the shape and internal structure of the moon from the clementine mission global topographic and gravitational field models derived from data collected by the clementine spacecraft reveal a new picture of the shape and internal structure of the moon the moon exhibits a 16 kilometer range of elevation with the greatest topographic excursions occurring on the far side lunar highlands are in a state of near isostatic compensation whereas impact basins display a wide range of compensation states that do not correlate simply with basin size or age a global crustal thickness map reveals crustal thinning under all resolvable lunar basins the results indicate that the structure and thermal history of the moon are more complex than was previously believed

analytic expressions for the velocity sensitivity to the elastic moduli for the most general anisotropic media for non linear kinematic inversion of elastic anisotropy parameters and related investigations of the sensitivity of seismic data the derivatives of the wavespeed phase velocity and group velocity with respect to the individual elastic moduli are required this paper presents two analytic methods called the eigenvalue and eigenvector methods to compute the derivatives of the wavespeeds for wave propagation in a general anisotropic medium which may be defined by up to 21 density normalized elastic moduli the first method employs a simple and compact form of the eigenvalue phase velocity and a general form of the group velocity and directly yields general expressions of the derivatives for the three wave modes qp qs 1 qs 2 the second method applies simple eigenvector solutions of the three wave modes and leads to other general forms of the derivatives these analytic formulae show that the derivatives are in general functions of the 21 elastic moduli as well as the wave propagation direction and they reflect the sensitivity of the wavespeeds to the individual elastic moduli meanwhile we give results of numerical investigations with some examples for particular simplified forms of anisotropy they show that the eigenvalue method is suitable for the qp qs 1 and qs 2 wave computations and mitigates the singularity problem for the two quasi shear waves the eigenvector method is preferable to the eigenvalue method for the group velocity and the derivative of the phase velocity because it involves simpler expressions and independent computations but for the derivative of the group velocity the derivative of the eigenvector is required both methods tackle the singularity problem and are applicable to any degree of seismic anisotropy for all three wave modes

including anisotropy in 3 d velocity inversion and application to marlborough new zealand summary two types of seismic velocity heterogeneity are often observed in a given region pronounced patterns of anisotropy shown by local earthquake shear wave splitting and seismic velocity structure imaged by local earthquake traveltimes we seek to combine these types of observations by including anisotropy in 3 d velocity inversion the fast polarization directions from local earthquake shear wave splitting are used to define an initial anisotropy model the ray paths are estimated for each of the shear wave splitting observations and the 3 d initial model is determined via an averaging process and a coherence analysis the initial magnitude of anisotropy at a node is dependent on the number of adjacent ray paths and the consistency of the shear wave splitting anisotropy measurements the traveltime inversion is parametrized with an isotropic component and two azimuthal anisotropy parameters for each node the ray paths are defined with approximate 3 d ray tracing and for each point along a ray path the velocity is defined as a function of the ray path azimuth at that point a blended approach is used to damp the perturbations to the magnitude of anisotropy and or perturbations to the fast direction tests with synthetic traveltime data show that the anisotropic velocity inversion method is reliable application to the marlborough region shows variations in anisotropy in the brittle crust ductile lower crust mantle and subducted slab the patterns are consistent with the shear wave splitting observations but show some additional features the maximum anisotropy is approximately 12 per cent oriented northeast between the awatere and wairau faults this high anisotropy may reflect deformation and extensive fracturing in a region of high total shear strain in the region of interaction of the ductile lower crust with the shallow subducting slab moderate anisotropy with east west orientation is imaged this is consistent with ductile deformation roughly parallel to the plate velocity

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

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

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

ray tracing of multiple transmitted reflected converted waves in 2 d 3 d layered anisotropic tti media and application to crosswell traveltime tomography

empirical green s functions from small earthquakes a waveform study of locally recorded aftershocks of the 1971 san fernando earthquake seismograms from 52 aftershocks of the 1971 san fernando earthquake recorded at 25 stations distributed across the san fernando valley are examined to identify empirical green s functions and characterize the dependence of their waveforms on moment focal mechanism source and recording site spatial variations recording site geology and recorded frequency band recording distances ranged from 3 0 to 33 0 km hypocentral separations ranged from 0 22 to 28 4 km and recording site separations ranged from 0 185 to 24 2 km the recording site geologies are diorite gneiss marine and nonmarine sediments and alluvium of varying thicknesses waveforms of events with moment below about 1 5 1021 dyn cm are independent of the source time function and are termed empirical green s functions waveforms recorded at a particular station from events located within 1 0 to 3 0 km of each other depending upon site geology with very similar focal mechanism solutions are nearly identical for frequencies up to 10 hz there is no correlation to waveforms between recording sites at least 1 2 km apart and waveforms are clearly distinctive for two sites 0 185 km apart the geologic conditions of the recording site dominate the character of empirical green s functions even for source spatial separations of up to 20 0 km the empirical green s functions at a particular site are consistent in frequency content amplification and energy distribution therefore it is shown that empirical green s functions can be used to obtain site response functions the observations of empirical green s functions are used as a basis for developing the theory for using empirical green s functions in deconvolution for source pulses and synthesis of seismograms of larger earthquakes

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

extrapolating strong ground motion of the silakhor earthquake ml 6 1 iran using the empirical green s function egf approach based on a genetic algorithm the main objectives of this article are to develop a technique to find source models that allow one to replicate observed strong ground motion records and to extrapolate strong ground motion synthe

a hybrid method for simulating near source broadband seismograms application to the 2003 bam earthquake mw 6 5 the main objective of this article is to simulate the three components of near source ground shaking recorded at bam station close to the causative fault during the destructive the 2003 bam earthquake where were strongly influenced by rupture directivity effect a hybrid technique composed of the theoretical green s function finite element and finite difference method proposed by spudich et al 1987 2003 compsyn and a 2 based finite fault approach proposed by beresnev and atkinson 1998a finsim are used for generating seismograms at low and high frequencies respectively a genetic algorithm technique is developed for minimizing the differences between the recorded and simulated data incorporating parameters within a predefined upper lower bound s values previously estimated for main shock by other investigators two different faulting models consist of a straight line segment and a straight line segment followed by a slightly north eastward branch are used the simulated three component seismograms at bam station in terms of elastic response spectra are validated by comparing the simulated time series with those of the observed data moreover the pulses involved in the recorded time series due to the rupture directivity are estimated and compared with those of the observed data a sensitivity analysis is performed for recognizing the influence of model parameter changes such as focal mechanism strike dip and rake rise time rupture velocity and hypocenter location on the simulated seismograms relatively good match of the simulated and observed time series particularly the two faulting models confirm the potentiality of the proposed technique and the suitability of seismological model parameters used this technique can be used for specific site hazard analysis of the bam region and linear nonlinear dynamic analysis of structures where were damaged during the bam earthquake particularly for retrofitting the well known international adobe buildings of arg e bam

early crust building enhanced on the moon s nearside by mantle melting point depression the moon s earth facing hemisphere hosts a geochemically anomalous region the procellarum kreep terrane which is widely thought to have provided radiogenic heat for mantle melting from 3 9 to 1 billion years ago however there is no agreement on such a link between this region and the earliest pulse of post differentiation crust building magmatism on the moon at 4 37 billion years ago whether this early magmatism was global or regional has been debated here we present results of high temperature experiments that show the nearside geochemical anomaly may have caused asymmetric early crust building via mantle melting point depression our results demonstrate that the anomalous enrichment in incompatible elements of this nearside reservoir dramatically lowers the melting temperature of the source rock for these magmas and may have resulted in 4 to 13 times more magma production under the nearside crust even without any contribution from radioactivity from thermal numerical modelling we show that radiogenic heating compounds this effect and may have resulted in an asymmetric concentration of post magma ocean crust building on the lunar nearside our findings suggest that the nearside geochemical anomaly has influenced the thermal and magmatic evolution of the moon over its entire post differentiation history early magmatism on the moon s nearside may have been enhanced by a geochemical anomaly lowering the melting point of the mantle source region according to high temperature experiments and thermal numerical modelling

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

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

the 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

the lunar mascons revisited the entire spectra of the surface topography and gravity field of lunar mascons are well presented by the high resolution clementine data the negative correlation between the topography and gravitational potential of the mascons suggests that they are dynamically supported both elastic support and viscous decay models are examined for the elastic support models the spectral characteristics and the lateral variations of the thickness of the elastic layer are determined on the basis of the thin spherical shell flexure formulation and using only the antivarying harmonics of the topography and potential an elastic layer thickness of about 50 km is required to support imbrium serenitatis and nectaris mascons about 35 km for crisium mascon and about 30 km for smythii and humorum mascons a layer of about 20 km thickness can support orientale mascon the strength envelopes of the upper 100 km of the moon within 4 3 gyr ago show that the elastic layer was not thick enough to support the mascons in the early history they decayed through viscous deformation of the lunar interior a lower limit of 6 1024 pa s is estimated for the lunar viscosity within 3 6 3 gyr ago we also determine the thicknesses of the crust and mare flows of the mascon basins on the basis of the assumption that the basins were isostatically compensated prior to the mascon formation the crust beneath the mascon basins is about 30 40 km except for crisium and orientale where the crust is about 20 km the mare flows of about 3 6 km are obtained for almost all of the mascon basins the topography and gravitational potential of aitken basin shows that the basin is compensated at 52 54 km depth the mantle beneath the basin has rebounded upward by about 20 30 km and is overlain by about 20 25 km of a mixture of the excavated crustal and mantle material the lack of a mascon and pervasive mare flows in the basin brings into question the current models of the mascon formation

anisotropic crosshole vsp traveltime tomography through triangular cell model with a normalized jacobian matrix and multistage inversion strategy to overcome the difficulty in forward and inversion problem in complex geological model including undulated topography and irregular subsurface interface we in this paper realize a multistage triangular shortest path method for multi phase seismic ray tracing and combine a nonlinear inversion solver damped minimum norm and constrained least squares problem solved by a conjugated gradient method to simultaneously invert four elastic parameters or four thomsen parameters in anisotropic media using combined direct and reflected arrival times for trading off between different parameter updating we normalize the sensitivity functions traveltimes derivatives with respect to different elastic or thomsen parameter changes to balance four updated elastic or thomsen parameters in simultaneous inversion process due to the magnitude and pattern of partial derivatives more sensitive to different phase slowness angles in addition in order to solve the multi solution problems of qsv wave inversion a strategy of multistage inversion is proposed for testing the efficiency and correctness of proposed inversion method we use the picked traveltimes in synthetic seismograms as the observed traveltimes in the inversion the results show that both inverted images by taking the picked traveltimes in synthetic seismograms as the observed data and by taking predicted traveltimes using ray tracing method as observed data have a similar imaging pictures which verify the efficiency and correctness of the proposed inversion method furthermore the inverted results by normalized kernel functions are better than that of inversion without applying the normalized kernel functions for both qp and qsv data and the results of the multistage inversion are better than that of the simultaneous inversion without multistage inversion applied in qsv wave inversion in addition both elastic and thomsen parameter inversions for the same anisotropic model indicate that there are no big differences between the two inverted results even though the sensitivity kernels related to the thomsen parameters have relatively large values

ion and electron microprobe study of troctolites norite and anorthosites from apollo 14 evidence for urkreep assimilation during petrogenesis of apollo 14 mg suite rocks abstract most of the moon s highland crust formed during the period 4 65 4 45 ga ago from a vast magma ocean up to 800 km deep hess and parmentier 1995 this early lunar crust comprises fe rich anorthosites with calcic plagioclase compositions subsequent evolution of the highland crust was dominated by troctolites anorthosites and norites of the mg suite this plutonic series is characterized by calcic plagioclase and mafic minerals with high mg 100 mg mg fe these rocks evidently formed by partial melting of ultramafic rocks of the lunar mantle but their bulk rock incompatible element characteristics are too enriched to represent such a primitive source previous studies have suggested that this enrichment in incompatible trace elements is the result of metasomatism of the crust by fluids rich in ree and p the products of this suggested metasomatic event are ree rich phosphates typically whitlockite deposited interstitially alternatively the incompatible element rich nature of these plutonic rocks may represent a characteristic of their parent magma acquired prior to crystallization of the plutons in an effort to distinguish the origin of this important lunar rock series we have analyzed the ree content of primary cumulus phases in ten mg suite cumulates using sims along with their major and minor element compositions by electron microprobe analysis nine of these samples have high mg s consistent with their formation from the most primitive parent melts of the mg suite the data presented here show that mg suite troctolites and anorthosites preserve major and trace element characteristics acquired during their formation as igneous cumulate rocks and that these characteristics can be used to reconstruct related aspects of the parent magma composition our data show that primitive cumulates of the mg suite crystallized from magmas with ree contents similar to high k kreep in both concentration and relative abundance the highly enriched nature of this parent magma contrasts with its primitive major element characteristics as pointed out by previous workers this enigma is best explained by the mixing of residual magma ocean urkreep melts with ultramagnesian komatiitic partial melts from the deep lunar interior the data do not support earlier models that invoke crustal metasomatism to enrich the mg suite cumulates after formation or models which call for a superkreep parent for the troctolites and anorthosites

focal mechanism determination in taiwan by genetic algorithm we determined the focal mechanism solutions for earthquakes with mag nitude ml 4 0 that occurred in the taiwan region between 1991 and 2005 first motion polarities of p waves recorded at over 700 seismic stations in taiwan were used because of the large number of events and stations involved we implemented the genetic algorithm in a nonlinear global search for the focal mechanism solutions the algorithm was tuned and validated through synthetic tests we finally determined the focal mechanisms of 1635 events with good qualities among 4188 earthquakes focal mechanism solutions for a majority of the earthquakes display a dominant pat tern of thrust fault type reflecting the compressive stress field due to the plate colli sion normal fault events occurred at intermediate depths in subduction zones which is likely the result of the bending of the subducting slabs strike slip faults are also found within the eurasia plate around the peikang basement high and in collision zones near ilan where the geometry of the colliding plates is complex our study pro vides a database of focal mechanisms for studying seismogenic structures and plate tectonics this database can also be used by structural seismologists to compute syn thetics for waveform tomography studies

grail identified gravity anomalies in oceanus procellarum insight into subsurface impact and magmatic structures on the moon abstract four quasi circular positive bouguer gravity anomalies pbgas that are similar in diameter 90 190 km and gravitational amplitude 140 mgal contrast are identified within the central oceanus procellarum region of the moon these spatially associated pbgas are located south of aristarchus plateau north of flamsteed crater and two are within the marius hills volcanic complex north and south each is characterized by distinct surface geologic features suggestive of ancient impact craters and or volcanic plutonic activity here we combine geologic analyses with forward modeling of high resolution gravity data from the gravity recovery and interior laboratory grail mission in order to constrain the subsurface structures that contribute to these four pbgas the grail data presented here at spherical harmonic degrees 6 660 permit higher resolution analyses of these anomalies than previously reported and reveal new information about subsurface structures specifically we find that the amplitudes of the four pbgas cannot be explained solely by mare flooded craters as suggested in previous work an additional density contrast is required to explain the high amplitude of the pbgas for northern flamsteed 190 km diameter the additional density contrast may be provided by impact related mantle uplift if the local crust has a density 2800 kg m3 then 7 km of uplift is required for this anomaly although less uplift is required if the local crust has a lower mean density of 2500 kg m3 for the northern and southern marius hills anomalies the additional density contrast is consistent with the presence of a crustal complex of vertical dikes that occupies up to 50 of the regionally thin crust the structure of southern aristarchus plateau 90 km diameter an anomaly with crater related topographic structures remains ambiguous based on the relatively small size of the anomaly we do not favor mantle uplift however understanding mantle response in a region of especially thin crust needs to be better resolved it is more likely that this anomaly is due to subsurface magmatic material given the abundance of volcanic material in the surrounding region overall the four pbgas analyzed here are important in understanding the impact and volcanic plutonic history of the moon specifically in a region of thin crust and elevated temperatures characteristic of the procellarum kreep terrane

the present day deformation of the central zagros from gps measurements 1 in 1997 and in 2000 we measured the distances between 14 geodetic benchmarks across the central zagros mountain belt the results show that about 10 mm yr of shortening in the central zagros is distributed across the mountain belt this shortening corresponds to roughly 50 of the total convergence between arabia and eurasia and is consistent in direction the persian gulf does not deform significantly the main zagros reverse fault is not an active kinematic boundary the internal deformation of the folded belt is rather homogeneous at the scale of our survey which does not allow us to detect any individual active blind fault however the strain pattern suggests that n s dextral strike slip faults may accommodate part of the deformation

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

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

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

40ar 39ar chronology of lunar meteorites northwest africa 032 and 773 the 40ar 39ar dating technique has been applied to the lunar meteorites northwest africa 032 nwa 032 an unbrecciated mare basalt and northwest africa 773 nwa 773 composed of cumulate and breccia lithologies to determine the crystallization age and timing of shock events these meteorites may have experienced stepped heating analyses of several different samples of nwa 032 gave complex age spectra but indistinguishable total ages with a mean of 2 779 0 014 gyr possible causes of the complex age spectra obtained from nwa 032 include recoil of 39ar or the presence of pre shock 40ar incorporated into shock melt veins the effects of shock veins were investigated by laser fusion of 20 small samples expected to contain varying proportions of the shock veins the laser ages show a narrow age distribution between 2 61 2 86 gyr and a mean of 2 73 0 03 gyr identical to the total age of 2 80 gyr obtained for the bulk sample diffusion calculations based on the stepped heating data indicate that ar release can be reconciled by release from feldspar and possibly shock veins at low temperatures followed by pyroxene at higher temperatures the exposure age of nwa 032 is 212 11 myr and it contains low trapped solar ar stepped heating of cumulate and breccia portions of nwa 773 also give a relatively young age of 2 91 gyr the presence of trapped ar in the breccia makes the age determination of this component less precise but release of ar appears to be from the same mineral phase assumed to be plagioclase in both lithologies a marked difference in exposure age between the 2 lithologies also exists with the breccia having spent 81 myr longer at the lunar surface this finding is consistent with the higher trapped ar content of this lithology assuming that 2 80 gyr and 2 91 gyr are the crystallization ages of nwa 032 and nwa 773 respectively these two meteorites are the youngest lunar mare basalts available for study

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

dynamic ray tracing in an anisotropic medium abstract we derive a dynamic ray tracing system for seismic waves in an anisotropic medium it consists of ten equations and can be solved numerically for isotropic media it does not reduce to the drt systems derived by other authors

thermal evolution of a thicker kreep liquid layer we consider the thermal evolution of the thickened potassium rare earth element and phosphorous kreep liquid layer that extends over a significant fraction of the lunar nearside with a prescribed thickness and heat production and beneath an insulating anorthosite crust this layer represents a subcrustal heat source beneath the procellarum imbrium terrane and may be responsible for the localized and anomalous enrichments of highly incompatible elements in this terrane in some models this thickened liquid layer is the thermal source for the remelting of mare basalts and also produces the parent magmas of the magnesian suite indeed a kreep liquid layer thickened from 5 to 10 km with more than 200 times chondritic heat producing elements does not continue to cool but undergoes a reheating and grows in thickness by dissolving several times its mass of anorthosite and ultramafic cumulates however such a liquid layer cannot give rise to the parent magmas to the magnesian suite because it cannot account for the extraordinarily high incompatible element content the primitive major element content or the positive end of the magnesian suite this growing layer will also form an impenetrable barrier to the eruption of mare basalts and is generally inconsistent with a number of geophysical constraints of the moon specifically the existence of mascons subsequent to the basin filling by mare basalts a thickened kreep liquid layer can however explain the asymmetry in the distribution of kreep rich rock on the lunar crust such a kreep layer must be efficiently cooled and be quickly solidified to avoid some of the difficulties described above a thinned anorthosite crust would allow efficient heat loss and induce crystallization of such a layer early in lunar history

lunar multiring basins and the cratering process abstract numerous studies of the lunar gravity field have concluded that the lunar moho is substantially uplifted beneath the young multiring basins this uplift is presumably due to the excavation of large quantities of crustal material during the cratering process and subsequent rebound of the impact basin floor using a new dual layered crustal thickness model of the moon the excavation cavities of some nearside multiring basins grimaldi and larger and younger than tranquillitatis were reconstructed by restoring the uplifted moho to its preimpact location the farside south pole aitken spa basin was also considered due to its importance in deciphering lunar evolution restoring the moho to its preimpact position beneath these basins resulted in a roughly parabolic depression from which the depth and diameter of the excavation cavity could be determined using these reconstructed excavation cavities the basin forming process was investigated excavation cavity diameters were generally found to be on the small side of most previous estimates for orientale the modeled excavation cavity lies within the inner rook ring additionally with the exception of the three largest basins serenitatis imbrium and south pole aitken the depth diameter ratios of the excavation cavities were found to be 0 115 0 005 a value consistent with theoretical and experimental results for impact craters orders of magnitude smaller in size the three largest basins however appear to have significantly shallower depths of excavation compared to this trend it is possible that this may reflect a different physical process of crater formation e g nonproportional scaling special impact conditions or postimpact modification processes the crustal thickness model also shows that each basin is surrounded by an annulus of thickened crust we interpret this thickened crust as representing thick basin ejecta deposits and we show that the radial variation in the thickness of these deposits is consistent with scaling laws obtained from small scale experimental studies if multiring basins ever possessed a terraced main crater rim this terraced zone may be presently unrecognizable at the surface due to the emplacement of ejecta deposits that exceed a few kilometers in thickness exterior to the excavation cavity rim we also show that the interiors of many basins were superisostatic before mare volcanism commenced those basins that were closest to approaching a premare isostatic state lie close to or within an anomalous geochemical province rich in heat producing elements

lunar rare earth element distribution and ramifications for feo and tio2 lunar prospector neutron spectrometer observations lunar prospector neutron spectrometer data have been used to map the global surface distribution of the incompatible rare earth elements gadolinium and samarium from the low altitude 30 15 km mapping orbit these results afford improved surface resolution and detailed views of the potassium rare earth elements and phosphorus kreep distribution within and around mare imbrium and elsewhere the gd and sm results serve as a complementary and independent check of the distribution of kreep on the moon in contrast with the lunar prospector gamma ray spectrometer results for thorium the neutron spectrometer observations reflect the presence of fe and ti as well as gd and sm the contributions of fe and ti are removed using high spatial resolution clementine spectral reflectance determinations of feo and tio2 abundances overall the resulting gd and sm abundance map agrees with the th abundance map determined using the lunar prospector gamma ray spectrometer in general the detailed features of the procellarum imbrium kreep terrane are found in both for example distinct highs in gd sm and th abundances are resolved over the craters mairan aristarchus kepler reinhold lalande and aristillus over the apennine bench and fra mauro regions and over the montes jura and montes carpatus indicating an enhanced abundance of kreep in these locations the neutron observations also provide constraints on feo and tio2 abundances for some high ti locales there is a significant disagreement with tio2 abundances inferred from clementine spectral reflectance

lunar cryptomaria physical characteristics distribution and implications for ancient volcanism cryptomaria lunar volcanic deposits obscured by crater and basin impact ejecta can provide important information about the thermal and volcanic history of the moon the timing of cryptomare deposition has implications for the duration and flux of mare basalt volcanism in addition knowing the distribution of cryptomaria can provide information about mantle convection and lunar magma ocean solidification here we use multiple datasets e g m3 lola lroc diviner to undertake a global analysis to identify the general characteristics e g topography surface roughness rock abundance albedo etc of lunar light plains in order to better distinguish between ancient volcanic deposits cryptomaria and impact basin and crater ejecta deposits we find 20 discrete regions of cryptomaria covering approximately 2 of the moon which increase the total area covered by mare volcanism to 18 of the lunar surface comparisons of light plains deposits indicate that the two deposit types volcanic and impact produced are best distinguished by mineralogic data on the basis of cryptomaria locations the distribution of mare volcanism does not appear to have changed in the time prior to its exposed mare basalt distribution there are several hypotheses explaining the distribution of mare basalts which include the influence of crustal thickness mantle convection patterns asymmetric distribution of source regions kreep distribution and the influence of a proposed procellarum impact basin the paucity of farside mare basalts means that multiple factors such as crustal thickness variations and mantle convection are likely to play a role in mare basalt emplacement

small area thorium features on the lunar surface 1 using an improved understanding of the lunar prospector gamma ray spectrometer lp grs spatial footprint we have derived a new map of global thorium abundances on the lunar surface this map has a full width half maximum spatial resolution of 80 km 2 and is mapped on the lunar surface using 0 5 0 5 pixels this map has allowed the identification and classification of 42 small area 3 g g in southwestern mare tranquillitatis near the apollo 11 landing site with our better understanding of the lp grs spatial footprint we have been able to constrain the surface thorium abundance at the compton belkovich thorium anomaly to 40 55 g g which is higher than any other measured location on the lunar surface and higher than most samples finally using 1 km pixel feo abundances from clementine and lp grs spatial footprint information we have been able to obtain plausible thorium distributions around kepler crater at a resolution of 1 km pixel the materials around kepler crater appear to be a relatively simple mixing of thorium rich mib compositions and high thorium mare basalts

the great lunar hot spot and the composition and origin of the apollo mafic lkfm impact melt breccias thorium rich mafic impact melt breccias from the apollo 14 17 missions that is those breccias identified with the composition known as lkfm are regarded largely as products of basin forming impacts that penetrated the feldspathic crust and sampled underlying mafic material and magma ocean residuum carrying the compositional signature of kreep potassium rare earth elements phosphorous despite considerable compositional variation among such breccias compositions of all of them correspond to mixtures of only four components 1 a norite with composition generally similar to that of apollo 15 basalt mean abundance 58 range 30 95 2 fo 90 dunite mean 13 range 1 27 3 feldspathic upper crust mean 29 range 4 50 and feni metal 0 1 1 7 petrographic evidence has shown that much of the feldspathic component but none of the kreep component is clastic this observation and the high proportion of kreep norite component in the breccias suggest that the melt zone of the impact or impacts forming the breccias contained little feldspathic material but consisted predominantly of material with the average composition of kreep norite the dunite component probably derives ultimately from the upper mantle these conclusions support the hypothesis that the breccias were not formed in typical feldspathic crust but instead by one or more impacts into what is designated here the great lunar hot spot that is the anomalous th rich terrane in the imbrium procellarum area identified by the apollo and lunar prospector gamma ray spectrometers the lkfm composition is a special product of the great lunar hot spot and is not the average composition of the lower crust in typical feldspathic highlands similarly mg suite and alkali suite plutonic rocks of the apollo collection are likely all differentiation products of the hot spot not of plutons that might occur in typical feldspathic crust

subsurface morphology and scaling of lunar impact basins impact bombardment during the first billion years after the formation of the moon produced at least several tens of basins the gravity recovery and interior laboratory grail mission mapped the gravity field of these impact structures at significantly higher spatial resolution than previous missions allowing for detailed subsurface and morphological analyses to be made across the entire globe grail derived crustal thickness maps were used to define the regions of crustal thinning observed in centers of lunar impact basins which represents a less unambiguous measure of a basin size than those based on topographic features the formation of lunar impact basins was modeled numerically by using the isale 2d hydrocode with a large range of impact and target conditions typical for the first billion years of lunar evolution in the investigated range of impactor and target conditions the target temperature had the dominant effect on the basin subsurface morphology model results were also used to update current impact scaling relationships applicable to the lunar setting based on assumed target temperature our new temperature dependent impact scaling relationships provide estimates of impact conditions and transient crater diameters for the majority of impact basins mapped by grail as the formation of lunar impact basins is associated with the first approximately 700 myr of the solar system evolution when the impact flux was considerably larger than the present day our revised impact scaling relationships can aid further analyses and understanding of the extent of impact bombardment on the moon and terrestrial planets in the early solar system

the imbrium impact event and the thorium distribution at the lunar highlands surface late in the moon s heavy bombardment period the impact that formed the imbrium basin excavated and melted a tremendous volume of material that was subsequently distributed over most of the moon s surface the apollo orbiting ray experiments metzger et al 1977 show that the imbrium projectile struck in a th rich area called the high th oval region here and regarded as a unique lunar geochemical province imbrium primary ejecta were thus probably rich in th it is shown here using ejecta deposit modeling that the distribution of th in the highlands surface along the ground tracks of the ray spectrometers is consistent with the distribution expected for imbrium ejecta deposits deep basins other than imbrium appear to have excavated regions of lower crust that were mafic and fe bearing but not th rich the possibility that the surface th distribution arises mainly from imbrium ejecta has implications for the nature of the moon s igneous differentiation and the nature of the proposed cataclysm or late bombardment with large meteoroids

nonlinear traveltime inversion scheme for crosshole seismic tomography in tilted transversely isotropic media crosshole seismic tomography often is applied to image the velocity structure of an interwell medium if the rocks are anisotropic the tomographic technique must be adapted to the complex situation otherwise it leads to a false interpretation we propose a nonlinear kinematic inversion method for crosshole seismic tomography in composite transversely isotropic media with known dipping symmetry axes this method is based on a new version of the first order traveltime perturbation equation it directly uses the derivative of the phase velocity rather than the eigenvectors of the body wave modes to overcome the singularity problem for application to the two quasi shear waves we applied an iterative nonlinear solver incorporating our kinematic ray tracing scheme and directly compute the jacobian matrix in an arbitrary reference medium this reconstructs the five elastic moduli or thomsen parameters from the first arrival traveltimes of the three seismic body waves qp qsv qsh in strongly and weakly anisotropic media we conducted three synthetic experiments that involve determining anisotropic parameters for a homogeneous rock reconstructing a fault embedded in a strongly anisotropic background and imaging a complicated four layer model containing a small channel and a buried dipping interface we compared results of our nonlinear inversion method with isotropic tomography and the traditional linear anisotropic inversion scheme which showed the capability and superiority of the new scheme for crosshole tomographic imaging

present day crustal deformation and plate kinematics in the middle east constrained by gps measurements in iran and northern oman summary a network of 27 gps sites was implemented in iran and northern oman to measure displacements in this part of the alpine himalayan mountain belt we present and interpret the results of two surveys performed in 1999 september and 2001 october gps sites in oman show northward motion of the arabian plate relative to eurasia slower than the nuvel 1a estimates e g 22 2m m yr 1 at n8 5 e instead of 30 5 mm yr 1 at n6 e at bahrain longitude we define a gps arabia eurasia euler vector of 27 9 0 5 n 19 5 1 4 e 0 41 0 1 myr 1 the arabia eurasia convergence is accommodated differently in eastern and western iran east of 58 e most of the shortening is accommodated by the makran subduction zone 19 5 2m m yr 1 and less by the kopet dag 6 5 2m m yr 1 west of 58 e the deformation is distributed in separate fold and thrust belts at the longitude of tehran the zagros and the alborz mountain ranges accommodate 6 5 2m m yr 1 and 8 2m m yr 1 respectively the right lateral displacement along the main recent fault in the northern zagros is about 3 2m m yr 1 smaller than what was generally expected by contrast large rightlateral displacement takes place in northwestern iran up to 8 mm yr 1 the central iranian block is characterized by coherent plate motion internal deformation 2m m yr 1 sites east of 61 e show very low displacements relative to eurasia the kinematic contrast between eastern and western iran is accommodated by strike slip motions along the lut block to the south the transition zone between zagros and makran is under transpression with right lateral displacements of 11 2m m yr 1

petrogenesis of lunar troctolites models of petrogenesis for lunar troctolites are severely constrained by the high mg 88 values of the most primitive members of the mg rich suite melts derived by partial melting of olivine cumulates to the lunar magma ocean have high mg but are strongly undersaturated with respect to plagioclase assimilation of lunar crust cannot bring these melts to the plagioclase liquidus without unduly reducing the mg values of olivine partial melts derived by melting a iherzolite primitive interior have higher normative plagioclase contents but require sources with mg 90 more terrestrial like mg 88 values are permitted if rising thermal plumes are capable of entraining the most mg rich cumulates of the magma ocean the mg values of lunar troctolites may therefore reflect a hybrid source composed of primitive mantle and mg rich cumulates of the magma ocean higher mg values may also arise from the reduction of small amounts of feo to fe alternatively the parent magmas to lunar troctolites may be impact melts of the anorthositic crust and the mg rich dunite cumulates of the magma ocean the latter were brought to the upper mantle during the overturn of the unstable cumulate pile of the magma ocean

excavation of the lunar mantle by basin forming impact events on the moon abstract global maps of crustal thickness on the moon derived from gravity measurements obtained by nasa s gravity recovery and interior laboratory grail mission have shown that the lunar crust is thinner than previously thought hyperspectral data obtained by the kaguya mission have also documented areas rich in olivine that have been interpreted as material excavated from the mantle by some of the largest lunar impact events numerical simulations were performed with the isale 2d hydrocode to investigate the conditions under which mantle material may have been excavated during large impact events and where such material should be found the results show that excavation of the mantle could have occurred during formation of the several largest impact basins on the nearside hemisphere as well as the moscoviense basin on the farside hemisphere even though large areas in the central portions of these basins were later covered by mare basaltic lava flows surficial lunar mantle deposits are predicted in areas external to these maria our results support the interpretation that the high olivine abundances detected by the kaguya spacecraft could indeed be derived from the lunar mantle

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

gravitational differentiation due to initial chemical stratification origin of lunar asymmetry by the creep of dense kreep abstract models for the evolution of the moon must explain a number of important characteristics of its magmatic history primary among them is the emplacement of mare basalts primarily on one side of the moon and in a region of the surface roughly correlating with that containing high subsurface concentrations of kreep it is thus important to explore mechanisms which will regionally concentrate a kreep layer early in lunar evolution and which 400 500 myr later give rise to mare basalt generation beneath the same region gravitational instability of a chemically dense ilmenite rich cumulate created during the fractionation of an anorthositic crust is one candidate model if so gravitational instability must occur at long wavelength to explain the hemispheric asymmetry we examine the rayleigh taylor instability of a dense layer near the surface of a sphere representing the lunar mantle in which the viscosity varies with depth our results show that spherical harmonic degree 1 is the fastest growing wavelength of instability if the viscosity of the dense layer is sufficiently low relative to that of the deeper mantle or if the viscosity of the mantle increases with depth however the viscosity increase cannot be distributed over a depth that is too large we explore whether a residual kreep like layer near the base of anorthositic crust might give rise to these needed conditions

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

the participation of ilmenite bearing cumulates in lunar mantle overturn abstract the ilmenite bearing cumulates ibc formed from the solidification of the lunar magma ocean are thought to have significantly affected the long term evolution of the lunar interior and surface their high density is considered to trigger rayleigh taylor instabilities which allow them to sink into the solidified cumulates below and drive a large scale overturn in the lunar mantle knowledge of how the ibc participate in the overturn is important for studying the early lunar dynamo chemistry of surface volcanism and the existence of present day partial melt at the lunar core mantle boundary despite early efforts to study this process as rayleigh taylor instabilities no dynamical models have quantified the degree of ibc sinking systematically we have performed quantitative 2 d geodynamical simulations to measure the extent to which ibc participate in the overturn after their solidification and tested the effect of a range of physical and chemical parameters our results show that ibc overturn most likely happened when the magma ocean had not yet fully solidified with the residual melt decoupling the crust and ibc resulting in 50 70 ibc sinking participation of the last dregs of remaining magma ocean melt is unlikely leaving its high concentrations of radiogenic elements close to the surface our simulations further indicate that foundered ibc can stay relatively stable at the core mantle boundary until the present day at temperatures consistent with the presence of a partially molten zone in the deep mantle as inferred from geophysical data 30 50 of the primary ibc remain at shallow depths throughout lunar history enabling their assimilation by rising magma to form high ti basalts