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Upland peat soils in close proximity to urban and industrial areas can be contaminated with high concentrations of atmospherically deposited lead. The peat soils of the Peak District (UK) are characterised by extensive eroding gullies. Fine-resolution digital topographic data were used to map the extent and depth of these gullies. Peat samples from eroding gully walls and suspended sediments were collected and analysed for lead content. Variability in lead concentrations of gully wall material and suspended sediments can be explained by differences in mean upslope gully depth. The lead content of suspended sediment exported from catchments characterised by shallow peat gullies is higher than that exported from catchments with deep peat gullies. The empirical relationship between sediment-associated lead concentration and mean upslope gully depth was combined with the gully depth mapping to produce a predictive spatial model of suspended sediment lead concentrations across the Peak District. This model may be particularly useful for catchment managers who are currently involved in the restoration of eroding peat soils in the Peak District uplands.

Compared with Phanerozoic strata, sulfate minerals are relatively rare in the Precambrian record; this is probably due to the lower concentrations of sulfate in dominantly anoxic oceans. Here, we present a compilation of sulfate minerals that are stratigraphically associated with the Ediacaran Shuram excursion (SE) – the largest negative δ13C excursion in Earth history. We evaluated 15 SE sections, all of which reveal the presence of sulfate minerals and/or enriched carbonate-associated sulfate concentrations, suggesting a rise in the sulfate reservoir. Notably, where data are available, the SE also reveals considerable enrichments in [Ba] relative to pre- and post-SE intervals. We propose that elevated seawater sulfate concentrations during the SE may have facilitated authigenesis of sulfate minerals. At the same time, the rise in Ba concentrations in shelf environments further facilitated barite deposition. A larger sulfate reservoir would stimulate microbial sulfate reduction and anaerobic oxidation of organic matter (including methane), contributing to the genesis of the SE. The existence of sulfate minerals throughout the SE suggests that oxidant pools were not depleted at that time, which challenges previous modelling results. Our study highlights the dynamic interplay of biogeochemical C, S and Ba cycles in response to the Shuram oxygenation event. Supplementary material: SEM and EDS data and figures S1-S4 and tables S1-S3 are available at: https://doi.org/10.6084/m9.figshare.c.5602560 Thematic collection: This article is part of the ‘Sulfur in the Earth system’ collection available at: https://www.lyellcollection.org/cc/sulfur-in-the-earth-system

Abstract The physical characteristics and impermeability of diamonds allow them to retain radiogenic 4He produced in-situ from radioactive decay of U, Th and Sm. This study investigates the U-Th/He systematics of fibrous diamonds and provides a first step in quantification of the uncertainties associated with determining the in-situ produced radiogenic 4He concentration. Factors determining the total amount of measured helium in a diamond are the initial trapped 4He, the in-situ produced radiogenic 4He, α-implantation, α-ejection, diffusion, and cosmogenic 3He production. Alpha implantation is negligible, and diffusion is slow, but the cosmogenic 3He component can be significant for alluvial diamonds as the recovery depth is unknown. Therefore, samples were grouped based on similar major and trace element compositions to determine possible genetically related samples. A correlation between the 4He and U-Th concentrations approximates the initial 4He concentration at the axis-intersect and age as the slope. In this study, the corrections were applied to eight fibrous cubic diamonds from the Democratic Republic of the Congo and two diamonds from the Jwaneng kimberlite in Botswana. A correlation exists between the 4He and U-Th concentrations of the group ZRC2, 3, and 6, and of the group CNG2, 3, and 4 and both correlations deviate significantly from a 71 Ma kimberlite eruption isochron. The U-Th/He dating method appears a promising new approach to date metasomatic fluid events that result in fibrous diamond formation and this is the first evidence that some fibrous diamonds can be formed 10s to 100s Myr before the kimberlite eruption.

Abstract The lithospheric mantle underpinning the Alto Paranaíba Igneous Province, southwestern São Francisco Craton, was investigated through a study of 82 diamonds and their mineral inclusions from the Coromandel (Douradinho River), Verde River (northern Coromandel), Abaeté, Frutal, and Romaria deposits. Mineral inclusion abundances show that lherzolite is the main diamond source-rock, followed by eclogite, harzburgite and minor websterite. The limited chemical depletion recorded in lherzolitic inclusions suggests a post-Archean origin or modification of the lithospheric mantle beneath this part of the São Francisco craton. Sinusoidal rare earth element patterns for lherzolitic garnet inclusions indicate variable but overall low degrees of metasomatism by fluids or silico‑carbonatitic (proto-kimberlitic) melts. These results contrast with previous studies on mineral inclusions in diamonds (Canastra range, southern Coromandel; Rio da Prata system, northeastern Coromandel; our new data on the Frutal area, southwestern Coromandel), where a dominance of harzburgitic inclusions documents a more depleted, likely Archean, cratonic root. Bulk rock compositions reconstructed from eclogitic and websteritic inclusions establish a clear link between subduction processes and diamond formation in the Coromandel region. Calculated bulk rare earth element patterns match typical sections of upper oceanic crust, where plagioclase accumulation is uncommon. Pyroxene inclusion-based geothermobarometry indicates that lherzolitic and websteritic diamonds formed and last resided along a ∼ 39 mW/m2 model geotherm. Projection of eclogitic garnet-clinopyroxene pairs onto this 39 mW/m2 geotherm places their origin near the base of the lithosphere (> 180 km depth). Low nitrogen contents and high aggregation states (up to 100 %B) indicate that eclogitic, websteritic, and part of the lherzolitic diamond populations experienced extended (2.0 Byr) mantle residence at high temperatures (> 1200 °C). The similarity in mantle residence temperatures and the shared presence of minor negative Eu anomalies for eclogitic and websteritic diamonds and their inclusions may be indicative of a common origin, following emplacement of subducted oceanic crust beneath the São Francisco Craton margin likely during a Paleoproterozoic orogeny (2.2–1.9 Ga). Based on our results, future exploration efforts in the Alto Paranaíba region should shift their focus from harzburgitic to lherzolitic and eclogitic indicator minerals to find new diamond deposits and kimberlites in this area.

The continental Pleistocene Laurentide Ice Sheet (LIS) had far-reaching marine influence in shaping the ocean-floor adjacent to ice margin. The basinwide submarine-canyon and deep-sea channel system of the Northwest Atlantic Mid-Ocean Channel (NAMOC) of the Labrador Sea is the submarine continuation of the drainge system of the LIS on land, forming an interconnected land/sea drainage system 6,000 km long, one of the word’s longest drainage systems of Pleistocene age. The submarine portion forms a dual system, consisting of the mud-dominated NAMOC with its tributaries and a submarine sandy braid-plain.

Studies on metal contamination in 25 de Mayo Island, Antarctica, yielded controversial results. In this work, we analyzed Antarctic marine sediments and Antarctic clam (Laternula elliptica) tissues to investigate the possible use of this mollusk as a biomonitor of metals and to identify the sources of metal pollution. Different types of paint from several buildings from Carlini Station were examined to assess their contribution to the local and random metal pollution. Five sediment samples, 105 L. elliptica specimens (40.2-78.0mm length) and four types of paint were analyzed to quantify Cd, Cr, Cu, Fe, Mn, Pb and Zn using inductively coupled plasma-optical emission spectrometry. Metal concentrations in sediments were lower than the global averages of the earth's crust, with the exception of Cd and Cu. These results were related to the contribution of the local fresh-water runoff. The different varieties of paint showed low levels of Cu, Mn, Fe and Zn, whereas a broad range of values were found in the case of Cr and Pb (20-15,100μg·g-1 and 153-115,500μg·g-1 respectively). The remains of the paint would be responsible for the significant increases in Cr and Pb which are randomly detected by us and by other authors. High levels of Fe and Cd, in comparison to other Antarctic areas, appear to be related to the terrigenous materials transported by the local streams. Accumulation indexes suggested that kidney tissue from L. elliptica could be an adequate material for biomonitoring pollution with Cd, Zn and probably also Pb. In general, relationships between size and metal contents reported by other authors were not verified, suggesting that this issue should be revised. elliptica could be adequate for biomonitoring pollution with Cd and Zn. Fil: Vodopivez, Leopoldo Cristian. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina Fil: Curtosi, Antonio. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina Fil: Villaamil Lepori, Edda Cristina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentina Fil: Smichowski, Patricia Nora. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Pelletier, Emilien. Université du Québec à Rimouski; Canadá Fil: Mac Cormack, Walter Patricio. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; Argentina

A subvertical gold-bearing Quartz-Fuchsite vein at the Dome mine, Timmins area, is located in a highly carbonatized rock at the contact with a unit of slate. The chemical composition (anhydrous basis) of the wall rock of the vein and diagnostic interelement relations indicate that its protolith is a komatiite. Intense carbonatization of the ultramafic rock was accompanied by gains in K 2 O, CaO, Rb, Sr, Ba, Au, As, and Sb, and by loss of H 2 O. Two distinct alteration stages can be recognized in the wall rock: an initial pervasive carbonatization of the komatiitic protolith, and a later, more intense fuchsite-pyrite alteration centered on a quartz-feldspar porphyry lens located in the zone of the carbonatized rock. Apart from shallower levels, no distinct alteration envelope is developed about the Quartz-Fuchsite vein, which actually lies in the least altered komatiite. This suggests that the vein-forming fluid was essentially at thermal and compositional equilibrium with local wall rocks. The Quartz-Fuchsite vein is interpreted as an integral part of a progressive wall-rock alteration sequence generated during regional compressive deformation. Early carbonate replacement reaction resulted in a drastic reduction of permeability in the komatiite. As a consequence, the vertical hydrothermal fluid flow became progressively confined to the less reactive quartz-feldspar porphyries, and a high pore fluid pressure regime was built up in the carbonatized komatiite, creating favorable conditions for hydraulic fracture and eraplacement of the Quartz-Fuchsite vein near the slate-komatiite contact. This metasomatically and structurally induced conduit provided a favorable drain for pumping fluids from depth and from adjacent wall rocks. Gold introduction is genetically related to the late fuchsite-pyrite alteration event.

Abstract The MIPAS spectrometer onboard the Envisat platform observed infrared emission from the Earth's limb between 2002 and 2012. It recorded high-resolution spectra during day and night, from pole to pole and between 6 and 70 km altitude in the nominal measurement mode or up to 170 km in special measurement modes, producing daily more than 1000 vertical profiles of various trace gases. The operational Level-2 data are processed by ESA/DLR but there exist three other, independent research Level-2 processors that are hosted by ISAC-CNR/University of Bologna, Oxford University, and KIT IMK/IAA. All four Level-2 processors rely on the same Level-1b data provided by ESA but their retrieval schemes differ. As part of ESA's Ozone Climate Change Initiative project, an intercomparison of the four MIPAS processors took place, in which vertical ozone profiles retrieved by these four processors from MIPAS nominal mode measurements were compared for 2007 and 2008. We present the results of this comparison exercise, which consisted of five parts: an information content study of the vertical averaging kernels, an intercomparison of zonal seasonal means and spreads, a determination of biases through comparison to ozonesonde and lidar measurements, a comparison to other satellite records (bias estimation and precision assessment with respect to ACE-FTS and Aura-MLS data), and a geophysical validation of the provided error bars using MIPAS–MIPAS collocations. The four processors demonstrate similar performance. All processors use the same Level-1b data from ESA, apply global fits, and use microwindows instead of the full spectrum. The main differences in the processing schemes include the choice of microwindows, the regularization approach, the treatment of negative retrieved values, and the cloud detection threshold. The different regularization schemes lead to a different trade-off between noise and resolution, but without a clear average advantage for any particular data set. The vertical resolution is typically 3–5 km and the single profile precision is about 2–3%. In the middle and upper stratosphere, at 25–45 km, all four MIPAS processors clearly show a high bias of 2 to 5% relative to all reference instruments. The similarity of the structure and magnitude of the bias among the MIPAS data sets indicates that the bias is most likely linked to the use of microwindows of the MIPAS AB band. The satellite intercomparisons show furthermore that for the KIT dataset, the onset of the high bias starts at a somewhat higher altitude (only above 35 km) than for the other three datasets. This is likely due to the more restrictive use of the AB band by the KIT processor, which comes at the cost of a coarser vertical resolution near the ozone volume mixing ratio (vmr) peak. In the troposphere, the Level-2 algorithms that suppress negative ozone values in the iterative retrieval process produce a larger positive bias than the algorithm that does not follow such a strategy. Our main conclusion is that the four MIPAS processors are more similar to each other than to any other reference instrument. This indicates that the observed biases are very likely instrument-related.

Local gold concentrations are found in laterally extensive pyrite-bearing, framework-supported, cobble and boulder conglomerates in the basal 30 m of the Mississagi Formation in the south eastern part of the Huronian outcrop belt. These were deposited as part of a valley-fill succession, in shallow gravel-bed braided rivers with local hyperconcentrated flows. The basal contact with underlying Archean psammites is typically highly irregular and shows no obvious sign of weathering suggesting that deposition took place soon after retreat of the glaciers responsible for deposition of the Ramsey Lake Formation. Highest gold concentrations are associated with moderately well-sorted medium to large pebble conglomerate that show some signs of reworking during low flow events. Depositional elements are typically lenticular and of limited lateral extent. Unlike the older pyritic quartz-pebble conglomerates at the base of the Matinenda Formation in the Elliot Lake and Blind River areas, these conglomerates contain no uraninite and are polymict with material derived from a highly restricted catchment area with marked local and regional topographic relief. Porous detrital allogenic pyrite and euhedral post-depositional pyrite have overlapping, generally positive δ34S values, indicating a closed system during diagenesis and metamorphism. The presence of biotite-enriched rims on many of the metavolcanic and metasedimentary clasts in the conglomerates suggests that gold was partly leached from the allogenic pyrite grains at the peak of the Penokean Orogeny at 1.85–1.5 Ga. The potential source of the Au-bearing detrital allogenic pyrite appears to be an as yet undiscovered Archean volcanic-hosted massive sulfide (VHMS) deposit located 1 to 8 km north of the deposit.

The Mesozoic Marine Revolution (MMR) was a major evolutionary episode involving the large-scale restructuring of shallow-marine benthic communities and the rise to dominance of the Modern Evolutionary Fauna. Although the majority of studies published on the MMR have been based on the body-fossil record, the ichnologic record yields valuable insights into this evolutionary event, most notably regarding the degree of infaunalization, complexity of infaunal tiering structures, and predation intensity. The main groups of bioturbators involved in the MMR were crustaceans, bivalves, echinoids, and “worms,” whereas the most important bioeroders were sponges, gastropods, bivalves, echinoids, and “worms.” The Triassic, encapsulated between two major mass extinctions, can be regarded as setting the stage for the MMR. The sparse ichnologic information available suggests that full recovery from the end-Permian mass extinction had taken place in equatorial carbonate settings by the Middle Triassic, although ichnofaunas show limited infaunalization and relatively simple tiering structures. However, a few key players, most notably some decapod crustaceans, were already dominant in carbonate settings. Jurassic ichnofaunas reveal a compositional turnover, signaling the rise to dominance of the Modern Evolutionary Fauna. This faunal turnover occurred by the Early Jurassic, as indicated by the taxonomic composition and increased diversity of bioturbation structures and the complexity of infaunal tiering. During the Cretaceous, a continuation of the trends established in the Jurassic was recorded. However, by the end of the Cretaceous, a modern-style benthic–pelagic coupling pattern was established, accompanied by an increase in global ichnodiversity. Rapid development of coccolithophores provided a new substrate (chalk) and an increasing flux of organic matter to the seafloor, enabling establishment of complex tiering structures, unknown in older deposits. The degree of macrobioerosion indicates an increasing participation of some players typical of modern communities. Paleogene bioturbation structures are similar to those of the late Mesozoic. Macrobioerosion styles also persisted across the Cretaceous–Paleogene boundary, albeit with an increased role for bioerosion by sponges and fishes later in the Paleogene. Predation pressures (drilling and durophagy) increased during the Eocene. Ichnofaunas in shallow-marine sediments record continued expansion of diversity during the Neogene, as well as more complex tiering structures. Predation pressure continued to rise, involving primarily marine mammals. Although the MMR for the most part took place in shallow, fully marine settings, the trace-fossil record also provides evidence for its expression in the deep sea and marginal-marine, brackish-water settings. Irregular echinoids and decapod crustaceans apparently had migrated to the deep sea by the Late Jurassic, whereas most of the main players of the MMR in fully marine settings (e.g., decapod crustaceans, bivalves, worms) were also dominant in brackish-water settings since the beginning of this major evolutionary event. Trace-fossil data indicate that infaunalization predates an increase of predation pressures by approximately 50 Myr, suggesting a complex set of feedback mechanisms between predation and infaunalization rather than simple cause and effect between the two. Turnover in ichnofaunal composition and the increased infaunalization that took place during the MMR strongly supports the “bulldozing hypothesis” (the notion that biological disturbance increased through the Phanerozoic), indicating a dramatic rise in bioturbational sediment processing by elements of the Modern Evolutionary Fauna. Fil: Buatois, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. University of Saskatchewan; Canadá Fil: Carmona, Noelia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; Argentina Fil: Curran, H. Allen. Smith College. Department of Geosciences; Estados Unidos Fil: Netto, Renata G.. Universidad de Vale do Rio dos Sinos; Brasil Fil: Mangano, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. University of Saskatchewan; Canadá Fil: Wetzel, Andreas. Universität Basel. Geologisch-Paläontologisches Institut; Suiza