Distribution, texture and composition of modern phosphate pellets in Peru shelf muds

Baker, Kaysee; Burnett, William C.

doi:10.1016/0025-3227(88)90090-4

Cited by 18 publications

(10 citation statements)

References 36 publications

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“…In the deeper part of the boxcore, coated foraminifers become less frequent. The F/P 2 O 5 ratio of the coating/fillings is lower (0.056) than the ratio for substituted francolite (0.148;McClellan, 1980), which have previously been observed in relatively young phosphorites (Price and Calvert, 1978;Thomson et al, 1984;Baker and Burnett, 1988). Calibrated 14 C ages for coated foraminifers are higher than "clean" (uncoated) foraminifers in the same sediment interval (Table 3).…”

Section: Ages Of Apatite Macro Particles In Bc484mentioning

confidence: 53%

“…Furthermore, high rates of phosphogenesis may be restricted to the small intrashelf basins, where the sediment is protected from the effects of winnowing. On the Peru Margin phosphorites were found to be irregularly distributed over the seafloor (Froelich et al, 1988;Baker and Burnett, 1988). As a consequence, recent phosphorite formation on the Oman Margin may have remained unobserved thus far.…”

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confidence: 99%

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Phosphogenesis and active phosphorite formation in sediments from the Arabian Sea oxygen minimum zone

2000

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In this study, porewater chemistry, solid-phase analysis and microscopic observations were combined to evaluate phosphogenesis in three boxcores located within the intensive oxygen minimum zone of the Arabian Sea. Three parameters, namely a decrease of the dissolved phosphate and fluoride concentrations with depth, saturation with respect to carbonate fluorapatite, and the presence of a solid-phase Ca-phosphate mineral, all indicate that phosphogenesis is currently taking place at all three sites. Authigenic apatite precipitation rates vary between 0.076 and 1.04 mmolP cm Ϫ2 yr Ϫ1 , and are of the same order of magnitude as reported for other high productivity areas. Precipitation of an intermediate precursor precedes francolite formation in the continental slope sediments on the Karachi Margin. Results of a diagenetic P model indicate that phosphogenesis is induced by high rates of organic matter degradation. Dissolution of fish debris is likely to provide a substantial additional source of phosphate. Redox iron cycling does not influence phosphogenesis in these environments. Model results suggest that sediment mixing is essential in promoting early diagenetic phosphogenesis. The highest rate of francolite formation was observed in a boxcore taken on the Oman Margin, where it contributes to the formation of a Holocene phosphorite deposit. This observation contrasts with previous reports of only old phosphorites in this area. Phosphorites are presently forming on the Oman Margin as a result of: (a) deposition of older, reworked material from the continental shelf, which has undergone an earlier phase of phosphogenesis; (b) a high input of reactive P (fish debris and degradable organic matter); (c) a relatively low sediment accumulation rate; and (d) the absence of winnowing on this location. Holocene phosphorite deposits may be less common on the Oman Margin than in other coastal upwelling areas because of the narrowness of the shelf and the steepness of the slope, which limit the area where phosphorite formation may occur. ᭧

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Section: Ages Of Apatite Macro Particles In Bc484mentioning

confidence: 53%

mentioning

confidence: 99%

Phosphogenesis and active phosphorite formation in sediments from the Arabian Sea oxygen minimum zone

2000

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“…Uncertainty remains concerning the chemical mechanism by which phosphate is removed from the ocean and into coastal sediment. Phosphorus in sediments exists in three main chemical forms, authigenic minerals Baker and Burnett, 1988;Froelich et al, 1988;Ruttenberg and Berner, 1993;Schuffert et al, 1994Schuffert et al, , 1998, organic form (e.g., Filipek and Owen, 1981) and adsorbed on sediment particles (Krom and Berner, 1981;Sundby et al, 1992;Jensen et al, 1995). Inorganic phosphorus, which is synthesized authigenically in pore water, generally accounts for around 70% of the total reactive phosphorus in marine sediment (Filippelli, 1997).…”

Section: Introductionmentioning

confidence: 99%

“…It is known that some marine phosphate precipitates as a carbonate fluorapatite (CFA) in marine sediment Baker and Burnett, 1988;Froelich et al, 1988;Schuffert et al, 1994Schuffert et al, , 1998. The phosphorus to fluorine (P/F) atomic ratio of CFA has been reported to be in the range 2/1-5/1 (Parker, 1975;Burnett, 1977;Jahnke, 1984;Gulbrandsen et al, 1984;Baker and Burnett, 1988;Froelich et al, 1988).…”

Section: Introductionmentioning

confidence: 99%

“…The phosphorus to fluorine (P/F) atomic ratio of CFA has been reported to be in the range 2/1-5/1 (Parker, 1975;Burnett, 1977;Jahnke, 1984;Gulbrandsen et al, 1984;Baker and Burnett, 1988;Froelich et al, 1988). Although it has been suggested that CFA forms in reductive non-phosphogenic sediment (Sundby et al, 1992;Lyons et al, 1996;Louchouarn et al, 1997), the existence of CFA has not been confirmed in such sediment.…”

Section: Introductionmentioning

confidence: 99%

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Vertical distributions of interstitial phosphate and fluoride in anoxic sediment: Insight into the formation of an authigenic fluoro-phosphorus compound.

2001

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In order to investigate the chemical form of authigenic phosphate compounds being precipitated in coastal sediments, the vertical distributions of dissolved phosphate and fluoride in pore water from the sediments of Funka Bay (Japan) were determined for the period from April 1997 to July 1998. The phosphate concentration in surface sediment pore water was typically 0-5 µM and increased up to 40-60 µM at 70 cm depth below the surface. In spring and summer, small maximums higher than 100 µM were found at a depth of around 20 cm, probably resulting from decomposition of organic matter and/or desorption of phosphate from the ambient sediment particles under anoxic conditions. Seasonal and vertical variations in the fluoride concentration of the pore water were in the range 53-74 µM. We found an inverse relationship between interstitial phosphate and fluoride concentrations, suggesting precipitation of an authigenic fluoro-phosphorus compound with a P/F atomic ratio of around 1/3 in the sediment. Formation of such a compound will greatly contribute to the global sink of phosphate from the ocean.

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Pétrographie et géochimie comparées des pellets phosphatés et de leur gangue dans le gisement phosphaté de Ras-Draâ (Tunisie). Implications sur la genèse des pellets phosphatés

et al. 2010

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The Paleocene-Early Eocene phosphate outcrop in the Ras-Draâ deposit (Tunisia; Fig.1) comprises alternances of P-rich strata (P 2 O 5 ≥ 18%) and P-poor ones (P 2 O 5 ≤ 2%). In phosphate rich strata, P is concentrated in rounded grains -so-called pellets -( 28 % ≤ P 2 O 5 ≤ 38 %) embedded in a matrix -so-called exogangue -much poorer in P (P 2 O 5 # 7%) than pellets. The study of pellets (whose size lies mainly between 100 and 500 µm), of their surrounding matrix and of poorly phosphatic sediments interlayered between the phosphatic strata, has been Microscopic observations of Ras-Draâ phosphorites, added to geochemical results, establish that pellets are small bodies, allochtonous to their matrix and whose composition is independent of that of this matrix. Fecal cylindrical bodies and subspherical pellets, the latest being supposed to proceed from the fecal bodies by fragmentation, are considered to have been formed by fishes, as P-rich and organic matter-rich faeces. These faeces turn out to be resistant to mechanical dispersion and to chemical diffusion of soluble elements from and in direction of sea water. This closeness is responsible for the strong reducing conditions having prevailed inside and during the pellets diagenesis.-3 - ABRIDGED ENGLISH VERSION

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Distribution, texture and composition of modern phosphate pellets in Peru shelf muds

Cited by 18 publications

References 36 publications

Phosphogenesis and active phosphorite formation in sediments from the Arabian Sea oxygen minimum zone

Phosphogenesis and active phosphorite formation in sediments from the Arabian Sea oxygen minimum zone

Vertical distributions of interstitial phosphate and fluoride in anoxic sediment: Insight into the formation of an authigenic fluoro-phosphorus compound.

Pétrographie et géochimie comparées des pellets phosphatés et de leur gangue dans le gisement phosphaté de Ras-Draâ (Tunisie). Implications sur la genèse des pellets phosphatés

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