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Amphibolite dehydration-melting: sorting out the solidus

Wyllie, Peter J. and Wolf, Michael B. (1993) Amphibolite dehydration-melting: sorting out the solidus. In: Magmatic processes and plate tectonics. Geological Society special publication. No.76. Geological Society , London, pp. 405-416. ISBN 9780585281353.

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Amphibolite melts under vapour-absent conditions by dehydration-melting, during which H_2O released from hornblende is transferred directly into H_2O-undersaturated silicate liquid. Five independent 1991 studies on amphibolite dehydration-melting differ from each other and from earlier conceptual treatments. Five solidi between 7 and 10 kb vary from 975°C to 740°C. Two solidi above 10 kb are near-vertical, near 975°C and 850°C. Some differences are due to different amphibolite compositions and mineralogy. We use the results of earlier experiments involving garnet, supported by our own new results, to construct a closed-system phase diagram for a simple, fully-hydra ted amphibolite (hornblende+ plagioclase) showing the solidus and the melting interval for ( hornblende+ garnet + other minerals+ liquid). The amphibolite vapour-absent solidus is defined by the beginnings of two multivariant reactions: (1) a near-vertical curve (large positive d P/dT) where the formation of augite dominates; and (2) a near-horizontal curve a t higher pressures where the formation of garnet dominates. The solidus curve bends back (estimated near 900°C, 9 kb) with slope changing to low positive dP/dT. The new phase diagram expands the field for liquid generation with garnet-amphibolite residues to much lower temperatures and pressures than the other recent experimental results, increasing the range from which small amounts of hydrous granitoid melts may be segregated by compaction. The reversed, near-horizontal slope of the solidus near 10 kb has interesting petrological consequences.

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Additional Information:© 1993 The Geological Society. This research was supported by the Earth Science section of the US National Science Foundation, grant EAR 89-04375.
Funding AgencyGrant Number
NSFEAR 89-04375
Series Name:Geological Society special publication
Issue or Number:76
Record Number:CaltechAUTHORS:20160302-092821295
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Official Citation:Peter J. Wyllie and Michael B. Wolf Amphibolite dehydration-melting: sorting out the solidus Geological Society, London, Special Publications, 76:405-416, doi:10.1144/GSL.SP.1993.076.01.20
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64955
Deposited By: Tony Diaz
Deposited On:02 Mar 2016 18:11
Last Modified:10 Nov 2021 23:37

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