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The identification of Late Carboniferous (317 ± 3 Ma) Daixi‐Wufenglou S‐type granites and Early Triassic (247 ± 2 Ma) Houzhang complex (comprising monzodiorite and monzogranite) in southeast China provides new insights into the bewildering tectonics of south China, before its final welding to the Eurasian continent. The Daixi‐Wufenglou granites have high K2O (4.01–6.54 wt%), A/CNK (1.02–1.34), high bulk initial 87Sr/86Sr (0.7094–0.7160) and low εNd(t) (−8.87 to −6.31), and low zircon εHf(t) (−8.1 to −1.9) and high δ18O (12.7–14.0‰), indicating derivation by partial melting of a Neoproterozoic basement as a result of the input of mantle‐derived heat in a back‐arc extensional setting, triggered by rollback of the Paleo‐Pacific plate subduction beneath the outboard proto‐Japan arc. The monzodiorites are shoshonitic, characterized by high K, Ni, Cr, and Mg#, and the monzogranites are adakitic, defined by high Sr/Y, (La/Yb)n and low Y, Yb. They have similar 87Sr/86Sr (0.7085–0.7087), εNd(t) (−5.92 to −5.34), and εHf(t) (−7.5 to −2.5), indicating their petrogenetic linkage. The monzodiorites and monzogranites represent early crystallization phases (cumulates) and residual melts of a mantle‐derived magma, generated from a metasomatically enriched mantle. Integrating these data with other geological information from south China and neighboring countries, we propose a new model for the tectonic evolution of the Late Paleozoic south China, which was controlled by the subduction of the Paleo‐Pacific Ocean plate. A distal continental back‐arc setting was produced by slab rollback in the early stages, and an active continental margin environment was produced by the accretion of the proto‐Japan arc in the later stages.

The Cathaysia Block in South China Block (SCB) is famous for its polyphase granitic magmatism and world-class mineralization, especially W, Sn and REE. Although isotopic data suggest that widespread igneous rocks were derived from Precambrian basement, outcrops of the basement rocks are rare in the Cathaysia Block. Therefore, the distribution of the Archean-Paleoproterozoic basement beneath Cathaysia Block is still unclear. The northeastern-striking Pingtan-Dongshan metamorphic belt (PDMB) is located along the coastal region of southeastern China, and consists mainly of voluminous granites and volcanic rocks with minor metasedimentary rocks. These metasedimentary rocks were intruded or captured by 160-143 Ma granites. U-Pb dating of detrital and metamorphic zircons from seven metasedimentary rocks indicates that their protoliths were deposited between 183 Ma to 160 Ma, rather than pre-Devonian as previously proposed. Dating of metamorphic zircons suggests that the most important metamorphism took place at ca 97 Ma, consistent with emplacement of A-type granites and mafic magmatism in the coastal region, and implying an extensional setting. Age spectra of detrital zircons in samples from the middle and southern PDMB exhibit a bimodal distribution with abundant Late Paleoproterozoic and Early Mesozoic zircons. In contrast, age spectra of detrital zircons from the northern PDMB display pronounced Neoproterozoic and Early Paleozoic age peaks as well as Late Paleoproterozoic and Early Mesozoic ones, suggesting a different provenance. The comparisons of age and Hf-isotope with the exposed rocks of the SCB suggest that the terrigenous material in these sediments was sourced from the Wuyi terrane, in the eastern Cathaysia Block. 3 The age spectra of detrital zircons from Early Paleozoic to Late Mesozoic sedimentary rocks in the SE SCB show that late Paleoproterozoic (1.9-1.8 Ga) detritus increases markedly in Middle Permian to Early Cretaceous sedimentary rocks. Comparison with zircon U-Pb-Hf isotopic data from exposed Paleoproterozoic rocks suggests that a Paleoproterozoic basement existed extensively beneath the eastern Cathaysia Block. It has been uplifted and eroded since Middle Permian time, and then covered by Late Cretaceous volcanic rocks. The uplift of the Paleoproterozoic basement was probably caused by the Late Paleozoic orogeny in the eastern Cathaysia Block.

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