A review of the geology and geodynamic evolution of the Palaeoproterozoic Earaheedy Basin, Western Australia

Abstract

The Palaeoproterozoic Earaheedy Basin is one of a series of basins that extend for about 700 km east-west and are part of the Capricorn Orogen, situated between the Archaean Pilbara and Yilgarn Cratons. The Earaheedy Basin contains sedimentary rocks that were deposited on the northern passive continental margin of the Yilgarn Craton, probably as a result of continental breakup at 1.8 Ga. The sedimentary rocks of the Earaheedy Group are divided into two Subgroups, Toloo and Miningarra, each representing different depositional environments and aggregating about 3000 m in thickeness. The Tooloo Subgroup consists of basal siliciclastic with minor platform carbonates, overlain by a 600-m-thick succession of Fe-rich rocks (granular iron-formation and hematitic shales). The Miningarra Subgroup is predominantly siliciclastic, but includes stromatolite-bearing carbonate sequences and was deposited during a more active depositional regime. Far field tectonic events at 1.76 and 1.65 Ga resulted in the deformation of the sedimentary package with progressive intensity from north to south, forming the Stanley Fold Belt and giving and overall asymmetric structure to the Basin. These events were followed by a large meteorite impact (Shoemaker Impact Structure), probably in the Neoproterozoic. The Earaheedy Basin is well endowed with Fe resources, represented by the granular iron-formation (Frere Formation, Tooloo Subgroup), particularly in the Stanly Fold Belt, where there was secondary enrichement.