Geotectonic framework of Permo¨CTriassic magmatism within the Korean Peninsula

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• 作者：Sung Won Kim^a ; Sanghoon Kwon^b ; Hee Jae Koh^a ;   ; ^{hjkoh@kigam.re.kr} ; Keewook Yi^c ; Youn-Joong Jeong^c ; M. Santosh^d
• 关键词：Geochronology ; Geochemistry ; Tectonics ; Triassic plutons ; Post-collision ; Subduction ; SHRIMP zircon U&ndash ; Pb dating
• 刊名：Gondwana Research
• 出版年：2011
• 出版时间：November 2011
• 年：2011
• 卷：20
• 期：4
• 页码：865-889
• 全文大小：4555 K

文摘

This study presents sensitive high-resolution ion microprobe (SHRIMP) U¨CPb zircon ages, and whole-rock chemical and isotopic (Sr-Nd) compositions of representative Triassic plutons from South Korea. The plutons from the Gyeonggi massif (Hongseong, Namyang, Yangpyeong and Odesan), the central Okcheon belt (Baeknok and Yongsan), and the Yeongnam massif (Sangju, Gimcheon, Hamyang and Macheon) yield zircon U¨CPb ages of ca. 232?26 Ma, 227?26 Ma, and 240?28 Ma, respectively. Among the Triassic plutonic suite in South Korea, those within the Gyeonggi massif are dominated by granite, syenite, monzonite, monzodiorite and gabbro. Plutons within the Okcheon belt are mainly by granite to quartz monzodiorite. The Yeongnam massif mainly incorporates granite to granodiorite and minor monzodiorite intrusions. The geochemical signatures of the Triassic plutons are characterized by Ta¨CNb troughs, depletion of P and Ti, and enrichment of LILE. Most plutons except Macheon monzodioritic pluton show high initial ⁸⁷Sr/⁸⁶Sr ratios (0.708248?.714678) and strongly negative ¦Å_Nd(T) (?20.3 to ?7.7) values, suggesting contribution from middle to upper crust. In contrast, the Macheon monzodioritic pluton in the Yeongnam massif shows relatively low initial ⁸⁷Sr/⁸⁶Sr ratios (0.706547-0.706629) and negative ¦Å_Nd(T) (?4.43 to ?3.62) values. The Middle Triassic syenite¨Cmonzonite¨Cgranite¨Cgabbro series in and around the Gyeonggi massif possess high-K calc-alkaline and shoshonitic affinity suggesting a post-collisional magmatic event following the Permo¨CTriassic collision between the North and South China blocks. The Triassic plutons in the Yeongnam massif and the Okcheon belt, together with a Permian Yeongdeok pluton in the Gyeongsang basin, show features typical of high- to medium-K calc-alkaline magmatism with LREE and LILE enrichments. This together with a depletion of Y and HREE suggests their formation in a subduction setting. Our results provide robust evidence to consider the Gyeonggi massif as an extension of the Qinling¨CDabie¨CSulu belt between the North and South China blocks in central China. The Okcheon belt and Yeongnam massif in South Korea, together with the continental margin of South China, are marked by a common Permian to Triassic magmatic episode, probably related to the paleo-Pacific slab subduction.