ANALYSIS OF AEROMAGNETIC DATA OVER MUTUM ... - RJEAS

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Research Journal in Engineering and Applied Sciences (ISSN: 2276-8467) 1(2):142-148Analysis of Aeromagnetic Data Over Mutum-Biyu and Environs, North–Eastern, Nigeriaof dark brown coloured ferromagnetic mineral plates3&4 that contains mineral iron in form of magnetite,which oxidizes to haematite, while the magnetic lowsare associated with granitic and allied rocks.The magnetic susceptibility contrast across a fracturezones are due to oxidation of magnetite to hematite,and /or infilling of fracture planes by dyke like bodieswhose magnetic susceptibilities are different fromthose of their host rocks (Bassey, et al, 2000), Suchgeological features appear as thin elliptical closuresor nosing on the residual magnetic map (Fig.3).Bearing this in mind, prominent elliptical closuresand nosing were identified on the residual magneticmap. The features / lineaments indicated are linesdrawn parallel to the closure and /or elongation of theanomalies. The residual lineaments map deducedindicated that 60% have NE-SW; 19% NW-SE; 13%E-W and 11% N-S direction as illustrated by azimuthdiagram figure 5.These correspond to Pan-Africanand Pre-Pan–African deformational episodes in thestudy area. These also compare favourably well withthose observed in the field (plates1, 2, 3& 4).Previous work in Mutum Biyu by Ofoegbu (1985),interpreted magnetic anomaly of two profiles in termsof dyke showed sharp observed anomaly for theselected points on the curve. The sharpness of theanomaly could be related to the iron mineralization inMutum Biyu. The presence of iron mineralization inMutum Biyu and Bantaji must have affected thegroundwater quality which is evident from spillagesof over head tanks of boreholes. The Hilberttransform analysis which tends to sharpen the edgesof anomalies and enhances the anomalous featuresconfirm the existence of N-S, E-W, NE-SW, andNW-SE trends of lineaments in the study area.Looking at figure 6 the analytical signalsconcentrated more in the south eastern portion ofstudy area. This may be explained that the basementcomplex outcropping here is not mineralogicallyhomogeneous. The contoured map (Fig.3) shows thepresence of remarkable magnetic features whichagree quite well when compared with geologic mapof (Fig.1). In addition, the presence of faults whichControl Rivers and stream channels in the area can beinterpreted as major fracture zones which originallydeveloped in the zones of weakness of the area.Magnetic source depth determination throughspectral analysis over Mutum Biyu and environssuggests two main source depths under the area. Thedeepest source lies between 661m close to Jalingoand 2722m around Bantaji town, and the shallowersource depths obtained ranges from 137m atGurumpawa to 590m close to Gidan Shanu. Thesecould be a result of intrusive bodies from CameroonVolcanic line in the study area; Table1 shows thecomputed magnetic source depths in the area.The results compared favourably with previous workobtained from gravity and magnetic analysis.Ofoegbu (1988) estimated the sediment thickness inUpper Benue that ranges from 500m to 460m.Osazuwa et al., (1981) estimated sediment thicknessthat ranges from 900m to 2200m from gravity datainterpretation, and 900m to 4900m from magneticdata. Nur.,(2000) estimated the sediment thicknessranges between 1500m to 2219 m for deeper source,and range between 330m to 414m for shallow source.CONCULUSIONSThe preliminary analysis of the aeromagnetic dataover Mutum Biyu and its environs indicated theexistence of two magnetic source depths; the deepestsource lies between 661m to 2722m and shallowersource depth obtained ranges from137m to 590m andcould be attribute of intrusive bodies. The structurallineaments/fractures observed from the residual andanalytical signal of the area are dominantly in NE-SW, with others trending NW-SE, E-W and N-Sdirection. Most high magnitude lineaments could beattributed to deep seated fractures, while the lowmagnitude could be attributed to shallow weatheredzones in the area as observed in the field. Theazimuth magnitudes and the trend of the fractures arein line with the Pan-African and Pre-Pan-Africandeformational episode in the area. Lineaments aresites of concentration of pegmatite’s dykes, quartzveins and ironstone that host mineralization inmedium grain granite at Monkin, Jalingo, MutumBiyu and Bantaji respectively. In addition, the resultshows area of groundwater resources in shallowweathered regolith basement suitable for locatingboreholes and hand dug wells, though for MutumBiyu and Bantaji the groundwater resource is affectedby oxidation of mineralized iron in Upper Bimasandstone. The iron mineralization in the area may beof economic importance, therefore, a further studyusing detailed integrated geophysical methods isrecommended.REFERECESBassey, N. E. Nur, A. and Obiefuna, G. I., (2000).Analysis of Aerial Photographic data over Guyukarea, North-eastern Nigeria. Journal of Mining andGeology Vol.36 (2), 45-152.Benkhelil, J., (1988). Structure et evolutionGeodynamique du basin intracontinetal Bull. Centresreach.Explor. Prod. Elf Aquitain. Vol.1207. 29-128.Ekwueme, B.N., (1994). Structural features ofsouthern Obudu plateau, Bamenda massif, SENigeria, Preliminary interpretation. Jour. Mining.Geol. Vol.30. (1), 45-59.Geological survey of Nigeria, (1975). Air BoneMagnetometer Survey Contour Map of TotalMagnetic Field Intensity of study area.Geological survey of Nigeria, (2006) Geological mapof study area.147
Research Journal in Engineering and Applied Sciences (ISSN: 2276-8467) 1(2):142-148Analysis of Aeromagnetic Data Over Mutum-Biyu and Environs, North–Eastern, NigeriaGrant, N.K., (1978). Structural distinction between ametasedimentary cover and underlying basement in600 m.y old Pan-African domain of northwestNigeria. West African Geol. Sic. Am. Bull.Vol. 89,50-58Markku, P., (2009). Fourier transform basedprocessing of 2D potential field data Version 1.0a(Software). Division of Geophysics, Department ofGeosciences FIN-90014 University of OuluFinland.Valley on the basis of new geophysical data. EarthEvol. Sci., Vol. 2, 26-135Spector, A. and Grant, F.S., (1970). Statistical modelsfor interpreting aeromagnetic data, Geophysics.Vol.35, 293- 302.Stefan, M., and Vijay, D., (1996). Depth estimationfrom the scaling power spectrum of potential fields?Geophysics. J. Int.Vol.124, 113-120Nur, A.M, Onuoha M.K. and Ofoegbu C.O., (1994).Spectral analysis of Aeromagnetic data over theMiddle Benue Trough, Nigeria. Journal of miningand geology, Vol. 30 (2), 211-217.Nur, A. (2000). Analysis of aeromagnetic data overYola arm of the Benue Trough, Nigeria. Mining andGeol.Vol.36 (1), 77-84Nur. A, Ofeogbu C.O. and Onuoha K.M. (1999).Estimation of the depth to the curie point Isotherm inthe upper Benue trough, Nigeria. Jour. Min. Geol.Vol.35 (1), 53-60.Nur. A, Ofeogbu C.O. and Onuoha K.M. (1999).Estimation of the depth to the curie point Isotherm inthe upper Benue trough, Nigeria. Jour. Min. Geol.Vol.35 (1), 53-60.Offodile, M.E., (1977). A review of the geology ofthe cretaceous of the Benue Trough in Geology ofNigeria (Ed. Kogbe, C.A), Pp319-330. Elizebethpress Lagos.Ofoegbu, C.O., (1985).Long wave magnetic anomalyand crustal structure underneath the Benue Troughand surrounding regions. Nig. J. Min. Geol.Vol. 22,45-50.Ofoegbu, C.O. (1988). An aeromagnetic study of partof the Upper Benue Trough, Nigeria. Jour. Afr.EarthSci., Vol.7, 77-90.Ofoegbu, C.O., and Mohan N.I., (1990).Interpretation of aeromagnetic anomalies over partsof south eastern Nigeria using three dimensionalHilbert transformation. Pageoph. Vol.134, 13-29Ofoegbu, C.O. and Onuoha, K. M. (1991). Analysisof magnetic data over the Abakaliki Anticlinorium ofthe lower Benue Trough, Nigeria. Marine and Petr.Geol. Vol.8, 174-183.Ofeogbu, C.O, Odigi, M.I. Okereke, C.S. andAhmed, N.M, (1992). Magnetic anomalies and thestructure of the Nigeria’s Oban massif: Journal. ofAfrican Earth Sciences Vol.15 (2), 217-280.Osazuwa, I.B., Ajakaiye, D. E and Verheijin, P.J.T.,(1981). Analysis of the structure of part of the Benue148
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