Pisida salt deposit, Libya

Abstract

The Pisida salt deposit, located about 165 kilometers west of Tripoli on the Mediterranean coast, covers an area of about 50 square kilometers in Libya. Thin layers of salts, less than 50 centimeters thick, are deposited on the surface as a result of the evaporation of the percolating sea water which is brought to the surface by capillary action. Halite (NaCl) and sylvite (KCl), the least soluble salts, crystallize at the surface, resulting in a relatively high content of magnesium in the residual brine. The deposits were investigated by collection and analyses of salts and brine samples from 19 test pits and two drill holes. The chemical analyses indicate that small amounts of potassium salts (Average 3.5 percent potassium) occur in the surface evaporites and the brine contains an appreciable amount of magnesium (Average 3 percent magnesium). Cores collected from the two drill holes indicate that the deposits are surficial and no salt stratum occurs at depth. Laboratory experiments indicate that fractional crystallization may be applied to recover potassium and magnesium salts from the brines at Pisida.