赵辉, 李舢, 王涛, 王文志, 焦永艳. 大兴安岭南段黄岗梁地区早白垩世岩浆作用的时代、成因及其构造意义[J]. 地质通报, 2015, 34(12): 2203-2218.
    引用本文: 赵辉, 李舢, 王涛, 王文志, 焦永艳. 大兴安岭南段黄岗梁地区早白垩世岩浆作用的时代、成因及其构造意义[J]. 地质通报, 2015, 34(12): 2203-2218.
    ZHAO Hui, LI Shan, WANG Tao, WANG Wenzhi, JIAO Yongyan. Age, petrogenesis and tectonic implications of the Early Cretaceous magmatism in the Huanggangliang area, southern Da Hinggan Mountains[J]. Geological Bulletin of China, 2015, 34(12): 2203-2218.
    Citation: ZHAO Hui, LI Shan, WANG Tao, WANG Wenzhi, JIAO Yongyan. Age, petrogenesis and tectonic implications of the Early Cretaceous magmatism in the Huanggangliang area, southern Da Hinggan Mountains[J]. Geological Bulletin of China, 2015, 34(12): 2203-2218.

    大兴安岭南段黄岗梁地区早白垩世岩浆作用的时代、成因及其构造意义

    Age, petrogenesis and tectonic implications of the Early Cretaceous magmatism in the Huanggangliang area, southern Da Hinggan Mountains

    • 摘要: 大兴安岭南段黄岗梁地区早白垩世碎斑熔岩和钾长花岗岩代表大兴安岭南段最广泛的一次岩浆活动产物,二者LA-ICP-MS锆石U-Pb年龄都为137.7±1.2Ma。该地区岩石大都具有高硅、钾,贫钙、镁,低铝的特点,体现了高度演化的高钾钙碱性-碱性系列特点;铝饱和指数显示其为准铝质-弱过铝质花岗岩。岩石稀土元素总量为116.98×10-6~350.51×10-6,具有强烈的负Eu异常,富集大离子亲石元素(如Rb、Ba、Th、U等)及高场强元素(如Nd、Zr、Hf等),亏损Ba、Sr、P、Ti、Nb等强不相容元素,显示出高分异I型花岗岩的特征。研究区早白垩世岩浆岩具有较高的全岩εNd(t)值(-0.8~+0.9)和正的锆石εHf(t)值(+1.9~+18.3),以及年轻的Nd模式年龄(993~855Ma)和Hf模式年龄(888~561Ma),表明其来源于新生的陆壳,可能有少量古老陆壳物质的参与。综合区域地质资料及大兴安岭南段的岩浆演化特征,这些早白垩世岩浆作用应形成于区域性伸展的构造背景,主体可能与蒙古-鄂霍茨克洋构造体系下的后造山伸展垮塌有关。

       

      Abstract: The Early Cretaceous porphyroclastic lava and K-feldspar granite in the Huanggangliang area of southern Da Hinggan Mountains both yielded LA-ICP-MS zircon U-Pb ages of 137.7±1.2Ma, which represent a widespread magmatic episode in the southern Da Hinggan Mountains. They are characterized by high content of SiO2, K2O and low content of CaO, MgO, and Al2O3 indicating high evolution magma. ASI values of the studied rocks are from 1.06 to 1.33, suggesting that they are metaluminous-weakly peraluminous, and belong to the high-K calc-alkaline to alkaline series. The total rare earth elements (ΣREE) vary in the range of 116.98×10-6 to 350.51×10-6, with strong negative Eu anomalies. The samples are enriched in large ion lithophile elements (LILE, e.g., Rb, Ba, Th, U) and high field strength elements (HFSEs, e.g., Nd, Zr, Hf), but depleted in incompatible elements, such as Ba, Sr, P, Ti and Nb. These characteristics indicate that they are mainly highly fractionated I-type granites. The Early Cretaceous magmatism has slightly high whole-rock εNd(t) values (-0.8 to +0.9)and positive zircon εHf(t) values (+1.9 to +18.3), with the young Nd modal ages (TDM=993-855Ma) and Hf modal ages (TDM2=888-561Ma), indicating that they were probably derived from juvenile crust, with minor old crustal materials. In view of the regional geology and the magmatic evolution in the southern Da Hinggan Mountains, the authors hold that these Early Cretaceous magmtic activities took place in a regional extensional setting. They were possibly related to the post-orogenic extension under the Mongolia-Okhotsk tectonic regime.

       

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