In this interview, Andrew Paterson, Managing Director at Great Boulder Resources, gives us an overview of geochemistry 101.

Here's what you will learn:

• Andrew's background and early career in Mining
• An overview of Great Boulder Resources
• An introductory look at geochemistry.
• What is it, how is it used, how are samples collected?

About Great Boulder Resources

This interview with Andrew Paterson was recorded on August 7, 2024.

Great Boulder is a mineral exploration with high-quality gold and base metals in Western Australia.

With a primary focus on definition of the company-making Mulga Bill deposit at Side Well, the Company is also exploring for gold at Whiteheads near Kalgoorlie and for zinc and lead at the Wellington project in the Earaheedy Basin.

Great Boulder trades on the ASX under the ticker GBR.

Links and Resources from this Episode

1. YouTube Interview with Andrew
2. Great Boulder's website
3. Great Boulder on LinkedIn
4. Great Boulder is listed on the ASX under ticker GBR
5. Great Boulder's 3D VRIFY presentation.

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Jargon in Today's Episode

• Intrusive related system: A type of mineral deposit formed from molten rock that pushed into existing rock layers.
• Alluvial cover: Loose material, like sand or gravel, deposited by rivers or other flowing water on top of solid rock, often hiding minerals below.
• Regolith: The layer of loose, weathered material covering solid rock, important in exploration to understand what’s above the target mineral.
• RC (Reverse Circulation) drilling: A method of drilling that uses air to blow rock chips from deep underground to the surface, commonly used in mineral exploration.
• Pathfinders: Elements or minerals (like bismuth or molybdenum) that geologists look for because they often indicate the presence of valuable minerals nearby, such as gold.

Timestamps

• (00:00) Episode overview
• (01:34) Andrew's background and experience
• (06:08) Great Boulder Resources overview
• (07:43) How does geochem guide exploration?
• (10:18) Geochemical indicators (pathfinders)
• (11:48) Costs associated with geochem collection
• (16:34) Challenges in interpreting geochem
• (18:26) Episode conclusion

Disclaimer

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Hello, and welcome to Rock Talk, where we explore the world of mining through casual and non technical conversations with industry experts. I'm Karl Woll, Senior Account Executive at VRIFY Technology. And in this episode, I'm joined by Andrew Paterson, Managing Director of Great Boulder Resources. Great Boulder is a gold and base metals exploration company in Western Australia.

In our conversation today, Andrew takes us through an introduction to all things geochemistry. I hear about geochem all the time, I know it's important for vectoring, but to be honest, I hardly knew anything about it. So it was great to sit down with Andrew, he did a terrific job of walking us through what exactly is geochem.

How is it collected? How expensive is it to collect and assay the data, and ultimately what is the value that we get from the data and how is it used by mining companies or exploration companies to advance their projects? Andrew was the perfect person to speak with because he has a background as a geologist and geochem has also been instrumental in advancing Great Boulders flagship project, the Side Well Project.

If you have any feedback or suggestions or you want to suggest a future topic or guest for a future episode, there is a link in the description or show notes of this episode where you can provide that feedback, or you can go to the website at rocktalkpod.com and that same form can be found there. And with that, let's jump into this week's conversation with Andrew Paterson.

Hi, Andrew. Thanks for joining me today. How are you?

I'm great. Thanks very much. I appreciate your time today.

No, I appreciate your time. From what I understand, you're going to be able to take us through a bit of a Mining 101 lesson on geochemistry and I'm looking forward to digging into that. Before we jump into the geochem side of things I would love to just get to know a little bit about you and a little bit about Great Boulder Resources.

So do you mind just giving us the quick background. I know you have a background as a geologist. So how did you get into mining and what has your career path looked like up to your point as Managing Director with Great Boulder?

Yeah. Well, as you say, I'm a geologist. I've, I've been in the industry for about 30 years and there wasn't any kind of particular aha moment that led me into geology, but I came from a a country upbringing. And so I was at school, I was considering careers that would get me in, you know, in the outdoors, kind of outdoor focus.

And somewhat stumbled into geology and enjoyed it and so I graduated about 30 years ago in Kalgoorlie which is a good place to start a career because obviously it's the heart of the West Australian gold industry And went straight into mining. So open pit and underground mining for several years around that area in gold and then later on in nickel and a lot of mining and production experience and sort of worked my way up into management roles. Which culminated in a Site Manager role in Meekatharra, sorry, in Mount Magnet in the Murchison here north of Perth, running all the mining and exploration up there. So that was, you know, that was, I suppose, 15 years ago, was my first introduction to exploration. And so it's somewhat morphed into exploration almost by accident, I suppose.

And as my career's progressed and I've gone into executive and corporate roles and become responsible for exploration programs, I've taken a greater and greater interest in it. And with the help of some experienced mentors for example our chairman, Greg Hall I've learned probably more about geoscience in the last 10 years than in the 20 years prior to that.

So it's been a really interesting learning curve and both challenging and extremely rewarding and I'm absolutely loving it. So it's good fun.

What are some of the things that you've found that you enjoy or maybe miss from I guess being more on when you think back to your early days as maybe a junior geologist versus to being more on the corporate side. What are the differences that you find?

I guess, you know, one difference is when you're a young geologist in a production role, every day there are time based pressures. You know, you have to get have to mark out the ore zone for the day or work out where the jumbo is going underground. You know, where's the, where's the next ore drive heading keeping track of grades, tracking ore coming out of the mine, heading to the mill.

There's a lot of time pressure and it's, as a result, it's a very fast-paced job. And if you're good at it, that in itself is quite rewarding and you get to the end of the month and you reconcile all your metal through the mill successfully, and, and that's, you know, that's a job well done. So there's, there's quite a consistent feedback loop.

By the same token, if you're not good at it, it can snowball really quickly and you can be in a whole world of pain very, very fast. So that, you know, that's a challenge. Exploration on the other hand is more, it's a slower pace. There are still time pressures but they're over longer periods of time.

So you might be talking weeks or months for, you know, assay turnaround and approvals and getting drilling programs completed. But the excitement there is really when you find something, it is very much the kind of thrill of discovery and that is that's, you know, a huge thing for any exploration geologist to find something.

Particularly if they do all the preparatory work and come up with a theory and test that theory and then find something at the end of that process, it's extremely rewarding and it's a huge kind of boost, I suppose, in the role. And then combining those in corporate life. You know, you then have the opportunity to employ and manage small teams of professional geologists or larger teams, obviously, as well. And watching those people learn and grow in the field and, and gain the confidence to go and find new discoveries themselves, that's also really, really rewarding and, and that's kind of where, I guess, Great Boulder's in a sweet spot and we've got a great project.

We've also got a really good team of young people out in the field, you know, doing sharp end geoscience every day, which is, is just awesome.

For those that aren't familiar with Great Boulder Resources and the Side Well Project in WA, could you give us the two minutes elevator pitch for the company and where things currently sit?

Yeah, absolutely. We're a small company, as I said before. We have a gold exploration focus where we would characterize ourselves as an advanced explorer in the sense that we've currently got two thirds of a million ounces in JORC resources in inferred and indicated category,

So two thirds of a million ounces, we're on track to deliver a million ounces in, in resource next year. And we've got a really good project. So, you know, we, we kind of see ourselves as in a, I suppose, a pre development phase where we've identified a project with large scale potential, probably multi million ounce potential. We've kind of already delivered a fair bit of our promise to, identify a million ounces in resource and then we'll start working on economic studies really and, and work out how to extract that. So, you know, to maximize value for the shareholders. And we've been doing that at this project at Side Well, which is about eight hours drive north of Perth at Meekatharra. Been working there for a bit over three years and it's a great project, really high grade there. It's quite technically challenging, so it's been a slow process and ultimately, a million ounces for a small company is a lot of drilling and that in itself takes time and obviously money so it's been in quite a, I guess, a slow but rewarding and we're well advanced on that.

Great. Thanks, Andrew.

Yeah, let's let's jump into geochemistry. So I yeah, it's something that I hear about all the time, but I admittedly know very little about. So I'm curious to dig into this. How does geochemistry guide the initial stages of mineral exploration?

Well it's really important because our initial deposit that we were drilling there, Mulga Bill, is actually obscured by alluvial cover so you get about 10 to 12 meters of alluvial material which on surface looks a lot like just basically alluvial sand and clay and so there's no surface signal of mineralization at all.

There's no geochemistry telling you you know, where to drill, basically. And, if you look on the presentation here on the VRIFY deck, it's also very flat. There's no, topography at all. You're looking east there towards Wiluna, north towards Mulga Bill and then west you can just see the town in the distance of about 10 kilometers away. So, you know, this is the kind of terrain that we're exploring in and you can see that paleo channel coming down across the surface there and in the middle distance is Mulga Bill. You can just see some of the drill pads. And so if you drive over that or you did soil sampling there you'd have no idea that there was a million ounces sitting underneath it.

So, the geochemistry there is super important to identify where to drill. And I'll, just quickly zoom in on Mulga Bill itself and you'll see what I mean. It's, it's firstly, You know if you look at it side on you can kind of see here that not only is there alluvial cover there, but then you've also got a depth or thickness there which varies from sort of 40 to 60 meters and there's almost no gold in that either. So if you're drilling down you might drill a 50 meter hole and not see anything at all. So what we found in geochemistry was that there's really not much signal near surface for gold but in fact there are other pathfinders that are associated with gold that stick around and the key one there is bismuth. Bismuth is really important because when a rock is weathered from a fresh new rock all the way down to weathered completely to clay, the bismuth will stay behind. So that's interesting, but the important thing is that bismuth and gold here are quite closely correlated. So if you find bismuth in the weathered material, you can be reasonably confident that the gold is fairly close by.

And what are some of the, I guess, other than bismuth are there other geo chemical indicators of a mineral deposit.

Yeah, so associated with the bismuth specifically some of the hot elements like molybdenum sometimes tellurium, sometimes copper, and they, those together indicate that it's probably an intrusive related system and what that means is basically kind of what it, what it sounds like is that underneath somewhere there's a big intrusion. Which is like a, originally a big hot body of magma injected into the ground by, you know, by essentially volcanic activity. And the fluid inside that magma was originally contained all these metals and as it was forced out due to heat and pressure up into the surrounding rock, which is where Mulga Bill is, it's left these chemical signatures behind.

So that, you know, that tells us that this is, is basically an intrusive related gold system, which is a specific type of gold system, but literally driven by an intrusion. So there's a big heat engine was there originally, and we're talking, you know, perhaps 2.6, 2.7 billion years ago, those are very old deposits and it, and when it came through the country, it left the gold behind, but it also left these associated elements behind as well.

And if you assay for all of those things, it gives you the bigger picture of what type of system you're looking for and, and where it might be, where, where it might go.

Okay. And if you're collecting geochemistry data, so you're running a survey across the tenements or the project area, what does that actually entail? So how do you collect the data? What does that typically cost? What's involved in that process?

Yeah, so there's a few ways you can do it. If you don't have alluvial cover, you can just literally dig a hole with a shovel and take a sample of the soil and assay that. So that's, you know, that collection is, is effectively free other than labor. Then send it off for assay. A gold assay in Australia might cost you around 12 to 15 dollars.

That's just for gold only. However, if, as in this case, the gold is quite mobile, you want to be looking for the other elements as well. So you do multi element assaying and we get in our assay scheme about 48 elements and that costs around 55 to 60 dollars. So it's quite expensive. And then, if you add on the fact that you've got alluvial cover means you actually need to drill a hole to get down below that to get your sample.

And so, you use the cheapest drill techniques you can, which in Australia is usually air core drilling, which is just a type of rotary drilling that gives you a fairly clean sample. So you might drill, you know, maybe drill 20 metres down, take a sample of the clay. And then continue drilling until you get to the top of the fresh rock and ideally take a sample of that as well.

And you, you know, you assay on the way down just in case you hit anything on the way. But they're kind of that, those are the important sampling points I suppose you want to sample in what we call the regolith, which is the weathered part of the of ground between fresh air and fresh rock. And then you get a sample of the fresh rock, which will tell you when you put all of those 48 elements together, you can tell, you know, what type of rock it is apart from just your visual assessment and whether there's any anomalous pathfinders.

So the first thing, obviously, if you're looking for a gold deposit, first thing you look at is the gold assays. But then the second thing you look at is all those pathfinders that I'm talking about like bismuth, copper, moly et cetera.

Okay. So imagine like with most forms of data, more is better. So how do you balance the cost? Because let's assume you're not going to just shovel one little hole and send that into the lab. You're probably going to do I don't know, I have no idea, but I'm guessing maybe a couple hundred.

How do you balance the costs of an extensive survey versus the potential rewards in terms of valuable data as an output?

Yeah, that's a good question and it really, it comes down to a comparison between the cost of getting that geochemical data versus the cost of just drilling holes blindly. And so as an example, an air core hole will cost around say 20 to 25 dollars per meter to drill. So that's quite cheap. Okay. An RC hole on the other hand might cost between 60 to 75 dollars a meter to drill. That's reverse circulation, which is a bigger drilling technique. It's, it's again, it's a percussion technique with, where compressed air, it's like having a hammer drill going down the hole and, and compressed air blowing the sample back up, so you can collect it. They're both good quality, relatively cheap drilling techniques. So, say if, if you again use Side Well as an example at Mulga Bill, we're drilling say around an average of about 100 meters down to get to the top of the fresh rock. So if you're drilling RC that might cost you six and a half to seven thousand dollars just to get that, that sample. And if you're just drilling for gold you don't know really where to drill, so you're going to have to drill maybe a hundred of those holes, and that's a lot of money. Whereas if you, if you drill a small amount of air core and, and get that sample as cheap as you can and then you get the multi element data and you start to build a, a, a kind of an, an anomaly, like a 3D or, or two dimensional anomaly, which will allow you to vector into where the gold is.

Then you might actually hit the gold on the first RC hole and save all of that money that you would otherwise waste on drilling. So it's really just an equation of, if you go in blind and drill a shitload of RC holes, you know, a program might cost you two or three hundred thousand dollars very quickly versus a relatively small amount of multi element assaying to get a much better result much faster.

So, yeah, that's, that's really the basics of it. I mean, in a very simple system the gold deposit might stick out of the ground and you can just go straight in and start drilling because everything is very easy to see. In a complex and highly weathered environment like Mulga Bill, you really need to do a lot more, I guess, sleuthing to work out where to drill before you start spending a lot of money, so it's, it's really just about efficiency.

And once you've collected that data, what are the main challenges in interpreting the data and analyzing it.

Yeah, it certainly, it helps to have a really good geochemist, so there's a software everyone uses called ioGAS, which is just a software for analysing and comparing various elements in the assay data. Easy to use but understanding what it means is really the key. So you need a good geochemist to tell you, you know, what rocks you're dealing with.

As an example at Mulga Bill all our rocks are quite similar chemically and visually they look very similar and it took us quite a while to be able to visually pick one type from another and chemically very, very similar as well. So we were lucky we had the services of Dr Scott Halley here in Australia who's one of the Australia's best geochemists and he very quickly zeroed in and said firstly you know, you've got bismuth coming out your ears, it's a massive bismuth anomaly so let's use bismuth and, and established that correlation between bismuth and gold. And then he saw that correlation also ran with molybdenum and silver and tungsten and so on. So he said, look, you've got an intrusive related system here, it's actually quite big. These are the chemicals that you need to concentrate on. So firstly he concentrated on the pathfinders which was the gold association.

Secondly, he used the other chemistry to tell us what rock types we were dealing with and, and, you know, what they look like in, in in a map view. And thirdly, he's also able to use the chemistry to establish the alteration patterns. So someone with those skills can get three different layers of information out of the same data set, which is just fantastic.

But it's also it's almost like magic when you see someone do it. It's not something that everybody is capable of. So you've got to have a really smart person at the controls to get the best out of your data.

Andrew, thanks so much for the overview of geochemistry. Really appreciate it. That was really interesting and I learned a lot. Before we sign off, is there anywhere that you would like to direct the listeners to follow along with any announcements or updates from Great Boulder as you continue to advance the project?

Yeah, I guess the first port of call is either the Australian Stock Exchange, asx.com.au or our website, greatboulder.com.au. And we have a YouTube channel. Often when we put out an announcement, which is, is a, you know, you know, printed announcement on the ASX, I'll then follow that up with videos and sometimes LinkedIn videos that I record myself, and we put them on our YouTube channel.

Which is linked on the website and also on LinkedIn. So either follow me on LinkedIn or the company, and you'll see all of those and links to all our announcements on there. So that's really, that's our main social media channel.

Great. Well, thanks again for your time, Andrew. Really appreciate it. And hope to talk to you again soon.

Absolutely. Thanks very much.