My understanding is that because a rock is composed of variety of minerals, so it does not have fix melting point, rather there is a range below which whole rock is solid and above which whole rock is liquid. I want to know this liquidus and solidus temperature for granite rock based on pressure (as we can't ignore role of pressure inside earth where granite is formed?
Dear Ather: there are "granites" and "granites", Besides de well known classification of Chapell and White, "I", "S", "A", and so on, all of them have a solidus temperature and a liquidus one, and a wide melting interval, but these are very different according to the mineralogy, water and other volatiles percentage, and pressure. So, yours it is not a straighforward question to answer. Most "granitic" material (including metasedimentary one) which undergoes partial fusion (anatexis) in the roots of magmatic arcs begins to melt at some 630-650°C, but complete fusion, that is the liquidus, is never achieved. Instead, the components with lower point of fusion of the rock form a felsic magma, leaving a refractory residue, called restite, usually composed of pyroxenes, amphiboles, sillimanite and cordierite, among other minerals. One thing is known: the less percentage of water a granitic magma has, the higher it will be emplaced in the crust, and the higher will be its melting (and solidification) point. With regards. Sebastian.
Please go through the book
1) Granite: From Segregation of Melt to Emplacement Fabrics
edited by J.-L. Bouchez, D. Hutton, W.E. Stephens
The solidus temperatures are 685, 652 and 67 C for initial fluid/melt mass ratio of 1.0, 0.1 and 0.01 respectively. as given in page no.21.
2) The Fourth Hutton Symposium on the Origin of Granites and Related Rocks ...
edited by Bernard Barbarin, W. E. Stephens
The liquidus and solidus temperatures are 925-665 C (initial4.5%H2O), 750-630 C
( initial 7% H2O) for rhyolitic magma. as given in diagram 2, page 65.
You can also check this article out
Beginning of melting in the granite system Qz-Or-Ab-An-H2O
Wilhelm Johannes
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