I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[15947]
Open Access
Abstract: The alteration of olivine-rich rocks to serpentine minerals, (hydr)oxides, and aqueous hydrogen through serpentinization is long thought to have influenced the distribution of habitable environments on early Mars and the evolution of the early Martian hydrosphere and atmosphere. Nevertheless, the planetary importance of Martian serpentinization has remained a matter of debate. To constrain the process and products of Martian serpentinization, we studied serpentinized iron-rich olivines from the 1.1-billion-year Duluth Complex. These data indicate that serpentinized iron-rich olivine would have been accompanied by a fivefold increase in hydrogen production relative to serpentinized terrestrial mantle peridotites. In contrast to previous expectations, this style of serpentinization yields hisingerite as the dominant iron serpentine mineral at comparatively low temperature and pH, consistent with meteorite mineralogy and in situ rover data. The widespread occurrence of oxidized iron-bearing phyllosilicates in highly magnetized regions of the Martian crust supports the hypothesis that serpentinization was more pervasive on early Mars than currently estimated.
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Feb 2023
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I12-JEEP: Joint Engineering, Environmental and Processing
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Open Access
Abstract: NASA, ESA and the UK are collaborating on a Mars Sample Return (MSR) mission which aims to retrieve drill cores of Martian rock for terrestrial analysis, starting with the Mars2020 rover which landed successfully in Jezero Crater in Feb. 2021. Up to 30 samples, inside sealed titanium sample tubes, are planned to be returned to Earth in later missions. Due to the potential for back-contamination of Earth from possible extant life on Mars, strict contamination control measures must be taken for the purposes of planetary protection, as well as to prevent contamination of the samples by Earth’s environment. These measures place restrictions on the way measurements can be performed on the samples until they have been sterilised or judged safe. As the first step of scientific analysis, all samples will undergo a set of measurements called Pre-Basic Characterisation. Pre-BC will include weighing, X-ray CT, and magnetic measurements. These data along with Basic Characterisation data will be used to decide experimental plans for multi instrument analyses on the Mars samples. X-ray Diffraction (XRD) is currently planned for a later stage of sample analysis after the sample tubes have been opened due to limitations with conventional commercial X-ray diffractometers. [1, 2]
While a conventional X-ray tube cannot provide an appropriate X-ray beam, a synchrotron source is capable of much higher intensities and precise wavelength selectivity. Synchrotron facilities also allow more suitable diffraction geometries for the size and shape of sample expected from MSR. We have carried out experiments with the help of Diamond Light Source’s I12-JEEP beamline to test the feasibility of XRD analysis of samples in sealed Mars2020 sample tubes and suitable instrument parameters for XRD of these samples. Titanium tubes were prepared as analogues to Mars2020 sample tubes. Three different geological analogues were used in place of the Mars samples: an Icelandic basaltic sand, a calcareous mudstone from Watchet Bay, UK, and a Devonian Fine Grained Sandstone, UK. Two different methods for preventing unwanted diffraction signal from the sample tube walls have also been tested: subtracting the diffraction spectrum of an empty tube from the tube-with-sample spectrum, and using energy-dispersive X-ray diffraction to exclude tube wall signal. We show that quantitative XRD phase analysis can be successfully carried out on returned Mars samples in unopened sample tubes using a synchrotron X-ray source, and thus could be included in the Pre-BC phase of returned sample science. This would provide mineralogical data much earlier in the sample science process, improving decision-making around sample science, curation, and handling.
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Feb 2023
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E01-JEM ARM 200CF
E02-JEM ARM 300CF
I14-Hard X-ray Nanoprobe
I18-Microfocus Spectroscopy
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Open Access
Abstract: Phyllosilicate minerals in the carbonaceous chondrites provide insights into processes in primitive parent bodies of the early Solar System. It is widely agreed that the CM- and CI-type carbonaceous chondrites underwent aqueous alteration on their parent bodies, resulting in phyllosilicate-rich matrices, where the dominant mineral phase is serpentine. There are many previous studies investigating phyllosilicate structure in carbonaceous chondrites, however, the presence of sulfur in these minerals and its effect on crystal lattice structure has not been studied in detail. We are investigating how the presence of sulfur (up to ≃9-10 wt% SO3) in serpentine phyllosilicate regions effects basal lattice spacing measurements of serpentine-like minerals in CM- and CI-type chondritic and related asteroidal material.
Four specimens are being studied for this work: Winchcombe and Aguas Zarcas (CM-type), and Ryugu samples (A0058-C2001-08, A0104-00200502 and A0104-01700602) from Hayabusa2 and Ivuna (CI-type). All samples are TEM wafers. We have used a multi-technique approach to study the samples, with the E01 JEOL ARM200CF and E02 JEOL ARM300CF electron microscopes at the ePSIC facility at Diamond Light Source in Harwell, UK. EDS compositional data has been collected using the E01 microscope, whilst HRTEM and HAADF imaging data has been collected at E02. At E02 we are also applying a new 4D-STEM nano-diffraction technique in order to collect lattice spacing data to correlate with our other HRTEM results. Fe-K XANES analyses on Winchcombe and Ryugu have been carried out using the I18 microprobe and I14 hard x-ray nanoprobe respectively, also at Diamond Light Source, to constrain Fe3+/ΣFe. By combining these techniques we aim to better understand the physical and chemical structure of serpentine-like minerals in carbonaceous chondrites.
Initial analyses have shown that sulfur presence in carbonaceous chondrite phyllosilicates reduces the basal lattice spacings of serpentine-like minerals. In these sulfur-bearing regions, we have been finding lattice spacings in the range ~0.60-0.74nm for the CM-type chondrites. For the CI-type, these range between ~0.65-0.76nm. Differences in the reduced lattice spacing ranges are likely related to the redox state of the sulfur. In Ryugu and other carbonaceous chondrites the sulfur appears reduced; its content in serpentine is low and we see FeS grains. Comparatively, in Winchcombe (and others) more of the sulfur seems to be in the serpentine structure.
We can conclude that in serpentine-like minerals, the presence of sulfur appears to reduce basal lattice spacing values compared to the expected d-spacing value of 0.70nm for serpentine. Possible reasons for this include further investigations into the valency of the sulfur ions, the bonding environment within serpentine layers, and the location of sulfur in either the octa- or tetrahedral lattice sites.
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Feb 2023
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
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Diamond Proposal Number(s):
[28470]
Abstract: The chemical structures of aluminosilicate hydrates presented in alkali-activated geopolymer materials underpin their performances. Mg-substituted sodium aluminosilicate hydrates (N(-M)-A-S-H) are likely to be present in alkali-activated geopolymer materials prepared using MgO-containing precursors, however, their atomic-level structures remain unclear. The lack of such knowledge made it challenging to identify and distinguish N(-M)-A-S-H from complex alkali-activated geopolymer systems (i.e., alkali-activated slag, alkali-activated Mg-rich minerals), and therefore brought challenges in understanding and predicting their durability. This study characterised for the first time the atomic structures of the synthetic N(-M)-A-S-H gels, prepared through ion-exchange or co-synthesis, using X-ray absorption near-edge spectroscopy (XANES) at Si, Al and Mg K-edge. The results suggest that the substitution of Mg in the extra-framework locations of the alkali aluminosilicate hydrates (N-A-S-H) leads to negligible changes in the coordination environments of the aluminosilicate framework. However, the Mg coordination environment is distinguishably different from other Mg-containing phases in the systems, e.g., hydrotalcite. The Mg K-edge XANES of N(-M)-A-S-H shows a 0.8–1.2 eV shift compared with hydrotalcite. The results presented in this study can be used as the fingerprint to probe the presence of N(-M)-A-S-H in alkali-activated geopolymer materials containing Mg element.
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Nov 2022
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B18-Core EXAFS
I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[21441, 24074]
Open Access
Abstract: Over 60 years of nuclear activity have resulted in a global legacy of contaminated land and radioactive waste. Uranium (U) is a significant component of this legacy and is present in radioactive wastes and at many contaminated sites. U-incorporated iron (oxyhydr)oxides may provide a long-term barrier to U migration in the environment. However, reductive dissolution of iron (oxyhydr)oxides can occur on reaction with aqueous sulfide (sulfidation), a common environmental species, due to the microbial reduction of sulfate. In this work, U(VI)–goethite was initially reacted with aqueous sulfide, followed by a reoxidation reaction, to further understand the long-term fate of U species under fluctuating environmental conditions. Over the first day of sulfidation, a transient release of aqueous U was observed, likely due to intermediate uranyl(VI)–persulfide species. Despite this, overall U was retained in the solid phase, with the formation of nanocrystalline U(IV)O2 in the sulfidized system along with a persistent U(V) component. On reoxidation, U was associated with an iron (oxyhydr)oxide phase either as an adsorbed uranyl (approximately 65%) or an incorporated U (35%) species. These findings support the overarching concept of iron (oxyhydr)oxides acting as a barrier to U migration in the environment, even under fluctuating redox conditions.
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Nov 2022
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I08-Scanning X-ray Microscopy beamline (SXM)
I18-Microfocus Spectroscopy
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Agnieszka
Dybowska
,
Paul
Schofield
,
Laura
Newsome
,
Richard
Herrington
,
Julian F. W.
Mosselmans
,
Burkhard
Kaulich
,
Majid
Kazemian
,
Tohru
Araki
,
Thomas J.
Skiggs
,
Jens
Kruger
,
Anne
Oxley
,
Rachel L.
Norman
,
Jonathan R.
Lloyd
Diamond Proposal Number(s):
[14882, 14908, 17882]
Open Access
Abstract: The Piauí laterite (NE Brazil) was initially evaluated for Ni but also contains economic concentrations of Co. Our investigations aimed to characterise the Co enrichment within the deposit; by understanding the mineralogy we can better design mineral processing to target Co recovery. The laterite is heterogeneous on the mineralogical and lithological scale differing from the classic schematic profiles of nickel laterites, and while there is a clear transition from saprolite to more ferruginous units, the deposit also contains lateral and vertical variations that are associated with both the original intrusive complex and also the nature of fluid flow, redox cycling and fluctuating groundwater tables. The deposit is well described by the following six mineralogical and geochemical units: SAPFE, a clay bearing ferruginous saprolite; SAPSILFE, a silica dominated ferruginous saprolite; SAPMG, a green magnesium rich chlorite dominated saprolite; SAPAL, a white-green high aluminium, low magnesium saprolite; saprock, a serpentine and chlorite dominated saprolite and the serpentinite protolith. Not all of these units are ‘ore bearing’. Ni is concentrated in a range of nickeliferous phyllosilicates (0.1–25 wt%) including serpentines, talc and pimelite, goethite (up to 9 wt%), magnetite (2.8–14 wt%) and Mn oxy-hydroxides (0.35–19 wt%). Lower levels of Ni are present in ilmenites, chromites, chlorite and distinct small horizons of nickeliferous silica (up to 3 wt% Ni). With respect to Co, the only significant chemical correlation is with Mn, and Mn oxy-hydroxides contain up to 14 wt% Co. Cobalt is only present in goethite when Mn is also present, and these goethite grains contain an average of 0.19 wt% Co (up to a maximum of 0.65 wt%). The other main Co bearing minerals are magnetite (0.41–1.89 wt%), chlorite (up to 0.45 wt%) and ilmenite (up to 0.35 wt%). Chemically there are three types of Mn oxy-hydroxide, asbolane, asbolane-lithiophorite intermediates and romanechite. Spatially resolved X-ray absorption spectroscopy analysis suggests that the Co is present primarily as octahedrally bound Co3+ substituted directly into the MnO6 layers of the asbolane-lithiophorite intermediates. However significant levels of Co2+ are evident within the asbolane-lithiophorite intermediates, structurally bound along with Ni in the interlayer between successive MnO6 layers. The laterite microbial community contains prokaryotes and few fungi, with the highest abundance and diversity closest to ground level. Microorganisms capable of metal redox cycling were identified to be present, but microcosm experiments of different horizons within the deposit demonstrated that stimulated biogeochemical cycling did not contribute to Co mobilisation. Correlations between Co and Mn are likely to be a relic of parent rock weathering rather than due to biogeochemical processes; a conclusion that agrees well with the mineralogical associations.
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Oct 2022
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I08-Scanning X-ray Microscopy beamline (SXM)
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Diamond Proposal Number(s):
[23049]
Open Access
Abstract: The persistence of organic carbon (OC) in natural environments is widely attributed to mineral protection, especially by iron (Fe) (oxyhydr)oxides. The effect of OC binding strength on the aging of Fe (oxyhydr)oxides and the mobility and fate of OC during aging however, is unknown. Here we investigate how OC binding strength controls the aging of ferrihydrite (Fh) and subsequent retention or release of the associated OC. We focus on carboxyl-rich OC coprecipitated with Fh and track the physiochemical properties and OC stability as a function of carboxyl-richness over time. In agreement with previous work we find that during carboxyl-rich OC coprecipitation with Fh, OC is adsorbed to the Fh particle surfaces and that increasing carboxyl-richness results in an increasing number of carboxylate-Fe bonds between the OC and the mineral particles and thus increasing OC binding strength. We show that OC substantially retards the aging of Fe (oxyhydr)oxide from Fh to more crystalline Fe minerals and that this retardation increases with increasing OC binding strength. We also show that the total amount of OC decreases during aging and that the proportion of the remaining OC that is non-desorbable with 0.1 M NaOH decreases during aging for OC with relatively low binding strength but increases during aging for OC with relatively high binding strength. Our results therefore indicate that OC with higher binding strength coprecipitated with Fh becomes proportionally more stable with the solid phase and thus less mobile during aging in natural environments. We suggest that our work might offer a deeper mechanistic insight into the processes responsible for OC persistence with minerals and thus the long-term preservation of OC in natural environments.
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Jul 2022
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[31641]
Open Access
Abstract: The rapidly recovered Winchcombe CM chondrite regolith breccia fall gives the opportunity to analyse the secondary alteration phases of this meteorite type in great detail, without the effects of terrestrial contamination. A key part of determining the record of parent body water-rock reactions is studying the mineralogy of phyllosilicates with SEM, (S)TEM-EDX and XAS to determine their structure and cation site occupancies including Fe2+/Fe3+. Linked to the secondary alteration and phyllosilicate mineralogy is the redistribution of sulphur, a process which has been linked to the extent of hydrous alteration [1]. Here we consider the identity and assemblages of secondary S-bearing phases - serpentines and tochilinite - in a polished section of Winchcombe in order to better understand the alteration histories of CM chondrites and the nature of their serpentine-like phases. We are also studying these phases of interest in a set of other fresh CM meteorites including the recent fall Aguas Zarcas. As part of the Winchcombe analytical team, we have analysed clast and matrix in the section P30543 [1] at the University of Leicester Advanced Microscopy Facility. An initial investigation identified various locations of interest for further FIB-TEM analysis and XAS. FIB lift-out sections measuring up to 15 × 8 µm were extracted using a FEI Quanta 200 3D FIB-SEM, and thinned to ~100 nm attached to TEM Cu-grids for TEM analysis. High-resolution TEM imaging and STEM EDX was performed using JEOL 2100 TEM’s. Fe K XANES and EXAFS were performed at Beamline I18 of Diamond Light Source on P30543 using the techniques described in [3,4] to quantify Fe3+/SFe. Although the hydrated sulphide tochilinite is present in small amounts as needle-like crystalline patches in this section, the dominant S-bearing low temperature phase is a S-bearing 1:1 structure serpentine. This can be distinguished from the tochilinite in composition, as tochilinite is ~43 wt% SO3 whereas the Sserpentine is typically ~6-10 wt% SO3. The S-bearing serpentine can in turn also be distinguished from Spoor serpentine in the same section by d001 spacings which are 0.62-0.70 and 0.70-0.74 nm respectively. The relatively scarce tochilinite has d-spacings of 0.54 nm. The S-poor and S-rich serpentine phases are both ferric, having Fe3+/SFe 0.5-0.75. In contrast the tochilinite is more ferrous. We are studying the relative abundances and textural characteristics of S-bearing serpentine compared to bona fide tochilinite in Winchcombe and other CM’s in order to provide fresh insights into the record of progressive waterrock reactions in their parent bodies. [1] Suttle M. et al. 2022 MAPS in prep. [2] Daly L. et al. 2022 MAPS in prep. [3] Hicks L. J. et al. (2020) MAPS 55, 2599–2618. [4] Piercy J.D., Bridges J.C. and Hicks L.J. (2022) GCA 326: 97-118.
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Jun 2022
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I08-Scanning X-ray Microscopy beamline (SXM)
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Diamond Proposal Number(s):
[23540]
Open Access
Abstract: Mineral-associated organic matter is an integral part of soil carbon pool. Biological processes contribute to the formation of such organo-mineral complexes when soil microbes, and in particular soil fungi, deposit a suite of extracellular metabolic compounds and their necromass on the mineral surfaces. While studied in bulk, micro- to nanoscale fungal–mineral interactions remain elusive. Of particular interest are the mutual effects at the interface between the fungal exometabolites and proximal mineral particles. In this work, we have grown saprotrophic and symbiotic fungi in contact with two soil minerals with contrasting properties: quartz and goethite, on top of X-ray transparent silicon nitride membrane windows and analyzed fungal hyphae by synchrotron-based scanning transmission X-ray microscopy in combination with near edge X-ray fine structure spectroscopy at C(K) and Fe(L) absorption edges. In the resultant chemical maps, we were able to visualize and differentiate organic compounds constituting the fungal cells, their extracellular metabolites, and the exometabolites adsorbing on the minerals. We found that the composition of the exometabolites differed between the fungal functional guilds, particularly, in their sugar to protein ratio and potassium concentration. In samples with quartz and goethite, we observed adsorption of the exometabolic compounds on the mineral surfaces with variations in their chemical composition around the particles. Although we did not observe clear alteration in the exometabolite chemistry upon mineral encounters, we show that fungal–mineral interaction result in reduction of Fe(III) in goethite. This process has been demonstrated for bulk systems, but, to our knowledge, this is the first observation on a single hypha scale offering insight into its underlying biological mechanisms. This demonstrates the link between processes initiated at the single-cell level to macroscale phenomena. Thus, spatially resolved chemical characterization of the microbial–mineral interfaces is crucial for an increased understanding of overall carbon cycling in soil.
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Jun 2022
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I07-Surface & interface diffraction
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Diamond Proposal Number(s):
[18591]
Open Access
Abstract: The adsorption of carboxylic acid molecules at the calcite (104) and the muscovite (001) surface was investigated using surface X-ray diffraction. All four investigated carboxylic acid molecules, hexanoic acid, octanoic acid, lauric acid, and stearic acid, were found to adsorb at the calcite surface. Whereas the shortest two carboxylic acid molecules, hexanoic acid and octanoic acid, showed limited ordering and a flexible, disordered chain, the two longest carboxylic acid molecules form fully ordered monolayers, i.e., these form highly structured self-assembled monolayers. The latter molecules are oriented almost fully upright, with a tilt of up to 10°. The oxygen atoms of the organic molecules are found at similar positions to those of water molecules at the calcite–water interface. This suggests that in both cases, the oxygen atoms compensate for the broken bonds at the calcite surface. Under the same experimental conditions, stearic acid does not adsorb to K+ and Ca2+-functionalized muscovite mica because the neutral molecules do not engage in the ionic bonds typical for the mica interface. These differences in adsorption behavior are characteristic for the differences of the oil–solid interactions in carbonate and sandstone reservoirs.
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May 2022
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