金矿床中毒砂标型特征及金的赋存状态

THE ARSENOPYRITE TYPOMORPHIC CHARACTERISTICS AND AU OCCURRENCE STATE IN THE GOLD DEPOSIT

几乎所有金矿床中的毒砂都含Au,而和黄铁矿一样都是"不可见金"的主要载体矿物。不可见Au通常优先富集于毒砂中。毒砂中的Au含量比共生的黄铁矿Au含量高2～5倍,甚至高1个数量级以上,Au的分布率亦相当高。含Au毒砂一般为自形晶、半自形晶,长柱状、板柱状以及菱柱状等。化学成分为富硫贫砷型,并以富含微量元素Sb和Ni、Se以及显微硬度偏低,晶胞参数α0值增大为特征。大多数含Au毒砂的光片没有显微Au存在,即使利用电子探针也难以发现。初步认为毒砂中的"不可见金"大多数是以纳米级微细粒状存在。

The arsenopyrite in almost all Au deposit bears gold. And it is the main bearing mineral of 'invisible gold', same as the pyrite. The invisible gold is usually concentrated in arsenopyrite in preference to any other. The Au in arsenopyrite is 2-5 times even one order of magnitude highter than that in pyrite and the Au distribution ratio is also very high. The Au-bearing arsenopyrite is generally euhedral, subhedral, long-prismatic, plate-prismatic and prismatic, etc. The chemical composition of it belongs to the type rich in S and poor in As and is characterized by richness in trace elements Sb, Ni, Se, low microhardness and the increased cell parameter a0. There is not microscopic Au in most polished sections with arsenopyrite, which is difficult to be discovered even by microprobe analysis. It is tentatively believed that the 'invisible gold'in arsenopyrite is mainly in the micrograined state of nanometer order.