Characterising rocks dredged from the Gulden Draak microcontinent
thesisposted on 28.03.2022, 19:27 authored by Robyn Gardner
Gulden Draak is a bathymetric feature 2-3 kilometres below the surface of the Indian Ocean 2,000 kilometres west of Perth, Western Australia. Four samples were selected from the continental rocks dredged from the knoll, three orthogneisses and one paragneiss. Minerals and textures indicate the samples were subjected to amphibolite to granulite facies metamorphism in multiple metamorphic events. U-Pb and Lu-Hf isotope analysis shows the samples have undergone a complex history of emplacement, metamorphism and partial remelting. The orthogneisses were originally emplaced prior to 2800 Ma, 1290 Ma and 1200 Ma respectively. Two samples, an orthogneiss and the paragneiss have Archaean age zircon cores. These events have been correlated with the Nornalup Complex in the Albany-Fraser Orogen formed as the Mawson and Yilgarn cratons collided. All samples were subsequently impacted by the Kuunga Orogen at ~500Ma: by isotope resetting, zircon partial melting and recrystallisation, growth of new metamorphic rims and/or lead loss. Lead loss evidence for the rifting event at ~136 Ma is also seen. At the time of the Gondwana breakup Gulden Draak was located south of the Naturalise Plateau very close to the Greater India-Antarctica-Western Australia triple point.