A material model for compositional resetting due to coupled mechanical and chemical effects

The compositional record in mineral grains is used to characterize temperatures (geothermometry), pressures (geobarometry), dates (geochronology) and durations (diffusion chronometry). However, the accessible record is limited by the timing of formation of a grain, either by primary crystallization or by recrystallization due to mechanical or chemical influences. In this presentation we would like to focus on recrystallization. One effect which causes recrystallization is the effect of lattice strain caused by the diffusion of ions of a different size in a mineral. While the lattice strain itself has been studied [1] in detail, the effect on recrystallization has only been shown qualitatively in experimental settings [2, 3] and field observations [4]. A model for a single crystal has been developed recently [5], but the effect on a polycrystalline rock has not been studied yet.

In this presentation we build on the model introduced by Haddenhorst et al. [5] for the evolution of a single olivine crystal. We simulate multiple crystals simultaneously and introduce a maximum volume constraint. This enables us to predict the composition and crystal sizes in a rock bearing multiple olivine crystals in a small volume (e.g. a dunite). Results of simulations and comparisons with real world examples will be shown.

 

References:

[1]: Blundy, J., & Wood, B. (1994). Prediction of crystal–melt partition coefficients from elastic moduli. Nature, 372 (6505), 452–454.

[2]: Bestmann, M., Pennacchioni, G., Grasemann, B., Huet, B., Jones, M. W. M., & Kewish, C. M. (2021). Influence of deformation and fluids on ti exchange in natural quartz. Journal of Geophysical Research: Solid Earth, 126 (12), e2021JB022548. Retrieved from https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2021JB022548

[3]: Beyer, C., & Chakraborty, S. (2021). Internal stress-induced recrystallization and diffusive transport in catio3-pbtio3 solid solutions: A new transport mechanism in geomaterials and its implications for thermobarometry, geochronology, and geospeedometry. American Mineralogist: Journal of Earth and Planetary Materials, 106 (12), 1940–1949.

[4]: Nachlas, W., & Hirth, G. (2015). Experimental constraints on the role of dynamic recrystallization on resetting the ti-in-quartz thermobarometer. Journal of Geophysical Research: Solid Earth, 120 (12), 8120–8137.

[5]: Haddenhorst, H. H., Chakraborty, S., & Hackl, K. (2023). A model for the evolution size and composition of olivine crystals. Proceedings in Applied Mathematics and Mechanics, 00, e202300081. https://doi.org/10.1002/pamm.202300081