3d numerical simulation of turbulence and sediment transport within a tidal inlet abstract turbulence and sediment transport models are incorporated into a three dimensional hydrodynamics model to investigate the mechanisms of morphologic evolution of scour holes within the indian river inlet delaware usa the inlet bed had eroded slightly since stabilizing the channel walls in late 1930s through 1976 the mean rate of bed erosion roughly doubled as a response to anthropogenic activities within the inlet such as the removal of 80 piles remaining from an old bridge severe erosion near the in water bridge supports and cofferdams for the replacement bridge necessitated channel bed stabilization that along with the remained debris from the removal of old bridge piles enhanced the growth of two deep scour holes on the bayside and oceanside of the bridge cofferdams scour hole and channel bed evolution has decreased drastically since 1994 the present investigation suggests that initially flow concentration through the cofferdams of the replacement bridge was the main reason for scour hole development bed shear stress over the forward facing slope of the scour hole entrains sediment from the bed and extends the scour hole along the inlet and in the vertical direction flow separation within the developed scour holes after channel bed stabilization enhances turbulence and appears to be the dominant mechanism for further scour hole development

an analytical model of hanging wall and footwall deformation at ramps on normal and thrust faults abstract we determine stress strain and structural evolution for an analytical model of moderate angle 10 20 ramps developed on both normal faults normal ramps and thrust faults thrust ramps in the model a frictionless sliding surface with ramp configuration separates two incompressible isotropic viscous half spaces of different viscosity hanging wall and footwall ramps are planar but ramp flat corners are locally rounded deformation is due solely to translation across the ramp and regional extension or shortening is ignored sliding down a normal ramp causes vertical extension and horizontal shortening in both the hanging wall and the footwall this conforms with reverse faults seen in experimental models of normal ramps the stress in the footwall has the same magnitude as that in the hanging wall but the footwall strain rate is reduced in magnitude by the ratio both a hanging wall syncline and a footwall anticline form the normal ramp migrates in front of the rising footwall at a rate v ss v where v is the sliding velocity but the ramp does not change shape the continuous ramp motion in the model may correspond to the creation of an extensional duplex or chaos zone in brittle rocks at a normal ramp mean compressive stress is lowered and deviatoric stress is raised favoring local faulting and fracture sliding up a thrust ramp causes stresses strain rates and strains of the opposite sign horizontal extension and vertical shortening in both walls is consistent with normal faulting both a hanging wall anticline and a footwall syncline form passively although the deviatoric stress is raised at the ramp so is the mean compressive stress inhibiting fracturing however the mean compressive stress is lowered on the adjacent flats favoring fracturing there

thrust fracture network and hydrothermal gold mineralization witwatersrand basin south africa abstract this paper examines the geometry and genesis of a mineralized thrust related fracture system developed at a major rheological interface between witwatersrand sediments and ventersdorp volcanics in the witwatersrand basin of south africa at the elandsrand gold mine the conglomeratic ventersdorp contact reef which separates these successions is imbricated by kilometre wide zones of minor thrusts containing ultracataclastic fault rocks associated with hydrothermal fluid flow several sets of fractures are intimately associated with the imbricates which link to underlying kilometre scale thrusts the fractures provided a linked fluid flow pathway and structural sites for precipitation of gold within the ventersdorp contact reef carrying 900f observed gold with the remaining 100ccupying post diagenetic matrix corrosion spaces within a few 100 m of fractures the relatively rigid volcanics deformed into low amplitude kilometre wavelength flexures centred on the imbricate zones and underlying kilometre scale thrusts these major structures controlled the thrust fracture system formation along the ventersdorp contact reef lava contact three progressive stages of structural evolution were identified 1 layer parallel shear across the contact with stratigraphy focused shallow fracture formation 2 propagation of a kilometre scale thrust towards the contact leading to kilometre scale flexure of the volcanics with layer parallel shearing in the limbs producing steep fractures and minor thrusts 3 propagation of the major thrust along the contact imbricating the sediments with shallow fracture formation in ramps

geometric analysis of fold development in overthrust terranes abstract fault bend folding fault propagation folding and detachment or decollement folding are three distinct scenarios for fold thrust interaction in overthrust terranes simple kink hinge models are used to determine the geometric associations implicit in each scenario bedding maintains constant thickness in the models except in the forelimb of the fold the forelimb is allowed to thicken or thin without limit the models address individual folds and the calculated fold geometries are balanced structures each mode of fold thrust interaction has a distinct set of geometric relationships final fold geometry is adequate in itself to discern many fault bend folds this is not the case for fault propagation and detachment folds these two fold forms have very similar geometric relationships some knowledge of the nature of the underlying thrust or decollement zone is usually needed to distinguish between them the geometry of a fold is altered in a predictable fashion by transport through an upper ramp hinge and by fault parallel shearing of the structure the shearing results in a tighter fold whereas transport through the ramp hinge produces a broader fold the viability of the geometric analysis technique is demonstrated through its application to a pair of detachment folds from the canadian cordillera the geometric analysis is also used to evaluate cross sections through subsurface structures in an example from the turner valley oil field the analysis indicates how the interpretation should be altered so as to balance the cross section the analysis reveals hidden assumptions and specific inconsistencies in structural interpretations

reply to discussion the timing of gold mineralization across the eastern yilgarn craton using u pb geochronology of hydrothermal phosphate minerals

distinguishing between local versus regional extension as a control on orogenic gold mineralisation the new 2 4moz castle hill camp wa abstract the significance of regional extension for orogenic gold mineralisation in the archaean eastern goldfields of western australia is not well established and there is a lack of consensus on both the timing and nature of extensional deformation the 2 4 moz castle hill gold camp located in the coolgardie domain is spatially associated with a nw se trending granitic pluton the kintore tonalite this pluton intruded prior to the gold mineralisation and is coeval with emplacement of the lower succession of the kalgoorlie greenstone sequence the kintore tonalite is located at a major change in the geometry of the kunanalling shear zone where the strike of the shear zone changes from the regional nw se trend to n s this change in the geometry of the kunanalling shear zone is interpreted to highlight the presence of an early transfer fault intersecting the kunanalling shear zone or step over zone on the kunanalling shear zone that was active at the time of greenstone emplacement this early architecture created a crustal scale pathway that facilitated the sourcing and emplacement of the tonalitic magma and also later gold bearing fluids from lower crustal levels three main deformation events that reactivated this early architecture have been delineated d1 d3 d1 is associated with ne sw directed compression reactivating nw trending shear zones and lithological boundaries causing reverse shearing folding and development of a pervasive foliation d2 is synchronous with the main gold event which occurred during nw se directed far field compression causing sinistral shearing on nw trending structures the development of n s striking faults the formation of mineralised quartz veins associated and vertical axis rotation of the kintore tonalite during the d2 stage gold was deposited with tellurobismuthite assemblages over the castle hill region associated with synchronous extensional and contractional features at the southern and northern ends of the kintore tonalite respectively d2 extensional structures related to mineralisation are local features linked to development of sinistral movement on the n s striking faults d3 is associated with ne sw directed compression and the development of n to ne trending dextral faults dominated by brittle deformation the primary control on the regional location of the gold system is interpreted to be early pre existing crustal architecture marked by the major strike change that hosts the tonalite the geometry of structures developed within the step over zone exerts a second order control on the location of deposits within the castle hill camp and fluids were focussed into areas of enhanced permeability during deformation individual deposits in the camp are hosted in mineralised structures that locally exhibit extensional kinematics but developed in an overall compressional regime

on the genesis and evolution of barchan dunes morphodynamics barchan dunes are crescent shaped formations of sand that can dominate both desert and subaqueous landscapes when the supply of sand is scarce because of the complexity and scale of the underlying phenomena the mechanisms governing the entire process from the genesis to the long term evolution of barchan fields still remain to be better understood herein we attempt to present a description of this process in a subaqueous environment by employing a large eddy simulation approach that couples turbulent flow and sand bed morphodynamics we show that the seeds of the emergent structure in barchan fields are random turbulent flow motions near the initially flat bed we also provide high resolution insights into phenomena such as barchan migration and merging and show how transverse sand waves are formed and migrate over the barchan horns furthermore the transverse sand waves over the barchan horns are shown to be the seeds of the newly born barchans at the end points of the two horns of a barchan through the process known as calving to show this we examine the celerity wavelength and amplitude of the transverse sand waves over the barchan as they approach the end of its horn the celerity and wavelength of these transverse sand waves are shown to be the defining factors in determining the frequency of the calving process the amplitude of the newly born barchans through calving is also shown to be associated with the amplitude of the transverse waves near the end of the horn the simulation data also show that the wavelength of the newly born barchans the distance between individual dunes is closely related to that of the transverse sand waves over their maternal barchan finally we use the simulation results to discuss past conclusions derived from theory conventional models and field observations

migration of fluid phases and genesis of basalt magmas in subduction zones dehydration and hydration reactions in both the downgoing lithosphere and the overlying mantle wedge have been examined in order to understand the role of h2o in the production of magmas at convergent plate boundaries the subduction of oceanic lithosphere occurring with increasing pressures and rising temperatures causes liberation of h2o from the slab amphibole which can be stable to the highest pt conditions among hydrous phases in the slab decomposes at around 90 km depth it follows that the subducted lithosphere is essentially anhydrous beneath volcanic arcs lying more than 110 km above the slab and that the supply of slab derived h2o is not a direct trigger for the production of arc magmas instead the h2o released from downgoing lithosphere reacts with the forearc mantle wedge to crystallize hydrous minerals serpentine talc amphibole chlorite and phlogopite this hydrated peridotite is dragged downward on the slab toward higher pt regions and releases h2o to shallower potential magma source regions in the mantle wedge combining experimental data on the stability of serpentine and talc with the thermal structure in the mantle wedge it is concluded that those minerals decompose beneath the forearc region on the other hand high pt experimental and thermodynamic data suggest that dehydration of amphibole and chlorite in the downdragged hydrated peridotite can take place just beneath a volcanic front phlogopite in the peridotite decomposes to release h2o at a deeper level about 200 km h2o liberated from the hydrated peridotite causes partial melting of overlying mantle wedge peridotites along with the migration of h2o through the above processes subduction components especially large ion lithophile elements can be overprinted on the magma source region which governs the geochemical characteristics of arc magmas

origin of high magnesian andesites in the setouchi volcanic belt southwest japan ii melting phase relations at high pressures melting phase relations of an augite olivine high magnesian andesite and an augite olivine basalt from the miocene setouchi volcanic belt in southwest japan have been studied under water saturated water undersaturated and under anhydrous conditions both the andesite and the basalt are characterized by low feo mgo ratios 0 86 and 0 76 in weight respectively and qualify as primary magmas derived from the upper mantle the andesite melt coexists with olivine orthopyroxene and clinopyroxene at 15 kbar and 1030 c under water saturated conditions and at 10 kbar and 1070 c under water undersaturated conditions 7 wt h2o in the melt the basalt melt also coexists with the above three phases at 11 kbar and 1305 c under anhydrous conditions and at 15 kbar and 1205 c in the presence of 4 wt water present studies indicate that high magnesian andesite magmas may be produced even under water undersaturated conditions by partial melting of mantle peridotite it is suggested that two types of high magnesian andesites in the setouchi volcanic belt augite olivine and bronzite olivine andesites were produced by different degrees of partial melting augite olivine andesite magmas whose mantle residual is lherzolite were formed by lower degrees of partial melting than bronzite olivine andesite magmas which coexist with harzburgite the basalt magmas which were often extruded in close proximity to the high magnesian andesite magmas are not partial melting products of a mantle peridotite which had previously melted to yield high magnesian andesite magmas

numerical modeling of bed deformation in laboratory channels a depth average model using a finite volume method with boundary fitted grids has been developed to calculate bed deformation in alluvial channels the model system consists of an unsteady hydrodynamic module a sediment transport module and a bed deformation module the hydrodynamic module is based on the two dimensional shallow water equations the sediment transport module is comprised of semiempirical models of suspended load and nonequilibrium bedload the bed deformation module is based on the mass balance for sediment the secondary flow transport effects are taken into account by adjusting the dimensionless diffusivity coefficient in the depth average version of the k e turbulence model a quasi three dimensional flow approach is used to simulate the effect of secondary flows due to channel curvature on bed load transport the effects of bed slope on the rate and direction of bed load transport are also taken into account the developed model has been validated by computing the scour hole and the

geodynamic setting of volcano plutonic rocks in so called paleo accretionary prisms fore arc activity or post collisional magmatism the shimanto belt as a case study abstract the cretaceous tertiary shimanto belt of southwestern japan is usually considered to be a simple accretionary prism taira et al 1982 ogawa 1985 whereas based on structural and sedimentological evidences charvet and fabbri 1987 and charvet et al 1990 proposed an alternative model in which a collision with an unknown microblock followed the formation of the accretionary prism and induced the early miocene main tectonism one characteristic of the shimanto belt is the occurrence of well developed magmatic bodies of middle miocene age 14 1 ma which can be used for testing the model they show numerous peculiarities 1 they consist predominantly of acidic volcano plutonic complexes mafic sills or lavas are present in a lesser amount 2 with respect to the supposed position of the subduction trench during miocene time and to the northern location of the setouchi volcanics considered as a volcanic front ca 13 ma this magmatism is a near trench magmatism 3 various tectono magmatic affinities are present the basaltic sills or lavas have mostly t to e morb type affinities an alkaline complex is present at ashizuri cape the most abundant magmatism consists of calc alkaline volcano plutonic bodies typically peraluminous in the southern part of shimanto and metaluminous near the northern border of the belt 4 metamorphic enclaves inter alia are often included in the calc alkaline complexes their highest p t conditions range between 0 7 0 8 gpa and 630 860 c a simple subduction model is not able to explain all these features the first necessity is to find a mechanism which develops a high thermal anomaly allowing the formation of magmas close to the trench according to thermal modelling the subduction of an oceanic plate even young does not provide enough heat secondly in well known mature accretionary prisms e g the barbados one the thickest part of the complex does not exceed 15 km in such conditions it is difficult to obtain pressures ranging from 0 7 to 0 8 gpa this is much more difficult if we consider that some granitic rocks were formed in the youngest part of the so called prism in the thinnest portion finally a simple subduction model does not explain the various magmatic affinities geochemical data show that the magmatic source of the ashizuri alkaline complex is likely to be an enriched mantle comparable to oib sources on the other hand the calc alkaline rocks may have been derived by mixing between mantellic components and crustal ones or in some cases by pure anatectic processes the upwelling of a hot asthenospheric mantle from which the ashizuri suite could have been derived may represent a heating source strong enough to make crustal materials melt the proposed collision model could explain 1 the heating source 2 the various magmatic affinities and also 3 the 0 7 0 8 gpa pressure invoking crustal thickening induced by the collisional event

archaean gold mineralisation in a normal motion shear zone at harbour lights leonora western australia although many archaean greenstone hosted mesothermal gold deposits are in steep reverse motion fault zones other fault geometries are prospective for mineralization harbour lights is one of a number of deposits at leonora hosted in a normal motion shear zone probably related to movement off the adjacent domal granitoid the deposit is also atypical in that mineralization predates the last deformation to affect the mine sequence but formed by similar processes to other mesothermal deposits in all respects other than the detail of shear zone geometry kinematics and timing

clear water scour around abutments in floodplains clear water scour around a bridge abutment in the floodplain of a compound channel was investigated experiments were conducted in a flume with a fixed bed main channel and a movable bed floodplain in which the abutment terminated flow depth discharge compound channel geometry and abutment length were varied and measurements of approach velocity distribution and scour depth were obtained a preliminary relationship for the dimensionless scour depth is suggested to illustrate the compound channel effects on scour the proposed relationship is limited to the range of values covered by the variables in this study

near real time scour monitoring system application to indian river inlet delaware scour hole monitoring is widely used by engineers in reaction to bridge scour current monitoring methods lack the ability to observe wide areas on operational time scales it is imperative that wide areas be observed after channel bed armoring countermeasures are taken because the armoring occupies an area larger than can be observed by traditional single point scour monitors the present bridge piers within the indian river inlet delaware are adjacent to deep scour holes that threaten the bridge a new scour monitoring system sm using two three dimensional profiling sonars was installed on the indian river inlet bridge to observe more than 19 000 m2 of bathymetry daily the system components configuration and operation are described and example data are presented bathymetric data collected by the sm compare favorably with historic high quality multibeam data from the u s army corps of engineers quantitative correlations with temporally consistent data from a single beam personal watercraft sur

the timing of gold mineralization across the eastern yilgarn craton using u pb geochronology of hydrothermal phosphate minerals the highly mineralized eastern goldfields of the eastern yilgarn craton is an amalgamation of dominantly neoarchaean granitoid greenstone terranes and domains that record a history of early rifting followed by westward directed collision with initial arc formation collision and clastic basin formation and final accretion to the western yilgarn proto craton between 2 66 and 2 60 billion years ago the gold deposits that define this region as a world class gold province are the product of orogenic processes that operated during accretion late in the tectonic history after initial compressional deformation d1 d2 and the majority of granitoid magmatism minor gold was also deposited throughout the entire tectonic history in magmatic hydrothermal related systems however such mineralization mostly 0 3 g t gold is nowhere economic unless it overprints or is overprinted by much higher grade orogenic gold lodes robust shrimp u pb geochronology of gold related hydrothermal xenotime and monazite supports structural studies that gold mineralization occurred during late transpressional events d3 d4 shortly before cratonization however westward migration of collision and accretion produced a complementary diachroneity in the timing of gold mineralization of 5 to 20 m y between c 2 65 ma in the east including laverton district kurnalpi terrane to c 2 63 ma in the west including kalgoorlie terrane across the eastern part of the craton the robust geochronology refutes previous suggestions that significant gold mineralization events extended from de to d4 in the evolution of the orogen and that the kalgoorlie gold deposits formed over a period of 45 m y the crustal continuum model is applicable within terranes where orogenic gold depositional events were penecontemporaneous but must be modified to account for diachroneity of orogenic events and gold mineralization across the eastern goldfields

three dimensional numerical model for flow and bed deformation around river hydraulic structures this paper describes a numerical model developed to simulate flow and bed deformation around river hydraulic structures the model solved the fully three dimensional reynolds averaged navier stokes equation expressed in a moving boundary fitted coordinate system to calculate the flow field with water and bed surfaces varying in time a nonlinear k e turbulence model was employed in order to predict flow near the structure where three dimensional flow is dominant the temporal change in bed topography was calculated by coupling a stochastic model for sediment pickup and deposition using a momentum equation of sediment particles in order to account for the effect of nonequilibrium sediment transport in validating the numerical model a spur dike and a bridge pier which are considered to be typical river engineering structures were selected by comparing the numerical results with observed laboratory experimental data the model was found to reproduce flow and scour geometry around these structures with

integrated model for meguma group lode gold deposits nova scotia canada meguma group lode gold deposits represent concentrations of a variety of auriferous quartz veins in lower paleozoic metaturbidites of the meguma terrane of southern nova scotia our studies incorporating extensive field regional and detailed mapping and laboratory petrography fluid inclusions geochemistry isotopes studies of 30 of these deposits in the eastern meguma terrane suggest that mineralization occurred at ca 370 ma 40 ar 39 ar dating of hydrothermal vein minerals during widespread incursion of mafic and felsic magmatism into the crust concurrent with subvertical shear zone development thus postdating regional acadian deformation by some 30 40 m y isotopic data s c o sr indicate that vein forming fluids were not solely magmatic and were in part exotic to the meguma group thus earlier magmatic and metamorphogenic lateral secretion models that considered either late stage magmatic fluids or the enveloping meguma group metasedimentary rocks as the sole source of vein components are invalidated

three dimensional simulation of scour inducing flow at bridge piers presently available formulas for estimating the maximum depth of scour near bridge piers often lead to unreliable results a fully three dimensional hydrodynamic model is therefore used in this study to simulate the flow occurring at the base of a cylindrical bridge pier within a scour hole the results of the numerical simulation are compared with laboratory observations by melville and raudkivi 1977 quantitative and qualitative agreement between the studies is quite good discrepancies between the results of the two studies are of an order that may be attributed to choices in numerical model parameters the simulations may be supplemented by lagrangian particle tracking to estimate the depth of the equilibrium scour condition

oxygen isotopic constraints on the geneses of the miocene outer zone granitoids in japan abstract miocene ilmenite series granitoids of the outer zone of southwest japan have been classified mineralogically into the southern s type and the northern i type oxygen isotopic ratios 18 o smow were determined on 45 representative samples from 17 granitic plutons the results indicate that the outer zone granitoids have much higher 18 o values than magnetite series granitoids of similar ages confirming a contribution from crustal sediments to the genesis of the ilmenite series granitoids and that s type granitoids are higher than i type with separation at 10 5 which is slightly higher than the 9 7 boundary in the lachlan fold belt of australia assuming the granitoids originated from mixtures of basaltic magmas from the upper mantle and sedimentary rocks of the accretionary complex from the fore arc basin mixing ratios were calculated the s type granitoids have sedimentary contributions of 64 45 wt with one exception while i type granitoids have that of 43 30 wt two trends are typically observed in the 18 o sio 2 diagram i granitoids having large variation in 18 o values but little variation in sio2 contents and ii vice versa the former granitoids solidified from heterogeneous magmas containing restite fragments but the latter crystallized from a completely homogenized magma with magmatic fractionation this type is associated with mineralization

asthenospheric injection and back arc opening isotopic evidence from northeast japan nd and sr isotopic compositions were determined for the tertiary volcanics from the back arc side of the ne japan arc sr isotopes show a linear trend through time from an enriched signature 87sr86sr 0 705437 to a depleted signature 87sr86sr 0 70270 in a complementary fashion nd isotopes start at low value nd 0 80 and show a gradual increase nd 8 3 with decreasing age isotopic change of nd and sr from the enriched signature to the depleted one is synchronous with the opening of the japan sea at 15 ma this synchronism indicates that the opening of the japan sea was initiated by the injection of the asthenosphere during the pre opening stage the mantle wedge was composed of a two layered structure the sub continental lithosphere and the underlying asthenosphere the volcanics of this stage characterized by an enriched isotopic signature were derived from a source with a higher proportion of sub continental lithosphere the sub continental lithosphere of the back arc side was thinned by the injection of the depleted asthenosphere which accelerated the growth of the morb source within the mantle wedge of the back arc side and resulted in magma generation with the depleted isotopic signature of nd and sr at the post opening stage

nonburied riprap mattress sizing for single piers in the presence of bedforms abstractthe present study focuses on riprap protection at single piers under live bed conditions the riprap mattress is displayed so that its top is leveled with the surrounding river bed for ease in the construction process over 48 laboratory experiments have been carried out to understand the trend of the required riprap mattress width to protect single piers against edge and bedform undermining failures the influence of bedform height on the required width is emphasized a simple expression is given to calculate the required riprap mattress width for low sediment transport rates the expressions given in the literature for clear water conditions are recovered

effects of stress in the evolution of large silicic magmatic systems an example from the miocene felsic volcanic field at kii peninsula sw honshu japan abstract miocene felsic volcanic field at the kii peninsula mfvk in southwest japan allows us to reveal temporal and spatial change of a large felsic volcanic system in response to changes in the local and regional stress field the mfvk was active episodically ejecting more than a few hundred cubic kilometers of magma in a span of hundred thousand to million years remnant of this large scale volcanism is characterized by a broad area of deeply incised and complex cluster of collapse calderas in the kii peninsula major conduits for ash flow tuff eruptions lie on the margins of the mfvk paleostress orientation of the hmax was inferred from lithologic distribution and structure in rocks in the mfvk the optimal tectonic stress orientation at the time of the mfvk formation was nne ssw to the present azimuth approximately 1500 km 3 of magma were erupted from the mfvk during a duration of 0 1 million to 1 6 myr this suggests an area normalized eruption rate of 10 2 to 10 3 km 3 ka km 2 this long term eruption rate of the mfvk is at the high end of rates for other large felsic volcanic fields lfvfs and ranks as one of the larger rates of lfvf worldwide the large eruption rate of the mfvk and the formation of a large magma chamber is discussed in relation to tectonic stress although a compressional stress field favors the formation of a sill like large magma chamber a larger magma supply rate is more essential we believe that a large rate of magma supply in combination with local and regional stress conditions in the early development of the mfvk promoted magma accumulation over eruption leading to the development of a large silicic magma chamber we suggest that such a large magma chamber can generate excess pressure inside the chamber itself that results in a local tumescence and counteracts the tectonic compressional stress field allowing magma to reach the surface this scenario is the most plausible explanation for the large eruption rates of caldera volcanoes under a compressional stress field the case of the mfvk is similar to the toba caldera indonesia which lies adjacent the geologic suture zone of wrench faults the sumatra faults

timing of rotational motion of southwest japan inferred from paleomagnetism abstract paleomagnetic field directions for the period younger than 35 ma are obtained from igneous rocks distributed in the san in district inner zone of southwest japan the remanent magnetization of samples between 30 and 35 ma old are fairly well grouped with a mean direction of d 65 9 i 48 6 and 95 6 5 this result establishes that southwest japan rotated clockwise 56 12 during the past 30 m y a declination value of about 60 is observed in the rocks of 28 ma d 52 2 i 33 5 and 21 ma d 69 9 i 49 5 comparing this with results from dacitic rocks with an age of 15 ma in other areas of southwest japan suggests that rotational motion did not occur possibly until 15 ma these results require that the rotation of southwest japan occurred just after the shikoku basin had been created

structural geology across a proposed archaean terrane boundary in the eastern yilgarn craton western australia abstract the eastern goldfields province of the archaean yilgarn craton western australia can be divided into several nw se trending terranes with different stratigraphic signature at least two main phases of penetrative ductile deformation affect the terranes d1 is a phase of nappe type transport mainly to the north along gently dipping ductile shear zones it is interpreted as a phase of regional extension contemporaneous with intrusion of massive granitoid plutons and possibly contemporaneous with deposition of felsic volcanics and metasediments in the greenstone belts terrane boundaries were probably formed during d1 d2 gave rise to steep nw se to n s trending foliations and upright folds d2 is strongly partitioned over the area for strain and vorticity the pattern of partitioning seems to be dependent on the position of granitoid plutons which give rise to development of d2 strain shadows d1 structures have been preserved mainly in these strain shadows terrane boundaries are transected by boundaries of d2 structural domains minor intrusion of granitoids continued during and after d2 d1 is possibly associated with arrival of a mantle plume below the yilgarn craton and d2 may be a phase of regional shortening in a thinned lithosphere weakened by the thermal event

the granny smith gold deposit the role of heterogeneous stress distribution at an irregular granitoid contact in a greenschist facies terrane the granny smith gold deposits formed late in the structural history of the yilgarn block at a high crustal level in a largely brittle structural regime gold mineralisation is located along a n s striking fault which wraps around the contact of a small granitoid intrusion in different sections of the fault mineralisation may be developed in the granitoid in the adjacent sedimentary sequence and or along the contact between them in the granitoid gold mineralisation is in conjugate networks of thin carbonate quartz veins and their alteration halos small displacements along veins are common in contrast veins and faults in the sedimentary rocks are subparallel to bedding spatial variations in the conjugate vein orientations indicate that the local stress field was heterogeneous and controlled by the shape of the granitoid contact the greatest variations in vein and implied stress orientations occur in zones where the contact is most irregular these are also the areas of richest mineralisation fluid flow was thus focused in a regional scale low mean stress region created by the geometry of the granitoid intrusion its irregular contact caused deposit scale variations in fluid flow and resulted in heterogeneous gold grades along the contact zone

modeling of riverbed evolution for bedload sediment mixtures a new computational methodology for fully coupled simulation of unsteady water and sediment movement in mobile bed alluvial rivers has been developed and tested the one dimensional approach treats bedload transport of nonuniform sediment mixtures with sorting and armoring effects considered spatial lag effects in nonequilibrium bedload transport are taken into account through innovative use of the recently developed notion of a loading law the new system of equations for water and sediment movement is solved in a fully coupled implicit manner using the preissmann finite difference scheme implemented to allow for either upstream or downstream induced mobile bed perturbations formal analysis of the coupled system sheds new light on boundary condition requirements for the multiple size class problem the fully coupled implicit solution has proven to be robust and stable and it respects the underlying volumetric conservation laws remarkably well as demonstrated in continuity analyses of computed bed e

the invincible deposit early gold mineralisation truncated by unaltered c 2665 ma conglomerate st ives eastern goldfields western australia abstract two distinct styles of mineralisation are recognised at the invincible deposit with bedding parallel shear related gold mineralisation type 1 and shallow dipping mineralised extension veins type 2 the different styles of mineralisation reflect formation during two discrete deformation events type 1 mineralisation is hosted in laminated mudstone of the upper black flag group and mineralised quartz veins and breccia zones are distributed throughout the mudstone rather than being associated with a single shear mineralised zones are associated with intense sodic alteration the early mineralised structures are strongly modified by east west horizontal d2 3 compression in contrast type 2 extension veins are undeformed and are best developed in the massive sandstone conglomerate footwall but also overprint type 1 veins in the mudstone unit throughout the mine the early type 1 mineralisation is truncated by unaltered conglomerate of the c 2665 ma merougil formation a 10 20 difference in strike dip is commonly present and indicates that the main mineralising event at invincible occurred prior to erosion and deposition of the merougil formation the strong modification of the mineralisation by horizontal east west d2 3 compression is also consistent with formation early in the deformation history during the c 2672 2660 ma d1 event gold deposition in the egt was episodic occurring over a prolonged period during extension and compression bedding vein relationships indicate southwest side down kinematics during the early mineralising event in weakly mineralised zones sub vertical extension veins cut across beds that dip 70 to the southwest in strongly mineralised zones bedding is sub vertical and large quartz breccia veins develop along the bedding above moderately west dipping shears that extend across the steep bedding the location of the steep strongly mineralised zones where bedding is sub vertical reflects enhanced dilation in these zones during southwest side down movement southwest side down movement could represent extensional slip on the laminated mudstone beds if the bedding was tilted into a developing basin early merougil basin the location of the invincible system at the eastern edge of the merougil basin likely reflects an association with early basin controlling faults

deformation mechanisms in the southeastern ramp region of the pine mountain block tennessee a field and petrofabric study of the southwestern part of the pine mountain thrust sheet shows that most deformation features may be attributed to one of two processes the first layer parallel compression is responsible for a a layer parallel maximum shortening direction in the mechanically twinned fabric of the limestone and dolomite country rock b transport parallel extension fractures and joints c transport normal stylolite surfaces and d some small thrusts the second bending at thrust ramp hinges is responsible for a non bedding parallel maximum shortening directions in mechanically twinned calcite from fracture fillings b transport normal extension fractures and joints and c small normal faults possible explanations for the failure of calcite in the country rock to twin in response to bending at the ramp include both 1 an early imposed pre thrusting calcite twin strain hardening and 2 deformation of the country rock by competing mechanisms such as pressure solution small normal faults are parallel to the strike of the thrust sheet and seem to have evolved from strike parallel extension fractures in response to continued extension both small thrusts and stylolite surfaces are rare in outcrop there seems to be no major change in deformation of rocks which have traveled through different fractions of the total ramp length so long as the rocks have passed onto the ramp

numerical simulation of contraction scour in an open laboratory channel a finite volume computer code developed at the institute for hydromechanics university of karlsruhe has been used to calculate the flow and sediment transport in a laboratory channel with constriction and movable bed the flow is calculated by solving the fully three dimensional reynolds averaged navier stokes equations with k e turbulence model the bed deformation is obtained from an overall mass balance equation for sediment transport and the bed load transport is simulated with a nonequilibrium model the calculated results for flow and scour development in the laboratory channel are compared with experimental measurements the sensitivity of the simulated results to the nonequilibrian adaptation length parameter in the nonequilibrium bed load transport model is investigated systematically which represents the main contribution of this paper

three dimensional calculation of scour around cylinders the flow of water around a cylinder was calculated by a numerical model the model used a finite volume method to solve the nontransient navier stokes equations for three dimensions on a general nonorthogonal grid the k e turbulence model was used to solve the reynolds stress term the flow field gave the shear stress on the boundaries which was used to calculate sediment concentration for the bed elements the diffusion convection equation for the sediment concentration was solved and continuity for the sediment concentration gave changes in the bed elevation using the modified bed a new flow field was calculated and also a new sediment concentration this sequence was repeated until the depth of the calculated scour hole was identical to the depth of the scour hole from a physical model study the rest of the geometry of the resulting scour hole compared well with the measured scour hole from the experimental study also other flow characteristics given by the numerical model were found to be in ag

numerical study of turbulence and wave damping induced by vegetation canopies article i nfo vegetation canopies control mean and turbulent flow structure as well as surface wave processes in coastal regions a non hydrostatic rans model based on nhwave ma et al 2012 is developed to study turbulent mixing surface wave attenuation and nearshore circulation induced by vegetation a nonlinear k e model accounting for vegetation induced turbulence production is implemented to study turbulent flow within the vegetation field the model is calibrated and validated using experimental data from vegetated open channel flow as well as nonbreaking and breaking random wave propagation in vegetation fields it is found that the drag related coefficients in the k e model cfk and cf can greatly affect turbulent flow structure but seldom change the wave attenuation rate the bulk drag coefficient cd is the major parameter controlling surface wave damping by vegetation canopies using the empirical formula of mendez and losada 2004 the present model provides accurate predictions of vegetation induced wave energy dissipation wave propagation through a finite patch of vegetation in the surf zone is investigated as well it isfound that the presenceof a finite patch of vegetation may generate strong pressure driven nearshore currents with an onshore mean flow in the unvegetated zone and an offshore return flow in the vegetated zone published by elsevier b v

beach response to a fixed sand bypassing system abstract indian river inlet is located at roughly the mid point of the atlantic coast of delaware and connects the ocean to two delaware inland bays jetties constructed in 1940 have maintained the inlet for navigation purposes but have also acted as a barrier to net northerly alongshore sediment transport causing downdrift erosion a mobile land based bypassing system was initiated in 1990 in an effort to counteract this erosion beach profile data from 1985 pre bypassing until 2008 are used to investigate the effect of the sand bypassing system on beaches adjacent to the inlet the downdrift beach experienced horizontal shoreline erosion between 10 and 60 m during the pre bypassing period but accreted 10 20 m during the bypassing period the mean shoreline location on the updrift beach during bypassing is 10 20 m landward erosion of its position during the pre bypassing period empirical orthogonal function eof amplitudes from analyses performed on mean removed elevation surfaces during the periods of highest bypassed volume average of 83 of design rate showed that the influence of the bypassing system on the downdrift beach extends to about 1500 m of the inlet an eof analysis showed that different morphologic responses were evident following the initiation of bypass operations temporal variations of shoreline and beach morphology were correlated to the temporal variations in bypassing rates on the downdrift beach only the downdrift beach response was greatest near the inlet for larger bypassing volumes correlation in these instances occurred with a roughly 1 year time lag suggesting that the beach quickly redistributes the bypassed sand eof amplitude and shoreline response are weakly correlated to bypassed volumes when the system bypassed smaller volumes average of 56 of design rate of sand suggesting that there is a minimum bypassing rate regardless of yearly variability below which the effect on the downdrift beach is obscured

intrusion related high temperature gold quartz veining in the cosmopolitan howley metasedimentary rock hosted gold deposit northern territory australia in the proterozoic cosmopolitan howley gold deposit northern australia quartz vein hosted gold mineralization occurs predominantly within 50 m of the noncarbonaceous footwall of carbonaceous slates although abundant veins farther away from or within carbonaceous slate are barren except for hydrofracture stock works in the hinge zone the gold bearing quartz veins qv1 are bedding concordant and occur in hornfels and slate in the steeply dipping fold limbs of the howley anticline the qv1 veins formed near the peak of contact metamorphism 550 degrees 620 degrees c and 240 200 mpa following the intrusion of the cullen granite batholith the vein alteration assemblage is k feldspar biotite andalusite or cordierite and mineralization was accompanied by large scale potassium metasomatism whereas sodium and calcium were leached from the country rocks the qv1 veins were overprinted first by superposed folding and then by reverse faulting later transpressional strike slip faulting was accompanied by extensive retrograde alteration the precipitation of sulfide lenses delta 34 s arsenopyrite 0 3 to 4 8 quartz veins qv2 with subeconomic gold enrichments and barren pegmatitic veins qv3 the involvement of a magmatic fluid in ore genesis at the cosmo howley deposit is indicated by 1 high fluorine contents in biotite from the alteration selvages of the gold quartz veins qv1 f 5 573 6 616 ppm 49 000 ppm at mt shoobridge 7 km west 2 mutual crosscutting relations of gold quartz veins with aplite dikes 3 the location of the deposit above i type granite at a vertical distance of less than 2 km most likely or 1 km and 4 the high salinity of the mineralizing fluid as estimated from the cl content of biotite in the alteration halos of the veins a magmatic derivation of the sulfur in the auriferous sulfides is consistent with isotopic data 0 3 to 7 2 5a4s calculated oxygen isotope compositions of the fluids which precipitated the successive generations of quartz veins qvi delta 18 o sub h 2 o 13 6 qv3 delta 18 o sub h 2 o 11 8 indicate that the isotopically heavy country rock chert nodules delta 18 o or 18 5 was infiltrated by an isotopically light

hydrothermal alteration ore fluid characteristics and gold depositional processes along a trondhjemite komatiite contact at tarmoola western australia tarmoola is a structurally controlled archean orogenic gold deposit hosted in greenschist facies metamorphosed komatiite and trondhjemite in the leonora district of the eastern goldfields province yilgarn craton high grade 1 g t au orebodies are located in komatiite wall rock adjacent to the eastern and northeastern margins of the asymmetrical north south striking tarmoola trondhjemite intrusion gold bearing veins postdate trondhjemite emplacement ca 2700 ma quartz diorite dikes ca 2667 ma and regional greenschist facies metamorphism textures and crosscutting relationships in gold bearing veins indicate two stages of hydrothermal fluid infiltration associated with a single gold related hydrothermal event a volumetrically dominant but gold poor stage i fluid and a gold rich stage ii fluid gold bearing veins contain stage i milky quartz and pyrite that are overprinted by stage ii quartz ankerite muscovite chalcopyrite sphalerite galena gold tellurides albite chlorite fuchsite epidote scheelite stage i hydrothermal alteration assemblages are different in trondhjemite and komatiite due to contrasting reactions between a common ore fluid and disparate wall rock chemistry stage ii fluid wall rock interaction was minor compared to stage i and is indicated by the overprinting of stage i mineral assemblages by stage ii microveins wall rock alteration proximal to veins in trondhjemite is characterized by replacement of igneous plagioclase amphibole biotite and metamorphic chlorite by hydrothermal quartz muscovite ankerite calcite pyrite chalcopyrite sphalerite galena tellurides and gold whereas in proximal alteration in komatiite metamorphic chlorite and talc are replaced by ankerite quartz muscovite albite chlorite fuchsite pyrite chalcopyrite sphalerite galena tellurides and gold the stage ii fluid was enriched in h2o co2 si ca k na s au ag cu pb w bi as mo zn and te based on fluid inclusion studies and stage ii mineral equilibria gold deposited from a homogeneous neutral to slightly alkaline ph 5 1 5 5 reduced low salinity 5 5 wt nacl equiv fluid that had a bulk composition of 78 mole percent h2o and 21 mole percent co2 and trace amounts of ch4 c2h6 h2 ar h2s and he gold deposition occurred at 300 50 c and 0 5 to 3 0 kbars assuming lithostatic fluid pressures gold precipitated at a 2 to 10 km depth stage ii gray quartz 18ofluid values range from 5 9 to 7 5 per mil whereas dfluid values calculated from the dehydration of muscovite grains and measured directly from bulk fluid inclusion analyses of stage ii gray quartz have ranges of 9 to 35 and 27 to 28 per mil respectively hydrothermal ore fluids were transported from greater crustal depths to the site of gold deposition during the district scale d3 event by shallowly w dipping reverse brittle ductile shear zones in supracrustal rock and along the steeply east dipping trondhjemite contact associated subhorizontal east west shortening caused the reactivation of the eastern trondhjemite margin and subparallel foliation which facilitated the transport of hydrothermal fluids and the generation of gold bearing veins and hydrothermal alteration zones in komatiite east west striking fractures in trondhjemite aided the lateral migration of ore fluids away from trondhjemite margins and the formation of east west striking gold bearing veins and broad alteration zones gold was most likely transported in the stage ii fluid as bisulfide complexes the sulfidation of trondhjemite and komatiite wall rock by the stage ii fluid caused the destabilization of au bisulfide complexes and gold deposition potassium ca and co2 metasomatism of komatiite wall rock may have enhanced gold deposition via the acidification of the stage ii fluid the physicochemical characteristics of the tarmoola ore fluid and relative timing of gold mineralization are consistent with the yilgarn wide 2650 to 2630 ma gold event the host rock chemistry vein and proximal wall rock alteration mineral assemblages and fluid temperature and pressures during gold deposition are also similar to that of earlier ca 2755 ma gold deposits in the leonora district

clear water scour at abutments in thinly armored beds experiments on local scour at short abutments ratio of abutment length to approaching flow depth less than unity namely vertical wall 45 wing wall and semicircular embedded in a bed of relatively fine noncohesive sediment overlain by a thin armor layer of coarser sediment were conducted for different flow conditions thickness of armor layers armor layer and bed sediments the abutments were aligned with the approaching flow in a rectangular channel the armor layer and the bed underneath it were composed of different combinations of uniform sediments in the experiments the approaching flow velocities were restricted to the clear water scour condition with respect to the armor layer particles depending on the approaching flow conditions three cases of scour at abutments in armored beds were identified effects of different parameters pertaining to scour at abutments are examined the comparison of the experimental data shows that the scour depth at an abutment with an armor layer in clear water scour condition under limiting stability of the surface particles approaching flow velocity nearly equaling critical velocity for the threshold motion of surface particles is always greater than that without armor layer for the same bed sediments the characteristic parameters affecting the maximum equilibrium nondimensional scour depth scour depth abutment length ratio identified based on the physical reasoning and dimensional analysis are excess abutment froude number flow depth abutment length ratio armor layer thickness armor particle diameter ratio and armor particle bed sediment diameter ratio the experimental data of clear water scour condition in thinly armored beds under limiting stability of surface particles were used to determine the equation of maximum equilibrium scour depth through regression analysis the estimated scour depths were in agreement with the experimental scour depths also an equation of maximum equilibrium scour depth in uniform sediments was obtained

geochronological constraints on pre syn and postmineralization events at the world class cleo gold deposit eastern goldfields province western australia recent geological and geochronological studies have led to a reevaluation of whether or not the majority of the lode gold deposits of the yilgarn craton formed nearly synchronously during an archean craton wide hydrothermal event as previously proposed the majority of reliable data indicate that gold mineralization took place at ca 2640 to 2625 ma however recent work in the far north of the eastern goldfields province provides structural evidence for instances of earlier gold mineralization and geochronological data for interpreted postore rocks that are considerably older than 2640 ma the documentation of xenotime and monazite in association with ore minerals at the cleo deposit provides a valuable means of determining the absolute age of gold mineralization at the cleo deposit high grade western lodes veins crosscut the sunrise shear zone at a high angle with only centimeter scale offset given that the stratigraphic sequence indicates at least several hundred meters offset across the shear zone the minimal offset of the western lodes veins indicates that gold mineralization was late in the history of movement in the shear zone the absolute ages of pre syn and postmineralization elements in the mine stratigraphic succession have been determined using a variety of geochronological techniques fuchsite micas formed in the sunrise shear zone yield an 40ar 39ar isochron age of 2667 19 ma rhyodacite porphyry dikes postdate the formation of the shear zone but predate the main phase of gold mineralization dike intrusion is constrained to 2674 3 ma by shrimp ii u pb analysis of zircons from these dikes rhenium os analysis of molybdenite from quartz chalcopyrite molybdenite veins that crosscut the porphyry dikes gives an age of formation at 2663 11 ma consistent with their relationship to the porphyry dikes both the dikes and these veins are crosscut by gold bearing western lodes veins mutually crosscutting relationships with ore minerals indicate that microscopic xenotime and monazite grains were deposited during ore formation in the western lodes ore zones shrimp ii u pb analyses of xenotime and monazite grains indicate that western lodes mineralization took place at 2654 8 ma at least 9 m y after the intrusion of the porphyry dikes 95 confidence evidence for substantial temporal separation between intrusive activity and gold mineralization is recorded by other researchers for other deposits associated with granitic intrusions in the leonora laverton area phlogopitic micas from a lamprophyre that crosscuts the whole succession including the sunrise shear zone yield an ar ar plateau age of 2080 4 ma this study constrains the timing of multiple events at cleo including the main phase of gold mineralization during a relatively short span of time however in the context of the larger debate about the existence of a dominant 2640 to 2625 ma period of gold mineralization and the extent of a proposed widespread pre 2660 ma mineralization event in the yilgarn craton the data from cleo are equivocal the 2654 8 ma age for mineralization being significantly older than 2640 ma but not significantly pre 2660 ma even if the maximum possible age is accepted

grain scale nonequilibrium sediment transport model for unsteady flow abstracta one dimensional 1d finite volume model is developed for simulating nonequilibrium sediment transport in unsteady flow the governing equations are the 1d mass and momentum conservation equations for sediment laden flow and the sediment continuity equation for both bed load and suspended load transport the rouse profile is modified to consider the nonequilibrium transport of suspended sediment the spatial lag between the instantaneous flow properties e g velocity bed shear stress and the rate of bed load transport in unsteady flow is quantified by using an adaptation length which is derived theoretically by applying the momentum principle in the bed load layer this new method for calculating the adaptation length is verified using data from several experiments and yields better results than other empirical formulas for a wide range of shear stress the nonequilibrium model is applied to simulate a series of laboratory dam break flows over erodible beds and the simulated results agree

the relations between mean rock stress and fluid flow in the crust with reference to vein and lode style gold deposits abstract fluid movement in the crust at the typical depths of formation of vein and lode style gold deposits will be dominated by upward flow focussing of upward flow into discrete channelways as required to form gold deposits is due to lateral gradients in fluid pressure fluid channelways should have lower fluid pressures than surrounding rock if lateral gradients are induced by variations in permeability this is however at variance with inferences from quartz vein structures of high relative fluid pressures during the formation of gold deposits focussing into zones of low mean rock stress will in contrast be associated with high relative fluid pressures in the zone of focussed fluid flow variations in mean rock stress are a direct consequence of a regional deviatoric stress acting on an inhomogeneous rock sequence analysis of stress fields shows a wide variety of potential sites of low mean stress dependent on the geometry of rock units and on patterns of faults fractures or shear zones a model of fluid focussing in the crust due to variations in mean stress is thus consistent with the large variety of structural setting of vein and lode gold deposits observed in nature use of the model through the technology of stress mapping has the potential to generate viable exploration targets

garnet orthopyroxene plagioclase quartz barometry refinement and application to the english river subprovince and the minnesota river valley recent experimental theoretical and thermodynamic studies permit better calibration of two reactions for geobarometry grossular pyrope quartz anorthite enstatite grossular almandine quartz anorthite ferrosilite if both reactions are applied using the same thermodynamic data and activity models they should yield the same pressure for a given garnet pyroxene plagioclase quartz assemblage application to a variety of high grade terrains generally yielded excellent results however poor results have been obtained for high fe rocks which can be traced to errors in activity models for garnet and or pyroxene either a two site ideal mixing model for orthopyroxene cf wood and banno 1973 underestimates enstatite activity for high fe orthopyroxenes or the ganguly and saxena 1984 model overestimates pyrope activity in low mg garnets

granitoid associated orogenic intrusion related and porphyry style metal deposits in the archean yilgarn craton western australia abstract the yilgarn craton hosts three types of archean granitoid associated metallogenic systems orogenic gold intrusion related and porphyry systems these systems may occur in the same terrane and share many broad characteristics including spatial coincidence with granitoids gangue silicate mineralogy metal associations and local structural controls features of archean orogenic gold systems spatially associated with granitoids include i a broad range of granitoid host compositions ii gold mineralization is mostly late with respect to yilgarn wide granitoid emplacement peak metamorphism and deformation iii orebodies are structurally controlled and iv gold deposition occurs over a large range of temperatures pressures and crustal depths 2 to 15 km from a co 2 rich low to moderate salinity reduced ore fluid that was derived from a metamorphic and or distal magmatic fluid source these systems do not display deposit scale vertical or lateral zonation of metals away from granitoid contacts host granitoid age composition or oxidation state are not important in controlling gold mineralization processes whereas structural setting and fluid flux are paramount archean intrusion related au mo w and mo au systems in the yilgarn craton are commonly small 2 bearing moderate to high salinity fluid during ore deposition archean porphyry cu mo au cu mo and cu au systems are spatially and temporally associated with volumetrically small pervasively altered felsic plutons and dikes surrounded by altered and mineralized supracrustal countryrock lateral zonation of metals away from porphyry centers commonly includes a decrease in cu au and ag au ratios with distance from the source pluton microthermometry studies on fluid inclusions in gold bearing veins suggest that early ore fluids were high temperature and high salinity and that mineralization occurred at 2 o 3 feo are demonstrated in phanerozoic terranes but are presently ill defined in the yilgarn craton crustal depth estimation is important in defining areas likely to have preserve shallow forming archean porphyry systems

mathematical modeling of suspended sediment in nonuniform flows a two dimensional vertical mathematical model for suspended sediment is presented the model is based on the width integrated convection diffusion equation for the sediment particles including settling effects the local fluid velocities and mixing coefficients are described by a new so called profile model which is based on the application of flexible profiles to represent the vertical distribution of the basic variables measured and computed velocities of strongly nonuniform flows were used for calibration of the profile model a stochastic approach is introduced to represent the sediment input at the bed a bed concentration or an upward sediment flux can be specified optional the convection diffusion equation is solved by a finite element method which proved to be better than a finite difference method an extensive sensitivity analysis is presented to show the influence of the main controlling parameters of the model finally a verification analysis is presented using flume and field data of dredged trenches

controlling mechanism of local scouring experimental study of clear water scouring around a circular cylinder shows that the scour mechanism is coupled to the three dimensional separation of the upstream boundary layer and the periodic vortex shedding in the wake of the cylinder the first scour appears in the wake of the cylinder the main scouring agent in the upstream region is a system of horseshoe vortices the vortices have a periodical character that causes a triple scour profile to develop in the upstream region during scouring the number and periods of horseshoe vortex shedding undergo no appreciable change despite the clear water stage the transport phenomenon is periodical transport of sediment takes place through turbulent scales of comparable size to macro length scales the size of horseshoe vortices are representative for the macroscale wake scouring is caused by the primary wake vortices and the accelerated side flow the process is characterized by a strong periodical transport and the formation of ripples the periodicity is controlled by the shedding frequency of the wake vortices collars attached to the cylinder cannot prevent the formation of the vortices

late archean granitoid hosted lode gold deposits yilgarn craton western australia deposit characteristics crustal architecture and implications for ore genesis granitoid hosted lode gold deposits constitute a sub group of late archean lode gold deposits in the yilgarn craton of western australia they share a number of common characteristics including 1 a strong structural control on a variety of scales 2 in most instances the presence of mineralisation in adjacent supracrustal sequence 3 wallrock alteration and vein assemblages consistent with the addition of sio2 k2o co2 s na2o but dependent on the p t conditions of the host environment and ore fluid 4 a metal association comprising au ag as bi te w mo and low concentrations of cu pb and zn and 5 deposition from a low moderate salinity near neutral h2o co2 ch4 fluid over a temperature and pressure range from 250 to 600 c and 1 to 4 kbar which corresponds to a range of crustal environments from lower greenschist to upper amphibolite facies these characteristics suggest that the granitoid hosted lode gold deposits represent a coherent genetic group that is equivalent to the more abundant greenstone hosted lode gold deposits of the craton in combination lode gold deposits irrespective of their host rocks and host terrane formed over a range of crustal levels and developed late in the tectonic sequence of the craton granitoids which host lode gold mineralisation are older than the inferred age of mineralisation by at least 10 million years and in combination with thermodynamic and isotope studies indicate that the host granitoids are not the dominant source of the ore fluid however the host granitoids do provide a structural and to a lesser extent chemical trap for gold bearing fluids in combination trace element and isotope studies of greenstone and granitoid hosted deposits suggest that the ore fluid originated from a deep mid to lower crustal source and at least interacted with granitic rocks at some stage the ore fluid composition is quite constant over the range of crustal levels from deep to shallow implying that the extent of modification by interaction with fluid conduit rocks is variable but not substantial

scour below a high vertical drop experimental results on scour below a high vertical drop drop height critical depth 1 in uniform sands and gravels are presented the experimental results are used to describe the effects of important parameters identified from the dimensional analysis on equilibrium scour depth the important observations are that the equilibrium scour depth increases with increase in densimetric froude number whereas the scour depth decreases with increase in sediment size and tailwater depth the time scale of scour depth that follows an exponential law is determined the nondimensional time scale decreases with increase in densimetric froude number

morb like tholeiites formed within the miocene forearc basin southwest japan abstract the shionomisaki igneous complex was formed autochthonously in the sedimentary basin which was the forearc basin during the miocene despite its occurrence near an island arc the shionomisaki igneous complex contains tholeiitic basic rocks which are petrologically similar to the mid oceanic ridge tholeiites morb although they are more enriched in lrees and th relative to n morb the basic rocks are associated with low k acidic rocks the existence of such an igneous complex suggests a forearc origin for the igneous members of some ophiolite complexes and provides evidence against the view that all ophiolite complexes containing igneous rocks of abyssal affinities must have formed in mid oceanic ridges

a thrust ramp model for gold mineralization at the archean trondhjemite hosted tarmoola deposit the importance of heterogeneous stress distributions around granitoid contacts the trondhjemite hosted tarmoola gold deposit is situated in the leonora district in the eastern goldfields province and is the largest granitoid hosted gold deposit in the yilgarn craton of western australia 100 t au the massive trondhjemite pluton intrudes a northwest striking shallowly northeast dipping supracrustal sequence that comprises greenschist facies metamorphosed basalt komatiite chloritic siltstones and a volcani clastic unit several east northeast striking quartz diorite dikes cut the trondhjemite and supracrustal sequence major ore zones 1 g t au occur 1 within the trondhjemite as discontinuous west northwest striking zones 2 along the steeply dipping eastern trondhjemite contact in the supracrustal and trondhjemite rocks and 3 subparallel to the shallowly dipping western trondhjemite margin in supracrustal rocks ore zones in the trondhjemite are controlled by west northwest striking steeply south west and northeast dipping conjugate quartz carbonate veins that contain minor pyrite chalcopyrite sphalerite galena gold and rare scheelite gold bearing veins in supracrustal rocks have a similar vein mineralogy and timing to that of the auriferous veins in trondhjemite deformation at tarmoola occurred during progressive regional east west directed shortening the first deformation event d 1 caused early barren isoclinally folded quartz carbonate veins and a pervasive foliation in supracrustal rock to be aligned subparallel to the steeply dipping eastern margin of the pluton during the gold mineralization event d 2 the trondhjemite pluton acted as a competent body within ductile supracrustal country rocks subhorizontal northwest southeast shortening caused auriferous conjugate veins in trondhjemite and the reactivation of the eastern contact and a preexisting subparallel foliation in the supracrustal rock the reverse movement of supracrustal rock along the sheared western trondhjemite contact caused the formation of west dipping gold bearing shear zones in the overlying supracrustal sequence the reactivation of the eastern trondhjemite contact caused the development of low mean stress zones adjacent to the contact hy drothermal ore fluids were focused into these regions to form ore zones the third deformation event d 3 produced brittle ductile shear zones quartz carbonate veins and brittle faults that offset lithological contacts and gold bearing veins

1d finite volume model of unsteady flow over mobile bed summary a one dimensional 1d finite volume method fvm model was developed for simulating unsteady flow such as dam break flow and flood routing over mobile alluvium the governing equation is the modified 1d shallow water equation and the exner equation that take both bed load and suspended load transport into account the non equilibrium sediment transport algorithm was adopted in the model and the van rijn method was employed to calculate the bed load transport rate and the concentration of suspended sediment at the reference level flux terms in the governing equations were discretised using the upwind flux scheme harten et al 1983 hll and hllc schemes roe s scheme and the weighted average flux waf schemes with the double minmod and minmod flux limiters the model was tested under a fixed bed condition to evaluate the performance of several different numerical schemes and then applied to an experimental case of dam break flow over a mobile bed and a flood event in the rillito river tucson arizona for dam break flow over movable bed all tested schemes were proved to be capable of reasonably simulating water surface profiles but failed to accurately capture the hydraulic jump the waf schemes produced slight spurious oscillations at the water surface and bed profiles and over estimated the scour depth when applying the model to the rillito river the simulated results generally agreed well with the field measurements of flow discharges and bed elevation changes modeling results of bed elevation changes were sensitive to the suspended load recovery coefficient and the bed load adaptation length which require further theoretical and experimental investigations

character and regional implications of the sheared archaean granite greenstone contact near leonora western australia abstract the boundary between greenstone belt rocks and deformed domal bodies of granite and gneissic granite in the area west and northwest of leonora is marked by a wide zone of high strain within which the dominant fabric elements are parallel to the boundary the high strain zone is arcuate the granitic body is domal in form consistent sense of shear movement indicators show that the greenstones moved down relative to the granite rocks from a continuous core of 1 6 km drilled 4 km southeast of leonora exhibit mesoscale recumbent folding and ductile faulting the upper 900 m of core is characterised by recumbent flexural slip folds with half wavelengths up to 660 m separated by discrete shear zones below about 1200 m rock type and structural character change at this depth greenschistfacies rocks are juxtaposed against amphibolite facies rocks across a major ductile shear thermodynamic data give estimates of 370 c 2 1 kbar for greenschist and 610 c 5 6 kbar for amphibolite facies with high fluid pressures dominated by water in low grade rocks and co 2 in high grade ones several kilometres of section have therefore been lost across this zone the amphibolite hosts broad and narrow shear zones within which movement sense is consistently normal the structural and metamorphic data suggest that emplacement of the domal granitic and gneissic rocks was temporally linked with normal ductile shearing the regional structural setting and juxtaposition of high and low grade rocks across the shear zone with abrupt changes in temperature and fluid composition suggests that the domes were emplaced as uprising hot deep seated rock in a regional extensional tectonic environment comparable to the tectonic setting of metamorphic core complexes

volcanism in nascent back arc basins behind the shichito ridge and adjacent areas in the izu ogasawara arc northwest pacific evidence for mixing between e type morb and island arc magmas at the initiation of back arc rifting mineral chemistry major and trace elements and 87sr 86sr ratios are presented for 29 igneous rocks dredged from the northern portion of the izu ogasawara arc these rocks are compositionally bimodal basement gabbro and trondhjemite from the arc are extremely poor in k2o 0 05 0 19 and rb 0 48 0 62 ppm and their ree patterns and sr isotope ratios indicate that there are island arc tholeiites quaternary volcanic rocks from the present volcanic front shichito ridge active arc back arc seamounts east side inactive arc and torishima knoll between the two back arc depressions incipient back arc basins behind the active arc have the same geochemical characteristics as the above plutonic rocks though they are not as depleted in k and rb rhyolite pumice from the backarc depression is also the depleted island arc tholeiite whereas basalts from the depression have compositions that are transitional between morb and island arc tholeiites in trace element ti ni cr v y and zr and mineral chemistries the back arc depression basalts have relatively high ban cen 0 66 1 24 cen ybn 1 1 1 9 and k ba 45 105 and low 87sr 86sr 0 70302 0 70332 and ba sr 0 1 0 2 which are similar to other back arc basin basalts and e type morb but are quite unlike the depleted island arc tholeiites the diverse trace element and sr isotope compositions of basalt andesite from the back arc depressions imply the interplay between e type morb and island arc tholeiite these chemical characteristics and the relationships of ce yb n vs ba ce n and ce yb n vs 87sr 86sr suggest that the back arc depression magmas are generated by mixing of e type morb and depleted island arc tholeiite magmas geochemical characters of the associated rhyolite from the depression are compatible with partial melting of lower crust

live bed scour at bridge piers the relationship between scour depth at cylindrical bridge piers founded in cohesionless sediments and mean approach flow velocity is defined for flows above the threshold of particle motion expe

transport of salt and suspended sediments in a curving channel of a coastal plain estuary satilla river ga abstract this study describes the transport of salt and suspended sediment in a curving reach of a shallow mesotidal coastal plain estuary circulation data revealed a subtidal upstream bottom flow during neap tide indicating the presence of a gravitational circulation mode throughout the channel during spring tide landward bottom flow weakened considerably at the upstream end of the channel and changed to seaward in the middle and downstream areas of the reach suggesting the importance of tidal pumping salt flux near bottom was landward at both ends of the channel during neap tide at spring however the salt flux diverged along the bottom of the thalweg suggesting that tidal pumping caused a transfer of salt vertically and laterally into the intertidal zone thus landward flux of salt is maintained even in the presence of subtidal seaward flow along the bottom at the downstream end of the channel landward bottom stress is greater than seaward stress preferentially transporting suspended sediments upstream compared with salt however the weight of the suspended sediments causes less upward transfer of sediments into the intertidal zone flood flow carried more suspended sediments landward at the upstream end compared with the downstream end we speculate that secondary flow in the curving channel picks up increasing amounts of suspended sediments along the sides during flood and adds them to the axial flow in the thalweg since the landward flow along the bottom of the thalweg weakens and even reverses during spring tide there appears to be a complex re circulation system for sediments re suspended in curving channels that complicates the picture of a net transport of sediments landward

clear water scour at comparatively large cylindrical piers abstractnew long duration clear water scour data were collected at single cylindrical piers with the objective of investigating the effect of sediment coarseness dp d50 dp pier diameter d50 median grain size on the equilibrium scour depth and improving the scour depth time evolution modeling by making use of the exponential function suggested in the literature experiments were carried out for the flow intensity close to the threshold condition of initiation of sediment motion imposing wide changes of sediment coarseness and flow shallowness d dp d approach flow depth the effect of sediment coarseness on the equilibrium scour depth was identified existing predictors were modified to incorporate this effect for u uc 1 0 dp d50 60 and d dp 0 5 the complete characterization of a known scour depth time evolution model was achieved for u uc 1 0 60 dp d50 500 and 0 5 d dp 5 0

numerical and experimental investigation of flow and scour around a circular pile the flow around a vertical circular pile exposed to a steady current is studied numerically and experimentally the numerical model is a three dimensional model the model validation was achieved against new experimental data which include two component laser doppler anemometry lda flow measurements and the hot film bed shear stress measurements and reported in the present paper and the data of others and a k w turbulence model was used for closure the model does not have a free surface facility and therefore is applicable only to cases where the froude number is small fr 0 0 2 the flow model was used to study the horseshoe vortex and lee wake vortex flow processes around the pile the influence on the horseshoe vortex of three parameters namely the boundary layer thickness the reynolds number and the bed roughness was investigated in the latter investigation the steady solution of the model was chosen a study of the influence of the unsteady solution on the previously mentioned flow processes was also carried out the ranges of the parameters covered in the numerical simulations are the boundary layer thickness to pile diameter ratio is varied from 2 x 10 2 to 10 2 the pile reynolds number from 10 2 to 2 10 6 and the pile diameter to roughness ratio from 2 to about 10 3 the amplification of the bed shear stress around the pile including the areas under the horseshoe vortex and the lee wake region was obtained for various values of the previously mentioned parameters the steady state flow model was coupled with a morphologic model to calculate scour around a vertical circular pile exposed to a steady current in the case of non cohesive sediment the morphologic model includes i a two dimensional bed load sediment transport description and ii a description of surface layer sand slides for bed slopes exceeding the angle of repose the results show that the present numerical simulation captures all the main features of the scour process the equilibrium scour depth obtained from the simulation agrees well with the experiments for the upstream scour hole some discrepancy up to 30 was observed however for the downstream scour hole the calculations show that the amplification of the bed shear stress around the pile in the equilibrium state of the scour process is reduced considerably with respect to that experienced at the initial stage where the bed is plane

one dimensional numerical model for nonuniform sediment transport under unsteady flows in channel networks in this study the proposed one dimensional model simulates the nonequilibrium transport of nonuniform total load under unsteady flow conditions in dendritic channel networks with hydraulic structures the equations of sediment transport bed changes and bed material sorting are solved in a coupling procedure with a direct solution technique while still decoupled from the flow model this coupled model for sediment calculation is more stable and less likely to produce negative values for bed material gradation than the traditional fully decoupled model the sediment transport capacity is calculated by one of four formulas which have taken into consideration the hiding and exposure mechanism of nonuniform sediment transport the fluvial erosion at bank toes and the mass failure of banks are simulated to complement the modeling of bed morphological changes in channels the tests in several cases show that the present model is capable of predicting sediment transport bed changes and bed material sorting in various situations with reasonable accuracy and reliability

sediment transport part i bed load transport a method is presented which enables the computation of the bed load transport as the product of the saltation height the particle velocity and the bed load concentration the equations of motions for a solitary particle are solved numerically to determine the saltation height and particle velocity experiments with gravel particles transported as bed load are selected to calibrate the mathematical model using the lift coefficient as a free parameter the model is used to compute the saltation heights and lengths for a range of flow conditions the computational results are used to determine simple relationships for the saltation characteristics measured transport rates of the bed load are used to compute the sediment concentration in the bed load layer a simple expression specifying the bed load concentration as a function of the flow and sediment conditions is proposed a verification analysis using about 600 alternative data shows that about 77 of the predicted bed load transport rates are within 0 5 and 2 times the observed values

numerical investigation of excessive surge induced by wave overtopping in an inlet bay system abstract during hurricane sandy wave overtopping occurred along the barrier beach in front of the rehoboth bay one of the delaware inland bays as indicated by field observations and the morphological profile model cshore cshore estimated a total overtopping volume of about 9 7 10 7 m 3 which is close to the storm surge induced water volume entering the bays through the inlet about 1 3 10 8 m 3 in this study we incorporated the wave overtopping result from cshore into the nearshore community model nearcom tvd to investigate the wave overtopping induced excessive surge ois in the delaware inland bays with the wave overtopping applied in the flux boundary condition the model successfully reproduced the high water level measured at the station located in the rehoboth bay additional numerical experiments for the separate effects of wave forcing and local winds are also carried out the results show that wave forcing has a minimal effect on the water level inside the bays the adjustment of local wind forcing does not qualitatively improve the agreement between the model and data the model with included wave overtopping predicted an excessive surge of about 20 cm in the rehoboth bay agreeing better with the measured data finally the responses of ois to different overtopping conditions were performed using an idealized model setup a strong asymmetry represented by a much longer draining period versus a shorter period of overtopping increase to the ois peak was found in the ois process for a given temporally symmetric time series of overtopping flux the asymmetric feature is caused by the imbalance between the overtopping flux and the discharge through the inter connecting channel inside the inland bays nonlinearity plays an important role in the process of ois as demonstrated in modeling ois tide surge interaction

one dimensional numerical modeling of sediment transport and bed deformation in open channels 1 a one dimensional numerical model for simulating unsteady flow and sediment transport in open channels is presented and tested the flow hydrodynamics is represented by the shallow water equations and the bed morphodynamics is represented by the exner equation and an additional equation describing the nonequilibrium sediment transport sediment size distribution is represented by the median grain diameter and the standard deviation instead of the usual modeling with multiple particle size classes various methods for computing bed elevation changes at a cross section due to erosion or deposition of sediment are proposed and tested including an innovative approach that relates the spatial pattern of erosion and deposition rates to boundary shear stress distribution which is calculated by the merged perpendicular method an explicit finite difference scheme is employed for solving the water and sediment governing equations the pertinence of the model is examined for two hypothetical cases the model is then tested on one set of laboratory experiments on bed degradation under steady flow showing excellent model data fit and indicating that incorporating a nonequilibrium sediment transport equation into the model structure is an important element in reproducing the bed degradation process finally the model is applied to simulate the morphological changes taking place in the ha ha river quebec after the failure of the ha ha dyke on july 1996 relevant results can be obtained in terms of changes in longitudinal bed profile and cross sectional geometry as well as water levels although some discrepancies are obtained between the simulated and surveyed cross sectional geometries mainly because bank failure and channel widening are not modeled

gold precipitation by fluid mixing in bedding parallel fractures near carbonaceous slates at the cosmopolitan howley gold deposit northern australia the proterozoic cosmopolitan howley gold deposit consists of quartz veins on the steeply dipping limbs of the howley anticline and is hosted by pelitic metasediments within the high temperature metamorphic aureole of proterozoic granites in the pine creek province of northern australia ore is restricted to a stratigraphic contact always occurring within noncarbonaceous hornfels within 50 m of carbonaceous slates similar veins farther away from or within carbonaceous slates are abundant but barren a companion paper establishes that ore formation occurred in response to hydrothermal activity accompanying granite intrusion and contact metamorphism the involvement of a magmatic brine in ore genesis is referred on the basis of fluorine concentrations in biotite from the potassic alteration selvages of the gold bearing veins from stable isotopic data and from mutual crosscutting relations of veins and felsic dikes this paper focuses on the fluid flow and chemical processes that formed the gold bearing quartz veins it is argued that lateral focusing of fluid flow into the subvertical vein hosting fractures led to mixing of the ascending magmatic brine or some metamorphic fluid with hydrocarbon rich fluid advected through carbonaceous slate in the steeply dipping fold limbs crock seal textures in some of the gold quartz veins indicate that this fluid flow and mixing were locally episodic the magmatic brine involved in the mixing was expelled from a crystallizing i type granite at depth or 0 24 these features indicate a redox state of tile magmatic fluid at or above the nno buffer by contrast gold deposition occurred at 2 to 3 log f o2 units below nno a weakly acid ph of 4 3 to 4 7 550 degrees or 100 ppb at or 500 degrees c that gold availability in ordinary metasediments may be insufficient to generate an effective ore fluid for high temperature gold deposition by metamorphic devolatilization if correct these predictions further emphasize the inferred role of magmatic fluids in the formation of gold deposits within high grade contact metamorphic aureoles

bed erosion in rectangular long contraction an experimental investigation into the general erosion within a long contraction problem is reported the experimental results are used to verify straub s theoretical one dimensional model for general erosion local scour near the side walls in the inlet region was also measured and the results are reported two different sizes of sand were used in the experiments

toward modeling turbulent suspension of sand in the nearshore 1 we present two depth and phase resolving models based on single and two phase approaches for suspended sediment transport under water waves both models are the extension of a wave hydrodynamic model cornell breaking wave and structure cobras in the two phase approach dilute two phase mass and momentum equations are calculated along with a fluid turbulence closure based on balance equations for the fluid turbulence kinetic energy k f and its dissipation rate f in the single phase approach the fluid flow is described by the reynolds averaged navier stokes equations while the sediment concentration is calculated by an advection diffusion equation for the conservation of sediment mass the fluid turbulence is calculated by k f f equations that incorporate the essential influence of sediment which can also be consistently deduced from the two phase theory by adopting a commonly used sediment flux boundary condition near the bed the proposed models are tested against laboratory measurements of suspended sediment under nonbreaking skewed water waves and shoaling broken waves although the models predict wave averaged sediment concentrations reasonably well the corresponding time histories of instantaneous sediment concentration are less accurate we demonstrate that this is due to the uncertainties in the near bed sediment boundary conditions in addition we show that under breaking waves the near bed sediment pickup cannot be solely parameterized by the bottom friction suggesting that other effects may also influence the near bed sediment boundary conditions

constriction effects in clear water scour at abutments the erosion process at a bridge abutment may be affected by the flow constriction when the abutment occupies a significant part of the flume width we devised a specific experimental campaign to investigate the effect of the obstruction ratio i e the ratio between the abutment length and the channel width on the erosion depth we performed homogeneous series of clear water scour experiments in each of which the obstruction ratio was the only parameter that varied the experimental results are presented in light of a dimensionless framework it was found that the effect of the obstruction ratio on the time development of local scour depth may not be large nevertheless significant effect can be observed even for relatively small values of the parameter during the earliest phases the latter are important for example for the step by step modeling of the erosion development under unsteady flow conditions we propose a simple equation to quantify the scour enhancement due to the flow constriction in c

structural controls of fluid flow and gold mineralization in the easternmost parts of the karagwe ankole belt of north western tanzania abstract gold mineralization in the biharamulo region of western tanzania is confined to the sheared low angle basement cover contact between archaean basement gneisses of the tanzania craton and the structurally overlying low grade metamorphic metasediments of the mesoproterozoic karagwe ankole belt regional scale fluid flow along this detachment is indicated by the pervasive silicification and retrogression of wall rocks to pervasively foliated phyllonites and pyritization of particularly metasediments commonly graphite rich in the hanging wall of the shear zone gold mining centres on specific structural sites along the detachment but also in stratigraphically higher sections in the structurally overlying metasediments zones of gold mineralization along the detachment correlate with ne trending ramp structures dip angles 20 35 that are most ideally orientated for slip and reactivation within the low angle phyllonitic detachment repeatedly overprinted auriferous quartz vein stockworks in quartzofeldspathic gneisses immediately below the detachment indicate brittle fracturing of the competent footwall lithotypes during slip along the weaker detachment in cases of massive silicification up to 50 m thick quartz blows are formed along the contacts between detachment phyllonites and footwall gneisses the multiple overprinting relationships of successive quartz vein generations in these zones of massive silicification suggests that the quartz blows acted as competent blocks in the weak detachment causing the repeated overprint of earlier silicification by later fracturing and quartz veining events gold mineralization above the detachment and in stratigraphically higher metasediments is closely associated with fold structures that form part of the low grade metamorphic fold and thrust belt veining is particularly abundant in competent lithotypes such as quartzite and chemically reactive ferruginous mafic sills overprinting relationships between quartz vein sets illustrate fluid flow during fold amplification and importantly the final lock up stage of folds during which much of the mineralization was introduced oxygen isotope values for quartz veins indicate fluids were likely derived from clastic mainly metapelitic sedimentary sequences of the karagwe ankole fold belt the data also implies that the partially reworked archaean granitoid greenstone basement of the tanzania craton has not contributed to the fluid evolution and possibly gold mineralization the extent 100 km of the basement cover detachment and associated alteration is indicative for a regional scale fluid system gold mineralization is however controlled by local structures and lithological contrasts that require the detailed mapping and sampling of the regional structure

nd and sr isotopic variations in acidic rocks formed under a peculiar tectonic environment in miocene southwest japan initial nd and sr isotopic ratios were obtained for middle miocene igneous rocks as well as for related rocks from the outer zone of southwest japan to investigate the petrogenesis of acidic magmas and their relation to a peculiar tectonic environment bearing on the back arc spreading of the japan sea on the nd sr diagram data points for the acidic rocks fall in the nd sr quadrant occupying different positions from those for sedimentary and old crustal rocks and seem to define several subparallel lines which extend towards the lower righthand sedimentary field the s type acidic rocks occupy an intermediate position between i type rocks and sedimentary ones a fact suggesting mixing of an igneous component and a sedimentary one the linear mixing trend observed on the nd sr diagram can be attained in the restricted case that the igneous component has similar sr nd concentration ratios to that of the sedimentary one which implies an intermediate to acidic composition for the igneous component inconsistency between the elemental and isotopic variations observed may be reconciled by considering that mixing probably in the relatively deep part of the crust might have occured prior to chemical differentiation processes the episodic igneous activity and the high heat energy required to melt such materials involving sedimentary rocks may be explained by a model in which a hot mantle region probably corresponding to the rising part of the mantle convection supplied the heating energy to the outer zone of southwest japan when passing beneath southwest japan in the course of movement of the hot rising part from the shikoku basin areas to the japan sea area

scour in long contractions experimental results on local scour in long contractions for uniform and nonuniform sediments gravels and sands under clear water scour are presented an emphasis was given to conduct the experiments on scour in long contractions for gravels the findings of the experiments are used to describe the effects of various parameters obtained from dimensional analysis on equilibrium scour depth under clear water scour the equilibrium scour depth increases with decrease in opening ratio and with increase in sediment size for gravels but the curves of scour depth versus sediment size have considerable sag at the transition of sand and gravel the scour depth decreases with increase in densimetric froude number for larger opening ratios and increases with increase in approaching flow depth at lower depths however it becomes independent of approaching flow depth at higher flow depths the effect of sediment gradation on scour depth is pronounced for nonuniform sediments which reduce scour depth significantly due to the formation of armor layer in the scour hole using the continuity and energy equations a simple analytical model for the computation of clear water scour depth in long contractions is developed with and without sidewall correction for contracted zone the models agree satisfactorily with the present and other experimental data also a new empirical equation of maximum equilibrium scour depth which is based on the experimental data at the limiting stability of sediments in approaching channel under clear water scour is proposed the potential predictors of the maximum equilibrium scour depth in long contractions are compared with the experimental data the comparisons indicate that the equations given by komura and lim are the best predictors among those examined

seismic reflection character of the hikurangi subduction interface new zealand in the region of repeated gisborne slow slip events summary we use seismic reflection data to map the geometry and character of the subduction interface in the gisborne area of the hikurangi subduction margin new zealand which experiences repeated shallow 15 km slow slip events the reflection character and geometry in this area is highly variable which we interpret to be related to the subduction of seamounts and underthrust sediments three zones of high amplitude interface reflectivity hrz 1 2 and 3 are interpreted to be the result of fluid rich sediments that have been entrained with subducting seamounts the interface above the hrz zones is shallower than the surrounding areas by 2 4 km due to the warping of the interface to accommodate seamount subduction these zones of high amplitude reflectivity and shallower interface geometry correlate broadly with locations of recorded slow slip events from 2002 to 2008 we hypothesize that effective stresses on the interface may be lower along the northeast margin in areas of high amplitude reflectivity due to 1 the enhanced underthrusting of fluid rich sediment 2 reduced overburden stresses where the interface has been warped to shallower depths to accommodate seamount subduction and 3 potential fluid flow concentration effects leading to overpressure along these shallower interface corrugations from our observations we propose localized reductions in effective stress caused by interface structural relief may be a potential factor in promoting shallow slow slip events

spatial temporal evolution of the eastern nanhui mudflat in the changjiang yangtze river estuary under intensified human activities abstract the eastern nanhui mudflat enm located in the southern flank of the changjiang yangtze river estuary plays a key role in storm protection defense against sea level rise and land resource provision for shanghai china s largest city recently there has been a great deal of concern for its evolutionary fate since a drastic reduction in the changjiang sediment discharge rate and an increased number of estuarine enclosures might negatively impact the environmental protection functions that this mudflat provides in this paper a novel method which employed the envelope lines of instantaneous shoreline positions identified in 436 landsat satellite images from 1975 to 2016 was used to demonstrate the evolution of the mudflat high and low tide lines in a detailed quantitative way our study reveals the southeast progradation rate of the mudflat doubled from 24 m yr in 713 1974 ce to 49 m yr in 1975 1995 ce probably due to the influence of the estuarine turbidity maximum zone shifting to the enm under the ample sediment input directly from the turbidity maximum zone the spatial evolution of the enm was governed predominantly by the changing morphology of the south passage due to the quick progradation of the enm which narrowed the south passage by pushing the south passage trumpet southeastward therefore the enm experienced rapid accretion during 1975 2016 the accretion rate of the high tide line increased 2 13 times due to vegetation and intertidal enclosures resulting in the rapid reduction of the intertidal area the area decreased from 97 km2 in 1976 to 66 km2 in 1995 mainly due to vegetation and continued decreasing to 12 km2 in 2006 due to the intertidal enclosures in contrast the accretion rate of the low tide line increased by 25 times due to subtidal enclosures and caused the intertidal area increased to 78 km2 in 2015 the almost disappeared intertidal zones in 2006 reappeared however this reappearance might be a temporary transitional state and once the subtidal enclosures are completed most of the intertidal zones will be replaced by enclosure land our study reveals that the drastic reduction in the changjiang sediment flow to the sea has not caused a decline in the enm in contrast the enm has experienced rapid accretion in the past 40 years resulting in the strengthening of its functional abilities to protect shanghai an unexpected outcome

origin of the granodiorite in the forearc region of southwest japan melting of the shimanto accretionary prism abstract in the forearc region of southwest japan felsic to intermediate volcano plutonic complexes of middle miocene age intruded into the shimanto accretionary complex possibly in association with megatectonic events such as the opening of the japan sea and resultant underthrusting of the newly borne shikoku basin philippine sea plate beneath the southwest japan arc activities of mantle derived magmas are also distinct in the forearc of middle miocene southwest japan tholeftic basalts are closely related to igneous activity of the shikoku basin and high mg andesites probably formed under anomalously high temperature conditions caused by the opening of japan sea two plutons uwajima and miuchi were chosen for understanding the origin of felsic magmas in the forearc region of southwest japan all granitic rocks of the plutons show enriched isotopic characteristics with higher 87 sr 86 sr and lower 143 nd 144 nd tha bulk earth which suggests that the contribution of crustal materials has a magma source however they have lower 87 sr 86 sr and higher 143 nd 144 nd than shimanto sediments and hence an additional component with lower 87 sr 86 sr and higher 143 nd 144 nd than granitic rocks must be required possible candidates for such components are coeval mantle derived magmas mass balance modelling between mantle derived magmas and shimanto sediments on the basis of their sr nd isotopic compositions suggested that mixing of anatectic melt of the shimanto sediments and porphyritic andesite magma evolved from high mg andesite as a possible mechanism of the origin of the granodiorites of the uwajima pluton injection of high mg andesite into the shimanto accretionary prism may triggered the melting of sediments calculated composition of anatectic melt of the shimanto sediment and p t condition of the gneissose enclave in the granodiorite suggest that the melting of sediments may have occurred at higher temperature conditions than those of the melting reactions involving biotite breakdown

local scour at vertical wall abutments under clear water flow conditions 1 new clear water tests on abutment scour are presented thirty one tests with sand bed and nine tests with lightweight pumice bed were carried out in a 28 m long 4 m wide flume tests typically lasted for 1 week or more vertical wall abutments with length to depth l d ratios from 9 up to 36 were used other test campaigns in the literature are added to the data focusing on abutments with 2 l d 100 the critical flow for scour inception at the abutment nose is found to decrease as l d increases the whole data are analyzed for searching the equilibrium scour depths with different methods the slope change in the plot of scour depth against the logarithm of time is the method selected for the group of tests run close to the threshold condition some trends regarding the dimensionless equilibrium scour depth are 1 dependence on the bed material specific gravity in the sense that pumice tests produce less scour and 2 increase of the scour depth as l d increases finally the morphology of the scour area in terms of volume and plan dimensions is given by new regression equations