Near-surface electrical profiling within Precambrian Basement Complex of Nigeria
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Date
2013
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Nigerian Institute of Physics
Abstract
University of Ilorin Dam Axis seated on a Precambrian Basement Complex in Nigeria was profiled using the Wenner array to investigate the vertical contacts and lateral changes in the geologic setting around the Dam Axis. Electrode spacings a = 5 m, 10 m, 15 m, 20 m, 25 m, and 30 m were used for prospecting the faults and fracture pattern in the area. The survey area lies within the basement rocks in the western part of Central Nigeria bounded by longitude 40 39’ 52” E and 40 40’ 0” E and latitude 80 27’ 5” N and 80 28’ 5” N. The study area falls within the eastern part of the Ilorin metropolis in the tropical climate region and has two distinct seasons dry and wet seasons. This survey was achieved through five profiles of 120 m in length each along the dam axis. Three of these profiles were at the bank of the dam, while the other two were obtained along the stream bank. The linear plot of apparent resistivity (ρa) against distance along each profile gave the distribution of resistivity values at each spacing of across the entire profile and the lithology call arrangements of the area. The profile along the dam bank shows low resistivity of three layers namely: wet sand (topsoil) of about 90 Ωm, gravel (mostly saturated) of about 200 Ωm, and basement (partially weathered) of about 600 Ωm. Conversely, profiles away from the dam bank showed laterite topsoil ranging from 120 - Ω180 m, a thin gravel layer of about 250 - 300 Ωm, and basement complex layers with almost 2577 Ωm. The 2-D pseudo sections revealed a depth to the unexposed granitic intrusion that appears in form of dyke in some profiles. Various vertical contacts were identified in the area.
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Keywords
Resistivity, Profiling, Equidistance, Traverses, Pseudo sections, Dam., Research Subject Categories::NATURAL SCIENCES