What a great announcement! I was very pleased to briefly glance over this this afternoon and have just had a second, more leisurely read. Progress in the pass week has further de-risked Riqueza a great deal and, while assays are awaited (but are on schedule – thanks @Eagleman79), this announcement gives confidence that the high sulfide and ex-sulfide zones will return grades in line with the surface results. My few thoughts on today’s announcement:
1. Mantos:
Very pleasing to see the mantos’ occurrence and thicknesses replicated in drill results. The photos so far don’t show any reason why drill intercept grades won’t reflect averages seen for mantos in the extensive surface rock chip dataset. This isn’t a surprise as the manto sequence intercepted in hole 4 occurs within about 20m vertical meters from surface as can be seen in figure 5.
Ross has previously commented that intersections of veins and mantos will likely result in occurrence of thicker, high grade zones and hole 4 seems to support this. Given the numerous veins at Humaspunco and the continuity of the manto sequence, I’m confident we’ll see similar ‘upgraded’ zones at other intersection sites both down- and along-slope which are a boon for increasing the value of the resource.
If further drilling shows that the mantos’ grade is in line with expectations, and that they occur as predicted throughout Humaspunco Hill, then these mantos and intersecting veins could themselves form a substantial, shallow, standalone resource. Earlier predictions by Dr West look pretty accurate volume wise (I came to a similar number independently); it’ll be really exciting to see if our informal grade estimates also match. I’m confident we’ll be close.
If the deeper drilling doesn’t provide positive results (so far it is!) then this upper zone could form a pretty decent ‘fall back’ result for Inca. As it is, I feel this zone will more likely represent a profitable pre-strip resource that could greatly improve economics for deeper mining at Riqueza. That, of course, is long term thinking.
2. Veins:
I think we all appreciate that mineralised veins continuing to depth, often thickening at depth, and discovery of six new ‘blind’ veins are all strong positives for the exploration program. In addition to these, I think another positive is company comment that grade will be variable but that sulfide occurrence, style, and distribution observed at depth broadly mimics that seen in surface samples. Prior to assays being announced, I take that as a confidence boost that vein grades should be in line with expectations of average values generated during the detailed channel sampling program. Note though, that in these deposit systems the value of Pb, Zn, and Ag will generally decrease with depth as formation temperature and pressure increase so we might see some decrease in grade with depth; Cu and Au concentration tend to increase with depth before Au drops away and Mo increases within a porphyry sequence.
Additional to the above, the noted decrease of barite and the increase of pyrite with depth are typical of this style of deposit. That we see a strong barite occurrence with high grade Pb-Zn-Ag at surface indicates limited erosion has occurred meaning we have a well preserved mineral system on our hands. At worst, erosion has removed a likely small volume of high grade material along with a potentially thick, low-grade to barren siliceous cap.
3. Intrusive Block:
Extremely pleased to see this intrusive body intersected at relatively shallow depth. Subvolcanic or hypabyssal rocks are igneous rocks that cool and solidify close to the Earth’s surface. Technically they are intrusive rocks formed at shallow level and have characteristics that differ to strictly intrusive or extrusive igneous rocks. The style of deposit seen at Riqueza generally occurs near the boundary between intrusive and volcanic rock with epithermal mineralisation occurring upwards in the volcanic sequence (or in this case the overlying limestone sediments), and mesothermal and porphyry mineralisation more restricted to the intrusive rocks below. My thoughts on this intrusive:
a. Shows that igneous activity is relatively shallow beneath Humaspunco as previously thought.
b. Chlorite alteration and the three cross cutting veins indicate this igneous body is slightly older than the main mineralising event at Riqueza.
c. Gratifying to see that this is not simply a big block of barren material but that it is mineralised by the three cross cutting. Additionally, I am interested to see if the occurrence of disseminated pyrite has any association with Au enrichment. It would be an ideal result if this older intrusive also happened to host low-grade Au – unlikely but still a possibility.
d. This igneous block would have helped prepare Humaspunco Hill for the mineralisation event by fracturing and weakening the limestone when it penetrated. With these fractures the mineralising fluids associated with younger intrusives would have had pre-formed pathways to assist them migrate to surface and precipitate our mineralisation. A further positive of this intrusive block is that its contacts with the limestone have acted as preferred fluid pathways allowing a much larger vein structure to occur on the footwall (deeper side) of the intrusive. Thicker zones (if they grade well) can potentially form large, high grade zones very beneficial for the resource model. I’d suggest that the hanging wall contact (shallow side) also hosts a thicker zone for vein 6. Steeper drilling might prove this for slightly deeper intersections.
All looking very good in the Humaspunco drill program so far, pre-assays. Four successful holes out of four; can’t get better than that!
GLTA and DYOR
Cheers,
Bornite
ICG Price at posting:
1.6¢ Sentiment: Buy Disclosure: Held
(20min delay)