解超明, 李才, 王明, 吴彦旺, 胡兆初. 藏北聂荣微陆块的构造亲缘性——来自LA-ICP-MS锆石U-Pb年龄及Hf同位素的制约[J]. 地质通报, 2014, 33(11): 1778-1792.
    引用本文: 解超明, 李才, 王明, 吴彦旺, 胡兆初. 藏北聂荣微陆块的构造亲缘性——来自LA-ICP-MS锆石U-Pb年龄及Hf同位素的制约[J]. 地质通报, 2014, 33(11): 1778-1792.
    XIE Chao-ming, LI Cai, WANG Ming, WU Yan-wang, HU Zhao-chu. Tectonic affinity of the Nyainrong microcontinent: Constraints from zircon U-Pb age and Hf isotopes compositions[J]. Geological Bulletin of China, 2014, 33(11): 1778-1792.
    Citation: XIE Chao-ming, LI Cai, WANG Ming, WU Yan-wang, HU Zhao-chu. Tectonic affinity of the Nyainrong microcontinent: Constraints from zircon U-Pb age and Hf isotopes compositions[J]. Geological Bulletin of China, 2014, 33(11): 1778-1792.

    藏北聂荣微陆块的构造亲缘性——来自LA-ICP-MS锆石U-Pb年龄及Hf同位素的制约

    Tectonic affinity of the Nyainrong microcontinent: Constraints from zircon U-Pb age and Hf isotopes compositions

    • 摘要: 聂荣微陆块位于安多与那曲之间,呈眼球状透镜体近东西向夹持于班公湖—怒江缝合带之中。聂荣微陆块主体由前寒武系结晶基底、古生代地层及中生代花岗岩岩基组成。为了更好地认识聂荣微陆块新元古代的岩浆事件,并对其构造演化进行约束,分析了基底岩石片麻岩的地球化学特征、LA-ICP-MS锆石U-Pb年龄及锆石原位Hf同位素。3件片麻岩样品的野外产状、矿物组成、结构特征及全岩地球化学特征均表明片麻岩原岩为中酸性侵入岩;样品锆石微量元素示踪、成因分析研究表明,锆石具有岩浆锆石的典型特征;锆石U-Pb年龄在820~843Ma之间,代表了片麻岩原岩的时代。片麻岩的锆石饱和温度估算结果显示,岩体岩浆源区的初始温度为794~856℃。锆石εHf(t)值变化范围较小,介于-0.8~0.5之间,平均值为0.3;二阶段模式年龄TDM2为1.58~1.96Ga。结合区域资料,安多片麻岩原岩形成的大地构造背景与裂解拉张的环境密切相关,初步认为微陆块上发育的新元古代岩浆事件是罗迪尼亚大陆全球裂解事件的产物,并可能与扬子板块边缘的裂解事件相关。

       

      Abstract: Located between Amdo County and Nagqu County, the Nyainrong microcontinent is a EW-trending lenticular body in the middle of the Bangong Co-Nujiang River suture zone. The Nyainrong microcontinent is composed predominately of crystalline basement, Paleozoic strata, and Mesozoic granitoids. To better understand the Neoproterozoic tectono-thermal event in the Nyainrong microcontinent and constrain its tectonic evolution, the authors conducted detailed field observation, precise zircon U-Pb dating and geochemical study of the basement orthogneiss in the Amdo area. The field occurrence, mineral composition, textural characteristics, and whole-rock geochemical features of the three gneiss samples indicate that the protolith of the gneisses was intermediate-acid intrusive rock. Gneiss zircon trace element tracing and genetic analysis show that the zircon has typical characteristics of magmatic zircon. The 206Pb/238U concordant ages of the zircon vary in the range of 820~843Ma, corresponding to the Neoproterozoic, which is the formation age of the protolith. Zircon saturation temperature estimates suggest that the initial temperatures of the magmatic source are 794~856℃, whereas the εHf(t) values are -0.8~0.5, 0.3 on average. The two-stage Hf-isotope model ages (TDM2) range from 1.58 to 1.96Ga. Combined with regional data, the authors hold that the tectonic setting of the Amdo gneiss protolith was closely related to the extensional environment resulting from stretching of the lithosphere. It is preliminarily considered that the Neoproterozoic magmatic events in the microcontinent might have resulted from the breakup of the Rodinia Supercontinent, with the tectonic setting possibly related to the breakup of the Yangtze plate continental margin.

       

    /

    返回文章
    返回