Towards the development of a fossil bone geochemical standard: An inter-laboratory study

Abstract

Ten international laboratories participated in an inter-laboratory comparison of a fossil bone composite with the objective of producing a matrix and structure-matched reference material for studies of the bio-mineralization of ancient fossil bone. We report the major and trace element compositions of the fossil bone composite, using in-situ method as well as various wet chemical digestion techniques. For major element concentrations, the intra-laboratory analytical precision (%RSD r) ranges from 7 to 18%, with higher percentages for Ti and K. The %RSD r are smaller than the inter-laboratory analytical precision (%RSD R; <15–30%). Trace element concentrations vary by ∼5 orders of magnitude (0.1 mg kg −1 for Th to 10,000 mg kg −1 for Ba). The intra-laboratory analytical precision %RSD r varies between 8 and 45%. The reproducibility values (%RSD R) range from 13 to <50%, although extreme value >100% was found for the high field strength elements (Hf, Th, Zr, Nb). The rare earth element (REE) concentrations, which vary over 3 orders of magnitude, have %RSD r and %RSD R values at 8–15% and 20–32%, respectively. However, the REE patterns (which are very important for paleo-environmental, taphonomic and paleo-oceanographic analyses) are much more consistent. These data suggest that the complex and unpredictable nature of the mineralogical and chemical composition of fossil bone makes it difficult to set-up and calibrate analytical instruments using conventional standards, and may result in non-spectral matrix effects. We propose an analytical protocol that can be employed in future inter-laboratory studies to produce a certified fossil bone geochemical standard.