characterization of magma from inclusions in zircon apatite and biotite work well feldspar less so detrital zircon grains are employed to decipher sediment provenances and crustal evolution and they provide unique evidence of hadean crust mantle differentiation processes we demonstrate that mineral inclusions in zircon provide valuable information on the conditions under which zircon crystallized zircon grains from selected plutonic rocks from dronning maud land antarctica contain inclusions of apatite biotite amphibole and pyroxenes that accurately reflect the chemical compositions of the equivalent phases in the host rock matrix and the compositions of the whole rocks high concentrations of y and low concentrations of sr in apatite inclusions in zircon are diagnostic of evolved felsic granitoid host rocks in contrast the relative abundances and compositions of plagioclase and alkali feldspar inclusions in zircon are decoupled from the composition of the whole rock and they are generally indicative of granitic melts regardless of the bulk rock this is best explained by the late crystallization of zircon relative to the bulk of the feldspars we conclude that inclusions of apatite and mafic phases in zircon constrain the potential source rocks of detrital zircon whereas feldspar inclusions do not

flow structure modification and drag reduction induced by sediment stratification in coastal tidal bottom boundary layers abstract the karman prandtl logarithm formula of velocity distribution has been widely used to depict flow structures and estimate parameters including bed roughness length and friction velocity in coastal tidal bottom boundary layers however the basic assumptions are of homogeneous flow but the effects of stratification should be taken into account here field observations of hydrodynamics and sediment dynamics were carried out in the well mixed area outside of the changjiang estuary china during may 31 june 2 2011 velocity profiles within the 2 m bottom layer suggest that the flow structure is prominently influenced when the gradient of suspended sediment concentration reaches o 0 1 kg m 4 the direct application of the log fit method resulted in a pronounced deviation from the actual boundary parameters the extended log fit method was used to represent the tidally averaged vertical flow structure indicating that the modification of the flow structure diminishes down to the bed and the calculated z0 based on the lowest layer close to the bed 0 22 0 38 m above the bed in the observation approaches the real value the observed data were also used to examine the modified logarithmic velocity distribution model in which the flux richardson number is modified with an empirical constant a to parameterize the stratification effects it was found that the constant a is approximately 1 which is significantly different from previous studies results of a vertical one dimensional model supported the above findings the sediment stratification effects should be taken into account and the logarithmic velocity distribution model tends to be applicable in the water layers very close to the bed

amphibole sponge in arc crust pressure temperature time paths followed by arc magmas ascending through the lithosphere dictate the phase assemblage that crystallizes and hence the compositions of liquid fractionates here we use la yb and dy yb versus sio 2 relationships from selected volcanoes to show that amphibole is an important mineral during differentiation of arc magma production of intermediate and silicic arc magmas occurs as magmas stall and cool in the mid lower crust where amphibole is stable because amphibole is rarely a phenocryst phase we term this cryptic amphibole fractionation if this process is as widespread as our investigation suggests then 1 amphibole cumulates may act as an effective filter for water dissolved in mantle derived magmas 2 amphibole cumulates may act as a fertile source of intracrustal melts and fluids and 3 recycling of amphibole cumulates has the potential to return incompatible trace elements and water to the mantle

impact of geological complexity of the fruitland formation on combined co2 enhanced recovery sequestration at san juan basin pilot site abstract in this study we present well log and 3d seismic interpretations of a coalbed methane reservoir in the late cretaceous fruitland formation in the area surrounding the southwest regional partnership on carbon sequestration s san juan basin carbon sequestration pilot site in new mexico usa the interpretation incorporated geophysical logs from 38 wells located in a 23 km 2 area surrounding the pilot site which lies near the southern edge of the high rate fruitland coal production fairway located along the axis of the san juan basin log interpretations revealed three coal bearing zones upper middle and lower within the fruitland formation that are approximately 7 4 7 and 8 5 m 23 15 5 and 28 ft thick respectively the interpretations indicate that each of these coal zones is split by a parting into upper and lower beds making a total of six mappable coal beds in the area surrounding the co 2 injection well the combined thickness of the upper two coal beds in the upper coal zone varies between 3 5 and 4 8 m 11 5 to 15 7 ft and that of the middle beds from 2 to 4 3 m 6 6 to 14 1 ft thick the thickness of the individual coal beds in the lower coal zone varies from about 2 7 to 4 25 m 9 to 14 ft for the upper bed and from about 3 to 5 5 m 10 to 18 ft for the basal coal bed partings separating the upper and lower coal beds in each zone are on average about 2 m 7 ft in the upper and middle zones and about 1 m 3 5 ft in the lower zone seismic response of the upper middle and lower coal zones was interpreted and correlated through the 23 km 2 area the stratigraphic complexity of this coalbed methane reservoir is also accompanied by considerable structural disharmony between the three coal zones the reservoir complexity revealed in this study may account for lower than expected co 2 injectivity and preferential injection into the lower coal zone during the pilot test

along strike segmentation of the abanico basin central chile new chronological geochemical and structural constraints the andes of central chile are composed mostly of cenozoic volcanic rocks erupted during the opening and subsequent inversion of the intra arc volcano tectonic abanico basin until recently the internal segmentation of this inverted basin was poorly understood based on a combination of u pb geochronology u th he thermochronology whole rock geochemistry and structural data we propose that the abanico basin can be divided into two main segments separated by the nw striking piuquencillo fault and conjugate ne striking faults stratigraphic units defined in the northern segment abanico and farellones formations cannot be correlated with the rocks of the southern segment coya machali formation and teniente volcanic complex in terms of lithofacies depositional ages and geochemistry the northern and southern segments also show temporal differences in their tectonic evolution an early deformation event beginning at 22 ma affected only the northern segment and is associated with the formation of progressive unconformities between the abanico and farellones formations and also with crustal thickening as reflected in the geochemistry of the farellones formation a second stage of crustal thickening and exhumation began at 12 ma as suggested by a sharp increase of the la yb ratios in the northern segment in the southern segment this event is reflected by only a moderate increase of la yb ratios and by the transition between the coya machali formation and the teniente volcanic complex finally a third stage of exhumation and crustal thickening beginning at 7 ma affected both the northern and southern segments this last stage was the main exhumation event affecting the rocks of the andes of central chile and is recorded in the geochemistry of igneous rocks by a sharp increase in the la yb ratios in the southern segment

geologic controls on transgressive regressive cycles in the upper pictured cliffs sandstone and coal geometry in the lower fruitland formation northern san juan basin new mexico and colorado three upper pictured cliffs sandstone tongues in the northern part of the san juan basin record high frequency transgressive episodes during the late cretaceous and are inferred to have been caused by eustatic sea level rise coincident with differential subsidence outcrop and subsurface studies show that each tongue is an amalgamated barrier strand plain unit up to 100 ft 30 m thick successive upper pictured cliffs tongues display an imbricate relation and are offset basinward reflecting net shoreline progradation northeastward upper pictured cliffs barrier strand plain sandstones underlie and bound thickest fruitland coal seams on the seaward side controls on fruitland coal seam thickness and continuity are a function of local facies distribution in a coastal plain setting shoreline positions related to transgressive regressive cycles and basin subsidence during periods of relative sea level rise the pictured cliffs shoreline was temporarily stabilized allowing thick coastal plain peats to accumulate although some coal seams in the lower fruitland tongue override abandoned pictured cliffs shoreline deposits many pinch out against them differences in the degree of continuity of these coal seams relative to coeval shoreline sandstones are attributed to either differential subsidence in the northern part of the basin multiple episodes of sea level rise local variations in accommodation and progradation stabilization of the shoreline by aggrading peat deposits or a combination of these factors fruitland coalbed methane resources and productivity are partly controlled by coal seam thickness other important factors include thermal maturity fracturing and overpressuring the dominant production trend occurs in the northern part of the basin and is oriented northwestward coinciding with the greatest fruitland net coal thickness similar relationships between trends of thick coal seams of coeval origin with stacked shoreface sandstones exist in other western interior basins in the united states and serve as models for coalbed methane exploration in other basins of the world

suspended sediment transport and benthic boundary layer dynamics abstract the mellor yamada level ii turbulence closure model is used to examine the dynamics of a benthic boundary layer bbl carrying sediment in suspension using flow and sediment properties from observations in the florida straits implications for sediment transport in this and similar environments are discussed model results indicate that three size classes provide an adequate representation of the frequency distribution of a moderately well sorted sand size sediment the benthic boundary layer responds to a stabilizing suspended sediment concentration gradient by a reduction of about 45 in the bottom stress damping of turbulence and by a decrease in the slope of the velocity profile the velocity field in the lowermost portion of a neutrally stratified bottom boundary layer is governed by the relationship u u k ln z z 0 to recover the predicted velocity distribution in the sediment stratified bbl from this relationship von karman s constant k must be reduced by about 15 the model however treats k as internally invariant applying similarity theory to the model output yields u u k ln z z 0 where k k 1 ar f a is an empirically determined constant and rf is the flux richardson number in this case k may be interpreted as a modified von karman s constant increases in the angle of turning of the current vector 5 and enhancement of the ekman like nature of the current spiral are predicted these model predictions are consistent with findings from studies of stably stratified atmospheric boundary layers and sediment laden channel flows

an apatite for progress inclusions in zircon and titanite constrain petrogenesis and provenance apatite has recently gained considerable attention as a mineral with many uses within the earth and planetary sciences apatite chemistry has recently given new insight into a wide range of geological processes and tools for example magmatism metasomatism planetary geochemistry and geochronology we expand the utility of apatite here by presenting a novel way to fingerprint magma chemistry and petrogenesis using apatite inclusions within robust titanite and zircon we present trace element data from apatite mineral inclusions shielded within magmatic zircon and titanite importantly apatite inclusion and host titanite chemistries detailed in this study allow estimation of the whole rock sr and sio2 we show how these data can be used to assess the degree of fractionation of the host magma and to calculate key trace element abundances and ratios we demonstrate that the inclusions can be linked to discrete periods in the crystallization history of the host phases thus providing insight into petrogenesis the results highlight that apatite compositions might discriminate modern granitoids younger than 2 5 ga from archean proterozoic transitional granitoid compositions sanukitoid signatures development of such a petrological tool has important potential for interpretation of provenance and a better understanding of the secular evolution of the continental crust including that of early earth

distribution and dispersal of suspended particulate matter on the ebro continental shelf northwestern mediterranean sea abstract hydrographic data water and bottom sediment samples and a geoprobe tripod experiment were used to examine the distribution and dynamics of suspended particulate matter on the ebro shelf in the northwestern mediterranean sea in the absence of strong winds and storms primary sediment supply from the ebro river is dispersed along the shelf by a general southward flow in such calm conditions suspended matter concentrations on the shelf are lower than 3 mg l and transfer of material from the shelf to the slope takes place principally over the shelf edge north of the columbretes islands very fine sediment deposited in a mid shelf mud belt 30 80 m deep is cohesive and resistant to erosion only relatively rare strong storms are able to resuspend particles from the deeper central region of this cohesive deposit when resuspension takes place suspended particulate matter concentration increases and the general dispersal pattern of suspended matter is altered near the seafloor distribution of suspended matter is greatly influenced by the distribution of the mid shelf muds from which particles are resuspended resuspension occurs more intensively and frequently along the shallower 20 40 m edge of the cohesive deposit and near the delta

effects of biological activity on the entrainment of marine sediments nowell a r m jumars p a and eckman j e 1981 effects of biological activity on the entrainment of marine sediments mar geol 42 133 153 the effects of animal tracks and fecal pellet production on the critical entrainment velocity of marine sediments were examined experimentally laboratory measurements in a free surface seawater flume were made using three sediment sizes effects of three species of polychaetes and two species of bivalves were tested boundary shear velocity was calculated from the mean velocity profile in the logarithmic region of the boundary layer measurements were made with a hot film anemometer tracking doubled the boundary roughness and decreased the critical entrainment velocity by 20 ambient or free sediments were more easily entrained than fecal mounds which were restrained from movement by mucous adhesion between the fecal coils isolated pellets such as those egested by amphicteis scaphobranchiata transported readily as bedload over a cohesive sediment surface

magmatic evolution of the giant el teniente cu mo deposit central chile elteniente the world s largest cu deposit is hosted in late miocene and pliocene plutons that intrude the older teniente volcanic complex or farellones fm 14 2 6 5 ma the late miocene and pliocene plutonic host rocks of the deposit include sequentially the relatively large 450 km teniente mafic complex laccolith 8 9 1 4 ma the smaller 30 km sewell equigranular tonalite complex 7 05 0 14 ma and associated andesitic sills 8 2 0 5 to 6 6 0 4 ma small dacitic porphyry stocks 51km 6 09 0 18 ma the unusual cuand s rich porphyry a anhydrite bearing granitoid stock 51km 5 67 0 19 ma the teniente dacite porphyry dike 51km 5 28 0 10 ma minor latite dikes 4 82 0 09 ma and finally a small dacite intrusion 4 58 0 10 ma these plutonic rocks are all isotopically similar to each other sr sr1 4 0 7039 0 7042 end1 4 2 5 to 3 5 and also to the teniente volcanic complex extrusive rocks but distinct from both older late oligocene to early miocene volcanic rocks sr sr1 4 0 7033 0 7039 end1 4 3 8 to 6 2 and younger pliocene post mineralization mafic dikes and lavas sr sr1 4 0 7041 0 7049 end1 4 1 1 to 1 1 multiple cu mineralized magmatic hydrothermal breccia pipes were emplaced into these plutonic rocks during the same time period as the felsic porphyry intrusions between at least 6 31 0 03 and 4 42 0 02 ma these mineralized breccia pipes which formed by exsolution of magmatic fluids from cooling plutons have their roots below the deepest level of mining and exploration drilling and were derived from the same magma chamber as the felsic porphyries 44 km below the paleosurface to produce the 100 10 tonnes of cu in the deposit requires a batholith size 4600 km amount of magma with 100 ppm cu we suggest that both the mineralized magmatic hydrothermal breccias and the progressively smaller volumes of more fractionated but isotopically equivalent late miocene and pliocene felsic plutonic rocks that host the deposit were derived from the roof of a large long lived thermally and chemically stratified open system magma chamber or magmatic plumbing system recharged from below by mantle derived magmas only when this system fully solidified did post mineralization mafic olivine hornblende lamprophyre dikes 3 85 0 18 to 2 9 0 6 ma pass through the system from the mantle to the surface the significant progressive temporal isotopic evolution to higher sr sr from 0 7033 to 0 7049 and lower end from 6 2 to 1 1 that occurred between the late oligocene and pliocene in the vicinity of el teniente for mafic mantle derived magmas and by implication their sub arc mantle source region was due in part to increased mantle source region contamination by subducted crust tectonically eroded off the continental margin the post mineralization olivine hornblende lamprophyres also imply extensive hydration of the mantle below this portion of the andean arc by the pliocene which may have played a role in producing oxidized volatile rich magmas and mineralization at elteniente

regional geochemistry of tertiary igneous rocks in central chile implications for the geodynamic environment of giant porphyry copper and epithermal gold mineralization the giant porphyry copper molybdenum deposits of central chile formed within a thick sequence of cretaceous to pliocene volcanic rocks the predominantly calc alkaline basaltic andesites of the cretaceous las chilcas formation are characterized by la smn ratios of 1 8 to 2 5 and sm ybn of 1 8 to 2 8 the upper oligocene to lower miocene abanico formation variously defined as the los pelambres abanico or coya machali formations ranges from basalt to rhyolite in composition and exhibits a broad southward transition from calc alkaline to tholeiitic all samples from this formation are characterized by lree enrichment and moderately or locally strongly fractionated hree la smn 1 3 4 1 sm ybn 1 5 5 8 the basaltic andesites and andesites of the middle miocene salamanca formation have ree chemistry similar to that of the upper cretaceous strata la smn 1 5 2 7 sm ybn 1 6 2 7 the overlying middle miocene farellones formation ranges from tholeiitic to calc alkaline and from basalt to andesitic and has a similar lree enrichment and fractionated hree la smn 1 7 2 5 sm ybn 1 7 3 3 the pliocene la copa rhyolite complex however is strongly lree enriched and hree depleted la smn 3 8 3 9 sm ybn 4 2 4 7 overall the trace element geochemistry of the cretaceous to middle miocene volcanic rocks is characterized by enriched lree and negative nb anomalies consistent with an arc setting with only minor differences in the abundance of most elements crustal thickening during the miocene in central chile has been suggested to have been responsible for a transition from an amphibole to garnet dominated residual mineralogy resulting in the release of fluids that enabled the formation of giant copper porphyry deposits however the gradual increase in la yb through the early middle and late miocene reported in earlier studies and interpreted to be a response to crustal thickening is not observed in the regional data instead a rapid change in the geochemical signature between the end of the eruption of the farellones formation and the eruption of the high la yb la copa rhyolite complex implies a more abrupt change in the tectonic environment isotopic data broadly support this although lower epsilon nd values in the farellones formation imply a greater role for crustal contamination in younger suites in the absence of gradual crustal thickening it is suggested that the subduction of the juan fernandez ridge may have been the key geodynamic process responsible for the genesis of the three middle miocene to lower pliocene giant porphyry copper deposits in central chile possibly by promoting crustal scale faulting and even acting as a source of metals

model based interpretation of sediment concentration and vertical flux measurements in a shallow estuarine environment a one dimensional numerical model describing tidally varying vertical mixing and settling was used to interpret sediment concentrations and vertical fluxes observed in the shoals of south san francisco bay by two acoustic doppler velocimeters advs at elevations of 0 36 m and 0 72 m above bed measured sediment concentrations changed by up to 100 g m 3 over the semidiurnal tidal cycle these dynamics were dominated by local resuspension and settling multiple particle class models suggested the existence of a class with fast settling velocities ws of 9 0 10 4 m s 1 in spring and 5 8 10 4 m s 1 in fall and a slowly settling particle fraction ws of 1 10 7 m s 1 in spring and 1 4 10 5 m s 1 in fall modeled concentrations of slowly settling particles at 0 36 m were as high as 20 g m 3 during fall and varied with the spring neap cycle while fine sediment concentrations in spring were constant around 5 g m 3 analysis of in situ water column floc size distributions suggested that floc properties in the lower part of the water column were most likely governed by particle size distribution on the bed and not by coagulation validating our multiple particle size approach a comparison of different sediment bed models with respect to model performance sensitivity and identifiability suggested that the use of a sediment erosion model linear in bottom shear stress b e m b c was the most appropriate choice to describe the field observations when the critical shear stress c and the proportionality factor m were kept constant

characteristics and origins of coal cleat a review abstract cleats are natural opening mode fractures in coal beds they account for most of the permeability and much of the porosity of coalbed gas reservoirs and can have a significant effect on the success of engineering procedures such as cavity stimulations because permeability and stimulation success are commonly limiting factors in gas well performance knowledge of cleat characteristics and origins is essential for successful exploration and production although the coal cleat literature spans at least 160 years mining issues have been the principal focus and quantitative data are almost exclusively limited to orientation and spacing information few data are available on apertures heights lengths connectivity and the relation of cleat formation to diagenesis characteristics that are critical to permeability moreover recent studies of cleat orientation patterns and fracture style suggest that new investigations of even these well studied parameters can yield insight into coal permeability more effective predictions of cleat patterns will come from advances in understanding cleat origins although cleat formation has been speculatively attributed to diagenetic and or tectonic processes a viable mechanical process for creating cleats has yet to be demonstrated progress in this area may come from recent developments in fracture mechanics and in coal geochemistry

paleoclimate controls on late paleozoic sedimentation and peat formation in the central appalachian basin u s a abstract in the central appalachian basin at least two major climate changes affected sedimentation during the late paleozoic stratigraphically these two changes are indicated by the distribution of coal beds the variation in coal quality and the variation in rock lithologies in latest mississippian or earliest pennsylvanian time the climate changed from dry seasonal tropical to ever wet equable tropical the equable climate prevailed into the middle pennsylvanian influencing the morphology and geochemistry in peat forming environments many of the peat deposits which formed under the equable climate were probably domed raised bogs low concentrations of dissolved solids in peat formation water resulted in low buffering capacity organic acids caused acidic ph another climate change occurred in late middle pennsylvanian time when evapopation periodically exceeded rainfall resulting in an increase of both dissolved solids and ph 4 to 7 in surface and near surface water throughout the remainder of the pennsylvanian the surfaces of peat deposits were probably planar not domed water in peat forming and other depositional environments became more nearly neutral the coal beds derived from these peats are highly variable in both ash and sulfur contents drier or more seasonal climates are also indicated by sequences of 1 calcareous sandstone and shale 2 nonmarine limestone that shows shallow water and subaerial exposure features and 3 calcareous paleosols that have caliche characteristics our data and observations indicate that physical depositional environment models for the origin of coal do not adequately explain variations in mineral matter content and composition in commercial quality coal beds in the central appalachian basin stratigraphic variation in mineral matter in coal beds and in syngenetic and early diagenetic minerals in rocks associated with the coal beds appears to be better explained by changes in geochemical conditions of nonmarine sedimentation paleoclimate was a principle control on these geochemical conditions

modeling of cbm production co2 injection and tracer movement at a field co2 sequestration site sequestration of carbon dioxide in unmineable coal seams is a potential technology mainly because of the potential for simultaneous enhanced coalbed methane production ecbm several pilot tests have been performed around the globe leading to mixed results numerous modeling efforts have been carried out successfully to model methane production and carbon dioxide co sub 2 injection sensitivity analyses and history matching along with several optimization tools were used to estimate reservoir properties and to investigate reservoir performance geological and geophysical techniques have also been used to characterize field sequestration sites and to inspect reservoir heterogeneity the fate and movement of injected co sub 2 can be determined by using several monitoring techniques monitoring of perfluorocarbon pfc tracers is one of these monitoring technologies as a part of this monitoring technique a small fraction of a traceable fluid is added to the injection wellhead along with the co sub 2 stream at different times to monitor the timing and location of the breakthrough in nearby monitoring wells or offset production wells a reservoir modeling study was performed to simulate a pilot sequestration site located in the san juan coal basin of northern new mexico several unknown reservoir properties at the field site were estimatedmore by modeling the coal seam as a dual porosity formation and by history matching the methane production and co sub 2 injection in addition to reservoir modeling of methane production and co sub 2 injection tracer injection was modeled tracers serve as a surrogate for determining potential leakage of co sub 2 the tracer was modeled as a non reactive gas and was injected into the reservoir as a mixture along with co sub 2 geologic and geometric details of the field site numerical modeling details of methane production co sub 2 injection and tracer injection are presented in this paper moreover the numerical predictions of the tracer arrival times were compared with the measured field data results show that tracer modeling is useful in investigating movement of injected co sub 2 into the coal seam at the field site also such new modeling techniques can be utilized to determine potential leakage pathways and to investigate reservoir anisotropy and heterogeneity less

fracture and 3d seismic interpretations of the fruitland formation and cover strata implications for co2 retention and tracer movement san juan basin pilot test abstract this study presents data on faults and fractures in the fruitland formation and its cover strata at a carbon sequestration pilot site in the high rate fruitland coal fairway in the northeastern san juan basin the study incorporates satellite imagery fracture detection and shear wave anisotropy logs and 3d seismic to identify potential issues that could impact long term reservoir integrity co2 flow and retention the properties of fracture networks within the reservoir and sealing strata are important to understand in carbon sequestration and enhanced recovery efforts fracture networks exert significant control on the ability of a reservoir to retain co2 for long thousand year time frames with minimal leakage local structural complexity at the pilot site resulted in tracer migration patterns that differed from predictions based on regional descriptions of fracture and cleat orientations measured in areas several miles from the site perfluorocarbon pfc tracer breakthrough in the production stream of nearby producing wells for example occurred first in a well to the east in a direction close to the presumed butt cleat trend rather than in a well at equal distance along what had been assumed to be the more permeable face cleat trend the study reveals local tectonic complexity not suggested by well log derived structure maps of the area and suggests that fractures and faults disrupt the local fruitland coal reservoir and the overlying kirtland shale primary seal

co2 sequestration potential of charqueadas coal field in brazil abstract although coal is not the primary source of energy in brazil there is growing interest to evaluate the potential of coal from the south of the country for various activities the i2b coal seam in the charqueadas coal field has been considered a target for enhanced coal bed methane production and co 2 sequestration a detailed experimental study of the samples from this seam was conducted at the netl with assistance from the pontificia universidade catolica do rio grande do sul such properties as sorption capacity internal structure of the samples porosity and permeability were of primary interest in this characterization study the samples used were low rank coals high volatile bituminous and sub bituminous obtained from the i2b seam it was observed that the temperature effect on adsorption capacity correlates negatively with as received water and mineral content langmuir co 2 adsorption capacity of the coal samples ranged 0 61 2 09 mmol g the upper i2b seam appears to be overall more heterogeneous and less permeable than the lower i2b seam the lower seam coal appears to have a large amount of micro fractures that do not close even at 11 mpa of confining pressure

a traversing system to measure bottom boundary layer hydraulic properties this study describes a new convenient and robust system developed to measure benthic boundary layer properties with emphasis placed on the determination of bed shear stress and roughness height distribution within estuarine systems by using velocity measurements this system consisted of a remotely operated motorised traverser that allowed a single adv to collect data between 0 and 1 m above the bed as a case study we applied the proposed traversing system to investigate bottom boundary layer bbl hydraulic properties within coombabah creek queensland australia four commonly employed techniques 1 log profile lp 2 reynolds stress rs 3 turbulent kinetic energy tke and 4 inertial dissipation id used to estimate bed shear stresses from velocity measurements were compared bed shear stresses estimated with these four methods agreed reasonably well of these the lp method was found to be most useful and reliable additionally the lp method permits the calculation of roughness height which the other three methods do not an average value of bed shear stress of 0 46 n m2 roughness height of 4 3 mm and drag coefficient of 0 0054 were observed within coombabah creek results are consistent with that reported for several other silty bed estuaries

boundary layer turbulence and flow structure over a fringing coral reef measurements of velocity and rates of turbulence were made across a fringing coral reef in the gulf of aqaba red sea to determine the effect that the rough topography has on boundary layer mixing and flow dynamics observations were made at two fore reef sites and a nearby sandy slope the friction velocity u and drag coefficient cd were determined directly from turbulent reynolds stresses measured using acoustic doppler velocimeters values of cd for the coral substrates ranged from 0 009 to 0 015 three to five times greater than over the sandy bottom site the turbulence dissipation rate e was determined by fitting spectra of vertical velocity to the theoretical 5 3 law expected for the inertial subrange of turbulence there was a local balance between production and dissipation of turbulent kinetic energy signifying that we could estimate u from either the mean velocity profile turbulence or dissipation rate of turbulent kinetic energy estimates from all three measures agreed well with mean u uo ranging from 0 10 6 0 03 to 0 12 6 0 03 indicating that existing turbulent boundary layer flow theory can be applied to flows over the rough topography of coral reefs the bottom topography by enhancing both reef scale and local drag and mixing levels allows reef biota to more effectively exchange dissolved and particulate matter with oceanic waters

predicting suspended sediment concentration on continental shelves field observations of the near bottom suspended sediment concentration current and wave at a depth of 90 m on the washington shelf and at a depth of 1 5 m on the coastal beaufort sea show that wave induced oscillatory flow plays a dominant role in resuspending bottom sediment the suspended sediment concentration can be reasonably predicted from the measured flow data by applying a diffusion model good agreement between the predicted and observed concentrations is obtained by using a reference concentration proportional to the square root of the excess boundary shear stress for a sediment bed consisting of multiple grain sizes the differential rate at which material is eroded leads to a significant change in the surfacial grain size composition the fraction of the fine grain sediment in the surface layer decreases sharply with increasing boundary shear stress a procedure is presented to model this change of the grain size distribution in the surface layer the analysis indicates that neglecting the change of the surfacial grain size distribution with flow may overestimate the erosion depth by a factor of 10 at bottom orbital velocities exceeding 70 cm s 1

tracking changes in crustal thickness during orogenic evolution with sr y an example from the north american cordillera global compilations indicate that the geochemistry of arc magmatism is sensitive to moho depth magmatic products are prevalent throughout the history of cordilleran orogenesis and can be employed to constrain the timing of changes in crustal thickness as well as the magnitude of those changes we investigate temporal variations in crustal thickness in the united states cordillera using sr y from intermediate continental arc magmas our results suggest that crustal thickening began during the late jurassic to early cretaceous and culminated with 55 65 km thick crust at 85 95 ma crustal thicknesses remained elevated until the mid eocene to oligocene after which time crustal thicknesses decreased to 30 40 km in the miocene the results are consistent with independent geologic constraints and suggest that sr y is a viable method for reconstructing crustal thickness through time in convergent orogenic systems

measurements in the bottom boundary layer on the amazon subaqueous delta abstract an instrumented bottom tripod geoprobe recorded flow and suspended sediment data in the bottom boundary layer above the lower foresets of the amazon subaqueous delta in 65 m mean water depth in february 1990 after about two weeks of operation the apparent seafloor at the tripod site rapidly elevated over a 14 hour period by about 44 cm this sudden change which was detected by an acoustic altimeter and which caused the loss of signals from the lowermost geoprobe current and optical sensors is thought to have been caused by the incursion of a dense bottom layer of fluid mud that migrated downslope from shallower sections of the foresets the fluid mud migration across the outer part of the foresets if a repetitive and occasional process in this region could be a major mechanism for episodic seaward growth of the delta current velocity profiles are used to estimate shear velocities u and roughness lengths zo during the first two weeks of measurements the extremely energetic semi diurnal tidal motion required correction of the estimates of u and zo for acceleration average values of u and zo for the two week period were 1 7 cm s and 0 3 cm respectively the effects of strong stratification due to flocculated near bottom suspended sediment on the estimates of u are significant for the lower values of u u

fractional crystallization of primitive hydrous arc magmas an experimental study at 0 7 gpa differentiation of mantle derived hydrous basaltic magmas is a fundamental process to produce evolved intermediate to sio2 rich magmas that form the bulk of the middle to shallow continental and island arc crust this study reports the results of fractional crystallization experiments conducted in a piston cylinder apparatus at 0 7 gpa for hydrous calc alkaline to arc tholeiitic magmas fractional crystallization was approached by synthesis of starting materials representing the liquid composition of the previous higher temperature experiment temperatures ranged from near liquidus at 1 170 c to near solidus conditions at 700 c h2o contents varied from 3 0 to more than 10 wt the liquid line of descent covers the entire compositional range from olivine tholeiite 1 170 c to high silica rhyolite 700 c and evolves from metaluminous to peraluminous compositions the following crystallization sequence has been established olivine clinopyroxene plagioclase spinel orthopyroxene amphibole titanomagnetite apatite quartz biotite anorthite rich plagioclase and spinel are responsible for a marked increase in sio2 content from 51 to 53 wt at 1 040 c at lower temperatures fractionation of amphibole plagioclase and fe ti oxide over a temperature interval of 280 c drives the sio2 content continuously from 53 to 78 wt largest crystallization steps were recorded around 1 040 c and at 700 c about 40 of ultramafic plutonic rocks have to crystallize to generate basaltic andesitic liquids and an additional 40 of amphibole gabbroic cumulate to produce granitic melts andesitic liquids with a liquidus temperature of 1 010 c only crystallize 50 over an 280 c wide range to 730 c implying that such liquids form mobile crystal mushes 50 crystals in long lived magmatic systems in the middle crust allowing for extensive fractionation assimilation and hybridization with periodic replenishment of more mafic magmas from deeper magma reservoirs

tide induced sediment resuspension and the bottom boundary layer in an idealized estuary with a muddy bed abstract sediment transport and bottom boundary layer bbl in an idealized estuary with a muddy bed were studied by numerical simulations the focus was placed on description and prediction of the dynamics of nepheloid layer a fluid mud layer developed in the estuary because of the coupling effect of the seawater and resuspended sediment concentration the princeton ocean model was coupled to a sediment transport model to conduct the numerical experiments a semidiurnal tide with a spring neap cycle was used to force the model at the estuary entrance a stability function was introduced to the bottom drag coefficient cd for a slip bottom boundary condition in order to consider the effects of sediment induced stratification when the seawater density is not affected by the resuspended sediments spring tides resuspend sediments to the sea surface near the estuary entrance where the bottom stress is larger than the critical stress value the sediment distribution in the bbl near the entrance is dominantl

suspended sediment transport under estuarine tidal channel conditions abstract a modified version of the geoprobe tripod has been used to monitor flow conditions and suspended sediment distribution in the bottom boundary layer of a tidal channel within san francisco bay california measurements were made every 15 minutes over three successive tidal cycles they included mean velocity profiles from four electromagnetic current meters within 1 m of the seabed mean suspended sediment concentration profiles from seven miniature nephelometers operated within 1 m of the seabed near bottom pressure fluctuations vertical temperature gradient and bottom photographs additionally suspended sediment was sampled from four levels within 1 m of the seabed three times during each successive flood and ebb cycle while the instrument was deployed std nephelometer measurements were made throughout the water column water samples were collected each 1 2 hours and bottom sediment was sampled at the deployment site from these measurements estimates were made of particle settling velocity ws from size distributions of the suspended sediment friction velocity u from the velocity profiles and reference concentration ca was measured at z 20 cm these parameters were used in the suspended sediment distribution equations to evaluate their ability to predict the observed suspended sediment profiles three suspended sediment particle conditions were evaluated 1 individual particle size in the 4 11 62 5 0 5 m range with the reference concentration ca at z 20 cm c 2 individual particle size in the 4 6 size range flocs representing the 7 11 size range with the reference concentration ca at z 20 cm cf and 3 individual particle size in the 4 6 size range flocs representing the 7 11 size range with the reference concentration predicted as a function of the bed sediment size distribution and the square of the excess shear stress in addition computations of particle flux were made in order to show vertical variations in horizontal mass flux for varying flow conditions

turbulent stresses and secondary currents in a tidal forced channel with significant curvature and asymmetric bed forms acoustic doppler current profilers are deployed to measure both the mean flow and turbulent properties in a channel with significant curvature direct measurements of the reynolds stress show a significant asymmetry over the tidal cycle where stresses are enhanced during the flood tide and less prominent over the ebb tide this asymmetry is corroborated by logarithmic fits using 10 min averaged velocity data a smaller yet similar tendency asymmetry in drag coefficient is inferred by fitting the velocity and estimated large scale pressure gradient to a one dimensional along channel momentum balance this smaller asymmetry is consistent with recent modeling work simulating regional flows in the vicinity of the study site the asymmetry in drag suggests the importance of previously reported bed forms for this channel and demonstrates spatial and temporarily variations in bed stress secondary circulation patterns observed in a relatively straight section of channel appear driven by local curvature rather th

characteristics of suspended particles at an 11 hour anchor station in san francisco bay california hourly measurements of suspended sediment in situ floc size distributions constituent grain size distributions total concentrations and average particle densities are presented for five depths from an 11 hour anchor station in san francisco bay the flocs formed well sorted distributions with modal sizes between 100 and 500 m whereas the disaggregated sediment was poorly sorted with about the same volume of material in all size classes and relatively little material coarser than 100 m for both types of size spectra concentrations at the coarse end of the size distribution fall off rapidly at a size range which varied with bottom shear stress the settling rates corresponding to the modal floc diameters were generally related to the maximum disaggregated diameters by a square relationship but turbulence appeared to limit floc size in the coarsest samples both the floc and disaggregated grain size vary with total concentration suggesting that flocs are relatively stable entities which do not change during alternating settling and resuspension

low angle dunes in the changjiang yangtze estuary flow and sediment dynamics under tidal influence it has long been highlighted that important feedbacks exist between river bed morphology sediment transport and the turbulent flow field and that these feedbacks change in response to forcing mechanisms however our current understanding of bedform dynamics is largely based on studies of steady flow environments and cohesionless bed conditions few investigations have been made under rapidly changing flows here we examine flow and sediment dynamics over low angle dunes in unsteady flows in the changjiang yangtze estuary china topography flow and sediment data were collected over a reach ca 1 8 km long through a semi diurnal tidal cycle in a moderate tide of flood season the results show that 1 roughness length derived from the upper flow changes little with the flow reversing and displays the same value on both the ebb and flood tide moreover the variability of individual bedform features plays an important role in roughness length variation 2 shear stress over the crest of low angle dunes roughly represents the total spatially averaged stress over dunes in this study area which has significant implications for advancing numerical models 3 changes in morphology flow and sediment dynamics over dunes through time reveal how low angle dunes evolve within a tidal cycle 4 the clockwise hysteresis loops between flow dynamics and bedform features height and aspect ratio are also observed the combination of suspended sediment transport and bedload transport on dune transformation and migration attributes to the clockwise hysteresis the specific sediment composition of the riverbed in some extent affects the mechanism of sediment transport related to the exchange between suspended sediment and riverbed but further investigation is needed to figure out the mechanism behind this for extended series of tides such as spring neap tide and tides in flooding and dry season

estimates of bottom roughness length and bottom shear stress in south san francisco bay california a field investigation of the hydrodynamics and the resuspension and transport of particulate matter in a bottom boundary layer was carried out in south san francisco bay south bay california during march april 1995 using broadband acoustic doppler current profilers detailed measurements of turbulent mean velocity distribution within 1 5 m above bed have been obtained a global method of data analysis was used for estimating bottom roughness length zo and bottom shear stress or friction velocities u field data have been examined by dividing the time series of velocity profiles into 24 hour periods and independently analyzing the velocity profile time series by flooding and ebbing periods the global method of solution gives consistent properties of bottom roughness length zo and bottom shear stress values or friction velocities u in south bay estimated mean values of zo and u for flooding and ebbing cycles are different the differences in mean zo and u are shown to be caused by tidal current flood ebb inequality rather than the flooding or ebbing of tidal currents the bed shear stress correlates well with a reference velocity the slope of the correlation defines a drag coefficient forty three days of field data in south bay show two regimes of zo and drag coefficient as a function of a reference velocity when the mean velocity is 25 30 cm s 1 the ln zo and thus the drag coefficient is inversely proportional to the reference velocity the cause for the reduction of roughness length is hypothesized as sediment erosion due to intensifying tidal currents thereby reducing bed roughness when the mean velocity is 25 30 cm s 1 the correlation between zo and the reference velocity is less clear a plausible explanation of scattered values of zo under this condition may be sediment deposition measured sediment data were inadequate to support this hypothesis but the proposed hypothesis warrants further field investigation

the distribution and timing of molybdenite mineralization at the el teniente cu mo porphyry deposit chile this journal is published under the terms of green open access authors may post a copy of the accepted i e post peer review version of their paper https doi org 10 2113 econgeo 110 2 387 in a repository of their choice or to their personal website after the relevant embargo period has passed the embargo period will be 12 months from formal online publication

suspended particulate layers and internal waves over the southern monterey bay continental shelf an important control on shelf mud belts 1 physical and optical measurements taken over the mud belt on the southern continental shelf of monterey bay california documented the frequent occurrence of suspended particulate matter features the majority of which were detached from the seafloor centered 9 33 m above the bed in fall 2011 an automated profiling mooring and fixed instrumentation including a thermistor chain and upward looking acoustic doppler current profiler were deployed at 70 m depth for 5 weeks and from 12 to 16 october a long range autonomous underwater vehicle performed across shelf transects individual spm events were uncorrelated with local bed shear stress caused by surface waves and bottom currents nearly half of all observed spm layers occurred during 1 week of the study 9 16 october 2011 and were advected past the fixed profiling mooring by the onshore phase of semidiurnal internal tide bottom currents at the start of the 9 16 october period we observed intense near bed vertical velocities capable of lifting particulates into the middle of the water column this updraft event appears to have been associated with nonlinear adjustment of high amplitude internal tides over the mid and outer shelf these findings suggest that nonlinear internal tidal motions can erode material over the outer shelf and that once suspended this spm can then be transported shoreward to the middle and shallow sections of the mud belt this represents a fundamental broadening of our understanding of how shelf mud belts may be built up and sustained

physical properties of turbulent benthic boundary layers generated by internal waves physical properties of active turbulent benthic boundary layers tbbl generated by basin scale internal waves were studied within a northern hemisphere thermally stratified lake a microstructure profiler was used to measure the nature of the turbulence within the tbbls while a series of thermistor chains were used to monitor the thermal structure of the lake it was observed that a wind driven anticlockwise diurnal period vertical mode one kelvin wave generated large scale motions within the water column and that the interactions between this wave and the sloping lakebed induced tbbls a simple model based on potential energy change and boundary shearing was shown to describe the mean tbbl thickness

adakites without slab melting high pressure differentiation of island arc magma mindanao the philippines abstract new geochemical data for pleistocene magmatic rocks from the surigao peninsula eastern mindanao the philippines demonstrate typical adakitic traits including elevation of sr y and depletion of the heavy rare earth elements 87sr 86sr and 143nd 144nd ratios of the adakites do not support melting of the subducted philippine sea plate but resemble pliocene arc lavas generated in the same subduction zone excepting the heavy rare earth elements the adakites and arc lavas also possess similar ratios of incompatible elements suggesting that the adakites were ultimately derived from melting of the mantle wedge the wide range of sio2 in the adakites and its strong correlation with trace element concentrations and ratios indicate two possible mechanisms for generating the adakitic signature 1 adakitic melt was produced from basaltic arc magma by fractional crystallisation of a garnet bearing assemblage 2 solidified basaltic rock containing garnet melted to yield adakitic magma in either case the basaltic precursor was generated from fluid modified mantle then differentiated within the garnet stability field in surigao this requires differentiation within mantle the surigao example suggests that any subduction zone has the potential to produce adakitic magma if basalt crystallises at sufficient depth this has important implications for the geodynamics of modern and ancient subduction zones that have generated similar rocks

estimating bottom stress in tidal boundary layer from acoustic doppler velocimeter data bed stresses in the bottom boundary layer of the york river estuary virginia were estimated from three dimensional near bottom velocities measured by acoustic doppler velocimeters advs and also by a profiling array of electromagnetic current meters by assuming the measurements were made in a constant stress layer four methods of stress estimation were evaluated using advs direct covariance cov measurement turbulent kinetic energy inertial dissipation utilizing the kolmogorov spectrum and log profile the four methods yielded similar estimates of frictional velocity u based on adv output from both 14 cm and 44 cm above bed all eight estimates of average u were consistent with the overall mean of 1 10 cm s to within the 95 confidence interval for individual burst estimates the cov method worked slightly better nearer the bed possibly because of the sensitivity of cov to the upper limit of the constant stress layer the inertial dissipation method performed marginally well at 14 cm above bed likely because of sediment induced stratification and insufficient separation of turbulent production and dissipation scales the log profile method was the most variable and appeared most sensitive to stratification and to the thickness of the constant stress layer the turbulent kinetic energy method was the most consistent at both heights and appears most promising for further development results encourage future use of the adv in estuarine environments but also favor the simultaneous use of several methods to estimate bottom stress

variation of gas flow properties in coal with probe gas composition and fabric examples from western canadian sedimentary basin abstract flow properties permeability and diffusivity of subbituminous to high volatile bituminous coals from the horseshoe canyon and mannville formations of the western canada sedimentary basin have been investigated using both solid coal plugs and samples crushed to between 0 8 mm and 0 6 mm 20 30 mesh the coals examined have contents of vitrinite between 65 98 inertinite up to 31 and rare liptinite macerals permeability of crushed coal ranges from 1 46 10 5 md to 7 60 10 3 md whereas coal plug permeability is between 0 38 md to 0 01 md average diffusivity of crushed coal is estimated to be on the order of 10 11 m 2 s this difference of up to four orders of magnitude between crushed and coal plug permeability is attributed to different stress conditions during sample testing and the influence of coal cleat and coal fractures on coal plug permeability the permeability of crushed coal is influenced by coal matrix properties including maceral content and micro fabric the coals with greatest amount of inertinite have the greatest matrix permeability and diffusivity due to the greater macro and meso porosity of inertinite increasing effective stress with all other factors kept constant leads to a decrease in coal plug permeability coal plug permeability declines exponentially with increasing effective stress which is attributed to the closure of permeability pathways due to compaction of coal at high effective stress levels probe gas type influences plug permeability helium permeability measurements are higher than permeability measured with methane or nitrogen permeability difference with probe gas is attributed to a combination of different probe gas molecule size relative swelling effects of probe gas on coal and associated changes at in situ stress during tests

trace element partitioning between apatite and silicate melts we present new experimental apatite melt trace element partition coefficients for a large number of trace elements cs rb ba la ce pr sm gd lu y sr zr hf nb ta u pb and th the experiments were conducted at pressures of 1 0 gpa and temperatures of 1250 c the rare earth elements la ce pr sm gd and lu y and sr are compatible in apatite whereas the larger lithophile elements cs rb and ba are strongly incompatible other trace elements such as u th and pb have partition coefficients close to unity

experimental study of co2 brine rock interaction during co2 sequestration in deep coal seams abstract co 2 sequestration in deep coal seams is a potential option for reducing greenhouse gas emissions once co 2 is injected into coal seams sealing capability of the cap rock is critical to investigate and quantify reactions over time between co 2 cap rocks and brine associated with selected cap rocks of the no 3 coalbed of the qinshui basin in china batch experiments were conducted for reacting powdered rock samples 180 220 m with co 2 and brine as well as co 2 free brine at 160 c and 15 mpa the analysis of leachate chemistry indicated significant mobilization of major elements from dissolution of carbonate and silicate minerals in the coal measure strata analysis of reacted solids by xrd and sem also revealed appreciable changes in mineralogical compositions for lithic sandstone after reaction with co 2 brine the contents of quartz plagioclase illite and chlorite increased considerably whereas the contents of illite smectite biotite and kaolinite decreased more or less the calcareous mudstone reacting with co 2 brine and co 2 free brine all showed major mineralogical alteration after 12 days of treatment the modeling results identified key chemical processes but they also showed that the models are not capable of covering all possible contingencies the precipitation of carbonate minerals could also enhance the security of co 2 sequestration in deep coal seams

continuous measurements of discharge from a horizontal acoustic doppler current profiler in a tidal river 1 acoustic doppler current profilers adcps can be mounted horizontally at a river bank yielding single depth horizontal array observations of velocity across the river this paper presents a semideterministic semistochastic method to obtain continuous measurements of discharge from horizontal adcp hadcp data in a tidal river in the deterministic part single depth velocity data are converted to specific discharge by applying the law of the wall which requires knowledge of local values of the bed roughness length z0 a new filtration technique was developed to infer cross river profiles of z0 from moving boat adcp measurements width averaged values of z0 were shown to be predominantly constant in time but differed between ebb and flood in the stochastic part of the method specific discharge was converted to total discharge on the basis of a model that accounts for the time lag between flow variation in the central part of the river and flow variation near the banks model coefficients were derived using moving boat adcp data the consistency of mutually independent discharge estimates from hadcp measurements was investigated to validate the method analyzing river discharge and tidal discharge separately inaccuracy of the method is attributed primarily to mechanisms controlling transverse exchange of momentum which produce temporal variation in the discharge distribution over the cross section specifically development of river dunes may influence the portion of the discharge concentrated within the range of the hadcp

a model dependent method for inverting vertical profiles of scattering to obtain particle size spectra in boundary layers abstract a method for obtaining particle size spectra from vertical profiles of scattering strength in planetary boundary layers is presented it is assumed that the boundary layer is horizontally homogeneous and that the vertical turbulent diffusion of particles can be modeled from a knowledge of the surface friction velocity equilibrium boundary layer profiles for each class of suspended particles are assumed to be established resulting from the balance between vertical turbulent diffusion and gravitational settling the forward problem thus models the depth dependent scattering as the sum across size classes weighted by number density and scattering cross section in accordance with established scattering theory constrained inverses produce the size spectra results of inversions from synthetic ocean data are presented for optical transmissometry and acoustic backscattering inversions of acoustic field data from the hebble experiment are also presented finally the applications of the work presented for the design of ocean boundary layer experiments its application in other fields and the directions for future research are discussed

magnetic anomaly interpretation across the southern central andes 32 34 s the role of the juan fernandez ridge in the late tertiary evolution of the margin marine and terrestrial magnetic surveys have been integrated to study the tectonic structure of the convergent margin of chile between 32 34 s three magnetic domains have been identified oceanic continental margin and subaerial the oceanic domain has seafloor spreading anomalies 16 37 ma to 18 39 5 ma disturbed by anomalies of the juan fernandez hot spot chain in the continental margin the most prominent fabric are e w anomalies in the upper slope corresponding to onshore e w anomalies of large intrusive bodies onshore a n s lineament of short wavelength anomalies defines the roots of a cretaceous volcanic arc a resembling lineament offshore indicates a submerged older volcanic arc and that continental basement extends to 50 km landward of the trench absolute cenozoic plate motion for nazca and south american plates and dating of the juan fernandez chain provide a kinematic model of ridge continent collision the reconstruction indicates rapid southward migration of the collision point along 1400 km of the margin from 20 to 11 ma 20 cm yr 1 from 11 ma to present the collison point has migrated at a slower rate along 375 km of the margin 3 5 cm yr 1 the predicted location of the subducted portion of the juan fernandez chain coincides with the south edge of the southward migrating flat slab segment of the subducted lithosphere and with a cluster of deep earthquakes indicating a causal relationship in the last 10 myr the ridge has separated a sediment starved trench to the north where subduction erosion may dominate from a sediment filled trench to the south where recent sediment accretion dominates these observations indicate that subduction of the juan fernandez chain plays a major role in arc forearc tectonics

bottom stress estimates and their prediction on the northern california continental shelf during code 1 the importance of wave current interaction abstract high quality near bottom boundary layer measurements obtained at a midshelf location 90 m water depth in the code region off northern california are described bottom tripod velocity measurements and supporting data obtained during typical spring and early summer conditions june 1981 during code 1 are analyzed to obtain bath velocity profiles and mean bottom stress and bottom roughness estimates during the time period described the mean near bottom 0 997 approximately 30 percent of the time effects induced by unsteadiness from internal waves result in some degradation of the profiles 0 96 r 0 997 the rest of the time mean stress profiles indicate the logarithmic layer is approximately a constant stress layer the near bottom flow field is composed of mean currents and oscillatory currents due to well typing mean u values estimated from measurements greater than 30 cm above the bottom have magnitudes of 0 5 1 0 cm s 1 mean stress valu

biological interference of optical backscatterance sensors in tampa bay florida abstract optical backscatterance obs d a instruments inc 1 sensors for measuring suspended solids concentrations have been deployed in tampa bay to monitor resuspension of bottom sediments this paper describes biological factors that affected the obs sensors deployed in tampa bay and discusses deployment strategies that minimize biological interference phytoplankton may interfere with the obs sensors when the suspended solids concentration is near or below the sensor response threshold fish swimming in front of the obs sensors caused spikes in the obs sensor output so the median average was more appropriate than the mean average an algal slime on the obs sensors caused excessive backscatterance that dominated the backscatterance from suspended material because of the fouling problem deployments were limited to less than a week and obs sensors were cleaned daily if possible calibration of obs sensors with water samples collected from tampa bay was satisfactory when biological interference was not significant when properly deployed the obs sensors can successfully monitor sediment resuspension in tampa bay and similar subtropical estuaries

suspended sediment transport in an estuarine tidal channel within san francisco bay california abstract a recently developed instrumentation system has been used to monitor simultaneously flow conditions and suspended sediment distribution in the bottom boundary layer of a tidal channel within san francisco bay california measurements were made every 15 min over six successive flood and ebb tidal cycles they included mean velocity profiles from four electromagnetic current meters within 1 m of the seabed mean suspended sediment concentration profiles from seven miniature nephelometers placed within 1 m of the seabed near bottom pressure fluctuations vertical temperature gradient and bottom photographs additionally suspended sediment was sampled from four levels within 1 m of the seabed three times during the tidal cycle the instrument system was retrieved during each slack water period to exchange suspended sediment sample bags while the instrument was deployed std nephelometer measurements were made thoughout the water column and water samples were collected each 1 h and bottom sediment was sampled at the deployment site size distributions of the suspended sediment samples estimates of particle settling velocity s friction velocity u and reference concentration c a at z 20 cm were used in the suspended sediment distribution equations to evaluate their ability to predict the observed suspended sediment profiles three suspended sediment particle conditions were evaluated 1 individual particle sizes in the 4 11 62 5 0 5 m size range with the reference concentration c a at z 20 cm c 2 individual particle sizes in the 4 6 size range flocs representing the 7 11 size range with the reference concentration c a at z 20 cm c f and 3 individual particle sizes in the 4 6 size range flocs representing the 7 11 size range with the reference concentration predicted as a function of the bed sediment size distribution and the square of the excess shear stress an analysis was also carried out on the sensitivity of the suspended sediment distribution equation to deviations in the primary variables s u and c a in addition computations of mass flux were made in order to show vertical variations in mass flux for varying flow conditions

an instrument system for monitoring and sampling suspended sediment in the benthic boundary layer abstract an instrument system has been constructed that can monitor and sample suspended sediment distributions in the benthic boundary layer it consists of miniature nephelometers and suspended sediment samplers placed within one meter of the seabed the system is capable of continuously monitoring suspended sediment profiles at eight levels between 14 and 100 cm above the seabed and collecting suspended sediment samples at four levels 20 50 70 and 100 cm at three times during a deployment period the suspended sediment system is designed to fit onto the instrumented tripod geoprobe which contains four electromagnetic current meters pressure sensor bottom stereo camera two temperature sensors transmissometer and a savonius rotor current meter sensor operation data recording and sediment sampling events are synchronized thus detailed measurements of the near bottom flow conditions are made concurrently with suspended sediment measurements the combined system has been used in sediment transporting environments within san francisco bay california and puget sound washington

evidence for distinct stages of magma history recorded by the compositions of accessory apatite and zircon accessory minerals contain a robust and accessible record of magma evolution however they may reflect relatively late stage conditions in the history of the host magmas in the normally zoned criffell granitic pluton scotland whole rock wr compositions reflect open system assimilation and fractional crystallisation at depths of 11 km whereas amphibole barometry and the absence of inherited zircon suggest that the observed mineral assemblages crystallised following emplacement of magmas with little or no crystal cargo at depths of 4 6 km the crystallisation history is documented by large trace element variations amongst apatite crystals from within individual samples decreasing lree and th concentrations in apatite crystals from metaluminous samples reflect broadly synchronous crystallisation of allanite whereas lower lree and th and more negative nd anomalies in apatites from peraluminous samples reflect the effects of monazite crystallisation wr evolution is likely to have occurred within a deep crustal hot zone where h2o rich 6 wt low viscosity magmas segregated and ascended adiabatically in a super liquidus state leading to resorption of most entrained crystals stalling emplacement and crystallisation resulted from intersection with the h2o saturated liquidus at 4 km h2o contents are as important as temperature in the development of super liquidus magmas during ascent blurring distinctions between apparently hot and cold granites the trace element contents of most accessory minerals are controlled by competitive crystallisation of other accessory minerals in small melt batches consistent with the incremental assembly of large granitic plutons

predicting ripple roughness and sand resuspension under combined flows in a shoreface environment ripple measurements and flow and sediment dynamical data obtained from the shoreface of the middle atlantic bight using instrumented tripods were analyzed to evaluate various predictors of ripple geometry and roughness ripple roughness controls on sand resuspension and suspended sediment concentration profiles under combined waves and currents were also evaluated the limited observation of sand ripples in the field indicates that the grant and madsen 1982 method overestimates ripple roughness while the nielsen 1981 method tends to under predict ripple roughness a modified ripple predictor is thus proposed based on the grant and madsen method and it is shown to give reasonable predictions under the present experiment conditions this modified ripple prediction along with wave current and suspended sediment concentration data recorded by the tripods were then brought into the combined flow bottom boundary layer model of grant and madsen 1986 and the modified rouse equation of glenn and grant 1987 to calculate sand resuspension coefficient 0 and to predict suspended sediment concentration profiles it was found that under low energy fair weather conditions sand ripples are in the equilibrium range and ripple roughness increases with the bed shear stress this causes strong vortex activity close to seabed and thus higher resuspension coefficient reference concentrations are moderate due to this high resuspension coefficient even though bed shear stresses are low under moderate storm conditions ripple break off occurs and ripple roughness will decrease with bed shear stress this reduces the vortex activity and hence sand resuspension coefficient 0 the combination of this moderately high bed shear stress and reduced but still moderate ripple roughness favours sand suspension and produces the highest reference concentration for the encountered experimental conditions as bed shear stress is further increased ripples are nearly washed out and sand resuspension coefficient is further decreased approaching the previously suggested constant value of 1 3 10 4 this corresponds with the lowest reference concentration despite the high bed shear stress suspended sediment concentrations predicted by the modified rouse equation using this time variable resuspension coefficient and properly calculated bottom boundary layer parameters are reasonable compared to the field measured concentration profiles

discharge estimation from h adcp measurements in a tidal river subject to sidewall effects and a mobile bed horizontal acoustic doppler current profilers h adcps can be employed to estimate river discharge based on water level measurements and flow velocity array data across a river transect a new method is presented that accounts for the dip in velocity near the water surface which is caused by sidewall effects that decrease with the width to depth ratio of a channel a boundary layer model is introduced to convert single depth velocity data from the h adcp to specific discharge the parameters of the model include the local roughness length and a dip correction factor which accounts for the sidewall effects a regression model is employed to translate specific discharge to total discharge the method was tested in the river mahakam representing a large river of complex bathymetry where part of the flow is intrinsically three dimensional and discharge rates exceed 8000 m3 s 1 results from five moving boat adcp campaigns covering separate semidiurnal tidal cycles are presented three of which are used for calibration purposes whereas the remaining two served for validation of the method the dip correction factor showed a significant correlation with distance to the wall and bears a strong relation to secondary currents the sidewall effects appeared to remain relatively constant throughout the tidal cycles under study bed roughness length is estimated at periods of maximum velocity showing more variation at subtidal than at intratidal time scales intratidal variations were particularly obvious during bidirectional flow conditions which occurred only during conditions of low river discharge the new method was shown to outperform the widely used index velocity method by systematically reducing the relative error in the discharge estimates

apatite in igneous systems apatite is a minor but ubiquitous mineral in most igneous rocks although the modal proportion of apatite in common rocks is generally low it can reach high concentrations in enclaves cumulates and other rocks of low abundance i e rocks that constitute a small volume of the crust and mantle e g nelsonites the presence of apatite in most rocks is due not only to its low solubility in naturally occurring melts and aqueous solutions but also to the limited ability of common rock forming minerals to accept the amount of phosphorus that occurs in most rocks into their structure in this paper we will discuss some aspects of the occurrence texture composition physical chemistry and petrogenetic significance of apatite in felsic rocks i e andesite to rhyolite and their plutonic analogs in mafic i e basalts and related rocks and plutonic analogs and ultramafic rocks of the earth s crust and mantle fluorapatite is by far the most common member of apatite family found in igneous rocks however most natural fluorapatite contains some chlorine and hydroxyl as well and these constituents can attain high concentrations in some cases the other halogens bromine and iodine also occur in apatite but their concentrations are much lower than chlorine and fluorine many cations commonly substitute for calcium and phosphorus in apatite however they rarely reach concentrations that warrant the definition of a separate mineral species apatite can be described by the general formula a5 xo4 3z following sommerauer and katz lehnert 1985 the a site accommodates large cations e g ca2 sr2 pb2 ba2 mg2 mn2 fe2 ree3 eu2 cd2 na pan and fleet ch 2 in this volume and comprises two sites that exhibit vii fold

paleoclimate controls on stratigraphic repetition of chemical and siliciclastic rocks climate is a primary control on sediment flux from continental sources into sedimentary systems in warm climates siliciclastic input is greatest under highly seasonal rainfall nonseasonal conditions favor formation of end member chemical rocks perennially wet climates are conducive to coal formation whereas dry climates produce carbonates and or evaporites stratigraphic repetition of siliciclastic and chemical rocks therefore appears to be related to paleoclimate cycles as well as to transgressive regressive events and tectonics

adakite like signature of late miocene intrusions at the los pelambres giant porphyry copper deposit in the andes of central chile metallogenic implications adakite like features are recognized in the late miocene 10 ma porphyritic intrusions of the los pelambres giant porphyry copper deposit central chile 32 s located within the southern portion of the flat slab segment 28 33 s of the chilean andes the al and na rich porphyries of los pelambres display distinctly higher sr y 100 300 and lan ybn 25 60 ratios than contemporaneous and barren magmatic units e g la gloria pluton cerro aconcagua volcanic rocks of the same andean magmatic belt strong fractionation of heavy rare earth elements hree absence of eu anomalies high sr y and zr sm and low nb ta ratios suggest melt extraction from a garnet amphibolite source the late miocene adakite like porphyritic intrusions at los pelambres formed closely related in time and space to the subduction of the juan fernandez ridge jfr hotspot chain along the chilean margin current tectonic reconstructions reveal that at the time of formation of the los pelambres rocks a w e segment of the jfr started to subduct beneath them producing a slow down of a previously rapid southward migration of a ne ridge trench collision these particular tectonic conditions are favorable for the origin of the los pelambres porphyry suite by melting of subducting young hotspot rocks under flat slab conditions the incorporation of crustal components into the oceanic lithopheric magma source by subduction erosion is evidenced by the sr nd isotope composition of the los pelambres rocks different from the morb signatures of true adakites a close relationship apparently exists between the origin of this adakite like magmatism and the source of the mineralization in the los pelambres porphyry copper deposit

on the relationship between bedload and suspended sand transport on the inner shelf long island new york data obtained by a near bottom profiling concentration and velocity system pcv deployed in 10 m water depth at a site 1 km from the long island coastline are used to examine links between bedload and suspended sand concentrations calculations of bedload areal concentration c are based on the empirical results of vincent et al 1981 and use the theoretical formulations of grant and madsen 1978 1979 to describe the interaction between wave and current boundary layers suspended sand concentrations were obtained directly from an acoustic concentration meter acm average suspended sand profiles cz were found to fit closely to a log linear profile cz c1 1 a loge z z1 where c1 is the sand concentration at a height z1 1 cm from the bed and a is empirically determined as 0 22 0 005 a linear correlation is observed between the areal bedload concentration c the volume of bedload per unit area of the bed and the suspended sand concentration 1 cm above the bed c1 with a correlation coefficient of 0 82 significant at the 1 level and supports the hypothesis of einstein 1950 that bedload and suspended load are related through bedload concentration it is also shown that the sedment threshold criterion of komar and miller 1973 when expressed as a ratio here called the komar ratio can be used as a useful predictor for c1 under conditions where the wave orbital currents are much greater than the mean flow these relationships offer the opportunity for the calculation of both bedload and suspended sand transport rates from measurements of the steady current velocity and wave parameters combined with information defining the surficial sediments and local bottom topography

high sr y arc magmas and porphyry cu mo au deposits just add water porphyry cu mo au deposits are commonly associated with intermediate composition arc related igneous rocks with high sr y and la yb ratios and such rocks are equated by some researchers with melts derived from subducted oceanic crust undergoing eclogite facies metamorphism adakites however similar geochemical characteristics are readily developed in normal asthenospheric mantle wedge derived magmas by fractionation of amphibole and or garnet and or by interaction with crustal materials during ascent through the upper plate lithosphere while there is widespread evidence for such fractionation and contamination processes in porphyry magmas there is little direct evidence for an origin by slab melting the enhanced fertility of arc magmas relates primarily to their high water content which is required for the formation of magmatic hydrothermal systems upon shallow crustal emplacement magmatic water contents 4 wt percent h 2 o cause abundant amphibole garnet fractionation but suppression of plagioclase crystallization at deep crustal levels resulting in increasing sr y and la yb ratios with differentiation commonly into adakitic ranges but not reflecting slab melting additional factors that affect arc magma fertility are relatively high oxidation states and sulfur content but these are secondary to the requirement for sufficient water thus arc magmatic suites with high sr y ratios and evidence for the presence of hydrous phenocryst phases hornblende and or biotite are indeed prospective for porphyry cu mo au deposits but only because these parameters indicate high magmatic water content