Development of a recrystallized grain size piezometer for hematite based on high-temperature torsion experiments

Siemes, Heinrich; Rybacki, E.; Klingenberg, Birgit; Rosière, Carlos Alberto

doi:10.1127/0935-1221/2011/0023-2103

Cited by 13 publications

(15 citation statements)

References 7 publications

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“…The polygonal hematite grain morphology is similar to textures interpreted as recrystallized hematite in previous study of WFZ surfaces (Ault et al, 2015). These morphologies are analogous to that observed in long-duration hematite torsion (Siemes et al, 2003;Siemes et al, 2011) and dry heating (Vallina et al, 2014) experiments to 1000-1100 °C.…”

Section: Evidence For Elevated Fault Surface Temperaturessupporting

confidence: 83%

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Thermochronometric and textural evidence for seismicity via asperity flash heating on exhumed hematite fault mirrors, Wasatch fault zone, UT, USA

McDermott

Ault

Evans

et al. 2017

Earth and Planetary Science Letters

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Section: Evidence For Elevated Fault Surface Temperaturessupporting

confidence: 83%

“…Lobate grains are similar to those observed in torsion and dry heating experiments conducted at lower temperatures (300-800 °C; Siemes et al, 2003;Siemes et al, 2011;Vallina et al, 2014).…”

Section: Evidence For Elevated Fault Surface Temperaturessupporting

confidence: 73%

Thermochronometric and textural evidence for seismicity via asperity flash heating on exhumed hematite fault mirrors, Wasatch fault zone, UT, USA

McDermott

Ault

Evans

et al. 2017

Earth and Planetary Science Letters

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“…Experimental deformation studies are essential for interpreting tectonic and metamorphic histories of rocks from mineral textures and microstructures. Although Fe‐Ti oxides are an important class of common crustal minerals, few studies have investigated the high‐temperature strength and deformation textures of Fe‐Ti‐oxide minerals in detail, with the exception of hematite (Siemes et al, , , ). Magnetite occurs widely as an accessory mineral in igneous rocks and is abundant in iron ore deposits and banded iron formations.…”

Section: Introductionmentioning

confidence: 99%

High‐Temperature Deformation Behavior of Synthetic Polycrystalline Magnetite

et al. 2019

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We performed a series of deformation experiments on synthetic magnetite aggregates to characterize the high‐temperature rheological behavior of this mineral under nominally dry and hydrous conditions. Grain growth laws for magnetite were additionally determined from a series of static annealing tests. Synthetic magnetite aggregates were formed by hot isostatic pressing of fine‐grained magnetite powder at 1,100 °C temperature and 300‐MPa confining pressure for 20 hr, resulting in polycrystalline material with a mean grain size around 40 μm and containing 2–4% porosity. Samples were subsequently deformed to axial strains of up to 10% under constant load conditions at temperatures between 900 and 1,150 °C in a triaxial deformation apparatus under 300‐MPa confining pressure at applied stresses in the range of 8–385 MPa or in a uniaxial creep rig at atmospheric pressure with stresses of 1–15 MPa. The aggregates exhibit typical power‐law creep behavior with a mean stress exponent of 3 at high stresses, indicating a dislocation creep mechanism and a transition to near‐Newtonian creep with a mean stress exponent of 1.1 at lower stresses. The presence of water in the magnetite samples resulted in significantly enhanced static grain growth and strain rates. Best‐fit flow laws to the data indicate activation energies of around 460 and 310 kJ/mol for dislocation and diffusion creep of nominally dry magnetite, respectively. Based on the experimentally determined flow laws, magnetite is predicted to be weaker than most major silicate phases in relatively dry rocks such as oceanic gabbros during high‐temperature crustal deformation.

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“…Compaction took place in this model at a temperature of about 700 K. On the other hand, a creep activation energy of 356 kJ mol −1 is rather high for a carbonaceous chondritic composition, which is dominated by phyllosilicates / serpentine. The activation energies of species involved (in particular hydrated minerals) vary from O(10 kJ mol −1 ) (serpentine, see Hilairet et al 2007) to O(100 kJ mol −1 ) by one order of magnitude, for instance, E = 251 kJ mol −1 corresponding to hematite (see Siemes et al 2011). Consequently, compaction will proceed at lower temperatures and will be much more efficient than in the case of an olivine-dominated ordinary chondritic composition.…”

Section: Modelmentioning

confidence: 99%

Modelling the internal structure of Ceres: Coupling of accretion with compaction by creep and implications for the water-rock differentiation

Neumann

Breuer

Spohn

2015

A&A

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Aims. We model the compaction of a Ceres-like body that accretes from the protoplanetary dust as a porous aggregate. To do this, we use a comprehensive numerical model in which the accretion starts with a km-size seed and the final radius reaches ≈500 km. Our goal is to investigate the interplay of accretion and loss of porosity by hot pressing. We draw conclusions for the evolution of the porosity profile and the present-day porosity distribution on Ceres. In particular, we test the hypothesis that Ceres' low density can be explained by a porous interior instead of by the presence of ice, and whether compaction occurs due to creep or due to dehydration of hydrated minerals. Methods. We extended our thermal evolution model from previous studies to model compaction of an accreting asteroid that is initially porous. We considered two different compositions of Ceres suggested by other workers. The porosity change was calculated according to the thermally activated creep flow. Depending on the composition, parameters relevant for compaction were changed self-consistently with the mineral phases. Results. We find that compaction of initially porous Ceres is dominated by creep and only slightly perturbed by the dehydration. In particular, dehydration alone cannot lead to compaction because creep can occur before the dehydration. Depending on the accretion duration, timing of the compaction varies from between a few million years and more than one billion years. Thereby, late accretion cannot prevent compaction to an average porosity of <2.5%. We provide the evolution as well as the present-day porosity and temperature profiles for Ceres. The temperature allows for the existence of liquid water in the interior of Ceres at a depths of ≥5−33 km. Depending on the composition, either iron melt is produced regardless of the accretion timing or only for an accretion within the first 4 Ma relative to calcium-aluminium-rich inclusions. This argues for a small metallic core.

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Development of a recrystallized grain size piezometer for hematite based on high-temperature torsion experiments

Cited by 13 publications

References 7 publications

Thermochronometric and textural evidence for seismicity via asperity flash heating on exhumed hematite fault mirrors, Wasatch fault zone, UT, USA

Thermochronometric and textural evidence for seismicity via asperity flash heating on exhumed hematite fault mirrors, Wasatch fault zone, UT, USA

High‐Temperature Deformation Behavior of Synthetic Polycrystalline Magnetite

Modelling the internal structure of Ceres: Coupling of accretion with compaction by creep and implications for the water-rock differentiation

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