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6th International Archean Symposium
6th International Archean Symposium

Plate tectonic limits on the assembly of cratonic Australia

Oral

Talk Description

Since at least the Neoarchean, the development of Earth’s continents has occurred within a global system of tectonic plates. For a better understanding, it is necessary to mesh detailed analyses of component terranes within the broader spatio-temporal framework of the tectonic plate system. Although several reviews of Proterozoic tectonic events are available for the Australian continent and their links to events on other continents, there is no generally accepted model of cratonic assembly. Since the 1980s, it is clear that prior to the Nuna (Columbia) supercontinent, several disparate Archean cratons and supercratons were formed that by the time of the supercontinent Rodinia, were brought to coherency along several major orogenic belts. However, the details of the major events, and in particular the timing of convergence and the configuration of plate margins, have remained elusive due to the major orogenic belts being largely unexposed, and heavily reworked during later intraplate orogenesis. For each scenario tested, we reconcile geological evidence recording tectonic events within a geodynamically sound plate reconstruction. Two continuous tectonic scenarios for the Paleo- to Mesoproterozoic assembly of the cratonic lithosphere of Australia are presented here. The scenarios are founded on those tectonic events that are relatively well established and well supported by data. For the intervening periods and areas that are disputed, mostly due to scarcity of data, we test geodynamic criteria to explore a) which possibilities are better supported by our geodynamic criteria, and b) the implications of those models for the larger-scale plate tectonic setting. The geodynamic criteria considered here are: (1) The lifespan of oceanic crust. (2) It takes 6-10 Myr from the onset of subduction to establishment of a magmatic arc above the subducting slab. (3) Termination of subduction by a) collision, b) soft docking, or c) clogging. (4) 3D slab orientations at depth. (5) Long-lived systems lend preference to elongated subduction systems like the Andean, with the interaction of several large plates, rather than the congested Caribbean-style systems with many small microplates. In the models we are presenting, non-preserved intra-oceanic subductions are not included as the geological record is predominantly available at the edges of the cratons. The time frame we are considering in this set of models includes the assembly of two super continents: Nuna (1900-1800 Ma) and Rodinia (1300 - 900 Ma), and the processes of the transition between them.

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