钱程, 陆露, 汪岩, 郭荣荣, 唐振. 内蒙古白乃庙岛弧发现古元古代变质基底——来自双胜地区斜长角闪岩年龄和地球化学的证据[J]. 地质通报, 2020, 39(6): 905-918.
    引用本文: 钱程, 陆露, 汪岩, 郭荣荣, 唐振. 内蒙古白乃庙岛弧发现古元古代变质基底——来自双胜地区斜长角闪岩年龄和地球化学的证据[J]. 地质通报, 2020, 39(6): 905-918.
    QIAN Cheng, LU Lu, WANG Yan, GUO Rongrong, TANG Zhen. Age and geochemistry of amphibolite in Shuangsheng area eastern Inner Mongolia New evidence from the Paleoproterozoic basement of Bainaimiao island arc[J]. Geological Bulletin of China, 2020, 39(6): 905-918.
    Citation: QIAN Cheng, LU Lu, WANG Yan, GUO Rongrong, TANG Zhen. Age and geochemistry of amphibolite in Shuangsheng area eastern Inner Mongolia New evidence from the Paleoproterozoic basement of Bainaimiao island arc[J]. Geological Bulletin of China, 2020, 39(6): 905-918.

    内蒙古白乃庙岛弧发现古元古代变质基底——来自双胜地区斜长角闪岩年龄和地球化学的证据

    Age and geochemistry of amphibolite in Shuangsheng area eastern Inner Mongolia New evidence from the Paleoproterozoic basement of Bainaimiao island arc

    • 摘要: 白乃庙岛弧位于兴蒙造山带南缘,是研究古亚洲洋早古生代地质的重要单元,其基底属性存在争议。在内蒙古东部阿鲁科尔沁旗附近开展地质调查过程中,在双胜地区发现了一套古元古代变质杂岩,为白乃庙岛弧基底属性研究提供了新素材。对该杂岩中的斜长角闪岩进行岩相学、年代学和地球化学研究。该斜长角闪岩原岩属于辉长岩类,至少经历了2期变质作用,LA-ICP-MS锆石U-Pb年龄研究表明变质年龄为1924±17 Ma和1814.2±9.4 Ma。地球化学研究显示,该岩石原岩属拉斑玄武岩系列,具有富铁、镁、钙、钛,贫碱,高Na2O/K2O(2.05~3.12),中等Mg#值(41.09~51.71)等特征,稀土和微量元素曲线特征与洋岛玄武岩相似,推测其来源于岩石圈地幔,形成于大洋板内背景。双胜地区变质杂岩可能记录了古元古代哥伦比亚超大陆聚合过程中的洋陆转化事件。结合区域资料,推测白乃庙岛弧具有统一的前寒武纪基底,与华北克拉通具有极好的构造亲缘性。

       

      Abstract: Located on the south margin of the Xing'an-Mongolian orogenic belt, Bainaimiao arc is an important part for studying the early Paleozoic geology of the Paleo-Asian Ocean, but its basement property is still controversial.During the geological survey in Ar Horqin Banner, eastern Inner Mongolia, the authors discovered a set of Paleoproterozoic metamorphic complexes in Shuangsheng area, which provides new evidence for the study of the basement property of Bainaimiao arc.In this paper, amphibolite in the metamorphic complex was studied in the aspects of petrography, geochronology and geochemistry.The results show that the protolith of the amphibolite belongs to gabbronite, and had undergone at least two stages of metamorphism at 1924±17 Ma和1814.2±9.4 Ma respectively.Geochemical features show that the protolith of the amphibolite belongs to tholeiitic series, characterized by relatively high Fe, Mg, Ca, Ti, and Na2O/K2O(2.05~3.12), medium Mg#(41.09~51.71), and relatively low alkali, with curve characteristics of rare earth and trace elements similar to those of OIB, suggesting that the protolith originated from lithosphere mantle and was formed in ocean intraplate.The metamorphic complex from Shuangsheng area may have recorded the event of ocean-continent transformation during the assembly of the Columbia supercontinent in the Paleoproterozoic.Combined with regional data, it is concluded that Bainaimiao arc had a uniform Precambrian basement, which had tectonic affinity to the North China Craton definitely.

       

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