长江中下游铁帽金矿床的物质组份及金的赋存状态

长江中下游铁帽金矿矿石分为四种类型:蜂窝状矿石、松散土状矿石、胶状矿石及块状矿石.前三者金含量较高.主要载金矿物为针铁矿、水针铁矿、赤铁矿、水赤铁矿、铜的次生矿物(铜蓝、蓝铜矿、辉铜矿、孔雀石)、石英以及残留的原生硫化物等.表生金、银矿物以然自金、银金矿为主,多呈显微金,个别为细粒、中粒金.粒度从原生矿石带→次生金富集带下部→次生金富集带上部有增大的趋势.表生金的成色为828-982,一般为921.大大高于原生带中的金,金、银的赋存状态以吸附状态及以独立的金、银矿物两种形式存在.自然金一般呈包体金、粒间金、裂隙金等形式嵌布于载体矿物中.

ON STUDY OF ORE MATERIAL COMPOSITION AND GOLD OCCURRENCE OF GOSSAN-TYPE GOLD DEPOSITS FROM MID-LOWER REACHES OF YANGTZE RIVER

The Middle and Lower Yangtze area is one of the ipmortant metallogenetic zones of iron, copper, sulfur and gold, and its gossan-type gold ore depesits in Chin are much interesting. Gossan-type gold deposit is of important economical value. By the study of ore chemical composition of gossan-type gold deposits from the middle and lower reaches of Yangtze River, we find that, ore structures of gossan-type gold deposits can be divided into four types. honeycomb, loose soil-sandy, colloidal and massive; the massive has lower gold grade. By meas of microscopic examination and X-ray and differential thermal analyses, the major supergcnc minerals association of gossan-gold ores arc secondary gold, ferrohydrite (goethite, hemetite, etc.), oxides and hydroxides of manganess (chalcophanitc, psilomelans and pyrolussite, etc.), covellite, azurite, malachite, chalcocitc, secondary quartz and remanent primary pyrite ect. Among them the most important gold-carriesr minerals arc geothite, hematite, malachite and secondary quartz, etc. The shapes of secondary gold and silver minerals are more irregular, coarser, and with higher gold fineness in gossan-type gold deposits than those in its provenance. The most secondary gogld granularity is microgold, but individual gold grains are of fine to medium size. The gold fineness of secondary gold is 828-982, generally 921 in Middle and Lower Yangtzc gossan-type gold deposits. Secondary gold and silver as in a absorbed state or independent minerals occur in ores.