Shear localisation in upper mantle peridotites

Drury, M. R.; Vissers, R. L. M.; Wal, D. van der; Strating, E. H. Hoogerduijn

doi:10.1007/bf00879044

Cited by 113 publications

(81 citation statements)

References 75 publications

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“…A weak LPO and lower dislocation density of olivine and the presence of four-grain junctions in the small-grained area are clear evidence that grain-boundary sliding influenced the deformation of olivine (Hirth and Kohlstedt 1995). A similar change in the deformation mechanism in the mylonite zone has been reported by Drury et al (1991), Jin et al (1998), Ueda et al (2008), Linckens et al (2011), andDrury et al (2011).…”

Section: Deformation Mechanismsupporting

confidence: 51%

Characterization of olivine fabrics and mylonite in the presence of fluid and implications for seismic anisotropy and shear localization

Jung

Austrheim

2014

Earth Planet Sp

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The Lindås Nappe, Bergen Arc, is located in western Norway and displays two high-grade metamorphic structures. A Precambrian granulite facies foliation is transected by Caledonian fluid-induced eclogite-facies shear zones and pseudotachylytes. To understand how a superimposed tectonic event may influence olivine fabric and change seismic anisotropy, two lenses of spinel lherzolite were studied by scanning electron microscope (SEM) and electron back-scattered diffraction (EBSD) techniques. The granulite foliation of the surrounding anorthosite complex is displayed in ultramafic lenses as a modal variation in olivine, pyroxenes, and spinel, and the Caledonian eclogite-facies structure in the surrounding anorthosite gabbro is represented by thin (<1 cm) garnet-bearing ultramylonite zones. The olivine fabrics in the spinel bearing assemblage were E-type and B-type and a combination of A-and B-type lattice preferred orientations (LPOs). There was a change in olivine fabric from a combination of A-and B-type LPOs in the spinel bearing assemblage to B-and E-type LPOs in the garnet lherzolite mylonite zones. Fourier transform infrared (FTIR) spectroscopy analyses reveal that the water content of olivine in mylonite is much higher (approximately 600 ppm H/Si) than that in spinel lherzolite (approximately 350 ppm H/Si), indicating that water caused the difference in olivine fabric. Fabric strength of olivine gets weaker as the grain size reduced, and as a result, calculated seismic properties for the two deformation stages reveal that P-and S-velocity anisotropies are significantly weaker in the mylonite. Microtextures and LPO data indicate that the deformation mechanism changed from dominant dislocation creep in spinel lherzolite to dislocation creep accompanied by grain-boundary sliding in mylonite. Shear localization in the mylonite appears to be originated from the grain size reduction through (1) enhanced dynamic recrystallization of olivine in the presence of water and (2) Zener pinning of clinopyroxene or (3) by ultracomminution during the pseudotachylyte stage.

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Section: Deformation Mechanismsupporting

confidence: 51%

Characterization of olivine fabrics and mylonite in the presence of fluid and implications for seismic anisotropy and shear localization

Jung

Austrheim

2014

Earth Planet Sp

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“…Moreover, the micrographs suggest a smaller grain size may be present in the shear zone. Smaller grain size have been observed within the shear zone of olivine aggregates during frictional sliding experiments [Boettcher, et al, in press] and within naturally occurring peridotite shear zones [Drury, et al, 1991]. From the strength profile (Figure 25a), we assert that the shear zone formed after approximately 6 seconds of deformation at ~76 MPa.…”

Section: Appendix C: Unique Experimental Observationsmentioning

confidence: 83%

Experimental and seismological constraints on the rheology, evolution, and alteration of the lithosphere at oceanic spreading centers

deMartin¹

2007

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Oceanic spreading centers are sites of magmatic, tectonic, and hydrothermal processes. In this thesis I present experimental and seismological constraints on the evolution of these complex regions of focused crustal accretion and extension. Experimental results from drained, triaxial deformation experiments on partially molten olivine reveal that melt extraction rates are linearly dependent on effective mean stress when the effective mean stress is low and non-linearly dependent on effective mean stress when it is high. Microearthquakes recorded above an inferred magma reservoir along the TAG segment of the Mid-Atlantic Ridge delineate for the first time the arcuate, subsurface structure of a long-lived, active detachment fault. This fault penetrates the entire oceanic crust and forms the high-permeability pathway necessary to sustain long-lived, high-temperature hydrothermal venting in this region. Long-lived detachment faulting exhumes lower crustal and mantle rocks. Residual stresses generated by thermal expansion anisotropy and mismatch in the uplifting, cooling rock trigger grain boundary microfractures if stress intensities at the tips of naturally occurring flaws exceed a critical stress intensity factor. Experimental results coupled with geomechanical models indicate that pervasive grain boundary cracking occurs in mantle peridotite when it is uplifted to within 4 km of the seafloor. Whereas faults provide the high-permeability pathways necessary to sustain high-temperature fluid circulation, grain boundary cracks form the interconnected network required for pervasive alteration of the oceanic lithosphere. This thesis provides fundamental constraints on the rheology, evolution, and alteration of the lithosphere at oceanic spreading centers.

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“…For this reason, experimental, field-based, and modelling studies have focussed on the role of olivine for mantle rheology in the last decades, concluding that grain size reduction and dominant diffusion creep may be the best candidate to account for quasi-viscous strain localisation (Rutter and Brodie, 1988;Drury et al, 1991;Bercovici and Ricard, 2012). Their conclusion is based on the fact that (1) grain size reduction is a ubiquitous feature of ductile shear zones, and (2) diffusion creep (including grain boundary sliding) is grain size sensitive, unlike dislocation creep which does not -or to a lesser extent in the case of disGBS (Hansen et al, 2011) -depend on grain size (Karato et al, 1986;Hirth and Kohlstedt, 2003).…”

Section: Introductionmentioning

confidence: 99%

Evidence of phase nucleation during olivine diffusion creep: A new perspective for mantle strain localisation

Précigout

Stünitz

2016

Earth and Planetary Science Letters

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Shear localisation in upper mantle peridotites

Cited by 113 publications

References 75 publications

Characterization of olivine fabrics and mylonite in the presence of fluid and implications for seismic anisotropy and shear localization

Characterization of olivine fabrics and mylonite in the presence of fluid and implications for seismic anisotropy and shear localization

Experimental and seismological constraints on the rheology, evolution, and alteration of the lithosphere at oceanic spreading centers

Evidence of phase nucleation during olivine diffusion creep: A new perspective for mantle strain localisation

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