Journal de géologie et géophysique
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Exploration of Lead-Zinc (Pb-Zn) Mineralization Using Very Low Frequency Electromanetic (VLF-EM) in Ishiagu, Ebonyi State

Mbah Victor O, Onwuemesi AG, Aniwetalu and Emmanuel U

Very low frequency Electromagnetic (VLF-EM) exploration over the Ishiagu area of Abakaliki Basin, Lower Benue Trough, Nigeria was carried out to determine the Pb-Zn mineralization in the sedimentary bedrock. The conductivity contrast between the conductive mineralized veins and the host rock as generated by induction mechanism was used to delineate the potential zones of Pb-Zn mineralization. Results of high in-phase and quadrature readings due to strong EM induction were detected in the survey area and on the average, the deeper sources response range from 4.7% to about 7.6%, while the shallower sources response range from 8.8% to about 17.1% and these probably indicate the presence of Pb-Zn deposits with thick overburden in the northern part. Current density maps show the Pb- Zn mineralized veins trends in NW-SE direction with their subordinates in N-S direction. The central part of the study area displays very sharp VLF tipper responses indicating shallow sources, while the northern part displays broad VLF tipper responses indicating deeper sources. These readings correlate to the depth values over the Pb-Zn mineralized veins which range from 10 to 13 m in the central part and 16 to 22 m in the northern part of the mapped area. The high VLF anomalies delineated from Ishiagu area, in the SW part of Abakaliki basin as a rule yielded a high conductivity contrast result well-suited with the Pb-Zn mineralization and geologic information of the area.