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    内蒙古东七一山萤石矿微量、稀土元素特征及对成矿物质来源的指示

    Characteristics of trace and rare earth elements in Dongqiyishan fluorite deposit, Inner Mongolia: Indication of ore-forming material sources

    • 摘要:研究目的】东七一山萤石矿是北山成矿带东段与碱长花岗岩有关的超大型萤石矿,矿体主要赋存在碱长花岗岩、大理岩及安山岩中,受北东向、近南北向断裂构造控制。【研究方法】本文在对东七一山萤石矿床地质特征研究基础上,开展矿床萤石和围岩的稀土、微量元素地球化学特征研究。【研究结果】结果显示,萤石微量元素曲线变化趋势一致且相对地壳明显富集Bi、Cd和Mo等高温元素,表明这些萤石样品具有高温成矿及同源性特征。萤石与碱长花岗岩具有相似的稀土元素地球化学特征,10件萤石样品的Y/Ho比值范围为21.02~28.52; La/Ho比值为3.58~15.23;样品均落在Tb/La-Tb/Ca图解的热液成因区;萤石的Sm/Nd比值为0.26~0.42,碱长花岗岩的的Sm/Nd比值为0.30~0.33; δEu值为0.60~0.64,平均值为0.62,表现为显著的负异常; δCe值为0.89~0.94,平均值为0.91,显示弱的负异常。【结论】结合矿床地质特征,认为东七一山萤石矿床为中高温岩浆热液脉状萤石矿床,属于区内与碱长花岗岩有关的钨锡稀有萤石成矿系统的产物,成矿流体以岩浆热液为主,成矿物质F主要来源于深部碱长花岗岩大岩体,Ca主要来源于大理岩地层。

       

      Abstract: This paper is the result of mineral exploration engineering. Objective The Dongqiyishan fluorite deposit is a super-large fluorite deposit, which is related to alkali feldspar granite in the eastern part of the Beishan metallogenic belt. The orebodies are hosted in alkali feldspar granite, griotte and andesite, which are controlled by the rupture and fracture zones near SN or NE dipping. Methods On the basis of studying the geological characteristics of Dongqiyishan fluorite deposit, carry out the studies of rare earth and trace elements geochemistry of fluorite and wall rocks in the fluorite deposit. Results The results show that the trace elements curves in fluorites are consistent, and obviously enriched in high-temperature elements such as Bi, Cd and Mo relative to the crust values, indicating that these fluorite samples have the characteristics of high temperature mineralization and homology. Fluorites and alkali feldspar granites have similar geochemical characteristics of rare earth. The Y/Ho ratios of 10 fluorite samples are ranging from 21.02 to 28.52, the La/Ho ratios ranging from 3.58 to 15.23. The samples all falling into the hydrothermal region of Tb/La-Tb/Ca diagram, except one close to the sedimentary. The Sm/Nd ratios of fluorites ranging from 0.26 to 0.42, and the Sm/Nd ratios of alkali feldspar granites ranging from 0.26 to 0.42. The δEu vaule ranging from 0.6 to 0.64, and the δCe vaule ranging from 0.89 to 0.94. Conclusions Combined with the geological characteristics of the deposit, It is considered the genetic type of the deposit is medium-high temperature magmatic hydrothermal filled type, which belongs to the tungsten-tin-rare -fluorite metallogenic system related to alkali feldspar granite in the area. The ore-forming fluid of Dongqiyishan fluorite deposit is mainly magmatic hydrothermal. The ore-forming material F mainly comes from the deep alkali feldspar granite body, and the Ca mainly comes from the marble strata.

       

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