Major element, trace element, Nd isotopic data and U–Pb zircon ages of quartz ± Fe-oxide ± garnet ± accessory mineral-bearing rocks (hereafter referred to as QFeGA), as well as Pb isotope data from ca. 1685 Ma high Fe–Ti meta-tholeiites and the Rasp Ridge Gneiss are presented. These rocks are found in the Proterozoic Willyama Supergroup, Broken Hill Domain, southeastern Australia. U–Pb zircon dating of the QFeGA rocks yielded ages of ca. 1600 Ma, comparable to the accepted age of the Olarian Orogeny, with no evidence of inherited zircons from a detrital component. Despite the U/Pb age, the lack of detrital zircons in combination of bulk rock major and trace element geochemistry, suggests that the QFeGA rocks formed during the early stages of the geological evolution of the Broken Hill Domain (ca. 1710–1685 Ma) in a progressively deepening ensialic rift environment, due to seafloor hydrothermal activity similar to hydrothermal sediments at present day spreading centres, rather than during the Olarian Orogeny. The Nd isotope compositions of the QFeGA rocks (εNd = − 2.2 to − 6.6) are comparable to those of other garnet-rich rocks associated with the Broken Hill deposit and with the metasedimentary rocks of the Willyama Supergroup. This suggests that the hydrothermal fluids responsible for the deposition of the QFeGA protoliths were in equilibrium with the Willyama supracrustal sequence.