MCMC inversion of the transient and steady-state creep flow law parameters of dunite under dry and wet conditions

The rheology of the upper mantle impacts a variety of geodynamic processes, including postseismic deformation following great earthquakes and post-glacial rebound. The deformation of upper mantle rocks is controlled by the rheology of olivine, the most abundant upper mantle mineral. The mechanical p...

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Main Authors: Masuti, Sagar, Barbot, Sylvain
Other Authors: Asian School of the Environment
Format: Article
Language:English
Published: 2022
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Online Access:https://hdl.handle.net/10356/162772
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spelling sg-ntu-dr.10356-1627722022-11-12T23:31:15Z MCMC inversion of the transient and steady-state creep flow law parameters of dunite under dry and wet conditions Masuti, Sagar Barbot, Sylvain Asian School of the Environment Earth Observatory of Singapore Science::Geology Transient Creep Steady-State Creep The rheology of the upper mantle impacts a variety of geodynamic processes, including postseismic deformation following great earthquakes and post-glacial rebound. The deformation of upper mantle rocks is controlled by the rheology of olivine, the most abundant upper mantle mineral. The mechanical properties of olivine at steady state are well constrained. However, the physical mechanism underlying transient creep, an evolutionary, hardening phase converging to steady state asymptotically, is still poorly understood. Here, we constrain a constitutive framework that captures transient creep and steady state creep consistently using the mechanical data from laboratory experiments on natural dunites containing at least 94% olivine under both hydrous and anhydrous conditions. The constitutive framework represents a Burgers assembly with a thermally activated nonlinear stress-versus-strain-rate relationship for the dashpots. Work hardening is obtained by the evolution of a state variable that represents internal stress. We determine the flow law parameters for dunites using a Markov chain Monte Carlo method. We find the activation energy 430 ± 20 and 250 ± 10 kJ/mol for dry and wet conditions, respectively, and the stress exponent 2.0 ± 0.1 for both the dry and wet cases for transient creep, consistently lower than those of steady-state creep, suggesting a separate physical mechanism. For wet dunites in the grain-boundary sliding regime, the grain-size dependence is similar for transient creep and steady-state creep. The lower activation energy of transient creep could be due to a higher jog density of the corresponding soft-slip system. More experimental data are required to estimate the activation volume and water content exponent of transient creep. The constitutive relation used and its associated flow law parameters provide useful constraints for geodynamics applications. Ministry of Education (MOE) National Research Foundation (NRF) Published version This research was supported by the National Research Foundation Singapore under the NRF Fellowship scheme—National Research Fellow Award No. NRF-NRFF2013-04—and by the Singapore Ministry of Education under the Research Centres of Excellence initiative. SB is supported by the National Science Foundation of the United States (EAR-1848192). 2022-11-08T08:08:52Z 2022-11-08T08:08:52Z 2021 Journal Article Masuti, S. & Barbot, S. (2021). MCMC inversion of the transient and steady-state creep flow law parameters of dunite under dry and wet conditions. Earth, Planets and Space, 73(1). https://dx.doi.org/10.1186/s40623-021-01543-9 1880-5981 https://hdl.handle.net/10356/162772 10.1186/s40623-021-01543-9 2-s2.0-85119866634 1 73 en NRF-NRFF2013-04 Earth, Planets and Space © The Author(s) 2021. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Science::Geology
Transient Creep
Steady-State Creep
spellingShingle Science::Geology
Transient Creep
Steady-State Creep
Masuti, Sagar
Barbot, Sylvain
MCMC inversion of the transient and steady-state creep flow law parameters of dunite under dry and wet conditions
description The rheology of the upper mantle impacts a variety of geodynamic processes, including postseismic deformation following great earthquakes and post-glacial rebound. The deformation of upper mantle rocks is controlled by the rheology of olivine, the most abundant upper mantle mineral. The mechanical properties of olivine at steady state are well constrained. However, the physical mechanism underlying transient creep, an evolutionary, hardening phase converging to steady state asymptotically, is still poorly understood. Here, we constrain a constitutive framework that captures transient creep and steady state creep consistently using the mechanical data from laboratory experiments on natural dunites containing at least 94% olivine under both hydrous and anhydrous conditions. The constitutive framework represents a Burgers assembly with a thermally activated nonlinear stress-versus-strain-rate relationship for the dashpots. Work hardening is obtained by the evolution of a state variable that represents internal stress. We determine the flow law parameters for dunites using a Markov chain Monte Carlo method. We find the activation energy 430 ± 20 and 250 ± 10 kJ/mol for dry and wet conditions, respectively, and the stress exponent 2.0 ± 0.1 for both the dry and wet cases for transient creep, consistently lower than those of steady-state creep, suggesting a separate physical mechanism. For wet dunites in the grain-boundary sliding regime, the grain-size dependence is similar for transient creep and steady-state creep. The lower activation energy of transient creep could be due to a higher jog density of the corresponding soft-slip system. More experimental data are required to estimate the activation volume and water content exponent of transient creep. The constitutive relation used and its associated flow law parameters provide useful constraints for geodynamics applications.
author2 Asian School of the Environment
author_facet Asian School of the Environment
Masuti, Sagar
Barbot, Sylvain
format Article
author Masuti, Sagar
Barbot, Sylvain
author_sort Masuti, Sagar
title MCMC inversion of the transient and steady-state creep flow law parameters of dunite under dry and wet conditions
title_short MCMC inversion of the transient and steady-state creep flow law parameters of dunite under dry and wet conditions
title_full MCMC inversion of the transient and steady-state creep flow law parameters of dunite under dry and wet conditions
title_fullStr MCMC inversion of the transient and steady-state creep flow law parameters of dunite under dry and wet conditions
title_full_unstemmed MCMC inversion of the transient and steady-state creep flow law parameters of dunite under dry and wet conditions
title_sort mcmc inversion of the transient and steady-state creep flow law parameters of dunite under dry and wet conditions
publishDate 2022
url https://hdl.handle.net/10356/162772
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