桃江锰矿锰帽形成的地球化学过程

THE GEOCHEMICAL PROCESS OF Mn ORE CAPPING IN TAO JIANG MANGANESE DEPOSIT

桃江锰矿区发育有较完整的表生氧化剖面，根据不同深度矿石的结构构造、矿物组合及化学成分特征，将表生氧化剖面分成三个带：氧化矿石带、过渡矿石带和原生矿石带。桃江锰矿原生矿石矿物主要为含锰碳酸盐，表生富集作用包括两个地球化学过程：可溶杂质的溶解淋失作用和锰质的氧化残留作用。在过渡矿石带中，可溶性杂质发生大规模溶解迁移，锰质发生相对富集；氧化矿石带中，碳酸锰氧化成难溶的高价锰的氧化物，使锰质残留下来，形成富锰的氧化帽。过渡矿石中易溶组份的淋失，不仅使矿石品位相对升高，同时可在矿石内部形成大量孔隙，促使矿石内部碳酸锰与大气和水直接接触，加速了矿石中锰质的氧化作用。

The weathering profile is well developed in Taojiang mangamese deposit.According to the difference of structure,mineral assemblage and chemical composition of manganese ore,we divided the weathering profile into three zones:oxidized ore zone,transitional ore zone and primary ore zone.The primary ore minerals of Taojiang deposit are manganiferous carbonates.The enrichmment of manganese in oxidized ore includs two important geochemical processes,ie the solution and loss of soluble impurities,the oxidization and precipitation of manganese.In transitional ore zone,most of soluble materials were moved out,manganese become rich relatively.In oxidized zone,rhodochrositie was oxidized into insoluble pyrolusite,manganese would not be leached out,and the weathering manganese ore capping was developed.In transitional ore zone,impurities not only leached out from the ore,but also formed many pores in the ore,which made it possible that atomsphere contacted with rhodochrosite thus oxidization rate of manganese speeded up.