Constraining transformation weakening in plagioclase-pyroxene mixtures
International audience Mafic rocks are a key constituent of the oceanic and lower continental crust. Strain localisation and fabric development in these rocks is controlled by the active deformation mechanisms. From studies of natural rocks it has been established that strain localisation and weaken...
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HAL CCSD
2022
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Online Access: | https://insu.hal.science/insu-03810469 https://doi.org/10.5194/egusphere-egu22-2627 |
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BRGM: HAL (Bureau de Recherches Géologiques et Minières) |
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English |
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[SDU]Sciences of the Universe [physics] [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
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[SDU]Sciences of the Universe [physics] [SDU.STU]Sciences of the Universe [physics]/Earth Sciences Lee, Amicia Stünitz, Holger Soret, Mathieu Précigout, Jacques Constraining transformation weakening in plagioclase-pyroxene mixtures |
topic_facet |
[SDU]Sciences of the Universe [physics] [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
description |
International audience Mafic rocks are a key constituent of the oceanic and lower continental crust. Strain localisation and fabric development in these rocks is controlled by the active deformation mechanisms. From studies of natural rocks it has been established that strain localisation and weakening in mafic rocks is directly related to fluid availability and resultant mineral reactions. Understanding the interplay between reactions, fluid availability, and deformation aids in quantifying the stresses and rates of deformation processes. We have conducted an experimental investigation to constrain the weakening mechanisms in gabbro. Shear experiments were performed in a Griggs-type apparatus at 800-900°C, and 1.2-1.5 GPa with a shear strain rate of 10 ⁵s 1 . The starting material consists of mixed powders with <100 μm sized grains of plagioclase and clinopyroxene from an undeformed sample of the Kågen Gabbro in Northern Norway. Experiments have been conducted with 'as is' (dried at 110°C) starting material and with 0.1% added water. The experiments at 800°C are very strong with a peak shear stress ~0.8 GPa whilst the 900°C experiments are weaker, reaching peak stresses of ~0.35 GPa. The 800°C experiments show evidence of mineral reactions with newly formed phases making up 10-25% of the sample. In these reaction zones, plagioclase and clinopyroxene have reacted to produce amphibole and garnet. Additionally S-C' mylonitic fabrics have developed in these samples. The 900°C samples show minimal evidence for mineral reactions (2-5% new material) or crystal-plastic deformation mechanisms. The lack of mineral reactions in the rheologically weak experiments (900°C) and abundance of reaction products in the mechanically strong experiments (800°C) is conflicting to our inferences of natural studies. However, if partial melting takes place in the higher temperature experiments, it may account for the pronounced strength decrease. We plan to conduct EBSD and TEM analysis to determine crystallographic properties and ... |
author2 |
Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO) Bureau de Recherches Géologiques et Minières (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC) Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS) Géodynamique - UMR7327 Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS) |
format |
Conference Object |
author |
Lee, Amicia Stünitz, Holger Soret, Mathieu Précigout, Jacques |
author_facet |
Lee, Amicia Stünitz, Holger Soret, Mathieu Précigout, Jacques |
author_sort |
Lee, Amicia |
title |
Constraining transformation weakening in plagioclase-pyroxene mixtures |
title_short |
Constraining transformation weakening in plagioclase-pyroxene mixtures |
title_full |
Constraining transformation weakening in plagioclase-pyroxene mixtures |
title_fullStr |
Constraining transformation weakening in plagioclase-pyroxene mixtures |
title_full_unstemmed |
Constraining transformation weakening in plagioclase-pyroxene mixtures |
title_sort |
constraining transformation weakening in plagioclase-pyroxene mixtures |
publisher |
HAL CCSD |
publishDate |
2022 |
url |
https://insu.hal.science/insu-03810469 https://doi.org/10.5194/egusphere-egu22-2627 |
op_coverage |
Online, Austria |
genre |
Northern Norway |
genre_facet |
Northern Norway |
op_source |
EGU22 https://insu.hal.science/insu-03810469 EGU22, May 2022, Online, Austria. ⟨10.5194/egusphere-egu22-2627⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.5194/egusphere-egu22-2627 insu-03810469 https://insu.hal.science/insu-03810469 BIBCODE: 2022EGUGA.24.2627L doi:10.5194/egusphere-egu22-2627 |
op_rights |
http://creativecommons.org/licenses/by/ |
op_doi |
https://doi.org/10.5194/egusphere-egu22-2627 |
_version_ |
1799486152037629952 |
spelling |
ftbrgm:oai:HAL:insu-03810469v1 2024-05-19T07:46:01+00:00 Constraining transformation weakening in plagioclase-pyroxene mixtures Lee, Amicia Stünitz, Holger Soret, Mathieu Précigout, Jacques Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO) Bureau de Recherches Géologiques et Minières (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC) Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS) Géodynamique - UMR7327 Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC) Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS) Online, Austria 2022-05-23 https://insu.hal.science/insu-03810469 https://doi.org/10.5194/egusphere-egu22-2627 en eng HAL CCSD info:eu-repo/semantics/altIdentifier/doi/10.5194/egusphere-egu22-2627 insu-03810469 https://insu.hal.science/insu-03810469 BIBCODE: 2022EGUGA.24.2627L doi:10.5194/egusphere-egu22-2627 http://creativecommons.org/licenses/by/ EGU22 https://insu.hal.science/insu-03810469 EGU22, May 2022, Online, Austria. ⟨10.5194/egusphere-egu22-2627⟩ [SDU]Sciences of the Universe [physics] [SDU.STU]Sciences of the Universe [physics]/Earth Sciences info:eu-repo/semantics/conferenceObject Conference papers 2022 ftbrgm https://doi.org/10.5194/egusphere-egu22-2627 2024-05-02T00:09:59Z International audience Mafic rocks are a key constituent of the oceanic and lower continental crust. Strain localisation and fabric development in these rocks is controlled by the active deformation mechanisms. From studies of natural rocks it has been established that strain localisation and weakening in mafic rocks is directly related to fluid availability and resultant mineral reactions. Understanding the interplay between reactions, fluid availability, and deformation aids in quantifying the stresses and rates of deformation processes. We have conducted an experimental investigation to constrain the weakening mechanisms in gabbro. Shear experiments were performed in a Griggs-type apparatus at 800-900°C, and 1.2-1.5 GPa with a shear strain rate of 10 ⁵s 1 . The starting material consists of mixed powders with <100 μm sized grains of plagioclase and clinopyroxene from an undeformed sample of the Kågen Gabbro in Northern Norway. Experiments have been conducted with 'as is' (dried at 110°C) starting material and with 0.1% added water. The experiments at 800°C are very strong with a peak shear stress ~0.8 GPa whilst the 900°C experiments are weaker, reaching peak stresses of ~0.35 GPa. The 800°C experiments show evidence of mineral reactions with newly formed phases making up 10-25% of the sample. In these reaction zones, plagioclase and clinopyroxene have reacted to produce amphibole and garnet. Additionally S-C' mylonitic fabrics have developed in these samples. The 900°C samples show minimal evidence for mineral reactions (2-5% new material) or crystal-plastic deformation mechanisms. The lack of mineral reactions in the rheologically weak experiments (900°C) and abundance of reaction products in the mechanically strong experiments (800°C) is conflicting to our inferences of natural studies. However, if partial melting takes place in the higher temperature experiments, it may account for the pronounced strength decrease. We plan to conduct EBSD and TEM analysis to determine crystallographic properties and ... Conference Object Northern Norway BRGM: HAL (Bureau de Recherches Géologiques et Minières) |