| 扬子板块西北缘碧口地块南一里花岗岩成因研究 |
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| 引用本文：骆金诚,赖绍聪,秦江锋,胡瑞忠.2011.扬子板块西北缘碧口地块南一里花岗岩成因研究[J].地球学报,32(5):559-569. |
| DOI：10.3975/cagsb.2011.05.06 |
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| 基金项目:国家自然科学基金(编号: 40872060); 教育部博士点基金(编号: 20096101110001); 西北大学地质学系国家基础科学人才培养基地创新基金(编号: XDCX08-08) |
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| 中文摘要:本文对扬子板块西北缘南一里岩体进行了系统的地球化学研究, 探讨了该岩体的岩石成因、成岩物质来源及其地质意义。该岩体具有高SiO2(70.27%~71.21%)、Al2O3(14.97%~16.19%)、K2O(3.11%~3.83%)含量, A/CNK=1.04~1.08, 以低Y(<10.01×10-6)和HREE(e.g. Yb<0.70×10-6)为特征, 富集Rb、Th、U、K、Sr, 亏损Ba、Nb、Ta、P和Ti, 稀土总量73.55×10-6~93.86×10-6。Eu异常不明显(0.67~0.83)。具有较高的Sr/Y(33.01~50.53)和(La/Yb)N(15.30~23.04)比值及强分异的稀土元素组成。结合岩体产出的时空位置, 表明南一里岩体形成于典型的后碰撞构造环境, 可能是三叠纪华北和扬子板块的碰撞作用导致该区地壳明显增厚, 在伸展-减薄的构造体制下, 地壳中变玄武质和泥质岩石通过角闪岩脱水发生部分熔融形成。 |
| 中文关键词:南一里花岗岩 地球化学 岩石成因 地壳深熔 碧口地块 |
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| Genesis of Nanyili Granite in Bikou Block, Northwest Margin of Yangtze Plate |
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| Abstract:The Nanyili granite pluton is located in Bikou block on the northwestern margin of the Yangtze Plate. This paper reports the geochemistry of the Nanyili granite and discusses its genesis, ore-forming material source and geological significance. The granite has high SiO2 (70.27%~71.21%), Al2O3 (14.97%~16.19%) and K2O (3.11%~3.83%) content with its A/CNK being 1.04~1.08, low Y (<10.01×10-6) and HREE (e.g., Yb<0.70×10-6). The ∑REE has a range of 73.55×10-6~93.86×10-6, characterized by enrichment of Rb, Th, U, K, Sr and depletion of Ba, Nb, Ta, Ti and P, slightly negative Eu anomalies (δEu=0.67~0.83) and high Sr/Y(33.01~50.53) and (La/Yb)N(15.30~23.04) ratios with strongly fractionated REE patterns. According to these properties, in combination with a comprehensive analysis of the regional geological-tectonic settings, it is thought that the Nanyili granite pluton was formed in a typical post-collsional tectonic environment. It is probable that the collision between the North China and Yangtze plates during the Triassic resulted in obvious thickening of the crust. Under the extension and thinning tectonic mechanism, the metabasaltic and metapelitic rocks of the crust were partially melted through the amphibolitic dehydration. |
| keywords:Nanyili granite geochemistry petrogenesis crustal anatexis Bikou block |
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