an equivalent discontinuous modeling method of jointed rock masses for dem simulation of mining induced rock movements abstract the discrete element method dem is of obvious and inherent advantages in simulating large displacements and discontinuous deformations of rock masses and thus is suitable to simulate the mining induced rock movements however when the region of the dem calculation model is large for example when both the length and width of the research area are larger than several hundreds of meters the rock mass in the model range often contains a large number of actual joints if the calculation model is built according to the distribution of the actual joints the calculation model of dem will consist of a large number of blocks which would lead to the impossibility of numerical calculations to address this problem an equivalent discontinuous modeling method edmm of jointed rock masses for dem simulation of mining induced rock movements is proposed in this paper in this method an actual geological body with a complex joint system will be simplified into an equivalent discontinuous model edm which is a dem calculation model with a simple hypothesis joint system the approach for determining the mechanical parameters i e the cohesive strength c the internal friction angle the joint normal stiffness jkn and the joint shear stiffness jks of the hypothetical joints of the edm is the core of the proposed edmm the main procedure of the proposed edmm is composed of 1 for each subarea of an edm building a group of equivalent discontinuous cube models edcms that are of different joint spacings 2 determining the joint mechanical parameters of each edcm based on the mechanical properties of the actual rock masses of the subarea 3 establishing the relationships between the joint spacings and joint mechanical parameters for each subarea of edm and 4 determining the mechanical parameters of the hypothesis joints in each subarea of the edm according to these relationships by exploiting the edm the dem numerical simulation is performed to simulate the mining induced rock movements and failures to demonstrate the applicability the proposed edmm was employed to simulate the rock movements and failures triggered by mining under the western open pit final slope of yanqianshan iron mine

granite ascent and emplacement during contractional deformation in convergent orogens based on a case study in the central maine belt of west central maine u s a it is proposed that crustal scale shear zone systems provide an eaective focussing mechanism for transfer of granite melt through the crust in convergent orogens during contractional deformation flow of melt in crustal materials at depths below the brittle plastic transition is coupled with plastic deformation of these materials the flow is driven by pressure gradients generated by buoyancy forces and tectonic stresses within the oblique reverse central maine belt shear zone system stromatic migmatite and concordant to weakly discordant irregular granite sheets occur in zones of higher strain which suggests percolative flow of melt to form the migmatite leuco somes and viscous flow of melt channelized in sheet like bodies possibly along fractures cyclic fluctuations of melt pressure may cause instantaneous changes in the eaective permeability of the flow network if self propa gating melt filled tensile and or dilatant shear fractures are produced due to melt enhanced embrittlement in homogeneous migmatite and schlieric granite occur in zones of lower strain which suggests migration of partially molten material through these zones en masse by granular flow and channelized flow of melt carrying entrained residue founded on the central maine belt case study we develop a model of melt extraction and ascent using the driving forces stress conditions and crustal rheologies in convergent especially transpressive orogens ascent of melt becomes inhibited with decreasing depth as the solidus is approached for intermedi ate a h2o muscovite dehydration melting the water saturated solidus occurs between 400 and 200 mpa near the brittle plastic transition during high t low p metamorphism where the balance of forces favors sub horizontal fracture propagation emplacement of melt may be accommodated by ductile flow and or stoping of wall rock and inflation may be accommodated by lifting of the roof at shallower crustal levels and or sink ing of the pluton floor the resultant plutons have sub horizontal tabular geometries with floors that slope down to the ascent conduits although these plutons may have locally discordant relations with country rock structures when viewed at the crustal scale granite ascent and emplacement in convergent orogens are syn tec tonic processes 1998 elsevier science ltd all rights reserved

residence of ree y th and u in granites and crustal protoliths implications for the chemistry of crustal melts a systematic study with laser ablation icp ms scanning electron microscopy and electron microprobe revealed that 70 95 wt of ree except eu y th and u in granite rocks and crustal protoliths reside within reeythu rich accessories whose nature composition and associations change with the rock aluminosity the accessory assemblage of peraluminous granites migmatites and high grade rocks is composed of monazite xenotime in low ca varieties apatite zircon thorthosilicate uraninite and betafite pyrochlore metaluminous granites have allanite sphene apatite zircon monazite and thorthosilicaie peralkaline granites have aeschinite fergusonite samarskite bastnaesite fluocerite allanite sphene zircon monazite xenotime and th orthosilicate granulite grade garnets are enriched in nd and sm by no less than one order of magnitude with respect to amphibolite grade garnets granulitegrade feldspars are also enriched in lree with respect to amphibolite grade feldspars accessories cause non henrian behaviour of ree y th and u during melt solid partitioning because elevated fractions of monazite xenotime and zircon in common migmatites are included within major minerals their behaviour during anatexis is controlled by that of their host settling curves calculated for a convecting magma show that accessories are too small to settle appreciably being separated from the melt as inclusions within larger minerals biotite has the greatest tendency to include accessories thereby indirectly controlling the geochemistry of ree y th and u we conclude that ree y th and u are unsuitable for petrogenetical modelling of granitoids through equilibrium based trace element fractionation equations

fracturing and diking in incompletely crystallized granitic plutons abstract dikes in granitic plutons commonly have mineralogic and textural characteristics indicating a genetic relation to their host the contact between the dike and the host is marked signifcantly by interlocking unfractured crystals rather than by truncations and overgrowths although megascopically the contacts between dike and host pluton may be exceedingly sharp and planar an explanation of these relationships by fracturing an incompletely crystallized host rather than by entirely post magmatic fracturing with subsequent diking is postulated to be consistent with experimental date and certain petrologic observations published experimental research indicates that fracturing of crystal melt systems may occur if there is at least 70 crystals in the system at which point the system is capable of transmitting compressive and shear stresses via a crystalline framework dilatancy pumping of melt into fracture zones and subsequent hydraulic fracturing is thought to be one possible way late stage fluids of granitic systems evolve into dikes in granitic plutons such as leucogranites aplites and pegmatites interlocking textures between dike and host may also develop if magma from some distant source is interjected along the plane of fracturing in crystal melt systems

synthetic aperture radar observations of resonantly generated internal solitary waves at race point channel cape cod 1 synthetic aperture radar images revealed the two dimensional propagation characteristics of short period internal solitary waves in race point channel in massachusetts bay the images and in situ measurements of the flow in the channel are used to infer the likely generation mechanism of the waves the solitary waves are generated during the ebb phase of the tide within the channel on some occasions two trains of internal waves are generated presumably at the same location but at slightly different phases of the ebb tide the main characteristics of the two layer flow are described based on the criticality of the froude number it is suggested that these two individual packets of waves result from flow passage through resonance where the froude number is one one packet is generated as the flow passes through the transcritical regime during the acceleration phase of the ebb tidal current and another packet is generated during the deceleration phase both packets propagate upstream when the tide slacks but with slightly different propagation directions

deformation of incompletely crystallized magma systems granitic gneisses and their tectonic implications certain textures in two feldspar calc alkaline granitic gneisses have been identified as indicators of the presence of intercrystalline melt during deformation of crystal melt mushes fluid relocation or fracting is to be expected in an incompletely crystallized magmatic system as deviatoric stresses are applied to it relocation of late stage fluids capable of crystallizing k feldspar quartz microaplite and myrmekite to low pressure zones such as the pressure shadow region around earlier crystals occurs within some developing mylonitic gneiss fabrics and results in a distinctive assemblage of textures strain in these rocks is expressed by various brittle and ductile features and by fluid relocation textures the petrogenesis of these particular gneisses is therefore both magmatic and metamorphic contrasting with gneiss forming processes that had no participating magmatic component migmatitic complexes evolving by partial anatexis of non magmatic rocks in a tectonically active environment are not

theory of melt segregation a review abstract the processes by which melt is extracted from partially molten source regions at depth are collectively known as melt segregation during the past three years a dynamical theory has been developed which provides a unified description of the mechanical thermodynamical and chemical aspects of melt segregation in this theory a partially molten region is regarded as a deformable porous medium or matrix saturated with melt migration of melt relative to the matrix can be driven either by the buoyancy of the melt or by nonhydrostatic pressure gradients associated with the deformation of the matrix this paper reviews the basic governing equations of the theory and the solutions which have been obtained during the past three years

post emplacement melt flow induced by thermal stresses implications for differentiation in sills abstract we present the first steps of a new explanation model for differentiation in sills using a combination of geochemical data and field observations numerical modeling and dimensional analysis geochemical data from a saucer shaped dolerite sill intruded into the karoo basin south africa reveal a differentiation process which causes d shaped profiles the geometry name is based on the variation in whole rock mg number mg mg mg fe from floor to roof in a sill the d shaped geochemical profiles represent sheet intrusions with the most primitive composition i e high mg in its center and progressively more evolved composition i e low mg towards the upper and lower margins the differentiation is reversed compared to the normal differentiation produced by fractional crystallization c shaped profiles c shaped profiles are believed to be formed by segregation of crystals from the magma we propose that the opposite the d shaped profile may result from melt segregation from the crystal mush this is achieved by porous melt flow through a consolidated crystal network after the main phase of emplacement and before complete solidification we show that a significant flow is feasible under natural occurring conditions an underpressure of magnitude 108 pa develops at the cooling margins due to volume reduction of the crystallizing porous melt the resulting pressure gradient is the driving force for the melt flow towards cooling margins considered in this work as a result the margins will be enriched in the incompatible elements associated with the melt phase while the center will be depleted we show that the amount of flow is primarily a function of viscosity of the melt and permeability of the crystal network which in turn is a transient phenomenon dependent on a number of parameters diagrams have been constructed to evaluate the feasibility of substantial melt extraction in terms of these poorly constrained parameters data from the golden valley sill and many other natural occurrences of d and i shaped geochemical profiles show a reasonable agreement with our predictions of melt flow potential and are thus well explained by the presented model we conclude that in order to fully understand differentiation processes occurring in sheet intrusions we need to account for post emplacement segregation of melt from crystals and not only segregation of crystals from melt

numerical investigation of lake bed seepage patterns effects of porous medium and lake properties abstract three dimensional steady state numerical models were used to investigate the relative significance of several factors controlling lake bed seepage patterns lake depth lake bed slope orientation of an asymmetric lake with respect to a regional hydraulic gradient lake bed sediments and heterogeneity and anisotropy of the porous medium we considered both inflow and flow through lakes and our focus was on the details of seepage flux at the lake bed not on the surrounding porous medium while porous medium factors anisotropy and heterogeneity are important we found several conditions where lake bed factors were nearly as important in controlling the distribution of seepage varying lake bed slope from 0 013 to 0 04 in different simulations had a significant effect on shoreline seepage rates were 10 40 higher for lakes of low slope than lakes of steep slope also significantly elevated seepage in some cases a local maximum was observed offshore at the break in bed slope between the sloping side and flat central portions of the lake bed whenever the surrounding porous medium had a high anisotropy 1000 or 100 for flow through lakes in media of high anisotropy the annual volume of groundwater inseepage was significantly higher about 20 in lakes with steep bed slope compared to those with low slope this effect of slope was smaller at lower anisotropy for an asymmetric flow through lake a lake with a steep bed slope on one side moderate slope on the other the percentage of lake bed experiencing inseepage was greatest when the steep side was downgradient and the effect was larger at higher anisotropy these effects illustrate the complex interaction between lake bed slope and the anisotropy of the surrounding porous medium in controlling lake groundwater exchange adding low conductivity lake sediments and decreasing their conductivity shifted groundwater seepage further offshore in inflow lakes increasing the anisotropy of the surrounding porous medium had the same effect adding sediments and increasing anisotropy also decreased nearshore seepage in flow through lakes but without increasing offshore seepage in this case the net effect was a smaller annual volume of lake groundwater exchange at the same time the percentage of the lake bed experiencing inseepage increased in flow through lakes even as the annual volume of inseepage was decreasing thus for flow through lakes a larger area of inseepage may not be a good indicator of a greater volume of inseepage lake depth did not have a significant effect on the quantity or distribution of seepage to inflow or flow through lakes many of the physical factors investigated here influence the amount of lake groundwater exchange and the proportions of nearshore and offshore seepage therefore they are potentially significant to lake water quality and ecology in addition to hydrology

formation of diatexite migmatite and granite magma during anatexis of semi pelitic metasedimentary rocks an example from st malo france petrological and geochemical variations are used to investigate the introduction formation of granite magma from diatexite migmatites derived from partial melting experiments show that protoliths of pelite metasedimentary rocks of pelitic to greywacke composition at st and greywacke composition yield up to 40 vol malo france anatexis occurred at relatively low temperatures granite melt over the temperature range 650 900 c and pressures 800 c 4 7 kbar principally through muscovite typical of anatexis of the continental crust conrad et dehydration melting biotite remained stable and serves as a tracer al 1988 vielzeuf holloway 1988 patino douce for the solid fraction during melt segregation the degree of partial johnston 1991 vielzeuf montel 1994 patino douce melting calculated from modal mineralogy and reaction stoichiometry harris 1998 therefore to make a granite magma was 40 vol there is a continuous variation in texture the melt fraction must be segregated from a solid fraction mineralogy and chemical composition in the diatexite migmatites of much greater volume and then collected together mesocratic diatexite formed when metasedimentary rocks melted the type of melt residuum separation process depends sufficiently to undergo bulk flow or magma flow but did not on the melt fraction present experience significant melt residuum separation mesocratic diatexite melt residuum separation at low degrees of partial that underwent melt segregation during flow generated 1 memelting f and consequently low melt fraction mf lanocratic diatexites at the places where the melt fraction was has been documented from metatexite migmatites in removed leaving behind a biotite and plagioclase residuum enriched these rocks melt segregation produced centimetre scale in tio2 feot mgo cao sc ni cr v zr hf th u and leucosomes distributed in a host composed of layers that ree and 2 a complementary leucocratic diatexite enriched in have melted and others that have not e g henkes sio2 k2o and rb where the melt fraction accumulated leucocratic johannes 1981 gupta johannes 1982 dougan 1983 diatexite still contained 5 15 vol residual biotite mg number sawyer 1987 tait harley 1988 barbey et al 1990 40 44 and 10 20 vol residual plagioclase an22 anatectic brown 1994 leucosomes represent small volumes of granite magma developed from the leucodiatexite first by further felsic magma formed when melt was squeezed out of the melt residuum separation then through fractional crystallization deforming matrix mclellan 1988 sawyer 1991 1994 most biotite in the anatectic granite is magmatic mg number brown 1994 brown et al 1995 and collected in low18 22 pressure sinks such as shear bands and inter boudin

wave driven porewater and solute circulation through rippled elastic sediment under highly transient forcing waves induce porewater flow and solute transport through permeable marine sediment however past studies have ignored high frequency pressure pulses under the assumption that the porewater flow field is adequately represented by a time averaged one or that the saturated sediment is incompressible we modeled porewater flow and solute transport inside ripples forced by instantaneous pressure profiles along the sediment water interface swi with 0 1 s temporal resolution the transient pressure profiles were taken from a field data driven large eddy simulation model of wave driven oscillatory flow the simulations suggest that in elastic permeable and saturated sediment a time averaged representation of the flow field may be inadequate and that this also leads to shortcomings in how transport is modeled bursts in fluid flushing occur when high frequency pressure fluctuations were considered leading to larger long term average fluid fluxes compared to a steady flow field driven by a time averaged pressure profile the pressure perturbations along the swi propagate within a few milliseconds to meter depths within the sediment leading to strongly transient porewater velocity fields this leads to enhanced dispersion of solutes and larger time averaged solute fluxes however enhanced solute flux across the swi diminished through time with increasing permeability the high frequency transient pressures and sediment elastic properties we considered have been largely ignored and unrecognized future observational and modeling studies should consider these processes especially since they mediate timing sensitive biogeochemical reactions

seasonal variation of solitary wave properties in lake constance 1 the properties of internal solitary waves isws depend on the stratification of the water body in most climatic regions the stratification in lakes and oceans varies during the year and hence the properties of the isws can also be expected to change over the seasons on the basis of a long term temperature time series recorded over 6 years this paper investigates seasonal changes in the characteristic properties of isws in lake uberlingen a subbasin of lake constance a large number of isws with amplitudes ranging from 3 m to 30 m were identified more than 15 of the leading isws of a wave train were associated with density inversions often indicating shear instabilities or trapped cores for all waves the propagation depth and the value of a nonlinearity index nlp providing the degree of nonlinearity were determined propagation depth being the rest height of the isotherm undergoing maximum displacement and nlp the ratio between wave amplitude and propagation depth the index nlp was found to be a good parameter for predicting the occurrence of inversions the statistical analysis of the wave properties derived from the observations revealed that the degree of nonlinearity of the isws changes with season complementary to the statistical analysis the seasonally averaged isw properties were compared with wave prototypes obtained numerically from the dubreil jacotin long djl and the stratified korteweg devries kdv models the simulations indicate that the typical stratification and its seasonal variation are responsible for the degree and the seasonality of nonlinearity of the isws

melt segregation structures in granitic plutons when melt fraction increases beyond a critical value migmatites behave as magmas conversely when melt fraction decreases crystallizing magmas form solid framework mushes and behave as solids the richness in preserved mesoscopic melt segregation structures in migmatites is not matched by melt segregation structures in granitic bodies this paper identifies melt segregation structures in granites and compares them to structures in migmatites the rarity of segregation structures in granites is a consequence of the solid framework mush allowing for cryptic melt extraction from its pores the relatively short duration of solidification of the mush and the fragile nature of the solid framework identifying segregation features in granitoids at outcrop scale provides the basis for understanding the physical processes that lead to chemical and mineralogical differentiation in granitic magmas

fracture size estimation using data from multiple boreholes abstract the size of a fracture within a rock mass can be obtained using data sampled from boreholes or exposed surfaces in this study fracture sizes are estimated using data from multiple boreholes the fractures are assumed to be elliptical all having the same aspect ratio but not necessarily occurring parallel to each other formulae for estimating the mean and standard deviation of the characteristic fracture size are developed by considering the number of intersections between the fractures and the boreholes a method is proposed to infer the probability density function of the fracture size from the number of fractures which is obtained by random sampling of fractures in adjacent boreholes the fracture distribution is assumed to follow the form of a fractal exponential or lognormal distribution the performance of the method is validated using monte carlo simulations with different inputs of size distribution fracture density orientation and mean fracture size

a new semi deterministic block theory method with digital photogrammetry for stability analysis of a high rock slope in china abstract this study proposed a new semi deterministic block theory nsdbt method in which the sizes and spatial positions of discontinuities along with their orientations were incorporated hence the locations volumes and sliding forces of key rock blocks could be obtained which could directly provide quantitative reference for support design the nsdbt method was applied to analyze the stability of a high rock slope of changhe dam located in sichuan province southwest china required geological data for the analyses was obtained from field and laboratory investigations the mechanical parameters of discontinuities were obtained by laboratory direct shear tests and geometric characteristics of discontinuities were obtained by digital photogrammetry a total of 3540 discontinuities were identified the analysis results showed that a 57 7 key blocks were excluded owing to taking the formation probability of key blocks into consideration b comparing the results of the calculation and field investigation it was found that the calculated locations of dangerous discontinuities were in good agreement with the failed blocks investigated in the field note the failed blocks include blocks that have developed into real rockfalls and dangerous blocks identified by a field survey c on the studied slope 355 key blocks were searched of which 175 123 and 57 were tetrahedral pentahedral and hexahedral blocks respectively d the volumes of key blocks ranged from 0 01 to 22 83 m 3 and most of them were smaller than 4 m 3 e the sliding forces of key blocks were range from 0 01 to 390 98 kn and most of them were smaller than 50 kn and f water had a great impact on the stability of the slope especially for sampling window 3 in summary the studied slope was stable on the whole but there existed some local small key blocks

the stochastic assessment of strength and deformability characteristics for a pyroclastic rock mass abstract a practical procedure is described for implementing probabilistic determination of rock mass strength and deformability properties of a pyroclastic rock medium in order to carry out this procedure the discontinuity properties of rock mass are collected in the field and laboratory studies are conducted on the intact rock samples the appropriate statistical distributions are fitted on the available data by using the chi square goodness of fit technique for the estimation of strength and deformability of rock mass input parameters of the generalized hoek brown empirical equations are replaced by previously defined probability density functions after running monte carlo simulations potential ranges of the strength and deformability values of the investigated rock mass are accomplished the simulation results suggest that it is promising to represent the random characters of rock mass mechanical properties when used with proper empirical or analytical relationships

close spatial relationship between plutons and shear zones this paper explores the relationship between granitic plutons and transcurrent shear zones using examples from the borborema province northeastern brazil syntectonic plutons of this province generally have en cornue shapes and were emplaced preferentially within or at the margins of wide regional scale transcurrent shear zones particularly where shear zones intersect major lithological boundaries it is argued that the plutons shapes and their closeness to shear zones are indicative of a causal relationship between granite plutons and shear zones with the support of numerical models it is further argued that pluton emplacement in transcurrent terranes is controlled by low mean pressure magma traps at the shoulders of shear zones resulting from strain incompatibility caused by regional variations in rheological properties

mechanisms and controls on the formation of sand intrusions sandstone intrusions are found in all sedimentary environments but have been reported most commonly from deep water settings they also appear to be more frequently developed in tectonically active settings where applied tectonic stresses facilitate development of high fluid pressures within the sediments a variety of mechanisms have been cited as triggers for clastic intrusions these include seismicity induced liquefaction application of tectonic stresses excess pore fluid pressures generated by deposition related processes and the influx of an overpressured fluid from deeper within the basin into a shallow sand body the formation of sandstone dykes and sills is investigated here by considering them as natural hydraulic fractures when the seal on an unconsolidated overpressured sand body fails the resulting steep hydraulic gradient may cause the sand to fluidize the fluidized slurry can then inject along pre existing or new fractures to form clastic intrusions the scale and the geometry of an intrusive complex is governed by the stress state depth and pre existing joints or faults within the sedimentary succession as well as the nature of the host sediments for the simplest tectonic setting where the maximum stress in a basin is vertical gravitational loading small irregular intrusions commonly result in the formation of sills at shallow depths within a few metres of the surface whereas at greater depth dykes and sills forming clastic intrusion networks are more typical a simple relationship is derived to calculate the maximum burial depth at which a dyke sill complex forms as a function of the source bed to sill height the bulk density of the surrounding sediments and the ratio of the vertical to horizontal effective stresses k 0 when applied to three examples of large scale dyke sill complexes developed within paleocene and eocene deep water reservoir sand bodies of the north sea maximum burial depths in a range of 375 to c 500 m 450 700 m and 550 850 m are estimated for intrusion of each of the three complexes

fluid circulation and seepage in lake sediment due to propagating and trapped internal waves 1 it has long been known that surface gravity waves induce significant seepage through the porous layer found at the lake bottom away from coastal regions however the pressure signature of surface waves at the lake bottom is weak we consider fully nonlinear internal gravity waves whose long wavelength and slow motion implies a sustained and strong pressure perturbation even in the deep regions of the lake we argue that internal waves can induce significant seepage through the sediment layer in regions where surface gravity waves have negligible impact the pressure profile at the fluid porous layer interface is computed from the exact dubreil jacotin long theory giving a reliable profile even for large waves this profile is used in conjunction with darcy s law to compute the seepage within the porous region we find that the geometric distribution of seepage is strongly controlled by both the ratio of porous media thickness to the horizontal length of the pressure perturbation and the bottom topography when it is present based on work on the interaction of internal solitary waves with the bottom boundary layer we develop a model to account for the changes in permeability due to wave induced instabilities in the bottom boundary layer and enhanced benthic turbulence this turbulence acts to unplug the pores near the surface by lifting the detritus that clogs them the resulting changes in permeability significantly enhance exchange between the free fluid and the porous medium on the downstream side of the wave

melt segregation in the continental crust distribution and movement of melt in anatectic rocks the grain and outcrop scale distribution of melt has been mapped in anatectic rocks from regional and contact metamorphic environments and used to infer melt movement paths at the grain scale anatectic melt is pervasively distributed in the grain boundaries and in small pools consequently most melt is located parallel to the principal fabric in the rock typically a foliation short branched arrays of linked melt bearing grain boundaries connect melt depleted parts of the matrix to diffuse zones of melt accumulation protoleucosomes where magmatic flow and alignment of euhedral crystals grown from the melt developed the distribution of melt leucosome and residual rocks normally melanocratic in outcrop provides different but complementary information the residual rocks show where the melt came from and the leucosomes preserve some of the channels through which the melt moved or sites where it pooled different stages of the melt segregation process are recorded in the leucosome melanosome arrays regions where melting and segregation had just begun when crystallization occurred are characterized by short arrays of thin branching leucosomes with little melanosome a more advanced stage of melting and segregation is marked by the development of residual rocks around extensive branched leucosome arrays generally oriented along the foliation or melting layer places where melting had stopped or slowed down before crystallization began are marked by a high ratio of melanosome to leucosome because most of the melt has drained away very few leucosomes remain to mark the melt escape path this is common in melt depleted granulite terranes many migmatites contain abundant leucosomes oriented parallel to the foliation mostly these represent places where foliation planes dilated and melt drained from the matrix via the branched grain boundary and larger branched melt channel leucosome arrays collected melt collected in the foliation planes was partially or fully expelled later when discordant leucosomes formed leucosomes or veins oriented at high angles to the foliation layering formed last and commonly lack melanocratic borders hence they were not involved in draining the matrix of the melting layer discordant leucosomes represent the channels through which melt flowed out of the melting layer

transfer of nonsorbing solutes to a streambed with bed forms theory a theoretical analysis of the exchange of nonsorbing solutes between a permeable streambed and the overlying water of a stream or river is presented in this paper in a companion paper elliott and brooks this issue the results of experimental studies of such exchange are presented the analysis focuses on water movements into within and out of the bed which result from the presence of bed forms ripples and dunes and highlights the mechanisms of pumping and turnover pumping is the movement of fluid through the bed induced by steady dynamic pressure variations over bed forms turnover occurs as moving bed forms trap and release interstitial fluid the detailed analysis was used to generate the distribution of the residence time of solute within the bed which can be used to calculate the net mass exchange due to pumping and turnover

flow induced uptake of particulate matter in permeable sediments we demonstrate the fast transfer of suspended particles from the boundary layer into the upper strata z 2 x 10 l l m2 incubated in a laboratory flume increased pressure up and downstream of small mounds z 2 5 cm drove water 5 5 cm into the core carrying suspended particles 1 pm to 2 2 cm sediment depth within 10 h simultaneously decreased pressure at the downstream slope of the protrusions drew pore fluid from deeper layers z 5 10 cm to the surface in the sediment friction reduced the velocity of the particulate tracers resulting in size fractionation and layers of increased particle concentration ripple topography 0 8 2 8 cm high enhanced interfacial particle 1 pm flux by a factor 2 3 when compared to a level control core the pathways of the particle and solute tracers below a sediment ripple are explained with a source sink model that describes the pore flow velocity field our results suggest that bedform induced interfacial flows are important for the uptake of particulate organic matter into permeable shelf sediments

sediment resuspension and mixing by resonantly generated internal solitary waves the observation of internal solitary waves isws propagating upstream along a strongly stratified bottom layer on the california shelf is reported an increased concentration of particulates in the water column accompanies the passage of these isw packets the estimated local richardson number in the bottom vicinity is around 1 4 and a vertical coefficient of eddy diffusivity of order 1022 m2 s21 is associated with the upstream propagating leading isw the leading isw gave rise to reversed flow in an 8 m layer above the bottom it is argued that the upstream propagating isws were generated by resonant flow over bottom topography internal waves generated in this way seem to be frequent in the record of a month long experiment model results suggest that the isws can carry up to 73 of such generated long wave energy the ocean conditions at the site are similar to those of other coastal sites which suggests that the phenomenon described here may be common

sediment resuspension mechanisms associated with internal waves in coastal waters 1 large amplitude vertically trapped internal waves can induce sizable velocities and trigger hydrodynamic instabilities in the bottom boundary layer thereby contributing to the resuspension of sediments and the maintenance of sediment concentration in the water column we discuss numerical simulations of several different situations in which the boundary layer in the wave footprint undergoes hydrodynamic instability with a resultant increase in the incidence of spatiotemporal structures that could facilitate sediment resuspension for the case of internal solitary waves we provide bounds in parameter space separating regions in which internal waves can be expected to efficiently resuspend sediment from those in which the boundary layer in the wave footprint is both laminar and stable a notable finding is that the onset of instability is a strong function of the background current the lagrangian transport of passive particles due to the instability is explored and some quantitative measures of the efficiency of the particle transport process are provided we subsequently discuss the evolution of the power spectra of the bottom shear stress with time and find that while the general characteristics of the instability are robust lowering either the reynolds number or the strength of the background current leads to an increase in the typical length scales associated with the mature instability finally we discuss instabilities during the internal wave generation process and alternative instability mechanisms when the bottom is not flat

pore pressure in a wind swept rippled bed below the suspension threshold toward elucidating how a wavy porous sand bed perturbs a turbulent flow above its surface we record pressure within a permeable material resembling the region just below desert ripples contrasting these delicate measurements with earlier studies on similar impermeable surfaces we run separate tests in a wind tunnel on two sinusoidal porous ripples with aspect ratio of half crest to trough amplitude to wavelength of 3 and 6 for the smaller ratio pore pressure is a function of streamwise distance with a single delayed harmonic decaying exponentially with depth and proportional to wind speed squared the resulting pressure on the porous surface is nearly identical to that on a similar impermeable wave pore pressure variations at the larger aspect ratio are greater and more complicated consistent with the regime map of kuzan et al 1989 the flow separates creating a depression at crests unlike flows on impermeable waves the porous rippled bed diffuses the depression upstream reduces surface pressure gradients and gives rise to a slip velocity thus affecting the turbulent boundary layer pressure gradients within the porous material also generate body forces rising with wind speed squared and ripple aspect ratio partially counteracting gravity around crests thereby facilitating the onset of erosion particularly on ripples of high aspect ratio armored with large surface grains by establishing how pore pressure gradients scale with ripple aspect ratio and wind speed our measurements quantify the internal seepage flow that draws dust and humidity beneath the porous surface

magma flow within the tavares pluton northeastern brazil compositional and thermal convection crystallization coupled with gravity removal of depleted interstitial melt has long been recognized as a mechanism of magma differentiation similarly heat released by synplutonic basaltic magma intrusions has long been recognized as capable of driving convection in granite chambers direct evidence of these processes has seldom been described in granites in the tavares pluton we mapped a number of melt extraction structures from pores of a crystal liquid mush an effectively solid magma where crystals form an interconnected skeleton and a variety of flow structures such as 1 meter scale tear or mushroom shaped blobs representing within chamber diapirs 2 meter scale ellipsoids representing frozen thermal plumes of granite driven by heat released from disrupted diorite intrusions and 3 ladder dikes and snail structures representing cross sections of several superposed cylindrical magma channels possibly feeders of diapirs and plume heads a fundamental feature of the structures in the tavares pluton is that they are well delineated by mafic schlieren developed at active channel margins we postulate a new model for the origin of marginal schlieren which combines shear flow sorting and melt escape from the flowing magma into an effectively solid surrounding mush extraction structures representing melt extraction from mush pores into melt pockets and schlieren representing regions where melt escaped into surrounding mush pores are both favored by magmas that form an interconnected solid framework at low crystal fractions 50 because these mushes are ductile and permeable favorable magmas are those with a high wetting angle between melt and solid 60 and a propitious crystal size and shape distribution we propose a model of compositional and thermal convection that accounts for all described structures

compositional convection in a reactive crystalline mush and melt differentiation fractional crystallization and partial melting involve relative motion of liquid and solid phases and chemical and thermal interactions between them to elucidate some physical principles of thermosolutal convection in a reactive porous medium we describe experiments on the directional solidification of aqueous ammonium chloride solutions the addition of small amounts of a polymerizing agent permits variation of the solution viscosity independently of thermal conditions the phase diagram and permeability solutions were cooled from below and crystallization developed at the base of the tank generating at first a field of thin plumes of light residual fluid released from the boundary layer at the top of the mush the interstitial fluid within the mush also became unstable eventually the onset of convection occurring when the porous medium rayleigh number of the mush reached a critical value this threshold value was found to be 25 at low initial superheat and to decrease with increasing superheat local thermodynamic equilibrium between crystals and liquid within the mush coupled the evolution of temperature composition and porosity convective motions locally caused dissolution and precipitation and hence fluctuations of porosity developed dissolution occurred preferentially in the central parts of upwellings and the upflow gradually focused being ultimately channelized into narrow chimneys devoid of crystals all else being equal the areal density of chimneys was greater the lower the viscosity chimney diameter increased with increasing solution viscosity in the liquid above the growing mush the convective plumes were very similar to salt fingers depending on solution viscosity and temperature gradient they exhibited a phenomenon of collective instability such that vertical motion was disrupted by wave instabilities the base plate temperature chosen was above the eutectic and hence the total amount of crystals at the end of experiments with the same initial composition and the same final temperature was a constant fixed by the phase diagram the spatial distribution of crystals and the final porosity of the mush were however determined by the strength of compositional convection as measured by the porous medium rayleigh number when no convection occurred mush thickness finally became equal to the initial layer thickness and the system was homogeneous when compositional convection occurred the overlying reservoir underwent chemical evolution and mush growth slowed dramatically in experiments with progressively lower solution viscosity and hence more vigorous convection final mush thickness was progressively less and final porosity lower final mush thickness was found to scale with solution viscosity to the power 0 33 during fractional crystallization of magma the effects of compositional convection can be recorded in the chemical and mineralogical features of cumulate rocks we speculate that fossil chimney structures can be found in the lower zone of the bushveld ultramafic complex in the form of iron rich platinum bearing dunite pipes this could explain the adcumulate nature of the lower zone rocks and the chemical and mineralogical similarities between the pipes and the overlying merensky reef the merensky reef would be interpreted as a hiatus in mush growth the results may also have applications to the flow structure in regions of partial melting and in the earth s core

opening mode fracture in siliceous mudstone at high homologous temperature effect of surface forces in analogy to high temperature sintering of ceramics and metal powder compacts the formation of opening mode fractures in siliceous mudstone during natural in situ combustion of hydrocarbons is attributed to contractile surface forces between mineral grains and an interstitial melt phase a comparison between bulk density increase during sintering and created fracture space indicates that fracturing resulted from contraction of the rock matrix due to porosity reduction grain scale mass transfer and high temperature mineral formation it is suggested that contractile surface forces between mineral grains and between mineral grains and pore fluid contribute to subcritical fracture formation under a wide range of subsurface conditions

internal solitary waves in the coastal mixing and optics 1996 experiment multimodal structure and resuspension 1 observations of internal solitary waves isws and of their role in sediment resuspension during the coastal mixing and optics 1996 cmo 96 experiment are reported the largest resuspension events observed in the experiment can be related to retarded flow under the wave footprint two distinctly different periods of resuspension events could be distinguished based on the prevailing atmospheric conditions a calm period which we consider characteristic of nominal conditions and an energetic period during which two major storms occurred isws arrived at the mooring site from a variety of sources though a common intermodal dynamics seemed to occur repeatedly both mode 1 and mode 2 isws have been observed the present analysis of the month long portion of the cmo 96 data set constitutes the first reported observations insofar as we are aware of mode 2 waves on the continental shelf both mode 1 and mode 2 isws were found to stimulate resuspension the mode 2 waves seem to be generated locally by resonant or topographic interactions with mode 1 isws internal wave fields of the type described here are expected to exist in a variety of other shallow seas as well

high frequency internal waves in large stratified lakes observations are presented from lake biwa and lake kinneret showing the ubiquitous and often periodic nature of high frequency internal waves in large stratified lakes in both lakes high frequency wave events were observed within two distinct categories 1 vertical mode 1 solitary waves near a steepened kelvin wave front and vertical mode 2 solitary waves at the head of an intrusive thermocline jet were found to have wavelengths 64 670 m and 13 65 m respectively and were observed to excite a spectral energy peak near 10 23 hz 2 sinusoidal vertical mode 1 waves on the crests of kelvin waves vertically coherent in both phase and frequency and bordering the thermocline jets in the high shear region trailing the vertical mode 2 solitary waves vertically incoherent in both phase and frequency were found to have wavelengths between 28 37 and 9 35 m respectively and excited a spectral energy peak just below the local maximum buoyancy frequency near 10 22 hz the waves in wave event categories 1 and 2 were reasonably described by nonlinear wave and linear stability models respectively analysis of the energetics of these waves suggests that the waves associated with shear instability will dissipate their energy rapidly within the lake interior and are thus responsible for patchy turbulent events that have been observed within the metalimnion conversely the finite amplitude solitary waves which each contain as much as 1 of the basinscale kelvin wave energy will propagate to the lake perimeter where they can shoal thus contributing to the maintenance of the benthic boundary layer

alternative water resources in granitic rock a case study from kinmen island taiwan kinmen island is a small tectonically stable granitic island that has been suffering from a scarcity of fresh water resources due to excessive annual evapotranspiration over annual precipitation recent studies further indicate that shallow 0 70 m sedimentary aquifers the major sources of groundwater supply have already been over exploited therefore this preliminary study is to investigate the existence of exploitable water resources that can balance the shortage of fresh water on this island site characterization data are obtained from island wide geophysical surveys as well as small scale tests performed in a study area formed by three deep maximum depth to 560 m vertical boreholes installed in mid east kinmen northeast to taiwu mountain vertical fracture frequency data indicate that the rock body is fractured with a spatially correlated pattern from which three major fracture zones depths 0 70 330 360 and below 450 m can be identified geologic investigations indicate that the deepest fracture zone is caused by the large scale steeply dipping taiwushan fault this fault may have caused a laterally extensive low resistivity zone a potential fractured aquifer near taiwu mountain the middle fracture zone is induced by the taiwushan fault and intersects the fault approximately 21 m southeast of the study area below a depth of 350 m slug testing results yield fracture transmissivity varying from 4 8 10 7 to 2 2 10 4 m2 s cross hole tests have confirmed that hydraulic connectivity of the deeper rock body is controlled by the taiwushan fault and the middle fracture zone this connectivity may extend vertically to the sedimentary aquifers through high angle joint sets despite the presence of a flow barrier formed by doleritic dike at about 300 m depth the existence of fresh as well as meteoric water in the deeper rock body manifests that certain flow paths must exist through which the deeper fractured aquifers can be connected to the upper rock body therefore groundwater stored within the taiwushan fault and the associated low resistivity zone can be considered as additional fresh water resources for future exploitation

contrasting stratified plutons exposed in tilt blocks eldorado mountains colorado river rift nv usa abstract roof to floor exposures of mid miocene plutons in tilt blocks south of las vegas nv reveal distinct but strongly contrasting magma chamber statigraphy the searchlight and aztec wash plutons are well exposed stratified intrusions that show a similar broad range in composition from 45 75 wt sio 2 homogeneous granites that comprise about one third of each intrusion are virtually identical in texture and elemental and isotopic chemistry mafic rocks that are present in both plutons document basaltic input into felsic magma chambers isotopic compositions suggest that mafic magmas were derived from enriched lithospheric mantle with minor crustal contamination whereas more felsic rocks are hybrids that are either juvenile basaltic magma crustal melt mixtures or products of anatexis of ancient crust young mesozoic or miocene mafic intraplate despite general similarities the two plutons differ markedly in dimensions and lithologic stratigraphy the searchlight pluton is much thicker 10 vs 3 km and has thick quartz monzonite zones at its roof and floor that are absent in the aztec wash pluton isotopic and elemental data from searchlight pluton suggest that the upper and lower zones are cogenetic with the granite we interpret the finer grained slightly more felsic upper zone to represent a downward migrating solidification front and the lower zone to be cumulate in contrast the upper part of the aztec wash pluton is granite and a heterogeneous mafic rich injection zone with distinct isotopic chemistry forms the lower two thirds of the intrusion similar mafic rocks are relatively sparse in searchlight pluton and do not appear to have played a central role in construction of the pluton large felsic and composite dikes that attest to repeated recharging and intrachamber magma transfer are common in the aztec wash pluton but absent in the searchlight pluton thus although both intrusions were filled by similar magmas and both developed internal stratification the two intrusions evolved very differently the distinctions may be attributable to scale and resulting longevity and or to subtle differences in tectonic setting

finite element modelling of shear zone development in viscoelastic materials and its implications for localisation of partial melting the development of shear zones initiating on random weaker initial perturbations is modelled numerically for low deborah number viscoelastic materials considering the influence of effective viscosity contrast power law rheology strain softening and different imposed bulk deformation geometries ranging from pure to simple shear conjugate shear zones initiate at 90 to one another and rotate with increasing bulk deformation the basic pattern not being markedly influenced by the vorticity of imposed deformation the rate of propagation of individual conjugate shear zones is little affected by increased effective viscosity contrast between matrix and inclusion but is promoted by power law rheology however the most marked effect is observed for strain softening behaviour where rapid propagation produces straighter and narrower shear zones the localisation of strain is reflected in a correspondingly heterogeneous stress distribution in particular mean stress or pressure is higher in the extending near planar weaker zones of localised shear melting of gneissic or pelitic compositions is pressure dependent with free water present increased pressure promotes melting whereas the opposite is true for water absent melting for water present conditions a positive feedback could develop between localised shearing increased pressure and partial melting this is potentially more effective in concentrating melt in shear zones than shear heating where melt related softening has a negative feedback effect

numerical investigation of solitary internal wave induced global instability in shallow water benthic boundary layers abstract the time dependent boundary layer induced by a weakly nonlinear solitary internal wave in shallow water is examined through direct numerical simulation waves of depression and elevation are both considered the mean density field corresponds to that typical of the coastal ocean and lakes where the lower fraction of the water column is subject to the stabilizing effect of a diffuse stratification sufficient resolution of the inviscid dynamics of the boundary layer is ensured through use of a legendre spectral multidomain discretization scheme in the vertical direction at higher reynolds numbers where the simulations become underresolved because of restrictions in available computational resources spectral accuracy and numerical stability at the scales of physical interest are preserved through use of a penalty scheme in the vertical and explicit spectral filtering thus a highly accurate description of the qualitative dynamics of the wave induced global instability is possible and finesca

elliptical fracture network modeling with validation in datong mine china roof coal recovery rate and the performance of gas extraction are essentially controlled by the fractures within coal rock mass thus it is important to generate the accurate fracture network ahead of mining face in this study ten boreholes located differently from the 8212 working face of tashan mine in datong coal mining group china were drilled with the help of borehole video instruments the location orientation of each fracture and the fracture number of different intersection type on each borehole wall were mapped with the advancing of mining face these data were analyzed using the matlab toolbox rjns3d and dips to determine structural homogeneity zone to find the number of fracture sets that exist in the coal rock mass volume density frequency for each set and the probability distributions of orientation fracture size in 3 d sampling biases associated with orientation spacing were corrected during the process the constructed fracture networks were validated by comparing the observed mean spacing along normal vector of mean orientation for each set and the predict value on similar scanlines

the sphene centered ocellar texture an effect of grain supported flow and melt migration in a hyperdense magma mush abstractthe sphene centered ocellar texture consists of leucocratic ocelli with sphene titanite crystals at the center enclosed in a biotite rich matrix this texture has been recognized worldwide in hybrid intermediate rocks on the basis of structural petrological and geochronological data from selected outcrops of the variscan ribadelago pluton nw iberian massif we propose that the ocelli were formed by migration and accumulation of a residual melt through a plagioclase and biotite dominated crystalline framework at the late stage of crystallization the magma acted as a hyperdense suspension and reacted to the pressure gradient caused by the regional stress field entering the domain of grain supported flow microstructures reveal that aligned crystal domains arose in the crystal framework from the shearing and compaction of the crystal mush and behaved as magmatic microshears relative displacement of adjacent crystal clusters along these microshears corresponded to the onset of reynolds di

rock structure characterization of a magnetite gneiss with foliation parallel discontinuities for footwall slope design abstract the warramboo magnetite iron ore deposit in south australia is predominantly hosted by gneiss design of the footwall slope requires an assessment of the role of foliation parallel discontinuities as planes of weakness parallel to the slope a review of published studies of joint spacing and joint persistence in gneiss shows spacing and persistence of foliation parallel discontinuities relative to non foliation parallel discontinuities varies greatly foliation parallel discontinuities form a spectrum between simply being one joint set in a blocky rock mass through to being a significant anisotropic weakness based on detailed analysis of the characteristics and frequency of foliation in drill core in the warramboo magnetite deposit it is inferred based on analysis of spacing that foliation parallel discontinuities are no more frequent or persistent than other joints therefore the rock mass is blocky rather than anisotropic and footwall slopes steeper than the foliation dip are viable

on the thermal viability of dikes leaving magma chambers dikes beginning to propagate away from a magma source are thin and grow slowly and thus are susceptible to freezing a self similar solution is obtained for a dike propagating down a temperature gradient when the wallrock and magma temperatures are equal at the chamber wall the solution applies only to the special case of a single component magma intruded at the solidus temperature but provides insight into the case in which the magma temperature is above the solidus the dike propagation velocity relative to that in the absence of freezing is determined by a single dimensionless parameter for sufficiently large magma freezing chokes the dike faster than propagation can elastically widen it and the dike cannot grow if the magma intrudes at a temperature above the solidus there is some value of above which the dike will propagate a certain distance and freeze and below which it will propagate until depletion of the source or three dimensional elastic effects promote freezing for reasonable parameters this process can explain why basaltic dikes are found far from obvious source regions while granitic dikes are scarce except in the immediate vicinity of granitic plutons even if a rhyolite is 5 orders of magnitude more viscous than a basalt however this distinction can be offset if the rhyolite has an excess source pressure only 1 order of magnitude greater than that of the basalt

sedimentation in large lakes processes associated with sedimentation in these lakes is in its infancy the large lakes of the world are precious resources that provide their nearby inhabitants with abundant fresh water food economical transpor tation and recreation they also provide additional benefits to the geologist unique paleoclimatic records and useful basins in which to test models of aquatic sedimentary processes this paper summarizes the global distribution oflarge lakes and focuses upon their geological attributes

effects of current bed form induced fluid flow on the thermal regime of sediments 1 heat transport associated with current bed form fluid exchange affects biogeochemical and ecological process in a variety of aquatic settings we simulate turbulent flow over dunes induced darcy flow in sediments and sediment heat transport forced by a diel variation of water column temperature heat conduction dominates when the water column current cannot induce rapid fluid exchange heat advection becomes important with increasing sediment permeability and or current velocity resulting in a complicated space time temperature pattern weak temperature variations are found beneath dune crests where water upwells out of the sediments strong variations are located below dune stoss faces where water downwells the relative dominance of heat conduction versus advection is captured by a global peclet number that depends on dune geometry and hydrodynamic and thermal properties including the period of thermal forcing thermally induced fluid viscosity variations cause periodic but nonsymmetric changes in fluid flux through the sediments but do not significantly influence temperature patterns

hyporheic exchange with heterogeneous streambeds laboratory experiments and modeling 1 hyporheic exchange is generally analyzed with the assumption of a homogeneous hyporheic zone in reality streambed sediments have a heterogeneous structure and this natural heterogeneity produces spatially variable interfacial fluxes and complex hyporheic exchange patterns to assess the basic effects of sediment structure on hyporheic exchange we performed salt and dye injection experiments in a recirculating laboratory flume with two heterogeneous sediment beds characterized by negative exponential correlated random hydraulic conductivity fields dye injections showed that the hyporheic flow structure was controlled by the spatial relationship of bed forms to high and low permeability regions of the streambed as no existing model could represent these effects we developed a new finite element model to calculate the pore water flow field resulting from the interaction of the bed form induced boundary head distribution and the heterogeneous sediment structure a numerical particle tracking approach was then used to assess the resulting hyporheic exchange the combined flow transport model did an excellent job of predicting the complex hyporheic flow pathways in the heterogeneous bed and the net hyporheic exchange up to t 30 hours the heterogeneous hydraulic conductivity field caused both greater spatial variability in the water flux through the bed surface and a greater average interfacial flux than would have occurred with a homogeneous bed the layered correlation structure of the streambed produced an effective anisotropy that favored longitudinal pore water flow and caused a relatively rapid decrease of the mean pore water velocity with depth as a result solute penetration into the bed was confined to a more shallow region than would have occurred with a homogeneous bed the combination of faster near surface transport and shallower solute penetration produced a shorter mean hyporheic residence time on the basis of the combination of experimental results and model simulations we conclude that the structural heterogeneity of streambed sediments produces more spatially limited hyporheic exchange that occurs with greater spatial variability and at a higher overall rate

mafic injections in situ hybridization and crystal accumulation in the pyramid peak granite california located in the northern sierra nevada the middle jurassic pyramid peak granite and associated dioritic rocks display superbly exposed interlayered sheets of mafic felsic and hybrid rocks the mafic hybrid layers show a consistent asymmetry sharply chilled on one side and gradational through hybrids to granite on the other and dip to the southwest load casts and silicic pipes along the chilled mafic northeastern margins of the sheets indicate that depositional way up is to the southwest and that the adjacent mount tallac roof pendant was the original floor of the intrusion orientations of the pipes indicate that the layers were tilted after deposition and solidification we interpret the sheets to be intramagmatic flows that formed by injections of mafic magma into a silicic magma chamber followed by flow across the crystal rich base of that chamber the granitic and hybrid rocks interlayered with the mafic sheets represent material that accumulated on the chamber floor between episodes of mafic replenishment most contamination of the mafic sheets probably occurred because of flow front instabilities generated as the mafic magma entered and spread across the chamber floor the upward gradation from diorite to granite with decreasing abundance and size of mafic enclaves can best be explained by convective stirring at the upper boundaries of the dioritic replenishments the pyramid peak granite was probably initiated as a thin concordant sheet intruding into gently dipping jurassic supracrustal rocks the pluton was constructed incrementally with many replenishments of felsic and mafic magma and dominantly solidified by accumulation of crystals on the floor of the chamber the present steep dips of the layers suggest that downward warping of the chamber floor may have been a factor in accommodating the incrementally constructed pluton

a review of criteria for the identification of magmatic and tectonic foliations in granitoids abstract foliations in granitoids can form by magmatic flow submagmatic flow high temperature solid state deformation and moderate to low temperature solid state deformation a review of previous work suggests that no single criterion can consistently distinguish foliations in granitoids formed by flow during ascent diapiric emplacement and expansion emplacement during regional deformation or regional deformation post dating emplacement however a magmatic origin is favoured for foliations defined by the alignment of igneous commonly euhedral minerals particularly where the foliation is parallel to internal or external pluton contacts foliations formed during expansion or ballooning of diapirs may be strictly magmatic in origin although some studies suggest that solid state deformation also may occur if so we would hope to find evidence of deformation of crystal melt systems and that the solid state deformation occurred at high temperatures the inference of syntectonic foliations is most convincing where magmatic and high temperature solid state foliations are subparallel these foliations are continuous with regionally developed foliations in the wall rocks synkinematic porphyroblasts are present in the wallrocks and igneous minerals have the same age as metamorphic minerals associated with the regional cleavage a strictly tectonic origin for foliations in granitoids is favoured when the foliation is defined by metamorphic minerals no alignment of igneous minerals occurs the foliation is locally at high angles to pluton wallrock contacts and the foliation is continuous with a regionally developed cleavage

stochastic fracture geometry modeling in 3 d including validations for a part of arrowhead east tunnel california usa abstract eight hundred and fifty nine fractures of a gneissic rock mass were mapped using 16 scanlines placed on steep rock exposures that were within 300 m of a tunnel alignment before the tunnel excavation these data were analyzed using the software package fracntwk to find the number of fracture sets that exist in the rock mass 3 d fracture frequency for each set and the probability distributions of orientation trace length fracture size in three dimensions 3 d and spacing for each of the fracture sets in obtaining these distributions corrections were applied for sampling biases associated with orientation trace length size and spacing developed stochastic 3 d fracture network for the rock mass was validated by comparing statistical properties of observed fracture traces on the scanlines with the predicted fracture traces on similar scanlines the one dimensional 1 d fracture frequency of the rock mass in all directions in 3 d was calculated and is presented in terms of a stereographic plot the 1 d fracture frequency along the tunnel alignment direction was predicted to be about 6 5 fractures m before the tunnel excavation this prediction was found to be in excellent agreement with the observed values obtained about 1 year later during the tunnel excavation this was another validation conducted for the developed 3 d fracture network

submagmatic microfractures in granites microstructures in hercynian granite plutons of the pyrenees indicate fracturing of plagioclase crystals in the presence of melt this is represented mainly by quartz and or feldspar that fills fractures electron microprobe analyses demonstrate that in compositional agreement with the rims of the zoned plagioclase the feldspar infillings are more sodic with decreasing melt fraction fracturing resulted from concentration of stress at contacts between grains while the granite was submagmatic i e when the melt was below the critical fraction for magmatic flow material compositionally far from eutectic is petrologically the best candictate to develop submagmatic fractures because during cooling the volume fraction of melt remains low for a large temperature range a strong tendency for microfractures to be oblique to flow foliation may constitute a new criterion for shear sense in magmas

vortex shedding and sediment resuspension associated with the interaction of an internal solitary wave and the bottom boundary layer 1 in this note we present results on the interaction of fully nonlinear internal solitary waves with the oceanic bottom boundary layer we show that for fully nonlinear solitary waves it is the interaction of the wave induced velocity field with the upstream boundary layer vorticity that leads to a vortex shedding instability beneath the wave the vortex shedding provides an efficient mechanism for transporting sediment out of the bottom boundary layer bottom boundary stress profiles suggest that the vortex shedding can lead to the resuspension of sediment in contrast to past studies we find that neither a separation bubble or a wave with a recirculating region are required for vortex shedding to occur