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| Titel |
Hydrothermal fluoride and chloride complexation of indium: an EXAFS study |
| VerfasserIn |
Anselm Loges, Denis Testemale, Simo Huotari, Ari-Pekka Honkanen, Vasily Potapkin, Thomas Wagner |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250141842
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| Publikation (Nr.) |
 EGU/EGU2017-5392.pdf |
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| Zusammenfassung |
| Indium (In) is one of the geochemically lesser studied ore metals, and the factors that
control the hydrothermal transport and deposition are largely unknown. It has no
ore deposits of its own and is commonly mined as a by-product of Zn ores, and
there are very few minerals that contain In as an essential structural component.
Recently, industrial application of In in touch screen devices has drastically increased
demand, which is projected to exceed supply from the current sources in the near
future. Since the most relevant In sources are hydrothermal sphalerite ores and to a
lesser extent hydrothermal greisen-type deposits in evolved granitic plutons, the
aqueous geochemistry of In is of particular interest for understanding its ore forming
processes.
As a first step towards a comprehensive model for hydrothermal In solubility and
speciation, we have studied In speciation in fluoride and chloride bearing solutions at 30-400˚
C and 500 bar using X-Ray Absorption Spectroscopy (XAS) measurements. The experiments
were conducted in a unique hydrothermal autoclave setup at beamline BM30B–FAME at the
European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Our results show
that the complexation of In changes dramatically between 30 and 400˚ C. Below
ca. 200˚ C, fluoride complexes are the most stable ones, but they break down at
higher temperatures. Chloride complexes on the other hand become increasingly
stable with increasing temperature. This behavior has interesting consequences for
natural ore forming systems. In Cl-rich systems (e.g. massive sulfide ores formed in
sea floor environments), cooling can be an effective precipitating mechanism. In
F-rich systems, fluoride complexation can extend In mobility to low temperatures
and In will only precipitate when F is effectively removed from the fluid, e.g. by
mixing with a Ca-rich fluid and precipitation of fluorite (CaF2) as is commonly
observed in skarn or greisen-type deposits. Due to In complexing with both F and
Cl, depending on temperature, In distribution also has great potential as a fluid
chemistry/temperature indicator in a wide range of different hydrothermal ore-forming
systems. |
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