Observations en bathyscaphe de formations volcano-sédimentaires aux environs de Madère

Bathyscaph dives off Madeira permitted discovering at a depth of about 1200 m, a morphologic feature interpreted as a volcanic crater or a small caldera. Between 900 m and 1700 m deep, volcano-sedimentary formations, interpreted as hyaloclastites of explosive origin, were observed. It is assumed that these formations were initially deposited at shallower depths and may reflect the subsidence of the Madeira archipelago owing to the great thickness of its volcano-sedimentary series (more than 6000 m).     

Mantle heterogeneity and crustal recycling in Archean granite-greenstone belts: Evidence from Nd isotopes and trace elements in the Rainy Lake area, Superior Province, Ontario, Canada

The 2685–2752 Ma old granite-greenstone crust in the Rainy Lake area, Ontario, consists of metaigneous and metasedimentary rocks that range in composition from tholeiite to monzogranite and include anorthosite, trachyandesite, monzodiorite and high-silica rhyodacite. Major element, rare earth and other trace element data are the basis for modelling the formation of the crust by melting of large-ionlithophile element enriched and unenriched mantle, by melting of basalt at mantle to crustal levels and by melting of monzodiorite and tonalite at crustal levels.

All metaigneous rocks lie on a ¹⁴³Nd/¹⁴⁴Nd vs. ¹⁴⁷Sm/¹⁴⁴Nd isochron with an age of 2737 ±42 Ma and an initial ¹⁴³Nd/¹⁴⁴Nd of 0.509178 ±33 (ε_Nd = +1.9). This age is consistent with U-Pb zircon ages, which suggests the Nd isotopic system has been unaffected since the crust-forming events. The positive initial ε_Nd's are further evidence for time-averaged depletion in Sm/Nd relative to CHUR for the Archean mantle. The similarity of the initial Nd isotopic composition for both mantle-derived and crustally-derived rocks suggests rapid recycling of crustal components, which were previously derived from depleted mantle sources.

Initial ¹⁴³Nd/¹⁴⁴Nd ratios on individual rocks range from ε_Nd = +3.3 to ε_Nd = −0.4. Younger granitoids have lower ε_Nd values (+1.5 to −0.1) relative to tholeiites and monzodiorites crystallized from mantle-derived melts (+3.3 to +1.0). Thus, incorporation of slightly older crust (ca. 100–200 Ma) in some of the granitoid source areas is possible. Mantle-derived rocks form an isochron of 2764 ±58 Ma that represents a minimum age for enrichment processes in the mantle sources for the Rainy Lake area. Consideration of data from the Abitibi belt suggests such enrichment processes in the mantle may have preceded crust-forming events in a wide area of the Superior Province, perhaps by as much as 50–70 Ma.     

Quartz diorites derived by partial melting of eclogite or amphibolite at mantle depths

Rare earth elements, Rb, Sr, Ba and K have been determined in tonalite, trondhjemite, dacite, tholeiite and graywacke from the 2700 m.y. old Early Precambrian greenstone-granite terrane of northeastern Minnesota-northwestern Ontario, and also in trondhjemite from the 3550 m.y. old Morton Gneiss, southwestern Minnesota; and the Mesozoic Craggy Peak Pluton, Klamath Mountains, California.The Early Precambrian tholeiites have trace element compositions similar to modern oceanic tholeiites, while the quartz dioritic rocks, regardless of age, have total rare earth contents lower than that of tholeiitic basalts, with near chondritic heavy rare earth contents. Rb, Sr, Ba and K contents of the quartz diorites are about five times that of oceanic tholeiites, with similar alkali and alkaline earth ratios. The Early Precambrian graywacke has a rare earth content intermediate between greenstone and quartz diorite, reflecting its provenance.It is proposed that the analyzed quartz dioritic rocks, whether plutonic tonalite, dacite porphyry, gneissic or plutonic trondhjemite, or trondhjemite dikes had similar modes of origin, and were derived by partial melting of amphibolite or eclogite of basaltic or gabbroic composition at depths greater than thirty kilometers, leaving a residue consisting predominantly of garnet and clinopyroxene.     

Effects of Salinity and Temperature on Bacterial Biodiversity in Hangu Solar Saltworks,China

正1 Introduction The multi-pond solar saltworks inhabit diverse microbial groups in which a gradient of salinities range from seawater to Na Cl precipitation.Along the salinity gradient,the majority of microbial community changes     

Intermobility of barium,strontium, and lead in chloride and sulfate leach solutions

Iron(III)-precipitates formed by the oxidation of dissolved Fe(II) are important sorbents for major and trace elements in aquatic and terrestrial systems. Their reductive dissolution in turn may result in the release of associated elements. We examined the reductive dissolution kinetics of an environmentally relevant set of Fe(II)-derived arsenate-containing Fe(III)-precipitates whose structure as function of phosphate (P) and silicate (Si) content varied between poorly-crystalline lepidocrocite, amorphous Fe(III)-phosphate, and Si-containing ferrihydrite. The experiments were performed with 0.2–0.5 mM precipitate-Fe(III) using 10 mM Na-ascorbate as reductant, 5 mM bipyridine as Fe(II)-complexing ligand, and 10 mM MOPS/5 mM NaOH as pH 7.0 buffer. Times required for the dissolution of half of the precipitate (t_50%) ranged from 1.5 to 39 h; spanning a factor 25 range. At loadings up to ~ 0.2 P/Fe (molar ratio), phosphate decreased the t_50% of Si-free precipitates, probably by reducing the crystallinity of lepidocrocite. The reductive dissolution of Fe(III)-phosphates formed at higher P/Fe ratios was again slower, possibly due to P-inhibited ascorbate binding to precipitate-Fe(III). The slowest reductive dissolution was observed for P-free Si-ferrihydrite with ~ 0.1 Si/Fe, suggesting that silicate binding and polymerization may reduce surface accessibility. The inhibiting effect of Si was reduced by phosphate. Dried-resuspended precipitates dissolved 1.0 to 1.8-times more slowly than precipitates that were kept wet after synthesis, most probably because drying enhanced nanoparticle aggregation. Variations in the reductive dissolution kinetics of Fe(II) oxidation products as reported from this study should be taken into account when addressing the impact of such precipitates on the environmental cycling of co-transformed nutrients and contaminants.

     

Spatial mode estimation for functional random fields with application to bioturbation problem

This work provides a useful tool to study the effects of bioturbation on the distribution of oxygen within sediments. We propose here heterogeneity measurements based on functional spatial mode. To obtain the mode, one usually needs to estimate the spatial probability density. The approach considered here consists in looking each observation as a curve that represents the history of the oxygen concentration at a fixed pixel.     

Identifizierung von Stickstoffverbindungen niederer molarer Masse in Abläufen einer kommunalen Kläranlage mit biologischer Reinigungsstufe

Identification of Nitrogen-containing Compounds of Low Molecular Weight in Effluents of Biologically Treated Municipal Wastewater Enriching methods based on reversed phases were developed for the investigation of low-molecular compounds containing nitrogen in municipal wastewater effluent. The enriched mixtures were treated gas chromatographically without derivatization under different conditions. By application of the PBM-algorithm to the GC/MS spectra of the enriched samples (concentration factor 1000...20000), 133 nitrogen-containing compounds could be identified with a probability of occurence of at least 30% put out. Seventeen of these compounds were identified with > 90% probability and another ten with 80...90% probability. 9-Methylacridine was found in nine of ten processed samples investigated. The nitrogen content of the 133 identified compounds was estimated at about 20% of the low-molecular fraction of DON (dissolved organic nitrogen).     

The formation and evolution of massive stellar clusters in IC4662

We present a multiwavelength study of the formation of massive stellar clusters, their emergence from cocoons of gas and dust, and their feedback on surrounding matter. Using data that span from radio to optical wavelengths, including Spitzer and Hubble Space Telescope ACS observations, we examine the population of young star clusters in the central starburst region of the irregular Wolf–Rayet galaxy IC4662. We model the radio-to-infrared (IR) spectral energy distributions of embedded clusters to determine the properties of their Hii regions and dust cocoons (sizes, masses, densities, temperatures), and use near-IR and optical data with mid-IR spectroscopy to constrain the properties of the embedded clusters themselves (mass, age, extinction, excitation, abundance). The two massive star-formation regions in IC4662 are excited by stellar populations with ages of ～4 Myr and masses of ～3×10⁵ M_⊙ (assuming a Kroupa initial mass function). They have high excitation and subsolar abundances, and they may actually be comprised of several massive clusters rather than the single monolithic massive compact objects known as ‘super star clusters’ (SSCs). Mid-IR spectra reveal that these clusters have very high extinction values, A _V ～20–25 mag, and that the dust in IC4662 is well mixed with the emitting gas, not in a foreground screen.     

The effect of spacecraft radiation sources on electron moments from the Cassini CAPS electron spectrometer

Data from the Cassini plasma spectrometer (CAPS) electron spectrometer (ELS) have been found to be contaminated with an energy-independent background count rate which has been associated with radiation sources on Cassini. In this paper we describe this background radiation and quantitatively assess its impact on numerically integrated electron moments. The general properties of such a background and its effects on numerical moments are derived. The properties of the ELS background are described and a model for the background presented. A model to generate synthetic ELS spectra is presented and used to evaluate the density and temperature of pure noise and then extended to include ambient distributions. It is shown that the presence of noise produces a saturation of the electron density and temperature at quasi-constant values when the instrument is at background, but that these noise level moments are dependent on the floating spacecraft potential and the orientation of the ELS instrument with respect to the spacecraft. When the ambient distribution has a poor signal-to-noise ratio (SNR) the noise determines the density and temperature; however, as the SNR increases (increasing primarily with density) the density and temperature tend to those of the ambient distribution. It is also shown that these noise effects produce highly artificial density-temperature inverse correlations. A method to subtract this noise is presented and shown to correct for the presence of the noise. Simulated error estimates for the density and temperature are also presented. The analysis described in this paper not only applies to weak background noise, but also to more significant penetrating backgrounds such as those in radiation belt regions of planetary magnetospheres.     

New U/Th ages for Pleistocene megafauna deposits of southeastern Queensland,Australia

Arguments over the extinction of Pleistocene megafauna have become particularly polarised in recent years. Causes for the extinctions are widely debated with climate change, human hunting and/or habitat modification, or a combination of those factors, being the dominant hypotheses. However, a lack of a spatially constrained chronology for many megafauna renders most hypotheses difficult to test. Here, we present several new U/Th dates for a series of previously undated, megafauna-bearing localities from southeastern Queensland, Australia. The sites were previously used to argue for or against various megafauna extinction hypotheses, and are the type localities for two now-extinct Pleistocene marsupials (including the giant koala, Phascolarctos stirtoni). The new dating allows the deposits to be placed in a spatially- and temporally constrained context relevant to the understanding of Australian megafaunal extinctions. The results indicate that The Joint (Texas Caves) megafaunal assemblage is middle Pleistocene or older (>292 ky); the Cement Mills (Gore) megafaunal assemblage is late Pleistocene or older (>53 ky); and the Russenden Cave Bone Chamber (Texas Caves) megafaunal assemblage is late Pleistocene (～55 ky). Importantly, the new results broadly show that the sites date prior to the hypothesised megafaunal extinction ‘window’ (i.e., ～30–50 ky), and therefore, cannot be used to argue exclusively for or against human/climate change extinction models, without first exploring their palaeoecological significance on wider temporal and spatial scales.