Stephen Eguba Ekwok

This inclusive innovation study aimed to generate a high-resolution metallogenic potential map of the mineral-rich Oban Massif in southeastern Nigeria by integrating structural, lithological, and hydrothermal alteration indicators from airborne geophysical data. A comprehensive suite of high-resolution airborne magnetic and radiometric data was processed. The total magnetic intensity data (TMI) as well as grids of first and second vertical derivatives (FVD, SVD), analytic signal (ASIG), tilt angle derivative (TAD), and total horizontal derivative (THD) were subjected to the Centre for Exploration Targeting (CET) procedure to elucidate the subsurface architecture. The analysis revealed a polyphase deformation history dominated by a NE-SW structural trend, which provides critical migration pathways for mineralizing fluids. A direct spatial correlation was established between elevated magnetic intensities and anomalous potassium concentrations, delineating a prospective zone for igneous-related gold mineralization. Lithological diversity, including shales, hornfels, gneiss, schist, and granitoids, was identified. Radiometric K/Th ratios ranging from -0.5 to 1.5 %/ppm were recorded, with specific anomalous zones (exceeding the background range of 0.16-1 %/ppm) signaling potential for gold-silver, polymetallic, molybdenum, tungsten, and rare earth element deposits. Depth estimates from source parameter imaging (SPI), standard Euler deconvolution (SED), and 2-D forward modeling indicate sediment thicknesses extending to approximately 2580 m. The outcome is a new, targeted framework that moves beyond regional assessment to define specific exploration targets, thereby providing a direct tool for identifying prospective mineralization hosts within the Oban Massif.

The Nigerian sector of the Iullemmeden Basin is characterized by widespread metallic and non-metallic mineral potentials. In this inclusive innovation work, total magnetic intensity (TMI) data were used to detect the structural elements associated with tectonic events and map the probable zones of mineralization within the study area. The TMI data were upward continued to 100 m before the application of softsign function (SF), and enhanced horizontal gradient amplitude (EHGA) filters. Subsequently, the Centre for Exploration Targeting (CET) grid analysis tool was applied on the enhanced grids to generate structural maps. The observed geologic structures, which suggest polyphase deformations are characterized by E-W, NE-SW, NNE-SSW orientations. The mapped lineaments correspond to structural elements triggered by several tectonic events. The main NE-SW structural direction matches the regional strike orientation. The tilt depth technique (TDT), source parameter imaging (SPI) and standard Euler deconvolution (SED) depth approximation methods plus the 2D forward modellings indicated depth values of ≤ 2800 m. The 2D forward models suggest that the underlying basement has undergone significant stress, thereby creating faults and an undulating surface. Generally, the geologic structures create favorable conditions for migration and accumulation of polymetallic mineralization (Cu, Pb, Zn, Ag), precious metals (gold), special metals (Sn, W, Ta, Li), and radioactive minerals (U, Th) associated with both the sedimentary formations and underlying basement structures.

Some vertical electrical sounding (VES) data from tectono-thermal environments usually plot anomalously on a VES curve, thereby distorting the curve trend at the points of their occurrence. These datasets usually plot noisily in the form of a sudden rise and drop in electrical resistivity values. They constitute abnormal datasets that are usually deleted to recover trends and consequently develop confidence in both the datasets and the modelling and interpretational processes. This study was conducted to assess their origin and consequently gain an understanding of their contributions to groundwater accumulation and transmission in saprock aquifers. The results, supported by co-located drilling and pumping test data, show that these datasets are indicators of subsurface conditions where high-resistivity unconformal structures directly overlie saturated (low-resistivity) porous media, provided that the resistivity of the first breakout point is less than those from subsequent points. Remote sensing data reveal that these types of curves are common in hard rock and metasedimentary environments. Borehole groundwater yields can also be assessed qualitatively from the number and trend of breakoff points. The integrity of the breakoff points must be affirmed by using more sensitive equipment for data acquisition and repeating the measuring process using different potential electrode separations and—where possible—VES profile orientation.

The particle swamp optimization procedure was applied to high-quality magnetic data acquired from the Precambrian Obudu basement complex in Nigeria with the object of estimating the distinctive body parameters (depth (z), index angle (θ), amplitude coefficient (K), shape factor (Sf), and location of the origin (x₀)) of magnetic models. The magnetic models were obtained from four profiles that ran perpendicular to the observed magnetic anomalies within the study area. Profile A–A’ with a length of 2600 m is characterized by inverted model parameters of K = 315.67 nT, z = 425.34 m, θ = 43°, Sf = 1.15, and x₀ = 1554.86 m, while profile B–B’ with a length of 5600 m is described by K = 257.71 nT, z = 543.75 m, θ = 54°, Sf = 0.96, and x₀ = 3645.42 m model parameters. Similarly, profile C–C’ with a length of 3000 m is defined by K = 189.53 nT, z = 560.87 m, θ = 48, Sf = 1.2, and x₀ = 1950 m. Profile D–D’, which is well-defined by a 2500 m length, started at the crest of the observed magnetic anomaly and displays inverted model parameters of 247.23 nT, 394.16 m, 39°, 1.26, and 165.41 m. Correlatively, the estimated shape factor of the four models (Sf = 1.15, 0.96, 1.2, and 1.26) shows that the magnetic models are linked to thin sheets. Furthermore, quantitative interpretations of the models show that the PSO operation is rapid and proficient.

In this paper, certain areas of the Kingdom of Saudi Arabia (KSA) are assessed in order to map potential geothermal energy zones. To evaluate high-resolution aerial magnetic data, spectral depth analysis using a modified centroid approach was used. The calculated geothermal parameters were gridded in order to delineate the regions characterised by a shallow Curie point depth (CPD) and a high geothermal gradient (GG) as well as a high heat flow (HF). The CPD, GG and HF calculated from the analysed data varied in the ranges of 6.0–15.0 km, 40.0–100.0 °C/km and 90.0–270.0 mW/m², respectively. The obtained results show the concurrence of the positions of shallow CPD (83.5 °C/km) and high HF (>211.0 mW/m²). The geothermal systems that are oriented in the E–W direction are related to the Red Sea tectonics, the tectonic opening of the Red Sea/Gulf of the Suez Rift, hot subterranean anomalies and high enthalpy from radioactive granites. Likewise, the geologic structures (fractures and faults) related to the Red Sea tectonics serve as channels for the movement of hydrothermal fluids and the deposition of associated minerals. All in all, another geophysical study involving deep boreholes, and seismic, magnetotelluric, electromagnetic and geochemical data should be conducted to evaluate and estimate precisely the economic reserves of geothermal resources.

Aeromagnetic data from the Ogoja region, Southeast Nigeria, were enhanced using high-precision methods including the tilt angle of total horizontal gradient (TAHG), the softsign function (SF), and the improved logistic function (IL) with the aim of creating a new structural map. This new map can help improve the understanding of the trend, spatial distribution, and pattern of the lineaments. The TAHG, SF, and IL methods generated geologic structures with correlating trends, distributions, and patterns. However, the SF and IL techniques mapped the borders of geologic structures more precisely. The lineaments extracted from the SF and IL maps were reduced to equator (RTE) magnetic data, and a GIS was used to create structural maps with NE–SW, NW–SE, NNE–SSW, and NNW–SSE orientations. Furthermore, the depths (0–2100 m) of these geologic structures were estimated using the tilt depth technique (TDT). The high lineament density and thin sedimentation observed in the study area were triggered by the widespread Santonian igneous intrusions associated with the Abakaliki Anticlinorium. The techniques applied in our study can be employed in areas with the same conditions around the world for the precise delineation of geologic structures from magnetic and gravity data.