Abstract:
The Ishiagu lead-zinc deposits of southeastern Nigeria are associated with folded shales of the Asu
River Group. The PbZn mineralization is restricted to a series of closely spaced, steeply dipping subparallel
fractures which trend NW-SE and typically form en-echelon patterns. Along a second set of fissures, oriented
NE-SW and of an earlier generation than the NW-SE system, only the gangue minerals (siderite and quartz) are
characteristic. The style of mineralization is exclusively fissure-filling, whereas the distinctive pattern of
mineralization--ore plus gangue minerals in the NW-SE fractures and gangue minerals in the NE-SW
fissures-suggests two separate phases of epigenetic hydrothermal emplacement.
