Geological interpretation of aeromagnetic data in some parts of northcentral Nigeria

Abstract Airborne magnetic data and field observations were used to define structural trends in some parts of North Central Nigeria. The aeromagnetic anomalies of the Jurassic Younger Granite complexes are distinctive with relatively high amplitudes and short wave-lengths and are directly associated with the outcrop patterns of the intrusions. The mosaic pattern of magnetic anomalies may be used to identify the Younger Granite ring complexes. The aeromagnetic data also contain evidence of linear structural discontinuities. some of these linear features are long and extend through the survey area. They are identified by a pattern of contour offsets and probably reflect deep crustal features cutting some of the Younger Granite known to be mineralised. In particular, a major fault is mapped which cuts the Ririwai complex to the East. This fault trending NW-SE, appears to extend southwards through the area. The lineaments probably acted as conduit through which mineralized fluid flowed. The regional trends of structures are revealed on the aeromagnetic map, these being mainly northeast-southwest and northwest-southeast. The Northwest-southeast trends are superimposed on the northeast-southwest trends. This overprinting of one magnetic anomaly trend over the other suggests that the Northeast-southwest lineaments are older than the northwest-southeast lineament patterns Three known tin-bearing ring complexes show strong magnetic anomalies which make them more prominent than the other complexes on the coloured magnetic anomaly map. This characteristic should assist in locating new provinces for primary tin deposits.