Phosphate delta-O-18 determination of modern rodent teeth by direct laser fluorination - An appraisal of methodology and potential application to palaeoclimate reconstruction

• Published in: Geochimica et cosmochimica acta 2001-08, Vol.65 (15), p.2535-2553
• Main Authors: Lindars, Elaine S, Grimes, Stephen T, Mattey, David P, Collinson, Margaret E, Hooker, Jerry J, Jones, Tim P
• Format: Article
• Language: English
• ISSN: 0016-7037
• DOI: 10.1016/S0016-7037(01)00606-8

A direct laser-fluorination (DLF) method is presented for phosphate delta-O-18 analysis (mass 1-2 mg). The automated system heats samples in the presence of excess BrF5 using a 25 W CO2 laser, at 10.66 microns. delta-O-18 ratios of the liberated O2 were measured using a dual inlet Optima mass spectrometer. As DLF measures whole apatite oxygen, non-phosphate bound oxygen must be removed by pre-treatment. Two methods were investigated: 1) heating to 1000 C; and 2) heating to 400 C followed by laser fusing. Method 2 is recommended as samples heated to 1000 C showed evidence of oxygen exchange with atmospheric water. To validate the DLF method, and show the potential of rodent teeth in palaeoclimate reconstruction, modern rodent teeth delta-O-18 results from 2 species are presented). Large inter- and intra-jaw heterogeneity indicates that single teeth cannot be used for palaeothermometry. Using equations, derived from lab rodents, an ingested water value of 5.6 +/- 2.2 per mil was calculated for Apodemus salvaticus, only 1.3 per mil lower than measured local water (-4.3 per mil). This suggests that the phosphate delta-O-18 of rodent teeth can be used as a proxy for palaeoclimate reconstruction. (Author)