Ann: Explains High Grade Exploration Results , page-52

re: Ann: TRF: Explains High Grade Exploration... Hi Happycats,

This is my take on the mineralisation and the 'right angles' structural description - an enigmatic geological puzzle:


1. The original 'gold zone' was depicted as being a sub-horizontal thrust plane (actually dipping gently to the west). Within this plane there are rod-like shoots of quartz-gold ore, plunging gently to the west that the local miners were mining down with their adits. OGX appear to have hit this zone down plunge of one adit, with their drill hole CDPD04, and got one nice gold intersection of 3.4m at 38 g/t Au, indicating that the shoot continues down plunge, for a total plunge extent of about 620m. Unfortunately their maps do not differentiate angled holes from vertical holes or show the customary tic symbol to denote drill hole azimuth, but most of their holes are drilled at a steep declination to 080 degrees. They also took a bulk sample of this shoot of ore from the old workings (presumably the face, or relict vein material on the drive walls) and this naturally carried ore grade.

Of the two southernmost drives on their may, the smaller drive appears to me to follow an overlying shoot of mineralisation, which as far as I can make out from their limited figures, sits above and just to the north of that in the larger, southernmost drive. It is the relative position of the workings on these two shoots that prompts my ultimate structural interpretation.

2. Where the story started to puzzle me though was the next bit. They appeared to have an exploration model that the gold seen in the largest adit and extending down plunge of it would also extend laterally, along strike to the north and south for 1,600m along the thrust plane (for 620m by 1,600m in their pre-assay drill hole estimate). This then gave them an originally-depicted huge 'blue unit' (on an early block diagram) of potential gold mineralisation, with a potentially vast tonnage, at the implied grade of the intersection they had got down plunge of one of the old workings.

Significantly though, the local miners had already investigated this possibility to some extent and ruled it out. In the main adit in the south they did what you always do when driving on high grade ore: they crosscut to the north and south to see how wide the shoot was and how far it went, but stopped after a few metres every time because it had no width extent, and instead they continued the far more challenging drive down plunge, despite the usual problems of depth, haulage distance upslope and water ingress (which is what probably beat them in the end rather than falling grades). If there had been any easy high grade to the north or south you can bet they would have driven north and south instead!

3. Anyway, OGX tested their exploration model by drilling the thrust-plane 'slab' of potential gold mineralisation over a strike length of 1.6km, along strike to the north and south of the adits.

And if you look at their assay results from this drilling in the 13th February release you can see what they got. They got what the original miners got: a couple of OK intersections, down plunge of the main adit and the three smaller adits to the north of it, but very low gold values everywhere else in the thrust plane ..and do not confuse the 'CDPD' drillhole assay results on that diagram with the other 'C' series of assays on that diagram, which are just underground vein samples from within the old adits, even though the two different assay sets are not noted in the rather insufficient legend of Fig. 1.

What that tells me is that there is nothing potentially economic in the way of gold mineralisation on that thrust plane apart from the narrow shoots that the previous miners located and drove on. i.e. OGX have tested their model of a potential huge slab of gold mineralisation occupying the thrust plane over an area 1,600m by 620m by 3.4m thick, at a grade like 38g/t (for an implied 2.5mt of potential resource), and eliminated that possibility.

They suggest that the gold assays were incomplete at the time of the Feb 13 release, but I can find no other results from that drilling programme over the subsequent four months, so I think we can safely assume that the gold story remains as it is depicted in Fig.1 and the table accompanying it in the Feb 13th release:

i.e. some impressive, but very localised gold assays from vein chip samples and one bulk sample taken in the old mine workings (3 widely separated small adits), and nothing else to speak of in any of the holes between or along strike, apart from CDP004 that appears to have fortuitously jagged one of the narrow ore shoots some distance down plunge.

(Do correct me if I am wrong though and there have been more results released from this drilling programme since Feb 13. I just find any. It looks more like a case of: 'Nothing else of note. Nothing to release.')

4. This then brings me to the sudden surprise of the silver intersection. (No mention yet that the gold model may have fallen over, in fact it still appears to be intact ..and of course it might be). But suddenly this one, thick, very high-grade silver intersection has become the 'blue slab' modelled along the sub horizontal thrust plane on their block diagrams, even though it is described as being 'at right angles' to the previous gold mineralisation.

This 'right angles to' could be seen to imply that the gold is not now an extensive slab, and is now interpreted as the more-localised, narrow, plunging shoots that the miners were following down the west-dipping thrust plane. Whilst this one silver intersection is now interpreted to occupy the thrust plane itself (i.e. is a 600m, by 1,600m by now 17.6 m thick slab. OMG!).

So perhaps the shoots of gold ore are now just narrow, westward plunging rod-structures, plunging down a westward dipping thrust plane - a not uncommon geological configuration, but now that the thrust plane is no longer a huge slab of gold ore, it has become instead an even huger slab of silver ore.


5. So what to make of all this? Well, so far the only decent silver drill intersection has come, like the only decent gold intersection, from a drill hole that was located close to or down plunge of the original miners adits (about 10m down plunge of the main adit in fact, looking at from Fig.1 in the 8th May release). Oh, and it did get a little gold too - another gold assay result: 0.73m at 4.8g/t, followed by a whole lot of not very much else.

And now they have 'analysed' the other drill holes by XRF and found 8 more holes that carry the same silver mineralisation. (It's a pity that they haven't released a map showing where these holes are, or any indication of the 'tenor' of mineralisation from these successful analyses, but never mind).

And in the 14 May company presentation there is a photograph of the core interval in CDP002 that was prevously interpreted to also carry the silver mineralisation. It is highly broken compared to the country rock, brown coloured, and is described as 'muddy'. It looks and sounds to me like a fault breccia. An oxidised fault breccia. Where one might certainly be able to get epithermal or mesothermal silver mineralisation, and to have it locally enriched by oxidation as well.

And we wait for the other eight holes to be assayed with our fingers crossed.




Anyway, that's as far as it goes for now.

If I were to make my own interpretation of the geological structure and controls on mineralsiation at Cascavel, from the rather incomplete data that has been released, I would think this:

1. There are a series of stacked, west-dipping thrusts cutting the stratigraphic sequence.

2. East-west cross-cutting, steeply-dipping structures intersect this thrust plane, and these structural intersections are the loci of narrow, rod-like, west-plunging shoots of quartz-gold mineralisation. Individually, these shoots have little strike extent, and they appear to be too widely spaced to mine as a single body.

These east-west cross structures may either be steeply dipping, east-west striking cross-faults (the ones shown on the maps), or the steeply-dipping axial planes of subtler east-west trending flexures in the thrust planes.

My best bet is that the economic gold mineralisation is restricted to the intersections between the west-dipping, sub-horizontal thrust planes and the steeply dipping, east-west striking cross faults, both of which are shown on OGX's geological maps.

It looks as though it is these structural intersections that the original miners were driving down, following narrow shoots of high grade quartz-gold ore, until the water got to much for their pumps and they gave up.

3. The newly reported silver mineralisation as described in hole CDPD021 is occurring between a lower and upper gold shoot, i.e. between two separate gold shoots on an upper and a lower gold mineralised thrust plane. Drill hole CDP 021 was drilled at -65* to 080, intended to intersect the west-dipping thrust planes, and the silver mineralisation has been interpreted to be mineralisation filling the entire width of the zone between these two thrust planes - hence the big blue slab on some of the block diagrams.

4. However my feeling is that the upper and lower gold bearing shoots in CDPD021 may be on the same steeply-dipping east-west cross-structure: i.e. they are corresponding structural intersections, on upper and lower thrust planes, cut by the same steeply dipping east-west fault. In which case, it may be that this fault structure rather than the thrust plane is what is hosting the silver mineralisation, and that CDPD021 has therefore cut this structure at a steep angle, the true width of which is much less. The alternative being the apparent OGX interpretation: that the silver is being hosted by a laterally extensive, sub-horizontal, highly-altered inter-thrust breccia, which has therefore been cut at close to true width.

As usual, I may be completely wrong about all this, and it is only my geological interpretation of the limited information that has been released. But there it is for what it is worth. I'd be interested to know how it looks from your point of view HC.

With regards,







(Do not take any action on anything I say, as I am not a financial adviser and this is not intended as financial or geological advice).