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Subsolidus and melting relations for the join CaCO_3-MgCO_3 at 10 kbar

Byrnes, Alan P. and Wyllie, Peter J. (1981) Subsolidus and melting relations for the join CaCO_3-MgCO_3 at 10 kbar. Geochimica et Cosmochimica Acta, 45 (3). pp. 321-328. ISSN 0016-7037. doi:10.1016/0016-7037(81)90242-8.

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Mixtures of pure dry CaCO_3 and MgCO_3 were reacted at 10 kbar in a piston-cylinder apparatus. Solidus and liquidus boundaries were delineated by interpretation of quenched textures. X-ray determined compositions of quenched carbonates are not a reliable guide to the phase relations. The binary melting loop for CaCO_3-MgCO_3 extends from CaCO_3 at 1460°C through a liquidus minimum near 30 wt% MgCO_3 and 1075°C, and it is terminated at the incongruent melting reaction for dolomite solid solution at 1125° C (liquid with 32 wt% MgCO_3) Magnesite solid solution dissociates at 1090°C to produce dolomite + periclase + CO_2, truncating the dolomite-magnesite solvus. The 10 kb liquidus minimum at 1075°C and 30 wt% MgCO_3 occurs at lower temperature and higher Ca/Mg ratio than the 27 kbar liquidus minimum at 1290°C and 38 wt% MgCO_3. This relationship suggests that the first liquid produced by melting of a carbonate-bearing peridotite has increasing Mg/Ca ratio with increasing pressure. These phase relations provide part of the framework required to trace paths of crystallization of kimberlite and carbonatite magmas.

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Alternate Title:Subsolidus and melting relations for the join CaCO3-MgCO3 at 10 kbar
Additional Information:© 1981 Pergamon Press Ltd. Received 18 August 1978; accepted in revised form 16 October 1980. This research was supported by the Earth Sciences Section, National Science Foundation. Grant EAR 76-20410. We thank Drs J. R. GOLDSMITH and R. C. NEWTON for comments on an early draft of this manuscript.
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NSFEAR 76-20410
Issue or Number:3
Record Number:CaltechAUTHORS:20160209-151053933
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Official Citation:Alan P Byrnes, Peter J Wyllie, Subsolidus and melting relations for the join CaCO3-MgCO3 at 10 kbar, Geochimica et Cosmochimica Acta, Volume 45, Issue 3, March 1981, Pages 321-328, ISSN 0016-7037, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64345
Deposited By: Tony Diaz
Deposited On:09 Feb 2016 23:20
Last Modified:10 Nov 2021 23:29

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