文章摘要
贺昕宇.中天山东段国宝山三叠纪高铷天河石花岗岩年代学及岩石地球化学研究[J].矿产勘查,2019,(12):2899-2905
中天山东段国宝山三叠纪高铷天河石花岗岩年代学及岩石地球化学研究
Geochronology and geochemistry of Triassic high Rb amazonite granite from Guobaoshan in eastern segment of the middle Tianshan
投稿时间：2019-08-24  
DOI：
中文关键词: 天河石花岗岩  东天山  地球化学  锆石U-Pb定年
英文关键词: amazonite granite, east Tianshan, geochemistry, Zircon U-Pb dating
基金项目:全国公益性基础地质调查项目(编号:DD20160011)资助。
作者单位
贺昕宇 有色金属矿产地质调查中心, 北京 100012 
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中文摘要:
      文章通过中天山东段国宝山天河石花岗岩岩石地球化学和锆石U-Pb定年研究,探讨其成岩年龄、岩体成因和成岩构造背景。该花岗岩具富硅(SiO2 =72.70%～74.20 %)、富碱(Na2O+K2O=8.99%～9.20%)、钠质(Na2O/K2O=1.35～1.55)、弱过铝(A/CNK=1.01～1.08)和铁质(FeOT/MgO=4.11～57.77)特征,岩浆分异指数较高(DI=94.01～95.83)；富集U、Sm、Zr、Hf、Ta等高场强元素(HFSE)和Rb、Nd、Pb元素,亏损Sr、P、Eu、Ti、Y等元素,稀土总量低(∑REE=55.34×10-6～140.52×10-6),轻稀土较重稀土略富集(LREE/HREE=0.97～1.47),具明显的铕负异常(δEu＝0.003～0.04)。锆石U-Pb定年结果显示国宝山天河石花岗岩年龄为(247 ± 3)Ma,天河石伟晶岩脉侵位于(202 ± 3)Ma。天河石花岗岩岩石地球化学特征表明其为典型的A型花岗岩,结合区域地质背景分析,显示该岩体形成于板内张性构造环境；天湖岩群和星星峡岩群中的片岩和片麻岩为国宝山天河石花岗岩的主要贡献源岩,幔源岩浆内侵于中地壳使之发生部分熔融,且母岩浆经历了较强的结晶作用。
英文摘要:
      This paper reports geochemical and zircon LA-ICP-MS data of the Guobaoshan amazonite granite in order to constrain their formation age, research the origin of the magma and analyse the geodynamic setting. Geochemically, the Guobaoshan amazonite granites are characterized by high SiO2 (72.70%~74.20 %), alkali (Na2O+K2O of 8.99%~9.20%), differentiation indices (94.01-95.83) and sodium (Na2O/K2O of 1.35-1.55), are metaluminous (molar A/CNK of 1.01-1.08) and ferroan (FeOT/MgO of 4.11-57.77). The granites are enriched in high strength field elements (U、Sm、Zr、Hf、Ta) as well as Rb, Nd and Pb, whereas depleted in Sr, P, Eu, Ti, Y. In addition, the Guobaoshan batholith has low ∑REE of 55.34-140.52 ppm and is richer in LREE than HREE. Eu anomalies are obviously negative. Zircon U-Pb dating yields a crystallization age of (247 ± 3) Ma and amazonite pegmatite dyke intruded in (202 ± 3) Ma. These geochemical features indicate that the primary magma of the Guobaoshan amazonite granites originated from schists and gneisses of the Tianhu Group and Xingxingxia Group, due to the intraplating of mantle derived magma and the successive partial melting of the middle crust. Meanwhile, the parental magma also experienced fractional crystallization. The Guobaoshan amazonite granites are typical A-type granites and formed in within-plate extensional tectonic environment.
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