A dimensional analysis to quantify the thermal budget around lithospheric‐scale shear zones

Duprat-Oualid, Sylvia; Yamato, Philippe; Schmalholz, Stefan M.

doi:10.1111/ter.12144

Cited by 17 publications

(18 citation statements)

References 27 publications

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“…Independent thermometric estimations across the MFT indicate a systematic cumulative increase of the temperature of 50–70 °C from the slightly deformed wall rocks toward the damage zone and fault core, suggesting a causal relationship between deformation and heating (Burg & Gerya, ; Nabelek & Liu, ). Alternatively, the observed increase of temperature along the strain gradient could reflect fast advection coupled with focused erosion (e.g., Duprat‐Oualid et al, ) or upwelling of deep, hot fluids within the deformation zone (e.g., Gottardi et al, ). The heating potential of each mechanism is discussed in the next sections integrating the analytical results with the major outcomes obtained from 2‐D thermomechanical modeling.…”

Section: Discussionmentioning

confidence: 99%

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Time‐Dependent Heat Budget of a Thrust from Geological Records and Numerical Experiments

et al. 2020

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We present thermometric measurements and numerical simulations of the thermal budget of a shallow thrust (5–7 km of depth). We determine the temperatures of synkinematic minerals by chlorite geothermometer and illite crystallinity index and sheared veins with stable isotope and fluid inclusion microthemometry. The fault zone attained temperature higher than the wall rocks (ΔT of ~50 °C). Some heavily damaged rocks retain a minor but systematic record of a further temperature increase up to 150 °C, and the isotopic signal of fluids indicates a proximal source localized close to the fault zone. We simulated the geological evolution with a suite of elasto‐visco‐plastic thermomechanical models using a 2‐D finite difference code that reproduces the stress, strain, temperature, and pressure variations occurring within the thrust zone. Results indicate that shear heating during distributed cataclastic flow can account for a moderate and persistent temperature increment (ΔT 5–30 °C). Transient higher temperature pulses (50–90 °C) are reproduced simulating coseismic slip along narrow fault planes localized within the broad cataclastic zone. Integration of analytical data and numerical results supports the slow creeping frictional‐viscous deformation as effective mechanism explaining the low‐T part of the thermal history. Seismic deformation equivalent to moment magnitude Mw > 6.5–7.0 earthquakes is required to fully account for the thermal signal, including the extreme peak temperature.

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Section: Discussionmentioning

confidence: 99%

“…However, the question on which mechanism is responsible for heating is still open. With this respect, three major processes may control the thermal budget of a fault zone: advection, upwelling of hot fluids, and shear heating (Burg & Gerya, 2005;Duprat-Oualid et al, 2015;Nabelek & Liu, 1999).…”

Section: Significance Of the Mean Thermal Signalmentioning

confidence: 99%

Time‐Dependent Heat Budget of a Thrust from Geological Records and Numerical Experiments

et al. 2020

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“…In models 2a and 2b, both shear heating and advection are important for the formation of the inverted isotherms (e.g. Duprat‐Oualid et al ., ) but shear heating is preponderant to generate the shear zone. Furthermore, model 2a shows that the region of significant shear heating can be local and transient and that shear heating does not occur continuously in time along the entire shear zone.…”

Section: Discussionmentioning

confidence: 99%

Shear zone and nappe formation by thermal softening, related stress and temperature evolution, and application to the Alps

Schmalholz

Duretz

2015

Journal Metamorphic Geology

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We present the results of two-dimensional thermo-mechanical numerical simulations of the formation of kilometre-scale shear zones and tectonic nappes which are generated by thermal softening during horizontal shortening. This model is thermo-mechanically coupled and conserves energy by converting mechanical work into heat. The results show that in homogeneous material, the temperature increase in shear zones caused by viscous heating can be~100°C. The characteristic width of the thermally perturbed part of the deforming zone is three times larger than the width of the corresponding shear zone because of diffusive heating of the wall rock. Therefore, temperature variations initiated by shear heating may be difficult to identify based on petrological inferences of field data. During lithospheric shortening with a bulk rate of 2.5 9 10 À15 s À1 , a nappe forms in the crust at a depth of~45 km. Peak temperatures in the nappe reach~600°C (~100°C increase due to shear heating). Significant shear heating occurs only locally and is not active continuously in time along the entire crustal shear zone. Peak values of the maximal principal stress locally reach 2.5 GPa in the nappe. Peak values of temperature and maximal principal stress increase locally to~770°C (~300°C increase due to shear heating) and~3.8 GPa, respectively, if the applied bulk shortening rate is 5 9 10 À15 s À1 and if higher effective viscosities for the crust are applied. In the model lithosphere, high differential stresses (>500 MPa) and significant stress deviations from the lithostatic pressure (>50%) occur only locally and are transient. The highest average effective viscosity of the model lithosphere is~2 9 10 22 Pa s, which is in agreement with the estimates for the continental lithosphere. A characteristic feature of the presented dynamic nappe model is a significant stress decrease and cooling within a hundred thousand to 2 million years. These rates of decompression and cooling are discussed in the context of microstructural and metamorphic observations. The results also show that differential stresses in mature shear zones can be several hundred MPa smaller than at the onset of shear zone formation, which suggests that estimates based on microstructural analysis of rocks in ductile shear zones provide minimum values. The presented model could explain the formation of coherent Alpine nappes with inferred high-pressure (1.5-2.5 GPa) and ultrahigh-pressure (>3 GPa) conditions in 40-60 km depth at the base of an orogenic wedge.

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“…These dimensionless numbers (see Section 3.4) are defined: (i) for the three thermal processes inherent to the thrust activity (i.e. heat diffusion, heat advection and shear heating; see Duprat-Oualid et al 2015) and (ii) for the two additional kinematic processes (i.e. erosion and accretion).…”

Section: Numerical Parametric Studymentioning

confidence: 99%

“…Several theoretical, numerical and analytical studies have already addressed this problem of temperature evolution around thrust zones (e.g. Brewer 1981;Molnar & England 1990;England & Molnar 1993;Royden 1993;Duprat-Oualid et al 2013, 2015. However, the metamorphic zonations do not necessarily correspond to the local instantaneous thermal field.…”

Section: Introductionmentioning

confidence: 99%

On the meaning of peak temperature profiles in inverted metamorphic sequences

Duprat-Oualid

Yamato

2017

Geophysical Journal International

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A dimensional analysis to quantify the thermal budget around lithospheric‐scale shear zones

Cited by 17 publications

References 27 publications

Time‐Dependent Heat Budget of a Thrust from Geological Records and Numerical Experiments

Time‐Dependent Heat Budget of a Thrust from Geological Records and Numerical Experiments

Shear zone and nappe formation by thermal softening, related stress and temperature evolution, and application to the Alps

On the meaning of peak temperature profiles in inverted metamorphic sequences

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