Woodlawn In-Mine Exploration
A review was undertaken of near-mine exploration opportunities, compiling and ranking the highest priority targets which have potential to add to the mine’s resource base. These targets provide for both extensions to known massive sulphide positions and discovery of new lens. The targets include:
A program of in-fill reserve definition drilling has been designed for the G2 Lens where 2016 drilling confirmed significant high-grade mineralisation adjacent to the proposed route of the decline. Further drilling for resource modelling was completed in August 2017, confirming G2 has two key mineralised horizons G2 Main, and G2 Hanging-wall in shallow position which will be the first area accessed in the new underground mine, and currently does not comprise any of the production make-up in currently publlished reserves. Mineral Resources update is underway.
The significant intercepts specific to the G2 Main zone are:
- 14.0m at 12.4% ZnEq from 146.0 (7.5% Zn, 1.0% Cu, 1.7% Pb, 0.1g/t Au, 9g/t Ag) WNDD0114
Including: 6.9m at 21.6% ZnEq from 150.6m (13.0% Zn, 1.9% Cu, 2.8% Pb, 0.1g/t Au, 22g/t Ag)
- 6.8m @ 7.9% ZnEq from 113.8m (5.3% Zn, 0.3% Cu, 1.6% Pb, 0.1g/t Au, 8g/t Ag) WNDD0118
- 10.7m @ 5.3% ZnEq from 124.5m (3.7% Zn, 0.5% Cu, 0.2% Pb, 0.1g/t Au, 2g/t Ag) WNDD0118
- 5.6m @ 18.3% ZnEq from 90.7m (2.5% Zn, 0.1% Cu, 1.7% Pb, 1.8g/t Au, 418g/t Ag) WNDD0120
- 7.6m @ 10.0% ZnEq from 100.0m (2.4% Zn, 0.1% Cu, 1.5% Pb, 2.6g/t Au, 124g/t Ag) WNDD0121
- 5.0m @ 6.1% ZnEq from 116.0m (3.6% Zn, 0.1% Cu, 2.0% Pb, 0.1g/t Au, 9g/t Ag) WNDD0121
- 5.3m @ 6.9% ZnEq from 185.2m (1.8% Zn, 1.4% Cu, 0.4% Pb, 0.3g/t Au, 8g/t Ag) WNDD0123
- 5.8m @ 14.3% ZnEq from 209.7m (0.1% Zn, 4.4% Cu, 0.2g/t Au, 12g/t Ag) WNDD0123
- 3.7m @ 4.0% ZnEq from 214.3 (0.1% Zn, 1% Cu, 0.6g/t Au, 10g/t Ag) WNDD0129
- 7.5m @ 5.5% ZnEq from 221.0 (0.2% Zn, 1.6% Cu, 0% Pb, 0.2g/t Au, 5g/t Ag) WNDD0129
- 4.0m @ 6.0% ZnEq from 206.0 (0.2% Zn, 1.8% Cu, 0.1g/t Au, 6g/t Ag) WNDD0131
- 5.0m @ 10.5% ZnEq from 136.0 (5% Zn, 0.2% Cu, 3.7% Pb, 0.4g/t Au, 54g/t Ag) WNDD0132
- 5.0m @ 9.2% ZnEq from 141.2 (4.8% Zn, 0.5% Cu, 2.9% Pb, 0.1g/t Au, 14g/t Ag) WNDD0133
The significant intercepts from the G2 Hanging-wall zone are:
- 9.8m @ 28.0% ZnEq from 107m (8.7% Zn, 0.5% Cu, 5.2% Pb, 4.0g/t Au, 326g/t Ag) WNDD0110
Including 3.7m @ 56.0% ZnEq (18.7% Zn, 1.2% Cu, 10.0% Pb, 6.9g/t Au, 650g/t Ag)
- 4.9m @ 7.6% ZnEq from 117.6m (3.8% Zn, 0.2% Cu, 2.4% Pb, 0.4g/t Au, 28g/t Ag) WNDD0112
- 4.7m at 53.0% ZnEq from 107.2m (10.8% Zn, 0.7% Cu, 8.6% Pb, 10.4g/t Au, 802g/t Ag) WNDD0114
Including 2.7m at 87.2% ZnEq from 107.2m (18.4% Zn, 1.2% Cu, 14.4% Pb, 16.9g/t Au, 1299g/t Ag)
- 3.1m @ 15.8% ZnEq from 111.4m ( 3.4% Zn, 0.25% Cu, 1.2% Pb, 1.0g/t Au, 326g/t Ag) WNDD0115
- 2.4m 15.9% ZnEq from 108.1m (8.1% Zn, 0.41% Cu, 2.8% Pb, 0.8g/t Au, 119 g/t Ag) WNDD0116
- 1.3m @ 67.2% ZnEq from 89.3m (1.2% Zn, 0.9% Pb, 1.8g/t Au, 2118g/t Ag) WNDD0118
The G2 Hanging Wall zone is a new zone of high-grade mineralisation that has been discovered in the last year. Whilst the position is relatively small, its high grade means it will be a valuable addition to the early mine inventory. It is also thought that similar zones of high-grade mineralisation are likely to be present in the western Woodlawn lens system, but have been missed by the existing drill spacing creating an opportunity to delineate additional material.
Also of note is the newly defined copper mineralisation in the down plunge and footwall position to the G2 Main zinc stringer mineralisation. This copper mineralisation occurs as copper stringers in chlorite matrix plus zones of massive copper and pyrite sulphides. Relatively broad widths have been defined to date and the zone remains open down plunge.
Kate Lens - north extensions
A DHEM modelled plate from drill hole WNDD0053 has potential for an extension of the Kate Lens or a new lens positioned between Kate and D Lens. This is a relatively shallow target which could provide readily accessible, additional early production to the mine plan.
B Lens north
Drilling completed during the 1980s intersected broad zones of alteration positioned to the north of B Lens which indicate potential for either an extension to the B Lens system, or the edge of a new lens system in this area. These earlier holes include:
- W151 (drilled 1988): intersected 25m @ 2.8% ZnEq from 646m (0.52% Zn, 0.54% Cu, 0.1% Pb, 0.04g/t Au, 17g/t Ag)
- W139 (drilled 1983): intersected 25m @ 4.1% ZnEq from 658m (0.35% Zn, 1.1% Cu, 0.01% Pb, 0.01g/t Au, 7.9g/t Ag)
Both these intercepts were characterised by stringers of copper sulphides contained within zones of intense chlorite-pyrite alteration which provides a possible vector to massive sulphide mineralisation towards the north.
B Lens North Drilling
In 2016, two drill holes, for 1,268m, were drilled to test the concept of an extension to the B Lens mineralisation to the north-west. Significant intercepts were returned from both drill holes:
- 4.5m @ 5.8% ZnEq from 538m (2.3% Zn, 0.8% Cu, 0.5% Pb, 0.2g/t Au, 13g/t Ag) WNDD0105
- 11m @ 8.4% ZnEq from 569m (3.4% Zn, 0.9% Cu, 1.5% Pb, 0.12g/t Au, 18g/t Ag) WNDD0108
- Incl 5.7m @ 14.3% ZnEq from 575m (6.1% Zn, 1.4% Cu, 3.2% Pb, 0.18g/t Au, 35g/t Ag)
- 2.5m @ 19.5% ZnEq from 552m (7.7% Zn, 1.3% Cu, 3.9% Pb, 1.8g/t Au, 100g/t Ag) WNDD0108
The drill holes were surveyed with down hole electro-magnetics (DHEM) and the modelled responses of the results (“plates”) indicate potential for a mineralised zone of dimensions 250m x 150m and extending out to the mineralisation limits as identified in hole WNDD0105. Based on these DHEM plates and the existing intercepts an Exploration Target can be defined of approximately 0.6Mt to 1.1Mt with grades of 7.0% ZnEq – 14% ZnEq.
These latest results confirm the north western extension to the B Lens system at Woodlawn with new high-grade mineralisation that has the potential to substantially add to the mining inventory. Underground access to this new zone would utilise the same development infrastructure as the main B Lens, enhancing the economics and timing of Woodlawn mining.
A large DHEM conductor structurally below, in the footwall of Kate Lens was drilled with a single hole late in the Feasibility Study drilling program which intersected minor sulphides. This hole deviated from the main DHEM target; however, the zone of strong alteration is interpreted to be related to massive sulphides nearby and remains to be tested.
The last hole of the Phase II program, WNDD0104, intersected the central part of the new Lisa Lens, returning 12m @ 20% ZnEq (12.0% Zn, 1.6% Cu, 2.0% Pb, 0.7g/t Au, 23g/t Ag), from 222m depth. Excellent potential exists to extend and further prove-up this new position in the up- and down-dip structural positions. This is a relatively shallow position that can have an early impact on mine production.
Prior to Heron acquiring the Woodlawn project in 2014, TriAusMin had drilled a limited number of high grade intercepts within the down-plunge position of I Lens, including 14.5m @ 31% ZnEq (11.7% Zn, 3.7% Cu, 3.7% Pb, 1.9g/t Au, 121g/t Ag) from 551m (WLTD011W1). Such holes make up a portion of the I Lens Mineral Resource estimate; however, the mineralisation has not been closed off down-plunge and along strike. This area provides excellent opportunities to expand the resource base and potentially discover new lens positions.
The Cowley Hills prospect is located 2.5 km north of Woodlawn and consists of a Woodlawn-style VMS deposit that was partially mined from underground in 1990 (approximately 35,000t extracted). A single historical hole drilled in 1985, W158, was surveyed as part of the current program with high powered DHEM and resulted in the modelling of a 60m x 80m sized plate located in the down-dip position of the known mineralisation. A single hole was drilled to test this lower zone of mineralisation and provide a sample for metallurgical test work. A zone of massive and semi-massive sulphides was intersected close to the plane of the DHEM plate. The assays for the intercept are:
- 5.2m @ 5.5% ZnEq from 200m (2.0% Zn, 0.5% Cu, 0.6% Pb, 0.6g/t Au, 29g/t Ag) in CHDD0001
This intercept indicates the continuation of the sulphide lens at depth, albeit at a lower grade than what was previously mined (the intercept is typical stringer mineralisation as normally seen at the contact of high grade lenses). Further drilling is warranted to better define the mineralisation, focussing on the zones both above the CHDD001 intercept where grades are expected to improve, and to the south down-plunge.
Zn equivalents (ZnEq) in this release are based on the formula: Zn (%) + 0.81 x Pb(%) + 3.12 x Cu(%) + 0.86 x Au(g/t) + 0.03 x Ag(g/t). All these metals are expected to be recoverable. Refer to the announcement of 22 April 2015 entitled “Preliminary Economic Assessment Delivers Strong Business Case for the Woodlawn Zinc-Copper Project” for further information.