Authigenic apatite formation and burial in sediments from non-upwelling, continental margin environments
- Yale Univ., New Haven, CT (United States)
Evidence for precipitation of authigenic carbonate fluorapatite (CFA) in Long Island Sound and Mississippi Delta sediments suggests that formation of CFA is not restricted to environments of active coastal upwelling. The authors present porewater data suggestive of CFA formation in both these areas. Application of a sequential leaching procedure, designed specifically to separate authigenic carbonate fluorapatite from other phosphorus-containing phases, including detrital apatite of igneous or metamorphic origin, provides strong supporting evidence for authigenic apatite formation in these sediments. The size of the authigenic apatite reservoir increases with depth, indicating continued formation of CFA during early diagenesis. This depth increase is mirrored by a decrease in solid-phase organic P at both sites, suggesting that CFA is forming at the expense of organic P. Mass balance considerations, application of diagenetic models to intersitital water nutrient data, and the saturation state of the interstitial water are consistent with this interpretation. Diagenetic redistribution of phosphorus among the different solid-phase reservoirs is observed at both sites, and results in near perfect retention of P by these sediments over the depth intervals sampled. Formation of CFA in continental margins which do not conform to the classically defined regions of phosphorite formation renders CFA a quantitatively more important sink than has previously been recognized. Including this reservoir as a newly identified sink for reactive P in the ocean, the residence time of P in the modern ocean must be revised downward. The implication for ancient oceans of CFA formation in continental margin sediments other than phosphorites is that phosphorite formation may be less a representation of episodicity in removal of reactive P from the oceans than of localized concentration of CFA in phosphatic sediments by secondary physical processes. 90 refs., 5 figs., 2 tabs.
- OSTI ID:
- 6573533
- Journal Information:
- Geochimica et Cosmochimica Acta; (United States), Vol. 57:5; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
APATITES
ORIGIN
COASTAL WATERS
SEDIMENTS
CONTINENTAL MARGIN
DEPTH
DIAGENESIS
INTERSTITIAL WATER
LEACHING
LONG ISLAND SOUND
MASS BALANCE
MISSISSIPPI
PHOSPHORITES
PHOSPHORUS
REMOVAL
RETENTION
SATURATION
UPWELLING
WATER
ATLANTIC OCEAN
DEVELOPED COUNTRIES
DIMENSIONS
DISSOLUTION
ELEMENTS
ESTUARIES
GROUND WATER
HYDROGEN COMPOUNDS
MINERALS
NONMETALS
NORTH AMERICA
OXYGEN COMPOUNDS
PHOSPHATE MINERALS
PHOSPHATE ROCKS
ROCKS
SEAS
SEDIMENTARY ROCKS
SEPARATION PROCESSES
SURFACE WATERS
USA
540310* - Environment
Aquatic- Basic Studies- (1990-)