Determination of Rare Earth Elements in Biological and Mineral Apatite by EPMA and LAMP-ICP-MS

Abstract

Procedures are outlined, and a comparison made for the determination of rare earth elements (REE) in apatite by two separate microanalytical techniques: electron probe microanalysis (EPMA), and laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAMP-ICP-MS). Wellcharacterised, compositionally-homogeneous mineral apatite grains were used as a reference material, bulk REE determinations having previously been made by instrumental neutron activation analysis (INAA). Good agreement was found between the two microanalytical techniques, and with the data by INAA. Detection limits for LAMP-ICP-MS are comparable with INAA (typically 0.5–5 μg/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 contrasting terrestrial depositional environments at Olduvai Gorge (Tanzania), and to modern and fossil fish teeth from marine and freshwater environments. The data indicate that the microdistribution of REE in these biological apatites is not homogeneous, and that the relative abundances of these elements can provide information on the palaeoenvironment during the fossilisation processes.

To whom correspondence shouls be addressed