HIGH RESOLUTION MAGNETIC FIELD SIGNATURES OVER AKURE AND ITS ENVIRONS, SOUTHWESTERN NIGERIA
Journal: Earth Science Malaysia (ESMY)
Author: Cyril C. Okpoli
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
Aeromagnetic data over Akure, Southwestern Nigeria was quantitatively and qualitatively analyzed to unravel subsurface magnetic anomalies. The analyses made on the IGRF corrected aeromagnetic data acquired was used to estimate depth to anomalous sources using 2-D power spectrum, werner deconvolution and 3-D Euler deconvolution. We gridded and sampled the aeromagnetic dataset; while the spectral analysis transforms the spatial data into frequency domain and provides a relationship between radially average spectrum of the magnetic anomalies and depths to the respective sources. Werner and Euler estimate and examines the shape, type of magnetic field within a window and calculate 3-D source locations based on its structural index. The characteristic nature of the magnetic anomalies as expressed by the profiles that is indicative of the different rock types (charnokite, porphyritic granite, grey gneiss, migmatite). Qualitative interpretation results revealed the following ranges for reduction to equator, upward and downward continuation, analytical signal, vertical derivative as; -418.29nT to 532.35nT, -96.7T to 17 5.4nT, -544.53nT to 597.70nT, -0.0nT to 2.199nT, -0.1nT to 0.1nT; while the quantitative interpretation results revealed-power spectrum, werner deconvolution and euler deconvolution as: 3.0m to 11.0m, 20.6m to 650m, 166.29m to – 323.05m respectively. Location, source and depth of magnetic anomaly have been unraveled.