The borate deposits in Chile.

The boron resources of Chile are all located in the northern part of the co untry mainly in the evaporitic basins known as 'salares' (salt flats) and a re genetically related to Upper Tertiary - Quaternary volcanic activity. Th e most important deposits are located in the Andean basins of the Altiplano at Surire, Ascotan, Aguas Calientes Norte, Quisquiro, Aguas Calientes Sur, Maricunga and Pedernales. In addition other Altiplano basins may have boro n resources, but have yet to be evaluated. The borates are present primaril y in horizons known as 'barras' and usually form lenses wh ich interdigitat e with evaporitic and elastic detrital sediments. In other instances boron minerals form nodules referred to as 'papas' which are up to decimeters in diameter. Economic accumulations of boron are always located within the fir st few meters of the saline deposits. The only Chilean economic boron-beari ng mineral is ulexite, a Ca-Na berate; other minerals appear in minor amoun ts. Boren is also present in the lithium-rich brines of the Salar de Atacam a from which boron can be recovered as by-product of lithium extraction (0, 84 g/l as polyborates). A third, and far less important type of deposit, Is present in the Pampa del Tamarugal within berate-rich horizons associated with paleosols. Finally, other boron accumulations, currently not exploitab le, are associated with geothermal brines and the nitrate industry, both as by-products.