Semi‐Brittle Deformation of Carrara Marble: Hardening and Twinning Induced Plasticity
Name
JGR Solid Earth - 2021 - Rybacki - Semi‐Brittle Deformation of Carrara Marble Hardening and Twinning Induced Plasticity.pdf
Description
Published version
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5.79 MB
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Adobe PDF
Checksum (MD5)
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Author(s)
Rybacki, E
Niu, L
Evans, B
Date Issued
November 25, 2021
Journal
Journal of Geophysical Research: Solid Earth
Publisher
American Geophysical Union
Citation
Rybacki, E., Niu, L., & Evans, B. (2021). Semi-brittle deformation of carrara marble: Hardening and twinning induced plasticity. Journal of Geophysical Research: Solid Earth, 126, e2021JB022573.
Version
Final published version
Abstract
Semi-brittle flow occurs when crystal plasticity and cataclastic mechanisms operate concurrently
and may be common at mid-levels of the Earth's crust. Using a Paterson gas-deformation apparatus, we
performed 67 conventional triaxial deformation experiments on dry samples of Carrara marble in the
temperature range of T = 20–800°C; confining pressures (PC) were 30, 50,100, 200, and 300 MPa, and strain
𝐴𝐴 𝐴𝐴𝐴 rates ( ) were 10−3, 10−4, 10−5, and 10−6 s−1. Axial strains (ε) were ≲0.12. The measured (differential) stress,
𝐴𝐴 Δ𝜎𝜎 = 𝜎𝜎1 − 𝑃𝑃C, changes with strain at most applied conditions. At ε = 0.05, both stress and the hardening
coefficient (h), that is, the rate of increase of stress with strain, increase as T decreases and PC increases. At
T ≲ 400°C, h is quite large and the sensitivity of 𝐴𝐴 Δ𝐴𝐴 𝐴𝐴𝐴 𝜎𝜎 on is low, while both are sensitive to increasing pressure.
In this temperature range, the mechanical behavior of the marble is very similar to that exhibited by highstrength, high-ductility, hexagonal metals that deform by processes called twinning induced plasticity (TWIP).
Twinning and dislocation motion are abundant in the samples, as are inter- and intracrystalline microfractures.
The concurrent activation of these deformation mechanisms leads to complex relationships of 𝐴𝐴 Δ𝜎𝜎 and h with
the applied T - PC 𝐴𝐴 𝐴𝐴𝐴- conditions. This behavior suggests that peak stresses for calcite rocks deforming by
semi-brittle processes will occur at PC - T conditions of the middle crust, and that they might be more strongly
influenced by total strain rather than by strain rate.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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Creative Commons Attribution-NonCommercial
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DOI of Published Version
https://doi.org/10.1029/2021JB022573
