title: Probing atomic scale transformation of fossil dental enamel using Fourier transform infrared and nuclear magnetic resonance spectroscopy: a case study from the Tugen Hills (Rift Gregory, Kenya).
abstract: A series of fossil tooth enamel samples was investigated by Fourier transform infrared (FTIR) spectroscopy, (13)C and (19)F magic-angle spinning nuclear magnetic resonance (MAS NMR) and scanning electron microscopy (SEM). Tooth remains were collected in Mio-Pliocene deposits of the Tugen Hills in Kenya. Significant transformations were observed in fossil enamel as a function of increasing fluorine content (up to 2.8wt.%). FTIR spectroscopy revealed a shift of the ν1 PO4 stretching band to higher frequency. The ν2 CO3 vibrational band showed a decrease in the intensity of the primary B-type carbonate signal, which was replaced by a specific band at 864cm(-1). This last band was ascribed to a specific carbonate environment in which the carbonate group is closely associated to a fluoride ion. The occurrence of this carbonate defect was consistently attested by the observation of two different fluoride signals in the (19)F NMR spectra. One main signal, at ∼-100ppm, is related to structural F ions in the apatite channel and the other, at -88ppm, corresponds to the composite defect. These spectroscopic observations can be understood as resulting from the mixture of two phases: biogenic hydroxylapatite (bioapatite) and secondary fluorapatite. SEM observations of the most altered sample confirmed the extensive replacement of the bioapatite by fluorapatite, resulting from the dissolution of the primary bioapatite followed by the precipitation of carbonate-fluorapatite. The ν2 CO3 IR bands can be efficiently used to monitor the extent of this type of bioapatite transformation during fossilization.
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, UMR CNRS 7590, UMR IRD 206, Institut de Minéralogie et de Physique des Milieux Condensés (IMPMC), 4 place Jussieu, 75252 Paris, cedex 05, France.
authors.forename: Haohao
authors.initials: H
authors.lastname: Yi
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, UMR CNRS 7590, UMR IRD 206, Institut de Minéralogie et de Physique des Milieux Condensés (IMPMC), 4 place Jussieu, 75252 Paris, cedex 05, France. Electronic address: etienne.balan@impmc.upmc.fr.
authors.forename: Etienne
authors.initials: E
authors.lastname: Balan
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, CNRS UMR 7574, Laboratoire de Chimie de la Matière Condensée de Paris, Collège de France, 11, Place Marcelin Berthelot, 75005 Paris, France.
authors.forename: Christel
authors.initials: C
authors.lastname: Gervais
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, UMR CNRS 7193 Institut des Sciences de la Terre Paris (ISTeP), 4 place Jussieu, 75252 Paris, cedex 05, France.
authors.forename: Loïc
authors.initials: L
authors.lastname: Ségalen
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, UMR CNRS 7193 Institut des Sciences de la Terre Paris (ISTeP), 4 place Jussieu, 75252 Paris, cedex 05, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Roche
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, UMR CNRS 7193 Institut des Sciences de la Terre Paris (ISTeP), 4 place Jussieu, 75252 Paris, cedex 05, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Person
authors.affiliation: CNRS, CEMHTI UPR3079, Univ. Orléans, F-45071 Orléans, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Fayon
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, UMR CNRS 7590, UMR IRD 206, Institut de Minéralogie et de Physique des Milieux Condensés (IMPMC), 4 place Jussieu, 75252 Paris, cedex 05, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Morin
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, CNRS UMR 7574, Laboratoire de Chimie de la Matière Condensée de Paris, Collège de France, 11, Place Marcelin Berthelot, 75005 Paris, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Babonneau
mesh_terms: D000818:Animals; D001031:Apatites / Q000737:chemistry; D066241:Carbon-13 Magnetic Resonance Spectroscopy; D003460:Crystallization; D003743:Dental Enamel / Q000737:chemistry* / Q000648:ultrastructure; D005580:Fossils; D007630:Kenya; D009682:Magnetic Resonance Spectroscopy; D017550:Spectroscopy, Fourier Transform Infrared; D014732:Vibration
chemical_list: D001031:Apatites
keywords: Bioapatite; Carbonate defect; FTIR spectroscopy; Fossil enamel; MAS NMR spectroscopy