The age and significance of the Ngadarunga Granite in Proterozoic central Australia

Abstract

The emplacement of the Ngadarunga Granite in the Arunta Region of central Australia directly constrains the timing of the first high-grade metamorphic, tectonic and magmatic event in the Arunta Region, and the timing of the geographically extensive unconformity that separates the earliest regional basin phase from younger, overlying sedimentary successions. Previous dating had correlated this event with the 1880–1840 Ma Barramundi Orogeny interpreted in far north Australia, linking the Arunta Region to the ‘Barramundi’ model of widespread synchronous cratonisation in the period 1880–1840 Ma. New data revise this granite emplacement to 1803 ± 6 Ma, placing it in the younger 1810–1800 Ma Stafford Event of the Arunta Region. The provenance of detrital zircons in early Arunta Region sedimentary rocks was dominated by crystalline rocks formed in the period 1840–1880 Ma. Thus, the earliest rocks in the Arunta Region were deposited after ca. 1840 Ma in a basin marginal to 1880–1840 Ma continental crust, and their subsequent tectonism began with the Stafford Event.