DETERMINATION OF RARE-EARTH ELEMENTS IN BIOLOGICAL AND MINERAL APATITE BY EPMA AND LAMP-ICP-MS

Procedures are outlined, and a comparison made for the determination o f rare earth elements (REE) in apatite by two separate microanalytical techniques: electron probe microanalysis (EPMA), and laser ablation m icroprobe-inductively coupled plasma-mass spectrometry (LAMP-ICP-MS). Well-characterised, compositionally-homogeneous mineral apatite grains were used as a reference material, bulk REE determinations having pre viously been made by instrumental neutron activation analysis (INAA). Good agreement was found between the two microanalytical techniques, a nd with the data by INAA. Detection limits for LAMP-ICP-MS are compara ble with INAA (typically 0.5-5 mu g/g in the apatite matrix), and are generally 1 to 2 orders of magnitude better than EPMA. The techniques were applied to the microanalysis of fossilised bone recovered from co ntrasting terrestrial depositional environments at Olduvai Gorge (Tanz ania), and to modern and fossil fish teeth from marine and freshwater environments. The data indicate that the microdistribution of REE in t hese biological apatites is not homogeneous, and that the relative abu ndances of these elements can provide information on the palaeoenviron ment during the fossilisation processes.