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 Resources.
Heron also holds a portfolio of advanced stage exploration tenements adjacent to and contiguous with the Woodlawn site covering the prospective felsic volcanic units that host the Volcanogenic Massive Sulphide (VMS) deposit at Woodlawn.
The last five years have seen Heron develop the Woodlawn Zinc-Copper Project from planning through to construction, commissioning and ramping up to commercial production. Construction activities commenced in September 2017 and were completed in the June 2019 quarter. Commissioning activities are completed and ramp-up proceeding with the first lead and zinc concentrate produced, transported to and shipped from Port Botany and Port Kembla in September and October. The first revenue from sales of concentrate was received in October 2019.
Woodlawn Project - Development Progress March 2020
- Safety: 4 LTI’s were recorded at Woodlawn during the six months to 31 December 2019, there was improvement in January & February 2020 with no further LTI’s. The Company remains committed to achieving zero harm and further initiatives are underway by Heron and its contractors on improving safety management systems and procedures.
- Construction: Construction activities are complete and the 12 month defects liability period is now current for all work portions. Ramp up is progressing with Crusher and Ball Mill having run at design “name-plate” throughputs of 175tph and 125tph respectively. Isa Mill and flotation circuits have also run at design “name-plate” throughputs of 190tph.
- Tailings Reclaim Processing: Hydraulic mining operation ramped up and running to design capacities. The reclaim circuit has demonstrated operating capability at design throughput capacity of 190tph. Various issues with the flotation pumping circuit have been encountered, however considerable progress is now being made with pump, sump and pipe modifications having been implemented in the flotation plant.
- Underground Ore Processing: A total of 65,000 tonnes of underground ore was processed from commissioning in August through to the end of December 2019, with a further 30,000 tonnes of underground ore processed in February. This enabled the completion of commissioning in the crusher and ball mill circuit. This circuit continues to be ramped up with lower grade development ore, mining of the first Kate Lens ore will occur in March with processing scheduled for April 2020.
- Concentrate Production/Sales: Planned shipments of lead totalling 2,350 dry metric tonnes and zinc of 4,390 dry metric tonnes were delivered during the December quarter. The first copper product (commissioning ore and tailings) was shipped in February 2020, and the second shipment of zinc shipment was also despatched in February 2020. Concentrate production is progressing with grade and recoveries improving, particularly zinc. Copper and lead selectivity has been sub optimal, particularly whilst processing tailings and low grade commissioning ore, however is expected to improve as the circuit continues to be optimised. With the improved consistency in production more regular shipments of all products will be scheduled.
- Underground Mine: The underground mine operation has continued to make progress with a total of 4.2km of development completed by the end of 31 December 2019, and a further 680M achieved in January and February 2020. Some extraordinary causes of delay included regional bushfire smoke leading to mine air quality issues, and some critical equipment failures with the mining contractor. Despite these delays, development ore from Kate lens is scheduled for late March and stope ore in April 2020. The south decline is now approximately 290M below surface and has reached the first level of the Kate orebody. Paste filling commenced with the paste plant successfully commissioned and three stopes filled. The Company initiated discussions with its mining contractor, Pybar, with the objective of delivering an improvement in mine productivity, and the first signs of this improvement were evident in February 2020.
- Hydraulic Mining: Hydraulic mining has continued in the main production area of Tailings Dam South (TDS). Efficient hydraulic mining practices have now been established and work has progressed on improving the reliability of monitoring and pumping infrastructure.
- Community: Heron have continued to develop strong links in the community involving regular meetings with local government and emergency services leaders, and meetings with local representatives to provide updates on project progress. Air quality monitoring in particular was challenged due to the significant levels of smoke in the atmosphere from regional bushfires. A number of Heron employees were impacted by these regional fires with some absences from work either through personal fire impacts or being involved with volunteer agencies.
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An attractive Feasibility Study was completed in mid-2016. The Feasibility Study for the “Starter Case” of the Woodlawn Project envisages an initial 9.3 year Reserves-based mine life with significant exploration upside in the underground mineralised system and regional prospects, and contemplates campaign treatment processing of 1.0-1.5Mtpa from two separate production sources – underground and tailings. The Project has an annual steady state production target of approximately 40kt (88Mlbs) zinc in concentrate, 10kt (20Mlbs) copper in concentrate and 12kt (25Mlbs) lead in concentrate, along with associated gold and silver.
A $240M funding package was subsequently approved by shareholders in August 2017 to fully fund the construction of the project and comprises debt, equity and a silver stream. Construction and development work commenced on site in September 2017, led by Engineering, Procurement and Construction (EPC) contractor Sedgman under a Guaranteed-Maximum-Price (GMP) style contract.
Exploration within the project area is active and continuing, targeting additions to the mine’s resource base. A large number of available targets provides for both extensions to known massive sulphide positions and potential discovery of new lenses.
Heron Resources 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.
The Woodlawn deposit was discovered in 1969 and operated from 1978 to 1998 under various owners.
It was mined as both an open pit and underground operation and ran a tailings retreatment operation for a number of years. The mine was closed in March 1998 due to prevailing low metal prices and external corporate issues with the then-owner, Denehurst Limited.
During the operations the mine processed:
- 8.0Mt @ 8.3% Zn, 1.6% Cu, 3.1% Pb and 62g/t silver (Ag) from the Woodlawn open pit between 1978-1987;
- 530,000t @ 13.0% Zn, 1.6% Cu 2.2% Pb and 33g/t Ag from the satellite Currawang mine between 1991-1995, and
- 5.8Mt @ 10.1% Zn, 1.6% Cu, 4.1% Pb, 0.5g/t gold (Au) and 90 g/t Ag from the Woodlawn Underground between 1987-1998.
Post mine closure, the mineral rights contained within the Woodlawn Mining Licence (SML20) were purchased by an entity, which became TriAusMin Ltd. Since that time, work focused on evaluating the potential to re-process the medium grade tailings from previous mining operations and to re-develop the underground mine.