Gravity and magnetic data were analyzed in
conjunction with available geological data to determine the origin of observed
positive gravity anomaly at Waza and its possible relationship to mafic
intrusions. The data analysis includes the construction of a Bouguer gravity
anomaly, isostatic residual gravity anomaly, total magnetic gradient and Euler
solutions maps, and two and one-half dimensional gravity models. A positive
gravity anomaly that occurs in Waza has amplitude of 35 mGal and can be
separated into two parts. The top of the
disturbing body causing the anomaly cannot be deeper than 4 km. We believe the
anomaly is probably caused by a body of basaltic rocks lying at the
upper surface of the Precambrian basement and originate from a self-propagating
disturbance of magmatic loads on a pre-existing zone of lithospheric weakness.Melt migration might have been aided by tectonic and flexural stresses,
such that the intrusion is limited in extent to the melting region of the plume
and did not reach the surface. The model calculated to satisfy the observed
anomaly consists of a 2.5 Km-thick slab underlain by a 10.5 km deep column.
This model is interpreted to represent a sheet or saucer-like mafic intrusion
that has a thick deep feeder. Detailed geophysical studies would be necessary
to locate any possible economic occurrences.
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