mud plumbing system of an isolated phreatic eruption at akita yakeyama volcano northern honshu japan abstract a small phreatic eruption occurred on 16 august 1997 at the flank of a dacite lava dome of akita yakeyama northern honshu japan air falls and viscous mudflows were discharged from two craters mudflow effusion preceded discrete explosions followed by a fine ash discharge the air fall deposit consists of an upper fine ash deposit and a lower ballistic dominated poorly sorted tephra in which ranges in grain size from fine ash to blocks of ca 50 cm both air fall and mudflow deposits were composed of fine mud and coarse lithic fragments which contained abundant liquid water lithic fragments comprise fresh dacite of the host lava dome and hydrothermally altered stratocone andesite intensely altered andesite fragments contain quartz cristobalite andalusite pyrophyllite 7 a kaolin and anhydrite some mineral assemblages indicate hydrothermal temperatures greater than 300 c rare sandstone fragments are likely to be lacustrine from ca 1000 m depth the surface morphology of the mudflow deposits indicates that the mud contained ca 30 vol water the cube root similarity rules on crater size and the cloud shape of buried explosions provided energy of 3 5 10 9 j at depths of 6 10 m based on the observed crater size 20 m and fountain like cloud shape the depth estimate is consistent with the abundance of coarse dacite fragments derived from shallow lava in the explosion deposit thermodynamic energy release of ca 1 10 11 j was calculated based on the following estimated parameters product volume of 1 10 3 m 3 hydrothermal temperatures of 300 350 c and pressures of 11 24 mpa corresponding to the estimated source depth the thermodynamic estimation represents the total energy released during the eruption whereas the similarity rule yields an energy value as created by discrete explosions mud ascended from a hot aquifer at 1000 m depth first effused as a mudflow and was then expelled explosively from another crater explosivity depends on the shallow geologic structures reduction of pressure within the shallow permeable breccia resulted in effusive mudflow whereas overpressure confined by rigid dacite lava yielded explosive eruptions the mud plumbing system which includes deep aquifer mud and shallow explosions seems to be typical of phreatic eruptions

formation of iron carbon alloys in basaltic magma at uivfaq disko island the role of carbon in mafic magmas two types of metallic iron were identified in a collection of samples from the tertiary iron bearing basalts of uivfaq disko island greenland high carbon iron has 2 9 4 0 wt carbon and eutectic textures of iron and cohenite fe 3 c similar to those of commercial white cast iron it occurs in approximately spherical bodies up to 15 mm in diameter that appear to have been immiscible metallic liquids within basaltic magma low carbon samples have 1 8 2 0 wt carbon and textures similar to those of commercial hypereutectoid steel they occur principally as large up to 22 tons cumulate masses both types of metal could have crystallized at low pressure from iron carbon liquids of their present bulk carbon contents fe ni co cu and p oxides in basaltic magma were reduced by carbon derived principally from assimilated cretaceous tertiary sediments niand ni cu ratios of the metal are similar to those of terrestrial basalts the magma contained excess carbon graphite so the metal formed as

numerical simulation of fluctuations of hintereisferner otztal alps since ad 1850 a one dimen iona l ice oow mod el was adapted to reconstruc t flu ctuations of hintereisferner otztal alps sin ce the last postglacial maximum in the mid 19th cen tury both front posi tions and lo ngi tudina l ice thi ckness profiles were considered as forcing fun ction the specifi c mass balance was used the model was calibrated with the period 1953 91 because sin ce 1953 the mass balance has been determined directly for the period before 1953 as a fir st step so call ed d endro mass bala nces derived from tree rings were use d then th e mass bala nce was also parameterized as a function of temperature a nd precipitation from adjacent climate stations with both forcings hintereisferner could be reconstructed back to about 1850 with a n accuracy that li es within the accuracy of the model 200 m grid point distance

siderophile geochemistry of ureilites a record of early stages of planetesimal core formation abstract new bulk compositional data including trace siderophile elements such as ir os au and ni are presented for 25 ureilites without exception ureilites have siderophile abundances too high to plausibly have formed as cumulates ureilites undoubtedly underwent a variety of smelting by which c was oxidized to co gas while olivine feo was reduced to fe metal however pressure buffered equilibrium smelting is not a plausible model for engendering the wide range 75 96 mol of mafic silicate core mg among ureilites the smelting reaction produces too much co gas even supposing a disequilibrium process with the smelt gas leaking out of the mantle none of the ureilites least of all the ureilite with the most reduced highest olivine core mg alh84136 has the high fe metal abundance predicted by the smelted cores model in principle the fe metal generated by smelting could have been subsequently lost but siderophile data show that ureilites never underwent efficient depletion of fe metal ureilites display strong correlations among siderophile ratios such as au ir ni ir co ir as ir se ir and sb ir ureilite siderophile depletion patterns loosely resemble siderophile fractionations presumably nebular in origin among carbonaceous chondrites however zn for an element of moderate volatility is anomalously high in ureilites a tight correlation between au and ni extrapolates to the low ni au side of the compositional range of carbonaceous chondrites from this mismatch mild but nonetheless significant depletions of refractory siderophile elements such as ir and os and moderate depletions of strongly siderophile weakly chalcophile elements such as ni and au we infer that the ureilite siderophile fractionations are largely the result of a non nebular process i e removal of s rich metallic melt possibly with minor entrainment of fe metal several lines of trace element evidence indicate that melt porosity during ureilite anatexis was at least moderate the ureilite pattern of very mild depletions of extremely siderophile elements but much deeper depletions of moderately siderophile chalcophile elements suggests that asteroidal core formation probably occurs in two discrete stages in general separation of a considerable proportion several wt of s rich metallic melt probably occurs long before and at a far lower temperature than separation of the remaining s poor fe metal apart from the fe metal itself only extremely siderophile elements wait until the second stage to sequester mainly into the core

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

oxygen isotope studies of achondrites abstract oxygen isotope abundances provide a powerful tool for recognizing genetic relationships among meteorites among the differentiated achondrites three isotopic groups are recognized l snc mars 2 earth and moon and 3 hed howardites eucrites diogenites the hed group also contains the mesosiderites main group pallasites and silicates from iiiab irons the angrites may be marginally resolvable from the hed group within each of these groups internal geologic processes give rise to isotopic variations along a slope 1 2 fractionation line as is well known for terrestrial materials variations of 17o from one planet to another are inherited from the inhomogeneities in the solar nebula as illustrated by the isotopic compositions of chondrites and their constituents among the undifferentiated achondrites five isotopic groups are found 1 aubrites 2 winonaites and iab iiicd irons 3 brachinites 4 acapulcoites and lodranites and 5 ureilites the isotopic compositions of aubrites coincide with the earth and moon and also with the enstatite chondrites these bodies apparently were derived from a common reservoir the isotopic composition of which was established at the chondrule scale by nebular processes isotopic similarities between chondrites and achondrites are seen only for the following instances 1 enstatite chondrites and aubrites 2 h chondrites and he irons and 3 l or ll chondrites and iva irons the isotopic data also support the following genetic associations 1 winonaites and iab iiicd irons 2 acapulcoites and lodranites and 3 ureilites and dark inclusions of c3 chondrites an attempt to reconcile the whole planet isotopic compositions of earth mars and the eucrite parent body with mixing models of their chemical compositions failed it is not possible to satisfy both the chemical and isotopic compositions of the terrestrial planets using known primitive solar system components

the miller range 090340 and 090206 meteorites identification of new brachinite like achondrites with implications for the diversity and petrogenesis of the brachinite clan miller range mil 090340 and mil 090206 are olivine rich achondrites originally classified as ureilites we investigate their petrography mineral compositions olivine cr valences equilibration temperatures and for mil 090340 oxygen isotope compositions and compare them with ureilites and other olivine rich achondrites we conclude that they are brachinite like achondrites that provide new insights into the petrogenesis of brachinite clan meteorites mil 090340 6 has a granoblastic texture and consists of 97 modal by area olivine fo molar mg mg fe 71 3 0 6 it also contains minor to trace augite chromite chlorapatite orthopyroxene metal troilite and terrestrial fe oxides approximately 80 by area of mil 090206 5 has a granoblastic texture of olivine fo 72 3 0 1 plus minor augite and chromite similar to mil 090340 but also containing minor plagioclase the rest of the section consists of a single crystal of orthopyroxene 11 3 mm poikilitically enclosing rounded grains of olivine fo 76 1 0 6 augite chromite metal and sulfide equilibration temperatures for mil 090340 and mil 090206 calculated from olivine spinel olivine augite and two pyroxene thermometry range from 800 to 930 c in both samples symplectic intergrowths of ca poor orthopyroxene opaque phases fe oxides sulfide metal occur as rims on and veins patches within olivine before terrestrial weathering the opaques were probably mostly sulfide with minor metal all petrologic properties of mil 090340 and mil 090206 are consistent with those of brachinite clan meteorites and largely distinct from those of ureilites oxygen isotope compositions of olivine in mil 090340 18o 5 08 0 30 17o 2 44 0 21 and 17o 0 20 0 12 are also within the range of brachinite clan meteorites and well distinguished from ureilites olivine cr valences in mil 090340 and the granoblastic area of mil 090206 are 2 57 0 06 and 2 59 0 07 respectively similar to those of three brachinites also analyzed here brachina hughes 026 nova 003 they are higher than those of olivine in ureilites even those containing chromite the valence systematics of mil 090340 mil 090206 and the three analyzed brachinites lower fo more oxidized cr are consistent with previous evidence that brachinite like parent bodies were inherently more oxidized than the ureilite parent body the symplectic orthopyroxene sulfide metal assemblages in mil 090340 mil 090206 and many brachinite clan meteorites have superficial similarities to characteristic reduction rims in ureilites however they differ significantly in detail they likely formed by reaction of olivine with s rich fluids with only minor reduction mil 090340 and the granoblastic area of mil 090206 are similar in modal mineralogy and texture to most brachinites but have higher fo values typical of brachinite like achondrites the poikilitic pyroxene area of mil 090206 is more typical of brachinite like achondrites the majority of their properties suggest that mil 090340 and mil 090206 are residues of low degree partial melting the poikilitic area of mil 090206 could be a result of limited melt migration with trapping and recrystallization of a small volume of melt in the residual matrix these two samples are so similar in mineral compositions cr valence and cosmic ray exposure ages that they could be derived from the same lithologic unit on a common parent body

chronological and geomorphological investigation of fossil debris covered glaciers in relation to deglaciation processes a case study in the sierra de la demanda northern spain abstract in this study fossil debris covered glaciers are investigated and dated in the sierra de la demanda northern spain they are located in glacial valleys of approximately 1 km in length where several moraines represent distinct phases of the deglaciation period several boulders in the moraines and fossil debris covered glaciers were selected for analysis of 10 be surface exposure dating a minimum age of 17 8 2 2 ka was obtained for the outermost moraine in the san lorenzo cirque and was attributed to the global last glacial maximum lgm or earlier glacial stages based on deglaciation dates determined in other mountain areas of northern spain the youngest moraines were dated to approximately 16 7 1 4 ka and hence correspond to the gs 2a stadial oldest dryas given that the debris covered glaciers fossilize intermediate moraines it was deduced that they developed between the lgm and the oldest dryas coinciding with a period of extensive deglaciation during this deglaciation phase the cirque headwalls likely discharged large quantities of boulders and blocks that covered the residual ice masses the resulting debris covered glaciers evolved slowly because the debris mantle preserved the ice core from rapid ablation and consequently they remained active until the end of the late glacial or the beginning of the holocene for the san lorenzo cirque and the holocene thermal maximum for the mencilla cirque the north facing part of the mencilla cirque ensured longer preservation of the ice core

dynamics of shallow hydrothermal eruptions new insights from vulcano s breccia di commenda eruption understanding the dynamics and effects of hydrothermal eruptions is crucial to the hazard assessment in both volcanic and geothermal areas eruptions from hydrothermal centres may occur associated with magmatic phases but also as isolated events without magmatic input with the most recent examples being those of te maari tongariro new zealand in 2012 and ontake japan in 2014 the most recent caldera of the island of vulcano southern italy hosts in its centre the la fossa cone active since 5 5 ka and now characterised by continuous fumarolic degassing in historical times la fossa cone has experienced several hydrothermal eruptions with the most violent event being the breccia di commenda eruption that occurred during the thirteenth century ad based on analysis of 170 stratigraphic logs we show that the breccia di commenda eruption occurred in three main phases after an opening low intensity ash emission phase phase 1 the eruption energy climaxed during phase 2 when a series of violent explosions produced an asymmetric shower of ballistic blocks and the contemporaneous emplacement of highly dispersed lithic rich blast like pyroclastic density currents pdcs the tephra units emplaced during phase 2 ranging in volume from 0 2 to 2 7 105 m3 were covered in turn by thin ash fall deposits phase 3 the dynamics of the most violent and intense stage of the eruption phase 2 was investigated by numerical simulations a three dimensional numerical model was applied describing the eruptive mixture as a eulerian eulerian two phase non equilibrium gas particle fluid plus a one way coupled lagrangian ballistic block fraction at the initial simulation time a mass of about 109 kg with initial overpressure above 10 mpa and a temperature of 250 c was suddenly ejected from a 200 m long eastward inclined nne ssw trending fissure the mass release formed blast like pdcs on both sides of the fissure and launched ballistic blocks eastwards field investigations and numerical simulations confirm that hydrothermal explosions at la fossa cone include intense ballistic fallout of blocks emission of pdcs potentially travelling beyond the la fossa caldera and significant ash fallout the hazard associated with both ballistic impact and pdc ingress as associated with hydrothermal eruption is significantly larger with respect to that associated with vulcanian type events of la fossa

connectivity of molten fe alloy in peridotite based on in situ electrical conductivity measurements implications for core formation in terrestrial planets abstract the connectivity of molten fe s in peridotite has been experimentally investigated by means of in situ electrical conductivity measurements at high temperatures and 1 gpa starting materials were powdered mixtures of peridotite klb 1 with various amounts 0 3 6 13 19 24 vol of the 1 gpa eutectic composition in the fe fes binary system at temperatures above the eutectic point in the fe fes system 980 c and below the solidus of klb1 1200 c molten fe s in a solid silicate matrix interconnects when the volume fraction is over 5 conductivity temperature paths indicate that in the presence of partial silicate melting the connectivity of molten fe s in a peridotite matrix is inhibited based on observations of retrieved samples the percolation threshold of fe s melts in the presence of low to moderate degrees of silicate melt is estimated at 13 2 vol these results indicate that if the volume fraction of fe alloy in a planetesimal was initially greater than 5 and if early heating by decay of radionuclides raised the temperature of the interior above the fe alloy melting point initial metal segregation was controlled by permeable flow of molten iron alloy in a solid silicate matrix these conditions were likely met by many terrestrial objects in the early solar nebula efficient removal of residual fe alloy 5 vol from silicate requires high degree melting of silicate so that metal can segregate as droplets giant impacts during the final stage of accretion of large planetary objects could supply the energy required for high degrees of melting alternatively if initial metal segregation were delayed until a planetary object grew to large size 1000 km in diameter release of gravitational potential energy due to metal segregation could contribute enough heat to form a magma ocean

ureilite petrogenesis a limited role for smelting during anatexis and catastrophic disruption a popular model for ureilites assumes that during anatexis in an asteroidal mantle pressure buffered equilibrium smelting partial reduction coincident with partial melting engendered their conspicuous mafic silicate core mg diversity 75 96 mol several mass balance problems arise from this hypothesis smelting inevitably consumes a large proportion of any plausible initial carbon while generating significant proportions of fe metal and copious proportions of co gas the most serious problem concerns the yield of co gas if equilibrium smelting produced the ureilites entire 21 mol range in olivine core mg the proportion of gas within the asteroidal mantle assuming plausibly low pressure 80 bar should have reached 85 vol based on the remarkably stepwise cooling history inferred from ureilite texture and mineralogy a runaway co leaky process that can loosely be termed smelting appears to have occurred probably triggered by a major impact the runaway scenario appears likely because by le ch telier s principle co leakage would tend to accelerate the smelting process also the copious volumes of gas produced by smelting would have led to explosive mass leaky eruptions into the vacuum surrounding the asteroid loss of mass would mean diminution of interior pressure which would induce further smelting leading to further loss of mass basalt and so on such a disruptive runaway process may have engendered the ureilites distinctive reduced olivine rims but the only smelting according to this scenario was a short lived disequilibrium process that reduced only the olivine rims not the cores and the ureilites were cooling not melting during the abortive smelting episode

projections of glacier change in the altai mountains under twenty first century climate scenarios we project glacier surface mass balances of the altai mountains over the period 2006 2100 for the representative concentration pathway rcp 4 5 and rcp8 5 scenarios using daily near surface air temperature and precipitation from 12 global climate models in combination with a surface mass balance model the results indicate that the altai glaciers will undergo sustained mass loss throughout the 21st for both rcps and reveal the future fate of glaciers of different sizes by 2100 glacier area in the region will shrink by 26 10 for rcp4 5 while it will shrink by 60 15 for rcp8 5 according to our simulations most disappearing glaciers are located in the western part of the altai mountains for rcp4 5 all glaciers disappearing in the twenty first century have a present day size smaller than 5 0 km2 while for rcp8 5 an additional 7 of glaciers in the initial size class of 5 0 10 0 km2 also vanish we project different trends in the total meltwater discharge of the region for the two rcps which does not peak before 2100 with important consequences for regional water availability particular for the semi arid and arid regions this further highlights the potential implications of change in the altai glaciers on regional hydrology and environment

glacier volume estimation from ice thickness data applied to the muz taw glacier sawir mountains china in this work ground penetrating radar gpr data global position system gps data landsat remote sensing images and digital elevation model dem srtm were used to study the muz taw glacier in the sawir mountains by a variety of interpolation methods spatial pattern of thickness of the muz taw glacier was obtained the results show that there are obvious differences between the available gpr transverse profiles the lower transverse profile has typical u type topographic feature the maximum glacier thickness is up to 116 4 m glacier thickness distribution in the higher profile is relatively flat with an average about 70 90 m the longitudinal profile forms a ladder like distribution which in the middle of the ice bedrock topography has obvious depression the average longitudinal ice thickness is about 80 89 m the maximum ice thickness is up to 122 61 m in addition the preliminary estimation of the average thickness and total terminus ice volume were approximately 60 5 m and 0 195 km3 respectively

effects of explosion energy and depth to the formation of blast wave and crater field explosion experiment for the understanding of volcanic explosion we made field explosion experiments as an analogue of volcanic explosion to understand the relationship between the explosion condition and the resultant surface phenomena the main parameters we employed were explosion depth and explosion energy through the experiments we confirmed that scaled depth which is the depth divided by cube root of energy is the main parameter determining the properties of explosive volcanism the energy assigned to blast wave decreased exponentially against the scaled depth the scaled crater diameter became maximum when the scaled depth was about 4 10 3 m j scaled crater diameters by nuclear chemical subsurface and some volcanic explosions were almost the same from the scaling law the overpressure at crater rim was estimated to be several mpa which corresponded to typical rock strength probably the ground forming materials were broken inside the area where overpressure exceeded their strength

depositional mechanics and sequences of base surges songaksan tuff ring cheju island korea the songaksan mount in the southwestern part of cheju island korea is a taalian tuff ring produced by phreatomagmatic explosions at an aquifer a detailed analysis of proximal to distal facies changes reveals that the tuff ring sequence can be represented by 21 sedimentary facies one lateral facies sequence lfs and three vertical facies sequences vfs the vfs 1 and 2 are representative of facies relationships in horizontal near vent deposits the vfs 1 comprises scour fill bedded tuff inversely graded tuff massive tuff and laminated tuff from base to top the vfs 2 is a variant of the vfs 1 replaced by an inversely graded lapilli tuff unit at the base the sequences suggest traction carpet suspension and minor traction sedimentation from a high concentration near vent base surge the lfs 1 and the vfs 3 are distilled from outward dipping flank deposits both sequences begin with disorganized lapilli tuff followed successively by stratified lapilli tuff dune bedded lapilli tuff very thinbedded tuff and accretionary lapilli they are suggestive of waning base surge which decreases in particle concentration suspended load fall out rate and flow regimes with an increase in traction and sorting these facies sequences suggest that a base surge experiences flow transformation with its flow characters changing with time and space a near vent base surge is turbulent uniformly mixed and highly concentrated and produces scour fill bedded tuff as capacity decreases the surge transforms into a dense and laminar underflow and a dilute and turbulent upper part gravity transformation depositing inversely graded massive and normally graded lapilli tuff ensuing loss of sediment load and mixing of ambient air result in flow dilution surface transformation stratified and dune bedded units are produced by tractional processes of turbulent and low concentration surge further dilution causes deceleration and cooling and results in precipitation of moistened ash and accretionary lapilli from suspension

highly siderophile elements in ureilites abstract the abundances of the highly siderophile elements hse ru pd re os ir and pt were determined by isotope dilution mass spectrometry for 22 ureilite bulk rock samples including monomict augite bearing and polymict lithologies this report adds significantly to the quantity of available pt and pd abundances in ureilites as these elements were rarely determined in previous neutron activation studies the ci normalized hse abundance patterns of all ureilites analyzed here except alha 81101 show marked depletions in the more volatile pd with ci chondrite normalized pd os ratios excluding alha 81101 averaging 0 19 0 23 2 this value is too low to be directly derived from any known chondrite group instead the hse bulk rock abundances and hse interelement ratios in ureilites can be understood as physical mixtures of two end member compositions one component best represented by sample alha 78019 is characterized by superchondritic abundances of refractory hse rhse ru re os ir and pt but subchondritic pd rhse and is consistent with residual metal after extraction of a s bearing metallic partial melt from carbonaceous chondrite like precursor materials the other component best represented by sample alha 81101 is rhse poor and has hse abundances in chondritic proportions the genesis of the second component is unclear it could represent regions within the ureilite parent body upb in which metallic phases were completely molten and partially drained or it might represent chondritic contamination that was added during disruption and brecciation of the upb removal of carbon rich melts does not seem to play an important role in ureilite petrogenesis removal of such melts would quickly deplete the ureilite precursors in re os and as au which is inconsistent with measured osmium isotope abundances and also with literature as au data for the ureilites removal of 26 al during silicate melting may have acted as a switch that turned off further metal extraction from ureilite source regions

mineralogy of coexisting pyroxenes in magnesian ureilites and their formation conditions abstract the occurrence of orthopyroxene in two magnesian ureilites found in antarctica yamato y 791538 and lew85440 has been confirmed by electron probe microanalysis and by single crystal x ray diffraction the first coexisting equilibrium pigeonite orthopyroxene pair has been found in y791538 the lew85440 orthopyroxene coexists with minor augite the orthopyroxenes and olivines in y791538 y74659 and lew85440 have almost identical compositions but the ca contents of their coexisting clinopyroxenes differ considerably these phase assemblages can be explained by crystallization of mafic silicates with a similar composition oxygen fugacity and oxygen isotope anomaly at different temperature above 1220 c the high temperature crystallization of refractory mg rich silicates and the possible preservation of the oxygen isotope anomaly of precursor carbonaceous chondrites like materials may be consistent with their formation processes probably through local melting of more matrices than mg rich silicates and crystal growth induced by the planetesimal scale collision

ureilites trace element clues to their origin carbonaceous vein separates from kenna and havero as well as bulk kenna were analyzed by rnaa for ag au bi br cd cs ge in ir ni pd os rb re sb se te tl u and zn the data are reviewed together with four earlier chicago analyses of bulk ureilites linear regressions confirm the presence of two metal components with the following cl normalized ratios ir ni 14 6 1 ge ni 5 4 2 4 au ni 2 3 0 9 the high ir component is enriched in vein separates and hence belongs to veins the lowir component belongs to the ultramafic rock vein material is enriched in all elements analyzed by us except zn and accounts for most of the c noble gases and presumably siderophiles in the meteorite most of the properties of ureilites apparently can be explained by the cumulate model of berkley et al 1980 with certain modifications comparison of ureilites with three other ultramafic rocks from different planets earth s mantle lunar dunite and chassigny suggests that the ureilite parent body had a primitive chondritic composition similar to c3v chondrites but richer in metal and carbon it melted causing depletion of incompatibles to a mean abundance of 0 02 cl and incomplete segregation of metal fes and c fractional crystallization or melting of metal in the presence of s and c apparently can explain the fractionations of ir re ni au and perhaps ge obviating the need for extraneous sources of vein metal or unusual parent body compositions noble gases from the parent material may have been retrapped in carbon during magmatism provided the system was closed

primary igneous carbon in ureilites petrological implications the ureilite meteorites are carbonaceous olivine pyroxene achondrites they typically contain up to 4 wt carbon carbonaceous matrix as graphite diamond and lonsdaleite shock degradation has effectively obliterated primary textures in the carbonaceous matrix of previously described ureilites a factor that has hampered efforts to explain the origin of this material in contrast the antarctic ureilite alha78019 displays perfectly preserved primary textures in the carbonaceous matrix characterized by euhedral graphite blades intergrown with fe ni metal and sulfide diamonds are absent this petrographic feature suggests that most graphite in ureilites originated by crystallization from a c rich metallic phase assuming that fo2 is controlled by c co co2 reactions the compositions of silicates and metals in ureilites imply a two stage redox history the noble gases and rare earths of ureilites are discussed in light of this model

fe mg fe mn relations of meteorites and primary heterogeneity of primitive achondrite parent bodies abstract we examine fe mg mn relations of meteorites as represented on plots of molar fe mg ratio vs molar fe mn ratio and use them to consider whether it is meaningful to classify achondrites as primitive or evolved first we demonstrate that fe mg fe mn plots can be used to identify some of the major processes that have affected meteorite parent bodies during both the nebular condensation and accretion and the planetary igneous stages of their evolution examination of compositions of chondrites on this diagram reveals distinct patterns that result from three nebular processes 1 volatility controlled mn mg fractionation 2 metal silicate fractionation under highly reducing conditions and 3 subsequent oxidation leading to variations in feo mgo ratio ordinary chondrites ocs show a characteristic pattern that records all three of these processes and suggests that the latter two are coupled examination of the compositions of achondrites on this diagram shows that all of those that have been classified as primitive lodranites acapulcoites winonaites iab silicate inclusions brachinites and ureilites are easily distinguished from those that have been classified as evolved sncs heds and lunar basalts the mn mg ratios of the former are chondritic while those of the latter are superchondritic hence they plot in two graphically distinct regions of the fe mg fe mn diagram a simple melting calculation reveals that this distinction results principally because the former are residues and the latter are melts or cumulate products of melts rather than because the latter are more evolved additionally however some of the groups classified as primitive achondrites show fe mg fe mn patterns similar to that of ocs constant but distinct mno mgo ratios over large ranges of feo mgo ratio we argue that these trends reflect primary heterogeneity resulting from the same nebular processes as those that affected ocs and therefore preserve evidence that more of the materials that accreted to form planetesimals experienced these processes than is apparent from known chondrites this evidence is preserved principally because these meteorites are residues in contrast groups commonly classified as evolved achondrites show fe mg fe mn patterns that reflect only igneous processing and any evidence for primary heterogeneity of their parent bodies has been obliterated again this is principally because these meteorites represent melts rather than beause they are more evolved usage of the terms primitive and evolved to describe achondrites should be clearly defined

northwest africa 1500 plagioclase bearing monomict ureilite or ungrouped achondrite northwest africa nwa 1500 is an ultramafic meteorite dominated by coarse 100 500 m olivine 95 96 augite 2 3 and chromite 0 6 1 6 in an equilibrated texture plagioclase 0 7 1 8 occurs as poikilitic grains up to 3 mm in vein like areas that have concentrations of augite and minor orthopyroxene other phases are cl apatite metal sulfide and graphite olivine ranges from fo 65 73 with a strong peak at fo 68 69 most grains are reverse zoned and also have 10 30 m reduction rims in terms of its dominant mineralogy and texture nwa 1500 resembles the majority of monomict ureilites however it is more ferroan than known ureilites fo 75 and other mineral compositional parameters are out of the ureilite range as well furthermore neither apatite nor plagioclase have ever been observed and chromite is rare in monomict ureilites nevertheless this meteorite may be petrologically related to the rare augite bearing ureilites and represent a previously unsampled part of the ureilite parent body upb the mn mg ratio of its olivine and textural features of its pyroxenes are consistent with this interpretation however its petrogenesis differs from that of known augite bearing ureilites in that 1 it formed under more oxidized conditions 2 plagioclase appeared before orthopyroxene in its crystallization sequence and 3 it equilibrated to significantly lower temperatures 800 1000 c from two pyroxene and olivine chromite thermometry formation under more oxidized conditions and the appearance of plagioclase before orthopyroxene could be explained if it formed at a greater depth on the upb than previously sampled however its significantly different thermal history compared to ureilites may more plausibly be explained if it formed on a different parent body this conclusion is consistent with its oxygen isotopic composition which suggests that it is an ungrouped achondrite nevertheless the parent body of nwa 1500 may have been compositionally and petrologically similar to the upb and may have had a similar differentiation history

origin and evolution of the ureilite parent magmas multi stage igneous activity on a large parent body analyses of olivine and pigeonite cores interpreted as cumulate crystals in eight low shock ureilites show well defined correlations between fe x where x is one of the minor elements mn cr ca al ti p or ni and fe mg ratios for the lithophile minor elements these trends are linear with positive slope and pass through or near the origin indicating various degrees of feo reduction of the parent magmas the trends shown by p and ni are consistent with this interpretation and additionally require equilibrium crystallization of 20 27 mole metal graphite was most likely the reducing agent which implies that the ureilites equilibrated at different pressures because the graphite fo2 buffer is pressure dependent there is no evidence for fractionation of olivine or pryroxene in any of these trends the ca ti and al trends show significant scatter indicating that there must have been multiple parent magmas with very similar mg mn and mgcr ratios but different mgal mgca and mgti ratios cao al2o3 ratios vary by a factor of 3 among the eight magmas and are superchondritic 14 32 molar similar to lunar mare basalts we propose the following model for generation and crystallization of ureilite parent magmas upm chondritic material undergoes 10 25 partial melting leaving a plagioclase depleted residue the magma or magmas form a differentiated crust on the ureilite parent body upb with mafic cumulates and plagioclase cumulates spatially separated later remelting 10 of the mafic cumulates produced the upm siderophile elements indicate that the source region of the upm had not experienced segregation of metal such as would occur during core formation in the source region the pressure must have been at least 0 5 1 kb because only at pressures this high does the graphite buffer allow iron oxide to be the stable phase relative to metallic iron the graphite bearing upm were emplaced at various levels in the crust where they were reduced to various extents dependent on depth ureilites are early olivine pigeonite cumulates from these magmas compositions of interstitial low ca pyroxenes indicate that the trapped interstitial liquids from which they crystallized had lower mnmg crmg camg almg and namg ratios than the upm and indicate an abrupt change in liquid composition coincident with impact excavation of ureilites this interstitial material may be derived by mixing a shock melt of nearby olivine pigeonite cumulates with residual primary liquid our model predicts that the upb had a differentiated crust did not have a core and was at least 235 km in radius the lack of a ureilite like body among spectrally analyzed asteroids suggests that either the spectral signature of the upb is not that of ureilites themselves perhaps of carbon free feldspathic material instead that the upb is not intact or that ureilites did not originate in the asteroid belt

depositional processes of the suwolbong tuff ring cheju island korea the suwolbong pyroclastic sequence in the western part of cheju island korea comprises partly preserved rim beds of a quaternary basaltic tuff ring whose vent lies about 1 km seaward of the present shoreline the sequence consists of breccia lapillistone lapilli tuff and tuff eighteen sedimentary facies are established and organized into six lateral facies sequences lfs and seven vertical facies sequences vfs the lfs 1 4 and 5 begin with massive lapilli tuff which transforms downcurrent into either planar bedded lfs 1 undulatory bedded lfs 4 or climbing dune bedded lfs 5 lapilli tuff units they are representative of relatively dry base surge whose particle concentration decreases downcurrent with a progressive increase in both tractional processes and sorting the lfs 2 begins with disorganized and massive lapilli tuff and transforms into crudely stratified units downcurrent it results from relatively wet base surge in which sorting is poor due to the cohesion of damp ash the lfs 3 comprises well sorted lapilli tuff and stratified tuff further downcurrent suggestive of deposition from combined fall and surge of relatively dry hydroclastic eruption all seven vertical facies sequences generally comprise two facies units of coarse grained fines depleted lapilli tuff and an overlying fine grained tuff these sequences are suggestive of deposition from base surge that consists of a turbulent head and a low concentration tail depositional processes in the suwolbong tuff ring were dominated by a relatively dry base surge the base surge comprises turbulent and high concentration suspension near the vent whose deposits are generally unstratified due to the lack of tractional transport as the base surge becomes diluted downcurrent through fallout of clasts and mixing of ambient air it develops large scale turbulent eddies and is segregated into coarse grained bedload and overlying fine grained suspension forming thinly stratified units further downcurrent the base surge may be either cooled and deflated or pushed up into the air depending on its temperature the suwolbong tuff ring comprises an overall wet to dry cycle with several dry to wet cycles in it suggestive of overall decrease in abundance of external water and fluctuation in the rate of magma rise

volume measurements of mittivakkat gletscher southeast greenland here we present ground penetrating radar measurements of mittivakkat gletscher southeast greenland to estimate an empirical volume area scaling relationship at an individual glacier between a previous direct volume survey in 1994 and one in 2012 the glacier volume has decreased from 2 02 km 3 to 1 44 km 3 while the study area has decreased from 17 6 km 2 to 15 8 km 2 these results are in accordance with the cumulative mass loss observed by long term mass balance measurements 1995 96 2011 12 at mittivakkat gletscher and confirm that the glacier is in severe climatic disequilibrium aar 0 17 the observed scaling exponent 3 14 and coefficient c 0 00025 km 3 2 are outside the range of global scaling parameters but sensitive to small uncertainties nevertheless existing global volume area scaling relationships estimate the volume of mittivakkat gletscher within 31 and 15 of the measured 1994 and 2011 volumes respectively

determination of total ice volume and ice thickness distribution of two glaciers in the hohe tauern region eastern alps from gpr data global warming is causing an apparent rapid retreat of many glaciers worldwide in addition to mass balance investigation the determination and monitoring of total glacial ice volume and ice thickness distribution are important parameters for understanding the interactions between climate and the complex glacier system because of spatially irregular and sparse datasets scaling of volume and ice thickness distribution is often a challenging problem this study focuses on two small 100 m were identified in the data the acquired gpr data are irregularly distributed and the spatial density is too low to calculate reasonable bedrock topography with standard interpolation approaches thus one main focus of this study was to develop an appropriate interpolation technique eventually kriging technique and a glacial mechanically based interpolation parameter were used mean calculated ice thicknesses for the two investigated glaciers are 40 50 m with a maximum of 150 165 m no direct validation data are available so different considerations support the computed bedrock topography

dynamic behaviour analysis of glacier de saint sorlin france from 40 years of observations 1957 97 mass balance and dynamic measurements carried out on glacier de saint sorlin since 1957 provide a good opportunity to study the dynamics of this glacier ice flow analysis shows that dynamic changes have been important over the last 40 years and that these changes are not consistent with the concepts usually used in glacier modelling present velocities are larger than the 1960 velocities although the thickness decreased everywhere 10 30 m in the ablation zone a simple numerical ice flow model which does not include longitudinal stress gradients has been used to investigate these phenomena this model allows us to infer the sliding velocity from observed surface and calculated deformation velocities we conclude that 1 the sliding velocity cannot be described by weertman analysis or empirical relations which link the sliding to the thickness and surface slope 2 the inferred sliding velocity is uniform over at least half of the glacier and 3 there is no clear link between the sliding process and the quantity of water coming from surface ablation furthermore it may not be reasonable to calibrate model flow parameters from geometry changes because the surface geometry is relatively insensitive to velocity changes over some decades

petrology of chromite in ureilites deconvolution of primary oxidation states and secondary reduction processes abstract ureilites are ultramafic achondrites thought to be residues of partial melting on a carbon rich asteroid they show a trend of feo variation olivine fo from 74 to 95 that suggests variation in oxidation state whether this variation was established during high temperature igneous processing on the ureilite parent body upb or preserved from nebular precursors is a subject of debate the behavior of chromium in ureilites offers a way to assess redox conditions during their formation and address this issue independent of fo we conducted a petrographic and mineral compositional study of occurrences of chromite cr rich spinel in ureilites aimed at determining the origin of the chromite in each occurrence and using primary occurrences to constrain models of ureilite petrogenesis chromite was studied in lew 88774 fo 74 2 nwa 766 fo 76 7 nwa 3109 fo 76 3 hah 064 fo 77 5 lap 03587 fo 74 9 cms 04048 fo 76 4 lap 02382 fo 78 6 and eet 96328 fo 85 2 chromite occurs in lew 88774 5 vol nwa 766 early chromite also occurs in a melt inclusion in olivine in hah 064 and in a metallic spherule in olivine in lap 02382 lap 03587 and cms 04048 contain m sized chromite pyroxene symplectic exsolutions in olivine indicating high cr valence in the primary olivine eet 96328 contains a round grain of chromite that could be a late crystallizing phase tiny chromite grains in melt inclusions in eet 96328 formed in late closed system reactions for 7 of the 8 ureilites we conclude that the relatively oxidizing conditions evidenced by the presence of primary or early chromite pertain to the period of high t igneous processing the observation that such conditions are recorded almost exclusively in low fo samples supports the interpretation that the ureilite feo variation was established during igneous processing on the upb

climate sensitivity of storglaciaren sweden an intercomparison of mass balance models using era 40 re analysis and regional climate model data estimates of glacier contributions to future sea level rise are often computed from mass balance sensitivities derived for a set of representative glaciers our purpose is to investigate how mass b

fe bearing phases in a ureilite fragment from the asteroid 2008 tc3 almahata sitta meteorites a combined mossbauer spectroscopy and x ray diffraction study the iron bearing phases in a ureilite fragment as 051 from the almahata sitta meteorite are studied using mossbauer spectroscopy x ray diffraction xrd and electron microprobe analysis empa as 051 has a typical ureilite texture of medium to coarse grained silicates olivine orthopyroxene and pigeonite with minor opaques fe ni metal troilite and graphite the silicate compositions determined by empa are homogeneous olivine fo90 2 orthopyroxene en86 3fs8 6wo5 1 and pigeonite en81 6fs8 9wo9 5 and are similar to those of magnesian ureilites the modal abundance of mineral phases was determined by rietveld refinement of the powder xrd data the mossbauer spectra at 295 k and 78 k are composed of two sharp well defined paramagnetic doublets superimposed on a well resolved magnetic sextet and other weak absorption features the two paramagnetic doublets are assigned to olivine and pyroxene orthopyroxene and pigeonite and the ferromagnetic sextet to kamacite magnetic hyperfine field 33 2 t in agreement with the xrd characterization the mossbauer results also show the presence of small amounts of troilite fes and cohenite fe ni co 3c using the mossbauer data the relative abundance of each fe bearing phase is determined and compared with the results obtained by xrd

trace element analysis of ureilites new constraints on their petrogenesis abstract six ureilites alha77257 alha81101 alh82130 pca82506 kenna and novo urei were analyzed using neutron activation analysis for ca sc cr mn fe co ni zn ga ree w re os ir and au we examined bulk samples as well as acid treated samples in the bulk samples the refractory siderophiles concentrations range from approximately 0 1 to 1 0 times ci chondrites while the volatile siderophiles range from about 0 07 to 0 3 times ci chondrites rare earth elements rees in ureilites are quite depleted and display light and heavy rare earth enrichments the antarctic meteorites display either much less pronounced v shaped patterns or no enrichment in the light rare earths at all in terms of the new trace element results ureilites do not fall into the coherent groups that other workers have defined by chemical or petrographic characteristics trace elements do provide additional constraints on the models for the petrogenesis of ureilites in particular the siderophile element abundances call for simplified models of chemical processing rather than the complex multistage processing called for in silicate fractionation models ree concentrations on the other hand imply multistage processing to produce the ureilites none of the ureilite petrogenesis models extant account for the trace element data these new data and the considerations of them with respect to the proposed ureilite petrogenesis models indicate that the direction of modelling should be toward contemplation of mixtures and how the components we observe in ureilites behave under such conditions

planetesimal differentiation revealed by the hf w systematics of ureilites abstract determining the timescales of the accretion and chemical differentiation of meteorite parent bodies provides some of the most direct constraints on the formation of planetesimals and the earliest stages of planet formation we present high precision hf w isotope data for a comprehensive set of ureilites ultramafic mantle restites derived from a partially melted and incompletely differentiated asteroid all samples are characterized by strong 182w deficits indicating that silicate melt extraction on the ureilite parent body at 3 3 0 7 ma after cai formation postdated core formation in iron meteorite parent bodies by 2 3 ma thermal modeling of planetesimal heating by 26al decay combined with the new hf w data indicates that the ureilite parent body accreted at 1 6 ma after cai formation and therefore more than 1 ma later than iron meteorite parent bodies but more than 0 5 ma earlier that most chondrite parent bodies due to its relatively late accretion the ureilite parent body contained too little 26al to cause complete melting and therefore would have probably remained incompletely differentiated even without exhaustion of 26al by silicate melt segregation our results show that both in terms of degree of differentiation and accretion timescale the ureilite parent body is intermediate between fully differentiated and undifferentiated bodies implying that there is an inverse correlation between extent of melting and metal silicate separation versus time of accretion and differentiation

origin of ureilite meteorites and implications for planetary accretion although ureilites have been considered bizarre meteorites our analysis of their properties suggests that they formed by simple well known processes we conclude that 1 ureilites are the sole rock type in a major fraction of their parent body 2 they are partial melt residues and not cumulates 3 removal of 90 of the al in the basalts would largely stop radioactive heating if 26al was the heat source ensuring that large volumes of ureilite like material were generated 4 they formed in a large chondritic body that had a heterogeneous o isotopic composition 5 slow diffusion of o in solid and molten silicates ensured that partial melting did not homogenize the o isotopes of the residues 6 the puzzling absence of the basaltic melts that accompanied ureilite formation probably results from ejection into space by explosive volcanism together these conclusions provide a simple plausible origin for ureilites that accounts for most of their properties ureilites are residues from the partial melting of isotopically heterogeneous chondritic material we suggest that other meteorite parent bodies and planetesimals may have experienced similar histories and that ureilites provide important constraints on the accretionary and igneous histories of planets and asteroids

fractional melting and smelting on the ureilite parent body we investigate petrologic and physical aspects of melt extraction on the parent asteroid of the ureilite meteorites upb we first develop a petrologic model for simultaneous melting and smelting reduction of feo by c at various depths for a model starting composition determined from petrologic constraints to have been cv like except for elevated ca al 2 5 ci we determine 1 degree of melting 2 the evolution of mg 3 production of co co2 gas and 4 the evolution of mineralogy in the residue as a function of temperature and pressure we then use these relationships to examine implications of fractional vs batch melt extraction in the shallowest source regions 30 bars melting and smelting begin simultaneously at 1050 c so that mg and the abundance of low ca pyroxene initially pigeonite ultimately pigeonite orthopyroxene begin to increase immediately however in the deepest source regions 100 bars smelting does not begin until 1200 c so that mg begins to increase and low ca pyroxene pigeonite appears only after 21 melting the final residues in these two cases obtained just after the demise of augite match the end members of the ureilite mg range 94 76 in pyroxene abundance and type in all source regions production of co co2 by smelting varies over the course of melting the onset of smelting results in a burst of gas production and very high incremental gas melt ratios up to 2 5 by mass after a few s melting however these values drastically decline to 0 05 in the final increments physical modelling based on these relationships indicates that melts would begin to migrate upwards after only 1 2 melting and thereafter would migrate continuously fractionally and rapidly reaching the surface in a year in a network of veins dikes all melts produced during the smelting stage in each source region have gas contents sufficient to cause them to erupt explosively and be lost however since in all but the shallowest source regions part of the melting sequence occurs without smelting fractional melting implies that a significant fraction of upb melts may have erupted more placidly to form a thin crust 3 3 km thick for a 100 km radius body our calculations suggest that melt extraction was so rapid that equilibrium trace element partitioning may not have been attained we present a model for disequilibrium fractional melting in which ree partitioning is limited by diffusion on the upb and demonstrate that it produces a good match to the ureilite data the disequilibrium model may also apply to trace siderophile elements and might help explain the overabundance of these elements in ureilites relative to predictions from the smelting model our results suggest that melt extraction on the upb was a rapid fractional process which can explain the preservation of a primitive oxygen isotopic signature on the upb

regional and global volumes of glaciers derived from statistical upscaling of glacier inventory data 1 very few global scale ice volume estimates are available for mountain glaciers and ice caps although such estimates are crucial for any attempts to project their contribution to sea level rise in the future we present a statistical method for deriving regional and global ice volumes from regional glacier area distributions and volume area scaling using glacier area data from 123 000 glaciers from a recently extended world glacier inventory we compute glacier volumes and their sea level equivalent sle for 19 glacierized regions containing all mountain glaciers and ice caps on earth on the basis of total glacierized area of 741 103 68 103 km2 we estimate a total ice volume of 241 103 29 103 km3 corresponding to 0 60 0 07 m sle of which 32 is due to glaciers in greenland and antarctica apart from the ice sheets however our estimate is sensitive to assumptions on volume area scaling coefficients and glacier area distributions in the regions that are poorly inventoried i e antarctica north america greenland and patagonia this emphasizes the need for more volume observations especially of large glaciers and a more complete world glacier inventory in order to reduce uncertainties and to arrive at firmer volume estimates for all mountain glaciers and ice caps

are ureilites residues from partial melting of chondritic material the answer from magpox calculations performed using magpox show that no bulk compositions having chondritic ca al ratio and within the range of chondritic si mg ratios can produce the olivine pigeonite ureilites which constitute 65 of those for which modal abundances are known as residues of single stage equilibrium partial melting calcium aluminum ratios of 2 3 5 ci are required in addition all the ureilites could not have formed from a single composition at various degrees of reduction because they show no correlation between pigeonite olivine ratio and mg ratio materials with various al mg ratios ranging from subchondritic to superchondritic are required if these materials are primitive i e created by nebular processes rather than planetary igneous processes they are unknown in the meteorite record excess accretion relative to chondrites of 5 10 mol of a high temperature condensate component which was itself almost completely depleted in corundum due to early fractionation could create the necessary compositions the plausibility that such processes occurred on a parent body sized scale is difficult to assess in contrast lodranites can be produced as residues of 3 30 equilibrium partial melting of an average ordinary chondritic composition at the appropriate level of reduction although many features of ureilites suggest that they are relatively primitive residues produced by low degrees of melting of chondritic materials and thus resemble lodranites and other groups of primitive achondrites their predominantly pigeonite olivine mineralogy remains difficult to explain within this simple scenario

low sea level rise projections from mountain glaciers and icecaps under global warming the mean sea level has been projected to rise in the 21st century as a result of global warming such projections of sea level change depend on estimated future greenhouse emissions and on differing models but model average results from a mid range scenario a1b suggests a 0 387 m rise by 2100 refs 1 2 the largest contributions to sea level rise are estimated to come from thermal expansion 0 288 m and the melting of mountain glaciers and icecaps 0 106 m with smaller inputs from greenland 0 024 m and antarctica 0 074 m here we apply a melt model and a geometric volume model to our lower estimate of ice volume and assess the contribution of glaciers to sea level rise excluding those in greenland and antarctica we provide the first separate assessment of melt contributions from mountain glaciers and icecaps as well as an improved treatment of volume shrinkage we find that icecaps melt more slowly than mountain glaciers whose area declines rapidly in the 21st century making glaciers a limiting source for ice melt using two climate models we project sea level rise due to melting of mountain glaciers and icecaps to be 0 046 and 0 051 m by 2100 about half that of previous projections

primary magmatic carbon in ureilites evidence from cohenite bearing metallic spherules metallic spherules containing cohenite fe ni metal sulfides and rare phosphorus bearing minerals occur as inclusions within olivine and pigeonite grains in five low shock ureilites the bulk compositions mineralogy and textures of these spherules indicate that they represent fe ni c s alloys that existed as droplets of immiscible metallic liquid in the magma s from which ureilites crystallized at magmatic temperatures these alloys were carbon saturated and probably coexisted with graphite in the magma this is consistent with the occurrence of graphite crystals as inclusions in olivine in some ureilites and supports the view that graphite in ureilites was a primary magmatic component graphite could have been a residue from the solid source materials that melted to produce the ureilite parent magma s or could have crystallized from the magma s the metallic liquids separated into immiscible fe c liquids and fe s liquids after they were trapped within silicates the fe c liquids contained 4 5 wt c and 3 7 wt ni cohenite was the liquidus phase and started to crystallize at 1200 1225 c forming euhedral and subhedral crystals at the eutectic 1175 c iron containing 7 9 ni and 1 8 c crystallized along with cohenite at lower temperatures the iron exsolved cohenite and possibly iron

sequence of the 1895 eruption of the zao volcano tohoku japan abstract the most recent major eruption event of the zao volcano comprised a series of phreatic eruption episodes on 15 and 19 february 22 august and 27 28 september 1895 with several precursory vulcanian eruptions during february july 1894 all were generated at the okama crater lake located inside the umanose caldera the eruption products consist mainly of hydrothermally altered ash with altered blocks except for ash from 1984 the eruption deposits of 1895 are divided lithologically into six layers 1 6 comparison of the document with the lithofacies of deposits shows that layers 1 2 3 4 and 5 6 were correlated respectively with eruption episodes of 15 february episode 1 19 february episode 2 22 august episode3 and 27 28 september episode 4 during these four episodes ca 0 5 0 5 1 5 and 98 of the total mass of the products had been discharged based on lithologic stratigraphic granulometric and component analyses and on distributional features for these layers the following depositional mechanisms were inferred layers 1 3 and 4 were formed mainly from their related small pyroclastic density currents whereas layer 2 resulted mainly from a small pyroclastic fall in contrast layers 5 and 6 are larger scale near vent pyroclastic fall deposits from ash clouds and eruption clouds which might have included some juvenile fragments the three early episodes in 1985 led to the climactic episode of 27 28 september furthermore the andesitic magma chamber at

glacier change in western north america influences on hydrology geomorphic hazards and water quality the glaciers of western canada and the conterminous united states have dominantly retreated since the end of the little ice age lia in the nineteenth century although average rates of retreat varied from strong in the first half of the twentieth century with glaciers stabilizing or even advancing until 1980 and then resuming consistent recession this retreat has been accompanied by statistically detectable declines in late summer streamflow from glacier fed catchments over much of the study area although there is some geographical variation over recent decades glaciers in northwest bc and southwest yukon have lost mass dominantly by thinning with relatively low rates of terminal retreat and glacier fed streams in that region have experienced increasing flows in many valleys glacier retreat has produced geomorphic hazards including outburst floods from moraine dammed lakes mass failures from oversteepened valley walls and debris flows generated on moraines in addition to these hydrologic and geomorphic changes evidence is presented that glacier retreat will result in higher stream temperatures possibly transient increases in suspended sediment fluxes and concentrations and changes in water chemistry with climate projected to continue warming over the twenty first century current trends in hydrology geomorphology and water quality should continue with a range of implications for water resources availability and management and hydroecology particularly for cool and cold water species such as salmonids copyright 2008 john wiley sons ltd

petrogenesis and provenance of ungrouped achondrite northwest africa 7325 from petrology trace elements oxygen chromium and titanium isotopes and mid ir spectroscopy northwest africa nwa 7325 is an ungrouped achondrite that has recently been recognized as a sample of ancient differentiated crust from either mercury or a previously unknown asteroid in this work we augment data from previous investigations on petrography and mineral compositions mid ir spectroscopy and oxygen isotope compositions of nwa 7325 and add constraints from cr and ti isotope compositions on the provenance of its parent body in addition we identify and discuss notable similarities between nwa 7325 and clasts of a rare xenolithic lithology found in polymict ureilites nwa 7325 has a medium grained protogranular to poikilitic texture and consists of 10 15 vol mg rich olivine fo 98 25 30 vol diopside wo 45 mg 98 55 60 vol ca rich plagioclase an 90 and trace cr rich sulfide and fe ni metal we interpret this meteorite to be a cumulate that crystallized at 1200 c and very low oxygen fugacity similar to the most reduced ureilites from a refractory incompatible element depleted melt modeling of trace elements in plagioclase suggests that this melt formed by fractional melting or multi stage igneous evolution a subsequent event likely impact resulted in plagioclase being substantially remelted reacting with a small amount of pyroxene and recrystallizing with a distinctive texture the bulk oxygen isotope composition of nwa 7325 plots in the range of ureilites on the ccam line and also on a mass dependent fractionation line extended from acapulcoites the e54cr and e50ti values of nwa 7325 exhibit deficits relative to terrestrial composition as do ordinary chondrites and most achondrites its e54cr value is distinct from that of any analyzed ureilite but is not resolved from that of acapulcoites as represented by acapulco in terms of all these properties nwa 7325 is unlike any known achondrite however a rare population of clasts found in polymict ureilites the magnesian anorthitic lithology are strikingly similar to nwa 7325 in mineralogy and mineral compositions oxygen isotope compositions and internal textures in plagioclase these clasts are probably xenolithic in polymict ureilites and could be pieces of nwa 7325 like meteorites using constraints from chromium titanium and oxygen isotopes we discuss two possible models for the provenance of the nwa 7325 parent body 1 accretion in the inner solar system from a reservoir similar to that of acapulcoites in 17o e54cr and e50ti or 2 early 1 ma after cai formation accretion in the outer solar system beyond the snow line before 54cr and 50ti anomalies were introduced to this region of the solar system the mid ir emission spectrum of nwa 7325 obtained in this work matches its modal mineralogy and so can be compared with spectra of new meteorites or asteroids planets to help identify similar materials and or the parent body of nwa 7325

pyroxene selective impact smelting in ureilites abstract a characteristic feature of ureilite meteorites is reduction of feo but the reduction is usually confined to the rims of olivine in the lar 04315 lap 03587 and almahata sitta ureilites pyroxene was extensively reduced by impact smelting in lar 04315 the impact caused nearly all of the original pigeonite to melt or otherwise become sufficiently structurally compromised to allow smelting and yet a minor proportion of the pyroxene escaped smelting and survived with its original composition en 74 1 wo 10 2 olivine mosaicism confirms that lar 04315 experienced a major shock event the smelted pyroxenes also show a distinctive patchiness in their interference colors although each grain s basic optical continuity often including twinning is still discernible they also have reduced compositions are ubiquitously porous 15 and contain sprinklings of fe metal and felsic glass for the most part the olivine underwent only very slight reduction much of the small pyroxene component of lap 03587 shows the same oddly porous texture lar 04315 also contains large traces of silica and felsic glass with a typical composition of in wt 61 sio 2 23 al 2 o 3 11 cao 3 7 na 2 o glass these two phases together form selvages that line the walls of many of the largest voids in the rock silica is a by product of pyroxene smelting the felsic glass probably derives largely from interstitial basaltic melt that predated the impact however the comparatively stiff surrounding included silica may have promoted unusually high melt retention within lar 04315 through the smelting episode one aspect of which was a major stream out through the same large voids of co x gas the impact smelted pyroxene of lap 03587 is enigmatic because this ureilite also features little shocked euhedral graphite laths and no olivine mosaicism the fine grained ureilitic component of almahata sitta appears to have likewise formed by impact smelting but with more extensive melting of pyroxene especially a ca rich pyroxene component more pulverization and melting of olivine and more displacement of both however in places the original coarse equant ureilite texture is still discernible in relict form ordinarily an impact shock melts olivine before or at least no later than pyroxene but in the case of lar 04315 and lap 03587 the great shock event evidently occurred when the material was already anatectic or very nearly so and thus the difference in melting temperature between pyroxene and olivine 300 degrees lower for pyroxene was decisive if literature inferences of extremely fast cooling rates implying shallow burial depths are accurate the proportion of co x gas generated by ureilite smelting exceeded by a very large factor of order 10 3 but possibly much greater the volume represented as porosity in the final ureilites the outflow of so much gas may have by near surface explosive expansion and jetting enhanced the thoroughness of the impact triggered catastrophic impact disruption of the parent asteroid

the partitioning of fe ni and co between olivine metal and basaltic liquid an experimental and thermodynamic investigation with application to the composition of the lunar core abstract the partitioning of fe ni and co between mg rich olivine lunar basaltic liquid and metal has been measured over a range of temperatures and pressures the results of the olivine metal partitioning may be compared to those predicted from thermodynamic calculation in general the agreement is good although the calculated distribution coefficients are slightly greater then those experimentally determined this discrepancy increases with increasing temperature and pressure but it is not possible to ascertain unambiguously which thermodynamic data might be responsible at lower temperatures inversion of the equilibria to yield cosmothermometers for measuring the temperature of equilibration between olivine and metal gives results for the pallasite meteorites in excellent agreement with independent estimates the results have been applied to apollo 15 green glass presumed to approximate a primitive melt from the lunar mantle to deduce the composition of fe ni co metal in equilibrium with the lunar mantle this composition is approximately by weight 54 60 fe 38 45 ni and 1 co consequently if metal has separated from the lunar mantle under equilibrium conditions to form a small lunar core this core will be nickel rich with a ni fe ratio of 0 7 0 15

the physical basis of glacier volume area scaling ice volumes are known for only a few of the roughly 160 000 glaciers worldwide but are important components of many climate and sea level studies which require water flux estimates a scaling analysis of the mass and momentum conservation equations shows that glacier volumes can be related by a power law to more easily observed glacier surface areas the relationship requires four closure choices for the scaling behavior of glacier widths slopes side drag and mass balance reasonable closures predict a volume area scaling exponent which is consistent with observations giving a physical and practical basis for estimating ice volumes glacier volume is insensitive to perturbations in the mass balance scaling but changes in average accumulation area ratios reflect significant changes in the scaling of both mass balance and ice volume

explosive volcanism and the graphite oxygen fugacity buffer on the parent asteroid s of the ureilite meteorites the 39 ureilite meteorites are in many respects primitive objects they are highly carbonaceous averaging 3 0 wt c mostly as graphite yet their consistently coarse grained textures and plagioclase depleted compositions imply that they are igneous despite diverse mafic silicate mg mg fe and pyroxene olivine ratios plagioclase is totally absent among 35 monomict unbrecciated ureilites even among 4 polymict brecciated ureilites the average al concentration is only 0 28 0 04 wt we suggest that the ureilites are residues from partial melting of graphite rich source materials which formed sufficiently deep in a relatively large low f o2 asteroid or more likely asteroids for graphite to be stable even at magmatic t the al rich basaltic magmas that ascended from the residues were nearly quantitatively lost from the asteroid during pyroclastic eruptions graphite entrained in the ascending magmas was oxidized by an extremely pressure sensitive reaction into cox the expansion of which into the vacuous environment of the asteroid engendered pyroclastic exit velocities greatly in excess of the asteroid s escape velocity carbon would oxidize long before the attainment of magmatic temperatures in small asteroids but we infer that basalt dissipative explosive volcanism was common on all c rich asteroids that were roughly 100 200 km in radius and heated to widespread deep melting and most unmetamorphosed chondritic meteorites are c rich based on the ureilites consistently modest depletions of light rare earth elements siderophile elements and feni metal we infer that the melt fraction was removed mostly by equilibrium batch partial melting late stage ureilite evolution involved an abrupt increase in the cooling rate implying a drop in environmental temperature and a slight amount of graphite oxidation implying a drop in pressure the simplest model to account for this non sequitur and for the conversion of some of the graphite into diamonds is catastrophic impact disruption of the primary asteroid the remarkably efficient removal of the final traces of melt from the ureilites is difficult to explain by any model but possibly was caused by thermal migration along steep thermal gradients engendered after the catastrophic disruption

quantifying the effects of climate and surface change on glacier mass balance when a mass balance is computed using an outdated map that computation does not reveal the actual mass change but older maps often must be used for practical reasons we present a method by which with a few additional measurements each year a mass balance computed with an outdated map can be transformed into an actual mass change this is done by taking into account the influence of changes in areal extent and changes in the surface elevation of the glacier since the map was made this method is applied to south cascade glacier washington u s a as an example the computed cumulative mass balance from 1970 to 1997 would have been 16 too negative if the 1970 map had not been updated while the actual volume change of a glacier is relevant to hydrological studies the change that would have occurred on a constant or static surface is more relevant to certain glacier dynamics problems and most climate problems we term this the reference surface balance and propose that such a balance which deliberately omits the influence of changes in area and surface elevation is better correlated to climatic variations than the conventional one which incorporates those influences

pyroclastic density current from the 1888 phreatic eruption of bandai volcano ne japan abstract the great eruption of july 15 1888 at bandai volcano produced large phreatic explosions and a major debris avalanche toward the northern foot this eruption is characterized as follows 1 there was no significant precursor 2 the eruption and collapse of the volcanic edifice were triggered by an earthquake with a magnitude of about 5 3 the initial explosions were accompanied with a pyroclastic density current 4 the main explosive eruption quickly ceased a few minutes after the eruption began 5 a subsequent late stage plume rose buoyantly to a height of 5000 m falling with a heavy warm rain which generated a lahar and 6 ejected materials were made up wholly of pre existing rock fragments with no juvenile glass shards the main branch of the pyroclastic density current cascaded from the summit for a distance of 6 km along the biwazawa valley on the southeast flank the heim coefficient of the reconstructed energy line slope for the density current is 0 223 to 0 296 the estimated velocity using these values is less than 100 m s the density current deposit consists of normally graded parallel bedded or scour fill cross bedded thin layers of coarse ash and lapilli except for coarse massive breccia near the vent the sedimentary structures and grain size data suggest that the pyroclastic materials were transported in traction saltation and true suspension the estimated velocity is competent for transportation of the deposit the time sequence suggests that the seismic shocks and subsequent collapse of the edifice broke the confined hydrothermal system and caused the phreatic explosions the pressurized hydrothermal fluids had been presumably stored due to self sealing of the system because hydrothermal activities had been vigorous at the summit region until the july 15 seismic shocks collapse of the dry and dense initial eruption column generated the density current which spilled toward the opposite side of the crater along the topographic lows the change from the collapse to the late stage ascending plume results from a decrease in the rock fragment contents which made the plume light and wet this is because that a decrease in the fraction of rock fragments causes an increase in the fraction of steam produced within the plume the occurrence of the water flushed ash fall and lahar during the late stage eruption is consistent with this model

metamorphic angrite northwest africa 3164 5167 compared to magmatic angrites abstract northwest africa nwa 3164 and 5167 are two angrites with a granulitic texture unlike that of other angrites with a variable up to millimeter grain size besides mineralogical and chemical similarities to other angrites nwa 3164 and 5167 exhibit unique characteristics ca rich olivine dominates in nwa 3164 49 vol fo57 nwa 5167 40 vol fo59 fassaitic clinopyroxene is the second major phase in nwa 3164 29 vol in nwa 5167 36 vol with a significant tschermak component in addition two al rich phases are present plagioclase an99 and hercynitic spinel 6 and 7 vol respectively for nwa 3164 17 and 4 vol respectively for nwa 5167 heavily weathered iron sulfide and kamacite 9 wt in nwa 3164 4 wt in nwa 5167 are the remaining minor phases a unique feature among angrites all mineral phases are homogeneous like other angrites nwa 3164 and 5167 exhibit a superchondritic ca al ratio with negligible amounts of alkalis and very low silica content the presence of metal results from the incorporation of exogenous iron following impact subsequent annealing resulted in the observed granulitic texture major element composition indicates that both nwa 3164 and 5167 are derived from a picritic angrite precursor after incorporation of metal and annealing after correction for iron and fo90 olivine incorporation bulk rock ree abundances of both nwa 3164 and nwa 5167 appear lower than those of quenched angrites showing the lowest absolute abundances among angrites laser ablation inductively coupled plasma mass spectrometry la icp ms analyses of clinopyroxene olivine and anorthite indicate that difference of rare earth element ree abundances between nwa 3164 and nwa 5167 can be explained by adding traces of phosphate to nwa 3164 nwa 3164 5167 trace elements abundances are similar showing depletion in volatile elements and enrichment in refractory lithophile elements such as ca ti and al the most incompatible elements are depleted as well unlike other angrites this indicates that the source of these younger angrites was more depleted in incompatible elements when compared to the older magmatic angrites the low hf w is understood as the result of exogenous iron incorporation and therefore the hf w and w isotopic heterogeneity of the angrite parent body apb mantle is secondary comparison with other angrites suggests that iron incorporation may be necessary to explain their low hf w and w isotopic compositions

s process os isotope enrichment in ureilites by planetary processing abstract ubiquitous nucleosynthetic isotope anomalies relative to the terrestrial isotopic composition in mo ru and other elements are known from both bulk chondrites and differentiated meteorites but os isotope ratios reported from such meteorites have been found to be indistinguishable from the terrestrial value the carriers of s and r process os must thus have been homogeneously distributed in the solar nebula as large os isotope anomalies are known from acid leachates and residues of primitive chondrites the constant relative proportions of presolar s and r process carriers in such chondrites must have been maintained during nebular processes it has long been assumed that partial melting of primitive chondrites would homogenize the isotopic heterogeneity carried by presolar grains here ureilites carbon rich ultramafic achondrites dominantly composed of olivine and low ca pyroxene are shown to be the first differentiated bulk solar system materials for which nucleosynthetic os isotope anomalies have been identified these anomalies consist of enrichment in s process os heterogeneously distributed in different ureilites given the observed homogeneity of os isotopes in all types of primitive chondrites this os isotope variability among ureilites must have been caused by selective removal of s process poor os host phases probably metal during rapid localized melting on the ureilite parent body while mo and ru isotope anomalies for all meteorites measured so far exhibit s process deficits relative to the earth the opposite holds for the os isotope anomalies in ureilites reported here this might indicate that the earth preferentially accreted olivine rich restites and inherited a s process excess relative to smaller meteorite bodies consistent with earth s high mg si ratio and enrichment of s process nuclides in mo ru and nd isotopes our new os isotope results imply that caution must be used when applying nucleosynthetic isotope anomalies as provenance indicators between different classes of meteorites

volume area scaling vs flowline modelling in glacier volume projections volume area scaling provides a practical alternative to ice flow modelling to account for glacier size changes when modelling the future evolution of glaciers however uncertainties remain as to the validity of this approach under non steady conditions we address these uncertainties by deriving scaling exponents in the volume area relationship from one dimensional ice flow modelling we generate a set of 37 synthetic steady state glaciers of different sizes and then model their volume evolution due to climate warming and cooling as prescribed by negative and positive mass balance perturbations respectively on a century timescale the scaling exponent derived for the steady state glaciers 1 56 differs from the exponents derived for the glaciers in transient non steady state by up to 86 nevertheless volume projections employing volume area scaling are relatively insensitive to these differences in scaling exponents volume area scaling agrees well with the results from ice flow modelling in addition the scaling method is able to simulate the approach of a glacier to a new steady state if mass balance elevation feedback is approximated by removing or adding elevation bands at the lowest part of the glacier as the glacier retreats or advances if area changes are approximated in the mass balance computations in this way our results indicate that volume area scaling is a powerful tool for glacier volume projections on multi century timescales

182hf 182w chronometry and early differentiation of the ureilite parent body abstract eight samples spanning the bulk chemical range of monomict ureilites have been analyzed for their w isotopic composition and hf w in order to elucidate the differentiation history of the ureilite parent body the ureilites studied here show sub chondritic hf and w concentrations and low hf w ratio and all show clear 182 w deficits relative to bulk chondrites the w isotope data provide evidence that the ureilite parent body differentiated within 1 to 2 million years after the start of the solar system such early accretion and differentiation is comparable to the parent bodies of various magmatic iron meteorites as well as the hed parent body however the trace element fractionations and by inference melting processes are very different an early smelting partial melting event coupled with metal silicate segregation however can reproduce the observed hf w data in ureilites and is consistent with petrological and other chemical evidence for a missing basaltic component and with primitive oxygen and noble gases compositions

tungsten and hafnium distribution in calcium aluminum inclusions cais from allende and efremovka recent 182hf 182w age determinations on allende ca al rich refractory inclusions cais and on iron meteorites indicate that cais have initial e182w 3 47 0 20 2 identical to that of magmatic iron meteorites after correction of cosmogenic 182w burn out 3 47 0 35 2 either the allende cais were isotopically disturbed or the differentiation of magmatic irons groups iiab iid iiiab and ivb all occurred 103 which is lowered by the ubiquitous presence of metal inclusions to 180hf 184w 10 in bulk fassaite metal alloy ni 50 is the sole host of w 500 ppm in ef2 while opaque assemblages oas and secondary veins are the hosts of w in golfball a large metal alloy grain from ef2 em2 has 180hf 184w 100 ppm w with no detectable pt or s this vein provides evidence for transport of oxidized w in the cai because of the ubiquitous distribution of oas interpretations of the 182hf 182w isochron reported for allende cais include i all w in the oas was derived by alteration of cai metal or ii at least some of the w in oas may have been equilibrated with radiogenic w during metamorphism of allende since ii cannot be ruled out new 182hf 182w determinations on cais from reduced cv3 chondrites are needed to firmly establish the initial w isotopic composition of the solar system

analysis of scaling methods in deriving future volume evolutions of valley glaciers volume area scaling is a common tool for deriving future volume evolutions of valley glaciers and their contribution to sea level rise we analyze the performance of scaling relationships for deriving volume projections in comparison to projections from a one dimensional ice flow model the model is calibrated for six glaciers nigardsbreen rhonegletscher south cascade glacier sofiyskiy glacier midre lovenbreen and abramov glacier volume evolutions forced by different hypothetical mass balance perturbations are compared with those obtained from volume area v a volume length v l and volume area length v a l scaling results show that the scaling methods mostly underestimate the volume losses predicted by the ice flow model up to 47 for v a scaling and up to 18 for v l scaling by the end of the 100 year simulation period in general v l scaling produces closer simulations of volume evolutions derived from the ice flow model suggesting that v l scaling may be a better approach for deriving volume projections than v a scaling sensitivity experiments show that the initial volumes and volume evolutions are highly sensitive to the choice of the scaling constants yielding both over and underestimates however when normalized by initial volume volume evolutions are relatively insensitive to the choice of scaling constants especially in the v l scaling the 100 year volume projections differ within 10 of initial volume when the v a scaling exponent commonly assumed 1 375 is varied by 30 to 45 0 95 2 00 and the v l scaling exponent q 2 2 is varied by 30 to 45 q 1 52 3 20 this is encouraging for the use of scaling methods in glacier volume projections particularly since scaling exponents may vary between glaciers and the scaling constants are generally unknown

glacier volume area relation for high order mechanics and transient glacier states 1 glacier volume is known for less than 0 1 of the world s glaciers but this information is needed to quantify the impacts of glacier changes on global sea level and regional water resources observations indicate a power law relation between glacier area and volume with an exponent 1 36 through numerical simulations of 3d high order glacier mechanics we demonstrate how different topographic and climatic settings glacier flow dynamics and the degree of disequilibrium with climate systematically affect the volume area relation we recommend more accurate scaling relations through characterization of individual glacier shape slope and size an ensemble of 280 randomly generated valley glaciers spanning a spectrum of plausible glaciological conditions yields a steady state exponent 1 46 this declines to 1 38 for glaciers that are 100 years into a sustained retreat which corresponds exceptionally well with the observed value for present day glaciers

the potential for sea level rise new estimates from glacier and ice cap area and volume distributions projections of sea level rise from mountain glaciers and ice caps for the next century and beyond should be based on an assessment of the ice available for melting projections to date are based on all regions except greenland and antarctica the latter are considered separately by the ipcc yet no sound estimates for the appropriate volume of ice and its potential for sea level rise are evident in the literature an ice cap data set is compiled allowing the separate treatment of glacier area coverage data glacier inventory data are comprehensive enough in some regions to allow the estimation of glacier size distributions the differences in the distributions are related to a metric of the regional topographic variability allowing glacier size distributions to be estimated on a 1 latitude longitude grid of cells containing glaciers appropriate volume area scaling for glaciers and for ice caps gives global estimates of glacier and ice cap volumes by size class this leads to an estimate of the total ice volume of 0 087 0 010 106 km3 and a sea level rise equivalent of 0 241 0 026 m the glaciers and ice caps contribute 41 and 59 to these estimates respectively these values are based on data sets compiled during several decades mainly in the second half of the 20th century we compare our results to published results that include the glaciers and icecaps at the margins of the greenland and antarctic ice sheets

effect of explosion energy and depth on the nature of explosion cloud a field experimental study field explosion experiments using dynamite were carried out to investigate the effect of explosion energy and depth on the nature of explosion cloud the scaling law of explosion was established among the energy depth and the nature of explosion cloud shape height and duration of flow out the shape of explosion cloud changed systematically from funnel type via elongated to short types with increasing the scaled depth of explosion at the shallow scaled depth both scaled height and scaled duration increased with increasing scaled depth both values reached the maximum at 0 003 0 004 m j1 3 of cube root scaled depth and then decreased with increasing scaled depth if the cube root scaled depth was over about 0 01 m j1 3 we could not observe any explosion cloud on the ground surface these experimental results should be applicable to the understanding of volcanic explosions if the buoyant effect of internal heat in the explosion cloud was negligible and ground medium is identical we applied these results to the explosion clouds of usu phreatic explosion at 14 53 h on 17 april 2000 and estimated that the explosion energy and the depth were 4 109 j and 6 m respectively errors caused by uncertainty of scaling factors are less than one order of magnitude for the energy and depth

origin and history of ureilitic material in the solar system the view from asteroid 2008 tc3 and the almahata sitta meteorite asteroid 2008 tc3 approximately 4 m diameter was tracked and studied in space for approximately 19 h before it impacted earth s atmosphere shattering at 44 36 km altitude the recovered samples 680 individual rocks comprise the meteorite almahata sitta ahs approximately 50 70 of these are ureilites ultramafic achondrites the rest are chondrites mainly enstatite ordinary and rumuruti types the goal of this work is to understand how fragments of so many different types of parent bodies became mixed in the same asteroid almahata sitta has been classified as a polymict ureilite with an anomalously high component of foreign clasts however we calculate that the mass of fallen material was 0 1 of the pre atmospheric mass of the asteroid based on published data for the reflectance spectrum of the asteroid and laboratory spectra of the samples we infer that the lost material was mostly ureilitic therefore 2008 tc3 probably contained only a few percent nonureilitic materials similar to other polymict ureilites except less well consolidated from available data for the ahs meteorite fragments we conclude that 2008 tc3 samples essentially the same range of types of ureilitic and nonureilitic materials as other polymict ureilites we therefore suggest that the immediate parent of 2008 tc3 was the immediate parent of all ureilitic material sampled on earth we trace critical stages in the evolution of that material through solar system history based on various types of new modeling and re evaluation of published data we propose the following scenario 1 the ureilite parent body upb accreted 0 5 0 6 ma after formation of calcium aluminum rich inclusions cai beyond the ice line outer asteroid belt differentiation began approximately 1 ma after cai 2 the upb was catastrophically disrupted by a major impact approximately 5 ma after cai with selective subsets of the fragments reassembling into daughter bodies 3 either the upb before breakup or one of its daughters after breakup migrated to the inner belt due to scattering by massive embryos 4 one daughter after forming in or migrating to the inner belt became the parent of 2008 tc3 it developed a regolith mostly 3 8 ga ago clasts of enstatite ordinary and rumuruti type chondrites were implanted by low velocity collisions 5 recently the daughter was disrupted fragments were injected or drifted into earth crossing orbits 2008 tc3 comes from outer layers of regolith other polymict ureilites from deeper regolith and main group ureilites from the interior of this body in contrast to other models that have been proposed this model invokes a stochastic history to explain the unique diversity of foreign materials in 2008 tc3 and other polymict ureilites

petrology of unique achondrite queen alexandra range 93148 a piece of the pallasite howardite eucrite diogenite parent body abstract queen alexandra range que 93148 is a small 1 1 g olivine rich achondrite mg 86 that contains variable amounts of orthopyroxene mg 87 and kamacite 6 7 wt ni with minor augite olivine in que 93148 contains an unusual suite of inclusions 1 5 100 m sized lamellae with a cao and cr2o3 rich 10 and 22 wt respectively composition that may represent a submicrometer scale intergrowth of chromite and pyroxene s 2 75 500 m sized lamellar symplectites composed of chromite and two pyroxenes with minor metal 3 15 20 m sized irregularly shaped symplectites composed of chromite and pyroxene s 4 100 150 m sized elliptical inclusions composed of chromite two pyroxenes metal troilite and rare whitlockite type 1 2 and 3 inclusions probably formed by exsolution from the host olivine during slow cooling whereas type 4 more likely resulted from early entrapment of silicate and metallic melts followed by closed system oxidation queen alexandra range 93148 can be distinguished from most other olivine rich achondrites ureilites winonaites lodranites acapulcoites brachinites eagle station type pallasites and pyroxene pallasites as well as from mesosiderites by some or all of the following properties o isotopic composition fe mn mg relations of olivine cao and cr2o3 contents of olivine orthopyroxene compositions molar cr cr al ratios of chromite metal composition texture and the presence of the inclusions in terms of many of these properties it shows an affinity to main group pallasites nevertheless it cannot be identified as belonging to this group meteorite que 93148 appears to be a unique achondrite possibly it should be considered to be a pyroxene pallasite that is genetically related to main group pallasites alternatively it may be derived from the mantle of the pallasite howardite eucrite diogenite parent body

formation of ureilites by nebular processes oxygen isotopic data are presented for 23 ureilites including 14 antarctic meteorites they show a much greater range in isotopic composition than those previously studied most noteworthy is the fact that unlike other achondrite groups the ureilites do not fall on a mass dependent isotopic fractionation trend but rather fall along an extrapolation of the 16o mixing line defined by components of allende and other c3 chondrites correlations between isotopic and chemical data imply that the isotopic and chemical variations are due primarily to processes in the solar nebula and not to igneous processes within a parent body the ureilite parent body accreted with isotopic and chemical heterogeneities which were not much modined by subsequent parent body processes the precursor materials were related in some way to the c3 carbonaceous chondrites

climate variability and glacier reaction in the austrian eastern alps a carefully homogenized climate dataset is used to interpret glacier behaviour in the austrian alps periods of glacier advance are generally more maritime and cooler with reduced sunshine duration and increased precipitation sum during the ablation period periods of retreat are associated with a more continental warmer climate with increased sunshine duration and reduced precipitation sum three recent sub periods of austrian glacier behaviour are documented by direct measurement of glacier mass balance before 1965 more negative 1965 81 more positive since 1982 more negative a long term mass balance series in the eastern part of the austrian alps parameterized by snow depth measurements indicates very clearly that periods of more negative mass balance have a higher correlation to summer air temperature and a lower correlation to winter accumulation periods of more positive mass balance are highly correlated to winter accumulation and only slightly correlated to summer temperature the positive mass balance period 1965 81 is also characterized by negative north atlantic oscillation index values which caused an increased meridional circulation mode resulting in a northwesterly to northerly precipitation regime during winter

the mineralogy and petrology of i type cosmic spherules implications for their sources origins and identification in sedimentary rocks abstract i type cosmic spherules are micrometeorites that formed by melting during atmospheric entry and consist mainly of iron oxides and feni metal i types are important because they can readily be recovered from sedimentary rocks allowing study of solar system events over geological time we report the results of a study of the mineralogy and petrology of 88 i type cosmic spherules recovered from antarctica in order to evaluate how they formed and evolved during atmospheric entry to constrain the nature of their precursors and to establish rigorous criteria by which they may be conclusively identified within sediments and sedimentary rocks two textural types of i type cosmic spherule are recognised 1 metal bead bearing met spherules dominated by ni poor 100 and suggest that metal from h group ordinary cm cr and iron meteorites may form the majority of particles oxidation during entry heating increases in the series met 80 wt ni comprising a particle mass fraction of

an investigation of the behavior of cu and cr during iron meteorite crystallization the measured cu and cr contents in magmatic iron meteorites appear to contradict the behavior predicted by experimental fractional crystallization studies currently available to investigate the origin of cu and cr concentrations observed in these meteorites a thorough set of solid metal liquid metal experiments were conducted in the fe ni s system in addition to cu and cr partitioning values were also determined for as au bi co mo ni pb rh ru sb sn v and zn from the experiments experimental results for cu and cr showed similar chalcophile partitioning behavior whereas these elements have differently sloped trends within magmatic iron meteorite groups thus fractional crystallization alone cannot control both the cu and cr concentrations in these iron meteorite groups a simple fractional crystallization model based on our experimental cu partitioning results was able to match the cu versus au trend observed in the s poor ivb iron meteorite group but not the decreasing cu versus au trends in the iiab and iiiab groups or the unique s shaped cu versus au trend in the iva group however the crystallization model calculations were found to be very sensitive to the specific choice for the mathematical expression of d cu suggesting that any future refinement of the parameterization of d cu should include a reassessment of the cu fractional crystallization trends the cr versus au trends in magmatic iron meteorite groups are steeper than those of cu and not explained by fractional crystallization other influences such as the removal of chromite from the crystallizing system or sampling biases during iron meteorite compositional analyses are likely responsible for the cr trends in magmatic iron meteorite groups

early petrologic processes on the ureilite parent body we present a petrographic and petrologic analysis of 21 olivine pigeonite ureilites along with new experimental results on melt compositions predicted to be in equilibrium with ureilite compositions we conclude that these ureilites are the residues of a partial melting smelting event textural evidence preserved in olivine and pigeonite record the extent of primary smelting in pigeonite cores we observe fine trains of iron metal inclusions that formed by the reduction of olivine to pigeonite and metal during primary smelting olivine cores lack metal inclusions but the outer grain boundaries are variably reduced by a late stage reduction event the modal proportion of pigeonite and percentage of olivine affected by late stage reduction are inversely related and provide an estimation of the degree of primary smelting during ureilite petrogenesis in our sample suite this correlation holds for 16 of the 21 samples examined olivine pigeonite liquid phase equilibrium constraints are used to obtain temperature estimates for the ureilite samples examined inferred smelting temperatures range from 1150 c to just over 1300 c and span the range of estimates published for ureilites containing two or more pyroxenes temperature is also positively correlated with modal percent pigeonite smelting temperature is inversely correlated with smelting depth the hottest olivine pigeonite ureilites coming from the shallowest depth in the ureilite parent body the highest temperature samples also have oxygen isotopic signatures that fall toward the refractory inclusion rich end of the carbonaceous chondrite anhydrous mineral ccam slope 1 mixing line these temperature depth variations in the ureilite parent body could have been created by a heterogeneous distribution of heat producing elements which would indicate that isotopic heterogeneities existed in the material from which the ureilite parent body was assembled

mineralogy of antarctic ureilites and a working hypothesis for their origin and evolution abstract mineralogical and crystallographic data and electron microprobe analyses of silicate minerals for antarctic ureilites y74123 y74130 y74659 y790981 alha77257 alha78019 and alh82106 extend the chemical and textural variations among ureilites beyond those known for non antarctic ureilites low ca pyroxenes possibly orthopyroxene poikilitically enclosed in olivine and coexisting with mg rich pigeonites have been identified in y74659 and alha77257 coexisting low ca pyroxene pigeonite and augite together with the very fe rich olivine in ureilites were observed in y74130 almost fe free pigeonite and diopside coexist in alh82106 no systematic differentiation trend has been reconstructed from these data but the pyroxene pairs yield formation temperatures above 1200 c a weak anticorrelation between mno and feo delineated by these pyroxenes suggests that a reduction reaction is responsible for the chemical variations a working hypothesis for ureilite formation involves high temperature episoded and a planetesimal scale collision which might have facilitated compaction and recrystallization of mafic silicates during the episodes fe ni s eutectic melt and a partial melt rich in ca al and fe might have been lost from a carbonaceous chondrite like source material

high sensitivity of north iceland trollaskagi debris free glaciers to climatic change from the little ice age to the present the trollaskagi peninsula is located in northern iceland between meridian 19 30 w and 18 10 w jutting out into the north atlantic to latitude 66 12 n the aim of this research is to study recent

chromium valences in ureilite olivine and implications for ureilite petrogenesis abstract ureilites are a group of ultramafic achondrites commonly thought to be residues of partial melting on a carbon rich asteroid they show a large variation in feo content olivine fo values ranging from 74 to 95 that cannot be due to igneous fractionation and suggests instead variation in oxidation state the presence of chromite in only a few of the most ferroan fo 75 76 samples appears to support such a model microxanes analyses were used in this study to determine the valence states of cr previously unknown in olivine cores of 11 main group ureilites the goal of this work was to use a method that is independent of fo to determine the oxidation conditions under which ureilites formed in order to evaluate whether the ureilite feo variation is correlated with oxidation state and whether it is nebular or planetary in origin two of the analyzed samples lew 88774 fo 74 2 and nwa 766 fo 76 7 contain primary chromite two others lap 03587 fo 74 4 and cms 04048 fo 76 2 contain sub micrometer sized exsolutions of chromite ca rich pyroxene in olivine and one eet 96328 fo 85 2 contains an unusual chromite grain of uncertain origin no chromite has been observed in the remaining six samples fo 77 4 92 3 chromium in olivine in all eleven samples was found to be dominated by the divalent species with valences ranging from 2 10 0 02 1 to 2 46 0 04 the non chromite bearing ureilites have the most reduced cr with a weighted mean valence of 2 12 0 01 i e cr2 cr3 7 33 all low fo chromite bearing ureilites have more oxidized cr with valences ranging from 2 22 0 03 to 2 46 0 04 eet 96328 whose chromite grain we interpret as a late crystallizing phase yielded a reduced cr valence of 2 15 0 07 similar to the non chromite bearing samples based on the measured cr valences magmatic 1200 1300 c oxygen fugacities fo2 of the non chromite bearing samples were estimated to be in the range iw 1 9 to iw 2 8 assuming basaltic melt composition consistent with fo2 values obtained by assuming olivine silica iron metal osi equilibrium for the primary chromite bearing ureilites the corresponding fo2 were estimated again assuming basaltic melt composition to be iw to iw 1 0 i e several orders of magnitude more oxidizing than the conditions estimated for the chromite free ureilites in terms of fo and cr valence properties ureilites appear to form two groups rather than a single cr valence or fo2 vs fo trend the chromite bearing ureilites show little variation in fo 74 76 but significant variation in cr valence while the non chromite bearing ureilites show significant variation in fo 77 95 and little variation in cr valence these groups are unrelated to petrologic type i e olivine pigeonite olivine orthopyroxene or augite bearing the chromite bearing ureilites also have lower contents of cr in olivine than most non chromite bearing ureilites consistent with predictions based on cr olivine melt partitioning in spinel saturated vs non spinel saturated systems under the assumption that at magmatic temperatures graphite gas equilibria controlled fo2 at all depths on the ureilite parent body we conclude 1 that ureilite precursor materials having the fo and cr valence properties now observed in ureilites are unlikely to have been preserved during planetary processing and 2 that the fo and cr valence properties now observed in ureilites are consistent with having been established by high temperature carbon redox control over a range of depths on a plausible sized ureilite parent body the apparent limit on ureilite fo values around 74 76 suggests that the precursor material s had bulk mg that of ll chondrites

characterization of low temperature pyroclastic surges that occurred in the northeastern japan arc during the late 19th century abstract three eruption events occurring in the central part of the northeastern japan arc were investigated and compared adatara ad1900 zao ad1895 and bandai ad1888 producing low temperature lt pyroclastic surges these events are characterized by steam eruptions ejecting no juvenile material these eruptions well preserved eruptive deposits and facies facilitated granulometric analyses of the beds which revealed the transport and deposition mechanisms of lt surges combining these results with those of investigations of documents reporting the events we correlated each eruption to the relevant individual bed and reconstructed the lt surge development sequence important findings related to the transport and deposition modes are the following 1 bed sets consisting of thin laminated ash and its overlying thick massive tuff were recognized in the adatara 1900 proximal deposits the bed set was probably produced by a strong wind that discharged and propagated quickly from the vent leading wind and a gravitationally segregated highly concentrated flow originated from the eruption column within a discrete eruption episode a similar combination might have occurred during the first surge of the bandai 1888 event 2 comparison of the proximal and distal facies for the largest eruption of adatara 1900 event indicates that the initial turbulence of the eruption cloud decreased rapidly transforming into a density stratified surge with a highly concentrated part near the base similar surges occurred in the climatic stage of zao 1895 3 bandai 1888 ejecta indicate massive beds deposited preferentially at topographic lows co occurring planar beds showed no topographic affection as indicated by the topographic blocking of a stratified surge the observed facies massive tuffs crudely stratified tuffs and thin bedded tuffs are compatible with those for high temperature surges at bandai absence of dune bedded tuffs and commonly poorer sorting in the lt surge deposits might be attributable to poor thermally induced turbulence of eruption columns condensation of vapor in the surges might have contributed to the poor sorting the estimated explosion energies were 6 10 13 j for adatara ad1900 6 5 10 10 j for zao ad1895 and 6 5 10 15 j for bandai ad1888 implying that the three events were hydrothermal eruptions with distinctive eruptive mechanisms regarding eruption sources the adatara 1900 event was caused solely by thermal energy of the hydrothermal fluid although magma intrusion likely triggered evolution of hydrothermal systems at zao in 1895 steam eruptions in the bandai 1888 event occurred simultaneously with sudden exposure of the hydrothermal system whose triggers require no internal energy

femgmn relations of ureilite olivines and pyroxenes and the genesis of ureilites abstract the fe mn fe mg relations of published microprobe analyses of ureilite olivine cores suggest that feo reduction in the magmatic stage was important in the genesis of some of these meteorites consideration of mg mn and fe mn partitioning between olivine and pigeonite cores shows that these two phases are not in equilibrium the data are consistent with combined fractional crystallization and feo reduction being the major processes of ureilite genesis few if any of the analyzed ureilites are consistent with a partial melting residue model

si bearing metal and niningerite in almahata sitta fine grained ureilites and insights into the diversity of metal on the ureilite parent body a detailed mineralogical and chemical study of almahata sitta fine grained ureilites ms 20 ms 165 ms 168 was performed to shed light on the origin of these lithologies and their sulfide and metal the almahata sitta fine grained ureilites silicates 0 5 mn fe 0 5s with some similarities to the mineralogy of enstatite e chondrites overall metal grains show a large compositional variability in ni and si concentrations niningerite grains probably formed as a by product of smelting via sulfidation the large si ni variation in fine grained ureilite metal could be the result of variable degrees of reduction during impact smelting inherited from coarse grained ureilite precursors or a combination of both large si bearing metal grains probably formed via coalescence of existing and newly formed metal during impact smelting bulk and in situ siderophile trace element abundances indicate three distinct populations of 1 metal crystallized from partial melts in ms 20 2 metal resembling bulk chondritic compositions in ms 165 and 3 residual metal in ms 168 almahata sitta fine grained ureilites developed their distinctive mineralogy due to severe reduction during smelting despite the presence of e chondrite and ureilite stones in the almahata sitta fall a mixing relation of e chondrites or their constituents and ureilite material in almahata sitta can be ruled out based on isotopic textural and mineral chemical reasons

experimental constraints on ureilite petrogenesis abstract this experimental study explores the petrogenesis of ureilites by a partial melting smelting process experiments have been performed over temperature 1150 1280 c pressure 5 12 5 mpa and low oxygen fugacity graphite co gas conditions appropriate for a hypothetical ureilite parent body 200 km in size experimental and modeling results indicate that a partial melting smelting model of ureilite petrogenesis can explain many of the unique characteristics displayed by this meteorite group compositional information preserved in the pigeonite olivine ureilites was used to estimate the composition of melts in equilibrium with the ureilites the results of 20 experiments saturated with olivine pyroxene metal and liquid with appropriate ureilite compositions are used to calibrate the phase coefficients and pressure temperature dependence of the smelting reaction the calibrated coefficients are used to model the behavior of a hypothetical residue that is experiencing fractional smelting the residue is initially olivine rich and smelting progressively depletes the olivine content and enriches the pyroxene and metal contents of the residues the modeled residue composition at 1260 c best reproduces the trend of ureilite bulk compositions the model results also indicate that as a ureilite residue undergoes isothermal decompression smelting over a range of temperatures ca al values and cr 2 o 3 contents are enriched at lower temperatures below 1240 c and tend to decrease at higher temperatures therefore fractional smelting can account for the high ca al and cr 2 o 3 wt values observed in ureilites we propose that ureilites were generated from an olivine rich cpx bearing residue smelting began when the residue was partially melted and contained liquid olivine and carbon these residues experienced varying degrees of fractional smelting to produce the compositional variability observed within the pigeonite bearing ureilites variations in mineral composition modal proportions and isotopic signatures are best described by heterogeneous accretion of the ureilite parent body followed by minimal and variable degrees of igneous processing

calibration of glacier volume area relations from surface extent fluctuations and application to future glacier change the volume and area change evolution of glaciers can be obtained by employing the volume area scaling approach during mass balance modelling this method usually requires information on the initial surface area and ice volume to adjust the volume area relation to the specific ice body however absolute volumetric data on glaciers are very rare so the applicability of volume area scaling is limited in order to use volume area scaling on glaciers for which only limited information is available a new method is presented to calibrate the volume area relation without prior knowledge of this relation by using glacier extent information from different times to validate the method and illustrate its practicability we model the range of probable future changes in ice volume and surface area of glaciar noroeste an outlet glacier of gran campo nevado ice cap southern chilean patagonia during the 21st century based on ipcc sres scenarios b1 and a2

evidence for oxidizing conditions in the solar nebula from mo and w depletions in refractory inclusions in carbonaceous chondrites abstract depletions of mo and w relative to other refractory metals of similar volatility re os ir ru pt are common in a suite of 16 ca al rich inclusions cais from 5 carbonaceous chondrites twelve of the 16 cais from allende grosnaja leoville and ornans show mo depletions six of these 12 inclusions also show w depletions the one cai analyzed from the essebi chondrite shows no depletions the mo and w depletions have a very characteristic pattern with mo always more depleted than w the same mo and w depletion pattern occurs in calculated refractory metal alloy compositions formed at oxygen fugacities 10 3 to 10 4 times greater than the canonical solar nebula oxygen fugacity we conclude that mo and w depletions are common in cais from carbonaceous chondrites and that the depletions result from high temperature oxidation the oxidation may have occurred during the evaporation of primitive dust into cais but is also consistent with condensation at high oxygen fugacities no potential alternative processes appear to be capable of producing the observed mo and w depletion patterns

metallic phases and siderophile elements in main group ureilites implications for ureilite petrogenesis abstract metallic phases and siderophile elements are critical to understanding the petrogenesis of the enigmatic ureilite meteorites we obtained petrographic major and minor element and the first in situ trace element data for metallic phases metal sulfides phosphide carbide in 24 main group ureilites of various petrographic types with fo 75 95 the most abundant type of metal 1 3 vol occurs as 10 40 m wide strips along silicate grain boundaries ni contents of this metal range from 0 to 7 3 wt and are correlated with co among all samples ni co 0 64 ci a less abundant type of metal occurs as 5 150 m diameter metallic spherules consisting of cohenite fe 3 c metal phosphide and sulfide enclosed in silicates preferentially low ca pyroxene most samples contain 2 types of sulfide 1 low cr 2 s 4 and troilite abundances of 17 mostly siderophile elements were measured by la icp ms in grain boundary metal spherules graphite sulfides and silicates average compositions of grain boundary metal in 10 samples show decreasing ci normalized abundance with increasing volatility interrupted by depletions in w mo ni and zn and enrichments in au as ga and ge ci normalized os abundances range from 2 to 65 and are correlated with increasing os pt os ni and os pd ratios ci normalized pt os ratios range from 0 3 to 1 bulk cohenite bearing spherules have siderophile element abundances indistinguishable from those of grain boundary metal in the same sample ci normalized patterns of most siderophile elements in the metal are within error identical to those of the bulk rock at 25 40 higher abundances in each sample there are no correlations between siderophile element abundances and fo we infer that at t 1200 c ureilites contained immiscible fe c 3 4 wt c and fe s melts small samples of which were trapped as the spherules within silicates the fe s melt was largely extracted from the rocks and the bulk of the residual fe c melt is now represented by the grain boundary metal assuming that ureilite precursor materials had ci or cv abundances of siderophile elements the large fractionations of hse observed in metal in 7 of the 10 samples require extremely high degrees 98 of batch fe s melt extraction which implies very high x fes wt fes fe fes in the precursors furthermore at such high degrees of fractionation the hse are so strongly concentrated into the residual metal that to match their relatively low absolute abundances in the ureilite metal very high initial metal contents are required together these constraints would imply that ureilite precursors had abundances of fe metal and fes 20 35 wt each far exceeding those of known cc or oc these requirements could be relaxed permitting lower more plausible degrees of melting and lower initial metal and sulfide abundances if ureilite precursors were volatile depleted to a greater extent than bulk cv we suggest that ureilite precursors contained to various degrees an overabundance relative to chondrites of refractory enriched material such as cais excess cais could also account for observed depletions of w and mo otherwise difficult to explain in the ureilite metal and lead to the observed range of siderophile element patterns and abundances among samples such a model can potentially explain the lack of correlation between siderophile element abundances and feo or olivine fo and reconcile the metal and siderophile element data with a redox model for ureilite petrogenesis

shock post shock annealing and post annealing shock in ureilites the thermal and shock histories of ureilites can be divided into four periods 1 formation 2 initial shock 3 post shock annealing and 4 post annealing shock period 1 occurred 4 55 ga ago when ureilites formed by melting chondritic material impact events during period 2 caused silicate darkening undulose to mosaic extinction in olivines and the formation of diamond lonsdaleite and chaoite from indigenous carbonaceous material alkali rich fine grained silicates may have been introduced by impact injection into ureilites during this period about 57 of the ureilites were unchanged after period 2 during period 3 events impact induced annealing caused previously mosaicized olivine grains to become aggregates of small unstrained crystals some ureilites experienced reduction as feo at the edges of olivine grains reacted with c from the matrix annealing may also be responsible for coarsening of graphite in a few ureilites forming euhedral appearing idioblastic crystals orthopyroxene in meteorite hills met 78008 may have formed from pigeonite by annealing during this period the rb sr internal isochron age of 4 0 ga for met 78008 probably dates the annealing event at this late date impacts are the only viable heat source about 36 of ureilites experienced period 3 events but remained unchanged afterwards during period 4 7 of the ureilites were shocked again as is evident in the polymict breccia elephant moraine eet 83309 this rock contains annealed mosaicized olivine aggregates composed of small individual olivine crystals that exhibit undulose extinction ureilites may have formed by impact melting chondritic material on a primitive body with heterogeneous o isotopes plagioclase was preferentially lost from the system due to its low impedance to shock compression brief melting and rapid burial minimized the escape of planetary type noble gases from the ureilitic melts incomplete separation of metal from silicates during impact melting left ureilites with relatively high concentrations of trace siderophile elements

experimental determination of crystal melt partitioning of ga and ge in the system forsterite anorthite diopside the crystal liquid partitioning of ga and ge has been measured experimentally between forsterite diopside anorthite and spinel and melts in the pseudoternary system forsterite anorthite diopside at one atmosphere pressure and 1300 c gallium is incompatible with forsterite and diopside d ga 0 024 and 0 19 respectively is only slightly incompatible in anorthite d ga 0 86 and is highly compatible in spinel d ga 4 6 the partition coefficient for ge is within a factor of two of unity for forsterite diopside and anorthite d ge 0 62 1 4 and 0 51 respectively but ge is incompatible in spinel d ge 0 1 the coefficients for the exchange of ga and al and the exchange of ge and si between minerals and melts generally are within a factor of two of unity as is expected from the geochemical coherence of these element pairs in natural samples the application of our results to the interpretation of natural basaltic and mantle samples from the earth and basalts from the moon and the shergottite parent body demonstrates that it is possible to discriminate between different mantle source compositions using ga al and ge si ratios the ge variation among lunar mare basalts may be indicative of a heterogeneous lunar mantle the substantial depletion of ge in chassigny relative to the other snc meteorites may be evidence of either a heterogeneous shergottite parent body spb mantle or of different geochemical behavior for ge in the spb