Silicon and oxygen self diffusion in enstatite polycrystals: the Milke et al. (2001) rim growth experiments revisited

Abart, Rainer; Kunze, Karsten; Milke, Ralf; Sperb, René P.; Heinrich, Wilhelm

doi:10.1007/s00410-004-0596-9

Cited by 43 publications

(25 citation statements)

References 20 publications

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“…1). In accordance with earlier observations (Abart et al. , 2004), the orthopyroxene on the quartz side of the rims has a higher electron back‐scatter capacity than on the olivine side, pointing to an enrichment of iron in orthopyroxene formed at the Opx/Qtz interface.…”

Section: Resultssupporting

confidence: 92%

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Matrix rheology effects on reaction rim growth I: evidence from orthopyroxene rim growth experiments

Milke

Abart

Kunze

et al. 2008

Journal Metamorphic Geology

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The rim-forming reaction quartz + olivine = orthopyroxene is used to investigate the effect of matrix rheology on rim growth rates. Orthopyroxene rim growth around olivine grains in quartz matrix is compared to rim growth around quartz grains in olivine matrix. At constant P and T, within one single capsule, orthopyroxene rims grow faster around quartz clasts in olivine matrix than around olivine clasts in quartz matrix. Fourier transform infra-red (FTIR) spectra indicate that the entire samples are water saturated due to water adsorption on the reactant grain surfaces. The increased orthopyroxene growth rates in olivine matrix as opposed to quartz matrix are interpreted in terms of matrix rheology, where in the two different matrix-inclusion arrangements the olivine matrix behaves "softer" and the quartz matrix "more rigid". The strain energy associated with accommodation of the negative reaction volume is higher for the quartz than the olivine matrix and reduces the free energy that drives orthopyroxene rim growth. Growth textures in both kinds of orthopyroxene rims indicate that the diffusivity of MgO slightly exceeds the diffusivity of SiO 2 . The relative mobility of MgO and SiO 2 at given P, T, fH 2 O seems to be controlled by energy minimization during orthopyroxene growth at the compressive Ol/Opx interface.Our experiments provide evidence for two previously overlooked effects relevant to rim growth reactions in metamorphic rocks: -diffusivity along chemical potential gradients to reaction sites is a function of rheology; -the relative diffusivity of components during reaction rim or corona growth is a function of local volume changes at the rim's interfaces.

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Section: Resultssupporting

confidence: 92%

“…In rims around olivine clasts about two‐third of the rim width is made up of indistinct palisades grown at the Opx/Ol interface. This proportion indicates that orthopyroxene replaces olivine at close to constant volume (relation 62:38), in accordance with stress minimization of a reaction in confined space (Abart et al. , 2004).…”

Section: Discussionsupporting

confidence: 62%

Matrix rheology effects on reaction rim growth I: evidence from orthopyroxene rim growth experiments

Milke

Abart

Kunze

et al. 2008

Journal Metamorphic Geology

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“…Reactions between incompatible minerals require transport of chemical components between reaction interfaces to occur, and this generally takes place in the intergranular medium of polycrystalline products. In the geological context, the most studied reaction is the growth of polycrystalline single rims of enstatite between forsterite and quartz, which was investigated over a wide range of temperatures and for various pressures (Yund 1997;Fisler et al 1997;Milke et al 2001Milke et al , 2007Milke et al , 2009Abart et al 2004;; see also Dohmen and Milke 2010). The growth rates of enstatite fall into two groups, following distinct Arrhenius lines separated by a gap of about four orders of magnitude at 1,000°C (Fig.…”

Section: Introductionmentioning

confidence: 99%

The effect of water on intergranular mass transport: new insights from diffusion-controlled reaction rims in the MgO–SiO2 system

Gardès

Wunder

Marquardt

et al. 2012

Contrib Mineral Petrol

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We experimentally investigate the effect of water on intergranular mass transport. The growth of enstatite single rims between forsterite and quartz and forsterite-enstatite double rims between periclase and quartz was performed at 1,000°C and 1.5 GPa for incremental water-solid fractions ranging from 0 to 5 wt%. A kinetics analysis based on time series ranging from 8 min to 18 h at 1 wt% H 2 O demonstrates that the growth of both the single and double rims is controlled by the transport of the chemical components in the intergranular medium. Inert platinum markers reveal that MgO is always the most mobile component, and the only one, except at the highest water fractions ([*2 wt%) where some mobility of SiO 2 is observed. Modelling yields that, in all of the rims from both the single and double rims, there is an increase by about six orders of magnitude between diffusivities in dry grain boundaries and in intergranular media with 5 wt% H 2 O of the bulk, therefore confirming that water/rock ratio is a parameter as important as temperature regarding reaction kinetics. The transition from dry to water-saturated conditions appears virtually instantaneous, occurring between 500 and 1,000 wt. ppm water-solid fraction. It corresponds to a jump of four to five orders of magnitude in diffusivities, in line with the gap between 'dry' and 'wet' enstatite single rim growth rates from various previous experimental investigations. At higher water-solid fractions, distinct increase in the diffusivities demonstrates the existence of two different intergranular transport mechanisms competing at water-saturated conditions. The first mechanism is diffusion in hydrous-saturated grain boundaries (HGBs), which dominates as long as pores are isolated. We estimate the Arrhenius law for MgO diffusion in enstatite HGBs to be d HGB D MgO HGB ¼ d HGB D 0 e ÀE=RT with E = 185 ± 20 kJ/mol and d HGB D 0 = 10 -14.7±0.9 m 3 /s, where d HGB is the effective width of the HGBs. The second mechanism is diffusion through fluid-filled channels, which dominates when pores are interconnected. A new description of the effect of water on intergranular mass transport is proposed.

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“…However, there are critical differences from experimentally reproduced reaction zone by Abart et al (2004). Firstly, the size contrast between the inner and outer zones is almost two orders of magnitude in the Horoman case, indicating that there must be discontinuity in garnet decomposition.…”

Section: The Mechanism and Timing Of Formation Of Lenticular Seemsmentioning

confidence: 83%

“…8). Abart et al (2004) experimentally reproduced a reaction zone (enstatite) between forsterite and quartz, which is zoned in terms of grain size, microstructure, and LPO. They interpreted that the outer zone composed of large enstatite grew from the initial forsterite quartz interface consuming quartz and that the inner zone composed of much finer enstatite grew consuming forsterite.…”

Section: The Mechanism and Timing Of Formation Of Lenticular Seemsmentioning

confidence: 88%

Formation and deformation mechanisms of pyroxene-spinel symplectite in an ascending mantle, the Horoman peridotite complex, Japan: An EBSD (electron backscatter diffraction) study

Odashima

Morishita

Ozawa

et al. 2007

Journal of Mineralogical and Petrological Sciences

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Symplectites, fine vermicular intergrowth (< 10 μm) of orthopyroxene, clinopyroxene, and spinel, and the surrounding lenticular coarser grained (100 200 μm) aggregate (seam) with the same mineral assemblage of the symplectites define remarkable foliation and lineation in spinel lherzolites of the Horoman complex, northern Japan. They are inferred to be products of reaction between garnet and olivine during decompression of the host peridotite accompanying deformation. Microstructure of a symplectite was investigated with automated electron backscattered diffraction (EBSD) analysis using a field emission gun SEM (FE SEM) in order to clarify reaction and deformation mechanisms and thereby better constraining mechanical interaction between the Earth's upper mantle and lower crust. The symplectite is composed of two segments with a large misorientation angle of ~ 60° only for spinel, and the two spinel crystals are in mirror symmetry with the segment boundary approximately parallel to the mirror plane. The segment boundary is interpreted as spinel law twin formed during phase transition from garnet. Each segment is further subdivided into several sectors with gradual lattice distortion smaller than a few degrees/mm and intra sector misorientation mostly smaller than 25° for all constituent minerals and with misorientation axes nearly perpendicular to the lineation and parallel to the foliation. The sector boundaries are inferred to be subgrain boundaries formed by dislocation creep of pyroxenes and spinel in the spinel stability field. The spinel twin suggests that a garnet was decomposed directly into entangled aggregate of pyroxenes and spinel, which grew from an embryo nucleated on the surface of the reactant garnet. The symplectite minerals in each sector show systematic crystallographic orientations (topotaxy) with each other. The topotaxial relationship in the fine intergrowth with subgrain structure demonstrates that the systematic crystallographic orientations were acquired when the crystals grew by decomposing the garnet and were later modified by deformation during the consecutive ascent of the complex.

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Silicon and oxygen self diffusion in enstatite polycrystals: the Milke et al. (2001) rim growth experiments revisited

Cited by 43 publications

References 20 publications

Matrix rheology effects on reaction rim growth I: evidence from orthopyroxene rim growth experiments

Matrix rheology effects on reaction rim growth I: evidence from orthopyroxene rim growth experiments

The effect of water on intergranular mass transport: new insights from diffusion-controlled reaction rims in the MgO–SiO2 system

Formation and deformation mechanisms of pyroxene-spinel symplectite in an ascending mantle, the Horoman peridotite complex, Japan: An EBSD (electron backscatter diffraction) study

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