华北克拉通对Rodinia超大陆裂解的响应——来自贺兰山北段小松山地区辉长岩地球化学、年代学及Hf同位素的新证据

    Response of the North China Craton to the Rodinia supercontinent breakup: New evidence from petrochemistry, chronology and Hf isotope of the gabbro in Xiaosongshan area of northern Helan Moun-tain

    • 摘要: 华北克拉通西缘贺兰山北段小松山地区辉长岩锆石U-Pb年代学、岩石地球化学和锆石Hf同位素的研究结果表明,辉长岩的侵位结晶年龄为835.5±5.3Ma,即形成于新元古代早期,属于板内拉斑玄武岩系列岩石,总体上略富集轻稀土元素、大离子亲石元素Rb、Ba、La,略亏损高场强元素Th、Nb、Zr、Hf等;具有较高的εHft)值(5.83~7.87),其单阶段模式年龄tDM1为1075~1155Ma,两阶段模式年龄tDM2为1176~1289Ma。综合研究发现,辉长岩的原始岩浆起源于中元古代富集型地幔,形成于华北陆块西缘的板内伸展环境,说明华北陆块响应了Rodinia超大陆裂解,也是Rodinia超大陆的一部分。

       

      Abstract: Zircon LA-ICP-MS U-Pb dating, petrochemistry and zircon Hf isotope study of the gabbros from Xiaoshongshan area of the North Helanshan show that the emplacement crystallization age is 835.5±5.3Ma, suggesting early Neoproterozoic. The gab-bros belong to intraplate tholeiite basalt series, and are slightly rich in LREE, rich in Rb, Ba, La, and slightly depleted in HFSE, Th, Nb, Ta, Zr and Hf; Hf isotopic data of the gabbros show high εHf(t) values (5.83~7.87), the single stage model age tDM1 is 1075~1155Ma, and the two stage model age tDM2 is 1176~1289Ma. Comprehensive studies suggest that the magma of gabbros originated from an enriched mantle in the Mesoproterozoic, and was formed in an intraplate extension setting on the western margin of the North China continental blocks. The authors thus infer that this magma event was a response of the North China continental blocks to the breakup of the Rodinia supercontinent. Therefore, it was also a part of the supercontinent.

       

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