Institution: | a University of Douala, Department of Earth Sciences. P.O. Box 24157, Douala, Cameroon;b University of Yaounde I, Department of Earth Sciences. P.O. Box 812, Cameroon;c TU-Bergakademie Freiberg, Institute of Geology, 09596 Freiberg/Sachsen, Germany;d Institute for Geological and Mining Research, Centre for Geological and Mining Research, P.O. Box: 333 Garoua, Cameroon |