四川雪宝顶W-Sn-Be矿床中矿物化学组成及矿床成因

雪宝顶矿床位于四川省的松潘甘孜造山带中,以出产大颗粒含W-Sn-Be-F-P的矿物而闻名,前人对该矿床已经开展了大量的研究,但缺乏对粗粒矿物的主次痕量元素研究。本次研究采用X射线荧光光谱(XRF)、电子探针(EMPA)和电感耦合等离子体质谱(ICP-MS)技术对矿床中各矿物的主次痕量元素进行测试分析。结果显示,雪宝顶矿床中的绿柱石、白钨矿、锡石、白云母、萤石、磷灰石、电气石,除富含W、Sn、Be、Na、K、Ca等主要成矿元素外,还富集Li、Rb、Cs等碱金属元素和F、B、P等挥发份。其中,雪宝顶绿柱石中富含Li(3484~4243μg/g)、Rb(39.3~71.1μg/g)、Cs(2955~3526μg/g);白云母中Li、Rb和Cs元素含量分别高达4243μg/g、72.3μg/g和3526μg/g;磷灰石中除主量元素P外,F(4.48%~5.21%)含量相对较高;电气石中的B含量高达30990~32880μg/g。雪宝顶矿床中的花岗岩岩体W、Sn、Be、Li、Rb、Cs、F、B、P等元素相对富集,但CaO含量(0.46%~0.82%)相对较低。其中Li、F、B、P等元素对成矿元素在成矿流体内的富集起到了极大的促进作用。矿区内大理岩是一种富Ca的方解石大理岩,为成矿提供了大量的Ca元素,有利于粗粒矿物的大规模沉淀。因此,粗粒矿物中的W、Sn、Be、Li、Rb、Cs、F、B、P等元素主要来源于原始岩浆流体,大理岩地层为粗粒矿物提供了大量的Ca元素。

Chemical Composition of Minerals in Xuebaoding W-Sn-Be Deposit, Sichuan Province: Constraints on Ore Genesis

BACKGROUND:The Xuebaoding deposit,located in the Songpan—Ganzi orogenic belt,Sichuan Province,is famous for coarse-grained W-Sn-Be-F-P-bearing minerals.Many studies have been carried out on this deposit,but there is a lack of research on major and trace elements of coarse-grained minerals.OBJECTIVES:To obtain major and trace element composition of minerals and provide constraints on ore genesis of the Xuebaoding deposit.METHODS:In this study,X-ray fluorescence spectrometry(XRF)and electron probe microanalysis(EMPA)were used to analyze the major elements of minerals in the deposit,and the trace elements were analyzed by inductively coupled plasma mass spectrometry(ICP-MS).RESULTS:The results showed that beryl,scheelite,cassiterite,muscovite,fluorite,apatite and tourmaline in the Xuebaoding deposit were rich in major ore-forming elements(W,Sn,Be,Na,K,Ca)and alkali metal elements such as Li,Rb,Cs,and volatiles such as F,B,and P.Beryl in the Xuebaoding deposit was rich in Li(3484-4243μg/g),Rb(39.3-71.1μg/g)and Cs(2955-3526μg/g).The content of Li,Rb and Cs in muscovite was as high as 4243μg/g,72.3μg/g and 3526μg/g,respectively.The content of F in apatite and B in tourmaline were 4.48%-5.21%and 30990-32880μg/g,respectively.The granites in the Xuebaoding deposit were relatively rich in W,Sn,Be,Li,Rb,Cs,F,B,P,with relatively low CaO content(0.46%-0.82%).Li,Rb,Cs,F,B,P were conducive to the enrichment of ore-forming elements in fluids.Marble in the mining area was calcite marble,which provided a large amount of Ca for mineralization and was conducive to the large-scale precipitation of coarse-grained minerals.CONCLUSIONS:W,Sn,Be,Li,Rb,Cs,F,B and P in coarse-grained minerals are mainly derived from magmatic fluids,where the marble strata provide a large amount of Ca for coarse-grained minerals.