Phosphorites, uranium deposits

Phosphorite deposits, 17 688, 691 Phosphorite uranium deposits, 17 520 Phosphorochloridate synthesis, 19 28 Phosphorodithioate DNA, 17 630 Phosphorodithioates, 17 630 Phosphorothioates, 17 629-630 synthesis of, 17 630 Phosphorous acid, 19 52 Phosphorous donor ligands, thorium and, 24 768 Phosphors... 

By far the most important ores of iron come from Precambrian banded iron formations (BIF), which are essentially chemical sediments of alternating siliceous and iron-rich bands. The most notable occurrences are those at Hamersley in Australia, Lake Superior in USA and Canada, Transvaal in South Africa, and Bihar and Karnataka in India. The important manganese deposits of the world are associated with sedimentary deposits the manganese nodules on the ocean floor are also chemically precipitated from solutions. Phosphorites, the main source of phosphates, are special types of sedimentary deposits formed under marine conditions. Bedded iron sulfide deposits are formed by sulfate reducing bacteria in sedimentary environments. Similarly uranium-vanadium in sandstone-type uranium deposits and stratiform lead and zinc concentrations associated with carbonate rocks owe their origin to syngenetic chemical precipitation. 

Phosphorite Deposits. Sedimentary phosphorites contain low concentrations of uranium in fine-grained apatite. Uranium of this type is considered an unconventional resource. Significant examples of these uranium ore types include the U.S. deposits in Elorida, where uranium is recovered as a by-product, and the large deposits in North African and Middle Eastern countries (16). 

Domestic. Estimates of U.S. uranium resources for reasonably assured resources, estimated additional resources, and speculative resources at costs of 80, 130, and 260/kg of uranium are given in Table 1 (18). These estimates include only conventional uranium resources, which principally include sandstone deposits of the Colorado Plateaus, the Wyoming basins, and the Gulf Coastal Plain of Texas. Marine phosphorite deposits in central Elorida, the western United States, and other areas contain low grade uranium having 30—150 ppm U that can be recovered as a by-product from wet-process phosphoric acid. Because of relatively low uranium prices, on the order of 20.67/kg U (19), in situ leach and by-product plants accounted for 76% of total uranium production in 1992 (20). 

Phosphorite Deposits in Florida, USA, and the large deposits in North African and Middle-eastern countries. Uranium is recovered as a by-product from Florida deposits. 

Christy AG, Alberius-Henning P, Lidin SA (2001) Computer modelling and description of nonstoichiometric apatites Cd5./2(V04)3li. and Cd5 /2(P04)3Bri as modified chimney-ladder stmctures with ladder-ladder and chimney-ladder couphng. J Sohd State Chem 156 88-100 Claike RS, Altschuler ZS (1958) Determination of the oxidation state of uranium in apatite and phosphorite deposits. Geochim Cosmochim Acta 13 127-142... 

Sedimentary marine phosphorites are composed principally of phosphatic minerals, and many contain significant amounts of disseminated uranium. These phosphorites have been classified as either miogeosynclinal or platform types. Four additional types that are low in uranium and of little economic importance are residual phosphorites, phosphatized rock, river pebble deposits and guano. 

Phosphorites that are richest and thickest and contain the most uranium are the miogeosynclinal type deposited on the outer parts of continental shelves where upwelling of deep marine waters has occurred. These waters were saturated with respect to phosphate and were probably the source of the phosphate in the phosphorites. These phosphorites are commonly present in thick miogeosynclinal sequences, where they are associated with carbonates, black shale, chert, carbonaceous mudstone and minor amounts of mudstone. " The Phosphoria Formation of the western U.S.A. is an example. 

Platform phosphorites are generally nodular, rather than bedded, and are associated with sandstone, limestone and glauconite. Most are low in uranium, but an exception is the Bone Valley Formation of the southeastern U.S.A. This unit has been reworked and enriched by re-exposure to sea water during a subsequent transgression. These phosphorites differ from shelf phosphorites in that they are near-shore sub-tidal and shoreline deposits, and they change facies oceanward to carbonate sediments. 

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