Morning Tim,
Great points and questions raised, some commentary on the points you made. I do note I am applying generalisations here, an Engineer considers 100 different factors and reasons why they may design or optimise a pit in a certain way based upon a suite of data (Environmental, Heritage, Hydro, Block Model, Geology, Geophysical, Community, Exclusion Areas, Faults & other geotechnical risks just to name a few).
400Mt Mineral Resource at Roche Dure, will further drilling expand this ?
For Roche Dure the 400Mt Mineral Resource does not have scope to expand by any large margin. What can happen at Roche Dure is that additional In-fill drilling could potentially increase more tonnage from lower confidence Inferred, to upgraded confidence Indicated or Measured. What does that mean ? If you look at the below overview on the left we see the Pit with the drilling hole information that the Geologist has at their disposal. - The Yellow Dots are Large RC Drilling Holes AVZ completed;
- The dark gray dots are pre-existing data from the Old Tin operation
- The red dots are the in-fill drilling AVZ recently completed
The closer together the drill hole spacing, the more confidence a geologist has in the data and allows the classification of that data at a higher JORC level i.e. in this case measured.
If you look at the classification on the right, where the green and blue (lower confidence level) sections are and compare that with the drill holes on the left, you see these areas don't have as many holes and they are further spaced apart
What this means is that if AVZ wanted to, they could complete further in-fill drilling in the green and blue areas. Considering the confidence they have already, this would be a waste of time and money, if you can get your project up and running based upon the data available at hand, it doesn't make sense to drill the whole pegmatite at say 25m x 25m spacing for example.
Of the 130Mt Ore Reserve, can we get this to 200Mt ?
There could be a plethora of reasons why the pit is currently modelled to extract 130Mt of reserves. One thing to note is that once a site is in production, their is a team of Engineers, Geo's, Survey, Geotechs, Planners who are constantly optimising the Mine Design based upon data and in field observations. Mine Plans for Large scale operations for most commodities are run and re-run on varying frequencies quarterly / annual / 5 years / LOM (it is a never ending optimisation process) More data = potential to increase value
There are always limitations for how close your Ore Reserve can get to your Mineral Resource. No Mine in the history of civilisation has extracted 100% (and no mine operating today will).
In the below left is the same overview of the drill holes at Roche Dure. The red line is an imaginary cross section, imagine if we sliced that section and then looked at it from side (that is essentially what the image on the right shows us, a cross sectional cut). When you look at the cross section you see a dashed line indicated a Geological Fault which the company has not drilled past, although we have a large section of what would be classified as inferred resource.
The mine pit design today would roughly look like the below (Very roughly drawn just to illustrate a point). That being not 100% of known resource, falls within reserves. Could be for anyone of a 100 different reasons as I have touched on previously. You might say that the deposit is open and dipping towards the south-east, which it clearly is. What an engineer onsite will have to consider in future, is it worth removing overburden to extend down to get the ore in the bottom right ? Do we wish to work with the known faults (along with a 100 other questions / considerations).
When I form the 3d shape in my head here, the pegmatite looks really pretty homogenous?
There is no other known hard rock resource that even comes close to what is at Manono (NONE). If i utilise the below drill hole data for just 1 of the drill holes, we have a 218 meter intercept which starts at 6.4m below the ground and extends through to the 224.9m mark below ground. The average grade of this intercept is 1.69% Li20. What you can see is that there are sections that are in excess of 2%, what you can guess is that there would be some sections of lower grade (still above the cutoff grade), that results in the total average being 1.69% Li20.
The Geo's and Engineers would build there block model and mining schedule to ensure a relatively steady feed grade into the plant (as every plant attempts to achieve). Hence why block modelling is so important, feeding 1.4% one month and feeding 2% the next is going to give you marginally different yields from the plant. Consistency is the goal !
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