Is plane strain a valid assumption in non-cylindrical fault-cored folds?

Shackleton, J. R.; Cooke, Michele L.

doi:10.1016/j.jsg.2007.03.011

Cited by 10 publications

(6 citation statements)

References 30 publications

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“…Folds produced within relatively thin layering (layers several times thinner than the wavelength) can grow to 4–5 times the amplitude of a fold in a medium without layering. Amplification through flexural slip folding was also noted by Shackleton and Cooke ().…”

Section: Kinematics and Mechanics Of Fault‐cored Anticlinessupporting

confidence: 54%

“…However, as discussed in more detail below, mechanical analyses of fault‐related folding have largely focused on passive folding by slip on faults; the mechanical layers required for buckle folding are absent in many analyses. Notable exceptions are the numerical simulations of Shackleton and Cooke () and Albertz and Lingrey () and analogue experiments of Bonanno et al () that showed that folding of layers above a blind fault is enhanced by allowing flexural slip at layer contacts.…”

Section: Introductionmentioning

confidence: 99%

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Growth of Fault‐Cored Anticlines by Flexural Slip Folding: Analysis by Boundary Element Modeling

Johnson

2018

JGR Solid Earth

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Fault‐related folds develop due to a combination of slip on the associated fault and distributed deformation off the fault. Under conditions that are sufficient for sedimentary layering to act as a stack of mechanical layers with contact slip, buckling can dramatically amplify the folding process. We develop boundary element models of fault‐related folding of viscoelastic layers embedded with a reverse fault to examine the influence of such layering on fold growth. The strength of bedding contacts, the thickness and stiffness of layering, and fault geometry all contribute significantly to the resulting fold form. Frictional contact strength between layers controls the degree of localization of slip within fold limbs; high contact friction in relatively thin bedding tends to localize bedding slip within narrow kink bands on fold limbs, and low contact friction tends to produce widespread bedding slip and concentric fold form. Straight ramp faults tend to produce symmetric folds, whereas listric faults tend to produce asymmetric folds with short forelimbs and longer backlimbs. Fault‐related buckle folds grow exponentially with time under steady loading rates. At early stages of folding, fold growth is largely attributed to slip on the fault, but as the fold increases amplitude, a larger portion of the fold growth is attributed to distributed slip across bedding contacts on the limbs of the fold. An important implication for geologic and earthquake studies is that not all surface deformation associated with blind reverse faults may be attributed to slip on the fault during earthquakes.

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Section: Kinematics and Mechanics Of Fault‐cored Anticlinessupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Growth of Fault‐Cored Anticlines by Flexural Slip Folding: Analysis by Boundary Element Modeling

Johnson

2018

JGR Solid Earth

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“…Given that area is a function of the bed thickness and the bed length, and if bed thickness is assumed to remain constant during deformation, it is possible to use the preservation of line lengths as an assessment of whether a section is restorable (Dahlstrom, 1969). In reality, bed thickness changes in fold cores due to mudstone (shale) thickening and out-of-plane transport (Shackleton and Cooke, 2007). For bed thickness to remain constant, deformation must be accommodated by bedding parallel slip (Tanner, 1989).…”

Section: Methodsmentioning

confidence: 99%

Palinspastic restoration of an exhumed deepwater system: A workflow to improve paleogeographic reconstructions

et al. 2015

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“…With ongoing contraction, on either side of the pinned portions of the folds, there is a component of out-of-plane motion (Fig. 14B), where displacement vectors on the faults deviate from the E-W contraction (Shackelton and Cooke, 2007). This type of system can explain key components of the overall kinematic development in the Ballarat East gold deposit, which we have deduced from the sense of slip associated with mineralized veins and on faults.…”

Section: Integrated Model For Au Mineralization At Ballarat Eastmentioning

confidence: 82%

Structural Constraints and Localization of Gold Mineralization in Leather Jacket Lodes, Ballarat, Victoria, Australia

Wilson

Osborne²,

Robinson

et al. 2016

Economic Geology

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Gold mineralization at the Ballarat East deposit, central Victoria, Australia, is hosted in lodes that are historically known as "leather jackets." These are quartz-dominant vein arrays related to low-displacement, W-dipping faults (≤45°) that transect the core and/or eastern limb of tight, asymmetric N-S-trending anticlines. The leather jacket lodes typically have dip extents from 5 to 65 m, widths of ≤20 m, and strike lengths up to hundreds of meters, but their along-strike continuity is disrupted by oblique, low-displacement listric faults known as "cross courses." The gold lodes are characterized by distinct phases of sulfide paragenesis with minor gold + arsenopyrite + pyrite defining the early sulfide stage. Late-stage coarse gold was precipitated with galena + sphalerite ± pyrrhotite ± chalcopyrite (late pyrite also occurs). The gold mineralization events are linked to low-strain mineralized fracture networks, which are closely related to the final deformation stages and the amplification of the major folds enclosing the lodes. This amplification produced domal fold culminations, with plunges ≤30°, and localized minor parasitic folds with shallower plunges (≤10°). A network of dilation sites, on the W-dipping faults, preferentially developed in the cores of anticlines, particularly in zones where there are changes in strike of bedding or fault bifurcation and refraction through contrasting sandstone and interbedded packages of sandstone and shale. Numerical three-dimensional simulations were undertaken to test our geologic observations and replicate conditions controlling the emplacement of the leather jacket lodes. Two different scenarios were investigated: first, to determine how changes in the local stress field orientation influences dilation and fluid infiltration; secondly, to test variations in fault geometry during the last stages of deformation-that is, within the final 2% of shortening, when most of the mineralized sites were created. Results show that strain and fluid flow localized along refracted sections of faults and around changes in dip, specifically on the shallower dipping sections within subvertical sandstone units. This is consistent with the observation that high-grade gold-bearing quartz is associated with localized changes in fault dip in thicker sandstone and sandstone-shale packages. There was also a component of strike-slip motion and near-field NW-to-SE or N-to-S stress fields, which can be attributed to the development of a component of out-of-plane motion during the development of fold culminations. The preferred model for the distribution of the high-grade auriferous vein arrays defining the leather jacket lodes is one of fold amplification and extension parallel to the fold axes, which produced an increasing out-of-plane relaxation. The main fluid conduits responsible for the leather jacket style of mineralization involve infiltration along steep bedding-parallel faults and veins that link up with the arrays of low-displacement W-dipping faults.

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Is plane strain a valid assumption in non-cylindrical fault-cored folds?

Cited by 10 publications

References 30 publications

Growth of Fault‐Cored Anticlines by Flexural Slip Folding: Analysis by Boundary Element Modeling

Growth of Fault‐Cored Anticlines by Flexural Slip Folding: Analysis by Boundary Element Modeling

Palinspastic restoration of an exhumed deepwater system: A workflow to improve paleogeographic reconstructions

Structural Constraints and Localization of Gold Mineralization in Leather Jacket Lodes, Ballarat, Victoria, Australia

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