GMPV1.1

EDI
Advances in analytical and experimental techniques in mineralogical and geochemical research

In this crossover session, we invite studies on the latest advancements in analytical and experimental techniques from all relevant fields dealing with geochemical processes or applying chemical/isotope data to assess the dynamics in geological systems. Relevant are all-new achievements of techniques more or less established in Earth sciences. Moreover, new techniques or experiments brand-new to Earth sciences are of particular interest. Techniques are welcome from mass spectrometry, photon/electron-based spectroscopy, including microscopy and measurements under various conditions (ambient to non-ambient) and spatial resolutions. The overarching breadth of this session will foster the exchange between the communities.

Co-organized by BG2/SSP1
Convener: Max Wilke | Co-conveners: Julien AmalbertiECSECS, Karen Appel, Daniel FrickECSECS
Presentations
| Thu, 26 May, 17:00–18:30 (CEST)
 
Room K1

Presentations: Thu, 26 May | Room K1

Chairpersons: Max Wilke, Julien Amalberti, Daniel Frick
17:00–17:06
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EGU22-1186
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ECS
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On-site presentation
Renelle Dubosq, David Schneider, Anna Rogowitz, and Baptiste Gault

Correlative analytical approaches involving high-spatial resolution microscopy techniques allow for the compositional measurements and spatial imaging of materials at the near-atomic scale. By combining electron backscatter diffraction (EBSD) mapping, electron channeling contrast imaging (ECCI), scanning transmission electron microscopy (STEM) and atom probe tomography (APT) on various geological materials such as minerals and glasses, we have successfully documented element mobility regulated by structural defects. Although these techniques were initially developed in the materials sciences, they are now being applied to a broad range of applications within many subdisciplines of geosciences including geochemistry, geochronology, and economic geology. In one set of experiments, we applied a correlative approach on naturally deformed pyrite from an orogenic gold mine in northern Canada to assess the impact of crystal-plastic deformation on the remobilization of trace elements. This study has led us to propose a new paragenetic model for metallic ore deposits in which deformation creates nanostructures that act as traps for base- and precious-metals. By applying our approach on pyrite that is rich with fluid inclusions, we have also documented two processes that led to proposing a new fluid inclusion-induced hardening model, which is in contrast to the more commonly reported weakening effect of fluids on minerals. To broaden the applications of our approach, we have applied the same suite of analytical techniques to a synthetic andesitic glass to assess whether nanoscale chemical heterogeneities can act as nucleation sites for gas bubbles. The combined results demonstrate the existence of nanoscale chemical heterogeneities within the melt and at the bubble-melt interface supporting the hypothesis that homogeneous nucleation could in fact be a variety of heterogeneous nucleation. The interactions between trace elements and structural defects plays a vital role in determining the mechanical properties of minerals, particularly in fluid-rich environments. These sub-nanometer scale exchanges consequently control meso- to tectonic-scale geological processes. Our research work not only demonstrates the latest advancements in analytical microscopy resolving long-standing geological problems but also brings us closer to bridging the gap between the fields of materials sciences and geosciences.

How to cite: Dubosq, R., Schneider, D., Rogowitz, A., and Gault, B.: Unraveling the secrets of the Earth through nanogeology: A correlative microscopy approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1186, https://doi.org/10.5194/egusphere-egu22-1186, 2022.

17:06–17:12
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EGU22-2517
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On-site presentation
Sylvia Walter, Veerle Cnudde, Oliver Plümper, and Geertje ter Maat

Understanding earth materials is critical to creating a sustainable, carbon-neutral society. Earth materials control the feasibility of subsurface energy storage, geothermal energy extraction, and are a source of critical elements for future-proof battery technologies. Perturbations to geological systems can also result in hazards, such as human-induced earthquakes. If we want to tackle the current, pressing scientific questions related to sustainable development for a circular economy, there is an urgent need to make multi-scale, multi-dimensional characterisations of earth materials available to a broad spectrum of earth-science disciplines. In addition to the society-relevant topics, the properties of earth materials determine how the Earth workson the most fundamental level.To overcome this challenge, 15 European facilities for electron and X-ray microscopy join forces to establish EXCITE. EXCITE is a Horizon Europe infrastructure project, and enables access to high-end microscopy facilities and to join the knowledge and experience from the different institutions. By doing so, EXCITE will develop community-driven technological imaging advancements that will strengthen and extend the current implementation of leading-edge microscopy for earth-materials research. In particular, the EXCITE strategy is to integrate joint research programmes with networking, training, and trans-national access activities, to enable both academia and industry to answer critical questions in earth-materials science and technology. As such, EXCITE builds a community of highly qualified earth scientists, develops correlative imaging technologies providing access to world-class facilities to particularly new and non-expert users that are often hindered from engaging in problem-solving microscopy of earth-materials.This presentation gives an overview EXCITE, its activities and open calls, and the progress of the first year of the project.

How to cite: Walter, S., Cnudde, V., Plümper, O., and ter Maat, G.: EXCITE: A European infrastructure to promote electron and X-ray microscopy of Earth materials, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2517, https://doi.org/10.5194/egusphere-egu22-2517, 2022.

17:12–17:18
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EGU22-3234
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ECS
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Virtual presentation
Ke Wang, Lin Ma, and Kevin G. Taylor

Due to the fine-grained nature of shale, organic matter particles are generally micro- and nano-scale in size. Functional groups differ between different organic matter types and as such provide unique chemical information for organic matter. Micro-FTIR can provide direct measurement to characterize sample features at the micrometer scale. However, optical diffraction limits its application at the nanometer scale. As a non-destructive high-resolution scanning probe technique, atomic force microscopy (AFM) is very powerful in nanoscale research and has been widely used in the fields of polymers, semiconductors, electrochemistry and biology. To provide a better combination of AFM’s unique advantages with nanoscale chemical analysis, the AFM-IR technique has been developed in recent years and also attracted the attention of geologists to explore the application in geological materials.

In this research, AFM-IR which is a quite new technique in geological research was used to investigate the in-situ geochemical characteristics of organic matter in shale. Nanoscale molecular composition of individual organic particles was captured nondestructively, and the distribution of typical functional groups was displayed via 2D IR mapping. In our samples, both alginite and inertinite display chemical homogeneity. The former is dominated by oxygenated and aliphatic contents which indicates a higher hydrocarbon generation potential, whereas the latter is dominated by aromatic carbon. In contrast, migrated solid bitumen particles show compositional heterogeneities at the nanometer scale as some are aromatic-rich and others are aliphatic-rich. Finally, linking this advanced nanochemical technique to potential applications in subsurface energy was explored. This research demonstrates that AFM-IR is a powerful tool to examine the in-situ nanoscale geochemical characteristics of different organic matter types, which can also provide implications for energy applications.

How to cite: Wang, K., Ma, L., and Taylor, K. G.: In-situ nanoscale geochemical characterization of organic matter in shale by AFM-IR, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3234, https://doi.org/10.5194/egusphere-egu22-3234, 2022.

17:18–17:24
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EGU22-4954
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ECS
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On-site presentation
Dominik Jaeger and Roland Stalder

Hydrous lattice point defects (OH defects) in quartz (SiO2) occur through coupled substitution of Si4+ with a trivalent cation (most commonly Al3+) and a hydroxyl group (OH-). These impurities can be used to investigate its host rock’s crystallization history and may therefore also serve as a tracer for sediment provenance analyses, but are also economically relevant (e.g., high purity quartz sources).

Transmission infrared (IR) spectroscopy has proven to be a very effective method to analyze OH defects down to concentrations of a few weight parts per million water equivalent. This technique, however, requires thin (100 to 200 µm), polished quartz wafers that are cut perpendicular to the crystallographic c-axis. Preparation of a statistically significant number (i.e. > 100) of grains using this approach is very time consuming and requires a skilled operator. Furthermore, IR spectral analysis so far does not follow a standardized protocol, possibly introducing individual biases and hampering reproducibility of as well as comparability between datasets.

In this work, we present a new, standardized procedure for sample preparation, measurement, and data analysis of OH defects in quartz. Sample preparation and IR measurements are significantly sped up and simplified and require relatively little specialized laboratory equipment. Additionally, our data analysis is performed largely automated and based on spectral deconvolution and generation of synthetic spectra before quantification, ensuring quick generation of reproducible results. This new protocol may therefore be another step towards making OH defect analysis accessible to a wider range of geoscientific fields.

How to cite: Jaeger, D. and Stalder, R.: Quantification of OH in quartz via infrared spectroscopy – new protocol for sample preparation and spectral analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4954, https://doi.org/10.5194/egusphere-egu22-4954, 2022.

17:24–17:30
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EGU22-7132
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ECS
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On-site presentation
Christian Albers, Robin Sakrowski, Georg Spiekermann, Lélia Libon, Max Wilke, Nicola Thiering, Hlynur Gretarsson, Martin Sundermann, Johannes Kaa, Metin Tolan, and Christian Sternemann

The determination of the electronic structure of iron-bearing compounds at high pressure and high temperature (HPHT) conditions is of crucial importance for the understanding of the Earth’s interior and planetary matter. Information on their electronic structure can be obtained by X-ray emission spectroscopy (XES) measurements, where the iron’s Kβ1,3 emission provides information about the spin state and the valence-to-core region focusses on the coordination chemistry around the iron and its electronic state. Furthermore, resonant XES (RXES) at the iron’s K-edge reveals even more detailed information about the electronic structure [1].

We present a setup to investigate the electronic structure of iron-bearing compounds in situ at HPHT conditions using XES and RXES. The HPHT conditions are accomplished by diamond anvil cells (DACs) in combination with a portable double-sided Yb:YAG-laser heating setup [2]. The spectroscopy setup contains a wavelength dispersive von Hamos spectrometer in combination with a Pilatus 100K area detector [3]. This setup provides a full Kβ1,3 emission spectrum including valence-to-core emission in a single shot fashion. In combination with a dedicated sample preparation and use of highly intense synchrotron radiation of beamline P01 at PETRA III, the duration of the measurements is shortened to an extend that in situ XES, including valence-to-core, as well as in situ spin state imaging becomes feasible. The use of miniature diamonds [4] enables RXES measurements at the Fe-K edge. By using different analyzer crystals for the von Hamos spectrometer, simultaneous Kα and Kβ detection are feasible, which provides L-edge and M-edge like information.

The presented sample is siderite (FeCO3), which is in focus of recent research as it is a candidate for the carbon storage in the deep Earth. Siderite exhibits a complex chemistry at pressures above 50 GPa and temperatures above 1400 K resulting in the formation of carbonates featuring tetrahedrally coordinated CO4-groups instead of the typical triangular-planar CO3-coordination. These carbonates are well understood on a structural level but information on their electronic structure is scarce [5-7]. We present information on the sample’s spin state at in situ conditions of about 75 GPa and 2000 K XES Kβ1,3 imaging  as well as RXES measurements for low and high pressure siderite at ambient temperature conditions for Kα and Kβ emission.

[1] M. L. Baker et al., Coordination Chemistry Reviews 345, 182 (2017)

[2] G. Spiekermann et al.,  Journal of Synchroton Radiation, 27, 414 (2020)

[3] C. Weis et al., Journal of Analytical Atomic Spectroscopy 34, 384 (2019)

[4] S. Petitgirard et al., J. Synchrotron Rad. , 24, 276 (2017)

[5] J. Liu et al., Scientific Reports, 5, 7640 (2015)

[6] M. Merlini et al., American Mineralogist, 100, 2001, (2015)

[7] V. Cerantola et al., Nature Communications 8, 15960 (2017)

How to cite: Albers, C., Sakrowski, R., Spiekermann, G., Libon, L., Wilke, M., Thiering, N., Gretarsson, H., Sundermann, M., Kaa, J., Tolan, M., and Sternemann, C.: Setup to study the electronic structure of iron-bearing compounds in situ at conditions of the Earth’s lower mantle , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7132, https://doi.org/10.5194/egusphere-egu22-7132, 2022.

17:30–17:36
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EGU22-13173
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On-site presentation
Ingrid Blanchard, Sylvain Petitgirard, Vera Laurenz, Nobuyoshi Miyajima, Max Wilke, Dave Rubie, Sergey S. Lobanov, Louis Hennet, Wolfgang Morgenroth, Rémi Tucoulou, Valentina Bonino, Xuchao Zhao, and Ian Franchi

High pressure and high temperature experiments performed with laser-heated diamond anvil cells (LH-DAC) are being extensively used in geosciences in order to study matter at conditions prevailing in planetary interiors. Due to the size of the apparatus itself, the samples that are produced are extremely small, on the order of few tens of micrometers. There are several ways to analyze the samples and extract physical, chemical or structural information, using either in situ or ex situ methods. Here, we will compare two nanoprobe techniques, namely nano X-ray fluorescence (nano-XRF) and Nanoscale secondary ion mass spectrometry (NanoSIMS), that can be used to analyze samples synthetized in LH-DAC and recovered using Focused Ion Beam. The two techniques are very different in various aspects, the most important one being that nano-XRF is a deeply penetrative but nondestructive method, whereas NanoSIMS is a surface sensitive and destructive method. The second major difference between the two techniques is that NanoSIMS can probe isotopes, whereas nano-XRF cannot. With both, it is possible to obtain the spatial distribution of chemical elements in the samples.

We used these two nanoprobes to retrieve elemental concentrations and ratios of dilute moderately and highly siderophile elements (few tens of ppm) in quenched experimental melts relevant for the formation of the core of the Earth. We will show those results and discuss the importance of proper calibration for the acquisition of quantifiable results. We have also performed metal–silicate partitioning experiments in which tungsten and molybdenum were incorporated. Those experiments are especially relevant to understand the core–mantle differentiation of the Earth, about 4.5 billion years ago. We will first present and compare metal–silicate partition coefficient obtained by both nano-XRF and NanoSIMS, and second also with results obtained independently by electron microprobe.

How to cite: Blanchard, I., Petitgirard, S., Laurenz, V., Miyajima, N., Wilke, M., Rubie, D., Lobanov, S. S., Hennet, L., Morgenroth, W., Tucoulou, R., Bonino, V., Zhao, X., and Franchi, I.: Chemical Analysis of Trace Elements at the Nanoscale in Samples Recovered from Laser-Heated Diamond Anvil Cell Experiments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13173, https://doi.org/10.5194/egusphere-egu22-13173, 2022.

17:36–17:42
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EGU22-6179
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ECS
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On-site presentation
Richard Wessels, Thijmen Kok, Hans van Melick, and Martyn Drury

The spatial distribution of mineral phases in a thin section provides information about the mineral reactions and deformation history of the sample. This information is often difficult to obtain using classical optical microscopy or SEM analyses, as the spatial resolution is too small to provide the necessary overview. SEM Automated Mineralogy (AM) delivers false colour mineral phase maps at the full thin section scale. Combined with full-sized PPL and XPL thin section scans, this provides an exceptional high-resolution overview of the mineral content and microstructures. Moreover, SEM-AM provides quantitative information about the mineral and bulk rock compositions, which can subsequently be used in thermodynamic modelling to establish P-T conditions for the entire, or a subset of, the rock sample.

The structural geology group at Utrecht University recently acquired a SEM-EDS system with Automated Mineralogy capabilities. The accuracy of the EDS system was compared against WDS microprobe measurements, while the SEM-AM based bulk rock composition of the thin section was compared against XRF data from the corresponding sample dummy. Subsequently, the SEM-AM bulk rock composition was used as input for thermodynamic modelling using Perple_X. Independent temperature estimates were established using; i) SEM-EBSD based CPO results on quartz, in conjunction with the quartz recrystallization mechanisms and recrystallized grain size; and ii) titanium-in-quartz using nano-SIMS analyses. Further constraints on fluid-rock-melt interactions were obtained by using LA-ICP-MS.

This workflow is applied to samples from the Cap de Creus region in northeast Spain. Located in the axial zone of the Pyrenees, the pre-Cambrian metasediments underwent HT-LP greenschist- to amphibolite-facies metamorphism, are intruded by pegmatite bodies, and overprinted by greenschist-facies shear zones. The SEM-AM workflow allowed to further constrain the prograde and retrograde P-T conditions in the different metamorphic zones. In addition, at the thin section scale, the results show temporal and spatial variations in the mineral reactions that occurred.  

In the near future, this workflow will be refined and included in the broader correlative microscopy workflow that will be applied in the H2020-funded EXCITE project (https://excite-network.eu/), a European collaboration of electron and x-ray microscopy facilities and researchers aimed at structural and chemical imaging of earth materials. The data will be made available in a FAIR manner through the EPOS (European Plate Observing System) data publication chain (https://epos-msl.uu.nl/).

How to cite: Wessels, R., Kok, T., van Melick, H., and Drury, M.: Constraining P-T conditions using a SEM Automated Mineralogy based workflow – an example from Cap de Creus, NE Spain, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6179, https://doi.org/10.5194/egusphere-egu22-6179, 2022.

17:42–17:48
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EGU22-6787
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ECS
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Virtual presentation
Po-Yen Tung, Hassan Sheikh, Matthew Ball, Farhang Nabiei, and Richard Harrison

Identification of unknown micro- and nano-sized mineral phases is commonly achieved by analysing chemical maps generated from hyperspectral datasets, particularly scanning electron microscope - energy dispersive X-ray spectroscopy (SEM-EDX). However, the accuracy and reliability are limited by subjective human interpretation and instrumental artefacts in the chemical maps. At the same time, machine learning has emerged as a powerful method to overcome the roadblocks. Here, we propose a self-supervised machine learning approach to not only identify unknown phases but also unmix the overlapped chemical signals of individual phases with no need for user expertise in mineralogy. This approach leverages the guidance of gaussian mixture modelling (GMM) clustering fitted on an informative latent space of pixel-wise elemental data points modelled using a neural network autoencoder, and deconvolutes the overlapped chemical signals of phases using non-negative matrix factorisation (NMF). We evaluate the reliability and the accuracy of the new approach using two hyperspectral EDX datasets. The first dataset was measured from an intentionally fabricated sample, where seven known mineral particles are physically overlapping with each other as well as the substrate. Without any prior knowledge, the proposed approach successfully identified all major phases and recovered the original chemical spectra of the individual phases with high accuracy. In the second case, the dataset was collected from a potential vehicular source of particulate matter air pollution, where identification of the individual pollution particles is complicated by the complex nature of the sample. The approach once again was able to identify the potential Fe-bearing ultrafine particles and isolate the background-subtracted elemental signal. We demonstrate a robust approach that potentially brings a significant improvement of mineralogical and chemical analysis in a fully automated manner. In addition, the proposed analysis process has been built into a user-friendly Python code with graphical user interface (GUI) for ease of use by general users.

How to cite: Tung, P.-Y., Sheikh, H., Ball, M., Nabiei, F., and Harrison, R.: Self-supervised Automated Mineralogical and Chemical Analysis for Hyperspectral Datasets, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6787, https://doi.org/10.5194/egusphere-egu22-6787, 2022.

17:48–17:54
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EGU22-9146
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ECS
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Virtual presentation
Ilya Kutuzov, Chunfang Cai, and Alon Amrani

Volatile organic sulfur compounds (VOSC) are known to occur in natural gas and petroleum reservoirs. These compounds are typically accompanied by H2S which together, degrade the quality of the petroleum, complicate production due to corrosion of piping, and pose a health risk to workers and local communities. The origins of both H2S and VOSC in natural gas are only partially understood with the latter being analyzed in only a few cases and its formation processes virtually unknown. Nevertheless, several studies have linked VOSC to H2S in processes such as thermochemical sulfate reduction (TSR) and kerogen cracking. Hence, VOSC have the potential to act as a proxy for the natural gas and H2S origins, in-situ TSR and fluid migration pathways.

To better understand the pathways of VOSC formation in natural gas reservoirs, we analyzed natural gas samples (Permian reservoirs, Sichuan Basin, China) and performed a series of pyrolysis experiments. The results of the experiments between methane (CH4) and H2S at 360°C for 4-96 hours revealed the only VOSC formed is methanethiol (MeSH) which was identified at ppm concentrations in all experiments. The δ34S values of the MeSH were 2 to 3‰ heavier than the initial H2S. For comparison, Meshoulam et al., (2021) reported that the reaction between H2S and pentane (i.e. “wet gas”) that yielded a variety of VOSCs from thiols to methyl-thiophenes in the gas phase and up to methyl-benzothiophenes in the liquid phase. The analysis of natural gases showed that the samples contain a large variety of thiols and sulfides. The diversity of VOSC identified carries some resemblance to that observed by Meshoulam et al., (2021) and may suggest these VOSC are the result of in-reservoir reaction of C2+ hydrocarbons with H2S. The analysis of δ34S values of the VOSCs showed they cover a range between +10 to +30‰ while most samples had their VOSC in a narrower range of approximately 8‰. Generally, samples show a positive correlation between H2S content and VOSCs concentration- thereby implying VOSCs formation in the gas-phase. The δ34S of thiols in five of the samples covered a narrower isotopic range of about 2‰ while the sulfides in the samples spread over a large isotopic range of up to 10‰. This observation suggests the thiols are in isotopic equilibrium with their associated H2S while the sulfides are not. The reason for this difference is unclear. Further analysis will shed more light on isotopic fractionations between VOSC and H2S and will thus allow identification of H2S origins in the studied area.

[1] Meshoulam, A., Said-Ahmad, W., Turich, C., Luu, N., Jacksier, T., Shurki, A., Amrani, A., 2021. Experimental and theoretical study on the formation of volatile sulfur compounds under gas reservoir conditions. Organic Geochemistry, 152, 104175

How to cite: Kutuzov, I., Cai, C., and Amrani, A.: The origins of volatile organic sulfur compounds in natural gas reservoirs, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9146, https://doi.org/10.5194/egusphere-egu22-9146, 2022.

17:54–18:00
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EGU22-3987
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ECS
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On-site presentation
Clémentine Antoine, Richard A. Spikings, Sean P. Gaynor, and Urs Schaltegger

Dating of the extrusive parts of large igneous provinces has been a challenge because of the lack of mineral phases that can be dated by high-precision techniques. This is the case for the rapidly emplaced Drakensberg lavas, part of the Karoo LIP in South Africa and Lesotho. The circulation of hot fluids through the lava stack during rapid emplacement of continental flood basalts develops relatively high degrees of fracturing and alteration of the rocks, which often results in the re-opening of isotopic systems and inaccurate dates. This alteration occurs on varying length scales, from the outcrop to the micrometric scales, creating Argon loss in minerals of interest for 40Ar/39Ar dating (i.e. plagioclase) and making the procedure of separation for step-heating 40Ar/39Ar a tedious and sometimes ineffective task. Here, we re-approach measuring 40Ar/39Ar by directly analyzing leached and unleached thin sections without having to go through mineral separation, and therefore effectively eliminating the mixing issue of mechanically separating the plagioclase crystals. Half of each plagioclase aliquot was leached in acid, and then irradiated at the TRIGA reactor (Oregon State). We used a 193nm excimer UV-laser attached to a noble gas extraction and purification line, and an Argus VI mass spectrometer at the University of Geneva on thick sections for in-situ analysis. Plagioclase separates from the same Karoo lava flow samples were previously analyzed for 40Ar/39Ar geochronology using step heating, on aliquots of both leached and unleached plagioclase separates, using the same noble gas analytical equipment. This allows for a direct comparison of the in-situ­ analysis, testing the potential differences between the two different analytical systems and a potential way of assessing differences in accuracy between the two. Preliminary results show that accurate ages can be achieved by this technique at the cost of a larger precision.  

How to cite: Antoine, C., Spikings, R. A., Gaynor, S. P., and Schaltegger, U.: 40Ar/39Ar In-Situ Dating of Altered Mafic Rocks in the Karoo Large Igneous Provinces., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3987, https://doi.org/10.5194/egusphere-egu22-3987, 2022.

18:00–18:06
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EGU22-7412
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ECS
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On-site presentation
Julien Amalberti, Peter van der Beek, Cody Colleps, and Maxime Bermard

Next generation, high-resolution datasets to assess the dynamics of geological systems are becoming increasingly important to answer scientific questions that require higher spatial and temporal resolution than the current state-of-the-art. Such questions involve the couplings and feedbacks between tectonic, climatic, and surficial processes that constitute a heavily debated topic in Earth-Systems research. Over the last decades, the insufficient temporal resolution of conventionally derived (U-Th)/He thermochronometric datasets has limited the necessary quantification to track recent changes in erosion rates and relief—two metrics essential to reconstruct the past dynamics of landscapes and evaluate the relative contribution of surface and tectonic processes on erosion.

To overcome this limitation, the ERC-funded COOLER project aims to further the development of high-resolution, ultra-low temperature thermochronology by setting up a world-leading 4He/3He laboratory at the University of Potsdam. The centerpiece of the newly established laboratory is a split-flight-tube multi-collector gas-source sector mass spectrometer from Thermo Scientific™ connected to a sample-gas preparation bench, which includes He gas purification equipment along with a diode laser for stepped-heat sample degassing. Important topics of research the instrument will be utilized for include 1) investigation of the glacial imprint on topography, 2) characterization of the couplings between tectonic activity and topographic relief development in response to glaciation, and 3) quantification of glacial erosion relative to fluvial erosion in mountain belts. In addition to serving researchers and students at the University of Potsdam and collaborating institutions, the facility will provide analytical, research, and educational opportunities within the frame of the COOLER project to researchers from across the globe through external workshops.

To illustrate the capabilities of the new laboratory, we present our analytical and experimental methodologies used to obtain reliable high-resolution 4He/3He datasets. We focus on accuracy and cross-calibration to ensure minimal analytical bias in our measurements. Growing efforts in the (geo)science community are aimed at establishing best standardization practices and ensuring consistencies between laboratories and/or communities. Accordingly, we focus on ensuring that our methodologies are leading toward a noble-gas standardized method to compare mass spectrometry capabilities over various laboratories, and analytical techniques among the noble-gas communities. Accordingly, our standardized approach, coupled with analytical automation will lead to significant improvement in the accessibility and efficiency of routine 4He/3He analyses for geologic applications.

How to cite: Amalberti, J., van der Beek, P., Colleps, C., and Bermard, M.: New high-resolution 4He/3He laboratory at the University of Potsdam: Toward standardized approaches for efficient and reliable routine 4He/3He analyses for thermochronology applications., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7412, https://doi.org/10.5194/egusphere-egu22-7412, 2022.

18:06–18:12
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EGU22-4301
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Presentation form not yet defined
Beyond Vienna: MS/MS Option for the Neoma MC-ICP-MS.
(withdrawn)
Grant Craig, Jenny Roberts, Markus Pfeifer, Claudia Bouman, Nicholas Lloyd, and Johannes Schwieters
18:12–18:18
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EGU22-11603
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Virtual presentation
Jasper A. Wassenburg and Nitesh Sinha

The isotope composition of rainfall provides information on the initial isotope composition of the moisture source, conditions during evaporation and condensation of water vapor, and the rain-out history of an air-parcel. A standard method to analyze the rainfall isotope composition is by using Cavity Ring Down Spectrometry (CRDS). The accuracy of the analysis highly depends on the water isotope standards used, which determines the degree to which absolute values from different labs can be compared. The amount of international water isotope standards like VSMOW2 and SLAP2 primary water standards is extremely limited; therefore the International Atomic Energy Agency recommends calibrating in-house water isotope standards once a year by using VSMOW2 and SLAP2. The isotope range between VSMOW2 and SLAP2 is extreme, with 55.5‰ for d18O and 427.5‰ for d2H. The isotope range used in a sequence poses a problem for CRDS techniques that are characterized by significant memory effects.

In this study, we compare the behaviors of two different CRDS systems: a Picarro L2140i and a LGR WIA 35EP. We evaluate the relation between isotope differences of subsequent samples and the memory effect. We show that after 100 injections, memory effects may still be visible in hydrogen. Even when the isotope composition of subsequent injections of the same standard or sample does not show a trend anymore, the raw isotope data seems biased towards the isotope composition of multiple different samples or standards run prior. Running long sequences of for example 1100 injections in high precision 17O mode, also requires several vaporizer septa changes. The timing of a septa change is important, because opening the vaporizer allows water vapor from the atmosphere to enter the otherwise closed system, from which it takes approx. 20 injections to recover to the prior absolute values. Here we aim to provide a more practicle approach to a calibration sequence architecture and number of injections per primary and in-house standards, taking into account the potential drift of the analyzers.

How to cite: Wassenburg, J. A. and Sinha, N.: Improving calibrations of in-house water isotope standards using CRDS and OA-CRDS: memory effects versus drift, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11603, https://doi.org/10.5194/egusphere-egu22-11603, 2022.

18:18–18:24
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EGU22-626
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Virtual presentation
Pallab Roy, Amzad Laskar, and Mao-Chang Liang

Stable oxygen isotopic composition (δ18O) of CO2 produced from carbonates in natural archives is a useful proxy for paleo precipitation and paleo temperature reconstruction. However, there exist multiple factors controlling the δ18O values, the applications of the δ18O alone for paleoclimate studies are thus limited. Anomaly in 17O in carbonates, expressed by Δ′17O=1000*ln(δ17O/1000+1)-λ*1000*ln(δ18O/1000+1) is another proxy to independently constrain aspects of climatic variables such as precipitation source variation and kinetic effects during carbonate precipitation. However, to use 17O anomaly for such studies, the triple oxygen isotope fractionation exponent (θ= lnα17/lnα18) must be known precisely. Knowledge of this parameter is central to emerging applications of carbonate triple oxygen isotopes to paleoclimate and paleo-hydrology studies. Though a number of theoretical and experimental studies have been carried out in the last few years, there remains no consensus on 𝛳 value for carbonate-water system, likely due to kinetic isotope fractionation during precipitation.

Here, we measured Δ′17O in synthetic carbonates as well as in the water from which the carbonates are precipitated to check how reliable the Δ′17O value of the parent water can be reconstructed from the carbonates or carbonate-digested CO2. To determine θcarbonate_CO2-water for precipitated carbonates, we synthesized carbonates in the laboratory at temperatures ranging from 10 ⸰C to 66 ⸰C using passive/active CO2 degassing method. Triple oxygen isotope compositions of the water were determined using water-CO2 equilibration followed by CO2-O2 exchange method and of the carbonate (CO2 liberated by acid digestion) using CO2-O2 exchange method. We analyzed our isotope data for their possible kinetic isotope effect and determined the 𝛳carbonate_CO2-water value for precipitated carbonates. We find that most of our synthetic carbonate samples did not attain the equilibrium. The 𝛳carbonate_CO2-water increases as the disequilibrium effect increases. We determined the θcarbonate_CO2-water from the samples precipitating in equilibrium. Furthermore, we do not find any differences in the 𝛳carbonate_CO2-water value for carbonate precipitated in equilibrium at 25 ⸰C and 35 ⸰C. An important issue of using Δ′17O in carbonates is to resolve the 𝛳acid for acid digestion which is resolved in the present study. Additionally, we determined the temperature dependent variation in 𝛳acid and find no significant changes between 0 ⸰C and 70 ⸰C.

How to cite: Roy, P., Laskar, A., and Liang, M.-C.: Triple oxygen isotope fractionation of carbonate during carbonate precipitation and acid digestion, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-626, https://doi.org/10.5194/egusphere-egu22-626, 2022.

18:24–18:30
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EGU22-3540
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On-site presentation
Urs Schaltegger, Sean P. Gaynor, Melissa Ruiz, and Alexey Ulianov

Geochronology is fundamental for the understanding of rates and mechanisms of Earth processes, including tectonics, crust formation, ore formation and magmatism. Analytical techniques are mostly applied to the mineral zircon, particularly LA-ICPMS and ID-TIMS dating, which offer the required accuracy, precision and analytical throughput to solve outstanding scientific questions. However, zircon can record multiple geological events within discrete crystallographic domains, so it is crucial to ensure that measurements are completed using optimal precision and accuracy while specifically targeting crystal domains of interest to resolve potentially complex zircon systematics. We explore here a case where the combination of xenocrystic and autocrystic growth zones within same crystals, together with decay damage related lead loss, leads to apparently protracted age spectra, which can erroneously be interpreted in terms of magmatic evolution.

We present LA-ICP-MS and ID-TIMS U-Pb zircon data from a Variscan, 335 Ma old granodiorite from the Alpine basement in the Aar massif (Switzerland), which highlight the potential complexities present in zircon samples and address the need for careful zircon pre-treatment. CL imagery of zircon reveals minor but pervasive secondary alteration, leading to the observed excess scatter in LA-ICPMS dates. Chemical abrasion (CA) as a pre-treatment prior to LA-ICPMS analysis significantly reduces this scatter. CA-ID-TIMS analyses of zircon from this sample yield extremely high precision due to very high radiogenic/common Pb ratios (Pb*/Pbc), with significant 206Pb/238U scatter. Due to the elevated precision of these analyses, it is possible to resolve a linear discordance for these data. This indicates that Pb-loss is not the only age component observed, and the volume of zircon analyzed via CA-ID-TIMS does not purely reflect Variscan igneous crystallization. Since CL images also show thin and poorly visible metamorphic rims, we carried out a physical abrasion (PA) pre-treatment prior to chemical abrasion to isolate the Variscan zircon zones from later Alpine overgrowth for CA-ID-TIMS analysis. We interpret a high-precision PA-CA-ID-TIMS 206Pb/238U age of 335.479 ± 0.041/0.096 Ma (internal non-systematic/external systematic error; MSWD=0.27) as best estimate for Variscan zircon crystallization for this sample. This age overlaps with the result of CA-LA-ICPMS analyses when properly accounting for the total analytical uncertainty, including matrix effects on concentration ratio standardization.

From these data we conclude: (1) mixing of two age components in zircon may lead to an apparent protracted range in 206Pb/238U age, which can be resolved if isotope analyses yield very high Pb*/Pbc ratios and thus are very precise. At lower precision zircon age spectra can be erroneously interpreted as reflecting protracted growth, since they will overlap concordia due to elevated 207Pb/235U uncertainties, as well as in between individual 206Pb/238U ages. (2) By combining physical and chemical abrasion, we can resolve the observed complexities, by selectively analyzing zircon domains of interest while simultaneously mitigating diffusive Pb-loss. (3) This study shows how analytical precision may dramatically impact on scientific interpretation, as less precise data can easily be mistaken to reflect prolonged magmatic growth, rather than two-component mixing with xenocrystic material. This difference can significantly impact the interpreted lifespan of magmatic systems.

How to cite: Schaltegger, U., Gaynor, S. P., Ruiz, M., and Ulianov, A.: Protracted U-Pb age spectra from complex zircon crystals resolved using high-precision geochronology and selective sample pre-treatment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3540, https://doi.org/10.5194/egusphere-egu22-3540, 2022.