the competition between thermal contraction and differentiation in the stress history of the moon the scarcity of both extension and compression features on the moon strongly constrains the history of the lunar radius to variations of less than 1 km over the past 3 8 gyr this limit has traditionally been interpreted as requiring a delicate balance between thermal contraction of the near surface and expansion of a substantial cold interior region recent theories of lunar origin e g giant impact in contrast favor a hot initial state we propose that a reconciliation may be possible by taking account of the volume change v v d due to differentiation we calculate stp densities based on simplified normative mineralogies for a suite of estimates of the bulk lunar composition of primary lunar basalt and of the residuum left when the maximum amount of the latter is extracted from the former typically v v d 2 to 5 an expansion equivalent to heating by 10 3 k provided the timing of differentiation is correct one might offset the cooling of a magma ocean as much as 630 km deep by differentiation of the remainder of the moon which need not start much below the solidus temperature a large but not impossible amount of gabbroic melt production is implied 100 times the volume of mare basalts known to have been extruded we do not address the detailed genetic relationship of this melt to the basalts observed on the lunar surface but point out that it need not have reached the surface directly or even have entered the crust in order for the expansion to have occurred to assess the timing of melt formation we investigate a simple conductive lunar thermal model which takes account of both v v d and thermal contraction our initial state is characterized by a central temperature t c and a depth z 0 above which the material derived from the magma ocean is already at the solidus and is not suceptible to volume changes upon further differentiation we find a range of models satisfying the limits on radius increase and decrease the hottest has t c 1210 k z 0 400 km without v v d we would need a larger or colder or both core e g t c 700 k for z0 200 400 km in agreement with previous investigators our modeling thus lends credence to the idea that the moon could have been initially 50 molten with the remainder relatively close to the solidus and yet experienced little volume change over the last 3 8 gyr

the oxygen isotope composition petrology and geochemistry of mare basalts evidence for large scale compositional variation in the lunar mantle to investigate the formation and early evolution of the lunar mantle and crust we have analysed the oxygen isotopic composition titanium content and modal mineralogy of a suite of lunar basalts our sample set included eight low ti basalts from the apollo 12 and 15 collections and 12 high ti basalts from apollo 11 and 17 collections in addition we have determined the oxygen isotopic composition of an apollo 15 kreep k potassium ree rare earth element and p phosphorus basalt sample 15386 and an apollo 14 feldspathic mare basalt sample 14053 our data display a continuum in bulk rock delta o 18 values from relatively low values in the most ti rich samples to higher values in the ti poor samples with the apollo 11 sample suite partially bridging the gap calculation of bulk rock delta o 18 values using a combination of previously published oxygen isotope data on mineral separates from lunar basalts and modal mineralogy determined in this study match with the measured bulk rock delta o 18 values this demonstrates that differences in mineral modal assemblage produce differences in mare basalt delta o 18 bulk rock values differences between the low and high ti mare basalts appear to be largely a reflection of mantle source heterogeneities and in particular the highly variable distribution of ilmenite within the lunar mantle bulk delta o 18 variation in mare basalts is also controlled by fractional crystallisation of a few key mineral phases thus ilmenite fractionation is important in the case of high ti apollo 17 samples whereas olivine plays a more dominant role for the low ti apollo 12 samples consistent with the results of previous studies our data reveal no detectable difference between the delta o 17 of the earth and moon the fact that oxygen three isotope studies have been unable to detect a measurable difference at such high precisions reinforces doubts about the giant impact hypothesis as presently formulated

global spatial deconvolution of lunar prospector th abundances 1 we have completed the first global spatial deconvolution analysis of planetary gamma ray data for lunar th abundances as measured by the lunar prospector gamma ray spectrometer we tested two different spatial deconvolution techniques jansson s method and the pixon method and determined that the pixon method provides superior performance the final deconvolved map results in a spatial resolution improvement of a factor of 1 5 2 the newly deconvolved data allow us to clearly delineate nearside th enhancements and depressions validate enhanced th abundances associated with specific lunar red spots and reveal new details of the th distribution at the aristarchus plateau

mineralogy and petrology of the lapaz icefield lunar mare basaltic meteorites five basaltic meteorites from the lapaz ice field are paired on the basis of their mineralogy and texture and represent a unique basalt type distinct from those in the apollo or luna sample collections lapaz icefield lap 02205 lap 02224 lap 02226 lap 02436 and lap 03632 all contain plagioclase pyroxene ilmenite spinel olivine and minor troilite metal phosphate baddeleyite and silica cristobalite brown glassy melt veins are ubiquitous and cross the primary igneous texture plagioclase the major mineral and occurring as laths in a subophitic texture is of narrow compositional range from an85 89 pyroxene also a major mineral is strongly zoned from augite and pigeonite cores to very iron rich rims ilmenite laths comprise approximately 3 5 of the basalts spinels show a large compositional range comparable to that documented in apollo 15 basalts indicating an early chromite rich stage followed by an intermediate to late stage with cr rich ulvspinel relatively large subhedral to skeletal olivine crystals fo46 62 are sparse and are too forich to be in equilibrium with the bulk rock indicating that these are xenocrysts rather than phenocrysts the presence of melt veins with a similar composition to the bulk rock maskelynitized plagioclase feldspar and metastable cristobalite indicate that these rocks underwent significant shock between 30 and 50 gpa calculated oxygen fugacity using spinel ilmenite iron metal equilibria is within the range defined by previous studies of lunar materials the bulk composition low mgo and low calculated temperatures together with modelling calculations indicate an origin by fractional crystallization of a more primitive low tio2 parent liquid similar to apollo 12 olivine basalt

inter and intra group compositional variations in apollo 15 pyroclastic green glass an electron and ion microprobe study abstract representative samples of the five compositionally distinct groups a e of apollo 15 pyroclastic green glass were systematically analyzed for major and trace element abundances by electron and ion microprobe techniques these primary magma compositions define a high co trend groups a and d and a low co trend groups b and c on sr zr ba and nd versus co variation diagrams group e glasses are significantly enriched in sr relative to the glass groups of the two trends pearce element ratio analyses and sr ca ba ca systematics indicate that olivine orthopyroxene and clinopyroxene controlled green glass compositions simple crystal liquid igneous fractionation processes involving such an assemblage however cannot explain the observed inter and intra group trace element variation trends the magmas represented by the high and low co trends are interpreted to have been erupted from two distinct but compositionally variable source regions a source mixing model involving differentiated cumulate trapped residual liquid and extremely fe rich components can successfully account for the compositional ranges of the two sources required to produce the observed chemical variations upon partial melting group e glasses appear to represent a magma erupted from a source with a more limited chemical variability the apollo 15 green glasses represent multiple eruptive events from three chemically distinct but compositionally variable source regions assuming that this mixing model is correct

the geochemistry and provenance of apollo 16 mafic glasses the regolith of the apollo 16 lunar landing site is composed mainly of feldspathic lithologies but mafic lithologies are also present a large proportion of the mafic material occurs as glass we determined the major element composition of 280 mafic glasses 10 wt feo from six different apollo 16 soil samples a small proportion 5 of the glasses are of volcanic origin with picritic compositions most however are of impact origin approximately half of the mafic impact glasses are of basaltic composition and half are of noritic composition with high concentrations of incompatible elements a small fraction have compositions consistent with impact mixtures of mare material and material of the feldspathic highlands on the basis of major element chemistry we identified six mafic glass groups vlt picritic glass low ti basaltic glass high ti basaltic glass high al basaltic glass kreepy glass and basaltic andesite glass these glass groups encompass 60 of the total mafic glasses studied trace element analyses by secondary ion mass spectroscopy for representative examples of each glass group 31 total analyses support the major element classifications and groupings the lack of basaltic glass in apollo 16 ancient regolith breccias which provide snapshots of the apollo 16 soil just after the infall of imbrium ejecta leads us to infer that most if not all of the basaltic glass was emplaced as ejecta from small or moderate sized impacts into the maria surrounding the apollo 16 site after the imbrium impact the high ti basaltic glasses likely represent a new type of basalt from mare tranquillitatis whereas the low ti and high al basaltic glasses possibly represent the composition of the basalts in mare nectaris both the low ti and high al basaltic glasses are enriched in light rees which hints at the presence of a kreep bearing source region beneath mare nectaris the basaltic andesite glasses have compositions that are siliceous ferroan alkali rich and moderately titaniferous they are unlike any previously recognized lunar lithology or glass group their likely provenance is within the procellarum kreep terrane but they are not found within the apollo 16 ancient regolith breccias and therefore were likely deposited at the apollo 16 site post imbrium the basaltic andesite glasses are the most ferroan variety of kreep yet discovered

origin of lead from green glass of apollo 15426 a search for primitive lunar lead a major obstacle in lunar u pb chronology is the elusiveness of the primary pb isotopic composition and u pb ratio and therefore the pb evolution for the early history of the moon in an attempt to seek the primitive lunar pb isotopic composition green glass from lunar clod 15426 49 was studied for u th pb systematics because it is extremely mg rich and known to be the most primitive among sampled lunar volcanic rocks green glass and yellow impact glass were handpicked washed with water then washed in an acid mixture 0 3 n hbr 0 2 n hf and the washes and residues were analyzed in contrast to the pb from apollo 17 orange glass pb from the surface of the green glass spherules is totally different from that of the spherule interior but is similar to lunar surface lead data for the interior pb yield a 207pb 206pb age of 3 41 ga because of the low pb concentration and high u pb ratio observed for the interior the initial pb was poorly defined nevertheless the data indicate that lunar pb evolved in an environment with 238u 204pb 19 55 which is considerably lower than those for mare basalts around 300 but higher than values for the earth 6 8

interior of the moon the presence of garnet in the primitive deep lunar mantle new trace element data have been generated by inductively coupled plasma mass spectrometry icp ms for 65 high and low ti mare basalts from the apollo 11 12 14 15 and 17 landing sites these data demonstrate that ratios of the high field strength elements and yttrium are generally chondritic in the mare source regions for the low ti basalts but nonchondritic in the high ti basalts and potassium rare earth elements and phosphorus kreep such differences can be explained by addition and subtraction respectively of ilmenite this interpretation is consistent with derivation of the basalts from lunar magma ocean lmo cumulates through which late stage ilmenite has sunk and mixed with earlier magma ocean products compositional differences between the mare basalts and volcanic glass beads suggest that at least some of the latter were derived from a garnet bearing source region siderophile and chalcophile element data suggest that the garnet bearing source escaped the lmo melting event and thus represents primitive moon material the remaining glasses are generally very low ti vlt and appear to have been derived from early lmo cumulates i e olivine and orthopyroxene similar to the vlt basalts the remaining glasses were derived from below the lmo cumulates and as the magmas rose they underwent sequential assimilation to varying degrees initially of an ilmenite rich cumulate followed by a kreep component this study presents geochemical evidence for the existence of garnet in a mare source and demonstrates the likelihood that the lmo was not whole moon thus preserving primitive lunar material which has acted as the source region for at least some of the volcanic glasses

petrography relationships and petrogenesis of the gabbroic lithologies in northwest africa 773 clan members northwest africa 773 2727 3160 3170 7007 and 10656

a sims study of lunar komatiitic glasses trace element characteristics and possible origin abstract in apollo 16 regolith breccias wentworth and mckay 1988 identified a suite of minute sio 2 37 5 52 al 2 o 3 12 5 32 tio 2 0 1 1 6 and ultra mg character atomic mg mg fe 0 90 of the glasses suggest a variety of possible origins from complex impact processes to complex volcanic processes involving rather unusual and primitive magmatism trace element data derived from in situ secondary ion mass spectrometric sims analysis of individual glass beads show a wide range of concentrations la n 25 290 yb n 16 120 ba 80 1000 ppm zr 182 800 ppm sr 70 230 ppm with distinguishable trace element characteristics ba sr 1 la yb n 1 5 2 5 eu sm n 0 1 0 3 low siderophile element concentrations incompatible element concentrations are highly correlated to each other and to fe the extent of trace element depletion or enrichment in these glasses appears to be correlated to the siderophile character of the element ionization potential or experimentally determined silicate melt fe metal partition coefficients k d 1 for co fe k d k d 1 for ba ree zr the ultra mg glasses are depleted in co relative to a bulk moon mg co exhibited by many lunar samples volcanic glasses basalts regolith breccia estimated upper mantle the low co and high incompatible element concentrations diminish the possibility that these glasses are a product of lunar komatiitic volcanism or impact excavation and melting of a very high mg plutonic unit the low siderophile fe and co concentrations suggest a complex impact melt process which involved impact into compositionally variable targets reduction of feo to fe metal partitioning of siderophile elements into the metal phase and efficient separation of that phase from the impact droplets

on the connection between mare basalts and picritic volcanic glasses the evolution of the major element compositions of mare basaltic liquids and coexisting crystals in low pressure fractionation processes has been modeled in order to examine the postulated link between picritic volcanic glasses and mare basalts existing models of equilibrium and fractional crystallization longhi 1977 1982 have been modified to include expressions for the cr spinel liquidus surface and the boundary between the armalcolite and ilmenite surfaces average molar partition coefficients for armalcolite liquid pairs are also included in the modifications results of the calculations show that most mare basalts are not derived by simple low pressure fractionation from parents with the compositions of picritic glasses as tabulated by delano 1986a also there is no indirect evidence as yet for posteruption fractionation of picritic magmas in the form of sufficiently magnesian mare type olivines at the apollo 12 and 15 landing sites however the calculations do suggest that luna 24 ferrobasalt and apollo 11 high k basalts could have been derived by simple near surface fractionation of known picritic compositions also xenocrystic olivines with mare like concentrations of tio2 and cao in high ti basalt 74275 provide evidence for the existence of a picritic magma at the apollo 17 site more importantly the calculations indicate that the picritic magmas would have fractionated to produce basalts with bulk and mineral compositions generally similar to those of mare basalts these latter results favor the hypothesis that mare basalts have fractionated nonprimary compositions and that the small number of observed linkages between basalts and picritic parents is a consequence of limited sampling

petrogenesis of primitive and evolved basalts in a cooling moon experimental constraints from the youngest known lunar magmas abstract we have conducted high temperature experiments over a range of pressures to constrain the petrogenesis of the youngest sampled lunar magmas which have contrasting primitive and evolved compositions our results indicate that at 3 ga melting still occurred within the same mantle depth range that produced crystalline mare basalts for the previous 1 ga although our data cannot support or confirm that the shallowest extents of melting moved deeper into the mantle by 3 ga as is predicted by most thermal evolution models furthermore melting still occurred in regions with low abundances of heat producing elements basaltic lunar meteorite nea 003a has some of the lowest abundances of incompatible trace elements among all mare basalts and no negative eu anomaly our experiments show that nea 003a is multiply saturated with olivine and low ca pyroxene on its liquidus at 1 1 gpa 215 km and 1330 c if the primitive nea 003a liquid composition is a minimally modified melt the relatively low mg of its source region 73 75 its lack of a eu anomaly and its chondritic initial nd isotopic composition indicate its source region likely escaped mixing during mantle overturn with later stage magma ocean cumulates that formed after plagioclase saturation this condition would require the sources of the ultramafic glasses to have experienced cumulate mixing or for assimilation of later stage magma ocean cumulates by the ultramafic glass parental magmas before eruption in order to account for their higher mg s and deeper negative eu anomalies alternatively nea 003a may have undergone some fractional crystallization in which case its more primitive source region would be deeper than 215 km and may approach the depth range of the ultramafic glass source regions iron and incompatible trace element rich basaltic lunar meteorites lap 02205 nwa 032 479 and nwa 4734 have nearly identical bulk compositions and have a multiple saturation point on their high pressure liquidus at

characterization of previously unidentified lunar pyroclastic deposits using lunar reconnaissance orbiter camera data 1 we used a lunar reconnaissance orbiter camera lroc global monochrome wide angle camera wac mosaic to conduct a survey of the moon to search for previously unidentified pyroclastic deposits promising locations were examined in detail using lroc multispectral wac mosaics high resolution lroc narrow angle camera nac images and clementine multispectral ultraviolet visible or uvvis data out of 47 potential deposits chosen for closer examination 12 were selected as probable newly identified pyroclastic deposits potential pyroclastic deposits were generally found in settings similar to previously identified deposits including areas within or near mare deposits adjacent to highlands within floor fractured craters and along fissures in mare deposits however a significant new finding is the discovery of localized pyroclastic deposits within floor fractured craters anderson e and f on the lunar farside isolated from other known similar deposits our search confirms that most major regional and localized low albedo pyroclastic deposits have been identified on the moon down to 100 m pix resolution and that additional newly identified deposits are likely to be either isolated small deposits or additional portions of discontinuous patchy deposits

apollo 15 green glass compositional distribution and petrogenesis abstract we have characterized a comprehensive suite of individual green glass beads from apollo 15 soil to determine interelement behavior and to constrain petrogenetic relationships we analyzed 365 particles for trace elements by instrumental neutron activation analysis and analyzed 52 of them selected to cover the compositional ranges observed for trace elements for major elements by electron microprobe analysis we confirm the observation of delano 1979 that the beads comprise discrete compositional groups although two of the groups he denned are further split on the basis of trace element compositions each of the resulting seven groups has distinct average rare earth abundances the coherence between major and trace element data was masked in previous studies by imprecision correlated error and nonrepresentative sampling of the different groups most of the compositional characteristics of the green glasses can be explained by a model for batch equilibrium melting of a nearly homogeneous ultramafic source region when the complicating effects of high pressure and low oxygen fugacity are taken into account the previously puzzling behavior of ni and co as apparently incompatible elements may arise from partial reduction of those elements to the zero oxidation state resulting in low mineral melt partition coefficients the model also offers explanations for why the green glasses form boomerang shaped trends on many two element variation diagrams and why certain compositions groups a and d are more abundant than glasses with other compositions

lunar ferroan anorthosites and mare basalt sources the mixed connection global overturn of a hot gravitationally unstable lunar mantle immediately following the solidification of a magma ocean and essentially complete by 4 4 ga explains several characteristics of lunar petrology lunar mare basalt sources are inferred to be depleted in europium and alumina these depletions are consensually attributed to complementary plagioclase floating from a magma ocean however the connection cannot be so simple and direct in contrast to the mare basalt source parent magma the ferroan anorthosite parent magma was more evolved by virtue of its lower mg fe ratio and ni abundances although less evolved in its poverty of clinopyroxene constituents flat rare earth pattern and lower incompatible element abundances the europium anomaly in mare sources is inferred to be present at 400 km depth too deep to have been directly influenced by plagioclase crystallization massive overturning of the post magma ocean mantle would have carried down clinopyroxene ilmenite and phases containing fractionated rare earths europium anomalies and some heat producing radionuclides these phases contributed to deep mare basalt sources upward moving phases would have been magnesian mafic minerals their immediate melting on pressure release contributed the magnesian suite of plutonic norites and troctolites that post date the anorthosites in the highlands crust

origin of the lunar highlands mg suite an integrated petrology geochemistry chronology and remote sensing perspective the mg suite represents an enigmatic episode of lunar highlands magmatism that presumably represents the first stage of crustal building following primordial differentiation this review examines the mineralogy geochemistry petrology chronology and the planetary scale distribution of this suite of highlands plutonic rocks presents models for their origin examines petrogenetic relationships to other highlands rocks and explores the link between this style of magmatism and early stages of lunar differentiation of the models considered for the origin of the parent magmas for the mg suite the data best fit a process in which hot solidus temperature at 2 gpa 1600 to 1800 c and less dense 3100 kg m3 early lunar magma ocean cumulates rise to the base of the crust during cumulate pile overturn some decompressional melting would occur but placing a hot cumulate horizon adjacent to the plagioclase rich primordial crust and kreep rich lithologies at temperatures of 1300 c would result in the hybridization of these divergent primordial lithologies producing mg suite parent magmas as urkreep primeval kreep is not the petrologic driver of this style of magmatism outside of the procellarum kreep terrane pkt mg suite magmas are not required to have a kreep signature evaluation of the chronology of this episode of highlands evolution indicates that mg suite magmatism was initiated soon after primordial differentiation 10 m y alternatively the thermal event associated with the mantle overturn may have disrupted the chronometers utilized to date the primordial crust petrogenetic relationships between the mg suite and other highlands suites e g alkali suite and magnesian anorthositic granulites are consistent with both fractional crystallization processes and melting of distinctly different hybrid sources

lunar rock rain diverse silicate impact vapor condensates in an apollo 14 regolith breccia abstract apollo 14 regolith breccia 14076 long known to be uniquely endowed with high alumina silica poor hasp material of evaporation residue origin has been found to contain a diverse suite of complementary condensates dubbed gasp gas associated spheroidal precipitates gasp occurs in two forms as glassy or extremely fine grained quenched melt spheroids mostly less than 5 m across and as quenched textured clasts up to 200 m across in two of the clasts origin by aggregation of spheroidal gasp is confirmed by the presence of relict spheroids gasp is distinctively depleted in the same refractory major oxides that are characteristically enriched in hasp al 2 o 3 and cao among the larger gasp spheroids al 2 o 3 is seldom 1 wt among the clasts excluding two instances of apparent contamination by na and k rich substrate derived melt bulk al 2 o 3 averages 0 3 wt depletion of al 2 o 3 and cao is also manifested by pyroxene compositions in some clasts e g in the largest clast en 82 wo 0 45 with 0 07 wt al 2 o 3 although gasp bulk compositions are nearly pure sio 2 mgo feo they are nonetheless highly diverse spheroid compositions range in mg from 7 to 84 mol and in feo sio 2 weight ratio from 0 002 to 0 67 bulk compositions and textures of many gasp spheroids suggest that liquid immiscibility occurred prior to quenching implying that these materials were some time after condensation at temperatures of 1680 c textural evidence for immiscibility includes lobate boundaries between silicic and mafic domains and a general tendency for quenched mafic silicates to be concentrated into a few limited patches rather than evenly dispersed the parent melt of the largest clast s pyroxene is inferred to have formed as a partial melt within the parent aggregation of gasp matter compositionally near the pyroxene cristobalite melt eutectic and thus at 1500 c a few gasp spheroids show possible signs of in flight collision coalescence but aggregation of the much larger clasts probably took place in mushy puddles on the lunar surface little mixing took place between these gasp puddles and the related hasp probably because gasp condensation did not commence until after an intermediate stage during which while neither net evaporation nor net condensation took place expansion of the vapor cloud carried the eventual gasp matter well apart from the hasp considering the characteristic length scale of lunar regolith mixing the concentration of both gasp and hasp into this single unique regolith sample 14076 is most consistent with a parent crater size diameter of 10 100 km i speculate that the 14076 regolith may have been unusually situated almost directly uprange from an unusually oblique large impact mercurian analogs of the 14076 impact condensates may have significant implications for remote sensing

the role of ilmenite in the source region for mare basalts evidence from niobium zirconium and cerium in picritic glasses abstract to investigate models for the generation of lunar high ti basalts we have analyzed lunar picritic glasses for zr nb ce and ti at high precision using ion microprobe techniques the picritic magmas represented by these glasses have experienced minor crystallization which has allowed us to partially eliminate the effects of post melting processes commonly experienced by crystalline high ti mare basalts the nb zr for these glasses ranges from 05 11 the high ti glasses generally tend to have higher values of nb zr 072 109 than the very low ti glasses 048 085 the crystalline mare basalts tend to have slightly higher nb zr than glasses with similar ti from the same site for example the apollo 17 a17 high ti basalts have nb zr of approximately 09 whereas the a17 high ti glasses have nb zr of 07 kreep has nb zr of approximately 06 thus zr is fractionated from nb to different degrees in the various picritic magmas the concentrations of zr nb and ce increase from the very low ti glasses to the high ti glasses and along the trajectory the nb ce and zr ce increase nb ce 25 1 6 and zr ce 4 15 for the picritic glasses overlap with kreep nb ce 36 and zr ce 5 zr ti and nb ti show a wide range of variation in these glasses both zr ti and nb ti in the glasses range from approximately 0014 to slightly less than 0003 the zr ti and nb ti for these glasses overlap with that of the crystalline mare basalts generally with increasing ti nb and zr zr ti and nb ti decrease the exceptions to this are the apollo 14 a14 glasses that exhibit an increase in nb ti and zr ti based on these data for the picritic glasses and experimentally determined partition coefficients for nb zr and ce the mantle sources for these picritic magmas are slightly to moderately fractionated from c1 chondrite and previous estimates of the bulk silicate moon our best fit model for our data and this observation is that both the very low ti and high ti picritic magmas were derived through small to moderate degrees of nonmodal melting of lunar mantle sources consisting of a mixture of late stage lmo cumulates derived after 95 crystallization of the lmo and early to intermediate lmo cumulates derived prior to 80 crystallization of the lmo the early lmo cumulates had nb zr zr ce and nb ce ratios near c1 chondrite whereas these ratios were fractionated in the late stage lmo cumulates this hybridization of mantle sources occurred during large scale overturning of the lmo cumulate pile the source for the low ti picritic magmas had very minor amounts of ilmenite whereas the source for the high ti picritic magmas probably contained less than 6 ilmenite for all the picritic magmas ilmenite was exhausted from the residua during melting models suggesting that the high ti magmas are derived through the assimilation of an ilmenite bearing cumulate layer or preferential assimilation of ilmenite by low ti primary magmas are not consistent with the nb zr ce and ti data magmas hubbard and minear 1975 wagner and grove 1993 1995 in particular the preferential assimilation by very low ti picritic magmas of ilmenite with expected nb ce 20 000 22 000 and nb zr 55 signatures would displace the resulting high ti magma too far from our observed data large scale overturning of the lmo cumulate pile also accounts for the trace element signatures found in the a14 picritic glasses the evolved signature found in these primitive very low ti picritic glasses is most likely a product of kreep incorporation into the lmo cumulate source rather than either contamination by evolved ilmenite bearing cumulates or incorporation of higher proportions of locally derived intercumulus melt

lunar volcanic glasses and their constraints on mare petrogenesis abstract volcanic glasses from the apollo 11 14 15 and 16 landing sites have been analyzed for major elements and ni by electron microprobe the 19 varieties of volcanic glass define two distinct chemical arrays that provide new insights into a the petrogenesis of mare basalts and b the structure of the deep lunar interior a simple model is proposed whereby mare basaltic liquids may have been derived from two isolated cumulate systems occurring at depths of 300 km and 400 km each system was itself composed of two lithologic components low ti vs high ti that underwent hybridization assimilation or mixing to generate the large compositional range of magmas observed within each array while the distribution of the two components within each system was locally heterogeneous data indicate that the components themselves were chemically uniform on at least a regional scale the surface correlated volatiles associated with the lunar volcanic glasses seem to have come from some other reservoir within the moon the simplicity of the chemical relationships observed among the lunar volcanic glasses allow specific predictions to be made we believe that they should readily reveal any strengths or weaknesses of this new model

the isotopic record of lunar volcanism abstract the timing and extent of lunar volcanism was determined primarily by the internal thermal evolution of the moon a late heavy bombardment produced most of the observable lunar basins easily recognized stratigraphic markers and also may have influenced lunar volcanism most of the nearside basins seem to have been produced 3 8 4 0 ga ago during a period often referred to as the lunar cataclysm the pre cataclysm period was characterized by formation of the lunar crust plutonic rocks within the crust and pre mare volcanism isotopic analysis of breccia clasts pre dating the cataclysm has yielded an outline of this period the isotopic record of post cataclysm mare volcanism is clear but incomplete because samples from the youngest mare areas are lacking specifically the isotopic data show that some lunar anorthosites formed 4 45 ga ago consistent with early formation of an anorthositic lunar crust some mg suite norites troctolites and dunites also formed approximately contemporaneously with the oldest anorthosites but others are up to 200 300 ma younger more evolved rocks granites and quartz monzodiorites also formed between 4 4 and 4 0 ga ago the earliest known pre mare volcanism at 4 25 ga ago included aluminous mare like basalts and an olivine gabbronorite similar to apollo 12 basalts kreep basalt volcanism began at least 4 1 ga ago approximately contemporaneously with that of the ancient mare like basalts and continued during the cataclysm recorded instances of high ti mare basalt volcanism began during or immediately after the cataclysm low ti mare basalt volcanism is the most recent for which samples are available the isotopic data record an early primary lunar differentiation during which mare basalt sources formed probably by crystallization of cumulus minerals from a lunar magma ocean the isotopic record of post cataclysm basalts indicates a heterogeneous lunar mantle and can be explained by partial melting of cumulate sources but more complex petrogenesis also has been suggested more complex petrogenetic processes including assimilation and assimilation fractional crystallization afc seem to be required for pre mare volcanics the isotopic data contain a hint that petrogenesis of the oldest pre mare volcanics may be linked to formation of the so called procellarum basin possibly the oldest and largest lunar basin such a basin would provide a geologic context for the pre mare volcanics and its formation may have been a defining moment in lunar history

pristine lunar glasses criteria data and implications major element analyses of several thousand glasses from all of the apollo landing sites have resulted in the identification of 25 groups of pristine i e volcanic glass the nickel in these pristine glasses is shown to be indigenous not meteoritic contamination and to be correlated with mg the chemical data indicate that these glasses are consistently better candidates for primary magmas than the majority of crystalline mare basalts the pristine glasses support the view that assimilative processes ringwood and kesson 1976 involving two cumulate systems in the differentiated mantle operated during mare petrogenesis the reality of those assimilative interactions is evident by the occurrence of two linear arrays among the chemistries of the glasses data suggest that these cumulate components in the differentiated mantle persist for lateral distances of at least 1000 km and therefore appear to be products of a vast magma ocean that existed early in lunar history alternative hypotheses claiming that the highlands crust and mare source regions were produced by serial magmatism without a magma ocean have not yet considered all of the constraints derived from the pristine glasses

density of high ti basalt magma at high pressure and origin of heterogeneities in the lunar mantle abstract the density of the apollo 14 black glass melt which has the highest tio 2 content of pristine mare glasses was measured to 4 8 gpa and 2100 k using an x ray absorption method a fit of the pressure density temperature data to the high temperature birch murnaghan equation of state yielded the isothermal bulk modulus k t 0 9 0 1 2 gpa its pressure derivative k 0 16 0 3 4 and the temperature derivative of the bulk modulus k t t p 0 0030 0 0008 gpa k at 1700 k the high ti basalt magma is less dense than the lunar mantle below about 1 0 gpa therefore the high ti basalt magma produced in the hybridized source 100 200 km can ascend to the lunar surface the basalt formed at the higher pressure could not ascend but move downwards and solidify in the lunar mantle the solidified high ti basalt components can create chemical heterogeneities in the lunar mantle and can cause the low velocity anomalies observed seismologically

the constitution and structure of the lunar interior the current state of understanding of the lunar interior is the sum of nearly four decades of work and a range of exploration programs spanning that same time period missions of the 1960s including the rangers surveyors and lunar orbiters as well as earth based telescopic studies laid the groundwork for the apollo program and provided a basic understanding of the surface its stratigraphy and chronology through a combination of remote sensing surface exploration and sample return the apollo missions provided a general picture of the lunar interior and spawned the concept of the lunar magma ocean in particular the discovery of anorthite clasts in the returned samples led to the view that a large portion of the moon was initially molten and that crystallization of this magma ocean gave rise to mafic cumulates that make up the mantle and plagioclase flotation cumulates that make up the crust smith et al 1970 wood et al 1970 this model is now generally accepted and is the framework that unifies our knowledge of the structure and composition of the moon the intention of this chapter is to review the major advances that have been made over the past decade regarding the constitution of the moon s interior much of this new knowledge is a direct result of data acquired from the successful clementine and lunar prospector missions as well as the analysis of new lunar meteorites as will be seen results from these studies have led to many fundamental amendments to the magma ocean model much of what we know from sample analyses has been previously summarized elsewhere and only their most important aspects will be discussed in this chapter the reader is referred to the relevant chapters in the books basaltic volcanism on the terrestrial planets basaltic volcanism study project 1981 the

the deep structure of lunar basins implications for basin formation and modification we present models for the structure of the crust and upper mantle beneath lunar impact basins from an inversion of gravity and topographic data from the nearside of the moon all basin models display a thinner crust and an elevated moho beneath the central basin region compared to surrounding areas a signature of the processes of basin excavation and mantle uplift during collapse of the transient cavity there is a general decrease in the magnitude of apparent uplift of mantle material with increasing basin age we attribute this relation primarily to enhanced rates of ductile flow of crustal material early in lunar history when crustal temperatures were relatively high and the effective elastic lithosphere was thin the more relaxed topographic and moho relief associated with older basins on the central nearside may in particular be at least partly a consequence of the extensive subsurface heating associated with the formation of the large procellarum basin the deep structure of the youngest basins constrains the geometry of the cavity of excavation and the amount of crustal material ejected beyond the basin rim from the volumes of the topographic basin of mare basalt fill and of uplifted mantle material the volume of crustal material ejected beyond the basin rim for an orientale sized event was of the order of 107 km 3 a near constant thickness of nonmare crustal material beneath the central regions of young basins of various diameters and preimpact crustal thicknesses suggests that the transient cavity excavated to at least the base of the crust for the largest basins significant excavation into the mantle may have been impeded by an abrupt increase in strength at the lunar moho

convective characteristics of the madden julian oscillation over the central indian ocean observed by shipborne radar during dynamo abstractthis study investigates the convective population and environmental conditions during three mjo events over the central indian ocean in late 2011 using measurements collected from the research vessel r v roger revelle deployed in dynamics of the mjo dynamo radar based rainfall estimates from the revelle c band radar are first placed in the context of larger scale tropical rainfall measuring mission trmm rainfall data to demonstrate that the reduced revelle radar range captured the mjo convective evolution time series analysis and mjo phase based composites of revelle measurements both support the recharge discharge mjo theory time series of echo top heights indicate that convective deepening during the mjo onset occurs over a 12 16 day period composite statistics show evident recharging discharging features in convection and the environment population of shallow isolated convective cells sst cape and the lower tropospheric moisture increase recharge substantially approximately tw

origin of the apollo 14 15 and 17 yellow ultramafic glasses by mixing of deep cumulate remelts abstract we examine the fo2 dependent melting conditions of the apollo 14 yellow intermediate ti ultramafic glasses and the melting processes that formed the full suite of lunar yellow ultramafic glasses multiple saturation experiments indicate that the apollo 14 yellow glass would have been in equilibrium with residual olivine and low ca pyroxene near 1530 c and 2 4 gpa at iw 2 at iw 2 the multiple saturation point moves to greater depth and higher temperature to 1580 c and 3 0 gpa combining the results of this study with that of krawczynski and grove 2012 on more ti rich apollo orange and red glass indicates that the fo2 induced change in multiple saturation pressure correlates with the fe ti molar feo tio2 mgo feo tio2 where tio2 all ti calculated as ti4 of the liquid further a decrease in the olivine fe mg exchange coefficient at lower fo2 suggests that fe2 is complexing more efficiently with ti3 at the expense of mg in the melt than it did with ti4 at higher fo2 processes involving assimilation and or fractionation and or melt wall rock reaction all fail to produce the within suite compositional variability observed in the apollo 14 15 and 17 yellow glasses mixing of remelted source cumulates combined with small amounts of olivine fractionation are the only mechanisms that can reproduce all three trends we present a quantitative model of the mixing process with simultaneous olivine fractionation remarkably the trends can be explained by mixing melts of an ultramafic source olivine pigeonite or orthopyroxene a clinopyroxene ilmenite bearing cumulate and kreep lunar mantle overturn is the most likely process that can reconcile the observed major and trace element compositional characteristics and the experimental results these two constraints are consistent with different models of lunar magma ocean crystallization snyder et al 1992 eklins tanton et al 2011 a complex hot thermal history is necessary to generate the magmas that mixed to form the yellow ultramafic glasses

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

lunar magma ocean crystallization revisited bulk composition early cumulate mineralogy and the source regions of the highlands mg suite abstract crystallization of the lunar magma ocean lmo has been numerically modeled and its products inferred from sample observations but it has never been fully tested experimentally this study is a reexamination of the lmo hypothesis by means of the first experimental simulation of lunar differentiation two end member bulk moon compositions are considered one enriched in refractory lithophile elements relative to earth and one with no such enrichment a two stage model of magma ocean crystallization based on geophysical constraints is simulated and features early crystal suspension and equilibrium crystallization followed by fractional crystallization of the residual magma ocean an initially entirely molten moon is assumed part 1 of this study presented here focuses on stage 1 of this model and considers the early cumulates formed by equilibrium crystallization differences in mantle mineralogy resulting from different bulk moon compositions and implications for the source regions of the highlands mg suite refractory element enriched bulk moon compositions produce a deep mantle that contains garnet and trace cr spinel in addition to low ca pyroxene and olivine in contrast compositions without refractory element enrichment produce a deep dunitic mantle with low ca pyroxene but without an aluminous phase the differences in bulk composition are magnified in the residual melt the residual lmo from the refractory element enriched composition will likely produce plagioclase and ilmenite earlier and in greater quantities both compositions produce mg rich early cumulate piles that extend from the core mantle boundary to 355 km depth if 50 equilibrium crystallization and whole moon melting are assumed these early lmo cumulates provide good fits for the source regions for a component of the high mg ni and co poor parental magmas of the mg suite cumulates if certain conditions are called upon the olivine in early lmo cumulates produced by either bulk moon composition is far too rich in cr to be reasonable for the source regions of the mg suite meaning either core formation in the presence of s and or c must be invoked to deplete the lmo and the crystallizing olivine in cr or that current estimates of the bulk lunar cr content are too high we infer that melts meeting the criteria of the mg suite parents could be produced from early lmo cumulates by solid state kreep and plagioclase hybridization near the base of the crust and subsequent partial melting additionally we propose a revised model for mg suite petrogenesis

a new look at the apollo 11 regolith and kreep although the apollo 11 mission landed in mare tranquillitatis 50 km from the nearest exposure of highlands small nonmare particles are conspicuous in the regolith the nonmare portion of the apollo 11 regolith is compositionally similar to the apollo 16 regolith at both sites most of the nonmare material is from the feldspathic highlands but some is mafic impact melt breccia with the chemical signature known as kreep for its high concentrations of k rare earth elements and p the composition of the apollo 11 regolith corresponds best to a mixture of 66 crystalline mare basalt 5 orange volcanic glass 20 material of the feldspathic highlands 8 kreep bearing impact melt breccia and 1 meteoritic material the volcanic glass and kreep bearing melt breccia components account for the high concentrations of mg and cr in the regolith the most kreep rich sample known from apollo 11 10085 1187 is an impact melt breccia that bears a strong textural and compositional similarity to a unique apollo 16 melt breccia 64815 although not of the maria such breccias are also not of the highlands provenance global data obtained from orbit show that kreep bearing materials are most common at low elevations in the imbrium procellarum region and are rare at high elevations thus as at apollo 16 the kreep bearing breccias of apollo 11 are probably ejecta from the imbrium impact into the low lying procellarum kreep terrane on the basis of these observation and others we suggest that the general acceptance of kreep as a material of the highlands is not supported by the data and results largely from historical accident

the basalts of mare frigoris this paper discusses the methodology and results of a detailed investigation of mare frigoris using remote sensing data from clementine lunar prospector and lunar reconnaissance orbiter with the objective of mapping and characterizing the compositions and eruptive history of its volcanic units with the exception of two units in the west mare frigoris and lacus mortis are filled with basalts having low tio2 to very low tio2 low feo and high al2o3 abundances these compositions indicate that most of the basalts in frigoris are high al basalts a potentially undersampled yet important group in the lunar sample collection for its clues about the heterogeneity of the lunar mantle thorium abundances of most of the mare basalts in frigoris are also low although much of the mare surface appears elevated due to contamination from impact gardening with the surrounding high th imbrium ejecta there are however a few regional thorium anomalies that are coincident with cryptomare units in the east the two youngest mare basalt units and some of the scattered pyroclastic deposits and volcanic constructs in addition mare frigoris lies directly over the northern extent of the major conduit for a magma plumbing system that fed many of the basalts that filled oceanus procellarum as interpreted by andrews hanna et al 2014 using data from the gravity recovery and interior laboratory mission the relationship between this deep reaching magma conduit and the largest extent of high al basalts on the moon makes mare frigoris an intriguing location for further investigation of the lunar mantle

lunar regional dark mantle deposits geologic multispectral and modeling studies clementine five channel uv visible uvvis data have been used to study seven regional dark mantle deposits dmds on the moon the dmds were mapped in distribution to determine their extent and stratigraphic relationship to other geologic units based upon the spectral properties for each dmd the crystallization of the beads in each deposit was inferred and used to estimate cooling rates in the volcanic plumes that emplaced the deposits deposits with a high concentration of glasses reflect volcanic plumes that had low optical densities and high cooling rates whereas deposits dominated by crystallized beads indicate plumes with slower cooling rates due to higher optical densities spectral data from each of the regional dmds show that their glass crystallized bead ratio can be estimated based upon their 415 750 and 750 950 nm values and comparison to laboratory spectra for the beads patches of young dark mantle in the sinus aestuum dmd represent one extreme with the bluest color highest 415 750 and weakest glass band absorption lowest 750 950 of all the dmds at the other extreme is the aristarchus plateau dmd with the reddest color and strongest glass band absorption the other nearside dmds including taurus littrow sulpicius gallus rima bode and mare vaporum lie between these two extremes due to intermediate mixtures of the crystallized beads and glasses with other local soils the orientale ring dmd on the western limb is dominated by volcanic glasses and is spectrally similar to the localized dmds found in alphonsus crater we have identified a central vent for the orientale ring dmd and model the eruption as degassing of a near surface dike to produce a 20 km high umbrella shaped plume with ejection velocities of 360 m s and deposition of the glasses at an average radius of 80 km from the vent although we cannot identify the exact sources for the other regional dmds probably because they are buried beneath younger mare the eruptions most likely resulted from dikes breaching the surface and producing a volcanic plume dominated by larger greater than submillimeter hot clasts that formed mare and sinuous rules the small percent of clasts that form the volcanic beads are carried by the expanding gas cloud to large distances in some cases 100 km to produce the observed continuous regional dmds the lack of basalt samples that can be petrologically related to the volcanic glasses may be a result of their spatial separation with the basalts flowing into the basins while the beads are deposited both into the basins and on the adjacent highlands

apollo 15 yellow brown volcanic glass chemistry and petrogenetic relations to green volcanic glass and olivine normative mare basalts abstract apollo 15 yellow brown glass is one of twenty five high mg primary magmas emplaced on the lunar surface in pyroclastic eruptions forty spherules of this glass were individually analyzed by electron microprobe and inaa for major and trace elements e g sc v cr co la ce nd sm eu ho tm yb lu hf ta and u the abundances demonstrate that this primary magma was produced by partial melting of differentiated cumulates in the lunar mantle models are developed to explain the possible source regions of several apollo 15 and apollo 12 low ti mare magmas as being products of hybridization involving three ancient differentiated components of a primordial lunar magma ocean a early olivine orthopyroxene cumulates b late stage clinopyroxene pigeonite ilmenite plagioclase cumulates and c late stage inter cumulus liquid isotopic constraints on sm nd fractionation and least squares tests of potential mixing models require models of apollo 15 yellow brown glass and apollo 12 and 15 olivine mare basalts involving low f 3 cumulate remelting of sources in which olivine and orthopyroxene are residual phases models of the apollo 15 green glass composition indicate higher 4 7 degrees of melting but with only a slight preference for orthopyroxene rich relative to orthopyroxene free sources the modeled dependence on residual orthopyroxene in mare source regions places source depths at 400 km or greater in order to maintain olivine and orthopyroxene on the liquidus hybridization at such depths would likely result from convective overturn of the primordial magma ocean and suggests that separate fractionating masses were positioned at various depths our models for developing hybridized source regions of primary low ti mare magmas do not require selective contamination of primary liquids the preferred model for apollo 15 yellow brown glass is presented as the commingling of 95 early cumulate olivine orthopyroxene 1 9 clinopyroxene 0 27 pigeonite 1 7 plagioclase 0 02 ilmenite and 0 56 trapped liquid respective proportions for the apollo 15 olivine mare basalt source model are 98 5 0 37 0 0 79 0 16 and 0 13 and the proportions used for the preferred apollo 12 olivine mare basalt model are 97 6 0 73 0 24 0 77 0 42 and 0 21 our preferred model for the green glass source composition f 0 07 requires the commingling of 97 4 early olivine orthopyroxene 0 18 clinopyroxene 1 32 pigeonite 0 85 plagioclase and 0 28 trapped liquid

the moon a personal recollection and memorial for professor lawrence a taylor an apollo stalwart abstract the first geochemical analysis of lunar samples returned by the apollo 11 mission revealed that the moon was highly differentiated and depleted in volatile elements stable isotope compositions show that earth and moon are closely related but they have evolved in totally dissimilar ways probably related to the deficiency of water in the moon as well as the vast differences in size currently available lunar samples come from cumulate source regions making the establishment of a bulk planetary composition more reliant on geophysical rather than geochemical properties

lu hf and sm nd evolution in lunar mare basalts lu hf and sm nd data for mare basalts combined with rb sr and total ree data taken from the literature suggest that the mare basalts were derived by small or 10 degrees of partial melting of cumulate sources but that the magma ocean from which these sources formed was light ree and hf enriched calculated source compositions range fromm lherzolite to olivine websterite nonmodal melting of small amounts of ilmenite or 3 in the sources seems to be required by the lu hf data a comparison of the hf and nd isotopic characteristics between the mare basalts and terrestrial oceanic basalts reveals that the epsilonhf epsilonnd ratios of low ti mare basalts are much higher than in terrestrial oceanic basalts the results are qualitatively consistent with the hypothesis that terrestrial basalt sources are partial melt residues whereas mare basalt sources are cumulates alternatively the results may imply that the terrestrial mantle has evolved in two or more stages of evolution and that the net effect was depletion of the mantle during the first approx 1 3 b y followed by enrichment during the last 1 2 b y or simply that there is a difference in lu hf crystal liquid partitioning relative to sm nd between the lunar and terrestrial mantles

beryllium systematics in young volcanic rocks implications for 10 be beryllium is an incompatible trace element that closely parallels neodymium in its geochemical behavior be analyses conducted on well characterized oceanic and arc volcanic rock suites as well as on marine sediments suggest a bulk solid liquid distribution coefficient of 0 03 0 06 for melting of the mantle and crystallization of basalts the be nd ratio for many volcanic rocks from diverse tectonic environments is approximately 05 similar to the ratio in chondrites be data for samples from volcanic arcs show that there are significant variations in 10be 9be among different arcs and that variations in 10be are not due to variations in be concentration alone for at least one volcano bogoslof the 10be 9be ratio is constant for samples that vary by a factor of three in both their be and 10be concentrations suggesting that 10be is an inherited magmatic signature and not simply a result of contamination near the surface in addition the be nd and pb isotope systems for this volcano are all consistent with a model in which small amounts of sediment were incorporated into the bogoslof source region provided the mantle wedge has the isotopic characteristics of depleted morb since 10be exists only in the uppermost tens of meters of oceanic sediments the data suggest an efficient return flux of sediment to the mantle at subduction zones

the mare basalt magma source region and mare basalt magma genesis given the available data we find that the wide range of mare basaltic material characteristics can be explained by a model in which 1 the mare basalt magma source region lies between the crustmantle boundary and a maximum depth of 200 km and consists of a relatively uniform peridotite containing 73 80 olivine 11 14 pyroxene 4 8 plagioclase 0 2 9 ilmenite and 1 1 5 chromite 2 the source region consists of two or more density graded rhythmic bands whose compositions grade from that of the very low tio2 magma source regions 0 2 ilmenite to that of the very high tio2 magma source regions 9 ilmenite these density graded bands are proposed to have formed as co crystallizing olivine pyroxene plagioclase ilmenite and chromite settled out of a convecting magma which was also parental to the crust in which these crystals were suspended since the settling rates of the different minerals were governed by stoke s law the heavier minerals settled out more rapidly and therefore earlier than the lighter minerals thus the crystal assemblages deposited nearest the descending side of each convection cell were enriched in heavy ilmenite and chromite with respect to lighter olivine and pyroxene and very much lighter plagioclase the reverse being the case for those units deposited near the ascending sides of the convection cells simultaneously with this density controlled settling of the crystals the heating of the magma at the bottom of the convection cells resulted in the partial remelting of significant amounts of suspended but settling plagioclase ilmenite and pyroxene this partial remelting process was also partially responsible for the decrease in the ilmenite content from 9 to 0 2 between the very high tio2 and the very low tio2 source regions and caused the plagioclases and pyroxenes in the former source regions to be more sodic and clinopyroxene richer respectively than in the latter 3 during the mare basalt epoch radiogenic induced remelting of various parts of the density graded bands led to the formation of the initial mare basalt magmas the viscosity of melting systems which decreases rapidly at about 30 5 partial melting appears to have limited the degree of partial melting of the source region to about 30 2 4 these 30 partial melts rose to the crust mantle boundary where they pooled in magma storage chambers the magmas remained in these chambers for different lengths of time cooled to different degrees and lost 0 to 30 olivine or 30 olivine plus 0 to 20 pyroxene by fractional crystallization those magmas which remained in the chambers for very short times and lost no or essentially no olivine before eruption were the parental magmas of the pyroclastic glass units those magmas which lost increasing amounts of olivine pyroxene were the parental magmas of the apollo 12 and 15 magmas the apollo 11 and 17 magmas and the luna 16 and 24 magmas respectively this fractional crystallization phase in the genesis of the magmas explains both the pattern of the mare basalt magmas in the pseudo quaternary phase diagrams and the decrease in the siderophile contents of the magmas as a function of their degree of fractionation 5 the magma storage chambers being located at the crust mantle boundary were located in the zone where urkreep formed during the initial differentiation of the moon due to the low melting point of kreep compared with the initially high temperatures of the magmas residuals of the urkreep layer were assimilated by the cooling magmas since the urkreep materials underwent varying degrees of fractional melting early in lunar history these urkreep residuals had varying degrees of light ree depletion thus the assimilation of up to a few percent of these residuals caused the magmas to have differing eu and light ree depletion patterns as well as a wide range in their ree abundances 6 the fractional crystallization and urkreep residual assimilation phase of mare basalt magma genesis ended with the eruption of the magmas onto the lunar surface

an investigation of potential pyroclastic deposits on the southeast limb of the moon abstract we investigated the physical and spectral properties of potential dark mantling deposits pdmds previously and newly identified on the se limb of the moon near the craters humboldt and petavius the goals of this investigation were to constrain the composition and mode of emplacement of these poorly studied deposits to identify interdeposit variations and to use these results to draw conclusions about regional and subsurface geologic processes our investigation involved an assessment of both the physical properties size texture morphology and spectral properties albedo absorption bands color ratios utilizing remote sensing data from multiple lunar orbital missions we found that many of the se limb deposits previously identified as possibly pyroclastic in origin were likely effusively emplaced however we also identified several likely pyroclastic deposits including three not previously mapped we found that the volcanic deposits across the study area comprise three major spectral groups one similar to mare fecunditatis one similar to mare australe and one similar to known glassy pyroclastic deposits elsewhere on the moon we conclude that volcanism across the se limb was likely fed from at least two distinct magma source regions and that the type and extent of surface expression of this volcanic activity was possibly influenced by regional variations in crustal thickness our documentation and analysis of the complex volcanic history in this region of the moon supports ongoing efforts to develop increasingly detailed interpretations of the volcanic history of the entire moon

a wet heterogeneous lunar interior lower mantle and core dynamo evolution while recent analyses of lunar samples indicate the moon had a core dynamo from at least 4 2 3 56 ga mantle convection models of the moon yield inadequate heat flux at the core mantle boundary to sustain thermal core convection for such a long time past investigations of lunar dynamos have focused on a generally homogeneous relatively dry moon while an initial compositionally stratified mantle is the expected consequence of a postaccretionary lunar magma ocean furthermore recent re examination of apollo samples and geophysical data suggests that the moon contains at least some regions with high water content using a finite element model we investigate the possible consequences of a heterogeneously wet compositionally stratified interior for the evolution of the moon we find that a postoverturn model of mantle cumulates could result in a core heat flux sufficiently high to sustain a dynamo through 2 5 ga and a maximum surface dipolar magnetic field strength of less than 1 t for a 350 km core and near 2 t for a 450 km core we find that if water was transported or retained preferentially in the deep interior it would have played a significant role in transporting heat out of the deep interior and reducing the lower mantle temperature thus water if enriched in the lower mantle could have influenced core dynamo timing by over 1 0 gyr and enhanced the vigor of a lunar core dynamo our results demonstrate the plausibility of a convective lunar core dynamo even beyond the period currently indicated by the apollo samples

lunar mare volcanism stratigraphy eruption conditions and the evolution of secondary crusts abstract lunar mare basalt deposits cover 17 of the lunar surface occur preferentially in topographic lows on the nearside and have a total volume estimated at 1 107 km3 analysis of returned samples and photogeologic and remote sensing studies shows that mare volcanism began prior to the end of heavy bombardment the period of cryptomare formation in pre nectarian times and continued until the copernican period a total duration approaching 3 5 4 ga stratigraphic analyses show that the flux was not constant but peaked in early lunar history during the imbrian period which spans the period 3 85 3 2 ga average volcanic output rate during this peak period was about 10 2 km 3 a very low relative to the present global terrestrial volcanic output rate and comparable to the present local output rates for individual volcanoes such as vesuvius and kilauea hawaii volcanic landforms indicate that many eruptions were of high volume and long duration some eruptions associated with sinuous rules may have lasted of the order of a year and emplaced 103 km3 of lava representing the equivalent in one year of about 70 000 years at the average flux shallow magma chambers were uncommon the nearsidefarside mare deposit asymmetry can be readily explained by differences in crustal thickness magma ascending from the mantle or from a buoyancy trap at the base of the crust should preferentially extrude to the surface on the nearside but should generally stall and cool in dikes in the farside crust extruding only in the deepest basins the occurrence of farside maria within craters whose diameter is generally near to or less than the thickness of the crust may be accounted for by the difference between local and regional compensation dikes that establish pathways to the surface on the nearside should have very high volumes comparable to the volumes associated with many observed flows and sinuous rilles an abundance of dikes should exist in the lower crust of the moon many more than those feeding surface eruptions the upper limit is 37 50 of the crust by volume the presence and abundance of such dike swarms have important implications for the interpretation of the average composition of the lunar crust and the composition of basin and crater ejecta the interplay between thermal contraction and differentiation leads to net cooling and ultimate contraction of the outer portions of the moon resulting in a regional horizontal compressive stress acting on the lunar crust in addition overall cooling and deepening of sources require the production of ever larger volumes of magma in order to reach the surface with time stresses became high enough so that few dikes could open to the surface causing eruptive activity to be severely diminished in the eratosthenian and perhaps to cease in the copernican period lower stress levels are required to terminate eruptive activity on the lunar farside consistent with the imbrian age of the farside maria and the nearside location of the youngest maria lunar mare deposits provide an example of the transition from primary crusts to secondary crusts and illustrate the significance of several factors in the evolution of secondary crusts such as crustal density variations in crustal thickness presence of impact basins state and magnitude of stress in the lithosphere and general thermal evolution these factors are also responsible for the extremely low volcanic flux even during periods of peak extrusion

oxidation states and ascent history of the apollo 17 volcanic beads as inferred from metal glass equilibria abstract the composition mode of occurrence and relationships of metal blebs in the apollo 17 74001 2 core have been examined to provide insight into variations in oxidation states during ascent and eruption of the lunar volcanic glasses the 74001 2 core is composed of 99 orange volcanic glasses and their crystallized equivalents black beads with olivine phenocrysts metal blebs and in the upper 8 cm of the core lithic fragments composing the remaining 1 in an analysis of this core twenty nine metal blebs larger than 4 m in size were discovered in thin sections taken along the length of the 68 cm deep core these blebs are classified into three types on the basis of their shape composition and distribution fourteen of the metal blebs were found trapped inside or between olivine phenocrysts type i blebs microprobe analyses showed that these spherical blebs have a homogeneous composition of 85 fe 14 ni and 1 1 co from core to rim six type ii rounded blebs were discovered trapped inside volcanic beads their core compositions are similar to the type i but near the rim these blebs have a sharp decrease in fe and increase in ni content in the lower half of the 74001 2 core where the beads are predominantly black many contain 5 m amoeba shaped type iii metal blebs type iii blebs are composed of fe with trace amounts of ni two angular metal fragments could not be classified into any of the three types we propose that the type i blebs formed initially at 4 0 km depth and 1 3 log units below iw at a pressure of 200 bars and a temperature of 1320 c by the formation of c o gas during graphite oxidation once trapped by olivine phenocrysts the blebs were buffered from further reactions with the melt the type ii blebs remained in contact with the melt during ascent and experienced loss of fe to the surrounding melt phase by oxidation reactions which range from 1 3 to 0 9 log below iw finally type iii blebs formed either by exsolution of fe during crystallization in the fire fountain or by loss of volatiles originally coordinated with fe to the volcanic gas phase under the reduced conditions in the fountain

compositional analyses of lunar pyroclastic deposits abstract the 5 band clementine uvvis data at 100 m pixel were used to examine the compositions of 75 large and small lunar pyroclastic deposits lpds and these were compared to representative lunar maria and highlands deposits results show that the albedo spectral color and inferred composition of most lpds are similar to those of low titanium mature lunar maria these lpds may have consisted largely of fragmented basalt with substantial components of iron bearing mafic minerals pyroxenes olivine and smaller amounts if any of volcanic glass several smaller lpds also show substantial highland components three classes of very large deposits can be distinguished from most lpds and from each other on the basis of crystallinity and possible titanium content of their pyroclastic components one class has spectral properties that are dominated by high titanium crystallized black beads e g taurus littrow a second consists of a mixture of high titanium glasses and beads with a higher glass bead ratio sulpicius gallus than that of taurus littrow and a third has a significant component of quenched iron bearing volcanic glasses aristarchus with possible moderate titanium contents although areally extensive these three classes of very large pyroclastic deposits compose only 20 of the 75 deposits studied 27 and eruption of such materials was thus likely to have been less frequent on the moon

exploring the lunar mantle with secondary ion mass spectrometry a comparison of lunar picritic glass beads from the apollo 14 and apollo 17 sites abstract the major element characteristics of lunar picritic beads indicate that their composition approaches that of primary basaltic liquids and therefore may be our best geochemical mineralogical probes of the lunar interior the picritic magmas appear to represent partial melting of a variety of mantle mineral assemblages secondary ion mass spectrometry sims analysis of individual glass beads collected from the apollo 14 a 14 and apollo 17 a 17 landing sites shows that although there is substantial major minor tio 2 al 2 o 3 and trace element variation at each site the glasses from each site have distinguishable trace element signatures ba sr lree hree the incompatible element characteristics of glasses of nearly identical major element chemistry are strikingly different between sites the contrast between the a 14 and a 17 glasses appears to be the result of a higher kreep component in all the a 14 glasses the incorporation of evolved kreep component into high mg magmas is not a result of either assimilation or magma mixing but incorporation during the partial melting episode that produced the picritic magmas this is a more thermally efficient mechanism for incorporation of the kreep component into a picritic magma calculated mantle chemistries based upon glass compositions low degrees of partial melting and mineralogical components used in previous models suggest that the difference between a 14 and a 17 mantle sources is a 0 1 1 4 kreep intercumulate melt this difference will increase with an increase in the degree of partial melting in the model calculations this intercumulate melt may interstitially reside in an evolved high ti cumulate component the juxtaposition of evolved high ti cumulates kreep and primitive low ti cumulates mantle components has been attributed to original mantle inhomogeneities density contrasts during magma ocean crystallization and sinking of high density evolved cumulates into less dense primitive cumulates within the context of either magma ocean or serial magmatism type models regardless of the model the trace element signatures of glasses and the basalts indicate that the character of the a 14 mantle source is intrinsically different from that of the a 17 mantle source this indicates large scale lateral and vertical inhomogeneities in the lunar mantle

mare glasses from apollo 17 constraints on the moon s bulk composition two previously unreported varieties of mare volcanic glass have been discovered in apollo 17 samples twenty three chemical types of volcanic glass have now been analyzed from the six apollo landing sites these volcanic glasses which may be samples of primary magmas derived from the differentiated lunar mantle define two linear arrays that seem to reflect regional if not global regularities among the source regions of these melts additional systematics among these glasses have been used to estimate the bulk composition of the moon the results suggest that the refractory lithophile elements e g ca al ti ree u are present at abundances of 1 7 chondrites the silicate portion of the moon appears to have a major element composition similar to a volatile si na k depleted earth s upper mantle the theory involving an earth fission origin of the moon can be tested further through trace element analyses e g ni on the volcanic glasses and through determination of the n 36ar ratio and noble gas isotopes from primordial lunar gas trapped within vesicles associated with mare volcanic glass

a new lunar high ti basalt type defined from clasts in apollo 16 breccia 60639 abstract this paper reports the detailed examination of three basalt clasts from apollo 16 breccia 60639 that represent a new variant of high ti basalt returned from the moon by the apollo 16 mission mineral chemistry and whole rock analyses were conducted on aliquots from three clasts breccia matrix basalt and basalt breccia matrix the basalt clasts which are not overtly porphyritic contain compositionally zoned pyroxene olivine and plagioclase crystals that represent the evolution of the magma during crystallization ilmenite does not exhibit major element compositional zoning within individual crystals mineral compositions are distinct between the basalt and breccia matrix lithologies in addition whole rock analyses identify clear compositional differences between the basalt and breccia matrix lithologies in both major and trace element concentrations the composition of the mixed lithology aliquots i e basalt breccia matrix do not indicate simple two component mixing i e compositions are not intermediate to the basalt and breccia end members this apparent incongruity can be accounted for by adding 19 40 plagioclase to an amalgamation of the average basalt and individual breccia clast compositions via impact mixing whole rock analyses are consistent with previous analyses of one 60639 basalt clast which were interpreted to indicate chemical similarity with apollo 11 and 17 basalts however both major and trace elements suggest that the 60639 basalt clasts examined here have compositions that are distinct from apollo 11 and 17 high ti basalts although the 60639 basalt clasts have similar characteristics to a variety of previously identified basalt types the more extensive whole rock analyses reported here indicate that they represent a type of apollo high ti basalt heretofore unrecognized in the apollo and lunar meteorite collections by placing these new analyses in the context of other mare basalt compositions a petrogenetic model for the basalts found in breccia 60639 is presented

distinct oxygen isotope compositions of the earth and moon the virtually identical oxygen isotope compositions of the earth and moon revealed by apollo return samples have been a challenging constraint for lunar formation models for a giant impact scenario to explain this observation either the precursors to the earth and moon had identical oxygen isotope values or extensive homogenization of the two bodies occurred following the impact event here we present high precision oxygen isotope analyses of a range of lunar lithologies and show that the earth and moon in fact have distinctly different oxygen isotope compositions oxygen isotope values of lunar samples correlate with lithology and we propose that the differences can be explained by mixing between isotopically light vapour generated by the impact and the outermost portion of the early lunar magma ocean our data suggest that samples derived from the deep lunar mantle which are isotopically heavy compared to earth have isotopic compositions that are most representative of the proto lunar impactor theia our findings imply that the distinct oxygen isotope compositions of theia and earth were not completely homogenized by the moon forming impact thus providing quantitative evidence that theia could have formed farther from the sun than did earth high precision measurements suggest that the earth and moon have distinct oxygen isotope compositions this implies distinct oxygen isotopic compositions of the proto earth and its impactor that were not fully homogenized by the moon forming impact

magmatic processes that produced lunar fire fountains reanalysis of the apollo 15 a b and c green glass beads from slide 15426 72 led to the discovery of patchy highly vesicular glass rims adhering to beads these rims are high in s and ni and low in mgo but otherwise compositionally similar to the green glasses we find that these rims represent a unique melt composition that places constraints on lunar magmatic processes combining the compositional data for the vesicular glass rims with new minor element data for the green glass beads leads us to hypothesize that the vesicular rim fluid originated near the green glass source at about 2 2 gpa these findings support the theory of a heterogeneous lunar mantle and suggest that sulfur did not drive the eruption from depth but that degassing volatiles into the vacuum did drive the final fire fountain eruption

anatexis of lunar cumulate mantle in time and space clues from trace element strontium and neodymium isotopic chemistry of parental apollo 12 basalts abstract in an effort to elucidate the processes of lunar mantle melting and the magma evolution of mare basalts within oceanus procellarum on the western lunar near side we have analyzed seven fine grained to vitrophyric apollo 12 basalts for trace elements five of these also have been analyzed for nd and sr isotopic compositions these samples represent all three main groups identified among the apollo 12 mare basalts and have been proposed as parental melts to their respective groups i e olivine pigeonite and ilmenite basalts the sources for these low ti mare basalts are postulated to have formed from crystallization of a global magma ocean li be systematics combined with ree data indicate that the specific sources for the apollo 12 low ti mare basalts were generated after 82 94 crystallization of this lunar magma ocean in fact it seems that all mare basalts analyzed from the apollo collections were generated from cumulates precipitated in the last 20 of the magma ocean chemical compositions of fine grained pigeonite and olivine basalts are consistent with 7 9 nonmodal in proportions not defined by experimental petrology and phase equilibria melting of a source consisting of 48 olivine 30 calcic clinopyroxene and 22 pigeonite as per neal et al 1994b sm nd and rb sr abundance data also suggest that the pigeonite and olivine basalt source contained from 0 3 to 0 5 trapped residual liquid from the magma ocean the compositions of the two fine grained ilmenite basalts are consistent with 5 7 partial melting of a source with subequal proportions of olivine 45 5 and pigeonite 42 5 and lesser amounts of clinopyroxene 11 5 and entrained plagioclase 0 5 furthermore the ilmenite source was nearly devoid of trapped liquid isotopic systematics of the apollo 12 fine grained parental basalts are consistent with their derivation from two distinct mantle source regions both of these sources were lree depleted for extended periods of time up to 600 million years for the ilmenite basalt source and up to 900 million years for the pigeonite and olivine basalt source due in part to the relatively small proportion of low sm nd trapped residual magma ocean liquid in the source by integrating this information on parental low ti apollo 12 basalts with mare basalt and picritic glass data from other landing sites as well as telescopic and remote sensing data we propose a model for melting of the lunar interior the upper 400 500 km of the lunar mantle is a consequence of incipient melting of the moon and formation of a global magma ocean this magma ocean became progressively enriched in incompatible elements as it precipitated the cumulate upper mantle this incompatible earliest extensive mare magmas high ti mare basalts were generated at shallow depths in the mantle from cumulate source regions that had trapped relatively large proportions of this incompatible element enriched residual magma ocean liquid these source regions also contained the late crystallizing phase ilmenite and thus generated high ti magmas the trapped liquid component contained elevated abundances of heat producing elements k u and th increasing the fertility of associated source regions with time melting moved progressively deeper in the mantle to source regions with less of the residual heat producing magma ocean liquid due to density contrasts the ilmenite bearing upper portions of the lunar mantle sank into the cumulate pile possibly carrying more fertile material with it and allowing melting of more mg enriched source regions to form the high ti picritic glass beads thus the major controlling factors in the melting of the lunar interior could be the proportion of trapped magma ocean liquid in the cumulate source and the sinking of more fertile ilmenite bearing material into the lower mantle

lunar magma transport phenomena abstract an understanding of the most significant events during the first ga or so of lunar history global differentiation associated with a lunar magma ocean lmo and the later generation of about 107 km3 of mare basalts depends profoundly on magma transport dynamics lmo evolution is dominated by the characteristics of hard turbulent convection of a fluid undergoing phase change quench protocrust formed at the ocean surface in early times is repeatedly disrupted by bolide impact ocean body tides and associated crustal foundering during this epoch the ocean temperature is set by the balance between convective heat brought to the surface and brown body radiation from the surface at later times the convective flow is organized into a number of regimes from top to bottom these include conductive crustal lid a viscous sublayer an inertial core a lower viscous sublayer and a mushy cumulate region crystal settling and flotation is restricted to the viscous sublayer regions dilatancy pumping may prevent the efficient expulsion of intercumulus melt during cumulate formation typical velocities within the inertial region are of order 10 m s because late stage ti rich cumulates are dense relative to the earlier mg rich cumulates hyper to sub solidus convection tends to mix lmo crystallization products numerical simulations that account simultaneously for compositional and thermal buoyancy effects indicate a characteristic mixing time 200 ma statistical measures of mixing variance and spatial correlation length quantify the details of mixing the darcy percolative and vein drain models of melt extraction are briefly discussed because compaction lengths are small 102 m the rate of melt extraction is governed by the balance between melt buoyancy and darcy friction differential melt matrix velocities are of order 10 km ma for nominal values appropriate for mare basalt melt extraction from a heterogeneous mixed lmo source transport of magma through the lunar lithosphere via a connected crack network seems highly probable for the range of inferred discharge rates applicable for lunar mare volcanism lmv 103 to 107 m3 s typical fracture widths and ascent speeds are 10 1 to 50 m and 10 1 to 10 m s respectively a simple model is proposed to evaluate the extent of fractionation as magma traverses cold lunar lithosphere if apollo green glasses are primitive and have not undergone significant fractionation en route to the surface then mean ascent rates of 10 m s and cracks of widths 40 m are indicated lunar tephra and vesiculated basalts suggest that a volatile component plays a role in eruption dynamics the predominant vapor species appear to be co co2 and cos near the lunar surface the vapor fraction expands enormously and vapor internal energy is converted to mixture kinetic energy with the concomitant high speed ejection of vapor and pyroclasts to form lunar fire fountain deposits such as the apollo 17 orange and black glasses and apollo 15 green glass

origin of lunar high titanium ultramafic glasses constraints from phase relations and dissolution kinetics of clinopyroxene ilmenite cumulates abstract phase equilibrium and dissolution kinetics experiments on synthetic late stage magma ocean cumulates are used to place constraints on hypotheses for the origin of lunar high ti ultramafic glasses models for the production of high ti lunar magmas have called for either 1 assimilation of late stage clinopyroxene ilmenite cumulates at shallow levels or 2 sinking of clinopyroxene ilmenite cumulates to form a hybrid mantle source to satisfy the constraints of our experiments we propose an alternative model that involves shallow level reaction and mixing of cumulates followed by sinking of hybrid high ti materials this model can fulfill compositional requirements imposed by the pristine lunar glass suite that are difficult to satisfy in assimilation models it also avoids difficulties that arise in overturn models from the low solidus temperatures of clinopyroxene ilmenite cumulates partially molten clinopyroxene ilmenite cumulates become gravitationally unstable with respect to underlying mafic cumulates only when they have cooled to within 30 c of their solidus 1125 c at 100 km depth at these temperatures the viscosity of mafic cumulates is too high to allow for growth and descent of clinopyroxene ilmenite diapirs on the appropriate time scale reaction and mixing between late stage liquids and mafic cumulates at shallow levels would produce a refractory hybrid material that is negatively buoyant at higher temperatures and could sink more efficiently to the depths inferred for production of high ti ultramafic glasses

early crustal building processes on the moon models for the petrogenesis of the magnesian suite abstract the plutonic rocks of the magnesian suite mg suite represent the period of lunar basaltic magmatism and crustal growth 4 46 to 4 1 ga that immediately followed the initial differentiation of the moon by magma ocean lmo formation and crystallization the volume and distribution of the mg suite and its petrogenetic relationship to latter stages of lunar magmatism mare basalts remains obscure these plutonic rocks exhibit a range of compositions and include ultramafics troctolites spinel troctolites norites and gabbronorites a distinguishing characteristic of this suite is that they contain some of the most magnesium rich phases fo95 90 that had crystallized from lunar magmas yet they also are significantly enriched in an incompatible element component referred to as kreep a late stage product of lmo crystallization containing abundant potassium k rare earth elements ree phosphorous p uranium and thorium ion microprobe analyses of individual mineral phases olivine pyroxene and plagioclase from the mg suite have shown some very unexpected characteristics that have profound implications on the origin of these basaltic magmas although the mg suite lithologies are typified by silicates with relatively high mg early liquidus phases such as olivine are fairly low in ni co and cr relative to more iron rich olivines in the younger mare basalts the high y and ti y in early phases such as olivine and orthopyroxene indicate that the parental basaltic melts were high in incompatible elements and contained an ilmenite fractionation signature however the y in olivine from many of the troctolites and ultramafic lithologies are only slightly greater than that of the olivine in the mare basalts whereas olivine in the norites gabbronorites and apollo 14 troctolites are exceedingly high the kreep component may have been added to the mg suite parent magmas by assimilation or mixing into the mantle source the volume of kreep required to be added to the parental magmas of the mg suite tends to favor the latter mechanism for kreep incorporation the extremely high abundances of kreep in the norites and gabbronorites are a product of substantial crystallization 40 to 70 of kreep enriched mg suite parental magmas basaltic magmatism associated with kreep extended for over 1 5 billion years and appears to have changed over time the early stages of this style of lunar magmatism mg suite appear to represent melting of early lmo cumulates with low abundances of ni co cr and v later stages of kreep rich basaltic magmatism seemed to clearly involve melting of a variety of lmo cumulate assemblages with higher incompatible element enrichment it appears that the heat derived from the kreep component was instrumental in at least initiating melting of the lunar mantle over this period of time

petrology and provenance of a very low titanium picrite clast in lunar highland regolith breccia 15295 clast 100 in regolith breccia 15295 could be a key to resolving the relationship s between mare basalts and lunar picritic glasses the clast is basaltic with texture mineralogy mineral compositions and calculated bulk composition suggesting that it crystallized in a thick lava flow or shallow intrusive body from a very low titanium vlt basaltic magma the estimated bulk composition of clast 15295 100 is primitive i e magnesian compared to those of known vlt basalts and is very close to those of vlt picritic green glasses especially the apollo 14 a green glass from these similarities we infer that clast 15295 100 is a crystalline product of a picritic magma similar to the apollo 14 a glass clementine and m3 remotely sensed data of the lunar surface were used to find areas that have chemical compositions consistent with those of clast 15295 100 not only near the apollo 15 site but in a broad region surrounding the site two regions are consistent with clast s 15295 100 compositional data the larger region is in southern mare imbrium and a smaller region is in the eastern half of sinus aestuum these locations should be considered as candidates for future missions focusing on sample science

high pressure phase equilibria and element partitioning experiments on apollo 15 green c picritic glass implications for the role of garnet in the deep lunar interior abstract we report results of nominally anhydrous near liquidus experiments on a synthetic analog to very low titanium apollo 15 green c lunar picritic glass from 2 to 5 gpa apollo 15 green c glass a15c is saturated with garnet and pyroxene on the liquidus at 3 gpa however such an assemblage is unlikely to represent the lunar mantle source region for this glass and instead an olivine orthopyroxene dominated source is favored in accord with earlier lower pressure experiments on a15c near liquidus garnet has a slight but significant majorite component at 5 gpa in this iron rich bulk composition as expected from our previous work in ordinary chondritic bulk compositions ion microprobe measurements of partitioning of sr ba sc nd sm dy yb y zr hf and th between garnet and coexisting melt in these experiments are the first garnet partition coefficients d values available that are directly relevant to lunar compositions d values for these garnets differ significantly compared to d values for garnets grown in more magnesian terrestrial bulk compositions which until now are all that have been available in modeling the possible role of garnet in the lunar interior for example d values for heavy rare earth elements are lower than are those from terrestrial basaltic systems these partitioning values are well described by the lattice strain partitioning model but predictive relationships for garnet partitioning using that model fail to match the measured values as was the case in our earlier work on chondritic compositions using our new d values in place of the terrestrial values in a variety of models of lunar petrogenesis we suggest that garnet is unlikely to be present in the source regions for very titanium poor lunar liquids despite its appearance on the liquidus of a15c

ion microprobe studies of trace elements in apollo 14 volcanic glass beads comparisons to apollo 14 mare basalts and petrogenesis of picritic magmas abstract the major element geochemistry of picritic lunar glass beads indicates that they represent primary basaltic liquid compositions and as such provide unique information concerning the origin of mare basalts and characteristics of the lunar interior this study used ion microprobe techniques for trace element analysis of individual glass beads representing seven compositionally distinct types of picritic glass beads from the apollo 14 site high ti glasses 17 11 tio2 red black orange intermediate ti glasses 5 4 tio2 yellow low ti glasses 2 8 tio2 lap low alkali picritic papike et al 1989 very low ti glasses ba sr 1 of these glasses are different from low ti mare basalts at other sites but are similar to crystalline basalts at the apollo 14 site the intermediate to high ti picritic glasses exhibit a flat to slightly positive lree slope and a negative hree slope the orange glass has a higher total ree abundance and a slightly larger negative eu anomaly than the red black and yellow glasses relative to the apollo 17 high ti glasses apollo 14 high ti glasses are enriched in ree lree hree y v zr sr ba and ba sr and are similar in alkali elements li rb co and sc trace element modeling within the context of liquid lines of descent and major element characteristics indicates that the picritic glass beads at the a 14 site are not related by low pressure fractional crystallization to each other or to crystalline basalts at the apollo 14 or other landing sites a possible exception is the relationship between lap and basalts of the high al basalt suite the wide range of primary magma compositions and the lack of petrogenetic linkage via crystal fractionation to crystalline basalts indicates that either a wide compositional range of evolved mare basalts has not yet been sampled or a unique mechanism is selectively tapping these picritic magmas directly from their mantle source region the wide range of major and trace element characteristics of the volcanic glass beads is consistent with derivation from mineralogically distinct sources which consist of varying proportions of olivine orthopyroxene clinopyroxene ilmenite plagioclase kreep component the evolved kreep component may have been incorporated into these primary picritic magmas by either assimilation fractional crystallization type processes afc or by hybridization of the mantle source the former appears less likely due to the general systematic increase in incompatible elements relative to ti concentration and the apparent lack of crystallization that is required in afc type models the hybridization processes may be the result of sinker mechanisms as proposed by ringwood and kesson 1976 a manifestation of original mantle inhomogeneities or a magma ocean stirred by large impacts

glasses in howardites impact melts or pyroclasts we have analyzed glasses in eight howardites with the aim of distinguishing their origins as impact melts or pyroclasts although theoretical calculations predict that pyroclastic eruptions could have taken place on vesta the occurrence of pyroclastic glasses in hed meteorites has not been documented this study involved petrographic examination of textures electron microprobe analysis of major and minor elements and la icp ms analysis for selected trace elements previously documented textural and compositional differences between lunar impact melt and pyroclastic glasses partly guided this study this work yielded no positive identification of pyroclastic glasses the most likely explanation is that pyroclastic glasses never formed either because vesta contains insufficient volatiles to have powered explosive eruptions or because eruptive conditions produced optically dense fire fountains that allowed melt drops to collect as lava ponds the impact melt glasses were grouped low alkali ca rich and k rich based on compositions we suggest that these glasses are the result of impacts onto known hed lithologies the low alkali glasses are impact melts of bulk hed lithologies we hypothesize that the ca rich and k rich glasses result from oversampling of plagioclase and of mesostasis that experienced liquid immiscibility respectively during micrometeorite impacts into eucrite targets

reading the moon s volcanic record by ion microprobe analysis of apollo 14 glass beads the application of secondary ion mass spectrometry to lunar volcanic problems is demonstrated by individually analyzing representative glass from the seven apollo 14 pyroclastic glass bead groups black orange yellow lap green a vlt and green b for selected trace elements e g rare earth elements ree ba sr zr v and co the trace element characteristics of glass beads are useful for differentiating impact from volcanic glass beads and identifying other volcanic glass types e g lap trace element modeling indicates that the bead groups are unrelated by low pressure fractional crystallization to each other to apollo 14 crystalline basalts or to basalts from other landing sites a possible exception is the relation between lap and apollo 14 aluminous basalts the absence of evolved basalts derived from primary magmas with volcanic glass compositions suggests either that these evolved basalts have not been sampled or that fire fountaining tapped mantle sources subtly different from crystalline mare basalt source regions hybridization of mantle source regions is preferred to assimilation fractional crystallization processes to explain the incorporation of the evolved potassium ree phosphorus kreep component identified in these primitive magmas apollo 14 volcanic glass and mare basalt trace element signatures indicate that the character of the apollo 14 mantle source region is intrinsically different from that of other sites which suggests that large scale mantle heterogeneities exist

radiative transfer modeling of compositions of lunar pyroclastic deposits 1 while over 100 lunar pyroclastic deposits have been identified remotely their compositions remain poorly constrained in this work we determine the compositions of three lunar regional pyroclastic deposits which are likely to contain large amounts of glass and for which we have high quality ground based spectra the aristarchus plateau mare humorum and sulpicius gallus we use radiative transfer theory and employ measured optical constants of glasses to predict the bidirectional reflectance of a particulate glass surface as a function of fe and ti concentration particle size and maturity in order to find the best spectral match to the remotely observed deposits tools are not available to model the optical effects of the unusual geometries of the ilmenite laths in the black beads so we address their effects on spectra of the regional pyroclastic deposits using computational mixing we find that model spectra of pure glass as opposed to devitrified black beads provide good matches to all three regions radiative transfer modeling predicts iron contents of 21 20 and 17 wt feo for aristarchus humorum and sulpicius gallus respectively and suggests that all three regions are low in titanium a result supported by lunar prospector neutron spectrometer data however we find that a moderate ti glass mixed with a small fraction of black beads cannot be ruled out for the sulpicius gallus region

petrogenesis of mare basalts a record of lunar volcanism returned rock and soil samples from our nearest planetary neighbor have provided the basis for much of our understanding of the origin and evolution of the moon of particular importance are the mare basalts which have revealed considerable information about lunar volcanism and the nature of the mantle as well as post magma generation processes this paper is a critical review of the petrogenetic models for the generation of mare basalts formulated over the last twenty years we have used all available mare basalt analyses to define a six fold classification scheme using tio2 contents as the primary division i e 1 wt very low ti or vlt 1 6 wt low ti 6 wt high ti a secondary division is made using al2o3 contents i e 11 wt low al 11 wt high al and a tertiary division is defined using k contents i e 2000 ppm low k 2000 ppm high k such divisions and subdivisions yield a classification containing twelve categories of which six are accounted for by the existing apollo and luna collections therefore we present our discussions in the form of six mare basalt rock types 1 1 high ti low al low k referred to as high ti low k 2 2 high ti low al high k referred to as high ti high k 3 3 low ti low al low k referred to as low ti 4 4 low ti high al low k referred to as high alumina 5 5 low ti high al high k referred to as vhk 6 6 vlt low al low k basalts referred to as vlt a variety of post magma generation processes have been invoked such as fractional crystallization either alone or combined with wallrock assimilation to explain the compositional ranges of the various mare basalt suites in order to evaluate these proposed petrogenetic processes this review is by rock type and is non site specific but for each rock type reference to particular lunar sample return missions is brought forth this permits a comparison of similarities and differences of broadly similar rock types correlated with geography on the moon which in turn allows a more thorough petrogenetic evaluation high ti mare basalts i e high ti low al low k are found at apollo 11 and apollo 17 sites however the a 11 basalts contain lower tio2 abundances a considerably larger range in trace element contents and the only occurrence of high ti high k mare basalts fractional crystallization and source heterogeneity within each site are the keys to understanding the petrogenesis of the high ti basalts low ti basalts including both low al k and high al k varieties are found at apollo 12 14 and 15 and luna 16 sites the low ti basalts exhibit a wide range of major and trace element compositions and require source heterogeneity fractional crystallization and some assimilation the high alumina mare basalts i e low ti high al low k are found at apollo 14 and luna 16 sites and exhibit a wide range of major and trace element compositions however in these examples source heterogeneity is not a major factor indeed fractional crystallization coupled with kreep assimilation particularly for the apollo 14 variants can explain the compositional ranges of these high alumina basalts the vhk mare basalts i e low ti high al high k have been sampled only at the apollo 14 locale and are products of a parental highalumina magma assimilating lunar granite very low ti vlt mare basalts i e vlt low al low k are found at apollo 17 and luna 24 sites fractional crystallization has had a major influence upon the range in vlt compositions but luna 24 vlt basalts have been derived from a source slightly different in composition from that for apollo 17 vlt varieties for example the luna 24 vlt basalts generally exhibit positive eu anomalies a unique property for mare basalts which almost always have negative eu anomalies the concept of a lunar magma ocean lmo is generally accepted and source modelling of all basalts invokes a mafic lmo cumulate source this is the only unifying model for mare basalt petrogenesis but the semantics and logistics of it are and will be debated for many years for example major convective overturn of the lmo appears plausible but whether this occurred on a local or planet wide scale to produce source heterogeneity remains to be determined

apollo 14 very low titanium glasses melting experiments in iron platinum alloy capsules this paper describes two techniques that have been developed to produce fe pt alloy capsules for high pressure experiments and reports liquidus phase relations of the apollo 14 very low titanium glasses determined using fe rich capsules afe 0 6 the liquid is multiply saturated with olivine and clinopyroxene at 22 kbar the multiple saturation is at least 3 kbar higher than that determined using pure fe capsules and corresponds to a source region at least 60 km deeper if olivine and clinopyroxene were the residual phases however we still need independent data on iron activity or oxygen fugacity of the glasses in order to choose a container of optimum composition preliminary experiments in fe poor alloy capsules suggest that the valence state of iron and the crystallization sequence in the melt have changed possibly as a result of oxidizing materials entrapped during the iron plating processes the feo content of the charge decreases linearly with increasing run duration in experiments using pure fe capsules the observation that iron rich globules grow with time suggests that the equilibrium fe bleb fe2o3 liq 3 feo liq might be established in the liquid at high pressure if this explanation is correct an appreciable amount of feo in the liquid could actually be fe2o3 and some natural lunar volcanic glasses may contain ferric iron as well

basaltic magmatism on the moon a perspective from volcanic picritic glass beads abstract it is widely accepted that basaltic magmas are products of partial fusion of periodotite within planetary mantles as such they provide valuable insights into the composition structure and processes of planetary interiors those compositions which approach primary melt compositions provide the most direct information about planetary interiors and serve as a starting point to understand basaltic evolution within the collection of lunar samples returned by the apollo and luna missions are homogeneous picritic glass beads of volcanic origin these picritic glasses are our closest approximations to primary magmas as such these glass beads provide a unique perspective concerning the origin of mare basalts the characteristics of the lunar interior and processes in the early differentiation of the moon we have obtained trace element data for these picritic glasses using sims techniques these data and literature isotopic and experimental data on the picritic glasses are placed within the framework of mare basaltic magmatism the volcanic glasses are very diverse in their trace element characteristics for example they have a wide range of ree pattern shapes and concentrations like the crystalline mare basalts all picritic glasses have a negative eu anomaly unlike the crystalline mare basalts there is little correlation between the size of the eu anomaly and overall ree concentrations trace element differences among the various glasses suggests that a kreep component was incorporated into their mantle source this implies large scale mixing of the lunar magma ocean derived cumulate pile subtle differences among glasses suggest that local mixing of sources may also have been an important process preservation of subtle chemical differences in the picritic glasses and crystalline basalts may be interpreted as indicating that they were produced by small to moderate degrees of partial melting and that the lunar mantle did not experience extensive melting during episodes of mare volcanism several lines of evidence are consistent with the view that the picritic glasses were derived from mantle sources that were compositionally distinct from the sources for crystalline mare basalts these are parallel but no common liquid lines of descent chemical differences between picritic glasses and the more primitive crystalline mare basalts experimental studies indicating that the picritic glasses are multiply saturated at depths greater than that of the mare basalts differences in lead isotopic data and the mode of eruption i e fire fountaining for glass beads these data also provide circumstantial evidence that suggests that the picritic glasses were derived from a source somewhat more volatile rich than that of the mare basalts several petrogenetic models are suggested by the trace element characteristics of the picritic glasses 1 1 partial melting of heterogeneous lunar mantle at depths greater than 300 km to produce the parental magmas picritic for both the mare basalts and picritic glasses picritic magmas represented by glass beads were erupted to the surface with small degrees of fractional crystallization while mare basalts were produced by larger degrees of fractional crystallization 15 30 of similar but not identical picritic magmas 2 2 picritic magmas represented by the glass beads were generated at depths greater than 400 km in a volatile enriched relative to the mare basalt source heterogeneous mantle while mare basalts are fractional crystallization products of picritic magmas generated at depths of less than 400 km 3 3 the picritic magmas represented by the glass beads represent polybaric melting that initiated at depths of at least 1000 km a primitive mantle component or less processed cumulate mantle components may have been involved in the generation of the picritic glasses in any of these models

low abundances of highly siderophile elements in the lunar mantle evidence for prolonged late accretion abundances of the highly siderophile elements hse re ir os ru pt and pd were determined for etchates and residues of highly purified lunar orange 74220 and 74001 1217 and 1218 and green 15421 65 and 15426 164 volcanic glasses most etchates have 100 pg g os and ir and in some instances have hse concentrations that approach chondritic relative abundances some etchates also have 187 os 188 os within the range of chondritic meteorites in contrast most residues have os concentrations of 50 pg g and have considerably suprachondritic 187 os 188 os ratios the disparities in os isotopic compositions between etchates and residues reflect the presence of at least two components in each of the glass fractions the components are interpreted to be the indigenous lunar glasses and a meteoritic contaminant mixing models suggest the indigenous components in orange and green glasses have os concentrations v25 pg g compared to terrestrial rocks with comparable mgo contents the concentration estimates suggest the lunar mantle sources of the volcanic glasses were depleted in hse by at least a factor of 20 relative to the terrestrial mantle consistent with os and ir concentrations in the lunar mantle of v0 15 ng g the hse depletion in the lunar mantle indicates that it may be missing a substantial share of late accreted materials the depletion is best explained as a consequence of the early formation of the lunar crust and subsequent isolation of the lunar mantle from late accreted materials given that the lunar crust was largely formed by 4 4 ga this suggests a preponderance of late accreted materials were added to the earth moon system subsequent to 4 4 ga and requires a substantial influx of mass into the inner solar system more than 150 ma after the formation of the solar system d 2004 elsevier b v all rights reserved

w hf isotope abundances and the early origin and evolution of the earth moon system abstract the decay of the short lived isotope 182hf to the isotope 182w early in solar system history provides clues to the origin and evolution of the earth and moon current time scales for the formation of proto planets in the solar system require early accretion of the proto earth accompanied with core formation which should lead to non chondritic radiogenic w isotope ratios 182w 184w in the earth s mantle surprisingly the observed ratio of 182w 184w in the earth s mantle is chondritic which requires special circumstances to explain halliday et al 1996 lee and halliday 1997 lee et al 1997 previous explanations include delayed core formation until 50 m yrs after the origin of the solar system or a very long time scale for accretion of the earth halliday et al 1996 lee and halliday 1997 lee et al 1997 in this paper we explore models consistent with the early formation of the proto earth a giant impact origin of the moon and substantial additional accretion to the earth following the impact the post impact processes responsible for the chondritic w isotopes may include late core mantle equilibration in the hot earth following the giant impact and later metal segregation and accretion in contrast to the earth various igneous rocks on the moon exhibit non chondritic positive anomalies in the ratio of 182w 184w the explanation for the lunar samples with chondritic w isotopes may also involve late metal segregation and accretion as in the earth the positive anomalies in lunar samples may be derived in part or whole through cosmogenic processes on the lunar surface hf w fractionation during core formation or hf w fractionation during lunar magma ocean crystallization if the latter the positive anomaly places constraints on the early differentiation of the lunar mantle and the duration of the crystallization of the lunar magma ocean the observed w hf systematics are best explained if the w anomalies are carried by late crystallizing ilmenite and high ca pyroxene which is later mixed into the source regions of the mare basalts in this model the crystallization of the magma ocean must occur in less than 40 million years this rapid crystallization implies that the very early lunar crust was not as stable and insulating as previously suggested and that the fundamental change from magmasphere to serial magmatism processes occurred very early in the evolution of the moon

isotopic evidence for a young lunar magma ocean abstract mare basalt sources and ferroan anorthosite suite cumulates define a linear array on a 146sm 144nd versus 142nd 144nd isochron plot demonstrating these materials were derived from a common reservoir at 4336 31 32 ma the minimum proportion of the moon that was in isotopic equilibrium at this time is estimated to be 1 3 of its entire volume based on the geographic extent from which the analyzed samples were collected and the calculated depths from which the samples were derived scenarios in which large portions of the moon were molten to depths of many hundreds of kilometers are required to produce the observed sm nd isotopic equilibrium between the mantle and crustal rocks at 4 34 ga this is a consequence of the fact that limited heating of a solid moon above the blocking temperature of the sm nd isotopic system is insufficient to diffusively homogenize radiogenic nd throughout the mantle and crust there are three scenarios that might account for global scale isotopic equilibrium on the moon relatively late in solar system history including 1 sm nd re equilibration of a solid moon resulting from widespread melting in response to mantle overturn or a very large impact 2 early accretion of the moon followed by delayed cooling due to the presence of an additional heat source that kept a large portion of the moon molten until 4 34 ga or 3 late accretion of the moon followed by rapid cooling of the magma ocean late in solar system history neither density driven overturn of the mantle nor a large impact are likely to homogenize the mantle and crust to the extent required by the sm nd isochron likewise secondary heating mechanisms such as tidal heating or radioactive decay are not efficient enough to keep the moon molten to the depth of the mare basalt source regions for many tens to hundreds of millions of years instead the age of equilibrium between such a compositionally diverse set of rocks produced on a global scale likely records the time of primordial solidification of the moon from a magma ocean this scenario accounts for both the petrogenetic characteristics of lunar rock suites as well as their sm nd isotopic systematics it is supported by the preponderance of 4 35 ga ages obtained for other hypothetical magma ocean crystallization products such as ferroan anorthosite suite rocks and k ree and p enriched cumulates that are thought to represent flotation cumulates of the magma ocean and the last vestiges of magma ocean solidification respectively

remelting mechanisms for shallow source regions of mare basalts abstract two mechanisms are studied which could induce remelting at shallow depths within the moon a radioactive heating model in which remelting is the result of lateral variations of the heat source concentration emplaced by the end of the initial differentiation event and a thermal insulation model in which remelting is induced by lateral variations of near surface conductivity as a result of a high porosity ejecta blanket created by basin forming impacts the effects of these perturbations are studied by evaluating the thermal evolution of an otherwise radially symmetric lunar model the radioactive heating models predict extensive pre basin volcanism which would probably remove from the source region many of the heat producing elements potentially responsible for melting therefore localized high concentrations of heat producing elements emplaced early would most probably not be heat sources for the basin filling mare basalts however they are plausible heat sources for pre basin mare basalts the thermal insulation model predicts a delay of about 200 m y between impact and volcanism thermal insulation may also allow for the persistence of source regions for young basalts at shallow depths if greater basin ages are correct from 4 2 to 3 9 ga and most volcanism occurred between 3 8 and 3 6 ga then the thermal insulation model may explain the delay between impact and basin filling if the basins formed during a terminal cataclysmic event at about 3 9 ga then the earliest stages of basin filling at about 3 8 ga may have been a result of melting beneath the basin as a result of mantle uplift basin filling may have been characterized by a migration of the source region from beneath the basin to beneath the adjacent highlands cooling of the top 200 km beneath the basin after 200 m y because of its high surface conductivity is consistent with the mascon support requirement

complex explosive volcanic activity on the moon within oppenheimer crater abstract oppenheimer crater is a floor fractured crater located within the south pole aitken basin on the moon and exhibits more than a dozen localized pyroclastic deposits associated with the fractures localized pyroclastic volcanism on the moon is thought to form as a result of intermittently explosive vulcanian eruptions under low effusion rates in contrast to the higher effusion rate hawaiian style fire fountaining inferred to form larger regional deposits we use lunar reconnaissance orbiter camera images and diviner radiometer mid infrared data chandrayaan 1 orbiter moon mineralogy mapper near infrared spectra and clementine orbiter ultraviolet visible camera images to test the hypothesis that the pyroclastic deposits in oppenheimer crater were emplaced via vulcanian activity by constraining their composition and mineralogy mineralogically we find that the deposits are variable mixtures of orthopyroxene and minor clinopyroxene sourced from the crater floor juvenile clinopyroxene and juvenile iron rich glass and that the mineralogy of the pyroclastics varies both across the oppenheimer deposits as a whole and within individual deposits we observe similar variability in the inferred iron content of pyroclastic glasses and note in particular that the northwest deposit associated with oppenheimer u crater contains the most iron rich volcanic glass thus far identified on the moon which could be a useful future resource we propose that this variability in mineralogy indicates variability in eruption style and that it cannot be explained by a simple vulcanian eruption a vulcanian eruption should cause significant country rock to be incorporated into the pyroclastic deposit however large areas within many of the deposits exhibit spectra consistent with high abundances of juvenile phases and very little floor material thus we propose that at least the most recent portion of these deposits must have erupted via a strombolian or more continuous fire fountaining eruption and in some cases may have included an effusive component these results suggest that localized lunar pyroclastic deposits may have a more complex origin and mode of emplacement than previously thought

a strontium and neodymium isotopic study of apollo 17 high ti mare basalts resolution of ages evolution of magmas and origins of source heterogeneities abstract a combined sr and nd isotopic study of 15 apollo 17 high ti mare basalts was undertaken to investigate geochronological and compositional differences between previously identified magma types a b1 b2 and c whole rock and mineral separates for one of the least evolved type b1 basalts 70139 yield sm nd and rb sr isochron ages of 3 71 0 12 ga and 3 65 0 13 ga respectively a more evolved type a basalt 71539 exhibits a slightly older sm nd isochron age of 3 75 0 07 ga and a rb sr isochron age of 3 67 0 10 ga although these two ages are non resolvable by themselves compilation of all available geochronological data allows resolution of type a and b1 b2 ages at high levels of confidence 99 the most reliably dated samples classified according to their geochemical type yield weighted average ages of 3 75 0 02 ga for type a n 4 and 3 69 0 02 ga for type b1 b2 n 3 basalts insufficient geochronological data are available to place the rare type c basalts within this stratigraphy we propose that age differences correlate with geochemical magma type and that early magmatism was dominated by eruption of type a basalts while later activity was dominated by effusion of type b1 and b2 basalts whole rock isotopic data yield distinct differences in initial sr and nd isotopic compositions between types a b1 b2 and c basalts types a b1 and c exhibit restricted intra group compositional variations and lie along well defined whole rock isochrons these data are consistent with petrogenetic models involving closed system fractionation of observed microphenocrysts from chemically and isotopically distinct parental magmas in contrast a wide range of type b2 initial isotopic compositions indicates mixing of several distinct components during magma evolution the sm nd whole rock isochron age for type a bl and c basalts of 3 79 0 15 ga is within error of apollo 17 eruptive activity however the very well defined sr whole rock isochron age of 4 02 0 05 ga is 270 to 330 ma older than eruptive ages isotopic and petrological arguments indicate that extensive rb sr fractionation did not occur at the time of melt generation therefore the 4 0 ga sr whole rock isochron age records a significant event at which time geochemical heterogeneities were established within the originally homogeneous basalt source regions types a and c sources were enriched in rb sr with little or no concurrent modification of 87 sr 86 sr sm nd or 143 nd 144 nd infiltration of similar aged kreep magmas into mantle cumulate sources cannot explain both sr and nd isotopic data instead we suggest a metasomatic origin in which rb transported as a chloride complex in halogen rich fluids was preferentially mobilized relative to sr and the rees

evidence for the trapped liquid shift effect in the mount ayliff intrusion south africa postcumulus trapped liquid shift in layered complexes produces cumulate minerals with more fractionated compositions than the original primary phases this effect is shown by olivine compositions from the base of the mount ayliff intrusion where varying proportions of olivine to interstitial liquid produce a suite of rocks which define a tight linear trend on a binary whole rock plot of mgo versus feo extrapolation of this trend constrains the composition of the primary cumulus olivine to the range fo84 86 whereas olivine actually present have compositions fo77 83 the magnitude of the discrepancy between the theoretical and observed olivine compositions correlates directly with the weight fraction of interstitial liquid these observations are quantitatively predicted by the trapped liquid shift model they also argue against significant migration of residual liquid trapped liquid shift is documented over a vertical interval of 60 m it occurred in rocks lying only 1 m above the basal contact of the intrusion and hence must be a comparatively rapid process

volatile and siderophile element geochemistry of the moon a reappraisal abstract lunar volcanic glasses lvg contain high abundances of many volatile elements as compared to mare basalts whereas the latter were derived from devolatilized source regions in the outer few hundred kilometers of the moon lvg are believed to come from a globally extensive source region at greater depths which is relatively rich in volatile components abundances of volatile elements in lvg and their source regions are reviewed and in many cases found to resemble those in the earth s mantle likewise siderophile element abundances including the highly siderophile elements ir os au and re are similar in the earth s mantle and in the source regions of lvg the close geochemical similarity between the lvg source region i e the lunar lower mantle and the terrestrial mantle constitutes strong evidence that protolunar material was derived primarily from the earth s mantle since highly siderophile elements are believed to have been added to the earth as an oxidised veneer at the end of its accretion and then convectively mixed into the mantle the removal of protolunar material from the earth must have occurred after this late addition which may represent carbonaceous chondritic or cometary material from the outer solar system it is widely believed that the moon was formed by the impact of a giant planetesimal on the protoearth the planetesimal is presumed to have formed in the inner solar system and to have differentiated internally into a mantle and core numerical modelling of the giant impact shows that most of the material now in the moon would have been derived from the mantle of the impactor however this is contradicted by the geochemical evidence provided by lvg which implies that the moon is composed mainly of material derived from the terrestrial mantle a possible answer to this dilemma is provided by the observation that the lvg source region reflects the geochemistry of the late oxidised veneer which accreted on the earth this suggests that protolunar material may have been removed from the earth s mantle by impacts from one or more high velocity 30 km s planetesimals composed mainly of ices and derived from the outer solar system the volatiles from the impacting planetesimals were lost after these collisions the impacts probably ejected material from the earth s mantle as jets of molten matter which was rapidly quenched thereby retaining a large proportion of its terrestrial volatile inventory

understanding the origin and evolution of water in the moon through lunar sample studies a paradigm shift has recently occurred in our knowledge and understanding of water in the lunar interior this has transpired principally through continued analysis of returned lunar samples using modern analytical instrumentation while these recent studies have undoubtedly measured indigenous water in lunar samples they have also highlighted our current limitations and some future challenges that need to be overcome in order to fully understand the origin distribution and evolution of water in the lunar interior another exciting recent development in the field of lunar science has been the unambiguous detection of water or water ice on the surface of the moon through instruments flown on a number of orbiting spacecraft missions considered together sample based studies and those from orbit strongly suggest that the moon is not an anhydrous planetary body as previously believed new observations and measurements support the possibility of a wet lunar interior and the presence of distinct reservoirs of water on the lunar surface furthermore an approach combining measurements of water abundance in lunar samples and its hydrogen isotopic composition has proved to be of vital importance to fingerprint and elucidate processes and source s involved in giving rise to the lunar water inventory a number of sources are likely to have contributed to the water inventory of the moon ranging from primordial water to meteorite derived water ice through to the water formed during the reaction of solar wind hydrogen with the lunar soil perhaps two of the most striking findings from these recent studies are the revelation that at least some portions of the lunar interior are as water rich as some mid ocean ridge basalt source regions on earth and that the water in the earth and the moon probably share a common origin

extratropical cyclones frontal waves and mars dust modeling and considerations 1 a mars gcm is utilized to investigate dust lifting and organization associated with extratropical cyclogenesis and frontal waves the model is applied at high resolution in simulations related to mars dust cycle a single extratropical synoptic weather event is examined to ascertain lifting transport and convergence divergence of dust by large scale cyclonic anticyclonic weather systems and the sub synoptic frontal waves that ensue low and high pressure cores develop travel eastward and remain mostly confined within the seasonal co2 polar cap the bulk of dust lifting occurs in the northern hemisphere western highlands associated with nocturnal down slope drainage flows and lifting infrequently occurs near the frontal convergence zone dust becomes organized and transported within circulations associated with the synoptic sub synoptic circulations accompanying the frontal waves dynamical considerations are invoked regarding frontogenesis revealing correlations with regards to dust lifting organization and transport implications of large scale extratropical weather systems on the martian dust cycle are discussed

petrogenesis of the apollo 14 high alumina basalts implications from ion microprobe analyses abstract in this study ion microprobe analyses of individual minerals are used to investigate the petrogenesis of the apollo 14 high al basalts we use trace element concentrations from individual minerals in the apollo 14 high al basalts to evaluate both endogenic and exogenic models the data show that if the apollo 14 high al basalts were produced by melting within the lunar mantle these basalts cannot be related to one another by closed system fractional crystallization of a single basaltic melt rather the trace element data show that variable amounts of a kreep component were added to the basalts by either assimilation mixing into mantle sources or impact melting single stage assimilation fractional crystallization models can only explain the data from this study if an excessively large mass of urkreep is assimilated into the parent magma before olivine crystallization alternatively the trace element data can be explained if the apollo 14 high al basalts were produced by melting multiple al rich mantle sources that contain different amounts of urkreep finally for impact melting to be a relevant process the data require that multiple large impact melts be formed from mixed kreep rich target lithologies the resulting impact melts must then crystallize to produce basalts with igneous textures high al2o3 concentrations uniform major element compositions and a wide range of incompatible trace element concentrations

volcanic glass signatures in spectroscopic survey of newly proposed lunar pyroclastic deposits moon mineralogy mapper spectroscopic observations are used to assess the mineralogy of five sites that have recently been proposed to include lunar dark mantle deposits dmds volcanic glasses have for the first time clearly been identified at the location of three of the proposed pyroclastic deposits this is the first time that volcanic glasses have been identified at such a small scale on the lunar surface from remote sensing observations deposits at birt e schluter and walther a appear to be glassy dmds deposits at birt e and schluter show 1 morphological evidence suggesting a likely vent and 2 mineralogical evidence indicative of the presence of volcanic glasses the walther a deposits although they show no morphological evidence of vents have the spectroscopic characteristics diagnostic of volcanic glasses the deposits of the freundlich sharonov basin are separated in two areas 1 the buys ballot deposits lack mineralogical and morphological evidence and thus are found to be associated with mare volcanism not with dmds and 2 the anderson crater deposits which do not exhibit glassy dmd signatures but they appear to be associated with possible vent structures and so may be classifiable as dmds finally dark deposits near the crater kopff are found to be associated with likely mare volcanism and not associated with dmds the spectral identification of volcanic glass seen in many of the potential dmds is a strong indicator of their pyroclastic origin

a chemical model for generating the sources of mare basalts combined equilibrium and fractional crystallization of the lunar magmasphere abstract it is generally considered that mare basalts were generated by the melting of a cumulate mantle formed in an early moon wide magma ocean or magmasphere however the nature and chemistry of this cumulate mantle and the logistics of its origin have remained elusive extensive studies of terrestrial layered mafic intrusions over the past sixty years have emphasized the imperfection of fractional crystallization and attendant crystal crystal and crystal liquid separation in a convecting magma chamber crystal liquid and crystal crystal separations were similarly inefficient during evolution of the lunar magma ocean lmo allowing for the trapping of interstitial liquid and entrainment of a small proportion of less dense plagioclase into the denser mafic cumulate mush indeed petrography of lunar highlands samples demonstrates this for anorthosites with 1 10 olivine the residual liquid after 80 90 crystallization was very evolved in fact kreepy and even in small proportions 1 5 would have a noticeable effect on the trace element chemistry of melts generated from these cumulates this trapped residual liquid would elevate total ree abundances in the cumulate pile while synchronously deepening the already negative eu anomaly essentially this trapped liquid will make the cumulate more fertile for melting to generate both kreep basalt and mare basalt magmas plagioclase entrained in the mafic cumulate pile adds an essential al component to the high ti basalt source and will moderate the requisite negative eu anomaly in the cumulate early in the evolution of the lunar mantle when the lmo still was largely liquid it is likely that vigorous convection was an important factor in crystallization such convection would allow crystals to remain suspended and in equilibrium with the lmo liquid for relatively long periods of time this extended period of equilibrium crystallization would then have been followed by fractional crystallization once plagioclase became a liquidus phase and began to float to form the lunar highlands crust previous authors have proposed a three component model for the evolution of high ti mare basalt source regions this model includes kreep early olivine rich high mg cumulates and late ilmeniterich low mg cumulates in various proportions however we propose a model for high ti basalt parent magmas which is in accord with studies of terrestrial layered intrusions this model for the high ti source includes trapped instantaneous residual liquid tirl 1 3 and entrainment of a small 2 5 proportion of plagioclase into the late stage cumulate pile in order to account for both the observed al compositions and trace element characteristics of high ti mare basalts melting of this relatively shallow ilmenite and clinopyroxene bearing late stage cumulate can generate high ti mare basalt magmas furthermore we are in agreement with other workers that only through a process of nonmodal melting will the high ti values for the parent magmas be realized large scale convective overturn of the cumulate pile and mixing of kreep with early and late stage cumulates is not required however localized overturn of the upper tenth of the cumulate pile is likely and in fact required to achieve an appropriate major element balance for the high ti mare basalt source region

the materials of the lunar procellarum kreep terrane a synthesis of data from geomorphological mapping remote sensing and sample analyses major features of the moon s procellarum kreep terrane include subdued relief and extensive resurfacing with mare basalt consistent with high concentrations of th and other heat producing elements at depth we relate the chemistry of sampled materials to the geomorphology th surface concentrations determined by the lunar prospector 2 pixels and feo and tio2 concentrations derived from clementine ultraviolet visible spectral data on the basis of geologic maps each pixel was classified as mare terra or mixed near the periphery of the terrane terra pixel compositions are relatively feldspathic in the interior they mainly represent imbrium basin rim or ejecta deposits and are mainly incompatible trace element rich norites and presumably represent materials from a thick section tens of kilometers of the pre imbrium crust of the terrane excavated by the imbrium event although imbrium ejecta are the principal source of surface terra materials the imbrium event did not create the th rich procellarum kreep terrane broad continuous expanses of mare pixels are observed with little interruption from protruding terra or terra penetrating craters the mare basalt dominated regoliths of these areas have a wide range of tio2 concentrations 18 leading to the conclusion that the high th concentrations are in the mare basalts and are not present in the regoliths as terra derived materials volcanic glasses and impact glasses of mare basalt composition collected from the procellarum kreep terrane support this conclusion

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

lunar and terrestrial crust formation planetary crusts may be accreted produced in primordial differentiation or built up piecemeal by serial magmatism the existence of old polygenetic laterally heterogeneous partial melt rocks in the lunar highlands suggests that the moon produced its early crust by serial magmatism this view can be reconciled with lunar eu anomalies previously thought to support the magma ocean model of crust formation if complications in the fractionation of mare basalts are recognized phase equilibrium and magmatic density information for mare basalts suggest a model in which plagioclase fractionation can occur even though plagioclase is not a near liquidus phase the cryptic fractionation of clinopyroxene in morb provides a precedent for this model the necessity for a lunar magma ocean is questioned but a role for a terrestrial magma ocean of sorts at depth is suggested