杨华本, 刘玉, 郑吉林, 梁中恺, 王晓勇, 唐雪峰, 苏燕平. 额尔古纳地块玻乌勒山地区新元古代斜长角闪岩-片麻状花岗岩的成因及其地质意义[J]. 地质通报, 2017, 36(2-3): 342-356.
    引用本文: 杨华本, 刘玉, 郑吉林, 梁中恺, 王晓勇, 唐雪峰, 苏燕平. 额尔古纳地块玻乌勒山地区新元古代斜长角闪岩-片麻状花岗岩的成因及其地质意义[J]. 地质通报, 2017, 36(2-3): 342-356.
    YANG Huaben, LIU Yu, ZHENG Jilin, LIANG Zhongkai, WANG Xiaoyong, TANG Xuefeng, SU Yanping. Petrogenesis and geological significance of Neoproterozoic amphibolite and granite in Bowuleshan area, Erguna massif, Northeast China[J]. Geological Bulletin of China, 2017, 36(2-3): 342-356.
    Citation: YANG Huaben, LIU Yu, ZHENG Jilin, LIANG Zhongkai, WANG Xiaoyong, TANG Xuefeng, SU Yanping. Petrogenesis and geological significance of Neoproterozoic amphibolite and granite in Bowuleshan area, Erguna massif, Northeast China[J]. Geological Bulletin of China, 2017, 36(2-3): 342-356.

    额尔古纳地块玻乌勒山地区新元古代斜长角闪岩-片麻状花岗岩的成因及其地质意义

    Petrogenesis and geological significance of Neoproterozoic amphibolite and granite in Bowuleshan area, Erguna massif, Northeast China

    • 摘要: 对大兴安岭北段额尔古纳地块东南缘玻乌勒山地区新元古代斜长角闪岩和片麻状花岗岩进行了LA-ICP-MS 锆石UPb定年和岩石地球化学分析,讨论额尔古纳地块的演化及其与Rodinia 超大陆聚合事件的关系。斜长角闪岩的锆石阴极发光图像显示核边结构,获得核部年龄904±4Ma 和边部年龄803~886Ma;片麻状花岗岩的锆石呈自形-半自形,发育岩浆成因的振荡环带,U-Pb 年龄为915±3Ma,表明其形成于新元古代。片麻状花岗岩SiO2=61.85%~67.63%,Mg#=36.9-47.9,Na2O+K2O=4.21%~9.29%,A/CNK=0.89~1.01,属于偏铝质系列。岩石富集轻稀土元素和大离子亲石元素,亏损高场强元素Nb、Ta 和Ti,具弱的Eu 负异常、低的初始Sr 比值和正的εNd(t)值,暗示片麻状花岗岩为年轻的初生地壳物质熔融形成。斜长角闪岩贫硅、Mg#较高,Ni、Cr、Co 含量较高,Zr/Hf、Nb/Ta 和Th/U 值低,具有平坦的稀土元素配分模式,与正常型洋中脊玄武岩相似,具有亏损地幔性质,同时富集大离子亲石元素Rb、Ba、K、Sr 和Pb,亏损高场强元素Nb、Ta、Ti 等,记录了消减带岩浆作用的信息,表明其为活动大陆边缘经过岛弧岩浆抽提的亏损地幔源区发生重新熔融形成。结合区域上新元古代岩浆事件的纪录,认为额尔古纳地块新元古代早期岩浆事件是Rodinia 超大陆聚合事件的响应,后期变质事件可能与Rodinia 超大陆裂解有关。

       

      Abstract: In this paper, the authors discuss LA-ICP-MS zircon U-Pb ages, major and trace element analyses for Neoproterozoic Bowuleshan amphibolite and gneissic granite on the southeastern margin of Erguna massif, northern Da Hinggan Mountains. The purpose is to elucidate the tectonic history of the Erguna massif and its relationship to the assemblage of the Rodinia supercontinent. Zircons collected from amphibolite exhibit core-rim structure in CL images, the U-Pb dating yielded the age of 904±4Ma for magmatic core and 889~915Ma for metamorphic rim. Zircons collected from gneissic granite are euhedral-subhedral in form, and display fine-scale oscillatory growth zoning in CL images, implying a magmatic origin. The dating age is 915±3Ma. Zircon U-Pb dating demonstrates that these rocks were emplaced during the Neoproterozoic. The Neoproterozoic gneissic granite in the Erguna massif has SiO2=61.85%~67.63%, Mg#=36.9~47.9, Na2O+K2O=4.21%~9.29%, and A/CNK=0.89~1.01, suggesting metaluminous characteristics, Moreover, the Neoproterozoic granitoids are enriched in LREEs and LILEs, and depleted in HREEs and high field strength elements (HFSEs, Nb, Ta, and Ti), with Eu negative anomalies (δEu=0.77~0.80) and low initial Sr isotope ratios and positive values for the εNd(t) value (3.52), which implies that their primary magmas were derived from partial melting of an original crust. In contrast, the Neoproterozoic amphibolite has low SiO2 (45.22%~49.16%), relatively high Mg#, high Ni, Cr, low Zr/Hf, Nb/Ta and Th/ U ratios, and Co content. The flat REE patterns are analogous to features of N-type MORB from the depleted mantle source, but are characterized by enrichment of LILEs (Rb, Ba, K, Sr and Pb) and depletion of HFSEs such as Nb, Ta and Ti; it records magmatic processes of subduction zone, and indicates that amphibolite was derived from partial melting of depleted mantle wedge with igneous activity in continental arcs, on the active continental margin. On such a basis, in combination with the regional characteristics of Neoproterozoic magmatic events, the authors have reached the conclusion that the Early Neoproterozoic magmatic events of the Erguna massif occurred in the context of the assembly of the Rodinia supercontinent, and later metamorphic events might correspond to the breakup of the Rodinia supercontinent.

       

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