| 五台山蒋村地区四集庄组——对滹沱群时代的再限定 |
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| 引用本文：杜利林,杨崇辉,路增龙,赵磊,耿元生,曹光跃,第五春荣,郭春丽,侯可军.2015.五台山蒋村地区四集庄组——对滹沱群时代的再限定[J].地球学报,36(5):599-612. |
| DOI：10.3975/cagsb.2015.05.09 |
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| 基金项目:国家自然科学基金项目(编号: 41172171); 中国地质调查项目(编号: 12120114021501); 全国地层委员会项目(编号: 1212011120142)和国家留学基金(编号: 201409110015) |
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| 中文摘要:滹沱群是华北最典型的古元古界地层之一, 限定其时代对建立早期地层年代格架和探讨华北早前寒武纪地质演化过程意义重大。本文对五台山地区蒋村镇附近的滹沱群地层进行了详细研究, 从与蒋村砾岩中石英斑岩砾石相同的基岩中选取了2件石英斑岩样品, 并获得其锆石U-Pb年龄结果分别为 (2166±17) Ma和(2138±17) Ma。据此, 限定蒋村地区碎屑沉积岩时代应小于2138 Ma。结合四集庄组底部发育厚层的砾岩和区域内2.2~2.1 Ga岩浆事件, 我们进一步认为滹沱群底界年龄为~2.2 Ga。由于滹沱群豆村亚群和东冶亚群经历了同期褶皱变形作用, 而侵入于蒋村四集庄组未变形正长花岗岩脉的锆石U-Pb年龄结果为(1816±18) Ma。因此, 本文限定豆村亚群、东冶亚群的时代为2.2~1.82 Ga。石英斑岩中锆石Lu-Hf同位素分析结果为176Lu/177Hf为0.000717~0.002239, 176Hf/177Hf为0.281399~0.281563, 其176Hf/177Hfi为0.281315~0.281496和εHf(t)为–3.37~4.11, 变化范围较大, 初步认为其源自于新太古代早期上地壳的部分熔融并有地幔物质添加。 |
| 中文关键词:五台山 蒋村 滹沱群 石英斑岩 锆石U-Pb年龄 |
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| The Sijizhuang Formation at Jiangcun Area of Wutai Mountains: Further Constraints on the Age of the Hutuo Group |
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| Abstract:The Hutuo Group is one of the classic Paleoproterozoic strata in North China, and its age is important for building the stratigraphy framework and investigating the early Precambrian evolution process in the North China Craton. In this paper, we probed into the stratigraphy of Hutuo Group at Jiangcun, Wutai Mountains area, and obtained the zircon U-Pb ages of (2166±17) Ma and (2138±17) Ma from two quartz porphyries, which are identical with the ages of quartz porphyry pebbles in conglomerates of the Hutuo Group. Therefore, we infer that the clastic rocks in Jiangcun were deposited after 2138 Ma. Considering the distribution of a large amount of conglomerates at the base of Sijizhuang Formation and the existence of 2.2~2.1 Ga magmatism in Wutai Mountains area, we further deduce that the initial deposition of Hutuo Group took place at ca. 2.2 Ga. In combination with the fact that Doucun and Dongye Subgroups underwent the similar deformation, and undeformed syenogranite vein of 1816±18Ma intruded into the Sijizhuang Formation, we hold that the deposition age of Doucun and Dongye Subgroup should be 2.2~1.82 Ga. A sample of quartz porphyry yielded the zircon 176Lu/177Hf of 0.000717~0.002239 and 176Hf/177Hf of 0.281399~0.281563. Based on the large variation of 176Hf/177Hfi and εHf(t) in zircons, we propose that the quartz porphyry mainly originated from the upper crust with the addition of the depleted mantle. |
| keywords:Wutai Mountain Jiangcun Hutuo Group quartz porphyry zircon U-Pb ages |
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