赞比亚铜带省铜矿成因分析

中非(赞比亚―刚果(金))沉积型铜矿以其拥有高品位的大型超大型铜、钴矿床和众多的世界级铜矿山而闻名于世。铜矿类型可分为沉积型铜矿、热液脉型铜矿、变质热液型铜矿三类。沉积型铜矿床形成后,受到深部含矿岩浆热液的侵入形成脉状铜矿,可能还有斑岩型铜钼矿的成矿作用,叠加富集原有的沉积型铜矿床。硫同位素结果显示,硫源主要为成岩硫化物和海水硫酸盐的混合硫,受到深源岩浆或岩浆热液叠加改造。沉积型铜矿成矿年龄880~735Ma,后期岩浆热液型铜钼矿成矿年龄为514~502Ma。这些发现对进一步认识总结中非铜矿带上的矿床成因及成矿规律具有重要意义。     

Discrimination of lithogenic and anthropogenic sources of metals and sulphur in soils of the central-northern part of the Zambian Copperbelt Mining District: A topsoil vs. subsurface soil concept

Samples of topsoil together with reference samples of subsurface soil from a depth of 80–90 cm were collected in the central-northern part of the Zambian Copperbelt to distinguish lithogenic sources of metals from anthropogenic contamination of soils caused by fallout of dust from mining operations, flotation ore treatment plants, tailings dams, smelters and slag dumping grounds. The total sulphur, Cu and Co contents were found to be significantly higher in topsoil relative to subsurface soil over a large part of the surveyed area, and Zn, Pb, As and Hg contents showed a definite increase in the close neighbourhood of smelters and in the direction of prevailing winds. This indicates that the increase of these elements in the topsoil is due to anthropogenic activities. The areal extent and degree of anthropogenic contamination of topsoil can be expressed by an enrichment index (EI) based on the average ratio of the actual and median concentrations of the given contaminants. Although the contamination of soil by dust fallout decreases progressively with depth in the soil profile, in areas strongly affected by mining and mineral processing the anthropogenic contamination by sulphur and copper can be traced to a depth of 80–90 cm. In contrast, the concentration of elements such as Cr, Ni, and V, that show a direct correlation with the content of iron in the soils, increases in the subsurface soil relative to the topsoil. This is particularly evident in areas underlain by rocks of the Katanga Supergroup.