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    周斌, 乔新星, 韩奎, 潘亮, 王峰, 范鹏. 2021: 西藏日多地区晚三叠世—早侏罗世雄来组火山岩的发现及其对直孔-松多古特提斯造山带演化的约束. 地质通报, 40(8): 1330-1343.
    引用本文: 周斌, 乔新星, 韩奎, 潘亮, 王峰, 范鹏. 2021: 西藏日多地区晚三叠世—早侏罗世雄来组火山岩的发现及其对直孔-松多古特提斯造山带演化的约束. 地质通报, 40(8): 1330-1343.
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    ZHOU Bin, QIAO Xinxing, HAN Kui, PAN Liang, WANG Feng, FAN Peng. 2021: Discovery of the Late Triassic-Early Jurassic volcanic rocks of Xionglai Formation and constraint on the tectonic evolution of Zhikong-Sumdo Paleo-Tethyan orogen in the Riduo area of Tibet. Geological Bulletin of China, 40(8): 1330-1343.
    Citation: ZHOU Bin, QIAO Xinxing, HAN Kui, PAN Liang, WANG Feng, FAN Peng. 2021: Discovery of the Late Triassic-Early Jurassic volcanic rocks of Xionglai Formation and constraint on the tectonic evolution of Zhikong-Sumdo Paleo-Tethyan orogen in the Riduo area of Tibet. Geological Bulletin of China, 40(8): 1330-1343.
    shu

    西藏日多地区晚三叠世—早侏罗世雄来组火山岩的发现及其对直孔-松多古特提斯造山带演化的约束

    Discovery of the Late Triassic-Early Jurassic volcanic rocks of Xionglai Formation and constraint on the tectonic evolution of Zhikong-Sumdo Paleo-Tethyan orogen in the Riduo area of Tibet

      摘要
    • 摘要: 对拉萨地块东段日多地区新厘定的雄来组火山岩进行了岩石地球化学、锆石U-Pb定年及Lu-Hf同位素研究。研究区雄来组火山岩以中基性熔岩及火山碎屑岩占优势为特征。LA-ICP-MS锆石U-Pb测年获得安山岩和玄武安山岩的206Pb/238U年龄加权平均值为201.3±6.0 Ma和184.5±4.4 Ma，表明雄来组火山岩形成于晚三叠世—早侏罗世。其中，基性火山岩SiO2含量为48.53%~49.92%，MgO含量较高，为10.68%~11.43%，Mg#值平均为72.67，高Cr（224.7×10-6~347.8×10-6）和Ni（90.1×10-6~109.7×10-6）含量，富集大离子亲石元素Rb、Th、U、Sr和轻稀土元素，亏损高场强元素Nb、Ta、P、Ti；中性火山岩的SiO2含量为53.93%~60.54%，Al2O3含量为14.74%~16.12%，MgO含量为2.45%~8.12%，富集大离子亲石元素Rb、Th、U、K、Ba和轻稀土元素，亏损高场强元素Nb、Ta、P、Ti，锆石εHf（t）值介于-12.25~-3.64之间，二阶段模式年龄（tDMC）为1621~2004 Ma。岩石地球化学特征和构造环境判别图解均指示，雄来组火山岩形成于后碰撞的构造背景，基性火山岩起源于亏损岩石圈地幔的部分熔融，中性火山岩起源于古老下地壳物质的部分熔融，上升过程中受古老地壳混染，代表了直孔-松多古特提斯造山带后碰撞伸展背景作用下的岩浆响应。

       

      Abstract: Zircon U-Pb dating, geochemical and Hf isotope analyses were carried out on the volcanic rocks of Xionglai Formation newly discovered in Riduo area, the eastern part of the Gangdese magmatic belt.The volcanic rocks of Xionglai Formation in Riduo area in the eastern part of Lhasa massif are mainly intermediate basic lava and pyroclastic rock.Zircon U-Pb dating of andesite and basaltic andesite yields weighted mean ages of 201.3 ±6.0 Ma and 184.5 ±4.4 Ma respectively, indicating that the Xionglai Formation volcanic rocks were formed in the Late Triassic-Early Jurassic.Geochemically, the basic volcanic rocks are characterized by low SiO2(48.53%~49.92%), high MgO(10.68%~11.43%), Mg#(72.67), Cr(224.7×10-6~347.8×10-6), and Ni(90.1×10-6~109.7×10-6), enriched in large ion lithophile elements(Rb, Th, U, Sr) and light rare earth elements(LREEs), and depleted in high field strength elements(Nb, Ta, P, Ti).The intermediate volcanic rocks are characterized by high SiO2(53.93%~60.54%), Al2O3(14.74%~16.12%), low MgO(2.45%~8.12%).They are enriched in light rare earth elements(LREEs), large ion lithophile elements(LILEs, e.g., Rb, Th, U and Ba), but depleted in high-field strength elements(e.g., Nb, Ta, P, Ti).Isotope analyses reveal that most samples have low zircon εHf(t) (-12.25~-3.64), and the values of tDMC range from 1621 Ma to 2004 Ma.Combining with regional geology, geochronological, geochemical and zircon Hf isotopic data, it is proposed that the Late Triassic-Early Jurassic volcanic rocks of Xionglai Formation were formed in post-collision tectonic setting as a magmatic response to post-collision and extension of Zhikong-Sumdo Paleo-Tethyan orogen.The basic volcanic rocks were derived from partial melting of a depleted lithospheric mantle, while the intermediate volcanic rocks were derived from partial melting of ancient lower crustal material and contaminated by ancient lower crust during ascending.

       

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