some observations on suspended sediment dynamics in storbregrova jotunheimen observations are reported of the dynamics of suspended sediment transport in the meltstream of storbreen in the jotunheimen fine sediment is transferred from the subglacial to the proglacial environment during low flow meltdominated periods and then removed from the catchment during high flow rainfall controlled events both diurnal and storm period sediment load discharge relationships involve clockwise hysteresis but separate multivariate rating curves define variations of load with streamflow according to 1 the relative importance of meltwater and rainfall runoff and 2 changes in the sediment source areas contributing to the stream at different times particle size variations in the suspended sediment also reflect varying source area influences

creep of simulated reservoir sands and coupled chemical mechanical effects of co2 injection 1 geological storage of co2 in clastic reservoirs and aquifers is expected to have a variety of coupled chemical mechanical effects to investigate the effects of co2 injection on creep phenomena we performed uniaxial compaction experiments on granular aggregates of quartz and feldspar under both wet and dry control conditions the experiments were performed in constant stress mode grain size temperature co2 partial pressure and effective stress were varied in order to determine their individual effect pore fluid ph was varied by the injection of co2 and by addition of acidic and alkaline additives pore fluid salinity was increased by the addition of nacl wet samples showed instantaneous compaction upon load application followed by time dependent creep from the mechanical data and microstructures the main compaction mechanism was inferred to be chemically enhanced microcracking in both quartz and feldspar with subcritical crack growth i e stress corrosion cracking controlling deformation in the creep stage the injection of co2 and the concomitant acidification of the pore fluid inhibited microcracking in both the quartz and feldspar samples in line with known effects of ph on stress corrosion cracking we infer that the injection of co2 into quartz and plagioclase bearing sandstones will inhibit grain scale microcracking process and that related geomechanical effects such as reservoir compaction and surface subsidence will be negligible compared with the poroelastic response

compaction permeability evolution and stress path effects in unconsolidated sand and weakly consolidated sandstone abstract the influence of stress paths on the mechanical behavior and coupled permeability evolution of quartz sand packings and soft sandstone have been investigated the proposed approach is mainly based on the performing drained compression tests keeping constant a stress path parameter k defined as the ratio of the horizontal to vertical effective stress increments macroscopic mechanical data and the stress path dependency of permeability have been measured in the elastic brittle and compaction regimes the micro structural characteristics of unconsolidated materials coarse rounded grains glass beads gb and angular grains durance sand ds and a weakly consolidated sandstone otter sherwood sandstone oss have been quantified in intact and deformed states combining petrophysical core analysis and multi scale imaging according to the feasibility of sub sampling of the different materials two different types of hydro mechanical behavior were evidenced for each material the weakly consolidated oss presents a mechanical behavior similar to the consolidated rocks with two distinct regimes of deformation the transition between these two regimes is a function of the stress path on the other hand the sand shows a gradual transition regime requiring the use of a curvature criterion to pick yield stresses this criterion has been validated on the basis of acoustic emissions analysis the modified cam clay model and the elliptical cap model allow capturing efficiently the yield envelopes the permeability measurements were performed with intermediate pressure ports to measure accurately the high permeable sand and to avoid end effects for oss permeability evolutions follow closely the volumetric strain evolutions in both the elastic and plastic regimes and are mainly controlled by the mean pressure before yield at these critical stresses the permeability drops drastically under the influence of deviatoric stress conversely for ds the correlation between strain and permeability is not obvious as permeability reduction is pronounced at an early stage of loading

compression behavior of canadian oil sands the compression behavior of canadian oil sands was investigated by running high stress oedometer compression tests up to 65 mpa an x ray microtomography investigation confirmed the significant disturbance affecting the core samples showing large pores located between dense intact clusters made up of angular sand grains compression tests confirmed the significant effects of disturbance on the com pression characteristics providing a much softer response without any memory of the significant load applied by the 3 to 4 km thick ice sheet during the quaternary period high stress compression allowed us to bring back the samples close to the in situ estimated porosity providing compression characteristics estimated fromaloading cycle close totheintact ones despiteobviousdifferencesinfabric includingtheeffects attributable to grain crushing at high stress creep behavior was also observed and an estimate of the order of magnitude of the creep strain corresponding to the quaternary period is provided doi 10 1061 asce gt 1943 5606 0000808 2013 american society of civil engineers ce database subject headings oils compression sand soil type x rays canada author keywords heavy oil oil sand high stress compression x ray microtomography core disturbance

characterization of glacial silt and clay using automated mineralogy glacial erosion produces vast quantities of fine grained sediment that has a far reaching impact on earth surface processes to gain a better understanding of the production of glacial silt and clay we use automated mineralogy to quantify the microstructure and mineralogy of rock and sediment samples from 20 basins in the st elias mountains yukon canada sediments were collected from proglacial streams while rock samples were collected from ice marginal outcrops and fragmented using electrical pulse disaggregation for both rock fragments and sediments we observe a log normal distribution of grain sizes and a sub micrometer terminal grain size we find that the abrasion of silt and clay results in both rounding and the exploitation of through going fractures the abundance of inter versus intragranular fractures depends on mineralogy and size unlike the relatively larger grains where crushing and abrasion are thought to exploit and produce discrete populations of grain sizes the comminution of fines leads to a grain size composition and rounding that is continuously distributed across size and highly dependent on source rock properties

strain rate and temperature dependence of omori law scaling constants of ae data implications for earthquake foreshock aftershock sequences 1 little is known about the temperature and strain rate dependence of acoustic emission ae activity ae hence we carried out a preliminary series of flow through triaxial compression tests on porous sandstones at different temperatures and strain rates the ae data exhibits clear foreshock and aftershock sequences with respect to the dynamic failure of the test specimen significant ae activity starts less than 5 min before sample failure irrespective of the strain rate the increase in the ae event rate is steeper and the foreshock exponent p is smaller in the slow strain rate tests it could be the reason why there are no easily recognisable foreshock sequences for most individual earthquakes the aftershock decay parameter p is a linear function of test temperature as it has also been inferred for natural seismicity the seismic b value decreases systematically with increasing deformation rate suggesting a greater proportion of small cracks in the slow strain rate tests hence the ae activity is a function of both strain rate and temperature

particle interaction in fjord suspended sediment abstract glacial flour enters the surface layer of howe sound a fjord in southwestern british columbia as a sediment plume which moves quickly down inlet while gradually mixing with the sea water flocculation occurs in the lower brackish waters of the surface layer although mixing and diffusion are the dominant processes for sediment to enter the marine water once in the underlying marine water zooplankton pelletization and biologic agglomeration of inorganic floccules predominate this generates a response in the order of days between the two layers in terms of sedimentation of particulate matter most particles settling in the fjord environment fall as 1 sand and silt grains containing attached clay particles 2 clay clasts possibly related to river mudballs 3 mineral bearing fecal pellets from pelagic zooplankton 4 large grain inorganic and colloidal floccules and 5 inorganic biogenic agglomerates analysis of sediment trap data has led to the following conclusions 1 water turbidity cannot be used to infer the downward flux of particles 2 size distributions of sediment deposited on the sea bed are a function of non lognormal size distributions from particles composing sub laminae

size and composition of inorganic colloids in a peri alpine glacial flour rich lake from june 2004 to october 2005 particle size distributions psd and the mineralogy of inorganic colloids in lake brienz a glacial flour rich swiss lake and in its tributaries the aare and lutschine rivers were quantified by single particle counting based on light scattering 0 1 2 m combined with transmission electronic microscopy coupled with energy dispersive spectroscopy and selected area electron diffraction the two lake tributaries differ in terms of the geology of their catchment area and in their hydrology the river lutschine s glacial regime is unperturbed while the river aare has been significantly modified by hydroelectric installations the dependence of the colloid concentration numbers on colloid diameters can be described by a power law distribution in all cases the power law slopes in the river aare were consistently smaller and the total colloid number concentrations consistently higher mean values 3 89 and 6 2 108 ml 1 respectively than in the river lutschine 3 61 and 1 7 108 ml 1 the measured psd in the lake were dependent on season and depth homogenous in the whole epilimnion in winter and modified by river intrusions in summer in this season the presence of a river turbid plume above the thermocline is a significant source of colloids in the epilimnion where their concentration was high mean value 5 1 107 ml 1 the same main mineral types were found in the different systems 2 1 minerals feldspars chlorite and quartz with a few particles of oxides differences in their relative concentrations in the rivers essentially reflecting the geological differences of the respective catchment areas made it possible to trace the origin of the mineral colloids present in lake surface waters throughout the year the relationship between colloid size and mineralogy was assessed showing that different minerals have distinct size distributions in the rivers where almost no aggregates were observed psd would essentially be the result of the nature particle formation and mineralogy of the colloids whereas in the lake aggregation and sedimentation processes would also play a role particularly in summer

a m gurnell and m j clark eds 1987 glacio fluvial sediment transfer an alpine perspective chichester etc john wiley and sons ltd

landslide reconstruction using seismic signal characteristics and numerical simulations case study of the 2017 6 24 xinmo landslide abstract landslide modeling based on seismic signal characteristics is an effective method to study landslide evolution the scientific challenge lies in how to systematically characterize and reconstruct the entire landslide evolution process using the recorded seismic data we selected the 2017 6 24 xinmo landslide as a case study empirical mode decomposition emd is used to analyze the seismic signals from 14 seismic stations near the landslide area numerical simulations using two dimensional discrete element methods dem are performed to simulate landslide dynamics using the calculated kinetic energy profile after analyzing the short time fourier transform stft and fast fourier transform fft characteristics of the signal the landslide process is reconstructed and compared with the dem simulation the landslide process is observed to consist of a stationary stage slipping stage transition stage entrainment transportation stage and a deposition stage this is the first study that uses seismic signals to identify a transition stage which is a feature that is difficult to constrain from field survey and analysis alone landslide development and movement in the transition stage are discussed considering the sedimentology of the study area this study provides improved theoretical guidance for the reconstruction and characterization of landslide processes by seismic signals

particle size analysis of the sediment suspended in a proglacial stream glacier de tsidjiore nouve switzerland hourly at a point samples of suspended sediment taken from the outflow stream of glacier de tsidjiore nouve switzerland over a 60 day sampling period n 1440 are shown to be dominantly composed of silt sized particles particle size sem and xrd analyses indicate a subglacial provenance for the suspended sediment temporal variations in particle size and sorting correspond poorly to fluctuations in water discharge being dominated by erratic hour to hour fluctuations and clockwise hysteresis over diurnal flow events examination of grain size and sorting dynamics over snowmelt and icemelt related ablation events during precipitation events and during glacier drainage events enables some inferences to be drawn regarding sediment source areas and supply regimes we conclude that although the bulk of the suspended sediment in the proglacial stream of glacier de tsidjiore nouve is derived directly from subglacial sources with occasional contributions from the valley train during rapid snowmelt and heavy rainfall periods a portion of the suspended load undergoes intermittent flush fall transfer through the proglacial zone which acts as a sediment source during rising flows and as a sink during periods of waning flow

comparison of fluid inclusion decrepitation and acoustic emission profiles of westerly granite and sioux quartzite abstract acoustic emissions recorded during slow heating of rocks at 1 atm have generally been attributed to intergranular stresses generated by differences in thermal expansion coefficients and elastic moduli of neighboring grains these experiments have considered only the solid phases in analysis of the results and little attention has been given to the role of intragranular or grain boundary fluid inclusions in initiating or facilitating fracturing in principle fluid inclusions may be thought of as a special case in which the neighboring grains are fluids rather than the usual solid mineral phases the major differences are that 1 the number of inclusions per unit volume is usually 10 2 to 10 6 times greater than the number of mineral grains in that same volume and that 2 the volume increase with temperature for most fluids is 1 2 orders of magnitude greater than for minerals thus when fluid inclusion grains are considered the absolute number of grain to grain contacts in a given sample volume is several orders of magnitude greater than if the inclusions are not considered further the magnitude of the stresses between any two adjacent grains may be much higher if one of the grains is a fluid inclusion owing to the larger coefficient of thermal expansion of the fluid relative to a solid phase as a result substantial overpressures may be generated at the fluid inclusion grain mineral grain contact during heating experiments these overpressures result in brittle failure when the stress around the inclusion exceeds the local strength of the host crystal in fluid inclusion terminology this fracturing event is referred to as decrepitation samples of westerly granite and sioux quartzite were heated at 2 c min in a gas flow stage in order to determine the decrepitation profiles number of decrepitations as a function of temperature of these rocks decrepitation was monitored visually during heating experiments and was evidenced by the explosive loss of fluids from the inclusion during a fracturing event decrepitation produces microfractures which originate at decrepitated fluid inclusions and propagate outward into the surrounding mineral four different types of inclusions based on room temperature phase ratios and distribution within the host phase were noted in westerly granite type 1 inclusions contain a single aqueous liquid type 2 are two phase liquid rich inclusions type 3 are mostly one phase fluid inclusions that occur in dense clusters in plagioclase and type 4 are two phase moderate density h 2 o co 2 salt inclusions type 5 inclusions are one phase aqueous liquid inclusions observed in sioux quartzite fluid inclusions in westerly granite decrepitate between 75 and 573 c with peaks at 275 300 c and 400 450 c type 4 inclusions in westerly granite tend to decrepitate at lower temperatures 75 300 c than other inclusion types initial fracturing of the quartz host surrounding type 1 inclusions primary decrepitation generally occurs over the range 100 400 c and the fractures continue to propogate through the quartz secondary decrepitation during further heating from 400 to 573 c fluid inclusions in sioux quartzite decrepitate between 188 and 573 c with a broad maximum at 250 450 c primary decrepitation generally occurs at 200 450 c while secondary decrepitation occurs at 350 573 c in sioux quartzite some small inclusions in both samples do not decrepitate until the quartz transition temperature 573 c is reached decrepitation profiles determined in this study display many similarities and differences when compared to previously published acoustic emission profiles of westerly granite and sioux quartzite owing to fundamental differences in the techniques used to measure acoustic emission and decrepitation and the potentially different energies associated with the two events it is unclear whether decrepitating fluid inclusions are recorded during acoustic emission studies however if decrepitating fluid inclusions are being recorded during acoustic emission measurements then our results suggest that 1 decrepitation contributes more to low temperature portions of acoustic emission profiles than to high temperature portions for both sioux quartzite and westerly granite 2 compared to westerly granite a larger percentage of acoustic emissions in the low temperature decrepitation profile of sioux quartzite is due to fluid inclusions 3 decrepitating fluid inclusions not stresses generated by solid solid interactions cause the majority of intragranular fracturing in quartz below the temperature of the transition in both these rocks

hydroclimatic influence on particle size distribution of suspended sediments evacuated from debris covered chorabari glacier upper mandakini catchment central himalaya abstract sediments released from high altitude glaciers exhibit varying evacuation patterns and transport characteristics owing to the presence of thick debris cover over the glacier despite the recent needs for integrated hydrometeorological studies in the himalaya little is known about the impacts of suspended sediment on hydropower generation reservoir sedimentation and abrasion of turbine components present study involves analysis of particle size distribution of suspended sediments to understand sediment evacuation patterns and transport characteristics in variable energy conditions during the ablation season peak suspended sediments were evacuated during extreme rainfall events the estimated seasonal modern sediment erosion rate varies from 0 6 to 2 3 mm y 1 for the study period 2009 2012 the analysis shows dominance of medium silt sized to fine sand sized particles having sediment size of 0 0156 0 25 mm corresponding to 70 80 without any significant seasonal variation these transported sediments show that they are poorly sorted coarser in nature with a nearly symmetrical to coarse skewed texture and kurtosis analysis suggesting mesokurtic distribution of sediments the particle size fraction ranges between 4 65 and 5 23 which is dominantly medium to coarse silty in texture results indicate that suspended sediments are evacuated in highly variable energy conditions through subglacial transport pathways because of increase in availability of meltwater with the progressive ablation season bulk geochemical characterization has been carried out to differentiate the source of suspended sediments and intensity of weathering chemical index of alterations cia values of sediment flux range from 54 68 to 55 18 compared to the upper continental crust ucc 50 indicating moderate intensity of weathering mean seasonal 2009 2012 elemental fluxes and their contribution to the suspended sediment flux reflect that si and al are responsible for about 85 of the total detrital elemental flux trace elements show high concentrations of radioactive elements like u th pb and rb that suggest their high anomalous presence in the catchment lithology an overall study indicates that the hydroclimatic conditions over the debris covered glacier play a dominant controlling factor in erosion transportation and evacuation of suspended sediments during the ablation season

shear strength and stress strain behaviour of athabasca oil sand at elevated temperatures and pressures the results of a series of triaxial compression tests on undisturbed samples of athabasca oil sand at elevated temperatures ranging from 20 to 200 c are summarized the material tested had experienced gradual unloading and depressurization as a result of erosion in the saline creek valley near fort mcmurray more deeply buried oil sands are known to contain much higher concentrations of dissolved hydrocarbon gases in the pore fluids the measured shear strength of athabasca oil sand did not change significantly as a result of the increased temperatures that were applied the strength of athabasca oil sand at 20 200 c was found to be greater than comparable shear strengths reported for dense ottawa sand at 20 c although heating to 200 c had little effect on shear strength it is recognized that pore pressure generation during undrained heating may cause substantial reduction of the available shearing resistance particularly in gas rich oil sands the experimental data were used to investigate the

particle size characteristics of suspended sediment transported in meltwater from the gangotri glacier central himalaya an indicator of subglacial sediment evacuation abstract proglacial meltwater streams draining out of the himalayan glaciers carry considerable amounts of suspended sediment with a variety of particle sizes because of the supraglacial englacial and subglacial debris as well as formation of sediments from erosion by the movement of the ice this paper examines particle size transported in the proglacial meltwater stream of gangotri glacier for seven consecutive melt seasons may october 2000 2006 in order to provide information on i temporal variations in the particle size distribution ii texture and mineralogy of the sediments and iii origin and evacuation pattern of the sediments our results indicate dominance of silt size 0 002 0 06 mm particles 71 followed by sand size 0 06 0 6 mm particles 24 and clay size

transport of suspended particulate matter in an antarctic fjord abstract vertical profiles of temperature salinity and light attenuation were used in conjunction with underwater photography and water samples to characterize the nature and dynamics of particle transport in an antarctic fjord most of the particles are sand sized 0 1 2 mm floccules comprised of individual grains in the 5 to 50 m size range the quartz silt grains are derived from basal debris laden meltwater originating from beneath the submerged valley glacier the meltwater buoyantly rises to form cold water interflows at mid water depths turbulent mixing near the seafloor also plays a role in the transport and break up of floccules together the midwater cold tongues and near bottom turbidity account for 87 of the total sediment load thus attesting to the importance of non surface transport mechanisms in polar fjords

experimental investigation of acoustic emissions and their moment tensors in rock during failure abstract we study acoustic emissions aes associated with shear and tensile failures around a horizontal borehole in a sandstone sample subjected to triaxial stress the aim is to relate the ae event rate to macroscopic observations of sample deformation and the percentage of isotropic and deviatoric components of the seismic moment tensors to the expected failure mechanisms the horizontal hole interferes with the applied load and forms a strongly spatially dependent anisotropic stress field focusing the crack initiation into both shear and tensile failures the recorded aes follows reasonably well existing damage models but the elastic solution of hoop stress does not represent the onset of failure around the borehole the focal mechanisms correlate with the orientation of macroscopic fractures in the sample events close to the borehole show a higher fraction of isotropic percentage in moment tensors compared to events occurring in the macroscopic fracture featuring higher double couple percentages the inhomogeneous stress field due to the borehole and the stress induced damage is strongly affecting the axial and radial velocities which in turn affect the waveforms of the recorded aes and the resulting moment tensors the vp vs ratio obtained from the ratio of isotropic to compensated linear vector dipole components of the moment tensors is close to that obtained from ultrasonic velocity measurements

experimental investigation of mechanical properties of bedded salt rock abstract because of salt cavern utilization for liquid gas and solid waste storage salt rock mechanical properties are needed for assessments of facility stability and safety bedded salt deposits are widespread and used as much or more than diapiric salt bodies as storage facility hosts but experimental data on the mechanical properties of bedded salt rock with impurities are far less common than data available on relatively pure diapiric salt rocks through laboratory uniaxial and triaxial compression experiments on rock salt halite interlayers anhydrite and bedded composite specimens anhydrite halite and mudstone halite differences in mechanical properties of the various lithologies are explored in the composite specimens the weakest or the most deformable component governs the behavior also the properties of bedded composite lithology specimens tend to be in between the property ranges of the pure lithologies the elastic modulus of the bedded salt rock increases from 5 3 to 24 1 gpa with an increase in the confining stress from 0 to 15 mpa with some evidence of sample damage the ductile transition for halite at the strain rates used is at about 3 10 mpa with increasing 3 the anhydrite halite composite lithology deformation showed strain hardening and a strong trend to ductile behavior as the halite bands tended to dominate the behavior strain incompatibility effects exist along interfaces between creeping and non creeping phases in anhydrite halite composite lithologies mudstone halite rocks tended to be extremely weak compared with all other specimens

correlations of suspended sediment size with bedrock lithology and glacier dynamics the hypothesized link between glacier surging and bedrock geology motivates this study of the suspended sediment size distributions sssd from surge type and non surge type glaciers we analyze sssds from proglacial streams in 20 individual basins comprising various fractions of metasedimentary ms and felsic plutonic rocks we compare the size distributions by performing tests of significance on the distribution statistics and a principal component analysis on discrete grain sizes we find that surge type and non surge type glaciers underlain solely by ms rocks have significantly different sssds while surge type glaciers as a whole have remarkably similar sssds regardless of the underlying bedrock geology these observations hint at a relationship between sediment characteristics and glacier surging though causation in either direction cannot be established without additional data

frac sand crushing characteristics and morphology changes under high compressive stress and implications for sand pack permeability sand consisting of round quartz grains is widely used as a proppant during hydraulic fracturing to produce natural gas from tight shale formations this paper presents results from sand characteriz

deep electrical structure and geological significance of tongling ore district abstract the tongling ore district is one of the most important cu polymetal producers in the lower yangtze river metallogenic belt of china to understand deep crust structure beneath the tongling ore district more comprehensively and objectively and to explore important scientific issues such as characteristics of lithospheric evolution the relationship between the crustal structure and metallogenesis it is necessary to study the variation of crust electrical structure in the study area for this purpose six magnetotelluric mt sounding profiles have been completed by sinoprobe 03 project based on the imaging results of the six profiles electrical conductivity structure of the crust has been analyzed the result shows that the geology beneath the profiles is characterized by layering in vertical direction and block division in horizontal direction the high resistivity features are related to the transparent zones detected at the upper crust in reflection seismic surveys the absence of reflectivity from the depths indicates a homogeneous zone which could often be related to granitic intrusions combining the regional tectonic evolution mt and other geophysical data we suggest that the high resistivity bodies crossing the tongling uplift reveals the center of magma activity and the layering in vertical direction in the lower crust reveals a normal lower crust model and propose a small scale underplating model which is different with both the partial melting of a thickened or delaminated lower continental crust model and the oceanic ridge subduction the underplating might be related to small scale lithospheric or lower crust delamination controlled by deep fault during the early cretaceous the result of this mt survey is important for constraining lithospheric evolution and metallogenesis in the lower yangtze metallogenic belt such as collision of north china craton and yangtze craton underplating models deep structure mechanisms of ne sw trending rift as well as graben basin and probable metallogenesis

temperature dependence of acoustic emission from impact fractured granites abstract pre failure damage accumulation in deformed rock as well as crack propagation in fracturing geomaterials is accompanied with the generation of elastic acoustic waves these processes are similar in main features in tectonic formations and under laboratory conditions therefore the data obtained in acoustic emission ae experiments are widely used for interpreting some trends in natural seismic processes however the laboratory experiments on rock loading are usually performed at room temperature while the temperature of geostructures at the depth of faulting can reach a few hundred degrees in this communication we present results of the ae study of impact induced damage in granites of two grain sizes performed at different temperatures the energy release distributions in ae time series dependences of event number on event energy were found to follow the gutenberg richter type relation in the temperature range 20 c to 300 c the b value in this range showed a trend to decrease with the increase of the sample temperature at higher temperatures up to 600 c the energy distributions exhibited the poissonian type exponential behavior thus evidencing the stochastic character of the process the distributions of time intervals between successive pulses exhibited the same trend but less pronounced

preslip and cascade processes initiating laboratory stick slip recent modeling studies have explored whether earthquakes begin with a large aseismic nucleation process or initiate dynamically from the rapid growth of a smaller instability in a cascade up process to explore such a case in the laboratory we study the initiation of dynamic rupture stick slip of a smooth saw cut fault in a 76 mm diameter cylindrical granite laboratory sample at 40 120 mpa confining pressure we use a high dynamic range recording system to directly compare the seismic waves radiated during the stick slip event to those radiated from tiny m 6 discrete seismic events commonly known as acoustic emissions aes that occur in the seconds prior to each large stick slip the seismic moments focal mechanisms locations and timing of the aes all contribute to our understanding of their mechanics and provide us with information about the stick slip nucleation process in a sequence of 10 stick slips the first few microseconds of the signals recorded from stick slip instabilities are nearly indistinguishable from those of premonitory aes in this sense it appears that each stick slip begins as an ae event that rapidly 20 s grows about 2 orders of magnitude in linear dimension and ruptures the entire 150 mm length of the simulated fault we also measure accelerating fault slip in the final seconds before stick slip we estimate that this slip is at least 98 aseismic and that it both weakens the fault and produces aes that will eventually cascade up to initiate the larger dynamic rupture

particle size and mineralogical composition of inorganic colloids in waters draining the adit of an abandoned mine goesdorf luxembourg particle size distributions and the mineralogy of inorganic colloids in waters draining the adit of an abandoned mine goesdorf luxembourg were quantified by single particle counting based on light scattering 100 nm 2 m combined with transmission electronic microscopy coupled with energy dispersive spectroscopy and selected area electron diffraction this water system was chosen as a surrogate for groundwaters the dependence of the colloid number concentration on colloid diameters can be described by a power law distribution in all cases power law slopes ranged from 3 30 to 4 44 depending on water ionic strength and flow conditions the same main mineral types were found in the different samples 2 1 phyllosilicates illite and mica chlorite feldspars albite and orthoclase calcite and quartz with a variable number of fe oxide particles the colloid mineralogical composition closely resembles the composition of the parent rock spatial variations in the structure and composition of the rock in contact with the waters i e fissured rock versus shear joints are reflected in the colloid composition the properties of the study colloids as well as the processes influencing them can be considered as representative of the colloids present in groundwaters

pore structure characteristics of debris flow source material in the wenchuan earthquake area abstract wide grading loose soils wgls are a special slope deposit that often serve as a source for debris flows in the western mountainous area of china previous research indicated that rainfall infiltration induced the migration of fine particles within soil slopes and lead to the initiation of shallow failure and subsequent debris flows clearly soil pore structure exerts a profound influence on seepage during rainfall infiltration which is closely related to soil permeability and corresponding internal erosion the current understanding of the mechanisms of fine particle migration is limited because of the complexity of wgls micropore structure the challenge lies in how to systematically characterize wgls pore structure so that it provides a foundation for future numerical simulations of fine particle migration induced debris flows in this study the characteristics of wgls pore structure were analyzed quantitatively using scanning electron microscopy the results revealed that wgls predominantly contained micropores and mesopores the pore size distribution exhibited a bimodal nature with one peak occurring at a pore diameter of 12 m and another at 72 m the pore complexity of all samples exceeded 0 75 which indicates a low aspect ratio for each pore the average diameter of the fine particles that migrated was then determined with a laboratory seepage test a preliminary jamming probability analysis based on three dimensional micropore reconstruction and average fine particle diameter indicate that jamming is most prevalent along the slope

a numerical characterization workflow for assessing the strength and failure modes of heterogeneous oil sands understanding the strength and failure modes of overburden and reservoir are critical components in safety assessments for oil sands surface mining and in situ thermal recovery operations currentl

detailed analysis of acoustic emission activity during catastrophic fracture of faults in rock abstract the detailed time space distribution of acoustic emission ae events during the catastrophic fracture of rock samples containing a pre existing joint or potential fracture plane is obtained under triaxial compression using a high speed 32 channel waveform recording system and the results are discussed with respect to the prediction and characterization of catastrophic fault failure ae activity is modeled quantitatively in terms of the seismic b value of the magnitude frequency relation the self excitation strength of the ae time series and the fractal dimension of ae hypocenters consistent with previous studies on rock samples containing a fracture plane with several asperities the present analyses reveal three long term phases of ae activity associated with damage creation on heterogeneous faults each clearly identifiable based on the above parameters a long term decreasing trend and short term fluctuation of the b value in the phase immediately preceding dynamic fracture are identified as characteristic features of the failure of heterogeneous faults based on the experimental results it is suggested that precursory anomalies related to earthquakes and other events associated with rock failure are strongly dependent on the heterogeneity of the fault or rock mass a homogeneous fault or rock mass appears to fracture unpredictably without a consistent trend in precursory statistics while inhomogeneous faults fracture with clear precursors related to the nature of the heterogeneity

experimental investigations of the weathering of suspended sediment by alpine glacial meltwater the magnitude and processes of solute acquisition by dilute meltwater in contact with suspended sediment in the channelized component of the hydroglacial system have been investigated through a suite of controlled laboratory experiments constrained by field data from haut glacier d arolla valais switzerland the effects of the water to rock ratio particle size crushing repeated wetting and the availability of protons on the rate of solute acquisition are demonstrated these free drift experiments suggest that the rock flour is extremely geochemically reactive and that dilute quickflow waters are certain to acquire solute from suspended sediment these data have important implications for hydrological interpretations based on the solute content of glacial meltwater mixing model calculations geochemical denudation rates and solute provenance studies

tectonics of an ultrahigh pressure metamorphic terrane the dabie shan tongbai shan orogen china ultrahigh pressure metamorphic rocks with coesite and diamond form a tectonic slice over 20 km thick called the eclogite zone within the dabie shan complex in the qinling orogen in central china the orogen separates the sino korean block in the north from the yangtze block in the south the dabie shan complex is a composite terrane made up of eclogite facies and amphibolite facies gneiss slices and represents fragments of the lower continental crust of the yangtze block the dabie shan complex is bounded in the south by a triassic foreland fold thrust belt and in the north by a greenschist facies metaclastic unit the foziling group which probably represents the passive continental apron deposits of the yangtze block farther north is a granulite facies gneiss complex the qinling group which has ultramafic slivers and includes the remnants of an island arc with two bounding suture zones north of the qinling group are early paleozoic active margin deposits of the sino korean block the eclogite zone in the dabie shan complex is sandwiched between amphibolite facies gneiss slices dating by sm nd rb sr and ar ar of two eclogite samples from the eclogite zone gives early to middle triassic ages 236 246 ma the initial end values indicate reworking of a 2 11 and 1 55 ga continental crust a himalayan type tectonic evolution is envisaged for the qinling orogen with the creation of a 100 km thick crustal thrust wedge through continuous underplating during the subduction of the yangtze continental lithosphere exhumation of the ultrahigh pressure metamorphic rocks was chiefly achieved by the southward propagation of the thrust planes thereby isostatically uplifting and eroding the earlier deeply subducted parts of the orogen a total of 680 km of southward thrusting in front of dabie shan is inferred based on the abrupt termination of the tanlu fault normal faulting possibly caused by gravitational collapse probably also had a role in the exhumation process

trends in large deformation analysis of landslide mass movements with particular emphasis on the material point method traditional geotechnical analyses for landslides involve failure prediction i e onset of failure and the design of structures that can safely withstand the applied loads the analyses provide limited information on the post failure behaviour modern numerical methods are able to simulate large mass movements and there is an opportunity to utilise such methods to evaluate the risks of catastrophic damage if a landslide occurs in this paper various large deformation analysis methods are introduced and their applicability for solving landslide problems is discussed since catastrophic landslides often involve seepage forces consideration of the coupled behaviour of soil and pore fluid is essential two approaches to model soil pore fluid coupling in large deformation analysis using the material point method mpm are introduced an example simulation is presented for each approach one on a model levee failure and the other on a natural cut slope failure the selborne experiment conducted by cooper and co workers in 1998 in the levee failure case mpm simulation was able to capture a complex failure mechanism including the development of successive shear bands the simulation was also able to predict excess pore pressure generation during the failure propagation and the subsequent consolidation stage the simulations demonstrated the importance of the dilation characteristics of soil as well as changes in geometry for the post failure behaviour in the selborne case mpm was able to simulate the progressive failure of brittle overconsolidated clay the evolution of shear stresses along the failure surface was also captured by the mpm the changes in the pore pressure and the actual shape of the failure surface were simulated by the mpm the importance of accurately modelling the shear band within the mpm framework is highlighted

from soil aggregates to riverine flocs a laboratory experiment assessing the respective effects of soil type and flow shear stress on particles characteristics particles eroded from hillslopes and exported to rivers are recognized to be composite particles of high internal complexity their architecture and composition are known to influence their transport behaviour within the water column relative to discrete particles to date hillslope erosion studies consider aggregates to be stable once they are detached from the soil matrix however lowland rivers and estuaries studies often suggest that particle structure and dynamics are controlled by flocculation within the water column in order to improve the understanding of particle dynamics along the continuum from hillslopes to the lowland river environment soil particle behaviour was tested under controlled laboratory conditions seven flume erosion and deposition experiments designed to simulate a natural erosive event and five shear cell experiments were performed using three contrasting materials two of them were poorly developed and as such can not be considered as soils whilst the third one was a calcareous brown soil these experiments revealed that soil aggregates were prone to disaggregation within the water column and that flocculation may affect their size distribution during transport large differences in effective particle size were found between soil types during the rising limb of the bed shear stress sequence indeed at the maximum applied bed shear stress the aggregated particles median diameter was found to be three times larger for the well developed soil than for the two others differences were smaller in the falling limb suggesting that soil aggregates underwent structural changes however characterization of particles strength parameters showed that these changes did not fully turn soil aggregates into flocs but rather into hybrid soil aggregate floc particles copyright 2013 john wiley sons ltd

acoustic emissions monitoring during inelastic deformation of porous sandstone comparison of three modes of deformation in some reservoirs large deformations can occur during oil or gas production because of the effective stress change for very porous rocks these production operations can be sufficient to cause inelastic deformation and irreversible damage rock formations can undergo deformation by different mechanisms including dilatancy or pore collapse in the laboratory it has been shown that the inelastic deformation and failure mode of porous rocks are pressure sensitive indeed when subjected to an overall compressive loading a porous rock may fail by shear localization compaction localization or by cataclastic compaction acoustic emission ae records provide important information to understand the failure mode of rocks the spatial evolution of damage as well as the source mechanisms can be followed using this technique in this paper we present three different laboratory axisymmetric compression experiments performed on bleurswiller sandstone which enable us to compare the acoustic emission signature of these three modes of deformation our data show that compaction localization and cataclastic compaction are characterized by similar acoustic signatures in terms of ae sources characteristics and evolution of ae number in comparison to the acoustic signature from shear localization this implies similar micromechanisms involved during compaction bands formation and cataclastic compaction

determination of mechanical properties of flysch using laboratory methods abstract the paper deals with the determination of the mechanical properties of heterogeneous rocks in the laboratory and proposes a methodology for predicting the rock mass strength of flysch formations consisting of siltstone sandstone alternations in different proportions in order to simulate such formations composite specimens comprising superimposed disks of intact sandstone and siltstone material with different thickness ratios were prepared wave velocity p and s uniaxial and triaxial compressive strength and young s modulus of the composite samples were determined in the laboratory according to the laboratory results the uniaxial compressive strength and young s modulus decrease with the increase of the siltstone percentage in the specimens and yield the strength of siltstone when the siltstone percentage in the rock is equal to 37 additionally the triaxial compression tests on composite samples revealed a significant decrease of the m i parameter for a siltstone percentage of only 17 a comparison is made between the results of the present study with similar laboratory and empirical references from literature finally it was possible to suggest how the relation between uniaxial compressive strength ci and siltstone percentage sl may differ according to the ratio of the compressive strength of the two main rocks weak and strong which comprise the heterogeneous rock

gis based mineral prospectivity mapping using machine learning methods a case study from tongling ore district eastern china abstract predictive modelling of mineral prospectivity using gis is a valid and progressively more accepted tool for delineating reproducible mineral exploration targets in this study machine learning methods including support vector machine svm artificial neural networks ann and random forest rf were employed to conduct gis based mineral prospectivity mapping of the tongling ore district eastern china the mineral systems approach was used to translate our understanding of the skarn cu mineral system into mappable exploration criteria resulting in 12 predictor maps that represent source transport physical trap and chemical deposition processes critical for ore formation predictive svm ann and rf models were trained by way of predictor maps and corroborated using a 10 fold cross validation the overall performance of the resulting predictive models was assessed in both training and test datasets using a confusion matrix set of statistical measurements receiver operating characteristic curve and success rate curve the assessment results indicate that the three machine learning models presented in this study achieved satisfactory performance levels characterized by high predictive accuracy in addition all models exhibited well interpretability that provided consistent ranking information about the relative importance of the evidential features contributing to the final predictions in comparison the rf model outperformed the svm and ann models having achieved greater consistency with respect to variations in the model parameters and better predictive accuracy importantly the rf model exhibited the highest predictive efficiency capturing most of the known deposits within the smallest prospective tracts the above results suggest that the rf model is the most appropriate model for cu potential mapping in the tongling ore district and therefore was used to generate a prospectivity map containing very high high moderate and low potential areas in support of follow up exploration the prospective areas delineated in this map occupy 13 97 of the study area and capture 80 95 of the known deposits the fact that two newly discovered deposits occur within the prospective areas predicted by the prospectivity model indicates that the model is robust and effective regarding exploration target generation

particle size and mineralogical composition of inorganic colloids in glacier melting water and overlying ice in an alpine glacier oberaargletscher switzerland

composite suspended sediment particles and flocculation in glacial meltwaters preliminary evidence from alpine and himalayan basins research over the last decade has shown that the suspended sediment loads of many rivers are dominated by composite particles these particles are also known as aggregates or flocs and are commonly made up of constituent mineral particles which evidence a wide range of grain sizes and organic matter the resulting in situ or effective particle size characteristics of fluvial suspended sediment exert a major control on all processes of entrainment transport and deposition the significance of composite suspended sediment particles in glacial meltwater streams has however not been established existing data on the particle size characteristics of suspended sediment in glacial meltwaters relate to the dispersed mineral fraction absolute particle size which for certain size fractions may bear little relationship to the effective or in situ distribution existing understanding of composite particle formation within freshwater environments would suggest that in stream flocculation processes do not take place in glacial meltwater systems because of the absence of organic binding agents however we report preliminary scanning electron microscopy data for one alpine and two himalayan glaciers that show composite particles are present in the suspended sediment load of the meltwater system the genesis and structure of these composite particles and their constituent grain size characteristics are discussed we present evidence for the existence of both aggregates or composite particles whose features are largely inherited from source materials and flocs which represent composite particles produced by in stream flocculation processes in the absence of organic materials the latter may result solely from electrochemical flocculation in the meltwater sediment system this type of floc formation has not been reported previously in the freshwater fluvial environment further work is needed to test the wider significance of these data and to investigate the effective particle size characteristics of suspended sediment associated with high concentration outburst events such events make a major contribution to suspended sediment fluxes in meltwater streams and may provide conditions that are conducive to composite particle formation by flocculation copyright 2002 john wiley sons ltd

scale of experiment and rock physics trends because rock is heterogeneous at all scales it is often invalid to assign a single porosity permeability resistivity or velocity to a volume in the subsurface well data demonstrate that these properties can vary appreciably between two points just a foot apart the same happens at the pore scale consider for example a ct scan of a 1 3 mm berea sandstone cube figure 1 the porosity of this sample as calculated by counting the blue pore space pixels is 0 164

geochemical weathering at the bed of haut glacier d arolla switzerland a new model waters were sampled from 17 boreholes at haut glacier d arolla during the 1993 and 1994 ablation seasons three types of concentrated subglacial water were identified based on the relative proportions of ca 2c h co 3 and so4 2 to si type a waters are the most solute rich and have the lowest relative proportion of si they are believed to form in hydrologically inefficient areas of a distributed drainage system most solute is obtained from coupled sulphide oxidation and carbonate dissolution so cd it is possible that there is a subglacial source of o2 perhaps from gas bubbles released during regelation because the high so4 2 levels found up to 1200 eq l are greater than could be achieved if sulphides are oxidized by oxygen in saturated water at 0 c c 414 eq l a more likely alternative is that sulphide is oxidized by fe 3c in anoxic environments if this is the case exchange reactions involving fe iii and fe ii from silicates are possible these have the potential to generate relatively high concentrations of hco3 with respect to so4 2 formation of secondary weathering products such as clays may explain the low si concentrations of type a waters type b waters were the most frequently sampled subglacial water they are believed to be representative of waters flowing in more efficient parts of a distributed drainage system residence time and reaction kinetics help determine the solute composition of these waters the initial water rock reactions are carbonate and silicate hydrolysis and there is exchange of divalent cations from solution for monovalent cations held on surface exchange sites hydrolysis is followed by so cd the so4 2 concentrations usually are 414 eq l although some range up to 580 eq l which suggests that elements of the distributed drainage system may become anoxic type c waters were the most dilute yet they were very turbid their chemical composition is characterized by low so4 2 h co3 ratios and high ph type c waters were usually artefacts of the borehole chemical weathering environment true type c waters are believed to flow through sulphide poor basal debris particularly in the channel marginal zone the composition of bulk runoff was most similar to diluted type b waters at high discharge and was similar to a mixture of type b and c waters at lower discharge these observations suggest that some supraglacial meltwaters input to the bed are stored temporarily in the channel marginal zone during rising discharge and are released during declining flow little of the subglacial chemical weathering we infer is associated with the sequestration of atmospheric co2 t he progression of reactions is from carbonate and silicate hydrolysis through sulphide oxidation by first oxygen and then fe iii which drives further carbonate and silicate weathering a crude estimate of the ratio of carbonate to silicate weathering following hydrolysis is 4 1 we speculate that microbial oxidation of organic carbon also may occur both sulphide oxidation and microbial oxidation of organic carbon are likely to drive the bed towards suboxic conditions hence we believe that subglacial chemical weathering does not sequester significant quantities of atmospheric co2 and that one of the key controls on the rate and magnitude of solute acquisition is microbial activity which catalyses the reduction of fe iii and the oxidation of fes2 copyright 2002 john wiley sons ltd

metallogeny of copper and iron deposits in the eastern yangtse craton east central china abstract the eastern yangtse craton of central to eastern china is an important fe cu metallogenic province based on studies of the regional geology and tectonic evolution this metallogenic belt is controlled by faults and aulacogens in the continental plate in the early yanshan epoch jurassic the dominant west northwest and east west lithospheric faults controlled the distribution of cu mo and au mineralization whereas in the late yanshan epoch cretaceous the north northeast and northeast lithospheric faults controlled cu fe mineralization in a mineral district the distribution of ore fields is under the dual control of basement fault s and near surface fault s based on the relation of ring and lineament faults to intrusions a three level model of vertical zonation is proposed systematic petrochemical studies of mesozoic igneous rocks and mineralization identify three subseries 1 a calc alkaline intermediate to silicic subseries rich in potassium 2 a calc alkaline intermediate to felsic subseries rich in sodium and 3 a calc alkaline intermediate to mafic subseries rich in sodium genetic types of ore deposits are diverse including fe and cu skarns cu porphyries fe ore magma injections ningwu luzong fe deposits from late orthomagmatic to pegmatitic pneumato hydrothermal and to mesothermal epithermal associated with subvolcanic rocks and remobilized sedimentary fe and or cu deposits the genetic types of ore deposits form two metallogenic series 1 a sedimentary metallogenic series active mainly in the paleozoic and 2 a magmatic hydrothermal metallogenic series consisting of three subseries active predominantly in the jurassic and cretaceous with the latter being more important in this region the superposition and compounding of these two metallogenic series contribute to many styles of mineralization in this mineral province

the significance of particle aggregation in the overbank deposition of suspended sediment on river floodplains abstract the effects of suspended sediment aggregation on rates of overbank deposition and on the grain size composition of deposited sediment were investigated using a combined field measurement and numerical modelling approach measurements of the in situ grain size characteristics of the suspended sediment load termed the effective size distribution of the river culm devon were obtained using a custom built water elutriation system samples of suspended sediment and of sediment deposited on the floodplain were analysed in the laboratory to determine the size distributions of their constituent discrete mineral particles termed the ultimate size distribution interpretation of these field data was aided by the development of a two dimensional finite difference model of flood hydraulics and suspended sediment dispersion and deposition field measurements and model predictions show that particle aggregation results in higher relative contributions of fine size fractions to overbank deposits aggregation may also provide a mechanism for explaining the poor agreement between theoretical and observed trends in relationships between mean deposit grain size and distance from the main channel suspended sediment aggregation is shown to cause significant increases in rates of floodplain deposition increases in deposition rates resulting from aggregation may however be less than expected because of the effects of aggregate shape and density the latter may offset increases in particle size so that the settling velocities of the largest aggregates do not increase appreciably with particle diameter

composite suspended sediment particles in river systems their incidence dynamics and physical characteristics most of the existing data on the effective particle size characteristics of fluvial suspended sediment derive from instantaneous sampling methods that may not be representative of the overall suspended sediment loads this presents difficulties when there is a need to incorporate effective particle size data into numerical models of floodplain sedimentation and sediment associated contaminant transfer we have used a field based water elutriation apparatus wea to assemble a large 36 flood database on the time integrated nature of the effective and absolute particle size characteristics of suspended sediment in four subcatchments of the river exe basin of southwest england these catchments encompass a wide range of terrains and fluvial environments that are broadly representative of much of the uk and temperate low relief northwest europe the wea provides important data on the physical characteristics of composite particles that are not attainable using other methods this dataset has allowed for the first time detailed interbasin comparisons of the time integrated particle size characteristics of suspended sediment and reliable estimates of the contribution of five effective size classes to the mean annual suspended sediment load of the study catchments the suspended sediment load of each river is dominated by composite rather than primary particles with for example almost 60 by mass of the sediment load of the river exe at thorverton transported as composite particles 16 m in size all the effective size classes contain significant clay components a key outcome of this study is the recognition that each catchment has a distinctive time integrated effective particle size signature in addition the time integrated effective particle size characteristics of the suspended loads in each of the catchments display much greater spatial variability than the equivalent absolute particle size distributions this indicates that the processes producing composite particles vary significantly between these catchments and this has important implications for our understanding of the dynamics of suspended sediment properties copyright 2007 john wiley sons ltd

glacial sediment production and development of hydro electric power in glacierized areas by jim bogen glaciology section norwegian water resources and energy administration p o box 5091 majorstua n 0301 oslo 3 norway abstract this paper discusses the results of a sediment monitoring programme carried out in connection with hydro electric power development plans in the river basins surrounding the jostedalsbreen ice cap in norway whereas the highest suspended sediment transport rates occur during years with several flash flood events the bed load is more dependent upon the duration of large magnitude flood events bed load transport has been obtained from annual measurements of deltaic growth in small lakes at the front of glaciers during the years 1968 86 the mean ratio of bed load to total load amounted to 0 30 0 50 of the total load but in years with large magnitude floods this ratio decreased the mean annual suspended sediment yield of norwegian glaciers ranges from 100 tonnes km2 a i to 1300 tonnes km2 a i valley glaciers cause the highest erosion rates with the exception of the small cirque glacier trollbergdalsbreen which is thought to be a soft bed glacier the investigation programme undertaken involved monitoring the volume of suspended sediments together with the size distribution mineralogy and shape of grains in general the valley glaciers supply more sand than the smaller cirque glaciers whereas particles in the fine sand and silt size ranges in almost all of the glaciers are angular in shape methods of comparing the abrasive capacity of the sediment load at various intakes in a power plant are discussed long term sediment supply from the glaciers was investigated by studies of varves and rythmites in sediment cores from glacier fed lakes introduction during the last few years several glacier areas in norway have been developed for hydro electric power in this paper the results of a sediment monitoring programme carried out in connection with hydro electric power plans in the river basins surrounding the jostedalsbreen ice cap are discussed the hydro electric power plans on the western side the breheimen stryn project involve diversions of water at 32 intakes fig

links between proglacial stream suspended sediment dynamics glacier hydrology and glacier motion at midtdalsbreen norway two hourly suspended sediment concentration variations observed during the summer of 1987 in the proglacial stream draining midtdalsbreen norway are modelled using multiple regression and time series techniques suspended sediment fluctuations are influenced by stream discharge variations diurnal hysteresis effects medium term sediment supply and transport variations and the recent suspended sediment concentration history of the stream they do not appear to be influenced by seasonal exhaustion or rainfall variations possible reasons for this are discussed large positive residuals from the fitted models are major pulses of suspended sediment unrelated to discharge variations these sediment flushes correlate with periods of enhanced glacier motion they cannot be explained by enhanced sediment production by subglacial erosion but are probably due to the tapping of subglacially stored sediment during sudden changes in the hydraulics and or configuration of the subglacial hydrological system seasonal changes in the lag between glacier motion peaks and suspended sediment flushes suggest that the subglacial hydrological system evolves over the summer from a distributed to a more channelized configuration

flocculation a key process in the sediment flux of a large glacier fed lake this study investigates the consequences of flocculation for sediment flux in glacier fed lillooet lake british columbia based on density fractal dimension in situ profiles of sediment concentration and size distribution and settling velocity equations presented in the literature sediment flux attributed to macroflocs during the late spring and summer accounts for a significant portion of sediment flux in the lake equivalent to at least one quarter of the average annual sediment flux fine sediment is reaching the lake floor faster in flocs than occurs if settling as individual grains this flux varies both spatially and temporally over the observation period suggesting a link between deposition via flocculation and the properties of bottom sediments macrofloc flux increased through june reached a peak during july and then declined into august macrofloc flux was greatest in the distal end of the first basin approximately 10 km from the point of inflow relatively high excess densities 0 1 g cm 3 at 500 m for flocs in situ are consistent with a composition dominated by inorganic primary particles microlaminations within lillooet lake varves have been linked by earlier workers to discharge events and the action of turbidity currents emanating from the lillooet river while turbidity currents undoubtedly occur in lillooet lake these results demonstrate flocculation as an adjunct process linking discharge lake level macrofloc flux bulk density and microlaminations in situ measurements of sediment settling velocity in glacier fed lakes are required to better constrain flux rates and permit comparison between flocculation in lacustrine environments with existing studies of estuarine marine and fluvial flocculation copyright 2009 john wiley sons ltd

damage stress and acoustic emission characteristics of the beishan granite crack initiation stress ci and crack damage stress cd of the beishan granite under uniaxial and triaxial compressions are determined

tracing organic matter sources in riverine suspended sediment implications for fine sediment transfers abstract the study of sediment transport in riverine systems has historically focussed on the inorganic fluxes although the suspended load is known to incorporate both inorganic and organic material research on freshwater flocculation indicates that sediment morphology and behaviour depend on both components as biologic material can alter the hydrodynamic and charge properties of composite particles which has implications for fine sediment transport and storage in stream systems this study evaluates both the supply and the quality of the organic matter comprising the suspended sediment in a salmon bearing stream in northern british columbia canada seasonally changing hydrodynamic and biologic conditions are considered in the context of suspended sediment seston size seston samples were collected in an event based design for analysis of organic matter sources suspended particulate inorganic and organic matter concentrations spm sim and som and effective particle size distributions epsd organic matter sources were assessed using carbon nitrogen c n ratios and the associated stable isotopic signals samples and environmental measurements were taken during spring melt pre spawn low flows active salmon spawning post spawn and select rainstorms spm and sim were elevated during active salmon spawning compared to that expected for the given hydrologic conditions seasonal patterns of c n ratios and stable isotopes indicate that organic matter types can be differentiated in seston samples and these sources of organic material exhibit changing dominance in the seston over time the isotopic signature of seston increases in salmon derived nutrients when live and decaying salmon are present within the study stream the largest suspended particles are observed during the period of active spawning when both live and rotting salmon modify instream conditions this appears to be a function of the combined influence of high sim low shear stress and low c n ratios the generation of increased floc or seston size is of ecological importance in this stream and riverine systems elsewhere as it regulates the freshwater transfers of locally derived nutrients and sediments out of the fluvial system

aeromagnetic 3d inversion imaging for intermediate acid intrusive bodies and its indication significance of deep ore prospecting in tongling ore concentration district in the tongling ore concentration district the intrusions are closely related to metallogenic activities and almost all endogenic metallic ore deposits it is hence of great significance to find and delineate concealed and semi concealed intermediate acid intrusive bodies in the new round of mineral exploration the 3d inversion imaging technique was applied in tongling based on 1 50 000 aeromagnetic data in order to detect intermediate acid intrusive bodies based on the inversion result the authors selected a suitable magnetic susceptibility boundary in combination with physical properties of the rocks as well as geological information identified 34 intermediate acid intrusive bodies and studied their 3d spatial shapes most of the intermediate acid intrusive bodies are consistent with geological mapping results at surface the inversion results not only reflect the distribution of the intermediate acid intrusive bodies at surface but also indicate their 3d spatial shapes at depth according to the horizon intrusive body prospecting model in combination with other metallogenic information 6 principles were established in search for ore prospect areas at depth based on rock bodies inferred by the aeromagnetic 3d inversion 6 deep prospecting areas were delineated and the data obtained provide important information for deep prospecting in the tongling ore concentration district

partial melting of slab window margins genesis of adakitic and non adakitic magmas abstract when a mid ocean spreading ridge subducts it typically splits apart at depth to form two tapered slab edges separated by asthenospheric mantle within a slab window we examine the fate of the slab edges using simplified slab window geometries specific thermal parameters and assumptions regarding shear stress and slab hydration six fundamental zones of slab anatexis are identified and classified according to expected melt and restite compositions non adakitic melts of granodioritic to tonalitic composition are generated along the plate edges at depths of 5 65 km whereas adakitic melts form proximal to the edges at depths of 25 90 km as anatexis proceeds the subducted crust is converted to a migmatite of slab melt and eclogitic restite much of the migmatite may shear away from the slab and become incorporated into the mantle the melts will rise and leave behind fragments of restite within mantle peridotite if the peridotite is part of the overriding plate then the restite fragments may become long term residents of the continental lithospheric mantle however if the restite becomes entrained in the asthenosphere it may undergo upwelling and melting or flow away as ductile streaks to become long term mantle heterogeneities slab windows are thereby identified as important sites for slab melting and geochemical replenishment of the mantle