Dear Mallickarjun,

At supersolidus temperatures, crustal rocks undergo partial melting to produce a sizable volume of anatectic melts. This process is common during high-grade metamorphism at amphibolite- to granulite-facies conditions. Migmatites are its typical products in which anatectic melts were not escaped from the anatectic systems.

Such a kind of crustal anatexis mainly occurs in extensional settings such as backarc and continental rifts, where the lithosphere is significantly thinned to cause upwelling of the asthenospheric mantle, transferring high heat flow into the lower crust for metamorphic dehydration and partial melting at crustal depths. While dehydrated and melt-extracted residues show HT to UHT granulitization, releassed fluids (aqueous solutions) result in amphibolitization of the overlying crustal rocks and escaped melts (hydrous, felsic) give rise to granitic intrusives in different sizes. 

Yong-Fei
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Dr. Yong-Fei Zheng

Professor of Geochemistry

School of Earth and Space Sciences

University of Science and Technology of China

Hefei 230026, China

Tel & Fax: +86 551 63603554

Email: [log in to unmask]

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-----原始邮件-----
发件人:"Mallickarjun Joshi" <[log in to unmask]>
发送时间:2018-06-21 22:06:08 (星期四)
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Dear All,

I wonder under what conditions a sizable volume of  the  anatectic melt formed as a consequence of high grade metamorphism in pelites would not be able to escape the system? 

Admittedly, metamorphism outlasting the deformation should be a likely precondition.

Moreover, should it also shed some light on the tectonic set up other than that  it is likely to have formed during the penultimate stages of the orogeny.

I would much appreciate  your opinion and any suggestions for references to understand the problem.

Thanks and regards

Mallickarjun Joshi
Centre of Advanced Study in Geology
Banaras Hindu University
India

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