Gerhard,
To my knowledge, the only fractionation data available for jarosites and
alunites are in the following publications:

Rye RO, Stoffregen RE (1995) Jarosite-water oxygen and hydrogen isotope
fractionations: preliminary experimental data.  Economic Geology 90:
2336-2342.

Stoffregen RE, Rye RO, Wasserman MD (1994) Experimental studies of alunite:
   I. 18O-16O and D-H fractionation factors between alunite and water at
   250-450 °C.  Geochimica et Cosmochimica Acta 58: 903-916.
Bob
   _______________________________________________________
   Robert R (Bob) Seal, II
   US Geological Survey
   954 National Center
   Reston, VA 20192
   703.648.6290 office
   703.648.6383 fax
   [log in to unmask]












                    Gerhard Strauch
                    <[log in to unmask]        To:     [log in to unmask]
                    Z.DE>                  cc:
                    Sent by: Stable        Subject:     water of crystallisation - isot
                    Isotope                fractionation
                    Geochemistry
                    <ISOGEOCHEM@LIS
                    T.UVM.EDU>


                    07/13/00 12:04
                    PM
                    Please respond
                    to Stable
                    Isotope
                    Geochemistry





Dear Isogeochemists,
isotopic fractionation (D and O) of water of crystallisation of various
salts has been investigated very well (for instances: gypsum: Fontes &
Gonfiantini, 1967; mirabilite: Stewart, 1974; Sofer & Gat, 1972 from
aqueous salts). O-isotope effect of goethite and iron oxide (Fe2O3) is
reported by Yapp, GCA 1990.
However, does anybody know references about isotope fractionation (D and/or
O between "mother solution" and OH-water) in Fe-hydroxy-sulfato complexes
(i.e. jarosite [(Me2Fe+++6(OH)12(SO4)4] or similar minerals)? These
Fe-minerals are mostly stable only at pH < 3. Therefore, investigations
seem to be rare.
Thanks in advance.
Gerhard Strauch
***************************