Titel
Localization of submicron inclusion re-equilibration at healed fractures in host garnet
Autor*in
D. Rhede
GFZ Potsdam
... show all
Abstract
Microstructures in Permian inclusion-bearing meta-pegmatite garnets from the Koralpe (Eastern Alps, Austria) reveal re-equilibration by coarsening of abundant submicron-sized inclusions (1 µm – 2 nm diameter) at the site of healed brittle cracks. The microstructures developed during Cretaceous eclogite facies deformation and the related overprinting of the host-inclusion system. Trails of coarsened inclusions (1 – 10 µm diameter) crosscut the garnet, defining traces of former fractures with occasional en-echelon overlaps. Trails are flanked by 10 – 100 µm wide ‘bleaching zones’ characterized by the absence of ≤1 µm sized inclusions in optical and SE images. FEG-microprobe data show that trails and bleaching zones can form isochemically, although some trails exhibit non-isochemical coarsening. Cross correlation EBSD reveals subtle garnet lattice rotation of up to 0.45° around consistent misorientation axes, spatially correlated with bleaching zones. Elevated dislocation density within these zones is confirmed by TEM observations. Brittle fracture enhanced diffusion rates in the lattice adjacent to crack planes, priming these areas to behave differently to the bulk of the garnet during Cretaceous metamorphism and facilitating localized coarsening of inclusions. The preferred mechanism for this is increased dislocation density near former cracks, with the dislocations interpreted as a plastic wake originating from crystal plastic deformation at the crack tip. This partially closed host-inclusion system clearly records the influence of deformation mechanisms on re-equilibration and contributes to a wider understanding of the interaction between deformation and chemical reaction during metamorphism.
Stichwort
DiffusionEBSDGarnetInclusionsFracturingRe-equilibration
Objekt-Typ
Sprache
Englisch [eng]
Persistent identifier
https://phaidra.univie.ac.at/o:397967
Erschienen in
Titel
Contributions to Mineralogy and Petrology
Band
168
Ausgabe
6
Seitenanfang
1
Seitenende
21
Verlag
Springer Science + Business Media
Verfügbarkeitsdatum
15.11.2015
Datum der Annahme zur Veröffentlichung
2014
Zugänglichkeit

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