Mackay sulphate of potash project is located approximately 785km from the Port of Wyndham in Western Australia. It is located near Lake Mackay, which is regarded as the biggest undeveloped SOP-bearing salt lake in the world.

Agrimin is developing the project with an estimated capital expenditure of £441m (A$545m).

The project is anticipated to produce an average of 426,000tpa of SOP over its initial 20-year mine life.

Pre-feasibility study (PFS) of the project was completed in May 2018, while the definitive feasibility study (DFS) is underway.

Construction and commissioning of the project is scheduled to be completed within 36 months following the completion of financing and off-take agreements.

Mackay Sulphate of potash project location and geology

Mackay sulphate of potash project is made up of 12 tenements extending in approximately 4,370km² across Lake Mackay.

The project lies above the Palaeoproterozoic Arunta complex and Neoproterozoic Amadeus and Ngalia basins.

The south-west of Lake Mackay comprises Proterozoic (Adelaidean) Bitter Springs Formation of the Amadeus Basin basal sequence. The sequence hosts Neoproterozoic Redcliff Pound Group, which comprises quartz arenite, chert, conglomerate, limestone, dolomite, and siltstone.

The Redcliff Pound group overlies the Mount Webb Granite, which is located above the Arunta Complex, an Archaean suite of schists.

The lake surface typically contains a thin crust of evaporite mineral deposits (mostly halite), underlain by a variable lakebed sequence.

The hypersaline brine present at Lake Mackay contains potassium and other elements, which resulted from weathering of rocks within the catchment area.

Mackay Sulphate of potash project reserves 

The indicated and inferred mineral resources of the Mackay SOP project were estimated to be 26.1Mt of SOP, as of May 2018. 

Mining and processing at Mackay Sulphate of potash project

The Mackay Sulphate of potash project will use conventional evaporation and processing methodology to process kainite, the targeted potassium-bearing salt.

Potassium-rich brine from the salt lake is planned to be extracted using the on-lake trench system. An estimated 66.3 million cubic metres (Mm³) of brine will be extracted annually over the initial mine life.

Brine will be transferred along the feed channel to the solar evaporation ponds with the assistance of two pumping stations. Kainite will be wet-harvested from the final evaporation pond and pumped to the processing plant.

The kainite salts will be crushed and fed to a flotation circuit to separate kainite from halite and other minor waste salts. The concentrated kainite will be decomposed to form schoenite.

The concentrated schoenite will pass through SOP conversion process using heated water resulting in dissolving magnesium sulphate (MgSO₄) and precipitating SOP.

The SOP produced will be dried, compacted, and sized to produce a dry granular SOP product. It will be exported through the Port of Wyndham. 

Infrastructure facilities 

Access to the project will be through a 350km new unsealed haul road from the existing RAV 10 network.

Raw water for the project will be sourced from the borefield located approximately 38km from the proposed processing plant site.

An onsite reciprocating gas-fired power plant will supply the required power for the project.

Gas supply for the project will be made through a pipeline from the Amadeus Gas Pipeline. The connecting pipeline is proposed to be constructed under a build-own-operate (BOO) contract.

Other infrastructure facilities will comprise access roads, reverse osmosis (RO) plant, a 200-room accommodation camp, and wastewater treatment facilities.

Contractors involved

Primero Group was engaged to design the engineering aspects of the processing plant of Mackay SOP project, in July 2019.

Consulting firms involved in preparing the PFS include Advisian, Hydrominex Geoscience & H&SConsultants, Knight Piesold, Global Potash Solutions, Saskatchewan Research Council, and Qube Bulk.

Environmental aspects of the PFS were undertaken by 360 Environmental & Strategen Environmental.