Chile Atacama

Increased arsenic concentrations are also found in some river waters dominated by base flow in arid areas. Such waters often have a high pH and alkalinity. For example, surface waters from the Loa River Basin of northern Chile (Atacama desert) contain naturally occurring arsenic in the range 190-21,800 p,g L (Caceres et al., 1992). The high arsenic concentrations correlate with high salinity. While geothermal inputs of arsenic are likely to be important, evaporative concentration of the base-flow-dominated river... 

Mineral Deposits. The only iodine obtained from minerals has been a by-product of the processing of nitrate ores in Chile. CaUche occurs in the Atacama desert of Northern Chile and west of the Andes mountains. The Atacama desert is known as the driest of the world s deserts, where measurable (>1 mm) rainfalls may be as infrequent as once every 5—29 years (58). The caUche deposits occur in an area averaging 700 km (north—south) by 30 km (east—west). The iodine may total over 5 x 10 t (59). 

Sa.Ia.rs and Lakes. Brines having high lithium concentration are found in salars of northern Chile, southwestern Bohvia, and northwestern Argentina. Brines of lower lithium concentration are found in salars in the western United States and the Tibetan Plateau. Brines pumped from beneath the surface of the Salar de Atacama (Chile) and Silver Peak (Clayton Valley, Nevada) are used for commercial production of lithium uti1i2ing solar evaporation (see Chemicals frombrines). The concentration of selected ions in brines from salars and lakes of potential commercial interest worldwide are shown in Table 1. 

The Chilean nitrate deposits are located in the north of Chile, in a plateau between the coastal range and the Andes mountains, in the Atacama desert. These deposits are scattered across an area extending some 700 km in length, and ranging in width from a few kilometers to about 50 km. Most deposits are in areas of low rehef, about 1200 m above sea level. The nitrate ore, caUche, is a conglomerate of insoluble and barren material such as breccia, sands, and clays (qv), firmly cemented by soluble oxidized salts that are predominandy sulfates, nitrates, and chlorides of sodium, potassium, and magnesium. Cahche also contains significant quantities of borates, chromates, chlorates, perchlorates, and iodates. 

Numerous theories exist as to how the Chilean deposits formed and survived. It has been postulated that the unique nitrate-rich caUche deposits of northern Chile owe their existence to an environment favorable to accumulation and preservation of the deposits, rather than to any unusual source of the saline materials (2). The essential conditions are an extremely arid climate similar to that of the Atacama desert in the 1990s, slow accumulation during the late Tertiary and Quaternary periods, and a paucity of nitrate-utilizing plants and soil microorganisms. 

A third source of brine is found underground. Underground brines ate primarily the result of ancient terminal lakes that have dried up and left brine entrained in their salt beds. These deposits may be completely underground or start at the surface. Some of these beds ate hundreds of meters thick. The salt bed at the Salat de Atacama in Chile is over 300 m thick. Its bed is impregnated with brine that is being pumped to solar ponds and serves as feedstock to produce lithium chloride, potassium chloride, and magnesium chloride. Seades Lake in California is a similar ancient terminal lake. Brine from its deposit is processed to recover soda ash, borax, sodium sulfate, potassium chloride, and potassium sulfate. 

Occurrence. Brine found in Seades Lake, California is the only brine source where boron is produced commercially. Other brine bodies such as the Great Salt Lake or brine from thermal weUs at the Salton Sea have been considered but have not been exploited. Brines at the Salar de Atacama in Chile also contain boron, but it is not presently extracted. 

Occurrence. Iodine [7553-56-2] is widely distributed in the Hthosphere at low concentrations (about 0.3 ppm) (32). It is present in seawater at a concentration of 0.05 ppm (33). Certain marine plants concentrate iodine to higher levels than occur in the sea brine these plants have been used for their iodine content. A significant source of iodine is caUche deposits of the Atacama Desert, Chile. About 40% of the free world s iodine was produced in Japan from natural gas wells (34), but production from Atacama Desert caUche deposits is relatively inexpensive and on the increase. By 1992, Chile was the primary world producer. In the United States, underground brine is the sole commercial source of iodine (35). Such brine can be found in the northern Oklahoma oil fields originating in the Mississippian geological system (see Iodine and iodine compounds). 

Occurrence. Numerous brines contain lithium in minor concentrations. Commercially valuable natural brines are located at Silver Peak, Nevada (400 ppm) (40,41), and at Seades Lake, California (50 ppm) (42,43). Great Salt Lake brine contains 40 ppm and is a source not yet exploited. Seawater contains less than 0.2 ppm. Lithium production started at Silver Peak in the 1970s. The concentration of lithium in the brine is diminishing, and now the principal production occurs from brine in the Salar de Atacama, Chile. 

Recovery Process. Lithium is extracted from brine at Silver Peak Marsh, Nevada, and at the Salar de Atacama, Chile. Both processes were developed by Foote Mineral Corp. The process at Silver Peak consists of pumping shallow underground wells to solar ponds where brines are concentrated to over 5000 ppm. Lithium ion is then removed by precipitation with soda ash to form a high purity lithium carbonate [554-13-2]. At the Atacama, virgin brine with nearly 3000 ppm lithium is concentrated to near saturation in lithium chloride [7447-41 -8]. This brine is then shipped to Antofagasta, Chile where it is combined with soda ash to form lithium carbonate. 

Economic Aspects and Uses. In 1976, one-third of the lithium produced in the United States was extracted from brines of Seades Lake and Silver Peak (44,45). Since then, lithium production at Seades Lake has been discontinued and the lithium concentration at Silver Peak is decreasing. During the 1980s lithium extraction was started at the Salar de Atacama, Chile. This is the largest lithium production plant in the wodd using brine as its raw material. 

New technology and development of brine reserves are increasing each year in the United States and abroad. This affects the uses and price of brine chemicals. For example, development of the Salar de Atacama in Chile in the 1980s as the largest producer of brine lithium in the world has affected lithium production and prices worldwide. Lithium production from Seades Lake brine has been discontinued, and the Silver Peak operation in Nevada is in a slow production decline caused by weaker brine grades. 

Robst AL, Lowenstein TK, Jordan TE, Godfrey LV, Ku T-L, Luo S (2001) A 106 ka paleoclimate record from drill core of the Salar de Atacama, northern Chile. Paleogeo Paleoclim Paleoecol 173 21-42 Rosholt JN (1957) Quantitative radiochemical methods for determination of the sources of natural radioactivity. Anal Chem 29 1398-1408... 

South America has two major areas, separated by the Andes Mountain ridges, where arid and semi-arid zones dominate. In the barren, coastal Atacama desert of Peru and northern Chile, precipitation is extremely limited and comes as winter mists or drizzles. In the rain shadow east of the Andes in Argentina, arid zones are widespread. South America apparently has only a slightly greater proportion of dry zones than North America. 

Constantino M. Torres, David B. Repke, Kelvin Chan, Dennis McKenna, Augustin Llagostera, and Richard E. Schultes. "Botanical, chemical, and contextual analysis of archaeological snuff powders from San Pedro de Atacama, Northern Chile." Current Anthropology 32 (1992) 640-49. 

Fig. 1. Distribution of copper deposits in northern Chile including those containing atacamite in the oxide zone. DFZ is the Domeyko Fault Zone and ACL is Antofagasta-Calama Lineament. The land between the High Andes and the coast is the hyper-arid central Atacama Desert.

Arancibia, G., Matthews, S.J., Perez De Arce, C. 2006. K-Ar and °Ar Ar geochronology of supergene processes in the Atacama Desert, Northern Chile tectonic and climatic relations. Journal Geological Society London, 163, 107-118. 

Leybourne, M.I. Cameron, E.M. 2006. Composition of groundwaters associated with porphyry-Cu deposits, Atacama Desert, Chile Elemental and isotopic constraints on water sources and water-rock reactions. Geochimica et Cosmochimica Acta, 70, 1616-1635. 

Palacios, C., Guerra, N., Townley, B., Lahsen, A. Parada, M. 2005. Copper geochemistry in salt from evaporate soils, Coastal Range of the Atacama Desert, northern Chile an exploration tool for blind Cu deposits. Geochemistry Exploration, Environment, Analysis, 5, 371-378. 

Reich, M., Palacios, C., Parada, M.A., Fehn, U., Cameron, E.M., Leybourne, M.I. Zuniga, A. 2008. Fluid inclusion, groundwater geochemistry, TEM and 36CI. Evidence for a genetic link between basinal brines and atacamite formation, Atacama Desert, Chile. Mineralium Deposita, 43, 663-675. 

Lithogeochemistry of the Quebrada Blanca Porphyry Cu Deposit, Atacama Desert, Northern Chile... 

In the longer term, ALMA (the Atacama Large Millimetre Array) will take over from FIRST. This will be a huge network of 96 radio dishes extending over an area of 10000 m. Its detectors will cover the frequency band from 70 to 950 GHz. Sponsored by Europe, the United States and Japan, ALMA will be built at an altitude of 5000 m on the Atacama plateau in Chile. 

It is a secondary mineral found associated with malachite and cuprite originally found at Atacama, Chile, whence its name. Other localities are Bohemia, South Australia, and in the United States in Arizona, Utah, and Wyoming. See also Cuprite and Malachite. 

CALICHE (Nitrate). The gravel, rock. soil, or alluvium cemented with soluble salts of sodium in the nitrate deposits of the Atacama Desert of northern Chile and Peru. The material contains from 14 to 25% sodium nitrate, 2 to 3% potassium nitrate, and up to I i sodium iodaic. plus some sodium chloride, sulfate, and borate. At one time, this was an important natural fertilizer. 

Caliche or Nitre- Bed. A term used in Chile for a layer of gravel or rocks contg Na nitrate (Chile saltpeter) together with Na sulfate (salt cake), Na chloride (table salt) small amts of other salts. Caliche varies in depth from 2 to 20ft and is covered by 1 to 12ft of sand overburden. The deposits are found in a desert in Atacama of province Tarapaca (Northern Chile) extending 400 miles north and south with a width of 5 to 40 miles. Deposits of Na nitrate, on a smaller scale have been found in Argentina, Bolivia, California and Peru (Ref 1, 2 3)... 

Rech JA, Currie BS, Michalski G, Cowan AM (2006) Neogene climate change and uplift in the Atacama Desert, Chile. Geology 34(9) 761-764... 

Uncertainty in the depth history of a sample is a primary source of uncertainty for the cosmogenic-nuclide paleoaltimeter. Because of the >2000-fold difference in rock density versus atmospheric density, a 0.5-m uncertainty in depth is equivalent to >l-km uncertainty in altitude. Uncertainty in the depth of a sample during exposure is particularly problematic in regions where loess deposits may episodically bury a surface. For example, Hancock et al. (1999) find cosmogenic evidence of an ephemeral 0.5-1.5 m silt cap on currently uncapped, 600-ka terraces in the Wind River basin, Wyoming. The duration of time required to deposit a sedimentary layer may also result in a complex exposure history that can only be deduced with depth profiles and multiple nuclides (Riihimaki et al. 2006). However, Dunai et al. (2005) suggest that some deposits in the hyperarid Atacama Desert, Chile, have remained at the same depth without erosion or deposition for >20 Ma. 

Examples of especially dry environments on Earth include the Atacama Desert of northern Chile and the Dry Valleys of Antarctica. Dose et al. (2001) exposed spores, conidia, and cells of several microbes to 15 months of desiccation in the dark at two locations of the Atacama Desert. Bacillus subtilis (bacteria) spores (survival 15%) and Aspergillus niger (fungi) conidia (survival 30%) outlived other species. Deinococcus radiodurans (bacteria) did not survive the desert exposure because they were readily killed at RH between 40% and 80%, which occurred during desert nights (Dose et al. 2001). 

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