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

Minerals

Béatrice Luais¹  Olivier Mathon²  Manuel Munoz³  Rémi Belissont⁴  Marie-Christine Boiron⁴ 

[1] 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;European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble, France;Geosciences Montpellier, Université de Montpellier, CNRS,CEDEX 5, 34095 Montpellier, France;Université de Lorraine, CNRS, GeoRessources, F-54000 Nancy, France;

关键词: micro-XANES;    micro-XRF;    Cu-bearing sulfides;    germanium;   

DOI  :  10.3390/min9040227

来源: DOAJ

【 摘 要 】

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.

【 授权许可】

Unknown