Crystal-field spectra of fassaite from the Angra dos Reis meteorite

Fassaitic pyroxene from the Angra dos Reis meteorite has striking spectral properties. The⁵⁷Fe Mössbauer spectra show no Fe^3&+;, and thus the absorption is thought to originate from a complex charge-transfer process. Intense absorption at 480 nm dominates the spectrum of the meteorite and may be important in the interpretation of telescope spectra of objects in space.     

Denitrifying bacteria and hydrogeochemistry in a natural wetland adjacent to farmlands in Chiba,Japan

This study combined bacterial incubation and hydrogeochemical methods to investigate denitrification in the surface water, top soil (0–20 cm), and shallow groundwater of the Ochi wetland in Japan. Surface water was rich in nitrate (40 mg/l) and denitrifying bacteria (700 per ml). Three functional zones in the wetland were identified in the top soil and shallow groundwater. In the upstream portion of the wetland (Zone I), the counts of denitrifying bacteria in top soil increased from 5200 to 14 970 per ml and nitrate decreased from 25·4 to 1·8 mg/l. Organic carbon concentrations decreased as sulfate increased from 4·0 to 9·6 mg/l in this zone. In the middle‐stream of the wetland (Zone II), all concentrations of major anions, iron, organic carbon, and total nitrogen content in top soil were relatively constant, but the counts of denitrifying bacteria increased up to 70 200 per ml. In the downstream portion of the wetland (Zone III), complete removal of nitrate resulted in sharp reduction of counts of denitrifying bacteria. Correspondingly, dissolved oxygen (DO), organic carbon, and total nitrogen increased in this zone. Counts of denitrifying bacteria were lower in shallow groundwater than in top soil; nitrate concentrations in shallow groundwater were also very low in this zone. DO and the oxidation/reduction potential data suggest that groundwater flows to the surface along an extended flow path, thus providing nitrate for the denitrifying community. Copyright © 2011 John Wiley & Sons, Ltd.     

Simulation of the impacts of diagenesis or low-grade metamorphism on neutrophilic microaerobic Fe(II)-oxidizing biofilm

The microaerobic iron-oxidizing bacteria in circumneutral environment produce extracellular polymeric substances(EPS)with unique morphologic features,such as stalks or sheaths,which can be regarded as geobiological signatures.The Archean and early Palaeoproterozoic oceans were anoxic with high soluble Fe(II)that were suggested to have been oxidized through the metabolism of Fe(II)-oxidizing bacteria.The precursor of the ultrafine hematite in banded iron formation(BIF),e.g.,ferrihydrite,was suggested to be the mineral record of microbial Fe(II)-oxidation at that time.However,both the biological materials and primary iron minerals were prone to being altered by diagenetic or low-grade metamorphic processes.This makes it difficult to interpret the genesis of Precambrian BIFs.Here,we report experimental simulation on the effects of diagenesis or low-grade metamorphism on neutrophilic microaerobic Fe(II)-oxidizing bacteria and their biomass.Stalks,sheaths,and iron oxide spheroidal aggregates are partially preserved after the 100 MPa/300°C treatments,which indicates the mixed organic matters and iron oxides could survive the diagenetic or low-grade metamorphic processes.Some organic-mineral mixing structures carry information on microbial processes,though they appear similar to pseudomorphs of fossilized bacteria.     

Bacterial symbiosis forming laminated iron‐rich deposits in Okuoku‐hachikurou hot spring,Akita Prefecture,Japan

Banded iron formations are the most characteristic of Archean–Paleoproterozoic sediment records. Laminated textures resembling banded iron formations can be observed in modern hot‐spring environments. Using sedimentological and microbiological techniques, we investigated the processes of laminar formation and considered the origin of lamination textures. An iron‐rich deposit at the Okuoku‐hachikurou hot spring in Japan exhibits sub‐millimeter laminations consisting of bacteria‐induced ferrihydrite and aragonite. The ferrihydrite particles are spherical and exhibit fine lamination, up to 100 µm thick in ferrihydrite‐rich parts. In aragonite‐rich parts, ferrihydrite particles form filamentous textures with diameters of 10–30 µm, but not laminations. Textural analysis using scanning electron microscopy and phylotype analysis using 16S rRNA indicated the bacterial contribution to ferrihydrite precipitation. A sheath‐like fabric showing a meshwork of nanometer‐order organic filaments, and sheath‐forming bacteria were observed in the deposit specimen etched by citric acid. Phylotype analysis detected in the iron‐rich deposits some bacterial types related to cyanobacteria, purple bacteria, and iron‐oxidizing bacteria. Iron‐oxidizing bacteria probably were responsible for precipitation of the ferrihydrite. Chemolithoautotrophic iron‐oxidizing bacteria are microaerophilic and thrive on Fe(II) in a redox gradient, but dissolved oxygen was not detected in the Okuoku‐hachikurou hot spring. Thus, a certain supply of oxygen is needed for metabolism of the microaerophilic iron‐oxidizing bacteria. The distribution of photosynthetic pigments in the iron‐rich parts indicates that the most likely source of oxygen is photosynthesis by cyanobacteria. This symbiotic relationship between cyanobacteria and iron‐oxidizing bacteria can explain the laminated texture of iron‐rich deposits in the Okuoku‐hachikurou hot spring. These laminations may reflect changes in photosynthetic intensity. There is presently some debate about the bacterial groups that may have played roles in precipitation of banded iron formations. This study presents a new bacterial model for iron precipitation and may provide a mechanism for sub‐millimeter laminations in banded iron formations deposited in shallow water.     

Sr isotopic fractionation in Allende chondrules: A reflection of solar nebular processes

True relative Sr isotopic compositions, determined by the double-spike technique, are reported for 8 olivine chondrules from Allende and a single chondrule from Richardton. The Richardton chondrule has an Sr composition identical with the whole meteorite, but the Allende chondrules are up to 1.4‰ per mass unit light-isotope enriched, closely similar to Ca-Al inclusions (CAI) from the same individual stone. The correspondence of the patterns for chondrules and CAI suggests that both groups of objects derived their fractionated Sr in similar ways. The lack of any detectable non-linear Sr isotopic anomaly in the objects suggests that their Sr compositions did not have some exotic or extrasolar origin, but were derived from normal solar system Sr by mass fractionation. The consistent light-Sr enrichment of Allende objects may be explained by several schemes, and all are heavily model-dependent. Most plausible to the author is that the CAI and chondrules derived their fractionated Sr from a region of the nebula made isotopically light by partial kinetic mass separation of elements in the vapour phase. Later, the solid objects may have moved to an isotopically more normal region, where the Allende matrix accreted.     

Significance of fossilized microbes from the Cambrian stromatolites in the Tarim Basin,Northwest China

Samples of the Cambrian microbial dolomites were collected from Penglaiba section,a well-exposed stratigraphic section in the northwestern area of the Tarim Basin.This study provides an analogue for mediated dolomites that can precipitate in microbial mats and biofilms.The Cambrian stromatolitic dolomites were studied using high-resolution scanning electron microscopy.The results are as follows:(1)dolomites with 50 nm to 100 nm spherical nanostructures are aggregated into minerals of larger sphericities;(2)nanospherical dolomites of 50 nm to 170 nm diameter are densely arranged as dumbbell-shaped or chained aggregates;(3)silicified filaments,as well as dumbbell-shaped and chain arrangements,are preserved as important microstructures.On the basis of sedimentological,compositional,geochemical,and petrographic data,the microstructures were interpreted as nanoglobules that function as bacteria in the nucleation and filament mineralization stages.The microstructures function as such because they are wrapped in extracellular polymeric substance(EPS)or mucus and mineralized fossils.Silicification accounts for the exceptional preservation of microbial mat structures,including biofilms,as well as filamentous and coccoid microbes.In addition,EPS process is capable of binding different elements,with preference for Si,Mg,and Ca.Such suitable composition favors microbe mineralization and dolomite nucleation on organic substrates.These microscopic structures suggest bacterial mineralization and provide visual evidence for the origin of microbial dolomites.     

The equation-of-states of Jilin ordinary chondrite and Nandan iron meteorite

Shock wave data for Jilin ordinary chondrite and Nandan iron meteorite are measured by electric-pin techniques on the dynamic high-pressure device equipped with a two-stage light gas gun, and then equation-of-states supposedly fit for describing theirP- V-E relations are chosen to evaluate the values of their parameters. Demonstrated from the comparison between P-V curves of equation-of-states and experimental data points, P-V relation of Jilin ordinary chondrite can be described by the universal equation-of-state, of which bulk modulus value of zero-pressure K_os = 48.10 GPa, its pressure derivativeK’ _os = 4.13. That of Nandan iron meteorite can be described by the three-term form of equation-of-state, of which the values of two matter parameters Q = 41.235 31 GPa, q = 12. 27179. The Hugoniot data and equation-of-states for Jilin ordinary chondrite and Nandan iron meteorite are first reported in this paper. The equation-of-state defined by Hugoniot data measurement provides strong empirical support for describing the compression of meteorites to high pressure. Project supported by the National Natural Science Foundation of China.     

Unique phenomenon of the accumulation of <Emphasis Type="Italic">terrestrial</Emphasis> metal iron particles in lacustrine deposits: Zhombolok volcanic region,East Sayan

The native iron particles that were previously detected by thermomagnetic and microprobe analyses in the sediments of different age in many regions of the world are of extraterrestrial origin. The similarity in the compositions, grain shapes, and sizes observed in the extraterrestrial and terrestrial particles of native iron testifies to the common production conditions of iron particles during the formation of planets. In this paper, the single finding of terrestrial iron in the lacustrine sediments of the Zhombolok volcanic region, East Sayan, is discussed. The uniqueness of the results indicates that the spatial distribution of the particles of native iron is limited to a fairly narrow area around their source—volcanic eruption or/and the fall of a large meteorite.     

A recent meteorite shower in Antarctica with an unusual orbital history

The Antarctic meteorite collection has proved to be a source of many important discoveries, including a number of previously unknown or very rare meteorite types. A thermoluminescence (TL) survey of meteorite samples recovered by the 1988/89 European expedition and pre-1988 American expeditions to the Allan Hills Main blue ice field resulted in the discovery of 15 meteorites with very high TL levels ( > 100 krad at 250°C in the glow curvc). It is likely that these samples are fragments of a single meteoroid body which: (1) fell very recently and (2) experienced a decrease in orbital perihelia from 1.1 AU to 1 AU within the last 10⁵ yr. Carbon-14 data for two of the samples confirm their young terrestrial age compared to most Antarctic meteorites. Studies of the cosmogenic isotopes in at least one non-Antarctic meteorite which also has very high natural TL, Jilin, indicate that the meteorite experienced a multi-stage irradiation history, the most recent stage being 0.4 Ma in duration following a major break-up of the object. These meteorites, and the few equivalent modern falls, are the only documented samples from bodies which were recently in Earth-approaching (Amor) orbits (i.e., with perihelion > 1.0 AU), as opposed to the Earth-crossing (Apollo) orbits which are the source of most other meteorites. Their rarity indicates that such rapid orbit changes are unusual for meteoroid bodies and may be the result of isolated, large break-up events.     

Biological Reduction of Nitrate and Perchlorate in Soil Microcosms: An Electron Donor Comparison of Glycerol,Emulsified Oil,and Mulch Extract

Diverse technologies have been developed and tested for their efficacy in remediating perchlorate-contaminated surface water, groundwater, and soil. Biological reduction, particularly when coupled with electron donor augmentation, has been shown to be one of the most cost-effective alternatives. Numerous electron donors have been evaluated in the literature, but few studies have compared standard vs. slow-release electron donors for sequential nitrate and perchlorate reduction. This study evaluated the efficacy and kinetics of biological reduction in soil microcosms augmented with emulsified oil (EO), glycerol, and mulch extract. Results indicated that EO and glycerol spiked at approximately 100 times stoichiometric excess (i.e., 100x) achieved similar overall reductions and degradation rates for nitrate and perchlorate, although nitrate appeared to exhibit zero order kinetics while perchlorate exhibited first order kinetics. The zero order rate constants for nitrate reduction were 3.32 mg/L d and 2.57 mg/L d for EO and glycerol, respectively. The first order rate constant for perchlorate reduction was 0.36 day⁻¹ for both EO and glycerol. Stable chemical oxygen demand (COD) concentrations also highlighted the slow-release properties of EO, which would reduce electron donor consumption in comparison to soluble substrates in soil remediation applications. The microcosms augmented with mulch extract failed to demonstrate any nitrate or perchlorate reduction due to the extract's lower COD concentration. Augmentation with compost or additional processing (i.e., concentration) would be necessary to make the extract a viable alternative.     

穿越逆冲断层的埋地管道非线性反应分析

穿越逆冲断层的埋地管道在地震作用下,容易发生局部屈曲或整体失稳等形式的破坏,研究逆冲断层作用下的埋地管道地震反应规律,对管道抗震设计及施工等具有重要的意义。本文将埋地管线及周围土体从半无限地球介质中取出,分别以空间薄壳单元和实体单元进行离散,采用非线性接触力学方法模拟管、土之间的滑移、分离及闭合现象;采用线性位移加载模拟断层的错动,考虑了系统初始应力状态的影响,对土体未开裂前的管土相互作用系统进行了拟静力数值分析;分析了位错量、土体刚度、埋设深度、径厚比及跨越角度对埋地管道反应的影响,得出了一些有益的结论。     

Reflectance spectral characterization and mineralogy of acid sulphate soil in subsurface using hypcrspectral data

Acid sulphate soil（ASS） is a kind of soil which is harmful to the environment.ASS is hard to efficiently assess efficiently in the subsurface,although it is detectable on the surface by remote sensing.This paper aims to explore a new way to rapidly assess ASS in the subsurface by introducing a proximal hyperspectral instrument,namely the HyloggerTM system which can rapidly scan soil cores and provide high resolution hyperspectral data.Some minerals in ASS,which usually act as indicators of the severity of ASS,such as iron oxides,hydroxides,and sulphates,as well as some clay minerals,such as kaolinite,have diagnostic spectral absorption features in the reflectance spectral range（400-2500 nm）.Soil cores were collected from a study area and hyperspectral data were acquired by HyloggerTM scanning.The main minerals related to ASS were characterized spectrally,and were subsequently identified and mapped in the soil cores based on their reflectance spectral characteristics.Traditional X-ray diffraction（XRD） and scanning electron microscope（SEM） were also applied to verify the results of the mineral identification.The main results of this study include the spectral characterisation of ASS and its main compositional minerals,as well as the distribution of these relevant minerals in different depth of cores.     

Petrogenesis of complex veins in the Chantonnay (L6f) chondrite

Two cross-cutting veins in the Chantonnay (L6f) chondrite illustrate different patterns of fractionation of total chondritic shock melts. The earlier vein, which is dark-colored and bears abundant host rock xenoliths, is strongly reduced and sodium-poor relative to the bulk meteorite. It resembles and may be cogenetic with melt pockets in Chantonnay. The later vein, which is lighter-colored and somewhat vesicular, lacks evidence of either Na loss or reduction but shows modest internal differentiation. Its metal and total iron contents (26.5 wt.%) are higher than normal for L-group chondrites.The trend of chemical fractionation recorded in the earlier Chantonnay vein resembles that reported for chondrules in ordinary chondrites, suggesting that chemical variations among chondrules in part reflect variations among their parental shock melts.     

RECOGNITION OF A BIOFILM AT THE SEDIMENT–WATER INTERFACE OF AN ACID MINE DRAINAGE-CONTAMINATED STREAM,AND ITS ROLE IN CONTROLLING IRON FLUX

Material collected over a month on plates attached to the bed of the Afon Goch, Anglesey, a stream highly contaminated by acid mine drainage (AMD), was either examined intact by electron microscopy or suspended and cultured to reveal the presence of microbiota. Certain of the aerobic microbiota were identified, the genus Pseudomonas formed the commonest isolate and cultures of Serratia plymuthica were grown in order to compare the biofilms formed with the material collected in the Afon Goch. The material at the sediment–water interface of the Afon Goch was of similar underlying morphology to that of the cultured biofilms. However, the former had a superficial granular coating of equidimensional (60–100 nm) and evenly spaced iron rich particles (determined by X-ray microanalysis). The sediment–water interface of this AMD-contaminated stream is therefore best described as a highly contaminated biofilm. Evidence from previous work suggests that the streambed is active in iron removal from the water column. The intimate association of iron with microbiota at the streambed, therefore, implies that iron flux prediction may not be possible from physical and chemical data alone but requires knowledge of biofilm physiology and ecology. Microbially mediated metal precipitation, both by single bacteria and by biofilms, has been reported elsewhere but mass balance considerations suggest that this explanation cannot hold good for the large amounts of iron hydroxide depositing from waters of the prevalent pH and redox status. Filtered stream water analyses indicate the presence of colloidal iron hydroxide and also its removal downstream where ochreous (iron hydroxide rich) material accumulates. The process of iron immobilization is likely to be the attraction and physical trapping of colloidal iron hydroxide by extracellular polymeric substances (EPS) which constitute the matrix of biofilms. © 1997 John Wiley & Sons, Ltd.     

The Niger (I) carbonaceous chondrite and implications for the origin of aggregates and isolated olivine grains in C2 chondrites

The origin of olivine grains in C2 carbonaceous chondrites is a controversial topic: directly condensed material or detrital remnants of preexisting chondrules? This study shows that the Niger C2 meteorite is similar to Murchison but reveals several interesting features in relation to the origin of the olivine. Microprobe analysis of olivine (Si, Fe, Mg, Ca, Mn, Cr), glass and nickel-iron inclusions within the grains, and Fe-S-O phase as well as the relationships between the olivine grains in the aggregates, between the grains and the interstitial phyllosilicate matrix, between the inclusions and their host olivine grains, and the morphology of some aggregates all show that two populations of olivine coexist, probably crystallized from chondrule melts rather than by direct condensation from a solar nebula gas. The characteristics of the nickel-iron inclusions within the olivine suggest a magmatic chondrule-making stage from previously condensed materials.     

Investigations on cosmic-ray-produced nuclides in iron meteorites, 3. Exposure ages,meteoroid sizes and sample depths determined by mass spectrometric analyses of potassium and rare gases

Three physical quantities define the essentials of the cosmic ray exposure history of a sample of an iron meteorite: (1) the cosmic ray exposure age T, (2) the pre-atmospheric “size” S of the irradiated body, and (3) the location, i.e. the “depth” D, of the samples within the body. To establish these quantities for a given sample three independent quantities must be determined experimentally. In the present work T is ascertained by the ⁴¹K/⁴⁰K method and the ⁴He and ²¹Ne concentrations (C₄ and C₂₁) are measured by the isotope dilution method. Signer and Nier's evaluation of the rare gas distribution in the meteorite Grant and the measured exposure age for this meteorite provide the relationships allowing to ascertain for any meteorite the quantities S and D from the ²¹Ne production rate (P₂₁ = C₂₁/T) and the ⁴He/²¹Ne ratio.Earlier measurements have provided data on the isotopic composition of potassium in 74 different iron meteorites. New rare gas measurements are reported for some 40 samples. Results on the age, size and depth are obtained for almost 60 samples. These data suggest that Signer and Nier's model is well suited for describing not only the rare gas distribution in a single selected meteorite (Grant) but also the exposure histories of the great majority of all irons. For a few samples, however, secondary breakups of the meteoroid and a two- or multiple-stage irradiation must be invoked. Further measurements are proposed for testing and, possibly, refining the still somewhat uncertain relationships between the abundances of cosmogenic nuclides and the quantities T, S, and D in very large meteorites.Histograms are presented showing the age distributions for irons of different chemical groups and of different size ranges.The feasibility and the relative merits of other methods for the determination of T, S, and D are discussed.     

Distinct distribution revealing multiple bacterial sources for 1-Omonoalkyl glycerol ethers in terrestrial and lake environments

The 1-O-monoalkyl glycerol ethers(MAGEs) were initially viewed as the biomarkers for sulfate-reducing bacteria(SRB) mediating anaerobic oxidation of methane in the marine environments. However, limited information is known about their distribution in terrestrial and other aquatic settings including soils, fresh water lakes, and cave sediments, which may obscure our understanding of their biological sources. Here we found that MAGEs were ubiquitous but differed obviously in distributional pattern among those environments. The surface soils are dominated generally by i C15:0-MAGE, followed by n C16:0-MAGE whereas the lake sediments show the opposite, resulting in significantly higher i C15:0/n C16:0 ratios in soils than in lake sediments. The cave deposits are characterized by considerably higher proportions of branched MAGEs than the former two environments. The logarithm of i C15:0/a C15:0 ratio shows a significant negative correlation with soil p H, likely reflecting an adaptation of microbial cell membrane to change in the ambient proton concentration. The MAGE profiles in cultured bacteria cannot fully explain the MAGE distribution in all the samples analyzed. Therefore, MAGEs in soil, lake sediments, and cave deposits likely have additional biological source(s) other than SRB and cultured MAGE-producing bacteria. The difference in MAGE pattern among environments is likely to be attributed to change in microbial communities.     

Blooms of the cyanobacterium Lyngbya majuscula in coastal Queensland, Australia: disparate sites, common factors

During the last decade there has been a significant rise in observations of blooms of the toxic cyanobacterium Lyngbya majuscula along the east coast of Queensland, Australia. Whether the increase in cyanobacterial abundance is a biological indicator of widespread water quality degradation or also a function of other environmental change is unknown. A bioassay approach was used to assesses the potential for runoff from various land uses to stimulate productivity of L. majuscula. In Moreton Bay, L. majuscula productivity was significantly (p<0.05) stimulated by soil extracts, which were high in phosphorus, iron and organic carbon. Productivity of L. majuscula from the Great Barrier Reef was also significantly (p<0.05) elevated by iron and phosphorus rich extracts, in this case seabird guano adjacent to the bloom site. Hence, it is possible that other L. majuscula blooms are a result of similar stimulating factors (iron, phosphorus and organic carbon), delivered through different mechanisms.     

Use of the index of TEC vertical variation disturbance in studying ionospheric effects of the Chelyabinsk meteorite

The results of an analysis of the ionospheric effects accompanying fall of the Chelyabinsk meteorite on February 15, 2013 are presented using a method of calculating the index of the disturbance of total electron content vertical variations (Wtec) according to data from the GPS receiver network. A substantial increase (by a factor of 2–3) in the Wtec index with a duration of ~1.5 h was observed in the studied region after the main height explosion accompanying the meteorite fall at 0320 UT. The ionospheric response in Wtec was most significant statistically registered at the radio rays “receiver–satellite” for the GPS located southward from the place of explosion.