Geology of the salt deposits and the salt industry of northern Chile

The study of the salt deposits of northern Chile is a cooperative project of the Institute de Investigaciones Geologicas (IIG) of Chile and the United Nations Special Fund and is part of a mineral resources survey, undertaken by these two organizations, of selected regions of northern Chile, during 1960-1963. The writer, an employee of the United States Geological Survey, worked in cooperation with the IIG and its predecessor organization, the Seccion Geologica of the Corporacion de Foment de la Produccion, during the period December 1954-March 1962, under the auspices of the United States Technical Aid program (AID). The work on salt deposits, which was started during 1961, has been under the auspices of the United Nations since April 1962, during completion of field work and preparation of this report.

This report summarizes the data gathered during the field investigation, including information on reserves, production, and composition of salts supplied by private companies and government bureaus. As such, it is in the nature of a progress report, lacking: 1) a comprehensive review of the literature which, at least in regard to the well-known nitrate deposits, is extensive; 2) completion of laboratory investigations of chemical, mineralogical, and isotopic composition; and 3) a review of theories of origin of the salts, mainly nitrate.

The salt deposits of northern Chile comprise the well-known nitrate deposits as well as salars that have been exploited principally for sodium chloride, sodium sulfate, and borate; bedded salt deposits and salt domes, and secondary salt deposits formed in the oxidation zone of metalliferous sulfide deposits. This report will discuss the nitrate deposits and associated sodium sulfate deposits, salars, and those secondary deposits, such as aluminum-magnesium sulfates or iron sulfates, which have been exploited for chemical use. Bedded salt deposits and salt domes, consisting mainly of halite and evidently restricted to one small area, were not studied. The numerous and important secondary copper deposits, as well as other metalliferous salt deposits, are beyond the scope of the report.