Radiogenic heat production estimation towards sustainable energy drive in northeastern Nigeria

<h2>Abstract</h2> An estimate of the radiogenic heat production (RHP) across the different petrologic units of northeastern, Nigeria was previously not performed. Hence, their geothermal potentials are not widely known. However, an airborne radiometric data of equivalent uranium, (eU), equivalent thorium (eTh,) and percentage potassium (% K) acquired by Nigerian geological survey agency (NGSA) in the year 2009 was deployed in the evaluation of the RHP across the major petrologic outcrops of northeastern, Nigeria. The objective of this study is to estimate the quantity of RHP across the 13 petrologic units of the northeastern Nigerian terrain via the use of an empirical equation (<mml:math><mml:mrow><mml:mrow><mml:mi>R</mml:mi><mml:mi>H</mml:mi><mml:mi>P</mml:mi><mml:mo>=</mml:mo><mml:mi>ρ</mml:mi><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mrow><mml:mn>0.0952</mml:mn><mml:mi>C</mml:mi></mml:mrow><mml:mi>u</mml:mi><mml:mo>+</mml:mo><mml:mn>0.0256</mml:mn><mml:mi>C</mml:mi><mml:mrow><mml:mi>T</mml:mi><mml:mi>h</mml:mi></mml:mrow><mml:mo>+</mml:mo><mml:mn>0.0348</mml:mn><mml:mi>C</mml:mi><mml:mi>k</mml:mi></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:math>. The petrologic units studied are; medium-coarse grained biotite-hornblende granites (<i>OGe</i>), porphyritic biotite-hornblende granites (<i>OGp</i>), banded gneiss (<i>bG)</i>, charnokytes (<i>Ch</i>), ignimbrites (<i>JYG</i>), migmatites-gneiss (<i>MG</i>), basalts (<i>bb</i>), Gombe sandstones (<i>GS</i>), Pindiga Formation (<i>PS</i>), Yolde Formation (<i>YL</i>), Bima sandstones (<i>BS</i>), Keri-Keri Formation (<i>KK</i>), and alluvium (<i>AL</i>). Basic/preliminary processing such as; signal integration, signal validation, and examination of spurious data were applied prior to the RHP computation. The results of the heat production analysis performed show the range of RHP to be from <mml:math><mml:mrow><mml:mn>1.11</mml:mn><mml:mi>μ</mml:mi><mml:mi>W</mml:mi><mml:mo>/</mml:mo><mml:msup><mml:mi>m</mml:mi><mml:mn>3</mml:mn></mml:msup></mml:mrow></mml:math> to <mml:math><mml:mrow><mml:mn>3.35</mml:mn><mml:mi>μ</mml:mi><mml:mi>W</mml:mi><mml:mo>/</mml:mo><mml:msup><mml:mi>m</mml:mi><mml:mn>3</mml:mn></mml:msup></mml:mrow></mml:math> Hence, the maximum heat production value of <mml:math><mml:mrow><mml:mn>3.35</mml:mn><mml:mi>μ</mml:mi><mml:mi>W</mml:mi><mml:mo>/</mml:mo><mml:msup><mml:mi>m</mml:mi><mml:mn>3</mml:mn></mml:msup></mml:mrow></mml:math> was recorded along porphyritic biotite-hornblende granites (<i>OGp</i>) rock block, while the least value of <mml:math><mml:mrow><mml:mn>1.11</mml:mn><mml:mi>μ</mml:mi><mml:mi>W</mml:mi><mml:mo>/</mml:mo><mml:msup><mml:mi>m</mml:mi><mml:mn>3</mml:mn></mml:msup></mml:mrow></mml:math> was recorded over alluvium (<i>AL</i>) rock outcrops. Furthermore, the spatial distribution of the RHP values over the study location shows a gradual increase from the middle, low heat production (sedimentary zones) to the high heat producing areas (granitic and metamorphic zones) around eastern and western parts. The petrologic units arranged in order of decreasing magnitude of radiogenic heat generation are; <i>OGp</i> > <i>MG > OGe/bG > bb > GS > Ch > JYG > BS > PS/YL > KK > AL.</i> On a general note, the petrologic units studied were classified as low in terms of geothermal character based on comparison with other previous global RHP studies.