Maiden Copper-Gold Mineral Resource Estimate
Alford East ISR Project, South Australia
The directors of Thor Mining Plc (“Thor”) (AIM, ASX: THR) are pleased to announce a maiden Mineral Resource Estimate of 177,000 tonnes of contained copper and 71,500 ounces of contained gold at its Alford East copper-gold project, located on the Yorke Peninsula, South Australia .
· Maiden Mineral Resource Estimate completed on the Alford-East Project (reported in accordance with JORC Code 2012) including Netherleigh Park, Liaway and Alford East prospects
· An Inferred Mineral Resource Estimate of
o 125.6 Mt at 0.14% Cu for 177,000 tonnes of contained copper
o 71,500 ounces of contained gold
· The resource estimate includes only oxide copper-gold mineralisation considered amenable to In Situ Recovery (ISR) techniques, and identical cut-off grades being used at operating ISR Copper projects such as Excelsior’s Gunnison project in Arizona, USA
· There is clear potential for resources growth, along strike and at depth
· The Alford East Project covers the northern extension of Alford Copper Belt, where to the south-west, EnviroCopper Ltd has reported an Inferred Mineral Resource of 66.1Mt @ 0.17% Cu for three deposits; Wombat, Bruce and Larwood (THR:ASX Announcement 15 August 2019).
Mick Billing, Executive Chairman of Thor Mining, commented:
“The copper-gold Alford East Project results have exceeded our expectations for a Maiden Mineral Resource Estimate”.
“There have been more than 500 recorded drill holes into these deposits, and it is a tremendous bonus to be able to apply proven ISR technology thinking to produce this initial resource estimate.”
“Significant growth potential exists for this resource, both at depth, and along strike and, while we commence testing activities to demonstrate the potential for ISR production, we will concurrently work towards increasing this resource.”
“Our objective will be to work towards technical feasibility of ISR production, which will be designed to allow continuation of traditional farming activities, as much as possible during operations, and following the end of the project life, with the land effectively undisturbed.”
A copy of the Tenement and Prospect Location Plan may be view via the following link:
The Alford East Copper-Gold Mineral Resources are 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 (THR:ASX 23 November 2020).
The Alford East Project lies within the Alford Copper Belt, a coherent zone of copper-gold oxide mineralization, within a structurally controlled north-south corridor consisting of deeply kaolinized and oxidized troughs within metamorphic units on the edge of the Tickera Granite.
A schematic showing Alford Copper Belt cross-section the coherent zone of ISR amenable copper-gold mineralization in trough of depth weathered metasediments (Drown, C., 2017, In-Sit copper Recovery investigation Moonta-Wallaroo District. SAEMC Conference December 2017) may be view via the following link:
Mineral Resource Statement Overview
Pursuant to ASX listing rule 5.8.1, and in addition to the JORC tables (attached) the company provides the following in respect of the Alford East Mineral Resource Estimate.
Alford East Mineral Resource Estimate and Reporting Criteria
Independent geological consultant Dr Graeme McDonald has reported the Mineral Resource Estimate in accordance with the JORC Code (2012), which is summarised in Table 1 below. A summary prepared by Dr McDonald forms part of this ASX release.
Table 1: Alford East Mineral Resource Estimate by JORC (2012) classification as at 22 January 2021, reported for oxide material only, at a cut-off grade of 0.05% Copper which is consistent with the assumed In Situ Recovery technique.
§ Figures are rounded to reflect appropriate level of confidence. Apparent differences may occur due to rounding.
§ Cut-off of 0.05% Cu
§ Thor earning up to 80% interest in Alford East Copper-Gold Project
Geology and Geological Interpretation
The Alford East Project is located in the south-eastern portion of the Gawler Craton, close to the Torrens Hinge Zone, the major north-northwest-trending structural lineament that defines its eastern margin. The project covers a number of prospective magmatic centres with associated IOCG style alteration and mineralisation.
Outcrop of the Proterozoic basement rocks are limited as they are extensively masked by a veneer (<15m in depth) of transported clays and dune sands. The geology interpreted largely from geophysical data and drillholes consists of the metamorphosed Palaeoproterozoic Wallaroo Group sediments and volcanics intruded by the Tickera granitoids, which were syntectonically emplaced during the Hiltaba thermal event.
The region is extensively mineralised, with strongly developed Cu-Au mineralisation and lesser Ag, Pb, Zn, Mo, Ni, Co, U, Ni and Ce. The mineralisation occurs in breccia and shear zones, parallel to the foliation, in country rocks consisting of Palaeoproterozoic schist, quartzite and hornfels intruded by porphyry and granite.
Locally, the oxide mineralisation is hosted within variably weathered and sheared metasedimentary basement lithologies. Low grade copper mineralisation is widespread throughout the project area and is associated with the presence of chalcocite as the dominant copper bearing mineral as well as native copper and malachite. In total, eight separate zones of oxide mineralisation were defined of various size and thickness. Three zones in the north associated with the Netherleigh Park and Liaway prospects and five in the south associated with the Alford East prospect. With deeper depressions and troughs within the weathering profile generally hosting greater accumulations of oxidized copper and gold mineralisation.
An image showing the eight identified mineralised domains at Alford East may be view via the following link:
Drilling techniques and hole spacing
The Alford East drillhole database used for the MRE contains a total of 512 holes for 40,385.65m of drilling. Comprising 440 Aircore (AC), 24 Reverse Circulation (RC), 11 Mud Rotary (MR) and 37 Diamond (DD) holes. The majority of holes have been drilled at angles of between 60o – 90° and approximately perpendicular to the strike of the mineralisation.
Holes were drilled by various companies between 1982 and 2015, with the majority (94%) drilled since 2002. In the north, across the Netherleigh Park and Liaway prospects, drillholes were located approximately 40m apart along 80m spaced sections with variable orientation from E-W to NW-SE. In the south, at the Alford East prospects, drillholes were located 80 to 160m apart on approximately 200m spaced E-W sections.
Geological and assay data for all drillholes was used in the geological interpretation and Mineral Resource Estimate.
An image showing drillhole density and type at Alford East may be view via the following link:
Sampling and sub-sampling
There is very little information about sampling techniques applied to drilling prior to 2002. Since 2002, the sampling methodology has been well documented. Drilling was undertaken by reputable drilling companies.
Aircore return samples were collected into polyurethane bags from the cyclone every metre and lined up on the ground adjacent to the rig. The polyurethane bags were then sampled as 3m composites via a spear or scoop into calico bags, which were then scanned with a portable XRF analyser and re-sampled at 1m intervals if Cu was detected over 400ppm.
HQ and NQ drill core was collected directly into trays, marked up by metre marks and secured as the drilling progressed. Core was cut into half longitudinally along a consistent line where possible , ensuring no bias in the cutting plane. A half was then collected on a metre basis where possible as determined by geological and lithological contacts.
An image showing the eight identified mineralised domains at Alford East may be view via the following link:
Sample analysis method
Historic RC and DD samples associated with drilling undertaken by MIM Exploration (pre 2002) were submitted for sample preparation and analysis at Analabs in Adelaide.
All AC and DD samples collected by Sandfire, Hillgrove and Argonaut (post 2002) were submitted to ALS in Adelaide for sample preparation and analysis undertaken at ALS in Perth. All samples were sorted and dried then pulverized and split to produce a 30g charge for Au fire assay (AA21). Assays for an additional 48 elements were collected via method ME-MS61.
As part of the post 2002 drilling, standards, blanks and duplicates (inserted every 20 samples) have all been applied in the QAQC methodology and are well documented. Sufficient accuracy and precision have been established for the type of mineralisation encountered and is appropriate for QAQC in the Mineral Resource Estimation.
A cross-section showing Mineralised Domains at (6253400nN) may be view via the following link:
The current Mineral Resource Inventory for the Alford East Project has been reported at a cut-off grade of 0.05% Cu. This is based on several factors including:
§ An analysis of the distribution of mineralised Cu assays at the Alford East Project
§ The cut-off grade of 0.05% Cu used in the Mineral Resource Estimate at the adjacent Bruce, Larwood and Wombat deposits (refer Thor Mining ASX announcement dated 15th August 2019 – “Substantial Mineral Resource Estimate for Moonta Copper”)
§ Proposed application of In-Situ Recovery (ISR) at the Alford East Project by Thor and
§ Identical cut-off grades being used at operating ISR Copper projects such as Excelsior’s Gunnison project in Arizona, USA.
No top cuts were applied.
Geology and mineralisation wireframes were generated in Micromine software using drillhole data supplied by Thor. Resource data was flagged with unique geology, oxidation and mineralisation domain codes as defined by the wireframes and composited to 2m lengths.
Due to differences in drillhole spacing and the shape and dimensions of the mineralisation between the northern and southern regions, separate block models were created for each region.
The northern block model has a parent block size of 20 x 40 x 10m with sub-blocks of 5 x 10 x 2m. The southern block model has a parent block size of 40 x 80 x 10m with sub-blocks of 5 x 10 x 2m. The different block sizes used adequately represent the respective mineralised volumes, with sub blocks estimated at the parent block scale.
Grade continuity analysis was undertaken in Micromine software for copper for the mineralised domains and models were generated in all three directions. Parameters generated were used in the block model estimation.
There is no bulk density data available for the oxide material at the Alford East project. As such, a review of the nearby copper oxide deposits of Wombat, Bruce and Larwood was undertaken. Examination of the Mineral Resource Estimate (refer Thor Mining ASX announcement dated 15th August 2019 – “Substantial Mineral Resource Estimate for Moonta Copper”) revealed an average bulk density across all three deposits for the oxide mineralisation of 2.2 g/cm3.
This value was applied during the Mineral Resource Estimate at the Alford East project. The value is within the range of expected values.
The resource classification has been applied to the Mineral Resource Estimate based on the drilling data spacing, grade and geological continuity, and data integrity.
All of the Mineral Resource has been classified as Inferred Mineral Resources. This is primarily due to the low data density and lower levels of confidence in the geology, mineralisation and mineral resource estimation.
The classification reflects the view of the Competent Person.
Mining and Metallurgy
Thor are considering the In-Situ Recovery (ISR) technique as a means of extracting the copper and gold, to exploit the oxidized nature of the mineralisation, together with the depth extent, size, grade and continuity. Specialist lixiviants will also be trialled to recover both copper and gold in an environmentally sensitive manner. Preliminary hydrological studies by EnviroCopper (ECR) on similar mineralisation associated with the nearby Alford West mineral resources have been positive. Similarly, preliminary metallurgical testwork at the Alford West project has confirmed that copper is present in phases amenable to leaching.
No other mining assumptions have been made at this stage.
No metallurgical testwork has been undertaken at Alford East and as such no recoveries have been applied to the Mineral Resource Estimate.
Eventual Economic Extraction
It is the view of the Competent Person that at the time of estimation there are no known issues that could materially impact on the eventual extraction of the Mineral Resource.
Next Step – Exploration Activities
Potential to grow the Alford East copper-gold Mineral Resource Estimate remains along strike and at depth. Historic aircore and reverse circulation drilling within the project area stopped within the mineralised oxide copper-gold zones as per cross-section 6257550mN with only limited deeper diamond holes continuing through the oxide copper mineralization. A diamond drilling program will hence be designed and implemented in the next few months to follow up on the depth extent of the oxide mineralization, adjacent to these mineralised diamond holes. In addition, drill holes will be placed along strike of the eight identified mineralised zones to confirm strike extent and continuity of the mineralization.
Initial work has highlighted the deeper depressions and troughs within the weathering profile generally host greater accumulation of the oxide copper and gold mineralisation, hence geophysics (gravity and electromagnetic) data will be reviewed to assist with mapping out these areas of interest for follow up drill testing.
A cross section at 6257550mN showing oxide copper mineralization open at depth adjacent to diamond hole MPBD3, may be viewed via the following link
Further work to increase confidence in the Mineral Resource Estimate includes drilling to delineate the boundaries of the Alford Copper Belt including closing off the Alford-East mineralization to the north, south and at depth; hydrogeological studies, and mineralogy and metallurgical studies to confirm the copper is in a phase amenable to ISR recovery.
Selected Alford East historic core available at the South Australian Drill Core Reference Library, will undergo specific gravity (S.G) measurements, and be submitted for analysis using the HyloggerTM core scanner for spectroscopic logging and imaging. This will help to characterise and identify the dominant clay and copper mineral species present, and reduce the number of new drill holes required for mineralogy and metallurgical testing.
In conjunction with the technical assessment Thor will continue ongoing stakeholder and community engagement, and regulatory activities.
The information contained within this announcement is deemed to constitute inside information as stipulated under the UK Market Abuse Regulation. Upon the publication of this announcement, this inside information is now considered to be in the public domain.
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