川西北马脑壳金矿床载金矿物特征及其成因意义

四川西北部九寨沟县的马脑壳金矿床的主要载金矿物有黄铁矿、毒砂、辉锑矿、雄黄和褐铁矿。有两种不同类型的黄铁矿 ,分别形成于沉积成岩期和热液成矿期。前者具草莓状结构 ,后者以环带结构为特征。粒度小晶形不规则的黄铁矿具有较高的含金量 ,而晶形完整和晶粒较大者含金量相对较低。辉锑矿和雄黄以细粒浸染状分布者含金量高 ,而以块状产出者金含量低甚至不含金。褐铁矿为表生氧化作用的产物 ,含有显微 -超显微单质金。对马脑壳金矿床载金矿物的研究表明 ,矿床形成于三个成矿期 ,即沉积 -成岩期、热液成矿期、表生氧化期 ,三个成矿期之间具有内在的联系。热液成矿期含矿流体的演化具有阶段性特征 ,流体的物理化学性质迅速变化有利于金的沉淀富集

CHARACTERISTICS OF THE GOLD-BEARING MINERALS AND THEIR SIGNIFICANCE TO THE ORE GENESIS OF THE MANAOKE GOLD DEPOSIT, NORTHWESTERN SICHUAN

The Mamaoke gold ore deposit is located in the Jiuzhaigou County, northwestern Sichuan Province. It is one of the important ore deposits in the triangle area of Shanxi Gansu Sichuan Provinces. The main gold bearing minerals include pyrite, arsenopyrite, stibnite, realgar, and limonite. There are two types of pyrite, which formed in the sedimentary diagenetic period and hydrothermal period. The former typically has framboidal texture, while the latter shows zoned texture . The gold content of pyrite with smaller grain size and anhedral shape is higher than that of those with larger grain size and euhedral shape. Stibnite and realgar occurring as micro disseminates normally have higher content of gold than those of massive ores. Limonite, formed in the supergenetic oxidation period, contains micro to super micro native gold. Studies of the gold bearing minerals in the Manaoke gold deposit show that the deposit formed in three different periods: sedimentary diagenetic period, hydrothermal period, and supergenetic oxidation period. The evolution of ore bearing hydrothermal fluids is characterized by stages. Sharp changes in physical chemical conditions of the ore bearing fluids are favorable for the gold precipitation.