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Zircon Ages and Geological Significances of Intermediate-mafic Dykes in Susong Terrene of Dabie Orogenic Belt(PDF)


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Zircon Ages and Geological Significances of Intermediate-mafic Dykes in Susong Terrene of Dabie Orogenic Belt
XIE Qing-lu LI Shuang-qing FANG Bo-wen ZHANG He CHEN Fu-kun
School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, Anhui, China
intermediate-mafic dyke Early Cretaceous U-Pb age inherited zircon delamination Susong terrene Dabie orogenic belt Yangtze Block
Numerous Early Cretaceous intermediate-mafic dykes intrude into the high-pressure metamorphic rocks of Susong Group in Susong terrene of Dabie orogenic belt. They are one of the important objects for understanding the process of mantle-crustal interaction during the deep subduction of the continental plate and the tectonic response in the uplift. Zircon U-Pb ages of these intermediate-mafic dykes obtained by the LA-ICP-MS technique were reported, and the geological implications were discussed. The single zircon gives a wide age range from ~2 600 Ma to ~127 Ma. Apparent U-Pb ages of more than one hundred zircon grains cluster around Archean (>2 500 Ma), Paleoproterozoic (1 850-2 500, 1 650-1 800 Ma), Neoproterozoic (720-850 Ma), Early Paleozoic (420-450 Ma), Early Mesozoic (190-230 Ma), and Early Cretaceous (120-140 Ma). Early Cretaceous zircon grains are typically of magmatic origin and yield a weighted mean U-Pb age of about 132 Ma, representing the emplacement time of the dykes. This magmatic event should be related to intense post-collisional magmatism in Dabie orogenic belt. Combined with morphology, internal structures, and trace element contents of zircons, it can be observed that their age patterns are well correlated with the tectonothermal events in Yangtze Block. The inherited zircons, which are older than Early Mesozoic and contained in intermediate-mafic dykes, are comparable with the age distribution of zircons from Yangtze Block, likely suggesting the Yangtze Block affinity of Susong terrene. From the evidence of the inherited zircons, it is speculated that the intermediate-mafic dykes in Susong terrene originate from the delamination of thickened lithosphere beneath Dabie orogenic belt on the background of Early Cretaceous strong lithospheric extension in the eastern of China.




Last Update: 2016-06-02