Grain boundary diffusion of Si, Mg, and O in enstatite reaction rims: a SIMS study using isotopically doped reactants

Milke, Ralf; Wiedenbeck, Michael; Heinrich, Wilhelm

doi:10.1007/s004100100277

Cited by 66 publications

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“…The observed stable isotope profiles do not contain any step discontinuities but have a significant slope all across the reaction rim (see Fig. 2 of Milke et al 2001). On the one hand, this feature hampers the determination of the position of the original quartz-forsterite interface from stable isotope signatures.…”

Section: Introductionmentioning

confidence: 99%

“…If the silicon and oxygen isotopic labels were transported passively with the diffusing species, flat isotopic profiles with step discontinuities at the position of the original quartz-forsterite interface as well as at the enstatite-forsterite and the enstatite-quartz interfaces would be expected (see Fig. 4 of Milke et al 2001). In this case the position of the original quartz-forsterite interface and, hence, the net material fluxes could be determined unambiguously from a jump discontinuity of the isotopic composition within the enstatite rim.…”

Section: Introductionmentioning

confidence: 99%

“…An alternative approach, which is based on the use of isotopically labelled reactants, was employed by Milke et al (2001). The authors synthesized enstatite reaction rims at quartz-forsterite contacts (see Fig.…”

Section: Introductionmentioning

confidence: 99%

“…The authors synthesized enstatite reaction rims at quartz-forsterite contacts (see Fig. 1a, b of Milke et al 2001). As reactants they used quartz, which was extremely enriched in 18 O and 29 Si, and forsterite with normal isotopic composition.…”

Section: Introductionmentioning

confidence: 99%

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

Abart

Kunze

Milke

et al. 2004

Contrib Mineral Petrol

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Milke et al. (Contrib Mineral Petrol 142:15-26, 2001) studied the diffusion of Si, Mg and O in synthetic polycrystalline enstatite reaction rims. The reaction rims were grown at 1,000°C and 1 GPa at the contacts between forsterite grains with normal isotopic compositions and a quartz matrix extremely enriched in 18 O and 29 Si. The enstatite reaction rim grew from the original quartz-forsterite interface in both directions producing an inner portion, which replaced forsterite and an outer portion, which replaced quartz. Here we present new support for this statement, as the two portions of the rim are clearly distinguished based on crystal orientation mapping using electron backscatter diffraction (EBSD). Milke et al. (Contrib Mineral Petrol 142:15-26, 2001) used the formalism of LeClaire (J Appl Phys 14: [351][352][353][354][355][356] 1963) to derive the coefficient of silicon grain boundary diffusion from stable isotope profiles across the reaction rims. LeClaire's formalism is designed for grain boundary tracer diffusion into an infinite half space with fixed geometry. A fixed geometry is an undesired limitation in the context of rim growth. We suggest an alternative model, which accounts for simultaneous layer growth and superimposed silicon and oxygen self diffusion. The effective silicon bulk diffusivity obtained from our model is approximately equal within both portions of the enstatite reaction rim: , in its outer portion. Microstructural evidence suggests that transient porosity and small amounts of fluid were concentrated at the quartz-enstatite interface during rim growth. This leads us to suspect that the presence of an aqueous fluid accelerated oxygen diffusion in the outer portion of the reaction rim. In contrast, silica diffusion does not appear to have been affected by the spatial variation in the availability of an aqueous fluid.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Abart

Kunze

Milke

et al. 2004

Contrib Mineral Petrol

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“…These models have been substantiated by a vast body of rigorous experimental work constraining the kinetics of reaction rim growth (e.g. Farver and Yund, 1996;Yund, 1997;Fisler et al, 1997;Milke et al, 2001;Watson and Price, 2002;Milke and Heinrich, 2002;Milke and Wirth, 2003;Abart and Schmidt, 2004;Schmid et al, 2009;Götze et al, 2010;Keller et al, 2008;Niedermeier et al, 2009;Dohmen and Milke, 2010;Keller et al, 2010;Joachim et al, 2011a, b;Mueller et al, 2012;Helpa et al, 2014Helpa et al, , 2015Jonas et al, 2015;Abart et al, 2016). Phenomenological models of disequilibrium elemental and isotopic compositions produced experimentally with incomplete diffusive element exchange (e.g.…”

Section: Reaction Kineticsmentioning

confidence: 99%

Arrested development – a comparative analysis of multilayer corona textures in high-grade metamorphic rocks

Ogilvie

Gibson

2017

Solid Earth

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Abstract. Coronas, including symplectites, provide vital clues to the presence of arrested reaction and preservation of partial equilibrium in metamorphic and igneous rocks. Compositional zonation across such coronas is common, indicating the persistence of chemical potential gradients and incomplete equilibration. Major controls on corona mineralogy include prevailing pressure (P ), temperature (T ) and water activity (aH 2 O) during formation, reaction duration (t) single-stage or sequential corona layer growth; reactant bulk compositions (X) and the extent of metasomatic exchange with the surrounding rock; relative diffusion rates for major components; and/or contemporaneous deformation and strain. High-variance local equilibria in a corona and disequilibrium across the corona as a whole preclude the application of conventional thermobarometry when determining P -T conditions of corona formation, and zonation in phase composition across a corona should not be interpreted as a record of discrete P -T conditions during successive layer growth along the P -T path. Rather, the local equilibria between mineral pairs in corona layers more likely reflect compositional partitioning of the corona domain during steadystate growth at constant P and T .Corona formation in pelitic and mafic rocks requires relatively dry, residual bulk rock compositions. Since most melt is lost along the high-T prograde to peak segment of the P -T path, only a small fraction of melt is generally retained in the residual post-peak assemblage. Reduced melt volumes with cooling limit length scales of diffusion to the extent that diffusion-controlled corona growth occurs. On the prograde path, the low melt (or melt-absent) volumes required for diffusion-controlled corona growth are only commonly realized in mafic igneous rocks, owing to their intrinsic anhydrous bulk composition, and in dry, residual pelitic compositions that have lost melt in an earlier metamorphic event.Experimental work characterizing rate-limiting reaction mechanisms and their petrogenetic signatures in increasingly complex, higher-variance systems has facilitated the refinement of chemical fractionation and partial equilibration diffusion models necessary to more fully understand corona development. Through the application of quantitative physical diffusion models of coronas coupled with phase equilibria modelling utilizing calculated chemical potential gradients, it is possible to model the evolution of a corona through P -T -X-t space by continuous, steady-state and/or sequential, episodic reaction mechanisms. Most coronas in granulites form through a combination of these endmember reaction mechanisms, each characterized by distinct textural and chemical potential signatures with very different petrogenetic implications. An understanding of the inherent petrogenetic limitations of a reaction mechanism model is critical if an appropriate interpretation of P -T evolution is to be inferred from a corona. Since corona modelling employing calculated chemical potential gradie...

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Current Awareness

2002

J. Mass Spectrom.

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In order to keep subscribers up‐to‐date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of mass spectrometry. Each bibliography is divided into 11 sections: 1 Books, Reviews & Symposia; 2 Instrumental Techniques & Methods; 3 Gas Phase Ion Chemistry; 4 Biology/Biochemistry: Amino Acids, Peptides & Proteins; Carbohydrates; Lipids; Nucleic Acids; 5 Pharmacology/Toxicology; 6 Natural Products; 7 Analysis of Organic Compounds; 8 Analysis of Inorganics/Organometallics; 9 Surface Analysis; 10 Environmental Analysis; 11 Elemental Analysis. Within each section, articles are listed in alphabetical order with respect to author (3 Weeks journals ‐ Search completed at 2nd. Jan. 2002)

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Grain boundary diffusion of Si, Mg, and O in enstatite reaction rims: a SIMS study using isotopically doped reactants

Cited by 66 publications

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

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

Arrested development – a comparative analysis of multilayer corona textures in high-grade metamorphic rocks

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