Si and O diffusion in olivine and implications for characterizing plastic flow in the mantle

Dohmen, Ralf; Chakraborty, Sumit; Becker, Hans‐Werner

doi:10.1029/2002gl015480

Cited by 179 publications

(141 citation statements)

References 23 publications

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“…The various studies yield a fairly consistent range for activation enthalpy of about 240 to 355 kJ mol −1 that may however be extended due to experimental uncertainties. These values are markedly lower than the value for diffusion of Si in olivine of 530 kJ mol −1 (Dohmen et al, 2002), relevant if dislocation climb was rate-controlling for the recovery processes (Karato et al, 1993). The requirement expressed by Eq.…”

Section: Quantitative Analysismentioning

confidence: 66%

Experimental deformation and recrystallization of olivine – processes and timescales of damage healing during postseismic relaxation at mantle depths

Trepmann¹,

Renner

Druiventak

2013

Solid Earth

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Abstract. Experiments comprising sequences of deformation (at 300 or 600 • C) and annealing at varying temperature (700 to 1100 • C), time (up to 144 h) and stress (up to 1.5 GPa) were carried out in a Griggs-type apparatus on natural olivine-rich peridotite samples to simulate deformation and recrystallization processes in deep shear zones that reach mantle depth as continuations of seismically active faults. The resulting olivine microfabrics were analysed by polarization and electron microscopy (SEM/EBSD, TEM). Core-and-mantle-like microstructures are the predominant result of our experiments simulating rapid stress relaxation (without or with minor creep) after a high-stress deformation event: porphyroclasts (> 100 µm) are surrounded by new grains comprising fragments and recrystallized grains with a wide range in size (2 to 40 µm). Areas with small grains (≤ 10 µm) trace former high-strain zones generated during initial high-stress deformation even after annealing at a temperature of 1100 • C for 70 h. A weak crystallographic preferred orientation (CPO) of new olivine grains is related to the orientation of the original host crystals but appears unrelated to the strain field. Based on these findings, we propose that olivine microstructures in natural shear-zone peridotites with a large range in grain size, localized fine-grained zones, and a weak CPO not related to the strain field are diagnostic for a sequence of high-stress deformation followed by recrystallization at low stresses, as to be expected in areas of seismic activity. We extended the classic Avrami-kinetics equation by accounting for time-dependent growth kinetics and constrained the involved parameters relying on our results and previous studies devoted to the kinetics of defect processes in olivine. Extrapolation to natural conditions suggests that the observed characteristic microstructure may develop within as little as tens of years and less than ten thousands of years. These recrystallization microstructures have a great diagnostic potential for past seismic activity because they are expected to be stable over geological timescales, since driving forces for further modification are not sufficient to erase the characteristic heterogeneities.

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Section: Quantitative Analysismentioning

confidence: 66%

Experimental deformation and recrystallization of olivine – processes and timescales of damage healing during postseismic relaxation at mantle depths

Trepmann¹,

Renner

Druiventak

2013

Solid Earth

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“…(1) Si is the rate-controlling species in wadsleyite and controls the plastic deformation. Although there is a lack of oxygen diffusion data for wadsleyite, Si is a good candidate for the slowest diffusion species in wadsleyite, as it is in olivine [Houlier et al, 1988;Dohmen et al, 2002].…”

Section: Discussionmentioning

confidence: 99%

“…[3] There are numerous studies on diffusivity in olivine, which have shown that Si is the slowest diffusing species [e.g., Houlier et al, 1988Houlier et al, , 1990Dohmen et al, 2002]. However diffusion studies in wadsleyite, a high-pressure polymorph of olivine and one of the major constituent minerals in the mantle transition zone, have been limited to Mg-Fe interdiffusion [Farber et al, 1994[Farber et al, , 2000Chakraborty et al, 1999;Kubo et al, 2004].…”

Section: Introductionmentioning

confidence: 99%

Silicon self‐diffusion in wadsleyite: Implications for rheology of the mantle transition zone and subducting plates

Shimojuku

Kubo

Ohtani

et al. 2004

Geophysical Research Letters

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[1] Si self-diffusion rates in Mg 2 SiO 4 polycrystalline wadsleyite were measured at 18 GPa and 1430 -1630°C using an isotopic tracer ( 29 Si) and secondary ion mass spectrometry. The volume diffusion coefficient (D v ) and grain-boundary diffusion coefficient (D gb ) were determined to be D v = 3.44 Â 10 À11 [m 2 /s] exp (À299 [kJ/mol]/RT) and dD gb = 1.14 Â 10 À17 [m 3 /s] exp (À248 [kJ/mol]/RT), respectively. Si diffusion rates in wadsleyite are about 5 orders of magnitude slower than Mg-Fe interdiffusion rates at 1400°C. Assuming that Si is the slowest diffusing species in wadsleyite, the geophysical model of the viscosity in the mantle transition zone can be explained by diffusion creep in wadsleyite for a grain size of about 0.5-5 mm. Some portions in cold subducting slabs, where the grain size reduces to less than 1 mm after the olivinespinel transformation, become weaker than the surrounding mantle.

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“…Since the diffusion coefficient is obtained for a temperature range of 1100 Dohmen et al 2002), we extrapolate the results down to lower temperatures. Measurements with the transmission electron microscope show that the chemical compositions of presolar silicate grains vary on the scale of a few tens nanometer (Nguyen et al 2007;Busemann et al 2009;Leitner et al 2012).…”

Section: Isotopic Diffusion In Thermally Evolving Planetesimalsmentioning

confidence: 99%

“…In order to compute the diffusion length of oxygen isotopes in presolar silicate grains, we adopt a diffusion coefficient of 18 O in olivine from Dohmen et al (2002). The diffusion coefficient D(T ) is given as…”

Section: Isotopic Diffusion In Thermally Evolving Planetesimalsmentioning

confidence: 99%

Diffusion of Oxygen Isotopes in Thermally Evolving Planetesimals and Size Ranges of Presolar Silicate Grains

Wakita

Nozawa

Hasegawa

2017

ApJ

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Presolar grains are small particles found in meteorites through their isotopic compositions which are considerably different from those of materials in the Solar System. If some isotopes in presolar grains diffused out beyond their grain sizes when they were embedded in parent bodies of meteorites, their isotopic compositions could be washed out, and hence the grains cannot be identified as presolar grains any more. We explore this possibility for the first time by self-consistently simulating the thermal evolution of planetesimals and the diffusion length of 18 O in presolar silicate grains. Our results show that presolar silicate grains smaller than ∼ 0.03µm cannot keep their original isotopic compositions even if the host planetesimals experienced maximum temperature as low as 600• C. Since this temperature corresponds to the one experienced by petrologic type 3 chondrites, the isotopic diffusion can constrain the size of presolar silicate grains discovered in such chondrites to be larger than ∼ 0.03µm. We also find that the diffusion lengths of 18 O reach ∼ 0.3 − 2µm in planetesimals that were heated up to 700-800• C. This indicates that, if the original size of presolar grains spans a range from ∼ 0.001µm to ∼ 0.3µm like that in the interstellar medium, the isotopic records of the presolar grains may be almost completely lost in such highly thermalized parent bodies. We propose that isotopic diffusion could be a key process to control the size distribution and abundance of presolar grains in some types of chondrites.

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Si and O diffusion in olivine and implications for characterizing plastic flow in the mantle

Cited by 179 publications

References 23 publications

Experimental deformation and recrystallization of olivine – processes and timescales of damage healing during postseismic relaxation at mantle depths

Experimental deformation and recrystallization of olivine – processes and timescales of damage healing during postseismic relaxation at mantle depths

Silicon self‐diffusion in wadsleyite: Implications for rheology of the mantle transition zone and subducting plates

Diffusion of Oxygen Isotopes in Thermally Evolving Planetesimals and Size Ranges of Presolar Silicate Grains

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