Stable isotope compositions of a suite of magmatic amphiboles from
alkaline basalts and andesitic rocks were examined to constrain the
effects of degassing processes on the hydrogen isotope compositions. The
Fe3+ (as Fe3+/Fe-total) and H2O contents, as well as the H isotope
compositions of the amphiboles, differ markedly (27-58%, 0.5-2.2 wt%,
-107 to -15 parts per thousand, respectively) but indicate systematic
variations. The observed trends can be explained either as
dehydrogenation or dehydration processes, both of which are coupled to
oxidation processes, the latter most probably related to O2-
substitution within amphiboles. The dehydrogenation-dehydration models
can be used to assess the primary compositions of the magmas. As an
important example, delta D values of amphiboles of Martian meteorites
are discussed in a similar context. Copyright (c) 2006 John Wiley &
Sons, Ltd.