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Preprints
https://doi.org/10.5194/egusphere-2022-311
https://doi.org/10.5194/egusphere-2022-311
20 May 2022
 | 20 May 2022

Epidote dissolution–precipitation during viscous granular flow: a micro-chemical and isotope study

Veronica Peverelli, Alfons Berger, Martin Wille, Thomas Pettke, Pierre Lanari, Igor M. Villa, and Marco Herwegh

Abstract. Deformation of polymineralic aggregates can be accommodated by viscous granular flow, a process mediated by the interplay among intracrystalline plasticity and dissolution–precipitation, each active in specific minerals at given P–T conditions. Common rock-forming minerals like quartz, feldspars and sheet silicates have been intensively studied in terms of deformation processes. Instead, the deformation behavior of epidote and its role during viscous granular flow is not well investigated, although this mineral is ubiquitous in granitic rocks deforming at greenschist-facies conditions. In this contribution, we provide microstructural and geochemical evidence for the occurrence of dissolution–precipitation of epidote during deformation of an epidote-quartz vein. The main part of the vein is deformed producing a fold, which is visible due to relicts of primary-growth layering inside the vein. The deformation mechanisms active during deformation include dynamic recrystallization of quartz by subgrain rotation recrystallization, producing grain-size reduction of the primary vein quartz. This occurs contemporaneously with dissolution and (re)precipitation of epidote, and grain-boundary sliding, leading to a combined process described as viscous granular flow. The combination of intracrystalline plasticity, grain boundary sliding and dissolution locally and repeatedly produce creep cavities. These represent not only loci for nucleation of new epidote grains at the expenses of dissolved one, but they also allow fluid-mediated transport of elements. The same trace element patterns between old epidote relicts and newly formed grains, with much narrower variability, indicate a process of chemical homogenization. The nature of the fluid mediating deformation is investigated using Pb–Sr isotope data of epidote, which suggest that deformation is assisted by internally recycled fluids with the addition of a syn-kinematic external fluid component.

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Journal article(s) based on this preprint

22 Nov 2022
Epidote dissolution–precipitation during viscous granular flow: a micro-chemical and isotope study
Veronica Peverelli, Alfons Berger, Martin Wille, Thomas Pettke, Pierre Lanari, Igor Maria Villa, and Marco Herwegh
Solid Earth, 13, 1803–1821, https://doi.org/10.5194/se-13-1803-2022,https://doi.org/10.5194/se-13-1803-2022, 2022
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

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This work studies the interplay of epidote dissolution-precipitation and quartz dynamic...
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