Structural modelling of subsurface geologic structures in Anambra and adjoining Bida Basins using aeromagnetic data: Implications for mineral explorations.

Abstract

Aeromagnetic data over parts of the Northern Anambra and Southern Bida basins have been evaluated with emphasis on the subsurface geologic structures controlling mineralization and delineating the geomorphology of the basin. Four aeromagnetic data sheets (246 (Kabba), 247 (Lokoja), 266 (Auchi), and 267 (Idah)) were acquired through purchase, assemblage, analysis, and interpretation using integrated processing techniques of Euler deconvolution, analytical signal (AS), source parameter imaging (SPI), and 3D magnetic inversion model. The data are collected laterally in a series of NW-SE trajectories spaced 2 km apart, with an average flight altitude of approximately 150 m, and tielines occurring at approximately 20 km intervals. Qualitative observation of TMI and RAM shows that the research region is greatly fractured, with structures orienting in the E-W direction. The spectral analysis result shows that the sedimentary infillings range from 0.60 to 4.03 km. 3D model and curie isotherm depth subsurface maps reveal deeper curie depths at Kabba, Adavi, and Itakpe zones (28.0–40.0 km) and shallow curie depths at Auchi, Osara, Idah, and Anyigba areas (18.0–27.0 km). The result from the heat flow model shows an inverse relationship with the Curie isotherm depth. The contact depth sources calculated from Euler depth assessments show that the majority of these contact sources are trending in the E-W directions. The overall structural geomorphology of the research region conforms to the general pattern of structural trends within the research region. Most of the structures are trending NNE-SSW, NNW-SSE, and NE-SW, while the minor structures trend in the E-W direction. 3D inversion results show a discrete subsurface geologic structure that may house minerals within the region.