Accessory mineral dating of the Boree Salt in the Adavale Basin, Queensland, Australia

Rock salt caverns are recognized as a promising option for underground hydrogen storage. However, our understanding of evaporite sequences is frequently limited by poorly constrained depositional ages. Here, we present morphometrics and U–Pb isotope data from zircon, apatite and rutile grains recovered from the Boree Salt, Adavale Basin, Australia. Zircon grains are subhedral and yield a range of U–Pb ages with a youngest cluster at 378 ± 4 Ma. Apatite and rutile grains are subhedral to anhedral and have youngest age clusters of 382 ± 29 and 378 ± 24 Ma, respectively, indistinguishable from zircon U–Pb ages. These data provide the first direct age constraint on salt deposition in the Adavale Basin, indicating a maximum depositional age of c. 378 Ma for the Boree Salt during the Late Devonian, younger than a previously inferred Middle Devonian age. A review of the maximum depositional ages for neighbouring strata to the Boree Salt suggests a bedded rather than diapiric salt. The constraint on salt structure from age context is relevant for the engineering of hydrogen storage caverns. Importantly, this study highlights the potential of accessory minerals recovered from salt to provide direct age constraints on evaporite deposition.