Gold mining in Ghana

Abstract

Ghana is a major player in the gold mining industry globally and in Africa in particular. The country is ranked 11th in the global league of gold producers and the second, only after South Africa, in Africa. Ghana's gold bearing rocks are confined to five parallel bands of metavolcanic and metasedimentary rocks locally called gold belts. The most dominant of these belts is the Ashanti belt, which accounts for nearly 80% of the gold mines and 90% of total annual gold output. Four main kinds of gold deposits exist in these gold-bearing corridors. These are placer or alluvial deposit, which occurs along stream courses draining these corridors, and quartz reef (free milling); extracted mainly by gravity concentration; sulphide ores and the oxidised sulphide ore; both of which are extracted by heap-leach methods. Non-sulphidic paleoplacer (free milling) ore occurs mainly in the Banket conglomerates of the Tarkwaian Formation. The premier valued gold is associated with well sorted and packed hematite rich conglomerates that occur in the thinner beds. The oxidised ores, associated mainly with the Birimian rock formation, occur in the weathered rocks and are derived from sulphides, principally arsenopyrite,and pyrites and their primary derivatives are the sulphide ores etc. Two main types of mining operations exist- large scale and artisanal mining. The artisanal miners exploit mainly placer or alluvial gold. The chemistry of gold ores, type of mining and processing technologies employed, present considerable challenges to water resources management in these mining area. Almost all surface water bodies within the mining areas are polluted and aquatic life in most of them is extremely low or non existent. Significant number of streams and shallow wells has disappeared due to over abstraction of groundwater for gold processing and dewatering of mines. Acid mine drainage is also a major concern. Though groundwater contamination is not a major concern in the mining areas due to impoverishment of the rocks of heavy metals, isolated cases of high arsenic, mercury, iron, manganese and aluminium concentrations in groundwater are of major concern for drinking water supply. Gold mining has also resulted in severe land degradation and major environmental concerns. © 2009 Nova Science Publishers, Inc. All rights reserved.