Modelling localization of deformation and fluid flow in a compressional orogen; implications for the Southern Alps of New Zealand

Clicks: 1
ID: 303158
1998
Free PDF
Article Quality & Performance Metrics
Overall Quality
Not rated
Combines reader engagement with the AI quality analysis. This article has not been analysed, so there is no overall score — reader engagement is measured and shown alongside.
AI Quality Assessment
Not analyzed
Readership in this journal

Ranked #7,466 of 8,486 articles by views in american journal of science

Most read Least read

Bar heights use a square-root scale. Only the 120 most-read articles are drawn; the journal has 8,486 in total.

Mint this article as an NFT
Not yet minted

Create a permanent, verifiable on-chain record of this article on the Scimatic Network. The NFT is held in your Journament account, and you can withdraw it to your own wallet at any time.

5 SUSD one-off · no wallet required
Sign in to mint
Abstract
Numerical experiments of coupled deformation and fluid flow, in a non-associated elastic-plastic (Mohr-Coulomb) material undergoing compression, illustrate the effect that the plastic properties of the material and the presence of a pore pressure can have upon the deformation. Boundary conditions imposed on the models are such that they imitate two-dimensional orthogonal continental collision. Deformation in a dry material is transient, with shear zones moving through the material toward the stationary boundary condition. In contrast, deformation in a wet material localizes into a paired synthetic and antithetic shear, with a small amount of deformation occurring between the two shears. Material softening due to a strain-dependent friction angle or cohesion localizes the deformation even more. The model results are compared to the continental collision which is currently producing the Southern Alps of New Zealand. The symmetry of the models compared to the asymmetry of collisional mountain belts is attributed to the conservative nature of the models. The Alpine Fault of the Southern Alps is mimicked by the synthetic shear of the models while backthrusts off the Alpine Fault, east of the Main Divide, are mimicked by the single antithetic shear. A non-zero dilation angle does not affect the deformation of a Mohr-Coulomb material directly but does have a significant effect on the fluid flow regime produced by deformation. Experiments showed that the ability of a deforming material to dilate provides a driving force for fluid flow and allows fluid to penetrate into regions of low static permeability. This result is most evident if the value of the dilation angle varies with plastic strain. The strain-dependent dilatant flow law creates regions of strain-hardening, where dilation allows fluid penetration, and regions of strain-softening, from which the fluid is expelled. This leads to spatial and temporal variations in the dynamic permeability which enhances the fluid flow. Flow rates are further enhanced by spatial and temporal variations in pore pressure. The flow rates calculated for a region with a hydrostatic pore pressure gradient and a static permeability of 10-18 m ^2^ were on the order of 6X10 (super -5) ma (super -1) , those for a lithostatic pore pressure gradient were on the order of 6X10 (super -4) ma (super -1) , and those for a pore pressure regime with steps from lithostatic to hydrostatic are on the order of 2X10 (super -3) ma (super -1) . These correspond to communication-scales of 20 m, 600 m, and 3 km respectively over 1 Ma and are minimum estimates. The model describing fluid flow within an active continental collision is extended to include flow driven by extensive deformation, particularly dilatant, which kneads fluid through the rock mass. Without deformation, fluid within rocks of low static permeability is effectively immobile.
Reference Key
openalex_W2318959249 Use this key to autocite in the manuscript while using SciMatic Manuscript Manager or Thesis Manager
Authors Phædra Upton
Journal american journal of science
Year 1998
DOI
10.2475/ajs.298.4.296
URL
https://ajs.scholasticahq.com/article/60783.pdf
Keywords Keywords not found

Citations

No citations found. To add a citation, contact the admin at info@scimatic.org

Comments

No comments yet. Be the first to comment on this article.