岳维好, 周家喜. 青海都兰县阿斯哈石英闪长岩岩石地球化学、锆石U-Pb年龄与Hf同位素特征[J]. 地质通报, 2019, 38(2-3): 328-338.
    引用本文: 岳维好, 周家喜. 青海都兰县阿斯哈石英闪长岩岩石地球化学、锆石U-Pb年龄与Hf同位素特征[J]. 地质通报, 2019, 38(2-3): 328-338.
    YUE Weihao, ZHOU Jiaxi. Geochemistry, zircon U-Pb age and Hf isotopic characteristics of the Asiha diorite in Dulan County, Qinghai Province[J]. Geological Bulletin of China, 2019, 38(2-3): 328-338.
    Citation: YUE Weihao, ZHOU Jiaxi. Geochemistry, zircon U-Pb age and Hf isotopic characteristics of the Asiha diorite in Dulan County, Qinghai Province[J]. Geological Bulletin of China, 2019, 38(2-3): 328-338.

    青海都兰县阿斯哈石英闪长岩岩石地球化学、锆石U-Pb年龄与Hf同位素特征

    Geochemistry, zircon U-Pb age and Hf isotopic characteristics of the Asiha diorite in Dulan County, Qinghai Province

    • 摘要: 都兰县阿斯哈石英闪长岩体呈岩基状产出。闪长岩全岩样品具有低SiO2(56.82%~61.15%)、富碱(Na2O+K2O为5.31%~6.02%)、低TFeO(6.09%~6.65%)和低TiO2(1.02%~1.25%)含量特征,属高钾钙碱性系列岩石。岩石中Cr(24.6×10-6~47.6×10-6)和Ni(12.8×10-6~17.6×10-6)含量不高,K、Ba、Rb、Th、U等大离子亲石元素富集,而Nb、Ta、P、Ti等高场强元素亏损,具有岛弧或活动大陆边缘弧岩浆的特征。用LA-ICP-MS测得锆石206Pb/238U年龄为232.6±1.4Ma,表明岩体为中三叠世形成。锆石具有明显偏低的εHft)值(-3.71~-0.84,平均为-2.31,t=232.6Ma)和偏老的t2DM年龄(1.32~1.50Ga,平均为1.41Ga),表明岩浆来源于古老地壳物质的熔融,很可能为研究区中元古代俯冲地壳物质。阿斯哈石英闪长岩的源区具有壳-幔混合特征,是幔源基性岩浆与古老壳源花岗质岩浆混合作用的产物,岩石形成于中三叠世晚期俯冲向碰撞转换的动力学背景下,代表东昆仑晚古生代—早中生代造山过程的岩浆记录。

       

      Abstract: The Asiha diorite in Dulan County is batholith shaped output. The whole rock samples have characteristics by SiO2 (56.82%~61.15%), rich alkali (Na2O+K2O=5.31%~6.02%), low total iron (TFeO=6.09%~6.65%) and low TiO2 (1.02%~1.25%). Therefore, the diorite belongs to of high-K calc-alkaline rocks. The values of Cr (24.6×10-6~47.6×10-6) and Ni (12.8×10-6~17.6×10-6) are not high. The diorite is enriched in the LILE such as K, Ba, Rb, Th, U and LREE and depleted in HFSE such as Nb, Ta, P and Ti. LA-ICP-MS zircon U-Pb dating results show that the crystallization age of the diorite is 232.6+1.4Ma, and the age belongs to the Middle Triassic. The zircons have relatively low εHf(t) values (t=232Ma, εHf(t)=-3.71~-0.84, -2.31 on average) and relatively old t2DM (1.32~1.50Ga, 1.41Ga on average), thus the magma should be derived from Proterozoic subducted crust. In summary, the magma had crust-mantle mixing characteristics, and the diorite was mainly derived from granitic magma of crust (Proterozoic subducted crust) and experienced activity of basic magma of the mantle. The rock was formed under the geodynamic background of conversion from subduction to collision, which represented the magma records of oceanic crust subduction from Late Paleozoic to Early Mesozoic in East Kunlun.

       

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