204 



UNITED STATES MINERAL RESOURCES 



years, and the recognized association of petroleum 

 and evaporites means that a high percentage of 

 basins favorable for evaporites in North America 

 have been explored by oil companies (Buzzalini and 

 others, 1969). The potash deposits in southeastern 

 New Mexico, eastern Utah, and southern Saskatche- 

 wan — mines which now supply roughly one-third of 

 all the woi'ld output of potassium compounds — ^were 

 discovered in this way. 



Many geologic guides to the locations of concealed 

 potassium salts and other evaporites are available. 

 Preliminary evaluation techniques include recon- 

 structing from geologic maps and other sources the 

 climatic, topographic, hydrologic, and geochemical 

 environments that existed at the time the sedimen- 

 tary rocks in the particular basin were deposited. 

 Arid climatic belts that favor deposition of evapo- 

 rites tend to occupy the same part of the globe, and 

 raleomagnetic and other techniques allow the geo- 

 graphic positions of depositional basins relative to 

 these belts to be reconstructed. Sedimentary rock 

 units that are most favorable for evaporites are 

 those that were deposited at latitudes favorable for 

 arid climates. Many other characteristics and con- 

 stituents of sedimentary rocks indicate the climate 

 that prevailed during sedimentation ; for instance, 

 certain organisms and chemical reactions are tem- 

 perature sensitive, and microfossils or other organic 

 materials, stable isotope percentages, and mineralo- 

 gy may therefore give data as to water temperature. 

 Still other prospecting techniques depend on inter- 

 pretational refinements of many kinds of field data. 

 Within favorable climatic belts, environments capa- 

 ble of fonning marine evaporite deposits were the 

 nearly enclosed basins and shallow shelf areas that 

 lay between the open sea and the landmasses. Sys- 

 tematic geologic mapping furnishes data essential to 

 the reconstruction of paleogeographic environment. 

 Processes involved in chemical sedimentation and di- 

 agensis are also becoming better understood. Once 

 an evaporite body has been found, numerous explora- 

 tory techniques can expedite the location of high- 

 grade potassium deposits. Evaporite mineral facies 

 have a fairly predictable pattern, and variations in 

 the quantities of certain trace elements such as 

 bromine can indicate areas and horizons of maximum 

 promise. 



At present production levels, potash reserves 

 available in crystalline deposits and brines within the 

 United States are suflSciently large to last at least 

 100 years. The very large deposits of Canada, how- 

 ever, are so close to the United States that costs of 

 transporting supplies from these deposits are not 

 excessive ; inasmuch as one-half of the world reserves 



and resources are in Canada, resources adequate for 

 thousands of years will continue to be available from 

 areas close to U.S. consumers. Potential resources of 

 the United States also are large and include submar- 

 ginal crystalline deposits, sea water, and potassium- 

 bearing silicate rocks (British Sulphur Corp., 1966) . 



World reserves and potential resources of potassi- 

 um compounds are enormous. Estimates of quanti- 

 ties in known deposits exceed 100 billion tons of 

 KoO ; this represents more than a 5,000-year world 

 supply at present consumption rates (Colorado 

 School of Mines, 1967) . Hypothetical and undiscov- 

 ered deposits increase the total probable resources to 

 a larger quantity, but as noted later, this increase 

 may not be great. 



SALT 



Among the marine evaporites, salt (the common 

 term for both the commodity and rock composed en- 

 tirely of halite, NaCl) is by far the most valuable 

 mineral resource, ranking with coal, limestone, iron, 

 and sulfur, as a basic industrial raw material. It is 

 used as a source of sodium, chlorine, soda ash, hydro- 

 chloric acid, caustic soda, and other compounds in- 

 dispensable in the manufacture of many other prod- 

 ucts and chemical reagents. Salt itself is important 

 in the production and preservation of foodstuffs as 

 well as for animal feed, water softening, snow and 

 ice removal, and roadbed stabilization (Hibpshman, 

 1971). Underground cavities created artificially in 

 rock salt deposits are used to store petroleum prod- 

 ucts and to dispose of industrial wastes ; the resource 

 value of some salt deposits may be determined more 

 by the possible storage capacity than by the need 

 for the salt that was removed to provide that ca- 

 pacity (Pierce and Rich, 1962). 



In the United States, leader of world production of 

 salt, more than 45 million tons of salt with a value of 

 more than $285 million was produced in 1970 by 54 

 companies, which operated 99 plants in 17 States. 

 China, the U.S.S.R., Germany, and the United King- 

 dom are the other major producers. Australia has 

 had the greatest recent increase in production 

 ( Jacoby, 1972) . Past growth of the industry has been 

 steady, and the future outlook is for an annual 

 growth of from 3 to 5 percent. 



The principal methods of producing salt in the 

 United States are (1) solution mining, (2) under- 

 ground mining, and (3) evaporation of natural brines 

 and sea water. About 70 percent of the salt produced 

 in the United States is extracted from natural or 

 synthetic brines or sea water; 30 percent is mined 

 as a solid (Kaufmann, 1960). 



Subsurface deposits of rock salt are the principal 



