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U-Pb dating was made by the LA-ICP-MS method for detrital zircons from the Wudangshan volcanic-sedimentary succession in the South Qinling. Samples comprise quartz sandstones of the Wudangshan Group collected from the base of the Yangping Formation and an upper layer of the Shuangtai Formation overlain its volcanic sequence, and two river-sand collections from the drainage systems cutting across the two formations, respectively. The results show that the Yangping detrital zircons are dominated by 830-780 Ma grains with a minor population of ~1.0-0.84 Ga and sporadic grains of ~2.6, ~2.4 and 2.0 Ga, whereas the Shuangtai zircons yield an upper intercept age of 763±33 Ma, identical to the timing of the Wudangshan volcanism within error, with few concordant grains of 1.9 and 0.86 Ga. Age spectra for the two river-sand samples are similar to those of the Yangping and Shuangtai Formations, respectively. It thus suggests that the Wudangshan strata are less than 780 Ma, whereas their major detrital zircon populations of 1.0-0.85 Ga and 830-780 Ma are consistent with timing of the Hannan magmatic activities along the northwestern margin of the South China Block. This suggests a Hannan or adjacent area provenance for the Wudangshan strata. The Wudang area is characterized by rift-related igneous events at ~755 and ~680 Ma, respectively, pointing to a tectonomagmatic history different from the Hannan area. It is inferred that the ~755 Ma magmatism is likely to indicate a separation of the South China Block from the supercontinent Rodinia, while the ~680 Ma event suggests a further split between the South Qinling and some unknown continent. Detrital zircon, U-Pb geochronology, South Qinling, South China Block, Neoproterozoic evolution Citation:Ling W L, Duan R C, Liu X M, et al. U-Pb dating of detrital zircons from the Wudangshan Group in the South Qinling and its geological significance.

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The Miaoya syenite and carbonatite complex is located in the southern margin of the South Qinling belt, central China. LA‐ICP‐MS zircon U–Pb dating reveals that the syenite and carbonatite have crystallization ages of 445.2 ± 2.6 Ma (MSWD = 0.66) and 434.3 ± 3.2 Ma (MSWD = 1.08), respectively. Both syenite and carbonatite display low ISr values (0.7004 to 0.7053) and depleted εNd(t) values of +1.1 to +5.5, with one‐stage Nd model ages of 0.65 to 0.94 Ga. Their zircon εHf(t) values are also similarly positive (+3.1 to +8.9), and one‐stage Hf model ages range from 0.71 to 0.92 Ga. Whole‐rock geochemistry suggests that the syenite belongs to the shoshonitic series and both syenite and carbonatite show identical REE and trace element patterns. The coeval intrusive ages, similar geochemical and Sr–Nd–Hf isotopic compositions suggest that the Miaoya carbonatite and associated syenite are genetically related to each other. We consider that the carbonatite could be a final product by protracted fractionation of a CO2‐rich alkaline melt. The depleted εNd(t) and zircon εHf(t) isotopes also indicate that the associated syenite and carbonatite could be originated from a mantle‐derived magma. The sources are likely composed of dominated HIMU mantle and minor EMI mantle. We propose that the Silurian Miaoya Complex was formed in the extensional rifting setting, associated with the mantle upwelling. Copyright © 2016 John Wiley & Sons, Ltd.

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