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    江南造山带东段桃岭岩体的地球化学特征及其成因

    Geochemical features and origin of Taoling pluton, eastern Jiangnan orogen

    • 摘要: 提要:位于江南造山带东段赣东北地区的桃岭岩体地球化学特征总体表现为高钾钙碱性系列,弱过铝质-强过铝质,高Mg#值。桃岭岩体富集轻稀土和大离子亲石元素,亏损高场强元素,具弱的Eu负异常(δEu=0.62~0.81)(样品TL-1除外δEu=0.47)。锆石LA-ICPMS U-Pb定年获得桃岭岩体的成岩年龄为早白垩世(140±1) Ma。岩体初始87Sr/86Sr为0.7131~0.7141,εNd(t)值为-7.43~ -6.71。结合前人研究,笔者认为早白垩世(约140 Ma)交代的地幔发生部分熔融,幔源岩浆底侵,使地壳深处(至少40 km)的变质沉积岩发生部分熔融,并且与少量的幔源岩浆发生了岩浆混合作用,形成了桃岭岩体。

       

      Abstract: Abstract:Taoling pluton is located in northeast Jiangxi Province in the eastern part of Jiangnan orogen. The pluton is characterized by high potassium calc alkaline series, weakly peraluminous - strongly peraluminous nature, and high Mg#. Taoling pluton is enriched in LREE and LREE, and depleted in HFSE, with weak negative Eu anomalies (δEu=0.62-0.81) (except for sample TL-1, whose δEu is 0.47). Zircon LA-ICPMS U-Pb dating shows that the pluton intruded at 140±1 Ma. The initial 87Sr/86Sr ratios and εNd(t) of the pluton are (0.7131-0.7141) and (-7.43 - -6.71), respectively. Combined with previous studies, the authors hold that the mafic magmas ascended from the metasomatized mantle and heated the lower crust, triggering partial melting of metasedimentary basement in the depth (>40 km) to form Taoling pluton, with the addition of relatively small amounts of mantle-derived materials.

       

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