Raman spectroscopy of fossil bioapatite - A proxy for diagenetic alteration of the oxygen isotope composition

Thomas D.B. ; McGoverin C.M. ; Fordyce R.E. ; Frew R.D. ; Gordon K.C. (2011)


Fossil bioapatite may yield biogeochemical signals of paleoenvironments captured by living organisms. Bioapatite may be diagenetically altered, however, with ions added or removed post-mortem; such change is typically assessed using destructive and demanding techniques. Here, Raman spectroscopy is used as a rapid and non-destructive way to identify significant diagenetic alteration of fossil bioapatite. We found spectral parameters of phosphate symmetric stretching (μ1-PO43-) to be very sensitive to variations in apatite chemistry, particularly with respect to common diagenetic components (CO32-, F-, Sr2+). The Raman spectral parameters were subsequently applied to a set of modern (biogenic) and geologic (magmatic) apatite samples as potential endmembers for diagenetic alteration. Raman spectra were also collected from enamel and dentin (respectively resistant vs. alteration-prone) of fossil teeth. Phosphate-oxygen isotopic values from the same enamel-dentin samples were used as an index of alteration and provided definition of Raman spectral parameters as relates to diagenetic alteration. Diagenetically altered samples were characterised by spectra with μ1-PO43- widths (at half maximum height) less than 13.0cm-1, and μ1-PO43- band positions greater than 964.7cm-1. Raman spectroscopy is shown to have potential as a tool for pre-screening fossil apatite samples before further analyses. © 2011 Elsevier B.V.

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