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Solid Earth An interactive open-access journal of the European Geosciences Union

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https://doi.org/10.5194/se-2018-39
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
07 May 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Solid Earth (SE).
Syn-kinematic hydration reactions, dissolution-precipitation creep and grain boundary sliding in experimentally deformed plagioclase-pyroxene mixtures
Sina Marti1, Holger Stünitz2,3, Renée Heilbronner1, Oliver Plümper4, and Rüdiger Kilian1 1Department of Environmental Sciences, Basel University, Switzerland
2Department of Geosciences, UiT the Arctic University of Norway, Norway
3Institut des Sciences de la Terre d’Orléans (ISTO), Université d’Orléans, France
4Department of Earth Sciences, Utrecht University, the Netherlands
Abstract. While it is widely observed that mafic rocks are able to exeprience high strains by viscous flow, details on their rheology and deformation mechanisms are poorly constrained. Here, rock deformation experiments on four different, water-added plagioclase-pyroxene mixtures are presented: (i) plagioclase(An60-70) – clinopyroxene – orthopyroxene, (ii) plagioclase(An60) – diopside, (iii) plagioclase(An60) – enstatite and (iv) plagioclase(An01) – enstatite. Samples were deformed in general shear at strain rates of 3 × 10−5 to 3 × 10−6 s−1, 800 °C and confining pressure of 1.0 or 1.5 GPa. Results indicate that dissolution-precipitation creep (DPC) and grain boundary sliding (GBS) are the dominant deformation mechanisms. Coinciding with sample deformation, syn-kinematic mineral reactions yield abundant nucleation of new grains; the resulting intense grain size reduction is considered crucial for the activity of DPC and GBS. In high strain zones dominated by plagioclase, a weak, non-random and geometrically consistent crystallographic preferred orientation (CPO) is observed. Usually, a CPO is considered a consequence of dislocation creep, but the experiments presented here demonstrate that a CPO can develop during DPC and GBS. This study provides new evidence for the importance of DPC and GBS in mid-crustal shear zones within mafic rocks, which has important implications on understanding and modelling of mid-crustal rheology and flow.
Citation: Marti, S., Stünitz, H., Heilbronner, R., Plümper, O., and Kilian, R.: Syn-kinematic hydration reactions, dissolution-precipitation creep and grain boundary sliding in experimentally deformed plagioclase-pyroxene mixtures, Solid Earth Discuss., https://doi.org/10.5194/se-2018-39, in review, 2018.
Sina Marti et al.
Sina Marti et al.
Sina Marti et al.

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Short summary
Using rock deformation experiments, deformation mechanisms and the rheology of fault rocks at mid-crustal levels are investigated. For the studied material, fluid-assisted mass-transport and grain sliding are the dominant deformation mechanisms, when small amounts of water are present. Our results provide new data on the rheology of plate-boundaries and fault zones and the wide range of presented microstructures will help to correlate observations from experiments and nature.
Using rock deformation experiments, deformation mechanisms and the rheology of fault rocks at...
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