a field experiment for calibrating landslide time of failure prediction functions over the last decades time of failure semi empirical prediction functions have been developed and applied to different landslides with mixed results in this study a field experiment was carried out to calibrate these functions with the simultaneous consideration of small size landslides and landslides that occur on slopes modified by human activities four years of continuous monitoring using an integrated platform consisting of both traditional sensors i e inclinometers piezometers load cells topographic measurement and innovative remote sensing equipment i e terrestrial sar interferometer resulted in the collection of a notably large amount of data several landslides affecting different slopes i e cut slopes cut slopes covered by spritz beton and slopes stabilised by anchored bulkheads were observed as part of the experiment thus facilitating the inference of detailed information for the pre failure behaviour nine landslides were back analysed thus allowing for calibration of the failure prediction functions for different types of slopes from these observations it was found that events occurring on slopes modified by human interventions could be effectively predicted using the voight function if suitable parameters are used as a general remark the landslides that originate from cut slopes in natural terrain behave similar to large landslides reported in the literature similar values of a and while landslides that originate from cut slopes covered by spritz beton and slopes stabilised by anchored bulkheads show values that are significantly lower and a values that are significantly higher than those of landslides on natural terrains

initial chronology of a recently discovered hydrothermal field at 14 45 n mid atlantic ridge two expeditions of the sevmorgeologija association 1991 1994 led to the discovery of two new hydrothermal sites on the mid atlantic ridge mar south of the 15 20 north fracture zone one around 14 45 n and the other around 14 42 n the northern one between 14 45 and 14 45 3 n has been studied in detail about 12 mounds have been mapped and 3 of them have been sampled using a large hydraulic grab sampler the largest one is about 200 m long and 200 m wide when progressively moving up on the slope of an uplifted block of the rift valley floor the sulphide samples have revealed ages ranging from about 10 ka to 60 ka the ages were obtained using the 230th 234u dating method used for chronological studies of diverse hydrothermal fields the general picture of this lateral location of the samples of different ages provides evidence of a shift in the focus of hydrothermal activity with time moreover there were rejuvenation stages of hydrothermal activity including black and white smokers

growth history of a diffusely venting sulfide structure from the juan de fuca ridge a petrological and geochemical study centimeter scale mineralogical and chemical analyses of a diffusely venting 280 c sulfide structure called roane from the mothra hydrothermal field on the juan de fuca ridge reveal a complex growth history these analyses document four well defined zones which from the exterior to the interior of the structure include a barite silica zone fossil worm tube zone a silica sulfide zone silica zone a sulfide silica zone outer sulfide zone and a sulfide gordaite silica zone inner sulfide zone these features are a product of a myriad of processes that include extensive mineral replacement ingress of seawater fracturing and breakout of hot hydrothermal fluids significant conductive cooling and the sustained broad scale outflow of warm fluids from the walls through a porous and permeable matrix roane lacks an open throughgoing chalcopyrite lined central conduit instead it hosts an anastomosing discontinuous network of tortuous channels within the interior of a sponge like matrix of amorphous silica sulfide sulfate and clay minerals megafaunal communities at the summit and sides of this mature diffusely venting chimney provide a constructional framework for new growth isolation of hydrothermal fluid from seawater during progressive fossilization of megafauna and the early formation of barite silica assemblages promote flow of higher temperature fluids within the interior continued isolation of interior higher temperature fluids through increased mineral precipitation and expansion of the structure leads to a zn sulfide pyrite dominated permeable matrix and a network of tortuous channels that form a central porous conduit this conduit is shielded by a weakly silicified metal sulfide inner wall and a strongly silicified outer wall the most outer portions of the walls are highly porous and sites of significant advection and mixing between hydrothermal fluids and seawater the mineralogy and chemistry of roane are strongly affected by ammonia ammonium buffering of the ph during cooling of the hydrothermal fluids the two major results of the buffering are 1 precipitation of zn sulfide at higher temperatures than are typical for bare rock systems leading to the correlation of cu zn cd and se and 2 increased deposition of amorphous silica and clay minerals

successional changes of middle miocene diatom assemblages in the northwestern pacific abstract miocene diatom assemblages in four sections in japan and at dsdp site 438 off the coast of northeast japan have been examined quantitatively in order to determine floral changes through time and to compare with the quantitative results from the equatorial pacific the areal distribution of some diatom levels reveals diachronous distribution across the subarctic boundary by the effect of a climatic wedge during the interval between 14 0 and 13 3 ma the middle miocene diatom assemblages turned from warm water assemblages to cold water assemblages and the number of first and last appearances of diatom species was highest at 13 8 ma the cold water diatom denticulopsis hustedtii increased abruptly in abundance at about 13 8 ma in the middle miocene the cyclic peaks in the abundance of denticulopsis hustedtii are recognized at 12 8 and 12 0 11 8 ma suggesting a cooling in the surface water temperatures during the late middle and early late miocene the pronounced abundances in both the cold water diatom denticulopsis hustedtii and the upwelling related diatom thalassionema nitzschioides are recognized and associated with the increased vigorous oceanic circulation and the increased upwelling caused by steepening of the latitudinal temperature gradient

biostratigraphy of the ulleung basin east sea japan sea abstract an interpretation of both micropaleontological and palynological analyses was carried out for eleven wells from the ulleung basin east sea japan sea based on bioevents of microfossil groups calcareous nannofossils foraminifera diatoms dinocysts spores and pollen twenty three datums are established the biostratigraphic and paleoenvironmental data indicate significant tectonic events such as subsidence 17 ma closing of the korea strait 15 ma and uplift in dolgorae deformed region 12 5 10 2 ma of the basin the high resolution sequence biostratigraphy correlated with wireline log and seismic data provided to be effective for constraining the interpretation of depositional systems tracts of the basin the paleogene reworked taxa in neogene section suggest that the provenance of sediments of the basin was southern offshore basins of korea and or southwestern japan kyushu area and the fukue basin

integration of ground based radar and satellite insar data for the analysis of an unexpected slope failure in an open pit mine abstract on 17 november 2016 an unexpected slope failure occurred in an undisclosed copper open pit mine the nature of the event urged for a thorough back analysis of slope monitoring data in order to assess its size and temporal evolution and to determine whether precursors potentially able to anticipate the failure were present to this aim satellite insar data spanning over the final 9 months before the event were in retrospect acquired and coupled with measurements from a ground based radar that was in use at the time of the failure although progressive deformation was detected by the ground based radar in correspondence of the two uppermost benches in the pit the satellite insar data revealed that the vast majority of the instability actually involved a large part of natural slope above the mine crest this sector was not visible by the ground based radar thanks to the short revisit time of the sentinel 1 mission clear slope accelerating creep was observed for the first time in satellite insar measurements over an open pit mine the delimitation of the area featuring accelerating creep behavior matched remarkably the source area of the failure as mapped in the field after the event considerations on the volume of the instability and on the development of the failure process both in space and time were consequently derived the results provided a clear example of the value of jointly using ground based and satellite interferometry to reduce the uncertainties inherent to the identification and characterization of impending catastrophic slope failures

redox state of seafloor hydrothermal fluids and its effect on sulfide mineralization abstract the redox conditions f o 2 f s 2 of seafloor hydrothermal fluids were calculated from dissolved h 2 and h 2 s concentrations at conditions of 300 and 350 c 71 409 bars and seawater salinity the results were compared with f o 2 f s 2 conditions estimated from black smoker mineralogy as reported by previous studies and our own investigations for various geological settings including the okinawa trough sediment rich hakurei and sediment poor jade fields the manus back arc basin felsic hosted pacmanus and basalt hosted vienna woods fields and the central indian ridge mafic ultramafic hosted kairei and basalt hosted edmond fields in most cases the calculated fluid f o 2 f s 2 conditions agree well with estimates from primary mineral assemblages and fes contents in sphalerite wurtzite this correlation suggests that the redox states of sulfide mineralization in chimneys typically reflect dissolved h 2 and h 2 s concentrations in vent fluids it should be noted that variable h 2 concentrations in vent fluids 0 01 19 mmol kg dominantly control not only fluid f o 2 but also f s 2 whereas the more uniform h 2 s concentrations 1 20 mmol kg have less of an influence on fluid f s 2 fluid sediment interaction elevates h 2 concentrations to over 1 mmol kg which sufficiently lowers f o 2 f s 2 to the pyrrhotite stability field however low h 2 s concentrations do not necessarily account for low f s 2 calculations for the h 2 poor 0 1 mmol kg and h 2 s rich 10 mmol kg fluids in some felsic hosted arc backarc systems indicate relatively high f o 2 f s 2 states consistent with the bornite pyrite chalcopyrite assemblages these redox conditions result from a combination of fluid mineral equilibria at relatively oxidizing conditions elevated h 2 s concentrations from magmatic degassing redox calculations at 350 c indicate that neither pyrite nor pyrrhotite is stable in the initial hot fluids of the tag and ultramafic hosted mid atlantic ridge systems due to the low h 2 s concentrations with cooling of these fluids either conductively or by interacting with seawater higher f s 2 and f o 2 result and fe sulfides are stable in agreement with the higher f o 2 f s 2 mineral assemblages observed

fault and stratigraphic controls on volcanogenic massive sulphide deposits in the strelley belt pilbara craton western australia abstract early archaean fe zn cu volcanogenic massive sulphide deposits of the strelley belt pilbara craton occur at the top of a volcanic dominated sequence at the interface of felsic volcanic rocks and siliceous laminites beneath an unconformity overlain by clastic sedimentary rocks the structure of the sulphur springs and kangaroo caves vms deposits is relatively simple with the present morphology reflecting original deposition rather than significant structural modification the rocks have been tilted giving an oblique cross sectional view of discordant high angle deep penetrating faults in the footwall which splay close to the zones of volcanogenic massive sulphide mineralization faults do not extend far into the overlying sedimentary cover indicating their syn volcanic and syn mineralization timing both the sulphur springs and kangaroo caves sulphide deposits are located within elevated grabens in a setting similar to massive sulphide mineralization in modern back are environments mineralization at sulphur springs and kangaroo caves is located at the edge of the grabens at the site of intersecting syn volcanic extensional faults

mineralogy sulphur isotope geochemistry and the development of sulphide structures at the broken spur hydrothermal vent site 29 10 n mid atlantic ridge a large collection of hydrothermal sulphides from the broken spur hydrothermal vent site including representative samples of mound sulphide materials has been characterized using optical mineralogy and sulphur isotope analysis young mound sulphides from broken spur have a pyrrhotite dominated mineralogy unusual for bare ridge vent systems however pyrrhotite is metastable and is ultimately converted to iron disulphides mature sulphides are indurated recrystallized and contain abundant quartz sulphide mound materials are developed by three major processes i coalescing of chimney structures ii accumulation of talus from mass wasting and iii precipitation and growth in response to hydrothermal flow progressive maturation of mound materials is by modification of primary textures development of mineralogical zoning and replacement of metastable phases sulphur isotope analysis of 35 mineral separates returned 34 s values of 0 5 to 3 2 these values are similar to those previously measured for broken spur and snakepit but are distinctly 32 s enriched compared to the tag active mound and some pacific sites seawater entrainment and sulphate reduction within the subsurface feeder zone below broken spur mounds do not appear to be important processes at broken spur in contrast to the tag active mound

internal structure and deformation of an unstable crystalline rock mass above randa switzerland part ii three dimensional deformation patterns the monitoring of slope displacements over time provides the basis for most rockslide early warning systems yet the prediction of catastrophic failure from these records is highly problematic and tenuous especially if the underlying kinematics and instability mechanism are poorly understood an example is the moving slope above the town of randa in the swiss alps this slope is considered typical of those in crystalline rock that lacks a natural highly persistent weakness plane dipping towards the valley that can serve as a through going detachment surface for kinematic release in part i the companion paper to this the findings from a comprehensive geological and geophysical investigation to image the internal structures of the unstable rock mass were presented in this paper we develop a kinematic model that describes the pattern of displacement vectors for the rock mass along these structures both on surface and at depth the displacements were estimated from 5 years of data from an extensive monitoring system which included surface geodetic and crackmeter measurements borehole inclinometer and extensometer measurements up to 120 m depth and microseismicity the results showed that the displacement field is highly heterogeneous internal deformation is accommodated by both shear and opening mode dislocation of faults and fracture zones which dip moderately to steeply into the slope microseismicity is most intense near the front of the scarp where surface translation in large part reflects the toppling of blocks accommodated by slip along the steeper dipping fractures the small displacement rates at the study site of up to 2 cm year coupled with a modest deviation of up to 15 from vertical of the boreholes posed severe problems for the estimation of horizontal displacements from the inclinometer data we describe the error analysis of these data in some detail since it is relevant for similar installations elsewhere conclusions drawn from this work highlight the importance of integrating various types of data in order to better understand the complex block kinematic processes whose evolution governs the long term progressive failure of unstable rock slopes

terrestrial laser scanning of rock slope instabilities this manuscript presents a review on the application of a remote sensing technique terrestrial laser scanning tls to a well known topic rock slope characterization and monitoring although the number of publications on the use of tls in rock slope studies has rapidly increased in the last 5 10 years little effort has been made to review the key developments establish a code of best practice and unify future research approaches the acquisition of dense 3d terrain information with high accuracy high data acquisition speed and increasingly efficient post processing workflows is helping to better quantify key parameters of rock slope instabilities across spatial and temporal scales ranging from cubic decimetres to millions of cubic metres and from hours to years respectively key insights into the use of tls in rock slope investigations include a the capability of remotely obtaining the orientation of slope discontinuities which constitutes a great step forward in rock mechanics b the possibility to monitor rock slopes which allows not only the accurate quantification of rockfall rates across wide areas but also the spatio temporal modelling of rock slope deformation with an unprecedented level of detail studying rock slopes using tls presents a series of key challenges from accounting for the fractal character of rock surface to detecting the precursory deformation that may help in the future prediction of rock failures further investigation on the development of new algorithms for point cloud filtering segmentation feature extraction deformation tracking and change detection will significantly improve our understanding on how rock slopes behave and evolve perspectives include the use of new 3d sensing devices and the adaptation of techniques and methods recently developed in other disciplines as robotics and 3d computer vision to rock slope instabilities research

active and relict sea floor hydrothermal mineralization at the tag hydrothermal field mid atlantic ridge the tag hydrothermal field is a site of major active and inactive volcanic hosted hydrothermal mineralization in the rift valley of the slow spreading mid atlantic ridge at 26 degree n the axial high is the principal locus of present magmatic intrusions the tag field contains three main areas of present and past hydrothermal activity 1 an actively venting high temperature sulfide mound 2 two former high temperature vent areas 3 a zone of low temperature venting and precipitation of fe and mn oxide deposits the volcanic centers occur at the intersections between ridge axis parallel normal faults and projected axis transverse transfer faults the intersections of these active fault systems may act as conduits both for magmatic intrusions from sources beneath the axial high that build the volcanic centers and for hydrothermal upwelling that taps the heat sources radiometric dating of sulfide samples and manganese crusts in the hydrothermal zones and dating of sediments intercalated with pillow lava flows in the volcanic center adjacent to the active sulfide mound indicate multiple episodes of hydrothermal activity throughout the field driven by heat supplied by episodic intrusions over a period of at least 140 times 10 sup 3 yr the sulfide deposits are built by juxtaposition and superposition during relatively long residence times near episodic axial heat sources counterbalanced by mass wasting in the tectonically active rift valley of the slow spreading oceanic ridge hydrothermal reworking of a relict hydrothermal zone by high temperature hydrothermal episodes has recrystallized sulfides and concentrated the first visible primary gold reported in a deposit at an oceanic ridge

a new practical method for prediction of geomechanical failure time abstract predicting the failure time of geo hazards is an important rock mechanics problem we first evaluated the validity of the inverse velocity inv method to predict failure time of rock mass and landslides this method utilizes rates of displacement or strain to predict the actual failure time tf so the value of total displacement or strain before failure is not crucial second we developed a new method for computing failure time predictions based on the slope gradient to predict tf termed the slo method finally a simple conceptualised model representing safe and unsafe predictions was proposed to validate these hypotheses prediction of rock mass failure in the asamushi and vaiont landslides in situ studies was conducted furthermore laboratory conditions were incorporated into the research which include predictions using circumferential strain and axial strain from uniaxial compression creep test on shikotsu welded tuff swt and predictions of failure time for inada granite under brazilian creep tests it was found that the slo method is better than the inv method slo gave safe predictions in all the cases in contrast inv tends to give unsafe predictions predicted failure time tfp tf our findings reveal that predictions using circumferential strain are better than those made using axial strain for swt and notably given failure with very short tertiary creep the methods tend to show limited reliability however the slo method could find extensive application in predicting failure time of geo hazards for instance roof wall failure in mines etc

mineralogical and geochemical features of sulfide chimneys from the meso zone central indian ridge hydrothermal activity is fairly well documented from most mid ocean ridges however despite various efforts there is only one hydrothermal field recognized so far in the indian ocean products of former hydrothermal activity were sampled in the fourth segment of the central indian ridge cir north of the rodriguez triple junction rtj near 23 s the mineralized area referred to as meso zone covers an area of about 0 6 km2 and is located at a water depth of 2850 m close to the height of a neovolcanic intrarift ridge hydrothermal mineralization is structurally controlled by fissures and cracks running both parallel and orthogonal to the general strike direction of the cir axis 152 n sulfides of the meso zone formed over a period of at least 30 000 years hydrothermal activity ceased 10 000 years ago detailed mineralogical and geochemical studies of sulfides establish the growth and decay of chimney structures which are mainly composed of pyrite marcasite and chalcopyrite chimneys show high concentrations of base metals particularly cu and fe more than 40 wt as well as high trace element contents like co up to 0 24 wt and as 1 wt in contrast sphalerite is rarely observed which is attributed to replacement and refining processes during the weathering and physical disintegration of the hydrothermal products the zn content is generally low 1 wt only selected samples show higher zn concentrations up to 7 9 wt remnants of chimney structures are characterized by the absence of sulfates but they contain minor amounts of amorphous silica

pliocene paleoclimatic interpretation of dsdp site 580 nw pacific using diatoms abstract high resolution quantitative diatom data are tabulated for the early part of the late pliocene 3 25 to 2 08 ma at dsdp site 580 in the northwestern pacific sample spacing averages 11 k y between 3 1 and 2 8 ma but increases to 14 to 19 k y prior to 3 1 ma and after 2 8 ma q mode factor analysis of the middle pliocene assemblage reveals four factors which explain 92 4 of the total variance of the 47 samples studied between 3 25 and 2 55 ma three of the factors are closely related to modern subarctic transitional and subtropical elements while the fourth factor which is dominated bycoscinodiscus marginatus and the extinct pliocene speciesneodenticula kamtschatica appears to correspond to a middle pliocene precursor of the subarctic water mass knowledge of the modern and generalized pliocene paleoclimatic relationships of various diatom taxa is used to generate a paleoclimate curve twt based on the ratio of warm water subtropical to cold water diatoms with warm water transitional taxa thalassionema nitzschioides thalassiosira oestrupii andcoscinodiscus radiatus factored into the equation at an intermediate 0 5 value the twt ratios at more southerly dsdp sites 579 and 578 are consistently higher warmer than those at site 580 throughout the pliocene suggesting the validity of the ratio as a paleoclimatic index diatom paleoclimatic data reveal a middle pliocene 3 1 to 3 0 ma warm interval at site 580 during which paleotemperatures may have exceeded maximum holocene values by 3 5 5 c at least three times this middle pliocene warm interval is also recognized by planktic foraminifers in the north atlantic and it appears to correspond with generalized depleted oxygen isotope values suggesting polar warming the diatom twt curve for site 580 compares fairly well with radiolarian and silicoflagellate paleoclimatic curves for site 580 planktic foraminiferal sea surface temperature estimates for the north atlantic and benthic oxygen isotope curves for late pliocene although higher resolution studies on paired samples are required to test the correspondence of these various paleoclimatic indices

silica diagenesis of neogene diatomaceous and volcaniclastic sediments in northern japan marine diatomaceous siliceous sediments in neogene sections of northern japan contrast with the monterey shale of california in containing many intercalations of acidic volcaniclastic sediments diagenesis of these sediments from deep boreholes and surface sections was investigated three diagenetic zones biogenic opal opal ct and quartz zones are recognized in siliceous sediments corresponding roughly to amorphous silica low cristobalite and quartz zones in acidic vitric volcaniclastic sediments opal ct consists almost exclusively of silica and water while low cristobalite contains appreciable amounts of a1 ca na and k in subsurface sections values of d 101 spacing of opal ct decrease progressively with increasing burial depth the progressive ordering is not associated with additional silica cementation in surface sections the behaviour of d 101 spacing is complicated owing to the modification of the progressive ordering developed during burial diagenesis by later silica cementation during uplift the cementing opal ct is probably precipitated from percolating groundwater which dissolves siliceous skeletons in porous diatomaceous mudstones overlying the opal ct porcellanite opaline cherts that form during burial diagenesis are designated as early opaline chert while those which form during uplift are later opaline chert the later opaline chert contains two groups of opal ct one is progressively ordered opal ct and the other is additionally cemented opal ct with higher d 101 spacing than that in the host porcellanite in diatomaceous siliceous sediments early opaline chert is scarce most if not all opaline cherts in surface sections are of later origin

identifying rock slope failure precursors using lidar for transportation corridor hazard management abstract in the thompson and fraser river valleys rockfall and rockslides are a hazard for railway traffic in the region in june 2013 a 2600 m 3 rockslide occurred in the white canyon causing damage to infrastructure and interruption to service in the year preceding this failure the slope was monitored using terrestrial light detection and ranging lidar as part of the railway ground hazards research program initiative the purpose of this study is to evaluate a hazard management strategy for transportation corridors exposed to steep slopes involving the identification of rockfall precursors prior to significant slope failures for this failure deformation was observed in the seven months preceding collapse with an accelerating period occurring in the final 28 days a distinct pattern of smaller rockfalls was observed around the perimeter of the deforming rock block as well as loss of surficial material over the slides tension crack this study shows that with lidar monitoring precursors to rock slope failures can be identified allowing for better rock slope hazard management by focusing attention on areas with the highest probability of failure

the fall dump a new perspective on the role of a shade flora in the annual cycle of diatom production and export flux investigations of diatom fluxes recorded in laminated sediments using scanning electron microscope techniques together with evidence from sediment trap studies have contributed to a reappraisal of the annual cycle of diatom production and export flux we propose that where there is a strong seasonal thermocline and nutricline a number of diatoms hitherto regarded as typical sparse summer flora characteristic of oligotrophic waters are able to generate substantial production at depth these species including rhizosolenia spp stephanopyxis palmeriana thalassiothrix spp and some coscinodiscus spp may represent a shade flora that have adapted to grow in low light conditions and or to regulate their buoyancy to move between a deep nutrient source and the euphotic zone although rates of growth and primary production are substantially lower than species characteristic of spring bloom or upwelling conditions the total primary production integrated over the several month period of summer stratification may be as significant as the spring bloom or greater the term fall or autumn bloom as a counterpart of the spring bloom is therefore a misnomer whereas the spring bloom involves a rapid burst of reproduction and sedimentation the fall dump is the sedimentation of a long lived episode of production lasting the duration of the seasonal thermocline and triggered by the fall winter mixing that breaks down stratification the fall dump may produce as much or in some cases more export production than the spring bloom the results of this study suggest that a reorientation of thinking on diatom ecology and palaeoecology may be required

integration of advanced monitoring and numerical modeling techniques for the complete risk scenario analysis of rockslides the case of mt beni florence italy on december 28 2002 a landslide occurred on the eastern flank of mt beni florence italy on a slope where jointed basalts and ophiolitic breccias overlie mesozoic limestones calcari a calpionelle formation the collapse was preceded by several forewarning signals the evolution of the slope deformation was the most important of them and its analysis was the starting point for a risk scenario assessment in fact during the management of the emergency period which began on april 13 2002 in effort to evaluate the actual extension of the landslide the distribution of the displacements within the mass its kinematical characteristics and its spatial and temporal evolution data obtained by means of geomechanical surveys laboratory analyses geotechnical investigations geophysical surveys seismic and gbinsar monitoring systems distometric and automatic and distinct element numerical modeling were integrated thus it has been possible to provide public authorities with all necessary information to plan suitable measures for risk management and reduction after the event the study was completed with a runout back analysis that highlighted successes and failures of the predictive investigations

sulfide mineralization in an ultramafic rock hosted seafloor hydrothermal system from serpentinization to the formation of cu zn co rich massive sulfides abstract the rainbow vent field is an ultramafic rock hosted seafloor hydrothermal system located on the mid atlantic ridge issuing high temperature acidic metal rich fluids hydrothermal products include cu zn co rich massive sulfides with characteristics comparable to those found in mafic volcanic hosted massive sulfide deposits petrography mineralogy and geochemistry of nonmineralized and mineralized rocks sampled in the rainbow vent field indicate that serpentinized peridotites host the hydrothermal vent system but serpentinization reactions occurred prior to and independently of the sulfide mineralization event the onset of sulfide mineralization is reflected by extensive textural and chemical transformations in the serpentine group minerals that show clear signs of hydrothermal corrosion element remobilization is a recurrent process in the rainbow vent field rocks and during simple peridotite serpentinization ni and cr present in olivine and pyroxene are incorporated in the pseudomorphic serpentine mesh and bastite respectively ni is later remobilized from pseudomorphic serpentine into the newly formed sulfides as a result of extensive hydrothermal alteration bulk rock geochemistry and correlation coefficients discriminate the different processes serpentinization sulfide mineralization and superficial seafloor low temperature processes related to the circulation of seawater e g carbonatization sulfide oxidation and b and u uptake

forecasting giant catastrophic slope collapse lessons from vajont northern italy rapid giant landslides or sturzstroms are among the most powerful natural hazards on earth they have minimum volumes of similar to10 6 10 7 m 3 and normally preceded by prolonged intervals of accelerating creep are produced by catastrophic and deep seated slope collapse loads similar to1 10 mpa conventional analyses attribute rapid collapse to unusual mechanisms such as the vaporization of ground water during sliding here catastrophic collapse is related to self accelerating rock fracture common in crustal rocks at loads similar to1 10 mpa and readily catalysed by circulating fluids fracturing produces an abrupt drop in resisting stress measured stress drops in crustal rock account for minimum sturzstrom volumes and rapid collapse accelerations fracturing also provides a physical basis for quantitatively forecasting catastrophic slope failure c 2003 elsevier science b v all rights reserved

insights into tide related variability at seafloor hydrothermal vents from time series temperature measurements abstract thermocouple thermistor array packages and an in situ gamma detector were deployed in 1994 at two vent sites on the northern cleft segment of the juan de fuca ridge continuous records of fluid temperatures were obtained in four separate locations over a period of 5 5 months and these data were supplemented by current meter observations made 2 5 km to the south within the axial valley temperatures measured at a location of focused high temperature flow showed that 1 the maximum temperature in the chimney was stable and did not exhibit tide related variability 2 temperatures within the chimney wall were variable on time scales of minutes indicating rapid shifts in amounts of cold seawater or hot vent fluid flowing across chimney walls and 3 the stable maximum temperature within the chimney conduit was 9 c less than the maximum fluid temperature recorded at the vent site during the same time interval and thus stable high temperatures within chimneys are not necessarily indicative of the maximum temperature within the vent structure or the hydrothermal system time series records from areas of diffuse flow indicate modulation of temperature and total radioactivity by tidally induced changes in bottom currents spectra of the current meter record and temperature records are similar with spectral peaks observed at 12 4 h 16 17 h inertial peak and 4 5 days phases between maxima in current tide and temperature records are consistent with temperature changes resulting from periodic shifts in currents from north to south and the subsequent northward or southward advection of warm fluids venting from multiple local sources periodic 12 4 h variability of temperature was also recorded by a thermocouple buried 1 cm within one of the deposits and is likely a result of periodic variations in the temperature at the boundary of the highly conductive sulfide deposit the time series results presented demonstrate the need for measuring and considering the effects of local currents when investigating causes of temporal variability within seafloor hydrothermal systems

development and application of a pseudo 3d pit slope displacement map derived from ground based radar slope monitoring plays an important role in the risk management of large open pit slopes historically displacement data derived from measuring geodetic prisms have been relied upon to delineate the boundaries of potential slope hazards however that data can be limited by its point measurement nature localized displacements at each prism may be misinterpreted when extended to the behavior of the entire slope and important displacements between prisms may be overlooked new technologies like ground based radar can provide high resolution full area coverage of a slope in combination with near real time acquisition and millimeter precision as a line of sight instrument these tools provide data on displacement magnitudes and rates but not true direction hence limiting their use in gaining understanding of the kinematics and behavior of the moving slope this paper describes a novel experiment in which two ground based synthetic aperture radar systems were simultaneously deployed to record continuous line of sight displacements of an open pit slope in stereo the displacement vectors were combined to create a pseudo 3 d displacement map for the slope which was subsequently used to interpret the influence of a major fault and the rock mass fabric in promoting different kinematic responses the data collected demonstrates that an improved understanding of the 3 d kinematics of a large rock slope can be achieved using advanced state of the art monitoring techniques to aid mine design

a model for growth of steep sided vent structures on the endeavour segment of the juan de fuca ridge results of a petrologic and geochemical study petrologic and geochemical studies of vent solids from the main endeavour field mef and the high rise field hrf juan de fuca ridge demonstrate that the steep sided vent structures characteristic of these sites form dominantly by flange growth combined with diffuse flow through sealed portions of structures and incorporation of flanges into structures geochemical calculations suggest that the prevalence of amorphous silica and flanges in endeavour deposits is the result of conductive cooling of vent fluids that have high concentrations of ammonia at endeavour as the temperature of vent fluid decreases ammonia ammonium equilibrium buffers ph and allows more efficient deposition of sulfide minerals and silica from fluids that have a higher ph than conductively cooled ammonia poor fluids present at most other unsedimented mid ocean ridge vent sites deposition of silica stabilizes flanges and allows structures to attain large size it also leads to diffuse flow and further conductive cooling by reducing the permeability and porosity of the structures and of feeder zones thus decreasing entrainment of seawater most inactive vent samples recovered from areas peripheral to the hrf and mef are similar to barite silica rich samples from the explorer ridge and axial seamount and likely formed from precipitation of silica and barite on a biological substrate active white smoker chimneys from the clam bed field located south of the hrf are pyrrhotite rich and likely formed from vent fluids that are depleted in zn and cd and enriched in pb and ba relative to fluids exiting trans atlantic geotraverse tag and cleft segment white smoker chimneys

twenty ninth canadian geotechnical colloquium the role of advanced numerical methods and geotechnical field measurements in understanding complex deep seated rock slope failure mechanisms the underlying complexity associated with deep seated rock slope stability problems usually restricts their treatment to phenomenological studies that are largely descriptive and qualitative quant

use of an integrated finite discrete element method discrete fracture network approach to characterize surface subsidence associated with sub level caving abstract the lkab kiruna sub level cave mine located in kiruna sweden is one of the most well studied sub level cave mines due to proximity of the city to the hanging wall the mine has developed a comprehensive surface deformation monitoring program which is perhaps unparalleled in the mining industry this surface monitoring scheme provides an excellent data source with which to constrain numerical modelling in this study a finite discrete element modelling approach coupled with a discrete fracture network fdem dfn is utilized to analyse the kiruna hanging wall surface subsidence with an emphasis on investigating the influence of discontinuity persistence and spacing the fdem dfn data interpretation uses a variety of novel approaches including time displacement hanging wall deformation characterization numerical inverse velocity analysis and virtual hanging wall inclinometer simulation to improve our understanding of the extent and mechanism of hanging wall failure with mine advance the simulated displacements correspond closely to the actual field data illustrating the ability of the proposed approach to reproduce sub level cave behaviour three distinct time displacement phases namely regressive progressive and steady state are observed in the fdem dfn models the paper also reviews the potential application of the inverse velocity method and virtual inclinometers in characterizing sub surface brittle failure associated with sub level caving

deep seated failure propagation in a fractured rock slope over 10 000 years the la clapiere slope the south eastern french alps abstract the la clapiere area tinee valley alpes maritimes france is a typical large complex unstable rock slope affected by deep seated gravitational slope deformations dgsd with tension cracks scarps and a 60 106 m3 rock slide at the slope foot that is currently active the slope surface displacements since 10 ka were estimated from 10be ages of slope gravitational features and from morpho structural analyses it appears that tensile cracks with a strike perpendicular to the main orientation of the slope were first triggered by the gravitational reactivation of pre existing tectonic faults in the slope a progressive shearing of the cracks then occurred until the failure of a large rock mass at the foot of the slope by comparing apertures variations and changes in direction between cracks of different ages three phases of slope surface displacement were identified 1 an initial slow slope deformation spreading from the foot to the top characterized by an average displacement rate of 4 mm yr 1 from 10 5 6 ka bp 2 an increase in the average displacement rate from 13 to 30 mm yr 1 from the foot to the middle of the slope until 3 6 ka bp and 3 development of a large failure at the foot of the slope with fast displacement rates exceeding 80 mm yr 1 for the last 50 years the main finding of this study is that such a large fractured slope destabilization had a very slow displacement rate for thousands of years but was followed by a recent acceleration the results obtained agree with several previous studies indicating that in situ monitoring of creep of a fractured rock slope may be useful for predicting the time and place of a rapid failure

the changing vision of marine minerals abstract non fuel marine minerals are reviewed from the perspective of resources and their value as active analogs that can advance understanding of types of ancient ore deposits that formed in marine settings the theory of plate tectonics is the largest influence in expanding our vision of marine minerals and in developing our understanding of geologic controls of mineralization in space and time prior to the advent of plate tectonics we viewed the ocean basins as passive sinks that served as containers for particulate and dissolved material eroded from land this view adequately explained marine placer deposits heavy minerals and gems aggregates sand and gravel and precipitates phosphorites and manganese nodules although numerous sites of placer mineral deposits are known on continental shelves worldwide current activity pertains to diamond mining off southwestern africa tin mining off southeastern asia and intermittent gold mining off northwestern north america which are all surpassed economically by worldwide recovery of marine sand and gravel in turn dwarfed by offshore oil and gas with the advent of plate tectonics plate boundaries in ocean basins are recognized as active sources of mineralization in the form of hydrothermal massive sulfide deposits and proximal lower temperature deposits hosted in oceanic crust mafic at ocean ridges and felsic at volcanic island arcs and of magmatic ni cu sulfide chromite and pge deposits inferred to be present in the oceanic upper mantle lower crust based on their occurrence in ophiolites some 300 sites of hydrothermal active and relict mineralization most of them minor are known at this early stage of seafloor exploration on ocean ridges in fore arc volcanoes at back arc spreading axes and in arc rifts deposits formed at spreading axes and transported off axis by spreading are present in oceanic lithosphere but are virtually unknown the tag trans atlantic geotraverse hydrothermal field in the axial valley of the mid atlantic ridge latitude 26 n is considered to exemplify a major volcanogenic massive sulfide vms deposit forming at a spreading axis the most prospective of these occurrences lie within the 200 nautical mile 370 km wide exclusive economic zone eez of the nations of the volcanic island arcs of the western pacific where metal content of massive sulfides ag au ba cu pb sb zn exceeds that at ocean ridges plate tectonics early provided a framework for mineralization on the scale of global plate boundaries and is providing guidance to gradually converge on sites of mineralization through regional scales of plate reorganization with the potential to elucidate the occurrence of individual deposits e g eocene carlin type gold deposits investigation of the spectrum of marine minerals as active analogs of types of ancient mineral deposits is contributing to this convergence consideration of questions posed by brian skinner 1997 of what we do and do not know about ancient hydrothermal mineral deposits demonstrates the ongoing advances in understanding driven by investigation of marine minerals

the influence of spreading rate basement composition fluid chemistry and chimney morphology on the formation of gold rich sms deposits at slow and ultraslow mid ocean ridges seafloor massive sulphide sms deposits are variably enriched in precious metals including gold however the processes invoked to explain the formation of auriferous deposits do not typically apply to mid ocean ridge settings here we show a statistically significant negative correlation between the average gold concentration of sms deposits with spreading rate at non sedimented mid ocean ridges deposits located at slow spreading ridges 20 40 mm a have average gold concentrations of between 850 and 1600 ppb however with increasing spreading rate up to 140 mm a gold concentrations gradually decrease to between 50 and 150 ppb this correlation of gold content with spreading rate may be controlled by the degree and duration of fluid rock interaction which is a function of the heat flux crustal structure faulting and the permeability of the source rocks deposits at ultraslow ridges including ultramafic hosted deposits are particularly enriched in gold this is attributed to the higher permeability of the ultramafic source rocks achieved by serpentinisation and the inherent porosity of serpentine minerals combined with relatively high gold concentrations in peridotite compared with mid ocean ridge basalt variations in fluid chemistry such as reducing conditions and the potential for increased sulphur availability at ultramafic hosted sites may also contribute to the high concentrations observed beehive chimneys which offer more favourable conditions for gold precipitation may be more prevalent at ultramafic hosted sites due to diffuse low velocity venting compared with more focussed venting at basalt hosted sites

seamount formation and associated caldera complex and hydrothermal mineralization in ancient oceanic crust troodos ophiolite cyprus abstract the inter graben zone between the solea and mitsero grabens in the northern part of the troodos ophiolite cyprus displays igneous tectonic and physiographic features that are characteristic of seamount volcanism at modern oceanic spreading centers in this zone the 200 m high alestos hill volcanic edifice consisting of pillow lavas with preserved lava tubes and cone sheet intrusions is interpreted to have developed as a seamount fed by a late stage off axis shallow level gabbroic pluton that was intrusive into young oceanic crust concentric cone sheet intrusions and associated faults and shear zones in and around the alestos hill seamount collectively form a seafloor caldera complex which probably formed during the extrusion of lavas and subsequent cauldron subsidence over the gabbroic pluton the ene trending elongated massive sulfide ore deposit formation in the alestos memi area represents a focused upflow zone for hydrothermal fluids driven by the same off axis gabbroic intrusion responsible for formation of the alestos hill seamount the ene trending and up to 150 m wide alestos memi fault zone dissects the elongated ore body in a dextral sense and might have provided a high permeability conduit in the upper crust for upwelling hydrothermal flow at the time of magmatism the geometry of this fault zone and its kinematic relations with a n s striking alestos forest normal fault in the west are suggestive of its transfer fault origin reminiscent of mineralized transfer faults found at the mid atlantic ridge the active tag hydrothermal mound with massive sulfide deposits that is located on a small volcanic dome 3 km off axis and along a transfer fault in the trans atlantic geotraverse tag area at 26 n provides a modern analogue for the alestos hill seamount and associated faulting and mineralization in the ancient oceanic crust of the troodos ophiolite these findings indicate that off axis magmatism played a major role in crustal accretion hydrothermal alteration and ore mineralization during the late stage evolution of the troodos ophiolite

divining gold in seafloor polymetallic massive sulfide systems hydrothermal fluids on the modern seafloor are important carriers of base and precious metals in a wide range of volcanic and tectonic settings the concentrations and distribution especially of gold and silver in associated seafloor massive sulfide sms deposits are strongly influenced by variable source rocks fluid chemistry and precipitation mechanisms compositional data of 130 sms deposits around the world show a large range of gold and silver grades in part reflecting strong buffering of the hydrothermal fluids by their host rocks geochemical reaction path modeling shows that in most cases the investigated hydrothermal fluids are undersaturated with gold and silver and solubilities can be orders of magnitude higher than the au and ag concentrations measured in the corresponding fluids precipitation of gold during conductive cooling of mid ocean ridge black smoker mor fluids occurs at low temperatures but can be very rapid with 90 of the gold deposited in the first 25 c of cooling below 150 c the result is a zn au polymetallic assemblage with au and ag deposited at the same time together with pb and sulfosalts in ultramafic dominated um systems the strongly reduced hydrothermal fluids promote the deposition of gold at higher temperatures and explain the correlation between gold and copper in these deposits in this case the lower stability of the auhs complex at low o2 buffered by fayalite magnetite and quartz results in gold deposition at 250 c with early bornite and chalcopyrite and before sphalerite and silver producing a high temperature cu au assemblage in sediment hosted sed systems the much higher ph stabilizes au hs 2 and keeps gold in solution to very low temperatures after the precipitation of chalcopyrite sphalerite and galena resulting in au poor polymetallic sulfides and very late stage deposition of gold commonly with amorphous silica in arc related arc systems gold deposition occurs at somewhat higher temperatures than in the mor case in part because the fluids start with higher gold concentrations this can be explained by probable direct magmatic contributions and the high o2 of the fluids which promotes the solubility of gold at the source during cooling gold precipitates at about 160 c with sphalerite tennantite silver and galena resulting in an au rich polymetallic sulfide assemblage the mixing of hydrothermal fluids with seawater generally causes oxidation and eventually a decrease in the ph at a mixing ratio of 1 1 causing an initial increase in the solubility of gold and silver this can delay gold deposition from aqueous species to very low temperatures these complex systematics make prediction of au and ag grades difficult however important new data are coming to light on the actual concentrations of the precious metals in hydrothermal fluids in particular the input of magmatic volatiles and leaching of pre existing gold can lead to significant increases in the au and ag concentrations of the venting fluids and earlier deposition in several cases it appears that at least part of the gold load is present as nanoparticles in suspension allowing bulk gold concentrations that may be far in excess of liquid saturation boiling at the seafloor is now widely observed even at great water depths close to the critical point of seawater model calculations of phase separation during boiling show the competing effects on gold solubility of h2 h2s and co2 partitioning into the vapor which can result in highly variable gold to base metal ratios in the deposits flashing of the vent fluids into steam at high temperatures is also commonly observed and can lead to spectacular au grades with a strong cu au association in the deepest and hottest vents

a laminated sediment sequence from the northern north atlantic ocean and its climatic record a remarkable 3 m thick sequence of laminated diatom ooze ldo has been recovered in the north atlantic ocean the ldo is monospecific and consists of the pennate diatom thalassiothrix longissima biostratigraphy and benthic oxygen isotope stratigraphy indicate that the ldo was deposited during substage 5e eem in analogy to recent observations of massive surface concentrations of diatoms in the equatorial pacific and neogene examples we suggest that the ldo represents numerous depositional events of thalassiothrix mats that were physically accumulated at a subarctic convergence front the occurrence of the ldo combined with other climate proxies indicates substantial geographic stability of ocean fronts in the north atlantic during substage 5e

native gold and gold rich sulfide deposits in a submarine basaltic caldera higashi aogashima hydrothermal field izu ogasawara frontal arc japan sulfide deposits with extremely high au concentrations up to 275 ppm avg 102 ppm n 15 high au ag ratios 0 24 n 15 and low cu cu zn ratios 0 03 n 15 were discovered in 2015 in active hydrothermal fields at a water depth of 760 m in a basalt dominated submarine caldera in the izu ogasawara frontal arc japan native gold grains occur in massive sulfide fragments concretions and metalliferous sediments from a sulfide mound 40 m across and 20 m high with up to 30 m high black smoker chimneys tiny native gold grains up to 14 m in diameter are mainly present in sulfide fallouts from chimney orifices and plumes larger native gold grains up to 150 m long occur mostly as discrete particles and or with amorphous silica and sulfides the larger gold grains are interpreted to represent direct precipitation from au bearing hydrothermal fluids circulating in and or beneath the unconsolidated sulfide mound deposits sulfur isotope compositions from a limited number of sulfide separates n 4 range from 4 3 to 5 8 34s similar to the quaternary volcanic rocks of the arc barite separates have values of 22 2 and 23 1 close to modern seawater values and indicate probable seawater sulfate origin the cu zn and pb concentrations in bulk samples of sulfide rich rocks are similar to those of volcanogenic massive sulfides formed in continental crustal environments the gold is interpreted to have formed by low temperature hydrothermal activity perhaps genetically different from systems with documented magmatic contributions or from seafloor hydrothermal systems in other island arc settings its presence suggests that basalt dominated submarine calderas situated on relatively thick continental crust in an intraoceanic arc setting such as the higashi aogashima knoll caldera may be perspective for gold mineralization

oceanographic variations over the last 150 000 yr in the japan sea and synchronous holocene with the northern hemisphere abstract the paleo hydrography in the japan sea called a mini ocean was reconstructed based on the high resolution analysis of diatom assemblages over the period of 150 000 yr the decrease of diatom fertilization in the japan sea when it was isolated from surrounding seas due to the drop of sea level during the glacial to stadial phase resulted in dissolution and or extremely low diatom production in the northern cores in the subarctic water masses the annual td derived paleo ssts c were controlled by the fluctuations of 2 kyr and 4 kyr periods at intervals of 20 kyr and 40 kyr over the last 160 kyr bp respectively a 23 kyr cycle is recognized during the periods from 140 ka to 100 ka according to the wavelet analysis after temperature and sea level increased both at 133 128 ka 60 53 ka and 15 10 ka oceanic warm water diatom species predominated at 127 119 ka and after 9 cal ka in the interstadial phase at 21 3 16 9 ka and 12 9 9 8 ka sea level and salinity increased as the transgression developed at 10 0 7 0 ka the oceanic association shifted from cold water species in the stadial period to warm water ones in the interstadial phase the fluctuations of td derived ssts c on century to millennial time scales during the holocene are well correlated with abrupt climatic events that different paleoclimatic proxies record in many regions of the northern hemisphere

hydrothermal vents near a mantle hot spot the lucky strike vent field at 37 n on the mid atlantic ridge the lucky strike hydrothermal field occurs in the summit basin of a large seamount that forms the shallow center of a 65 km long ridge segment near 37 n on the mid atlantic ridge the depth and chemistry of the ridge segment are influenced by the azores hot spot and this hydrothermal field is the first atlantic site found on crust that is dominated by a hot spot signature multiple hydrothermal vents occur over an area of at least 300 m by 700 m vent morphologies range from flanges and chimneys with temperatures of 200 212 c to black smoker chimneys with temperatures up to 333 c cooler fluids from northern vents have higher chlorinities and lower gas volumes while hotter southern fluids have chlorinities 20 below seawater with higher gas volumes suggesting phase separation has influenced their compositions all gas volumes in fluids are higher than those at tag and snake pit hydrothermal fields black smokers exhibit their typical mineralogy except that barite is a major mineral particularly at lower temperature sites which contrasts with previously investigated atlantic sites the fluid chemistry distribution of the relict sulfide deposits on the seamount summit in the areas investigated using dsv alvin and contact relationships between active vent sites and surrounding basaltic and sulfide substrate suggest that the hydrothermal system has a long history and may have recently been rejuvenated fauna at the lucky strike vent sites are dominated by a new species of mussel and include the first reported sea urchins the lucky strike biological community differs considerably from other vent fauna at the species level and appears to be a new biogeographic province the lucky strike field helps to constrain how variations in the basaltic substrate influence the composition of hydrothermal fluids and solids because basalt compositions at lucky strike are 10 30 times enriched in incompatible elements compared to other atlantic hydrothermal sites such as tag snake pit and broken spur the incompatible element

mineralogy and geochemistry of hydrothermal precipitates from kairei hydrothermal field central indian ridge the kairei hydrothermal field was the first confirmed active submarine hydrothermal system on the central indian ridge it has been suggested to be related to mafic as well as ultramafic host rocks based on vent fluid composition and the presence of ultramafic rocks in its vicinity in this study detailed geochemical and mineralogical analyses have been carried out on the hydrothermal precipitates from the kairei vent field in order to investigate the possible presence of indications for an ultramafic substrate at this vent site the studied samples included fragments of sulfide chimneys massive sulfides and talc bearing and silicified breccias three mineralization stages were identified 1 a high temperature stage consisting largely of chalcopyrite isocubanite and pyrite 2 a medium to low temperature stage characterized by the mineral assemblages of sphalerite and pyrite and 3 a weathering stage characterized by secondary cu sulfides bornite digenite covellite and idaite fe oxihydroxides opal a and cu chloride paratacamite and atacamite the sulfide geochemistry is characterized by high concentrations of cu and zn cu zn up to 29 3 wt n 17 and au mean 5 28 ppm n 17 which is comparable to results from seafloor massive sulfides collected from ultramafic hosted sites in the atlantic ocean but differs from those of typical mafic hosted deposits the high concentrations of cu and au at the kairei hydrothermal field could be an indication for the involvement of ultramafic rocks in the subseafloor ultramafic hosted au rich sulfide deposits may not be restricted to the atlantic ocean and may be common along all slow and intermediate spreading ridges

the formation of gold rich seafloor sulfide deposits evidence from the beebe hydrothermal vent field cayman trough the beebe vent field bvf in the cayman trough has built an auriferous massive sulfide deposit on the ultra slow spreading mid cayman spreading centre the genesis of auriferous sulfide deposits at mid ocean ridges is not fully understood although there is a growing recognition that slow and ultra slow spreading centres are conducive to gold mineralization analysis of hydrothermal precipitates from the bvf indicates that the highest gold contents are present within beehive diffusers which have developed a highly porous pyrrhotite framework the beehive structure allows vent fluids to effuse slowly while allowing ingress of seawater to cool the fluid the prevalence of pyrrhotite in the beehive samples lack of sulfates association between pyrrhotite and gold grains and results of thermodynamic modelling suggests gold precipitation occurred under highly reduced conditions even during mixing with seawater in contrast high temperature chimneys with a single orifice maintain high temperatures to the primary vent orifice and much of the gold is lost to seawater despite this both chimney types are relatively gold enriched which points to a further underlying cause for high gold at the bvf such as interaction of hydrothermal fluids with ultramafic lithologies in the basement the final gold composition of the deposit is partially controlled by loss of gold during mass wasting of the material with gold depletion most prevalent in blocks formed at beehive type chimneys the bvf demonstrates that the overall gold content of a massive sulfide deposit is the sum of basement precipitation and surface processes

understanding the kinematic behavior of the active gascons rockslide from in situ and satellite monitoring data abstract the monitoring of the 410 000 m3 coastal gascons rockslide began in 2009 this paper presents and analyzes combined in situ and satellite based monitoring data to interpret the kinematic behavior of the slide and the evolution of the rockslide and the possible mechanisms that can lead to an accelerating phase of movement the available data are 1 relative displacements measured by thirteen crackmeters and manually with an extensometer tape 2 absolute displacements obtained from inclinometers and vertical shape accelerometer arrays in boreholes total station surveys and satellite based point target analysis insar pta 3 the settlement of the railway ballast monitored by two horizontal shape accelerometer arrays 4 groundwater pressures from nine vibrating wire piezometers and 5 weather conditions the study indicates that the role of water on displacements varies spatially within the rockslide the rockslide s kinematic behavior enables us to develop evolution scenarios of the rockslide which could be useful to conduct a risk analysis this leads to the identification of critical zones for railroad safety the unique set of monitoring data helps to elucidate the complexity of the rockslide s behavior

measurement and interpretation of long term deformation of a rock slope at the ikura limestone quarry japan abstract more than 10 years of displacement measurements at the ikura limestone quarry in japan have clarified aspects of rock slope deformation arising from excavation in the quarry although the cause of most deformations can be explained theoretically those occurring in a rock slope just behind the tarumi working face proved perplexing contraction continued to occur on the rock slope although excavation of limestone had ceased at this face the cause of this continuous deformation was evaluated through numerical analysis employed to assess the stability of the rock slope an automatic 3d mesh generation technique was used to model the complex topography of the quarry resulting from the excavation and a finite element mesh model was rendered for each of the successive excavation stages elastic analysis then allowed the resulting rock slope deformation to be predicted the calculated results reveal that the rock slope continued to deform elastically after excavation had ceased on the tarumi face and that the on going excavation at the kawamukai working face located 400 m away from the rock slope was the probable cause the calculated results using appropriate elastic moduli were in good agreement with measured results the rock slopes are assessed as stable and the continuous deformation is believed to be elastic

chemical microenvironments within sulfide structures from the mothra hydrothermal field evidence from high resolution zoning of trace elements abstract massive portions of a 300 c black smoker finn and a diffusely venting intermediate temperature 200 c chimney roane recovered from the mothra hydrothermal field on the juan de fuca ridge have been analyzed in detail for bulk chemistry the size of the recovered pieces of chimney enabled physical segregation and analysis of distinct chemical zonation within the structures in particular large variations in the concentrations of minor and trace elements in the different mineralogical zones provide new insight into the processes involved in chimney growth that are not evident from the bulk mineralogy systematic zonation of trace and minor elements is strongly influenced by redox conditions multiple host phases single or dual fluid source and the mixing cooling history of the fluids even within an individual mineralogical zone distinct chemical microenvironments within the chimneys are recognized that provide a basis for detailed reconstruction of the changing conditions in the interiors of the chimneys during their growth in finn 14 discrete chemical microenvironments are recognized in 80 of 90 samples based on high resolution zoning of major and trace elements four of the microenvironments are cu rich three are zn rich one is fe rich with low cu two are ca rich three are sio2 rich and one is ba and sio2 rich in roane 24 discrete chemical microenvironments are recognized six of the microenvironments are sio2 poor

microstructural characterization and in situ sulfur isotopic analysis of silver bearing sphalerite from the edmond hydrothermal field central indian ridge abstract a close zn ag association has been noted recently in several polymetallic sulfide ore deposits from the indian ocean however the role of nanotextural controls on invisible silver distribution within sphalerite a significant ag carrier is still not well understood in this study typical zn sulfide samples from the edmond vent field central indian ridge can be roughly classified into three different groups based on their chemical compositions and mineral textures among them sulfosalt bearing fe poor zinc sulfides in sulfate dominant outer chimney walls usually contain higher contents of ag cu and pb up to wt levels than fe rich massive to disseminated sphalerite in zn fe rich chimney fragments coated by silicified crusts such sphalerite is represented by colloform botryoidal aggregates of optically anisotropic zns with a strongly disordered structure or hexagonal habit which are actually formed by coalescence and agglomeration of colloidal nanocrystalline particles using high resolution transmission electron microscopy hrtem and in situ micro xrd techniques we have investigated the ultrastructure and crystal chemistry of the 1 1 1 twin boundaries and wurtzite type stacking faults that occur in ag rich colloform or porous dendritic sphalerite submicroscopic electrum and ag nanoparticles appear to nucleate on the micro nano pore walls as cavity fillings or occur along grain boundaries between chalcopyrite tennantite inclusions and the host sphalerite interestingly the inhomogeneous distribution of precious metals and other chalcophile elements is generally concordant with the extent of recrystallization intragranular porosity as well as various degrees of structural disordering imperfectness i e bulk defect density in zns domains lattice defects and interfaces may play a limited role in promoting the simultaneous introduction of exotic impurities into colloform sphalerite during rapid growth even though certain morphological traits and aggregation state at the nanoscale seem to support a biogenic origin of these zns particles characterized by admixed polytypic intergrowth structures the mineralogical and geochemical features of highly defective sphalerite crystals in addition to their microscale s isotope signatures with relatively high 34 s values exhibit signs of abiologically mediated rapid precipitation caused by extensive mixing and cooling at edmond the physicochemical conditions and seafloor disequilibrium processes indicated by zns formation mechanism might facilitate the incorporation and enrichment of ag or other trace elements in hydrothermal sphalerite

a modified inverse velocity method for predicting the failure time of landslides abstract prediction of the failure time of landslides is always an important issue based on fukuzono s theory which suggests that the logarithm of the surface displacement velocity is proportional to the logarithm of the surface displacement acceleration in the final stage of the slope movement just before failure a modified inverse velocity method was proposed by introducing a controllable variable one landslide was detected in the certain open pit coal mine and four landslides were detected in the certain open pit iron mine by using ground based radar in the four landslides in the certain open pit iron mine the acceleration obviously decreased a few hours before failure which is inconsistent with the existing creep theory the traditional inverse velocity method and the modified inverse velocity method were employed to analyze the five landslides the analysis results show that the modified inverse velocity method can improve the effectiveness of prediction by reducing the prediction error caused by the acceleration decrease before failure the modified inverse velocity method proposed in this paper not only improves the prediction accuracy but also provides a study direction to improve the inverse velocity method that is it introduces controllable variables to improve the prediction accuracy

detection and spatial prediction of rockfalls by means of terrestrial laser scanner monitoring abstract a rock face affected by small rockfalls has been monitored using a ground based remote sensing apparatus terrestrial laser scanner tls the pilot study area corresponds to the main scarp of the 1881 puigcercos landslide pallars jussa catalonia spain four datasets of the slope were acquired from september 2007 to july 2008 in an ongoing project the geomorphological evolution of the rock face in terms of volume and frequency of rockfall was studied by the comparison of sequential datasets in addition to the detection of past events this study deals with the spatial prediction of rockfalls through the detection of pre failure deformation as a precursory indicator the high resolution and accuracy and the maximum range of the tls offer interesting prospects for both spatial location and prediction of rockfall

geotectonic setting of hydrothermal activity on the summit of lucky strike seamount 37 17 n mid atlantic ridge we have investigated the relations between volcanic tectonic and hydrothermal activity on lucky strike seamount 37 17 n mid atlantic ridge using a nested survey strategy involving collection of data from different deep sea mapping systems the highly tectonized seamount summit consists of three volcanic cones surrounding a relatively flat depression with a young lava lake in its center hydrothermal activity is focused mainly within the summit depression with most of the vents located proximal to the lava lake isolated active and inactive chimneys and mounds are widespread throughout the summit depression and occur on both volcanic pillow lava and hydrothermal sulfide rubble and hydrothermally cemented breccias substrates the large volume of sulfide rubble together with the nature of the sulfide structures indicates that hydrothermal activity has been episodic but ongoing for a long period of time hundreds to thousands of years on the basis of the distribution of hydrothermal deposits we propose a model of alternation between tectonic and volcanic control on hydrothermalism at lucky strike seamount midsegment melt focusing produces a spatially and temporally stable heat source that sustains focused high temperature hydrothermal activity over long time periods during periods of amagmatic extension active faulting within the summit depression provides multiple near surface fluid flow pathways for discharge of high temperature fluids and widespread deposition of massive sulfides during eruptive events rapid effusion of very hot lava creates a lava lake and hyaloclastite deposits the new sheet flows form a cap on the hydrothermal system and fluid upflow is reorganized discharge of high temperature fluids is restricted to isolated sites with relatively high permeability for example the edges of the lava lake much of the upwelling hydrothermal fluid pools in the subsurface conductively cools and mixes with entrained seawater before discharging as widespread low temperature diffuse flow hyaloclastites become cemented further augmenting the sealing of the system present day activity at lucky strike seamount represents this locally volcanically controlled phase of activity despite the segment as a whole being dominantly amagmatic

engineering geological characterization of clayey diatomaceous earth deposits encountered in highway projects in the tengchong region yunnan china abstract a type of clayey diatomaceous earth of pliocene mangbang formation n2m was encountered in highway projects in the tengchong region of yunnan province southwest china the tengchong clayey diatomaceous earth is characterized using multiple test methods such as granulometric analysis chemical analysis x ray diffraction xrd and scanning electron microscopy sem analysis shrinkage and swelling tests unconfined or uniaxial compression test triaxial test and direct shear tests the chemical and mineralogical compositions physical and hydraulic properties and engineering properties of the clayey diatomaceous earth are presented in this paper it is revealed that the tengchong clayey diatomaceous earth is an unusual soil or rock which has characteristics of both typical diatomaceous earth and swelling clayey soil or soft clay rock the diatoms in the earth enhance the connection between micro structures and improve the mechanical properties of diatomaceous earth however due to the existence of a significant amount of swelling clay minerals the tengchong clayey diatomaceous earth becomes swelling soft rock and is prone to engineering problems or geohazards based on the test results a number of issues regarding classification discrimination and geohazard control related with the clayey diatomaceous earth are discussed to provide both some basic understanding and new insight into the characteristics of the clayey diatomaceous earth deposits

kinematics and geological constraints of the slow moving pisciotta rock slide southern italy abstract the pisciotta landslide is a slow moving deep seated rock slide in the campania region of southern italy which has damaged a provincial road several times in the last decades and currently poses a hazard to the national railway that intersects the toe of the landslide the landslide involves an oligocene turbidite series which is composed of intercalated calcarenites marls and mudrocks the principal objectives of this study were to investigate the morphological evolution of the unstable slope quantitatively analyse ground deformations and construct an engineering geological model that is consistent with the spatial features of the landslide the long term evolution of the unstable slope was assessed through the examination of available aerial photos from 1943 to 2006 kinematic analyses of the ground deformations were conducted based on observed progressive displacement of the road as evident from the topographic maps and orthophotos 1955 2006 and the bi weekly displacement survey of 50 targets distributed across the landslide area september 2006 march 2009 the engineering geological model of the landslide was reconstructed from the stratigraphic data obtained from the study of borehole data and monitoring of inclinometers as well as from geological structural and geophysical surveys the analysis of the aerial photographs revealed an early stage of deformation in 1943 which has been gradually widening since then in addition to the main scarp and the landslide flanks other significant landslide structures such as the longitudinal and transverse cracks as well as the positive or negative morphologies were monitored and mapped in the subsequent years these studies indicated a progressive erosion of the upper part of the slope and a bulging of the foot long term kinematic analysis based on the progressive displacements of the road allowed the measurement of the ground deformations from 1955 to 2009 which revealed a cumulative horizontal displacement of up to 53 m and an average velocity of 0 98 m year 1 which has increased in the recent decades in addition the recent monitoring of the ground deformations demonstrated a continuous activity with an approximately constant rate of displacement and a composite kinematic history of the landslide body through differential displacements and associated velocities the engineering geological model of the landslide was found to be controlled by specific stratigraphic and structural constraints the landslide involves a stratigraphic interval of the saraceno formation nord calabrese tectonic unit with a largely marly argillaceous composition whose structural setting displays complex folding at the mesoscale and faulting with an approximately monocline attitude of bedding and a downslope dip direction at the macroscale the left flank of the landslide rests on a normal fault

fossil evidence for serpentinization fluids fueling chemosynthetic assemblages among the deep sea hydrothermal vent sites discovered in the past 30 years lost city on the mid atlantic ridge mar is remarkable both for its alkaline fluids derived from mantle rock serpentinization and the spectacular seafloor carbonate chimneys precipitated from these fluids despite high concentrations of reduced chemicals in the fluids this unique example of a serpentinite hosted hydrothermal system currently lacks chemosynthetic assemblages dominated by large animals typical of high temperature vent sites here we report abundant specimens of chemosymbiotic mussels associated with gastropods and chemosymbiotic clams in approximately 100 kyr old lost city like carbonates from the mar close to the rainbow site 36 n our finding shows that serpentinization related fluids unaffected by high temperature hydrothermal circulation can occur on axis and are able to sustain high biomass communities the widespread occurrence of seafloor ultramafic rocks linked to likely long range dispersion of vent species therefore offers considerably more ecospace for chemosynthetic fauna in the oceans than previously supposed

a rapidly deposited pennate diatom ooze in upper miocene lower pliocene sediment beneath the north pacific polar front abstract rapidly deposited thalassionema thalassiothrix pennate diatom oozes previously have been described in upper miocene lower pliocene sediment beneath the frontal boundary of the eastern equatorial pacific here we document a new occurrence of thalassionema thalassiothrix ooze in upper miocene lower pliocene sediment beneath the frontal boundary of the subarctic north pacific the ooze is a 6 m interval of siliceous sediment at ocean drilling program odp sites 885 886 that was rapidly deposited between approximately 5 0 and 5 9 ma bulk sediment in this interval may contain greater than 85 pennate diatom tests there are also abundant laminae and pockets that are composed entirely of thalassionema and thalassiothrix diatoms the presence of a rapidly deposited ooze dominated by pennate diatoms indicates unusual past conditions in the overlying surface waters time coincident deposition of such oozes at two distinct frontal boundary locations of the pacific suggests that the unusual surface water conditions were causally linked to large scale oceanographic change this same oceanographic change most likely involved 1 addition of nutrients to the ocean or 2 redistribution of nutrients within the ocean the occurrence and origin of pennate diatom oozes may be a key component to an integrative understanding of late neogene paleoceanography and biogeochemical cycling

determination of minimum detectable deformation of terrestrial laser scanning based on error entropy model terrestrial laser scanning tls is a widely used remote sensing technique which can produce very dense point cloud data very promptly and is particularly suited for surface deformation monitoring deformation magnitude is typically estimated by comparing tls scans over the same area but at different time epochs of interest however there is an issue related to such a method which is not clear that whether the difference between two successive surveys results from the surface deformation hence it is vital to determine the minimum detectable deformation mdd by a tls device with a given registration and point cloud error level in this paper the mdd is determined based on the computation of the point cloud error entropy the performance of the proposed method is extensively evaluated numerically using simulated plane board deformation point clouds under a range of distances and incidence angles this proposed method was also successfully applied to deformation monitoring of one landslide test site located in the wuhan university of technology the experimental results demonstrate that the theoretical mdd has a good match with the actual deformation and the deformation greater than mdd can be accurately detected by the tls device

the filon norte orebody tharsis iberian pyrite belt a proximal low temperature shale hosted massive sulphide in a thin skinned tectonic belt the filon norte orebody tharsis iberian pyrite belt is one of the largest pyrite rich massive sulphide deposits of the world the present structure of the mineralization consists of an internally complex low angle north dipping thrust system of variscan age there are three major tectonic units separated by thick fault zones each unit with its own lithologic and hydrothermal features they are internally organized in a hinterland dipping duplex sequence with high angle horses of competent rocks igneous and detritic rocks and massive sulphides bounded by phyllonites the mineralization is within the lower unit and is composed of several stacked sheets of massive sulphides and shales hosting a stockwork zone with no obvious zonation the intermediate unit is made up of pervasively ankeritized shales and basalts spilites here hydrothermal breccias are abundant the upper unit is the less hydrothermally altered one and consists of silicified dacites and a diabase sill the tectonic reconstruction suggests that the sequence is inverted and the altered igneous rocks were originally below the orebody carbon oxygen and sulphur isotopes in the massive sulphides and hydrothermal rocks as well as the mineral assemblage and the paragenetic succession suggest that the sulphide precipitation in the sea floor took place at a low temperature 150 c without indication at least in the exposed section of a high temperature copper rich event sporadic deep subsea floor boiling is probably responsible for the formation of hydrothermal breccias and the wide extension of the stockwork its co au enrichment is interpreted as being related with the superposition of some critical factors such as the relationship with black shales the low temperature of formation and the boiling of hydrothermal fluids the present configuration and thickness of the orebody is due to the tectonic stacking of a thin and extensive blanket 2 4 km2 of massive sulphides with low aspect ratio they were formed by poorly focused venting of hot modified seawater equilibrated with underlying rocks into the seafloor massive sulphide precipitation took place by hydrothermal fluid quenching bacteriogenic activity and particle settling in an unusual restricted euxinic and shallow basin brine pool with a low detritic input but with important hydrothermal activity related to synsedimentary extensional faulting resedimentation of sulphides seems to be of major importance and responsible for the observed well mixed proximal and distal facies the tectonic deformation is largely heterogeneous and has been mostly channelled along the phyllonitic tectonized shales deformation bands thus sedimentary and diagenetic textures are relatively well preserved outside the deformation bands in the massive sulphides superimposed variscan recrystallization is not very important and only some early textures are replaced by metamorphic tectonic ones the stockwork is much more deformed than the massive sulphides the deformation has a critical effect on the present morphology of the orebody and the distribution of the ore minerals this deposit is a typical example of the sheet like shale hosted anoxic low temperature and zn rich massive sulphides developed in a ensialic extensional basin

pge fractionation in seafloor hydrothermal systems examples from mafic and ultramafic hosted hydrothermal fields at the slow spreading mid atlantic ridge the distribution of platinum group elements pges in massive sulfides and hematite magnetite pyrite assemblages from the recently discovered basalt hosted turtle pits hydrothermal field and in massive sulfides from the ultramafic hosted logatchev vent field both on the mid atlantic ridge was studied and compared to that from selected ancient volcanic hosted massive sulfide vhms deposits cu rich samples from black smoker chimneys of both vent fields are enriched in pd and rh pd up to 227 ppb and rh up to 149 ppb when compared to hematite magnetite rich samples from turtle pits pd up to 10 ppb rh up to 1 9 ppb a significant positive correlation was established between cu and rh in sulfide samples from turtle pits pge chondrite normalized patterns with a positive rh anomaly and pd and au enrichment pd pt and pd au ratios close to global morb and high values of pd ir and pt ir ratios indicate mafic source rock and seawater involvement in the hydrothermal system at turtle pits similarly shaped pge chondrite normalized patterns and high values of pd pt and pd ir ratios in cu rich sulfides at logatchev likely reflect a similar mechanism of pge enrichment but with involvement of ultramafic source rocks

copper isotope systematics of the lucky strike rainbow and logatchev sea floor hydrothermal fields on the mid atlantic ridge in this paper we present the copper isotope signatures of black smoker sulfides massive sulfides and their alteration products and provide new insights into mineralization processes and applications of copper isotope geochemistry to sea floor hydrothermal systems on the mid atlantic ridge the hydrothermal systems studied include the lucky strike field at 37 17 n on a basaltic substrate and the rainbow and logatchev fields situated on ultramafic rock copper isotope variation in the hydrothermal precipitates was examined in conjunction with s isotopes and se and co concentrations the comparison between 65cu and se contents shows that subsurface precipitation of cu rich sulfides does not control significantly the 65cu values of the hydrothermal chimneys it appears that the major cause of copper isotope fractionation in hydrothermal systems up to 3 is the sea floor oxidation of primary copper sulfides enrichment in the heavy copper isotope can be explained by processes occurring at the sea floor such as hydrothermal reworking of previously altered sulfides by high temperature fluid massive sulfides characterized by negative 65cu values have undergone extensive recrystallization in these mineralogical assemblages isotopically heavy copper typical of altered sulfides has been leached and redeposited in the external zones or incorporated in hydrothermal fluids copper isotopes are therefore a promising tool for the study of supergene processes and the recycling of previously oxidized sulfides as well as a means of characterizing the degree of hydrothermal reworking of large sulfide deposits further studies of copper isotope fractionation under controlled laboratory experimental conditions are required to identify copper isotope fractionation during sulfide alteration in particular the possible biological mediation of copper isotope fractionation during sulfide oxidation may be an important direction for further studies

development of the california current during the past 12 000 yr based on diatoms and silicoflagellates detailed diatom and silicoflagellates records in three cores from the offshore region of southern oregon to central california reveal the evolution of the northern part of the california current during the past 12 000 yr the early holocene prior to 9 ka was characterizedbyrelativelywarmseasurfacetemperatures sst owingtoenhancednortherlyflowofthesubtropicalwaterscomparable tothemoderndavidsoncurrent progressivestrengtheningof thenorthpacifichighleadtointensificationofthesouthwardflowofthe california current at 8 ka resulting in increased coastal upwelling and relatively cooler sst which persisted until 5 ka reduced southward flow of the california current between 4 8 ka and 3 6 ka may have been responsible for a period of decreased upwelling modern seasonal oceanographic cycles as evidenced by increased spring early summer coastal upwelling and warming of early fall sst evolved between 3 5 and 3 2 ka widespread occurrence of paleoceanographic and paleoclimatic change between 3 5 3 0 ka along the eastern margins of the north pacific was likely a response to increasing enso variability in the tropical pacific published by elsevier b v

retrieval of historical surface displacements of the baige landslide from time series sar observations for retrospective analysis of the collapse event abstract landslides and resultant barrier lakes are significant threats to human lives and infrastructures three dimensional 3d surface displacements can give vital clues to the exploration of internal structure of landslides but they are difficult to be retrieved from spaceborne synthetic aperture radar sar observations due to the intrinsic limitation of sar imaging geometry meanwhile studies on predicting slope failure based on sar measured displacements are rarely seen here we used sar pixel offset tracking to investigate the baige landslide before the collapse on 10 october 2018 3d surface displacements retrieved by combining satellite sar and optical observations revealed heterogeneous spatial patterns within the landslide complex we observed linear secondary creep and accelerating tertiary creep prior to the failure from multi sensor sar data the possibility of forecasting the failure was demonstrated by applying an inverse velocity method to the time series displacements measured by sentinel 1 during the tertiary creep which is valuable for risk evaluation and disaster early warning

chemical and mineralogical influences on concentrations of trace metals in hydrothermal fluids abstract concentrations of trace metals in hydrothermal solutions from the southern juan de fuca ridge sjfr and the tag hydrothermal field on the mid atlantic ridge are influenced by the combined effects of source rock composition brine seawater mixing and complex interplay among various metals and minerals deposited and remineralized in vent mounds and chimneys copper mo and co show predicted sharp decreases in concentration for vent fluids as temperatures decrease below 350 c however concentrations of cu in 363 c fluids at the tag site are well above values determined from seawater basalt interactions due to subseafloor refining processes and remineralization of chalcopyrite concentrations of zn cd pb as and ga do not show any temperature dependence between 214 to 363 c however zn values do correlate well with cl on an area by area basis due to subseafloor mixing of brine with altered seawater zinc levels also correlate well with concentrations of cd pb and as for all vent fluid samples as well as with basalt and zn rich sulfides implying some continuity in behavior from source rock to vent fluid to sulfide minerals gallium values correlate with zn and cl levels for the sjfr but are high relative to zn at the tag site due to subseafloor refining processes concentrations of tl follow cl k and rb consistent with the behavior predicted for tl overall the cl and zn rich fluids from the sjfr are characteristic of a brine dominated system formed during recent volcanism in contrast high temperature fluids from the tag area are representative of a system that has evolved over the past 100 000 yr with high concentrations of cu co and ga that result from higher temperatures and complex refining processes within a large vent mound

on the monitoring and early warning of brittle slope failures in hard rock masses examples from an open pit mine abstract the management of unstable slopes is one of the most critical issues when dealing with safety in open pit mines suitable notice of impending failure events must be provided and at the same time the number of false alarms must be kept to a minimum to avoid financial losses deriving from unnecessary outages of the production works comprehensive slope monitoring programs and early warning systems are usually implemented to this aim however systematic procedures for their tuning are lacking and several key factors are often overlooked therefore the mitigation of slope failure risk is still a topic of great concern especially in open pit mines excavated through hard rock masses featuring markedly brittle behavior which supposedly provide little or no measurable precursors to failure in this paper 9 instabilities occurred at an undisclosed open pit mine and monitored by ground based radar devices were reviewed with the goal of characterizing the typical slope deformation behavior and defining the appropriate strategy for the setup of alarms the estimated mass of the case studies ranged from 1500 t to 750 000 t 5 instabilities culminated to failure whereas the other 4 although showing considerable amounts and rates of movement ultimately did not fail the analysis provided critical insights into the deformation of hard rock masses of high geomechanical quality and allowed the identification of signature parameters of the failure events general operative recommendations for effective slope monitoring and early warning were consequently derived

a physical model predicting instability of rock slopes with locked segments along a potential slip surface abstract better understanding the evolutionary mechanism of landslides is very important to predict their occurrence based on firm scientific grounds the stability of a rock slope is often dominated by one or more locked segments along a potential slip surface with a large bearing capacity to resist instability we propose three preliminary categories for locked segments and develop a physical model for predicting the instability of rock slopes with locked segments by coupling a one dimensional renormalization group model with a strain softening constitutive model based on the weibull distribution we found that the ratio of the strain at the peak strength point of a locked segment to the strain at its volume dilation point is exclusively dependent on the weibull shape parameter m and is approximately constant at 1 48 the accelerating displacement of the slope can be observed from the volume dilation point of the locked segment due to unstable fracture propagation the physical model for slopes with multiple locked segments is only related to the displacement corresponding to the volume dilation point of the first locked segment and the number of locked segments applying this model to two typical cases the yanchihe rockslide in china and the wedge rockslide in libby dam usa the results are in agreement with field records this work will help to better understand the failure mechanism of slopes with locked segments and may provide guidelines for disaster mitigation and prevention

pinguino in bearing polymetallic vein deposit deseado massif patagonia argentina characteristics of mineralization and ore forming fluids the pinguino deposit located in the low sulfidation epithermal metallogenetical province of the deseado massif patagonia argentina represents a distinct deposit type in the region it evolved through two different mineralization events an early in bearing polymetallic event that introduced in zn pb ag cd au as cu sn w and bi represented by complex sulfide mineralogy and a late ag au quartz rich vein type that crosscut and overprints the early polymetallic mineralization the indium bearing polymetallic mineralization developed in three stages an early cu au in as sn w bi stage ps1 a zn pb ag in cd sb stage ps2 and a late zn in cd ps3 indium concentrations in the polymetallic veins show a wide range 3 4 to 1 184 ppm in the highest indium values up to 1 184 ppm relate to the ps2 mineralization stage and are associated with fe rich sphalerites although significant in enrichment up to 159 ppm is also present in the ps1 paragenesis associated with sn minerals ferrokesterite and cassiterite the hydrothermal alteration associated with the polymetallic mineralization is characterized by advanced argillic alteration within the immediate vein zone and sericitic alteration enveloping the vein zone fluid inclusion studies indicate homogenisation temperatures of 308 2 327 c for ps1 and 255 312 4 c for ps2 and low to moderate salinities 2 to 5 eq wt nacl and 4 to 9 eq wt nacl respectively 34s values of sulfide minerals 0 76 to 3 61 indicate a possible magmatic source for the sulfur in the polymetallic mineralization while pb isotope ratios for the sulfides and magmatic rocks 206pb 204pb 207pb 204pb and 208pb 204pb ratios of 17 379 to 18 502 15 588 to 15 730 and 38 234 to 38 756 respectively are consistent with the possibility that the pb reservoirs for both had the same crustal source spatial relationships hydrothermal alteration styles s and pb isotopic data suggest a probable genetic relation between the polymetallic mineralization and dioritic intrusions that could have been the source of metals and hydrothermal fluids mineralization paragenesis alteration mineralogy geochemical signatures fluid inclusion data and isotopic data confirm that the in bearing polymetallic mineralization from pinguino deposit is a distinct type in comparison with the well known epithermal low sulfidation mineralization from the deseado massif

analysis of baishuihe landslide influenced by the effects of reservoir water and rainfall since the impoundment of the three gorges reservoir in june 2003 a number of new landslides have occurred and existing landslides have been made worse the 1 260 104 m3 baishuihe landslide located at 56 km west of the three gorges dam began to deform more noticeably after the first impoundment in early july 2003 the sliding of the two blocks comprising the landslide one an active block and the other a relatively stable block became apparent after approximately 5 years of monitoring field recordings show that the landslide displacement is affected by the combined effects of the rainfall and water level in the reservoir these effects have been investigated in the present paper including the deformation characteristics movement pattern direction displacement and velocity earmarking the temporal evolution of the active block based on a practical creep model of a large rock slide alert velocity thresholds for pre alert alert and emergency phases have been computed corresponding to the imminence of failure the alert velocity thresholds are being proposed to be included as a part of an early warning system of an emergency plan drawn up to minimize the adverse impact in the event of landslide failure the emergency plan is intended to be implemented as a risk management tool by the relevant authorities of the three gorges reservoir in the near future

detailed geological mapping of two contrasting second order segments of the mid atlantic ridge between oceanographer and hayes fracture zones 33 30 n 35 n we present detailed geological mapping of the axial valley floor and ridge flanks of two neighboring but contrasting spreading segments oh1 and oh3 of the mid atlantic ridge between oceanographer and hayes fracture zones new in situ observations from the submersible nautile correlated with swath bathymetry and acoustic backscattering data from these segments reveal that the along and across axis volcanic tectonic variability within second order segments is larger than commonly acknowledged segment oh1 is a long and robust segment with a narrow and shallow axial valley the most intense magmatic activity is found at the segment center where the thickest crust has been imaged suggesting focused magma supply away from this part of the segment faulting and sedimentary cover predominate in contrast the center of segment oh3 is dominated by extensive sedimentary cover fissuring and faulting furthermore the most recent constructional volcanism is located away from the segment center in a region of greater depth and thinner crust this relocation of volcanism suggests either a recent shift in the magmatic source or the last vestige of a centrally located source fed by lateral dike injection segment tip magmatic oscillations are suggested by the distribution of rock types at both segment ends serpentinized peridotites and associated dolerites are exposed at the massifs located at the intersection with nontransform offsets ntos whereas only basaltic rocks crop out on the nodal basin floors we suggest that the combination of low magmatic budget and extension taking place at the ntos during a segment retreat favors the uplift and exposure of ultramafic massifs

redox changes in a seafloor hydrothermal system recorded in hematite chalcopyrite chimneys abstract hydrothermal chimneys composed of hematite and chalcopyrite grow at the irina ii vent site logatchev hydrothermal field mid atlantic ridge hematite and chalcopyrite form layers that repeatedly alternate within the chimney wall the repeating alternation of hematite and chalcopyrite implies for repeating changes in the physico chemical parameters of the vent fluid the modeled stability diagrams of hematite and chalcopyrite at the physico chemical conditions of the irina ii hydrothermal site showed that the precipitation of these two fe minerals is primarily governed by the activity of h2s and ph fe isotope studies suggest that the successive deposition of chalcopyrite 56 54fe 0 20 and hematite 56 54fe 0 60 layers in the irina ii chimneys is a result of redox changes in the hydrothermal fluid the replacement of hematite by either magnetite or chalcopyrite at some places also suggests for a redox inversion in the hydrothermal system from oxic to reduced chondrite normalized rare earth element distribution patterns of the hematite layers show a strong negative eu anomaly which is interpreted to be a result of crystal chemical control on the rare earth element fractionation during hematite precipitation sr isotope systematics indicate significant and variable incorporation of seawater from 40 to 80 in the hydrothermal system nd pb isotope studies show that nd and pb in chalcopyrite and hematite layers are derived mainly from the underlying mafic and ultramafic rocks the chimneys are young 5 13 1 28 kyrs b p and their wall thickened inward the duration of redox cycles oxic and reducing within the scale of a single chimney is about several hundred years the hematite layers are enriched in w in sn and u indicating that primary hematite hydrothermal deposits at the seafloor may be a potential source for these strategic trace elements high concentrations of these elements in the studied hematite layers can be explained by their easy ion substitution for fe3 in the hematite crystal lattice whereas the most plausible source of the elevated w in and sn contents are the hydrothermal fluids the seawater is the possible major source of u

paleoceanography during the last 150 kyr off central japan based on diatom floras abstract the paleoceanographic history of the area above the northern boundary of the warm kuroshio current during the last two glacial interglacial cycles was reconstructed based on high resolution records of the diatom flora in core md01 2421 ecological categories of the diatom flora were extracted using q mode factor analysis the four most prominent factors explained 91 4 of the total variance cross spectral analyses were performed on temperature estimates derived from diatom data td the relative abundance of littoral neritic diatom associations and the oxygen isotope record of benthic foraminifera diatom derived temperatures show a 50 23 and 17 kyr periodicity with only the 23 kyr band coherent with that of benthic foraminiferal oxygen isotope values littoral neritic associations show a periodicity at 62 and 17 kyr coherent with td species composition and relative abundance of the diatom flora changed at the marine isotope stage boundaries when cold water and warm water mixed over the core site due to hydrographic disturbances by changes in transport trajectory of the kuroshio current transport and global climatic changes

hydrothermal processes at mid ocean ridges submarine hydrothermal systems are an integral component of crustal construction along the global system of mid ocean ridges thermally induced circulation of seawater through the permeable parts of the crust and upper mantle has been estimated to account for 34 of the predicted global oceanic heat flux which in turn comprises close to 25 of the total heat flux of the earth stein and stein 1994 and references therein discharge of hydrothermal fluids is manifest along mid ocean ridges as high temperature 200 400 c focused and lower temperature 200 c diffuse fluid flow off axis fluid flow may extend out to the crustal sealing age of 65 10 million years and may be responsible for more than 70 of the hydrothermal heat flux stein and stein 1994

recent tectonic magmatic and hydrothermal activity on the east pacific rise between 17 s and 19 s submersible observations the objective of the naudur cruise december 1993 of the submersible nautile was to study the interaction among magmatic tectonic and hydrothermal processes at a very fast spreading mid ocean ridge axis twenty three dives were completed both along and across the axis in four areas located between 17 10 and 18 45 s on the east pacific rise rock sulfides water and biological samples have been collected along each of the segments two main types of segments have been distinguished characterized either by the predominance of present day volcanic activity or by predominant tectonic activity linked to both types of activity 69 hydrothermal sites have been discovered and sampled they comprise four types interpreted as successive evolutionary stages the first are shimmering water sites which occur immediately after the formation of lava lakes and are characterized by large surface area and poorly developed associated fauna the second in areas dominated by recent volcanic activity have waters venting directly from lava fissures and more focused discharge areas through black smoker chimneys the third stage is represented by more mature hydrothermal vents and deposits along the faults bounding the eastern side of the axial graben in tectonic dominated areas the associated fauna is well developed the fourth stage corresponds to the reactivation of volcanic activity with lava flows young black smokers and diffuse venting associated with the faults bounding the axial graben fluids collected range from 200 to 340 c and show a wide variability in chemical and gas composition within each of the explored areas evidence of recent volcanic activity has been observed

failure forecast for large rock slides by surface displacement measurements forecasting the failure of large rock slides is difficult because of nonlinear time dependency and seasonal effects which affect the displacements starting from the accelerating creep theory prop

age and significance of miocene diatoms and diatomaceous sediments from northeast japan abstract neogene diatomaceous floras collected from marine sediments exposed in northeastern japan provide evidence of diatom evolution stratigraphic correlation and the geologic and paleoceanographic history of this region middle to late miocene diatom zones younger than the early middle miocene denticulopsis lauta zone have been established in the oga peninsula section an onshore sequence regarded as the neogene reference section for northeast japan correlative middle and late miocene diatom floras are not preserved in sediments recovered by ocean drilling program legs 127 and 128 in the japan sea emphasizing the importance of the time equivalent onshore deposits initial marine sedimentation is represented by lower middle miocene 16 15 ma littoral and shelf deposits exposed along the southern and eastern margins of the japan sea subsequent middle and late miocene deposition was marked by widespread deposition of bathyal diatomaceous sediments as recorded in the onnagawa and correlative formations in onshore sequences the major global cooling event at 13 ma is signaled in the japan sea area by the disappearance of subtropical warm water diatoms and the appearance of subarctic cold water floras an event coincident with a period of rapid subsidence in the japan sea the zonal marker species and the species mentioned in the text are illustrated

new quantitative displacement criteria for slope deformation process from the onset of the accelerating creep to brittle rupture and final failure abstract two quantitative displacement criteria for slope deformation were deduced through the combination of a one dimensional renormalization group model and the strain softening constitutive model of geological materials the criteria can be used to understand the mechanical process from the onset of the accelerating creep on a slope through brittle rupture to the final failure and landslides the study showed that according to the first criterion the displacement ratio between the brittle rupture and the onset of the accelerating creep is approximately 1 48 which can be used to predict the brittle rupture of a slope with continuous progressive deformation the second displacement criterion shows that the displacement ratio between the final failure and the onset of the accelerating creep is approximately 2 59 which can be used to predict the occurrence of the ultimate disaster thus the critical displacement prior to the failure of the slope can be predicted using a time series of monitoring displacement data the methodology proposed in this study was validated using data from two well known landslides the vajont landslide in italy and the xintan landslide in china the results verify the applicability of this method