noise based monitoring and imaging of aseismic transient deformation induced by the 2006 basel reservoir stimulation abstractwe have analyzed the time dependent properties of the ambient seismic wavefield between 0 1 and 8 hz to detect resolve monitor and image the deformation induced by the water injection associated with the stimulation of the 2006 deep heat mining project in the city of basel switzerland the application of passive methods allowed the detection of an aseismic transient of approximately 35 days duration that began with the onset of the reservoir stimulation peak deformation was reached some 15 days after the bleed off and after the induced seismicity ceased we resolved a significant increase in seismic velocities and a simultaneous decorrelation of the noise correlation coda waveforms the wavefield properties implied that the material response was monitored mainly in the sedimentary layer 2 5 km above the stimulated volume that was approximately 4 5 km deep we inverted the velocity change and decorrelation data to estimate the spatial distribution of the medium changes the resulting imag

empirical relationships among seismic velocity effective pressure porosity and clay content in sandstone we use a multivariate analysis to investigate the influence of effective pressure pe porosity and clay content c on the compressional velocity vp and shear velocity vs of sandstones laboratory measurements on water saturated samples of 64 different sandstones provide a large data set that was analyzed statistically for each sample relationships between effective pressure and vp and vs have been determined all samples were well fit by relationships that have an exponential increase in velocity at low pe tapering to a linear increase with pe for pe greater than 0 2 kbar there are differences in the pressure dependences of velocity for different rocks particularly at very low pressures however the differences cannot be attributed to or c for the combined set of measurements from all samples the best fitting formulations are vp 5 77 6 94 1 73c 0 446 pe e 16 7pe and vs 3 70 4 94 1 57c 0 361 pe e 16 7pe while this is admittedly a very simplified parameterization it is remarkable how well

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

sm nd age of lherzolite 67667 implications for the processes involved in lunar crustal formation abstract pristine samples from the lunar highlands potentially offer important information bearing on the nature of early crustal development on all the terrestrial planets one apparently unique sample of this group of lunar crustal rocks the feldspathic lherzolite 67667 was studied utilizing the sm nd radiometric system in an attempt to define its age and the implications of that age for the evolution of the lunar highlands data for 67667 precisely define an isochron corresponding to an age of 4 18 0 07 ae the observed lack of disturbance of the sm nd system of this sample may suggest that this time marks its crystallization at shallow depth in the lunar crust however the possibility that this age as well as those of other highland rocks indicate the time of their impact induced excavation from regions deep enough in the lunar crust to allow subsolidus isotopic equilibrium to be produced or maintained between their constituent minerals is also considered taken together bulk rock sm nd data for four high mg rocks including 67667 indicate that the chemical characteristics of all their source materials were established 4 33 0 08 ae ago and were intimately associated with the parent materials of kreep this finding provides more support for the concept of a large scale differentiation episode early in lunar history the possible roles of the crystallization of a global magma ocean endogenous igneous activity and of planetesimal impact in producing the observed geochemical and chronological aspects of lunar highland rocks are discussed

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

systematics of ni and co in olivine from planetary melt systems lunar mare basalts the systematics of co and ni in olivine from six apollo 12 olivine basalts were studied by sims techniques and correlated with major and minor element data obtained with the electron microprobe our results together with previous studies demonstrate that one of these basalts 12009 was extruded as a liquid onto the lunar surface and was parental to five other cumulates 12075 12020 12018 12040 and 12035 the concentrations of ni in zoned olivine phenocrysts behave as expected for a highly compatible element with initial estimated d ni 9 9 on the other hand co concentrations in olivine vary hardly at all and show flat patterns across crystals that retain normal zoning trends for mg fe mn and ni the explanation for this behavior is not that d co nearly equal 1 our estimated d co 4 or that co zoning has been erased by rapid diffusion of co compared to the other elements e g mg and fe that still show normal zoning the explanation for the behavior as originally suggested by kohn et al 1989 is that the increase in d co with crystallization exactly balances the depletion of co in the melt this decoupling of the behavior of ni and co in olivine results in significant increases in co ni with crystallization

a rock fragment related to the magnesian suite in lunar meteorite allan hills alha 81005 among the lunar samples that were returned by the apollo missions are many cumulate plutonic rocks with high mg molar mg mg fe in and abundances of kreep elements potassium rare earth elements phosphorus u th etc that imply kreep rich parental magmas these rocks collectively called the magnesian suite are nearly absent from sampling sites distant from imbrium basin ejecta including those of lunar highlands meteorites this absence has significant implications for the early differentiation of the moon and its distribution of heat producing elements k th u here we analyze a unique fragment of basalt with the mineralogy and mineral chemistry of a magnesian suite rock in the lunar highlands meteorite allan hills alh a81005 in thin section the fragment is 700 300 m and has a sub ophitic texture with olivine phenocrysts euhedral plagioclase grains an97 70 and interstitial pyroxenes its minerals are chemically equilibrated olivine has fe mn 70 consistent with a lunar origin and mg 80 which is consistent with rocks of the magnesian suite and far higher than in mare basalts it has a rich suite of minor minerals fluorapatite ilmenite zr armalcolite chromite troilite silica and fe metal ni 3 8 co 0 17 the metal is comparable to that in chondrite meteorites which suggests that the fragment is from an impact melt the fragment itself is not a piece of magnesian suite rock which are plutonic but its mineralogy and mineral chemistry suggest that its protolith which was melted by impact was related to the magnesian suite however the fragment s mineral chemistry and minor minerals are not identical to those of known magnesian suite rocks suggesting that the suite may be more varied than apparent in the apollo samples although alha81005 is from the lunar highlands and likely from the farside clast u need not have formed in the highlands it could have formed in an impact melt pool on the nearside and been transported by meteoroid impact lunar highlands meteorites should be searched for rock fragments related to the magnesian suite rocks but the fragments are rare and may have mineral compositions similar to some meteoritic impactor materials

in situ measurement of velocity stress sensitivity using crosswell continuous active source seismic monitoring abstractthe ability to characterize time varying reservoir properties such as the state of stress has fundamental implications in subsurface engineering relevant to geologic sequestration of co2 stress variation here in the form of changes in pore fluid pressure is one factor known to affect seismic velocity induced variations in velocity have been used in seismic studies to determine and monitor changes in the stress state previous studies conducted to determine velocity stress sensitivity at reservoir conditions rely primarily on laboratory measurements of core samples or theoretical relationships we have developed a novel field scale experiment designed to study the in situ relationship between pore fluid pressure and seismic velocity using a crosswell continuous active source seismic monitoring cassm system at the cranfield mississippi co2 sequestration field site we actively monitored seismic response for five days with a temporal resolution of 5 min the target was a 26 m thick inject

potential of ambient seismic noise techniques to monitor the st gallen geothermal site switzerland the failures of two recent deep geothermal energy projects in switzerland basel 2006 st gallen 2013 have again highlighted that one of the key challenges for the successful development and operation of deep underground heat exchangers is to control the risk of inducing potentially hazardous seismic events in st gallen after an injection test and two acid injections that were accompanied by a small number of micro earthquakes ml 0 2 operators were surprised by an uncontrolled gas release from the formation gas kick the killing procedures that had to be initiated following standard drilling procedures led to a ml3 5 earthquake with ambient seismic noise cross correlations from nine stations we observe a significant loss of waveform coherence that we can horizontally and vertically constrain to the injection location of the fluid the loss of waveform coherence starts with the onset of the fluid injections 4 days prior to the gas kick we interpret the loss of coherence as a local perturbation of the medium we show how ambient seismic noise analysis can be used to assess the aseismic response of the subsurface to geomechanical well operations and how this method could have helped to recognize the unexpected reservoir dynamics at an earlier stage than the microseismic response alone allowed

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

characterization of hydraulic properties of rocks using probability of fluid induced microearthquakes the use of borehole fluid injections is typical for exploration and development of hydrocarbon or geothermal reservoirs such injections often induce small magnitude earthquakes the nature of processes leading to triggering of such microseismicity is still not completely understood here we consider induced microseismicity using as examples two case studies of geothermal reservoirs in crystalline rocks and one case study of a tight gas sandstone reservoir in all three cases we found that the probability of induced earthquakes occurring is very well described by the relaxation law of pressure perturbation in fluids filling the pore space in rocks this strongly supports the hypothesis of seismicity triggered by pore pressure moreover this opens additional possibilities of using passive seismic monitoring to characterize hydraulic properties of rocks on the reservoir scale with high precision

competition between slow slip and damage on and off faults revealed in 4d synchrotron imaging experiments abstract in the continental crust faults may accommodate deformation through aseismic creep slow slip events or seismic slips that produce dynamic damage or a combination of these endmembers a variety of parameters controls the occurrence of these mechanical behaviors in a series of laboratory experiments we image centimeter scale faults during sliding under in situ conditions we perform four experiments of slip on centimeter scale crystalline rock samples prepared with a saw cut interface at 45 from the direction to the maximum compressive stress and at stress conditions of 2 3 km depth we image fault slip and off fault fracture development using 4d synchrotron x ray microtomography three faults have an initial rough interface and deformation occurs with increasing differential stress by a combination of slow slip events and off fault damage until catastrophic failure and the formation of new faults conversely the pre cut fault with a smooth initial surface deforms mainly by slow slip develops numerous striations along its slip plane and no microfractures are detected in the wall rock our experiments reproduce aseismic and seismic faulting behavior and demonstrate that the roughness of the fault plane is one of the parameters that control the transition between these two behaviors a fault with a rougher interface may tend to develop more off fault damage and seismic behavior for the rough fault experiments the secondary faulting occurs along a network of faults oriented at high angles from the pre existing saw cut plane a behavior similar to several earthquake sequences that occurred along orthogonal faults

time and duration of lunar highlands crust formation abstract all radiometric systems indicate that crust mantle differentiation on the moon is dominated by events which occurred very early in lunar history however due to remaining uncertainties in model parameters and assumptions in the calculation of model ages it is not yet possible to resolve the precise times of occurrence of these events nor the duration of the formation of the highlands crust the strongest time constraints are offered by direct radiometric ages of samples formed during this earliest period two possible candidates for this material norites 78236 and 73255 27 45 were examined utilizing the sm nd radiometric system sm nd systematics of 78236 show post crystallization disturbance but indicate that this norite crystallized in the lunar crust about 4 34 ae ago data for 73255 27 45 define an isochron and yield a crystallization age of 4 23 0 05 ae the initial nd isotopic composition of both norites is within uncertainty of a chondritic reference reservoir at the time of their respective crystallizations the implications for lunar crustal formation persisting over a time span of close to 350 m y are discussed

continuous active source seismic monitoring of co2 injection in abrine aquifer continuous crosswell seismic monitoring of a small scale co2injection was accomplished with the development of a noveltubing deployed piezoelectric borehole source this piezotube source wasdeployed on the co2 injection tubing near the top of the saline aquiferreservoir at 1657 m depth and allowed acquisition of crosswellrecordings at 15 minute intervals during the multiday injection thechange in traveltime recorded at various depths in a nearby observationwell allowed hour by hour monitoring of the growing co2 plume via theinduced seismic velocity change traveltime changes of 0 2 to 1 0 ms upto 8 percent were observed with no change seen at control sensorsplaced above the reservoir the traveltime measurements indicate that theco2 plume reached the top of the reservoir sand before reaching theobservation well where regular fluid sampling was occuring during theinjection thus providing information about the in situ buoyancy ofco2

a new view of lunar ferroan anorthosites postmagma ocean petrogenesis 1 new melting experiments in the range of 0 1 mpa to 4 7 gpa provide the basis for calculations of polybaric crystallization which show that both a 300 km deep magma ocean mo enriched in refractory elements and a 600 km deep magma ocean with refractory element concentrations similar to the earth s upper mantle produce sufficient amounts of differentiated residual liquid capable of crystallizing the troctolitic noritic mineral assemblages that are prevalent in lunar ferroan anorthosites lfa however the both oceans become saturated with augite after 20 30 crystallization of the plagioclase saturated residuum and thereafter are no longer capable of producing noritic assemblages a second set of melting experiments reveals the existence of a previously unrecognized equilibrium augite liquid pigeonite plagioclase and a thermal minimum on the pigeonite plagioclase liquidus surface at 0 6 gpa these equilibria will produce melts of mafic cumulates with lower wo content than those from which the cumulates originally formed in a postmagma ocean environment of overturning mafic cumulates melt thus formed and entrained in a buoyant segregation of plagioclase would then form diapiric masses that would crystallize troctolitic noritic assemblages after intruding upward diapiric intrusions could also provide the local deformational environment needed to produce the apparently high 95 plagioclase modes of the lfa an unstable density profile in the cumulate pile following crystallization of most of the mo should provide the impetus for overturn and the heat for partially remelting mafic cumulates

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

ages and stratigraphy of mare basalts in oceanus procellarum mare nubium mare cognitum and mare insularum accurate estimates of mare basalt ages are necessary to place constraints on the duration and the flux of lunar volcanism as well as on the petrogenesis of lunar mare basalts and their relationship to the thermal evolution of the moon we performed new crater size frequency distribution measurements in order to investigate the stratigraphy of mare basalts in oceanus procellarum and related regions such as mare nubium mare cognitum and mare insularum we used high resolution clementine color data to define 86 spectrally homogeneous units within these basins which were then dated with crater counts on lunar orbiter iv images our crater size frequency distribution measurements define mineralogical and spectral surface units and offer significant improvements in accuracy over previous analyses our data show that volcanism in the investigated region was active over a long period of time from 3 93 to 1 2 b y a total of 2 7 b y volumetrically most of the basalts erupted in the late imbrian period between 3 3 and 3 7 b y and we see evidence that numerous units have been resurfaced during the eratosthenian period significantly less basalt was erupted depending on the absolute model ages that one can assign to the lunar chronostratigraphic systems five units might be of copernican age younger basalts are generally exposed in the center of the investigated area that is closer to the volcanic centers of the aristarchus plateau and marius hills older basalts occur preferentially along the northwestern margin of oceanus procellarum and in the southeastern regions of the studied area i e in mare cognitum and mare nubium combining the new data with our previously measured ages for basalts in mare imbrium serenitatis tranquillitatis humorum australe and humboldtianum we find that the period of active volcanism on the moon lasted 2 8 b y from 4 b y to 1 2 b y on the basis of the basalts dated so far which do not yet include the potentially young basalts of mare smythii e g schultz and spudis 1983 we conclude that oceanus procellarum not only exhibits the widest range of ages of all investigated basins but probably also is the location of some of the youngest basalts on the lunar surface

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

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 november 2017 mw 5 5 pohang earthquake a possible case of induced seismicity in south korea the moment magnitude mw 5 5 earthquake that struck south korea in november 2017 was one of the largest and most damaging events in that country over the past century its proximity to an enhanced geothermal system site where high pressure hydraulic injection had been performed during the previous 2 years raises the possibility that this earthquake was anthropogenic we have combined seismological and geodetic analyses to characterize the mainshock and its largest aftershocks constrain the geometry of this seismic sequence and shed light on its causal factors according to our analysis it seems plausible that the occurrence of this earthquake was influenced by the aforementioned industrial activities finally we found that the earthquake transferred static stress to larger nearby faults potentially increasing the seismic hazard in the area

seismic velocity changes associated with aseismic deformations of a fault stimulated by fluid injection fluid pressure plays an important role in the stability of tectonic faults however the in situ mechanical response of faults to fluid pressure variations is still poorly known to address this question we performed a fluid injection experiment in a fault zone in shales while monitoring fault movements at the injection source and seismic velocity variations from a near distance 10 meters monitoring network we measured and located the p and s wave velocity perturbations in and around the fault using repetitive active sources we observed that seismic velocity perturbations dramatically increase above 1 5 mpa of injection pressure this is consistent with an increase of fluid flow associated with an aseismic dilatant shearing of the fault as shown by numerical modelling we find that seismic velocity changes are sensitive both to fault opening by fluid invasion and effective stress variations and can be an efficient measurement for monitoring fluid driven aseismic deformations of faults

pore pressure migration during hydraulic stimulation due to permeability enhancement by low pressure subcritical fracture slip understanding the details of pressure migration during hydraulic stimulation is important for the design of an energy extraction system and reservoir management as well as for the mitigation of hazardous induced seismicity based on microseismic and regional stress information we estimated the pore pressure increase required to generate shear slip on an existing fracture during stimulation spatiotemporal analysis of pore pressure migration revealed that lower pore pressure migrates further and faster and that higher pore pressure migrates more slowly these phenomena can be explained by the relationship between fracture permeability and stress state criticality subcritical fractures experience shear slip following smaller increases of pore pressure and promote migration of pore pressure because of their enhanced permeability the difference in migration rates between lower and higher pore pressures suggests that the optimum wellhead pressure is the one that can stimulate relatively permeable fractures selectively its selection optimizes economic benefits and minimizes seismic risk

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

northwest africa 773 lunar mare breccia with a shallow formed olivine cumulate component inferred very low ti vlt heritage and a kreep connection abstract lunar meteorite northwest africa 773 herein referred to as nwa773 is a breccia composed predominantly of mafic volcanic components including a prominent igneous clast lithology the clast lithology is an olivine gabbro cumulate which on the basis of mineral and bulk compositions is a hypabyssal igneous rock related compositionally to volcanic components in the meteorite the olivine gabbro lithology exhibits cumulus textures and in our largest section of it includes some 48 olivine fo 64 to fo 70 average fo 67 27 pigeonite en 60 fs 24 wo 16 to en 67 fs 27 wo 6 11 augite en 50 fs 17 wo 33 to en 47 fs 13 wo 40 2 orthopyroxene en 70 fs 26 wo 4 11 plagioclase an 80 to an 94 and trace barian k feldspar ilmenite cr spinel re merrillite troilite and fe ni metal the mg fe ratios of the mafic silicates indicate equilibration of fe and mg however the silicates retain compositional variations in minor and trace elements that are consistent with intercumulus crystallization accessory mineralogy reflects crystallization of late stage residual melt both lithologies breccia and olivine cumulate of the meteorite have very low ti vlt major element compositions but with an unusual trace element signature compared to most lunar vlt volcanic compositions i e relative enrichment in light ree and large ion lithophile elements and greater depletion in eu than almost all other known lunar volcanic rocks the calculated composition of the melt that was in equilibrium with pyroxene and plagioclase of the cumulate lithology exhibits a kreep like ree pattern but at lower concentrations melt of a composition calculated to have been in equilibrium with the cumulate assemblage plus excess olivine yields a major element composition that is similar to known green volcanic glasses one volcanic glass type from apollo 14 in particular green glass b type 1 has a very low ti concentration and ree characteristics including extremely low eu concentration that make it a candidate parent melt for the olivine gabbro cumulate we infer an origin for the parent melt of nwa773 volcanic components by assimilation of a trace element rich partial or residual melt by a magnesian vlt magma deep in the lunar crust or in the mantle prior to transportation to the near surface accumulation of olivine and pyroxene in a shallow chamber eruption onto a volcanic surface and incorporation of components into local predominantly volcanic regolith prior to impact mixing of the volcanic terrain and related hypabyssal setting and ejection from the surface of the moon volcanic components such as these probably occur in the oceanus procellarum region near the site of origin of the green volcanic glasses found in the apollo 14 regolith

subdivision of the mg suite noritic rocks into mg gabbronorites and mg norites mg suite noritic rocks can be divided into two groups the mg gabbronorites and the mg norites the rocks of these groups differ in ratios of high ca pyroxene to total pyroxene compositions of pyroxene and plagioclase assemblages of ti nb and zr bearing minerals compositions of chrome spinel bulk rock ti sm and sc sm and measured ages the two groups probably crystallized from different types of parent magmas two hypotheses are offered for the differences in composition of the parent magmas one hypothesis ascribes the differences to compositional heterogeneity of the mantle source areas the other hypothesis ascribes the differences to variations in extent of partial melting of the mantle source regions and variations in extent of assimilation of the anorthosite and the highly differentiated residual liquid that were produced during the primordial lunar differentiation

ages of pristine noritic clasts from lunar breccias 15445 and 15455 abstract rb sr and sm nd isotopic studies were undertaken of two apollo 15 breccias 15445 and 15455 collected near spur crater on the apennine front seven pristine lithic clasts including four norites one anorthositic norite one troctolitic anorthosite and one spinel troctolite as well as a matrix sample of 15445 were analysed in addition a k ar age determination was also made for a plagioclase separate from a different anorthositic norite clast sm nd isotopic data of a pristine mg norite sample 15445 17 from the large white clast b of breccia 15445 yielded a precise internal isochron age of 4 46 0 07 ga for 147 sm 0 00654 ga 1 and an initial 143 nd 144 nd of 0 506058 0 000078 normalized to 148 nd 144 nd 0 24308 corresponding to an initial nd of 0 71 however sm nd isotopic results of another mg norite sample 15445 247 chipped from the same clast b about 1 cm away from 15445 17 yielded a significantly younger isochron age of 4 28 0 03 ga and a higher initial 143 nd 144 nd of 0 506246 0 000037 corresponding to an initial nd of 0 35 the sm nd data indicate that clast b is heterogeneous and contains at least two similar lithologies the rb sr isotopic systems were severely disturbed for both norites no useful isochron ages were observed the sm nd age and nd data for a 15 mg norites 15445 17 and 15445 247 a 17 mgnorite 78236 and two mg gabbronorites 73255 27 45 and 67667 are clearly resolved from each other four distinct parental magmas are required for derivation of these two major groups of mg suite noritic rocks the rb sr isotopic system of an anorthositic norite clast 15455 228 was slightly disturbed and isotopic data defined an isochron age of 4 59 0 13 ga for 87 rb 0 0139 ga 1 or 4 55 0 13 ga for 87 rb 0 01402 ga 1 the corresponding initial 87 sr 86 sr for the rock is 0 69899 0 00006 and is in satisfactory agreement with the luni value of nyquist et al 1974 the sm nd system is more disturbed than the rb sr system for this rock a tie line between whole rock samples and a pyroxene separate gives a sm nd age of 4 53 0 29 ga which is in nominal agreement with the rb sr isochron age the 39ar40ar age of a plagioclase separate of the rock has a weighted average value of 3 83 ga suggesting that the age was reset by the imbrium impact event probably the sm nd and rb sr systems of the clast were also partly reset by this event our age results indicate that some mg suite rocks are as old as ferroan anorthosite suite rocks furthermore age data of three major crustal rocks a mg suite a ferroan anorthosite suite and an evolved suite show that they all have variable ages these observations are difficult to explain by the magma ocean hypothesis alone petrogenetic processes such as production of mg suite rocks by serial magmatism walker 1983 of ferroan anorthosite suite rocks by multiple diapiric intrusions longhi and ashwal 1985 and evolved suite rocks by continuous magmatism meyer et al 1988 1989 probably all played a role these processes seem to be able to accommodate the wide ranges of ages and different origins observed for lunar crustal rocks

anorthosite assimilation and the origin of the mg fe related bimodality of pristine moon rocks support for the magmasphere hypothesis the lunar magma ocean or magmasphere hypothesis always controversial has required considerable revision in recent years the geochemical bimodality of pristine rocks epitomized by a diagram of na na ca versus mg ratio has led to proposals that a major fraction of the crust the mg rich suite formed as cumulates in numerous intrusions slightly younger than the magmasphere the precise origin of the bimodality has been elusive however one previous suggestion was that na was lost as a volatile before the ferroan anorthosites crystallized from the magmasphere whereas the mg rich intrusives retained all of their original na however this model cannot fully explain the bimodality because the same bimodal pattern is manifested by plotting eu al a ratio of involatile elements versus mg ratio assimilation probably helped to engender the bimodal patterns mass energy balance calculations indicate that large proportions of plagioclase were probably assimilated from the older magmasphere generated ferroan anorthosite crust by most of the mg rich intrusive melts the magmasphere in the absence of assimilation probably did not yield appreciable plagioclase the ferroan anorthosite crust until fractional crystallization of mafic silicates had diminished the melt mg ratio to about 0 42 however assuming identical initial melt composition an mg rich intrusion assimilating ferroan anorthosite and perhaps also a small proportion of urkreep would have reached plagioclase saturation at much higher mg about 0 66 the current version of the magmasphere hypothesis ferroan anorthosites magmasphere flotation cumulates mg rich rocks products of slightly younger localized intrusions appears to be the only plausible mechanism for engendering the mg fe related bimodality

a two dimensional coupled hydro mechanical finite discrete model considering porous media flow for simulating hydraulic fracturing abstract in this study we propose a new coupled hydro mechanical model considering porous media flow fdem flow for simulating hydraulic fracturing which makes full use of the unique topological connection between joint elements and solid elements in the combined finite discrete element method fdem the joint elements form the flow channel for fluid through which flow obeys the cubic law in addition viscous forces of fluid are taken into account in fdem flow a simple example with analytical solution is given to verify the model then the effects of fluid viscosity on hydraulic fracturing are investigated by this model the simulated results show that when a low viscosity fluid is injected the fluid infiltrates the fracture rapidly the initiation pressure is lower than the theoretical value and the breakdown pressure is slightly larger than the initiation pressure when high viscosity fluid is injected fluid infiltrate into the cracks very slowly the initiation pressure is close to the theoretical value and the breakdown pressure is much larger than the initiation pressure

isotopic analysis of basaltic fragments from lunar breccia 14321 chronology and petrogenesis of pre imbrium mare volcanism fragments of aluminous mare basalts high potassium hk aluminous mare basalts and very high potassium vhk mare basalts from apollo 14 breccias have been studied extensively rb sr isochron ages of aluminous mare basalts reported herein range from 3 96 to 4 24 and possibly up to 4 33 ga 87rb 0 0139 ga 1 they include and extend the range for the oldest mare basalts reported clasts of aluminous basalts from breccia 14321 though similar to each other in petrography mineralogy and major element composition have widely differing trace element abundances and are separable into chemical subgroups dickinsonet al 1985 shervaiset al 1985a rb sr and sm nd isotopic analysis of the grouped rocks of dicktnsonet al 1985 grouped rocks hereinafter and hk and vhk basalts shihet al 1986a b 1987 indicates that they differ with respect to time of crystallization t vs initial isotopic composition i parameters t i plots in a systematic way data for this set of rocks suggests radiogenic growth of 87sr86sr in the basalt source region corresponding to 87rb86sr 0 06 similar to the whole moon value earlier proposed nyquistet al 1977 tridymite ferrobasalt and olivine basalt from 14321 display parent daughter evolution distinct from the grouped rocks of dickinsonet al 1985 and the hk and vhk rocks and do not appear to be isotopically related to these rocks assimilation of kreep dickinsonet al 1985 does not appear to be a reasonable mechanism for forming the grouped basalts but assimilation of urkreep residuals binder 1985 or a granitic component shihet al 1986a b 1987 by more primitive magma are alternative possibilities for explaining their trace elemental and isotopic characteristics nd values for the three whole rocks that were analyzed are near 0 the value for an undifferentiated moon these rocks may be linked to the mg suite of highland rocks

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

beginning and end of lunar mare volcanism mare volcanism on the moon is commonly attributed to an important but relatively short lived epoch of internal heating after 3 900 myr bp but before about 2 500 myr bp refs 1 2 although some studies suggested that mare volcanism had started earlier3 5 than times indicated by dated lunar samples only recently have photogeological spectral and geochemical data6 8 documented the importance of a pre 4 000 myr bp epoch similarly early earth based geological mapping revealed a bright rayed crater lichtenberg superposed by mare units9 thereby indicating that mare volcanism must have extended to times significantly more recent than 3 100 myr bp lunar orbital photography confirmed this inferred strati graphical relationship10 but crater statistics indicated that the youngest units were at least twice the age of copernicus or between 1 700 and 2 000 myr bp refs 11 13 we present here the inferred distribution and style of the early phases of mare volcanism based on current evidence and conclude that certain regions of the moon underwent two distinct pulses of igneous activity we then examine crater statistics for the post lichtenberg mare unit and other selected units and conclude that mare volcanism extended to a time comparable with that of the copernicus impact or 1 myr bp these reassessments of the oldest and youngest maria provide new constraints on geophysical models of the internal thermal history of the moon

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

orthopyroxene as a recorder of lunar crust evolution an ion microprobe investigation of mg suite norites the lunar mg suite which includes dunites troctolites and norites could make up 20 30 of the moon s crust down to a depth of 60 km the remainder is largely anorthositic this report focuses on norites because we have found that the chemical characteristics of orthopyroxene are effective recorders of their parental melt compositions many of the samples representing the mg suite are small and unrepresentative in addition they are cumulates and thus are difficult to study by whole rock techniques therefore we decided to study these rocks by sims techniques to analyze a suite of trace elements in orthopyroxene the 12 norite samples were selected from a recent compilation by warren who attempted to select the best candidate samples from the standpoint of their pristine character our present database includes greater than 300 superior electromagnetic pulse emp analyses and greater than 50 scanning ion mass spectroscopy sims analyses for 8 rare earth elements ree zr y and sr the mg s for the parental melts calculated from mg s in orthopyroxene show that most melts have mg s in the range of 0 36 0 60 this compares with a range of mg s for lunar volcanic picritic glass beads of 0 4 0 68 therefore although the cumulate whole rock compositions of the mg suite can be extremely magnesian the calculated parental melts are not anomalously high in mg a chemical characteristic of the mg suite norites that is more difficult to explain is the high kreep content of the calculated parental melts the ree contents for the calculated norite parental melts have ree that match or exceed the high k kreep component of warren therefore mixing of a kreep component and a picritic melt cannot by itself explain the high estimated ree contents of the melts parental to norites advanced crystallization following kreep incorporation especially of plagiclase may also be required

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

long term observation of in situ seismic velocity and attenuation 1 we conducted 1 year continuous measurements of in situ compressional wave velocity and attenuation across a distance of 12 m in a vault at the coast of miura bay japan using a piezoelectric transducer as the ultrasonic wave source we detected for the first time periodic variations in both velocity and attenuation with amplitudes of 0 3 and of 4 respectively corresponding to the diurnal and semidiurnal lunar and solar tides these variations correlate well with the in situ areal strain change due to tidal ocean loading estimated from the strain records about 100 m away from the observational site relative minimum velocity and relative maximum attenuation occur at every time of relative maximum areal strain expansion suggesting that opening closure of pores or cracks of in situ rocks is responsible for these periodic variations the velocity variation shows a remarkable 14 day periodicity corresponding to the spring and neap tides arising from a nonlinear response of the velocity change to tidal strain change such that the velocity change depends on how slowly the tidal dilatation departs from its peak value

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

a concise compilation of petrologic information on possibly pristine nonmare moon rocks ansrn q cr to facilitate systematic study of the surviving compositionally pristine endogenously igneous rocks of the ancient lunar crust a compilation has been generated of all likely samples along with key information on the petrologic characteristics and chemistry of each sample the compilation includes 260 samples besides information related to the likelihood of each sample being truly pristine i e mainly its texture and siderophile element abundances information is compiled on mineral content listing major phases present as well as basic information on mineral compositions on size expressed as mass and on whether a reasonably comprehensive chemical analysis has been published the compilation also classifies the samples into seven categories of confidence in the pristine composition of the samples reflecting an estimation of the relative likelihood that each arguably pristine sample is in fact pristine for many purposes it is crucial to avoid inclusion of polymict rocks in a data base on petrologic diagrams such as a plot of average mg mg 100 x molar mg mg fe in a low ca mafic silicate vs average an content in plagioclase rocks in the top three categories of the confidence in pristine character appear distinctly bimodal in composition with roughly half belonging to a ferroan suite characterized by high an despite relatively low mg when samples of low to moderate pristine character are included the bimodality appears less distinct sample mass can also be important with a data base restricted to samples more massive than i g there is a clear distinction in feldspar content and bulk density between ferroan and nonferroan mgsuite rocks such that only the ferroan suite rocks are likely to have formed as flotation cumulates with a data base including smaller samples the same basic pattern is seen but only in a blurred form as the two rock types show considerable overlap in their modal feldspar contents

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

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

mapping pressurized volcanic fluids from induced crustal seismic velocity drops volcanic eruptions are caused by the release of pressure that has accumulated due to hot volcanic fluids at depth here we show that the extent of the regions affected by pressurized fluids can be imaged through the measurement of their response to transient stress perturbations we used records of seismic noise from the japanese hi net seismic network to measure the crustal seismic velocity changes below volcanic regions caused by the 2011 moment magnitude m w 9 0 tohoku oki earthquake we interpret coseismic crustal seismic velocity reductions as related to the mechanical weakening of the pressurized crust by the dynamic stress associated with the seismic waves we suggest therefore that mapping seismic velocity susceptibility to dynamic stress perturbations can be used for the imaging and characterization of volcanic systems

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

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

northwest africa 773 lunar origin and iron enrichment trend the meteorite northwest africa 773 nwa 773 is a lunar sample with implications for the evolution of mafic magmas on the moon a combination of key parameters including whole rock oxygen isotopic composition fe mn ratios in mafic silicates noble gas concentrations a kreep like rare earth element pattern and the presence of regolith agglutinate fragments indicate a lunar origin for nwa 773 partial maskelynitization of feldspar and occasional twinning of pyroxene are attributed to shock deformation terrestrial weathering has caused fracturing and precipitation of carich carbonates and sulfates in the fractures but lunar minerals appear fresh and unoxidized the meteorite is composed of two distinct lithologies a two pyroxene olivine gabbro with cumulate texture and a polymict fragmental regolith breccia the olivine gabbro is dominated by cumulate olivine with pigeonite augite and interstitial plagioclase feldspar the breccia consists of several types of clasts but is dominated by clasts from the gabbro and more feo rich derivatives variations in clast mineral assemblage and pyroxene mg mg fe and ti ti cr record an igneous fe enrichment trend that culminated in crystallization of fayalite silica hedenbergitebearing symplectites the fe enrichment trend and cumulate textures observed in nwa 773 are similar to features of terrestrial ponded lava flows and shallow level mafic intrusives indicating that nwa 773 may be from a layered mafic intrusion or a thick differentiated lava flow nwa 773 and several other mafic lunar meteorites have lree enriched patters distinct from apollo and luna mare basalts which tend to be lree depleted this is somewhat surprising in light of remote sensing data that indicates that the apollo and luna missions sampled a portion of the moon that was enriched in incompatible heatproducing elements

chronology and petrogenesis of the lunar highlands alkali suite cumulates from kreep basalt crystallization alkalic rocks from the highlands of the moon though relatively minor in volume yield important information in understanding the later development of the lunar crust however until recently little information has been available on the crystallization ages of samples from this diverse suite of rocks previous workers suggested a link between pristine kreep basalts and lunar quartz monzodiorites and granites through mineral and chemical modelling of all known pristine highlands alkali suite has rocks and radiogenic isotopic analyses of rather large has clasts from the apollo 14 landing site we explore further this potential link two clasts of alkalic affinity from the western highlands of the moon have been analyzed for their neodymium and strontium isotopic compositions an alkali anorthosite 14304 267 yields a smnd mineral isochron of 4108 53 ma mswd 0 06 and an end t of 1 0 0 2 two splits of the same alkali norite clast 14304 270 and 14304 272 yield similar end values when calculated for this age rbsr systematics for alkali anorthosite 14304 267 scatter about a line which yields an age of 4336 81 ma however the large mean square of weighted deviates mswd for this line 12 3 indicates that the age is suspect and that rbsr sytematics may have been disturbed the smnd age for 14304 267 in conjunction with upb zircon ages for two other highlands alkali suite has rocks from the apollo 14 landing site and one from the apollo 16 landing site indicate production of has rocks over an extended time period spanning at least 300 million years from 4 34 to 4 02 ga since the last dregs of the lunar magma ocean lmo likely crystallized prior to 4 3 ma all rocks from this alkalic period cannot represent direct remnants of the late lmo and may include material resulting from the remelting of evolved portions of the moon by upward moving basaltic melts from the deep lunar interior these contaminated melts may be represented by pristine kreep basalts from the apollo 15 landing site these kreep basalt melts could have crystallized within the crust to form cumulate gabbros norites anorthosites monzodiorites and possibly granites with the proportion of trapped kreepy residual liquid determining the large ion lithophile element enrichment of the rock generally the proportion of trapped kreepy liquid is small 2 15 the broad age range for the lunar has indicates that parental kreep basalt magmatism was not a unique event but was an important process possibly repeated several times throughout the first 600 to 700 million years of lunar history

chronology geochemistry and petrology of a ferroan noritic anorthosite clast from descartes breccia 67215 clues to the age origin structure and impact history of the lunar crust the petrology major and trace element geochemistry and nd ar sr isotopic compositions of a ferroan noritic anorthosite clast from lunar breccia 67215 have been studied in order to improve our understanding of the composition age structure and impact history of the lunar crust the clast designated 67215c has an unusually well preserved igneous texture mineral compositions are consistent with classification of 67215c as a member of the ferroan anorthositic suite of lunar highlands rocks but the texture and mineralogy show that it cooled more rapidly and at shallower depths than did more typical ferroan anorthosites fans incompatible trace element concentrations are enriched in 67215c relative to typical fans but diagnostic signatures such as ti sm sc sm plagiophile element ratios and the lack of zr hf and nb ta fractionation show that this cannot be due to the addition of kreep alternatively 67215c may contain a greater fraction of trapped liquid than is commonly present in lunar fans 147sm 143nd isotopic compositions of mineral separates from 67215c define an isochron age of 4 40 0 11 gyr with a near chondritic initial 143nd of 0 85 0 53 the 40ar 39ar composition of plagioclase from this clast records a post crystallization thermal event at 3 93 0 08 gyr with the greatest contribution to the uncertainty in this age deriving from a poorly constrained correction for lunar atmosphere 40ar rb sr isotopic compositions are disturbed probably by the same event recorded by the ar isotopic compositions trace element compositions of fans are consistent with crystallization from a moderately evolved magma ocean and do not support a highly depleted source composition such as that implied by the positive initial 143nd of the ferroan noritic anorthosite 62236 alternatively the nd isotopic systematics of lunar fans may have been subject to variable degrees of modification by impact metamorphism with the plagioclase fraction being more strongly affected than the mafic phases 147sm 143nd isotopic compositions of mafic fractions from the 4 ferroan noritic anorthosites for which isotopic data exist 60025 62236 67016c 67215c define an age of 4 46 0 04 gyr which may provide a robust estimate for the crystallization age of lunar ferroan anorthosites

the petrogenesis of impact basin melt rocks in lunar meteorite shisr 161 this study explores the petrogenesis of shisr 161 an immature lunar regolith breccia meteorite with low abundances of incompatible elements a feldspathic affinity and a significant magnesian component our approach was to identify all clasts 0 5 mm in size in a thin section characterize their mineral and melt components and reconstruct their bulk major and minor element compositions trace element concentrations in representative clasts of different textural and compositional types indicate that the clast inventory of shisr 161 is dominated by impact melts that include slowly cooled cumulate melt rocks with mafic magnesian mineral assemblages minor exotic components are incompatible element rich melt spherules and glass fragments and a gas associated spheroidal precipitate our hypothesis for the petrologic setting of shisr 161 is that the crystallized melt clasts originate from the upper 1 km of the melt sheet of a 300 to 500 km diameter lunar impact basin in the moon s feldspathic highlands this hypothesis is based on size requirements for cumulate impact melts and the incorporation of magnesian components that we interpret to be mantle derived the glassy melts likely formed during the excavation of the melt sheet assemblage by an impact that produced a 15 km diameter crater the assembly of shisr 161 occurred in a proximal ejecta deposit of this excavation event a later impact into this ejecta deposit then launched shisr 161 from the moon our geochemical modeling of remote sensing data combined with the petrographic and chemical characterization of shisr 161 reveals a preferred provenance on the moon s surface that is close to pre nectarian riemann fabry basin

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

pristine highland clasts in consortium breccia 14305 petrology and geochemistry the apollo 14 site continues to provide pristine non mare rocks that contrast sharply with those from apollo 16 the archetypical highland site we characterize six small 1 cm samples of pristine highland crust that occur as clasts in polymict lunar breccia 14305 one is an alkali anorthosite the others include troctolite norite and anorthosite of the mg suite the alkali anorthosite 400 is a plagioclase adcumulate with minor intercumulus augite cerian fluorapatite with lree contents 30 000 x chondrite occurs as an inclusion in plagioclase enstatite troctolite 358 and magnesian anorthosite 361 have trace element characteristics similar to eastern mg suite rocks highlighting the importance of local variations in geochemical systematics that are superimposed on moon wide longitudinal variations the highly fractionated trace element abundances and highly magnesian mineral compositions of olivine orthopyroxenite 389 suggest a new previously unknown magma type related to the mg suite this magma may have formed in equilibrium with garnet alkali anorthosites and magnesian anorthosites troctolites cannot be related to a single parent magma by fractional crystallization or by variable kreep assimilation these suites represent separate parent magmas each of which may have been modified by mixing with kreep

isotopic studies of ferroan anorthosite 62236 a young lunar crustal rock from a light rare earth element depleted source isotopic analyses of mineral fractions and whole rocks from the ferroan anorthosite 62236 yield a sm nd isochron with an age of 4 29 0 06 ga and an initial end143 value of 3 1 0 9 we have also measured end142 anomalies of 0 25 on two fractions of 62236 these values are higher than the value of 0 1 predicted if 62236 was derived from a chondritic source at 4 29 ga but are consistent with the positive initial end143 value the sm nd isotopic composition of 62236 has been modified by the capture of thermal neutrons such that the 147sm 144nd 143nd 144nd and 142nd 144nd ratios measured on the mineral fractions and whole rocks must be corrected the corrections do not significantly alter the sm nd isotopic results determined on 62236 despite the fact that the ar ar and rb sr isotopic systematics of 62236 have been reset by impact metamorphism at 3 93 0 04 ga the sm nd systematics appear to have been unaffected the sm nd isotopic systematics of 62236 provide several constrains on models of lunar crustal differentiation provided they have not been reset since crystallization first the relatively young age of 62236 as well as the old ages determined on several crustal plutonic rocks of the mg suite require multiple sources of magmas on the moon very early in its history second positive end143 values determined on all analyzed ferroan anorthosites suggest that they were derived from sources depleted in light rare earth elements and third models based on initial end143 and present day end142 values suggest that the source of 62236 was depleted in light rare earth elements at 4 46 ga in order to reconcile these observations with the lunar magma ocean model 1 the magma ocean must have existed for a very short period of time and may have had a sub chondritic nd sm ratio and 2 the youngest ferroan anorthosites such as 62236 cannot be cumulates from the magma ocean but must form by other processes

stratigraphy of the lunar highland crust depths of burial of lunar samples from cooling rate studies current models of lunar crustal stratigraphy are based primarily on models of impact cratering coupled with what is known about the distribution of rock types in the ejecta blankets associated with the large multiring basins these models postulate an upper crust rich in the ferroan anorthosite component underlain by a more mafic noritic lower crust spudis 1993 we attempted to test these models by determining the depth at which various lunar plutonic rocks formed despite intense brecciation and shock many lunar highland samples retain vestiges of a prior magmatic history for example pyroxene samples preserve a record of their thermal history in such phenomena as cation ordering and exsolution textures by computer simulation of the growth of exsolution lamellae in augite and pigeonite we deduced cooling rates and from these estimated a depth of burial on the basis of a simple model for the thermal evolution of the lunar crust despite the fairly large uncertainties in the calculations it is clear that the ferroan anorthosite samples we studied formed at a depth between 10 and 20 km whereas some members of highland magnesian and alkali suites formed as cumulates in magma chambers intruded into the uppermost layers of the crust as yet there is no evidence to indicate that crystalline rocks from the lower half of the lunar crust are present in the samples returned by the apollo missions most samples derived from the lower crust appear to be impact melts oflow k fra mauro noritic composition

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

core formation in the earth and moon new experimental constraints from v cr and mn abstract the mantles of the earth and moon are similarly depleted in v cr and mn relative to the concentrations of these elements in chondritic meteorites the similar depletions have been used as evidence that the moon inherited its mantle from the earth after a giant impact event we have conducted liquid metal liquid silicate partitioning experiments for v cr and mn from 3 to 14 gpa and 1723 to 2573 k to understand the behavior of these elements during planetary core formation our experiments have included systematic studies of the effects of temperature silicate composition metallic s content metallic c content and pressure temperature has a significant effect on the partitioning of v cr mn with all three elements increasing their partitioning into the metallic liquid with increasing temperature in contrast pressure is not observed to affect the partitioning behavior the experimental results show the partitioning of cr and mn are hardly dependent on the silicate composition whereas v partitions more strongly into depolymerized silicate melts the addition of either s or c to the metallic liquid causes increased metal silicate partition coefficients for all three elements parameterizing and applying the experimental data we find that the earth s mantle depletions of v cr and possibly mn can be explained by core formation in a high temperature magma ocean under oxygen fugacity conditions about two log units below the iron wustite buffer though the depletion of mn may be due entirely to its volatility however more oxidizing conditions proposed in recent core formation models for the earth cannot account for any of the depletions additionally because we observe no pressure effect on the partitioning behavior the data do not require the mantle of the moon to be derived from the earth s mantle although this is not ruled out all that is required to create depletions of v cr and mn in a mantle is a planetary body that is hot enough and reducing enough during its core formation such conditions could have existed on the moon forming impactor