| 西秦岭临潭地区十里墩组上段形成时代及物源:来自LA-ICP-MS碎屑锆石U-Pb年龄的证据 |
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| 引用本文： | 高翔宇,裴先治,李佐臣,李瑞保,魏立勇,王盟,刘成军,高峰,梁国冰,邵嘉坤,穆可斌.西秦岭临潭地区十里墩组上段形成时代及物源:来自LA-ICP-MS碎屑锆石U-Pb年龄的证据[J].地球科学,2019,44(4):1389-1405. |
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| 作者姓名： | 高翔宇 裴先治 李佐臣 李瑞保 魏立勇 王盟 刘成军 高峰 梁国冰 邵嘉坤 穆可斌 |
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| 作者单位： | 1.长安大学地球科学与资源学院, 陕西 西安 710054 |
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| 基金项目： | 国家自然科学基金项目41472191中央高校基本科研业务费专项资金项目310827161010中国地质调查局地质调查项目12120114008901国家自然科学基金项目41502191国家自然科学基金项目41872233中央高校基本科研业务费专项资金项目2013G1271092中央高校基本科研业务费专项资金项目CHD2011TD020中国博士后基金面上项目2016M592726中央高校基本科研业务费专项资金项目310827161006国家自然科学基金项目41172186国家自然科学基金项目40972136中国地质调查局地质调查项目DD2016007901中央高校基本科研业务费专项资金项目2013G1271091 |
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| 摘 要： | 从前人的研究来看，十里墩组缺少限定其形成时代的标准化石，这导致其沉积时限尚有诸多争议，并且对于该套地层物源的相关研究甚少.以西秦岭临潭地区十里墩组上段碎屑岩为研究对象，进行LA-ICP-MS锆石U-Pb年代学研究，探讨其形成时代及物源.结果表明:十里墩组上部层位的2个样品中最小锆石年龄组加权平均年龄为265.7±6.5 Ma，即十里墩组上段沉积时代应不老于265.7±6.5 Ma，综合古生物化石信息将其形成年代厘定为中晚二叠世.所获得碎屑锆石年龄可划分为4组:①显生宙年龄组，265~467 Ma；②新元古代年龄组，564~996 Ma，该组有小段峰值，峰值年龄为955 Ma；③中元古代年龄组，1 099~1 539 Ma；④古元古代-太古代年龄组，1 622~3 153 Ma，该组年龄又可细分为古元古代中晚期年龄段:1 622~2 194 Ma，峰值为1 902 Ma；古元古代早期-太古代年龄段:2 343~3 153 Ma，峰值为2 516 Ma.综合研究认为，十里墩组上段的物源具多元性，包括华北板块南缘、祁连造山带东段以及西秦岭北缘构造带，且华北板块南缘古老基底为其主要物源.据沉积相、岩相古地理以及区域构造演化分析认为，十里墩组上段沉积于扬子板块俯冲伴随勉略洋收敛所形成的弧后盆地北缘斜坡地带.
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| 关 键 词： | 西秦岭造山带 临潭地区 十里墩组 LA-ICP-MS锆石U-Pb定年 岩石学 |
| 收稿时间： | 2018-05-02 |
Age and Provenance of Upper Shilidun Formation,Lintan, West Qinling Orogen: Constraints from LA-ICP-MS U-Pb Dating of Detrital Zircons |
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| Abstract: | According to previous studies, there are short of standard fossils to define the formed age of Shilidun Formation, which leads to many disputes about the depositionl time, and correlation studies on the provenance of Shilidun Formation are rare. LA-ICP-MS detrital zircon U-Pb dating was conducted for clastic rocks in the upper Shilidun Formation, Lintan area, to investigate the age and provenance in this study. The results show that the weighted mean age of the youngest zircon age group in the two samples is 265.7±6.5 Ma, representing the maximum depositional age of the upper Shilidun Formation. Taking the paleontological data into consideration, it is suggested that the upper Shilidun Formation was deposited in the Middle-Late Permian. The detrital zircon ages are divided into 4 groups:① Phanerozoic age group (265-467 Ma); ② Neoproterozoic age group (564-996 Ma), with a small peak at 955 Ma; ③ Mesoproterozoic age group (1 099-1 539 Ma); ④ Paleoproterozoic-Archaean age group (1 622-3 153 Ma), which can be subdivided into two groups:the Middle and Late Paleoproterozoic age group (1 622-2 194 Ma), with an obvious peak at 1 902 Ma; the Early Paleoproterozoic age group (2 343-3 153 Ma), with an obvious peak at 2 516 Ma.According to the characteristics of the detrital zircon spectra, it is thought that the upper Shilidun Formation has multi-sources, including the southern margin of the North China block, the eastern section of the Qilian orogenic belt, the northern margin of the West Qinling tectonic zone, and ancient basement of the southern margin of the North China block is main source region. Based on the sedimentary facies, lithofacies paleogeography and regional tectonic evolution, it is proposed that the upper Shilidun Formation should be formed in the northern slope of the back arc basin formed by the subduction of the Yangtze plate and the convergence of the Mianlue Ocean. |
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