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Hydrothermal Melting Curves in Silicate–Water Systems at Pressures greater than 10 Kilobars

Boettcher, A. L. and Wyllie, P. J. (1967) Hydrothermal Melting Curves in Silicate–Water Systems at Pressures greater than 10 Kilobars. Nature, 216 (5115). pp. 572-573. ISSN 0028-0836. doi:10.1038/216572a0.

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Fusion curves, or melting intervals, for many elements, minerals and rocks have now been measured experimentally to high pressures, but most determinations of melting relationships in the presence of water vapour have been limited to pressures below 10 kbar. It is well known that the solubility of water vapour under pressure in silicate liquids produces a marked depression of melting temperatures, as illustrated by the negative slopes, dP/dT, of the univariarit curves for the reactions: albite + vapour = liquid (Fig. 1); albite + nepheline + vapour = liquid (Fig. 2). Barth, Smith and Kadik and Khitarov have predicted that, because of the progressive change in the relative properties of water in vapour and liquid phases with increasing pressure, the slopes, dP/dT, of hydrothermal melting curves in silicate–water systems (solid–liquid–vapour) should change from negative to positive at moderate pressures, probably within the interval 3 kbar–10 kbar, with the curves passing through a temperature minimum where dT/dP = 0. We have recently extended water saturated univariant melting curves in the system NaAlSiO_4–SiO_2–H_2O from 10 to 35 kbar, using piston–cylinder apparatus, and none of the curves exhibited a temperature minimum where dT/dP = 0. Figs. 1 and 2 show some of our results. These are not complete phase diagrams; they show only the reactions encountered by two composition joins through the ternary system. Further reactions required by the existence of invariant points, I, and a singular point, S_5, will be illustrated elsewhere.

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Additional Information:© 1967 Nature Publishing Group. Received October 5, 1967. This research was supported by the US National Science Foundation, and the Advanced Research Project Agency.
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Advanced Research Projects Agency (ARPA)UNSPECIFIED
Issue or Number:5115
Record Number:CaltechAUTHORS:20160113-105310435
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63630
Deposited By: Tony Diaz
Deposited On:13 Jan 2016 19:28
Last Modified:10 Nov 2021 23:19

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