Existence of a possible subsurface ring complex in the northwestern part of the Nigerian Younger Granite province: a contribution from aeromagnetic and remote sensing data

Abstract

The study area lies within the north-western part of the Nigerian Younger Granite province. It is bounded by latitude 10°30′N and 11°00′N and longitude 8°00′E and 9°00′E. Previous geological and geophysical studies that were carried out in the study area focused mainly on the ring complexes with surface exposure while nothing is known about those without the surface exposure. This has resulted in gap in geo-scientific knowledge which this study aimed to fulfill. First vertical derivative (FVD) and Euler deconvolution of the aeromagnetic data along with processed DEM were used to achieve this purpose. Results of the interpretation revealed a magnetic anomaly, almost circular in shape, with characteristics that are similar to the anomalies that spatially coincide with the prominent ring complexes but without the outcrops that are associated with the complexes. This anomaly is interpreted to be an unexposed ring. Lineaments revealed by the results are mainly oriented in the E-W, NE-SW and NW-SE. The lineaments in the NE-SW and its conjugate are the most developed lineament system. Presence of ring complexes on and along the lineaments favours the opinion that the emplacement sites of the complexes are influenced by the reactivated Pan-African shear zones and transcurrent faults. In particular, the cross-over of major lineaments at the nonoutcropping anomaly may suggest a very weak zone that probably allowed the volcanic eruption that initiated the emplacement of the unexposed ring complex. Results of the Euler deconvolution suggest a cylindrical-like body for the unexposed ring complex, which is consistent with pluton geometry, and a depth that range from outcrop to 1,200 m for it.

Evidence of Structural Facts Inferred from Aeromagnetic Data Analysis over the Guider-Maroua Area (Northern Cameroon)

“…And as shown by [34], at regional scale, these lineament trends suggest that region is intensively affected by the reactivated Pan-African shear zones and transcurrent faults. In addition, the above mentioned trends are generally referred to as Brasiliano/Pan-African trends and are associated with the Brasiliano/Pan-African orogeny [35].…”

Geophysical Signature Location in the South-West of Chad: Structural Implications

“…Since the whole region contains a variety of rocks of different ages, it is not surprising that network of faults should be linked to different phases of tectonic activity [37]. The Cretaceous lineaments border the semi-grabens of the Cretaceous basins and are in agreement with the Guineo-Nubian lineaments which played several roles in different manners in the Cretaceous according to [38][39][40].…”