Apatite Composition and the Fugacities of HF and HCl in Metamorphic Fluids

Bruce W. D. Yardley*
Department of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ
*Present address: Department of Earth Sciences, The University, Leeds LS2 9JT.

Abstract: Microprobe analyses of the halogen contents of apatites from two samples of amphibolite-facies schist from Connemara, Ireland, have been used to calculate the fugacity ratios fHCl/fH2O and fHF/fH2O using the experimental data of Korzhinskiy. The results imply fugacities for both acids in the range 0.03 to 0.1 bars, but whereas for the lower grade rock fHF > fHCl, the migmatitic sample gives fHF⋍fHCl. An independent estimate of fHF/fH2O from the biotite composition in one sample is in acceptable agreement with the result obtained from apatite.

Keywords: apatite • halogens • metamorphic fluid • schist • Connemara • Ireland

Mineralogical Magazine; March 1985 v. 49; no. 350; p. 77-79; DOI: 10.1180/minmag.1985.049.350.10
© 1985, The Mineralogical Society
Mineralogical Society (www.minersoc.org)