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Physicochemical conditions for melting in the Earth's mantle containing a C-O-H fluid (from experimental data)

K. D. Litasov
Physicochemical conditions for melting in the Earth's mantle containing a C-O-H fluid (from experimental data)
Russian Geology and Geophysics (May 2011) 52 (5): 475-492

Abstract

Experimental data on phase transformations and melting in peridotite and eclogite systems with a C-O-H fluid at 6-30 GPa have been analyzed with special attention to the influence of redox conditions. It has been found that melting in systems with H (sub 2) O depends heavily on its total content and considerably on its solubility in nominally anhydrous rock-forming minerals. Partial melting occurs when the total H (sub 2) O content of the system exceeds the H (sub 2) O storage capacity in the rock under given physicochemical conditions. Melting in CO (sub 2) -containing systems is determined by carbonate stability and the chemical composition of the system, mainly its Na (sub 2) O and K (sub 2) O contents, and, to a smaller extent, the content of CO (sub 2) itself. Studies of peridotite and eclogite systems containing H (sub 2) O, CO (sub 2) , H (sub 2) O+CO (sub 2) , and a reduced C-O-H fluid show that most solidi flatten out at pressures above 6-8 GPa when intersecting the geotherms of subduction and average mantle. Mantle melting at constant pressure in the presence of a C-O-H fluid depends not only on temperature but also on redox conditions. The oxidation of the system causes redox melting. The stability boundary of a Fe-Ni alloy (it may coincide with the lithosphere-asthenosphere boundary under cratons, 200-250 km) and the 410-km discontinuity are paramount to redox and decarbonation-dehydration melting. Also, the paper provides evidence that subducted carbonates play the leading role in the "big" mantle wedge model for stagnant slabs. Volatile-containing eclogite systems melt at lower temperatures than peridotite ones (the difference is up to 100-200 degrees C). This suggests that eclogites are of global importance in mantle melting, which agrees with modern geochemical models.


ISSN: 1068-7971
Serial Title: Russian Geology and Geophysics
Serial Volume: 52
Serial Issue: 5
Title: Physicochemical conditions for melting in the Earth's mantle containing a C-O-H fluid (from experimental data)
Author(s): Litasov, K. D.
Affiliation: Russian Academy of Sciences, Siberian Branch, V. S. Sobolev Institute of Geology and Mineralogy, Novosibirsk, Russian Federation
Pages: 475-492
Published: 201105
Text Language: English
Publisher: Allerton Press, New York, NY, United States
References: 132
Accession Number: 2021-068032
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 202122
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