- Very positive assay results returned from an extensive regional soil sampling program
- The 19 kilometres of the Mt Gilmore Trend tested to date is extensively anomalous in cobalt and copper
- The sampling program has resulted in the discovery of multiple, new high-tenor cobalt-copper-gold anomalies across the wider Mt Gilmore Project area
- New anomalies discovered are substantially larger than those corresponding to the outcropping high-grade Cobalt Ridge sulphide deposit within Mt Gilmore
- A new style of cobalt mineralisation has also been identified as separate to the numerous Cobalt Ridge-style targets defined for further testing
- Work at Mt Gilmore is continuing – final results and identification and ranking of priority targets expected in early 2019
Very positive assay results returned from extensive regional soil sampling program
Corazon recently announced highly successful assay results from its on-going regional geochemical soil-sampling program at the Mt Gilmore Cobalt-Copper-Gold Project (Project) in New South Wales (ASX Announcement 22.11.18).
Corazon’s extensive geochemical sampling program has collected a total of 3,533 soil samples and 206 rock-chip samples at Mt Gilmore since Project acquisition in 2016, with 3,335 assays now returned. The program is designed to systematically test favourable basement lithologies for cobalt, copper and gold mineralisation along strike from the drill-defined Cobalt Ridge Deposit (Cobalt Ridge), which has the been Corazon’s priority target at the Project.
The soil-sampling program has been highly successful, and has resulted in the discovery of multiple, new, high-tenor cobalt-copper-gold anomalies – with soil sampling results of up to 450 ppm cobalt and 1,060 ppm copper, supported by rock chip samples grading up to 1,795 ppm cobalt and 16.3 % copper.
The sampling program has tested approximately 19 kilometres of the Mt Gilmore Trend and has identified extensive metal-rich anomalism in soils over basement rocks (Figures 1 and 2). The metal-association and size of these anomalies is significantly encouraging and suggests that the wider Project area hosts a substantial, long-lived hydrothermal mineralising event.
The Company’s geochemical sampling program has proven highly effective in mapping alteration and mineralisation within the outcropping basement rocks at Mt Gilmore, with results correlating positively with known mineralisation and identifying multiple new target areas.
The results to date have far exceeded the Company’s expectations, already identifying several new priority prospects, and, with most of the anomalous areas yet to be explored in detail, strong potential exists to define additional new targets. The tenor of these newly discovered cobalt anomalies are on par with the outcropping Cobalt Ridge Deposit and potential exists for the discovery of additional cobalt-copper-gold sulphide deposits.
The program is ongoing and this announcement is an update of previous ASX announcements dated the 26 April and 4 July 2018.
Two Styles of Cobalt Mineralisation Defined
Exploration to date has targeted the Cobalt Ridge style of mineralisation, which has a distinctive chalcophile element signature including cobalt-copper-gold-antimony metals. Analysis of the geochemical data has now identified an additional style of mineralisation, characterised by a broader metal association including cobalt-copper-antimony-silver-molybdenum – referred to as Gordonbrook Hill style mineralisation. Both styles of mineralisation are related to sulphide mineralisation, and sulphides have been identified on surface at most of the prospects.
The tenor of the anomalism across the different areas is very similar;
- The Cobalt Ridge Deposit has been extensively drill tested over about a 300 metre strike (ASX announcement 9 November 2018) and sits within a geochemical anomaly of approximately 900 metres by 400 metres in area. Peak soil sampling results are 171 ppm cobalt and 1,060 ppm copper, with rock chips as high as 57 ppm cobalt and 709 ppm copper.
- Outside of the Cobalt Ridge Deposit area, the Mt Gilmore Trend soil sample anomalies peak at 151 ppm cobalt and 472 ppm copper, with rock chip sampling returning up to 1,795 ppm cobalt and 16.3 % copper. It should be noted that the cobalt in soils for the Lantana #2 prospect are slightly elevated (peak 450 ppm cobalt), possibly due to this prospect being proximal to outcropping cobalt-rich ultramafic rocks.
The Cobalt Ridge style prospects include the Cobalt Ridge, Kerry Glen, Hassan’s and Lantana #2 anomalies (Figures 1 and 2). These are priority targets for on-going exploration and infill (detailed) soil sampling is underway. The size of these anomalies is very similar to the Cobalt Ridge Deposit and it is interpreted there will be a strong structural control to the mineralisation.
The Gordonbrook Hill style prospects include the Gordonbrook Hill, Lantana #1, May Queen and Morgan’s anomalies (Figures 1 and 2). In general, these areas are much larger anomalies than the Cobalt Ridge style targets, with anomalism associated with disseminated sulphides (pyrite-chalcopyrite-pyrrhotite) and magnetite. It is expected that more detailed sampling will identify multiple individual targets of both styles of mineralisation, within the larger anomalous areas. Infill sampling of these areas, for the better definition of priority targets, has yet to be undertaken.
Drilling continues to expand mineralised system at Cobalt Ridge
Corazon recently announced assay results from its recently completed drilling program at Mt Gilmore , which was focused on the Main Lode at Cobalt Ridge (ASX announcement 09.11.18). The majority of assay results have been returned from the drilling program that included 21 holes, with 2,233 metres of reverse circulation (RC) and 734.65 metres of core drilling, for a total of 2,967.65 metres.
Commenting on the results, Corazon’s Managing Director Brett Smith said; “this drilling has returned exceptional results and has enabled us to gain a much higher-level geological understanding of the deposit. Our ongoing work should enable us to more accurately express the potential of the Cobalt Ridge deposit, which is our core aim, and we expect to be able to announce more about this in the coming weeks.”
Cobalt Ridge remains substantially under-drilled and there is demonstrated potential to define additional areas of mineralisation. The Cobalt Ridge Main Lode remains open in all directions and is only one of numerous parallel mineralised trends, defined by historical workings and broad-spaced drilling, that have yet to be targeted with resource definition drilling.
The results from this drilling program have provided Corazon with a very good understanding of the controls on the mineralisation – knowledge that is being used to identify additional drilling targets within Cobalt Ridge, as well as regionally with the greater Mt Gilmore Project.
Cobalt Ridge Main Lode Drilling Program Overview
The recent drilling program focused on priority targets within and around the Cobalt Ridge Main Lode, one of numerous sulphide lodes defined within Cobalt Ridge. Drilling also tested some of the shallower features generated by the Company’s recently completed 3D Induced Polarisation (IP) geophysical survey, proximal to the Main Lode.
In total, 21 holes were drilled, including 2,233 metres of RC and 734.65 metres of core drilling, for a total of 2,967.65 metres. The majority of the assay results have been returned, with significant intercepts presented in Table 1. Results from holes MGRC057, 058, 059 and 060 are pending.
The east-west trending Cobalt Ridge Main Lode (Figure 3) has been tested over approximately 300 metres along strike, with drilling focusing on depths predominantly less than 170 metres below surface. The core of the mineralisation is approximately 150 metres in length, 15 to 35 metres in true width, with extensions continuing to the west and east. The broader zone includes multiple narrow higher-grade sulphide rich lodes. Numerous +1% cobalt assays have been returned from drilling, with the best result from this recent program of 5 metres @ 2.14% cobalt (Table 1 and Figure 4).
Table 1 Notes – Cobalt intercept calculation parameters: Greater than or equal to 0.3m down hole thickness, greater than or equal to 0.05% Co, greater than or equal to 0.05% Co cut-off and less than or equal to 3m internal dilution. Assay values at “lower than” detection limits are attributed a value of 50% of that detection limit for interval calculations.
Copper equivalents: The composited value of the cobalt-copper-gold mineralisation is presented as percentage copper equivalents (CuEq%). These metals have been historically extracted from small scale mining at Mt Gilmore and it is the Company’s belief that the cobalt, copper and gold are recoverable. Metallurgical test work completed by the Company support these assumptions. CuEq% = Cu% + (Co% * 8.35) + (ppm Au * 0.63). Metal prices used are Cu US$6,319/t, Co US$52,750/t and Au US$1,233/oz.
The recent drilling program has identified dominant trends for the cobalt-copper-gold sulphides, as well as structures (faults and shears) that may control the location of the mineralisation. This data is being worked back into geological models for the Cobalt Ridge Main Lode and are also being used to identify priority target areas within parallel zones of mineralisation (Cobalt Ridge lookalike trends) to the north and south of Cobalt Ridge. As can be seen in Figure 4, the geochemical anomaly within the Cobalt Ridge area is much more substantial than just the Cobalt Ridge Main Lode.
Highly successful completion of Phase 3 Metallurgical Testwork
During the June Quarter, Corazon completed its highly successful Phase 3 metallurgical testwork at Mount Gilmore. The Phase 3 metallurgical testwork focused on defining down-stream concentrate processing options, and the results demonstrated exceptional recovery rates of cobalt, copper and gold from drill samples from the Cobalt Ridge Deposit, using conventional processing routes (ASX announcement 17 May 2018).
Conventional flotation testwork delivered a high-grade cobalt-copper-gold concentrate – of up to 7.38% Co – from high grade Cobalt Ridge samples, as well as excellent concentrate grades from lower low-grade samples (see Table 2);
Table 2: Met Sample and Concentrate Grades
The combination of high grade concentrates and very high recoveries delivered in the testwork provides Corazon with the opportunity to potentially either produce a high-value bulk concentrate for direct sale, or to develop an in-house down-stream processing plant.
The Company has produced high-grade concentrates from simple flotation processing, with solvent extraction following standard pressure oxidation (POX), to deliver separate high-quality cobalt and copper sulphates. Gold is captured separately from the POX residue.
The mineralisation at Cobalt Ridge has several beneficial characteristics. A key advantage for the processing is the sulphide mineralisation at Cobalt Ridge, which allows for a smaller sulphide/metal concentrate to be produced prior to down-stream processing. This would likely significantly reduce the capital and operating costs of a down-stream plant, compared to having to process a bulk feed.
Down-stream testwork focused on the use of POX as the method for cobalt and copper extraction. POX was identified as the preferred process route due to its potentially lower cost, processing adaptability for variable mineralisation and its capacity to deliver environmentally stable and controlled waste products.
The POX testwork achieved excellent results, with up to 98.91% cobalt and 96.70% copper extraction. The solution from the POX underwent precipitation testing in order to assess metal removal, with solvent extraction testing being completed using conventional organics.
The testwork was managed by internationally recognised metallurgical consultants, METS Engineering and independently carried out at ALS Metallurgy in Balcatta, Western Australia.