| High-precision Dating and Geological Significance of Chang 7 Tuff Zircon of the Triassic Yanchang Formation, Ordos Basin in Central China |
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| 作者姓名： | ZHU Rukai CUI Jingwei DENG Shenghui LUO Zhong LU Yuanzheng QIU Zhen |
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| 基金项目： | This study was supported by the National Basic Research Program of China (973 Program) granted No. 2014CB239001. We are deeply grateful for Pecha, Mark E of Department of Geosciences, University of Arizona for assistance on the LA–ICPMS zircon U-Pb analysis and helpful comments. We also thank Dr Jahandar Ramezani of Massachusetts Institute of Technology for assistance on the CA-ID-TIMS zircon U-Pb analysis. |
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| 摘 要： | The Ordos Basin, as the second largest petroliferous basin of China, contains abundant oil and gas resources, oil shale, and sandstone-type uranium mineral resources. Chang 7 shale is not only the major source rock of the Mesozoic petroliferous system of the Basin, but is also crucial in determining the space-time distribution relationship of the shale section for the effective exploration and development of the Basin's oil and gas resources. To obtain a highly precise age of the shale development section, we collected tuff samples from the top and bottom profile of the Chang 7 Member, Yishi Village, Yaoqu Town, Tongchuan District, on the southern margin of the Ordos Basin and performed high-precision chemical abrasion(CA)–isotope dilution(ID)–thermal ionization mass spectrometry(TIMS) zircon U-Pb dating on the basis of extensive laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS) zircon U-Pb dating data. Our results show the precise ages of the top and bottom zircon in the Chang 7 shale to be 241.06±0.12 Ma and 241.558±0.093 Ma, respectively. We first obtained Chang 7 age data with Grade 0.1-Ma precision and then determined the age of the shale development in the Chang 7 Member to be the early-Middle Triassic Ladinian. This result is supported by paleontological evidence. The deposition duration of the Chang 7 shale is 0.5 Ma with an average deposition rate of the shale section being 5.3 cm/ka. Our research results provide time scale and basic data for further investigation of the basin–mountain coupling relation of the shale section, the sedimentary environment and volcanic ash and organic-matter-rich shale development relation, and the organism break-out and organic-matter enrichment mechanism.
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| 收稿时间： | 2018/8/1 0:00:00 |
| 修稿时间： | 2018/12/20 0:00:00 |
High‐precision Dating and Geological Significance of Chang 7 Tuff Zircon of the Triassic Yanchang Formation,Ordos Basin in Central China |
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| Authors: | ZHU Rukai CUI Jingwei DENG Shenghui LUO Zhong LU Yuanzheng and QIU Zhen |
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| Institution: | Research Institute of Petroleum Exploration and Development, Beijing 100083, China,Research Institute of Petroleum Exploration and Development, Beijing 100083, China,Research Institute of Petroleum Exploration and Development, Beijing 100083, China,Research Institute of Petroleum Exploration and Development, Beijing 100083, China,Research Institute of Petroleum Exploration and Development, Beijing 100083, China and Research Institute of Petroleum Exploration and Development, Beijing 100083, China |
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| Abstract: | The Ordos Basin, as the second largest petroliferous basin of China, contains abundant oil and gas resources, oil shale, and sandstone‐type uranium mineral resources. Chang 7 shale is not only the major source rock of the Mesozoic petroliferous system of the Basin, but is also crucial in determining the space‐time distribution relationship of the shale section for the effective exploration and development of the Basin's oil and gas resources. To obtain a highly precise age of the shale development section, we collected tuff samples from the top and bottom profile of the Chang 7 Member, Yishi Village, Yaoqu Town, Tongchuan District, on the southern margin of the Ordos Basin and performed high‐precision chemical abrasion (CA)–isotope dilution (ID)–thermal ionization mass spectrometry (TIMS) zircon U‐Pb dating on the basis of extensive laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) zircon U‐Pb dating data. Our results show the precise ages of the top and bottom zircon in the Chang 7 shale to be 241.06±0.12 Ma and 241.558±0.093 Ma, respectively. We first obtained Chang 7 age data with Grade 0.1‐Ma precision and then determined the age of the shale development in the Chang 7 Member to be the early‐Middle Triassic Ladinian. This result is supported by paleontological evidence. The deposition duration of the Chang 7 shale is 0.5Ma with an average deposition rate of the shale section being 5.3 cm/ka. Our research results provide time scale and basic data for further investigation of the basin–mountain coupling relation of the shale section, the sedimentary environment and volcanic ash and organic‐matter‐rich shale development relation, and the organism break‐out and organic‐matter enrichment mechanism. |
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| Keywords: | Ordos Basin Chang 7 Member tuff zircon U-Pb dating |
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