I18-Microfocus Spectroscopy
|
Diamond Proposal Number(s):
[31428]
Open Access
Abstract: High-precision estimates of Fe valence (Fe3+
/Σ
Fe, where Σ
Fe = Fe2+
+ Fe3+
) in glasses and isotropic minerals from Fe K-edge X-ray absorption near-edge structure spectroscopy (Fe-XANES) have greatly improved our understanding of magmatic fO2
in recent years. However, isotropic phases are not always present in the rock record, and our poor understanding of Fe3+
/Σ
Fe in anisotropic minerals, including near-ubiquitous clinopyroxene, hampers our ability to use them to investigate magmatic fO2
. Here we evaluate strategies for using pre-edge centroid positions obtained from Fe-XANES to determine Fe3+
/Σ
Fe in clinopyroxene powders and oriented single crystals. First, we show that clinopyroxene Fe3+
/Σ
Fe can be calibrated against pre-edge centroid positions collected from powdered reference materials characterised by Mössbauer spectroscopy, albeit with a precision of 11 % (1 σ
absolute). Second, spectra collected from oriented crystals reveal that centroid positions depend not only on crystal orientation but also that the nature of this dependence varies with Fe3+
/Σ
Fe. Nevertheless, we are able to determine Fe3+
/Σ
Fe in unknown, but oriented, clinopyroxene crystals with precisions of 12–19 % (1 σ
absolute). Applying clinopyroxene Fe-XANES to samples from Iceland and the Azores validates previously reported estimates of Fe3+
/Σ
Fe from stoichiometry. However, our findings confirm that determining clinopyroxene Fe3+
/Σ
Fe by Fe-XANES requires reference materials and unknowns to be reproducibly oriented to within a few degrees, a necessity that makes Fe-XANES ill-suited for routine analyses of clinopyroxene. We find that electron microprobe-based approaches readily and rapidly return more precise clinopyroxene Fe3+
/Σ
Fe determinations than the Fe-XANES approaches we describe here, and are hence more appropriate for measuring the large numbers of samples required to investigate the nature and causes of fO2
variability in magmatic systems.
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Jun 2026
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I13-1-Coherence
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Emily C.
Bamber
,
Fabio
Arzilli
,
Silvia
Cipiccia
,
Darren J.
Batey
,
Giuseppe
La Spina
,
Margherita
Polacci
,
Ali
Gholinia
,
Heath
Bagshaw
,
Danilo
Di Genova
,
Richard
Brooker
,
Daniele
Giordano
,
Pedro
Valdivia
,
Mike
Burton
Open Access
Abstract: Nanoscale crystals, or ‘nanolites’, are becoming increasingly recognised in both experimental products and natural samples of volcanic eruptions, across a range of magma compositions and explosivity. Nanolites can increase magma viscosity and influence eruptive style, due to the rheological impact of the nanoparticle suspension, by inducing chemical and structural changes in the residual melt and by facilitating heterogeneous bubble nucleation. Due to their large surface area, nanolites are also prone to aggregation. However, their morphology, spatial distribution and interaction in 3D has not yet been investigated.
Here we present a 3D, nanometre-scale visualisation and quantification of nanolites within scoriae of highly explosive basaltic volcanic eruptions, obtained using X-ray ptychography, a nanoscale microscopy technique. We find that titanomagnetite nanolites aggregate, forming elongate, irregular structures in 3D. Compositional heterogeneities are also observed within the matrix glass, as extraction of Fe and Ti from the melt during nanolite crystallisation forms differentiated, Si-rich boundary layers surrounding nanolites with higher viscosity. We support our 3D nanoscale observations with images acquired using SEM and STEM, utilising multi-scale imaging methods to visualise nanolite crystallisation in basaltic magmas. We find that syn-eruptive nanolite crystallisation can increase magma viscosity through their aggregation and impact on the composition of the residual melt, increasing the potential of magma fragmentation during ascent. Our results provide insight into the nanoscale structure of volcanic products and also the driving mechanisms of highly explosive basaltic volcanic eruptions.
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Mar 2026
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I20-Scanning-X-ray spectroscopy (XAS/XES)
|
Diamond Proposal Number(s):
[34350]
Open Access
Abstract: Deep-sea sediments hold large quantities of critical rare earth-elements and yttrium (REY) sequestered in nanoparticulate biogenic fluorapatite (Ca5(CO3)x(PO4)3−xF1+x). Understanding their enrichment processes and improving recovery and mineral processing methods require atomic-scale information about their chemical form, but it is difficult to obtain. Here, we use novel high-energy-resolution fluorescence-detected extended X-ray absorption fine structure (HERFD-EXAFS) spectroscopy to elucidate the local structure of gadolinium (Gd) in the highly enriched REY deposit from the Clarion–Clipperton fracture zone (CCFZ) in the Pacific Ocean. Our findings reveal that Gd is neither incorporated into the apatite structure nor precipitated alongside Ce in a Ce–PO4 precipitate. Instead, it is bound at short-range distances to Ca and PO4 in a defective apatite-type bonding environment within an amorphous matrix that encases fluorapatite nanocrystals. Density functional theory (DFT) suggests that Gd and Y, whose atomic fraction is ten times higher than that of Gd, are not dispersed throughout the amorphous matrix, but are likely segregated at medium-range distances. The entrapment of Ce, Gd, and Y within an amorphous matrix explains, at the microscopic level, why REY can be easily recovered through straightforward acid leaching. This is due to the intrinsic instability of disordered atomic structures compared to crystalline phases. This research highlights the complementarity of HERFD-EXAFS and DFT calculations for atomic-scale analysis of trace elements in complex natural matrices. It establishes a basis for their use across diverse terrestrial and marine materials.
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Feb 2026
|
|
I20-Scanning-X-ray spectroscopy (XAS/XES)
|
Diamond Proposal Number(s):
[21441, 18594]
Abstract: Vanadium (V) is a widespread trace element in the environment. At high concentration, due to anthropogenic emission such as mining activities and fossil fuels, it can be toxic to marine systems and terrestrial plants. However, the geochemical behaviour of V remains poorly understood. Here, this study aimed to understand the molecular scale V speciation, adsorption behaviour and bonding mechanisms of V(V) onto hematite as a function of geochemical factors (pH, ionic strength, and V(V) concentration), applying a multi-technique approach comprising aqueous chemical analysis and XAS supported by ATR-FTIR and PHREEQC geochemical speciation calculations. From these data, tetrahedral monovanadate formed a corner-sharing bidentate surface complex at 1.20 mM V(V) and pH 9 and 0.12 mM V(V) at all pH, while octahedral decavanadate formed at a V(V) concentration of 1.20 mM and pH < 7. The dominant coordination environment changed gradually from a mixture of octahedrally and tetrahedrally coordinated V at pH 3 to tetrahedral monovanadate at pH 9. These results demonstrate the marked effects of pH and initial V concentration on V(V) speciation at hematite surfaces, in turn affording predictions of the environmental behaviour of heavy metals released during a variety of anthropogenic activities (e.g. mining) across a range of geochemical conditions. It is envisioned these results will contribute to strategies for the treatment of lands contaminated with heavy metals predominantly through adsorption processes (e.g. mine sites).
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Dec 2025
|
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I18-Microfocus Spectroscopy
|
Diamond Proposal Number(s):
[31815]
Open Access
Abstract: Dehydroxylate I, a product of the thermal decomposition of serpentine, has been observed in heated carbonaceous chondrite meteorites. To better understand the occurrence of dehydroxylate I on carbonaceous asteroids, we have experimentally heated the carbonaceous chondrite Murchison from 400 to 550 °C at 25°C temperature steps, during which in situ micro X-ray diffraction (µXRD) patterns were collected using synchrotron radiation. µXRD was utilized such that the dehydroxylate I’s diffraction pattern could be isolated and characterized. This was successfully achieved, with the phase being detected at 400 °C. A diffraction pattern for dehydroxylate I was isolated at 525 °C, where it displayed crystallographic similarities to the mineral carlosturanite. We propose dehydroxylate I is produced when gaps form in serpentine’s tetrahedral sheet during its breakdown, which is consistent with previous studies on serpentine decomposition. The d-spacings for dehydroxylate I described here can be used to better identify it in natural and experimentally heated terrestrial and meteoritic samples.
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Dec 2025
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B22-Multimode InfraRed imaging And Microspectroscopy
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Marta
Morana
,
Lorenzo
Barni
,
Haixing
Fang
,
Giulia
Marras
,
Gianfelice
Cinque
,
Antonio
Angellotti
,
Fabrizio
Nestola
,
Alla
Logvinova
,
Denis
Mikhailenko
,
Luca
Bindi
,
Vincenzo
Stagno
Diamond Proposal Number(s):
[35052]
Open Access
Abstract: The investigation of mineral inclusions in diamonds represents a unique tool to better understand the mineralogy and composition of hidden portions of Earth's mantle and, hence, determine conditions of pressure and temperature at the time of diamond formation. Using a combination of experimental techniques and different geothermobarometric approaches, we characterized a natural diamond from Udachnaya kimberlite pipe entrapping nine inclusions; the inclusions are five garnets, three clinopyroxene and one sulfide and represent an eclogitic paragenesis. Here, we adopted, for the first time, the elastic geobarometry method to the garnet-diamond inclusion-host system to calculate the entrapment conditions for the diamond-garnet pair, resulting in 5.7(±0.3) GPa at 1154 °C. These P-T data are compared with estimates obtained through chemical geothermobarometry, employing T projection onto the local geotherm, a common approach used for eclogite xenoliths in absence of robust calibrated barometers. Our data demonstrate that elastic geobarometry for the garnet-diamond pair results to be a very reliable tool to determine the diamond formation also for eclogitic systems and this will allow to expand our knowledge on eclogitic diamonds in terms of depth of formation.
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Nov 2025
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E01-JEM ARM 200CF
E02-JEM ARM 300CF
I18-Microfocus Spectroscopy
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N.
Topping
,
J. C.
Bridges
,
L. J.
Hicks
,
L.
Petera
,
C. S.
Allen
,
J.
Ryu
,
D. G.
Hopkinson
,
M.
Danaie
,
L.
Blase
,
F. M.
Willcocks
,
G.
Douglas
,
H. G.
Changela
,
T.
Noguchi
,
T.
Matsumoto
,
A.
Miyake
Diamond Proposal Number(s):
[30752, 31953, 32874, 35976, 29615, 31641, 35046]
Open Access
Abstract: A correlative multi-technique approach, including electron microscopy and X-ray synchrotron work, has been used to obtain both structural and compositional information of a sulfur-bearing serpentine identified in several carbonaceous chondrites (Winchcombe CM2, Aguas Zarcas CM2, Ivuna CI, and Orgueil CI), and in Ryugu samples returned by the Hayabusa2 mission. S-K edge X-ray absorption spectroscopy was used to determine the oxidation state of sulfur in the serpentine in all samples except Ryugu. The abundance of this phase varies across these samples, with the largest amount in Winchcombe; ~12 vol% of phyllosilicates are identified as sulfur-bearing serpentine characterized by ~10 wt% SO3 equivalent. HRTEM studies reveal a d001-spacing range of 0.64–0.70 nm across all sulfur-bearing serpentine sites, averaging 0.68 nm, characteristic of serpentine. Sulfur-serpentine has variable S6+/ΣStotal values and different sulfur species dependent on specimen type, with CM sulfur-bearing serpentine having values of 0.1–0.2 and S2− as the dominant valency, and CIs having values of 0.9–1.0 with S6+ as the dominant valency. We suggest sulfur is structurally incorporated into serpentine as SH− partially replacing OH−, and trapped as SO42− ions, with an approximate mineral formula of (Mg Fe2+ Fe3+ Al)2-3(Si Al)2O5(OH)5-6(HS−)1-2(SO4)2−0.1-0.7. We conclude that much of the material identified in previous studies of carbonaceous chondrites as TCI-like or PCPs could be sulfur-bearing serpentine. The relatively high abundance of sulfur-bearing serpentine suggests that incorporation of sulfur into this phase was a significant part of the S-cycle in the early Solar System.
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Nov 2025
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B18-Core EXAFS
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Diamond Proposal Number(s):
[32381]
Open Access
Abstract: This study aimed at determining Ni and Co leaching kinetics from a New Caledonian laterite in an acidic medium (H2SO4 pH 1.5) and in a reductive environment (addition of SO32− or Fe(II)) at 46 °C. The mineralogical study revealed that Co was mainly carried by Mn oxyhydroxides in the limonite sample. Conversely, Ni was hosted by both Fe and Mn oxyhydroxides. In the presence of a reductive reagent, Mn oxyhydroxides dissolved rapidly compared to goethite, the main Fe oxyhydroxide in the sample. Co, Mn and Ni reductive leaching yields reached 79 %, 83 % and 9 % respectively after 2 days. Based on these results, a Mn oxides concentrate was produced in order to efficiently leach Co while limiting Fe oxyhydroxide dissolution. This concentrate resulted from a combination of particle size and gravity separation steps. The volume/mass of sample was drastically decreased since the mass of the final sample was only 3.3 % of the initial one. Co content increased from 0.16 wt% in the limonite to 2.3 wt% in the concentrate, representing an enrichment factor of 13.8 and recovery yield of 60 %. Co, Mn and Ni leaching yields reached 87 %, 95 % and 80 % respectively in the Mn oxides concentrate leaching experiment. The difference in Ni behaviour was consistent with the mineralogical composition: Ni was mainly carried by the goethite in the laterite, while it was hosted mainly by the Mn oxyhydroxides in the Mn oxides concentrate. This study gives a proof of concept for the development a robust pre-concentration process to recover Co.
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Nov 2025
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B22-Multimode InfraRed imaging And Microspectroscopy
|
A.
Angellotti
,
M.
Morana
,
L.
Barni
,
G.
Cinque
,
Y.
Lu
,
R.
Tao
,
G.
Marras
,
A.
Logvinova
,
L.
Bindi
,
D.
Mikhailenko
,
V.
Stagno
Diamond Proposal Number(s):
[35052]
Open Access
Abstract: Natural diamonds are exceptional carriers of mineralogical and chemical information from inaccessible depths of our planet. During their crystallization, they can host light elements such as H and N preserving a natural archive of mantle chemistry that, in turn, allows a better understanding of the chemical composition of the growth media, mechanisms of their formation and residence temperatures in the interior of Earth. However, how N and H distribute near entrapped minerals is still unknown. In this study we investigated the effect of chromite mineral inclusions on the spatial distribution of nitrogen and hydrogen in two natural diamonds of peridotitic origin using in situ synchrotron-based Fourier transform infrared microspectroscopy. From the acquisition and optimization of high-resolution maps, we determined the distribution of nitrogen, hydrogen, and nitrogen aggregation state.
Our results reveal a dependence between the absorption of H-related peaks with the incorporation of pairs of nitrogen atoms (NA-centers). We explain it as indication that chemical interactions between chromite and H might be masked by variations in the N aggregation state. We also conclude that synchrotron micro-FTIR is an advanced technique to assist the synthesis of N- (and H-) doped diamonds for industrial applications.
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Nov 2025
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Open Access
Abstract: Zircon (ZrSiO4) is the oldest-known mineral of Earth and an ubiquitous silicate in geochronology. More specifically, the accumulation of alpha decay damage in zircon over time significantly affects its physical and chemical properties, and can lead to a disturbance of the ages measured in this mineral. Therefore, analytical tools that enable comprehensive structural and chemical information at the nanoscale in this compound are highly sought after. In this context, we explore the electron energy-loss fine structures resulting from the excitation of O 1s and Si 2p core electrons in zircon, which are interpreted from ab initio calculations in a single-particle framework. An excellent agreement is obtained between the experimental and calculated fine structures, emphasizing the large distortion of the final electronic states induced by the core-hole potential. The O-K edge is particularly rich in information, with intense peaks dominated by O
- Zr
and O
- Si
hybrids. This work suggests that the near-edge structures from the O
and Si
excitations accessible from electron energy-loss spectroscopy or X-ray absorption spectroscopy could be used as tools to follow, interpret and understand structural and chemical modifications in zircon subject to natural radiation damage. We illustrate the potential of this approach through the evolution of near-edge fine structures in a zircon sample that exhibits a locally amorphized zone formed by ultrafast laser excitation.
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Oct 2025
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