Browsing by Author "Salawu, NB"

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    Edge detection and magnetic basement depth of Danko area, northwestern Nigeria, from low‑latitude aeromagnetic anomaly data
    (Springer, 2019) Salawu, NB; Olatunji, S; Adebiyi, LS; Olasunkanmi, NK; Dada, SS
    This study aims at estimating depths and boundaries of magnetic source bodies, in order to provide an indirect insight into subsurface geologic features within Danko area of Kebbi state. The study area is located within low magnetic latitude. Hence, the total magnetic intensity anomaly map was reduced to the magnetic equator. This is to center magnetic anomalies over their respective magnetic source bodies, which equally makes the interpretation of sources easier. Matched filtering of the reduced-to-equator (RTE) magnetic anomaly map indicates that the anomalies could be represented by two equivalent layers with some additional noise. The estimated mean depths of burial for the regional and residual sources are 1000 m and 500 m, respectively. Horizontal gradient magnitude and tilt derivative methods carried out on the RTE aeromagnetic anomaly map facilitated the identification of two distinct geologic trends bounded by a prominent fault suspected to be the documented Yelwa fault. Furthermore, the analytic signal map showed magnetic basement depth values between 50 and 900 m with an average value of 475 m, indicating a compelling alignment of results with the 500 m depth value for the residual matched filter layer. Several mineral occurrences have been found within the outcropping basement rocks of the study area. Hence, the combined appraisal of source edge locations and magnetic basement depth estimates offers useful information of the underlying basement configuration, which is highly essential for mineral exploration targets that are mostly obscured by regolith cover.
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    Geophysical inversion of geologic structures of Oyo Metropolis, Southwestern Nigeria from airborne magnetic data
    (Springer, 2019) Salawu, NB; Olatunji, S; Orosun, MM; Abdulraheem, TY
    High-resolution airborne magnetic data of Oyo Metropolis has been used to map subsurface geological features which in most cases, corresponds to the area of interest for mineral expedition. The airborne magnetic data was first reduced to the magnetic equator (RTE); this is normally done to make the data simpler to interpret. The RTE map was subjected to Fast Fourier Transform to separate the regional and residual magnetic anomalies and estimate their depths. An average depth of 2500 m and 500 m were obtained for the top of regional and residual sources respectively. 3D-Euler deconvolution and tilt derivative interpretation techniques were combined and used on the RTE map, to locate and estimate depths to geologic contacts and pegmatite intrusions attributed to lineaments. The resulting 3D-Euler depth solutions were plotted on the tilt derivative map of the study area. A very good correlation was highlighted, indicating that the methods are good interpretative techniques for mapping magnetic lineaments. The estimated depths obtained from 3D-Euler deconvolution method are in the range of 108.1–544.3 m for structural index 1.0 corresponding to intrusions (dykes), and the result of structural index 0.0 corresponding to geologic contacts are in the range of 5.9–295.2 m. The estimated depth parameters coupled with known geological information, were further used to produce the best image view of the subsurface geological features of the study area, using 2-D profile modeling technique. The result obtained from the 2-D profile model is in good agreement with the results obtained from the 3D-Euler deconvolution and tilt derivative methods, indicating locations and depths of various intrusions (dykes) and geologic contacts. The obtained results from this study will help shed more light into the structural framework of the study area and can help potential explorer target new areas for mineral exploration.
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    Interpretation of high resolution aeromagnetic data of Kaoje and its environ, western part of the Zuru Schist belt, Nigeria: implication for Fe–Mn occurrence
    (Helyon, 2020) Olasunkanmi, NK; Bamigboye, O; Olatunji, S; Salawu, NB; Bamidele, T
    This study presents an appraisal of mineralization potential and the geologic record of Kaoje and environs using high-resolution aeromagnetic data. The data were analyzed using the fast Fourier transform technique for reduction-to-equator (RTE), analytic signal (AS), total horizontal derivative (THDR), tilt derivative (TDR), spectral analysis and Euler deconvolution at varying spectral indices. The reduced to equator residual magnetic intensity range from -73.4 to 205.6 nT and are associated with contrasting lithology of the Sedimentary and Basement Complex rocks. The anomalies and analytic signal amplitude unfold and update the extension of Zuru Schist to the southern region of Kaoje, elongated banded gneiss within the schist body, pegmatite intrusion through the migmatite and NNW-SSE trending schist hosted manganite and sandstone-hosted goethite. Estimated depth to shallow and deeper magnetic sources ranged from 0 to 59 m and 225–415 m respectively, and the corresponding Euler solutions revealed perfect clustering along notable geologic features and minerals. The iron mineralization are revealed as sourced from the magmatic bodies that lie beneath the sedimentary rocks and a corresponding sphere geologic model within northwest and southwest of Kaoje at a depth range of 0–225 m. The structural trends suggested the tectonic events in the area and indicate an imprint of Zungeru-Anka transcurrent fault that serves as a conduit for iron mineralizing fluid to Kaoje.