张开江, 刘治博, 李海峰, 高轲, 王超, 王嘉星. 西藏班公湖-怒江缝合带中段去申拉组火山岩锆石U-Pb年龄及Hf同位素特征[J]. 地质通报, 2019, 38(6): 1018-1027.
    引用本文: 张开江, 刘治博, 李海峰, 高轲, 王超, 王嘉星. 西藏班公湖-怒江缝合带中段去申拉组火山岩锆石U-Pb年龄及Hf同位素特征[J]. 地质通报, 2019, 38(6): 1018-1027.
    ZHANG Kaijiang, LIU Zhibo, LI Haifeng, GAO Ke, WANG Chao, WANG Jiaxing. Zircon U-Pb age and Hf isotopic characteristics of Qushenla Formation volcanic rocks in the middle part of the Bangong Co-Nujiang suture, Tibet[J]. Geological Bulletin of China, 2019, 38(6): 1018-1027.
    Citation: ZHANG Kaijiang, LIU Zhibo, LI Haifeng, GAO Ke, WANG Chao, WANG Jiaxing. Zircon U-Pb age and Hf isotopic characteristics of Qushenla Formation volcanic rocks in the middle part of the Bangong Co-Nujiang suture, Tibet[J]. Geological Bulletin of China, 2019, 38(6): 1018-1027.

    西藏班公湖-怒江缝合带中段去申拉组火山岩锆石U-Pb年龄及Hf同位素特征

    Zircon U-Pb age and Hf isotopic characteristics of Qushenla Formation volcanic rocks in the middle part of the Bangong Co-Nujiang suture, Tibet

    • 摘要: 西藏班公湖-怒江缝合带广泛分布中生代岩浆活动,对于认识特提斯洋的演化有重要的启示。班公湖-怒江缝合带中段东卡错微陆块去申拉组安山岩的锆石U-Pb测年和Hf同位素测试结果显示,其中21个测点给出的锆石206Pb/238U年龄加权平均值为110.3±0.7Ma;εHft)值为-5.66~1.05,二阶段Hf模式年龄为1020~1448Ma,表现出壳幔混源的特征。综合区域构造沉积演化及前人研究成果,认为东卡错微陆块内发育的去申拉组火山岩很可能与早白垩世班公湖-怒江洋壳南向俯冲消减引起的板片断离有关,并形成于板内伸展环境,其岩浆来源于聂荣微陆块成熟地壳物质发生深熔或重熔作用形成的酸性熔体与古老岩石圈地幔部分熔融产生的基性熔体的混合。

       

      Abstract: Mesozoic magmatic activities are widely distributed in the Bangong Co-Nujiang suture zone in Tibet, and it is important to study them for understanding the evolution of the Tethys Ocean. This paper reports the zircon U-Pb dating and zircon Hf isotope data of the andesites of the Qushenla Formation in the Dongkaco microcontinental block of the middle Bangong Co-Nujiang suture zone. The zircon 206Pb/238U weighted age of the andesites obtained from 21 sites is 110.3±0.7Ma. Zircon Hf isotope analysis shows that the zircon εHf(t) varies in the range of -5.66~1.05, and second stage Hf model ages are 1020~1448Ma, showing the characteristics of crust-mantle mixing. Considering regional tectonic sedimentary evolution and previous research results, the authors hold that the volcanic rocks of the Qushenla Formation were probably related to the slab break-offduring southward subduction of the Bangong Co-Nujiang oceanic crust in the Early Cretaceous, and were produced in an intraplate extensional environment. The magma was derived from the mixing of acidic melt formed by deep melting or remelting of mature crustal material in Nyainrong microcontinent with basic melt formed by partial melting of ancient lithospheric mantle.

       

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