| 内蒙古科右前旗大石寨组火山岩锆石LA-ICP-MSU-Pb年龄及其形成背景 |
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| 引用本文： | 曾维顺,周建波,张兴洲,邱海峻.内蒙古科右前旗大石寨组火山岩锆石LA-ICP-MSU-Pb年龄及其形成背景[J].地质通报,2011,30(203):270-277. |
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| 作者姓名： | 曾维顺 周建波 张兴洲 邱海峻 |
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| 作者单位： | 1. 吉林大学地球科学学院，吉林 长春 130061； 2. 国土资源部油气资源战略研究中心，北京 100034 |
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| 摘 要： | 对大石寨组火山岩的形成时代和形成背景的认识存在较大的分歧。对采自建组剖面底部英安岩样品中的锆石进行阴极发光照相、微区原位LA-ICP-MS微量元素分析和U-Pb测年。锆石U-Pb同位素分析结果显示，锆石发育典型的岩浆震荡环带， 高Th/U(0.51~1.57)，轻稀土元素亏损，重稀土元素富集，具有强烈的正Ce异常和强烈的负Eu异常等特征，表明锆石均属于岩浆成因。22个分析点获得的谐和年龄为(314±1)Ma(MSWD=0.88)，代表了大石寨组火山岩的形成时代。结合前人的资料，认为大石寨组火山岩为裂陷早期的产物，而晚古生代的沉积岩石组合为在这一基础上发展起来的具有裂陷盆地性质的沉积组合。
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| 关 键 词： | 锆石 U-Pb年龄 大石寨组英安岩 古生代 内蒙古 |
LA-ICP-MS zircon U-Pb age of the volcanic rocks from the Dashizhai Formation in Keyouqianqi, Inner Mongolia, China and its tectonic setting |
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| ZENG Wei-shun,ZHOU Jian-bo,ZHANG Xing-zhou,QIU Hai-jun.LA-ICP-MS zircon U-Pb age of the volcanic rocks from the Dashizhai Formation in Keyouqianqi, Inner Mongolia, China and its tectonic setting[J].Geologcal Bulletin OF China,2011,30(203):270-277. |
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| Authors: | ZENG Wei-shun ZHOU Jian-bo ZHANG Xing-zhou QIU Hai-jun |
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| Institution: | 1. College of Earth Sciences, Jilin University, Changchun 130061, Jilin, China;2. Strategic Research Center of Oil & Gas Resources, Ministry of Land and Resources, Beijing 100034, China |
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| Abstract: | Timing and tectonic setting of volcanic rocks from Dashizhai Formation remain controversial. A combined study of cathodoluminescence images (CL), in situ LA-ICP-MS U-Pb isotope dating and trace element analysis were carried out for zircons from the Dashizhai Formation dacite. The zircon LA-ICP-MS U-Pb analysis shows that the zircons are of typical magmatic origin with oscillatory zoning, higher concentrations of Th, U, and REE. Th/U ratios of zircons range from 0.51 to 1.57. Chondrite-normalized REE were loss of light rare earth elements and significant enrichment of heavy rare earth elements. zircons have a strong positive Ce anomaly and negative Eu anomalies strongly, which shows these zircons are magmatic in origin. 22 points give a weighted average age (313±2)Ma(MSWD=2.8). These new data suggust that the protolith age of Dianshizhai Formation was at about 300 Ma. Together with geochemical data from previous works, it is suggested that the Dashizhai Formation volcanic rocks were formed in the rift basin, and the Late Paleozoic sedimentary rocks, including Zhesi Formation and Linxi Formation, were developed on this rift basin. |
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| Keywords: | zircon U-Pb age Dashizhai Formation dacite Paleozoic Inner Mongolia |
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