Browsing by Author "Onum, Stephen Adikwu"

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    Integrated airborne and ground geophysical investigation of mineral deposits in parts of Middle-Benue Trough, Nigeria
    (Federal University of Technology, Owerri, 2021-07) Onum, Stephen Adikwu
    An enhanced interpretation was carried out to delineate the tectonics and subsurface structural trend in parts of the Middle-Benue Trough that lays between latitudes 7 ◦ 30′–9 ◦ 0′N and longitudes 9 ◦ 00′–10◦ 30′E as well as it implications for mineralization. The desk study stage involved the acquisition of Landsat 8 imagery, image processing (Atmospheric Correction, Colour Composite, Band Rationing, Principal Component Analysis) were applied and result shows imagery highlighting areas where concentration of minerals and assemblage of alteration minerals, as iron-bearing minerals, hydroxyl-bearing minerals and hydrated sulphates occur, discriminating altered from unaltered rocks. In order to validate the results, nine (9) High Resolution Aeromagnetic data used were subjected to various filtering operations, the residual magnetic map showed the difference in locations of high and low magnetic intensities and many crustal magnetization patterns with majorly NE-SW trending of low magnetic susceptibility, The RTE magnetic anomaly map shows both low and high magnetic frequencies representing points of low and high magnetic signatures respectively in the area with a shift of orientation of anomalies as observed. The highest magnetic susceptibility values ranged from 14.6 to 570.8 nT, Analytic Signal map show relatively high magnetic amplitude observed to be associated with the highlands are interpreted as the basement rocks, intermediate magnetic amplitude is observed to be associated with moderate elevations and is interpreted as sandstone and magnetic mineral (magnetite and hematite) enrichment areas; while low magnetic amplitude is associated with lowlands. The First Vertical Derivative, Second Vertical Derivative, Upward Continuation, TDR filter was applied. Maps displayed most structural feature of the area such as the faults, folds, contacts and to some extent the shape of some lithology. The interpreted geological map from aeromagnetic dataset shows the geologic units, structures, deformation intensity and OH bearing, ferrumagnetisation and ferruginization alteration zones. Two zones (Bangagala as Zone 1 and Ibi as Zone 2) were selected for further investigations based on the anomalous attributes of the zones and varying(moderate to high) deformation intensity across the study area. Ground magnetic survey, em-vlf, electrical resistivity and induced polarization were employed to further investigate magnetic depleted areas as well as the degree of conductivity and resistivity across the interpreted chargeable bodies resulting from segregation of hydrothermal fluid, leading to the separation of chargeable bodies of associated minerals (e.g. lead, quartz e.t.c). The threedimensional voxel model was used to isolate chargeable bodies (potential mineralization) with chargeability >15msec which is regarded as anomalies of interest. The volume of the chargeable voxel was then computed and used for the probable reserve estimation. The estimated volume of chargeable body in zone 1(Bangagala) is 853,250 m3 with nearest estimate of 2,730,400 tonnes and estimated value of $1.3Billion. While, the estimated volume of chargeable body in zone 2 (Ibi) is 502,310 m3with nearest estimated of 1,607,392 tonnes and estimated values of $750Million.