Indicators of hot fluid migration in sedimentary basins: evidence from the UK Atlantic Margin

Microthermometric, petrographic and isotopic methods have been used to detect evidence for hot fluid flow in Mesozoic and Tertiary sediments from the NW UK continental margin, West of Shetland. New data presented here show that temperatures are hotter by c. 40°C in Tertiary samples than in the underlying Jurassic and Cretaceous sediments in wells 204/28-1, 206/5-2, 208/27-1, especially in cements from samples as young as mid–upper Eocene in age. Paleocene samples can be discriminated from older (Jurassic and Cretaceous) and younger (Eocene) sandstones on the basis of silica cement morphology and cathodoluminescence zonation. Jurassic, Cretaceous and Eocene quartz cements show oscillatory zoning as a consequence of relatively slow burial cementation. In direct contrast, rapid precipitation of silica cements from the cooling of hot fluids has produced unzoned cements in all but one Paleocene sample. No evidence for unzoned quartz cements was noted in any pre-Paleocene or Eocene samples. The restriction of hot fluid inclusions and unzoned cements to the Paleocene and post-Paleocene is consistent with lateral focusing of hot fluids. Isotopic data from kaolinites indicate that these fluids are best represented by mixtures of Mesozoic or Tertiary meteoric waters and marine porewaters that have undergone isotopic alteration through interaction with volcanic material. Our results indicate that hot fluid flow occurred over a relatively long time-scale (i.e. several million years), which may have important consequences for the degradation of reservoired hydrocarbons in West of Shetland Paleocene plays

Geochemistry and metallogeny of Neoproterozoic pyrite in oxic and anoxic sediments

The Neoproterozoic Dalradian Supergroup contains widespread diagenetic sulphides present as pyrite. The sulphides occur in both carbonaceous shales and glacial diamictites, that were deposited in relatively reducing and oxidising conditions respectively. The trace element compositions of the pyrite, and consequently the whole rock compositions, contrast between the two lithologies. The highest concentrations of selenium, tellurium and gold are all found in diamictite-hosted pyrite. The data suggest that increased mobility of these elements in oxidising conditions led to greater uptake when pyrite was precipitated. As one model for the formation of orogenic gold ore deposits assumes a sulphide-rich protolith, pyrite ultimately formed during relatively oxidising conditions could make a contribution, including the widespread pyrite precipitated during the Neoproterozoic ‘Snowball Earth’ glaciations

A black shale protolith for gold-tellurium mineralisation in the Dalradian Supergroup (Neoproterozoic) of Britain and Ireland

The Dalradian Supergroup of Britain and Ireland is mineralised by gold-tellurium vein deposits. The host succession includes carbonaceous, pyritic shales (pelites) which were a source of trace elements, including gold and tellurium. LA-ICP-MS mapping of pyrite crystals shows that late stages are enriched in gold, tellurium and lead, representing concentration of these elements during metamorphism and related hydrothermal activity. The sulphur isotope composition of the pyrite varies with stratigraphic position, reflecting an origin for the pyrite in the depositional environment through microbial sulphate reduction. Where pyrite was converted to pyrrhotite, trace element contents are much lower, indicating element liberation during metamorphism. These observations are consistent with a model of black shale protoliths for orogenic gold deposits

A solution concentration dependent transition from self-stratification to lateral phase separation in spin-cast PS:d-PMMA thin films

Thin films with a rich variety of different nano-scale morphologies have been produced by spin casting solutions of various concentrations of PS:d-PMMA blends from toluene solutions. During the spin casting process specular reflectivity and off-specular scattering data were recorded and ex situ optical and atomic force microscopy, neutron reflectivity and ellipsometry have all been used to characterise the film morphologies. We show that it is possible to selectively control the film morphology by altering the solution concentration used. Low polymer concentration solutions favour the formation of flat in-plane phase-separated bi-layers, with a d-PMMA-rich layer underneath a PS-rich layer. At intermediate concentrations the films formed consist of an in-plane phase-separated bi-layer with an undulating interface and also have some secondary phase-separated pockets rich in d-PMMA in the PS-rich layer and vice versa. Using high concentration solutions results in laterally phase-separated regions with sharp interfaces. As with the intermediate concentrations, secondary phase separation was also observed, especially at the top surface

Liquid–liquid equilibrium in polymer–fullerene mixtures; an in situ neutron reflectivity study

The composition profiles of a series of model polystyrene/fullerene bilayers are measured, before, during and after thermal annealing, using in situ neutron reflectometry. In combination with grazing-incidence X-ray diffraction measurements, these experiments, which quantify layer compositions as a function of molecular weight using changes in both scattering length density and layer thickness, extend and corroborate recent measurements on ex situ annealed samples and demonstrate that the composition profiles rapidly formed in these systems correspond to two co-existing liquid–liquid phases in thermodynamic equilibrium. The measurements also demonstrate a clear and systematic onset temperature for diffusion of the fullerenes into the PS layer that correlates with the known glass-transition temperatures of both the polymer (as a function of molecular weight) and the fullerene, revealing that the molecular mobility of the fullerenes in these systems is controlled by the intrinsic mobility of the fullerenes themselves and the ability of the polymer to plasticise the fullerenes at the interface. Over the temperature range investigated (up to 145 °C), measurements of equilibrated composition profiles as a function of temperature (during gradual cooling) reveal no significant changes in composition profile, other than those associated with the known thermal expansion/contraction of polystyrene thin-films

Modelling the effects of sediment compaction on salt marsh reconstructions of recent sea-level rise

This paper quantifies the potential influence of sediment compaction on the magnitude of nineteenth and twentieth century sea-level rise, as reconstructed from salt marsh sediments. We firstly develop a database of the physical and compression properties of low energy intertidal and salt marsh sediments. Key compression parameters are controlled by organic content (loss on ignition), though compressibility is modulated by local-scale processes, notably the potential for desiccation of sediments. Using this database and standard geotechnical theory, we use a numerical modelling approach to generate and subsequently ‘decompact’ a range of idealised intertidal stratigraphies. We find that compression can significantly contribute to reconstructed accelerations in recent sea level, notably in transgressive stratigraphies. The magnitude of this effect can be sufficient to add between 0.1 and 0.4 mm yr−1 of local sea-level rise, depending on the thickness of the stratigraphic column. In contrast, records from shallow (<0.5 m) uniform-lithology stratigraphies, or shallow near-surface salt marsh deposits in regressive successions, experience negligible compaction. Spatial variations in compression could be interpreted as ‘sea-level fingerprints’ that might, in turn, be wrongly attributed to oceanic or cryospheric processes. However, consideration of existing sea-level records suggests that this is not the case and that compaction cannot be invoked as the sole cause of recent accelerations in sea level inferred from salt marsh sediments

Designing effective antimicrobial nanostructured surfaces: highlighting the lack of consensus in the literature

Research into nanostructured materials, inspired by the topography of certain insect wings, has provided a potential pathway toward drug-free antibacterial surfaces, which may be vital in the ongoing battle against antimicrobial resistance. However, to produce viable antibacterial nanostructured surfaces, we must first understand the bactericidal mechanism of action and how to optimize them to kill the widest range of microorganisms. This review discusses the parameters of nanostructured surfaces that have been shown to influence their bactericidal efficiency and highlights the highly variable nature of many of the findings. A large-scale analysis of the literature is also presented, which further shows a lack of clarity in what is understood about the factors influencing bactericidal efficiency. The potential reasons for the ambiguity, including how the killing effect may be a result of multiple factors and issues with nonstandardized testing of the antibacterial properties of nanostructured surfaces, are then discussed. Finally, a standard method for testing of antimicrobial killing is proposed that will allow comparison between studies and enable a deeper understanding about nanostructured surfaces and how to optimize their bactericidal efficiency

Profile retrieval of a buried periodic structure using spin echo grazing incidence neutron scattering

When the neutron scattering technique, Spin Echo Resolved Grazing Incidence Scattering (SERGIS) concept, was originally put forward by Rekveldt [Physica B 1135, 234–236 (1997)] and Felcher et al. [Proc. SPIE 4785, 164 (2002)], they recognized that the specular scattering and the off-specular scattering could be spatially separated due to the tight neutron beam collimation in the scattering plane, a necessity for any reflectometry experiment. In this Letter, we show that it is possible to make large area measurements of periodic grating structures using SERGIS in a number of interesting scenarios. The SERGIS data can be analyzed using a dynamical theory, which makes it possible to effectively retrieve the lateral profile of a commercial periodic diffraction grating. Interestingly, this is still the case even when that grating is buried beneath a highly deuterated poly(methyl methacrylate-D8) polymer layer. We also clearly demonstrate that the maximum sensitivity to lateral structures is achieved when the specular reflection from the grating is excluded from the data analysis, demonstrating a feature of SERGIS that was proposed over two decades ago

Determination of the thin film structure of zwitterion doped poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate): a neutron reflectivity study

Doping poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is known to improve its conductivity, however little is known about the thin film structure of PEDOT:PSS when doped with an asymmetrically charged dopant. In this study, PEDOT:PSS was doped with diferent concentrations of the zwiterion 3-(N,N Dimethylmyristylammonio)propanesulfonate (DYMAP), and its effect on the bulk structure of the films characterized by neutron reflectivity. The results show that at low doping concentration, the film separates into a quasi bi-layer structure with lower roughness, (10%), increased thickness (18%), and lower electrical conductivity compared to the undoped sample. However when the doping concentration increases the film forms into a homogeneous layer and experiences an enhanced conductivity by more than an order of magnitude, a 20% smoother surface, and a 60% thickness increase relative to the pristine sample. Atomic force microscopy and profilometry measurements confirmed these findings, and AFM height and phase images showed the gradually increasing presence of DYMAP on the film surface as a function of the concentration. Neutron reflectivity also showed that the quasi bi-layer structure of the lowest concentration doped PEDOT:PSS is separated by a graded rather than a well defined interface. Our findings provide an understanding of the layer structure modification for doped PEDOT:PSS films that should be prove important for device applications

Propane selective carbon adsorbents from phenolic resin precursor

Novel carbon adsorbents for propane/propylene separation, with an unprecedented adsorption selectivity to propane – the minority component – were prepared from a phenolic resin precursor. The preparation conditions of the carbon molecular sieve adsorbents, such as pre-treatment with phosphoric acid; carbonization and post-treatment with propylene, were carefully investigated concerning their role on the separation performance. The best performing sample, MFF_8, was characterized by SEM, FTIR and small-angle X-ray scattering (SAXS). It was concluded that the pre-treatment with phosphoric acid was critical for obtaining the propane/propylene separation performance – adsorption ratio of ca. 2 at 1 bar and 25 °C; this sample was carbonized at 1100 °C and post-treated with propylene during 12 days. SAXS analysis indicates rod-shaped pores for the MFF_8 sample with a bimodal size distribution with averages of 0.4 nm and 3.7 nm, and HRTEM images show a network of earthworm micropores. The adsorption selectivity of this adsorbent to propane was assigned to the shape and size of the pores and the rigidity of propylene compared with propane for worming through the constriction of the ultra-micropores network. To the best knowledge of the authors, this is the first time a carbon molecular sieve (CMS) adsorbent with rod-shaped pores is reported. This new family of CMS adsorbents show great potential for equilibrium and kinetic based separations of adsorbates displaying different worming performances