GRAVITY INVESTIGATION OF OLDER GRANITE PLUTONS IN GUSAU AREA, SOKOTO STATE, NIGERIA.
GRAVITY INVESTIGATION OF OLDER GRANITE PLUTONS IN GUSAU AREA, SOKOTO STATE, NIGERIA.
No Thumbnail Available
Date
1996-01
Authors
AKU, M. O.
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Gravity measurements were made at one hundred and ninety-eight gravity stations established at 2 km interval on all motorable roads in an area of approximately 9,975 km2 surrounding the town of Gusau. To aid in interpretations, density etermination were made on 129 rock samples.
The result of the survey disclosed that the area is characterized by large negative Bouguer anomaly values between -30 and -70 mGals, with a mean value of -57 mGals for all the stations. The resulting regional trend shows a NE-SW trend which is apparent in the Bouguer anomaly and
geologic maps. It is a plane dipping southeast wards with a gradient of
0.44 mGal/km. The residual contour map displays negative closures
which correlate well with the granite plutons, thus confirming the acidic
(low density) nature of the Older Granites with respect to the host rock, the migmatite gneiss. The resultant second vertical derivative map of the Bouguer gravity corresponds remarkably well with the known surface geology; the elongated zero contours coinciding with most lithological
boundaries. Thus a properly designed second vertical derivative map can be a supplement to geologic mapping in the identification of lithological units. A three - dimensional interpretation of the residual anomaly indicates that the isolated Older Granite outcrops between the Maru and Wonaka -
Chafe schist belts in the central region of the survey area probably coalesce at depth into a single big body which is about 55 km in width and extends to a depth of about 5 km.
Description
THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL, AHMADU BELLO UNIVERSITY, IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF:-
Keywords
GRAVITY, INVESTIGATION, OLDER, GRANITE, PLUTONS, GUSAU AREA, SOKOTO STATE, NIGERIA.