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| 吉林中部小蜂蜜顶子组火山岩的形成时代及其地质意义:锆石U-Pb年代学和Hf同位素组成证据 | |
| 引用本文： | 张海洪,许文良,王枫,曹花花.吉林中部小蜂蜜顶子组火山岩的形成时代及其地质意义:锆石U-Pb年代学和Hf同位素组成证据[J].吉林大学学报(地球科学版),2016,46(5):1418-1429. |
| 作者姓名： | 张海洪 许文良 王枫 曹花花 |
| 作者单位： | 1. 吉林大学地球科学学院, 长春 130061; 2. 吉林省地质调查院, 长春 130021; 3. 中国海洋大学海洋地球科学学院, 山东 青岛 266100 |
| 基金项目： | 国家自然科学基金项目(41072038)，中国地质调查局项目(12120113098300)Supported by the National Natural Science Foundation of China Project (41072038) and China Geological Survey's Program Project (12120113098300) |
| 摘 要： | 本文对出露于吉林省中部地区的小蜂蜜顶子组标准剖面的流纹岩（样品号：JH21-1）和非标准剖面小蜂蜜顶子组的安山岩（样品号：JX1-1）进行了锆石LA-ICP-MS U-Pb年代学以及Hf同位素组成研究。2个样品中的锆石均呈自形-半自形，CL图像上显示条痕状吸收或典型的岩浆振荡生长环带，结合其Th/U比值（0.27~0.81），均暗示了它们的岩浆成因。定年结果表明：流纹岩（JH21-1）中锆石206Pb/238U加权平均年龄为（192±2）Ma （MSWD=4.8），其形成于早侏罗世；安山岩（JX1-1）中锆石206Pb/238U加权平均年龄为（172±1）Ma （MSWD=0.27），表明其形成于中侏罗世。前者与标准剖面时代一致，后者与小蜂蜜顶子组并非同一套火山岩。而2个样品中锆石的Hf同位素组成较为均一，εHf（t）值为+5.25~+9.37，二阶省模式年龄为803~1 177 Ma，暗示它们起源于中-新元古代新增生陆壳物质的部分熔融。综上所述，吉林中部地区侏罗纪岩浆事件至少可以划分为两期--早侏罗世和中侏罗世，结合区域构造演化历史，可以认为吉林省中部地区早-中侏罗世火山岩的形成应与古太平洋板块俯冲于欧亚大陆之下的地质作用相联系。 |
| 关 键 词： | 吉林中部 小蜂蜜顶子组 火山岩 锆石U-Pb年代学 岩石组合 构造意义 |
| 收稿时间： | 2015-12-07 |
Formation Timing of the Volcanic Rocks from the Xiaofengmidingzi Formation in Central Jilin Province and Its Geological Implications: Evidence from Zircon U-Pb Dating and Hf Isotope Compositions |
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| Zhang Haihong,Xu Wenliang,Wang Feng,Cao Huahua.Formation Timing of the Volcanic Rocks from the Xiaofengmidingzi Formation in Central Jilin Province and Its Geological Implications: Evidence from Zircon U-Pb Dating and Hf Isotope Compositions[J].Journal of Jilin Unviersity:Earth Science Edition,2016,46(5):1418-1429. | |
| Authors: | Zhang Haihong Xu Wenliang Wang Feng Cao Huahua |
| Institution: | 1. College of Earth Sciences, Jilin University, Changchun 130061, China; 2. Institute of Geologic Survey, Jilin Province, Changchun 130021, China; 3. College of Marine Geosciences, Ocean University of China, Qingdao 266100, Shandong, China |
| Abstract: | The data of LA-ICP-MS zircon U-Pb dating and Hf isotopes are reported for the rhyolite (JH21-1) from typical section and the andesite (JX1-1) from another section of the Xiaofengmidingzi Formation in the central Jilin Province, NE China. The zircons from two volcanic rocks are euhedral-subhedral in shape and display striped absorption or oscillatory growth zoning in the CL images, and have high Th/U ratios (0.27-0.81), implying their magmatic origin. The dating results indicate that the zircons from the rhyolite (JH21-1) yield a weighted mean 206Pb/238U age of (192±2) Ma (MSWD=4.8), i.e., the Early Jurassic, and the zircons from the andesite (JX1-1) yield a weighted mean 206Pb/238U age of (172±1) Ma (MSWD=0.27), i.e., the Middle Jurassic. The former is consistent with the timing of the typical section, and the latter is different from the typical Xiaofengmidingzi Formation. Their zircon εHf(t) (172-192 Ma) values range from +5.25 to +9.37, and Hf two-stage model ages vary from 803 Ma to 1 177 Ma,implying that their primary magmas were derived from partial melting of the juvenile lower crust. Taken together, it is suggested that the Jurassic magmatism can be subdivided into two stages, i.e., the Early Jurassic and Middle Jurassic. Combined with regional tectonic evolution history, we conclude that the Jurassic magmatism in the central Jilin Province could be related to the subduction of the Paleo-Pacific plate beneath the Eurasian continent. |
| Keywords: | central Jilin Province Xiaofengmidingzi Formation volcanic rocks zircon U-Pb chronology rock association tectonic implication |
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