| 川西新元古代双峰式火山岩成因的微量元素和Sm-Nd同位素制约及其大地构造意义 |
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| 引用本文： | 李献华,周汉文,李正祥,刘颖.川西新元古代双峰式火山岩成因的微量元素和Sm-Nd同位素制约及其大地构造意义[J].地质科学,2002,37(3):264-276. |
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| 作者姓名： | 李献华 周汉文 李正祥 刘颖 |
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| 作者单位： | 1. 中国科学院广州地球化学研究所, 广州, 510640;2. 中国地质大学, 武汉, 430074;3. Tectonic Special Research Centre, Department of Geology and Geophysics, The University of Western Australia, Nedlands, WA 6907, Australia |
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| 基金项目： | 国家杰出青年科学基金 ( 4972 530 9)，中国科学院 (KZCX2 10 1、KZ951 B1 4 13)，科学技术部 ( 95 预 2 5、G19990 4 32 0 1)资助 |
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| 摘 要： | 系统的微量元素和Sm-Nd同位素分析表明,川西地区早震旦世苏雄组双峰式火山岩中的大多数玄武岩具有高的正εNd(T)值(+5～+6)、大离子亲石元素和LREE富集,与现代典型的洋岛玄武岩和大陆溢流玄武岩省中的碱性玄武岩有非常相似的地球化学和同位素组成特征。酸性火山岩的εNd(T)值较低(+1.1～+2.6),地球化学特征总体上与A2-型花岗岩相似,它们是受地壳混染的OIB型玄武质岩浆在地壳中部的一个“双扩散”岩浆房通过结晶分异形成的。苏雄组双峰式火山岩形成于典型的大陆裂谷环境,非常类似于现代与地幔柱活动有关的高火山活动型裂谷火山岩,扬子块体西缘 800Ma前的裂谷作用和火山活动应是约825Ma前的华南地幔柱活动引发的结果。
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| 关 键 词： | 新元古代 双峰式火山岩 微量元素 Sm-Nd同位素 扬子块体 |
| 收稿时间： | 2000-11-27 |
| 修稿时间： | 2000年11月27 |
PETROGENESIS OF NEOPROTEROZOIC BIMODAL VOLCANICS IN WESTERN SICHUAN AND ITS TECTONIC IMPLICATIONS:GEOCHEMICAL AND Sm-Nd ISOTOPIC CONSTRAINTS |
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| Li Xianhua Zhou Hanwen , Li Zhengxiang Liu Ying.PETROGENESIS OF NEOPROTEROZOIC BIMODAL VOLCANICS IN WESTERN SICHUAN AND ITS TECTONIC IMPLICATIONS:GEOCHEMICAL AND Sm-Nd ISOTOPIC CONSTRAINTS[J].Chinese Journal of Geology,2002,37(3):264-276. |
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| Authors: | Li Xianhua Zhou Hanwen Li Zhengxiang Liu Ying |
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| Institution: | 1. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640;2. China University of Geosciences, Wuhan 430074;3. Tectonic Special Research Centre, Department of Western Australia, Nedlands, WA 6907, Australia |
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| Abstract: | The geochemical and Nd isotopic data were reported for the Neoproterozoic Suxiong bimodal volcanic rocks in the Kangdian Rift,western Sichuan.Most samples of basaltic rocks were characterized by high positive εNd(T) values(+5 to +6),pronounced enrichment in the incompatible trace elements,smooth LREE-enriched and “humped” trace element distribution patterns.They closely resembled the alkali basalts in the OIB and CFB provinces,such as the Hawaii OIB and the Ethiopian CFB.These features suggested that these basaltic rocks were most probably derived from an OIB-like mantle source.The differentiated basalt and trachyandesite samples showed relatively low εNd(T) values(+1.7 to +2.4) and Nb-Ta depletion due to contamination by the mafic lithosphere and/or crustal materials.The rhyolite and dacite samples had small positive εNd(T) values(+1.1 to +2.6),general enrichment in most incompatible trace elements but significant depletion of Nb,Ta,Ba,Sr,P,Eu and Ti.They shared geochemical characters of A2-type granites,and were interpreted to be formed through assimilation of OIB-type basaltic magma followed by fractional crystallization in a.double diffusive’magma chamber at the middle crust level.The geochemical and Nd-isotopic characters of the Suxiong bimodal volcanic successions formed within a typical continental rift environment,similar to those volcanics erupted in the Ethiopian Rift.The Kangdian Rift was likely part of a wider continental rift system triggered by a Neoproterozoic mantle plume beneath South China during the breakup of Rodinia. |
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| Keywords: | Neoproterozoic Bimodal volcanic rocks Trace elements Sm Nd isotopes The Yangtze Block |
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