EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Atom probe as a tool for understanding mineral physics and rock deformation: a case study of deformed wehrlite

Joseph Cukjati1, Reid Cooper1, Stephen Parman1, Ningli Zhao1, Austin Akey2, and Fernando Laiginhas3
Joseph Cukjati et al.
  • 1Earth, Environmental and Planetary Science, Brown University, Providence RI, USA (
  • 2Center for Nanoscale Systems, Harvard University, Cambridge MA, USA
  • 3Alabama Analytical Research Facility, University of Alabama - Tuscaloosa, Tuscaloosa AL, USA

Here we report Atom Probe Tomography (APT) analyses of grain and phase boundaries of laboratory-deformed, fine-grained mixtures of clinopyroxene and olivine (Zhao, et al., 2019).  The experiments show that the mixtures deform much more rapidly than either mineral endmember.  This enhanced deformation in the two-phase material is due to stress-driven reactions at the phase boundaries. Lower effective viscosities of phase mixtures may be critical to the initiation of plate tectonics and the formation of mantle shear zones.

The hypothesis presented here is that the ‘bulk rock’ – a wehrlite – deforms rapidly because conversion of one phase to the other occurs at phase boundaries (e.g., Sundberg & Cooper, 2008).  In this model, grain-scale transport of the shared (slowly-diffusing) mineralogical component Si4+ is not required.  The near-boundary gradients of olivine-insoluble ions are presented as evidence of the phase transformation which either dissolves olivine into clinopyroxene or vice versa.  

The resolving power of the APT makes it a promising tool for investigating the microphysics of rock deformation, bridging the atomic scale all the way to the plate-tectonic scale.

Sundberg M, Cooper RF (2008) Crystallographic preferred orientation produced by diffusional creep of harzburgite: effects of chemical interactions among phases during plastic flow. J Geophys Res Solid Earth 113(12):B12208.
Zhao N, Hirth G, Cooper RF, Kruckenberg SC, Cukjati J (2019) Low viscosity of mantle rocks linked to phase boundary sliding. Earth Planet Sci Lett 517:83–94.

How to cite: Cukjati, J., Cooper, R., Parman, S., Zhao, N., Akey, A., and Laiginhas, F.: Atom probe as a tool for understanding mineral physics and rock deformation: a case study of deformed wehrlite, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6581,, 2021.

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