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