GMPV3.2 | Fluid driven evolution of the Earth’s crust: influence of pathway networks, fluxes, and timescales
EDI
Fluid driven evolution of the Earth’s crust: influence of pathway networks, fluxes, and timescales
Convener: Ina AltECSECS | Co-conveners: Dörte JordanECSECS, Stylianos KarastergiosECSECS, Helen King, Christine V. Putnis
Orals
| Thu, 18 Apr, 08:30–10:15 (CEST)
 
Room -2.21
Posters on site
| Attendance Fri, 19 Apr, 10:45–12:30 (CEST) | Display Fri, 19 Apr, 08:30–12:30
 
Hall X1
Orals |
Thu, 08:30
Fri, 10:45
The importance of resources in the light of the energy transition to tackle climate change is now more important than ever. Therefore, we need to understand the formation of mineral resources to identify possible ore deposits. But not only extracting resources out of our earth is important but how to responsibly dispose of them and remediate environmental damages caused. One uniting factor for resource formation and environmental remediation is the role of fluids within the Earth’s crust. Their interaction with crustal material ranges from the nano- to the macro-scale. Each interaction process exhibits distinct physiochemical conditions related to, mineral substitution, growth, and deformation patterns. Some of these features are closely linked to melting, deformation, and destruction processes leading to fluid and element transfer, and enhanced chemical reactions over different spatial scales.
Deepening our understanding of those processes and integrating scales are fundamental to adapt exploration and potential environmental remediation strategies. Therefore, re-thinking existing models and timescales of fluid percolation within the Earth’s crust to enhance knowledge of provenance of fluids, mechanisms, time- and length-scales is necessary. It will contribute to modernising exploration and the diversification of the application of our findings in the fields of for example resource formation, geothermal energies, or carbon storage.
We invite multidisciplinary contributions that investigate fluid-rock interactions throughout the entire breadth of the topic, using fieldwork, microstructural and petrographic analyses, geochemistry, rock mechanics, thermodynamic as well as numerical modelling.

Orals: Thu, 18 Apr | Room -2.21

Chairpersons: Ina Alt, Stylianos Karastergios
08:30–08:35
08:35–08:45
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EGU24-11520
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On-site presentation
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Jaroslaw Majka, Maria Maraszewska, Daniel E. Harlov, Maciej Manecki, David A. Schneider, Igor Broska, and Perle Inge Myhre

A set of small iron oxide-apatite (IOA) ore bodies have been discovered within polydeformed and polymetamorphosed metasedimentary rocks on Prins Karls Forland, Svalbard. A complex tectonothermal history resulted in the development of various ore structure, varying from brecciated to mylonitised. Generally, the IOA ores are divided into two major geochemical subtypes: (1) fluorapatite-bearing with predominant low-Th monazite, and (2) F-Cl apatite-bearing with predominant high-Th monazite. Initial alteration of the ores resulted in liberation of REE and P from the apatite and redeposition as small (<30 mm), rounded monazite and xenotime crystals. REE and P in solution were likely transported during deformation that probably enhanced the transportation process. In fact, both the iron oxides and phosphates in the intensively deformed ores show features characteristic of fluid-assisted dissolution-reprecipitation creep. Subsequent stages of alteration caused either Th-enrichment of the monazite or even full replacement of low-Th monazite by a high-Th variety. In some of the ore bodies the original fluorapatite incorporated Cl, Mn, and Sr likely due to interaction with a Cl-rich fluid from the surrounding gabbroic and metasedimentary host rocks. The huge variability in the textures and the mineral assemblages from the ore bodies most likely reflect interaction with compositionally variable fluids that were liberated during the protracted tectonothermal evolution of the entire metamorphic complex. Hence, it is concluded that the IOA ores formed as a product of Fe, P, Ca, and REE fractionation from hypersaline fluids associated with the surrounding gabbros and metasedimentary rocks indicating that the ores were subjected to fluid activity during at least one metamorphic event.

How to cite: Majka, J., Maraszewska, M., Harlov, D. E., Manecki, M., Schneider, D. A., Broska, I., and Myhre, P. I.: Complex metamorphic and metasomatic history recorded by REE-phosphates in apatite-iron oxide ores from Svalbard, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11520, https://doi.org/10.5194/egusphere-egu24-11520, 2024.

08:45–08:55
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EGU24-20323
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ECS
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On-site presentation
Lorena Hernández Filiberto, Håkon Austrheim, and Andrew Putnis

Fluid migration within the Earth's crust significantly influences the development of shear zones. The Bergen Arcs have been a focal point for investigating the localization of rheologically weaker zones that facilitate shear zone formation, with various hypotheses proposed (Jamtveit et al. 2019; Incel et al. 2022). These zones may originate from seismic events, inducing brittle fracturing and creating pathways for mineral re-equilibration and ductile deformation.

This research concentrates on the island of Krossøy, located in the northernmost part of the Bergen Arcs, Western Norway, offering a unique perspective on deformation, textural evolution, and metamorphism compared to the extensively studied southern regions of Holsnøy and Radøy (Austrheim 1987; Mukai et al. 2014; Moore et al. 2020). Krossøy exposes anorthosites from the old granulitic basement, intruded by a series of subparallel mafic granulitic dykes forming a distinctive "dyke swarm," not documented elsewhere in the Bergen Arcs. We present our results on microstructural analysis through Electron Backscattered Diffraction (EBSD) and, mineral and chemical evolution using Electron Microprobe analysis (EMPA).

Given the plagioclase-rich nature of anorthosites, our results delineate the chemical and textural evolution of feldspars, tracing their journey from early-stage granulitic anorthosite formation approximately 930 Ma ago to the development of Caledonian mylonite (440-420 Ma) during shear zone activity under amphibolite facies conditions. By examining the fluid pathways, we seek to determine their relationship with the formation of rheologically weaker areas in the crust and how the dynamic interplay between fluid infiltration and deformation mechanisms may play an important role by changing the metamorphic conditions, textures and mineral assemblages in the rocks.

Austrheim, H. (1987). Eclogitization of lower crustal granulites by fluid migration through shear zones. Earth and Planetary Science Letters, 81(2–3), 221-232.

Incel, S., Labrousse, L., Hilairet, N. et al. (2022). Reaction-induced embrittlement of the lower continental crust. Geology, 47(3).

Jamtveit, B., Petley‐Ragan, A. et al. (2019). The Effects of Earthquakes and Fluids on the Metamorphism of the Lower Continental Crust. Journal of Geophysical Research: Solid Earth, 124(8), 7725-7755.

Moore J., Beinlich A., Piazolo S., Austrheim H. and Putnis A. Metamorphic differentiation via enhanced dissolution along high permeability zones. Journal of Petrology 61, 10, egaa096 (2020)

Mukai, H., Austrheim, H., Putnis, C. V., and Putnis, A. (2014). Textural Evolution of Plagioclase Feldspar across a Shear Zone: Implications for Deformation Mechanism and Rock Strength Journal of Petrology, 55(8), 1457-1477.

How to cite: Hernández Filiberto, L., Austrheim, H., and Putnis, A.: Fluid pathways and metamorphic evolution in the northern part of the Bergen Arcs: the island of Krossøy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20323, https://doi.org/10.5194/egusphere-egu24-20323, 2024.

08:55–09:05
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EGU24-11453
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ECS
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On-site presentation
Meissam Bahlali, Julia Woitischek, Carl Jacquemyn, Martin Purkiss, and Matthew Jackson

Sediment-hosted Cu deposits are a significant global source of copper. This study employs a mineral system approach, focusing on basin-scale groundwater flow as a key mechanism for Cu transport from source to trap. Numerical experiments using the open-source IC-FERST code investigate the controls on Cu transport in the Katangan Basin, Central African Copperbelt. The models developed for early and late stages of basin evolution incorporate fluid flow, heat and solute transport, and dynamic mesh optimization to enhance computational efficiency.

The early-stage model, corresponding to the salt deposition period, attributes the formation of saline brine to a dense residual phase resulting from evaporite formation. In the late-stage model, corresponding to Cu mobilization and mineralization, Cu dissolution and mineralization are simulated using a partition coefficient informed by experimental data.

Results reveal that density gradients induced by salinity and temperature variations play a crucial role in initiating convective groundwater flow. Highly saline, dense brines generated during salt deposition or dissolution form complex, downward-propagating plumes influenced by flow instabilities and geologic heterogeneity. Permeable faults and fractures in basement rocks enable groundwater to percolate, potentially mobilizing Cu from intra- or extra-basinal source rocks. Salinity and temperature gradients drive upwelling plumes, transporting Cu from deeper source rocks to shallower, organic-rich sedimentary rocks where mineralization occurs.

How to cite: Bahlali, M., Woitischek, J., Jacquemyn, C., Purkiss, M., and Jackson, M.: Integrated Modeling of Cu-Rich Fluid Migration and Mineralization in the Katangan Basin, Central African Copperbelt: Insights from Numerical Experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11453, https://doi.org/10.5194/egusphere-egu24-11453, 2024.

09:05–09:25
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EGU24-20271
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solicited
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Highlight
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On-site presentation
Benjamin Malvoisin, William Carlin, Fabrice Brunet, Bruno Lanson, Nathaniel Findling, Martine Lanson, Laurent Jeannin, Tiphaine Fargetton, and Olivier Lhote

The alteration of ferroan brucite, a common by-product of serpentinization, has been proposed as a H2 source at low temperature. Here, synthetic ferroan brucite with Fe/(Fe+Mg) = 0.2 was reacted with pure water at temperatures ranging from 348 to 573 K in 29 experiments either conducted in gold capsules or Ti-based reactors. H2 production monitoring with time and characterization of the reaction products revealed the occurrence of the following reaction: 3 Fe(OH)2brucite = Fe3O4 + H2 + 2 H2O. This reaction proceeds completely in ~ 2 months at 378 K and is thermally activated. The small grain size of the synthetic brucite (40-100 nm) is similar to observations in natural samples, and is probably responsible for the high reaction rate measured. H2 production reached a plateau and Fe-bearing brucite also precipitated as a reaction product, suggesting the achievement of equilibrium. The thermodynamic properties of Fe(OH)2 were refined based on the experimental dataset and differ by less than 5 % from previous estimates. However, ferroan brucite is predicted to be stable at an hydrogen activity one order of magnitude lower than previously calculated. As a result, significant H2 production during ferroan brucite alteration at low temperature requires efficient fluid renewal. Such a mechanism strongly differs from olivine serpentinization which can occur even at high activity in H2 and thus with limited water renewal.

How to cite: Malvoisin, B., Carlin, W., Brunet, F., Lanson, B., Findling, N., Lanson, M., Jeannin, L., Fargetton, T., and Lhote, O.: New thermodynamic and kinetic constraints on H2 production during ferroan brucite reaction at low temperature, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20271, https://doi.org/10.5194/egusphere-egu24-20271, 2024.

09:25–09:35
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EGU24-5717
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ECS
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Highlight
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On-site presentation
Maude Julia, Christine V. Putnis, François Renard, and Oliver Plümper

Coupled dissolution-precipitation reactions have been studied extensively recently for their ability to retain elements of interest into a stable solid form that can sequester potentially toxic elements. This is achieved through the initial dissolution of a substrate mineral in a fluid containing the target (often toxic) element. The dissolution leads to the supersaturation of a boundary layer at the mineral surface with respect to another solid phase containing the element of interest1. When the relative solubilities of the different minerals (in the aqueous fluid at the reaction interface) and their molar volume difference allow it, a coupled dissolution-precipitation can lead to the pseudomorphic replacement of the original substrate2. We tested this reaction for CaCO3 and cadmium (Cd) containing solutions as calcite (CaCO3) and otavite (CdCO3) form an almost perfect solid solution. We compared the reaction in similar solutions with different types of CaCO3: calcite single crystal, Carrara marble (polycrystalline calcite) and aragonite single crystals. For single calcite crystals, the reaction in a Cd-solution passivates the crystal’s surface due to the epitaxial growth of a (Ca,Cd)CO3 solid solution layer of low solubility. However, the random orientation of the grains in the Carrara marble samples and the change of crystal structure for the aragonite crystals modified the mechanism and allow the replacement of CaCO3 by (Ca,Cd)CO3 to take place3. Hydrothermal experiments and in situ fluid-cell atomic force microscopy (AFM) were used to observe the reaction both at room temperature and high pressure and temperature (200°C). In addition to SEM, BSE and EDX observations, synchrotron X-ray microtomography images were acquired on Carrara marble and aragonite samples at different stages of the reaction in order to gather more information about the replacement mechanism and the extent of Cd-uptake achievable through this process. The extent of the reaction was shown to be similar for the different solution concentrations used and limited in the case of Carrara marble. The porosity closes fast after the start of the reaction blocking the fluid pathways necessary for the reaction to proceed. The reaction in the aragonite samples seems to progress mainly through a reaction-induced fracture network probably created by the stress caused by the crystallographic structural differences between parent and product phases. Overall, these results demonstrate the capacity of CaCO3 to trap and store cadmium into a solid phase by a mechanism of coupled dissolution-precipitation.

 

(1)        Putnis, C. V.; Putnis, A. A Mechanism of Ion Exchange by Interface-Coupled Dissolution-Precipitation in the Presence of an Aqueous Fluid. Journal of Crystal Growth 2022, 600, 126840. https://doi.org/10.1016/j.jcrysgro.2022.126840.

(2)        Pollok, K.; Putnis, C. V.; Putnis, A. Mineral Replacement Reactions in Solid Solution-Aqueous Solution Systems: Volume Changes, Reactions Paths and End-Points Using the Example of Model Salt Systems. American Journal of Science 2011, 311 (3), 211–236. https://doi.org/10.2475/03.2011.02.

(3)        Julia, M.; Putnis, C. V.; King, H. E.; Renard, F. Coupled Dissolution-Precipitation and Growth Processes on Calcite, Aragonite, and Carrara Marble Exposed to Cadmium-Rich Aqueous Solutions. Chemical Geology 2023, 621, 121364. https://doi.org/10.1016/j.chemgeo.2023.121364.

How to cite: Julia, M., Putnis, C. V., Renard, F., and Plümper, O.: Potential sequestration of toxic elements: the specific example of cadmium and carbonates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5717, https://doi.org/10.5194/egusphere-egu24-5717, 2024.

09:35–09:45
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EGU24-11970
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ECS
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On-site presentation
Ewa Stępień and Maciej Manecki

The circulation of toxic elements through soils, sediments and aquatic environments remains a significant environmental problem, which implies several, often unrecognized health risks. Dissolution and precipitation reactions that result in formation of sparingly soluble crystalline compounds containing toxic elements e.g. As, appear to be a promising strategy for reducing their chemical mobility and bioavailability (Magalhães, 2002; Wang et. al., 2013).

In this study, the processes occurring at the interface of anglesite and solutions containing AsO43- ions were investigated. The results provide insight into the mechanism of As immobilization on the mineral surface through transformation of labile form into less reactive and more thermodynamically stable phases. Synthetic anglesite powder and fragments of natural anglesite crystals (Tsumeb, Namibia) were reacted for up to 3 months with solutions containing AsO43- (50 mg As/l) in the presence of Cl- ions at pH range 2 - 8. The experiments were conducted at room temperature (20 oC) or in the autoclave (120 oC).

Rapid sequestration of As from the solution was associated with precipitation of mimetite Pb5(AsO4)3Cl: over 66% of As was removed within 24 hours. After 7 days of the reaction, the concentration of As decreased from 50 to less than 11 mg As/L. The concentration of Pb2+ ranged from 0.6 mg Pb/L at pH 8 to 20 mg Pb/L at pH 2. Both, homogeneous and heterogeneous precipitation of mimetite was observed, and some anglesite crystals were covered by incrustations. At pH=2, mimetite was associated with schultenite PbHAsO4.

Scanning Electron Microscopy observations of the natural crystals surface, indicated that the reaction of As-containing solutions with anglesite at pH 4-8, involves dissolution of PbSO4, resulting in formation of etch pits, followed by precipitation of randomly intergrown mimetite as a loosely bound crust. The crust was formed in the vicinity but is separated from anglesite surface. In contrary, at very acidic conditions (pH=2), anglesite is replaced by a secondary phase as a result of a coupled dissolution and precipitation, leading to formation of lead arsenate pseudomorph. Surprisingly, temperature had no significant effect on the reaction, while the pH control is of great importance and determines the mechanism.

References:

Magalhães, M. C. F. (2002). Arsenic. An environmental problem limited by solubility. Pure and Applied Chemistry, 74(10), 1843–1850.

Wang, L., Putnis, C. V., Ruiz-Agudo, E., King, H. E., & Putnis, A. (2013). Coupled dissolution and precipitation at the cerussite-phosphate solution interface: Implications for immobilization of lead in soils. Environmental science & technology, 47(23), 13502-13510.

This research was funded by AGH University of Kraków project No 16.16.140.315.  

How to cite: Stępień, E. and Manecki, M.: Arsenate aqueous solution – anglesite PbSO4 interface: dissolution, precipitation, and arsenic sequestration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11970, https://doi.org/10.5194/egusphere-egu24-11970, 2024.

09:45–09:55
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EGU24-17340
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On-site presentation
Ashish Rajyaguru, Enzo Curti, Dario Ferreira Sanchez, Christian Appel, and Daniel Grolimund

Reactive transport of solutes in porous media involving dissolution/precipitation reactions may alter the physical properties of intact rocks, such as porosity and permeability. Such processes are difficult to predict and characterize due to heterogeneity at the pore scale, caused by the intimate coupling of chemical and transport processes. So far, experimental studies have mainly focused either on chemical aspects, using short time batch or microfluidic experiments, or on transport, using a porous medium in classical counter diffusion cells. The former approach offers a large flexibility in selecting and modifying parameters like pH, ionic strength, and element concentrations, and thereby allows the systematic derivation of chemical data such as mineral precipitation and dissolution at ex-situ conditions. The latter approach allows studying changes of (bulk) rock transport properties under realistic (in-situ) conditions over longer times, with limited knowledge of pore scale physical and chemical parameters, which may vary in space and time. Therefore, each of these methods limits a full characterization of the evolution of chemistry and transport properties in a realistic porous medium, particularly near the clogging zones that may form due to precipitation.

In this study, we present a methodology that allows the full chemical and physical characterization of reactive transport processes within a porous medium at the microscopic scale (1-10 um). We present experimental datasets that record, the chemical and physical evolution in 300 mm tapered glass capillaries filled with silica gel, in which precipitation of CaCO3 polymorphs has been induced via counter diffusion of Na2CO3 and CaCl2 reservoir solutions. Two counter diffusion systems, one containing 1 mM ZnCl2 in the CaCl2 titrant, the other without Zn, were prepared and evolved for three years. Optical microscopy and synchrotron-based techniques (micro XRF/XRT/XRD, micro XANES and SAXS) were used to characterize the system at selected times (1, 6, 12, 24, 36 months). In both experiments the precipitation of several calcite and/or vaterite crystal aggregates collectively reduced the gel porosity and formed clogging zones in the central part of the capillary. The data obtained for the Zn-free system show that vaterite crystals formed in the calcium rich part of the capillary (i.e., on the side of the CaCl2 titrant) remain stable for the entire duration of the experiment without converting to the more stable calcite. In the Zn-doped system, the vaterite crystals remain stable for 1 year and start to dissolve afterwards. The carbonate ions released via vaterite dissolution did not lead to the formation of new CaCO3 precipitates in the Ca-rich part of the capillary. Instead, a zinc hydroxy carbonate phase is formed.

Through this study, we show for the first time the evolution of a clogging zone in a porous medium at the microscopic scale over an extended period and under truly undisturbed in-situ conditions. Our results show that small concentrations of Zn2+ ions in the pore water have a strong effect on the precipitation/dissolution kinetics of CaCO3 polymorphs, as well as on their crystal morphology.

How to cite: Rajyaguru, A., Curti, E., Ferreira Sanchez, D., Appel, C., and Grolimund, D.: Zinc(II) ions under diffusive regime controls the stability of vaterite: Derivation of pore scale chemical dynamics near CaCO3 clogging interface via coupled micro-XRF/XRD/XANES and SAXS imaging., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17340, https://doi.org/10.5194/egusphere-egu24-17340, 2024.

09:55–10:05
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EGU24-12279
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Highlight
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On-site presentation
Oliver Plümper, Alireza Chogani, Helen E. King, and Benjamin Tutolo

Water, a principal component of Earth’s fluids, interacts with rocks in ways that profoundly influence lithospheric phenomena. These interactions are fundamental to both geochemical and geodynamic processes, extending their impact to areas of societal importance such as subsurface energy extraction and storage, and the formation of vital metal deposits for green energy technology. Additionally, the interplay between fluids and rocks significantly affects the Earth's carbon cycle, influencing atmospheric CO2 levels, climate, and overall planetary habitability. The traditional perspective suggests that fluids move through the lithosphere without being affected by the unique properties that emerge when matter is confined to the nanoscale. Contradicting this view, our research reveals that rocks involved in a variety of lithospheric processes consistently show nanoporosity, primarily with pores smaller than 100 nanometers. Within these small spaces, water behaves differently than it does in larger environments. Through molecular dynamics simulations, we have quantified water's relative permittivity—a critical factor in its geochemical behavior— when confined in natural nanopores. Our findings demonstrate that, under a wide range of lithospheric conditions, from ambient to extreme temperatures up to 700 °C and pressures up to 5 GPa, water's permittivity within these nanopores significantly deviates from that in its bulk state. Our thermodynamic equilibrium models indicate that this difference markedly reduces mineral solubility and alters ion speciation in natural settings. These pore-size-dependent properties may exert a primary influence on rock reactivity and the evolution of aqueous geochemistry during fluid-rock interactions.

How to cite: Plümper, O., Chogani, A., King, H. E., and Tutolo, B.: Nanopore Influence on the Geochemical Properties of Water in Earth's Lithosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12279, https://doi.org/10.5194/egusphere-egu24-12279, 2024.

10:05–10:15
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EGU24-13089
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ECS
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On-site presentation
Mattia Luca Mazzucchelli, Evangelos Moulas, Stefan M. Schmalholz, Boris Kaus, and Thomas Speck

The interpretation of mineral equilibria and reactions in rocks assumes uniform hydrostatic pressure across all phases. However, such condition is typically not satisfied in geological systems that are composed of multiple phases that are in contact with one another.  Stress gradients and non-hydrostatic stresses are to be expected in rocks in the lithosphere, even in the presence of fluids. This complexity challenges the reliability of existing hydrostatic thermodynamic models, and, currently, there is still no accepted theory for evaluating the thermodynamic effect of non-hydrostatic stress on reactions [e.g. 1, 2, 3, 4].

Molecular dynamics (MD) allows us to investigate first-order phase transitions in solid-liquid systems under stress, without the a-priori assumption of a specific thermodynamic potential [5]. With MD simulations the energy of the system, the pressure of the fluid, the stress of the solid, as well as the overall melting and crystallization process can be monitored until the stressed system attains the equilibrium conditions. Our findings indicate that under differential stress, the mean stress of the solid deviates progressively from the pressure of the fluid with which it is in equilibrium. At low differential stresses, deviations from the reference hydrostatic equilibrium are small, allowing accurate phase equilibria predictions by considering the fluid pressure as a proxy for equilibration pressure, as suggested by previous experimental investigations [6].

In the presence of substantial non-hydrostatic stresses, equilibrium between solid and fluid occurs at a fluid pressure significantly higher than hydrostatic thermodynamics predicts. However, the stressed system becomes unstable and a rim of a quasi-hydrostatically stressed solid eventually crystallizes around the initial highly stressed solid core. During the crystallization, the total stress balance is preserved until the newly formed solid-solid-fluid system reaches again a stable equilibrium. At the final equilibrium conditions only the low-stressed solid is exposed to the fluid, bringing back the equilibrium fluid pressure close to the value expected for the equilibrium at homogeneous hydrostatic conditions. Therefore, our results suggest that models describing equilibria and reactions in minerals and rocks under stress can assume that phase equilibria are accurately predicted by using the fluid pressure as a proxy of the equilibration pressure.

References

[1] Frolov, T., & Mishin, Y. 2010: Effect of nonhydrostatic stresses on solid-fluid equilibrium. I. Bulk thermodynamics. Physical Review B - Condensed Matter and Materials Physics, 82(17), 1–14.

[2] Hobbs, B. E., & Ord, A. 2015: Dramatic effects of stress on metamorphic reactions. Geology, 43(11), e372.

[3] Tajčmanová, L., Vrijmoed, J., & Moulas, E. 2015: Grain-scale pressure variations in metamorphic rocks: Implications for the interpretation of petrographic observations. Lithos, 216–217, 338–351.

[4] Wheeler, J. 2014: Dramatic effects of stress on metamorphic reactions. Geology, 42(8), 647–650.

[5] Mazzucchelli M., Moulas E., Kaus, B., Speck T. submitted: Fluid-mineral equilibrium under stress: insight from molecular dynamics. American Journal of Science.

[6] Llana-Fúnez, S., Wheeler, J., & Faulkner, D. R. (2012). Metamorphic reaction rate controlled by fluid pressure not confining pressure: Implications of dehydration experiments with gypsum. Contributions to Mineralogy and Petrology, 164(1), 69–79.

 

How to cite: Mazzucchelli, M. L., Moulas, E., Schmalholz, S. M., Kaus, B., and Speck, T.: Precipitation in fluid-mineral systems under differential stress investigated through molecular dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13089, https://doi.org/10.5194/egusphere-egu24-13089, 2024.

Posters on site: Fri, 19 Apr, 10:45–12:30 | Hall X1

Display time: Fri, 19 Apr 08:30–Fri, 19 Apr 12:30
Chairpersons: Ina Alt, Stylianos Karastergios
X1.57
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EGU24-2342
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ECS
Xin Liu, Jinqiang Tian, Zhuo Liu, and Fuyun Cong

The Tabei uplift is located in the northern part of the Tarim Basin, while the Lunan area is in the eastern part of Tabei uplift. The dryness coefficients of natural gas range from 0.62 to 0.99 (average: 0.92), the methane contents range from 30.42% to 96.4% (average: 85.10%), and the methane carbon isotopes range from -47.30‰ to -33.80‰ (average: -36.96‰) in the Lunnan area. Compared with the actual regional thermal evolution of the source rock, the natural gas exhibits excessively heavy dryness coefficients and methane carbon isotope characteristics. To investigate the genesis of heavy methane carbon isotopes and dry gas in different areas of the Tabei Uplift. Natural gas chemical composition and carbon isotope were used to analyze the genesis of natural gas, basin modeling was conducted to reconstruct the natural gas generation process, and the geologic causes of this phenomenon are discussed. The results show that the natural gas is primary cracking gas and sourced from marine type II kerogen. The dryness coefficient, methane carbon isotopes, and source rock maturity gradually increases from the west to the east. Instantaneous effects led to the dry gas and relative heavy methane carbon isotopes generated at a low maturity level. The current natural gas in the Ordovician reservoirs was all generated during the Himalayan orogeny. Long period pause of the gas generation between the two hydrocarbon generation phases is the main cause for the instantaneous effects.

How to cite: Liu, X., Tian, J., Liu, Z., and Cong, F.: The generation mechanism of deep natural gas, Tabei uplift, Tarim Basin, Northwest China: insights from instantaneous and accumulative effects, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2342, https://doi.org/10.5194/egusphere-egu24-2342, 2024.

X1.58
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EGU24-8161
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ECS
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Rinaldi Ikhram, Takashi Hoshide, Tsukasa Ohba, and Mega Fatimah Rosana

The presence of ophiolitic mélanges in the Indonesian archipelago has been acknowledged as pivotal for the paleo-tectonic reconstruction of the Southeast Asia Region (southwestern Sundaland). However, the occurrence of rodingite as an integral component of ophiolite in Indonesia has not been thoroughly documented. The rodingites within the Ciletuh Ophiolitic Mélanges in Western Java are notably fresh and widespread, providing a valuable opportunity to initiate comprehensive research on rodingites, particularly focusing on the interplay of metasomatism between serpentinite and meta-gabbro. These metasomatic processes can provide valuable insights into reconstructing the evolution of P-T conditions and elemental transfer involving fluids in a subduction zone. This study aims to focus on field occurrences, petrography, whole-rock geochemistry, with the application of P-T pseudosection modeling to describe their metamorphic conditions.

Rodingitized gabbro in Ciletuh occur as dykes intersecting serpentinized peridotite with sharp and diffuse contact. These dykes are controlled by faults in direction opposite perpendicular or diagonal to the shearing direction of serpentinites. Sheared-foliated rodingite and serpentinite are common, usually forming boudinages. Rodingites are classified into six types which are: (1) Fine to medium grain clinopyroxene rich, (2) Fine to medium grain hydrogarnet rich, (3) Coarse grain, (4) Schistose, (5) Diffused serpentinite-rodingite at peripheral dyke, and (6) Diffused serpentinite-rodingite embedded within serpentinite.  Type (1) to (3) are dykes which mostly composed by garnetized plagioclase (47-49%) and clinopyroxene (29-32%), orthopyroxene (20%), olivine (<3%), epidote (<5%), zoisite (<3%) with minor spinel and magnetite (2-4%). Type (4) is comprised of foliated mineralogical domains such as carbonate-rich and chlorite-rich domain. Types (5) and (6) are characterized with diffused contact of rodingite (hydrogarnets) and chloritized serpentinite. Chlorite reaction zones can be encountered at the contacts between rodingite and serpentinite, typically indicated by the presence of chloritized groundmass, chloritized serpentine mesh, chlorite and hydrogarnet veinlets, as well as partial clinopyroxene rim around hydrogarnet.

The general whole rock geochemical characteristics of rodingitized gabbro are indicated by low SiO2 content (34-42 wt%), high CaO (3-16 wt%), high MgO (17-32 wt%), medium Al2O3 (5-10 wt%), and FeOt (5-18 wt%), with high LOI (5-10 wt%). Significant whole rock geochemical variations characterize the serpentinite-rodingite reaction zones in both the sharp dykes (Type 1-3) and diffused (Type 5-6) contact. Serpentinite near the reaction zone exhibits enrichment in Al2O3, CaO, but depletion in MgO, FeO, and SiO2. Conversely, rodingitized gabbro experiences enrichment in MgO, slight enrichment in FeO, and depletion in CaO and Al2O3.  

P-T psedosection models show that rodingitization occured concurrently with serpentinization during medium to low-grade metamorphism at temperatures ranging from 200 to 490˚C. This process involved diffusional metasomatism with fluids derived from serpentinization and metamorphism of gabbro (e.g., Ca, Mg, and Al), considering the addition of H2O and other potential fluids during the exhumation of ophiolitic mélanges in the subduction slab.

How to cite: Ikhram, R., Hoshide, T., Ohba, T., and Rosana, M. F.: Rodingite Occurrence in Ciletuh Ophiolitic Mélange Complex (Indonesia): Evidence of Fluid-Rock Interaction in Subducted Oceanic Crust, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8161, https://doi.org/10.5194/egusphere-egu24-8161, 2024.

X1.59
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EGU24-16710
Andrea Billarent-Cedillo, Mark Jefferd, Helen E. King, Suzanne Hangx, and Oliver Plümper

In the upper crust, rock deformation commonly occurs in the presence of aqueous fluids, which are known to alter the material's response to stress. These fluids facilitate dissolution and precipitation, driving changes in the mineral composition and texture. The interaction between dissolution-precipitation and deformation in the upper crust has been studied in various natural geological cases, through experimentation, and modeling. Recently, there has been increased emphasis on understanding the role of fluids in deformation at the nanoscale. This experimental study aims to comprehend the effects of deformation on dissolution and precipitation at the nanoscale, specifically at the boundary between individual mineral grains.

Our research has focused on understanding quartz dissolution and precipitation at the grain boundary scale at hydrostatic pressures and temperature conditions representative of the upper 5 km of the crust. We report preliminary findings from our experiments on nano-milled quartz crystals, representing natural grain boundary geometry, in contact with different aqueous solutions in a closed system. The pH, salinity, and concentration of Si in solution were systematically altered to assess their impact on dissolution rates. By using 18O-doped solutions, coupled with nanoscale secondary ion mass spectrometry and atomic force microscopy, we can track the dissolved and re-precipitated material, and monitor the changes in the geometry of the nano-milled quartz surface. This constitutes the initial step in our effort to further explore and quantify the effects of differential stress at the grain boundary. Additionally, we present results from a pilot study designed to test how differential normal stress impacts asperity dissolution within quartz-quartz contacts. These experiments aim to improve our understanding of dissolution rates in relation to pressure solution, a significant deformation mechanism in sedimentary and fault rocks.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie initial training network (FluidNET) grant agreement no. 956125.

 

How to cite: Billarent-Cedillo, A., Jefferd, M., King, H. E., Hangx, S., and Plümper, O.: Nanoscale experiments of intergranular dissolution-precipitation to understand deformation mechanisms in the upper crust.  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16710, https://doi.org/10.5194/egusphere-egu24-16710, 2024.

X1.60
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EGU24-12899
Wolf-Achim Kahl, Christian Hansen, M. Mangir Murshed, Wolfgang Bach, and Juan Manuel Garcia

Fluid-aided mineral replacement plays a key role in metamorphic reactions and metasomatic mass transfers. Within the scope of this study we investigate the role of pore space evolution in the hydrothermal phase transition from gypsum to bassanite. We monitored the partial dehydration of gypsum to bassanite in-situ using an X-ray-transparent flow-through reaction cell (Kahl et al., 2016) during long-term hydrothermal percolation experiments. By repeated, intermittent X-ray microtomography (µ-CT) scans, we surveyed the evolution of the porous system created by the dissolution-reprecipitation process. The quantitative 3D image analysis of the obtained 4D image material shows that incipient bassanite formation takes place in domains well within the interior of the gypsum crystal, presumably located along nano- or microcracks (i.e. at the scale of grain boundaries of the selenite host, and maybe enhanced due to the presence of fluid inclusions), and not directly at the gypsum – fluid interface. After larger volumes of interconnected pores have formed in later stages of the experiment, bassanite nucleation becomes insignificant and bassanite growth is now the dominant fixation mechanism of hemihydrate. The fabric of the final reaction product is controlled by these later-stage elongate bassanite crystals that are oriented along [001] of the former gypsum crystal. Careful data analysis reveals that processes which strongly depend on transient characteristics of the fluid-hosting fabric component are easily obliterated from the rock record. Concerning the predictive numerical simulation of mineral replacement processes in general, these results reveal that the boundary conditions underlying mineral nucleation may not be deduced from observations of the resulting fabric of mineral growth.

 

Kahl, W.-A., Hansen, C., and Bach, W. (2016) A new X-ray-transparent flow-through reaction cell for a mu-CT-based concomitant surveillance of the reaction progress of hydrothermal mineral-fluid interactions. Solid Earth, 7(2), 651-658.

How to cite: Kahl, W.-A., Hansen, C., Murshed, M. M., Bach, W., and Garcia, J. M.: Porosity evolution determines available reaction mechanisms in water-rock interactions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12899, https://doi.org/10.5194/egusphere-egu24-12899, 2024.

X1.61
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EGU24-14807
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ECS
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Manon Amiot, Philippe Goncalves, and Flavien Choulet

Fluid flow within the continental crust, and the concomitant fluid-rock interactions, are likely responsible for mass transfer and significant change in bulk rock chemistry (i.e. metasomatism). Strain localization and formation of ore deposits are very commonly associated to metasomatism. Metasomatic processes are studied combining petrology, geochemistry, fluid inclusion analysis and/or thermodynamic modelling (P-T-X). To model and quantify the mass and fluid flux integrated with time, the driving forces and controlling factor, such as fluid chemistry (solubility, speciation, chlorinity …), P-T conditions and phase relations, the degree of disequilibrium between the fluid and the host-rock must be clearly identified.

This study focuses on phase relations modelling during metasomatic processes based on the mineralogical and chemical characterisation of metasomatic rocks from the Tauern Window. Samples are amphibole- and chlorite-bearing micaschists resulting from the transformation of a granodiorite under amphibolite conditions (550-570°C and 0.5-0.6 GPa). The studied outcrop is similar to some extent to Mg-metasomatic rocks reported in several localities in the Alps, including Dora Maira, Gran Paradiso or Monte Rosa and summarised in Ferrando (2012). Although all the localities reported in Ferrando (2012) and the Tauern window have their own characteristics (eg. different P-T conditions, fluid chemistry, mineralogy, age...), they also share similar features. For instance, the gain in Mg with respect to the protolith is systematically coupled with a gain in fluid, and a loss of Ca, Na and sometimes Si. This shared feature suggests that a unique and simple process must be involved in all these localities.

Thermodynamic models are developed using chemical potentials of perfectly mobile components of the system as variable (µi), following the definition of Korzhinskii (1959). It means that the chemical potential of the mobile component (MgO, CaO, Na2O, SiO2, H2O) is controlled by the environment, which we consider here as an externally-derived fluid. The computed projections and pseudo-sections show that the reequilibration of the granodiorite with the externally-derived fluid (high µMgO and low µCaO, µNa2O, µSiO2) induce a series of metasomatic reactions leading to the breakdown of the granodiorite assemblage into amphibole, then muscovite-chlorite and eventually talc. From these models, it is possible to quantify the amount of mass lost and gained along the defined reequilibration path and eventually estimated the required fluid flux.

How to cite: Amiot, M., Goncalves, P., and Choulet, F.: Phase relation modelling associated with metasomatic processes in open systems: application to an example of Mg-metasomatism from the Neves area, Tauern window, Eastern Alps., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14807, https://doi.org/10.5194/egusphere-egu24-14807, 2024.

X1.62
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EGU24-5003
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ECS
Yongsheng Huang, Satoshi Okumura, Kazuhisa Matsumoto, Naoko Takahashi, Hong Tang, Guoji Wu, Tatsumi Tsujimor, Michihiko Nakamura, Atsushi Okamoto, and Yuan Li

Serpentinite carbonation contributes to the deep carbon (C) cycle. Recently, geophysical and numerical studies have identified considerable hydrothermal alterations in deep bending faults beneath outer-rise regions, implying potentially significant C storage in the slab mantle. However, quantitative determination of C uptake in outer-rise regions is lacking. Here, we experimentally constrained the serpentinite carbonation in H2O–CO2–NaCl fluids under bending fault conditions to estimate C uptake in the slab mantle. We found that serpentinite carbonation produced talc and magnesite along the serpentinite surface. The porous reaction zones (49.2% porosity) promoted the progress of the carbonation reaction through a continuous supply of CO2-bearing fluids to the reaction front. Strikingly, NaCl effectively decreased the serpentinite carbonation efficiency, particularly at low salinities (< 5.0 wt%), which is likely attributed to the reduction in H2O and CO2 activities (aH2O and aCO2) and transport rate of reactants, the change in pH of fluids, and the enhancement of magnesite solubility. We fitted an empirical equation for the reaction rate of serpentinite carbonation in bending faults and found that this reaction could contribute to a flux of 25–100 Mt C/yr in subduction zones. Our results shed new light on the deep C cycle and the serpentinite carbonation in environments with high salinities.

How to cite: Huang, Y., Okumura, S., Matsumoto, K., Takahashi, N., Tang, H., Wu, G., Tsujimor, T., Nakamura, M., Okamoto, A., and Li, Y.: Importance of mantle serpentinite carbonation in bending faults for the deep carbon cycle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5003, https://doi.org/10.5194/egusphere-egu24-5003, 2024.

X1.63
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EGU24-19351
Kristian Drivenes, Jochen Knies, Tobias Kurz, Annina Margreth, and Jasmin Schonenberg

The Rolvsnes Granodiorite, comprising the major extent of the northern part of Bømlo Island, Western Norway, has been proposed to be an onshore analogue to the weathered basement rocks at Utsira High hosting significant petroleum resources. A total of 205 meters of core in three boreholes was collected crosscutting both fault zones and apparently tectonically undisturbed rocks. Four distinct lithologies were identified in the drillholes: A medium-grained (grano-)diorite, a range of biotite granites, a porphyritic granite, and aplites/pegmatites. All rock types display evidence of hydrothermal alteration as either pervasive discoloration or more localized veining. Early propylitic alteration of the granodiorite is easily observed macroscopically as distinct greening, caused by primary amphibole being replaced by epidote, and calcic plagioclase cores being altered to epidote+muscovite+quartz. The extent and transition of the alteration steps can be observed in the hyperspectral logs. A second generation of epidote can be observed as 1-2 mm veins crosscutting all lithologies. With decreasing temperature and/or higher fluid/rock ratio, biotite is altered to chlorite. Late infiltration of carbonic fluids is evident from calcite veins cutting former alteration types, and ankerite/Fe-rich dolomite + Fe-oxide veins associated with open fractures. 

The clay mineralogy is dominated by smectite and kaolinite, and several meter long sections of the drill cores are near or completely disintegrated from drilling and core handling due to the high smectite content. Kaolinite and smectite may occur together as alteration products, but in open fractures kaolinite is found as infilling in vugs and fractures lined with quartz or associated with the Fe-carbonates, with little or no smectite. This indicates that during late fluid circulation in the faults, kaolinite was precipitated directly from the fluid, and that smectite in the smectite-rich zones was a part of a low temperature pervasive alteration event.

K-Ar dating of the clay-rich alteration zones from this and former studies show a large range of ages, with the ages of the finest (<0.1 µm) fraction ranging from 31 Ma to 281 Ma. The oldest ages are likely mixed or inherited from early events, but apparent clusters around 30-50, 110-140, 200-210, and 265-280 Ma may provide indications of periods of low temperature alteration.   

How to cite: Drivenes, K., Knies, J., Kurz, T., Margreth, A., and Schonenberg, J.: From high-T Hydrothermal Alteration To Near-Surface Weathering – The Alteration History of the Rolvsnes Granodiorite, W Norway, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19351, https://doi.org/10.5194/egusphere-egu24-19351, 2024.

X1.64
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EGU24-20669
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ECS
Bernardo B. Khater, Renata S. Schmitt, Gustavo L. C. Pires, and Alessandro F. Palmeira

During active rifting, whenever magmatism is present, magma emplacement on the upper crust is usually controlled by brittle structures reactivating an inherited tectonic fabric. In the southeastern Brazilian margin, a Cretaceous NE-SW tholeiitic dyke swarm follows the trend of the Neoproterozoic Ribeira Belt. However, in the coastal area of Rio de Janeiro, it crosscuts orthogonally the Paleoproterozoic orthogneisses of the Cabo Frio Tectonic Domain. In order to investigate how these South Atlantic rift structures formed orthogonally to the inherited host fabric, detailed structural analysis on two key areas was performed, using geological mapping with high-resolution drone images, analyzing the relation of brittle structures, diabase dykes and host rocks. The main set of faults and fractures is oriented parallel to the NE-SW diabase dykes. Dykes bifurcate or change direction abruptly following faults and fractures. Three paleostresses regimes were characterized: (1) a strike-slip transtension with NNE-SSW and NE-SW strike-slip faults; (2) an extensional transtension with oblique NNE-SSW and ENE-WSW faults; and (3) a pure extension with NNE-SSW and ENE-WSW normal faults. The tholeiitic dykes were emplaced during phases 2 and 3 continuously. Syn-kinematic secondary minerals formed on the cataclasites and the host rocks by fluid interaction. Calcite, epidote, chlorite and iron oxide compose a low-grade metamorphism of Ca-, Fe- and Mg- assemblage. These minerals also registered different phases of deformation during paleostresses regimes, with crystallization/precipitation facilitated by thermal injection of the tholeiitic magmas. Increase in permeability of the host rocks by formation of faults and fractures also contributes for the fluid migration, thus contributing with hydrothermal alteration on the upper crust. These mineral reactions also corroborated with the weakening of the continental crust, allied with the increase of dilatant slip surfaces. The combination of these tectonic and hydrothermal processes enabled the emplacement of the NE-SW Serra do Mar Dyke Swarm into the Cabo Frio Tectonic Domain, disregarding the NW-SE inherited tectonic fabric.

How to cite: B. Khater, B., S. Schmitt, R., L. C. Pires, G., and F. Palmeira, A.: Magma Emplacement during active rifting in the upper crust: kinematics and petrology of diabase and host rocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20669, https://doi.org/10.5194/egusphere-egu24-20669, 2024.

X1.65
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EGU24-9404
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ECS
Maria M. Repczynska, Aitor Cambeses, Jose Francisco Molina, Pilar Montero, and Fernando Bea

It is now widely known that the fluids play a major role in the formation and evolution of the Earth´s crust. Fluids and melts formed by dehydration-melting reaction of muscovite, biotite and amphibole during prograde metamorphism can have a profound effect on the trace element and isotope composition on the crustal sources of magmas.

However, while the phase relations of these reactions as well as the textural and mineralogical evidence of fluid-rock interaction in high-grade metamorphic complexes are well studied, the mechanisms of the onset of fluid and melt generation by the dehydration melting along with the transport and geochemical impact of these mobile phases onto anhydrous minerals at the grain scale remain unclear.

We investigated the mechanisms of local reactions involved in the incipient dehydration/melting processes at different temperatures, the sequence of reactions and the interaction of the fluid and/or melt with the anhydrous mineral phases, by conducting analogue heating experiments of rock cylinders in a vertical furnace. The rock samples used in the experiments were granitoids and gneisses from the Iberian Massif (Spain) with variable content of biotite and muscovite. They were cut into cylinders with dimensions of about 3x20 cm and placed into a vertical furnace. The experiments were done under thermal gradient at sub- and supersolidus conditions (600-1200oC) at ambient pressure in an inert atmosphere of N2 and last up to 8 days.

First results show that significant compositional and textural changes in biotite and muscovite were produced in experimental runs at temperatures >850oC. Muscovite experienced dehydration melting breakdown to ultrabasic, very peraluminous melts with higher Na and lower K than the starting muscovite, small grains of aluminosilicates and large vesicles. Biotite underwent subsolidus dehydration, resulting in the formation of spinel and/or Fe-Ti oxides and alkali-rich aqueous fluid. Notably, K-feldspar did not nucleate at the dehydration site; instead, excess K and other incompatible elements (Li, Rb, Cs, Ba) were transported by fluids released from biotite and muscovite. These fluids subsequently induced metasomatic reactions in plagioclase, transforming it into K-feldspar. Additionally, Ca released from plagioclase contributed to the formation of titanite after ilmenite. The metasomatic changes were facilitated by fluid migration along micropores that were present in the starting plagioclase, highlighting the intricate processes involved in mica driven metamorphism and metasomatism. A second type of melt was generated with increasing temperature, characterized by higher silica and more granitic-like compositions, suggesting the involvement of quartz and feldspars in the melting reactions.

Although the experimental pressure conditions are much lower than those inside the crust, these analogous experiments allow us to investigate the mechanism by which fluids and melts are segregated from the reaction sites and the influence of rock texture. In these analogue experiments the breakdown of hydrous minerals is enhanced because they are outside their P-T stability fields. Besides, the formation of gas is maximized since its solubility in the melt is very low. Therefore, it allows us to investigate the importance of vesiculation in the creation of pathways for fluid and melt migration.

 

How to cite: Repczynska, M. M., Cambeses, A., Molina, J. F., Montero, P., and Bea, F.: Experimental insights into fluid and melt generation by dehydration reactions of micas with implications for crustal processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9404, https://doi.org/10.5194/egusphere-egu24-9404, 2024.