TY - JOUR
T1 - Effect of iron content on the creep behavior of Olivine
T2 - 2. Hydrous conditions
AU - Zhao, Yong Hong
AU - Zimmerman, Mark E.
AU - Kohlstedt, David L.
N1 - Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2018/5
Y1 - 2018/5
N2 - We have undertaken an experimental investigation of the effect of iron content on the viscosity of Fe-Mg olivine aggregates deformed under hydrous conditions in order to provide a basis for comparing convection models for the mantle of Earth with those for the more iron-rich mantle of Mars. Fine-grained samples of Fe-bearing olivine with fayalite contents, Fax, of x = 100, 75, 50, 30 and 10 were deformed in triaxial compressive creep primarily in the dislocation creep regime under water-saturated conditions at temperatures of 1273 to 1473 K and a confining pressure of 300 MPa. Nickel sleeves around the samples of Fa10, Fa30 and Fa50 set the oxygen fugacity at the Ni:NiO buffer and thus the water fugacity at ≲300 MPa, while Fe sleeves around samples of Fa75 and Fa100 set the oxygen fugacity at the Fe:FeO buffer and thus the water fugacity at ≲200 MPa. Samples were deformed in triaxial compression to a maximum strain of 0.2 at differential stresses from 10 to 300 MPa and strain rates from 10−7 to 10–3 s−1. In the dislocation creep field at a given temperature, the viscosity of samples of Fa50 is a factor of ∼10 smaller than the viscosity of samples of Fa30, while the viscosity of samples of Fa30 is a factor of ∼10 smaller than that of samples of Fa10. Our experimental results can be described by the flow law ε̇disl=Cdisl[Formula presented]ndisl XFa pdisl exp-[Formula presented]fH2O mdisl with Cdisl = 99.7 MPa−5/4 s−1, ndisl = 3.7, pdisl = 0.5, Qdisl 0 = 510 kJ/mol, αdisl = −120 kJ/mol, and mdisl = 5/4. This flow law indicates that the viscosity of olivine of a specific Fe:Mg ratio is a factor of ∼10 smaller than its counterpart deformed under anhydrous conditions. In a hydrous environment at the same thermodynamic conditions, the viscosity of the more Fe-rich mantle (∼Fa19) of Mars is a factor of ∼5 lower than that of the mantle (∼Fa8) of Earth.
AB - We have undertaken an experimental investigation of the effect of iron content on the viscosity of Fe-Mg olivine aggregates deformed under hydrous conditions in order to provide a basis for comparing convection models for the mantle of Earth with those for the more iron-rich mantle of Mars. Fine-grained samples of Fe-bearing olivine with fayalite contents, Fax, of x = 100, 75, 50, 30 and 10 were deformed in triaxial compressive creep primarily in the dislocation creep regime under water-saturated conditions at temperatures of 1273 to 1473 K and a confining pressure of 300 MPa. Nickel sleeves around the samples of Fa10, Fa30 and Fa50 set the oxygen fugacity at the Ni:NiO buffer and thus the water fugacity at ≲300 MPa, while Fe sleeves around samples of Fa75 and Fa100 set the oxygen fugacity at the Fe:FeO buffer and thus the water fugacity at ≲200 MPa. Samples were deformed in triaxial compression to a maximum strain of 0.2 at differential stresses from 10 to 300 MPa and strain rates from 10−7 to 10–3 s−1. In the dislocation creep field at a given temperature, the viscosity of samples of Fa50 is a factor of ∼10 smaller than the viscosity of samples of Fa30, while the viscosity of samples of Fa30 is a factor of ∼10 smaller than that of samples of Fa10. Our experimental results can be described by the flow law ε̇disl=Cdisl[Formula presented]ndisl XFa pdisl exp-[Formula presented]fH2O mdisl with Cdisl = 99.7 MPa−5/4 s−1, ndisl = 3.7, pdisl = 0.5, Qdisl 0 = 510 kJ/mol, αdisl = −120 kJ/mol, and mdisl = 5/4. This flow law indicates that the viscosity of olivine of a specific Fe:Mg ratio is a factor of ∼10 smaller than its counterpart deformed under anhydrous conditions. In a hydrous environment at the same thermodynamic conditions, the viscosity of the more Fe-rich mantle (∼Fa19) of Mars is a factor of ∼5 lower than that of the mantle (∼Fa8) of Earth.
KW - Experimental study
KW - High-temperature creep
KW - Hydrous iron-rich olivine aggregates
KW - Triaxial compression
KW - Viscosity
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U2 - 10.1016/j.pepi.2017.12.002
DO - 10.1016/j.pepi.2017.12.002
M3 - Article
AN - SCOPUS:85043595458
SN - 0031-9201
VL - 278
SP - 26
EP - 33
JO - Physics of the Earth and Planetary Interiors
JF - Physics of the Earth and Planetary Interiors
ER -