Hello everyone!
I am working on migmatites which are charcatreized by crystallisation
of garnet formed by melting reaction of biotite, sillimanite and quartz
at peak metamorphic conditions (700-750, 4-5Kbar), followed by
crystallisation of corona of cordierite around
garnet during the decompression stage.
I noticed on the field the presence of small (few cm) patchs of
leucosomes composed of cordierite, Kfs, plagioclase and quartz with
some rare biotites. It
seems to me that these patchs are generated by partial melting of
biotite, sillimanite, quartz during decompression stage.
My questions are,
1-If partial melting has occured also during decompression (not only at
peak conditions), what could this mean in term of tectonic evolution
of these migmatites???
2-What could be the difference in the tectonic forming processes if we
have only cordierite (exple corona around garnet) without melt during
the decompression??
Many thanks in advance to everyone who will help with his/her comments,
experience and opinion on this subject.
-----
Sara
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