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Germanium Crystal Chemistry in Cu-Bearing Sulfides from Micro-XRF Mapping and Micro-XANES Spectroscopy

Université de Lorraine, CNRS, GeoRessources, F-54000 Nancy, France
Centre de Recherches Pétrographiques et Géochimiques (CRPG), Université de Lorraine, CNRS, UMR 7358, 15 Rue Notre Dame des Pauvres, BP 20, CEDEX, F-54501 Vandoeuvre-lès-Nancy, France
Geosciences Montpellier, Université de Montpellier, CNRS, CEDEX 5, 34095 Montpellier, France
European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble, France
Author to whom correspondence should be addressed.
Minerals 2019, 9(4), 227;
Received: 18 March 2019 / Revised: 8 April 2019 / Accepted: 9 April 2019 / Published: 12 April 2019
Germanium is considered a critical element, with a demand that has sharply increased due to booming high-technology industries. To understand Ge incorporation mechanisms in natural systems, we investigate Ge speciation in Cu-bearing sulfide minerals using synchrotron X-ray fluorescence (XRF) chemical mapping and Ge K-edge µ-X-ray absorption near-edge structures (µ-XANES) spectroscopy. The samples investigated include (i) a homogeneous chalcopyrite from the Kipushi polymetallic deposit (Central African copperbelt, D.R. Congo) and (ii) a zoned Ge-rich chalcopyrite from the Barrigão Cu deposit (Iberian pyrite belt, Portugal). First, our spectroscopic analysis supports the occurrence of tetrahedrally-coordinated Ge4+ in chalcopyrite, independently from origins or zoning patterns observed for these minerals. Then, based on statistical analyses of XRF chemical maps, we demonstrate that tetravalent germanium most likely incorporates chalcopyrite through the Fe crystallographic site via coupled substitutions with the following form: (2x + 3y)Fe3+ ⟷ (x + 2y)(Ge,Sn)4+ + x(Zn,Pb)2+ + y(Cu,Ag)+, although the presence of lattice vacancies cannot be completely excluded. View Full-Text
Keywords: micro-XANES; micro-XRF; Cu-bearing sulfides; germanium micro-XANES; micro-XRF; Cu-bearing sulfides; germanium
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Belissont, R.; Munoz, M.; Boiron, M.-C.; Luais, B.; Mathon, O. Germanium Crystal Chemistry in Cu-Bearing Sulfides from Micro-XRF Mapping and Micro-XANES Spectroscopy. Minerals 2019, 9, 227.

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