27 Apr 2022
27 Apr 2022
Status: this preprint is currently under review for the journal ESSD.

A strontium isoscape of inland southeastern Australia

Patrice de Caritat1, Anthony Dosseto2, and Florian Dux2 Patrice de Caritat et al.
  • 1Geoscience Australia, GPO Box 378, Canberra ACT 2601, Australia
  • 2Wollongong Isotope Geochronology Laboratory, School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong NSW 2522, Australia

Abstract. The values and distribution patterns of the strontium (Sr) isotope ratio 87Sr / 86Sr in Earth surface materials is of use in the geological, environmental and social sciences. Ultimately, the 87Sr / 86Sr ratio of soil and everything that lives in and on it is inherited from the rock that is its parent material. In Australia, there are few large-scale surveys of 87Sr / 86Sr available, and here we report on a new, low-density dataset using 112 catchment outlet (floodplain) sediment samples covering 529,000 km2 of inland southeastern Australia (South Australia, New South Wales, Victoria). The coarse (< 2 mm) fraction of bottom sediment samples (depth ~0.6–0.8 m) from the National Geochemical Survey of Australia were milled and fully digested before Sr separation by chromatography and 87Sr / 86Sr determination by multicollector-inductively coupled plasma-mass spectrometry. The results show a wide range of 87Sr / 86Sr values from a minimum of 0.7089 to a maximum of 0.7511 (range 0.0422). The median 87Sr / 86Sr (± robust standard deviation) is 0.7199 (± 0.0112), and the mean (± standard deviation) is 0.7220 (± 0.0106). The spatial patterns of the Sr isoscape observed are described and attributed to various geological sources and processes. Of note are the elevated (radiogenic) values (≥~0.7270; top quartile) contributed by (1) the Palaeozoic sedimentary country rock and (mostly felsic) igneous intrusions of the Lachlan geological region to the east of the study area; (2) the Palaeoproterozoic metamorphic rocks of the central Broken Hill region; both these sources contribute radiogenic material mainly by fluvial processes; and (3) the Proterozoic to Palaeozoic rocks of the Kanmantoo, Adelaide, Gawler and Painter geological regions to the west of the area; these sources contribute radiogenic material mainly by aeolian processes. Regions of low 87Sr / 86Sr (≤~0.7130; bottom quartile) belong mainly to (1) a few central Murray Basin catchments; (2) some Darling Basin catchments in the northeast; and (3) a few Eromanga geological region-influenced catchments in the northwest of the study area; these sources contribute radiogenic material mainly by fluvial processes.

Patrice de Caritat et al.

Status: open (until 22 Jun 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on essd-2022-125', Patrick De Deckker, 05 May 2022 reply
  • RC2: 'Comment on essd-2022-125', Jurian Hoogewerff, 09 May 2022 reply
  • RC3: 'Comment on essd-2022-125', Anonymous Referee #3, 23 May 2022 reply

Patrice de Caritat et al.

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A strontium isoscape of inland southeastern Australia P. de Caritat, F. Dux, A. Dosseto

Patrice de Caritat et al.


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Short summary
Strontium isotopes are useful in geological, environmental, archaeological and forensic research, for instance to constrain or identify the source of materials such as minerals, artefacts or foodstuffs. Many regions and countries around the world have established strontium isotope databases and maps, i.e. isoscapes. In Australia, however, there are very few regional-scale assets, and this study establishes a new strontium isoscape for over 500,000 km2 of inland southeastern Australian.