Structural and Thermal Characterization of Geothermal Resources Using Aeromagnetic, Gravity, and Remote Sensing Data for Renewable Energy Exploration in Northeastern Chad Basin, Nigeria

Abstract

This study integrates aeromagnetic, gravity, and remote sensing datasets to assess the geothermal potential of the northeastern Chad Basin, Nigeria. The Total and residual magnetic intensity maps reveal magnetic anomalies ranging from 32918 to 33184.5 nT, and -58.7 to147.8nT linked to shallow intrusions and hydrothermally altered zones. Vertical derivative and analytic signal processing delineate structurally complex zones favorable for geothermal activity, while Source Parameter Imaging (SPI) and Curie Point Depth (CPD) analysis estimate geothermal gradients and heat flow, identifying high-potential blocks such as Block 2 and Block 6 with heat flows exceeding 340 mW/m² and Curie depths ranging from 8.49 to 19.87 km. Gravity data further support these findings by highlighting low-density anomalies and structural breaks that may enhance geothermal fluid movement, with Bouguer anomaly values ranging between -47.2 and -37.1 mGal. Remote sensing analysis identifies dense lineament trends (NE–SW and NW–SE), hydrothermal alterations, and high land surface temperatures, with LST values between 289.85 and 339.7 K, correlating with underlying geophysical anomalies. The integration of these methods confirms spatial consistency in geothermal indicators across geologically and structurally favorable zones, notably around Mafa (13°22?E, 12°08?N), Kesangala (13°25?E, 12°15?N), Monguno (13°37?E, 12°40?N), and Konduga (13°25?E, 11°57?N). These results underscore the basin’s elevated geothermal potential and provide a basis for targeted exploration and development

Introduction

1. Background and Significance:

• Geothermal energy is gaining global importance as a sustainable, base-load, low-carbon energy source.

• It is especially promising in energy-deficient regions like northeastern Nigeria, due to its continuous power potential and minimal environmental footprint.

• This study focuses on the Chad Basin in Nigeria, aiming to structurally and thermally characterize geothermal resources through integrated geophysical and remote sensing methods.

2. Methods Used:

A. Geophysical Techniques:

• Aeromagnetic Data: Helps detect subsurface structures such as faults and intrusions.

  • Techniques: First Vertical Derivative (FVD), Analytic Signal (AS), Source Parameter Imaging (SPI), Curie Point Depth (CPD) estimation using the centroid method.

• Gravity Data: Assesses density contrasts linked to geothermal sources.

  • Bouguer and residual gravity anomalies help map heat-related structures.

• Spectral Analysis: Used FFT on magnetic data from 16 blocks to determine Zt (top), Zo (centroid), and calculate CPD, geothermal gradient, and heat flow.

B. Remote Sensing Techniques:

• Landsat 9 thermal infrared (TIR) and multispectral data were used.

• Calculations included:

  • TOA Radiance, Brightness Temperature (BT)

  • NDVI, Proportion Vegetation (Pv), Surface Emissivity (ε)

  • Land Surface Temperature (LST)

• ASTER DEM was used to map lineaments and surface structural features.

3. Study Area and Geologic Setting:

• The region lies within Quaternary deposits (unconsolidated sand, clay, gravel).

• Covered areas include Konduga, Jere, Monguno, Mafa, Kilborani, Gajiram, and Ajiri.

• These deposits suggest young, flat terrains formed by sedimentary processes.

4. Results:

A. Magnetic and Structural Interpretation:

• TMI and RMI maps reveal magnetic anomalies, pointing to shallow intrusions and possible hydrothermal zones.

• FVD and AS maps identify structurally complex zones, conducive to geothermal activity.

• Lineament analysis reveals dominant NE–SW and NW–SE fault trends.

• SPI map shows source depths from 180–900 m, favorable for reservoir development.

B. Thermal Modelling (16 Blocks):

• Curie Point Depth (CPD): 3.94–8.48 km (avg. 6.28 km)

• Geothermal Gradient: 68.37–147.36 °C/km (avg. 96.42 °C/km)

• Heat Flow: 170.93–368.39 mW/m² (avg. 241.04 mW/m²)

• Blocks 2 and 6 (centered around 13.2°E, 12.2°N) show the most promising geothermal potential.

C. Thematic Maps:

• Curie Depth Map: Shallowest depths in central and southwestern regions (3.8–5.8 km), deeper in the northeast (>6.8 km).

• Geothermal Gradient Map: Highest gradients in southwest (~150°C/km), lowest in the northeast.

• Heat Flow Map: Highest values (>320 mW/m²) concentrated in the southwestern quadrant, indicating a geothermal anomaly.

5. Data Sources:

• Landsat 9 imagery and ASTER DEM from NASA/USGS.

• Gravity data from Bureau Gravimétrique International (BGI).

• Aeromagnetic data from Nigerian Geological Survey Agency (NGSA).

Conclusion

The integration of aeromagnetic, gravity, and remote sensing techniques has revealed a coherent geothermal framework within the northeastern Chad Basin. Magnetic data indicate shallow intrusions, fault zones, and high Curie point temperatures, particularly in the southwestern and central areas (12°00?N–12°30?N, 13°00?E–13°30?E), where elevated geothermal gradients and heat flows suggest viable geothermal reservoirs. Gravity anomalies confirm the presence of fractured, low density rocks and delineate major structural corridors aligned with mapped lineaments. Remote sensing data reinforce these findings by identifying areas of intense hydrothermal alteration, low vegetation indices, and high surface temperatures, especially in Mafa (13°22?E, 12°08?N), Kesangala (13°25?E, 12°15?N), and Kilborani (13°28?E, 12°20?N). The convergence of high heat flow, shallow Curie depths, significant structural deformation, and thermal anomalies strongly supports the presence of economically exploitable geothermal resources. This multidisciplinary approach provides a robust framework for future geothermal exploration in the region.

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Copyright

Copyright © 2025 Babagana A. Mustapha, Muhammad Muhammad Bello, Umar Suleiman, Sadiya Ahmad Muhammad, Mohammed Ibrahim Musa, Abba Kaka Alhaji Modu, Idris El-Yakub, Amina Jibril Muhammad. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.