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Volatile Components, Magmas, and Critical Fluids in Upwelling Mantle

Wyllie, Peter J. and Ryabchikov, Igor D. (2000) Volatile Components, Magmas, and Critical Fluids in Upwelling Mantle. Journal of Petrology, 41 (7). pp. 1195-1206. ISSN 0022-3530. doi:10.1093/petrology/41.7.1195.

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The phase diagram for lherzolite–CO_2–H_2O provides a framework for interpreting the distribution of phase assemblages in the upper mantle with various thermal structures, in different tectonic settings. Experiments show that at depths >80 km, the near-solidus partial melts from lherzolite–CO_2–H_2O are dolomitic, changing through carbonate–silicate liquids with rising temperatures to mafic liquids; vapor, if it coexists, is aqueous. Experimental data from simple systems suggest that a critical end-point (K) occurs on the mantle solidus at an undetermined depth. Isobaric (T–X) phase diagrams for volatile-bearing systems with K elucidate the contrasting phase relationships for lherzolite–CO_2–H_2O at depths below and above a critical end-point, arbitrarily placed at 250 km. At levels deeper than K, lherzolite can exist with dolomitic melt, aqueous vapor, or with critical fluids varying continuously between these end-members. Analyses of fluids in microinclusions of fibrous diamonds reveal this same range of compositions, supporting the occurrence of a critical end-point. Other evidence from diamonds indicates that the minimum depth for this end-point is 125 km; maximum depth is not constrained. Constructed cross-sections showing diagrammatically the phase fields intersected by upwelling mantle indicate how rising trace melts may influence trace element concentrations within a mantle plume.

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Additional Information:© 2000 Oxford University Press. Received September 7, 1999. Accepted January 14, 2000. We thank G. Brey, H. Keppler, O. Navon, W. Schreyer, and M. Wilson for helpful comments. This research was supported by the Earth Science Section of the US National Science Foundation, Grant EAR-9218806. This is Contribution 8721 of the Division of Geological and Planetary Sciences, California Institute of Technology.
Funding AgencyGrant Number
NSF Earth SciencesEAR-9218806
Subject Keywords: mantle solidus critical end-point dolomitic magma diamond inclusions critical fluids
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Caltech Division of Geological and Planetary Sciences8721
Issue or Number:7
Record Number:CaltechAUTHORS:20111209-135629440
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Official Citation:PETER J. WYLLIE and IGOR D. RYABCHIKOV Volatile Components, Magmas, and Critical Fluids in Upwelling Mantle J. Petrology (2000) 41(7): 1195-1206 doi:10.1093/petrology/41.7.1195
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:28402
Deposited By: Ruth Sustaita
Deposited On:09 Dec 2011 22:14
Last Modified:09 Nov 2021 16:56

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