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    北淮阳东段板桥岩体地球化学特征及同位素年代学研究

    Geochemical characteristics and isotope chronology study of the Banqiao granodiorite in the eastern part of North Huaiyang

    • 摘要: 位于北淮阳东段的板桥岩体为凌家冲杂岩体的重要组成部分,岩石类型为花岗闪长岩。该岩体偏铝质、富碱、高钾、贫钙,属于高钾钙碱性系列岩石; 稀土元素含量中等,(La/Yb)N与HREE/LREE值较高,重稀土元素相对亏损,铕弱负异常,属轻稀土元素富集型; 大离子亲石元素Rb、Ba、K、La、Nd富集,高场强元素Nb、Ta、Ti、P亏损。通过LA-ICP-MS锆石U-Pb定年,获得板桥岩体206Pb/238U年龄为129.0±1.9 Ma,表明该岩体形成于燕山晚期,是早白垩世岩浆活动的产物。板桥花岗闪长岩形成于后碰撞的伸展构造环境。

       

      Abstract: The Banqiao granodiorite in the eastern part of North Huaiyang, which consists mainly of granodiorite, is an important component of the Lingjiachong complex. The Banqiao granodiorite is characterized by meta-aluminum, rich alkali, high K and low Ca,suggesting that it belongs to the high K calc-alkalic series. Medium REE content, high(La/Yb)N and HREE/LREE ratios, distinct HREE depletion relative to LREE, and weak negative Eu anomalies indicate that the Banqiao granodiorite belongs to a LREE-enriched plutonic rock. Large-ion lithophile elements(LILE), such as Rb, Ba, K, La and Nd, are significantly enriched, while high field strength elements(HFSE), such as Nb, Ta, Ti and P, are depleted. LA-ICP-MS zircon U-Pb dating yields a 206Pb/238U age(129.0±1.9 Ma)for the Banqiao granodiorite, indicating that it formed in the Late Yanshanian and likely was the product of the Early Cretaceous magmatic activity. Based on the regional geological background of the study area and geochemical tectonic environment discrimination in this study,it can be concluded that the Banqiao granodiorite formed in the post-collision extensional tectonic setting.

       

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