Abstract
<p><strong>Abstract.</strong> 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<span class="thinspace"></span>km with an average of 21.65<span class="thinspace"></span>km, the geothermal gradient varies between 19.58 and 37.25<span class="thinspace"></span>°C<span class="thinspace"></span>km<sup>−1</sup> with an average of 27.25<span class="thinspace"></span>°C<span class="thinspace"></span>km<sup>−1</sup>, and the crustal heat flow varies between 48.41 and 93.12<span class="thinspace"></span>mW<span class="thinspace"></span>m<sup>−2</sup> with an average of 68.80<span class="thinspace"></span>mW<span class="thinspace"></span>m<sup>−2</sup>. Geodynamic processes are mainly controlled by the thermal structure of the Earth's crust; therefore this study is important for appraisal of the geo-processes, rheology, and understanding of the heat flow variations in the Bida Basin, north-central Nigeria.</p>
Highlights
This study aims at quantitative estimation of regional Curiepoint depth (CPD) and succeeding geothermal structures, namely geothermal gradients and subsurface crustal heat flow anomalies, in the whole of Bida Basin in north-central Nigeria using the spectral centroid analysis of the recently acquired high-resolution airborne magnetic (HRAM) data
Averaged power and wave-number-scaled power spectra for each of the 28 overlapping blocks were calculated and used to estimate the depth to the bottom of magnetic sources (DBMS), which serve as a proxy for CPDs
The right-hand side of the figure shows the slope of the high-wave-number portion of the spectra, which leads to the estimation of the depth to the top of magnetic sources (Zt), while the left-hand side shows the slope of the lower-wave-number part of the wave-number-scaled spectra, which leads to the estimation of centroid depth (Zo)
Summary
This study aims at quantitative estimation of regional Curiepoint depth (CPD) and succeeding geothermal structures, namely geothermal gradients and subsurface crustal heat flow anomalies, in the whole of Bida Basin in north-central Nigeria using the spectral centroid analysis of the recently acquired high-resolution airborne magnetic (HRAM) data. Several studies have shown that regional magnetic data can be used extensively to determine the thermal structure of the Earth’s crust in various geologic environments (Spector and Grant, 1970; Bhattacharyya and Leu, 1975, 1977; Byerly and Stolt, 1977; Blakely and Hassanzadeh, 1981; Okubo et al, 1985, 2003; Blakely, 1988, 1995; Maus et al, 1997; Tanaka et al, 1999; Chiozzi et al, 2005; Eppelbaum and Pilchin, 2006; Ross et al, 2006; Ravat et al, 2007; Trifonova et al, 2009; Gabriel et al, 2011, 2012; Bansal et al, 2011, 2013, 2016; Nabi, 2012; Hsieh et al, 2014; Nwankwo and Shehu, 2015; etc.). At temperature above CPT, the thermal agitation causes the spontaneous alignment of the various domains in the mineral to be destroyed (or randomized) to the extent that the ferromagnetic minerals become totally paramagnetic (Langel and Hinze, 1998)
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