Gorczyk, Weronika1, Tyler, Ian1, Aitken, Alan1, Kohanpour, Fariba1
1Centre of Exploration Targeting, School of Earth Science, University of Western Australia, Perth, Australia
Assembly of Australian Cratons as part of Nuna assembly has been a subject of debates for decades. Especially within Australian geoscience community the timing and style of Western Australia Craton (WAC) with Norther Australian Craton (NAC) collision causes a lot of controversy. The dispute arise mostly due to sparsity of data available. As the Proterozoic knowledge of Australian cratons, as well as others grew new models for Nunan assembly were proposed, and the literature become overcrowded with variable models, based on localised and limited data.
Here, without presenting any new data, an attempt is made to analyse existing models in a unbiased style, questioning and correlating all the tectonic and sedimentation events across WAC, NAC and SAC (Southern Australia Craton). The position and interactions with Laurentia and North China – which are believed to be proximal to Australia at the time of paleo-meso Proterozoic, as also considered.
To achieve this task, plate reconstruction software (GPlates) is used. Publicly available geological data that describe tectonic and sedimentary events affecting WAC, NAC and SAC, as well as paleomagnetic data to are taken into account to support or contradict conceptual models. The immense advantage of this approach is continuous space and time visual representation of the plates interactions and occurrence of events.
Three (with variations) time models of WAC and NAC collision are shownwith different subduction polarty: (1) 1800- 1765 Ma, (2) 1590-1550Ma, (3) ~1300 Ma. Essentially, in the first model one can corelate all the tectonic events across WAC an NAC and SAC with one another post-collision, but spatial problem arises between the cratons and events that follow. In the second model the collision of WAC and NAC can be corelated with metamorphic and magmatic events in Arunta region, as well as in Mt Isa, but does not allow for correlation of prevous events across WAC and NAC. The third model with subduction under WAC combines the tectonic evolution of Paterson region, Wankanki Arc and Stage I of Albany Fraser in a very elegant way, but again keeps WAC on a separate palate prior 1300 Ma, and does not allow for correlation of events across the cratons of with similar styles and timings. Pros and cons for all models will be presented, and the verdict will be left to you.
Weronika Gorczyk is a research fellow at Center of Exploration Targeting at University of Western Australia. She is a geodynamicist with interest in tectonic process from the edge of the plate to its interior.