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A flow law for ilmenite in dislocation creep: Implications for lunar cumulate mantle overturn
Author(s) -
Dygert Nick,
Hirth Greg,
Liang Yan
Publication year - 2016
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 - 10.1002/2015gl066546
Subject(s) - ilmenite , mantle (geology) , geology , geophysics , viscosity , forsterite , outer core , boundary layer , mechanics , inner core , mineralogy , materials science , composite material , physics
We present results from new deformation experiments and a dislocation creep flow law for synthetic ilmenite. The flow law predicts an effective viscosity more than 3 orders of magnitude lower than dry olivine at mantle stresses and temperatures. Using the flow law, we predict that lunar ilmenite‐bearing cumulates (IBC) will be weakened by the presence of low‐viscosity ilmenite. Dense, low‐viscosity IBC are expected to flow into the lunar interior by a process known as cumulate mantle overturn. Low‐viscosity IBC that sink to the core‐mantle boundary may be dynamically stable with respect to upwelling. A hot, stable layer of IBC surrounding the lunar core would suppress the development of a core dynamo. A layer of partially molten IBC can also explain the inferred zone of seismic attenuation around the lunar core, as well as a low‐viscosity layer suggested by tidal dissipation.