U-PB ZIRCON DATING OF TECTONOMAGMATIC EVENTS IN THE NORTHERN ARUNTA-INLIER, CENTRAL AUSTRALIA

The Mount Doreen area of the northern Arunta Inlier has a Proterozoic magmatic and tectonic history that extends over 300 Ma. The oldest uni t, the turbiditic Lander Rock beds (LRB), was folded and metamorphosed from greenschist to granulite grade during the Yuendumu Tectonic Even t. A U-Pb zircon age of 1880+/-5 Ma for the late-tectonic Ngadarunga G ranite provides a minimum age for this event and supports its correlat ion with the widespread Barramundi Orogeny of northern Australia. Two subsequent major deformations, the Hardy and the Wabudali Tectonic Pha ses, considered to represent discrete phases of the Strangways Orogeny , are tentatively placed at around 1770 Ma. The Hardy Tectonic Phase l ocally retrogressed the LRB and produced strong foliations in some gra nites, including one of the Carrington Suite dated at 1779+/-6 Ma. The Wabudali Tectonic Phase formed high-strain zones, in places more than 2 km wide, within which the sedimentary Reynolds Range Group was tigh tly folded and the LRB were refolded and retrogressed. Felsic volcanic s and arenites of the fault-bound Nicker beds and Patmungala beds, dat ed at 1772+/-5 Ma and 1799+/-10 Ma, respectively, were also tightly fo lded during the Strangways Orogeny. Juxtaposition of low-grade and hig h-grade LRB took place during faulting that occurred after the 1770 Ma tectonism, but prior to post-tectonic granites which may be indirectl y related to the similar to 1600 Ma Chewings Orogeny of the southern A runta Inlier. One post-tectonic granite (1635+/-9 Ma) is associated wi th a mafic to intermediate intrusive complex and another (1567+/-11 Ma ) is part of an extensive megacrystic suite that intrudes folded Reyno lds Range Group. Zircon inheritance was found in five of the six analy sed samples, with ages ranging from 1.85 to 3.45 Ga.