Fracture patterns in nonplane strain boudinage—insights from 3‐D discrete element models

Abe, Steffen; Urai, János L.; Kettermann, Michael

doi:10.1002/jgrb.50126

Cited by 17 publications

(23 citation statements)

References 44 publications

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“…This results in the formation of multiple subparallel fractures in the brittle layer normal to the direction of extension that grow in length and aperture with increasing strain [cf. Abe et al ., , Figure 8a]. The vertical stress is kept constant throughout the simulation at σ v = 0.002 model units.…”

Section: Deformation Simulationmentioning

confidence: 99%

The evolution of crack seal vein and fracture networks in an evolving stress field: Insights from Discrete Element Models of fracture sealing

2014

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Veins are ubiquitous in upper and middle crustal rocks. Due to strength and stiffness contrast to the host rock, veins can influence crack propagation. Here we present Discrete Element Models to investigate crack-vein interactions by simulating cycles of fracturing of a rock mass, sealing the cracks to form veins, and refracturing the rock mass after rotating the stress field. We observe different styles of interaction between new fractures and existing veins, depending on the strength ratio between vein and host rock and on the changes in the stress field between the different deformation stages. If the orientation of stress field does not change between deformation stages, ataxial crack seal veins are produced if the veins are weak and a bundle of subparallel microveins if the veins are strong. If the stress field is rotated between deformation stages, the interactions include reactivation, fracture deflection, and crosscutting. Reactivation of weak veins occurs even if the vein orientation is highly unfavorable relative to the stress field. Relays of fractures between reactivated veins form at a higher angle to the veins than expected. This demonstrates that the orientation of secondary veins does not reflect the regional stress field in a simple manner and that veins can strongly influence fracture connectivity, with implications for paleostress analysis and basin modeling. Simulation results compare well with field examples of multiphase vein networks in carbonates from Jebel Akhdar, Oman.

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Section: Deformation Simulationmentioning

confidence: 99%

The evolution of crack seal vein and fracture networks in an evolving stress field: Insights from Discrete Element Models of fracture sealing

2014

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“…A fracture appears when the stress in a spring connecting two particles exceeds the yield strength and the spring connection between the two corresponding particles is then removed. Discrete element modelling has been applied, for example, to study fracturing during detachment folding (Hardy and Finch, 2005) or to study the evolution of brittle boudinage in 2-D and 3-D (Abe and Urai, 2012;Abe et al, 2013).…”

Section: Numerical Simulations and Coupled Modelsmentioning

confidence: 99%

Folding and necking across the scales: a review of theoretical and experimental results and their applications

Schmalholz

Mancktelow

2016

Solid Earth

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Abstract. The shortening and extension of mechanically layered ductile rock generates folds and pinch-and-swell structures (also referred to as necks or continuous boudins), which result from mechanical instabilities termed folding and necking, respectively. Folding and necking are the preferred deformation modes in layered rock because the corresponding mechanical work involved is less than that associated with a homogeneous deformation. The effective viscosity of a layered rock decreases during folding and necking, even when all material parameters remain constant. This mechanical softening due to viscosity decrease is solely the result of fold and pinch-and-swell structure development and is hence termed structural softening (or geometric weakening). Folding and necking occur over the whole range of geological scales, from microscopic up to the size of lithospheric plates. Lithospheric folding and necking are evidence for significant deformation of continental plates, which contradicts the rigid-plate paradigm of plate tectonics. We review here some theoretical and experimental results on folding and necking, including the lithospheric scale, together with a short historical overview of research on folding and necking. We focus on theoretical studies and analytical solutions that provide the best insight into the fundamental parameters controlling folding and necking, although they invariably involve simplifications. To first order, the two essential parameters to quantify folding and necking are the dominant wavelength and the corresponding maximal amplification rate. This review also includes a short overview of experimental studies, a discussion of recent developments involving mainly numerical models, a presentation of some practical applications of theoretical results, and a summary of similarities and differences between folding and necking.

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“…7). In the Slochteren Pillow, the rupture pattern is consistent with stretching of the layer during the rise of the pillow (Abe et al, 2013), with two major boudin zones parallel to the crest, and smaller polygonal fractures in the crestal zone. In the Veendam Pillow, however, the largest ruptures are clearly off from the crest of the structure (Fig.…”

Section: Evolution Of the Internal Structure Of The Saltmentioning

confidence: 62%

Evolution of rheologically heterogeneous salt structures: a case study from the NE Netherlands

Raith

Strozyk

Visser³

et al. 2016

Solid Earth

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Abstract. The growth of salt structures is controlled by the low flow strength of evaporites and by the tectonic boundary conditions. The potassium-magnesium salts (K-Mg salts) carnallite and bischofite are prime examples of layers with much lower effective viscosity than halite: their low viscosity presents serious drilling hazards but also allows squeeze solution mining. In contrast, intrasalt anhydrite and carbonate layers (stringers) are much stronger than halite. These rheological contrasts within an evaporite body have an important control on the evolution of the internal structure of salt, but how this mechanical layering affects salt deformation at different scales is not well known. In this study, we use high-resolution 3-D seismic and well data to study the evolution of the Veendam and Slochteren salt pillows at the southern boundary of the Groningen High, northern Netherlands. Here the rock salt layers contain both the mechanically stronger Zechstein III Anhydrite-Carbonate stringer and the weaker K-Mg salts, thus we are able to assess the role of extreme rheological heterogeneities on salt structure growth. The internal structure of the two salt pillows shows areas in which the K-Mg salt-rich ZIII 1b layer is much thicker than elsewhere, in combination with a complexly ruptured and folded ZIII Anhydrite-Carbonate stringer. Thickness maps of supra-salt sediments and well data are used to infer the initial depositional architecture of the K-Mg salts and their deformation history. Results suggest that faulting and the generation of depressions on the top Zechstein surface above a Rotliegend graben caused the local accumulation of bittern brines and precipitation of thick K-Mg salts. During the first phase of salt flow and withdrawal from the Veendam area, under the influence of differential loading by Buntsandstein sediments, the ZIII stringer was boudinaged while the lens of Mg salts remained relatively undeformed. This was followed by a convergence stage, when the K-Mg salt-rich layers were deformed within the inflating salt pillows. This deformation was strongly disharmonic and strongly influenced by folding of the underlying, ruptured ZIII stringer, leading to thickening and internal deformation of the K-Mg salt layers.

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Fracture patterns in nonplane strain boudinage—insights from 3‐D discrete element models

Cited by 17 publications

References 44 publications

The evolution of crack seal vein and fracture networks in an evolving stress field: Insights from Discrete Element Models of fracture sealing

The evolution of crack seal vein and fracture networks in an evolving stress field: Insights from Discrete Element Models of fracture sealing

Folding and necking across the scales: a review of theoretical and experimental results and their applications

Evolution of rheologically heterogeneous salt structures: a case study from the NE Netherlands

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