High resolution rare-earth elements analyses of natural apatite and its application in geo-sciences: Combined micro-PIXE, quantitative CL spectroscopy and electron spin resonance analyses

The rare-earth element (REE) distribution in natural apatite is analysed by micro-PIXE, cathodoluminescence (CL) microscopy and spectroscopy and elect ron spin resonance (ESR) spectroscopy. The micro-PIXE analyses of an apatit e crystal from Cerro de Mercado (Mexico) and the summary of 20 analyses of six francolite (conodonts of Triassic age) samples indicate that most of th e REEs are enriched ill apatite and francolite comparative to average shale standard (NASC). The: analyses of fossil francolite revealing the REE-dist ribution not to be in balance with the REE-distribution of seawater and fis h bone debris. Strong inhomogenous lateral REE-distribution in fossil conod ont material is shown by CL-mapping and most probably not being a vital eff ect. Therefore. the resulting REE-signal from fossil francolite is the sum of vital and post-mortem incorporation. The necessary charge compensation f or the substitution of divalent Ca by trivalent REE being done by different kind of electron defects and defect ions. (C) 2000 Elsevier Science B.V. A ll rights reserved.