The directors of Thor Mining Plc (“Thor”) (AIM, ASX: THR, OTCQB: THORF) are pleased to provide an update on the Alford East Copper-Gold Project, SA, Australia.
Project highlights:
· Significant intercepts including:
- 21AED001 32.9m @ 0.4% Cu and 0.31g/t Au from 81.5m (AIM:THR Announcement 31.8.2021),
- 21AED002 59.9m @ 0.3% Cu from 21.9m (AIM:THR Announcement 31.8.2021),
- 21AED003 32.4m @ 0.2% Cu and NSR Au from 15m,
- 21AED004 55.9m @ 0.53% Cu from 7m, including
- 11.7m @ 1.0%Cu from 17.3m including
- 5.7m @ 1.23% and 0.16g/t Au from 17.3
- 21AED005 72.7m @ 1.0% Cu and 0.19g/t Au from 6.3m, including
18.2m @ 2.0% Cu and 0.34g/t Au from 15.8m ( AIM:THR Announcement 31.8.2021),
- A robust 3D geological model generated from recent drilling data highlights key structural and lithological controls on mineralisation and potential high-grade target zones.
- Initial hydrometallurgy trialling of an environmentally friendly glycine lixiviant shows positive gold and copper recovery.
- Phase two diamond drilling program is being designed, including continuing hydrogeology and hydrometallurgical studies.
Nicole Galloway Warland, Managing Director of Thor Mining, commented:
“The success of our first phase of drilling, with significant uplift in copper and gold grade, adjacent to the Netherleigh Fault, is very exciting and suggests the potential for extended zones of higher-grade copper and gold along strike and at depth.
Demonstrating Thor’s greater understanding of the geological and structural constraints through the new geological modelling is critical to the overall project’s development, especially as we plan our second phase of drilling and progress our hydrometallurgical studies.
These favourable initial hydrometallurgical results for the metal recovery for both copper and gold using a socially and environmentally friendly solution ‘glycine’ rather than conventional acid in-situ recovery (ISR) is significant, as Thor strives towards the in-situ assessment of the Alford East Project.”
Figure 1: Tenement & Prospect Location Plan and Mineral Resource Domains may be viewed on the following links:
http://www.thormining.com/sites/thormining/media/maps/21-001-4-ae-mre-%E2%80%93-location.jpg
https://www.thormining.com/sites/thormining/media/Maps/mre_ae_5-drilling.jpg
Alford East Project
The Alford East Copper-Gold Project is located on EL6529, where Thor is earning up to 80% interest from unlisted Australian explorer Spencer Metals Pty Ltd, covering portions of EL6255 and EL6529 (Figure 1) (ASX: THR Announcement 23 November 2020).
The Alford East Project covers the northern extension of the Alford Copper Belt, located on the Yorke Peninsula, SA. The Alford Copper Belt is a semi coherent zone of copper-gold oxide mineralisation, within a structurally controlled, north-south corridor consisting of deeply kaolinised and oxidised troughs within metamorphic units on the edge of the Tickera Granite (Figure 1), Gawler Craton, SA.
Utilising historic drill hole information, Thor completed an inferred Mineral Resource Estimate (MRE) (AIM: THR Announcement 26 January 2021):
- 125.6Mt @ 0.14% Cu containing 177,000t of contained copper
- 71,500oz of contained gold
Based on the nature on the oxide mineralisation, the deposit is considered amenable to In-Situ Recovery (ISR) techniques. For further information on ISR please refer to Thor’s website via this link for an informative video: www.youtube.com/watch?v=eG_1ZGD0WIw
Alford East Diamond Drilling Program Update
The first phase of drilling comprised nine diamond drillholes totalling 878m, with assays now received for all drillholes. This initial program for Thor focused only on the northern portion of the Alford East copper-gold deposit around the AE-5 mineralised domains (Figure 1 and 2), with drilling targeting areas open at depth and along strike.
Drillhole assay results are reported in Table B and C (Appendices).
Figure 2: Alford East Project AE-5 domain showing drillhole location plan may be viewed via the following link:
https://www.thormining.com/sites/thormining/media/Maps/ae-5-location-plan.jpg
For ISR purposes, drilling was limited to the deeply weathered lithological profile, testing the extent of the oxide zone and the depth boundary of the Top of Fresh Rock (TOFR). The copper-gold oxide mineralisation is hosted within deeply kaolinised (clay) and metasomatic altered units on the contact between the Olympic Domain Wallaroo Group metasediments and the Hiltaba Suite Tickera Granite, Gawler Craton (Figure 1). Copper oxide mineralogy is dominated by malachite and chalcocite.
Drill targeting, vectoring in on the hanging wall side of the north-south trending controlling structure, now referred to as Netherleigh Park Fault, intercepted zones of high-grade copper and gold grades resulted in significant grade uplift in comparison to the MRE.
Drillholes 21AED001, 21AED003 and 21AED005 (Section A-A’ 6,256,360mN) were drilled through the central portion of AE-5 (Figure 3), designed to validate the geological model and test areas, open at depth. The high-grade copper and gold intercepts in 21AED001 opens the mineralisation up at depth, whilst 21AED005 highlights the grade uplift along the Netherleigh Park Fault.
21AED004 (Section B-B’ 6,235,440mN) was drilled along strike to the north 21AED005, a continuation of higher copper grades along fault (Figure 2 and 4).
21AED002, 21AED006 and 21AED007 (Section C-C’ 6,235,600mN) were all drilled to the north of the AE-5 MRE domain, with assay results extending the known copper mineralisation along strike towards AE-8 (Figure 2, 3 and 6).
Multi-element analysis of the assay results highlights two distinct higher-grade zones of copper-gold mineralisation within a broader mineralised envelope. The lower of the two has a distinct IOCG geochemical signature – elevated Cu, Au, Mo, Co, Se, Bi & REE (Figure 6 log plot). This potentially reflects sulphide oxidation of primary mineralisation; whilst the upper zone has a more amorphous distribution typical of a supergene mineralised system .
Figure 3: Cross section 6,256,360mN looking NNE, showing 21AED001, 21AED003 and 21AED005 with c opper assays shown as cylinder down hole trace may be viewed via the following link:
Figure 4: Cross section 6,256,4400mN looking NNE, showing 21AED004, with copper assays shown as cylinder downhole trace may be viewed via the following link:
Figure 5: Cross section 6,256,600mN showing 21AED002 and 21AED007 , with copper assays shown as cylinder downhole trace may be viewed via the following link;
Figure 6: Multi-element log plot for 21AED001 showing two distinct higher grade copper zones with the lower gold rich zone reflecting IOGC geochemical signature may be viewed via the following link:
http://www.thormining.com/sites/thormining/media/Maps/21aed001_log-plot.jpg
New Alford East Geological Model
Based on the recent diamond drilling, a new robust 3D geological model was generated (Figure 7) using a combination of weathering, lithology, assay and structural data from logging, and regional geology, structural and geophysics (magnetics and gravity) data.
Key geological outcomes:
- The best oxide mineralisation seems to occur where a fault has facilitated a more deeply weathered profile.
- Some faults appear to have had minor vertical offset on them post-development of the weathering profile (for example, the north-east trending Netherleigh Park Fault, central to the project area).
- Mineralisation shows a preference to metasediments.
- A Sulphidic-Magnetic-Shale (SMS) stratigraphic-alteration unit, appears as a marker unit in the regional and more local magnetics images, as well as in the regional 3D magnetics and gravity inversions.
- The SMS unit was modelled using the information above, showing an overall synformal shape with AE3 sitting in the core or trough of overlying metasediments formed by the synform.
- Most supergene mineralisation appears to occur in the hanging wall of the SMS, whilst the weathered primary mineralisation (such as in the deeper sections of AE8 and AE5) appears to be associated with major faults, such as the central Netherleigh Park Fault.
Figure 7: 3D Geological Model – showing the major faults in black, cover in translucent brown, weathered rock in translucent green, fresh rock in translucent yellow, suphidic-magnetic-shale (SMS), and the resource domains in green may be viewed via the following link:
Hydrometallurgy
Thor’s objective is to identify an in-situ recovery pathway, ideally for both the copper and gold mineralisation at the Alford East Project, that is socially and environmentally friendly rather than using conventional acid in-situ recovery (ISR).
This has led to Thor engaging Mining Processing Solutions (MPS) trialling their alkaline Glycine Leaching Technology (GLT), branded as their GlyCatTM and GlyLeachTM processes, that have the capability to selectively leach base and precious metals using glycine as the principal, eco-friendly, reagent.
A preliminary ‘Discovery’ metallurgical test program has been carried out to determine the amenability of the Alford East mineralisation to metal recovery using GLT. The test work has involved two rounds of Diagnostic Leach Tests (DLTs), and one round of Bottle Roll Tests (BRTs) (Figure 8) on the two samples from 21AED001 (Table D). The two zones are highlighted in Figure 6. Ground water collected from Alford East was used in the laboratory test work to ensure water characteristic especially pH were tailored to Project conditions.
Table D: Samples Selected for testing – Fire and 4 Acid Digest assay Results (ALS Laboratories)
Figure 8: Overview of Test work may be viewed via the following link:
Initial Findings:
- Based on copper sequential analysis (identifies leachable copper mineralogy) – 15% of the copper from the upper zone and up to 50% from the lower zone should be theoretically leachable with GLT.
- Based on the gold diagnostic leach assays, extraction from the lower zone of up to 73.4% should be theoretically leachable with GLT. Upper zone had negligible gold.
- Diagnostic Leach test- designed to be initial comparison tests to ascertain the response to a range of conditions including a baseline cyanidation test.
- Bottle Roll tests (6):
- The composite sample performed very well with GLT, extracting 98.1% of the gold and over 40% of the copper.
- Lower zone using GLT extracting 78.3% of the gold and 33.5% of the copper, whilst the Lower zone using cyanide extracted 64.1% Au and 48.2% of the copper
- The alkaline Glycine Leaching Technology (GLT) has slower leaching dynamics, than cyanidation, so if given more time higher extractions would be expected
Next Step
Based on the new geological model, approximately 10 diamond drill holes have been designed to test potential high-grade zones (Figure 9):
- Along strike and up-dip of deeply weathered zones,
- Targeting controlling key structures including the Netherleigh Park Fault at depth especially where there are large gaps in existing data,
- Targeting intersection of SMS and Liaway offset Fault,
- Targeting intersection of Netherleigh Park Fault and Liaway Fault
- Targeting subordinate splays off Netherleigh Park Fault where there is evidence of a deep weathering trough.
In addition, hydrogeological water bores and pump testing is in planning to determine aquifer connectivity between holes, with initial focus in the northern area of the mineralisation.
Concurrent to drilling, hydrometallurgical work will continue to investigate and optimise both copper and gold metal extraction using environmentally friendly lixiviants.
Figure 9: Phase two proposed drillholes, targeting potential higher-grade zones open at depth and along strike may be viewed via the following link.
http://www.thormining.com/sites/thormining/media/pdf/asx-announcements/20202021/phase-2-drilling-proposal.jpg
This announcement is authorised for release to the market by the Board of Directors.
For further information, please contact:
Thor Mining PLC
Nicole Galloway Warland, Managing Director
Ray Ridge, CFO / Company Secretary
Tel: +61 (8) 7324 1935
Tel: +61 (8) 7324 1935
