新疆西天山智博铁矿床地球化学及同位素特征

    Isotope geochemical characteristics of the Zhibo iron deposit in western Tianshan Mountains, Xinjiang

    • 摘要: 智博铁矿位于新疆西天山阿吾拉勒铁成矿带东段,矿体以层状、似层状、透镜状产出于下石炭统大哈拉军山组玄武质安山岩中。智博铁矿成矿作用主要划分为岩(矿)浆期和热液期2个成矿期次,包括3个成矿阶段:磁铁矿+透辉石阶段、磁铁矿+绿帘石+钾长石阶段和石英+硫化物+碳酸盐阶段。智博铁矿地球化学特征表明,其成矿构造背景为早石炭世南天山洋向伊犁板块俯冲形成的岛弧环境;火山岩与磁铁矿石具有相同的物质来源,均来源于受俯冲带流体交代的亏损地幔楔部分熔融形成的玄武质岩浆。智博铁矿为岩浆(主要)-热液(次要)复合型矿床,受俯冲流体交代的亏损地幔楔部分熔融形成富铁的玄武质岩浆,岩浆沿深大断裂上侵形成早期火山岩,上侵过程中由于物理化学条件的改变在不混溶作用下形成铁矿浆,铁矿浆侵入早期火山岩地层形成岩浆期磁铁矿体;后期富铁的岩浆或矿浆热液使围岩发生矿化与蚀变,形成热液期磁铁矿体。

       

      Abstract: The Zhibo iron deposit is located in eastern Awulale metallogenic belt of Western Tianshan Mountains.The orebodies of the Zhibo iron deposit are hosted in basaltic andesite of the Lower Carboniferous Dahalajunshan Formation in layered, quasi-lamellar and lenticular forms.The mineralization process of the Zhibo iron deposit can be divided into two metallogenic periods, i.e., magmatic period and hydrothermal period, which consist of three metallogenic stages:magnetite + diopside, magnetite + K-feldspar + epidote and quartz + sulfide + carbonate stages.The geochemical characteristics of the Zhibo iron deposit show that its metallogenic tectonic setting was an island-arc environment.The geochemical data support derivation of volcanic rock and magnetite ore from basaltic magma formed by partial melting of depleted mantle wedge altered by fluids in subduction zones, with the same material source.The Zhibo iron deposit is a magmatic(mainly)-hydrothermal(subordinately) deposit.The basaltic magma intruded upward along deep fault and formed the primitive volcanic rock.Because of the change of physical-chemical conditions during its intrusion, the iron ore slurry was liquidized from the basaltic magma.The intrusion of the iron ore slurry into primitive volcanic rock might have been responsible for the formation of the magmatic type magnetite orebody and the alteration of the surrounding rocks by the residual magmatic hydrothermal fluid for the formation of the hydrothermal type magnetite orebody.

       

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