Friday, October 25, 2019

Westhaven - Shovelnose

I've been wanting to compile the data for Westhaven's Shovelnose deposit for some time. They keep publishing decent grades and thicknesses (link, link and link), and I wanted to see how the data holds together.

Shovelnose is a good exploration story. Work commenced on the property in 2011. In 2016, drilling identified low-grade disseminated mineralization in silicified rhyolites in the Alpine and Tower zones. It was recognized that this could be the upper part of a high-grade epithermal system, which was discovered in 2018.

So, using the previous post on epithermal deposits as a guide, we'll look at the the data to see:
  1. Number of mineralized structures
  2. Size potential - vertical and horizontal extents of the mineralization

Mineralized structures

Westhaven tell us that they have 2 principal veins and maybe splay, but when you put the data in 3D, the picture becomes more complicated.

Red and orange = 2019 DH; green = 2018 DH

However, if you look at the silver, it appears to be restricted to the core of the mineralized structures.

Silver restricted to core of veins

From this I've created a series of veins. It is quite complicated, there are many ways that you can join the dots, but we can see 2 principal structures and several splays and parallel veins.

potentially multiple splay veins between principal structures

We can also see that the thickest and highest grades appear where one of the splays intersects the main vein.

Mineralization Extents


Note: My elevations are based on the Government of Canada 50K topomaps (link), and will vary by a few meters from Westhaven's surveyed drill-holes and collars

We know that in LS-Epithermal deposits, the good grade mineralization is restricted to a quite a tight vertical range. In earlier presentations (link), they used to include this slide:

just a 100m extent..

According to their geologists, the decent Au mineralization is found over a ~100m vertical range, from 1250 to 1150, which isn't very special, but with the power of excel, I disagree with them:


Please note - I've clipped the >50 g/t values to show a bit more detail for the <10 g/t Au area.

We can see that the majority of the >3 g/t Au samples fall between 950 and 1200m, and a higher grade (>5 g/t Au) core between 1000 and 1150m.

So we have a 250m apparent vertical extent to mineralization. Not bad


Please note - I've clipped the >300 g/t values to show a bit more detail for the <50 g/t Ag area.

We see a similar distribution for silver.


I've broken out the horizontal extents by the two principal veins. We want to the extent of the >3 g/t mineralization and if there are any high-grade (>5 g/t Au) zones that are can be extended or infilled (hot holes drive share-prices)

Main Vein

We can see that the majority of the >2.5 g/t samples fall within a specific area that appears to have a 500m horizontal extent and a 100-200m vertical extent.

We can see that the down-dip extension to mineralization appears to be open, but you can see how variable the grades are, we have several holes that hit minimal Au adjacent to hole SN18-25.

Secondary vein

On the second vein we see that the >2.5 g/t zone extends for at least 400m along strike and a 100-120m vertical extent. We can see that the zone appears to be open along strike, so there is good potential to extend this zone. We also see a consistent zone of >5 g/t Au mineralization (~150m x 120m) in the center of the vein.


So far Westhaven have discovered a decent epithernal system, with 2 principal veins with a couple of reasonable sized zones of mineralization. From the long sections we can see that the high-grade (>2.5 g/t Au) zones are well drilled (~50m drill-hole spacing), and the lateral extents appear to limited.

So, where do Westhaven go now? They could continue drilling the known areas and pumping out PRs with decent intercepts, but after a while they'll need to come up with a resource, and from my back of the envelope calculations the current drilling have defined around ~700Kt (assuming an average 2m vein width), which isn't enormous.

Therefore, it is nice to see that Westhaven are looking for new areas (link) to explore to build on their initial discoveries to see if they can find new veins and get the project big enough to attract interest from bigger companies.

You can get my 3D model from here (link)

Friday, October 18, 2019

Low Sulfidation Epithermal deposits

Low Sulfidation (LS) Epithermal drivel 

Just a quick intro on LS-Epithermal vein deposits. Very simple, but there is a reason for this....

911 metallurgist has a great description of low sulfidation epithernal deposits here - link, from which are some important things to note (in general) about low sulfidation (LS) Epithermal deposits and districts:
  • There are often multiple, generally, parallel veins

  • That are associated with (normal) faults. In many districts, often there are blind veins (i.e. the veins don't outcrop on surface).

  • Ore-grade mineralization in a district generally occurs over a specific range*
  • Mineralization isn't distributed equally throughout the vein, but is found in  specific zones (ore-shoots)

*assuming no post-mineral faulting (e.g. San Dimas) or multiple mineralizing/stacked events (e.g. very large epithermal districts e.g. Guanajuato, +/- Valdecanas).

For exploration it is key to target this favorable horizon, as if you
  • Drill above = erratic occasional Au-Ag hits (but could see elevated As, Hg and Sb).
  • Drill below = may hit elevated base metal (Pb, Zn, Cu) grades and low/no Au-Ag (e.g. San Sebastian - Hugh zone (Hecla Mining))

So when you are looking at a company with LS-Epithermal projects you want to see:
  1. Land position - you want the company to control or have a good chunk of a district. There is no point getting to excited about a company with a small project as any decent mineralization will quickly leave the property.
  2. More veins = more potential for large tonnages and multiple ore-shoots (e.g. Las Chispas).
  3. Large vertical extent of high-grade mineralization - this is harder without drilling. Generally in LS-Epithermal deposits the bonanza zone is ~200m thick (bigger systems = larger vertical extents - Santo Nino vein, Fresnillo had a 3-400m vertical extent).

Rhys, D el al  (2017) - Gold’17 – February 2017 – Rotorua, New Zealand 82  l Structure of the Palmarejo Mining District