Mössbauer Spectroscopy with High Spatial Resolution: Spotlight on Geoscience

McCammon, Catherine

doi:10.1007/978-981-15-9422-9_5

Cited by 8 publications

(5 citation statements)

References 283 publications

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“…Mössbauer spectroscopy was performed on powdered endmember and single-crystal clinopyroxene samples sandwiched between cellophane in ∼0.5 mm diameter holes drilled through 0.5 mm-thick wafers of Pb foil. Multiple wafers were prepared for samples with low FeO T contents (<5 wt.%) to ensure that effective sample thicknesses were sufficient for high quality analysis (McCammon, 2021). Spectra were collected using a constant acceleration Mössbauer spectrometer with a nominal 450 MBq 57 Co high specific activity source in a 12 µm-thick Rh matrix in the Bayerisches Geoinstitut at the Universität Bayreuth.…”

Section: Mössbauer Spectroscopymentioning

confidence: 99%

“…Moreover, analytical spot sizes typically exceed 100 µm (McCammon, 1994), making the technique of limited use for studying magmatic crystals. Synchrotron Mössbauer spectroscopy offers exciting opportunities for working on small samples (spot sizes ≤50 µm) but is relatively challenging to access given the limited number of facilities available globally (McCammon, 2021). Crystal anisotropy also makes it challenging to use synchrotron-based Fe-XANES spectroscopy to determine clinopyroxene Fe 3+ /ΣFe, though this approach certainly warrants continued exploration thanks to its theoretically high precision (Dyar et al, 2002;McCanta et al, 2004;Steven et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

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Re-evaluating stoichiometric estimates of iron valence in magmatic clinopyroxene crystals

Neave¹,

Stewart²,

Hartley³

et al. 2023

Preprint

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Clinopyroxene is a major rock forming mineral capable of incorporating a wide range of metal cations. As a consequence, clinopyroxene preserves valuable archives of magmatic processes and understanding clinopyroxene is essential for understanding Earth’s broader chemical evolution. However, knowledge about the relative abundances of ferrous and ferric iron in magmatic clinopyroxenes remains poor because it is not currently possible to routinely measure the valence of iron in clinopyroxene crystals without either separating single crystals for bulk analysis or securing access to Mössbauer spectroscopy or a synchrotron radiation source to perform in-situ microanalysis. This is despite many magmatic clinopyroxene crystals seemingly containing appreciable quantities of ferric iron, highlighting the potential for developing widely applicable clinopyroxene-based oxybarometers. Here we integrate optimised electron probe microanalysis and Mössbauer spectroscopy on endmember and single-crystal clinopyroxenes to re-evaluate previously discredited approaches for estimating clinopyroxene ferric iron contents by stoichiometry. By ensuring that all major and minor elements in clinopyroxene crystals are measured with sufficient precision, we show that it is possible to readily obtain stoichiometric estimates of clinopyroxene ferric to total iron contents with similar precisions to those derived from Mössbauer spectroscopy (1σ∼ 3.5% absolute). Being able to robustly determine clinopyroxene ferric iron contexts enables us to propose a new scheme for assigning clinopyroxene components that explicitly accounts for ferric iron, which is primarily hosted within esseneite component (CaFe3+AlSiO6) in clinopyroxenes dominated by quadrilateral components and aegirine component (NaFe3+Si2O6) in alkali clinopyroxenes. Our new scheme provides a framework for documenting the full spectrum of clinopyroxene compositions in studies on both natural and experimental systems.

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Section: Mössbauer Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Re-evaluating stoichiometric estimates of iron valence in magmatic clinopyroxene crystals

Neave¹,

Stewart²,

Hartley³

et al. 2023

Preprint

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“…Geological and geochemical samples, as well as rare specimens of astronomical origin, have been frequently studied with Mössbauer methods. The spatial resolution of these methods is still of great interest [ 112 ].…”

Section: Future Perspectivesmentioning

confidence: 99%

Nuclear Resonance Vibrational Spectroscopy: A Modern Tool to Pinpoint Site-Specific Cooperative Processes

et al. 2021

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Nuclear resonant vibrational spectroscopy (NRVS) is a synchrotron radiation (SR)-based nuclear inelastic scattering spectroscopy that measures the phonons (i.e., vibrational modes) associated with the nuclear transition. It has distinct advantages over traditional vibration spectroscopy and has wide applications in physics, chemistry, bioinorganic chemistry, materials sciences, and geology, as well as many other research areas. In this article, we present a scientific and figurative description of this yet modern tool for the potential users in various research fields in the future. In addition to short discussions on its development history, principles, and other theoretical issues, the focus of this article is on the experimental aspects, such as the instruments, the practical measurement issues, the data process, and a few examples of its applications. The article concludes with introduction to non-57Fe NRVS and an outlook on the impact from the future upgrade of SR rings.

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“…Furthermore, the reduction of magmatic liquids by SO 2 degassing during magma ascent and sensitivity of hydrous glasses to beam damage add further complexity to interpreting results from Fe-XANES spectroscopy (Moussallam et al, 2016;Brounce et al, 2017;Cottrell et al, 2018). Glass and mineral Fe 3+ /ΣFe contents can also be determined by Mössbauer spectroscopy (e.g., McCammon, 2021). However, laboratory-based Mössbauer spectroscopy is ill suited to high analytical throughput and synchrotron-based Mössbauer spectroscopy can only be performed a limited number of facilities, limiting the overall utility of the approach.…”

Section: Introductionmentioning

confidence: 99%

“…However, it is possible that the reducing conditions under which these experiments were performed and the poor precision of unoriented Fe-XANES spectroscopy performed on experimentally produced clinopyroxene crystals masked the true nature of relationships between f O2 and clinopyroxene Fe 3+ /ΣFe. Indeed, we speculate that our poor understanding of clinopyroxene Fe 3+ /ΣFe contents in magmatic systems more generally reflects the challenges associated with determining Fe valence in mineral samples, whether by bulk methods or in situ microanalysis requiring access to a Mössbauer spectrometer or synchrotron radiation source (Canil and O'Neill, 1996;Dyar et al, 2002;McCammon, 2021;Steven et al, 2022). Neave et al (2024) recently re-evaluated previously discredited approaches for estimating clinopyroxene Fe 3+ contents from stoichiometric constraints (cf., McGuire et al, 1989;Canil and O'Neill, 1996).…”

Section: Introductionmentioning

confidence: 99%

Iron valence systematics in clinopyroxene crystals from ocean island basalts

Neave¹,

Stewart²,

Hartley³

et al. 2024

Preprint

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systems, which is commonly expressed in terms of oxygen fugacity (fO2). Magmatic fO2 varies between different tectonic settings and controls the trajectories along which magmas evolve and the properties of the volcanic gases they release into the atmosphere. Ocean island basalts (OIBs) derived at least in part from recycled mantle sources are increasingly thought to evolve under more oxidising conditions than midocean ridge basalts (MORBs) from relatively depleted sources. However, the oxybarometeric tools currently at our disposal are subject to a range of limitations, meaning that there are relatively few internally consistent estimates of fO2 across multiple settings. Our understanding of the nature and causes of fO2 variability within and between magmatic systems therefore remains limited. In Part I we demonstrated that previously discredited approaches for estimating clinopyroxene ferric iron contents can return comparably precise results to Mössbauer spectroscopy by optimising electron probe microanalysis techniques, raising the prospect of developing clinopyroxene-based oxybarometers. Here we present high-quality analyses of clinopyroxene crystals from OIBs erupted in Iceland and the Azores to determine their iron valence systematics and explore their potential use for oxybarometry. Although many studies assume that all iron in magmatic clinopyroxene crystals occurs as ferrous iron, we find that up to 50% of the total iron in magmatic clinopyroxene crystals may be ferric iron, with crystals from alkali systems typically containing more ferric iron than those from tholeiitic systems. Most ferric iron is hosted within esseneite component (CaFe3+AlSiO6), though some may also be hosted in aegirine component (NaFe3+Si2O6) in the most alkali crystals. Iron–magnesium exchange equilibria between clinopyroxene crystals and their host glasses return plausible fO2 estimates for a tholeiitic basalt from Holuhraun in Iceland and an alkali basalt from Pico in the Azores but are subject to considerable uncertainties because the influence of ferric iron on clinopyroxene-liquid equilibria are poorly understood. There is no current advantage in accounting for ferric iron when evaluating iron-magnesium exchange between clinopyroxene–glass pairs. Magmatic fO2 was also estimated by applying a recent parametrisation of ferric iron partitioning to determine the valence of iron in liquids in equilibrium with clinopyroxene crystals from Holuhraun and Pico. We infer that our samples from Holuhraun and Pico evolved at about one and half and two and a half log units above FMQ equilibrium, respectively. These values are in line with independent estimates from these eruptions and similar eruptions of OIB elsewhere, and demonstrate the considerable potential for further development of clinopyroxene-based oxybarometers.

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Mössbauer Spectroscopy with High Spatial Resolution: Spotlight on Geoscience

Cited by 8 publications

References 283 publications

Re-evaluating stoichiometric estimates of iron valence in magmatic clinopyroxene crystals

Re-evaluating stoichiometric estimates of iron valence in magmatic clinopyroxene crystals

Nuclear Resonance Vibrational Spectroscopy: A Modern Tool to Pinpoint Site-Specific Cooperative Processes

Iron valence systematics in clinopyroxene crystals from ocean island basalts

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