EGU2020-13710, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-13710
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Relocated micas in marble – indicators for postdeformational microfabric modification

Rebecca Kühn1, Florian Duschl2, Bernd Leiss3, and Torben Schulze3
Rebecca Kühn et al.
  • 1Halle University, Geodynamics, Halle, Germany (rebecca.kuehn@geo.uni-halle.de)
  • 2Universität Erlangen-Nürnberg, GeoZentrum Nordbayern, Erlangen, Germany (florian.duschl@fau.de)
  • 3Universität Göttingen, GZG, Göttingen, Germany (bleiss1@gwdg.de)

A relocation of mica grains in marbles can be observed as trace of newly precipitated calcite material in cathodoluminescence microscopy analysis. Mica grains relocate by rotation and/or translation from foliation parallel to new irregular orientations. The mica grains can be either located at calcite grain boundaries or within large calcite grains.

The process erases deformed, inclusion-rich calcite material and creates undeformed and mostly inclusion-free grains and can therefore be regarded as postdeformational. Not every mica present relocates and the choice of whether a specific mica relocates cannot be related to a specific primary orientation. Furthermore, no significant difference in composition between relocated and non-relocated mica grains can be observed. Newly precipitated calcite has less Mg than the dissolved grain material.

The precipitation of new calcite material at the calcite-mica interface is supposed to be the initial trigger leading to dissolution of inclusion-rich, deformed calcite material at the opposite side of the mica grain. The newly precipitated calcite material inherits the already existing calcite grain‘s crystallographic orientation.

Assuming this process occurs to a larger extent in a material, it might modify a deformation-related microfabric. Therefore, an interpretation in terms of deformation conditions should be done carefully, considering postdeformational dissolution-precipitation processes.

How to cite: Kühn, R., Duschl, F., Leiss, B., and Schulze, T.: Relocated micas in marble – indicators for postdeformational microfabric modification, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13710, https://doi.org/10.5194/egusphere-egu2020-13710, 2020

Display materials

Display file

Comments on the display material

AC: Author Comment | CC: Community Comment | Report abuse

Display material version 1 – uploaded on 05 May 2020
  • CC1: Comment on EGU2020-13710, Marian Holness, 06 May 2020

    I am very intrigued by your mica migration. I found something rather similar in quartz-rich metasediments. I would love to talk about this with you.

    Holness, M.B.  (2003) Growth and albitisation of K-feldspar in crystalline rocks in the shallow crust: a tracer for fluid circulation? Geofluids, 3, 89-102.