银多金属矿床中黝铜矿族银硫盐矿物的特征及其意义

Characteristics of Silver Sulphosalt Minerals of the Tetrahedrite Group in Silver Polymetallic Deposits and Their Significance

在国内外几个不同成因类型的银多金属矿床内产出的黝铜矿族银硫盐矿物中 ,除朗达矿床见有砷黝铜矿和含银砷黝铜矿外 ,较普遍共同发育有黝铜矿、含银黝铜矿和银黝铜矿 ,而后两者则是最主要或主要的工业银矿物之一。按国际矿物学协会新矿物及矿物命名委员会的矿物命名原则 ,黝铜矿族矿物所含的Fe、Zn、Hg、Cd、Mn等不可作为矿物种的命名元素。蔡家营矿床的含银黝铜矿和银黝铜矿以Fe、Zn含量近似而有别于其余矿床的富Fe贫Zn特征。这些矿床的矿石矿物组合和银硫盐矿物多在主要硫化物之后晶出的产状特征及其化学成分的近似性 ,反映出成矿溶液成分及成矿作用演化的相似性。因此 ,这些银硫盐矿物对矿床成因类型的判别没有指示意义 ,而其赋存状态和种属的查明 ,则为矿床经济评价和矿石选矿流程的确定及银的合理回收 ,提供了重要依据。

Comparative studies of some silver polymetallic deposits (Caijiaying, Xiasai, Lamo, Mount Isa and Langdal) with different genetic types show that they have almost the same ore mineral assemblages such as pyrite+pyrrhotite+galena+Fe_rich and Fe_poor sphalerite+chalcopyrite+arsenopyrite+silver sulphosalt minerals of the tetrahedrite group, and the formation of the main silver_bearing tetrahedrite and freibergite is often later than that of the main ore minerals. Therefore, it may be considered that the silver sulphosalts have not an indicating significance with regard to genetic types of these ore deposits, but reveal the similarity of the ore_forming solution and the ore_forming evolution of the ore deposits. Investigation of silver minerals in these ore deposits shows that the silver_bearing tetrahedrite and freibergite are among the most important or main industrial silver minerals. It must be pointed out that the silver_bearing tetrahedrite and freibergite of the Caijiaying deposit have about the same iron and zinc content, but differ from the Fe_rich and Zn_poor tetrahedrite and freibergite in the Xiasai, Lamo, Mount Isa and Langdal deposits. Moreover, copper and silver in silver sulphosalts of the tetrahedrite group show negative correlation, and their high or low silver content bears no relation to (Fe+Zn) at atomic proportion and Sb/(Sb+As) ratio. However, for the silver sulphosalts of the majority of Cu_Ag_Sb series, As/(As+Sb) ratios are exclusively lower than 0.1, suggesting that these minerals are characterized by richness of Sb and impoverishment of As. Identification of the mode of occurrence of silver in these ore deposits provides an important basis for economic evaluation of the deposits and the flotation of silver minerals in ores.