Selected Australian continental-scale lineaments: Observations and suggestions as to their origin

Abstract

Australia is transected by a network of systematic continental-scale lineaments that are considered to be zones of concentrated, aligned tectonic activity which have apparent continuity over vast distances. The dominant directions form an orthogonal pair trending west-northwest and north-northeast: the King Leopold and Halls Creek Mobile Zones in northwestern Australia are an example of this. The consistent distribution of large-scale gravity and geological lineaments implies a common basement involvement for both, despite their expression at different levels within the crust. Continental-scale lineaments generally exhibit little to no offset where they intersect each other, suggesting an oscillatory history with little net offset. Geologic and chronological evidence demonstrate that many of the lineaments have been zones of reactivation since at least the Early Proterozoic (∼1880 Ma) and that they appear to cross major terrane boundaries. The lineaments have been sites of early tectonic activity that have undergone reactivation, resulting in repeated structural and depocentre control that is geographically associated with the continental-scale corridors. Alternative models for the origin of continental-scale lineaments include: a) a pre-existing lineament network maintained in an ancient basement underlying the entire continent; b) lateral propagation of crustal-scale structures; and c) alignment of genetically unrelated lineaments giving the appearance of continuity.