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. Browser plugins and standalone players
for Flash are widely available but for users that either prefer not to use Flash or are using devices
that do not support it (most notably the iPad) we recently started converting the movies so that
they can also be viewed in browsers that support HTML5.
Open the Movie Selector and choose the layout and number of movies. S-X (entropy-composition)
and T-X (temperature-composition) movies are the larger plots; temperature, melt fraction,
melt productivity and entropy versus pressure are the smaller plots. Plots options, such as binary system,
source type, mixing ratio and melt regime can be applied separately or copied to all plots. Choose
between 'Heterogeneous' (pyroxenite and peridotite source in thermal but not chemical equilibrium) or
'Homogeneous' (a single source with the same bulk composition). A 'Normal' mixing ratio means that the
combined pyroxene and depleted perdotite have a fertile mantle-like composition; 'Low pyroxite' gives
an overall more depleted source and 'High pyroxenite' a more enriched one.
Go straight to the Movie Selector!
Buttons are provided for playing the combined movie in a browser window, downloading the .swf file,
printing (displaying the frame for a chosen pressure, without movie controls, so that the image can be
saved) and saving the query so that the same combination of movies can be revisited without using the
Movie Selector. By default output will be in Flash and, for various reasons, the pages use frames if
possible. The script should detect iPads and adjust accordingly. On any platform, you can also toggle
between using and not using Flash and / or frames manually.
Known bugs and limitations:
- There is no documentation! Basic documentation, including more detail about Movie Selector options
and movie playback controls, will be posted soon. Full explanation, with examples taken from the
available movies, will follow later.
- Only the Fo-En and Fo-Q systems have been updated and converted to non-Flash versions. Other systems
will work in Flash (but not look as nice) and will generate 'file not found' errors in the HTML5 version.
- The combined HTML5 files take a long time to load, especially on mobile devices. Please be patient:
once loaded, playback is only marginally slower than the Flash version.
- On earlier iPads, certain combinations of movies may time out before loaded. Using a layout
with fewer movies, such as the half or quarter page one, will help but these layouts have not been
fully implemented yet. Likewise the HTML5 version does not work properly in IE yet.
- There are some artifacts introduced by the Flash to HTML5 conversion. Most are mild and merely cosmetic
(e.g. dashed lines look odd; some rounded characters appear pixelated; S-X movies in particular
may flicker slightly and occasionally frames are not completely rendered). The most serious artifact
involves curved lines that are 'closed' by a spurious straight line. This is probably a bug in the
Google swiffy code, which otherwise does an impressive job; it may be corrected at some point but
we are also looking for a workaround.
The movie output has been most thoroughly
tested in Chrome, as that is the only browser available on all the platforms that we have access to.
It has been also been checked in Firefox, Safari, Internet Explorer (8 and 9) and Opera, and on Linux,
Mac, Windows (XP and 7) and iPad (2nd and 4th generation) where appropriate.