元谋、牟定地区红土化过程中金的富集机理

ENRICHMENT MECHANISM OF GOLD DURING THE PROCESS OF LATERITIZATION IN THE YUANMOUMOUDING AREA, YUNNAN

在对元谋县猛林沟、牟定县戍街两地红土化剖面的地质特征、次生矿物变化、主要元素及金含量变化进行研究的基础上．探讨了金在红土化剖面上的分布形式和红土化过程中全的活化、迁移及沉淀等的机理。笔者认为，区内保存完整的红土化剖面上存在金的双峰式富集，其中产于铁质硬壳层附近的上部金富集带是由于铁质胶体吸附的结果，而腐泥岩层附近的下部金富集带是由Eh变小、pH变大引起的；氧化还原作用是金活化、迁移、沉淀富集最重要的控制机制。

In terms of the regionally geological setting, the variation of secondary minerals, the analyses of majorand minor elements and gold contents of lateritic profiles in the Yuanmou-Mouding area, Yunnan Province,the model of gold distribution in the profiles and the enrichment mechanism of gold during the process of lateritization were discussed. There is a bimodal-enrichment of gold in the well-preserved profiles in the investigated area. The lower enrichment zone in saprolite resulted from precipitation of instable chloride complexes of gold in alkaline environment and its reduction, and the upper one in ferric duricrus at Xujie resulted from absorption of ferric colloids. Oxidation-reduction is important to the mobilisatio, migration,precipitation, and enrichment of gold during lateritization.