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

petrology and chemistry of two large granite clasts from the moon abstract pristine granite clasts in apollo 14 breccias 14321 and 14303 have estimated masses of 1 8 and 0 17 g respectively the 14321 clast is 60 k feldspar and 40 quartz with traces of extremely mg poor mafic silicates and ilmenite the 14303 clast is roughly 33 plagioclase 32 k feldspar 23 quartz 11 pyroxene and 1 ilmenite pyroxene and ilmenite are moderately mg rich plagioclase and pyroxene are strongly zoned both clasts are severely brecciated but monomict pristine both have abundant graphic intergrowths of k feldspar with quartz unlike the majority of similar earth rocks both clasts are devoid of hydrous phases the bulk composition of the 14321 clast is similar to those of several other lunar granitic samples but the 14303 clast is unique it bears as close a resemblance to kreep as it does to other lunar granites silicate liquid immiscibility may explain why the granites are low in ree relative to kreep

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

metasomatic products of the lunar magma ocean the role of kreep dissemination the origin of the incompatible element rich lunar component kreep is in the lunar magma ocean lmo the fractionated residual melt after crystallization of the lmo represents urkreep after warren and wasson 1979 the percentage of this residual melt is low enough to be within the realm of silicate liquid immiscibility sli this process has the ability to split the kreep signature into k and reep fractions which are manifest as lunar granite k and phosphate phases present in highland lithologies or as quartz ferrotroctolite in lunar soils reep we envisage this as a localized but significant process since only a small portion of urkreep undergoes sli norms of experimental and apollo 15 basaltic immiscible glasses suggest that thevreep fraction found in the lunar highlands has undergone post sli fractionation of at least fayalite this significantly reduces the density of the reep fraction and coupled with its low viscosity 10 15 poise it can percolate upward metasomatizing the lunar crust the higher viscosity of the granitic melt 30000 poise inhibits its mobility and it forms pods in the lower rust as required for vhk basalt petrogenesis with the identification of kreepy components the composition of urkreep can be calculated using experimental evidence the kreep components may be recombined to give the pre sli composition or liquid liquid kd s can be used to calculate a pre sli composition from lunar granite both calculated urkreep compositions are lower in mgo and al2o3 and higher in feo and p2o5 than reported low and high k kreep compositions the calculated ree abundances are higher and the ree profiles are slightly more lree enriched than the previously reported kreep compositions however the ree profile calculated using liquid liquid kd s is concave upwards compared to the lree enriched profile produced by recombining the kreep components pre sli whitlockite apatite fractionation occurred prior to immiscibility in order to generate the concave upwards profile the lree enriched profile represents the pre sli magma prior to phosphate fractionation the presence of superkreepy rock types can be accounted for by k and reep fraction assimilation and the compositions of olivine vitrophyres can now be modeled using analyzed lunar rock types without the inference of a mythical high mg component other more widespread kreepy rocks e g apollo 14 breccias apollo 15 kreep basalts lkfm basalts are produced by incorporation of the more widespread pre sli urkreep component the splitting of kreep into identifiable lithological components allows the petrogenesis and role of kreep in lunar evolution to be better understood

hf zr and ree partition coefficients between ilmenite and liquid implications for lunar petrogenesis hf zr and ree partition coefficients between ilmenite and coexisting liquid were determined under near lunar conditions ilmenite was synthesized at 1125 c under low oxygen fugacity fo2 10 12 4 from glass of a high ti mare basalt composition doped with 50 100 g g of ree and hf and 500 1000 g g of zr the partition coefficients d of ilmenite for hf and zr obtained by isotope dilution analysis are 0 41 and 0 33 respectively these values are significantly lower than those of ilmenite 3 0 and 1 8 respectively from a kimberlite megacryst fujimaki et al 1984a dree for the synthesized ilmenite are slightly smaller than those of ilmenite from the kimberlite megacryst and the dlu is 0 056 these results suggest that ilmenite may have played an important role in the lu hf evolution of lunar mare basalts using newly determined dlu and dhf for ilmenite the lu hf evolution or lunar cumulates and the coexisting magma was examined for several different crystallization sequences by a model calculation the lu hf variation trend of most high ti mare basalts is well explained by a small degree less than 5 of partial melting of the cumulates however a higher degree of partial melting is required to explain the variation of very low ti basalts green glass and apollo 12 low ti basalts apollo 15 low ti basalts could not be produced by simple partial melting but may require chromite crystallization as well

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

styles of interdistributary basin sedimentation mississippi delta plain louisiana abstract deposits in interdistributary basins are largely controlled by the relative rates of subsidence and the amount of sediment transported into the basin marine delta progradation and subsequent abandonment on approximately a 1000 to 1500 year cycle isolate extensive backswamp and marshy areas between major distributary channels the resulting interdistributary basins areally occupy a large portion of the lower alluvial valley and upper delta plain extensive backswamps occur at the apex of these basins and grade seaward into fresh brackish and saline marshes following delta lobe abandonment high subsidence rates combined with low sediment input lead to flooding of the basin both by marine incursion and the enlargement of lakes analyses of sedimentary processes in the barataria and atchafalaya basins of the louisiana delta plain reveal two contrasting styles of sediment accumulation thick sequences of peat interfingering with fine grained lacustrine marsh and backswamp deposits are characteristic of a basin starved of terrigenous clastic sediment barataria basin formation of a distributary channel in the basin atchafalaya basin results in the introduction of large quantities of coarser grained detrital clastics to the lowland coarsening upward lacustrine delta sequences which average several meters in thickness prograde tens of kilometers into the interdistributary basin ultimately coalescing with adjacent deltaic alluvial and backswamp deposits in the atchafalaya basin deposition of backswamp deposits with coarser grained lacustrine deltaic and alluvial sediments aggrades the interdistributary basin and delta plain in the process of prograding a distributary channel and marine delta once this marine delta complex is abandoned the site of active deposition shifts to another area the lack of detrital influx increases the relative subsidence rate and peat accumulation becomes the dominant process in the basin continual subsidence leads to complete inundation of the backswamp and termination of distributary channel in the basin an upstream channel avulsion or distributary formation may again initiate siliciclastic deposition in the basin

the origin and evolution of lunar high ti basalts periodic melting of a single source at mare tranquillitatis abstract five groups of basalts a b1 b2 b3 d with three principal ages exist at the apollo 11 site these range from the low k low rare earth element ree groups b1 b2 and b3 to the low k high ree group d basalts to the high k high ree group a basalts the group a basalts are the only high k 0 2 wt k2o basalts and youngest with an age of 3 59 02 ga groups b3 and b1 are 3 71 02 and 3 67 02 ga respectively group b2 basalts are the oldest at 3 85 02 ga group d basalts have not been dated fractionation modelling for major and trace elements indicates that the b1 basalts could have formed from a b3 like parent liquid the b2 and d basalts can also be related to liquids similar to the b3 b1 composition through the presence of varying amounts of modal whitlockite thus the entirety of low k high ti basalts at apollo 11 may have formed through melting of the same source region the group a basalt compositions are consistent with formation from a different parent liquid with the composition of apollo 11 orange glass modelling of major and trace elements in the apollo 11 orange glass indicate that the composition of the group a basalts is consistent with fractionation of this glass coupled with some assimilation 7 5 15 of an evolved kreep like material however this component is much younger than primitive kreep 4 4 ga this neukreep component similar to the composition of quartz monzodiorites described from the apollo 15 site probably represents evolved material formed during plutonism prior to the formation of the apollo 11 orange glass liquid

apollo 17 kreepy basalts evidence for nonuniformity of kreep breccia 72275 contains pristine kreepy basalt clasts that are not found among other samples collected at apollo 17 these basalts occur as discrete clasts and as clasts enclosed within basaltic microbreccias mineral and whole rock chemical analyses reveal that the microbreccias are compositionally indistinguishable from the basalt clasts samples of the 72275 matrix also have the same compositions as the basalts and the basaltic microbreccias 72275 was assembled in situ from a single flow or series of closely related flows of apollo 17 kreepy basalt before it was transported to the apollo 17 site as a rock type apollo 17 kreepy basalts are distinct from apollo 15 kreep basalts the apollo 17 samples have lower ree concentrations steeper negative slopes of the hree and are less magnesian than the apollo 15 samples the two basalt types cannot be related by fractional crystallization partial melting or assimilation this is evidence for the compositional nonuniformity of kreep as a function of geography

petrographic evidence for nonlinear cooling rates and a volcanic origin for apollo 15 kreep basalts most apollo 15 kreep basalts have textures indicative of linear cooling rates some samples have textures indicative of two stage cooling 15434 8 contains orthopyroxene phenocrysts up to 2 mm long in a much finer grained intersertal groundmass and probably has accumulated orthopyroxene 15404 5 has glomerocrysts of orthopyroxene and plagioclase also in a much finer grained intersertal groundmass clasts in glassy breccia 15358 have abundant 20 to 40 clear undevitrified orange yellow intersertal glass glassy intersertal textures indicative of late quenching phenocrysts by comparison with experiments on dynamic crystallization do not grow from multiply saturated magmas as are the apollo 15 kreep basalts at linear cooling rates therefore the phenocryst bearing samples provide evidence for their initially slow cooling and later rapid cooling two stage cooling is common in volcanic dynamic environments but cannot be expected in the static environment of crystallization of impact melt sheets even basin scale ones therefore these apollo 15 kreep basalts and by extrapolation all the other clast free homogeneous meteoritic siderophile absent apollo 15 kreep should be reexamined with the constraint that the apollo 15 kreep basalts were produced by igneous processes at 3 9 ga but managed to retain the trace element characteristics established at about 4 4 ga the common acceptance of total remelting by impact at 3 9 ga such as the imbrium basin event in the interpretation of the isotopic and chemical data is not permissible

an apatite rich ferroan mafic lithology from lunar meteorite alha81005 lunar meteorite alha81005 contains a clast of ferroan anorthositic troctolite with in vol 59 plagioclase avg an 95 4 27 olivine avg fo 52 2 11 clinopyroxene mg 50 70 wo 11 34 and 3 chlorapatite this clast is probably pristine and is unique among lunar samples its texture is igneous but is unusual in that pyroxene and apatite which probably cocrystallized have been brecciated and apparently resorbed and olivine has precipitated around them we discuss four possible explanations for this texture 1 a sudden decrease in pressure occurred causing liquidus pyroxene to become unstable relative to olivine 2 the bulk composition of the magma was sufficiently feo rich that pyroxene crystallized before olivine 3 a p2o5 rich 2 5 3 0 wt quartz normative basaltic magma that crystallized pyroxene plagioclase and phosphates was mixed with an olivine saturated magma that had a lower p2o5 content 4 an olivine saturated magma invaded a wall rock assemblage of pyroxene plagioclase and apatite the first two models require only one magma and are attractive because the average compositions of pyroxene olivine and plagioclase indicate that they crystallized from liquids with similar mg the first model cannot be assessed without knowing the bulk composition of the original magma and the initial pressure the second model cannot account for the brecciation and resorption of the pyroxene and apatite a model involving either magma mixing or wall rock magma reaction seems most likely the high p content and apatite whitlockite ratio indicate that the parent magma s had an unusually high volatile content for a lunar magma ree in whitlockite are 40 80 times kreep abundances the parent magma s must have had very high abundances of ree and la sm less than that of kreep the clast is also unusually mafic only 59 plagioclase for pristine ferroan rocks ferroan mafic lithologies appear to be an important component of alha81005 the apatite rich clast presents several petrologic and geochemical paradoxes which suggests that complex processes were involved in its formation

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

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

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

magnesian anorthosites and associated troctolites and dunite in apollo 14 breccias magnesian anorthosite a new type of pristine lunar highlands rock has been found in apollo 14 breccias it has primitive high ca and mg silicate mineral compositions and high and variable ree concentrations variations in ree contents can be accounted for by variations in modal abundance of ree rich apatite magnesian anorthosites are associated with troctolites and a dunite with very similar mineral compositions and it is suggested that all crystallized from a differentiated troctolitic intrusion the origin of the ree rich apatite is enigmatic it is unlikely to have crystallized from an igneous liquid in equilibrium with the major minerals in the anorthosite possible origins are assimilation of urkreep or metasomatism by ree rich fluids ree rich alkali anorthosites and gabbronorites are also found and are likely to be related to kreep basalt magmas lunar compositional associations are distributed in a regional rather than global manner

seventh foray whitlockite rich lithologies a diopside bearing troctolitic anorthosite ferroan anorthosites and kreep seventeen nonmare samples most of them pristine are characterized and implications of the new data are discussed five pristine samples are from apollo 14 near the center of the kreep rich zone in the moon s western hemisphere three of them are alkali anorthosites rich in ca phosphate whitlockite which apparently crystallized from magmas with ree contents roughly 6 those of high k kreep the alkali anorthosites probably formed from mg rich magmas that assimilated large amounts of urkreep but some might have formed by metasomatism of ferroan anorthosite by urkreep the gabbronorite norite classification scheme is not well suited to western hemisphere lithologies probably due mainly to the overriding effects of longitude petrochemistry correlations a diopside bearing mg rich lithology indicates that a low degree of melting was not a prerequisite for producing gabbroic high ca pyroxene rich mg rich magmas and suggests that some source regions of mg rich magmas were relatively ca rich several pristine kreep fragments from apollo 15 station 2 are texturally and compositionally much like other pristine kreep and thus reinforce the evidence that kreep is highly uniform the pristine anorthosites on the other hand demonstrate further that lunar anorthosites are diverse

rb sr and sm nd chronology of an apollo 17 kreep basalt sm nd and rb sr mineral isochrons were determined for an apollo 17 kreep pigeonite basalt clast 543 from breccia 72275 collected from boulder 1 station 2 in the valley of taurus littrow sm nd analyses of the basalt yield a precise mineral isochron age of 4 08 0 07 ga for 147sm 0 00654 ga 1 the rb sr mineral isochron age of 4 13 0 08 ga for 87rb 0 0139 ga 1 is concordant with the sm nd age however the rb sr isotopic system has been slightly disturbed probably by the serenitatis impact event 3 95 ga ago the sm nd age is interpreted as the crystallization age of this apollo 17 kreep basalt ages and initial 87sr 86sr and end values for this basalt and apollo 14 and 15 kreep basalts suggest that these two types of kreep basalts could be produced from sources having similar rb sr and sm nd ratios these new age data suggest that kreep basaltic volcanism started 200 ma earlier than the 3 85 ga age generally accepted from studies of apollo 15 pristine kreep basalts apollo 17 kreep basalts probably pre date the serenitatis impact strongly indicating that not all kreep basaltic volcanism was necessarily related to basin forming impacts the younger apollo 15 and 14 kreep basalts probably are related to the imbrium impact however the ages and end values for kreep basalts granites troctolites and norites from a variety of lunar sites form a linear array corresponding to source s with sm nd lower by 15 than the chondritic value slightly enriched in lree suggesting that these rocks could be genetically related formation of a common sm nd isotopic growth curve by these data is most easily explained by an early moon wide differentiation accompanying the formation and subsequent solidification of a global magma ocean

petrology of the apollo 11 highland component new data for 38 highland fragments hand picked from apollo 11 coarse fines are reported petrographic mineralogic and bulk chemical data show that 1 the apollo 11 highland component is non kreepy and like that of apollo 16 2 poikilitic rocks granulitic breccias and the anorthosite norite troctolite suite are the most abundant rock types followed by polymict breccias and glasses 3 both the ferroan anorthosite and mg rich plutonic suites are represented in the apollo 11 highland component 4 except for one sample the intermediate k fra mauro and high k fra mauro groups are not represented the data and observations are consistent with local derivation of the highland material from beneath relatively thin basalt flows and addition to the regolith via vertical mixing

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

evidence for metasomatism of the lunar highlands and the origin of whitlockite abstract the presence of rare earth element rich ree rich whitlockite in the relatively primitive ree poor lunar highlands presents a paragenetic problem to the petrologist comparison with occurrences in mare basalt mesostasis assemblages demonstrates that whitlockite in the lunar highlands has not resulted from the crystallization of the residual interstitial melt furthermore by the nature of ree partition coefficients for whitlockite it is demonstrated that they cannot have crystallized from kreepy melts rather we suggest that the only lunar melt which contains high enough ree abundances is the basic immiscible melt derived from a kreepy liquid we envisage that whitlockite found in the lunar highlands is a post cumulus metasomatic phase precipitated from a melt formed when urkreep underwent silicate liquid immiscibility the basic immiscible melt thus produced was able to percolate through the lunar highlands due to its low viscosity and act as a metasomatizing agent apatite is occasionally found as either epitactic overgrowths on the whitlockites mantled by whitlockite or in composite grains with whitlockite in all cases these apatites contain much lower ree contents than the corresponding whitlockite experimental results suggest either 1 1 apatite and whitlockite have essentially the same ree kd s 2 2 apatite has lower ree kd s than whitlockite both scenarios can be used to explain certain apatite whitlockite associations for example apatite and whitlockite having the same ree kd s can explain the situation where apatite appears to have crystallized after whitlockite this is because apatite crystallization requires a certain level of halogens in the melt these levels are only realized after whitlockite crystallization which enriches the residual melt in f and cl but depletes it in the rees therefore when apatite crystallizes it will contain lower ree abundances than whitlockite however relationships where apatite and whitlockite appear to have co crystallized or apatite crystallized before whitlockite require apatite to have lower ree kd s even if both experimental results are correct the whitlockite parental melt still requires ree abundances greater than in kreep urkreep the parental melt has similar ree abundances to a calculated reepy immiscible melt from kreep urkreep

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

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

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

cupri system configuration for nlc 91 and observations of pmse during salvo a the cornell university portable radar inter ferometer cupri provided nearly continuous monitor ing of the mesosphere above esrange sweden during the noctilucent cloud rocket and radar campaign of the sum mer of 1991 nlc 91 cupri probed the mesosphere above esrange from 78 to 91 km altitude with 300 meter resolution and was sensitive to the enhanced polar meso spheric summer echoes pmse that occur in the same altitude range as nlc formations out of the total of 264 hours of cup ri observation time p mse were present for 140 hours rocket salvo a was flown on the night of august 9 10 into an nlc event that occurred simul taneously with a thin and weakening pmse layer high resolution doppler spectrograms of this pmse event re vealed sawtooth like discontinuities at 83 km altitude which we interpret to be a distorted partial reflection layer which was advected across the radar beam