an amoeboid olivine inclusion aoi in ck3 nwa 1559 comparison to aois in cv3 allende and the origin of aois in ck and cv chondrites an amoeboid olivine inclusion in ck3 nwa 1559 0 54 1 3 mm consists of a diopside rich interior approximately 35 vol and an olivine rich rim approximately 65 vol it is the first aoi to be described in ck chondrites the apparent paucity of these inclusions is due to extensive parent body recrystallization the aoi interior contains irregular 3 15 m sized al bearing diopside grains approximately 70 vol 2 20 m sized pores approximately 30 vol and traces of approximately 2 m plagioclase grains the 75 160 m thick rim contains 20 130 m sized ferroan olivine grains some with 120o triple junctions a few coarse 25 50 m sized patches of plagioclase with 2 18 m thick diopside rinds occur in several places just beneath the rim the occurrence of olivine rims around aoi 1 and around many aois in cv3 allende suggests that ck and cv aois formed by the acquisition of porous forsteritic rims around fine grained rimless cais that consisted of diopside anorthite melilite and spinel individual aois in carbonaceous chondrites may have formed after transient heating events melted their olivine rims as well as portions of the underlying interiors in aoi 1 coarse plagioclase grains with diopside rinds crystallized immediately below the olivine rim secondary parent body alteration transformed forsterite in the rims of cv and ck aois into more ferroan olivine some of the abundant pores in the interior of aoi 1 may have formed during aqueous alteration after fine grained melilite and anorthite were leached out chondrite groups with large chondrules tend to have large aois aois that formed in dust rich nebular regions where cv and ck chondrites later accreted tend to be larger than aois from less dusty regions

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

euhedral awaruite in the allende meteorite implications for the origin of awaruite and magnetite bearing nodules in cv3 chondrites

dark inclusions in allende leoville and vigarano evidence for nebular oxidation of cv3 constituents dark lithic inclusions are known to occur in several cv3 chondrites we report petrologic chemical and oxygen isotopic data on examples from allende leoville and vigarano the allende inclusions comprise a petrographic sequence ranging from a type which contains chondrules and refractory inclusions and resembles cv3 or co3 chondrites to a type which contains porous aggregates of iron rich olivine oxygen isotopic compositions correlate with the sequence chondrule rich inclusions have compositions similar to the host meteorite bulk values whereas olivine aggregate rich inclusions have more 16o depleted compositions chemical compositions on the other hand do not correlate with the petrographic sequence the dark inclusions are all systematically enriched in iron and depleted in potassium and sodium relative to their host meteorites the inclusions appear to be fragments of cv3 parent bodies which were processed to different degrees prior to their incorporation as clasts into allende leoville and vigarano the processing homogenized olivine compositions presumably through heating and also involved oxygen exchange with 16o poorer surroundings either parent body metamorphism or nebular heating might have produced the petrographic and isotopic sequences however the most 16o depleted inclusions also have layered silicate rims surrounding them which are better attributed to gas solid reactions than parent body processes in particular andradite is abundant in the rims which implies that the rims grew under conditions significantly more oxidizing than those likely to have occurred on a cv3 parent body at least part of the processing therefore appears to have taken place prior to final accumulation of the material when the fragments were dispersed in the nebula the evidence for coupled oxidation and 16o depletion in the nebula suggests that other features of the cv3 group such as the oxidized and reduced subgroups ferrous rims on forsteritic olivines and coarse grained rims on chondrules may have been established by similar gas solid reactions prior to the final assembly of the meteorites

modal mineralogy of cv3 chondrites by x ray diffraction psd xrd abstract using position sensitive detector x ray diffraction psd xrd we determine a complete modal mineralogy for all phases present in abundances greater than 1 wt in vigarano efremovka mokoia grosnaja kaba and allende reduced cv3 samples are comprised of vol olivine 83 85 enstatite 6 5 8 1 anorthite 1 1 1 2 magnetite 1 4 1 8 sulphide 2 4 5 1 fe ni metal 2 2 2 the oxidized samples are comprised of olivine 76 3 83 9 enstatite 4 8 7 8 anorthite 1 1 1 7 magnetite 0 3 6 1 sulphide 2 9 8 1 fe ni metal 0 2 1 1 fe oxide 0 2 7 and phyllosilicate 1 9 4 2 when our modal data is used to calculate a bulk chemistry that is compared to literature data a near 1 1 correlation is observed psd xrd data indicates that olivine compositions may span almost the entire fe mg solid solution series in all cv samples and that these contain a component 4 13 of fine grained olivine that is more fe rich fa 60 than is typically reported modal mineralogy shows that there are mineralogic differences between cv3 samples classified as oxidized and reduced but that these sub classes are most clearly distinguished by the relative abundance of metal and ni content of sulphide rather than abundance of magnetite the most significant difference in modal mineralogy observed is the relative absence of phyllosilicate in reduced cv that essentially escaped aqueous alteration fayalite ferrous olivine and magnetite are typically considered secondary alteration products the abundances of these minerals overlap in oxidized and reduced samples and correlate positively supporting common conditions of formation in a relatively oxidizing environment the abundances of fayalite ferrous olivine and magnetite show no relationship to petrographic type and if these abundances were used as a proxy for alteration allende would be the least altered cv contrary to all previous data the implication is that thermal metamorphism on the parent body was de coupled from formation of fe rich secondary minerals low temperature fluid assisted metamorphism can also not easily explain the origin of fayalite ferrous olivine and magnetite since the reduced cvs appear to be largely unaffected by this process parent body models require an anhydrous low temperature mechanism of secondary alteration the alternative is that these phases formed prior to accretion of the final cv parent body

oxygen isotopes in magnetite and fayalite in cv chondrites kaba and mokoia we report in situ measurements of o isotopic compositions of magnetite and primary and secondary olivine in the highly unequilibrated oxidized cv chondrites kaba and mokoia in both meteorites the magnetite and the secondary olivine fayalite fa90 100 have o isotopic compositions near the terrestrial fractionation tf line the mean 17o 17o 0 52 18o value is about 1 in contrast the compositions of nearby primary chondrule low feo olivines fa1 2 are well below the tf line 17o values range from 3 to 9 krot et al 1998 summarized evidence indicating that the secondary phases in these chondrites formed by aqueous alteration in an asteroidal setting the compositions of magnetite and fayalite in kaba and mokoia imply that the o isotopic composition of the oxidant was near or somewhat above the tf line in mokoia the fayalite and magnetite differ in 18o by 20 whereas these same materials in kaba have virtually identical compositions the difference between mokoia magnetite and fayalite may indicate formation in isotopic equilibrium in a water rich environment at low temperatures 300 k in contrast the similar compositions of these phases in kaba may indicate formation of the fayalite by replacement of preexisting magnetite in dry environment with the o coming entirely from the precursor magnetite and silica the 17o of the oxidant incorporated into the cv parent body as phyllosilicates or h2o appears to have been much 7 8 lower than that in that incorporated into the ll parent body choi et al 1998 which suggests that the o isotopic composition of the nebular gas was spatially or temporally variable

mineralogy and petrology of amoeboid olivine inclusions in co3 chondrites relationship to parent body aqueous alteration petrographic and mineralogic studies of amoeboid olivine inclusions aois in co3 carbonaceous chondrites reveal that they are sensitive indicators of parent body aqueous and thermal alteration as the petrologic subtype increases from 3 0 to 3 8 forsteritic olivine fa0 1 is systematically converted into ferroan olivine fa60 75 we infer that the fe si and o entered the assemblage along grain boundaries forming ferroan olivine that filled fractures and voids as temperatures increased fe 2 from the new olivine exchanged with mg 2 from the original aoi to form diffusive haloes around low feo cores cations of mn 2 ca 2 and cr 3 were also mobilized the systematic changes in aoi textures and olivine compositional distributions can be used to refine the classification of co3 chondrites into subtypes in subtype 3 0 olivine occurs as small forsterite grains fa0 1 free of ferroan olivine in petrologic subtype 3 2 narrow veins of feo rich olivine have formed at forsterite grain boundaries with increasing alteration these veins thicken to form zones of ferroan olivine at the outside aoi margin and within the aoi interior by subtype 3 7 there is a fairly broad olivine compositional distribution in the range fa63 70 and by subtype 3 8 no forsterite remains and the high fa peak has narrowed fa64 67 even at this stage there is incomplete equilibration in the chondrite as a whole e g data for coarse olivine grains in isna co3 8 chondrules and lithic clasts show a peak at fa39 we infer that the mineral changes in aoi identified in the low petrologic types required aqueous or hydrothermal fluids whereas those in subtypes 3 3 largely reflect diffusive exchange within and between mineral grains without the aid of fluids

physical properties of chondrules in different chondrite groups implications for multiple melting events in dusty environments chondrite groups cv ck cr with large average chondrule sizes have low proportions of rp plus c chondrules high proportions of enveloping compound chondrules high proportions of chondrules with thick igneous rims and relatively low proportions of type i chondrules containing sulfide in contrast chondrite groups cm co oc r eh el with smaller average chondrule sizes have the opposite properties equilibrated ck chondrites have plagioclase with relatively low na equilibrated oc r eh and el chondrites have more sodic plagioclase enveloping compound chondrules and chondrules with igneous rims formed during a remelting event after the primary chondrule was incorporated into a dustball repeated episodes of remelting after chondrules were surrounded by dust would tend to produce large chondrules rp and c chondrules formed by complete melting of their precursor assemblages remelting of rp and c chondrules surrounded by dust would tend to produce porphyritic chondrules as small dust particles mixed with the melt providing nuclei for crystallizing phenocrysts this process would tend to diminish the numbers of rp and c chondrules correlations among these chondrule physical properties suggest that chondrite groups with large chondrules were typically surrounded by thick dust rich mantles that formed in locally dusty nebular environments chondrules that were surrounded by thick dust mantles tended to cool more slowly because heat could not quickly radiate away slow cooling led to enhanced migration of sulfide to chondrule surfaces and more extensive sulfide evaporation these chondrules also lost na the plagioclase that formed from equilibrated ck chondrites was thus depleted in na

alkali magmatism on a carbonaceous chondrite planetesimal recent isotopic and paleomagnetic data point to a possible connection between carbonaceous chondrites and differentiated planetary materials suggesting the existence perhaps ephemeral of transitional objects with a layered structure whereby a metal rich core is enclosed by a silicate mantle which is itself overlain by a crust containing an outermost layer of primitive solar nebula materials this idea has not received broad support mostly because of a lack of samples in the meteoritic record that document incipient melting at the onset of planetary differentiation here we report the discovery and the petrologic isotopic characterization of uh154 11 a ferroan trachybasalt fragment enclosed in a renazzo type carbonaceous chondrite cr its chemical and oxygen isotopic compositions are consistent with very low degree partial melting of a vigarano type carbonaceous chondrite cv from the oxidized subgroup at a depth where fluid assisted metamorphism enhanced the na content its microdoleritic texture indicates crystallization at an increasing cooling rate such as would occur during magma ascent through a chondritic crust this represents direct evidence of magmatic activity in a carbonaceous asteroid on the verge of differentiating and demonstrates that some primitive outer solar system objects related to icy asteroids and comets underwent a phase of magmatic activity early in the solar system with its peculiar petrology uh154 11 can be considered the long sought first melt produced during partial differentiation of a carbonaceous chondritic planetary body bridging a previously persistent gap in differentiation processes from icy cometary bodies to fully melted iron meteorites with isotopic affinities to carbonaceous chondrites

a weathering index for ck and r chondrites we present a new weathering index wi for the metallic fe ni poor chondrite groups ck and r based mainly on transmitted light observations of the modal abundance of crystalline material that is stained brown in thin sections wi 0 95 vol wi 6 significant replacement of mafic silicates by phyllosilicates brown staining reflects mobilization of oxidized iron derived mainly from terrestrial weathering of ni bearing sulfide with increasing degrees of terrestrial weathering of ck and r chondrites the sulfide modal abundance decreases and s se and ni become increasingly depleted in addition bulk cl increases in antarctic ck chondrites probably due to contamination from airborne sea mist

fault rupture propagation through previously ruptured soil abstractsurface fault rupture during recent earthquakes has significantly damaged structures although several researchers have studied surface fault rupture the effects of fault rupture propagating through soil that has been ruptured previously have not been investigated yet faults rupture multiple times so that native soil deposits will have likely undergone previous ruptures that would have developed shear bands within the soil and the stress state of the soil will have evolved because of these events in addition the predominant modes of soil shearing during the fault rupture process have not been characterized fully numerical simulations are performed to analyze the mechanics of dip slip surface fault rupture and to explore the effects of previously ruptured soil the numerical results demonstrate that the soil rupture process occurs in two distinct stages first broad deformation occurs before strain localization which is followed by more localized deformation after shear band formation str

the matrices of unequilibrated ordinary chondrites implications for the origin and history of chondrites abstract the matrices of sixteen unequilibrated ordinary chondrites all witnessed falls were studied microscopically in transmitted and reflected light and analyzed by electron microprobe selected specimens were also studied by scanning electron microscopy these studies indicate that the fine grained opaque silicate matrix of type 3 unequilibrated chondrites is compositionally mineralogically and texturally distinct from the chondrules and chondrule fragments and may be the low temperature condensate proposed by larimer and anders 1967 1970 examination of the matrices of unequilibrated chondrites also shows that each meteorite has been metamorphosed with the alteration ranging in intensity from quite mild where the matrix has been only slightly altered to a more severe metamorphism that has completely recrystallized the opaque matrix most of the metamorphic changes in the matrix occurred without significant effects on the compositions or textures of the chondrules the metamorphic alteration probably resulted from a combination of processes including thermal metamorphism and the passage of shock waves the present appearance of each unequilibrated chondrite is a result of the particular temperature and pressure conditions under which it and its components formed plus the subsequent metamorphic alteration it experienced

chondrules matrix and coarse grained chondrule rims in the allende meteorite origin interrelationships and possible precursor components bulk compositions of 20 chondrules 13 coarse grained chondrule rims and two composite samples of matrix material from cv3 allende were determined by instrumental neutron activation analysis three rare nonporphyritic cv chondrules from allende leoville and vigarano were analyzed by broad beam electron microprobe analysis chondrule precursor components deduced from chondrule compositions are characterized by 1 refractory and semi refractory lithophiles with low feo 2 common siderophiles and chalcophiles 3 common to slightly volatile lithophiles si cr mn and modal pyroxene with moderately high feo feo mgo 4 moderately volatile siderophiles and 5 alkalies these precursor components can be explained by plausible processes occurring in the solar nebula the precursor components of coarsegrained rims are apparently the same as those of chondrules these components differ from those inferred previously for oc eh or cm co chondrules in general the compositions of coarse grained rims are more similar to the mean chondrule composition than to those of the chondrules they enclose rim siderophile contents are generally 2 5x greater than those in the chondrules and 0 5 to 2x those in bulk allende rims as a group are more homogeneous than chondrules suggesting that rims formed from finer grained precursors several chondrules and rims have fractionated rare earth patterns and may have been affected by metamorphism the enclosure of some coarse grained rims by fine grained matrix like rims that are almost certainly of nebular origin indicates that coarse grained rims were also formed in the nebula two matrix samples are similar in composition to some coarse grained rims suggesting that matrix was derived from similar compositional reservoirs of nebular dust chondrules with coarse grained rims were reheated in space following the accretion of dusty coatings this restricts plausible chondrule forming mechanisms to those that allow multiple nebular heating events

progressive alteration in cv3 chondrites more evidence for asteroidal alteration abstract the oxidized cv3 chondrites can be divided into two major subgroups or lithologies bali like cv3oxb and allende like cv3oxa in which chondrules calcium aluminum rich inclusions cais and matrices show characteristic alteration features weisberg et al 1997 krot et al 1997d kimura and ikeda 1997 the cv3oxb lithology is present in bali kaba parts of the mokoia breccia and possibly in grosnaja and allan hills alh 85006 it is characterized by the presence of the secondary low ca phyllosilicates saponite and sodium phlogopite magnetite ni rich sulfides fayalite fa 90 ca fe rich pyroxenes fs10 50wo45 50 and andradite phyllosilicates replace primary ca rich minerals in chondrules and cais which suggests mobilization of ca during aqueous alteration magnetite nodules are replaced to various degrees by fayalite ca fe rich pyroxenes and minor andradite fayalite veins crosscut fine grained rims around chondrules and extend into the matrix thermodynamic analysis of the observed reactions indicates that they could have occurred at relatively low temperatures 300 c in the presence of aqueous solutions oxygen isotopic compositions of the coexisting magnetite and fayalite plot close to the terrestrial fractionation line with large 18ofayalite magnetite fractionation 20 we infer that phyllosilicates magnetite fayalite ca fe rich pyroxenes and andradite formed at relatively low temperatures 300 c by fluid rock interaction in an asteroidal environment secondary fayalite and phyllosilicates are virtually absent in chondrules and cais in the cv3oxa lithology which is present in allende and its dark inclusions axtell alha81258 alh 84028 lewis cliff lew 86006 and parts of the mokoia and vigarano breccias instead secondary nepheline sodalite and fayalitic olivine are common fayalitic olivine in chondrules replaces low ca pyroxenes and rims and veins forsterite grains it also forms coarse lath shaped grains in matrix secondary ca fe rich pyroxenes are abundant we infer that the cv3oxa lithology experienced alteration at higher temperatures than the cv3oxb lithology the presence of the reduced and cv3oxa lithologies in the vigarano breccia and cv3oxa and cv3oxb lithologies in the mokoia breccia indicates that all cv3 chondrites came from one heterogeneously altered asteroid the metamorphosed clasts in mokoia krot and hutcheon 1997 may be rare samples of the hotter interior of the cv asteroid we conclude that the alteration features observed in the oxidized cv3 chondrites resulted from the fluid rock interaction in an asteroid during progressive metamorphism of a heterogeneous mixture of ices and anhydrous materials mineralogically similar to the reduced cv3 chondrites

oxygen isotopic evolution of the solar nebula studies of the three oxygen isotopes in chondrite meteorites demonstrate that diverse o reservoirs characterized by their 17o values were present in the solar nebula the discovery that some chondritic materials have o isotopic compositions that cannot be explained by mass dependent fractionation of an initially well mixed reservoir has important implications for the history of the solar nebula on a plot of 17o versus 18o or 17o 16o versus 18o 16o terrestrial samples with the main exception of stratospheric ozone fall along a single line the terrestrial fractionation or tf line having a slope 0 52 an indication that the parental reservoir was homogenized a convenient measure of o isotopic heterogeneity is the deviation from the tf line 17o 17o 0 52 18o a popular model to explain the evolution of chondritic oxygen compositions during nebular and asteroidal aqueous alteration processes calls for the nebula to have formed from solids having 18o 40 and 17o 41 17o 20 and a gas having a composition roughly estimated to be 18o 30 and 17o 24 17o 9 this model encounters serious difficulties when examined in detail in particular it cannot readily account for the o isotopic compositions of both chondrules and refractory inclusions from individual chondrite groups or for the differences between groups particularly in the compositions of chondrules magnetite fe3o4 is a key phase for o isotope studies because during its formation by the oxidation of ferrous metal or fes all o comes from the oxidant probably h2o it appears that most and possibly nearly all magnetite formed during aqueous alteration processes that occurred in asteroids in all chondrite groups studied to date 17o of the magnetite is greater than or equal to that of the chondrule silicates if the h2o originated in the ambient local nebula then at the time of accretion the 17o of the nebular gas was generally higher than that of the solids an alternative view is that the heterogeneity in the o isotopic composition of chondrites indicates that the nebula formed from diverse batches of presolar materials the precise o isotopic composition of the mix varying during the accretion history of the nebula the large compositional gaps between groups suggest that agglomeration of nebular dust to form chondrites did not proceed at a constant rate but that periods with turbulence levels low enough to allow agglomeration were punctuated by periods of high turbulence during which the composition of the inner nebula sampled by chondrites changed appreciably

tunnel framed building interaction comparison between raft and separate footing foundations in this paper the influence of the foundation configuration raft or separate footings on tunnel soil framed building interaction is investigated using geotechnical centrifuge testing tunnelling

high resolution body wave tomography models of the upper mantle beneath eastern china and the adjacent areas 1 we present new 3 d tomographic models of vp vs and vp vsratio anomalies in the upper mantle beneath ec and adjacent areas this data was collected and interpreted with the goal of clarifying geodynamic processes that caused spatially variable event histories throughout eastern china ec during mesozoic to cenozoic time the tomographic images were constructed by inverting body wave travel times recorded at 1300 stations within the upgraded china national seismic network and 9 temporary arrays resolution tests for different depths and the featured velocity anomalies verify that the tomographic images capture the velocity heterogeneities in the upper mantle to depths of 700 km the salient features of vp vs and vp vsratio anomalies can be clearly identified these include strong multiscale heterogeneities occupying the upper mantle beneath ec and differences in the spatial scale of anomalies found beneath northern and southern areas of ec these features demonstrate a degree of spatial variability in the geodynamic evolution of ec we propose two mechanisms to explain these patterns first the western front of the subducted slab may have imparted greater horizontal compressional stress in areas where it impinged further eastward into ec these areas would experience stronger convection and an altered stress regime in the upper mantle creating significant thermal anomalies beneath the south china block scb relative to the eastern north china craton ncc second differing thermal states and viscosities for the eastern ncc and the cathaysia block cab resulted in differing responses to regional deformation the archean hinterland of the eastern ncc specifically has a colder thermal state and higher viscosity and therefore exhibits only small scale heterogeneities due to the effect of shear localization the neoproterozoic cab has a relatively warm thermal state with lower viscosity and thus deformed more continuously

testing presence of relict fractures in granitoid saprolites by centrifuge modeling abstract granitoid saprolites formed from the chemical weathering of granitoid rocks contain relict fractures however saprolites may be considered as homogeneous soils because these relict fractures are not as visible as those in rock masses the presence of these fractures is not as widely accepted as those that occur in stiff and expansive clays while they can play an important role in slope excavation in this study the centrifugal modeling technique is employed to verify the presence of relict fractures in granitoid saprolites by demonstrating their effect on the displacement and force induced by excavation in cut slopes centrifugal tests are carried out using four slope models one homogeneous and three fracture containing and the displacement and force induced by excavation are monitored a comparative analysis of the results for different models shows that the presence of relict fractures has a significant effect on the excavation induced behavior of cut slopes the displacement and force generated during centrifuging are distinctly larger in the fracture containing models than in the homogeneous model particularly for the model with outward dipping fractures experimental results are used to confirm the presence and mechanical implications of relict fractures in granitoid saprolite slopes

silicate darkening in the kobe ck chondrite evidence for shock metamorphism at high temperature the kobe ck4 chondrite like most metamorphosed ck chondrites exhibits pronounced silicate darkening of matrix and chondrule mesostases our petrographic and scanning electron microscopic study reveals that the matrix of kobe consists mostly of intermixtures of two types of fine grained olivine one forms subhedral to anhedral normal crystals the other fills interstices of the subhedral to anhedral olivine crystals exhibiting a complex network of veinlets the latter type of olivine contains high densities of small spherical vesicles 0 05 3 m in diameter and grains 0 05 5 m of magnetite and pentlandite as well as round to anhedral grains 1 10 m of plagioclase low ca pyroxene diopside and chlorapatite the vesicular olivine is particularly abundant in regions of matrix that exhibit a relatively high degree of darkening and commonly fills chondrule mesostases the vesicular olivine is clearly the principal cause of the silicate darkening in kobe the internal texture of the vesicular olivine closely resembles those of local melts produced from the matrices of experimentally and naturally shocked carbonaceous chondrites the occurrence and texture of the vesicular olivine suggest that it resulted from recrystallization of partially melted matrix olivine by shock kobe exhibits light shock effects in olivine that are consistent with shock stage s2 that is too low to explain the occurrence of olivine melting we suggest that the vesicular olivine in kobe was produced by shock metamorphism at a relatively mild shock pressure 600 c thus it is probable that the shock effects in olivine manifest as fracturing and deformation were relatively minor but heating was strong enough to cause partial melting of matrix olivine

siderophile element anomalies in ck carbonaceous chondrites implications for parent body aqueous alteration and terrestrial weathering of sulfides abstract ck chondrites constitute the most oxidized anhydrous carbonaceous chondrite group most of the fe occurs in magnetite and in feo rich mafic silicates the two observed ck falls karoonda and kobe along with thirteen relatively unweathered ck finds have unfractionated siderophile element abundance patterns in contrast a sizable fraction of ck finds 9 of 24 investigated shows fractionated siderophile abundance patterns including low abundances of ni co se and au the most extreme depletions are in ni 0 24 of normal ck and au 0 14 of normal ck this depletion pattern has not been found in other chondrite groups out of the 74 ck chondrites listed in the meteoritical bulletin database 2006 excluded considerably paired specimens see http tin er usgs gov meteor metbull php we analyzed 24 and subclassified the ck chondrites in terms of their chemical composition and sulfide mineralogy sl siderophiles low six samples for large depletions in ni co se and au 50 of sulfides lost sm siderophiles medium two cks for moderately low ni and co abundances sulfides are highly altered or partly lost sh siderophiles high one specimen for enrichments in ni co se and au normal for unfractionated samples 13 samples the sole sh sample may have obtained additional sulfide from impact redistribution in the parent asteroid we infer that these elements became incorporated into sulfides after asteroidal aqueous processes oxidized nebular metal thermal metamorphism probably also played a role in their mineral siting the siderophile losses in the sl and sm samples are mainly the result of oxidation of pentlandite pyrite and violarite by terrestrial alteration followed by leaching of the resulting phases some antarctic ck chondrites have lost most of their sulfides but retained ni co se and au presumably as insoluble weathering products

chondrules in ck carbonaceous chondrites and thermal history of the cv ck parent body ck chondrites are the only group of carbonaceous chondrites with petrologic types ranging from 3 to 6 it is commonly reported than 15 vol of ck4 6 samples are composed of chondrules the modal abundance of chondrules estimated here for 18 ck3 6 including 5 ck3s ranges from zero totally recrystallized to 50 5 although almost all chemically re equilibrated with the host matrix we recognized in ck3s and tanezrouft tnz 057 ck4 up to 85 of chondrules as former type i chondrules mean diameters of chondrules range from 0 22 to 1 05 mm for karoonda ck4 and tnz 057 ck4 respectively up to 60 of chondrules in ck3 4 are surrounded by igneous rims from 20 m to 2 mm width zoned olivines were found in unequilibrated chondrules from dag 431 ck3 an nwa 4724 ck3 8 nwa 4423 ck3 9 and tnz 057 ck4 we modeled fe mg interdiffusion profiles measured in zoned olivines to evaluate the peak metamorphic temperatures and time scales of the ck parent body metamorphism and proposed a two stage diffusion process in order to account for the position of inflection points situated within chondrules time scales inferred from fe mg interdiffusion in olivine from unequilibrated chondrules are on the order of tens to a hundred of thousand years from 50 to 70 000 years for peak metamorphic temperatures of 1140 and 920 k respectively these durations are longer than what is commonly accepted for shock metamorphism and shorter than what is required for nuclide decay using the concept of a continuous cv ck metamorphic series which is reinforced by this study we estimated peak metamorphic temperatures 850 k for cv 850 920 k for ck3 and 920 1140 k for ck4 6 chondrites considering a duration of 70 000 years

satellite observation of coal mining subsidence by persistent scatterer analysis ground subsidence persistently occurs in abandoned coal mining areas this paper presents an investigation of ground subsidence measurement using persistent scatterers recorded by space borne synthetic aperture radar sar during the period from november 1992 to october 1998 twenty five jers 1 sar interferometric pairs were obtained and used to measure subsidence in the gaeun coal mining area korea to validate the subsidence estimated by the persistent scatterers sar interferometry ps technique the results were compared with the degree of crack level obtained by a 1997 field survey the study area was divided into five classes based on measured crack levels the line of sight los subsidence rate of each group was estimated by the phase of 135 scatterers selected from the five classes the maximum subsidence was measured by radar as 11 2 cm over 6 yr the mean subsidence rate of one class was found to be 0 5 cm yr where cracks most severely developed the radar estimated subsidence agrees well with the degree of crack level the ps technique is useful for the measurement of ground subsidence in abandoned coal mining areas even in mountainous regions

magnetite in the unequilibrated ck chondrites implications for metamorphism and new insights into the relationship between the cv and ck chondrites bulk isotopic and elemental compositions of cv and ck chondrites have led to the suggestion that both originate from the same asteroid it has been argued that magnetite compositions also support this model however magnetite has been studied almost exclusively in the equilibrated type 4 6 cks magnetite in seven unequilibrated cks analyzed here is enriched in mgo tio2 and al2o3 relative to the equilibrated cks suggesting that magnetite compositions are affected by metamorphism magnetite in cks is compositionally distinct from cvs particularly in abundances of cr2o3 nio and tio2 although there are minor similarities between cv and equilibrated ck chondrite magnetite this is contrary to what we would expect if the cvs and cks represent a single metamorphic sequence cv magnetite should resemble ck3 magnetite as both were metamorphosed to type 3 conditions oxygen fugacities and temperatures of cvox and ck chondrites are also difficult to reconcile using existing cv ck parent body models mineral chemistries which eliminate issues of bulk sample heterogeneity provide a reliable alternative to techniques that involve a small amount of sample material cv and ck chondrite magnetite has distinct compositional differences that cannot be explained by metamorphism

determination of the petrologic type of cv3 chondrites by raman spectroscopy of included organic matter abstract this paper reports the first reliable quantitative determination of the thermal metamorphism grade of a series of nine cv3 chondrites allende axtell bali mokoia grosnaja efremovka vigarano leoville and kaba the maturity of the organic matter in matrix determined by raman spectroscopy has been used as a powerful metamorphic tracer independent of the mineralogical context and extent of aqueous alteration this tracer has been used along with other metamorphic tracers such as fe zoning in type i chondrules of olivine phenocrysts presolar grain abundance and noble gas abundance bulk and p3 component the study shows that the petrologic types determined earlier by induced thermoluminescence were underestimated and suggests the following values pt allende axtell 3 6 pt bali mokoia grosnaja 3 6 pt efremovka leoville vigarano 3 1 3 4 pt kaba 3 1 the most commonly studied cv3 allende is also the most metamorphosed bali is a breccia containing clasts of different petrologic types the attribution suggested by this study is that of clasts of the highest petrologic types as pointed out by iom maturity and noble gas bulk abundance cv3 chondrites have complex asteroidal backgrounds with various degrees of aqueous alteration and or thermal metamorphism leading to complex mineralogical and petrologic patterns fe mg chemical zoning in olivine phenocrysts on the borders of type i chondrules of porphyritic olivine and pyroxene rich textural types has been found to correlate with the metamorphism grade this suggests that chemical zoning in some chondrules often interpreted as exchanges between chondrules and nebular gas may well have an asteroidal origin furthermore the compositional range of olivine matrix is controlled both by thermal metamorphism and aqueous alteration this does not support evidence of a nebular origin and does not necessarily mirror the metamorphism grade through fe mg equilibration on the other hand it may provide clues on the degree of aqueous alteration vs thermal metamorphism and on the timing of both processes in particular mokoia experienced significant aqueous alteration after the metamorphism peak whereas grosnaja which has similar metamorphism grade did not

the onset of metamorphism in ordinary and carbonaceous chondrites ordinary and carbonaceous chondrites of the lowest petrologic types were surveyed by xray mapping techniques a variety of metamorphic effects were noted and subjected to detailed analysis using electron microprobe scanning electron microscopy sem transmission electron microscopy tem and cathodoluminescence cl methods the distribution of cr in feo rich olivine systematically changes as metamorphism increases between type 3 0 and type 3 2 igneous zoning patterns are replaced by complex ones and cr rich coatings develop on all grains cr distributions in olivine are controlled by the exsolution of a cr rich phase probably chromite cr in olivine may have been partly present as tetrahedrally coordinated cr3 separation of chromite is nearly complete by petrologic type 3 2 the abundance of chondrules showing an inhomogeneous distribution of alkalis in mesostasis also increases with petrologic type tem shows this to be the result of crystallization of albite residual glass compositions systematically change during metamorphism becoming increasingly rich in k glass in type i chondrules also gains alkalis during metamorphism both types of chondrules were open to an exchange of alkalis with opaque matrix and other chondrules the matrix in the least metamorphosed chondrites is rich in s and na the s is lost from the matrix at the earliest stages of metamorphism due to coalescence of minute grains progressive heating also results in the loss of sulfides from chondrule rims and increases sulfide abundances in coarse matrix assemblages as well as inside chondrules alkalis initially leave the matrix and enter chondrules during early metamorphism feldspar subsequently nucleates in the matrix and na re enters from chondrules these metamorphic trends can be used to refine classification schemes for chondrites cr distributions in olivine are a highly effective tool for assigning petrologic types to the most primitive meteorites and can be used to subdivide types 3 0 and 3 1 into types 3 00 through 3 15 on this basis the most primitive ordinary chondrite known is semarkona although even this meteorite has experienced a small amount of metamorphism allan hills alh a77307 is the least metamorphosed co chondrite and shares many properties with the ungrouped carbonaceous chondrite acfer 094 analytical problems are significant for glasses in type ii chondrules as na is easily lost during microprobe analysis as a result existing schemes for chondrule classification that are based on the alkali content of glasses need to be revised

shock metamorphism of carbonaceous chondrites abstract we have studied shock effects in carbonaceous chondrites using optical microscopy of thin sections and find that our petrographic classification of progressive shock metamorphism in ordinary chondrites can also be applied to carbonaceous chondrites we find that sixty nine carbonaceous chondrites can be assigned to four shock stages si to s4 largely on the basis of shock effects in olivine the least shocked chondrite groups are cm2 and co3 thirty six out of thirty eight members are classified as shock stage s1 differences between the mean shock levels of certain groups of chondrites e g co3 and cv3 are probably due to stochastic differences in the sampling of their parent bodies however there is an overall tendency for the mean shock level of carbonaceous chondrites and ordinary chondrites to increase with increasing petrologic type that may reflect real differences in the shock level of near surface materials on their parent bodies caused by intrinsic variations in the chemical and physical properties of these materials petrologic type 2 and 3 chondrites are more porous and richer in volatiles than types 4 to 6 the greater porosity of types 2 3 causes higher post shock temperatures and melting at lower pressures and the higher volatile contents ensure that strongly shocked material is more readily dispersed on release from high pressure we suggest that type 2 3 material shocked above 20 30 gpa normally escapes from the parent asteroids and forms particles that are too small to survive as meteorites in the cv3 group there is a correlation between the degree of chondrule flattening and the intensity of shock metamorphism analogous to that discovered in ordinary chondrites by sneyd et al 1988 suggesting that shock rather than static overburden pressure is responsible for chondrule flattening we infer that the correlations are due to collapse of pores under shock pressures of at least 5 10 gpa and that shock is an important process affecting many physical properties of type 2 4 chondrites

the relationship between ck and cv chondrites ck chondrites are highly oxidized meteorites containing abundant magnetite and trace amounts of fe ni metal although the group is predominately composed of equilibrated meteorites types 4 6 in recent years a significant number of new samples have been classified as being either ck3 or ck3 anomalous these unequilibrated cks often display a close affinity with members of the cv oxidized subgroup cks and cvs oxidized subgroup may therefore form a continuum and by implication could be derived from a single common parent body to investigate the relationship between these two groups a detailed study of the oxygen isotope composition opaque mineralogy and major and trace element geochemistry of a suite of cv and ck chondrites has been undertaken the results of oxygen isotope analysis confirm the close affinity between cv and ck chondrites while excluding the possibility of a linkage between the co and ck groups magnetites in both cv and ck chondrites show significant compositional similarities but high ti contents are a diagnostic feature of the latter group the results of major and trace element analysis demonstrate that both cv and ck chondrites show overlapping variation supporting evidence for a single common source for both groups comes from their similar cosmic ray exposure age distributions recent reflectance spectral analysis is consistent with both the cvs and cks being derived from eos family asteroids which are believed to have formed by the catastrophic disruption of a single large asteroid thus a range of evidence appears to be consistent with cv and ck chondrites representing samples from a single thermally stratified parent body in view of the close similarity between cv and ck chondrites some modification of the present classification scheme may be warranted possibly involving integration of the two groups one means of achieving this would be to reassigned ck chondrites to a subgroup of the oxidized cvs it is recognized that a full evaluation of this proposal may require further study of the still poorly understood ck3 chondrites

compositional and petrographic similarities of cv and ck chondrites a single group with variations in textures and volatile concentrations attributable to impact heating crushing and oxidation abstract greenwood et al 2010 gathered data on o isotopic and elemental compositions and reevaluated literature data for cv and ck chondrites they concluded that these two chondrite groups originated on the same parent asteroid with ck chondrites being metamorphosed cv chondrites which are otherwise missing types 4 through 6 to test this interpretation we have gathered new instrumental neutron activation analysis inaa data for cv and ck chondrites and reexamined their petrographic features the new inaa data like the older data show scatter attributable to weathering effects but we conclude that the refractory lithophile abundances are the same in cv and ck in agreement with the greenwood et al interpretation several volatile elements are significantly lower in ck than in cv chondrites among the elements we determine the greatest difference between cv and ck is found for br for which the cv ck ratio is 4 as and sb are about 20 lower in ck than cv and smaller differences are observed for zn ga and se it seems likely that volatiles were lost during impact heating events that also provided the heat responsible for metamorphic recrystallization within statistical uncertainty chondrules in cv and ck chondrites are the same size and have similar textural distributions a significant petrographic difference between ck and cv chondrites cited by kallemeyn et al 1991 was the much higher percentage of igneous rims around cv chondrules however we now recognize that many chondrules in ck3 8 nwa 1559 have igneous rims and in ck4 chondrites igneous rims are recognizable by their associated sulfide rich rings there are no quantifiable cv ck differences in igneous rim abundances we used ca and al maps to show that ck chondrites have cai abundances similar to those of cv chondrites it thus appears that there are no resolvable pre metamorphic petrographic differences between cv and ck chondrites we recommend that the ck designation be abandoned and that the cv group be acknowledged as spanning the range of petrologic types 3 6 we suggest that ck3 chondrites be designated cv3oxk most ck4 chondrites are highly fragmental collisional crushing appears to be much more common than in cv chondrites it seems likely that ck chondrites formed from reduced cv3 materials after the latter was impacted buried aqueously altered and annealed

estimation of building damage due to excavation induced ground movements building damage due to excavation induced ground movement is evaluated using a damage criterion based on the average state of strain in the distorting portion of the structure and by considering the effect of building shear stiffness on the distortions imposed by the ground settlement profile physical model tests and numerical simulations correlated with case studies of building distortion and damage have been used to evaluate these relationships for masonry bearing wall structures the distinct element method was used to numerically model each masonry unit as a block with the contacts between blocks having the stiffness and strength characteristics of mortar in plane displacements at the corners of the wall sections permitted determination of the average state of strain and the components of rigid body tilt angular distortion lateral strain at the base and the contribution of bending strain to the lateral strain in the upper portion of the wall the increase in angular distortion with increase in the ratio of ground structure shear stiffness decrease in building shear stiffness was examined for both elastic and cracked building walls cracking significantly reduced effective wall stiffness making the wall more conformable to the ground settlement profile which increased angular distortion causing it to approach the distortion change in ground slope that would occur in the absence of the structure

metamorphosed calcium aluminum rich inclusions in ck carbonaceous chondrites ck chondrites are the only group of carbonaceous chondrites with petrologic types ranging from 3 to 6 although cks are described as calcium aluminum rich inclusion cai poor objects the abundance of cais in the 18 ck3 6 we analyzed ranges from zero to approximately 16 4 during thermal metamorphism some of the fine grained cais recrystallized as irregular assemblages of plagioclase ca rich pyroxene olivine ca poor pyroxene magnetite coarse grained cais display zoned spinel fassaite destabilization and secondary grossular and spinel secondary anorthite grossular ca rich pyroxene and spinel derive from the destabilization of melilite which is lacking in all cais investigated the al mg isotopic systematics measured in fine and coarsegrained cais from tanezrouft tnz 057 was affected by mg redistribution the partial equilibration of al mg isotopic signatures obtained in the core of a coarse grained cai cg1 cai in tnz 057 may indicate a lower peak temperature for mg diffusion of approximately 540 580 c while grossular present in the core of this cai indicates a higher temperature of around 800 c for the metamorphic event on the parent body of tnz 057 excluding metamorphic features the similarity in nature and abundance of cais in ck and cv chondrites confirms that cvs and cks form a continuous metamorphic series from type 3 to 6

charts for the mining induced deflection of buildings this study investigates the flexural deformations of buildings induced by mining related subsidence a two stage solution previously applied to the tunnelling problem is used buildings are model

oxygen isotope and chemical compositions of magnetite and olivine in the anomalous ck3 watson 002 and ungrouped asuka 881595 carbonaceous chondrites effects of parent body metamorphism we report in situ o isotope and chemical compositions of magnetite and olivine in chondrules of the carbonaceous chondrites watson 002 anomalous ck3 and asuka a 881595 ungrouped c3 magnetite in watson 002 occurs as inclusion free subhedral grains and rounded inclusion bearing porous grains replacing fe ni metal in a 881595 magnetite is almost entirely inclusion free and coexists with ni rich sulfide and less abundant ni poor metal oxygen isotope compositions of chondrule olivine in both meteorites plot along carbonaceous chondrite anhydrous mineral ccam line with a slope of approximately 1 and show a range of 17o values from approximately 3 to 6 one chondrule from each sample was found to contain o isotopically heterogeneous olivine probably relict grains oxygen isotope compositions of magnetite in a 881595 plot along a mass dependent fractionation line with a slope of 0 5 and show a range of 17o values from 2 4 to 1 1 oxygen isotope compositions of magnetite in watson 002 cluster near the ccam line and a 17o value of 4 0 to 2 9 these observations indicate that magnetite and chondrule olivine are in o isotope disequilibrium and therefore not cogenetic we infer that magnetite in ck chondrites formed by the oxidation of pre existing metal grains by an aqueous fluid during parent body alteration in agreement with previous studies the differences in 17o values of magnetite between watson 002 and a 881595 can be attributed to their different thermal histories the former experienced a higher degree of thermal metamorphism that led to the o isotope exchange between magnetite and adjacent silicates

cv chondrites more than one parent body abstract cv chondrites are one of the most studied group of carbonaceous chondrites based on a number of mineralogical features they have been divided into three sub groups cvoxa cvoxb and cvred these sub groups are classically interpreted as coming from a single parent body with a common protolith affected by significant parent body fluid assisted metasomatism occurring at different temperatures and or redox conditions in this work we studied a set of 53 cv chondrites we classified them into the three sub groups measured their apparent chondrule sizes and their matrix modal abundance we measured the triple oxygen isotopic composition for 17 of them the distributions of chondrule size and matrix abundances in cvoxa and cvoxb cannot be statistically distinguished conversely cvred and cvox have distinct distributions these two robust and simple petrographic indicators combined with the previous knowledge of the peak metamorphic temperatures experienced by these meteorites show that cvox and cvred originate from two distinct parent bodies on the other hand cvoxa and cvoxb likely originate from the same parent body with cvoxa representing deeper more metamorphosed levels for clarification of the chondrite classification scheme in which one group should ultimately represent a single parent body we propose to divide the cv group into two proper groups and not subgroups as in the current scheme keeping the names cvred and cvox these two groups can be readily separated by estimating the average nickel content of their sulfides

origin of magnetite in oxidized cv chondrites in situ measurement of oxygen isotope compositions of allende magnetite and olivine magnetite in the oxidized cv chondrite allende mainly occurs as spherical nodules in porphyritic olivine po chondrules where it is associated with ni rich metal and or sulfides to help constrain the origin of the magnetite we measured oxygen isotopic compositions of magnetite and coexisting olivine grains in po chondrules of allende by an in situ ion microprobe technique five magnetite nodules form a relatively tight cluster in oxygen isotopic composition with delta 18o values from 4 8 to 7 1 and delta 17o values from 2 9 to 6 3 seven coexisting olivine grains have oxygen isotopic compositions from 0 9 to 6 3 in delta 18o and from 4 6 to 7 9 in delta 17o the delta 17o values of the magnetite and coexisting olivine do not overlap they range from 0 4 to 2 6 and from 4 0 to 5 7 respectively thus the magnetite is not in isotopic equilibrium with the olivine in po chondrules implying that it formed after the chondrule formation the delta 17o of the magnetite is somewhat more negative than estimates for the ambient solar nebula gas we infer that the magnetite formed on the parent asteroid by oxidation of metal by h2o which had previously experienced minor o isotope exchange with fine grained silicates

a shock metamorphic model for silicate darkening and compositionally variable plagioclase in ck and ordinary chondrites abstract silicate darkening in ordinary chondrites oc is caused by tiny grains of metallic fe ni and troilite occurring mainly within curvilinear trails that traverse silicate interiors and decorate or in some cases cut across silicate grain boundaries highly shocked oc characterized by olivine grains with undulose to mosaic extinction tend to have greater degrees of silicate darkening than lightly shocked oc this indicates that silicate darkening is probably a result of shock metamorphism the low fe fes eutectic temperature 988 c renders metal and troilite susceptible to melting and mobilization during shock heating a few oc also contain thin melt veins of chromite this implies that localized shock temperatures reached 1635 c in these meteorites silicate darkening is also evident in ck carbonaceous chondrites where magnetite and pentlandite grains form analogous curvilinear trails it is possible that magnetite and pentlandite in ck chondrites were mobilized during shock metamorphism and dispersed through silicate interiors alternatively metal and troilite may have been dispersed and then transformed into magnetite and pentlandite during subsequent oxidation of these chondrites unshocked oc tend to have plagioclase with uniform compositions shocked oc tend to have plagioclase with more variable albeit still stoichiometric compositions the low impedance of plagioclase to shock compression makes it particularly susceptible to melting and mobilization this is consistent with the molten appearance of plagioclase in highly shocked oc e g rose city and paragould ck chondrites also have compositionally variable plagioclase the common association of silicate darkening with compositionally variable plagioclase is consistent with the hypothesis that both are products of shock metamorphism some ck and oc chondrites exhibit light shock effects in olivine that are consistent with equilibrium peak shock pressures that are too low to account for the silicate darkening or opaque shock veins in these meteorites therefore the olivine in these chondrites may have been annealed after intense shock produced these effects a few ck chondrites that contain olivine with undulose or mosaic extinction e g lew87009 and eet83311 may have been shocked again after annealing

determining chondrule size distributions from thin section measurements a method is described for correcting thin section derived chondrule sizes for three common sources of bias 1 the non equatorial sectioning of chondrules 2 the non zero thickness of thin sections and 3 the unequal probability of sectioning different size chondrules application of the correction procedure to chondrule data from co chondrites results in a reduction of mean and median chondrule diameters an increase in minimum diameters and transforms nearly log normal distributions to distributions that conform to a weibull probability function the weibull function form of co chondrule size distributions is similar to the form of chondrule distributions in ordinary chondrites obtained by disaggregation analyses

analysis of the evolution of ground movements in a low densely urban area by means of dinsar technique abstract this paper presents an application example of the use of the differential interferometry synthetic aperture radar technique dinsar for monitoring ground movements in a geologically complex area around the village of suria ebro basin catalonia ne spain associated to underground mining activities and to the presence of a salt dome the analysis has been mostly performed in a rural environment affected by ground movements with different patterns magnitudes and causes a total of fifty sar images recorded between 1995 and 2007 were processed to generate the interferograms in order to study the non linear trends or changes of the ground surface behavior the dinsar technique was applied in two sets of images the interferometric results in the form of vertical displacement rate maps were checked against conventional surveying and gps measurements the results present a significant discrepancy in some location due to the wrapping of the phase when both fast and significant deformations occur in order to avoid the latter effect and improve the accuracy of the results all sar images were reprocessed using topographic leveling and gps data of different monitored points to support the dinsar interpretation a detailed geological reconnaissance of the study area was carried out as well as an inventory of ground movement indicators four different patterns of ground movement have been identified active shifting subsidence associated to the progression of the mining exploitation fronts residual subsidence on abandoned galleries with a decreasing rate of closure uplifting due to the intrusion of the salt dome and sudden ground collapses sinkholes caused by the dissolution of soluble materials laying close to the ground surface

distribution of aliphatic amines in co cv and ck carbonaceous chondrites and relation to mineralogy and processing history the analysis of water soluble organic compounds in meteorites provides valuable insights into the prebiotic synthesis of organic matter and the processes that occurred during the formation of the solar system we investigated the concentration of aliphatic monoamines present in the hot acid water extracts of the unaltered antarctic carbonaceous chondrites dom 08006 co3 and mil 05013 co3 and the thermally altered meteorites allende cv3 lap 02206 cv3 gra 06101 cv3 alh 85002 ck4 and eet 92002 ck5 we have also reviewed and assessed the petrologic characteristics of the meteorites studied here to evaluate the effects of asteroidal processing on the abundance and molecular distributions of monoamines the co3 cv3 ck4 and ck5 meteorites studied here contain total concentrations of amines ranging from 1 2 to 4 0 nmol g of meteorite these amounts are one to three orders of magnitude below those observed in carbonaceous chondrites from the ci cm and cr groups the low amine abundances for cv and ck chondrites may be related to their extensive degree of thermal metamorphism and or to their low original amine content although the co3 meteorites dom 08006 and mil 05013 do not show signs of thermal and aqueous alteration their monoamine contents are comparable to those observed in moderately extensively thermally altered cv3 ck4 and ck5 carbonaceous chondrites the low content of monoamines in pristine co carbonaceous chondrites suggests that the initial amounts and not asteroidal processes play a dominant role in the content of monoamines in carbonaceous chondrites the primary monoamines methylamine ethylamine and n propylamine constitute the most abundant amines in the co3 cv3 ck4 and ck5 meteorites studied here contrary to the predominance of n amino acid isomers in co3 and thermally altered meteorites there appears to be no preference for the larger n amines

oxidation during metamorphism of the ordinary chondrites subtle but progressive changes in the compositions and relative abundances of olivine pyroxene and metal with increasing metamorphic grade in equilibrated types 4 6 ordinary chondrites indicate that these meteorites experienced oxidation of metallic fe during heating oxygen fugacities calculated from these mineral assemblages increase with petrologic type the hypothesis of oxidation during chondrite metamorphism differs from a commonly accepted idea that chondritic fe was reduced by graphite the mineralogies of unequilibrated type 3 chondrites do not conform to the progressions in equilibrated chondrites allowing the possibility that fe may first have been reduced through reaction with graphite at the onset of metamorphism although there are conflicting observations supporting both oxidation and reduction in these meteorites as temperatures increased to levels appropriate for types 4 6 chondrites the activity of graphite may have been lowered by its dissolution in taenite and in any case oxygen fugacities appear to have been well within the stability field of graphite precluding its reaction at these temperatures oxidation state was largely controlled by equilibrium between ferromagnesian silicates and metal oxygen fugacities calculated from chondrite mineral equilibria are 2 3 log units below previously reported intrinsic o2 measurements we propose that progressive oxidation during metamorphism was promoted by interaction with small amounts of an oxidizing vapor derived by heating ices originally accreted into the parent asteroids assuming that this vapor was pure h2o the watenrock weight ratio required to account for the observed oxidation of fe in h and l chondrites is very modest less than several per mil progressive oxidation in the metamorphic sequence resulted from different degrees of reaction with such a fluid possibly caused by temperature variations or evolution of the composition of the fluid as it permeated through the body the presence of even minor amounts of a vapor phase during metamorphism affects interpretations of the volatile trace element and oxygen isotopic fractionations observed in ordinary chondrites and inferred to have formed by nebular or parent body processes