Characterising fluid composition and source in a greenfields terrane: west Arunta Orogen, Western Australia

Finch, Emily G.1,2,3, Kelsey, David E.1,3

1Mineral Exploration Cooperative Research Centre, Perth, Australia, 2University of South Australia, Adelaide, Australia, 3Geological Survey of Western Australia, Perth, Australia

Discovering major mineral deposits is increasingly difficult because easily findable deposits located at Earth’s surface have already been discovered. Exploration focus has now consequently shifted to relatively unexplored regions where basement rocks are commonly obscured by sedimentary cover. Exploration success in covered regions requires understanding of whole mineral systems. Fluids are crucial to understanding hydrothermal mineral systems, because fluids are present during all stages of ore formation: in the source region, throughout transport, and in deposition of metals.

The Arunta Orogen is one such underexplored and largely covered terrane, and is a key focus for the Geological Survey of Western Australia in the National Drilling Initiative. It is comprised of two Paleoproterozoic provinces overlain by sedimentary basins, and spans east–west across the Northern Territory, with the westernmost extent crossing into Western Australia. The Northern Territory component of the Arunta Orogen contains several mineral prospects and deposits, but the Western Australian component (the west Arunta) is one of the continent’s least explored regions for mineral deposits due to its remoteness, paucity of outcrop, and lack of detailed study aimed at constraining key geological factors such as lithostratigraphy and age. Limited work on the west Arunta indicates the region is prospective for copper, gold, uranium, and sedimentary-exhalative base metal deposits, but little to no analysis of alteration signatures or fluid source has been undertaken there to date.

Basement rocks of the west Arunta have undergone multiple high-temperature metamorphic and deformation events, most of which appear to postdate fluid infiltration events of interest, making these rocks unsuitable for fluid inclusion studies. Instead, minerals such as apatite can preserve information about fluids they have formed from or interacted with, and can be used to infer fluid characteristics such as composition and potential source. Additionally, apatite can be used as an exploration tool because it is an indicator mineral for different rock types and mineralisation styles.


Dr Emily Finch is UniSA’s MinEx CRC Embedded Researcher, working within the Geological Survey of Western Australia and forming a collaborative link between GSWA and UniSA. The focus of her research is on mineralising systems, with a particular interest in fluid chemistry and sources in under-explored regions of Western Australia.

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