Lithospheric controls on mineral systems

It is now widely accepted that contrasts in composition, rheology, evolution and sub-continental lithospheric mantle (SCLM) architecture observed at craton margins leads to the localisation of many Proterozoic-Phanerozoic mineral deposits on the margins of the old Archean cratons. However, the Archean cratons themselves are composed of amalgamated terranes and lithospheric blocks that came together via Archean tectonic processes. Subsequent 'suture' zones between these blocks provided a major control on post-collision mineralisation events. Like the craton margins of the modern Earth, these ancient terrane boundaries form major lithospheric discontinuities and SCLM geometry contrasts. As a result, this [now] intra-cratonic architecture provides a major control on the location of many Archean mineral deposits. This work, based on a craton-scale study of the Yilgarn Craton of Western Australia, maps the lithosphere using Sm-Nd isotopes from granitoids. This method allows the imaging of the micro-cratonic blocks that make up the Yilgarn Craton. It can be shown that the major gold, nickel and iron systems cluster within terranes of specific affinity, and along paleo-craton margins between these old blocks. This work shows that the intra-cratonic architecture can be effectively imaged and used to identify prospective regions/belts within a large craton. It also shows that lithospheric architecture is a fundamental control on the location of gold, nickel and iron mineral systems.