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Monday, March 26, 2018

Lupaka - a blast from the past

Lupaka Reports 9.86 g/t Au-Eq. over 130 m from Underground Sampling Program at the Invicta Gold Project

fuck me, that sounds great (link), but it is bullshit. 



They aren't lying directly to you, they've just resurrected one of those old favorite sleights of hand (ECU Silver were famous for doing this) by trying to impress you by misrepresenting the size of their penes mineralization by using the strike length rather than width.

I guess 12m @ 18.1 g/t AuEq wasn't good enough.

Here is an annotated doodle from the map accompanying the PR



I do like the fact that much more sampling has come from the Footwall vein, there is a sample every 5m (give or take), but only every 20m on the hanging-wall vein. I wonder which is better?

Even better is the way that they generously decided to include some of the HW assays (e.g. samples CH_16, 19 and 20) into the FW zone so that they could 'improve' its grade.

So now it is my turn to do some bad math:



I split out the assays by sample location (FW, HW and Combined)

  • FW vein
    • average width = 4.6m
    • average grade = 8.4 g/t AuEq
  • HW evein
    • average width = 5.8m
    • average grade = 6.7 g/t AuEq
  • 'Combined' veins
    • average width = 8.4m
    • average grade = 10.6 g/t AuEq
Not to shabby, but definitely not what was advertised on the tin. It also shows that the intersection zone between the FW and HW veins is an attractive exploration target to follow up and down dip as they could define a small, but high-grade ore-shoot. 











Wednesday, March 21, 2018

Deposit data

The USGS publish a lot of free data on mineral deposits through their open file reports. These reports often include the source data and spreadsheets.

Generic link - https://www.usgs.gov/science-explorer-results?es=Grade+and+Tonnage+Models

Deposit specific links

  • Porphyry deposits - link and an older version link 
  • Sediment hosted Cu deposits - link
  • Sediment hosted Zinc deposits - link
  • Sediment hosted Au deposits - link
  • VMS - link

Please note that these reports aren't produced every year, so the data will be a bit out of date (up to 10 years depending on the deposit type).


As this post is very boring, here are some boobies

A beautiful pair of Boobies






Mineral deposits - a summary

Asiamet - Beutong

Asiamet have released a flurry of press releases this month, they've raised money (link) and recommenced drilling on the Beutong porphyry Cu-Au deposit (link).

It contains a decent amount of metal:


Or a global resource of 511Mt @ 0.48% Cu and 0.13 g/t Au or 0.56% CuEq.

If we plot them on the USGS chart of doom, we can see if Beutong is good enough to tickle the hairy balls of a major mining company?

Note: the log scale to the axes
Nope, at the moment it is nothing more than a friendly caress and a slight squeeze.

So what do Asiamet need to do to get it into the top right corner of the chart - the Acquisition Zone? To grab a major by the short and curlies, they'll need to:
  • Double the resource but keep it at the same grade - 1Bt @ 0.56% CuEq
  • Increase the grade, but keep the tonnage the same - ~500Mt @ 0.6% CuEq
To do this, they need to drill, but are there any obvious area where they can start?

I compiled the summary drill-hole data for Beutong - leapfrog model is here - link). Resources have been defined in 3 main areas.



East Porphyry

If we look at a plan map, we can see that the best intercepts all of the >0.5% Cu have come from the small (350m x 150m) quartz-stockwork. There is minor mineralization (<0.3% CuEq) in the host sedimentary units (grey). To the east sits an unmineralized (post-mineral) breccia. There is a small high-grade core, but this has been closed off (i.e. drilling has defined it limits with no obvious areas for expansion).

red line = surface outline of the stockwork zone
Looking at a section through the East Porphyry, we can see the stockwork is narrow (200-300m wide) but a few drill-holes (e.g. hole BEU0800D01 - 293m @ 0.6% Cu and 0.11 g/t Au starting at ~450m depth) have intersected >0.5% Cu mineralization to ~700m depths.


The skarn zone sits to the north - left
This deep continuation of mineralization hasn't been fully explored and with some targeted, long drill-holes will add some tonnage to the East Porphyry resources.



The question is, will anyone care that most of the potentially resources will be at >400m depth and probably beyond the limits for an open pit mine, and too small and low grade for a block cave?

West Porphyry

There has been much less drilling on the Western Porphyry zone, but the results are generally poorer than at the East Porphyry. Some 'round the world' drilling (holes going in every compass direction) have moderate intervals of generally low grade (>0.5% Cu and minor Au).

Green circles - areas where drilling has intersected >0.5% Cu
However, there are a couple of areas where drilling hit some moderate zones of >0.5% Cu that need follow-up drilling to see if they are part of something more substantial or just some lucky hits.




Skarn

A small skarn zone is found just north of the East Porphyry. Its given some great hits - e.g. BC007-01 - 48m @ 1.63% Cu and 0.88\ g/t Au.

getting worse with depth

However, it look like we have some supergene enrichment (link - a very complicated presentation , but slide 20 is a good). With higher Cu grades close to surface and grades decreasing with depth.






Summary

Even tough there are some areas where the current resources can be added to, I don't think that there is enough in the current resource areas to make the project enticing enough for a major.

For me, I believe that Asiamet need to find something new. We know that porphyries tend to occur in clusters, and, if they have not already done so, a decent portion of the 2018 exploration budget should be used for regional exploration to find some new targets.

Friday, March 16, 2018

Porphyry preamble

Ahh porphyries, conjuring vision of untold riches hidden in the bleak hills of the Andes or the mosquito infested jungles of Indonesia and Colombia.

However, ignoring the BS that explo-cos spout about their project being great because in reality, most aren't.

The CAPEX for a decent sized porphyry (or any large scale mine) typically run into the billions. No junior company can ever develop them, and so the best that they can do is entice a major to fund the project beyond the resource drilling stage.

However, ignoring the FOMO-mania that happens when metal prices go crazy, in general, most mining companies like to focus on projects that can support a minimum production profile, for example:
  • 100,000 tonnes of copper or 100,000 ounces of gold a year for >10 years
The idea is that the project will pay back the CAPEX (a novel idea), produce lots of cash for many years.

Here is a nice chart from the USGS (link) that displaying CuEq% grade vs tonnage for various copper deposits. Porphyries sit towards the large but low grade end of the spectrum. I've added some annotations and some well known projects.

blue crosses = porphyry projects

Remember: this chart uses the total resources for a project. Many projects have a high-grade core or are a combination of heap leach oxide and higher grade sulfide ores (with economics and cut-offs).

Smaller and/or lower grade projects do get developed, but often they are brownfield projects adjacent to an operation that mined a neighboring higher grade deposit.

What you want is:

  • A project that is in the top right part of the chart = takeover target 
  • An exploration stage project that shows the potential to get into the top right area.
What you want to look for are projects that are a decent size >200Mt and a reasonable grade - around 0.6% CuEq or >1 g/t AuEq, or show the potential to get there.

However, grade and tonnes aren't the only factors that impact a project's economics, but it is a good starting point.