Fingerprinting the source of mineralising fluids in IOCG systems, Mount Woods Inlier

Iron oxide copper gold (IOCG) deposits are sulphide-poor, low-Ti, magnetite and/or hematite rich ore-bodies with associated polymetallic (Cu, Au, Ag, U, REE, Bi, Co, Nb, P) enrichment. Scientists and explorationists have sought the next giant IOCG deposit since the discovery of Olympic Dam. Exploration has been hampered by a lack of clarity in modelling and classification of IOCG deposits. This study aims to determine the source of mineralisation in both economic and subeconomi IOCG mineralised systems from the Mt Woods Inlier, Gawler Craton, South Australia. Magnetite separates and whole rock samples were subjected to Nd isotopic analysis, REE and trace element distribution, XRF and petrographic analysis. Petrographic analysis of samples suggests three generations of magnetite; primary/magmatic, massive vein, and disseminated metasomatic magnetite. LREE enrichment is ubiquitous amongst a mixture of single-fluid and multi-fluid systems. Ore samples from Prominent Hill show no evidence of multiple phases of fluid alteration based on REE or isotopic data. Additionally, primitive εNd values in ore samples suggest derivation from a single generation of fluid sourced from a mantle reservoir. The Taurus prospect harbours similar signatures. The results presented here are contrary to previous IOCG mineralisation models, thus are significant for explorationists and researchers.