| 湘南道县辉长岩包体的锆石LA-ICP-MS定年、Hf同位组成及其地质意义 |
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| 引用本文： | 孔华,许明珠,张强,唐宇蔷,赵佳进.湘南道县辉长岩包体的锆石LA-ICP-MS定年、Hf同位组成及其地质意义[J].吉林大学学报(地球科学版),2016,46(3):627-638. |
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| 作者姓名： | 孔华 许明珠 张强 唐宇蔷 赵佳进 |
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| 作者单位： | 1. 中南大学有色金属成矿预测与地质环境监测教育部重点实验室, 长沙 410083;
2. 中南大学地球科学与信息物理学院, 长沙 410083 |
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| 基金项目： | 中国地质调查局地质矿产调查评价专项(1212011121116 |
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| 摘 要： | 道县虎子岩碱性玄武岩筒产出较多的辉长岩包体。用于锆石定年的辉长岩样品的岩石化学特征显示：其K2O、Fe2O3、TiO2高于其他同类样品，稀土元素、微量元素总量也相对较高，样品的K*值（2KN/（TaN+LaN））为7.60>1，显示岩浆具有亲岛弧性质，反映源区地幔受到较强的交代作用；Nb*值（2 NbN/（KN+LaN））为0.11<1，反映基性岩浆侵入时受到了地壳混染；辉长岩中的锆石具有清晰的韵律环带，Th/U值=0.91~4.35，具有岩浆锆石的特征；锆石206Pb/238U加权平均年龄为（201.50±0.53）Ma，代表了辉长岩的结晶年龄；εHf （t）值为-0.88~4.45，投点落入球粒陨石附近，暗示强烈的壳幔交换作用；Hf模式年龄平均为751 Ma，反映早期地壳对岩石源区的贡献。Hf同位素组成特征反映辉长质岩浆是在印支晚期局部拉张背景下，岩石圈上地幔上隆减压熔融的产物。
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| 关 键 词： | 辉长岩包体 锆石U-Pb定年 Hf同位素示踪 道县 |
| 收稿时间： | 2015-10-12 |
LA-ICP-MS Zircon U-Pb Dating and Hf Isotope Feature of Gabbro Xenolith and Its Geological Significance in Huziyan Basalt of Daoxian County,Southern Hunan Province |
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| Kong Hua,Xu Mingzhu,Zhang Qiang,Tang Yuqiang,Zhao Jiajin.LA-ICP-MS Zircon U-Pb Dating and Hf Isotope Feature of Gabbro Xenolith and Its Geological Significance in Huziyan Basalt of Daoxian County,Southern Hunan Province[J].Journal of Jilin Unviersity:Earth Science Edition,2016,46(3):627-638. |
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| Authors: | Kong Hua Xu Mingzhu Zhang Qiang Tang Yuqiang Zhao Jiajin |
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| Institution: | 1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Central South University, Changsha 410083, China;
2. School of Geosciences and Info-Physics, Central South University, Changsha 410083, China |
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| Abstract: | There are many gabbro xenoliths in Huziyan alkali basalt pipe in Daoxian County. The geochemical analysis of one gabbro dating sample show that it has high content of K2O, Fe2O3 and TiO2, compared with other gabbro samples, which suggests that the gabbro xenolith is product of crystallization differentiation of late-stage magma. The K* value (2KN/(TaN+LaN)) is 7.60 (>1), displaying the magma source experienced metasomatism. The Nb* value(2 NbN/(KN +LaN)) is 0.11(<1), implying crust contamination during basic magma intrusion. Zircon grains are chosen from gabbro xenolith for LA-ICP-Ms U-Pb dating and Hf isotope analysis. Zircon grains in the gabbro have clear crystallization zoning, the ratio of Th/U is 0.91~4.35, these features imply that these zircon grains have magmatic origin. The average age of 206Pb/238U is (201.50±0.53) Ma(1σ, MSWD=4.6), which represents the emplacement age of the gabbro xenolith. According to Hf isotope compositions, the calculated model age is 751 Ma, indicating the earlier crustal material gave contributions to source area, the values of εHf(t) are -0.88~4.45, in the figure of εHf(t)-t, the points of zircon grains lie in the area neighbored to evolution curve of chondrite mantle, which are different apparently from their Nd isotope geochemistry. Geochemical characteristics show that the deeply strong material exchange progress between deep crust and mantle in southern Hunan area. In Late Indosinian epoch, there occurred mantle uplift induced by partial extensions, which resulted in progressively the mantle melting to from gabbro magma. The gabbro magma underplated at the bottom of lithosphere and became one part of its consistent. |
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| Keywords: | gabbro xenoliths zircon U-Pb dating Hf isotope tracing Daoxian County |
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