spatial and temporal variations in rockfall determined from tls measurements in a deglaciated valley switzerland steep u shaped valleys produced by glaciation are commonly eroded by rockfall in this study we investigate modern and long term power law predicted rates of rock wall retreat in a deglaciated valley our emphasis is on the 5 2 km2 calcareous cliffs covering in the lauterbrunnen valley switzerland terrestrial laser scans were collected during nine field campaigns over 18 months to provide a continuous coverage of most of the valley walls results indicate a total of 122 rockfalls with volumes ranging between 0 06 0 01 and 119 34 1 07 m3 different size groups of rockfall events were correlated with environmental factors e g freeze thaw cycles temperature precipitation and seismicity using a linear regression with variable lag times of 0 6 months the highest correlation factor r 0 6 p 0 08 90 significance level is observed for freeze thaw cycles and rockfall events smaller than 1 m3 with a 2 month delay between temperature extremes and rockfall frequency magnitude relationships for rockfall events were calculated to predict less frequent larger rockfall events that did not occur during the observation period a monte carlo analysis was applied to the frequency magnitude relationship to evaluate the sensitivity of results to their stochastic nature an average power law exponent of 1 71 0 09 was calculated using linear regression the calculated exponents are similar to other studies in calcareous rock settings conducted over different observation durations finally we determine an average total eroded volume of 2 0 0 01 0 6 103 m3 yr and a corresponding long term power law predicted cliff retreat rate of 0 39 0 02 0 12mm yr

comparison of three gis based models for predicting rockfall runout zones at a regional scale site specific information about the level of protection that mountain forests provide is often not available for large regions information regarding rockfalls is especially scarce the most efficient way to obtain information about rockfall activity and the efficacy of protection forests at a regional scale is to use a simulation model at present it is still unknown which forest parameters could be incorporated best in such models therefore the purpose of this study was to test and evaluate a model for rockfall assessment at a regional scale in which simple forest stand parameters such as the number of trees per hectare and the diameter at breast height are incorporated therefore a newly developed geographical information system gis based distributed model is compared with two existing rockfall models the developed model is the only model that calculates the rockfall velocity on the basis of energy loss due to collisions with trees and on the soil surface the two existing models calculate energy loss over the distance between two cell centres while the newly developed model is able to calculate multiple bounces within a pixel the patterns of rockfall runout zones produced by the three models are compared with patterns of rockfall deposits derived from geomorphological field maps furthermore the rockfall velocities modelled by the three models are compared it is found that the models produced rockfall runout zone maps with rather similar accuracies however the developed model performs best on forested hillslopes and it also produces velocities that match best with field estimates on both forested and nonforested hillslopes irrespective of the slope gradient

objective landslide detection and surface morphology mapping using high resolution airborne laser altimetry a map of extant slope failures is the most basic element of any landslide assessment without an accurate inventory of slope instability it is not possible to analyze the controls on the spatial and temporal patterns of mass movement or the environmental human or geomorphic consequences of slides landslide inventory maps are tedious to compile difficult to make in vegetated terrain using conventional techniques and tend to be subjective in addition most landslide inventories simply outline landslide boundaries and do not offer information about landslide mechanics as manifested by internal deformation features in an alternative approach we constructed accurate high resolution dems from airborne laser altimetry lidar data to characterize a large landslide complex and surrounding terrain near christchurch new zealand one dimensional circular 2 d and spherical 3 d statistics are used to map the local topographic roughness in the dems over a spatial scale of 1 5 to 10 m the bedrock landslide is rougher than adjacent unfailed terrain and any of the statistics can be employed to automatically detect and map the overall slide complex furthermore statistics that include a measure of the local variability of aspect successfully delineate four kinematic units within the gently sloping lower half of the slide features with a minimum size of surface folds that have a wavelength of about 11 to 12 m and amplitude of about 1 m are readily mapped two adjacent earthflows within the landslide complex are distinguished by a contrast in median roughness and texture and continuity of roughness elements the less active of the earthflows has a surface morphology that presumably has been smoothed by surface processes the laplacian operator also accurately maps the kinematic units and the folds and longitudinal levees within and at the margins of the units finally two dimensional power spectra analyses are used to quantify how roughness varies with length scale these results indicate that no dominant length scale of roughness exists for smooth unfailed terrain in contrast zones with different styles of landslide deformation exhibit distinctive spectral peaks that correspond to the scale of deformation features such as the compression folds the topographic based analyses described here may be used to objectively delineate landslide features generate mechanical inferences about landslide behavior and evaluate relatively the recent activity of slides published by elsevier science b v

debris flow analyst da a debris flow model considering kinematic uncertainties and using a gis platform abstract although the main driving force of debris flows is simply gravity the dynamic processes are very complex kinematic uncertainties during motion make it difficult to exactly simulate debris flows in traditional numerical simulation models of debris flows the kinematic uncertainties are generally not considered in the lagrangian description in addition the challenge of obtaining accurate simulation parameters further suggests the necessity of probabilistic modeling of debris flows in this study a novel statistical debris flow simulation model debris flow analyst model is proposed in the lagrangian description in which the inherent stochasticity in the motion of a debris flow is described by stochastic differential equations sdes in this model the accelerations of moving debris are calculated by newton s second law and their locations are estimated based on monte carlo simulation according to case studies the proposed model provides results close to the analytical solution in a 1 d simulation of dam breaks in the eulerian description and reduces some numerical oscillations additionally the debris flow analyst model can produce reasonable results based on a single phase rheological model in 2 d simulations of a debris flow in tibet and a flow like landslide triggered by storms on 4 5 november 1993 in hong kong from the theoretical perspective our model is equivalent to the total variation diminishing tvd scheme in the eulerian description in addition the statistical model provides a new tool to estimate kinematic uncertainties in the hazard analysis of debris flows on gis platforms

assessment of rockfall susceptibility by integrating statistical and physically based approaches in val di fassa dolomites eastern italian alps rockfalls constitute the most significant gravity induced natural disaster that threatens both the inhabitants of the valley who are few and the thousands of tourists who populate the area in summer and winter to assess rockfall susceptibility we developed an integrated statistical and physically based approach that aimed to predict both the susceptibility to onset and the probability that rockfalls will attain specific reaches through field checks and multi temporal aerial photo interpretation we prepared a detailed inventory of both rockfall source areas and associated scree slope deposits using an innovative technique based on gis tools and a 3d rockfall simulation code grid cells pertaining to the rockfall source area polygons were classified as active or inactive based on the state of activity of the associated scree slope deposits the simulation code allows one to link each source grid cell with scree deposit polygons by calculating the trajectory of each simulated launch of blocks by means of discriminant analysis we then identified the mix of environmental variables that best identifies grid cells with low or high susceptibility to rockfalls among these variables structural setting land use and morphology were the most important factors that led to the initiation of rockfalls we developed 3d simulation models of the runout distance intensity and frequency of rockfalls whose source grid cells corresponded either to the geomorphologically defined source polygons geomorphological scenario or to study area grid cells with slope angle greater than an empirically defined value of 37 empirical scenario for each scenario we assigned to the source grid cells an either fixed or variable onset susceptibility the latter was derived from the discriminant model group active inactive membership probabilities comparison of these four models indicates that the geomorphological scenario with variable onset susceptibility appears to be the most realistic model nevertheless political and legal issues seem to guide local administrators who tend to select the more conservative empirically based scenario as a land planning tool

chemistry of springs across the mariana forearc shows progressive devolatilization of the subducting plate abstract cold springs upwelling through large serpentinite mud volcanoes in the outer half of the mariana forearc provide a unique window into processes of devolatilization of the subducting pacific plate we have sampled upwelling pore waters with lower chlorinity than seawater from six sites on five serpentinite mud volcanoes by conventional gravity and piston coring by push coring from the rov jason by drilling on odp legs 125 and 195 and by manned submersible the sites range from 13 47 n to 19 33 n and 52 to 90 km from the mariana trench axis corresponding to approximate depths to the top of the downgoing plate of 16 to 29 km the composition of the springs varies systematically over this distance nearer the trench the upwelling waters have much higher ca and sr than seawater and much lower carbonate alkalinity sulfate na cl k rb and b farther from the trench the waters show the opposite trends relative to seawater chlorinity is consistently lower than in seawater and shows large variations that are not systematic with distance from the trench cs is consistently higher than in seawater and increases with distance from the trench all of the waters have high ph and are heavily depleted in mg si li f and 87sr 86sr relative to seawater they tend to be enriched in o18 o16 except for odp drilling none of the cores was long enough to produce an asymptotic compositional trend with depth we have inferred the end member compositions of the upwelling waters by extrapolation against mg at two sites we were able to compare data from gravity cores with data from drill cores or push cores collected at springs to estimate the effects of reactions that occur at shallow depth below the seafloor on mixing of the upwelling waters with seawater these effects are different for sites high in dissolved ca nearer the trench vs those high in alkalinity farther from the trench common to both are large losses from solution of 1 ca as caco3 and in exchange for na 2 mg in exchange for na or ca and as brucite 3 sulfate probably reduced by microbes or possibly precipitated as gypsum 4 sr ba si and f na is consistently leached from the solids into solution whereas k and o18 o16 are relatively unreactive we infer that the upwelling waters are uniformly saturated with caco3 and that the excess h2o and the trends in ca sr alkalinity and sulfate with distance from the trench result from introduction of h2o and dissolved carbonate and sulfate from an external source the sediment and altered basalt at the top of the subducting plate the concurrent trends in na cl b cs and especially k and rb indicate that these species originate from the top of the subducting plate in response to increasing temperature these systematic variations across the outer forearc imply that the solutions ascend more or less vertically from the source region and do not travel long distances laterally along the decollement before ascending based on leaching of k the 150 c isotherm is crossed approximately beneath big blue seamount at a depth of 22 km below the seafloor 70 km behind the trench by this point it appears that carbonate dissolution has joined dehydration as a significant process at the top of the subducting plate

coal depositional models and the distinction between alluvial and delta plain environments abstract the distinction between coal bearing upper and lower delta plain deposits in the rock record may be based on the presence or absence of features indicative of basinal influence and on the geometry of coal seams discriminating between alluvial plain and upper delta plain sequences is more difficult but is considered possible on coal seam geometry and coal seam splitting patterns other features such as the cross sectional shape of channel deposits may also be useful

topography reveals seismic hazard the devastating earthquake in the chinese province of sichuan struck an area that was not expected to suffer seismic activity of such magnitude yet topographic analyses of the region indicate active deformation suggesting a way of refining maps of earthquake risk elsewhere

complex mineral zoning patterns caused by ultra local equilibrium at reaction interfaces chemically zoned minerals are useful records of temporal variations in ambient conditions and bulk chemical composition of the fl uid from which the minerals precipitate in fl buffered systems zoning of mineral compositions is expected to refl ect directly the evolution of fl composition here we show that during rapid fl uid rock reactions ultra local equilibrium can form complex mineral zoning patterns even when the overall system is highly fl uid buffered we reacted cleaved calcite single crystals with aqueous arsenate phosphate solutions with molar ratios of as as p between 0 01 and 0 15 at 250 c and water saturated pressure we fithat complex zoning patterns and solid solution between hydroxylapatiteand arsenate bearing hydroxylapatite that pseudomorphically replaced calcite formed within hours and these zoning patterns were destroyed within days during secondary reactions we propose a two stage reaction process in the formation of the fi nal reaction product 1 on an hour time scale calcite is dissolved and replaced by compositionally heterogeneous apatite the thin reaction interface fllayer becomes extremely enriched in arsenic at an ultra local scale as the reaction removes phosphate faster than the interface fl uid can re equilibrate with the bulk fl uid 2 the heterogeneous apatite is replaced by homogeneous apatite that refl ects the bulk fl uid composition over a longer days time scale through interface coupled dissolution precipitation this paper highlights the complexity that can arise from ultra local fl uid composition variations due to rapid fl uid rock interaction in a short lived fl uid fl ow event for example during a seismic cycle subsequent interpretation of complex zoning patterns as refl ecting the evolution of bulk fl uid would be erroneous

rodingitization and hydration of the oceanic lithosphere as developed in the leka ophiolite north central norway abstract ophiolite complexes in mountain chains may give supplementary information on the hydration of the oceanic lithosphere to that obtained from dredged and drilled samples from the ocean floor the ultramafic mantle and the layered ultramafic to anorthositic crustal sequences of the cambrian 497 ma leka ophiolite are variably serpentinized and chloritized grossular rodingite rodingite s s has been found over a c 500 m long and tens of meters wide zone in the layered crustal section of the complex and is developed in both pyroxenites and gabbro anorthosite layers shear zones and meter wide fracture zones where the rock has developed a fracture cleavage are oriented at high angel to the layering and these zones were the main conduits for transport of fluid and solute between the various lithologies some 5 15 cm thick layers of anorthosite or leucogabbro have been rodingitized around such a fractures zone with the development of three distinct metasomatic zones along the plagioclase layer a central grossular dominated zone with clinopyroxene clinozoisite prehnite chlorite and minor titanite rodingite zone extends for up to 3 m along strike and gives way to a clinozoisite dominated zone typically 0 5 m wide with additional grossular clinopyroxene and chlorite which is followed outward by a lile enriched zone lile zone with clinozoisite phlogopite k feldspar plagioclase and preiswerkite the lile zone extends more than 3 m out from the clinozoisite dominated zone clz zone assuming constant volume the rodingite formed from the plagioclase layer by addition of 20 g of cao per 100 g of rock all na 2 o c 2 g was removed from both rodingite and clz zones ti and v increase almost 10 in the rodingite compared to its protolith k ba rb and cs are strongly enriched in the lile zone compared to the protolith and suggest interaction with sea water the lithologies alternating with the plagioclase layers clinopyroxenite wehrlite websterite and dunite display textures indicating a number of ca releasing cpx chl cpx srp cpx amph and ca consuming opx cpx2 ol cpx2 cpx1 cpx2 reactions the replacement textures are distributed around fracture and shear zones with the ca releasing reactions in the core and the ca consuming reactions in distal parts forming a metasomatic column out from the fluid pathways serpentinization and chloritization of clinopyroxene was the main ca source for the rodingitization process this first description of rodingite in a layered sequence of an ophiolite complex indicates that the hydration of the oceanic lithosphere occurred at various structural levels and was associated with ca metasomatism also in places where rodingite s s is lacking the different lithologies exchanged elements through transport on shear and fracture zones

mineral chemistry and stable isotope constraints on the magmatism hydrothermal alteration and related pge base metal sulphide mineralisation of the mesoarchaean baula nuasahi complex india the baula nuasahi complex on the southern flank of the singhbhum archaean nucleus in north eastern india exposes a series of mesoarchaean igneous suites these are 1 a gabbro anorthosite unit which is petrographically homogeneous although mineral chemistry data hint at a subtle eastward differentiation 2 a peridotite unit with three chromitite layers together with 3 a pyroxenite unit which display cumulate textures modal layering and for the peridotite unit differentiation trends in both mineralogy and mineral chemistry and 4 the bangur gabbro 3 1 ga which defines an oblong intrusion crosscutting the older igneous suites in the southern part of the complex with a curvilinear nw trending apophysis 2 km long and up to 40 m wide magmatic breccia comprising ultramafic and chromitite wall rock clasts in a gabbro matrix is exposed at the contact of the main bangur gabbro body and also forms the entire bangur gabbro apophysis concentrations of platinum group minerals pgms are found where the breccia contains abundant chromitite clasts and two types of platinum group element pge mineralisation are recognised type 1 pt 1 1 14 2 pd 0 1 2 1 ppm with an average pt pd 8 9 is a contact type mineralisation which occurs in the breccia at the contact between the bangur intrusion and its ultramafic host the pgms pt alloys isoferroplatinum and sulphides braggite malanite are enclosed by pyroxene and plagioclase reflecting a magmatic origin significant wall rock assimilation by the magma giving rise to the bangur gabbro is indicated by changes in pyroxene composition and by the presence of relicts of chromite from the host now altered to secondary ferritchromite in the contact zone type 2 pge mineralisation pt 0 3 1 6 pd 1 8 6 0 ppm with pt pd 0 5 3 0 is restricted to the breccia apophysis of the bangur gabbro where it occurs in the breccia matrix associated with an intense hydrothermal alteration which does not exist in the contact zone pgms pge arsenides tellurides bismuthides and antimonides and where present base metal sulphides bmss form intergrowths with hydrous silicates reflecting a hydrothermal origin oxygen isotope geothermometry documents the main stages of hydrothermal alteration within a decreasing temperature range between 700 1 000 and 500 600 c and oxygen hydrogen and sulphur isotopes show that the hydrothermal fluids were derived from the magma rather than an external source pervasive hydrothermal alteration in the breccia apophysis likely represents upward channelling of late magmatic fluids along a narrow near vertical subplanar conduit which led away from the main magma chamber we suggest that type 2 mineralisation was produced by late magmatic hydrothermal remobilisation and reconcentration of type 1 pge mineralisation and that the composition of the hydrothermal fluids controlled whether bmss were enriched along with the pgms

the genesis of archaean chromitites from the nuasahi and sukinda massifs in the singhbhum craton india abstract the chromitite deposits of the nuasahi and sukinda massifs are part of layered ultramafic bodies which occur within archaean low grade metamorphic rocks of the iron ore group iog in the singhbhum craton of the indian shield the chromitite seams are interlayered with dunite and associated with orthopyroxenite detailed electron microprobe study reveals very high mg numbers 0 66 0 82 and cr numbers 0 75 0 87 for chromite in massive chromitite from the seams high fo content fo 92 95 for olivine in dunite and high en content en 89 94 for orthopyroxene in orthopyroxenite our study suggests that the original igneous compositions for these minerals are preserved in the respective monomineralic rocks and can be used to evaluate the primary magmatic petrogenesis of the rocks the primitive compositions of the minerals in monomineralic rocks suggest high degree of partial melting of the source mantle during the mesoarchaean the parental magma from which the massive chromitites crystallized was of siliceous high mg basaltic or boninitic compositions similar to the compositions of spatially associated chromite bearing siliceous high mg basalts of the iron ore group the parental magma may have generated due to the interaction of a depleted mantle with a fluid enriched melt possibly derived in response to the dehydration of a subducting slab monomineralic chromitite layers formed either in response to mixing of magmas or due to the suppression of silicate mineral crystallization in response to elevated h 2 o concentrations in the parent magmas the parental magmas that produced chromitites may have intruded into the volcano sedimentary greenstone belts of a supra subduction zone setting

thermodynamic constraints on mineral carbonation of serpentinized peridotite abstract carbonation of serpentinite appears to be a promising process to mitigate rising concentrations of atmospheric co2 however given that chemical affinities of mineral carbonation reactions in serpentinized peridotite change drastically with temperature protolith and the activities of dissolved constituents this process is incompletely understood in this report numerical models are used to investigate the heterogeneous phase equilibria and the speciation of intergranular fluids during mineral carbonation of serpentinite dunite at 100 200 300 and 400 c the results suggest that temperature dependent activity gradients of both aqueous carbon dioxide aco2 aq and aqueous silica asio2 aq determine the carbonation potential of serpentinite at low to moderate temperatures there is ample thermodynamic driving force for the carbonation of serpentinite as the gradients in asio2 aq and aco2 aq set between talc quartz magnesite and serpentine brucite equilibria are steepest with increasing temperature these activity gradients become smaller because the stability fields of brucite serpentine and talc expand toward higher aco2 aq and asio2 aq while the stability field of magnesite contracts in addition the enhanced solubility of quartz toward higher temperatures shifts the talc quartz magnesite equilibrium to very high aco2 aq field observations of carbonated serpentinite reveal a rather simple sequence of arrested carbonation reactions which is typically fossilized as spatially distinct metasomatic zones a zone of serpentinized peridotite is followed by a zone of serpentine carbonate then talc carbonate and finally quartz carbonate our modeling results not only reproduce these observations they also suggest that complete carbonation is favored at low to moderate temperatures since complete carbonation of serpentinite is achieved at relatively small fluid to rock ratios at temperatures 200 c prolonged fluid influx at low temperatures can result in decarbonation and silicification of the altered rock in contrast at temperatures 200 c decarbonation and silicification reactions are unlikely even at very high fluid to rock ratios since serpentinized peridotite is highly reactive in the presence of co2 aq its widespread exposure at slow and ultraslow spreading mid ocean ridges may represent a significant sink for co2 in the global carbon cycle our modeling results can be used to evaluate fluid rock interactions in active or fossil mineral carbonation systems if the mineralogy is known and the temperature of formation can be constrained independently the asio2 aq aco2aq oxygen fugacity fo2 g and ph can be estimated in turn if the alteration temperature asio2 aq and aco2 aq are known governing phase equilibria can be approximated the latter is a promising tool to monitor the reaction progress during co2 sequestration into serpentinized peridotite

solution to the volume problem in serpentinization kernel pattern consists of a rim of completely serpentinized peridotite surrounding a core of partly serpentinized or unserpentinized peridotite it is found adjacent to shear zones in some serpentinites kernels are commonly rectangular with length width ratios of 1 to 3 the boundary between the completely serpentinized rim and the unserpentinized core is commonly cut at a high angle by cross fractures the cross fractures which contain either picrolite or chrysotile asbestos taper out in the core and widen in the rim they are almost always perpendicular to the core rim boundary and point into the core of the kernel in this sense they are radially distributed in the rim the kernel pattern can be observed in thin section in outcrop and on the megascopic scale of tens of metres cross fractures represent expansion fractures in serpentinite in the rim of the kernel caused by an increase in volume acompanying serpentinization of the peridotite in the core of the kernel as the serpentinization front penetrates into the kernel the serpentinized peridotite expands however the serpentinite in the rim cannot expand and must fracture to accommodate the increase in volume as serpentinization proceeds more expansion occurs extending the fractures farther into the core and requiring the fractures in the existing serpentinite to widen these fractures are subsequently filled by serpentine minerals the resulting pattern consists of a rim of serpentinite cut by serpentine veins that surrounds a core of peridotite measured densities of cross fractures in the rims of kernels are consistent with those expected from the magnitude of the volume change accompanying serpentinization of peridotite

in situ carbonation of peridotite for co2 storage the rate of natural carbonation of tectonically exposed mantle peridotite during weathering and low temperature alteration can be enhanced to develop a significant sink for atmospheric co2 natural carbonation of peridotite in the samail ophiolite an uplifted slice of oceanic crust and upper mantle in the sultanate of oman is surprisingly rapid carbonate veins in mantle peridotite in oman have an average 14c age of 26 000 years and are not 30 95 million years old as previously believed these data and reconnaissance mapping show that 104 to 105 tons per year of atmospheric co2 are converted to solid carbonate minerals via peridotite weathering in oman peridotite carbonation can be accelerated via drilling hydraulic fracture input of purified co2 at elevated pressure and in particular increased temperature at depth after an initial heating step co2 pumped at 25 or 30 c can be heated by exothermic carbonation reactions that sustain high temperature and rapid reaction rates at depth with little expenditure of energy in situ carbonation of peridotite could consume 1 billion tons of co2 per year in oman alone affording a low cost safe and permanent method to capture and store atmospheric co2

use of a three dimensional laser scanner to digitally capture the topography of sand dunes in high spatial resolution we herein report the results of a eld study that was designed to test the feasibility of using ground based lidar to map the topography of a sand dune in high spatial resolution a portable cyrax 2500 three dimensional 3d laser scanner was used to digitally capture the topography of a barchan roughly 4 m tall and 50 m long located in the white sands national monument new mexico we performed eleven scans around the barchan and obtained the elevation relative to the inter dune at at roughly 1 4 million points on the dune surface the elevation point data were then interpolated to yield a continuous surface model of the dune topography with c 10 cm spatial resolution and c 6 mm position accuracy the results from this eld study clearly demonstrate the potential of ground based lidar as a mapping tool for use in aeolian research and other earth science applications the 3d surface model of the dune can describe the morphology with hitherto unprecedented detail moreover the surface of the dune is mapped with a minimum of foot traf c on the dune itself copyright 2004 john wiley sons ltd

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

effects of serpentinization on the lithospheric strength and the style of normal faulting at slow spreading ridges rock deformation experiments indicate that serpentinization can strongly influence the strength and tectonics of the oceanic lithosphere strength versus depth profiles calculated for conditions appropriate for slow spreading ridges indicate that the presence of serpentinite can reduce the integrated strength of the lithosphere by up to 30 results from flexural fault models indicate that if serpentinization is isolated to fault zones strain localization should be enhanced providing an explanation for the variations in the style of normal faulting along slow spreading ridge segments at segment centers where serpentinites are scarce deformation is accommodated on closely spaced faults with small throws at the segment ends where serpentinites are most abundant faults are widely spaced and have large throws q 1997 elsevier science b v

iron partitioning and hydrogen generation during serpentinization of abyssal peridotites from 15 n on the mid atlantic ridge aqueous dihydrogen h2 aq is produced in copious amounts when seawater interacts with peridotite and h2o oxidizes ferrous iron in olivine to ferric iron in secondary magnetite and serpentine poorly understood in this process is the partitioning of iron and its oxidation state in serpentine although both impose an important control on dihydrogen production we present results of detailed petrographic mineral chemical magnetic and mosbauer analyses of partially to fully serpentinized peridotites from the ocean drilling program odp leg 209 mid atlantic ridge mar 15 n area these results are used to constrain the fate of iron during serpentinization and are compared with phase equilibria considerations and peridotite seawater reaction path models in samples from hole 1274a mesh rims reveal a distinct in to out zoning from brucite at the interface with primary olivine followed by a zone of serpentine brucite magnetite and finally serpentine magnetite in the outermost mesh rim the compositions of coexisting serpentine mg 95 and brucite mg 80 vary little throughout the core about 30 50 of the iron in serpentine brucite mesh rims is trivalent irrespective of subbasement depth and protolith harzburgite versus dunite model calculations suggest that both partitioning and oxidation state of iron are very sensitive to temperature and water to rock ratio during serpentinization at temperatures above 330 c the dissolution of olivine and coeval formation of serpentine magnetite and dihydrogen depends on the availability of an external silica source at these temperatures the extent of olivine serpentinization is insufficient to produce much hydrogen hence conditions are not reducing enough to form awaruite at t 330 c hydrogen generation is facilitated by the formation of brucite as dissolution of olivine to form serpentine magnetite and brucite requires no addition of silica the model calculations suggest that the iron distribution observed in serpentine and brucite is consistent with formation temperatures ranging from 150 to 250 c and bulk water to rock ratios between 0 1 and 5 these conditions coincide with peak hydrogen fugacities during serpentinization and are conducive to awaruite formation during main stage serpentinization the development of the common brucite rims around olivine is either due to an arrested reaction olivine brucite serpentine brucite or reflects metastable olivine brucite equilibria developing in the strong gradient in silica activity between orthopyroxene talc serpentine and olivine serpentine brucite

the assessment of rockfall hazard at the base of talus slopes fragmental rockfall is characterized by the independent movement of individual rock fragments after detachment from a rock face the continued operation of the process leads to the accumulation of talus slopes on talus slopes the rockfall shadow extends beyond the base of the talus and consists of scattered boulders that have run out beyond the base of the slope the landing probability of boulders in the shadow is examined return periods of the order of 1000 years relative to a house site are typical rockfall behaviour particularly with respect to run out into the shadow can be assessed using geological evidence empirical methods physical modelling and computer based analytical models an empirical minimum shadow angle of 27 5 i e the angle between the distal limit of the shadow and the top of the talus slope is suggested and would be useful in rockfall vulnerability studies at the base of talus slopes as a first approximation to shadow limits it is preferable to the use of the rockfall fahrb

rockfall hazard analysis using lidar and spatial modeling abstract rockfalls have been significant geohazards along the canadian class 1 railways cn rail and cp rail since their construction in the late 1800s these rockfalls cause damage to infrastructure interruption of business and environmental impacts and their occurrence varies both spatially and temporally the proactive management of these rockfall hazards requires enabling technologies this paper discusses a hazard assessment strategy for rockfalls along a section of a canadian railway using lidar and spatial modeling lidar provides accurate topographical information of the source area of rockfalls and along their paths spatial modeling was conducted using rockfall analyst a three dimensional extension to gis to determine the characteristics of the rockfalls in terms of travel distance velocity and energy historical rockfall records were used to calibrate the physical characteristics of the rockfall processes the results based on a high resolution digital elevation model from a lidar dataset were compared with those based on a coarse digital elevation model a comprehensive methodology for rockfall hazard assessment is proposed which takes into account the characteristics of source areas the physical processes of rockfalls and the spatial attribution of their frequency and energy

matrix rheology effects on reaction rim growth i evidence from orthopyroxene rim growth experiments the rim forming reaction quartz olivine orthopyroxene is used to investigate the effect of matrix rheology on rim growth rates orthopyroxene rim growth around olivine grains in quartz matrix is compared to rim growth around quartz grains in an olivine matrix at constant p t within one single capsule orthopyroxene rims grow faster around quartz clasts in olivine matrix than around olivine clasts in quartz matrix fourier transform infra red spectra indicate that the entire samples are water saturated because of water adsorption on the reactant grain surfaces the increased orthopyroxene growth rates in olivine matrix as opposed to quartz matrix are interpreted in terms of matrix rheology where in the two different matrix inclusion arrangements the olivine matrix behaves softer and the quartz matrix more rigid the strain energy associated with accommodation of the negative reaction volume is higher for the quartz than the olivine matrix and reduces the free energy that drives orthopyroxene rim growth growth textures in both kinds of orthopyroxene rims indicate that the diffusivity of mgo slightly exceeds the diffusivity of sio2 the relative mobility of mgo and sio2 at given p t fh2o seems to be controlled by energy minimization during orthopyroxene growth at the compressive ol opx interface our experiments provide evidence for two previously overlooked effects relevant to rim growth reactions in metamorphic rocks i diffusivity along chemical potential gradients to reaction sites is a function of rheology and ii the relative diffusivity of components during reaction rim or corona growth is a function of local volume changes at the rim s interfaces

alteration of the subducting oceanic lithosphere at the southern central chile trench outer rise hydrothermal circulation and brittle faulting processes affecting the oceanic lithosphere are usually confined to the upper crust for oceanic lithosphere created at intermediate to fast spreading rates lower crust and mantle rocks are therefore relatively dry and undeformed however recent studies at subduction zones suggest that hydration of the oceanic plate is most vigorous at the trench outer rise where extensional bending related faulting affects the hydrogeology of the oceanic crust and mantle to understand the degree of hydration we studied the seismic velocity structure of the incoming nazca plate offshore of southern central chile 43 s here the deep sea trench is heavily filled with up to 2 km of sediments seismic refraction and wide angle data complemented by seismic reflection imaging of sediments are used to derive a two dimensional velocity model using joint refraction and reflection traveltime tomography the seismic profile runs perpendicular to the spreading ridge and trench axes the velocity model derived from the tomography inversion consists of a 5 3 km thick oceanic crust and shows p wave velocities typical for mature fast spreading crust in the seaward section of the profile with uppermost mantle velocities as fast as 8 3 km s approaching the chile trench seismic velocities are significantly reduced however suggesting that the structures of both the oceanic crust and uppermost mantle have been altered possibly due to a certain degree of fracturing and hydration the decrease of the velocities roughly starts at the outer rise 120 km from the deformation front and continues into the trench even though the trench is filled with sediment basement outcrops in the outer rise frequently pierce the sedimentary blanket anomalously low heat flow values near outcropping basement highs indicate an efficient inflow of cold seawater into the oceanic crust hydration and crustal cracks activated by extensional bending related faulting are suggested to govern the reduced velocities in the vicinity of the trench considering typical flow distances of 50 km water might be redistributed over most of the trench outer rise area where trapped in faults seawater may migrate down to mantle depth causing up to 9 of serpentinization in at least the uppermost 2 km of the mantle between the outer rise and the trench axis

landslide risk zonation along mountainous highway considering rock mass classification landslide and especially rockfall hazard widely occurs along cut slopes in mountainous regions the risk assessment of mass movements is still one of most challenging problems in slope engineering geology we propose a routine method to assess rock slide and rockfall risk of cut slopes essentially based on slope properties and rock mass structure the method is a lean low cost path to a risk estimate rock block size is simplified into two classes small with a volume less than 1 0 m3 and large greater than 1 0 m3 studies indicate that for a slope with n small medium rock blocks the possibility of rockfalls can be estimated by 1 1 p n in which p is the likelihood of one small rock block fall the possibility of other types of mass movement can be determined by the first order second moment fosm method based on this an exponent equation was adopted to evaluate the consequence and the risk the methodology is demonstrated by a case study from the mountains of mentougou district beijing china based on the investigations of geological conditions i e lithology weathering and rock mass structure and some historical mass movement data of the cut slopes a zonation map for rockfall and rock slide risk along a 17 km section of a road is presented the result is supported by mass movement event observations in the recent 2 years

combining airborne and terrestrial laser scanning for quantifying erosion and deposition by a debris flow event abstract we quantified the sediment volume transported by a major debris flow event in the halltal austrian alps using a combination of terrestrial tls and airborne laser scanning als which has rarely been carried out before a digital terrain model dtm derived from als data pre event surface was combined with a dtm derived from tls data post event surface both datasets were aligned and compared in a cut and fill analysis estimating differential volumes the main focus lay on the evaluation and accuracy assessment of the applied method tie point based registration of both datasets proved to be insufficient additional alignment by multi station adjustment was necessary to minimise the averaged height error between both datasets amounting for a volumetric error of less than 10 which is comparable to pure als campaigns larger errors were estimated for complex terrain with low scanning resolutions a particular problem in data processing was the low and dense shrub vegetation in the study area which required a specifically adapted filter algorithm an insufficient ground representation was observed for the als data overestimating ground heights for averaged 70 cm despite these limitations the approach proved to be suitable for accurate extreme event quantification the starting zones of the debris flows lie at the bedrock debris interface where runoff is concentrated volumes of 5000 to 12 000 m3 were assessed volume estimation worked better for the erosional than for the depositional features this is because the erosional gullies are relatively deep and the calculation is not affected by pre event vegetation while erosion and sedimentation are balanced for one of the three catchments investigated the deposited volumes are higher than the detected eroded volumes for the other two the reasons are not fully understood the magnitude of the flows was determined by catchment size topographical characteristics and deforestation by a major wildfire in 1946

precambrian continental crust of india and its evolution the indian precambrian continental crust exhibits a variety of geological features fashioned at different times by different geotectonic processes the bulk of this crust was formed prior to 2600 m y ago and remobilized at least twice between 2600 2000 m y ago early proterozoic mobile belt epmb and 2000 1500 m y ago middle proterozoic mobile belt mpmb three early precambrian nucleii karnataka kn jeypore bastar jbn and singhbhum sn appear to have survived in the craton and are characterized by low grade supracrustals and tonalitic trondhjemite gneisses formed 3800 2600 m y ago the epmb event involved sedimentation amphibolite granulite facies metamorphism and co 2 k metasomatism and produced amphibolite facies rocks and k granites in the north and charnockite and other granulite facies rocks in the south gold sporadically distributed in the supracrustal rocks of the craton was remobilized during the epmb event k granites form a garland around the central dharwar craton sugg

landslide inventory maps new tools for an old problem landslides are present in all continents and play an important role in the evolution of landscapes they also represent a serious hazard in many areas of the world despite their importance we estimate that landslide maps cover less than 1 of the slopes in the landmasses and systematic information on the type abundance and distribution of landslides is lacking preparing landslide maps is important to document the extent of landslide phenomena in a region to investigate the distribution types pattern recurrence and statistics of slope failures to determine landslide susceptibility hazard vulnerability and risk and to study the evolution of landscapes dominated by mass wasting processes conventional methods for the production of landslide maps rely chiefly on the visual interpretation of stereoscopic aerial photography aided by field surveys these methods are time consuming and resource intensive new and emerging techniques based on satellite airborne and terrestrial remote sensing technologies promise to facilitate the production of landslide maps reducing the time and resources required for their compilation and systematic update in this work we first outline the principles for landslide mapping and we review the conventional methods for the preparation of landslide maps including geomorphological event seasonal and multi temporal inventories next we examine recent and new technologies for landslide mapping considering i the exploitation of very high resolution digital elevation models to analyze surface morphology ii the visual interpretation and semi automatic analysis of different types of satellite images including panchromatic multispectral and synthetic aperture radar images and iii tools that facilitate landslide field mapping next we discuss the advantages and the limitations of the new remote sensing data and technology for the production of geomorphological event seasonal and multi temporal inventory maps we conclude by arguing that the new tools will help to improve the quality of landslide maps with positive effects on all derivative products and analyses including erosion studies and landscape modeling susceptibility and hazard assessments and risk evaluations

depositional setting and geometric structure of the beypazari lignite deposits central anatolia turkey abstract the neogene beypazari basin is one of the important coal districts of central anatolia with approximately 600 million short tons lignite reserves the coal bearing neogene sediments occurring in the beypazari basin are divided into seven formations in ascending order coraklar hirka akpinar cayirhan bozbelen and kirmir formations with sariyar limestone and teke volcanics the coraklar formation consists of cross bedded sandstones channel fill conglomerates mudstones carbonaceous shales and volcanoclastic pebblestones which are fluvial in origin the lower lignite seam occurs in the lower part of the coraklar formation the upper lignite seam occurs in the uppermost part of the coraklar formation and is overlain by the hirka formation with a sharp contact the hirka formation consists mainly of alternating shale mudstone bituminous shale claystone tuffite and silicified limestone and they all are apparently of lacustrine origin the lignite deposite occur in the cayirhan and koyuna ili parts of the beypazari neogene basin the cayirhan coal field consists of lower and upper lignite seams but the koyuna ili field contains only an upper lignite seam the lower lignite seam which does not crop out at the surface indicates a fluvial origin of the lignite deposits based on the lateral discontinuity and the lower sulphur content of the lower lignite seam and the sedimentologic and stratigraphic features of the associated sediments but the uniform stratigraphic and sedimentologic features high sulphur content and wide spread distribution of the upper lignite seam indicate that the upper lignites were deposited probably in a mud flat facies of playa lake environment the lower and upper lignites are completely different in relation to the depositional environment the geometry and degree of rank in lateral directions the lateral spreading and geometry of the lower lignite deposits were controlled by channel floodplain and well drained marshes of a fluvial system on the basis of recent drillings and field investigations the lower lignite deposit has been demonstrated to be a linear spreading parallel to the axis of the channel fills and throughcross beds in clastic sediments of fluvial facies therefore the lower lignite deposits trend along a northeastern direction and is not expected to be as widely spread as the upper lignites

listvenite and related rocks perspectives on terminology and mineralogy with reference to an occurrence at cregganbaun co mayo republic of ireland the rock listvenite is named and defined by reference to historical observations and recommendations are made so that listvenite s s can be distinguished from related carbonate rich alteration products of ultramafic rocks the mineralogy and tectonic setting of listvenite are reviewed taking into account the descriptions and classifications used in the literature the petrography of listvenite and related rocks at cregganbaun serves as a reference to illustrate the characteristics of true listvenite and closely related products of listvenitic alteration

metamorphic record of high pressure dehydration of antigorite serpentinite to chlorite harzburgite in a subduction setting cerro del almirez nevado filabride complex southern spain

high temperature alteration of abyssal ultramafics from the islas orcadas fracture zone south atlantic ultramafic rocks dredged from the islas orcadas fracture zone along the sw indian ocean ridge 6 e and 54 s show evidence of progressive hydration beginning at temperatures greater than 600 c and perhaps as high as 900 c and continuing to less than 50 c there are two principal types of alteration present in the ultramafic rocks both of which are the result of hydration reactions the first type of alteration involves hydration of original clinopyroxene orthopyroxene and olivine to amphibole talc secondary olivine and serpentine the second is a vein type of alteration and results in the formation of veins of amphibole chlorite talc and serpentine the alteration appears to be episodic the sequence of events suggested by the petrography is 1 clinopyroxene altering to amphibole 2 orthopyroxene altering to talc or talc olivine 3 supersolvus hornblende veining 4 coexisting actinolite hornblende veining 5 chlorite chlorite actinolite or chlorite secondary clinopyroxene veining 6 talc veining 7 serpentine veining and 8 pervasive serpentinization the alteration fluid is most likely seawater it is suggested that the high temperature alterations may reflect seawater circulation into the upper mantle

geochemistry and mineralogy of pd in the magnetitite layer within the upper gabbro of the mesoarchean nuasahi massif orissa india palladium concentrations of 1 3 ppm with an average pt pd ratio of 0 15 have been located for the first time in a magnetitite layer in the nuasahi massif in orissa india this layer occurs at a high stratigraphic level in the complex and is nearly 4 km long and 5 12 m thick the sections of the pd rich zone identified to date extend over a distance of 1 km at the southern end of the layer several phases of mineralization are evident the first primary assemblage of platinum group minerals pgm contains pd sulfides vysotskite pd pb alloys zvyagintsevite and a pd in alloy a mineral probably new to mineralogy these pgm are confined to central magnetite grains in the magnetitites the magnetite grains with exsolved fine laths of ilmenite at centers are referred to as central magnetite grains these central magnetite grains are commonly surrounded by blebs of ilmenite and magnetite that contain the majority of the pgm these are dominated by pd antimonides variably altered to pd oxides and other pgm including ptas2 sperrylite rus2 laurite and irrhass irarsite hollingwothite many of these pgm also occur in the interstitial silicates with rare occurrences in the central magnetite grains we propose that the platinum group elements pge crystallized during a minor sulfide saturation event that occurred as the magnetitites crystallized this event produced the minor cu sulfides in these magnetitites later introduction of antimony and arsenic during the alteration event that produced the blebby ilmenite and magnetite led to the more primary pgm being succeeded by the main pgm assemblage dominated by pd antimonides these are associated with secondary cu minerals and sperrylite subsequent oxidation during weathering in the hot wet indian climate produced the pd oxides the nuasahi massif is a sill like archean layered ultramafic mafic intrusion genetically linked to high mg siliceous basalt or boninites and is characterized by unusually thick layers of chromitite pge are concentrated in these chromitites and in the base metal sulfide bearing breccias in the overlying gabbro the pd in the magnetitites described here indicates the presence of a third level where pge are concentrated and a magma that crystallized to produce pge concentrations at three stratigraphic levels in the massif this indicates that similar thin sill like intrusions hosting unusually thick chromitites may also have pge concentrations at a number of stratigraphic levels

optimization of lidar scanning and processing for automated structural evaluation of discontinuities in rockmasses terrestrial light detection and ranging lidar can be used for the delineation and evaluation of geomechanically controlled hazards the united states geological survey 1 has adopted the use of lidar through numerous projects as discussed in 2 other examples of the use of lidar surveys for geological data collection include discussion of the process of acquiring digital outcrop models for stratigraphic modelling 3 mapping basalt flow units 4 structural mapping of a large landslide 5 and evaluation of rockfall source and accumulation zones 6 7 in non geologicalbased applications lidar has been used for projects ranging from volumetric analysis in open pit mines 8 to recording and cataloguing archaeological digs in ancient ruins 9 the equipment mobility accuracy and rate of data collection in comparison to conventional surveying and stereophotogrammetric methods have allowed existing surface analysis projects to proceed at unprecedented levels of detail and have promoted new applications the use of terrestrial ground based lidar as a structural analysis and measurement tool has been investigated in detail by kemeny and post 10 feng and roshoff 11 pringle et al 12 slob et al 13 and others once the data is acquired and the primary 3d model is generated as x y z data points with intensity scalars or mapped colourization via photo coupling the analytical process can proceed in a similar fashion to modern photogrammetric techniques such as those applied by haneberg et al 14 both applications can replace traditional field mapping processes including the use of a compass or inclinometer to measure orientation photos and notebooks to keep records and manual data entry further the conventional measurement of

control of the products of serpentinization by the fe2 mg 1 exchange potential of olivine and orthopyroxene it is argued that the high mg content mg number1 4 95 3 of the serpentine minerals in serpentinized peridotite is a consequence of the environmental femg 1 exchange potential imposed on the system by the abundance of olivine and orthopyroxene mass balance in the serpentinization reaction then requires the precipitation of an ironrich mineral that in most cases is magnetite this causes hydrogen to be evolved in an oxygen conserved reaction the low variance mineral assemblage ol srp brc mag sets the chemical potentials of h2o sio2 and o2 internally at an early stage in the process but the paragenetic assessment of serpentinites is rendered difficult by the variable and usually unknown fe3 content of the serpentine minerals particularly lizardite whole rock analyses of highly to completely serpentinized peridotites reveal fe sfe ratios40 4 with an average value 0 69 similar to that of magnetite 0 67 this feature may be attributed to the presence of high fe lizardite as has been found in mo ssbauer spectroscopy studies electron microprobe and scanning electron microcope analyses in the literature exhibit element trends e g decreasing si vs sfe a p f u for olivinepseudomorph lizardite and with some exceptions for bastite lizardite that show a substitution of the cronstedtite component fe charge balanced ontand m sites cronstedtite substitution will be favoured at low temperature and or low hydrogen fugacity and in these circumstances less magnetite will be evolved during serpentinization in some cases none at all some bastite lizardites from sea floor settings show evidence of m site vacancy substitution of fe for fe in the course of progressive serpentinization micrometer to millimeter scale variations in sio2 potential may well be present but their influence on fe in lizardite seems to be limited to a few cases of lizardite associated with orthopyroxene chrysotile is on average more mg rich and less variable in fe mg ratio than lizardite facts that may be attributed to the greater fe content of lizardite chrysotile veins provide the best record available to us of the environmental femg 1 exchange potential in the pore fluid attending serpentinization this potential serves as a robust control on serpentine and brucite compositions although it may fail after olivine and orthopyroxene have been armoured or eliminated and in more open system environments high water rock ratio such as on the sea floor or at serpentinite host rock contacts the default assumption in microprobe analyses that measured iron is all fe can lead to inappropriate petrological conclusions in the case of serpentinites

depositional response to foreland deformation in the carboniferous of eastern kentucky the appalachian basin is a typical foreland basin that has subsided episodically under the loads of successive thrust sheets the dynamics of basin subsidence and upwarping of basin margin arch systems reflects the flexural properties of the lithosphere quantitative models of the lithosphere depend on assumed rheological properties this study attempts to test these geodynamic models in a part of the appalachian basin mississippian deposition is correlated with waning acadian tectonism orogenic quiescence coincided with basin overdeepening and uplift of the cincinnati arch or forebulge although the foreland basin was mudstone dominated shoaling along the crest of the basin margin arch system resulted in reworking and wedges of unconformities in contrast the onset of alleghenian orogenesis during the pennsylvanian is reflected in a thick wedge of terrigenous clastic sediments the pennsylvanian basin fluctuated between underfilled restricted marine and overfilled nonmarine conditions rapid response of the basin to thrust sheet loading is inferred these characteristics of mississippian and pennsylvanian deposition support a viscoelastic model of the lithosphere

rock avalanche and rock glacier a compound landform study from hornsund svalbard abstract on the northern coast of the hornsund fjord at sw svalbard numerous rock block accumulations flank the foot of rotjesfjellet ridge whereas these accumulations are widely described as rock glaciers this study shows that other factors also influence formation of these landforms in this study morphometric profiling and terrain analyses lichenometry optical granulometry schmidt hammer measurements geophysical measurements using electric resistivity tomography geodetic measurements using terrestrial lidar and rockfall modelling were used to clarify the formation of one unusual block accumulation the morphometric analysis of a detailed 0 5 m dem and relief profiles showed distinctly different morphology of one of four studied block accumulations the electric resistivity tomography revealed an ice core in the accumulation the schmidt hammer sampling helped to establish relatively younger age of the lobe like left part of accumulation and finally the lichenometry was employed to place the event on the approximate position on the timescale in conclusion the unusual block accumulation is a result of two consequent processes first a typical foothill rock glacier has developed and consequently a large rock avalanche occurred adding material and deforming the nw part of the accumulation based on the results of lichenometry the rock avalanche was estimated to be 250 50 years old the study thus presents one of the few reported slope deformation events from the recently deglaciated arctic areas

dynamic control on serpentine crystallization in veins constraints on hydration processes in oceanic peridotites deformation and hydration processes are intimately linked in the oceanic lithosphere but the feedbacks between them are still poorly understood especially in ultramafic rocks where serpentinization results in a decrease of rock density that implies a volume increase and or mass transfer serpentinization is accompanied by abundant veining marked by different generations of vein filling serpentines with a high variety of morphologies and textures that correspond to different mechanisms and conditions of formation we use these veins to constrain the role of deformation and mass transfer processes during hydration of oceanic peridotites at slow spreading ridges we have selected a representative set of veins from ocean floor serpentinites of the mid atlantic ridge near kane transform fault 23 n and characterized these in detail for their microstructures and chemistry by coupling optical and electron microscopy sem tem with electron microprobe analyses four main veining episodes v1 to v4 accompany the serpentinization the first episode identified as vein generation v1 is interpreted as the tectonically controlled penetration of early seawater dominated fluid within peridotites enhancing thermal cracking and mesh texture initiation at 3 4 km up to 8 km depth and at t 300 350 c the two following vein stages v2 and v3 formed in a closed diffusive system and accommodate volume expansion required to reach almost 50 serpentinization of the protolith the cracks exploited by these veins were caused by the progressive unroofing at depths of 4 to 2 km along a detachment fault degree and rate of serpentinization seem to be controlled by the capacity of the system to create space and to drive the mass transfer needed for ongoing serpentinization and this capacity is in turn linked to the exhumation rate and local tectonics during this period water consumed by hydration may prevent the establishment of convective hydrothermal cells the onset of an open hydrothermal system in the shallow lithosphere 2 km where brittle fracturing and advective transfer dominate and enable the completion of serpentinization is marked by the last vein generation v4 these results show a complete history of alteration with the crystallization of different types of serpentine recording different tectonic events chemical conditions and modes of hydrothermal alteration of the lithosphere

coal facies studies in the eastern united states coals in the eastern united states east of the mississippi river have been the subject of a number of coal facies studies going back to the 19th century such studies would not necessarily fall within a strict modern classification of coal facies studies but if a study encompassed some aspects of paleobotany palynology petrology geochemistry or sedimentology we assumed that some data and interpretations may be of use in evaluations of the facies references are presented as a guide for further research with annotation in the tables

metamorphism of deep seated rocks from the garrett ultrafast transform east pacific rise near 13 25 s in spite of 10 years of extensive exploration of the east pacific rise the petrology of the fast slipping transforms remains poorly documented in 1980 metagabbros and serpentinites were dredged from the deepest trough 4616 4820 m in depth of the garrett ultrafast transform which intersects the east pacific rise near 13 25 s 16 cm yr total spreading rate previous works on their protolith concluded that the samples consist of serpentinized refractory upper mantle and lower crust gabbroic cumulates in addition several ultramafic rocks showing evidences of magmatic impregnation were believed to represent mantle crust transition zone as observed in ophiolite complexes the present work focuses on the postigneous evolution of the rocks affected by hydrothermal circulation an early stage of amphibolitization occurred at about 700 400 c and probably down to 300 c in the most evolved gabbros ti fe gabbros the amphibole compositional variations suggest evolution of the metasomatic solution and temperature through time from the amphibolite facies down to the lower greenshist facies high chlorine ferruginous hornblendes 3 5 wt cl found in veins of the ferrogabbros suggests that pore fluids in this type of material evolved in situ to a ferruginous brine the decreasing temperature 300 200 c and further fracturing favored more or less pervasive serpentinization of the olivine rich samples ultramafics and olivine gabbros the release of ca in the solution contributed to the alteration of the plagioclase bearing rocks troctolites and gabbros which were invaded by calc silicates hydrogrossular prehnite pumpellyite and epidote a process which is referred to as rodingitization the occurrence of monomineralic veins of al pumpellyite in some metagabbros suggests very low o2 conditions in the lower ocean crust ph2o 2 kbar low o2 also inferred from the composition of the other calc silicates and indicates low permeability and limited fluid circulation during retrograde metamorphism further uplift and emplacement of the rocks on the seafloor of the transform domain were accompanied by low temperature crystallization of zeolite and aragonite high mg and co2 in monomineralic veins and clay minerals in veins and in external alteration rims the garrett s samples are by many respects comparable to typical ocean floor metabasites from various settings the rocks recorded igneous and metamorphic transformations similar to those expected beneath spreading ridges unaffected by transform tectonics the metamorphism is a consequence of the dynamics of spreading propagation of the cracks and penetration of seawater deeper in the cooling crust however the extent of fissuring and the subsequent hydration probably increase drastically with proximity to the garrett transform most of the observed metasomatic reactions have a limited extent and occurred at depth without significant deformation of the rocks rapid uplift of the rocks initiated by vertical components of the transform tectonics was probably induced by serpentinization of the ultramafics buoyancy of serpentinite and intense mass wasting at the surface of seafloor however emplacement by diapirism is not completely ruled out if the dredged samples are relatively undeformed poorly altered rocks carried up by protusions of ductile serpentine which is now too fragile to be sampled by dredging

the application of high resolution sequence stratigraphy to fluvial systems a case study from the upper carboniferous breathitt group eastern kentucky usa the pennsylvanian pikeville hyden and four corners formations of the breathitt group in eastern kentucky usa contain six major facies associations along with a number of subassociations these facies associations are offshore siltstone rhythmically bedded mouthbar heteroliths predominantly fine grained floodplain deposits minor channel fills major distributary channels and major stacked fluvial bodies the stacked fluvial bodies are incised into a variety of open marine and delta plain deposits have widths of several kilometres and exhibit a range of sandy fill types these fluvial complexes are interpreted as incised valley fills parasequences and parasequence sets are not identifiable nonetheless it is possible to identify systems tracts on the basis of sequential position facies associations and systematic changes in architectural style and sediment body geometries the studied portion of the breathitt group comprises stacked 4th order sequences which occur in lowstand transgressive and highstand sequence sets related to the development of a lower frequency base level cycle in the lowstand sequence set incision associated with successive 4th order sequence boundaries has commonly removed all the hst and tst of the underlying sequences such that succeeding 4th order incised valley fills are amalgamated within the transgressive sequence set incision is at a minimum and incised valley fills tend to stack discretely with the maximum amount of fine grained tst and hst between them the highstand sequence set is transitional between the lowstand and transgressive sequence sets in terms of the amount of transgressive and highstand deposits preserved incised valley fills tend to stack discretely

dip slope mapping of sedimentary terrain using polygon auto tracing and airborne lidar topographic data abstract dip slope mapping is a fundamental task for landslide investigation and mitigation however most dip slope mapping methods involve visual interpretations and manual processes that are inevitably subjective and time consuming the advent of high resolution digital elevation models dem and increases in computing power have provided opportunities to improve the dip slope mapping process this study proposes a polygon auto tracing method for generating dip slope maps based on airborne light detection and ranging lidar data and a customized spatial analysis toolset developed in python this method requires the input of strata boundaries produced for sedimentary terrain based on 2 m resolution lidar dems the method begins by deriving the raster layer of the dip direction of the bedding and it then executes a series of raster calculations among the three raster layers slope aspect and dip direction to extract the dip slope raster cells using the clustering pattern of the dip slope raster cells we implement the point density analysis tool to determine the dip slope areas the arcgis modelbuilder platform is used to lay out an automated workflow for the proposed polygon auto tracing method using the customized toolset for demonstration purposes we successfully mapped 298 dip slopes in the study area which frequently experiences dip slope landslides and is located in the sedimentary terrain of northern taiwan the dip slope mapping results were compared and validated against two government funded visually interpreted dip slope maps our dip slope mapping results were also used in a daylight analysis along major freeways to identify potential locations of daylighted dip slopes

unraveling the sequence of serpentinization reactions petrography mineral chemistry and petrophysics of serpentinites from mar 15 n odp leg 209 site 1274 1 the results of detailed textural mineral chemical and petrophysical studies shed new light on the poorly constrained fluid rock reaction pathways during retrograde serpentinization at mid ocean ridges uniformly depleted harzburgites and dunites from the mid atlantic ridge at 15 n show variable extents of static serpentinization they reveal a simple sequence of reactions serpentinization of olivine and development of a typical mesh texture with serpentine brucite mesh rims followed by replacement of olivine mesh centers by serpentine and brucite the serpentine mesh rims on relic olivine are devoid of magnetite conversely domains in the rock that are completely serpentinized show abundant magnetite we propose that low fluid flux serpentinization of olivine to serpentine and ferroan brucite is followed by later stages of serpentinization under more open system conditions and formation of magnetite by the breakdown of ferroan brucite modeling of this sequence of reactions can account for covariations in magnetic susceptibility and grain density of the rocks citation bach w h paulick c j garrido b ildefonse w p meurer and s e humphris 2006 unraveling the sequence of serpentinization reactions petrography mineral chemistry and petrophysics of serpentinites from mar 15 n odp leg 209 site 1274 geophys res lett 33 l13306

experimental study of the carbonation of partially serpentinized and weathered peridotites abstract carbonation of partially serpentinized and weathered peridotites was studied experimentally under hydrothermal conditions t 200 c p co 2 130 180 bars experiments were performed in a closed system using whole rock drill core samples height 1 cm diameter 1 cm as starting material the initial samples were composed mainly of meshwork serpentine relicts of primary olivine and an olivine weathering product deweylite assemblage two types of solutions each with a total salt content corresponding to that of average seawater 35 g l dissolved salts were used 1 a na ca cl solution 12 5 g l cacl2 22 5 g l nacl and 2 a nacl solution 35 g l nacl after 15 25 days of experimental treatment the samples were partly covered with carbonates in addition noticeable carbonation reactions had occurred below the sample surfaces within zones with thicknesses up to 250 m in the na ca cl solution both the olivine relicts and the deweylite assemblage were partly replaced by calcite along the surrounding serpentine veins however the extent of calcitization was found to be considerably larger for the deweylite assemblage than for the olivine bulk fluid analyses show an increase in the mg and si concentrations with reaction time in the nacl solution the deweylite assemblage was partly dissolved resulting in large voids within the reaction zone in contrast the olivine was replaced by magnesite under the conditions of our experiments the meshwork serpentine was not reactive but aided fluid infiltration into the rock samples the experimentally produced microtextures closely resemble those found in natural examples our study elucidates the mechanisms by which carbonates form in ultramafic rocks under relatively high p co 2 t conditions and particularly in the presence of ca bearing aqueous solutions the existence of a serpentine meshtexture and the presence of weathering products formed from primary mg silicates may have significant beneficial effects on in situ co2 mineral sequestration in ultramafic rocks

digital outcrop models applications of terrestrial scanning lidar technology in stratigraphic modeling abstract laser ranging is extremely accurate and efficient terrestrial scanning lidar light detection and ranging applied to outcrop stratigraphic mapping enables researchers to capture laser range data at a rate of thousands of individual x y z and laser intensity points per second these data in conjunction with complementary remotely and directly sampled data are used to conduct high precision facies characterization and to construct 3d geological computer models outcrop data are presented here to explain our workflow and to discuss the construction of rock based 3d digital outcrop models doms reproducibility and quantification are the drivers of this methodology high resolution terrestrial lidar acquisition processing interpretation and visualization are discussed and applied to mapping of geological surfaces in three dimensions laser generated models offer scientists an unprecedented visualization medium in a quantitative 3d arena applications of this technology include constructing and visualizing complex 3d earth models from outcrops for improved reservoir modeling flow simulation in hydrocarbon and aquifer systems and property modeling to constrain forward seismic modeling

lizardite versus antigorite serpentinite magnetite hydrogen and life the serpentinization of peridotite operates according to one or the other or a combination of two end member mechanisms in low temperature environments 50 300 c where lizardite is the predominant serpentine mineral olivine is consumed by reaction with h2o but its composition mg remains unchanged mg rich lizardite magnetite and dihydrogen gas brucite are products of the reaction at higher temperatures 400 600 c rates of mgfe diffusion in olivine are orders of magnitude faster with the result that the growth of mg rich antigorite can be accommodated by a compositional adjustment of olivine eliminating the need to precipitate magnetite and evolve hydrogen this latter end member mechanism probably best reflects the situation in the forearc mantle wedge

a remote sensing approach for landslide hazard assessment on engineered slopes earthworks such as embankments and cuttings are integral to road and rail networks but can be prone to instability necessitating rigorous and continual monitoring to date the potential of remote sensing for earthwork hazard assessment has been largely overlooked however techniques such as airborne laser scanning als are now ripe for addressing these challenges this research presents the development of a novel hazard assessment strategy combining high resolution remote sensing with a numerical modeling approach the research was implemented at a railway test site located in northern england u k als data and multispectral aerial imagery facilitated the determination of key slope stability variables which were then used to parameterize a coupled hydrological geotechnical model in order to simulate slope behavior under current and future climates a software toolset was developed to integrate the core elements of the methodology and determine resultant slope failure hazard which could then be mapped and queried within a geographical information system environment results indicate that the earthworks are largely stable which is in broad agreement with the management company s slope hazard grading data and in terms of morphological analysis the remote methodology was able to correctly identify 99 of earthworks classed as embankments and 100 of cuttings the developed approach provides an effective and practicable method for remotely quantifying slope failure hazard at fine spatial scales 0 5 m and for prioritizing and reducing on site inspection

quantitative risk assessment of rock slope instabilities that threaten a highway near canmore alberta canada managing risk calculation uncertainty in practice we present a quantitative risk assessment qra to guide decision making for selection of rock fall protection strategies the analysis corresponds to a section of highway near canmore alberta ca

rockfall activity from an alpine cliff during thawing periods abstract rockfall activity during thawing periods was investigated by collecting rockfall debris fallen on the snow covered talus slope in a cirque in the japanese alps near surface rock temperature was also monitored on the cirque wall maximum rockfall activity occurs on average about 10 days after the meltout of the cirque wall the intensive activity is rarely associated with precipitation events or diurnal frost cycles on the rockface a thermal conduction model suggests that rockfalls at this site occur most frequently when the seasonal thawing front penetrates to a depth of about 1 m in the bedrock while the freeze thaw penetration controls the maximum dimensions of detachable rock mass joint spacing on the rockface affects the size distribution of rockfall debris boulder falls resulting from seasonal frost weathering are considered to be the most important process responsible for the contemporary modification of the cirque wall the rockfall volume during a thawing period is usually 1 3 m3 which is equivalent to the rate of cirque wall retreat of the order of 0 01 mm year 1 however big boulder falls that occur once per decade can increase the retreat rate significantly

serpentine mineral replacements of natural olivine and their seismic implications oceanic lizardite versus subduction related antigorite we report on microstructural data obtained by optical microscopy and transmission electron microscopy concerning the crystallographic relationships of serpentine minerals with their host olivine in two contrasting situations in the first case mesh textured lizardite liz is developed in a standard 60 serpentinized oceanic harzburgite from the oman ophiolite where olivine converts to columnar lizardite the joined columns are perpendicular to the basal plane 001 liz corresponding to the pseudofibres observed optically the plane 001 liz is locally parallel to the narrow boundary ol liz thus column orientations register the interface of serpentinization the ol liz relationships are not strictly topotactic but reflect preferred cracking orientations in olivine parallel to 010 ol in the second case antigorite atg develops in a rare sample of antigorite schist in a kimberlite from moses rock colorado plateau representative of a suprasubduction zone mantle wedge high resolution transmission electron microscopy hrtem images along 010 atg show domains of very regular modulation with a 43 center dot 5 a wavelength m 17 where m is the number of silicate tetrahedra along the wave with few defects indicative of hp ht antigorite and also heavily kinked regions as fingerprints of strong tectonic shear tem imaging and electron diffraction patterns reveal two topotactic relationships between antigorite and olivine 100 atg 010 ol and atg ol the planes in contact are 001 atg 100 ol and 001 atg 010 ol respectively the 010 atg 001 ol and antigorite lamellae are parallel to the forsterite b axis in both cases the topography of olivine serpentine interfaces is controlled by open fluid pathways along microcracks oriented according to the anisotropy of the olivine aggregate in the cases studied the serpentine aggregate exhibits a preferred orientation inherited from that of the peridotite these results have some relevance to the seismic anisotropy of serpentinized mantle anisotropy of propagation of seismic waves as a result of the olivine fabric is maintained and reinforced with the development of lizardite conversely the development of antigorite produces a trench parallel fast s wave polarization and an anisotropy that is lowered at low degrees of serpentinization and then increased with increasing serpentinization

integrating field measurements a geomorphological map and stochastic modelling to estimate the spatially distributed rockfall sediment budget of the upper kaunertal austrian central alps abstract the estimation of catchment scale rockfall rates relies on the regionalisation of local measurements here we propose a new framework for such a regionalisation by the example of a case study in the upper kaunertal austrian central alps 62 5 km 2 measurements of rockfall deposition during 12 months onto six collector nets within the study area were combined with published mean annual rates from the literature and a probability density function was fitted to these data a numerical model involving a random walk routing scheme and a one parameter friction model was used to simulate rockfall trajectories starting from potential rockfall source areas that were delineated from a digital elevation model rockfall rates sampled from the fitted probability density function were assigned to these trajectories in order to model the spatial distribution and to estimate the amount of rockfall deposition by recording all trajectories as edges of a network of raster cells and by aggregating the latter to landforms or landform types as delineated in a geomorphological map of the study area rockfall sediment flux from sources to different landforms could be quantified specifically the geomorphic coupling of rockfall sources to storage landforms and the glacial and fluvial sediment cascade was investigated using this network model the total rockfall contribution to the sediment budget of the upper kaunertal is estimated at c 8000 mg yr 1 16 5 of which is delivered to the glaciers and hence to the proglacial zone the network approach is favourable for example because multiple scenarios involving different probability density functions can be calculated on the basis of the same set of trajectories and because deposits can be back linked to their respective sources while the methodological framework constitutes the main aim of our paper we also discuss how the estimation of the budget can be improved on the basis of spatially distributed production rates

photogrammetry and laser scanning for analyzing slope stability and rock fall runout along the domodossola iselle railway the italian alps abstract in italy railways crossing the alpine valleys are a vital means of civil and commercial communications with the rest of europe the geomorphologic configuration and the climatic conditions especially in winter and spring can cause rock fall events resulting in railway service interruptions and damage to infrastructure and in the worst case to people there were rock fall events at a slope adjacent to the domodossola iselle railway most recently in 2004 this paper evaluates the stability of a mountain slope and maps rock fall hazards through the modeling of potential runout trajectories traditional geological geomorphological and geo engineering surveys were combined with data derived from digital terrestrial photogrammetry stereo photographic pairs of rocky outcrops in inaccessible areas were acquired from a helicopter data from photogrammetry topographic measurements and laser scanning were then integrated to build a digital model of the slope to characterize the rock mass and block geometry and to define possible runout trajectories the geomatic methods used have yielded oriented stereo images orthophotos and precise digital models of rocky wedges geometrical and structural characteristics of slopes such as joint attitude spacing and persistence and block volumes were also derived the results were used together with a deterministic limit equilibrium method to evaluate slope stability we assessed the probabilistic distribution of rock fall end points and kinetic energy along the rock falling paths and existing barriers and created a hazard map based on the spatial distribution of trajectories rock fall transit density and kinetic energy

geological and morphological study of the jiufengershan landslide triggered by the chi chi taiwan earthquake the jiufengershan rock and soil avalanche is one of the largest landslides triggered by the chi chi earthquake taiwan 1999 the landslide destabilized the western limb of the taanshan syncline along a weak stratigraphic layer it involved a flatiron remnant which was almost entirely mobilized during the earthquake the avalanche was slowed down by ns trending ridges located downstream along the jiutsaihu creek the landslide affected a 60 m thick and 1 5 km long sedimentary pile composed of shales and sandstones which dip 228se toward a transverse valley the triggering mechanism and the sliding process were analyzed by means of geological and morphological data from aerial photographs and observed in the field a high resolution airborne light detection and ranging lidar image taken 2 5 years after the landslide allows the identification of morphological structures along the sliding surface and the landslide accumulation the sliding surface shows several deformation structures such as fault scarps and folds these structures are interpreted in terms of basal shear stresses created during the avalanche three major joint sets were identified at the sliding surface the isopach map of the landslide was calculated from the comparison between elevation models before and after the earthquake the coseismic volume of mobilized material and landslide deposit data are 4210 6 m 3 and 5010 6 m 3 respectively the geometry of the landslide accumulation in the field has an irregular star shape the morphology of the deposit area shows a sequence of smooth reliefs and depressions that contrast with the neighboring ridges d 2005 elsevier b v all rights reserved

comparison of airborne laser scanning terrestrial laser scanning and terrestrial photogrammetry for mapping differential slope change in mountainous terrain traditional mapping and monitoring of active slope processes in mountainous terrain is challenging given often difficult site accessibility obstructed visibility and high complexity of the terrain for example the rockfall hazard evaluation system employed by canadian railways relies partly on visibility of the rockfall source zone from track level which is often impossible for large or complex slopes in the mountains and elsewhere recent advancements in remote sensing data collection and analysis algorithms have helped resolve some of these issues by allowing the slope processes to be mapped and thereby understood with a greater degree of accuracy and confidence than was previously possible for example a better understanding of the rate of movement of material around a natural rock slope affecting a transportation corridor would certainly improve any assessment of the hazards caused by those movements various remote sensing technologies have the capability to be used to assess these process

subduction interface processes recorded by eclogite facies shear zones monviso w alps abstract the monviso ophiolite lago superiore unit constitutes a well preserved almost continuous upper fragment of oceanic lithosphere subducted at c 80 km depth thereby providing a unique opportunity to study mechanical coupling processes and meter scale fluid rock interactions occurring at such depths in present day subduction zones it is made of i a variably thick 50 500 m section of eclogitized basaltic crust associated with minor calcschist lenses overlying a 100 400 m thick metagabbroic body and of ii a c 1 km thick serpentinite sole we herein focus on the three major eclogite facies shear zones found at the top of the unit at the boundary between basalts and gabbros and between gabbros and serpentinites respectively strain localization occurred at lithological interfaces irrespective of material strength while ductile deformation dominates along the shear zones local brittle behavior is demonstrated by the existence of numerous eclogite breccias of fe ti metagabbros and widespread garnet fractures possibly linked with intermediate depth eclogite facies micro seismicity these m to hm sized fragments of fe ti metagabbros were later sheared and disseminated within serpentinite schists along the gabbro serpentinite boundary lower shear zone lsz pervasive and focused fluid flow is attested in the lsz by significant alteration of bulk rock compositions weakening of the rocks and widespread crystallization of hydrous parageneses by contrast the intermediate shear zone isz shows evidence for more restricted short range fluid flow the activity of both the isz and lsz ceased during early lawsonite eclogite facies exhumation when deformation localized deeper within the serpentinite sole allowing for the detachment and preservation of this large ophiolitic fragment

age of the baula pge mineralization orissa india and its implications concerning the singhbhum archaean nucleus abstract two types of platinum group element pge mineralization are identified in the mafic facies of the baula complex intruding the gabbro anorthosite unit of the singhbhum archaean nucleus the first pt dominated is magmatic the pgm are included in the magmatic silicates of a gabbro norite intrusion the bangur gabbro cutting the complex s ultramafic facies and are found preferentially where the gabbro incorporates clasts of dunite and chromitite near the gabbro ultramafics contact the second pd dominated is hydrothermal the pgm are associated with hydrous silicates located in the gabbro matrix of a magmatic breccia in which the blocks are from the baula ultramafic facies the originating fluids for the second type of mineralization were exsolved from the magma and concentrated pge and volatile elements we see no evidence of remobilization or external fluid contamination a structural study has demonstrated that a the breccia was provoked by the intrusion of the upper part of the bangur gabbro and b the breccia matrix corresponds to the bangur gabbro consequently both types of pge mineralization are associated with the same magmatic event a zircon age of 3122 5 ma has been obtained for the main bangur gabbro intrusion and similar ages 3123 7 and 3119 6 ma have been obtained on the pge mineralized gabbro matrix of the breccia this supports the hypothesis of a genetic link between the bangur gabbro with its pt dominated pge and the breccia with its pd dominated pge giving a mean weighted age of 3121 3 ma for the mineralization sm nd data on eight gabbro samples of the baula complex yielded a similar age of 3205 280 ma the dating of these events places them close to the broad scale stabilization of the singhbhum archaean nucleus estimated at 3 1 ga and defines one of the oldest pge mineralizing events ever recorded the bangur gabbro shows many affinities with the gabbro anorthosite unit of the singhbhum archaean nucleus in terms of age of emplacement and isotopic composition it may be therefore that the bangur gabbro actually forms part of the gabbro anorthosite unit and that a fundamental control of its two types of pge mineralization is the presence of ultramafic clasts

serpentinization of olivine gabbro in central indian ridge insights into h2 production during alteration in lower oceanic crust and sustenance of life at slow spreading ridges abstract we investigated the textural compositional characteristics across olivine interfaces in variably serpentinized olivine gabbro samples dredged from the vityaz megamullion in the northern central indian ridge cir the results are used to understand the role temperature and different chemical properties in infiltrating fluid e g seawater hydrothermal solution on the pattern of compositional evolution during progressive alteration in olivine gabbro the development of two distinct types of replacement rims i e type 1 and type 2 are conspicuous in our samples type 1 pseudomorphic mesh rim that formed within individual olivine grains occurs in two different textural modes a as successive layers of fe rich xmg 0 89 0 02 lizardite magnetite clay and calcite towards the olivine interface and b as homogeneous rim of comparatively fe poor lizardite xmg 0 93 0 01 magnetite replacement of olivine by talc and chlorite is evident towards the clinopyroxene and plagioclase grain boundaries respectively local precipitation of clay minerals is also observed at the inner interface of talc layer and within intra olivine fractures type 2 rim is characterized by the development of inter olivine mg rich lizardite xmg 0 97 0 01 magnetite layer cross cutting type 1 veins thus post dates type 1 replacement the process of cir olivine gabbro alteration records at least two stages of serpentinization any presence of brucite has not been observed suggesting relatively higher silica activity at reacting interfaces during olivine gabbro alteration than that of peridotite serpentinization at temperature log a sio 2 aq log a h 2 o log a al 3 a h 3 and log a ca 2 a h 2 and or temperature during progressive alteration of olivine type 2 replacement attests greater extent of magnetite precipitation as compared to type 1 serpentinization which may indicate increasing fluid rock ratio in the system and or decreasing magnitude of fe intake into serpentine structure with ongoing alteration importantly it implies release of h2 aq during olivine gabbro serpentinization which is consistent with that observed during peridotite serpentinization this corroborates that alteration in the deepest part of the oceanic crust may play an important role on the sustenance of biosphere in slow spreading ridges

pseudomorphic replacement of diopside during interaction with ni mg cl2 aqueous solutions implications for the ni enrichment mechanism in talc and serpentine type phases abstract a hydrothermal experimental study of diopside interaction with ni mg cl2 aqueous solutions has been carried out to clarify the replacement mechanism and pattern of element mobilization and its relevance to peridotite alteration three different solution compositions were used with ni mg ratios of 0 0 5 and 1 respectively experiments were carried out in cold seal pressure vessels at 300 600 c and 100 mpa pressure for 15 days in gold capsules for 600 c nicl2 experiments the solutions were also spiked with 50 h218o to study the behavior of isotopic exchange and hence the replacement mechanism the diopside pseudomorph interface is compositionally and structurally sharp after the mgcl2 experiments pure talc and or serpentine comprised the replacement phases whereas reaction in the ni bearing fluids produced talc willemseite and or lizardite nepouite series compositions additionally a complex rim of ni poor and ni rich regions developed in the nicl2 and ni mg cl2 experiments raman spectroscopy of the ni rich talc from the experiment with 18o enriched solution showed a shift of 10 1 cm 1 for the si o bridging si band towards lower wavenumbers relative to unspiked solution experiments indicating that 18o was incorporated into the silicate framework thus the reaction progressed via an interface coupled dissolution precipitation mechanism overgrowths of an olivine type phase at 500 600 c and serpentine type phases in 300 400 c experiments were also observed for a simple binary composition e g ni mg of the interacting solution the fluid composition different ni mg ratio at the reacting interface and its silica activity has a strong control on the phase precipitated the sequential formation of a ni poor inner phase and ni rich outer phase indicates a stepwise increase in ni incorporation within the neo formed phase that is representative of a cyclic dissolution precipitation process during supergene enrichment of ni in natural ore deposits additionally ca transport occurs in the opposite direction to ni during alteration which may be important as a geochemical tracer for economic ni deposits and as a source of ca for the rodingitization processes that are often associated with peridotite occurrences

the role of reacting solution and temperature on compositional evolution during harzburgite alteration constraints from the mesoarchean nuasahi massif eastern india abstract we investigate the microtextural chemical features of partially serpentinized harzburgites from the lower ultramafic unit of the mesoarchean nuasahi massif eastern india in order to understand the role of reacting fluid composition and temperature on the phase evolution across replacement interfaces during progressive alteration two distinct types of pseudomorphic replacement textures are identified type 1 replacement texture was developed after primary orthopyroxene and is composed of talc olivine lizardite tremolite magnetite primary olivine was replaced by mesh textured mg rich lizardite magnetite at the center of the olivine grains and successive layers of relatively fe rich lizardite magnesite and calcite toward olivine rims defining type 2 replacement texture the nuasahi harzburgite was initially out of equilibrium with respect to h 2 o co 2 bearing reacting solution and the secondary compositions have mainly evolved in the cao mgo feo sio 2 al 2 o 3 h 2 o co 2 system as a result of fluid rock interaction the alteration process across orthopyroxene interfaces has started at relatively higher temperature conditions 400 h 2 o c o 2 aq ratio in the solution across replacement interfaces the fe 2 mg 1 chemical exchange potential of the equilibrating system plays an important role in dictating the fe mg ratio of the secondary compositions and the molar proportions of magnetite the precipitation of tremolite and calcite in some isolated areas reflects a variation in ca activity in the reacting fluid the precipitation of carbonates may also be associated with an increase in ph in the interfacial solution the pattern in phase evolution across type 1 interfaces suggests a greater extent of diffusion of solutes toward inner interfaces relative to the rim center during progressive alteration of the nuasahi harzburgite possibly due to an increase in permeability in replaced phases with increasing magnitude of diffusion toward type 1 inner reacting interfaces the widespread presence of arrested replacement features suggests an alteration event under low fluid rock ratio and or sluggish reaction kinetics with decreasing temperature

preparation and analysis of coal seam data utilizing paleoenvironment modeling hazard 7 coal eastern kentucky abstract pennsylvanian strata of the hazard coalfield eastern kentucky contain fluvial upper delta plain facies characterized by thick localized coals bay fill shales levee silt and sandstones and channel fill sands and gravels although the deltaic nature of these sediments has long been established mining and exploration activities in the district require a thorough understanding of small areas within the delta environment coal quantity and quality trends in the hazard 7 seam the major producer in the area have been examined in detail the 7 coal accumulated in a peat swamp restricted laterally by a major fluvial channel three types of non coal parting are recognized thin tabular fine grained partings resulted from periods of increased terrigenous influx into the swamp lenticular crevasse splay deposits locally split the coal wedge shaped fine to coarse grained partings of probable levee origin are found along the channel margin post swamp deposits consist of thick bay fill shales thin shales silt and sandstones deposited on floodplains and channel fill sandstones and gravels the modeling technique discussed provides guidance for mine development and regional exploration by prediction of coal seam quantity and quality trends from local geologic features the thickest 7 coal is split by thin tabular partings and is overlain by thick shale sequences coal overlain by silt and sandstone is thinner and unsplit and typically of higher heat value regional seam thinning due to channel scour is recognized factors which control the configuration of the coal seam include position within the peat swamp proximity to the fluvial channel swamp burial processes and paleochannel sinuosity

analysis of lidar derived topographic information for characterizing and differentiating landslide morphology and activity abstract this study used airborne laser altimetry lidar to examine the surface morphology of two canyon rim landslides in southern idaho the high resolution topographic data were used to calculate surface roughness slope semivariance and fractal dimension these data were combined with historical movement data global positioning systems gps and laser theodolite and field observations for the currently active landslide and the results suggest that topographic elements are related to the material types and the type of local motion of the landslide weak unconsolidated materials comprising the toe of the slide which were heavily fractured and locally thrust upward had relatively high surface roughness high fractal dimension and high vertical and lateral movement the body of the slide which predominantly moved laterally and consists mainly of undisturbed older canyon floor materials had relatively lower surface roughness than the toe the upper block consisting of a down dropped section of the canyon rim that has remained largely intact had a low surface roughness on its upper surface and high surface roughness along fractures and on its west face unrelated to landslide motion the upper block also had a higher semivariance than the toe and body the topographic data for a neighboring older and larger landslide complex which failed in 1937 are similarly used to understand surface morphology as well as to compare to the morphology of the active landslide and to understand scale dependent processes the morphometric analyses demonstrate that the active landslide has a similar failure mechanism and is topographically more variable than the 1937 landslide especially at scales 20 m weathering and the larger scale processes of the 1937 slide are hypothesized to cause the lower semivariance values of the 1937 slide at smaller scales