| 羌塘中部各拉丹冬一带鄂尔陇巴组火山岩特征及其构造环境 |
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| 引用本文：白云山,李莉,牛志军,崔江利.2005.羌塘中部各拉丹冬一带鄂尔陇巴组火山岩特征及其构造环境[J].地球学报,26(2):113-120. |
| DOI：10.3975/cagsb.2005.02.03 |
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| 基金项目:国土资源部地质调查项目(编号:2000130000135) |
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| 中文摘要:分布于羌塘中部各拉丹冬一带鄂尔陇巴组火山岩，锆石U—Pb同位素年龄值为212Ma，时代属晚三叠世。岩性主要为由玄武岩、安山岩、英安岩、流纹岩和凝灰岩等组成的一套基性一中性一中酸性一酸性岩石组合。主元素以低TiO2、富碱(K2O Na2O)为特征，为钙碱性系列至碱性系列，球粒陨石标准化的稀土元素配分模式为LREE中等富集型，MORB标准化的微量元素配分型式表现为大离子亲石元素K、Rb、Ba及高场强元素Th的高度富集和Ti的亏损，Ba／L平均为32．46，显示岩浆形成于岛弧构造环境。Sr、Nd同位素地球化学也支持这一结论。地质、地球化学及年代学综合分析研究表明，各拉丹冬一带鄂尔陇巴组火山岩形成于晚三叠世岛弧构造环境。 |
| 中文关键词:羌塘中部 晚三叠世 岛弧 构造环境 |
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| Characteristics and Tectonic Setting of Eerlongba Formation Volcanic Rocks in Geladandong Area of Central Qiangtang |
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| Abstract:The Eerlongba Formation volcanic rocks in Geladandong area of central Qiangtang, consisting of the assemblage of basalt, andesite, rhyolite and tuff, are of basic-intermediate-intermediate-acid-acid series. The zircon U-Pb isotopic value is 212 Ma, suggesting Late Triassic. The main elements are characterized by low TiO 2 and high alkali (K 2O+N 2O), belonging to calc-alkalic-alkalic series. The chondrite-normalized REE patterns indicate that they are enriched in LREE. In addition, the MORB-normalized trace element patterns are characterized by the enrichment of LILE such as K, Rb, Ba and High Field Strength element of Th as well as the depletion of Ti. The average Ba/La ratio is 32.46, suggesting that the magma was formed in the island arc setting. The isotope geochemistry of Sr and Nd also supports this conclusion. Comprehensive geological, geochemical and chronological studies indicate that the volcanic rocks were formed in the Late Triassic island arc setting. |
| keywords:central Qiangtang Late Triassic island arc tectonic setting |
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