Abstract
Aeromagnetic data over Abakaliki area of lower Benue trough, Nigeria was interpreted qualitatively and quantitatively using Oasis montaj software. The qualitative interpretation unveiled basic intrusive bodies like dykes, laccolites and batholitic bodies in the area. It also revealed fault zone which trends southeastern part of the study area. Quantitative interpretation was carried out by forward and inverse modeling, source parameter imaging and Euler deconvolution methods. Depth obtained by source parameter imaging (SPI) ranged from 99.50 to 5930.78 m. Results from this study indicate that deep seated bodies are predominant in the southwestern part of the area, while shallow bodies are predominant in the southeastern part of the area. The anomalies over the area were modeled by bodies in the form of sphere and ellipsoid by varying the total magnetic intensity parameters. Depth obtained by model A is 546 m with susceptibility value of 0.0180 signifying limestone. The height of Model B is 50 m signifying outcrop, likely to be the outcrop near college of Agricultural Sciences of Ebonyi State University, Abakaliki, with susceptibility value of -0.0017 signifying calcite. Depth obtained for models C, D and E are 956, 6366 and 477 m respectively, with respective susceptibility values of -0.0134, -0.009 and -0.006 signifying rock salt, quartz and Calcite. Maximum depth obtained by forward and inverse modeling is 6366m while that obtained by source parameter imaging is 5930.78 m. Key words: Abakaliki area, aeromagnetic anomalies, qualitative and quantitative interpretation, intrusive bodies, hydrocarbon accumulation.
Highlights
The study of geophysics has helped man to locate buried materials usually of geophysical interest in the earth’s sub-surface
The results of this study suggest that the magnetic anomalies over the study area are caused by intrusive bodies of basic composition with different thicknesses and fault zone in the sedimentary area
The result of qualitative analysis shows that the magnetic anomalies are predominant in the southeastern part of the study area
Summary
The study of geophysics has helped man to locate buried materials usually of geophysical interest in the earth’s sub-surface. These materials usually manifest as anomalies which could be sensed by different geophysical. The subsurface which is based on the variation of the magnetic field of the earth that results from the magnetic properties of the underlying rocks is studied using magnetic survey. Magnetic survey may be carried out in air (aeromagnetic), land and sea. The magnetic field of the earth acts on the magnetic minerals in the crust, inducing a secondary field which reflects the distribution of the minerals. The main magnetic field induces a field which varies slowly from one place to another while the crustal field which is the portion of the magnetic field associated with the magnetism induced by the earth’s main magnetic field varies more rapidly (Reford, 1962)
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