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Surface reaction kinetics of volcanic materials at hydrothermal conditions – an in-situ experiment at the Surtsey volcanoThe diversity and functioning of microbial life is a key research topic in the field of marine geochemistry and geobiology. For understanding biological processes at the temperature limit of functional life, it is necessary to gain insights about microbe-rock-fluid interactions under natural hydrothermal conditions within the basaltic ocean crust. Although there has been research in the field of biological interactions on olivine and tephra surface in laboratories and samples from volcanos ([1], [2]), the kinetics of microbe-rock-fluid interactions has not been systematically evaluated by in-situ experiment in a natural reservoir.During the ICDP SUSTAIN Expedition 5059 at the Surtsey volcano off the southern coast of Iceland in 2017, a borehole was endowed with a subsurface observatory to analyze the evolution of olivine (Fo90) and volcanic glass surfaces embedded in PEEK containers at fixed temperatures ranging from 25°C to 125°C for two years ([3]). This incubation experiment delivers novel data of surface reaction kinetics under defined conditions in a natural setting.In-depth analysis of the sample surface with vertical scanning interferometry, atomic force microscopy as well as Raman spectrometry provides insights into solid-fluid reactions of volcanic minerals. On the one hand, this analysis delivers a quantitative and qualitative breakdown of the chemical and physical alteration of natural matter below the oceanic crust. On the other hand, the in situ experiment facilitates a validation of a range of experiments that have been performed in laboratories under similar conditions. The possibility to gain knowledge about dissolution and precipitation on the interface of common seafloor materials within a natural hydrothermal system is critical step towards understanding submarine microbial life. [1] Konhauser, K. O., Schiffman, P., and Fisher, Q. J., Microbial mediation of authigenic clays during hydrothermal alteration of basaltic tephra, Kilauea Volcano, Geochem. Geophys. Geosyst., 3( 12), 1075, doi:10.1029/2002GC000317, 2002.[2] Malvoisin, B., Brunet, F., Carlut, J., Rouméjon, S., and Cannat, M. (2012), Serpentinization of oceanic peridotites: 2. Kinetics and processes of San Carlos olivine hydrothermal alteration, J. Geophys. Res., 117, B04102, doi:10.1029/2011JB008842.[3] Türke, A., et al. (2019). "Design of the subsurface observatory at Surtsey volcano, Iceland." Sci. Dril. 25: 57-62.

During the last decades, X-ray (micro-)computed tomography has gained increasing attention for the description of porous skeletal and shell structures of various organism groups. However, their quantitative analysis is often hampered by the difficulty to discriminate cavities and pores within the object from the surrounding region. Herein, we test the ambient occlusion (AO) algorithm and newly implemented optimisations for the segmentation of cavities (implemented in the software Amira). The segmentation accuracy is evaluated as a function of (i) changes in the ray length input variable, and (ii) the usage of AO (scalar) field and other AO-derived (scalar) fields. The results clearly indicate that the AO field itself outperforms all other AO-derived fields in terms of segmentation accuracy and robustness against variations in the ray length input variable. The newly implemented optimisations improved the AO field-based segmentation only slightly, while the segmentations based on the AO-derived fields improved considerably. Additionally, we evaluated the potential of the AO field and AO-derived fields for the separation and classification of cavities as well as skeletal structures by comparing them with commonly used distance-map-based segmentations. For this, we tested the zooid separation within a bryozoan colony, the stereom classification of an ophiuroid tooth, the separation of bioerosion traces within a marble block and the calice (central cavity)-pore separation within a dendrophyllid coral. The obtained results clearly indicate that the ideal input field depends on the three-dimensional morphology of the object of interest. The segmentations based on the AO-derived fields often provided cavity separations and skeleton classifications that were superior to or impossible to obtain with commonly used distance-map-based segmentations. The combined usage of various AO-derived fields by supervised or unsupervised segmentation algorithms might provide a promising target for future research to further improve the results for this kind of high-end data segmentation and classification. Furthermore, the application of the developed segmentation algorithm is not restricted to X-ray (micro-)computed tomographic data but may potentially be useful for the segmentation of 3D volume data from other sources.

We reconstruct the 3-D microstructure of centimetre-sized olivine crystals in rocks from the Almirez ultramafic massif (SE Spain) using combined X-ray micro computed tomography (μ-CT) and electron backscatter diffraction (EBSD). The semidestructive sample treatment involves geographically oriented drill pressing of rocks and preparation of oriented thin sections for EBSD from the μ-CT scanned cores. The μ-CT results show that the mean intercept length (MIL) analyses provide reliable information on the shape preferred orientation (SPO) of texturally different olivine groups. We show that statistical interpretation of crystal preferred orientation (CPO) and SPO of olivine becomes feasible because the highest densities of the distribution of main olivine crystal axes from EBSD are aligned with the three axes of the 3-D ellipsoid calculated from the MIL analyses from μ-CT. From EBSD data we distinguish multiple CPO groups and by locating the thin sections within the μ-CT volume, we assign SPO to the corresponding olivine crystal aggregates, which confirm the results of statistical comparison. We demonstrate that the limitations of both methods (i.e. no crystal orientation data in μ-CT and no spatial information in EBSD) can be overcome, and the 3-D orientation of the crystallographic axes of olivines from different orientation groups can be successfully correlated with the crystal shapes of representative olivine grains. Through this approach one can establish the link among geological structures, macrostructure, fabric and 3-D SPO-CPO relationship at the hand specimen scale even in complex, coarse-grained geomaterials.

In a drillcore sample of serpentinized harzburgite from the uppermost oceanic crust (Mid-Atlantic Ridge, ODP Leg 209, Site 1270), we demonstrate using high-resolution 3D-microtomography that micron-sized open cavities are present. The development of porosity is interpreted to result from dissolution of brucite and/or olivine. Petrographic observations indicate that voids are integrated in a network of carbonate veins, the formation of which is linked to changing alkalinity in conjunction with dissolution reactions. Partial carbonate filling of pore spaces indicates that under static conditions low-temperature carbonation leads to clogging of fluid pathways and thus to a reduction in permeability. Electron microprobe analyses show that the inner walls of open voids are lined with Fe-rich precipitates. We propose that the iron in those phases was released by brucite or olivine dissolution and was subsequently oxidized and precipitated as ferric hydroxide. Thermodynamic computations show that this process may be a potential source of catabolic energy for microorganisms inhabiting serpentinites. The proposed carbonation mechanism implies that carbonate precipitation may start soon after exposure of the abyssal peridotites, when dissolution of brucite and weathering of olivine begin, and continue until the phases become inaccessible to seawater. Predicting carbonation rates of abyssal peridotites will hence require understanding of permeability reactions.

Publisher's version (útgefin grein), Surtsey, the youngest of the islands of Vestmannaeyjar, is an oceanic volcano created by explosive basaltic eruptions during 1963-1967 off the southern coast of Iceland. The subsurface deposits of the volcano were first sampled by a cored borehole in 1979. In summer 2017, three cored boreholes were drilled through the active hydrothermal system of the volcano by the International Continental Scientific Drilling Program (ICDP) SUSTAIN Expedition 5059. These cores are expected to provide the first glimpse of microbial life in very young and native basaltic tuff of the oceanic crust. To reduce the contamination of the subsurface environment, seawater circulating fluid was filtered and passed through two UV-sterilizing treatments. One of the boreholes has been equipped with a subsurface observatory dedicated in situ experiments for monitoring water-rock interactions and microbial processes in sterile, artificial basaltic glass and in olivine granules. With temperatures ranging from 25 to 125 °C, the subsurface observatory provides a precise geothermal window into an active hydrothermal system and thus represents an exceptional natural laboratory for studying fluid-rock-microbe interactions at different temperature regimes and facilitates experimental validation of active submarine microbial processes at the limit of functional life, about 121 °C. Comparisons with the 1979 and 2019 drill cores will provide time-lapse observations of hydrothermal processes over a 50-year timescale. Here, we present the technical design of the observatory and the incubation chamber experiments deployed from September 2017 to summer 2019., We thank all members of the SUSTAIN onsite and science teams and the Surtsey Research Society for their contributions to the drilling project. Bernd Zimanowski, at the University of Würzburg, produced the sterile basaltic glass for the current in situ experiments. The SUSTAIN project was funded by the International Continental Scientific Drilling Program (ICDP; led by Marie D. Jackson), the Icelandic Science Fund, ICF-RANNÍS (the IceSUSTAIN consortium led by Magnús T. Guðmundsson), the Bergen Research Foundation and K. G. Jebsen Centre for Deep Sea Research at the University of Bergen, Norway (led by Steffen Leth Jørgensen), the German Research Foundation (DFG; led by Wolfgang Bach and Bernd Zimanowski), and DiSTAR, University of Naples, Federico II, Italy (led by Piergiulio Cappelletti). The University of Utah, USA (Marie D. Jackson) and the two Icelandic power companies, Reykjavík Energy and Landsvirkjun, contributed additional funds. Anonymous reviewers made valuable improvements to the report.

With the increase in the number of risk assessment tools and clinical algorithms in many areas of science and medicine, this Perspective article provides an overview of research findings that can assist in informing the choice of an instrument for practical use. We take the example of violence risk assessment tools in criminal justice and forensic psychiatry, where there are more than 200 such instruments and their use is typically mandated. We outline 10 key questions that researchers, clinicians and other professionals should ask when deciding what tool to use, which are also relevant for public policy and commissioners of services. These questions are based on two elements: research underpinning the external validation, and derivation or development of a particular instrument. We also recommend some guidelines for reporting drawn from consensus guidelines for research in prognostic models.

This work aims to study the possibility of producing lightweight aggregates from hazardous ornamental stone granitic waste in addition to clayey deposit. Six batch compositions were prepared in different proportions bracketed between zero and 50% clay in the blank and 1:1 sample, respectively. The raw materials and the lightweight aggregates are characterized using X-ray powder diffraction (XRD), X-ray fluorescence (XRF), differential thermal analysis (DTA), transmitted light microscopy (TLM), cathodoluminescence (CL), X-ray micro-computed tomography (3D-μXCT) and SEM microscopy attached with energy dispersive X-ray analysis (EDAX). The results revealed that the contents of silica, alumina and total fluxes control the amount and viscosity of the liquid phase inside the aggregates during firing. The bloated aggregates show decrease in bulk density when the temperature and clay content increase. The microstructural and microchemical analyses show that a glassy phase is the major component in the lightweight aggregates. Some neogenic/remnant phases are randomly disseminated in the dominant glassy groundmass. The highly viscous melt, developed during firing, is the main reason for the small homogeneous pores in the blank sample. In contrast, the lower viscosity of the melt in the 1:1 sample is responsible for the existence of larger bubbles. All the prepared aggregates after firing at 1200 °C are lightweight aggregates which could be used in lightweight concrete as thermal and acoustic insulators.

Serpentinite mud volcanism in the Mariana forearc provides a window into the shallow portions of an active subduction zone. Fluid–rock interactions and related mass transfers into the mantle wedge can be assessed by studying the trace element compositions of slab-derived fluids and serpentinized mantle wedge materials brought to the seafloor by the serpentinite mud volcanoes. We investigated variably serpentinized ultramafic clasts from the Yinazao, Fantangisna, and Asut Tesoru mud volcanoes recovered on International Ocean Discovery Program Expedition 366 to examine the transfer of fluid-mobile elements (FMEs) from the slab to the wedge. These mud volcanoes sample the slab–wedge interface at depths of ~13–18 km and estimated temperatures of 80–250 °C. Our samples represent the serpentinized forearc and exhibit a multi-phase serpentinization history, as apparent from microfabrics, mineralogy, and in situ major and trace elemental analyses of distinct generations of serpentine. Initial hydration of the forearc mantle occurred under reducing conditions by Si-rich fluids. Early serpentine is characterized by generally high concentrations of Li, Sr, Rb, Cs, and Ba. Subsequent fluid–rock interactions were driven by Si-rich and FME-poor fluids and at later stages by Si- and FME-poor fluids in the mud volcano conduits, the latter of which resulted in the abundant formation of Fe-rich brucite. Iowaite and hematite indicate that less reducing conditions prevailed during the alteration of clasts after their emplacement at the seafloor. Concentrations of B are generally high but our dataset does not allow distinguishing slab- from seawater-derived B. Serpentine from the shallow-sourced Yinazao exhibits high Rb/Cs ratios of ≤37, highest concentrations of Li, but lowest Rb, Sr, Ba, and Cs contents. The serpentinizing fluids were derived from expulsion of sedimentary pore waters and by the breakdown of opal in the subducted sediments. Serpentine at the intermediate-sourced Fantangisna has Rb/Cs ratios of Including data from the South Chamorro serpentinite mud volcano (18 km slab depth; Kahl et al., 2015, Lithos), we provide a detailed record of slab dehydration reactions at shallow forearc depths and the related mobilization of FMEs as well as their transport into the mantle wedge. Our study demonstrates that slab-derived fluids undergo extensive alteration during the interaction with mantle wedge peridotite. Pore waters from the serpentinite mud volcanoes hence provide incomplete insight into the processes at depth; fluid signatures at the slab–wedge interface as well as their across-forearc changes are best recorded in early hydration products such as serpentine.

SummaryBackgroundDepression increases the risk of a range of adverse outcomes including suicide, premature mortality, and self-harm, but associations with violent crime remain uncertain. We aimed to determine the risks of violent crime in patients with depression and to investigate the association between depressive symptoms and violent crime in a cohort of twins.MethodsWe conducted two studies. The first was a total population study in Sweden of patients with outpatient diagnoses of depressive disorders (n=47 158) between 2001 and 2009 and no lifetime inpatient episodes. Patients were age and sex matched to general population controls (n=898 454) and risk of violent crime was calculated. Additionally, we compared the odds of violent crime in unaffected half-siblings (n=15 534) and full siblings (n=33 516) of patients with the general population controls. In sensitivity analyses, we examined the contribution of substance abuse, sociodemographic factors, and previous criminality. In the second study, we studied a general population sample of twins (n=23 020) with continuous measures of depressive symptoms for risk of violent crime.FindingsDuring a mean follow-up period of 3·2 years, 641 (3·7%) of the depressed men and 152 (0·5%) of the depressed women violently offended after diagnosis. After adjustment for sociodemographic confounders, the odds ratio of violent crime was 3·0 (95% CI 2·8–3·3) compared with the general population controls. The odds of violent crime in half-siblings (adjusted odds ratio 1·2 [95% CI 1·1–1·4]) and full siblings (1·5, 95% CI 1·3–1·6) were significantly increased, showing some familial confounding of the association between depression and violence. However, the odds increase remained significant in individuals with depression after adjustment for familial confounding, and in those without substance abuse comorbidity or a previous violent conviction (all p

The Almirez ultramafic massif (SE Spain) preserves the transformation of high-P antigorite (Atg-) serpentinite to chlorite (Chl-) harzburgite (1.6–1.9 GPa; 680–710 °C), a metamorphic reaction that is the primary source of water at the intermediate depth of subducting slabs. We present a detailed μ-CT and EBSD study of oriented samples across the Atg-serpentinite dehydration isograd to investigate the textural evolution during serpentinite dehydration to peridotite and its relation to stress orientations and the kinematics of subducting slabs. Above the Atg-out isograd, Atg-serpentinite shows a prograde mylonitic foliation and a weak Shape Preferred Orientation (SPO) of oxide aggregates defining a N—S stretching lineation. The antigorite Crystal Preferred Orientation (CPO) is characterized by [001]Atg perpendicular to the foliation, and the poles to (100)Atg and (010)Atg distributed in a girdle-like symmetry with [100]Atg nearly parallel to the stretching lineation. The antigorite microstructure and CPO are consistent with deformation by dislocation creep, twinning, and dissolution-precipitation creep. These textures record the long-term shear deformation near the slab interface where the main compressive stress, σ1, was at an acute angle to the foliation. Below the Atg-out isograd, Atg-serpentinite dehydrated to unfoliated, coarse-grainedChl-harzburgite with granofels or spinifex textures distributed in alternating decameter-sized lenses. Crystallization of granofels and spinifex Chl-harzburgite records, respectively, a sequence of slow and fast fluid draining events during serpentinite dehydration under the same orientation of the principal stresses that resulted in the shear deformation of the Atg-serpentinite. Both textural types exhibit coarse-grained textures with systematic mineral CPOs and SPOs and microstructures without evidence of major ductile deformation. The texture of the granofels Chl-harzburgite formed by a topotactic dehydration reaction after Atg-serpentinite coupled to compaction leading to an olivine layering subparallel to the Atg-serpentinite foliation. The olivines of granofels Chl-harzburgite are rounded and display a weak CPO that can be accounted for by the topotactic reaction 〈100〉Atg||〈100〉Ol and (001)Atg||(010)Ol after Atg-serpentinite. Similarly, orthopyroxene shows a marked CPO consistent with the topotactic reaction (100)Opx||(001)Atg and [001]Opx||[100]Atg. Spinifex Chl-harzburgite displays systematic mineral SPO and CPO. Spinifex olivines are tabular on (100)Ol and elongated along [001]Ol (c > b >> a), and define a ESE–WNW platelet lineation. The average texture is characterized by [001]Ol,Opx subparallel to a strong ESE–WNW oxide aggregate lineation, and [100]Ol,Opx and [001]Ol,Opx within a plane of similar orientation to the Atg-serpentinite foliation. The SPOs and CPOs of spinifex Chl-harzburgites are composed of up to four orientation populations of tabular olivines, where one population is volumetrically dominant in all samples. Relative to the main orientation population, the CPO of olivine shows clustered distribution of [100]Ol and [010]Ol maxima rotated at systematic angles around [001]Ol. These clustered CPOs and SPOs show a remarkable correlation with the orientation of the principal paleostresses. The preponderant orientation population of tabular olivines lies on the plane of maximum compression (σ2–σ3 plane) and has [010]Ol and its (100)Ol tabular faces nearly perpendicular to the Atg-serpentinite foliation. This population can be accounted for by oriented growth of platy crystals perpendicular to σ1. The other populations lie in the plane perpendicular to the least compressive stress (σ3) and the planes of maximum shear. The driving force and causes for the oriented crystallization of tabular olivine in these planes is uncertain, but their correlation with paleostresses suggests a cause-effect relationship. Spinifex and granofels Chl-harzburgites show a marked ESE–WNW oxide aggregate lineation that differs in orientation from that of Atg-serpentinite and is approximately parallel to the intermediate compressive stress (σ2). These lineations and the platelet lineation of spinifex Chl-harzburgite may be due to along-strike fluid flow below the permeability barrier that constituted the Atg-out dehydration isograd. Our study shows that the kinematics of the slab, paleostresses, and fluid flow exert a dynamic control on the textures of Atg-serpentinite dehydrating to peridotite in subducting slabs.

Thrombotic microangiopathies are rare, life-threatening diseaseswhose care involves physicians from multiple specialties. The past five years haveseen major advances in our understanding of the pathophysiology, classification,and treatment of these conditions. Their timely diagnosis and prompt treatment cansave lives.This review is based on pertinent articles published up to 17 December2017 that were retrieved by a selective search of the National Library of Medicine'sPubMed database employing the terms "thrombotic microangiopathy," "thromboticthrombocytopenic purpura," "hemolytic-uremic syndrome," "drug-induced TMA," and"EHEC-HUS."The classic types of thrombotic microangiopathy are thrombotic thrombo -cytopenic purpura (TTP) and typical hemolytic-uremic syndrome (HUS), also knownas enterohemorrhagic Escherichia coli-associated HUS (EHEC-HUS). There are anumber of further types from which these must be differentiated. The key test,beyond a basic hematological evaluation including a peripheral blood smear, ismeasurement of the blood level of the protease that splits von Willebrand factor,which is designated ADAMTS13 (a disintegrin and metalloprotease with thrombo -spondin type 1 motif, member 13). The quantitative determination of ADAMTS13, ofADAMTS13 activity, and of the ADAMTS13 inhibitor serves to differentiate TTP fromother types of thrombotic microangiopathy. As TTP requires urgent treatment,plasmapheresis should be begun as soon as TTP is suspected on the basis of afinding of hemolysis with schistocytes and thrombocytopenia. The treatment shouldbe altered as indicated once the laboratory findings become available.Rapid differential diagnosis is needed in order to determine the specifictype of thrombotic microangiopathy that is present, because only patients with TTPand only a very small percentage of those with atypical hemolytic-uremic syndrome(aHUS) can benefit from plasmapheresis. The establishment of a nationwideregistry in Germany with an attached biobank might help reveal yet unknowngenetic predispositions.

Serpentine seamounts located on the outer half of the pervasively fractured Mariana forearc provide an excellent window into the forearc devolatilization processes, which can strongly influence the cycling of volatiles and trace elements in subduction zones. Serpentinized ultramafic clasts recovered from an active mud volcano in the Mariana forearc reveal microstructures, mineral assemblages and compositions that are indicative of a complex polyphase alteration history. Petrologic phase relations and oxygen isotopes suggest that ultramafic clasts were serpentinized at temperatures below 200 °C. Several successive serpentinization events represented by different vein generations with distinct trace element contents can be recognized. Measured in situ Rb/Cs ratios are fairly uniform ranging between 1 and 10, which is consistent with Cs mobilization from sediments at lower temperatures and lends further credence to the low-temperature conditions proposed in models of the thermal structure in forearc settings. Late veins show lower fluid mobile element (FME) concentrations than early veins, suggesting a decreasing influence of fluid discharge from the subducting slab on the composition of the serpentinizing fluids. The continuous microfabric and mineral chemical evolution observed in the ultramafic clasts may have implications as to the origin and nature of the serpentinizing fluids. We hypothesize that opal and smectite dehydration produce quartz-saturated fluids with high FME contents and Rb/Cs between 1 and 4 that cause the early pervasive serpentinization. The partially serpentinized material may then be eroded from the basal plane of the suprasubduction mantle wedge. Serpentinization continued but the interacting fluids did not carry a pronounced sedimentary signature, either because FMEs were no longer released from the slab, or due to an en route loss of FMEs. Late chrysotile veins that document the increased access of fluids in a now fluid-dominated regime are characterized by reduced trace element contents with a slightly increased Rb/Cs ratio near 10. This lack of sediment-dominated geochemical signatures consistently displayed in all late serpentinization stages may indicate that the sediment-derived fluids have been completely reset (i.e. the FME excesses were removed) by continued water–rock reaction within the subduction channel. The final stage of buoyant rise of matrix and clasts in the conduits is characterized by brucite-dominated alteration of the clasts from the clast rim inward (independent of the intra-clast fabric relations), which corresponds to re-equilibration with alkaline, low-silica activity fluids in the rising mud.

The exposure of mantle peridotite to water at crustal levels leads to a cascade of interconnected dissolution-precipitation and reduction-oxidation reactions—a process referred to as serpentinization. These reactions have major implications for microbial life through the provision of hydrogen (H 2 ). To simulate incipient serpentinization under well-constrained conditions, we reacted centimeter-sized pieces of uncrushed harzburgite with chemically modified seawater at 300 oC and 35 MPa for ca. 1.5 yr (13 441 h), monitored changes in fluid chemistry over time, and examined the secondary mineralogy at the termination of the experiment. Approximately 4 mol% of the protolith underwent alteration forming serpentine, accessory magnetite, chlorite, and traces of calcite and heazlewoodite. Alteration textures bear remarkable similarities to those found in partially serpentinized abyssal peridotites. Neither brucite nor talc precipitated during the experiment. Given that the starting material contained ~4 times more olivine than orthopyroxene on a molar basis, mass balance requires that dissolution of orthopyroxene was significantly faster than dissolution of olivine. Coupled mass transfer of dissolved Si, Mg, and H + between olivine and orthopyroxene reaction fronts was driven by steep activity gradients and facilitated the precipitation of serpentine. Hydrogen was released in significant amounts throughout the entire experiment; however, the H 2 release rate decreased with time. Serpentinization consumed water but did not release significant amounts of dissolved species (other than H 2 ) suggesting that incipient hydration reactions involved a volume increase of ~40%. The reduced access of water to fresh olivine surfaces due to filling of fractures and coating of primary minerals with alteration products led to decreased rates of serpentinization and H 2 release. While this concept might seem at odds with completely serpentinized seafloor peridotites, reaction-driven fracturing offers an intriguing solution to the seemingly self-limiting nature of serpentinization. Indeed, the reacted sample revealed several textural features diagnostic of incipient reaction-driven fracturing. We conclude that fracturing must have far reaching impacts on the rates of serpentinization and H 2 release in peridotite-hosted hydrothermal systems.

Serpentinization of mantle peridotite generates molecular hydrogen that can be exploited by microorganisms to gain metabolic energy; however, the mechanisms that control hydrogen generation and magnetite formation during serpentinization remain poorly understood. We have examined partly to completely serpentinized peridotites recovered during the Ocean Drilling Program and find a remarkable variation in the abundance of magnetite. Some completely serpentinized peridotites have as much as 6.15 wt% magnetite, whereas others are nearly magnetite free (

Petrophysical experiments, using acoustic velocities to characterise anisotropies of mechanical behaviour of rocks are of essential relevance to understand the geomechanical behaviour of sandstone reservoirs under changing stress fields. Here, we present high-resolution X-ray microtomography (μ-CT) as a supplementary research tool to interpret anisotropic ultrasound velocities in sandstones with variation of isotopic stress. Specimens of two Lower Cretaceous sandstones (localities Bentheim and Obernkirchen, both Germany) have been used in petrophysical laboratory experiments under dry conditions to study ultrasonic sound velocities (frequency of signal input 1 MHz). Subsequently, oriented micro-plugs drilled from the sandstone samples were investigated using high-resolution X-ray microtomography. By means of image processing of the reconstructed scan images, geometric attributes such as mean structural thickness, orientation and tortuosity were evaluated from the μ-CT data for both pore space and grain skeleton. Our observations clearly indicate the different roles of pore space and grain skeleton in regard to the propagation of ultrasonic waves: because the pores do not transmit the waves, it was sufficient to investigate the average thickness of this fabric element. In contrast, as the ultrasonic waves traverse the rock via the adjacent grains, it was necessary to survey the actual travel lengths of seismic waves in the sandstone grain skeleton.

The range of substrates that the bone-eating marine worm Osedax is able to consume has important implications for its evolutionary history, especially its potential link to the rise of whales. Once considered a whale specialist, recent work indicates that Osedax consumes a wide range of vertebrate remains, including whale soft tissue and the bones of mammals, birds and fishes. Traces resembling those produced by living Osedax have now been recognized for the first time in Oligocene whale teeth and fish bones from deep-water strata of the Makah, Pysht and Lincoln Creek formations in western Washington State, USA. The specimens were acid etched from concretions, and details of the borehole morphology were investigated using micro-computed tomography. Together with previously published Osedax traces from this area, our results show that by Oligocene time Osedax was able to colonize the same range of vertebrate remains that it consumes today and had a similar diversity of root morphologies. This supports the view that a generalist ability to exploit vertebrate bones may be an ancestral trait of Osedax. peerReviewed