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| 陇山杂岩的LA-ICP-MS锆石U-Pb年龄及其地质意义 | |
| 引用本文： | 何艳红,孙勇,陈亮,李海平,袁洪林,柳小明.陇山杂岩的LA-ICP-MS锆石U-Pb年龄及其地质意义[J].岩石学报,2005,21(1):125-134. |
| 作者姓名： | 何艳红 孙勇 陈亮 李海平 袁洪林 柳小明 |
| 作者单位： | 1. 西北大学大陆动力学教育部重点实验室,西安,710069 2. 西北大学大陆动力学教育部重点实验室,西安,710069;中国科学院地质与地球物理研究所,北京,100029 3. 陕西省区域地质调查院,西安,712000 |
| 摘 要： | 陇山杂岩位于华北克拉通西南缘,构造位置与小秦岭地区遥相呼应,主要为一套中、深变质的火山-侵入岩和碎屑岩系正变质花岗质片麻岩具有高SiO2,Al2O3,高Na2O/K2O(>2.0)以及Sr/Y(>20)和La/Yb(N)(>10)特征,与太古代TTG岩套(奥长花岗岩-英云闪长岩-花岗闪长岩)的地化特征相似,是陇山杂岩内部首次发现并报道的TTG质片麻岩系露头;LA-ICP-MS锆石U-Pb测年结果显示三组峰值年龄:1.90Ga(1.90-1.95Ga)、2.35Ga(2.35-2.40Ga)和2.50Ga(2.45-2.50Ga)1.90Ga的Th/U为0-0.08,2.35Ga和2.50Ga的Th/U几乎都大于0.1,指示陇山杂岩经历了1.9Ga透入性的变质事件、2.35Ga和2.50Ga岩浆事件,2.50Ga代表了英云闪长岩的形成时限本文地球化学以及年代学研究结果与华北克拉通内部记录一致。陇山杂岩与太华杂岩、涑水杂岩和登封杂岩等共同构成了华北地块南缘基底岩系的出露带,广泛且强烈的1.9Ga变质年龄记录显示本地区也可能受到了早元古代前Rodinia超大陆的影响 |
| 关 键 词： | 陇山杂岩 锆石U—Pb年代学 TFG LA—ICP—MS 华北克拉通 |
| 文章编号： | 1000-0569/2005/021(01)-0125-34 |
| 修稿时间： | 2003年11月21 |
Zircon U-Pb chronology of Longshan complex by LA-ICP-MS and its geological significance |
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| HE YanHong,SUN Yong,CHEN Liang,LI HaiPing,YUAN HongLin,LIU XiaoMing The Key Laboratory of Continental Dynamics of the Ministry Education,Northwest University,Xi''an,China Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,China Geological Surrey of Shannxi Province,Xi''an,China.Zircon U-Pb chronology of Longshan complex by LA-ICP-MS and its geological significance[J].Acta Petrologica Sinica,2005,21(1):125-134. | |
| Authors: | HE YanHong SUN Yong CHEN Liang LI HaiPing YUAN HongLin LIU XiaoMing The Key Laboratory of Continental Dynamics of the Ministry Education Northwest University Xi'an China Institute of Geology and Geophysics Chinese Academy of Sciences Beijing China Geological Surrey of Shannxi Province Xi'an China |
| Abstract: | Longshan complex located in the southwestern margin of North China Craton ( NCC) , is a set of metamorphosed volcanic-sedimentary assemblage, including granitic gneisses, amphibolite, aluminum gneisses and marbles. Its tectonic position is comparable with the Lesser Qinling zone to the East. The granitic gneisses from Longxian -Guanshan cross section are geochemically high in SiO2 and Al2O3 contents, and Na2 O/K2 O (>2.0) , Sr/Y (>20) and La/Yb (?) (>10) ratios, resembling the geochemical characteristics of Archaean TTG ( trondhjemite-tonalite-granodiorite) suite. The in situ U-Pb dating on zircons by LA-ICP-MS, yields three age groups at 1. 90Ca ( 1. 90 - 1. 95Ga) , 2. 35Ga ( 2. 35 - 2. 40Ga) and 2. 50Ga (2.45 - 2. 50Ga). The analytical points for the first age group have a Th/U ratio ranging from 0 to 0.08, suggesting their metamorphic origin, whereas the analytical points for the last two age groups have Th/U ratios higher than 0. 1, implying their igneous origin. And the 2. 5Ga. represents the formation age of tonalitic gneisses. The geochemical and geochronologic results are closely related to the temporal evolution of the basement of the North China Craton, indicating that Longshan complex, together with Taihua complex, Sushui complex, Dengfeng complex, should make up the basement outcrops along southern margin of the North China Craton ( NCC). The extensive and intensive 1. 9Ga metamorphic events indicate the south margin of Ordos block are also affected by the Pre-Rodinia supercontinent event. |
| Keywords: | Long-shan Complex Zircon U-Pb chronology TTG LA-ICP-MS North China Craton |
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