The version of this announcement including diagrams can be viewed at www.saltlakepotash.com.au/asx-announcements/

Highlights:

– Initial Mineral Resource Estimate for the whole of Lake Way contains 73 million tonnes of SOP, including:

• Measured Resource – Lake Way Playa 6.9Mt @ 15.4kg/m³
• Measured Resource – Williamson Pit 32Kt @ 25.5kg/m³
• Indicated Resource – Paleochannel 3.7Mt @ 13.6kg/m³
• Inferred Resource – Lake Way Playa & Paleovalley Sediment 62Mt @ 15.2kg/m³

– Lake Way confirmed as very high-grade with consistent brine chemistry both laterally and at depth, with an average grade of 14.5kg of SOP per cubic metre of brine across the Lake Way tenements (Measured and Indicated)

– The Company has successfully delineated a Paleochannel in excess of 30km in length along the eastern boundary of Lake Way, which supports the ability and optionality to produce brine from two separate sources (lake playa and paleochannel)

– Test pumping of historical bores at Lake Way has provided important data that supports efficient production by pumping from the paleochannel resource

– The Mineral Resource Estimate for the ‘whole of lake’ will enable the Company to finalise technical studies for a larger production scenario with an anticipated release date towards the end of Q2 2019

Salt Lake Potash Limited (the Company or Salt Lake Potash) (ASX/AIM:SO4) is pleased to advise of a significant extension of the Mineral Resource Estimate at Lake Way following completion of an exploration program across the ‘whole of the lake’. The estimated total Mineral Resource Estimate at Lake Way has increased to 73 million tonnes (Mt) of SOP calculated using Total Porosity and 8.2Mt of SOP calculated using Drainable Porosity. Thirdly, the model is now being further refined by establishing a site evaporation trial, where a scaled down version of an evaporation pond system is established on site and brine is evaporated under actual field conditions. Both brine chemistry and salt production are closely monitored.

Table 1: Resource Table

1.     An average Drainable Porosity ranging from 3-15% has been applied

Salt Lake Potash’s Chief Executive Officer, Mr Tony Swiericzuk said:

“It is extremely pleasing to present the Lake Way Mineral Resource Estimate for the ‘whole of lake” that confirms the significant size and very high-grade resource at Lake Way.

It reinforces our current review process to consider a larger scale scenario at Lake Way and we anticipate releasing the technical results of the larger scale scenario towards  the end of Q2 2019.”

Lake Way Project

Salt Lake Potash is focussed on the rapid development of the Lake Way Project, being a high grade salt-lake brine Sulphate of Potash (SOP) operation. Lake Way’s location and logistical advantages make it the ideal Lake for the Company’s first SOP operation.

Lake Way is located in the Northern Goldfields Region of Western Australia, less than 15km south of Wiluna. The surface area of the Lake is over 270km². The northern end of the Lake is largely covered by a number of Mining Leases, held by Blackham Resources Limited (Blackham), the owner of the Wiluna Gold Mine. The Company’s Memorandum of Understanding with Blackham (see ASX Announcement dated 12 March 2018) allows for an expedited path to development at Lake Way.

Introduction

The maiden Mineral Resource Estimate reported in July 2018 was limited to the area within the Blackham Tenement boundary. Subsequent to this, the Company has undertaken an extensive exploration program covering the remaining areas of Lake Way including the delineation of the Paleochannel which runs along the eastern boundary of the Lake Way Project. 

Salt Lake Potash has now finalised the exploration program that has supported a ‘whole of lake’ Mineral Resource Estimate, covering the playa surface and the Paleochannel aquifers of Lake Way.

The Mineral Resource Estimate for the ‘whole of lake’ will enable Salt Lake Potash to finalise technical studies for a larger production scenario with an anticipated release date towards the end of Q2 2019. 

Mineral Resource Estimate

The Company engaged an independent hydrogeological consultant with substantial salt lake brine expertise, Groundwater Science Pty Ltd, to complete the Mineral Resource Estimate for the Lake Way Project. 

The Lake Way Mineral Resource Estimate describes a brine hosted resource.  The minerals are dissolved in brine, and the brine is contained within pore spaces of the host sediment.  A small portion of the resource is contained in the Williamson  Pit Lake.

The Mineral Resource Estimate of 73Mt is hosted within approximately 15 billion cubic metres of sediment ranging in thickness from a few metres to over 100m, beneath 189km² of Playa Lake surface including the paleochannel basal sand unit of 20m thickness and 30km length.

The Mineral Resource Estimate for Lake Way is divided into resource classifications that are controlled by the host geological units:

• Lake Bed Sediment
• Paleovalley Sediment
• Paleochannel Basal Sands

The mineral resource estimate is summarised in the Tables below.  An overview of each resource classification is provided in the subsequent paragraphs.  Details of the estimation methodology are provided in the body of this report.

The estimated SOP tonnage represents the SOP within the in-situ contained brine with no recovery factor applied. The amount of contained brine which can be extracted depends on many factors including the permeability of the sediments, the drainable porosity, and the recharge dynamics of the aquifers.

Table 2: Measured Resource

Table 3: Indicated Resource

Table 4: Inferred Resource

1.      The Drainable Porosity does not include the significant resource potentially available through the recharge cycle. Refer Appendix 1.

The northern section of Mineral Resource Estimate (including the Blackham tenements) has been classified into a Measured category for the upper 8m of lakebed sediments. The resources contained within the lakebed sediments below 8m, and the southern section of the lake at all depths, are all classified in the Inferred category. The Paleochannel running along the eastern boundary of the lake has been classified in the Indicated category.

The Company will continue the exploration program as it looks to increase the resource definition in the southern section of the lake and ultimately convert the Mineral Resource Estimate into Ore Reserves following further technical studies.

2018 Resource Estimate for Lake Way

In July 2018, the Company completed a scoping study for a 50,000tpa demonstration plant supported by an indicated resource for the 55.4km² area of the Blackham tenements on Lake Way totaling 1.9Mt of SOP with an excellent brine chemistry of 15.49Kg/m³ K₂SO₄ and a measured resource from the Williamson pit of 32kt with a highly concentrated chemistry of 25.5Kg/m³ K₂SO_4.

The Resource was calculated on the shallow (6m average depth) Playa Lake Sediment only. This resource has now been extended to 8m depth and to include 87km² of Salt Lake Potash’s tenement covering the open playa area of Lake Way and upgraded to measured.  The Williamson Pit resource remains unchanged.

Williamson Pit – Measured Resource Estimate

The Measured Resource dissolved in the Williamson Pit Lake Comprises 32Kt SOP dissolved in 1.26Mm³ brine at an average grade of 24.4kg/m³ SOP.

Lakebed Sediment (North) – Measured Resource Estimate

The Measured Resource is hosted in the Lake Bed Sediments in the northern part of the lake where data density is sufficient to support the Measured Resource classification.

The resource comprises 6.9Mt SOP hosted in the total porosity of the sediment which includes 1.8Mt SOP within the drainable porosity of the sediment. 

The resource is contained within the top 8m of sediment, which can reasonably be drained by pumping from trenches and occupies an area of 139.5km² of the Lake Way playa surface.  Islands and a zone of dewatered sediment have been removed from the area used to calculate the resource.

Brine chemistry was defined by assay of brine samples taken from 9 hand dug pits, 13 Auger drillholes, and 49 excavated test pits.  The average brine grade is 15.2kg/m³ SOP.

Total Porosity was defined by laboratory determination of 16 intact samples obtained by hollow core auger drilling and 24 Shelby Tubes advanced during excavation of test pits. Total porosity averages 42%.

Drainable porosity was defined by laboratory determination of 24 intact samples obtained by hollow core auger drilling and Shelby Tubes advanced during excavation of test pits.  Extended duration pumping trials were undertaken to provide field estimates of drainable porosity to validate the laboratory determination.  Drainable porosity by all methods averaged 11%.

Lakebed Sediment (South) – Inferred Resource Estimate

The Inferred Resource is hosted in the Lake Bed Sediments in the southern part of the lake where data density is insufficient to support a higher classification.  In this area continuity of brine grade and sediment porosity is assumed which constrains the resource classification to Inferred. 

The resource comprises 2.1Mt SOP hosted in the total porosity of the sediment which includes 0.5Mt SOP within the drainable porosity of the sediment. 

The resource is contained within the top 8m of sediment, which can reasonably be drained by pumping from trenches and occupies the 41.6km² area of the Lake Way playa surface.  Islands on the Playa surface have been removed from the area used to calculate the resource.

Brine chemistry and sediment porosity was assumed to be equivalent to the average of the northern part of the lake.

Paleochannel Basal Sand – Indicated Resource Estimate

The Indicated Resource is hosted in the Basal Sands that infill the deepest 20m of the paleochannel. 

The resource comprises 3.7Mt SOP hosted in the total porosity of the sediment which includes 1.4Mt SOP hosted in the drainable porosity of the sediment. 

The geometry and volume of the basal sand was defined by detailed gravity and passive seismic geophysical survey, validated against the extensive historical drilling data set. The total sediment volume is 686 million cubic meters.

Total porosity and drainable porosity were benchmarked against comparable paleochannel sands and a value of 40% total porosity and 15% drainable porosity was applied. 

Brine chemistry was defined by assay of multiple brine samples taken from two historic test bores that were pumped for 24 hours. The average brine grade is 13.6kg/m³ SOP.

Paleovalley Sediment – Inferred Resource Estimate

The Inferred Resource is hosted in the predominately silt and clay sediments that infill the paleovalley from the base of the Lake Bed Sediments to basement or the Basal Sands. 

The resource comprises 60Mt SOP hosted in the total porosity of the sediment which includes 4.5Mt SOP within the drainable porosity of the sediment.  The proportion of the brine held in drainable porosity is much lower in this unit due to the fine-grained lithology.

The geometry and volume of the Paleovalley Sediment was defined by detailed gravity and passive seismic geophysical survey, validated against the extensive historical drilling data set. The total sediment volume is 9,900 million cubic meters.

Brine chemistry is assumed to be continuous from the surface of the playa to the base of the Paleovalley Sediment based on comparable assay results from the lake bed sediments and the paleochannel sands.

Porosity was estimated against comparable sediments, and 40% total porosity and 3% drainable porosity has been applied in the resource estimation.

Future Work

The Mineral Resource Estimate for the ‘whole of lake’ will enable Salt Lake Potash to finalise technical studies for a larger production scenario with an anticipated release date towards the end of Q2 2019.

The Company will continue the exploration program at Lake Way as it looks to increase the resource definition in the southern section of the lake and ultimately convert the Mineral Resource Estimate into Ore Reserves following further technical studies.

Construction of the first phase of the Lake Way Evaporation Ponds is progressing well. The first phase will enable de-watering of the Williamson Pit. The utilisation of the Williamson Pit brine will accelerate Salt Lake Potash’s pathway to first production of SOP at Lake Way.

For further information please visit www.saltlakepotash.com.au or contact:

Summary of Resource Estimate and Reporting Criteria

This ASX Announcement has been prepared in compliance with JORC Code 2012 Edition and the ASX Listing Rules.  The following is a summary of the pertinent information used in the Mineral Resource Estimate with full details provided in the JORC Code Table 1 included as Appendix 4.

Geology and Geological Interpretation

The investigation area is in the Northern Goldfields Province on the Archaean Yilgarn Craton.

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 palaeodrainages 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 palaeochannel clay and basal sands in the deepest portion.

The Sediments infilling the paleochannel are described below:

Lake Bed Sediment

Recent (Cainozoic), unconsolidated silt, sand and clay sediment containing variable abundance of evaporite minerals, particularly gypsum. The unit is ubiquitous across the salt lake surface. The thickness of the unit ranges from approximately 3 to 20m. This unit hosts the Measured and Inferred Resource.

The upper part of the unit comprises unconsolidated, gypsiferous sand and silt from surface to around 1.5m depth. The unit is widespread, homogeneous and continuous with the thickest parts in the centre and southern portion of the lake. This is underlain by well sorted, lacustrine silt and clay.

Palaeovalley Sediment

The Paleovalley sediment consists of Tertiary clay and silt that overlies basement or the Basal Sand.

Paleochannel Basal Sand

Tertiary, unconsolidated fine, medium to coarse grained sand interbedded with silt, clay and some lignite horizons. 

Hydrological Setting

Surface Water

Lake Way receives episodic surface water inflow from West and East Creeks which lie to the north of the playa and other smaller creek lines to the west. The Playa is a terminal feature in the surface water system, i.e. there are no drainage lines that exit the playa.

Surface water recharge is a significant part of the water balance for salt-lake playa brine potash operations as described in Turk’s (1972) description of the Bonneville Salt Flats (now Wendover Potash Mine) and EPM’s (2013) proposed potash operation at Sevier Lake.

The morphology of the playa shape and surface is consistent with the classification system described by Bowler (1986).  The northern part of the Playa exhibits morphology typical of significant surface water influence and periodic inundation (smooth playa edges, one island). The southern part of the playa exhibits morphology consistent with a groundwater dominated playa with rare inundation (irregular shoreline, numerous islands). The frequency of inundation across the lake may be influenced by prevailing south-easterly winds driving water to the north eastern end of the Lake.

The Lake Way catchment area is 3,767km². The catchment was defined using Geoscience Australia’s 1 second DEM and MapInfo Discover Hydrology Package.

A runoff model was developed for the Lake Way Catchment using the WaterCress software package (Groundwater Science 2018b). The model was constructed and calibrated to the adjacent and analogous Gascoyne River catchment, and then run using the catchment area defined for Lake Way and historic rainfall data from the Wiluna BOM station from 1907 to 2017.

The average annual rainfall for the Lake Way Catchment is 260mm/year.  The run-off model estimates that on average 3.9% of rainfall runs off to the Lake. Most of the heavy rainfall occurs in December to March and as such 71% of significant runoff events (runoff depth >5mm) occur during this period. The average annual modelled run-off to the Playa is 38GL/year but this is highly variable and ranges from zero in years 1910 and 1936, up to a maximum of 314GL in 1936 and more recently 283GL in 1995.

Groundwater

The Lake is inferred to be a terminal groundwater sink on the basis of the large area of the lake and the shallow water table observed at all sites beneath the lake which will facilitate evaporative loss. Groundwater beneath the lake is hypersaline and comprises the brine potash resource.

The drilling undertaken at Lake Way has identified 2 aquifer units:

·      Cainozoic Playa Lake Sediments exhibit variable lithology comprising sand, silt and clay. Permeability is higher in the surface gypsiferous sands from which brine flows freely.  The lake sediments beneath the surface sands are higher in clay content and rely on flow from macro and micro remnant structures.

·      Tertiary Palaeochannel basal sands comprising fine to coarse grained, well sorted sand. The extent of the paleochannel has been defined through the passive seismic geophysical survey and can be seen to be several hundred metres wide throughout. 

Geological Interpretation

The geological model of the deposit was developed in Leapfrog by Zephyr Professional Ltd.

The basement topography model is based on interpretation of the passive seismic survey data tied to the historic drilling data set. The Basal Sand is then modelled to infill the channel to a depth of 20m above the channel thalweg.

The geological model provides the volumes that were then used to estimate dissolved mineral tonnage contained in the pore space of the host rock.

Drilling and Sampling Techniques

Auger Drilling

Thirteen auger holes were drilled to a maximum depth of 7m.  The hollow stem auger method was applied, this enables a continuous core to be captured.

Drilling the top 1.5m was achieved with little difficulty however, as the hole got deeper the denser, stiffer clays made progress difficult leading to refusal at around 5m for most holes.

Once the holes were drilled the bores were completed with slotted PVC to just below the water table, gravel packed to 0.5mbgl and a bentonite seal to the surface.  Before the installation of the Bentonite seal each piezometer was developed using a hand held Wattera development system. 

Excavator Test Pits

Test pits were dug using an amphibious digger to a depth of approximately 4m or refusal.

Excavator Test Trenches

Test trenches were dug using an amphibious digger to a depth of approximately 4m or refusal.  The trenches were nominally 100m long and the slopes were battered for stability.

Historic Production Bores

Two historic investigation bores were used to obtain brine samples and test the hydraulic parameters of the aquifer. These bores were installed by AGC Woodward Clyde in 1992 on behalf of WMC Engineering to identify a mine water supply.

Prior to testing, the integrity of the bores was checked by downhole camera survey of the bore holes.

Historic Drilling

An extensive historic drillhole dataset was obtained from WAMEX.  Drill logs were re-interpreted to provide stratigraphic intersections to inform the geological model and provide control to the geophysical model described below.

Geophysics

A Horizontal to Vertical Spectral Ratio (HVSR) passive seismic survey was completed over 20 survey transects on the Salt Lake Potash tenements. The aim of the survey was to determine depth to bedrock, identify paleochannels and estimate their volumes.

The final HVSR passive seismic data has been processed and velocity analysis completed with amplitude-depth cross-sections generated for each survey transect. The data highlighted an interpreted fresh bedrock interface below Lake Way as an acoustic impedance contrast layer, as well as highlighting shallower layering within the unconsolidated sedimentary cover deposits (paleochannel sands). This is interpreted as the upper and lower extents of the paleochannel sands.

Brine samples

Brine samples were obtained from all test pits, test trenches, water bores and auger holes completed as piezometers.  In all instances the brine sample represents a bulk average sample of the open interval of each drillhole and excavation.

Geological Samples

Geological samples were taken from each drilling and excavation method and geologically logged.

Porosity Samples

Porosity samples were obtained from test pit excavation by pushing Shelby Tubes into the sediment and nominally 1m depth intervals.  These samples were sealed to prevent moisture loss and submitted to the laboratory for total and drainable porosity determination.

Hollow core auger samples were taken at nominally 1m depth intervals.  These samples were sealed to prevent moisture loss and submitted to the laboratory for total and drainable porosity determination.

Hydraulic Testing

Trench Pumping Trials

Test Trenches were pumped for between 5 and 90 days. The brine drawdown around the trench was measured using piezometer areas extending 100m from the trench.  This data was used to determine drainable porosity and aquifer hydraulic conductivity.

Brine samples were taken at regular intervals during pumping to assess the stability of brine composition over time.

Test Pit Recharge tests

The aquifer hydraulic conductivity at each test pit was tested by pumping brine out of the pits and then measuring the rate of water level recovery with a pressure transducer as the pits were refilled by brine inflow from the surrounding aquifer. 

Auger Piezometer Slug Tests

Auger drillholes completed as piezometers were hydraulically tested by slug tests that comprise instantaneously introducing, then removing a slug (cylinder) of know volume from the piezometer.  The rate of water level recovery following slug insertion and withdrawal is measured with a pressure transducer and the rate of recovery is analysed to determine hydraulic conductivity.

Historic Production Bores

Two historic investigation bores were test pumped to determine aquifer parameters.  The bores were pumped by Global Groundwater Pty Ltd at a constant rate for 24 hours.  Water level drawdown in the pumped bore, and in nearby observation bores was monitored manually and by data logger.  The data was analysed to determine aquifer properties of transmissivity (Product of bulk average hydraulic conductivity and aquifer thickness), Storage coefficient and boundary conditions.

Sample Analysis Method

Brine Chemistry Determination

The Primary Laboratory was Bureau Veritas Minerals Laboratory in Perth. Duplicate samples were sent to the secondary laboratory; Intertek, Perth.

Porosity

Porosity determination was undertaken by Core Laboratories Australia Pty Ltd, Perth.

Total Porosity was determined gravimetrically by weighing before and after drying at 60 degrees to stable final weight.

Drainable Porosity was determined gravimetrically by re-saturating samples with formation brine and spinning in a centrifuge at 3,700 rpm until brine production stopped. The samples were weighed before and after re-saturation and centrifuge.

Verification and QA/QC

QA/QC of brine chemistry determination comprised

·      Duplicate samples send to a secondary laboratory

·      Ionic ratio checks to identify outliers

·      Charge Balance Check

Resource Estimation Methodology

The resource is calculated as the tonnage of minerals dissolved in the liquid brine contained in pores within the hostrock. Tonnages are calculated as dissolved minerals in brine on a dry weight by volume basis e.g. kilograms potassium per cubic meter of brine. The potassium tonnage of the resource is then calculated as:

Rock volume x volumetric porosity = brine volume

Brine volume x concentration = tonnage.

Williamson Pit

The mineralisation contained within the Williamson Pit was previously reported in the Company’s ASX Announcement dated 31 July 2018.  That estimate remains unchanged and comprises 0.032Mt SOP dissolved in 1.26Mm³ brine at an average grade of 24.4kg/m³ SOP.

Lake Bed Sediment

Area

The lateral extent of the resource is defined by the tenement boundaries and the playa boundary as defined in Geoscience Australia’s 1:250K topographic dataset.

The islands in the north and south of the playa have been removed from the resource.

The Williamson pit has resulted in a zone of dewatered material extending out some 500m from the mine pit.  This area has been removed from the resource estimate.

The lake was then split into 2 areas, the north portion where almost all test work has been completed, and the south portion where little test work has been completed due to accessibility and the only very recent granting of the final Exploration lease on the lake. The North end of the lake is being reported here as a measured resource and the south as an inferred resource.

The total area of the North and South of the lake are 139.5 and 41.6km² respectively.

Thickness

The thickness of the resource estimate has been constrained to 8 m below ground surface on the basis that production trenches are unlikely to exceed that depth.

Porosity

Drainable porosity determined from field pumping trials averages 11% by volume.  Drainable porosity determined from laboratory analysis of intact samples averages 10% by volume.

Total porosity determined from laboratory analysis of intact samples averages 42% by volume.

Table 5: Total Porosity and Drainable Porosity

Solute Concentration

Brine chemistry has been interpolated using Ordinary Kriging with a grid size of 100m x 100m, a search distance of 6,000m and 2 search passes. Average concentrations have been calculated from the grid for the Measured Resource (North portion of the lake), this average has been used to calculate the Resource for the southern, inferred resource.

Treatment of Islands

The islands have been removed from the Lake Bed Sediment Resource.  Experience at other lakes has consistently shown that shallow brine beneath islands is diluted, likely by infiltrating rainfall.  Furthermore, brine harvesting by trenches is unlikely to be practical through the sand dunes and elevated topography of the islands.

Paleovalley Sediment

Area

The lateral extent of the resource is defined by the tenement boundaries and the playa edge. The total area is 181.1km².

Volume

The volume of sediment infilling the paleovalley has been exported from the geological model. The Volume is 9,900Mm³. This yields an average sediment thickness of 54m for the sediment extending from 8m depth (base of lake bed sediment) to the top of basement or Paleochannel Basal Sand.

Porosity

The Total Porosity and Drainable Porosity has been estimated from lithology and benchmarking against other studies completed in comparable geological settings. Total porosity is applied as 40%.  Drainable porosity is applied as a low value of 3% based on the fine-grained lithology of the host sediment which will retain much of the contained brine.

Solute Concentration

Solute concentration is inferred to be continuous from the Playa Surface to the base of the Paleovalley Sediment.  The average value is 15.2kg/m³ SOP.

Paleochannel Basal Sand

Area

The extent and thickness of the Paleochannel Basal Sand Resource is defined by the geological model. The total volume of the unit is estimated to be 686Mm³.

Porosity

The Total Porosity and Drainable Porosity has been estimated from lithology and benchmarking against other studies completed in comparable geological settings.  Total porosity is applied as 40%.  Drainable porosity is applied as 15%. 

Solute Concentration

Solute concentration is derived as the average value of the two pumping test bores completed in the basal sand unit, LW5-7 and LW3-4. Multiple samples were taken from each bore during the 24 hour constant rate pumping test undertaken at each bore. The average SOP concentration is 13.6kg/m³ SOP. No spatial interpolation was undertaken.

Classification Criteria

Williamson pit

The estimated resource hosted in the Williamson Pit mine lake has a very high degree of confidence, since the geometry of the mine pit was accurately surveyed and the concentration of the brine was samples at numerous locations and depths and is quite consistent. 

The resource is reported as a Measured Resource on the basis that the estimate is adequate to support a mine plan (in this case pumping infrastructure and pumping rate).

Lake Bed Sediments (North)

The estimated resource in the northern part of the lake has a high degree of confidence.

The resource estimate and associated hydrological data set are considered adequate to support a mine plan.  In this case the mine plan comprises design of a production trench network and construction of a groundwater flow simulation model to estimate and plan brine production rates. The resource is reported as a Measured Resource.

The thickness of the geological unit is well defined, being simply 8m; the assumed limit of excavation. The area is well defined by the extent of the playa surface.

Brine concentration is defined by a high density or data points and is quite consistent spatially.  There is a high degree of confidence that the brine concentration is accurately defined.

Aquifer total porosity and drainable porosity are well defined by a large number of samples at a range of depths, and drainable porosity values are validated by extended pumping field trials that comprise the drainage of very large volumes of sediment.

Aquifer properties of hydraulic conductivity are well defined by a well distributed data set of test pits and extended duration pumping trials.

The lake water balance due to rainfall and inundation is understood from a reasonably constrained catchment run-off model.

The Measured Resource estimate is based on 49 test pits, 5 trench tests and 13 auger holes. Data points are distributed on an approximate 500m by 500m grid in the northwest and on a 5km x 5km grid for the remainder of the lake.  There is irregularity due to greater density of pits around the proposed pond locations, the causeway, the Williamson Pit dewatered zone and tenure access constraints to the immediate east of the playa.

Lake Bed Sediments (South)

The estimated resource in the southern part of the lake has a low degree of confidence. 

The resource estimate is based on assumed continuity of grade and porosity and is not adequate to support a mine plan.  The resource is reported as an Inferred Resource.

The thickness of the geological unit is well defined, being simply 8m; the assumed limit of excavation.

The area is well defined by the extent of the playa surface.

Brine grade is assumed to be continuous and consistent from the north to the south of the lake.  This assumption is not yet confirmed by test work.

Total Porosity and Drainable Porosity are assumed to be continuous and consistent from the north to the south of the lake.  This assumption is based on lithology logged in historic drilling but is not yet confirmed by test work.

Hydraulic properties are assumed to are assumed to be continuous and consistent from the north to the south of the lake.  This assumption is based on lithology logged in historic drilling but is not yet confirmed by test work.

The Inferred Resource Estimate is based on a very limited number of drillholes. The geology is defined by 10 historic drillholes oriented on a transect across the southern end of the Lake, and the geophysical survey. Brine Grade is assumed to be continuous from the data in the northern part of the Lake.  

Potash Brine projects typically exhibit low spatial variability in brine grade since the brine resource is generated in-situ by evaporation of a fairly consistent groundwater source which is subject to sporadic mixing and dilution due to infiltration of rainwater, and subsequent re-concentration by evaporation. Drill spacing in the range of 2.5km  to 10km is typical (Houston et al 2011).

Paleovalley Sediment

The estimated resource in Paleovalley sediment has a low degree of confidence.  The Resource estimate is based on assumed continuity of grade and porosity and is not adequate to support a mine plan. The resource is reported as an Inferred Resource.

The volume of the geological unit is well defined by a geological model based on detailed geophysical survey validated to an extensive drilling data set.

The area is well defined by the extent of the playa surface.

Brine grade is assumed to be continuous and consistent from the Playa surface to the base of the geological unit.  This assumption is supported by only a limited number of data points where brine chemistry at surface and at depth are available.

Total Porosity and Drainable Porosity values are based on lithology logged in historic drilling and on benchmarking of comparable projects in Tertiary paleochannels in Western Australia. The values are not yet confirmed by test work.

Hydraulic properties of the units inferred from the lithology of the unit, and the response to pumping of two test bores.

For this unit a mine plan comprises design of a production bore array to depressurise the underlying basal sand and induce downward vertical leakage from the paleovalley sediment. A groundwater flow simulation model calibrated to long term pumping trials will be needed to estimate and plan the rate at which vertical leakage of brine can be induced.

The Inferred Resource Estimate is based on a limited number of drillholes. The 49 test pits, 5 trench tests and 13 auger holes terminate above the top of the unit, and continuity of brine grade with depth is assumed based on consistent experience at other salt lake playas, and data demonstrating continuous brine grade in the underlying Basal Sand unit.  The geological model that defines the volume is based on 224 historic drillholes and the geophysical survey.

Paleochannel Basal Sand

The estimated resource in Paleochannel Basal Sand has a moderate degree of confidence. 

The data is adequate to allow confident interpretation of the geological framework which is based on a good density of drilling and geophysical data.  The continuity of brine concentration between very widely spaced samples is however assumed.   The estimate is adequate to apply modifying factors in a Feasibility Study but is not adequate to support a detailed mine plan. The resource is reported as an Indicated Resource.

Total Porosity and Drainable Porosity values are based on lithology logged in historic drilling and on benchmarking of comparable projects in Tertiary paleochannels in Western Australia. The values are not yet confirmed by test work.

Hydraulic properties of the units inferred from the lithology of the unit, and the response to pumping of two test bores.

The Indicated Resource Estimate is based on two data points that inform brine grade and hydrogeological properties.  The geological model is based on a larger number of drillholes (23 of 224 drillholes are within the paleochannel extent) and the geophysical survey.

Results

The results of the Mineral Resource Estimate are summarised in the tables below.

Table 6: Measured Resource

Table 7: Indicated Resource

Table 8: Inferred Resource

  Note:              1) Conversion factor of K to SOP (K₂SO₄ equivalent) is 2.23

                   2) Williamson Pit and Lakebed Sediment (North – Blackham tenements only) resource estimate reported previously as maiden resource 31 July 2018.

Cut-off Grades

Within the salt-lake extent no low-grade cut-off or high-grade capping has been implemented due to the consistent nature of the brine assay data. No aggregate intercepts have been calculated.

Mining and Metallurgical Methods and Parameters

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. 

Validation test work has been completed to confirm the process flowsheet to be used at the Lake Way Project to recovery SOP from the Lake Brine (refer ASX Announcement 31 October 2018).

Environmental impacts are expected to be; localized reduction in saline groundwater level, surface disturbance associated with trench, bore, and pond construction and accumulation of salt tails. The project is in a remote area and these impacts are not expected to prevent project development.

The project is located with the Goldfields Groundwater Proclamation Area. A license to take groundwater will be required under the Rights in Water and Irrigation Act 1914.  This Act is administered by the Government of Western Australia Department of Water and Environmental Regulation.

Forward Looking Statements

This announcement may include forward-looking statements. These forward-looking statements are based on Salt Lake’s expectations and beliefs concerning future events. Forward looking statements are necessarily subject to risks, uncertainties and other factors, many of which are outside the control of Salt Lake, which could cause actual results to differ materially from such statements. Salt Lake makes no undertaking to subsequently update or revise the forward-looking statements made in this announcement, to reflect the circumstances or events after the date of that announcement.

Competent Person Statement

The information in this report that relates to Mineral Resources and Exploration Results for Lake Way is based on information compiled by Mr Ben Jeuken, who is a member Australian Institute of Mining and Metallurgy and a member of the International Association of Hydrogeologists. Mr Jeuken is employed by Groundwater Science Pty Ltd, an independent consulting company. Mr Jeuken has sufficient experience, which is relevant to the style of mineralisation and type of deposit under consideration and to the activity, which he is undertaking to qualify as a Competent Person as defined in the 2012 Edition of the ‘Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves’. Mr Jeuken consents to the inclusion in the report of the matters based on his information in the form and context in which it appears.

Production Target

The Lake Way Demonstration Plant Production Target stated in this report is based on the Company’s Scoping Study as released to the ASX on 31 July 2018. The information in relation to the Production Target that the Company is required to include in a public report in accordance with ASX Listing Rule 5.16 and 5.17 was included in the Company’s ASX Announcement released on 31 July 2018. The Company confirms that the material assumptions underpinning the Production Target referenced in the 31 July 2018 release continue to apply and have not materially changed.

The information contained within this announcement is deemed to constitute inside information as stipulated under the Market Abuse Regulations (EU) No. 596/2014. Upon the publication of this announcement, this inside information is now considered to be in the public domain

Appendix 1: Extraction Method and Implication for Resource Estimate

Overview

Mining methods employed for brines is different to those required for mining solid minerals. The typical mining method for brines is to pump the brine resource from trenches or bores that are installed in the geological unit that hosts the brine.  The rate that the brine can be pumped is controlled by the hydraulic conductivity (permeability) of the host rock.  For the Lake Way Project, the mining methods for each host geological unit are summarised in the table below.

Table 9: Mining Method

Williamson Pit Lake

Brine from the Williamson Pit Lake will be pumped directly from the pit into the evaporation pond for processing.  The mining rate is controlled only by the capacity of the pumping infrastructure.

Lake Bed Sediment

The shallow Lake Bed Sediments aquifer will be mined by pumping brine from a network of trenches excavated into the playa surface to a depth of nominally 6m, though trenches may be deepened over time.

The production of brine is cyclic as described below.

Stage 1 – Initial Resource

The initial brine resource comprises:

·      Brine dissolved in water held in Drainable Porosity, (5% of the total aquifer volume).

·      Brine dissolved in water held in Retained Porosity, (35% of total aquifer volume).

The remaining volume is occupied by solid material (sand, silt and clay grains comprising 60% of the aquifer volume).

The combined porosity (Total Porosity) then comprises the total SOP brine resource held in the Lake Bed Sediments aquifer.

Stage 2 – Production Cycle

During production the brine drains under gravity toward the trench and is subsequently removed by pumping.  This creates a hydraulic gradient toward the trench and brine is drawn some distance through the aquifer toward the trench (typically hundreds of meters depending on aquifer permeability).

Over time the aquifer immediately surrounding the trench is partially dewatered.  This means that the drainable brine has been removed from the sediment, but the retained brine is still held in place by surface tension.

Stage 3 – Recharge Cycle

Western Australian Salt Lake playas receive some water input from rainfall and run-off annually.  Direct rainfall lands on the playa each year, and most years, heavy, cyclonic rain events cause run-off from the surrounding catchment onto the Playa.  This water infiltrates the playa surface and re-fills the drainable pores in the aquifer.  The larger rainfall events usually occur from January through to March.

Stage 4 – Mixing Cycle

The water that has infiltrated and refilled the drainable porosity then mixes (by physical diffusion) with the brine held in retained porosity.

Through repeated production cycles the total brine resource is mined.  The concentration of brine pumped from the production trenches will decline over time as the total resource is depleted over repeated production cycles.

The pumping rate is controlled by the hydraulic conductivity of the host sediment.  The concentration of produced brine will change over time and will be controlled by the tonnage contained in total porosity and the mechanism of mixing between repeated production cycles.

Paleovalley Sediment

The paleovalley sediment is predominately fine grain and exhibits low permeability.  The brine held in these sediments cannot be drained directly to bores because the permeability is too low to allow useful bore yields.

A proportion of the brine held in these sediments can be removed by underdrainage to the underlying Basal Sand unit.

Brine is removed from the Basal Sand unit by pumping from bores.  This depressurises the Basal Sand unit and induces downward brine leakage from the overlying sediment.  The rate of leakage will be very low; however, the areal extent is very large and significant volumes can be abstracted in this way.

Only a relatively small fraction of the total porosity can be removed from a fine-grained unit by this method.

Paleochannel Basal Sand

The brine will be produced by pumping from bores constructed into the Paleochannel Basal Sand. Pumping from a deep, confined aquifer results in reduced pressure in the aquifer and this induces brine flow toward the bores.  Brine flow is sourced via downward vertical leakage from the overlying fine-grained silts and clays, and by lateral flow from the adjacent basement aquifer that surrounds the channel.

It is important to understand that the aquifer is not dewatered.  This means that the pore spaces are not drained under gravity to be filled with air. The aquifer is only depressurised, and this results in flow through fully saturated pores toward the pumped bore.

Appendix 2: Location Details for Drill Holes / Test Pits

Note: All holes are vertical, with an RL of approximately 492m

Appendix 3: Brine Assay Results

Lake Bed Sediment

Paleochannel Basal Sand

Appendix 4: JORC Code, 2012 Edition – Table 1

Section 1 Sampling Techniques and Data

Section 2 Reporting of Exploration Results

Section 3 Estimation and Reporting of Mineral Resources

(Criteria listed in section 1, and where relevant in section 2, also apply to this section.)