Indium and Antimony Distribution in a Sphalerite from the “Burgstaetter Gangzug” of the Upper Harz Mountains Pb-Zn Mineralization

Thomas Schirmer,Peter Felfer,Wilfried Ließmann,Chandra Macauley

doi:10.3390/min10090791

Thomas Schirmer, Peter Felfer + Show 2 more

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https://doi.org/10.3390/min10090791

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Abstract

The sphalerite from the Burgstaetter Gangzug, a vein system of the Upper Harz Mountain nearby the town of Clausthal-Zellerfeld, exhibits a very interesting and partly complementary incorporation pattern of Cu, In and Sb, which has not yet been reported for natural sphalerite. A sphalerite specimen was characterized with electron probe micro-analysis (EPMA) and atom probe tomography (APT). Based on the EPMA results and a multilinear regression, a relation expressed as Cu = 0.98In + 1.81Sb + 0.03 can be calculated to describe the correlation between the elements. This indicates, that the incorporation mechanisms of In and Sb in the structure differ substantially. Indium is incorporated with the ratio Cu:In = 1:1 like in roquesite (CuInS2), supporting the coupled substitution mechanism 2Zn2+ → Cu+ + In3+. In contrast, Sb is incorporated with a ratio of Cu:Sb = 1.81:1. APT, which has a much higher spatial resolution indicates a ratio of Cu: Sb = 2.28: 1 in the entire captured volume, which is similar to the ratio calculated by EPMA, yet with inhomogeneities at the nanometer-scale. Analysis of the solute distribution shows two distinct sizes of clusters that are rich in Cu, Sb and Ag.

Highlights

Compositional results determined by electron probe micro-analysis (EPMA) are presented first, followed by the atom probe tomography (APT)
The element composition was assessed via EPMA through a qualitative peak search throughout the sample and the following elements were found in significant concentrations: S, Fe, Cu, Zn, Cd, In and Sb
Compositional results determined by EPMA are presented first, followed by the APT characterization

Summary

Introduction

As elements like indium (In) and antimony (Sb) are essential for production of light-emitting diodes (LEDs) and laser diodes (in InGaN or InGaP), thin films for liquid-crystal displays (LCD, in indium tin oxide (ITO)) or for semiconductor applications (In, Sb), the sources of these elements are becoming more and more important. An understanding of the geochemistry of these elements is increasingly of interest. During the last years in the Harz Mountain region, efforts have been made to assess the availability of In in tailings of the Rammelsberg mine site. One topic of the investigations was the incorporation, concentration and distribution of In within the different mineral compounds of these tailings (pyrite, chalcopyrite, sphalerite, galena, barite). Sphalerite turned out to be the most promising candidate for In-enrichment (see Section 1.2)

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