OXYGEN-ISOTOPE PARTITIONING BETWEEN PHOSPHATE AND CARBONATE IN MAMMALIAN APATITE

The oxygen isotope compositions of phosphate and structural carbonate in mammalian enamel and bone apatite are Linked to that of body water at constant body temperature near 37 degrees C, but the isotope system atics of oxygen in structural carbonate are not well understood. Using coupled measurements of the oxygen isotope composition of structural carbonate and phosphate from horse tooth enamel, the apparent oxygen i sotope fractionation factor between structural carbonate and body wate r is estimated to be 1.0263 +/- 0.0014. These estimates provide a quan titative basis for using the oxygen isotope composition of structural carbonate in mammalian biogenic apatite for ecological, climatological , and physiological reconstruction.