Structural controls of Pb-Zn mineralization of Enyigba district, Abakaliki, Southeastern Nigeria

Abstract

The lead-zinc deposit of Enyigba and its environs are localized in the cretaceous sedimentary rocks of the Albian Asu River Group in the Lower Benue Trough, Southeastern Nigeria. The Albian Asu River Group is made up of shale, siltstone, sandstone and limestone. The deposits were formed epigenetically through the crystallization of hydrothermal solutions and are localized within the fractures, hence the need to study the trend of the fractures in the rock unit where the mineral deposits are being hosted. In order to study the fractures, two units of the formation were identified and designated as units A and B. The ore field extends to about 3.7 km strike length with an average width of 5 m. From the detailed field mapping, the identified structures that control the mineralization are fold, fault and joint/fractures in which the fractures predominate. The total measured identified fractures is 503 in number and are represented in rose diagram, histogram and stereographic net which shows that they trend NW-SE and N-S directions, and dip SW-NE direction.