Remnants of arc-related Mesoarchaean oceanic crust in the Tartoq Group of SW Greenland

The Tartoq Group, located in SW Greenland, consists of supracrustal rocks of mainly tholeiitic basaltic composition, including pillow lavas, sills/dykes and gabbros, as well as ultramafic rocks. Metamorphic grade ranges from greenschist facies to granulite facies. The Tartoq Group crops out as a series of blocks and slivers that are imbricated with originally intrusive Mesoarchaean TTG orthogneisses. The supracrustal rocks form part of a SE vergent fold and thrust belt consistent with the imbrication of TTG gneisses and supracrustal rocks along a convergent margin. LA-ICP-MS U–Pb zircon dating of an intrusive TTG sheet yields a minimum age of 2986 ± 4 Ma for the Tartoq Group. This age is consistent with MC-ICP-MS Lu–Hf and Sm–Nd isotopic whole-rock data for mafic samples from different blocks of the Tartoq Group, which yield errorchron ages of 3189 ± 65 Ma and 3068 ± 220 Ma, respectively. The mafic supracrustal rocks of the Tartoq Group have chondrite-normalized REE patterns with La_CN/Sm_CN of 0.67–1.96 and rather flat primitive mantle-normalized multi-element patterns, except for scattered LILE contents, and generally negative Nb-anomalies with Nb/Nb* of 0.26–1.31. Th/Yb varies between 0.06 and 0.47 and Nb/Yb between 0.45 and 4.4 indicative of an arc affinity when compared to rocks from modern settings. The similar geochemistry of the different lithological units, together with their coeval formation, as evident from trace element geochemical trends, supports a co-magmatic origin for the rock assemblage and their formation as imbricated relics of oceanic crust. Accordingly, we propose that the Tartoq Group represents remnants of Mesoarchaean oceanic crust, which formed in a suprasubduction zone geodynamic environment.     

Assessing hyporheic exchange and associated travel times by hydraulic, chemical, and isotopic monitoring at the Steinlach Test Site, Germany

First results of a multi-disciplinary hyporheic monitoring study are presented from the newly established Steinlach Test Site in Southern Germany. The site is located in a bend of the River Steinlach (mean discharge of 1.8 m³/s) underlain by an alluvial sandy gravel aquifer connected to the stream. The overall objective is a better understanding of hyporheic exchange processes at the site and their interrelations with microbial community dynamics and biochemical reactions at the stream–groundwater interface. The present paper focuses on the distribution of lateral hyporheic exchange fluxes and their associated travel times at the Steinlach Test Site. Water level dynamics in various piezometers correspond to the different domains of hydraulic conductivity in the shallow aquifer and confirms hyporheic exchange of infiltrated stream water across the test site. Hydrochemical compositions as well as increased damping of continuous time series of electrical conductivity (EC) and temperature at the respective piezometers confirmed the inferred distribution of hyporheic flowpaths. Mean travel times ranging from 0.5 days close to the stream to more than 8 days in the upstream part of the test site could be estimated from deconvolution of EC and δ¹⁸O–H₂O data. The travel times agree well with the presumed flowpaths. Mg/Ca ratios as well as model fits to the EC and δ¹⁸O data indicate the presence of an additional water component in the western part of the test site which most likely consists of hillslope water or groundwater. Based on the mean travel times, the total lateral hyporheic exchange flux at the site was estimated to be of the order of 1–2 L/s.     

Cadmium stable isotope cosmochemistry

Cadmium stable isotope compositions are reported for a comprehensive suite of carbonaceous, ordinary, enstatite, and Rumuruti chondrites as well as achondrites and lunar samples (soils, breccias, pristine anorthosite). The Cd isotope analyses were performed by multiple collector ICP-MS with an external reproducibility of ±0.43‰ (2 sd) for δ^114/110Cd. None of the samples shows evidence of nucleosynthetic anomalies and cosmogenic isotope effects from neutron-capture by ¹¹³Cd were only observed for two lunar samples.The Cd stable isotope compositions of type 1, 2, and some type 3 carbonaceous chondrites, EH4 enstatite chondrites, eucrites, and the Earth are essentially identical at δ^114/110Cd ≈ 0.0 ± 0.4. This suggests that the portion of the solar nebula from which the inner solar system bodies accreted was homogeneous with respect to its Cd isotope composition. It also indicates that the primary volatile element depletion of the inner solar system did not involve partial kinetic Rayleigh evaporation or condensation. Furthermore no resolvable Cd isotope effects were generated during the accretion and initial differentiation of the planetary bodies.In contrast, the analyses reveal large Cd isotope effects for ordinary and some enstatite chondrites, which display δ^114/110Cd values between about −8 and +16. Smaller fractionations are observed for the Rumuruti and some type 3 to 5 carbonaceous chondrites. These Cd isotope variations are thought to reflect secondary depletion or redistribution of Cd, due to open system thermal metamorphism on the meteorite parent bodies.One CAI and chondrule separates from the Allende meteorite have unexpectedly high Cd concentrations and fractionated light Cd isotope compositions with δ^114/110Cd ≈ −1 to −4. These characteristics may have been established by the interaction of originally Cd-poor materials with a volatile-rich gas prior to the final accretion of the Allende parent body. The general Cd enrichment of the lunar soil and regolith mainly reflects early volcanic activity. However, decreasing Cd abundances in lunar soils correlate well with an enrichment of the heavy Cd isotopes. This relationship is best explained by suppressed Rayleigh fractionation in response to space weathering.     

Hypocenter migration of fluid-induced earthquake swarms in the Tjörnes Fracture Zone (North Iceland)

The Tjörnes Fracture Zone separates Iceland's North Volcanic Zone from Kolbeinsey-Ridge (Greenland-Sea). Seismicity mainly occurs in swarms, often 100 and more per day, with similar waveforms and frequently offshore.We analysed three earthquake swarms between June and September 2004, recorded by 35 stations, i.e. the permanent Icelandic SIL network and a temporary setup of land and ocean-bottom-seismometers, and 5 swarms of the years 1994-1997 only using the sparser SIL network. Events occurring in the same swarm often show similar waveforms at the same station. We cross-correlated these time series by using a new approach of three component cross-correlation in order to relocate the hypocenters relative within the swarms and to precisely determine the direction and velocity of migration. Our method delivered good relocations with small spatial and temporal errors. This allows the interpretation and characterisation of the observed earthquake swarms. We try to classify observed migration velocities by comparing them to typical fluid- and crack-propagation velocities and determine focal-mechanisms and orientation of the best fitting plane through the hypocenter distribution.We separate the investigated events into two types of earthquake swarms, supposedly dike-induced and hydrothermally- or gas-induced swarms, by pointing out typical characteristics of both types and by comparing them to similar events of other volcanic regions. Based on different migration velocities, we will discuss possible mechanisms and their triggers of all single clusters within a swarm. Hypothetic models will be established, trying to explain the processes during the swarm episodes and to derive possible pre-eruptive patterns from the character of seismicity.     

Assessing Metal-Induced Changes in the Visible and Near-Infrared Spectral Reflectance of Leaves: A Pot Study with Sunflower (<Emphasis Type="Italic">Helianthus annuus</Emphasis> L.)

The aim of this study was to monitor changes in leaf spectral reflectance due to phytoaccumulation of trace elements (Cd, Pb, and As) in sunflower mutant (M5 mutant line 38/R4-R6/15-35-190-04-M5) grown in spiked and in situ metal-contaminated potted soils. Reflectance spectra (350–2500 nm) of leaves were collected using portable ASD spectroradiometer, and respective leaves sample were analyzed for total metal contents. The spectral changes were quite noticeable and showed increased visible and decreased NIR reflectance for sunflower grown in soil spiked with 900 mg As kg^?1, and in in situ metal-contaminated soils. These changes also involved a blue-shift feature of red-edge position in the first derivatives spectra, studied vegetation indices and continuum removed absorption features at 495, 680, 970, 1165, 1435, 1780, and 1925 nm wavelength. Correlograms of leaf-metal concentration and reflectance values show highest degrees of overall correlation for visible, near-infrared, and water-sensitive wavelengths. Partial least square and multiple linear regression statistical models (cross-validated), respectively, based on Savitzky–Golay filter first-order derivative spectra and combination of spectral feature such as vegetation indices and band depths yielded good prediction of leaf-metal concentrations.     

First Late Triassic Record of a Paleoentomofauna from South America(Malargüe Basin,Mendoza Province,Argentina)

<正>Late Middle Triassic to early Late Triassic insects from Argentina have been previously described from the Bermejo and Cuyana Basins where they have been recovered from the Ischichuca-Los Rastros and Potrerillos-Cacheuta Formations,respectively.The insect fauna discussed herein was collected during field studies in 1986/1987 from the Llantenes section(Norian to Rhaetian? Late Triassic),which is situated in the Malargue Basin in southern Mendoza province.The insect remains were found in the upper part of the Llantenes section (Llantenes Formation),which is built up of two coarsening-upwards cycles reflecting a deltaic progradation of a fluvial into a lacustrine environment(lower part),succeeded by repeated progradations into a floodplain-dominated environment(upper part;with finds of insects,conchostracans,fish remains,plant fragments,and drifted logs).The new finds represent the youngest Triassic insect records described from Argentina and even from South America in its entirety.There is only one contemporaneous fossil assemblage in Gondwana:in the Clarence/Moreton Basin(Aberdare Conglomerate;Late Norian)in Australia.The new Triassic insects include an impression of an isolated Mecopterida-like wing(Mendozachorista volkheimeri gen.et sp.nov.; Mendozachoristidae fam.nov.),coleopteran elytra of the Permosynidae(Ademosyne rosenfeldi sp.nov.and Ademosyne llantenesensis sp.nov.)and other isolated body fragments.This new Late Triassic entomofauna from Argentina is of considerable importance in the reconstruction of the biotic recovery of continental environments in Gondwana after the catastrophic mass extinction at the P/T boundary.     

A high field strength element perspective on early lunar differentiation

Lunar rocks are inferred to tap the different fossil cumulate layers formed during crystallisation of a lunar magma ocean (LMO). A coherent dataset, including Zr isotope data and high precision HFSE (W, Nb, Ta, Zr, Hf) and REE (Nd, Sm, Lu) data, all obtained by isotope dilution, can now provide new insights into the processes active during LMO crystallisation and during the petrogenesis of lunar magmas. Measured ⁹²Zr and ⁹¹Zr abundances agree with the terrestrial value within 0.2 ε-units. Incompatible-trace-element enriched rocks from the Procellarum KREEP Terrane (PKT) display Nb/Ta and Zr/Hf above the bulk lunar value (ca. 17), and mare basalts display lower ratios, generally confirming the presence of complementary enriched and depleted mantle reservoirs on the Moon. The full compositional spectrum of lunar basalts, however, also requires interaction with ilmenite-rich layers in the lunar mantle. Notably, the high-Ti mare basalts analysed display the lowest Nb/Ta and Zr/Hf of all lunar rocks, and also higher Sm/Nd at similar Lu/Hf than low-Ti basalts. The high-Ti basalts also exhibit higher and strongly correlated Ta/W (up to 25) and Hf/W (up to 140), at similar W contents, which is difficult to reconcile with ortho- and clinopyroxene-controlled melting. Altogether, these patterns can be explained via assimilation of up to ca. 20% of ilmenite- and clinopyroxene-rich LMO cumulates by more depleted melts from the lower lunar mantle. Direct melting of ilmenite-rich cumulates or the possible presence of residual metals in the lunar mantle both cannot easily account for the observed Ta/W and Hf/W patterns. Cumulate assimilation is also a viable mechanism that can partially buffer the Lu/Hf of mare basalts at relatively low values while generating variable Sm/Nd. Thus, the dichotomy between low Lu/Hf of lunar basalts and high time integrated source Lu/Hf as inferred from Hf isotope compositions can potentially be explained. The proposed assimilation model also has important implications for the short-lived nuclide chronology of the Earth-Moon system. The new Hf/W and Ta/W data, together with a compilation of existing W-Th-U data for lunar rocks, indicate that the terrestrial and lunar mantles are indistinguishable in their Hf/W. Virtually identical εW and Hf/W in the terrestrial and lunar mantle suggest a strong link between final core-mantle equilibration on Earth and the Moon forming giant impact. Previously, linear arrays of lunar samples in ¹⁸²W vs. Hf/W and ¹⁴²Nd vs. Sm/Nd spaces have been interpreted as isochrons, arguing for LMO crystallisation as late as 250 Myrs after solar system formation. Based on the proposed assimilation model, the ¹⁸²W and ¹⁴²Nd in many lunar magmas can be shown to be decoupled from their ambient Hf/W and Sm/Nd source compositions. As a consequence, the ¹⁸²W vs. Hf/W and ¹⁴²Nd vs. Sm/Nd arrays would constitute mixing lines rather than isochrons. Hence, the lunar ¹⁸²Hf-¹⁸²W and ¹⁴⁶Sm-¹⁴²Nd data would be fully consistent with an “early” crystallisation age of the LMO, even as early as 50 Myrs after solar system formation when the Moon was probably formed.     

Towards sectoral and standardised vulnerability assessments: the example of heatwave impacts on human health

The relevance of climate change is especially apparent through the impacts it has on natural and societal systems. A standardised methodology to assess these impacts in order to produce comparable results is still lacking. We propose a semi-quantitative approach to calculate vulnerability to climate change, with the ability to capture complex mechanisms in human-environmental systems. The key mechanisms are delineated and translated into a deterministic graph (impact chain). A fuzzy logic algorithm is then applied to address uncertainty regarding the definition of clear threshold values. We exemplify our approach by analysing the direct impacts of climate change on human health in North Rhine-Westphalia, Germany, where the urban heat island potential, the percentage of elderly population as well as the occurrence of heat waves determine impact intensity. Increases in heatwaves and elderly population will aggravate the impacts. While the influence of climatic changes is apparent on larger spatial scales, societal factors determine the small scale distribution of impacts within our regional case study. In addition to identifying climate change impact hot spots, the structured approach of the impact chain and the methodology of aggregation enable to infer from the results back to the main constituents of vulnerability. Thus, it can provide a basis for decision-makers to set priorities for specific adaptation measures within the complex field of climate change impacts.     

Atmospheric input of nitrogen into the North Sea: ANICE project overview

The aim of the atmospheric nitrogen inputs into the coastal ecosystem (ANICE) project is to improve transport–chemistry models that estimate nitrogen deposition to the sea. To achieve this, experimental and modelling work is being conducted which aims to improve understanding of the processes involved in the chemical transformation, transport and deposition of atmospheric nitrogen compounds. Of particular emphasis within ANICE is the influence of coastal zone processes. Both short episodes with high deposition and chronic nitrogen inputs are considered in the project. The improved transport–chemistry models will be used to assess the atmospheric inputs of nitrogen compounds into the European regional seas (the North Sea is studied as a prototype) and evaluate the impact of various emission reduction strategies on the atmospheric nitrogen loads. Assessment of the impact of atmospheric nitrogen on coastal ecosystems will be based on comparisons of phytoplankton nitrogen requirements, other external nitrogen inputs to the ANICE area of interest and the direct nitrogen fluxes provided by ANICE. Selected results from both the experimental and modelling components are presented here. The experimental results show the large spatial and temporal variability in the concentrations of gaseous nitrogen compounds, and their influences on fluxes. Model calculations show the strong variation of both concentrations and gradients of nitric acid at fetches of up to 25 km. Aerosol concentrations also show high temporal variability and experimental evidence for the reaction between nitric acid and sea salt aerosol is provided by size-segregated aerosol composition measured at both sides of the North Sea. In several occasions throughout the experimental period, air mass back trajectory analysis showed connected flow between the two sampling sites (the Weybourne Atmospheric Observatory on the North Norfolk coast of the UK and Meetpost Noordwijk, a research tower at 9 km off the Dutch coast). Results from the METRAS/SEMA mesoscale chemistry transport model system for one of these cases are presented. Measurements of aerosol and rain chemical composition, using equipment mounted on a commercial ferry, show variations in composition across the North Sea. These measurements have been compared to results obtained with the transport–chemistry model ACDEP which calculates the atmospheric inputs into the whole North Sea area. Finally, the results will be made available for the assessment of the impact of atmospheric nitrogen on coastal ecosystems.