A microbeam XAFS study of aqueous chlorozinc complexing to 430°C in fluid inclusions from the knaumühle granitic pegmatite, saxonian granulite massif, Germany

Abstract

The synchrotron X-ray microprobe (X26A) at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory was used to collect zinc K-edge absorption spectra from saline (ca. 36 wt% NaCl equiv.) fluid inclusions in quartz from the Knaumühle granitic pegmatite, in the Saxonian Granulite Massif, Germany, at temperatures ranging between 30° and 430°C. XAFS spectra were also obtained from one fluid inclusion that was experimentally re-equilibrated at a high pressure of hydrogen. The temperature of the fluid inclusions was controlled during analysis with a programmable heating stage. Analysis of the XAFS data shows that ZnCl42- is the dominant aqueous zinc species in the fluid inclusions up to the average trapping temperature (430°C). Furthermore, the mean Zn-Cl bond length decreases uniformly from 2.31 ± 0.01 Å at room temperature to 2.26 ± 0.02 Å at 430°C. The predominance of the tetrahedral chlorocomplex, rather than ZnCl20, at high temperatures is most probably due to the high chloride concentrations of the inclusion brine.

Department(s)

Physics, Astronomy, and Materials Science

Document Type

Article

Keywords

Chlorozinc complex, Fluid inclusion, Granitic pegmatite, Hydrothermal fluid, Metalliferous brine, Synchrotron X-ray fluorescence, Synchrotron X-ray microprobe, X-ray absorption fine structure

Publication Date

12-1-1998

Journal Title

Canadian Mineralogist

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