very preliminary reference moon model abstract the deep structure of the moon is a missing piece to understand the formation and evolution of the earth moon system despite the great amount of information brought by the apollo passive seismic experiment alsep the lunar structure below deep moonquakes which occur around 900 km depth remains largely unknown we construct a reference moon model which incorporates physical constraints and fits both geodesic lunar mass and polar moment of inertia and love numbers and seismological body wave arrivals measured by apollo network data in this model the core radius is constrained by the detection of s waves reflected from the core in a first step for each core radius a radial model of the lunar interior including p and s wave velocities and density is inverted from seismic and geodesic data in a second step the core radius is determined from the detection of shear waves reflected on the lunar core by waveform stacking of deep moonquake apollo records this detection has been made possible by careful data selection and processing including a correction of the gain of horizontal sensors based on the principle of energy equipartition inside the coda of lunar seismic records and a precise alignment of sh waveforms by a non linear inversion method the very preliminary reference moon model vpremoon obtained here has a core radius of 380 40 km and an average core mass density of 5200 1000 kg m 3 the large error bars on these estimates are due to the poorly constrained s wave velocity profile at the base of the mantle and to mislocation errors of deep moonquakes the detection of horizontally polarized s waves reflected from the core and the absence of detection of vertically polarized s waves favour a liquid state in the outermost part of the core all these results are consistent within their error bars with previous estimates based on lunar rotation dissipation williams et al 2001 and on lunar induced magnetic moment hood et al 1999

further constraints on the deep lunar interior 1 we have inverted the most recent set of geophysical observations pertinent to lunar interior properties including mass m and moment of inertia i as determined by lunar prospector the two love numbers k2 and h2 as well as monthly tidal dissipation q obtained from more than 35 years of lunar laser ranging data in wanting to assess the ability of these parameters to constrain lunar mantle and core structure we have used a stochastically based sampling algorithm to invert the geophysical data to obtain radial density and shear wave velocity profiles the results indicate a small liquid fe core r 1 thereby favouring the fluid core hypothesis in addition shear wave velocities for the lower mantle region depths 1100 km are generally found to be lower than upper mantle velocities and can be interpreted as implying the presence of partial melt which can explain the unusually low lunar monthly tidal q of 30

improved gravity field of the moon from lunar prospector an improved gravity model from doppler tracking of the lunar prospector lp spacecraft reveals three new large mass concentrations mascons on the nearside of the moon beneath the impact basins mare humboltianum mendel ryberg and schiller zucchius where the latter basin has no visible mare fill although there is no direct measurement of the lunar farside gravity lp partially resolves four mascons in the large farside basins of hertzsprung coulomb sarton freundlich sharonov and mare moscoviense the center of each of these basins contains a gravity maximum relative to the surrounding basin the improved normalized polar moment of inertia 0 3932 0 0002 is consistent with an iron core with a radius of 220 to 450 kilometers

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

the complex stratigraphy of the highland crust in the serenitatis region of the moon inferred from mineral fragment chemistry large impact basins are natural drill holes into the moon and their ejecta carries unique information about the rock types and stratigraphy of the lunar crust we have conducted an electron microprobe study of mineral fragments in the poikilitic melt breccias collected from the taurus mountains at the apollo 17 landing site these breccias are virtually unanimously agreed to be impact melt produced in the serenitatis impact event they contain lithic fragments and much more abundant mineral fragments of crustal origin we have made precise microprobe analyses of minor element abundances in fragments of olivine pyroxene and plagioclase to provide new information on the possible source rocks and the crustal stratigraphy in the serenitatis region these data were also intended to elucidate the nature of the cryptic geochemical component in breccias such as these with low k fra mauro basalt compositions we chose the finest grained i e most rapidly quenched breccias for study to avoid reacted and partly assimilated fragments as much as possible most of the mineral fragments appear to have been derived from rocks that would fall into the pristine igneous mg suite as represented by lithic fragments in the apollo collection or reasonable extensions of it gabbroic rocks were more abundant in the target stratigraphy than is apparent from the apollo sample collection some pyroxene and plagioclase but probably not much olivine could be derived from feldspathic granulites which are metamorphosed polymict breccias some mineral fragments are from previously unknown rocks these include highly magnesian olivines up to fo94 possibly volcanic in origin that exacerbate the difficulty in explaining highly magnesian rocks in the lunar crust it appears that some part of the lunar interior has an mg 100 mg mg fe atomic greater than the conventional bulk moon value of 80 84 other volcanic rocks including mare basalts and rapidly cooled impact melt rocks do not contribute significantly to the fragment population nor do ferroan anorthosites contribute more than a tiny part of even the plagioclase fragment population a few mineral fragments that are consistent with the cryptic low k fra mauro chemical component were found and these appear to be from gabbroic sources the mineral fragment populations cannot be mixed in their observed proportions to produce the whole rock composition because the fragments are more refractory and deficient in ti p and alkalis a preferential contribution to the melt from a rock similar to sodic ferrogabbro can partly resolve the discrepancy the population of mineral fragments requires a very diverse population of igenous rocks that are not all related to each other demonstrating the existence of a complex crust built of numerous separate igneous plutons many of these plutons may have crystallized at shallow depths the chemical composition of the melt breccias in combination with the mineral fragment data and an understanding of the cratering process suggests that the deepest crust sampled by the serenitatis impact not necessarily the deepest crust was basaltic in composition including kreep and gabbroic rocks like sodic ferrogabbro and lacking abundant olivine rich material these were overlain by mg suite rocks of varied types including norites and troctolites that supplied most of the olivine mineral fragments granulites which are metamorphosed and more feldspathic breccias were abundant near the surface remote sensing indicates that the entire serenitatis region lacks ferroan anorthosite consistent with the results of our study

lunar composition a geophysical and petrological synthesis lunar compositional constraints are derived on the basis of geophysical data in particular the lunar seismic model as revised by nakamura and petrological arguments only in the case of extreme assumptions can critical aspects of bulk lunar composition be demonstrated to be equivalent to the present day terrestrial mantle specifically the moon has an mg number that is too low and an alumina abundance that is too high over a broad range of crustal densities the presence of a metallic core at least 150 km in radius is necessary to reconcile the upper mantle lunar seismic model with mass and moment of inertia constraints a significant seismic discontinuity at 500 km depth may mark the lowest extent of early lunar differentiation possibly representing a transition between highly fractionated upper mantle and less fractionated perhaps even primordial middle lower mantle

elasticity of single crystal orthoferrosilite the elastic moduli of a synthetic single crystal of pure fesio3 orthoferrosilite have been measured at 1 bar and 20 c by brillouin spectroscopy the moduli are in megabars c11 1 98 c22 1 36 c33 1 75 c44 0 59 c55 0 58 c66 0 49 c12 0 84 c13 0 72 c23 0 55 a comparison of the pyroxene crystal structure with elasticity data shows that distortion of the tetrahedral chains parallel to c is related to c33 straight or extended chains increase c33 and highly kinked chains weaken the structure however the ferrosilite data show that beyond a certain degree of distortion the tetrahedral chains are essentially passive previous models of pyroxene elasticity have indicated that c11 should be most sensitive to composition this is supported by the current study and is reflected in the elasticity data via a positive linear correlation of c11 with the size of the m1 octahedron as measured by the average m1 0 distance the average longitudinal modulus c 11 c11 c22 c33 3 varies linearly with composition in the system orthoenstatite orthoferrosilite whereas the average shear moduli c 44 and c 12 are constant for fe contents of at least 20 by comparison data for the solid solution forsterite fayalite are consistent with a linear variation of modulus versus composition between the end members for all three average moduli we suggest that this difference between orthopyroxene and olivine is due to a strong preference of fe2 for the m2 octahedral site in pyroxene the isotropic shear modulus is 30 lower for ferrosilite than enstatite despite a similar contrast in end member values of the olivine data are consistent with a linear variation of between fo100 and fa100 at high temperatures fe and mg in orthopyroxene will be randomly distributed and a linear variation of with molar content of fe is expected a comparison of laboratory elasticity data with observed mantle properties shows that vp vs and of the upper mantle are satisfied by pure olivine however the data strongly suggest that without the coexistence of a garnet phase no more than 10 orthopyroxene may be present in a model mantle assemblage ca clinopyroxene increases the upper limit on mantle garnet content but does not greatly affect constraints on the quantity of orthopyroxene in the upper mantle

does the moon possess a molten core probing the deep lunar interior using results from llr and lunar prospector 1 it is the main purpose of this study to examine the deeper structure of the moon in the light of four numbers these are lunar mass m mean moment of inertia i second degree tidal love number k2 and the quality factor q accounting for tidal dissipation within the solid body of the moon the former two have been measured by lunar prospector to high precision and more than 30 years of lunar laser ranging llr data have led to an estimate of the second degree tidal love number and quality factor the inverse problem dealt with here of obtaining information on the lunar density and s wave velocity profile from the four numbers follows our earlier investigations by employing an inverse monte carlo sampling method we present a novel way of analyzing the outcome using the bayes factor the advantage lies in the fact that rather than just looking at a subset of sampled models we investigate all the information sampled in different runs i e take into account all samples in order to estimate their relative plausibility the most likely outcome of our study based on the data their uncertainties and prior information is a central core with a most probable s wave velocity close to 0 km s density of 7 2 g cm3 and radius of about 350 km this is interpreted as implying the presence of a molten or partially molten fe core in line with evidence presented earlier using llr regarding the dissipation within the moon

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

chemical composition and origin of apollo 15 impact melts to better understand the apennine front we have analyzed 14 apollo 15 impact melt rocks including hand samples rake samples and coarse fines for major fused bead microprobe and trace element inaa abundances the melt rocks show a remarkable diversity of chemical composition although all but one have typical kreep incompatible element patterns they appear to form five chemical groups all but the most kreep rich of which may represent single impacts three groups are of low k fra mauro composition none correspond to very high alumina vha compositions the compositions are unlike nearly all other impact melts and regoliths from highland sites indicating a distinct provenance for the apollo 15 samples serenitatis basin impact melt compositions apollo 17 poikilitic boulders are not duplicated although one apollo 17 aphanitic melt sample 73215 is similar to one of the apollo 15 groups the apollo 15 group consisting only of 15445 and 15455 remains the best candidate for imbrium basin impact melt while the most kreep rich group probably consists of melts produced in varied post imbrium impacts into the apennine bench formation apollo 15 kreep basalt flows the most populated group was previously unrecognized and could be either pre or post imbrium basin it is possible that it not 15445 15455 represents imbrium melt one unique sample has a non kreep incompatible element pattern with low abundances and a positive eu anomaly its target was rather primitive and would not appear to be of regional extent or present in the area in post imbrium times it is either a pre imbrian melt or exotic the apennine front does not consist of a monolithic lkfm composition but shows a much wider diversity of compositions than was previously recognized

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

on the source region of the lunar mare basalt the lack of pervasive flooding of the south pole aitken spa basin raises questions about the mare basalt source region models whether deep or shallow this paper investigates the dichotomy between the nearside imbrium sized flooded basins and the unflooded spa basin by modeling the effects of giant impacts on the dynamics of the lunar mantle we allow an initially spherically symmetric moon model to evolve through mantle convection for a few hundred million years and then let an imbrium or spa sized impact occur the subsequent thermal convection in the lunar mantle resulting from the thermal energy introduced by an impact is determined for the next 100 m y the mantle is assumed to be incompressible with an infinite prandtl number and a temperature dependent viscosity it is shown that the mantle circulation induced by an imbrium sized impact can only slightly push aside the radioactive rich potassium rare earth element and phosphorous kreep layer from beneath the surrounding crust this concentrates the radioactive elements beneath the low thermal conductive ejecta blanket and provides a suitable condition for enhancement of radioactive heating and subsequent partial melting and basaltic flow to the basin on the other hand a spa sized impact is capable of generating mantle circulation vigorous enough to strip away the kreep layer from beneath the surrounding crust within a time period of 40 m y this removal prevents radioactive heating and partial melting beneath the surrounding crust thus explaining the lack of flooding of spa basin these results are insensitive to the time of impacts but are strongly dependent on their sizes

geochemical constraints on the seismic properties of the lunar mantle abstract thermodynamic modeling of phase relations and physical properties in the na2o tio2 cao feo mgo al2o3 sio2 fe fes system and a monte carlo inversion procedure have been used to calculate the density and velocity distribution in the mantle and core radii of the moon from the mass and moment of inertia constraints from recent lunar prospector gravity measurements for the computation of the phase diagram for a given chemical composition we have used a method of minimization of the total gibbs free energy and self consistent thermodynamic data for minerals and solid solutions for the crustal thickness and density of 60 km and 3 0 g cm 3 the largest core radii are estimated to be 530 km for an fes troilite core 4 1 of total mass 490 km for a eutectic fe fes core 3 4 445 km for an fe 10 wt s core 2 9 and 350 km for an fe core 2 the existence of an fe fes core of intermediate radius of 250 400 km is compatible with recent lunar core information and lend support to a chemically stratified lunar mantle the sensitivity of density and seismic velocities to temperature pressure and composition variations is examined the modeling results indicate that we can determine the permissible density and velocity ranges in the zoned lunar mantle with confidence the maximum and minimum density changes at depths of the lunar mantle consistent with geochemical constraints and mass and moment of inertia requirements are found to be 3 22 g cm 3 3 44 g cm 3 at depths of 60 500 km and 3 34 g cm 3 3 52 g cm 3 at depths between 500 km and the core mantle boundary core free models of the moon are possible only if the lower mantle densities are between 3 49 and 3 52 g cm 3 20 wt feo wt the calculated field of seismic velocities in the zoned lunar mantle shows that over a broad range of mantle compositions temperatures and densities the maximum variations are as follows 4 23 km s 1 v s 4 69 km s 1 and 7 41 km s 1 v p 8 24 km s 1 at depths of 60 500 km and 4 24 km s 1 v s 4 64 km s 1 and 7 63 km s 1 v p 8 39 km s 1 at depths between 500 km and the core mantle boundary these petrologically and geophysically admissible ranges of velocities and densities may constitute a significant constraint for the analysis of internal structure of the moon using the apollo seismic data

chemical fractionation in the silicate vapor atmosphere of the earth despite its importance to questions of lunar origin the chemical composition of the moon is not precisely known in recent years however the isotopic composition of lunar samples has been determined to high precision and found to be indistinguishable from the terrestrial mantle despite widespread isotopic heterogeneity in the solar system in the context of the giant impact hypothesis this level of isotopic homogeneity can evolve if the proto lunar disk and post impact earth undergo turbulent mixing into a single uniform reservoir while the system is extensively molten and partially vaporized in the absence of liquid vapor separation such a model leads to the lunar inheritance of the chemical composition of the terrestrial magma ocean hence the turbulent mixing model raises the question of how chemical differences arose between the silicate earth and moon here we explore the consequences of liquid vapor separation in one of the settings relevant to the lunar composition the silicate vapor atmosphere of the post giant impact earth we use a model atmosphere to quantify the extent to which rainout can generate chemical differences by enriching the upper atmosphere in the vapor and show that plausible parameters can generate the postulated enhancement in the feo mgo ratio of the silicate moon relative to the earth s mantle moreover we show that liquid vapor separation also generates measurable mass dependent isotopic offsets between the silicate earth and moon and that precise silicon isotope measurements can be used to constrain the degree of chemical fractionation during this earliest period of lunar history an approach of this kind has the potential to resolve long standing questions on the lunar chemical composition

petrologic province maps of the lunar highlands derived from orbital geochemical data orbital and sample geochemical data from the lunar highlands are combined in variation diagrams to determine a the coincidence between the two data sets and b the geologic validity of extrapolating observed diagrammatic relations to an image format we examined three variation diagrams mg 100 mg mg fe molar versus th ti c ratio normalized to chondrites al versus mg th ti c and fe versus th ti c for the orbital data within each diagram we establish a petrologic classification based on the data s clustering or coincidence with sample compositions or both the spatial distributions of each diagram s classes are shown as petrologic units on color coded classification maps the mg th ti c diagram which is similar to the mg sm ti c diagram that has been used in sample studies is inferior to the al mg th ti c diagram in discriminating kreep from mg suite rock types the orbital geochemical spectrometers analyzed the regolith in which mg varies much less than al although the fe th ti c diagram shows a diverse distribution of orbital data similar to that shown by the al mg th ti c diagram it is unable to discriminate adequately between kreep and mg suite rock types the fe th ti c diagram is nonetheless very useful because of its greater areal coverage orbital and soil sample compositions of the four highland landing sites correspond in both the al mg th ti c and the fe th ti c data the diagrams show some units of virtually pure anorthosite and norite most units show the effects of mixing of pristine rock types in the regolith one unit which dominates the eastern limb and farside highlands has a composition so mafic that with the chosen end members it requires a 30 mare basalt component we interpret this to mean that the highlands experienced a significantly greater amount of mare volcanism before the end of heavy bombardment than has been previously suggested the average global composition of the highlands under the apollo groundtracks is that of anorthositic gabbro an average that has significant implications for the role of near global plagioclase fractionation in lunar crustal genesis our analysis has shown that the simultaneous use of orbital and sample geochemical data in variation diagrams can 1 bridge the mechanical gap between orbital and sample studies by relating orbital data to sample petrology 2 present the results of several elemental databases as one map for rapid geologic analysis and 3 display quantitative mixing relations of different crustal materials in a spatial format this technique will be valuable for petrologic interpretation of the global geochemical data to be received from the future lunar geosciences orbiter mission

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

dynamic deformation of the accretionary prism excites very low frequency earthquakes 1 we have detected anomalous very low frequency earthquakes within the accretionary prism along the nankai trough southwestern japan centroid moment tensor inversion analysis reveals that the earthquake hypocenters are distributed at 10 km depth above the upper surface of the subducting philippine sea plate and within 50 70 km landward of the trough axis the focal mechanisms indicate reverse faulting their hypocenters are distributed beneath a deformation zone of an accretionary prism in sea floor topography these observations suggest that the occurrence of very low frequency earthquakes is related to numerous reverse fault systems within the accretionary prism and that the earthquakes reflect the dynamics of deformation within this accretionary prism

the procellarum kreep terrane implications for mare volcanism and lunar evolution geophysical remote sensing and sample data demonstrate that the procellarum and imbrium regions of the moon make up a unique geochemical crustal province here dubbed the procellarum kreep terrane geochemical studies of imbrium s ejecta and the crustal structure of the imbrium and serenitatis basins both suggest that a large portion of the lunar crust in this locale is composed of a material similar in composition to apollo 15 kreep basalt kreep basalt has about 300 times more uranium and thorium than chondrites so this implies that a large portion of moon s heat producing elements is located within this single crustal province the spatial distribution of mare volcanism closely parallels the confines of the procellarum kreep terrane and this suggests a causal relationship between the two phenomena we have modeled the moon s thermal evolution using a simple thermal conduction model and show that as a result of the high abundance of heat producing elements that are found in the procellarum kreep terrane partial melting of the underlying mantle is an inevitable outcome specifically by placing a 10 km kreep basalt layer at the base of the crust there our model predicts that mare volcanism should span most of the moon s history and that the depth of melting should increase with time to a maximum depth of about 600 km we suggest that the 500 km seismic discontinuity that is observed in the apollo seismic data may represent this maximum depth of melting our model also predicts that the kreep basalt layer should remain partially molten for a few billion years thus the imbrium impact event most likely excavated into a partially molten kreep basalt magma chamber we postulate that the kreep basalt composition is a by product of mixing urkreep with shallow partial melts of the underlying mantle since mg suite rocks are likely derived from crystallizing kreep basalt the provenance of these plutonic rocks is likely to be unique to this region of the moon

hydrocarbon prospects of southern indus basin pakistan the southern indus basin extends approximately between lat 23 and 28 31 primen and from long 66 e to the eastern boundary of pakistan of the 55 exploratory wells drilled 1955 1984 27 were based on results of multifold seismic surveys five commercial oil discoveries and one gas discovery in cretaceous sands three gas discoveries in paleocene limestone or sandstone and one gas condensate discovery from lower eocene limestone prove that hydrocarbons are present the main hydrocarbon fairways are mesozoic tilted fault blocks tertiary reefal banks and drape and compressional anticlines older reservoirs are accessible toward the east and northeast and younger mature source rocks are to the west including offshore of the badin block oil field area the indus offshore basin reflects sedimentation associated with mesozoic rifting of the pakistan indian margin superimposed by a terrigenous clastic depositional system comprised of deltas shelves and deep sea fans of the indus river

secular effects of oceanic tidal dissipation on the moon s orbit and the earth s rotation the earth and moon are considered as a two body system in gravitational isolation from the sun and other planets the lunar orbit is taken as circular and the solid earth is assumed to be a rigid sphere with no tidal deformation so that there are no precessional torques other than those arising from the tidally deformed ocean numerical solutions to laplace s tidal equations with dissipation by linear bottom friction are used to obtain ocean wide distributions of tidal amplitude for two idealized continentalities a single circular continent spherical cap centered at the north pole and a single spherical cap centered on the equator calculations are made for two different values of the frictional resistance coefficient thus giving rise to four sets of solutions the computed tidal amplitudes are used to calculate the oceanic tidal torque which in turn is used to integrate the orbital equations backward in time for solution of the two body problem the coriolis parameter and the tidal frequencies change with time thus requiring that the tidal equations be solved several times during the course of each orbital integration in this manner the earth s rotational and the moon s orbital histories are determined on a geologic time scale for each of the four models the calculated position of the lunar orbit at 4 5 billion years ago is found to range from 38 to 53 earth radii in the four models and corresponds to a sidereal month of 330 to 550 hours the sidereal day would have been 12 to 18 hours with a relative inclination of 3 to 22 between the terrestrial and lunar poles these results are in sharp contrast to those from previous studies of the earth moon system most of which indicated a roche limit approach of the two bodies roughly 1 to 2 billion years ago and presented therefore a time scale difficulty in theories of lunar origin this contrast arises mainly from the fact that previous modelers avoided solution of laplace s tidal equations by prescribing a constant frictional phase lag angle between the angular position of the moon and the major axis of the second degree harmonic of the tidally deformed surface of the earth the amount of phase lag was established from the present astronomically deduced rate of tidal dissipation but this precluded dynamic variations in tidal torque over geologic time which are critical for determination of the orbital time scale the present rate of oceanic tidal dissipation is evidently anomalously high because of the near resonance of the oceanic response in both frequency and shape to the tidal forcing for the earth and moon to have evolved to their present separation from a distance of less than about 35 earth radii solely on the basis of oceanic tidal dissipation would have required the m2 response to have been near resonance for a significant portion of geologic history a rather implausible scenario the calculations reported here show that on the contrary frictional coupling between the earth and moon was much weaker than at present throughout most of the orbital history and consequently the moon s closest approach could not have been as small as 35 earth radii although idealized continentalities were used in these calculations the general conclusion of a weaker frictional coupling in the past is believed to be relatively insensitive to the continental configuration this is because at faster paleorotation the semidiurnal tidal frequencies would be resonant only with smaller scale normal modes of the ocean rather than with global scale modes as at present the time scale difficulty heretofore present in models of orbital evolution is thereby eliminated it should be noted that the orbital history developed here supports the theory of binary planetary accretion for lunar origin as opposed to fission or tidal capture

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

lunar mg suite thermobarometry and petrogenesis of parental magmas using compilations of internally consistent thermodynamic data on minerals and advances in quantifying the energetics of crystalline solid solutions we have recalculated the pressures and temperatures of equilibration of troctolite sample 76535 and a number of spinel cataclasites the five phase assemblage olivine orthopyroxene clinopyroxene cr spinel plagioclase which occurs in symplectite assemblages in 76535 gives equilibration temperatures from 800 900 c and pressures from 200 to 250 mpa indicating a deep 40 50 km crustal source spinel cataclasite assemblages give minimum pressures of 100 mpa mg suite magmas were apparently intruded throughout the lunar crust early in lunar history the textures and equilibration temperatures in many mg suite samples are consistent with sub solidus recrystallization and the mg rich minerals of some refractory troctolites and dunites may be residues of a crustal melting process or products of subsolidus elemental redistribution the sm nd age of 4 26 0 06 ga of troctolite 76535 most likely represents the time of sub solidus recrystallization and or partial melting in an attempt to identify the primary source material for the mg suite magmas a variety of models were tested using the melts and magfox codes a good fit between mineral compositions and crystallization sequences is obtained by 20 batch melting at 0 5 gpa of an average whole moon composition with an mg of 0 85 melts formed by batch melting at higher pressures and melts formed by poly baric partial fusion over the pressure range from 2 0 to 0 3 gpa were either too poor in mg and or crystallized clinopyroxene before orthopyroxene mixing with 10 20 urkreep which is required to satisfy the ree constraints of the mg suite reduces the mg of the parental magmas and requires a whole moon mg closer to that of the terrestrial mantle

abundance and distribution of iron on the moon the abundance and distribution of iron on the moon is derived from a near global data set from clementine the determined iron content of the lunar highlands crust 3 percent iron by weight supports the hypothesis that much of the lunar crust was derived from a magma ocean the iron content of lower crustal material exposed by the south pole aitken impact basin on the lunar farside is higher 7 to 8 percent by weight and consistent with a basaltic composition this composition supports earlier evidence that the lunar crust becomes more mafic with depth the data also suggest that the bulk composition of the moon differs from that of the earth9s mantle this difference excludes models for lunar origin that require the earth and moon to have the same compositions such as fission and coaccretion and favors giant impact and capture

apollo lunar seismic experiment final summary processing and initial analysis of the entire set of apollo lunar seismic data collected continuously from 1969 through 1977 have now been completed recent results include 1 better defined deep moonquake locations which appear to be bounded rather sharply between about 800 km and 1000 km depths with concentrations near both boundaries and 2 middle mantle 500 to 1000 km depth seismic velocities of vp 8 3 0 4 km sec and vs 4 6 0 2 km sec which are significantly higher than previous estimates and represent an increase of velocities from the upper mantle as opposed to a decrease in previous estimates

a komatiite component in apollo 16 highland breccias implications for the nickel cobalt systematics and bulk composition of the moon the lunar crust at the apollo 16 landing site contains substantial amounts of a primitive component in which the ferromagnesian group of elements is concentrated the composition of this component can be retrieved via an analysis of mixing relationships displayed by lunar breccias it is found to be a komatiite which is compositionally similar to terrestrial komatiites both in major and minor elements the komatiite component of the lunar crust is believed to have formed by extensive degrees of melting of the lunar interior at depths greater than were involved in the formation of the lunar magma ocean which was parental to the crust after formation of the anorthositic crust it was invaded by extensive flows and intrusions of komatiite magma from these deeper source regions the komatiites became intimately mixed with the anorthosite by intensive meteoroid impacts about 4 5 b y ago thereby accounting for the observed mixing relationships displayed by the crust the compositional similarity between lunar and terrestrial komatiites strongly implies a corresponding similarity between the compositions of their source regions in the lunar interior and the earth s upper mantle the composition of the lunar interior can be modelled more specifically by combining the komatiite composition with its liquidus olivine composition as determined experimentally in proportions chosen so as to produce a cosmochemically acceptable range of mg si ratios for the bulk moon except for higher feo and lower na2o the range of compositions thereby obtained for the bulk moon is very similar to the composition of the earth s upper mantle the effects of meteoritic contamination on the abundances of cobalt and nickel in lunar highland breccias were subtracted on the assumption that the contaminating projectiles were chondritic the cobalt and nickel residuals thereby obtained were found to correlate strongly with the mg fe content of the breccias demonstrating that the co and ni are associated with the ferromagnesian component of the breccias and are genuinely indigenous to the moon the lunar highland co and ni residuals also display striking ni co versus ni correlations which follow a similar trend to those displayed by terrestrial basalts picrites and komatiites the lunar trends provide further decisive evidence of the indigenous nature of the co and ni residuals and suggest the operation of extensive fractionation controlled by olivine liquid equilibria in producing the primitive component of the lunar breccias indigenous nickel abundances at the apollo 14 15 and 17 sites are much lower than at the apollo 16 site although rocks from all sites follow the same ni co versus ni trends it is suggested that the primitive component at the apollo 14 15 and 17 sites was generally of basaltic composition in contrast to the komatiitic nature of the apollo 16 primitive component

apollo 16 site geology and impact melts implications for the geologic history of the lunar highlands the geology of the apollo 16 site is reconsidered on the basis of data from photogeology geochemical remote sensing and lunar samples the site possesses an upper surface of anorthositic gabbro and related rocks mafic components were deposited as basin ejecta the events involved in its geological evolution were the nectaris impact and the imbrium impact the role of large local craters in the history of the region was to serve as topographic depressions to accumulate basin ejecta the most abundant melt composition at apollo 16 is an aluminous variety of lkfm basalt supplied by the nectaris impact as ejected basin impact melt the mafic lkfm melt may have been supplied by the imbrium impact more aluminous melt groups are probably derived from local small craters the remainder of the deposits in the region are composed of anorthositic clastic debris derived from the nectaris basin the local crustal substrate and imbrium and other basins

apollo 14 aluminous mare basalts and their possible relationship to kreep thirty six aluminous mare basalt fragments from breccia 14321 and other apollo 14 basalts are statistically divided into two broad groups comprising five subgroups using la sm and yb data major element compositions petrographic characteristics and mineral compositions are similar for the five groups however there is an eight fold increase in ree abundances from group 5 to group 1 with group 1 having a ree pattern similar to kreep groups 1 to 3 may be related by partial melting of a source similar to that proposed by unruh et al 1984 for feldspathic basalt 12038 however groups 4 and 5 cannot be as closely matched by larger degrees of partial melting of this source groups 1 to 4 could also be produced by assimilation of a kreep component by a magma similar in composition to group 5 such a magma can be produced by partial melting of an olivine orthopyroxene source that crystallized from a magma with chondritic relative ree abundances

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

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

geophysical constraints on lunar bulk composition and structure a reassessment theoretical lunar mantle seismic velocity and density profiles are calculated for a series of proposed bulk compositions present day selenotherms and models for early differentiation and evolution the seismic velocity profiles are compared to the most recent observational model derived from the complete apollo data set to evaluate compositional implications the mantle density profiles are compared to mean density moment of inertia and crustal density thickness constraints to evaluate the need for a metallic core the calculated seismic velocity profiles are in qualitative agreement with the observational model in two general respects 1 a quasicontinuous velocity decrease occurs in the upper mantle due to the large thermal gradients that characterize all three of the considered thermal models 2 a discontinuous velocity increase occurs at the spinel to garnet transition approximately 500 km depth due mainly to the higher garnet velocities as compared to olivine and orthopyroxene in the upper mantle all four of the considered bulk compositions spanning a range of plausible feo and al2o3 contents are allowed when uncertainties in the temperature profile and depth of differentiation are taken into account however in the middle mantle depths 500 km the most aluminous models those with larger garnet abundances consistently produce larger velocity increases that are most nearly in accord with the observational model in general models that assume differentiation of the upper mantle only that are more aluminous in bulk composition and that have strong thermal gradients in the upper mantle but smaller gradients in the middle mantle result in calculated velocity profiles that most nearly agree with the observational velocity model an alternate differentiation model in which the middle mantle is dominated by mgo rich mafic silicates is also in accord with the observational seismic velocity model but results in density decreases that appear to violate stability arguments in every case calculated mantle density increases are insufficient to match the one standard deviation upper limit on the moment of inertia even when the most favorable combinations of allowed crustal thickness and density are assumed agreement with the moment of inertia upper limit is obtained if metallic cores representing 1 4 of the lunar mass are added to the bulk composition such cores are larger than needed to explain the observed depletions of lunar siderophile elements if the moon formed entirely from terrestrial mantle material

melting relations of peridotite and the density crossover in planetary mantles melting relations of primitive peridotite were studied up to 25 gpa the change of the liquidus phase from olivine to majorite occurs at 16 gpa we confirmed the density crossover of the feo rich peridotite melt and the equilibrium olivine fo90 at 7 gpa sinking of equilibrium olivine fo95 in the primitive peridotite melt was observed up to 10 gpa the compression curves of feo rich peridotitic and komatiite melts reported in this and earlier work suggest that the density crossover in the earth s mantle will be located at 11 12 gpa at 2000 c consistent with an previous estimation by c b agee and d walker the density crossover can play a key role in the moon and the terrestrial planets such as the earth venus and mars majorite and some fraction of melt could have separated from the ascending diapir and sunk downwards at the depths below the density crossover this process could have produced a garnet rich transition zone in the earth s mantle the density crossover may exist in the feo rich lunar mantle at around the center of the moon the density crossover which exists at the depth of 600 km in the martian mantle plays a key role in producing a fractionated mantle which is the source the parent magmas of the snc meteorites

seismic velocity structure of the lunar mantle i have inverted the recently completed set of seismic arrival times from the apollo lunar seismic network to estimate the average seismic velocities in three sections of the lunar mantle two for the upper mantle and one for the middle mantle the method used is a variation of the linearized least squares inversion where the inversion is accomplished in steps the estimated average velocities in the upper mantle decrease from vp 7 74 km s and vs 4 49 km s in the section above 270 km depth to vp 7 46 km s and vs 4 25 km s in the section between 270 and 500 km depth confirming the earlier finding of negative gradients based on seismic amplitude variations the average velocities in the middle mantle between the depths of 500 km and 1000 km of vp 8 26 km s and vs 4 65 km s are significantly higher than those in the upper mantle contradicting earlier estimates based on more limited data the higher velocities may suggest initial melting of the moon down to at least 1000 km depth

a chemical and petrological model of the lunar crust and implications for lunar crustal origin we utilize a variety of lunar sample and orbital geochemical data in conjunction with current knowledge of impact cratering processes to develop a chemical and petrological model of the lunar crust orbital chemical data indicate that the upper highlands surface on the moon has the bulk composition of anorthositic gabbro al2o3 26 28 wt greater than 90 of the area covered is dominated by material having compositional affinities with the ferroan anorthosites rather than with apollo type mg suite rocks considerations of the cumulative bombardment history of the moon indicate that the outer zone of impact brecciation extends tens of kilometers into the crust given the resolution of the orbital gamma ray data the ferroan anorthositic composition derived for the highlands surface may represent the bulk composition of the upper half of the lunar crust the observed enrichment in noritic components in basin ejecta with increasing basin size together with considerations of impact melt petrogenesis in lunar basins suggest that the bulk composition of the lower lunar crust is noritic al2o3 20 wt samples of lower crustal material are probably present in the apollo collections in the form of low k fra mauro lkfm and very high alumina vha basaltic impact melts our estimated value of total crustal al2o3 content 24 25 wt suggests that the lunar crust contains too much aluminum to have originated by a purely serial magmatism mechanism the large abundance of plagioclase within the lunar crust is probably a result of global scale fractionation of plagioclase in early lunar history the magma ocean hypothesis of crustal origin more readily explains the bulk composition of the lunar crust