Abstract:Sr ratio = 0.702±0.046, 2σ), respectively. Initial ε Nd value indicates that the magma should be derived from the crustal material. This initial ε Nd value also corresponds well with those from the Precambrian granitoids from North-China Craton rather than those of South-China Craton.
“…이를 통해 한반도의 여러 구성암체들에 대한 많은 정밀한 연대자료들이 많이 보고되었으며, 이는 현생 화강암질 암체도 마찬가지다(예, Williams et al, 2009;Kee et al, 2010;Kim, J. et al, 2011;Kim, S.W. et al, 2011 Park, et al, 2000;Chang et al, 2003;Lee et al, 2005aLee et al, , 2005bLee et al, , 2010bLee et al, , 2011 …”
Nd isotopic compositions analyzed from the Phanerozoic granitoids of Korea are integrated and discussed. Variations in Nd isotopic compositions can be explained either by temporal trend or by regional differences. Among the three active periods, first two periods during the Permian-Triassic and Jurassic seem to show variations from rather high ε Nd (t) values at the beginning to lower ε Nd (t) values during the later stages. Such trends probably reflect melting of the subducting oceanic crust and producing magma with higher proportion of depleted mantle derived materials during the early stage of subduction process, and subsequent magmas with greater proportion of old continental crust with progress of subduction. However, the Cretaceous-Paleogene period of active magmatism displays higher ε Nd (t) values during the advanced stage of the igneous activities, which is opposite to the previous active periods. The other explanation is that such differences in ε Nd (t) reflect regional differences, based on the observations that such high-ε Nd (t) granitoids distribute in the northeastern Gyeongbuk Province and Gyeongsang Basin. If this is the case, the regions with highr ε Nd (t) values may have distinct crustal evolution histories, e.g. younger average age. The choice between the two hypothesis could be made through further studies.
“…이를 통해 한반도의 여러 구성암체들에 대한 많은 정밀한 연대자료들이 많이 보고되었으며, 이는 현생 화강암질 암체도 마찬가지다(예, Williams et al, 2009;Kee et al, 2010;Kim, J. et al, 2011;Kim, S.W. et al, 2011 Park, et al, 2000;Chang et al, 2003;Lee et al, 2005aLee et al, , 2005bLee et al, , 2010bLee et al, , 2011 …”
Nd isotopic compositions analyzed from the Phanerozoic granitoids of Korea are integrated and discussed. Variations in Nd isotopic compositions can be explained either by temporal trend or by regional differences. Among the three active periods, first two periods during the Permian-Triassic and Jurassic seem to show variations from rather high ε Nd (t) values at the beginning to lower ε Nd (t) values during the later stages. Such trends probably reflect melting of the subducting oceanic crust and producing magma with higher proportion of depleted mantle derived materials during the early stage of subduction process, and subsequent magmas with greater proportion of old continental crust with progress of subduction. However, the Cretaceous-Paleogene period of active magmatism displays higher ε Nd (t) values during the advanced stage of the igneous activities, which is opposite to the previous active periods. The other explanation is that such differences in ε Nd (t) reflect regional differences, based on the observations that such high-ε Nd (t) granitoids distribute in the northeastern Gyeongbuk Province and Gyeongsang Basin. If this is the case, the regions with highr ε Nd (t) values may have distinct crustal evolution histories, e.g. younger average age. The choice between the two hypothesis could be made through further studies.
“…Figure 8.Plot of Ɛ Nd (t) versus age for the Pyeongan Supergroup samples and the Yeongnam Massif basements. Literature data for the Yeongnam Massif basement rocks are from Lee, Kim & Lee (2011) and references therein. Grey-shaded area represents the Nd isotopic evolution path of the rocks that make up the Yeongnam Massif.…”
The upper Palaeozoic succession (Pyeongan Supergroup) in central eastern Korea is well correlated with the equivalent successions distributed in North China, suggestive of the Korean upper Palaeozoic being part of the Sino-Korean Block. Detrital zircon U–Pb ages and Sm–Nd isotope compositions of the Pyeongan Supergroup in the Samcheok coalfield of the Taebaeksan Basin were analysed. A single predominant zircon age peak at c. 1.9 Ga (> 70%) is marked in all sedimentary units, followed by varying amounts of minor late Palaeozoic grains (up to 30%). The rarity of Meso- to Neoproterozoic- and Silurian-aged zircons confirms that sediment influx from the South China and Qinling blocks was insignificant. The 2.0–1.8 Ga-dominated zircon age pattern and the Nd isotope composition (average εNd(0) = −15.5±4.0) of the Pyeongan Supergroup most closely reflect the signature of the Yeongnam Massif basements, which supports a previous hypothesis that the Pyeongan Supergroup was mostly derived from a palaeo-orogen located to the east–southeast. Relatively higher εNd(0) values (> −10.1) in the lowermost and the upper parts of the succession are closely matched by the increased occurrence of syn-depositional-aged zircons, which indicates considerable mixing of juvenile materials at c. 320 Ma and 260 Ma. Both arc-related magmatic events are interpreted to have been related to oceanic subduction, suggesting that the eastern margin of the Sino-Korean Block was an active continental margin during late Palaeozoic times.
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