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    北淮阳东段山七岩体地球化学特征、LA-ICP-MS 锆石U-Pb年龄及地质意义

    Geochemical characteristics and LA-ICP-MS zircon U-Pb geochronology of the Shanqi intrusion in eastern North Huaiyang and their geological significance

    • 摘要: 北淮阳东段山七岩体岩性为石英闪长岩,SiO2、Al2O3含量中等,富碱质,Mg#低,具偏铝质碱性系列岩石特征。稀土元素含量中等,LaN/YbN值和LREE/HREE值均较大,HREE相对于LREE明显亏损,具较弱的Ce负异常,轻稀土相对富集,分馏较明显,重稀土分馏不明显。岩石富集大离子亲石元素(LILE)Rb、Ba、K和高场强元素(HFSE)Zr、Hf、Y,明显亏损Nb、Ta、Ti、P、U。通过LA-ICP-MS锆石U-Pb定年,获得山七岩体206Pb/238U年龄为128.2±3.3Ma,属早白垩世早期。主量元素及微量元素地球化学特征均表明山七岩体岩浆来源于地壳,受地幔物质混染。

       

      Abstract: The Shanqi quartz diorite in eastern North Huaiyang is characterized by medium contents of SiO2 and Al2O3, and enrichment in alkali and low Mg#, suggesting that it belongs to metaluminous alkaline series. It has high LaN/YbNand LREE/HREE ratios, and is depleted in HREE relative to LREE, with a weak Ce negative anomaly. Relative enrichment in LREE shows high fractionation but HREE has no distinct fractionation. It is also enriched in LILE such as Rb,Ba,K and HFSE such as Zr,Hf,Y,but depleted significantly in Nb,Ta,Ti,P and U. LA-ICP-MS zircon U-Pb dating yields a 206Pb/238U age of 128.2 ± 3.3 Ma for the Shanqi intrusion, implying that it is early Early Cretaceous in age. The geochemical characteristics of the major and trace elements indicate that the Shanqi intrusion derived from the crust but contaminated with the mantle.

       

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