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Four aeromagnetic map sheets of ½ 0 x ½ 0 on a scale of 1: 100,000 covering some parts of Lower Benue Trough were analysed using spectral techniques to estimate the average depth of magnetic sources. The result indicates a two-layered source model. The deeper magnetic sources are located atdepths which vary between 1.16 km and 6.13 km, with an aver...
Citations
... They inferred that the exceedingly high temperature that prevailed at the time of formation of these minerals suggests that the area might not hold any significant hydrocarbon potentials. Igwesi and Umego (2013) employed spectral analysis method to estimate the average depth of magnetic sources covering some parts of lower Benue trough and obtained a depth for deeper magnetic sources ranging from 1.16 km to 6.13 km, with an average depth of 3.03 km while the depths to the shallower magnetic sources range from 0.06 km to 0.37 km, with an average depth of 0.22 km showing the presence of magnetic intrusive bodies within the sediments. Abdullahi et al. (2014) interpreted aeromagnetic data over Afikpo and Nkalagu areas of the lower Benue trough for metallic deposits and hydrocarbons using 2D/3D modeling and spectral analysis techniques. ...
... The areas where the maximum sedimentary thickness was obtained from the modeling traversing along WSW-NNE also correlate with areas where the maximum depth was obtained from the spectral analysis at WSW and NNE parts. The depth results of the present study compares favorably with the depth results obtained by earlier researchers who have worked within the lower Benue trough (Obi et al., 2010;Ugwu & Ezema, 2012;Igwesi & Umego 2013;Abdulahi et al. 2014;Obiora et al. 2018;Osinowo & Taiwo 2020). The igneous intrusions of gabbro and diabase delineated from the current study closely agrees with the results of Ugwu and Ezema (2012) who also delineated igneous intrusions of granite, dolerite, basalt and rhyolite from their modeling results. ...
The aeromagnetic data of Nkalagu and Abakaliki areas were interpreted using spectral analysis and modeling to estimate depth to the sedimentary thickness, nature of intrusive, susceptibility values and types of minerals associated with them. The total magnetic intensity was processed to produce the residual magnetic map which was divided into 21 overlapping blocks. Each block was subjected to a spectral program plot (SPP) developed with MATLAB to obtain depths to the top boundary Zt and depth to the centroid Z0. The spectral analysis revealed depths to the top boundary Zt, which is the depth to magnetic basement ranging from 0.77 to 2.34 km with an average value of 1.72 km and the centroid depth ranging between 2.22 and 5.93 km, with an average depth of 3.55 km. The modeling estimated depths of profile 1, 2, 3, and 4 at 5 km, 1 km, 1.68 km and 1.32 km respectively with an average depth of 2.3 km and respective susceptibility values of 0.002, 0.003, 0.003 and 0.003 respectively, indicating the presence of igneous intrusions of gabbro, diabase and metamorphosed sedimentary rocks of quartzite and schist, with iron rich minerals like pyrite, limonite, cassiterite and arsenopyrite. The maximum depth values of 2.34 km and 5 km obtained from the two depth estimation methods confirm feasibility depths for hydrocarbon accumulations. In view of the above results, it is evident that the presence of intrusions delineated from the modeling results accounts for the mineralization in the area and can also destroy any hydrocarbon present since the presence of numerous intrusions are an indication of exceedingly high temperature history.
... They inferred that the exceedingly high temperature that prevailed at the time of formation of these minerals suggests that the area might not hold any significant hydrocarbon potentials. Igwesi and Umego (2013) employed spectral analysis method to estimate the average depth of magnetic sources covering some parts of lower Benue trough and obtained a depth for deeper magnetic sources ranging from 1.16 km to 6.13 km, with an average depth of 3.03 km while the depths to the shallower magnetic sources range from 0.06 km to 0.37 km, with an average depth of 0.22 km showing the presence of magnetic intrusive bodies within the sediments. Abdullahi et al. (2014) interpreted aeromagnetic data over Afikpo and Nkalagu areas of the lower Benue trough for metallic deposits and hydrocarbons using 2D/3D modeling and spectral analysis techniques. ...
... The areas where the maximum sedimentary thickness was obtained from the modeling traversing along WSW-NNE also correlate with areas where the maximum depth was obtained from the spectral analysis at WSW and NNE parts. The depth results of the present study compares favorably with the depth results obtained by earlier researchers who have worked within the lower Benue trough (Obi et al., 2010;Ugwu & Ezema, 2012;Igwesi & Umego 2013;Abdulahi et al. 2014;Obiora et al. 2018;Osinowo & Taiwo 2020). The igneous intrusions of gabbro and diabase delineated from the current study closely agrees with the results of Ugwu and Ezema (2012) who also delineated igneous intrusions of granite, dolerite, basalt and rhyolite from their modeling results. ...
The aeromagnetic data of Nkalagu and Abakaliki areas were interpreted using spectral analysis and modeling to estimate depth to the sedimentary thickness, nature of intrusive, susceptibility values and types of minerals associated with them. The total magnetic intensity was processed to produce the residual magnetic map which was divided into 21 overlapping blocks. Each block was subjected to a spectral program plot (SPP) developed with MATLAB to obtain depths to the top boundary Zt and depth to the centroid Z0. The spectral analysis revealed depths to the top boundary Zt, which is the depth to magnetic basement ranging from 0.77 to 2.34 km with an average value of 1.72 km and the centroid depth ranging between 2.22 and 5.93 km, with an average depth of 3.55 km. The modeling estimated depths of profile 1, 2, 3, and 4 at 5 km, 1 km, 1.68 km and 1.32 km respectively with an average depth of 2.3 km and respective susceptibility values of 0.002, 0.003, 0.003 and 0.003 respectively, indicating the presence of igneous intrusions of gabbro, diabase and metamorphosed sedimentary rocks of quartzite and schist, with iron rich minerals like pyrite, limonite, cassiterite and arsenopyrite. The maximum depth values of 2.34 km and 5 km obtained from the two depth estimation methods confirm feasibility depths for hydrocarbon accumulations. In view of the above results, it is evident that the presence of intrusions delineated from the modeling results accounts for the mineralization in the area and can also destroy any hydrocarbon present since the presence of numerous intrusions are an indication of exceedingly high temperature history.
... Although mining of the lead-zinc ores commenced in all districts as early as 1925, the southern Benue Trough deposits have been relatively less studied. Several related work did in the past include Igwesi and Umego (2013), Abdullahi et al (2019), Bello et al (2017), Onuoha and Ofoegbu (1991), Nwogbo (1997) among others. This study is aimed at determining the mineralization in the southern part, depth to basement sources and the heat flow so as to guide prospective investors. ...
... Results from both depth estimate methods agreed largely with other published works in the study area. Onuoha and Ofoegbu (1991) estimated 1.6km to 5km for deeper source around middle Benue, while 60m to 1.2km was obtained for shallow magnetic source; Nwogbo (1997) got 2km to 2.62km for deeper source and 70m to 0.63km for shallow source from spectral analysis of upper Benue trough; Igwesi and Umego (2013), assessed a depth of 3.03km. However, this present work is focused on Southern Benue Trough and thus, contributes to the previous works. ...
... Although mining of the lead-zinc ores commenced in all districts as early as 1925, the southern Benue Trough deposits have been relatively less studied. Several related work did in the past include Igwesi and Umego (2013), Abdullahi et al (2019), Bello et al (2017), Onuoha and Ofoegbu (1991), Nwogbo (1997) among others. This study is aimed at determining the mineralization in the southern part, depth to basement sources and the heat flow so as to guide prospective investors. ...
... Results from both depth estimate methods agreed largely with other published works in the study area. Onuoha and Ofoegbu (1991) estimated 1.6km to 5km for deeper source around middle Benue, while 60m to 1.2km was obtained for shallow magnetic source; Nwogbo (1997) got 2km to 2.62km for deeper source and 70m to 0.63km for shallow source from spectral analysis of upper Benue trough; Igwesi and Umego (2013), assessed a depth of 3.03km. However, this present work is focused on Southern Benue Trough and thus, contributes to the previous works. ...
The techniques of aeromagnetic data analysis were employed to elucidate depth to magnetic basement sources, lead-zinc (pb-zn) mineralisation and heat flow in parts of Southern Benue Trough. The study area covers an area extent of about 18,150 sq. Km, latitude 05 0 30'N-06 0 30'N and longitude 007 0 30'E-009 0 00'E. The digital aeromagnetic data consisting of Total Magnetic Intensity with geospatial attributes covering six (6) sheets 302 (Nkalagu), 303 (Abakaliki), 304 (Dangha), 313 (Afikpo), 314 (Ugep) and 315 (Ikom) were used in this study. Several magnetic digital filtering methods such as reduce to pole, low/high pass, etc were applied on the data before analysis for lineaments, mineralisation, and depth to magnetic sources. Zones of broad magnetic anomalies were found in the north eastern and south eastern part of the study area like Otam-Izekwe, Enyigba, Uburu, Abakaliki, Ndieze Izzi, Isiagu, Obubra, Oturekpe, Mkpani, Idomi, Enona, Ugep, etc. Depth estimates to the magnetic basement sources from spectral analysis range from 0.65km to 1.155 km, while depth estimate from source parameter imaging (SPI) stretches from 0.679km to 7.723km. The north western part of the study area is the deepest. Pb-zn mineralization within the study area is found to be structurally controlled trending in NE-SW and NW-SE directions. The heat flow values range from 0.65-1.95Wm-2 , pb-zn mineralization is within 0.9-1.4Wm-2 and Curie point depth range from 0.75km to 2.1km.
... Application of 2-D spectral inversion to the interpretation of potential field data is now usually applied for basement depth determination established [9] . Different studies have therefore carried out magnetic basement estimation using spectral inversion method [10][11][12][13][14][15][16][17] . Ekwok et al. [10] assessed the depth to shallow and deep magnetic sources in some parts of southeastern Nigeria, using high resolution airborne magnetic data. ...
... The results of the spectral depth determined in the present study agree with the results of some previous researchers that had worked within the area of study. Igwesi and Umego [11] , analyzed aeromagnetic data of some parts of Lower Benue Trough using spectral analysis technique to calculate the average depth of causative magnetic sources. The result for the basement depth of the deeper magnetic sources vary between 1.16 km and 6.13 km with an average depth of 3.03 km while, the shallow depth varies between 0.06 km and 0.37 km having an average depth of 0.22 km. ...
Spectral analysis of high-resolution airborne magnetic data of part of Benue Trough was used to estimate the depths of anomalous magnetic sources within the study area. This paper was aimed at the determination of sedimentary thickness of the study area and to infer favourable areas for possible petroleum exploration. Several data enhancement techniques were used to digitally enhance the data to improve the signal-to-noise ratio. The total magnetic intensity was subjected to regional-residual separation using polynomial fitting of the first order, with the residual field revealing magnetic intensity values ranging from-79.8 to-16.5nT. Several clusters of circular magnetic anomaly closures with very clear amplitudes which occur especially in the northern and mid part of the area revealed edges of intrusive bodies. The structures observed within the location from the residual maps revealed dominant trends in the NE-SW and N-S direction. The result of 2D spectral analysis revealed a two-depth model, with the depth to the first layer (D1) varying from 0.135 km to 0.200 km with an average depth of 0.158 km while second layer depth (D2) varies from 2.585 km to 4.878 km with the average depth of 3.415 km. This result therefore, indicates that the average basement depth of the study area as deduced from power spectrum inversion is about 3.415km. The mean sedimentary thickness of 3.415km obtained and the near absence of intrusive bodies especially in the northern part of the study area thus reveal favourable conditions for hydrocarbon exploration.
... Application of 2-D spectral inversion to the interpretation of potential field data is now usually applied for basement depth determination established [9] . Different studies have therefore carried out magnetic basement estimation using spectral inversion method [10][11][12][13][14][15][16][17] . Ekwok et al. [10] assessed the depth to shallow and deep magnetic sources in some parts of southeastern Nigeria, using high resolution airborne magnetic data. ...
... The results of the spectral depth determined in the present study agree with the results of some previous researchers that had worked within the area of study. Igwesi and Umego [11] , analyzed aeromagnetic data of some parts of Lower Benue Trough using spectral analysis technique to calculate the average depth of causative magnetic sources. The result for the basement depth of the deeper magnetic sources vary between 1.16 km and 6.13 km with an average depth of 3.03 km while, the shallow depth varies between 0.06 km and 0.37 km having an average depth of 0.22 km. ...
Spectral analysis of high-resolution airborne magnetic data of part of Benue Trough was used to estimate the depths of anomalous magnetic sources within the study area. This paper was aimed at the determination of sedimentary thickness of the study area and to infer favourable areas for possible petroleum exploration. Several data enhancement techniques were used to digitally enhance the data to improve the signal-to-noise ratio. The total magnetic intensity was subjected to regional-residual separation using polynomial fitting of the first order, with the residual field revealing magnetic intensity values ranging from-79.8 to-16.5nT. Several clusters of circular magnetic anomaly closures with very clear amplitudes which occur especially in the northern and mid part of the area revealed edges of intrusive bodies. The structures observed within the location from the residual maps revealed dominant trends in the NE-SW and N-S direction. The result of 2D spectral analysis revealed a two-depth model, with the depth to the first layer (D1) varying from 0.135 km to 0.200 km with an average depth of 0.158 km while second layer depth (D2) varies from 2.585 km to 4.878 km with the average depth of 3.415 km. This result therefore, indicates that the average basement depth of the study area as deduced from power spectrum inversion is about 3.415km. The mean sedimentary thickness of 3.415km obtained and the near absence of intrusive bodies especially in the northern part of the study area thus reveal favourable conditions for hydrocarbon exploration.
... Unlike the geothermal methods, magnetic methods are based on utilization of magnetic data to calculate the CPD on a regional scale (Selim and Aboud, 2013). Multiple investigations (e.g., Espinosa-Cardeña and Campos-Enriquez, 2008;Obaje, 2009;Eletta and Udensi 2012;Salako 2012;Abdulsalam et al., 2013;Ikumbur et al., 2013;Igwesi and Umego 2013;Saibi et al., 2015;Bello et al., 2017;Mohammed et al., 2019;Abdullahi et al., 2019;Elbarbary et al., 2022) utilized aeromagnetic magnetic data elsewhere in order to determine the CPD on both a regional and local scale. ...
Spectral analysis of the pole reduced magnetic anomaly data and inversion of complete Bouguer anomaly data are employed here as there is no previous published data regarding for the determination of the Curie point depth (CPD), Conrad depth (CD) and lithospheric mantle thickness in the central main Ethiopian rift (CMER) and its environs. The results confirm that the CPD, range between 7.68 and 20.3 km, CD, range between 16 and 25 km and lithospheric mantle thickness, range between 13.4 and 27. 8 km. These results indicate that the CMER magnetic crust occur close to the CD and lithospheric mantle thickness, but below the Moho depth beneath the study area. Based on the results on CPD, we estimate the magnitude of the geothermal gradient and heat flow in the study area. The results confirm that the geothermal gradient, range between 32.4 and 65 °C km⁻¹ and heat flow, range between 80 and 160 mWm⁻². These results are found to be inversely correlated with the CPD. It is a commonly known fact that shallow CPDs generate negative magnetization. Similarly, in this study, it is recorded low magnetic anomalies overlap with shallow (less than 13.1 km) CPDs in line with high (110-160 mWm⁻²) heat flow and high (48-64 °C km⁻¹) geothermal gradient values are determined to occur beneath the CMER. These results associate with the presented geotectonic and geothermal signatures of the study area.
... Estimation of relief on the basement surface may be related to structures that harbour hydrocarbon in overlying sedimentary basins [8]. Several studies have been carried out for the estimation of depth to the basement using the spectral inversion method and 3D Euler Deconvolution [8,13,15,[23][24][30][31][32]44,47,49,50]. Ofoegbu [51] estimated the thickness of the sediments in the Lower and Middle Benue Trough to vary between 0.5 and 7.0 km. ...
Spectral technique and Euler Deconvolution were applied to high-resolution aeromagnetic data of parts of Benue trough to estimate the depth of anomalous magnetic sources within the study area; Data enhancement techniques such as total magnetic intensity map, reduction to pole, regional-residual separation and upward continuation maps were employed to identify different magnetic anomalies, structural trends representing the tectonics of the location were observed trending NE-SW and N-S directions; The result of 3D Euler deconvolution for the structural index (SI) = 0, 1, 2, 3 gave depths to magnetic sources that range from -589;3 m to -2678;8 m, -459;0 m to -2691;9 m, -294;6 m to -2817;5 m, - 430;2 m to -2780;6 m respectively; The depth estimates from 2-D spectral revealed a two-layer model; The shallow magnetic depth ranges between 0;135 km to 0;200 km with a mean depth of 0;158 km and the depth to magnetic basement vary between 2;585 km to 4;878 km with a mean depth of 3;415 km; This result, therefore, indicates that the average basement depth of the study area obtained from the spectral analysis is 3;415km; This investigation, therefore provides appropriate sedimentary thickness for suitable hydrocarbon prospecting within the study area.
... These values agree closely with those obtained from the spectral depth analysis of the same data in this work. The depths from source parameter imaging and spectral analysis also agree closely with those of some previous researchers in Lower Benue Trough 3,17,18,19,20,21 . ...
... The deep depth to basement from the spectral analysis is shallowest (pink colour) around Agana area but deepest (blue colour) around Oturkpo area. These depths are found to be within the range of depths obtained by earlier researchers that worked in Lower Benue Trough 3,17,19 . The results from the two interpretation methods revealed basement depths sufficient for hydrocarbon accumulation. ...
... These values agree closely with those obtained from the spectral depth analysis of the same data in this work. The depths from source parameter imaging and spectral analysis also agree closely with those of some previous researchers in Lower Benue Trough 3,17,18,19,20,21 . ...
... The deep depth to basement from the spectral analysis is shallowest (pink colour) around Agana area but deepest (blue colour) around Oturkpo area. These depths are found to be within the range of depths obtained by earlier researchers that worked in Lower Benue Trough 3,17,19 . The results from the two interpretation methods revealed basement depths sufficient for hydrocarbon accumulation. ...
Airborne gravity data over parts of the Lower Benue Trough of Nigeria were analyzed and interpreted to determine the basement depth of the source to gravity anomaly over the area. The study area lies within latitude to North and longitude to East in the Lower Benue Trough of Nigeria. The data were interpreted by source parameter imaging (SPI) and spectral depth analysis techniques. The basement depth obtained from SPI method ranges from-0.79 to-6.57 km while the basement depth from the spectral analysis shows the deep source varying from 1.91 to 6.50 km and the shallow source varying from 0.83 to 1.89 km. The depth to basement of the deep source is deepest around Oturkpo area but shallowest around Agana area. The maximum depths obtained from the two methods agree with each other and show thick sediments that are sufficient for hydrocarbon accumulation in the study area.
