The Mineralogy and Geochemistry of Phosphorites

Nathan, Y.

doi:10.1007/978-3-642-61736-2_8

Cited by 67 publications

(52 citation statements)

References 55 publications

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“…In all other Ap, most researchers agree that CO3 substitutes for PO4 (e.g. McClellan, 1980;Nathan, 1984;Binder and Troll, 1989;McArthur, 1990) although neither the structural change produced by the substitution of a tetrahedral PO33-group with a triangular CO32-group, nor how the charge balance is maintained, are explained. Much chemical evidence exists to support the hypothesis of CO3/PO4 substitution such as the high inverse correlation between the P atoms and the sum of the Si, S and C atoms (Fig.…”

Section: X04 Substitutionmentioning

confidence: 99%

“…For example, many researchers think that CO3 substitutes PO4 (e.g. McClellan, 1980;Nathan 1984;Binder and Troll, 1989;McArthur, 1990) but the exact mechanism of CO3 substitution in the Ap structure is still a matter of dispute. Through comparison of the crystal chemistry of Ap samples from carbonatites, especially from early-state carbonatites, with those from alkaline igneous pegmatitic, hydrothermal, metamorphic and sedimentary rocks, we have endeavoured to gain more information on substitution mechanisms.…”

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confidence: 99%

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Some aspects of the crystal-chemistry of apatites

Liu

Comodi

1993

Mineral. mag.

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Twenty-four apatite (Ap) samples mainly from carbonatite and alkaline rocks were studied by electron microprobe, IR spectroscopy and X-ray powder diffraction. The crystal structures of six were refined using single crystal X-ray diffraction data to R = 1.7-2.5%. The generally high Si content of Ap from carbonatite and alkaline rock has been related to the presence of characteristic Si-O absorptions in IR spectra. Bands, whose intensities change with Si content, were observed at 520, 650, 930 and 1160 cm -1. The IR absorption features of v3 CO3 mode of Ap from carbonatite are different from those of v3 CO3 mode of Ap from sedimentary rock. This phenomenon is probably due to the different effects of F and OH on the CO3 substitution for PO4. The structural refinements yield more information on the CO3=PO 4 substitution, which is now supported also by the geometrical evolution of the tetrahedron with increasing CO3 content: the tetrahedral size decreases and the angle distortion increases with Ccontent. It is likely that the triangular planar CO3 group is disordered on the four faces of PO4 3-tetrahedron. It was observed also that Ap from early-stage carbonatite is OH-dominant with considerable LREE, Si, CO3 and negligible Mn, Fe, Mg, K, S and C1 contents. They have high Sr/Mn, Si/S and C/S ratios.

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Section: X04 Substitutionmentioning

confidence: 99%

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confidence: 99%

Some aspects of the crystal-chemistry of apatites

Liu

Comodi

1993

Mineral. mag.

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“…HAP is the thermodynamically most stable phase and often, when precipitated in the presence of foreign ions, substitution of calcium, phosphate and/or hydroxyls by some of these ions take place. Thus, substitutions of OH -by F -or Cl -ions, of the phosphate by sulfate and carbonate and of the calcium by Sr 2+ , Mg 2+ and Na + ions have been reported (Heughebaert et al, 1983;Legeros R.Z & Legeros J.P., 1984;Moreno & Varughese, 1981;Nathan, 1984). A considerable amount of the work done for the identification of calcium phosphate minerals which precipitates spontaneously has been based on the stoichiometric molar ratio of calcium to phosphate calculated from the respective changes in the solutions.…”

Section: Biomineralization: Physicochemical Backgroundmentioning

confidence: 98%

Prosthetic Aortic Valves: A Surgical and Bioengineering Approach

Mavrilas¹,

Apostolakis²,

Koutsoukos³

2011

Aortic Valve Surgery

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“…The low oxide totals obtained probably reflect the presence of carbonate and hydroxide groups substituting for the phosphate and fluoride anions. In addition, the presence of crystal water and organic matter in the inhomogeneous aggregates of crystallites in francolite may add to the low measured values of total oxides (Nathan, 1984). Low total oxide values correspond to lowered values of all three main constituents of francolite: CaO, P 2 O 5 , and fluoride (e.g., Sample 128-799B-45R-2, 38^0 cm; PL 1, Fig.…”

Section: X-ray Fluorescence Bulk Chemistry and Microprobe Analysesmentioning

confidence: 99%

“…According to these ranges, most phosphate particles may represent francolite, a calcium-fluor apatite. Francolite is characterized by its large variability in composition due to the large amount of substitution possibilities (e.g., Nathan, 1984). The low oxide totals obtained probably reflect the presence of carbonate and hydroxide groups substituting for the phosphate and fluoride anions.…”

Section: X-ray Fluorescence Bulk Chemistry and Microprobe Analysesmentioning

confidence: 99%

Phosphates and Glauconites of Sites 798 and 799

Föllmi¹,

Breymann²

1992

Proceedings of the Ocean Drilling Program, 127/128 Scientific Results

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Glauconites and phosphates have been detected in almost all investigated samples at Sites 798 (uppermost Miocene or lower Pliocene to Pleistocene) and 799 (early middle Miocene to Pleistocene). Autochthonous occurrences appear in very minor quantities (generally below 0.2%) throughout the drilled sequences, whereas allochthonous accumulations are limited to the lower Pliocene or uppermost Miocene sequence at Site 798 (glauconites) and to the upper and middle Miocene sequence at Site 799 (upper and middle Miocene: glauconites; middle Miocene: phosphates). X-ray fluorescence, microprobe, and bulk chemical analyses indicate high variabilities in cations and anions and generally low oxide totals. This is probably related to the substitution of phosphate and fluoride aniors by hydroxide and carbonate anions in phosphates and to the depletion of iron, aluminum, and potassium cations and the enrichment in hydroxide and crystal water in glauconites. Gradients in pore-water contents of dissolved phosphate and fluoride at Sites 798 and 799 suggest a depth of phosphate precipitation between 30 and 50 mbsf, with fluoride as the limiting element for phosphate precipitation at Site 798. Phosphate and fluoride appear to be balanced at Site 799.Crude extrapolations indicate that the Japan-Sea sediments may have taken up approximately 7.2 × I0 10 g P tota i/yr during the Neogene and Pleistocene. This amount corresponds to approximately 0.3% of the estimated present-day global transfer of phosphorus into the sediments and suggests that the Japan Sea constitutes an average sink for this element. The two main carriers of phosphorus into the present Japan Sea are the Tshushima and the Liman currents, importing approximately 6.6 × I0 10 g P and 5.7 × I0 10 g P per year, respectively. Bulk chemical analyses suggest that at least 36% of P total in the sediments is organically bound phosphorus. This rather high value, which corresponds to the measured Japan-Sea deep-water Porganic^totai ratios, probably reflects rapid transport of organic phosphorus into the depth of the Japan Sea.

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The Mineralogy and Geochemistry of Phosphorites

Cited by 67 publications

References 55 publications

Some aspects of the crystal-chemistry of apatites

Some aspects of the crystal-chemistry of apatites

Prosthetic Aortic Valves: A Surgical and Bioengineering Approach

Phosphates and Glauconites of Sites 798 and 799

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