文献类型：期刊文献

英文题名：Distribution and Substitution Mechanism of Ge in a Ge-(Fe)-Bearing Sphalerite

作者：Cook, Nigel J.[1];Etschmann, Barbara[1,2,3];Ciobanu, Cristiana L.[1];Geraki, Kalotina[4];Howard, Daryl L.[5];Williams, Timothy[6];Rae, Nick[2,5];Pring, Allan[3,7];Chen, Guorong[8];Johannessen, Bernt[5];Brugger, Joel[2,3]

机构：[1]Univ Adelaide, Sch Chem Engn, Adelaide, SA 5005, Australia;[2]Monash Univ, Sch Geosci, Clayton, Vic 3800, Australia;[3]S Australian Museum, Adelaide, SA 5000, Australia;[4]Diamond Light Source, Didcot OX11 0QX, Oxon, England;[5]Australian Synchrotron, Clayton, Vic 3168, Australia;[6]Monash Univ, Monash Ctr Electron Microscopy, Clayton, Vic 3800, Australia;[7]Flinders Univ S Australia, Sch Chem & Phys Sci, Adelaide, SA 5000, Australia;[8]E China Univ Sci & Technol, Sch Mat Sci & Engn, Key Lab Ultrafine Mat, Minist Educ, Shanghai 200237, Peoples R China

年份：2015

卷号：5

期号：2

起止页码：117

外文期刊名：MINERALS

收录：;WOS:【SCI-EXPANDED(收录号:WOS:000357152700001)】；

基金：We gratefully acknowledge the Diamond Light Source Synchrotron facility for beamline access and excellent collaboration during our visit to UK (experiment sp7563). Part of this research was undertaken on the XAS and X-ray fluorescence microscopy (XFM) beamlines at the Australian Synchrotron, Victoria, Australia. We sincerely thank Bernhardt Saini-Eidukat and Frank Melcher for making the sample available to us. Rongping Wang (Australian National University (ANU), Canberra, Australia) generously provided the GeSe2 glass sample. The authors acknowledge the use of facilities within the Monash Centre for Electron Microscopy and the use of equipment funded by Australian Research Council (ARC) grant RIEFP99. The manuscript benefitted from the comments from three anonymous reviewers.

语种：英文

外文关键词：synchrotron radiation; XANES spectroscopy (Ge; Fe; Cu K-edges); sphalerite; germanium; oxidation state

摘要：The distribution and substitution mechanism of Ge in the Ge-rich sphalerite from the Tres Marias Zn deposit, Mexico, was studied using a combination of techniques at m- to atomic scales. Trace element mapping by Laser Ablation Inductively Coupled Mass Spectrometry shows that Ge is enriched in the same bands as Fe, and that Ge-rich sphalerite also contains measurable levels of several other minor elements, including As, Pb and Tl. Micron- to nanoscale heterogeneity in the sample, both textural and compositional, is revealed by investigation using Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM) combined with Synchrotron X-ray Fluorescence mapping and High-Resolution Transmission Electron Microscopy imaging of FIB-prepared samples. Results show that Ge is preferentially incorporated within Fe-rich sphalerite with textural complexity finer than that of the microbeam used for the X-ray Absorption Near Edge Structure (XANES) measurements. Such heterogeneity, expressed as intergrowths between 3C sphalerite and 2H wurtzite on [1 1 ($) over bar 0] zones, could be the result of either a primary growth process, or alternatively, polystage crystallization, in which early Fe-Ge-rich sphalerite is partially replaced by Fe-Ge-poor wurtzite. FIB-SEM imaging shows evidence for replacement supporting the latter. Transformation of sphalerite into wurtzite is promoted by (111)* twinning or lattice-scale defects, leading to a heterogeneous ZnS sample, in which the dominant component, sphalerite, can host up to similar to 20% wurtzite. Ge K-edge XANES spectra for this sphalerite are identical to those of the germanite and argyrodite standards and the synthetic chalcogenide glasses GeS2 and GeSe2, indicating the Ge formally exists in the tetravalent form in this sphalerite. Fe K-edge XANES spectra for the same sample indicate that Fe is present mainly as Fe2+, and Cu K-edge XANES spectra are characteristic for Cu+. Since there is no evidence for coupled substitution involving a monovalent element, we propose that Ge4+ substitutes for (Zn2+, Fe2+) with vacancies in the structure to compensate for charge balance. This study shows the utility of synchrotron radiation combined with electron beam micro-analysis in investigating low-level concentrations of minor metals in common sulfides.