古阿雷, 任军平, 王杰, 左立波, 孙宏伟, 许康康, 陈靖, EZEKIAHChikambwe, EVARISTOKasumba. 赞比亚东北部陇都地区首次发现中元古代辉长岩:哥伦比亚超大陆裂解在班韦乌卢地块的响应[J]. 地质通报, 2022, 41(1): 34-47. DOI: 10.12097/j.issn.1671-2552.2022.01.003
    引用本文: 古阿雷, 任军平, 王杰, 左立波, 孙宏伟, 许康康, 陈靖, EZEKIAHChikambwe, EVARISTOKasumba. 赞比亚东北部陇都地区首次发现中元古代辉长岩:哥伦比亚超大陆裂解在班韦乌卢地块的响应[J]. 地质通报, 2022, 41(1): 34-47. DOI: 10.12097/j.issn.1671-2552.2022.01.003
    GU Alei, REN Junping, WANG jie, ZUO Libo, SUN Hongwei, XU Kangkang, CHEN Jing, EZEKIAH Chikambwe, EVARISTO Kasumba. The first discovery of Mesoproterozoic gabbro in Nondo area, Northeastern Zambia: Response of the Bangweulu Block to the Columbia supercontinent breakup[J]. Geological Bulletin of China, 2022, 41(1): 34-47. DOI: 10.12097/j.issn.1671-2552.2022.01.003
    Citation: GU Alei, REN Junping, WANG jie, ZUO Libo, SUN Hongwei, XU Kangkang, CHEN Jing, EZEKIAH Chikambwe, EVARISTO Kasumba. The first discovery of Mesoproterozoic gabbro in Nondo area, Northeastern Zambia: Response of the Bangweulu Block to the Columbia supercontinent breakup[J]. Geological Bulletin of China, 2022, 41(1): 34-47. DOI: 10.12097/j.issn.1671-2552.2022.01.003

    赞比亚东北部陇都地区首次发现中元古代辉长岩:哥伦比亚超大陆裂解在班韦乌卢地块的响应

    The first discovery of Mesoproterozoic gabbro in Nondo area, Northeastern Zambia: Response of the Bangweulu Block to the Columbia supercontinent breakup

    • 摘要: 赞比亚东北部陇都地区位于班韦乌卢地块中东部,区内首次发现中元古代基性岩浆侵入事件,对于了解班韦乌卢地块中元古代构造演化历史及哥伦比亚超大陆的重建具有重要意义。针对研究区的辉长岩进行了系统的岩相学、LA-MC-ICP-MS锆石U-Pb年代学、岩石地球化学和锆石Hf同位素研究。结果表明,辉长岩锆石中17粒具有他形板柱状,内部结构呈条带状、面状等特征,Th/U值较高(0.13~1.58),显示基性岩浆锆石属性,207Pb/206Pb年龄加权平均值为1544±17 Ma,代表了辉长岩的侵位结晶年龄,即中元古代。辉长岩主量元素SiO2含量介于49.99%~50.18%之间,MgO含量(2.69%~2.78%)和Mg#值(24.88~25.70)较低,TFeO(14.47%~14.62%)和TiO2含量(2.68%~2.76%)较高,属于高钛板内拉斑玄武岩系列岩石;微量元素特征显示:轻、重稀土元素分馏明显((La/Yb)N=8.53~9.57),具弱的负Eu异常(0.82~0.86),大离子亲石元素(LILE)Rb、Ba、Pb等相对富集、Sr相对亏损,高场强元素(HFSE)Nb、Ta、Ti等相对亏损,具有大陆溢流玄武岩(CFB)亲缘性;锆石Hf同位素结果显示,辉长岩的原始岩浆起源于中元古代早期亏损地幔源区,形成于板内伸展拉张环境,结合全球构造演化历史,认为班韦乌卢地块应是古—中元古代哥伦比亚超大陆的组成部分,研究区中元古代辉长岩的形成可能与哥伦比亚超大陆的裂解有关。

       

      Abstract: The Nondo area is located in the middle east of Bangweulu Block, northeastern Zambia.A Mesoproterozoic mafic magma intrusion event was first discovered in the Nondo area, which is of great significance for the understanding of the evolution of the Proterozoic structure in Bangweulu Block and the reconstruction of Columbia supercontinent.The systematic studies of petrology, LA-MC-ICP-MS zircon U-Pb geochronology, petrogeochemistry and Lu-Hf isotopes were conducted on the gabbro pluton developed in this area.Seventeen zircons from the gabbro show irregular and plate columnar in shape, with zonal and planar structure, and have high Th/U ratios (0.13~1.58), indicating a mafic magma origin.Zircon U-Pb dating yields an average weighted age of 1544±17 Ma, which represents the forming age of gobbro.The pluton is geochemically characterized by low contents of SiO2 (49.99%~50.18%), MgO (2.69%~2.78%) and Mg# (24.88~25.70) contents and high contents of TFeO (14.47%~14.62%) and TiO2 (2.68%~2.76%), and belongs to high Ti intraplate tholeiitic series.Its trace elements are characterized by enrichment of large ion lithophile elements (LILEs, e.g., Rb, Ba, and Pb), depletion of Sr and high field strength elements (HFSEs, e.g., Nb, Ta, and Ti), obvious fractionation of light and heavy rare earth elements with (La/Yb)N=8.53~9.57 and weak Eu negative anomaly (δEu = 0.82~0.86), showing affinity with continental flood basalts (CFB).The zircon Hf isotope results show that the original magma of gabbro was originated from the early Mesoproterozoic depleted mantle and formed in the intraplate extensional environment.Combined with the global tectonic evolution history, it is suggested that the Bangweulu Block should be a part of Paleo-Mesoproterozoic Columbia supercontinent, and the formation of Mesoproterozoic gabbro pluton in the area is probably related to the break-up of the Columbia supercontinent.

       

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