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The effect of H 2 O and CO 2 on planetary mantles
Author(s) -
Wyllie Peter J.
Publication year - 1978
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl005i006p00440
Subject(s) - solidus , peridotite , amphibole , mantle (geology) , crystallite , water vapor , forsterite , analytical chemistry (journal) , mineralogy , quartz , materials science , geology , chemistry , geochemistry , crystallography , alloy , organic chemistry , composite material , chromatography
The solidus for peridotite‐H 2 O‐CO 2 is a divariant surface traversed by univariant lines that locate the intersections of subsolidus divariant surfaces for carbonation or hydration reactions occurring in the presence of H 2 O‐CO 2 mixtures. Vapor phase compositions are normally buffered to these lines; the buffering capacity of carbonates is much greater than that of amphibole and phlogopite. Near the buffered curve for the solidus of partly carbonated peridotite, extending to higher pressures and lower temperatures from an invariant point near 26 kb‐1200°C, there is a temperature maximum on the peridotite‐vapor solidus. On the CO 2 side of the maximum, above 26 kb, CO 2 /H 2 O is greater in liquid than in vapor, and liquids are SiO 2 ‐poor; on the H 2 O side of this maximum (including all pressures below 26 kb), H 2 O/CO 2 is greater in liquid than in vapor, and liquids change from forsterite‐normative to quartz‐normative with increasing H 2 O/CO 2 in vapor. Even traces of H 2 O and CO 2 , in minerals or vapor, lower mantle solidus temperatures through hundreds of degrees compared with the volatile‐free solidus.