江西吴家金矿床地质地球化学特征

GEOLOGICAL AND GEOCHEMICAL CHARACTERISTICS OF WUJIA GOLD DEPOSIT, RUICHANG COUNTY, JIANGXI PROVINCE

本文通过对江西瑞昌吴家铁帽型金矿床的解剖,建立了一个比较完整的氧化剖面,指出了金、银的富集部位及金、银的赋存状态.并对氧化剖面各亚带的成矿元素、微量元素、稀土以及Eh-pH值进行了分析,其结果表明与次生金的迁移、富集具有明显的相关性.

Wujia deposit in Ruichang county, Jiangxi province, is a gossan-type gold deposit. The typical oxidation section is subdivided into four zones from the upper to the lower: 1. the gossan zone poor in gold (gold leaching subzone); 2. the secondary gold enrichment gossan zone; 3. the oxide-sulfide transition zone; 4. the primary sulfide zone. Secondary gold and silver are usually concentrated in the middle-lower parts of gossan (i.e. the secondary gold enrichment subzone). Au and Ag are mainly occurred as fracture-filling form to which inclusion and interstice form are next. Native gold is in micro -grains. Geochemical evolution of mineralizers, ore-forming elements, trace elements, REE, Eh-Ph values have been measured indicating that enrichment of gold in the oxidation section is coincided with that of Ag,Cu,Bi, HREE, not with Pb, Zn, Mn, Ni etc. The secondary Au enrichment zone can be formed only when (Mn/Fe) 10^(-4)<10, (Ni/Fe)×10^(-4)<1, Ni/Co<0.7,. En-Ph values are different in the four zones, Ph (4.5—7.2) and Eh (0.442——0.543V) in the secondary gold enrichment zone, Ph (5.9——7.8) and Eh (0.48——0.572V) in gold-poor gossan zone, PH (2.1) and Eh (0.623——0.635V) in the primary sulfide xone. Au dissolution is possioly occurred at the begining of the oxidation stage with Ph<3 and Eh>0.6V but Au precipitation and emplacement occurred under Ph>3 and Eh<0.6V.