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

the source region and melting mineralogy of high titanium and low titanium lunar basalts deduced from lu hf isotope data five high ti basalts from the apollo 11 and 17 landing sites have been analyzed for their hafnium isotope composition these data serve to better constrain the hafnium isotope variation of the moon s mantle variations in initial hf and nd values of low and high ti basalts imply that the source region mineral assemblages of these lunar magma types are distinct low ti basalts have higher initial hf values at a given nd value than high ti basalts the differences in the hafnium and neodymium isotopic composition of low and high ti basalts reflect the fact that the source of low ti basalts had a lu hf n ratio approximately four times greater than its sm nd n ratio in contrast the high ti source region had subequal lu hf n and sm nd n ratios if it is assumed that mare basalts are partial melts of the moon s cumulate mantle the differences between low and high ti basalts can only be explained by these mare magma types being generated from melting sources with distinctly different mineral assemblages the large lu hf fractionations relative to sm nd fractionations of low ti basalts can best be produced by an assemblage of olivine and orthopyroxene with trace amount of clinopyroxene that crystallized early in the history of the lunar magma ocean lmo the subequal lu hf n and sm nd n fractionations of high ti basalts can be produced from a variety of ilmenite bearing mineral assemblages low and high ti basalts have similar lu hf ratios approximately 0 6 times chondrite the low lu hf ratios measured for these mare magmas contrast sharply with the high lu hf ratios greater than chondritic calculated for their sources from initial hf values and an assumed chondritic bulk moon initial hf value the difference between the measured lu hf of a lava vs the calculated lu hf of its source implies that during partial melting lu was preferentially retained in the residual source relative to hf in order to explain the extreme fractionation of measured lu hf ratios we suggest mare basalts can best be explained using a polybaric melting model initial melting of a garnet bearing source followed by continued melting in the spinel stability field can produce the required lu hf fractionations and produce a liquid that last equilibrated with a residuum of olivine and orthopyroxene

merwinite structured phases as a potential host of alkalis in the upper mantle two previously unknown na and k rich phases were synthesized near the solidus of the model cmas lherzolite interacted with the caco3 na2co3 kcl melt at 7 gpa they coexist with forsterite garnet and chloride carbonate melt stoichiometry and unit cell parameters measured by means of powder diffraction indicate that one of the phases corresponds to k na 2ca4mg2si4o15 with about 0 1 a p f u al although single crystal x ray measurements of this phase did not allow the solution of the crystal structure we suggest that the structure of this phase includes mixed sio4 and si2o7 units single crystal diffraction experiments of the other alkali rich phase with composition ca2 06na0 86k0 08 3 00 mg0 53si0 45al0 03 1 01si2 00o8 showed that it exhibits the merwinite structure space group p21 a with lattice parameters a 12 987 2 b 5 101 1 c 9 130 2 a 92 36 1 v 604 3 2 a3 and z 4 the structure was refined to r1 0 031 using 2619 independent reflections in the structure na is hosted at the large ca sites whereas si replaces mg at the octahedral site and occurs in the usual tetrahedral coordination ordering induced distortion provokes a change in coordination of the ca na atoms with respect to pure merwinite merwinite phases with lower k na contents 0 08 0 18 a p f u coexist with forsterite clinopyroxene and immiscible carbonate chloride and silicate melts at higher temperatures up to 1510 c at 7 and 5 5 gpa these phases including alkali rich ones at solidus show a general formula ca3 2x na k 2x mg1 xsix si2o8 with x up to 0 45 where the na k content negatively correlates with ca and positively correlates with si the present experimental and crystal chemical data prove that merwinite structured phases may be efficient hosts for alkalis in the upper mantle they are mineralogical indicators of either the interaction of mantle peridotites with alkaline carbonatitic liquids or high pressure crystallization of silica undersaturated cao and alkali rich melts

the origin of crystalline residues in stardust al foils surviving cometary dust or crystallized impact melts abstract samples returned by the stardust mission from comet 81p wild 2 provide an unequaled opportunity to investigate cometary formation and evolution crystalline silicates have been identified in impact craters in stardust al foil yet their origin is ambiguous they may be original cometary components or they may have grown from melt generated by impact we have now studied experimental impacts of the calcium silicate mineral wollastonite using scanning and transmission electron microscopy to document the relationship between impact feature shape and crystal lattice orientation in impact residue wollastonite can have a characteristic acicular habit forming crater shapes that indicate crystal orientation upon impact from extracted impact residue we determined the lattice orientation of crystalline material for comparison with the whole particle orientation we assume that crystallization from melt without surviving seed nuclei should result in randomly oriented crystallite growth with no preferred direction for individual crystals however we find that the majority of crystalline material in the residue retains b axis orientation parallel to the long axis of the crater form this together with impact parameter calculations and lack of al incorporation by the residue suggesting melting did not occur indicates that these crystals and by analogy the majority of al free crystalline silicates in stardust foil are surviving remnants of the impactor furthermore amorphous wollastonite residue probably did not form via melting and subsequent quenching but instead by high pressure amorphization or degradation of unquenchable phases finally one crystal studied appears to be a new high pressure temperature polymorph of casio3 indicating that such polymorphs may be observed in stardust residues in craters

a model for the thermal and chemical evolution of the moon s interior implications for the onset of mare volcanism crystallization of the lunar magma ocean creates a chemically stratified moon consisting of an anorthositic crust and magma ocean cumulates overlying the primitive lunar interior within the magma ocean cumulates the last liquids to crystallize form dense ilmenite rich cumulates that contain high concentrations of incompatible radioactive elements the underlying olivine orthopyroxene cumulates are also stratified with later crystallized denser more fe rich compositions at the top this paper explores the chemical and thermal consequences of an internal evolution model accounting for the possible role of these sources of chemical buoyancy rayleigh taylor instability causes the dense ilmenite rich cumulate layer and underlying fe rich cumulates to sink toward the center of the moon forming a dense lunar core after this overturn radioactive heating within the ilmenite rich cumulate core heats the overlying mantle causing it to melt in this model the source region for high tio2 mare basalts is a convectively mixed layer above the core mantle boundary which would contain small and variable amounts of admixed ilmenite and kreep this deep high pressure melting as required for the generation of mare basalts occurs after a reasonable time interval to explain the onset of mare basalt volcanism if the content of radioactive elements in the core and the chemical density gradients above the core are sufficiently high but within a range of values that might have been present in the moon regardless of details implied by particular model parameters gravitational overturn driven by the high density of magma ocean fe rich cumulates should concentrate high tio2 mare basalt sources and probably a significant fraction of radioactive heating toward the center of the moon this will have important implications for both the thermal evolution of the moon and for mare basalt genesis

seismic observations of splitting of the mid transition zone discontinuity in earth s mantle the transition zone of earth9s mantle is delineated by globally observed discontinuities in seismic properties at depths of about 410 and 660 kilometers here we investigate the detailed structure between 410 and 660 kilometers depth by making use of regional stacks of precursors to the ss phase the previously observed discontinuity at about 520 kilometers depth is confirmed in many regions but is found to be absent in others there are a number of regions in which we find two discontinuities at about 500 and 560 kilometers depth an effect which can be interpreted as a splitting of the 520 kilometer discontinuity these observations provide seismic constraints on the sharpness and observability of mineralogical phase transitions in the mantle transition zone

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

the importance of melt tio2 in affecting major and trace element partitioning between fe ti oxides and lunar picritic glass melts abstract lunar mare basalts and picritic glasses have tio2 abundances ranging from less than 1 wt to over 16 any high ti mare basalt or picritic glass petrogenetic model must include fe ti oxides in the mantle source or invoke fe ti oxide assimilation during magma ascent to the lunar surface we conducted partitioning experiments to investigate high field strength element hfse rare earth element ree and transition metal distribution between fe ti oxides and lunar picritic glass melts over a range of melt compositions our results suggest that ilmenite melt and armalcolite melt hfse cr and v partition coefficients dhfse dcr dv are strongly dependent on melt tio2 content whereas ilmenite melt ree partition coefficients appear to be insensitive to melt composition as tio2 increases in picritic glass melts hfse cr and v activities in melt also increase and fe ti oxide melt dhfse dcr and dv decrease the effect of ti on partitioning behavior can be attributed to the formation of fe o ti melt species in high ti melts ilmenite dhfse range from compatible in oxides in equilibrium with low ti melts to incompatible in oxides in equilibrium with depolymerized high ti picritic glass melts dhfse are inversely correlated with tio2 abundance in the melt and become nearly constant for melts with more than 6 8 tio2 we present simple partitioning models that utilize the solubility of ilmenite and armalcolite in melt to effectively predict hfse partition coefficients across a wide range of picritic glass melt compositions the hfse budget of ilmenite cumulates that crystallize from the lunar magma ocean strongly depends on the composition of the magma ocean low ti and high ti lunar basalts can be produced by an ilmenite or armalcolite bearing hybridized mantle source or by assimilation of late stage magma ocean cumulates the dependence of dhfse and dcr on melt tio2 is consistent with the formation of lunar type 1 armalcolite from high tio2 picritic glass melt however lunar type 2 and 3 armalcolite have a more complicated yet undetermined history of formation

re examination of the lunar magma ocean cumulate overturn hypothesis melting or mixing is required abstract there is a long standing hypothesis that the last fraction of the lunar magma ocean crystallized into a layer of dense ti rich cumulate minerals at shallow depths 100 km early in the moon s history many questions remain about the stability of these high ti cumulates it has been suggested that the cumulates subsequently sank deep into the moon because of gravitational instability but high ti material is required at shallower depths by 3 5 ga to create the high ti mare basalts and picritic glasses the high ti material may have re erupted from depth or some or all of it may have remained at shallow depths throughout lunar history data on phase stabilities bulk compositions densities and temperatures of melting and crystallizing in addition to results from numerical modeling suggest that the high ti cumulates would sink only under highly specific conditions five scenarios for sinking high ti cumulate materials are examined and only two are found plausible in particular it is found that simple sinking of solidified high ti cumulates is unlikely because the temperature at which the cumulates solidify is low and viscosity under these conditions is very high it is however possible that high ti cumulates mixed with a substantial fraction of olivine would have viscosity low enough to allow them to sink as solids further because clinopyroxene and ilmenite melt in a ratio of 2 1 remelted high ti cumulates would be negatively buoyant and sink as liquids percolating downward through the underlying mantle and beginning to recrystallize ilmenite at 200 km depth making a hybrid heterogeneous mantle

survival of pyropic garnet in subducting plates abstract an experimental study has been conducted to clarify the conditions and kinetic aspects of the pyroxene garnet transformation by using synthetic polycrystals two pyroxenes garnet in the cao mgo al 2 o 3 sio 2 system the run products recovered from the in situ x ray diffraction experiments in a double stage multi anvil system at 15 5 20 4 gpa and 800 1600 c were carefully analyzed by scanning electron microscopy our results show that the pyroxene garnet transformation proceeds by overgrowth of garnet absorbing the surrounding pyroxene components above 1550 c at 18 4 gpa and 1320 c pyroxenes enstatite diopside directly decomposed to the assemblages wadsleyite stishovite ca perovskite without dissolving in garnet the pyroxene garnet transformation requires much higher temperatures than those needed for transformation of olivine to wadsleyite 1000 c and of pyroxenes to their high pressure phases 1300 c in laboratory time 10 3 s and grain 10 5 m scales therefore the pyroxene garnet transformation is likely to be kinetically inhibited at low temperatures in the subducting plate and the pyropic garnet could survive in the transition zone instead of equilibrium majoritic garnet

direct detection of projectile relics from the end of the lunar basin forming epoch the lunar surface a key proxy for the early earth contains relics of asteroids and comets that have pummeled terrestrial planetary surfaces surviving fragments of projectiles in the lunar regolith provide a direct measure of the types and thus the sources of exogenous material delivered to the earth moon system in ancient 3 4 billion years ago ga regolith breccias from the apollo 16 landing site we located mineral and lithologic relics of magnesian chondrules from chondritic impactors these ancient impactor fragments are not nearly as diverse as those found in younger 3 4 ga to today regolith breccias and soils from the moon or that presently fall as meteorites to earth this suggests that primitive chondritic asteroids originating from a similar source region were common earth moon crossing impactors during the latter stages of the basin forming epoch

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

magnesium isotopic composition of the moon abstract the mg isotopic compositions of 47 well characterized lunar samples including mare basalts highland rocks regolith breccias and mare and highland soils were measured to address the behavior of mg isotopes during lunar magmatic differentiation constrain the mg isotopic composition of the moon and evaluate the degree of mg isotopic fractionation between planetary bodies the 26 mg values range from 0 61 0 03 to 0 02 0 06 in 22 mare basalts from 0 34 0 04 to 0 18 0 06 in 3 highland rocks from 0 33 0 05 to 0 14 0 08 in 7 regolith breccias from 0 23 0 05 to 0 14 0 07 in 6 highland soils and from 0 41 0 05 to 0 20 0 09 in 9 mare soils the limited mg isotopic variation among bulk mare and highland soils and regolith breccias indicates negligible mg isotope fractionation by lunar surface processes by contrast the large mg isotopic fractionation between low ti and high ti basalts suggests the source heterogeneity produced during fractional crystallization of the lunar magma ocean with ilmenite having lighter mg isotopic compositions than olivine and pyroxene overall the moon has a weighted average mg isotopic composition 26 mg 0 26 0 16 indistinguishable from the earth 26 mg 0 25 0 07 and chondrites 26 mg 0 28 0 06 suggesting homogeneous mg isotopic distribution in the solar system and the lack of mg isotope fractionation during the moon forming giant impact

high pressure phase relations and thermodynamic properties of caal4si2o11 cas phase abstract phase relations in caal4si2o11 were examined at 12 23 gpa and 1000 1800 c by multianvil experiments a three phase mixture of grossular kyanite and corundum is stable below about 13 gpa at 1000 1800 c at higher pressure and at temperature below about 1200 c a mixture of grossular stishovite and corundum is stable indicating the decomposition of kyanite above about 1200 c caal4si2o11 cas phase is stable at pressure higher than about 13 gpa the triple point is placed at 14 7 gpa and 1280 c the equilibrium boundary of formation of cas phase from the mixture of grossular kyanite and corundum has a small negative slope and that from the mixture of grossular stishovite and corundum has a strongly negative slope while the decomposition boundary of kyanite has a small positive slope enthalpies of the transitions were measured by high temperature drop solution calorimetry the enthalpy of formation of caal4si2o11 cas phase from the mixture of grossular kyanite and corundum was 139 5 15 6 kj mol and that from the mixture of grossular stishovite and corundum was 94 2 15 4 kj mol the transition boundaries calculated using the measured enthalpy data were consistent with those determined by the high pressure experiments the boundaries in this study are placed about 3 gpa higher in pressure and about 200 c lower in temperature than those by zhai and ito zhai s ito e 2008 phase relations of caal4si2o11 at high pressure and high temperature with implications for subducted continental crust into the deep mantle phys earth planet inter 167 161 167 combining the thermodynamic data measured in this study with those in the literature dissociation boundary of cas phase into a mixture of ca perovskite corundum and stishovite and that of grossular into ca perovskite plus corundum were calculated to further constrain the stability field of cas phase the result suggests that the stability of cas phase would be limited at the bottom of transition zone and top of the lower mantle when sediments are subducted into the deep mantle it is also suggested that cas phase may be stable at the depth of the upper part of the lower mantle when partial melting of basalt occurs at the depth

melting experiments on the enstatite diopside join at 70 224 kbar including the melting of diopside melting relations on the enstatite diopside en mg2si2o6 di camgsi2o6 join including the compositions of crystalline phases and melts coexisting along the solidi were experimentally determined in the pressure range 70 224 kbar with a split sphere anvil apparatus ussa 2000 melting is peritectic in enstatite rich compositions at 70 124 kbar 1840 2100 c and eutectic at higher pressures while the diopside rich clinopyroxene melts azeotropically at 70 165 kbar and up to 300 c lower temperatures than the eutectic orthopyroxene is replaced with enstatite rich clinopyroxene at 120 kbar and 2090 c first garnet with 17 mol di forms on the solidus at 158 kbar and 2100 c two garnets coexist on the solidus at 165 183 kbar and 2100 c garnet coexists with casio3 perovskite at 183 224 kbar 2100 2230 c and two coexisting perovskites are stable at higher pressures the melting curve of diopside was determined at 80 170 kbar the slope becomes negative at 140 kbar and 2155 c at 170 kbar and 2100 c diopside with 96 di breaks down to garnet with 89 di and casio3 perovskite the new data were used to calculate an improved temperature pressure phase diagram for the cmas system which can be useful for estimating the mineralogy of the earth s upper mantle

a laser ablation icp ms study of apollo 15 low titanium olivine normative and quartz normative mare basalts apollo 15 low ti mare basalts have traditionally been subdivided into olivine and quartz normative basalt types based on their different sio2 feo and tio2 whole rock compositions previous studies have reconciled this compositional diversity by considering the olivine and quartz normative basalts as originating from different lunar mantle source regions to provide new information on the compositions of apollo 15 low ti mare basalt parental magmas we report a study of major and trace element compositions of whole rocks pyroxenes and other phases in the olivine normative basalts 15016 and 15555 and quartz normative basalts 15475 and 15499 results show similar rare earth element patterns in pyroxenes from all four basalts the estimated equilibrium parental melt compositions from the trace element compositions of pyroxenes are similar for 15016 15555 and 15499 additionally an independent set of trace element distribution coefficients has been determined from measured pyroxene and mesostasis compositions in sample 15499 these data suggest that fractional crystallization may be a viable alternative to compositional differences in the mantle source to explain the 25 difference in whole rock tio2 and corresponding differences in sio2 and feo between the apollo 15 olivine and quartz normative basalts in this model

earth moon system planetary science and lessons learned the origin and evolution of the moon is now well understood many bizarre theories were proposed to account for our satellite before these were swept away by the data from the apollo missions we now understand with the benefit of hindsight that we are looking at a very ancient object whose surface has changed little for the past 3 5 b y nevertheless the moon remains a unique body in the solar system the moon formed as the result of a glancing collision with the earth of a mars sized impactor late in the accretional history of the earth when both bodies had differentiated into metallic cores and silicate mantles the impactor is derived from the neighborhood of the earth as shown by similarities in o and cr isotopes our satellite is mostly derived from the mantle of the impactor rather than from the mantle of the earth the moon melted perhaps entirely and a thick 50 km feldspathic crust dated at 4460 40 ma floated on the ocean of magma the closest analogue may be the crust of mercury the interior crystallized into cumulate zones of differing mineralogy from which the mare basalts were later derived by partial melting the impact history of the lunar surface has provided insights into planetary accretion the planetesimal hypothesis and the bombardment history in the inner solar system debate continues whether the concentration of impact produced basins constitutes a cataclysm or the tail end of accretion a notable example and a target for future missions is the 2500 km diameter south pole aitken basin that may provide insights into the nature of the deep lunar crust remaining significant problems include whether the moon has a small metallic core while the deep interior structure is not well understood new seismic and heat flow data are an urgent priority

high pressure minerals in shocked meteorites heavily shocked meteorites contain various types of high pressure polymorphs of major minerals olivine pyroxene feldspar and quartz and accessory minerals chromite and ca phosphate these high pressure minerals are micron to submicron sized and occur within and in the vicinity of shock induced melt veins and melt pockets in chondrites and lunar howardite eucrite diogenite hed and martian meteorites their occurrence suggests two types of formation mechanisms 1 solid state high pressure transformation of the host rock minerals into monomineralic polycrystalline aggregates and 2 crystallization of chondritic or monomineralic melts under high pressure based on experimentally determined phase relations their formation pressures are limited to the pressure range up to 25 gpa textural crystallographic and chemical characteristics of high pressure minerals provide clues about the impact events of meteorite parent bodies including their size and mutual collision velocities and about the mineralogy of deep planetary interiors the aim of this article is to review and summarize the findings on natural high pressure minerals in shocked meteorites that have been reported over the past 50 years

correlated δ 18 o and ti in lunar zircons a terrestrial perspective for magma temperatures and water content on the moon zircon grains were separated from lunar regolith and rocks returned from four apollo landing sites and analyzed in situ by secondary ion mass spectrometry many regolith zircons preserve magmatic 18o and trace element compositions and although out of petrologic context represent a relatively unexplored resource for study of the moon and possibly other bodies in the solar system the combination of oxygen isotope ratios and ti provides a unique geochemical signature that identifies zircons from the moon the oxygen isotope ratios of lunar zircons are remarkably constant and unexpectedly higher in 18o 5 61 0 07 vsmow than zircons from earth s oceanic crust 5 20 0 03 even though mare basalt whole rock samples are nearly the same in 18o as oceanic basalts on earth 5 6 thus the average fractionation of oxygen isotopes between primitive basalt and zircon is smaller on the moon 18o wr zrc 0 08 0 09 than on earth 0 37 0 04 the smaller fractionations on the moon suggest higher temperatures of zircon crystallization in lunar magmas and are consistent with higher ti in lunar zircons phase equilibria estimates also indicate high temperatures for lunar magmas but not specifically for evolved zircon forming melts if the solidus temperature of a given magma is a function of its water content then so is the crystallization temperature of any zircon forming in that melt the systematic nature of o and ti data for lunar zircons suggests a model based on the following observations many of the analyzed lunar zircons are likely from k rare earth elements p kreep zr rich magmas zircon does not saturate in normal mafic magmas igneous zircons in mafic rocks are typically late and formed in the last most evolved portion of melts even if initial bulk water content is moderately low the late zircon forming melt can concentrate water locally in general water lowers crystallization temperatures in which case late igneous zircon can form at significantly lower temperatures than the solidus inferred for a bulk rock composition although lunar basalts could readily lose h2 to space during eruption lowering water fugacity the morphology large size and presence in plutonic rocks suggest that many zircons crystallized at depths that retarded degassing in this case the crystallization temperatures of zircons are a sensitive monitor of the water content of the parental magma as well as the evolved zircon forming melt if the smaller 18o zircon mare basalt values reported here are characteristic of the moon then that would suggest that even highly evolved zircon forming magmas on the moon crystallized at higher temperature than similar magmas on earth and that magmas though not necessarily water free were generally drier on the moon

magmatic evolution of the moon although incomplete because of the imperfect and somewhat random sampling of rock types by the apollo and luna missions 1969 1976 the history of lunar magmatism has been reconstructed by numerous researchers over the past three decades these reconstructions have illustrated the continuous nature of lunar magmatism from 4 6 to approximately 2 0 ga and the large influence of early differentiation and catastrophic bombardment on lunar mantle dynamics magmatism and eruptive style in this review we group magmatism into multiple stages of activity based on sampled rock types and evaluate the models for each stage stage 1 is early lunar differentiation and associated magmatism partial melting of the moon soon after accretion was responsible for producing an anorthositic crust and a differentiated lunar interior the extent of lunar melting and mantle processing depends strongly on the mechanisms that induced melting estimates for the time over which melting and crystallization occurred range from tens to hundreds of millions of years stage 2 is the disruption of lunar magma ocean cumulates soon after the crystallization of most of the lunar magma ocean the cumulate pile experienced gravitational overturn this resulted in transport of late forming cumulates into the deep lunar mantle and mixing of magma ocean cumulates on a variety of scales stage 3 is the post magma ocean highland magmatism whereas the ferroan anorthositic crust was probably produced during the crystallization of a magma ocean the slightly younger mg suite and alkali suite plutonic rocks may have been generated by decompressional melting of early magma ocean cumulates during cumulate pile overturn a kreep and crustal signature was incorporated into these primitive basaltic magmas through assimilation near the base of the lunar crust or through melting of a hybridized mantle the alkali suite could represent either the differentiation products of mg suite parental magmas or a separate but contemporaneous episode of basaltic magmatism stage 4 is pre basin volcanism sample analysis and remote sensing data indicate that early lunar volcanism kreep basalts and high alumina basalts was contemporaneous with periods of highlands plutonism and catastrophic bombardment of the lunar surface the relationship between early stages of lunar volcanism and the contemporaneous plutonism is not clear the kreep basalts may be volcanic equivalents to both the mg suite and alkali suite stage 5 is the late remelting of magma ocean cumulates and eruption of mare basalts basin associated eruption of mare basalts occurred during and following the late stages of catastrophic bombardment this volcanic activity was possibly an extension of the thermal event that initiated pre basin volcanism mare basalts exhibit a wide range of composition resulting from near surface fractionation of chemically distinct primary basaltic magmas most likely mare basalts were produced by small to moderate degrees of partial melting of hybrid cumulate sources in the deep lunar mantle alternatively the mixed chemical signatures observed in many mare basalts may be interpreted as indicating assimilation of late stage evolved cumulates by melts produced deep in the cumulate pile the wide range of compositions exhibited by the mare basalts compared with earlier episodes of basaltic magmatism may reflect the thermal regime in the lunar mantle that limited the extent of partial melting and melt source homogenization

an ancient reservoir of volatiles in the moon sampled by lunar meteorite northwest africa 10989 abstract northwest africa nwa 10989 is a recently found lunar meteorite we used to elucidate the history of volatiles h and cl in the moon through analysis of its phosphates the petrology bulk geochemistry and mineralogy of nwa 10989 are consistent with it being a lunar meteorite with intermediate iron bulk composition composed of 40 of mare basaltic material and 60 non mare material but with no obvious kreep rich basaltic components it is probable that the source region for this meteorite resides near a mare highlands boundary possibly on the farside of the moon analyses of chlorine and hydrogen abundances and isotopic composition in apatite and merrillite grains from nwa 10989 indicate sampling of at least two distinct reservoirs of volatiles one being similar to those for known mare basalts from the apollo collections while the other potentially represents a yet unrecognized reservoir in situ th u pb dating of phosphates reveal two distinct age clusters with one ranging from 3 98 0 04 to 4 20 0 02 ga similar to the ages of cryptomare material and the other ranging from 3 32 0 01 to 3 96 0 03 ga closer to the ages of mare basalts known from the apollo collections this lunar breccia features mixing of material among which a basaltic d poor volatile reservoir which doesn t appear to have been recorded by apollo samples

oxygen isotope evidence for rapid mixing of the hed meteorite parent body abstract the 16 o 17 o and 18 o abundances of howardites eucrites and diogenites have been used to assign them to a single hed parent body thought to be asteroid 4 vesta we report the first evidence of oxygen isotopic heterogeneity among hed meteorites indicating incompletely mixed sources new high precision oxygen isotope measurements of 34 hed meteorites reveal that most have the same 17 o consistent with a very rapid early history of large scale mixing on vesta however howardites are on average very slightly enriched in 16 o whereas ibitira caldera pasamonte and alha78132 are 16 o depleted compared to other investigated eucrites the 17 o of ibitira is completely different from all other heds measured some of the results for eucrites and diogenites can be explained by partial melting and rapid mixing of the interior of vesta others require a separate parent body or indicate that parts of the outer layer of vesta retained some primary isotopic heterogeneity the oxygen isotopic composition of howardites provides an upper limit for the amount of admixed carbonaceous chondritic material into the hed parent body regolith

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

isotopes as tracers of the sources of the lunar material and processes of lunar origin ever since the apollo programme isotopic abundances have been used as tracers to study lunar formation in particular to study the sources of the lunar material in the past decade increasingly precise isotopic data have been reported that give strong indications that the moon and the earth9s mantle have a common heritage to reconcile these observations with the origin of the moon via the collision of two distinct planetary bodies it has been proposed i that the earth moon system underwent convective mixing into a single isotopic reservoir during the approximately 10 3 year molten disc epoch after the giant impact but before lunar accretion or ii that a high angular momentum impact injected a silicate disc into orbit sourced directly from the mantle of the proto earth and the impacting planet in the right proportions to match the isotopic observations recently it has also become recognized that liquid vapour fractionation in the energetic aftermath of the giant impact is capable of generating measurable mass dependent isotopic offsets between the silicate earth and moon rendering isotopic measurements sensitive not only to the sources of the lunar material but also to the processes accompanying lunar origin here we review the isotopic evidence that the silicate earth moon system represents a single planetary reservoir we then discuss the development of new isotopic tracers sensitive to processes in the melt vapour lunar disc and how theoretical calculations of their behaviour and sample observations can constrain scenarios of post impact evolution in the earliest history of the earth moon system

standardizing the reporting of δʹ17o data from high precision oxygen triple isotope ratio measurements of silicate rocks and minerals abstract accurate and precise 17o data are important for quantifying and understanding processes responsible for variations of oxygen triple isotope ratios in nature without universally agreed numerical values of rl and rl in the definition 17o ln 1 17o rlln 1 18o rl however as is currently the situation for measurements on rocks and minerals reported 17o data may not be directly comparable furthermore the accuracy of 17o measurements is linked to calibration at the ppm level of individual laboratory s working standard o2 relative to the vsmow water reference or to the vsmow slap scale whereas few laboratories have the facility to make high precision 17o and 18o measurements on silicates and waters both points may be addressed by defining a reference line from measurements of a pair of silicates which differ substantially in oxygen isotopic composition comparable to the difference between vsmow and slap rather than by assigning rl and rl values arbitrarily the resulting reference line has no physical significance however because 17o values reported relative to it are independent of the calibration of the working standard o2 this greatly facilitates 17o reproducibility and comparability we propose silicate standards for this purpose and report comparative measurements from two institutions of the respective 17o and 18o values relative to vsmow together with 17o data relative to various assigned reference lines we also report 17o measurements of uwg 2 garnet san carlos olivine and nbs 28 quartz relative to our reference line the proposed standards are 1 krs khitostrov rock standard 18o 25 20 which consists of sintered fine grained constituents primarily garnet of a very low 18o amphibolite grade palaeoproterozoic rock from khitostrov karelia russia 2 skfs stevns klint flint standard 18o 33 93 consisting of thermally dehydrated grains of a high 18o nodule of flint sampled from just below the exposed cretaceous palaeogene boundary at stevns klint southeast zealand island denmark both silicates fluorinate readily using standard laser assisted procedures and the associated low blanks allow for overnight pre treatment small quantities of these materials may be supplied on request for standardizing 17o measurements of silicate rocks and minerals according to the proposed procedure

geochemistry and oxygen isotope composition of main group pallasites and olivine rich clasts in mesosiderites implications for the great dunite shortage and hed mesosiderite connection evidence from iron meteorites indicates that a large number of differentiated planetesimals formed early in solar system history these bodies should have had welldeveloped olivine rich mantles and consequentially such materials ought to be abundant both as asteroids and meteorites which they are not to investigate this great dunite shortage we have undertaken a geochemical and oxygen isotope study of main group pallasites and dunitic rocks from mesosiderites oxygen isotope analysis of 24 main group pallasites 103 replicates yielded a mean 17o value of 0 187 0 016 2 which is fully resolved from the hed 17o value of 0 246 0 014 2 obtained in our earlier study and demonstrates that both groups represent distinct populations and were derived from separate parent bodies our results show no evidence for 17o bimodality within the main group pallasites as suggested by a number of previous studies olivine rich materials from the vaca muerta mount padbury and lamont mesosiderites and from two related dunites nwa 2968 and nwa 3329 have 17o values within error of the mesosiderite average this indicates that these olivine rich materials are co genetic with other mesosiderite clasts and are not fragments from an isotopically distinct pallasite like impactor despite its extreme lithologic diversity the mesosiderite parent body was essentially homogeneous with respect to 17o a feature best explained by an early phase of large scale melting magma ocean followed by prolonged igneous differentiation based on the results of magma ocean modeling studies we infer that mg rich olivines in mesosiderites formed as cumulates in high level chambers and do not represent samples of the underlying mantle by analogy recently documented mg rich olivines in howardites may have a similar origin although the dawn mission did not detect mesosiderite like material on vesta evidence linking the mesosiderites and heds includes i their nearly identical oxygen isotope compositions ii the presence in both of coarse grained mg rich olivines iii both have synchronous lu hf and mn cr ages iv there are compositional similarities between the metal in both and v mesosiderite like material has been identified in a howardite breccia the source of the mesosiderites remains an outstanding question in meteorite science the underrepresentation of olivine rich materials amongst both asteroids and meteorites results from a range of factors however evidence from pallasites and mesosiderites indicates that the most important reason for this olivine shortage lies in the early catastrophic destruction of planetesimals in the terrestrial planet forming region and the subsequent preferential loss of their olivine rich mantles

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

elasticity of diopside to 8 gpa and 1073 k and implications for the upper mantle abstract simultaneous measurements of elastic wave velocities and density have been conducted on diopside by a combined ultrasonic interferometry and x ray diffraction methods at pressure and temperature conditions relevant to the earth s upper mantle the current study not only yielded the first direct measurement of the shear modulus at high pressures but also enabled a simultaneous determination of the bulk and shear properties and their pressure and temperature derivatives from the measured density and velocities finite strain analysis of the experimental data results in ks0 116 4 7 gpa k s 0 4 9 1 ks t p 0 012 1 gpa gpa g 0 1 6 1 and g t p 0 011 1 gpa k with these results and the same finite strain equations the p and s wave velocities of diopsidic mantle clinopyroxene were calculated along a 1600 k adiabatic geotherm in comparison with other mantle minerals the seismic velocities of diopsidic clinopyroxene at upper mantle depths are 1 3 higher than those of orthopyroxene 1 2 and 6 8 lower than those of olivine and majoritic garnet respectively

the titanium contents of lunar mare basalts lunar mare basalt sample data suggest that there is a bimodal distribution of tio2 concentrations using a refined technique for remote determination of tio2 we find that the maria actually vary continuously from low to high values the reason for the discrepancy is that the nine lunar sample return missions were not situated near intermediate basalt regions moreover maria with 2 4 wt tio2 are most abundant and abundance decreases with increasing tio2 maria surfaces with tio2 5 wt constitute only 20 of the maria although impact mixing of basalts with differing ti concentrations may smear out the distribution and decrease the abundance of high ti basalts the distribution of basalt ti contents probably reflects both the relative abundances of ilmenite free and ilmenite bearing mantle sources this distribution is consistent with models of the formation of mare source regions as cumulates from the lunar magma ocean

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

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

constraining the composition and thermal state of the mantle beneath europe from inversion of long period electromagnetic sounding data 1 we reexamine the problem of inverting c responses covering periods between 1 month and 1 year collected from 42 european observatories to constrain the internal structure of the earth earlier studies used the c responses which connect the magnetic vertical component and the horizontal gradient of the horizontal components of electromagnetic variations to obtain the conductivity profile of the earth s mantle here we go beyond this approach by inverting directly for chemical composition and thermal state of the earth rather than subsurface electrical conductivity structure the primary inversion parameters are the composition of the earth s mantle within the system cao feo mgo al2o3 sio2 and geotherm given these parameters we calculate mineral modes at the prevailing physical conditions and combine these with laboratory based models for the conductivity of individual minerals to estimate the bulk earth electrical conductivity structure from which c responses are calculated to further constrain the radial density profile we also invert for mass and moment of inertia the results agree with earlier geophysically derived conductivity and seismic velocity models and confirm that inversion of geophysical data for compositional parameters planetary composition and thermal state is feasible the inversion indicates most probable lower mantle geothermal gradients of 0 58 k km core mantle boundary temperatures of 2900 c bulk earth molar mg si ratios of 1 1 intermediate between the chondrite and pyrolite models and no significant change in mantle composition across the 670 km seismic discontinuity

shock induced deformation of shergottites shock pressures and perturbations of magmatic ages on mars shergottites and chassignites practiced major deformation effects whose nature magnitude and relevance were controversially evaluated and disputatively debated our studies of many shocked shergottites present contrary to numerous previous reports ample evidence for pervasive shock induced melting amounting of at least 23 vol of the shergottite consisting of maskelynite and pyrrhotite partial melting of pyroxene titanomagnetite ilmenite and finding of several high pressure polymorphs and pressure induced dissociation reactions our results cast considerable doubt on using the refractive index ri or cathodoluminescence cl spectra of maskelynite in estimating the magnitudes of peak shock pressure in both shergottites and ordinary chondrites ri of maskelynite was set after quenching of the feldspar liquid before decompression to maskelynite glass followed by glass relaxation after decompression at the closure temperature of relaxation the ri procedure widely practiced in the past 38 years revealed unrealistic very high pressure estimates discrepant with the high pressure mineral inventory in shocked shergottites and ordinary chondrites and with results obtained by robust laboratory static experiments shergottites contain the silica high pressure polymorphs the scrutinyite structured polymorph seifertite a monoclinic ultra dense polymorph of silica with zro2 structure stishovite a dense liquidus assemblage consisting of stishovite na hexa aluminosilicate na cas and both k lingunite and ca lingunite applying individual high pressure silica polymorphs alone like stishovite to estimate the equilibrium shock pressure is inadequate due to the considerable shift of their nominal upper pressure bounds intrinsically induced by spatially variable absorptions of minor oxides like al2o3 na2o feo mgo and tio2 this practice revealed variable pressure estimates even within the same shergottite subjected to the same peak shock pressure occurrence of na cas stishovite lack of the naalsio4 ca ferrite structured polymorph or jadeite indicates that the peak shock pressures barely exceeded 22 gpa we present convincing and ample evidence refuting the claim that the shock induced high pressure inventory in shergottites and ordinary chondrites are disequilibrium assemblages resulted from local pressure spikes in excess of 80 gpa and during the decompression stage such scenario calls for a series of incomplete and quenched retrograde reactions starting with the crystallization of mg silicate perovskite magnesiowustite if the claimed peak shock pressure was in excess of 80 gpa this would be followed by replacement of this pair by majorite pyrope ss magnesiowustite or akimotoite magnesiowustite below 23 gpa and 2000 degrees c polycrystalline ringwoodite above 16 gpa respectively and finally replacement by polycrystalline olivine below 16 gpa such incomplete retrograde reactions were never encountered in any shergottite chassignite or shocked ordinary chondrite so far olivine ringwoodite phase transformation in the l6 y 791384 commences with the coherent mechanism producing ringwoodite lamellae with their 111 planes parallel to the 100 of olivine followed by the incoherent mechanism due to build up of strain in the parental olivine this is in accord with the olivine ringwoodite settings produced in static laboratory experiments in a multi anvil device olivine ringwoodite phase transitions were also encountered in comparable settings in the shergottite nwa 1068 application of experimentally obtained kinetic parameters of the olivine ringwoodite phase transitions reveals possible duration of the natural dynamic events up to few seconds thus unambiguously refuting the claimed disequilibrium decompression mechanism the shock induced pervasive melting of labradorite pyrrhotite titanomagnetite ilmenite and partial melting of clinopyroxene strongly suggests shock induced partial to complete resetting of the ar ar rb sr sm nd re os u pb and lu hf radiometric systems this also casts considerable doubt on the radiometric ages shorter than 575 ma reported in the past 38 years to allegedly be the igneous crystallization ages these short ages probably resulted from partial or total shock induced age resetting c 2012 elsevier ltd all rights reserved

high pbehavior of anorthite composition and some phase relations of the cao al2o3 sio2 system to the lower mantle of the earth and their geophysical implications 1 multianvil experiments with long experimental durations have been made with the anorthite composition caal2si2o8at pressure temperature p t conditions of 14 25 gpa and 1400 2400 c at subsolidus conditions these experiments demonstrated three phase assemblages grossular gr kyanite ky stishovite st at 14 gpa gr calcium alumino silicate phase cas st at 18 gpa and cas casio3 perovskite capv st at above 20 gpa which are related by the reactions gr ky cas st and gr st cas capv following the method of schreinemakers we combined our data with the literature data to deduce ap tphase diagram for a portion of the cao al2o3 sio2system at subsolidus conditions which subsequently helped to solve some long lasting discrepancies in the high pbehavior of the compositions of anorthite and grossular the crystal chemistry of the cas and capv solid solutions was examined and new substitution mechanisms were firmly established along the solidus the melting reaction at 14 gpa is peritectic while that at 22 gpa is eutectic for both pressures st is the first phase to melt out and the melt is generally andesitic for the an composition its density starts to be significantly higher than the density of pyrolite at 2 5 gpa a much lower pressure than that for the or ab or qtz composition 7 5 10 gpa so that the an enriched continental crust material should readily plunge into the upper mantle

pre 4 2 ae mare basalt volcanism in the lunar highlands abstract the concept that the plutonism of the lunar highlands and the mare type volcanism are two separate problems in both time 4 4 ae versus apollo 14 breccia 14305 contains a clast 122 which is an olivine gabbronorite that is texturally and mineralogically similar to several apollo 12 basalts e g 12005 12035 12040 it consists of cumulus olivine 40 modal fo 62 70 and ti chromite 2 5 modal post cumulus phases include low ca pyroxene 29 modal wo 7 13 en 68 75 augite 10 modal wo 31 40 en 47 50 plagioclase 15 modal an 82 93 and ilmenite 4 modal 5 7 mgo the tio2 content of this rock 4 3 cao al2o3 1 0 cao 5 1 mgo feo 1 0 mgo 21 9 the ree pattern normalized to chondritic abundances is approximately 30 ch and hump shaped with a pronounced eu depletion and a non kreepy signature a four point rb sr isochron reveals an age of 4 23 0 05 ae the sample has a low initial 87sr 86sr 0 69911 3 the data presented here show that non kreepy mare type volcanism commenced at least as early as 4 2 ae in the fra mauro region and probably across much of the lunar surface massive bombardment during the terminal cataclysm and the subsequent veneer of younger mare basalts has obliturated most of the evidence for these ancient volcanic events these old mare type volcanics may be related to basin forming events such as made procellarum i e impact triggered igneous activity

ballistic ejecta from the 1988 1989 andesitic vulcanian eruptions of tokachidake volcano japan morphological features and genesis abstract during the 1988 1989 activity of the andesitic stratovolcano tokachidake several eruptions were of the vulcanian type and ejected morphologically diverse ballistic ejecta these ejecta are firstly classified into two groups 1 those derived from juvenile material and 2 those derived from accessory material secondly the ejecta derived from juvenile material are divided into three types according to the morphological features which dominate such as jointing viscosity and vesicularity accordingly these ejecta are termed jointed blocks plastic bombs and vesiculated bombs the ejecta derived from accessory material are termed vent breccia blocks it is proposed that the morphological differences between these ejecta reflect both the nature of the magma and the processes occurring in the vent prior to vulcanian eruption and following eruption until shortly after landing a comparison with other vulcanian eruptions indicates the eruption energy of tokachidake volcano was relatively small

density profiles of oceanic slabs and surrounding mantle integrated thermodynamic and thermal modeling and implications for the fate of slabs at the 660 km discontinuity abstract we have calculated the mineralogical properties of the earth s mantle and the lithological units constituting the subducting oceanic slabs within a wide range of p t conditions within the cao feo mgo al2o3 sio2 system except for the basalt top layer of a slab for which the system is extended to include na2o the mineralogical data are then converted using the appropriate p v t relations to bulk densities the calculated adiabatic density vs depth profile of the mantle between 200 and 725 km depths is in good agreement with geophysical and experimental data the density data of the different compositional units are combined with calculated thermal structures for a variety of slab mantle systems to construct equilibrium density profiles as a function of depth the mean equilibrium densities of the slabs within the transition zone 400 660 km depth are found to be 0 04 0 05 g cm3 greater than those of the ambient mantle within the same depth interval for the entire upper mantle density differences between slabs and ambient mantle are slightly less but the slabs still remain denser than the latter at 670 km depth slabs have lower density than the ambient lower mantle because of the commencement of perovskite forming reactions within the mantle and displacements of these reaction boundaries to higher pressures within the slabs as a consequence of their negative p t slopes if perovskite forming reactions within slabs are hindered for kinetic sluggishness then neutral buoyancy would be achieved when the slabs have penetrated 100 km into the lower mantle however using the available data on the kinetics of spinel to perovskite plus periclase reaction we conclude that the reaction would go to completion in a peru type young slab 41 myr and very likely also in a tonga type old slab 110 myr before these penetrated 100 km into the lower mantle thus slabs should always remain negatively buoyant and therefore continue to subduct through the lower mantle once it penetrates through the 660 km discontinuity despite a negative buoyancy force a slab could deflect at the top of the lower mantle 660 km because of factors resisting subduction namely viscosity jump low dip angle slab roll back and metastable persistence of olivine in cold slabs if published scale model experiments represent realistic approximations of the factors affecting plate subduction then according to our density data any slab with a dip angle of 40 50 would bend at the 660 km discontinuity if there is a viscosity jump of at least by a factor of 10 and trench migration the basalt top layer of a slab is denser than other slab components and the ambient mantle at all depths to 660 km and therefore should continue to sink into the lower mantle especially if a slab directly penetrates the 660 km barrier instead of peeling off in the transition zone to form a perched eclogite or piclogite layer as previously proposed the harzburgite layer which is sandwiched between denser basalt and lherzolite layers faces greater resistance to subduction especially in a young slab and thus could significantly contribute to the deformation of a slab near the 660 km discontinuity

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

oxygen isotope and petrological study of silicate inclusions in iie iron meteorites and their relationship with h chondrites abstract the origin of silicate bearing irons especially those in groups iab iiicd and iie is poorly understood as silicate should have separated rapidly from molten metal here we report the results of high precision oxygen isotope analysis of silicate inclusions in eleven group iie meteorites and a petrological study of silicate inclusions in ten iie irons including those in garhi yasin and tarahumara which have not been described in detail before oxygen isotopes have also been analysed in 20 h chondrites to investigate their possible relationship with the iie irons based on petrographic observations and mineral analysis the silicate bearing iie meteorites have been divided into four types according to the nature of their silicate inclusions 1 primitive chondritic 2 evolved chondritic 3 differentiated with 10 vol orthopyroxene and 4 differentiated with 17 o variation a wide range of values is seen in the dataset as a whole group iie irons with differentiated silicates with the exception of colomera have a range of mean 17 o values that is essentially identical to those of the h4 6 chondrites 0 60 0 77 and 0 61 0 76 respectively colomera inclusions which are differentiated with 17 o value and plot 2 away from the next nearest iie iron however in view of the textural similarities to other iie inclusions a separate source for colomera is deemed unlikely three iie irons with primitive chondritic inclusions garhi yasin netschaevo and techado have relatively low mean 17 o values of 0 56 0 57 as well as relatively reduced silicates with fa 15 17 olivine which have been called hh chondrites given the significant overlap in their oxygen isotope compositions a genetic relationship between iie irons and h chondrites is supported by our new data however derivation of both groups from one parent body seems unlikely instead both groups probably sampled similar precursor materials and accreted at a similar nebular location our data suggest that the iie meteorites formed on an internally heated h hh chondrite like body that experienced the initial stages of differentiation in response to radiogenic heating however prior to full differentiation the iie parent body experienced a major hit and run style collision that resulted in silicate metal mixing the initial stages of this event involved a phase of rapid cooling that prevented unmixing of metal and silicates reassembly of the iie parent body produced a large regolith blanket that facilitated subsequent slow cooling the iie parent body has probably experienced numerous subsequent less catastrophic collisions the development of alkali glass textures in some differentiated inclusions is probably the result of one of these later events

phase relations on the diopside jadeite hedenbergite join up to 24 gpa and stability of na bearing majoritic garnet abstract phase relations on the diopside di hedenbergite hd jadeite jd system modeling mineral associations of natural eclogites were studied for the compositions mol di70jd30 di50jd50 di30jd70 di20hd80 and di40hd10jd50 using a toroidal anvil with hole 7 gpa and a kawai type 6 8 multianvil apparatus 12 24 gpa we established that di hd and jd form complete series of solid solutions at 7 gpa and melting temperatures of pure di 1980 c and jd 1870 c for that pressure were estimated experimentally the melting temperature for the di50jd50 composition at 15 5 gpa is 2270 c the appearance of garnet is clearly dependent on initial clinopyroxene composition at 1600 c the first garnet crystals are observed at 13 5 gpa in the jadeite rich part of the system di30jd70 whereas diopside rich starting material di70jd30 produces garnet only above 17 gpa the proportion of garnet increases rapidly above 18 gpa as pyroxene dissolves in the garnet structure and pyroxene free garnetites are produced from diopside rich starting materials in all experiments garnet coexists with stishovite st at a pressure above 18 gpa pyroxene is completely replaced by an assemblage of majorite maj st casio3 perovskite ca pv in ca rich systems whereas maj is associated with almost pure jd up to a pressure of 21 5 gpa above 22 gpa maj and st are associated with naalsio4 with calcium ferrite structure cf we established that an hd component also spreads the range of pyroxene stability up to 20 gpa in the di70jd30 system at 24 gpa an assemblage of maj ca pv mgsio3 with ilmenite structure mg il was obtained the experimentally established correlation between na si and al contents in maj and pressure in grt maj pyroxene assemblages may be the basis for a majorite geobarometer the results of our experiments are applicable to the upper mantle and the transition zone of the earth 400 670 km and demonstrate a wide range of transformations from eclogite to perovskite bearing garnetite in addition the mineral associations obtained from the experiments allowed us to simulate parageneses of inclusions in diamonds formed under the conditions of the transition zone and the lower mantle

oxygen and iron isotope constraints on near surface fractionation effects and the composition of lunar mare basalt source regions oxygen and iron isotope analyses of low ti and high ti mare basalts are presented to constrain their petrogenesis and to assess stable isotope variations within lunar mantle sources an internally consistent dataset of oxygen isotope compositions of mare basalts encompasses five types of low ti basalts from the apollo 12 and 15 missions and eight types of high ti basalts from the apollo 11 and 17 missions high precision whole rock d 18 o values referenced to vsmow of low ti and high ti basalts correlate with major element compositions mg tio2 a l 2o3 the observed oxygen isotope variations within low ti and high ti basalts are consistent with crystal fractionation and match the results of mass balance models assuming equilibrium crystallization whole rock d 56 fe values referenced to irmm 014 of high ti and low ti basalts range from 0 134 to 0 217 and 0 038 to 0 104 respectively iron isotope compositions of both low ti and high ti basalts do not correlate with indices of crystal fractionation possibly owing to small mineral melt iron fractionation factors anticipated under lunar reducing conditions the d 18 o and d 56 fe values of low ti and the least differentiated high ti mare basalts are negatively correlated which reflects their different mantle source characteristics e g the presence or absence of ilmenite the average d 56 fe values of low ti basalts 0 073 0 018 n 8 and high ti basalts 0 191 0 020 n 7 may directly record that of their parent mantle sources oxygen isotope compositions of mantle sources of low ti and high ti basalts are calculated using existing models of lunar magma ocean crystallization and mixing the estimated equilibrium mantle olivine d 18 o value and equilibrium oxygen fractionation between olivine and other mineral phases the differences between the calculated whole rock d 18 o values for source regions 5 57 for low ti and 5 30 for high ti mare basalt mantle source regions are solely a function of the assumed source mineralogy the oxygen and iron isotope compositions of lunar upper mantle can be approximated using these mantle source values the d 18 o and d 56 fe values of the lunar upper mantle are estimated to be 5 5 0 2 2r and 0 085 0 040 2r respectively the oxygen isotope composition of lunar upper mantle is identical to the current estimate of earth s upper mantle 5 5 0 2 and the iron isotope composition of the lunar upper mantle overlaps within uncertainty of estimates for the terrestrial upper mantle 0 044 0 030

oxygen isotope constraints on the origin and differentiation of the moon we report new high precision laser fluorination three isotope oxygen data for lunar materials terrestrial silicates with a range of 18 o values 0 5 to 22 9 were analyzed to independently determine the slope of the terrestrial fractionation line tfl 0 5259 0 0008 95 confidence level this new tfl determination allows direct comparison of lunar oxygen isotope systematics with those of earth values of 17 o for apollo 12 15 and 17 basalts and luna 24 soil samples average 0 01 and are indistinguishable from the tfl the 18 o values of high and low ti lunar basalts are distinct average whole rock 18 o values for low ti lunar basalts from the apollo 12 5 72 0 06 and apollo 15 landing sites 5 65 0 12 are identical within error and are markedly higher than apollo 17 high ti basalts 5 46 0 11 evolved low ti lapaz mare basalt meteorite 18 o values 5 67 0 05 are in close agreement with more primitive low ti apollo 12 and 15 mare basalts modeling of lunar mare basalt source composition indicates that the high and low ti mare basalt mantle reservoirs were in oxygen isotope equilibrium and that variations in 18 o do not result from fractional crystallization instead these differences are consistent with mineralogically heterogeneous mantle sources for mare basalts and with lunar magma ocean differentiation models that result in a thick feldspathic crust an olivine pyroxene rich mantle and late stage ilmenite rich zones that were convectively mixed into deeper portions of the lunar mantle higher average 18 o wr values of low ti basalts compared to terrestrial mid ocean ridge basalts 0 18 suggest a possible oxygen isotopic difference between the terrestrial and lunar mantles however calculations of the 18 o of lunar mantle olivine in this study are only 0 05 higher than terrestrial mantle olivine these observations may have important implications for understanding the formation of the earth moon system 2006 elsevier b v all rights reserved

a dynamic origin for the global asymmetry of lunar mare basalts we propose that the hemispheric asymmetry fig 1 of mare basalts may be explained as a result of hydrodynamic instabilities associated with a layer of mixed ilmenite rich cumulates ic and olivine orthopyroxene opx overlying a metallic core this mixed layer mic should form shortly after the solidification of the magma ocean p c hess and e m parmentier earth planet sci lett 134 1995 501 514 because of gravitational differentiation of chemically dense ic material that is expected to form below the anorthositic crust in the final stages of magma ocean crystallization a e ringwood and s e kesson proc lunar planet sci conf 7 1976 1697 1722 ic material is rich in heat producing elements and thermal expansion due to radiogenic heating causes the mic layer to become less dense than overlying mantle the time required for the mic layer to become thermally buoyant may explain a delay of mare volcanism until about 500 ma after solidification of the magma ocean our analyses of the resulting rayleigh taylor instability and numerical modeling of thermo chemical convection show that the instabilities produce spherical harmonic degree 1 thermal and compositional structure if a lunar metallic core is sufficiently small less than 250 km in radius fl 2000 elsevier science b v all rights reserved

stability of clinopyroxene at pressure temperature conditions of the transition region abstract the stability of diopside at conditions of 16 19 gpa and 1250 1900 c was determined using a 6 8 type multi anvil apparatus at pressures of 17 18 gpa diopside undergoes a decomposition reaction to an assemblage of casio3 perovskite ca mg sio3 garnet or ilmenite depending on temperature the clapeyron slope for the breakdown reaction download download full size image is 2 mpa k 1 when coupled with a re examination of clinopyroxene stability in other more complex peridotite systems the experimental data are consistent with a recent proposal that the 520 km discontinuity in the transition region is caused by the exsolution of casio3 rich perovskite from garnet rich in majorite component

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

high pressure and high temperature phase relations in diopside camgsi2o6 abstract phase transformations in diopside ca 0 92 mg 1 08 si 2 o 6 were studied by quench experiments at pressures of 18 24 gpa and temperatures of 1000 2400 k using an ma8 type multi anvil apparatus at moderate temperatures diopside decomposed into the assemblage of two components one with mgsio 3 stoichiometry and the other with casio 3 stoichiometry the mgsio 3 component crystallized into mg 2 sio 4 stishovite then transformed into mg 2 sio 4 stishovite mgsio 3 ilmenite and mgsio 3 perovskite with increasing pressure the casio 3 component was observed always as a glass in the recovered samples it is likely that casio 3 formed the cubic perovskite type structure under pressure at higher temperature diopside transformed into mg ca sio 3 garnet and casio 3 perovskite and then to mgsio 3 and casio 3 perovskites the solubility of ca into mg ca sio 3 garnet decreases with increasing pressure the stability field of ca bearing garnet is expanded to lower temperature range compared to that of pure mgsio 3 garnet the present results clarify the phase relations of diopside to the uppermost part of the lower mantle

the application of a calibrated 3d ballistic trajectory model to ballistic hazard assessments at upper te maari tongariro abstract on 6 august 2012 upper te maari crater tongariro volcano new zealand erupted for the first time in over one hundred years multiple vents were activated during the hydrothermal eruption ejecting blocks up to 2 3 km and impacting 2 6 km of the tongariro alpine crossing tac hiking track ballistic impact craters were mapped to calibrate a 3d ballistic trajectory model for the eruption this was further used to inform future ballistic hazard orthophoto mapping revealed 3587 impact craters with a mean diameter of 2 4 m however field mapping of accessible regions indicated an average of at least four times more observable impact craters and a smaller mean crater diameter of 1 2 m by combining the orthophoto and ground truthed impact frequency and size distribution data we estimate that approximately 13 200 ballistic projectiles were generated during the eruption the 3d ballistic trajectory model and a series of inverse models were used to constrain the eruption directions angles and velocities when combined with eruption observations and geophysical observations the model indicates that the blocks were ejected in five variously directed eruption pulses in total lasting 19 s the model successfully reproduced the mapped impact distribution using a mean initial particle velocity of 200 m s with an accompanying average gas flow velocity over a 400 m radius of 150 m s we apply the calibrated model to assess ballistic hazard from the august eruption along the tac by taking the field mapped spatial density of impacts and an assumption that an average ballistic impact will cause serious injury or death casualty over an 8 m 2 area we estimate that the probability of casualty ranges from 1 to 16 along the affected track assuming an eruption during the time of exposure future ballistic hazard and probabilities of casualty along the tac are also assessed through application of the calibrated model we model a magnitude larger eruption and illustrate that the probability of casualty could reach 100 in localised areas of the track in contrast ballistics ejected from a smaller eruption did not reach the track as was the case with the 21 november 2012 eruption the calibrated ballistic model can therefore be used to improve management of ballistic hazards both at tongariro and also once recalibrated to other volcanoes worldwide

mantle transition zone structure along a profile in the sw pacific thermal and compositional variations summary events from the south pacific recorded in the tien shan region are studied with a migration method to measure discontinuity depth along a profile between the mariana and molucca sea subduction zones deflections of the upper mantle discontinuities within and between the subduction zones are investigated using pp precursors filtered to periods of 3 to 10 s we find p wave reflections near the 410 520 and 660 km discontinuities the 410 km discontinuity is elevated in the subduction region and near the predicted depth 410 km in the average velocity region in some cases we find negative polarities of the reflection from the 410 km discontinuity which may indicate water induced melting above the olivine to wadsleyite transition the 520 km discontinuity is shallow between the two subduction zones and deepens towards the mariana backarc region this discontinuity topography may be due to detection of both the wadsleyite to ringwoodite transition in a depleted downwelling elevated region and the formation of calcium perovskite in a more fertile upwelling depressed region the 660 km discontinuity is split in the halmahera slab with one reflection each near 600 and 700 km depth consistent with a cold sinking slab and detection of phase transitions for both garnet and olivine to perovskite respectively in the region between the subduction areas we find a downward deflection of the 660 km discontinuity with short length scale 100 300 km undulations that may reflect compositional variation

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

an analysis of apollo lunar soil samples 12070 889 12030 187 and 12070 891 basaltic diversity at the apollo 12 landing site and implications for classification of small sized lunar samples lunar mare basalts provide insights into the compositional diversity of the moon s interior basalt fragments from the lunar regolith can potentially sample lava flows from regions of the moon not previously visited thus increasing our understanding of lunar geological evolution as part of a study of basaltic diversity at the apollo 12 landing site detailed petrological and geochemical data are provided here for 13 basaltic chips in addition to bulk chemistry we have analyzed the major minor and trace element chemistry of mineral phases which highlight differences between basalt groups where samples contain olivine the equilibrium parent melt magnesium number mg atomic mg mg fe can be calculated to estimate parent melt composition ilmenite and plagioclase chemistry can also determine differences between basalt groups we conclude that samples of approximately 1 2 mm in size can be categorized provided that appropriate mineral phases olivine plagioclase and ilmenite are present where samples are fine grained grain size 0 3 mm a paired samples t test can provide a statistical comparison between a particular sample and known lunar basalts of the fragments analyzed here three are found to belong to each of the previously identified olivine and ilmenite basalt suites four to the pigeonite basalt suite one is an olivine cumulate and two could not be categorized because of their coarse grain sizes and lack of appropriate mineral phases our approach introduces methods that can be used to investigate small sample sizes i e fines from future sample return missions to investigate lava flow diversity and petrological significance

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

comparative petrology geochemistry and petrogenesis of evolved low ti lunar mare basalt meteorites from the lapaz icefield antarctica new data is presented for five evolved low ti lunar mare basalt meteorites from the lapaz icefield antarctica lap 02205 lap 02224 lap 02226 lap 02436 and lap 03632 these basalts have nearly identical mineralogies textures and geochemical compositions and are therefore considered to be paired the lapaz basalts contain olivine fo64 2 and pyroxene fs32wo8en60 to fs84 86 wo15en2 0 crystals that record extreme chemical fractionation to fe enrichment at the rims and evidence for silicate liquid immiscibility and incompatible element enrichment in the mesostasis the basalts also contain feni metals with unusually high co and ni contents similar to some apollo 12 basalts and a single phase network of melt veins and fusion crusts the fusion crust has similar chemical characteristics to the whole rock for the lapaz basalts whereas the melt veins represent localized melting of the basalt and have an endogenous origin the crystallization conditions and evolved nature of the lapaz basalts are consistent with fractionation of olivine and chromite from a parental liquid similar in composition to some olivine phyric apollo 12 and apollo 15 basalts or lunar low ti pyroclastic glasses however the young reported ages for the lapaz mare basalts 2 9 ga and their relative incompatible element enrichment compared to apollo mare basalts and pyroclastic glasses indicate they cannot be directly related instead the lapaz mare basalts may represent fractionated melts from a magmatic system fed by similar degrees of partial melting of a mantle source similar to that of the low ti apollo mare basalts or pyroclastic glasses but which possessed greater incompatible element enrichment despite textural differences the lapaz basalts and mare basalt meteorite nwa 032 have similar ages and compositions and may originate from the same magmatic system on the moon

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

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

thermal and magmatic evolution of the moon as with all science our continually developing concepts of lunar evolution are firmly tied to both new types of observations and the integration of these observations to the known pool of data this process invigorates the intellectual foundation on which old models are tested and new concepts are built just as the application of new observational tools to lunar science in 1610 galileo s telescope and 1840 photography yielded breakthroughs concerning the true nature of the lunar surface the computational and technological advances highlighted by the apollo and post apollo missions and associated scientific investigations provided a new view of the thermal and magmatic evolution of the moon 1 1 pre apollo view of the thermal and magmatic evolution of the moon many of the early views of the moon manifested in mythology and art throughout the world were primarily tied to lunar and terrestrial cycles and the relationships between the sun and the moon prophetically myths involving the lunar deities mwuetsi from zimbabwe and coyolxauhqui from mexico told of rather violent or catastrophic events in which the moon was expunged from the earth numerous ancient scientific observations were made about the nature of the moon ranging from those uncovered in early neolithic sites that correctly identified mare crisium and mare humorum to the insights made by greek philosophers such as anaxagoras ca 500 428 b c and democritus ca 460 370 b c who attached terrestrial analogues to its character stone mountains with the advent of the telescope 1610 and photography 1840 as scientific tools for lunar exploration semiquantitative data could be collected that would provide an intellectual foundation for scientific interpretation initially modern terrestrial geological analogs were extended to the moon lunar highlands volcanic craters seas combined with the rigors of computational modeling these observational data were extended to predict the original thermal state of the moon and its thermal and magmatic history its proximity to the earth

high pressure transitions of diopside and wollastonite phase equilibria and thermochemistry of camgsi2o6 casio3 and casi2o5 catisio5 system abstract phase transitions of camgsi2o6 diopside and casio3 wollastonite were examined at pressures to 23 gpa and temperatures to 2000 c using a kawai type multiavil apparatus enthalpies of high pressure phases in casio3 and in the casi2o5 catisio5 system were also measured by high temperature calorimetry at 17 18 gpa diopside dissociates to casio3 rich perovskite mg rich mg ca sio3 tetragonal garnet gt above about 1400 c the solubilities of casio3 in garnet and mgsio3 in perovskite increase with temperature at 17 18 gpa below about 1400 c diopside dissociates to ca perovskite mg2sio4 stishovite the mg si phases coexisting with ca perovskite change to mg2sio4 stishovite to ilmenite and finally to mg perovskite with increasing pressure casio3 wollastonite transforms to the walstromite structure and further dissociates to ca2sio4 larnite casi2o5 titanite the latter transition occurs at 9 11 gpa with a positive clapeyron slope at 1600 c larnite titanite transform to casio3 perovskite at 14 6 0 6 gpa calibrated against the transition pressure of mg2sio4 the enthalpies of formation of casio3 walstromite and casi2o5 titanite from the mixture of cao and sio2 quartz at 298 k have been determined as 76 1 2 8 and 27 8 2 1 kj mol respectively the latter was estimated from enthalpy measurements of titanite solid solutions in the system casi2o5 catisio5 because casi2o5 titanite transforms to a triclinic phase upon decompression the enthalpy difference between titanite and the triclinic phase is only 1 5 4 8 kj mol using these enthalpies of formation and those of larnite and casio3 perovskite the transition boundaries in casio3 have been calculated the calculated boundaries for the wollastonite walstromite larnite titanite transitions are consistent with the experimental determinations within the errors the calculated boundary between larnite titanite and ca perovskite has a slope of 1 3 1 8 0 4 mpa k and is located at a pressure about 2 gpa higher than that determined by am mineral 79 1994 1219

calcium 48 isotopic anomalies in bulk chondrites and achondrites evidence for a uniform isotopic reservoir in the inner protoplanetary disk thermal ionization mass spectrometry tims was used to measure the calcium isotopic compositions of carbonaceous ordinary enstatite chondrites as well as eucrites and aubrites we find that after correction for mass fractionation by internal normalization to a fixed 42 ca 44 ca ratio the 43 ca 44 ca and 46 ca 44 ca ratios are indistinguishable from terrestrial ratios in contrast the 48 ca 44 ca ratios show significant departure from the terrestrial composition from 2 e in eucrites to 4 e in co and cv chondrites isotopic anomalies in e 48 ca correlate with e 50 ti e 48 ca 1 09 0 11 e 50 ti 0 03 0 14 further work is needed to identify the carrier phase of 48 ca 50 ti anomalies but we suggest that it could be perovskite and that the stellar site where these anomalies were created was also responsible for the nucleosynthesis of the bulk of the solar system inventory of these nuclides the earth has identical 48 ca isotopic composition to enstatite chondrites eh and el and aubrites this adds to a long list of elements that display nucleosynthetic anomalies at a bulk planetary scale but show identical or very similar isotopic compositions between enstatite chondrites aubrites and earth this suggests that the inner protoplanetary disk was characterized by a uniform isotopic composition idur for inner disk uniform reservoir sampled by enstatite chondrites and aubrites from which the earth drew most of its constituents the terrestrial isotopic composition for 17 o 48 ca 50 ti 62 ni and 92 mo is well reproduced by a mixture of 91 enstatite 7 ordinary and 2 carbonaceous chondrites the earth was not simply made of enstatite chondrites but it formed from the same original material that was later modified by nebular and disk processes the moon forming impactor probably came from the same region as the other embryos that made the earth explaining the strong isotopic similarity between lunar and terrestrial rocks

high pressure γ camgsi2o6 does penta coordinated silicon exist in the earth s mantle in situ x ray diffraction experiments with natural fe and al bearing diopside single crystals and density functional theory dft calculations on diopside end member composition indicate the existence of a new high pressure diopside polymorph with rare penta coordinated silicon on compression diopside transforms to the phase at 50 gpa which in turn on decompression is observed to convert to the known phase below 47 gpa the new diopside polymorph constitutes another recent example of penta coordinated silicon vsi in over compressed metastable crystalline silicates suggesting that vsi may exist in the transition zone and the uppermost lower mantle in appreciable quantities not only in silicate glass and melts but also in crystalline phases contained in the coldest parts of subducted stagnant slabs vsi may have significant influences on buoyancy wave velocity anomalies deformation mechanisms chemical reactivity of silicate rocks and seismicity within the slab

unusual micro and nano inclusions in diamonds from the juina area brazil abstract a series of uncommon micro and nano inclusions has been identified in diamonds from the rio soriso placer deposit in mato grosso state brazil the micro inclusions are variable in size from 1 to 300 m usually they are polymineralic being formed predominantly by intergrowths of carbonates silicates and other minerals carbonates are represented mostly by dolomite and occasionally by calcite silicates found are coesite wollastonite ii cuspidine and monticellite sulphides and ilmenite form micro inclusions as well nano inclusions are different from micro inclusions not only in size not exceeding 200 nm they are usually included in micro inclusions among nano inclusions halides nacl kcl cacl2 and pbcl2 anhydrite spinel phlogopite pbo2 tio2 with an pbo2 structure native fe and other phases are identified all these minerals are of the eclogitic association they are either associated with coesite or are included in a diamond with a light organic carbon isotopic composition with 13c from 14 to 25 pdb this confirms our earlier conclusion that diamonds from the juina area may have formed as a result of subduction of the crustal material to depths of at least the lower transition zone or even the lower mantle the pressure estimates for the investigated diamonds vary in a range from 3 to 10 gpa an interesting assemblage of calcite cuspidine wollastonite monticellite fluid identified in one of the studied diamonds is considered as a product of a reaction of wollastonite fluid forming cuspidine monticellite the presence of numerous pores cavities and bubbles in mineral inclusions and identification of an association of volatile containing mineral inclusions such as halides nacl kcl cacl2 and pbcl2 fluorine containing silicate cuspidine and phlogopite emphasize the important role of volatiles particularly chlorine and fluorine in the formation of the diamonds

comment on the triple oxygen isotope composition of the earth mantle and understanding δ17o variations in terrestrial rocks and minerals by pack and herwartz earth planet sci lett 390 2014 138 145

crystal chemistry of ca bearing majorite single crystals of ca bearing majorite a garnet with composition cao 49mg2sl mgsi sipi2 have been synthesized at 18 2 gpa and 2050 0c this sample is the first silicate garnet to display ordering on both octahedral and dodecahedral sites behavior that may increase the compositional flexibility of garnet affect element partitioning at high pressure and stabilize the garnet structure in the transition zone and upper portion of the lower mantle the garnet is tetragonal space group 14 a z 8 a 11 5816 9 c 11 5288 13 a v 1546 39 29 a3 and like mgsio majorite displays twinning by twofold rotation about 110

oxygen isotope variation in primitive achondrites the influence of primordial asteroidal and terrestrial processes a detailed oxygen isotope study of the acapulcoites lodranites winonaites brachinites and various related achondrites has been undertaken to investigate the nature of their precursor materials high levels of terrestrial alteration displayed by many of these samples have been mitigated by leaching in ethanolamine thioglycollate eatg solution due to their high metal and sulphide content acapulcoite lodranite and winonaite samples show much greater isotopic shifts during weathering than brachinites as observed in previous studies antarctic weathered finds are displaced to lighter oxygen isotope compositions and non antarctic finds to heavier values leached primitive achondrite residues continue to show high levels of oxygen isotope heterogeneity this variation is reflected in the 2 error on group mean 17o values which decrease in the following order acapulcoite lodranite clan brachinites winonaites on an oxygen three isotope diagram the acapulcoite lodranite clan define a limited trend with a slope of 0 61 0 08 and an intercept of 1 43 0 27 r2 0 78 a broad positive correlation between 17o and olivine fayalite contents displayed by both acapulcoite and lodranite samples may be the result of early aqueous alteration and subsequent dehydration winonaites experienced a greater degree of differentiation than the acapulcoite lodranite clan and define a distinct mass fractionation line with a slope of 0 53 0 01 and an intercept of 0 53 0 04 r2 1 a number of samples currently classified as acapulcoites nwa 725 nwa 1052 and dho 1222 have oxygen isotope compositions indicating that they are winonaites the relatively high level of oxygen isotope heterogeneity displayed by the brachinites supports their designation as primitive achondrites a number of ungrouped olivine rich achondrites divnoe nwa 4042 nwa 4363 nwa 4518 nwa 5400 zag b as well as the unique plagioclase rich achondrites gra 06128 and gra 06129 have similar oxygen isotope compositions to the brachinites it remains unclear whether the brachinites and related olivine rich achondrites are from a single or multiple parent bodies the primitive achondrites and related samples represent material from at most only 18 parent bodies compared to an estimated 65 for the iron meteorites this suggests that asteroidal mantle material is underrepresented in the meteorite record early fragmentation of differentiated asteroids followed by preferential destruction of their silicate rich mantles offers a possible explanation for this discrepancy on an oxygen three isotope diagram primitive chondrule bearing winonaites dho 1222 nwa 725 nwa 1052 nwa 1463 mt morris wisconsin plot close to the young russell y r slope 1 line with more evolved samples extending away from it towards the ccam line a similar relationship is shown by the cr chondrites the acapulcoite lodranite clan plots between the slope 1 and ccam lines however the precursor material to the clan may have had a composition close to the slope 1 line prior to parent body processing these relationships support the view that primordial oxygen isotope variation in the early solar system is best represented by the slope 1 y r line

exsolution kinetics of majoritic garnet from clinopyroxene in subducting oceanic crust abstract mechanisms and kinetics of exsolution of majoritic garnet from ca tschermak rich clinopyroxene were examined at 14 0 15 6 gpa 1250 1590 c and h2o undersaturated conditions 800 1170 wt ppm h2o by time resolved in situ synchrotron x ray diffraction measurements textural observations of recovered samples revealed that majoritic garnet had exsolved along the grain boundaries of parent clinopyroxene analyses of the kinetic data obtained indicate that exsolved majoritic garnet grew by diffusion controlled growth and the growth kinetics can be described by k2 m2 s 7 4 10 5 exp 389 kj mol 1 rt the exsolution of majoritic garnet from clinopyroxene would be kinetically inhibited at temperatures below 800 c in geological time scales 105 106 years when the parent grain size is larger than 1 mm we constructed possible phase relations of subducting mid ocean ridge basalt morb taking the exsolution kinetics into consideration when the effect of reaction kinetics is considered the density contrast between the morb component of a subducting slab and surrounding mantle becomes significantly reduced relative to that calculated for the equilibrium morb assemblage

the origin of aubrites evidence from lithophile trace element abundances and oxygen isotope compositions abstract we report the abundances of a selected set of lithophile trace elements including lanthanides actinides and high field strength elements and high precision oxygen isotope analyses of a comprehensive suite of aubrites two distinct groups of aubrites can be distinguished a the main group aubrites display flat or light ree depleted ree patterns with variable eu and y anomalies their pyroxenes are light ree depleted and show marked negative eu anomalies b the mount egerton enstatites and the silicate fraction from larned display distinctive light ree enrichments and high th sm ratios mount egerton pyroxenes have much less pronounced negative eu anomalies than pyroxenes from the main group aubrites leaching experiments were undertaken to investigate the contribution of sulfides to the whole rock budget of the main group aubrites sulfides contain in most cases at least 50 of the rees and of the actinides among the elements we have analyzed those displaying the strongest lithophile behaviors are rb ba sr and sc the homogeneity of the 17 o values obtained for main group aubrite falls 17 o 0 009 0 010 2 suggests that they originated from a single parent body whose differentiation involved an early phase of large scale melting that may have led to the development of a magma ocean this interpretation is at first glance in agreement with the limited variability of the shapes of the ree patterns of these aubrites however the trace element concentrations of their phases cannot be used to discuss this hypothesis because their igneous trace element signatures have been modified by subsolidus exchange finally despite similar o isotopic compositions the marked light ree enrichments displayed by mount egerton and larned suggest that they are unrelated to the main group aubrites and probably originated from a distinct parent body

the chlorine isotopic composition of the moon insights from melt inclusions abstract the moon exhibits a heavier chlorine cl isotopic composition compared to the earth several hypotheses have been put forward to explain this difference based mostly on analyses of apatite in lunar samples complemented by bulk rock data the earliest hypothesis argued for cl isotope fractionation during the degassing of anhydrous basaltic magmas on the moon subsequently other hypotheses emerged linking cl isotope fractionation on the moon with the degassing during the crystallization of the lunar magma ocean lmo currently a variant of the lmo degassing model involving mixing between two end member components defined by early formed cumulates from which mare magmas were subsequently derived and a kreep component which formed towards the end of the lmo crystallization seems to reconcile some existing cl isotope data on lunar samples to further ascertain the history of cl in the moon and to investigate any evolution of cl during magma crystallization and emplacement events which could help resolve the chlorine isotopic variation between the earth and the moon we analysed the cl abundance and its isotopic composition in 36 olivine and pyroxene hosted melt inclusions mi in five apollo basalts 10020 12004 12040 14072 and 15016 olivine hosted mi have an average of 3 3 1 4 ppm cl higher cl abundances 11 9 ppm on average are measured for pyroxene hosted mi consistent with their formation at later stages in the crystallization of their parental melt compared to olivines chlorine isotopic composition 37 cl of mi in the five apollo basalts have weighted averages of 12 8 2 4 and 10 1 3 2 for olivine and pyroxene hosted mi respectively which are statistically indistinguishable these isotopic compositions are also similar to those measured in apatite in these lunar basalts with the exception of sample 14072 which is known to have a distinct petrogenetic history compared to other mare basalts based on our dataset we conclude that post mi entrapment no significant cl isotopic fractionation occurred during the crystallization and subsequent eruption of the parent magma and that cl isotopic composition of mi and apatite primarily reflect the signature of the source region of these lunar basalts our findings are compatible with the hypothesis that in the majority of the cases the heavy cl isotopic signature of the moon was acquired during the earliest stages of lmo evolution interestingly mi data from 14072 suggests that apollo 14 lunar basalts might be an exception and may have experienced post crystallization processes possibly metasomatism resulting in additional cl isotopic fractionation recorded by apatite but not melt inclusions

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 composition and origin of the lunar crust constraints from central peaks and crustal thickness modeling spectral reflectance data of lunar central peaks haverevealedthatthemoon scrustvariesbothlaterallyand vertically in composition we correlate the depths of origin of materials that make up central peaks with a geophysi cally derived dual layered crustal thickness model and nd that the peak compositions are consistent with this strati edmodel specically peakscomposedexclusivelyofrocks containing more than 85 plagioclase by volume come from this model s upper crust whereas peaks that contain some norite or gabbro norite come from the model s lower crust extrapolating these data we nd that the moon s upper crust is composed of 884 plagioclase correspond ingto29to32wt al 2o3 t hemost maclowerportion of the crust is composed of 658 plagioclase having an al2o3 content that lies between 18 and 25 wt we show that the lower portion of the crust is consistent with having formed by cumulateflotation in a lunar magma ocean

thermodynamic properties and phase relations in mantle minerals investigated by first principles quasiharmonic theory this research has been motivated by geophysics and materials physics the objective of this research has been to advance materials theory and computations for high pressure and high temperature applications to the point that it can make a difference in our understanding of the earth understanding of the mineralogy composition and thermal structure of the earth evolves by close interaction of three fields seismology geodynamics and mineral physics earth s structure is imaged by seismology which obtains body wave velocities and density throughout the earth s interior fig 1 interpretation of this data relies on knowledge of aggregate properties of earth forming materials either measured in laboratory or calculated in many cases by both however the conditions of the earth s interior especially at the core may be challenging for important experiments and materials computations have emerged to contribute decisively to this field earth s evolution is simulated by geodynamics but these simulations need as input information about rheological and thermodynamic properties of minerals including phase transformation properties such as clapeyron slopes our research has concentrated on the phases of the earth s mantle particularly the deep mantle whose conditions are more challenging for experiments the mantle accounts for 83 of the earth s volume in this article we will review the essential first principles approach used to investigate solids at high temperatures and pressures summarize their performance for mantle minerals fig 2 and point to critical results that have stirred us in the current research path the success is remarkable but some limitations point the way to future developments in this field figure 1 a velocities and density profiles kennett et al 1995 b earth s cross section and c composition and mineralogy of earth s layers figure 2 phases proportions versus depth and or pressure ol mg fe 2sio4 olivine also known as phase mg fe

magnesium stable isotopes support the lunar magma ocean cumulate remelting model for mare basalts we report high precision mg isotopic analyses of different types of lunar samples including two pristine mg suite rocks 72415 and 76535 basalts anorthosites breccias mineral separates and lunar meteorites the mg isotopic composition of the dunite 72415 25 mg 0 140 0 010 26 mg 0 291 0 018 the most mg rich and possibly the oldest lunar sample may provide the best estimate of the mg isotopic composition of the bulk silicate moon bsm this 26 mg value of the moon is similar to those of the earth and chondrites and reflects both the relative homogeneity of mg isotopes in the solar system and the lack of mg isotope fractionation by the moon forming giant impact in contrast to the behavior of mg isotopes in terrestrial basalts and mantle rocks mg isotopic data on lunar samples show isotopic variations among the basalts and pristine anorthositic rocks reflecting isotopic fractionation during the early lunar magma ocean lmo differentiation calculated evolutions of 26 mg values during the lmo differentiation are consistent with the observed 26 mg variations in lunar samples implying that mg isotope variations in lunar basalts are consistent with their origin by remelting of distinct lmo cumulates