我国褐硫砷铅矿的发现及矿物学特征

First discovery of baumhauerite in China and its mineralogical characteristics

运用微区原位X射线衍射及电子探针显微分析等技术在国内首次研究了盘龙铅锌矿床内褐硫砷铅矿。研究表明,褐硫砷铅矿以不规则粒状集合体与重晶石、白云石、闪锌矿、黄铁矿伴生,粒度从几微米到300微米左右,电子探针数据显示该区褐硫砷铅矿的经验式为Pb3.12(As2.81Sb1.13)∑3.95S8.94,与理想式Pb3(As,Sb)4S9一致。微区X射线衍射表明该矿物为三斜晶系,晶胞参数为:a=22.86,b=7.95,c=7.95,α=90.28°,β=96.96°,γ=90.42°,Z=4.该矿物的特点是含较高的Sb,不含Ag,As、Sb呈显著负相关,存在Sb替换As现象,区内褐硫砷铅矿与多种其他硫盐类矿物同时出现,共同指示着低氧逸度、适当硫活度的成矿环境,且硫盐矿物富集处也为矿床富矿段。

By applying technologies like in-situ X-ray micro-diffraction and electron probe microanalysis,this paper conducted the first study on baumhauerite from Panlong Pb-Zn deposit in China.The study showed that baumhauerite occurred as irregular granular aggregate in association with barite,dolomite,sphalerite and pyrite.The diameters of the grains ranged from a few microns to around 300 microns.According to the results of electron microprobe analysis,the empirical formula of baumhauerite in this area was Pb3.12（As2.81Sb1.13）∑3.95S8.94,which was in conformity with the ideal formula Pb3（As,Sb）4S9.In-situ X-ray micro-diffraction revealed that the mineral was of anorthic system with cell parameters as follows：a=22.86,b=7.95,c=7.95,α =90.28°,β=96.96°,γ =90.42°,and Z=4.This mineral was characterized by high Sb,Ag-free and negative correlation between As and Sb,as well as substitution of Sb for As.The occurrence of both baumhauerite and other sulfosalt minerals in this area indicated that the metallogenic environment was featured by low oxygen fugacity and medium sulfuractivity while the concentration spots of sulfosalt minerals overlapped the enriched part of the deposit.