carbon isotope systematics of a mantle hotspot a comparison of loihi seamount and morb glasses the carbon isotope geochemistry of glasses from loihi seamount has been compared with that of morb glasses stepped heating shows two carbon components in both sample suites 1 isotopically light carbon avg 13c 26 3 released 600 c regarded as indigenous the high temperature component in morb samples varied from 52 to 169 ppm c average 13c 6 6 consistent with previous studies overall mord average 13c 6 4 0 9 and new results for indian ocean glasses are similar to atlantic and pacific ocean samples carbon release profiles produced by stepped heating may be typical of locality but there are no significant differences in 13c values between morb samples from different areas lower yields 17 110 ppm c correlated with depth in the loihi samples suggest that they are partially degassed this degassing has not affected 13c values significantly avg 5 8 loihi tholeiites have higher 13c avg 5 6 than the alkali basalts avg 7 1 carbon abundances correlate well with he concentration data comparison of the 13c values with trace element and he sr nd and pb isotope data from the literature suggests that the loihi samples with highest 13c have high3he 4he and possibly the least depleted143nd 144nd and87sr 86sr the carbon isotope data are consistent with previous models for loihi involving several mantle sources lithospheric contamination and mixing the slightly higher 13c of loihi tholeiites suggests that the undegassed plume component manifested by high3he 4he values might have 13c about 1 higher than the morb average

fluid chemistry structural setting and emplacement history of the rosario cu mo porphyry and cu ag au epithermal veins collahuasi district northern chile the rosario cu mo ag deposit is located in the collahuasi district of northern chile it comprises high grade cu ag au epithermal veins superimposed on the core of a porphyry cu mo orebody rosario has mining reserves of 1 094 million metric tons mt at 1 03 percent copper an additional 1 022 mt at 0 93 percent copper occurs in the district at the nearby ujina and quebrada blanca porphyry deposits the rosario reserve contains over 95 percent hypogene ore whereas supergene sulfide ores dominate at ujina and quebrada blanca mineralized veins are hosted within lower permian volcanic and sedimentary rocks lower triassic granodiorite and late eocene porphyritic quartz monzonite the rosario fault system a series of moderate southwest dipping faults has localized high grade cu ag au veins at cerro la grande similar high grade cu ag au veins are hosted in north northeast trending sinistral wrench faults normal movement in the rosario fault system is interpreted to have been synchronous with sinistral strike slip deformation at la grande hydrothermal alteration at rosario is characterized by a k feldspar core focused in the rosario porphyry that grades out to a secondary biotite albite magnetite assemblage paragenetic relationships indicate that magnetite was the earliest formed alteration product but has been replaced by biotite albite vein crosscutting relationships indicate that k feldspar formed during and after biotite albite alteration chalcopyrite and bornite were deposited in quartz veins associated with both k feldspar and biotite albite assemblages the early hydrothermal fluid was a hypersaline brine 40 45 wt nacl that coexisted with vapor between 400 degrees and 600 degrees c weakly mineralized illite chlorite intermediate argillic alteration of the early k and na silicate assemblages was caused by moderate temperature 250 degrees 350 degrees c moderate salinity brines 10 15 wt nacl molybdenite was precipitated in quartz veins that formed between the potassic and intermediate argillic alteration events these fluids were 350 degrees to 400 degrees c with salinities between 10 and 15 wt percent nacl porphyry style ore and alteration minerals were overprinted by structurally controlled quartz alunite pyrite pyrophyllite dickite and muscovite quartz phyllic alteration assemblages the quartz alunite pyrite alteration formed at 300 degrees to 400 degrees c from fluids with a salinity of 10 wt percent nacl the pyrophyllite dickite assemblage formed between 250 degrees and 320 degrees c from dilute 5 wt nacl fluids an upward flared zone of muscovite quartz pyrite altered rocks surrounds the fault controlled domain of advanced argillic alteration thick veins 0 5 2 m wide of fault hosted massive pyrite chalcopyrite and bornite precipitated brines with a salinity of 30 wt percent nacl at temperatures of 250 degrees to 300 degrees c pressure depth estimates indicate that at least 1 km of rock was eroded at rosario between formation of the k na silicate and advanced argillic assemblages this erosion was rapid occurring over a period of 1 8 m y the rosario porphyry intruded immediately after the incaic tectonic phase implying that it was emplaced as the domeyko cordillera underwent gravitational collapse expressed as normal faults in the upper crust gravitational sliding potentially accelerated exhumation and helped to promote telescoping of the high sulfidation environment onto the rosario porphyry the hydrothermal system responsible for porphyry cu mineralization at rosario was partially exhumed prior to the formation of high sulfidation ore and alteration assemblages this implies that emplacement of a second blind intrusion occurred somewhere beneath the rosario and cerro la grande high sulfidation vein systems and is supported by the fault geometry and zoning of precious metals and sulfosalts at the district scale

albedo matters understanding runaway albedo variations on pluto abstract the data returned from nasa s new horizons reconnaissance of the pluto system show striking albedo variations from polar to equatorial latitudes as well as sharp longitudinal boundaries pluto has a high obliquity currently 119 that varies by 23 over a period of less than 3 million years this variation combined with its regressing longitude of perihelion 360 over 3 7 million years creates epochs of super seasons where one pole is pointed at the sun at perihelion thereby experiencing a short relatively warm summer followed by its longest possible period of winter darkness in contrast the other pole experiences a much longer less intense summer and a short winter season we use a simple volatile sublimation and deposition model to explore the relationship between albedo variations latitude and volatile sublimation and deposition for the current epoch as well as historical epochs during which pluto experienced these super seasons our investigation quantitatively shows that pluto s geometry creates the potential for runaway albedo and volatile variations particularly in the equatorial region which can sustain stark longitudinal contrasts like the ones we see between tombaugh regio and the informally named cthulhu regio

pluto pits and mantles on uplands north and east of sputnik planitia abstract the highlands region north and east of sputnik planitia can be subdivided into seven terrain types based on their physiographic expression the northern rough uplands are characterized by jagged uplands and broad troughs and it may contain a deeply eroded ancient mantle dissected terrain has been interpreted to have been eroded by paleo glaciation the smooth uplands and pits terrain contains broad rolling uplands surrounding complexes of pits some of which contain smooth floors the uplands are mantled by smooth surfaced deposits possibly derived from adjacent pits through low power explosive cryovolcanism or through slow vapor condensation the eroded smooth uplands appear to have originally been smooth uplands and pits terrain modified by small scale sublimation pitting the bright pitted uplands features intricate texturing by reticulate ridges that may have originated by sublimation erosion volatile condensation or both the bladed terrain is characterized by parallel ridges oriented north south and is discussed in a separate paper the dark uplands are mantled with reddish deposits that may be atmospherically deposited tholins their presence has affected long term landform evolution widespread pit complexes occur on most of the terrain units most appear to be associated with tectonic lineations some pits are floored by broad expanses of ices whereas most feature deep conical depressions a few pit complexes are enclosed by elevated rims of uncertain origin

differentiation and cryovolcanism on charon a view before and after new horizons abstract before the arrival of the new horizons probe at the pluto charon system we developed a series of models that predicted that kuiper belt objects even as small and as cold as charon have experienced internal ice rock differentiation and possibly cryovolcanism confronting these predictions is a wide array of spectroscopy imagery and other data from new horizons in this article we compare the predictions against the new observations and find that they largely support the expected history of the pluto system and the evolution of charon following the collision of two partially differentiated impactors with radii 1000 km a disk of material formed around pluto from which charon and pluto s other moons formed because the impactors did not completely differentiate the disk contained rocky material from their crusts explaining the moons different densities and compositions long lived radionuclides in charon assisted by ammonia antifreeze in the ice melted ice and created a subsurface ocean that eventually refroze 1 7 2 5 gyr ago the freezing of this ocean would have created extensional stresses that possibly created serenity chasma and could have led to widespread resurfacing explaining the apparently younger age of vulcan planum buildup of radiogenic heat then created a second smaller ocean that refroze 0 5 1 7 gyr ago as it froze cryovolcanism would have been enabled possibly creating kubrick mons charon s moated mountains such as kubrick mons have a natural explanation as cryovolcanoes depressing a thin lithosphere over a cryomagma chamber we offer further predictions about other aspects of charon s surface our previous predictions that charon is a world shaped by geological activity have been largely borne out by new horizons observations

the importance of changing oceanography in controlling late quaternary carbonate sedimentation on a high energy tropical oceanic ramp north western australia the north west shelf is an ocean facing carbonate ramp that lies in a warm water setting adjacent to an arid hinterland of moderate to low relief the sea floor is strongly affected by cyclonic storms long period swells and large internal tides resulting in preferentially accumulating coarse grained sediments circulation is dominated by the south flowing low salinity leeuwin current upwelling associated with the indian ocean gyre seaward flowing saline bottom waters generated by seasonal evaporation and flashy fluvial discharge sediments are palimpsest a variable mixture of relict stranded and holocene grains relict intraclasts both skeletal and lithic interpreted as having formed during sea level highstands of marine isotope stages mis 3 and 4 are now localized to the mid ramp the most conspicuous stranded particles are ooids and peloids which 14c dating shows formed at 15 4 12 7 ka in somewhat saline waters during initial stages of post last glacial maximum lgm sea level rise it appears that initiation of leeuwin current flow with its relatively less saline but oceanic waters arrested ooid formation such that subsequent benthic holocene sediment is principally biofragmental with sedimentation localized to the inner ramp and a ridge of planktic foraminifera offshore inner ramp deposits are a mixture of heterozoan and photozoan elements depositional facies reflect episodic environmental perturbation by riverine derived sediments and nutrients resulting in a mixed habitat of oligotrophic coral reefs and large benthic foraminifera and mesotrophic macroalgae and bryozoans indicators holocene mid ramp sediment is heterozoan in character but sparse most probably because of the periodic seaward flow of saline bottom waters generated by coastal evaporation holocene outer ramp sediment is mainly pelagic veneering shallow water sediments of marine isotope stage 2 including lgm deposits phosphate accumulations at 200 m water depth suggest periodic upwelling or fe redox pumping whereas enhanced near surface productivity probably associated with the interaction between the leeuwin current and indian ocean surface water results in a linear ridge of pelagic sediment at 140 m water depth this ramp depositional system in an arid climate has important applications for the geological record inner ramp sediments can contain important heterozoan elements mid ramp sediments with bedforms created by internal tides can form in water depths exceeding 50 m saline outflow can arrest or dramatically slow mid ramp sedimentation mimicking maximum flooding intervals and outer ramp planktic productivity can generate locally important fine grained carbonate sediment bodies changing oceanography during sea level rise can profoundly affect sediment composition sedimentation rate and packaging

dunes on pluto the surface of pluto is more geologically diverse and dynamic than had been expected but the role of its tenuous atmosphere in shaping the landscape remains unclear we describe observations from the new horizons spacecraft of regularly spaced linear ridges whose morphology distribution and orientation are consistent with being transverse dunes these are located close to mountainous regions and are orthogonal to nearby wind streaks we demonstrate that the wavelength of the dunes 0 4 to 1 kilometer is best explained by the deposition of sand sized 200 to 300 micrometer particles of methane ice in moderate winds

the effect of wave induced turbulence on the ocean mixed layer during tropical cyclones field observations on the australian north west shelf 1 field observations of water temperature on the australian north west shelf eastern indian ocean with the support of numerical simulations are used to demonstrate that the injection of turbulence generated by the wave orbital motion substantially contributes to the mixing of the upper ocean measurements also show that a considerable deepening of the mixed layer occurs during tropical cyclones when the production of wave induced turbulent kinetic energy overcomes the contribution of the current generated shear turbulence despite a significant contribution to the deepening of the mixed layer the effect of a background current and atmospheric forcing are not on their own capable of justifying the observed deepening of the mixed layer through most of the water column furthermore variations of a normally shallow mixed layer depth are observed within a relatively short timescale of approximately 10 hours after the intensification of wave activity and vanish soon after the decay of storm surface waves this rapid development tends also to exclude any significant contribution by wave breaking as small rates of vertical diffusivity for wave breaking induced turbulence would require longer timescales to influence the depth of the mixed layer

bladed terrain on pluto possible origins and evolution abstract bladed terrain on pluto consists of deposits of massive ch 4 which are observed to occur within latitudes 30 of the equator and are found almost exclusively at the highest elevations 2 km above the mean radius our analysis indicates that these deposits of ch 4 preferentially precipitate at low latitudes where net annual solar energy input is lowest ch 4 and n 2 will both precipitate at low elevations however since there is much more n 2 in the atmosphere than ch 4 the n 2 ice will dominate at these low elevations at high elevations the atmosphere is too warm for n 2 to precipitate so only ch 4 can do so we conclude that following the time of massive ch 4 emplacement there have been sufficient excursions in pluto s climate to partially erode these deposits via sublimation into the blades we see today blades composed of massive ch 4 ice implies that the mechanical behavior of ch 4 can support at least several hundred meters of relief at pluto surface conditions bladed terrain deposits may be widespread in the low latitudes of the poorly seen sub charon hemisphere based on spectral observations if these locations are indeed bladed terrain deposits they may mark heretofore unrecognized regions of high elevation

the ch4 cycles on pluto over seasonal and astronomical timescales abstract pluto s surface is covered in numerous ch4 ice deposits that vary in texture and brightness as revealed by the new horizons spacecraft as it flew by pluto in july 2015 these observations suggest that ch4 on pluto has a complex history involving reservoirs of different composition thickness and stability controlled by volatile processes occurring on different timescales in order to interpret these observations we use a pluto volatile transport model able to simulate the cycles of n2 and ch4 ices over millions of years by assuming fixed solid mixing ratios we explore how changes in surface albedos emissivities and thermal inertias impact volatile transport this work is therefore a direct and natural continuation of the work by bertrand et al 2018 which only explored the n2 cycles results show that bright ch4 deposits can create cold traps for n2 ice outside sputnik planitia leading to a strong coupling between the n2 and ch4 cycles depending on the assumed albedo for ch4 ice the model predicts ch4 ice accumulation 1 at the same equatorial latitudes where the bladed terrain deposits are observed supporting the idea that these ch4 rich deposits are massive and perennial or 2 at mid latitudes 25 70 forming a thick mantle which is consistent with new horizons observations in our simulations both ch4 ice reservoirs are not in an equilibrium state and either one can dominate the other over long timescales depending on the assumptions made for the ch4 albedo this suggests that long term volatile transport exists between the observed reservoirs the model also reproduces the formation of n2 deposits at mid latitudes and in the equatorial depressions surrounding the bladed terrain deposits as observed by new horizons at the poles only seasonal ch4 and n2 deposits are obtained in pluto s current orbital configuration finally we show that pluto s atmosphere always contained over the last astronomical cycles enough gaseous ch4 to absorb most of the incoming lyman flux

winter and spring evolution of northern seasonal deposits on mars from omega on mars express the omega visible near infrared imaging spectrometer on mars express has observed the retreat of the northern seasonal deposits during martian year 27 28 from the period of maximum extension close to the northern winter solstice to the end of the retreat at l s 95 we present the temporal and spatial distributions of both co 2 and h 2o ices and propose a scenario that describes the winter and spring evolution of the northern seasonal deposits during winter the co 2 rich condensates are initially transparent and could be in slab form a water ice annulus surrounds the sublimating co 2 ice extending over 6 of latitude at l s 320 decreasing to 2 at l s 350 and gradually increasing to 4 5 at l s 50 this annulus first consists of thin frost as observed by the viking lander 2 and is then overlaid by h 2o grains trapped in the co 2 rich ice layer and released during co 2 sublimation by l s 50 h 2o ice spectrally dominates most of the deposits in order to hide the still several tens of centimeters thick co 2 ice layer in central areas of the cap we propose the buildup of an optically thick top layer of h 2o ice from ice grains previously embedded in the co 2 ice and by cold trapping of water vapor from the sublimating water ice annulus the co 2 ice signature locally reappears between l s 50 and 70 what emerges from our observations is a very active surface atmosphere water cycle these data provide additional constraints to the general circulation models simulating the martian climate copyright 2011 by the american geophysical union

classification of the australian continental shelf based on predicted sediment threshold exceedance from tidal currents and swell waves abstract estimates of significant wave height and period together with tidal current speed over a semi lunar cycle were used to predict the area on the australian continental shelf over which unconsolidated sediment was mobilised threshold exceedance these sediment entraining processes were examined independently to quantify their relative importance on the continental shelf using observed grain size data mobilisation from swell waves occurred on 31 and tidal currents on 41 of the continental shelf swell wave energy is sufficient to mobilise fine sand 0 1 mm diameter to a water depth of 142 m on the otway shelf near the western entrance to bass strait tidal currents in king sound northwest shelf are capable of mobilising large areas of medium sand 0 35 mm diameter 100 of the time superimposing the distribution of threshold exceedance by wave and tidal currents indicates that there are areas on the shelf where either wave induced or tidal currents dominate some areas where waves and tides are of relatively equal importance and still other areas where neither is significant we define six shelf regions of relative wave and tidal energy zero no mobility waves only wave dominated mixed tide dominated and tides only our results provide a predictive process based understanding of the shelf sedimentary system that has applications to marine engineering projects and to regional studies of pollution dispersal and accumulation where significant shelf sediment mobilisation is a factor

wet season fine sediment dynamics on the inner shelf of the great barrier reef fine sediment dynamics were recorded in february 2007 in coastal waters of the great barrier reef during a moderate flood of the tully river an estuarine circulation prevailed on the inner continental shelf with a surface seaward velocity peaking at 0 1 m s 1 and a near bottom landward flow peaking at 0 05 m s 1 much of the riverine mud originating from eroded soils was exported onto a 10 km wide coastal strip during the rising stage of the river flood in the first flush in coastal waters suspended sediment concentration peaked at 0 2 kg m 3 near the surface and 0 4 kg m 3 at 10 m depth during calm weather and 0 5 kg m 3 near the surface and 2 kg m 3 at 10 m depth during strong winds when bottom sediment was resuspended diurnal irradiance at 4 m depth was almost zero for 10 days the sedimentation rate averaged 254 33 g m 2 d 1 over the 28 day study period and concentrations of dissolved and particulate nutrients originating from the river were high the observed low irradiance would have prevented coral photosynthesis while the sedimentation rate would have been lethal to some juvenile corals the mud may ultimately be minnowed out over long periods however flushing of the mud occurs at time scales much longer than the flood event and the mud is likely to affect coral physiology for significant periods after the flood has subsided the data show the need to better control erosion on farmed land for the conservation of coral reefs on the inner shelf of the great barrier reef

pluto s global surface composition through pixel by pixel hapke modeling of new horizons ralph leisa data abstract on july 14th 2015 nasa s new horizons mission gave us an unprecedented detailed view of the pluto system the complex compositional diversity of pluto s encounter hemisphere was revealed by the ralph leisa infrared spectrometer on board of new horizons we present compositional maps of pluto defining the spatial distribution of the abundance and textural properties of the volatiles methane and nitrogen ices and non volatiles water ice and tholin these results are obtained by applying a pixel by pixel hapke radiative transfer model to the leisa scans our analysis focuses mainly on the large scale latitudinal variations of methane and nitrogen ices and aims at setting observational constraints to volatile transport models specifically we find three latitudinal bands the first enriched in methane extends from the pole to 55 n the second dominated by nitrogen continues south to 35 n and the third composed again mainly of methane reaches 20 n we demonstrate that the distribution of volatiles across these surface units can be explained by differences in insolation over the past few decades the latitudinal pattern is broken by sputnik planitia a large reservoir of volatiles with nitrogen playing the most important role the physical properties of methane and nitrogen in this region are suggestive of the presence of a cold trap or possible volatile stratification furthermore our modeling results point to a possible sublimation transport of nitrogen from the northwest edge of sputnik planitia toward the south

cyclone pumping sediment partitioning and the development of the great barrier reef shelf system a review abstract the modern great barrier reef gbr is part of the world s largest and best known mixed terrigenous carbonate continental margin the gbr shelf contains three shore parallel sedimentary belts an inner shelf zone of terrigenous sedimentation at depths of 0 22 m a middle shelf zone of sediment starvation at depths of 22 40 m and an outer shelf reef tract with its inner edge at ca 40 m depth these zones are controlled by the dynamics of northward fair weather along shelf drift driven by southeasterly trade winds and by the regular passage of tropical cyclones cyclones cause wind driven north directed middle shelf flows in excess of 130 cm s which erode the seabed concentrate the sparse mobile sediment into sand ribbons and advect suspended load onto the outer part of the nearshore terrigenous sediment prism and into inter reef depocentres within the outer shelf reef tract cyclones largely control the input of new sediment into the gbr system via river flooding seabed erosion or reef breakage they also help to control the partitioning and dispersion of the three main shore parallel belts of sediment and hence stratigraphic accumulation acting as a sediment pump especially during interglacial highstands cyclones have exerted great control on the development of the modern gbr province and its sediments by maintaining a broad shelf parallel zone of episodically mobilised sediment and scoured seabed upon which coral reefs have been unable to form cyclones may also have partly controlled the timing of initiation of the first gbr at 0 6 mybp contrary to current models gbr storm beds are most likely to be preserved intact close to the shoreline and become coarser grained away from the shoreline for the central gbr highstand shedding only applies to carbonate sediment at the scale of local reefs system wide oceanographic controls cause high rates of carbonate sedimentation on the slope during both sea level rise and highstand concomitantly terrigenous sediment accumulates fastest on the slope during sea level rise and slowest during sea level lowstand and highstand

methane distribution on pluto as mapped by the new horizons ralph mvic instrument abstract the data returned from nasa s new horizons spacecraft have given us an unprecedented detailed look at the pluto system new horizons ralph mvic multispectral visible imaging camera is composed of 7 independent ccd arrays on a single substrate among these are a red channel 540 700 nm near infrared channel 780 975 nm and narrow band methane channel 860 910 nm by comparing the relative reflectance of these channels we are able to produce high resolution methane equivalent width based on the 890 nm absorption band and spectral slope maps of pluto s surface from these maps we can then quantitatively study the relationships between methane distribution redness and other parameters like latitude and elevation we find pluto s surface to show a great diversity of terrains particularly in the equatorial region between 30 n and 30 s latitude methane equivalent width also shows some dependence on elevation while spectral slope shows very little

a post new horizons global climate model of pluto including the n 2 ch 4 and co cycles abstract we have built a new 3d global climate model gcm to simulate pluto as observed by new horizons in 2015 all key processes are parametrized on the basis of theoretical equations including atmospheric dynamics and transport turbulence radiative transfer molecular conduction as well as phases changes for n 2 ch 2 and co pluto s climate and ice cycles are found to be very sensitive to model parameters and initial states nevertheless a reference simulation is designed by running a fast reduced version of the gcm with simplified atmospheric transport for 40 000 earth years to initialize the surface ice distribution and sub surface temperatures from which a 28 earth year full gcm simulation is performed assuming a topographic depression in a sputnik planum sp like crater on the anti charon hemisphere a realistic pluto is obtained with most n 2 and co ices accumulated in the crater methane frost covering both hemispheres except for the equatorial regions and a surface pressure near 1 1 pa in 2015 with an increase between 1988 and 2015 as reported from stellar occultations temperature profiles are in qualitative agreement with the observations in particular a cold atmospheric layer is obtained in the lowest kilometers above sputnik planum as observed by new horizons s rex experiment it is shown to result from the combined effect of the topographic depression and n 2 daytime sublimation in the reference simulation with surface n 2 ice exclusively present in sputnik planum the global circulation is only forced by radiative heating gradients and remains relatively weak surface winds are locally induced by topography slopes and by n 2 condensation and sublimation around sputnik planum however the circulation can be more intense depending on the exact distribution of surface n 2 frost this is illustrated in an alternative simulation with n 2 condensing in the south polar regions and n 2 frost covering latitudes between 35 n and 48 n a global condensation flow is then created inducing strong surface winds everywhere a prograde jet in the southern high latitudes and an equatorial superrotation likely forced by barotropic instabilities in the southern jet using realistic parameters the gcm predict atmospheric concentrations of co and ch 4 in good agreement with the observations n 2 and co do not condense in the atmosphere but ch 4 ice clouds can form during daytime at low altitude near the regions covered by n 2 ice assuming that nucleation is efficient enough this global climate model can be used to study many aspects of the pluto environment for instance organic hazes are included in the gcm and analysed in a companion paper bertrand and forget icarus this issue

self consistent generation of tectonic plates in time dependent three dimensional mantle convection simulations 1 presented here are self consistent three dimensional simulations of mantle convection some of which display an approximation of plate tectonic behavior that is continuous in space and time plate behavior arises through a reasonable material description of silicate deformation with a simple yield stress being sufficient to give first order plate like behavior however the required yield strength or fault frictional coefficient is much less than experimentally determined values toroidal poloidal ratios are within geologically observed limits the sensitivity of the system to yield strength and the form of strength envelope is systematically investigated optimum plate character is obtained in a narrow range of yield strength below which diffuse boundaries and above which episodic behavior and eventually a rigid lid are observed models with mobile lids develop very long wavelength horizontal structure the longest wavelength possible in the domain two dimensional models display much greater time dependence than three dimensional models

geology before pluto pre encounter considerations the cameras of new horizons will provide robust data sets that should be imminently amenable to geological analysis of the pluto system s landscapes in this paper we begin with a brief discussion of the planned observations by the new horizons cameras that will bear most directly on geological interpretability then we broadly review the major geological processes that could potentially operate on the surfaces of pluto and its major moon charon we first survey exogenic processes i e those for which energy for surface modification is supplied externally to the planetary surface impact cratering sedimentary processes including volatile migration and the work of wind we conclude with an assessment of the prospects for endogenic activity in the form of tectonics and cryovolcanism

physical state and distribution of materials at the surface of pluto from new horizons leisa imaging spectrometer abstract from earth based observations pluto is known to be the host of n2 ch4 and co ices and also a dark red material very limited spatial distribution information is available from rotational visible and near infrared spectral curves obtained from hemispheric measurements in july 2015 the new horizons spacecraft reached pluto and its satellite system and recorded a large set of data the leisa spectro imager of the ralph instruments are dedicated to the study of the composition and physical state of the materials composing the surface in this paper we report a study of the distribution and physical state of the ices and non ice materials on pluto s illuminated surface and their mode and degree of mixing principal component analysis as well as various specific spectral indicators and correlation plots are used on the first set of 2 high resolution spectro images from the leisa instrument covering the whole illuminated face of pluto at the time of the new horizons encounter qualitative distribution maps have been obtained for the 4 main condensed molecules n2 ch4 co h2o as well as for the visible dark red material based on specific spectral indicators using either the strength or the position of absorption bands these 4 molecules are found to indicate the presence of 3 different types of ices n2 rich ch4 co ices ch4 rich co n2 ices and h2o ice the mixing lines between these ices and with the dark red material are studied using scatter plots between the various spectral indicators ch4 is mixed at the molecular level with n2 most probably also with co thus forming a ternary molecular mixture that follows its phase diagram with low solubility limits the occurrence of a n2 rich ch4 rich ices mixing line associated with a progressive decrease of the co ch4 ratio tells us that a fractionation sublimation sequence transforms one type of ice to the other forming either a n2 rich ch4 rich binary mixture at the surface or an upper ch4 rich ice crust that may hide the n2 rich ice below the strong ch4 rich h2o mixing line witnesses the subsequent sublimation of the ch4 rich ice lag left behind by the n2 co sublimation n spring summer or a direct condensation of ch4 ice on the cold h2o ice s autumn the weak mixing line between ch4 containing ices and the dark red material and the very sharp spatial transitions between these ices and this non volatile material are probably due to thermal incompatibility finally the occurrence of a h2o ice red material mixing line advocates for a spatial mixing of the red material covering h2o ice with possibly a small amount intimately mixed in water ice from this analysis of the different materials distribution and their relative mixing lines h2o ice appears to be the substratum on which other ices condense or non volatile organic material is deposited from the atmosphere n2 rich ices seem to evolve to ch4 dominated ices possibly still containing traces of co and n2 as n2 and co sublimate away the spatial distribution of these materials is very complex the high spatial definition of all these composition maps as well as those at even higher resolution that will be soon available will allow us to compare them with pluto s geologic features observed by lorri panchromatic and mvic multispectral imagers to better understand the geophysical processes in action at the surface of this astonishingly active frozen world

epidote trace element chemistry as an exploration tool in the collahuasi district northern chile the collahuasi district of northern chile hosts several late eocene early oligocene world class porphyry cu mo deposits including rosario ujina and quebrada blanca deposits and associated high sulfidation epithermal mineralization at la grande mineralization is hosted by intermediate to felsic intrusive and volcanic rocks of the upper paleozoic to lower triassic collahuasi group which experienced lower greenschist facies regional metamorphism prior to mineralization extensive hydrothermal alteration zones surround the porphyry and epithermal deposits associated with hypogene ore forming processes however outside of the observed sulfide halo the limits of geochemical anomalism associated with mineralization are difficult to define due to mineralogical similarities between weak distal propylitic alteration and regional metamorphism affecting the host rocks recent advancements in laser ablation inductively coupled plasma mass spectrometry analysis of epidote from hydrothermal alteration zones around porphyry and skarn deposits have shown that low level hypogene geochemical anomalies can be detected at distances farther from the center of mineralization than by conventional rock chip sampling selective analysis of propylitic epidote from the collahuasi district indicates that anomalous concentrations of distal pathfinder elements in epidote including as 50 ppm sb 25 ppm pb 100 ppm and mn 5 000 ppm were detectable 1 5 to 4 0 km from deposit centers significantly the concentrations of these trace elements in epidote were obtained from samples that contained whole rock concentrations of

near inertial ocean response to tropical cyclone forcing on the australian north west shelf the regional ocean modeling system roms was applied to the australian north west shelf nws to hindcast the ocean response to four intense historical tropical cyclones tcs while the four cyclones had very different trajectories across the nws all passed within 150 km of a long term vertical mooring located on the continental shelf in 125 m depth the observed ocean response at this relatively shallow southern hemisphere shelf site was characterized by the development of a peak in the counter clockwise ccw near inertial kinetic energy mixed layer deepening and subsequent restratification strong near inertial isotherm oscillations were also observed following two of the cyclones roms reproduced these features and also showed that the peak in the near inertial ccw kinetic energy was observed on the left side of each cyclone trajectory the time rate of change of near inertial kinetic energy depended strongly on the storm rossby number i e defined based on the storm speed the storm length scale and the coriolis frequency the shallow water depth on the nws resulted in first a more rapid decay of near inertial oscillations than in the deep ocean and second a generation efficiency the ratio of near inertial power to the rate of wind work of up to 10 smaller than found for cyclones propagating across deeper water the total energy put into near inertial motions is nevertheless large compared to the background tidal energy the rapid decay of near inertial motions emphasizes the importance of frictional effects in characterizing the response to cyclone forcing in shallow seas

mineralogic and stable isotope zonation at the surface over the el salvador porphyry copper deposit chile we examined in detail the mineralogic and stable isotope characteristics of alteration minerals exposed at the surface of the el salvador porphyry copper deposit a total of 276 samples was collected from 203 localities over an area of 5 km 2 at elevations between 2 900 and 3 300 m the alteration assemblages can be separated into two groups broadly corresponding to the stages previously identified from underground studies although the early stage k silicate alteration identified underground is not evident at the surface a transitional to late stage is characterized at the surface by assemblages of 1 muscovite andalusite with trace diaspore including some areas rich in andalusite and 2 muscovite with trace diaspore there is a sharp contact outward with a marginal propylitic assemblage chlorite calcite epidote pyrophyllite occurs as a retrograde overprint of muscovite in both of the transitional to late stage assemblages these assemblages are concentrically zoned and centered on a core of least altered granodiorite porphyry a late intramineral intrusion the muscovite andalusite assemblage occurs up to 500 m away from the granodiorite porphyry and andalusite rich zones are located near the brecciated margin of the porphyry further outward is the muscovite zone from 500 to 1 500 m wide the pyrophyllite overprint overlaps the contact of the muscovite andalusite and muscovite zones and occurs mainly above 3 000 m elevation such that its present distribution is controlled largely by topography very late alteration minerals occur in radial pebble dikes of hydrothermal breccia and their extensions and they are dominated by an advanced argillic assemblage of alunite aluminum phosphate sulfate minerals diaspore zunyite pyrophyllite dickite with residual muscovite in one case a breccia extends upward and appears to be the root of a 300 500 m outcrop 80 m thick of massive quartz alunite replacement of rhyolite pure mineral separates were prepared from these samples for o h and s isotope analysis including 48 samples of silicate minerals muscovite pyrophyllite dickite and supergene kaolinite and 20 samples of alunite some supergene in origin information on mineral assemblage was used to estimate temperatures of formation which then allowed calculation of the isotopic composition of associated hydrothermal fluids the fluid responsible for forming the muscovite had a relatively narrow range of isotopic composition 6 5 1 5 per mil 18 o and 40 10 per mil d the heaviest 18 o and d values about 8 and 35 per mil respectively were obtained from the samples with andalusite muscovite diaspore assemblage this composition is close to that expected for a magmatic fluid with 10 to 20 percent meteoric water component responsible for forming the other muscovite samples the fluid compositions calculated for the very late stage alunite range from 5 and 30 per mil to 1 and 40 per mil 18 o and d respectively this range in composition agrees with the trend predicted for magmatic vapor absorbed by local groundwater the latter similar in composition to that responsible for forming the supergene kaolinite there is no systematic spatial zonation of the alunite samples in terms of isotopic composition or paleotemperature the temperature estimates from s isotope geothermometry are higher than those based on mineral assemblage possibly caused by partial supergene replacement of some hypogene alunites there is no strong isotopic zonation of hydrothermal minerals from surface alteration assemblages at el salvador that can be applied to generate clear exploration guidelines by contrast mapping of alteration mineralogy in the field backed up by laboratory checking of mineralogy and examination of relict minerals and replacement textures in thin section clearly indicates the center of the late intramineral intrusion

basins fractures and volcanoes global cartography and topography of pluto from new horizons abstract the 2015 new horizons flyby has produced the first high resolution maps of morphology and topography of pluto and charon the most distant objects so mapped global integrated mosaics of pluto were produced using both lorri framing camera and mvic line scan camera data showing the best resolution data obtained for all areas of the illuminated surface 78 of the body a unique feature of the pluto imaging data set is the observation of terrains illuminated only by light scattered from atmospheric haze allowing us to map terrains in the southern hemisphere that would otherwise have been in darkness mvic 4 color data were combined with the panchromatic map to produce full color global maps digital elevation models dems over 42 of pluto were produced using combinations of mvic hemispheric scans and lorri mosaics from which slopes at scales of 1 km can be determined pluto can be divided into regions each with distinct topographic signatures corresponding with major physiographic terrain types large areas of pluto are comprised of low relief moderately cratered plains units deeply pitted and glaciated plains east of sputnik planitia are elevated 0 7 km the most dominant topographic feature on pluto is the 1200 by 2000 km wide depression enclosing the bright sputnik planitia ice sheet the surface of which is 2 5 to 3 5 km deep relative to the rim and 2 km deep relative to the mean radius the partial ring of steep sided massifs several of which are more than 5 km high along the western margins of sputnik planitia produce some of the locally highest and steepest relief on pluto with slopes of 40 50 the second major topographic feature is a complex eroded ridge trough system 300 400 km wide and at least 3200 km long extending north to south along the 155 meridian this enormous structure has several kilometers of relief it may predate the large impact event forming the basin though some post sputnik planitia deformation is evident the large depressed partially walled plain hyecho palus lies due southwest of sputnik planitia near the center of hyecho palus lie the circular constructional edifices wright and piccard montes wright mons rises 4 5 km above these plains with a central depression 4 5 km deep whereas piccard mons best observed in haze light rises 5 5 km above the plains but has a bowl shaped central depression 5 5 km below the plains for a total relief of up to 11 km the greatest observed on pluto both of these features are interpreted as constructional volcanic in nature additional prominent topographic features include a 2 3 km high and 600 km wide dome centered on the illuminated iau pole and the amoeboidal plateaus of bladed terrains in the equatorial region which rise 2 5 km above local terrains and are the highest standing geologic units on the encounter hemisphere the mean elevations in the integrated dem for the two radio occultation areas are consistent with the 5 6 km difference in elevation as determined independently by the radio experiment and a limb profile near the egress point confirms the presence of elevated bladed terrains in that area local relief of 3 5 km at massifs troughs and pits supports conclusions that the icy shell of pluto is relatively rigid numerous examples of topographic control of ice or frost deposition occur across pluto including the distinct coloration of the polar dome the elevated terrains of eastern tombaugh regio and along the ridge trough system where ridge tops and fossae rims are covered in different ices than at lower elevations the topographic hypsogram of pluto s encounter hemisphere is strongly bimodal due to the large sputnik planitia depression otherwise the topographic signature of pluto is controlled by deviations from the otherwise dominant low plains including elevated bladed terrain plateaus and the depressed volcanic province including wright and piccard montes

sulfur isotopic zonation in the cadia district southeastern australia exploration significance and implications for the genesis of alkalic porphyry gold copper deposits the alkalic porphyry gold copper deposits of the cadia district occur in the eastern lachlan fold belt of new south wales australia the district comprises four porphyry deposits ridgeway cadia quarry cadia hill and cadia east and two iron copper gold skarn deposits big cadia and little cadia almost 1 000 tonnes of contained gold and more than four million tonnes of copper have been discovered in these systems making cadia the world s largest known alkalic porphyry district in terms of contained gold porphyry gold copper ore at cadia is associated with quartz monzonite intrusive complexes and is hosted by central stockwork and sheeted quartz sulfide carbonate vein systems the cadia porphyry deposits are characterized by cores of potassic and or calc potassic alteration assemblages and peripheral halos of propylitic alteration with late stage phyllic alteration mostly restricted to fault zones hematite dusting is an important component of the propylitic alteration assemblage and has produced a distinctive reddening of feldspar minerals in the volcanic wall rocks around the mineralized centers sulfide mineralization is strongly zoned at ridgeway and cadia east with bornite rich cores surrounded by chalcopyrite rich halos and peripheral zones of pyrite mineralization the cadia hill and cadia quarry deposits have chalcopyrite rich cores and pyrite rich halos and cadia hill contains a high level bornite rich zone distinctive sulfur isotopic zonation patterns have been identified at ridgeway cadia hill and cadia east the deposit cores are characterized by low 34ssulfide values 10 to 4 consistent with sulfide precipitation from an oxidized sulfate predominant magmatic fluid at 450 to 400 c pyrite grains that occur in the propylitic alteration halos typically have 34ssulfide values near 0 there is a gradual increase in 34ssulfide values outwards from the deposit cores through the propylitic halos water rock interaction during propylitic alteration caused magmatic sulfate reduction and concomitant oxidation of ferrous iron bearing minerals resulting in enrichment of 34s in pyrite and also producing the distinctive reddened hematite rich alteration halos to the cadia deposits these results show that sulfur isotope analyses have potential applications in the exploration of alkalic porphyry style deposits with zones of depleted 34ssulfide values most prospective for high grade mineralization

the pilbara coast a riverine coastal plain in a tropical arid setting northwestern australia abstract the unifying feature of the pilbara coast of northwestern australia is that it is a sedimentary repository for a range of rivers that drains a high relief precambrian rocky hinterland and discharges sediments along a coastal plain which fronts a wave dominated environment in a tropical arid climate the combination of fluvial and shoreline accretion processes coastal cementation coastal erosion and ancestral landform architecture such as residual pleistocene limestone ridges and large outcrops of precambrian bedrock has produced a complex coastal system during the quaternary as a result the coast is dominated by active deltas beach dune shores inactive eroding parts of deltas and their barriers limestone barrier coasts bays associated with eroded limestone barriers and archipelago ria coasts quaternary sediments throughout the area while varied in their distribution and history at the smaller scales exhibit a recurring pattern of lithotopes and lithologies in the region there are three main quaternary suites pleistocene red siliciclastic sediments alluvium deltaic sediments and aeolian sand that form an inland zone pleistocene limestones that form local barriers and a holocene system within which are the sedimentary suites of deltas beach dunes tidal flats and tidal embayments

reaction mechanism for the replacement of calcite by dolomite and siderite implications for geochemistry microstructure and porosity evolution during hydrothermal mineralisation carbonate reactions are common in mineral deposits due to co2 rich mineralising fluids this study presents the first in depth integrated analysis of microstructure and microchemistry of fluid mediated carbonate reaction textures at hydrothermal conditions in doing so we describe the mechanisms by which carbonate phases replace one another and the implications for the evolution of geochemistry rock microstructures and porosity the sample from the 1 95 moz junction gold deposit western australia contains calcite derived from carbonation of a metamorphic amphibole plagioclase assemblage that has further altered to siderite and dolomite the calcite is porous and contains iron rich calcite blebs interpreted to have resulted from fluid mediated replacement of compositionally heterogeneous amphiboles the siderite is polycrystalline but nucleates topotactically on the calcite as a result the boundaries between adjacent grains are low angle boundaries 10 which are geometrically similar to those formed by crystal plastic deformation and recovery growth zoning within individual siderite grains shows that the low angle boundaries are growth features and not due to deformation low angle boundaries develop due to the propagation of defects at grain faces and zone boundaries and by impingement of grains that nucleated with small misorientations relative to each other during grain growth the cores of siderite grains are aligned with the twin planes in the parent calcite crystal showing that the reactant fe entered the crystal along the twin boundaries dolomite grains many of which appear to in fill space generated by the siderite replacement also show alignment of cores along the calcite twin planes suggesting that they did not grow into space but replaced the calcite where dolomite is seen directly replacing calcite it nucleates on the fe rich calcite due to the increased compatibility of the fe bearing calcite lattice relative to the pure calcite both reactions are interpreted as fluid mediated replacement reactions which use the crystallography and elemental chemistry of the calcite experiments of fluid mediated replacement reactions show that they proceed much faster than diffusion based reactions this is important when considering the rates of reactions relative to fluid flow in mineralising systems

cyclone induced hyperpycnal turbidity currents in a submarine canyon 1 density currents such as turbidity currents are major transport agents in various terrestrial lacustrine and marine environments worldwide however a gap exists between those who study the deposits by turbidity currents turbidite on a field scale and those who study turbidity currents using small scale laboratory experiments and theoretical numerical models we report two typhoon triggered hyperpycnal turbidity current events observed in a submarine canyon our findings verify turbidite sequences with the characteristics of suspended sediment carried by passing turbidity currents that displayed distinct waxing and waning phases our study also confirms the direct link between typhoon triggered hyperpycnal flows in a small mountainous river and turbidity currents in a nearby submarine canyon that transport sediment to the deep sea efficiently

modeling cryogenic mud volcanism on pluto abstract subsurface ice cryofluids and ice interactions with ammonia for cryovolcanic materials give the potential ingredients for the formation of mud volcanoes on pluto in order to constrain the possible morphology from images acquired by the new horizons spacecraft we have modeled the formation of mud volcanoes isostatic layers of ice overlain by denser material from a series of possible solid liquid mud compositions methane and ammonia as well as accounting for the full range of eruption variables e g mud viscosity conduit diameter and eruption duration we categorize them into nine specific scenarios based on the composition of the top ice layer and mud composition from these scenarios the maximum height of the potential mud volcano can be calculated we find that ammonia mud sources produce smaller edifice heights and wider flow profiles compared to methane dominant mud cryovolcanoes assuming certain preliminary parameters we also propose the evolution and development of the edifice of wright mons in as little as 3 8 million years given a 10 wt ammonia subsurface mud composition if characterized on pluto s surface mud volcanoes would provide an interesting insight on the subsurface dynamics of solids and cryofluids on pluto

the geology of pluto and charon through the eyes of new horizons nasa s new horizons spacecraft has revealed the complex geology of pluto and charon pluto s encounter hemisphere shows ongoing surface geological activity centered on a vast basin containing a thick layer of volatile ices that appears to be involved in convection and advection with a crater retention age no greater than 10 million years surrounding terrains show active glacial flow apparent transport and rotation of large buoyant water ice crustal blocks and pitting the latter likely caused by sublimation erosion and or collapse more enigmatic features include tall mounds with central depressions that are conceivably cryovolcanic and ridges with complex bladed textures pluto also has ancient cratered terrains up to 4 billion years old that are extensionally faulted and extensively mantled and perhaps eroded by glacial or other processes charon does not appear to be currently active but experienced major extensional tectonism and resurfacing probably cryovolcanic nearly 4 billion years ago impact crater populations on pluto and charon are not consistent with the steepest impactor size frequency distributions proposed for the kuiper belt

petrology and geochemistry of propylitic alteration at southwest tintic utah systematic variations in mineral assemblages fluid inclusion characteristics mineral chemistry and isotopic ratios document the chemical and thermal evolution of hydrothermal fluids responsible for late alteration in a small porphyry copper system near tintic utah propylitic alteration of volcanic rock can be subdivided into actinolite epidote and chlorite subzones an actinolite subzone containing actinolite epidote chlorite and calcite extends 250 m away from the secondary biotite zone an epidote subzone containing epidote chlorite and calcite is present up to 500 m away from the secondary biotite zone a chlorite subzone of chlorite and calcite is present up to 2 km from the secondary biotite zone chlorite which occurs in each subzone varies systematically in fe mg and mn content the ratio fe fe mg increases from 0 27 at the secondary biotite zone to 0 48 in the outer propylitic zone accompanied by a decrease in activity of clinochlore from 0 15 to 0 02 mno increases from 0 23 to 0 44 wt percent the fe super 3 content of epidote also systematically decreases from the actinolite subzone outward the activity of clinozoisite in the epidote ranges from 0 038 at the secondary biotite zone to 0 21 700 m away from the secondary biotite zone in the outer epidote subzone systematic changes in chlorite and epidote compositions reflect increasing log a sub mg super 2 a 2 sub h super and log a sub fe super 2 a 2 sub h super with increasing distance from the hydrothermal biotite zone and decreasing temperature and salinity fluid inclusion homogenization temperatures decrease away from the secondary biotite zone with a horizontal thermal gradient of 78 degrees c km temperatures range from 351 degrees to 160 degrees c in propylitic alteration salinities also decrease outward from 7 3 to 0 0 equiv wt percent nacl hydrothermally altered rocks are systematically depleted in 18 o outward from the phyllic alteration zone into the chlorite subzone as recorded by whole rock samples 10 9 to 1 7ppm calcite 10 4 1 6ppm and quartz veins 2 8 to 0 8ppm calculated delta 18 o and delta d values for the actinolite subzone are 5 and 55 per mil respectively values as low as 15 1 and 120 per mil are recorded at the outer limits of sampling in the chlorite subzone these latter values indicate that outer propylitic alteration is dominated by isotopically unevolved local meteoric water however the large variations in hydrogen and oxygen isotope compositions recorded across the zoned propylitic alteration are too large to have been produced from an isotopically homogeneous fluid given the measured range of alteration temperatures 350 degrees 200 degrees c rather the variations in isotopic compositions and salinity of the propylitic alteration fluids are consistent with the progressive mixture of unevolved 18 o and d depleted low salinity local meteoric water with a much more 18 o and d enriched higher salinity fluid the later phyllic alteration also formed from a similar 18 o and d enriched fluid we suggest that these isotopically enriched fluids more likely evolved from local meteoric water through extensive exchange at very low water rock ratios with the igneous rocks at depth in the hydrothermal system at tintic an alternative explanation is that 18 o and d enriched fluids represent a late incursion of magmatic water unlike many other porphyry copper systems participation of such 18 o and d enriched fluids in the waning stages of hydrothermal alteration at tintic contrasts with the usual domination of isotopically unevolved meteoric water at these stages e g propylitic phyllic in many porphyry copper systems sheppard et al 1971 taylor 1974 gustafson 1978 at tintic isotopically enriched fluids coexist with and even displace meteoric water during propylitic and phyllic alteration respectively

observed glacier and volatile distribution on pluto from atmosphere topography processes simulations of the levels of nitrogen methane and carbon monoxide over thousands of years confirm the existence of a nitrogen glacier in sputnik planitia pluto s deepest basin tanguy bertrand and francois forget have developed a model for volatile transport on pluto and use it to simulate the evolution of n2 ch4 and co on the dwarf plant over tens of thousands of earth years the model predicts n2 ice accumulation in the deepest low latitude basin and the threefold increase in atmospheric pressure that has been observed to occur since 1988 this points to atmospheric topographic processes as the origin of the prominent equatorial n2 glacier known as sputnik planitia formerly sputnik planum this is one of four papers on the geology of sputnik planitia in this issue of nature in news views amy barr puts these latest contributions into context pluto has a variety of surface frosts and landforms as well as a complex atmosphere1 there is ongoing geological activity related to the massive sputnik planitia glacier mostly made of nitrogen n2 ice mixed with solid carbon monoxide and methane2 covering the 4 kilometre deep 1 000 kilometre wide basin of sputnik planitia1 3 near the anti charon point the glacier has been suggested to arise from a source region connected to the deep interior or from a sink collecting the volatiles released planetwide1 thin deposits of n2 frost however were also detected at mid northern latitudes and methane ice was observed to cover most of pluto except for the darker frost free equatorial regions2 here we report numerical simulations of the evolution of n2 methane and carbon monoxide on pluto over thousands of years the model predicts n2 ice accumulation in the deepest low latitude basin and the threefold increase in atmospheric pressure that has been observed to occur since 19884 5 6 this points to atmospheric topographic processes as the origin of sputnik planitia s n2 glacier the same simulations also reproduce the observed quantities of volatiles in the atmosphere and show frosts of methane and sometimes n2 that seasonally cover the mid and high latitudes explaining the bright northern polar cap reported in the 1990s7 8 and the observed ice distribution in 20152 the model also predicts that most of these seasonal frosts should disappear in the next decade

the nitrogen cycles on pluto over seasonal and astronomical timescales abstract pluto s landscape is shaped by the endless condensation and sublimation cycles of the volatile ices covering its surface in particular the sputnik planitia ice sheet which is thought to be the main reservoir of nitrogen ice displays a large diversity of terrains with bright and dark plains small pits and troughs topographic depressions and evidences of recent and past glacial flows outside sputnik planitia new horizons also revealed numerous nitrogen ice deposits in the eastern side of tombaugh regio and at mid northern latitudes these observations suggest a complex history involving volatile and glacial processes occurring on different timescales we present numerical simulations of volatile transport on pluto performed with a model designed to simulate the nitrogen cycle over millions of years taking into account the changes of obliquity solar longitude of perihelion and eccentricity as experienced by pluto using this model we first explore how the volatile and glacial activity of nitrogen within sputnik planitia has been impacted by the diurnal seasonal and astronomical cycles of pluto results show that the obliquity dominates the n2 cycle and that over one obliquity cycle the latitudes of sputnik planitia between 25 s 30 n are dominated by n2 condensation while the northern regions between 30 n and 50 n are dominated by n2 sublimation we find that a net amount of 1 km of ice has sublimed at the northern edge of sputnik planitia during the last 2 millions of years it must have been compensated by a viscous flow of the thick ice sheet by comparing these results with the observed geology of sputnik planitia we can relate the formation of the small pits and the brightness of the ice at the center of sputnik planitia to the sublimation and condensation of ice occurring at the annual timescale while the glacial flows at its eastern edge and the erosion of the water ice mountains all around the ice sheet are instead related to the astronomical timescale we also perform simulations including a glacial flow scheme which shows that the sputnik planitia ice sheet is currently at its minimum extent at the northern and southern edges we also explore the stability of n2 ice deposits outside the latitudes and longitudes of the sputnik planitia basin results show that n2 ice is not stable at the poles but rather in the equatorial regions in particular in depressions where thick deposits may persist over tens of millions of years before being trapped in sputnik planitia finally another key result is that the minimum and maximum surface pressures obtained over the simulated millions of years remain in the range of milli pascals and pascals respectively this suggests that pluto never encountered conditions allowing liquid nitrogen to flow directly on its surface instead we suggest that the numerous geomorphological evidences of past liquid flow observed on pluto s surface are the result of liquid nitrogen that flowed at the base of thick ancient nitrogen glaciers which have since disappeared

laser probe 40 ar 39 ar ages of early and late stage alteration assemblages rosario porphyry copper molybdenum deposit collahuasi district i region chile sensibly identical laser probe 40 ar 39 ar dates of 32 9 or 0 5 2sigma and 32 9 or 0 6 ma are determined for respectively early stage hydrothermal biotite and late stage hydrothermal muscovite from the giant rosario porphyry copper deposit in the collahuasi district of northern chile the age determinations were carried out on ca 1 cm 2 1 to 0 5 mm thick wafers of altered rock or on smaller chips broken therefrom obviating the requirement for mineral separation and permitting direct petrographic control of the analytical procedure the age data although not unambiguous imply that this extremely large hydrothermal center was emplaced over a short interval hydrothermal activity in this central andean transect migrated eastward over a period of ca 3 to 4 m y from copaquire through quebrada blanca to rosario the intensity of mineralization increasing with time rosario chuquicamata and la escondida the largest of the west fissure domeyko fault system array were apparently emplaced coevally in the terminal stage of the late eocene early oligocene metallogenic episode

the dark side of iapetus abstract this paper presents new photometric and spectrophotometric observations of the dark leading hemisphere of saturn s satellite iapetus spectrophotometry from 0 3 1 0 um may 1979 shows the dark hemisphere to be very red similar to a few asteroids and the moon but with no spectral features attributable to olivine or pyroxene near infrared spectrophometry in the regions 1 4 2 5 um may 1981 and 3 0 3 8 um february 1981 reveals water ice absorption bands probably resulting from the polar caps intruding onto the dark hemisphere the reflectance of iapetus is unlike that of carbonaceous chondrites or c type asteroids and most closely resembles the reflectance and low albedo of carbonaceous organic residue from the murchison c2 carbonaceous chondrite the murchison material has the same red slope and a probable spectral feature near 0 6 um seen in iapetus data three hypotheses for the formation of the dark hemisphere are discussed in light of the observational data the favored hypothesis is that debris from phoebe or other unknown outer satellites of saturn impacts the dark hemisphere of iapetus as poynting robertson drag causes the debris to spiral toward saturn the high velocity impacts preferentially remove ice from the satellite s surface causing enrichment of included carbonaceous material intrinsic to iapetus the reflectance of phoebe itself is significantly different from that of iapetus suggesting that relatively little phoebe debris lies on the dark hemisphere there remains the possibility that the impacting debris originates from another body of composition similar to the murchison residue and that this material is exposed on the surface of iapetus

a study of tropical cyclone influence on the generation of internal tides 1 an investigation is made into modifications of the semidiurnal internal tide on the western australian shelf by a passing tropical cyclone current mooring observations are presented taken during the passage of tropical cyclone bobby 1995 over these mooring locations the observations reveal large vertical excursions at near inertial frequency of the isotherm during and following the cyclone s passage this coincides with diminishing semidiurnal baroclinic tides to gain dynamical insight into the observations a fully three dimensional free surface nonlinear hydrostatic model is applied to the western australian shelf the model is initialized with realistic stratification and forced by representative tides and cyclone winds the wind forcing is derived from an idealized analytical cyclone model prescribed from observed cyclone track and central pressure data and the tidal forcing allows for the generation of internal tides the cyclone modifies stratification by turbulent mixing upwelling downwelling and density advection up or down the shelf slope this results in significant changes to internal tide characteristic paths and hence the internal tide generation process on the continental slope mixing is enhanced over the shelf due to shallow topography with respect to the shelf slope region creating a strong density front at the shelf edge observations and modeling show that the water column response to the cyclone passage is most abrupt in shallow water at 125 m then at 300 m depth the model reproduces the main features of the observed inertial oscillations concomitant with the dampening of m2 internal tides after the passage of the cyclone

calc silicate mineralization in active geothermal systems detailed study of the calc silicate mineralogy in the cerro prieto geothermal system was used to demonstrate examples for thermodynamic evaluation of phase relations among minerals of variable composition and to calculate the chemical characteristics of hydrothermal solutions compatible with the observed calc silicate assemblages in general there is a close correlation between calculated and observed fluid compositions calculated fugacities of o 2 at about 320 degrees c in the cerro prieto geothermal system are about five orders of magnitude less than those at the nearby salton sea geothermal system this observation is consistent with the occurrence of fe super 3 rich epidotes and andradite garnets in the latter system and the presence of prehnite at cerro prieto modified journal abstract

40ar 39ar and re os geochronology of porphyry copper molybdenum deposits and related copper silver veins in the collahuasi district northern chile the rosario and ujina porphyry cu mo deposits together with porphyry copper mineralization at the nearby quebrada blanca deposit constitute the third largest concentration of copper mineralization associated with the domeyko fault system in northern chile at rosario fault hosted cu ag rich massive sulfide veins are associated with pyrophyllite alunite quartz altered rocks the rosario massive sulfide veins cut biotitealbite magnetite k feldspar and illite chlorite altered rocks associated with porphyry style copper molybdenum mineralization similar massive sulfide veins occur in the la grande area 1 to 2 km south of rosario copper ore at ujina is associated with a k feldspar biotite altered quartz monzonite intrusion the k feldspar biotite assemblage has been overprinted by white mica chlorite alteration new geochronologic data presented in this paper constrain the ages of hydrothermal activity in the rosario and ujina deposits the 40ar 39ar biotite illite and alunite dates at 2 sigma error and a re os molybdenite date at 0 5 error are reported for porphyritic rocks and hydrothermal alteration from the rosario and ujina mineralized centers a weighted mean 40ar 39ar plateau age of 34 4 plus or minus 0 3 ma is obtained for igneous biotite in a monzonite porphyry that hosts copper mineralization at the rosario deposit illite and hypogene alunite from separate overprinting alteration events yielded 40ar 39ar ages of 34 5 plus or minus 0 5 ma plateau age and 32 6 plus or minus 0 3 ma plateau age respectively an re os age of 33 3 plus or minus 0 2 ma for molybdenite at rosario is slightly younger than the 40ar 39ar age of illite but older than the alunite a weighted mean plateau age of 32 7 plus or minus 1 6 ma for hypogene alunite from the la grande cu ag au vein south of rosario is indistinguishable from the age of rosario alunite at ujina the weighted mean 40ar 39ar plateau age of igneous biotite for a monzonite intrusion that hosts copper mineralization is 35 2 plus or minus 0 3 ma the monzonite is intruded by postmineralization porphyry dikes of similar composition from which igneous biotite yielded a 40ar 39ar age of 34 7 plus or minus 0 3 ma igneous biotite in the rosario porphyry cooled through its closure temperature during and after the formation of illite implying that porphyry style ore and alteration minerals in the rosario deposit had formed by 34 3 ma the age of alunite at rosario and la grande indicate that a second discrete episode of hydrothermal activity was superimposed 1 8 plus or minus 0 4 m y later onto the earlier formed porphyry cu system hydrothermal activity at ujina is constrained by the 40ar 39ar ages of igneous biotite in the premineralization and postmineralization intrusions and occurred during a minimum interval of 0 5 plus or minus 0 4 m y the biotite granite at la profunda 1 5 km east of ujina has a igneous biotite age of 81 2 plus or minus 2 9 ma indicating that this intrusion is unrelated to the mineralized eocene oligocene porphyry intrusions at ujina rosario and quebrada blanca the 40ar 39ar data for igneous biotite in the rosario and ujina porphyries are cooling ages after multiple hydrothermal events in most cases these are minimum hydrothermal ages i e ages of the last high temperature hydrothermal event to have affected the samples not magmatic ages however the biotite age for the inca porphyry is possibly only slightly younger than the intrusion age because biotite has not been affected by later hydrothermal alteration

wind driven circulation on the north west shelf of australia abstract in this study the wind driven circulation of the north west shelf of australia is examined along its length the offshore distance to the 200 m isobath is generally greater than 150 km which means the shelf is relatively wide compared to other continental shelves to study the circulation of the north west shelf two sets of data collected during 1981 and 1982 are examined the cross shelf structure of the circulation and the associated pressure field are determined from current meter and tide gauge data collected across the shelf meteorological data collected at three locations along the shelf are used to estimate surface wind stress empirical orthogonal analysis is applied to separate in the frequency domain the dominant modes of motion and the associated wind stress with these data the dynamical balances on the shelf are examined generally the cross shelf force balances are geostrophic for the alongshelf balances all of the terms considered namely acceleration coriolis force al

recognizing propylitic alteration associated with porphyry cu mo deposits in lower greenschist facies metamorphic terrain of the collahuasi district northern chile implications of petrographic and carbon isotope relationships the collahuasi district is a porphyry cu mo subprovince located on the andean high plateau of northern chile late eocene early oligocene mineralization in the district involved hydrothermal alteration of the upper paleozoic to lower triassic collahuasi group granodiorites diorites andesites dacites and rhyolites which had previously experienced regional lower greenschist facies metamorphism as well as uneconomic porphyry style mineralization and associated sericitic alteration alteration mapping represents an effective technique for prospecting for hydrothermal deposits but in low grade metamorphic terrains recognition of propylitic assemblages that represent the boundary of the mineralizing system is hampered by their resemblance to metamorphic mineral assemblages our results from collahuasi indicate that petrographic criteria can distinguish propylitic alteration from the effects of lower greenschist facies metamorphism but distinctions vary with rock type mafic intermediate and felsic rocks with varying degrees of propylitic alteration can be distinguished from background metamorphism mainly by the presence of calcite however propylitic alteration can also be distinguished by high whole rock 13c values and carbon contents 19 1 to 1 4 and up to 0 79 wt respectively that result from the incorporation of magmatic co2 during the mineralizing events lower 13c values 32 7 to 13 1 and carbon contents 0 09 wt were recorded in other types of hydrothermal alteration intermediate argillic sericitic and potassic alteration and associated with background metamorphism they reflect a dominantly 13c depleted carbon component that remains in the rocks after extensive co2 degassing during emplacement alteration by hydrothermal fluids or contamination by organic carbon carbon and oxygen isotope compositions of calcite from propylitic alteration which range from 12 to 0 3 and 6 6 to 25 9 respectively are consistent with a predominantly magmatic origin for the carbonates although subsequent resetting of the oxygen isotopes by local ground water and minor contributions of organic carbon are recorded in some samples spatial variation in 13c values and carbon contents of outcrop samples from the collahuasi district delineate zones of high magmatic co2 component that correspond exclusively to propylitic alteration surrounding economic deposits

color composition and thermal environment of kuiper belt object 486958 arrokoth introduction the new horizons spacecraft flew past 486958 arrokoth provisional designation 2014 mu69 on 1 january 2019 arrokoth is a member of the subclass of trans neptunian or kuiper belt objects kbos known as the cold classical kbos cckbos most kbos formed in a disk of planetesimals that extended to about 30 au from the sun neptune eventually disrupted that disk by migrating outward through it with the migration halted by the sparseness of the disk beyond 30 au that event eliminated most members of the planetesimal disk but a minority were emplaced into dynamically excited orbits in the present day kuiper belt cckbos differ from those objects in having formed well beyond the 30 au edge of the main planetesimal disk they remain approximately where they formed on low inclination near circular orbits between 42 and 47 au from the sun relicts of the early solar system their distributions of colors albedos sizes and binarity differ from those of the more excited kbos rationale initial results from the exploration of arrokoth were published previously more data have since been received from the spacecraft allowing a more detailed analysis we analyze a high spatial resolution color imaging observation near infrared spectral imaging and microwave radiometry of arrokoth the infrared spectral data have been processed to compensate for the changing range and scale during the observation our multiple scattering radiative transfer models provide compositional constraints from the infrared spectral imagery microwave thermal radiometry at 4 2 cm wavelength is combined with heat transport models that account for the bilobate shape of arrokoth and for self radiation results at visual wavelengths arrokoth s reflectance rises toward longer wavelengths this red coloration is typical of the broader cckbo population that has been studied using telescopic observations color differences across the surface of arrokoth correspond to geological features these color differences are subtle with deviations of just a few percent around the prevailing red coloration some of the color variations are associated with albedo markings such as the bright neck between the two lobes bright splotches associated with a large pit or crater on the smaller lobe and poorly resolved small bright spots methanol ice ch3oh and complex organic tholins dominate the near infrared reflectance spectrum with h2o ice contributing little or no detectable absorption at the 4 2 cm microwave wavelength of new horizons radio system arrokoth s winter night side glows with an average brightness temperature of 29 5 k this emission probably emerges from below the cold winter surface at depths where warmth from the previous summer lingers our models show that self radiation more than compensates for self shadowing in the neck region between the two lobes resulting in warmer temperatures in that region by up to a few kelvin conclusion the nearly uniform coloration across arrokoth is consistent with expectations for an object that accreted too quickly for the composition of the available nebular solids to have changed during the course of its accretion radiolysis and photolysis from long exposure to space radiation would be expected to result in a dark space weathered surface veneer that is distinct from the more pristine interior but there is little evidence for such a coating perhaps because radiolytically processed material is eroded away faster than it accumulates the abundance of ch3oh ice and apparent scarcity of h2o ice appear to be signatures of a distinct environment in the cold dust shaded midplane of the outer nebula during formation of the solar system in this region temperatures would have been low enough that volatile co and ch4 could freeze onto dust grains enabling production of ch3oh and perhaps also destruction of h2o when the nebular dust dissipated some time after arrokoth s formation exposure to sunlight would have raised its temperature rapidly driving off condensed co and ch4 the temperature has remained too cold to crystallize amorphous h2o volatile species may remain trapped in amorphous h2o ice within arrokoth s interior but the infrared spectrum shows little evidence for such ice at the surface although the neck region gets slightly warmer than the rest of arrokoth s surface this effect is small relative to the winter summer temperature contrast and is thus unlikely to account for the distinctly higher albedo and slightly less red material that is seen there a more plausible explanation for the neck s albedo and color contrasts involves texture changes induced by the merger of the two lobes or subsequent downslope movement of material there

mineralogy of the aktogai giant porphyry cu deposit in kazakhstan insights into the fluid composition and oxygen fugacity evolution abstract it has been proposed that most giant porphyry cu deposits are closely associated with oxidized magmas most recently many methods including zircon trace elements mn content in apatite and magnetite ilmenite mineral pair were used to reveal the primary magmatic oxygen fugacity of the porphyry cu deposits hydrothermal alterations are products of water rock reactions and can form various hydrothermal minerals which can be used for exploration the aktogai group including aktogai aidarly and kyzilkia contains more than 12 5 mt cu 0 4 wt and 80 t au 0 007 g t 0 4 g t chlorites show significant variations in the aktogai deposit which are responsible for degrees of tschermak and di trioctahedral substitution chlorites are divided into type i and ii based on fe fe mg ratios of chlorites which are predominately controlled by hydrothermal fluid composition and oxygen fugacity the chlorite i have higher fe fe mg ratios than chlorite ii the formation temperatures of chlorite are 248 322 c based on empirical geothermometry t5 sericites belong to muscovite and phengitic muscovite and their compositions are controlled by tschermak and fe 3 vi al 3 vi substitution water rock reaction leaches out some elements into hydrothermal fluids therein si 4 and k precipitate as quartz and sericite at all alteration stages but fe 2 and ca 2 precipitate as specific minerals such as chalcopyrite and calcite at main mineralization or late stage the chlorite i form under a fe rich condition with high water rock ratio while chlorite ii form under a low water rock ratio and fe poor condition which may be responsible for the sulfides and epidote precipitation according to zircon trace elements mn content in apatite magnetite ilmenite mineral pair and fe fe mg and fe 3 tfe ratios of chlorites the oxygen fugacity changes from high at magmatic and early hydrothermal stages through low at main mineralization stage to slightly high at late or post mineralization stage our results combined with previous works suggest that fe contents and fe fe mg ratios of chlorites are good indicators for exploration

primordial n2 provides a cosmochemical explanation for the existence of sputnik planitia pluto abstract the presence of n2 in the surface environment of pluto is critical in creating pluto s richness of features and processes here we propose that the nitrogen atoms in the n2 observed on pluto were accreted in that chemical form during the formation of pluto we use new horizons data and models to estimate the amounts of n2 in the following exterior reservoirs atmosphere escape photochemistry and surface the total exterior inventory is deduced to be dominated by a glacial sheet of n2 rich ices at sputnik planitia or by atmospheric escape if past rates of escape were much faster than at present pluto s atmosphere is a negligible reservoir of n2 and photochemical destruction of n2 may also be of little consequence estimates are made of the amount of n2 accreted by pluto based on cometary and solar compositions it is found that the cometary model can account for the amount of n2 in sputnik planitia while the solar model can provide a large initial inventory of n2 that would make prodigious atmospheric escape possible these consistencies can be considered preliminary evidence in support of a primordial origin of pluto s n2 however both models predict accreted ratios of co n2 that are much higher than that in pluto s atmosphere possible processes to explain missing co that are given quantitative support here are fractional crystallization from the atmosphere resulting in co burial at the surface and aqueous destruction reactions of co subject to metastable thermodynamic equilibrium in the subsurface the plausibility of primordial n2 as the primary source of pluto s nitrogen vs nh3 or organic n can be tested more rigorously using future constraints on the 14 n 15 n ratio in n2 and the 36ar n2 ratio

ocean worlds in the outer solar system many outer solar system bodies are thought to harbor liquid water oceans beneath their ice shells this article first reviews how such oceans are detected we then discuss how they are maintained when they formed and what the oceans likely characteristics are we focus in particular on europa ganymede callisto titan and enceladus bodies for which there is direct evidence of subsurface oceans we also consider candidate ocean worlds such as pluto and triton

a three dimensional barotropic model of the response of the australian north west shelf to tropical cyclones abstract a three dimensional barotropic model using a coordinate or depth transformation and forced with tropical cyclone wind and atmospheric pressure fields has been applied to the continental shelf and slope regions of the australian north west shelf the atmospheric pressure field of the cyclone causes a nearly isostatic sea level response and weak currents in an unbounded ocean the wind field would produce currents that circulate around the center of the cyclone and eject water thus tending to reduce sea level the coastline forms a boundary for the ejected water resulting in a large sea level rise and strong currents between the cyclone path and the coastline the model provides a good description of the vertical current shear as observed at a number of moorings during two different cyclones sea level rises are accurately modeled and a reasonable description of observed current strengths is achieved however the predicted currents and sea level changes at offshore stations are sensitive to the

global albedos of pluto and charon from lorri new horizons observations abstract the exploration of the pluto charon system by the new horizons spacecraft represents the first opportunity to understand the distribution of albedo and other photometric properties of the surfaces of objects in the solar system s third zone of distant ice rich bodies images of the entire illuminated surface of pluto and charon obtained by the long range reconnaissance imager lorri camera provide a global map of pluto that reveals surface albedo variegations larger than any other solar system world except for saturn s moon iapetus normal reflectances on pluto range from 0 08 1 0 and the low albedo areas of pluto are darker than any region of charon charon exhibits a much blander surface with normal reflectances ranging from 0 20 0 73 pluto s albedo features are well correlated with geologic features although some exogenous low albedo dust may be responsible for features seen to the west of the area informally named tombaugh regio the albedo patterns of both pluto and charon are latitudinally organized with the exception of tombaugh regio with darker regions concentrated at the pluto s equator and charon s northern pole the phase curve of pluto is similar to that of triton the large moon of neptune believed to be a captured kuiper belt object kbo while charon s is similar to that of the moon preliminary bond albedos are 0 25 0 03 for charon and 0 72 0 07 for pluto maps of an approximation to the bond albedo for both pluto and charon are presented for the first time our work shows a connection between very high albedo near unity and planetary activity a result that suggests the kbo eris may be currently active

hydrothermal alteration and stable isotope systematics of the babine porphyry cu deposits british columbia implications for fluid evolution of porphyry systems the eocene babine intrusive suite of west central british columbia hosts a number of porphyry copper deposits most significantly bell granisle and morrison all deposits feature central potassic zones containing the ore zones and peripheral propylitic zones in addition granisle and bell feature superimposed sericite carbonate zones between the potassic and propylitic zones and the bell deposit also possesses a superimposed phyllic stockwork zone which hosts most of the ore calculated fluid compositions from potassic zone biotites of all deposits yield a range from delta 18 o sub h 2 o 6 to 8 per mil whereas plagioclases yield delta 18 o sub h 2 o 1 to 7 per mil since plagioclase samples yield more 18 o depleted fluids than coexisting biotites and delta sub plagioclase biotite values are very small it appears that isotopically lighter fluids were present in later stages of potassic alteration oxygen isotope values from the sericite carbonate and phyllic alteration zones yield fluid compositions more 18 o depleted than magmatic fluids requiring the incorporation of isotopically light ground waters calculated hydrogen isotope values of potassic propylitic and sericite carbonate fluids fall in the range of 40 to 110 per mil these results in combination with the delta 18 o data suggest that the alteration events were caused by mixtures of magmatic and meteoric waters phyllic and argillic alteration fluids delta d sub h 2 o 100 to 130 and 140ppm respectively indicate fluids dominantly of meteoric origin the stable isotope data in combination with the petrologic and field relations suggest that early alteration fluids were derived from the magma and in peripheral areas fluids evolved at very low water rock ratios incorporation of external fluids in later alteration was responsible for the texturally destructive cation leaching alteration and remobilization of the ores differences in the stable isotope systematics and salinities of porphyry copper deposits compared to meteoric hydrothermal systems and epithermal ore deposits indicate that the systems are fundamentally distinct the strong density contrast between the high salinity magmatic fluids and low salinity meteoric waters most likely inhibits mixing resulting in separation of the hydrothermal systems

carbon isotope evidence for microbial involvement in exotic copper silicate mineralization huinquintipa and mina sur northern chile exotic copper silicate and oxide mineralization a peripheral facies of several cenozoic porphyry cu mo systems in northern chile is traditionally ascribed to the lateral migration of cu rich initially highly acidic waters away from active zones of supergene leaching and sulfide enrichment copper precipitation as cu fe silicates and cu mn fe oxides in permeable accumulating pediment gravels or underlying fractured bedrock resulted in part from fluid neutralization attending hydrolytic alteration supergene activity was most intense in the late oligocene early miocene during a protracted middle cenozoic semiarid interval along the lower pacific slope of the central andean cordillera occidental samples from the huinquintipa and mina sur deposits contiguous with respectively the 32 7 to 34 4 ma rosario collahuasi and 31 1 to 34 6 ma chuquicamata porphyry centers were examined for carbon isotope evidence of the conditions of ore formation carbon was extracted as co2 from representative high grade chrysocolla rich samples using four different techniques combustion pyrolysis crushing and edta leaching and has a widely varying isotopic composition consistent with mixing of atmosphere derived carbon with a 13c value of 0 per mil plant derived carbon with 13c values between 25 and 15 per mil and carbon with exceptionally low 13c values of 47 per mil the extremely light carbon sampled primarily by leaching with a 10 percent edta solution is most plausibly ascribed to a microbial consortium including anaerobic methanogenic microbes the presence of mineralized carbon having such low 13c values provides evidence that microbial metabolism may have contributed directly to copper silicate precipitation in these deposits lower 13c values at huinquintipa than at mina sur could be attributed to higher water tables and higher toxic metal contents in the mineralizing fluids the new data reinforce the role played by microbes in the economically critical supergene modification of porphyry and epithermal ore deposits in the semiarid environment

element transport and enrichment during propylitic alteration in paleozoic porphyry cu mineralization systems insights from chlorite chemistry abstract chlorite is one of the most widely developed minerals in propylitic alteration around porphyry deposits and can be used to investigate element transport and enrichment processes during hydrothermal alteration the paleozoic tuwu porphyry cu deposit metal reserve 0 7 mt cu 0 67 located in the southern margin of the central asian orogenic belt is one of the most economical and largest porphyry cu deposits in nw china the tuwu porphyry cu deposit comprises an early porphyry cu mineralization including potassic propylitic and phyllic alteration stages and later overprinting cu mineralization periods with chlorite found in both chlorite from the propylitic zone at tuwu is geochemically similar to propylitic chlorite in younger cenozoic porphyry systems but enriched in mg and k and depleted in fe and al relative to the overprinting chlorite scandium v ti and ga are enriched and li sr mn and zn are depleted in the tuwu propylitic chlorite proximal to the orebody consistent with cenozoic deposits compared with metamorphic chlorite from proterozoic metamorphic terranes in australia tuwu propylitic chlorite has higher mg and k lower fe al and as our results suggest propylitic alteration in the tuwu district is probably the product of cooling of fluids derived from the magmatic hydrothermal system but not from peripheral waters and trace element variations in chlorite are mainly controlled by temperature although other factors such as fault development could affect variation trends the common elemental features of chlorite in both paleozoic and cenozoic porphyry cu deposits indicate it could act as a potential tool for mineral exploration

petrology of philippine geothermal systems and the application of alteration mineralogy to their assessment abstract philippine geothermal systems occur in the vicinity of large holocene calc alkaline volcanic complexes wells drilled in these areas encountered multiple intrusions the latest dikes are the subsurface manifestations of the youngest heat source commonly at least two hydrothermal regimes are juxtaposed in a single area with the latest being in equilibrium with the present temperature and chemical regime alteration by neutral ph water is pervasive and abundant a contact metamorphic aureole also occurs near intrusives alteration due to acid sulfate fluids is generally confined to permeable structures neutral ph alteration is divided into four zones on the basis of key clay minerals and two subzones are defined by calc silicates these are the smectite ambient to 180 c transition 180 230 c illite 230 320 c and biotite 270 340 c zones subzones are defined by epidote 250 340 c and amphibole 280 340 c the four main zones of acid alteration are kaolinite ambient to 120 c dickite kaolinite 120 200 c dickite pyrophyllite 200 250 c and pyrophyllite illite 230 320 c where relict high temperature alteration reaches the surface the area being drilled is usually the outflow zone of the present system these hydrothermal mineral assemblages are used 1 as geothermometers 2 to assist in determining the depth at which the production casing will be set during drilling 3 to estimate fluid ph and other chemical parameters 4 to predict possible corrosion and scaling tendencies of the fluids 5 as a measure of permeability and possible cold water influx into wells 6 as a guide to field hydrology and 7 to estimate roughly the thickness of the eroded overburden

internal tide dynamics in a topographically complex region browse basin australian north west shelf 1 field observations and numerical circulation modeling revealed the spatial variability of the tidally driven dynamics in the topographically complex continuously stratified macrotidal environment of the browse basin on the australian north west shelf internal wave generation occurred at a number of discrete topographic features and the resultant interaction of multiple waves led to a spatially variable internal wave climate the generation of baroclinic energy was most intense in regions where the barotropic tide was aligned with steep topography generation of low mode internal waves occurred at the inner shelf break where the ratio of tidal excursion distance to topographic length scale was large in contrast generation of high mode beam like internal waves occurred at the outer shelf break where the ratio of tidal excursion distance to topographic length scale was very small the most efficient conversion from barotropic to baroclinic energy occurred at the outer shelf break the internal waves generated at the inner and outer shelf breaks interacted to produce a partly standing internal wave resulting in a large along shelf energy flux and discrete locations with small ratios of horizontal kinetic energy to available potential energy this phenomenon is likely to occur in other regions with semienclosed topography and multiple generation sites

the pluto system initial results from its exploration by new horizons the pluto system was recently explored by nasa s new horizons spacecraft making closest approach on 14 july 2015 pluto s surface displays diverse landforms terrain ages albedos colors and composition gradients evidence is found for a water ice crust geologically young surface units surface ice convection wind streaks volatile transport and glacial flow pluto s atmosphere is highly extended with trace hydrocarbons a global haze layer and a surface pressure near 10 microbars pluto s diverse surface geology and long term activity raise fundamental questions about how small planets remain active many billions of years after formation pluto s large moon charon displays tectonics and evidence for a heterogeneous crustal composition its north pole displays puzzling dark terrain small satellites hydra and nix have higher albedos than expected

geological mapping of sputnik planitia on pluto abstract the geology and stratigraphy of the feature on pluto informally named sputnik planitia is documented through geologic mapping at 1 2 000 000 scale all units that have been mapped are presently being affected to some degree by the action of flowing n2 ice the n2 ice plains of sputnik planitia display no impact craters and are undergoing constant resurfacing via convection glacial flow and sublimation condensation of atmospheric n2 onto the surface to form a bright mantle has occurred across broad swathes of sputnik planitia and appears to be partly controlled by pluto s obliquity cycles the action of n2 ice has been instrumental in affecting uplands terrain surrounding sputnik planitia and has played a key role in the disruption of sputnik planitia s western margin to form chains of blocky mountain ranges as well in the extensive erosion by glacial flow of the uplands to the east of sputnik planitia

late paleozoic early triassic magmatism on the western margin of gondwana collahuasi area northern chile abstract the basement in the altiplano high plateau of the andes of northern chile mostly consists of late paleozoic to early triassic felsic igneous rocks collahuasi group that were emplaced and extruded along the western margin of the gondwana supercontinent this igneous suite crops out in the collahuasi area and forms the backbone of most of the high andes from latitude 20 to 22 s rocks of the collahuasi group and correlative formations form an extensive belt of volcanic and subvolcanic rocks throughout the main andes of chile the frontal cordillera of argentina choiyoi group or choiyoi granite rhyolite province and the eastern cordillera of peru thirteen new shrimp u pb zircon ages from the collahuasi area document a bimodal timing for magmatism with a dominant peak at about 300 ma and a less significant one at 244 ma copper mo porphyry mineralization is related to the younger igneous event initial hf isotopic ratios for the 300 ma zircons range from about 2 to 6 indicating that the magmas incorporated components with a significant crustal residence time the 244 ma magmas were derived from a less enriched source with the initial hf values ranging from 2 to 6 suggestive of a mixture with a more depleted component limited whole rock 144nd 143nd and 87sr 86sr isotopic ratios further support the likelihood that the collahuasi group magmatism incorporated significant older crustal components or at least a mixture of crustal sources with more and less evolved isotopic signatures

remote sensing for mineral exploration abstract remote sensing is the science of acquiring processing and interpreting images and related data acquired from aircraft and satellites that record the interaction between matter and electromagnetic energy remote sensing images are used for mineral exploration in two applications 1 map geology and the faults and fractures that localize ore deposits 2 recognize hydrothermally altered rocks by their spectral signatures landsat thematic mapper tm satellite images are widely used to interpret both structure and hydrothermal alteration digitally processed tm ratio images can identify two assemblages of hydrothermal alteration minerals iron minerals and clays plus alunite in northern chile tm ratio images defined the prospects that are now major copper deposits at collahuasi and ujina hyperspectral imaging systems can identify individual species of iron and clay minerals which can provide details of hydrothermal zoning silicification which is an important indicator of hydrothermal alteration is not recognizable on tm and hyperspectral images quartz has no diagnostic spectral features in the visible and reflected ir wavelengths recorded by these systems variations in silica content are recognizable in multispectral thermal ir images which is a promising topic for research

time interval between volcanism and burial metamorphism and rate of basin subsidence in a cretaceous andean extensional setting 40ar 39ar ages were obtained from basaltic flows belonging to a 9 km thick sequence generated in an extensional ensialic setting of an arc back arc basin type during the early cretaceous and presently exposed along the coastal range of central chile the basalts have been affected by very low to low grade burial metamorphism mostly under prehnite pumpellyite facies age values obtained from primary volcanic and secondary metamorphic minerals permit to quantify the time interval between volcanism and burial metamorphism a plateau age of 119 1 2 ma from primary plagioclase represents the best estimation of the age of the volcanism whereas adularia in low variance assemblages contained in amygdules gave a plateau age of 93 1 0 3 ma which is interpreted as the age of the metamorphism considering the p t conditions estimated for this metamorphic event the c 25 ma time interval between volcanic emplacement and prehnite pumpellyite facies metamorphism the rate of basin subsidence in this extensional geodynamic setting would be comprised in the interval 150 180 m ma

pluto s haze as a surface material pluto s atmospheric haze settles out rapidly compared with geological timescales it needs to be accounted for as a surface material distinct from pluto s icy bedrock and from the volatile ices that migrate via sublimation and condensation on seasonal timescales this paper explores how a steady supply of atmospheric haze might affect three distinct provinces on pluto we pose the question of why they each look so different from one another if the same haze material is settling out onto all of them cthulhu is a more ancient region with comparatively little present day geological activity where the haze appears to simply accumulate over time sputnik planitia is a very active region where glacial convection as well as sublimation and condensation rapidly refresh the surface hiding recently deposited haze from view lowell regio is a region of intermediate age featuring very distinct coloration from the rest of pluto using a simple model haze particle as a colorant we are not able to match the colors in both lowell regio and cthulhu to account for their distinct colors we propose that after arrival at pluto s surface haze particles may be less inert than might be supposed from the low surface temperatures they must either interact with local materials and environments to produce distinct products in different regions or else the supply of haze must be non uniform in time and or location such that different products are delivered to different places

oxygen and hydrogen isotope characteristics of hydrothermal alteration at the ann mason porphyry copper deposit yerington nevada late cenozoic normal faulting has tilted a 3 by 5 km block containing the mid jurassic ann mason porphyry copper deposit 90o w and exposed the hydrothermal alteration pattern in cross section from 1 to 6 km palcodepth oxygen and hydrogen isotopes have been used to deduce sources of hydrothermal fluids fresh samples of the host yerington batholith pluton have typical calc alkaline magmatic isotopic compositions 18 o whole rock 6 7 7 0 d biotite 85 to 88 the various types of hydrothermally altered rocks have similar d and 18 o values only slightly isotopically shifted from original magmatic values except along an axial zone within and above the orebody in this zone altered rocks are enriched in 18 o by 1 to 3 5 per mil and 18 o values increase with decreasing palcodepth the 18 o values of the whole rock and or feldspar and the d values of biotite chlorite and or actinolite in the various alteration zones are as follows propylitic alteration is widespread and is isotopically similar to fresh rock 18 o 6 2 to 7 2 per mil d 82 to 92 per mil potassic alteration characterized by 100 percent alteration of hornblende to biotite and cu mineralization occurs at 3 5 km palcodepth along the axis of the mineralizing granite porphyry dike swarm 18 o 6 5 to 8 4 per mil d 68 to 96 per mil sodic calcic alteration characterized by hydrothermal oligoclase actinolite sphene occurs laterally alongside and below the ore zone at 3 to 6 km palcodepth 18 o 5 7 to 8 4 per mil d 67 to 90 per mil late stage sodic albite chlorite alteration occurs at 1 to 4 km palcodepth in the vicinity of the axial zone 18 o 6 7 to 9 6 per mil d 79 to 85 per mil the youngest late stage sericitic alteration occurs at the shallowest levels primarily at 1 to 2 km palcodepth and displays a distinct 18 o and d enrichment 18 o 9 8 to 10 4 per mil d 61 per mil integration of stable isotope data geologic field relations and phase equilibria constraints indicates that the high salinity fluids responsible for potassic alteration and cu mineralization were of internal magmatic origin but that synchronous deep convecting saline sodic calcic fluids were largely derived from external nonmagmatic sources a third type of fluid also external but lower in temperature and much more dilute was prevalent at shallow levels and caused latestage sericitic alteration this was either an isotopically heavy coastal meteoric water or a seawater

low grade regional metamorphism in the mesozoic cenozoic volcanic sequences of the central andes all the mesozoic and cenozoic volcanic rocks of the central andes from southern ecuador to central chile except recent ones have been affected by episodes of regional metamorphism without change in texture and structure the metamorphism which ranges from low zeolite to greenschist facies can be classified as burial metamorphism because there is an overall increase in metamorphic grade with stratigraphic depth in the individual volcanic sequences separated by regional unconformities some sequences display metamorphic patterns transitional to ocean floor and to geothermal field types reflecting variations along and across the andes in tectonic setting and thermal gradients volcanism was closely followed by metamorphism during each cycle characterizing the geological history of the central andes the episodic nature of the metamorphism has led to breaks in metamorphic grade at regional unconformities and repetition of facies series where strata of higher grade may even overlie those of lower grade the existence of permeability controlled distribution patterns of secondary minerals within individual flows shows that gradients of chemical activity rate of reaction and pfluid were acting in addition to temperature and p tot overall gradients during the regional metamorphism the alteration is accompanied by chemical changes and disturbances of the k ar and rb sr isotope systems similarities between mesozoic facies series in the western and eastern flanks of the andes are consistent with a mechanism of ensialic spreading subsidence

radio occultation measurements of pluto s neutral atmosphere with new horizons abstract on 14 july 2015 new horizons performed a radio occultation ro that sounded pluto s atmosphere down to the surface the sensitivity of the measurements was enhanced by a unique configuration of ground equipment and spacecraft instrumentation signals were transmitted simultaneously by four antennas of the nasa deep space network each radiating 20 kw at a wavelength of 4 2 cm the polarization was right circular for one pair of signals and left circular for the other pair new horizons received the four signals and separated them by polarization for processing by two independent receivers each referenced to a different ultra stable oscillator the two data streams were digitized filtered and stored on the spacecraft for later transmission to earth the results reported here are the first to utilize the complete set of observations we calibrated each signal to remove effects not associated with pluto s atmosphere including the limb diffraction pattern we then applied a specialized method of analysis to retrieve profiles of number density pressure and temperature from the combined phase measurements occultation entry sounded the atmosphere at sunset at 193 5 e 17 0 s on the southeast margin of an ice filled basin known informally as sputnik planitia sp occultation exit occurred at sunrise at 15 7 e 15 1 n near the center of the charon facing hemisphere above 1215 km radius 25 km altitude there is no discernible difference between the measurements at entry and exit and the ro profiles are consistent with results derived from ground based stellar occultation measurements at lower altitudes the ro measurements reveal horizontal variations in atmospheric structure that had not been observed previously and they are the first to reach the ground the entry profile has a strong temperature inversion that ends 3 5 km above the surface and the temperature in the cold boundary layer beneath the inversion is nearly constant 38 9 2 1 k and close to the saturation temperature of n 2 the exit profile has a much weaker inversion that extends all the way to the ground where the air temperature is 51 6 3 8 k three factors appear to be responsible for the presence of a cold boundary layer in the entry profile forget et al 2017 a substantial diurnal cycle of sublimation and condensation of n 2 ice in sp the local time of the ro observation and confinement within sp by the surrounding topography and katabatic winds we have also determined the surface pressure and the local radius at both entry and exit the best pressure reference is the mean value 11 5 0 7 microbar at 1189 9 0 2 km