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| 华北陆块南缘小秦岭地区早白垩世埃达克质花岗岩的 LA-ICP-MS 锆石 U-Pb 年龄、Hf 同位素和元素地球化学特征 | |
| 引用本文： | 高昕宇,赵太平,高剑峰,薛良伟,原振雷.华北陆块南缘小秦岭地区早白垩世埃达克质花岗岩的 LA-ICP-MS 锆石 U-Pb 年龄、Hf 同位素和元素地球化学特征[J].地球化学,2012(4):303-325. |
| 作者姓名： | 高昕宇 赵太平 高剑峰 薛良伟 原振雷 |
| 作者单位： | 1. 中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广东广州510640 2. 中国科学院研究生院,北京100049 3. 香港大学地球科学系,香港999077 4. 河南省国土资源科学研究院,河南郑州450053 |
| 基金项目： | 国家基础研究发展计划（2006CB403502）;河南省科技攻关项目（豫财招标采购（2006）26407号） |
| 摘 要： | 文峪和娘娘山花岗岩体位于华北陆块南缘小秦岭地区,侵位于太古宇太华岩群中,主要岩性为二长花岗岩.LA-ICP-MS 锆石 U-Pb 定年结果显示,文峪和娘娘山黑云母二长花岗岩体形成时间分别为(135±7) Ma 和(139±4) Ma,普遍含有大量继承锆石.两个岩体均属于具有高硅(SiO2=64.80%~73.30%)、... |
| 关 键 词： | 锆石 U-Pb 年龄 Hf 同位素 成因机制 文峪花岗岩体 娘娘山花岗岩体 小秦岭 |
LA-ICP-MS zircon U-Pb ages, Hf isotopic composition and geochemistry of adakitic granites in the Xiaoqinling region, the south margin of the North China block |
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| GAO Xin-yu,ZHAO Tai-ping,＊,GAO Jian-feng,XUE Liang-wei,and YUAN Zhen-lei.LA-ICP-MS zircon U-Pb ages, Hf isotopic composition and geochemistry of adakitic granites in the Xiaoqinling region, the south margin of the North China block[J].Geochimica,2012(4):303-325. | |
| Authors: | GAO Xin-yu ZHAO Tai-ping ＊ GAO Jian-feng XUE Liang-wei and YUAN Zhen-lei |
| Institution: | 1. CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou510640, China;2. Graduate University of Chinese Academy of Sciences, Beijing 100049, China;3. Department of Earth Sciences, the University of Hong Kong, Hong Kong 999077, China;4. Academy o f Land and Resources of Henan Province, Zhengzhou 450053, China |
| Abstract: | Wenyu and Niangniangshan granites in the Xiaoqinling region, Henan Province, is tectonically located in the south margin of the North China Craton and intruded into the Archean Taihua Group. The two granites mainly consist of monzogranite. LA-ICP-MS zircon U-Pb dating of Wenyu and Niangniangshan granites give weighted average ages of （135±7） Ma and （139±4） Ma, with abundant inherited zircon. The similar ages of these two granites indicate they belong to the same magmatic event. The two granites are roughly contemporaneous and geochemically similar to each other, i.e., both of them are high K calc-alkaline and metaluminous-peraluminous, enriched in silica （SiO2 = 64.80%~73.30%）, aluminum （Al2O3 = 14.24%~19.21%）, alkali （K2O ＋ Na2O = 7.66%~9.37%） contents and low MgO （0.21%~0.73%） content, ACNK values （0.93~1.24）, LREE, relatively depleted in HREE （ΣLREE/ΣHREE = 13.7~21.8）. Except the fifth intrusive stage of Wenyu granite, both granites are enriched in Sr, Ba, depleted in low Y, Yb, with slightly negative to positive Eu anomalies （δEu = 0.64~1.27, average 0.82）, suggesting adakitic affinity formed by partial melting of the thickened lower crust, with garnet residual and no plagioclase residual. The fifth intrusive stage of Wenyu granite have medium Sr and Ba contents, and low Y and Yb contents, with obvious negative Eu anomaly （δEu = 0.63~0.70, average 0.66）, formed during the transition from thickened crust to normal crust. The Wenyu granite show εHf（t） values ranging from -19.92 to -12.25 and tDM2 ages of 1961~2442 Ma, suggesting that the primary magma originated from Paleoproterozoic continental crust; while the εHf（t） values of the Niangniangshan granite range mainly from -29.74 to -20.18, with the exception of one point, -8.08. Correspondingly, the tDM2 ages range between 2460 Ma and 3057 Ma, with the exception of one 1699 Ma, suggesting that the primary magma originated from Late Archean continental crust. The εHf（t） values and tDM2 of their inherited zircons also indicate both granites were formed by Paleoproterozoic and Late Archean crustal material, which is consistent with crustal growth histroy of the North China craton. The geochemistry data suggest that both granites were originated from partial melting of the thickened lower crust resulting from underplating of mantle derived magma. The differences between early stage granite and the late stage granite reflect the process of the shallow migration of granitic magmatism source or magma chamber and the transformation of crustal tectonic regimesfrom compression and thickening to extension and thinning. |
| Keywords: | zircon U-Pb age Hf isotopic petrogenesis Wenyu granite Niangniangshan granite Xiaoqinling region |
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