GEOPHYSICAL INTERPRETATION OF HIGH RESOLUTION AEROMAGNETIC DATA OF PART OF SOUTHWESTERN NIGERIA FOR SUBSURFACE MAPPING
GEOPHYSICAL INTERPRETATION OF HIGH RESOLUTION AEROMAGNETIC DATA OF PART OF SOUTHWESTERN NIGERIA FOR SUBSURFACE MAPPING
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Date
2018-09
Authors
AHMED, Zubairu
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Abstract
High resolution aeromagnetic data of part of southwestern Nigeria (Longitude 20 30ʹ E and 50 00ʹ E and Latitude 60 00ʹ N and 80 00ʹ N) were interpreted qualitatively and quantitatively. First and second vertical derivatives, total horizontal derivative, analytic signal, theta angle and tilt derivatives were employed in the qualitative interpretation with the aim of delineating geological structures (anomalies) and their trends. Euler deconvolution and Werner deconvolution as well as forward modelling and inversion were employed in the quantitative interpretation which was aimed at determining depths to magnetic sources. The results of qualitative interpretation show high amplitude of the magnetic field intensity in the Basement Complex region and low amplitude in the Sedimentary Basin and some part of the Basement Complex associated with the schist. The directions of linear features delineated correlate with the geology of the study area. The trending patterns of the linear features are NE-SW, NW-SE, NNE-SSW and E-W. The NE-SW trending structures coincide with the structures from the Atlantic Ocean, the NNE-SSW structures provide a possible link to the Ifewara-Kalangai fault axis and the NW-SE trends could probably be due to the separation of the South American continent from Africa to accommodate the emerging Atlantic Ocean. The windowed Euler solution points coincide with regions having anomalies whose depths (<100 m - >9000 m) gave useful information about topography of the basement. The estimated depths range from Werner deconvolution was from 1.4 to 5.0 km. Modelling of anomalies using Geosoft GM-SYS have shown that Ifewara fault is about 3.2 km deep.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF A DOCTORATE DEGREE IN APPLIED GEOPHYSICS
DEPARTMENT OF PHYSICS
FACULTY OF PHYSICAL SCIENCES
AHMADU BELLO UNIVERSITY, ZARIA
NIGERIA
Keywords
GEOPHYSICAL INTERPRETATION,, HIGH RESOLUTION,, AEROMAGNETIC DATA,, PART OF SOUTHWESTERN NIGERIA,, SUBSURFACE MAPPING