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The system CaO-SiO_2-CO_2-H_2O. II—The petrogenetic model

Wyllie, P. J. and Haas, J. L., Jr. (1966) The system CaO-SiO_2-CO_2-H_2O. II—The petrogenetic model. Geochimica et Cosmochimica Acta, 30 (5). pp. 525-543. ISSN 0016-7037. doi:10.1016/0016-7037(66)90063-9.

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In each of the three isobaric invariant reactions below 900° C on the vapor-saturated liquidus surface of the system CaO-SiO_2-CO_2-H_2O at 1 kilobar pressure, the vapor phase is extremely rich in H_2O. The effect of adding H_2O to the vapor phase on the temperatures of successive decarbonation reactions in the system CaO-SiO_2-CO_2 (involving the formation of wollastonite, spurrite and dicalcium silicate) is illustrated in the petrogenetic model. At 1 kilobar pressure the primary fields of spurrite and calcite on the vapor-saturated liquidus surface are separated by a field boundary extending down to a peritectic at 677° C. Examination of the melting reactions and the decarbonation reactions plotted in the petrogenetic model shows that the latter intersect the former with increasing pressure, and the first result of this at pressures above 1 kilobar is that a primary field for wollastonite replaces the peritectic on the vapor-saturated liquidus surface. Then, calcite and wollastonite can be co-precipitated from a liquid down to temperatures below 700° C. Applications to carbonatites are discussed briefly. If an igneous intrusion gives off enough H_2O during crystallization to flush CO_2 gas from the pores of a siliceous limestone in contact with it, partial melting of the limestone could conceivably occur. This possibility should be considered seriously in studies of thermal metamorphism.

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Alternate Title:The system CaO-SiO2-CO2-H2O. II—The petrogenetic model
Additional Information:© 1966 Published by Elsevier Ltd. Received 30 June 1965, Available online 7 April 2003. We wish to thank D. M. Roy for her help and advice during the experimental study, A. K. Temple for discussion of the paper, and the National Science Foundation for support of the research at The Pennsylvania State University in 1961-1962 by Grant G-19588; manuscript preparation costs were covered by Grant GP-1870.
Group:UNSPECIFIED, Division of Geological and Planetary Sciences
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Issue or Number:5
Record Number:CaltechAUTHORS:20160112-091148930
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Official Citation:P.J Wyllie, J.L Haas Jr., The system CaO-SiO2-CO2-H2O. II—The petrogenetic model, Geochimica et Cosmochimica Acta, Volume 30, Issue 5, May 1966, Pages 525-543, ISSN 0016-7037, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63575
Deposited By: Ruth Sustaita
Deposited On:12 Jan 2016 18:56
Last Modified:10 Nov 2021 23:18

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