李仰春, 张克信, 吴淦国, 肖庆辉, 杨晓平, 张达, 赵焕利, 韩振哲, 刘旭光. 2013: 大-小兴安岭接合部早—中侏罗世侵入岩SHRIMP锆石U-Pb定年及成因. 地质通报, 32(5): 717-729.
    引用本文: 李仰春, 张克信, 吴淦国, 肖庆辉, 杨晓平, 张达, 赵焕利, 韩振哲, 刘旭光. 2013: 大-小兴安岭接合部早—中侏罗世侵入岩SHRIMP锆石U-Pb定年及成因. 地质通报, 32(5): 717-729.
    LI Yang-chun, ZHANG Ke-xin, WU Gan-guo, XIAO Qing-hui, YANG Xiao-ping, ZHANG Da, ZHAO Huan-li, HAN Zhen-zhe, LIU Xu-guang. 2013: Zircon U-Pb ages and causes of the Early-Middle Jurassic granites in the Da-Xiao Xinganling Copula. Geological Bulletin of China, 32(5): 717-729.
    Citation: LI Yang-chun, ZHANG Ke-xin, WU Gan-guo, XIAO Qing-hui, YANG Xiao-ping, ZHANG Da, ZHAO Huan-li, HAN Zhen-zhe, LIU Xu-guang. 2013: Zircon U-Pb ages and causes of the Early-Middle Jurassic granites in the Da-Xiao Xinganling Copula. Geological Bulletin of China, 32(5): 717-729.

    大-小兴安岭接合部早—中侏罗世侵入岩SHRIMP锆石U-Pb定年及成因

    Zircon U-Pb ages and causes of the Early-Middle Jurassic granites in the Da-Xiao Xinganling Copula

    • 摘要: 大-小兴安岭接合部出露的大面积侵入岩传统认为属于华力西期。通过对3个典型岩体的解剖,获得了最新的锆石SHRIMP U-Pb年龄,花岗闪长岩形成年龄为169Ma±2Ma和177.4Ma±1.7Ma,闪长质包体为179Ma±2Ma,主量、微量元素特征表明,它们为形成于早—中侏罗世的高钾钙碱性系列I型花岗岩。各岩体和闪长质包体均具有低ISr(平均0.704668)和正εNd(t)(1.3837~3.10652)值特点,包体发育针柱状角闪石和空心磷灰石,反映岩体成因与地幔具有密切的联系。地质学、岩石学和地球化学的详细研究表明,各岩体具有壳幔混合成因,花岗质岩浆主要是从地幔中分离出的新生地壳和原有古老地壳部分熔融产生的岩浆,与来自亏损地幔岩浆相互混合形成的。通过区域动力学分析,认为本区大陆地壳生长可能经历了2个连续过程,首先是晚古生代造山期后岩石圈拆沉导致软流圈地幔上隆及幔源岩浆的底垫作用;区域上大范围三叠纪沉积记录的缺失说明此时应是北方造山带强烈的造山时期,这一机制很可能与蒙古-鄂霍次克海闭合造山有密切联系,之后岩石圈板块拆沉,并导致先存新生地壳和原有老地壳的部分熔融,形成花岗质岩浆,可能是引起本区大陆地壳生长的重要机制。

       

      Abstract: Da-xiao xinganling copula large areas of intrusive rocks on the traditional understanding for the Variscan. In view of these intrusive rock, we anatomy for three typical intrusive body, and access to the latest zircon SHRIMP U-Pb age, granodiorite age 169Ma±2Ma and 177.4Ma±1.7Ma, diorite enclaves age 179Ma±2Ma. Combined with characteristics of the main elements and microelement, it showed that they formed in early-middle Jurassic-high potassium calc-alkaline series I type granite. The three of intrusive bodies host rock and diorite enclaves have low ISr(an average of 0.704668) and positive εNd(t) (1.3837~3.10652) value characteristics, diorite enclaves development needle cylindrical hornblende and hollow apatite, the characteristics of the intrusive rocks reflect granite genesis and mantle has the close relation. Geology, petrology and geochemistry of the detailed research shows that the intrusive bodies has the crust-mantle mixed origin, granitic magma source is mainly from the mantle of separation of a newborn crust, and its and the original ancient partial melting of crust of magma and produce from depleted mantle magmatic mutual mix formation. Through the regional dynamics analysis, this paper puts forward the continental crust growth may experience two continuous process, the first is late Paleozoic post-orogenic lithosphere delamination effect, causing asthenosphere mantle uplift and mantle-derived magma mattresses effect; Secondly, a wide range of areas lack Triassic sedimentary records, explain at this time should be the northern orogenic belt strong orogenic period, this mechanism may be closely related with the Mongolia-okhotsk closed orogenic, after the lithosphere plate delamination, and lead to the pre-existing new crust and the original ancient crust partial melting, thus forming granitic magma. This may be is the important mechanism of continental crustal growth in Da-xiao xinganling copula.

       

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