Oil & Gas Geology ›› 2015, Vol. 36 ›› Issue (5): 736-744.doi: 10.11743/ogg20150504

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Zircon U-Pb dating of volcanic rocks of Changling Fault Depression in the southern Songliao Basin and its geological significance

Li Ruilei1,2, Zhu Jianfeng2, Liu Wei3, Liu Manli2, Lu Jianlin4, Wang Baohua4, Chen Guangyu2   

  1. 1. College of Energy Resources, China University of Geosciences, Beijing 100083, China;
    2. Research Institute of Exploration and Development, Northeast Branch Corporation, SINOPEC, Changchun, Jilin 130062, China;
    3. College of Earth Sciences, Jilin University, Changchun, Jilin 130061, China;
    4. Wuxi Institute of Petroleum Geology, Exploration and Production Research Institute, SINOPEC, Wuxi, Jiangsu 214126, China
  • Received:2014-12-24 Revised:2015-03-05 Online:2015-10-28 Published:2015-10-23

Abstract: Volcanic rocks are the main basin fillings during the formation of fault depression in the Songliao Basin,and their accurate dating is the basis of the rifting timing and layer subdivision.Twenty volcanic rocks samples were collected from the Changling Fault Depression and dated with LA-ICP-MS zircon U-Pb ages.Zircon U-Pb dating shows that the previous recognized Huoshiling Fm volcanic rocks formed between 110~119 Ma and should be grouped into the 1st Member of the Yingcheng Fm.While the previously recognized Yingcheng Fm volcanic rocks formed between 100~109 Ma and should be grouped into the 3rd Member of the Yingcheng Fm.Petrologically,the volcanic rocks are composed dominantly of andesite,trachyte,rhyolitic tuff and rhyolite,which are displayed in TAS diagram.Geochemical data show that the volcanic rocks have similar features such as light rare earth elements enrichment and negative Eu anomalies,indicating their affinity.As the deepest structure unit in the southern Songliao Basin,new layer subdivision and correlation strategy need to be proposed.And the results also indicate that the syn-rift stage of the southern Songliao Basin started at the Early Cretaceous rather than the previously believed Late Jurassic,which means the corresponding structure-sedimentary and hydrocarbon formation history need to be further recognized.

Key words: zircon U-Pb dating, layer subdivision, initiation of fault depression, volcanic rock, Changling Fault Depression

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