A magmatic failed rift beneath the Gongola arm of the upper Benue trough, Nigeria?

A magnetic anomaly map of the Gongola arm of the upper Benue trough was compiled from existing half-degree sheets of the upper Benue trough. The map is dominated by an elongated NE-SW magnetic low anomaly that stretches over a 100 km distance and has an average width of about 20 km. A combination of Werner deconvolution and forward modeling techniques on selected profiles across the major NE-SW anomaly lead to the conclusion that the anomaly may be caused by predomonantly mafic rocks at depths of between 6 and 10 km, well below the base of the sediments, which are generally not more than 4.5 km thick. The presence of large and continuous bodies of mafic rocks indicated by these results suggests that the area is an old rift, affected by the activity of a mantle plume that gave rise to the mafic intrusions, which did not reach the surface but remained within the basement rocks.