云南个旧锡多金属矿集区稀散元素铟的分布富集特征

Indium Distribution and Enrichment Characteristics in Gejiu Sn-Polymetallic Orefield Area in Yunnan Province

以云南个旧锡多金属矿集区不同类型岩矿石为研究对象,应用等离子体质谱、岩矿鉴定及高精度电子探针等分析手段,研究稀散元素铟(In)在花岗岩、沉积岩和变质岩中的分布特征及其在矿石矿物中的富集规律。结果显示,斑状黑云母花岗岩中In与Sn存在明显的同消共长关系,In主要分布在提供成矿物质来源的岩体中;斑状黑云母花岗岩中In的富集系数最大,沉积岩中In主要富集在个旧组赋矿地层的矽卡岩中,变质岩中In无明显富集;矿区层间氧化物矿石中In高度富集,而原生硫化物矿石中In仅微弱富集;矿石中元素In与Sn、Zn具有正相关关系,电子探针分析矿石矿物锡石中未检测到In,但在闪锌矿中检测到大量In的存在,表明沉淀成矿过程中,In并不进入锡石中,而是主要进入到闪锌矿等硫化物矿物中。

Different types of rocks from the Gejiu Sn-polymetallic orefield in Yunnan province were studied for the indium(In)distribution features in the granite,sedimentary and metamorphic rocks.The In enrichmentregularity in ore minerals was also analyzed via plasma mass spectrometry,petrographic identification and high-precision electron probe microanalysis(EPMA).Our results show that In content in the granites has clear relation with Sn,which plays an important role in the In enrichment.Indium is distributed in the source of ore-forming materials in the intrusion,and the In enrichment coefficient is higher in porphyritic biotite granite.The indium is mainly concentrated in the skarn of Gejiu Group limestone ore host,and there is no distinct In enrichment in metamorphic rocks.The indium is highly concentrated in the interlayer oxide ore but only weakly enriched in the primary sulfide ore,and In has positive correlation with Sn and Zn in the two types of ores.Indium is detected by EMPA in sphalerite but not in cassiterite,which indicates that In enters sphalerite and other sulfide minerals rather than cassiterite during ore precipitation.