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    完达山地块跃进山矽卡岩型铜金矿区酸性侵入岩锆石U-Pb年龄、地球化学特征及成因

    Zircon U-Pb age, geochemistry and genesis of acid intrusive rocks in the Yuejinshan skarn type copper-gold deposit, Wandashan block

    • 摘要: 跃进山小型矽卡岩型铜金矿床位于完达山地体西南部,矿体主要赋存于矽卡岩、花岗斑岩及其构造裂隙中,呈扁豆状或脉状。本文对矿区花岗闪长岩和花岗斑岩进行锆石U-Pb年代学和岩石地球化学研究,以了解矿床形成时代、成岩(矿)构造背景及矿床成因。测年结果表明,花岗斑岩和花岗闪长岩成岩年龄分别为(115.8±1.0)Ma和(126.9±1.7)Ma,铜金矿化时代与花岗斑岩成岩时代基本一致,为早白垩世晚期。岩石地球化学研究表明,花岗闪长岩属过铝质钙碱性系列岩石,稀土配分模式图为轻稀土富集,重稀土亏损,具较强的铕负异常,无铈异常,岩浆主要来源于壳源物质;花岗斑岩属过铝质钙碱性系列岩石,轻稀土富集,重稀土亏损,具弱铕负异常,无铈异常,相对富集大离子亲石元素(Rb、Ba、K、Sr)和不相容元素(U、Th),亏损高场强元素(Ta、Nb、P、Ti)和HREE,岩浆来源于壳幔物质混合源区,形成于碰撞后构造环境,成岩成矿作用与太平洋板块强烈俯冲作用后的伸展体制密切相关。

       

      Abstract: Located in the southwest part of the Wandashan block, the Yuejinshan copper-gold deposit is a skarn type deposit, and its orebodies are hosted in skarns, granite porphyries and the tectonic fractures. The orebodies show lenticular or veined forms. LA-ICP-MS zircon U-Pb dating and geochemical data are reported for granite porphyries and granodiorites in the Yuejinshan coppergold deposit in order to constrain its formation time, petrogenesis and the minerogenetic geotectonic background. The zircon LAICP-MS U-Pb age dating results show that the petrogenic ages of granite porphyries and granodiorites respectively are(115.8±1.0) Ma and(126.9 ±1.7)Ma respectively, and the copper-gold mineralization age is consistent with petrogenetic age of granite porphyry. Geochemical study indicates that the granodiorites are peraluminous calc-alkaline granite. The chondrite-normalized REE patterns of granodiorites display LREE enrichment and HREE depletion, with a distinct Eu anomaly, and their magma came from the lower crust. The granite porphyries belong to peraluminous calc-alkaline granite. The REE patterns show that granite porphyries exhibit pronounced LREE enrichment and HREE depletion, enrichment of large-ion lithosphile elements (Rb, Ba, K, Sr) and incompatible elements (U, Th), and depletion of high field-strength elements (Ta, Nb, P, Ti) and HREE. The magma of granite porphyries came from crust-mantle mixture, and the copper-gold deposit formed in the collision of post-collision extensional tectonic setting. The metallogenic materials formed intermediate-acid magma heat source, and magmatism and mineralization took place in the extensional tectonics after the Pacific plate subduction.

       

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