胡培远, 翟庆国, 唐跃, 王海涛, 朱志才, 吴昊. 西藏北拉萨地块新元古代中期变质辉长岩及其地质意义[J]. 地质通报, 2018, 37(8): 1400-1405.
    引用本文: 胡培远, 翟庆国, 唐跃, 王海涛, 朱志才, 吴昊. 西藏北拉萨地块新元古代中期变质辉长岩及其地质意义[J]. 地质通报, 2018, 37(8): 1400-1405.
    HU Peiyuan, ZHAI Qingguo, TANG Yue, WANG Haitao, ZHU Zhicai, WU Hao. The Middle Neoproterozoic meta-gabbro from the North Lhasa terrane of Tibet and its geological implications[J]. Geological Bulletin of China, 2018, 37(8): 1400-1405.
    Citation: HU Peiyuan, ZHAI Qingguo, TANG Yue, WANG Haitao, ZHU Zhicai, WU Hao. The Middle Neoproterozoic meta-gabbro from the North Lhasa terrane of Tibet and its geological implications[J]. Geological Bulletin of China, 2018, 37(8): 1400-1405.

    西藏北拉萨地块新元古代中期变质辉长岩及其地质意义

    The Middle Neoproterozoic meta-gabbro from the North Lhasa terrane of Tibet and its geological implications

    • 摘要: 青藏高原各陆块的前寒武纪演化历史及其在冈瓦纳大陆聚合过程中所处的构造位置目前不清楚。通过青藏高原中部北拉萨地块念青唐古拉岩群中变质辉长岩SHRIMP锆石U-Pb定年和锆石Hf同位素组成研究,锆石U-Pb定年结果为663±7Ma,相当于新元古代中期,代表变质辉长岩的原岩形成时代,这是北拉萨地块首次报道该时代的基性岩浆记录。变质辉长岩中锆石具有较低的εHft)值(-1.5~+2.3),表明其原岩的岩浆来自富集的地幔源区。结合北拉萨地块已有的变质记录可知,变质辉长岩的原岩可能形成于造山环境。目前定义的"念青唐古拉岩群"实际上是由时代不同、成因不同,甚至来源不同的构造岩片组成,随着工作的深入,有必要对其进行解体。念青唐古拉岩群中的前寒武纪岩浆和变质记录与东非造山带的活动时限较一致,因而北拉萨地块可能与东非造山带具有亲缘性。

       

      Abstract: The Precambrian evolution of the ancient terranes in the Tibetan Plateau and their roles in the assembly of Gondwana supercontinent remain unclear. This paper reports SHRIMP zircon U-Pb dating and zircon Hf isotopic analysis data of the meta-gabbro from the Nyainqentanglha Group of North Lhasa terrane, Tibet. Zircon U-Pb dating yielded a weighted mean age of 663±7Ma, which represents the crystallization age of the protolith of meta-gabbro and is reported for the first time for the North Lhasa terrane. The meta-gabbro has low εHf(t) values (-1.5 to +2.3), suggesting an enriched magma source. Considering previous Precambrian studies in the North Lhasa terrane, the authors hold that the meta-gabbros were probably formed in an orogenic setting. The Nyainqentanglha Group is actually composed of a suite of tectonic slices with different sizes, ages, and petrogenesises. Thus, it should be disassembled in the future research. The metamorphic and magmatic records in the Nyainqentanglha Group are comparable with those of the East African orogen, suggesting that the North Lhasa terrane probably originated from the northern segment of the East African orogen during the assembly of Gondwana supercontinent.

       

    /

    返回文章
    返回