Summary:
The intracratonic Elk Point Basin is a major sedimentary geological feature in western Canada and the northwest USA. It contains one of the world's largest stratabound potash resources. The nature of this type of deposition is largely continuous with predictable depths and thickness. It is estimated to host >5 billion tonnes of ore (Orris, 2014) and is mined at a number of locations, including Mosaic's Belle Plaine. Esterhazy and C'olonsay potash facilities. Saskatchewan potash represents almost 25% of the global potash production due to its relatively low-cost, bulk tonnage mining methods. (Orris. 2014).
The Prairie Evaporite hosts rich deposits of evaporite minerals including halite (NaCl), sylvite (KCl) and locally, carnallite. There arc a number of insoluble clay-rich zones that arc not recovered in the solution mining process. The potash deposit at Belle Plaine is uniform and laterally continuous. Solution mining methods can more easily accommodate any local variations in geological condition due to the non-selective concentrate mining process.
Three potash deposits of economic importance occur in Saskatchewan: the Esterhazy, Belle Plaine and Patience Lake Members. The Belle Plaine Potash Facility is a solution mine that recovers potash from each of the Estcrhazy, Belle Plaine and Patience Lake Members. The following is a summary of the key stratigraphic units for the Belle Plaine Potash Facility:
• Patience Lake Member: The uppermost member of the Prairie Evaporite Formation with potash production potential. Between the top of the Prairie Evaporite Formation and the top of the Patience Lake Member is a 0 to 45 ft. (0 to 14 tn) thick unit of halite with clay bands called the salt back. The sylvite-rich horizons within the Patience Lake Member arc mined using conventional underground mining techniques in the Saskatoon. Saskatchewan area and by solution mining techniques at Belle Plaine.
• Belle Plaine Member: The Belle Plaine Member underlies the Patience Lake Member and is separated from it by a zone of low grade sylvinitc. The Belle Plaine Member is mined using solution mining techniques at Belle Plaine.
• Esterhazy Member: The Esterhazy Member is separated from the Belle Plaine Member by the White Bear Marker Beds, a sequence of clay scams, low-grade sylvinitc, and halite. The Esterhazy Member is mined using conventional underground techniques at Mosaic's Esterhazy Potash Facility in southeastern Saskatchewan and by solution mining techniques at Belle Plaine.
The potash mined at Belle Plaine is a mixture of halite and sylvite and in some parts of the Mining Area,small amounts of carnallite. There are a number of clay-rich zones that are not recovered in the solution mining process that recovers a concentrate from a portion of the minerals rather than the entire bed.
There are distinct features that are correlated between core and geophysical logging and applied to indicate relative ore quality. The key characteristics that are interpreted using remote data include K.C1 grade, bedding identification, and carnallite presence. The potash deposit at Belle Plaine is uniform and laterally continuous. When properly calibrated, the gamma response can be converted to indicate the amount of potash in the geological unit as %KC1.The neutron-density log is used to indicate the presence of carnallite. These correlations arc possible based on understanding from examination of core.
The three mineable potash-bearing members underlying the Belle Plaine property are, in ascending stratigraphic order, the Esterhazy Member, the Belle Plaine Member and the Patience Lake Member. The White Bear Formation marker beds occur between the Belle Plaine and Esterhazy Members.
Deposit Dimensions:
Patience Lake
Average Mineable Thickness: 67.6 ft (20.6 m)
Average Grade: 28.4% KCl, 18.0% K2O
Local Naming Convention: 30 Beds
Belle Plaine
Average Mineable Thickness: 19.2 ft (5.9 m)
Average Grade: 32.8% KCl, 20.7% K2O
Local Naming Convention: 20 Beds
Esterhazy
Average Mineable Thickness: 16.7 ft (5.1 m)
Average Grade: 35.7% KCl, 22.5% K2O
Local Naming Convention: 10 Beds
Potash mineralization contains sylvinite; a mixture of the iron oxide-stained halite, sylvite and locally, carnallite. When present interstitially or as massive pods, carnallite can deteriorate rapidly or be preferentially dissolved. The color of the potash can vary from light orange to deep red rimmed crystals. The mineralization can be locally bedded or massive. The halite and sylvite crystals can range from small to more typically coarse to large. This can be attributed to the conditions during deposition as there has been no alteration.
Carnallite is considered an impurity in solution mining and can result in dilution of the potash grade. The mineralogy of carnallite results in liberation of magnesium into the brine that is not removed through processing. Because the magnesium remains in suspension, there is reduced carrying capacity for KC1.