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

作　　者：LING WenLi DUAN RuiChun LIU XiaoMing CHENG JianPing MAO XinWu PENG LianHong LIU ZaoXue YANG HongMei REN BangFang 

机构地区：[1]Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China [2]State Key Laboratory of Geological Process and Mineral Resources, China University of Geosciences, Wuhan 430074, China [3]Yichang Institute of Geology and Mineral Resources, Yichang 443003, China [4]State Key Laboratory of Continental Geodynamics, Northwest University, Xi'an 710069, China [5]Geological Survey of Hubei Province, Wuhan 430022, China [6]Tianjin Institute of Geology and Mineral Resources, Tianjin 300170, China

出　　处：《Chinese Science Bulletin》2010年第22期2440-2448,共9页

基　　金：supported by theNational Natural Science Foundation of China (40373015, 40673025 and40821061);the Ministry of Education of China and the State Admini-stration of Foreign Expert Affairs of China (B07039)

摘　　要：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 For-mation 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 domi-nated 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 tectono-magmatic 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.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 fiver-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 fiver-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 tiff-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.

关 键 词：碎屑锆石 武当山 南秦岭 地质意义 Pb 岩浆活动 石英砂岩 火山沉积 

分 类 号：P54[天文地球—构造地质学] P542.3[天文地球—地质学]