ASSEMBLING NUNA: WHAT, WHEN AND WHERE? A PERSPECTIVE FROM DEEP-TIME PLATE RECONSTRUCTION MODELLING (Invited Presentation)

Nuna, also termed Columbia, is generally viewed as a Laurentia-centric supercontinent that formed during the Palaeoproterozoic, primarily due to collisions from ~1900 Ma to ~1800 Ma with probable maximum extent at about ~1600 Ma. Reconstructions using detailed spatial constraints on existing blocks of Palaeoproterzoic and older continental crust, extensive geochronological, isotope geochemical, ore deposit and geological data compilations from all continents suggests that the amalgamation process began several hundred million years earlier, possibly by ~2200 Ma with the amalgamation of the Congo, West African, Amazonian and Siberian blocks, and that most of Laurentia and the East European craton only joined by ~1800 Ma. Antarctica and Australia formed the final stages of amalgamation at ~1600 Ma.

Block amalgamation processes reflect several long-lived, accretionary orogens, both internal and peripheral in character, producing a sequence of important belts of economic interest, reflected by early stage VHMS mineralization, later orogenic gold mineralization and post-accretionary uranium mineralization. Accretion of many narrow domains appears to be a feature of Nuna amalgamation, similar to the case for Pangaea but unlike the situation for Rodinia.

Continental crust for the Nuna supercontinent appears to have been distributed across tropical to temperate latitudes with little continental crust in the polar regions, unlike the situation for Rodinia and Gondwana/Pangaea. Climatic conditions are thus likely to have been different to those of other supercontinents, possibly influencing the development of some ore deposits.