Estimation of depths to the bottom of magnetic sources and ensuing geothermal parameters from aeromagnetic data of Upper Sokoto Basin, Nigeria (original) (raw)
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Arabian Journal of Geosciences, 2017
Understanding the thermal distribution within the crust and rheology of the earth's lithosphere requires the knowledge of the Depth to the Bottom of Magnetic Sources (DBMS). This depth is an important parameter in this regard, which can be derived from aeromagnetic data and can be used as a representation for temperature at depth where heat flow values can be evaluated. In this work, high-resolution aeromagnetic (HRAM) data of part of Chad Basin (covering about 80% of the entire basin), an area bounded by eastings 769,000 and 1,049,900 mE and northings 1,200,000 and 1,500,000 mN, were divided into 25 overlapping blocks and each block was analyzed using spectral fractal analysis method. The spectral analysis method was used to obtain the Depth to the Top of Magnetic Source (DTMS), centroid depth, and DBMS. From the calculated DBMS, the geothermal gradient and heat flow parameters were evaluated and the result obtained shows that DBMS varies between 18.18 and 43.64 km. Also the geothermal gradient was found to be varying between 13.29 and 31.90°C/km and heat flow parameters vary between 33.23 and 79.76 mW/m 2 , respectively. The heat distribution of this area is one of the key parameters responsible for various geodynamic processes; therefore, this work is important for numerically understanding the thermal distribution in Chad Basin, Nigeria since rock rheologies depend on temperature, which is a function of depth.
Geothermal Energy Science
A regional estimation of Curie-point depths (CPDs) and succeeding geothermal gradients and subsurface crustal heat flow has been carried out from the spectral centroid analysis of the recently acquired high-resolution aeromagnetic (HRAM) data of the entire Bida Basin in north-central Nigeria. The HRAM data were divided into 28 overlapping blocks, and each block was analysed to obtain depths to the top, centroid, and bottom of the magnetic sources. The depth values were then used to assess the CPD, geothermal gradient, and subsurface crustal heat flow in the basin. The result shows that the CPD varies between 15.57 and 29.62 km with an average of 21.65 km, the geothermal gradient varies between 19.58 and 37.25 °C km<sup>−1</sup> with an average of 27.25 °C km<sup>−1</sup>, and the crustal heat flow varies between 48.41 and 93.12 mW m<sup>−2</sup> with an average of 68.80 mW m<sup>−2</sup>. Geodynamic processes are mainly controlled by t...
Sains Malaysiana, 2022
Geothermal energy resources have been established globally to be among the sustainable and environmentally harmless means of energy generation. Curie-point depths (CPD), temperature gradients, and heat flow data over the study area were computed using a spectral analysis method in order to have a preliminary view of the geothermal implications (prospect) of the current area. Aeromagnetic data acquired by the Nigerian Geological Survey Agency (NGSA) in the year 2009 was used for the research. The results showed the minimum, maximum, and the average CPD values as 8.18 km, 31.48 km, and 13.0 km, respectively. The minimum, maximum and average thermal gradients obtained were 18.42 °C/km, 70.91 °C/km, and 50.2 °C/km, respectively. The heat flow data obtained ranged from 33.15 mW/m 2 to 177.28 mW/m 2 , with an average value of 110.65 mW/m 2. Locations depicting shallow CPDs anomalies (Alkaleri, Darazo, Dukku, Misau, Wuyo, Deba, and Tula), also showed conformity with high heat flow areas. As such, they are regarded as areas of promising geothermal prospects and are recommended for further detailed investigation. Locations depicting a high magnetic susceptibility contrast from a generated analytic signal map, as well as high temperature gradients, high heat flow, and shallow CPDs are attributed to crustal thinning along the sedimentary basin and magmatic intrusions along basement areas, respectively. The magnetic depth to the basement calculated for the study area using the source parameter imaging (SPI) method ranges from 0.610 km to 3.055 km. The present study has provided an insight on preliminary information, regarding new areas of possible geothermal prospects for further detailed investigation.
The Wikki Warm Spring (WWS) is located on the Kerri-Kerri formation of tertiary age. This forms part of the Benue Basin, which links up with the Chad Basin in the north and extends southwest to the Anambra Basin in Nigeria. The stratigraphy of the WWS region consists of alluvium, the Kerri-Kerri formation, the Gombe formation, the Pindiga formation, the Yolde formation, the Bima formation, and basement rocks as the oldest. We estimate the depth to the bottom of magnetic sources (DBMS) in the WWS region using the fractal sources distribution approach on aeromagnetic data to identify the geothermal system of the WWS region. The adopted computational method is based on statistical methods of depth determination from the radial power spectrum assuming a fractal distribution of magnetic sources. The average estimated DBMS at the WWS source location is 10.72 ± 0.54 km. The obtained results imply an average thermal gradient of 54.11 °C km-1 and heat flow value of 135.28 mW/m 2. Generally, shallow DBMS values are obtained in the northeastern region of the WWS area and these increase towards the southwestern region when regional variation patterns of estimated depths are considered. The generally shallow DBMS obtained in the study area is attributed to magmatic intrusion or diapirism in the subsurface and emphasizes the effects of large-scale tectonic events, particularly the basin-initiating event, as major influences on the thermal history. Results will contribute to decisions on where to drill boreholes for further geothermal energy exploration in the region.
Crustal thermal regime of Ikogosi warm spring, Nigeria inferred from aeromagnetic data
Arabian Journal of Geosciences, 2011
Spectral analysis method was applied to aeromagnetic data obtained for Ikogosi warm spring (IWS) area of southwestern Nigeria. This was done with the objective of determining the bottom of the magnetized crust called Curie point depth (CDP) and understand the nature and extent of the local geothermal system at depth beneath IWS. The depth to the centroid, Z o , of the deepest distribution of the magnetic dipoles was obtained by computing least-squares fit to the lowest-frequency segment of the azimuthally averaged log power spectrum. The average depth to the top of the deepest crustal block was computed as the depth to the top, Z t , of the second lowestfrequency segment of the spectrum. The depth to the bottom of the deepest magnetic dipoles, the inferred Curie point depth, was then calculated from Z b =2Z o −Z t. The Curie depth estimates for IWS range between 4.68 and 11.38 km (below sea level). We also estimate the heat flow and Curie temperature using a one-dimensional conductive heat transport model. The average heat flow, 42 mW m −2 , and geothermal gradient, 32°C/km, obtained suggest a low enthalpy thermal regime. The Curie temperature for the region varies between 153°C and 350°C. Also, an inverse linear relationship between heat flow and Curie depths was determined. Good agreement between the Curie point depths derived from heat flow data and magnetic data suggests that the Curie point depth analysis is useful to estimate the regional thermal structure and the tectonic settings.
Open Journal of Geology, 2019
Analysis of high resolution of aeromagnetic data was carried out over Lamurde, Adamawa state northeastern Nigeria to determine the Curie point depth (CPD), heat flow and geothermal gradient. The aeromagnetic data used for this work was obtained at Nigerian geological survey agency, the total magnetic intensity was processed to produce the residual magnetic map which was divided into 4 overlapping blocks, each block was subjected to spectral analyses to obtain depths to the top boundary and centroid, while depth to bottom of the magnetic sources was calculated using empirical formula. The depths values obtained were then used to assess the CPD, heat flow and geothermal gradient in the area. The result shows that the CPD varies between 9.62 and 10.92 km with an average of 10.45 k, the heat flow varies between 150.73 and 132.78 mWm −20 •˚C −1 with an average of 139.12 mWm −20 •˚C −1 and the geothermal gradient in the study area varies between 12.16 and 15.67 ˚C/km with an average of 13.39 ˚C/km. In view of the above results, the high heat flow may be responsible for maturation of hydrocarbon in Benue Trough as well as responsible for the lead Zinc Mineralization. Again by implication, Lamurde area can be a good area for geothermal reservoir exploration for an alternative source for power generation.
African Scientific Reports, 2024
In a bid to explore unconventional electricity generation sources and reduce effects of fossil fuels, this study evaluates geothermal resource potentials over parts of Southwestern Nigeria, precisely depth to the bottom of magnetic source (DBMS), heat flow, geothermal gradient and their relationships. Regional-residual anomaly separation was conducted, and spectral analysis was applied on the residual anomaly component of 14 aeromagnetic data sheets. Depth to the bottom of magnetic source varies between 1.87 and 6.26 km, with average value of 3.50 km, heat flow varies between 23.18 and 77.38 mWm −2 , with average value of 43.79 mWm −2 , while geothermal gradient varies between 9.27 and 30.95°C/km with average value of 17.52°C/km. Northcentral region has the highest heat flow (77.4 mWm −2), followed by Northeast (68.3 mWm −2), Southwest has the least (< 40.0 mWm −2) while Southeast has values in between the extremes. A comparison between the average heat flow and that of 'thermally stable' continental regions of the world (60 or 65) mW/m 2 gives 72.98 or 67.37% respectively. The estimated heat is probably from mantle plumes, radioactive sources or heat generated from pressures within basements that are overlaid by thick thermally insulated sediments, hence hot magmatic fluid flows into fractured basement and cause hydrothermal alterations of surrounding rocks. Since most geodynamic operations depends on thermal structure of the earth's crust, the result of this study has undoubtedly contributed significantly to the body of existing thermal knowledge and closed the information gap regarding crustal temperature distribution at depth in Southwest part of Nigeria and Nigeria in general.
Egyptian Journal of Petroleum, 2017
This study, which spans latitude 5°N-5.30 I N and Longitude 13°E-13.5°E with an approximate area of about 3400 km 2 within the Northwestern Sokoto basin of Nigeria, aims to delineate possible source of stress regime, determining the structural features and their corresponding trend directions, delineating lithologic boundaries as evidenced by magnetic disturbances caused by different rock types and estimating the hydrocarbon viability within the study area by interpreting the behavior of the geophysical data obtained from the Nigeria Geological Survey Agency, NGSA in half degree sheet. The aeromagnetic data was subjected to both qualitative and quantitative analytical techniques using Oasis Montaj software, version 8.1. The result of the qualitative analysis generated some magnetic gradient maps showing dominant and minor magnetic structures trending E-W, NE-SW and NW-SE. These trends are possible fault indicators within the region. Similarly, the qualitative analysis revealed lithologic boundaries trending in the E-W and NW-SE direction. The dominant E-W trend possibly highlights the stress regime and also represents the Pre-Pan African Orogeny that was characterized by small brittle deformation which resulted in the development of conjugate strike-slip fault systems while the truncated NE-SW, NW-SE trends indicate Pan-African Orogeny. On the other hand, quantitative analysis performed on the aeromagnetic data by means of Source Parameter Imaging (SPI) quantitative method reveals depth to deep seated magnetic sources to range from 54.1 m to 3384.4 m but with an average of about 739 m. The dominant E-W tectonic magnetic trending structures and a thickness average of 739 m limit the possibility of oil and gas exploration. Thus the possibility of hydrocarbon exploration even when seismic sections are run within the study area will be very minimal.
Journal of Geoscience, Engineering, Environment, and Technology
The assessment of geothermal potentials over part of the upper Benue trough corresponding to Kaltungo, Guyok, Lau and Dong areas, North Eastern Nigeria using spectral depth analysis of aeromagnetic data has been carried out. The study area is bounded by latitudes 9o00’N and 10o00’N and longitudes 11o00’E and 12o00’E. This research work is necessitated by the need for renewable and alternative sources of energy for use in Nigeria. Regional/residual separation was carried out on the total magnetic field using polynomial fitting method of order one. The residual map was divided into nine overlapping blocks for the spectral analysis. The centroid depths and depth to top of basement were obtained from the plot of log of power spectrum against wavenumber. These two parameters were used to estimate the Curie point depth using , where and are Curie depth, centroid depth and depth to top of basement respectively. The results from the spectral analysis suggested that in the parts of the U...