Skip to Main content Skip to Navigation
Journal articles

The role of deformation-reaction interactions to localize strain in polymineralic rocks: Insights from experimentally deformed plagioclase-pyroxene assemblages

Nicolas Mansard 1, 2 Holger Stünitz 1, 2, 3 Hugues Raimbourg 1, 2 Jacques Précigout 1, 2
2 Géodynamique - UMR7327
INSU - CNRS - Institut national des sciences de l'Univers, UO - Université d'Orléans : UMR7327, BRGM - Bureau de Recherches Géologiques et Minières (BRGM), ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327 : UMR7327
Abstract : In order to study the mutual effect of deformation and mineral reactions, we have conducted shear experiments on fine-grained plagioclase-pyroxene assemblages in a Griggs-type solid-medium deformation apparatus. Experiments were performed at a constant shear strain rate of 10−5 s−1, a confining pressure of 1 GPa and temperatures of 800, 850 and 900 °C. While the peak stress of plagioclase + orthopyroxene assemblages reaches values between those of the end-member phases, the strength of polymineralic materials strongly decreases after peak stress and reaches flow stresses that stabilize far below those of the weaker phase (plagioclase). This weakening correlates with the coeval development of high-strain shear zones where new phases are preferentially produced, including new pyroxene, plagioclase and amphibole. The reaction products mostly occur as intimately mixed phases within fine-grained and interconnected shear bands, together with different compositions with respect to the starting material. This indicates that deformation significantly enhances the kinetics of mineral reactions, which in turn strongly weaken the deforming sample, here attributed to a switch to grain-size-sensitive diffusion creep through phase nucleation and grain size reduction. Such an interplay between deformation and mineral reactions may have strong implications for the initiation, development, and durability of shear zones in the lower crust.
Complete list of metadatas

Cited literature [54 references]  Display  Hide  Download

https://hal-insu.archives-ouvertes.fr/insu-02476212
Contributor : Nathalie Pothier <>
Submitted on : Wednesday, February 12, 2020 - 3:15:48 PM
Last modification on : Wednesday, September 23, 2020 - 4:39:17 AM
Long-term archiving on: : Wednesday, May 13, 2020 - 5:07:56 PM

File

1-s2.0-S0191814119303487-main....
Files produced by the author(s)

Identifiers

Collections

Citation

Nicolas Mansard, Holger Stünitz, Hugues Raimbourg, Jacques Précigout. The role of deformation-reaction interactions to localize strain in polymineralic rocks: Insights from experimentally deformed plagioclase-pyroxene assemblages. Journal of Structural Geology, Elsevier, 2020, 134, 104008 (18 p.). ⟨10.1016/j.jsg.2020.104008⟩. ⟨insu-02476212⟩

Share

Metrics

Record views

136

Files downloads

30