Geochemical characteristics of trace elements and tectonic setting of sandstones from the Upper Ordovician Pingliang Formation, southwestern margin of Ordos Basin: A case study of the Duanjiaxia profile, Longxian County
Liuzhu Rui-Zhi1,2, He You-Bin2, Li Hua2, Huang Wei2
1 Research Institute of Petroleum Exploration & Development,PetroChina,Beijing 100083,China; 2 School of Geosciences,Yangtze University,Wuhan 430100,China
Abstract Due to the lack of reliable sedimentary provenance data,the geological setting and its provenance of the southwestern margin of Ordos Basin in Late Ordovician is uncertain. In this paper,the sandstone of Upper Ordovician Pingliang Formation in Duanjiaxia profile of Longxian area is selected for a systematic study. Using the methods including the comprehensive analysis on the measured geological profile,analysis of microscopic thin section and trace elements,the following results are obtained: (1)the thin section analysis shows that the sandstone is well sorted but poorly rounded. Clastic grains are dominated by quartz,while the rock fragments are mainly composed of polycrystalline quartz,carbonate sand debris,and a little matrix,which means that the turbidite sandstone has been reworked by obvious traction of deep-water;(2)Rare Earth Element(REE)distribution model shows that the sandstone is rich in LREE and is short of HREE and has the negative Eu-anomaly,indicating that the provenance may derive from the intermediate and acid rock in the upper crust;(3)the provenance discrimination diagrams show that the sandstone of the Pingliang Formation is a mixture of sedimentary rock and granite,while the magmatic component is dominated by intermediate and acid rock;(4)Geochemical data of the sandstone suggests that the geological setting significantly belong to continental island arc and passive continental settings. The study area in Longxian during the Late Ordovician period was located in the back arc basin. At that time,the southwestern margin of the North China Craton with the full trench-arc-basin system was changed from the passive continental margin into the active continental margin.
Fund:Financially supported by the National Natural Science Foundation of China(Nos. 41472096,41502101)
Corresponding Authors:
He You-Bin,born in 1964,is a professor in School of Geosciences,Yangtze University. Now he is engaged in sedimentology. E-mail: heyb122@163.com.
About author: Liuzhu Rui-Zhi,born in 1992,is a candidate of Ph.D. in Research Institute of Petroleum Exploration & Development,PetroChina. Now he is engaged in sedimentology. E-mail: lzrz201220@163.com.
Cite this article:
Liuzhu Rui-Zhi,He You-Bin,Li Hua et al. Geochemical characteristics of trace elements and tectonic setting of sandstones from the Upper Ordovician Pingliang Formation, southwestern margin of Ordos Basin: A case study of the Duanjiaxia profile, Longxian County[J]. JOPC, 2020, 22(2): 333-348.
Liuzhu Rui-Zhi,He You-Bin,Li Hua et al. Geochemical characteristics of trace elements and tectonic setting of sandstones from the Upper Ordovician Pingliang Formation, southwestern margin of Ordos Basin: A case study of the Duanjiaxia profile, Longxian County[J]. JOPC, 2020, 22(2): 333-348.
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