SHRIMP UPb zircon geochronology of granites in the Arunta Inlier, central Australia: implications for Proterozoic crustal evolution

Abstract

New SHRIMP UPb zircon isotopic ages are reported for ten granitic suites in the eastern Arunta Inlier. These data, combined with previous UPb zircon studies in the region, constrain the timing of major Palaeoproterozoic igneous events within the Arunta Inlier, and establish a geochronological framework for understanding lithostratigraphic relationships, tectonic events, and geochemical and isotopic evolution of the granites in the region. Most granites in the Arunta Inlier, including both syn-tectonic and post-tectonic types, yield zircon ages in the range of 1770-1710 Ma, which are significantly younger than the 1880-1850 Ma “orogenic” Barramundi Igneous Association recognised throughout many other Proterozoic terrains in northern Australia. No rocks of the Barramundi Association have been identified in this study. The previously proposed Barramundi-type suites, including the Jervois and Dneiper granites, yield ages of 1771 ± 6 and 1771 ± 15 Ma, respectively. Many of the granite suites contain inherited zircons with ages in the range of 1890-1830 Ma, similar to the age of the Barramundi Association. This, and the age of the Atnarpa Igneous Complex (Zhao and Cooper, 1992), which is coeval with, but geochemically distinct from, the Barramundi Association, suggest that the 1880-1850 Ma orogenic event affected the Arunta Inlier, but has been obscured by the younger tectonic events. The youth of tectonic events in the Arunta Inlier as compared with other Proterozoic terrains of northern Australia may have resulted from the inlier being located on the southern margin of the Northern Australian Orogenic Province during the Palaeoproterozoic, with the generation of granites in the Arunta Inlier possibly being related to subduction. The combined data indicate that major granitic activity occurred at: 1880-1850, 1820, 1770-1750, 1730-1710, 1660-1650 and 1615-1590 Ma. This result is broadly consistent with earlier summaries of the other Proterozoic terrains in northern Australia, although the intensity of each episode varies in different regions.