Mapping Australia’s Hidden Copper-Gold Giants: The IOCG Revolution.
- Noel Ong
- May 16
- 5 min read
Updated: May 21
In a world where major mineral discoveries are increasingly elusive and hidden beneath cover, Geoscience Australia has crafted a powerful lens into the Earth’s potential—mineral systems-based prospectivity mapping. This approach, backed by decades of data and a deep understanding of geology, is turning Australia into a frontier once again, particularly in the hunt for Iron Oxide Copper-Gold (IOCG) deposits.
Since 2010, Geoscience Australia has carried out six major regional mineral potential mapping studies targeting IOCG and uranium systems (Figure 1). These studies span key terrains: eastern Yilgarn Craton, Western Australia (A, orogenic Au), northern Queensland (B, IOCG and uranium mineral systems), central-eastern South Australia (C, IOCG and uranium mineral systems), southern Northern Territory (D, IOCG and uranium mineral systems), southern Arunta region (E, IOCG), and Tennant Creek to Mt Isa region (F, IOCG). The base map used in these studies illustrates Australia's geological framework, with sedimentary basins in pale yellow and green, and older outcropping units in darker hues (Skirrow et al., 2019).
Figure 1: Regional-scale mineral potential mapping studies undertaken by Geoscience Australia since 2010 (source: Ore Geology Reviews 113 (2019) 103011)
The Science Behind the Discovery
IOCG deposits are not just about copper and gold—they're about systems. They form through a series of interlocking geological events (Figure 2):
Energy to drive these fluids through the crust.
Architecture (structure pathways), like faults and shear zones, that act as superhighways for the fluids.
Sources of metals and fluids, often magmatic or sedimentary.
Ore deposition gradients where physical or chemical gradients cause the minerals to precipitate (Wyborn et al., 1994; McCuaig et al., 2010).
This schematic outlines the critical processes required for an IOCG system to form.
Figure 2: Presents a schematic of a mineral system showing that ore formation occurs when four critical components—source, energy, pathway, and trap—coincide in both time and space. These components may operate at different geological scales and times, with ore deposition occurring when mass and energy converge and physical or chemical changes trigger precipitation.
Mineral potential mapping is a predictive tool that integrates geological knowledge and diverse datasets to highlight areas most likely to host mineral deposits. Rather than relying solely on known occurrences, it uses geophysical, geochemical, and geological indicators to assess where mineral systems could have formed, even in unexplored or covered regions (Figure 3).
The mapping workflow developed by Geoscience Australia involves five key steps: (1) developing a mineral systems model; (2) identifying mappable geological proxies for ore-forming processes; (3) selecting and normalising spatial data layers; (4) assigning weightings based on importance, applicability, and confidence; and (5) integrating all components into a final prospectivity map. This structured approach enables consistent, data-rich, and knowledge-driven predictions across vast terrains.
Figure 3: Summarises this workflow, showing how knowledge inputs and spatial data are combined through a scoring and rule-based inference framework to produce final prospectivity outputs. This method ensures a robust, transparent process for evaluating mineral potential. (source: Ore Geology Reviews 113 (2019) 103011)
From Concept to Greenfields Discovery
The method’s value is most apparent when it predicts success where none existed before. Exploration teams using this model have made new copper-gold discoveries in areas previously considered barren. In an age of declining discovery rates, this is no small feat. It underscores the power of data-rich, knowledge-driven exploration at a time when surface clues are no longer sufficient.
Perhaps the greatest success lies in the tool’s ability to spotlight greenfields terrains—areas under cover, where the cost of drilling blind is high. With a decision-support framework like this, companies can reduce exploration risk, and governments can better target where to invest in new geoscientific data.
To map mineral potential, Geoscience Australia developed an IOCG mineral system model based on the inclusion of all of the criteria listed in the definition (Figure 4). This model helps identify geological environments that are highly favourable for IOCG mineralisation, while also ensuring that important variants of IOCG systems are not overlooked.
Figure 4: Presents a multi-scale model of IOCG systems based on the hematite-rich Olympic Dam type. At the lithospheric scale, it illustrates the deep mantle source of metals (S2), fluid and magma pathways (P), and energy sources such as mafic underplates (D). At the regional to deposit scale, it highlights possible host-rock sources (S1), structural pathways (P), heat sources (D), and zones where ore is deposited due to physico-chemical gradients (G). This comprehensive view captures the scale and complexity of IOCG systems. (source: Ore Geology Reviews 113 (2019) 103011)
Samso’s Concluding Comments
This work by Geoscience Australia is a masterclass in turning theory into action. What Skirrow and his team have developed is not just a predictive model—it's a strategic tool that reshapes how we think about resource discovery. As someone who has walked the terrain of countless mineral provinces, I can tell you that this methodology offers a real path forward for unlocking Australia’s vast covered terranes.
The integration of science, data, and mineral systems thinking is exactly what our industry needs. With every overlay and every fuzzy logic equation, this model chips away at the guesswork and opens doors to deposits yet to be discovered. For those in the exploration game, this is a call to look again—and look deeper.
References
McCuaig, T. C., Beresford, S., & Hronsky, J. M. A. (2010). Translating the mineral systems approach into an effective exploration targeting system. Ore Geology Reviews, 38(3), 128–138.
Schofield, A. (2012). A knowledge-driven approach to prospectivity mapping for IOCG deposits: Application to the Gawler Craton, South Australia. Geoscience Australia Record.
Skirrow, R. G., Murr, J., Schofield, A., Huston, D. L., van der Wielen, S., Czarnota, K., et al. (2019). Mapping iron oxide Cu-Au (IOCG) mineral potential in Australia using a knowledge-driven mineral systems-based approach. Ore Geology Reviews, 113, 103011.
Wyborn, L. A. I., Heinrich, C. A., & Jaques, A. L. (1994). Australian Proterozoic mineral systems: essential ingredients and mappable criteria. In Proceedings of the Australian Institute of Mining and Metallurgy Annual Conference.
Mapping iron oxide Cu-Au (IOCG) mineral potential in Australia using a knowledge-driven mineral systems-based approach by Geoscience Australia - Roger G. Skirrow, James Murr, Anthony Schofield, David L. Huston, Simon van der Wielen, Karol Czarnota, Rohan Coghlan, Lindsay M. Highet, Daniel Connolly, Michael Doublier, Jingming Duan
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