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MRW was funded by a NERC PhD studentship at the University of Manchester. PLM thanks STFC for their support (ST/M001814/1). We are grateful to SSRL for continued support for imaging at beamline 6-2 at SLAC. We are also grateful to the Manchester X-Ray Imaging Facility, which was funded in part by the EPSRC (grants EP/F007906/1, EP/F001452/1 and EP/I02249X/1). Ancient stromatolites can provide key insights into the early evolution of life on Earth. Neoarchean fenestrate stromatolites from the ∼2520 Ma Upper Nauga Formation (Transvaal Supergroup, South Africa) preserve cuspate morphologies. They possess clearly delineated support and drape structures interpreted as dolomitized microbial mat material. Petrographic observations show that the biogenic structures are composed of planar-s to non-planar ferroan dolomite, encased in ferroan calcite, including herringbone calcite textures. The cuspate stromatolites were analyzed using Synchrotron Rapid Scanning X-Ray Fluorescence (SRS-XRF) and more conventional techniques to determine: (i) whether element distributions could be distinguished in ancient stromatolites at both cm to dm scales, (ii) whether element distributions show variation between biogenic and abiogenic textures, and (iii) the sample’s paragenesis. The distributions of Ca, Fe, Mn, Pb, Cu, As, Br, Al, Si, P, and S directly correspond to dolomitized stromatolitic structures and show trace element distributions are principally controlled by calcite and dolomite occurrence. Dolomite formation was mainly driven by seawater-derived fluids given the high concentrations of Fe and retention of marine shale-normalized rare earth element and yttrium (REYSN) patterns, however the spatial association of dolomite to stromatolite structures may reflect microbially-influenced mineral nucleation. Given the complexity of this sample’s paragenetic evolution, trace metal distributions cannot be conclusively tied to specific metabolic pathways, bioaccumulation or passive binding, however, the results show SRS-XRF can be used for quantifiable, spatial, in-situ investigation of ancient microbialites. Postprint

Attempts to extend methods for dating archaeological bones beyond that of radiocarbon dating, such as amino acid racemization, have met with limited success owing to the dependence on multiple environmental factors and controls. Despite facing similar challenges, deamidation of glutamine has recently been investigated as a potential indicator of ‘thermal age’ in archaeological bones, as well as a measure of their preservation quality. Here, we analysed bones from different Middle Palaeolithic layers from Grotte Mandrin (France), as well as undertook a series of simulated diagenetic experiments, to investigate whether deamidation can be used as a tool for the relative dating of bones.

UV-B radiation may affect atmospheric circulation and influence climate, as well as affecting all biological life on Earth. However, past environmental and climate reconstructions (using various multi-proxy approaches) generally do not focus on UV-B. Ultraviolet-Absorbing Compounds (UACs) in pollen grains are an indicator of the UV-B level received by plants, and it is possible to measure the abundance of UACs in pollen using Fourier Transform Infrared (FTIR) micro-Spectroscopy, providing a promising approach to UV-B reconstruction. This research reconstructed UAC levels in individual Cedrus atlantica (Atlas cedar) pollen grains within sediment samples from a 20 m core at Lake Sidi Ali, Middle Atlas, Morocco, spanning the Holocene. Correlations between UACs and other palaeoenvironmental proxies from the same core are discussed, including, oxygen stable isotopes (18O) which reflect winter rainfall, local dust sedimentation, and lake sediment CaCO3 and Total Organic Carbon (TOC), as well as independent 10Be-derived Total Solar Irradiance (TSI). Correlations between these proxies may indicate solar-related temperature and humidity fluctuations at Lake Sidi Ali, considering mechanisms of varied ocean and terrestrial circulation under different levels of solar activity, although there is some chronological uncertanty due to different sampling resolutions. A positive correlation between UAC levels and winter rainfall at Morocco implies connections between oceanic circulation and solar activity, while the relationship with local dust sedimentation reveals how solar irradiation may influence the Saharan dry air mass contribution to Morocco. Analysis of single pollen grains using FTIR presents several challenges in obtaining clean spectra, which can be a source of uncertainty with this approach. To minimise noise in FTIR spectra, Cedrus pollen grains should be measured using the same orientation under microscope. As this is not always posssible, we developed a protocol to evaluate spectra quality to filter out spectra that had excessive noise, or were deemed not to be a pollen grain. We also assess the minimum effective number of pollen grains that require measurement to provide a statisitcally significant sample and thereby improve the quality of UAC data. Our protocol represents good practice in developing a robust UAC data set, which can allow for UV-B and solar radiation levels to be inferred. Future work aims to quantitatively reconstruct UV-B levels using a modern UAC calibration.

Incorporation of reduced inorganic sulfur (S) into organic matter (OM) in euxinic environments is considered a vital route through which OM is preserved for millions of years. However, precipitation of iron sulfides is believed to compete with OM preservation via sulfurisation. High resolution geochemical, petrographic, and electron microprobe (EMPA) analyses were employed to better understand S controls on OM preservation with particular focus on iron sulfides precipitation in organic S-rich mudstones from the Kimmeridge Clay (KCF), Monterey (MF), and Whitby Mudstone [Grey Shale (GS) and Jet Rock (JR) Members] Formations. Analyses indicated that S in the KCF and MF is mostly bound to OM as shown by the relatively high abundance of organic sulfur compounds (OSCs) in their pyrolysates. The relatively low amounts of iron (Fe) in these mudstones permitted extensive reaction of S and OM to occur efficiently, promoting preservation of high amounts OM through sulfurisation. State-of-the-art EMPA imaging of total S and Fe indicated that the S was mainly bound to organics, supporting the geochemical analyses. In contrast, S in the GS and JR was predominantly sequestered as pyrite (FeS2) rather than organically bound, as indicated by the relatively low quantity/absence of OSCs in their pyrolysates, hence, preservation through sulfurisation was less significant in these settings. EMPA imaging of S in these mudstones shows discrete shapes ranging in geometry and size and in most cases correlated with Fe in the corresponding Fe EMPA images, confirming that the S exists in discrete authigenic FeS2. Overall, in line with previous research, this study indicates that preservation of OM through sulfurisation is an important pathway for sequestration of OM. However, an abundance of reactive Fe could hinder this process by preferentially reacting with reduced S, to form iron sulfides (mainly FeS2), thus impeding reactions between OM and S to occur efficiently.

International audience; Myriapods were, together with arachnids, the earliest animals to occupy terrestrial ecosystems, by at least the Silurian. The origin of myriapods and their land colonization have long remained puzzling until euthycarcinoids, an extinct group of aquatic arthropods considered amphibious, were shown to be stem-group myriapods, extending the lineage to the Cambrian and evidencing a marine-to-terrestrial transition. Although possible respiratory structures comparable to the air-breathing tracheal system of myriapods are visible in several euthycarcinoids, little is known about the mechanism by which they respired. Here, we describe a new euthycarcinoid from Upper Devonian alluvio-lagoonal deposits of Belgium. Synchrotron-based elemental X-ray analyses were used to extract all available information from the only known specimen. Sulfur X-ray fluorescence (XRF) mapping and spectroscopy unveil sulfate evaporation stains, spread over the entire slab, suggestive of a very shallow-water to the terrestrial environment prior to burial consistent with an amphibious lifestyle. Trace metal XRF mapping reveals a pair of ventral spherical cavities or chambers on the second post-abdominal segment that do not compare to any known feature in aquatic arthropods, but might well play a part in air-breathing. Our data provide additional support for amphibious lifestyle in euthycarcinoids and show that different respiratory strategies were used during the marine-to-terrestrial transition in the myriapod lineage.

Significance Jawless, boneless, and virtually without fossil record, hagfish have long escaped systematists’ grip on their place among other fish. Yet their systematic resolution is critical to define vertebrates as a clade. Here we report an unequivocal fossil hagfish from the Cretaceous Mediterranean. Using this fossil to calibrate the evolutionary history of the group, our analysis supports hagfish and lampreys as sister groups, which likely diverged from one another in early Paleozoic times. As a result, vertebrates have a deep dichotomy, where some fossil jawless vertebrates sit closer to hagfish and lampreys than to jawed vertebrates. We showed that morphology-based analysis converged onto molecular inferences when characters are coded nonindependently, providing a case study for morphological–molecular conflicts in animal phylogeny., Hagfish depart so much from other fishes anatomically that they were sometimes considered not fully vertebrate. They may represent: (i) an anatomically primitive outgroup of vertebrates (the morphology-based craniate hypothesis); or (ii) an anatomically degenerate vertebrate lineage sister to lampreys (the molecular-based cyclostome hypothesis). This systematic conundrum has become a prominent case of conflict between morphology- and molecular-based phylogenies. To date, the fossil record has offered few insights to this long-branch problem or the evolutionary history of hagfish in general, because unequivocal fossil members of the group are unknown. Here, we report an unequivocal fossil hagfish from the early Late Cretaceous of Lebanon. The soft tissue anatomy includes key attributes of living hagfish: cartilages of barbels, postcranial position of branchial apparatus, and chemical traces of slime glands. This indicates that the suite of characters unique to living hagfish appeared well before Cretaceous times. This new hagfish prompted a reevaluation of morphological characters for interrelationships among jawless vertebrates. By addressing nonindependence of characters, our phylogenetic analyses recovered hagfish and lampreys in a clade of cyclostomes (congruent with the cyclostome hypothesis) using only morphological data. This new phylogeny places the fossil taxon within the hagfish crown group, and resolved other putative fossil cyclostomes to the stem of either hagfish or lamprey crown groups. These results potentially resolve the morphological–molecular conflict at the base of the Vertebrata. Thus, assessment of character nonindependence may help reconcile morphological and molecular inferences for other major discords in animal phylogeny.

Trace element inventories are known to correlate with specific histological structures in bone, reflecting organismal physiology and life histories. By studying trace elements in fossilised bone, particularly in individuals with cyclic bone growth (alternating fast/slow bone deposition), we can improve our understanding of the physiology of extinct organisms. In this study we present the first direct comparison between optical histology (bone tissue identification) and synchrotron-based chemical mapping, quantification, and characterisation of trace elements (biochemistry) within cyclic growth tissues, in this case within bones of a cave hyaena (Crocuta crocuta spelaea). Results show distributions of zinc, an element strongly associated with active ossification and bone growth, correlating with (1) fast-growing tissue of zonal bone (cyclic growth) in an extinct hyaena and (2) secondary osteons (remodelling) in both extant and extinct hyaena. Concentrations and coordination chemistry of zinc within the fossil sample are comparable to those seen in extant bone suggesting that zinc is endogenous to the sample and that the chemistry of bone growth has been preserved for 40 ka. These results demonstrate that the study of trace elements as part of the histochemistry has wide utility for reconstructing growth, diet and other lifestyle factors in archaeological and fossil bone.

Introduction: The purpose of the IRIS (Infrared and Raman for Interplanetary Spectroscopy) laboratory is to produce laboratory spectra for the mid-infrared spectrometer MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) on the ESA/JAXA BepiColombo mission to Mercury. This device will map the mineralogy of the hermean surface spectral features in the 7-14 µm range, with a spatial resolution of ~ 500 meters [1,2]. For the interpretation the data from MERTIS, we need laboratory spectra for comparison. A wide range of natural mineral and rock samples such as terrestrial impact rocks and meteorites [e.g., 3-5] was studied for this purpose. Since we do not have natural samples from surface of Mercury, we produced synthetic analogs based on MESSENGER data and laboratory experiments [6-9]. A central component for such mixtures will be glass to replicate material formed by impact events and lava extrusion and explosive volcanism (i.e., pyroclastic debris) [e.g. 10]. We present results of our ongoing study of synthetic glasses. These synthetic glasses will be studied in the mid-infrared to obtain spectra for the IRIS database, the material will also used for future mixtures and experiments. Samples and Techniques: Sample Production: In order to simulate the petrologic evolution of magmas on early Mercury, we synthesized analog material under controlled temperature, pressure and oxidation state [7-9]. The glass was produced following a procedure described in [11] with the oxidation state controlled by exposing the sample to a CO-CO2 gas-mixture equivalent to four orders of magnitude below the iron-wüstite buffer (IW-4). For in-situ studies we selected run products from earlier, similar laboratory experiments [9]. Infrared Spectroscopy: For the bulk powder FTIR diffuse reflectance analyses, powder size fractions 0-25 µm, 25-63 µm, 63-125 µm, and 125-250 µm were measured, in addition to a polished sample. We used a Bruker Vertex 70 v infrared system with a MCT detector at the IRIS laboratories at the Institut für Planetologie in Münster. Analyses were conducted under low pressure to reduce atmospheric bands, analyses were made in reflectance from 2-20 µm. FTIR microscope analyses for in-situ studies in polished blocks and thin sections were conducted using a Bruker Hyperion 1000/2000 System at the Hochschule Emden/Leer. We used a 250×250 µm sized aperture. In addition, a Perkin-Elmer Spotlight-400 FTIR spectrometer at the University of Manchester was used to map samples using an adjoining Focal Plane Array (FPA) mapping unit with a resolution of 6.25 µm × 6.25 µm. Results: Figure 1 gives an example of an area mapped using micro-FTIR. Sample 131_1 is based on the MESSENGER derived composition of the Mercurian High Magnesium Regions (HMg) [9]. Spectra in Fig.2 are of the Mg-poor (5.2 wt%) glassy component in this sample. Compared with spectra of glasses based on the Inter Crater Planes (ICP) (21.5 wt% MgO), 123_3 (17.7 wt% MgO) and 126_3 (12.2 wt% MgO), we see generally spectra typical for glassy materials. The single Reststrahlenband (RB) shifts with increasing MgO from 9.3 µm to 9.9 µm, and the CF from 7.9 µm to 8.2 µm. The two examples for bulk powders (Fig.3) have low MgO contents: 1.6 wt% (Low Mg C) and 4.7 wt % (Low Mg B) [9]. Different grain size fractions show intensity correlated with increasing grain size (Fig. 3). The RB and CF features are basically similar for all size fractions, but an characteristical Transparency Feature (TF) appears in the finest fraction (0-25 µm). The Low Mg B sample has the TF at 11.7 µm, the CF at 7.8 µm and the RB at 9.4 µm. Low-Mg C shows the CF from 7.6 µm to 7.7 µm, the RB at 9.2 µm – 9.3 µm and a TF at 11.6 µm. Summary & Conclusions: The sieved size fractions of the bulk glass material show typical features for highly crystalline materials. They follow a trend of band shifts for CF and RB towards longer wavelengths with increasing MgO contents [3,4]. We will present further glasses cover higher MgO contents (>6 wt%) to provide material for the whole range of expected Mercurian regolith glass compositions [7-9]. However, for a complete picture of the hermean surface, we expect mixtures of glassy and crystalline material. This will be the next step in our study, where we will obtain spectra of mixtures representing various regions on Mercury [e.g.7,8]. Furthermore, the impact of space weathering, which changes the structural and thus spectroscopic properties of grain surfaces will be taken into account [12,13,14]. References: [1] Rothery D.A. et al. (2020) Space Space Rev. 216, 66 [2] Hiesinger H. et al. (2020) in prep. [3] Morlok et al. (2020) Icarus 335, 113410 [4] Morlok et al. (2019) Icarus 324, 86-103 [5] Weber et al. (2020) Earth and Planetary Science Letters 530, 115884 [6] Weider S.Z. et al. (2015) Earth and Planetary Science Letters 416, 109-120 [7] Namur and Charlier (2017) Nature Geoscience 10, 9-15 [8] Namur O. et al. (2016) Earth and Planetary Science Letters 448, 102-114 [9] Namur O. et al. (2016) Earth and Planetary Science Letters 439, 117-128 [10] Fasset C.I. (2016) Journal of Geophysical Research: Planets 121, 1900-1926 [11] Renggli C. and King P. (2018) Rev.Min.Geochem 84, 229-255 [12] Weber I. et al. (2020) Earth & Planetary Science Letters 530, 115884 [13] Stojic et al. (2020) Icarus (submitted) [14] Stojic et al. (2020) LPSC 51, 1875

We have synthesized and analyzed by mid-infrared reflectance spectroscopy silicate glasses that are representative for the glasses on the surface of Mercury. The glass compositions are based on high-pressure laboratory experiments and the resulting compositions of the glass phase. The spectra are of interest for investigating the surface of Mercury using the MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) instrument on board of the ESA/JAXA BepiColombo mission.Both powdered fractions and polished blocks have been analyzed. Powdered size fractions of 0–25 μm, 25-63 μm, 63-125 μm, and 125–250 μm were measured in reflectance in the thermal infrared (2–20 μm). Spectra for powdered bulk glasses (1.6 wt% - 19.0 wt% MgO) show a single, dominating Reststrahlenband (RB, 9.3–9.8 μm), a Christiansen Feature (CF; 7.6 μm - 8.1 μm), and a size dependent Transparency Feature (TF; 11.6–11.9 μm). Micro-FTIR analyses of polished blocks of glasses (3.4–26.5 wt% MgO) have characteristic bands at 7.8–8.2 μm (CF), and 9.3–9.9 μm (RB). Only few olivine crystalline features were observed.Spectral features correlate with compositional characteristics, e.g. SiO2 content or SCFM (SiO2/(SiO2 + CaO + FeO + MgO) index. The strongest correlation between band features CF and the strong RB are with Mg/Si. No simple mixture of glass spectra from this study is able to reproduce the entire ground based spectrum of the surface of Mercury. However, Mg-rich glasses reproduce identified features at 8.5 μm, 9.9 μm and 12.4 μm.

Endochondral ossification is the process by which bone is deposited during development, growth and repair of the skeleton. The regulation of endochondral ossification is extremely important as developmental flaws can result in severe skeletal abnormalities. However, until recently the limitations of available methodologies have restricted our understanding of this fundamental physiological process. The analysis of chemical elements that are intimately associated with discrete biochemical stages of ossification within bone could provide new insight to such processes at the atomic level. In this study we present detailed characterisation of the elemental inventory within actively ossifying bone during development in mice using synchrotron microfocus X-ray techniques. X-ray fluorescence imaging showed differential distributions of Zn, Sr and Ca, which may be correlated with the processes of cartilage replacement (Zn), active ossification (Sr) and fully ossified tissues (Ca). Quantification of these trace elements confirmed their relative distributions. These results represent the first detailed visualisation of local endochondral ossification processes using trace elemental mapping. Such studies have far reaching applications not only in the medical field, but to our understanding of the evolution of the bony skeleton given that trace element inventories have been shown to be preserved through deep time (millions of years).

Faunal remains from archaeological sites allow for the identification of animal species that enables the better understanding of the relationships between humans and animals, not only from their morphological information, but also from the ancient biomolecules (lipids, proteins, and DNA) preserved in these remains for thousands and even millions of years. However, due to the costs and efforts required for ancient biomolecular analysis, there has been considerable research into development of accurate and efficient screening approaches for archaeological remains. FTIR spectroscopy is one such approach that has been considered for screening of proteins, but its widespread use has been hindered by the fact that its predictive accuracy can vary widely depending on the extent of sample preservation and the instrument used. Further, screening methods for ancient DNA (aDNA) analysis are scarce. Here we present a new approach to vastly improve upon FTIR-based screening methods prior to ZooMS (Zooarchaeology by Mass Spectrometry) and aDNA analysis through the use of random forest-based machine learning. To do so, we use ATR-FTIR to examine three sets of archaeological bone assemblages and analyse them by ZooMS (for taxonomic identification). Two of these are from Palaeolithic contexts, dominated by terrestrial fauna and include specimens with a variety of preservational conditions. The third set consists of Holocene faunal remains, with variable levels of preservation and is dominated by cetaceans. Using the Holocene faunal remains, we were able to more consistently evaluate ATR-FTIR-based screening for mtDNA as well as ZooMS success. We report on the potential of machine learning in ATR-FTIR-based screening for ancient mtDNA analysis, and our machine learning models conclusively improve the accuracy prior to usage of ATR-FTIR-based screening for ZooMS by 20–40%. The results also suggest this approach potentially allows for a universal screening system, applicable across multiple sites and largely independent of the spectrometers used.

A new micro-fluidic method, which is known as the Micro-Reactor Simulated-Channel (MRSC) method, has been employed to rapidly determine the effective diffusion coefficients of lithium in three important representative low permeability lithologies including: Melechov granite (Czech Republic), Borrowdale tuff, and Land's End Cornish granite (both UK). The concept of MRSC is similar to the micro chemical reactor which enables fast measurements to be done on a small intact sample. The effective diffusion coefficients were measured and comparisons between the MRSC results and conventional column methods showed excellent agreement. Our measured effective diffusion coefficient for Melechov granite is 1.7 × 10−12 m2/s, directly comparable to previous conventional measurements. However the measurement time of the MRSC method is at least one order of magnitude faster than the conventional method and only requires small reaction volumes (as small as 10 ml). In addition, by exploiting the advantages of the MRSC method, the effects of velocity and concentration on diffusive transport for the two different UK rock types have also been investigated. Depending on flow rate and inlet tracer concentration, the effective diffusion coefficient for lithium in the Cornish granite ranges between 0.9 and 1.5 × 10−11 m2/s while that measured for the Borrowdale tuff varies between 1.2 and 1.6 × 10−11 m2/s.

International audience; Carbon compounds are ubiquitous and occur in a diversity of chemical forms in many systems including ancient and historic materials ranging from cultural heritage to paleontology. Determining their speciation cannot only provide unique information on their origin but may also elucidate degradation processes. Synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy at the carbon K-edge (280−350 eV) is a very powerful method to probe carbon speciation. However, the short penetration depth of soft X-rays imposes stringent constraints on sample type, preparation, and analytical environment. A hard X-ray probe such as X-ray Raman scattering (XRS) can overcome many of these difficulties. Here we report the use of XRS at ∼6 keV incident energy to collect carbon K-edge XANES data and probe the speciation of organic carbon in several specimens relevant to cultural heritage and natural history. This methodology enables the measurement to be done in a nondestructive way, in air, and provides information that is not compromised by surface contamination by ensuring that the dominant signal contribution is from the bulk of the probed material. Using the backscattering geometry at large photon momentum transfer maximizes the XRS signal at the given X-ray energy and enhances nondipole contributions compared to conventional XANES, thereby augmenting the speciation sensitivity. The capabilities and limitations of the technique are discussed. We show that despite its small cross section, for a range of systems the XRS method can provide satisfactory signals at realistic experimental conditions. XRS constitutes a powerful complement to FT-IR, Raman, and conventional XANES spectroscopy, overcoming some of the limitations of these techniques.

The hindlimb of theropod dinosaurs changed appreciably in the lineage leading to extant birds, becoming more ‘crouched' in association with changes to body shape and gait dynamics. This postural evolution included anatomical changes of the foot and ankle, altering the moment arms and control of the muscles that manipulated the tarsometatarsus and digits, but the timing of these changes is unknown. Here, we report cellular-level preservation of tendon- and cartilage-like tissues from the lower hindlimb of Early Cretaceous Confuciusornis. The digital flexor tendons passed through cartilages, cartilaginous cristae and ridges on the plantar side of the distal tibiotarsus and proximal tarsometatarsus, as in extant birds. In particular, fibrocartilaginous and cartilaginous structures on the plantar surface of the ankle joint of Confuciusornis may indicate a more crouched hindlimb posture. Recognition of these specialized soft tissues in Confuciusornis is enabled by our combination of imaging and chemical analyses applied to an exceptionally preserved fossil., Birds have a more crouched posture compared to their theropod dinosaur ancestors. Here, Jiang and colleagues describe a lower hindlimb of the Early Cretaceous bird Confuciusornis with soft tissues apparently preserved even as molecules, indicating a somewhat more modern posture in ancient birds.

The processes of adsorption and co-precipitation at mineral surfaces during reactions with aqueous fluids play a critical role in controlling the mass transfer and bioavailability of nutrients and contaminants. Significant advances have been made in our understanding of these two processes through the application of synchrotron-based analytical techniques including X-ray Absorption Spectroscopy (XAS), X-ray surface scattering methods, X-ray fluorescence, and glancing incidence diffraction. Along with these methodologies, a wide range of other techniques involving infra-red spectroscopy, atomic-force microscopy, electron and particle beams have also contributed to understanding atomic-scale processes at mineral surfaces. Here, the basics of each of these synchrotron methods are introduced along with an illustrative example from the literature. The allied techniques are also discussed. After this introduction, two case studies dealing with major contemporary environmental problems that involve adsorption and co-precipitation are presented. The first concerns the mobility of arsenic in groundwater. Currently, dissolved arsenic species pose an environmental threat to millions of people. The second case study considers the speciation and uptake of uranium within UK radioactive waste sludge. Clean-up of these sludges is expected to be a challenging technological problem, and the insights provided through understanding the attachment of the uranium to the sludge minerals may be critical to devising a successful remediation strategy.

Polarization-dependent grazing incidence X-ray absorption spectroscopy (XAS) measurements were completed on oriented single crystals of magnesite [MgCO3] and brucite [Mg(OH)2] reacted with aqueous uranyl chloride above and below the solubility boundaries of schoepite (500, 50, and 5 ppm) at pH 8.3 and at ambient (PCO2 = 10(-3.5)) or reduced partial pressures of carbon dioxide (PCO2 = 10(-4.5)). X-ray absorption near edge structure (XANES) spectra show a striking polarization dependence (χ = 0° and 90° relative to the polarization plane of the incident beam) and consistently demonstrated that the uranyl molecule was preferentially oriented with its Oaxial═U(VI)═Oaxial linkage at high angles (60-80°) to both magnesite (101̅4) and brucite (0001). Extended X-ray absorption fine structure (EXAFS) analysis shows that the "effective" number of U(VI) axial oxygens is the most strongly affected fitting parameter as a function of polarization. Furthermore, axial tilt in the surface thin films (thickness ∼ 21 Å) is correlated with surface roughness [σ]. Our results show that hydrated uranyl(-carbonate) complexes polymerize on all of our experimental surfaces and that this process is controlled by surface hydroxylation. These results provide new insights into the bonding configuration expected for uranyl complexes on the environmentally significant carbonate and hydroxide mineral surfaces.

Bone remodelling is a crucial biological process needed to maintain elemental homeostasis. It is important to understand the trace elemental inventories that govern these processes as malfunctions in bone remodelling can have devastating effects on an organism. In this study, we use a combination of X-ray techniques to map, quantify, and characterise the coordination chemistry of trace elements within the highly remodelled bone tissues of extant and extinct Sirenia (manatees and dugongs). The dense bone structure and unique body chemistry of sirenians represent ideal tissues for studying both high remodelling rates as well as unique fossilisation pathways. Here, elemental maps revealed uncorrelated patterning of Ca and Zn within secondary osteons in both extant and fossil sirenians, as well as elevated Sr within the connecting canals of fossil sirenians. Concentrations of these elements are comparable between extant and fossil material indicating geochemical processing of the fossil bone has been minimal. Zn was found to be bound in the same coordination within the apatite structure in both extant and fossil bone. Accurate quantification of trace elements in extant material was only possible when the organic constituents of the bone were included. The comparable distributions, concentrations, and chemical coordination of these physiologically important trace elements indicate the chemistry of bone remodelling has been preserved for 19 million years. This study signifies the powerful potential of merging histological and chemical techniques in the understanding of physiological processes in both extant and extinct vertebrates.

The detailed chemical analysis of fossils has the potential to reveal great insight to the composition, preserva- tion and biochemistry of ancient life. Such analyses would ideally identify, quantify, and spatially resolve the chemical composition of preserved bone and soft tissue structures, but also the embedding matrix. Mapping the chemistry of a fos- sil in situ can place constraints on mass transfer between the enclosing matrix and the preserved organism(s), and there- fore aid in distinguishing taphonomic processes from origi- nal chemical zonation remnant within the fossils themselves. Conventional analytical methods, such as scanning electron microscopy (SEM) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) have serious limitations in this case, primarily, an inability to provide large (i.e., decime- ter) scale chemical maps. Additionally, vacuum chamber size and the need for destructive sampling preclude anal- ysis of large and precious fossil specimens. However, the recent development of Synchrotron Rapid Scanning X-ray Fluorescence (SRS-XRF) at the Stanford Synchrotron Radi- ation Lightsource (SSRL) allows the non-destructive chem- ical analysis and imaging of major, minor, and trace element concentrations of large paleontological and archeological specimens in rapid scanning times. Here we present elemen- tal maps of a fossil reptile produced using the new SRS-XRF method. Our results unequivocally show that preserved bio- logical structures are not simply impressions or carbonized remains, but possess a remnant of the original organismal biochemistry. We show that SRS-XRF is a powerful new tool for the study of paleontological and archaeological sam- ples.

Around the world large quantities of sludge wastes derived from nuclear energy production are currently kept in storage facilities. In the UK, the British government has marked sludge removal as a top priority as these facilities are nearing the end of their operational lifetimes. Therefore chemical understanding of uranium uptake in Mg-rich sludge is critical for successful remediation strategies. Previous studies have explored uranium uptake by the calcium carbonate minerals, calcite and aragonite, under conditions applicable to both natural and anthropogenically perturbed systems. However, studies of the uptake by Mg-rich minerals such as brucite [Mg(OH)2], nesquehonite [MgCO3·3H2O] and hydromagnesite [Mg5(CO3)4(OH)2·4H2O], have not been previously conducted. Such experiments will improve our understanding of the mobility of uranium and other actinides in natural lithologies as well as provide key information applicable to nuclear waste repository strategies involving Mg-rich phases. Experiments with mineral powders were used to determine the partition coefficients (Kd) and coordination of UO22+ during adsorption and co-precipitation with brucite, nesquehonite and hydromagnesite. The Kd values for the selected Mg-rich minerals were comparable or greater than those published for calcium carbonates. Extended X-ray absorption fine structure analysis results showed that the structure of the uranyl-triscarbonato [UO2(CO3)3] species was maintained after surface attachment and that uptake of uranyl ions took place mainly via mineral surface reactions.

An experimental technique has been developed and applied to the problem of determining effective diffusion coefficients and partition coefficients of Sr in low permeability geological materials. This technique, the micro-reactor simulated channel method (MRSC), allows rapid determination of contaminant transport parameters with resulting values comparable to those determined by more traditional methods and also creates product surfaces that are amenable for direct chemical analysis. An attempt to further constrain mass flux was completed by detailed ion beam analysis of polished tuff surfaces (tuff is a polycrystalline polyminerallic aggregate dominated by silicate phases) that had been reacted with Sr solutions at concentrations of 10−5, 10−3 and 10−1 mol l−1. Ion beam analysis was carried out using beams of both protons (using particle induced X-ray emission and elastic backscattering spectrometry or EBS) and alpha-particles (using Rutherford backscattering spectrometry). The ion beam analyses showed that increased solution concentrations resulted in increased surface concentrations and that in the highest concentration experiment, Sr penetrated to at least 4 μm below the primary interface. The Sr surface concentrations determined by EBS were 0.06 (±0.05), 0.87 (±0.30) and 2.40 (±1.0) atomic weight % in the experiments with starting solution concentrations of 10−5, 10−3, and 10−1 mol l−1, respectively.

The application of the recently developed synchrotron rapid scanning X-ray fluorescence (SRS-XRF) technique to the mapping of large objects is the focus of this review. We discuss the advantages of SRS-XRF over traditional systems and the use of other synchrotron radiation (SR) techniques to provide corroborating spectroscopic and diffraction analyses during the same analytical session. After reviewing routine techniques used to analyze precious specimens, we present several case studies that show how SR-based methods have been successfully applied in archeology and paleontology. For example, SRS-XRF imaging of a seventh-century Qur'ān palimpsest and an overpainted original opera score from Luigi Cherubini is described. We also review the recent discovery of soft-tissue residue in fossils of Archaeopteryx and an ancient reptile, as well as work that has successfully resolved the remnants of pigment in Confuciusornis sanctus, a 120-million-year-old fossil of the oldest documented bird with a fully derived avian beak.

Well-preserved fossils of pivotal early bird and nonavian theropod species have provided unequivocal evidence for feathers and/or downlike integuments. Recent studies have reconstructed color on the basis of melanosome structure; however, the chemistry of these proposed melanosomes has remained unknown. We applied synchrotron x-ray techniques to several fossil and extant organisms, including Confuciusornis sanctus, in order to map and characterize possible chemical residues of melanin pigments. Results show that trace metals, such as copper, are present in fossils as organometallic compounds most likely derived from original eumelanin. The distribution of these compounds provides a long-lived biomarker of melanin presence and density within a range of fossilized organisms. Metal zoning patterns may be preserved long after melanosome structures have been destroyed.

Synchrotron X-ray reflectivity (SXR) was used to measure the thickness of the water film that adsorbs on a { 1 0 1 ¯ 4 } cleavage surface of calcite (CaCO3) in a sample chamber where relative humidity could be controlled within the range from

Evolution of flight in maniraptoran dinosaurs is marked by the acquisition of distinct avian characters, such as feathers, as seen in Archaeopteryx from the Solnhofen limestone. These rare fossils were pivotal in confirming the dinosauria-avian lineage. One of the key derived avian characters is the possession of feathers, details of which were remarkably preserved in the Lagerstätte environment. These structures were previously simply assumed to be impressions; however, a detailed chemical analysis has, until now, never been completed on any Archaeopteryx specimen. Here we present chemical imaging via synchrotron rapid scanning X-ray fluorescence (SRS-XRF) of the Thermopolis Archaeopteryx , which shows that portions of the feathers are not impressions but are in fact remnant body fossil structures, maintaining elemental compositions that are completely different from the embedding geological matrix. Our results indicate phosphorous and sulfur retention in soft tissue as well as trace metal (Zn and Cu) retention in bone. Other previously unknown chemical details of Archaeopteryx are also revealed in this study including: bone chemistry, taphonomy (fossilization process), and curation artifacts. SRS-XRF represents a major advancement in the study of the life chemistry and fossilization processes of Archaeopteryx and other extinct organisms because it is now practical to image the chemistry of large specimens rapidly at concentration levels of parts per million. This technique has wider application to the archaeological, forensic, and biological sciences, enabling the mapping of “unseen” compounds critical to understanding biological structures, modes of preservation, and environmental context.

Biofilm development on mineral surfaces and related changes in surface reactivity were studied using batch and flow through experiments. An artificial groundwater was used as the primary nutrient medium, Pseudomonas aeruginosa (PAO1) was the model microbial organism and 'mineral' surfaces were kept as simple as possible by using glass or a polished quartz tile. Experiments were also completed with very low concentrations (100 mg l(-1)) of iron, Fe(2+ ), in the solution. In situ confocal laser scanning microscopy of developing colonies during the live growth phase, and of thick, mature biofilms, revealed only sporadic coverage of biofilm cells and associated polymers at the 'mineral-microbe interface'. Imaging and analysis of biofilm-conditioned surfaces doped with Fe(2+ )-rich solutions allowed the locus and form of Fe-rich mineral precipitation to be determined and show that biological surface components can cause mineral precipitation from dilute dissolved species which might otherwise remain in solution.

Four different sets of experiments were completed in order to constrain vivianite [Fe3(PO4)2 · 8H2O] reactivity under conditions pertinent to As(V)-bearing groundwater systems. Firstly, titration experiments were undertaken in the pH range 4-9 to determine the zero point of charge (ZPC) of vivianite; showing that the ZPC lies at a pH of approximately 5.3. Secondly, the steady state dissolution rates of vivianite far from equilibrium were measured in aqueous solutions in the pH range 2–10 at 18.5 °C (±3 °C) using a fluidized bed reactor. The rate of vivianite dissolution, R, is given by (1) R ( moles s - 1 cm - 2 ) = 1.18 × 10 - 10 a H + 0.77 + 1 × 10 - 15 + 6.92 × 10 - 24 a H + - 1 The dissolution rate exhibits an exponential increase with increase in the activity of the H+ ion (aH+) in solution at 2 8. Thirdly, the sorption of arsenate [As(V)] onto natural well-crystallized vivianite in the pH range 3–11 under static flow conditions was determined. 25–40% of As(V) from a starting concentration (C0) of 100 μM was adsorbed onto vivianite. Static adsorption experiments were also completed at two lower As(V) concentrations (C0 = 10 and 1 μM). Sorption was determined to be only weakly dependent on pH. Fourthly, the final part of this study investigated the sorption of As(V) onto vivianite at pH 9 under dynamic flow conditions. An input solution of 4 mM As(V) was applied to water saturated columns, followed by leaching with deionised water (DIW). Breakthrough curves show that the retention and exchangeability of As within the column is enhanced with vivianite present, consistent with solid phase analysis of unreacted and reacted solid materials. A simple calculation based on a model shallow Bengal sediment having about 0.2 wt% of vivianite and total initial dissolved As concentrations of 100 μM showed that under such conditions 88% of dissolved As(V) could potentially be adsorbed onto vivianite. These results will help to better understand As mobility in the presence of the Fe(II) mineral phase vivianite, thus providing better prediction of As mobility in partially reduced environments.

Multiple Internal Reflection Fourier Transform Infra-Red (MIR-FTIR) spectroscopy was developed and used for in situ flow-through experiments designed to study the process of organic acid promoted silicate dissolution. In tandem with the FTIR analysis, ex situ X-ray scattering was used to perform detailed analyses of the changes in the surface structure and chemistry resulting from the dissolution process. Phthalic acid and forsteritic glass that had been Chemically Vapour Deposited (CVD) onto an internal reflection element were used as reactants, and the MIR-FTIR results showed that phthalic acid may promote dissolution by directly binding to exposed Mg metal ion centers on the solid surface. Integrated infrared absorption intensity as a function of time shows that phthalic acid attachment apparently follows a t(1/2) dependence, indicating that attachment is a diffusive process. The diffusion coefficient of phthalic acid was estimated to be approximately 7 x 10(-6) cm(2) s(-1) in the solution near the interface with the glass. Shifts in the infrared absorption structure of the phthalate complexed with the surface compared to the solute species indicate that phthalate forms a seven-membered ring chelate complex. This bidentate complex efficiently depletes Mg from the glass surface, such that after reaction as much as 95% of the Mg may be removed. Surface depletion in Mg causes adsorbate density to fall after an initial attachment stage for the organic ligand. In addition, the infrared analysis shows that silica in the near surface polymerizes after Mg removal, presumably to maintain charge balance. X-ray reflectivity shows that the dissolution rate of forsteritic glass at pH 4 based on Mg removal in such flow-through experiments was equal to 4 x 10(-12) mol cm(-2) s(-1) (geometric surface area normalized). Reflectivity also shows how the surface mass density decreases during reaction from 2.64 g cm(-3) to 2.2 g cm(-3), consistent with preferential loss of Mg from the surface. Auxiliary batch experiments with forsteritic glass films deposited onto soda glass were also completed to add further constraints to the mechanism of reaction. By combining reflectivity with diffuse scatter measurements it is shown that the primary interface changes little in terms of atomic-scale roughness even after removal of several hundred angstroms of material. These measurements unequivocally show how a dicarboxylic acid bonds to and may chelate the dissolution of a magnesium-bearing silicate. At the molecular level the solid surface retreat may best be described by a depinning model where Mg is preferentially removed and residual silica tetrahedra polymerize and act to episodically "pin" the surface. (c) 2008 Elsevier Ltd. All rights reserved.

Feldspar minerals are thermodynamically unstable in the near-surface environment and their surfaces are well known to react readily with aqueous solutions, leading to incongruent dissolution at low pH values, but congruent dissolution at neutral and high pH values. Interactions with mineral surfaces are an important control on the environmental transport of trace elements and detrital feldspars are abundant in soils and sediments. However, the interactions of metal ions in solution with the reacting feldspar surface have not been widely explored. The interactions of Pb(II), U(VI) and Np(V) ions with the feldspar surface have therefore been studied. Lead is taken up by the microcline surface at pH 6 and 10, but no uptake could be measured at pH 2. There was measurable uptake of Pb(II) on the plagioclase surface at pH 2, 6 and 10. Uptake always increased with pH. In most conditions, Pb(II) reacts through cation exchange process although, at high pH, a discrete phase, probably hydrocerrusite, is observed by atomic force microscopy (AFM) to precipitate on the plagioclase surface. Supersaturation with hydrocerrusite in these conditions is expected from thermodynamic calculations. Uptake of uranyl ion (UO22+), generally through surface complex formation, could only be measured at pH 6 and 10. At pH 6 and an initial U(VI) concentration above 21.0 mu M, precipitation of becquerelite (Ca[(UO2)(3)O-2(OH)(3)](2)center dot 8H(2)0), identified by AFM and characterised by grazing incidence X-ray diffraction and X-ray photoelectron spectroscopy, is observed on plagioclase. The U(VI) concentration range in which becquerelite precipitation begins (dissolved U(VI) 1-5 mu M.) is consistent with that predicted from thermodynamic modelling. On plagioclase feldspar, secondary ion mass spectrometry showed diffusion of uranium into the altered surface layer. Uptake of the neptunyl ion (Np(V)) was found at pH 6 and 10 for microcline and at pH 2, 6 and 10 for plagioclase, and was generally lower than uptake of U(VI). By combining batch sorption experiments with imaging and surface analysis, and thermodynamic modelling, it has been possible to gain a mechanistic insight into the reactions of the feldspar surface with metal ions in solution. (C) 2007 Elsevier Ltd. All rights reserved.

Exceptionally high-quality X-ray absorption spectroscopy (XAS) spectra of the As K-edge measured on a garnet from the Central Oslo Rift (Jamtveit et al. 1993) are presented and interpreted. The best fit to the extended X-ray absorption fine structure (EXAFS) spectrum indicates that arsenic occurs predominantly as As5+ in the tetrahedral Si4+ site. The first shell As-O bond lengths of 1.69 angstrom are identical to those observed for As5+-O in sodium arsenate and the edge position of 11872 eV is also characteristic of As5+. Determination of oxidized As within the structure places an important constraint on fluid chemistry, but perhaps even more importantly, EXAFS fitting of outer shells (As-Ca 3.07,3.75, 5.71, 6.11 angstrom; As-Fe/Al 3.47, 5.35 angstrom; As-Si 3.88, 5.60, 5.91 angstrom) in this high-quality data set gives unequivocal evidence that AsO4-3 substitutes for SiO4-4 in the garnet tetrahedral site. This is, to the best of our knowledge, the first Such XAS study yielding direct evidence, through outer shell fitting, for both the coordination environment and oxidation state of arsenic within (as opposed to sorbed onto) a silicate mineral.

Various processes in the Earth's crust for which confined fluids have a controlling effect are discussed. Recent work which has led to a better understanding of the properties of confined fluids is highlighted. We introduce the five papers in this special edition of Chemical Geology which represent current research trends in the study of confined fluids within the context of the geosciences.

In situ measurements of mineral surface evolution during the process of pressure solution are possible with the high brightness of synchrotron X-ray sources. This capability has been explored through the use of newly developed reaction vessels that allow transmission of the incident and scattered X-ray beam through a low atomic weight piston. Several new vessels are described, along with details of computational algorithms that are used to simulate X-ray scattering in this unconventional geometry. Results using calcite (CaCO 3 ) and halite (NaCl) as reactant crystals are presented and compared to other atomic-scale measurements of surface dissolution processes. Calcite was reacted with an unsaturated fluid at 30 bars of pressure for approximately 24 h. During reaction the root mean square surface roughness ( σ ) evolved from 13.7 A (± 0.5 A) to 19.5 A (± 1.0 A), giving a roughening rate of: d σ /d t = +6.3 × 10 − 5 A s − 1 . This is consistent with other measurements made with free calcite surfaces and is driven almost entirely by chemical disequilibrium. Analysis of the surface ex situ post-reaction gives an identical σ value, showing that the in situ measurements are well-constrained. Experiments also at 30 bars but in a saturated solution indicate that the calcite surface does not significantly roughen, giving the result that pressure solution of calcite at this pressure cannot be monitored in experiments of several days duration. Experiments with halite, a much more reactive phase, in saturated solutions showed the reflectivity profile to be dynamic on a time scale of hours. This experiment was left to reach equilibrium over 108 days and then re-analyzed, showing that σ had increased from 34 A (± 2 A) to 41 A (± 2 A), giving a roughening rate of: d σ /d t ≤ +6.4 × 10 − 7 A s − 1 . This is two orders of magnitude smaller than the calcite roughening rate caused by chemical disequilibrium and provides the first direct in situ atomic-scale measurement of the rate of surface roughening due to pressure solution.

Oxidative dissolution of a primary Mn-silicate phase (rhodonite) was studied via synchrotron X-ray techniques. The study was designed to combine the element-specific chemical technique of Glancing Incidence X-ray Absorption Spectroscopy (GIXAS) with the surface structural technique of X-ray scattering in order to produce the first depth resolved study of Mn-silicate low-temperature reactivity. A chemo-mechanically polished polycrystalline rhodonite sample was characterized and then reacted with pH 3.5 nitric acid. The surface originally had a mosaic structure and 15.5 (±1) Å r.m.s. roughness. Surface composition was not measurably different from bulk rhodonite before reaction, indicating that the surface preparation regimen had not produced an altered surface. After 1 h of reaction, the roughness of the mineral surface decreased and reflectivity oscillations developed, resulting from the formation of a leached layer. This layer was 74.7 (±2) Å thick with an electron density equal to 72% of that of bulk rhodonite (equal to the loss of ~1 in 2 Mn atoms). Both the primary and the buried interfaces had similar roughnesses; 4.9 and 4.5 (±1.0) Å , respectively. Diffuse scatter indicated that the correlation length between surface features also decreased. The GIXAS analysis showed that the Mn remaining in the surface had become oxidized, with the degree of oxidation decreasing as a function of depth. Oxidation penetrated at least 140 Å into the structure. A further 2.5 h of reaction at pH 3.5 caused dissolution of the leached layer and reduced the thickness of this altered region to 16.0 (±2) Å , while surface roughness increased slightly to 6.2 (±1.0) Å . Depletion of Mn in this region increased only slightly relative to the first reaction step; the electron density was 67% that of bulk rhodonite, equivalent to the loss of 2 in 3 Mn atoms. The thickness of the oxidized region however, persisted. Analysis by XPS on the same specimen corroborates the X-ray results.

The electrochemical oxidation of chalcopyrite (CuFeS2) has been studied at pH 4 using voltammetry, coulometry, X-ray photoelectron spectroscopy (XPS) and both ex situ and in situ atomic force microscopy (AFM). Between 500 and 650 mV an anodic oxidation peak is observed, prior to the onset of the main decomposition reactions. Chalcopyrite electrodes in contact with electrolyte show some release of Cu into solution even without an applied potential. At 500 and 650 mV, the loss of Cu from the surface increases by a factor of 2 and 6, respectively. Oxidation at 500 mV results in the formation of a mixed oxide or hydroxide of iron, coincident with islands (

An integrated approach involving the use of ion chromatography–inductively coupled plasma-mass spectrometry (IC–ICP-MS), X-ray absorption spectroscopy (XAS) and sequential extraction procedures has been employed to elucidate the solution and solid phase speciation and partitioning of As in a polluted urban watercourse. Dissolved As concentrations exceeding 130 μg l −1 and comprising entirely inorganic species were determined in the waters of Tinker Brook, a contaminated stream. Upon mixing with a relatively As-free stream, White Ash Brook, both the total concentration of dissolved As and the proportion of As(V) were observed to decrease dramatically below values expected for conservative mixing. This was ascribed to adsorption onto the Fe (oxyhydr)oxides that characterise White Ash Brook on the basis of sequential extraction and direct analysis of the solids via XAS . The shift in oxidation state is speculated to be due to the faster rate of adsorption of As(V) on Fe (oxyhydr)oxides than As(III) in this fast flowing stream system. During periods of reduced supply of anthropogenic As, a small, secondary input of As(III) to White Ash Brook is detectable, delivered by a small ochreous seepage. The Fe (oxyhydr)oxide As-rich deposits surrounding this discharge may also act as a significant source of As upon dissolution during stormflow conditions.

Aspects of the (bio)geochemical cycling of metals (including Fe, Cu, Pb, Zn, Hg, As, Sb, U, Tc, Np) at or near the Earth's surface are discussed with reference to the recent work of the authors. Key stages of the breakdown of metalliferous minerals, transport of metals as solution complexes or colloidal precipitates, and interaction of metals in solution with the surfaces of minerals are considered. Emphasis is on molecular-scale observations using techniques such as scanning probe microscopy, photoelectron and (synchrotron) X-ray spectroscopies. The importance of the biological/mineralogical interface is also emphasized with reference to the bacterial colonization of mineral surfaces and formation of biofilms, and their influence on mineral surface reactivity and flow of fluids through rocks and sediments. Also noted is the importance of relating molecular and micro-scale observations to macroscopic phenomena. Molecular-scale understanding is central to attempts to model many processes of relevance in mineral exploration and exploitation, and in the containment of hazardous wastes and remediation of polluted areas. Mineralogists have a central role to play in the relevant environmental sciences and technologies.

Dissolution of a simulated British Magnox waste glass is governed by two pH-dependent processes. At low pH, dissolution is governed by reactions occurring predominantly at non-Si sites and residual Si-rich gels develop at the glass surface as B, Al and modifier cations are selectively leached. Here, extensive proton promoted hydrolysis of BO and AlO bonds is coupled with hydration and ion exchange processes. Hydrolysis of siloxane bonds governs the rate of dissolution at high pH and the glass dissolves congruently as the silicate network breaks down extensively. Differences in the surface chemistries and morphologies of glass samples reacted in strongly acidic and highly alkaline media reflect the net effects of these processes. The rate of the congruent dissolution process is influenced by the activity of silicic acid. The results are compared with published data for other glass formulations and are discussed in the context of proposed kinetic dissolution models.

Feldspar minerals are the most abundant minerals in the earth’s crust. Therefore, alteration reactions involving feldspars and aqueous fluids must be accounted for in a wide variety of geochemical processes, especially weathering, diagenesis, and trace element transport during fluid flow. The work presented here is, to the best of our knowledge, the first direct in situ measurement of the cation exchange process at the feldspar surface. It is known that incongruent dissolution occurs under acidic conditions and this is ascribed to an initial step of cation–proton exchange at the near surface of the mineral. Cation depletion has been confirmed in other studies by ex situ analysis of reacted feldspar grains, and indirect chemical methods have been used to infer that this exchange reaction is rapid. We have used specular x-ray reflectivity both in situ and ex situ to monitor the structural changes that occur on a polished oligoclase feldspar (001) surface in contact with dilute aqueous solutions. Starting material was Ab 74 with an r.m.s. surface roughness (σ) of 6.1 A. Upon addition of distilled deionised water into the reaction cell the reflectivity of the surface changed immediately to produce a reflectivity profile consistent with the formation of a leached layer 32.4 A thick. The model electron density (ρ) of this leached layer is consistent with complete removal of Na and Ca from this layer (ρ layer = 0.79 ρ olig ). Changes to this surface in distilled water were monitored for 19.5 h, during which time the leached layer/fluid surface roughness and layer thickness did not change. This confirms previous studies which concluded that the formation of a leached layer is rapid and that the layer itself stabilises quickly. Upon acidification of the reactant fluid to pH 3.1, the layer thickness did not change. Acidification did cause the leached layer/fluid surface to roughen to σ = 7.1 A. Leached layer thickness was corroborated ex situ by XPS depth profiling of the same sample after the x-ray reflectivity experiments. Na depletion measured by X-ray photoelectron spectroscopy analysis is significant to between 25 and 30 A depth. This demonstrates the broad agreement between the techniques and shows that in situ studies are now possible. Along with information about layer thickness and the roughness of the leached layer/fluid surface, the x-ray data have also been used to constrain the roughness at the interface between the leached layer and the unreacted bulk feldspar. This interface is approximately 15 A rough, which may suggest that cation leaching from the surface is not uniform. Models of the feldspar dissolution process must account for the three-dimensional nature of this reaction volume.

A high resolution reflectivity diffractometer (HRRD) has been recently commissioned on Station 2.3 at the SRS, Daresbury Laboratory. Using the instrument which is x-ray wavelength tunable, the characterization of the interface structure in an ion-assisted deposited Co/Cu multilayer has been carried out. In order to improve the electron density contrast of the sample, we have used an x-ray energy near the Cu K edge of 8.989 keV. By scanning the normal (specular), near normal (off specular), and parallel axes (transverse) of the surface, we have obtained useful reflectivity intensity data. By applying simulations to the data, we have determined a total roughness (rms) of 6.0±0.5 A with a significant contribution from correlated interfacial roughness (4.2±0.2 A). Other detailed structural information obtained has successfully demonstrated that the commissioned instrument is a viable tool for reflectivity studies.

Colour and pattern are key traits with important roles in camouflage, warning and attraction. Ideally, in order to begin to understand the evolution and ecology of colour in nature, it is important to identify and, where possible, fully characterise pigments using biochemical methods. The phylum Mollusca includes some of the most beautiful exemplars of biological pigmentation, with the vivid colours of sea shells particularly prized by collectors and scientists alike. Biochemical studies of molluscan shell colour were fairly common in the last century, but few of these studies have been confirmed using modern methods and very few shell pigments have been fully characterised. Here, we use modern chemical and multimodal spectroscopic techniques to identify two porphyrin pigments and eumelanin in the shell of marine snails Clanculus pharaonius and C margaritarius. The same porphyrins were also identified in coloured foot tissue of both species. We use high performance liquid chromatography (HPLC) to show definitively that these porphyrins are uroporphyrin I and uroporphyrin III. Evidence from confocal microscopy analyses shows that the distribution of porphyrin pigments corresponds to the striking pink-red of C. pharaonius shells, as well as pink-red dots and lines on the early whorls of C. margaritarius and yellow-brown colour of later whorls. Additional HPLC results suggest that eumelanin is likely responsible for black spots. We refer to the two differently coloured porphyrin pigments as trochopuniceus (pink-red) and trochoxouthos (yellow-brown) in order to distinguish between them. Trochopuniceus and trochoxouthos were not found in the shell of a third species of the same superfamily, Calliostoma zizyphinum, despite its superficially similar colouration, suggesting that this species has different shell pigments. These findings have important implications for the study of colour and pattern in molluscs specifically, but in other taxa more generally, since this study shows that homology of visible colour cannot be assumed without identification of pigments.

In-situ synchrotron X-ray reflectivity (SXR) measurements of the calcite-water interface were made. These data were used to model the angstrom-scale interfacial width and electron density profile of the interface. Measurements were made on the (10T4) cleavage surface of Iceland spar calcite in contact with pure N 2 , humid N 2 , deionized water, and dilute nitric acid solutions at 25°C. The measurements were performed in an X-ray transparent reaction cell in which fluid pH was monitored during SXR data acquisition. Analysis of the data indicated that the pristine calcite surface in contact with pure N 2 has an interfacial width (statistical roughness) of 2.60 ± 0.15 A. Exposure to water vapor (humid N 2 ) resulted in the deposition of a water film 19.9 ± 0.4 A thick. There was no evidence from the SXR data that the adsorbed water film caused roughening of the calcite surface. However, when reacted with deionized water the calcite was roughened, yielding an interfacial width of 23.1 A. During successive reactions with fluids having decreasing initial pH the calcite/fluid interfacial width increased from 23.1 to 45.3 A. The SXR results indicate that intraterrace areas participate in the dissolution of calcite. A linear correlation was observed between interfacial width of the intraterrace areas and the quantity of calcite dissolved.

In many applications, particularly in Earth Sciences, the main interest for microPIXE analysis is in determining one-dimensional trace element profiles. In these cases it is advantageous to carry out scanning along a line rather than over an area or as a series of points, since both the counting statistics and the spatial resolution are optimised. This paper describes the system used in Oxford to collect linescan data and the off-line processing techniques used to calibrate the linescan profiles. As an example of the use of linescan data results of a study of As zoning in skarn garnets are presented. Skarn garnets are formed during contact metamorphism and hydrothermal alteration of carbonate rocks and often show strong zoning with respect to major and minor elements. Samples from the Central Oslo Rift have been studied using microPIXE and in particular show a strong zoning in As and W, probably reflecting a sudden change in the growth conditions. In addition to the striking zonation patterns, the As and W levels are to our knowledge the highest ever recorded in these types of garnet. Elemental maps and linescan data are presented

The aim of palaeontological research is to decipher the evolution, biology and function of life on Earth by studying the fossil remains of organisms preserved in the geological record. Most often the material that survives over tens of millions of years is typically hard, biomineralized tissue such as bone and shell. This is mostly due to the inherent robust physical and chemical properties of such hard biomaterials. ‘Soft tissues’ including hair, feathers, skin, internal organs, cuticles and plant matter rapidly degrade in most environments, but in exceptional and isolated circumstances, these less durable biomaterials can be preserved over millions of years. The morphological details revealed by such preservation have not only allowed palaeontologists to interpret and reconstruct how many ancient and now long-extinct organisms may have appeared, but have also provided insight to their biology, ecology, behaviour, physiology and possible interactions with their environment. However, one extremely important characteristic of ancient organisms has until recently been conspicuously elusive: colour. Colour is known to play a vital role in many facets of the behaviour of living organisms, including adaptations to specific environments such as camouflage, and also has direct impacts upon ecology, such as communication and sexual selection. Indications of colour in fossilized organisms may help to resolve these characters in fossil remains and how they may have influenced the evolution of a species. In some very rare cases, fossils may show a visible indication of pigment patterns such as spots or stripes, but positive identification of specific colour or pigment mechanisms has so far remained extremely difficult. This is in part due to the limitations, such as detection limits, of analytical techniques that may be used to search for pigments, and partly due to the entrenched belief that the chemistry and micromorphology of a living organism is altered or replaced by a number of fossilization processes to such a degree that all useful information has been lost. In recent years, a growing number of studies have investigated the potential preservation of pigments within fossil tissues, with particular emphasis falling upon melanin. The focus on melanin is a result of the fact that melanin is almost ubiquitous in life on Earth, having been identified in a wide variety of living organisms including most chordates (Figure 1), many groups of invertebrates including echinoderms, sponges, molluscs and arthropods, and is also observed in plants, fungi and bacteria. Its presence in both highly derived and more primitive species indicates that melanogenesis represents a very ancient biosynthetic pathway utilized by the earliest life on the planet. Indeed, the tyrosinase enzyme, a key copper-bearing participant in melanogenesis, may have evolved from an extremely primitive biochemical function going back over one billion years (Van Holde et al., 2001). Additionally, the focus on melanin is also a result of the fact that unlike some of the other forms of pigmentation, melanin is stored in organelles – melanosomes – that form diagnostic shapes indicative of the type of melanin pigment contained within. This structural component, albeit microscopic in scale, has the potential to be preserved over millions of years and may be detectable by standard imaging techniques such as scanning electron microscopy (SEM). Zhang et al. (2010) was one of the first of several studies by different groups to identify melanosomes preserved in fossil tissues. Using SEM imaging, they provided evidence of melanosome like structures, rod-shaped eumelanosomes (~2 microns in length) and spherical phaeomelanosomes (~1 micron in diameter) preserved in the feathers of derived theropod (predatory) dinosaurs and birds from the Cretaceous Period (~120 million years old, China). This and several subsequent studies proceeded to present whole-organism pigment reconstruc