Transient and steady state creep response of ice I and magnesium sulfate hydrate eutectic aggregates
Journal of Geophysical Research E: Planets
By: C. McCarthy, R.F. Cooper, D.L. Goldsby, W.B. Durham, and S. H. Kirby
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Abstract
Using uniaxial compression creep experiments, we characterized the transient and steady state deformation behaviors of eutectic aggregates of system ice I and MgSO4 11H2O (MS11; meridianiite), which has significance because of its likely presence on moons of the outer solar system. Synthetic samples of eutectic liquid bulk composition, which produce eutectic colonies containing 0.35-0.50 volume fraction MS11, were tested as functions of colony size and lamellar spacing, temperature (230-250 K), and confining pressure (0.1 and 50 MPa) to strains ???0.2. Up to a differential stress of 6 MPa, the ice I-MS11 aggregates display an order of magnitude higher effective viscosity and higher stress sensitivity than do aggregates of pure polycrystalline ice at the same conditions. The creep data and associated microstructural observations demonstrate, however, that the aggregates are additionally more brittle than pure ice, approaching rate-independent plasticity that includes rupture of the hydrate phase at 6-8 MPa, depending on the scale of the microstructure. Microstructures of deformed samples reveal forms of semibrittle flow in which the hydrate phase fractures while the ice phase deforms plastically. Semibrittle flow in the icy shell of a planetary body would truncate the lithospheric strength envelope and thereby decrease the depth to the brittle-ductile transition by 55% and reduce the failure limit for compressional surface features from 10 to ???6 MPa. A constitutive equation that includes eutectic colony boundary sliding and intracolony flow is used to describe the steady state rheology of the eutectic aggregates. Copyright ?? 2011 by the American Geophysical Union.
Suggested Citation
McCarthy, C., Cooper, R., Goldsby, D., Durham, W., and Kirby, S.H., 2011, Transient and steady state creep response of ice I and magnesium sulfate hydrate eutectic aggregates: Journal of Geophysical Research E: Planets, v. 116, no. 4, https://doi.org/10.1029/2010JE003689.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Transient and steady state creep response of ice I and magnesium sulfate hydrate eutectic aggregates |
| Series title | Journal of Geophysical Research E: Planets |
| DOI | 10.1029/2010JE003689 |
| Volume | 116 |
| Issue | 4 |
| Publication Date | April 20, 2011 |
| Year Published | 2011 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Journal of Geophysical Research E: Planets |