Abstract
Structural analysis using aeromagnetic data over parts of southern Bida (Nupe) basin, Nigeria and the surrounding basement rocks was carried out to highlight linear structures and infer the effects of such features on the tectonic events in the survey area. The basin consists of the basal Lokoja Formation, overlain by the Patti Formation and capped by the Agbaja Formation. The basal Lokoja Formation is a sequence of matrix supported conglomerates and sandstones overlying the Pre–Cambrian to lower Palaeozoic basement. Magnetic rocks (iron ore) occur at the central, north eastern and south southern sections of the study area. Trend characteristics of magnetic lineaments were highlighted using the Euler deconvolution method. Werner and Euler deconvolution of aeromagnetic data profiles were utilized to determine the depth to magnetic sources. Depth to magnetic sources along aeromagnetic data profiles ranges from 0.01 km to 0.51 km with an average value of 0.128 km. Deductions made from the research are; mineralization is structurally controlled in parts of the survey area with kaolin occurring along a lineament around Share, western part of the survey area. The occurrence of subsurface linear structures may be due to discontinuities caused by faulting of country rock. Lineaments’ trends inferred include the east–west, north–south, northeast–southwest, north northeast–south southwest and northwest–southeast directions, with the north northeast–south southwest trend being dominant. Werner deconvolution plots for profiles ZZ and HH located at the central and southern sections of the survey area respectively; are inferred to be basement rock fractures beneath the sedimentary rock.
Highlights
The interpretation of aeromagnetic maps involves interpreting the basement structures and detailed examination of structures and lithologic variations in the sedimentary section
Since sedimentary rocks are characterized by low susceptibility values, a northeast–southwest trending magnetic high anomaly occurring at the central part of the basin section results from underlying magnetic basement rocks
The regional magnetic field (Figure 6) shows contour lines trending in a dominant northwest–southeast direction; and this is in agreement with trend of the basin
Summary
The interpretation of aeromagnetic maps involves interpreting the basement structures and detailed examination of structures and lithologic variations in the sedimentary section. Linear features are clearly discernible on aeromagnetic maps and often indicate the form and position of individual folds, faults, joints, veins, lithologic contacts, and other geologic features that may lead to the location of individual mineral deposits. They often indicate the general geometry of subsurface structures of an area thereby providing a regional structural pattern (Onyewuchi et al, 2012)
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