Work in the latter part of the 1980s yielded the hypothesis that ocean ridge
basalts are
the end product of near-fractional, adiabatic melting processes occurring in
the upper
mantle beneath ocean ridges. Quantitative modelling of this process had,
however,
remained an elusive goal. A general synthesis of the phase equilibria
constraints
available up to that point to constrain the origin of ocean floor basalts
was presented by
Hess [1992]. Kinzler and Grove [1992a] and Walter and
Presnall [1994]
presented new data relevant for modeling lherzolite melting. Niu and
Batiza [1991]
presented a method for calculating major element compositions of melts from
peridotites as
a function of changing pressure. Kinzler and Grove [1992a,b] and
Langmuir et
al. [1992] presented methods for calculating the major element compositions
of melts from
peridotite as a function of changing pressure and source composition.
Compositional
information on melt fractions of peridotite previously unattainable were
presented by
Baker and Stolper [1994]. These authors used an innovative experimental
technique for
isolating small percent melts from peridotite by impregnating the peridotite
with diamonds
to create a small fraction of pore space in which the small melt fractions
pool. This
technique provides data that will enable us to fine-tune our ability to
accurately model
processes of near-fractional melting. Progress has also been made in our
efforts to
quantify the effects of crystallization and other magma modification
processes that occur
to mantle-derived magma as it is transported and cooled to form oceanic
crust [ Grove et al., 1992; Langmuir et al., 1992].