On admission to the official list of the ASX, the company will acquire the Growth Pipeline which holds several gold assets considered Advanced Projects. In keeping with our growth strategy, near-surface open pit projects will be prioritised for their potential to be rapidly verified and progressed through to Development Status.
Advanced Projects are projects with historical drilling, operations or resources on existing Mining Leases:
• Hadleigh Castle ML
• Blackjack ML
Ashby Mining Limited does not own Maroon Gold Pty Ltd’s Blackjack Processing Facility, Blackjack ML, Far Fanning gold project and surrounding EL’s which will become assets of Ashby Mining Limited on the company’s admission to the official list of the ASX.
Ashby Mining Limited does not own Denjim Pty Ltd, which is the registered holder of the Hadleigh Castle ML and Burdekin gold projects. Ashby Mining may acquire 50% of Denjim Pty Ltd upon finalisation of the ongoing litigation proceedings being resolved to the satisfaction of Ashby Mining Limited. The Prospectus sets out in further detail the relevant conditions that must be satisfied prior to the acquisition of Denjim Pty Ltd. The Prospectus may be viewed in Australia at the following website: https://apply.automic.com.au/AshbyMining.
Hadleigh Castle ML
The Hadleigh Castle Gold Mine is located on Mining Lease 10344 and was an open pit and underground mine that operated between 1998 and 2005. The mine is located 38 km east of Charters Towers, 125 km by road from Townsville of which 107 km is bitumen covered road.
A key geological feature is the Rishton Mine Corridor Structure – a regional scale structural zone considered highly prospective for gold mineralisation. Numerous open pit targets have been prioritised and the ML also contains the Hadleigh Castle Underground project.
- Hadleigh Castle Open Pit
- Hadleigh Castle East
- Captains Open Pit
- Hadleigh Castle Underground
Initial exploration and drilling programs will focus on open pit opportunities and will be designed to provide confidence in tonnes and grade of known mineralisation within and beneath the scoping study Whittle open pit mine design. Newly identified mineralised structures amendable to surface mining will also be evaluated.
Upon completion of drilling and updated resource estimations, open pit mine designs will be completed to support feasibility studies.
1. Hadleigh Castle Open Pit
The company is currently evaluating the open pit potential at Hadleigh Castle historical mine.
The existing open pit is only 40m deep and is located on the permitted Mining Lease with historical gold production of 32koz gold from 384kt at average 2.9 g/t Au. The project last operated in 2005. Historically, the prospective area has been systematically drilled at 25m x 12.5m intervals.
An updated JORC (2012) resource in 2021 to 1.544kt at 1.75g/t for 91.7koz gold and a Scoping Study Whittle optimisation demonstrated pit expansion to 150m depth.
There is also additional potential to add further gold inventory to an Open Pit scenario from gold mineralisation in the hanging wall, footwall, strike extensions and remnant stope material, improving the strip ratio.
The next step is a resource and verification drilling program to improve the confidence in an updated Hadleigh Castle Open Pit resource estimate. This can be used to progress the project to development status.
2. Hadleigh Castle East
The Hadleigh Castle East Project, with similar geology to Hadleigh Castle, lies approximately 700 meters to the east of the Hadleigh Castle Mine within the same ML. There are numerous shallow historical workings and favourable ground magnetics.
Approximately 560 meters of RC drilling was completed between 1987 and 1990 with numerous gold intercepts. A 1994 soil sampling program (14,000 samples) showed a NE trending 50 ppb gold anomaly with a core of >1,000 ppb Au. This is a higher core value than a similar anomaly at Captain which was historically mined.
Multi-element soil sampling, with follow-up drilling will be undertaken to verify historical drilling and support open pit resource estimation within the existing mining lease.
3. Captain Open Pit
The Captain gold deposit is located approximately 700 meters south-west of the Hadleigh Castle Open Pit.
It is located at an intersection of the Rishton Mine Corridor Structure and a SW striking splay structure and shows similar characteristics to the main Hadleigh Castle structures and geology.
Soil sampling in 1994 showed a >50 ppb gold anomaly at surface. Drilling was undertaken in 1993 and a small open cut was mined for 220 ounces of gold production. The area contains numerous gold intercepts in historical drilling coincident with favourable ground magnetic geophysical anomalies.
More detailed exploration is required to assess the mineralisation potential. Targets include down dip potential and a footwall zone which appears to be an extension of Lode 1 from the Hadleigh Castle deposit.
Three shallow holes were drilled in 1987 with the most promising intersection 6m at 1.43 g/t gold at 24 meters depth. Further gold grades were returned using a blast hole rig to obtain cuttings to a 24 m depth.
Structural mapping and ground magnetics indicate this is related to the Rishton Mine Corridor Structure and Hadleigh Castle mineralisation.
The target can easily be tested with ground magnetics, IP geophysics and drilling to assess open pit resource potential.
5. Hadleigh Castle Underground
Hadleigh Castle has been mined by open cut and underground to a total depth of 425 metres over 5 phases of mining since discovery in 1884. The mine was last operated in 2005 with 250 koz gold mined over a period of several years. The current JORC (2012) inferred resource is 861kt at 5.6g/t for 155 koz gold.
The gold mineralisation consists of a series of sub parallel stacked system of quartz veins (dipping to SSW) with gold and minor sulphides plus Ag hosted by altered granites (sericitic and chloritic altered envelope up to 200m thick and over 400m in length). It is situated at the intersection of the ENE trending Rishton Mine Corridor Structure and a NW trending structure.
The last production and exploration drill programs extended 50m below the deepest production levels with grade control drilling returning 24m @ 6.6g/t gold and exploration hole HCD031 returning 7.7m @ 10.5g/t gold including: 3.4m @ 22.31g/t gold, 1.8m @ 30.4g/t Au.
Updated resource modelling illustrates width, grade and ounces per vertical metre are increasing with depth.
Hadleigh Castle Geology
The project area lies within the Palaeozoic Lolworth-Ravenswood Block, which forms an E-W trending segment within the Tasman Fold Belt system. The geology of the region is dominated by the Ravenswood Batholith which has a surface areal extent of more than 6,000km2. The Ravenswood intrusions were emplaced into basement lithologies ranging from Neoproterozoic to Cambrian age amphibolite facies meta-sedimentary and meta-igneous rocks and Cambrian to Ordovician age volcanics and sediments.
The Ravenswood intrusive complex was intruded in multiple phases beginning in the early to mid-Ordovician and with further phases in the mid-Silurian to mid-Devonian and late-Carboniferous to early Permian. Gold mineralisation in the Charters Towers Goldfield is broadly contemporaneous with mid-Silurian to mid-Devonian magmatism. Intrusions of this age are typically I-type hornblende- and biotite-bearing granodiorites and tonalites that make up 60% of the current exposure of the Ravenswood Batholith. Regionally, mineralisation is also hosted by younger Carboniferous-Permian intrusive bodies including the Mount Leyshon gold deposit, which is hosted by a Permian subvolcanic porphyry-breccia complex.
At the Hadleigh Castle Mine the mineralisation and alteration is associated with an E-W striking, south dipping, structural contact between the Crescent Granodiorite, to the north, and Rishton (Boatswain) Granodiorite to the south. The stacked Hadleigh Castle lodes are shallow dipping to the south-southwest perpendicular to this contact.
The contact represents a portion of Rishton Mine Corridor Structure. The Rishton Mine Corridor Structure is a regional scale (14 km) ENE striking structure which is significant as being the primary structural control for gold mineralisation at Hadleigh Castle. Gold mineralisation is hosted in quartz veins and shears related to the Rishton Mine Corridor Structure.
Hadleigh Castle Production History
Gold was discovered at Hadleigh Castle in 1871 at the same time as the Charters Towers lodes to the west. Recorded historical production from Hadleigh Castle consists of approximately 2.1 million tonnes of ore averaging 3.7 g/tonne Au. This includes more recent underground mining of 0.9 million tonnes averaging 4.5 g/t gold during the period from 1997-2005.
Historically, mining and exploration activity was mostly focused on the RCMS structural trend extending between the Hadleigh Castle mine and the Disraeli gold deposit, which is 8 km to the west-southwest of Hadleigh Castle. Mining along this trend includes Joe’s Delight, Robinson Crusoe and Captains. There has also been mining in the Kirk gold field at Margaret and Himalaya prospects. Recorded historical production on the tenements surrounding the Hadleigh Castle mine consists of 1.1 million tonnes averaging 1.98 g/tonne Au.
Hadleigh Castle is interpreted as an Orogenic Gold deposit considered broadly contemporaneous with mid-Silurian to mid-Devonian magmatism. Intrusions of this age make up 60% of the current exposure of the Ravenswood Batholith. The Siluro-Devonian granite intrusive event (420-400 Ma) in North Queensland gave rise to the Charters Towers Goldfield and nearby deposits which produced over 6 Moz (180 t) of gold, along with substantial silver (Ag), lead (Pb) and copper (Cu) (Kreuzer 2005; Kreuzer et al., 2007). The deposits are mostly granite hosted massive quartz veins with up to 10% sulphides.
Orogenic Gold deposits in the region have demonstrated depth continuity to 1,300 metres. Hadleigh Castle has only been tested to 450 metres and remains open at depth.
Intrusive Related Gold
Regionally, mineralisation is also hosted by younger Carboniferous-Permian intrusive bodies including the Mount Leyshon gold deposit which was hosted by a Permian subvolcanic porphyry-breccia complex. Permo-Carboniferous intrusion related deposits (345-260 Ma) are associated with felsic magmatism and there are several styles, including tin-tungsten, IRGD (Au) and copper, molybdenum and epithermal gold and silver deposits. Despite the variety of deposit styles present, recent studies show that they are broadly related to the same magmatic and tectonic events. Commodity type and mineralisation styles are thought to be more related to level of crustal emplacement, magmatic controls such as composition, reduction-oxidation state and degree of fractionation (Morrison, 2017). An endowment of +20 Moz gold is attributable to IRGD in North Queensland (Morrison, 2017).
Blackjack /John Bull
Historically, two gold reef systems have recorded production:
- Blackjack: oxide pits and underground mine.
- John Bull: deeper historical underground mine
Total recorded production from historical underground workings is 107,584 ounces at an average grade of 42 g/t Au.
Three shallow oxide pits were mined along the Blackjack underground mine trend during the 1980’s. From north to south, the pits are called the Newton Butler, Blackjack PC and Blackjack South. The pits cover a strike length of about 700 meters with an average depth of 15 meters.
Limited RC drilling has been completed below the pits to a depth of 60 meters but there is no drilling along strike. Mineralisation appears continuous both down dip and along strike.
Based on available data, there appears potential to expand the current pits along strike and down dip.
Waste Dumps and Tailings Dams
Historical waste dumps are located on the Hadleigh Castle ML and at Kirk, Robinson Crusoe, Joes Delight and Disraeli.
Preliminary studies in 2017 on Hadleigh Castle waste dump material suggest that quartz – sulphide mineralisation can be sorted using sensor-based technology to realise significant upgrade. Within the Hadleigh Castle ML10344, plus the dumps at Kirk, Robinson Crusoe, Disraeli, and Joes Delight there is an estimated 5m tonnes of waste rock containing limited gold content.
During its operational life, the mill at Rishton, adjacent to the Disraeli and Joes Delight pits, treated about 5 million tonnes of ore from the above mines as well as district mines including Blue Gold, Far Fanning, Welcome, Christian Kruk, Puzzler, and others. Recovery was approximately 90%. The tailings are stored in an above ground site adjacent to the Disraeli pit and in the Disraeli pit. Testing will be undertaken to assess if there is economic potential to retreat historical tailings.