The deposit is a salt-lake brine deposit. The lake setting is typical of a Western Australian palaeovalley environment. Ancient hydrological systems have incised palaeovalleys into Archaean basement rocks, which were then infilled by Tertiary-aged sediments typically comprising a coarse- grained fluvial basal sand overlaid by palaeovalley clay with some coarser grained interbeds. The clay is overlaid by recent Cainozoic material including lacustrine sediment, calcrete, evaporite and aeolian deposits.

The province is characterised by granite–greenstone rocks that exhibit a prominent northwest tectonic trend and low to medium-grade metamorphism. The Archaean rocks are intruded by East– West dolerite dykes of Proterozoic age, and in the eastern area there are small, flat-lying outliers of Proterozoic and Permian sedimentary rocks. The basement rocks are generally poorly exposed owing to low relief, extensive superficial cover, and widespread deep weathering. A key characteristic of the goldfields is the occurrence of paleochannel aquifers. These paleodrainages are incised into the Archean basement and in-filled with a mixed Tertiary and Quaternary sedimentary sequence.

The paleochannel sediments of Lake Way are characterised by a mixed sedimentary sequence including sand, silts and clays of lacustrine, aeolian, fluvial and colluvial depositional origins. These near-surface deposits also include chemically-derived sediments of calcrete, silcrete and ferricrete. Beneath eastern parts of the playa, there is a deep paleochannel that is infilled with Tertiary-aged paleochannel clay and basal sands in the deepest portion.

It is assumed that the Brine resource will be mined by gravity drainage to a network of trenches excavated into the Playa Surface and an array of production bores completed in the paleochannel basal sand.

Brine Evaporation
Solar evaporations ponds covering 909ha will be constructed on the lake playa. These ponds will be used to concentrate the brine extracted from the Lake Way resource and precipitate potassiumcontaining harvest salts. The location of Lake Way is ideal for a solar evaporation process. Data from the Lake Way weather station has been correlated with historical data from nearby weather stations at Wiluna Township and Wiluna Airport to provide an average water evaporation rate for the project of 3896mm per annum (10.7mm/day) and average rainfall of 260mm per annum (net evaporation of 3,636mm per annum).

The operational area of the evaporation ponds is distributed between various pond types based on mass balance modelling that supports the 245,000t per annum SOP production rate.

Salt Harvest
The primary pond network is designed to support 12 months of steady-state salt growth before harvest. To enable a continuous harvest strategy, pond constr ........