GD6.1

EDI
Long-term rheology , heat budget and dynamic permeability of deforming and reacting rocks: from laboratory to geological scales

The goal of this session is to reconcile short-time/small-scale and long-time/large-scale observations, including geodynamic processes such as subduction, collision, rifting, or mantle lithosphere interactions. Despite the remarkable advances in experimental rock mechanics, the implications of rock-mechanics data for large temporal and spatial scale tectonic processes are still not straightforward, since the latter are strongly controlled by local lithological stratification of the lithosphere, its thermal structure, fluid content, tectonic heritage, metamorphic reactions, and deformation rates.

Mineral reactions have mechanical effects that may result in the development of pressure variations and thus are critical for interpreting microstructural and mineral composition observations. Such effects may fundamentally influence element transport properties and rheological behavior.
Here, we encourage presentations focused on the interplay between metamorphic processes and deformation on all scales, on the rheological behavior of crustal and mantle rocks, and time scales of metamorphic reactions in order to discuss
(1) how and when up to GPa-level differential stress and pressure variations can be built and maintained at geological timescales and modeling of such systems,
(2) deviations from lithostatic pressure during metamorphism: fact or fiction?
(3) the impact of deviations from lithostatic pressure on geodynamic reconstructions.
(4) the effect of porous fluid and partial melting on the long-term strength.
We, therefore, invite the researchers from different domains (rock mechanics, petrographic observations, geodynamic and thermo-mechanical modeling) to share their views on the way forward for improving our knowledge of the long-term rheology and chemo-thermo-mechanical behavior of the lithosphere and mantle.

Co-organized by GMPV7/NP3/TS2
Convener: Yury Podladchikov | Co-conveners: Lucie Tajcmanova, Shun-ichiro Karato, Evangelos MoulasECSECS, Magdalena Scheck-Wenderoth
Presentations
| Wed, 25 May, 08:30–11:47 (CEST), 13:20–14:05 (CEST)
 
Room -2.91

Presentations: Wed, 25 May | Room -2.91

Chairperson: Evangelos Moulas
Field and models
08:30–08:37
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EGU22-11149
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Presentation form not yet defined
Loic Labrousse, Marie Baisset, and Alexandre Schubnel

Mutual links between metamorphic reactions and rheological properties of rocks under pressure, temperature and deviatoric stress are a major source of discrepancy of thermo-mechanical models when it comes to predict strain localization for instance. The interactions between metamorphism and strain are also considered as a possible cause for unexpected mechanical instabilities, e.g. mechanical failure, in lithological units buried deep in convergent plate boundaries.

The partially transformed granulite facies anorthosites on the Holsnøy Island, Bergen Arcs, Norwegian Caledonides, constitute one of the few archetypical exposure of crustal rocks deforming and reacting at the same time in the eclogite facies conditions. In these rocks, eclogite-facies paragenesis develops with devitrification patterns in « brittle » pseudotachylyte, and in their damage walls, along a pervasive network of « ductile » shear zones, as well as « statically » along digitations following the preserved granulite facies foliation, with no apparent relation to strain.

The present study, that follows recent advances in the understanding of relationships between crystallization of pyroxene and local scale pressure field, or modeling of the interaction between the eclogitization reactions sequence and strain localization, focuses on the first steps of incipient plagioclase destabilization along eclogite facies « fingers ». 

Granulite facies plagioclase, close to 40 % anorthite in composition, is subject to reactions both in the NASH and CASH subsystems, with contrasted stoechiometries and kinetics. Petrological observations evidence that the lowermost pressure reaction in the CASH system (an + H2O = zo + ky + qz), occurs unbalanced, with high kinetics and reaction volume change and therefore initiates strain within plagioclase grains, that react by twinning and subgrains individualization. This early stage of intra-grain transformation induces an effective grain size reduction, and favors fluid percolation, therefore promoting the eclogitization progression. The reaction occurring inside of plagioclase grains also affects their grain boundaries where kyanite and transient reactions products, such as potential melts, accumulate also altering the overall aggregate properties. 

We claim that this early, fast and pervasive reaction is a significative, yet underrated, step of mechanical alteration of the burying continental rocks.

How to cite: Labrousse, L., Baisset, M., and Schubnel, A.: Early reaction of plagioclase : an underrated alteration step during burial of the continental crust, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11149, https://doi.org/10.5194/egusphere-egu22-11149, 2022.

08:37–08:47
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EGU22-10318
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ECS
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solicited
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Highlight
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Virtual presentation
Cindy Luisier, Philippe Yamato, Horst R. Marschall, Evangelos Moulas, and Thibault Duretz

Eclogitization reactions in mafic rocks involve large volume changes, porosity evolution and fluid transfer. They impact many important geological processes such as the localization of deformation and fluid channeling at intermediate depth in subduction zone. The study of exhumed eclogitic bodies in orogens shows that eclogitization of the oceanic crust is heterogeneous from both a structural and metamorphic point of view. For example, in the European Alps, the Allalin metagabbro shows high strain areas, consisting of hydrous metagabbros, fully equilibrated under eclogite-facies conditions during the Alpine orogeny. Conversely, large volumes of low strain, fluid-undersaturated gabbros remained largely unaffected by the high-pressure (HP) metamorphism, locally preserving igneous textures and even, occasionally, relics of their magmatic mineralogy. The intensity of deformation as well as the degree of eclogitization in the metagabbro have been shown to be directly related to the extent of pre-Alpine hydration during high-temperature hydrothermal alteration [1]. However, the influence of this degree of hydration on (1) reaction kinetics and/or (2) enhancing rheological contrasts leading to heterogeneous deformation patterns and metamorphic conditions is still debated.

In order to address this issue, we propose a multidisciplinary study involving petrographic and microtextural observations combined with 2D thermo-mechanical numerical models allowing to discuss the role of pre-Alpine hydrothermal alteration on the development of HP metamorphic assemblages.

We present petrographic and textural data from three different types of rocks from the Allalin metagabbros: i) undeformed and mostly untransformed metagabbros, with relics of igneous augite and plagioclase, ii) coronites, with olivine pseudomorphs showing different levels of hydration, rimmed by a garnet corona, and iii) eclogitized metagabbros, with olivine and plagioclase sites fully replaced by high-pressure assemblages.

The role of protolith hydration on the observed range in metamorphic facies is then tested by using 2D thermo-mechanical models that allow to simulate the deformation of a strong and dry rock with several randomly oriented weak and hydrous zones. Our results show that the shearing of heterogeneous rock can lead to the formation of localized ductile shear zone within a matrix that remains relatively undeformed but where plastic deformation can occur. The associated P field is also highly heterogeneous, with P ranging from 1 to 3 GPa. The deformation patterns and P modelled may suggest that locally hydrated portions of the gabbro acted as rheological perturbations sufficiently efficient in producing the structural and metamorphic record now observed in the field.

 

 

[1] Barnicoat, A. C. & Cartwright, I. (1997) Journal of Metamorphic Geology 15, 93–104

How to cite: Luisier, C., Yamato, P., Marschall, H. R., Moulas, E., and Duretz, T.: Eclogitization of the Allalin gabbro under heterogeneous stress conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10318, https://doi.org/10.5194/egusphere-egu22-10318, 2022.

08:47–08:54
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EGU22-8776
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On-site presentation
Stefania Corvò, Matteo Maino, Antonio Langone, Filippo Luca Schenker, Leonardo Casini, Sandra Piazolo, and Silvio Seno

The record of metamorphic conditions may be highly heterogeneous in spatially close rocks with different composition and rheology. The Cima di Gagnone area (Central Alps) represents an example of ultrahigh–pressure and high–temperature ultramafic lenses enveloped within amphibolite–facies metasediments. Structural investigations demonstrate that the rheologically strong ultramafics and eclogites and weak metapelites experienced a common Alpine deformation history in a single tectonic unit, excluding their coupling within a tectonic mélange (Maino et al., 2021). New structural, microstructural and petrological analyses and thermodynamic modelling results on the metasediments, confirming that all rocks generally experienced medium pressure and medium temperature conditions of 1.0–1.2 GPa and 640–700 °C, followed by a retrograde stage around 0.6–0.8 GPa and 600–675 °C. However, significantly higher P–T conditions of 1.3–3.0 GPa and 750–850 °C are locally developed close to the rheological boundary depicted by the micaschists-peridotite contact (Corvò et al., 2021; Piccoli et al., 2021). Rock and mineral chemistry changes during growth of new mineral phases indicate a local melt/fluid interaction (i.e., metasomatism) between metasediments and ultramafics during the high temperature deformation. The local occurrence of (U)HP and HT conditions is demonstrated by the absence of significant melting in the unit, although around the peridotite lenses, metapelites show hydrated assemblage at T>800 °C were stable at variable P stage. U-Pb zircon and monazite dating indicate that local HP and HT conditions were accomplished at the early stage of Alpine exhumation (~36 Ma), while the rocks fa form the rheological boundaries records only pre–Alpine ages. Our results documented that, even though weak metasediments share the same structural evolution with the strong UM, large differences in the local metamorphic conditions (ΔP up to 2 GPa; ΔT up to 160 °C) are recorded in relation to the distance from the UM lenses. Fluid–assisted metasomatism is further documented as being strongly localized at the interface between ultramafic lenses and the metapelitic host throughout all part of the metamorphic evolution, including the HP–HT stage. Therefore, in the Cima di Gagnone type–locality, the interplay between metapelites and ultramafic exerts a crucial first–order control to allow assemblage equilibrium during HT metamorphism and amphibolite–facies retrogression. These new findings exclude that the different metamorphic record may be attributed only to differential preservation during the retrograde path. Our new P–T–t–D paths highlight the crucial role of the rheological boundaries in modify the P-T metamorphic records without varying lithostatic pressure and thus depth conditions.

References:

Maino, M., Adamuszek, M., Schenker, F.L., Seno, S., Dabrowski, M., 2021. Sheath fold development around deformable inclusions: Integration of field-analysis (Cima Lunga unit, Central Alps) and 3D numerical models. J. Struct. Geol. 144, 104255.

Corvò, S., Maino, M., Langone, A., Schenker, F. L., Piazolo, S., Casini, L., & Seno, S., 2021. Local variations of metamorphic record from compositionally heterogeneous rocks (Cima di Gagnone, Central Alps): Inferences on exhumation processes of (U) HP–HT rocks. Lithos, 390, 106126.

Piccoli, F., Lanari, P., Hermann, J., & Pettke, T., 2021. Deep subduction, melting, and fast cooling of metapelites from the Cima Lunga Unit, Central Alps. Journal of metamorphic geology

How to cite: Corvò, S., Maino, M., Langone, A., Schenker, F. L., Casini, L., Piazolo, S., and Seno, S.: Local variations of metamorphic record from compositionally heterogeneous rocks: Inferences on exhumation processes of (U)HP-HT rocks (Cima di Gagnone, Adula-Cima Lunga unit) , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8776, https://doi.org/10.5194/egusphere-egu22-8776, 2022.

08:54–09:01
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EGU22-9093
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Highlight
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Presentation form not yet defined
Timm John, Sascha Zertani, Johannes C. Vrijmoed, Caroline Brachmann, and Oliver Plümper

When a fluid is introduced into dry rocks at high-pressure conditions, it acts as a catalyst and facilitates re-equilibration. This often promotes weakening and subsequent ductile deformation. Here, we present a detailed micro-structural and mineral chemical study of eclogitization of initially dry continental crustal rocks in the absence of ductile deformation. The studied sample features an incomplete (fluid-induced) transition from lower crustal granulite to eclogite, and the transition is fully preserved. None of the mineral phases show any signs of ductile deformation, indicating that the transformation was entirely static. Material transport during the reaction was limited to the availability of fluids. Detailed analysis of the local assemblages along the transect reveals that the reaction occurs in three distinct steps: The plagioclase-plagioclase grain boundaries were the first to re-equilibrate followed by clinopyroxene-plagioclase and garnet-plagioclase grain boundaries. Lastly, the grain boundaries that included only garnet and/or clinopyroxene are involved in the transformation. Thermodynamic modelling of local equilibria at dry conditions and with H2O in excess reveals that this stepwise transformation is caused by the varying reactivity of the local assemblages at the prevailing P-T conditions. Those reactions that result in the largest decrease of the Gibbs free energy from the dry case to the case with H2O in excess occur first. Once the reaction is facilitated, this effect is amplified because the density increase is largest at those grains boundaries that have reacted first, creating new fluid pathways through volume reduction. The calculated stable local mineral assemblages are consistent with those present in the sample indicating that element transport is limited, also supported by the observation that the fabric of the granulite is preserved in the eclogite. Our results demonstrate that reactive fluid flow is guided by the local energy budget along the grain boundaries, and that element transport during static re-equilibration is limited to the extent where it is thermodynamically advantageous.

How to cite: John, T., Zertani, S., Vrijmoed, J. C., Brachmann, C., and Plümper, O.: Grain-scale equilibrium reactions guide fluid-driven eclogitization of dry crustal rocks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9093, https://doi.org/10.5194/egusphere-egu22-9093, 2022.

09:01–09:08
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EGU22-10147
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ECS
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Presentation form not yet defined
Lisa Kaatz, Stefan M. Schmalholz, Julien Reynes, Jörg Hermann, and Timm John

High-grade dry granulites of Holsnøy (Western Norway) were subducted during the Caledonian orogeny and reached eclogite-facies conditions at ~2 GPa and 700° C. However, they stayed in a metastable state until brittle deformation enabled infiltration of an aqueous fluid, which triggered the kinetically delayed eclogitization. Field observations reveal an interconnected network of hydrated eclogite-facies shear zones surrounded by unaltered and pristine granulites. The formation of these features is highly controlled by deformation, fluid infiltration and fluid-rock interaction.

At first, the shear zone evolution was analyzed to better understand the relation between strain localization within the shear zones and the progressive widening of these shear zones from cm- to m-wide thickness. The results showed that widening overcomes the effect of stretching during progressive fluid-rock interaction and strain accumulation, if either a substantial amount of continuously infiltrating fluid and/or numerous repetitive fluid pulses enter the system.

Therefore, investigations have been carried on the H2O contents in nominally anhydrous minerals of the granulite and eclogite. The H2O contents were measured using Fourier transform infrared spectroscopy. Garnet (grt), clinopyroxenes (cpx) and plagioclase (plg) have been measured with a close look on spatial repartition of OH at the grain scale and at the shear zone scale. The aim is to decode the link between fluid infiltration, mineral reaction, and deformation. There are no significant compositional changes between granulite and eclogite, which means that the fluid mainly worked as a catalyst without mass transfer beside H2O. The analyses across a shear zone profile reveal three major observations: (i) average H2O contents of the grt cores increase from granulite towards the shear zone (from 10 to 50 µg/g), (ii) average H2O contents of the cpx increase, too (from 145 to 310 µg/g), (iii) the plg stores limited amounts of H2O until a phase separation leads into an symplectites consisting of albite-rich plg (anhydrous) and clinozoisite (hydrous). The H2O contents of the minerals are interpreted to be a result of two different diffusional mechanisms acting simultaneous at different spatial scales and rates. The H2O increase in grt and cpx cores without mineral reaction is a result of hydrogen diffusion (H+/H2), which is much faster and pervasive than the porous influx of an aqueous fluid (H2O), which, contemporaneously, caused the formation of hydrous phases.

The above findings are combined in a 1D numerical shear zone model to reproduce the measured mineral chemical data and the respective H2O-contents. The results shed light on the dynamic weakening processes caused by the influx of H+/H2 in combination with synkinematic mineral reactions.

How to cite: Kaatz, L., Schmalholz, S. M., Reynes, J., Hermann, J., and John, T.: H2O contents in nominally anhydrous minerals and its effect on the formation of eclogite-facies, hydrous shear zones (Holsnøy, Western Norway), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10147, https://doi.org/10.5194/egusphere-egu22-10147, 2022.

09:08–09:15
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EGU22-10383
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ECS
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Presentation form not yet defined
Iskander Ibragimov and Evangelos Moulas

Ophiolite complexes are commonly found outcropping along ancient suture zones in continental regions. Many geological studies suggest that, during subduction initiation, a small remnant of the oceanic crust can be thrusted upon continenal regions. This thrusting occurs during a process that is generally termed as “ophiolite obduction”. Despite the relatively small volume of the ophiolite rocks, their occurence provides important geologic/geodynamic constraints for the processes of subduction initiation. 
Following the seminal work of Cloos (1993), oceanic lithosphere that is older than 10 Myrs is dense enough, and as a result, facilitates oceanic subduction in a spontaneous manner. This suggestion is based on the fact that buoyancy is one of the most important forces relevant to large-scale geodynamics. However, old oceanic lithosphere is also expected to be cold and, as a consequence, mechanically strong. The increased strength of the oceanic lithosphere hinders subduction initiation and makes ophiolite obduction difficult.
In this work we perform systematic numerical simulations to investigate the effects of initial geometry and convergence velocity on subduction initiation and ophiolite obduction. We use LaMEM to calculate 2D thermo-mechanical models that include the effects of visco-elasto-plastic rheology. In addition, we have incorporated a thermodynamically-consistent density structure for the crust and mantle. In this way, buoyancy forces are calculated in a consistent manner based on the pressure and temperature fields of the thermo-mechanical models. Our results show that when the oceanic lithosphere is older than 10Myr, subduction is very difficult and does not initiate in a spontaneous manner. Our systematic simulations provide insights for the range of conditions and parameters of oceanic subduction and ophiolite emplacement.

References
Cloos, M. (1993) Lithospheric Buoyancy and Collisional Orogenesis: Subduction of Oceanic Plateaus, Continental Margins, Island Arcs, Spreading Ridges, and Seamounts. Geological Society of America Bulletin, 105, 715-737.
https://doi.org/10.1130/0016-7606(1993)105<0715:LBACOS>2.3.CO;2

How to cite: Ibragimov, I. and Moulas, E.: Geodynamic constraints on ophiolite emplacement, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10383, https://doi.org/10.5194/egusphere-egu22-10383, 2022.

09:15–09:22
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EGU22-2449
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On-site presentation
Pavlina Hasalová, Karel Schulmann, Anne-Sophie Tabaud, and Jitka Míková

During orogenic processes continental crust experiences significant partial melting. Repeated thermal pulses or fluctuation in fluid content can even cause multiple anatectic events that result in complex intrusion suits. The Vosges Mountains (NE France) reveal two chronologically and geochemically distinct tectono-magmatic events. An early major pulse of Mg‒K magmatism was followed ten millions years later by development of a magma-rich detachment zone and intrusion of Central Vosges Granite forming a felsic MASH zone. This MASH zone is characterized by the production of a large quantity of anatectic melts that interacted with the older Mg‒K granites and surrounding granulites and metasedimentary rocks. We aim to understand how such hybridization processes impact on the crustal rocks rheology, deformation as well as its geochemistry and geochronology. Three different granite varieties were distinguished: (i) the older Mg‒K granite end-member that is coarse-grained with a high proportion of feldspar phenocrysts, zircon U-Pb ages of 340 Ma and specific geochemical signature; (ii) Medium-grained type has a smaller amount of phenocrysts and shows advanced brecciation where fine-grained Pl+Kfs+Qtz form discontinuous corridors to an interconnected network surrounding fractured phenocrysts. Its geochemical signature suggests that this represents a mixing of Mg−K and Central Vosges granites, as confirmed by the presence of both inherited (340 Ma) and younger (330‒310 Ma) zircon domains; (iii) Isotropic medium-grained granite that shows geochemical signature typical for the Central Vosges Granite in which younger zircon domains (310‒320 Ma) dominate over inherited xenocrysts (340 Ma). These three granite varieties represent different stages of magma hybridization by the break up of the older Mg‒K granite by the younger Central Vosges Granite magmas. The interaction between new melt and previously crystallized granitoids results in variety of granite textures, fabrics, chemical compositions, isotopic signatures and deformational behavior. In summary, the resulting signature is result of interplay of melt transfer and interaction in the MASH zone.

How to cite: Hasalová, P., Schulmann, K., Tabaud, A.-S., and Míková, J.: Hybridization of magmas by break down of partially molten granitic rock and its assimilation , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2449, https://doi.org/10.5194/egusphere-egu22-2449, 2022.

09:22–09:29
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EGU22-4325
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On-site presentation
Petra Maierová, Pavlína Hasalová, Karel Schulmann, and Pavla Štípská

The common view of melt transport in the continental crust involves an initial stage of percolation along grain boundaries, melt segregation into leucosomes and dykes, coalescence of small melt conduits into larger ones and quick nearly vertical melt flow leading to formation of plutons. An entirely different style of melt migration was described in the Bohemian Massif, eastern European Variscan belt. There, a sequence of metaigneous migmatites was described where veins are lacking, leucosomes are rare and relics of melt are spread along grain boundaries. Textural, geochemical and compositional variations in these rocks show that they formed due to equilibration with melt coming from an external source, and that pervasive flow along grain boundaries was the dominant mechanism of melt transport.

The question arises, at what conditions this style of melt transport can operate and what consequences the different styles of melt transport have on the crustal-scale tectonics. We address this question by means of a 2D crustal-scale model of two-phase flow using the code ASPECT (aspect.geodynamics.org). The system of pores through which the melt flows is not resolved in our model and it is described only by its permeability. A low permeability describes material with pores along grain boundaries while a high permeability corresponds to a system of leucosomes, dykes or cracks

For different material properties and thermal conditions we obtain different styles of melt migration and characteristics of the modeled crust. The melt can form a diffuse zone in the lower–middle crust, km-scale waves of high melt fraction gathering into sub-vertical channels, or a horizontal zone with high melt fraction in the middle crust. The lower crust is depleted and the middle crust is enriched in incompatible elements, and composition of the middle crust typically shows km-scale variations. The compositional variations are obtained even in the models with low permeability that corresponds to the melt percolation along grain boundaries, in agreement with the characteristics of the Bohemian migmatites.

How to cite: Maierová, P., Hasalová, P., Schulmann, K., and Štípská, P.: Pervasive melt migration in hot continental crust – numerical models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4325, https://doi.org/10.5194/egusphere-egu22-4325, 2022.

Inclusions
09:29–09:36
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EGU22-575
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ECS
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On-site presentation
Hugo van Schrojenstein Lantman, David Wallis, Mattia Bonazzi, Jay Thomas, Maartje Hamers, Martyn Drury, and Matteo Alvaro

The measurement of residual stresses in exhumed rocks yields valuable information about metamorphic temperature and pressure, deformation and rheology, and stress state. However, the state of elastic strain and stress at the surface of a sample does not necessarily correspond to the state well below the surface. When a sample under elastic strain is cut, polished, or otherwise prepared for analysis, a part of the constraining rock is removed, allowing for the partial relaxation of the elastic strain. To be able to work with residual elastic strain and stress with analytical methods that probe the upper few microns of a sample, the process of strain relaxation must be well understood.

For this work we used high-angular resolution EBSD to analyse stressed quartz inclusions in natural garnet from a range of settings, and in several samples grown in piston-cylinder experiments that were previously analysed with Raman spectroscopy for inclusion pressures. The experimental samples are not expected to have undergone plastic deformation in the garnet during cooling, as the majority of the pressure within the inclusion built up during decompression at room temperature. Additionally, the inclusion pressures in buried inclusions matches what is expected for the experimental conditions, suggesting no plastic yielding. Thus, in these samples we can isolate elastic strain from potential plastic deformation. One of the experimental samples was analysed with TEM to test this expectation.

Forescatter images reveal topographical effects resembling quartz and adjacent garnet “extruding” out of the sample. Furthermore, rotations of the quartz lattice and the garnet lattice immediately around the quartz inclusion are observed. The rotation axis of the misorientation generally lies in the plane of the sample surface. TEM analysis revealed a number of dislocations in experimental garnet where these were not expected. However, a significant degree of bending of a wedge of garnet between the original sample surface and a quartz inclusion is also observed.

The dislocations observed with TEM do not fit with the model of the experiments. Also, the formation of dislocations before sample preparation does not explain the dependence of the rotation axis on the surface orientation. A likely scenario for the deformation measured with EBSD is that the partial relaxation of elastic strains in stressed quartz inclusions in garnet as result of sample preparation induced local distortion of the inclusion and host. Additionally, the persistence of topographical features related to this relaxation despite several steps of polishing suggests that relaxation is not instantaneous but occurs over time.

How to cite: van Schrojenstein Lantman, H., Wallis, D., Bonazzi, M., Thomas, J., Hamers, M., Drury, M., and Alvaro, M.: Strain relaxation around stressed quartz inclusions in garnet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-575, https://doi.org/10.5194/egusphere-egu22-575, 2022.

09:36–09:43
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EGU22-1247
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ECS
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Presentation form not yet defined
Nicola Campomenosi, Boriana Mihailova, Ross John Angel, Marco Scambelluri, and Matteo Alvaro

The contrast in the thermoelastic properties between one inclusion and its surrounding host is commonly exploited to back-calculate the pressure (P) and temperature (T) conditions of inclusion entrapment. This is elastic thermobarometry and it is based on the elastic properties of minerals rather than chemical equilibrium. The effect of inclusion confinement is the inclusion residual pressure (P-inc), which can be determined via Raman spectroscopy. For a given host-inclusion system, a specific P-inc corresponds a P-T line along which the confinement effects between the two crystals disappear: the isomeke. By definition, this line potentially represents the P-T conditions of inclusion entrapment. Away from the isomeke, the inclusion exhibits over- or under-pressure with respect to the external pressure. The position and slope of the isomeke can be calculated using the equations of state of both the host and the inclusion [1].

In this contribution, we show how zircon-in-garnet isomekes can be partially investigated via in-situ Raman spectroscopy at high T and ambient P by comparing the evolution of the Raman peak position of the inclusion with respect to a free zircon crystal at the same temperature. Several zircon inclusions in pyrope-rich garnets from the Dora-Maira whiteschists (Western Alps) were heated up and brought from the over- to the under-pressure domain across their corresponding isomeke. At temperatures above the isomeke, we found that zircon inclusions in garnet can be reset on the timescale of laboratory experiments: after cooling down the P-inc was different from the original. We interpret this reset as the result of viscous relaxation at the host-inclusion boundary [2] and annealing of submicron dislocations of the garnet host at high temperature. Importantly, for similar heating rate and T range, viscous relaxation occurs more easily when the inclusions are in the under-pressure domain. This suggest that original confinement effects of zircon in a garnet host whose exhumation path mostly occurs within the inclusion under-pressure domain can be easily reset to record P-T conditions on the retrograde path, while those from a garnet host whose exhumation path mostly occurs within the inclusion over-pressure domain can be better preserved. Therefore, since the isomekes of zircon with garnet are steep in P-T, this system may be more reliable for high T and low P terranes for which the exhumation path passes directly or quickly into the over-pressure domain [3]. On the other hand, for UHP domains such as Dora-Maira resetting occurs [4] due to the exhumation path being steep and thus in the under-pressure domain until low pressures.   

[1] Angel et al. 2015 Journal of Metamorphic Geology33(8), 801-813. [2] Zhong et al. 2020 Solid Earth11(1), 223-240.  [3] Gilio et al. 2021 Journal of Metamorphic Geology 10.1111/jmg.12625 [4] Campomenosi et al. 2021 Contributions to Mineralogy and Petrology176(5), 1-17  

This work was supported by the Alexander von Humboldt foundation and the ERC-StG TRUE-DEPTHS grant (number 714936) to M. Alvaro

How to cite: Campomenosi, N., Mihailova, B., Angel, R. J., Scambelluri, M., and Alvaro, M.: Fast resetting of zircon in garnet inclusion pressures: implications for elastic geothermobarometry., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1247, https://doi.org/10.5194/egusphere-egu22-1247, 2022.

09:43–09:50
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EGU22-4494
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Presentation form not yet defined
Evangelos Moulas, Konstantin Zingerman, Anatoly Vershinin, Vladimir Levin, and Yuri Podladchikov

Elastic thermobarometry has been at the forefront of research during the last decade. Using state-of-the-art spectroscopic and diffraction methods it has been possible to assess the residual elastic strain of mineral inclusions in an in-situ manner (Mazzucchelli et al., 2021; Zhong et al., 2019). The interpretation of residual stress/strain and its extrapolation to geological conditions requires mechanical models, that are based on continuum mechanics, which provide the range of pressure-temperature (P-T) conditions where host and inclusion are under homogeneous stress. This set of conditions may correspond to the entrapment conditions if the system is purely elastic. In the case of viscous/plastic relaxation of the host-inclusion system, the inferred P-T conditions represent apparent-entrapment conditions that could lie anywhere between the conditions of the true entrapment and the conditions of viscous/plastic relaxation (Moulas et al., 2020; Zhong et al., 2020). Thus, the interpretation and validity of elastic barometry strongly relies on the purely elastic behavior of the host-inclusion system.

The commonly employed elastic solutions assume a linear-elastic behavior and deal only with small-strain approximations. However, large values of residual stresses/strains may indicate that the range of decompression for such host-inclusion systems requires the incorporation of material/geometric non-linearity. In this work, we provide new numerical and analytical solutions for the non-linear, elasto-plastic behavior of host-inclusion systems. Our analytical solutions are based on new published models that describe the Neo-Hookean behavior of materials and reduce to the Murnaghan equation of state when the deformation is purely volumetric (Levin et al., 2021). We find that for the range of residual pressures that is commonly employed in barometric applications (<1GPa) the incorporation of geometric non-linearity does not influence the results significantly. Nevertheless, the incorporation of plasticity and the combined non-linear elastic and plastic behavior may lead to results that render elasto-thermobarometry inapplicable for very large compression/decompression ranges. Our results can be useful for benchmarking: a) models relevant to elasto-thermobarometry and b) geodynamic models that require the treatment of large volumetric deformations during the exhumation from lithospheric/mantle depths.

References

Levin, V.A., Podladchikov, Y.Y., Zingerman, K.M., 2021. An exact solution to the Lame problem for a hollow sphere for new types of nonlinear elastic materials in the case of large deformations. European Journal of Mechanics - A/Solids 90, 104345. https://doi.org/10.1016/j.euromechsol.2021.104345

Mazzucchelli, M.L., Angel, R.J., Alvaro, M., 2021. EntraPT: An online platform for elastic geothermobarometry. American Mineralogist 106, 830–837. https://doi.org/10.2138/am-2021-7693CCBYNCND

Moulas, E., Kostopoulos, D., Podladchikov, Y., Chatzitheodoridis, E., Schenker, F.L., Zingerman, K.M., Pomonis, P., Tajčmanová, L., 2020. Calculating pressure with elastic geobarometry: A comparison of different elastic solutions with application to a calc-silicate gneiss from the Rhodope Metamorphic Province. Lithos 378–379, 105803. https://doi.org/10.1016/j.lithos.2020.105803

Zhong, X., Andersen, N.H., Dabrowski, M., Jamtveit, B., 2019. Zircon and quartz inclusions in garnet used for complementary Raman thermobarometry: application to the Holsnøy eclogite, Bergen Arcs, Western Norway. Contributions to Mineralogy and Petrology 174, 50. https://doi.org/10.1007/s00410-019-1584-4

Zhong, X., Moulas, E., Tajčmanová, L., 2020. Post-entrapment modification of residual inclusion pressure and its implications for Raman elastic thermobarometry. Solid Earth 11, 223–240. https://doi.org/10.5194/se-11-223-2020

How to cite: Moulas, E., Zingerman, K., Vershinin, A., Levin, V., and Podladchikov, Y.: Large-strain elastoplastic formulations for host-inclusion systems with applications to elasto-thermobarometry and geodynamic models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4494, https://doi.org/10.5194/egusphere-egu22-4494, 2022.

09:50–09:57
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EGU22-8422
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ECS
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Highlight
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Presentation form not yet defined
Xin Zhong, Marisa Germer, Alexandra Pohl, Vincent Könemann, Olga Brunsmann, Philip Groß, Jan Pleuger, and Timm John

The Adula nappe is located at the eastern flank of the Lepontine dome in the Swiss Alps. It consists mainly of orthogneiss and paragneiss with intercalated lenses of eclogite, amphibolite and metasediments. Previous petrological studies on the peak pressure and temperature (P-T) conditions yield somewhat inconsistent results, particularly the pressure in the southern part of the nappe, but in general exhibit an increasing trend in both P-T towards the south. In this work, we applied zirconium-in-rutile thermometer and quartz-in-garnet Raman elastic barometer to constrain the P-T conditions using samples covering most of the nappe with high spatial coverage within the 600 km2 area to obtain an internally consistent dataset. Based on the results of zirconium-in-rutile thermometer, the temperature gradually increases from the north at ca. 540 °C to the south at ca. 680 °C. Using the quartz-in-garnet elastic barometer, the calculated entrapment pressure increases from ca. 2.0 GPa to ca. 2.2 GPa from the north to the middle-south region of the Adula nappe, but rapidly falls to ca. 0.8-1.2 GPa towards the southern region, where the temperature exceeds ca. 650 °C. It is speculated that due to the temperature increase towards the south, viscous relaxation became activated that led to an apparent drop of the recorded residual quartz inclusion pressure. This suggests that by applying a pure elastic model to high temperature conditions, one may potentially underestimate of the formation pressure of garnets. Therefore, this study may provide information on the limit of the quartz-in-garnet (pure) elastic barometry technique. Moreover, it may offer a potential opportunity to constrain the duration of the near-isothermal decompression path if a viscoelastic model can be applied, which requires not only the equation of state of minerals but also the creep behavior of the inclusion-host system.

How to cite: Zhong, X., Germer, M., Pohl, A., Könemann, V., Brunsmann, O., Groß, P., Pleuger, J., and John, T.: Chronometry of a nappe-scale thermal event inferred by thermobarometry and viscous relaxation of quartz inclusion pressure (Adula nappe, Alps), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8422, https://doi.org/10.5194/egusphere-egu22-8422, 2022.

Reactive transport
Coffee break
Chairperson: Magdalena Scheck-Wenderoth
10:20–10:27
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EGU22-10316
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Highlight
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Presentation form not yet defined
Johannes C. Vrijmoed and Yury Y. Podladchikov

We developed a numerical thermodynamics laboratory called “Thermolab” to study the effects of the thermodynamic behavior of non-ideal solution models on reactive transport processes in open systems. The equations of state of internally consistent thermodynamic datasets are implemented in MATLAB functions and form the basis for calculating Gibbs energy. A linear algebraic approach is used in Thermolab to compute Gibbs energy of mixing for multi-component phases to study the impact of the non-ideality of solution models on transport processes. The Gibbs energies are benchmarked with experimental data, phase diagrams and other thermodynamic software. Constrained Gibbs minimization is exemplified with MATLAB codes and iterative refinement of composition of mixtures may be used to increase precision and accuracy. All needed transport variables such as densities, phase compositions, and chemical potentials are obtained from Gibbs energy of the stable phases after the minimization in Thermolab. We demonstrate the use of precomputed local equilibrium data obtained with Thermolab in reactive transport models. In reactive fluid flow the shape and the velocity of the reaction front vary depending on the non-linearity of the partitioning of a component in fluid and solid. We argue that non-ideality of solution models has to be taken into account and further explored in reactive transport models. Thermolab Gibbs energies can be used in Cahn-Hilliard models for non-linear diffusion and phase growth. This presents a transient process towards equilibrium and avoids computational problems arising during precomputing of equilibrium data.

How to cite: Vrijmoed, J. C. and Podladchikov, Y. Y.: Thermolab: a thermodynamics laboratory for non-linear transport processes in open systems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10316, https://doi.org/10.5194/egusphere-egu22-10316, 2022.

10:27–10:34
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EGU22-10445
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ECS
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On-site presentation
Marko Repac, Annelore Bessat, Stefan Schmalholz, Yury Podladchikov, Kurt Panter, and Sebastien Pilet

The lithosphere and the asthenosphere are characterized by different heat transport mechanisms, conductive for the lithosphere, convective for the asthenosphere. The zone associated with the transition between these two distinct mechanisms is known as the "Thermal Boundary Layer" (TBL). How the melt is transported across this zone is an important question regarding intraplate magmatism and for the nature of the seismic Low-Velocity Zone. Numerous studies and models suggest that primary magmas from intraplate volcanos are the product of low degree partial melting in the asthenosphere, while the differentiation process takes place in the crust or shallow lithospheric mantle. The question is how low degree melt ascends through the TBL and the lithospheric mantle. The thermal structure of the lithosphere is characterized by a high geothermal gradient, which questions the ability of melt to cross the lithospheric mantle without cooling and crystallizing. Since the base of the lithosphere is ductile, the possible modes of magma transport are porous flow or porosity waves. For these reasons, we would like to understand how melt is transported and what are the implications on the evolution of primitive melt, going from the convective part of the geotherm to the conductive part of the geotherm and further across the lithosphere.

We present the results of a thermo-hydro-mechanical-chemical (THMC) model1 for reactive melt transport using the finite difference method. This model considers melt migration by porosity waves and a chemical system of forsterite-fayalite-silica. Variables, such as solid and melt densities or MgO and SiO2 mass concentrations, are functions of pressure, temperature, and total silica mass fraction (CtSiO2). These variables are pre-computed with Gibbs energy minimization and their variations with evolving P, T, and CtSiO2 are implemented in the THMC model. We consider P and T conditions relevant across the TBL. With input parameters characteristic for alkaline melt and conditions at the base of the lithosphere, we obtain velocities between 1 to 150 m yr-1,which is a velocity similar to melt rising at mid-ocean ridges2. This implies the inability of primary melts to cross the lithosphere. However, melt addition to the base of the lithosphere is important to understand mantle metasomatism, and could, to some extent, contribute to physical properties of the Lithosphere-Asthenosphere Boundary and Mid Lithosphere Discontinuity observed with geophysical methods. We suggest that the appearance of alkaline magmas at the surface requires multiple stage processes as melts rising in the lithosphere progressively modify the geotherm allowing new melts to propagate to the surface. Our earlier modeling results1 demonstrated that a single porosity wave has a minor impact on chemical evolution. In this study, we search for a mechanism responsible for stabilizing porosity wave motion to some lateral location forcing consecutive waves to follow the same ascent path. The passage of a large number of quickly rising porosity waves over a long time through the same path would accumulate large melt to rock ratios and cause significant chemical evolution.

 

  • Bessat et at., 2022, G3, in press
  • Connolly et al. 2009, Nature 462, 209-212.

How to cite: Repac, M., Bessat, A., Schmalholz, S., Podladchikov, Y., Panter, K., and Pilet, S.: Reactive Melt Transport Using Porosity Waves Across the Thermal Boundary Layer., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10445, https://doi.org/10.5194/egusphere-egu22-10445, 2022.

10:34–10:41
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EGU22-8033
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ECS
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Virtual presentation
Lawrence Hongliang Wang, Viktoriya M. Yarushina, and Yury Podladchikov

Two-phase flow equations that couple solid deformation and fluid migration have opened new research trends in geodynamical simulations and modelling of subsurface engineering operations. The physical nonlinearity of fluid-rock systems and strong coupling between flow and deformation in such equations lead to interesting predictions such as the spontaneous formation of focused fluid flow in ductile/plastic rocks. However, numerical implementation of two-phase flow equations and their application to realistic geological environments with complex geometries and multiple stratigraphic layers is challenging. Here, we present an efficient pseudo-transient solver for two-phase flow equations. We first study the focused fluid flow under the viscous regime without considering the elasticity. The roles of material parameters, reservoir topology, geological heterogeneity, and porosity are investigated. We show that focused fluid channels are the natural outcome of the flow instability of the two-phase system with a low ratio (< 0.1) between shear viscosity and bulk viscosity. We also confirm the previous studies that  decompaction weakening is necessary to elongate the porosity profile. The permeability exponents play the dominant role in the speed of wave propagation. The numerical models study fluid leakage from high porosity reservoirs into less porous overlying rocks. Geological layers present in the overburden do not stop the propagation of the localized channels but rather modify their width, permeability, and growth speed. We further validate our conclusions by modelling the full two-phase system with viscoelastic rheology and elastic solid and fluid compressibility (Yarushina et al., 2015). The Deborah number (De), solid (Ks), and fluid (Kf) bulk moduli are thus introduced into the governing equations. We found that the elasticity makes a difference when the Deborah number approaches one by speeding up the channel propagation. At the same time, its effect is rather limited when Deborah's number is small (e.g., 0.1). The effects of compressibility of the solid and fluid, on the other hand, are not found significant within the reasonable ranges of the bulk moduli.

 

How to cite: Wang, L. H., Yarushina, V. M., and Podladchikov, Y.: Modelling focused fluid flow: What matters?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8033, https://doi.org/10.5194/egusphere-egu22-8033, 2022.

10:41–10:48
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EGU22-12215
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ECS
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Presentation form not yet defined
Andrey Frendak, Yury Alkhimenkov, Lyudmila Khakimova, Ivan Utkin, Yury Podladchikov, and Stefan Schmalholz

Many geodynamic processes are coupled. For example, in the partially molten mantle, the solid and molten mantle phases interact chemically during porous melt flow. For such two-phase reactive melt migration, solid and melt densities are functions of temperature, pressure, and chemical composition. Numerical models of such coupled physical-chemical systems require special treatment of the various couplings and concise numerical implementation. We elaborate a 2-D thermo-hydro-mechanical-chemical (THMC) numerical model for melt migration by porosity waves coupled to chemical reactions (Bessat et. al., 2021). We consider a simple ternary chemical system of forsterite-fayalite-silica to model melt migration within partially molten peridotite around the lithosphere-asthenosphere boundary. Our THMC model can simulate porosity waves of different shapes depending on the ratio of shear to bulk viscosity and the ratio of decompaction to compaction bulk viscosity. For an initial circular (blob-like) porosity perturbation, having a 2-D Gaussian shape, the geometry of the propagating reactive porosity wave remains blob-like if all viscosities are similar. If the decompaction bulk viscosity is smaller than the compaction bulk viscosity, so-called decompaction weakening, then the propagating porosity wave evolves into a channelized form. Our simulations quantify the variation from a blob-like to a channel-like porosity wave as a function of the viscosity ratios. We describe the 2-D THMC numerical algorithm which is based on the pseudo-transient finite difference method. Furthermore, we quantify the impact of channelization on the chemical differentiation during melt flow. Particularly, we quantify the evolution of the total silica concentration during melt migration as a function of the degree of channelization.

References

Bessat, A., Pilet, S., Podladchikov, Y. Y., & Schmalholz, S. M. (2022). Melt migration and chemical differentiation by reactive porosity waves. Geochemistry, Geophysics, Geosystems. In press.  

How to cite: Frendak, A., Alkhimenkov, Y., Khakimova, L., Utkin, I., Podladchikov, Y., and Schmalholz, S.: Channelizing of melt flow by reactive porosity waves and its impact on chemical differentiation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12215, https://doi.org/10.5194/egusphere-egu22-12215, 2022.

10:48–10:55
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EGU22-7325
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Presentation form not yet defined
Viktoriya Yarushina and Yury Podladchikov

Coupled hydro-mechano-chemical (HMC) modeling is a topic of active ongoing research in various branches of Earth sciences and subsurface engineering. In engineering applications, HMC modeling is used to assess the feasibility of permanent CO2 storage in mafic and ultramafic rocks. The deformation and stresses building during the reaction is believed to induce fracturing, increase permeability and thus promote extensive reactions between CO2 and host rock. CCS in depleted reservoirs faces challenges related to possible CO2 leakage through old plugged and abandoned wells. When CO2 reaches the well, old cement compositions react with cement, compromising well integrity due to chemical degradation. In geology, coupled reactions and deformation are involved in melt extraction and migration, influencing the dynamics of volcanic systems and the evolution of subduction zones.

A large focus of previous studies was whether or not it is possible to achieve 100% of the reaction. Common reactive transport models predict that the reaction product will clog the pores, which will stop the fluid flow and thus further reactions. However, recent developments suggest that reaction progress depends on the assumed reaction kinetics and the constitutive models used in coupled models. Models that account for solid volume change as in mineral replacement reactions have a much higher potential for preserving porosity than the common dissolution-precipitation model, thus predicting the complete reaction. It is often assumed that reaction processes are transport-dominated, i.e., that all dissolved material is carried away by pore fluid. Then it precipitates on the available pore space leading to clogging and permeability reduction. However, recent observations suggest that while some reactions might be associated with dissolution and precipitation at the nano-scale, aqueous species transport is limited, and reaction products do not precipitate in the pores but rather stay attached to the primary mineral. Thus, the overall effect is the same as in mineral replacement reactions.

Using a combination of effective media theory and irreversible thermodynamics approaches, we propose a new model for reaction-driven mineral expansion, which preserves porosity and limits unrealistically high build-up of the force of crystallization by allowing inelastic failure processes at the pore scale. To fully account for the coupling between reaction, deformation, and fluid flow, we derive macroscopic poroviscoelastic stress-strain constitute laws that account for chemical alteration and viscoelastic deformation of porous rocks. These constitutive equations are further used with macroscopic conservation laws to illustrate the mutual impact of reactive transport and mechanical deformation on simple 1D examples of wellbore stability and fluid transport.

How to cite: Yarushina, V. and Podladchikov, Y.: A multiscale model for coupled chemical reaction and deformation of porous rocks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7325, https://doi.org/10.5194/egusphere-egu22-7325, 2022.

10:55–11:02
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EGU22-11836
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ECS
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On-site presentation
Lyudmila Khakimova, Evangelos Moulas, Ivan Utkin, and Yury Podladchikov

Classical Fickian linear diffusion of inert or trace-like elements is restricted to ideal solution models of components with equal molar mass. Simultaneous diffusion of multiple concentrations is well-treated by the classical Maxwell-Stefan model. Quantitative predictions of concentrations evolution in real mixtures require careful replacement of concentration gradients by gradients of chemical potentials. Coupling of multi component diffusion to mechanics result in pressure gradients that contribute to Gibbs-Duhem relationship. We aim at developing of thermodynamically admissible multicomponent thermo-chemo-mechanical (TMC) model with ensured non-negative entropy production. We also ensure correct equilibrium limit with zero gradients of chemical potentials of individual components and satisfaction of classical Gibbs-Duhem and Maxwell relationships under pressure gradients. Following recent Tajčmanová et al. (2021) we consider both molar and mass formulations. We present optimal pseudo-transient numerical scheme for multi-diffusional fluxes coupled to visco-elastic bulk deformation.

Tajčmanová, L., Podladchikov, Y., Moulas, E. and L. Khakimova. The choice of a thermodynamic formulation dramatically affects modelled chemical zoning in minerals. Sci Rep 11, 18740 (2021).

How to cite: Khakimova, L., Moulas, E., Utkin, I., and Podladchikov, Y.: Thermo-chemo-mechanical coupling in Maxwell-Stefan multi-component diffusion, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11836, https://doi.org/10.5194/egusphere-egu22-11836, 2022.

Reaction and deformation
11:02–11:09
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EGU22-9608
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Highlight
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Virtual presentation
Stefan Markus Schmalholz, Evangelos Moulas, Ludovic Räss, and Othmar Müntener

The dehydration of serpentinite during subduction and the associated formation of dehydration veins is an important process for the global water cycle and the dynamics of the subducting plate. Field observations suggest that olivine veins can form by dehydration during viscous shear deformation of serpentinite. However, this hypothesis of olivine vein formation, involving the coupling of rock deformation, dehydration reactions and fluid flow, has not been tested and quantified by hydro-mechanical-chemical (HMC) models. Here, we present a new two-dimensional HMC numerical model to test whether olivine veins can form by dehydration during viscous shearing of serpentinite. The applied numerical algorithm is based on the pseudo-transient finite difference method. We consider the simple reaction antigorite + brucite = forsterite + water. Volumetric deformation is viscoelastic and shear deformation is viscous with a shear viscosity that is an exponential function of porosity. In the initial model configuration, total and fluid pressures are homogeneous and in the antigorite stability field. Small, initial perturbations in porosity, and hence in viscosity, cause pressure perturbations during far-field simple shearing. During shearing, the fluid pressure can locally decrease and reach the thermodynamic pressure required for the dehydration reaction, so that dehydration is triggered locally. The simulations show that dehydration veins form during progressive shearing and grow in a direction parallel to the maximum principal stress. During the dehydration the porosity can increase locally from 2% (initial value) to more than 50% inside the dehydration vein. The numerical model allows quantifying the mechanisms and variables that control the evolution of porosity and fluid pressure. We show that the porosity evolution is controlled by three mechanisms: (1) volumetric deformation of the porous solid, (2) temporal variation of the solid density and (3) mass transfer during the dehydration reaction. We quantify the evolution of the fluid pressure that is controlled by five variables and processes: (1) the total pressure of the porous rock, (2) elastic effects of the total volumetric deformation, (3) the temporal variation of porosity, (4) the temporal variation of solid density and (5) mass transfer during the dehydration reaction. This model supports the observation-based hypothesis of the formation of olivine veins due to dehydration during viscous shearing of serpentinite. More generally, our HMC model provides quantitative insights into the evolution of porosity, and hence dynamic permeability, fluid pressure and mass transfer during dehydration reactions in deforming rock.

How to cite: Schmalholz, S. M., Moulas, E., Räss, L., and Müntener, O.: Formation of olivine veins by dehydration during viscously deforming serpentinite: a numerical study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9608, https://doi.org/10.5194/egusphere-egu22-9608, 2022.

11:09–11:16
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EGU22-12437
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Presentation form not yet defined
Yury Podladchikov and Ivan Utkin

The simplest kinetic normal growth model assumes linear dependence of the transformation rate (or the velocity of the phase boundary) on overstepping of equilibrium conditions (or the degree of metastability).   Under pressure gradients within the phases, the equilibrium state requires zero spatial gradient of difference of the chemical potentials of the two chemical components. This can be achieved by diffusional redistribution of the fraction of two components. At the phase boundary, equilibrium requires the equality of both chemical potentials. Accordingly, at the phase boundary, the linear kinetic model may assume the first component exchange between the phases to be proportional to the chemical potential difference of this component and the phase boundary velocity to be proportional to the chemical potential difference of the second complementary component. The phenomenological proportionality constants are needed to quantify the "mobility" of the phase boundary and intensity mass exchange between phases. These phenomenological material parameters can either be taken from an experiment or derived from a Cahn-Hilliard-type model. Cahn-Hilliard-type model resolving the fine structure of advancing phase boundary  ‘can derive, rather than postulate, a kinetic relation governing the mobility of the phase boundary and check the validity of the "normal growth" approximation’ (Truskinovsky, 1994).

Truskinovsky, L. About the “normal growth” approximation in the dynamical theory of phase transitions. Continuum Mech. Thermodyn 6, 185–208 (1994). https://doi.org/10.1007/BF01135253

How to cite: Podladchikov, Y. and Utkin, I.: Normal growth versus Cahn-Hilliard models for kinetics of the first-order phase transformations in binary mixtures under pressure gradients, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12437, https://doi.org/10.5194/egusphere-egu22-12437, 2022.

11:16–11:23
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EGU22-6103
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Highlight
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Presentation form not yet defined
Lucie Tajcmanova, Yury Podladchikov, and Ivan Utkin

Understanding rocks at the microscale is essential to comprehending Earth's history and making reasonable predictions about how planetary processes may change in the future.  

Advanced models for complex rock microstructures, such as symplectites or a development of exsolution lamellae, have been developed (Kuhl & Schmid, 2007; Petrishcheva & Abart, 2009). Despite of this recent valuable progress in our understanding of these microstructures, the mechanisms controlling its evolution especially from slowly cooled rocks are still not complete.

Commonly, such models focus solely on the chemical process. Interestingly, mechanics, i.e. stress and pressure redistribution, may also play an important role on microstructure evolution. In this contribution, we investigate the coupled, chemo-mechanical, effect for representative rock microstructures. We provide a comparison between purely chemical vs. coupled chemo-mechanical systems and provide predictions on the evolution of the given microstructures in 3D.

References:

Kuhl, E., Schmid, D.W. (2007). Computational Modeling of Mineral Unmixing and Growth. Comput Mech 39, 439–451.

Petrishcheva, E., & Abart, R. (2009). Exsolution by Spinodal Decomposition I: Evolution Equation for Binary Mineral Solutions with Anisotropic Interfacial Energy. American Journal of Science, 309(6), 431-449.

 

How to cite: Tajcmanova, L., Podladchikov, Y., and Utkin, I.: The role of mechanics in the modelling of common rock microstructures, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6103, https://doi.org/10.5194/egusphere-egu22-6103, 2022.

11:23–11:30
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EGU22-9773
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ECS
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Virtual presentation
Mattia L. Mazzucchelli, Evangelos Moulas, Boris Kaus, and Thomas Speck

Mountain building, earthquake generation, and volcanic eruptions occur in Earth’s lithosphere and have direct impacts on society. Understanding the mechanism of geodynamic processes relies on the determination of the pressure-temperature history which is recorded by rocks that have been involved in geodynamic processes. In most cases, the interpretation of the conditions attained by rocks is based on the assumption that the stresses in the Earth are hydrostatic. However, non-hydrostatic stresses are observed in the lithosphere, and the significance of the magnitude of the differential stress on phase equilibria is still actively contested among researchers who hold completely incompatible views about the use of various thermodynamic potentials (e.g. [1-3]).

The problem of phase equilibria under non-hydrostatic stress has been explored in several rock-deformation experiments (on mm scale), in which recrystallization of minerals was observed under an applied non-hydrostatic stress [4-6]. However, during experiments, stress and pressure heterogeneities may develop in the sample (e.g. [6]). Therefore, the direct effect of the applied non-hydrostatic stress on the thermodynamics of the reactions cannot be separated from the effect caused by local pressure variations in the sample itself.

Here, we explore the effect of non-hydrostatic stress on the thermodynamics of mineral reactions by investigating a system at the molecular scale. With Molecular Dynamics (MD) we perform coexistence simulations in which two phases are brought in contact and equilibrated at given temperature, pressure, and stress conditions. As expected, the obtained stress component normal to the phase-phase interfaces is homogeneous across the system. Our data suggest that the direct effect of non-hydrostatic stress on the solid-liquid equilibria is rather minor for geological applications, consistent with theoretical predictions [7,8]. However, our analysis does not take into account the indirect effect of stress heterogeneities at the sample scale. Spatial variations of stress can reach GPa level and can therefore indirectly affect phase equilibria.

M.L. Mazzucchelli is supported by an Alexander von Humboldt research fellowship.

References

[1] Wheeler, J. Geology 42, 647–650 (2014);

[2] Hobbs, B. et al. Geology 43, e372 (2015);

[3] Tajčmanová, L. et al. Lithos 216–217, 338–351 (2015)

[4] Hirth, G. et al. J. Geophys. Res. 99, 11731–11747 (1994)

[5] Richter, B. et al. J. Geophys. Res. Solid Earth 121, 8015–8033 (2016)

[6] Cionoiu, S. et al. Sci. Rep. 9, 1–6 (2019)

[7] Sekerka, R. et al. Acta Mater., 52(6), 1663–1668 (2004)

[8] Frolov, T. et al. Phys. Rev. B Condens. Matter Mater. Phys. 82, 1–14 (2010)

How to cite: Mazzucchelli, M. L., Moulas, E., Kaus, B., and Speck, T.: The influence of non-hydrostatic stress on mineral equilibria: insights from Molecular Dynamics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9773, https://doi.org/10.5194/egusphere-egu22-9773, 2022.

11:30–11:37
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EGU22-11811
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ECS
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Presentation form not yet defined
Yury Alkhimenkov, Ivan Utkin, Lyudmila Khakimova, Celso Alvizuri, and Yury Podladchikov

Understanding the physical processes governing earthquake nucleation has been a hot topic since the last decade. A lot of research has been done trying to explain the physics of seismic triggering events. However, the exact physics behind seismic events nucleation is still poorly understood. The outcome of our recent research is the new theory of earthquake nucleation (Alkhimenkov et. al., 2021). The simplest visco-plastic or elasto-plastic rheology allows us to model spontaneous earthquake nucleation. We consider pure shear boundary conditions and slowly increase stress in the model reflecting the stress increase e.g., due to tectonic forces in real rocks. Once the stress field reaches the yield surface, the strain localization occurs, resulting in slowly developing fractal shear bands. As time evolves, shear bands grow spontaneously, and stress drops take place in the medium. Such stress drops are caused by the instantaneous development of new shear bands, their intersections, and intersections with the boundaries of the numerical domain. A stress drop corresponds to a particular new strain localization pattern. The new strain localizations act as seismic sources and trigger seismic wave propagation (Minakov and Yarushina, 2021). We suggest that the (seismic) radiation pattern of the focal mechanism might be similar to a particular moment tensor source, typical for realistic earthquakes (Alvizuri et al., 2018). This new modeling approach is based on conservation laws without any experimentally derived constitutive relations.

References

Alkhimenkov Y., Utkin I., Khakimova L., Alvizuri C., Quintal Q., Podladchikov Y. Spontaneous earthquake nucleation in elasto-plastic media. 19th Swiss Geoscience Meeting 2021, Geneva, Switzerland.

Minakov, A. and Yarushina, V., 2021. Elastoplastic source model for microseismicity and acoustic emission. Geophysical Journal International, 227(1), pp.33-53.

Alvizuri, C., Silwal, V., Krischer, L. and Tape, C., 2018. Estimation of full moment tensors, including uncertainties, for nuclear explosions, volcanic events, and earthquakes. Journal of Geophysical Research: Solid Earth, 123(6), pp.5099-5119.

How to cite: Alkhimenkov, Y., Utkin, I., Khakimova, L., Alvizuri, C., and Podladchikov, Y.: The simplest visco- or elasto-plastic rheology allowing to spontaneous earthquake nucleation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11811, https://doi.org/10.5194/egusphere-egu22-11811, 2022.

11:37–11:47
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EGU22-12496
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solicited
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Highlight
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Virtual presentation
Thibault Duretz, René de Borst, Ludovic Räss, Phillippe Yamato, Tim Hageman, and Laetitia Le Pourhiet
Strain localisation is a key process that allows for the emergence of tectonic plates and controls their long-term deformation. Upper crustal levels are relatively cold and their rheology is thus governed by frictional plasticity. In order to predict the formation of tectonic plates and quantify the deformation of the Earth's upper shell, geodynamic modelling simulation tools must reliably account for deformation in the frictional plastic realm. 
Nevertheless, the simulation of frictional plastic strain localisation poses severe issues. Commonly employed implementations (visco-plastic and visco-elasto-plastic) often fail to accurately satisfy force balance and suffer from a lack of convergence upon mesh refinement. These problems are intimately linked to the fact that commonly employed models do not encompass any characteristic spatial or temporal scales of localisation. Various regularisation techniques can thus be used as a remedy. Here we investigate three popular regularisation techniques, namely viscoplasticity, gradient plasticity and the use of a Cosserat medium, and discuss their potential application for geodynamic modelling.  

How to cite: Duretz, T., de Borst, R., Räss, L., Yamato, P., Hageman, T., and Le Pourhiet, L.: Numerical modelling of lithospheric deformations with frictional plasticity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12496, https://doi.org/10.5194/egusphere-egu22-12496, 2022.

Lunch break
Chairperson: Lucie Tajcmanova
13:20–13:27
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EGU22-13185
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Highlight
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Virtual presentation
Philippe Yamato, Thibault Duretz, Marie Baïsset, and Cindy Luisier

Metamorphic reactions can lead to drastic changes in rocks mechanical properties. Indeed, during such transformations, the nucleation of new phases with different strength, grain size and/or density compared to the primary phases is enhanced, and transient processes due to the ongoing reaction are then activated.

Eclogitization of lower crustal rocks during continental subduction constitutes an emblematic transformation illustrating these processes. In such tectonic context, it has been shown that eclogitization seems to be closely associated with the occurrence of seismogenic events. However, the mechanisms that trigger brittle failure in such high pressure environments remain highly debated. Indeed, whether the change in density or the change in rheology can lead to embrittlement is still enigmatic.

By using 2D compressible mechanical numerical models we studied the impact of the strong negative volume change of the eclogitization reaction on the rocks rheological behaviour. We show that eclogitization-induced density change occurring out of equilibrium can, by itself, generates sufficient shear stress to fail the rocks at high-pressure conditions.

Rupture initiation at depth in continental subduction zones could therefore be explained by volume changes, even without considering the modifications of the rheological properties induced by the transformation. Our results also indicate that the negative volume change associated with brittle failure can enhance the propagation of the eclogitization process by a runaway mechanism as long as the reaction is not limited by the lack of reactants.

 

How to cite: Yamato, P., Duretz, T., Baïsset, M., and Luisier, C.: Brittle failure at high-pressure conditions: the key role of reaction-induced volume changes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13185, https://doi.org/10.5194/egusphere-egu22-13185, 2022.

13:27–13:37
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EGU22-13215
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solicited
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Highlight
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Presentation form not yet defined
Taras Gerya

In the recent decade, numerical modelling approaches based on combination of staggered finite differences with marker in cell techniques became increasingly popular in geodynamics due to their simplicity, flexibility and computational efficiency. Here, I present new version of popular 3D thermomechanical code i3ilvis, which has been fundamentally revised to include the following methodological advances (Gerya, 2019 and references therein):

  • Full thermomechanical coupling (through global Picard iteration) including compressible time-dependent mass conservation equation and adiabatic and shear heating effects in the energy conservation equation.
  • Regularized visco-elasto-viscoplastic rheological model with/without dilation. (Duretz et al., 2019) based on global thermomechanical Picard iteration.
  • Accurate continuity-based velocity interpolation for marker advection applicable for both compressible and incompressible flows.
  • Free surface stabilization against “drunken sailor” instability.
  • Accurate 3D rotation of elastic stresses on markers.
  • Dislocation-diffusion creep rheology with grainsize evolution(Bercovici and Ricard, 2012) including newton iteration for dislocation creep to compute effective viscosity for markers.

The new code is OpenMP parallel and has already been successfully tested for cases of realistic 3D geodynamic modeling including tectono-magmatic model of continental breakup to oceanic spreading transition and spontaneous subduction initiation scenario associated with slab bending and normal faulting.

 

Bercovici, D., Ricard, Y. (2012) Mechanisms for the generation of plate tectonics by two- phase grain-damage and pinning. Phys. Earth. Planet. Inter. 202-203, 27–55.

Duretz, T., de Borst, R., Le Pourhiet, L. (2019) Finite thickness of shear bands in frictional viscoplasticity and implications for lithosphere dynamics. Geochemistry, Geophysics, Geosystems, 20, 5598–5616.

Gerya T.V. (2019) Introduction to Numerical Geodynamic Modelling. Second Edition. Cambridge University Press, 472 pp.

 

How to cite: Gerya, T.: New i3elvis: Robust visco-elasto-plastic geodynamic modelling code based on staggered finite differences and marker in cell, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13215, https://doi.org/10.5194/egusphere-egu22-13215, 2022.

Lab experiments and models
13:37–13:44
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EGU22-11487
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ECS
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Highlight
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Presentation form not yet defined
Sarah Incel, Marie Baisset, Loic Labrousse, and Alexandre Schubnel

Geological processes involving deformation and/or reactions are highly influenced by the rock grain size, especially if diffusion-controlled processes take place such as long-range metamorphic reactions and diffusion creep. Although many processes, inducing grain-size reduction, are documented and understood at relatively high stresses and low temperatures (e.g., cataclasis) as well as at lower stress and higher temperature conditions (e.g., bulging, subgrain rotation), deformation twinning, a plastic deformation mechanism active in various minerals at lower temperatures, has been neglected as cause for grain-size reduction so far. We conducted experiments on natural plagioclase-bearing aggregates at 2.5 to 3 GPa confining pressure and temperatures of 720 to 950 °C using two different deformation apparatus, a DDIA and a Griggs press, as well as a piston-cylinder apparatus. Regardless of the apparatus type, we observe the breakdown of plagioclase into an eclogite-facies paragenesis, which is associated with partial melting in the high pressure, high temperature domain of the eclogite facies. In contrast to the sample that experienced hydrostatic conditions in the piston-cylinder press, the deformed samples reveal melt patches inside of several plagioclase grains. These patches coincide with the occurrence of deformation twins in plagioclase that formed due to differential stress. The ability of plagioclase to form deformation twins and their exploitation for melt initiation significantly lowers the effective grain size of plagioclase-rich rocks and thus impacts their reactivity and deformation behavior.

How to cite: Incel, S., Baisset, M., Labrousse, L., and Schubnel, A.: Deformation-facilitated melting of plagioclase, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11487, https://doi.org/10.5194/egusphere-egu22-11487, 2022.

13:44–13:51
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EGU22-3549
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Presentation form not yet defined
Alexandre Schubnel, Arefeh Moarefvand, Julien Gasc, Damien Deldicque, and Loïc Labrousse

Antigorite dehydration is considered as one of the potential triggering mechanisms of intermediate depth earthquakes in subduction zones. Here, the evolution of p-wave velocities were measured during antigorite dehydration experiments at pressure and temperature conditions representative of the upper mantle (1 to 2.5 GPa) for the first time.

Experiments were realized on a natural antigorite serpentinite from Corsica (Gasc et al. 2011), using a 3rdgeneration Griggs-type apparatus equipped with p-wave velocity ultrasonic monitoring (Moarefvand et al. 2021).Velocities were measured maintaining constant hydrostatic pressure conditions at  1, 1.5, 2 and 2.5 GPa, and slowly heating the sample beyond dehydration temperatures. At each pressure conditions, two experiments were carried out at a maximum temperature of 650°C or 700°C respectively, in order to investigate reaction kinetics and equilibrium overstepping. Experiments were quenched once the dehydration was completed, in order to preserve the microstructure.

In all our experiments, P-wave velocity decreased dramatically at the onset of dehydration.  This important drop in elastic properties is related to the fracturing and porous space generated by water release. At 700°C temperature, observed velocity drops were faster, and more pronounced compared to experiments performed at 650°C, indicating that the dehydration reaction progress was faster and more important. The velocity drop also got smaller with increasing pressure, but remained noticeable, even at 2.5GPa, a pressure at which the reaction volume change is negative. This indicates that even in the absence of fluid overpressures, the reaction is accompanied by an important amount of microcracking/softening. Recovered samples were then analyzed using scanning electron microscopy (SEM) and Electron backscatter diffraction (EBSD). With these microstructural data, the final reaction progress/advancement was estimated and we show that in situ measurements of p-wave velocity represent a good proxy for reaction progress and kinetics.

Our study opens up the door to a vast domain, where mineral reactions kinetics could be monitored in situ outside the synchrotron environment, via a direct access to elastic properties. It also reveals our need to apply state of the art effective medium theory modeling of porous and cracked aggregates when computing elastic properties of hydrating/dehydrating mineral assemblages. Finally, the elastic softening observed upon dehydration, even above 2GPa, tends to confirm the dehydration stress transfer model (Ferrand et al. 2017) for intermediate depth earthquake triggering.

 

references:

- Ferrand, Thomas P., et al. "Dehydration-driven stress transfer triggers intermediate-depth earthquakes." Nature communications 8.1 (2017): 1-11.

- Gasc, Julien, et al. "Simultaneous acoustic emissions monitoring and synchrotron X-ray diffraction at high pressure and temperature: Calibration and application to serpentinite dehydration." Physics of the Earth and Planetary Interiors189.3-4 (2011): 121-133.

- Moarefvand, Arefeh, et al. "A new generation Griggs apparatus with active acoustic monitoring." Tectonophysics816 (2021): 229032.

How to cite: Schubnel, A., Moarefvand, A., Gasc, J., Deldicque, D., and Labrousse, L.: Evolution of P-wave velocities during antigorite dehydration at pressures up to 2.5GPa , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3549, https://doi.org/10.5194/egusphere-egu22-3549, 2022.

13:51–13:58
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EGU22-11490
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ECS
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Presentation form not yet defined
Alina Sabitova, Sergey Stanchits, Viktoriya Yarushina, Georgy Peshkov, Lyudmila Khakimova, and Vladimir Stukachev

Nowadays, environmental awareness has become one of the key directions of humankind development. There are a lot of projects aimed at preserving the environment: ensuring the environmental safety of geothermal energy facilities; study of global geodynamics and its influence on the composition, state, and evolution of the biosphere; geoecological substantiation of safe placement, storage, and disposal of toxic, radioactive and other wastes, etc. An essential role is assigned to the storage of increasing volumes of carbon dioxide gas. This problem requires complex approaches and solutions. Given that both CO2 and radioactive storage are long-term projects, it is necessary to investigate the creep process to monitor the state of the underground environment and assess the risks of leakage. A viscous deformation of the formation accompanies the prolonged loading. Viscosity is an essential parameter in coupling fluid flow and deformation processes occurring on Earth [Sabitova et al., 2021]. At the same time, focused fluid flow is a common phenomenon in sedimentary basins worldwide. Flow structures often penetrate the sandy reservoir rocks and clay-rich caprocks [Peshkov et al., 2021]. The impacts of the viscoelastic deformation of clay-rich materials need to be evaluated from an experimental and modeling perspective to understand better the mechanisms forming such structures. Here, we present multistage triaxial laboratory creep experiments with acoustic emission analysis conducted on samples from the Barents Sea. We performed lithological and geochemical characterization of each sample as a petroleum system element. Bulk and shear viscosities used in numerical models are calculated for all samples. The experimental curves are explained using the theoretical model for porous rock viscoelastoplastic (de)compaction [Yarushina et al., 2020].

References:

Sabitova, A., Yarushina, V. M., Stanchits, S., Stukachev, V., Khakimova, L., & Myasnikov, A. (2021). Experimental compaction and dilation of porous rocks during triaxial creep and stress relaxation. Rock Mechanics and Rock Engineering, 54(11), 5781-5805.

Peshkov, G. A., Khakimova, L. A., Grishko, E. V., Wangen, M., & Yarushina, V. M. (2021). Coupled Basin and Hydro-Mechanical Modeling of Gas Chimney Formation: The SW Barents Sea. Energies, 14(19), 6345.

Yarushina, V. M., Podladchikov, Y. Y., & Wang, L. H. (2020). Model for (de) compaction and porosity waves in porous rocks under shear stresses. Journal of Geophysical Research: Solid Earth, 125(8), e2020JB019683.

How to cite: Sabitova, A., Stanchits, S., Yarushina, V., Peshkov, G., Khakimova, L., and Stukachev, V.: Creep and acoustic emission in Shales from the Barents Sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11490, https://doi.org/10.5194/egusphere-egu22-11490, 2022.

13:58–14:05
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EGU22-12337
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ECS
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Presentation form not yet defined
Elena Grishko, Viktoriya Yarushina, Maria Bobrova, Sergei Stanchits, Alexander Minakov, and Vladimir Stukachev

Microseismicity and acoustic emission (AE) studies are a part of earthquake science. Compared to ordinary earthquakes, microseismic events are characterized by higher frequencies, lower magnitudes, shorter duration, and more complex source mechanisms. The researchers associate the induced seismicity with different processes: borehole breakouts, tunnel excavations, hydraulic fracturing, wastewater injection, and stimulation of geothermal reservoirs.

Acoustic emission represents elastic waves generated spontaneously due to the formation of microfractures when the rock is undergoing a sufficiently high load. AE can be used to obtain continuous data at various stages of the deformation process: from distributed plastic failure to localized macroscopic failure. The spatial distribution of AE events indicates the location of fractures, and the source mechanism provides information about the failure mode: a tensile fracture, a shear fracture, or a combination of both.

This work shows the results of an experimental study of borehole breakouts in sandstones. We measured AE during the deformation experiments and applied the moment tensor analysis to microseismic waveforms. We used a continuum mechanics model of Minakov and Yarushina [2021] to relate the laboratory AE data to the deformation processes. The comparison of the failure patterns and corresponding seismic responses obtained in laboratory and simulations, allows to classify the deformation regimes in real rocks based on seismic observables.

EG, MB, SS, and VS gratefully acknowledge support from the Ministry of Science and Higher Education of the Russian Federation under agreement No. 075-15-2020-119 within the framework of the development program for a world-class Research Center.

 

References:

  • Minakov, A., Yarushina, V., Elastoplastic source model for microseismicity and acoustic emission, Geophysical Journal International, Volume 227, Issue 1, October 2021, Pages 33–53, https://doi.org/10.1093/gji/ggab207

How to cite: Grishko, E., Yarushina, V., Bobrova, M., Stanchits, S., Minakov, A., and Stukachev, V.: Experimental and numerical investigation of acoustic emission and its moment tensors in sandstones during failure based on the elastoplastic approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12337, https://doi.org/10.5194/egusphere-egu22-12337, 2022.