the cosmogenic 21ne production rate in quartz evaluated on a large set of existing 21ne 10be data abstract based on a compilation of published combined 10 be and 21 ne cosmogenic nuclide data sets from quartz samples obtained at eth zurich we assess the 21 ne 10 be p21 p10 production rate ratio with the goal to determine the 21 ne production rate p21 in quartz a variety of sliding erosion islands in a 21 ne 10 be versus 10 be diagram were evaluated to find the one that fits the data best which in turn yields the most probable p21 if the 10 be production rate is known the approach minimizes the influence of samples with a complex exposure history a best fit value for p21 p10 sp sp the 10 be fraction being produced by spallation as opposed to production by muons of 4 23 0 17 is obtained for a 10 be half life of 1 39 ma adopting a p10 sp value in quartz of 4 41 0 52 at g 1 yr 1 this yields a p21 of 18 7 2 3 at g 1 yr 1 it is possible that 2 of the 21 ne is produced by fast muons

denudation rates and a topography driven rainfall threshold in northern chile multiple cosmogenic nuclide data and sediment yield budgets abstract the quantification of geomorphic process rates on the outcrop and the orogen scale is important to describe accurately the interaction between the relative effects of erosion tectonics and climate on landscape evolution we report single and paired cosmogenic nuclide 10 be 26 al and 21 ne derived erosion rates and exposure ages on hillslope interfluves from the tectonically active western central andes that show a distinct spatial variation a positive correlation of erosion rates with elevation and present day rainfall rates is observed erosion rates at lower altitudes the hyperarid coastal cordillera and the western escarpment with the northern part of the atacama desert are extremely low and of the order of 10 100 cm my nominal exposure ages 1 6 my in contrast erosion rates at higher altitudes the semiarid western cordillera range up to 4600 cm my nominal exposure ages 0 02 0 1 my this latter average long term bedrock erosion rate record suggested to be coupled to an orographically controlled pattern of rainfall is also reflected in the pattern of denudation rates derived from a short term decadal record of limited sediment yield data specifically denudation rates calculated from sediment flux data are of a similar order of magnitude as erosion rates deduced from long lived cosmogenic nuclides from bedrock hillslope interfluves of the western cordillera nevertheless the production and the supply of sediment from the western andean slope are very limited analysis of multiple cosmogenic nuclides allows simultaneous determination of erosion rates and exposure ages but also reveals complex exposure histories of non bedrock samples such as boulders or amalgamated clast samples notably this study shows that saturation of nuclides usually assumed in studies where only a single nuclide is analyzed is rather the exception than the rule as revealed by erosion island plots constant erosion that started much later than the formation age of the rocks or episodic erosion by spalling can partially explain non steady state concentrations and more complicated exposure scenarios furthermore the use of multiple nuclides with different half lives allowed us to infer that no significant variations in long term erosion rates have occurred and that at the western escarpment erosion rates have been low and constant for most of the late neogene nevertheless the time intervals necessary to reach steady state concentrations for cosmogenic nuclides can be quite different from those needed for landscapes to reach steady state

the variety of lithologies in the yamato 86032 lunar meteorite implications for formation processes of the lunar crust abstract we performed a petrologic mineralogical geochemical and isotopic study of several lithologies in the y 86032 feldspathic breccia this study leads us to conclude that y 86032 likely originated on the lunar farside y 86032 is composed of several types of feldspathic clasts granulitic breccias and minor basaltic clasts set in a clastic matrix we identify an an97 anorthosite that has an contents similar to those of nearside fans mg molar mg mg fe 100 values vary significantly from 45 to 80 covering the ranges of both nearside fans and the mg gap between fans and the mg suite a light gray feldspathic lg breccia making up 20 of the investigated slab 5 2 3 6 cm2 mainly consists of fragments of anorthosites an93 anorthosite more sodic than nearside fans lg also contains an augite plagioclase clast which either could be genetically related to the an93 anorthosite or to slowly cooled basaltic magma intruded into the precursor rock the na rich nature of both an93 anorthosite and this clast indicates that the lg breccia was derived from a relatively na rich but incompatible element poor source the mg variation indicates that the an97 anorthosite is a genomict breccia of several types of primary anorthosites granulitic breccias in y 86032 have relatively high mg in mafic minerals the highest mg values in mafic minerals for the an97 anorthosite and granulitic breccias are similar to those of mg rich lithologies recently described in dhofar 489 basaltic clasts in the dark gray matrix are aluminous and the zoning trends of pyroxene are similar to those of vlt or lt basalts the crystallization of these basaltic clasts pre date the lithification age of the clastic matrix at 3 8 ga the low k contents of plagioclase in both the anorthositic and basaltic clasts and generally low incompatible element abundances in all the lithologies in y 86032 indicate that kreep was not involved during the formation of the precursor lithologies this observation further suggests that urkreep did not exist in the source regions of these igneous lithologies all these facts support the idea that y 86032 was derived from a region far distant from the pkt and that the lithic clasts and fragments are indigenous to that region an an97 anorthositic clast studied here has distinct sm nd isotopic systematics from those previously found for another an97 anorthositic clast and an93 anorthosite and suggests either that an97 anorthosites come from isotopically diverse sources or that the sm nd isotopic systematics of this clast were reset 4 3 ga ago these lines of geochemical isotopic and petrologic evidence suggest that the lunar crust is geochemically more heterogeneous than previously thought

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

sixth foray for pristine nonmare rocks and an assessment of the diversity of lunar anorthosites eleven nonmare samples are characterized generally both compositionally and petrographically five are almost certainly pristine ferroan anorthosite 10056c alkali anorthosite 14047c ferroan anorthosite 14312c anorthositic troctolite 14321c3 and granite 14321c4 and four are probably pristine norite 14318c noritic anorthosite 67215 quasi pristine ferroan anorthosite 73217c and norite 78527 five are unique anorthosites extending the diversity of lunar anorthosites considerably alkali anorthosites particularly 14047c are extremely rich in incompatible elements the first anorthosite from apollo 11 with manifestations of pristinity 10056c appears to be a normal member of the ferroan group however the first pristine ferroan anorthosites from apollo 14 and 17 to be studied in detail 14312c and 73217c both have unusually sodic plagioclase by ferroan standards with only 75 plagioclase 67215 is the first large 273 g probably pristine ferroan sample with less than 83 plagioclase the nature of the correlations between longitude and such parameters as eu and sm concentrations and sc sm ti sm and ca na ratios among pristine ant samples has been elucidated because five of the new pristine samples are from a western site apollo 14 interestingly ferroan anorthosite 14312c has ca na sc sm and ti sm ratios close to the normal ferroan values but significantly displaced in the direction of the nonferroan western pristine rocks this suggests that the composition longitude relationships are as old as the late stages of the crystallization of the putative magma ocean

the last phase of the storegga slide simulation of retrogressive slide dynamics and comparison with slide scar morphology the prehistoric storegga slide one of the world largest known submarine slides took place about 8200 years ago most likely the slide was triggered by an earthquake in a steeper slope area in the distal part of the slide the present day s morphology of the slide area indicates that major parts of the slide took place as a sequential failure process spreading successively from the far end to the present shelf edge numerical simulations illustrating this retrogressive back stepping behaviour are presented for the last phase of the storegga slide as it reached today s upper headwall the applied rheological model is based on a bingham fluid with a history dependent yield strength and consistency

controls on subaerial erosion rates in antarctica erosion rates offer insight on landscape development and the relative importance of chemical and physical processes of weathering minimal chemical weathering makes antarctica an ideal location in which to compare the physical weathering of carbonate rocks to other lithologies here we report the first cosmogenic nuclide derived erosion rates for carbonate rocks in antarctica carbonate samples collected in the southernmost ellsworth mountains reflect a 36cl erosion rate of 0 22 0 02 mm ka this erosion rate is consistent with other reported antarctic erosion rates but is lower than 36cl erosion rates derived from other arid regions in the world these results are integrated with a continent wide reanalysis of 28 erosion rate studies 200 measurements which comprise numerous rock types and other cosmogenic nuclides by combining cosmogenic nuclide derived erosion rates across studies the larger trends provide insight into factors e g lithology glacial history and availability of abrasive material affecting subaerial erosion rates in antarctica statistical analysis of the compiled data set shows differences based on lithology with sandstone having the largest range of erosion rates the compiled data also reveals higher erosion rates in areas with a large potential sediment supply like the dry valleys samples collected from boulders yield lower erosion rates than those collected from bedrock likely due to a combination of physical processes that affect boulders and bedrock differently and glacial history which can affect the apparent cosmogenic nuclide derived erosion rate

large deformation finite element modelling of progressive failure leading to spread in sensitive clay slopes the occurrence of large landslides in sensitive clays such as spreads can be modelled by progressive development of large inelastic shear deformation zones shear bands the main objective of the present study is to perform large deformation finite element modelling of sensitive clay slopes to simulate progressive failure and dislocation of failed soil mass using the coupled eulerian lagrangian cel approach available in abaqus finite element software the degradation of undrained shear strength with plastic shear strain strain softening is implemented in abaqus cel which is then used to simulate the initiation and propagation of shear bands due to river bank erosion the formation of horsts and grabens and dislocation of soil masses that lead to large scale landslides are simulated this finite element model explains the displacements of different blocks in the failed soil mass and also the remoulding of soil around the shear bands the main advantages of the present finite element model over othe

minimum 10be exposure ages of early pliocene for the table mountain plateau and the sirius group at mount fleming dry valleys antarctica using accelerator mass spectrometry ams we have measured 10be and 26al in quartz from granites and sandstones from table mountain and mount fleming antarctica our data show that the plateau surface at table mountain had formed by early pliocene time at the latest granites fringing but within the sirius group at table mountain give a minimum exposure age of 2 6 ma for this deposit a sandstone clast on the ferrar dolerite surface just outside and below and thus postdating the sirius group has a minimum age of 2 9 ma two samples from the sirius group at mount fleming have 10be concentrations that have reached secular equilibrium this deposit is at least 4 8 m y old the sirius group at mount fleming cannot have been deposited after 3 0 2 5 ma as implied by biostratigraphic data our dates contradict the hypothesis that in the pliocene east antarctica was deglaciated and the climate was significantly warmer and wetter the preservation of these surfaces indicates a continuous cold desert in the dry valleys since the beginning of the pliocene the high 10be concentrations we have measured cannot be reconciled with uplift of the transantarctic mountains at a rate of 1 km m y during the past 3 m y

mineralogy and geochemistry of lunar meteorite queen alexandra range 93069 queen alexandra range que 93069 is a glass rich regolith breccia derived from the lunar highlands the high abundance of glassy fragments the presence of agglutinates the small size of all mineral and glass fragments the presence of mostly melt rocks and the low abundance of pristine lunar crustal rocks all indicate that que 93069 is derived from a mature regolith this conclusion is also supported by its high siderophile element content the most common mafic mineral is pyroxene with compositions that indicate derivation from ferroan ant suite rocks rare gabbro differentiation products may be indicated by the presence of silica fayalitic olivine and one pyroxferroite grain lithic fragments are mostly meta melt rocks of ant composition the glass compositions are dominated by troctolitic anorthosite compositions followed by gabbroic anorthosite and noritic anorthosite most glasses are ol normative in composition some rare basic glasses of noritic composition were observed glass fragments and matrix glasses are alkali poor except for some rare alkali rich shards the bulk chemical composition of que 93069 as well as the rare earth element ree abundance pattern is very similar to that of other highlands meteorites such as mac 88105 and y 86032 and to average lunar highlands crust one small porous clast was found to be very rich in volatile elements as well as in most lithophile and siderophile elements as this sample also contains abundant sulfides the enrichments could be related to element mobilization and redistribution by volatile sulfur species

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

development of progressive failure in sensitive clay slopes the development of progressive failure in sensitive clay slopes is analysed using principles from fracture mechan ics where failure stress depends on a material property toughness and length of an existing weakness unlike traditional soil mechanics where failure stress is generally assumed to be only a function of material strength an existing weakness or partially developed failure surface can propagate due to sudden loads as might be induced by seasonal erosion cycles small local landslides at a river bank or earthquake shaking the paper examines the growth of the failure surface over time due to such loads the analysis shows that a large landslide in sensitive clay can occur after a number of seasonal erosion cycles with no obvious trigger it also shows that a larger load due to either a small landslide or earthquake can cause a de veloping failure surface to propagate freely toward general collapse large landslides in sensitive clay are often preceded by a smaller landslide at the river bank but can be triggered by large earthquakes or may occur for no obvious reason the agreement between predictions and real behaviour suggests that the model for progressive failure of large landslides in sen sitive clay deserves further consideration

10be and 26al production rates deduced from an instantaneous event within the dendro calibration curve the landslide of kofels otz valley austria surface exposure dating requires the knowledge of cosmogenic nuclide production rates when determining time integrated production rates the exposure ages of the calibration samples need to be accurately known the landslide of kofels austria is very well suited for this purpose it is the largest landslide in the crystalline alps of austria dating back to 7800 100 years bc ams 14c dating of buried wood which is well within the 14c dendro calibration curve exposed quartz veins were sampled from the tops of large boulders from the toe of the landslide for analysis of 10be and 26al to calculate sea level high geomagnetic latitude 60 open sky radionuclide production rates corrections were applied for altitude and latitude for shielding by surrounding mountains for sample geometry vegetation and snow cover and for sample thickness the production rates for an exposure age of 10 000 years are 5 75 0 24 10be atoms yr g sio2 and 37 4 1 9 26al atoms yr g sio2 a 26al 10be ratio of 6 52 0 43 can be calculated the influence of the geomagnetic field on these production rates has been estimated using two different geomagnetic field records our production rates should be a good approximation for the use of surface exposure dating between about 5000 and 13 000 years bp

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

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

production rate of cosmogenic 21ne in quartz estimated from 10be 26al and 21ne concentrations in slowly eroding antarctic bedrock surfaces abstract we estimated the production rate of 21ne in quartz using a set of samples from slowly eroding sandstone surfaces in the antarctic dry valleys geologic evidence as well as cosmogenic 10be and 26al concentrations indicate that i these sites have experienced millions of years of surface exposure at low erosion rates and ii steady erosion has been sustained long enough that surface 10be and 26al concentrations have reached equilibrium with the erosion rate under these conditions surface cosmogenic 21ne concentrations should be a function only of the erosion rate and the 21ne production rate as the erosion rate can be determined from 10be and 26al concentrations this allows an estimate of the 21ne production rate estimating the reference 21ne production rate on this basis with the assumption that all 21ne production is by neutron spallation yields a poor fit to measured 21ne concentrations and a systematic residual that is correlated with the erosion rate of the sample site the same steady erosion assumption with a production model that includes production by deeply penetrating muons yields a good fit both to our measurements and to similar independent measurements from an antarctic bedrock core both data sets together yield a total reference 21ne production rate of 18 3 0 4 atoms g 1 a 1 of which 0 66 0 10 atoms g 1 a 1 is due to muon interactions

lunar granulites and their precursor anorthositic norites of the early lunar crust lunar granulites are breccias with metamorphic textures they are not pristine having been contaminated with meteoritic siderophiles nonetheless they constitute an abundant class of highlands rocks that are important because they are ancient and kreep free they may represent our best samples of the early lunar crust the granulites can be divided into ferroan and magnesian groups and each group can be subdivided on the basis of mineral composition and ree concentrations textural and compositional data show that some of the granulites especially 67215 and 67415 may be derived from distinct anorthositic norite precursors while some other granulites 79215 78155 are clearly polymict even the polymict granulites probably had anorthositic norites as their dominant precursors and not anorthosites norites or troctolites the granulites have compositions similar to those of the two lunar meteorites one of which yamato 791197 is ferroan the other alha81005 magnesian these meteorites are soil breccias from an unknown location distant from the apollo landing sites and contain anorthositic norites as abundant clasts compositions of granulites and lunar meteorites more closely resemble the average composition of lunar highlands as determined by remote sensing than do those of any other returned lunar samples the predominance of plutonic anorthositic norite precursors in material having the composition typical of highlands suggests that plutonic anorthositic norites were more abundant in the early lunar crust than is implied by their scarcity among pristine rocks from apollo missions

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

controlling factors for post failure evolution of subaqueous landslides subaqueous slope failures can evolve in various patterns whereas some slides run out and further evolve into highly mobile turbidity currents others maintain a continuum like structure and remain

catastrophic failure of submerged slopes in normally consolidated sediments the application of fracture mechanics methods to shear band growth in granular materials requires careful consideration of the elasto plastic nature of the material behaviour in this paper the palmer and rice fracture mechanics approach is applied to the problem of catastrophic shear band propagation in a submerged slope built of normally consolidated sediments this allows for catastrophic unstable and progressive stable types of soil failure to be properly distinguished many submerged landslides are triggered by earthquakes via the shear strength degradation due to the excess pore water pressure accumulation the conventional analysis assumes that the excess water pressure zone develops simultaneously along the entire landslide length often reaching several kilometres when a mechanism of the catastrophic shear band propagation is considered a much shorter excess water pressure zone e g several hundred metres can still cause a full scale landslide often generating a tsunami wave of consid

magmatic evolution of lunar highland rocks estimated from trace elements in plagioclase a new bulk silicate moon model with sub chondritic ti ba sr ba and sr al ratios abstract the compositions of host magmas of ferroan anorthosites fan host magmas were estimated from secondary ion mass spectrometry analyses of plagioclase in lunar highland rocks the evolution of the magmas was investigated by considering phase relations based on the melts algorithm and by re examining partition coefficients for trace elements between plagioclase and melts data little affected by post magmatic processes were selected by using plagioclase with relatively primitive sc and co contents the fan host magma contained 90 174 ppm sr 40 119 ppm ba and 0 5 1 3 tio2 and had sub chondritic sr ba and ti ba ratios it is difficult to account for the formation of fan host magma on the basis of magma evolution processes of previously proposed bulk silicate moon models with chondritic ratios for refractory elements at global scale therefore the source of the fan host magma must have had primordial sub chondritic sr ba and ti ba ratios the fan host magmas were consistent in refractory elements with the estimated host mafic magma for feldspathic crust based on lunar meteorites and some very low ti mare rocks from lunar meteorites here we propose an alternative bulk silicate moon model the cbsm model which is enriched in crustal components of proto bodies relative to the present whole earth moon system

composition and evolution of the lunar crust in the descartes highlands apollo 16 samples from the north ray crater ejecta blanket apollo 16 were investigated by petrographic microscope electron microprobe instrumental neutron activation and xray fluorescence analyses and 40ar 39ar and rb sr dating techniques nine major groups of monomict and polymict breccias were defined on the basis of microscopic texture and these were further subdivided into chemical subgroups on the basis of characteristic elements such as al mg fe cr ree ni and co the polymict breccias fragmental breccias granulitic breccias and impact melt breccias are the result of multiple impact induced mechanical mixing and melting and of thermal and impact metamorphism of rock and mineral clasts derived from primordial igneous crustal rocks for calculations of mixing models it was found that end members consisting of the pristine igneous rock components present as discrete samples at the apollo 16 site and supplemented by kreep dunite and a meteoritic component yield the best fits for the composition of polymict breccias the end member rocks a re ferroan anorthosite various magnesian gabbronorites including sodic ferrogabbro and feldspathic lherzolite and spinei troctolite the following model is proposed for the composition and stratigraphy of the target for north ray crater the lower section of the stratigraphy is composed of a megabreccia with clasts of highly feldspathic polymict breccias kreep free old eastern highland rock suite interpreted as nectaris ejecta descartes formation the top section contains kreep bearing polymict breccias kreep bearing young western highland rock suite and appears to be similar to the lithologies found in the cayley plains this material interpreted as cayley formation may be a distant facies of imbrium basin ejecta deposits of the imbrium basin the petrographic differences between these two major selenographic units the descartes and the cayley formations in the apollo 16 area are more distinct than the chemical differences the petrographic and chemical composition of the primordial igneous upper crust in the regions of the nectaris and imbrium basins has been calculated by subtraction of the kreep and meteoritic components from the bulk composition of the descartes and cayley materials the nectaris crust which is better constrained consists of 86 87 a northosite 4 sodic ferrogabbro 0 5 1 3 feldspathic lherzolite 6 8 regular magnesian gabbronorite 1 8 2 8 dunite and 0 1 spinel troctolite a model for the evolution of the upper lunar crust in the descartes highlands is proposed on the basis of isotope ages and clast matrix relationships of polymict breccias essential features of this model in sequenial order are 1 development of multiple layers of kreep free early feldspathic fragmental megabreccias and impact melt sheets on the primordial crust in the time period from 4 4 aeons to the time of the nectaris impact which could have occurred as late as 3 85 aeons ago 2 excavation of these megabreccias by the nectaris event and deposition of a nectarian feldspathic fragmental megabreccia in the descartes area 3 introduction of kreep basaltic material into the upper crust mainly west and northwest of the descartes site and formation of kreepy impact melt sheets most probably from 4 05 to 3 80 aeons ago 4 imbrium impact at 3 8 aeons ago and deposition of kreep bearing imbrian feldspathic fragmental breccias at the descartes site which form the cayley formation and 5 redeposition mixing and melting of all preexisting breccias yielding kreep bearing and kreep poor post cayley fragmental breccias and melt ejecta glass bombs as the result of small impacts craters 1 5 km in diameter in the cayley plains and the descartes mountains respectively

evolved mare basalt magmatism high mg fe feldspathic crust chondritic impactors and the petrogenesis of antarctic lunar breccia meteorites meteorite hills 01210 and pecora escarpment 02007 antarctic lunar meteorites meteorite hills 01210 and pecora escarpment 02007 are breccias that come from different regolith lithologies on the moon met 01210 is composed predominantly of fractionated low ti basaltic material and is classified as an immature predominantly basaltic glassy matrix regolith breccia pca 02007 is a predominantly feldspathic regolith breccia consisting of metamorphosed feldspathic noritic troctolitic and noritic anorthosite clasts agglutinate and impact glasses as well as a number of basaltic clasts with mare and possible non mare affinities the basalt clasts in met 01210 have undergone fenner trend enrichments in iron and may also have witnessed late stage crystallization of zircon or a zirconium rich mineral some of the features of met 01210 are similar to other basaltic lunar breccia meteorites e g northwest africa 773 elephant moraine 87521 96008 yamato 793274 981031 but it is not paired with them the presence of metamorphic anorthositic clasts as well as agglutinates indicates a small regolith component similarities with previously discovered evolved e g lapaz icefield 02205 northwest africa 032 and ferroan e g asuka 881757 yamato 793169 basaltic lunar meteorites suggest a similar mare source region for met 01210 despite lack of evidence for pairing pca 02007 shares many features with other feldspathic regolith breccias e g yamato 791197 queen alexandra range 94281 including a high mg fe whole rock composition glass spherules agglutinate fragments and a diverse clast inventory spanning the range of ferroan anorthosite and high magnesium suite rocks some of the basalt fragments in this sample are fractionated and have an igneous origin however the majority of the basalt fragments are impact melt clasts pca 02007 supports previous studies of feldspathic lunar meteorites that have suggested an aluminous crust for the moon with compositions more similar to magnesium granulite breccias than ferroan anorthosites a chondrule like fragment found in pca 02007 and unlike any previously described lunar material is described and tentatively identified as the remnants of a chondritic lunar impactor this clast is porphyritic with equant olivines that have forsterite rich cores fo 98 extreme normal zonation to more fayalitic rims fo 44 and a mineral assemblage with rare earth element abundances distinct from described lunar material and more similar to chondrules found in ordinary or carbonaceous chondrites its discovery and description is significant for understanding the composition of lunar impactors previously the main evidence for chondritic lunar impactors was from chondritic relative abundances and near chondritic ratios of highly siderophile elements in lunar impact melt breccias however the presence of this clast along with two other chondritic clasts from apollo soils 12037 and 15602 provides clues to the identity of ancient meteorite impactors on the moon

an ancient sm nd age for a ferroan noritic anorthosite clast from lunar breccia 67016 strontium and neodymium systematics have been examined in a clast of ferroan noritic anorthosite from apollo 16 breccia 67016 two splits 328 and 326 of the same clast give different sm nd results split 328 gives a well defined internal isochron age of 4 562 0 068 ga and an initial 143nd 144nd ratio of 0 50673 10 corresponding to nd 0 1 0 2 2 optimized error relative to the murchinson carbonaceous chondrite the pyroxene separate from split 326 lies on the same isochron in contrast the plagioclase and whole rock from split 326 fall below this line indicating a small scale disturbance of the sm nd system this may reflect either an isotopic exchange between the plagioclase and a low sm nd mineral or a loss of radiogenic 143nd from the plagioclase possibly during the period of major impacts at 3 9 ga the preservation of an extremely old age for the noritic ferroan anorthosite 67016 328 suggests a rapid cooling of this rock at an early stage in the evolution of the lunar magma ocean this old age is also consistent with giant impact models for the formation of the moon but implies a relatively early event pre 4 50 ga and therefore rapid accretion and differentiation of the terrestrial planets

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

simplified stability analysis of strain softening slopes under drawdown conditions the progressive failure of slopes is often induced by drawdown and strain softening of the soil thus the stability level of a strain softening slope under drawdown conditions should be evaluated while considering progressive failure a simplified method was developed to analyze the stability of a strain softening slope based on a new algorithm for determining the subsidiary shear deformation under drawdown conditions the parameters of the method could be easily determined the predictions of the failure behavior of the slope that were obtained using the proposed method were close to the observations of centrifuge model tests under drawdown conditions thus the method was confirmed to be effective in analyzing the stability evolution of the strain softening slopes induced by the drawdown of water level this proposed method was used to evaluate the stability of a real world slope under drawdown conditions the results showed that there is a significant evolution in the safety factor of the slope as the water level decreases the safety factor of a slope is overestimated if the progressive failure behavior is not considered the strain softening behavior and initial water level have a significant effect on the safety factor and critical slip surface of the slope

simulating retrogressive slope failure using two different smoothed particle finite element methods a comparative study abstract various smoothed particle finite element methods spfems have been developed to simulate large deformation problems but their efficiency and accuracy in simulating progressive landslides in sensitive clays have remained unclear in this study a series of numerical analyses are carried out to investigate the development of retrogressive landslides by two spfems an edge based strain smoothing pfem espfem and a node based strain smoothing pfem nspfem in view of their outstanding performance in large deformation analysis a strain softening mohr coulomb mc model is adopted to simulate the behaviour of sensitive clays during landslide assuming a poisson s ratio of 0 49 to ensure undrained conditions the influence of mesh density on the development of retrogressive failure is evaluated for two spfems numerical analyses of three mesh sizes 0 2 m 0 15 m and 0 12 m are carried out sequentially with all results demonstrating that 1 the spread retrogressive landslides with horsts and grabens can be achieved by both spfems with the adopted soil model 2 run out and retrogression distances decrease as mesh density increases for both methods 3 retrogressive collapse occurs earlier for espfem but is delayed for nspfem with increased mesh density 4 nspfem allows faster calculations and reduces mesh dependency problems when compared with espfem and 5 the increase of shape factor can accelerate retrogressive evolution of landslides finally a real landslide in sensitive clay at sainte monique quebec is simulated to demonstrate espfem s computational efficiency and accuracy

additional complexity in the lunar crust petrology of sodic anorthosites and sulfur rich ferroan noritic anorthosites lunar breccia 67016 contains two suites of unusual highlands rocks sulfur rich noritic anorthosites and sodic anorthosites mineral compositions of the sulfur rich noritic anorthosites closely match those of ferroan anorthosites unusually large amounts of sulfides and sulfidation reactions involving olivine in these clasts probably reflect endogenous volatile transfer the sodic anorthosites are mafic poor with mineral compositions intermediate between those of pristine ferroan and alkali anorthosites rare examples of pristine rocks with similar mineral compositions are known and may represent a distinct class of lunar crustal rocks

geochemical studies of feldspathic fragmental breccias and the nature of north ray crater ejecta major and trace element analyses of clasts and matrix from feldspathic fragmental breccias show that these breccias are not all alike but vary widely in their bulk compositions and clast assemblages these studies together with analyses of other north ray crater large rocks reveal the major components to be anorthosites ferroan anorthositic norites magnesian granulites feldspathic melt rocks and vha impact melts the ferroan anorthositic norites are important lunar crustal rocks identified here for the first time the kreepy vha melts are found to be much more important in north ray crater ejecta than was previously assumed sodic ferrogabbro is an important minor component the compositional characteristics of bulk breccias and feldspathic melt rocks are modeled quantitatively as mixtures of two to five components anorthosites ferroan anorthositic norites magnesian granulites sodic ferrogabbros and vha melt rocks breccia 67455 is unique in consisting wholly of ferroan kreep free components

geochemistry of lunar crustal rocks from breccia 67016 and the composition of the moon global differentiation of the moon has produced a plagioclase rich crust overlying an ultramafic mantle we have conducted a major and trace element study of anorthositic clasts from an apollo 16 breccia to investigate the geochemical features of these highlands lithologies and their role in lunar crustal evolution samples analyzed for this study have aluminous alkali poor compositions and varied feo and mgo contents al2o3 25 35 na2o 0 3 1 k2o 1 ferroan noritic and 1 magnesian troctolitic respectively these mafic enriched varieties have considerably higher lithophile element concentrations at levels similar to that of the bulk lunar crust the ferroan noritic clasts may represent a fundamental type of igneous rock in the lunar crust which has not been widely recognized liyb ratios of highlands and mare rocks demonstrate the complementary nature of the lunar crust and mantle which is best explained by a global differentiation event such as crystallization of a magma ocean the most primitive mantle derived lunar material for which data are available the apollo 15 green glass has liyb virtually identical to those of the mafic enriched anorthosites providing an estimate of the magma ocean composition the moon and the earth have liyb ratios that are similar to each other but the absolute abundances of both li and yb appear to be higher in the moon the liyb ratios of the earth and moon are distinct from those of ci and ordinary chondrites and the eucrite parent body but are similar to those of cv co and el chondrites precluding a unique match between the composition of the earth and moon

a new model for large landslides in sensitive clay using a fracture mechanics approach a new model is proposed for the development of large landslides in sensitive clay and supported by concepts from fracture mechanics a key assumption in this new model is that the complete failure surface develops before the onset of significant movement thus predetermining the final extent of failure the appearance of retrogression is actually the rear ward advancing disruption of a monolithic slide mass over a growing zone of liquefied clay it is seen that the likelihood of propagation of failure and the resulting occurrence of a large landslide depend primarily on the brittleness of the sensitive clay the potential length of shear band propagation is limited by slope geometry and increases for higher riverbanks and for flatter slopes above the riverbank the model explains why large landslides in sensitive clay often terminate just adjacent to a reverse break in slope such as an older landslide crater or a stream gully the model also indicates that large landslides in sensitive clay could be expected to occur suddenly after a large single perturbation such as an earthquake or after a seemingly innocuous small trigger following the accumulation of a large number of annual load cycles as observed fre quently in nature

experimental and numerical investigation of the saint adelphe landslide after the 1988 saguenay earthquake on 25 november 1988 after the saguenay earthquake a landslide occurred in the municipality of saint adelphe the soil profile indicated that the deposit was composed of a stiff clay crustal layer

finite element analysis of progressive failure of carsington embankment progressive failure occurs when brittle soils are loaded non uniformly the average shear stress at collapse is less than peak strength the effect cannot be examined by conventional limit equilibrium stability analysis the carsington embankment slipped in 1984 just before it reached full height the slide was 30 m deep and 500 m long and instrumentation had been installed and read up to the moment of collapse the strengths of the soils involved were carefully established as was the exact geometry of the slip limit equilibrium analysis showed that at collapse the average shear stress mobilized was less than peak strength with a safety factor based on peak strength of 1 2 since the soils involved were brittle progressive failure was a probable cause of the discrepancy finite element analyses were performed in which strain softening soil properties were assumed some of these analyses are reported here the pre failure displacements the collapse height and collapse mechanism were recovered by t

large deformation finite element modelling of earthquake induced landslides considering strain softening behaviour of sensitive clay large scale landslides in sensitive clays cannot be explained properly using the traditional limit equilibrium or lagrangian based finite element fe methods in the present study dynamic fe anal

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

simple criteria for ploughing and runout in post failure evolution of submarine landslides this paper extends shear band propagation analysis of slope failures to the investigation of ploughing and runout phenomena in submarine landslides the ability to predict the two different modes of post failure landslide evolution is critical for determining the tsunami hazard and type of landslide impact on offshore structures the proposed analysis is based on the analogy between ploughing and spreading failures it uses the energy balance approach to develop the criterion for progressive shear band propagation driven by accumulation of sliding material on top of the stable slope this criterion is then combined with the kinematic passive block mechanism to produce analytical ploughing failure criteria formulated in terms of the critical rise in the seabed level if the minimum rise of the seabed level at which ploughing can take place is larger than the maximum possible free standing step in the seabed surface the first passive failure block will start crumbling over top the stable zone causing the l

lewis cliff 86360 an antarctic l chondrite with a terrestrial age of 2 35 million years we measured the concentrations of the cosmogenic radionuclides 10be half life 1 51 106 a 26al 7 05 105 a and 36cl 3 01 105 a in lewis cliff lew 86360 an l chondrite from the lewis cliff stranding area east antarctica in addition the concentrations and isotopic compositions of he ne and ar were measured the combined results yield a terrestrial age of 2 35 0 15 ma only one other stony meteorite with a similar terrestrial age 2 ma is known from the allan hills stranding area alh 88019 whereas all previously dated stony meteorites from antarctica are younger than 1 ma we argue that lew 86360 spent most of its terrestrial residence time deep inside the ice near the base of the glacier where ice flow rates are much lower than at the surface the terrestrial ages of lew 86360 and alh 88019 are consistent with existing hypotheses concerning the stability and persistence of the east antarctic ice sheet

progressive failures in eastern canadian and scandinavian sensitive clays observations from past events are used to show that the concept of progressive failure may explain translational progressive landslides and spreads large landslides occurring in sensitive clays during progressive failure the strain softening behaviour of the soil causes unstable forces to propagate a failure surface further in the slope translational progressive landslides generally take place in long gently inclined slopes instability in a steeper upslope area is followed by redistribution of stress which increases earth pressure further downslope passive failure may therefore occur in less inclined ground heaving the soil spreads are usually trigged by erosion of a deposit having a higher angle near the toe instability starts near the toe of the slope and propagates into the deposit reducing earth pressure this may lead to the formation of an active failure with dislocation of the deposit into horsts and grabens the failure mechanism of both types of landslides is controlled by the stress

geotechnical centrifuge modelling of retrogressive sensitive clay landslides sensitive clay landslides represent a significant geohazard due to their well known potential for extensive retrogressive failures on the scale of multiple hectares which could encompass surround