does planetary differentiation really fractionate iron isotopes the difference in the mean fe isotope composition of samples from the earth moon mars and vesta has been recently interpreted as tracking contrasted planetary accretion mechanisms f poitrasson a n halliday d c lee s levasseur n teutsch iron isotope differences between earth moon mars and vesta as possible records of contrasted accretion mechanisms earth planet sci lett 223 2004 253 266 using newly produced fe isotopic data on terrestrial and lunar samples pallasites eucrites and martian meteorites weyer et al s weyer a d anbar g p brey c munker k mezger a b woodland iron isotope fractionation during planetary differentiation earth planet sci lett 240 2005 251 264 reinterpreted these data as fingerprinting planetary differentiation in particular these authors suggested that partial melting in the terrestrial and lunar mantles produced melts isotopically heavy it is shown here that the inference of weyer et al s weyer a d anbar g p brey c munker k mezger a b woodland iron isotope fractionation during planetary differentiation earth planet sci lett 240 2005 251 264 is strongly biased by the sampling approach taken notably these authors used olivine in place of the host bulk peridotites 57fe signatures despite this mineral has been shown to be frequently isotopically lighter than coexisting phases and they analyzed lunar samples heavily affected chemically by the meteoritic bombardment a process known to alter fe isotope signatures their pallasite metal silicate fractionation data are also likely biased by the approach adopted to estimate the iron isotope composition of the different mineral phases in fact their conclusion of fe isotopic fractionation during basalt extraction from planetary mantles is invalidated by the observation that basaltic shergottites and eucrites have 57fe indistinguishable from those of chondrites therefore the heavier fe isotopic composition of the moon relative to the earth itself heavier than most chondrites and achondrites remains best explained by loss of light iron isotopes during the high temperature event accompanying the interplanetary impact that led to the formation of the moon f poitrasson a n halliday d c lee s levasseur n teutsch iron isotope differences between earth moon mars and vesta as possible records of contrasted accretion mechanisms earth planet sci lett 223 2004 253 266 f poitrasson s levasseur n teutsch significance of iron isotope mineral fractionation in pallasites and iron meteorites for the core mantle differentiation of terrestrial planets earth planet sci lett 234 2005 151 164

geochemical characteristics and hydrocarbon generation modeling of the jurassic source rocks in the shoushan basin north western desert egypt abstract the shoushan basin is an important hydrocarbon province in the western desert egypt but the origin of the hydrocarbons is not fully understood in this study organic matter content type and maturity of the jurassic source rocks exposed in the shoushan basin have been evaluated and integrated with the results of basin modeling to improve our understanding of burial history and timing of hydrocarbon generation the jurassic source rock succession comprises the ras qattara and khatatba formations which are composed mainly of shales and sandstones with coal seams the toc contents are high and reached a maximum up to 50 the toc values of the ras qattara formation range from 2 to 54 wt while khatatba formation has toc values in the range 1 47 wt the ras qattara and khatatba formations have hi values ranging from 90 to 261 mghc gtoc suggesting types ii iii and iii kerogen vitrinite reflectance values range between 0 79 and 1 12 vrr rock eval t max values in the range 438 458 c indicate a thermal maturity level sufficient for hydrocarbon generation thermal and burial history models indicate that the jurassic source rocks entered the mature to late mature stage for hydrocarbon generation in the late cretaceous to tertiary hydrocarbon generation began in the late cretaceous and maximum rates of oil with significant gas have been generated during the early tertiary paleogene the peak gas generation occurred during the late tertiary neogene

no iron isotope fractionation between molten alloys and silicate melt to 2000 c and 7 7 gpa experimental evidence and implications for planetary differentiation and accretion abstract whether core mantle differentiation of terrestrial planets fractionates iron isotope is currently a debated issue melting experiments corresponding to the conditions inferred for core differentiation in an early silicate magma ocean were performed at 1750 and 2000 c and from 1 to 7 7 gpa to address this question the starting mixtures correspond to a devolatilized ci chondrite composition and oxygen fugacity conditions were 2 log units below the iron wustite buffer scanning electron microscopy observations electron microprobe chemical analyses and plasma source mass spectrometric isotope analyses of the experimental charges show that chemical and iron isotope equilibrium was reached at 2000 c within 100 s no fe isotope fractionation was found between the fe ni alloy and the ultramafic silicate melt at this temperature this result holds within the 2 7 7 gpa pressure range and is likely to remain valid at higher pressures and temperatures the addition of sulfur to the system does not alter this conclusion the compilation of all experiments conducted at 2000 c yields 57 fe metal silicate glass 0 047 0 063 our results suggest that significant iron isotope fractionation is unlikely during equilibration of molten core forming materials in a deep magma ocean this process therefore cannot explain the heavier fe isotope composition of the moon relative to the earth itself heavier than mars vesta and chondrite parent bodies

high thermal maturity in the lower saxony basin intrusion or deep burial abstract the lower saxony basin lsb is situated at the southern rim of the northern permian basin the most important hydrocarbon bearing province in europe in its southern part areas of high thermal maturation up to 6 rr occur which were previously explained as being caused by magmatic intrusions of turonian to santonian age that affected carboniferous to lower cretaceous rocks in this area 2d numerical basin modelling was carried out in order to reconstruct the temperature histories along two parallel n s trending seismic sections along these sections new data about maturity distribution and temperature history were obtained by vitrinite reflectance measurements and apatite fission track analysis for the areas with highest maturity values low coalification gradients were established which agree well with earlier published data on wells further towards the west this new information does not support previous hypotheses on high heat flows from magmatic intrusions even if lateral heat transport is taken into account instead comparisons with a recently published map of the subsurface structure of the lsb indicate that maturity distribution may be closely related to major tectonic structures deep burial of individual structures of the lsb which are bordered by deep e w to ese wnw trending faults is further suggested by a rapidly increasing thicknesses of preserved cretaceous strata towards the south and b structural restoration of one of the seismic sections to achieve a fit between measured and calculated palaeo temperature and vitrinite reflectance data deep burial of carboniferous source rocks during cretaceous time has to be assumed due to an inversion phase in the early and middle upper cretaceous major amounts of sediment were removed and further uplift occurred in tertiary times in contrast the northern part of the lsb experienced maximum burial and temperatures during tertiary times

early stages of core segregation recorded by fe isotopes in an asteroidal mantle ureilites displays 56 fe values higher than average chondrite 29 segregation of fe sulfide melts explains the high 56 fe values in ureilites 30 formation of a core can begin at very low degrees of melting through the circulation of a fe s melt 31 through a silicate mantle 32 33 earth and planetary science letters in press 11 3 15 34 2 35 abstract 36 37 ureilite meteorites are achondrites that are debris of the mantle of a now disrupted 38 differentiated asteroid rich in carbon they provide a unique opportunity to study the differentiation 39 processes of such a body we analyzed the iron isotopic compositions of 30 samples from the ureilite 40 parent body upb including 29 unbrecciated ureilites and one ureilitic trachyandesite alm a 41 which is at present the sole large crustal sample of the upb the 56 fe of the whole rocks fall within a 42 restricted range from 0 01 to 0 11 with an average of 0 056 0 008 which is significantly 43 higher than that of chondrites we show that this difference can be ascribed to the segregation of s 44 rich metallic melts at low degrees of melting at a temperature close to the fe fes eutectic and 45 certainly before the onset of the melting of the silicates 1100 c in agreement with the marked s 46 depletions and the siderophile element abundances of the ureilites these results point to an efficient 47 segregation of s rich metallic melts during the differentiation of small terrestrial bodies 48 49

a comparison of burial maturity and temperature histories of selected wells from sedimentary basins in the netherlands sedimentary basins in the netherlands contain significant amounts of hydrocarbon resources which developed in response to temperature and pressure history during mesozoic and cenozoic times quantification and modelling of burial maturity and temperature histories are the major goals of this study allowing for a better understanding of the general geological evolution of the different basins as well as petroleum generation all major basins in the netherlands encountered at least one time of inversion and therefore moderate to high amounts of erosion in order to determine the amount of inversion the basins have experienced a 1d study was performed on 20 wells within three basins west netherlands central netherlands and lower saxony basins new vitrinite reflectance values were obtained and existing data re evaluated to gain a good data base the burial histories of six wells two for each studied basin are presented here to demonstrate the differences in basin evolution that led to their present shape and petroleum potential the permo triassic subsidence phase can be recognized in all three basins but with varying intensity in the jurassic the basins experienced different relative movements that culminated in the cretaceous when the influence of the inversion caused erosion of up to 2 500 m most wells show deepest burial at present day whereas the timing of maximum temperature differs significantly springer verlag 2007

iron isotope differences between earth moon mars and vesta as possible records of contrasted accretion mechanisms the iron isotope compositions of shergotty nakhla chassigny snc meteorites thought to come from mars eucrites and diogenites assumed to sample asteroid 4 vesta and rocks from the moon and earth have been measured using high precision plasma source mass spectrometry the means of eight samples from mars and nine samples from vesta are within error identical despite a range of rock types they are lighter by 0 1 in 57fe 54fe compared to the average of 13 terrestrial mantle derived rocks the latter value is identical within uncertainty with a previously published mean of 46 igneous rocks from the earth the average for 14 lunar basalts and highland plutonic rocks covering a broad spectrum of major element composition is heavier by 0 1 in 57fe 54fe relative to our estimate for the earth s mantle and therefore 0 2 heavier than the eucrites diogenites and snc meteorites however the data scatter somewhat and the apollo 15 green glass and apollo 17 orange glass are identical to samples from mars and vesta there is no clear relationship between petrological characteristics and fe isotope composition despite a wide spectrum of samples instead contrasted planetary isotopic signatures are clearly resolved statistically after evaluating alternative scenario it appears that the most plausible explanation for the heavier fe in the earth and moon is that both objects grew via processes that involved partial vaporisation leading to kinetic iron isotope fractionation followed by minor loss this is consistent with the theory in which the moon is thought to have originated from a giant impact between the proto earth and another planet combined with numerical simulations fe isotope data can offer the potential to provide constraints on the processes that occurred in planetary accretion

iron and zinc isotope fractionation during magmatism in the continental crust evidence from bimodal volcanic rocks from hailar basin ne china abstract this study presents fe zn isotope data for a suite of well characterized bimodal volcanic rocks from hailar basin northeast china to understand the mechanism of fe isotope fractionation in highly differentiated igneous rocks the samples range from basaltic trachyandesites to trachytes rhyodacites and rhyolites the 56 fe values increase with increasing sio 2 contents with the rhyolites having the highest 56 fe up to 0 64 0 02 among the previously reported data for igneous rocks at a similar sio 2 the lack of correlation between 56 fe and rb la argues against the effect of fluid exsolution on fe isotopes the 56 fe do not show a clear correlation with 66 zn and radiogenic isotopes suggesting that thermal diffusion or crustal contamination cannot produce the high 56 fe in hailar volcanic rocks fe isotopic variation in hailar volcanic rocks can be explained by two steps of magmatism during the first step partial melting of basaltic trachyandesites with an average 56 fe of 0 09 0 14 produced trachytes rhyodacites with an average 56 fe of 0 24 0 27 modelling using rhyolite melts shows that fe isotopes can be fractionated by preferential partitioning of isotopically different fe 3 and fe 2 between the solid residue and partial melt the second step involves formation of rhyolites with significantly high 56 fe through partial melting or extensive crystallization of crust materials during which isotopically heavy fe preferentially partition into the rhyolitic melt therefore fractionation of fe isotopes between melts and minerals can result in high 56 fe in sio 2 rich igneous rocks and apparent fe isotope heterogeneity within the continental crust

mechanism of crystal redistribution in a sheet like magma body constraints from the nosappumisaki and other shoshonite intrusions in the nemuro peninsula northern japan processes of crystal separation in a magma heavily laden with crystals without phase change are investigated from observations on frozen magma systems nosappumisaki and other shoshonite intrusions in the nemuro peninsula japan for which the origin of the crystals and the initial conditions are well constrained the nosappumisaki intrusion is 120 m in thickness and extends for more than 1 5 km it exhibits a wide range of lithological variation principally as a result of crystal redistribution after intrusion crystals in each lithology can be clearly divided into two kinds according to their composition and texture those present before the intrusion of the magma phenocrysts and those that crystallized in situ after intrusion from the vertical change in mode and size of phenocrysts it is shown that 1 augite phenocrysts were rapidly deposited with little overgrowth after intrusion by significant coagulation or clustering on a time scale of more than a few years and 2 plagioclase phenocrysts definitely denser than the melt but concentrated in the upper level floated by counter flow of massive deposition of augite phenocrysts these results indicate that in a magma heavily laden with crystals of a few millimeters in size 20 vol crystal crystal and crystal melt interaction play an important role in the separation of crystals from the host melt

geothermal history and petroleum generation in the norwegian south viking graben revealed by pseudo 3d basin modelling abstract hydrocarbon exploration in the norwegian south viking graben 57 45 60 15 n began in the late 1960s and has now entered a mature phase a map based pseudo three dimensional 3d basin modelling study is performed in order to unravel regional trends in hydrocarbon generation and expulsion and to evaluate the remaining potential of this mature petroleum province generation and expulsion from all major source rock horizons in the area the draupne heather hugin and sleipner formations is simulated using a pseudo 3d model comprising 36 isochronous geological events the map based pseudo 3d model is built from 1d models combined with subsurface and source rock quality maps hydrocarbon expulsion from the middle and upper jurassic source rocks in the area occurred in two major phases the first phase lasted from palaeocene to middle miocene with peak oil and gas expulsion during the early miocene the second quaternary phase of expulsion which supplied 11 and 13 of all oil and gas respectively is related to increased subsidence rates during this period a total of 74 109 sm3 oil and 8 2 1012 sm3 gas has been expelled in the area the frigg area in the north is with 2 9 1012 sm3 gas expelled the most gas prone area and the greater balder area seems to be the most oil prone area with 17 109 sm3 oil expelled the lower syn rift section of the upper jurassic draupne formation dominated oil expulsion 54 of all expelled oil whilst the heather formation dominated gas expulsion with 37 of all gas expelled model predictions were successfully applied to explain the fill and secondary alteration history of the greater balder area norway the modelling supports the draupne formation origin of the oils in the greater balder area as well as the presence of oils deriving from multiple charge phases found in correlation studies based on the modelled cumulative volumes expelled and estimates for in place volumes in the area generation accumulation efficiencies gaes of 1 01 1 05 for oil and 9 67 12 89 for gas have been estimated for the south viking graben in light of comparisons with other petroleum systems and critical evaluation of the elements of the petroleum systems the estimated gaes should be regarded as encouraging for further exploration of the area

reactivated basement structures affecting the sedimentary facies in a tectonically quiescent epicontinental basin an example from nw switzerland abstract the jurassic deposits in the southern part of central europe accumulated in a shallow epicontinental sea and their deposition has usually been believed to have corresponded to a phase of tectonic quiescence neither on conventional seismic records nor in outcrops obvious indications of synsedimentary tectonics were found nonetheless subtle variations in lithofacies and thickness occur above faults in the crystalline basement in fact preexisting structures became reactivated in the jurassic during major extensional phases when the tethys and the north atlantic opened this reactivation led to differential subsidence and or to rotation of fault bounded blocks but the sediments were deformed mainly flexurally as vertical movements in the basement were dissipated by triassic salt thus the depositional area was morphologically differentiated into swells and depressions in siliciclastic muddy environments swells were characterized by hardbottoms and hiatus beds depressions were filled by distal tempestites and gravity deposits in carbonate settings reefs nucleated on swells marls and muds were deposited in depressions many of them gravity deposits reactivation of faults occurred only during short episodes and was not synchronous throughout the study area and reactivation of individual faults was episodic and probably controlled by the palaeostress field and the faults orientation reactivation of deep rooted faults is also documented by hydrothermal activity which led to vein mineralization and alteration of minerals today exposed in nearby basement units the chronostratigraphic ages of the hydrothermal processes coincide with phases of enhanced subsidence during the sinemurian aalenian bajocian bathonian and oxfordian in turn facies changes of the sedimentary cover should be useful to predict basement structures when no seismic records are available

numerical simulation of the thermal maturation oil generation and migration in the songliao basin northeastern china abstract the discovery of the giant daqing oil field in the songliao basin led to the realisation of the significant petroleum potential of non marine basins in order to reconstruct the basin evolution and oil formation an integrated organic geochemical basin modelling study along a regional transect across the songliao basin was conducted it provided a regional heat flow evolution model and revealed post orogenic or late syn orogenic maturation in the central depression and pre orogenic maturation in the southeast uplift zone kinetic parameters of petroleum generation for the lacustrine source formations are the basis for the simulation of oil generation and migration in the songliao basin using the principle activation energy peaking at 54 kcal mol and a pre exponential factor of about 4 2 1027 ma 1 the simulation obtained a relatively good match with the measured transformation ratios the qingshankou formation in the west and east central depressions constituted the major source in the basin major oil generation migration and accumulation occurred during the early tertiary in the west central depression the generated oils migrated upwards into the yaojia formation followed by the updip migration into the daqing anticline and towards the local structural high along the west slope in contrast the oil migration in the east central depression was dominated by the downward movement from the lower member of the qingshankou formation followed by the updip migration towards the caoyang anticline the simulated oil accumulations are in good agreement with discovered oil fields implying a potential application of the model for prediction and evaluation of new exploration targets in the basin

experimental evidence for the absence of iron isotope fractionation between metal and silicate liquids at 1 gpa and 1250 1300 c and its cosmochemical consequences abstract iron isotope fractionation during metal silicate differentiation has been proposed as a cause for differences in iron isotope compositions of chondrites iron meteorites and the bulk silicate earth stable isotope fractionation however rapidly decreases with increasing temperature we have thus performed liquid metal liquid silicate equilibration experiments at 1250 1300 c and 1 gpa to address whether fe isotope fractionation is resolvable at the lowest possible temperatures for magmatic metal silicate differentiation a centrifuging piston cylinder apparatus enabled quantitative metal silicate segregation elemental tin or sulphur was used in the synthetic metal oxide mixtures to lower the melting temperature of the metal the analyses demonstrate that eight of the 10 experimental systems equilibrated in a closed isotopic system as was assessed by varying run durations and starting fe isotope compositions statistically significant iron isotope fractionation between quenched metals and silicates was absent in nine of the 10 experiments and all 10 experiments yield an average metal silicate fractionation factor of 0 01 0 04 independent of whether graphite or silica glass capsules were used this implies that fe isotopes do not fractionate during low pressure metal silicate segregation under magmatic conditions in large bodies such as the earth fractionation between metal and high pressure 20 gpa silicate phases may still be a possible process for equilibrium fractionation during metal silicate differentiation however the 0 07 0 02 heavier composition of bulk magmatic iron meteorites relative to the average of bulk ordinary carbonaceous chondrites cannot result from equilibrium fe isotope fractionation during core segregation the up to 0 5 lighter sulphide than metal fraction in iron meteorites and in one ordinary chondrite can only be explained by fractionation during subsolidus processes

modelled palaeo temperature on voring offshore mid norway the effect of the lower crustal body abstract the voring area offshore mid norway has a complex geological history has experienced several extensional phases and was significantly influenced by the break up of the north atlantic we have modelled a cross section over the voring basin aiming to 1 reconstruct the basin evolution in a realistic way and 2 to investigate the heat flow and temperature history in the basin for the modelling we used the following tectonic events the opening of the basin during the permo triassic an event during the middle to late cretaceous and an event in the late cretaceous paleocene the theoretical effects of the lithospheric stretching are depending on the palaeo water depths of the area we present a prediction of the palaeo water depth and a sensitivity analysis of the influence of the palaeo water depth on the estimated beta factors in the area a lower crustal high velocity body found in the area is often interpreted as magmatic underplating related to the break up of the norwegian sea we show the temperature history calculated by models that were run with and without assumption of underplating by a magmatic body emplaced during the early tertiary the observed vitrinite reflectance in the voring area is best explained by numerical calculations of the vitrinite reflectance without a magmatic underplating our conclusion is that the lower crustal body is not related to magmatic underplating or to significant sill intrusions the body may consist of older mafic rocks or a mixture of old continental crust and mafic intrusions

an assessment of iron isotope fractionation during core formation abstract iron is a ubiquitous element in terrestrial and extra terrestrial settings and can provide clues as to the conditions during which planetary scale processes occurred one example of this is determining the conditions accompanying metal core formation in rocky planets and planetesimals for at least two decades there has been a growing database of experimental and natural data aimed at understanding whether iron isotopes fractionate during the separation of silicate and metal while it has been argued that the data are not in agreement with one another it is apparent that once criteria are established that prove equilibrated samples there is good agreement amongst the different studies when looked at as a function of the metallic composition proving equilibrium is critical in these types of experiments the three isotope experimental technique for establishing equilibrium is found to be both mathematically and fundamentally sound further it is clear that the question of whether there is an equilibrium iron isotope fractionation between metal and silicate is not straightforward and that it can vary significantly as a function of temperature pressure metallic composition oxygen fugacity and silicate composition

on the iron isotope composition of mars and volatile depletion in the terrestrial planets iron is the most abundant multivalent element in planetary reservoirs meaning its isotope composition expressed as 57fe may record signatures of processes that occurred during the formation and subsequent differentiation of the terrestrial planets chondritic meteorites putative constituents of the planets and remnants of undifferentiated inner solar system bodies have fe57 0 an isotopic signature shared with the martian shergottite nakhlite chassignite snc suite of meteorites the silicate earth and moon as represented by basaltic rocks are distinctly heavier fe57 0 1 however some authors have recently argued on the basis of iron isotope measurements of abyssal peridotites that the composition of the earth s mantle is fe57 0 04 0 04 indistinguishable from the mean martian value to provide a more robust estimate for mars we present new high precision iron isotope data on 17 snc meteorites and 5 mineral separates we find that the iron isotope compositions of martian meteorites reflect igneous processes with nakhlites and evolved shergottites displaying heavier fe57 0 05 0 03 whereas mgo rich rocks are lighter fe57 0 01 0 02 these systematics are controlled by the fractionation of olivine and pyroxene attested to by the lighter isotope composition of pyroxene compared to whole rock nakhlites extrapolation of the fe57 snc liquid line of descent to a putative martian mantle yields a 57fe value lighter than its terrestrial counterpart but indistinguishable from chondrites iron isotopes in planetary basalts of the inner solar system correlate positively with fe mn and silicon isotopes while mars and iv vesta are undepleted in iron and accordingly have chondritic 57fe the earth experienced volatile depletion at low 1300 k temperatures likely at an early stage in the solar nebula whereas additional post nebular fe loss is possible for the moon and angrites

on the iron isotope heterogeneity of lithospheric mantle xenoliths implications for mantle metasomatism the origin of basalts and the iron isotope composition of the earth with the aim to better understand the cause of the iron isotope heterogeneity of mantle derived bulk peridotites we compared the petrological geochemical and iron isotope composition of four xenolith suites from different geodynamic settings sub arc mantle patagonia subcontinental lithospheric mantle cameroon oceanic mantle kerguelen and cratonic mantle south africa although correlations were not easy to obtain and remain scattered because these rocks record successive geological events those found between 57fe mg some major and trace element contents of rocks and minerals highlight the processes responsible for the fe isotope heterogeneity while partial melting processes only account for moderate fe isotope variations in the mantle 0 9 the kinetic nature of rapid metasomatic exchanges between low viscosity melts fluids and their wall rocks peridotite in the mantle is the likely explanation for this large range there are a variety of responses of fe isotope signatures depending on the nature of the metasomatic processes allowing for a more detailed study of metasomatism in the mantle with fe isotopes the current database on the iron isotope composition of peridotite xenoliths and mafic eruptive rocks highlights that most basalts have their main source deeper than the lithospheric mantle finally it is concluded that due to a complex geological history fe isotope compositions of mantle xenoliths are too scattered to define a mean isotopic composition with enough accuracy to assess whether the bulk silicate earth has a mean 57fe that is chondritic or if it is 0 1 above chondrites as initially proposed

investigation of magnesium isotope fractionation during basalt differentiation implications for a chondritic composition of the terrestrial mantle to investigate whether magnesium isotopes are fractionated during basalt differentiation we have performed high precision mg isotopic analyses by multi collector inductively coupled plasma mass spectrometry mc icp ms on a set of well characterized samples from kilauea iki lava lake hawaii usa samples from the kilauea iki lava lake produced by closed system crystal melt fractionation range from olivine rich cumulates to highly differentiated basalts with mgo content ranging from 2 37 to 26 87 wt our results demonstrate that although these basalts have diverse chemical compositions mineralogies crystallization temperatures and degrees of differentiation their mg isotopic compositions display no measurable variation within the limits of our external precision average 26 mg 0 36 0 10 and 25 mg 0 20 0 07 uncertainties are 2sd this indicates that mg isotopic fractionation during crystal melt fractionation at temperatures of 1055 c is undetectable at the level of precision of the current investigation calculations based on our data suggest that at near magmatic temperatures the maximum fractionation in the 26 mg 24 mg ratio between olivine and melt is 0 07 two additional oceanic basalts two continental basalts bcr 1 and bcr 2 and two primitive carbonaceous chondrites allende and murchison analyzed in this study have mg isotopic compositions similar to the kilauea iki lava lake samples in contrast to a recent report u wiechert a n halliday non chondritic magnesium and the origins of the inner terrestrial planets earth and planetary science letters 256 2007 360 371 the results presented here suggest that the bulk silicate earth has a chondritic mg isotopic composition 2007 published by elsevier b v

experimental quantification of the fractionation of fe isotopes during metal segregation from a silicate melt abstract fractionation of fe isotopes between a silicate melt and metallic alloys has been quantified experimentally at 1500 c the effects of oxygen fugacity and run duration have been investigated to distinguish between kinetic and equilibrium fractionations a new experimental setup is presented in which metallic fe is produced by reduction of oxidized iron from a silicate melt due to a change of redox conditions this metallic fe is physically removed from the silicate and sequestered as a pt fe alloy bulk analyses of the silicate and metallic fractions using multi collector icp ms methods are coupled with in situ analyses using an ion microprobe experimental results indicate that significant isotopic fractionation of fe occurs during metal segregation during the early stages of the experiments we find evidence for kinetic fractionation caused by faster diffusion of 54 fe along concentration gradients in the alloy this process leads to the formation of a metallic phase which is isotopically light compared to the residual silicate metal silicate fractionation up to 2 35 a m u the data are used to quantify the difference in diffusion coefficient of each isotope of iron providing a means to predict fe isotope fractionation during fe diffusion in metallic alloys on the other hand this state of affairs is transient in nature and at superliquidus temperature the systems rapidly reach a state of isotopic equilibrium in which the metal is isotopically heavier than the silicate melt by about 0 2 0 15 a m u these results are consistent with the range of variation observed in natural samples these kinetic and equilibrium data provide an experimental framework to understand the observed variability among igneous and meteoritic materials formed at high temperature particularly for iron and pallasite meteorites

late cretaceous neo tethyan slab roll back evidence from zircon u pb o and whole rock geochemical and sr nd fe isotopic data of adakitic plutons in the himalaya tibetan plateau

numerical modelling of burial and temperature history as an approach for an alternative interpretation of the bramsche anomaly lower saxony basin the lower saxony basin germany is one of the several sedimentary basins within the central european basin system in its southwestern part anomalously high maturity of organic matter has been observed to reach 4 5 vrr in upper jurassic and lower cretaceous sedimentary rocks in an area which coincides with a magnetic and a positive gravimetric anomaly this anomaly was often interpreted as the consequence of a deep seated igneous intrusion the so called bramsche massif however results obtained from calibrated numerical modelling are not in accordance with this scenario instead a burial by approximately 4 km of now eroded cretaceous rocks was revealed to be the probable cause for the anomaly data and modelling results from six boreholes and two pseudo wells support this view

new information on the thermal history of the southwestern lower saxony basin northern germany based on fission track analysis the southwestern part of the lower saxony basin lsb is characterized by gravity and magnetic anomalies and by an extremely high thermal maturity of organic matter this was for many years attributed to a late cretaceous intrusion but actually deep burial is being debated the complex thermal history of the area has been studied by fission track analysis zircon data provide evidence for widespread hydro thermal activity during the permian and upper jurassic lower cretaceous apatite ages indicate a major cooling event in the mid cretaceous 89 72 ma reflecting the time of inversion of the lsb during the cretaceous the cooling of the basin centre was rapid compared to the basin margins apatite fission track ages from borehole samples which are recently within the upper part of the apaz indicate a young heating of the sedimentary sequences until present

biodegradation of oil in uplifted basins prevented by deep burial sterilization biodegradation of crude oil by bacterial activity which has occurred in the majority of the earth s oil reserves is known to reduce greatly the quality of petroleum in reservoirs for economically successful prospecting for oil it is therefore important to understand the processes and conditions in geological formations that lead to oil biodegradation although recent studies speculate that bacterial activity can potentially occur up to temperatures as high as 150 degrees c refs 3 4 it is generally accepted that effective petroleum biodegradation over geological timescales generally occurs in reservoirs with temperatures below 80 degrees c ref 2 this appears however to be at odds with the observation that non degraded oils can still be found in reservoirs below this temperature here we compile data regarding the extent of oil biodegradation in several oil reservoirs and find that the extensive occurrence of non biodegraded oil in shallow cool basins is restricted to those that have been uplifted from deeper hotter regions of the earth we suggest that these petroleum reservoirs were sterilized by heating to a temperature around 80 90 degrees c during deep burial inactivating hydrocarbon degrading organisms that occur in the deep biosphere even when such reservoirs are subsequently uplifted to much cooler regions and filled with oil degradation does not occur implying that the sterilized sediments are not recolonized by hydrocarbon degrading bacteria

thermal equilibration of iron meteorite and pallasite parent bodies recorded at the mineral scale by fe and ni isotope systematics abstract in this work a femtosecond laser ablation la system coupled to a multi collector inductively coupled plasma mass spectrometer fs la mc icp ms was used to obtain laterally resolved 30 80 m high precision combined ni and fe stable isotope ratio data for a variety of mineral phases olivine kamacite taenite schreibersite and troilite composing main group pallasites pmg and iron meteorites the stable isotopic signatures of fe and ni at the mineral scale in combination with the factors governing the kinetic or equilibrium isotope fractionation processes are used to interpret the thermal histories of small differentiated asteroidal bodies as fe isotopic zoning is only barely resolvable within the internal precision level of the isotope ratio measurements within a single olivine in esquel pmg the isotopically lighter olivine core relative to the rim 56 54 fe rim core 0 059 suggests that the olivines were largely thermally equilibrated the observed hint of an isotopic and concentration gradient for fe of crudely similar width is interpreted here to reflect fe loss from olivine in the process of partial reduction of the olivine rim the ranges of the determined fe and ni isotopic signatures of troilite 56 54 fe of 0 66 to 0 09 and schreibersite 56 54 fe of 0 48 to 0 09 and 62 60 ni of 0 64 to 0 29 may result from thermal equilibration schreibersite and troilite likely remained in equilibrium with their enclosing metal to temperatures significantly below their point of crystallization the ni isotopic signatures of bulk metal and schreibersite correlate negatively with isotopically lighter ni in the metal of pmgs and isotopically heavier ni in the metal of the iron meteorites analyzed as such the light ni isotopic signatures previously observed in pmg metal relative to chondrites may not result from heterogeneity in the solar nebula but rather reflect fractionation in the metal schreibersite system comparison between the isotope ratio profiles of fe and ni determined across kamacite taenite interfaces 56 54 fe kam tae 0 51 to 0 69 and 62 60 ni kam tae 1 59 to 2 50 and theoretical taenite sub solidus diffusive isotopic zoning broadly constrain the cooling rates of esquel cms 04071 pmgs and udei station iab to between 25 and 500 c myr

integrated geothermal modeling on different scales in the northeast german basin geothermal modeling is an important part of large scale basin studies based on a new 3d structural model of the northeast german basin the present day regional geothermal field is modeled range and regional trend of the modeled temperature values are in agreement with the published data due to the high spatial resolution the calculated temperature distribution provides additional information with respect to areas where no measured data is available the results are used as input and boundary parameters for small scale models of geothermal energy production in general in many regions not enough data is available to define all necessary physical or chemical parameters for modeling in this context data obtained from the large scale model help to constrain unknown parameters subsequently the small scale model is used to simulate various production schemes focusing on enhanced predictions with respect to the possible lifetime of such installations the simulation results also show the need for elaborated models if reliable predictions of the temperature evolution are required

assessment of temperature gradients in multianvil assemblies using spinel layer growth kinetics 1 we present an empirical equation to link the thickness of a mgal2o4 spinel layer growing at the interface between mgo and al2o3 multianvil high pressure assembly pieces to pressure p temperature t and time t extending the recent study of watson et al 2002 to the pressure range 6 16 gpa and temperature range 1673 2273 k for the spinel thickness x we obtain this equation can be used to assess the thermal gradient in any multianvil assembly where mgo and al2o3 filler pieces are in contact at p t conditions within the mgal2o4 spinel stability field as an illustration we show that the central hot spot in which temperatures can be considered constant is close to 1 mm long in a common octahedral multianvil assembly with 8 mm edge length and rhenium furnace while it extends to 3 mm long in an octahedron with 18 mm edge length using a straight graphite heating element in addition we present the results of a spinel growth experiment performed at 2273 k and 15 gpa with 18o enriched mgo which shows that oxygen is mobile at a length scale exceeding that of the spinel layer this finding raises the possibility that under some circumstances growth of spinel and of reaction product layers in other oxide systems might be accomplished by concurrent fluxes of oxygen and cations this mobile oxygen model differs from the more conventional mg al exchange model proposed by watson and price 2002 for the lower pressure experiments and might explain the observed differences in systematics between the high and low pressure data sets

source rock heterogeneity of the upper jurassic draupne formation north viking graben and its relevance to petroleum generation studies abstract the upper jurassic draupne formation in the north viking graben north sea has been studied to identify lateral and vertical variations in source rock characteristics and their effect on the timing of petroleum generation fourteen source rock samples from the western flank of the graben and five from the eastern flank were analysed using rock eval analysis microscopy open system pyrolysis gas chromatography and kinetic experiments two major organic facies with different petroleum generation characteristics were identified a stratigraphically higher thermally less stable facies corresponding to a type ii kerogen with hi hydrogen index values of 350 mg hc g toc and a stratigraphically lower more stable type ii iii facies with hi values

experimental evidence for mo isotope fractionation between metal and silicate liquids stable isotope fractionation of siderophile elements may inform on the conditions and chemical consequences of core mantle differentiation in planetary objects the extent to which mo isotopes fractionate during such metal silicate segregation however is so far unexplored we have therefore investigated equilibrium fractionation of mo isotopes between liquid metal and liquid silicate to evaluate the potential of mo isotopes as a new tool to study core formation we have performed experiments at 1400 and 1600 c in a centrifuging piston cylinder tin was used to lower the melting temperature of the fe based metal alloys to 1400 c while variable fe oxide contents were used to vary oxygen fugacity in graphite and mgo capsules isotopic analyses were performed using a double spike technique in experiments performed at 1400 c the 98mo 95mo ratio of silicate is 0 19 0 03 0 19 0 03 95 confidence interval heavier than that of metal this fractionation is not significantly affected by the presence or absence of carbon molybdenum isotope fractionation is furthermore independent of oxygen fugacity in the range iw 1 79 to iw 0 47 which are plausible values for core formation experiments at 1600 c show that at equilibrium the 98mo 95mo ratio of silicate is 0 12 0 02 0 12 0 02 heavier than that of metal and that the presence or absence of sn does not affect this fractionation equilibrium mo isotope fractionation between liquid metal and liquid silicate as a function of temperature can therefore be described as mometal silicate98 95 4 70 0 59 105 t2 our experiments show that mo isotope fractionation may be resolvable up to metal silicate equilibration temperatures of about 2500 c rendering mo isotopes a novel tool to investigate the conditions of core formation in objects ranging from planetesimals to earth sized bodies

quantitative hc potential evaluation using 3d basin modelling application to franklin structure central graben north sea uk abstract 3d basin modelling is now used by some oil companies for exploration purposes the potentiality of this tool is not fully expressed but it seems that it should become the core of the basin evaluation process in the near future in this paper the methodology of 3d basin modelling in a relatively mature area is presented this methodology is based on a four step process which includes 1 3d block building 2 gridding 3 backward modelling and 4 forward modelling these processes are illustrated through a case study performed on the franklin structure central graben north sea uk the main results of this study show that petroleum migration is a 3d process that cannot in this specific case be properly addressed by 2d basin modelling alone furthermore the global hydrocarbon mass balance only accessible by 3d modelling shows that only 2 of the total hydrocarbons generated by the source rocks are present in the main reservoir

modelling the petroleum generation and migration of the third member of the shahejie formation es3 in the banqiao depression of bohai bay basin eastern china abstract the mudstones in the third member of the shahejie formation es3 are the primary source rocks in the banqiao depression of bohai bay basin they are rich in organic matter with total organic carbon toc content up to 3 5 the sandstones in the es3 member are the deepest proven hydrocarbon reservoir rocks with measured porosity and permeability values ranging from 3 6 to 32 4 and from 0 01 md to 3283 7 md respectively one two and three dimensional basin modelling studies were performed to analyse the petroleum generation and migration history of the es3 member in the banqiao depression based on the reconstruction of the burial thermal and maturity history in order to evaluate the remaining potential of this petroleum province the modelling results are calibrated with measured vitrinite reflectance ro borehole temperatures and some drilling results of 63 wells in the study area calibration of the model with thermal maturity and borehole temperature data indicates that the present day heat flow in the banqiao depression varies from 59 8 mw m2 to 61 7 mw m2 and the paleo heat flow increased from 65 ma to 50 4 ma reached a peak heat flow values of approximately 75 mw m2 at 50 4 ma and then decreased exponentially from 50 4 ma to present day the source rocks of the es3 member are presently in a stage of oil and condensate generation with maturity from 0 5 to 1 8 ro and had maturity from 0 5 to 1 25 ro at the end of the dongying formation ed deposition 26 ma oil generation 0 5 ro in the es3 member began from about 37 ma to 34 ma and the peak hydrocarbon generation 1 0 ro occurred approximately from 30 ma to 15 ma the modelled hydrocarbon expulsion evolution suggested that the timing of hydrocarbon expulsion from the es3 member source rocks began from 31 ma to 10 ma with the peak hydrocarbon expulsion shortly after 26 ma secondary petroleum migration pathways in the es3 member of the banqiao depression are modelled based on the structure surfaces at 26 ma and present day respectively the migration history modelling results have accurately predicted the petroleum occurrences within the es3 member of the banqiao depression based on the calibration with drilling results of 10 oil producing wells one well with oil shows and 52 dry holes six favorable zones of oil accumulations in the es3 member of the banqiao depression are identified especially oil accumulation zones i and ii due to their proximity to the generative kitchens short oil migration distances and the presence of a powerful drive force

silicon in the earth s core the earth and moon have iron isotopic abundances that are slightly heavy compared with mars the asteroid vesta and primitive meteorites the reason for this has been unclear one suggestion is that there was a large scale isotopic equilibration during the giant impact the collision between the early earth and a mars sized body that created the moon but this has seemed unlikely given that most other elements do not show the effect an analysis of 44 meteorite and terrestrial samples now shows that the silicon isotopic compositions of basaltic rocks from the earth and moon are also distinctly heavy the finding is consistent with the isotopic equilibration model and it suggests that silicon was already partitioned into the earth s core as a light element before the moon formed the silicon isotopic compositions of basaltic rocks from the earth and moon are distinctly heavy the similar isotopic composition of the bulk silicate earth and the moon are consistent with large scale isotopic equilibration during the giant impact indicating that si was already a light element in the earth s core before the moon formed small isotopic differences between the silicate minerals in planets may have developed as a result of processes associated with core formation or from evaporative losses during accretion as the planets were built up basalts from the earth and the moon do indeed appear to have iron isotopic compositions that are slightly heavy relative to those from mars vesta and primitive undifferentiated meteorites1 2 3 4 chondrites explanations for these differences have included evaporation during the giant impact that created the moon when a mars sized body collided with the young earth however lithium5 and magnesium6 lighter elements with comparable volatility7 8 9 reveal no such differences rendering evaporation unlikely as an explanation here we show that the silicon isotopic compositions of basaltic rocks from the earth and the moon are also distinctly heavy a likely cause is that silicon is one of the light elements in the earth s core we show that both the direction and magnitude of the silicon isotopic effect are in accord with current theory10 based on the stiffness of bonding in metal and silicate the similar isotopic composition of the bulk silicate earth and the moon is consistent with the recent proposal11 that there was large scale isotopic equilibration during the giant impact we conclude that si was already incorporated as a light element in the earth s core before the moon formed

the iron isotope composition of enstatite meteorites implications for their origin and the metal sulfide fe isotopic fractionation factor abstract despite their unusual chemical composition it is often proposed that the enstatite chondrites represent a significant component of earth s building materials based on their terrestrial similarity for numerous isotope systems in order to investigate a possible genetic relationship between the fe isotope composition of enstatite chondrites and the earth we have analyzed 22 samples from different subgroups of the enstatite meteorites including eh and el chondrites aubrites main group and shallowater and the happy canyon impact melt we have also analyzed the fe isotopic compositions of separated magnetic and non magnetic phases from both enstatite chondrites and achondrites on average eh3 5 chondrites 56fe 0 003 0 042 2 standard deviation n 9 including previous literature data as well as el3 chondrites 56fe 0 030 0 038 2 sd n 2 have identical and homogeneous fe isotopic compositions indistinguishable from those of the carbonaceous chondrites and average terrestrial peridotite in contrast el6 chondrites display a larger range of isotopic compositions 0 180 enstatite achondrites aubrites also exhibit a relatively large range of fe isotope compositions all main group aubrites are enriched in the light fe isotopes 56fe 0 170 0 189 2 sd n 6 while shallowater is isotopically relatively heavy 56fe 0 045 0 101 2 sd n 4 number of chips we take this variation to suggest that the main group aubrite parent body formed a discreet heavy fe isotope enriched core whilst the shallowater meteorite is most likely from a different parent body where core and silicate material remixed this could be due to intensive impact induced shearing stress or the ultimate destruction of the shallowater parent body analysis of separated enstatite meteorite mineral phases show that the magnetic phase fe metal is systematically enriched in the heavier fe isotopes when compared to non magnetic phases fe hosted in troilite which agrees with previous experimental observations and theoretical calculations the difference between magnetic and non magnetic phases from enstatite achondrites provides an equilibrium metal sulfide fe isotopic fractionation factor of 56femetal troilite 56femetal 56fetroilite of 0 129 0 060 2 se at 1060 80 k which confirms the predictions of previous theoretical calculations

non chondritic magnesium and the origins of the inner terrestrial planets abstract high precision magnesium mg isotope data obtained using a large geometry high resolution mc icpms are reported for 9 carbonaceous and ordinary chondrites 9 eucrites and diogenites generally considered to originate from asteroid 4 vesta together with 4 martian meteorites and a variety of terrestrial and lunar materials the variation in mg isotopic composition found for mafic and ultramafic rocks mafic minerals and chondrites is smaller than reported previously the range of 26mg and 25mg of 0 6 and 0 3 defines a single mass dependent fractionation line consistent with a homogeneous mix of nucleosynthetic components data for the earth mars and vesta display no systematic mg isotopic differences despite large variations in the level of depletion in moderately volatile elements lunar mare basalts exhibit a significant range in 26mg 0 53 to 0 05 and 25mg 0 27 to 0 02 attributable to magmatic differentiation in the lunar magma ocean lmo lunar basalts derived from early segregated cumulates and thought to be the most primitive are on average slightly 0 17 26mg heavy relative to basalts from the earth mars and vesta however the difference is not well resolved more strikingly all differentiated planets and planetesimals as sampled have mg that is on average isotopically heavy compared with most chondrites analyzed thus far chondrules and cais also are generally heavy in terms of mg so this might reflect sorting of material in the proto planetary disk such an explanation would be similar to one previously proposed hewins r h and herzberg c t 1996 earth planet sci lett 144 1 7 to explain the non chondritic si mg of the earth in this model chondrule like objects separate from volatile rich planetary dust by accumulation in stagnant regions between eddies in the solar nebula small 1 km planetesimals formed by accumulation of such molten material then develop into planetary embryos and thence to larger terrestrial planets by combinations of runaway growth and collisions as such accumulation of molten chondrule like droplets provides an explanation that obviates some of the dynamic difficulties associated with the onset of planetary accretion the non chondritic mg isotopic composition of the earth is consistent with data for li and has important implications for earth s bulk composition and putative hidden reservoirs

a reassessment of the iron isotope composition of the moon and its implications for the accretion and differentiation of terrestrial planets abstract the fe isotope composition of planetary bodies may provide constraints on their accretion modes and or differentiation processes but to do so the fe isotope systematics of key planetary reservoirs needs to be determined to investigate this for the moon we measured the fe isotope compositions for a suite of 33 bulk lunar mare basalts and highland rocks combined with published data a compendium of 73 different lunar bulk rocks reveals a statistically significant fe isotope difference between low ti and high ti mare basalts yielding average 57fe 0 127 0 012 2se n 27 and 57fe 0 274 0 020 2 se n 25 respectively relative to the irmm 14 isotopic reference material as lunar basalts are thought to reflect the fe isotope composition of their respective mantle sources the estimated relative proportion of the low ti and high ti source mantle suggests that the lunar upper mantle 57fe value should be close to 0 142 0 026 whilst the composition of highland rocks ferroan anorthosites and mg suite rocks should provide a more global view of the moon the calculation of the mean 57fe value of 15 available highland rock analyses yields 57fe 0 078 0 124 such a value is not defined precisely enough to be of critical use for comparative planetology ferroan anorthosites and mg suite rocks also give unresolvable means it appears that fe isotope heterogeneity among the lunar highland rocks is caused by non representatively too small sample aliquots of coarse grained rocks it can also be the result of mixed lithologies for some when the kinetic effect of olivine tending towards low 57fe and feldspar with predominantly high 57fe is cancelled a more precise 57fe value of 0 094 0 035 is calculated it is indistinguishable from the mean 57fe of impact melts and is also similar to the upper lunar mantle estimate obtained from mare basalts collectively this newly determined fe isotope composition of the bulk moon is indistinguishable from that of the earth and heavier than those reported for other planetary bodies this planetary isotope relationship is only observed for silicon given the currently available mass dependent stable isotope database because both iron and silicon reside in the earth s metallic core in significant quantities this may point to the involvement of metallic cores of the earth and moon in the interplanetary fe and si isotope fractionation rather than via high pressure metal silicate fractionation at the core mantle boundary this would more likely be achieved by partial vaporization of the liquid outer metallic core in the aftermath of a moon forming giant impact

finite element analysis and ray tracing modeling of petroleum migration separate phase flow is the dominant transport mechanism for secondary migration of petroleum phases commonly two different methods are used for the modeling of separate phase flow full 3d modeling finite element analysis which leads to the physically best description but can only be performed on low resolution grids and flowpath modeling ray tracing which can be performed on high resolution grids but is based on simplified physical assumptions a new approach that integrates both methods allows a physically realistic description without losing any of the original geometric information this new approach cuts processing times considerably

iron and sulphur isotopes from the carajas mining province para brazil implications for the oxidation of the ocean and the atmosphere across the archaean proterozoic transition abstract mineralogical analyses and major and trace element geochemistry combined with iron and sulfur isotopes were applied to banded iron formations bifs and pyrite bearing sandstones from the carajas mineral province brazil the bifs belong to the 2 7 ga old grao para group and show a rather simple mineralogy hematite and quartz or cryptocrystalline silica their ree y patterns suggest deposition under marine sub oxic conditions fe isotopes show highly positive values 57 fe irmm 14 2 06 0 34 in average which can be explained by the partial oxidation of fe 2 aq in the surface ocean subsequent to the upwelling of deep anoxic seawater the resulting iron oxy hydroxides likely formed in the shallow photic zone as a seasonal process and acquired highly positive iron isotope signature values consistent with a rayleigh distillation model the pyrite bearing sandstones belong to the aguas claras formation of palaeoproterozoic younger age and were cored at the base of the giant azul manganese deposit diagenetic pyrite is characterized by positive 57 fe irmm 14 1 02 0 2 and 34 s vctd 11 97 0 12 average values that are different from values of modern marine biogenic pyrite results likely indicate that dissolved sulfate was the limiting factor controlling biogenic pyrite formation at that time near zero 33 s values 0 013 0 003 indicate minimal mass independent sulfur isotope fractionation mif s consistent with the 2 1 ga age previously obtained from the aguas claras pyrites this result suggests deposition at a time when the oxygen partial pressure in the atmosphere was already high enough 10 5 to 10 2 pal or present atmospheric level to hinder mif s by photochemical reactions incidentally this also confirms that the giant mn deposit of carajas is in the same age range 2 1 0 2 ga as other mn ores in gabon and south africa pointing to the importance of mn precipitation in paleoproterozoic times

kinetic iron stable isotope fractionation between iron ii and iii complexes in solution abstract iron stable isotope fractionation between tris 2 2 bipyridine iron ii fe ii bipy 3 2 and iron iii chloride complexes has been measured using plasma source mass spectrometry the experimental protocol involves complexing fe ii ion with 2 2 bipyridine in a fe ii fe iii chloride solution and then separating the fe ii and fe iii solution species in 6 m hcl on an anion exchange resin large isotopic variations of 57 fe and 56 fe are experimentally measured in the two separated solution fractions with isotopic fractionations increasing from fe ii fe iii 25 to 174 units for 57 fe 54 fe and 17 to 117 units for 56 fe 54 fe the increase in fractionations correlates with a decrease in the mole fraction of fe ii in the solution fe fe ii fe ii fe iii that results from the dissociation and breakdown of fe ii bipy 3 2 complex in 6 m hcl solution the data variations are mainly ascribed to a kinetic fractionation occurring during this dissociation reaction mass balance calculations assuming that a rayleigh law describes the overall isotopic trends suggest a kinetic fractionation of ca 1 010 100 units the magnitude of this fractionation is attributed to the rupturing of the strong covalent bonds between 2 2 bipyridine and fe ii ion the experimental data confirm that the coordination chemistry of iron exhibits a profound control on its isotopic behaviour and that kinetic fractionations may play an important role in its isotope geochemistry as was also found in the pioneering experimental studies of the sulphur isotopic system in solution

gallium isotopic evidence for the fate of moderately volatile elements in planetary bodies and refractory inclusions abstract the abundance of moderately volatile elements such as zn and ga show variable depletion relative to ci between the earth and primitive meteorite chondrites parent bodies furthermore the first solar system solids the calcium aluminum rich inclusions cais are surprisingly rich in volatile element considering that they formed under high temperatures here we report the ga elemental and isotopic composition of a wide variety of chondrites along with five individual cais to understand the origin of the volatile elements and to further characterize the enrichment of the volatile elements in high temperature condensates the 71 ga permil deviation of the 71ga 69ga ratio from the ga ipgp standard of carbonaceous chondrites decreases in the order of ci cm co cv and is inversely correlated with the al ga ratio this implies that the ga budget of the carbonaceous chondrites parent bodies were inherited from a two component mixing of a volatile rich reservoir enriched in heavy isotope of ga and a volatile poor reservoir enriched in light isotope of ga calcium aluminum rich inclusions are enriched in ga and zn compared to the bulk meteorite and are both highly isotopically fractionated with 71 ga down to 3 56 and 66 zn down to 0 74 the large enrichment in the light isotopes of ga and zn in the cais implies that the moderately volatile elements were introduced in the cais during condensation in the solar nebula as opposed to secondary processing in the meteorite parent body and supports a change in gas composition in which cais were formed

significance of iron isotope mineral fractionation in pallasites and iron meteorites for the core mantle differentiation of terrestrial planets abstract seven bulk chondrites with 57 fe 54 fe values between 0 1 and 0 relative to irmm 14 tend to be slightly lighter than 11 bulk iron meteorites which have 57 fe 54 fe values ranging from 0 04 to 0 2 at the mineral scale taenite from two iron meteorites cranbourne and toluca shows 57 fe 54 fe values heavier by up to 0 3 than their kamacite counterpart thus calling into question the significance of bulk iron meteorite data on three pallasites esquel marjalahti and springwater we measured a heavier iron isotope composition for the metal fractions compared to the coexisting olivines as previously observed on two other pallasites eagle station and imilac but the range of 57 fe 54 fe differences from 0 32 to 0 07 is larger than that originally found troilite from two pallasites appears to be even heavier than the metal fraction whereas schreibersite is lighter than its olivine counterpart there is thus a general tendency for minerals within a given rock to show a heavier fe isotope composition as the coordination number of fe increases although troilite is an exception to this rule iron meteorites are classically considered as remnants of asteroid cores and pallasites as core mantle interfaces the simultaneous finding that the metal fractions of pallasites have a higher 57 fe 54 fe signature than the coexisting olivines and that the iron meteorites are slightly heavier than chondrites could be taken as an indication that planetary core mantle differentiation is accompanied by sizeable iron isotope fractionation in this hypothesis mass balance constraints imply that resultant planetary mantles should be isotopically lighter than the chondritic starting material that is not observed however since all planetary mantles analyzed so far have 57 fe 54 fe values equivalent to or heavier than those of chondrites it thus appears that the moderate temperature and pressure metal silicate fractionation that occurred in pallasite and iron parent bodies is not readily transposable to planets as far as fe isotopes are concerned instead these mantle signatures could reflect equilibrium fractionation at a higher temperature or the lack of a global core mantle equilibration at the planetary scale overall these new results show that the mass dependent isotopic scatter observed among inner solar system bodies from the bulk rock to the planetary scale 0 3 57 fe 54 fe is more restricted than previously thought this likely confirms a homogenization process that occurred in the protoplanetary accretion disk between refractory inclusion condensation and chondrule formation

sulfur controlled iron isotope fractionation experiments of core formation in planetary bodies abstract a series of high pressure and temperature experiments were conducted to better constrain the fe isotope fractionation during core mantle differentiation in planetesimal and planetary bodies synthetic mixtures of oxides and metal having varying amounts of sulfur approximating terrestrial and martian compositions were melted at 1 2 gpa and 1650 c iron isotopic equilibrium between the resulting metal and glass run products was verified for all experiments using the three isotope technique purified fe from metal and glass was analyzed by multiple collector icp ms in high resolution mode iron alloy and silicate glass show a well resolved 57femetal silicate of 0 12 0 04 in a sulfur free system isotope fractionation increases with sulfur content to 0 43 0 03 at 18 wt sulfur in the metal these results cannot be easily interpreted within the context of known fe isotope ratios in most natural samples of planetary and asteroidal mantles and therefore suggest more complex processes affected the fe isotope fractionation therein however to reconcile martian meteorite iron isotopic signatures with geophysical models using this new experimental data requires a smaller amount of sulfur in the martian core than previous estimates with an upper limit of 8 wt