A strontium isoscape of northern Australia

Abstract. Strontium isotopes (87Sr/86Sr) are useful to trace processes in the Earth sciences as well forensic, archaeological, palaeontological, and ecological sciences. As very few large-scale Sr isoscapes exist Australia, we have identified an opportunity determine 87Sr/86Sr ratios on archived fluvial sediment samples from low-density National Geochemical Survey of Australia. The present study targeted northern parts Western Northern Territory, Queensland, north 21.5∘ S. were taken mostly a depth ∼60–80 cm floodplain deposits at or near outlet large catchments (drainage basins). A coarse (<2 mm) grain-size fraction was air-dried, sieved, milled, digested (hydrofluoric acid + nitric followed by aqua regia) release total Sr. then separated chromatography, ratio determined multicollector inductively coupled plasma mass spectrometry. results demonstrate wide range isotopic values (0.7048 1.0330) over survey area, reflecting diversity source rock lithologies, geological processes, bedrock ages. spatial distribution shows coherent (multi-point anomalies smooth gradients), (>100 km) patterns that appear be broadly consistent with surface geology, regolith/soil type, and/or nearby outcropping bedrock. For instance, extensive black clay soils Barkly Tableland define >500 km long northwest–southeast-trending unradiogenic anomaly (87Sr/86Sr <0.7182). Where sedimentary carbonate mafic/ultramafic igneous rocks dominate, low moderate generally recorded (medians 0.7387 0.7422, respectively). Conversely, In proximity Proterozoic metamorphic basement Tennant, McArthur, Murphy, Mount Isa regions, radiogenic (>0.7655) observed. potential correlation between mineralization elevated these regions needs investigated greater detail. Our date indicate incorporating soil/regolith regional, exploratory geoscience investigations can help identify types under (shallow) cover, constrain (e.g. weathering dispersion), and, potentially, recognize components mineral systems. Furthermore, resulting isoscape future models derived therefrom also utilized studies aim investigate, for example, past modern animal (including humans) dietary habits migrations. new isotope dataset Australia region is publicly available (de Caritat et al., 2022a; https://doi.org/10.26186/147473).