nominally hydrous magmatism on the moon for the past 40 years the moon has been described as nearly devoid of indigenous water however evidence for water both on the lunar surface and within the lunar interior have recently emerged calling into question this long standing lunar dogma in the present study hydroxyl as well as fluoride and chloride was analyzed by secondary ion mass spectrometry in apatite ca5 po4 3 f cl oh from three different lunar samples in order to obtain quantitative constraints on the abundance of water in the lunar interior this work confirms that hundreds to thousands of ppm water of the structural form hydroxyl is present in apatite from the moon moreover two of the studied samples likely had water preserved from magmatic processes which would qualify the water as being indigenous to the moon the presence of hydroxyl in apatite from a number of different types of lunar rocks indicates that water may be ubiquitous within the lunar interior potentially as early as the time of lunar formation the water contents analyzed for the lunar apatite indicate minimum water contents of their lunar source region to range from 64 ppb to 5 ppm h2o this lower limit range of water contents is at least two orders of magnitude greater than the previously reported value for the bulk moon and the actual source region water contents could be significantly higher

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

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

lunar apatite with terrestrial volatile abundances the moon is thought to be depleted relative to the earth in volatile elements such as h cl and the alkalis nevertheless evidence for lunar explosive volcanism has been used to infer that some lunar magmas exsolved a co rich and co 2 rich vapour phase before or during eruption although there is also evidence for other volatile species on glass spherules until recently there had been no unambiguous reports of indigenous h in lunar rocks here we report quantitative ion microprobe measurements of late stage apatite from lunar basalt 14053 that document concentrations of h cl and s that are indistinguishable from apatites in common terrestrial igneous rocks these volatile contents could reflect post magmatic metamorphic volatile addition or growth from a late stage interstitial sulphide saturated melt that contained 1 600 parts per million h 2o and 3 500 parts per million cl both metamorphic and igneous models of apatite formation suggest a volatile inventory for at least some lunar materials that is similar to comparable terrestrial materials one possible implication is that portions of the lunar mantle or crust are more volatile rich than previously thought

effects of internal structure and local stresses on fracture propagation deflection and arrest in fault zones the way that faults transport crustal fluids is important in many fields of earth sciences such as petroleum geology geothermal research volcanology seismology and hydrogeology for understanding the permeability evolution and maintenance in a fault zone its internal structure and associated local stresses and mechanical properties must be known this follows because the permeability is primarily related to fracture propagation and their linking up into interconnected clusters in the fault zone here we show that a fault zone can be regarded as an elastic inclusion with mechanical properties that differ from those of the host rock as a consequence the fault zone modifies the associated regional stress field and develops its own local stress field which normally differs significantly both as regard magnitude and orientation of the principal stresses from the regional field the local stress field together with fault rock heterogeneities and interfaces discontinuities fractures contacts determine fracture propagation deflection along discontinuities interfaces and arrest in the fault zone and thereby its permeability development we provide new data on the internal structure of fault zones in particular the fracture frequency in the damage zone as a function of distance from the fault core new numerical models show that the local stress field inside a fault zone modelled as an inclusion differ significantly from those of the host rock both as regards the magnitude and the directions of the principal stresses also when the mechanical layering of the damage zone due to variation in its fracture frequency is considered the numerical models show abrupt changes in local stresses not only between the core and the damage zone but also within the damage zone itself abrupt changes in local stresses within the fault zone generate barriers to fracture propagation and contribute to fracture deflection and or arrest also analytical solutions of the effects of material toughness the critical energy release rate of layers and their interfaces show that propagating fractures commonly become deflected into and often arrested at the interfaces generally fractures propagating from a compliant soft layer towards a stiffer one tend to become deflected and arrested at the contact between the layers whereas fractures propagating from a stiff layer towards a softer one tend to penetrate the contact thus it is normally easier for fractures to propagate from the host rock into the damage zone than vice versa similarly it is easier for fractures to propagate from the outer stiffer parts of the damage zone to the inner softer parts and from the stiff host rock to the outer damage zone than in the opposite directions these conclusions contribute to increased understanding as to how fractures propagate and become arrested within fault zones and how the fault zone thickness is confined at any particular time during its evolution

a seismic model of the lunar mantle and constraints on temperature and mineralogy abstract we determine seismic profiles of the moon s interior using travel times obtained from a re analysis of the apollo data due to the limited number of quakes and stations travel times errors were determined and used in the inversions our model has a mean crustal thickness of about 30 km in the region of the apollo network with a 10 km zone of brecciation below the crust mean values of seismic velocities in the upper mantle are rather well constrained and are in the range 7 6 7 8 and 4 35 4 45 km s 1 for p and s waves respectively velocity variations in the middle mantle are less well defined in the zone of deep moonquakes below 740 km depth velocities increase slightly to 8 15 0 23 and 4 5 0 10 km s 1 for p and s waves respectively we analyse the seismic profile in term of mineralogy and temperature constraints our preferred models are a pyroxenite model for the upper mantle and a magnesian rich model for the lower mantle with increasing mg with depth we find temperatures of about 1100 k elastic lithosphere limit and 1500 k thermal lithosphere limit for radii of about 1400 and 1000 km respectively and show that the lunar mantle is probably depleted in th and u by at least 70 compared to an earth reference value of 25 7 ppb u for a crustal thickness of 40 km with a mean 1010 ppb th concentration we then find bulk th and u abundances comparable to and possibly lower than currently accepted terrestrial values

the role of magma buoyancy on the eruption of lunar basalts it has long been recognized that mare basalts on the moon are preferentially located both on the earth facing hemisphere and within large impact basins a popular model that accounts for this observation assumes that these magmas were denser than the lunar crust that they accumulated at the crust mantle interface and that eruptions occurred only when this magma chamber became overpressurized in this paper we re evaluate this model and argue that it is not consistent with the available data nor with models of dike propagation as an alternative hypothesis we propose that magma buoyancy is the predominant factor that determines whether mare basalts erupt at the surface or form crustal intrusions instead we have computed the densities of mare basaltic magmas and find that some are in fact less dense than the moon s upper anorthositic crust based on the widely accepted view that the lunar crust becomes more mafic with depth we also show that all mare basaltic magmas should be less dense than the lower portion of the crust thus if the upper anorthositic crust was regionally removed by an impact event then any mare basaltic magma could have risen to the surface there based on buoyancy considerations alone in support of this model we note that mare basalts are indeed found wherever geophysical crustal thickness models predict the upper crust to be absent furthermore many of the basalts that erupted within the anorthositic highlands are predicted to be less dense than the underlying crust based on remote sensing data the high titanium flows within oceanus procellarum are somewhat problematical to our model in that an anorthositic crust is predicted to be present beneath them using results from recent lunar thermal models we suggest that these magmas may have overcome their negative buoyancy in the crust by possessing superliquidus temperatures if magma buoyancy does indeed control whether or not a basaltic eruption will occur then this implies that the quantity of magma produced beneath the south pole aitken basin was about 10 times less than that of the nearside fl 2001 elsevier science b v all rights reserved

distribution characteristics and controlling factors of vertical joint spacing in sand mud interbedded strata abstract nearly 3 600 vertical joints were measured in sand mud interbedded rock masses from 30 outcrops in the yan an area china information such as joint spacing joint aperture and the thickness of sandstone formations was obtained results show that the vertical joints are well developed in the study areas and the fracture spacing tolayer thickness ratio s t can reach 0 79 the joint spacing has a strong positive linear relationship with the thickness of the sandstone layer and presents a lognormal distribution in each sandstone layer however the morphology of the lognormal distribution is related to the degree of joint development the higher the degree of joint development the smaller skewness of the joint spacing distribution in addition although the value of s t for saturate joint is generally 0 8 1 2 the vertical joints may reach saturation at greater s t by penetrating multiple layers of sandstone when the intervening soft layer is thin

spacing and distribution of bed perpendicular joints throughout layered shallow marine carbonates granada basin southern spain abstract this contribution focuses on the controls exerted by sedimentological petrographic and mechanical rock properties on the distribution of bed perpendicular joints throughout layered carbonates the study was conducted on tortonian shallow marine skeletal grainstones and rudstones cropping out in the granada basin southern spain the results of combined field and laboratory analyses are consistent with the rock grain size of the studied carbonates exerting a key control on distribution of the bed perpendicular joints a positive correlation between joint spacing and mechanical unit thickness is computed for the grainstones whereas joints are almost absent in rudstones the rock grain size affected the diagenetic processes such as cementation and dissolution and therefore the resulting porosity and uniaxial compressive strength ucs values quantitative data show that higher ucs values are commonly associated with greater calcite amounts lower values of porosity and finer grain sizes and hence denser bed perpendicular joint sets in conclusion this study documents that it is possible to infer the density of bed perpendicular joints in layered carbonates based on the sedimentological petrographic and mechanical parameters considering the impact that this type of joints has on subsurface fluid flow the acquired knowledge can help the management of geofluids as well as the overall prediction of carbonate reservoir quality

a permeability model for naturally fractured carbonate reservoirs abstract based on a detailed structural study performed on a reservoir surface analogue a fracture permeability model for carbonate reservoirs is proposed this involves four hierarchical systems each one assumed to convey fluids exclusively to that of immediately higher order new basic equations are then provided simulating hydrodynamic reservoir response the large scale first order structures consist of faults to which high permeability structures damage zones are associated at the meter scale stratabound joint systems together with bedding joints bounding the mechanical layers form a connected network transporting fluids to the fault system at a lower scale down to crystal size non stratabound joints constitute a pervasive and capillary fracture network which conveys fluids within the rock mass the non fractured host rock constitutes the lower permeability system at the crystal scale as no published works include an effective integration of detailed structural and numerical models the present study aims at covering a significant gap in the literature also providing appropriate theoretical basis for subsequent studies on fracture network modeling and reservoir simulation besides its application in the field of reservoir development and management the illustrated model may also be useful in environmental studies involving ground fluids such as e g in the field of special toxic nuclear waste management

direct measurement of hydroxyl in the lunar regolith and the origin of lunar surface water remote sensing discoveries of hydroxyl and water on the lunar surface have reshaped our view of the distribution of water and related compounds on airless bodies such as the moon the origin of this surface water is unclear but it has been suggested that hydroxyl in the lunar regolith can result from the implantation of hydrogen ions by the solar wind here we present fourier transform infrared spectroscopy and secondary ion mass spectrometry analyses of apollo samples that reveal the presence of significant amounts of hydroxyl in glasses formed in the lunar regolith by micrometeorite impacts hydrogen isotope compositions of these glasses suggest that some of the observed hydroxyl is derived from solar wind sources our findings imply that ice in polar cold traps could contain hydrogen atoms ultimately derived from the solar wind as predicted by early theoretical models of water stability on the lunar surface we suggest that a similar mechanism may contribute to hydroxyl on the surfaces of other airless terrestrial bodies where the solar wind directly interacts with the surface such as mercury and the asteroid 4 vesta

the magma ocean concept and lunar evolution the model of lunar evolution in which the anorthositic plagioclase rich oldest crust of the moon is formed over a period of 300 myr or less by crystallization as it floats on a global ocean of magma tens or hundreds of km thick is examined in a review of petrological and theoretical studies consideration is given to the classification of lunar rocks the evidence for primordial deep global differentiation constraints on the depth of the molten zone the effects of pressure on mineral stability relationships mainly liquid vs mainly magmifer ocean models and the evidence for multiple ancient differentiation episodes a synthesis of the model of primordial differentiation and its aftereffects is presented and the generalization of the model to the earth and to mars mercury venus and the asteroids is discussed

mechanism for joint saturation in mechanically layered rocks an example from southern israel abstract over 700 joint spacings were measured along a 190 m scanline within a single limestone bed of the turonian gerofit formation southern israel by investigating joints belonging to a single systematic set confined to a bed of uniform thickness one can factor out the major influences of bed thickness lithology and mechanical properties on joint set development joint spacing distributions and fracture spacing ratios fsr vary dramatically along the length of the scanline and correlate directly with throughgoing fracture zones belonging to the same tectonic stress regime regions cross cut by fracture zones display narrower median joint spacings fsr of 1 3 and unimodal joint spacing distributions where fracture zones are absent joint spacings have wider medians fsr of 0 8 and multimodal distributions because fracture zones most likely represent areas of high strain and laboratory experiments demonstrate a systematic decrease in fracture spacing with increasing strain regions of the bed cross cut by fracture zones are likely at a more advanced stage of joint set development and hence closer to saturation than other regions joint saturation in the gerofit formation may be achieved by a shift in scale from single layer to multi layer jointing as the development of throughgoing joints prevents the formation of additional bedding confined joints

mineralogy of the last lunar basalts results from clementine the last major phase of lunar volcanism produced extensive high titanium mare deposits on the western nearside which remain unsampled by landing missions the visible and near infrared reflectance properties of these basalts are examined using clementine multispectral images to better constrain their mineralogy a much stronger 1 m ferrous absorption was observed for the western high titanium basalts than within earlier maria suggesting that these last major mare eruptions also may have been the most iron rich these western basalts also have a distinctly long wavelength 1 m ferrous absorption which was found to be similar for both surface soils and materials excavated from depth supporting the interpretation of abundant olivine within these deposits spectral variation along flows within the imbrium basin also suggests variations in ilmenite content along previously mapped lava flows as well as increasing olivine content within subsequent eruptions

constraints on volatile concentrations of pre eruptive lunar magma abstract until recently the moon had long been thought to be depleted of volatiles such as h 2 o s co x and cl 2 researchers have recently measured volatile concentrations in the minerals glasses and inclusions of lunar samples and the results show that lunar rocks contain volatiles that are more similar to terrestrial materials than was previously thought mare basalts are located on the earth facing hemisphere in large impact basins and they are not representative of the feldspathic highlands thus it is likely that the density of lunar mafic magma exceeds that of the highland rocks based on buoyancy alone according to this observational fact we calculate the density of mare basalt to give a constraint for the maximum amount of water mare basalt can contain because water can effectively decrease the density of mare magma our result shows that water contained in the pre eruptive magma could not have been more than 1000 ppm otherwise the density of very low ti basaltic magma would be less than that of the highland rocks additionally if magma contains other species of volatiles such as c o s f or cl 2 the water in the pre eruptive magma would have to be much less than 1000 ppm because volatiles such as co 2 can effectively decrease the solubility of water in silicate melts based on these calculations on densities and a comparison with water in morb we conclude that the moon s water is not as great as has been recently suggested

origin of basalt fire fountain eruptions on earth versus the moon fire fountain eruptions of basaltic magma occur on earth at centers such as kilauea hawaii and deposits from apparently similar eruptions have been found on the lunar surface the driving force for terrestrial fire fountain eruptions is the exsolution of dissolved co 2 based on gases dissolved in melt inclusions trapped in olivine phenocrysts and the relatively high oxidation state of these magmas gases released at the vent show that so 2 and eventually h 2 o are partitioned into the co 2 rich gas adding to the gas volume in contrast analytical and experimental studies of lunar samples indicate that the gas phase responsible for driving the lunar eruptions was co rich and produced by the oxidation of c graphite carried in the slowly ascending low f o 2 basalt the graphite oxidation occurs when the pressure in the ascending lunar magma reaches that of the graphite gas reaction surface 40 1 mpa or 8 km depth for the apollo 17 orange glass magma as graphite is oxidized some feo is reduced potentially forming a fe rich metal phase and fe rich metal spherules are present in beads in lunar glass deposits other gas species such as s cl and f partitioned variously into co rich lunar volcanic gas and appear in surface coatings on the glass spherules modeling of the magma flow from 8 km depth to the lunar surface shows that the gas bubble volume fraction assuming initial c at 50 500 ppm levels ranges from 0 5 to 0 8 at the surface the exit velocity ranges from 15 to 35 m s and the low viscosity magma fragments only as it erupts at the lunar surface

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

water hydrogen in the lunar mantle results from petrology and magma ocean modeling abstract measurements of hydroxyl or water in lunar materials are being used to suggest that melting source regions within the moon contained tens to hundreds of ppm water the compositions of magmatic source regions in the moon can be calculated using magma ocean fractional solidification models given an initial bulk composition our magma ocean models demonstrate that to make a source region with 10 to 200 ppm water the bulk magma ocean must contain 100 to 1000 ppm water or more and in a 1000 km deep lunar magma ocean 1000 ppm water is equivalent to 5 of an earth ocean by weight as solidification of the magma ocean continues water and other incompatible elements are progressively enriched in the evolving liquids the final kreep like liquids would contain the greatest fraction of water we suggest that a bulk magma ocean with over 100 ppm water is prohibited by constraints on these kreep like final magma ocean liquids and by the thermodynamic equilibrium requirement with metallic iron in mare basalts we conclude that bulk lunar interior water contents must be at the low end of the range posited by recent observations

ages of mare basalts on the lunar nearside the chronology of lunar volcanism is based on radiometric ages determined from apollo and luna landing site samples regional stratigraphic relationships and crater degradation and size frequency distribution data for units largely defined prior to the end of the apollo program here we report on new crater size frequency distribution data for 139 spectrally and morphologically defined basalt units which are exposed in six nearside impact basins australe tranquillitatis humboldtianum humorum serenitatis and imbrium crater size frequency distribution measurements are a statistically robust and accurate method to derive absolute model ages of unsampled regions of the moon compared to crater degradation ages crater size frequency ages performed on spectrally defined units offer significant improvements in accuracy our investigation showed that 1 in the investigated basins lunar volcanism was active for at least 1 5 2 0 b y starting at about 3 9 4 0 b y and ceasing at 2 0 b y 2 most basalts erupted during the late imbrian period at about 3 6 3 8 b y 3 significantly fewer basalts were emplaced during the eratosthenian period 4 basalts of copernican age were not found in any of the investigated basins 5 lunar basin filling volcanism probably started within 100 m y after the formation of the individual basins we also assessed the relationship between impact basin age and the history of mare basalt emplacement in these basins we found that 1 in all pre nectarian basins australe and tranquillitatis as well as in the humboldtianum basin which is of nectarian age the distribution of surface ages is clearly dominated by only a single peak in the number of erupted units at 3 6 3 8 b y 2 in the younger basins humorum serenitatis and imbrium a second peak at 3 3 3 5 b y is observed 3 basalt eruptions younger than 2 6 b y occur only intermittently and 4 in the youngest basins serenitatis and imbrium we see an extended period of active basin filling volcanism 1 5 1 6 b y which is 500 m y longer than in the australe and humorum and even 1 0 b y longer than in tranquillitatis and humboldtianum

petrogenesis of mare basalts a record of lunar volcanism returned rock and soil samples from our nearest planetary neighbor have provided the basis for much of our understanding of the origin and evolution of the moon of particular importance are the mare basalts which have revealed considerable information about lunar volcanism and the nature of the mantle as well as post magma generation processes this paper is a critical review of the petrogenetic models for the generation of mare basalts formulated over the last twenty years we have used all available mare basalt analyses to define a six fold classification scheme using tio2 contents as the primary division i e 1 wt very low ti or vlt 1 6 wt low ti 6 wt high ti a secondary division is made using al2o3 contents i e 11 wt low al 11 wt high al and a tertiary division is defined using k contents i e 2000 ppm low k 2000 ppm high k such divisions and subdivisions yield a classification containing twelve categories of which six are accounted for by the existing apollo and luna collections therefore we present our discussions in the form of six mare basalt rock types 1 1 high ti low al low k referred to as high ti low k 2 2 high ti low al high k referred to as high ti high k 3 3 low ti low al low k referred to as low ti 4 4 low ti high al low k referred to as high alumina 5 5 low ti high al high k referred to as vhk 6 6 vlt low al low k basalts referred to as vlt a variety of post magma generation processes have been invoked such as fractional crystallization either alone or combined with wallrock assimilation to explain the compositional ranges of the various mare basalt suites in order to evaluate these proposed petrogenetic processes this review is by rock type and is non site specific but for each rock type reference to particular lunar sample return missions is brought forth this permits a comparison of similarities and differences of broadly similar rock types correlated with geography on the moon which in turn allows a more thorough petrogenetic evaluation high ti mare basalts i e high ti low al low k are found at apollo 11 and apollo 17 sites however the a 11 basalts contain lower tio2 abundances a considerably larger range in trace element contents and the only occurrence of high ti high k mare basalts fractional crystallization and source heterogeneity within each site are the keys to understanding the petrogenesis of the high ti basalts low ti basalts including both low al k and high al k varieties are found at apollo 12 14 and 15 and luna 16 sites the low ti basalts exhibit a wide range of major and trace element compositions and require source heterogeneity fractional crystallization and some assimilation the high alumina mare basalts i e low ti high al low k are found at apollo 14 and luna 16 sites and exhibit a wide range of major and trace element compositions however in these examples source heterogeneity is not a major factor indeed fractional crystallization coupled with kreep assimilation particularly for the apollo 14 variants can explain the compositional ranges of these high alumina basalts the vhk mare basalts i e low ti high al high k have been sampled only at the apollo 14 locale and are products of a parental highalumina magma assimilating lunar granite very low ti vlt mare basalts i e vlt low al low k are found at apollo 17 and luna 24 sites fractional crystallization has had a major influence upon the range in vlt compositions but luna 24 vlt basalts have been derived from a source slightly different in composition from that for apollo 17 vlt varieties for example the luna 24 vlt basalts generally exhibit positive eu anomalies a unique property for mare basalts which almost always have negative eu anomalies the concept of a lunar magma ocean lmo is generally accepted and source modelling of all basalts invokes a mafic lmo cumulate source this is the only unifying model for mare basalt petrogenesis but the semantics and logistics of it are and will be debated for many years for example major convective overturn of the lmo appears plausible but whether this occurred on a local or planet wide scale to produce source heterogeneity remains to be determined

model for the origin ascent and eruption of lunar picritic magmas a model for the origin ascent and eruption of the lunar a17 orange glass magma has been constructed using petrological constraints from gas solubility experiments and from analyses of the lunar sample 74220 to better determine the nature and origin of this unique explosive eruption three stages of the eruption have been identified stage 1 of the eruption model extends from 550 km the a17 orange glass magma source region based on phase equilibria studies to 50 km depth in the moon stage 2 extends from 50 km to 500 m where a c o h s gas phase formed and grew in volume based on melt inclusion analyses and measurements the volume of the gas phase at 500 m depth below the surface is calculated to be 7 to 15 vol of the magma closed system using the minimum and maximum estimates of co h2o and s loss from the melt in stage 3 depths shallower than 450 m the rising magma exsolved an additional 800 900 ppm h2o and 300 ppm s increasing the moles in the gas by a factor of 3 to 4 the closed system gas phase is calculated to reach 70 vol at 130 m depth enough to fragment the magma and form pyroclastic beads however fragmentation bead formation is interpreted to have occurred at depths ranging from 600 to 300 m below the lunar surface based on the pressure necessary to explain the c content of the orange glass beads the gas volume 70 required to fragment the ascending magma at this depth is a factor of 5 greater than the volume determined for closed system degassing of an orange glass magma at 500 m strongly implying that the gas was produced by open system degassing as the magma ascended from greater depths formation of the dike carrying the magma up from the 550 km deep source is considered to occur by a crack propagation mechanism wilson and head 2003 2017 the rapid dike propagation process facilitates gas collection by open system degassing in the upper part of the dike this is necessary to achieve the gas volumes required for magma fragmentation at 600 m depths and the magma ascent velocities to explain the wide areal distribution of the bead deposit the explosive nature of the picritic orange glass eruption and the homogeneity of the bead compositions are consistent with this gas assisted eruption scenario as is the evidence of a fe metal forming reduction event during stage 2 followed by a stage 3 oxidation event in the ascending magma

on the potential for lunar highlands mg suite extrusive volcanism and implications concerning crustal evolution abstract the lunar magnesian suite mg suite was produced during the earliest periods of magmatic activity on the moon based on the cumulate textures of the samples and a lack of evidence for mg suite extrusives in both the sample and remote sensing databases several petrogenetic models deduce a predominantly intrusive magmatic history for mg suite lithologies considering that 18 of the lunar surface is covered by mare basalt flows which are substantially higher in density than estimated mg suite magmas 2900 versus 2700 kg m3 the apparent absence of low density mg suite volcanics is surprising were mg suite magmas predominantly intrusive or have their extrusive equivalents been covered by subsequent impact ejecta and or later stage volcanism if mg suite magmas were predominantly intrusive what prevented these melts from erupting or if they are present as extrusives what regions of the moon are most likely to contain mg suite volcanic deposits this study investigates buoyancy driven ascent of mg suite parental melts and is motivated by recent measurements of crustal density from grail mg suite dunite troctolite and spinel anorthosite parental melts 2742 2699 and 2648 kg m3 respectively are considered all of which have much lower melt densities relative to mare basalts and picritic glasses mg suite parental melts are more dense than most of the crust and would not be expected to buoyantly erupt however about 10 of the lunar crust is greater in density than mg suite melts these areas are primarily within the nearside southern highlands and south pole aitken sp a basin mg suite extrusions and or shallow intrusions were possible within these regions assuming crustal density structure at 4 1 ga was similar to the present day crust we review evidence for mg suite activity within both the southern highlands and sp a and discuss the implications concerning crustal evolution as well as mg suite petrogenesis lower crustal densities measured by grail are consistent with the lack of observed mg suite extrusives if mg suite extrusive volcanism was prevented by the low density of the crust it would suggest the lunar crust was fractured shortly after solidification 4 3 ga the thermal and stress state of the lunar crust may have also inhibited mg suite extrusion

constraints on the preeruptive volatile concentrations in the columbia river flood basalts many of the columbia river flood basalts that erupted in the states of oregon washington and idaho during the miocene are remarkably iron rich 12 17 wt total feo and under volatile free conditions would have been too dense to erupt through continental crust their eruption through 20 km of sialic crust sets limits on their minimum preeruptive total volatile h2o co2 concentrations these limits are obtained by quantitatively comparing the average density of the overlying crustal column with the calculated effect of dissolved h2o or exsolved co2 on the density of various columbia river tholeiitic basalts as a function of depth minimum total volatile h2o co2 concentrations range to 4 wt and are therefore considerably higher than those found in tholeiitic basalts at oceanic islands like hawaii these conclusions are consistent with the strong enrichments in other incompatible elements e g k p ba observed in the columbia river flood basalts such high concentrations of h2o co2 would have had a marked effect on the solidus temperature of the source region which may explain the remarkably large individual flow volumes 103 km3 that characterize this flood basalt province

the lunar magma ocean reconciling the solidification process with lunar petrology and geochronology abstract the moon is thought to have originated with a magma ocean that produced a plagioclase flotation crust as solidification proceeded ages of anorthositic crust range over at least 200 million years the model for solidification presented here integrates chemical and physical constraints of lunar magma ocean solidification to determine 1 the final thickness of flotation crust generated by a fractionally solidifying magma ocean 2 the timescale of crystallization before plagioclase is a stable phase 3 the timescale of solidification after the formation of the plagioclase flotation crust and 4 the post overturn lunar mantle composition and structure we find that magma oceans of as much as 1000 km depth are consistent with creating an anorthositic crust 40 to 50 km in thickness solidification of the magma ocean prior to formation of the flotation crust may occur on the order of 1000 years and complete solidification would require additional ten to tens of millions of years reconciling these short model timescales with radiometric dates of crustal samples requires either a very late forming moon combined with finding older crustal ages to be incorrect or calling on tidal heating of the crust by the early earth to prolong solidification gravitationally driven overturn of cumulates during tidal heating provides a mechanism for creating the compositions and ages of the lunar mg suite of crustal rocks further we find that upon crystallization the moon likely began with an azimuthally heterogeneous gravitationally stable mantle after magma ocean cumulate overturn this result may help explain the experimentally determined origin of picritic glasses at similar depths but from different source materials

experimental determination of natural carbonate rock dissolution rates with a focus on temperature dependency abstract the denudation of carbonate rocks at landscape scale is controlled by factors like mineral composition temperature precipitation runoff fracture spacing and vegetation cover knowledge on carbonate denudation is important in order to understand landscape development and long term terrestrial marine carbon transport but there are few laboratory studies done on weathering rates of natural carbonate rocks under the low temperatures relevant for glacial interglacial periods to enhance the understanding of carbonate dissolution kinetics we studied low temperature dissolution reactions of various natural triassic carbonate rocks belonging to the lower muschelkalk in germany we conducted batch and flow through experiments investigating the direct correlation of dissolution rates with temperature and to establish whether the fine grained carbonate rocks micrite are more reactive than the coarser grained sparitic limestones by increasing the temperature from 5 to 26 c far from equilibrium dissolution rates of micritic and sparitic limestone samples increased from 2 42 10 07 to 10 88 10 07 and 4 19 10 07 to 7 74 10 07 mol m 2 s 1 respectively specific surface areas ssa of about 0 006 0 01 m 2 g the dissolution rates of dolomite rock samples varied only slightly from 1 06 10 07 to 2 02 10 07 mol m 2 s 1 ssa approximately 0 002 m 2 g in the temperature range 5 25 c at circum neutral ph the obtained apparent activation energies are in the range of earlier experiments done at higher temperatures but there is a distinct difference between the calcite in the micrite 51 kj mol and sparitic 20 22 kj mol lithologies indicating that the dissolution mechanisms are not the same using these activation energies in modelling of natural carbonate denudation we see that there is a clear effect of changing temperature but this is mostly through the increased solubility at lower temperatures and not through the increasing far from equilibrium dissolution rates at higher temperatures formation of fluid pathways by preferential dissolution of framework calcite crystals is suggested to form infiltration pathways and affect denudation rates the difference in crystal size between the micritic and sparitic limestones will affect the formation of such pathways larger crystals may create fewer and larger conduits and this is expected to be more important for the long term denudation than the differences in activation energies

hydrogen isotope ratios in lunar rocks indicate delivery of cometary water to the moon water has been found in many lunar rock samples but its sources are unknown isotopic analyses of apollo samples of lunar mare basalts and highlands rocks suggest that a significant volume of water was delivered to the moon by comets shortly after its formation by giant impact