Formation of chocolate-tablet boudins: Results from scaled analogue models

Zulauf, J.; Zulauf, Gernold; Göttlich, J.; Peinl, M.

doi:10.1016/j.jsg.2014.09.005

Cited by 15 publications

(7 citation statements)

References 27 publications

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“…3D boudin analysis has shown that identifying multistage deformation with the same failure mode is in general not possible from a 2D section alone (Virgo et al, 2018. Similarly, tablet boudins formed either in one episode of pure flattening (Zulauf et al, 2011), in nonplane strain (Abe et al, 2013), or through polyphase deformation during rotating plane strain (Zulauf et al, 2014) look identical in sections but reveal their deformation history in map view. Finite strain can also be underestimated when secondary reworking of boudins that have been parallelised to the extension axis by in-plane folding goes unnoticed (Zulauf & Zulauf, 2005, Zulauf et al, 2020a.…”

Section: Introductionmentioning

confidence: 99%

Spacing and Strain During Multiphase Boudinage in 3D

Bamberg¹,

Hagke²,

Virgo³

et al. 2022

Preprint

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We analyse the effects of thickness on brittle boudinage in a metre-scale sample of marble containing a layer of amphibolite recording two phases of ductile pinch-and-swell followed by five generations of brittle boudinage. The amphibolite geometry was reconstructed in 3D, employing a method we call ‘outcrop-scale tomography’. Our data suggests that strain localisation depends on the ration of grain size and layer thickness of amphibolite. In very thin layers (few grains across), strain is diffuse throughout the entire layer, leading to macroscopically homogeneous stretching. Strain localisation increases when layer thickness is more than 10 grains, first through narrow tensile necks and shear zones (<10-20x average grain size), then through extension fractures, and finally shear fractures emerge. The disappearance of shear fractures in thinner layers can be explained by a geometry-related compressive stress decrease in the pinches and expected shear band width exceeding layer thickness. This results in localized shear evolving only in thicker layers. Successive reactivation between fracture generations, geometrical complexity, in the form of splays and branches, and the thickness-dependence of localised strain govern fracture distribution in the layer. We infer a second, temporal trend that records the progressive embrittlement of the rocks as they cool during exhumation, evidenced by a switch from shear to extensional fracturing. In the final stages, the marble is brittle enough to allow fracture propagation from the amphibolite across the material interface and the formation of throughgoing brittle faults.

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Section: Introductionmentioning

confidence: 99%

Spacing and Strain During Multiphase Boudinage in 3D

Bamberg¹,

Hagke²,

Virgo³

et al. 2022

Preprint

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“…Boudins occur in a wide range of tectonic settings and at all scales (Goscombe et al, 2004;Gueguen et al, 1997;Jolivet et al, 2009;Reuning et al, 2009;Schoenherr et al, 2009;Strozyk et al, 2014). Boudins can be diagnostic for polyphase deformation, since polyaxial stretching results in a different 3D structure than polyphase deformation in different directions (Abe et al, 2013;Ghosh, 1988;Reber et al, 2010;Zulauf et al, 2014). This diversity makes boudins ideal structures to understand better and quantify rock deformation in the brittle and ductile regime.…”

Section: Introductionmentioning

confidence: 99%

“…However, boudinage is a complex phenomenon that involves different deformation mechanisms and has complex shapes in 3D (e.g. Abe et al, 2010;Goscombe et al, 2004;Passchier, 2001;Weiss, 1972;Zulauf and Zulauf, 2005;Zulauf et al, 2014;Zulauf et al, 2011). Using numerical models, the different failure modes observed in the field could be reproduced, (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Whereas analogue models may be conducted without initial fractures and show how brittle and ductile processes are important in boudinage (e.g. Zulauf et al, 2003;Zulauf et al, 2014), numerical models commonly prescribe initial fractures in the competent layer, thus introducing boundary conditions e.g. on boudin lengthwidth ratio, and rendering multi-stage boudinage models challenging.…”

Section: Introductionmentioning

confidence: 99%

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Outcrop-scale tomography: Insights into the 3D structure of multiphase boudins

Hagke

Bamberg

Virgo

et al. 2018

Journal of Structural Geology

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We analyze the 3D geomorphology of a boudinaged amphibolite layer encased in marble using meter-scale tomography by serial sectioning, high resolution imaging and 3D reconstruction of a 2 m³ block from a quarry in the high-grade core of the Naxos core complex. Local uncertainties in the model are resolved by dissolution of marble in selected slabs, yielding a large, highly accurate 3D model. Results show five generations of brittle extension of the amphibolite in ductile marble, although examination of the boudinaged layer on the outside of the block only suggested one generation. Most prominent are the rotated domino boudins, where part of the dilatancy between domino boudins can be shown to be due to later reactivation. Shear fractures between domino boudins have relatively large throw gradients, indicating ductile rupture. Layer-parallel stretch as measured by reconstruction of domino boudins decreases with amphibolite layer thickness although the layer has undergone the same bulk stretch everywhere. This suggests that with decreasing layer thickness deformation becomes delocalized, offering tantalizing glimpses of rheology under metamorphic conditions.

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“…Boudins occur in a wide range of tectonic settings and at all scales (Goscombe et al, 2004;Gueguen et al, 1997;Jolivet et al, 2009;Reuning et al, 2009;Schoenherr et al, 2009;Strozyk et al, 2014). Boudins can be diagnostic for polyphase deformation, since polyaxial stretching results in a different 3D structure than polyphase deformation in different directions Ghosh, 1988;Reber et al, 2010;Zulauf et al, 2014). This diversity makes boudins ideal structures to understand better and quantify rock deformation in the brittle and ductile regime.…”

Section: Introductionmentioning

confidence: 99%

Outcrop-scale tomography: insights into the 3D structure of multiphase boudins

Hagke

Bamberg

Virgo

et al. 2018

Preprint

View full text Add to dashboard Cite

We analyze the 3D geomorphology of a boudinaged amphibolite layer encased in marble using meter-scale tomography by serial sectioning, high resolution imaging and 3D reconstruction of a 2 m³ block from a quarry in the high-grade core of the Naxos core complex. Local uncertainties in the model are resolved by dissolution of marble in selected slabs, yielding a large, highly accurate 3D model.Results show five generations of brittle extension of the amphibolite in ductile marble, although examination of the boudinaged layer on the outside of the block only suggested one generation. Most prominent are the rotated domino boudins, where part of the dilatancy between domino boudins can be shown to be due to later reactivation. Shear fractures between domino boudins have relatively large throw gradients, indicating ductile rupture. Layer-parallel stretch as measured by reconstruction of domino boudins decreases with amphibolite layer thickness although the layer has undergone the same bulk stretch everywhere. This suggests that with decreasing layer thickness deformation becomes delocalized, offering tantalizing glimpses of rheology under metamorphic conditions.

show abstract

Formation of chocolate-tablet boudins: Results from scaled analogue models

Cited by 15 publications

References 27 publications

Spacing and Strain During Multiphase Boudinage in 3D

Spacing and Strain During Multiphase Boudinage in 3D

Outcrop-scale tomography: Insights into the 3D structure of multiphase boudins

Outcrop-scale tomography: insights into the 3D structure of multiphase boudins

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