扬子西缘中元古代晚期双峰式岩浆岩年代学及其构造意义
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P534.3;P588.1;P597+.3

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陕西地调融媒体平台建设与服务研究项目(202006)


Chronology of late Mesoproterozoic bimodal igneous rocks in the western margin of the Yangtze Block and its tectonic significance
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    摘要:

    扬子西缘中元古代晚期岩浆岩对揭示扬子陆块构造演化过程及其与Rodinia超大陆的关联至关重要。本文对扬子西缘撮科地区斜长角闪岩和花岗岩进行了锆石U-Pb年龄、全岩主微量元素和Hf-Nd同位素分析。锆石U-Pb定年结果显示花岗岩和斜长角闪岩年龄分别为1 160.5 Ma和1 170.2 Ma,属于双峰式岩浆岩组合。斜长角闪岩属于拉斑玄武岩系列,富集大离子亲石元素和轻稀土元素,无明显的Nb和Ta异常,具有洋岛玄武岩(OIB)特征,具有正的εNd(t)和εHf(t)值,来自软流圈地幔的部分熔融。花岗岩具有较高的Fe/Mg和Ga/Al值,属于A型花岗岩系列,具有正的εNd(t)和εHf(t)值,表明其来自新生地壳的部分熔融。地球化学特征表明撮科斜长角闪岩和花岗岩形成于被动大陆边缘板内裂谷盆地,与格林维尔造山运动无关。结合前人研究成果,认为扬子西缘中元古代晚期属于被动大陆边缘裂谷环境,扬子陆块应位于超大陆的边缘位置。

    Abstract:

    The late Mesoproterozoic igneous rocks in the western margin of Yangtze Block are important for understanding the tectonic evolution and its role in reconstruction of the Rodinia supercontinent. In this paper, we report new zircon U-Pb ages, whole rock major and trace elements, and Nd-Hf isotopic analyses of the plagioclase amphibolites and granites in the Cuoke area on the western margin of the Yangtze Block. Geochronological results show that the granites and plagioclase amphibolites have similar late Mesoproterozoic zircon U-Pb ages of 1 160.5 Ma and 1 170.2 Ma, constituting a bimodal igneous assemblage. The plagioclase amphibolites belong to the tholeiite series and characterized by enrichment in LREEs and LILEs, and have OIB-like affinities with No obvious Nb and Ta anomalies, and with positive εNd(t) and εHf(t) values, indicating that they were derived from the asthenospheric mantle source. The granites belong to the peralkaline A-type series and characterized by have high Fe/Mg and Ga/Al ratios, with positive εNd(t) value and εHf(t) values, indicating that they were derived partially from the newly formed crust. Geochemical characteristics indicate that the Cuoke plagioclase amphibolite and granite were likely formed in an intra-plate rift basin on the passive continental margin, and are unrelated to the Grenvillian Orogen in the western Yangtze Block. Based on previous research results, it is believed that the western margin of the Yangtze Block during the late Mesoproterozoic belonged to a passive continental margin rift environment, and the Yangtze Block was in the peripheral rather in the center in the configuration of Rodinia.

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吴迪,康璐燕,安楚, 2025. 扬子西缘中元古代晚期双峰式岩浆岩年代学及其构造意义[J]. 岩石矿物学杂志, 44(5):1051~1070.
WU Di, KANG Lu-yan, AN Chu, 2025. Chronology of late Mesoproterozoic bimodal igneous rocks in the western margin of the Yangtze Block and its tectonic significance[J]. Acta Petrologica et Mineralogica, 44(5): 1051~1070.

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  • 收稿日期:2024-08-11
  • 最后修改日期:2025-05-10
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  • 在线发布日期: 2025-09-25
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