Structural Interpretation of Aeromagnetic Data for Regional Controls on Gold Mineralization in Northwestern Nigeria

Abstract

The aim of this study is to delineate regional structures associated with gold mineralization in part of northwestern Nigeria using aeromagnetic data. The dataset, comprising Total Magnetic Intensity (TMI), was processed and analyzed using residual anomaly separation, reduction-to-equator (RTE), First Vertical Derivative (FVD), lineament extraction, and Source Parameter Imaging (SPI) techniques. The results show TMI values ranging from 32,893.9 nT to 33,077.5 nT, indicating distinct lithological variations. Residual magnetic anomalies vary between –94.0 nT and 76.3 nT, reflecting both shallow and deep sources. The RTE correction improved anomaly symmetry, while FVD and lineament maps revealed dominant NE–SW and NW–SE structural trends, with subordinate E–W and N–S orientations, concentrated between latitudes 11°30?–12°30?N and longitudes 7°30?–8°30?E. SPI depth estimates range from 143 m to 737 m, with shallow anomalies (150–250 m) located in the south and west, and deeper anomalies (>500 m) concentrated in the northeast. These findings are significant as they reveal a structurally complex terrain with basement highs, intrusives, and depressions that control mineralization. The delineated structures provide valuable targets for gold exploration and contribute to an improved understanding of the regional tectonic framework.

Introduction

Airborne geophysical surveys, particularly aeromagnetic methods, offer efficient, cost-effective means of studying subsurface geology. This study leverages aeromagnetic data to identify structural features (faults, fractures, shear zones) that are potential hosts of gold mineralization in the Nigerian Basement Complex, specifically in parts of Kano and Katsina States.

Key Objectives

• Map subsurface structures that control mineralization using aeromagnetic data.

• Delineate lineaments and magnetic anomalies that indicate prospective gold zones.

• Apply modern processing and interpretation techniques (e.g., RTE, FVD, SPI, AS).

• Improve understanding of regional tectonic framework for mineral exploration.

Geological Context

• The study area lies within the Nigerian Basement Complex, composed of Precambrian-Pan-African rocks: migmatite, gneiss, schist, quartzite, phyllite, and granite.

• It covers parts of the Kazaure and Malumfashi schist belts, known to host gold deposits, often structurally controlled within faults and shear zones.

Data & Methodology

• Data Source: Aeromagnetic and satellite gravity data from the Nigeria Geological Survey Agency (NGSA).

• Software Tools: Oasis Montaj, ArcGIS, and Rockware.

• Processing Steps:

  • Gridding (using minimum curvature)

  • Regional-residual separation (to isolate shallow anomalies)

  • Reduction to Magnetic Equator (RTE)

  • First Vertical Derivative (FVD)

  • Analytic Signal (AS)

  • Source Parameter Imaging (SPI)

Interpretation Techniques

• Qualitative: Visual mapping of magnetic anomalies and lineaments to identify geological structures.

• Quantitative: Estimating depth and geometry of sources using SPI and derivatives.

Key Results

1. Total Magnetic Intensity (TMI):

   • Ranges from 32,893.9 nT to 33,077.5 nT.

   • Highlights magnetite-rich intrusives (highs) and altered zones (lows).

2. Residual Magnetic Map:

   • Values between –94.0 nT and 76.3 nT.

   • Emphasizes shallow features and structural discontinuities.

3. Reduction to Equator (RTE):

   • Centers anomalies over sources.

   • Reveals NE–SW and N–S trends, typical of regional deformation zones.

4. First Vertical Derivative (FVD):

   • Enhances shallow magnetic contrasts.

   • Shows dominant NE–SW and NW–SE lineaments, linked to faults and fractures.

5. Lineament Mapping:

   • Dense network of linear features, suggesting intense deformation.

   • These are structurally important for fluid flow and gold deposition.

6. Source Parameter Imaging (SPI):

   • Depths range from 143 m to 737 m.

   • Shallow anomalies (150–250 m) dominate the south and west.

   • Deeper zones (>500 m) occur in the northeast, suggesting basin structures.

Structural Significance

• The dominant lineament orientations (NE–SW, NW–SE) correlate with known tectonic trends in gold-bearing regions.

• Fractures, faults, and shear zones mapped in the study likely serve as pathways for hydrothermal fluids, making them prime targets for gold exploration.

Conclusion

This study delineates the regional structures associated with gold mineralization in part of northwestern Nigeria using aeromagnetic data, including TMI, residual separation, RTE, FVD, lineament analysis, and SPI. The Total Magnetic Intensity (TMI) ranges between 32,893.9 nT and 33,077.5 nT, reflecting clear lithological variations. Residual anomalies vary from –94.0 nT to 76.3 nT, distinguishing shallow and deep magnetic sources. The reduced-to-equator (RTE) correction enhanced anomaly positioning, improving structural interpretation. The First Vertical Derivative (FVD) and lineament maps delineated dominant NE–SW and NW–SE fault trends, with subordinate E–W and N–S orientations, concentrated between latitudes 11°30?–12°30?N and longitudes 7°30?–8°30?E, suggesting zones of intense deformation favorable for mineralization. Source Parameter Imaging (SPI) revealed depth variations from 143 m to 737 m, with shallow sources (150–250 m) concentrated in the south and west, while deeper anomalies (>500 m) dominate the northeast. These results highlight a structurally complex terrain in which basement highs, intrusives, and deep depressions provide favorable conditions for gold mineralization, thereby identifying priority exploration targets within the study area.

References

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Copyright

Copyright © 2025 Umar Suleiman, Babagana A. Mustapha, Omogbai Sefiya Audu, Baba -Ettenu Sunday Godday, Agbali Shedrach Eneojoh, Maikori Bitrus Buba, George Josephine Muknaan. 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.