| 甘肃北山北带北亚带西缘泥盆纪火山岩地球化学特征 |
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| 引用本文： | 代文军,刘明强.甘肃北山北带北亚带西缘泥盆纪火山岩地球化学特征[J].甘肃地质学报,2008(3):13-21. |
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| 作者姓名： | 代文军 刘明强 |
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| 作者单位： | 甘肃省地矿局第三地勘院;甘肃省地质调查院; |
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| 基金项目： | 中国地质调查局1:5万红岭幅、阿勒腾闹尔梗兑乌勒幅、双沟山幅区调项目成果(编号:200113000057)。 |
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| 摘 要： | 分布于甘肃北山北亚带西缘（双沟山—马鞍山北一带）的泥盆纪火山岩主要为一套浅变质的安山岩、英安岩、流纹岩，局部见少量玄武岩。岩石硅碱成分显示为钙碱性系列，钠质类型；稀土总量为（65．48×10^-6～196．69×10^-6）。属轻稀土富集型，稀土配分型式为右倾曲线；微量元素配分型式类似于岛弧及活动大陆边缘特征，具明显的ULE富集和Nb、Ti等的亏损；同时，从基性到中性熔岩的εNd（t）均为正值（6．46～6．59），暗示其源区类似亏损地幔源区。Y-Nb和Rb-（Y＋Nb）构造判别图解显示本区中酸性火山岩形成于岛弧环境。综合分析火山岩的岩石学、地球化学特征，并结合区域构造背景，认为该套火山岩产于活动大陆边缘岛弧带环境，属俯冲型火山作用，形成于俯冲造山带的构造背景。
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| 关 键 词： | 岩石地球化学 构造环境 火山岩 泥盆纪 甘肃北山北亚带 |
GEOCHEMICAL FEATURES OF DEVONIAN VOLCANIC ROCK
IN THE WESTERN EDGE OF SUB-NORTH-ZONE
OF BEISHAN IN GANSU PROVINCE |
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| DAI Wen-jun and LIU Ming-qiang.GEOCHEMICAL FEATURES OF DEVONIAN VOLCANIC ROCK
IN THE WESTERN EDGE OF SUB-NORTH-ZONE
OF BEISHAN IN GANSU PROVINCE[J].Acta Geologica Gansu,2008(3):13-21. |
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| Authors: | DAI Wen-jun and LIU Ming-qiang |
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| Institution: | 1. No. 3 Geology and Mineral Exploration Team;Gansu Provincial Bureau of Geology and Mineral Exploration and Development;Lanzhou 730050;China;2. Geological Survey of Gansu Province;Lanzhou 730000;China |
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| Abstract: | Devonian volcanic rock situated in the edge of sub-north-zone of Beishan in Gansu Province is mainly composed of a suite of low metamorphic rocks of andesite, rhyolite, dacite, and a few of basalt in the local. The composition of rocks meet the feature of sodium type of calc-alkaline series. It is the concentration of light rare earth elements with the total rare earth of （65.48×10^-6～196.69×10^-6）, and Chondrite-normalized REE pattern incline to the right. The distribution pattern of trace elements have the similar features of island arc and active continental margin, obvious concentration of LIFE and the loss of Nb, Ti. The values of ε＇Nd （t）, from basic rocks and intermediate rock, are positive, which indicate the same characteristics as depleted mantle source. The discrimination diagram of Y-Nb and Rb-（Y ＋Nb） reveals that acidic volcanic rock formed in the environment of island arc. The analyzing results of the features of petrology and geochemistry, and regional tectonic settings support that this suite of volcanic rock formed in the environment of active continental margin and island arc, and is the results of volcanism of subduction with the tectonic setting of subducted orogenic belt. |
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| Keywords: | petro-geochemistry tectonic setting volcanic rock Devonian System sub-north zone of Beishan in Gansu Province |
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