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Unusual phosphate concretions related to groundwater flow in a continental environment.

Abstract : Occurrence of phosphate cemented-sandstone concretions in alluvial sand containing archaeological layers implies that they have formed during the last 2000 years. Morphology and petrography of the concretions indicates a relationship with groundwater cementation. The phosphate cement of the concretions consists of concentric isopachous aureoles, about 10 mm thick, that wrap the detrital grains. Aureoles are formed of collophane, the cryptocrystalline or amorphous variety of hydroxyapatite. Geochemical modeling indicates that the apatite cement likely results from the leaching of a preexisting phosphate deposit (bones?) in an acidic soil environment and the precipitation of dissolved phosphate under pH control at the mixing zone of down-moving soil-water with the calcite-saturated groundwater.
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https://hal-mines-paristech.archives-ouvertes.fr/hal-00646828
Contributor : Médard Thiry <>
Submitted on : Wednesday, November 30, 2011 - 5:59:04 PM
Last modification on : Friday, November 13, 2020 - 3:30:07 AM

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Médard Thiry, Jean Galbois, Jean-Michel Schmitt. Unusual phosphate concretions related to groundwater flow in a continental environment.. Journal of Sedimentary Research, Society for Sedimentary Geology, 2006, 76, pp.866-870. ⟨10.2110/jsr.2006.067⟩. ⟨hal-00646828⟩

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