Lake Johnston is a near-term production project. The project tenure comprises 2 exploration licences, 2 general purpose licences, 4 miscellaneous licences and 10 mining leases with the underlying tenure being vacant crown land. Ore can be processed through the 1.5Mtpa Emily Ann processing facility, a conventional nickel sulphide flotation plant. The flotation circuit has historically produced a smeltable quality nickel concentrate with a grade of approximately 13.5% Ni with low arsenic levels. The plant underwent a $7 million refurbishment in 2011. In addition to the Maggie Hays and Emily Ann underground mines (closed in 2012 and 2007 respectively), facilities at Lake Johnston include tailings storage facilities covering approximately 42ha, the Windy Hill accommodation village (140 person capacity), offices, workshops and associated support facilities and an airstrip.
The Maggie Hays Nickel Mine is a sub-level caving operation that was closed in 2012 during a period of depressed nickel prices. Since acquisition in 2014, the Maggie Hays resource was remodelled by Poseidon and the mine design and schedule altered to maximise nickel production from the highest grade sections of the orebody which would otherwise have been sterilised under the old mine plan. A total resource of 52,000 tonnes of nickel metal remains at Maggie Hays at a grade of 1.5% Ni.
The Emily Ann orebody was mined out by Lion Ore in 2007. Poseidon’s geological team spent time re-evaluating and carefully remodelling the geological data in and around the deposit and realised that previous explorers had not fully realised or tested the exploration potential. It was Poseidon’s view that the incorrect geological model had been applied to the deposit and in 2015 after a short drill campaign, Poseidon demonstrated this through the Abi Rose Discovery. To date, six out of six diamond holes have intersected massive nickel sulphides just 300m north of the historical workings.
The majority of historical nickel exploration has focused on the two styles of mineralisation interpreted by previous operators of the tenements based upon the known and mined nickel mineralisation. Poseidon has demonstrated through the Abi Rose Discovery that one of the exploration models was incorrect and that re-evaluation of historical exploration in the light of an updated, “intrusive-style” model can lead to immediate success in an environment where it was thought no further potential existed. Many of Western Australia’s latest nickel discoveries have come from recognition that intrusive-style nickel mineralisation appears to be a lot more common than previously believed by the industry.
Further to this a third style of nickel mineralisation has been identified by Poseidon’s geological team that has not been fully tested. Historical drilling that has intersected this third, conceptual “target zone” in the past has in fact encountered nickel sulphide mineralisation, however the results were not recognised for what they were and no follow-up was completed. A very large proportion of the western flank of the belt remains untested for this style of mineralisation.
Lake Johnston is located approximately 440km east of Perth and 117km west of Norseman, Western Australia. It is accessed by the Hyden – Norseman road with access to project tenements supported via dirt tracks and gridlines. Operations at Lake Johnston were historically managed on a fly-in/fly-out basis (“FIFO”). Flights to and from site were most recently operated by Maroomba Airlines out of Perth, landing at an unsealed air strip located near Lake Johnston.
Infrastructure associated with Lake Johnston comprises:
- Maggie Hays boxcut, portals and decline and Emily Ann boxcut, portals and decline (flooded);
- Haul roads and site access roads;
- Maggie Hays Run of Mine (“ROM”) pad and waste dump and Emily Ann ROM pad and waste dump;
- Crushing, screening and grinding plant;
- Concentrate production plant;
- Concentrate storage shed and weighbridge;
- Concrete production and storage infrastructure;
- Fill Plant;
- Dewatering and potable/process water bore network, including Lake Hope North discharge and settling ponds;
- Windy Hill Camp – 140 person camp (approximately seven kilometres South of the Emily Ann Mine);
- Contractor managed Five MW diesel generating power station;
- Offices, workshops and associated support facilities;
- Two paddock tailings storage facilities (TSF1 & 2);
- Three operational production bores;
- Two rising mains collecting water from underground sumps;
- Reverse osmosis plants;
- Process water ponds; and
- A package sewage treatment plant and adjoining evaporation ponds.
A highlight of the Lake Johnston concentrate is its very low As content, which provides an opportunity to create blended concentrates with low/moderate As content, below penalty thresholds from third party smelters.
The vast majority of concentrate shipments since restart have assayed less than 10ppm As. See graph below.
Lake Johnston concentrate shipment assays (post-2011 restart) showing Ni and As assays