Spinifex biogeochemistry across arid Australia: Mineral exploration potential and chromium accumulation

Spinifex (Triodia spp.) grasslands cover vast areas of arid Australia, across a variety of soils and landscapes. These grasses are deep rooted and long lived, hence have great potential as a biogeochemical sampling medium for mineral exploration. This study discusses the results of analyses of Triodia pungens and Triodia scariosa from field sites over buried Au mineralisation (Coyote, Oberon and Tunkillia Prospects). At each site there is a multi-element anomaly in the vegetation over the projected mineralisation, the haloes are of different scales depending on the local landscape setting and dispersion potential of each element associated with mineralisation. The magnitude of the anomalies is similar for each site independent of underlying substrate. Overall, spinifex chemical composition has the potential to act as a point indicator of substrate geochemistry with very minimal dispersion (hundreds of metres only) that can delineate the extent of a potential ore deposit.This study also discusses the Cr accumulation potential of T. pungens and T. scariosa, discovered during the mineral exploration studies, from several field sites (Coyote, Oberon, Tunkillia and North Miitel Prospects). Triodia species are shown to be able to accumulate Cr up to potentially toxic levels independent of substrate concentration. This could be due to accumulation (active transport) or the lack of a barrier mechanism (passive uptake) within the plant.

► Triodia pungens and T. scariosa delineate ore bodies at multiple scales with multiple elements at several sites.
► Spinifex species are shown to accumulate Cr to potentially toxic levels.
► This Cr is concentrated at the tip and is associated with opaline silica deposits.
► Cr uptake in spinifex is not shown to be regulated to low levels as with other plant species at the same sites.