MINING IN AFRICA SPECIAL — Ghana’s ongoing gold rush

Ghana has a long history of gold production, with more than 41 million oz. having been produced since 1880.

The country’s vast mineral potential is best exemplified by the Ashanti mine, which has been in continuous production since the late 19th century. Gold reserves are still in the range of 18 million oz., with plenty of potential for more to be found. Current cash costs are around US$175 per oz., and production reached an annual rate of 1 million oz. in 1994. Ghana, the former British colony of the Gold Coast, has been independent since 1957. The country covers 239,000 sq. km, about the same area as the state of Oregon. The population is about 15 million, more than half of whom are subsistence farmers. English is widely spoken, and Christianity is a main religion.

The country’s president, retired Flight Lieutenant Jerry Rawlings, first came to power in 1981. He won 58% of the vote in the latest election, in 1992, although it should be noted that most opposing political parties boycotted that election.

Ghana adopted measures to attract foreign investment after a marked deterioration in its economy took place in the 1970s and early 1980s. Annual gold production, for example, declined to about 700,000 oz. in 1973 from a high of more than 900,000 oz. in 1960, and then to an all-time low of about 280,000 oz. in 1983.

In 1983, the government launched a recovery program to reverse this downtrend and revitalize the economy. This program appears to have been a success, as more than US$1 billion was invested in the Ghanaian gold industry alone in recent years.

Most of Ghana lies within the Precambrian Guinean Shield of West Africa, the main rock units being the metamorphosed and folded Birimian, Tarkwaian and Dahomeyan systems, the Togo series and the Buem Formation.

The Birimian (intensely folded, metamorphosed and, in places, assimilated by granitoid bodies) is important as a host rock for deposits of gold, diamonds, bauxite, manganese and iron.

Gold in the Birimian is mainly in the form of auriferous quartz veins or “reefs” and as sulphide ore. The quartz veins, up to 30 metres wide and up to several hundred metres long, have been the most important source of gold. Gold deposits are also found as blanket reefs or conglomerate beds (similar to those in South Africa) in the Tarkwaian, and in placer deposits in streams draining areas of primary mineralization.

In 1925, A.E. Kitson, director of the Gold Coast Geological Survey, noted “strong resemblance in many aspects of the PreCambrian geology of Canada to that of the Gold Coast.”