T9.3 : Metallic ore mineral studies; Comparing analyses of natural and synthetic minerals with ab initio calculations:
There is a disagreement between the iron isotopic measurements performed on ore hydrothermal minerals (pyrite and hematite, in particular), the parametric calculations derived from Mössbauer spectroscopy and INRXS (Polyakov and Mineev, 2000, Polyakov et al., 2007), and our ab initio calculations (Blanchard et al., 2009, 2012). For this reason, we conduct experimental studies aiming at precipitating oxides and sulphides under well characterized hydrothermal conditions in order to provide reference isotopic fractionation factors (Saunier et al., 2011). Moreover, it is necessary to develop methods for in situ isotope measurements, coupling femtosecond laser ablation and MC-ICP-MS* to study the isotopic zonation in the vicinity of mineral interfaces to understand the mechanisms of isotopic exchange between minerals. Ultrafast laser ablation based on femtosecond pulses is essential to make precise and accurate in situ iron isotope measurements (Horn et al., 2006). Finally, computing the isotopic fractionation factors between mineral and aqueous species remains a challenge for non-traditional isotopes and our theoretical efforts are focused in this direction. The ultimate goal is to build a correct theory to predict the fractionation of stable isotopes of iron at various temperatures between the main mineral phases and aqueous species for studying geological issues such as the genesis of metal deposit genesis or of ancient sediments.
*MC-ICP-MS: Multicollector-Inductively Coupled Plasma-Mass Spectrometry