A GEOPHYSICAL INVESTIGATION OF THE SUBSURFACE STRUCTURES BETWEEN RISHIWA AND GESHERE RING COMPLEXES USING MAGNETIC METHOD
A GEOPHYSICAL INVESTIGATION OF THE SUBSURFACE STRUCTURES BETWEEN RISHIWA AND GESHERE RING COMPLEXES USING MAGNETIC METHOD
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Date
2015-06
Authors
BELLO, Yusuf Ayoola
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Abstract
In this research, the 'surface gap‘ between Rishiwa and Geshere Younger Granites was investigated using both ground and airborne magnetic survey. This was informed by the suspicion of Geshere Younger Granite being an extension of Rishiwa Younger Granite. The effects of both diurnal and secular variations were removed from the magnetic data - both airborne and ground. Power spectrum analysis was used to investigate the likely noise level in the aeromagnetic data by calculating the cut off wavelength, 6 km, and this noise level was filtered out using low-pass filter. The data set was subsequently subjected to appropriate enhancement and interpretation techniques. Qualitative interpretations including second vertical derivative and analytic signal defined distinct pattern of the magnetic signatures. The second vertical derivatives of the aeromagnetic map revealed the presence of a boundary within the gap which coincided with abrupt change in the magnetic contrast observed on analytic signal map of the aeromagnetic data. Euler solution of the aeromagnetic data with structural index of zero (SI = 0 for contact) revealed the presence of a major contact between the two Younger Granites with a depth ranging from 0.3 to 1.1 km, some unexposed part of Rishiwa, and also indicates the possibility that both Younger Granites may be a single Younger Granite that might have been separated by plate movement aided by fault.The analytic signal of the ground magnetic data delineates boundaries in between the two Younger Granites and finally 2D Werner solutions of the ground magnetic data produced more contact than dyke solutions with depth range of 15 m to 150 m.
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A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES AHMADU BELLO UNIVERSITY, ZARIA
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD
OF A
MASTERS DEGREE IN APPLIED GEOPHYSICS
DEPARTMENT OF PHYSICS,
FACULTY OF SCIENCE
AHMADU BELLO UNIVERSITY, ZARIA
NIGERIA
Keywords
GEOPHYSICAL,, INVESTIGATION,, SUBSURFACE,, STRUCTURES,, RISHIWA,, GESHERE RING,, COMPLEXES,, MAGNETIC,, METHOD,