Earlier in 2019 we announced a 71% increase in the JORC Resource for 7.7Mt of gold-copper-cobalt. Metallurgy is favourable and we are keen to advance this major project.
In March 2019, we annouced the JORC Resource update, which grew the resource by 71% based on 2018's drilling to an Inferred Resource of 7.7Mt @ 1.06 g/t gold, 0.51% copper and 0.08% cobalt for 260,000oz Au, 38,000t Cu and 5,900t Co.
The Carlow Castle - Quod Est gold-copper-cobalt (Au-Cu-Co) deposits are located 28 km northeast of the Radio Hill processing plant. Carlow Castle and Quod Est are structurally controlled mineralised zones occurring almost at right angles to each other. The Carlow Castle South deposit is hosted by east-west shears in basalt and ultramafics. Oxidation of the primary mineralisation occurs to depths of 25-65 m below the surface. The Quod Est deposit is hosted by north-south shears immediately north of Carlow Castle South in basalt with oxidation of the primary mineralisation down to an estimated 25-40 m below the surface.
The structurally controlled mineralisation at Carlow comprises chalcopyrite, chalcocite, cobaltite, pyrite and gold in constantly variable amounts within shears and brecciated zones in chloritized basalt. Minor tellurobismuthite, hessite and uraninite also occur.
The Carlow Castle portion strikes east-west, being fault terminated at each end. Drill definition has been completed over the 1000 m strike length which has a flattened sinusoidal form. At the western end mineralisation dips steeply north, at the eastern end the mineralisation dips steeply south. Mineralisation in Carlow Castle has been shown to extend to at least 250 m below surface.
The Quod Est portion strikes approximately north-south dipping steeply east with a strike length of about 200 m and is fault terminated to the north and potentially at depth. Drilling has identified additional mineralised zones to the east of Quod Est; at this stage these are of very limited extent but given the prevalence of historic workings in the area, potential exists to expand these lodes. Al Maynard & Associates (AM&A) updated the Carlow Castle Mineral Resource estimate in March 2019.
Carlow Castle is located 28 km north-east of Artemis’ Radio Hill processing plant, via gazetted roads, and approximately 45 km by road east of the city of Karratha (Figure 2). Access is via the Northwest Coastal Highway and then by the unsealed Cheratta road which passes through the Project area. Carlow Castle is on the granted exploration license E47/1797 held by KML No 2 Pty Ltd, a 100% owned subsidiary of Artemis Resources.
The gold-cobalt-copper mineralisation at Quod Est and Carlow Castle South is hosted in chloritic shear zones within the predominantly Archean mafic sequence. The ore zones appear partially oxidised above 20m with sulphides extending to depth, the primary sulphides are chalcopyrite, cobaltite and pyrite; the presence of chalcocite in some samples indicates supergene enrichment in the upper portions of the sulphide zone.
The structural environment of the area is complex; Quod Est strikes north-south and dips steeply to the east whereas Carlow South strikes east-west and dips steeply to the north.
Artemis has redrilled the deposit with a total of 188 RC and 12 diamond drill holes totalling 24,721.6 m drilled on regular grids during 2017 and 2018.
The resource at Carlow Castle South was modelled in 2018 by Mr Philip A. Jones. The Mineral Resource estimate was completed using the drilling data provided by Artemis to model the resource within confining wireframes c onstructed on the geologically interpreted lodes using a generic metal factor calculated by (Au ppm * $36.97 ($USD1282.10/oz) * 90% mining and metallurgical recovery + Co% * $408.75 ($54500/tonne) * 75% mining and metallurgical recovery + Cu% * $44.73 * 75% mining and metallurgical recovery) >$30.
Four domains, based on the strike of the mineralisation, were used in the modelling. High grade cuts were also applied using Mean + 2 Standard Deviations of the domained assays. Grades were extrapolated in the model using an Inverse Distance Squared (ID2) algorithm. AM&A estimated the total Inferred Mineral Resource at Carlow Castle South and Quod Est to be approximately 7.7 Mt at 1.06 g/t Au, 0.08% Co, 0.51% Cu using upper cut grades.
|Tonnes||Au g/t||Cu %||Co %||Contained Au (oz)||Contained Cu (t)||Contained Co (t)|
|Quod Est Oxidised||100,000||1.31||0.66||0.18||4,212||660||180|
|Quod Est Fresh||200,000||1.15||0.5||0.2||7,395||1,000||400|
|Quod Est East Oxidised||20,000||1.14||0.56||0.15||733||112||30|
|Quod Est East Oxidised||40,000||1.45||0.54||0.23||1,865||216||92|
Geology and mineralisation
The Carlow Castle South Au-Co-Cu deposit is hosted by east-west shears in basalt and ultramafics. Oxidation of the primary mineralisation occurs to depths of 25-65 m below the surface. The Quod Est Au-Cu-Co deposit is hosted by north-south shears immediately north of Carlow Castle South in basalt with oxidation of the primary mineralisation down to an estimated 25-40 m below the surface.
Carlow Castle regional geology
A total of 188 RC and 12 diamond drill holes totalling 24,721.6 metres, were drilled at Carlow Castle by Artemis in 2017 and 2018, Since there is no adequate QA/QC data and reporting on the earlier drilling at Carlow Castle, only these Artemis holes were used for this reported resource modelling and Mineral Resource estimate. A listing of all the collar locations of the Artemis drill holes used in the resource modelling is provided in Artemis’ ASX announcement of 6 March 2019.
A field geologist supervised all the drilling and logged the drill samples for lithologies, weathering, alteration, mineralisation etc. Reference samples were collected for each metre and stored in chip trays for future reference.
Sample recoveries were recorded by the geologist in the field during logging and sampling. If poor sample recoveries were encountered during drilling, the supervising geologist and driller endeavoured to rectify the problem to ensure maximum sample recovery.
The majority of samples were dry. Where wet sample was encountered, the cleanliness of the cyclone and splitter were closely monitored by the supervising geologist and maintained to a satisfactory level to avoid contamination and ensure representative samples were being collected.
The down-hole intervals logged by the geologist as being mineralised or show significant alteration were sampled and assayed at 1 m intervals while the unmineralised intervals were composited and assayed over 3 m intervals. If a 3 m composite returned assays above normal background levels these intervals were re-sampled and assayed over 1 m intervals.
The HQ3 (triple tube) diamond drilling was completed using a truck mounted Evolution FH3000 Diamond Drill. The core was logged by the site geologist with core recoveries, lithologies, alteration type and intensity, mineralogies and fractures/structures recorded. Down-hole surveys were taken at 30 metre intervals down each hole after the holes were completed using a magnetic instrument for holes ARC024 to ARC028 inclusive and using a gyroscope for holes ARC036 to ARC081 inclusive.
Topography and surveying
LandSurveys based in Karratha surveyed the topography using photogrammetry (0.035m resolution) in January 2018. A hand-held GPS was used to locate the drill hole collars prior to drilling. The collars of all the completed holes were subsequently picked up with DGPS with an accuracy of within 1 cm. The grid system used, common to all Artemis drilling is GDA94 (MGA 94 Zone 50).
Samples from the RC drilling for each metre were collected through a rig-mounted cyclone and split using a rig-mounted static cone splitter. A 2-4 kilogram sub-sample was collected for laboratory multi-element analysis.
The remainder of the sample, following removal of the portion for chemical analysis, has been retained at site for potential future use in preliminary metallurgical test work.
HQ3 diamond drill core was cut by trained technicians along the long-axis using a diamond saw, with cutting intervals marked up by the geologist. The sampling intervals were nominally 1m, adjusted to match lithological/mineralisation boundaries. Field duplicates were taken at regular intervals and submitted for analysis.
Since the drill intersections are slightly oblique to the mineralisation the recorded sample intervals in the mineralisation have apparent widths slightly greater than the true width of the mineralisation.
The 188 RC and 12 diamond drill holes in the Carlow Castle database included 22,676 samples assayed for each of modelled assays, i.e. gold, cobalt and copper, along with the suite of other elements described earlier.
Drill holes used for resource modelling
Total Depth (m)
Num. Samples Assayed
18CCAD001 - 18CCAD012
ARC001 - ARC189
The majority of the drill samples were assayed as 1 m intervals, and some of the diamond drilling at shorter intervals. For consistency, the estimation composites were composited to standard 1m intervals to minimise any volume variance effects.
The drilling data was split into four domains reflecting the changes in strike of the mineralised lodes. A parallel set of gold, cobalt and copper assays with upper grade cuts applied were modelled. Separate upper cuts were calculated for each domain at the mean + 2 standard deviations.
The drilling database received by AM&A for this resource estimate was supplied by the Company as Excel spread sheets including each of drill hole collar coordinates, down-hole surveys, down hole lithology logs, sample recovery data and assays. The data as received was entered into MineMap© software and checks were made to ensure that the hole IDs were correct and sample intervals did not overlap or were negative. No errors were found in the data.
Mineral Resource Estimate
The mineralisation envelope was digitised using MineMap© software on cross sections, snapping to the drill intercepts using a generic metal factor calculated using London Metal Exchange (“LME”) prices at 31 December 2018 by (Au ppm * $36.97 ($USD1282.10/oz) * 90% mining and metallurgical recovery + Co% * $408.75 ($54500/tonne) * 75% mining and metallurgical recovery + Cu% * $44.73 * 75% mining and metallurgical recovery) > metal factor 30. This total metal factor cut-off was chosen to define the mineralised envelope because the copper, cobalt and gold are strongly associated with each other in the veins and are considered to have reasonable prospects of economic extraction.
Carlow Castle project wireframes
Sample intervals within the interpreted lode below the designated 30 metal factor content were included within the lode wireframe where in this internal dilution did not drop the total intersection below 30 metal factor and where it provided improved continuity with other adjacent drill intersections of the lode. The mineralised zones on each cross-section were then linked by wireframes to produce “solids”. The base of oxidation was triangulated from the drill hole geology logs.
Four domains, based on the strike of the mineralisation, were used in the modelling. High grade cuts were also applied using mean + 2 standard deviations of the domained assays. Grades were extrapolated in the model using an Inverse Distance Squared (ID2) algorithm.
The model was validated by comparing the estimation composites against the estimated blocks in plan and section views.
The estimate was classified as Inferred on the basis of the spacing of the drill intersections, quality of the drilling and sampling and the degree of understanding of the geological controls on the mineralisation. The Inferred Mineral Resource at Carlow Castle and Quod Est was reported within the lode wireframes above a 0.3 g/t Au lower grade cut-off, to be approximately 7.7 million tonnes at 1.06 g/t Au, 0.08% Co, 0.51% Cu. This estimate was completed applying capped grades. No previous mining has been recorded within the area of the modelled resources, however there are a number of old workings along strike from the deposit.
Artemis has completed preliminary metallurgical testwork on the Carlow Castle Au-Co-Cu Project at ALS Metallurgy in Western Australia focussing on the metallurgical amenability of selected samples from the Carlow Castle deposit employing conventional gravity gold, cyanide leach and flotation processes.
Analysis of the metallurgical results from these samples indicate:
- A significant gold component ranging up to 48% is recoverable using gravity separation;
- Most of the balance of the non-gravity gold is recoverable in sulphide concentrates as a by-product using standard flotation. This gold could be sold in concentrates as a credit or recovered on site using a cyanide leach process.
- Quick floating copper minerals produced a high-grade, premium copper concentrate of approximately 30% Cu;
- Deleterious elements including arsenic are easily managed with a light concentrate polishing using regrind or blend control;
- Recoveries depended on mineralogy with 77–85% copper recoveries achieved. Unrecovered copper minerals are predominantly represented by non-floating silicates or secondary oxide copper minerals.
- Cobalt recoveries ranged 73-79%;
- Saleable Cobalt concentrate grades ranging 2.3–5.3% Co were produced
- Cobaltite (CoAsS) is the dominant cobalt bearing mineral - and is therefore intrinsically linked to arsenic affecting it sale price.
- Testwork continues to improve cobalt concentrate grades and ultimately aims to maintain optimal recovery and reduce shipping/smelter treatment charges.
Targeting lower specification concentrates, but at a lower sale price, will minimise processing capital costs while producing high specification concentrates, commanding higher sale prices, will require a higher capital input. A trade-off study of capital and operating expense versus revenue from differing grade product streams will be evaluated prior to final flowsheet selection to optimise financial returns.
The results of the metallurgical testwork program released on 11 February 2019 provides Artemis with a basis to plan and advance project development activities. The planned development work bringing Carlow Castle through a Pre-Feasibility Study and into production includes:
- Resource delineation drilling including improved definition of existing resources and conceptual mining studies;
- Structural and geotechnical drilling; and
- Further metallurgical testing of alternative low-cost process flowsheets to improving cobalt flotation chemistry and optimise gold cyanide leach recoveries to produce doré on site.
A detailed development timeline for Carlow Castle is being developed.
Prospectivity and proposed exploration and project development
The number of old workings and surface geochemical anomalies along strike and within the tenement indicate that the prospectivity of the Carlo Castle lease can considered moderately high.
Artemis exploration objectives are to further develop knowledge of the geological controls on mineralisation and improve confidence in the resource at Carlow Castle. Further plans are to convert the Inferred Mineral Resources to Indicated, and the complete initial mine optimisation evaluation and financial modelling.
A program of approximately 5,000m of drilling is planned, to drill three critical sections at Carlow East and Carlow West
The majority of Carlow Castle activity will be resource drilling and definition, however the recently completed aircore drilling shows continuation of mineralization to the west. Testing of this area will require a new heritage survey and POW approvals.
Whilst clearly structurally controlled the system at Carlow is yet to be defined, with currently two styles being considered.
- A continuation west south west within the broad geological sequence as a dominantly shear system, or,
- Arcing to the south around the Andover Complex intrusion as a ring and radial fracture system.
Both systems will require more detailed soil sampling on 100m x 100 m spacing to identify the broad location of mineralization in conjunction with geophysics, preferably HeliSAM to develop close definition of the structural setting to better define the broad location of mineralisation.
Any high priority targets identified by the geochemical and geophysical surveys are planned to be tested by aircore drilling in 2020.