Transient creep, aseismic damage and slow failure in Carrara marble deformed across the brittle-ductile transition

AbstractChanges in stress applied to mantle rocks, such as those imposed by earthquakes, commonly induce a period of transient creep, which is often modelled based on stress transfer among slip systems due to grain interactions. However, recent experiments have demonstrated that the accumulation of stresses among dislocations is the dominant cause of strain hardening in olivine at temperatures ≤600 °C, raising the question of whether the same process contributes to transient creep at higher temperatures. Here, we demonstrate that olivine samples deformed at 25 °C or 1150–1250 °C both preserve stress heterogeneities of ~1 GPa that are imparted by dislocations and have correlation lengths of ~1 μm. The similar stress distributions formed at these different temperatures indicate that accumulation of stresses among dislocations also provides a contribution to transient creep at high temperatures. The results motivate a new generation of models that capture these intragranular processes and may refine predictions of evolving mantle viscosity over the earthquake cycle.

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Brittle-ductile transition, instability modes of crustal rock and the estimation of shallow great earthquake depth

Physics and Chemistry of the Earth ◽

10.1016/0079-1946(89)90008-6 ◽

1990 ◽

Vol 17 ◽

pp. 45-54 ◽

Cited By ~ 1

Author(s):

Wang Zichao ◽

Wang Shengzu

Keyword(s):

Great Earthquake ◽

Crustal Rock ◽

Brittle Ductile Transition ◽

Instability Modes

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Fault reactivation and strain partitioning across the brittle-ductile transition

Geology ◽

10.1130/g46516.1 ◽

2019 ◽

Vol 47 (12) ◽

pp. 1127-1130 ◽

Cited By ~ 8

Author(s):

Gabriel G. Meyer ◽

Nicolas Brantut ◽

Thomas M. Mitchell ◽

Philip G. Meredith

Keyword(s):

Fault Slip ◽

Fault Reactivation ◽

Ductile Deformation ◽

Tectonic Deformation ◽

Gradual Change ◽

Bulk Rock ◽

Total Deformation ◽

Bulk Strain ◽

Brittle Ductile Transition ◽

Ductile Flow

Abstract The so-called “brittle-ductile transition” is thought to be the strongest part of the lithosphere, and defines the lower limit of the seismogenic zone. It is characterized not only by a transition from localized to distributed (ductile) deformation, but also by a gradual change in microscale deformation mechanism, from microcracking to crystal plasticity. These two transitions can occur separately under different conditions. The threshold conditions bounding the transitions are expected to control how deformation is partitioned between localized fault slip and bulk ductile deformation. Here, we report results from triaxial deformation experiments on pre-faulted cores of Carrara marble over a range of confining pressures, and determine the relative partitioning of the total deformation between bulk strain and on-fault slip. We find that the transition initiates when fault strength (σf) exceeds the yield stress (σy) of the bulk rock, and terminates when it exceeds its ductile flow stress (σflow). In this domain, yield in the bulk rock occurs first, and fault slip is reactivated as a result of bulk strain hardening. The contribution of fault slip to the total deformation is proportional to the ratio (σf − σy)/(σflow − σy). We propose an updated crustal strength profile extending the localized-ductile transition toward shallower regions where the strength of the crust would be limited by fault friction, but significant proportions of tectonic deformation could be accommodated simultaneously by distributed ductile flow.

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Brittle-ductile transition: semi-brittle behavior

Tectonophysics ◽

10.1016/0040-1951(89)90295-3 ◽

1989 ◽

Vol 167 (1) ◽

pp. 75-79 ◽

Cited By ~ 19

Author(s):

John V. Ross ◽

Peter D. Lewis

Keyword(s):

Brittle Behavior ◽

Brittle Ductile Transition

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Geochemistry of syntectonic, crustal fluid regimes along the Lithoprobe Southern Canadian Cordillera Transect

Canadian Journal of Earth Sciences ◽

10.1139/e95-134 ◽

1995 ◽

Vol 32 (10) ◽

pp. 1699-1719 ◽

Cited By ~ 13

Author(s):

Bruce E. Nesbitt ◽

Karlis Muehlenbachs

Keyword(s):

Deep Convection ◽

Canadian Cordillera ◽

Depth Of Penetration ◽

Crustal Fluid ◽

Quartz Veins ◽

Economic Significance ◽

Rock Types ◽

Brittle Ductile Transition ◽

Fluid Convection ◽

Convection Model

In conjunction with the Lithoprobe southern Canadian Cordillera program, an extensive examination of geochemical indicators of origins, movement, chemical evolution, and economic significance of paleocrustal fluids was conducted. The study area covers approximately 360 000 km2from the Canadian Rockies to Vancouver Island. Research incorporated petrological, mineralogical, fluid-inclusion, δ18O, δD, δ13C, and Rb/Sr studies of samples of quartz ± carbonate veins and other rock types. The results of the study document a variety of pre-, syn-, and postorogenic, crustal fluid events. In the Rockies, a major pre-Laramide hydrothermal event was identified, which was comprised of a west to east migration of warm, saline brines. This was followed by a major circulation of meteoric water in the Rockies during Laramide uplift. In the southern Omineca extensional zone, convecting surface fluids penetrated to the brittle–ductile transition at 350–450 °C and locally into the underlying more ductile rocks. A principal conclusion of the study is that most quartz ± carbonate veins in metamorphic rocks in the southern Canadian Cordillera precipitated from deeply converted surface fluids. This conclusion supports a surface fluid convection model for the genesis of mesothermal Au–quartz veins, common in greenschist-facies rocks worldwide. The combination of our geochemical results with the results of other Lithoprobe studies indicates that widespread and deep convection of surface fluids in rocks undergoing active metamorphism is a commonplace phenomena in extensional settings, while in compressional-thrust settings the depth of penetration of surface fluids is more limited.

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