gravel ripples on the inner scotian shelf abstract sidescan sonar and photo video surveys have revealed the presence of symmetrical gravel bedforms interpreted as wave generated ripples with wavelengths of 1 3 to 3 0 m occurring in patches and narrow ribbons in depths of 15 to 65 m on the inner scotian shelf direct observations and sediment sampling from the pisces iv submersible have been used to ground truth surface based survey dam and to quantify relationships between the bedforms and the processes responsible for their formation the ripples are formed in polymodal sandy gravels with modal sizes ranging from 0 1 to 45 mm evaluation of threshold criteria for coarse sediments together with an 11 year record from a nearby wave rider buoy suggests that existing models for wave entrainment of gravel on rippled surfaces ove estimate the critical velocity by a factor of approximately 2 and that conditions suitable for transport of the coarsest 45 mm size mode sampled in the ripple crests occur on average 43 hr yr analysis of gravel ripples on the inner scotian shelf and of other examples noted in the recent literature extends the range of empirical data for oscillation ripple wavelengths by a factor of 3 and for ripple grain size by a factor of 5 the gravel ripples display a linear scaling to wave orbital diameter similar to that reported for orbital ripples in sand use of such relations for paleoenvironmental interpretation of gravel ripples preserved in the rock record is complicated by the difficulty of selecting appropriate grain size and wave parameters conditions suitable for potential formatio of large scale symmetrical ripples in coarse sediments extend from the outer continental shelf to shallow shore face settings with possible fetch lengths as short as 20 km under intense storms

package fluids 1 computer programs for analysis of fluid inclusion data and for modelling bulk fluid properties the computer package fluids contains five sets of computer programs written in c for the calculation of fluid properties both model fluids and data from fluid inclusions can be analysed in the programs bulk density molar volume and composition of fluid inclusions are calculated with the program bulk which uses microthermometric data micro raman spectroscopic data cation ratios and volume fraction estimations as input the program offers a broad variety of equations of state which are selected according to the fluid system or the temperature and pressure conditions of interest the isochores that correspond to the output or test v x properties of fluid inclusions are calculated by the program isoc in calculating the isochores this program takes account of the compressibility and expansion of selected host minerals the program test allows different equations of state to be compared directly with experimental data thereby facilitating selection of the most adequate model in the programs bulk and isoc loner is a group of programs that handle individual equations of state eos for all fluid systems presented in the programs bulk and isoc aqso is a group of programs that allows purely empirical modelling of electrolyte bearing aqueous solutions henry s law for dilute gas bearing aqueous solutions and osmotic coefficients for dilute electrolyte bearing aqueous solutions the programs are available on the university of leoben web site at http www unileoben ac at buero62 minpet ronald

types geological features and geodynamic significances of gold copper deposits in the kanggurtag metallogenic belt eastern tianshan nw china occupying the middle of the central asia paleozoic accretionary and collisional orogenic belt the eastern tianshan area has a great economic potential due to au cu mineralization during syn and post orogenic events in the kanggurtag au cu metallogenic belt three major types of gold deposits have been recognized ductile shear zone hosted gold deposits magmatic hydrothermal gold deposits and epithermal gold deposits four kinds of copper deposits have also been identified recently the porphyry type the skarn type the magmatic type and volcanic sedimentary type tectonically the development of these late paleozoic gold and copper deposits was closely associated with the subduction and collision of the ancient tianshan ocean that intervened between the tarim craton and the siberian block in the early to mid carboniferous n dipping subduction beneath the dananhu arc generated magmatic intrusions leading to formation of the porphyry cu deposits the magmatic front migrated southward to form the yamansu arc upon the kanggurtag accretionary wedge in the latest carboniferous to early permian during the closure of the ancient tianshan ocean large mafic ultramafic complexes were emplaced resulting in several magmatic copper nickel deposits gold deposits of the shear zone type are controlled by the kanggurtag ductile shear zone which is related to collisional orogenesis the epithermal gold deposits are associated with extensional tectonics and post tectonic volcanic activity the tectonic settings geological features and temporal and spatial distributions of these different types of gold and copper deposits reflect to a great extent the accretionary and collisional tectonics that occurred between the northern margin of the tarim block and the southern margin of the siberian block

context camera investigation on board the mars reconnaissance orbiter 1 the context camera ctx on the mars reconnaissance orbiter mro is a facility instrument i e government furnished equipment operated by a science team not responsible for design and fabrication designed built and operated by malin space science systems and the mro mars color imager team marci ctx will 1 provide context images for data acquired by other mro instruments 2 observe features of interest to nasa s mars exploration program e g candidate landing sites and 3 conduct a scientific investigation led by the marci team of geologic geomorphic and meteorological processes on mars ctx consists of a digital electronics assembly a 350 mm f 3 25 schmidt type telescope of catadioptric optical design with a 5 7 field of view providing a 30 km wide swath from 290 km altitude and a 5000 element ccd with a band pass of 500 700 nm and 7 m pixels giving 6 m pixel spatial resolution from mro s nearly circular nearly polar mapping orbit raw data are transferred to the mro spacecraft flight computer for processing e g data compression before transmission to earth the ground data system and operations are based on 9 years of mars global surveyor mars orbiter camera on orbit experience ctx has been allocated 12 of the total mro data return or about 3 terabits for the nominal mission this data volume would cover 9 of mars at 6 m pixel but overlapping images for stereo mosaics and observation of changes and meteorological events will reduce this area ctx acquired its first instrument checkout images of mars on 24 march 2006

late holocene sea levels in ireland the course of irish sea levels during the late holocene is not well known yet it is an understanding of this period that will prove crucial in the definition and management of future sea level changes the coastline of ireland embraces wide environmental and glacio isostatic contrasts which serve and to some extent control sea level events at both local and regional scales making definitive resolution of relative sea level changes difficult in the southwest the picture is of inexorable relative sea level rise studies in co kerry show a gradual submergence of terrestrial facies by estuarine and in places marine materials pollen and diatom studies together with 14c dates suggest a decreasing rate of relative sea level rise in the last 2500 years often associated with geomorphological changes sites on the south coast of ireland confirm the evidence from the southwest in cork harbour recent relative sea level rise since 2100 bp was responsible for marginal land submergence while elsewhere rising water levels appear to have caused rapid barrier migrations and coast erosion palaeoenvironmental evidence from this region suggests a distinctive pattern of sea level change associated with sedimentary and or crustal dynamics which is not encountered elsewhere in northwest europe the overall rate of relative sea level change on the south and southwest coasts falls between 0 6 and 1 1 mm year over the last 5000 years in the north there is a clear east to west variation in relative sea level trends following an isostatically controlled peak 3 to 1 m od between 6500 bp east and 3500 bp west falling sea levels from 3500 to 1500 bp have been followed by a general slow rise although there are still local anomalies to this pattern most noticeably at malin head where sea level is currently falling at 2 4mm year relative sea level signatures in ireland differ markedly between the north and south coasts furthermore geomorphological and ecological contexts of this rise vary from east to west providing a complex all ireland framework for future investigations

mineralogy of the sulphide deposits at sulitjelma northern norway abstract the pyritic vms deposits at sulitjelma northern norway have been regionally metamorphosed at amphibolite facies during the caledonide orogen the deposits contain a wide diversity of sulphide sulphosalt and related minerals which are systematically discussed with reference to their occurrence paragenesis and mineral chemistry most of these minerals are however rare to absent within the massive deposits which are dominantly composed of pyrite with subordinate chalcopyrite sphalerite and pyrrhotite galena arsenopyrite cubanite molybdenite stannite and tetrahedrite occur in minor amounts syn metamorphic mobilisation has however resulted in the redistribution of a range of elements including cu pb sb as ni and au these elements have been reconcentrated into mobilised segregations where they have crystallised under retrograde conditions into a range of discrete phases ore mobilisation which took place along tectonically controlled pathways is however of a highly localised nature with a considerable range in mineral textures and parageneses observed in different samples typical associations within these mobilisates include a range of cu pb sb and cu pb as sulphosalts including bournonite meneghinite seligmannite and jordanite breithauptite nisbite costibite arsenopyrite and gudmundite co existing galena is characterised by elevated concentrations of ag bi and se argentian tetrahedrite 9 17 wt ag the chief ag carrier in the deposits as well as other ag bearing phases including pyrargyrite hessite and empressite are strongly enriched in the mobilisates gold as electrum 50 75 wt au and more rarely as aurostibite is also relatively enriched in the mobilisate samples over those from more massive parts of the deposits a further range of minerals including native antimony native arsenic allargentum dyscrasite argentite mckinstryite jalpaite and native silver occur as low temperature breakdown products of earlier formed minerals preserved textures do not contradict a model involving more than a one phase of mobilisation during the metamorphic evolution

thermal behavior of metal nanoparticles in geologic materials although significant progress has been made in understanding the behavior of natural nanoparticles in earth s critical zone i e surface and near surface environment little is known about nanoparticle stability in higher temperature environments where they are increasingly being found here we report the first direct observations of the thermal behavior of natural nanoparticles at near atomic scale revealing that their thermal stability is dependent on particle size and on the surrounding host mineral native au nanoparticles mean diameter 4 nm incorporated in arsenian pyrite from refractory au ores were observed under the transmission electron microscope during in situ heating to 650 c while isolated au nanoparticles melt with the melting point being a function of size we show that when incorporated in arsenian pyrite au nanoparticles become unstable unless the nanoparticle size distribution coarsens by diffusion driven solid state ostwald ripening this change in nanoparticle stability starts above 370 c setting an upper temperature and size limit for the occurrence of nanoparticulate au in refractory sulfides these findings not only provide new insights into the behavior of nanoparticulate au and other metals during geological processes and throughout their metallurgical recovery from refractory ores but also provide a new tool to define the thermal history of nanoparticle bearing geologic and planetary materials

lithospheric flexure and gravity spreading of olympus mons volcano mars the structural architecture of large volcanoes is governed substantially by gravity driven deformation that is manifest as distinct processes such as basement flexure or volcanic spreading temporal effects and the mutual interplay of these processes have been investigated only to a limited extent and so we present novel numerical models of the time dependent deformation associated with them the models simulate the combined effects of lithospheric flexure and volcanic spreading during growth increments of an elastoplastic volcanic cone different spreading scenarios are considered by a variable coupling decoupling behavior at the interface between volcano and basement we apply our models to olympus mons on mars which is characterized by upper to middle flank terraces on the shield is encircled by a basal scarp that has an average slope of 30 and is surrounded by distant deposits that resemble large scale slumping features on earth our results are consistent with the interpretation that terraces on olympus mons flanks form by thrust faulting that results from lithospheric flexure the presence and expression of terraces depend on the coupling of volcano and basement on the time of volcano growth relative to mantle relaxation and on the cohesion of the edifice the encircling scarp may be related to a very low friction detachment at the edifice base which leads to a normal fault regime on the lowermost flanks with time and volcano growth predicted stress and faulting regimes migrate only slightly indicating that the structural architecture of volcanoes is largely set in the very early stages of formation

epithermal deposits in north xinjiang nw china the north xinjiang region nw china is an important part of the central asia orogenic belt situated at the junction of siberia tarim and kazakhstan plates it is an area characterized by multiple stages of phanerozoic continental growth during which several porphyry and epithermal systems were formed the relationship of these mineral systems to the geodynamic evolution of the region has not yet been well understood in this paper we list the main geological characteristics of 21 significant epithermal precious and base metal deposits in north xinjiang and classify them into high sulfidation and low sulfidation styles with the latter being predominant we have selected seven epithermal deposits representing different styles formed under different tectonic regimes and discuss their geology and geochemistry in some detail the deposit scale geology and geochemistry of epithermal systems in north xinjiang are essentially similar to those in other parts of the world all epithermal deposits in north xinjiang are hosted in volcanic rocks with ages ranging from devonian to triassic with the early carboniferous volcanic sequences being the most important followed by the permian and triassic the devonian early carboniferous host rocks belong to the calc alkaline series that developed in pre collisional arc back arc basin systems whereas the permian triassic host volcanic rocks of shoshonite series formed in post subduction regimes available isotopic ages of these epithermal systems cluster in two periods early carboniferous 320 ma and late carboniferous triassic 320 220 ma reflecting two metallogenic episodes that occurred during subduction related accretion and post subduction collision regimes respectively accordingly three groups of epithermal deposits in north xinjiang can be recognized as 1 pre collisional deposits without or with negligible collisional related modification 2 deposits formed in collision regime and 3 ore systems strongly overprinted by fluid flow in post subduction collision regime

topographic control of oceanic flows in deep passages and straits saddle points between neighboring deep ocean basins are the sites of unidirectional flow from one basin to the next depending on the source of bottom water flow in these sites appears to be topographically controlled so the interface between the bottom water and the water above adjusts itself to permit bottom water flow from the basin that contains a source of bottom water into the next examples in the atlantic include flow in the romanche fracture zone the vema channel the ceara abyssal plain the anegada jungfern passage and the discovery gap but there are many more theoretical predictions of volume flux using a method that requires only conductivity temperature depth data archives and detailed knowledge of bathymetry near the saddle point are compared with volume flux estimates using current meters and or geostrophic estimates for seven cases the ratio of prediction to volume flux estimate ranges from 1 0 to 2 7 some ocean straits that separate adjacent seas are also found to critically control bidirectional flows between basins theory of the influence of rotation on such critical flows is reviewed predictions of volume flux in eight cases are compared with ocean estimates of volume flux from traditional methods

state of stress faulting and eruption characteristics of large volcanoes on mars the formation of a large volcano loads the underlying lithospheric plate and can lead to lithospheric flexure and faulting in turn lithospheric deformation affects the stress field beneath and within the volcanic edifice and can influence magma transport modeling the interaction of these processes is crucial to an understanding of the history of eruption characteristics and tectonic deformation of large volcanoes we develop models of time dependent stress and deformation for the tharsis volcanoes on mars by means of a finite element code we calculate stresses and displacements due to a volcano shaped load emplaced on an elastic plate overlying a viscoelastic mantle models variously incorporate growth of the volcanic load with time and a detachment between volcano and lithosphere the models illustrate the manner in which time dependent stresses induced by lithospheric plate flexure beneath the volcanic load may affect eruption histories and the derived stress fields can be related to tectonic features on and surrounding martian volcanoes as a result of flexure there are three regions where stresses become sufficiently large to cause failure by faulting according to the mohr coulomb criterion at the surface of the plate just outward of the volcano near the base of the elastic lithosphere beneath the center of the volcano and on the upper flanks of the volcano early in its growth history normal faulting is the dominant mode of failure predicted for the first region consistent with circumferential graben observed around the tharsis montes and with the scarp at the base of olympus mons interpreted as a large offset listric normal fault normal faulting mostly radially oriented is predicted for the second region failure in the third region is predicted to consist of thrust faulting circumferentially oriented on the upper and middle flanks and radially oriented on the lower flanks in models simulating a growing volcano this portion of the edifice is subsequently covered by later units which exhibit lower stresses and are not predicted to fail this volume of early failure remains the most highly stressed area in the edifice concentric terraces interpreted by some workers as thrust faults on the upper flanks of olympus mons may correspond to the predicted circumferential thrust features if the most recent increments of volcano growth were relatively large or in the presence of local material property or stress field variations for volcanoes detached from the plate predicted failure in the edifice takes the form of radial normal faulting near the volcano base the addition of a local extensional stress arising from the regional topographic slope yields a pattern of predicted faulting which closely matches that observed on the tharsis montes including the development of radial rifts on the lower volcano flanks to the northeast and southwest and the asymmetric formation of circumferential flank graben this stress state is also consistent with an interpretation of the aureole deposits of olympus mons as the result of gravity sliding along a basal detachment our models also suggest an explanation for the lack of strike slip features predicted by previously published flexural models around the tharsis volcanoes for a given load increment the first mode of near surface failure for most of the area immediately outward of the load is circumferential normal faulting and graben formation as the volcano grows and the flexural response to the increasing load proceeds the predicted failure mode in a portion of this annular region surrounding the volcano changes to strike slip faulting because normal faulting has been predicted to have taken place earlier however it is likely that release of later stresses will occur by reactivation and growth of these normal faults and graben rather than by the formation of new strike slip faults

modelling a cohesive frictional debris flow an experimental theoretical and field based study the rheology of debris flows is difficult to characterize owing to the varied composition and to the uneven distribution of the components that may range from clay to large boulders in addition to water few studies have addressed debris flow rheology from observational experimental and theoretical viewpoints in conjunction we present a coupled rheological numerical model to characterize the debris flows in which cohesive and frictional materials are both present as a first step we consider small scale artificial debris flows in a flume with variable percentages of clay versus sand and measure separately the rheological properties of sand clay mixtures a comparison with the predictions of a modified version of the numerical model bing shows a reasonable agreement between measurements and simulations as application to a field case we analyse a recent debris flow that occurred in fjaerland western norway for which much information is now available the event was caused by a glacial lake outburst flood glof originating from the failure of a moraine ridge in a previous contribution breien et al landslides 2008 5 271 280 we focused on the hydrological and geomorphological aspects in particular we documented the marked erosion and reported the change in sediment transport during the event in contrast to the laboratory debris flows the presence of large boulders and the higher normal pressure inside the natural debris flow requires the introduction of a novel rheological model that distinguishes between mud to clast supported material we present simulations with a modified bing model with the new cohesive frictional rheology to account for the severe erosion operated by the debris flow on the colluvial deposits of fjaerland we also suggest a simple model for erosion and bulking along the slope path numerical simulations suggest that a self sustaining mechanism could partly explain the extreme growth of debris flows running on a soft terrain

overwash occurrence consequent on morphodynamic changes following lagoon outlet closure on a coarse clastic barrier the reduction in sediment volume of an ebb tide delta as a consequence of lagoon outlet closure on a coarse clastic barrier in southeast ireland initiated a sequence of beachface and barrier changes downdrift elimination of sediment supply to the ebb delta caused a cessation of downdrift longshore swash bar welding and led to beach volume reductions which in turn allowed a temporal sequence of beach and nearshore morphodynamic domains to develop these domains then controlled the sedimentation regime of the barrier adjacent to the old outlet a temporal sequence of a dissipative barrier b reflective barrier and c inner reflective barrier face outer dissipative subtidal wave regimes match respectively periods of a barrier crest build up by crestal dune development b barrier crest instability barrier width increasing barrier height decreasing due to rhythmic overwash and c a return to barrier crest stability with limited aeolian accretion two barriers at different stages in this sequence are discussed

isotope and fluid inclusion geochemistry and genesis of the qiangma gold deposit xiaoqinling gold field qinling orogen china abstract the qiangma gold deposit is hosted in the 1 9 ga taihua supergroup metamorphic rocks in the xiaoqinling terrane qinling orogen on the southern margin of the north china craton the mineralization can be divided as follows quartz pyrite veins early quartz polymetallic sulfide veinlets middle and carbonate quartz veinlets late stages with gold being mainly introduced in the middle stage three types of fluid inclusions were identified based on petrography and laser raman spectroscopy i e pure carbonic carbonic aqueous co 2 h 2 o and aqueous inclusions the early stage quartz contains pure carbonic and co 2 h 2 o inclusions with salinities up to 12 7 wt nacl equiv bulk densities of 0 67 to 0 86 g cm 3 and homogenization temperatures of 280 365 c the early stage is related to h 2 o co 2 n 2 ch 4 fluids with isotopic signatures consistent with a metamorphic origin 18 o water 3 1 to 5 2 d 37 to 73 the middle stage quartz contains all three types of fluid inclusions of which the co 2 h 2 o and aqueous inclusions yield homogenization temperatures of 249 346 c and 230 345 c respectively the co 2 h 2 o inclusions have salinities up to 10 9 wt nacl equiv and bulk densities of 0 70 to 0 98 g cm 3 with vapor bubbles composed of co 2 and n 2 the isotopic ratios 18 o water 2 2 to 3 6 d 47 to 79 suggest that the middle stage fluids were mixed by metamorphic and meteoric fluids in the late stage quartz only the aqueous inclusions are observed which have low salinities 0 9 9 9 wt nacl equiv and low homogenization temperatures 145 223 c the isotopic composition 18 o water 1 9 to 0 5 d 55 to 66 indicates the late stage fluids were mainly meteoric water trapping pressures estimated from co 2 h 2 o inclusions are 100 285 mpa for the middle stage suggesting that gold mineralization mainly occurred at depths of 10 km fluid boiling and mixing caused rapid precipitation of sulfides and native au through boiling and inflow of meteoric water the ore forming fluid system evolved from co 2 rich to co 2 poor in composition and from metamorphic to meteoric as indicated by decreasing 18 o water values from early to late the carbon sulfur and lead isotope compositions suggest the hostrocks within the taihua supergroup to be a significant source of ore metals integrating the data obtained from the studies including regional geology ore geology and fluid inclusion and c h o s pb isotope geochemistry we conclude that the qiangma gold deposit was an orogenic type system formed in the tectonic transition from compression to extension during the jurassic early cretaceous continental collision between the north china and yangtze cratons

large scale landslide simulations global deformation velocities and basal friction the cause of the apparent small friction exhibited by long runout landslides has long been speculated upon in an attempt to provide some insight into the matter this paper describes results obtained from a discrete particle computer simulation of landslides composed of up to 1 000 000 two dimensional discs while simplified the results show many of the characteristics of field data the volumetric effect on runout preserved strata etc and with allowances made for the two dimensional nature of the simulation the runouts compare well with those of actual landslides the results challenge the current view that landslides travel as a nearly solid block riding atop a low friction basal layer instead they show that the mass is completely shearing and indicate that the apparent friction coefficient is an increasing function of shear rate the volumetric effect can then be understood with all other conditions being equal different size slides appear to travel with nearly the same average velocity however as the larger landslides are thicker they experience smaller shear rates and correspondingly smaller fractional resistance

the coupled geochemistry of au and as in pyrite from hydrothermal ore deposits the ubiquity of au bearing arsenian pyrite in hydrothermal ore deposits suggests that the coupled geochemical behaviour of au and as in this sulfide occurs under a wide range of physico chemical conditions despite significant advances in the last 20years fundamental factors controlling au and as ratios in pyrite from ore deposits remain poorly known here we explore these constraints using new and previously published empa la icp ms sims and pixe analyses of as and au in pyrite from carlin type au epithermal au porphyry cu cu au and orogenic au deposits volcanogenic massive sulfide vhms witwatersrand au iron oxide copper gold iocg and coal deposits pyrite included in the data compilation formed under temperatures from 30 to 600 c and in a wide variety of geological environments the pyrite au as data form a wedge shaped zone in compositional space and the fact that most data points plot below the solid solubility limit defined by reich et al 2005 indicate that au1 is the dominant form of au in arsenian pyrite and that au bearing ore fluids that deposit this sulfide are mostly undersaturated with respect to native au the analytical data also show that the solid solubility limit of au in arsenian pyrite defined by an au as ratio of 0 02 is independent of the geochemical environment of pyrite formation and rather depends on the crystal chemical properties of pyrite and post depositional alteration compilation of au as concentrations and formation temperatures for pyrite indicates that au and as solubility in pyrite is retrograde au and as contents decrease as a function of increasing temperature from 200 to 500 c based on these results two major au as trends for au bearing arsenian pyrite from ore deposits are defined one trend is formed by pyrites from carlin type and orogenic au deposits where compositions are largely controlled by fluid rock interactions and or can be highly perturbed by changes in temperature and alteration by hydrothermal fluids the second trend consists of pyrites from porphyry cu and epithermal au deposits which are characterised by compositions that preserve the au as signature of mineralizing magmatic hydrothermal fluids confirming the role of this sulfide in controlling metal ratios in ore systems

lituya bay landslide impact generated mega tsunami 50th anniversary on july 10 1958 an earthquake mw 8 3 along the fairweather fault triggered a major subaerial landslide into gilbert inlet at the head of lituya bay on the southern coast of alaska the landslide impacted the water at high speed generating a giant tsunami and the highest wave runup in recorded history the mega tsunami runup to an elevation of 524 m caused total forest destruction and erosion down to bedrock on a spur ridge in direct prolongation of the slide axis a cross section of gilbert inlet was rebuilt at 1 675 scale in a two dimensional physical laboratory model based on the generalized froude similarity a pneumatic landslide tsunami generator was used to generate a high speed granular slide with controlled impact characteristics state of the art laser measurement techniques such as particle image velocimetry piv and laser distance sensors lds were applied to the decisive initial phase with landslide impact and wave generation as well as the runup on the headland piv provided instantaneous velocity vector fields in a large area of interest and gave insight into kinematics of wave generation and runup the entire process of a high speed granular landslide impact may be subdivided into two main stages a landslide impact and penetration with flow separation cavity formation and wave generation and b air cavity collapse with landslide run out and debris detrainment causing massive phase mixing formation of a large air cavity similar to an asteroid impact in the back of the landslide is highlighted a three dimenional pneumatic landslide tsunami generator was designed constructed and successfully deployed in the tsunami wave basin at osu the lituya bay landslide was reproduced in a three dimensional physical model at 1 400 scale the landslide surface velocities distribution was measured with piv the measured tsunami amplitude and runup heights serve as benchmark for analytical and numerical models

the global topography of mars and implications for surface evolution elevations measured by the mars orbiter laser altimeter have yielded a high accuracy global map of the topography of mars dominant features include the low northern hemisphere the tharsis province and the hellas impact basin the northern hemisphere depression is primarily a long wavelength effect that has been shaped by an internal mechanism the topography of tharsis consists of two broad rises material excavated from hellas contributes to the high elevation of the southern hemisphere and to the scarp along the hemispheric boundary the present topography has three major drainage centers with the northern lowlands being the largest the two polar cap volumes yield an upper limit of the present surface water inventory of 3 2 to 4 7 million cubic kilometers

deltaic deposits at aeolis dorsa sedimentary evidence for a standing body of water on the northern plains of mars a fundamental long standing question regarding mars history is whether the flat and low lying northern plains ever hosted an ocean the best opportunity to solve this problem is provided by stratigraphic observations of sedimentary deposits onlapping the crustal dichotomy here we use high resolution imagery and topography to analyze a branching network of inverted channel and channel lobe deposits in the aeolis dorsa region just north of the dichotomy boundary observations of stacked cross cutting channel bodies and stratal geometries indicate that these landforms represent exhumed distributary channel deposits observations of depositional trunk feeder channel bodies a lack of evidence for past topographic confinement channel avulsions at similar elevations and the presence of a strong break in dip slope between topset and foreset beds suggest that this distributary system was most likely a delta rather than an alluvial fan or submarine fan sediment transport calculations using both measured and derived channel geometries indicate a minimum delta deposition time on the order of 400 years the location of this delta within a thick and widespread clastic wedge abutting the crustal dichotomy boundary unconfined by any observable craters suggests a standing body of water potentially 105 km2 in extent or greater and is spatially consistent with hypotheses for a northern ocean

further evidence for a mass movement origin of the olympus mons aureole analysis of the ridge graben and fracture patterns on the aureole material surrounding olympus mons lends further support to an origin by gravity sliding of the outer flanks of the shield the patterns provide evidence of the nature of sliding especially in the last stages of emplacement no part of the slide need have traveled the whole extent of the aureole for the slides to occur on a shallow slope reduction of shear strength of the materials involved is required possibly by melting of ground ice triggering mechanisms could be volcanically related marsquakes and possibly stresses induced on the surrounding area by the growing olympus mons volcano

textural control on gold distribution in as free pyrite from the dongping huangtuliang and hougou gold deposits north china craton hebei province china article i nfo pyrite from the dongping huangtuliang and hougou gold deposits hebei province china was investigated using a combination of ore microscopy including back scattered imaging and in situ laser ablation inductively coupled plasma mass spectroscopy la icp ms a range of elements including au te ag pb bi cu co ni and as was analyzed with the aim to constrain the textural controls and influence of superimposed deformation on the distribution of invisible gold in as free pyrite thedatasetshowsexcellentcorrespondence betweenmeasuredhighgoldvaluesandthreekeytexturalcriteria i areasofclusteredtellurideinclusions especiallyindongping ii microshearingandfracturing brecciation dongping and huangtuliang and iii pyrite recrystallization huangtuliang invisible gold is only at trace levels in the hougou and gold bearing telluride minerals are not observed this is considered to result from larger scale remobilization of gold during advanced brecciation and recrystallization of pyrite pyrite grains containing clustered inclusions have by far the highest gold concentrations up to 1 wt with consistent values of thousands of ppm au interpretation of textures and la icp ms data infers that in these areas the distribution of telluride inclusions extends pervasively from micron to nanoscale i e as fields of nanoparticles local employment of coupled dissolution reprecipitation reaction between pyrite and fluids driving the k metasomatic alteration dated at 150 ma is invoked to explain such patterns syn deformational grain scale mobilization of gold and other elements took place leading to a portion of the gold being recrystallized within fractures and microshears the deformational event leads to gold enrichment in the huangtuliang pyrite where brittle fracturing brecciation has been followed by a resorption and recrystallization in the latter case foam textured pyrites again without as can contain up to hundreds of ppm gold theinterpreted sequenceof pyritepost depositional eventsis inaccordancewith the protracted magmaticevolution of the area starting with variscan alkaline intrusions 390 ma and reactivated during the yanshanian orogeny 150 ma thestudyshows i thatas freepyritecanreadilycontainsignificantamountsofinvisiblegold bothasnanoparticles

genesis of the hydrothermal gold deposits in the canan area lepaguare district honduras the canan area honduras is characterized by a gold bearing ore deposit that is associated with quartz veined shear zones gold mineralization occurs in low to medium grade metamorphic host rocks graphitic and sericitic schists hydrothermal fluids which are associated with the emplacement of cretaceous tertiary granodioritic intrusions are responsible for the formation of quartz veins and the hydrothermal alteration of wall rocks three main altered zones have been detected in the wall rocks as far as 150 cm from the quartz veins the distal zone up to 50 cm thick contains quartz chlorite and illite the intermediate zone is the thickest up to 80 cm and is marked by quartz muscovite sulphides kaolinite and native elements such as au and ag the proximal zone which is close to the quartz veins is rather thin up to 25 cm and contains clay minerals al oxides hydroxides and sulphides the transition from the distal to the proximal zone is accompanied by the enrichment of sio2 and the depletion of all other major elements except for fe2o3 tot precious metals occur in the highest concentrations in the intermediate zone au up to 7 6 ppm and ag up to 11 ppm we suggest that gold was transported as a reduced sulphur complex and was precipitated from the hydrothermal solution by the reaction of the sulphur complexes with fe2 from the alteration of the mafic minerals of the host rock fluid wall rock interactions seem to be the main cause of gold mineralization genetic relationships with a strike slip fault system hydrothermal alteration zones within the metamorphic wall rocks and an entire set of geochemical anomalies are consistent with orogenic type gold deposits of the epizonal class

gold and silver metallogeny of the south china fold belt a consequence of multiple mineralizing events abstract the south china fold belt is part of the south china block that is interpreted to be the result of multiple tectonic and magmatic events that formed a collage of accreted proterozoic and phanerozoic terranes the jurassic to early cretaceous yanshanian period 180 90 ma a time of major tectono thermal events that affected much of eastern and southeastern china is of great metallogenic importance in the fold belt this period is linked to subduction of the pacific plate beneath the eurasian continent and is manifested by voluminous volcano plutonic activity of predominantly calc alkaline affinity the distribution of gold and silver deposits in the south china fold belt indicates the presence of two distinct metallogenic provinces a region of basement uplifts which are controlled by shear zones and form neoproterozoic inliers of metamorphosed iron rich rock types defines the first province in this province orogenic lodes and volcanic related epithermal deposits represent the more significant precious metal mineralization the second province is essentially confined to a belt of yanshanian felsic intermediate volcanic and subvolcanic rocks that extends along most of the southeastern china coast in an area known as the coastal volcanic belt deposits in the coastal volcanic belt are silver and or copper rich volcanic hosted and epithermal in character the precious metal metallogeny of the south china fold belt is interpreted to have developed in at least three stages one as a result of collision events during the caledonian orogeny ca 400 ma the second during the indosinian orogeny ca 200 ma and the third during or soon after the formation of the yanshanian magmatic belt yanshanian orogeny 180 90 ma the latter was responsible for a hydrothermal event that affected large sections of the belt and its proterozoic substrate this may have resulted in the redistribution and enrichment of precious metals from preexisting orogenic gold lodes in neoproterozoic basement rocks which are now exposed as windows in zones of tectonic uplift the yanshanian hydrothermal activity was particularly widespread in the coastal volcanic belt and resulted in the formation of both low and high sulfidation epithermal gold and silver and locally copper and other base metal mineralization it is suggested that the coastal volcanic belt has greater potential for world class epithermal and porphyry deposits than previously realised

distribution and petrogenetic behaviour of trace elements in granitic pegmatite quartz from south norway the present study documents that the trace element distribution in granitic quartz is highly sensitive to cafc processes in granitic melts igneous quartz efficiently records both the origin and the evolution of the granitic pegmatites aluminium p li ti ge and na in that order of abundance comprises 95 of the trace elements most samples feature 1 ppm of any of these elements the remnant 5 includes k fe be b ba and sr whereas the other elements are present at concentrations lower than the detection limit potassium fe be and ti are relatively compatible hence obtain the highest concentrations in early formed quartz phosphorous ge li and al are relatively incompatible and generally obtain the highest concentrations in quartz that formed at lower temperatures from more evolved granitic melts the ge ti the ge be the p ge and the p be ratios of quartz are strongly sensitive to the origin and evolution of the granitic melts and similarly the rb sr and the rb k ratios of k feldspars may be utilised in petrogenetic interpretations however the quartz trace element ratios are better at distinguishing similarities and differences in the origin and evolution of granitic melts after evaluating the different trace element ratios the ge ti ratio appears to be most robust during subsolidus processes in the igneous systems hence probably should be the preferred ratio for analysing and understanding petrogenetic processes in granitic igneous rocks

stability of rock slopes in valles marineris mars 1 new slope measurements from the mars orbiter laser altimeter mola in conjunction with the rock mass rating system rmr permit inversions of slope height and angle from wallrock and interior deposits within valles marineris troughs for strength and lithology wallrock 50 rmr 65 is stronger than interior deposits 30 rmr 55 these values are consistent with layered igneous rock beneath wallrock slopes with interior deposits consistent with partially indurated sedimentary or volcaniclastic rocks larger volumes of landslide debris relative to terrestrial slides are related to the reduced martian gravity seismicity along trough bounding normal faults likely triggered the landslides in the adjacent wallrock the weaker interior deposits are located sufficiently far from a border fault and on its hangingwall to have remained stable during the seismogenic faulting in valles marineris

fault propagation folds induced by gravitational failure and slumping of the central costa rica volcanic range implications for large terrestrial and martian volcanic edifices long sublinear ridges and related scarps located at the base of large volcanic structures are frequently interpreted as normal faults associated with extensional regional stress in contrast the ridges bordering the central costa rica volcanic range ccrvr are the topographic expression of hanging wall asymmetric angular anticlines overlying low angle thrust faults at the base of the range these faults formed by gravitational failure and slumping of the flanks of the range due to the weight of the volcanic edifices and were perhaps triggered by the intrusion of magma over the past 20 000 years the thrust fault underlying alajuela ridge rises from a depth of 700 m at a dip of 15 over a distance of a few kilometers it ramps up at 600 m depth on a 40 slope and terminates in the axis of the forward syncline 400 m below the surface the hanging wall of this fault has been thrusted about 200 m away from the volcanic range axis thrusting on the lower flanks of the ccrvr is compensated by extension on the range axis with formation of summit grabens shallow seismicity in the volcanic range suggests that thrusting is still active we postulate that at kilauea volcano hawaii the gravity and magma induced slumping of the southern flank on low angle thrust faults generates hanging wall anticlines similar to those observed in costa rica these anticlines are hypothesized to occur along the base of the volcano where the thrust faults ramp up toward the sea bottom ridges and scarps between 2000 and 5000 m below sea level are interpreted as the topographic expression of these folds we further suggest that the scarps of the ccrvr and kilauea are valid scaled terrestrial analogs of the perimeter scarp of the martian volcano olympus mons we suggest that the crust below olympus mons has failed under the load of the volcano triggering the radial slumping of the flanks of the volcano on basal thrusts the thrusting would have in turn formed the anticlinal ridges and scarps that surround the edifice the thrusting seems to be preferential toward the northwest and southeast and a northeast southwest rift zone seems to have developed perpendicular to the regional topographic gradient the thrust faults may extend all the way to the base of the martian crust about 40 km and they may have been active until almost the end of the volcanic activity we suggest that gravitational failure and slumping of the flanks of volcanoes is a process common to most large volcanic edifices in the ccrvr and at kilauea this slumping of the flanks is a slow intermittent process but it could evolve to rapid massive avalanching leading to catastrophic eruptions thus monitoring of uplift and displacement of the folds related to the slump tectonics could become an additional effective method for mitigating volcanic hazards

hydrothermal transport and depositional processes in archean lode gold systems a review abstract compelling evidence now exists for the formation of archean lode gold deposits over a substantial range in metamorphic conditions and crustal depth the commonality of ore fluid isotopic and geochemical characteristics the extreme fluid rock ratios within actual ore zones and the observed depth continuity within individual orebodies all suggest that these deposits formed within vertically extensive crustal scale hydrothermal systems calculations based on new thermodynamic data and estimated ore fluid conditions suggest that gold would have been transported as au hs 2 over most of this range gold transport in the ore fluids that formed some diopside and diopside k feldspar class deposits t 550 c would have been as aucl2 whereas the au hs complex may have been significant in some of the lower temperature 270 c less alkaline ore fluids the high solubility of gold in lode gold ore fluids at amphibolite facies conditions 10 s to 1000 s ppb suggests that fluids may have been undersaturated in gold within their source regions promoting the ore fluid s capacity to retain gold in solution over the large transport distances involved ore depositional mechanisms were also likely to vary between crustal levels fluid rock interactions and wallrock sulphidation in particular appear to be the most important type of precipitation mechanism however with decreasing depth of formation the scope of other depositional mechanisms notably phase separation and fluid mixing becomes greater

a drowned holocene barrier spit off cape ann massachusetts seismic profiles and bathymetric contours reveal a drowned barrier spit on jeffreys ledge off cape ann massachusetts seaward dipping internal reflectors indicate that a regressive barrier formed during the early holocene low sea level stillstand preservation of the barrier spit may have been favored by its large size as much as 20 m thick by an ample sediment supply from unconsolidated glacial drift and by the subsequent rapid sea level rise the barrier spit is present in water depths of 50 to 70 m and indicates a low relative sea level stand of 50 m this value confirms the low relative sea level stand of 47 m postulated by oldale et al 1983 for northeast massachusetts and new hampshire on the basis of the submerged delta of the merrimack river and it indicates that the barrier and delta were contemporaneous oldale et al 1983

possible ancient oceans on mars evidence from mars orbiter laser altimeter data high resolution altimetric data define the detailed topography of the northern lowlands of mars and a range of data is consistent with the hypothesis that a lowland encircling geologic contact represents the ancient shoreline of a large standing body of water present in middle mars history the contact altitude is close to an equipotential line the topography is smoother at all scales below the contact than above it the volume enclosed by this contact is within the range of estimates of available water on mars and a series of extensive terraces parallel the contact in many places

formation of olympus mons and the aureole escarpment problem on mars based on morphologic interpretation of viking orbiter images it is postulated that on the summit area of arsia mons mars there is a several kilometer thick ice cover in addition numerous linear striae on the flanks of arsia mons resemble terrestrial washboard moraines behind which there may be substantial dead ice deposits this implies that glacier phenomena are active in the tharsis region these features may have bearing on the formation of the aureole deposits of olympus mons olympus mons has been the cause of dispute among geologists for years and several contrasting models have been proposed to explain the up to 10 km high distal escarpment and broad lobate aureole deposits below one model by hodges and moore 1979 assumed 2 3 km thick ice under which volcanism proceeded at an early stage to build olympus mons thereby leading to the growth of the high cliff section it has been argued that the origin of the aureole has not been satisfactorily explained modifications of the hodges and moore hypothesis are proposed to explain some aspects of both the aureole formation and the escarpment at the lava aureole boundary the assumption is made that volcanism that persisted was mostly localized on the olympus mons massif throughout the aureole development and that a blanket of ice and wind blown dust covered the lower flanks of the volcano deposition of volcanic products on the flank blanket led to faulting and sliding of material away from the summit area thereby creating the aureole deposits and scarp further eruptions of lavas in the summit area substantially elevated the cliff segment and additions of lavas off the cliffs into the wing area led to further creeping of the lower flank region thus generating the vast aureoles therefore the aureole formation succeeded and resulted from olympus mons volcanic activity and is one of the youngest features of olympus mons and not older as has been postulated

mechanisms to account for the longshore spacing of overwash throats on a coarse clastic barrier in southeast ireland abstract the longshore spacing of overwash throats on two contrasting sections of a coarse clastic reflective barrier beach in southeast ireland is examined for evidence of spatial periodicity a fixed barrier section carnsore with an irregular barrier top dune field exhibits random longshore throat positions related to pre existing irregularities in the seaward dune boundary a free barrier section tacumshin without a barrier top dune field shows regular longshore throat positions with a peak throat to throat periodicity of between 30 40 m similar longshore periodicity is found in persistent high level beach cusps above mhws though not always spatially in phase there is no consistent near shore rhythmic morphology that can account for this spacing the storm event which generated the tacumshin overwash appears to have dominant longer incident wave periods than normal in celtic sea storms on weight of circumstantial evidence it is reasoned that this dominant wave period range 9 11 s can be related to a zero mode sub harmonic edge wave whose longshore wavelength matches the peak periodicity of overwash spacing overwash sites on this reflective barrier may be determined by an edge wave controlled extension of run up which generates high level cusps and thereby creates washover routeways the presence or absence of a barrier top dune field is a secondary control on whether washover is successful in reaching the back barrier usually only where surge penetration and pre existing dune irregularities coincide does washover occur

the pristine shape of olympus mons on mars and the subaqueous origin of its aureole deposits abstract the tallest volcano in the solar system olympus mons on mars is bordered by at least ten enormous sub circular hummocky deposits forming a welded halo termed the aureole the aureole units or simply aureoles which are the deposits of landslides from olympus mons have dramatically transformed the pristine size and shape of the volcanic edifice topographic data are used to determine the amount of collapsed material and so reconstruct the original outline of olympus mons before the landslides took place under the assumption that the edifice did not start failing until it had reached this maximum size due to post aureole deposition on the eastern and southern flanks and to the uncertainty of the slippage level on the northern side the reconstruction is sufficiently precise along the western and north western olympus mons flank it is more uncertain for the northern flank while it is not feasible around the rest of the volcano it appears that the radius along the western and north western olympus mons before the collapse of the aureole landslides was approximately 200 km longer or more the results show that the volume of the aureoles even if enormous is insufficient to fill the ideal conical edifice which would be obtained prolonging the olympus mons flanks with present slope angles thus an overhang remains in the pre aureole reconstructed olympus mons which would also explain the onset of instability that led to the aureole collapse further a drape deposit blanketing the southern acheron fossae ridge just at the front of the western w aureole landslide deposit and a fan channel system carved on the same w aureole are investigated and it is suggested that these morphologies have been emplaced in subaqueous setting while the drape may indicate a landslide thrust water splash akin to a tsunami deposit caused by the fast travelling w aureole landslide the fan channel system is similar to certain morphologies in the terrestrial oceans a numerical model of the collapse of the western aureole unit in water shows final runouts on both acheron ridge and amazonis planitia compatible with observations provided that the friction angle is extremely small of the order of a tenth of degree simulations indicate that the w aureole could have reached acheron fossae ridge with velocities in excess of 100 m s which would explain the several tens of km long distance reached by the landslide thrust tsunami deposit in short morphological and numerical lines of evidence would indicate a subaqueous origin for the largest w aureole landslide

rafted pumice a new model for the formation of the medusae fossae formation mars abstract the medusae fossae formation mff mars could be deposits of materials originally formed as hyaloclastites erupted from vents which formed the basal units of olympus mons volcano and subsequently collapsed as landslides to form the aureole materials these low density hyaloclastites subsequently floated on the northern sea as pumice rafts and drifted to the southwest where they encountered the boundary of the southern highlands to form the mff

rheological constraints on martian landslides we use a dynamic finite difference model to simulate martian landslides in the valles marineris canyon system and olympus mons aureole using three different modal rheologies frictional bingham and power law the frictional and bingham modes are applied individually fluidized rheology is treated as a combination of frictional and power law modes general fluidization can include pore pressure contributions whereas acoustic fluidization does not we find that general fluidization most often produces slides that best match landslide geometry in the valles marineris this implies that some amount of supporting liquid or gas was present in the material during failure the profile of the olympus mons aureole is not well matched by any landslide model suggesting an alternative genesis in contrast acoustic fluidization produces the best match for a lunar slide a result anticipated for dry crust with no overlying atmosphere the presence of pressurized fluid during valles marineris landsliding may be due to liquid water beneath a thin cryosphere 1 2 km or flash sublimation of co2

la icp ms trace element analysis of pyrite from the chang an gold deposit sanjiang region china implication for ore forming process abstract the chang an gold deposit yunnan province is one of five large gold deposits in the ailaoshan gold belt that is the most important ore belt of the sanjiang tethyan metallogenic domain geochemical study of pyrite in the deposit was conducted using laser ablation inductively coupled plasma mass spectroscopy three types of hydrothermal pyrite were identified in the ores and wall rocks i e the coarse euhedral crystals in syenite py1 the coarse grains disseminated in altered sandstones or sandstone ores py2 and the fine grained euhedral pyrite in sandstone ores py3 their trace elements exhibit different concentrations associations and rim core zoning implying different geneses and crystallization processes the cores of py1 were formed by magmatic fluids and have the lowest concentrations of au as cu and zn the cores of py2 were formed by metamorphic fluids and have relatively high au ag ni pb and cu concentrations the py3 grains and the growth rims of py1 and py2 show consistently high contents of au as pb and co suggesting that all of them were rapidly deposited from a mixing fluid system that was probably composed of fluids of metamorphic and magmatic origins this interpretation is supported by the observation that the high grade ores generally contain lots of py2 and py3 hence we consider that the deposit was formed during india asia collision slightly postdate the 33 35 ma tectono magmatism

olympus mons aureole deposits new evidence for a flank failure origin 1 the origin of the rough textured aureoles that surround the immense olympus mons volcano on mars is controversial we present data from the mars global surveyor and mars odyssey missions to demonstrate that at least two of the aureole lobes are derived from the volcano s flanks in large and probably catastrophic mass movement events leaving behind headwalls that constitute the basal scarp this evidence stems from the morphology and internal structure of aureole blocks which exhibit remnants of volcanic flow units on their surfaces our claim is supported by plausible reconstructions of the prefailure flanks structural analogs to known flank failure events at hawaiian volcanoes suggest that repeated cycles of flank growth and collapse at olympus mons allow generation of the observed aureoles from a protoedifice similar in size and shape to the present one

fluid origin and structural enhancement during mineralization of the jinshan orogenic gold deposit south china the jinshan orogenic gold deposit is a world class deposit hosted by a ductile shear zone caused by a transpressional terrane collision during neoproterozoic time ore bodies at the deposit include laminated quartz veins and disseminated pyrite bearing mylonite most quartz veins in the shear zone with and without gold mineralization were boudinaged during progressive shear deformation with three generations of boudinage structures produced at different stages of progressive deformation observations of ore controlling structures at various scales indicate syn deformational mineralization fluid inclusions from pyrite intergrown with auriferous quartz have 3he 4he ratios of 0 15 0 24 ra and 40ar 36ar ratios 575 3 060 18ofluid values calculated from quartz are 5 5 8 4 and d values of fluid inclusions contained in quartz range between 61 and 75 the 13c values of ankerite range from 5 0 to 4 2 and ankerite 18o values from 4 4 to 8 0 the noble gas and stable isotope data suggest a predominant crustal source of ore fluids with less than 5 mantle component data also show that in situ fluids were generated locally by pervasive pressure solution and that widespread dissolution seams acted as pathways of fluid flow migration and precipitation the in situ fluids and fluids derived from deeper levels of the crust were focused by deformation and deformation structures at various scales through solution dissolution creep crack seal slip and cyclic fault valve mechanisms during progressively localized deformation and gold mineralization

analysis of a new geomorphological inventory of landslides in valles marineris mars abstract we completed a systematic mapping of landslides in a 10 5 km 2 area in tithonium and ius chasmata valles marineris mars where landslides are abundant using visual interpretation of medium to high resolution optical images we mapped and classified the geometry of 219 mass wasting features including rock slides complex compound failures rock avalanches debris flows and rock glacier like features for a total landslide area of a lt 4 4 10 4 km 2 44 of the study area a proportion larger than previously recognised studying the landslide inventory we showed that the probability density of landslide area p a l follows a power law with a scaling exponent 1 35 0 01 significantly different from the exponents found for terrestrial landslides 2 2 and 2 4 this indicates that the proportion of large landslides a l 10 7 m 2 is larger on mars than on earth we estimated the volume v l of a subset of 49 deep seated slides in our study area and found that the probability density of landslide volume p v l obeys a power law trend typical of terrestrial rock falls and rock slides with a slope 1 03 0 01 from the combined analysis of landslide area and volume measurements we obtained a power law dependency comparable to a similar relationship obtained for terrestrial bedrock landslides v l 1 2 0 8 a l 1 25 0 03 from the fall height h l and run out length l l of a subset of 83 slides unaffected by topographic confinement we obtained the mobility index heim s ratio h l l l a measure of the apparent friction angle of the failed materials 14 4 0 4 slope stability simulations and back analyses performed adopting a limit equilibrium method and using monte carlo approaches on failed and stable slopes suggest that the large landslides in valles marineris were seismically induced

fragmentation in the val pola rock avalanche italian alps 1 grain size data from the deposit of the 1987 val pola rock avalanche central italian alps are compared with data concerning rock avalanching rock fragmentation and comminution the weibull distribution fits a small part of the entire particle size distribution of debris samples with a mean value of the curve shape factor of 0 54 0 28 this is typical of multiple comminution or fragmentation with much shearing a fractal distribution fits over a greater size range computed fractal dimensions range between 1 3 and 3 2 within the deposit with average values of about 2 6 2 7 these values cover the range between the theoretical values of the plane of weakness model 1 97 and the pillar of strength model 2 84 and are close to the theoretical value for the constrained comminution model 2 58 these suggest that both texturally mature and immature deposits are present and that more than a single comminution process acted during the rock avalanche motion variation of the grain size distribution within the deposit and grain size segregation show as trends in the fractal dimension and arise from variation in the fragmentation process a variety of different physical and empirical laws suggest that 1 30 of the energy expended in the rock avalanche was consumed in fragmentation

la icp ms trace element analysis of pyrite from the xiaoqinling gold district china implications for ore genesis abstract the xiaoqinling district the second largest gold producing district in china is located on the southern margin of the north china craton it consists of three ore belts namely the northern ore belt the middle ore belt and the southern ore belt pyrite from the dahu gold deposit in the northern ore belt and wenyu and yinxin gold deposits in the southern ore belt were investigated using a combination of ore microscopy and in situ laser ablation inductively coupled plasma mass spectrometry la icp ms a range of trace elements was analyzed including au te ag pb bi cu co ni zn mo hg as and si the results show that there are no systematic differences between the trace element compositions of pyrite in the three deposits from different ore belts in general au concentrations in pyrite are low from 2 rich ore fluids spatial association with large scale compressional structures of the qinling orogen 18 o and d data suggestive of mixing between metamorphic and meteoric waters 34 s and pb isotopic data that point to a mixed crustal mantle source all point to typical orogenic type gold deposits high ni concentrations up to 8425 ppm of pyrite possibly linked to deep seated mafic ultramafic metamorphic rocks provide further evidence on the orogenic gold deposit affinity but against the model of a granitic derivation of the mineralizing fluid as previously suggested by some workers generally low au concentration in pyrite is also consistent with those from worldwide orogenic gold deposits therefore the gold mineralization in the xiaoqinling district is described as orogenic type and is probably related to indosinian collision between the north china craton and the yangtze craton

the olympus mons aureole formation by gravitational spreading new observations of the aureole deposits of olympus mons are in agreement with previous suggestions that the aureole lobes could have been formed by movement under gravity away from the observed scarps the characteristic corrugated morphology of the aureole is probably secondary formed by erosion along structural inhomogeneities geometries of the corrugations and translational faults in the aureole deposits favor a mechanism of emplacement that involves material with substantial shear strength rather than viscous flow estimates of the aspect ratios of terrestrial landslides nappes and ash flows suggest that the aureole deposits are more similar in overall shape to slide emplaced bodies than to pyroclastic flows although martian physical conditions permit the formation of ash flows there is no positive evidence for their existence a gravitational spreading mechanism is proposed that involves imbricate thrusting in distal regions analogous with terrestrial thrust sheets corrugations in the aureole developed by erosion along imbricate or listric faults basal shear stresses on the decoupling surface may have been of the order of 106 pa 10 bars the nature of the decoupling surfaces in the proximal regions is uncertain but is likely to have been the topographic surface in distal parts the aureole deposits were probably emplaced as a series of sheets by spreading under gravity from an ancestral olympus mons which extended farther to the northwest than does the present volcano as a result of the accumulation of lavas under the then prevailing stress conditions recent lava eruptions from the volcano have been concentrated in northeast and southwest sectors indicating a changed stress regime since aureole emplacement

ice lubricated gravity spreading of the olympus mons aureole deposits abstract gravity sliding and spreading at low strain rates can account for the general morphology and structure of the aureoles and basal scarp of olympus mons detachment sliding could have occurred around the volcano if either pore fluid pressures were exceptionally high greater than 90 or the rocks had very low resistance to shear about 1 105 pa or 1 bar because of the vast areal extent and probable shallow depth of the detachment zone development of ubiquitous high pore fluid pressures beneath aureole forming material was unlikely however a zone of sufficiently weak material consisting of about 10 interstitial or interbedded ice could have been present if so a simple rheologic model for the aureole deposits can be applied that consists of a thin ductile layer overlain by a thicker brittle layer according to this model extensional deformation would have occurred near the shield and compressional deformation in its distal parts proximal grabens and distal corrugations on aureole surfaces support this model a submarine slide at kitimat arm british columbia is a valid qualitative analogy for the observed features and inferred emplacement style of the aureole deposits ground ice processes have been considered the cause of many geologic features on mars a 3 average concentration of ground ice in the regolith is predicted by theoretical models for the ice budget and cryosphere ice may have been deposited in higher concentrations below the aureole forming material the source of the ice could have been juvenile water circulated hydrothermally by olympus mons volcanism the basal scarp of olympus mons apparently demarcates the transition between the upper stable part of the shield and its lower part that decoupled and formed the aureole deposits this transition may reflect a change in the bulk shear strength of the shield caused either by a radial dependence in the abundance of ice or fluid in the shield materials or by the concentration of intrusive dikes within the volcano other martian volcanoes exhibit virtually no evidence of similar large scale gravity spreading and basal scarps perhaps such evidence if it existed has been buried by lava flows or perhaps the smaller size of other volcanoes did not permit the development of these features

mars and earth comparison of cold climate features abstract on earth glacial and periglacial features are common in areas of cold climate on mars the temperature of the present day surface is appropriate for permafrost and the presence of water is suspected from data relating to the outgassing of the planet from remote sensing measurements over the polar caps and elsewhere on the martian surface and from recognition of fluvial morphological features such as channels these observations and the possibility that ice could be in equilibrium with the atmosphere in the high latitudes north and south of 40 latitude suggest that glacial and periglacial features should exist on the planet morphological studies based mainly on viking pictures indicate many features that can be attributed to the action of ice among these features are extensive talus aprons debris avalanches flows that resemble glaciers or rock glaciers ridges that look like moraines various types of patterned ground scalloped scarps and chaotically collapsed terrain that could be attributed to thermokarst processes and landforms that may reflect the interaction of volcanism and ice

shoreface translation and the holocene stratigraphic record examples from nova scotia the mississippi delta and eastern australia abstract classic descriptive models of barrier sedimentation have been developed with data from the atlantic and gulf coasts of the united states these models are dominated by low to moderate rates of relative sea level rsl rise and wave energy barriers respond by landward recycling of sediment through the mechanism of shoreface retreat sedimentation processes on the central coast of new south wales n s w australia consist of rapid rsl rise in early holocene times followed by a stillstand since 6500 b p wave energy is relatively high year round and sand sources for barrier formation are only found on the inner shelf barrier sedimentation on the central coast of n s w exhibits a thick composite sequence composed of a basal marine transgressive sand overlain by regressive beach and dune facies the louisiana coast surrounding the mississippi delta is underlain by compacting deltaic muds which generate very rapid rates of rsl rise the louisiana coast experiences low wave energy punctuated by high energy tropical and extra tropical storm events barrier sediments accumulate from the erosion of deltaic headlands and undergo a transformation from subaerial barrier island systems to subaqueous shoals located on the inner shelf drumlins experience coastal erosion on the eastern shore of nova scotia and provide a sediment source for compartmented estuary mouth barriers an ongoing moderate rise of rsl results from the passage of a glacial forebulge wave energy is intermediate between louisiana and n s w and displays a seasonal pattern dominated by frequent winter storms coastal barrier sedimentation is episodic consisting of a period of beach ridge progradation followed by barrier destruction and re establishment further landward the three contrasting sedimentary sequences found in examples from louisiana n s w and nova scotia indicate that presently available sedimentation models from locations such as the middle atlantic or texas coasts of the united states may only represent well documented regional case studies a true generalised coastal sedimentation model is required which can identify the parameters controlling vertical and horizontal translation of the depositional surface and provide relationships between these parameters which quantitatively predict the genesis distribution and geometry of coastal sedimentary facies

an early paleozoic orogenic gold belt along the jiang shao fault south china evidence from fluid inclusions and rb sr dating of quartz in the huangshan and pingshui deposits abstract there are several gold deposits in the eastern section of the regional jiang shao fault between the yangtze and cathaysia blocks in south china auriferous quartz veins in these deposits are strictly hosted in second order ne trending ductile shear zones the ores generally contain low amounts of sulfide minerals

the geological setting of lode gold deposits in the central southern urals a review the late paleozoic uralides represent one of the largest lode gold metallogenic provinces in the world in the southern urals gold distribution is heterogeneous and is confined mainly to two tectonostratigraphic zones namely the main uralian fault and the east uralian zone the important lode gold districts within and in the immediate hangingwall of the first order crustal suture of the main uralian fault are characterized by a complex tectonic history of earlier compressional tectonics involving thrusting folding and reverse faulting and later transcurrent shearing gold mineralization is hosted by second and third order brittle to brittle ductile strike slip faults that developed late during the kinematic history of the main uralian fault strike slip reactivation of earlier compressional structures was related to the late stage docking of the passive margin of the east european platform with island arc complexes of the southern urals an event that is tentatively related to changes in plate motion during the final stages of terrane accretion during the upper permian and lower triassic gold mineralization was controlled by the permeability characteristics of the hydrothermal conduits as well as by competence contrasts and geochemistry of the mainly volcanic host rocks mineralization occurred at relatively shallow crustal levels 2 6 km and largely post dates peak metamorphism of the host rocks the large and very large up to 300 to au gold deposits of the east uralian zone are hosted by upper paleozoic granitoid massifs gold mineralization is temporally associated with the main phase of regional scale compressional tectonics and granite plutonism during the upper carboniferous and lower permian controlling structures have a dominantly east west strike and occur as hybrid shear tensional vein systems in competent granitoids subjected to east west directed regional shortening deformation textures and alteration mineral assemblages indicate lower amphibolite facies conditions of mineralization close to peak metamorphic conditions that are associated with the mid permian regional metamorphism and tectonism gold deposits in the southern urals are therefore polygenetic and are temporally and genetically distinct in each of the two major mineralized tectonostratigraphic zones of this well preserved collisional orogenic belt the different timing of ore fluid generation and fluid discharge is interpreted to be the result of the different tectonic metamorphic and magmatic evolution of terranes in the southern urals

coarse clastic barrier beaches a discussion of the distinctive dynamic and morphosedimentary characteristics abstract coarse clastic barriers are common on mid and high latitude coasts they possess a morphosedimentary and dynamic distinctiveness which sets them apart from sandy fineclastic barrier forms the reflective nature of the seaward barrier favors the development of zero mode sub harmonic edge waves particularly during long period swells 10 20 s manifest in the formation of high level cusps in some circumstances the pattern of recent overwashing of the barrier is related to cusps lack of distinct tidal passes due partly to the high seepage potential of coarse barriers means that very little sediment is transported seaward thus the barriers roll steadily onshore and sections show a variety of washover facies related to the volume of overwash surges

the aureole of olympus mons mars as the compound deposit of submarine landslides abstract the enigmatic deposits building up the olympus mons aureole on mars are likely among the largest landslide remnants in the solar system these deposits exhibit an extraordinary run out distance up to nearly 700 km in spite of a fall height some 100 times smaller after quantifying the mobility of the olympus mons aureole lobes it is suggested based on dynamical considerations and morphological analysis that the aureole could be the consequence of a series of gigantic subaqueous landslides in order to bring evidence in favor of this interpretation comparisons are drawn between the different landslide deposits on earth and mars emphasizing the similarity with the rock avalanches of the canary islands and the hawaii the results of experimental subaqueous debris flows are also analyzed and numerical calculations are introduced to simulate the dynamics of flow in analogy with certain subaqueous landslides on earth it is possible that the outstanding run out of the aureole lobes was a consequence of hydroplaning a natural lubrication by water during flow

raman microspectrometry of fluid inclusions abstract for many kinds of fluid inclusions the coupling of microthermometry and raman microspectrometry is still the only viable option to obtain compositions of single fluid inclusions a review is given on the basis of 16 years of experience and helped with about 120 references of the instrumentation analytical conditions and methodology of the application of raman microspectrometry to gaseous aqueous and hydrocarbon inclusions and their daughter minerals

pressure fluctuations phase separation and gold precipitation during seismic fracture propagation gold mineralization at croagh patrick western ireland occurs in quartz veins associated with three synchronous oblique tensile shear systems the veins evolved by progressive thickening of isolated en echelon lensoid tensile fractures that show a power law relation between their length and thickness a change in power law exponent marks the linking of the en echelon arrays by large oblique tensile veins fluid inclusion data show that gold was deposited due to unmixing of an h 2 o co 2 nacl fluid at 320 240 c and 160 30 mpa primarily due to decreases in fluid pressure evidence for phase separation is only observed in the large linking veins and is abundant close to intersections of the vein arrays these sites are where high gold grades occur the distribution of gold is believed to reflect both spatial and temporal variations in fluid pressure fluctuation during seismic fracture propagation controlled by the vein growth mechanism and zones of maximum dilation

a comparison of observed and theoretical postglacial relative sea level in atlantic canada two extreme models of late wisconsinan ice cover in atlantic canada and the northeastern u s a are shown to produce postglacial relative sea level curves that bracket existing field observations at six sites throughout the region this suggests that the true late wisconsinan ice distribution is probably intermediate to the two contrasting reconstructions proposed both ice models predict the existence of four relative sea level zones an innermost zone closest to the centre of glaciation in which relative sea level falls continuously throughout postglacial time an outermost zone in which it rises continuously and two transitional zones in which it first falls and then rises in varying proportions according to the distance from the ice margin the distinctive forms of the relative sea level curves are probably representative of each of the zones and are unlikely to be significantly perturbed even by large local ice readvances they therefore establish patterns with which future field data are expected to conform the form that the geological record of relative sea level change is likely to take within each zone is discussed and promising settings for the collection of new data are proposed the common practice of separating relative sea level into an isostatic and a eustatic component is analysed and shown to be incorrect as usually applied the practice is also shown to be unnecessary because the models discussed in this paper predict changes in relative sea level that can be compared directly with the observations

pyrite and pyrrhotite textures and composition in sediments laminated quartz veins and reefs at bendigo gold mine australia insights for ore genesis the various types textures and compositional zoning of pyrite in the gold bearing saddle reefs quartz veins and surrounding sedimentary rocks provide new information on the potential source and timing of gold and arsenic and related fluid processes responsible for mineralization at bendigo nodular diagenetic pyrite in the black shale tops to sandstone turbidites is enriched in invisible gold and arsenic with mean values of 0 61 ppm au 1 300 ppm as and au ag 1 based on la icpms analyses other elements enriched in the diagenetic pyrite within the organic rich shales are mn zn mo cu v ba ag cd tl co ni bi pb and te in contrast euhedral and growth zoned hydrothermal pyrite in the turbidites and bedding parallel laminated quartz veins contains lower contents of most trace elements but has higher contents of invisible au and as especially on the outermost rim of the pyrite the gold rich pyrite rims generally become thicker a few to hundreds of microns in proximity to the gold bearing saddle reefs pyrite in the reef commonly has the highest levels of invisible au and as and the lowest levels of other trace elements it is characterized by au ag 1 and au pb 0 01 in the deepest stratigraphic levels below known productive gold reefs diagenetic pyrite in the most carbonaceous shales has been replaced by pyrrhotite during metamorphism la icpms analyses reveal that the disseminated pyrrhotite contains similar levels of ni and co to the diagenetic pyrite but is strongly depleted in as and au the spatial relationships between organic rich shales folded bedding parallel laminated quartz veins and gold arsenic bearing saddle reefs combined with the consistent trends in the trace element composition of pyrite hosted by these three geological elements is interpreted to indicate that the black shales were an initial source of au and as and the laminated quartz veins acted as the initial pathways for hydrothermal fluid flow carrying au and as from the source shales to the saddle reefs maximum gold and arsenic input into the reefs principally as free gold plus arsenopyrite occurred late during deformation toward the end of the hydrothermal cycle and is expressed by the au as rich rims to hydrothermal pyrite in the sedimentary host rocks laminated quartz veins and reefs this corresponds with final fold lockup and the development of through going fault arrays linking adjacent anticlines the source of au and as for this final and most economically important fluid flow event is considered to be from carbonaceous shales deeper in the basin where original gold bearing diagenetic arsenian pyrite reacts with organic matter and is converted to pyrrhotite with release of au as and s to the metamorphic fluid

mineralogy and geochemistry of gold bearing arsenian pyrite from the shuiyindong carlin type gold deposit guizhou china implications for gold depositional processes arsenian pyrite in the shuiyindong carlin type gold deposit in guizhou china is the major host for gold with 300 to 4 000 ppm au and 0 65 to 14 1 wt as electron miroprobe data show a negative correlation of as and s in arsenian pyrite which is consistent with the substitution of as for s in the pyrite structure the relatively homogeneous distribution of gold in arsenian pyrite and a positive correlation of as and au with au as ratios below the solubility limit of gold in arsenian pyrite suggest that invisible gold is likely present as au1 in a structurally bound au complex in arsenian pyrite geochemical modeling using the laser ablation inductively coupled plasma mass spectrometry la icp ms analysis of fluid inclusions for the major ore forming stage shows that the dominant au species were au hs 2 77 and auhs aq 0 23 gold hydroxyl and gold chloride complexes were negligible the ore fluid was undersaturated with respect to native au with a saturation index of 3 8 the predominant as species was h3aso30 aq pyrite in the shuiyindong deposit shows chemical zonation with rims richer in as and au than cores reflecting the chemical evolution of the ore bearing fluids the early ore fluids had relatively high activities of as and au to deposit unzoned and zoned arsenian pyrite that host most gold in the deposit the ore fluids then became depleted in au and as and formed as poor pyrite overgrowth rims on gold bearing arsenian pyrite arsenopyrite overgrowth aggregates on arsenian pyrite indicate a late fluid with relatively high activity of as the lack of evidence of boiling and the low iron content of fluid inclusions in quartz suggest that iron in arsenian pyrite was most likely derived from dissolution of ferroan minerals in the host rocks with sulfidation of the dissolved iron by h2s rich ore fluids being the most important mechanism of gold deposition in the shuiyindong carlin type deposit

topography of the shield volcano olympus mons on mars olympus mons one of the largest known shield volcanoes in the solar system covers an area of 3 2 105 km2and has a diameter of 600 km excluding its vast aureole deposits the structure is five times larger than the largest shield volcano on the earth it is situated on the north west flank of the tharsis volcanic region a broad topographic rise on the martian surface the volcano has three physical subdivisions the summit caldera the terraced upper flanks and the lower flanks which terminate in a scarp 2 10 km high that nearly surrounds the structure a large block of images of the tharsis region including olympus mons was obtained by the viking mission1 here we present a topographic map of olympus mons compiled using various combinations of stereo pairs of these images together with stereoscopic perspective views generated by image processing techniques

gold mineralization of the chencai suichang uplift and tectonic evolution of zhejiang province southeast china abstract a metallogenic model is proposed in which gold and base metal mineralization in se china is related to plate interactions along the pacific margin with southeast asia from about 900 to 70 ma all depositional orogenic and metallogenic processes can be explained by subduction events along northeast trending zones with progressive accretion and cratonization along the continental margin these subduction zones moved southeast for a distance of less than 150 km as a result the area is one of crustal reworking in which the rocks and mineral deposits of earlier events have been repeatedly modified the chencai suichang uplift is an uplifted crustal block in central zhejiang province of mainland china in which the proterozoic basement is exposed as tectonic windows in overlying mesozoic volcanics several gold and base metal deposits are located in these proterozoic windows as well as in the younger volcanics most economic deposits were formed during the last major tectono magmatic event affecting the area the yanshanian 160 170 ma event although there is evidence for earlier mineralization that has been remobilized during the yanshanian it is suggested that crustal reworking was particularly important in remobilising and upgrading gold mineralization the model presented is supported not only by local geology and isotopic data but also by the regional distribution of gold deposits which are arranged in a 50 km wide belt parallel to the yanshanian subduction zone three major episodes of mineralization occurred during 1 a subduction related period of metamorphism partial melting and mesothermal fluid generation and mineralization in the lower crust during the caledonian 2 subduction related volcano plutonic activity with epithermal mineralization during the early yanshanian and 3 hydrothermal mineralization during late yanshanian tectono magmatic event in the third two main categories of metallogenic control are recognized namely 1 hydrothermal fluid generation in the lower crust and 2 upper crust structural and lithological controls on mineralization

oceans on mars an assessment of the observational evidence and possible fate the edges of the northern plains and interpreted to be shorelines remaining from these former standing bodies of water we examine the elevations and geologic relations along these contacts in detail and find little support for their interpretation as shorelines some contacts are clearly of volcanic origin and all have significant variations in elevation better support for the former presence of water over large parts of the northern plains is provided by the vastitas borealis formation vbf most of the post noachian fill within the northern basin is ridged plains of lower hesperian age interpreted to be volcanic in origin overlying the ridged plains is the vbf a thin veneer of material of upper hesperian age the vbf may have been deposited from large floods support for this interpretation is the similarity in age between the outflow channels and the vbf the presence of the vbf at the lower ends of the outflow channels and identification of numerous features in the outcrop areas of the vbf that are suggestive of basal melting of an ice sheet to cover all the area over which the vbf is exposed would require 2 3 10 7 km 3 of water spread over the entire surface of mars this volume is equal to a global layer global equivalent layer or gel 156 m deep we find no support for the larger estimates of ocean volumes that range up to 3 10 8 km 3 and which imply comparable amounts of water per unit area as are currently present on the surface of the earth under present climatic conditions on mars an ocean would freeze in a geologically short time period 10 4 years then would sublimate away at rates strongly dependent on the presence or absence of debris on the ice surface the present vbf is interpreted as a sublimation residue from the ponded outflow channel effluents the fate of a volume of water thought to have been emplaced by the outflow channels 2 3 10 7 km 3 is largely accounted for by the presence of other existing reservoirs on the planet an approximately 20 30 m gel of water is estimated to be in the present polar caps and a 50 m gel may have escaped to space since the hesperian leaving 80 m gel unaccounted for this amount may be partly trapped in other volatile rich deposits on the surface and a significant amount could have reentered the groundwater system by south polar basal melting and been progressively cold trapped at the base of a growing cryosphere on the basis of our assessment of the hesperian aged deposits we predict that testing of the clifford and parker 2001 hypothesis that a noachian aged ocean covered up to one third of the surface of mars will be made very difficult by the enhanced degradation rates in the noachian and subsequent geological events in the northern lowlands index terms 6225 planetology solar system objects mars 4267 oceanography general paleoceanography 5407 planetary sciences atmospheres evolution 5470 planetary sciences surface materials and properties 1635 global change oceans 4203 keywords mars oceans channels shorelines hesperian

reassessing rock mass properties and slope instability triggering conditions in valles marineris mars the rock walls of the valles marineris valleys vm in the equatorial area of mars exhibit several gravitational failures which resulted in a series of large landslides up to several hundred cubic kilometers in volume questions arise as to forces at play and rock strength in the stability of the walls of vm in this work we address the stability analysis of the walls of vm by considering the strength of the materials of the walls and the causes of landslides using finite element calculations and the limit analysis upper bound method we explore the range of cohesion and friction angle values associated with realistic failure geometries and compare predictions with the more classical culmann s translational failure model our analysis is based both on synthetic simplified slope profiles and on the real shape of the walls of vm taken from the mola topographic data validation of the calibrated cohesion and friction angle values is performed by comparing the computed unstable cross sectional areas with the observed pre and post failure profiles the estimated failure surface geometry and ridge crest retreat this offers a link between rock mass properties slope geometry and volume of the observed failure represented in dimensionless charts the role of groundwater flow and seismic action on the decrease of slope stability is also estimated pseudo static seismic analyses provide another set of dimensionless charts and show that low seismicity events induced by meteoroid impacts consistent with the size of craters could be a cause for some of the observed landslides if poor rock properties for vm are assumed analyses suggest that rock mass properties are more similar to their earth equivalents with respect to what has been previously supposed

overwash processes along a gravel beach in south east ireland recent overwashing and to a more limited extent overtopping has occurred on a gravel dominated beach just west of carnsore point in south east ireland at relatively low points swash excursions have breached the duneline and extensive gravel fans have formed on landward facing slopes also at interbreach positions swash ramps have been built up in front of previously eroding dune cliffs allowing overtopping at heights of up to 5 m above mhwost spreading a veneer of sediment over the adjacent dune ridge in both cases events appear to be preceded by erosion and backbeach sand and gravel deposition stratigraphic textural and fabric analyses assist in identifying environmental conditions that prevailed during overwash throat and fan and overtopping ramp sedimentation

slope failure and volcanic spreading along the submarine south flank of kilauea volcano hawaii 1 new multichannel reflection data and high resolution bathymetry over the submarine slopes of kilauea volcano provide evidence for current and prior landsliding suggesting a dynamic interplay among slope failure regrowth and volcanic spreading disrupted strata along the upper reaches of kilauea s flank denote a coherent slump correlated with the active hilina slump the slump comprises mostly slope sediments underlain by a detachment 3 5 km deep extension and subsidence along the upper flank is compensated by uplift and folding of the slump toe which surfaces about midway down the submarine flank uplift of strata forming papa u seamount and offset of surface features along the western boundary of kilauea indicate that the slump has been displaced 3 km in a south southeast direction this trajectory matches coseismic and continuous ground displacements for the hilina slump block on land and contrasts with the southeast vergence of the rest of the creeping south flank to the northeast slope sediments are thinned and disrupted within a recessed region of the central flank demonstrating catastrophic slope failure in the recent past debris from the collapsed flank was shed into the moat in front of kilauea building an extensive apron seaward sliding of kilauea s flank offscraped these deposits to build an extensive frontal bench a broad basin formed behind the bench and above the embayed flank uplift and back tilting of young basin fill indicate recent and possibly ongoing bench growth the hilina slump now impinges upon the frontal bench this buttress may tend to reduce the likelihood of future catastrophic detachment

mobility and topographic effects for large valles marineris landslides on mars 1 recent experiments on dry granular flows over horizontal plane bare some similarities with large martian landslides observed in valles marineris vm however martian normalized runout are twice as large as those that observed in dry granular flow experiments numerical simulations on theoretical 2d and real 3d topographies reconstructed from remote sensing data show that slope effects significantly reduce the shift between experimental results and martian observation however topography effects are not strong enough to explain the high mobility of martian landslides as a result other physical and or geological processes should play a key role into the dynamics of martian landslides a new mobility is defined that makes it possible to characterize the dynamics of the flow regardless of the geometry of the released mass and of the underlying topography

barrier and lagoon coast evolution under differing relative sea level regimes examples from ireland and nova scotia abstract although the coasts of southern ireland and eastern nova scotia possess many basic similarities especially in terms of geology glacial history sediment character resistance to erosion and wave and tide regimes there is a fundamental contrast in holocene sea level history in ireland recent the past 4000 years sea level rise has been limited to less than 1 mm year by contrast the atlantic coast of nova scotia has been experiencing sea level rises up to three to five times greater over the same period under these markedly differing relative sea level rise regimes barrier and lagoon evolution has varied considerably in ireland barrier lagoon form is controlled by local basement expression particularly through the emergence of headlands creating largely closed sediment systems and the requirement to maintain cross shore drainage it is this latter factor that leads to a simple four fold categorization of the irish barriers and lagoons from freshwater seepage to open tidal environments the nova scotian examples are associated with rapidly moving erosional fronts with local basement control relegated to a subordinate role at the expense of rapid changes in sediment supply barriers can both grow and decay under these conditions subject to certain critical but as yet ill defined thresholds simultaneously forcing development and destruction of adjoining lagoons these major differences also find expression in sedimentary sequences

invisible gold distribution on pyrite and ore forming fluid process of the huangshan orogenic type gold deposit of zhejiang se china implications from mineralogy trace elements impurity and fluid inclusion studies the huangshan orogenic type gold deposit in zhejiang of se china occurred in quartz pyrite veins it is hosted by phyllonite that underwent greenschist facies metamorphism along a large jiangshan shaoxing tectonic belt with a ne sw direction trace elemental characteristics ore forming process and invisible gold on different forms of pyrite and quartz are studied the au associated pyrite can be classified into two categories recrystallized pyrite and euhedral pyrite the precipitation of invisible au on pyrite is mainly derived by co and ni with auhs2 complex in the mineralizing fluids in different events the xps results revealed that valence states of au3 replaced 2fe2 in the pyrite and au0 replaced si4 in the quartz structure the electron paramagnetic resonance and trace elemental results suggested that the element pairs of ge li al in quartz and mn co ni in pyrite have distinct impurities as identified a fluid inclusion study showed that the auriferous quartz is characterized by low saline and co2 rich fluids coexistence of the type i type iii inclusions and same range of homogenization temperature with different mode are evidences of immiscible fluid process the temperature pressure values of ca 250 c 1250 bar and ca 220 c 780 bar for gold precipitation have been calculated by intersection of coexisting fluids during the entrapment the huangshan orogenic type gold deposit may be associated with the wuyi yunkai orogeny during the early paleozoic including an upper mid greenschist facies metamorphism 450 420 ma all the features suggest that the huangshan gold deposit is probably a product linking with the early paleozoic orogeny in south china

volcanic spreading and lateral variations in the structure of olympus mons mars the olympus mons volcano on mars is notable not only for its immense height and width but also for substantial asymmetries in its structure the gently sloped northwest flank extends to a much greater distance from the central caldera complex than the more steeply sloped southeast flank furthermore the northwest flank exhibits lower flank extensional faults whereas the southeast shows upper flank compressional terraces and lower flank upthrust blocks however both the northwest and southeast flanks exhibit characteristic concave upward profiles and steep bounding scarps in contrast to other sectors the nw se asymmetries are aligned with the regional slope from the tharsis rise but an understanding of the underlying causes has remained elusive we use particle dynamics models of growing spreading volcanoes to demonstrate that these flank structures could reflect the properties of the basement materials underlying olympus mons we find that basal slopes alone are insufficient to produce the observed concave upward slopes and asymmetries in flank extent and deformation style that are observed at olympus mons instead lateral variations in basal friction are required these variations are most likely related to the presence of sediments transported and preferentially accumulated downslope from the tharsis rise such sediments likely correspond to ancient phyllosilicates clays recently discovered by the mars express mission

ancient oceans in the northern lowlands of mars evidence from impact crater depth diameter relationships 1 we present depth d and diameter d data for 2269 martian impact craters in the diameter range 6 216 km distributed over 11 52 106 km2 of terrain that samples several geologic settings and the full range of latitudes and elevations throughout the northern lowlands of mars our data indicate that there are three major crater types that fall into two major populations those craters that contain vastitis borealis formation vbf and those that do not the deepest type 1 craters comprise a late hesperian early amazonian age population that does not contain vbf type 2 type 3 and subdued type 1 craters comprise a population of hesperian age craters partially buried by the vbf the unique d d distribution of type 3 craters and photogeologic evidence suggest an erosional style for the vbf that requires sublimation processes indicating that the vbf contained a substantial amount of ice type 3 craters occur throughout the northern lowland plains at elevations below 2400 m if the vbf is a sedimentary deposit left by a large body of standing water in the northern lowlands of mars then the northern lowland plains contained a body of water with a volume of 6 107 km3 or the equivalent of a 430 m global ocean during the late hesperian early amazonian this also implies that the vbf contains 4 106 km3 of material in agreement with the estimated amount of material eroded from the outflow channels surrounding chryse basin and washed into the northern lowlands

aureole deposits of the martian volcano olympus mons the aureole of grooved terrain that surrounds the large shield volcano olympus mons consists of several overlapping roughly circular sheets each 0 5 to 1 5 km thick the surfaces of these materials bear abundant curvilinear ridges and troughs 10 to 100 km long and 1 to 5 km wide which form anastomosing patterns that vary in length and width over the aureole the aureole is asymmetric to olympus mons extending almost 1000 km northwest from the center of the volcano but only 600 km southeast the lobate form of the deposits the pressure ridges on their surfaces and the deflection of aureole material around barriers indicate that the deposits were emplaced as viscous flows high resolution viking orbiter pictures show the aureole material to be unstratified and it is inferred to contain randomly distributed large dark blocks whose weathering products form dark streaks in the talus on the flanks of ridges a pyroclastic origin is proposed for the aureole the following sequence is suggested at least six great pyroclastic eruptions occurred prior to the construction olympus mons they formed very fluid ash flows that became viscous during late stages of emplacement and pressure ridges formed on the surfaces of the deposits before they finally came to rest the oldest and most extensive aureole deposit finely grooved terrain was considerably modified by erosion prior to being partly covered by later eruptions a positive gravity anomaly over the olympus mons area may define the site of a near surface magma chamber that was the source of the pyroclastic eruptions

mars stratigraphy and gravimetry of olympus mons and its aureole olympus mons and its surroundings have been investigated using impact crater statistics crater retention ages of all major geological units show that their emplacement occurred during three time intervals the underlying fractured plains are part of the northern plains in general n 1 4 10 3 km 2 this time is followed by the time interval represented by crater retention ages n 1 8 10 4 to 3 10 3 km 2 some lava flows in the fractured plains the smooth plains and the aureole materials were emplaced during this time the aureole probably developed by some sort of collapse of the outer parts of an ancient volcano proto olympus mons underlying the present shield its remnants may show in the scarp and small parts of the shield not covered by younger lava flows the third interval covers crater retention ages n 1 5 10 5 to 3 10 4 km 2 this volcanic activity followed a period of dormancy a series of lava flows forming caldera and present shield surface and flooding a depression around the shield are distinguishable the regional stratigraphy is discussed as part of the global geological history the question of the genesis of the aureole material is addressed by gravity models the topographic mass of olympus mons contributes about 80 to the aureole gravity high northwest of the mountain the gravity high of the entire aureole can be explained by a density model consisting of the topographic masses of olympus mons and the aureole materials it does not require additional high density materials underneath the aureole thus aureole materials of an allochthonous origin by collapse are in agreement with the gravity data however the gravity data do not preclude an autochthonous and volcanic origin of the aureole materials in the latter case possible subsurface intrusions should have no density contrasts with the surroundings

ancient ocean on mars supported by global distribution of deltas and valleys the climate of early mars could have supported a complex hydrological system analysis of ancient deltaic deposits and valley networks reveals the presence of a planet wide equipotential surface in the northern lowlands indicative of the existence of a vast ocean on mars 3 5 billion years ago

gold telluride nanoparticles revealed in arsenic free pyrite pyrite the most abundant sulfide on earth and a common component of gold deposits can be a significant host for refractory gold this is the first documentation of pore attached composite au telluride nanoparticles in arsenic free pyrite trace elements mapping in pyrite from an intrusion hosted au deposit with orogenic overprint dongping china shows trails of tellurides overlapping co ni zonation intragranular microfracturing anomalous anisotropy and high porosity are all features consistent with devolatilization attributable to the orogenic event the pyrite hosted nanoparticles are likely the frozen solid expression of te rich au ag pb bearing vapors discharged at this stage nanoparticle formation as presented here provides the smallest scale tool to fingerprint au trapping during crustal metamorphism

architecture and depositional pattern of the quaternary deep sea fan of the amazon abstract the quaternary deep sea fan of the amazon is composed of four superimposed lens shaped channel levee complexes covering most of the fan surface and controlled by allocyclic processes high amplitude sea level variations of recent glacial cycles induced river fed turbiditic currents that discharged directly into the submarine canyon during low sea level in contrast individual channel levee systems and associated terminal lobes are governed by two distinct autocyclic processes 1 an initial phase of avulsion and adjustment with unconfined sand deposition high amplitude reflection packets and 2 down fan progressive aggradation progradation of a graded channel levee lobe system when a new equilibrium profile is reached during the latter phase the system acts as a particularly efficient sand cleaning and separating factory that is responsible for the high reservoir potential of such turbidites

valles marineris landslides evidence for a strength limit to martian relief abstract unresolved controversies in martian geology surround the role of active tectonics and a wetter climate early in mars history and particularly the history and amount of liquid water at or near the surface among the various lines of evidence brought into such debates are the massive landslides along the walls of valles marineris which generally have been interpreted as resulting from marsquakes and therefore necessitating active tectonics under either wet or dry conditions we analyze valles marineris landslides using digital elevation data from the mars orbiter laser altimeter mola and find that a relief limit consistent with the intact strength of evaporites or other weak sedimentary rock defines an upper bound to the length and relief of unfailed slopes as would material with the strength properties of basalt lithology subjected to ground accelerations of about 0 2 g in contrast to prior interpretations of valles marineris landslides we propose an alternative complementary hypothesis that does not require significant pore water pressures or ground acceleration based on the close correspondence between back calculated material strength properties and values consistent with portions of the chasm walls at least locally being composed of relatively weak materials such as potentially frozen evaporites and or mixtures of ash fall or flow deposits ice hydrated salts and lava flows

acheron fossae mars tectonic rifting volcanism and implications for lithospheric thickness 1 the acheron fossae region is an ancient crustal block exposed in the northwestern tharsis province on mars it is named after the acheron fossae a particularly well developed system of extensional tectonic grabens this study is the first to describe the tectonic inventory in detail using topographic and image data from the global surveyor and mars express missions we see the extensional tectonics along the east west trending topographic high of acheron fossae as a surface expression of upwelling asthenospheric material that initiated regional uplift crustal extension and breakup and associated volcanic activity in noachian time the tectonic architecture and the dimensions of the extensional structures are comparable to those of terrestrial continental rifts an area of elevated topography and strong erosion which constitutes a regional landmark in the eastern acheron fossae region is interpreted as a rift related center of volcanism caused by local magmatic uprise and involvement of the lithosphere the extension across the acheron fossae reaches values between 1 2 km and 8 7 km comparable to young continental rifts on earth crater statistics indicate an absolute cratering model age between 3 9 ga and 3 7 ga for the rifting the uplift observed on the flanks of the acheron fossae indicates a fairly thin and thus hot lithosphere using flexural analysis we have constrained the elastic lithosphere thickness at the time of rifting to 8 9 11 3 km corresponding to thermal gradients between 28 and 41 k km 1 these heat flows are substantially larger than noachian heat flow values previously reported but are consistent with the presence of rift related volcanism and a magmatically very active environment

invisible gold in arsenian pyrite and arsenopyrite from a multistage archaean gold deposit sunrise dam eastern goldfields province western australia the sunrise dam gold mine 11 1 moz au is the largest deposit in the archaean laverton greenstone belt eastern goldfields province yilgarn craton western australia the deposit is characterized by multiple events of fluid flow leading to repeated alteration and mineralization next to a major crustal scale structure the au content of arsenian pyrite and arsenopyrite from four mineralizing stages d1 d3 d4a and d4b and from different structural and lithostratigraphic environments was measured using in situ laser ablation inductively coupled plasma mass spectrometry pyrite contains up to 3 067 ppm au n 224 whereas arsenopyrite contains up to 5 767 ppm n 19 gold in arsenopyrite d4a stage was coprecipitated and remained as invisible gold nanoparticles and or lattice bound during subsequent deformation events in contrast gold in pyrite is present not only as invisible gold but also as micrometer size inclusions of native gold electrum and au ag tellurides pristine d1 and d3 arsenian pyrite contains relatively low au concentrations 26 ppm the highest au concentrations occur in d4a arsenian rich pyrite that has recrystallized from d3 pyrite textures show that this recrystallization proceeded via a coupled dissolution reprecipitation process and this process may have contributed to upgrading au grades during d4a in contrast au in d4b pyrite shows grain scale redistribution of invisible gold resulting in the formation of micrometer scale inclusions of au minerals the speciation of au at sunrise dam and the exceptional size of the deposit at province scale result from multiple fluid flow and multiple au precipitating mechanisms within a single plumbing system

lava effusion rate definition and measurement a review measurement of effusion rate is a primary objective for studies that model lava flow and magma system dynamics as well as for monitoring efforts during on going eruptions however its exact definition remains a source of confusion and problems occur when comparing volume flux values that are averaged over different time periods or spatial scales or measured using different approaches thus our aims are to 1 define effusion rate terminology and 2 assess the various measurement methods and their results we first distinguish between instantaneous effusion rate and time averaged discharge rate eruption rate is next defined as the total volume of lava emplaced since the beginning of the eruption divided by the time since the eruption began the ultimate extension of this is mean output rate this being the final volume of erupted lava divided by total eruption duration whether these values are total values i e the flux feeding all flow units across the entire flow field or local i e the flux feeding a single active unit within a flow field across which many units are active also needs to be specified no approach is without its problems and all can have large error up to 50 however good agreement between diverse approaches shows that reliable estimates can be made if each approach is applied carefully and takes into account the caveats we detail here there are three important factors to consider and state when measuring giving or using an effusion rate first the time period over which the value was averaged second whether the measurement applies to the entire active flow field or a single lava flow within that field and third the measurement technique and its accompanying assumptions

modelling gravel barrier response to storms and sudden relative sea level change using xbeach g abstract this paper investigates the response of a mixed sand and gravel msg barrier coastline to storms and sudden relative sea level change using the numerical model xbeach g the barrier beaches of southern hawke s bay new zealand provide a natural laboratory for the work owing to spatial variability in instantaneous land deformation that occurred during the 1931 hawke s bay earthquake historic 1931 and contemporary 2017 morphodynamics of one tectonically uplifted 1 5 m and one subsided 0 78 m barrier were modelled under energetic waves hs 1 6 m xbeach g was designed to simulate pure gravel beach morphodynamics but despite this the model demonstrated high quantitative skill when calibrated for the msg coast results reveal the storm impact regimes of each profile and potential linkages to decadal scale barrier development observed in historical beach profile data storm swash processes at the uplifted profile indicate long term barrier stability due to a lack of change at the barrier crest and ridge building observed in model simulations provides a potential formative mechanism for decadal scale beach progradation at the subsided barrier modelled historic crest build up up to 0 3 m and narrowing over 5 m indicate an overtopping mode of response to sudden relative sea level rise simulation results are consistent with historical beach profile observations that also show chronic narrowing of the subsided barrier through time simulations of the modern barrier draw attention to the possibility that it may be on a trajectory toward catastrophic breakdown under extreme conditions but further work is needed to distinguish the relative importance of historical sudden sea level rise versus deficits in sediment supply to this shoreline

gold and trace element zonation in pyrite using a laser imaging technique implications for the timing of gold in orogenic and carlin style sediment hosted deposits laser ablation icp ms imaging of gold and other trace elements in pyrite from four different sedimenthosted gold arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit an early synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace elements in particular as ni pb zn ag mo te v and se and a later hydrothermal stage where gold forms as either free gold grains in cracks in overgrowth metamorphic and or hydrothermal pyrite or as narrow goldarsenic rims on the outermost parts of the overgrowth hydrothermal pyrite compared to the diagenetic pyrites the hydrothermal pyrites are commonly depleted in ni v zn pb and ag with cyclic zones of co ni and as concentration the outermost hydrothermal pyrite rims are either as au rich as in moderate to highgrade deposits such as carlin and bendigo or co ni rich and as au poor as in moderate to low grade deposits such as sukhoi log and spanish mountain the early enrichment of gold in arsenic bearing syngenetic to diagenetic pyrite within black shale facies of sedimentary basins is proposed as a critical requirement for the later development of carlin style and orogenic gold deposits in sedimentary environments the best grade sediment hosted deposits appear to have the gold climax event toward the final stages of deformation related hydrothermal pyrite growth and fluid flow

sediment accumulation in low sedimentation wave dominated glaciated inlets abstract many fjords situated in lowland areas of resistant bedrock are characterized by a comparatively low fluvial sediment flux and are often dominated by wave processes several such fjords in eastern canada are used as examples to develop a generalized sediment distribution model physiographically the fjords can be subdivided into nearshore platforms basin slopes and basin floors where there has been marine transgression the principal sediment source is shoreline erosion of glacial till in areas of crustal rebound late glacial and early holocene muds deposited on highs are eroded as they come within the zone of wave erosion with the falling sea level storm waves resuspend fine grained sediment in water depths of many tens of metres and produce near bottom turbid water zones within basins fine sand and silt settle out rapidly leading to the deposition of graded beds on the basin floors residual sand and gravel accumulate on the near shore platforms while silt and mud prograde over or are advected beyond basin slopes burying older basin fill sediment

geomorphological response of the east frisian barrier islands to sea level rise an investigation of past and future evolution abstract post glacial sea level rise has resulted in shoreline erosion in many places sandy barrier islands migrate in a landward direction in order to compensate for the rise in sea level several models for the possible response of the east frisian barrier islands and tidal flats to the holocene sea level rise are summarized the historical morphological development of the region has been influenced by a sea level rise of ca 0 25 m per century in the future sea level rise especially if sea level rise is accelerated in response to human influences will change the morphology of this coastal zone several developmental models are considered which predict the geomorphological response of the east frisian coastal zone to sea level rise four possible scenarios are conceivable depending on island width back barrier lagoon area and human protection measures