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Melting in the Earth's Crust

Wyllie, P. J. and Tuttle, O. F. (1960) Melting in the Earth's Crust. In: Structure of the Earth's crust and deformation of rocks. Proceedings (International Geological Congress. 21st). No.18. Det Berlinske Bogtrykkeri , Copenhagen, pp. 227-235.

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Investigation of the effect of volatile materials on the melting temperatures of rocks suggests that partial melting occurs readily within the earth's crust. Granites and shales begin to melt at 660°C in the presence of water vapor at 4000 bars pressure. If the water contains 4 weight per cent hydrogen fluoride, the melting temperature of granite is lowered to 590°C. At 1000 bars the minimum liquidus temperature in the system Ca0-CO_2-H_2O is 675°C; at 4000 bars the liquidus minimum is 640°C. Addition of MgO lowers the melting temperature at 1000 bars to 625° C. A value of 30° C/km. is reasonable for geothermal gradient in geosynclines and if this remains constant with increasing depth, a temperature of 620°C is attained at 20 km. (about 5000 bars pressure). The compositions of many geosynclinal rocks may be represented in terms of granite, shale, and carbonates, and the above experimental results indicate that such rocks will be partially melted at 20 kms. depth provided volatiles are present. The extent of melting will depend upon bulk composition and especially upon the proportion of available volatiles. Partial melting therefore plays an important role in the metamorphism and deformation of rocks in orogcnic zones.

Item Type:Book Section
Additional Information:© 1960 Det Berlinske Bogtrykkeri. Manuscript received August 11th, 1959. This work has been supported by the National Science Foundation.
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Series Name:Proceedings (International Geological Congress. 21st)
Issue or Number:18
Record Number:CaltechAUTHORS:20160330-143640183
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:65771
Deposited By: Tony Diaz
Deposited On:30 Mar 2016 23:20
Last Modified:03 Oct 2019 09:50

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