Zircon ages constrain the time of deformation events in The Granites-Tanami region, northwest Australia.

Abstract

Dating of extensive granitoids in the The Granites‐Tanami Block of northern Australia has enabled time limitations on deformational events, including five Palaeoproterozoic events (D1‐D5) and one older, almost Neoarchaean event. D1 is present in the basal Tanami Group, D2 to D5 help define other stratigraphic groups in the region. The intrusive rocks have been dated by traditional zircon and stepwise lead evaporation techniques. A post‐D2/pre‐D3 foliated and boudinaged leucocratic tonalite gave 1870 ± 3 Ma. A syn‐D3 foliated and boudinaged tonalite 1858 ± 3 Ma and a post‐D3/pre‐D4 foliated tonalite 1840 ± 11 Ma. Two unmetamorphosed and post‐D5 granitoids gave 1797 ± 1 Ma and 1787 ± 3 Ma, respectively. Some deformation events are separated by as little as 10 to 20 million years. These times of intrusive igneous activity exactly replicate other igneous events, many of which are volcanic, in the Halls Creek Province 400 km to the northwest, which strengthens proposed geological relationships between the two regions. A granitic gneiss in a basement inlier gives 2487 ± 3 Ma, a Neoarchaean age. Tectonic uplift in the Carboniferous is deduced from concordia lower intercept data that is similar to the eastern Arunta Block. Further age definition of D1 D2 and D5 is under current investigation.