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Russell-St. Lazare, Harrowby |
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Manitoba, Canada |
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Potash
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The Russell-St. Lazare potash solution mine at Harrowby is located in far southwest Manitoba, ~290 km west to WNW of Winnipeg, and about 16 km west of the town of Russell (#Location: Russell processing plant - 50° 45' 19"N, 101° 27' 14"W ).
Potash was first discovered in Manitoba in an oil well drilled in 1951, leading to a potash rush and exploration programs carried out by several companies. Since then, sporadic exploration has been undertaken by a wide range of companies. Historically the deposit has been divided into the two blocks, namely the northern Russell and southern St. Lazare deposits, with separate title holders and differing approaches. Whilst both blocks have been explored extensively for potash since the 1960's, work has been most intense during periods of buoyant potash prices in the 1980s and again starting in 2005 (Nicholas, 2018).
A major investigation of the Russell block was undertaken by Canamax Resources (an Amax subsidiary), commencing in 1980, and completed in 1987. This culminated in a feasibility study for development of the deposit, and the drilling of a cored pilot hole for an underground mine shaft, with the aim of establishing a conventional room and pillar underground mine. At this stage Canamax had diluted its interest and the title to the Russell deposit had passed to Manitoba Potash Corporation (51% Canamax; 49% Manitoba Government), but the project proceeded no further. Subsequently, after Entreprise Miniére et Chimique had acquired, undertaken a project evaluation and disposed of the Canamax share of Manitoba Potash Corporation, that share was purchased by BHP in 2006. BHP conducted additional studies and produced a development plan for a similar room and pillar mine in 2009. This second development plan also did not come to fruition (Nicholas, 2018).
During the same period, the St Lazare block was held by a range of companies. Initially, between 1956 and 1966, a number of smaller title holders that were consolidated into Sylvite of Canada, who drilled 10 holes at St Lazare, but allowed their lease to lapse in 1977. Meanwhile, between 1964 and 1966, Prairie Potash drilled 15 holes to the south of the Sylvite area, and conducted feasibility studies, but also allowed their lease to lapse in 1977. In 1980, International Minerals & Chemical Corporation (Canada) Ltd. (IMC), explored the area south of the Sylvite program area, but relinquished the title in 1982. Between 2005 and 2010, Agrium held a 450 km2 potash exploration permit over section of the area, which they subsequently cancelled. Between 2007 and 2009, Western Potash Corp. held three potash exploration permits adjacent to those of Agrium and drilled 9 holes, but then withdrew in favour of their Milestone project in Saskatchewan.
In 2013, the Government of Manitoba acquired both the St Lazare permits, and the 51% of Manitoba Potash Corporation from BHP, and hired the consulting company MICON International to divest its leases and assets in a transparent public bidding process. Eventually, in 2016, the Potash Agri Development Corporation of Manitoba, PADCOM, was selected as the successful bidder (Nicholas, 2018).
In 2018 PADCOM and Beechy Potash Products partnered to develop a small selective underground potash solution project, initially at a rate of 100 000 tonnes of Muriate of Potash (MOP) per annum, concentrating on the northern, or Russell block. The pilot plant commenced operation in June 2023, and after a year of operation is being ramped up for commercial production in July 2024.
The Beechy solution mining process employed involves drilling two 18 cm diameter cased wells to a depth of ~827 m, the base of the mineralised Esterhazy Potash Member. At that depth, both wells are wedged to horizontal and drilled uncased along the lower contact of the potash bed as 1.6 km long curved wells within the plane of the potash member, until both meet, and connect to form a loop. The two holes are drilled with the same concave direction, to form a crescent shape in plan. At their widest separation the flat curved pair of wells are ~250 m apart, converging at either extremity. Hot (>85°C) un-saturated brine is pumped into the injection well, then through the first 1600 m flat curved section where the bulk of the dissolution occurs; then returns on the second curved section to the return/production well. As production proceeds, new curved wells are drilled progressively outward from the earlier curved wells. Caverns form along the curve, outward from the horizontal wells, with salt deposited inside the curves, whilst hot KCl saturated brines are brought to surface via the return/production well. NOTE: KCl solubility is temperature sensitive; NaCl is not. The flow direction can be reversed and earlier flat return curved sections utilised for injection to a newly drilled curved well. Brine pressure in the mine is less than actual formation pressure and hydro fracturing is not used in the development or operation of the mining system. Caverns develop around these horizontal wells to a height of 2 m with a halite floor and back. The KCl extraction rate is 80%.
At surface, the processing plant comprises a crystallisation circuit, a centrifuge to dewater the product and a product dyer. Hot (80°C) KCl-saturated brine from the mine is brought to the plant from the production well. The brine is cooled in the crystallisers to temperatures of between 15 and 30°C. The potash crystallises as the brine cools. The crystal slurry is pumped to the centrifuge to remove the brine, with the dewatered crystal being transferred to the dryer. The cooled brine is reheated and pumped back to the mine feed injection wells. For a 100 000 tpa of MOP, the flow to the processing plant is 2 m3 per minute at about 90°C. The mining and processing details in the paragraphs above are drawn from the PADCOM Environment Act Proposal Report, dated September (2021).
The Russell-St. Lazare deposit is hosted by the Middle Devonian Prairie Evaporite Formation, the deposits of which defines the 800 km long, WNW-ESE aligned Saskatchewan Potash Belt, the world's largest potash producing mineral province. Russell falls within a relatively narrow, up tp 35 km wide x 200 km long strip of potash and/or halite bearing facies of this formation that extends across into Manitoba, and runs parallel to the border with Saskatchewan. Of this, potash bearing facies covers an area of ~2247 km2. The Russell-St. Lazare resource itself, has a triangular shape that expands southward from zero to 25 km in width over a 65 km strike length, parallel to the border.
For detail of the setting, geology, stratigraphy, potash distribution, potash units and their characteritics, and other mines and projects within the belt, see the separate Saskatchewan Potash Belt record.
The host Prairie Evaporite Formation was deposited between 387.7 and 382.7 Ma in the Givetian, within the Saskatchewan Sub-basin of the NW-SE elongated Elk Point Basin. It is underlain by the Winnipegosis Formation, which comprises a lower, shallow-water, platformal carbonate, that extends throughout the Elk Point Basin with a fairly constant thickness of 13 m. This is overlain by an argillaceous interval separating it from a thicker bank facies. The latter are characterised by pinnacle reefs, which form localised positive basement carbonate mounds that extend upwards, from a few metres, to as much as 110 m, into the overlaying Prairie Evaporite Formation. These mounds may locally disrupt the potash beds. Intermound facies are a thin, anhydrite rich fine carbonate facies which grade upwards into the Prairie Evaporite Formation (Nicolas, 2015).
The overlying Prairie Evaporite Formation varies from a maximum of 218 m in the basin centre to zero on the basin margin, and is divided into lower and upper sections, separated by a unit composed of anhydrite and laminated dolomite, known as the Shell Lake Member. This member varies from 1 to 5 m in thickness, with thicker sections, where it may locally reach 40 m. Below the Shell Lake Member, it has been referred to as the Whitkow Member, and is composed of a Lower Anhydrite, and an Upper Salt Unit. Above the Shell Lake Member, a thickness of predominantly halite similar to the upper salt unit of the Whitkow Member is developed. This unit appears to vary from <10 to as much as 90 m (e.g., Yang, Love and Smith, 2021) in thickness. This halite unit is capped by the appearance of potash laminae and thin beds of sylvite and/or carnallite, followed by 4 main potash bearing members, the Esterhazy, White Bear, Belle Plaine and Patience Lake members, which can each be up to 7 m thick, separated from one another by halite beds. Both the potash and halite beds are cut by numerous thin conformable clay seams (Nicolas, 2015).
Only two of the four potash beds, the Esterhazy and White Bear, extend into Manitoba, and are buried at depths of 200 to 2750 m below surface. The best developed section of the Prairie Evaporite Formation reaches 133 m in thickness, rapidly thinning eastward toward the salt-dissolution edge. The salt dissolution edge runs roughly north-south, and represents the furthest eastern extent of salt and potash occurrence that has not been removed by circulating meteoric water. West of the salt edge, the top of the Prairie Evaporite Formation dips gently to the SW at depths ranging from 785 m near the community of Russell in the north, to ~2670 m near the Canada-US border in the south. The top of the formation is marked by a change from the hanging wall halite that overlies the uppermost potash member, to the Second Red Bed Member of the Dawson Bay Formation which consists of grey, brown and red shale and argillaceous mudstone. Much of the remainder of the Dawson Bay Formation is occupied by the water-bearing Burr and Neely members that form the lower beds of the regional Manitoba aquifer, and are composed of limestone and dolomite, with some local interbedded anhydrite (Nicolas, 2015).
In the area of known potash occurrence in Manitoba, the Esterhazy Member thickness averages between 5.6 m in the north and 2 m at its southernmost extremity. It is comparable in thickness and grades of sylvite, insoluble mineral and carnallite to the potash deposits at Rocanville and Esterhazy in southeastern Saskatchewan. The headframe of the Rocanville mine is <5 km west of the Saskatchewan-Manitoba border and the edge of the Russell-St. Lazare mine resource margin (Nicolas, 2015).
The Prairie Evaporite potash members in the Russell-St. Lazare area have been intersected by 41 test drill holes, 30 of which have core through the potash beds. In addition, there is a good cross-section of 2-D seismic lines and two 3-D seismic blocks. Depths to the top of the Prairie Evaporite in this area range from 785 to 1050 m. The isopachs of the formation vary from up to 139 m in thickness, but thin eastward due to the proximity to the dissolution edge. However, despite the favourable depth and grade, challenges to conventional mine development included proximity of the salt-dissolution edge and the concomitant eastward decrease of the salt-back thickness (i.e., salt between the top of the Esterhazy Member and the base of the Second Red Bed Member of the Dawson Bay Formation). A thick salt back is essential in conventional mining to provide a mechanically competent back, and water tight seal above the mine workings to prevent inflow of water from the high volume/pressure aquifers above, and consequent flooding of the operation. In proximity to the salt-dissolution edge, solution collapse and other features deleterious to the integrity of the sat-back are amplified. Mining is also complicated by the presence of petroleum reservoirs in the overlying sequence (Nicolas, 2015).
Of the 41 drill holes in the Russell-St. Lazare area, 13 are in the Russell block, all of which encountered potash in the Esterhazy Member with ore grades over mineable widths. Seismic data have identified five Winnipegosis reef complexes that affect the overlying formations, although no major salt removal, or collapse structures, were identified. The proximity of the salt-dissolution edge has resulted in a decrease in both the total formation and salt-back thickness over a 3 km distance toward the east. The seismic data also identified a large porous zone within the overlying Dawson Bay Formation (Nicolas, 2015).
The St. Lazare section of the deposit is both the eastern continuation of the Rocanville mine resource across the Saskatchewan-Manitoba border, and of the Russell block to the north. Data from a 26.6 km2 seismic survey by Agrium in 2005 reveal the Prairie Evaporite Formation in this part of the deposit varies from 74 to 139 m in thickness. It also identifies five geological anomalies that reflect the loss of the Hubbard Salt in the hanging wall of the Dawson Bay Formation, the presence of structural lows and amplitude anomalies in the Shell Lake Member, the presence of Winnipegosis mound complexes and three collapse structures, one of which is directly related to a Winnipegosis pinnacle reef. Another adjacent seismic survey by Western Potash identified several Winnipegosis reef complexes of varying sizes and shapes, as well as collapse structures and basement faults (Nicolas, 2015).
Mineral Resources
The following resource estimates have been calculated and reported:
Russell Block (ADM Consulting Ltd., unpublished report for BHP, 2009, quoted by Nicolas, 2015),
392 Mt of contained KCl @ 22.5% K2O and an average mining thickness of 2.74 m
St. Lazare Block (Bannatyne 1983, quoted by Nicolas, 2015),
650 Mt of contained KCl @ 20.9% K2O at a cut-off of 2.74 m mining thickness and 16% K2O.
The most recent source geological information used to prepare this decription was dated: 2015.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Russell Processing Plant
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Haugen, H. and Guillas, D., 2021 - Potash Solution Mining Project, Removing the Potash Only by Selective Solution Mining: in Potash and Agri Development Corporation of Manitoba (PADCOM), Environment Act Proposal (EAP) Application, 109p.
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Nicolas, M.P.B. and Yang, C., 2022 - Stratigraphy and distribution of the potash-bearing members of the Devonian Prairie Evaporite, southwestern Manitoba (parts of NTS 62F, K): in Report of Activities 2022, Manitoba Natural Resources and Northern Development, Manitoba Geological Survey, pp. 87-95.
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Nicolas, M.P.B., 2015 - Potash deposits in the Devonian Prairie Evaporite, southwestern Manitoba (parts of NTS 62F, K): in Report of Activities 2015, Manitoba Mineral Resources, Manitoba Geological Survey, pp. 97-105
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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