Introduction:  Hydrated silica has been detected from orbit in Jezero crater [Tarnas et al., 2019] and holds great promise for the astrobiology science goals of the M2020 mission and the MSR Program. Early entombment within an hydrated silica matrix has been shown to minimize the molecular degradation of microorganisms during advanced diagenesis [Alleon et al., 2016a,b; Alleon et al., 2018].

On sol 0910, a float rock was automatically selected by the AEGIS system after a rover drive when entering the margin unit from the Jezero delta top. The target is a light-toned partially buried float with lustrous appearance.

LIBS: The chemistry of 9/10 points reveal a homogeneous composition, enriched in SiO₂. The average SiO₂ for these 9 points is 75.0 wt.% while the average total of quantified oxides is 83.5 wt. %.  

VISIR reflectance: The reflectance spectra share an overall blue slope, and exhibit absorptions at 1.9 µm (H₂O), 2.2 µm (X-OH) and 1.4 µm (OH & H₂O). The chemistry derived from LIBS (mean Al₂O₃< 2 wt.%) leads to the attribution of the 2.2 µm band to Si-OH. All such absorptions are present within spectra of terrestrial hydrated silica.

What type of hydrated silica? The reflectance spectra show that this target contains both Si-OH and molecular water. The position of absorption bands departs from what is typically observed for opals and chalcedony is at present the closest spectral analogue in term of band depths and position.

What origin? A 2.2 µm band has been observed in the IR spectra from the fan top and the margin unit, together with carbonate signatures. The LIBS derived chemistry of the targets suggest that this 2.2 band is related to hydrated silica. This suggests that the formation of the hydrated silica is associated with carbonate formation (locally or in the catchment) and that AEGIS_0910A may have the same origin. One possible scenario that is being investigated is that this silica material could represent the precipitates from a fluid that dissolved the ubiquitous olivine found in Jezero floor and delta, and concomitantly precipitated carbonates that are abundant in delta-rocks and the marginal unit ([Calvé et al., LPSC 2024; Wiens et al., LPSC 2024]).

Here, IR spectroscopy reveals that this hydrated silica-rich material is more crystalline that the hydrated silica deposits previously reported on Mars from orbit and in situ at Marias Pass, Gale crater [Pan et al., 2021; Gabriel et al., 2022; Ruff et al., 2011; Rapin et al., 2018].

Summary: Two independent lines of evidence, IR and LIBS, reveal that the float rock analyzed on sol 910 is made of hydrated silica. This target is unique so far in the SuperCam dataset (> 500 targets), but may be linked to high SiO₂ points observed in the carbonate-rich delta bedrock units. Based on IR, this rock seems more akin to a micro-crystalline type silica, in contrast to previous observations of silica from the ground. Such a target may have trapped and preserved biosignatures, together with unique information on the paleoenvironmental conditions of the Jezero crater.

How to cite: Beck, P. and the Supercam and M2020 team members: Multi-spectroscopic detections of hydrated-silica in the Jezero crater   , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4623, https://doi.org/10.5194/egusphere-egu24-4623, 2024.

Diffuse Reflectance Infrared Fourier Transform Spectroscopy (FTIR DRIFT) is a widely used method for investigating soil organic materials. The existing literature suggests variations in sample preparation techniques for soil analysis. Notably, the powdering and drying method may influence the presence of organic materials, clay minerals, and carbonates. These minerals are occasionally found as coatings on different mineral surfaces and sometimes as part of the matrix within soil aggregates. This study examined four topsoils of distinct types from Hungary: Arenosol, Leptosol, Gleysol, and Phaeozem (WRB2022). The samples were pulverized both to < 250 µm and < 63 µmAnd also various procedures for drying were used: 1-hour drying sessions at 50 °C, 100 °C, 150 °C, 200 °C, and 250 °C, as well as overnight drying at 50 °C, 100 °C, and 150 °C. Additionally, samples were measured without undergoing extra drying at room temperature. This study aimed to focus on significant organic material bands.

Pulverization has a more pronounced effect on FTIR DRIFT spectra in soils with aggregates, furthermore, when the original soils contain a higher proportion of sand fraction. The drying method affects the measured absorbance values at the highlighted wavenumbers with an underlined influence on the aliphatic components range. Support of the National Research, Development, and Innovation Office (Hungary) under contract K142865, and Eötvös Loránd Research Network SA41/2021 are gratefully acknowledged.

How to cite: Szalai, Z., Karlik, M., Jakab, G., Vancsik, A., Hatvani, I. G., Cseresznyés, D., and Király, C.: Effect of sample preparation on the FTIR DRIFT spectra in the case of soils with different organic material content, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10421, https://doi.org/10.5194/egusphere-egu24-10421, 2024.

The Dellen impact structure is located in a ca. 20 km wide basin filled by two lakes in the east central Sweden. The complex structure is covered by a thick moraine deposit, and most impact melted material can be found as loose blocks and boulders scattered throughout the moraine. Geophysical measurements show the presence of a coherent impact melt body about 9 km wide and 200-500 m thick for which impact ages  between 90, 110, to 140 Ma were determined [1]-[2]. 

The impact melt glass (commonly referred as dellenite) consisting of phenocrysts of subhedral orthopyroxene (Wo₄En₆₃Fs₃₃), skeletal plagioclase (average An₅₉Ab₃₈Or₃), and euhedral magnetite within a glassy matrix of rhyolitic composition. MicroFTIR measurements performed in the glass matrix and euhedral glass blebs within the skeletal plagioclase show the presence of 1.4 wt% water in the rhyolitic glass. We estimated that the dellenite vitrified at ca. P=200-300 bar by comparing the glass water content  with the water solubility of a similar composition silicate melt following  Papale's model [3].

Dellenite orthopyroxene was studied by polarized FTIR spectroscopy, Mössbauer spectroscopy, single crystal X-ray diffraction and EMPA. They are iron rich enstatite (Wo₄ En₆₃ Fs₃₃) with a Fe³⁺/Fe_tot ratio of 1.6%. They have very weak to absent OH vibrational bands in the IR spectra, corresponding to H₂O contents ranging from 0 to 39 ppm H₂O, a variability suggesting H loss during post-formation processes, which may occur via the relatively fast redox reaction Fe²⁺ +OH^- =Fe³⁺ +O^2- +½H₂. 

In volcanic pyroxenes H loss may be a common process occurring at different moments from crystallization to post-eruption. However, H incorporation in pyroxene is associated with point defects governed by slow kinetics diffusion rates, which are retained in the structure when H is lost. By reversing the redox reaction the original H content of pyroxene can thus be recovered by thermal annealing experiments under reducing conditions [4]-[5].

In order to restore H that was possibly lost, dellenite pyroxenes were thermally annealed under hydrogen atmosphere (at 1 Atm) in a horizontal glass-tube furnace by thermal annealing experiments at 700°C for 17 hours. FTIR spectra were recorded after each heating step. All the samples increased their hydrogen content and the final average water content is 77 ppm. 

Cation partition as derived by the SC-XRD and EMPA were used to calculate the orthopyroxene closure temperature (Tc) which is expression of the cooling rate for the cpx-host rock. Preliminary results point to a high Tc (833°C) due to a quite fast host-rock cooling rate. 

A tentative model for the evolution of the rhyolitic portion of the Dellen impact melt is under development merging geophysical data with our experimental data on water content of pyroxene and glass, and pyroxene geospeedometry.  

References:

[1]Henkel H (1992) Tectonophysics 216, 31-40

[2]Mark DF Lindgren P Fallick AE (2014) Geological Society of London Special Publication 378, 349-366

[3]Papale P (1999) Am Mineral 84, 477-792

[4]Weis FA Skogby H Stalder R (2016)  Am Mineral 101(10): 2233-2247

[5]Nazzareni S Barbarossa V Skogby H Zanon V Petrelli M (2020)  CMP 175:87

How to cite: Nazzareni, S., Giuli, G., and Skogby, H.: Dellen crater impact melt rock: pyroxenes as a proxy for melt thermal history and water content, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17632, https://doi.org/10.5194/egusphere-egu24-17632, 2024.

The Styrian Basin, situated in the transition zone between the Pannonian Basin and the Eastern Alps, is believed to have formed above a lithospheric wedge, which have been affected by a subduction. The Late Miocene-Pliocene alkali basalts sampled the subcontinental lithospheric mantle beneath the area, bringing mantle xenoliths to the surface (e.g., [1] [2]). These xenoliths are amphibole-rich, indicating extensive modal metasomatism at mantle depth. Our goal is to better understand the possible fluid and melt-related processes in these xenoliths by studying fluid and melt inclusions in them. In the studied samples, one category of xenoliths contains both fluid and melt inclusions (co-entrapped), while the other contains only fluid inclusions. We carried out 3D confocal Raman mapping, Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM), Electron Microprobe Analysis (EMPA), and Scanning Electron Microscope with Energy Dispersive Spectroscopy (SEM-EDS). Our primary objectives are to 1) gain insights into the nature of metasomatic agents based on fluid and melt inclusions and 2) test the applicability of 3D Raman mapping on inclusions. The studied inclusions are primary (fluid inclusions) and pseudosecondary (fluid and melt inclusions), occurring in orthopyroxene, clinopyroxene, and amphibole. The fluid inclusions are irregular to negative crystal-shaped (3-100 μm), whereas melt inclusions are glass-rich with rounded to negative crystal shapes (4-15 μm).

A series of 3D Raman mapping on these fluid inclusions has revealed complex phase assemblages comprising fluid and solid phases (magnesite, silicate glass, pyrite, talc, anhydrite, and nahcolite). The fluid is dominated by CO₂ (up to 99.3 mol%) and H₂O (up to 8.7 mol%). EMPA indicates that the trapped silicate glass in the melt inclusions is H₂O-bearing (up to 3.3 wt%) and exhibits an evolved composition (i.e., trachyandesitic composition with SiO₂ between 54.31-60.65 wt%) relative to the host basalt of the studied xenoliths.

We discovered pargasitic amphiboles within SiO₂-rich glass in the melt inclusion that co-entrapped with the CO₂-H₂O-rich fluid phase (where H₂O content is likely high relative to mantle fluids). This strongly suggests that amphiboles were likely crystallized from an immiscible SiO₂-rich melt and CO₂-H₂O-rich fluid that could have been circulating in the mantle wedge above a subducted slab. This immiscible component is suggested to be a metasomatic agent that modified this mantle portion beneath the Styrian Basin.  Furthermore, this study revealed that the laser-induced heating effect could overestimate sulfides in the 3D Raman models, while silicate glass could be underrepresented due to its low Raman scattering properties. However, complementary FIB-SEM serial slicing provides a clear outline of silicate glass in fluid inclusions. Despite these limitations, 3D Raman mapping has proven to be a powerful tool for unravelling complex phase assemblages in inclusions.

This research was supported by the NKFIH_FK research fund nr. 132418 to M. Berkesi. Part of this research was funded by the Doctoral School of Earth Sciences of the University of Pécs.

References:

[1]. Aradi et al., 2019; Földtani Közlöny, 149 (1). pp. 35-49.

[2]. Aradi et al., 2017; Tectonics, 36, 2987–3011.

Keywords: 3D Raman mapping, complex inclusions, mantle metasomatism, subduction zone, Styrian Basin.

How to cite: Myovela, J. L., Aradi, L. E., Spránitz, T., Hegedűs, M., Konečný, P., Kovács, J., and Berkesi, M.: Unravelling metasomatic agent in amphibole-rich upper mantle xenoliths from the Styrian Basin (W-Carpathian Pannonian Region): Insights from 3D Raman mapping of complex inclusions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16706, https://doi.org/10.5194/egusphere-egu24-16706, 2024.

Jarosite, a hydrous K-rich sulfate mineral, was found in fine-grain quantities on the Martian surface by the Opportunity rover in 2004. Jarosite found in some terrestrial settings can form a complete solid solution with ammoniojarosite through substitution of the ammonium ion (NH₄⁺) which replaces K⁺ within its crystal structure. Requiring water and acidic conditions to form, jarosite stands as a potential indicator of ancient N-bearing environments on the Martian surface. The Mars Perseverance rover is currently exploring the Martian surface with analytical instrumentation that may be capable of detecting N-rich jarosite, including the SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) and the PIXL (Planetary Instrument for X-ray Lithochemistry) detectors. To investigate the detection of N in jarosite with Raman and X-ray spectroscopy, we analyzed several terrestrial samples of jarosite and ammoniojarosite using laser Raman spectroscopy and electron-excited Wavelength Dispersive X-ray Spectroscopy (WDS). Comparison of high wavenumber regions of Raman spectra with WDS spectra of N K-α X-rays on the same samples will be used to investigate detection and quantification of N as ammonium in jarosite.

How to cite: Bushmaker, S., Nachlas, W., and Bonamici, C.: X-ray and Raman spectroscopy of jarosite and ammoniojarosite from several terrestrial localities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12017, https://doi.org/10.5194/egusphere-egu24-12017, 2024.

Exploring the Raman oxygen isotope signatures of calcite and vaterite

Oxygen isotope tracers have been increasingly used to differentiate between solid-state and fluid-mediated mineral transformation pathways (e.g., Julia et al. 2023). When ¹⁸O enrichment within oxyanion bearing minerals is analysed using Raman spectroscopy, the kinetically hindered formation of different isotopologues can also provide an in-situ timer for these processes (King et al. 2014). However, at present we assume that each isotopologue band in the vibrational spectrum has an equivalent intensity when present at the same concentration within the crystal structure. Here we test this hypothesis by exploring the vibrational spectra of two important oxyanion-bearing minerals, calcite and vaterite. These are polymorphs of CaCO₃ and reflect a metastable, transition phase and the thermodynamically most stable mineral expected in many natural systems found at the Earth’s surface.

Here we have used a joint experimental and theoretical approach to demonstrate that isotopic substitution changes both band positions and band intensities to different extents, depending on the vibrational spectroscopy method used and the bands examined. Density functional theory simulations (King et al. 2022) show that for calcite, the most intense Raman bands, the υ₁ symmetrical stretching, related to individual isotopologues are found to have very similar intensities and are not affected by changes in isotopologue distribution within the material. Splitting of some bands due to changes in symmetry correlate to observed effects in experimentally produced ¹⁸O enriched calcite.In contrast, vaterite vibrational bands were found to change more extensively upon isotope substitution, thus they can only be used to evaluate relative changes in the ¹⁸O concentration within the material. These results are expected to contribute to a deeper und less ambiguous understanding of evaluating isotopic enrichment effects in the vibrational spectra of calcium carbonates.

Julia et al. 2023 Chemical Geology, 621, 121364.

King et al. 2014 Crystal Growth & Design, 14, pp. 3910.

King et al. 2022 Crystals, 13, 48.

How to cite: King, H. E. and Živković, A.: Exploring the Raman oxygen isotope signatures of calcite and vaterite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12281, https://doi.org/10.5194/egusphere-egu24-12281, 2024.

The volcanic landscapes of Iceland's Westfjords are marked by the intriguing presence of Plagioclase Ultraphyric Basalts (PUBs), distinctive lava formations that are a focal point of this research. Characterized by plagioclase contents so high (up to 50-60%) that they approach the crystallinity of a crystal mush, these formations offer a unique opportunity to explore the extreme end of lava crystallinity and the influence of abundant large plagioclase crystals on lava viscosity and flow. The main aim of this research is to understand how the abundance of large plagioclase crystals influences the viscosity and flow of lavas at the extreme end of lava crystallinity, as well as better understand the origin of the crystal cargo. The interplay between the crystals and the magma is crucial for better understanding the origins and flow characteristics of these volcanic formations. This is achieved through an interdisciplinary approach, combining petrographical and geochemical analyses, including Inductively Coupled Plasma (ICP) for major element trace element analysis, with Anisotropy of Magnetic Susceptibility (AMS) to determine the flow direction within the lava. This comprehensive method provides insights into the crystallization conditions of magmas and minerals, as well as the textural and compositional characteristics of the plagioclase crystals. The outcomes of this research are not only crucial for understanding the unique aspects of the Westfjords’ volcanic regions but also have significant implications for predicting volcanic hazards and refining magma dynamics models, thereby enhancing our ability to mitigate the impacts of volcanic activity.

How to cite: Jones, P., Caracciolo, A., Marshall, E. W., and Piispa, E. J.: Understanding the flow dynamics of a Plagioclase Ultraphyric Basalt- a case study from the Westfjords, Iceland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1209, https://doi.org/10.5194/egusphere-egu24-1209, 2024.

The Karkonosze granite (~320–312 Ma) is interpreted as a syn-collisional to magmatic arc intrusion. It is known for distinct symptoms of post-magmatic activity, including formation of intragranitic pegmatites observed in Szklarska Poręba quarry with overprinted W–Sn–Mo–Bi hydrothermal mineralization (e.g., Kozłowski et al., 1978; Pieczka & Gołębiowska, 2012).

Tin mineralization in the granite quarry at Szklarska Poreba is represented by cassiterite (Karwowski et al., 1972), Sn-rich titanite, malayaite, stokesite, and rare tin sorosilicates – kristiansenite, kozłowskiite and silesiaite (Evans et al., 2008;  Pieczka et al., 2022, 2023) The presence of all the above-mentioned mineral phases was confirmed by chemical microanalysis using the electron probe microanalyzer JEOL SuperProbe JXA-8230 and structure refinement. Cassiterite was recognized in an association mainly with scheelite, molybdenite, wolframite, chalcopyrite, and pyrite. These minerals crystallized from high-temperature aqueous fluids, subsequently followed by sulphide-rich stage (Karwowski et al., 1973). Sn-rich titanite, forming an isomorphic series with malayaite, CaTi[SiO₄]O–CaSn[SiO₄]O, shows chemical heterogeneity, with a maximum SnO₂ content up to 15.88 wt% (32 mol% Sn end-member), and elevated Nb₂O₅ (up to 9.85 wt%), Ta₂O₅ (up to 7.88 wt%), and Sc₂O₃ (up to 1.90 wt%). Malayaite is close to the pure Sn end-member, it contains up to 97 mol% Sn end-member with minor Fe, Nb, Ta contents. Stokesite, CaSnSi₃O₉·2H₂O, occurs as a rim grown around the outermost parts of Sn-rich titanite crystals, veinlets cutting cassiterite, and in direct contact with fluorite. Its crystals were also observed on surfaces or within fractures in bismuthinite.

The initial source of Sn was related to the final stage of pneumatolytic processes, in the granitic complex with successive development during hydrothermal activity. Fluid inclusion studies indicate that cassiterite crystalized at temperatures of 515–470ºC (Kozłowski et al., 2002).

The precipitation of Sn-rich titanite was likely initiated under elevated metal activities at slightly lower temperatures and high oxygen fugacity.

Stokesite, representing the final stage of the Sn assemblage, slowly crystallized in free spaces, was found in a direct contact with fluorite, which homogenization temperature in the Szklarska Poręba assemblage was estimated at 159-172 ^oC (Kozłowski & Matyszczak, 2022). Therefore, stokesite and fluorite may have formed during the same stage of hydrothermal processes. Since no alterations had been observed on the cassiterite grains, a secondary source of tin for later Sn-rich minerals was excluded.

How to cite: Mil, K., Gołębiowska, B., Włodek, A., and Pieczka, A.: Tin mineralization in post-magmatic processes: a case of post-magmatic activity in the Szklarska Poręba Huta quarry, Lower Silesia, SW Poland , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-764, https://doi.org/10.5194/egusphere-egu24-764, 2024.

At high temperatures, alkali feldspar consists of a continuous solid-solution between the Na (albite) and K (K-feldspar) end members. Below about 600°C, a miscibility gap opens, the limits of which are determined by the so-called solvus. Alkali feldspar of intermediate composition tends to exsolve when cooled from temperatures of magmatic or metamorphic crystallization, forming an intergrowth of Na- and K-rich lamellae, a microstructure referred to as perthite. Initially, coherency is maintained across the lamellar interfaces and it may be preserved over geological times. Since the lattice parameters of alkali feldspars strongly depend on composition, the exsolution lamellae must be strained to maintain coherency at the interfaces. The elastic energy required to strain the lamellae counteracts exsolution and equilibrium compositions of coexisting coherent exsolution lamellae define a coherent solvus which lies below the solvus for strain-free phase equilibria. Segregation of Na and K and subsequent lamellar coarsening is achieved by thermally activated Na-K interdiffusion. Therefore, compositions and widths of the exsolution lamellae could be used to reconstruct cooling histories. Knowing the shape and position of the coherent solvus is key for the corresponding geo-speedometry applications.

To determine the coherent solvus, initially homogeneous disordered, gem-quality alkali feldspar was annealed at temperatures between 440°C and 560°C and at atmospheric pressure, which caused it to exsolve into coherently intergrown 10 to 20 nm wide lamellae, the compositions of which were directly determined with atom probe tomography.

The application of different annealing times showed that thermodynamic equilibrium was reached during the experiments. The obtained lamellar composition define points on the coherent solvus, which were for the first time measured directly for alkali feldspars.

Additionally, equilibrium Na-K partitioning experiments between NaCl-KCl melt and the same alkali feldspars as used for the exsolution experiments were performed at atmospheric pressure and at temperatures between 800°C and 1000°C to calibrate a thermodynamic mixing model supplemented by a model for the elastic energy required for coherent exsolution. The coherent solvus calculated from the thermodynamic model and the directly measured coherent solvus are in excellent agreement. This indicates that the developed models provide an adequate description of phase equilibria in coherent lamellar intergrowth. The directly measured coherent solvus and the models form a solid base for potential applications of geo-speedometry in coherently exsolved alkali feldspars.

How to cite: Heuser, D., Dubosq, R., Bian, G., Petrishcheva, E., Habler, G., Gault, B., Lengauer, C. L., Rentenberger, C., and Abart, R.: The coherent solvus of disordered alkali feldspar determined with atom probe tomography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18335, https://doi.org/10.5194/egusphere-egu24-18335, 2024.

Rare earth elements (REE) are essential in many green, modern technologies and play a critical role in a more sustainable future [1]. However, there is a substantial risk to their supply as the availability of REE deposits with minable concentrations are limited [2]. A better understanding of the mechanisms controlling REE concentration in minerals would have applications in more efficient practices as well as REE separation techniques and recycling.

Our study investigated the reaction of multi-component REE (La, Ce, Pr, Nd, and Dy) aqueous solutions with carbonate grains of dolomite, aragonite and calcite at hydrothermal conditions (21-210 °C). Two different solutions were prepared (i) a solution with equal concentrations of each of the five REE: (ii) a solution with the concentrations of the five REEs normalized to a Post Archean Shale standard (PAAS), to mimic the rare earth element concentrations in continental crust and natural fluids.

The interaction between the REE bearing fluids with each of the carbonate grains resulted in the replacement of the host carbonate grain with a series of REE minerals following a complex crystallization sequence (lanthanite → kozoite → bastnasite → cerianite). We have found that for most of the experiments at 165 °C, when using the equal concentration solutions, the crystallization of kozoite was promoted and the REE ratio in the newly formed solids was similar to the REE ratio in solution. In contrast, when PAAS solutions were used, REE-bearing crystals were zoned or had a heterogenous distribution of REEs, often coupled with the formation of discreet REE phases (e.g., cerianite). In addition, chemical signatures indicating the presence of metastable REE-bearing phases that transformed to more thermodynamically stable polymorphs were found in multiple samples as well as symplectite textures formed by the reaction of adjacent phases. Overall, our experiments demonstrate that the polymorph selection, crystallization pathway, the kinetics of mineral formation and the chemical texture of the newly formed rock during the mineral-fluid interaction process are dependent on the REE concentrations in solution, their ionic radii, temperature, time, and solubility of the host grains.

References

[1] Sinding-Larsen, R., Wellmer, F.W.,. Non-renewable resource issues: Geoscientific and societal challenges, Non-Renewable Resource Issues: Geoscientific and Societal Challenges 2012.

[2] Jordens, A., Cheng, Y.P., Waters, K.E.,. A review of the beneficiation of rare earth element bearing minerals. Miner. 2013 Eng. 41, 97-114.

How to cite: Maddin, M., Rateau, R., Szucs, A. M., Terribli, L., and Rodriguez-Blanco, J. D.: Complex Multi-Stage Replacement Reactions in the REE-CaCO3 System, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2001, https://doi.org/10.5194/egusphere-egu24-2001, 2024.

The interactions between clay minerals and organic matter, specifically adsorption, are widely recognized as a crucial mechanism for promoting the preservation of organic matter within sedimentary environments. This paper discusses the genesis and adsorption of clay minerals, especially their influence on the process of organic matter enrichment in sedimentary environments. The composition of clay minerals found in sediments serves as an indicator of both the climatic and lithological characteristics of the provenance area. Smectite formation is favored in mafic provenance, while the coexistence of illite and chlorite suggests cold and arid conditions. Additionally, an abundance of kaolinite indicates intense chemical weathering of the provenance area. The physical and chemical properties of clay minerals and organic matter significantly influence adsorption. Smectite is thought to adsorb more organic matter due to its greater surface area. Selective adsorption of high molecular weight, aromatic, and aliphatic compounds dissolved organic matter onto mineral surfaces may have played a role in kerogen formation. Moreover, the preservation of organic matter via clay mineral adsorption is intricately linked to the sedimentary environment. Disparities in nutrient elements during the clay minerals synsedimentary period can impact biological productivity. Furthermore, the pH and solution metal ions of the water column influence the quantity and type of organic matter adsorbed. The contribution of adsorption to organic matter preservation is influenced by redox conditions, and this contribution can be observed through density separations. Additionally, we present several recommendations for future research. Firstly, diagenesis alters the clay mineral assemblage in sedimentary rocks. However, it may be possible to reconstruct the clay mineral assemblage based on morphological, mineralogical, and chemical composition characteristics. Secondly, studies have indicated that clay minerals can facilitate the precipitation of carbonate minerals, providing insights into the formation of abiotic carbonate minerals. Finally, the practical applications of clay minerals in shale oil and gas exploration are underscored, such as their ability to predict sweet-spot areas and control reservoir properties.

How to cite: Zhao, T., Xu, S., and Gou, Q.: Differential adsorption of clay minerals: Implications for organic matter enrichment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3030, https://doi.org/10.5194/egusphere-egu24-3030, 2024.

Mineral replacement reactions are essential for the understanding of the genesis and chemistry of REE-bearing carbonatite deposits. Many of these reactions involve interaction of Ca-Mg and REE carbonate phases, leading to the formation of minerals with complex compositions and structures.

This study explores the oriented surface precipitation of REE carbonates during the interaction of individual and multiple REE-bearing aqueous solutions with calcite and aragonite (CaCO₃) at low hydrothermal conditions (25-220 °C). This mineral-fluid interaction is translated into a temperature-dependent solvent-mediated surface precipitation and subsequent pseudomorphic mineral replacement of the CaCO₃ seeds by newly formed REE carbonates. This complex replacement sequence includes the crystallisation of metastable kozoite (orthorhombic REECO₃OH) via the formation of individual spindle-shaped crystals following a transient non-random orientation on the surface of the host grains, gradually covering their full surfaces.

Our experiments show that the likelihood of formation of the oriented overgrowth and its stability are controlled by structural constraints which in turn depend on four factors: temperature, ionic radii and ionic potential of the REE in the system, and dissolution rate of the host CaCO₃ minerals. Also, we demonstrate that REE elements can be rapidly immobilized as REE hydroxicarbonates, even at low hydrothermal conditions. An explanation of the epitaxial overgrowth’s configuration and the atomic arrangement of the structures of the CaCO3 polymorphs and REE-kozoite will be discussed. 

[1] Szucs AM et al. Reaction Pathways toward the Formation of Bastnäsite: Replacement of Calcite by Rare Earth Carbonates. Crystal Growth & Design, 2021;21(1):512–527.
[2] Szucs AM et al. Targeted Crystallization of Rare Earth Carbonate Polymorphs at Hydrothermal Conditions via Mineral Replacement Reactions. Global Challenges. 2022;2200085.

How to cite: Rodriguez-Blanco, J., Szucs, A. M., Rateau, R., Maddin, M., and Terribili, L.: Temporal growth of epitaxial layers in the CaCO3-REECO3OH system during mineral replacement processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4776, https://doi.org/10.5194/egusphere-egu24-4776, 2024.

Photocatalysis is a promising water purification technology, that harnesses the power of light-induced reactions to degrade contaminants. Utilizing visible light in the reactions is imperative, as it comprises a significant portion of the solar spectrum, which aligns with sustainable practices. Graphitic carbon nitride (g-C₃N₄) is a photocatalyst active in visible light, characterized by high chemical and thermal stability, ease of synthesis, and relatively low cost. However, its performance is limited by charge carrier mobility and charge recombination. These limitations might be addressed by synthesizing heterostructures, i.e. composites containing two or more semiconductors. Heterojunctions between g-C₃N₄ and layered double hydroxides (LDH) have shown increased photocatalytic efficiency. LDH are crystalline, hydrotalcite-like materials that enhance the charge separation and light absorption by the heterostructure. These materials can be obtained through various synthesis methods, including coprecipitation and hydrothermal treatment, influencing their properties. Thus, this study aimed to compare heterostructures obtained by different synthesis routes and asses their photocatalytic efficiency.

Three synthesis methods were used to obtain Zn-Cr LDH/g-C₃N₄ heterostructures: coprecipitation, adsorption/coprecipitation, and hydrothermal treatment. For g-C₃N₄ preparation, melamine was heated at 550°C for 5 h. The coprecipitation method involved dissolving zinc and chromium nitrates in DI water, then adding it to a suspension of g-C₃N₄, while simultaneously adding a solution of NaOH and Na₂CO₃. The adsorption/coprecipitation method was based on adding zinc and chromium nitrates to a g-C₃N₄ suspension, then after 30 minutes adding a solution of NaOH and Na₂CO₃. The hydrothermal method included dissolving zinc and chromium nitrates in the g-C₃N₄ suspension, adding NaOH and Na₂CO_3, then placing the suspension in an oven for 24 h at 100°C. The obtained materials were characterized by XRD, SEM/TEM, XPS, TRFL, N₂ adsorption/desorption, and photoelectrochemical measurements. The photocatalytic activity of heterostructures was assessed in batch experiments in aqueous solutions containing 1 ppm of estrone, with a 150 W LED lamp as a source of visible light.

The XRD patterns of obtained materials confirmed the formation of layered phases. The hydrothermal heterostructure was characterized by sharper reflections, which suggested higher structural order and/or larger crystallites. The average specific surface values (S_BET) showed that the hydrothermal composite was characterized by the highest S_BET - 124 m²/g. This indicated its higher porosity, compared to the materials obtained by other methods. The TRFL studies proved that the heterojunctions have lower recombination rates and longer lifetimes of charge carriers. The results of photochemical measurements suggested superior electronic conductivity and charge transfer efficiency for the hydrothermal heterostructure. The determined photoelectrochemical properties agreed well with the photocatalytic activity of heterostructures, which was the highest for the hydrothermal composite. This material led to a 99.5% estrone concentration loss after 60 minutes of reaction, in comparison to 49.9% and 75.8% loss assessed for the materials obtained by coprecipitation and adsorption/coprecipitation, respectively. The results of this study demonstrated the advantage of using the hydrothermal method to obtain LDH/g-C₃N₄ heterostructures with a high efficiency of pollutant photodegradation from aqueous solutions.

This research was funded by the AGH University of Science (Krakow, Poland), grant number 16.16.140.315.

How to cite: Jędras, A., Matusik, J., Dhanaraman, E., Fu, Y.-P., and Cempura, G.: Zn-Cr LDH/g-C3N4 heterostructure for estrone photodegradation: what is the effect of synthesis methods on materials’ properties and degradation efficiency?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9600, https://doi.org/10.5194/egusphere-egu24-9600, 2024.

The widespread occurrence of zearalenone (ZEN) in a variety of grain products and animal feed, coupled with its capacity to accumulate in the food chain, poses a significant health risk for both humans and animals. Its ability to induce estrogen-like effects may disrupt the body's estrogen levels, thereby contributing to reproductive system diseases, even at very low concentrations. The removal of ZEN from aqueous environment is predominantly challenging due to its weakly polar nature, compounded by its high thermal stability. Photodegradation, especially when applying mineral-based photocatalysts, stands out as a promising strategy for environmentally friendly mycotoxin removal. It not only demonstrates cost-effectiveness but also entails the production of negligible secondary pollutants.

Our research employed platy kaolinite (M), synthetic calcined kaolinite nanotubes (MNC), and halloysite purchased from Sigma-Aldrich (HS) as supports for TiO₂, g-C₃N₄, or combination of TiO₂/g-C₃N₄ semiconductors. Each synthesis was designed to consistently yield ~20 wt% of the semiconductor or its mixture in the samples, maintaining a TiO₂ to g-C₃N₄ ratio of 1:1. The sol-gel method was used for TiO₂ synthesis [1], while porous g-C₃N₄ nanosheets were prepared by heating melamine at 550°C, with the addition of ammonium chloride in a 1:1 ratio. The structural, textural, morphological, and light absorption properties of the obtained samples were characterized through XRD, N₂ adsorption/desorption, UV-Vis DRS spectroscopy, Raman spectroscopy, SEM, and TEM..

The UV-induced photodegradation kinetics experiments (365 nm, 10 mW/cm²) were carried out at a consistent initial ZEN concentration of ~10 ppm. ZEN concentrations were determined with high-pressure liquid chromatography (HPLC). The TiO₂-loaded photocatalysts exhibited the slowest photodegradation kinetics, resulting in the final removal of ~41.9% by the M-based sample, ~63.4% by the HS-based sample, and ~86.9% by the MNC-based sample. Conversely, the impregnation with g-C₃N₄ and TiO₂/g-C₃N₄ led to materials exhibiting the fastest kinetics, effectively removing over ~99.9% of the initial ZEN concentration. Notably, the nanotubular-based photocatalysts demonstrated slightly faster kinetics than those observed for the M-based materials and were comparable to those noted for the pure g-C₃N₄. Analogous experiments under visible light irradiation highlighted the synergistic effect for the combination of  both semiconductors, characteristic of Z-scheme heterojunction structures. Among the MNC-based samples, the least efficient photodegradation was demonstrated by the g-C₃N₄-containing sample (~13.7%), slightly higher for the TiO₂-containing sample (~20.3%), and the most efficient removal was observed for the sample containing both semiconductors (~36.6%).

The conducted experiments revealed a significant potential of kaolinite and halloysite nanotubes as carriers for semiconductors in the effective removal of ZEN from aqueous solutions. Future aspects of our research will involve detailed investigations into the degradation pathways of ZEN and the electrochemical characterization of the materials used.

This project was supported by the National Science Centre Poland, under a research project awarded by Decision No. 2021/43/B/ST10/00868.

References:
[1] Dziewiątka K., Matusik J., Trenczek-Zając A., Cempura G. (2023). TiO₂-loaded nanotubular kaolin group minerals: The effect of mineral support on photodegradation of dyes as model pollutants. Applied Clay Science, Elsevier, volume 245, 107123. 

How to cite: Dziewiątka, K., Matusik, J., and Cempura, G.: Efficient photodegradation of zearalenone: Unraveling the potential of photocatalysts based on kaolin group minerals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9623, https://doi.org/10.5194/egusphere-egu24-9623, 2024.

Apatite is a ubiquitous mineral in plutonic carbonatites (magmatic carbonate-rich rocks) and associated rock types (Chakhmouradian et al., 2017). Carbonatites are enriched in incompatible elements such as P and rare earth elements (REE), which are accommodated into apatite structure among many other elements (e.g., Hughes and Rakovan, 2015), making apatite a suitable tracer for changes in magmatic-hydrothermal geochemistry.

Sokli carbonatite complex, located in eastern Lapland, Finland, is the westernmost intrusion of the Kola Alkaline Province (Vartiainen, 1980 and references therein). The Sokli complex encompasses multiple generations of carbonatite magmatism, which compositionally span from calcite carbonatite to dolomite carbonatite to late-stage Ba, Sr, REE-enriched dolomite-rich veins. Carbonatites are associated with several generations of phoscorites, exotic magnetite-apatite cumulates typically found in carbonatite complexes. Apatite is present in most rock types in the complex, from an accessory to a rock-forming mineral.

The Sokli complex has been studied for decades (O’Brien and Hyvönen, 2015), but the composition and role of magmatic apatite has not been discussed in detail outside of phosphorous mineralization studies. Previous studies indicate that with progressive fractionation the concentrations of Ba, Sr, REE, and F increase in whole-rock and mineral compositions (O’Brien and Hyvönen, 2015 and references therein). Questions that still remain open include whether apatite has recorded the proposed different magmatic and metasomatic stages and if apatite chemistry could provide arguments for the proposed liquid immiscibility relationship between carbonatites and phoscorites (Lee et al., 2004).

A variety of apatite-bearing rock types from the Sokli complex were sampled. The composition of apatite will be studied in situ for major and trace elements with electron microprobe analyzer (EPMA) and laser ablation inductively coupled mass spectrometry (LA-ICP-MS), respectively.

References cited:

Chakhmouradian, A.R., Reguir, E.P., Zaitsev, A.N., Couëslan, C., Xu, C., Kynický, J., Mumin, A.H., Yang, P., 2017. Apatite in carbonatitic rocks: Compositional variation, zoning, element partitioning and petrogenetic significance. Lithos 274–275, 188–213.

Hughes, J. M., Rakovan, J. F. 2015. Structurally robust, chemically diverse: apatite and apatite supergroup minerals. Elements 11, 165–170.

Vartiainen, H., 1980. The petrography, mineralogy and petrochemistry of the Sokli carbonatite massif northern Finland. Geological Survey of Finland, Bulletin 313.

O’Brien, H., E. Hyvönen. 2015. The Sokli carbonatite complex in Maier, W.D., Lahtinen, R., O’Brien, Hugh (Eds.), Mineral Deposits of Finland. Elsevier. 305–325.

Lee, M.J., Garcia, D., Moutte, J., et al., 2004. Carbonatites and phoscorites from the Sokli complex, Finland. In: Wall, F., Zaitsev, A.N. (Eds.), Phoscorites and Carbonatites from Mantle to Mine: The Key Example of the Kola Alkaline Province. The Mineralogical Society of Britain and Ireland, London, 133–162.

How to cite: Karvinen, S., Beier, C., and Heinonen, A.: Apatite in the Sokli carbonatite complex, Finland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12115, https://doi.org/10.5194/egusphere-egu24-12115, 2024.

There is a constant search for materials that could be used as geochemical barriers and fillers for radioactive waste storage containers. One of effective methods of immobilizing toxic elements is their precipitation in the form of sparingly soluble crystalline phases. The purpose of this study was to test the effectiveness of co-precipitation of Th from aqueous solutions in the form of crystalline lead phosphates. Such phases have high stability and low solubility and the presence of Pb has an additional effect on reducing the radiation.

Three sets of experiments were carried out by adding reagents into a solution containing non-radioactive Th at a concentration of 400 ppm:

(A) a solution containing PO₄^3- ions (at a concentration of 1 g/L);

(B) a solution containing Pb²⁺ and a solution containing PO₄^3- ions (at concentrations of 3.5 g/L and 1 g/L, respectively) added dropwise simultaneously;

(C) solutions containing Pb²⁺, PO₄^3-, and Cl^- ions (at concentrations of 3.5 g/L, 1.0 g/L, and 0.12 g/L, respectively) added dropwise simultaneously.

All experiments were repeated at pH = 3, 5 and 7. No reaction occurred in experiment (A), while in experiments (B) and (C) the solid phases crystallized, and the Th concentration dropped from 400 to about 0.05 ppm. In the absence of Cl (experiment B), the reaction at pH=3 led to the formation of "phosphoschultenite" PbHPO₄ while at pH = 5 and 7 Th-bearing hydroxylpyromorphite Pb₅(PO₄)₃OH was formed. In the presence of Cl ions (experiments C), Th-bearing pyromorphite Pb₅(PO₄)₃Cl was formed over the entire pH range. Th was removed from solution by coprecipitation with Pb and incorporation of Th into lead phosphate structure.

The results showed that Pb must be present for Th to be effectively immobilized from solution in the form of phosphate phases. The presence of Cl is not as important as the presence of Pb in terms of removal efficiency, but it may be crucial for the long-term stability of the precipitated phases, since Pb₅(PO₄)₃Cl has higher stability and lower solubility than Pb₅(PO₄)₃OH. These findings pave the way for development of potential innovative techniques for immobilizing Th from waste and contaminated solutions, which could have implications for the safety and long-term viability of various nuclear waste disposal programs. This research was funded by National Science Center research grant no. 2021/43/O/ST10/01282.

How to cite: Manecki, M., Wrona, P., Brzoska, A., and Staszel, K.: Immobilization of radioactive Th by coprecipitation with lead apatites, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14330, https://doi.org/10.5194/egusphere-egu24-14330, 2024.

Sulfuric acid speleogenesis (SAS) is a general cave formation process in carbonate rocks in the presence of sulfuric acid. Such caves are mainly formed at and above the water table by abiotic or/and biotic oxidation of hydrogen sulfide (H₂S). One possible source of H₂S may be volcanic activity. The oxidation of H₂S produces sulfuric acid that immediately reacts with carbonate host rock, producing replacement gypsum and CO₂.

The Western Cordillera in the Peruvian Andes, characterized by volcanic and tectonic activity, features substantial travertine deposits. Among the most interesting and, at the same time, less known are the Mulapampa travertines located in the vicinity of the active Ampato-Sabancaya Volcanic Complex (ASVC). There are numerous collapse sinkholes in the travertine cover, and within three of them, caves have been found. discovered in three of them. Particularly interesting is the Gruta con lago cave, the bottom of which is located at the level of the current water table (ca. 40 m below ground level). It does not have the characteristic morphology of active SAS caves, but several speleogenetic by-products – mainly thick gypsum deposits – are typical of such features.

Mineralogical studies of sediment samples from the lake at the bottom of Gruta con lago corroborated the sulfuric acid genesis of the cave. Native sulfur was detected in those samples, among others. Microscopic examination of native sulfur crystals reveals traces of substantial corrosion attributable to the activity of sulfur bacteria. In the same cave lake's bottom sediments, framboidal pyrites formed inside the biofilms (presumably of sulfate-reducing bacteria) were found. Common secondary minerals in SAS caves, such as barite or celestine, are present on the cave bottom and walls.

This research was funded by the National Science Centre (Poland), grant No 2020/39/B/ST10/00042, and the Institute of Earth Sciences, University of Silesia, Poland.

How to cite: Tyc, A., Ciesielczuk, J., Gaidzik, K., and Powolny, T.: Sulfuric acid speleogenetic by-products and secondary minerals in caves of the Mulapampa travertines (Western Cordillera, Andes, Peru), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17099, https://doi.org/10.5194/egusphere-egu24-17099, 2024.

Arsenic is a world-wide serious health problem occurring in various types of rocks, soil, and contaminated water resources. However, it is not always an acute health problem, as concentrations are often comparably low. But recently, it gained increasing attention with the introduction of new laws in Germany (and the EU) regarding the deposition of excavated sediments, e.g., in the context of the construction of tunnels or the mining of gravel and sand etc. The decision on whether excavated material can be used as backfill or needs landfilling depends on the analysis and classification relative to specified limit values. In the latter scenario, this can result in a significant increase in costs. It is mandatory to determine the heavy metals and arsenic (among other parameters) in the solid sample and to produce and analyze an eluate of the sample to identify soluble harmful elements that could potentially contaminate the groundwater.

At a first glance, arsenic contents in solid and in eluate often show erratic patterns, which could not be explained. In clastic sediments, an often observed (weak) correlation between arsenic and iron in solid analyses led to the assumption that arsenic is bound in iron-hydroxides. However, a comprehensive examination of the chemistry and mineralogy of a large number of samples did not reveal any clear correlations. Therefore, we studied drill-core samples and sediment profiles of poorly consolidated Miocene clastic sediments, including gravel, sands, clay and silt from different areas of the Northern Alpine foreland basin (mostly from the Munich and Ingolstadt areas).

Based on geochemical analyses, we found different “arsenic-types”: Some samples show the expected correlation pattern for arsenic in the solid and the eluate. Some samples, however, show high arsenic in the solid and low arsenic concentrations in the eluate. Also, remarkably, samples with rather low arsenic contents in the solid and high arsenic in the eluate were observed. No systematic correlation with other chemical elements or with macroscopic characteristics, e.g. grain size, could be identified. Our detailed mineralogical investigation of more than 30 samples showed that XRD analysis, which is usually used to identify the mineralogy in the finest fraction, is not sufficient to explain this behavior. Therefore, we separated all mineral phases (also in the clay fraction) and analyzed their mineral chemistry (in particular their arsenic content) with SEM, their texture with high-resolution Keyence microscopy (2000x), and combined the results with extensive leaching experiments.

Our results imply that mineralogy is the key to understanding the elution behavior of arsenic. Regarding the binding characteristics of arsenic, three different mineral types can be distinguished: 1) Fe-, Si- and Al-Hydroxides (minor tourmaline, apatite and zircon) can bind arsenic relatively well (no arsenic in the eluate), 2) chlorite and mica can adsorb high amounts of arsenate but with a weak bond (high As in eluate) and 3) smectite which releases its arsenate step-by-step with the increasing degree of swelling. The study showed that only with a detailed mineralogical and mineral-chemical analysis profound predictions on the elution behavior of arsenic can be made.

How to cite: Aßbichler, D., Weichselgartner, N., Diesner, N., Kayalar, M., Otte, C., Heuss-Aßbichler, S., Tautenhahn, S., and Friedrich, A. M.: Mineralogy – the key to understanding and predicting the elution behavior of arsenic , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14683, https://doi.org/10.5194/egusphere-egu24-14683, 2024.

Quartz is ubiquitous within continental crust and can virtually be found within all rock types (plutonic, metamorphic and sedimentary). During erosion, weathering and sedimentation processes, it has a very high preservation potential and is often used to trace sediments production and transport dynamics. The QUARTZ project (Multi-methods characterization of quartz for source-to-sink tracing in alluvial sediment and dosimetry approaches – French ANR) aims to use quartz as a tracer for sediment sourcing river dynamics by combining conventional characterization method such as Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), Laser Induced Breakdown Spectroscopy (LIBS), and Cathodo-Luminescence (CL), with dosimetric methods, such as Electronic Spin Resonance (ESR) and Optically Stimulated Luminescence (OSL) which are more classically used for Quaternary sediment dating. To this end, one must define a robust quartz chemico-structural and dosimetric signature that can be compared from one sample to the other. We also aim to better understand ESR, OSL, and CL signals controlled by structural quartz defects. These can be either intrinsic (e.g. dislocations, missing/supplementary O or Si), or extrinsic (foreign atoms), each technique being more or less sensitive to these different defects.

In this study, we apply this multi-method approach to the various bedrock lithologies of the Strengbach catchment (ca.40 km²) draining a low mountain range located in the easternmost France (Vosges). These are largely dominated by crystalline metamorphic and plutonic rocks, with secondary Triassic sandstones (Buntsandstein). Bedrock samples have been treated mechanically and chemically to extract quartz grains. These grains have been analyzed using ESR and OSL techniques and mounted on thick sections (100 µm) for CL, LA-ICP-MS, and LIBS analyses. 100-µm thick-sections were used to prevent quartz tearing apart under LA-ICP-MS laser beam. Quartz characterization was completed by the study of whole-rock bedrock thick sections, analyzed with CL, LA-ICP-MS and LIBS approaches.

Preliminary results allow identifying specific quartz chemico-structural signatures not only depending on rock type (gneiss, granite, sandstone) but also on formation process (magmatic, recrystallized, metamorphic or sedimentary). Further comparison between quartz analysis in whole rock and in separated grains samples permit to assess the impact of the chemical treatment on the quartz signatures and to identify quartz populations likely to be more represented in the alluvial sediments produced by the different lithologies. Finally, ongoing analyses point out the complex contribution of trace elements to OSL, ESR and CL signals.

How to cite: Aupart, C., Lerouge, C., Lach, P., Trichard, F., Boulay, M., Rizza, M., Valla, P., Voinchet, P., Rixhon, G., and Tissoux, H.: Quartz chemico-structural characterization: a tool for sediment source tracing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8723, https://doi.org/10.5194/egusphere-egu24-8723, 2024.

Concrete is one of the most sought-after materials in our time, second only to water in importance to developed and emerging nations alike. It has been a crucial component of major infrastructure projects for thousands of years. In the year 2022 alone, China, the largest producer of concrete, manufactured approximately 2.1 million metric tons of cement, a key ingredient in modern concrete formulations. Various concrete mixes, tailored for specific applications, have been perfected and are widely used in the industry. In broad terms, concrete consists of about three-fifths sand and rock fragments (aggregates), one-fifth cement, and one-fifth water. This combination makes it the world's most widely used building material, particularly for large structures which are reinforced with steel rods. Aggregates can be sourced from crushed rock or naturally occurring sand and gravel, but the type of aggregate used significantly influences the overall properties and robustness of the final product. The mineralogical composition of the rock itself is closely related to the quality and resilience of the concrete. Understanding the mineralogy and chemistry of the lithotypes used allows for predicting their interaction with other concrete constituents, preventing undesirable chemical reactions. Such reactions can compromise the safety and resilience of the finished product, and ultimately prevent the use of materials that would otherwise perform poorly. Among the many concrete pathologies that may arise from the use of inadequate raw materials, internal sulfate attack (ISA) mainly occurs when sulfide-bearing aggregates are used. This leads to complex chemical reactions resulting in the oxidation of sulfide phases and the release of sulfur into the cement paste. Consequently, severe cracking and internal swelling significantly compromise concrete integrity. The European standard (EN 12620:2008) is a widely used guideline that recommends a total sulfur content in aggregates not exceeding 1.0 wt.%. This threshold is reduced to 0.1 wt.% when pyrrhotite is detected in the lithotype to be used as an aggregate. Given that pyrrhotite is the second most common sulfide found in nature, it is crucial to identify and quantify the various sulfide minerals that may be present and to understand how they can affect finished concrete structures. The use of automated mineralogy, represented by software systems such as QEMSCAN, emerges as a powerful solution for identifying and quantifying pyrrhotite and any other sulfide phases in aggregates for concrete. It is a scanning electron microscope (SEM)-based system that uses backscattered electron (BSE) image segmentation and simultaneous acquisition of energy-dispersive X-ray (EDS) spectra to classify mineral phases using a pre-defined list of mineral spectra. Preliminary results from QEMSCAN analysis of both thin sections and mounts comprised of ground rock of different grain sizes have been promising. This SEM-based system can analyze whole rock samples and crushed aggregates, providing accurate results over different size intervals. Despite the expected negative correlation between sample grain size and pyrrhotite content, the results vary from 2.71 to 5.59 wt.% for total pyrrhotite content in the analyzed samples. Moreover, when averaged over all grain sizes, these results align with those obtained through traditional optical petrography.

How to cite: Titon, B., Duchesne, J., and Fournier, B.: Use of automated mineralogy for the quantification of pyrrhotite in concrete aggregates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4169, https://doi.org/10.5194/egusphere-egu24-4169, 2024.

Greenhouse gases, especially CO₂, have been increasing worldwide. To address this issue, carbon capture and storage (CCS) technology has been researched and developed to decrease atmospheric CO₂ concentrations. Among the various methods studied, mineral carbonation is an emerging technique that involves the reaction between Ca-Mg-Fe bearing basaltic rocks and CO₂ to store it in the rocks through the formation of carbonate minerals. The CarbFix project in Iceland is an example of this method. However, there is still much to learn about the physicochemical relationships between water, dissolved ions, and growing crystals in complex multicomponent systems at the atomic and nanoscale, which are essential for the successful implementation of CCS in basaltic reservoirs.

One of the methods being explored in this study involves the utilization of supercritical CO₂, which is achieved above the critical temperature and pressure of 30.97 °C and 73.773 bar, respectively. Under these conditions, CO₂ exhibits both liquid and gaseous properties. This work shows the results of an experiment conducted in basaltic crystals and basaltic glasses at the temperature and pressure range of 100 and 200 ºC, and 64 to 79 bar, to investigate the reaction between CO_2(sc), water, natural forsterite and basaltic glass, which have demonstrated that under these conditions we have the partial dissolution of the previous mineralogical phases, and the subsequent formation of new alteration phases, but also the precipitation of carbonates with Ca, Mg and Fe. We will compare our results with studies of carbonation of synthetic forsterite.  

How to cite: Pierozzi, A., Rateau, R., Orlando, A., Borrini, D., and Rodriguez Blanco, J. D.: Carbonation experiment of basaltic crystals and glasses using supercritical CO2 under different PT conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4658, https://doi.org/10.5194/egusphere-egu24-4658, 2024.

In order to explore the favorable reservoir characteristics and diagenetic evolution laws of the Cretaceous Kukebai Formation in the Kekeya area of the southwestern Tarim Basin, and provide theoretical basis for oil and gas exploration and development in the study area, comprehensive data such as core, cast thin sections, and carbon and oxygen isotopes were used to carry out the classification of diagenetic facies types and the study of diagenetic evolution models. The results indicate that the reservoir of the Kukebai Formation in the study area is mainly composed of feldspar lithic sandstone and lithic feldspar sandstone, with mainly developed diagenetic processes such as compaction, cementation, and dissolution. The diagenetic stage is in the middle diagenetic stage A. The Kukebai Formation reservoir mainly develops four types of diagenetic facies: moderately compacted dissolution facies, moderately compacted cementation facies, strongly compacted compaction facies, and strongly cemented facies. Among them, the strong compacted phase becomes a dense reservoir due to mechanical compaction in the early stage of diagenesis, and is mainly distributed in the sand mud interbedded layers of sedimentary microfacies between river channels and estuarine dams; The strongly cemented phase is densified in the early diagenetic stage due to the precipitation of a large amount of carbonate cement, mainly developed in the sand mud interbedded layers near the mud end of underwater distributary channels and the sedimentary microfacies of estuarine dams; The dissolution effect of medium compacted dissolution phase sandstone is strong, and the reservoir properties are the best, mostly appearing in the upper part of distributary channel sand bodies with strong sedimentation and water accumulation dynamics; The medium compacted and cemented sandstone has moderate compaction, and the reservoir properties are relatively good. It mainly develops in the lower part of distributary channel sand bodies with strong hydrodynamics. There are two types of favorable reservoirs in the study area, namely the medium compacted cementation phase and the medium compacted dissolution phase sandstone.

How to cite: Wang, H. and Zhang, L.: Reservoir characteristics and diagenetic evolution of Kukebai Formation in Kekeya area, Southwest Depression of Tarim Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2730, https://doi.org/10.5194/egusphere-egu24-2730, 2024.