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

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

    • 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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