Woodlawn Zinc-Copper Project
Updated February 2017
The Woodlawn Project is based at the former Woodlawn Mine site located 30 km south of Goulburn and 220 km southwest of Sydney, and comprises two significant poly-metallic resource-based assets; the Woodlawn Underground Project (WUP) and the Woodlawn Tailings Retreatment Project (WRP).
Woodlawn is a high-grade, volcanogenic massive-sulphide (VMS) deposit situated in New South Wales, Australia, located approximately 50km northeast of Canberra, and 250km southwest of Sydney.
The Woodlawn Project benefits from a mining lease (SML 20) that has recently been renewed for a further 15 years, and major project approvals (statutory approval) that allows for mining operations at the Woodlawn site until 31 December 2034. The mineral rights and production are 100%-owned by Heron.
Heron also holds a portfolio of tenements adjacent to the Woodlawn site covering the prospective felsic volcanics that host the Woodlawn VMS deposit. The Woodlawn site (SML 20) is surrounded by a larger exploration license (EL 7257) which is held 100% by Heron. This exploration license, of 179km², includes the previous Currawang Mine located 9km to the north of Woodlawn. The Currawang Mine provided satellite feed to the previous Woodlawn operations.
Historically, the Woodlawn Mine operated from 1978 to 1998 and processed 13.8 million tonnes of ore from the Woodlawn open pit, underground and satellite deposits grading 9.1% zinc, 1.6% copper; 3.6% lead, 0.5g/t gold and 74g/t silver. The mine was closed in March 1998 due to prevailing low metal prices and external corporate issues. Post mine closure, the mineral rights contained within the Woodlawn Mining Licence SML20 were purchased by TriAusMin Ltd. Since that time, work has focused on evaluating the potential to re-process tailings from previous mining operations (termed the Woodlawn Retreatment Project – WRP), and to re-develop the underground mine (the Woodlawn Underground Project – WUP). Regional exploration has also been undertaken in the vicinity of Woodlawn with the objective of discovering new, high grade satellite deposits (Woodlawn Exploration Project – WEP).
Since the Heron-TriAusMin merger in August 2014, Heron's strategic focus has been on advancing the Woodlawn Underground Project (WUP).
Heron conducted a 2014/15 drill program at Woodlawn Zinc-Copper Project. The drillholes and assay received confirmed the high-grade tenor of the Kate Lens mineralisation. The diamond drilling at Woodlawn conducting exploration/resource drilling and tested the geotechnical conditions for the proposed box-cut, portal and access to the existing decline on the eastern side of the pit. This first drill phase achieved the objective of defining the Kate Lens mineralisation plus identified a number of new or extensional mineralised positions. Click here for a summary of the Phase one drill program.
The Preliminary Economic Assessment study on the Woodlawn Zinc-Copper Project has been completed as announced 22 April 2015 delivered a strong business case for the project. The full PEA technical report released 2 June 2015 can be viewed HERE.
The Feasibility Study commenced immediately after the completion of this highly successful PEA, and was delivered on 29/6/16. The A$11 million study supports the viability of the Starter Case to deliver quality zinc, copper and lead concentrates to market over a significant Reserves-based mine life. This study underpins the Board’s decision to advance an accelerated program to secure project finance and bring the Woodlawn Project into production in 2018. Read announcement »
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. Previously reported significant results include:
- 11m @ 11% ZnEq from 133m (6.3% Zn, 0.5% Cu, 3.3% Pb, 0.1g/t Au, 10g/t Ag), WNDD0106
- 9.8m @ 28% ZnEq from 107m (8.7% Zn, 0.5% Cu, 5.2% Pb, 4.0g/t Au, 326g/t Ag), WNDD0110
- Including 3.7m @ 56% ZnEq% (18.7% Zn, 1.2% Cu, 10.0% Pb, 6.9g/t Au, 650g/t Ag), WNDD0110
- 6.0m @ 10% ZnEq from 140m (7.9% Zn, 0.2% Cu, 0.7% Pb, 0.2g/t Au, 13g/t Ag), WNDD0110
- 2.9m @ 9% ZnEq from 160m (5.1% Zn, 0.3% Cu, 2.8% Pb, 0.5g/t Au, 11g/t Ag), WNDD0111
The proposed program will consist of approximately 26 diamond core holes for 4,300m and will include a number of geotechnical holes to assess and sterilise the proposed route of the decline. The program is expected to deliver a significant addition to the early production reserve base and will be drilled to a level where stope design and development can be readily undertaken. Encouraging recent metallurgical testwork on the G2 mineralisation and a broader “early production” composite returned higher metal recoveries than those used in the FS.
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.
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.
Phase II Drilling Program
The Phase II drilling program at Woodlawn commenced in April 2015 was completed on 14 November 2015.
Woodlawn Project Flythrough July 2016
Take a fly through the Woodlawn Zinc-Copper Project, with a look at the mineralisation block model and proposed development.