A Possibly Extensive Crustal Failure System of Economic Interest

Landsat studies of large areas in Nigeria and Saudi Arabia have shown parallel alignments of remarkably‐straight lineaments about 40 km apart of hundreds of kilometres in length, dispersed amongst many members of other systems and randomly‐oriented individuals. These apparent crustal failure zones influence the sites of intrusives (including some economically mineralized), extrusives and some important oilfields. In both main areas studied, families of intrusives aligned along the lineaments system show a minimum age of 520–540 m.y., but evidence of their existence can be detected on images from Quaternary to Cambrian in Saudi Arabia. Although usually there is little ground surface evidence of horizontal dislocation of comparable dimensions, evidence exists of vertical movements of sections bounded by these features.