U-Pb dating of detrital zircons from the Wudangshan Group in the South Qinling and its geological significance

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 similar to 1.0-0.84 Ga and sporadic grains of similar to 2.6, similar to 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 similar to 755 and similar to 680 Ma, respectively, pointing to a tectonomagmatic history different from the Hannan area. It is inferred that the similar to 755 Ma magmatism is likely to indicate a separation of the South China Block from the supercontinent Rodinia, while the similar to 680 Ma event suggests a further split between the South Qinling and some unknown continent.