indicators of aqueous alteration in cm carbonaceous chondrites microtextures of a layered mineral containing fe s o and ni a petrographic and transmission electron microscopy study of the mighei murchison and murray cm carbonaceous chondrites shows that much of the cm matrix material was probably produced by aqueous alteration of olivine pyroxene sulfide and metal the amount of cm matrix appears to be proportional to the degree of alteration as suggested by mcsween 1979 and microtextures of pcp poorly characterized phase provide evidence of the progressive alteration pcp is divided into two major types one occurs in chondrules and aggregates and consists largely of an fe ni s o phase type i and the other occurs in matrix and consists of the fe ni s o phase and cronstedtite in various proportions type ii microtextures of pcp suggest that it resulted from a three stage alteration process 1 1 type i was produced by alteration of kamacite in chondrules and aggregates presumably early in the parent body regolith 2 2 as the alteration advanced olivine and pyroxene were converted to serpentine type i pcp separated from chondrules and aggregates into the matrix during regolith gardening simultaneously the fe ni s o phase reacted with si released by alteration of olivine and pyroxene producing well formed platy cronstedtite and coherent intergrowths of the fe ni s o phase and cronstedtite the fe ni s o phase also recrystallized into platy and pod like crystals fe s ni cr and p were leached out of type i pcp and were deposited as small grains of fe ni sulfides magnetite chromite and a mineral unidentified containing fe ni cr and p as a result pcp came to consist primarily of the fe ni s o phase and cronstedtite i e type ii pcp 3 3 during continued alteration the well formed crystals of the fe ni s o phase cronstedtite and their intergrowths in type ii pcp were replaced by poorly formed fibers in comparison to other cm chondrites mighei murchison and murray are relatively unaltered their matrices retain abundant amounts of the fe ni s o phase and cronstedtite commonly as distinctive pcp grains which account for a large proportion of the fe in these meteorite matrices in more altered cm chondrites much of the fe ni s o phase was probably consumed to produce cronstedtite magnetite and sulfides with further alteration cronstedtite itself reacted with the serpentine to form ferroan serpentine thus the cm matrix was increasingly enriched in mg with alteration and pcp was increasingly degraded and intimately mixed with the magnesian phyllosilicates

the cr renazzo type carbonaceous chondrite group and its implications abstract a petrologic geochemical and oxygen isotopic study of eight meteorites identified as cr renazzo type chondrites reveals that they have a set of similar properties that distinguishes them from other chondrite groups and confirms cr as a carbonaceous chondrite group characteristics of the cr group include 1 1 abundant large multilayered fe ni metal rich type i chondrules 2 2 abundant matrix and dark inclusions di that contain microchondrules microfragments and magnetite framboids and platelets 3 3 unique assemblages of serpentine and chlorite rich phyllosilicates and ca carbonates 4 4 ca carbonate rims on chondrules 5 5 abundant fe ni metal with a positive ni vs co trend and a solar ni co ratio 6 6 low abundance of refractory rich inclusions 7 7 amoeboid olivine aggregates aoa with mn rich and mn poor forsterite and 8 8 oxygen isotopic compositions that form a unique mixing line the cr chondrites are breccias consisting of two major components the large layered chondrules and the matrix dark inclusions al rais is an anomalous member in having a higher abundance of the dark inclusion component 70 vol and this accounts for its having a higher volatile content than other members of the group the conditions that prevailed during aqueous alteration of the cr chondrites differed from those of other hydrated chondrite groups and may be the result of a higher temperature environment than that for the ci and cm chondrites the cr chondrite components chondrules matrix dark inclusions etc experienced aqueous alteration to differing degrees prior to assembly of the host chondrites and dark inclusions represent a lithology that was altered by water to a greater degree than the rest of the meteorite the overall degree of hydration in cr chondrites varies among meteorites with al rais being the most hydrated the oxygen isotopic variation of the whole rocks chondrules and matrices may be related to degree of hydration indicating that cr chondrites interacted with a water rich component having heavy oxygen and that was the same as ci and cm water

oxygen and magnesium isotope compositions of calcium aluminum rich inclusions from cr2 carbonaceous chondrites abstract we report both oxygen and magnesium isotope compositions measured in situ using a cameca ims 1280 ion microprobe in 20 of 166 cais identified in 47 polished sections of 15 cr2 renazzo type carbonaceous chondrites two additional cais were measured for oxygen isotopes only most cr2 cais are mineralogically pristine only few contain secondary phyllosilicates sodalite and carbonates most likely products of aqueous alteration on the cr2 chondrite parent asteroid spinel hibonite grossite anorthite and melilite in 18 cais have 16o rich 17o 23 3 1 9 2 error compositions and show no evidence for postcrystallization isotopic exchange commonly observed in cais from metamorphosed cv carbonaceous chondrites the inferred initial 26al 27al ratios 26al 27al 0 in 15 of 16 16o rich cais measured are consistent with the canonical value of 4 5 5 10 5 and a short duration 0 9 2 2 0 7 my eight of the 166 cr2 cais identified are associated with chondrule materials indicating that they experienced late stage incomplete melting during chondrule formation three of these cais show large variations in oxygen isotope compositions 17o ranges from 23 5 to 1 7 suggesting dilution by 16o depleted chondrule material and possibly exchange with an 16o poor 17o 5 nebular gas the low inferred 26al 27al 0 ratios of these cais 2 my after crystallization of cais with the canonical 26al 27al 0 and suggest evolution of the oxygen isotope composition of the inner solar nebula on a similar or a shorter timescale because cais in cr2 and cv chondrites appear to have originated in a similarly 16o rich reservoir and only a small number of cr2 and cv cais were affected by chondrule melting events in an 16o poor gaseous reservoir the commonly observed oxygen isotope heterogeneity in cais from metamorphosed cv chondrites is most likely due to fluid solid isotope exchange on the cv asteroidal body rather than gas melt exchange this conclusion does not preclude that some cv cais experienced oxygen isotope exchange during remelting instead it implies that such remelting is unlikely to be the dominant process responsible for oxygen isotope heterogeneity in cv cais the mineralogy oxygen and magnesium isotope compositions of cais in cr2 chondrites are different from those in the metal rich ch and cb carbonaceous chondrites providing no justification for grouping cr ch and cb chondrites into the cr clan

origin of zoned metal grains in the que94411 chondrite laser ablation inductively coupled plasma mass spectrometry la icp ms was used to measure distributions of the siderophile elements p v cr fe co ni mo ru rh pd w re os ir and pt in metal grains in the metal rich chondrite que94411 with a spatial resolution of similar to 30 mum the platinum group elements pges except pd exhibit radial zoning in these grains that mimics that previously observed in ni and co the concentrations of these elements decreases from the cores to the rims of the grains the pge distributions support a condensation origin for the enhanced refractory element abundances in the zoned grains the lack of zoning in pd refutes an origin by a redox controlled process and none of the pge ni relationships support an origin by fractional crystallization from a metallic melt several models of grain formation were explored including equilibrium fractional condensation which failed to yield the correct radial zoning the zoning may be the product of a nonequilibrium fractional condensation process in which the refractory siderophiles remained supersaturated in the cooling solar nebula or of diffusion between refractory enhanced fe ni cores and other fe ni metal that may have been deposited later from the solar nebula copyright c 2001 elsevier science ltd

infrared spectroscopic taxonomy for carbonaceous chondrites from speciation of hydrous components mid infrared absorption spectra for all types of carbonaceous chondrites were obtained in this study to establish a versatile method for spectroscopic classification of carbonaceous chondrites infrared spectra were measured using a conventional kbr pellet method and diamond press method spectra of hydrous carbonaceous chondrites exhibit intense o h stretching vibrations ci chondrites are identifiable by a characteristic sharp absorption band appearing at 3685 cm 1 which is mainly attributable to serpentine x ray diffraction analysis showed the presence of serpentine however yamato y 82162 c1 does not have the band at 3685 cm 1 because of its thermal metamorphism cm and cr chondrites have an intense absorption band at approximately 3600 cm 1 this absorption tends to appear in cm chondrites more strongly than cr chondrites because the intensity ratios of an oh stretching mode at 3520 cm 1 compared to 3400 cm 1 for cm chondrites are in the range of 0 95 1 04 which is systematically higher than those of cr chondrites 0 86 0 88 therefore the two types of chondrites are distinguishable by their respective infrared spectra the spectrum feature of the tagish lake meteorite is attributable to neither ci nor cm chondrites co chondrites are characterized by weak and broad absorption at 3400 cm 1 cv chondrites have weak or negligible absorption of water ck chondrites also have no water induced absorption ch and cb chondrites have a sharp absorption at 3692 cm 1 indicating the presence of chrysotile which is also supported by observations of x ray diffraction and tem the combination of spectroscopic classification and the diamond press method allows classification of carbonaceous chondrites of very valuable samples with small quantities as one example carbonaceous chondrite clasts in brecciated meteorites were classified using our technique infrared spectra for a fragment of carbonaceous clasts 1 g separated from willard b and tsukuba were measured the 3685 cm 1 band found in ci chondrites was clearly detected in the clasts indicating that they are ci like clasts

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

clasts in the cm2 carbonaceous chondrite lonewolf nunataks 94101 evidence for aqueous alteration prior to complex mixing clasts in the cm2 carbonaceous chondrite lonewolf nunataks lon 94101 have been characterized using scanning and transmission electron microscopy and electron microprobe analysis to determine their degrees of aqueous alteration and the timing of alteration relative to incorporation of clasts into the host the provenance of the clasts and the mechanism by which they were incorporated and mixed with their host material are also considered results show that at least five distinct types of clasts occur in lon 94101 of which four have been aqueously altered to various degrees and one is largely anhydrous the fact that they have had different alteration histories implies that the main part of aqueous activity occurred prior to the mixing and assimilation of the clasts with their host further the presence of such a variety of clasts suggests complex mixing in a dynamic environment involving material from various sources two of the clasts one containing approximately 46 vol carbonate and the other featuring crystals of pyrrhotite up to approximately 1 mm in size are examples of unusual lithologies and indicate concentration of chemical elements in discrete areas of the parent body ies possibly by flow of aqueous solutions

acfer 182 and paired samples an iron rich carbonaceous chondrite similarities with alh85085 and relationship to cr chondrites three samples of a new fe rich chondrite were found in the sahara in 1990 and 1991 acfer 182 acfer 207 acfer 214 the samples are paired and the meteorite will be designated as acfer 182 the chondrite is chemically texturally and mineralogically similar to the allan hills meteorite alh85085 one important difference between the two meteorites is the smaller average chondrule size in alh85085 the major components of acfer 182 in decreasing abundance are 1 1 highly altered by terrestrial weathering matrix 2 2 mineral and polymineralic silicate fragments and aggregates 3 3 chondrule fragments 4 4 chondrules 5 5 metal 6 6 fine grained dark inclusions the abundance of chondrules is lower and the average chondrule size 90 m smaller than in most other chondrites chondrule fragments are often so large that they cannot be derived from the present chondrule population apparently size sorting has prevented accumulation of the larger parent chondrules several spectacular ca al rich inclusions were found rich in ca dialuminate hibonite or zr y sc bearing phases the chemical composition of acfer 182 and of alh85085 are almost indistinguishable major chemical signatures are 1 1 uniform enrichment of fe and other nonvolatile metals relative to ci chondrites by about 70 2 2 absence of enrichment in refractory lithophiles characteristic of most type 2 and 3 carbonaceous chondrites 3 3 strong depletion of volatile and moderately volatile elements based on the oxygen isotopic composition the chemical composition and the abundances of chondrules and matrix acfer 182 should be classified as a carbonaceous chondrite considering their affinity to carbonaceous chondrites and their high bulk iron content the two meteorites acfer 182 and alh85085 are designated as ch chondrites there are mineralogical and chemical similarities among acfer 182 alh85085 and cr chondrites which distinguish these meteorites from other types of carbonaceous chondrites 1 1 low feo contents of olivine and pyroxene and correspondingly high metal contents 2 2 high cr content in olivine 3 3 abundant fine grained dark inclusions 4 4 abundant ca dialuminate caal4o7 in cais 5 5 similarities in oxygen isotopic composition 6 6 low contents of moderately volatile elements 7 7 low refractory element contents 8 8 presence of a unique component of subsolar rare gases these observations suggest similar conditions of formation for the components of these meteorites a single common parent body is unlikely in view of the differences in chemical composition and in the size distribution of individual components

alh85085 a unique volatile poor carbonaceous chondrite with possible implications for nebular fractionation processes abstract allan hills 85085 is a unique chondrite with affinities to the al rais renazzo clan of carbonaceous chondrites its constituents are less than 50 m in mean size chondrules and microchondrules of all textures are present nonporphyritic chondrules are unusually abundant the mean compositions of porphyritic nonporphyritic and barred olivine chondrules resemble those in ordinary chondrites except that they are depleted in volatile elements ca al rich inclusions are abundant and largely free of nebular alteration they comprise types similar to those in cm and co chondrites as well as unique types calcium dialuminate occurs in several inclusions metal silicate and sulfide compositions are close to those in cm co chondrites and al rais and renazzo c1 chondrite clasts and metal rich reduced clasts are present but opaque matrix is absent siderophile abundances in alh85085 are extremely high e g fe si 1 7 solar and volatiles are depleted e g na si 0 25 solar s si 0 03 solar nonvolatile lithophile abundances are similar to those in al rais renazzo and cm and co chondrites alh85085 agglomerated when temperatures in the nebula were near 1000 k in the same region where renazzo al rais and the ci chondrites formed agglomeration of high temperature material may thus be a mechanism by which the fractionation of refractory lithophiles occurred in the nebula chondrule formation must have occurred at high temperatures when clumps of precursors were small after agglomeration alh85085 was annealed and lightly shocked c1 and other clasts were subsequently incorporated during late stage brecciation

unusual forms of magnetite in the orgueil carbonaceous chondrite the orgueil ci carbonaceous chondrite contains magnetite fe3o4 that displays a rich and seemingly unique variety of morphologies while many have already been described recent images provide far greater definition and thus provide more unambiguous identification of trapezohedral crystals and possibly also trisoctahedral forms although it is an extremely abundant terrestrial mineral and commonly occurs in well developed crystals neither of these forms have been recognized previously from magnetite the barrel shaped arrays of magnetite discs plaquettes are also unique it appears as if the circumstances for the formation of these unusual crystals were somehow exceptional their morphologies and association with sulfates and carbonates suggest an aqueous origin

heavily hydrated lithic clasts in ch chondrites and the related metal rich chondrites queen alexandra range 94411 and hammadah al hamra 237 fine grained heavily hydrated lithic clasts in the metal rich cb chondrites queen alexandra range que 94411 and hammadah al hamra 237 and ch chondrites such as patuxent range pat 91546 and allan hills alh 85085 are mineralogically similar suggesting genetic relationship between these meteorites these clasts contain no anhydrous silicates and consist of framboidal and platelet magnetite prismatic sulfides pentlandite and pyrrhotite and fe mn mg bearing ca carbonates set in a phyllosilicate rich matrix two types of phyllosilicates were identified serpentine with basal spacing of similar to0 73 nm and saponite with basal spacings of about 1 1 1 2 nm chondrules and feni metal grains in cb and ch chondrites are believed to have formed at high temperature 1300 k by condensation in a solar nebula region that experienced complete vaporization the absence of aqueous alteration of chondrules and metal grains in cb and ch chondrites indicates that the clasts experienced hydration in an asteroidal setting prior to incorporation into the ch and cb parent bodies the hydrated clasts were either incorporated during regolith gardening or accreted together with chondrules and feni metal gains after these high temperature components had been transported from their hot formation region to a much colder region of the solar nebula

refractory calcium aluminum rich inclusions and aluminum diopside rich chondrules in the metal rich chondrites hammadah al hamra 237 and queen alexandra range 94411 the metal rich chondrites hammadah al hamra hh 237 and queen alexandra range que 94411 paired with que 94627 contain relatively rare 1 vol calcium aluminum rich inclusions cais and al diopside rich chondrules forty cais and cai fragments and seven al diopside rich chondrules were identified in hh 237 and que 94411 94627 the cais 50 400 mum in apparent diameter include a 22 56 pyroxene spinel melilite forsterite rim b 11 28 forsterite bearing pyroxene spinel melilite anorthite forsterite rim c 2 5 grossite rich spinel melilite pyroxene rim d 2 5 hibonite melilite spinel pyroxene forsterite rim e 1 2 hibonite bearing spinel perovskite melilite pyroxene rim f 1 2 spinel melilite pyroxene anorthite and g 1 2 amoeboid olivine aggregate each type of cai is known to exist in other chondrite groups but the high abundance of pyroxene spinel melilite cais with igneous textures and surrounded by a forsterite rim are unique features of hh 237 and que 94411 94627 additionally oxygen isotopes consistently show relatively heavy compositions with delta o 17 ranging from 6 parts per thousand to 10 parts per thousand 1 sigma 1 3 parts per thousand for all analyzed cai minerals grossite hibonite melilite pyroxene spinel this suggests that the cais formed in a reservoir isotopically distinct from the reservoir s where normal o 16 rich delta o 17 20 cais in most other chondritic meteorites formed

shock melts in que 94411 hammadah al hamra 237 and bencubbin remains of the missing matrix we have studied the cb carbonaceous chondrites queen alexandra range que 94411 hammadah al hamra hh 237 and bencubbin with an emphasis on the petrographical and mineralogical effects of the shock processing that these meteorite assemblages have undergone iron nickel metal and chondrule silicates are the main components in these meteorites these high temperature components are held together by shock melts consisting of droplets of dendritically intergrown fe ni metal sulfide embedded in silicate glass which is substantially more feo rich 3040 wt than the chondrule silicates feo 5 wt fine grained matrix material which is a major component in most other chondrite classes is extremely scarce in que 94411 and hh 237 and has not been observed in bencubbin this material occurs as rare hydrated matrix lumps with major and minor element abundances roughly similar to the ferrous silicate shock melts and cl we infer that hydrated fine grained material compositionally similar to these matrix lumps was originally present between the fe ni metal grains and chondrules but was preferentially shock melted other shock related features in que 94411 hh 237 and bencubbin include an alignment and occasionally strong plastic deformation of metal and chondrule fragments

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

xenoliths and microxenoliths in h chondrites sampling the zodiacal cloud in the asteroid main belt abstract xenoliths are inclusions of a given meteorite group embedded in host meteorites of a different group xenoliths with dimensions between a few m and about 1 mm microxenoliths are meteorite trapped analogues of micrometeorites collected on the earth however they have the unique features of sampling the zodiacal cloud 1 at more ancient times than those sampled by micrometeorites and 2 at larger distances from the sun corresponding to the asteroid main belt than that sampled by micrometeorites 1 au herein we describe a systematic search for new xenoliths and microxenoliths in h chondrites aimed at determining their abundance in these ordinary chondrites analyzing their mineralogy and searching for possible correlations with host meteorite properties sixty six sections from 40 meteorites have been analyzed twenty four new xenoliths have been discovered about 87 of them are microxenoliths i e 1 mm in their largest dimension all the newly discovered xenoliths and microxenoliths are composed of carbonaceous chondritic material hence the zodiacal cloud was dominated by carbonaceous material even in past epochs all the new xenoliths and microxenoliths have been found in regolith breccias hydrous phase rich xenoliths and microxenoliths in h4 and h5 chondrites attest that their embedding happened after the end of the thermal metamorphism all these data suggest that xenoliths and microxenoliths were embedded when their host meteorites were part of the parent body regolith this combined with the h chondrite impact age distribution attests that the embedding may have happened as early as 3 5 gyr ago

hydrogen isotopic composition of water from fossil micrometeorites in howardites we have measured the hydrogen isotopic composition d h ratios of the water from 13 carbonaceous chondritic microclasts ccms size 1 mm trapped in two howardites kapoeta and yamato 793497 early in the evolution of solar system the division into tochilinite rich magnetite rich olivine poor magnetite rich olivine rich ccm types is corroborated by the hydrogen isotopic compositions both mineralogy and hydrogen isotopic compositions demonstrate that tochilinite rich ccms represent cm2 chondritic matter in contrast there is no good match between the isotopic and mineralogical properties of the magnetite rich ccms and the known groups of carbonaceous chondrites suggesting that magnetite rich ccms represent a new kind of chondritic matter not yet sampled in meteorite collections this demonstrates that the view of the asteroid belt revealed by the collection of meteorites is incomplete the study of micro clasts offers a unique opportunity to better decipher the nature and relative abundance of asteroids the average hydrogen isotopic composition of water belonging to ccms d h 152 0 4 8 x 10 6 1 sigma m is similar to that of antarctic micrometeorites amms d h 161 2 3 8 x 10 6 1 sigma m the similarity in terms of mineralogy and hydrogen isotopic composition between ccms and amms demonstrates that the composition of the micrometeorites has not been modified over the whole history of the solar system it indicates that the composition of the micrometeorite flux onto earth has been and is dominated by a mixture of cm2 like magnetite rich olivine poor magnetite rich olivine rich carbonaceous chondritic matter exemplified by ccms found in howardites because ccms have not suffered atmospheric entry they provide an abundant source of pristine micrometeorites the average d h ratio of the whole population of ccms is identical within errors to that of the earth 149 3 x 10 6 the match between the ccms d h ratio and that of the earth is especially remarkable because 1 three different populations of ccms are needed to make the d h ratio of the earth 2 there is no single carbonaceous chondrite group for which a similar match exists this observation suggests that ccms population might be representative of the late veneer agent s that delivered water to the earth

the cr chondrite clan implications for early solar system processes in this paper we review the mineralogy and chemistry of calcium aluminum rich inclusions cais chondrules feni metal and fine grained materials of the cr chondrite clan including cr ch and the metal rich cb chondrites queen alexandra range 94411 hammadah al hamra 237 bencubbin gujba and weatherford the members of the cr chondrite clan are among the most pristine early solar system materials which largely escaped thermal processing in an asteroidal setting bencubbin weatherford and gujba may be exceptions and provide important constraints on the solar nebula models these constraints include 1 multiplicity of cai formation 2 formation of cals and chondrules in spatially separated nebular regions 3 formation of cais in gaseous reservoir s having o 16 rich isotopic compositions chondrules appear to have formed in the presence of o 16 poor nebular gas 4 isolation of cais and chondrules from nebular gas at various ambient temperatures 5 heterogeneous distribution of al 26 in the solar nebula and 6 absence of matrix material in the regions of cai and chondrule formation

compositional and kinetic controls on liquid immiscibility in ferrobasalt rhyolite volcanic and plutonic series we present major element compositions of basalts and their differentiation products for some major tholeiitic series the dry low pressure liquid lines of descent are shown to approach or intersect the experimentally defined compositional space of silicate liquid immiscibility ferrobasalt rhyolite unmixing along tholeiitic trends in both volcanic and plutonic environments is supported by worldwide occurrence of immiscible globules in the mesostasis of erupted basalts unmixed melt inclusions in cumulus phases of major layered intrusions such as skaergaard and sept iles and oxide rich ferrogabbros closely associated with plagiogranites in the lower oceanic crust liquid immiscibility is promoted by low pressure anhydrous fractional crystallization that drives the low al2o3 high feo liquids into the two liquid field kinetic controls can be important in the development of two liquid separation the undercooling that occurs at the slow cooling rates of plutonic environments promotes early development of liquid immiscibility at higher temperature in contrast rapid cooling in erupted lavas leads to large undercoolings and liquid immiscibility develops at significantly lower temperatures unmixing leads to the development of a compositional gap characterized by the absence of intermediate compositions a feature of many tholeiitic provinces the compositions of experimental unmixed silica rich melts coincide with those of natural rhyolites and plagiogranites with high feotot and low al2o3 suggesting the potential role of large scale separation of immiscible si rich liquid in the petrogenesis of late stage residual melts no trace of the paired ferrobasaltic melt is found in volcanic environments because of its uneruptable characteristics instead fe ti p rich gabbros are the cumulate products of immiscible fe rich melts in plutonic settings the immiscibility process may be difficult to identify because both melts crystallize the same phases with the same compositions the two liquids might form incompletely segregated emulsions so that both liquids continue to exchange as they crystallize and remain in equilibrium even if segregated both melts evolve on the binodal surface and exsolve continuously with decreasing temperature the two liquids do not differentiate independently and keep crystallizing the same phases with differentiation further evolution by fractional crystallization potentially drives the bulk liquid out of the twoliquid field so that very late stage liquids could evolve into the single melt phase stability field

a radar survey of m and x class asteroids abstract we observed ten m and x class main belt asteroids with the arecibo observatory s s band 12 6 cm radar the x class asteroids were targeted based on their albedos or other properties which suggested they might be m class this work brings the total number of main belt m class asteroids observed with radar to 14 we find that three of these asteroids have rotation rates significantly different from what was previously reported based on their high radar albedo we find that only four of the fourteen 16 psyche 216 kleopatra 758 mancunia and 785 zwetana are almost certainly metallic 129 antigone has a moderately high radar albedo and we suggest it may be a ch cb bencubbinite parent body three other asteroids 97 klotho 224 oceana and 796 sarita have radar albedos significantly higher than the average main belt asteroid and we cannot rule out a significant metal content for them five of our target asteroids 16 psyche 129 antigone 135 hertha 758 mancunia and 785 zwetana show variations in their radar albedo with rotation we can rule out shape and composition in most cases leaving variations in thickness porosity or surface roughness of the regolith to be the most likely causes with the exception of 129 antigone we find no hydrated m class asteroids w class rivkin a s howell e s lebofsky l a clark b e britt d t 2000 icarus 145 351 368 to have high radar albedos

chondritic lithic clasts in the cb ch like meteorite isheyevo fragments of previously unsampled parent bodies the cb ch like chondrite isheyevo is characterized by the absence of fine grained interchondrule matrix material the only present fine grained material is found as chondritic lithic clasts in contrast to the pristine high temperature components of isheyevo these clasts experienced extensive aqueous alteration in an asteroidal setting hence the clasts are foreign objects that either accreted together with the high temperature components or were added later to the final isheyevo parent body during regolith gardening in order to constrain the origin and secondary alteration of the clasts in isheyevo we studied their mineralogy petrography structural order of the polyaromatic carbonaceous matter and oxygen isotopic compositions of carbonates three main groups of clasts were defined based on mineralogy and petrology group i clasts consist of phyllosilicates carbonates magnetite and lath shaped fe ni sulfides group ii clasts contain different abundances of anhydrous silicates embedded in a hydrated matrix sulfides magnetite and carbonates are rare with only a few exceptions groups i and ii clasts did not experienced significant thermal metamorphism group iii clasts are characterized by the absence of magnetite and the presence of fe ni metal in addition to aqueous alteration they experienced thermal metamorphism as reflected by the structure of their polyaromatic carbonaceous matter while there are some similarities between the isheyevo clasts ci chondrites and the matrices of cm and cr chondrites on the whole the characteristics of the clasts do not match those of any of these aqueously altered meteorite classes nor do they match those of similar material in various types of chondritic clasts present in other meteorite groups we conclude that the isheyevo clasts represent fragments of previously unsampled parent bodies

a warning system for stromboli volcano based on statistical analysis in this paper we describe a warning system based on statistical analysis for the purpose of monitoring ground deformation at the sciara del fuoco stromboli volcano sicily after a statistical analysis of ground deformation time series measured at stromboli by the monitoring system known as theodoros theodolite and distancemeter robot observatory of stromboli the paper describes the solution adopted for implementing the warning system a robust statistical index has been defined in order to evaluate the movements of the area a fuzzy approach has been proposed to evaluate an ai alarm intensity index which indicates the level of hazard of the sciara del fuoco sliding

aqueous alteration and brecciation in bells an unusual saponite bearing cm chondrite the petrological and mineralogical characteristics of the unusual cm2 chondrite bells have been investigated in detail by scanning electron microscopy sem electron microprobe analysis epma and transmission electron microscopy tem bells is a highly brecciated chondrite which contains few intact chondrules a very low abundance of refractory inclusions and is notable in having an unusually high abundance of magnetite which is disseminated throughout the fine grained matrix fragmental olivines and pyroxenes are common and based on compositional data appear to have been derived from chondrules as a result of extensive brecciation the fine grained mineralogy of matrix in bells differs considerably from other cm chondrites and has closer affinities to matrix in ci chondrites the dominant phases are fine grained saponite interlayered with serpentine and phases such as tochilinite and cronstedtite which are typical of cm chondrite matrices are entirely absent pentlandite pyrrhotite magnetite anhydrite calcite and rare ti oxides also occur as accessory phases based on its oxygen and noble gas isotopic compositions zadnik 1985 rowe et al 1994 bells can be considered to be a cm2 chondrite although its bulk composition shows some departures from the typical range exhibited by this group however these variations in bulk chemistry are entirely consistent with the observed mineralogy of bells the unusual fine grained mineralogy of bells matrix can be reasonably attributed to the combined effects of aqueous alteration and advanced brecciation in a parent body environment extensive brecciation has assisted aqueous alteration by reducing chondrules and mineral grains into progressively smaller grains with high surface areas which are more susceptible to dissolution reactions involving aqueous fluids this has resulted in the preferential dissolution of fe rich chondrule olivines which are now completely absent in bells although present in other cm chondrites the formation of saponite in bells probably resulted from the dissolution of relatively silica rich phases such as pyroxene and olivine that were derived from chondrules the result of such dissolution reactions would be to increase the activity of silica in the fluid phase at least on a localized scale stabilizing saponite in preference to serpentine an increase in asio2 would also have destabilized preexisting cronstedtite which may have reacted to form magnetite and mg fe serpentine under conditions of constant o2

magnetite morphologies in the essebi and haripura cm chondrites many of the unusual magnetite morphologies previously observed only in the ci chondrites have been seen in the cm chondrites essebi and haripura these include heavily textured spheroids which are possibly spherulites found both singly and in groups of up to a dozen and ranging in size from 4 to 10 m in diameter collections of microcrystals varying from 0 3 to 6 m in diameter spheres of 1 to 6 m in diameter layered nearly circular plates forming a spheroidal plaquette 7 5 m in diameter clusters of variable sized nodules 1 5 to 6 m with concave features framboidal magnetite and finally collections of less distinctive globules

formation history of ci like phyllosilicate rich clasts in the tsukuba meteorite inferred from mineralogy and noble gas signatures abstract fine grained angular black clasts with longest dimensions up to 800 m were found dispersed in a brecciated region in the tsukuba meteorite the clasts much darker than the dark portions of the light dark structure in the tsukuba host are characterized by the presence of plaquette spherulitic and framboidal magnetites and pseudo hexagonal pyrrhotite synchrotron radiation x ray diffraction analyses showed that the major silicate phases in the clasts are saponite and serpentine transmission electron microscopy tem revealed that the phyllosilicates have compositions quite similar to those in the orgueil ci carbonaceous chondrite therefore mineralogically and chemically the clasts resemble ci chondrites and are quite different from the host h5 6 chondrite tsukuba the clasts serve as an indicator of temperatures during regolith lithification of the tsukuba parent body because their mineralogy and noble gas compositions are subject to change during weak heating the 001 basal spacing of saponite in the clast is 13 2 a which indicates that saponite retains interlayer water molecules this observation and the presence of serpentine suggest that the clasts as a whole have never been heated above 500 c noble gas analyses showed that the clasts contain large amounts of solar and primordial noble gases the results of stepwise heating analyses indicate that no apparent thermal loss of noble gases from the clasts occurred consistent with the mineralogical evidence tem observation revealed that the periphery of a clast was transformed into amorphous phases indicating that only the periphery was heated to 700 c based on the results of our analyses the formation history of the clasts can be evaluated as follows constituents of the clasts had been exposed to solar wind on the surface of the ci chondrite like parent body and formed the clasts after ejection from the ci like parent body the ci like meteoroid accreted to the tsukuba parent body after early thermal metamorphism that reached 700 1000 c the clasts must have been located in the regolith because they were found among the light dark structure in the meteorite and contain abundant solar noble gases impacts into the regolith have crushed the clasts into smaller pieces and probably induced lithification of the regolith material during lithification the peripheries of the clasts were heated briefly to 700 c but the temperature of the interior of the clasts has never exceeded 500 c this is the first evidence constraining temperature during lithification of the ordinary chondrite parent body regolith finally the tsukuba meteoroid including the ci like clasts was ejected from the tsukuba parent body and fell onto the earth after a transit time of 8 1 ma

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

new integrated geodetic monitoring system at stromboli volcano italy stromboli is a composite volcano forming the northernmost island of the aeolian archipelago volcanic arc tyrrhenian sea on december 28th 2002 lava flows outpoured from the northern wall of the ne crater and descended into the sciara del fuoco sdf a deep depression marking the nw flank of the volcano edifice on december 30th 2002 two landslides occurred on the northern part of the sdf they moved a mass in the order of tens of millions of cubic meters both above and below sea level the landslide produced a tsunami causing significant damage to the eastern coast of the island reaching the other aeolian islands and the sicilian and southern italian coasts this event led to the upgrading of the ground deformation monitoring system already existing on the island the new requirement was the real time detection of the deformations related to potential slope failures of the sdf to this end a remotely controlled monitoring system based both on gps and geodetic techniques was planned and set up in a few months the new monitoring system allowed to continuously measure the ground deformations occurring on the sdf by integrating both terrestrial and satellite geodetic techniques although this system was severely damaged during the 7 month long eruption it allowed to monitor important eruptive phases for the first time an accurate data set on the actual mass movements of the sdf and the crater area was available it provided data that significantly supported the civil protection authorities in making decisions and constrains theories related to landslide movements and volcanic activity after the end of the eruption the system was overhauled in order to optimize the instruments and set up a monitoring system aimed at measuring deformations forecasting other flank collapses

evidence for an asteroid comet continuum from simulations of carbonaceous microxenolith dynamical evolution abstract micrometeoroids with 100 and 200 m size dominate the zodiacal cloud dust such samples can be studied as micrometeorites after their passage through the earth atmosphere or as microxenoliths i e submillimetric meteorite inclusions microxenoliths are samples of the zodiacal cloud dust present in the asteroid main belt hundreds of millions years ago carbonaceous microxenoliths represent the majority of observed microxenoliths they have been studied in detail in howardites and h chondrites we investigate the role of carbonaceous asteroids and jupiter family comets as carbonaceous microxenolith parent bodies the probability of low velocity collisions of asteroidal and cometary micrometeoroids with selected asteroids is computed starting from the micrometeoroid steady state orbital distributions obtained by dynamical simulations we selected possible parent bodies of howardites vesta and h chondrites hebe flora eunomia koronis maria as target asteroids estimates of the asteroidal and cometary micrometeoroid mass between 2 and 4 au from the sun are used to compute the micrometeoroid mass influx on each target the results show that all the target asteroids except koronis receive the same amount within the uncertainties of asteroidal and cometary micrometeoroids therefore both these populations should be observed among howardite and h chondrite carbonaceous microxenoliths however this is not the case carbonaceous microxenoliths show differences similar to those existing among different groups of carbonaceous chondrites e g ci cm cr but two sharply distinct populations are not observed our results and the observations can be reconciled assuming the existence of a continuum of mineralogical and chemical properties between carbonaceous asteroids and comets

a new metal rich chondrite grouplet abstract a new grouplet of primitive metal rich chondrites here called the cb c carbonaceous b bencubbinite chondrites has been recognized it includes bencubbin weatherford hammadah a1 hamra hh 237 and queen alexandra range que 94411 paired with que 94627 their mineral compositions as well as their oxygen and nitrogen isotopic compositions indicate that they are closely related to the cr and ch chondrites all of which are members of the more inclusive cr clan cb chondrites have much greater metal silicate ratios than any other chondrite group widely increasing the range of metal silicate fractionation recorded in solar nebular processes they also have the greatest moderately volatile lithophile element depletions of any chondritic materials metal has compositional trends and zoning patterns that suggest a primitive condensation origin in contrast with metal from other chondrite groups cb chondrites as well as other cr clan chondrites have much heavier nitrogen higher 15n 14n than that in other chondrite groups the primitive characteristics of the cb chondrites suggest that they contain one of the best records of early nebular processes another chondrite grosvenor mountains 9555 1 is petrographically similar to the cb chondrites but its mineral and oxygen and nitrogen isotope compositions indicate that it formed from a different nebular reservoir

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

oxygen isotopic compositions of chondrules from the metal rich chondrites isheyevo ch cbb mac 02675 cbb and que 94627 cbb abstract it has been recently suggested that 1 ch chondrites and the cbb ch like chondrite isheyevo contain two populations of chondrules formed by different processes i magnesian non porphyritic cryptocrystalline and barred chondrules which are similar to those in the cb chondrites and formed in an impact generated plume of melt and gas resulted from large scale asteroidal collision and ii porphyritic chondrules formed by melting of solid precursors in the solar nebula 2 porphyritic chondrules in isheyevo and ch chondrites are different from porphyritic chondrules in other carbonaceous chondrites krot et al 2005 krot et al 2008a krot et al 2008b in order to test these hypotheses we measured in situ oxygen isotopic compositions of porphyritic magnesian type i and ferroan type ii and non porphyritic magnesian and ferroan cryptocrystalline chondrules from isheyevo and cbb chondrites mac 02675 and que 94627 paired with que 94611 using a cameca ims 1280 ion microprobe on a three isotope oxygen diagram 17o vs 18o compositions of chondrules measured follow approximately slope 1 line data for 19 magnesian cryptocrystalline chondrules from isheyevo 24 magnesian cryptocrystalline chondrules and 6 magnesian cryptocrystalline silicate inclusions inside chemically zoned fe ni metal condensates from cbb chondrites have nearly identical compositions 17o 2 2 0 9 2 3 0 6 and 2 2 1 0 2 respectively these observations and isotopically light magnesium compositions of cryptocrystalline magnesian chondrules in cbb chondrites gounelle et al 2007 are consistent with their single stage origin possibly as gas melt condensates in an impact generated plume in contrast 17o values for 11 type i and 9 type ii chondrules from isheyevo range from 5 to 4 and from 17 to 3 respectively in contrast to typical chondrules from carbonaceous chondrites seven out of 11 type i chondrules from isheyevo plot above the terrestrial fractionation line we conclude that i porphyritic chondrules in isheyevo belong to a unique population of objects suggesting formation either in a different nebular region or at a different time than chondrules from other carbonaceous chondrites ii isheyevo cb and ch chondrites are genetically related meteorites they contain non porphyritic chondrules produced during the same highly energetic event probably large scale asteroidal collision iii the differences in mineralogy petrography chemical and whole rock oxygen isotopic compositions between ch and cb chondrites are due to various proportions of the nebular and the impact produced materials

the condensation origin of zoned metal grains in queen alexandra range 94411 implications for the formation of the bencubbin like chondrites thermodynamic analysis of the compositional profiles across large chemically zoned fe ni metal grains in the bencubbin like chondrite queen alexandra range que 94411 suggests that these grains formed by non equilibrium gas solid condensation under variable oxidizing conditions isolation degree and cr depletion factors the oxidizing conditions must have resulted from the complete vaporization of nebular regions with enhanced dust gas ratios similar to 10 40 x solar because the origin of each of the metal grains studied requires different condensation parameters dust gas ratio isolation degree and cr depletion factor a high degree of heterogeneity in the formation region of the bencubbin like chondrite metal is required to preserve compositional zoning of the metal grains and prevent their melting and sulfidization the grains must have been removed from the hot condensation region into cold regions where the accretion of the bencubbin like asteroidal body took place

mineralogy and petrography of c asteroid regolith the sutter s mill cm meteorite based upon our characterization of three separate stones by electron and x raybeam analyses computed x ray microtomography raman microspectrometry and visible ir spectrometry sutter s mill is a unique regolith breccia consisting mainly of various cmlithologies most samples resemble existing available cm2 chondrites consisting ofchondrules and calcium aluminum rich inclusion cai set within phyllosilicate dominatedmatrix mainly serpentine pyrrhotite pentlandite tochilinite and variable amounts of ca mg fe carbonates some lithologies have witnessed sufficient thermal metamorphism totransform phyllosilicates into fine grained olivine tochilinite into troilite and destroycarbonates one finely comminuted lithology contains xenolithic materials enstatite fe crphosphides suggesting impact of a reduced asteroid e or m class onto the main sutter smill parent asteroid which was probably a c class asteroid one can use sutter s mill tohelp predict what will be found on the surfaces of c class asteroids such as ceres and thetarget asteroids of the osiris rex and hayabusa 2 sample return missions which willvisit predominantly primitive asteroids c class asteroid regolith may well contain a mixtureof hydrated and thermally dehydrated indigenous materials as well as a significantadmixture of exogenous material would be essential to the successful interpretation ofmineralogical and bulk compositional data

petrology of alh85085 a chondrite with unique characteristics abstract alh85085 has several characteristics which set it apart from any known chondritic group its chondrules are smaller 25 75 m the majority are cryptocrystalline and all are volatile na k s depleted feni metal is more abundant 40 9 wt than in any other chondrite and sulfide abundance is low 1 1 matrix material does not surround the chondrules and fragments but occurs as lithic clasts lumps up to 300 m across the bulk composition of alh85085 is lower in na si and s si and higher in ni si fe si and mg si than in other chondritic groups the ca si al si and mg si ratios are closest to those of the renazzo chondrite grouplet cr matrix lumps are most similar to cr and murchison group cm chondrite matrices survival of this fragile matrix material as lithic clasts indicates that they were added just prior to the agglomeration of the chondrite all components chondrules fragments matrix lumps fall within a narrow size range which may be the result of aerodynamic sorting if so the sorting must have occurred after chondrule solidification and following a period of chondrule breakage since fragments from larger chondrules are present the ni vs co trend in the feni metal overlaps that of metal in cr chondrites and bencubbin these trends are similar to those of calculated nebular condensation paths indicating a nebular origin the cryptocrystalline texture and volatile depletion of the chondrules indicate that most chondrules were heated to temperatures above the liquidus although alh85085 cannot now be assigned to any known chondrite group it shares many similarities with cr chondrites and the bencubbin metal silicate chondritic assemblage and may be part of a chondritic group closely related to these meteorites

the fountain hills unique cb chondrite insights into thermal processes on the cb parent body we report the results of an extensive study of the fountain hills chondritic meteorite this meteorite is closely related to the cba class mineral compositions and o isotopic ratios are indistinguishable from other members of this group however many features of fountain hills are distinct from the other cb chondrites fountain hills contains 23 volume percent metal significantly lower than other members of this class in addition fountain hills contains porphyritic chondrules which are extremely rare in other cba chondrites fountain hills does not appear to have experienced the extensive shock seen in other cb chondrites the chondrule textures and lack of fine grained matrix suggests that fountain hills formed in a dust poor region of the early solar system by melting of solid precursors refractory siderophiles and lithophile elements are present in near ci abundances within a factor of two related to the enhancement of metal moderately volatile and highly volatile elements are significantly depleted in fountain hills the abundances of refractory siderophile trace elements in metal grains are consistent with condensation from a gas that is reduced relative to solar composition and at relatively high pressures 10 3 bars fountain hills experienced significant thermal metamorphism on its parent asteroid combining results from the chemical gradients in an isolated spinel grain with olivine spinel geothermometry suggests a peak temperature of metamorphism between 535 c and 878 c similar to type 4 ordinary chondrites

insight on recent stromboli eruption inferred from terrestrial and satellite ground deformation measurements abstract the multi parametric permanent system tilt and gps networks robotized geodetic station for monitoring ground deformation at stromboli volcano was set up in the 1990s and later greatly improved during the effusive event of 2002 2003 unlike other volcanoes e g mt etna the magnitude of ground deformation signals of stromboli is very small and through the entire period of operation of the monitoring system only two major episodes of deformation in 1994 1995 and 2000 which did not lead to an eruption but rather pure intrusion were measured similarly to the 2002 2003 eruption no important deformations were detected in the months before the 2007 eruption however unlike the 2002 2003 eruption gps and tilt stations recorded a continuous deflation during the entire 2007 eruption which allowed us to infer a vertical elongated prolate ellipsoidal source centered below the summit craters at depth of about 2 8 km b s l due to its geometry and position this source simulates an elongated plumbing system connecting the deeper lp magma storage depth from 5 to 10 km with the hp shallower storage 0 8 3 km both previously identified by petrologic and geochemical studies this result represents the first contribution of geophysics to the definition of the plumbing system of stromboli at intermediate depth finally no deformation due to the plumbing system was measured for a long time after the end of the eruption meanwhile the new terrestrial geodetic monitoring system installed within the sciara del fuoco on the lava fan formed during the eruption indicated that during the first months after the end of the eruption the ground velocity progressively decreased in time suggesting that part of the deformation was due to the thermal contraction of the lava flow

automatic recognition of landslides based on neural network analysis of seismic signals an application to the monitoring of stromboli volcano southern italy in the last 9 years the amount and the quality of geophysical and volcanological observations of stromboli s activity have undergone a marked increase this new information highlighted that the landslides on the sciara del fuoco flank are tightly linked to the volcanic activity actually at the beginning of the december 28 2002 effusive eruption the seismic monitoring network was less dense than now and therefore it is not known if there was an increase in the landslide rate before the eruption despite this it is known that a big landslide occurred 2 days after the beginning of the eruption which caused a tsunami december 30 2002 more recently the effusive eruption in february 2007 was preceded by an increase in landslides on the sciara del fuoco flank which were recorded by the seismological monitoring system that had been improved after the 2002 2003 crisis these episodes led us to believe that monitoring the sciara del fuoco flank instability is an important topic and that landslides might be significant short term precursors of effusive eruptions at the stromboli volcano to automatically detect landslide signals we have developed a specialized neural algorithm this can distinguish between landslides and the other types of seismic signals usually recorded at the stromboli volcano i e explosion quakes and volcanic tremor the discrimination results show an average performance of 98 67 according to the experience of the crisis of 2007 to identify changes that can be considered as precursors of effusive eruptions we set up an automatic decision making method based on the neural network responses this method can operate on a continuous data stream it calculates a landslide percentage index lpi that depends on the number of records that are classified by the net as landslides over a given time interval we tested the method on february 27 2007 including the beginning of the effusive phase the index showed an increase as early as at 09 00 utc on that day and reached its maximum value 100 at 12 00 about 40 min before the onset of the eruption after the beginning of the effusive phase the index remains high due to the blocks that roll down along the slope from the front of the lava flow on the basis of these tests we propose a decision making method that is able to recognize a trend in the lpi similar to that of 2007 eruption allowing the identification of precursors of effusive phases at the stromboli volcano

petrology and geochemistry of chondrules and metal in nwa 5492 and gro 95551 a new type of metal rich chondrite abstract northwest africa nwa 5492 and grosvenor mountains gro 95551 are metal rich chondrites having silicate olivine and pyroxene compositions that are more reduced than those in other metal rich chondrites such as the ch and cb chondrites additionally sulfides in nwa 5492 and gro 95551 are more abundant and not related to the metal as in the cb chondrites average metal compositions in nwa 5492 and gro 95551 are close to h chondrite metal oxygen isotope ratios of nwa 5492 and gro 95551 components chondrules and fragments show a range of compositions with most having 17o values 0 since there is no matrix component their average chondrule fragment oxygen isotopic compositions are considered to be representative of whole rock and 17o values are sandwiched between the values for enstatite e and ordinary o chondrites these data argue for a close relationship between nwa 5492 and gro 95551 and suggest that they are the first examples of a new type of metal rich chondrite oxygen isotope ratios of chondrules in nwa 5492 and gro 95551 show considerable overlap with chondrules in o e and r chondrites with average compositions indistinguishable from ll3 chondrules suggesting considerable mixing between these solar system materials during chondrule formation and or that their precursors experienced similar formation environments and or processes another characteristic shared between nwa 5492 and gro 95551 and o e and r chondrites is that they are all relatively dry low abundances of hydrated minerals compared to many c chondrites and have fewer smaller cais than many c chondrites no cais were found in nwa 5492 or gro 95551 but they contain rare al rich chondrules we suggest that o e r and the nwa 5492 and gro 95551 chondrites are closely related solar system materials

alh 85085 nitrogen isotope analysis of a highly unusual primitive chondrite alh 85085 is an unusual fine grained primitive chondrite which does not fit into any of the known meteorite classes it shows many chemical similarities to the equally unusual meteorites bencubbin weatherford and renazzo nitrogen isotope analysis shows that alh 85085 like bencubbin weatherford and renazzo contains highly 15 n enriched nitrogen indeed alh 85085 has the highest 15 n measured in any whole rock meteorite totalling to 858 but reaching 1497 in the 850 875 c temperature increment however the distribution of isotopically heavy nitrogen in alh 85085 is different from that observed for bencubbin thus precluding a direct relationship between these meteorites isotopically heavy nitrogen occurs in alh 85085 in two sites carbonaceous material 15 n ca 860 13 c ca 1 c n ca 65 75 and in fine grained fe ni metal or opaque chondritic matrix clasts 15 n ca 990 a third very 15 n enriched nitrogen carrier with 15 n 1500 might also be located in the matrix it is probable that there is only a single component with elevated 15 n 1500 and that it occurs in at least three discrete sites mixed with varying amounts of nitrogen having more isotopically normal 15 n 0 50 the identity of the hosts of the isotopically heavy nitrogen have not been fully determined but it is becoming clear that an increasing number of brecciated meteorites some of which do not seem to be related in other ways show evidence of having sampled a reservoir rich in 15 n this may be a result of the introduction of heavy nitrogen during brecciation its 15 n values and distribution throughout the meteorites brought about by mixing with variable amounts of more isotopically normal nitrogen and subsequent vaporization and re condensation processes

evidence for fractional condensation and reprocessing at high temperatures in ch chondrites we performed a detailed study of silica rich components src in the paired ch chondrites acfer 182 and 207 these srcs appear either as chondrules or fragments and they contribute 0 1 vol to the bulk meteorite they usually contain a silica and a silicate portion both portions are in most cases cryptocrystalline and have bulk sio2 concentrations between 65 and 85 wt the silicate generally has a pyroxene normative composition the silica often appears as blebs within the silicate matrix or vice versa if there are no blebs silica and silicate still form rounded interfaces the srcs are depleted in refractory elements like ca al and ti relative to ci a few src like objects are extremely rich in mn and show no depletion in refractory elements we conducted micro raman studies on the silica portions of the srcs to determine their structure and we identified several silica phases quartz cristobalite glass and a yet unidentified polymorph the silicate portion is glass when the silica is glass and crystalline when the silica is crystalline the low contents of al and ca make an igneous origin of the srcs very unlikely and the absence of metal excludes the formation by reduction of pyroxene we suggest instead a fractional condensation origin of the srcs from a si enriched gas after removal of gaseous mg by forsterite condensation additional evidence for fractional condensation is provided by a unique layered object with olivine in the core pyroxene and metal at the rim and silica at the outermost border these layers record the condensation sequence two chondrules were found with several percent of mn and high cr na and k contents providing further evidence for condensation from a fractionated gas the texture of the srcs and the occurrence of cristobalite and silica glass however require formation by liquid immiscibility at high temperatures above 1968 k and subsequent fast cooling therefore we propose a 2 stage model for the formation of srcs in ch chondrites 1 fractional condensation of forsterite enstatite and sio2 rich phases and 2 reheating of sio2 rich components to temperatures above 1968 k followed by rapid cooling all other phases identified in ch chondrites can be understood within the framework of this model thus the extremely unequilibrated ch chondrites provide a wealth of evidence for fractional condensation processes in the early solar nebula in metals meibom et al 1999 and in silicates

formation of metal and silicate globules in gujba a new bencubbin like meteorite fall gujba is a coarse grained meteorite fall composed of 41 vol large kamacite globules 20 vol large light colored silicate globules with cryptocrystalline barred pyroxene and barred olivine textures 39 vol dark colored silicate rich matrix and rare refractory inclusions gujba resembles bencubbin and weatherford in texture oxygen isotopic composition and in having high bulk 15n values 685 the 3he cosmic ray exposure age of gujba 26 7 ma is essentially identical to that of bencubbin suggesting that they were both reduced to meter size fragments in the same parent body collision the gujba metal globules exhibit metal troilite quench textures and vary in their abundances of troilite and volatile siderophile elements we suggest that the metal globules formed as liquid droplets either via condensation in an impact generated vapor plume or by evaporation of preexisting metal particles in a plume the lower the abundance of volatile elements in the metal globules the higher the globule quench temperature we infer that the large silicate globules also formed from completely molten droplets their low volatile element abundances indicate that they also formed at high temperatures probably by processes analogous to those that formed the metal globules the coarse grained bencubbin weatherford gujba meteorites may represent a depositional component from the vapor cloud enriched in coarse and dense particles a second class of bencubbin like meteorites represented by hammadah al hamra 237 and que 94411 may be a finer fraction derived from the same vapor cloud

highly 15n enriched chondritic clasts in the cb ch like meteorite isheyevo the metal rich carbonaceous chondrites cb and ch have the highest whole rock 15n enrichments 15n up to 1500 among planetary materials they are also characterized by the absence of interchondrule fine grained matrix the only fine grained material is present as lithic clasts which experienced extensive aqueous alteration in contrast to the surrounding high temperature components chondrules refractory inclusions metal grains hence the clasts are foreign objects that were incorporated at a late stage into the final parent body of isheyevo their origin is poorly constrained based on mineralogy petrography and thermal processing of the aromatic carbonaceous component different types of clasts have been previously identified in the cb ch like chondrite isheyevo here we focus on the rare lithic clasts characterized by the presence of anhydrous silicates chondrules chondrule fragments and cais their mineralogy and oxygen isotopic compositions reveal them to be micro chondrules fragments of chondrules and refractory inclusions related to those in the isheyevo host suggesting accretion in the same region in contrast to previously studied idps or primitive chondritic matrices the fine grained material in the clasts we studied is highly and rather uniformly enriched in heavy nitrogen with bulk 15n values ranging between 1000 and 1300 it is also characterized by the presence of numerous 15n hotspots 15n ranging from 1400 to 4000 no bulk d 240 or localized deuterium enrichments were observed these clasts have the highest bulk enrichment in heavy nitrogen measured to date in a fine grained material they represent a unique material of asteroidal or cometary origin in our collection of cosmomaterials we show that they were 15n enriched before their incorporation in the final parent body of isheyevo they experienced an extensive aqueous alteration that most likely played a role in redistributing 15n over the whole fine grained material and may have significantly modified its initial hydrogen isotopic composition based on a review of isotopic fractionation models we conclude that the nitrogen isotopic fractionation process its timing and its location are still poorly constrained the 15n rich clasts may represent the surviving original carrier of the 15n anomaly in isheyevo whole rock

a strongly hydrated microclast in the rumuruti chondrite nwa 6828 implications for the distribution of hydrous material in the solar system hydrous carbonaceous microclasts are by far the most abundant foreign fragments in stony meteorites and mostly resemble ci1 cm2 or cr2 like material their occurrence is of great importance for understanding the distribution and migration of water bearing volatile rich matter in the solar system this paper reports the first finding of a strongly hydrated microclast in a rumuruti chondrite the r3 6 chondrite northwest africa 6828 contains a 420 325 m sized angular foreign fragment exhibiting sharp boundaries to the surrounding r type matrix the clast is dominantly composed of magnetite pyrrhotite rare ca carbonate and very rare mg rich olivine set in an abundant fine grained phyllosilicate rich matrix phyllosilicates are serpentine and saponite one region of the clast is dominated by forsteritic olivine fa 1 au between the formation regions of ordinary and carbonaceous chondrites the occurrence of a hydrous microclast in an r chondrite attests to the presence of such material also in this region at least at some point in time and documents the wide distribution of water bearing possibly zodiacal cloud material in the solar system