Geochemical discrimination of igneous zircon in the Gawler Craton, South Australia

Abstract

Zircon from spatially and temporally distinct igneous rock units across the Gawler Craton, Australia, show subtle differences in trace and rare earth element ratios. These igneous suites range in composition from granite, rhyolite to gabbro and originate from the ca 2450 Ma Sleaford Complex, the ca 1850 Ma Donington Suite, the ca 1633–1608 Ma St Peter Suite, the ca 1595–1587 Ma Gawler Range Volcanics and the ca 1595–1575 Ma Hiltaba Suite granites. The geochemical characterisation of zircon is carried out on relatively unaltered samples in order to establish primary signatures and to understand the processes controlling the geochemical signatures of the igneous suites. A range of zircon morphologies and internal textures that are preserved in these igneous suites infer the geological history of the host rock, including metamorphism and multiple episodes of zircon saturation suggesting a complex magma evolution. Despite differences in whole-rock geochemistry between igneous suites, zircon largely overlaps geochemically. However, subtle differences in Th/U, U/Hf and (Nb + Ta)/P ratios are evident between the Donington Suite, Gawler Range Volcanics and Hiltaba Suite. This is likely due to the tectonic setting, composition of the crystallising magma and timing of zircon crystallisation in the magma evolution. The subtle geochemical differences in zircon show the potential of using these ratios to aid in provenance studies with large populations of zircon that are of similar age. However, as the dataset is limited and focused only on unaltered samples, further work needs to be undertaken to look at the altered counterparts of these igneous suites.

KEY POINTS

1. Zircon recovered from unaltered samples of spatially and temporally distinct igneous suites in the Gawler Craton is used here.

2. Th/U, U/Hf and (Nb + Ta)/P ratios of zircon can discriminate the Donington Suite, Gawler Range Volcanics and Hiltaba Suite.

3. Zircon morphologies, internal textures and geochemical characteristics are a value aid to provenance studies.

Keywords:

• zircon
• geochemistry
• Gawler Craton
• accessory mineral
• Hiltaba Suite
• magmatism

Acknowledgements

Anthony Reid is gratefully thanked for assistance with samples. David Kelsey and Sarah Gilbert from Adelaide Microscopy are also thanks for their help with the collection of SEM and LA-ICP-MS data. Many thanks to Dr Yongjun Lu and Elizabeth Jagodzinski for their reviews, which have significantly improved the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The data that support the findings of this study are openly available in Mendeley Data at http://dx.doi.org/10.17632/gjjwbwb895.1

Additional information

Funding

The work has been supported by the Mineral Exploration Cooperative Research Centre whose activities are funded by the Australian Government’s Cooperative Research Centre Program. This is MinEx CRC Document 2020/3. This project is also supported by the Commonwealth Scholarship Program for South Australia.