Nigeria’s Hidden Heat: New National Analysis Points to a Deep Geothermal Giant in the Northwest

Nigeria has long been defined by its oil wealth, but beneath its crystalline basement rocks and sedimentary basins lies another energy story that has never been told at national scale. A new study published in Natural Resources Research has delivered the first comprehensive, multi-parameter geothermal assessment of the entire country, and its central finding is striking: the northwest of Nigeria sits atop a thermal regime so intense that nearly 99 percent of its surface heat flow cannot be explained by the radioactive decay of elements in the crust. Something deeper, whether mantle upwelling, thinning of the lithosphere, or deep tectonic reactivation, appears to be feeding heat into the region, and the Sokoto Basin has emerged as the country’s principal geothermal prospect.

The research, led by Samuel O. Sedara of the CSIR-National Geophysical Research Institute in Hyderabad and Adekunle Ajasin University in Nigeria, together with colleagues from Nigerian institutions, integrated an unusually broad set of data. The team compiled 175 heat-flow and geothermal gradient records alongside 1,300 radiometric measurements of the three heat-producing isotopes: uranium-238, potassium-40 and thorium-232. These measurements were organized across six geomorphic regions of the country, covering the northwest, northeast, north-central, southeast, south-south and southwest zones, allowing the authors to compare thermal behavior between Nigeria’s ancient crystalline basement complexes and its younger sedimentary basins for the first time in a single analytical framework.

What makes the study methodologically distinctive is its reliance on an independent multi-criteria decision analysis, or MCDA, framework designed to strip subjectivity out of geothermal favorability mapping. Rather than assigning weights to different geophysical parameters by expert judgment alone, the researchers derived weights objectively using Shannon entropy, a statistical measure of the information content of each variable, and cross-checked them with the analytic hierarchy process, which achieved a consistency ratio of just 0.003, far below the 0.10 threshold generally accepted as reliable. From this foundation the team constructed three composite indices: a thermal index, a heat-flow-weighted index, and a three-parameter geothermal favorability threshold index, each designed to explicitly separate conductive heat flow, the heat arriving from deeper sources, from radiogenic heat flow generated within the crust itself.

That separation is the analytical heart of the paper. Continental heat flow has two principal contributors: the slow decay of uranium, thorium and potassium in crustal rocks, and heat conducted upward from the mantle and lower lithosphere. By computing the ratio of conductive to radiogenic heat flow for each region, the authors could ask a deceptively simple question: is a region hot because its rocks are radioactive, or because something beneath the crust is supplying additional heat? In the northwest, the answer was unambiguous. The region recorded the dataset’s highest conductive heat flow at 151.4 milliwatts per square meter and a geothermal gradient of 56.0 degrees Celsius per kilometer, and its conductive-to-radiogenic ratio of roughly 86 means that 98.8 percent of the surface heat flow cannot be attributed to crustal radioactivity.

The implications of that number are profound. A purely radiogenic explanation for the northwest’s thermal anomaly is inconsistent with the data, the authors conclude, and a deeper heat source is required. While surface measurements and Curie point depth estimates, which track the depth at which magnetic minerals lose their magnetization and provide an independent proxy for crustal temperature, cannot distinguish among mantle upwelling, lithospheric thinning, or deep tectonic reactivation as the specific mechanism, the decoupling between conductive and radiogenic heat is real and quantified. This is, according to the study, the primary geoscientific result: Nigeria’s northwest is not merely warm, it is anomalously hot for reasons rooted in the deep Earth, placing it in a geodynamic category that few expected for a region far from active plate boundaries.

Crucially, the finding does not rest on a single line of evidence. The researchers subjected their rankings to a battery of independent validations. Bootstrap resampling with 1,000 iterations tested the stability of the favorability class boundaries at plus or minus 0.50 standard deviations. A random forest regression model, a machine learning algorithm that builds predictions from many decision trees, achieved a coefficient of determination of 0.702, a moderate but respectable performance given the small regional sample. K-means unsupervised clustering, which groups regions by similarity without reference to the MCDA labels, produced a silhouette score of 0.397 and an adjusted Rand index of 0.074, modest values the authors attribute candidly to the limited number of data points, since with only six regions even a single misclassification sharply depresses the agreement metric. The team is explicit that these machine learning results should be read as supporting evidence within the overall multi-method framework rather than as standalone proof.

The convergence, however, is what gives the northwest result its weight. Curie point depth-derived heat flow, random forest regression, bootstrap validation and prior independent studies all point to the same region. Across every composite index, the northwest ranks first, with a thermal index of plus 1.715, a heat-flow-weighted index of plus 1.864 and a geothermal favorability threshold index of plus 1.343. The Sokoto Basin, which spans Sokoto, Kebbi and Zamfara states, together with nearby northwest sedimentary terrains, is continuously identified as the most attractive exploration target in the country. The authors recommend urgent geophysical investigation of the basin and slim-hole drilling, along with a dedicated thermal model to establish actual temperature-at-depth profiles before any full exploration campaign begins.

The study also redraws the map of geothermal opportunity in a second, very different way. The southeast region, with a thermal index of plus 0.490, represents not a secondary version of the northwest prospect but an entirely distinct type of geothermal target. Its thermal regime is radiogenically sourced and dominated by potassium-40, meaning its heat comes from the decay of radioactive elements within crustal rocks rather than from below. That character makes the southeast better suited to direct-use applications, such as district heating, agricultural drying and greenhouse warming, than to power generation, and the authors caution that it cannot be directly compared with the northwest. The north-central and northeast regions emerge as moderately favorable, while the south-south and southwest rank as unfavorable in this screening.

The authors are careful to frame the scope of their conclusions. This was a regional-scale screening exercise, and it did not address the factors that ultimately determine whether a geothermal prospect can be developed: permeability, fluid content, reservoir depth, sustainable extraction rates and drilling feasibility. Those questions remain prerequisites for any actual development decision, and no amount of surface and magnetic data can substitute for them. Yet the study transforms the starting point for Nigerian geothermal exploration. By quantifying, for the first time at national scale, where the country’s heat comes from and how strongly each region scores across independently weighted and validated indices, it converts a diffuse sense of possibility into a ranked, evidence-based agenda. If subsequent geophysics and drilling confirm what the numbers suggest, the Sokoto Basin could place Nigeria on the geothermal map, adding a firm, weather-independent renewable resource to an energy economy in urgent need of diversification.

Subject of Research: National-scale geothermal resource assessment of Nigeria using multivariate and machine learning analysis of heat flow and radiometric data

Article Title: A New Multivariate Analysis of Geothermal Assessment of Nigeria’s Crystalline Basement and Sedimentary Basins: Thermal and Geodynamic Implications

Article References: Sedara, S. O., Alabi, O. O., Adekanle, O. J., Adekanye, O. O., & Christopher, O. A. (2026). A New Multivariate Analysis of Geothermal Assessment of Nigeria’s Crystalline Basement and Sedimentary Basins: Thermal and Geodynamic Implications. Natural Resources Research. https://doi.org/10.1007/s11053-026-10773-1

Image Credits: AI Generated

DOI: 10.1007/s11053-026-10773-1

Keywords: geothermal energy, Nigeria, heat flow, radiogenic heat production, Sokoto Basin, multi-criteria decision analysis, random forest, Curie point depth, geothermal gradient, crystalline basement, sedimentary basins, geodynamics