Environmental association of iron minerals and iron concentrations in soils close to abandoned manganese mine - a multivariate analytical approach

Environmental association of iron (Fe) minerals and Fe concentrations in soils close to the Kgwakgwe Mn oxide ore abandoned mine, Botswana are investigated in this study. Four hundred soil samples were obtained from a 4 km² area close to the abandoned mine. The Fe minerals in the soil samples were identified by x-ray diffractometry and the Fe concentrations by atomic absorption spectrophotometry. Results were processed using the statistical package for social science (SPSS). Iron minerals namely hematite and goethite were found in soils from the study area but only hematite in soils from the control site. Also Fe concentrations in soils from the study area were significantly higher than those from the control site. The correlations depicted very weak associations of these parameters. Hematite contributed significantly in the formation of the five clusters, goethite's contribution was for three of the clusters, and Fe concentrations in soils were for two of the clusters. At Kgwakgwe, exposed surfaces of mine workings, ferruginous shale and country rocks through wind erosion release particulate air matter, rich in Fe into the atmosphere which are transported over short distances and deposited on soils. Through chemical alteration processes, hematite is hydrated to goethite and neomineralization of goethite from the ferruginous shale occurs in the surrounding soils.