Mineralization signatures of the magnetite-dominant Acropolis prospect, Olympic Dam IOCG district, South Australia

Summary

The Acropolis prospect is a vein-style magnetite (±apatite ±hematite) system located ~20 km southwest from the giant Olympic Dam iron-oxide copper gold (IOCG) deposit, South Australia. A whole rock dataset comprising 4,864 core samples from fourteen drillholes was analysed using multivariate statistics to understand and identify geochemical signatures of mineralization at Acropolis. Statistical analyses included principal component analysis, hierarchical and k-means clustering. The results of statistical analyses are overlaid and interpreted relative to a 3D implicit geological model of the prospect, and encompass a projection of mineralization signature as PC1.

The mineralization footprint of Acropolis is multi-element and typified by a distinct ‘magnetite’ signature of Fe-V-Ni-Co. Such a signature is developed in the western part of the prospect and represents samples containing >60 wt% Fe. In contrast, the ‘hematite’ signature displays an association of REE, W, Sn, Sb, U, Th, Ca, and P and is present throughout the prospect. Furthermore, kriged values of Cu (> 200 ppm) demonstrate an offset from Ferich veins, thus supporting a genetic model in which (earlier) Cu-Au-deficient veins in which magnetite is the dominant Fe-oxide are subsequently overprinted by Cu-bearing hematite-dominant mineralization.

Results obtained provide insights into the evolution from magnetite- to hematite-dominant IOCG systems and may offer a proxy for exploration and discovery of economically significant IOCG deposits at shallower levels in the eastern Gawler Craton.

• Acropolis
• magnetite-dominant IOCG
• statistical analysis
• implicit modelling