Status of acid mine drainage and metal leaching studies in Ghana
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Date
2011-01
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Mine Drainage and Related Problems
Abstract
This chapter reviews the status of acid mine drainage studies and management inGhana. Acid drainage, and the contaminants associated with it, has been acknowledgedas the single largest environmental problem facing the mining industry worldwide.Metals mobilised from acid rock/mine drainage conditions invade the environment withdisastrous consequences. Fortunately, knowledge of both local and regional geology andgeochemical processes can lead to a better understanding of the phenomenon and itsenvironmental impacts. This knowledge has constituted the bases of managementstrategies, defining practices in acid drainage prediction, prevention, control, treatmentand monitoring, developed to reduce risk of formation of acid drainage from mine wastesin most developed countries. These management approaches rely on the correctidentification of mine rock, both in the pre-mining phase and as an ongoing part of mineplanning. The Birimian and Tarkwaian Rocks Systems are the main source of gold inGhana. Gold mineralisation in the Birimian occur in the form of quartz - veined gold inmainly carbonaceous phyllites while mineralisation in disseminated sulphides is in themetavolcanics. Base metal sulphides and sulphosalts including arsenopyrite, pyrite,sphalerite, pyrrohorite, and terahedrites dominate ore mineralogy. Althoughmineralisation in the Tarkwaian is not directly associated with sulphide-bearing rocks,dolerite intrusions among the Tarkwaian country rocks have been reported to containconsiderable sulphide minerals. These sulphide - bearing lithologies present potential acidgenerating sites. Various studies of stream drainage emanating from some mine siteshave recorded pH values as low as 2.4 with associated high doses of As (23. mg/L), Mn(15 mg/L) and Fe (103mg/L). Low pH (<3.4) and high trace metals have been reportedfrom some boreholes in mining areas. Areas outside mining centres with similar geologyhave water bodies with similar low pH and high metal content. Unfortunately, acid mine drainage and metal leaching management practices are still a very gray area in Ghana.Mining environmental management in itself is a novelty in Ghana. The guidelines formining environmental management and Environmental Regulations are two key tools formining environmental management in Ghana. However, these do not have definitebenchmarks, protocols and methodologies to guide companies in the evaluation of rocksfor acid generating potential in Environmental Impact Assessment (EIA) processes.Limited studies on the subject matter has been carried out by mining companies on themine scale and largely restricted to the mine site, as part of the project's EIA. © 2010 by Nova Science Publishers, Inc. All rights reserved.