Copperstone Resources AB: Drillhole COS18364 Returns 103m With 0.42% Copper Mineralisation East Of Granliden Hill
Published 21 September 2018
Copperstone Resources AB (“Copperstone” or “the Company”) is pleased to announce significant copper assay results from drillhole COS18364 in the Granliden Hill area.
103m of semi-continuous chalcopyrite mineralisation intercepted from 315-418m returning 0.42% Cu and 3.24g/t Ag and containing an 11m zone from 343-354m returning 2.62% Cu, 17.5g/t Ag and 0.2g/t Au.
Drill hole COS18364
COS18364 was collared east of Granliden Hill approximately 200m north of COS18360 and was drilled due west at -60 degrees dip to a length of 663.80m. From 35.9m the drill hole intercepted a thick package of mafic amygdaloidal lava overlying banded siltstone / arenite (with pyrrhotite) and underlying quartz porphyritic rhyolite. Within the lower part of the drillhole there are also intercalated zones of micro-diorite, minor hydrothermal breccia and younger post-mineral intermediate dykes. Mineralisation consists exclusively of chalcopyrite with subordinate pyrrhotite, pyrite, arsenopyrite and minor bornite. Mineralisation styles are either irregular stockwork-like veining over continuous zones, or discreet narrow veins. A single thick intercept of continuous chalcopyrite was intercepted from 347-348.15m (1.15m) and returned 16.15% Cu, >100g/t Ag and 0.58g/t Au. This intercept is contained in a high grade zone from 343-354m (11m) grading 2.62% Cu, 17.46g/t Ag and 0.2g/t Au. In some places veins are associated with micro-brecciation textures, associated with quartz and in general with little to no visual wall-rock alteration effect.
Note that all lengths quoted above are drilled intercept lengths only and the true width of mineralisation is not known. Composite grades are weighted averages with no capping applied. Choice of composite zone is based purely on the visual recognition of mineralisation pattern.
Ongoing laboratory testing
At the moment laboratory testing is still ongoing for drill holes COS18360, COS18362 and COS18363.A further 11 drill holes from the NANR campaign (2004-2007) and the earlier Copperstone campaign 2015 have also been sampled. The main objective of the latter is to close the gaps within the sample string so that composite grades can be determined.
Chalcopyrite mineralisation found in COS18364 is similar in style and patterns to that found in all drill holes from the Granliden Hill area. In many drill holes, the style of mineralisation is composed of thicker high grade (>1% Cu) veins, surrounded by areas of narrower veinlets forming broader zones of low grade (<1% Cu) mineralisation. In some instances high grade veins are more isolated, or intercepts of lower grade envelopes do not intercept any high grade veins. This pattern is repeatable and gives an insight into the macro patterns along the length of the mineralised zone. At this stage the true widths and lengths of individual zones and veins are not known but it is clear that these features are widely distributed across the Granliden Hill area with an estimated trend ranging from north-south to northeast-southwest.
Chalcopyrite mineralisation does appear to cross-cut the host geology package and suggests strong structural control. In the 2018 campaign three drill holes have also found a felsic granitoid rock (stock) that also appears to have a north-east trend. This southern igneous body could potentially be syn-mineral and possibly causative to the mineralisation. The bias of individual intercepts and widths of uncapped weighted average composited grade are largely dependent on the drillhole azimuth and dip relative to the overall trend of the mineralised zone.
Core Assays and Quality Assurance / Quality Control
All drill core boxes were delivered by the Drill Contractor to the secure Copperstone Site Office 1km from the drill site. Before transport to Malå, preliminary inspection and logging is carried out by Copperstone personnel. Core is then logged in detail at the Copperstone Facility in Malå before zones for sampling are selected. Once sample zones are identified and ticketed core boxes are then collected for laboratory analysis.
Sample preparation including half-core sawing, crushing, splitting and pulverizing has been carried out at ALS Minerals Laboratories, an accredited laboratory based in Malå. Prepared 50g aliquot pulps are then couriered to their Analytical Laboratory in Ireland. Sample analysis is then 4-acid digestion followed by ICP finish (ME-MS61) for 49 elements, including Ag, Cu and Zn. All samples with greater than 10,000ppm (1%) Cu and / or Zn are re-run with 4-acid digestion and then ICP-AES finish (Cu-OG62 and Zn-OG62) with results reported in percentage. Gold values are determined with a 30g fire assay fusion with AAS finish (Au-AA23).
In total 73 samples each with a drill length of 2.0m were submitted for assay from COS18364.This represents approximately 23% of the NQ core in this drillhole. The certificated copper-gold standard reference samples used are OREAS 501C and OREAS 502C, as well as blanks and duplicate samples inserted at regular intervals in the sampling sequence in order to maintain Quality Control (accuracy and precision).A total of 12 qaqc samples (4 blanks, 4 standards and 4 duplicates) were submitted at a 1:20 frequency. All qaqc results reported by ALS are within acceptable limits for the two batches submitted for COS18364.
“This is our best intercept since we began exploration in the Granliden area. In fact this drillhole is top in both the single assay result and cumulative length of copper mineralisation categories, and that is very exciting. Again we have found another significant long intercept of copper mineralisation, and this has strengthened the potential for extending the area of known mineralisation significantly beyond the historical limits of Granliden Hill. It’s now obvious that the system is large and spread out across at least 1.0km north-south up to a few old holes north of Granliden Hill. We can’t say anything now about the possibility for an economic outcome but I’m very excited about the possibilities. Nowhere else in Sweden is there such a possibility I believe. Now that drilling is complete we are working on the modelling of this data and building a picture of the potential mineral resources. This work is changing the future of this company” comments Chris McKnight CEO of Copperstone.
For further information, please contact Chris McKnight (CEO) at +46(0)580-88890, or firstname.lastname@example.org or refer to Copperstone webpage: www.copperstone.se.
This press release contains insider information which Copperstone Resources AB (publ) is obliged to publish according to the EU market abuse regulation (MAR). The information was delivered by the above mentioned contact for publishing 21st September 2018 at 0830 CET.