大兴安岭北段争光金矿英安斑岩地球化学特征、锆石U-Pb年龄及Hf同位素组成
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国家自然科学基金项目(面上项目,重点项目,重大项目)


Geochemical Characteristics, Zircons U-Pb Ages and Hf Isotopic Composition of the Dacite Porphyry from Zhengguang Au Deposit in Northern Great Xing’an Range
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    摘要:

    争光金矿位于大兴安岭北段多宝山矿集区内,矿区内火成岩的成岩时代、岩石成因及成岩背景研究薄弱。因此,本文对矿区内英安斑岩进行了主微量元素、锆石U-Pb年龄和Hf同位素组成的系统研究,以期为探讨同时代火成岩的成因及矿床成矿背景提供帮助。锆石LA-ICP-MS U-Pb测年结果表明,争光金矿英安斑岩形成于早奥陶世(478~481Ma)。岩石地球化学特征显示,英安斑岩属准铝-过铝质高钾钙碱性系列,具有SiO2≥56%(平均为63.91%)、高铝(Al2O3平均14.85%)、低镁(MgO平均2.70%)、低Y和Yb(Y=6.00×10-6~7.74×10-6,Yb=0.70×10-6~0.92×10-6)、高锶(平均368×10-6)、高Mg#(56.84~60.60)、轻重稀土分馏明显((La/Yb)N=8.74~11.54)和Eu异常不明显的特点,类似于俯冲洋壳成因埃达克岩。锆石εHf(t)介于13.03~13.31之间,两阶段模式年龄(tDM2)为605~624Ma。综合岩石地球化学特征和锆石Hf同位素组成,我们认为争光英安斑岩由俯冲的新生洋壳发生部分熔融形成。本文研究结果也表明,早奥陶世,兴安地块和松嫩地块之间存在洋壳,并且该洋壳向兴安地块俯冲。

    Abstract:

    Zhengguang Au deposit is located at the Duobaoshan ore-concentrated area, northern of Great Xing’an Range. In order to constrain petrogenesis of contemporaneous igneous rocks and corresponding metallogenic background, a systematic study on major and trace elemental, geochronology and Hf isotope geochemistry was performed for the dacite porphyry in the Zhengguang Au deposit. Zircon LA-ICP-MS U-Pb dating indicates that dacite porphyry formed in early Ordovician(478~481Ma). Geochemical data shows that the dacite porphyry belongs to metaluminous or peraluminous and high-K calc-alkaline series and is characterized by SiO2≥56%(on average, 63.91%), high alumina contents (Al2O3, on average, 14.85%), low magnesium contents (MgO, average 2.70%), low Y and Yb contents (Y =6.00×10-6 to 7.74×10-6, Yb = 0.70×10-6 to 0.92×10-6), high strontium contents (an average of 368×10-6), high Mg# values, significant fractionation between light REE and heavy REE( (La/Yb) N = 8.74~11.54) , and unobvious Eu anomalies. All of these geochemical features are similar to those of adakites generated by partial melting of a subducted oceanic crust. Furthermore, zircon εHf(t) range from 13.03-13.31 with Hf isotope Two-stage model ages(tDM2) from 605Ma to 624Ma. Both geochemical characteristics and Hf isotope compositions suggest that the dacite porphyry in Zhengguang Au deposit was formed by partial melting of a juvenile subducted oceanic crust. The results of this study also demonstrate that there is a subduction of an oceanic plate, which is located between the Xing’an block and Songnen block, beneath the Xing’an block during the early Ordovician.

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车合伟,周振华,马星华,欧阳荷根,刘军.2015.大兴安岭北段争光金矿英安斑岩地球化学特征、锆石U-Pb年龄及Hf同位素组成[J].地质学报,89(8):1417-1436.
CHE Hewei, ZHOU Zhenhua, MA Xinghua, OUYANG Hegen, LIU Jun.2015. Geochemical Characteristics, Zircons U-Pb Ages and Hf Isotopic Composition of the Dacite Porphyry from Zhengguang Au Deposit in Northern Great Xing’an Range[J]. Acta Geologica Sinica,89(8):1417-1436.

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  • 收稿日期:2014-11-20
  • 最后修改日期:2015-03-24
  • 录用日期:2015-08-11
  • 在线发布日期: 2015-08-12
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