Correspondence analysis applied to a comparison of some rhyolitic zones in the Noranda area (Quebec, Canada)

Correspondence analysis was applied to 177 chemical analyses (major elements) of rocks from some rhyolitic zones of the Noranda area (Quebec). The objective was to grade the individual sample sections with respect to their attractiveness considering the chemical alterations related to mineralization. The results obtained show that it is possible to differentiate sections from different rhyolitic horizons.     

Synergies and tradeoffs in how managers,scientists, and fishers value coral reef ecosystem services

Managing ecosystems in a changing environment faces the challenge of balancing diverse competing perspectives on which ecosystem services – nature's benefits – to prioritize. Consequently, we measured and compared how different stakeholders (managers, scientists and fishers) prioritize specific coral reef ecosystem services. Managers’ priorities were more aligned with scientists’ priorities but all stakeholder groups agreed that fishery, education, and habitat were high priorities. However, stakeholder groups differed in the extent to which they prioritized certain services. Fishers tended to assigned greater estimates to fishery and education, managers to culture, and scientists to coastal protection. Furthermore, using network analysis to map the interactions between stakeholders’ priorities, we found distinct synergies and trade-offs in how ecosystem services were prioritized, representing areas of agreement and conflict. In the fishers’ network, trade-offs emerged between two services, both of a higher priority, such as fishery and habitat. Conversely, in the scientists’ network, trade-offs emerged between services of a higher and lower priority, such as habitat and culture. The trade-offs and synergies that emerged in the managers’ network overlap with both fishers’ and scientists’ suggesting a potential brokering role that managers can play in balancing both priorities and conflicts. We suggest that measuring ecosystem service priorities can highlight key areas of agreement and conflict, both within and across stakeholder groups, to be addressed when communicating and prioritizing decisions.     

Impacts of Spatial Partitioning in Hydroecological Models: Predicting Grassland Productivity with RHESSys

Environmental models constructed with a spatial domain require choices about the representation of space. Decisions in the adaptation of a spatial data model can have significant consequences on the ability to predict environmental function as a result of changes to levels of aggregation of input parameters and scaling issues in the processes being modelled. In some cases, it is possible to construct a systematic framework to evaluate the uncertainty in predictions using different spatial models; in other cases, the realm of possibilities plus the complexity of the environmental model in question may inhibit numeric uncertainty estimates. We demonstrate a range of potential spatial data models to parameterize a landscape‐level hydroecological model (RHESSys). The effects of data model choice are illustrated, both in terms of input parameter distributions and resulting ecophysiological predictions. Predicted productivity varied widely, as a function of both the number of modelling units, and of arbitrary decisions such as the origin of a raster grid. It is therefore important to use as much information about the modelled environment as possible. Combinations of adaptive methods to evaluate distributions of input data, plus knowledge of dominant controls of ecosystem processes, can help evaluate potential representations. In this case, variance‐based delineation of vegetation patches is shown to improve the ability to intelligently choose a patch distribution that minimizes the number of patches, while maintaining a degree of aggregation that does not overly bias the predictions.     

Pattern and timing of the northwestern Barents Sea Ice Sheet deglaciation and indications of episodic Holocene deposition

The origin of two acoustic sediment units has been studied based on lithological facies, chronology and benthic stable isotope values as well as on foraminifera and clay mineral assemblages in six marine sediment cores from Kveithola, a small trough west of Spitsbergenbanken on the western Barents Sea margin. We have identified four time slices with characteristic sedimentary environments. Before c. 14.2 cal. ka, rhythmically laminated muds indicate extensive sea ice cover in the area. From c. 13.9 to 14.2 cal. ka, muds rich in ice‐rafted debris were deposited during the disintegration of grounded ice on Spitsbergenbanken. From c. 10.3 to 13.1 cal. ka, sediments with heterogeneous lithologies suggest a shifting influence of suspension settling and iceberg rafting, probably derived from a decaying Barents Sea Ice Sheet in the inner‐fjord and land areas to the north of Kveithola. Holocene deposition was episodic and characterized by the deposition of calcareous sands and shell debris, indicative of strong bottom currents. We speculate that a marked erosional boundary at c. 8.2 cal. ka may have been caused by the Storegga tsunami. Whilst deposition was sparse during the Holocene, Kveithola acted as a sediment trap during the preceding deglaciation. Investigation of the deglacial sediments provides unprecedented details on the dynamics and timing of glacial retreat from Spitsbergenbanken.     

Coupling of early diagenetic processes and sedimentary dynamics in tropical shelf environments: the Gulf of Papua deltaic complex

Tropical mobile mud belts represent a major class of biogeochemical and diagenetic systems characterized by extensive and frequent physical reworking of fine-grained, organic-rich deposits underlying oxygenated waters. Large regions of the Gulf of Papua, Papua New Guinea deltaic complex are dominated by such conditions. A reworked mud belt lies within the inner shelf between 10 and 20 m depth on a sedimentary clinoform derived from coalescing deltas. Deposits across the topset are typically suboxic, nonsulfidic over the upper 0.5–1 m, and have low to moderate maximum pore water concentrations of dissolved Fe(II) and Mn(II) (100–200, but up to 800 μM). Sediments are reactive, with surficial ΣCO₂ production 0.1–0.3 mM d⁻¹ and benthic O₂ fluxes 23±15 mmol m⁻² d⁻¹ (upper 20 cm). The highest rates occur within inner topset deposits (10–20 m) and near the high accumulation rollover region of the topset–foreset beds (40–50 m). Lower rates are found inshore along intertidal channels—mangrove fringe and within scoured or exposed consolidated deposits of the middle topset region. Remineralization rate patterns are independent of relative dominance by terrestrial or marine carbon in sediments. Dissolved O₂ usually penetrates 2–5 mm into surface sediments when macrofaunal burrows are absent. More than 75% of the highly reactive sedimentary Fe(III) pool (350–400 μmol g⁻¹) is typically diagenetically reduced in the upper 0.5 m. Pore water can be measureably depleted at depths >0.5 m, but dissolved H₂S generally remains below detection over the upper 1–2 m. As in other deltaic topset regions, concentration gradients often indicate that compared to many marine deposits of similar sediment accumulation rates, relatively refractory C_org is supplied to the SO₄ reducing zone. Sedimentary C/S ratios are 4–6 within the suboxic topset regions but decrease to <3 in offshore foreset beds where sulfidic diagenesis dominates. Only 15–20% of the diagenetically reduced Fe(II) is pyritic and a maximum of 10–25% is carbonate, implying that most Fe(II) is associated with authigenic or lithogenic silicates or oxides. The dominance of suboxic, nonsulfidic diagenetic processes reflect coupling between delivery of oxide-rich terrestrial debris, remobilization and reoxidation of deposits, and repetitive entrainment/remineralization of both labile and refractory organics. Distinct sedimentary indicators of reactive, suboxic mobile mud belts within tropical climatic zones are: abundant total highly reactive Fe (ΣFeR )>300 μmol g⁻¹; most reactive Fe is diagenetically reduced (ΣFe(II)/ΣFeR0.7–0.8); the proportion of diagenetically reduced Fe present as pyrite is low (Py–Fe(II)<0.2); C/S 4–8; and C_org/particle surface area <0.4 (mg C m⁻²). These depositional environments must be most common in tropical climates during high sea stand.     

Arsenic Management Through Well Modification and Simulation

Arsenic concentrations can be managed with a relatively simple strategy of grouting instead of completely destroying a selected interval of well. The strategy of selective grouting was investigated in Antelope Valley, California, where groundwater supplies most of the water demand. Naturally occurring arsenic typically exceeds concentrations of 10 µg/L in the water produced from these long-screened wells. The vertical distributions of arsenic concentrations in intervals of the aquifer contributing water to selected supply wells were characterized with depth-dependent water-quality sampling and flow logs. Arsenic primarily entered the lower half of the wells where lacustrine clay deposits and a deeper aquifer occurred. Five wells were modified by grouting from below the top of the lacustrine clay deposits to the bottom of the well, which reduced produced arsenic concentrations to less than 2 µg/L in four of the five wells. Long-term viability of well modification and reduction of specific capacity was assessed for well 4-54 with AnalyzeHOLE, which creates and uses axisymmetric, radial MODFLOW models. Two radial models were calibrated to observed borehole flows, drawdowns, and transmissivity by estimating hydraulic-conductivity values in the aquifer system and gravel packs of the original and modified wells. Lithology also constrained hydraulic-conductivity estimates as regularization observations. Well encrustations caused as much as 2 µg/L increase in simulated arsenic concentration by reducing the contribution of flow from the aquifer system above the lacustrine clay deposits. Simulated arsenic concentrations in the modified well remained less than 3 µg/L over a 20-year period.     

Exosphere generation of the Moon investigated through a high-energy neutral detector

Observation of the lunar exosphere is a tool for remote sensing of the surface properties. The sources of this exosphere are related to the interactions of the lunar surface with the solar radiation, with the solar wind or Earth??s magnetospheric plasma, and with the interplanetary dust and meteorites. In fact, the exospheric particles are continuously created and subsequently lost in the interplanetary space, photo-ionized or re-adsorbed by the surface. Eventually, the estimation of the surface composition is not possible without the knowledge of the active release mechanisms. The relative weight of the different release processes of the various atoms, ions and molecules from the surface is still an open debate. Investigation of the Moon??s release processes and interaction with the near-Earth environment is of crucial importance for both determining the relative process release contribution and understanding the surface evolution of other airless bodies, like Mercury and the giant planets?? moons. In this work, an attempt to analyze the processes that take place on the surface of these small airless bodies, as a result of their exposure to the space environment, has been realized by means of the MonteCarlo Environment Simulation Tool (EST), applied to the Moon. The model results show that the different release processes can be identified by analysing the exospheric energy distribution. Finally, the instrument concept of the ??Analizzatore Lunare di ENA?? (ALENA), part of the MAGIA payload and specifically designed for detecting the high-energy particles released from the lunar surface is presented.     

Predictions of MESSENGER Neutron Spectrometer measurements for Mercury's north polar region

From radar images of Mercury's poles and MESSENGER Neutron Spectrometer (NS) measurements obtained during the spacecraft's flybys of Mercury, predictions of neutron count rates and their uncertainties are calculated for Mercury's north polar region as of the end of the MESSENGER primary orbital mission. If Mercury's poles contain large amounts of water ice, as has been suggested on the basis of the radar data, then during the one-year-long orbital mission the NS should detect signals indicative of excess polar hydrogen with a significance of at least 4σ, where σ is the standard deviation derived from Poisson counting statistics. If the polar deposits are not enriched with hydrogen, but are dominated by other elements, such as sulfur, then the MESSENGER neutron measurements should be able to confirm the absence of deposits having surface concentrations in excess of 50 wt% H₂O on permanently shadowed floors of craters near Mercury's north pole. Because of the large spatial footprint of the NS data, individual polar deposits will not be spatially resolved, but longitudinal asymmetries may be detected if residual systematic uncertainties are sufficiently low.     

The Aitik Cu–Au–Ag deposit in northern Sweden: a product of high salinity fluids

The Aitik Cu–Au–Ag deposit is located in northern Sweden and is hosted by strongly deformed 1.9 Ga Svecofennian volcano-sedimentary rocks. The main copper mineralization, which occurs as disseminations and veinlets, is hosted by garnet–biotite schist. Subeconomic mineralization in the footwall to the ore is hosted by feldspar–biotite–amphibole gneiss and porphyritic quartz monzodiorite. The deposit has been affected by post-mineralization metamorphic and igneous activity. Fluid inclusions in six samples of copper-mineralized quartz veins record the presence of three different fluid populations. The main ore was deposited from an aqueous, highly saline (31–37 eq. wt% NaCl + CaCl₂) fluid. This fluid was trapped in inclusions intimately associated with the main chalcopyrite mineralization. Later bornite deposition took place from a less saline (18–27 eq. wt% NaCl + CaCl₂), aqueous fluid. A third fluid composed of almost pure CO₂, interacted with the copper-rich system during a post-ore event. The Aitik Cu–Au–Ag deposit shares some features with both porphyry-type and Fe-oxide–Cu–Au deposits. A high calcium content of the ore fluids, similar to other Cu–Au deposits in northern Scandinavia, suggests a contribution to the salinity of the mainly magmatic-hydrothermal fluids from evaporitic rocks in stratigraphically lower units.     

Inverse theory in the earth sciences—an introductory overview with emphasis on Gandin's method of optimum interpolation

In 1963, Gandin published a monograph on “optimum interpolation for the objective analysis of meteorological fields, ? a method that is similar mathematically to geodetical least-squares prediction and collocation, simple kriging, and spectral interpolation. The common problem is the interpolation or extrapolation or estimation of a continuous spatial property from finitely many observations. Gandin 's method is presented in an inverse-theoretical context with focus on a methodological comparison with related methods. Underlying mathematical assumptions as well as geological implications are discussed. An introductory overview of inverse methods in the earth sciences is given, with emphasis on methods with a structure analysis step.