Investigation of contaminant plumes emanating from residual mine deposits in the Limpopo Province of South Africa, results from geophysical surveys

P.K. Nyabeze, B. Yibas, E. Sakala

In the proceedings of: GeoManitoba 2012: 65th Canadian Geotechnical Conference

Session: T2D - Seepage and Hydrogeology

ABSTRACT: Geophysical surveys were carried out along the peripheral zones of old mine dumps in the Limpopo Province of South Africa. The aim of the project was to screen areas for possible migrating contaminant plumes in the semi-arid region. The investigated gold mines are located in the eastern part of the country. The mines in the study area were abandoned hence there was a need to monitor and mitigate possible groundwater contamination and plume migration. The residual mine deposits were extensively weathered due to exposure to the atmosphere. Terrain electrical conductivity data was recorded using a Geonics EM34 frequency domain electrical conductivity meter. Potential contaminant flow paths were delineated in areas with high electrical conductivity (EC) anomalies above 30 mS/m. The geo-electric depth models show that EC plumes are well defined and continue at depth. Results of electrical resistivity tomography (ERT) surveys showed that EC values above 100 mS/m occur below the 60 m depth. The elevated EC values above 100 mS/m for groundwater occurring in the vicinity of the mine dumps could be attributed to the presence of near surface contaminant plumes probably migrating from the residual mine deposits. The results of the survey are useful for designing remediation measures and utilisation of groundwater resources. The terrain electrical conductivity profiling and ERT methods were found to be efficient tools for mapping potential contaminant plumes.

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