Stable carbon-isotopic compositions of lipids isolated from the ammonia-oxidizing chemoautotroph Nitrosomonas europaea

For the ammonia-oxidizing bacterium Nitrosomonas europaea, grown autotrophically using semicontinuous culturing, average biomass was depleted in ¹³C relative to CO₂ dissolved in the medium by ca. 20‰ and the total-lipid extract was depleted in ¹³C relative to biomass by 3.7‰. The n-alkyl lipids (weighted average of fatty acids) and isoprenoid lipids (weighted average of hopanoids) were both depleted in ¹³C relative to biomass by about 9‰. The large depletion in the isoprenoid lipids seems to indicate that isotopic fractionations associated with the biosynthesis of methylerythritol phosphate (MEP) affected at least two carbon positions in each isoprene unit. Among the fatty acids, trans-9-hexadecenoic acid was most depleted (13.0‰ relative to biomass), followed by cis-9- hexadecenoic acid (9.6‰) and hexadecanoic acid (6.9‰). Isotopic relationships between the three acids suggest that significant isotope effects were associated with the desaturation and cis to trans isomerization of fatty acids. Given these observations, hopanoids produced by ammonia-oxidizing bacteria growing in natural waters are likely to be depleted in ¹³C by 26–30‰ relative to dissolved CO₂. Since CO₂ at aquatic oxyclines is often depleted in ¹³C, the range of δ values expected for hopanoids is ca. −34‰ to −55‰. The δ values of geohopanoids observed in numerous studies and attributed to unspecified chemoautotrophs fall within this range.     

Lithofacies succession of maar crater deposits in the Eifel area (Germany)

ABSTRACT Maar craters often contain exceptionally preserved fossils and maar sediments may reflect detailed environmental changes. Volcanosedimentary processes in a Middle Eocene maar crater lake are illustrated by the deposits of Eckfeld Maar in the Tertiary Hocheifel Volcanic Field (Rhenish Massif, Germany). The maar origin of the basin is evident from a circular negative gravity anomaly which indicates a low-density funnel-shaped basin filling. From the facies analysis of an Eocene (Eckfeld) and a Pleistocene (Döttingen) maar we develop a lithozone classification for the interpretation of maar sediments: syn-/post-eruptive breccias are followed by a fining-upwards sequence of lacustrine mud with coarse layers and final swamp deposits. From the facies analysis and regional geological data we reconstruct the pre- to post-eruptive history of a maar crater prior to post-Eocene uplift. These observations can be used for the interpretation of Tertiary and Quaternary maar craters that are ideal fossil and sediment traps.     

Petrology of the tin-bearing granite-leucogranites of the Piaoak Massif, Northern Vietnam

The Piaoak tin-bearing granite-leucogranites located in the Caobang Province of Northern Vietnam compose a stock-like hypabyssal body. Host rocks are represented by Early Devonian carbonate sequences and Early Triassic ??black?? shales. The geochronological age of the Piaoak granite-leucogranites corresponds to the Late Cretaceous: T = 83.5 ± 6.2 Ma, ⁸⁷Rb/⁸⁶Sr method; T = 89.7 ± 1.0 Ma, ³⁹Ar/⁴⁰Ar method. The massif has a simple basic to acid order: two-mica and muscovite granite-leucogranite ?? raremetal aplites, pegmatites ?? tin-bearing greisens and hydrothermal veins. The petrographic and microstructural studies revealed a sharp change in crystallization conditions of the granite-leucogranite magma at the late magmatic stage and formation of muscovite via incongruent melting of protolithionite. The study of melt and coexisting fluid inclusions showed that solidus crystallization occurred under fluid-saturated conditions at 635?C600°C. In composition, the granite-leucogranites of the Piaoak Massif correspond to the raremetal-plumasite geochemical type (according to L.V. Tauson), and reach Li-F facies in terms of their rare-element composition. The composition of aplites and pegmatites demonstrates that granite-leucogranite magma did not accumulate lithophile and volatile components in the residual melt during differentiation, but was initially enriched in rare-metals. It is most probable that the melt was generated from Proterozoic lithotectonic complexes and overlaying Lower Triassic ??black?? shales.     

Metal content and environmental risk assessment around high-altitude mine sites

Gold mining activities in Apolobamba area, northwest of La Paz, Bolivia have created serious environmental concern and great risk to human health. The current methods used to extract gold are too primitive resulting in metal contamination of soil and water. The objectives of this study were to: (1) determine the degree of metal pollution, and (2) assess the risk to human health and environment in the Apolobamba area. Soil, water, sediment samples, and mine spills were collected and analyzed. Metals including Pb, Cu, Zn, Cd, and Hg concentrations were higher in surface soils than in subsurface soils indicating active atmospheric deposition of metals. Sediment samples had elevated levels of metals probably from mine spills discharged into the Sunchulli River. Surface soils in the Sunchulli community show the highest levels of Pb and Hg in all soil samples and may pose a risk to the health of the human population and environment.     

The fast variable maser source IRAS 05338-0624

A new OH maser was detected in January 2008 toward the infrared source IRAS 05338-0624 in the dark cloud L1641N. The observations were carried out on the Nan cay Radio Telescope (France) in the 1667 and 1665 MHz OH lines. In the spectra of both lines, thermal OH emission from the surrounding molecular cloud is present at radial velocities V _LSR = 6–9 km/s. In addition, a narrow maser feature is present in both lines at V _LSR = 2 km/s in the profiles obtained on January 7, 2008; the peak flux densities at 1667 and 1665 MHz are 1.5 and 0.4 Jy, respectively. No OH maser emission was detected in February–July 2008. Then, a maser feature was again observed in the 1665 MHz line on August 20, 2008, at the same velocity as in January, V _LSR = 2 km/s, with a peak flux density of 0.4 Jy. No 1667 MHz counterpart was observed with an upper limit of ～0.1 Jy. Emission in both OH lines was again absent on September 18. The source was also observed in the H₂O line at λ = 1.35 cm on the 22-m radio telescope of the Pushchino Radio Astronomy Observatory (Russia) on February 7 and 13, 2008. In both cases, a maser feature was detected at V _LSR = 9 km/s, with peak flux densities of 35 and 15 Jy, respectively. After the its apparent absence in April, H₂O maser emission reappeared on May 14, 2008, at V _LSR = 7 km/s with a flux density of about 15 Jy. The history of previous observations of the object in the OH and H₂O lines is traced. The maser displays strong and rapid flux variability in the lines of both molecules, as is typical of young low-luminosity stellar objects at early stages of their evolution.     

On the multi-century Southern Hemisphere response to changes in atmospheric CO2-concentration in a Global Climate Model

Summary The transient response of the Southern Hemisphere to climate change is examined using an intermediate complexity climate model. Unlike previous studies, the Southern Ocean response on the centennial to multi-centennial time-scale is assessed in some detail. It is shown that changes in atmospheric CO₂-concentrations lead to an increase in the strength of the Antarctic Circumpolar Current (ACC) by ∼20 Sv by 2750 for an atmospheric CO₂-concentration of 750 ppm. This increase is predominantly the result of an enhanced steric height gradient. The increase in the strength of the ACC induces changes in its steering around topographic features. This change in ACC pathway causes increased surface flow of colder waters into some regions (reducing the rate of warming) and increased surface flow of warmer waters into others (increasing the rate of warming). This meridional shifting of the ACC causes changes in atmospheric temperature in the Southern Hemisphere to be nonuniform. It is also shown that the strength and location of the Antarctic Bottom Water (AABW) overturning cell is affected by increased atmospheric CO₂. For a CO₂-concentration scenario increasing gradually to 750 ppm, AABW production initially decreases, then recovers and eventually increases. New production zones form, which extend AABW production all the way from the Weddell Sea eastward into the Ross Sea. These new production zones are the result of increased areas of atmosphere-ocean interactions, due to decreased sea-ice coverage, although the overturned waters are now warmer and fresher due to climate change. A new production zone of Antarctic Intermediate water is also established in the Southeast Pacific Ocean, poleward of its present-day location.     

中国南方海相含油气保存单元的层次划分与综合评价

以最近十年中国南方的海相新区油气勘探评价成果为依托 ,以油气成藏和整体封闭保存体系评价为核心 ,在渝东—湘鄂西、中下扬子和滇黔桂三大区域划分出 9个有利区块 5 1个含油气保存单元 ,并将其归纳为四个层次。综合评价认为 ,方西和石柱保存单元具有较好的整体封存体系 ,属持续性含油气保存单元 ,为首选勘探目标 ;江汉盆地南部、句容—海安区块、南鄱阳坳陷、楚雄盆地东北部具备或基本具备整体封存条件 ,属于沉积重建型含油气保存单元 ,通过精细勘探可望获得商业性油气流 ;楚雄盆地西北部、南盘江坳陷、十万大山盆地和渝东—湘鄂西地区利川复向斜由于晚期强烈构造改造而仅存在部分封存体系 ,需要攻关探索 ;思茅、渝东—湘鄂西地区的花果坪和桑植—石门地区已失去整体封闭保存条件 ,仅局部存在封存体系 ,地质条件高度复杂 ,勘探风险甚高。     

The aboveground biomass of desert steppe and its spatiotemporal variation in western Inner Mongolia

A precise understanding of the aboveground biomass of desert steppe and its spatio-temporal variation is important to understand how arid ecosystems respond to climate change and to ensure that scarce grassland resources are used rationally. On the basis of 756 ground survey quadrats sampled in western Inner Mongolia steppe in 2005–2011 and remote sensing data from the Moderate Resolution Imaging Spectroradiometer (MODIS)—the normalized difference vegetation index (NDVI) dataset for the period of 2001–2011—we developed a statistical model to estimate the aboveground biomass of the desert steppe and further explored the relationships between aboveground biomass and climate factors. The conclusions are as follows: (1) the aboveground biomass of the steppe in the research area was 5.27 Tg (1 Tg=10¹² g) on average over 11 years; between 2001 and 2011, the aboveground biomass of the western Inner Mongolia steppe exhibited fluctuations, with no significant trend over time; (2) the aboveground biomass of the steppe in the research area exhibits distinct spatial variation and generally decreases gradually from southeast to northwest; and (3) the important factor causing interannual variations in aboveground biomass is precipitation during the period from January to July, but we did not find a significant relationship between the aboveground biomass and the corresponding temperature changes. The precipitation in this period is also an important factor influencing the spatial distribution of aboveground biomass (R²=0.39, P<0.001), while the temperature might be a minor factor (R²=0.12, P<0.01). The uncertainties in our estimate are primarily due to uncertainty in converting the fresh grass yield estimates to dry weight, underestimates of the biomass of shrubs, and error in remote sensing dataset.     

PGE geochemistry of the Eagle Ni–Cu–(PGE) deposit, Upper Michigan: constraints on ore genesis in a dynamic magma conduit

The Eagle Ni–Cu–(PGE) deposit is hosted in mafic–ultramafic intrusive rocks associated with the Marquette–Baraga dike swarm in northern Michigan. Sulfide mineralization formed in association with picritic magmatism in a dynamic magma conduit during the early stages in the development of the ~1.1?Ga Midcontinent Rift System. Four main types of sulfide mineralization have been recognized within the Eagle deposit: (1) disseminated sulfides in olivine-rich rocks; (2) rocks with semi-massive sulfides located both above and below the massive sulfide zone; (3) massive sulfides; and (4) sulfide veins in sedimentary country rocks. The disseminated, massive and lower semi-massive sulfide zones are typically composed of pyrrhotite, pentlandite and chalcopyrite, whereas the upper semi-massive sulfide ore zone also contains pyrrhotite, pentlandite, and chalcopyrite, but has higher cubanite content. Three distinct types of sulfide mineralization are present in the massive sulfide zone: IPGE-rich, PPGE-rich, and PGE-unfractioned. The lower and upper semi-massive sulfide zones have different PGE compositions. Samples from the lower semi-massive sulfide zone are characterized by unfractionated PGE patterns, whereas those from the upper semi-massive sulfide zone show moderate depletion in IPGE and moderate enrichment in PPGE. The mantle-normalized PGE patterns of unfractionated massive and lower semi-massive sulfides are subparallel to those of the disseminated sulfides. The results of numerical modeling using PGE concentrations recalculated to 100% sulfide (i.e., PGE tenors) and partition coefficients of PGE between sulfide liquid and magma indicate that the disseminated and unfractionated massive sulfide mineralization formed by the accumulation of primary sulfide liquids with similar R factors between 200 and 300. In contrast, the modeled R factor for the lower semi-massive sulfide zone is <100. The fractionated sulfide zones such as those of the IPGE-rich and PPGE-rich massive sulfides and the upper semi-massive sulfide zone can be explained by fractional crystallization of monosulfide solid solution from sulfide liquids. The results of numerical modeling indicate that the sulfide minerals in the upper semi-massive sulfide zone are the products of crystallization of fractionated sulfide liquids derived from a primary sulfide liquid with an R factor similar to that for the disseminated sulfide mineralization. Interestingly, the modeled parental sulfide liquid for the IPGE-rich and PPGE-rich massive sulfide zones has a higher R factor (~400) than that for the unfractionated massive sulfide mineralization. Except one sample which has unusually high IPGE and PPGE contents, all other samples from the Cu-rich sulfide veins in the footwall of the intrusion are highly depleted in IPGE and enriched in PPGE. These signatures are generally consistent with highly fractionated sulfide liquids expelled from crystallizing sulfide liquid. Collectively, our data suggest that at least four primary sulfide liquids with different R factors (<100, 200–300, ~400) were involved in the formation of the Eagle magmatic sulfide deposit. We envision that the immiscible sulfide liquids were transported from depth by multiple pulses of magma passing through the Eagle conduit system. The sulfide liquids were deposited in the widened part of the conduit system due to the decreasing velocity of magma flow. The presence of abundant olivine in some of the sulfide ore zones indicates that the ascending magma also carried olivine crystals. Sulfide saturation was attained in the parental magma due in large part to the assimilation of country rock sulfur at depth.