Abstract
The results of a magnetic study of the Naraguta area, North Central Nigeria are presented here. Regional-residual separation was carried out using Least Square method. The resultant regional map revealed a regional trending in a NW-SE direction. The magnetic residual values range from -487.828nT to +405.447nT. Short to moderately long dislocations were found in the residual magnetic map. Several magnetic closures of various sizes were also noticed. While the discontinuities indicate the presence of minor to moderately long geologic fault in the area, the closures depict the type and size of the anomalies that lie beneath the area. Magnetic lineaments trending in a NE-SW direction has been identified to pass through the study area. This concentration of magnetic lineaments may be connected with the occurrence of younger granites in the study area since almost all known younger granite complexes lie within the region dominated by this trends. Also a prominent ENE-WSW anomaly low has been identified in the Jos-Bukuru complex. The trend of the anomaly is believed to be roughly parallel to that of the main structural feature of the Benue trough indicating the probability that the Benue trough and the younger granite intrusive are related considering the stress, which initiated the formation of these features. 2-D spectral analysis of the magnetic anomalies over the area has been carried out in an effort to estimate the depth to magnetic sources. The result shows that the deeper sources have an average depth of 2.03 Km while the shallower sources have an average depth of 265m. Keywords: Lineaments, Trend, Magnetic Anomalies, Younger Granites
Highlights
The study area is situated in North CentralNigeria and covers an area of about 2970.25km[2] and it is bounded by latitudes 9o30’ and 10 o00’ and longitude 8o30’ and 9 o00’
The Residual aeromagnetic map over Naraguta in central Nigeria has been interpreted in this study
Short to moderately long dislocations were noticed in the magnetic map which is indicative of short to moderately long geologic faults
Summary
Nigeria and covers an area of about 2970.25km[2] and it is bounded by latitudes 9o30’ and 10 o00’ and longitude 8o30’ and 9 o00’. If the frequency unit is in radians per (i) The Naraguta (sheet 168) aeromagnetic map was kilometer the mean depth of burial of the ensemble is digitized and reproduced using ILWIS 3.2 (Academic) given by (ii) The regional magnetic field was determined by fitting a 2 dimensional first degree polynomial surface to the (3) Where m is the slope of the best fitting straight line. The truncation effect was reduced by applying a cosine tapper to the observed data before Fourier transformation (Kangkolo, 1996; Akanbi & Udensi, 2006) It has been found (Pal et al, 1978) that in the use of spectral approach to magnetic source depth determinations, the error in depth prediction increases with the depth of source and is related to the map size. The map size required for adequate results should be much larger
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