新疆哈密新发现的铷矿床成因:来自矿床地质和地球化学的证据

Genesis of the newly discovered rubidium deposit in Hami,Xinjiang:evidence from deposit geology and geochemistry

新疆哈密新发现的张宝山铷矿床是近年东天山地区典型的超大型稀有金属矿床。为研究花岗岩成矿作用、指导东天山地区稀有金属找矿工作,在详实的野外地质调查的基础上,开展了岩相学、矿物学和岩石地球化学研究,揭示矿床成因。地球化学研究表明,岩体高硅、富碱,且Na_(2) O>K_(2)O、高F(>2%)、高Rb,∑REE含量介于21.4×10^(-6)~190.4×10^(-6)之间,具强烈的负Eu异常特征。稀土元素配分模式具“M”型四分组效应。微量元素以富含Li、Rb、Cs、W、Sn、Nb、Hf、Th、Ga等稀有、稀散元素为特征,为稀有金属矿化提供了物质基础。岩浆演化不同相带中F含量高,且寄主于云母中,F与稀有金属元素形成络合物迁移到岩体中。电子探针分析表明,铷主要以类质同象赋存在造岩矿物钾长石及白云母中,且矿脉中Rb的品位与这2种矿物含量呈正比,含铷岩体先后侵入淡色花岗岩、含天河石花岗岩、天河石花岗岩、含黄玉天河石花岗岩、黄玉钠长石花岗岩、含天河石花岗伟晶岩脉。越演化到晚期,Rb品位越高。综合分析认为,张宝山铷矿经历了多阶段的演化过程,属岩浆结晶分异和交代成因,类型属岩浆-热液型矿床,形成时代为印支晚期。

The newly discovered Zhangbaoshan rubidium deposit,located in Hami,Xinjiang,is a typical super-large,rare metal deposit in the East Tianshan area.Based on geological field surveys,mineralogy petrology,and geochemistry studies were conducted to study the granite mineralization and guide the prospecting of rare metals in this region to reveal the ore genesis.Research around the geochemical analysis of major and trace elements,rare earth elements(REE)shows that the petrochemical composition of rock mass was characterized by high silicon,alkali rich,Na_(2) O>K_(2)O,high F(>2%),high Rb,and∑REE contents ranging from 21.4×10^(-6) to 190.4×10^(-6),with strong negative Eu anomaly.The distribution pattern of lanthanon has an"M"type REE tetrad effect.The trace elements are characterized by rich rare and scattered elements such as Li,Rb,Cs,W,Sn,Nb,Hf,Th,and Ga,which provide a material basis for rare metal mineralization.Element F,hosted in mica,has a high content in different phase bands of the magmatic evolution stage.F and rare metal elements form a series of complex compounds,which will migrate to the rock mass.Electron probe analysis indicates that element Rb presents isomorphism in the rock-forming minerals potassium feldspar and muscovite.The concentration of Rb in the veinis positively connected with the amount of potassium feldspar and muscovite.The rubidium-bearing rock body successively invaded the light granite,amazonite-bearing granite,amazonite granite,topaz-bearing amazonite granite,topaz albite granite,and amazonite-bearing granite pegmatite veins.The comprehensive analysis argues that the Zhangbaoshan rubidium deposit experienced multi-stage evolution and belongs to the magmatic crystallization and differentiation along with the metasomatismgenesis.The deposit type is a magmatic-hydrothermal deposit,whose formation era is in the late Indosinian period.