Geochronology of metasedimentary and granitic rocks in the Tanami Province: 1880–1790 Ma geodynamic setting of the North Australian Craton

Dating of detrital zircons from the Paleoproterozoic Tanami Group shows that Archean detritus dominates the lower part of the succession, and c. 1865 Ma detritus with a minor c. 2500 Ma component dominates the upper part. Detrital zircon ages for the upper Stubbins Formation in Western Australia are consistent with a correlation with the upper Dead Bullock Formation in the Northern Territory, whereas previously collected data for the Mount Charles Formation are consistent with a correlation with the lower Dead Bullock Formation. Metasedimentary rocks with a dominant c. 1865 Ma detrital zircon age component were deposited over much of the North Australian Craton between c. 1865 and 1840 Ma, possibly within a back-arc setting related to a plate margin north of the currently preserved craton. Tectonism at c. 1865 Ma in the northeastern part of the craton may represent remnants of a larger orogen that acted as the dominant source of sediment. The widespread occurrence of metasedimentary rocks with this distinctive provenance signature suggests craton assembly was largely complete prior to deposition. Dates of 1807–1800 Ma for granitic rocks in the western part of the orogen confirm that they were emplaced during the 1810–1790 Ma Stafford Event. These granitic rocks form part of an >800 km-long west-northwesterly trending magmatic belt, the development of which was coeval with bimodal magmatism, extension and sedimentation in other parts of the craton. This magmatism may have been a consequence of intraplate extension, possibly driven by processes along the southern craton margin. Folding and orogenic Au mineralization in the Granites–Tanami Orogen during the Stafford Event may reflect transient compression punctuating a more prolonged period of extension. Citation: Maidment, DW, Wingate, MTD, Claoué-Long JC, Bodorkos, S, Huston, D, Whelan, JA, Bagas, L, Lambeck, A and Lu, Y 2020, Geochronology of metasedimentary and granitic rocks in the Granites–Tanami Orogen: 1885–1790 Ma geodynamic evolution: Geological Survey of Western Australia, Report 196, 50p