Abstract The Paleocene-Eocene Thermal Maximum (PETM) was an abrupt global warming event associated with a large injection of carbon into the ocean-atmosphere system, as evidenced by a diagnostic carbon isotope excursion (CIE). Evidence also suggests substantial hydrologic perturbations, but details have been hampered by a lack of appropriate proxies. To address this shortcoming, here we isolate and measure the isotopic composition of hydroxyl groups (OH − ) in clay minerals from a highly expanded PETM section in the North Sea Basin, together with their bulk oxygen isotope composition. At this location, we show that hydroxyl O- and H-isotopes are less influenced than bulk values by clay compositional changes due to mixing and/or inherited signals and thus better track hydrologic variability. We find that clay OH − hydrogen-isotope values (δ 2 H OH ) decrease slowly prior to the PETM and then abruptly by ∼8‰ at the CIE onset. Coincident with an increase in relative kaolinite content, this indicates increased rainfall and weathering and implies an enhanced hydrologic cycle response to global warming, particularly during the early stages of the PETM. Subsequently, δ 2 H OH returns to pre-PETM values well before the end of the CIE, suggesting hydrologic changes in the North Sea were short-lived relative to carbon-cycle perturbations.
Mafic igneous rocks, such as basalt, are composed of abundant calcium-and magnesium-rich silicate minerals widely proposed to be suitable for scalable carbon dioxide removal (CDR) by enhanced rock weathering (ERW).Here, we report a detailed characterization of the mineralogy, chemistry, particle size and surface area of six mined basalts being used in large-scale ERW field trials.We use 1-D reactive transport modelling (RTM) of soil profile processes to simulate inorganic CDR potential via cation flux (Mg 2+ , Ca 2+ , K + and Na + ) and assess the release of the essential plant nutrients phosphorus (P) and potassium (K) for a typical clay-loam agricultural soil.The basalts are primarily composed of pyroxene and plagioclase feldspar (up to 71 wt%), with accessory olivine, quartz, glass and alkali feldspar.Mean crushed particle size varies by a factor of 10, owing to differences in the mining operations and grinding processes.RTM simulations, based on measured mineral composition and N 2 -gas BET specific surface area (SSA), yielded potential CDR values of between c. 1.3 and 8.5 t CO 2 ha -1 after 15 years following a baseline application of 50 t ha -1 basalt.The RTM results are comparative for the range of inputs that are described and should be considered illustrative for an agricultural soil.Nevertheless, they indicate that increasing the surface area for slow-weathering basalts through energy intensive grinding prior to field application in an ERW context may not be warranted in terms of additional CDR gains.We developed a function to convert CDR based on widely available and easily measured rock chemistry measures to more realistic determinations based on mineralogy.When applied to a chemistry dataset for >1300 basalt analyses from 25 large igneous provinces, we simulated cumulative CDR potentials of up to c. 8.5 t CO 2 ha -1 after 30 years of weathering, assuming a single application of basalt with a SSA of 1 m 2 g -1 .Our RTM simulations suggest that ERW with basalt releases sufficient phosphorus (P) to substitute for typical arable crop P-fertiliser usage in Europe and the USA offering potential to reduce demand for expensive rock-derived P.
In 2019, BYK Additives (Widnes, UK; www.byk.com ) marked the 55th anniversary of the discovery by Dr Barbara Zsusanna (Susanna) Neumann of the extraordinary product known as Laponite®. The range of Laponite® products developed in the UK during the early 1960s is one of the first examples of truly nanodimensional materials manufactured on an industrial scale, at a time when the field of nanotechnology was only being hinted at (Feynman, 1959). These hectorite-like synthetic nanoclays with very unusual properties have been an enduring commercial success for the UK company that first patented and introduced them to the market, Laporte Industries, which is now a part of the BYK company. The Laponite® brand has proved tremendously popular with academic and industrial scientists worldwide, being cited in >3000 patents and >2500 published academic articles.
Abstract Temporary excavations during the construction of the Glendoe Hydro Scheme above Loch Ness in the Highlands of Scotland exposed a clay-rich fault gouge in Dalradian Supergroup psammite. The gouge coincides with the mapped trace of the subvertical Sronlairig Fault, a feature related in part to the Great Glen and Ericht–Laidon faults, which had been interpreted to result from brittle deformation during the Caledonian orogeny ( c. 420–390 Ma). Exposure of this mica-rich gouge represented an exceptional opportunity to constrain the timing of the gouge-producing movement on the Sronlairig Fault using isotopic analysis to date the growth of authigenic (essentially synkinematic) clay mineralization. A series of fine-size separates was isolated prior to K–Ar analysis. Novel, capillary-encapsulated X-ray diffraction analysis was employed to ensure nearly perfect, random orientation and to facilitate the identification and quantification of mica polytypes. Coarser size fractions are composed of greater proportions of the 2 M 1 illite polytype. Finer size fractions show increasing proportions of the 1 M illite polytype, with no evidence of 2 M 1 illite in the finest fractions. A series of Illite Age Analysis plots produced excellent R 2 values with calculated mean ages of 296 ± 7 Ma (Late Carboniferous–Early Permian) for the oldest (2 M 1 ) illite and 145 ± 7 Ma (Late Jurassic–Early Cretaceous) for the youngest (1 M ) illite. The Late Carboniferous–Early Permian (Faulting event 1) age may represent resetting of earlier-formed micas or authigenesis during dextral displacement of the Great Glen Fault Zone (GGFZ). Contemporaneous WNW(NW)–ESE(SE) extension was important for basin development and hydrocarbon migration in the Pentland Firth and Moray Firth regions. The Late Jurassic–Early Cretaceous (Faulting event 2) age corresponds with Moray Firth Basin development and indicates that the GGFZ and related structures may have acted to partition the active extension in the Moray Firth region from relative inactivity in the Pentland Firth area at this time. These new age dates demonstrate the long-lived geological activity on the GGFZ, particularly so in post-Caledonian times where other isotopic evidence for younger tectonic overprints is lacking.
Abstract Uraniferous particles from contaminated environmental samples were analysed by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDXA) and microfocus extended X-ray absorption fine structure (mEXAFS) spectroscopy. The particles of interest are uranium oxides, which were released into the environment by the combustion of scrap depleted uranium (DU) metal at a factory in Colonie, New York, USA. Most of the identified particles appear to have primary, ‘as emitted’ morphologies; some have evidence of minor dissolution, including corrosion pitting. Polycrystalline and often hollow microscopic spheres were identified, which are similar to particles produced by DU munitions impacting armoured targets. They are attributed to the autothermic oxidation of melt droplets. The compositions of the analysed spheres are dominated by UO 2+x with variable amounts of U 3 O 8 , two of the least soluble and least bioaccessible phases of U. These particles, collected from dusts and soils, have survived more than 25 y in the terrestrial environment. This study further supports the case for using Colonie as an analogue for battlefield DU contamination.
<p>Volcanoes in island arcs can undergo edifice evolution that includes submarine and subaerial volcanism, providing a dynamic environment of magmatic heat and volatiles that drives hydrothermal fluid flow with potential inputs from sea and/or meteoric water. This, in turn, can generate significant hydrothermal alteration that can result in economic deposits of industrial minerals. One example includes bentonite, a smectitic rock composed dominantly of montmorillonite.</p><p>Economically viable bentonite deposits are typically only 0.5 &#8211; 5 meters thick and<strong> </strong>although Wyoming-type bentonites comprise 70% of the world&#8217;s known deposits, they are commonly no thicker than 8 m. The island of Milos is Europe&#8217;s largest and actively mined calcium bentonite resource from volcanic piles exceeding 80 m thickness. Here, we use the Milos island example to understand how magmatism, volcanic edifice evolution and hydrothermal activity interact. We integrate field relationships of volcanic stratigraphy and alteration zones, with clay mineralogy (XRD), stable (S, O and H) isotope analysis and high precision geochronology (CA-ID-TIMS zircon U-Pb, and alunite Ar-Ar) to elucidate the timescales, thermal drivers and fluid components that lead to the development of a globally important bentonite resource.</p><p>A vertical transect through bentonite-altered volcanic stratigraphy indicates multiple magmatic pulses ca. 2.8 Ma with a submarine andesitic cryptodome and accompanying pepperitic hyaloclastite. Cumulative volcanic and sub-volcanic processes occurred over ca. 170 kyrs, resulting in a vertically and laterally extensive volcanic pile overlain by an episode of magmatic quiescence and brackish-water diatomaceous sediments. It is overlain by a silicic pyroclastic flow host to pervasive silica-alunite-kaolinite alteration. Stable isotopic analyses of bentonite indicate a hydrothermal origin at around 70&#176;C with the fluid being sourced from sea and meteoric waters. The timing of formation is defined by a maximum duration of ca. 170 kyrs, with clear geological evidence that a significant period of alteration occurred within < 20 kyrs at ~ 2.64 Ma. Alunite sulfur isotope compositions reflect steaming ground activity that could be interpreted as the oxidised, shallower level counterpart to a boiling geothermal system linked to development of extensive bentonite. However, the timing of alunite can be clearly resolved to > 1.5 myrs after bentonite formation to ~ 1.0 Ma, supporting a later overprint origin due to relatively recent steam heating of groundwater after emergence of the submarine system.</p><p>This study identifies key parameters that have resulted in the formation of an economic-scale bentonite resource on the emergent island of Milos. We conclude that the hydrology needed to form a bentonite deposit is not constrained to the marine environment and can be connected to emergent parts of the volcanic edifice. High precision geochronology indicates bentonite development happens on volcanic timescales (10 to 100 kyrs). A cumulative volcanic and sub-volcanic pile coeval with the formation of bentonite suggests multiple magmatic episodes over narrow timeframes provide and sustain the thermal driver for significant bentonite development. After emergence and development of a groundwater system, the subsequent steam heating is deleterious to grade and results in the development of alunite-kaolinite overburden.</p>
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