U‐Pb zircon ages and a revised chronology for the Tennant Creek Inlier, Northern Territory

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Abstract
New U‐Pb zircon ages, combined with previous Rb‐Sr data, provide a geochronological framework for the Tennant Creek Inlier of Northern Australia. Ages of 1870± 20 Ma and 1846± 8 Ma are advanced for the igneous crystallization of the Tennant Creek and Cabbage Gum Granites, respectively. A lower concordia intercept age of 248 ± 27 Ma is thought to relate to zircon dilation and Pb loss resulting from late Palaeozoic uplift, alteration and/or erosion. If previously analysed volcanics from the Bernborough Formation also lost Pb at that time, they have a primary age of 1870 ± 15 Ma. This provides a temporal estimate for deposition of the Warramunga Group, the major geological component of the Tennant Creek Inlier. At any single site, Rb‐Sr total‐rock ages are younger than U‐Pb zircon ages, possibly up to 400 Ma so for the Cabbage Gum Granite. Previously reported Rb‐Sr total‐rock ages of about 1650–1660 Ma probably define igenous crystallization of several other felsic magmas. Granite emplacement thus occurred both before and after the main 1810 Ma tectonothermal event and accompanying mineralization. The present work shows that the Warramunga Group was formed at the same time as major elements of the Pine Creek Geosyncline (Nimbuwah Complex) and Mount Isa Inlier (Leichhardt Metamorphics), and also close in time to early components of the Arunta and Granites‐Tanami Inliers, 1870 Ma was therefore an important time for generation of new crust in the northern and central parts of Australia.