Sedimentary Phosphate Deposits Research Articles

Use of sea water in the flotation of carbonate rich sedimentary phosphate rock

There is an appreciable amount of carbonaceous sedimentary phosphate deposits in the northern Africa and the Middle East which are expected to gain importance in the near future because of the depletion of the deposits in Florida. In many of the regions where phosphate deposits are found there is a shortage of fresh water, and sea is not very far. The use of sea water instead of fresh water in flotation of carbonaceous phosphate rock is successfully demonstrated. Thus an appreciable reduction in the operating cost and an ample amount of saving in the fresh water resources of the region is expected.

Geochemistry of a Tertiary sedimentary phosphate deposit: Baja California Sur, Mexico

The San Gregorio Formation in Baja California Sur, a phosphate-enriched sedimentary unit of late Oligocene to early Miocene age, has been analyzed in two areas (La Purisima and San Hilario) for its chemical composition (major oxides, Cu, Cd, Cr, Co, V, and rare-earth elements — REE) and isotopic composition (δ 18O and δ 13C). A detrital and a marine component were determined from major oxides. The detrital component consists of an unaltered volcanic-ash fraction and a terrigenous clay-silt fraction. The marine component, which accumulated initially as biogenic and hydrogenous material, is now present as opal-A, opal-CT, CaCO 3, organic matter, and an authigenic phosphate fraction, mostly pelletal and composed of the carbonate-fluorapatite mineral francolite. The minor elements have been partitioned into these components by assuming a constant composition for the two detrital fractions. The composition of the marine component of minor elements can then be interpreted by assuming that the stoichiometry of the original accumulating organic matter was equal to that of modern plankton. The Cu and Cd contents in the marine component of all rocks require that the seawater-derived fractions of these two metals were supplied to the seafloor solely by organic matter. Enrichments of Cr and V at both sites required an additional marine input. On the basis of their geochemistry in the modern ocean, Cr and V could have precipitated, or been adsorbed, onto settling particles from an O 2 minimum zone in which the O 2 content was low enough to promote denitrification rather than oxygen respiration. An enrichment of the REE, now within the apatite fraction, resulted from their adsorption onto particulates also in the O 2 minimum zone and to the dissolution and alteration of biogenic phases (predominantly silica) within the sediment. Co and Fe 2O 3 show no enrichment above a detrital contribution. The δ 18O-values of apatites from the La Purisima site are heavier than those of apatites from the San Hilario site, whereas the δ 13C-values show the opposite trend. One possible interpretation of these variations is that δ 18O reflects seawater values and δ 13C sediment pore water values. This interpretation suggests that upwelling rates and primary productivity within the water column were greater at La Purisima, an interpretation that is corroborated by a greater abundance of apatite measured in outcrop at La Purisima. The Ce anomalies of the phosphate-enriched samples also differ between the two sites, indicating that they also recorded water masses, similar to the δ 18O-values.

Flotation of a carbonate rich sedimentary phosphate rock

A large portion of the world's phosphate reserves are sedimentary type containing appreciable amounts of carbonate minerals. These are the most difficult type of deposits to beneficiate. The depletion of other reserves easier to beneficiate, necessitates research to find methods of mineral processing for carbonate rich sedimentary phosphate deposits. In this study, a new flotation method is described which was applied successfully in a laboratory scale flotation cell. Flotation of Al-Jalamid phosphate rock (sedimentary type with high carbonates and low silica content) found in northern Saudi Arabia was studied using a fatty acid as collector and sodium sulfate as a flotation aid.

The stable isotopic composition of a phosphorite deposit: δ 13C, δ 34S, and δ 18O

The stable isotopes of carbon and sulfur in a major marine sedimentary phosphate deposit from the northwestern United States (the Phosphoria Formation of Permian age) characterize the chemical properties of the depositional environment. The δ 34S and δ 13C analyses suggest deposition under conditions of variable redox from a solution the acidity of which was controlled by reaction with carbonate rocks and exchange with seawater. The δ 18O concentration of apetite indicates phosphatization in a shallow sea, during three glacial and intervening interglacial stages. These data tend to corroborate the interpretation of field studies by others, that the apatite formed on a continental shelf in an area of intense oceanic upwelling during several episodes of sea level change.

Phosphorus, phosphorites and skeletal evolution at the Precambrian—Cambrian boundary

Clustering of sedimentary phosphate deposits around the Precambrian–Cambrian boundary is related to a global phosphogenic event. This event probably resulted from a complex interplay of factors and had a profound effect on the biota, with high concentrations of phosphorus in the photic zone producing an increase in the total shallow marine biomass, faunal diversification, the precipitation of skeletal structures and explosive evolution.

A reevaluation of the spatial and temporal distribution of sedimentary phosphate deposits in the light of plate tectonics; discussion

A reevaluation of the spatial and temporal distribution of sedimentary phosphate deposits in the light of plate tectonics; discussion

A reevaluation of the spatial and temporal distribution of sedimentary phosphate deposits in the light of plate tectonics; reply

A reevaluation of the spatial and temporal distribution of sedimentary phosphate deposits in the light of plate tectonics; reply

A reevaluation of the spatial and temporal distribution of sedimentary phosphate deposits in the light of plate tectonics

A new compilation of paleolatitudes of sedimentary phosphate deposits using worldwide paleomagnetic data confirms the hypothesis that the majority formed at low-latitude locations. A number of Jurassic and possibly some Cambrian deposits formed at intermediate latitudes (30 degrees -50 degrees ). Phosphorites range in age from lower Proterozoic to Recent. There has been sporadic deposition of phosphate during this time, as continents drifted into low-latitude locations. It is proposed that there is no direct genetic link between periods of volcanism, orogenesis, formation of evaporites, and episodes of phosphogenesis. All these features are indirectly genetically related through plate tectonics to particular phases in the rifting and separation of continental and oceanic components of plates. In the case of diverging plates, volcanism and tectonism are an early-stage feature, evaporites intermediate-, and phosphorites late-stage features. Models are developed to explain the different sedimentary sequences that develop in north-south and east-west seaways. No model is presently available for epeiric seas.A temporal model is also proposed to explain the distribution of phosphorus in sediments in the last 3,400 m.y. The association of phosphorus with iron and organic matter in the hydrosphere is particularly critical to the model. Even the temporal model is influenced to some extent by plate tectonics.

A geochemical model for evaluating theories on the genesis of Florida's sedimentary phosphate deposits

Present ionic concentrations of Ca++,HCO 3 - ,and HPO 4 = in surface and groundwater runoff in Florida indicate that phosphorus is being concentrated in rock through dissolution and reprecipitation, with calcium phosphate increasing at the expense of calcium carbonate. Analog computer simulation of a systems model of this process suggests that significant enrichment can occur in 20 million years. The degree of enrichment depends on the supply of new phosphorus to Florida through rain and oceanic exchange processes. If the calcium phosphate content of original rock is 0.5 to 1.0 percent (0.52 to 1.05 percent P2O5),a formation with 10 to 20 percent calcium phosphate (CaPO4or 10.5 to 21.0 percent P2O5)as in the Hawthorn Formation (Miocene)may result. Nutrient upwelling along the continental slope coupled with transport to the estuaries by lateral eddy diffusion can supply an additional 400 mg P|m2|yr which, if deposited, would result in a sediment with a 4.3 percent CaPO4 (4.5 percent P2O5)content. If this is enriched later by resolution, 40 percent CaPO4 (42 percent P2O5)results. Through geologic time, the ocean may be considered as a source of phosphorus to the land through rain or estuarine sediment.