The Gawler Craton is best known for the discovery of Olympic Dam in 1975, which was the culmination of nearly a decade of exploration. Olympic Dam is a monster in the world class category so this discovery is not something you find often. Not long after, several smaller mines were discovered such as Prominent Hill, Cairn HiIl and Carrapateena proving that the Gawler Craton is a very fertile place.
The Olympic Dam mine is a large poly-metallic underground mine located in South Australia, 550 km NNW of Adelaide. It is the fourth largest copper deposit and the largest known single deposit of uranium in the world. Copper is the largest contributor to total revenue, accounting for approximately 70% of the mine's revenue, with the remaining 25% from uranium, and around 5% from silver and gold. BHP has owned and operated the mine since 2005. The mine was previously owned by Western Mining Corporation. - Wikipedia
The discovery of Olympic Dam by Western Mining Corporation Resources Limited (Now part of BHP) sparked a rush for land around the discovery. Olympic Dam was a major discovery in an area that had little work at that time.
Figure 1: Olympic Dam copper-uranium mines and pant is situated in South Australia, 560km north-west of Adelaide. (source: Mining Technology)
In the mid 1990s, a small exploration company, Dominion Mining Limited discovered the Challenger Gold Mine (Figure 2). It was a blind discovery that came from regional calcrete sampling. Have a read of the Samso Insight that I published in November 2019 - Challenger Gold Mine - Calcrete Anomaly Exploration Success.
The discovery of Challenger brought about a hive of activity that resulted in companies like Helix Resources Limited (ASX: HLX) who announced news of drill holes hitting a 150 metre wide zone of gold mineralisation along the Yarlbrinda Shera Zone at Tunkillia (Source: AFR - Nov 19, 1996).
The excitement that amplified the activities was due to Helix returning assays including 35m at 4.4 grams per tonne and 112m at 1g/t beneath a sand cover of between 60 metres and 100 metres (Source: AFR - Nov 19, 1996).
Figure 2: The Challenger Gold Mine was discovered by Dominion Mining Limited in 1995. (Source: Microsoft News)
The significance of Challenger is that it produced a resource of over 1.2 Moz of gold but there are no cousins, brothers or sisters in the immediate area. There are small deposits like those in the Jumbuck project that was formerly in Tyranna Resources Limited (ASX: TYX) and now sold to Marmota Limited (ASX: MEU). Marmota have themselves found the Aurora Tank deposit which has yet to have resources but is definitely showing the same kind of mineralising signals as those discovered in the Jumbuck Project.
There are no significant deposits within a couple hundred kilometres. The closest significant deposit is the Tunkillia and Tarcoola to the south east or Cairn Hill to the north east. When you compare this to Kalgoorlie, there are hundreds of mines of all sizes and major exploration projects within that space.
Currently, the market space has changed and I see there have been a lot more attention on the Gawler Craton.
Where is the Gawler Craton?
Most investors in the ASX think of the Yilgarn Craton as the Mecca of the Australian Goldfields. When you mention Kalgoorlie, most people think of the Goldfields. When you move up the levels of understanding, names such as the Pilbara, Ballarat, and maybe Cloncurry begin to appear. However, names such as Cadia (New South Wales) and Olympic Dam, which are the world-class deposits, are lesser known to virtually being unheard of in many cases. I think it is lesser known because they are not in the realms of your average investors' playing space.
And if you mention the Gawler Craton, I will safely say that the average Joe will have no idea of its significance. Some parts of the brokering fraternity do not even pay attention to this area.
The Gawler Craton is the oldest and largest geological province in South Australia, preserving a complex tectonic history spanning from c. 3200 Ma to 1450 Ma. The craton comprises a Meso- to Neoarchaean core enclosed by Palaeoproterozoic to Mesoproterozoic rocks. The Mesoarchaean history of the Gawler Craton is dominated by felsic magmatism, the Neoarchaean to Palaeoproterozoic history by sedimentation and bimodal volcanism, and the Mesoproterozoic history by felsic volcanism. - Source: South Australian Department of Energy and Mining.
Figure 3: The Gawler Craton. (Source: Gum, Justine 2019. Gold mineral systems and exploration, Gawler Craton, South Australia, MESA Journal 91, Issue 3)
What all the geological jargon means is that the Gawler Craton is old and has had a lot of structural deformations, reheating, deposition and redepositing of mineralisation.
In summary, it is a damn good place to be looking for minerals as it is a large cooking pot with everything thrown into it.
According to the department, the Gawler Craton is prospective for the following commodities:
Metals: Cu, Au Fe, Ag, Pb, Zn, Co, Ni, Cr, Mn Ti, V, PGE, Mo, W, Sn, REE
Industrial minerals: graphite, kaolin, talc, magnesite, limestone, dolomite, barite, vein-silica, manganese oxide
Gem: jade, diamonds, chalcedony/agate
Construction materials: vast resources of road making material (limestone, dolomite, quartzite, sandstone, gneiss), dimension stone (granite) and regolith clay (brickmaking & refractory) Energy minerals: U3O8, thorium
As for what else could be in the area, the following list that is straight out of the website gives a good idea of what is already there and what could be there:
Demonstrated:
FeO-Cu-Au-Ag±U (haematite- and magnetite-dominated styles) (Olympic Cu-Au Province, e.g. Olympic Dam, Prominent Hill, Hillside, Moonta, Carapateena Prospect)
Iron ore as massive hematite deposits by supergene enrichment, (e.g. Iron Monarch, Iron Duke, Wilgerup)
Iron ore as magnetite-bearing banded iron formation (e.g. Middleback Range, Bungalow Prospect, Hawks Nest, Skylark), to magnetite-rich metasediment (e.g. Warramboo)
Iron ore as magnetite and hematite skarn/replacement styles (e.g. Peculiar Knob, Snaefell, Wilcherry Hill)
Intrusion-related Au (Central Gawler Gold Province, e.g. Tarcoola, Tunkilla Prospect, Barns Prospect, Weednanna Prospect)
Shear-hosted Cu, Au, U (e.g. Cairn Hill)
Shear to unconformity-related U (e.g. Driver River in central Eyre Peninsula)
Regolith deposits, including kaolin (e.g. Poochera), supergene copper (e.g. Hillside, Alford West) and regolith manganese oxide (e.g. Hercules West, Jamieson Tank, Pier Dam)
Orogenic Au (e.g. Challenger)
Volcanogenic Pb-Zn-Ag (e.g. Menninnie Central and Telaphone Dam Prospect) and Cu-Fe (e.g. West Doora)
Epithermal-style Ag-Pb-Zn (e.g. Paris) and Au-Ag-Pb-Zn (e.g. Parkinson Dam)
Sedimentary-hosted Pb-Zn (Hutchison Group, e.g. Miltalie Mine, Mangalo Mine, Atkinson’s Find, Smithams)
Graphite (e.g. Uley Graphite Mine, Kookaburra Gully, Koppio, Wilclo South)
Metasomatic talc, magnesite and jade (Katunga Dolomite)
Possible:
VHMS deposits (Hall Bay Volcanics, Oakdale prospect southern Eyre Peninsula)
Late Archaean komatiitic and magmatic intrusive-hosted Ni-Cr-PGE (Lake Harris Greenstone Belt, Aristarchus)
Magmatic Ni-Cr-Cu sulphides and PGE (Fowler and Christie Domains)
Unconformity and Palaeochannel U and Au (e.g. Corunna Conglomerate)
Diamondiferous kimberlite
Intrusion-related W and Sn (e.g. Moonbi W prospect, Zealous Sn prospect)
Fe-Ti-V styles (e.g. Malbooma Anorthosite Complex, Wigetty prospect)
Why Should Investors be Interested?
As I have been getting acquainted with the South Australian mineral scene, I have come to learn that there is indeed a lot of things happening. Like many participants in the mineral exploration industry, the focus has overwhelmingly been West Australian centred over the last two years.
Due to the pandemic, the mineral resource industry has been West Australia first and the rest of Australia second. Anything outside of Australia is just too hard. I have had a couple of clients with projects in Arizona, USA, South Korea, Thailand and Chile. They are still viable as they have established crews that are based in the country, otherwise, these kinds of projects just seem to fester away.
Anything new is way too hard, or at least that's how it seems anyway.
I have noticed an increasing list of South Australian projects coming into the spotlight. Something else I have learnt is that there are a few interesting companies that are based in Adelaide. Here are just a few that I know:
Indiana Resources Limited (based in Perth but the project is in South Australia)
These are the ones that I know are active but I am pretty sure I have left some out. I have included the energy companies just for completion.
What I like About the Gawler Craton
In my humble opinion, the Gawler Craton due to its remoteness and lack of exploration activities for the last twenty years is literally the last frontier. When you look at the size of the area, you can start to appreciate the remoteness and the potential cost of exploring in this area.
When we talk about remoteness we think of Australia, so it is not that big a statement. What makes this a great project location is that the remoteness is coupled by the lack of interest by the capital markets to fund any exploration for the last twenty years. What this lack of interest means for an optimistic exploration geologist, is the thought of a blank canvas to discover new deposits.
What do I mean by a blank canvas? The volume of discoveries in the Yilgarn (Figure 4) has made many participants in the industry question - what else can be found? Comments are supported with the thousands of deposits being uncovered over the many decades of exploration with the numerous metalliferous provinces that exist within the Yilgarn Craton.
In contrast, the Gawler Craton is no competition with the number of discoveries that could rival those in the Yilgarn (Figure 3). The location of good discoveries have been few and far between for decades. In addition to the difficulty of finding mineral deposits, the lack of infrastructure has meant that the size of discoveries need to be at a significant size to be economically viable.
Figure 4: Map of the Yilgarn Craton showing the locations of komatiite-hosted nickel, orogenic gold and BIF-hosted iron deposits. Modified after Mole et al (2013). [1]
So to me, the Gawler Craton is just a blank canvas and where you discover something is entirely up to the participants who have the "Who Dares Win" strategy. We all know that this simply means the size of your pocket and that gut instinct.
Shear hosted Mineralisation: Challenger - Tarcoola - Tunkillia Province.
My experience in this region lies in my recent research into areas in Australia that would make me want to go explore and find potential giant deposits. I look from the view point of a junior company with limited funding and time to discovery. This means that one would rule out Porphyry Copper or any IOCG - Iron Oxide Copper Gold style deposits.
My criteria is that the project has to be cost effective. IOCH and Porphyry projects tend to be costly and that would not be practical for the average junior. Hence, for the purposes of this Insight, we will not entertain the part of the Gawler Craton where these styles are present, such as the Olympic Dam Province.
There are three main players in the immediate area, Marmota Limited, Barton Gold Limited and Indiana Resources Limited (Figure 6). Barton and Indiana are new players to the region, having done work within the last 12 months. On the other hand, Marmota has been working on their ground since 2016. Their focus has been primarily on the Aurora Tank project. The other company that has been working in this region for about the same time frame is Tyranna Resources Limited. However, Tyranna has since sold their package to Marmota.
Figure 5: Tenement map of the major players in the Challenger - Tarcoola - Tunkillia Province.
Companies such as Indiana Resources Limited have picked up over 5,000 square km, a big acreage of land within the Turnkillia mineral field (Figure 6). Their package makes good sense as they are adjacent to the Tarcoola and Turnkillia gold mines.
Figure 6: Tenement holdings for Indiana Resources Limited in the South Australian Gawler Craton. (Source Indiana Resources Limited)
The proximity to the two existing mines creates a good exit strategy. This exit strategy is one that is all about infrastructure and the need for current players to work together for the mutual benefits of all. One of the issues with remote projects is that your discovery at most times, needs to be of a significant size for monetisation.
Having the two mines present and a motivated neighbour to build infrastructure will help Indiana create value from smaller discoveries. I think that the neighbours will work well together as their mutual benefits are sealed in a good working relationship.
Indiana is working on the Lake Labyrinth Shear Zone which has been highlighted as the probable source of all the previous drilling results. Their work currently is in delineating the existing mineralisation and building the case for more extensions to the current results.
Current work is focused on the Minos prospect (Figure 8) and that makes sense as they have been getting some very good numbers. The numbers coming back are consistent with those that Challenger, Tyranna and Marmota have reported in the past.
The latest results from Indiana is proof of my thoughts on this region. Announced on the 13th July, Indiana released the following numbers:
21m @ 8.43 g/t Au from 176m including 1m @159 g/t Au
2m @ 18.4 g/t Au from 162m including 1m @ 35.6 g/t Au
23m @ 6.44 g/t Au from 186m including 1m @ 118 g/t Au
10m @ 8.83 g/t from 39m including 3m @ 26.03 g/t Au
Figure 7: The main exploration activity of Indiana Resources Limited. (Source: Indiana Resources Limited).
When you look at Figure 7, and you look at the individual prospects such as Minos and compare to the entire tenement package of Indiana (Figure 5 and Figure 6), you get an appreciation of the potential of the province. Minos is a mere speck in the overall scheme of things. Like all of these projects, funding is the key. The good news for Indiana is that they are most likely onto something at their Minos prospect.
Minos (Figure 8) is proving to be a growing beast as the current results are supporting historical works. The potential scale and the probable continuation of strike for the mineralising system looks promising as well. The exploration geologist blood in me can't help but be optimistic of the potential.
If optimism is the thought, then I am thinking of elephant scale. I am thinking World Class system in the hands of a junior. If scepticism is in the thought, then I am thinking, big area, need lots of money, hard to find, looking for a needle in the hay stack.
Both views are valid but what is common is the fact that the opportunity arises due to the fact that there is a need for money and the challenge to cover a large land tenure.
Figure 8: Drilling results from the Minos Prospect. (Source: Indiana Resources Limited)
Barton Gold Limited holds the most prominent position as they have the Challenger, Tunkilliana and the Tarcoola gold mines (Figure 9). The combined resources come up to around 1.1 Moz Au and is JORC 2012 compliant with a tenement coverage of just over 4,600 square km.
Figure 9: Barton Gold Limited Tenement map. (Source: Edited from Barton Gold)
I have not looked at Barton in great detail. I know that trying to make old mines work is very challenging but if they have good funding behind them, it will work. As an exploration geologist, I am always in favour of finding your own deposit.
I will look into them at a later date because they will be a force, if funding is not an issue for them. If all the inflationary issues take hold, the assets which are most advanced will become more economical.
Marmota Limited will be the biggest player in terms of tenement coverage (Figure 10) as it has just picked up the Jumbuck project from Tyranna Resources Limited. When the transaction is completed (within two months of writing), they will hold over 10,000 square km of land in the area. How they will handle the exploration commitments will be interesting.
Marmota has had some good success in defining the Aurora Tank project (Not JORC) over the years and that has shown that supergene oxide gold deposits are abundant.
Figure 10: Tenement map for Marmota Limited excluding Jumbuck. (Source: Marmota Limited)
Historical drilling from Marmota and Tyranna (Jumbuck Project) has also indicated that Challenger type mineralisation (primary mineralisation) exists in the area. This is also something that is now becoming more obvious in the Indiana projects (e.g Minos).
Conclusions
This is a rather lengthy Insight but I felt the need to put things in context. The Gawler Craton is a large place. The three companies I talked about have thousands of sqkm. Most companies play with hundreds of sqkm and that is considered big. One of the most important aspects of mineral exploration is to get access to the land, so that you can do work.
The key aspect of my Insight is the lack of intense exploration in the Gawler Craton, the lack of interest for a good part of two decades and the lack of capital that encourages exploration in this part of the world. I think I have mentioned this numerous times in this insight and I cant stress this enough. If you have ever tried to look for stories in this industry and you are asking the question "Where can i find good tenements", you will agree that it is a pretty well populated space.
What is even more compelling is that there are world class deposits that have been discovered and mined in the Gawler Craton for over three decades. However, only about two thirds of the area have been touched extensively. The focus in the Gawler has always been the IOCH style and there have been many endeavours over the years, but I have not seen much news on discoveries.
I highlight Indiana Resources because of the Minos prospect. What you need to look at is where Minos (Figure 8) is at the scale of the Lake Labyrinth Shear (Figure 11). Then you take a step back and look at where that Lake Labyrinth Shear is in relation to one of the tenements in the area (Figure 7).
* I have not mentioned any other projects from Barton or Marmota for the sake of unfamiliarity and not because I do not think that they are prospective. I have not had time to look at them for this Insight.
Figure 11: Location of the Lake Labyrinth Shear Zone (LLSZ). Note the location of the Minos prospect in relation to the regional aspect of the LLSZ.
To get a good handle of why I am bullish on the Gawler Craton stems from this article that I wrote in 2019 - Challenger Gold Mine - Calcrete Anomaly Exploration Success. You can understand that since that discovery in the 1990s, there have only been two major discoveries in Tunkillia and Tarcoola in this area.
Tyranna Resources came and followed up on the findings left behind since the discovery came up with some good signs. Marmota explored and discovered Aura Tank. However, they have not come up with resources. I am assuming that it is only a matter of time before they come up with a JORC statement. What they do with Jumbuck will be interesting. The commitments on that area alone is nearly AUD3M. Maybe some M&A action will be happening.
It will be interesting in the coming twelve months to see how my optimism will pan out.
References:
[1] Choi, Eunjoo. 2020. Alkaline magmatism as a probe into the evolution of the lithospheric mantle in the Yilgarn Craton, Western Australia MSc Thesis.
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