红色粘土型金矿成因矿物学特征

CHARACTERISTICS OF GENETIC MINERALOGY OF RED-CLAY TYPE OF GOLD DEPOSIT

红色粘土型金矿是表生湿热气候条件下含金基岩经不彻底的红土化作用而形成的一种新类型金矿床。以云南上芒岗、贵州老万场和湖北蛇屋山金矿为例 ,对红色粘土型金矿的成因矿物学特征进行了研究。结果表明 ,表生成因的高岭石 +伊利石 +针铁矿 +自然金组合可作为该类型金矿的标型矿物组合 ;高岭石的 ( 0 0 1 ) X射线衍射峰半高宽可作为标型特征反映介质的酸性程度和硅、铝的饱和程度 ,进而指示金的富集部位 ;针铁矿中的铝置换率可反映红土化程度和粘土中的含水量 ,进而指示古潜水面的位置 ;金的粒度、形态和赋存状态可反映金的迁移富集程度和富集机制。

As a new type of gold deposit, the red clay type of gold deposit developed from gold bearing bedrock by incomplete lateritization under humid and wet climate is one of the front issues studied in economic geology recently. The characteristics of genetic mineralogy of this type of gold deposits such as Shangmanggang of Yunnan, Laowanchang of Guizhou and Shewushan of Hubei are studied in this paper.The results show that the supergene mineral assemblage of kaolinite + illite + goethite + native gold is the typomorphic mineral assemblage of the red clay type of gold deposit. The width at half high of (001) X ray diffraction peak of kaolinite can operate as typomorphic peculiarity to show the acidity and Si and Al saturation in weathering fluid,and further indicate the enrichment location of gold. Al substitution of goethite shows the lateritization degree and the water content in red clay profile, and further indicates the position of ancient groundwater table. The granularity, morphology and existent states of gold can imply the migration and enrichment degree and the reprecipitation mechanism of gold.