Serpentinites associated with eclogitic rocks were examined from three areas: the Alps, Cuba, and the Himalayas. Most serpentinites have low Al/Si and high concentrations of Ir‐type platinum group ...elements (PGE) in bulk rock compositions, indicating that they are hydrated mantle peridotites. A few samples contain high Al/Si and low concentrations of Ir‐type PGE, suggesting that they are ultramafic cumulates. Among the hydrated mantle peridotites, we identified two groups, primarily on the basis of Al/Si and Mg/Si ratios: forearc mantle serpentinites and hydrated abyssal peridotites. Forearc serpentinites occur in the Himalayas and along a major deformation zone in Cuba. All serpentinites in the Alps and most serpentinites in Cuba are hydrated abyssal peridotites. Himalayan serpentinites have low Al/Si and high Mg/Si ratios in bulk rock compositions, and high Cr in spinel; they were serpentinized by fluids released from the subducted Indian continent and enriched in fluid‐mobile elements, and show high 87Sr/86Sr, up to 0.730, similar to the values of rocks of the subducted margin of the Indian continent. Although Himalayan serpentinites have a similar refractory geochemical signature as the Mariana forearc serpentinites, the former contain markedly high concentrations of fluid‐mobile elements and high 87Sr/86Sr compared to the latter that were hydrated by subducted Pacific Ocean crust. The data indicate that the enrichment of fluid‐mobile elements in forearc serpentinites depends on the composition of subducted slabs. Alpine serpentinites and most Cuban serpentinites show moderate Al/Si similar to abyssal peridotites. Hydration of peridotites near the seafloor is supported by micro‐Raman spectra of earlier formed lizardite, high δ34S (+11 to +17‰) of sulphides, and elevated 87Sr/86Sr, ranging from 0.7037 to 0.7095. The data support the contribution of S and Sr from seawater and sediments. These serpentinites are not highly enriched in fluid‐mobile elements because serpentinization occurred at a high water/rock ratio. Alkali elements are conspicuously unenriched in all serpentinites. This lack of alkali enrichment is explained by slab retention of alkalis. This is also consistent with the observation of relatively low alkali concentrations in volcanic front magmas, since partial melting related to the volcanic fronts is triggered by dehydration of serpentinites.
The behavior of As in paddy fields is of great interest considering high As contents of groundwater in several Asian countries where rice is the main staple. We determined the concentrations of Fe, ...Mn, and As in soil, soil water, and groundwater samples collected at different depths down to 2 m in an experimental paddy field in Japan during the cycle of flooded and non-flooded periods. In addition, we measured the oxidation states of Fe, Mn, and As in situ in soil samples using X-ray absorption near-edge structure (XANES) and conducted sequential extraction of the soil samples. The results show that Fe (hydr)oxide hosts As in soil. Arsenic in irrigation waters is incorporated in Fe (hydr)oxide in soil during the non-flooded period, and the As is quickly released from soil to water during the flooded period because of reductive dissolution of the Fe (hydr)oxide phase and reduction of As from As(V) to As(III). The enhancement of As dissolution by the reduction of As is supported by high As/Fe ratios of soil water during the flooded period and our laboratory experiments where As(III) concentrations and As(III)/As(V) ratios in submerged soil were monitored. Our work, primarily based on data from an actual paddy field, suggests that rice plants are enriched in As because the rice grows in flooded paddy fields when mobile As(III) is released to soil water.
Spring phytoplankton blooms play a major role in the carbon biogeochemical cycle of the Oyashio region, western subarctic Pacific, where the seasonal biological drawdown effect on seawater pCO₂ is ...one of the greatest among the world’s oceans. However, the bloom often terminates before depleting macronutrients, and the initiation and magnitude of the bloom is heterogeneous. We conducted a high resolution taxonomic and physiological assessment of phytoplankton in relation to the different physicochemical water masses of Coastal Oyashio Water (COW), Oyashio water (OYW), and modified Kuroshio water (MKW) in the Oyashio region from April to June 2007. Massive diatom blooms were found in April. Then, chlorophyll a concentration, cell abundance of diatom taxa, and the maximum photosystem II photochemical efficiency (F
v/F
m) were positively correlated with the mixing ratios of COW, suggesting that the spring bloom in April was strongly affected by the intrusion of COW. In the OYW, intensive blooms occurred from the middle of May under low dissolved iron (DFe) concentration (< 0.26 nM). Redundancy analysis showed that while diatom blooms accompanied by COW were related to DFe concentration, this was not the case in the OYW. These results indicated that diatoms in the OYW possess different iron adaptation strategies compared with diatoms in thewater masses affected by COW. This led to the spatial heterogeneity of the Oyashio spring bloom. The results presented here demonstrate that water mass characterization with detailed assessments of phytoplankton taxonomy and physiological status can improve our understanding of marine ecosystems.
Single‐layer particulate coatings with special anti‐reflection (AR) properties were deposited by an electrostatic attraction between the negatively charged colloidal particles and the positively ...charged surface of polyelectrolyte multilayers (see Figure). It is shown that the AR properties of the coating depend on the number of sequential depositions as well as on the treatment of the particles after deposition.
Two-dimensional (2-D) compact photonic crystal reflectors on suspended InP membranes were studied under normal incidence. We report the first experimental demonstration of 2-D broadband reflectors ...(experimental stopband superior to 200 nm, theoretical stopband of 350 nm). They are based on the coupling of free space waves with two slow Bloch modes of the crystal. Moreover, they present a very strong sensitivity of the polarization dependence, when modifying their geometry. A compact (50×50 μm 2 ) demonstrator was realized and characterized, behaving either as a broadband reflector or as a broadband transmitter, depending on the polarization of the incident wave. Experimental results are in good agreement with numerical simulations.
Dead zooplankton, including crustaceans, are increasingly recognized as important agents of vertical carbon export from surface waters and in marine food webs. Quantifying the contribution of ...passively sinking copepods (PSCs) to vertical fluxes of total particulate organic carbon (POC) is important for understanding marine ecosystem carbon budgets. Information on this is limited because identifying PSCs in sediment trap samples is difficult. Generally, swimmers (undecomposed metazoans, including PSCs, caught in sediment traps) are removed from a trap sample before the POC content is measured, although ignoring PSCs causes the total POC flux to be significantly underestimated. We quantified temporal and regional variability in PSC flux and con tribution of PSCs to total POC flux (PSCs + detrital sinking particles, generally analyzed to estimate detrital POC flux) at the Mackenzie Shelf margins in the Beaufort Sea. Six datasets were used to examine PSC flux variability at ~100 m depth, which is deeper than the winter pycnocline depth (30−50 m), at the continental margin. The average (±SD) annual PSC flux (1378 ± 662 mg C m−2 yr−1, n = 6 datasets) and PSC contribution to the total POC flux (21 ± 10%, n = 6) suggested that PSCs, especially Pareuchaeta glacialis, were important agents of POC export from the surface layer (~100 m) to deeper water at the inter-regional and multiyear scales. We propose a hypothesis that processes controlling PSC flux variability may vary seasonally, perhaps relating to life cycle (reproduction) in winter (February) and osmotic stress in July−October when the PSC flux is relatively high.
Adsorption of rare earth elements (REE) onto the cell walls of
Bacillus subtilis (a gram-positive bacterium) and
Escherichia coli (a gram-negative bacterium) was studied between pH 2.5 and 4.5 and at ...various bacterial concentrations. The distribution coefficients of REE between the bacterial cell surface and water showed a pattern with a prominent enrichment of heavy REE (HREE), including a maximum around Sm and Eu. There was also an enrichment around Pr accompanied by a decline for Nd, which was attributed to the tetrad effect. The occurrence of M-type tetrad effect suggests that REE form inner sphere complexes during their adsorption onto bacteria.
The enrichment of the distribution coefficients in the HREE region was more enhanced at higher bacterial concentrations, which could not be explained by one type of binding sites on the bacterial surface. Instead, the data are consistent with two ligand types for the sorption of REE. The pattern of bacterial distribution coefficients can be explained by the stability constants of REE with carboxylate and phosphate groups, suggesting that they are most likely responsible for the adsorption of REE on the bacterial cell surface.
Microbial mats and thermal waters at the Nakafusa hot spring (Nagano Prefecture, Japan) were also examined to evaluate whether the REE patterns of natural samples could be used as indicators of the presence of bacteria. The apparent distribution coefficients of REE displayed a pattern similar to that obtained in the laboratory experiments using pure bacterial strains. The results suggest that the REE pattern of chemical sedimentary rocks may be used to identify the bacterial contribution to the deposition of the rocks in the geological record.
This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).
This article has been retracted at the request of the ...Editor-in-Chief of British Journal of Anaesthesia. The study is retracted for the following reasons:
Statistical analysis suggests that the data may be fabricated. Y Saitoh provided a statement in a personal communication to a member of the editorial board of British Journal of Anaesthesia that the study was not approved by the Institutional Review Board and that no evidence exists to support the study findings. Additionally, the Japanese Society of Anesthesiologists has recommended retraction of this article: http://www.anesth.or.jp/english/pdf/news20170925.pdf.
The Quetico Intrusions are a series of ultramafic–mafic igneous rocks that occur along the northern Quetico subprovince boundary. These intrusions show lithological zoning from cores of ...olivine-bearing ultramafic rocks to margins of hornblendite and gabbroic rocks, and they are commonly accompanied by Cu–Ni–platinum group element (PGE) sulphide mineralization. We identified three additional Quetico Intrusions in the centre and southern part of the Quetico subprovince, bringing the entire Quetico Intrusion array to be over 125
km in length across the subprovince. The Samuels Lake intrusion in the centre of the subprovince has an U–Pb age of 2688
+
6/−5
Ma, which is similar to the age of ∼2690
Ma for the Quetico Intrusions along the northern subprovince boundary, suggesting that all the Quetico Intrusions are likely to be contemporaneous. The parental magmas of the intrusions were Mg-rich based on the high Mg of olivine and clinopyroxene, and they were hydrous as evidenced by abundant hornblende, early crystallization of clinopyroxene, and the common occurrence of mafic pegmatite. The bulk rocks show arc geochemical signatures, including a high concentration of large ion-lithophile elements combined with a low concentration of high field-strength elements. The mineral compositions of pyroxene and hornblende also plot in the field of arc igneous rocks. The data suggest the derivation of the parental magmas from a mantle wedge or a refractory mantle that was previously metasomatized in a subduction setting.
The Quetico Intrusions display many similarities with Alaskan/Ural-type zoned mafic–ultramafic intrusions along major sutures of Phanerozoic orogenic belts. Common features include their geodynamic settings, internal lithological zoning, mineralogy and mineral chemistry, and common association with PGE mineralization. The striking similarities between the two indicate that the late Archean Quetico Intrusions likely formed in a tectonic setting similar to that of the Alaskan/Ural-type intrusions. We propose that the parental magmas for the Quetico Intrusions formed during the very early stage of accretion of the Wawa arc to the Wabigoon subprovince. Oblique accretion of the Wawa arc likely steepened the subduction angle, which allowed upwelling of hot asthenospheric mantle. This resulted in high degrees of partial melting in the mantle wedge to produce the Quetico Intrusions.
Mount Pinatubo in the Philippines, known for its cataclysmic eruption in 1991, hosts several porphyry copper deposits and active geothermal systems. An underlying mafic melt supplied much of the ...sulphur for the dacitic magma and its injection into the dacitic magma chamber triggered the eruption. The eruption caused purging of the sulphur-rich fluid from the dacite to the atmosphere and extensive fracturing. Similar events took place at Bingham Canyon, Utah, site of the largest copper and gold deposit in North America at 38 Ma. The Bingham Canyon mineralization took place beneath an active stratovolcano and pyroclastic flows contemporaneous with the mineralization show evidence for magma mingling. Ascent of mafic melt supplied sulphur and chalcophile elements to the felsic magma, which consolidated to form the Bingham stock and its underlying magma chamber. Injections of the mafic melt caused periodic eruptions of felsic magma to form the stratovolcano and deposition of sulphide minerals in highly fractured rocks in and around the stock.PUBLICATION ABSTRACT
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