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    晋南地区孤峰山岩体年代学、地球化学特征及地质意义

    Geochronlogy, geochemistry and geological implications of the Gufengshan granite in the southern Shanxi Province

    • 摘要: 早白垩世岩浆作用是研究华北克拉通破坏的理想窗口,但对其中部地区的研究程度明显偏低。文章选择晋南地区孤峰山岩体开展了锆石U-Pb年龄和地球化学特征分析。结果表明,孤峰山岩体由石英二长闪长岩组成,成岩年龄为(133.0±0.5)Ma,形成于早白垩世早期。地球化学特征上,岩体具有全碱含量中等(K2O+Na2O含量为7.11%~7.40%)、富钠(Na2O含量为4.17%~4.38%)、准铝质(A/CNK为0.80~0.97)的特点,属高钾钙碱性系列I型花岗岩;富集大离子亲石元素(如Rb、Ba、K)及Th元素,亏损高场强元素(如Ta、Nb、P、Ti),稀土元素总量中等((152.76~199.85)×10−6),负铕异常不明显(δEu为0.93~0.97),具有明显陆壳成分特征。结合区域地质背景及本次研究成果,认为岩体形成与华北克拉通破坏对中部地区的影响有关。

       

      Abstract: The early Cretaceous magmatism is an ideal window for studying the mechanism of North China Craton destruction, but the research in its central area is obviously shallow. This paper studied zircon U-Pb dating and geochemical characteristics of the Gufengshan granite pluton. The results show that the granite pluton is mainly composed of quartz monzodiorite. The weighted average age is (133.0±0.5) Ma, suggesting that it was emplaced in the early stage of the Early Cretaceous. The geochemistry indicates that it is characterized with medium total alkali content(K2O+Na2O=7.11%~7.40%), Na richness (Na2O =4.17%~4.38%), and metaluminous rock (A/CNK=0.80~0.97), belonging to the high-K calc-alkaline I-type series. It is also characterized with the enrichment of large ion lithophile elements (Rb, Ba, K) and Th, depletion in high field-strength elements (Ta, Nb, P and Ti), medium rare earth element contents (ΣREE= (152.76~199.85)×10−6), and weak negative Eu anomalies (δEu=0.93~0.97), which is geochemically similar to the continental crust composition. Combined with local geological setting and research findings this time, it indicated that the orogenesis of Gufengshan granite pluton was related to the tectonic influence of the North China Craton’s destruction on its central area.

       

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