oxygen isotope studies of carbonaceous chondrites abstract the carbonaceous chondrites display the widest range of oxygen isotopic composition of any meteorite group as a consequence of the interaction of primordial isotopic reservoirs in the solar nebula these isotopic variations can be used to identify the reservoirs and to determine conditions and loci of their interactions we present a comprehensive set of whole rock analyses of cv co ck cm cr ch and ci chondrites as well as selected components of some of these meteorites a simple model is developed which describes the isotopic behavior during parent body aqueous alteration processes the process of thermal dehydration also produces a recognizable effect in the oxygen isotopic composition

coordinated mineralogical and isotopic analyses of a cosmic symplectite discovered in a comet 81p wild 2 sample we have discovered in a stardust mission terminal particle a unique mineralogical assemblage of symplectically intergrown pentlandite fe ni 9s8 and nanocrystalline maghemite fe2o3 mineralogically similar cosmic symplectites cos have only been found in the primitive carbonaceous chondrite acfer 094 and are believed to have formed by aqueous alteration the o and s isotopic compositions of the wild 2 cos are indistinguishable from terrestrial values the metal and sulfide precursors were thus oxidized by an isotopically equilibrated aqueous reservoir either inside the snow line in the wild 2 comet or in a larger kuiper belt object close association of the stardust cos with a kool mineral assemblage kosmochloric ca rich pyroxene feo rich olivine and albite that likely originated in the solar nebula suggests the cos precursors also had a nebular origin and were transported from the inner solar system to the comet forming region after they were altered

olivine in terminal particles of stardust aerogel tracks and analogous grains in chondrite matrix abstract the dearth of both major and minor element analyses of anhydrous silicate phases in chondrite matrix has thus far hindered their comparison to the wild 2 samples we present 68 analyses of olivine fa 0 97 in the coarse grained terminal particles of stardust aerogel tracks and a comprehensive dataset 10 3 analyses of analogous olivine grains 5 30 m isolated in ci cm cr ch co cv3 oxidized cv3 reduced c3 ungrouped acfer 094 and ningqiang l ll 3 0 4 eh3 and kakangari chondrite matrix these compositions reveal that wild 2 likely accreted a diverse assortment of material that was radially transported from various carbonaceous and ordinary chondrite forming regions the wild 2 olivine includes amoeboid olivine aggregates aoas refractory forsterite type i and type ii chondrule fragments and or microchondrules and rare relict grain compositions in addition we have identified one terminal particle that has no known compositional analog in the meteorite record and may be a signature of low temperature aqueous processing in the kuiper belt the generally low cr content of feo rich olivine in the stardust samples indicates that they underwent mild thermal metamorphism akin to a petrologic grade of 3 05 3 15

an igneous fragment from cluster idp l2011 21 an analog for the source of pyrrhotite and taenite in comet 81p wild 2 captured in stardust aerogel

the cosmochemical behavior of mercury abstract we review long standing reports of both the hg paradox that hg abundances in meteorites are inconsistent with its volatile behavior and the anomalous 196 hg 202 hg ratios in all types of extraterrestrial material a careful study of the literature suggests that both results may be due to overestimation of 202 hg abundances from neutron activation analysis we reevaluate hg condensation in the solar nebula using both volatility trends for chondritic meteorites and thermodynamic calculations the extent of hg depletion in allende indicates a 50 condensation temperature of 350 k thermodynamic calculations show that hg condenses into various metal alloys at 300 k or lower at lower temperatures hg can be incorporated into fe ni sulfides as a trace element we investigate chemisorption as a method for incorporating hg into solid material in the solar nebula a large fraction of hg can chemisorb on metal surfaces at temperatures as high as 515 k depending on the grain size

a new method of surface modeling and its application to dem construction a new method of surface modelling based on the fundamental theorem of surfaces smts is presented eight different test surfaces are employed to comparatively analyze the simulation errors of smts and the classical methods of surface modeling in gis including tli triangulated irregular network with linear interpolation spline idw inverse distance weighted and kriging numerical tests show that smts is much more accurate than the classical methods smts theoretically gives a solution to the error problem that has long troubled dem construction as a real world example smts is used to construct a dem of the da fo si coal mine in shaan xi province china its root mean square error rmse is compared with those of dems constructed by the four classical methods the results show that although smts also has a higher accuracy in the real world example the improvement of accuracy is less distinct than that expected from the numerical tests the accuracy loss seems to be caused by location differences between sampling points and the central points of lattices of the simulated surfaces two alternative ways are proposed to solve this problem

matrices of carbonaceous chondrite meteorites the morphology classification and chemistry of the matrices of carbonaceous chondrite cc meteorites is reviewed based on recent research results the various kinds of ccs are examined in terms of their matrix mineralogy alteration processes in ccs are discussed

constraints on the formation environment of two chondrule like igneous particles from comet 81p wild 2 using chemical and petrologic evidence and modeling we deduce that two chondrule like particles named iris and callie from stardust cometary track c2052 12 74 formed in an environment very similar to that seen for type ii chondrules in meteorites iris was heated near liquidus equilibrated and cooled at 100 c hr and within 2 log units of the iw buffer with a high partial pressure of na such as would be present with dust enrichments of 103 there was no detectable metamorphic nebular or aqueous alteration in previous work ogliore et al 2012 reported that iris formed late 3 myr after cais assuming 26al was homogenously distributed and was rich in heavy oxygen iris may be similar to assemblages found only in interplanetary dust particles and stardust cometary samples called kool particles callie is chemically and isotopically very similar but not identical to iris

transmission electron microscopy of the low ca hydrated interplanetary dust particle transmission electron microscopy of a hydrated interplanetary dust particle indicates that it consists largely of a poorly crystalline phyllosilicate containing fe mg and al with an interlayer spacing of 10 to 12aand so is distinct from the major phyllosilicate in ci and cm carbonaceous chondrites the silicate is probably an fe and mg rich smectite or mica submicron spherical to euhedral pyrrhotite and pentlandite are prominent unusual low ni 3 at ni pentlandite is also common and typically occurs as rectangular platelets unlike many chondritic interplanetary dust particles olivine is rare and pyroxene was not observed other less abundant phases are magnetite chromite and an unidentified phase containing fe mg si ca and mn this particle differs from a hydrated micrometeorite described previously by brownlee 1 indicating there are mineralogically different subsets of hydrated interplanetary dust particles despite gross similarities in mineralogy between the particle and the carbonaceous chondrites they show appreciable differences in detail

comparing wild 2 particles to chondrites and idps we compare the observed composition ranges of olivine pyroxene and fe ni sulfides in wild 2 grains with those from chondritic interplanetary dust particles idps and chondrite classes to explore whether these data suggest affinities to known hydrous materials in particular wild 2 olivine has an extremely wide composition range from fa096 with a pronounced frequency peak at fa1 the composition range displayed by the low calcium pyroxene is also very extensive from fs48 to fs0 with a significant frequency peak centered at fs5 these ranges are as broad or broader than those reported for any other extraterrestrial material wild 2 fe ni sulfides mainly have compositions close to that of fes with less than 2 atom ni to date only two pentlandite grains have been found among the wild grains suggesting that this mineral is not abundant the complete lack of compositions between fes and pentlandite with intermediate solid solution compositions suggests but does not require that fes and pentlandite condensed as crystalline species i e did not form as amorphous phases which later became annealed while we have not yet observed any direct evidence of water bearing minerals the presence of ni bearing sulfides and magnesium dominated olivine and low ca pyroxene does not rule out their presence at low abundance we do conclude that new investigations of major and minorelement compositions of chondrite matrix and idps are required

record of low temperature alteration in asteroids most chondritic materials experienced diverse styles of secondary alteration resulting in formation of hydrous and anhydrous oxygen bearing minerals silicates oxides and carbonates phyllosilicates magnetite calcite dolomite breunnerite ferrous olivine hedenbergite wollastonite grossular monticellite forsterite andradite nepheline sodalite brearley 2003 2005 and references therein petrographic mineralogic oxygen and short lived isotope systematics 26al 26mg 53mn 53cr 129i 129xe suggest that alteration occurred in the presence of aqueous solutions under variable physico chemical conditions temperature water rock ratio ph f o2 and fluid compositions in an asteroidal setting it started within 1 2 m y after formation of the cv cais was multistage and lasted up to 15 m y krot et al 2006 and references therein here we review bulk o isotopic compositions of chondritic materials o isotopic compositions of secondary minerals produced during asteroidal alteration and possible effects of fluid assisted thermal metamorphism on o isotopic exchange in primary high temperature minerals melilite and anorthite in the cv and co cais the implications of these data for understanding temperatures of alteration water rock ratios and oxygen isotopic composition of water that probably accreted into chondrite parent bodies in the form of ice are discussed the inferred or measured o isotopic composition of the meteoritic water is close to the terrestrial fractionation line 17o 2 it is very different from the inferred o isotopic compositions of the sun 17o 25 clayton 2002 yurimoto and kuramoto 2004 hashizume and chaussidon 2005 lyons and young 2005 suggesting significant evolution of o isotopic composition of the gaseous reservoir in the inner protoplanetary disk over its short 3 5 m y life time

dynamic pyrometamorphism during atmospheric entry of large 10 micron pyrrhotite fragments from cluster idps petrological changes in ni free and low ni pyrrhotite and much less in pentlandite during atmospheric entry flash heating of the sulfide idps l2005e40 l2005c39 and l2006a28 support 1 ferrous sulfide oxidation with vacancy formation and fe 3 ordering and 2 fe oxide formation and sulfur vapor loss through abundant vesicles melting of metastable chondritic aggregate materials at the idp surface has occurred all changes e g formation of a continuous maghmite rim proceeded as solid state reactions at a peak heating temperature of 700 c this temperature in combination with particle size and density suggest a 10 km s 1 entry velocity the idps probably belonged to cluster idps that entered the atmosphere with near earth or earth crossing asteroid velocities they could be debris from extinct or dormant comet nuclei which is consistent with shock comminution of pyrrhotite in these idps

evidence for aqueous activity on comet 81p wild 2 from sulfide mineral assemblages in stardust samples and ci chondrites abstract the discovery of nickel copper and zinc bearing iron sulfides from comet 81p wild 2 wild 2 represents the strongest evidence in the stardust collection of grains that formed in an aqueous environment we investigated three microtomed tem sections which contain crystalline sulfide assemblages from wild 2 and twelve thin sections of the hydrothermally altered ci chondrite orgueil detailed structural and compositional characterizations of the sulfide grains from both collections reveal striking similarities the stardust samples include a cubanite cufe 2 s 3 grain a pyrrhotite fe ni 1 x s pentlandite fe ni 9 s 8 assemblage and a pyrrhotite sphalerite fe zn s assemblage similarly the ci chondrite sulfides include individual cubanite and pyrrhotite grains cubanite pyrrhotite assemblages pyrrhotite pentlandite assemblages as well as possible sphalerite inclusions within pyrrhotite grains the cubanite is the low temperature orthorhombic form which constrains temperature to a maximum of 210 c the stardust and orgueil pyrrhotites are the 4c monoclinic polytype which is not stable above 250 c the combinations of cubanite and pyrrhotite as well as pyrrhotite and pentlandite signify even lower temperatures the crystal structures compositions and petrographic relationships of these sulfides constrain formation and alteration conditions taken together these constraints attest to low temperature hydrothermal processing our analyses of these minerals provide constraints on large scale issues such as heat sources in the comet forming region aqueous activity on cometary bodies and the extent and mechanisms of radial mixing of material in the early nebula the sulfides in the wild 2 collection are most likely the products of low temperature aqueous alteration they provide evidence of radial mixing of material e g cubanite troilite from the inner solar system to the comet forming region and possible secondary aqueous processing on the cometary body

mineralogy of interplanetary dust particles from the olivine infrared class analytical electron microscopy observations establish that olivine is abundant and the predominant silicate phase in threeinterplanetary dust particles idps from the olivine infrared spectral category two of the particles have microstructures resembling those of most non hydrous chondritic idps consisting of micron to sub micron grains together with a matrix composed of amorphous carbonaceous material and sub 500grains in addition to olivine theseparticles respectively contain enstatite and magnetite and pentlandite plus ca rich clinopyroxene the third idp consists mostly of olivine and pyrrhotite with little or no matrix material olivine grains in this particle contain prominent solar flare ion tracks with densities corresponding to a space exposure age between 103 to 105 years although the three particles have olivine rich mineralogies in common other aspects of their mineralogies and microstructures suggest that they experienced different formation histories the differences between the particles indicate that the olivine infrared spectral category is a diverse collection of idps that probably incorporates several genetic groups

matrix mineralogy of the orgueil ci carbonaceous chondrite a petrographic and transmission electron microscopic study of the orgueil ci carbonaceous chondrite shows that the matrix consists mainly of fe bearing mg rich serpentine and smectite saponite as well as a poorly crystallized fe rich material that contains minor variable s and ni the fe rich material is probably ferrihydrite a ferric hydroxide the ferrihydrite occurs in small particles 80 a in diameter and the s and ni are probably adsorbed on its surfaces the serpentine and saponite occur in poorly crystallized fine crystallites fine phyllosilicates that are intimately associated with the ferrihydrite coarsely crystallized phyllosilicates coarse phyllosilicates occur in clusters relatively free of ferrihydrite the ferrihydrite is a major matrix constitutent and probably accounts for most of the fe3 as well as the superparamagnetic fraction in the orgueil matrix the textures suggest that the fine phyllosilicates resulted from alteration of the coarse phyllosilicates the alteration probably involved a substantial amount of water and coincided with the period of sulfate vein formation during the aqueous alteration magnetite grains disaggregated from framboids and fe ni sulfides were replaced by ferrihydrite simultaneously aqueous solutions reacted with the coarse phyllosilicates and precipitated ferrihydrite producing intimate pervasive mixtures with the fine phyllosilicates the matrix mineralogy of the orgueil chondrite suggests that orgueil experienced considerably different alteration conditions from the cm chondrites the mineralogical and petrological differences between ci and cm chondrites can not simply be explained as the result of different degrees of aqueous alteration

insight into the silicate and organic reservoirs of the comet forming region abstract cometary interplanetary dust particles idps collected in earth s stratosphere currently represent the best way to sample outer solar system primordial dust the fine grained sub m minerals of idps show some strong similarities to the textures expected for primary condensates from the solar nebula in this study we have analysed a set of idps for combined bulk carbon nitrogen and hydrogen isotopes and high precision oxygen isotopes by nanosims 50l this study concentrates on combining isotopic analyses including high precision oxygen on the silicate and organic components within the same sample on fine grained primordial materials oxygen isotope analyses reveal that some idps are more 16 o rich than any bulk meteorite compositions extending to o isotope compositions in between chondritic and solar like values 17 o 20 18 o 20 the 16 o rich idps display more primitive organic signatures than the chondritic like 16 o poor idps but rather interestingly they also have lower presolar grain abundances the 16 o poor signatures probably indicate an abundant component of chondritic like material processed in the inner protoplanetary disk in order to explain the association of relatively processed material silicates and organics with high presolar grain abundances we propose a model whereby the initial dust component is 16 o rich solar like and originally present homogenously throughout the protoplanetary disk outward radial transport potentially associated with aerodynamic sorting led to an influx of processed silicates from the inner solar system with chondritic like isotopic signatures comet accretion that occurred late or at smaller heliocentric distance included higher abundances of this chondritic like component and hence had more 16 o poor o isotope compositions presolar grains whose extreme isotopic signatures were destroyed during early homogenisation of solar nebula dust continue to accrete onto the protoplanetary disk with time such that the later formed comets those with a higher proportion of processed silicates within their source also had time to accumulate a higher abundance of presolar grains a similar pattern is observed in the organics with decreasing d and c h from increased exchange with nebula gas in idps that contain more 16 o poor chondritic like material

pyrrhotite varieties from the 9 1 km deep borehole of the ktb project we used transmission electron microscopy tem to study pyrrhotite from the german continental deep drilling kontinentale tiefbohrung ktb project our goals were to determine the distribution of structure types with depth and to establish relationships between the bulk thermomagnetic behavior and the microstructures of pyrrhotite in samples from the deep section of the borehole 9080 m below surface which is equivalent to an in situ temperature of similar to 260 degrees c the dominant variety of pyrrhotite is 1c that has a mostly disordered vacancy distribution faint diffuse superstructure reflections in the selected area electron diffraction saed patterns indicate some nc like ordering occurs probably in small domains in addition to the disordered pyrrhotite a 5c type is also present according to bulk thermomagnetic measurements pyrrhotite grains from 9080 m are antiferromagnetic at room temperature we attribute this behavior to the dominance of the disordered 1c type in the upper section of the hole at 564 and 2325 m several pyrrhotite varieties occur but the 4c type is most common in agreement with the ferrimagnetic character of most pyrrhotite grains optical microscopy of pyrrhotite grains that are covered with a magnetic colloid reveal intergrown ferrimagnetic and antiferromagnetic lamellae tem images show that these grains are intergrowths of 4c 5c and nc types we interpret these microstructural variations to be responsible for the variation in magnetic properties within single pyrrhotite grains

comprehensive examination of large mineral and rock fragments in stardust tracks mineralogy analogous extraterrestrial materials and source regions abstract transmission electron microscopy examination of 87 large fragments from 16 carrot shaped and bulbous stardust sd tracks was performed to study the range and diversity of materials present in comet wild 2 olivines and low ca pyroxenes represent the largest proportions of fragments observed however a wide range of minerals and rocks were found including probable ferromagnesian al rich and si rich chondrule fragments a refractory inclusion possible matrix mineral lithic clasts and probable condensate minerals these materials combined with fine grained components in the tracks are analogous to components in unequilibrated chondrite meteorites and cluster interplanetary dust particles idps two unusual lithologies in the bulbous tracks are only observed in chondritic porous idps and may have direct links to idps the absence of phyllosilicates indicates that comet wild 2 may be a dry comet that did not accrete or form significant amounts of hydrated phases some large mineral fragments in the sd tracks are analogous to large mineral idps the large variations of the coarse grained components within and between all 16 tracks show that comet wild 2 is mineralogically diverse and unequilibrated on nearly all scales and must have accreted materials from diverse source regions that were widely dispersed throughout the solar nebula

deep high amplitude reflections from a major shear zone above the subducting juan de fuca plate seismic reflection data show that a regionally extensive band of landward dipping reflections exists above the subducting juan de fuca plate at the western canadian continental margin the reflections truncate at depth a major terrane boundary mapped near the surface and must have a structural origin many reflections are very strong having reflection coefficients locally as high as 10 20 these amplitudes are consistent with theoretical calculations of reflections from sharp poirosity contrasts if the pores are very thin however seismic data from the accreted sedimentary melange farther seaward from which much of the deep reflective zone is derived suggest that significant porosity contrasts do not occur alone because higher reflection amplitudes are found in regions of inferred high strain both geometric and amplitude constraints imply that the deep reflective layering represents intensely sheared rocks possibly originating close to the subduction decollement

the formation and alteration of the renazzo like carbonaceous chondrites iii toward understanding the genesis of ferromagnesian chondrules to better understand the formation conditions of ferromagnesian chondrules from the renazzo like carbonaceous cr chondrites a systematic study of 210 chondrules from 15 cr chondrites was conducted the texture and composition of silicate and opaque minerals from each observed feo rich type ii chondrule and a representative number of feo poor type i chondrules were studied to build a substantial and self consistent data set the average abundances and standard deviations of cr2o3 in feo rich olivine phenocrysts are consistent with previous work that the cr chondrites are among the least thermally altered samples from the early solar system type ii chondrules from the cr chondrites formed under highly variable conditions e g precursor composition redox conditions cooling rate with each chondrule recording a distinct igneous history the opaque minerals within type ii chondrules are consistent with formation during chondrule melting and cooling starting as s and ni rich liquids at 988 1350 c then cooling to form monosulfide solid solution mss that crystallized around olivine pyroxene phenocrysts during cooling fe ni metal crystallized from the s and ni rich liquid and upon further cooling mss decomposed into pentlandite and pyrrhotite with pentlandite exsolving from mss at 400 600 c the composition texture and inferred formation temperature of pentlandite within chondrules studied here is inconsistent with formation via aqueous alteration however some opaque minerals fe ni metal versus magnetite and panethite present in type ii chondrules are a proxy for the degree of whole rock aqueous alteration the texture and composition of sulfide bearing opaque minerals in graves nunataks 06100 and grosvenor mountains 03116 suggest that they are the most thermally altered cr chondrites

mineralogy and petrology of stardust particles encased in the bulb of track 80 tem investigation of the wild 2 fine grained material abstract we have characterized by transmission electron microscopy the mineralogy of samples extracted from the walls of the stardust track 80 more than 500 fragments were studied using conventional imaging electron diffraction and edx microanalysis two categories of particles are distinguishable in equal proportions wt the first one is comprised of relatively large crystalline grains 1 m on average dominated by silicates olivine and pyroxene they display a wide range of compositions and microstructures comparable to those found in terminal particles minor phases including magnetite and apatite are also present their occurrence suggests that the wild 2 material underwent aqueous alteration to some extent the second type of particle called gems like material is made of silica rich glassy clumps embedding iron sulfide beads and vesicles their microstructure is characteristic of thermally modified particles that have suffered strong interaction with the silica aerogel during the hypervelocity impact this melted material may form by shedding of melted and vaporized material but given the shape of the impact track and high diversity of surviving mineral compositions much of it originated from fine grained aggregates that disaggregated during the collection chemical mapping at the nano scale allowed the localization of individual components within the silica rich glass they are dominated by mg rich components with a size less than 300 nm the average composition of this thermally modified material is close to the solar abundance for the major elements fe mg and s the fine grained material has probably not been chemically fractionated in the protoplanetary disk before its incorporation in comet wild 2 unlike the sulfur depleted matrix of chondrites from these two categories of particles we deduce that wild 2 is likely made of an assemblage of relatively large evolved grains first category cemented by a fine grained material with primitive chemistry second category the pre impact configuration of the incident material deduced from this study seems comparable to the matrix of the most primitive chondrites 3 0 or to chondritic porous interplanetary dust particles

magnetic properties of synthetic analogues of pyrrhotite ore in the grain size range 1 24 µm summary iron and sulphur in proportions appropriate to fe 7 s 8 were reacted in evacuated quartz tubes for 24 hr at 500 c quenching produces predominantly hexagonal pyrrhotite whereas further prolonged annealing at 250 c produces monoclinic pyrrhotite we mainly report the properties of material cooled from 500 ca t 10 c min 1 which is predominantly monoclinic but probably contains hexagonal pyrrhotite together with pyrite fes 2 this material which we refer to as non ideal pyrrhotite may be a better analogue of pyrrhotite ore than ideal synthetic monoclinic pyrrhotite the samples were characterized by x ray mossbauer evect and thermomagnetic analyses the slow cooled non ideal monoclinic pyrrhotite exhibits thermal stability intermediate between monoclinic and hexagonal pyrrhotites one striking observation is that the deviation from ideal monoclinic pyrrhotite increases with decreasing particle size particles about 1 mm in size have a low saturation magnetization value of about 6 am2 kg 1 indicating a lower concentration of ferrimagnetic monoclinic pyrrhotite saturation magnetization 18 am2 kg 1 than particles of about 6 mm and above saturation magnetization 12 am2 kg 1 on the other hand magnetization process parameters coercive force ratio of saturation remanence to saturation magnetization coercive force of remanence median destructive and inductive fields the magnetic susceptibility follow well behaved power law dependences on particle size similar to monoclinic pyrrhotite magnetic domain patterns in the slow cooled non ideal pyrrhotite are similar in type and style to those observed in synthetic monoclinic pyrrhotite and in natural pyrrhotite particles in rocks dynamic observations of domain walls in changing external alternating and direct magnetic fields are consistent with macroscopic obser vations of magnetization change with field the critical size for the monodomain multidomain transition in synthetic monoclinic pyrrhotite at about 1 mm is essentially the same as that previously determined for natural pyrrhotite grains in rocks the observations suggest that the domain walls lie normal to the c axis of the structure consistent with the known magnetocrystalline anisotropy symmetry of monoclinic pyrrhotite the type and style of the magnetic microstructures of hexagonal pyrrhotite are quite diverent from those of monoclinic pyrrhotite the domain patterns are on a much smaller scale wavy and sometimes resemble those of a hexagonal material such as magnetoplumbite or cobalt

mineralogy of iron sulfides in cm1 and ci1 lithologies of the kaidun breccia records of extreme to intense hydrothermal alteration the polymict kaidun microbreccia contains lithologies of c type chondrites with euhedral iron sulfide crystals of hydrothermal origin our fib tem study reveals that acicular sulfides in a cm1 lithology are composed of fe rich pyrrhotite with nonintegral vacancy superstructures nc pyrrhotite troilite and pentlandite all showing distinct exsolution textures based on phase relations in the fe ni s system we constrain the temperature of formation of the originally homogeneous monosulfide solid solution to the range of 100 300 c in some crystals the exsolution of pentlandite and the microtextural equilibration was incomplete probably due to rapid cooling we use thermodynamic modeling to constrain the physicochemical conditions of the extreme hydrothermal alteration in this lithology unless the cm1 lithology was sourced from a large depth in the parent body internal pressure 85 bar or the temperatures were in the lower range of the interval determined the water was likely present as vapor previously described light 34s compositions of sulfides in kaidun s cm1 lithology are likely due to the loss of 34s enriched h2s during boiling platy sulfide crystals in an adjacent intensely altered ci1 lithology are composed of fe poor monoclinic 4c pyrrhotite and nc pyrrhotite and probably formed at lower temperatures and higher fs2 relative to the cm1 lithology however a better understanding of the stability of fe poor pyrrhotites at temperatures below 300 c is required to better constrain these conditions

iron and iron nickel sulfides in chondritic interplanetary dust particles abstract we report the results of a study of iron and iron nickel sulfides in chondritic anhydrous and hydrated interplanetary dust particles idps the idps were characterized using chemical and mineralogical techniques including energy dispersive x ray analyses and transmission electron microscopy it is widely believed that the first sulfur containing mineral to form in the early solar nebula should have been stoichiometric fes troilite and that pyrrhotite is of secondary origin all examined interplanetary dust particles both anhydrous and hydrous types contain more pyrrhotite than troilite suggesting that the former was a common possibly predominant nebular condensate phase pyrrhotite could form from sulfidation of troilite after the latter had exfoliated from substrate metal grains in contrast to anhydrous idps hydrated ones contain ni rich sulfides including pentlandite which are probably of secondary origin

planetesimal sulfate and aqueous alteration in cm and ci carbonaceous chondrites water soluble sulfate salts extracted from six cm chondrites have oxygen isotope compositions that are consistent with an extraterrestrial origin the 17 o of sulfate are correlated with previously reported whole rock 18 o and with an index of meteorite alteration and may display a correlation with the date of the fall the enrichments and depletions for 17 o of water soluble sulfate from the cm chondrites relative to the terrestrial mass dependent fractionation line are consistent with sulfate formation in a rock dominated asteroidal environment and from aqueous fluids that had undergone relatively low amounts of oxygen isotope exchange and little reaction with anhydrous components of the meteorites it is unresolved how the oxidation of sulfide to sulfate can be reconciled with the inferred low oxidation state during the extraterrestrial alteration process oxygen isotope data for two ci chondrites orgueil and ivuna as well as the ungrouped c2 chondrite essebi are indistinguishable from sulfate of terrestrial origin and may be terrestrial weathering products consistent with previous assertions our oxygen isotope data however can not rule out a preterrestrial origin either copyright 2005 elsevier ltd

a terrestrial origin for sulfate veins in ci1 chondrites white sulfate veins are a very well known petrological feature of the chemically primitive ci1 carbonaceous chondrites sulfate veins were first described in the orgueil meteorite in 1961 almost one century after its fall however we have observed such veins to form easily during typical sample storage we suggest that all ci1 sulfate veins formed during the terrestrial residence of these heavily brecciated porous stones reacting with atmospheric water sulfates originally present in the meteorites dissolved and remobilized and or sulfides oxidised filling the many open spaces offered to them by the very porous rock sulfate veins in ci1 chondrites can no longer be used as evidence of a late stage oxidation event in the ci1 parent body or of centimeter scale fluid transport on the parent asteroid

mineralogy and texture of fe ni sulfides in ci1 chondrites clues to the extent of aqueous alteration on the ci1 parent body to better understand the role of aqueous alteration on the ci1 parent body we have analyzed the texture composition and mineral associations of iron nickel sulfides in four of the five known ci1 chondrites the most commonly occurring sulfide present in the ci1 chondrites is the iron deficient fe ni sulfide pyrrhotite fe ni 1 xs that has a composition close to that of stoichiometric troilite fes three of the ci1s alais ivuna and tonk also contain pentlandite fe ni 9s8 although pentlandite is a rare phase in ivuna cubanite cufe2s3 was found in both alais and ivuna in this study although it has also been reported in orgueil macdougall and kerridge 1977 the pyrrhotite grains in all four chondrites form hexagonal rectangular or irregular shapes and show no evidence of ni or co zoning the pyrrhotite grains in orgueil and ivuna are in general smaller and show more corrosions or embayments than those in alais or tonk we suggest that the precursor sulfide present in the ci1 chondrites was troilite which during brecciation and oxidation on the parent body at a temperature of 100 c or less converted the troilite to magnetite and pyrrhotite with pentlandite inclusions subsequently continued alteration on the parent body removed pentlandite partially from alais tonk and ivuna completely from orgueil leaving behind pyrrhotite with spaces corrosions where the pentlandite had been ni derived from the pentlandite was incorporated into ferrihydrite onto the surface of which the ni na sulfate ni bloedite formed based on the size and abundant corrosions within pyrrhotite grains combined with observations from other authors we conclude that orgueil and ivuna have undergone a greater degree of alteration than alais and tonk further work is needed to assess the conditions under which pentlandite would be dissolved preferentially to pyrrhotite as the study of terrestrial literature indicates that the latter mineral is preferentially removed

connection between micrometeorites and wild 2 particles from antarctic snow to cometary ices we discuss the relationship between large cosmic dust that represents the main source of extraterrestrial matter presently accreted by the earth and samples from comet 81p wild 2 returned by the stardust mission in january 2006 prior examinations of the stardust samples have shown that wild 2 cometary dust particles contain a large diversity of components formed at various heliocentric distances these analyses suggest large scale radial mixing mechanism s in the early solar nebula and the existence of a continuum between primitive asteroidal and cometary matter the recent collection of concordia antarctic micrometeorites recovered from ultra clean snow close to dome c provides the most unbiased collection of large cosmic dust available for analyses in the laboratory many similarities can be found between antarctic micrometeorites and wild 2 samples in terms of chemical mineralogical and isotopic compositions and in the structure and composition of their carbonaceous matter cosmic dust in the form of concordia antarctic micrometeorites and primitive idps are preferred samples to study the asteroid comet continuum

silicate minerals and si o glass in comet wild 2 samples transmission electron microscopy a transmission electron microscope tem study of seven comet wild 2 samples shows that three samples consist mainly of olivine and pyroxene and four samples consist of mg fe bearing si o glass with minor amounts of fe ni sulfide and metal the olivine in the silicate rich samples differs in fayalite content between the samples and shows a wide range of fayalite content within individual samples indicating that the degree of thermal metamorphism on the comet if any was extremely low one olivine grain has a high density of dislocations with burgers vector b 001 suggesting that the wild 2 particles experienced hypervelocity impacts before capture the structural type and composition of pyroxene differ between the samples and within individual samples both low ca and high ca pyroxenes are present enstatite occurs as ortho and clinoenstatite suggesting that the wild 2 particles contain materials that went through distinct high temperature and cooling histories one silicate rich sample exhibits a zone texture consisting of a core of low ca pyroxene surrounded by an inner rim of mg fe bearing si o rich glass and an outer rim of melted aerogel the texture suggests that the inner rim was formed by the mixing of melted cometary low ca pyroxene and melted aerogel during capture heating the four mg fe bearing si o glass rich samples show close similarities in mineralogy and texture to the inner rim of the zoned silicate rich sample the four samples are probably secondary products formed by interaction between melted cometary silicates and melted aerogel during the capture process

mineralogy and oxygen isotope systematics of magnetite grains and a magnetite dolomite assemblage in hydrated fine grained antarctic micrometeorites

magnetite in comet wild 2 evidence for parent body aqueous alteration the mineralogy of comet 81p wild 2 particles collected in aerogel by the stardust mission has been determined using synchrotron fe k x ray absorption spectroscopy with in situ transmission xrd and x ray fluorescence plus complementary microraman analyses our investigation focuses on the terminal grains of eight stardust tracks c2112 4 170 0 0 c2045 2 176 0 0 c2045 3 177 0 0 c2045 4 178 0 0 c2065 4 187 0 0 c2098 4 188 0 0 c2119 4 189 0 0 and c2119 5 190 0 0 three terminal grains have been identified as near pure magnetite fe3o4 the presence of magnetite shows affinities between the wild 2 mineral assemblage and carbonaceous chondrites and probably resulted from hydrothermal alteration of the coexisting feni and ferromagnesian silicates in the cometary parent body in order to further explore this hypothesis powdered material from a cr2 meteorite nwa 10256 was shot into the aerogel at 6 1 km s 1 using a light gas gun and keystones were then prepared in the same way as the stardust keystones using similar analysis techniques to the eight stardust tracks a cr2 magnetite terminal grain establishes the likelihood of preserving magnetite during capture in silica aerogel