differences in the degree of weathering between antarctic and non antarctic meteorites inferred from infrared diffuse reflectance spectra abstract infrared diffuse reflectance spectra were measured for antarctic and non antarctic meteorites to compare the degree of terrestrial weathering by using the integrated intensity of absorption bands near 3 m caused by hydrous minerals and the intensity of absorption bands near 7 4 m 1350 cm 1 probably caused by hydrous carbonates non antarctic ordinary chondrite finds usually show large values of the integrated intensity of the 3 m band whereas non antarctic ordinary chondrite falls show small intensities some antarctic ordinary chondrites are as fresh as non antarctic ordinary chondrite falls in the sense of the integrated intensity of the 3 m band some antarctic eucrites show large values of the integrated intensity of the 3 m band although the degree of weathering on the a b c scale is reported to be a weathering produced hydrous carbonates seem to be ubiquitous in antarctic ordinary chondrites because the spectra of all the antarctic ordinary chondrites measured show the presence of the 7 4 m band non antarctic ordinary chondrite falls show very weak 7 4 m bands suggesting only little weatheringproduced hydrous carbonates diffuse reflectance spectra were also measured for the mixtures of akaganeite goethite artinite or calcite with the nuevo mercurio h5 ordinary chondrite to examine spectral changes and to compare them with those of meteorites absorption bands near 7 m of diffuse reflectance spectra are sensitive to the presence of carbonates

preferential flow of a nonaqueous phase liquid in dry sand geotechnical centrifuge testing is used to examine the preferential fingered flow of a nonaqueous phase liquid napl in a uniform dry sand the results of nine experiments containing a total of 87 observations of napl finger behavior are analyzed the observed finger tip velocities range from 0 01 to 0 3 cm s while the observed finger widths range from 0 3 to 3 6 cm from the experimental data it is concluded that asymptotically the napl fingers are not fully saturated for comparison the behavior of water fingers is examined using the same experimental setup in contrast to the napl fingers and in agreement with other work reported in the literature the water fingers are found to be fully saturated in addition it is confirmed that the water finger properties can be well predicted from known porous medium and fluid properties a scaling analysis is presented that allows the napl finger properties to be inferred from models developed to describe water finger properties the analysis predicts napl finger velocities to within 15 and napl finger widths to within 50 if both finger types are assumed saturated by adjusting the analysis to account for the fact that the napl fingers are not fully saturated napl finger widths can be predicted within to 10 and napl finger velocities to within 30

noble gases in h chondrites and potential differences between antarctic and non antarctic meteorites abstract thirty one antarctic h chondrites from the allan hills have been analyzed for their noble gases seven of the specimens contain solar gases thirteen have a cosmic ray exposure age around 8 ma both fractions are as observed for h chondrites from the rest of the world scrutiny of the data for paired samples yields a minimum number of 17 independent falls with 6 falls required for the 8 ma peak of exposure age the distribution of exposure ages as well as that of radiogenic 4 he and 40 ar yield no evidence that h chondrites from the allan hills region represent a mixture of populations that is different from that brought to moderate latitudes of the earth in more recent times

chemical studies of differentiated meteorites i labile trace elements in antarctic and non antarctic eucrites abstract we report data for ag au bi cd co cs ga in rb sb se te tl u and zn determined by rnaa in 25 antarctic and 9 non antarctic eucrites including the cumulate eucrites moore co and serra de mage compositional variations for a given element in a population range from

comparisons of antarctic and non antarctic achondrites and possible origin of the differences abstract in order to discuss differences between antarctic and non antarctic achondrites we investigated pairing of mainly the yamato achondrites by mineralogical techniques in addition to five paired specimens of the y74159 type polymict eucrites three new groups distinct from the y74159 type have been recognized one group y791960 of howarditic polymict eucrites is similar to those of non antarctic origin some antarctic monomict eucrites differ in texture and chemistry from the non antarctic specimens more than 50 diogenite specimens recovered from the yamato bare ice field can be grouped into two falls of separate locations compared with 8 from the usa collection and 9 from the non antarctic groups thirty antarctic ureilites are separate falls 2 pairings and their individual masses are small these observations suggest that discussion of differences between the antarctic and non antarctic achondrites largely depends on detection of pairings of the antarctic specimens the pairings of the specimens from victoria land have not been as well characterized as those of the yamato mountains comparisons with non antarctic meteorites show that the antarctic heds and ureilites differ from non antarctic specimens by the following criteria 1 1 polymict eucrites excluding those with howarditic affinity have not been found in the non antarctic collections 2 2 magnesian ureilites and augite bearing ureilites were found only in antarctica the differences may not be attributed to just one factor the above evidence of two unique diogenite falls preserved on the restricted ice fields suggests that the yamato diogenites may represent falls on restricted areas in the distant past the discovery of many small unique eucrites and ureilites suggests that within the large number of small specimens on a bare ice field there is a higher chance of finding unique varieties

evidence for differences in the thermal histories of antarctic and non antarctic h chondrites with cosmic ray exposure ages 20 ma antarctic h chondrites show a different range of induced thermoluminescence properties compared with those of h chondrites that have fallen elsewhere in the world recent noble gas data show that this difference is displayed most dramatically by meteorites with cosmic ray exposure ages less than 20 ma and they confirm that the differences cannot be attributed to weathering or to the presence of a great many fragments of an unusual antarctic meteorite annealing experiments on an h5 chondrite and other measurements on a variety of ordinary chondrites have shown that induced tl properties are sensitive to the thermal histories of the meteorites the authors conclude that the event s that released the less than 20 ma samples which are predominantly those with exposure ages of 8 plus minus 2 ma produced two groups with different thermal histories one that came to earth several 10 sup 5 years ago and that are currently only found in antarctica and one that is currently falling on the earth

terrestrial weathering of antarctic stone meteorites formation of mg carbonates on ordinary chondrites abstract white efflorescences of weathering origin occur superposed on fusion crusts or along fractures in the interiors of approximately 5 of all meteorites in the us antarctic collection efflorescences from equilibrated ordinary chondrites consist of the hydrous mg carbonates nesquehonite hydromagnesite x ray diffraction and scanning electron microscope studies of efflorescences from lew 85320 h5 show abundant elongate prismatic crystals of nesquehonite idiomorphic not pseudomorphous after lansfordite with minor local encrustations of hydromagnesite abundances of na k ca and rb in efflorescences from lew 85320 suggest that the observed contents of these elements would require only modest fractionation of chondritic composition whereas extensive fractionation would be required to derive the observed cation ratios from terrestrial sea salts therefore cations in evaporite minerals on antarctic meteorites are most likely not products of contamination by terrestrial marine salts the mg in the efflorescences probably originated from weathering of meteoritic olivine other cations in the efflorescences are also of meteoritic provenance thermodynamic analysis of the reaction forsterite water carbon dioxide nesquehonite silica at antarctic temperatures and pco 2 indicates spontaneity for all water activities greater than 0 65 compatible with the presence of liquid water as brines and or thin films

differences between antarctic and non antarctic meteorites an assessment abstract the discovery of a statistically significant number of meteorites in antarctica over the past 20 years has posed many questions one of the most intriguing suggestions that came up during the study of the antarctic samples was that there might be a difference between the parent populations of antarctic and non antarctic meteorites this interpretation was put forward after the detection of a significant difference in the abundances of volatile and mobile trace elements in h l and c chondrites and achondrites other major differences include the occurrence of previously rare or unknown meteorites different meteorite type frequencies petrographic characteristics oxygen isotopic compositions and smaller average masses in addition antarctic meteorites have greater terrestrial residence ages and have collected on the ice shield over several 10 5 years the reality of numerous such differences has now been established beyond doubt however the main question regarding the cause of these differences remains it seems that they have a wide variety of origins ranging from pre terrestrial traits to collection recovery effects and terrestrial weathering studies of terrestrial weathering have shown that over the long time the meteorites spend in and on the ice even subtle processes can produce substantial effects for future investigations it will be important to pay more attention to the weathering status of samples and to develop a more reliable and quantitative weathering index e g based on infrared reflectance spectrometry or differential scanning calorimetry not all differences between the antarctic and non antarctic meteorite populations can be explained by weathering pairing or different collection procedures variable trace element abundances and distinct differences in the thermal history and thermoluminescence characteristics have to be interpreted as being pre terrestrial in origin such differences imply the existence of meteoroid streams whose existence poses problems in the framework of our current knowledge of celestial mechanics however several independent studies support the existence of such meteoroid streams thus being consistent with the suggestion of a time variable influx of extraterrestrial material to earth the generally smaller average size of antarctic meteorites may be the cause for the different meteorite type frequency and the higher abundance of rare samples because smaller meteorites may come from a slightly different parent population in this paper we summarize the contributions in this series and provide a review of the current state of the question for the reality and cause of differences between antarctic and non antarctic meteorites

the discovery and initial characterization of allan hills 81005 the first lunar meteorite antarctic meteorite alha81005 discovered in the allan hills region of victoria land is a polymict anorthositic breccia which differs from other meteorites in mineralogical and chemical composition but is strikingly similar to lunar highlands soil breccias the petrologic character and several independent lines of evidence identify alha81005 as a meteorite from the moon two small clasts of probable mare basalt occur among the highlands lithologies in thin section 81005 22 this lunar specimen which shows relatively minor shock effects has generated new ideas on the types of planetary samples we may find on the earth and has added fresh excitement to the antarctic meteorite program

facies characteristics and magma water interaction of the white trachytic tuffs roccamonfina volcano southern italy the quaternary white trachytic tuffs formation from roccamonfina volcano southern italy comprises four non welded trachytic pyroclastic sequences bounded by paleosols each of which corresponds to small to intermediate volume explosive eruptions from central vents from oldest to youngest they are white trachytic tuff wtt cupa wtt aulpi wtt s clemente and wtt galluccio the wtt galluccio eruption was the largest and emplaced 4 km3 of magma the internal stratigraphy of all four wtt eruptive units is a complex association of fallout surge and pyroclastic flow deposits each eruptive unit is organized into two facies associations facies association a below facies association b the emplacement of the two facies associations may have been separated by short time breaks allowing for limited reworking and erosion facies association a consists of interbedded fallout deposits surge deposits and subordinate ignimbrites this facies association involved the eruption of the most evolved trachytic magma and pumice clasts are white and well vesiculated the grain size coarsens upward in facies association a with upward increases of dune bedform wavelengths and a decrease in the proportion of fine ash these trends could reflect an increase in eruption column height from the onset of the eruption and possibly also in mass eruption rate facies association b comprises massive ignimbrites that are progressively richer in lithic clast content this association involved the eruption of more mafic magma and pumice clasts are gray and poorly vesiculated facies association b is interpreted to record the climax of the eruption phreatomagmatic deposits occur at different stratigraphic levels in the four wtt and have different facies characteristics the deposits reflect the style and degree of magma water interaction and the local hydrogeology very fine grained lithic poor phreatomagmatic surge deposits found at the base of wtt cupa and wtt galluccio could record the interaction of the erupting magma with a lake that occupied the roccamonfina summit depression renewed magma water interaction later in the wtt galluccio eruption is indicated by fine grained lithic bearing phreatomagmatic fall and surge deposits occurring at the top of facies association a they could be interpreted to reflect shifts of the magma fragmentation level to highly transmissive regional aquifers located beneath the roccamonfina edifice possibly heralding a caldera collapse event

centrifuge modeling of nonaqueous phase liquid movement and entrapment in unsaturated layered soils four geotechnical centrifuge tests with different soil layered systems were performed to investigate the movement and entrapment of water and of light nonaqueous phase liquids lnapls in unsaturated layered soil deposits the tests were performed at 20 g and a vadose zone condition was created during the centrifuge tests by lowering the water table from the initially water saturated condition during the water drainage stage the water distribution within the models and the dynamic air water capillary pressure saturation relationships of the three sands were obtained using tensiometers and resistivity probes after achieving the unsaturated condition a model lnapl soltrol 220 or silicon oil was injected near the soil surface and the movement and entrapment were monitored during the redistribution stage until the lnapl reached the top of the water table complex lnapl preferential flow and entrapment patterns were observed in the layered models with different textural interfaces due to the relative movement of all three phases water nonaqueous phase liquid napl and air the centrifuge tests data coupled with the numerical analyses show that napl properties subsurface soil structures initial water saturation and napl infiltration rate affect the variation in entrapment conditions in heterogeneous unsaturated soil deposits

mineralogical comparison and cooling history of lunar and chondritic vesicular melt breccias lunar vesicular melt breccia 77135 was mineralogically compared with ll chondritic analog yamato 790964 to elucidate impact melting processes microprobe analyses were made of pyroxenes plagioclases and olivines and of bulk compositions of the glasses which appear to be solidified from impact melts notable similarities between the lunar and chondritic melt breccias are 1 abundant vesicles 2 similar pyroxene chemical zoning trends 3 presence of variable amounts of clastic material and 4 similar chemical compositions except for k and na contents of the glass and mesostasis some constraints on the cooling history are estimated from mg fe diffusion profiles in olivine and pyroxene the burial depth of lunar sample 77135 during cooling was not large 0 2 100 m for the chondrite the burial depth during cooling is probably smaller than that of the lunar analog even if the size of the chondrite parent body is small it is probable that impact melts were produced and a layer of ejecta debris was produced which was sufficiently thick to homogenize mg fe chemical zoning of olivines

are there real differences between antarctic finds and modern falls meteorites abstract recent reports of differences between antarctic and non antarctic meteorite collections include some based on mass frequency distributions and relative abundances of types using the modern falls of harvey and cassidy 1989 as a model of what a meteorite collection free of post fall processing should be like we compare the relative abundance of different types of stony meteorites for the antarctic finds and the modern falls reconstructing the antarctic mass frequency distributions using a model based on field observations of antarctic meteorite loss due to weathering wind transport and search inefficiencies we create an idealized antarctic meteorite mass frequency distribution that is identical in shape essentially lognormal to the modern falls using our model we find no difference between the antarctic finds and modern falls within reasonable estimates of error

lunar basalt breccia identified among antarctic meteorites the antarctic meteorite elephant moraine eet 87521 is a lunar mare basalt breccia this 30 7 g meteorite was originally identified as a brecciated eucrite1 but new petrographic evidence from a more representative thin section fig 1 indicates that it is a breccia of mainly very low titanium vlt basalt and should be reclassified as a lunar meteorite the four or five antarctic lunar meteorites collected previously at allan hills yamato mountains and macalpine hills alha81005 y79117 y793274 y82192 82193 y86032 and mac88104 88105 have all sampled only the plagioclase rich lunar highlands2 3 which dominate the surface of the moon eet87521 extends the lunar meteorite collections to include the less abundant basaltic provinces the maria of the lunar crust

ordinary chondrites multivariate statistical analysis of trace element contents abstract we used standard multivariate discriminant functions borrowed from linear discriminant analysis and logistic regression to compare contents of mobile trace elements co au sb ga se rb cs te bi ag in tl zn cd in various populations of l4 6 or h4 6 chondrites to aid in our analysis we developed a non standard randomization simulation method that permits probability assignments on a distribution free basis because the sample database for antarctic l4 6 chondrites is very limited we could not establish that mildly and strongly shocked

scaling unstable infiltration in the vadose zone this technical note examines the feasibility of physically modelling unstable water flow in the form of fingers in the vadose zone a scaling analysis is performed based on published expressions for the width and velocity of fingers as well as the distance between fingers particular reference is given to the use of a geotechnical centrifuge as an experimental apparatus for modelling this phenomenon initial results are presented for 1g and 10g fingers from a preliminary experimental program undertaken to explore the analysis these results agree with the scaling analysis presented and indicate that finger scaling using centrifugal modelling techniques is possible

chemical studies of h chondrites ii weathering effects in the victoria land antarctic population and comparison of two antarctic populations with non antarctic falls abstract we report rnaa data for 14 siderophile lithophile and chalcophile volatile mobile trace elements ag au bi cd co cs ga in sb se te tl u zn in interior portions of 45 different h4 6 chondrites 49 samples from victoria land antarctica and 5 h5 chondrites from the yamato mts antarctica relative to h5 chondrites of weathering types a and b all elements are depleted 10 at statistically significant levels in extensively weathered types b c and c samples probably by leaching on the ice sheet surface contents of 8 elements in extensively weathered samples may provide a qualitative ranking for terrestrial surface residence chondrites of weathering types a and b seem compositionally uncompromised and as useful as contemporary falls for trace element studies when data distributions for these 14 trace elements in non antarctic h chondrite falls and unpaired samples from victoria land and from the yamato mts queen maud land are compared statistically numerous significant differences are apparent concentrations of 8 elements differ significantly in the victoria land and non antarctic h5 chondrite populations essentially the same compositional differences and 53 mn content and shock history differences appear when h4 6 populations are compared contents of 8 elements differ when queen maud land and victoria land populations are compared and 5 for the queen maud land non antarctic comparison these and other differences give ample cause to doubt that the various sample populations derive from the same parent population the observed differences do not reflect weathering chance or other trivial causes a preterrestrial source must be responsible the least unlikely of these involves a temporal variation in the source regions from which meteoroids derive

comparisons between antarctic and non antarctic meteorites based on carbon isotope geochemistry abstract the whole rock c isotopic composition of a suite of ordinary chondrites indicates that there is a difference between antarctic and non antarctic meteorites however this apparent distinction is not due to an inherent difference in the meteorite source populations but is rather a result of the presence of antarctic weathering products mainly bicarbonates which affect the overall 13 c of these meteorites when these weathering products are removed either by acid washing or combustion to 500 c the perceived division also disappears leading to the conclusion that ordinary chondrites both antarctic and non antarctic have similar 13 c values a similar effect is noted in data from three separate groups of achondrites the ureilites heds and sncs however here the weathering products do not influence total c data in the case of the ureilites this is readily understood since the indigenous c content is high the heds and sncs on the other hand with low indigenous c abundance contain relatively lower concentrations of weathering products compared to ordinary chondrites which can be removed by combustion to 200 c this suggests a different complement of weathering products in the achondritic and chondritic meteorites an effect which may be related to differences in chemistry or porosity the almost ubiquitous occurrence of weathering products with distinctive c isotopic composition highlights the importance of removing all terrestrial contaminants from meteorites with low indigenous c budgets before attempting any interpretation concerning their c abundance or isotopic composition the c chemistry of ci cm and cr chondrites is also subject to problematic interpretation whilst the indigenous c abundance is too high to be compromised by the addition of terrestrial weathering products the inhomogeneous distribution of an array of components with widely varying isotopic signatures leads to a random distribution of 13 c values analyses of individual components insoluble macromolecular material carbonates and silicon carbide reveal that there are no gross differences in c chemistry between antarctic and non antarctic chondrites the few distinctions that do exist might readily be explained by weathering or isotopic exchange in antarctic whilst not forming a separate population antarctic carbonaceous chondrites may extend the range of properties of non antarctic chondrites beyond the currently known limits

identification of meteoroid streams from apollo asteroids in the adelaide radar orbit surveys a search is made for asteroid related meteoroids among the 3759 orbits determined in the two adelaide radar meteor orbit surveys of the 1960s these are the only southern hemisphere surveys yet completed all meteor orbits are compared to the orbits of all known comets and established meteor showers for the comets comparatively modest numbers of correlated meteors are found in contrast a similar comparison with the orbits of all aten apollo and amor asteroids discovered through 1986 october reveals strong meteor associations for several of the apollo asteroids a new and powerful technique is developed which allows the recognition of streams associated with specific parent objects when large orbit surveys are analyzed apart from 3200 phaethon the geminid parent meteoroid streams are found to be associated with 1566 icarus 2101 adonis 2201 oljato 2212 hephaistos 1937 ub hermes 5025 p l 1982 ta and 1984 kb these all give rise to meteors of velocity at least 22 km sec 1 there is also evidence of meteor activity for a few other apollos no streams are found for any of the atens or amors theoretical radiants and velocities are calculated for all asteroids of perihelion distance less than 1 025 au which approach the earth to within 0 1 au and it is shown that the lack of observed meteor streams for each can be explained in terms of the radiants being inaccessible from the adelaide site 35 s the lack of observations at the appropriate time of year or the expected meteor velocities being below 20 km sec 1 and hence producing little ionization and having a severely reduced probability of detection it therefore appears that meteoroid streams are a general feature associated with apollo asteroids

chemical studies of l chondrites iv antarctic non antarctic comparisons abstract we report shock facies and rnaa data for 13 siderophile lithophile and chalcophile volatile mobile trace elements ag au bi cd co cs ga in rb se te tl zn in interior portions of 19 different l3 6 chondrites from victoria land antartica comparison of these data for essentially unweathered antarctic samples with those previously published for 39 l4 6 chondrite falls indicate substantial differences the victoria land population lacks the most heavily shocked 35 gpa representatives found in the non antarctic population while contents of nearly all trace elements studied are lower at statistically significant levels in strongly shocked 22 gpa falls than in mildly shocked 22 gpa ones this is not true for the victoria land population contents of most trace elements vary with petrologic type of heavily shocked facies d 22 35 gpa l chondrites from victoria land such a variation is not observed for non antarctic falls or mildly shocked samples of either population l4 6 chondrites from victoria land contain significantly lesser amounts of nearly every trace element than do falls these differences are reflected in correlations between elements including the putative cosmothermometric trace elements bi in and tl while antarctic weathering could account for the compositional differences between antarctic and non antarctic l chondrites such processes cannot be responsible for the shock differences observed physical and chemical differences between other sorts of antarctic and non antarctic meteorites suggest rather that the l chondrite differences are preterrestrial in origin if so the parent region s for the victoria land samples that fell to earth 0 1 to 1 myr ago generally formed and or evolved under higher temperature conditions than those regions yielding contemporary falls the dominant influence of late shock that altered mobile trace element contents of l chondrites falls is not evident in samples from victoria land