Abstract

Early Cretaceous felsic volcanic-intrusive complexes are widespread in the Gan-Hang Volcanic Belt (GHVB) andaccompany abundant uranium ore resources. However, the petrogenesis and tectonic signi？cance of these rocks arenot well understood. We present zircon U-Pb geochronology, major- and trace-element geochemistry, and Sr-Nd-Hf isotopic compositions of the Yuhuashan Complex and hosted ma？c microgranular enclaves (MMEs) from the south-western part of the GHVB. The Yuhuashan Complex consists of rhyolitic porphyritic lava and subvolcanic porphyriticgranite that are metaluminous to weakly peraluminous and have pronounced A-type geochemical characteristics. Theywere formed at a high temperature and can be further classi？ed as of A₂ subtype af？nity. The Yuhuashan A-type gra-nitic rocks were generated largely by partial melting of Proterozoic metamorphic rocks. Our new data, together withpreviously published data, suggest that the Early Cretaceous A₂-type granitic rocks formed along the GHVB duringan extensional event. The MMEs hosted in the Yuhuashan porphyritic granite exhibit igneous textures, suggestingquenching of ma？c magmas that comingled with the host granitic magma. Zircons from the MMEs have similar U-Pbages but higher ε_Hf(t) values, compared to the host granite. Hence, the MMEs and host granite likely crystallized fromdifferent magma sources, providing direct evidence for ma？c-felsic magma-mingling processes. The MMEs have high MgO and K₂O contents and show shoshonitic af？nities. Geochemical and isotopic data imply that the MMEs werederived from a phlogopite-bearing lithospheric mantle source that had been metasomatized by previous subduction-related ？uids or melt. Underplating of such high-temperature ma？c magmas could have induced lower-crustal rocksto partially melt and generate the Yuhuashan A-type complex. A backarc extensional setting, related to the rollback ofa subducted paleo-Paci？c-derived plate, is favored to explain the petrogenesis of the Yuhuashan Complex and MMEs.

文章信息：    Zhao, K.D., Liu, G.Q., Jiang, S.Y., 2019. Petrogenesis and tectonic implications of the Yuhuashan A-type volcanic-intrusive complex and mafic microgranular enclaves in the Gan-Hang Volcanic Belt, Southeast China. Journal of Geology, 127, 37-59.