Linking the Windmill Islands, east Antarctica and the Albany–Fraser Orogen: Insights from U–Pb zircon geochronology and Hf isotopes

Abstract

U–Pb and Hf isotopic data from metasedimentary and magmatic rocks from the Windmill Islands in Wilkes Land, East Antarctica, confirm age and crustal evolution links between the Albany–Fraser Orogen and this part of East Antarctica. Detrital zircon age data indicate that the protoliths to the metasedimentary rocks of the Windmill Islands have maximum depositional ages of c. 1350Ma. Metamorphic zircon growth at c. 1300Ma and a crystallisation age of c. 1315Ma for the protoliths to an orthogneiss that intrudes the metasedimentary rocks provide a minimum depositional age. Significant detrital zircon age components are identified at 1790Ma, 1595Ma and 1390Ma. The 1350–1300Ma depositional interval and the detrital age components suggest that the Windmill Islands metasedimentary rocks can be linked to metasedimentary rocks of the Arid Basin in the Albany–Fraser Orogen. The sediment sources were likely to be the West Australian Craton as well as a significant component from the c. 1410Ma Loongana Arc in the Madura Province. This combination of sources suggests a back-arc setting for the Arid Basin, consistent with the short interval between deposition and high thermal gradient metamorphism. The magmatic rocks in the Windmill Islands have intrusive ages of c. 1315Ma, 1250–1210Ma and 1200–1160Ma. The first phase of magmatism was likely to be derived from melting of Arid Basin metasedimentary rocks, based on abundant inherited zircon with similar ages to the surrounding metasedimentary rocks. The final two phases of magmatism have juvenile εHf(t) values consistent with a greater proportion of mantle melt sources.