Summary:
Potash is the common name given to a group of minerals and chemicals that contain potassium (K) which is a basic nutrient for plants and an important ingredient in fertilizer. Potash is produced as potassium chloride (KCl) in Saskatchewan from sylvinite rock that is a mixture of Sylvite (KCl) and Halite (NaCl) minerals. The KCl content is measured and refer to it in terms of potassium oxide (%K2O) equivalence. %K2O grade is equivalent to KCl content using the mineralogical conversion factor of 1.583. Jansen potash deposit is composed of combinations of halite (NaCl), sylvite (KCl) with variable mounts of disseminated insolubles and clay seams.
The Jansen potash deposit is located within the Williston Basin, a large, intracratonic, horizontally bedded sedimentary basin.
The potash beds are hosted within the Prairie Evaporite (PE) formation, in regionally extensive, horizontal layers during the repeated, cyclical evaporation of a shallow, inland sea during the Devonian period.
In Jansen, the potash is at a depth of approximately 800 metres to approximately 1,050 metres. Two Potash members are present in Jansen those being the Patience Lake and Belle Plaine members. The Patience Lake member is further subdivided into Upper Patience Lake (UPL) and Lower Patience Lake (LPL) sub-members. The LPL sub-member is the potash horizon targeted for Jansen. The LPL sub-member is composed of sylvite (KCl), halite (NaCl) with variable amounts of disseminated insolubles and clay seams. Carnallite (KCl.MgCl2.6H2O), a mineral which can impact processing and ground stability, occasionally occurs in place of sylvite within the potash layer.
The potash deposit extends from east to west in the province and, based on information available to date, shows relative uniformity, except where there are anomalies due to local dissolutions of the potash beds or clay seams. The main types of anomalies are called washout, leach and collapse anomalies.
Local Geology
During the Middle Devonian period, the Alberta Basin and the Williston Basin formed one larger unit, the Elk Point Basin, which was connected to the ocean in the northwest. Later, basin restrictions began to increase its salinity and induced the deposition of the Prairie Evaporite (PE) which hosts the potash bearing members. Middle Devonian cyclic deposition continued with Manitoba Group and Saskatchewan Group after the Elk Point Group sediments. The Jansen potash deposit is located within the Williston Basin, a large, intracratonic, structurally simple, and horizontally bedded sedimentary basin. The Williston Basin extends from southern Saskatchewan, Canada into the northern states of the United States of America.
Deposition of sediments in the basin began during the Cambrian geological time period, followed by an intense period of limestone, dolomite, evaporite, sandstone, and shale deposition during the geological time periods Ordovician, Silurian, and Devonian ending with Cretaceous sediments.
Deposition of sediments in the basin began during the Cambrian geological time period, followed by an intense period of limestone, dolomite, evaporite, sandstone, and shale deposition during the geological time periods Ordovician, Silurian, and Devonian ending with Cretaceous sediments. The potash beds are approximately 900 metres below surface, at the top of the PE Formation which conformably overlies the predominantly carbonate layers of Winnipegosis Formation. There are three main potash bearing members present in the PE Formation. Two are present in the Jansen area, those being the Patience Lake and Belle Plaine members. The Patience Lake member is further subdivided into Upper Patience Lake (UPL) and Lower Patience Lake (LPL) sub-members.
The LPL sub-member is the potash horizon targeted for Jansen. These potash members were deposited in regionally extensive (hundreds of kilometres), horizontal layers during the repeated, cyclical periods of evaporation of a shallow, inland sea during the Devonian Period. Mineralization within the potash layers consists of a layered, repetitive sequence of sylvite (KCl) with halite (NaCl) and thin layers of insoluble dolomitic clay material (clay seams). Carnallite (KCl.MgCl2.6H2O), a mineral which can impact processing and ground stability, occasionally occurs in place of sylvite within the potash layer.
The Dawson Bay formation, includes the Second Red Beds member and the Dawson Bay carbonate members on top and overlays the PE Formation.
Approximately 400 metres below the PE Formation are the Cambrian-Ordovician Winnipeg and Deadwood formations. Sediments of these formations were deposited in near shore, shallow water marine environments on top of the Precambrian rocks. The coarse to fine sands of the formations, host a vast deep saline aquifer that is used for brine disposal.
Mineral Deposit
The Jansen Lower Patient Lake (LPL) sub-member is hosted within the Prairie Evaporite (PE) Formation, and was deposited in regionally extensive, horizontal layers during the repeated, cyclical evaporation of a shallow, saltpan environment during the Devonian period. LPL potash is composed of combinations of halite (NaCl), sylvite (KCl) with variable amounts of disseminated insolubles and clay seams.
The LPL is subdivided into four mineralization cycles for detailed geological characterization of the potential mining horizon. The LPL sub-member is an approximately five metres thick potash unit interspersed with thin clay seams. The LPL top is marked by a clay seam (named the 406) that is overlain by an approximately 2.5 metres thick halite unit. The bottom of the LPL unit is marked by a clay seam (named the 401). The mineralization of the LPL is restricted to the 406 to 401 interval. The clay seams are consistent throughout the potash basin and the Jansen area and can be easily correlated between the drill holes.
Safe mining practice in the Prairie Evaporate Formation requires a competent rock immediately above the top of the LPL sub-unit. The interval clay seams, mainly consists of halite with some minor insoluble bands, traditionally known as the Shadow band (SB) and Henry Marker (HM). These are considered potential geotechnical hazards as they, in some areas, weaken the mining roof and may require extra ground support or additional cutting and increase the dilution. Their effect was taken into account in reserve calculations.