Ogah Arewa James, Abubakar Fahad
ZASTAL, National Space Research and Development Agency, Kano, Nigeria.
Department of Geosciences, Confluence University of Science and Technology, Osara, Kogi, Nigeria.
Sci Rep. 2024 Jan 18;14(1):1637. doi: 10.1038/s41598-024-52270-6.
The analytical hierarchy process (AHP) was employed to delineate the mineralisation potential across the notable schist belts in northwestern Nigeria. High-resolution aeromagnetic and aeroradiometric datasets were taken into consideration. This was achieved by using advanced signal enhancement techniques to study the structures, identify the hydrothermal alteration zones (that could serve as a pathway for mineralisation), and understand the geologic settings. Amongst the enhancement techniques are first vertical gradient, analytic signal, CET grid analysis and porphyry, Euler deconvolution, and K/Th ratio. The analytic signal reveals lithologic contact, structures and anomalous occurrences that aided the classification of the site into three magneto-lithologic zones: high (> 0.094 nT/m), intermediate (0.028 to 0.094 nT/m), and low magnetic zones (< 0.028 nT/m). The high magnetic zones (HMZ) were considered the main magnetic source outlines, which are inferred to be dominantly intrusive zones for hydrothermal activities. The 3-dimensional Euler deconvolution reveals highly magnetic and intrusive depth sources to be within the range of < 100 to 500 m. The Centre for Exploration Targeting (CET) grid technique revealed the structural distribution from which the lineament density map was produced. The orientations of the prevalent structural anomalies are E-W, NE-SW, WNW-ESE and NW-SE, with similar orientations observed from the first vertical gradient and the analytic signal. The highly dense structural zones coincide with the high magnetic zones and high-frequency amplitudes of the analytic signal and the vertical gradient map, respectively. Additionally, the CET porphyry detects the centres of the intrusive porphyries to be within zones of high lineament density. This reveals that the mineralisation potential of the area is structurally controlled. On the other hand, radioelement maps (eU, eTh, and K%) and ternary maps were used for lithological classification. The radiometric ternary map revealed the highly radioactive zones and the superior concentration of individual radioelements in their respective areas. The K/eTh ratio map delineates highly potassic alteration zones. The AHP model and weighted overlay tool were employed to integrate the analytic signal, lineament density, and K/Th ratio. Consequently, the mineralisation potential of the study site was revealed and classified into high, moderate, and low. This result was validated using known mine sites. There was a total agreement, with 87.5% of mines plotting within the high mineralisation potential class and 12.5% in the moderate class. Promising targets were identified for development.
层次分析法（AHP）被用于描绘尼日利亚西北部显著片岩带的矿化潜力。研究考虑了高分辨率航空磁力和航空放射性数据集。这是通过使用先进的信号增强技术来研究构造、识别热液蚀变带（可作为矿化通道）并了解地质背景来实现的。这些增强技术包括一阶垂直梯度、解析信号、CET网格分析和斑岩分析、欧拉反褶积以及钾/钍比值。解析信号揭示了岩性接触、构造和异常情况，有助于将该区域划分为三个磁岩性带：高磁带（> 0.094 nT/m）、中磁带（0.028至0.094 nT/m）和低磁带（< 0.028 nT/m）。高磁带（HMZ）被认为是主要的磁源轮廓，推断主要是热液活动的侵入带。三维欧拉反褶积显示高磁性和侵入深度源在< 100至500米范围内。勘探目标中心（CET）网格技术揭示了构造分布，并据此生成了线性密度图。主要构造异常的方向为东西向、北东 - 南西向、西北西 - 东南东向和西北 - 东南向，在一阶垂直梯度和解析信号中也观察到了类似方向。高密度构造带分别与高磁带以及解析信号和垂直梯度图的高频振幅重合。此外，CET斑岩分析检测到侵入斑岩的中心位于线性密度高的区域。这表明该区域的矿化潜力受构造控制。另一方面，放射性元素图（eU、eTh和K%）和三元图用于岩性分类。放射性三元图揭示了高放射性区域以及各区域中单个放射性元素的较高浓度。钾/钍比值图描绘了高钾蚀变带。层次分析法模型和加权叠加工具被用于整合解析信号、线性密度和钾/钍比值。因此，研究区域的矿化潜力得以揭示并分为高、中、低三类。该结果通过已知矿点进行了验证。结果完全一致，87.5%的矿点落在高矿化潜力类别中，12.5%落在中等类别中。确定了有开发前景的目标。
