Phosphorite deposits

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. 

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... 

Phosphorite deposits are currently forming in areas of high organic productivity and low detrital input. These are typically coastal upwelling zones adjacent to arid continental lands. Phosphorites form at slow rates, so low detrital input is important to prevent dilution or burial. As shown in Figure 18.10, sites of formation include the continental margins of Peru, Chile, and southwest Africa. 

Role of Phosphorite Deposition in the Crustal-Ocean-Atmosphere Factory... 

Locations of disseminated (nonphosphorite) authigenic CFA occurrence, as well as locations of phosphorites. Areas with substantial phosphorite deposits include the East China Sea between Korea and Japan, Ceara Rise, Saanich Inlet, eastern and western equatorial Pacific, California Borderland Basins, Gulf of St. Lawrence, Labrador Sea, Long Island Sound, Gulf of Mexico, North Atlantic continental platform, and Iberian margin in the northeastern Atlantic. Source From Ruttenberg, K. C. (2003). Treatise on Geochemistry, Elsevier Ltd. pp. 585-643. 

The abundance of phosphate in sedimentary rocks as a function of geologic age showing the episodicity of giant phosphorite deposition. Source-. From Cook, P. J., and McElhinny, M. W. (1979) Economic Geology 74, 315-330. 

Significant amounts of manganese and phosphorite deposits are present on the top of the Blake Plateau, which lies at the foot of the continental margin off the southeastern United States at depths of 500 to 900 m. The Gulf Stream has eroded most of the unconsolidated sediments at this location, leaving only a carbonate platform, which has become covered with pavements of manganese and phosphorite covering an area of 5000 km ... 

Riggs, S.R. Paleoceanographic Model of Neogene Phosphorite Deposition, U.S. 

Solid phosphates constitnte many minerals, notably Apatites, which are also fonnd in living organisms as rigid components such as bones and teeth see Biomineralization). Amorphous Phosphorite deposits are important somces of phosphate fertihzers. 

Burnett W. C. (1977) Geochemistry and origin of phosphorite deposits from off Peru and Chile. Geol. Soc. Am. Bull. 88, 813-823. 

The mining of phosphate rock (mostly from terrestrially emplaced marine phosphorite deposits) for use as agricultural fertilizer has increased dramatically in the latter half of this century (F72). In addition to fertilizer use, deforestation, increased cultivation, urban and industrial waste disposal all have enhanced phosphorus transport from terrestrial to aquatic systems, often with deleterious results. For example, elevated phosphorus concentrations in rivers resulting from these activities have resulted in eutrophication in some lakes and coastal areas, stimulating nuisance algal blooms and promoting hypoxic or anoxic conditions harmful or lethal to natural populations (e.g., Caraco, 1995 Fisher et al., 1995 Melack, 1995). 

Cook P. J. and McElhinny M. W. (1979) A re-evaluation of the spatial and temporal distribution of sedimentary phosphorite deposits in light of plate tectonics. Econ. Geol. 74, 315-330. 

Filippelli G. M. and Delaney M. L. (1992) Similar phosphorus fluxes in ancient phosphorite deposits and a modern phosphogenic environment. Geology 20, 709-712. 

Riggs S. R. (1984) Paleoceanographic model of Neogene phosphorite deposition US Atlantic continental margin. Science 223, 123-131. 

Further evidence that Kazakov s (1937) inorganic hypothesis is quite inadequate to account for the formation of modern phosphorite deposits off... 

Dietz, R.S. and Emery, K.O., 1950. Submarine phosphorite deposits off California and Mexico. Calif. J. Mines Geol., 46 7—15. 

McKelvey, V.E., Swanson, R.W. and Sheldon, R.P., 1953. The Permian phosphorite deposits of the western United States. Congres Geologique International, Alger, 1952. Comptes Rendus de la Dix-neuvieme Session Origine des Gisements de Phosphates des Chaux, 11 45—64. 

Since apatites serve as a row material for P fertilizer production, the impurities of heavy metals are the source of great pollution of agroecosystems. In general, the major phosphorite deposits are of marine origin and occur as sedimentary beds ranging from a few centimeters to tens of meters in thickness. The biogenic matter produced in water column settles to the sediment surface and decomposes, releasing P04- to the sea water and pore water. 

There may also be natural fluctuations within this cycle that occur over time-scales ranging from thousands of years (glacial-interglacial) to millions of years as demonstrated in Fig. 14-8. In this figure, the abundance of P in known phosphorite deposits is plotted as a function of geologic time. Notice that this is a semi-log plot, so that the amount of P stored in phosphorites in different time intervals varies by... 

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