Viscous anisotropy of two-phase composites, and applications to rocks and structures

Treagus, Susan H.

doi:10.1016/s0040-1951(03)00239-7

Cited by 30 publications

(26 citation statements)

References 40 publications

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“…Efforts to date to generalize relationships for the flow of multiphase system have often been inspired but have mostly been unsuccessful (Bloomfield and Covey-Crump 1993;Ji 2004;Treagus 2003;Tullis et al 1991). Predictably, the best quantitative models occur where phases have the least contrasting rheologies.…”

Section: Rheological Behavior Of Multiphase Systemsmentioning

confidence: 99%

Rheological and Thermal Properties of Icy Materials

et al. 2010

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Laboratory measurements of physical properties of planetary ices generate information for dynamical models of tectonically active icy bodies in the outer solar system. We review the methods for measuring both flow properties and thermal properties of icy planetary materials in the laboratory, and describe physical theories that are essential for intelligent extrapolation of data from laboratory to planetary conditions. This review is structured with a separate and independent section for each of the two sets of physical properties, rheological and thermal. The rheological behaviors of planetary ices are as diverse as the icy moons themselves. High-pressure water ice phases show respective viscosities that vary over four orders of magnitude. Ices of CO 2 , NH 3 , as well as clathrate hydrates of CH 4 and other gases vary in viscosity by nearly ten orders of magnitude. Heat capacity and thermal conductivity of detected/inferred compositions in outer solar system bodies have been revised. Some low-temperature phases of minerals and condensates have a deviant thermal behavior related to paramount water ice. Hydrated salts have low values of thermal conductivity and an inverse dependence of conductivity on temperature, similar to clathrate hydrates or glassy solids. This striking behavior may suit the dynamics of icy satellites.

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Section: Rheological Behavior Of Multiphase Systemsmentioning

confidence: 99%

Rheological and Thermal Properties of Icy Materials

et al. 2010

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“…The normal component is appropriate for shortening normal or parallel to the layering, whereas the shear component is appropriate for directions at 45° to the layering. The normal and shear viscosities of a layered medium respectively coincide with the upper (Voigt) and lower (Reuss) bounds on the effective viscosity [e.g., Treagus , 2003]. …”

Section: Introductionmentioning

confidence: 99%

A two‐phase composite in simple shear: Effective mechanical anisotropy development and localization potential

2012

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[1] We present a combined shape and mechanical anisotropy evolution model for a two-phase inclusion-bearing rock subject to large deformation. A single elliptical inclusion embedded in a homogeneous but anisotropic matrix is used to represent a simplified shape evolution enforced on all inclusions. The mechanical anisotropy develops due to the alignment of elongated inclusions. The effective anisotropy is quantified using the differential effective medium (DEM) approach. The model can be run for any deformation path and an arbitrary viscosity ratio between the inclusion and host phase. We focus on the case of simple shear and weak inclusions. The shape evolution of the representative inclusion is largely insensitive to the anisotropy development and to parameter variations in the studied range. An initial hardening stage is observed up to a shear strain of g = 1 irrespective of the inclusion fraction. The hardening is followed by a softening stage related to the developing anisotropy and its progressive rotation toward the shear direction. The traction needed to maintain a constant shear rate exhibits a fivefold drop at g = 5 in the limiting case of an inviscid inclusion. Numerical simulations show that our analytical model provides a good approximation to the actual evolution of a two-phase inclusion-host composite. However, the inclusions develop complex sigmoidal shapes resulting in the formation of an S-C fabric. We attribute the observed drop in the effective normal viscosity to this structural development. We study the localization potential in a rock column bearing varying fraction of inclusions. In the inviscid inclusion case, a strain jump from g = 3 to g = 100 is observed for a change of the inclusion fraction from 20% to 33%.

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“…These numerous layers then intrinsically lead to a high anisotropy parallel to the plane of simple shear as an aggregate response, by which the folding can approach the flexural flow regime. Several studies have indeed demonstrated an important effect of layer and matrix anisotropy on folding (Treagus, 2003;Kocher et al, 2006Kocher et al, , 2008Toimil and Griera, 2007). As such, anisotropy in the viscous matrix, within single-layers or as an aggregate multilayer response, strongly influences the occurrence of the buckling instability and also correlates positively with fold amplitude amplification rate.…”

Section: Effect Of Anisotropy On Foldingmentioning

confidence: 98%

Mechanisms of flexural flow folding of competent single-layers as evidenced by folded fibrous dolomite veins

Torremans

Muchez

Sintubin

2014

Journal of Structural Geology

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a b s t r a c tFlexural flow is thought unlikely to occur in naturally deformed, competent isotropic single-layers. In this study we discuss a particular case of folded bedding-parallel fibrous dolomite veins in shale, in which the internal strain pattern and microstructural deformation features provide new insights in the mechanisms enabling flexural flow folding. Strain in the pre-folding veins is accommodated by two main mechanisms: intracrystalline deformation by bending and intergranular deformation with bookshelf rotation of dolomite fibres. The initially orthogonal dolomite fibres allowed a reconstruction of the strain distribution across the folded veins. This analysis shows that the planar mechanical anisotropy created by the fibres causes the veins to approximate flexural flow. During folding, synkinematic veins overgrow the pre-folding fibrous dolomite veins. Microstructures and dolomite growth morphologies reflect growth during progressive fold evolution, with evidence for flexural slip at fold lock-up. Homogeneous flattening, as evidenced by disjunctive axial-planar cleavage, subsequently modified these folds from class 1B to 1C folds. Our study shows that the internal vein fabric has a first-order influence on folding kinematics. Moreover, the fibrous dolomite veins show high viscosity contrasts with the shale matrix, essential in creating transient permeability for subsequent mineralising stages in the later synkinematic veins during progressive folding.

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Viscous anisotropy of two-phase composites, and applications to rocks and structures

Cited by 30 publications

References 40 publications

Rheological and Thermal Properties of Icy Materials

Rheological and Thermal Properties of Icy Materials

A two‐phase composite in simple shear: Effective mechanical anisotropy development and localization potential

Mechanisms of flexural flow folding of competent single-layers as evidenced by folded fibrous dolomite veins

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