Phosphorites continental

The ocean is host to a variety and quantity of inorganic raw materials equal to or surpassiag the resources of these materials available on land. Inorganic raw materials are defined here as any mineral deposit found ia the marine environment. The mineral resources are classified generally as iadustrial minerals, mineral sands, phosphorites, metalliferous oxides, metalliferous sulfides, and dissolved minerals and iaclude geothermal resources, precious corals, and some algae. The resources are mosdy unconsoHdated, consoHdated, or fluid materials which are chemically enriched ia certain elements and are found ia or upon the seabeds of the continental shelves and ocean basias. These may be classified according to the environment and form ia which they occur (Table 1) and with few exceptions are similar to traditional mineral deposits on land. 

Continental Shelf. Most consohdated mineral deposits found on the continental shelf are identical to those found on land and are only fortuitously submerged. Exceptions include those laid down in shallow marine seas or basins in earlier geochemical environments such as bedded ironstones, limestones, potash, and phosphorites. 

Table 18.1 Average Compositions of the Earth s Upper Continental Crust, Shale, Iron-Manganese Oxides, Phosphorite, and Various Types of Marine Sediments (All in Units of ppm. Unless Noted otherwise), along with Seawater and a Hydrothermal Vent Solution from the East Pacific Rise (both in Units of 10 g L ). 

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. 

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. 

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 ... 

Phosphorites (manne apatites) are dense, hght-brown-to-black concretions, ranging in size from sands to nodules and irregular masses. Phosphorites have been found off Argentina, Chile, Japan, Mexico, Peru, South Africa, and Spain, and several islands in the Indian Ocean. Some also have been found off the west coast of North America and on the eastern North American continental shelf These deposits occur where water upwelling transports phosphorus and where the rate of sedimentation is slow. The... 

The average composition of marine phosphorites on continental margins is summarized in Table 2, and the enrichment factors E m (phosphorite/shale) for various elements are plotted in Figure 23. (phosphorite/shale) values of 1 (within a factor of 2) for Li, B, Mg, Al, Si, K, Ti, Fe, Ga, and Bi indicate their aluminosilicate origin. The moderate enrichment of Sc, V, Cr, Y, Zr, Nb, REEs, and Th, and high enrichment of Ag, Cd, and U probably result from their replacement of Ca in CFA, facilitated by their similar ionic radii. However, the enrichment of biophile elements S, Se, Cu, Zn, Mo, Sn, Sb, Au, and Hg is also related to the occurrence of sulfides and organic matter in the samples (Li, 2000). 

Factor analysis results of marine phosphorite data from the South African continental margin (Parker, 1975 Parker and Siesser, 1972) show four components (Figure 24(a)) FI (glauconite... 

CFA is omnipresent in pelagic sediments, ferromanganese nodules, and seamount crusts, and marine phosphorites on continental margins and seamounts. Supply of phosphate by oxidation of organic matter and pre-concentration of phosphate by iron oxyhy dr oxides, supply of calcium by dissolution of carbonates or carbonates acting as substrates, and supply of fluorine from seawater are all important factors in the formation of marine phosphorites. 

Heggie D. T., Skyring G. W., O Brien G. W., Reimers C., Herczeg A., Moriarty D. J. W., Burnett W. C., and Milnes A. R. (1990) Organic carbon cychng and modern phosphorite formation on the East Austrahan continental margin an overview. In Phosphorite Research and Development, Geol. Soc. Spec. Publ. 52 (eds. A. J. G. Notholt and... 

O Brien G. W. and Veeh H. H. (1980) Holocene phosphorite on the east Australian continental margin. Nature 288, 690-692. 

Parker R. J. and Siesser W. G. (1972) Petrology and origin of some phosphorites from the South African continental margin. J. Sedim. Petrol. 42, 434-440. 

Watkins R., Nathan Y., and Bremner J. M. (1995) Rare earth elements in phosphorite and associated sediment from the Namibian and South African continental shelves. Mar. Geol. 129, 111-128. 

Froelich P. N., Arthur M. A., Burnett W. C., Deakin M., Hensley V., Jahnke R., Kaul E., Dim K.-H., Roe K., Soutar A., and Vathakanon C. (1988) Early diagenesis of organic matter in Peru continental margin sediments phosphorite precipitation. Mar. Geol. 80, 309-343. 

Figure 8 Observed cumulative mass/age distributions of major sedimentary lithological types. Explanation of abbreviations gr denotes graywackes sh, shales ark, arkoses ss, sandstones dol, dolostones evap, evapor-ites Im, limestones phosp, phosphorites CB, continental basement P, platforms MOB, mature erogenic belts OD, oceanic domain (after Veizer, 1988c).

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

Phosphorite, for our purposes, is the term applied to calcium phosphate rocks, whether they are accumulations of bones, precipitates directly from sea water or replacements of calcareous rocks. They are very extensive on the earth, occurring on all continental land masses with the possible exception of Antarctica, where commercial deposits have not yet been found. Phosphorites comprise the principal geologic storage bin for inorganic phosphates. 

Vast continental phosphorites exist in parts of the Florida Peninsula,... 

Reiterating, the phosphatic mineral of such phosphorites is essentially francolite, a carbonate fluorapatite of somewhat variable composition (McConnell, 1971 Rooney and Kerr, 1967). Although not proven to be contained within the apatitic phase through isomorphic substitution, some of the continental phosphorites are of considerable interest because of accumulations of uranium, thorium, yttrium, rare earths, scandium, and vanadium therein. These rarer components are thought to be related to diagenetic processes, in which case they were extracted from sea water during the early formative histories of the phosphorites. 

Nodular phosphorites are well known from continental shelves, mostly at depths of from 100 to 500 m, which are believed to be replacements of fossiliferous limestone and other sediments by francolite, essentially in situ... 

Romankevich, Ye.A. and Baturin, G.N., 1972. Composition of the organic matter in phosphorites from the continental shelf of southwest Africa. Geochem. Int., 9 464— 470. 

The Permian Phosphoria Formation in the northwestern Interior United States contains two phosphatic and organic-ncarbon-rich shale members, the Meade Peak Phosphatic Shale Member and the Retort Phosphatic Shale Member. Ihese rocks were formed at the periphery of a foreland basin between the Paleozoic continental margin and the North American cratonic shelf. The concentration, distribution, and coincidence of phosphorite, organic carbon, and many trace elements within these shale members probably were coincident with areas of optimum trophism and biologic productivity related to areas of upwelling. In the Phosphoria sea upwelling is indicated to have occurred by sapropel that was deposited adjacent to shoals near the east flank of the depositional basin. 

Heggie DT, Shyring GW, O Brien GW, Reimers C, Heiczeg A, Moriarty DJW, Burnett WC, Milnes AR (1990) Orgaiuc carbon cycling and modem phosphorite formation on the east Australian continental margin an overview. In Phosphorite Research and Development. Notholt AJG, Jarvis I (eds) Geol Soc (London) Spec Pub 52 87-117... 

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