scholarly journals Progressive weakening within the overriding plate during dual inward dipping subduction

2022 ◽  
Author(s):  
ZHIBIN LEI ◽  
J. Davies
Keyword(s):  
Strain Rate ◽  
Dominant Role ◽  
Viscosity Reduction ◽  
Mantle Flow ◽  
Complex Deformation ◽  
Geodynamic Process ◽  
Multiple Parameters ◽  
Lithosphere Thinning ◽  
Subducting Plate ◽  
Deformation Patterns

Dual inward dipping subduction often produces complex deformation patterns in the overriding plate. However, the geodynamic process of how dual inward dipping subduction relates to this deformation is still poorly understood. Here we apply a composite viscosity, dependent on multiple parameters, e.g., temperature, pressure, strain rate etc., in 2-D thermo-mechanical numerical modelling to investigate how dual inward dipping subduction modifies the rheological structure of the overriding plate. Three variables are investigated to understand what controls the maximum degree of weakening. We find that the initial length and thickness of the overriding plate are negatively correlated with the magnitude of viscosity reduction. While the initial thickness of the subducting plate positively relates to the magnitude of viscosity reduction. The progressive weakening can result in a variety of stretching states ranging from 1) little or no lithosphere thinning and extension, to 2) limited thermal lithosphere thinning, and 3) localised rifting followed by spreading extension. Compared with single sided subduction, dual inward dipping subduction further reduces the magnitude of viscosity of the overriding plate. It does this by creating a dynamic fixed boundary condition for the overriding plate and forming a stronger upwelling mantle flow underlying the overriding plate. Three types of feedback weakening cycles are recognised, among which the strain rate weakening mechanism plays the dominant role in lowering the viscosity of the overriding plate throughout the simulation. Strain rate weakening is also a precondition for initiating thermal weakening, strain localisation and lithosphere thinning.

Finite Deflections of a Rigid-Viscoplastic Strain-Hardening Annular Plate Loaded Impulsively

1968 ◽  
Vol 35 (2) ◽  
pp. 349-356 ◽  
Author(s):  
Norman Jones
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
Strain Rate Sensitivity ◽  
Annular Plate ◽  
Dominant Role ◽  
Plate Thickness ◽  
Rate Sensitivity ◽  
Finite Deflections ◽  
Analytical Treatment ◽  
Rigid Plastic

A relatively simple analytical treatment of the behavior of a rigid-plastic annular plate subjected to an initial linear impulsive velocity profile is presented. The influence of finite deflections has been included in addition to strain-hardening and strain-rate sensitivity of the plate material. It is shown, for deflections up to the order of twice the plate thickness, that strain-hardening is unimportant, strain-rate sensitivity has somewhat more effect, while membrane forces play a dominant role in reducing the permanent deflections.

Tearing Resistance of Advanced Double Hulls

1997 ◽  
Vol 41 (01) ◽  
pp. 69-80
Author(s):  
Mark D. Bracco ◽  
Tomasz Wierzbicki
Keyword(s):  
Steady State ◽  
Cutting Force ◽  
Average Error ◽  
Small Scale ◽  
Complex Deformation ◽  
Scale Models ◽  
State Force ◽  
Deformation Patterns ◽  
Double Hull ◽  
Tearing Resistance

This paper studies the cutting by a wedge of advanced double hull (ADH) small-scale models. A total of six cutting experiments were performed with six different wedge geometries. Complex deformation patterns observed in the damaged specimens were simplified to obtain a closed-form upper bound for the steady-state cutting force. The ADH steady-state cutting force solution varied from 6% above to 12% below the experimental mean steady-state force. The absolute average error is 5%.

The Effect of Materials Testing Mode on Mechanical Behavior Under Temperature Influence in Complex Deformation Processes

2007 ◽  
Author(s):  
S. Anurag ◽  
Y. B. Guo
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Material Testing ◽  
Materials Testing ◽  
Plasticity Model ◽  
Complex Deformation ◽  
Material Constants ◽  
Dynamic Mechanical ◽  
Dynamic Mechanical Behavior ◽  
Deformation Processes

Complex deformation processes such as forming and machining involve large strain, high strain rate, high temperatures, strain rate/temperature coupling, and potential loading history effects. The conventional empirical and semi-empirical plasticity models are not adequate for characterizing dynamic mechanical behavior of work materials at the complex loading scenarios. The accuracy of characterizing the dynamic mechanical behavior in deformation processes using any constitutive models is strongly affected by materials testing data in which a constitutive model is fitted. Tension or compression tests have been widely used to approximate material properties in various manufacturing processes. However, it has been a critical question whether tension or compression test should be utilized for capturing the true nature of complex material deformations. In this study, the influences of two material testing modes on mechanical behavior of AISI52100 steel (62 HRc) were investigated using the internal state variable (ISV) plasticity model. Twenty material constants have been found by nonlinear fitting the ISV plasticity model to the base line test data obtained from each deformation mode. It has shown that the material testing modes have profound effects on some materials constants of the ISV model. The stress sensitivity study to ISV model parameters has identified the critical material constants for reflecting the nature of material deformation. The different testing modes have significant influence on the material constants associated with isotropic hardening rather than kinematic hardening.

scholarly journals Oblique collision and deformation partitioning in the SW Iberian Variscides

Solid Earth ◽  
2016 ◽  
Vol 7 (3) ◽  
pp. 857-872 ◽  
Author(s):  
Irene Pérez-Cáceres ◽  
José Fernando Simancas ◽  
David Martínez Poyatos ◽  
Antonio Azor ◽  
Francisco González Lodeiro
Keyword(s):  
Finite Strain ◽  
Lateral Displacement ◽  
Point Of View ◽  
Variscan Orogeny ◽  
Strain Partitioning ◽  
Complex Deformation ◽  
Oblique Collision ◽  
Deformation Partitioning ◽  
Oblique Convergence ◽  
Deformation Patterns

Abstract. Different transpressional scenarios have been proposed to relate kinematics and complex deformation patterns. We apply the most suitable of them to the Variscan orogeny in SW Iberia, which is characterized by a number of successive left-lateral transpressional structures developed in the Devonian to Carboniferous period. These structures resulted from the oblique convergence between three continental terranes (Central Iberian Zone, Ossa-Morena Zone and South Portuguese Zone), whose amalgamation gave way to both intense shearing at the suture-like contacts and transpressional deformation of the continental pieces in-between, thus showing strain partitioning in space and time. We have quantified the kinematics of the collisional convergence by using the available data on folding, shearing and faulting patterns, as well as tectonic fabrics and finite strain measurements. Given the uncertainties regarding the data and the boundary conditions modeled, our results must be considered as a semi-quantitative approximation to the issue, though very significant from a regional point of view. The total collisional convergence surpasses 1000 km, most of them corresponding to left-lateral displacement parallel to terrane boundaries. The average vector of convergence is oriented E–W (present-day coordinates), thus reasserting the left-lateral oblique collision in SW Iberia, in contrast with the dextral component that prevailed elsewhere in the Variscan orogen. This particular kinematics of SW Iberia is understood in the context of an Avalonian plate salient currently represented by the South Portuguese Zone.

scholarly journals High 3He/4He in central Panama reveals a distal connection to the Galápagos plume

2021 ◽  
Vol 118 (47) ◽  
pp. e2110997118
Author(s):  
David V. Bekaert ◽  
Esteban Gazel ◽  
Stephen Turner ◽  
Mark D. Behn ◽  
J. Marten de Moor ◽  
...  
Keyword(s):  
Mantle Flow ◽  
Transport Mechanisms ◽  
Lithosphere Thinning ◽  
Enriched Mantle ◽  
Deep Interior ◽  
Southern Central ◽  
Galapagos Plume ◽  
Central Panama ◽  
Slab Window ◽  
Lava Geochemistry

It is well established that mantle plumes are the main conduits for upwelling geochemically enriched material from Earth's deep interior. The fashion and extent to which lateral flow processes at shallow depths may disperse enriched mantle material far (>1,000 km) from vertical plume conduits, however, remain poorly constrained. Here, we report He and C isotope data from 65 hydrothermal fluids from the southern Central America Margin (CAM) which reveal strikingly high 3He/4He (up to 8.9RA) in low-temperature (≤50 °C) geothermal springs of central Panama that are not associated with active volcanism. Following radiogenic correction, these data imply a mantle source 3He/4He >10.3RA (and potentially up to 26RA, similar to Galápagos hotspot lavas) markedly greater than the upper mantle range (8 ± 1RA). Lava geochemistry (Pb isotopes, Nb/U, and Ce/Pb) and geophysical constraints show that high 3He/4He values in central Panama are likely derived from the infiltration of a Galápagos plume–like mantle through a slab window that opened ∼8 Mya. Two potential transport mechanisms can explain the connection between the Galápagos plume and the slab window: 1) sublithospheric transport of Galápagos plume material channeled by lithosphere thinning along the Panama Fracture Zone or 2) active upwelling of Galápagos plume material blown by a “mantle wind” toward the CAM. We present a model of global mantle flow that supports the second mechanism, whereby most of the eastward transport of Galápagos plume material occurs in the shallow asthenosphere. These findings underscore the potential for lateral mantle flow to transport mantle geochemical heterogeneities thousands of kilometers away from plume conduits.

scholarly journals Progressive Deformation Patterns from an Accretionary Prism (Helminthoid Flysch, Ligurian Alps, Italy)

Geosciences ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 26 ◽  
Author(s):  
Pierre Mueller ◽  
Matteo Maino ◽  
Silvio Seno
Keyword(s):  
Regional Scale ◽  
Kinematic Model ◽  
Outer Part ◽  
Accretionary Prism ◽  
Shear Zones ◽  
Low Grade ◽  
Progressive Deformation ◽  
Complex Deformation ◽  
Ligurian Alps ◽  
Deformation Patterns

This paper reports the results of a field-based structural investigation of a well-exposed paleo-accretionary prism, which experienced complex deformation in a low-grade metamorphic setting. Field analyses focused on the description of structural fabrics, with the main emphasis upon parameters like the orientation, style and kinematics of foliations, folds and shear zones. We address the research to the south-westernmost part of the Alpine chain, the Ligurian Alps, where, despite their origin as turbidite sequences deposited into the closing Alpine Tethys Ocean, the Helminthoid Flysch Nappes are presently distributed in the outer part of the chain, above the foreland. The new dataset highlights different deformation patterns related to the different spatial distribution of the flysch units. This regional-scale partitioning of strain is hence associated with progressive deformation within a two-stage geodynamic evolution. Correlations among the different orogenic domains allow the proposal of a kinematic model that describes the motion of the Helminthoid Flysch from the inner to the outer part of the orogen, encompassing the shift from subduction- to collision-related Alpine geodynamic phases.

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