Thermal Fatigue: A Possible Source of Structural Modifications in Meteorites

Levi, F. A.

doi:10.1111/j.1945-5100.1973.tb01250.x

Cited by 20 publications

(17 citation statements)

References 17 publications

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“…The blocky fracturing found in sample 13 (15.9-GPa peak pressure) is distributed homogeneously, and fracture orientations are more or less parallel to the cleavage directions of olivine. The fractures are reminiscent of those described by Levi [1973Levi [ , 1976 and may have a thermal origin or, alternatively, may reflect massive brittle failure at the Hugoniot elastic limit. The fractures separate blocks which are slightly misoriented with respect to each other but which exhibit no undulatory extinction, implying essentially no plastic strain within these blocks.…”

Section: Resultsmentioning

confidence: 79%

“…These zones of localized deformation surround regions of relatively unbroken olivine, suggesting the occurrence of heterogeneous yielding under shock, perhaps similar to that discussed by Grady [1977]. At a smaller scale, however, the regions between these fractured zones contain numerous microcracks ( Figure 6b) which are oriented along cleavage planes [see Snee and Ahrens, 1975;Reimold and Stbffler, 1978;Levi, 1973Levi, , 1976. With increasing pressure these small fractures tend to lose their planarity and apparent crystallographic constraint, sometimes taking on a wavy (or flowlike) appearance ( Figure 6c).…”

Section: Stbffier 1978] As Well As With the X Ray Data Of Hbrz Andmentioning

confidence: 70%

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Shock effects in olivine and implications for Hugoniot data

Jeanloz¹

1980

J. Geophys. Res.

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Deformation produced in single‐crystal olivine samples by shock wave stresses ranging between 16 and 75 GPa are documented by microscopy and spectroscopy. No evidence was found for phase transformation throughout the ‘mixed‐phase’ region (about 25 to 70 GPa) contrary to expectations based on the current interpretations of Hugoniot data. Samples retrieved from peak pressures above 20 GPa exhibit extensive plastic strain; a distinctive microundulatory extinction (mosaicism) is associated with elevated dislocation densities. Shock effects in olivine are relatively minor compared to those typical of other silicates: only traces of diaplectic glass are found at pressures above about 50 GPa, and there is no evidence of melting, recrystallization, or recovery. Although civilian (reconstructive) phase transformation has been previously inferred from the Hugoniot data for olivine, this textural evidence is inconsistent with such a process. Calculations of transformation rates for olivine similarly indicate that reconstructive phase transformation is very unlikely under experimental shock conditions and that the Hugoniot data represent highly nonequilibrium states. A new, crystallographically based model is presented for the behavior of olivine under shock: it successfully reproduces the Hugoniot data and is in accord with all available observations. According to this model, olivine is compressed into a slighlty randomized, olivinelike structure at shock pressures above about 20–30 GPa and does not undergo a polymorphic transformation or an increase in cation coordination number. Some evidence indicates that many other silicates may behave similarly and remain untransformed in shock experiments. The results of this study suggest that the current interpretations of shock wave data for silicates and their geophysical applications may need reappraisal.

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Section: Resultsmentioning

confidence: 79%

Section: Stbffier 1978] As Well As With the X Ray Data Of Hbrz Andmentioning

confidence: 70%

Shock effects in olivine and implications for Hugoniot data

Jeanloz¹

1980

J. Geophys. Res.

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“…The earliest primitive laboratory experiments were carried out by Griggs (1936) and Blackwelder (1933), who concluded that thermal stress weathering is likely insignificant, unless rapid cooling is achieved via water quench. However, more modern laboratory experiments of (Collins & Stock, 2016;Delbo et al, 2014;Hazeli, El Mir, Papanikolaou, Delbo, & Ramesh, 2018;Levi, 1973;Luque, Ruiz-Agudo, Cultrone, Sebastián, & Siegesmund, 2011) have demonstrated that thermal stress weathering is operative even in anhydrous environments.…”

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confidence: 99%

Unraveling the Mechanics of Thermal Stress Weathering: Rate‐Effects, Size‐Effects, and Scaling Laws

et al. 2019

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Thermal stress weathering is now recognized to be an active and significant geomorphological process on airless bodies. This study aims to understand the key factors governing thermal stresses in rocks on airless bodies through extensive numerical calculations and analytic analyses. Microscopic (grain‐scale) thermal stresses are driven primarily by the maximum diurnal temperature variation at said depth. Macroscopic (rock‐scale) thermal stresses are more complex. For rock sizes larger than the thermal skin depth, macroscopic thermal stresses are driven primarily by second (and higher) order spatial gradients of temperature. For rock sizes smaller than the thermal skin depth, macroscopic thermal stresses are primarily driven by the ratio of rock size to thermal skin depth. Additionally, scaling relations for diurnal surface temperature variation, time‐rate‐of‐change of surface temperature, as well as peak microscopic (grain‐scale) and macroscopic (rock‐scale) thermal stresses are derived to provide a more accessible modeling tool. These scaling relations are remarkably accurate when compared to both the numerical calculations as well as three‐dimensional finite element calculations. The model formulation, results, and scaling relations provided here allow the estimation of diurnal temperatures and thermal stresses on rocks of various size and materials on airless bodies at any orbital distance with a broad spectrum of spin rates. Lastly, we postulate and confirm that there is a critical spin rate where macroscopic thermal stresses will be greatest.

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“…In point of fact it was observed (Levi, 1973) on treated meteorite samples that in some cases the effects of thermal cycling on olivine crystals appeared to be increased in the vicinity of metals. The metal used in the artificial sample was mostly granulated mild steel.…”

Section: Experimental Techniquesmentioning

confidence: 92%

“…Bipyramidal and prismatic cleavage appeared as new features, not existing in the original material. It is known that similar features may be found in meteorites, when a sufficient degree of metamorphism is present, and may be induced as a consequence of shock (Muller and Hornemann, 1969) or low-temperature thermal cycling (Levi, 1973(Levi, , 1976.…”

Section: Figmentioning

confidence: 96%