the terrestrial alteration of saharan shergottites dar al gani 476 and 489 a case study of weathering in a hot desert environment abstract rare earth element ree and other selected trace and minor element concentrations were determined in various phases of dar al gani 476 and 489 two basaltic shergottites recently found in the libyan sahara whereas merrillite and feldspathic glass compositions do not seem to have been altered since the fall of these meteorites olivine and pyroxenes commonly show light ree enrichments sometimes accompanied by ce anomalies that are attributed to terrestrial alteration sr and ba enrichments are also observed the calcium carbonate that resides in most cracks is essentially devoid of ree but a fine grained amorphous silicate material that fills some veins and pockets has striking light ree enrichments and elevated p sr and ba it is argued that this material likely to be impact melt as well as the notoriously light ree poor olivine and pyroxenes were preferentially affected by a crustal light ree rich contaminant caution is urged when using whole rock or even mineral separate compositional and isotopic data for hot desert meteorites

lunar highland meteorites and the composition of the lunar crust abstract major minor and trace element data obtained by neutron activation techniques and by spark source mass spectrometry ssms on two lunar meteorites mac88104 and mac88105 are reported both mac samples were also analysed for their contents and isotopic compositions of rare gases additional ssms data were obtained on four lunar highland meteorites previously found in antarctica alha81005 y791197 y82192 and y86032 mac88104 and mac88105 are very similar in chemistry suggesting that they are pieces of a single fall event the bulk chemical composition of mac88104 5 is not very different from the other lunar highland meteorites highly aluminous with relatively low contents of ree and siderophile element concentrations slightly above 1 of a ci chondritic level however mafic element concentrations mg cr mn etc are slightly lower in mac88104 5 than in the other lunar highland meteorites the contents of solar rare gases in the two mac samples are low indicating only a small regolith contribution in agreement with rare petrographically identifiable regolith components the mac samples and also y82192 and y86032 are classified as fragmental breccias with negligible regolith components in contrast to alha81005 and y791197 which are regolith breccias with high solar wind derived rare gas contents there is no correlation among lunar meteorites between peak shock pressures and solar gas contents indicating that peak shock pressures of up to 25 gpa do not lead to gas loss a low 26al activity vogt et al 1990 and high contents of cosmogenic rare gases in mac88104 5 suggest a long exposure 400 000 years in the lunar sub surface k ar ages are in excess of 3 9 by lunar highland meteorites and compositionally similar granulitic rocks from the apollo 16 and 17 landing sites contain about 1 of a ci chondritic component according to siderophile and volatile element contents but independent of the amount of regolith components apparently the major fraction of meteoritic elements in these rocks was not provided by micrometeorites impacting the regolith the abundances of siderophile e g ir and volatile elements may therefore reflect the last spike of accretion of the moon after the formation of the anorthositic crust lunar meteorites of highland origin are chemically different from the bulk of the apollo 16 highland samples in having higher fe mg ratios and lower contents and less fractionated patterns of incompatible and siderophile elements since lunar highland meteorites are associated with at least three but probably four different fall events and since they are not derived from chemically exotic front side terranes they may represent a better sampling of the average chemical composition of the lunar crust than previous estimates based on returned lunar samples and remote sensing data a comparison between an average highland composition derived by taylor 1982 and an estimate based on lunar highland meteorites shows that the taylor composition contains higher concentrations and more fractionated incompatible elements mainly because of a substantial amount of kreep a trace element rich highly fractionated component from the front side of the moon not present at the sites from which the lunar meteorites come

major lunar crustal terranes surface expressions and crust mantle origins in light of global remotely sensed data the igneous crust of the moon can no longer be viewed as a simple globally stratified cumulus structure composed of a flotation upper crust of anorthosite underlain by progressively more mafic rocks and a residual melt kreep sandwich horizon near the base of the lower crust instead global geochemical information derived from clementine multispectral data and lunar prospector gamma ray data reveals at least three distinct provinces whose geochemistry and petrologic history make them geologically unique 1 the procellarum kreep terrane pkt 2 the feldspathic high lands terrane fht and 3 the south pole aitken terrane spat the pkt is a mafic province coincident with the largely resurfaced area in the procellarum imbrium region whose petrogenesis relates to the early differentiation of the moon here some 40 of the th in the moon s crust is concentrated into a region that constitutes only about 10 of the crustal volume this concentration of th average 5 ppm and by implication the other heat producing elements u and k led to a fundamentally different thermal and igneous evolution within this region compared to other parts of the lunar crust lower crustal materials within the pkt likely interacted with underlying mantle materials to produce hybrid magmatism leading to the magnesian suite of lunar rocks and possibly kreep basalt although rare in the apollo sample collection widespread mare volcanic rocks having substantial th enrichment are indicated by the remote data and may reflect further interaction between enriched crustal residues and mantle sources the fht is characterized by a central anorthositic region that constitutes the remnant of an anorthositic craton resulting from early lunar differentiation basin impacts into this region do not excavate significantly more mafic material suggesting a thickness of tens of kilometers of anorthositic crust the feldspathic lunar meteorites may represent samples from the anorthositic central region of the fht ejecta from deep penetrating basin impacts outside of the central anorthositic region however indicate an increasingly mafic composition with depth the spat a mafic anomaly of great magnitude may include material of the upper mantle as well as lower crust thus it is designated a separate terrane whether the spa basin impact simply uncovered lower crust such as we infer for the fht remains to be determined

trans dimensional joint inversion of seabed scattering and reflection data this paper examines joint inversion of acoustic scattering and reflection data to resolve seabed interface roughness parameters spectral strength exponent and cutoff and geoacoustic profiles trans dimensional trans d bayesian sampling is applied with both the number of sediment layers and the order zeroth or first of auto regressive parameters in the error model treated as unknowns a prior distribution that allows fluid sediment layers over an elastic basement in a trans d inversion is derived and implemented three cases are considered scattering only inversion joint scattering and reflection inversion and joint inversion with the trans d auto regressive error model including reflection data improves the resolution of scattering and geoacoustic parameters the trans d auto regressive model further improves scattering resolution and correctly differentiates between strongly and weakly correlated residual errors

subglacial water drainage storage and piracy beneath the greenland ice sheet meltwater drainage across the surface of the greenland ice sheet gris is well constrained by measurements and modeling yet despite its critical role knowledge of its transit through the subglac

lunar meteorites siderophile element contents and implications for the composition and origin of the moon abstract six lunar meteorites have thus far been discovered in antarctica although these meteorites are of undocumented lunar geographic provenance all other available lunar samples obtained from the apollo and luna programs came from a relatively minuscule region of the central nearside around which a polygon could be drawn covering just 4 7 of the lunar surface the five lunar meteorites that are now well studied represent at least two but probably three separate lunar source craters alha81005 and y791197 are probably from separate craters and compound meteorite y82192 6032 is certainly from a crater of its own at least alha81005 and y791197 and probably also at least in a loose sense y82192 6032 are highlands regolith breccias thus their compositions may be appropriately compared with compositions of apollo and luna highlands regolith samples compared with average highlands regolith samples from the central nearside apollo sites lunar meteorites have lower concentrations of siderophile elements in general and especially au ge and ni among anorthositic apollo samples i e mainly those from apollo 16 au ir and to a lesser extent ge ir ratios tend to be hyperchondritic most previous models for lunar regolith siderophile geochemistry assumed that the apollo 16 samples are representative of the overall lunar highlands such models tended to conclude that the hyperchondritic au ir and ge ir ratios were consequences of variations in the compositions of moon striking projectiles as a function of time it was even speculated that these temporal variations were consequences of the heterogeneous accretion of a moon with a general enrichment in refractory elements the lunar meteorites suggest that hyperchondritic au ir and ge ir are not general features of the highlands but peculiarities of the apollo 16 region or more generally the central nearside the high ni contents of the apollo 16 megaregolith substantially in excess of the ni implied by a model in which all meteoritic debris has an h chondritic ni ir ratio have been interpreted to imply that the mg rich fraction of the lunar crust is extremely ni rich and thus similar in siderophile geochemistry to terrestrial komatiites this coincidence has been interpreted as confirmation that the moon formed by modified fission from the earth s mantle after core formation plus late accretion effects had established the final siderophile pattern of the earth s mantle however the lunar meteorites and a survey of data for the luna 20 highlands regolith sample suggest that the high ni content of the apollo 16 regolith is strictly a peculiarity of the apollo 16 region and not a general feature of the moon s crust the anomalous siderophile composition of the central nearside regolith probably stems from a combination of regional heterogeneity in cratering projectile compositions plus regional enrichments in relatively labile siderophile elements most notably au ge and perhaps to a certain extent ni which might be loosely correlated with the anomalously high concentration of kreep over the central nearside

mineralogy and geochemistry of lunar meteorite queen alexandra range 93069 queen alexandra range que 93069 is a glass rich regolith breccia derived from the lunar highlands the high abundance of glassy fragments the presence of agglutinates the small size of all mineral and glass fragments the presence of mostly melt rocks and the low abundance of pristine lunar crustal rocks all indicate that que 93069 is derived from a mature regolith this conclusion is also supported by its high siderophile element content the most common mafic mineral is pyroxene with compositions that indicate derivation from ferroan ant suite rocks rare gabbro differentiation products may be indicated by the presence of silica fayalitic olivine and one pyroxferroite grain lithic fragments are mostly meta melt rocks of ant composition the glass compositions are dominated by troctolitic anorthosite compositions followed by gabbroic anorthosite and noritic anorthosite most glasses are ol normative in composition some rare basic glasses of noritic composition were observed glass fragments and matrix glasses are alkali poor except for some rare alkali rich shards the bulk chemical composition of que 93069 as well as the rare earth element ree abundance pattern is very similar to that of other highlands meteorites such as mac 88105 and y 86032 and to average lunar highlands crust one small porous clast was found to be very rich in volatile elements as well as in most lithophile and siderophile elements as this sample also contains abundant sulfides the enrichments could be related to element mobilization and redistribution by volatile sulfur species

new lunar meteorites impact melt and regolith breccias and large scale heterogeneities of the upper lunar crust we have analyzed nine highland lunar meteorites lunaites using mainly inaa several of these rocks are difficult to classify dhofar 081 is basically a fragmental breccia but much of its groundmass features a glassy fluidized texture that is indicative of localized shock melting also much of the matrix glass is swirly brown suggesting a possible regolith derivation we interpret dar al gani dag 400 as an extremely immature regolith breccia consisting mainly of impact melt breccia clasts we interpret dhofar 026 as an unusually complex anorthositic impact melt breccia with scattered ovoid globules that formed as clasts of mafic subophitic impact melt the presence of mafic crystalline globules in a lunar material even one so clearly impact heated suggests that it may have originated as a regolith our new data and a synthesis of literature data suggest a contrast in al2o3 incompatible element systematics between impact melts from the central nearside highlands where apollo sampling occurred and those from the general highland surface of the moon impact melts from the general highland surface tend to have systematically lower incompatible element concentration at any given al2o3 concentration than those from apollo 16 in the case of dhofar 026 both the bulk rock and a comparatively al poor composition 14 wt al2o3 7 g g sm extrapolated for the globules manifest incompatible element contents well below the apollo 16 trend impact melts from luna 20 57e distribute more along the general highland trend than along the apollo 16 trend siderophile elements also show a distinctive composition for apollo 16 impact melts ni ir averaging 1 8x chondritic in contrast lunaite impact melt breccias have consistently chondritic ni ir impact melts from luna 20 and other apollo sites show average ni ir almost as high as those from apollo 16 the prevalence of this distinctive ni ir ratio at such widely separated nearside sites suggests that debris from one extraordinarily large impact may dominate the megaregolith siderophile component of a nearside region 2300 km or more across highland polymict breccia lunaites and other kreep poor highland regolith samples manifest a strong anticorrelation between al2o3 and mg the magnesian component probably represents the chemical signature of the mg suite of pristine nonmare rocks in its most pure form unaltered by the major kreep assimilation that is so common among apollo mg suite samples the average composition of the ferroan anorthositic component is now well constrained at al2o3 29 30 wt implying about 17 19 wt modal mafic silicates in good agreement with the composition predicted for flotation crust over a ferroan magma ocean warren 1990

the magma ocean concept and lunar evolution the model of lunar evolution in which the anorthositic plagioclase rich oldest crust of the moon is formed over a period of 300 myr or less by crystallization as it floats on a global ocean of magma tens or hundreds of km thick is examined in a review of petrological and theoretical studies consideration is given to the classification of lunar rocks the evidence for primordial deep global differentiation constraints on the depth of the molten zone the effects of pressure on mineral stability relationships mainly liquid vs mainly magmifer ocean models and the evidence for multiple ancient differentiation episodes a synthesis of the model of primordial differentiation and its aftereffects is presented and the generalization of the model to the earth and to mars mercury venus and the asteroids is discussed

magnesian anorthosites and a deep crustal rock from the farside crust of the moon abstract among over thirty lunar meteorites recovered from the hot deserts and antarctica dhofar 489 is the most depleted in thorium 0 05 ppm feo and rare earth elements ree dhofar 489 is a crystalline matrix anorthositic breccia and includes clasts of magnesian anorthosites and a spinel troctolite the mg mg fe mol mg numbers 75 85 of olivine and pyroxene grains in this meteorite are higher than those of the apollo ferroan anorthosites such materials were not recovered by the apollo and luna missions however remote sensing data suggest that the estimated concentrations of th and feo are consistent with the presence of such samples on the farside of the moon the differentiation trend deduced from the mineralogy of the anorthositic clasts define a magnesian extension of the ferroan anorthosite fan trend constructed from the apollo samples the presence of magnesian anorthositic clasts in dhofar 489 still offers a possibility that the farside trend with magnesian compositions is more primitive than the fan trend and may require a revision of this classical differentiation trend the ar ar age of dhofar 489 is 4 23 0 034 gyr which is older than most ar ages reported for highland rocks returned by apollo the old ar ar age of impact formation of this breccia and the presence of a fragment of spinel troctolite of deep crustal origin suggest that a basin forming event on the farside excavated the deep crust and magnesian anorthosites before formation of imbrium

global elemental maps of the moon the lunar prospector gamma ray spectrometer lunar prospector gamma ray spectrometer spectra along with counting rate maps of thorium potassium and iron delineate large compositional variations over the lunar surface thorium and potassium are highly concentrated in and around the nearside western maria and less so in the south pole aitken basin counting rate maps of iron gamma rays show a surface iron distribution that is in general agreement with other measurements from clementine and the lunar prospector neutron detectors

petrography mineralogy and geochemistry of lunar meteorite sayh al uhaymir 300 we report here the petrography mineralogy and geochemistry of lunar meteorite sayh al uhaymir 300 sau 300 sau 300 is dominated by it fine grained crystalline matrix surrounding mineral fragments plagioclase pyroxene olivine and ilmenite and lithic clasts mainly feldspathic to noritic mare basalt and kreepy rocks are absent glass melt veins and impact melts are present indicating that the rock has been subjected to a second impact event feni metal and troilite grains were observed in the matrix major element concentrations of sau 300 al 2 o 3 21 6 wt and feo s 16 wt are very similar to those of two basalt bearing feldspathic rei regolith breccias calcalong creek and yamato y 983885 however the rare earth element ree abundances and pattern of sau 300 resemble the patterns of feldspathic highlands meteorites e g queen alexandra range que 93069 and dar al gani dag 400 and the average lunar highlands crust it has a relatively lree enriched 7 to 10 x ci pattern with a positive eu anomaly similar to 11 x ci values of fe mn ratios of olivine pyroxene and the bulk sample are essentially consistent with l lunar origin sau 300 also contains high siderophile abundances with a chondritic ni ir ratio sau 300 has experienced moderate terrestrial weathering as its bulk sr concentration is elevated compared to other lunar meteorites and apollo and luna samples mineral chemistry and trace clement abundances of sau 300 fall within the ranges of lunar feldspathic meteorites and fan rocks sau 300 is a feldspathic impact melt breccia predominantly composed of feldspathic highlands rocks with a small amount of mafic component with a bulk mg of 0 67 it is the most mafic of the feldspathic meteorites and represents a lunar surface composition distinct from any other known lunar meteorites oil the basis of its low th concentration 0 46 ppm and its lack of kreepy and mare basaltic components the source region of sau 300 could have been within a highland terrain a great distance from the imbrium impact basin probably on the far side of the moon

fabric analysis of allende matrix using ebsd fabric analysis of the interstitial matrix material in primitive meteorites offers a novel window on asteroid formation and evolution electron backscatter diffraction ebsd has allowed fabrics in these fine grained materials to be visualized in detail for the first time our data reveal that allende a cv3 chondrite possesses a uniform planar short axis alignment fabric that is pervasive on a broad scale and is probably the result of deformational shortening related to impact or gravitational compaction interference between this matrix fabric and the larger more rigid components such as dark inclusions dis and calcium aluminium rich inclusions cais has lead to the development of locally oriented and intensified matrix fabrics in addition dis possess fabrics that are conformable with the broader matrix fabric these results suggest that dis were in situ prior to the deformational shortening event responsible for these fabrics thus providing an argument against dark inclusions being fragments from another lithified part of the asteroid kojima and tomeoka 1996 fruland et al 1978 moreover both dis and allende matrix are highly porous 25 corrigan et al 1997 mobilizing a highly porous di during impact induced brecciation without imposing a fabric and incorporating it into a highly porous matrix without significantly compacting these materials is improbable we favor a model that involves allende dis cais and matrix accreting together and experiencing the same deformation events

chemistry of the calcalong creek lunar meteorite and its relationship to lunar terranes the calcalong creek lunar meteorite is a polymict breccia that contains clasts of both highlands and mare affinity reported here is a compilation of major minor and trace element data for bulk clast and matrix samples determined by instrumental neutron activation analysis inaa petrographic information and results of electron microprobe analyses are included the relationship of calcalong creek to lunar terranes especially the procellarum kreep terrane and feldspathic highlands terrane is established by the abundance of thorium incompatible elements and their kreep like ci chondrite normalized pattern feo and tio2 the highlands component is associated with apollo 15 kreep basalt but represents a variant of the kreep derived material widely found on the moon sources of calcalong creek s mare basalt components may be related to low titanium lt and very low titanium vlt basalts seen in other lunar meteorites but do not sample the same source the content of some components of calcalong creek are found to display similarities to the composition of the south pole aitken terrane what appear to be vlt relationships could represent new high aluminum low titanium basalt types

chemical alteration and ree mobilization in meteorites from hot and cold deserts the effects of terrestrial weathering on ree mobilization are evaluated for a variety of uncommon meteorites found in antarctica and in hot deserts the meteorites analyzed include 7 non cumulate eucrites 10 shergottites 3 nakhlites 2 lunar meteorites 4 angrites 10 acapulcoites 1 winonaite and 1 brachinite in situ concentration measurements of lanthanides and selected other minor and trace elements were made on individual grains by secondary ion mass spectrometry sims in antarctic meteorites oxidation converts ce 3 to ce 4 which is less soluble than the trivalent ree resulting in ce anomalies the mineral most affected is low ca pyroxene however not all grains of a given mineral are and distinct analyses of a single grain can even yield ree patterns with and without ce anomalies the effect is most pronounced for antarctic eucrites in which ce anomalies are observed not only in individual minerals but also in whole rock samples although ce anomalies are observed in meteorites from hot deserts as well the most characteristic signs of chemical alteration in this environment are a lree enrichment with a typical crustal signature as well as sr ba and u contaminations these can modify the whole rock ree patterns and disturb the isotope systematics used to date these objects the lree contamination is highly heterogeneous affecting some grains and not others of a given mineral mainly olivine and low ca pyroxene the two minerals with the lowest ree concentrations the major conduit for ree movement is through shock induced cracks and defects and the highest levels of contamination are found in altered material filling such veins and cracks meteorites that experienced low shock levels and those that are highly recrystallized are the least altered copyright 2003 elsevier ltd

lunar highland meteorite dhofar 026 and apollo sample 15418 two strongly shocked partially melted granulitic breccias studies of lunar meteorite dhofar 026 and comparison to apollo sample 15418 indicate that dhofar 026 is a strongly shocked granulitic breccia or a fragmental breccia consisting almost entirely of granulitic breccia clasts that experienced considerable post shock heating probably as a result of diffusion of heat into the rock from an external hotter source the shock converted plagioclase to maskelynite indicating that the shock pressure was between 30 and 45 gpa the post shock heating raised the rock s temperature to about 1200 c as a result the maskelynite devitrified and extensive partial melting took place the melting was concentrated in pyroxene rich areas all pyroxene melted as the rock cooled the partial melts crystallized with fine grained subophitic poikilitic textures sample 15418 is a strongly shocked granulitic breccia that had a similar history but evidence for this history is better preserved than in dhofar 026 the fact that dhofar 026 was previously interpreted as an impact melt breccia underscores the importance of detailed petrographic study in interpretation of lunar rocks that have complex textures the name impact melt has in past studies been applied only to rocks in which the melt fraction formed by shock induced total fusion recently however this name has also been applied to rocks containing melt formed by heating of the rocks by conductive heat transfer assuming that impact is the ultimate source of the heat we urge that the name impact melt be restricted to rocks in which the bulk of the melt formed by shock induced fusion to avoid confusion engendered by applying the same name to rocks melted by different processes

lunar ferroan anorthosite petrogenesis clues from trace element distributions in fan subgroups the rare earth elements ree and selected other trace elements were measured in plagioclase and pyroxene from nine samples of the lunar ferroan anorthosite fan suite of rocks samples were selected from each of four fan subgroups previously defined by james et al 1989 plagioclase compositions are homogeneous within each sample but high and low ca pyroxenes from lithic clasts typically have different ree abundances from their counterparts in the surrounding granulated matrices measured plagioclase low ca pyroxene concentration ratios for the ree have steeper patterns than experimentally determined plagioclase low ca pyroxene partition coefficients in most samples textural and trace element evidence suggest that although subsolidus equilibration may be responsible for some of the discrepancy plagioclase compositions in most samples have been largely unaffected by intermineral redistribution of the ree the ree systematics of plagioclase from the four subgroups are broadly consistent with their derivation through crystallization from a single evolving magma however samples from some of the subgroups exhibit a decoupling of plagioclase and pyroxene compositions that probably reflects the complexities inherent in crystallization from a large scale magmatic system for example two anorthosites with very magnesian mafic minerals have highly evolved trace element compositions major element compositions in plagioclase also do not reflect the evolutionary sequence recorded by their ree compositions finally a noritic anorthosite breccia with relatively ferroan mafic minerals contains several clasts with high and variable ree and other trace element abundances although plagioclase ree compositions are consistent with their derivation from a magma with a kreepy trace element signature very shallow ree patterns in the pyroxenes suggest the addition of a component enriched in the light ree

northwest africa 773 lunar origin and iron enrichment trend the meteorite northwest africa 773 nwa 773 is a lunar sample with implications for the evolution of mafic magmas on the moon a combination of key parameters including whole rock oxygen isotopic composition fe mn ratios in mafic silicates noble gas concentrations a kreep like rare earth element pattern and the presence of regolith agglutinate fragments indicate a lunar origin for nwa 773 partial maskelynitization of feldspar and occasional twinning of pyroxene are attributed to shock deformation terrestrial weathering has caused fracturing and precipitation of carich carbonates and sulfates in the fractures but lunar minerals appear fresh and unoxidized the meteorite is composed of two distinct lithologies a two pyroxene olivine gabbro with cumulate texture and a polymict fragmental regolith breccia the olivine gabbro is dominated by cumulate olivine with pigeonite augite and interstitial plagioclase feldspar the breccia consists of several types of clasts but is dominated by clasts from the gabbro and more feo rich derivatives variations in clast mineral assemblage and pyroxene mg mg fe and ti ti cr record an igneous fe enrichment trend that culminated in crystallization of fayalite silica hedenbergitebearing symplectites the fe enrichment trend and cumulate textures observed in nwa 773 are similar to features of terrestrial ponded lava flows and shallow level mafic intrusives indicating that nwa 773 may be from a layered mafic intrusion or a thick differentiated lava flow nwa 773 and several other mafic lunar meteorites have lree enriched patters distinct from apollo and luna mare basalts which tend to be lree depleted this is somewhat surprising in light of remote sensing data that indicates that the apollo and luna missions sampled a portion of the moon that was enriched in incompatible heatproducing elements

evolution of the lunar crust sims study of plagioclase from ferroan anorthosites abstract the lunar crust down to a depth of 65 km is composed of older 4 5 ga ferroan anorthosites and younger 4 43 4 17 ga mg suite lithologies which include dunites troctolites and norites the anorthosites are generally inferred to represent floating cumulates in a lunar magma ocean possible depth 800 km moon s radius 1 738 km the cumulates that are inferred to be located near the base of the magma ocean are dominantly olivine and pyroxene the last dregs of the magma ocean are enriched in incompatible elements and have been named kreep k rare earth elements p kreep formed in this manner is probably concentrated near the crust mantle boundary at 70 km depth we are attempting to characterize melts parental to ferroan anorthosites and mg suite norites by analyzing rees la ce nd sm eu dy er yb and ba sr and y in their cumulus plagioclase if the cumulus grains have not been compromised by postcrystallization effects and if we know the relevant mineral melt partition coefficients ds we can invert the trace element data for plagioclase to parental melt compositions melts parental to ferroan anorthosites are estimated to contain ree at concentrations ten to fifty times chondrites melts parental to the earlier crystallizing anorthosites lower ree have virtually no eu anomaly while melts parental to later crystallizing anorthosites higher ree have small negative eu anomalies this is qualitatively consistent with the fractionation of eu relative to other ree by crystallization of plagioclase with large positive eu anomalies melts parental to the mg suite have much higher total ree and very large negative eu anomalies the characteristics of mg suite norite parental magmas may have been derived by the assimilation of kreep near the crust mantle boundary by mg rich basaltic melts formed deeper in the cumulate pile or near the contact between the lower cumulate horizons of the magma ocean and primitive unprocessed lunar mantle 800 km

four lunar mare meteorites crystallization trends of pyroxenes and spinels we studied crystallization trends of pyroxene and spinel in four antarctic meteorites known to be derived from mare regions of the moon y 793169 and a 881757 ya meteorites are unbrecciated igneous basalts eet 87521 is a fragmental breccia and y 793274 is a regolith breccia all have relatively low bulkrock tio2 content and the ya meteorites are uncommonly ancient our electron probe microanalysis epma data indicate that the ya meteorites and the dominant mare components of y 793274 and eet 87521 conform to a general trend for ti poor low ti and very low ti mare basalts their pyroxenes show a strong correlation between fe fe mg fe and ti ti cr ti both ratios typically increasing from core to rim these trends presumably reflect local crystallization differentiation of interstitial melt previous studies m j drake and coworkers have suggested that the detailed configurations of such fe vs ti trends may reflect the bulk tio2 contents of the parent magmas basalts as a more systematic approach to this problem we plot bulk rock tio2 as a function of the fe 0 50 intercept of each rock s pyroxene fe vs ti trend we call this intercept the fe normalized ti based on our data for eet 87521 the ya meteorites and apollo 12 basalts 12031 and 12064 plus literature data for several other ti poor mare basalts we find a strong correlation between fe normalized ti and the bulk tio2 content of the parent basalt this correlation confirms that fragmental breccia eet 87521 is nearly pure very low ti vlt basalt and that the ya meteorites for which bulk rock tio2 results scatter due to unusually coarse grain size a 881757 or scarcity of available sample y 793169 are pieces of an uncommonly ti poor but not quite vlt variety of low ti mare basalt extrapolating from this correlation the dominant mare component of regolith breccia y 793274 is probably of vlt affinity besides the normal mare pyroxene trend of strong correlation between fe and ti y 793274 includes two additional pyroxene compositional trends both showing a wide range of ti despite relatively constant and low by mare standards fe the most magnesian of these trends consists of a single clast with a mode of orthopyroxene mgo rich ilmenite these two trends are of uncertain origin possibly one or both represents the highland component of this regolith breccia although unlike most highland pyroxenes these appear relatively unaltered by impact brecciation and metamorphism compositions of spinels in the coarse grained a 881757 show an extraordinary distribution chromite and ulvospinel components vary among grains but are nearly constant within grains despite its old age and unusually coarse grain sizes mineralogical evidence i e heterogeneity within both pyroxene and spinel typical pyroxene exsolution scale very coarse by mare standards but exceeded by the pyroxenes of eet 87521 and y 793274 indicates that a 881757 was cooled only slightly more slowly than typical mare basalts and may have formed near the center of an uncommonly thick lava flow both of the vlt basaltic lunar meteorite breccias eet 87521 and y 793274 are composed dominantly of pyroxenes with exsolution coarser than normal for mare basalts possibly vlt basalt flows tend to be systematically thicker and thus more slowly cooled than more ti rich flows

mineralogy petrology and shock history of lunar meteorite sayh al uhaymir 300 a crystalline impact melt breccia sayh al uhaymir sau 300 comprises a microcrystalline igneous matrix grain size s4 the association of maskelynite with melt pockets and shock veins indicates a subsequent local 28 45 gpa shock stage s2 s3 excursion which was probably responsible for lofting the sample from the lunar surface subsequent fracturing is attributed to atmospheric entry and probable breakup of the parent meteor

ion microprobe investigation of plagioclase and orthopyroxene from lunar mg suite norites implications for calculating parental melt ree concentrations and for assessing postcrystallization ree redistribution the lunar mg suite which includes dunites troctolites and norites makes up to 20 30 of the moon s crust down to a depth of 60 km the remainder is largely anorthosite this report focuses on norites which consist mostly of orthopyroxene and plagioclase because we have found that both phases are effective recorders of their parental melt compositions in an earlier report we analyzed orthopyroxene from twelve samples three from apollo 14 two from a 15 and seven from a 17 by sims for eight ree la ce nd sm eu dy er yb inversion of these data to estimated melt compositions yielded extremely high ree concentrations similar to kreep in this study we report sims ree data for plagioclase from these same twelve samples the major objective of this study is to estimate parental ree concentrations from both orthopyroxene and plagioclase data to see if both data inversions produce concordant melt compositions and thus better constrain the composition of melts parental to mg suite norites the estimated ree concentrations from both phases show some evidence of slight postcrystallization ree redistribution comparison of the observed ratio of ree for pyroxene plagioclase to the ratio of the ds for pyroxene plagioclase is consistent with ree redistribution which involves lree diffusing from pyroxene into plagioclase and hree diffusing from plagioclase into pyroxene however apparently these postcrystallization exchanges have not seriously affected our ability to estimate melt ree concentrations the estimated melt ree concentrations using both plagioclase and orthopyroxene are similar to high k kreep especially for melts parental to a 15 norites this study provides support for mineral trace element inversion estimates for parental melts even though these lunar crustal lithologies experienced high temperature annealing apparently the cores of plagioclase and pyroxene continue to carry a record of their igneous crystallization history