Estimating depth to the bottom of magnetic sources at Wikki Warm Spring region, northeastern Nigeria, using fractal distribution of sources approach

Abstract

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.

Determination of Geothermal Energy Sources in Masu Area Northeastern Nigeria Using Spectral Analysis of Aeromagnetic Data

“…Critical observations from values in Table 1 show that the heat flow and geothermal gradient increase as the Curie depth decreases. This trend agrees with the results obtained by another researcher who estimated an average Curie depth in Wikki Warm Spring, located in parts of Benue basin, which links up the Chad Basin in the north to be10.72 km, with an average thermal gradient of 54.11°C/km and average heat flow values of 135.28 mWm -2 [2]. It was reported that heat flow close to 60 mWm -2 is required for considerable generation of geothermal energy, while values ranging from 80 to 100 mWm -2 and above indicate anomalous geothermal condition [22].…”

Curie point depth, thermal gradient, and heat flow in the Colombian Caribbean (northwestern South America)

“…It has been applied in Turkey (Dolmaz et al 2005), Nigeria (Kasidi and Nur 2012), South Africa (Nyabeze and Gwavava 2016) and East and South East Asia (Tanaka et al 1999). The Fractal method has been applied in South Africa (Nyabeze and Gwavava 2018), Central India (Bansal et al 2013), Western USA (Bouligand et al 2009), Germany (Bansal et al 2011), Nigeria (Abraham et al 2015) and Mexico (Espinosa-Cardeña et al 2016).…”

“…The centroid method is based on mechanical statistical principles (Spector and Grant 1970), and on the assumption that the magnetic anomalies constitute an uncorrelated random distribution of magnetic sources (Abraham et al 2015;Bansal et al 2010Bansal et al , 2011. The power spectrum of the reduced to the pole, magnetic anomalies is defined as (Blakely 1996;Spector and Grant 1970): where h is the mean depth to the top of the magnetic source ensemble, t is the thickness of the magnetic ensemble, M is the magnetic moment, S 2 (k, a, b) is a function of the magnetic ensemble mean horizontal dimensions (a, b), k corresponds to the radial wave number in cycles/km, and Cm = 10 −7 is the proportionality constant to transform Eq.…”

“…The geothermal gradient is a measure of how the temperature varies with depth. In a 1D Earth the geothermal gradient (Nondorf 2016;Sigismondi and Ramos 2008) and heat flow are related by the Fourier's law (Abraham et al 2015;Kasidi and Nur 2013): where q is heat flow, is thermal conductivity, and dt/dz is the geothermal gradient. Temperature measurements at different depths along a borehole constitute the most common way to establish the geothermal gradients.…”

“…The Curie temperature of magnetite, 580 °C, is assumed for this study as the temperature at which crustal rocks lose their magnetic properties. In several studies (Abraham et al 2015;Anakwuba and Chinwuko 2015;Kasidi and Nur 2013) this temperature was assumed. The Curie point depth (CPD) corresponds to the depth at which the rocks reach such a temperature (Tissot and Welte 1984).…”