SHRIMP U-PB ZIRCON GEOCHRONOLOGY OF GRANITES IN THE ARUNTA-INLIER, CENTRAL AUSTRALIA - IMPLICATIONS FOR PROTEROZOIC CRUSTAL EVOLUTION

New SHRIMP U-Pb zircon isotopic ages are reported for ten granitic sui tes in the eastern Arunta Inlier. These data, combined with previous U -Pb zircon studies in the region, constrain the timing of major Palaeo proterozoic igneous events within the Arunta Inlier, and establish a g eochronological framework for understanding lithostratigraphic relatio nships, 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 r ange of 1770-1710 Ma, which are significantly younger than the 1880-18 50 Ma ''orogenic'' Barramundi Igneous Association recognised throughou t many other Proterozoic terrains in northern Australia. No rocks of t he Barramundi Association have been identified in this study. The prev iously proposed Barramundi-type suites, including the Jervois and Dnei per granites, yield ages of 1771+/-6 and 1771+/-15 Ma, respectively. M any of the granite suites contain inherited zircons with ages in the r ange of 1890-1830 Ma, similar to the age of the Barramundi Association . This, and the age of the Atnarpa Igneous Complex (Zhao and Cooper, 1 992), which is coeval with, but geochemically distinct from, the Barra mundi Association, suggest that the 1880-1850 Ma orogenic event affect ed the Arunta Inlier, but has been obscured by the younger tectonic ev ents. The youth of tectonic events in the Arunta Inlier as compared wi th other Proterozoic terrains of northern Australia may have resulted from the inlier being located on the southern margin of the Northern A ustralian Orogenic Province during the Palaeoproterozoic, with the gen eration of granites in the Arunta Inlier possibly being related to sub duction. The combined data indicate that major granitic activity occur red at: 1880-1850, 1820, 1770-1750, 1730-1710, 1660-1650 and 1615-1590 Ma. This result is broadly consistent with earlier summaries of the o ther Proterozoic terrains in northern Australia, although the intensit y of each episode varies in different regions.