EGU21-9404
https://doi.org/10.5194/egusphere-egu21-9404
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Trace-element migration during crystal-plastic deformation in UHP rutile: dislocations in low-angle boundaries as high-diffusivity pathways.

Rick Verberne1, Hugo van Schrojenstein Lantman2, Steven Reddy3,4, Matteo Alvaro2, David Wallis5, Denis Fougerouse3,4, Antonio Langone6, Marco Scambelluri7, David Saxey3, and William Rickard3
Rick Verberne et al.
  • 1Center for Star and Planet Formation, Globe Institute, University of Copenhagen, Øster Voldgade 5–7, DK-1350 Copenhagen
  • 2Department of Earth and Environmental Sciences, University of Pavia, Via A. Ferrata, 1 I-27100 Pavia, Italy
  • 3Geoscience Atom Probe, ARCF, John de Laeter Centre, Curtin University, Perth, WA 6845, Australia.
  • 4School of Earth and Planetary Sciences, Curtin University, Perth, WA 6845, Australia
  • 5Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom
  • 6Institute of Geosciences and Earth Resources, National Research Council (C.N.R), 27100 Pavia, Italy
  • 7Department of Earth, Environment and Life Sciences, University of Genoa, Corso Europa 26, 16132 Genoa, Italy

The trace-element composition of rutile is commonly used to constrain P-T-t conditions for a wide range of metamorphic systems. Recent studies have highlighted the importance of micro- and nanostructures in the redistribution of trace elements in rutile via high-diffusivity pathways and dislocation-impurity associations. In this contribution, we investigate the effect of crystal-plastic deformation of rutile on its composition by combining microstructural and petrological analyses with atom probe tomography. The studied sample is from an omphacite vein of the ultrahigh-pressure metamorphic Lago di Cignana unit, Western Alps, Italy. Zr-in-rutile thermometry and inclusions of quartz in rutile and of coesite in omphacite constrain rutile deformation to around the prograde HP-UHP boundary at 500–550 °C. Crystal-plastic deformation of a large rutile grain resulted in low-angle boundaries that generate a total misorientation of ~25°. Dislocations constituting the low-angle boundary are enriched in common (Fe, Zr) and uncommon trace elements (Ca). The Ca is interpreted to be derived from the grain exterior, suggesting diffusion of trace elements along the dislocation cores. The potential for dislocation microstructures to act as fast diffusion pathways must be evaluated when applying traditional geochemical analyses as compositional disturbances caused by the presence of dislocation might lead to erroneous interpretations.

How to cite: Verberne, R., van Schrojenstein Lantman, H., Reddy, S., Alvaro, M., Wallis, D., Fougerouse, D., Langone, A., Scambelluri, M., Saxey, D., and Rickard, W.: Trace-element migration during crystal-plastic deformation in UHP rutile: dislocations in low-angle boundaries as high-diffusivity pathways., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9404, https://doi.org/10.5194/egusphere-egu21-9404, 2021.

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