the effect of extracellular polymeric substances on the adhesion of bacteria to clay minerals and goethite abstract the functions of extracellular polymeric substances eps during the adhesion of bacillus subtilis to kaolinite montmorillonite and goethite were examined by a direct comparison of the adhesion behaviors of native and eps free cells via cation exchange resin cer treatment using batch experiments attenuated total reflectance fourier transform infrared atr ftir spectroscopy and potentiometric titration the eps removal had no apparent influence on bacterial adhesion when the wet bacteria mineral mass ratio was low ofe bonds were important for adhesion to goethite in addition to electrostatic forces repulsion for clays and attraction for goethite absence of chemical interactions may also cause the relatively much weaker bacterial adhesion to clay minerals than to goethite the absence of eps did not change the interaction mode of the adhesion to clay minerals but enhanced the chemical interactions via carboxyl groups for bacteria goethite adhesion the potentiometric titration results coupled with the atr ftir spectra showed a significant increase in site concentrations of the cer treated bacteria as compared to the native cells changes in surface site concentrations and chemical interactions that were accompanied by the eps removal may reasonably explain the influences of eps on bacterial adhesion to different minerals

crystal growth and disequilibrium distribution of oxygen isotopes in an igneous ca al rich inclusion from the allende carbonaceous chondrite abstract ts34 is a type b1 ca al rich inclusion cai from the allende cv3 chondrite consisting of spinel melilite ti al rich clinopyroxene fassaite and minor anorthite in an igneous texture oxygen and magnesium isotopic compositions were measured by secondary ion mass spectrometry in spots of known chemical composition in all major minerals in ts34 using the sequence of formation from dynamic crystallization experiments and from chemical compositions of melilite and fassaite the oxygen isotopic evolution of the cai melt was established oxygen isotopic compositions of the constituent minerals plot along the carbonaceous chondrite anhydrous mineral line the spinel grains are uniformly 16o rich 17o 22 7 1 7 2sd while the melilite grains are uniformly 16o poor 17o 2 8 1 8 irrespective of their akermanite content and thus their relative time of crystallization the fassaite crystals exhibit growth zoning overprinting poorly developed sector zoning they generally grow from ti rich to ti poor compositions the fassaite crystals also show continuous variations in 17o along the inferred directions of crystal growth from 16o poor 17o 3 to 16o rich 17o 23 covering the full range of oxygen isotopic compositions observed in ts34 the early crystallized 16o poor fassaite and the melilite are in oxygen isotope equilibrium and formed simultaneously the correlation of oxygen isotopic compositions with ti content in the fassaite imply that the oxygen isotopic composition of the cai melt evolved from 16o poor to 16o rich during fassaite crystallization presumably due to oxygen isotope exchange with a surrounding 16o rich nebular gas formation of spinel the liquidus phase in melts of this composition predates crystallization of all other phases so its 16o rich composition is a relic of an earlier stage anorthite exhibits oxygen isotopic compositions between 17o 2 and 9 within the range of those of fassaite indicating co crystallization of these two minerals during the earliest to intermediate stage of fassaite growth the melilite and fassaite yield an 26al 26mg mineral isochron with an initial value of 26al 27al 0 5 003 0 075 10 5 corresponding to a relative age of 0 05 0 02 myr from the canonical al mg age of cais these data demonstrate that both 16o rich and 16o poor reservoirs existed in the solar nebula at least 0 05 myr after the birth of the solar system

direct and indirect impact of the bacterial strain pseudomonas aeruginosa on the dissolution of synthetic fe iii and fe ii bearing basaltic glasses abstract this study investigates the direct and indirect bacterial contributions that influence the dissolution of basaltic glass in this regard three different types of glasses with or without fe in the reduced fe ii or oxidized fe iii states were prepared on the basis of a simplified basaltic glass composition in order to prevent the direct contact between the glasses and the model siderophore producing strain pseudomonas aeruginosa the glass samples were isolated in dialysis bags and immersed at 25 c and ph 6 5 in bacterial cultures throughout the dissolution experiments the following parameters were monitored determination of bacterial growth quantification of siderophore i e pyoverdine production microscopic observation of the glass surface and determination of dissolution kinetics isolating the glass from the bacterial suspension only triggered the biosynthesis of siderophores in the fe iii bearing glass dissolution experiments siderophores were produced in the presence of fe ii bearing and fe free glass independently on the experimental setup the siderophore production appeared to be either continuous in the absence of fe glass free control fe free glass dissolution experiments or stopped as soon as the bacteria entered their stationary phase when an fe source was present fe ii and fe iii bearing glass dissolution experiments the increase in the dissolution rates of each glass was correlated to the complex stability constants of the siderophore with the metallic cations in presence kfe2

microbial dolomite in fresh water carbonate deposits this article reports evidence for biologically mediated precipitation of dolomite in a fresh water spring in the south east of spain build ups in the spring consisted of calcite minor dolomite barite and gypsum crystals formed by the mineralisation of microbial biofilms and bryophytes a detailed microscopic study coupled with geochemical analysis of the dolomite precipitating biofilms showed that dolomite crystals occurred in association with living coccoid micro organisms providing strong evidence that micro organisms play a fundamental role in the precipitation of this mineral many of the calcite crystals observed were associated with extracellular polymeric substances moreover microbial involvement in the precipitation of calcite was further supported by the presence of living cyanobacteria within the calcite crystals two different types of build up were found in the spring soft spongy moss tufa and laminated crusts two types of crusts were identified as follows simple pink crusts and laminated crusts the latter forming in both sub aquatic and sub aerial environments sub aquatic accumulation of simple detached pink crust fragments occurred sporadically both tufa and the carbonate crusts hosted cyanobacterial dominated biofilms with different bacteria and diatoms and their extracellular polymeric substances the 13c values of calcite showed some biogenic involvement in the origin of this mineral the 18o values were similar in the tufa and carbonate crusts and corresponded to current climatological characteristics the occurrence of different groups of minerals carbonates and sulphates in close spatial association with micro organisms suggests the presence of different macro environmental and micro environmental conditions that facilitate mineral precipitation within biofilms these findings extend the known range of aerobic microbial dolomites to include springs and show that the precipitation of both dolomite and calcite carbonates occurs while organisms are alive

microstructural analysis of wark lovering rims in the allende and axtell cv3 chondrites implications for high temperature nebular processes a coordinated electron backscatter diffraction ebsd and transmission electron microscope tem study was undertaken to obtain information on the origin of rims on refractory inclusions in the allende and axtell cv3 chondrites these measurements were supported by theoretical modeling using density functional theory crystal orientation analysis of wark lovering rims via ebsd revealed pyroxene grains with similar crystallographic orientations to one another in both inclusions an epitaxial relationship between grains within the diopside and anorthite rim layers was observed in allende tem examination of the rims of both samples also revealed oriented crystals at depth the microstructural data on the rims suggest that grain clusters grew in the form of three dimensional islands density functional theory calculations confirm that formation of oriented grain islands is the result of energy minimization at high temperature the results point toward condensation as the mode of origin for the rims studied here

a link between oxygen calcium and titanium isotopes in 26 al poor hibonite rich cais from murchison and implications for the heterogeneity of dust reservoirs in the solar nebula placs platy hibonite crystals and related hibonite rich calcium aluminum rich inclusions cais hereafter collectively referred to as plac like cais have the largest nucleosynthetic isotope anomalies of all materials believed to have formed in the solar system most plac like cais have low inferred initial 26al 27al ratios and could have formed prior to injection or widespread distribution of 26al in the solar nebula in this study we report 26al 26mg systematics combined with oxygen calcium and titanium isotopic compositions for a large number of newly separated plac like cais from the murchison cm2 chondrite 32 cais studied for oxygen 26 of these also for 26al 26mg calcium and titanium our results confirm 1 the large range of nucleosynthetic anomalies in 50ti and 48ca our data range from 70 to 170 and 60 to 80 respectively 2 the substantial range of 17o values 28 to 17 with 17o 17o 0 52 18o and 3 general 26al depletion in plac like cais the multielement approach reveals a relationship between 17o and the degree of variability in 50ti and 48ca plac like cais with the highest 17o 17 show large positive and negative 50ti and 48ca anomalies while those with the lowest 17o 28 have small to no anomalies in 50ti and 48ca these observations could suggest a physical link between anomalous 48ca and 50ti carriers and an 16o poor reservoir we suggest that the solar nebula was isotopically heterogeneous shortly after collapse of the protosolar molecular cloud and that the primordial dust reservoir in which anomalous carrier phases were heterogeneously distributed was 16o poor 17o 17 relative to the primordial gaseous co h2o reservoir 17o 35 however other models such as co self shielding in the protoplanetary disk are also considered to explain the link between oxygen and calcium and titanium isotopes in plac like cais

the genesis of actively growing siliceous stromatolites evidence from lake specchio di venere pantelleria island italy this study documents the attributes of siliceous stromatolites growing in the lake specchio di venere on the volcanic island of pantelleria italy in a setting characterized by very shallow cold waters and pools and by scattered hydrothermal activity which exhales mainly co2 at emission point temperatures of 34 to 58 c the saturation indexes indicate that the lake waters are saturated with respect to tridymite cristobalite chalcedony and quartz and slightly undersaturated with respect to amorphous silica common roughly laminated and poorly lithified stromatolites show scanning electron microscope sem evidence for silicified microbial mat structures including biofilms filamentous and coccoid cells and extracellular polymeric substances eps the screening of bacterial 16s rrna libraries indicates that autotrophic and heterotrophic bacterial communities colonize surface and core levels of the stromatolites locally the stromatolites show a granular non porous fabric where filaments and silica sheets are not apparent inhomogeneity in the stromatolite fabric corresponds with varying dna content and different structures of the colonizing bacterial communities non porous stromatolite levels being microbially colonized to a lesser extent based on fourier transform ft raman and ft infrared investigations the laminated stromatolite contains early diagenetic tridymite in addition to amorphous silica opal a whereas the non porous stromatolite shows an essentially amorphous character the laminated stromatolite is thought to form at relatively low rates of silica precipitation and with a possible microbial mediation in terms of microbial cells and their eps accelerating the onset of amorphous silica nucleation it is suggested that high porosity probably favoured a consistent flux of silica rich fluids that triggered the opal a to tridymite transformation thus strengthening the preservation of biosignals non porous stromatolite growth could reflect temporal or localised changes in environmental conditions that caused variations in the degree of silica saturation in the lake waters inducing abiotic silica accumulation accelerated opal a deposition could have obscured primary filamentous fabrics and limited the flux of pore fluid needed for sustaining the process of silica maturation

the role of bacterial extracellular polymeric substances in geomicrobiology abstract the last two decades have seen geomicrobiology evolve into a broad field encompassing a wide range of environmentally significant processes such as proton and metal adsorption onto cell surfaces and the effect of microbes on mineralisation redox cycling and contaminant transport within this sphere research groups have conducted studies using bacteria fungi diatoms and sludges all of which can play a part in geochemical processes here we review research on the role played by microbial extracellular polymeric substances eps focussing on bacterial and cyanobacterial eps we conclude by outlining future research directions in order to investigate unresolved questions in the field the effect of eps on metal adsorption is complex whereas some studies report an increase in metal adsorption when cells contain eps some report no differences yet others report a decrease these discrepancies may reflect differences in molecular and functional group composition of the eps eps provides a template for adsorption of metal cations to which carbonate ions are attracted to induce local mineral supersaturation this may be behind observed changes in both crystal polymorphism favouring formation of less stable polymorphs and crystal morphology where the presence of eps promotes the formation of rounded smoothed crystals or spheroids the role of eps in mineral dissolution bioleaching and corrosion is equivocal eps alone appears to have little effect on mineral dissolution bioleaching or biocorrosion instead it appears that eps increases rates of mineral weathering and leaching by forming complexes with metallic ions released by the mineral surface which may themselves catalyse bioleaching in the case of sulphides eps in biofilms forms effective barriers to the transport of particulate phases and exerts important controls on the transport and deposition of natural and engineered nanoparticles much less is known about the role of eps in the cycling of redox sensitive trace metals intuitively and as observed in microbial mats with sulphate reducing bacteria eps is a labile electron donor for microbial metabolism that could affect metal biogeochemistry but this remains to be conclusively demonstrated in laboratory experiments hence in this and other areas further studies are required to develop a mechanistic basis for including the effects of eps in biogeochemical models

chronological study of oxygen isotope composition for the solar protoplanetary disk recorded in a fluffy type a cai from vigarano abstract fluffy type a ca al rich inclusions cais containing reversely zoned melilite crystals are suggested to be aggregates of direct condensates from solar nebular gas we conducted an investigation of 26 al 26 mg systematics of a fluffy type a cai from vigarano named v2 01 with known oxygen isotopic distributions of reversely zoned melilite crystals we also conducted oxygen isotope measurements of coexisting minerals two of six reversely zoned melilite crystals show continuous variations in magnesium isotopic composition with 25 mg decreasing along the inferred direction of crystal growth which supports the idea that they originated through condensation petrography suggests that the constituent minerals of v2 01 formed in the following order first spinel and fassaite enclosed by melilite then reversely zoned melilite crystals and spinel and diopside in the wark lovering rim the spinel enclosed by melilite has 16 o rich compositions 17 o 24 and on an al mg evolutionary diagram plots along model isochron with an initial value of 26 al 27 al 0 5 6 0 2 10 5 the fassaite enclosed by melilite crystals shows variable oxygen isotopic compositions 17 o 12 and 17 and plots on an isochron with 26 al 27 al 0 5 6 0 2 10 5 the oxygen isotopic compositions of reversely zoned melilite showed continuous variations in 17 o along the inferred direction of crystal growth suggesting that surrounding nebular gas during the formation of the reversely zoned melilite changed from 16 o poor 17 o values larger than 10 to 16 o rich 17 o 25 the six reversely zoned melilite crystals show indistinguishable initial 26 al 27 al values with an average 26 al 27 al 0 of 4 7 0 3 10 5 which is clearly distinguishable from the value of enclosed spinel and fassaite indicating a younger formation age than the enclosed spinel and fassaite the spinel and diopside from the wark lovering rim show 16 o rich compositions 17 o 23 with 26 al 27 al 0 4 5 0 4 10 5 the values of 26 al 27 al 0 are consistent with the formation sequence inferred from petrography the formation period for the v2 01 cai is estimated to be 0 18 0 07 myr from the difference in initial 26 al 27 al values these data suggest that the oxygen isotopic composition of solar nebular gas surrounding the cai changed from 16 o rich to 16 o poor and back to 16 o rich during the first 0 2 myr of solar system formation

high temperature rims around calcium aluminum rich inclusions from the cr cb and ch carbonaceous chondrites abstract we describe the mineralogy petrology and oxygen isotopic compositions of high temperature rims around mineralogically pristine calcium aluminum rich inclusions cais from the cr cb and ch carbonaceous chondrites in cr chondrites nearly all cais are surrounded by single or multi layered rims composed of cai like minerals relict cais inside chondrules in which the rims were resorbed by the host chondrule melt aleon et al 2002 makide et al 2009 are the only exception a complete multi layered rim sequence from inside outward spinel hibonite perovskite melilite anorthite replacing melilite al diopside forsterite is rarely observed al diopside forsterite rims are more common the cr cais and all rim layers are uniformly 16o rich 17o 24 indicating formation in a 16o rich gaseous reservoir the mineralogy petrology and 16o rich compositions of these rims suggest formation by evaporation condensation melting and thermal annealing in the formation region of the host cais we define such rims as the primordial wark lovering wl rims in ch chondrites most cais are uniformly 16o rich and surrounded by the primordial wl rims one of the 16o rich cais is surrounded by an anorthite al diopside wl rim showing a range of 17o values from 24 to 6 17o decreases towards the cai core we infer that this rim experienced incomplete melting and o isotope exchange in an 16o poor nebular gas most likely during chondrule formation most cais in cb chondrites and about 10 of cais in ch chondrites are uniformly 16o depleted igneous inclusions 17o values between individual cais vary from 12 to 5 these cais have diverse mineralogies grossite rich hibonite rich melilite rich spinel rich and al ti diopside forsterite rich but are surrounded by the mineralogically similar igneous rims composed of melilite al diopside and ca rich forsterite 0 5 1 4 wt cao the igneous rims and the host igneous cais have identical within uncertainties of our sims measurements o isotope compositions suggesting that they crystallized from isotopically similar but chemically distinct melts we suggest that the uniformly 16o depleted igneous rims around the uniformly 16o depleted igneous cais in cb and ch chondrites formed during melting of pre existing cais in an impact generated plume invoked for the origin of cb chondrites krot et al 2005 followed by o isotope exchange with an 16o poor plume gas 17o 2 condensation of gaseous sio and mg into cai melt and its subsequent crystallization we conclude that high temperature rims around cais from cr ch and cb chondrites recorded thermal processing in gaseous reservoirs with different oxygen isotopic compositions in contrast to the isotopically heterogeneous wl rims around cv cais our data provide no evidence that cais were transported between 16o rich and 16o poor gaseous reservoirs multiple times we suggest instead that oxygen isotope heterogeneity in the cv wl rims resulted from a fluid rock interaction on the cv parent asteroid

microbially mediated carbonate precipitation in a hypersaline lake big pond eleuthera bahamas microbial metabolism impacts the degree of carbonate saturation by changing the total alkalinity and calcium availability this can result in the precipitation of carbonate minerals and thus the formation of microbialites here the microbial metabolic activity the characteristics and turnover of the extracellular polymeric substances and the physicochemical conditions in the water column and sediments of a hypersaline lake big pond bahamas were determined to identify the driving forces in microbialite formation a conceptual model for organomineralization within the active part of the microbial mats that cover the lake sediments is presented geochemical modelling indicated an oversaturation with respect to carbonates including calcite aragonite and dolomite but these minerals were never observed to precipitate at the mat water interface this failure is attributed to the capacity of the water column and upper layers of the microbial mat to bind calcium a layer of high mg calcite was present 4 to 6 mm below the surface of the mat just beneath the horizons of maximum photosynthesis and aerobic respiration this carbonate layer was associated with the zone of maximum sulphate reduction it is postulated that extracellular polymeric substances and low molecular weight organic carbon produced at the surface i e the cyanobacterial layer of the mat bind calcium both aerobic and anaerobic heterotrophic microbes consume extracellular polymeric substances each process accounting for approximately half of the total consumption and low molecular weight organic carbon liberating calcium and producing inorganic carbon the combination of these geochemical changes can increase the carbonate saturation index which may result in carbonate precipitation in conclusion the formation and degradation of extracellular polymeric substances as well as sulphate reduction may play a pivotal role in the formation of microbialites both in marine and hypersaline environments

26al 26mg chronology and oxygen isotope distributions of multiple melting for a type c cai from allende abstract disequilibrium oxygen isotopic distributions of ca al rich inclusions cais correspond to multiple melting events in the solar nebula 26al 26mg systematics may be applicable for age differences among such melting events we have carried out a coordinated study of detailed petrographic observations and in situ oxygen and magnesium isotope measurements for a type c cai ek1 04 2 from the allende cv3 meteorite to determine the melting events and their ages the cai consists mainly of spinel anorthite olivine and pyroxene and has a core and mantle structure petrography of the core suggests that the crystallization sequence of the core minerals is from spinel anorthite olivine and to pyroxene the mantle has the same mineral assemblage as the core and shows incomplete melting and solidification textures oxygen isotopic compositions of the minerals are distributed along the carbonaceous chondrite anhydrous mineral ccam line 18o 44 to 9 which indicates to preserve a chemical disequilibrium status in the cai spinel shows a 16o rich signature 18o 43 while anorthite is 16o poor 18o 8 olivine and pyroxene in the core have the same oxygen isotopic composition 18o 15 which indicates their equilibrium olivine and pyroxene in the mantle have variable oxygen isotopic compositions and are slightly depleted in 16o 18o 13 to 4 compared with the same minerals in the core the 26al 26mg systematics is consistent with the disequilibrium status observed according to the petrography and oxygen isotopes spinel is plotted on a line of 26al 27al 0 3 5 0 2 10 5 anorthite is plotted on a line of 1 5 10 7 and olivine and pyroxene in the core are plotted on a line of 1 7 10 6 plots of olivine and pyroxene in the mantle are scattered below the isochron of these minerals in the core this study indicates that the ek1 04 2 type c cai underwent multiple heating events after the formation of its cai precursor the precursor cai was formed 0 4 myr after the formation of the solar system defined by canonical cai formation at least 1 6 myr after the precursor cai formation the cai was partially melted and the melt exchanged oxygen isotopes with surrounding 16o poor nebular gas 16o poor olivine and pyroxene in the core crystallized from the melt subsequently al rich chondrules accreted onto the cai and the cai experienced partial melting again and recrystallized to form the mantle the oxygen and magnesium isotopes in anorthite were redistributed during thermal metamorphism in the allende parent body our study reveals that the cai had been retained in the solar nebula for at least 1 6 myr and underwent multiple melting events in the nebula and oxygen and 26al 26mg systematics has been partially disturbed depending on crystal sizes by metamorphism on the parent body

high precision al mg systematics of forsterite bearing type b cais from cv3 chondrites abstract in order to further elucidate possible temporal relationships between different varieties of calcium aluminum rich inclusions cais we measured the aluminum magnesium isotopic systematics of seven examples of the rare type known as forsterite bearing type b fob inclusions from four different cv3 carbonaceous chondrites allende efremovka nwa 3118 and vigarano the primary phases forsterite al ti rich diopside spinel melilite and anorthite in each inclusion were analyzed in situ using high precision secondary ion mass spectrometry sims in all cases minerals with low al mg ratios all except anorthite yield well defined internal al mg isochrons with a range of initial 26al 27al ratios 26al 27al 0 ranging from 5 30 0 22 10 5 down to 4 17 0 43 10 5 anorthite in all cases is significantly disturbed relative to the isochrons defined by the other phases in the same cais and in several cases contains no resolved excesses of radiogenic 26mg 26mg even at 27al 24mg ratios greater than 1000 the fact that some fobs preserve 26al 27al 0 of 5 2 10 5 close to the canonical value of 5 23 0 13 10 5 inferred from bulk magnesium isotope measurements of cv cais b jacobsen et al 2008 demonstrates that fobs began forming very early contemporaneous with other more refractory cais the range of 26al 27al 0 values further shows that fobs continued to be reprocessed over 200 000 years of nebular history consistent with results obtained for other types of igneous cais in cv chondrites the absence of any correlation between of cai fob formation or reprocessing times with bulk composition or cai type means that there is no temporal evolutionary sequence between the diverse cai types the initial 26mg value in the most primitive fob sj101 is significantly lower than the canonical solar system value of 0 040 0 029

magnesium isotope analysis of olivine and pyroxene by sims evaluation of matrix effects abstract the performance of multi collector secondary ion mass spectrometry mc sims for mg isotope ratio analysis was evaluated using 17 olivine and 5 pyroxene reference materials rms the mg isotope composition of these rms was accurately and precisely determined by multi collector inductively coupled plasma mass spectrometry mc icp ms and these measured isotope ratios were used to evaluate sims instrumental mass bias as a function of the forsterite fo content of olivine the magnitude of the mg isotope matrix effects were 3 in 25mg and are a complex function of olivine fo content that ranged from fo59 3 to fo100 in addition to these mg isotope matrix effects si ion yields and mg si ion ratios varied as a complex function of the fo content of the olivine rms for example si ion yields varied by 33 based on the observations we propose instrumental bias correction procedures for sims mg isotope analysis of olivine using a combination of mg si ratios and fo content of olivine using this correction method the accuracy of 25mg analyses is 0 3 except for analysis of olivine with fo86 88 where instrumental biases and mg si ratios change dramatically with fo content making it more difficult to assess the accuracy of mg isotope ratio measurements by sims over this narrow range of fo content five pyroxene rms 3 orthopyroxenes and 2 clinopyroxenes show smaller ranges of instrumental bias 1 4 in 25mg as compared to the olivine rms the instrumental bias for the 3 orthopyroxene rms do not define a linear relationship with respect to enstatite en content that ranged from en85 5 96 3 the clinopyroxene rms have similar en and wollastonite wo contents but have 25mg values that differ by 0 5 relative to their 25mg values determined by mc icp ms these results indicate that additional factors e g minor element abundances likely contribute to sims instrumental mass fractionation in order to better correct for these sims matrix effects additional pyroxene rms with various chemical compositions and known mg isotope ratios are needed

role of the bacterium thiobacillus in the formation of silicates in acidic mine tailings acidophilic chemolithotrophic bacteria such as thiobacillus are commonly found in sulfidic mine tailings they oxidize fe ii and reduced sulfur species from sulfide minerals left in tailings and produce acidic leachates loaded with heavy metals our study of the kam kotia mine tailings cu zn ore an abandoned mine located near timmins ontario canada showed that thiobacillus played an important role in the in situ formation of silicates transmission electron microscopic observations of ultrathin sections of tailings revealed the presence of bacteria with fine grained silica sio2 associated with their cell walls under laboratory conditions mimicking the chemistry of the pore waters of the tailings i e identical ph fe si and so4 thiobacillus promoted the rapid formation 48 h of amorphous silica at low ph values ph 2 2 2 3 while an abiotic system with the same chemical conditions did not show silica precipitation however in the presence of fe oxides silica formation was not observed because dissolved si was preferentially sorbed to the surface of the oxides in addition when the cells were grown in the presence of micas biotite and muscovite under acidic conditions mixed mg al si fe silicate precipitates were formed on the surface of thiobacillus these results indicate that si cycling and solubility in mine tailings could be strongly influenced by bacteria especially in sulfide depleted tailings like the kam kotia ones where the formation of fe oxide is negligible

bacterial extracellular polymeric substances eps mediate caco3 morphology and polymorphism abstract the effect of bacterial extracellular polymers eps on calcium carbonate morphology and polymorphism was investigated by means of free drift mineralisation experiments conducted using cells of the eps producing thermotolerant bacillus licheniformis s 86 the cells either had the eps layer intact native cells or had the eps layer removed eps free cells experiments were also undertaken in the absence of cells but with the addition of the extracted eps solution it was found that the abiotic control and eps free cell experiments contained vaterite and calcite when sampled after 12 h and 48 h whereas the native cell and eps solution experiments contained only calcite these results suggest that the presence of eps inhibits vaterite precipitation it is proposed that dissolved organic carbon doc released from the eps complexes ca 2 ions in solution reducing the calcium carbonate saturation and favouring calcite precipitation over vaterite after 7 days all experiments contained only calcite however distinct morphological differences between the calcite crystals precipitated in the four experiments were preserved after a period of 7 days suggesting that crystal morphology may indicate the biological conditions under which calcite precipitated

26 al 26 mg and 207 pb 206 pb systematics of allende cais canonical solar initial 26 al 27 al ratio reinstated abstract the precise knowledge of the initial 26 al 27 al ratio 26 al 27 al 0 is crucial if we are to use the very first solid objects formed in our solar system calcium aluminum rich inclusions cais as the time zero age anchor and guide future work with other short lived radio chronometers in the early solar system as well as determining the inventory of heat budgets from radioactivities for early planetary differentiation new high precision multi collector inductively coupled plasma mass spectrometry mc icp ms measurements of 27 al 24 mg ratios and mg isotopic compositions of nine whole rock cais six mineralogically characterized fragments and three micro drilled inclusions from the cv carbonaceous chondrite allende yield a well defined 26 al 26 mg fossil isochron with an 26 al 27 al 0 of 5 23 0 13 10 5 internal mineral isochrons obtained for three of these cais a44a ajef and a43 are consistent with the whole rock cai isochron the mineral isochron of ajef with 26 al 27 al 0 4 96 0 25 10 5 anchored to our precisely determined absolute 207 pb 206 pb age of 4567 60 0 36 ma for the same mineral separates reinstate the canonical 26 al 27 al 0 of 5 10 5 for the early solar system the uncertainty in 26 al 27 al 0 corresponds to a maximum time span of 20 ka thousand years suggesting that the allende cai formation events were culminated within this time span although all allende cais studied experienced multistage formation history including melting and evaporation in the solar nebula and post crystallization alteration likely on the asteroidal parent body the 26 al 26 mg and u pb isotopic systematics of the mineral separates and bulk cais behaved largely as closed system since their formation our data do not support the supra canonical 26 al 27 al ratio of individual minerals or their mixtures in cv cais suggesting that the supra canonical 26 al 27 al ratio in the cv cais may have resulted from post crystallization inter mineral redistribution of mg isotopes within an individual inclusion this redistribution must be volumetrically minor in order to satisfy the mass balance of the precisely defined bulk cai and bulk mineral data obtained by mc icp ms the radiogenic 208 pb 206 pb ratio obtained as a by product from the pb pb age dating is used to estimate time integrated 232 th 238 u ratio value of cais limited variations among the minerals within a single cai contrasted by much larger variations among the bulk cais suggest th u fractionation occurred prior to crystallization of igneous cais if interpreted as primordial heterogeneity the value can be used to calculate the mean age of the interstellar dust from which the cais condensed

the nature and origin of type b1 and b2 caal rich inclusions in the allende meteorite abstract the type b ca al rich inclusions in the allende carbonaceous chondrite form a continuous range from the mineralogically concentrically zoned b1 subtype to the unzoned b2 subtype these subtypes differ in i structure texture grain size and shape ii mineralogical proportions and compositions iii accessory mineralogy iv relative abundance of spinel framboids v rim layering vi major element chemistry and vii degree of secondary alteration these differences together with observations on the crystallization of synthetic melts suggest that the b1 inclusions crystallised relatively rapidly from molten parental material while b2 types crystallised relatively slowly close to the solidus from material that had not been completely melted the same data are used to construct an evaporative residue model for the origin of the parental type b materials in the model dust in the protosolar nebula was heated with removal of more volatile elements leaving completely melted type b1 residues at the highest temperatures and incompletely melted less highly evaporated type b2 residues at lower temperatures

distinct mineral weathering effectiveness and metabolic activity between mineral weathering bacteria burkholderia metallica f22 and burkholderia phytofirmans g34 abstract bacteria play important roles in mineral weathering soil formation and the cycling of elements however little is known regarding the interactions between silicate minerals and burkholderia strains in this study mineral weathering bacteria burkholderia metallica f22 and b phytofirmans g34 isolated from the rhizosphere soil of a dominant grass deyeuxia arundinacea l beauv grown on mineral rich and nutrient poor soil were compared for their potash feldspar weathering and metabolic activities during the mineral weathering process although the two strains showed similar mobilization of si strain f22 demonstrated significantly higher al ranging from 41 to 143 and fe ranging from 47 to 4 8 fold mobilization from the mineral compared to strain g34 in addition strain f22 produced higher gluconic acid ranging from 68 to 24 fold and exopolysaccharides ranging from 57 to 2 2 fold than strain g34 significantly lower ph ranging from 2 61 to 3 45 and higher dehydrogenase activity ranging from 24 to 19 fold were observed in the presence of strain f22 than in the presence of strain g34 during the mineral weathering process redundancy analysis illustrated strong positive correlations between the concentrations of gluconic acid and exopolysaccharides and the dissolved al and fe these results demonstrated that the two mineral weathering burkholderia strains behaved differently with respect to mineral weathering and in their metabolic activities the results also suggested that burkholderia metallica f22 promoted potash feldspar weathering by increasing mineral weathering related metabolic activities during the weathering process

oxygen isotopic and chemical zoning of melilite crystals in a type a ca al rich inclusion of efremovka cv3 chondrite abstract different oxygen isotopic reservoirs have been recognized in the early solar system fluffy type a ca al rich inclusions cais are believed to be direct condensates from a solar nebular gas and therefore have acquired oxygen from the solar nebula oxygen isotopic and chemical compositions of melilite crystals in a type a cai from efremovka cv3 chondrite were measured to reveal the temporal variation in oxygen isotopic composition of surrounding nebular gas during cai formation the cai is constructed of two domains each of which has a core mantle structure reversely zoned melilite crystals were observed in both domains melilite crystals in one domain have a homogeneous 16o poor composition on the carbonaceous chondrite anhydrous mineral ccam line of 18o 5 10 which suggests that the domain was formed in a 16o poor oxygen isotope reservoir of the solar nebula in contrast melilite crystals in the other domain have continuous variations in oxygen isotopic composition from 16o rich 18o 40 to 16o poor 18o 0 along the ccam line the oxygen isotopic composition tends to be more 16o rich toward the domain rim which suggests that the domain was formed in a variable oxygen isotope reservoir of the solar nebula each domain of the type a cai has grown in distinct oxygen isotope reservoir of the solar nebula after the domain formation domains were accumulated together in the solar nebula to form a type a cai

exploring the efficiency of stepwise dissolution in removal of stubborn non radiogenic pb in chondrule u pb dating abstract chondrules in chondritic meteorites are unique witnesses of nebular and asteroidal processes that preceded large scale planetary accretion together with refractory calcium aluminium rich inclusions cais they are the sources of our knowledge of the initial evolution of the early solar system we have investigated a single very large 10 mm in longer dimension chondrule hereafter the mega chondrule a25 2 extracted from the allende cv3 chondrite we characterised texture mineralogy and mineral chemistry of this chondrule and studied its al mg u pb and u isotope systematics we also studied the distribution of u th and pb and measured pb isotopic composition in individual minerals of a25 2 by secondary ion mass spectrometry sims the main difficulty in absolute age determination was the presence of pervasive and resilient non radiogenic pb in the search for the best way to separate radiogenic pb from non radiogenic pb components of terrestrial and asteroidal origins we used various protocols of multi step leaching and assessed their efficiency in generating data suitable for the construction of an isochron testing the data filtering procedure led us to explore the behaviour of the stepwise leaching method in the presence of pervasive and resilient non radiogenic pb the model age patterns observed in the final hf partial dissolution steps were probably induced by isotopic fractionation although step leaching did not yield fractions with highly radiogenic pb a pb pb isochron age corrected for measured 238u 235u was obtained by 1 data filtering process based on strict analytical and geochemical criteria to include in the pb pb isochron only leaching steps free from terrestrial contamination and 2 arithmetically recombined analyses to cancel the effects of leaching induced isotopic fractionation this extensive data processing yielded the age of 4568 5 3 0 ma which we consider reliable within its uncertainty limits although it is not as precise as and more model dependent than the age that could have been obtained if pb isotopic compositions were more radiogenic the 238u 235u ratio of the mega chondrule is 137 764 0 016 which is similar to the ratios obtained from single chondrules yet slightly different from small pooled allende chondrules the initial 27al 26al ratio inferred from internal isochron obtained from sims al mg isotope measurements is 5 4 6 5 10 6 which corresponds to 4565 0 0 8 ma assuming homogeneous distribution of 26al throughout the protoplanetary disk at the canonical level 5 2 10 5 this age is 3 5 3 1 ma younger than the pb isotopic age calculation of 26al 26mg age assuming initial 27al 26al 0 of 1 36 0 72 10 5 in the cv chondrule forming region yields the age of 4566 4 0 8 which is consistent with the pb isotopic age

heterogeneous distribution of 26al at the birth of the solar system evidence from refractory grains and inclusions we review recent results on o and mg isotope compositions of refractory grains corundum hibonite and calcium aluminum rich inclusions cais from unequilibrated ordinary and carbonaceous chondrites we show that these refractory objects originated in the presence of nebular gas enriched in 16o to varying degrees relative to the standard mean ocean water value the 17osmow value ranges from approximately 16 to 35 and recorded heterogeneous distribution of 26al in their formation region the inferred 26al 27al 0 ranges from approximately 6 5 10 5 to 2 10 6 there is no correlation between o and mg isotope compositions of the refractory objects 26al rich and 26al poor refractory objects have similar o isotope compositions we suggest that 26al was injected into the 26al poor collapsing protosolar molecular cloud core possibly by a wind from a neighboring massive star and was later homogenized in the protoplanetary disk by radial mixing possibly at the canonical value of 26al 27al ratio approximately 5 10 5 the 26al rich and 26al poor refractory grains and inclusions represent different generations of refractory objects which formed prior to and during the injection and homogenization of 26al thus the duration of formation of refractory grains and cais cannot be inferred from their 26al 26mg systematics and the canonical 26al 27al 0 does not represent the initial abundance of 26al in the solar system instead it may or may not represent the average abundance of 26al in the fully formed disk the latter depends on the formation time of cais with the canonical 26al 27al ratio relative to the timing of complete delivery of stellar 26al to the solar system and the degree of its subsequent homogenization in the disk the injection of material containing 26al resulted in no observable changes in o isotope composition of the solar system instead the variations in o isotope compositions between individual cais indicate that o isotope composition of the cai forming region varied because of coexisting of 16o rich and 16o poor nebular reservoirs gaseous and or solid at the birth of the solar system or because of rapid changes in the o isotope compositions of these reservoirs with time e g due to co self shielding in the disk

26al 26mg isotope systematics of the first solids in the early solar system high precision bulk aluminum magnesium isotope measurements of calcium aluminum rich inclusions cais from cv carbonaceous chondrites in several laboratories define a bulk 26al 26mg isochron with an inferred initial 26al 27al ratio of approximately 5 25 10 5 named the canonical ratio nonigneous cv cais yield well defined internal 26al 26mg isochrons consistent with the canonical value these observations indicate that the canonical 26al 27al ratio records initial al mg fractionation by evaporation and condensation in the cv cai forming region the internal isochrons of igneous cv cais show a range of inferred initial 26al 27al ratios 4 2 5 2 10 5 indicating that cai melting continued for at least 0 2 ma after formation of their precursors a similar range of initial 26al 27al ratios is also obtained from the internal isochrons of many cais igneous and nonigneous in other groups of carbonaceous chondrites some cais and refractory grains corundum and hibonite from unmetamorphosed or weakly metamorphosed chondrites including cvs are significantly depleted in 26al at least some of these refractory objects may have formed prior to injection of 26al into the protosolar molecular cloud and its subsequent homogenization in the protoplanetary disk bulk aluminum and magnesium isotope measurements of various types of chondrites plot along the bulk cv cai isochron suggesting homogeneous distribution of 26al and magnesium isotopes in the protoplanetary disk after an epoch of cai formation the inferred initial 26al 27al ratios of chondrules indicate that most chondrules formed 1 3 ma after cais with the canonical 26al 27al ratio

microbes produce nanobacteria like structures avoiding cell entombment microsedimentary structures referred to as nanobacteria like particles were described from modern carbonate environments where they form in close spatial association with sulfate reducing bacteria srb however the exact mechanism of their formation as well as their paleontological significance remains controversial here we report on an investigation of microbe mineral interactions in experimentally produced carbonate globules the experiments were carried out under anoxic conditions at 30 c with desulfovibrio brasiliensis a srb known to mediate dolomite formation we observed that extracellular polymeric substances eps secreted by the microbial community play a key role in the mineralization process nanobacteria like particles represent the early stage of carbonate nucleation within the eps which progressively evolve to larger globules displaying a grainy texture we excluded the possibilities that these structures are fossils of nanobacteria dissolution surfaces or artifacts created during sample preparation d brasiliensis cells are predominantly located outside of the eps aggregates where mineral growth takes place as a result they remain mobile and are rarely entombed within the mineral this self preservation behavior may not be limited to d brasiliensis other microbes may produce or may have produced during the geological past biogenic minerals through a similar process mineralization within eps explains why microbial relics are not necessarily present in biogenic carbonates

fluffy type a ca al rich inclusions in the allende meteorite abstract allende fluffy type a s fta s are a distinct sub group of ca al rich inclusions whose primary mineral assemblage consists of al rich melilite ak 0 33 spinel that is commonly very v rich perovskite and frequently hibonite some contain relatively coarse grained melilite up to 1 5 mm that is intensely kink banded and commonly reversely zoned hibonite and v rich spinel others contain much finer grained and strain free melilite 50 m and have not been found to contain hibonite or v rich spinel some fta s contain both coarser and finer grained melilite and textural relationships indicate that the latter is replacing the former fta s are characterized by extremely irregular shapes and 60 75 volume per cent of fine grained secondary alteration products many are aggregates of innumerable nodules each of which is surrounded by a wark lovering type rim sequence these nodules are frequently separated from one another by matrix like clastic rim material other fta s do not have nodular structure structural and mineralogical characteristics of their wark lovering rims suggest that fta s did not achieve their shapes by deformation of a liquid or a hot plastic solid in contrast to those in type b inclusions formation of reverse zoning in the coarser grained melilite crystals in fta s cannot be understood in terms of crystallization from a liquid but are readily explainable by condensation from a solar nebular gas during a period of falling pressure further evidence against a liquid origin is the wide range of spinel compositions within individual coarser grained fta s the fact that the reversely zoned melilite crystals cannot have been produced in any kind of sublimation or distillation process precludes formation of these inclusions as volatilization residues fta s are aggregates in some of which are preserved vapor solid condensate grains that formed at high temperature in the solar nebula

plagioclase rich inclusions in carbonaceous chondrite meteorites liquid condensates plagioclase rich inclusions in carbonaceous chondrites are of two types 1 mm cm sized ca al rich inclusions cais with 30 60 vol anorthite and up to 35 vol each of ti al pyroxene tpx melilite and spinel and 2 smaller 3 mm ca chondrules similar to those found in ordinary chondrites containing more sodic plagioclase pyroxene olivine and spinel the cais which were formerly named type i and thought to be intermediate between type a and type b cais are shown to be an independent type renamed type c with distinctive chemical and mineralogical compositions type c cais have group i or group ii trace element patterns low initial 26al27al ratios of 5 10 6 typical ak 35 55 melilite tpx with 2 12 tio2 and opaque grains osirrumopt alloy nuggets and fremdlinge smaller than 10 m the textures sequence of crystallization and concentric zonation indicate that they crystallized from melt droplets the texture of the anorthite ranges from coarse laths to a fine grained groundmass reflecting increasing retardation of its nucleation the few cais with the coarse laths cooled slowly 2 5 h from below the liquidus but the majority cooled faster from completely molten material as the elemental abundances in type c s are dominated by volatility the melts were not formed by planetary magmatic processes evaporative residues and remelted solid condensates are also ruled out because the compositions of naturally occurring experimentally produced and thermodynamically calculated residues and solid condensates differ from those of type c cais type c cais have compositions similar to those calculated for liquid condensates under high solar gas pressure 1 atm or in dust rich environments and are probably liquid condensates the few type c cais that crystallized from incompletely molten materials may have been reheated liquid condensates or mixed liquidsolid condensates

internal 26al 26mg isotope systematics of a type b cai remelting of refractory precursor solids high precision sims 26 al 26 mg isotope analyses were performed for a pristine type b1 cai leoville 3535 1 on multiple mineral phases that include aluminum rich zoned melilite mantle ak20 ak60 magnesium rich melilite ak70 fassaite spinel and anorthite in the core the data yield a well defined internal isochron with an inferred initial 26 al 27 al ratio of 5 002 0 065 10 5 which is lower than those of bulk cais and pristine fine grained cais assuming homogeneous dis tribution of 26 al in the early solar system leoville 3535 1 formed 50 ka after the time corresponding to the bulk cai iso chron one anorthite analysis near the grain boundary adjacent to melilite shows sub lm scale heterogeneous magnesium distribution though the 26 al 26 mg data plot on the isochron regression thus the internal 26 al 26 mg system of the cai remained closed since the last melting event that crystallized anorthite high precision magnesium isotope analyses of magnesium rich minerals fassaite magnesium rich melilite and spinel show a small amount of scatter from the regression line 0 1 beyond analytical uncertainties most spinel and some fassa ite data are systematically displaced below and above the regression line respectively it is likely that spinel remained unmelted at the time of the last melting event while fassaite and anorthite crystallized from a partial melt the regression line made by fassaite and anorthite data shows an initial 26 al 27 al ratio indistinguishable from that using all data mass dependent fractionation of magnesium isotopes in spinel is the same as those in melilite and fassaite d 25 mg 5 indicating that magnesium isotope fractionation presumably from evaporative magnesium loss predated the last melting event thus a majority of the cai appears to have escaped magnesium isotope exchange with nebular gas during the last melting event except for the outer rim of the melilite mantle that shows slightly lower d 25 mg values the 26 al 26 mg systematics of this leoville type b cai suggest it experienced a final melting event at 50 ka after the initial al mg fractionation event this may correspond to melting during the active protostar stage known as class i during which sporadic high temperature heating events repeatedly affected refractory solids in the solar nebula 2012 elsevier ltd all rights reserved

nucleation of calcium carbonate on bacterial nanoglobules nucleation of calcium carbonate on microbial cell material may have been the dominant mode of microbial carbonate formation during most of earth s history current knowledge predicts that nucleation takes place on the cell surface or on extracellular polymeric substances however the initial nucleation steps have not been described in detail and the process remains elusive here we describe the bacterial nucleation of calcium carbonate at the nanometer scale in our precipitation experiment with sulfate reducing bacteria srb the bulk of calcium carbonate precipitates on hundreds of individual globules 60 200 nm in diameter globules originate from the srb cell surface but calcify significantly only when released to the culture medium similar globules have been observed albeit at a much larger scale in other bacterial precipitation experiments and in many natural microbial carbonates suggesting that the process we describe could be an important step in microbial calcification

black sea thermohaline properties long term trends and variations the current knowledge about spatial and temporal dynamics of the black sea s thermohaline structure is incomplete because of missing data and sparse distribution of existing measurements in space and time this study presents 56 year continuous simulations of the black sea s hydrodynamics using the 3d general estuarine transport model getm without incorporating any relaxation towards climatological or observational data fields this property of the model allows us to estimate independent temporal trends in addition to resolving the spatial structure the simulations suggest that the intermediate layer temperature is characterized by a weak positive trend warming whereas the surface temperature does not show a clear linear trend different salinity trends have been established at the surface negative upper weaker negative and main halocline positive three distinct dynamic periods are identified 1960 1970 1970 1995 1995 2015 which exhibit pronounced changes in the black sea s thermohaline properties and basin circulation strengthening of the main cyclonic circulation accompanied by intensification of the mesoscale anticyclonic eddy formation is found both events strongly affect the sea surface salinity but contribute in opposing directions specifically strong composite large scale circulation leads to an increase in sea surface salinity while enhanced formation of mesoscale anticyclones decreases it salinity evolution with time is thus the result of the competition of these two opposing yet interdependent processes

oceanography of the black sea a review of some recent results abstract a new synthesis of the black sea oceanography is presented primarily based on studies carried out in the southern black sea as well as on some recent work covering the entire basin obtained in a new era of increasing cooperation between the riparian countries a review of the physical environment is given seasonal and interannual climatic variability of the system are discussed in relation to its hydrology water mass variability and formation are studied with emphasis on the inflow of mediterranean waters pycnocline variability shelf and internal mixing and double diffusive convection the general circulation of the basin and the roles of stratification topography and coastline variations in determining the behaviour of the rapid unstable boundary currents and upwelling along the coast are discussed based on hydrographic data and satellite observations impacts of the physical processes on the ecosystem are discussed

the formation of rims on calcium aluminum rich inclusions step i flash heating abstract wark lovering rims of six calcium aluminum rich inclusions cais representing the main cai types and groups in allende efremovka and vigarano were microsurgically separated and analysed by neutron activation analysis naa all the rims have similar 4x enrichments relative to the interiors of highly refractory lithophile and siderophile elements the naa results are confirmed by ion microprobe and scanning electron microscope sem analyses of rim perovskites and rim metal grains less refractory eu yb v sr ca and ni are less enriched in the rims the refractory element patterns in the rims parallel the patterns in the outer parts of the cais in particular the rims on type b1 cais have the igneously fractionated rare earth element ree pattern of the melilite mantle below the rim and not the ree pattern of the bulk cai proving that the refractory elements in the rims were derived from the outer mantle and were not condensates onto the cais the refractory elements were enriched in an al2o3 rich residue 50 m thick after the most volatile 80 of the outermost 200 m of each cai had been volatilized including much mg si and ca some volatilization occurred below the rim and created refractory partial melts that crystallized hibonite and gehlenitic melilite the required flash heating probably exceeded 2000 c but for only a few seconds in order to melt only the outer cai and to unselectively volatilize slow diffusing o isotopes which show no mass fractionation in the rim the volatilization did however produce heavy mass fractionated mg in rims in some cais this was later obscured when normal mg diffused in from accreted olivine grains at relatively high temperature not the lower temperature meteorite metamorphism and created the 50 m set of monomineralic rim layers of pyroxene melilite and spinel

oxygen isotopic composition of the solar nebula gas inferred from high precision isotope imaging of melilite crystals in an allende cai high precision isotope imaging analyses of reversely zoned melilite crystals in the gehlenitic mantle of type a cai on01 of the allende carbonaceous chondrite reveal that there are four types of oxygen isotopic distributions within melilite single crystals 1 uniform depletion of 16o 18o 10 2 uniform enrichment of 16o 18o 40 3 variations in isotopic composition from 16o poor core to 16o rich rim 18o 10 to 30 20 to 45 and 10 to 35 with decreasing akermanite content and 4 16o poor composition 18o 10 along the crystal rim hibonite spinel and perovskite grains are 16o rich 18o 45 and adjoin 16o poor melilites gas solid or gas melt isotope exchange in the nebula is inconsistent with both the distinct oxygen isotopic compositions among the minerals and the reverse zoning of melilite fluid rock interaction on the parent body resulted in 16o poor compositions of limited areas near holes cracks or secondary phases such as anorthite or grossular we conclude that reversely zoned melilites mostly preserve the primary oxygen isotopic composition of either 16o enriched or 16o depleted gas from which they were condensed the correlation between oxygen isotopic composition and akermanite content may indicate that oxygen isotopes of the solar nebula gas changed from 16o poor to 16o rich during melilite crystal growth we suggest that the radial excursions of the inner edge of the protoplanetary disk gas simultaneously resulted in both the reverse zoning and oxygen isotopic variation of melilite due to mixing of 16o poor disk gas and 16o rich coronal gas gas condensates aggregated to form the gehlenite mantle of the type a cai on01

oxygen isotopic zoning of reversely zoned melilite crystals in a fluffy type a ca al rich inclusions from the vigarano meteorite the oxygen isotopic microdistributions within melilite measured using in situ secondary ion mass spectrometry correspond to the chemical zoning profiles in single melilite crystals of a fluffy type a ca al rich inclusions cais of reduced cv3 vigarano meteorite the melilite crystals show chemical reverse zoning within an individual single crystal from the akermanite rich core to the akermanite poor rim the composition changes continuously with the crystal growth the zoning structures suggest that the melilite grew in a hot nebular gas by condensation with decreasing pressure the oxygen isotopic composition of melilite also changes continuously from 16o poor to 16o rich with the crystal growth these observations suggest that the melilite condensation proceeded with change consistent with an astrophysical setting around the inner edge of a protoplanetary disk where both 16o rich solar coronal gas and 16o poor dense protoplanetary disk gas could coexist fluffy type a cais could have been formed around the inner edge of the protoplanetary disk surrounding the early sun

formation and changes of the black sea cold intermediate layer abstract the local properties of the cold intermediate layer cil in the black sea are examined over the period 1960 2015 using a 3d numerical model and realistic forcing the simulations demonstrate a substantially large multi annual cil variability and confirm two major mechanisms i cooling of the surface waters in the basin interior in winter and ii transportation of cold water masses formed in winter on the north western shelf nws transported by the main cyclonic current and by mesoscale eddies on the shelf break both processes are crucially important for the cil formation as was suggested by previous studies the novel element of the present study is the quantification of the relative importance of these mechanisms during a prolonged time period in particular i plays a key role for the cil formation in the basin interior while ii controls cil renewal along the main cyclonic current and basin exterior as well as in the south eastern region in order to isolate the effects of basin circulation and the nws cold water masses contribution the distribution of passive tracer originating from the nws is studied tracer distribution in the basin interior indicates that a large fraction of the cold nws water is transported via the main cyclonic current to the eastern convergence and anticyclonic areas a smaller fraction of the cold nws water is transported to the central part of the basin the cooling capacity of the cil is highly variable and decreases drastically in the last decade of simulation approaching zero due to changes in regional weather conditions

seasonal interannual and mesoscale variability of the black sea upper layer circulation derived from altimeter data 1 topex poseidon and ers altimeter data comprising the period from may 1992 to may 1999 are assimilated into a shallow water model for providing a dynamically consistent interpretation of the sea surface height variations and estimation of the temporal and spatial characteristics of the upper layer circulation in the black sea these 7 year long observations offer a new capability for interpretation of major transient and quasi permanent features of the upper layer circulation the instantaneous flow fields involve a complex eddy dominated system with different types of structural organizations in which the eddies and the gyres of the interior cyclonic cell interact continuously among themselves and with meanders and filaments of the rim current the circulation possesses a distinct seasonal cycle whose major characteristic features repeat every year with some year to year variability an organized two gyre winter circulation system disintegrates gradually into a series of interconnecting eddies in the summer and autumn months which are also characterized by more pronounced and complex mesoscale activity in the peripheral flow system our analyses suggest a revised schematic circulation picture of the major quasi permanent and recurrent elements of the black sea

well resolved variations in the formation ages for ca al rich inclusions in the early solar system recent whole rock magnesium isotopic data for calcium aluminum rich inclusions cais in chondrite meteorites indicate that the primary nebular fractionation of aluminum from magnesium probably by condensation occurred within 20 000 years at 4 567 ga however high precision multicollector ion microprobe data for diverse cais from vigarano cv3 yield internal isochrons with a clearly resolved spread in initial 26al 27al meaning that cais formed and were reprocessed over a much longer time span primitive unmelted cais have a consistent value of 5 2 0 1 10 5 melted cais range from 5 17 10 5 to 4 24 10 5 and one single object with a complex multistage history has an internal range of 26al 27al 4 77 2 77 10 5 the entire range corresponds to an age span of 0 7 ma thus not all cais formed at time zero and only the most primitive cais should be used as benchmarks for earliest solar system chronology

a once molten coarse grained ca rich inclusion in allende a compact spheroidal type b inclusion in allende contains melilite laths that project radially inward from the inclusion edge which show interference growth textures the combined textural and chemical features of this object cannot be explained by independent vapor solid condensation of grains in space followed by random aggregation of these grains into an inclusion rather it probably formed from a once molten droplet that crystallized in response to radiative cooling from its outer surface the crystallization sequence in this and another similar inclusion in which oxygen isotopes have been measured is melilite spinel anorthite fassaite this sequence supports the idea that oxygen isotopic heterogeneities in coarse grained inclusions were formed after complete solidification of these objects by partial exchange with a less16o rich gas and not during or before a melting event

climatic variability of the sub surface sea temperatures in the aegean black sea system and relation to meteorological forcing non smoothed yearly temperature records with minimal statistical uncertainties are constructed for winter and summer of the period 1950 2000 in two areas in the aegean sea for the sub surface layer of 80 120 m and two areas in the black sea for the sub surface layer of sigma theta isopycnals between 14 5 and 15 4 the specific areas are selected mostly because of the dense hydrographic data coverage they have during the period 1950 2000 two trend regimes appear in both seas a period of decreasing sea temperatures from the early mid 1960s to the early mid 1990s and an apparent warming afterwards trends in sea temperatures correlate with trends in the north atlantic oscillation nao and partly the east atlantic west russian eawr indexes but the signs of nao and or eawr cannot sufficiently justify the winter to winter temperature changes in the entire study area in examining the wind flows in the sea level pressure maps for characteristic winters in which local peaks in the sea temperature records occur we identify particular sea level pressure structures that are not accounted for by the typical north atlantic or east atlantic west russia positive or negative dipoles in addition there are winters when the siberian high induces local maxima in sea temperatures in the study area a spectral coherence analysis of the unfiltered winter sea temperature and the corresponding teleconnection nao eawr records shows that common spectral and coherence peaks exist at 5 6 9 10 and 15 17 years

the upper layer circulation of the black sea its variability as inferred from hydrographic and satellite observations quasi synoptic hydrographic data and satellite imagery are used to describe the circulation and the structural variability of the black sea with particular emphasis on the turkish coast the circulation is indicated to involve a variable cyclonic circulation with no apparent central locus and a well defined cyclonic rim current containing meanders and interacting eddy fields confined to the shelf slope interspersed between the coastal eddies are filaments and intense jets often with dipole eddies at their termina the extension of these features across the shelf slope into the central basin offshore waters implies important dynamical processes related to the shelf deep basin exchanges these features are often steered by the topography and evolve continuously through the mixed baroclinic barotropic instability of the rim current

182hf 182w age dating of a 26al poor inclusion and implications for the origin of short lived radioisotopes in the early solar system refractory inclusions calcium aluminum rich inclusions cais represent the oldest solar system solids and provide information regarding the formation of the sun and its protoplanetary disk cais contain evidence of now extinct short lived radioisotopes e g 26al 41ca and 182hf synthesized in one or multiple stars and added to the protosolar molecular cloud before or during its collapse understanding how and when short lived radioisotopes were added to the solar system is necessary to assess their validity as chronometers and constrain the birthplace of the sun whereas most cais formed with the canonical abundance of 26al corresponding to 26al 27al of 5 10 5 rare cais with fractionation and unidentified nuclear isotope effects fun cais record nucleosynthetic isotopic heterogeneity and 26al 27al of 5 10 6 possibly reflecting their formation before canonical cais thus fun cais may provide a unique window into the earliest solar system including the origin of short lived radioisotopes however their chronology is unknown using the 182hf 182w chronometer we show that a fun cai recording a condensation origin from a solar gas formed coevally with canonical cais but with 26al 27al of 3 10 6 the decoupling between 182hf and 26al requires distinct stellar origins steady state galactic stellar nucleosynthesis for 182hf and late stage contamination of the protosolar molecular cloud by a massive star s for 26al admixing of stellar derived 26al to the protoplanetary disk occurred during the epoch of cai formation and therefore the 26al 26mg systematics of cais cannot be used to define their formation interval in contrast our results support 182hf homogeneity and chronological significance of the 182hf 182w clock

geomicrobiology of carbonate silicate microbialites from hawaiian basaltic sea caves abstract modern microbial mats and microbialites are described from basaltic sea caves on the island of kauai hi the mats grow on the ceilings and walls in the photic zone of several open caves where fresh water seeps out of the rock scanning sem and transmission electron microscopy tem showed that the active mats are dominated by filamentous and nonfilamentous cyanobacteria in the surface layers and heterotrophic bacteria in deeper layers energy dispersive x ray analysis revealed that copious amounts of extracellular polymeric substances eps are rich in mg si o and ca likely concentrated from solution petrographic microscopy and electron microprobe analysis of the mineralized microbialites showed textures reminiscent of stromatolitic laminations consisting mainly of alternating calcium carbonate calcite and aragonite and magnesium rich silicate kerolite thin coatings rich in magnesite hydromagnesite and monohydrocalcite surround the microbialites on the rock surfaces and are likely inorganic in origin within the mats minerals tend to form and concentrate within or around dense matrices of eps microenvironments with geochemical conditions favorable for mineral crystallization likely develop in the mats as a result of the mucilaginous extracellular material and the development of bacterial microcolonies in addition copious amounts of extracellular polymers bind ions from solution and provide nucleation sites for mineral crystallization and growth this combination of biological and inorganic processes can explain the occurrence of the secondary minerals in these caves as well as the stromatolitic textures of the microbialites

phosphate stromatolites from condensed cephalopod limestones upper jurassic southern spain upper jurassic phosphate stromatolites of the almola sierra southern spain encrust macrofossils and hardgrounds and form oncoids included within pelagic condensed fossiliferous limestones their accretion was determined by bacterially mediated precipitation of phosphate by the trapping and binding of fine siliciclastics and pelagic biomicrite and by the encrustation of benthonic foraminifera phosphorous trace elements and rare earth elements were concentrated from degraded organic matter and seawater by stromatolite building communities which mediated the formation of phosphate rich and fe al si rich organic gels under oxic conditions favouring the precipitation of amorphous mineral precursors acp and fe al si oxyhydroxides the observed ce enrichment for some stromatolites is explained by oxidative scavenging of ce4 from seawater by fe mn oxyhydroxides the bacterially mediated gels were able to migrate and fill the voids of the stromatolite structure and later changed to carbonate fluorapatite haematite and poorly crystalline fe rich clays under postoxic conditions phosphatization of trapped carbonate particles also occurred the phosphate stromatolites formed on a sediment starved pelagic swell during periods of no carbonate sedimentation and hardground development stromatolite lamination provides evidence for rhythmic alternation between bacterially mediated phosphogenesis sedimentation and erosion suggesting episodic changes in the sedimentary environment although some of the parameters that controlled phosphate precipitation associated with the stromatolites local high organic productivity sediment starvation moderate depth of deposition and physicochemical conditions were similar to those found in modern and ancient phosphogenic settings the palaeogeographical framework and the intensity of sedimentary processes were different to those of the world s major phosphorite deposits

variations in initial 26al 27al ratios among fluffy type a ca al rich inclusions from reduced cv chondrites abstract al mg mineral isochrons of three ca al rich inclusions cais that formed primarily by condensation one fine grained spinel rich inclusion and two fluffy type a cais from the reduced cv chondrites efremovka and vigarano were obtained by in situ al mg isotope measurements using secondary ion mass spectrometry the slope of the isochron obtained for the fine grained spinel rich inclusion gives an initial 26al 27al value 26al 27al 0 of 5 19 0 17 10 5 this is essentially identical to the solar system initial 26al 27al determined by whole rock al mg isochron studies for cais in cv chondrites in contrast the isochron slopes for the two fluffy type a cais from their al mg mineral isochrons 4 703 0 082 10 5 and 4 393 0 084 10 5 are significantly lower than the solar system initial value the range of 26al 27al 0 values of the three cais from 5 19 0 17 to 4 393 0 084 10 5 corresponds to a formation age spread of 0 17 0 04 myr this formation age spread is similar to that of igneous cais from cv chondrites the data suggest that condensation and melting of minerals occurred in the hot nebular gas contemporaneously for 0 2 myr at the very beginning of our solar system if 26al was distributed homogeneously in the cai forming region alternatively the observed variations in 26al 27al 0 among fluffy type a cais would also raise a possibility of heterogeneous distributions of 26al in the forming region