Karstic morphologies and mining implications in the Central African Republic

In the south and west of the Central African Craton (Zaire, South Congo, Angola) polymetallic (especially Cu) deposits are concentrated in Neoproterozoic limestones well-exposed in areas with a typical karstic morphology. In North Zaire and the Central African Republic, the covered karst is expressed by a cryptokarstic landscape with pseudokarstic depressions, especially in the vicinity of Bangui. At Bakouma, the karst has very deep troughs filled by Eocene lacustrine elastic deposits. The Proterozoic limestones and dolomites have been explained according to a ramp model. The Cu mineralisation is present in coastal (coastal plain and beach) and sometimes lagoonal facies, in which barite has also been found. At Bakouma, the primary stock of P results of the early phosphatisation of a coastal stromatolitic reef and the organic matter scattered in the lagoonal deposits. Afterwards, supergene processes concentrated the P, U and Cu in the Eocene sediments in the karstic troughs. The karstic network is very suitable for the concentration of various metals and perhaps diamond. A systematic survey of the karstic cavities is proposed. (C) 1997 Elsevier Science Limited.