comment on the origin of eucrites diogenites and olivine diogenites magma ocean crystallization and shallow magma processes on vesta by b e mandler and l t elkins tanton mandler and elkins tanton 2013 recently proposed an upgraded magma ocean model for the differentiation history of the giant asteroid 4 vesta they show that a combination of both equilibrium crystallization and fractional crystallization processes can reproduce the major element compositions of eucritic melts and broadly the range of mineral compositions observed in diogenites they assert that their model accounts for all the howardites eucrites and diogenites heds and use it to predict the crustal thickness and the proportions of the various lithologies here we show that their model fails to explain the trace element diversity of the diogenites contrary to their claim the diversity of the heavy ree enrichment exhibited by the orthopyroxenes in diogenites is inconsistent with crystallization of these cumulates in either shallow magma chambers replenished by melts from a magma ocean or in a magma ocean thus proportions of the various hed lithologies and the crustal thickness predicted from this model are not necessarily valid

geochemistry of diogenites still more diversity in their parental melts we report on the major and trace element abundances of 18 diogenites and o isotopes for 3 of them our analyses extend significantly the diogenite compositional range both in respect of mg rich e g meteorite hills met 00425 mgo 31 5 wt and mg poor varieties e g dhofar 700 mgo 23 wt the wide ranges of siderophile and chalcophile element abundances are well explained by the presence of inhomogeneously distributed sulfide or metal grains within the analyzed chips the behavior of incompatible elements in diogenites is more complex as exemplified by the diversity of their ree patterns apart from a few diogenite samples that contain minute amounts of phosphate and whose incompatible element abundances are unlike the orthopyroxene ones the range of incompatible element abundances and particularly the range of dy yb ratios in diogenites is best explained by the diversity of their parental melts we estimate that the feo mgo ratios of the diogenite parental melts range from about 1 4 to 3 5 and therefore largely overlap the values obtained for non cumulate eucrites our results rule out the often accepted view that all the diogenites formed from parental melts more primitive than eucrites during the crystallization of a magma ocean instead they point to a more complex history and suggest that diogenites were derived from liquids produced by the remelting of cumulates formed from the magma ocean

chemical characteristics and origin of h chondrite regolith breccias abstract we report petrologic data and contents of ag bi cd co cs ga in rb se te tl and zn trace elements spanning the volatility mobility range in light and dark portions of h chondrite regolith breccias and l chondrite fragmental breccias the chemical petrologic characteristics of h chondrite regolith breccias differ from those of non brecciated chondrites or fragmentai breccias petrologic characteristics and at least some trace element contents of h chondrite regolith breccias reflect primary processes contents of the most volatile mobile elements may reflect either primary or secondary processing possibly within layered h chondrite parent object s chemical petrologic differences existed in different regions of the parents regolith formation and gardening and meteoroid compaction were not so severe as to alter compositions markedly

the metamorphic history of eucrites and eucrite related meteorites and the case for late metamorphism we report induced thermoluminescence tl data for separates from three howardite eucrite and diogenite hed meteorites and the vaca muerta mesosiderite the results of thermal modeling of the surface of their parent body are also described the tl sensitivities for matrix samples from the lew 85300 302 and 303 paired eucrites and the bholghati howardite are lower than the tl sensitivities for the clasts which is consistent with regolith working of the matrix in fairly mature regoliths within an isochemical series of hed meteorites tl sensitivity reflects metamorphic intensity but clast to clast variations in the tl sensitivities of the vaca muerta mesosiderite and clasts in the eet 87509 513 and 531 paired howardite primarily reflect differences in mineralogy and petrology thermoluminescence peak temperatures indicate that all the components from the lew 85300 302 and 303 paired eucrites experienced a reheating event involving temperatures 800 c which is thought to have been due to impact heating and therefore that the event was concurrent with or postdated brecciation the vaca muerta clasts are essentially unmetamorphosed but the induced tl data indicate that the remaining howardite eucrite dioenite and mesosiderite hedm meteorites experienced metamorphism to a variety of intensities but involving temperatures 800 c cause a change in tl peak temperature feldspars from a variety of terrestrial and extraterrestrial sources show this behavior and x ray diffraction and kinetic studies suggest that it is indirectly related to al si disordering cooling rates are not consistent with autometamorphism following the initial igneous event or with heating by subsequent eruptions of lava onto the surface of the hed parent body instead our thermal models suggest that the metamorphism occurred within a regolith ejecta blanket of up to a few kilometers thick with different levels of metamorphism corresponding to different thicknesses of blanket between essentially 0 and 2 km rather than different burial depths in a regolith of uniform thickness we argue that metamorphism occurred 3 9 ga ago and was associated with the resetting of the ar ar system for the hed meteorites

partition coefficients for calcic plagioclase implications for archean anorthosites by the use of a multiple aliquot technique combined with statistical calculations to overcome effects of alteration and contamination we have determined partition coefficients d s for rare earth elements rees between natural high ca plagioclase megacrysts and their basaltic matrices some of the basalts that we investigated are shown experimentally to crystallize only high ca plagioclase over approximately a 20 30 c temperature interval below the liquidus the ree d s agree well with experimentally determined values and predict equilibrium melts for archean anorthosites that agree well with coeval basaltic flows and dikes furthermore the d s appear to be valid for both tholeiitic and alkali basalts over a range of mg numbers 34 58 and ree concentrations la from 3 50 ppm similarly calculated d s for co sc cr rb sr cs ba hf ta and th also predict equilibrium melts for anorthosites that agree reasonably well with coeval basaltic flows and dikes the apparent values for co sc and ta seem good to better than 50 whereas the standard deviations for rb and th are equal to their means making the d s of questionable value the others are useful probably to within a factor of 2 experimental studies of the d for total fe as feot indicate a value of about 04 at an oxygen fugacity slightly below that of the qfm buffer a by product of the feot experiments was the experimental d s for mgo tio2 and k2o which could be compared with the d s from natural assemblages from the d s that were determined we suggest that plagioclase megacrysts in the bad vermilion lake anorthosite were in equilibrium with melts having the composition of tholeiitic basalts at an oxygen fugacity slightly below the qfm buffer the predicted melts have an feot content of about 13 k2o of about 15 tio2 of about 1 3 a chondrite normalized ree pattern that is nearly flat at 10 to 20 chondrites with a slight depletion of lrees other incompatible trace elements at 10 to 20 chondrites and cr and co at 0 01 to 0 1 chondrites this range of compositions is essentially identical to the tholeiitic flows and dikes in archean greenstone belts we therefore suggest that the moderately fe rich tholeiites that are hosts to plagioclase megacrysts in greenstone belts form the parental melts for megacrysts which make up the bad vermilion lake anorthositic complex and probably other similar archean anorthositic complexes

crustal partial melting on vesta evidence from highly metamorphosed eucrites we have performed a mineralogical and geochemical study of eight metamorphosed basaltic eucrites these are classified into granulitic eucrites and type 4 7 eucrites on the basis of their textures and pyroxene mineralogy and display mineralogical evidence for high temperature metamorphism including partial melting in particular rare earth element ree patterns of a number of the eucrites studied show varying degrees of light ree depletion due to partial melting with subsequent melt extraction a simple correlation between metamorphic grade as deduced from pyroxene mineralogy and the degree of light ree depletion was not detected this can be explained by the fact that homogenization exsolution and inversion of pigeonite would have required prolonged heating at moderate temperatures not vert similar800 1000 c whereas partial melting would have taken place over a short time interval where temperatures exceeded that of the solidus the eucrites studied therefore record a two stage thermal regime consisting of short high temperature reheating events superimposed on long duration global crustal metamorphism the short reheating events may have been caused by impact events and or intrusions of hot magmas the results of this study demonstrate that the thermal history of eucritic crust was more complex than can be explained by a simple burial model alone in particular the origin of stannern trend eucrites requires contamination of main group magmas by partial melts extracted from residual eucrites

postcumulus processes in layered intrusions during the postcumulus stage of solidification in layered intrusions fluid dynamic phenomena play an important role in developing the textural and chemical characteristics of the cumulate rocks one mechanism of adcumulus growth involves crystallization at the top of the cumulate pile where crystals are in direct contact with the magma reservoir convection in the chamber can enable adcumulus growth to occur to form a completely solid contact between cumulate and magma another important process may involve compositional convection in which light differentiated melt released by intercumulus crystallization is continually replaced by denser melt from the overlying magma reservoir this process favours adcumulus growth and can allow adcumulus growth within the pore space of the cumulate pile calculations indicate that this process could reduce residual porosities to a few percent in large layered intrusions but could not form pure monomineralic rocks intercumulus melt may also be replaced by more primitive melt during episodes of magma chamber replenishment dense magma emplaced over a cumulate pile containing lower density differentiated melt may sink several metres into the underlying pile in the form of fingers reactions between melt and matrix may lead to changes in mineral compositions mineral textures and whole rock isotope compositions another important mechanism for forming adcumulate rocks is compaction in which the imbalance of the hydrostatic and lithostatic pressures in the cumulate pile causes the crystalline matrix to deform and intercumulus melt to be expelled for cumulate layers from 10 to 1000 metres in thickness compaction can reduce porosities to very low values 1 and form monomineralic rocks the characteristic time scale for such compaction is theoretically short compared to the time required to solidify a large layered intrusion during compaction changes of mineral compositions and texture may occur as moving melts interact with the surrounding matrix both compaction and compositional convection can be interrupted by solidification in the pore spaces compositional convection will only occur if the rayleigh number is larger than 40 if the residual melt becomes lower in density and the convective velocity exceeds the solidification velocity measured by the rate of crystal accumulation in the chamber orthocumulates are thus more likely to form in rapidly cooled intrusions where residual melt is frozen into the pore spaces before it can be expelled by compaction or replaced by convection

mineralogical records of early planetary processes on the howardite eucrite diogenite parent body with reference to vesta abstract mineralogical information recovered from the howardite eucrite diogenite hed meteorites was employed to reconstruct the history of the parent body and relate it to 4 vesta these interpreted crustal evolution processes were then compared to the expected geological features on the surface of a likely proto planet 4 vesta the original crustal materials of the hed parent body were preserved as mineral grains and lithic clasts but in many eucrites fe mg ratios in pyroxenes were homogenized by diffusion after crystallization the crystallization trend of the protocrust has been deciphered by 1 examining monomict and crystalline samples and using their mineralogical and chemical information to formulate a sequence of crystallization and cooling trends and by 2 reconstructing the original crust prior to cratering events from lithic clasts and mineral fragments in polymict breccias such as howardites and polymict eucrites mineral components are identical both in the individual hed and in polymict breccias and no remnants of primitive materials were preserved in the polymict breccias a layered crust model reconstructed from such breccias consists of an upper crust with extrusive lava like eucrites that have been brecciated and metamorphosed diogenite mantle and cumulate eucrites of varying thickness between them this model can be used to explain the surface geological features of vesta observed from the hubble space telescope a large crater with diogenitic orthopyroxene at the crater floor is consistent with the deepest diogenitic layer of the layered crust model and an underlying olivine layer is expected from early crystallized olivine in the crystal fractionation model the old terrain of eucritic surface materials of vesta can be howardites polymict eucrites or regolith like eucrites produced from eucrites extruded and impacted on the surface partial melting models of eucrites seem to be favored by the rare earth element ree chemistry and experimental studies unfortunately partial melting models have not demonstrated how the hed parent body is converted to a layered crust without producing any metamorphosed primitive material in the layered crust the origin of cumulate eucrites with systematic variation of textures and chemistries of pyroxene can be explained by the layered crust model with excavation and mixing of trapped liquid discovery of basaltic materials with na rich plagioclase and augite in iron meteorites which are the products of partial melting suggests that eucrites may be unique to a body that underwent large scale differentiation and metamorphism

zonal and vertical structure of the madden julian oscillation abstract a statistical study of the three dimensional structure of the madden julian oscillation mjo is carried out by projecting dynamical fields from reanalysis and radiosonde data onto space time filtered outgoing longwave radiation olr data mjo convection is generally preceded by low level convergence and upward motion in the lower troposphere while subsidence cooling and drying prevail aloft this leads to moistening of the boundary layer and the development of shallow convection followed by a gradual and then more rapid lofting of moisture into the middle troposphere at the onset of deep convection after the passage of the heaviest rainfall a westerly wind burst region is accompanied by stratiform precipitation where lower tropospheric subsidence and drying coincide with continuing upper tropospheric upward motion the evolution of the heating field leads to a temperature structure that favors the growth of the mjo the analysis also reveals distinct differences in the vertical structure

photomosaics of the cathodoluminescence of 60 sections of meteorites and lunar samples 1 cathodoluminescence cl petrography provides a means of observing petrographic and compositional properties of geological samples not readily observable by other techniques we report the low magnification cl images of 60 sections of extraterrestrial materials the images we report include ordinary chondrites including type 3 ordinary chondrites and gas rich regolith breccias enstatite chondrites co chondrites and a cm chondrite eucrites and a howardite lunar highland regolith breccias and lunar soils the cl images show how primitive materials respond to parent body metamorphism how the metamorphic history of el chondrites differs from that of eh chondrites how dark matrix and light clasts of regolith breccias relate to each other how metamorphism affects eucrites the texture of lunar regolith breccias and the distribution of crystallized lunar spherules lunar chondrules and how regolith working affects the mineral properties of lunar soils more particularly we argue that such images are a rich source of new information on the nature and history of these materials and that our efforts to date are a small fraction of what can be done

composition and classification of clasts in the st mesmin ll chondrite breccia abstract seven samples of the unique st mesmin meteorite have been analyzed by instrumental and radiochemical neutron activation analysis for na ca sc cr mn fe co ni zn ga ge se in sm yb ir and au st mesmin is unique in being the only ordinary chondrite known to contain an unmelted xenolith of another ordinary chondrite data for two host matrix samples and three light clasts are consistent with their classification as ll chondrite material the composition of the large dark xenolith confirms earlier evidence that it is an h chondrite volatile abundances are consistent with it being highly shocked petrologic type 4 material in an olivine microporphyry siderophile abundances are mostly about 0 13 times ll abundances an apparent indication of metal loss during the shock melting which produced the clast as in other regolithic chondrites the dark host has higher contents of highly volatile elements than do the light clasts we suggest that this results from a combination of differences in intensity of preexisting metamorphism as well as a redistribution of volatiles during regolith gardening the h group xenolith in st mesmin is a relatively recent addition to the parent body

petrogenesis of the zagami meteorite inferences from synchrotron x ray sxrf microprobe and electron microprobe analyses of pyroxenes abstract the zagami meteorite is a shergottite a basalt rich in pigeonite augite and maskelynite glass shocked plagioclase it is one of the snc meteorites which are inferred to have formed on mars major and minor element abundances in pyroxene principally pigeonite from newly available unm samples were determined by electron microprobe abundances of trace elements ni cu zn and ga were obtained by synchrotron x ray sxrf microprobe many pigeonite grains have normally zoned rims and reversely zoned cores so that the most magnesian pigeonite forms rings or annuli in thin section view in three dimensions the most magnesian pigeonite may form tubes or hourglass shapes the cores commonly contain magmatic inclusions other pigeonites have irregular or multiple magnesian regions with magmatic inclusions among and between them abundances of ni and cr in the magnesian zones and cores are partially decoupled from abundances of other compatible mg and incompatible fe ti elements the textures chemical zoning and element decouplings in the pigeonites are consistent with igneous crystal growth at moderate cooling rates not isothermally or near equilibrium from element partitioning and mass balance the unm zagami is estimated to contain 20 5 or less cumulus pyroxene half augite and half pigeonite half the proportion suggested by equilibrium distribution of fe mg between pigeonite and melt this inconsistency may be resolved if all pigeonite melt element partitioning was affected by the rapid growth of the pigeonites the composition of the parental magma for the unm zagami calculated by mass balance on bulk and pyroxene compositions is similar to the 1170 c melt of the bmnh zagami not the 1140 c melt inferred as parental by other workers the inference that the pyroxene zoning patterns reflect only magmatic events is consistent with an igneous age of 180 m y for zagami

composition and origin of nuevo laredo trend eucrites new bulk rock analyses are reported for the eucritic meteorites alha81001 lakangaon and nuevo laredo alha81001 resembles ibitira as both have far lower concentrations of na than any other eucrite lakangaon and nuevo laredo are the two most ferroan low mgfe of all eucrites monomict eucrites have previously been divided into three geochemical classes a main group and the nuevo laredo and stannern trends the nuevo laredo trend which is characterized by limited variations of incompatible element contents despite considerable variations in mg mg fe ratio and v content clearly formed out of melt s undergoing fractional crystallization probably as partial cumulates the less distinctive main group eucrites are often assumed to be primary basalts geochemically but one step equilibrium partial melting removed from the bulk composition of the eucrite parent asteroid this partial melting model seems more appropriate for the stannern trend which is characterized by moderate high mg mg fe despite moderate high incompatible element contents our new data and a review of literature data suggest that most of the so called main group eucrites actually belong to the nuevo laredo trend while few if any belong to the stannern trend or any other partial melting trend the nuevo laredo trend may be part of a series of fractional crystallization products that began with orthopyroxenite cumulates diogenites the bulk mgo mgo feo ratio of the eucrite parent asteroid is generally estimated at 0 67 by assuming that typical eucrites are primary basalts but if typical eucrites are diogenite comagmatic fractional crystallization products the bulk mgo mgo feo of the parent asteroid must be considerably higher probably about 0 81

ocean temperature and salinity components of the madden julian oscillation observed by argo floats new diagnostics of the madden julian oscillation mjo cycle in ocean temperature and for the first time salinity are presented the mjo composites are based on 4 years of gridded argo float data from 2003 to 2006 and extend from the surface to 1 400 m depth in the tropical indian and pacific oceans the mjo surface salinity anomalies are consistent with precipitation minus evaporation fluxes in the indian ocean and with anomalous zonal advection in the pacific the argo sea surface temperature and thermocline depth anomalies are consistent with previous studies using other data sets the near surface density changes due to salinity are comparable to and partially offset those due to temperature emphasising the importance of including salinity as well as temperature changes in mixed layer modelling of tropical intraseasonal processes the mjo forced equatorial kelvin wave that propagates along the thermocline in the pacific extends down into the deep ocean to at least 1 400 m coherent statistically significant mjo temperature and salinity anomalies are also present in the deep indian ocean

the perils of partition difficulties in retrieving magma compositions from chemically equilibrated basaltic meteorites abstract the chemical compositions of magmas can be derived from the compositions of their equilibrium minerals through mineral magma partition coefficients this method cannot be applied safely to basaltic rocks either solidified lavas or cumulates which have chemically equilibrated or partially equilibrated at subsolidus temperatures i e in the absence of magma applying mineral melt partition coefficients to mineral compositions from such rocks will typically yield magma compositions that are strongly fractionated and unreasonably enriched in incompatible elements e g rees in the absence of magma incompatible elements must go somewhere they are forced into minerals e g pyroxenes plagioclase at abundance levels far beyond those established during normal mineral magma equilibria further using mineral magma partition coefficients with such rocks may suggest that different minerals equilibrated with different magmas and the fractionation sequence of those melts i e enrichment in incompatible elements may not be consistent with independent constraints on the order of crystallization subsolidus equilibration is a reasonable cause for incompatibleelement enriched minerals in some eucrites diogenites and martian meteorites and offers a simple alternative to petrogenetic schemes involving highly fractionated magmas or magma infiltration metasomatism

the irradiation history of the ghubara l5 regolith breccia we measured cosmic ray products noble gases radionuclides thermoluminescence and nuclear tracks and trace element contents and mineralogy of samples of three orthogonal and mutually intersecting cores 41 46 cm long of a 101 6 kg ghubara individual 1958 805 at the natural history museum london the xenoliths like the host have high concentrations of trapped solar gases and are heavily shocked while contents of noble gases and degree of shock loading in this individual and three others differ somewhat the data indicate that ghubara is a two generation regolith breccia contents of cosmogenic 26al and 10be and low track densities indicate that the ghubara individuals were located more than 15 cm below the surface of an 85 cm meteoroid because of its large size ghubara s cosmic ray exposure age is poorly defined to be 15 20 ma from cosmogenic nuclides ghubara s terrestrial age based on 14c data is 2 3 ka not only is ghubara the first known case of a 2 generation regolith breccia on the macro scale it also has a complicated thermal and irradiation history

propagation and initiation mechanisms of the madden julian oscillation 1 an observational study of the propagation and onset mechanisms of the madden julian oscillation mjo is performed using cyclostationary empirical orthogonal function analysis and a kelvin rossby wave decomposition method for the noaa outgoing longwave radiation and the ncep ncar reanalysis data in these analyses two different regions of surface convergence are observed ahead of mjo convection by different wind components as previously found in a sst coupled gcm simulation at the leading edge of enhanced convection the friction induced meridional convergence appears during the developing phase when the enhanced convection is located over the indian ocean and the maritime continents another region of surface convergence is identified just east of an enhanced convection core and this tends to pull the convective core to the east the surface convergence is formed by zonal wind convergence and kelvin and rossby waves both play a comparable role in the formation of the convergence zone therefore the frictional kelvin rossby wave cisk conditional instability of the second kind is regarded as a primary factor for the eastward propagation of the mjo over the western indian ocean moistening in the boundary layer occurs 2 weeks earlier than the beginning of a new mjo cycle this moistening accompanies low level convergence by encircling kelvin waves which propagated from the region of enhanced convection during the previous cycle as well as by rossby waves generated from the region of reduced convection over the indian ocean this earlier formation of the boundary layer moisture convergence provides a favorable environment for triggering new convection this interaction of kelvin and rossby waves also accounts for the suppression of convection from the western side of the convection core for example over the indian ocean anomalous surface divergence appears at the western edge of the enhanced convection due to both circumnavigating kelvin waves from the region of reduced convection of the previous cycle and rossby waves from the region of the enhanced convection itself thus the mjo is a self maintaining and self generating form of tropical variability through the interaction between convection and large scale circulation in the presence of boundary layer dynamics

thermoluminescence constraints on the metamorphic shock and brecciation history of basaltic meteorites abstract induced thermoluminescence measurements have been performed on eighteen eucrites thirteen howardites plus seven splits from the bholghati howardite six diogenites and fifteen mesosiderites in order to help clarify their metamorphic shock and brecciation history the tl sensitivities of the basaltic meteorites reflect their bulk composition and the effects of 1 igneous processes diogenites and mesosiderites and 2 the mixing of materials of different compositions e g diogenitic and eucritic during brecciation howardites can be observed two previously unclassified mesosiderites lew87006 and eet87500 are assigned to class a and b respectively on the basis of their tl sensitivities the eucrites show a 15 fold range of tl sensitivities which correlate with petrographie indicators of metamorphic intensity we therefore describe a petrologic type scale based on tl and petrographie evidence where the least metamorphosed eucrites are type 1 and most equilibrated are type 8 we see no evidence for two discrete metamorphic environments corresponding to the equilibrated and unequilibrated eucrites the temperature of the dominant tl peak observed for basaltic meteorites and experiments in which four eucrites with diverse petrographie properties were annealed at various temperatures in the laboratory suggests the metamorphic equilibration temperatures for most basaltic meteorites were 800 c this estimate is generally consistent with palaeotemperatures determined from two pyroxene olivine pyroxene and oxygen isotope equilibria assuming this temperature was typical of conditions during metamorphism then burial depths for type 5 eucrites were 350 m and

achondrites and igneous processes on asteroids the possible roles of partial melting and fractional crystallization in the formation of eucrite and ureilite achondrites are discussed summarizing the results of recent petrological investigations and theoretical modeling efforts typical data are presented graphically and it is found that there is as yet no consensus on the correct model of achondrite evolution and hence no agreement on the chemistry of the parent bodies assuming that the ureilites formed as adcumulates their properties support a role for fractionation in relatively small bodies even though the magmatic composition of the ureilite parent bodies is different from that of terrestrial cumulates

the association of the evolution of intraseasonal oscillations to enso phase abstract the pacific ocean intraseasonal kelvin wave is a leading oceanic mode that links intraseasonal tropical atmospheric variations with interannual variations in the coupled ocean atmosphere system this study considers the premise that these waves may evolve differently with their associated weather patterns during different phases of el nino southern oscillation enso if atmospheric and oceanic intraseasonal modes interact and evolve differently during various stages of enso this result may provide useful information with regard to the role of these intraseasonal processes in enso evolution this work utilizes signals of the oceanic kelvin wave as a statistical basis for a simple composite averaging technique that is applied during different phases of enso to objectively analyze the evolution of oceanic and the associated portions of atmospheric intraseasonal oscillations results confirm the above premise and suggest that coupling between kelvin waves and atmospheric convection evolves differen

the genesis of diogenites and hed parent body petrogenesis abstract samples of clasts and whole rocks from eighteen of the twenty four known diogenites orthopyroxenite breccia meteorites have been studied by combined inaa empa in order to elucidate their petrogenetic history the incompatible elements a12o3 and tio2 are positively correlated in diogenite orthopyroxenes these elements determined by empa are also positively correlated with incompatible trace elements such as yb determined by inaa on bulk samples these correlations indicate that most diogenites may form a single igneous fractionation sequence the incompatible minor and trace elements are decoupled from the major elements for essentially constant mg tio2 varies by about 4 times and yb by about 8 times hence there is no strong evidence for igneous fractionation preserved in the major element composition of orthopyroxenes geothermometry calculations using two pyroxene and spinelorthopyroxene thermometers show that these phases in diogenites maintained equilibrium to temperatures in the range 650 880 c far below likely magmatic temperatures in some diogenites orthopyroxenes of differing composition are in breccia contact therefore the low equilibration temperatures were achieved in the diogenites prior to brecciation decoupling of major and trace elements was most likely caused by slow subsolidus cooling in the diogenite pluton which allowed ca fe and mg to reach diffusive equilibration incompatible trace elements likely have much lower diffusivities in orthopyroxene and therefore may have largely preserved their magmatic distributions the extensive variation in incompatible trace elements indicates that either the diogenites were formed through an extensive crystallization interval or that partition coefficients greatly increased during crystallization if the former were true one would expect to find substantial amounts of plagioclase in the diogenites if they are comagmatic with eucrites this is contrary to observations a model in which diogenites crystallized from one or more melts of approximately orthopyroxenitic composition can satisfy both the mineralogie and trace element constraints

impact of atmospheric intraseasonal oscillations on the indian ocean dipole during the 1990s abstract effects of atmospheric intraseasonal oscillations isos on the indian ocean zonal dipole mode iozdm are investigated by analyzing available observations and a suite of solutions to an ocean general circulation model namely the hybrid coordinate ocean model hycom data and model solutions for the period 1991 2000 are analyzed a period that includes two strong iozdm events during 1994 and 1997 and a weak one in 1991 both the data analysis and model results suggest that atmospheric isos play a significant role in causing irregularity of the two strong iozdm events and the premature termination of the weak one of particular interest is a basinwide wind driven oceanic resonance with a period near 90 days involving the propagation of equatorial kelvin and first meridional mode rossby waves across the basin before the onset of the strong 1997 dipole wind variability had significant power near 90 days and the resonance was strongly excited associated with the resonance was a deepened t

the thermal and radiation exposure history of lunar meteorites we have measured the natural and induced thermoluminescence tl of seven lunar meteorites in order to examine their crystallization irradiation and recent thermal histories lunar meteorites have induced tl properties similar to apollo samples of the same provenance highland or mare indicating similar crystallization and metamorphic histories macalplne hills 88104 5 has experienced the greatest degree of impact regolith processing among the highland dominated meteorites the basaltic breccia que 94281 is dominated by mare component but may also contain a significant highland component for the mare dominated meteorites eet 87521 may have a significant highland impact melt component while asuka 881757 and y 793169 have been heavily shocked the thermal history of y 793169 included slow cooling either during impact processing or during its initial crystallization our natural tl data indicate that most lunar meteorites have apparently been irradiated in space a few thousand years with most less than 15 000 a elephant moraine 87521 has the lowest irradiation exposure time being less than 1 000 a either the natural tl of alha81005 asuka 881757 and y 82192 was only partially reset by lunar ejection or these meteorites were in small perihelia orbits less than or equal to 0 7 au

the mjo kelvin wave transition 1 as the madden julian oscillation mjo moves eastward from the indian to the pacific ocean it typically accelerates becomes less strongly coupled to convection and becomes more similar to a dry kelvin wave this transition is analyzed using observations of outgoing longwave radiation and era interim reanalyses of surface pressure and 850 hpa zonal wind two individual example events as well as composites are shown the transitions are well defined with distinct disturbances on either side of the transition whose identities as mjo or kelvin waves are clear in some cases there appears to be a pre existing kelvin wave passing through the mjo from the west to the east but this feature is not apparent in the composites the transitions occur at different longitudes in different events over a wide range from the eastern indian to the central pacific oceans

the development of upper tropospheric wind over the western hemisphere in association with mjo convective initiation abstractthis study examines the structure and driving mechanisms of upper tropospheric intraseasonal zonal wind anomalies over the western hemisphere wh during the convective initiation of the madden julian oscillation mjo over the indian ocean using composite and budget analyses the initiating mjo convection is more often associated with wh upper tropospheric intraseasonal easterly wind anomalies and when it is it tends to develop a stronger and zonally broader envelope of enhanced convection than events associated with westerly wind anomalies the wh upper tropospheric zonal wind anomaly associated with the mjo is often described as a dry kelvin wave radiated from mjo convection but the results show that both the structure and driving mechanisms are different from the ones of theoretical kelvin waves unlike the theoretical kelvin wave the zonal wind anomaly is not driven mainly by the zonal pressure gradient force and it is strongly coupled with rotational wind associated with subtropical and

radar enabled recovery of the sutter s mill meteorite a carbonaceous chondrite regolith breccia doppler weather radar imaging enabled the rapid recovery of the sutter s mill meteorite after a rare 4 kiloton of tnt equivalent asteroid impact over the foothills of the sierra nevada in northern california the recovered meteorites survived a record high speed entry of 28 6 kilometers per second from an orbit close to that of jupiter family comets tisserand s parameter 2 8 0 3 sutter s mill is a regolith breccia composed of cm mighei type carbonaceous chondrite and highly reduced xenolithic materials it exhibits considerable diversity of mineralogy petrography and isotope and organic chemistry resulting from a complex formation history of the parent body surface that diversity is quickly masked by alteration once in the terrestrial environment but will need to be considered when samples returned by missions to c class asteroids are interpreted

mjo initiation in the real time multivariate mjo index abstractmadden julian oscillation mjo initiation in the real time multivariate mjo rmm index is explored through an analysis of observed case studies and composite events specific examples illustrate that both the dates of mjo initiation and the existence of the mjo itself can vary substantially among several well known mjo indices depending on whether the focus is on convection or circulation composites of primary mjo initiation events in which the rmm index rapidly increases in amplitude from a non mjo state to an mjo state are presented and are supplemented by two case studies from the 1985 86 winter season results illustrate that for primary mjo initiation events in the indian ocean rmm phase 1 slowly eastward propagating 850 hpa 200 hpa easterly westerly anomalies over the indian ocean precede the amplification of the rmm index by at least 10 days while suppressed convection over the western pacific ocean precedes the amplification by 5 days these local eastern hemispheric prede

the natural thermoluminescence of meteorites iii lunar and basaltic meteorites natural thermoluminescence tl data have been obtained for the lunar meteorite macalpine hills 88104 5 and for 65 eucrites howardites diogenites and mesosiderites in order to investigate their recent thermal and radiation histories all these meteorites have low levels of natural tl compared to chondrites which is primarily because they display anomalous fading i e fading by non classical mechanisms however some have especially low natural tl 5 krad at 250 c in the glow curve which cannot be attributed to anomalous fading or thermal fading over especially large terrestrial ages and which must reflect heating within the last 105 106 y in some cases this heating may have been associated with shock e g lew85303 or regolith processes kapoeta but in most cases bununu lowicz the diogenites alha77256 alha84001 eet79002 and maybe others solar heating at perihelia 0 8 au may be responsible for the low tl values the fraction of basaltic meteorites thought to have had small perihelia about 20 is comparable to the fraction of chondrites with low natural tl and to the fraction of observed falls and fireballs with small perihelia this may imply ejection from the asteroid belt via similar mechanisms assuming plausible values for cosmic ray dose rate and that the natural tl of mac88104 5 was totally drained by ejection from the moon the parameters for tl decay determined in the present study suggest that the moon earth transit times for mac88104 and mac88105 were 2 000 and 1 800 y respectively compared with 19 000 and 2 500 y for y791197 and alha81005 respectively although they are clearly not paired the possibility that mac88104 5 and alha81005 were ejected from the moon by the same event should be considered since diverse rock types are found in close proximity on the lunar surface the natural tl data confirm most previous published pairings among basaltic meteorites and suggest others

northern hemisphere mid winter vortex displacement and vortex split stratospheric sudden warmings influence of the madden julian oscillation and quasi biennial oscillation we investigate the connection between the equatorial madden julian oscillation mjo and different types of the northern hemisphere mid winter major stratospheric sudden warmings ssws i e vortex displacement and vortex split ssws the mjo ssw relationship for vortex split ssws is stronger than that for vortex displacement ssws as a result of the stronger and more coherent eastward propagating mjos before vortex split ssws than those before vortex displacement ssws composite analysis indicates that both the intensity and propagation features of mjo may influence the mjo related circulation pattern at high latitudes and the type of ssws a pronounced quasi biennial oscillation qbo dependence is found for vortex displacement and vortex split ssws with vortex displacement split ssws occurring preferentially in easterly westerly qbo phases the lagged composites suggest that the mjo related anomalies in the arctic are very likely initiated when the mjo related convection is active over the equatorial indian ocean around the mjo phase 3 further analysis suggests that the qbo may modulate the mjo related wave disturbances via its influence on the upper tropospheric subtropical jet as a result the mjo related circulation pattern in the arctic tends to be wave number one wave number two 25 30 days following phase 3 i e approximately phases 7 8 when the mjo related convection is active over the western pacific during easterly westerly qbo phases which resembles the circulation pattern associated with vortex displacement vortex split ssws

basaltic volcanism on the eucrite parent body petrology and chemistry of the polymict eucrite alha80102 the polymict eucrite meteorite alha80102 i s an unequilibrated breccia of basaltic and gabbroic clasts in a fragmental matrix clasts include basalts of many textural types cumulate gabbro black glass and ferroan troctolite plagioclase silica fe rich olivine ilmenite mesostasis ferroan troctolite has not been previously reported from eucrites or howardites it is interpreted as the end product of fractional crystallization of eucritic magmas bulk and trace element compositions by electron microprobe and inaa of clasts and matrix from alha80102 are similar to those of other eucrites the meteorite contains clasts similar to juvinas and to stannern a clast of cumulate eucrite gabbro is enriched in the light rare earths la lu 2xci this clast is interpreted as an unrepresentative sample of metamorphically equilibrated gabbro lree enriched magmas need not be invoked alha80102 is similar to other polymict eucrites from the allan hills and may be paired with alha76005 alha77302 and alha78040

the madden julian oscillation observed during the toga coare iop global view abstract during the toga coare intensive observing period november 1992 february 1993 two pronounced madden julian oscillation mjo events associated with super cloud clusters and westerly wind bursts were observed this paper presents a global view of the mjos including the origin of the super clusters in the indian ocean their migration into the maritime continent and the toga coare large scale soundings array lsa in the western equatorial pacific and their rapid decay over cold water of the eastern pacific the structure and evolution of the mjo are examined with emphasis on the coupling between large scale motion and convection because of differences in propagation speeds the positions of maximum zonal wind perturbations relative to deep convection undergo systematic changes during the travel of the mjo however the centers of deep convection always coincide with those of large scale ascent the super cloud cluster accompanies a wide area of warm air in the upper troposphere over the warm

reequilibration of olivine with trapped liquid in the duluth complex minnesota a 525 m long drill core ddh 221 through the partridge river intrusion in northeastern minnesota consists of mesocumulates and or orthocumulates of troctolite olivine gabbro and olivine gabbronorite the cumulus olivine whose composition fo 31 to fo 71 is a function of the amount of intercumulus liquid followed an equilibrium crystallization path with this liquid estimates of the primary magmatic compositions of the olivine are fo 57 to fo 79 none of the olivine in the drill core samples has retained an original cumulus composition i e one that was in equilibrium with the parental magma the plagioclase is strongly zoned and the cumulus cores an 59 to an 73 are thought to record crystallization from the parental magma

lithification of gas rich chondrite regolith breccias by grain boundary and localized shock melting we studied the fine grained matrices 150 m of 14 gas rich ordinary chondrite regolith breccias in an attempt to decipher the nature of the lithification process that converted loose regolith material into consolidated breccias we find that there is a continuous gradation in matrix textures from nearly completely clastic class a to highly cemented class c breccias in which the remaining clasts are completely surrounded by interstitial shock melted material we conclude that this interstitial material formed by shock melting in the porous regolith in general the abundances of solar wind implanted 4he and 20ne are inversely correlated with the abundance of interstitial shock melted feldspathic material chondrites with the highest abundance of interstitial melted material class c experienced the highest shock pressures and temperatures and suffered the most extensive degassing it is this interstitial feldspathic melt that lithifies and cements the breccias together those breccias with very little interstitial melt class a are the most porous and least consolidated

ion microprobe investigation of exsolved pyroxenes in cumulate encrites determination of selected trace element partition coefficients we have examined the partitioning of selected minor and trace elements in exsolved pyroxenes from cumulate eucrites by secondary ion mass spectrometry sims solid solid partition coefficients d s for al cr ti seven rees sr y and zr have been determined between low ca and high ca pyroxenes from moore county binda serra de mage and moama equilibrium temperatures of the co existing pyroxenes were calculated to constrain the relevant temperatures for the partition coefficients trace element abundance patterns are similar for pyroxenes from the four cumulate eucrites and thus indicate similar distribution behaviors of the trace elements during exsolution there is a significant hree enrichment over lrees in the low ca pyroxenes and abundances of the rees in augite are greater than those found in the low ca pyroxene hosts this ree behavior reflects the pyroxene crystal structures the calculated solid solid partition coefficients are found to vary systematically as expected from pyroxene crystal chemical arguments calculated subsolidus equilibration temperatures are within the expected range produced by pyroxene solvus temperature composition relations and consistent with petrographic observations of the cumulates the trace element patterns and abundances indicate that three of the four cumulates examined binda moama serra de mage were formed from the same melt or similar melts crystallizing under similar conditions in their parent body moore county has much higher trace element concentrations and this suggests that it either formed from a more evolved melt than the other three cumulates and crystallized later in the fractionation sequence or alternatively it was derived from a different melt system

determination of parental magmas of hed cumulates the effects of interstitial melts an evaluation of trapped melts effects during crystallization and subsolidus equilibration of cumulates is necessary to constrain the composition of their parental magmas in this paper a simple mass balance approach is described it allowes to estimate trace element abundances in these parental melts from phase compositions it is used to discuss the genesis of cumulate eucrites and diogenites the ree behavior is in full agreement with the view that cumulate eucrites formed from melts similar to noncumulate eucrites trapped melt fractions ranging from 10 wt for moama to 30 wt for moore county were involved the origin of diogenites is more complex the assumption that eucrites and diogenites shared the same parental melts cannot satisfactorily explain the diversity of incompatible trace element ratios e g dy yb observed in diogenitic orthopyroxenes even if interstitial melt effects are taken into account moreover some diogenites unambiguously crystallized from magmas displaying significant hree heavy rare earth elements enrichments more likely diogenites formed from distinct batches of parental magmas as previously proposed by mittlefehldt 1994 fowler et al 1995 and shearer 1997

mechanistic analysis of the suppressed convective anomaly precursor associated with the initiation of primary mjo events over the tropical indian ocean a primary madden julian oscillation mjo event is one with no immediately preceding mjo event most primary mjo events initiating over the tropical indian ocean are preceded by a local suppressed convective anomaly sca based on daily outgoing longwave radiation and atmospheric circulation reanalysis data composite analyses are performed to reveal the dynamical and thermodynamical mechanisms responsible for the generation of the precursor sca associated with anomalous descending motion during the developing stage before the maximum sca the anomalous descending motion in the upper troposphere is dynamically forced by anomalous convergence over the eastern equatorial indian ocean the anomalous convergent winds result from changes in subtropical circulation structures forced by extratropical disturbances in association with equatorward advection of positive potential vorticity in the lower troposphere the anomalous stable boundary layer with a strong thermal inversion is the dominant factor leading to descending motion the sea surface temperature sst perturbations in the tropical indian ocean are an external forcing that generates the sca through surface energy exchange the negative sst anomalies in the northwestern portion of the tropical indian ocean act as a heat sink to cool the lower tropospheric atmosphere forcing strong descending motion and forming an anomalous anticyclone north of the equator meanwhile the positive sst anomalies in the southeastern portion act as a heat source that forces anomalous divergent westerlies and northwesterlies toward the warmer sst area thus anomalous descending motion is induced around the equator

the polymict eucrites the polymict eucrites are a suite of about 14 polymict achondritic meteorites that contain at least 90 vol of eucritic material and are found both in antarctica and elsewhere they are part of a continuum of polymict breccias that includes howardites and polymict diogenites rare gas data suggest that some are gas rich regolith breccias the clasts contained in polymict eucrites sample a variety of lithologies from their parent body and include eucritic clasts alkali enriched eucrites pyroxene cumulate eucrites two pyroxene mafic rocks possibly feldspar cumulate eucrites diogenites fayalitic lithologies and a variety of other mineral clasts the eucritic clasts are probably samples of near surface lithologies on the parent body but the presence of two pyroxene mafic rocks is considered to be evidence of magmatic activity at pressures in excess of 1 kbar in the parent body partial melt models may explain some of the diversity among the clasts but cumulus processes are believed to have been important if pressures greater than 1 kbar are confirmed then the basaltic achondrite parent body bap must have a diameter in excess of 200 km the variety of lithologies suggests that not all basaltic achondrites are samples of igneous rocks formed by single stage melting of a chondritic asteroid but are instead samples of an evolved and diverse crust produced by serial magmatism

chemical and physical studies of type 3 chondrites 2 thermoluminescence of sixteen type 3 ordinary chondrites and relationships with oxygen isotopes thermoluminescence tl sensitivity values for sixteen type 3 ordinary chondrites fourteen of them from antarctica have been measured the values obtained normalized to the tl sensitivity of the dhajala meteorite range from 1 6 allan hills a77216 to 0 010 allan hills a77176 and include two reckling peak a80207 and allan hills a77176 that are particularly low they fill a hiatus in the tl distribution that previously existed between st mary s county and bishunpur the latter being a meteorite with one of the lowest tl sensitivities known the histogram of tl sensitivity values now shows a single distribution with higher values preferred it resembles the histogram for l chondrites occupying the petrologic types 3 4 5 and 6 there is a tendency for the tl sensitivity of meteorites to decrease as 18o increases equilibrated meteorites have tl sensitivities of 5 50 and 18o 4 5 to 5 0 while the most primitive meteorites with tl 0 01 have 18o 5 7 to 6 2 meteorites with intermediate tl have intermediate 18o theoretically it is possible that the range of 18o values observed may reflect progressive loss of o in the form of co at very low temperatures but very restrictive physical conditions and a complex history seem to be required

the thermoluminescence sensitivity metamorphism relationship in ordinary chondrites experimental data on the mechanism and implications for terrestrial systems hydrothermal annealing experiments have been performed on samples of the sharps meteorite in order to investigate the mechanism responsible for the metamorphism related 105 fold range in the thermoluminescence tl sensitivity in ordinary chondrites duplicate 50 mg samples of meteorite were annealed under the following conditions a 168 h at 785 c and 1 kbar b the same time temperature and pressure but with 2 wt water c 174 h at 855 c and 0 77 kbar with 2 wt water and 2 molal sodium disilicate nadisi d the same time temperature and pressure as the preceding samples but with 10 wt h2o and 2 molal nadisi samples annealed under the first three sets of conditions showed little or no change in their tl sensitivities however the samples annealed with 10 wt water and 2 molal nadisi showed a 3 to 10 fold increase in tl sensitivity and the temperature of the tl peak was suggestive of feldspar in the high temperature form we suggest that these data are consistent with the tl sensitivity metamorphism relationship in ordinary chondrites being due to the formation of the tl phosphor feldspar by the crystallization of chondrule glass

petrology of the polymict eucrite petersburg abstract the polymict eucrite petersburg contains eucritic and diogenitic materials which span a broad range of compositions the present study focuses on four eucritic clasts for which bulk compositions and mineralogical data were acquired the broad compositional range of these clasts documents the diversity of the parent regolith clast a is ree rich 26 chondrite and magnesian mg 48 7 composition of this clast can best be explained by partial melting of a source region distinctly different from that of other noncumulate eucrites composition of eucritic clast b is similar to compositions of cumulate eucrites in ree and sr abundances but it has a much lower mg than moore county clasts c and d are similar in texture mineralogy and composition to main group eucrites the presence of anomalous clast a in the same polymict breccia as typical eucrite clasts c and d emphasizes the variability of source materials from which eucritic melts were derived on the hed parent body ies after final accretion this breccia apparently was exposed to a minor episode of thermal metamorphism causing 30 m wide alteration rims around larger pyroxene fragments and causing alteration of pyroxenes at the edges of eucritic clasts this metamorphism completely altered the mg of smaller matrix pyroxenes less than 40 60 m in size to values closer to the bulk mg of the meteorite

the effect of trapped liquid crystallization on cumulus mineral compositions in layered intrusions a series of calculations have been carried out to evaluate the effect on cumulus mineral compositions of solidification of trapped intercumulus liquid in orthocumulates the calculation assumes local equilibrium between phases and that the system remains chemically closed during crystallization of the trapped liquid the latter assumption is held to be valid on a scale of tens to hundreds of centimeters it is not necessary to know the composition of the trapped liquid as the calculation only requires an estimate of feo content and trapping temperature the change in composition of a mineral from that of the initially precipitated cumulus crystals to the final composition after complete solidification is termed the trapped liquid shift its magnitude depends on the modal proportions of cumulus phases and the initial porosity and is only weakly dependent on initial phase compositions trapped liquid shifts are significant when compared with mineral composition changes occurring during fractional crystallization crystallization of 30 trapped liquid gives rise to shifts of up to 10 mol percent in mg number of olivine or pyroxene the size of the shift becomes greater when the initial cumulus assemblage has a lower total feo mgo content and vice versa as a result of the relationship between trapped liquid shift and cumulus mode mineral composition variations and trends may be generated in sequences of cumulates which originally had constant compositions of cumulus minerals for example in a cyclic unit grading from a pyroxenitic base to an anorthositic top crystallization of a uniform proportion of trapped liquid will result in an apparent iron enrichment trend from bottom to top of the cycle as has been observed in the upper critical zone of the bushveld complex

147 sm 143 nd and 176 lu 176 hf systematics of eucrite and angrite meteorites comparative planetary geochemistry provides insight into the origin and evolutionary paths of planetary bodies in the inner solar system the eucrite and angrite achondrite groups are particularly interesting because they show evidence of early planetary differentiation we present 147sm 143nd and 176lu 176hf analyses of eight noncumulate basaltic eucrites two cumulate eucrites and three angrites which together place new constraints on the evolution and differentiation histories of the crusts of the eucrite and angrite parent bodies and their mantle mineralogies the chemical compositions of both eucrites and angrites indicate similar evolutionary paths and petrogenetic models with formation and isolation of differentiated crustal reservoirs associated with segregation of ilmenite we report a 147sm 143nd mineral isochron age for the moama cumulate eucrite of 4519 34 ma mswd 1 3 this age indicates protracted magmatism within deep crustal layers of the eucrite parent body lasting up to about 50 ma after the formation of the solar system we further demonstrate that the isotopic compositions of constituent minerals are compromised by secondary processes hindering precise determination of mineral isochron ages of basaltic eucrites and angrites we interpret the changes in geochemistry and consequently the erroneous 147sm 143nd and 176lu 176hf internal mineral isochron ages of basaltic eucrites and angrites as the result of metamorphic events such as impacts effects from pressure temperature and peak shock duration on the surfaces of the eucrite and angrite parent bodies

mixing relations of the howardite eucrite diogenite suite a new statistical approach of independent component analysis for the dawn mission dawn has recently revealed that the surface of vesta is heterogeneously covered by polymictic regoliths represented by mixtures of howardite eucrite and diogenite hed meteorites mixing relations of the hed suite are examined here using a new computational statistical approach of independent component analysis ica we performed eight component ica si ti al cr fe mn mg and ca for 209 hed bulk rock compositions the ica results indicate that the hed bulk rock compositions can be reduced into three independent components ic and these ic vectors can reasonably explain compositional variation petrographic observations and the mixing relations of the hed suite the ic 1 vector represents a eucrite variation that extends from cumulate eucrite toward main group mg and incompatible element enriched eucrites the ic 2 vector represents a compositional variation of howardites that extends from diogenites to mg eucrites indicating the well known two component mixing trend of diogenite and eucrite the ic 3 vector represents a compositional variation defined by diogenites and olivine bearing diogenites suggesting mixing of olivine and orthopyroxene among the three ics the diogenite eucrite mixing trend ic 2 is most statistically robust and dominates the compositional variations of the hed suite our ica study further indicates that the combination of only three elements mg si and fe approximates the eight component ica model and that the limited number of resolvable ray spectra obtained by the dawn mission possibly discriminates olivine lithologies from the olivine free regolith breccias on the surface of vesta

chemical and physical studies of type 3 chondrites vii annealing studies of the dhajala h3 8 chondrite and the thermal history of chondrules and chondrites abstract samples of the dhajala h3 8 chondrite have been annealed for 10 hours at 600 700 800 900 and 1000 c and at 1000 c for 1 2 20 and 100 h and their thermoluminescence tl properties measured the tl sensitivity decreased by a factor of 2 after annealing at but at higher temperatures fell by an order of magnitude an abrupt increase in the temperature of the tl peak from 172 9 cto231 8 c and a steady increase in the width of the peak from 169 7 cto212 5 c were caused by the annealing treatment the tl phosphor in dhajala is thought to be feldspar predominantly in the high temperature disordered form but the present data indicate that a contribution from the low temperature form is also present and that this low temperature component is converted to the high form by the annealing treatment the low temperature feldspar is located in a few of the chondrules 20 of those separated from the meteorite which are also noteworthy for having high tl sensitivities these chondrules must have suffered greater crystallization of their mesostasis than the other chondrules and equilibrated to lower temperatures it is argued that for compositional reasons their mesostasis constituted less of a barrier to diffusion and therefore equilibration presumably the post metamorphic cooling rate of the meteorite through the stability field of the low form was slow enough to permit some crystallization and the width and temperature of the tl peaks for petrologic types 3 5 3 9 are somehow related to cooling rate based on tl there is no indication of a correlation between petrologic type and cooling rate for types 3 5 3 9 this is not consistent with a simple single internally heated meteorite parent body

chemical and physical studies of type 3 chondrites iv annealing studies of a type 3 4 ordinary chondrite and the metamorphic history of meteorites abstract samples of a type 3 4 chondrite have been annealed at 400 1000 c for 1 200 hours their thermoluminescence properties determined and analyzed for k na mn sc and ca by instrumental neutron activation analysis after annealing at 900 c the samples showed a 50 decrease in tl sensitivity while after annealing at 1000 c it fell to 0 1 0 01 times its unannealed value and loss of na and k occurred the tl and compositional changes resemble those observed for the equilibrated kernouve chondrite after similar annealing treatments except that the sharp tl decrease and element loss occurred at 1100 c this difference is presumably due to petrographic differences in the feldspar of the two meteorites the temperature and the width of the tl peak showed a discontinuous increase after annealing at 800 c peak temperature jumped from 130 to 200 c and peak width increased from 90 to 150 c the activation energies for these tl changes are 7 10 kcal mole similar increases in the tl peak temperature have been reported in tl studies of amelia va albite where they were associated with the low to high temperature transformation however the activation energy for the transformation is 80 kcal mole these changes in tl emission characteristics resemble trends observed in type 3 ordinary chondrites and it is suggested that type 3 3 3 5 chondrites have a low feldspar as tl phosphor and 3 5 have high feldspar as the phosphor thermoluminescence therefore provides a means of palaeothermometry for type 3 ordinary chondrites

the parent magmas of the cumulate eucrites a mass balance approach the cumulate eucrite meteorites are gabbros that are related to the eucrite basalt meteorites the eucrite basalts are relatively primitive nearly flat ree patterns with la approx 8 30 x ci but the parent magmas of the cumulate eucrites have been inferred as extremely evolved la to greater than 100 x ci this inference has been based on mineral magma partitioning and on mass balance considering the cumulate eucrites as adcumulates of plagioclase pigeonite only both approaches have been criticized as inappropriate here mass balance including magma equilibrium pigeonite equilibrium plagiociase is used to test a simple model for the cumulate eucrites that they formed from known eucritic magma types that they consisted only of magma crystals in chemical equilibrium with the magma and that they were closed to chemical exchange after the accumulation of crystals this model is tested for major and rare earth elements ree the cumulate eucrites serra de mage and moore county are consistent in both ree and major elements with formation by this simple model from a eucrite magma with a composition similar to the nuevo laredo meteorite serra de mage as 14 magma 47 5 pigeonite and 38 5 plagioclase moore county as 35 magma 37 5 pigeonite and 27 5 plagioclase these results are insensitive to the choice of mineral magma partition coefficients results for the moama cumulate eucrite are strongly dependent on choice of partition coefficients for one reasonable choice moama s composition can be modeled as 4 nuevo laredo magma 60 pigeonite and 36 plagioclase selection of parent magma composition relies heavily on major elements the ree cannot uniquely indicate a parent magma among the eucrite basalts the major element composition of y 791195 can be fit adequately as a simple cumulate from any basaltic eucrite composition however y 791195 has lree abundances and la lu too low to be accommodated within the model using any basaltic eucrite composition and any reasonable partition coefficients postcumulus loss of incompatible elements seems possible it is intriguing that serra de mage moore county and moama are consistent with the same parental magma could they be from the same igneous body on the eucrite parent asteroid 4 vesta

a magma ocean on vesta core formation and petrogenesis of eucrites and diogenites abstract available evidence strongly suggests that the hed howardite eucrite diogenite meteorites are samples of asteroid 4 vesta abundances of the moderately siderophile elements ni co mo w and p in the hed mantle indicate that the parent body may have been completely molten during its early history during cooling of a chondritic composition magma ocean equilibrium crystallization is fostered by the suspension of crystals in a convecting magma ocean until the crystal fraction reaches a critical value near 0 80 when the convective system freezes and melts segregate from crystals by gravitational forces the extruded liquids are similar in composition to main group and stannern trend eucrites and the last pyroxenes to precipitate out of this ocean before convective lockup span the compositional range of the diogenites subsequent fractional crystallization of a main group eucrite liquid which has been isolated as a body of magma produces the nuevo laredo trend and the cumulate eucrites the predicted cumulate mineral compositions are in close agreement with phase compositions analyzed in the cumulate eucrites thus eucrites and diogenites are shown to have formed as part of a simple and continuous crystallization sequence starting with a magma ocean environment on an asteroidal size parent body that is consistent with vesta

the origin of eucrites diogenites and olivine diogenites magma ocean crystallization and shallow magma chamber processes on vesta the asteroid 4 vesta is one of the very few heavenly bodies to have been linked to samples on earth the howardite eucrite diogenite hed meteorite suite this large and diverse suite of meteorites provides a detailed picture of vesta s igneous and postigneous history we have used the range of igneous rock types and compositions in the hed suite to test a series of chemical models for solidification processes following peak melting magma ocean conditions on vesta fractional crystallization cannot have been a dominant early process in the magma ocean because it leads to excessive fe enrichment in the melt models that are dominated by equilibrium crystallization cannot produce orthopyroxene cumulates diogenites our best models invoke 60 70 equilibrium crystallization of a magma ocean followed by continuous extraction of the residual melt into shallow magma chambers fractional crystallization in these magma chambers combined with continuous or periodic addition of more melt from the slowly compacting crystal mush magmatic recharge can produce all of the igneous hed lithologies noncumulate and cumulate eucrites diogenites dunites harzburgites and olivine diogenites magmatic recharge can also explain the narrow range in eucrite compositions and the variability of incompatible trace element concentrations in diogenites we predict an internal structure for vesta that permits excavation of the heds during the formation of the rheasilvia basin while remaining consistent with observations from the dawn mission and most impact models

deep ocean impact of a madden julian oscillation observed by argo floats using the new argo array of profiling floats that gives unprecedented space time coverage of the upper 2000 meters of the global ocean we present definitive evidence of a deep tropical ocean component of the madden julian oscillation mjo the surface wind stress anomalies associated with the mjo force eastward propagating oceanic equatorial kelvin waves that extend downward to 1500 meters the amplitude of the deep ocean anomalies is up to six times the amplitude of the observed annual cycle this deep ocean sink of energy input from the wind is potentially important for understanding phenomena such as el nino southern oscillation and for interpreting deep ocean measurements made from ships

the global response to tropical heating in the madden julian oscillation during the northern winter a life cycle of the madden julian oscillation mjo was constructed based on 21 years of outgoing long wave radiation data regression maps of ncep ncar reanalysis data for the northern winter show statistically significant upper tropospheric equatorial wave patterns linked to the tropical convection anomalies and extratropical wave patterns over the north pacific north america the atlantic the southern ocean and south america to assess the cause of the circulation anomalies a global primitive equation model was initialized with the observed three dimensional 3d winter climatological mean flow and forced with a time dependent heat source derived from the observed mjo anomalies a model mjo cycle was constructed from the global response to the heating and both the tropical and extratropical circulation anomalies generally matched the observations well the equatorial wave patterns are established in a few days while it takes approximately two weeks for the extratropical patterns to appear the model response is robust and insensitive to realistic changes in damping and basic state the model tropical anomalies are consistent with a forced equatorial rossby kelvin wave response to the tropical mjo heating although it is shifted westward by approximately 20 longitude relative to observations this may be due to a lack of damping processes cumulus friction in the regions of convective heating once this shift is accounted for the extratropical response is consistent with theories of rossby wave forcing and dispersion on the climatological flow and the pattern correlation between the observed and modelled extratropical flow is up to 0 85 the observed tropical and extratropical wave patterns account for a significant fraction of the intraseasonal circulation variance and this reproducibility as a response to tropical mjo convection has implications for global medium range weather prediction copyright 2004 royal meteorological society

ancient water on asteroid 4 vesta evidence from a quartz veinlet in the serra de mage eucrite meteorite abstract the meteorite serra de mage a eucrite inferred to be from the asteroid 4 vesta contains quartz veinlets they are identical to antitaxial or crack seal quartz veinlets in terrestrial rocks and are extraterrestrial and ancient because they pre date a 4 40 ga metamorphism the quartz was likely deposited from liquid water solutions as are terrestrial veins other potential solvents or transport mechanisms are inadequate or unlikely because there is no indication of internal magmatic water in the eucrite meteorites and thus in vesta the water from which the veinlet was deposited probably came from outside vesta by analogy with water ice deposits on the moon and mercury vesta and similar asteroids may have had or now have polar ice deposits possibly derived from comet impacts

lithium systematics in howardite eucrite diogenite meteorites implications for crust mantle evolution of planetary embryos we present lithium li abundances and isotope compositions in a suite of howardites eucrites and diogenites heds these meteorites most likely originated from asteroid vesta and were delivered to earth by a series of independent impact events the li concentrations show striking differences between li poor diogenites plus cumulate eucrites and li enriched eucrites whilst howardites have li abundances intermediate between eucrites and diogenites contrary to li elemental inter group differences li isotope compositions are irresolvable among these individual groups of hed meteorites despite their wildly distinct petrography attesting to insignificant li isotope fractionation during formation of a thick basaltic crust by melting of the vestan mantle the mean li isotope composition of bulk silicate vesta is estimated at 3 7 0 6 1 intermediate to that of the earth versus mars and moon but identical with these terrestrial bodies within uncertainty this further validates largely homogeneous inner solar system solids from the li isotope perspective and supports the lack of loss of moderately volatile elements from planetary embryos during their magmatic histories because li does not follow depletion trends inferred from more volatile elements pasamonte eucrite has the same li isotope composition as other eucrites although it may not be directly linked to vesta these observations are also important for generating li elemental and isotope signatures in juvenile basaltic crusts of large terrestrial planets and numerous planetary embryos in the early solar system a combination of cv l chondrites may be less suitable for building vesta from li perspective but this may face sampling bias of available data and only further analyses may resolve this issue alternatively significant shift of 1 towards heavier li isotope compositions must have occurred during thermal processing of cv l 2 2 2 8 mixture in order to account for the observed li isotope systematics in hed meteorites no correlation is observed between li versus zn fe or si isotopes respectively implying unrelated processes of forming stable isotope variations observed in hed meteorites

composition and petrology of hed polymict breccias the regolith of 4 vesta the polymict breccias of the howardite eucrite and diogenite hed clan of meteorites preserve records of regolith processes that occur on vesta their putative home world these breccias howardites polymict eucrites and polymict diogenites are impact engendered mixtures of diogenites and eucrites the compositions of polymict breccias can be used to constrain the lithologic diversity of the vestan crust and the excavation depths of these materials we have done petrological and compositional studies of multiple samples of 5 polymict eucrites and 28 howardites to investigate these issues older analyses were done on samples of approx 0 5 gram mass by inaa newer analyses on samples of approx 5 gram mass by xrf and icp ms we estimate the percentage of eucritic material poem of polymict breccias by comparing their al and or ca contents to those of average basaltic eucrite and diogenite our samples have poem ranging from 28 to 98 adding two polymict diogenites from extends the range to poem 10 one hypothesis is that ancient well mixed vestan regolith has poem approx 67 and has a higher content of admixed impactor material several of our howardites have poem of 59 74 al and or ca contents 10 of poem 67 about a third have ni contents 300 micro g g suggesting they contain 2 chondritic material cm and or cr these may be regolithic howardites only one lew 85313 contains ne dominated by a solar wind sw component pca 02066 is dominated by impact melt material of polymict parentage and petrologically appears to be a mature regolith breccia yet it does not contain sw ne gro 95602 falls within the poem window contains sw ne yet has a ni content of 193 micro g g its petrologic characteristics suggest it was formed from immature regolith no polymict breccia clasts no glass trace element characteristics of the polymict breccias demonstrate the dominance of main group eucrites as the basaltic component mixing diagrams of zr nb ba hf and ta with al show no evidence for a significant contribution from stannern trend eucrites an exception is polymict eucrite lew 86001 poem 92 which is dominated by stannern trend basaltic debris howardite lap 04838 poem 84 has higher incompatible trace concentrations than other polymict breccias excluding lew 86001 and either contains a stannern trend basaltic component or has a significant contributions from evolved eucrites like nuevo laredo

a new look at the midlatitude mjo teleconnection in the northern hemisphere winter the midlatitude to madden julian mjo teleconnection in the northern hemisphere wintertime was investigated using twenty years of outgoing long wave radiation and national center for atmospheric research national centers for environmental prediction re analysis data it is revealed through empirical orthogonal functions and regression analyses that the tropical upper level divergence convergence associated with enhanced reduced tropical convection has a subtropical counterpart of upper level convergence divergence as the convective region of mjo moves eastward from the indian ocean to the western pacific the divergent circulation connecting the tropics and subtropics moves eastward from an analysis of vertical motion diagnosed by the generalized omega equation it was revealed that the position of the subtropical rossby gyres of the mjo with respect to the asian pacific jet was the most important factor affecting the existence of the localized divergence convergence and associated lower level vertical motion in the subtropics as the subtropical rossby gyres pass by the longitudinal position of the asian pacific jet vertical motion occurs to meet the balance required by quasi geostrophic theory since this anomalous vertical motion is large enough to cause convection at that region the diabatic heating process reinforces the vertical motion furthermore other dynamical processes neglected in quasi geostrophic theory are activated and contribute to the vertical motion balancing the diabatic heating as a result of the vertical motion near the jet entrance region in the subtropics the vorticity advection by vertical wind and the tilting of vorticity become important since these two terms are similar in shape and magnitude they reinforce each other during the development phase of the midlatitude mjo teleconnection combining these two terms we define the baroclinic jet source bjs in order to evaluate the bjs as a source for the midlatitude mjo teleconnection a numerical experiment is carried out the linear barotropic model is forced by only two terms yet the model captured clearly the main feature of the midlatitude mjo teleconnection copyright 2006 royal meteorological society

metamorphism of eucrite meteorites studied quantitatively using induced thermoluminescence eucrite meteorites1 are especially important in studies of the early solar system because they are the simplest and most ancient products of a process that was widespread in the inner solar system2 3 basaltic volcanism they are also the meteorites for which there is least doubt of an asteroidal origin4 5 after volcanism the eucrites experienced a period of metamorphism6 either inside the asteroid as it cooled from igneous temperatures7 or on the surface of the asteroid as a result of impact heating8 induced thermoluminescence studies provide a new and quantitative means of determining relative metamorphic intensities for these meteorites using this technique we show that the eucrites constitute a continuous metamorphic series and not as commonly assumed two groups of metamorphosed and non metamorphosed meteorites9 these studies are the first application of the induced thermoluminescence technique to igneous rocks and we suggest that the method may well have application to other basalts

al sm eu sr systematics of eucrites and moon rocks implications for planetary bulk compositions abstract analysis of the eu and sr anomalies of eucrites and lunar rocks allows constraints to be placed on the bulk compositions of the eucrite parent body epb and the moon the elements al ree and sr all are essentially incompatible with the major minerals of these small low o 2 bodies except for plagioclase into which al sr and eu tend to concentrate therefore the hypothesis that al ree and sr in the epb and the moon are all in proportions close to those in the bulk solar system i e chondrites leads to certain predictions about the concentrations of these elements in samples affected by plagioclase fractionation the predictions are almost ideally fulfilled by eucrites and lunar samples for the epb the ratios ree al sr al and sr ree are constrained to be probably within 10 almost certainly within 20 of the chondritic ratios for the more complicated moon the constraints are less precise ree al is very probably within 25 of chondritic sr al and sr ree are probably within 35 of chondritic these findings are proof that there is a strong similarity between the bulk compositions of the planets and the compositions of chondritic meteorites the eucrites sm eu sr systematics are also valuable sources of constraints on the distribution coefficients for eu and sr into plagioclase at low o 2 from the slope of data for noncumulate eucrites on a eu sm plot d eu pl liq can be inferred to be 1 1 0 1 0 2 from the slope on a sr sm plot d sr pl liq can be inferred to be 1 5 0 3 in the case of d eu this is in excellent agreement with experimental data in the case of d sr the empirical result is probably more appropriate for eucritic systems than most experimental data which due to compositional effects scatter widely

differentiation and magmatic activity in vesta evidenced by 26al 26mg dating in eucrites and diogenites abstract the 26 al 26 mg short lived chronometer has been widely used for dating ancient objects in studying the early solar system here we use this chronometer to investigate and refine the geological history of the asteroid 4 vesta ten meteorites widely believed to come from vesta 4 basaltic eucrites 3 cumulate eucrites and 3 diogenites and the unique achondrite asuka 881394 were selected for this study all samples were analyzed for their 26 mg and 27 al 24 mg ratios in order to construct both whole rock and model whole rock isochrons mineral separation was performed on 8 of the hed s in order to obtain internal isochrons while whole rock al mg analyses of hed s plot on a regression that could be interpreted as a vestan planetary isochron internal mineral isochrons indicate a more complex history crystallization ages obtained from internal 26 al 26 mg systematic in basaltic eucrites show that vesta s upper crust was formed during a short period of magmatic activity at 2 66 0 58 1 39 million years ma after calcium aluminum inclusions after cai we also suggest that impact metamorphism and subsequent age resetting could have taken place at the surface of vesta while 26 al was still extant cumulate eucrites crystallized progressively from 5 48 0 60 1 56 to 7 25 ma after cai model ages obtained for both basaltic and cumulate eucrites are similar and suggest that the timing of differentiation of a common eucrite source from a chondritic body can be modeled at 2 88 0 12 0 14 ma after cai i e contemporaneously from the onset of the basaltic eucritic crust based on their cumulate texture we suggest cumulate eucrites were likely formed deeper in the crust of vesta diogenites have a more complicated history and their 26 al 26 mg systematics show that they likely formed after the complete decay of 26 al and thus are younger than eucrites this refined chronology for eucrites and diogenites is consistent with a short magma ocean stage on 4 vesta from which the basaltic eucrites rapidly crystallized in order to explain the younger age and the complex history of diogenites we postulate that a second episode of magmatism was possibly triggered by a mantle overturn we bring a refined chronology of the geological history of vesta that shows that the asteroid has known a more complex differentiation than previously thought

chemical studies of h chondrites iii regolith evolution of the fayetteville chondrite parent abstract data for ag au bi cd co cs ga in rb sb se te tl and zn in consortium samples of solar gas and track rich dark matrix and dark and light clasts in the fayetteville h chondrite regolith breccia were determined by radiochemical neutron activation analysis the matrix proved chemically homogeneous at a level never before observed in an ordinary chondrite most dark clasts had similar mean trace element concentrations as matrix but were compositionally much more heterogeneous two clasts were unusual one having apparently formed from impact melted soil the other representing a mixture of 90 matrix 10 c2m chondrite the single light clast proved compositionally similar to h4 6 chondrite falls except for its higher contents of labile bi cd in and tl relative to matrix all other samples seemed cs deficient other h chondrite regolith breccias studied in the past had shown peculiar cs and or rb contents so that these alkalis seem diagnostic of such breccias dark portions of such breccias apparently represent compacted regolith soil produced by isochemical comminution of normal dark and light clasts the dark clasts in turn likely represent primordial nebular condensate although it is possible that they represent planetary cold traps that garnered labile elements generated elsewhere in the parent body

thermoluminescence and the shock and reheating history of meteorites iv the induced tl properties of type 4 6 ordinary chondrites abstract the induced thermoluminescence tl properties of 121 equilibrated ordinary chondrites have been measured the samples were 74 h and 47 l chondrites of which 33 h and 32 l were from antarctica the distribution of tl sensitivities for non antarctic l chondrites differs from that of non antarctic h chondrites consistent with a greater proportion of the former class suffering post metamorphic shock data on the effect of laboratory annealing on tl sensitivity and step wise ar release measurements enable the meteorites to be sorted into three shock related temperature groups

planetary scale circulations forced by intraseasonal variations of observed convection abstract interhemispheric differences of the madden julian oscillation mjo are investigated in a linearized primitive equation model heating is prescribed from the observed life cycle of the mjo in which anomalous convection is concentrated in the eastern hemisphere the dynamical response in the eastern hemisphere has the form of a forced disturbance that involves kelvin and rossby components these dynamical components propagate eastward along with the prescribed heating and have zonal wavenumber 2 structure in accord with observed behavior the behavior in the eastern hemisphere also resembles that emerging from frictional wave cisk in which heating follows autonomously from the circulation when the prescribed heating collapses near the date line the rossby component dissipates the kelvin component however continues to advance across the western hemisphere where it propagates at more than twice the speed of the disturbance in the eastern hemisphere the disturbance in the western hemisphere

clinopyroxene ree distribution coefficients for shergottites the ree content of the shergotty melt abstract ree distribution coefficients were measured between synthetic pyroxenes and melts similar in composition to the inferred shergotty intercumulus liquid by in situ analysis with the electron microprobe using samples doped to per cent concentration levels these coefficients exhibit a strong positive correlation with pyroxene wollastonite content recommended values for augites similar in composition to the shergotty cumulus augite cores wo32en48 are d la 0 023 d ce 0 039 d nd 0 10 d sm 0 17 d eu 0 16 d gd 0 20 d yb 0 29 and d lu 0 30 recommended values for pigeonites similar in composition to the shergotty cumulus pigeonite cores wo12en58 are d la 0 002 d ce 0 004 d nd 0 019 d sm 0 031 d yb 0 13 and d lu 0 13 these values resemble distribution coefficients measured for terrestrial basalts of higher mg fe than the shergotty melt rather than those of more evolved siliceous rocks of similar mg fe to the shergotty melt thus it appears that mg fe is considerably less important than other factors in determining distribution coefficient values for pyroxenes ree abundances were computed for the shergotty intercumulus melt using distribution coefficients measured for the natural phase compositions these computed abundances display lree depletion such lree depleted abundance patterns cannot be generated by simple partial melting of a mafic mineral assemblage having the lree enriched patterns required for a two stage sm nd evolution history this result implies that either 1 the melting process was complex e g continuous melting 2 the source region had a more complex history than that of the simple 2 stage model or 3 shergotty does not satisfy the closed system assumption of the calculation and has suffered post magmatic lree enrichment

thermoluminescence and the origin of the dark matrix of fayetteville and similar meteorites abstract the induced thermoluminescence properties and carbon contents of the dark matrix and light clasts of 6 regolith breccias have been measured the tl sensitivity of the matrix normalized to that of the clasts decreases from 0 8 to 0 3 with increasing inert gas content increasing abundances of highly volatile elements and carbon and decreasing amounts of interstitial grain boundary glass for meteorites with the highest inert gas contents fayetteville and leighton the matrix samples have broader tl peaks by 10 c and lower peak temperatures by 10 c than the light clasts whereas meteorites with low inert gas contents e g pantar do not show this difference in the tl properties of the two lithologies it is argued that the data are consistent with the formation of the dark matrix by comminution of the light clasts with the addition of a component perhaps cm like chondrites with tl properties distinct from those of ordinary chondrites the present data are inconsistent with the matrix being a new primitive material akin to type 3 ordinary chondrites or with the dark matrix being related to the clasts by purely thermal processes

the richfield ll3 chondrite richfield is a moderately shocked shock stage s4 ll3 7 genomict breccia find consisting mainly of light colored recrystallized clasts and dark clasts exhibiting significant silicate darkening a few impact melt rock clasts and ll5 chondrite clasts also occur the cosmic ray exposure age of 14 5 ma is indistinguishable from the main exposure peak for ll chondrites 15 ma although the exposure ages indicate little he loss the gas retention ages indicate high gas losses that must have occurred prior to or during ejection from the ll parent body