the Yeongdong-Gwangju basin can be also explained by the mantle-crust mixing. Combined geochemical and isotopic signatures indicate that a simple binary mixing model is inadequate to explain both the geochemical and isotopic data. The chemistry of the granites is considered likely to reflect the composition of the igneous protolith that derived from depleted mantle, which explains why most Mesozoic granites in South Korea are represented by I-types, regardless of their temporal and spatial position. Nd-Sr isotopic signatures of the Mesozoic granites and basement rocks indicate that the continental crust beneath the Korean peninsular is vertically structured by the successive underplating of mantle-derived materials. It is postulated that the crust is vertically stratified from the surface to the lowermost crust with late Archean to early Proterozoic, early to middle Proterozoic (ca. 1·9 Ga), middle Proterozoic (ca. 1·5 Ga), and late Proterozioc (younger than 1·5 Ga) components.

Provenance Analysis of Lower Cretaceous Sindong Group Sandstones in the Gyeongsang Basin, Korea, Using Integrated Petrography, Quartz Sem-Cathodoluminescence, and Zircon Zr/Hf Analysis

“…Jurassic granites (197-158 Ma) form a large batholith and are generally medium-to coarse-grained porphyritic biotite granites (Jwa 2004). They are mainly felsic I-type, peraluminous, and formed in a calc-alkaline continental-arc environment (Cheong and Chang 1996a, 1996bJwa 2004;Kim et al 2005). The Jurassic granites are thought to have been emplaced at 18-25 km depths (Hong 2001).…”

“…The Jurassic granites are thought to have been emplaced at 18-25 km depths (Hong 2001). Jwa (2004) posited that the Triassic and Jurassic granites can be separated into high-and low-temperature granites, respectively, based on their Zr contents.…”

Petrogenesis and Solidification Depth of the Jurassic Daebo and Cretaceous Bulguksa Granitic Rocks in South Korea

“…These characteristics are different from the original adakite of the magnetite series, derived from partial melting of subducted oceanic crust (Ishihara et al ., 2005). On the basis of Sr–Nd isotope analysis, Jwa (2004) concluded that the source material of the Daebo granitic rocks was continental crust. Thus, there is a possibility that the adakitic magmas of the Daebo granitic rocks were derived from partial melting of the lower continental crust.…”

“…The Bulguksa granitic rocks in the Gyeongsang basin are of the magnetite series and had a large contribution from mantle derived material (Jwa, 2004). Thus, the Bulguksa granitic rocks in the Gyeongsang basin are considered to have been derived from magmas that were produced by partial melting of a mantle wedge due to water supplied from the subducted oceanic plate (the Izanagi–Kula plate).…”

Fluid inclusion characteristics of hematite-bearing quartz vein from the Daenam mine, Republic of Korea

“…It was formed in a relatively immature arc system and at less than 2 kbar emplacement pressure (Cheong et al, 1998). The Cretaceous granites are considered to be derived from a mixed source comprising metasomatized upper mantle and crustal materials (Jwa, 2004).…”