Showing papers in "Journal of Structural Geology in 1998"

TL;DR: In this paper, feedback relations between migmatites, crustal-scale shear-zone systems and granites using examples from the Cadomian belt of western France and the northern Appalachian orogen of the eastern U.S.A.

TL;DR: In this article, it was suggested that the room problem for granites could be largely accommodated by downward movement of country rock beneath the magma chamber, and the present steep attitudes of these structures in many plutons may have developed gradually as the floor of the chamber (along with the underlying solidified granite and country rock) sank during continuing episodes of replenishment.

TL;DR: In this article, a case study in the Central Maine Belt of west-central Maine, U.S.A. is presented, where the authors show that crustal-scale shear zone systems provide an eAective focussing mechanism for transfer of granite melt through the crust in convergent orogens.

TL;DR: In this article, a stress feedback mechanism operating in the seismogenic upper crust of the lithosphere is proposed to accelerate the occurrence of future earthquakes on some faults that are optimally oriented while relaxing stress levels on others.

TL;DR: In this paper, it was shown that deformation was initiated by sinking of greenstones, which rapidly subsided; the domes then rose passively as accommodation structures, and the resulting deformation is part of a larger process involving partial convective overturn of the crust.

TL;DR: In this paper, the authors show that when the size of the slipping patch is much smaller than the dimensions of the fault plane, and strength recovery is geologically instantaneous, the displacement profile follows an approximately linear decrease towards the tip similar to natural examples.

TL;DR: The 40Ar/39Ar data conform to kinematic observations that contraction and extension in the Caledonian nappe region were sequential, and that the change from contraction (convergence) to extension (divergence) was quick as discussed by the authors.

TL;DR: In this article, a series of peridotite specimens were collected near one of the pseudotachylyte fault veins to investigate the mechanisms of shear localization, and microstructural analyses showed at least three deformation stages.

TL;DR: In this paper, the authors considered the case where the zone boundaries are stretched and the shear direction between the two boundaries is parallel to one of the principal stretching directions of the boundaries, and established a model which includes this general case also taking into consideration volume change.

TL;DR: In this paper, different macroscopic modes of brittle rock failure (extensional fracturing, extensional-shear fracturing, compressional shear failure and reshear of existing faults) can be represented on plots of differential stress vs effective vertical stress for a set of material properties.

TL;DR: In this paper, shape fabric and distribution anisotropy of magnetite grains in a highly ferromagnetic syenite are determined for three mutually perpendicular planes on about 600 magnetite grain.

TL;DR: In this paper, the structural evolution of accretionary wedges was modeled in a series of analog experiments with systematically varying initial boundary conditions, and the two principle parameters investigated were basal friction and thickness of sediment Input (relative to subducted sediment Output).

TL;DR: In this paper, the authors analyzed 15 extensional folds in the Salmon, Horse Prairie and Medicine Lodge basins and found that they typically have an upright to steeply inclined bisecting surface, an interlimb angle of 141°, and a plunge of 19°.

TL;DR: In this article, a full three-dimensional kinematic model of shear zones with monoclinic flow geometry is presented, and a number of unusual and potentially problematic structural features such as stretching lineations normal to displacement direction, foliations normal to the shear zone boundary, switching of the position of principal finite strain axes X, Y and Z during progressive deformation, and strain gradients along shear regions that may give rise to obliqueness of fabric elements of the same age in adjacent rock volumes.

TL;DR: In this paper, the along-strike displacement variation of 20 well-exposed normal faults from the Canyonlands, Utah, is described and analyzed, and three distinct lateral tip geometries are recognized, referred to informally as types A, B and C.

TL;DR: In this paper, a non-linear decay of the shear stress and the effects of bounding bed thickness (d) were taken into account for the competent beds bounded by two incompetent layers nearly identical in thickness.

TL;DR: In this article, the boundary hierarchy is defined as the relationship between the boundary misorientations, their enclosed domain size and their frequency distribution, and measured the misorientation across every grain and subgrain boundary can be found.

TL;DR: In this article, two groups of mineralised reverse shear zones formed as conjugate, near-optimally oriented sets during ESE subhorizontal shortening adjacent to a major transpressional shear system.

TL;DR: In this paper, a detailed fault mapping using three-dimensional seismic reflection datasets from the central North Sea is presented, showing that the complex 3D geometries are primarily a function of intersections between fault surfaces oriented in all directions in space.

TL;DR: Fault zones within turbidite-dominated orogenic systems, typified by the Lachlan Orogen of eastern Australia, are characterised by higher than average strain and intense mica fabrics, transposition foliation and isoclinal folds, poly-deformation with overprinting crenulation cleavages, and steeply to moderately plunging meso- and micro-folds.

TL;DR: In this paper, the Stillwater seismogenic normal fault in Dixie Valley, Nevada has been historically active and is located in an area of high heat flow and hydrothermal activity, and three primary structural elements are identified in the fault zone: a relatively wide fault core with breccia pods embedded in cataclasites, a damage zone (with arrays of mesoscopic fractures), and protolith.

TL;DR: In this paper, a study of an entire segment of the Southern Apennines of Italy, extending from the Pollino mountain range to the south, to the Agri Valley to the north, is presented.

TL;DR: In this article, a complex six-parameter plot representing the evolution history of a salt diapir can be simplified into three separate graphs, which are then integrated into a single diagram.

TL;DR: In this paper, a detailed structural analysis indicates that brittle deformation predates plastic strain and mylonites progressively develop by plastic reactivation of cataclastic shear zones during greenschist facies metamorphic conditions.

TL;DR: In this article, the authors test the behaviour of three constitutive models, i.e., elasticity, rigid-plasticity, and elasto-linearity, to describe the initiation and evolution of faulting.

TL;DR: In this paper, the level of emplacement and final form of felsic and mafic igneous rocks of the Wichita Mountains Igneous Province, southwestern Oklahoma, U.S.A. are discussed in light of magma driving pressure, lithostatic load, and crustal magma traps.

TL;DR: In a low metamorphic grade shear zone from Quadrilatero Ferrifero (southeastern Brazil), granitoid rocks have been transformed into phyllonites and mylonites via activation of crystal-plastic processes in quartz and fluid-assisted reaction-softening in feldspars as discussed by the authors.

TL;DR: In this article, the relation between the deformational behavior of two-phase rocks and the grain size distributions of the constituent phases is investigated, and the usefulness of the concept of an average grain size is discussed.

TL;DR: In this paper, a single layer of stiff mixed plasticine and silicone that overlays a Newtonian silicone was used to simulate the folding process in obliquely convergent settings, and the fold hinges rotated parallel with the long axis of the horizontal finite strain ellipse.

TL;DR: In this paper, the authors describe the characteristics of the joints and influences on joints, including the roles of faults, folds and beds, and demonstrate the control on joint patterns of subtle changes in the stress system.