Department of Geology and Geophysics, University of Utah, 135 S. 1460 E. Rm 719, Salt Lake City, UT 84112, USA.
Rapid Commun Mass Spectrom. 2007;21(17):2853-9. doi: 10.1002/rcm.3149.
The oxygen isotope ratio of CO(2) liberated from structural carbonate in tooth enamel apatite was measured at phosphoric acid reaction temperatures of 25 degrees C, 60 degrees C and 90 degrees C, and it was found that apparent acid fractionation factors for pristine enamel, fossilized enamel, and calcite follow different temperature relationships. Using sealed vessel reactions normalized to alpha(25) = 1.01025 (the fractionation factor for calcite at 25 degrees C), the apparent fractionation factor at 90 degrees C (alpha*(90)) for pristine enamel ranged between 1.00771 and 1.00820, and between 1.00695 and 1.00772 for fossilized enamel. Apparent fractionation factors for common acid bath reactions are similar to those for sealed vessel reactions. A significant correlation exists between alpha*(90) and F(-) content, suggesting that change in the acid fractionation factor may be related to the replacement of OH(-) with F(-) during fossilization of bioapatite. These results have important implications for making accurate comparisons between modern and fossil tooth enamel delta(18)O values, and for the uniformity of isotope data produced in different laboratories using different acid reaction temperatures.
从牙釉质磷灰石结构碳酸盐中释放出的 CO2 的氧同位素比值在 25°C、60°C 和 90°C 的磷酸反应温度下进行了测量，结果发现原始牙釉质、化石牙釉质和方解石的表观酸分馏因子遵循不同的温度关系。使用密封容器反应归一化到 alpha(25) = 1.01025（25°C 时方解石的分馏因子），原始牙釉质在 90°C 时的表观分馏因子（alpha*(90)）在 1.00771 到 1.00820 之间，化石牙釉质在 1.00695 到 1.00772 之间。常见酸浴反应的表观分馏因子与密封容器反应的类似。alpha*(90)与 F(-)含量之间存在显著相关性，表明酸分馏因子的变化可能与生物磷灰石化石过程中 OH(-)被 F(-)取代有关。这些结果对在不同实验室使用不同酸反应温度生成的现代和化石牙釉质 delta(18)O 值之间进行准确比较以及同位素数据的一致性具有重要意义。
