Amplitude Versus Offset (AVO) An Emerging Tools for Mineral Exploration in the Basement Complex: Case Study of Zaria, North Central Nigeria.

The mining industry has traditionally used geologic field mapping, electromagnetic and potential field techniques, and drilling to explore for new mineral deposits, but with new discoveries of large near-surface deposits becoming increasingly rare and the known reserves of most economic minerals in decline, it is clear that new deep exploration techniques are required to meet the future needs of industry and society. With gravity and magnetic methods unable to resolve targets beyond about 500 m, high-resolution seismic reflection techniques similar to those used by the petroleum industry, but modified for the hardrock environment, show the greatest potential for extending exploration to depths of 3 km, the current maximum depth of mining. A high resolution seismic technique has recently been carried out in Zaria to delineate and characterise the structures and lithologies within the batholith using AVO analysis. The geology of Zaria revealed that it is made up of Precambrian rocks that consist of granite that form the major part of the batholiths along with low grade meta-sediments and gneisses that constitute the country rock into which the granitic batholiths intruded. The results of the AVO analysis showed a general trend of increase of amplitude with offset. Three AVO types were identified, which include type -3 that corresponds with occurrence of sills, type -4 that corresponds with the occurrence of granite and gneisses and type -5 that identified the occurrence of fracture basement. The effectiveness in the identification of the various lithologies and structures showed that AVO will serve as an effective tool for mineral exploration in the nearest future.