辽北晚三叠世埃达克质花岗岩年代学、地球化学及地质意义

    Geochronology and geochemistry of the Late Triassic adakitic granites and their geological implications in northern Liaoning province

    • 摘要: 本文对华北克拉通北缘东段辽宁北部开原地区高家店花岗闪长岩岩体进行了岩相学、地球化学、锆石U-Pb定年以及Hf同位素研究,为华北板块北缘晚三叠世岩浆岩活动研究提供了新的资料。锆石U-Pb定年研究表明其形成时间为晚三叠世中期(222~221Ma)。花岗闪长岩地球化学特征表现为高SiO2(67.04-68.65 wt%)、Al2O3(16.25-16.78 wt%)、Na2O(4.57-4.98 wt%)、Sr(368.6-813.2×10-6),低Y(6.9-13.9×10-6)、Yb(0.83-1.17×10-6)以及高Sr/Y值(53.6-74.0),显示典型埃达克质岩石特征。锆石 Hf 同位素分析显示 ε Hf ( t) 值介于 9.51 ~12.24之间,反映了源区亏损的特征。综合地球化学特征和前人研究成果,辽北地区高家店埃达克质花岗闪长岩形成于古亚洲洋闭合后,地壳减薄,伸展环境下,为下地壳拆沉部分熔融的产物。

       

      Abstract: This article conducted petrological, geochemical, zircon U-Pb dating, and Hf isotope research on the Gaojiadian granodiorite intrusion in the northern Liaoning, eastern section of the North edge of the North China Craton. The research provides new data for the study of Late Triassic magmatic activities in the northern margin of the North China plate. Zircon U-Pb dating research shows that it was formed during the Middle Triassic period (222~221Ma). The geochemical characteristics of granodiorite are high SiO2 (67.04-68.65 wt%), Al2O3 (16.25-16.78 wt%), Na2O (4.57-4.98 wt%), Sr (368.6-813.2×10-6), low Y (6.9-13.9×10-6), Yb (0.83-1.17×10-6), and high Sr/Y value (53.6-74.0), showing typical Adakite characteristics. Zircon Hf isotope analysis shows ε Hf (t) values between 9.51 and 12.24, reflecting the depleted source region characteristics. Based on the comprehensive geochemical characteristics and previous research results, the Gaojiadian adakite granodiorite in the northern Liaoning area formed during the extension environment after the closure of the Palaeo-Asian Ocean, with thinning of the crust and partial melting of the lower crust due to crustal thinning and extension.
        

       

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