周新, 樊炳良, 余佳树, 易金龙, 冯德新. 藏东纽多石墨矿床含矿花岗岩锆石U-Pb年龄及岩石地球化学特征[J]. 地质通报, 2020, 39(10): 1518-1526.
    引用本文: 周新, 樊炳良, 余佳树, 易金龙, 冯德新. 藏东纽多石墨矿床含矿花岗岩锆石U-Pb年龄及岩石地球化学特征[J]. 地质通报, 2020, 39(10): 1518-1526.
    ZHOU Xin, FAN Bingliang, YU Jiashu, YI Jinlong, FENG Dexin. The zircon U-Pb age and geochemical characteristics of ore-bearing granite in the Niuduo graphite deposit eastern Tibet[J]. Geological Bulletin of China, 2020, 39(10): 1518-1526.
    Citation: ZHOU Xin, FAN Bingliang, YU Jiashu, YI Jinlong, FENG Dexin. The zircon U-Pb age and geochemical characteristics of ore-bearing granite in the Niuduo graphite deposit eastern Tibet[J]. Geological Bulletin of China, 2020, 39(10): 1518-1526.

    藏东纽多石墨矿床含矿花岗岩锆石U-Pb年龄及岩石地球化学特征

    The zircon U-Pb age and geochemical characteristics of ore-bearing granite in the Niuduo graphite deposit eastern Tibet

    • 摘要: 藏东察雅—左贡地区可能存在一条晶质石墨矿带,从北向南已发现纽多、地果、青果3处石墨矿床,找矿潜力巨大。以矿区基本地质特征为基础,对含矿岩体花岗岩的岩石学、岩石地球化学及锆石U-Pb同位素进行研究,结果表明含矿花岗岩具有富钾、过铝、钙碱性S型花岗岩的特征;稀土元素配分曲线呈右倾斜的轻稀土元素富集型,轻、重稀土元素分馏明显,具有明显的负Eu异常,微量元素特征显示亏损Nb、Ba、Sr、P、Ti等高场强元素,尤其亏损Ti,相对富集Rb、K、U等大离子亲石元素;样品锆石具有明显的振荡环带和较高的Th/U值(普遍大于0.4),属于典型的岩浆成因锆石,用LA-ICP-MS技术测得锆石206Pb/238U年龄为258.1±1.9 Ma(95%置信度,MSWD=3.5,n=35),表明岩体形成时代为晚二叠世。岩石地球化学特征表明,纽多花岗岩来源于陆壳杂砂岩的部分熔融,且成岩温度较高,可能是碰撞造山导致地壳加厚增温重熔形成的。

       

      Abstract: There may be a crystalline graphite ore belt from Chaya to Zuogong in eastern Tibet, which has great potential for prospecting.Three graphite orebodies were discovered from north to south, i.e., Niuduo, Diguo and Qingguo.The latest geological survey shows that the Niuduo graphite deposit is expected to reach the scale of large-scale deposits, but the theoretical research work remains very insufficient.In this paper, based on the basic geological characteristics of the mining area, the authors studied the petrology, petrogeochemistry and zircon U-Pb chronology of the ore-bearing rock mass.The results show that the ore-bearing granite has the characteristics of K-rich, peraluminium, calc-alkaline S-type granite, and the REE distribution curve is right-inclined LREE enrichment type, with obvious LREE fractionation and obvious negative Eu anomaly.Trace element characteristics show that high field strength elements such as Nb, Ba, Sr, P and Ti are deficient, especially Ti, while large ion lithophile elements such as Rb, K and U are relatively enriched.Zircons in the samples have obvious oscillatory zones with high Th/U ratios(generally higher than 0.4), suggesting typical magmatic zircons.The 206Pb/238U age of zircons determined by LA-ICP-MS is 258.1+1.9 Ma, MSWD=3.5(n=35), and the age of zircons is Late Permian.Geochemistry shows that the Niuduo granite originated from partial melting of continental crustal complex sandstone, and the diagenetic temperature was relatively high.It may have been formed by collisional orogeny resulting in crustal thickening, warming and remelting.

       

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