Physics

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Browsing Physics by Subject "Anomalies"

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    Inversion of Gravity data of Nyabisawa-Bugumbe area of Migori greenstone belt, Kenya
    (2018) Odek, Antony
    Migori greenstone belt is one of the major mineral prospects in Kenya, major mining activities are currently conducted by the local artisans using open cast methods. In order to subject the prospect to industrial use, a good understanding of the geophysical features in the subsurface which are likely to control the distribution of minerals is necessary. In this study, a 2-D lithoprediction model of Nyabisawa-Bugumbe area was developed from geologically constrained inversion of gravity field data. The measured gravity field data were subjected to cleaning process to remove perturbations which were not of geophysical interest, and later enhanced by removing long wavelength anomalies which are as a result of regional trend. The density variations were then inverted for the geometrical parameters of the model. Gravity high trending NW-SE around Nyabisawa, Kirengo towards Nyambeche was delineated. The gravity high is bounded by two major faults along rivers Migori and Munyu. Integrating the 2-D inversion of gravity data and the geology of the area, the gravity field perturbation is associated with banded iron formations.
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    Near Surface Anomaly Depth Estimation Using Downward Continuation
    (2018-10) Odek, Antony
    Depth estimation in gravity survey is very important in mineral prospecting. It does not only inform the choice of the optimal point for mineral exploration but also very important in analyzing economical viability of the mines. A number of depth determination techniques ranging from empirically derived formulae to modern automated analysis of gravity data have been developed. In this study, downward continuation filtering technique has been used to filter the near surface perturbations on the gravity field which are suspected to be as a result of minerals. The measured total magnetic field data of Migori greenstone belt was first subjected to cleaning process to remove the effects which are not of geophysical interest, and later enhanced by removing long wavelength anomalies which are as a result of regional magnetic trend. The complete Bourguer anomaly was then subjected to downward continuation at depths of 0 m, 500 m, 1000 m and 1500 m. The near surface features seem to be filtered at a depth of 1500 m, leaving the deeply seated features. This result with the available geological information is a good indicator of the possible depth of the near surface anomaly causative bodies. The result was further improved by integrating it with the geochemical analysis of rock samples. Shallow gravity structures are mapped from the surface to a limiting depth of approximately 1,500 m. These structures agree well with the geochemical results that shows presence of minerals and known geology of the area.
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    Power spectral analysis and edge detection of magnetic data of Migori greenstone belt, Kenya.
    (2020-04) Odek, Antony1; Githiri, John 2; K’Orowe, Maurice 2; Ambusso, Willis 3
    With the continuous extraction of minerals in Migori greenstone belt, exploration is currently evolving from surface based exploration to subsurface exploration. This necessitates a good understanding of the geophysical features in the subsurface which are likely to have a direct bearing on the distribution of minerals. In this study, the measured total magnetic field data was subjected to cleaning process to remove perturbations which are not of geophysical interest, and later enhanced by removing long wavelength anomalies which are as a result of regional magnetic trend. Power spectral analysis of geologically constrained magnetic intensity field data was then conducted, in order to obtain the limiting depth of the anomaly causative bodies. Edge detection techniques were then employed on the delineated magnetic field intensity anomalies trending WNW-ESE along the belt. The power spectral analysis shows bodies of high magnetic field intensity from the ground surface to a limiting depth of approximately 400 m. The anomalous region is bounded by two major faults along rivers Migori and Munyu. Integrating the 2-D inversion of magnetic field intensity data and the geology of the area, the magnetic field perturbation is associated with banded iron formations which act as the host for the minerals.