An Improved Approach to Characterize Potash-Bearing Evaporite Deposits, Evidenced in North Yorkshire, United Kingdom

Abstract

Traditionally, potash mineral deposits have been characterized using downhole geophysical logging in tandem with geochemical analysis of core samples to establish the critical potassium (% K2O) content. These techniques have been employed in a recent exploration study of the Permian evaporite succession of North Yorkshire, United Kingdom, but the characterization of these complex deposits has been led by mineralogical analysis, using quantitative X-ray diffraction (QXRD). The novel QXRD approach provides data on K content with the level of confidence needed for reliable reporting of resources and also identifies and quantifies more precisely the nature of the K-bearing minerals. Errors have also been identified when employing traditional geochemical approaches for this deposit, which would have resulted in underestimated potash grades.QXRD analysis has consistently identified polyhalite (K2Ca2Mg(SO4)4⋅2(H2O) in the Fordon (Evaporite) Formation and sylvite (KCl) in the Boulby Potash and Sneaton Potash members as the principal K-bearing host minerals in North Yorkshire. However, other K hosts, including kalistrontite (K2Sr(SO4)2) a first recorded occurrence in the UK, and a range of boron-bearing minerals have also been detected.Application of the QXRD-led characterization program across the evaporitic basin has helped to produce a descriptive, empirical model for the deposits, including the polyhalite-bearing Shelf and Basin seams and two, newly discovered sylvite-bearing bittern salt horizons, the Pasture Beck and Gough seams. The characterization program has enabled a polyhalite mineral inventory in excess of 2.5 billion metric tons (Bt) to be identified, suggesting that this region possesses the world's largest known resource of polyhalite.

The influence of gas and humidity on the mineralogy of various salt compositions – implications for natural and technical caverns

“…Kieserite is present with about 1 %, whereas anhydrite is below detection limit. Due to their similar atomic structure and common chemical composition, some peaks overlap in the XRD spectrum, making their identification difficult (Kemp et al, 2016). Errors for the quoted mineral concentrations are better than ±2 % for mineral concentrations > 50 %, ±5 % for mineral concentrations between 50 % and 10 %.…”

“…The geochemical characterisation of dissolutionrecrystallization processes in complex multiphase potassium-rich mineral assemblages is challenging (Kemp et al, 2016). Generally, depending on the minerals which are in contact with solution, various saturation stages are reached one after the other, causing a selective dissolution and fragmentation of minerals from their solid state, accompanied by recrystallization and various phase transitions (Voigt et al, 2001;Röhr, 1981;Durie, 1964).…”

Innovation in Resourcing Geological Materials as Crop Nutrients

“…The geopolitical world of potash changed completely with the discovery and development of the Canadian potash deposits, which led to the start of the present global potash market, with commercial production starting in 1962, closely followed by the UKÕs Boulby potash mine in 1969 (Woods 1979). More recent developments in the UK have led to large-scale plans to mine polyhalite (K 2 SO 4 AE2CaSO 4 AEMgSO 4 AE2H 2 O) as an additional K source that also supplies Ca, Mg and S (up to 20 million tonnes per year; Kemp et al 2016;Sirius Minerals 2016).…”

Multiple isotope tracers from Permian-Triassic hydrated sulfates: Implications for fluid-mineral interaction

“…Upper Permian potash-bearing rocks, including primary formed polyhalite and carnallite KMgCl 3 6H 2 O, are found in the Delaware basin in the western Texas and south-eastern New Mexico (Lowenstein, 1988;Barker and Austin, 1993) as well as in NE England (Armstrong et al, 1951;Kemp et al, 2016) and the Zechstein basin of Germany (Kampschulte et al, 1998). The origin of polyhalite of Permian age from the Zdrada platform and Peribaltic Basin of Poland was investigated by Peryt et al (1998) and Peryt et al (2005), the authors concluding that it formed by reaction of anhydrite with marine brines.…”