DETRITAL ZIRCON CORRELATION OF GRANULITE-FACIES METASEDIMENTS WITH LOW-GRADE SEDIMENTARY SEQUENCES, HARTS RANGE REGION, CENTRAL AUSTRALIA

The Arunta Inlier of central Australia has long been considered a Palaeo- to Mesoproterozoic terrane. However, recent geochronology indicates that upper amphibolite to granulite facies metasediments in the Harts Range region were in fact deposited in the late Neoproterozoic to Cambrian and metamorphosed in the Early Ordovician, coeval with sedimentation in the surrounding Centralian Superbasin. SHRIMP dating of detrital zircons from low-grade Neoproterozoic to Cambro-Ordovician sediments in the Centralian Superbasin yields age spectra remarkably similar to those from remnant detrital zircons in high-grade metasediments in the intervening Harts Range. Both the basin sequences and metasediments contain zircons with ages consistent with derivation from surrounding Arunta Inlier basement (~1.9-1.7 Ga), the Grenville-age Musgrave Inlier to the southwest (~1.2-1.0 Ga) as well as a late Neoproterozoic group (0.65-0.55 Ga), possibly derived from Antarctic sources. The relative proportion of Arunta-age zircons decreases up-section in both high and low grade sequences, whilst the abundance of 0.65-0.55 Ga zircons increases until it is the dominant population in the latest Cambrian rocks. The increasing abundance of Neoproterozoic zircons appears to be linked with a major change in basin dynamics and the development of the intracratonic Larapintine seaway across central Australia. The close similarity between detrital zircon signatures of the high-grade metamorphics and sediments suggests that the metasediments are effectively part of the Centralian Superbasin. Sediments in the Harts Range area were metamorphosed at ~800 °C and ~10 kbar at ~475 Ma, coeval with the maximum development of the Larapintine Seaway across the region and continued shallow-water sedimentation in the adjacent basins. Regionally recumbent mid-crustal fabrics accompanying near-isothermal decompression and a lack of topographic expression at the surface suggests that the tectonism took place in an extensional setting.