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dc.contributor.authorZolotov, M. Yu.
dc.contributor.authorMironenko, M. V.
dc.contributor.authorShock, E. L.
dc.date.accessioned2021-02-12T21:41:06Z
dc.date.available2021-02-12T21:41:06Z
dc.date.issued2006-01-01
dc.identifier.citationZolotov, M. Y., Mironenko, M. V., & Shock, E. L. (2006). Thermodynamic constraints on fayalite formation on parent bodies of chondrites. Meteoritics & Planetary Science, 41(11), 1775-1796.
dc.identifier.issn1945-5100
dc.identifier.doi10.1111/j.1945-5100.2006.tb00451.x
dc.identifier.urihttp://hdl.handle.net/10150/656214
dc.description.abstractThermochemical equilibria are calculated in the multicomponent gas-solution-rock system in order to evaluate the formation conditions of fayalite, (Fe0.881.0Mg0.120)2SiO4, Fa88100, in unequilibrated chondrites. Effects of temperature, pressure, water/rock ratio, rock composition, and progress of alteration are evaluated. The modeling shows that fayalite can form as a minor secondary and transient phase with and without aqueous solution. Fayalite can form at temperatures below ~350 degrees C, but only in a narrow range of water/rock ratios that designates a transition between aqueous and metamorphic conditions. Pure fayalite forms at lower temperatures, higher water/rock ratios, and elevated pressures that correspond to higher H2/H2O ratios. Lower pressure and water/rock ratios and higher temperatures favor higher Mg content in olivine. In equilibrium assemblages, fayalite usually coexists with troilite, kamacite, magnetite, chromite, Ca-Fe pyroxene, and phyllosilicates. Formation of fayalite can be driven by changes in temperature, pressure, H2/H2O, and water/rock ratios. However, in fayalite-bearing ordinary and CV3 carbonaceous chondrites, the mineral could have formed during the aqueous-to-metamorphic transition. Dissolution of amorphous silicates in matrices and/or silica grains, as well as low activities of Mg solutes, favored aqueous precipitation of fayalite. During subsequent metamorphism, fayalite could have formed through the reduction of magnetite and/or dehydration of ferrous serpentine. Further metamorphism should have caused reductive transformation of fayalite to Ca-Fe pyroxene and secondary metal, which is consistent with observations in metamorphosed chondrites. Although bulk compositions of matrices/chondrites have only a minor effect on fayalite stability, specific alteration paths led to different occurrences, quantities, and compositions of fayalite in chondrites.
dc.language.isoen
dc.publisherThe Meteoritical Society
dc.relation.urlhttps://meteoritical.org/
dc.rightsCopyright © The Meteoritical Society
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.subjectunequilibrated meteorites
dc.subjectaqueous alteration
dc.subjectthermal metamorphism
dc.subjectolivine
dc.titleThermodynamic constraints on fayalite formation on parent bodies of chondrites
dc.typeArticle
dc.typetext
dc.identifier.journalMeteoritics & Planetary Science
dc.description.collectioninformationThe Meteoritics & Planetary Science archives are made available by the Meteoritical Society and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information.
dc.eprint.versionFinal published version
dc.description.admin-noteMigrated from OJS platform February 2021
dc.source.volume41
dc.source.issue11
dc.source.beginpage1775
dc.source.endpage1796
refterms.dateFOA2021-02-12T21:41:06Z


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