GEOLOGY AND POTASH RESERVES OF THE UPPER DEVONIAN PRIPYAT BASIN, BELARUS

The Pripyat Basin, which produces about 16 percent of the world’s potash, was a focus area of a global assessment of potash resources. The Pripyat Basin developed during formation of the northwest-trending Donbass-Pripyat Rift. Rifting began prior to the Middle Frasnian (369 Ma) and extended through the Famennian (367 to 364 Ma). Repeated influx of marine waters during the Frasnian led to deposition of ~500 m of halite, carbonate rocks, clays, and anhydrite of the Liven sequence, which is divided into 7 evaporite cycles containing 4 potash horizons. Repeated influx of marine waters during the Famennian led to deposition approximately 1,500 m of halite, carbonate rocks, clays, anhydrite, and volcanic rocks of the Lebedyan sequence. The 600 m-thick lower salt sub-formation consists mainly of halite. The 980 m-thick upper salt sub-formation is contains at least 60 potash-bearing salt horizons. Horizon II, the best documented horizon, ranges from 2 to 2.9 m thick, and contains 51 alternating halite and sylvinite-halite layers 0.5 to 8 cm thick. Clay laminae and 8 clay layers increase in frequency higher in this horizon. The alternating mineral layering is attributed to salinity fluctuations related to alternating influxes of higher salinity brines and fresher water in a shallow brine pool on the order of decimeters to a meter in depth. The dominance of halides over sulfates indicates marine waters were of the chloride-rich, sulfate-poor type. Initial precipitation was of carnallite was followed by alteration of the carnallite to sylvite as subsurface, secondary brines moved through the basin.

Globally, the Pripyat Basin is the third largest source of potash after the Elk Point Basin in Canada and the Solikamsk Basin in Russia. In 2012, Belaruskali Corp. exported 6.4 Mt of KCl mainly to China and India. Present production is from 6 mines that access 4 potash horizons in the vicinity of Starobin, Belarus. Reported potash ranges from 14 Bt in reserves in the Starobin area to 42 Bt in resources for the basin. The area of the basin underlain by potash-bearing Famennian salt is 15,160 km² and most of that is above a depth of 3 km, a depth feasible for mining. Potash grades generally range from 10 to 18% K₂O.