Some Fundamentals Of Potash Geology As A Guide To Exploration Available to Purchase

Practically all potash discoveries to date, with the exception of the European deposits, have been fortuitous finds brought about by oil well wildcatting. Many untouched and untested saline basins remain to be explored for potash. A knowledge of the geochemistry of the potash salts, coupled with an understanding of structural relationships, is essential to success in effectively exploring new areas for potash. All the continents of the world contain soluble sedimentary evaporite deposits which range in age from Cambrian to Pliocene. A review of existing conditions in the Mediterranean provides an illustration of the magnitude of evaporation processes. Deposition of the evaporites takes place in restricted ocean basins, and if uninterrupted and subjected to ideal conditions, follows a regular order of chemical separation. Primary deposition within the basin consists of limestone and dolomite, which are followed by gypsum. This in turn is followed by halite, which has the greatest range of deposition of the numerous chloride and sulfate salts and which is present until complete evaporation has occurred. The most readily soluble salts and last to precipitate are the potassium and magnesium salts, chiefly as carnallite and minor amounts of sylvite. An uninterrupted cycle of evaporation never takes place. Repetitions and disturbances of the sedimentary evaporite cycle caused in influx of fresh and sea water and the occasional loss of concentrated brines occur frequently. Subsequent to burial of the evaporites, metasomatic changes occur within the salts of primary deposition. Deep burial results in the alteration of gypsum to anhydrite through the loss of water, which produces a decrease in volume of the bed. This change triggers tectonic changes within incompetent salt beds, giving rise to structural features within the salts. The released water moves upward through the halite until it encounters the carnallite-sylvite beds which are readily soluble. Saturation and heat frequently produce beds of various potash minerals. The solution movement and reprecipitation of the dissolved salts is primarily controlled by structure. This combination of structure and saturated solutions may form widespread deposits of relatively pure potash minerals. In exploration of potash, the bromine content of the salts furnishes information regarding the stage of evaporation attained at the time of deposition of any particular salt horizon. An encounter with secondary evaporite minerals within the potash suite reveals conditions existing at the time off reprecipitation and furnishes positive clues as to the possible presence and direction of movement of economically valuable potash salts in those areas where the structure is also known.