Biogeochemical expression of buried iron-oxide‑copper‑gold (IOCG) mineral systems in mallee eucalypts on the Yorke Peninsula, southern Olympic Domain; South Australia

We report on the results of a regional scale biogeochemical sampling program conducted on the Yorke Peninsula, South Australia, utilising four locally occurring Eucalyptus species with mallee-form. Our purpose is to determine if there is an empirical relationship between Cu accumulation in the mallee leaves and elevated Cu in the underlying basement rocks - such that the mallee species might be a useful biogeochemical exploration tool in this area. The basement rocks of the Yorke Peninsula are prospective for iron oxide‑copper‑gold (IOCG) mineralisation but are mantled by Cambrian to Quaternary sedimentary rocks of variable thickness that inhibit traditional surface geochemical exploration techniques. There is no evidence to link Cu concentrations to dust contamination or fertiliser usage. Leaves of the four mallee species have comparable log normal population distributions of Cu, with a range between 1.6 ppm and 10 ppm. Higher concentrations of Cu (> 6 ppm) occur more commonly within 3 km of known Cu occurrences. These results suggest that all four mallee species have the ability to concentrate higher amounts of Cu in their leaves when the underlying/local geology also contains elevated Cu. The results suggest that biogeochemical sampling of multiple mallee species over large regions could be a useful exploration technique in covered areas of southern Australia where mallee species are widespread and densely populated.