Solar Pan processing

Exploited Quaternary potash deposits encompass both MOP and SOP mineral associations across a range of climatic and elevation settings. Interestingly, all are nonmarine brine-fed depositional hydrologies, with the exception of the now buried SOP evaporite associations of the Danakil Depression of Ethiopia.

All economic potash plants in Quaternary systems do not mine a solid product but derive their potash via cryogenesis or solar evaporation of lake brines. There are a number of potash mineral occurrences in intermontane depressions in the high Andes in what is a high altitude polar tundra setting (Koeppen ET), none of which are commercial.

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Dead Sea salt reef

Similarly, there a number of non-commercial potash (SOP) mineral and brine occurrences in various hot arid desert regions in Australia, northern Africa and the Middle East (Koeppen BWh). In the Danakhil, it is essential to distinguish between the current non-potash climate (BWh) over the Dallol saltflat in Ethiopia, with its nonmarine brine feed and the former now-buried marine fed potash (SOP)/halite evaporite system. The latter is the target of current exploration efforts in the basin, focused on sediments now buried 60-120m below the Dallol saltflat surface (Salty Matters). Nowhere in the Quaternary are such dry arid climates (BWh) associated with commercial accumulations of potash minerals.

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Quaternary potash occurrences with commercial potash plants denoted by an asterisk. A) Distribution of selected Quaternary potash occurrences on a Koeppen climate base (climate base from Kottek et al., 2006). Main Climates: A; tropical, B; arid, C; warm temperate, D; snow, E; polar. Precipitation: W; desert, S; steppe, f: fully humid, s: summer dry, w; winter dry, m; monsoonal. Temperature: h; hot arid, k; cold arid, a; hot summer, b; warm summer, c; cool summer, d; extremely continental, F: polar frost, T; polar tundra. Molleweide equal-area projection. B) Distribution of selected Quaternary potash occurrences plotted with respect to altitude, latitude and koppen climate (data for this figure extracted with permission from SaltWork GIS database version 1.8 and compiled in MapInfo®).

Climatically most commercial potash brine systems in Quaternary-age sediments are located in cooler endorheic intermontane depressions (BWk, BSk) or in the case of the Dead Sea an intermontane position in the sump of the Dead Sea, the deepest position of any continental landscape on the earth’s surface (-417 msl). The association with somewhat cooler and or less arid steppe climates implies a need for greater volumes of brine to reside in a landscape in order to facilitate the precipitation of significant volumes of potash bitterns To better understand the variety of potash in Quaternary associations we shall focus on some of the intermontane closed basin deposits that are currently commercial brine-recovery potash operations, namely: the Dead Sea (BSh, MOP); Qaidam Basin (BWk, MOP); Lop Nur (BWk, SOP); Salar de Atacama (BWk, MOP and SOP); Wendover (BSk, MOP) and the Great Salt Lake (BSk; SOP, mothballed sodium sulphate) and Moab (BSk; MOP). The Moab evaporation pans draw on brines sourced in a flooded former potash (Carboniferous salt) mine (Cane Creek) and pumped into a series of solar evaporation pans. A similar post-flood note can be made on the cryogenic MOP that is recovered each winter from solution brines pumped to the surface from the flooded Belle Plain Mine (Devonian salt).


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