金矿床中毒砂标型特征及金的赋存状态——以湖南金矿床为例

湖南含砷金矿资源储量大，分布广，类型多.矿床中的砷矿物主要为毒砂，几乎所有金矿床中的毒砂都含Au（一般120×10^-6~250×10^-6），且比共生的黄铁矿含Au量高2~5倍，甚至1个数量级以上.毒砂中金的分布率高达64.3%~94.05%.毒砂的生成期有早、晚2期.化学成分为富S亏As型，并以富含微量元素Sb（Se）、Ni、Co而贫Mn及晶胞参数a₀值增大等为标型特征.大多数含Au毒砂均含有相当数量的“不可见金”，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”多呈纳米级微细粒状存在.

TYPOMORPHIC CHARACTERISTICS OF ARSENOPYRITE IN GOLD DEPOSIT AND OCCURRENCE OF GOLD: A case study of gold deposits in Hunan Province

As-bearing gold deposits in Hunan Province are broadly distributed,with large reserves and multiple types. The main As mineral is arsenopyrite,which in most of gold deposits contains Au (generally 120×10-6 to 250×10-6). The Au content in arsenopyrite is two to five times higher than that in the coexisting pyrite or more. The Au distribution rate in arsenopyrite is up to 64.3%-94.05% . The arsenopyrite was formed in two stages. It is chemically enriched in S and depleted in As,with rich Sb(Se),Ni and Co,poor Mn,and increased of unit cell parameter(a0). Most of the Au-bearing arsenopyrite contains invisible gold,which cannot be found even by electron microprobe. The invisible Au in arsenopyrite mostly occurs as nanometer fine grains.