The Aberfoyle Project located on EL27/2004 consists of three main prospects: 1) Storey’s Creek tungsten prospect, 2) Aberfoyle-Lutwyche-Kookaburra tin and tungsten mines, and 3) the Royal George tin deposit.
Exploration Licence 27/2004 is located in northeast Tasmania (Figure 1), 57 km southeast of Launceston. Access to the northern portion of the tenement is via the sealed Storey’s Creek Road (B42) from Avoca, approximately 50 km southwest of St Marys. The Aberfoyle Project contains a number of abandoned historic mines including the Storey’s Creek, Lutwyche, Rex Hill, Royal George and Aberfoyle mines.
The local geology of EL27/2004 consists of alternating beds of Silurian sandstone, siltstone and shale which typify the Mathinna Supergroup. Sandstone beds are fine to medium grained, massive, occasionally feldspathic, locally metamorphosed to quartzite and the dominant lithology of the unit. Mudstone and siltstone beds are thin, featureless and often highly sheared.
Location, geology and historical mines - EL27/2004
The Mathinna Supergroup was deformed and metamorphosed to low grades, with bedding folded into tight recumbent folds that are overprinted with a disjunctive cleavage formed during the development of upright chevron folds. Both recumbent and chevron folds are deformed by southwest verging open folds and associated northwest striking crenulation cleavage. Regional faulting also strikes northwest and often hosts mineralisation in zones of high shearing.
The succession is intruded by the Devonian Ben Lomond Granite, which is widely accepted as the source of mineralisation, and younger dolerite dykes of Jurassic age.
Prospects within the two sections of Exploration Licence 27/2004
Aberfoyle-Lutwyche Vein Field
High-grade tin mineralisation at Aberfoyle occurs mainly as Cassiterite and Wolframite within a swarm of steeply dipping quartz veins which strike to the north. Host rocks to the mineralisation are mudstones, siltstones and sandstones of the Mathinna beds.
Historic records and recent drilling indicate the Aberfoyle mineralised vein system is up to 60m wide, 800 m in length and extends approximately 400 m in the down dip direction.
Mineralisation was discovered at Aberfoyle in 1916, with the deposit seeing underground mining activities until its closure in 1982.
Production is recorded at 2.1 million tonnes of ore at 0.91% Sn and 0.28% WO3.
Plan view of Aberfoyle-Lutwyche with surface drilling and possible open pit outlines
Cross section of Aberfoyle Mine
The nearby Lutwyche prospect is comprised of two sets of mineralised veins which can be traced along strike for approximately 750 m before being obscured by Permian sediments. Other significant zones of mineralisation in the immediate area include the Gipps Creek, Kookaburra, Brocks Show, and Rex Hill prospects. At Rex Hill mineralisation strongly zoned, becoming Sn richer with depth and is associated with both quartz veining and greisenised granite.
In 2014 Niuminco and TNT Mines commissioned an Independent Consultant to compile and review the historical reports at Aberfoyle and Lutwyche with the view to potential open pit mining of lower-grade tin & tungsten halos around the mined vein array.
Based on the geological framework and a relational database of drilling data, a 3-D resource model was developed and the following JORC Code (2012) Exploration Targets were identified. In addition, potential sources of additional process feed were identified in re-processing of tailings.
The Exploration Targets tabled below are a statement or estimate of the exploration potential of a mineral deposit in a defined geological setting where the statement or estimate, quoted as a range of tonnes and a range of grade (or quality), relates to mineralisation for which there has been insufficient exploration to estimate a Mineral Resource.
|Project Area||Exploration Target Ranges|
|Tonnes||Metal Grade CM= (Sn+WO3)|
|Aberfoyle Open Cut||5.50Mt – 7.50Mt||0.2% CM* - 0.25% CM*|
|Lutwyche UG below 6 level||1.08Mt – 1.47Mt||0.7% CM – 1.2% CM|
|Lutwyche Surface to 6 level||0.50Mt – 1.10Mt||0.7% CM – 1.2% CM|
|Kookaburra Veins||0.60Mt – 1.50Mt||0.7% CM – 1.2% CM|
|Royal George||0.60Mt -1.20Mt||0.34% Sn – 0.41% Sn|
EL27/2004 - JORC Code (2012) Exploration Targets
Historical exploration to date has identified sufficient near surface and underground tin mineralisation to warrant further investigation. It is proposed that infill drilling is conducted across the mineralised trend, aiming to provide the geological confidence to upgrade the Exploration Targets tabled above to Mineral Resources of Inferred category or better. Additional exploration is also proposed at Aberfoyle to better define the remnant mineralised “vein swarm”.
Additional vein systems nearby have limited work conducted on them. In particular the Lutwyche South East vein system, located SE of main Lutwyche system extends for 500m and is identified by strong soil chemistry and electrical geophysics. Also the 40m wide Kookaburra vein system located 200m SW of main Lutwyche vein system is related to an Aberfoyle vein known as Johnson’s Vein, and they could be the same vein. This would connect the Lutwyche and Aberfoyle systems together, adding great confidence to the potential for an unmined and under-explored vein systems at Kookaburra and Lutwyche. All these targets warrant drilling.
The Lutwyche vein system is an essentially unmined deposit (1.1Mt @ 0.45%WO3 and 0.45% Sn), similar in size to the Storeys Creek mine. It has been accessed by a cross-cut from the deepest levels of the Aberfoyle Mine, and subjected to underground drilling from that location. Little near-surface drilling has been completed.
Drill collar plan Lutwyche – Kookaburra area (current and planned drill holes in red).
Digitization of historical data here is incomplete but the general geometry of the deposit is shown below:
Lutwyche underground development and surface veining – plan view
Lutwyche surface and underground drill traces – oblique view to NW