Recognition of the Phanerozoic “Young granite gneiss” in the central Yeongnam massif

Abstract

Up to now, all the high-grade gneisses of the Korean peninsula have been regarded as Precambrian basement rocks and presence of the Phanerozoic high-grade metamorphic rocks have remained unknown. However, such granite gneiss is discovered through this study from the central Yeongnam massif near Gimcheon. SHRIMP zircon U-Pb age determinations on the granite gneiss, having well-developed gneissic foliations and migmatitic textures, reveal concordant age of ca. 250 Ma indicating the Early Triassic emplacement of this pluton, which is in contradict to the previous belief that it is a Precambrian product. Even though the granite gneiss reveals well-developed gneissic foliations and some zircons show rather low Th/U ratios, the metamorphic age has not been determined successfully. However, the age of metamorphism can be constrained as middle Triassic considering the absence of any evidences of metamorphism from the nearby granitic plutons having emplacement ages of ca. 225 Ma. Early Triassic emplacement and subsequent Middle Triassic metamorphism of the granite gneiss from the Yeongnam massif bear a remarkable resemblance to the case of South China block. We suggest the possibility that Early to Middle Triassic metamorphism of the Korean peninsula might be products of the intracontinental collisional events not directly related with the Early Triassic continental collision event.

SHRIMP U–Pb ages of detrital zircons from the Early Cretaceous Nakdong Formation, South East Korea: Timing of initiation of the Gyeongsang Basin and its provenance

“…Samples SJS‐7 and SJR‐3 record prominent Triassic ages with nearly the same age range of ca 210 Ma to 250 Ma. Triassic igneous rocks with similar ages are distributed over a wide area in the Yeongnam Massif (S. Kim et al, ; Song, Lee, Park, Fitzsimons, & Cawood, ). For example, the Bukcheon and Agyang diorites, which are the two closest Triassic plutons to the southern Nakdong sample localities, yield U–Pb zircon ages of (227.3 ±1.9) Ma and (229.3 ±1.9) Ma, respectively (Moon, Moon, & Jwa, ).…”

“…Samples SJS-7 and SJR-3 record prominent Triassic ages with nearly the same age range of ca 210 Ma to 250 Ma. Triassic igneous rocks with similar ages are distributed over a wide area in the Yeongnam Massif (S Kim et al, 2011;Song, Lee, Park, Fitzsimons, & Cawood, 2015)…”

The tectonic setting of the eastern margin of the Sino-Korean Block inferred from detrital zircon U–Pb age and Nd isotope composition of the Pyeongan Supergroup (upper Palaeozoic – Lower Triassic), Korea

“…2014 b ; Song et al . 2015). They generally exhibit positive to slightly negative ε Nd values, which supports the interpretation that the relatively high Nd isotope composition of the Gohan Formation is a result of mixing of Permian juvenile volcanic materials with the recycled sediments derived from the Yeongnam Massif basements (Fig.…”

Magmatic response to the interplay of collisional and accretionary orogenies in the Korean Peninsula: Geochronological, geochemical, and O-Hf isotopic perspectives from Triassic plutons

“…The arc magmatism occurred extensively along the margin of the Yeongnam Massif in the earliest Triassic (ca. 250 Ma), as represented by the Yeongdeok adakite (Yi et al, 2012a), and sodic metagranitoids and orthogneisses in the adjacent area (Cheong et al, 2014;Song et al, 2015). The initiation of arc magmatism may be traced back to the middle Permian, considering the SHRIMP zircon ages (266-261 Ma) of diorite-granodiorite xenoliths found in the Yeongdeok pluton and Andong tonalitic gneiss (Yi et al, 2012b;Cheong et al, 2013Cheong et al, , 2014.…”