While we wait for the next update, here's some data related to the current drilling at NE Riqueza, together with some personal comment. The drilling is targeting Cu porphyry/skarn/carbonate replacement mineralisation based on a typical Cu porphyry exploration model.
The data is mainly extracted from ICG announcements since 2018, with the 14 drill holes planned at the start of the programme overlaid on topographic and geochem maps – it adds to the geophysics data I posted earlier on this thread. Original drill hole numbering is used.
Topography
The first map is a vertical view from Google Maps followed by a Lidar topographic image from the AMAGRAD survey with colour coded elevation. They give an appreciation of the distinct topographic features being targeted.
Hole 41’s collar is at 4,502m above mean sea level and about 350m higher than the drilling water collection point near hole 4. For comparison, the top of Ayers Rock/Uluru is about 350m higher than the surrounding plain and the contrast between drilling in this Peruvian alpine environment and the upcoming Frewena drilling in the Northern Territory is notable.
ICG envisaged changes to the original plan as drilling progressed and it looks like that is happening - hole 3 was not drilled before the rig moved to the east side of the river where it started hole 8 about mid-Aug and may well have moved on to the next hole by now.
Potassic Anomalies
This map shows potassic (K) anomalies overlaid on the magnetics map, both from the AMAGRAD survey.
The potassic anomalies are from ICG Fig.1, 27.9.18 where they are called “strong K anomalies related to alteration”. They are of interest because in the exploration model, potassic alteration is the alteration style closest to a porphyry core. Other alteration styles, typically more distal from a porphyry core, have been found in holes 1/2/4 and they vector to a porphyry to the east (towards holes 8 and 9).
AMAGRAD radiometrics measure potassium at the surface and do not necessarily reflect potassium below surface. So, a potassic anomaly is not a definitive indication of a nearby porphyry core, but it is a positive sign particularly when coexistent with a chargeability anomaly indicative of porphyry style disseminated sulphides (see map posted earlier).
Geochem, Soil Sampling
Here are individual maps of Cu, Zn, Mo, Pb, Au and Ag relative concentrations from the soil sampling survey. They are overlaid with the drill holes. The maps are extracted from ICG App.1, 2.12.19. The survey sampling was at 200m spacing (25 samples per sq km).
The Cu and Zn maps show that except in the vicinity of holes 3 and 4, the Cu and Zn concentrations exhibit zoning with Zn generally north of Cu.
You can see that Zn, Pb and Ag concentrations generally coincide well and Mo coincides with Ag.
Holes 1,2 and 4 have been drilled and assays are awaited. Cu mineralisation was visible in hole 4. The remaining holes to be completed that are in the vicinity of good Cu concentrations, are holes 8, 9, 42 and 43, and also 6 and 7.
Zn-Pb-Ag polymetallic ores are typical of carbonate replacement deposits (e.g. Riqueza Humaspunco) and the coincidence of these metals indicates that potential in holes 5, 44, 6 and 7.
Cu/Zn zoning and distal Zn-Pb-Ag carbonate replacement are consistent with the exploration model.
Rock Chips
Assay results for 202 rock chip samples in the NE Riqueza area are given in ICG App.2, 16.6.20. Each of the 202 samples provided measurable amounts of the same 6 metals as the soil sampling. To allow relative comparison of the significance of each assay, I have used Cu Equivalent (with recovery rates not included) based on market prices of about 1 month ago.
The metals with the highest value in the 202 samples were Cu (96), Zn (90), Pb (11) and Mo (5) and Cu and Zn were second highest in the 16 cases where they were not first. In other words Cu and Zn dominate.
The following is a plot of the assays for each sample limited to showing % CuEq values greater than 0.01%. The samples have been ordered from L to R by Cu/Zn ratio. Note that the y-axis with % CuEq values is logarithmic.
You can see how Cu and Zn dominate and that Pb values in particular are significant within the high Zn samples. Ag is the next highest metal in many of the high Cu samples.
The next plot shows the location of the samples in the same area as covered by the geophysics and soil sample maps. The blue coloured circles identify those samples with more Cu than Zn, as measured by CuEq, and the red with more Zn than Cu. The size of the circles reflect Cu/Zn or Zn/Cu ratio, again as determined by CuEq, with the small circles identifying samples up to 10 times higher, intermediate circles from 10 to 100 times higher, and the large circles greater than 100 times higher.
The locations show that rock chips were not recovered everywhere, but where they were, the Cu and Zn assay data seem to relate well to the soil survey Cu and Zn concentrations. There is no particular pattern by circle size but the blue/red colour difference clearly shows the Cu/Zn zoning, with Zn dominant along the ridge running north from hole 8, and Cu dominant in the vicinity of holes 8/9/42/43.
Summary
It seems that we have the best chance of finding Cu porphyry/skarn deposits in the vicinity of 8/9/42/43, carbonate replacement deposits (including skarn) in the vicinity of 5/44 and 41, and 6/7 have the potential for all three.
Drill hole 9 is located at the southern end of the very large “unexplained” 3D magnetic vector inversion feature that extends north towards the chevron-like topographic feature and has figured prominently in a number of ICG announcements. ICG have stated a number of times that any of the drill holes could strike a target “capable of hosting significant forms of mineralisation”. The variation in the anomalies shown here supports this view, and this does not include geology and structural anomalies which the drilling will help identify and define.
Remember, "it ain't over till the fat lady sings".
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