impact melt rocks from the ries structure germany an origin as impact melt flows abstract the production of impact melt rocks and glasses is a characteristic feature of hypervelocity impact events on earth and other planetary bodies this investigation represents the first detailed study of an unusual series of coherent impact melt rocks intermittently exposed around the periphery of the 24 km diameter 14 5 ma ries impact structure germany optical and analytical scanning electron microscopy sem reveals that the groundmass comprises sanidine plagioclase quartz and ilmenite decreasing order of abundance with the interstices filled by either fresh or devitrified glassy mesostasis primary crystallites display skeletal dendritic and or spherulitic textures indicating rapid crystallization from a melt the mesostasis is characterized by extreme chemical heterogeneity e g feo and al 2 o 3 contents from 1 to 62 80 wt this is likely due to a combination of crystal liquid fractionation during rapid cooling and crystallization of an originally incompletely homogenized melt vapor phase crystallization of sanidine and cristobalite occurred in miarolitic cavities during late stage cooling of the impact melts the most likely protolith for the impact melt rocks are granitic rocks present in the crystalline basement target the high volatile content of the mesostasis suggests that a large volatile component was retained from this protolith field observations together with analytical data and micro textures indicate that the ries impact melt rocks were molten at the time of and after deposition field relations with other impactites also suggest that these rocks were emplaced subsequent to the excavation stage of crater formation and that they are not therefore ballistic ejecta thus it is proposed that the ries impact melt rocks were emplaced as ground hugging impact melt flows that emanated from different regions of the evolving transient cavity during the modification stage of crater formation this is consistent with and in fact predicted by field relations which indicate that these rocks overlie unequivocal ejecta this represents the first recognition of impact melt flows near the rim of a terrestrial impact structure and is consistent with observations of such features on the moon and venus

introduction to the special issue the formation and evolution of ceres occator crater abstract ceres the largest body in the asteroid belt was explored from orbit for the first time by the dawn mission the 92 km diameter occator crater contains bright regions or faculae which are one of the most remarkable discoveries of dawn s exploration of ceres a pit within the center of the crater contains both the cerealia facula and a central dome the vinalia faculae are located in the eastern crater floor occator s faculae are composed mostly of sodium carbonate and their single scattering albedo is the highest of any material on ceres surface the faculae do not occur in other impact craters on ceres and occator s extensive interior lobate materials are unusual understanding the driving forces behind the formation of occator crater and its faculae has the potential to lead us to a new understanding of the processes and conditions in ceres past and to possibly provide constraints about the present day internal state in this special issue we present a variety of investigations which use dawn data theoretical modeling and laboratory experiments to investigate occator crater and its faculae the results of these investigations are summarized and synthesized in the final paper of this collection herein we introduce ceres and the dawn mission and summarize the geophysical geological mineralogical and geochemical properties of ceres as derived from dawn data we also discuss the regional setting of occator crater and introduce occator crater itself

physical constraints on impact melt properties from lunar reconnaissance orbiter camera images abstract impact melt flows exterior to copernican age craters are observed in high spatial resolution 0 5 m pixel images acquired by the lunar reconnaissance orbiter camera lroc narrow angle camera nac impact melt is mapped in detail around 15 craters ranging in diameter from 2 4 to 32 5 km this survey supports previous observations suggesting melt flows often occur at craters whose shape is influenced by topographic variation at the pre impact site impact melt flows are observed around craters as small as 2 4 km in diameter and preliminary estimates of melt volume suggest melt production at small craters can significantly exceed model predictions digital terrain models produced from targeted nac stereo images are used to examine the three dimensional properties of flow features and emplacement setting enabling physical modeling of flow parameters qualitative and quantitative observations are consistent with low viscosity melts heated above their liquidii superheated with limited amounts of entrained solids

impactoclastic density current emplacement of terrestrial meteorite impact ejecta and the formation of dust pellets and accretionary lapilli evidence from stac fada scotland abstractwe present an impactoclastic density current model for terrestrial meteorite impact ejecta emplacement that is based on a hitherto unreported threefold sequence of lithofacies in the recently identified stac fada impact ejecta outflow blanket in scotland massive suevite division a grades seamlessly up into massive suevite containing whole and broken accretionary lapilli division b and this is overlain by a thin layer of clast supported dust pellets division c the sequence closely resembles sequences in accretionary lapilli bearing ignimbrites emplaced by pyroclastic density currents at volcanoes and we deduce similar emplacement mechanisms we propose that 99 of the thickness of the stac fada ejecta blanket as seen at outcrop was deposited from a single depletive spatially decelerating granular fluid based density current that rapidly waxed and then waned a previously unreported thin layer of pellets division c records direct fallout from a residual atmospheric dust plume we pro

precambrian reidite discovered in shocked zircon from the stac fada impactite scotland terrestrial impact events have had a profound influence on earth s geological geochemical and biological evolution however the record of precambrian impacts is poorly constrained due to the dynamic nature of plate tectonics erosion and deposition of younger rocks that may destroy or cover the evidence here we report the first precambrian occurrence of the rare mineral reidite zrsio4 within grains of shocked zircon in the ca 1 18 ga stac fada member stoer group northwestern scotland the reidite preserved as 2 m wide lamellae is unambiguous evidence of shock pressures in excess of 30 gpa and confirms the impact origin for the stac fada deposit the reidite lamellae are locally deformed and sites of deformation record its decomposition to baddeleyite zro2 and amorphous silica the first natural example of this transformation the findings demonstrate that reidite and baddeleyite may form and be transported in high energy ejecta without physical or chemical breakdown and are stable during sedimentary diagenesis and low grade metamorphism thus reidite may be preserved over time scales exceeding 1 b y establishing the use of reidite within detrital shocked zircon from precambrian strata as a viable and valuable means of recognizing and characterizing ancient terrestrial impact events

mineralogical analysis of the ac h 6 haulani quadrangle of the dwarf planet ceres abstract ac h 6 haulani is one of five quadrangles that cover the equatorial region of the dwarf planet ceres this quadrangle is notable for the broad spectrally distinct ejecta that originate from the crater haulani which gives the name to the quadrangle these ejecta exhibit one of the most negative bluest visible to near infrared spectral slope observed across the entire body and have distinct color properties as seen in multispectral composite images besides haulani here we investigate a broader area that includes other surface features of interest with an emphasis on mineralogy as inferred from data obtained by dawn s visible infrared mapping spectrometer vir combined with multispectral image products from the dawn framing camera fc so as to enable a clear correlation with specific geologic features our analysis shows that crater haulani stands out compared to other surface features of the quadrangle albedo maps obtained in the near infrared range at 1 2 m and 1 9 m reveal that the floor and ejecta of haulani are indeed a patchwork of bright and dark material units visible to near infrared spectral slopes display negative values in crater haulani s floor and ejecta highlighting bluish younger terrains diagnostic spectral features centered at 2 7 m and 3 1 m respectively indicate a substantial decrease in the abundances of magnesium bearing phyllosilicates and ammoniated phyllosilicates in crater haulani s floor and bright ejecta similar but less prominent spectral behavior is observed in other geologic features of this quadrangle while the general trend in quadrangle ac h 6 for these two mineral species is to increase from the northwest to the southeast however it is worth noting that the correlation between the 2 7 m and 3 1 m spectral parameters is generally strong in the haulani crater s area but much weaker elsewhere which indicates a variable degree of mixing between these two major mineral phases in moving away from the crater finally the region of crater haulani displays a distinct thermal signature and a local enhancement in calcium and possibly sodium carbonate minerals which is hardly found in the rest of the quadrangle and is likely the result of intense hydrothermal processes following the impact event these evidences all together confirm the young age of crater haulani as they have not been erased or made elusive by space weathering processes

occator crater in color at highest spatial resolution abstract the geology of the outstanding crater occator on ceres has been studied by combining highest resolution color images and other information from the dawn mission thus surface and sub surface layers and geologic processes can be understood and interpreted in a consistent manner in order to achieve this morphometry absolute surface unit ages color and the distribution of foci of activity were the key data these data show that the ascent of brine from reservoir s at depth and deposition of its salts on the surface persisted much longer than initially thought possible as an immediate result of the primary impact the youngest depositional processes of bright material occurred less than 2 ma ago also the bright cerealia and vinalia faculae are not the only traces of this activity updoming is present on the southwestern crater floor faculae coincide with fractures and vents and indicate complex mechanisms of the deposition of bright carbonate rich material due to the large age difference between the occator impact itself modeled cooling times of heated crater material and the recent activity at the faculae we conclude that endogenic forces were lately acting the distribution and thickness of surface and sub surface brine layers are far from homogeneous in the upper crust beneath occator further evidence regarding the distribution of materials has been derived from the distribution of the ejecta and the transition of ejecta to background material outside the crater

sulfur based hazardous waste solidification existing uses for sulfur are relatively advanced and offer limited opportunities to consume significant new supplies currently sulfur is in net surplus on a global basis and with environmental regulations greater sulfur recovery from petroleum and gas processing is mandated the outlook is clear there will be substantial and growing surpluses in global sulfur supply in the foreseeable future sulfur prices are likely to be under pressure and producers could face substantial and growing disposal fees therefore new markets must be found for sulfur to avoid disposal crises one potential new market is the production of sulfur solidified concrete this is a thermoplastic composite of mineral aggregates bound together with chemically modified sulfur the product is more durable than portland cement there may be monetizeable benefits in reducing greenhouse gas emissions that would enhance the attraction of sulfur solidified cement applications the main objective of this study is to evaluate experimentally the potential use of sulfur as a solidifying agent for hazardous waste to achieve this objective the study reviewed the sulfur concrete literature analyzed locally produced sulfur evaluated a number of sulfur polymer modifiers and physical stabilizing agents designed a set of experiments and evaluated the produced product for its hydro mechanical chemical properties the results indicated that the manufactured sulfur polymer cement is an excellent candidate for waste management practices such as solidification stabilization of hazardous waste barrier systems for landfilling of hazardous waste and waste water treatment plants

spectral investigation of quadrangle ac h 3 of the dwarf planet ceres the region of impact crater dantu abstract mapping ceres surface composition in the dantu region located between 21 66 n and 90 180 e offers the unique possibility to investigate changes in the surface composition related to different stratigraphic levels of ceres crust dantu is located in a huge depression named vendimia planitia which possibly represents a completely degraded impact basin formed in the beginning of ceres geological history most parts of this depression are characterized by strong phyllosilicate absorptions which are stronger than elsewhere on ceres surface this spectral signature possibly is related to the material emplaced at the time of the vendimia impact event excavating material from deeper regions of ceres crust subsequent impacts in this basin reach far deeper into ceres crust than any impact events outside of vendemia planitia which could explain the spectral signature of dantu possibly pointing to a higher concentration of ammonium bearing phyllosilicates in ceres deeper crust spectral differences with respect to the small fresh craters on dantu s floor are probably related to grain size effects causing a bluish visible slope as observed by fresh impact craters on other places on ceres the local enrichment of carbonates in the dantu area could also be associated with the impact event and may have been formed by additional impact triggered and or post impact alteration processes

mass movement and landform degradation on the icy galilean satellites results of the galileo nominal mission the galileo mission has revealed remarkable evidence of mass movement and landform degradation on the icy galilean satellites of jupiter weakening of surface materials coupled with mass movement reduces the topographic relief of landforms by moving surface materials down slope throughout the galileo orbiter nominal mission we have studied all known forms of mass movement and landform degradation of the icy galilean satellites of which callisto by far displays the most degraded surface callisto exhibits discrete mass movements that are larger and apparently more common than seen elsewhere most degradation on ganymede appears consistent with sliding or slumping impact erosion and regolith evolution sliding or slumping is also observed at very small 100 m scale on europa sputter ablation while probably playing some role in the evolution of ganymede s and callisto s debris layers appears to be less important than other processes sputter ablation might play a significant role on europa only if that satellite s surface is significantly older than 108 years far older than crater statistics indicate impact erosion and regolith formation on europa are probably minimal as implied by the low density of small craters there impact erosion and regolith formation may be important on the dark terrains of ganymede though some surfaces on this satellite may be modified by sublimation degradation while impact erosion and regolith formation are expected to operate with the same vigor on callisto as on ganymede most of the areas examined at high resolution on callisto have an appearance that implies that some additional process is at work most likely sublimation driven landform modification and mass wasting the extent of surface degradation ascribed to sublimation on the outer two galilean satellites implies that an ice more volatile than h2o is probably involved

massive ice avalanches on iapetus mobilized by friction reduction during flash heating the great distance travelled by long runout landslides observed previously on the earth and mars requires a mechanism of friction reduction identification and analysis of long runout landslides on saturn s moon iapetus suggests that the iapetian landslides are enabled by flash heating of the icy sliding surface

ceres impact craters relationships between surface composition and geology abstract impact craters of different geological ages sizes and morphologies are not only the most obvious surface features on ceres surface the investigation of their spectral properties in combination with ceres geology and topography reveals not only lateral compositional variations in ceres surface material but also possible stratigraphic differences within ceres crust spectral properties of impact craters with different ages do show distinct trends implying variations with increasing exposure duration of the impact material onto ceres surface local concentrations of h2o ice and carbonates are associated with the youngest either recently emplaced or excavated surface deposits on the contrary regionally higher amounts of ammoniated phyllosilicates originate from deeper regions of ceres crust and strengthen the theory of ammonia being a primordial constituent of ceres the blue spectral slope clearly associated with relatively weak absorptions of oh bearing and or ammoniated phyllosilicates is limited to fresh impact material either the blue spectral slope diminishes slowly with increasing geologic age due to space weathering processes or shortly as a result of gravitation induced slumping forming a fine and loosely consolidated regolith

the geology of the occator quadrangle of dwarf planet ceres floor fractured craters and other geomorphic evidence of cryomagmatism abstract the dawn science team is conducting a geological mapping campaign at ceres during the nominal mission including iterative mapping using data obtained during each orbital phase we are using geological mapping as a method to identify the geologic processes that have modified the surface of dwarf planet ceres we here present the geology of the ac 9 occator quadrangle located between 22 s 22 n and 216 288 e the ac 9 map area is within the topographically high region named hanami planum features of note within the profile include impact craters occator azacca lociyo nepen and kirnis four of these craters have fractured shallow floors morphometrically comparable to floor fractured craters ffcs on the moon similar to models for the formation of the lunar ffcs we suggest that these ceres ffcs are a result of cryomagmatic uplift under the crater floors a set of regional linear structures called the samhain catenae do not have any obvious relationship to impact craters many of the catenae are comprised of smaller structures that have linked together suggestive of en echelon fractures it has been suggested that these fractures formed due to the uplift of hanami planum due to cryromagmatic plumes

resolved spectrophotometric properties of the ceres surface from dawn framing camera images we present a global spectrophotometric characterization of the ceres surface using dawn framing camera fc images we identify the photometric model that yields the best results for photometrically correcting images corrected fc images acquired on approach to ceres were assembled into global maps of albedo and color generally albedo and color variations on ceres are muted the albedo map is dominated by a large circular feature in vendimia planitia known from hst images li et al 2006 and dotted by smaller bright features mostly associated with fresh looking craters the dominant color variation over the surface is represented by the presence of blue material in and around such craters which has a negative spectral slope over the visible wavelength range when compared to average terrain we also mapped variations of the phase curve by employing an exponential photometric model a technique previously applied to asteroid vesta schroder et al 2013b the surface of ceres scatters light differently from vesta in the sense that the ejecta of several fresh looking craters may be physically smooth rather than rough high albedo blue color and physical smoothness all appear to be indicators of youth the blue color may result from the desiccation of ejected material that is similar to the phyllosilicates water ice mixtures in the experiments of poch et al 2016 the physical smoothness of some blue terrains would be consistent with an initially liquid condition perhaps as a consequence of impact melting of subsurface water ice we find red terrain positive spectral slope near ernutet crater where de sanctis et al 2017 detected organic material the spectrophotometric properties of the large vendimia planitia feature suggest it is a palimpsest consistent with the marchi et al 2016 impact basin hypothesis the central bright area in occator crater cerealia facula is the brightest on ceres with an average visual normal albedo of about 0 6 at a resolution of 1 3 km per pixel six times ceres average the albedo of fresh bright material seen inside this area in the highest resolution images 35 m per pixel is probably around unity cerealia facula has an unusually steep phase function which may be due to unresolved topography high surface roughness or large average particle size it has a strongly red spectrum whereas the neighboring less bright vinalia faculae are neutral in color we find no evidence for a diurnal ground fog type haze in occator as described by nathues et al 2015 we can neither reproduce their findings using the same images nor confirm them using higher resolution images fc images have not yet offered direct evidence for present sublimation in occator

mineralogical analysis of quadrangle ac h 10 rongo on the dwarf planet ceres abstract quadrangle ac h 10 rongo lat 22 s to 22 n lon 288 360 e shows a fairly homogeneous topography with the presence of notable elevations such as ahuna mons liberalia mons and part of samhain and uhola catenae the deepest areas correspond to the rongo crater region the areas between samhain and uhola catenae and the region of the quadrangle south of ahuna mons a substantial variability in the 2 7 m band depth distribution is observed across the rongo quadrangle indicating an east west gradient in the abundance of mg phyllosilicates the nh4 phyllosilicates distribution appears quite homogeneous except some localized regions such as crater haulani s ejecta the flanks of ahuna mons and crater begbalel the two band depths at 2 7 and 3 1 m display an overall low correlation suggesting a variable degree of mixing between mg phyllosilicates and nh4 phyllosilicates at the local scale mineralogical phases other than phyllosilicates are observed quadrangle rongo includes sodium carbonate rich regions such as the flanks of ahuna mons the ejecta of xevioso crater located in the southern edge of liberalia mons and crater begbalel which often display a reduction in both the 2 7 and 3 1 m band depths associated with an increased band depth at 4 m related to the presence of na rich carbonate phases this suggests recent hydrothermal activity in this area due to several episodes of cryovolcanism or impacts that unveiled a peculiar composition in the shallow subsurface alternatively the crust in this region might show a variable degree of compactness such that the formation of na carbonates is favored only in specific locations de sanctis et al 2016 ruesch et al 2016 zambon et al 2017 from a geological standpoint quadrangle ac h 10 rongo shows a correlation between its two main geologic units platz et al 2017 and the distribution of mg phyllosilicates suggesting a link between geology and mineralogy in this area

ceres occator crater and its faculae explored through geologic mapping abstract occator crater is one of the most recognizable features on ceres because of its interior bright regions which are called the cerealia facula and vinalia faculae here we use high resolution images from dawn 35 m pixel to create a detailed geologic map that focuses on the interior of occator crater and its ejecta occator s asymmetric ejecta indicates that the occator forming impactor originated from the northwest at an angle of 30 45 perhaps closer to 30 some of occator s geologic units are analogous to the units of other complex craters in the region the ejecta crater terrace material hummocky crater floor material and talus material the geologic units that make occator unique are the bright occator pit fracture material this is the unit that corresponds to the cerealia facula and vinalia faculae and the extensive well preserved lobate materials we propose that the lobate materials are a slurry of impact melted and non impact melted target material which flowed around the crater interior before solidifying to form deposits geomorphologically consistent with impact melts elsewhere in the solar system we sub divide the lobate materials on the basis of their surface textures it is likely that knobby or smooth lobate materials form if the lobate material entrains or does not entrain blocks respectively post impact inflation is suggested to form the hummocky lobate material the vinalia faculae formed within the hummocky lobate material we find that the knobby lobate material and the outer edge of the cerealia facula formed prior to the central pit the central dome formed after the formation of the central pit while the majority of the cerealia facula besides the outer edge could have formed continued to form and or have been modified after the formation of the central pit the cerealia facula may have initially been emplaced in a similar process to the vinalia faculae and the surface of the cerealia facula appear to have somewhat darkened over time the insights into occator crater and its faculae derived from our geologic mapping will be synthesized together with inputs from all of the studies in this special issue in scully et al 2018a

a meteorite from the cretaceous tertiary boundary cretaceous tertiary boundary sediments are now widely recognized to contain the record of a large asteroid or comet impact event1 probably at the site of the chicxulub crater on the yucatan peninsula2 after nearly two decades of intensive research however much remains unknown about the specific nature of the projectile and of the impact event itself here we describe a 2 5 mm fossil meteorite found in sediments retrieved from the cretaceous tertiary boundary in the north pacific ocean that we infer may be a piece of the projectile responsible for the chicxulub crater geochemical and petrographic analyses of this meteorite indicate that it probably came from a typical metal and sulphide rich carbonaceous chondrite rather than the porous aggregate type of interplanetary dust considered typical of cometary materials3 the fact that meteorite survival should be enhanced by impacts at low asteroidal velocities4 also implies that this meteorite had an asteroidal rather than a cometary origin

the various ages of occator crater ceres results of a comprehensive synthesis approach abstract the 90 5 km occator crater with its peculiar and unique bright spots is one of the most prominent and renowned feature on ceres occator attracted broad public attention in scientific media as it is proposed to exhibit signs of post impact cryovolcanic activity in order to understand the time sequence of deposition several attempts were made during dawn s primary mission by different research groups to date geomorphologic key units using superposed crater densities resulting absolute model formation ages for occator s ejecta and its interior lobate deposits range from 200 ma to 78 ma and about 100 ma to 6 9 ma but were based on different cratering chronology models measurements on image data at varying resolution and different statistical and methodological approaches here we present the results of a comprehensive approach of determining absolute model formation ages for occator this is achieved by using the best resolved framing camera image data by careful treatment of secondary crater admixture and the natural variability of crater detection and sizes by different crater analysts and by applying appropriate objective criteria for count area selection in this context we evaluate previously published model ages and explain why our results are likely to yield more consistent and robust information about the formation age of occator we also show that in contrast to previous publications csfds measured on occator s less competent ejecta blanket and its more competent cryovolcanic or impact melt related interior lobate deposits ilds are so similar to each other that the slight differences might rather be explained by different scaling parameters in different target materials or that the ilds have formed almost contemporaneously or only shortly after the occator forming impact

space weathering on airless bodies space weathering refers to alteration that occurs in the space environment with time lunar samples and to some extent meteorites have provided a benchmark for understanding the processes and products of space weathering lunar soils are derived principally from local materials but have accumulated a range of optically active opaque particles oaopq that include nanophase metallic iron on in rims formed on individual grains imparting a red slope to visible and near infrared reflectance and larger iron particles which darken across all wavelengths such as are often found within the interior of recycled grains space weathering of other anhydrous silicate bodies such as mercury and some asteroids produce different forms and relative abundance of oaopq particles depending on the particular environment if the development of oaopq particles is minimized such as at vesta contamination by exogenic material and regolith mixing become the dominant space weathering processes volatile rich bodies and those composed of abundant hydrous minerals dwarf planet ceres many dark asteroids outer solar system satellites are affected by space weathering processes differently than the silicate bodies of the inner solar system however the space weathering products of these bodies are currently poorly understood and the physics and chemistry of space weathering processes in different environments are areas of active research

bright carbonate surfaces on ceres as remnants of salt rich water fountains abstract vinalia and cerealia faculae are bright and salt rich localized areas in occator crater on ceres the predominance of the near infrared signature of sodium carbonate on these surfaces suggests their original material was a brine here we analyze dawn framing camera s images and characterize the surfaces as composed of a central structure either a possible depression vinalia or a central dome cerealia and a discontinuous mantling we consider three materials enabling the ascent and formation of the faculae ice ascent with sublimation and carbonate particle lofting pure gas emission entraining carbonate particles and brine extrusion we find that a mechanism explaining the entire range of morphologies topographies as well as the common composition of the deposits is brine fountaining this process consists of briny liquid extrusion followed by flash freezing of carbonate and ice particles particle fallback and sublimation subsequent increase in briny liquid viscosity leads to doming dawn observations did not detect currently active water plumes indicating the frequency of such extrusions is longer than years

the discovery of iron barringerite in lunar meteorite y 793274 abstract the higher phosphide barringerite fe ni 2p has been found in a thin section of the y 793274 lunar meteorite this meteorite originated from a highlands mare boundary and contains mare and highlands components in a 2 1 ratio the original report of barringerite was from the ollague pallasite however there is uncertainty whether the barringerite in this pallasite may have formed terrestrially terrestrial weathering or artificial heating as the source of the barringerite in the lunar meteorite can be excluded therefore y 793274 seems to contain the first unambiguous extraterrestrial occurrence of barringerite

geochemical modeling based rehabilitation proposal for abandoned sulfidic flotation mill tailings kirki thrace ne greece a total number of eight 8 tailings dams are found at the kirki flotation plant and are either built on impermeable neogene formations or permeable alluvial deposits of the kirkalon and eirini streams the tailings dams were originally constructed without any environmental concerns nowadays their embankments are highly eroded and toxic material is readily transported to the nearby streams resulting in degradation of the quality of both stream waters and sediments stream water sampling revealed that concentrations of dissolved pb mn cd and so4 increase rapidly in the vicinity of the kirki flotation plant four case specific phreeqc scenarios were employed including direct precipitation evaporation mixing with rain water and mixing with stream water in order to investigate the effect of interaction between water accumulated on the surface of the tailings dams and the precipitation or dissolution of heavy metal bearing phases that may control heavy metal solubility all tests performed concluded that such interaction plays a very important role in the environmental behavior of the toxic tailings material of the kirki flotation plant based on the results of the phreeqc tests the proposed rehabilitation plan includes the construction of a sealing system in order to eliminate tailings dam wall erosion and infiltration effects the suggested plan is limited to dams 2 3 4 5 6 7 and 8 whereas dam 1 is empty and requires no remediation additionally and only for dams 5 7 and 8 built on top of permeable alluvial formations a few meters above the ground water head chemical improvement of the tailings material is suggested to limit toxic pollutants dissolution in particular installation of lime piles is proposed in order to further improve the quality of possible small scale low quality percolating solutions that might migrate to underground aquifers

hydro mechanical evaluation of soil stabilized with cement kiln dust in arid lands this study evaluates the potential use of cement kiln dust ckd a waste product from the cement industry for enhancing the mechanical as well as the hydraulic properties of soils in arid lands stabilized products will play a major role in reducing slope failures pavement damage and the design of containment barriers for hazardous waste in arid lands various tests to determine the different physical properties of the stabilized matrix were conducted and the optimum mixture that produces maximum internal energy and minimum hydraulic conductivity was selected the effect of soaking and unsoaking of the treated specimens on the mechanical properties was also evaluated the effect of metal ion concentration and conjugate anions on the resultant hydraulic conductivity was evaluated the optimum percentage of ckd was calculated by using stress strain data newton s divided difference and simpson s integration technique the analyses have shown that 6 by weight of ckd is the optimum mix design which increases the shear strength and decreases the hydraulic conductivity to less than 10 9 m s therefore the treated soil could be used as a soil based barrier layer for containment of hazardous waste

north atlantic volcanic margins dimensions and production rates early tertiary lithospheric breakup between eurasia and greenland was accompanied by a transient 3 m y igneous event emplacing both the onshore flood basalts of the north atlantic volcanic province navp and huge extrusive complexes along the continent ocean transition on the rifted continental margins seismic data show that volcanic margins extend 2600 km along the early eocene plate boundary in places underlain by high velocity 7 2 7 7 km s lower crustal bodies quantitative calculations of navp dimensions considered minimum estimates reveal an areal extent of 1 3 106 km2 and a volume of flood basalts of 1 8 106 km3 yielding a mean eruption rate of 0 6 km3 yr or 2 4 km3 yr if two thirds of the basalts were emplaced within 0 5 m y the total crustal volume is 6 6 106 km3 resulting in a mean crustal accretion rate of 2 2 km3 yr thus navp ranks among the world s larger igneous provinces if the volcanic margins are considered the velocity structure of the expanded crust seaward of the continent ocean boundary differs from standard oceanic and continental crustal models based on seismic velocities this volcanic margin crust can be divided into three units of which the upper unit corresponds to basaltic extrusives the regionally consistent velocity structure and geometry of the crustal units suggest that the expanded crust including the high velocity lower crust which extends some distance landward of the continent ocean boundary was emplaced during and subsequent to breakup the volcanic margin crust was formed by excess melting within a wide zone of asthenospheric upwelling probably reflecting the interaction of a mantle plume and a lithosphere already extending

ceres ezinu quadrangle a heavily cratered region with evidence for localized subsurface water ice and the context of occator crater abstract dawn is the first spacecraft to visit and orbit ceres the largest object in the asteroid belt and the only dwarf planet in the inner solar system the dawn science team undertook a systematic geologic mapping campaign of ceres entire surface here we present our contribution to this mapping campaign a geologic map and geologic history of the ezinu quadrangle located in the northern mid latitudes from 21 66 n and 180 270 e from our map we reconstruct the geologic history of ezinu quadrangle which is dominated by impact cratering large impact craters that formed a few hundreds to tens of millions of years ago such as datan messor ninsar and occator are surrounded by ejecta and contain the products of mass wasting hummocky crater floor material and talus material and crater wall collapse terrace material two of these large impact craters are the sources of lobate flows which we interpret as melt flows emplaced after the ballistically deposited ejecta morphological evidence suggests these lobate flows are rich in water ice bearing material that was excavated during the formation of the impact craters there are only a few localized occurrences of lobate flows suggesting that the water ice bearing source materials have restricted extents and or are deeply buried within ceres subsurface the quadrangle also contains a variety of linear features secondary crater chains are formed by the impact of locally and globally sourced material and pit chains and grooves are formed by the collapse of surficial materials into sub surface fractures the ezinu quadrangle contains the northern portion of occator crater which is the host crater of prominent bright regions called faculae our geologic analysis therefore also provides context for the future investigation of occator and its intriguing faculae

a possible brine reservoir beneath occator crater thermal and compositional evolution and formation of the cerealia dome and vinalia faculae abstract the dawn spacecraft has imaged several putative cryovolcanic features on ceres and several lines of evidence point to past cryovolcanic activity at occator crater it is therefore possible that cryovolcanism played a key role in delivering sodium carbonate and chloride enriched brines to ceres surface in recent geological times the detection of a 200 km 200 km negative bouguer anomaly beneath occator suggests the presence of a low density region beneath the crater if this region is a residual partially crystallized cryomagma chamber excess pressures caused by its gradual freezing or stresses produced by the occator forming impact could have facilitated the delivery of cryolavas to the surface in the geologically recent past here the progressive solidification of a cryomagma chamber beneath occator and implications for the delivery of cryolavas to the surface has been explored models for the behavior of cryolavas at ceres surface and for the formation of the cerealia dome and vinalia faculae are also presented minimal crystallization of a subsurface fluid reservoir located at the crust mantle boundary could have driven cryolavas enriched in chloride salts and nh3 to ceres surface however cryolavas enriched in sodium carbonates would have had to have existed at shallower levels in the crust in order to be delivered to the surface via pressure driven ascent depending on the size of the reservoir cryolavas could have been driven to ceres surface for tens to hundreds of millions of years after cooling of the cryomagma chamber commenced the mineralogy at occator is suggestive of subsurface cryomagma reservoirs enriched in sodium carbonate and chloride salts aqueous solutions enriched in chloride salts and or ammonia would have arrived at the surface at warm enough temperatures to erupt if transported in propagating fractures that traveled at least 10 5 m s additionally if the cerealia dome was formed from viscous cryolava extrusions bulk kinematic lava viscosities may have been between 106 108 m2 s at the onset of relaxation plausible relaxation times to form the dome which are linked to bulk cryolava rheology are found to have ranged from 2 5 to 273 days moreover the low volatile content necessary to drive explosive eruptions on ceres supports the possibility that cerealia and vinalia faculae were emplaced as a consequence of ballistic eruptions the enigmatic geology of occator crater is consistent with a diversity of exchange processes operating on ceres in the geologically recent past further the processes that have occurred at occator could shed light on the changing geology associated with a relic ocean world future studies of occator and ceres should be undertaken with these results in mind

geological mapping of the ac 10 rongo quadrangle of ceres abstract the dawn spacecraft arrived at dwarf planet ceres in spring 2015 and imaged its surface from four successively lower polar orbits at ground sampling dimensions between 1 3 km px and 35 m px to understand the geological history of ceres a mapping campaign was initiated to produce a set of 15 quadrangle based geological maps using the highest resolution framing camera imagery here we present the geological map of the ac 10 rongo quadrangle which is located at the equator encompassing the region from 22 n to 22 s and 288 to 360 e the total relief within the quadrangle is 11 1 km with altitudes ranging from about 7 3 km to 3 8 km we identified nine geological units based on surface morphology and surface textural characteristics the dominant and most widespread unit is the cratered terrain crt representing ancient reworked crustal material its consistent formation age across the quadrangle is 1 8 ga two edifices unit th ahuna mons and an unnamed tholus within begbalel crater are interpreted to be of cryo volcanic origin the southwest portion of the quadrangle is dominated by ejecta material ye emplaced during the formation of the 260 km diameter yalode impact basin at about 580 ma rayed crater ejecta material cr is dominant in the eastern part of the quadrangle but also occurs in isolated patches up to a distance of 455 km from the 34 km diameter source crater haulani the remaining five geological units also represent impact crater materials degraded rim crdeg bright crater cb hummocky floor cfh talus ta and crater c materials widespread yalode and haulani ejecta materials can potentially be utilised as stratigraphic markers therefore it is essential to consistently map their full areal extent and to date their formations using impact crater statistics

α pbo2 type nanophase of tio2 from coesite bearing eclogite in the dabie mountains china comment our efforts to introduce defects in rutile by conventional mechanical grinding as used for tem study did not produce any defects or twinning experimental saed patterns of rutile with intercalated alpha pbo2 type tio2 lamellae are consistent with those expected from calculated patterns the values and precision of lattice parameters of alpha pbo2 type tio2 derived from such saed patterns are also consistent with crystal data from x ray diffraction studies

nanoscale constraints on the shock induced transformation of zircon to reidite abstract in a hypervelocity impact event the temperatures and pressures generated by the shock waves far exceed the values produced by endogenic processes the shock induced processes can modify the distribution of trace elements in zircon grains located in target rocks potentially affecting the geochemical reliability of zircon but also providing an opportunity to better understand the mechanisms of shock deformation the formation of reidite lamellae by the shock induced phase change of zircon has previously been proposed to be a diffusionless martensitic transformation with no associated atomic mobility over nanometre length scales however nanoscale characterization of the zircon reidite interface and a low angle boundary within the reidite by atom probe tomography transmission electron microscopy and correlative analytical techniques shows localised enrichment of particular trace elements y al ca be mg mn and ti these observations indicate the presence of additional short range diffusional components to explain the local compositional variations observed at the nanoscale for the high pressure transformation of zircon to reidite lamellae a new model for this transformation is proposed that consists of two stages 1 the early stage of the impact event where the shock waves induce defects in the zircon grain and trigger a phase transformation resulting in trace element segregation by interface migration and 2 the recovery stage where the trace elements and shock induced defects migrate to areas of lower energy

the thermometry of enstatite chondrites a brief review and update due to the discoveries in antarctica the number of known enstatite chondrites has doubled in the last few years and many rare or previously unknown types have been collected most notably many el3 and eh3 chondrites we have applied the five major enstatite chondrite thermometers to the new and previously known enstatite chondrites the thermometers being 1 kamacite quartz enstatite oldhamite troilite kqeot 2 oldhamite 3 alabandite niningerite 4 sphalerite and 5 phosphide metal measured temperatures based on the kqeot and oldhamite systems are 800 c 1000 c with the type 3 enstatite chondrites having values similar to those of type 4 6 it seems likely that these temperatures relate to events prior to parent body metamorphism such as nebula condensation or chondrule formation and were not significantly reset by later events measured temperatures for alabandite niningerite metal phosphide and sphalerite in eh chondrites increase from 300 c 400 c to 600 c 800 c with petrographic indications of increasing metamorphism in contrast measured temperatures for all el chondrites including the most heavily metamorphosed are generally 400 c apparently el chondrites cooled more slowly than the eh chondrites regardless of metamorphism experienced measured temperatures for the alabandite niningerite metal phosphide and sphalerite are actually closure temperatures for the last thermal event suffered by the meteorite and the fast cooling rates indicated are most consistent with processes occurring in thick regoliths

mass wasting features and processes in vesta s south polar basin rheasilvia 1 the rheasilvia crater is vesta s largest impact basin it is a 500 km diameter complex crater centered near the south pole and overlying the 400 km diameter impact basin veneneia using framing camera fc data from the dawn spacecraft s low altitude mapping orbit 20 m pixel and a digital terrain model derived from high altitude mapping orbit stereo data we identified various mass wasting features within the south polar region these features include intra crater mass movements flow like and creep like structures slumping areas landslides and curved radial and concentric ridges intra crater mass wasting features are represented by lobate slides talus material dark patches on the crater wall spurs along the crater rim and boulders slumping areas develop in compact material whereas landslides form in relatively loose material both may be triggered by seismic shaking induced by impacts intra crater mass wasting and slid and slumped materials are homogeneously distributed throughout the basin slumping and sliding processes have contributed most efficiently to basin degradation flow like and creep like features originate from granular material and cluster between 0 e and 90 e an area exposing shocked and fractured material from the rheasilvia impact event the radial curved ridges are likely to be remnants of the early rheasilvia collapse process when radially moving masses were deflected by the coriolis effect the concentric ridges are artifacts from the crater rim collapse curved ridges at the intersection of rheasilvia and veneneia and on rheasilvia s central peak may also have been influenced by the rheasilvia basin relaxation process and an oblique impact respectively

resurfacing of titan by ammonia water cryomagma the cassini titan radar mapper observed on titan several large features interpreted as cryovolcanic during the october 26 2004 pass at high northern latitudes lopes r m c and 43 colleagues 2007 icarus 186 395 412 to date models of ammonia water resurfacing have not been tied to specific events or evolutionary stages of titan we propose a model of cryovolcanism that involves cracking at the base of the ice shell and formation of ammonia water pockets in the ice as these ammonia water pockets undergo partial freezing in the cold ice shell the ammonia concentration in the pockets increases decreasing the negative buoyancy of the ammonia water mixture if the ice shell is contaminated by silicates delivered in impacts the liquid solid density difference would be even less while the liquid cannot easily become buoyant relative to the surrounding ice these concentrated ammonia water pockets are sufficiently close to the neutral buoyancy point that large scale tectonic stress patterns tides non synchronous rotation satellite volume changes solid state convection or subsurface pressure gradients associated with topography would enable the ammonia to erupt effusively onto the surface rather than suggesting steady state volcanism over the history of the solar system we favor a scenario where the cryovolcanic features could have been associated with episodic potentially late geological activity

new insight into lunar impact melt mobility from the lro camera 1 the lunar reconnaissance orbiter camera lroc is systematically imaging impact melt deposits in and around lunar craters at meter and sub meter scales these images reveal that lunar impact melts although morphologically similar to terrestrial lava flows of similar size exhibit distinctive features e g erosional channels although generated in a single rapid event the post impact mobility and morphology of lunar impact melts is surprisingly complex we present evidence for multi stage influx of impact melt into flow lobes and crater floor ponds our volume and cooling time estimates for the post emplacement melt movements noted in lroc images suggest that new flows can emerge from melt ponds an extended time period after the impact event

timing of optical maturation of recently exposed material on ceres on ceres multispectral imaging data from the dawn spacecraft show a distinct bluish characteristic for recently exposed material from the subsurface in for example crater ejecta ejecta blankets of presumably old craters show a more reddish spectrum we selected areas in which fresh material from the cerean subsurface was exposed at a specific time in the past and no later geologic process is expected to have changed its surface composition or its cratering record for each area we determined two color ratios and the crater retention age the measured color ratios show an exponential diminishment of the bluish characteristic over time although the cause of the color change remains uncertain the time dependent change in spectral properties is evident which could help identify the process

rapid formation of the small isles tertiary centre constrained by precise 40ar 39ar and u pb ages the relative chronology of magmatic and tectonic events is key to an understanding of the influence of the iceland plume on the north atlantic in particular the location and duration of magmatism is of fundamental importance initial widespread flood basalt formation occurred in baffin island greenland and britain before complete plate break up at 56 ma after which time magmatism became concentrated in the active rift zone historically the british tertiary igneous province btip has been instrumental in advancing many concepts of igneous petrology however the absolute age and duration of the province remains unresolved here we present new internally consistent 40ar 39ar ages that help to constrain the volcanic activity in the small isles centre to within 2 my this short duration has implications for the onset of magmatism in the larger north atlantic province the rapid unroofing of the rum volcano and more significantly some of the evidence used to propose pulsing of the iceland plume

carbonaceous chondrites as analogs for the composition and alteration of ceres the mineralogy and geochemistry of ceres as constrained by dawn s instruments are broadly consistent with a carbonaceous chondrite cm ci bulk composition differences explainable by ceres s more advanced alteration include the formation of mg rich serpentine and ammoniated clay a greater proportion of carbonate and lesser organic matter amounts of magnetite sulfide and carbon that could act as spectral darkening agents and partial fractionation of water ice and silicates in the interior and regolith ceres is not spectrally unique but is similar to a few other c class asteroids which may also have suffered extensive alteration all these bodies are among the largest carbonaceous chondrite asteroids and they orbit in the same part of the main belt thus the degree of alteration is apparently related to the size of the body although the ammonia now incorporated into clay likely condensed in the outer nebula we cannot presently determine whether ceres itself formed in the outer solar system and migrated inward or was assembled within the main belt along with other carbonaceous chondrite bodies

geology of ceres north pole quadrangle with dawn fc imaging data abstract the dawn framing camera repeatedly imaged ceres north pole quadrangle ac 1 asari latitudes 66 n at a resolution of 35 m pixel through a panchromatic filter enabling the derivation of a digital terrain model dtm and an ortho rectified mosaic using this dataset a photo geologic map and stratigraphy complemented with absolute model ages of impact craters were produced we identified the following key surface features an ancient 4 5 km high isolated dome with a non impact origin recent lobate materials on crater interiors possibly formed as high speed flows of collapsed rim material and recent bright areas in permanently shadowed regions psrs which we interpret as ice accumulation mostly by infall of exogenic material crater morphologies and dimensions do not differ from those in other quadrangles suggesting the widespread influence of a rheologically weak target during the crater formation process there is a paucity of lobate materials associated with impact cratering in contrast to previous identifications with lower spatial resolution imagery

an investigation of the bluish material on ceres the dwarf planet ceres shows spatially well defined regions which exhibit a negative blue spectral slope between 0 5 and 2 5 m comparisons with planetary bodies known to exhibit a blue slope and spectral properties of materials identified on ceres surface based on infrared wavelength signatures indicate the spectral changes could be related to physical properties of the surface material rather than variations in its composition the close association of bluish surface regions to fresh impact craters implies a possible relationship to an impact triggered alteration and or space weathering processes the bluish regions could be linked with blankets of ultra fine grains and partly amorphous phyllosilicates which form larger agglomerates due to the sticky behavior of impact induced phyllosilicate dust and or the amorphization of the ejecta material during the impact process space weathering processes micro meteoritic impacts temperature changes cause a reversal of the agglutination process and a re crystallization of the surface material with time resulting in a reddening of the spectral slope

tectonic analysis of fracturing associated with occator crater abstract occator crater a ceres crater that hosts multiple bright spots on its floor has several sets of fractures associated with it a tectonic analysis of each of these fracture sets suggests that the concentric and radial fractures around the central pit and the concentric fractures high on the crater wall near the rim most likely formed due to well known impact cratering processes uplift of the crater floor due to magmatic injection is suggested to have resulted in the concentric floor fractures at the base of the crater wall as well as the cross cutting fractures in the lower part of the southwestern wall a mathematical analysis shows that a cryomagmatic plume diapir could have both reached the height necessary to cause fracturing within occator and that the stresses required are reasonable expansion a lobate flow from beneath is proposed to have formed those linear fractures associated with the vinalia faculae circumferential fractures surrounding occator appear to have formed due to the volumetric compaction of the ejecta blanket over the buried pre existing topography

effects of frost on the mechanical behaviour of champlain sea clays this paper presents the mechanical behaviour of champlain sea clays when subjected to one cycle of freeze thaw it appears that most of the characteristics namely the undrained shear strength the thaw consolidation volume change and the strength after consolidation are related to the initial liquidity index and can thus be easily predicted results also show that frozen thawed champlain sea clays present a dilatant behaviour very similar to that of granular materials key words sensitive clays frost laboratory strength compressibility

field observations of frost action in intact and weathered champlain sea clay this paper presents the results of a field study on frost action in sensitive saint alban clay both in an intact state never subjected to any freeze thaw cycles and in its weathered state corres

cryogenic flow features on ceres implications for crater related cryovolcanism craters on ceres such as haulani kupalo ikapati and occator show postimpact modification by the deposition of extended plains material with pits multiple lobate flows and widely dispersed deposits that form a diffuse veneer on the preexisting surface bright material units in these features have a negative spectral slope in the visible range making it appear bluish with respect to the grey toned overall surface of ceres we calculate the drop height to runout length ratio of several flow features and obtain a coefficient of friction of 0 1 the results imply higher flow efficiency for flow features on ceres than for similar features on other planetary bodies with similar gravity suggesting low viscosity material the special association of flow features with impact craters could either point to an impact melt origin or to an exogenic triggering of cryovolcanic processes

mineralogy and temperature of crater haulani on ceres we investigate the region of crater haulani on ceres with an emphasis on mineralogy as inferred from data obtained by dawn s visible infrared mapping spectrometer vir combined with multispectral image products from the dawn framing camera fc so as to enable a clear correlation with specific geologic features haulani which is one of the youngest craters on ceres exhibits a peculiar blue visible to near infrared spectral slope and has distinct color properties as seen in multispectral composite images in this paper we investigate a number of spectral indices reflectance spectral slopes abundance of mg bearing and nh4 bearing phyllosilicates nature and abundance of carbonates which are diagnostic of the overall crater mineralogy plus a temperature map that highlights the major thermal anomaly found on ceres in addition for the first time we quantify the abundances of several spectral endmembers by using vir data obtained at the highest pixel resolution 0 1 km the overall picture we get from all these evidences in particular the abundance of na and hydrous na carbonates at specific locations confirms the young age of haulani from a mineralogical viewpoint and suggests that the dehydration of na carbonates in the anhydrous form na2co3 may be still ongoing

hydro mechanical evaluation of stabilized mine tailings in this study mine tailings waste was stabilized using a combination of lime fly ash type c and aluminum treated samples were subjected to mineral identification for evaluating the formation of ettringite and gypsum also unconfined compression hydraulic conductivity and cyclic freeze and thaw tests were performed to evaluate the hydro mechanical properties of the stabilized samples experimental results have shown that the application of lime and fly ash type c to high sulfate content tailings has improved its plasticity workability and volume stability moreover upon addition of aluminum to lime and fly ash in a sulfate rich environment ettringite and calcium sulfo aluminate hydrate are formed in these samples application of 5 lime 10 fly ash type c in combination with 110 ppm aluminum resulted in the formation of a solid monolith capable of producing more than 1 000 kpa of unconfined compressive strength and reduced tailings permeability to 1 96 10 6 cm s 1 which is less than the recommended permeability of 10 5 cm s 1 by most environmental protection agencies for reusability of solidified stabilized samples the permeability of the treated tailings samples remained below the recommended permeability even after exposing the treated samples to 12 freeze and thaw cycles therefore based on the experimental results it is concluded that treatment of high sulfate content tailings with lime and fly ash combined with the availability of aluminum for reactions is a successful method of solidifying highly reactive mine tailings

origin of small pits in martian impact craters we propose a numerical model for the formation of the closely spaced pits found in the thin ejecta related deposits superposed on the floors interior terrace blocks and near rim ejecta blankets of well preserved martian impact craters our model predicts the explosive degassing of water from this pitted material which is assumed to originally be water bearing impact melt rich breccia at the time of deposition this process is analogous to what occurred in the fall out suevite deposits at the ries impact structure in germany at ries impact heating of water bearing target material resulted in the rapid degassing of its water and other volatiles the martian environment plays an important role in enhancing the effects of this degassing by increasing the flow speed of the escaping gas the high flow rate of gas through particulate materials such as suevite tends to quickly form segregation channels or vent pipes similar to those found in the ries deposits these pipes act as conduits for the efficient high speed escape of the gas and small clasts that it entrains escaping gas and entrained clasts abraded and eroded the conduit walls flaring them to form pits above a network of pipes

ceres evolution and current state 1 we modeled several thermal evolution scenarios for ceres to explore the nature of large wet protoplanets and to predict current day evidence that might be found by close inspection such as by the dawn mission the density for ceres is near 2 1 suggesting a water content between 17 and 27 by mass short and long lived radioactive nuclide heating is considered even if only long lived radionuclide heating is assumed the water ice in ceres melts quickly and a water mantle forms but an approximately 10 km crust does not melt the circulating warm water would alter the silicates as heat is lost by conduction through the frozen crust water begins to freeze out at the base of the crust solid state convection begins and transports more heat as well as perhaps material dissolved or entrained in the water to or near the surface ceres water layer eventually but perhaps not entirely freezes forming a layered density structure with perhaps some liquid water remaining today our differentiated models are in agreement with the recently measured difference between the equatorial and polar radii we find that ceres existence and evolution depend critically on it containing water at formation and this depends strongly on the combination of when it accreted and the amount of 26al present in the pre ceres 1 km sized objects slightly more 26al or earlier accretion produces a dry vesta like object melting and freezing plus mineralization would lead to several dimensional changes over time creating topographic features zones of weakness and perhaps disruptions in the crust

mobility of large rock avalanches evidence from valles marineris mars measurements of h l height of drop length of runout vs volume for landslides in valles marineris on mars show a trend of decreasing h l with increasing volume this trend which is linear on a log log plot is parallel to but lies above the trend for terrestrial dry rock avalanches this result and estimates of 10 4 to 10 5 pa yield strength suggest that the landslides were not water saturated as suggested by previous workers the offset between the h l vs volume trends shows that a typical martian avalanche must be nearly two orders of magnitude more voluminous than a typical terrestrial avalanche in order to achieve the same mobility this offset might be explained by the effects of gravity on flows with high yield strengths these results should prove useful to future efforts to resolve the controversy over the mechan ics of long runout avalanches

on the resurfacing of ganymede by liquid water volcanism abstract a long popular model for producing ganymede s bright terrain involves flooding of low lying graben with liquid water slush or warm soft ice the model suffers from major problems however including the absence of obvious near surface heat sources the negative buoyancy of liquid water and the lack of a mechanism for confining the flows to graben floors we present new models for cryovolcanic resurfacing to overcome these difficulties tidal heating within an ancient laplace like orbital resonance showman and malhotra 1997 icarus 127 93 showman et al 1997 icarus 129 367 provides a plausible heat source and could allow partial melting to occur as shallow as 5 10 km depth our favored mechanism for delivering this water to the surface invokes the fact that topography such as a global set of graben causes subsurface pressure gradients that can pump water or slush upward onto the floors of topographic lows graben despite the negative buoyancy of the liquid these eruptions can occur only within the topographic lows furthermore as the low areas become full the pressure gradients disappear and the resurfacing ceases this provides an explanation for the observed straight dark bright terrain boundaries water cannot overflow the graben so resurfacing rarely embays craters or other rough topography pure liquid water can be pumped to the surface from only 5 10 km depth but macroscopic bodies of slush ascending within fractures can reach the surface from much greater depths due to the smaller negative buoyancy of slush a challenge for these models is the short predicted gravitational relaxation timescale of topographic features at high heat flows the resurfacing must occur before the graben topography disappears we also evaluate alternate resurfacing mechanisms such as pumping of liquid water to the surface by thermal expansion stresses and buoyant rise of water through a silicate contaminated crust that is denser than liquid water and conclude that they are unlikely to explain ganymede s bright terrain

geologic mapping of the ac 11 sintana quadrangle assessing diverse crater morphologies abstract a geologic map at a scale of 1 1 000 000 of the ac 11 sintana quadrangle 21 66 s and 0 90 e from the dwarf planet ceres and based on data from nasa s dawn spacecraft was produced as part of a geologic mapping campaign in order to investigate the surface structure stratigraphy composition and surface modifying processes the sintana quadrangle is geologically dominated by cratered terrain with morphologically distinct crater types the most prominent craters sintana hamori jarimba tupo annona and darzamat have complex structures including smooth crater material covering their floors collapsed crater walls forming terraces and central ridges multiple gravity driven blocky mass wasting features indicate post impact crater modification and are indicative of an ice rich subsurface in which there is no topographic or structural evidence of endogenic activity visible in the quadrangle absolute age estimates suggest that the entire surface in the quadrangle was resurfaced 1 1 ga ago possibly by kerwan related impact induced melting

discovery of a meteoritic ejecta layer containing unmelted impactor fragments at the base of paleocene lavas isle of skye scotland evidence for meteorite impacts in the geological record may include the presence of shocked minerals spherule layers and geochemical anomalies however it is highly unusual to find unmelted crystals from the actual impactor within an ejecta layer here we detail the first recorded occurrence of vanadium rich osbornite tivn on earth from two sites on skye northwest scotland which are interpreted as part of a meteoritic ejecta layer tivn has only previously been reported as dust from comet wild 2 but on skye it has been identified as an unmelted phase both ejecta layer sites also contain niobium rich osbornite tinbn which has not previously been reported an extraterrestrial origin for these deposits is strongly supported by the presence of reidite a high pressure zircon polymorph which is only found naturally at sites of meteorite impact barringerite fe ni 2p baddeleyite zro2 alabandite mns and carbon bearing native iron spherules together with planar deformation features and diaplectic glass in quartz further support this thesis we demonstrate through field relationships and ar ar dating that the meteorite strike occurred during the mid paleocene this is the first recorded mid paleocene impact event in the region and is coincident with the onset of magmatism in the british palaeogene igneous province bpip the skye ejecta layer deposits provoke important questions regarding their lateral extent at the base of the bpip and the possibility of their presence elsewhere beneath the much larger north atlantic igneous province

experimental shock deformation in zircon a transmission electron microscopic study abstract in recent years apparently shock induced and thus impact characteristic microdeformations in the form of planar microdeformation features and so called strawberry granular texture have been observed in zircons in rocks from confirmed impact structures and from the k t boundary the nature of the planar microdeformations in this mineral is however still unknown and critical information is needed regarding the shock pressure range in which these deformation effects are produced we experimentally shock deformed two series of thin zircon zrsio 4 target plates cut perpendicular to the c axis at shock pressures of 20 40 and 60 gpa the recovered samples were characterized by optical and scanning electron microscopy in addition one sample series was studied by transmission electron microscopy tem microdeformation effects observed at 20 gpa include pervasive micro cleavage and dislocation patterns plastic deformation is indicated by a high density of straight dislocations in glide configuration the dominant glide systems are 010 micro cleavages induced by shear stresses during the compression stage occur mostly in the 100 planes the large density of dislocations at crack tips shows that plastic deformation was initiated by the micro cracking processs at 40 gpa the sample was partly transformed from the zircon z to a scheelite cawo 4 type s structure planar deformation features pdfs containing an amorphous phase of zircon composition are present in the not yet transformed zircon relics the phase with scheelite structure initiated in the 100 planes of zircon consists of thin 0 1 to several m bands that crosscut the zircon matrix the phase transformation is displacive martensitic and can be related by 100 z 112 s and 001 z s the scheelite structure phase is densely twinned with twins in the 112 plane the 60 gpa sample consists completely of the scheelite structure phase crosscutting and displacing relationships between twins and pdfs demonstrate that pdfs are formed in the zircon structure i e before the phase transformation to the scheelite structure occurred most likely at the shock front crystallographic orientations of optically visible planar features in zircon in comparison with orientations of planar defects at the tem scale suggest that the optically visible features are more likely planar microfractures than pdfs

the vanishing cryovolcanoes of ceres ahuna mons is a 4 km tall mountain on ceres interpreted as a geologically young cryovolcanic dome other possible cryovolcanic features are more ambiguous implying that cryovolcanism is only a recent phenomenon or that other cryovolcanic structures have been modified beyond easy identification we test the hypothesis that cerean cryovolcanic domes viscously relax precluding ancient domes from recognition we use numerical models to predict flow velocities of ahuna mons to be 10 500 m myr depending upon assumptions about ice content rheology grain size and thermal parameters slower flow rates in this range are sufficiently fast to induce extensive relaxation of cryovolcanic structures over 108 109 years but gradual enough for ahuna mons to remain identifiable today positive topographic features including a tholus underlying ahuna mons may represent relaxed cryovolcanic structures a composition for ahuna mons of 40 ice explains the observed distribution of cryovolcanic structures because viscous relaxation renders old cryovolcanoes unrecognizable

considerations for effusive cryovolcanism on europa the post galileo perspective 1 cryovolcanic resurfacing is a popular mechanism to explain relatively young surface units on icy satellites of jupiter saturn uranus and neptune prior to the galileo data acquired between 1996 and 2001 europa was thought to have undergone significant cryovolcanic resurfacing facilitated by a global ocean beneath the icy surface however close examination of galileo data at resolutions much better than those of voyager images show that many of the features previously thought to be cryovolcanic are commonly best explained by other formative mechanisms including tectonism and diapirism in this study i present an examination of the characteristics of a variety of europan surface features for which effusive cryovolcanism is a possible origin including apparently lobate flows certain elliptical to circular lenticulae and low lying smooth low albedo surfaces a review of cryovolcanic eruption theory together with galileo data analysis of europan surface geology and composition indicates that cryovolcanism is a viable though not unequivocal explanation for some of these features some constraints on cryomagma properties and lithospheric structure are offered for these cases the presence of small volume low viscosity effusions is supported by observations and modeling some positive relief lenticulae could represent more viscous effusions although diapirism may be a preferable explanation however strong evidence is lacking for cryovolcanic resurfacing on a large scale on the basis of our experience with galileo images of europa and ganymede voyager era inferences for widespread cryovolcanism on icy satellites may be overstated and will need to be carefully reexamined in the light of new data from upcoming spacecraft missions

the unique geomorphology and structural geology of the haulani crater of dwarf planet ceres as revealed by geological mapping of equatorial quadrangle ac 6 haulani abstract the dwarf planet ceres has been explored by nasa s dawn spacecraft with the goal of characterizing its geology mineralogy topography shape and internal structure one outcome of this exploration is the production of geologic maps meant to unveil the geologic history of ceres in this paper we present the geologic map of the ac 6 haulani quadrangle lat 22 s 22 n long 0 72 e based on low altitude mapping orbit lamo 35 m pixel data supplemented with color and spectral data as well as a digital terrain model from the high altitude mapping orbit hamo 135 m pixel vertical accuracy of about 10 m the 34 km diameter haulani crater is one of the youngest features on ceres and the most prominent one in the quadrangle haulani was formed on a topographical transition in north south direction and shows a complex morphology with a variety of lobate flows and tectonic features multiple cracks and depressions around the crater indicate the failure of subsurface material these were likely formed by the subsidence of material due to the instability of the subsurface the mapping of ac 6 haulani suggests that ceres is built up of layers with different material properties we propose that ceres has a solid crust and a variable ice rich subsurface consistent with previous and recent models of ceres interior

utilization of atikokan coal fly ash in acid rock drainage control from musselwhite mine tailings a site specific study is carried out to assess the suitability of utilizing atikokan coal fly ash afa as a buffering material to control and mitigate the generation of acid rock drainage from reactive musselwhite mine tailings the physical chemical and mineralogical properties of the fly ash and mine tailings are determined via experiments followed by six kinetic column permeation tests to monitor the leaching properties of the coal fly ash and coal fly ash mine tailings mixtures the results of the experiments indicate that the hydraulic conductivities of high calcium afa and the ash tailings mixtures are significantly reduced upon contact with acidic drainage the ph of the pore fluid has increased from acidic ph 4 to alkaline ph 8 and above chemical analyses after the kinetic column permeation tests further indicate that concentrations of regulated elements in the leachate from the ash tailings mixtures are well below the guideline limits set by the ontario environmental authority for acce