Characterization of Germanium Speciation in Sphalerite (ZnS) from Central and Eastern Tennessee, USA, by X-ray Absorption Spectroscopy

Julien Bonnet (1, 2) , Jean Cauzid (1) , Denis Testemale (3) , Isabelle Kieffer (4) , Olivier Proux (4) , Andrei Lecomte (1) , Laurent Bailly (2)

1 GeoRessources
2 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
3 NEEL - MRS - Matériaux, Rayonnements, Structure
4 OSUG - Observatoire des Sciences de l'Univers de Grenoble

X-ray absorption near edge structure (XANES) spectroscopy was used on zoned sphalerites (ZnS) from two world-class Mississippi Valley Type deposits, the Central and Eastern Tennessee Mining district, USA, in order to investigate germanium oxidation states. Due to the low germanium concentrations of these samples, it was necessary to perform the X-ray absorption spectroscopy (XAS) in fluorescence mode. The overlapping of the Zn Kalpha and Ge Kalpha emission lines meant that a high energy-resolution was required. This was achieved using crystal analyzers and allowed a bandwidth of 1.3 eV to be obtained. Experimental spectra were compared to XANES calculations and three configurations of germanium incorporation into sphalerite were identified. The first two, the most prevalent, show germanium (II) and (IV) surrounded by sulfur atoms in tetrahedral coordination, suggesting the replacement of Zn by Ge. In the third configuration, germanium (IV) is surrounded by oxygen atoms. This third configuration is unexpected for a zinc sulfide mineral and it resembles that of argutite (GeO2).

Domaines: Géochimie

Julien Bonnet, Jean Cauzid, Denis Testemale, Isabelle Kieffer, Olivier Proux, et al.. Characterization of Germanium Speciation in Sphalerite (ZnS) from Central and Eastern Tennessee, USA, by X-ray Absorption Spectroscopy. Minerals, 2017, 7 (5), pp.79. ⟨10.3390/min7050079⟩. ⟨hal-01630859⟩