Skip to Main content Skip to Navigation
Theses

Modes de localisation des déformations dans les Failles de détachement océaniques : le cas extrême d'une dorsale lente à très faible budget magmatique

Abstract : The Southwest Indian Ridge in its eastern part has particularly low magmatic inputs and is therefore a natural laboratory to study oceanic accretion in an extreme configuration for which the divergence of the plates is almost completely accommodated by large offset normal faults, also called detachment faults. These faults exhume mantle-derived peridotites. Very little is known about the deformation mechanisms that operate at the lower levels of the lithosphere, prior to serpentinization.We studied the deformation textures, analyze strain localization mechanisms, as well as mineralogical assemblages associated with these mechanisms from a corpus of almost 400 samples of serpentinized peridotites dredged during the SMoothSeafloor cruise (2010). All samples display heterogeneous deformation combining brittle (fracturation, kinks) and plastic mechanisms (undulose extinction, subgrain boundaries, dynamic recrystallization). For example, microfracturation and kinks are locally accompanied by partial recrystallization of the primary minerals into fine-grained aggregates along orthopyroxene grains. These textures result from high stress and high temperature conditions at the base of the lithosphere, where the root of the active detachment.We use these microstructural observations to constrain a 2D thermomechanical model of lithospheric extension, in which we explore two weakening mechanisms seen in the samples: serpentinization (temperatures < 350°C) and grain size reduction (> 800°C). Combining the two, we develop detachment faults in a thick lithospheric context (20-25 km), with fault topography and offsets that are consistent with geological observations in the eastern SWIR.
Document type :
Theses
Complete list of metadatas

https://tel.archives-ouvertes.fr/tel-03027071
Contributor : Abes Star :  Contact
Submitted on : Friday, November 27, 2020 - 1:03:29 AM
Last modification on : Saturday, November 28, 2020 - 3:29:53 AM

File

BICKERT_Manon_va2.pdf
Version validated by the jury (STAR)

Identifiers

  • HAL Id : tel-03027071, version 1

Collections

Citation

Manon Bickert. Modes de localisation des déformations dans les Failles de détachement océaniques : le cas extrême d'une dorsale lente à très faible budget magmatique. Sciences de la Terre. Université de Paris, 2019. Français. ⟨NNT : 2019UNIP7050⟩. ⟨tel-03027071⟩

Share

Metrics

Record views

86

Files downloads

39