A GRAVITY SURVEY OF THE IGNEOUS INTRUSIONS IN THE RANO AREA OF KANO STATE, NIGERIA

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Date
1987-10
Authors
OLADOSU, Michael Olanrewaju
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Abstract
Gravity measurements carried out in the Rano area of Kano State show that the area is characterized by large negative Bouguer anomalies ranging Erom -38 mGa1 to -68 mGal. A regional anomaly ranging from about -60 mGal in the southeastern part to about -48 mGal in the northwestern part of the area is tentatively correlated with gradual thining of the crust from southeast to the northwest, away from the Jurassic Younger Granite Province and the Jos Plateau. Negative residual anomalies in the area with amplitudes ranging from -4 mGal to -6 mGal correlate well with granite bodies thus confirming the acidic (low density) nature of the Older Granites. A prominent positive residual anomaly with an amplitude of about 20 mGal is correlated with a basic igneous intrusion in the eastern part of the area. The western half of the area also shows two positive residual anomalies uncorrelated with the surface geology, but also ascribed to sub-surface basic intrusions. From three dimensional modelling using approximate density contrasts, it has been estimated that the granite bodies extend to depths ranging from about 3 km to 4 km, and that the basic igneous intrusions extend to depths in the range of 5 km and 6 km.
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Thesis submitted to the Postgraduate School, Ahmadu Bello University, in partial fulfillment of the requirements for the award of the degree of MASTER OF SCIENCE IN APPLIED GEOPHYSICS Department of Physics Faculty of Science Ahmadu Bello University Zaria, Nigeria. October, 1987
Keywords
GRAVITY,, SURVEY,, IGNEOUS,, INTRUSIONS,, RANO AREA,, KANO STATE,, NIGERIA
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