Lake Johnston is a near-term production project with excellent advanced exploration targets from the Maggie Hays mine. The Project has a modern 1.5Mtpa treatment plant and large ground position, with numerous life extension exploration targets identified requiring follow up by Poseidon.
The majority of historical nickel exploration has focused on the western margin of the greenstone belt around and along strike from the Maggie Hays and Emily Ann nickel sulphide deposits. The geology consists of a west-facing succession of mafic and felsic volcanics, some sediment horizons, including BIF, and two, potentially three, ultramafic units.
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 (mining at Emily Ann ceased in March 2007), 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 project tenure comprises 10 exploration licences, 2 general purpose licences, 4 miscellaneous licences, 11 mining leases and 1 prospecting licence and the underlying tenure is vacant crown land. The total resource inventory for Lake Johnston was estimated by the previous owner at 3.8Mt grading 1.49% Ni (Maggie Hays) and 334kt grading 4.18% Ni (Emily Ann) for approximately 70.500t of contained nickel.
Exploration potential exists in a number of areas such as Johnny Turk, Taylor Rock and Mt Glasse.
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