This suite of binary phase diagram ‘movies’ can be used to understand the energetic balances
controlling isentropic melt productivity of coexisting pyroxenite and peridotite sources that are in
thermal but not chemical equilibrium. Scripts allow movies for multiple plots (e.g. S-X, P-T and melt
fraction versus pressure) to be viewed and controlled simultaneously. The user may choose between many
different systems, homogeneous or heterogeneous sources, with variable mixing proportions, and batch or
fractional melting regimes.
The solid and liquid phases used in the thermodynamic calculations are based on end-member phases
in the MELTS database, with some tweaks for extrapolation to high enough pressures to freeze the
'pyroxenite' source. All the binary systems (e.g. forsterite-enstatite, forsterite-quartz) are simplified
in the sense that sub-solidus reactions that do not affect melting at the compositions of interest are ignored.
Some systems, such as olivine-orthopyroxene, are constructed in way that is not totally realistic for the phases
involved but rather mimics the behavior of mantle lithologies as a whole (e.g. limited solid solution
between olivine and opx allows the model 'peridotite' and 'pyroxenite' to melt simultaneously, albeit briefly).
Systems labelled as 'simplified' are further adjusted so that solidii of the constituent phases are sub-parallel
so that competing effects on the melt productivity may be separated.
In Smith et al. 2003, we presented preliminary calculations on the energetics of melting of
peridotite-pyroxenite ‘marble-cake’ mantle, in the limit of chemical isolation but thermal
equilibrium between the lithologies. The strongest result was that sorting a given bulk composition
into different lithologies cannot yield large amounts of extra melt production compared to melting the
uniform source, although the balance of contributions from high pressure (eclogite) and low pressure
(peridotite) melts is perturbed. Following the approach established in Asimow et al. (1995; 1997) and
Asimow & Stolper (1999) we showed that this is the case both in the natural system (using an
extension of Adiabat_1ph that we are currently incorporating into libalphaMELTS) and in carefully
constructed binary systems.
Originally the files were in QuickTimeTM format and composite movies were assembled manually
but the large file sizes involved did not lend themselves well to presentation. As part
of the original development of the MAGMA website, all the binary phase diagrams were remade in Flash
format and CGI scripts were written to control movie playback. At the time, browser plugins and standalone
players were widely available but, as some devices did not support Flash (most notably the iPad)
we started converting the movies using Google's Swiffy tool (now no longer available).
Go straight to the Movie Selector!
Adobe recently announced that they will withdraw support for Flash in 2020. We are working on a new
movie server that will not use Flash during playback at all. In the meantime, we have installed Mozilla's
Shumway on the server side so that you may view movies as HTML5 objects instead. If you would like to be able
to use the movie controls, but you prefer not to install the Flash plugin, then we recommend downloading
Google Chrome (or using Microsoft Edge, if available). Chrome and Edge have built-in Flash players, and you can
choose to restrict Flash to certain sites. Composite movies with full controls, which may
be played off-line, are also available. Please see the Documentation page, linked to the right, for more
details on these and other options.
