vulnerability of coral reefs to bioerosion from land based sources of pollution ocean acidification oa the gradual decline in ocean ph and co32 caused by rising levels of atmospheric co2 poses a significant threat to coral reef ecosystems depressing rates of calcium carbonate caco3 production and enhancing rates of bioerosion and dissolution as ocean ph and co32 decline globally there is increasing emphasis on managing local stressors that can exacerbate the vulnerability of coral reefs to the effects of oa we show that sustained nutrient rich lower ph submarine groundwater discharging onto nearshore coral reefs off west maui lowers the ph of seawater and exposes corals to nitrate concentrations 50 times higher than ambient rates of coral calcification are substantially decreased and rates of bioerosion are orders of magnitude higher than those observed in coral cores collected in the pacific under equivalent low ph conditions but living in oligotrophic waters heavier coral nitrogen isotope 15n values pinpoint not only site specific eutrophication but also a sewage nitrogen source enriched in 15n our results show that eutrophication of reef seawater by land based sources of pollution can magnify the effects of oa through nutrient driven bioerosion these conditions could contribute to the collapse of coastal coral reef ecosystems sooner than current projections predict based only on ocean acidification

the fluid dynamics of a basaltic magma chamber replenished by influx of hot dense ultrabasic magma this paper describes a fluid dynamical investigation of the influx of hot dense ultrabasic magma into a reservoir containing lighter fractionated basaltic magma this situation is compared with that which develops when hot salty water is introduced under cold fresh water theoretical and empirical models for salt water systems are adapted to develop a model for magmatic systems a feature of the model is that the ultrabasic melt does not immediately mix with the basalt but spreads out over the floor of the chamber forming an independent layer a non turbulent interface forms between this layer and the overlying magma layer across which heat and mass are transferred by the process of molecular diffusion both layers convect vigorously as heat is transferred to the upper layer at a rate which greatly exceeds the heat lost to the surrounding country rock the convection continues until the two layers have almost the same temperature the compositions of the layers remain distinct due to the low diffusivity of mass compared to heat the temperatures of the layers as functions of time and their cooling rate depend on their viscosities their thermal properties the density difference between the layers and their thicknesses for a layer of ultrabasic melt 18 mgo a few tens of metres thick at the base of a basaltic 10 mgo magma chamber a few kilometres thick the temperature of the layers will become nearly identical over a period of between a few months and a few years during this time the turbulent convective velocities in the ultrabasic layer are far larger than the settling velocity of olivines which crystallise within the layer during cooling olivines only settle after the two layers have nearly reached thermal equilibrium at this stage residual basaltic melt segregates as the olivines sediment in the lower layer depending on its density the released basalt can either mix convectively with the overlying basalt layer or can continue as a separate layer the model provides an explanation for large scale cyclic layering in basic and ultrabasic intrusions the model also suggests reasons for the restriction of erupted basaltic liquids to compositions with mgo 10 and the formation of some quench textures in layered igneous rocks

micro computed tomography applications for high resolution skeletal density determinations an example using annually banded crustose coralline algae warming and acidification of the world s oceans are expected to have widespread consequences for marine biodiversity and ecosystem functioning however due to the relatively short record of instrumental observations one has to rely upon geochemical and physical proxy information stored in biomineralized shells and skeletons of calcareous marine organisms as in situ recorders of past environments of particular interest is the response of marine calcifiers to ocean acidification through the examination of structural growth characteristics here we demonstrate the application of micro computed tomography micro ct for three dimensional visualization and analysis of growth skeletal density and calcification in a slow growing annually banded crustose coralline alga clathromorphum nereostratum increment width 380 m x ray images and time series of skeletal density were generated at 20 m resolution and rebinned to 40 60 80 and 100 m for comparison in a sensitivity analysis calcification rates were subsequently calculated as the product of density and growth linear extension while both skeletal density and calcification rates do not significantly differ at varying spatial resolutions the latter being strongly influenced by growth rates clear visualization of micron scale growth features and the quantification of structural changes on subannual timescales requires higher scanning resolutions in the present study imaging at 20 m resolution reveals seasonal cycles in density that correspond to summer winter variations in skeletal structure observed using scanning electron microscopy sem micro ct is a fast non destructive and high resolution technique for structural and morphometric analyses of temporally banded paleoclimate archives particularly those that exhibit slow or compressed growth or micron scale structures

assessment of global and regional tectonic models for faulting in the ancient terrains of mars structural landforms within parts of the heavily cratered terrain of mars were studied in order to test various models of global fracturing landforms analyzed were scarps grabens simple ridges and channel wall scarps many of these landforms predate graben formation in tharsis very few structural landforms were found to be either radial to tharsis or normal to principal stress trajectories calculated for tharsis isostasy or flexural loading these results suggest either that the structures are locally derived or if they were produced by tharsis activity that the state of stress in tharsis was different from that which produced the classic graben systems association of narrow valley networks with subdued grabens in one portion of margaritifer sinus suggests that one episode of narrow valley formation coincided with flexural loading in tharsis crustal fracturing in oxia palus that predates outflow channel formation does not correlate with tharsis tectonism and may reflect fracturing by the proposed chryse multiring basin to the north in contrast to previous studies no evidence was found for either an orthogonal martian grid or conjugate sets of shear fractures it is concluded that mars probably did not experience significant tidal despinning calculations of thermal stress within a cooling early lithosphere performed for varying lithospheric thicknesses predict large scale tensile near surface failure many of the large ridges in memnonia that predate classical tharsis centered tectonism may reflect normal faulting generated in part by thermal stress

the moon re examined abstract recent geochemical and geophysical data from the moon enable a revision of earlier interpretations regarding lunar origin structure and bulk composition earth and moon show many similarities among their isotopic compositions but they have evolved in totally dissimilar ways probably related to the deficiency of water in the moon as well as the vast differences in size and internal pressure although some global geochemical trends such as volatile depletion based on k u ratios have been established current lunar samples come from differentiated regions making the establishment of a bulk composition more reliant on bulk geophysical properties or isotopic similarities although it remains unclear how the latter relate to whole moon composition the lack of fractionation effects among the refractory and super refractory elements indicates that the proto lunar material seems unlikely to have been vaporized while the depletion of volatile elements may place lower limits on proto lunar temperatures the apparent lack of geochemical evidence of an impacting body enables other possible impactors such as comets to be considered

new results and implications for lunar crustal iron distribution using sensor data fusion techniques remote measurements of the moon have provided iron maps and thus essential constraints for models of lunar crustal formation and mare basalt petrogenesis a bulk crustal iron map was produced for the equatorial region from apollo gamma ray agr spectrometer measurements and a global iron variation map from recent clementine spectral reflectance csr measurements both iron maps show bimodal distribution but have significantly different peak values and variations in this paper csr data have been recalibrated to pyroxene in lunar landing site soils a residual iron map is derived from the difference between agr bulk and recalibrated csr pyroxene iron abundances the most likely interpretation is that the residual represents ferrous iron in olivine this residual iron is anticorrelated to basin age with older basins containing less olivine suggesting segregation of basin basalt sources from a progressively fractionating underlying source region at the time of basin formation results presented here provide a quantitative basis for 1 establishing the relationship between direct geochemical gamma ray x ray and mineralogical near ir remote sensing data sets using sensor data fusion techniques to allow 2 simultaneous determination of elemental and mineralogical component distribution on remote targets and 3 meaningful interpretation of orbital and ground based spectral reflectance measurements when calibrated data from the lunar prospector mission are available mapping of bulk crustal iron and iron bearing soil components will be possible for the entire moon similar analyses for data from the near earth asteroid rendezvous near mission to asteroid 433 eros will constrain models of asteroid formation

community production modulates coral reef ph and the sensitivity of ecosystem calcification to ocean acidification coral reefs are built of calcium carbonate caco3 produced biogenically by a diversity of calcifying plants animals and microbes as the ocean warms and acidifies there is mounting concern that declining calcification rates could shift coral reef caco3 budgets from net accretion to net dissolution we quantified net ecosystem calcification nec and production nep on dongsha atoll northern south china sea over a 2 week period that included a transient bleaching event peak daytime ph on the wide shallow reef flat during the nonbleaching period was 8 5 significantly elevated above that of the surrounding open ocean 8 0 8 1 as a consequence of daytime nep up to 112 mmol c m 2 h 1 diurnal averaged nec was 390 90 mmol caco3 m 2 d 1 higher than any other coral reef studied to date despite comparable calcifier cover 25 and relatively high fleshy algal cover 19 coral bleaching linked to elevated temperatures significantly reduced daytime nep by 29 mmol c m 2 h 1 ph on the reef flat declined by 0 2 units causing a 40 reduction in nec in the absence of ph changes in the surrounding open ocean our findings highlight the interactive relationship between carbonate chemistry of coral reef ecosystems and ecosystem production and calcification rates which are in turn impacted by ocean warming as open ocean waters bathing coral reefs warm and acidify over the 21st century the health and composition of reef benthic communities will play a major role in determining on reef conditions that will in turn dictate the ecosystem response to climate change

europium mass balance in polymict samples and implications for plutonic rocks of the lunar crust abstract from correlations of sm concentration and sm eu ratio with th concentration for a large number of polymict samples from various locations in the lunar highlands and the value of 0 91 g g for the mean th concentration of the highlands surface crust obtained by the orbiting gamma ray experiments we estimate the mean concentrations of sm and eu in the lunar surface crust to be between 2 and 3 g g sm and 0 7 and 1 2 g g eu the compositional trends indicate that there is no significant enrichment or depletion of eu on the average compared to sm relative to chondritic abundances i e there is no significant eu anomaly in average upper crust although rich in plagioclase 70 the upper crust does not offer evidence for a gross vertical separation of plagioclase from the final liquid from which it crystallized this and the chondritic ratio of eu al in average highlands material imply that the net effect of the processes that led to formation of the lunar crust was to put most of the al and incompatible elements in the crust the concentration of eu in most polymict samples from the highlands exceeds that which can be supplied by the fraction of kreep necessary to supply the incompatible trace elements plus the fraction of plagioclase necessary to supply the al if the plagioclase has the composition of that in ferroan anorthosite among plutonic rocks only plagioclase in rocks from the magnesian suite can supply the excess eu in the polymict rocks owing to the intermediate value of the mean mg fe ratio of the crust a significant fraction of the mafic rocks of the lunar highlands must have lower mg fe ratios than the norites and troctolites of the magnesian suite of plutonic rocks a large fraction of the plagioclase in the lunar crust is associated not with ferroan anorthosite but with more mafic rocks e g norite anorthositic norite there is little evidence in the eu data that the lunar crust ever consisted of a thick shell of nearly pure plagioclase as envisioned in some formulations of the magma ocean model of its formation

coral macrobioerosion is accelerated by ocean acidification and nutrients author posting the author s 2014 this is the author s version of the work it is posted here by permission of geological society of america for personal use not for redistribution the definitive version was published in geology 43 2015 7 10 doi 10 1130 g36147 1

sm nd isotopic and geochemical study of the archean tonalite amphibolite association from the eastern indian craton we report the results of a sm nd isotopic major element and rare earth element ree study of the older metamorphic group omg tonalite amphibolite association of the eastern indian craton the older metamorphic tonalite gneisses omtg have been previously dated to be 3 8 ga using sm nd isotope systematies and 3 2 3 4 ga by rb sr and pb pb dating the results of this study indicate that the protoliths of the omg amphibolites are 3 3 ga isochron age 3 30 0 06 ga nd 0 9 0 7 and therefore the omtg which intrude into the associated amphibolites cannot be any older than 3 3 ga the amphibolites display light ree enrichment ce yb n 2 2 6 7 la 30 100 x chondrite and nearly flat heavy ree patterns tb lu n 1 2 1 9 the basaltic parents of the amphibolites were probably generated by the partial melting of a spinel lherzolite mantle strong linear relationships between the amphibolites and tonalites in 147sm 144nd 143nd 144nd space isochron age 3 29 0 04 ga nd 0 8 0 8 imply that they are genetically related the tonalites display fractionated ree patterns la 100 300 x chondrite with moderate heavy ree depletions tb lu n 1 9 3 4 the isotopic major element and ree data are consistent with the derivation of the omtg from partial melting of omg amphibolites or equivalent rocks at amphibolegarnet stabilization depths an initial nd t value of 0 9 0 7 for the amphibolites indicates the presence of a slightly depleted mantle source at 3 3 ga with 147sm 144nd between 0 20 and 0 22 it is suggested that the growth of continental crust in the eastern indian craton occurred in response to magmatic underplating in a plume setting

hotspots basalts and the evolution of the mantle the trace element concentration patterns of continental and ocean island basalts and of mid ocean ridge basalts are complementary the relative sizes of the source regions for these fundamentally different basalt types can be estimated from the trace element enrichment depletion patterns their combined volume occupies most of the mantle above the 670 kilometer discontinuity the source regions separated as a result of early mantle differentiation and crystal fractionation from the resulting melt the mid ocean ridge basalts source evolved from an eclogite cumulate that lost its late stage enriched fluids at various times to the shallower mantle and continental crust the mid ocean ridge basalts source is rich in garnet and clinopyroxene whereas the continental and ocean island basalt source is a garnet peridotite that has experienced secondary enrichment these relationships are consistent with the evolution of a terrestrial magma ocean

a young solidification age for the lunar magma ocean abstract the time at which the lunar magma ocean solidified can be determined from the lu hf isotope systematics of lunar rocks derived from magma sources that formed during crystallization of the lunar magma ocean the final magma ocean crystallization product termed urkreep is enriched in incompatible elements including k ree and p we have determined the initial hf isotopic compositions of four samples two kreep basalts and two mg suite norites the incompatible trace element compositions of these samples are controlled by an urkreep component and therefore the initial hf isotopic compositions of these samples represent the hf isotopic evolution of urkreep in order to correct the effects of neutron irradiation on the hf isotopic compositions of these samples we have developed a model that uses the stable hf and sm isotopic compositions measured on an irradiated sample to determine and correct for the thermal and epithermal neutron fluence that has modified the hf isotopic composition of the sample we use our corrected results to calculate a 176 lu 176 hf urkreep model age of 4353 37 ma and the 176 lu 177 hf of urkreep to be 0 0153 0 0033 the lu hf model age is concordant with the re calculated sm nd urkreep model age of 4389 45 ma and we take the average of these ages 4368 29 ma to represent the time at which urkreep formed this age is concordant with the age of the most reliably dated ferroan noritic anorthosite as well as 142 nd model ages for the formation or re equilibration of mare basalt sources taken together these ages indicate that the moon experienced a widespread large scale magmatic event around 4370 ma most plausibly attributed to solidification of the lunar magma ocean

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

exploration of crustal mantle material for the earth and moon using reflectance spectroscopy abstract near infrared reflectance spectra have been acquired a for moses rock diatreme in se utah using an airborne imaging spectrometer ais and b for small areas in and around the large lunar impact crater copernicus using a spectrometer on earth based telescopes the high spectral resolution and precision of these data allow several mineral components of surface material to be identified and analyzed in a spatial context the derived mineralogical information is used to address specific geological problems for the terrestrial study the distribution of the measured abundance of mantle derived ultramafic microbreccia across moses rock dike indicates that flow stabilized into a few channels during the violent eruption for the lunar study the variety of rock types identified in crustal material of deep seated origin is distinct from the dominant rock types sampled from the upper lunar crust and suggests a complex crustal evolution

archean plate tectonics constraints and inferences the earth has been cooling since archean time the higher temperatures beneath archean ridges resulted in more partial melting which extended down to greater depths than at present the archean oceanic crust was much thicker 20 km than modern crust 5 km this inference is compatible with previous ideas of suspected oceanic crust the thicker oceanic crust in the archean tended to resist subduction similar to modern aseismic ridges but could not prevent it short lived episodes of intra arc spreading followed by cordilleran type compression may have produced archean greenstone belts archean meta tonalites represent a significant part of the continental crust and were probably produced by melting of the subducted slab which was favored by the higher mantle temperatures

mesozoic c cycle perturbations and climate evidence for increased resilience of the cretaceous biosphere to greenhouse pulses the mesozoic c isotope record traces the history of the global carbon cycle major perturbations of the carbon cycle triggered by extraordinary volcanic activity are recorded in negative spikes cou

coral sr u thermometry coral skeletons archive past climate variability with unrivaled temporal resolution however extraction of accurate temperature information from coral skeletons has been limited by vital effects which confound and sometimes override the temperature dependence of geochemical proxies we present a new approach to coral paleothermometry based on results of abiogenic precipitation experiments interpreted within a framework provided by a quantitative model of the coral biomineralization process decarlo et al 2015a investigated temperature and carbonate chemistry controls on abiogenic partitioning of sr ca and u ca between aragonite and seawater and modeled the sensitivity of skeletal composition to processes occurring at the site of calcification the model predicts that temperature can be accurately reconstructed from coral skeleton by combining sr ca and u ca ratios into a new proxy which we refer to hereafter as the sr u thermometer here we test the model predictions with measured sr ca and u ca ratios of 14 porites sp corals collected from the tropical pacific ocean and the red sea with a subset also analyzed using the boron isotope 11b ph proxy observed relationships among sr ca u ca and 11b agree with model predictions indicating that the model accounts for the key features of the coral biomineralization process by calibrating to instrumental temperature records we show that sr u captures 93 of mean annual temperature variability 26 30 c and has a standard deviation of prediction of 0 5 c compared to 1 c using sr ca alone the sr u thermometer may offer significantly improved reliability for reconstructing past ocean temperatures from coral skeletons

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

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

the magma ocean as an impediment to lunar plate tectonics potential for plate tectonics on a planet is determined by several factors besides the obvious one of temperature one of the most important of these is the ratio zc zl where zc and zl are the thicknesses of the crust and tectonic lithosphere respectively a high zc zl ratio imparts a low bulk density and thus a high buoyancy to the lithosphere cooling of the lithosphere can offset a limited degree of compositional buoyancy but for realistic assumptions regarding crustal and mantle densities lithosphere geotherms and the spatial variability of the zc zl ratio systematic lithosphere subduction i e plate tectonics is unlikely on any planet with average zc zl ratio greater than about 0 25 during a magma ocean phase zc zl must be 1 so systematic lithosphere subduction is impossible in general zl is closely linked to the average planet temperature whereas zc is only weakly related to t but is sensitive to the planet s pressure depth gradient dp dz i e its size which governs the fate of al during deep melting crystallization processes the moon has probably always had zc zl too high or in later times lithosphere thickness too high to sustain plate tectonics conceivably plate tectonics operated over the first few million years of lunar evolution particularly if the early interior was cooler than generally assumed and a true magma ocean never developed or only developed after gradual warming of the deep interior however weighing against this scenario in addition to the wide array of evidence in favor of the magma ocean hypothesis are the consistently moderate to young by lunar standards ages of geochemically evolved lunar rocks

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

pristine lunar glasses criteria data and implications major element analyses of several thousand glasses from all of the apollo landing sites have resulted in the identification of 25 groups of pristine i e volcanic glass the nickel in these pristine glasses is shown to be indigenous not meteoritic contamination and to be correlated with mg the chemical data indicate that these glasses are consistently better candidates for primary magmas than the majority of crystalline mare basalts the pristine glasses support the view that assimilative processes ringwood and kesson 1976 involving two cumulate systems in the differentiated mantle operated during mare petrogenesis the reality of those assimilative interactions is evident by the occurrence of two linear arrays among the chemistries of the glasses data suggest that these cumulate components in the differentiated mantle persist for lateral distances of at least 1000 km and therefore appear to be products of a vast magma ocean that existed early in lunar history alternative hypotheses claiming that the highlands crust and mare source regions were produced by serial magmatism without a magma ocean have not yet considered all of the constraints derived from the pristine glasses

lunar ferroan anorthosites mineralogy compositional variations and petrogenesis detailed petrologic study of a suite of lunar ferroan anorthosites indicates that their mineral compositional variations are generally consistent with derivation of these anorthosites from a common parent magma there are continuous compositional variations in major elements and smooth trends in minor elements mg fe in plagioclase al ti cr in pyroxene relict textures zoning and possible primary trends of mineral compositional variations are preserved in many of the anorthosites the presence of heterogeneous bimodal and or trimodal pyroxene compositions suggests that some of the anorthosites are polymict rocks however they are composed entirely of ferroan anorthosite suite lithologies some aspects of the mineral composition data suggest that complex processes operated during formation of the ferroan anorthosites the lack of a well defined positive or negative trend of pyroxene mg mg fe versus plagioclase anorthite content the homogenization of mineral compositions in some anorthosites and the varied and apparently enriched mn contents of pyroxenes in some anorthosites suggest that original igneous compositional characteristics have been altered during and or after crystallization processes operative during anorthosite formation may have included some mixing of different melts trapping of variable amounts of intercumulus liquid postcrystallization redistribution of elements or perturbations both during adcumulus growth and subsequent to crystallization by impact events feo and mgo contents of the highly calcic plagioclase typical of these anorthosites suggest that the plagioclase melt distribution coefficients for these elements need to be reassessed

metamorphic history of the eucritic crust of 4 vesta the petrologic properties of eucrites indicate that most formed as rapidly cooled lava flows that were subsequently metamorphosed at 800 c for periods of about 1 myr we have modeled the development of the eucritic crust of the eucrite parent body assumed to be asteroid 4 vesta by the eruption and subsequent burial of lava flows serial magmatism the burial of the flows causes them to reheat to metamorphic temperatures 800 c provided that the initial thermal gradient in the upper 5 km was steep as it would be if 26al was the heat source our model shows that most eucrites were metamorphosed for periods over 1 myr in a crust between 15 and 25 km thick if volcanism lasted only 1 to a few myr longer periods of volcanism do not result in high enough peak metamorphic temperatures to be consistent with eucrite data the hot lower crust in vesta provides an environment in which even small few meters dikes could have cooled slowly enough to produce cumulate eucrites and possibly diogenites

cogenetic rock fragments from a lunar soil evidence of a ferroan noritic anorthosite pluton on the moon abstract the impact that produced north ray crater apollo 16 landing site exhumed rocks that include relatively mafic members of the lunar ferroan anorthositic suite bulk and mineral compositions indicate that a majority of 2 4 mm lithic fragments from sample 67513 including impact breccias and monomict igneous rocks are related to a common noritic anorthosite precursor compositions and geochemical trends of these lithic fragments and of related samples collected along the rim of north ray crater suggest that these rocks derived from a single igneous body this body developed as an orthocumulate from a mixture of cumulus plagioclase and mafic intercumulus melt after the plagioclase had separated from any cogenetic mafic minerals and had become concentrated into a crystal mush 70 wt plagioclase 30 wt intercumulus melt we present a model for the crystallization of the igneous system wherein system is defined as cumulus plagioclase and intercumulus melt the initial accumulation of plagioclase is analogous to the formation of thick anorthosites of the terrestrial stillwater complex however a second stage of formation is indicated involving migration of the cumulus plagioclase intercumulus melt system to a higher crustal level analogous to the emplacement of terrestrial massif anorthosites compositional variations of the lithic fragments from sample 67513 are consistent with dominantly equilibrium crystallization of intercumulus melt the highly calcic nature of orthocumulus pyroxene and plagioclase suggests some reaction between the intercumulus melt and cumulus plagioclase perhaps facilitated by some recrystallization of cumulus plagioclase bulk compositions and mineral assemblages of individual rock fragments also require that most of the mafic minerals formed in close contact with cumulus plagioclase not as separate layers the distribution of compositions and by inference modes has a narrow peak at anorthosite and a broader larger peak at noritic anorthosite characteristics of the samples and their geochemical trends imply an origin in a system that was large relative to the unknown size of the impact that produced the brecccas of ferroan noritic anorthosite composition that were excavated later by the formation of north ray crater and they appear to be consistent with an origin of the suite within a perched plagioclase cumulate if the moon s crust formed by accumulation of plagioclase in a magma ocean ferroan noritic anorthosite formed as an orthocumulate is an alternative to extensive adcumulus formation of ferroan anorthosite 90 vol plagioclase this provides a relatively mafic ferroan anorthositic component 15 vol mafics which is required by mass balance models of compositions of polymict lunar crustal materials the inferred bulk composition of the system of cumulus plagioclase and intercumulus melt is similar to that of ferroan regolith breccia macalpine hills 88104 5 a lunar highland meteorite and may represent a common and widespread component of the moon s early highland crust

pristine rocks 8th foray plagiophile element ratios crustal genesis and the bulk composition of the moon compositional diversity among pristine nonmare rocks is probably too great for both the mg rich and ferroan anorthosite groups to be generated by a single magma based on ratios of plagiophile elements which have plagioclase liquid distribution coefficients close to unity but much smaller crystal liquid distribution coefficients for olivine and low ca pyroxene e g al sr eu ga and to lesser degrees k and ba because plagiophile elements are virtually confined to a single mineral bulk rock ratios of plagiophile elements are nearly immune to sampling errors on a plot of eu al versus mg ferroan anorthosites are separated from all other pristine nonmare rocks by a considerable gap stochastic processes e g differential entrapment of interstitial liquid or differential crystallization of minor phases might conceivably explain the general diversity of plagiophile ratios but a nonrandom process must be invoked to account for a gap in the spectrum of ratios a single magma probably cannot account for even the mg rich pristine rocks subset based on diversity of plagiophile ratios among samples with similar mg ratios plagiophile ratios also constrain the bulk composition of the moon previous work suggests that ferroan anorthosites formed by relatively uncomplicated processes i e flotation of plagioclase cumulates over a primordial magmasphere this model implies that ferroan anorthosite plagiophile ratios are straightforwardly related to those of the bulk silicate fraction of the moon for refractory elements plagiophile ratios among ferroan anorthosites exactly match those expected under such a model assuming the bulk moon ratios are approximately chondritic plagioclase ratios indicate that k which is volatile and ga which is volatile and siderophile are depleted relative to chondrites ratios among nonvolatile elements confirm that the moon formed out of materials akin to chondritic meteorites

the ferroan anorthositic suite the extent of primordial lunar melting and the bulk composition of the moon the geochemical bimodality among compositionally pristine lunar rocks is strong evidence that a major component of the moon s crust is fundamentally unrelated to the plagioclase flotation crust that accumulated over the primordial magma ocean the ferroan anorthositic suite fas has all the characteristics expected for a series of magma ocean plagioclase flotation cumulates but we estimate based on mass balance for al2o3 that 30 wt of the crust and 20 wt of the crust s total al2o3 or roughly 15 of the bulk moon al2o3 content assumed to be 3 4 wt was emplaced by postmagma ocean mg suite serial magmatism remelting of plagioclase bearing magma ocean cumulates cannot plausibly account for the late emplacement of al2o3 because the only plagioclase rich cumulates produced by a deep ultramafic magma ocean would have mg ratios too low to engender the mg suite conceivably remelting of garnet rich magma ocean cumulates supplied the late al2o3 but only if the bulk moon al2o3 content is substantially higher than generally assumed high pressures in the magma ocean acted to enhance the py pyroxene pyroxene olivine ratio of the mo cumulates and the al2o3 content of whatever pyroxene formed remelting of pyroxene rich mo cumulates could conceivably have supplied the late mg suite al2o3 to the crust the source region would have to encompass roughly 40 wt of the mantle another possible source for late al2o3 addition is a large portion of the deepest mantle that avoided more than a slight degree of partial melting and thus remained al rich during formation of the magma ocean the source region would have to encompass 20 30 wt of the mantle ascent of diapiric masses from the lowermost mantle would likely coincide with trigger or be triggered by a large scale overturn of the gravitationally unstable mo cumulate pile with concomitant pressure release melting in which case the mg suite parental melts would be derived from a mix of deepest mo cumulates and the even deeper primitive mantle the popular giant impact hypothesis of lunar origin implies an extremely hot beginning for the moon suggesting that the deep interior was either molten or depleted in al2o3 by differentiation in hot protomoons as it formed origin of 30 wt of the moon s crust by postmagma ocean serial magmatism is more consistent with coaccretion models that form the moon without a giant hot impact in any scenario with a large fraction of the crust originating by partial remelting of deep magma ocean cumulates mass balance for al2o3 implies that the bulk moon normative py ratio must be greater than roughly 0 5 i e significantly higher than generally estimated in this respect the moon appears more compositionally similar to chondritic silicates than to the earth s upper mantle

production and cycling of calcium carbonate in a shelf edge reef system st croix u s virgin islands applications to the nature of reef systems in the fossil record abstract geologic reefs are the end products of not only constructive processes that produce calcium carbonate but also of destructive processes e g bioerosion and wave action that reduce solid substrate to sediment and of physical processes that rework the reef fabric and transport sediment a study was conducted at cane bay on the island of st croix u s virgin islands to quantify the suite of processes that have influenced holocene reef development data on carbonate production reef accretion bioerosion and sediment transport were used to construct a detailed carbonate budget and to apply the findings of this study to the character of reefs observed in the fossil record total carbonate production on the reef ranged from 0 to 5 78 kg m2 per year with a reef wide average of 1 21 kg m2 per year 1 13 by corals 0 02 by coralline algae 0 06 by primarily molluscs forams and echinoderms based on 7 cores only 0 91 kg m2 per year of this have been retained within the reef interior the remaining 0 24 kg m2 per year of sediment along with the 0 06 kg m2 per year contributed directly by molluscs etc are deposited within reef channels and are probably flushed from the reef by major storms of the material recovered in the cores 58 was either loose sediment and rubble or open void space much of the recognizable coral material was demonstrably reworked and out of place accretion rates across the shelf generally increased with water depth as a result of active slumping along the steepening reef face over the past 2 000 3 000 years the importance of detrital material in the reef fabric and the major role played by secondary processes that constantly rework the substrate have resulted in a reef whose interior is more of a garbage pile than an in place assemblage of corals cemented together into a rigid framework the physical similarities between the detrital fabric of the reef at cane bay and those found in many ancient deposits imply that the general processes operating along the cane bay shelf have persisted during much of the evolution of ancient reefs it is proposed that our modern models overemphasize the importance of in place framework as a criterion for an ecologic reef

melting equilibria in multicomponent systems and liquidus solidus convergence in mantle peridotite the melting of undepleted mantle peridotite proceeds through a temperature interval which decreases with increasing pressure if liquidus and solidus actually meet in the range 100 150 kb as suggested by herzberg 1983 peridotite must transform there directly to a melt of its own composition thermodynamic analysis shows that such a liquidus solidus meeting would be very unlikely in a system as chemically complex as mantle peridotite and would require that unanticipated phase equilibrium relations suppress all incongruent melting behavior but takahashi and scarfe s 1985 preliminary experiments suggest that the upper mantle itself may indeed have a special composition with respect to phase equilibrium relations between liquids and solids at very high pressure if so mantle peridotite composition cannot be generated as a crystal accumulate or melting residue because these two popular theories of origin are difficult to reconcile with a supposed eutecticlike composition if upper mantle peridotite were itself a solidified liquid composition produced either as a partial melt or more likely as a crystallization residue of some more primitive melt composition representative of the whole mantle an approach of liquidus to solidus might be expected at high pressure although the phase relations of herzberg 1983 and herzberg and o hara 1985 remain implausible

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

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

comparison of equatorial pacific sea surface temperature variability and trends with sr ca records from multiple corals coral sr ca is widely used to reconstruct past ocean temperatures however some studies report different sr ca temperature relationships for conspecifics on the same reef with profound implications for interpretation of reconstructed temperatures we assess whether these differences are attributable to small scale oceanographic variability or vital effects associated with coral calcification and quantify the effect of intercolony differences on temperature estimates and uncertainties sr ca records from four massive porites colonies growing on the east and west sides of jarvis island central equatorial pacific were compared with in situ logger temperatures spanning 2002 2012 in general sr ca captured the occurrence of interannual sea surface temperature events but their amplitude was not consistently recorded by any of the corals no long term trend was identified in the instrumental data yet sr ca of one coral implied a statistically significant cooling trend while that of its neighbor implied a warming trend slopes of sr ca temperature regressions from the four different colonies were within error but offsets in mean sr ca rendered the regressions statistically distinct assuming that these relationships represent the full range of sr ca temperature calibrations in jarvis porites we assessed how well sr ca of a nonliving coral with an unknown sr ca temperature relationship can constrain past temperatures our results indicate that standard error of prediction methods underestimate the actual error as we could not reliably reconstruct the amplitude or frequency of el nino southern oscillation events as large as 2 c our results underscore the importance of characterizing the full range of temperature sr ca relationships at each study site to estimate true error

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

the moon a personal recollection and memorial for professor lawrence a taylor an apollo stalwart abstract the first geochemical analysis of lunar samples returned by the apollo 11 mission revealed that the moon was highly differentiated and depleted in volatile elements stable isotope compositions show that earth and moon are closely related but they have evolved in totally dissimilar ways probably related to the deficiency of water in the moon as well as the vast differences in size currently available lunar samples come from cumulate source regions making the establishment of a bulk planetary composition more reliant on geophysical rather than geochemical properties

kca chronology of lunar granites abstract k ca age determinations were undertaken for three lunar granitic samples 14321 1062 14303 206 and 12013 141 k ca isotopic analyses of bulk samples of seven pristine lunar igneous rocks including four mare basalts 10017 15555 14321 1394 and 14305 304 371 one norite 15445 17 one anorthosite 60025 one kreep basalt 72275 543 and seven meteorites juvinas pasamonte moore county stannern y75011 84b zagami and shergotty were also performed the k ca mineral isochron for lunar granitic clast 14321 1062 yields an age of 4 06 0 07 ga for 40k 0 5543 ga 1 and an initial 40 ca 44 ca of 47 141 0 010 normalized to 42 ca 44 ca 0 31221 the k ca age is in excellent agreement with the rb sr and sm nd ages and is slightly older than the average 39ar 40ar and u pb zircon ages low precision k ca ages of 4 04 0 64 ga and 3 76 0 72 ga were obtained for lunar granites 14303 206 and 12013 141 respectively due to their lower k ca ratios initial 40 ca 44 ca values for seven lunar and seven meteoritic bulk samples are similar and yield an average initial 40 ca 44 ca of 47 136 0 002 2 m and 0 006 2 p assuming this value as the lunar initial 40 ca 44 ca a ten to twenty fold fractionation for k ca during the formation of granite 14321 is calculated for a two stage model the large k ca enrichment is consistent with a granite genesis model involving a silicate liquid immiscibility process literature data for lunar granites studied so far exhibit a wide range of ages from 3 9 to 4 4 ga thus lunar granites probably represent samples from about eight different intrusive bodies the positive k and k ca correlations of lunar rocks strongly supports an early global lunar differentiation however most granites were probably not directly produced from this early differentiation event

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

heterozoan carbonates from the equatorial rocky reefs of the galapagos archipelago strongly influenced by seasonal and interannual i e el nino southern oscillation upwelling the equatorial setting of the galapagos archipelago is divided into well defined temperature nutrient and calcium carbonate saturation aragonite regions to understand the relationship between oceanographic properties and sediment grain associations grain size carbonate content and components from sea floor surface samples were analysed representing the main geographical regions of the galapagos archipelago the shallow water rocky reefs of the galapagos archipelago are characterized by mixed carbonate siliciclastic slightly gravelly sands despite minor differences in carbonate content major differences exist in the distribution and composition of key carbonate producing biota halimeda is absent and benthic foraminifera occur in extremely low abundance the western side of the galapagos archipelago is strongly influenced by nutrient rich low aragonite subtropical water which generates a heterozoan carbonate biofacies in a tropical realm resembling cold water counterparts i e serpulid echinoderm gastropod barnacle and bryozoan rich facies the central east region is composed of a transitional heterozoan biofacies biofacies observed in the northern region have an increased occurrence of tropical corals albeit with a minor overall contribution to the carbonate components although the temperature gradient would allow for a broader distribution of photozoan biofacies the increased nutrient concentration and related reduced light penetration from the upwelled waters favour heterozoan carbonate factories mimicking cool water deeper or higher latitude environments the recent sedimentary record of the galapagos archipelago presents a range of tropical heterozoan carbonate communities responding to more than simply latitude or temperature but a much more complex mixture of physical evolutionary and geological processes

the polymict eucrites the polymict eucrites are a suite of about 14 polymict achondritic meteorites that contain at least 90 vol of eucritic material and are found both in antarctica and elsewhere they are part of a continuum of polymict breccias that includes howardites and polymict diogenites rare gas data suggest that some are gas rich regolith breccias the clasts contained in polymict eucrites sample a variety of lithologies from their parent body and include eucritic clasts alkali enriched eucrites pyroxene cumulate eucrites two pyroxene mafic rocks possibly feldspar cumulate eucrites diogenites fayalitic lithologies and a variety of other mineral clasts the eucritic clasts are probably samples of near surface lithologies on the parent body but the presence of two pyroxene mafic rocks is considered to be evidence of magmatic activity at pressures in excess of 1 kbar in the parent body partial melt models may explain some of the diversity among the clasts but cumulus processes are believed to have been important if pressures greater than 1 kbar are confirmed then the basaltic achondrite parent body bap must have a diameter in excess of 200 km the variety of lithologies suggests that not all basaltic achondrites are samples of igneous rocks formed by single stage melting of a chondritic asteroid but are instead samples of an evolved and diverse crust produced by serial magmatism

chronologic implications for slow cooling of troctolite 76535 and temporal relationships between the mg suite and the ferroan anorthosite suite abstract ages have been obtained using the 87 rb 87 sr 147 sm 143 nd and 146 sm 142 nd isotopic systems for one of the most slowly cooled lunar rocks apollo 17 mg suite troctolite 76535 the 147 sm 143 nd 146 sm 142 nd and rb sr ages derived from plagioclase olivine and pyroxene mineral isochrons yield concordant ages of 4307 11 ma 4299 29 35 ma and 4279 52 ma respectively these ages are slightly younger than the age determined on ferroan anorthosite suite fas rock 60025 and are therefore consistent with the traditional magma ocean model of lunar differentiation in which the mg suite is intruded into the anorthositic crust however the sm nd ages record when the rock passed below the closing temperature of the sm nd system in this rock at 825 c whereas the rb sr age likely records the closure temperature of 650 c a cooling rate of 3 9 c ma is determined using the ages reported here and in the literature and calculated closure temperatures for the ar ar pb pb rb sr and sm nd systems this cooling rate is in good agreement with cooling rates estimated from petrographic observations slow cooling can lower apparent sm nd crystallization ages by up to 80 ma in the slowest cooled rocks like 76535 and likely accounts for some of the variation of ages reported for lunar crustal rocks nevertheless slow cooling cannot account for the overlap in fas and mg suite rock ages instead this overlap appears to reflect the concordance of mg suite and fas magmatism in the lunar crust as indicated by ages calculated for the solidus temperature of 76535 and 60025 of 4384 24 ma and 4383 17 respectively not only are the solidus ages of 76535 and 60025 nearly concordant but the sm nd isotopic systematics suggest they are derived from reservoirs that were minimally differentiated prior to 4 38 ga although the sr isotopic composition of 60025 indicates its source was minimally differentiated the sr isotopic composition of 76535 indicates it underwent fractionation just prior to solidification of the 76535 these observations are consistent with both a magma ocean or a serial magmatism model of lunar differentiation in either model differentiation of lunar source regions must occur near the solidification age of thee samples perhaps the best estimate for the formation age of lunar source regions is the rb sr model age of the 76535 source region age of 4401 32 ma this is in good agreement with sm nd model ages for the formation of ur kreep and suggests that differentiation of a least part of the moon could not have occurred prior to 4 43 ga

mineralogy of the lunar crust results from clementine received 1997 december 5 accepted in revised form 1998 september 15 abstract the central peaks of 109 impact craters across the moon are examined with clementine ultraviolet visible uvvis camera multispectral data the craters range in diameter from 40 to 180 km and are believed to have exhumed material from 5 30 km beneath the surface to form the peaks including both upper and lower crustal rocks depending on whether craters have impacted into highlands or basins representative five color spectra from spectrally and spatially distinct areas within the peaks are classified using spectral parameters including key ratio which is related to mafic mineral abundance and spectral curvature linked to absorption band shape which distinguishes between low and high ca pyroxene and olivine the spectral parameters are correlated to mineralogical abundances related in turn to highland plutonic rock compositions the derived rock compositions for the various central peaks are presented in a global map from these results it is evident that the lunar crust is compositionally diverse both globally and at local 100 m scales found within individual sets of central peaks although the central peaks compositions imply a crust that is generally consistent with previous models of crustal structure they also indicate a more anorthositic crust than generally assumed with a bulk plagioclase content of 8 1 evolving from pure anorthosite near the surface towards more mafic low ca pyroxene rich compositions with depth comparable to anorthositic norite evidence for mafic plutons occurs in both highlands and basins and represent all mafic highland rock types however the lower crust is more compositionally diverse than the highlands with both a greater range of rock types and more diversity within individual sets of central peaks

in quest of lunar regolith breccias of exotic provenance a uniquely anorthositic sample from the fra mauro apollo 14 highlands polymict samples can be used to establish mass balance constraints regarding the bulk composition of the lunar crust and to gauge the degree of regional heterogeneity in the composition of the lunar crust the most ideally polymict type of sample is finely mixed regolith lunar soil or its lithified equivalent regolith breccia fortunately lunar regolith breccias can occasionally be found at great distances from their points of origin most of the known lunar meteorites are regolith breccias we are searching for examples of exotic regolith samples among the apollo regolith breccia collection most of the 21 apollo regolith breccias analyzed for this study strongly resemble the local soils over which they were collected nine regolith breccias from apollo 16 are surprisingly mature compared to previously analyzed apollo 16 regolith breccias and six of the seven from apollo 16 station 5 have lower more local soil like mg ratios than previously analyzed regolith breccias from this station several of the apollo 14 regolith breccias investigated show significantly highermg and lower al than the local soils the most interesting sample we have investigated is 14076 1 from a lithology that constitutes roughly half of a 2 0 g pebble the presence of spherules indicates a regolith derivation for 14076 1 yet its highly aluminous 30 wt al2o3 composition is clearly exotic to the 1 6 km traverse surface over which the apollo 14 samples were collected this sample resembles soils from the descartes apollo 16 highlands far more than it does any other polymict sample from the fra mauro apollo 14 region the i sfeo maturity index is extremely low but this may be a result of thermal annealing a variety of siderophile elements occur in 14076 1 at typical regolith concentrations the chemistry of the second most aluminous regolith sample from apollo 14 14315 can only be roughly approximated as a mixture of local regolith and 14076 1 like material however the low a priori statistical probability for long distance horizontal transport by impact cratering along with the relatively high contents of incompatible elements in 14076 1 despite its high al content suggest that this regolith breccia probably originated within a few hundred kilometers of the appollo 14 site if so its compositional resemblance to ferroan anorthosite tends to suggest that the regional crust is or originally was far richer in ferroan anorthosite than implied by the meager statistics for pristine rocks from this site thus 14076 1 tends to strengthen the hypothesis that ferroan anorthosite originated as the flotation crust of a global magmasphere

early differentiation of the moon evidence from trace elements in plagioclase bulk samples and plagioclase mineral grains from lunar cataclastic ferroan anorthosites were analyzed for trace elements by instrumental neutron activation analysis some pure plagioclase crystals have lower concentrations of cr co sc and heavy rees than previous analyses indicated concentrations of sr eu na ga and the rees in plagioclases from different anorthosites vary in a systematic way and the trace element patterns of plagioclases from pristine norites and troctolites are very different from the plagioclase pattern of anorthosites the following model is suggested to account for these observations 1 melting of a large fraction of the moon formation of a magma ocean precipitation of olivine and later pyroxene followed by flotation of cumulus plagioclase 2 mixing of kreep with a mafic component enriched in mg cr and co 3 precipitation of noritic and troctolitic cumulates and metallic iron from this magma and 4 eruption of these kreep and mg rich lavas and or distribution of these materials over the front side of the moon by basin forming impacts 3 9 4 0 b y ago

inheritance of silicate differentiation during lunar origin by giant impact abstract the giant impact model for the origin of the moon is usually assumed to entail no significant fractionation of nonvolatile lithophile elements relative to a simple binary mixture of impactor silicates plus protoearth silicates if anything the most refractory lithophile elements al ca sc ti v y zr nb ree hf ta th and u are sometimes assumed to be enriched as a cohesive group however the mechanism of giant impact tends to derive the moon selectively from the peripheral portions of the impactor and the earth the earth may have been hot enough before the impact to be completely molten particularly if it was insulated by a thick accretionary atmosphere however analysis of the likely number and timing of major impacts in the prehistory of the impactor indicates that a fully molten undifferentiated condition for that relatively small body is unlikely given the selective sampling of the giant impact any significant vertical differentiation within the noncore portion of the impactor would have been largely inherited by the moon if the impactor was appreciably bigger than mars perovskite probably crystallized along the base of its magma ocean at lower pressures majorite would have been important the process of impactor differentiation inheritance has been modeled using previous physical models of the giant impact to constrain the depth provenance of the materials contributed from the impactor to the moon the protoearth is assumed to be fully molten results indicate that if a few tens of a percent of the impactor crystallized prior to the collision significant fractionations of ratios such as hf yb ite hf ite zr ca al an ti al would have been inherited by the moon where ite stands for a variety of incompatible trace elements most notably th u and la the net fractionation effects are much more pronounced in models in which jetting occurs than in models that do not simulate jetting on balance assuming at least a slight amount of jetting occurs these admittedly imprecise results indicate that the giant impact hypothesis implies a very peculiar composition for the refractory lithophile component of the moon the moon has until now generally been assumed to contain refractory lithophile elements in chondritic proportion to one another and for some ratios such as hf yb sm al and ba al geochemical observations appear to confirm this assumption however modeling of impactor differentiation inheritance implies that the giant impact hypothesis and the chondritic refractory moon hypothesis are probably mutually incompatible

bioerosion traces in the great barrier reef over the past 10 to 30 kyr abstract bioerosion traces preserved in coral reef framework provide insight into past environmental conditions and reef health however few studies have explored the relationship between bioerosion reef growth history and environmental changes the international ocean drilling program iodp expedition 325 sampled late glacial to deglacial reef sequences that developed from 30 to 10 ka on the shelf edge adjacent to the modern great barrier reef gbr this study quantifies spatiotemporal patterns of macrobioerosion intensity macrobioerosion intensity referred to as bi of trace ichnogenera entobia sponges gastrochaenolites bivalves and maeandropolydora trypanites worms based on detailed observations of 13 drill holes from two cross shelf transects in two regions hydrographers passage in the southern central gbr and noggin pass in the north our high resolution stratigraphic and temporal records of bioerosion activity are defined and compared to published multi proxy paleoenvironmental interpretations from the exp 325 cores coralgal assemblages geochronology and lithology are used to understand the controls on the multi scale spatiotemporal patterns of bioerosion across and along the gbr shelf and within individual holes noggin pass is characterized by significantly higher bioerosion activity than hydrographers at each transect changes in bioerosion intensity are observed to be coeval with some major reef sequence boundaries however due to the unconsolidated nature and limited recovery many boundaries have inconclusive trends statistical analysis is used to interpret the relationship of bioerosion intensity to various factors including paleo water depth lithology coral and algal assemblages transect location geomorphic feature vertical accretion and reef sequences terrigenous sediment flushing depositional regime and a pronounced latitudinal gradient in sea surface temperature are likely to have contributed to the significant regional differences in bioerosion intensity between northern and southern transects and also during reef demise bioerosion at both transects is highest in the proto barrier reef 4 sites when compared to all fringing terrace reefs reef 3a 3b and 4 higher bioerosion tends to occur when vertical accretion is at its extremes its lowest and highest limits the enhanced bioerosion alongside lowest reef accretion in a sea level rise scenario reef 3a 3b and 4 might have contributed to reef degradation prior to its demise

vnir spectral variability of the igneous stratified stillwater complex a tool to map lunar highlands lunar highlands are plagioclase rich terrains produced by crystal floating in a magma ocean system lunar samples revealed the presence of anorthositic plagioclase 90 samples from the highlands associated to more mafic rocks recently remote sensing data permit mapping those terrains with high spatial and spectral resolution allowing detection of plagioclase and mafic crystal field c f absorptions in this paper we have studied bidirectional spectral characteristics in the visible near infrared vnir of rocks from the stillwater complex a cumulitic igneous stratified complex with composition varying from mafic to sialic e g pyroxenite anorthosite we investigated both slabs and powders of these rocks to give indication of the spectral variability of rock analogs of lunar crust from a mineralogical point of view samples have been spectrally separated in four main groups considering the different c f absorption association reflectance and spectral shape for both slab and powder spectra more spectral details can be obtained from the analysis of powder spectra than from the slab spectra the composition of rocks can be addressed by studying spectral parameters such as the position and the intensity of the absorption e g band center and band depth the analysis of our plagioclase pyroxene bearing samples indicates that mafic composition can be clearly obtained for samples characterized by one pyroxene phase even for few amounts of pyroxene from powder spectra on the other hand slab spectra show clear pyroxene absorptions only for rocks with mafic abundance at least 20 the intensity of the mafic absorptions of these samples shows a linear trend with respect to the abundance of pyroxenes orthopyroxene clinopyroxene for samples with ferrosilite amount less than ca 25 considering all pyroxene bearing samples the band depth of slab spectra are linearly related to the volumetric distribution of ferrous iron in pyroxenes

the columbia river basalts between 17 million and 6 million years ago 200 000 square kilometers of the american northwest were flooded by basaltic lava that erupted through fissures in the crust up to 150 kilometers long larger individual eruptions covered over a third of the columbia plateau in a few days the lavas represent partial melts of the earth s mantle that were only slightly modified by near surface upper crustal processes the abundant chemical and mineralogical data now available offer an opportunity to study mantle composition and the processes involved in the evolution of the earth s crust

dynamic crystallization studies on the grande ronde pillow basalts central washington dynamic crystallization experiments were performed to reproduce textural and mineralogic features of some grande ronde columbia river pillow basalts and thereby estimate cooling rates of the various pillow textural zones the essential petrographic features of these pillows can be experimentally duplicated by melting at the liquidus temperature 1140 c followed by isothermal drop crystallization at 1125 c and then linear cooling to subsolidus temperatures at rates between 2400 c hr to reproduce vitrophyric rims and 10o hr to reproduce the holocrystalline interiors in both cooling experiments and the pillows the al content of pyroxenes and the fe content of plagioclase display a systematic variation with respect to cooling rate or position within the pillow pyroxene grain size data derived from the cooling experiments display a linear relationship with cooling rate but are strongly influenced by the original melting temperature pyroxenes crystallized during experiments originally melted at liq

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

a low viscosity lunar magma ocean forms a stratified anorthitic flotation crust with mafic poor and rich units much of the lunar crust is monomineralic comprising 98 plagioclase the prevailing model argues the crust accumulated as plagioclase floated to the surface of a solidifying lunar magma ocean lmo whether 98 pure anorthosites can form in a flotation scenario is debated an important determinant of the efficiency of plagioclase fractionation is the viscosity of the lmo liquid which was unconstrained here we present results from new experiments conducted on a late lmo relevant ferrobasaltic melt the liquid has an exceptionally low viscosity of 0 22 0 19 0 11 to 1 45 0 82 0 46 pa s at experimental conditions 1 300 1 600 c 0 1 4 4 gpa and can be modeled by an arrhenius relation extrapolating to lmo relevant temperatures our analysis suggests a low viscosity lmo would form a stratified flotation crust with the oldest units containing a mafic component and with very pure younger units old impure crust may have been buried by lower crustal diapirs of pure anorthosite in a serial magmatism scenario

control of climate and local topography on dynamic evolution of badland from southern italy calabria abstract this work deals with an integrated geomorphological and chemical physical study of calanchi landforms in site caulonia of se calabria southern italy developed on of late pliocene quaternary clay deposits the aim of this paper is to investigate how topography and rainfall quantity may affect runoff and slope processes in calanchi landforms by influencing the physical chemical and mineralogical properties of clayey sediments to this purpose a comparison has been made among the physical chemical and mineralogical features of calanchi materials sampled after a rainy period precipitation mean annual rainfall of 709 6 mm wet year with those sampled after relatively dry period mean annual rainfall of 431 4 mm dry year and in different topographic settings opposite flanks of a catchment exhibiting different steepness and lengths i e w to nw facing and e to ne facing slopes using a multivariate statistic approach which adopts the principal component analysis pca method to extract factors it has been possible to make a hypothesis of the main processes responsible for dynamic evolution of the study area the rainfall quantity coupled with topography has to be considered as the main control factor inducing changes in the physical chemical mineralogical parameters

two stage models for lunar and terrestrial anorthosites petrogenesis without a magma ocean two stage diapiric models for lunar ferroan anorthosites and terrestrial massif anorthosites are examined the lunar model is developed to explain early lunar differentiation in the absence of a magma ocean if correct the terrestrial model serves as an analog for the development of lunar anorthositic diapirs there is field and textural evidence of transport of mostly crystalline anorthositic material within the terrestrial complexes this evidence combined with the absence of anorthositic lavas and phase equilibrium constraints inhibiting the production of hyperaluminous magmas is consistent with the detachment of plagioclase rich crystalline mushes from large uppermost mantle plutons and multiple diapiric intrusion of these mushes into the upper sialic crust with attendant anatexis rudimentary dynamical calculations suggest that a simple single layer source for the diapirs is improbable either there were several parental magma chambers or there was a single large chamber that was repeatedly replenished the lunar model is a development of wetherill s 1975 suggestion that following accretion the outer portion of the moon consisted of a stack of overlapping layered intrusions and that reheating of these intrusions mobilized their anorthositic layers which intruded upwards to produce the anorthositic lunar crust dynamical calculations show that gravitational instabilities in anorthositic layers 1 km thick could develop into diapirs on a reasonable time scale 50 100 m y only if the outer portion of the moon was partially remelted we suggest that partial melting of the interior due to the decay of long lived radionuclides with the subsequent onset of global convection heated the stack of intrusions from below thus causing melting and allowing the anorthositic diapirs to grow and ascend fairly rapidly as the convecting zone thickened a mass expulsion of anorthositic material out of the lunar interior may have occurred

chronology and complexity of early lunar crust abstract the least equivocal age and petrographic data on lunar rock samples suggest that 1 1 the lunar anorthostic crust was formed by about 120 ma after the primary accretion of the moon at 4 56 ga it may have been completed earlier it was formed in a large magma system probably at least several hundred kilometers in depth with rare earths not appreciably fractionated from chondritic relative abundances 2 2 at least some members of the diverse mg suites of rocks norites troctoliles dunites crystallized very soon after lunar accretion within a very few 100s of ma after 4 56 ga and cannot presently be distinguished chronologically from anorthositic crust formation however their parental magmas had clearly evolved from chondritic incompatible trace element patterns 3 3 a trace element rich material kreep was formed by about 4 3 ga ago as residues from the previous episodes with a remarkably constant rare earth pattern this residue was subsequently reworked in melting and impact processes such that most samples which contain it have ages around 3 9 4 0 ga whether impact or volcanic in immediate origin 4 4 the onset of ferrous mare basalt volcanism began much earlier about 4 33 ga than was once assumed and was in process before the end of the most intense period of bombardment 3 9 4 0 ga ago the sources for this mare volcanism are complementary in characteristics to kreep and were also in place by 4 4 or 4 3 ga ago at a depth of several hundred kilometers these characteristics of lunar materials demonstrate that lunar crustal formation happened quickly in a complex fashion and affected depths in the mantle to at least several hundreds of kilometers

lunar ferroan anorthosite petrogenesis clues from trace element distributions in fan subgroups the rare earth elements ree and selected other trace elements were measured in plagioclase and pyroxene from nine samples of the lunar ferroan anorthosite fan suite of rocks samples were selected from each of four fan subgroups previously defined by james et al 1989 plagioclase compositions are homogeneous within each sample but high and low ca pyroxenes from lithic clasts typically have different ree abundances from their counterparts in the surrounding granulated matrices measured plagioclase low ca pyroxene concentration ratios for the ree have steeper patterns than experimentally determined plagioclase low ca pyroxene partition coefficients in most samples textural and trace element evidence suggest that although subsolidus equilibration may be responsible for some of the discrepancy plagioclase compositions in most samples have been largely unaffected by intermineral redistribution of the ree the ree systematics of plagioclase from the four subgroups are broadly consistent with their derivation through crystallization from a single evolving magma however samples from some of the subgroups exhibit a decoupling of plagioclase and pyroxene compositions that probably reflects the complexities inherent in crystallization from a large scale magmatic system for example two anorthosites with very magnesian mafic minerals have highly evolved trace element compositions major element compositions in plagioclase also do not reflect the evolutionary sequence recorded by their ree compositions finally a noritic anorthosite breccia with relatively ferroan mafic minerals contains several clasts with high and variable ree and other trace element abundances although plagioclase ree compositions are consistent with their derivation from a magma with a kreepy trace element signature very shallow ree patterns in the pyroxenes suggest the addition of a component enriched in the light ree

melt segregation from partially molten source regions the importance of melt density and source region size the compressibility of basic melt at 1 atmosphere is about an order of magnitude higher than that of mantle minerals consequently the density contrast between melt and the principal residual crystals in mantle source regions is expected to decrease with increasing source region depth the increasingly olivine normative character of primary melts produced at greater depths is also expected to result in a decrease in this density contrast with increasing source region depth once vertical permeability is established by melt generated during partial melting buoyancy driven melt percolation can under some circumstances segregate melt from the residual crystals in its source region on a geologically rapid time scale limits to this process are provided by cooling of the source region freezing melt in and rigidity of the crystalline matrix mechanically trapping melt source region size influences these limits strongly consequently small partially molten diapirs km in diameter may be able to trap large melt fractions 30 but larger source regions would be unable to do so the reduction in density contrast with pressure reduces the buoyant force driving melt percolation and provides another limit to melt segregation diapirs at depth may thus stably contain large fractions of melt but may decompress and unload their melt during ascent this effect would be enhanced in small diapirs and may be relevant to the genesis of komatiitic magma melt compression may also be a factor in explaining why the very different maximum depths inferred for typical basic melt segregation from source regions on different planets 500 km on the moon 250 km on mars 100 km on earth correspond to similar pressures 25 35 kbar at greater pressures melt may no longer be capable under ordinary conditions of segregating upwards by buoyancy this may also help to explain why depleted peridotites overlie more fertile peridotites and how deep regions of the mantle are able to remain fertile over geologic time

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

diverse coral communities in naturally acidified waters of a western pacific reef anthropogenic carbon dioxide emissions are acidifying the oceans reducing the concentration of carbonate ions co32 that calcifying organisms need to build and cement coral reefs to date studies of a handful of naturally acidified reef systems reveal depauperate communities sometimes with reduced coral cover and calcification rates consistent with results of laboratory based studies here we report the existence of highly diverse coral dominated reef communities under chronically low ph and aragonite saturation state ar biological and hydrographic processes change the chemistry of the seawater moving across the barrier reefs and into palau s rock island bays where levels of acidification approach those projected for the western tropical pacific open ocean by 2100 nevertheless coral diversity cover and calcification rates are maintained across this natural acidification gradient identifying the combination of biological and environmental factors that enable these communities to persist could provide important insights into the future of coral reefs under anthropogenic acidification

mineral compositions in pristine lunar highland rocks and the diversity of highland magmatism high precision electron microprobe analyses of olivine and pyroxene in pristine lunar highland rocks confirm the dichotomy between ferroan anorthosites and the mg suite ferroan anorthosites plot as coherent trends consistent with formation in a complex global magma system lack of coherent compositional trends in the mg suite rocks indicates derivation from numerous magmas

the macalpine hills lunar meteorite and implications of the lunar meteorites collectively for the composition and origin of the moon the mac88104 mac88105 meteorite is a lunar highlands regolith breccia even more anorthositic than previously available samples of highlands regolith clasts studied include two unusual pristine rocks one a 2 5 mm slightly granulitic clast rated as probably pristine contains extraordinarily fe rich fo40 olivine the other a 5 mm clast with clear vestiges of a poikilitic cumulate texture has silicate compositions that extend the range of the mg suite in the direction of the high mg end of the ferroan anorthositic suite the pyroxene of the latter clast is relatively ca rich and poorly equilibrated by lunar cumulate standards suggesting that it may have formed in an uncommonly shallow intrusion the four lunar highlands meteorites are all regolith breccias or in one case a marginal type between regolith breccia and ordinary polymict breccia and they probably represent three to four separate lunar source craters the proportion of regolith breccias is higher among lunar highlands meteorites than among rock samples from the classic highlands site apollo 16 9 regolith breccias for the majorelement composition of the crust the highlands meteorites confirm that the two low th central nearside sites luna 20 and especially apollo 16 are approximately representative the consistently high al2o3 composition indicated for the upper crust supports the magmasphere hypothesis for the trace element composition of the crust the highlands meteorites indicate that the central nearside apollo and luna sites are in several respects grossly unrepresentative concentrations of siderophile elements are far lower in highlands meteoritic regolith breccias than in their central nearside counterparts the high overall siderophile levels and hyperchondritic niir and auir ratios characteristic of highlands materials from apollo 16 and apollo 14 are evidently idiosyncracies of the central nearside concentrations of incompatible elements including k th and u are far lower in the highlands meteorites than in regolith samples from the central nearside this trend implies that certain lower limits on the bulk moon content of u and associated refractory lithophile elements should be relaxed models of lunar origin implying large enrichments of refractory lithophile elements are not favored by the new constraints from these meteorites

lunar feldspathic meteorites constraints on the geology of the lunar highlands and the origin of the lunar crust abstract the composition of the lunar crust provides clues about the processes that formed it and hence contains information on the origin and evolution of the moon current understanding of lunar evolution is built on the lunar magma ocean hypothesis that early in its history the moon was wholly or mostly molten this hypothesis is based on analyses of apollo samples of ferroan anorthosites 90 plagioclase molar mg mg fe mg 75 and the assumption that they are globally distributed however new results from lunar meteorites which are random samples of the moon s surface and remote sensing data show that ferroan anorthosites are not globally distributed and that the apollo highland samples used as a basis for the model are influenced by ejecta from the imbrium basin in this study we evaluate anorthosites from all currently available adequately described lunar highland meteorites representing a more widespread sampling of the lunar highlands than apollo samples alone and find that 80 of them are significantly more magnesian than apollo ferroan anorthosites interestingly luna mission anorthosites collected outside the continuous imbrium ejecta are also highly magnesian if the lunar highland crust consists dominantly of magnesian anorthosites as suggested by their abundance in samples sourced outside imbrium ejecta a reevaluation of the lunar magma ocean model is a sensible step forward in the endeavor to understand lunar evolution our results demonstrate that lunar anorthosites are more similar in their chemical trends and mineral abundance to terrestrial massif anorthosites than to anorthosites predicted in a lunar magma ocean this analysis does not invalidate the idea of a lunar magma ocean which seems a necessity under the giant impact hypothesis for the origin of the moon however it does indicate that most rocks now seen at the moon s surface are not primary products of a magma ocean alone but are products of more complex crustal processes

composition of the lunar highland crust from near infrared spectroscopy near infrared reflectance spectra of the lunar highlands are synthesized to obtain global information about the composition of the lunar near side crust immature exposed surfaces from small fresh craters mountains and massifs and large craters with central peaks are included in a survey of rock types across the lunar near side compositions recognized in these data include anorthosite noritic gabbric and troctolitic mineral assemblages three quarters of the areas studied that represent samples from the upper 1 2 km of lunar crust exhibit noritic compositions with different amounts of pyroxene and or brecciation alteration norites are ubiquitous across the near side and show no spatial clustering associated with any of the major basins in contrast to this noritic megaregolith of the upper crust material representing stratigraphically deeper zones 5 15 km of the lunar crust is dominated by gabbros anorthosites and troctolites with less than a quarter of the areas studied exhibiting a noritic composition the origin of the noritic megaregolith and its relation to deeper crustal material is thus somewhat of an enigma the current limited statistics for areas identified as anorthosites and troctolites are insufficient to derive global spatial distributions gabbroic areas however are notably concentrated in the western hemisphere although incomplete for a global assessment of crustal materials these data demonstrate that the lunar near side crust is clearly mineralogically heterogeneous both laterally and vertically and not well mixed below 1 2 km

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

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

comparative planetology and the origin of continental crust abstract this paper summarizes crustal evolution in silicate planets the moon mercury mars venus and meteorite parent bodies and outlines a general theory for the origin of continental crust based on comparative planetology and terrestrial evidence silicate planets and some meteorite parent bodies have undergone early global differentiation nonplate tectonic followed by a late basin forming bombardment and a long basaltic second differentiation evidence for analogous stages except a late bombardment can be found in terrestrial geology modified by conditions of hydrous magma generation and persistent tectonism continental crust is inferred to have largely been formed in the early archean by andesitic volcanism accompanying catastrophic early degassing this global crust was disrupted by basin forming impacts that initiated mantle upwelling and sea floor spreading basaltic overplating and underplating from mantle plumes continued on the continents producing greenstone belts mafic dike swarms and by partial melting of underplated basalt and sialic crust the granitoids of archean granite greenstone terrane this process produced most of the present continental crust by 2 5 ga ago when the global tectonic style evolved into the present one of tectonism marginal to and within continents subsequent crustal evolution has largely been deformation metamorphism anatexis and rearrangement of previously formed crustal segments not separation of new sialic crust from the mantle the crustal growth that has occurred since the archean has primarily been crustal thickening resulting directly or indirectly from generation of basalt in the subcontinental tectosphere viewed in the light of evidence from comparative planetology the continents are interpreted as the greatly altered remnants of an originally global primordial crust the result of an evolutionary sequence shared by all the silicate planets to some degree depending on their mass volatile content and location in the solar system this theory can be tested by deep drilling in archean terranes to locate remnants of the original crust by determination of the composition of the highland crust of mars and by investigations of the crust of venus

lunar and terrestrial crust formation planetary crusts may be accreted produced in primordial differentiation or built up piecemeal by serial magmatism the existence of old polygenetic laterally heterogeneous partial melt rocks in the lunar highlands suggests that the moon produced its early crust by serial magmatism this view can be reconciled with lunar eu anomalies previously thought to support the magma ocean model of crust formation if complications in the fractionation of mare basalts are recognized phase equilibrium and magmatic density information for mare basalts suggest a model in which plagioclase fractionation can occur even though plagioclase is not a near liquidus phase the cryptic fractionation of clinopyroxene in morb provides a precedent for this model the necessity for a lunar magma ocean is questioned but a role for a terrestrial magma ocean of sorts at depth is suggested

static compression and olivine flotation in ultrabasic silicate liquid piston cylinder techniques have been used to observe static compressions of ultrabasic silicate liquids to 6 gpa and 2000 c compressions are measured by bracketing sinking and floating of olivine crystals of known density at run conditions komatiite peridotite and their liquid mixtures with fe2sio4 all show constant density changes with pressure of 0 07 g cm3 gpa along their liquidi these results confirm shock wave studies and ultrasonic studies which show weak compositional effects on compressibility of basic to ultrabasic silicate liquid the techniques converge in supporting the conjecture of stolper et al 1981 that ultrabasic silicate liquids may be denser than their equilibrium coexisting olivines and pyroxenes at high compressions the pressure of this density inversion is 7 8 gpa for the compositions studied olivine flotation provides an important constraint upon earth evolution models that include extensive melting during early differentiation it also provides a mechanism for concentrating high mg si olivine in the upper mantle without unduly perturbing other geochemical parameters a full evaluation of the physical and geochemical consequences is required at an early date

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