In Situ Analysis of Non-Traditional Isotopes by SIMS and LA–MC–ICP–MS: Key Aspects and the Example of Mg Isotopes in Olivines and Silicate Glasses

Abstract

Isotopic variation for traditional elements (H, C, N, O and S) has been widely used in the past 40 years in Earth and planetary sciences to study many processes with an emphasis on environments where fluids are present (e.g., Valley and Cole 2011). More recent developments have allowed high-precision measurements of isotope ratios of what has been called non-traditional elements (i.e., Mg, Si, Fe, Zn, Cu, Mo), which are usually less fractionated than traditional elements by at least an order of magnitude (see this volume). These non-traditional stable isotopes can give insights on processes where fluids are not present (e.g., metal–silicate fractionation, e.g., Georg et al. 2007 and review by Poitrasson et al. 2017, this volume), evaporation processes during planetary formation (e.g., Paniello et al. 2012, Wang and Jacobsen 2016, and review by Moynier et al. 2017 this volume), igneous differentiation (e.g., Williams et al. 2009; Sossi et al. 2012; and review by Dauphas et al. 2017, this volume), and on biological processes (e.g., Walczyk and von Blanckenburg 2002, and review by Albarede et al. 2017 this volume). Among all these non-traditional isotopic systems, Mg isotopes are of major importance because (i) Mg is a major constituent of the silicate portion of planetary bodies, (ii) Mg has more than two isotopes (24Mg, 25Mg and 26Mg) allowing to study processes leading to various types of mass fractionation (Young et al. 2002; Young and Galy 2004; Davis et al. 2015) and (iii) 26Mg excesses produced by the radioactive decay of short-lived 26Al (T1/2=0.73 Ma) (Lee et al. 1976) are a key tool for early Solar system chronology (see reviews by Dauphas and Chaussidon 2011; Chaussidon and Liu 2015). Note that in addition, significant Mg isotopic …