Earth Science Frontiers ›› 2020, Vol. 27 ›› Issue (4): 184-198.DOI: 10.13745/j.esf.sf.2019.9.3

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Zircon U-Pb geochronology and geochemistry of the Kekebieketi basic complex in Fuyun, Xinjiang and the geological significance

PEI Shengliang1(), DING Rufu2,*(), SHAN Lihua2, YANG Wusheng3   

  1. 1. China Institute of Geo-Environmental Monitoring, Beijing 100081, China
    2. China Non-Ferrous Metals Resource Geological Survey, Beijing 100012, China
    3. College of Earth Sciences, Guilin University of Technology, Guilin 541006, China
  • Received:2018-08-13 Revised:2018-11-24 Online:2020-07-25 Published:2020-07-25
  • Contact: DING Rufu


The Kekebieketi basic complex is located in the south of Xinjiang Erqisi metallogenic belt. The copper-nickel ore body was discovered in 2016, with good metallogenic potential. In this paper, we report the petrographic, geochemical and chronological characteristics of the complex in order to understand its formation age, tectonic environment and petrogenesis. The complex is mainly controlled by NW and NWW trending structures. The main petrofacies are hornblende pyroxenite, gabbro and a few diorite. Hornblende pyroxenite is mainly ore-bearing facies, and the pyrite and chalcopyrite are stellate, veined and disseminated. The complex had a magnesia ferro ratio between 0.8 and 2.0, containing mainly iron basalts. Trace elements results showed that the complex is depleted in compatible (Cr, Co, Ni) and high field strength (Nb, Ta, Zr, Hf, Th) elements, and enriched in large-ion lithophile element (Ba, U, K, Pb, Sr) elements. The total rare earth elements (ΣREE) content was (29.77-148.02)×10-6 and decreased with increasing basicity. The distribution patterns of REE in each petrofacies were roughly parallel, and fractionation between light and heavy REE showed strong right leaning. Sulfur isotope δ34S of sulfide varied from -0.6‰ to -0.4‰, with typical mantle-sourced sulfur characteristics. The results of La-ICP-MS U-Pb dating of zircon showed that the ages of Kekebieketi gabbro and diorite were 330.3±0.7 and 328.9±0.6 Ma, respectively. Combined with the regional geological background, we considered the magmatic emplacement and crystallization occurred in the mid- and late-stage of the Early Carboniferous in a post-collisional extension setting. In addition, we speculated that the Kekebieketi basic complex is the product of moderately evolving magma, and it may have experienced fractional crystallization of olivine in the deep magma chamber. After that, the middle and upper magma rose and experienced fractional crystallization of orthopyroxene. At the same time, the addition of silicon in the upper crust led to magmatic sulfur saturation to form chalcopyrite.

Key words: zircon U-Pb age, petrogeochemistry, basic complex, petrogenesis, Xinjiang, Kekebieketi

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