scales and dynamics of submesoscale coherent vortices formed by deep convection in the northwestern mediterranean sea since 2010 an intense effort in the collection of in situ observations has been carried out in the northwestern mediterranean sea thanks to gliders profiling floats regular cruises and mooring lines this integrated observing system enabled a year to year monitoring of the deep waters formation that occurred in the gulf of lions area during four consecutive winters 2010 2013 vortical structures remnant of wintertime deep vertical mixing events were regularly sampled by the different observing platforms these are submesoscale coherent vortices scvs characterized by a small radius 5 8 km strong depth intensified orbital velocities 10 20 cm s 1 with often a weak surface signature high rossby 0 5 and burger numbers o 0 5 1 anticyclones transport convected waters resulting from intermediate 300 m to deep 2000 m vertical mixing cyclones are characterized by a 500 1000 m thick layer of weakly stratified deep waters or bottom waters that cascaded from the shelf of the gulf of lions in 2012 extending down to the bottom of the ocean at 2500 m the formation of cyclonic eddies seems to be favored by bottom reaching convection occurring during the study period or cascading events reaching the abyssal plain we confirm the prominent role of anticyclonic scvs and shed light on the important role of cyclonic scvs in the spreading of a significant amount 30 of the newly formed deep waters away from the winter mixing areas since they can survive until the following winter they can potentially have a great impact on the mixed layer deepening through a local preconditioning effect

sources of spatial complexity in two coastal plain soil landscapes abstract the spatial pattern of soils and soil properties in soil landscapes is considered here as a function of 1 systematic variation along catenas or associated with spatial patterns of soil forming factors and 2 local pseudo random variations associated with local disturbances or small unobserved variations in soil forming factors the problem is approached at two study sites in the u s atlantic coastal plain using algebraic graph theory and the spectral radius of the soil adjacency matrix as a measure of complexity the matrix is constructed based on the observed spatial contiguity of soil taxa and soil factor sequences sfs are defined for each site based on systematic soil variation associated with variations in parent material topography sandy surface thicknesses and secondary podzolization the spectral radii of the networks described by the adjacency graphs are compared to those associated with the maximum for a graph of the same size and the maximum associated with control entirely by variations in soil forming factors at the clayroot study site which is entirely cropland complexity of the adjacency matrix is less than the maximum that could be accounted for by the four identified sfs due to redundant information in the sfs the littlefield site by contrast has a spectral radius greater than here where about half the site is forested the contingent variation is likely associated with effects of individual trees on soil morphology the utility of the adjacency analysis is in identifying whether soil heterogeneity is likely associated with sfs or with contingent factors not captured in sfs

extreme water mass anomaly observed in the hawaii ocean time series extremely anomalous water mass properties with deviations as high as 35 were observed in the thermocline during january 2001 at the hawaii ocean time series site north of oahu the spatial distribution of the anomalous waters is consistent with a submesoscale vortex with radius 15 km possibly a remnant of a mesoscale eddy the most plausible source location of the anomalous waters is offshore of mexico near baja california given the southwestward subtropical gyre circulation it is unlikely that these waters were transported directly westward to hawaii unusual northward transport of equatorial waters along the north american coast during the 1997 98 el nino event and subsequent transport southwestward in the core of a california undercurrent eddy is more plausible el nino modulation of eddy transport and diffusion of water mass properties may substantially impact the mean distribution of properties in the north pacific subtropical gyre

topographic vorticity generation submesoscale instability and vortex street formation in the gulf stream meanders and eddies are routinely observed in the gulf stream along the south atlantic bight we analyze here the instability processes that lead to the formation of submesoscale eddies on the cyclonic side of the gulf stream at the exit of the florida straits using very high resolution realistic simulations the positive relative vorticity and potential vorticity on the cyclonic side of the gulf stream are strongly intensified in the straits due to topographic drag along the continental slope the bottom drag amplifies the cyclonic shear by generating large positive vertical vorticity values within the sloped turbulent bottom boundary layer downstream from the straits the current becomes unstable to horizontal shear instability rolls up and forms a street of submesoscale vortices the vortices expand as they propagate northward along the shelf where they can generate large vertical displacements and enhance cross shelf exchanges

island wakes in deep water abstract density stratification and planetary rotation distinguish three dimensional island wakes significantly from a classical fluid dynamical flow around an obstacle a numerical model is used to study the formation and evolution of flow around an idealized island in deep water i e with vertical island sides and surface intensified stratification and upstream flow focusing on wake instability coherent vortex formation and mesoscale and submesoscale eddy activity in a baseline experiment with strong vorticity generation at the island three types of instability are evident centrifugal barotropic and baroclinic sensitivities are shown to three nondimensional parameters the reynolds number re rossby number ro and burger number bu the dependence on re is similar to the classical wake in its transition to turbulence but in contrast the island wake contains coherent eddies no matter how large the re value when re is large enough the shear layer at the island is so narrow that the ver

slope channel linkage and sediment delivery on north carolina coastal plain cropland this paper presents the results of field measurements conducted in a small 19 4 ha agricultural basin on the north carolina coastal plain the overall objective of the study is to determine the magnitude of soil erosion and sediment delivery as a result of storm runoff the results suggest that erosion in the region is more rapid and extensive than previously thought fields at the site are experiencing accelerated soil loss with rates often comparable to those of the southeastern piedmont a region long recognized as having rapid and problematic soil loss this casts doubt on some assessments of the coastal plain as being a stable non eroding landscape however much of the soil mobilized is redistributed and stored within the watershed with only a small portion of the soil eroded from slopes leaving the basin on an event time frame copyright 2002 john wiley sons ltd

the ribagorda sand gully east central spain sediment yield and human induced origin abstract gullies are developed under different climatic conditions and lithologies however those formed on sands have been scarcely described this paper reports the study of the ribagorda sand gully 2 57 ha in area east central spain the main objectives were to characterize and quantify its geomorphic dynamics and to trace its origin we described the landforms of the gully and measured the surface strength of the sand we monitored for six years the filling of the storage areas of three check dams built downstream from the gully and related it with rainfall characteristics we also described the nature of the sediments trapped by the dams and estimated the amount of sediment eroded since the gully formation finally we consulted historical records and maps to determine past land uses and transformations that may have affected the origin of the gully the study shows a high diversity of landforms denoting active processes consistent with a measured mean annual sediment yield of 114 mg ha 1 yr 1 a statistically significant relationship exists between the mass of sediment mg and 1 the total rainfall mm p 0 0007 or 2 the analysed rainfall intensities among five identified facies in the sedimentary wedge the sandy ones are predominant the total amount of sediment eroded by the ribagorda gully since its origin was 962 800 mg the results are unequivocal signs of an intense geomorphic activity within the gully with an alluvial fan type deposition in the dams we interpret that the ribagorda gully was initiated by deforestation after the 13th century when forests began to be intensively logged and before the 18th century when the gully was first indirectly described in print the age origin evolution and dynamics of this gully indicate that this landscape is currently evolving towards a new steady state after human disturbances over centuries given the gully evolution and local extent we suggest that no correction measures are needed for its management

variation in suspended sediment concentration during storm discharges in three small streams in upper osun basin central western nigeria the suspended sediment concentration response of three small streams draining quartzites and quartz schists in south western nigeria to storms of varying magnitude are presented a total of 1468 water samples from 62 storm responses with peak stream discharge values ranging from 80 to 120 l s 2 were analysed and storm and suspended sediment concentration hydrographs and hysteresis loops were used to depict the response patterns the six different types of responses identified include the single and multiple discharge peak rises with sediment lead and lag and also the mixed response patterns both valley slope and channel erosion constituted important sources of suspended sediment however sediment availability exhaustion and flushing effects determined the variation in the different response types

eddy topography interactions and the fate of the persian gulf outflow the persian gulf feeds a warm and salty outflow in the gulf of oman northern arabian sea the salt climatological distribution is relatively smooth in the gulf of oman and the signature of a slope current carrying salty waters is difficult to distinguish hundreds of kilometers past the strait of hormuz in contrast to other outflows of the world ocean this study focuses on the mechanisms involved in the spreading of persian gulf water pgw in the gulf of oman using a regional primitive equation numerical simulation the authors show that the dispersion of pgw occurs through a regime that is distinct from for example the one responsible for the mediterranean outflow dispersion the background mesoscale eddy field is energetic and participates actively to the spreading of pgw remotely formed eddies propagate into the gulf of oman and interact with the topography leading to submesoscales formation and pgw shedding eddy topography interactions are isolated in idealized simulations and reveal the formation of intense frictional boundary layers generating submesoscale coherent vortices scvs interactions take place at depths encompassing the pgw depth thus scvs trap pgw and contribute to its redistribution from the boundaries to the interior of the gulf of oman the overall efficiency of these processes is confirmed by a strong contribution of eddy salt fluxes in the interior of the basin and is quantified using particle statistics it is found to be a highly dispersive regime with an approximated eddy diffusivity of inline image

the effect of water on the viscosity of a haplogranitic melt under p t x conditions relevant to silicic volcanism the viscosities of hydrous haplogranitic melts synthesized by hydrothermal fusion at 2 kbar pressure and 800 to 1040 c have been measured at temperatures just above the glass transition and at a pressure of 1 bar using micropenetration techniques the micropenetration viscometry has been performed in the viscosity range of 109 pa s to 1012 pa s the samples ranged in water content from 0 4 to 3 5 wt for samples with up to 2 5 wt h2o the water contents have been determined using infrared spectroscopy obtained before and after each viscometry experiment to be constant over the duration of the measurements above this water content a measurable loss of water occurs during the viscometry the viscosity data illustrate an extremely nonlinear decrease in viscosity with added water the viscosity drops drastically with the addition of 0 5 wt of water and then shallows out at water contents of 2 wt an additional viscosity datum point obtained from the analysis of fluid inclusions in a water saturated hpg8 confirms a near invariance of the viscosity with the addition of water between 2 and 6 wt these measurements may be compared directly with the data of hess et al 1995 in press for the effects of excess alkali and alkaline earth oxides on the viscosity of hpg8 also obtained at 1 bar the viscosity of the melts compared on an equivalent molar basis increases in the order h2o li2o na2o k2o rb2o cs2o bao sro cao mgo beo the extraordinary decrease in melt viscosity with added water is poorly reproduced by the calculation scheme of shaw 1972 for the range of water contents investigated here the speciation of water in the quenched glasses can be used to quantify the dependence of the viscosity on hydroxyl content considering only the hydroxyl groups as active fluidizers in the hydrous melts the nonlinearity of the viscosity decrease and the difference with the effects of the alkali oxides becomes larger consequences for degassing calcalkaline rhyolite are discussed

hydrogeomorphic linkages of sediment transport in headwater streams maybeso experimental forest southeast alaska hydrogemorphic linkages related to sediment transport in headwater streams following basin wide clear cut logging on prince of wales island southeast alaska were investigated landslides and debris flows transported sediment and woody debris in headwater tributaries in 1961 1979 and 1993 widespread landsliding in 1961 and 1993 was triggered by rainstorms with recurrence intervals 24 h precipitation of 7 0 years and 4 2 years respectively occurrence distribution and downstream effects of these mass movements were controlled by landform characteristics such as channel gradient and valley configuration landslides and channelized debris flows created exposed bedrock reaches log jams fans and abandoned channels the terminus of the deposits did not enter main channels because debris flows spread and thinned on the unconfined bottom of the u shaped glaciated valley chronic sediment input to channels included surface erosion of exposed till rain splash sheet erosion and freeze thaw action and bank failures bedload sediment transport in a channel impacted by 1993 landslides and debris flows was two to ten times greater and relatively finer compared with bedload transport in a young alder riparian channel that had last experienced a landslide and debris flow in 1961 sediment transport and storage were influenced by regeneration of riparian vegetation storage behind recruited woody debris development of a streambed armour layer and the decoupling of hillslopes and channels both spatial and temporal variations of sediment movement and riparian condition are important factors in understanding material transport within headwaters and through channel networks copyright 2004 john wiley sons ltd

the influence of nonlinear mesoscale eddies on near surface oceanic chlorophyll oceanic rossby waves have been widely invoked as a mechanism for large scale variability of chlorophyll chl observed from satellites high resolution satellite altimeter measurements have recently revealed that sea surface height ssh features previously interpreted as linear rossby waves are nonlinear mesoscale coherent structures referred to here as eddies we analyze 10 years of measurements of these ssh fields and concurrent satellite measurements of upper ocean chl to show that these eddies exert a strong influence on the chl field thus requiring reassessment of the mechanism for the observed covariability of ssh and chl on time scales longer than 2 to 3 weeks the dominant mechanism is shown to be eddy induced horizontal advection of chl by the rotational velocities of the eddies

event based suspended sediment dynamics in a central new york watershed abstract using discharge and sediment data collected from 23 events between 2008 and 2010 in a 311 km2 watershed of central new york we investigated event sediment dynamics of the studied watershed after showing the statistical difference of the data in different seasons we examined the detailed hysteresis patterns of all events spring events had figure eight with anticlockwise figure 8 ac clockwise c anticlockwise ac and complicated patterns summer events had c ac figure 8 ac figure 8 c and complicated patterns fall and winter events had the same patterns as those in summer as well as a weak loop pattern the diversity of patterns within and between seasons suggests that detailed processes of sediment transport were not only complicated during one event but also varied from season to season although hysteresis analysis failed to identify these detailed processes and the associated sediment sources in such a relatively large watershed it successfully revealed a common feature dominating the transport processes event sediment transport was generally supply limited further analysis on the correlation between event sediment yield ssye and event peak discharge qpeak indicated that i events with clockwise patterns tended to have more ssye than those with other patterns for the same qpeak and ii data from all events may be statistically well described by a single ssye qpeak equation regardless of hysteresis patterns this equation i reveals that complicated event transport processes may be lumped into a simple process over events and ii reflects the general supply limited nature identified by hysteresis analysis using this equation and the magnitude frequency analysis we further discovered that in the past 21 years sediment was mainly transported by more frequent but relatively small discharges with the recurrence interval no more than 0 5 year

cooling rates and crystallization dynamics of shallow level pegmatite aplite dikes san diego county california pegmatites of the pala and mesa grande pegmatite districts san diego county california are typically thin sheet like composite pegmatite aplite dikes aplitic portions of many dikes display pronounced mineralogical layering referred to as line rock characterized by fine grained garnet rich bands alternating with albite and quartz rich bands thermal modeling was performed for four dikes in san diego county including the 1 m thick himalaya dike the 2 m thick mission dike the 8 m thick george ashley dike and the 25 m thick stewart dike calculations were based on conductive cooling equations accounting for latent heat of crystallization a melt emplacement temperature of 650 c into 150 c fractured gabbroic country rock at a depth of 5 km and an estimated 3 wt initial h 2o content in the melt cooling to 550 c at the center of each dike occurred in 9 years for the stewart dike 340 days for the george ashley dike 22 days for the mission dike and 5 days for the himalaya dike based on these calculations growth rates for large pegmatitic minerals such as the 10 cm long himalaya hanging wall tourmaline crystals may have been on the order of 10 5 cm s crystal size distribution csd studies of garnet from layered aplites suggest growth rates of about 10 6 cm s these results indicate that the dikes cooled and crystallized rapidly with variable nucleation rates but high overall crystal growth rates initial high nucleation rates coincident with emplacement and strong undercooling can account for the millimeter size aplite grains lower nucleation rates coupled with high growth rates can explain the decimeter size minerals in the hanging walls cores and miarolitic cavities of the pegmatites the presence of tourmaline and or lepidolite throughout these dikes suggests that although the melts were initially h 2o undersaturated high melt concentrations of incompatible or fluxing components such as b f and li h 2o aided in the development of large pegmatitic crystals that grew rapidly in the short times suggested by the conductive cooling models

quantification of nucleation delay in magmatic systems experimental and theoretical approach we developed a model to predict nucleation delay of olivine plagioclase and clinopyroxene in basaltic melts and alkali feldspar and quartz in felsic melts the model based upon classical nucleation theory was improved by applying modifications inspired by diffuse interface theory the theoretical calculations were compared to results available in the literature basalts and from new experiments on a hydrous 4 wt water metaluminous granitic composition conducted in piston cylinder apparatus at 600 mpa and temperatures from 500 to 800 c the experimental results and the modelled nucleation delays in silicate melts agree within a factor of 5 which creates an opportunity for better understanding of the nucleation kinetics and crystallization timing of melts of various compositions we demonstrate the implications of nucleation delay and discuss possible applications of this newly developed model to dry and hydrous felsic melts we present the nucleation delay of feldspar and quartz in dry rhyolitic melt and its influence on the formation of obsidian and we compare the nucleation delay of these minerals in a hydrous granitic melt against the typical internal structure of a granitic pegmatite dike

geographical variability of the first baroclinic rossby radius of deformation global 1 83 18 climatologies of the first baroclinic gravity wave phase speed c1 and the rossby radius of deformation l1 are computed from climatological average temperature and salinity profiles these new atlases are compared with previously published 5 83 58 coarse resolution maps of l1 for the northern hemisphere and the south atlantic and with a 1 83 18 fine resolution map of c1 for the tropical pacific it is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5 15 owing to seemingly minor computational errors geographical variations in the new high resolution maps of c1 and l1 are discussed in terms of a wkb approximation that elucidates the effects of earth rotation stratification and water depth on these quantities it is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c1 and l1 at any particular location in the world ocean this is rationalized from consideration of the wkb approximation

sims measurements of δ34s in sulfide minerals from adjacent vein and stratabound ores abstract the effects of sample matrix and secondary ion energy on the instrumental fractionation of sulfur isotopes have been studied for troilite pyrite and galena using the cameca ims 3f ion microprobe an analytical procedure is described for the measurement of 34 s on negatively charged sulfur ions from pyrite and galena with a reproducibility better than 1 5 sulfur isotope ratios were measured in pyrite and galena from adjacent stratabound manto orebodies and crosscutting veins in the hualgayoc district of northern peru isotopic compositions 34 s cdt of sulfur in pyrite and galena from vein and manto deposits have a total range from 20 to 10 sulfur in manto galenas has a wide range of isotopic compositions and is usually isotopically heavier than pyrite when both minerals have been analyzed in the same sample isotopic disequilibrium between pyrite and galena suggests precipitation from separate fluids consistent with textural evidence that galena is paragenetically later than pyrite and often replaces it formation of ore minerals in the veins appears to have overlapped temporally with the later stages of manto mineralization and continued after manto formation ceased sulfur isotope values in pyrite and galena from veins are lower by about 5 on average than the same sulfides in the mantos and 34 s values of vein galenas decrease over the course of vein formation this shift of 34 s toward lower values with time may be the result of increased mixing with sulfur from diagenetic sulfides or a decrease in the 34 s value of aqueous sulfide due to oxidation of the ore fluid in the later stages of deposition the latter hypothesis is favored because the lead isotopic compositions of the same vein minerals do not indicate an influx of sediment derived lead and because of the appearance of barite in the final stages of several vein deposits the majority of pyrite and galena analyses from vein and manto ores are compatible with precipitation from ore fluids having 34 s of aqueous sulfur of 0 5 this result indicates that the associated igneous rocks may have been the source of sulfur in the ore minerals as well as of lead low values of 34 s in manto galena may be accounted for by incorporation of sulfur derived from diagenetic iron sulfides

the influence of plant cover and land use on slope channel decoupling in a foothill catchment a case study from the carpathian foothills southern poland this paper examines the influence of plant cover and land use on slope channel decoupling in the stara rzeka stream catchment 22 4 km2 and its subcatchment dworski potok stream 0 3 km2 the stara rzeka catchment is situated in the marginal part of the carpathian foothills and is characterized by a relief of low and medium hills the catchment is used for agriculture but unlike other foothill catchments it has a relatively extensive unfragmented area of forests 41 3 per cent grasslands and pastures 13 8 per cent are mainly along the broad and flat valley floor in the cultivated area 38 5 per cent of the northern low hill part of the catchment the fields are long narrow and separated by boundary strips they stretch from the hilltops to the valley bottom and are traditionally ploughed along the slopes the research into slope wash was carried out at six sites downslope august 1989 to october 1990 and on experimental plots 1989 1991 transport of suspended matter was determined in the channels of the stara rzeka and dworski potok streams 1987 1991 the results show that transport and export of the material on the slopes depend on the morphology of the slope and on the agricultural use of the area the mosaic of fields which are used differently makes the soil wash process very intensive only if the slopes are ploughed and unprotected by a dense cover of vegetation the material displaced is mostly accumulated at the foot of the slopes or at the bottom of the valley footslope areas and flat valley bottoms covered with grass function as a barrier separating the slope and the river bed these features generally negate the transfer of slope originated material to the bed of the stream copyright 2002 john wiley sons ltd

gully erosion and sediment transport in a small subtropical catchment south china discharge and sediment concentration were monitored at two dams as well as gully erosion at four locations during 1988 1989 in the shenchong experimental basin 0 73 km2 located in subtropical deqing county guangdong province the temporal pattern of sediment concentration at the basin outlet is closely related to gully discharge and due to the proximity of the gully sediment source to the gauging station the hysteresis pattern at the lower dam is dominantly clockwise discharge thresholds exist in the sediment concentration discharge relationships at both the upper and the lower dams at the upper dam they are related to the presence of local wetlands which act as a buffer to sediment transport in the channel at the lower dam they result from variable sources of sediment as well as early flow cessation in gullies computation of sediment yield from gullies confirms that they accounted for over 85 of the sediment load that passed through the lower dam

event sequence and sediment exhaustion in the lower panuco basin mexico abstract although large tropical river systems transport the majority of the world s runoff and sediment few studies have examined the dynamics of suspended sediment transport in this setting this includes mexico which contains two of the larger river basins draining into the gulf of mexico this study provides a detailed analysis of discharge q and suspended sediment transport dynamics for the lower panuco basin 98 227 km2 of eastern mexico including the lower moctezuma lower tamuin and panuco rivers daily values of discharge and suspended sediment concentration ssc are examined for three stations spanning from the late 1950s to early 1990s although the panuco is a large basin the relationship between discharge and suspended sediment concentration represents a departure from the oft reported study by heidel trans am geophys union 37 1956 56 instead of sediment lagging discharge the sediment wave precedes discharge by an average of 1 7 days displaying pronounced clockwise positive hysteresis this may be due to the sources of runoff and sediment which are derived primarily in the lower reaches of the basin because of precipitation patterns geology and basin morphometry the distinct differences in lithology between the tamuin and moctezuma basins which join in the coastal plain to form the rio panuco allow the influence of geologic setting to be considered q ssc relations display positive hysteresis where the sediment is derived from erodible tertiary shale deposits in the moctezuma basin in contrast q ssc relations in the rio tamuin which transports less suspended sediment because of its karstic setting are more linear due to these relations being dependent on the entrainment of bed material consideration of the sequence of events during the rainy season suggests that much of the hillslope derived sediment is flushed through the system by early events which would occur because of exhaustion of hillslopes sediments q ssc relations are increasingly linear during later events in the rio panuco which is likely due to these events transporting a higher proportion of sediment entrained from the channel this is manifest by a reduction in lead times as the number of days between peak ssc and peak q for early and late events significantly decreases from 2 6 to 0 9 respectively large events 750 m3 s in the latter part of summer and early fall having high suspended sediment concentrations could be due to the replenishment of hillslope sediments or due to the contribution of sediment from source areas that were not previously exhausted the findings from this study are likely common to most drainage systems having seasonal bimodal streamflow regimes whereas the seasonal signature of q ssc relations is likely enhanced in those settings where agriculture is a major component of the landscape

fluvial sediment delivery to a coastal plain estuary in the atlantic drainage of the united states abstract drastic changes in sediment production in drainage basins can have significant impacts on sediment yield to estuaries however significant but less spectacular changes in fluvial sediment regimes have not greatly influenced sediment output of some rivers in the united states atlantic drainage the limited influence of moderate or incremental changes in fluvial sediment systems on estuarine sediment delivery may be attributable to the large proportion of eroded sediment which is stored within the basins and the transport limited nature of long term sediment yields a sediment budget for the pee dee river basin and waccamaw river winyah bay estuary of the carolinas shows that only a small proportion of gross eroded sediment within the basin about 4 reaches the estuary on an average annual basis because the system appears to be transport limited it is estimated that an 88 reduction in the quantity of eroded sediment reaching streams would be necessary to produce significant change in sediment yield to the estuary any increase in sediment production would not be reflected at all in the estuary unless it was accompanied by a corresponding increase in fluvial sediment conveyance capacity estuarine sedimentary records thus may not reflect some significant changes in fluvial sediment systems

the physical and chemical evolution of fluids in rare element granitic pegmatites associated with the lacorne pluton quebec canada abstract co magmatic rare element be li nb ta granitic pegmatites associated with the lacorne monzogranite pluton of the preissac lacorne batholith quebec range from a least evolved beryl type in the pluton through a transitional beryl spodumene type to a most evolved spodumene type in mafic country rocks they possess internal lithologic fabrics and primary fluid inclusions that provide evidence for saturation of the magma with aqueous fluids immediately after the formation of aplite in the beryl pegmatite and pene contemporaneously with formation of the beryl spodumene and spodumene pegmatites the early fluids are represented by aqueous liquid vapor type 1a and aqueous liquid vapor solid type 2 inclusions in beryl from beryl and beryl spodumene pegmatites and are estimated to have been trapped between 500 and 550 c and at 3 5 kb on the basis of microthermometric measurements analyses of the compositions of the precipitates from decrepitated inclusions and the nature of the solids trapped these fluids are interpreted to have been nacl dominated 16 wt nacl eq and to have contained appreciable fe and dissolved co2 in spodumene pegmatite the equivalent fluid which was trapped at 450 to 500 c contained significant mn li and cs in place of fe consistent with corresponding trends in the chemical evolution of the host rock volatile rich mainly secondary aqueous fluid inclusions type 1b trapped in beryl are interpreted to reflect temporary sharp drops in pressure later in the crystallization history of the beryl bearing pegmatites due to local fluid overpressures that led to brecciation and consequent pressure release these inclusions have high salinity are cacl2 rich and are considered to represent magmatic hydrothermal fluids that acquired their calcium as a result of their interaction with the host lacorne pluton incursion of cacl2 rich fluids into the spodumene pegmatites is interpreted to have occurred earlier in their crystallization history i e upon emplacement of the pegmatites as shown by the fact that a high proportion of primary inclusions in spodumene in these pegmatites contains considerable calcium and calcium contents are generally higher in inclusions in spodumene than in beryl the inclusions in the spodumene pegmatites are thought to have acquired their calcium through interaction of the fluids with the amphibolites metabasalts that host these intrusions the crystallization of the pegmatites terminated with the entrapment of low salinity aqueous carbonic fluids type 3 inclusions in quartz 6 10 wt nacl eq which most likely formed as a result of the unmixing of the magmatic fluid into separate aqueous and carbonic fluids probably at temperatures between 250 and 350 c the results of this study show that aqueous fluid saturation can take place at an early stage of pegmatite emplacement and that magma evolution is matched by changes in the solute chemistry of the exsolving aqueous fluid they also show that evolution to a more volatile rich composition h2o f li may have contributed to the increased mobility of later magma batches thereby helping to explain the regional zonation of the pegmatites from beryl type within the pluton to spodumene type in the adjacent amphibolite

monitoring the crystallization of water saturated granitic melts in real time using the hydrothermal diamond anvil cell critical aspects of the crystallization dynamics of h2o saturated melts of a typical granitic composition as well as granitic melts enriched in lithium 8800 ppm were investigated in real time experiments using the hydrothermal diamond anvil cell at 480 700 c and 220 960 mpa complete crystallization of the charges was achieved within 5 118 h with average crystal growth rates ranging from 3 to 41 cm year for quartz and from 18 to 58 cm year for alkali feldspars demonstrating that crystals formed from a silicate melt in the presence of a coexisting aqueous phase crystallize rapidly the combination of substantial nucleation delays low nucleation densities and rapid growth rates for quartz and alkali feldspars led to the formation of euhedral megacrysts of these minerals in the vicinity of clusters comprised of much smaller muscovite or spodumene crystals subsolidus replacement processes initiated during crystal fluid interactions after the silicate melt was consumed were directly observed in the experiments the experimental results underscore the important role of water as a medium for the transport of essential elements such as si al na and k from the silicate melt to the newly formed crystals and provide important insights into the crystallization of miarolitic pegmatites

sediment concentration versus water discharge during single hydrologic events in rivers relations between sediment concentration c and water discharge q for a hydrologic event such as a flood are studied qualitatively by analyzing smoothed temporal graphs discharge and concentration vs time in terms of mode spread and skewness comparing cq ratios at a given discharge on the rising and falling limbs of the discharge hydrograph provides a consistent reliable method for categorizing c q relations five common classes of such relations are single valued straight or curved clockwise loop counterclockwise loop single valued plus a loop and figure eight temporal graph mode and skewness influence the type of relation whereas temporal graph spread affects the details of the particular c q relation its graphical breadth shape orientation and plotted location field examples of the various types of relations are given including varieties that heretofore have received little attention such as the figure eight explanations for each type of c q relation are discussed

can oceanic submesoscale processes be observed with satellite altimetry high resolution 2 km and hourly observations of surface currents from high frequency radars are analyzed in terms of sea level anomalies sla and compared with data from two satellite altimeter ground tracks purpose is to investigate whether ocean submesoscale processes can be observed with satellite altimetry our results highlight two major problems that must be overcome before being able to resolve submesoscale processes with altimetry i signal contamination from high frequency motions and in particular from incoherent internal tides near inertial oscillations have no effect on sla and ii measurement noise which prevents the computation of accurate cross track currents on scales o 10 km the latter may be overcome by future satellite altimeter missions but the former will require taking into account the effect of mesoscale variability on internal tide propagation in regions where internal tides are significant citation chavanne c p and p klein 2010 can oceanic submesoscale processes be observed with satellite altimetry geophys res lett 37 l22602 doi 10 1029 2010gl045057

contrasting soils and landscapes of the piedmont and coastal plain eastern united states abstract the piedmont and coastal plain physiographic provinces comprise 80 percent of the atlantic coastal states from new jersey to georgia the provinces are climatically similar the soil moisture regime is udic the soil temperature regime is typically thermic from virginia through georgia although it is mesic at altitudes above 400 m in georgia and above 320 m in virginia the soil temperature regime is mesic for the piedmont and coastal plain from maryland through new jersey the tightly folded structurally complex crystalline rocks of the piedmont and the gently dipping layer cake clastic sedimentary rocks and sediments of the coastal plain respond differently to weathering pedogenesis and erosion the different responses result in two physiographically contrasting terrains each has distinctive near surface hydrology regolith drainage morphology and morphometry the piedmont is predominantly an erosional terrain interfluves are as narrow as 0 5 to 2 km and are convex upward valleys are as narrow as 0 1 to 0 5 km and generally v shaped in cross section alluvial terraces are rare and discontinuous soils in the piedmont are typically less than 1 m thick have less sand and more clay than coastal plain soils and generally have not developed sandy epipedons infiltration rates for piedmont soils are low at 6 15 cm h the soil saprolite soil rock and saprolite rock boundaries are distinct can be placed within 10 cm and are characterized by ponding and or lateral movement of water water movement through soil into saprolite and from saprolite into rock is along joints foliation bedding planes and faults soils and isotopic data indicate residence times consistent with a pleistocene age for most piedmont soils the coastal plain is both an erosional and a constructional terrain interfluves commonly are broader than 2 km and are flat valleys are commonly as wide as 1 km to greater than 10 km and contain numerous alluvial and estuarine terrace sequences that can be correlated along valleys for tens of kilometers coastal plain soils are typically as thick as 2 to 8 m have high sand content throughout and have sandy epipedons these epipedons consist of both a and e horizons and are 1 to 4 m thick in coastal plain soils the boundaries are transitional between the solum and the underlying parent material and between weathered and unweathered parent material infiltration rates for coastal plain soils are typically higher at 13 28 cm h than are those for piedmont soils indeed for unconsolidated quartz sand rates may exceed 50 cm h water moves directly from the soil into the parent material through intergranularpores with only minor channelization along macropores joints and fractures the comparatively high infiltration capacity results in relatively low surface runoff and correspondingly less erosion than on the piedmont uplands due to differences in piedmont and coastal plain erosion rates topographic inversion is common along the fall zone surfaces on cenozoic sedimentary deposits of the coastal plain are higher than erosional surfaces on regolith weathered from late precambrian to early paleozoic crystalline rocks of the piedmont isotopic paleontologic and soil data indicate that coastal plain surficial deposits are post middle miocene to holocene in age but most are from 5 to 2 ma thus the relatively uneroded surfaces comprise a pliocene landscape in the eastern third of the coastal plain deposits that are less than 3 5 ma include alluvial terraces marine terraces and barrier back barrier complexes as morphostratigraphic units that cover thousands of square kilometers isotopic and soil data indicate that eastern piedmont soils range from late pliocene to pleistocene in age but are predominantly less than 2 ma old thus the eroded uplands of the piedmont peneplain comprise a pleistocene landscape

exploring the effect of lithium on pegmatitic textures an experimental study the effect of lithium li on the development of pegmatitic textures was evaluated experimentally at h 2 o saturated and h 2 o undersaturated conditions at 500 mpa pressure and temperatures ranging from 400 to 800 c the addition of 3700 ppm li to a starting material of common granitic composition lake county obsidian reduces the crystallization and melting temperatures by approximately 50 70 and 200 c respectively and promotes the formation of quartz feldspar graphic and granophyric intergrowths the presence of li in the hydrous granitic system lowers significantly the degree of undercooling needed for the development of graphic and granophyric intergrowths to 85 110 c in comparison with the li free systems where approximately 200 c of undercooling is necessary the feldspar crystals developed in li bearing samples can incorporate from 150 to 250 ppm li assume skeletal and spherulitic morphologies and exhibit one order of magnitude faster growth rates than crystals in li free samples the results of this study attest to the effectiveness of li as a fluxing agent and highlight the crucial role it plays in the development of pegmatitic textures leading to important implications for the conditions of formation of li bearing granitic pegmatites

lithium and nd isotopic constraints on the origin of li poor pegmatite with implications for li mineralization abstract although volumetrically minor in the upper continental crust pegmatites host lots of rare metal mineralization e g li be pegmatites and associated mineralization were generally thought to originate from extreme differentiation of a parent granite system we propose an alternative model to interpret the genesis of pegmatite and factors controlling li mineralization based on combined nd and li isotopic studies on the li poor pegmatites barren from the qinghe pegmatite field of the altai orogen nw china the qinghe pegmatites show significantly varied nd isotopic compositions end t 4 3 1 7 which overlap the surrounding schists 6 5 1 5 but lower than the granites 2 2 9 of the orogen these data together with the low ree 3 3 41 ppm and absence of biotite in the pegmatites suggest they were not derived from extreme differentiation of a parent granite as traditionally thought but from low degrees of partial melting of the schists involving muscovite dehydration melting under amphibolite facies conditions the pegmatites are characterized by heavy li 7li 4 1 14 5 and low li abundance 3 6 50 ppm which contrast to that of local schist 7li 0 9 3 0 li 24 123 ppm and granite 7li 0 9 3 0 li 24 70 ppm and also to that of global li rich pegmatites 7li 1 0 10 li 500 ppm modeling study indicates that li poor pegmatites always have heavy li signature compared with li rich pegmatites due to the abundance of biotite in the source the formation of li rich pegmatite with li mineralization is attributable to the distinct source characteristics with abundant fluxing components like li na co32 and hco3 and sufficient alumina rich clay phases and the fluxing components probably originated from evaporate interlayers in the source

soil redistribution and pedologic transformations in coastal plain croplands in agricultural basins of the southeastern coastal plain there are typically large disparities between upland soil erosion and sediment delivered to streams this suggests that colluvial storage and redistribution of eroded soil within croplands is occurring and or that processes other than fluvial erosion are at work this study used soil morphology and stratigraphy as an indicator of erosion and deposition processes in a watershed at littlefield north carolina soil stratigraphy and morphology reflect the ways in which mass fluxes associated with cultivation transform the local soils fluvial aeolian and tillage processes were all found to be active in the redistribution of soil the soil transformations are of five general types first erosion and compaction in the cultivated area as a whole result in the thinning of arenic and grossarenic paleudults and paleaquults to form arenic typic and aquic paleudults and paleaquults second redistribution of surficial material within the fields results in transitions between arenic and typic or aquic subgroups as loamy sand a and e horizons are truncated or accreted third aeolian deposition at forested field boundaries leads to the formation of compound soils with podzolized features fourth sandy rill fan deposits at slope bases create cumulic soils distinct from the loamy sands of the source area or the darker finer terrace soils buried by the fan deposits finally tillage and fluvial deposition in upland depressions results in the gradual burial of rains poorly drained typic paleaquults soils results confirm the importance of upland sediment storage and redistribution and the role of tillage and aeolian processes as well as fluvial processes in the region copyright 1999 john wiley sons ltd

evidence for lithium aluminosilicate supersaturation of pegmatite forming melts new experimental data on the solubility of lithium li at spodumene lialsi2o6 and petalite lialsi4o10 saturation at 500 mpa and 550 750 c reveal evidence for lithium supersaturation of pegmatite forming melts before the formation of li aluminosilicates the degree of li enrichment in granitic melts can reach 11 000 ppm above the saturation value before the crystallization of li aluminosilicate minerals at lower temperatures comparison of the experimental results with the spodumene rich moblan pegmatite quebec is consistent with extreme li enrichment of the pegmatite forming melt prior to emplacement which cannot be explained with equilibrium crystallization of li aluminosilicates from a common granitic melt the results of this study support the model of disequilibrium fractional crystallization through liquidus undercooling as the most plausible mechanism for the generation of such li rich ore resources

sediment export by water from an agricultural catchment in the loam belt of central belgium abstract an agricultural drainage basin of 250 ha was selected in the belgian loam belt to evaluate sediment export by water water discharge was continuously measured at the outlet of the catchment and suspended sediment samples were taken proportional with discharge during rainfall events from these samples supended sediment concentration and grain size distribution were determined within the catchment regular surveys were conducted in order to obtain detailed data on vegetation cover soil surface parameters and erosion and sedimentation features important variations in sediment yield were detected at various time scales ranging from a year over a season to one event these variations could be linked with processes occurring within the catchment due to the development of a vegetation cover the suspended sediment concentrations were lower during the summer period than during the winter period for the same discharge the evolution in both suspended sediment concentration and grain size distribution during the winter period is explained by variations in the soil surface state of the fields as well as the development of a rill and gully network the positive hysteresis observed within a single event is explained by taking into account the distance between the sediment source and the catchment outlet and not by sediment flushing our analysis shows that the role of the main factors controlling the geomorphic response of such a catchment can be identified only if measurements at the outlet are complemented by detailed data on the conditions within the catchment catchment model calibration and validation are therefore impossible if this information is lacking

somali current rings in the eastern gulf of aden 1 new satellite based observations reveal that westward translating anticyclonic rings are generated as a portion of the somali current accelerates northward through the socotra passage near the mouth of the gulf of aden rings thus formed exhibit azimuthal geostrophic velocities exceeding 50 cm s are comparable in overall diameter to the width of the gulf of aden 250 km and translate westward into the gulf at 5 8 cm s ring generation is most notable in satellite ocean color imagery in november immediately following the transition between southwest boreal summer and northeast winter monsoon regimes the observed rings contain anomalous fluid within their core which reflects their origin in the equator crossing somali current system estimates of socotra passage flow variability derived from satellite altimetry provide evidence for a similar ring generation process in may following the winter to summer monsoon transition cyclonic recirculation eddies are observed to spin up on the eastern flank of newly formed rings with the resulting vortex pair translating westward together recent shipboard and lagrangian observations indicate that vortices of both sign have substantial vertical extent and may dominate the lateral circulation at all depths in the eastern gulf of aden

truncation and accretion of soil profiles on coastal plain croplands implications for sediment redistribution soil stratigraphy and morphology in a small agricultural watershed on the coastal plain at clayroot north carolina indicate long term decadal scale patterns of the redistribution of sediment the most dramatic truncation of the soil profile occurs on convex upper slopes and suggests tillage and aeolian erosion as the major processes of soil loss thicker soils immediately downslope from convexities are consistent with redistribution by tillage but significant aeolian soil loss also occurs from some fields thinner apparently truncated soils were also associated with relatively steeper lower slope areas where contemporary rilling was observed the presence of thicker cumulic soils at toeslopes where small fans are observed at rill termini and about a half meter of alluvium in drainage ditches indicates that water erosion is also quite prominent distinctive soil stratigraphy is found in areas of aeolian deposition where podzolization in sandy surface deposits has created compound soil profiles on convex slopes tillage and wind erosion result in net soil loss with the former dominating on wetter soils and when plowing occurs and aeolian processes dominating on drier hilltops and when no till or minimum tillage practices are followed soils are thicker immediately downslope from convexities with thinner soils and rill erosion on lower slopes thickened soils and colluvial deposition in the form of thin fan deposits occur at toeslopes and in depressions the borders of fields often have thicker soils because of aeolian deposition water wind and tillage processes are all significant in soil redistribution at the clayroot site with relative importance in space and time controlled by topography soil properties seasonal moisture and vegetative cover and tillage practices

sediment budgets for a sediment laden river the lower wei river in the period 1960 1990 fluvial sediment delivery is the main form of sediment transfer from the land to the sea but this process is currently undergoing significant variations due to the alteration of catchment and base level controls related to climate change and human activities especially the widespread construction of dams using the lower wei river as an example and an integrated approach this study investigates the variation of fluvial sediment delivery as well as the connectivity under the effects of both controls based on hydrological records and channel cross section surveys sediment budgets were constructed for two periods 1960 1970 1970 1990 after the dam was closed in 1960 in the period 1960 1969 due to the elevated base level 327 2 1 62m caused by the dam the aggradation rate was 0 451x10 8 tyr 1 in the channel and 0 716x10 8 tyr 1 on the floodplain indicating that the positive lateral connectivity between these locations was enhanced as a consequence serious sediment storage resulted in a sediment delivery ratio sdr that was smaller than that occurring before 1960 in the period 1970 1990 sweeping soil and water conservation swc measures were implemented resulting in a reduction of the connectivity between the trunk and tributaries and a decrease of similar to 31 in the mean sediment input in addition together with the base level fluctuation in the range of 327 47 0 49m the annual variation in sediment storage was primarily dependent on the water sediment regime affected by the swc the negative lateral connectivity was enhanced between the channel and floodplain via bank erosion consequently the aggradation rate was reduced by 89 on the floodplain and by 96 in the channel sediment output continued to decrease primarily due to the swc practices and climate changes in this period whereas the sdr increased due to the enhanced longitudinal connectivity between the upstream and downstream copyright c 2014 john wiley sons ltd

slope channel decoupling in wolumla catchment new south wales australia the changing nature of sediment sources following european settlement within a few decades of european settlement channel incision transformed discontinuous river courses throughout wolumla catchment on the south coast of new south wales australia the development of continuous channels greatly increased sediment delivery from the catchment this paper documents the character timing and proportion of sediment sourced from upland valley fills channel expansion sites and gully networks volumes of material transferred from these sources are compared with estimates of sediment eroded from hillslopes and the movement of sediment off the slopes to the valley floor is assessed although disturbance of slopes resulted in significant movement of materials most of this material has been stored on slope in trapped tributary fills and along lower order drainage lines the slopes are effectively decoupled from the channel sediment accumulation in farm dams over the past few decades has been negligible around 75 of the total volume of material released from creeks in wolumla catchment since 1865 i e 5500 103 m3 has been derived from channel incision into valley fills at the base of the escarpment sediment flushing occurred within a few decades of catchment disturbance bedrock confinement in the middle and lower catchment resulted in very efficient downstream transfer of materials although gully networks and channel expansion sites have released a relatively small volume of material these sources are the greatest contemporary source of sediment in wolumla catchment

controls on chemical evolution and rare element enrichment in crystallising albite spodumene pegmatite and wallrocks constraints from mineral chemistry abstract internal differentiation and consequent geochemical evolution in pegmatites are significant processes in the development of economically viable deposits of metal bearing minerals albite spodumene pegmatites which represent important resources of li and ta worldwide challenge the general rules of pegmatite petrogenesis as these are nearly homogeneous bodies with little or no intrusion scale pegmatite zonation bulk intrusion concentrations of li are in the uppermost range obtained by magmatic enrichment experiments around 2 wt li2o and extensive volumes of saccharoidal or platy albite are present in leinster southeast ireland weakly zoned to homogeneous albitised spodumene pegmatites and their wallrocks were studied to compare mineral chemistry variations and understand the internal evolution of pegmatites characteristics linked to the poor development of zonation and links between internal evolution and pegmatite wallrock interactions leinster pegmatites present mineralogical textural and geochemical characteristics coherent with li saturation and possibly supersaturation prior to crystallisation weak border to centre zonation in the thickest bodies can be attributed to geochemically evolved initial melt likely leading to nearly contemporaneous crystallisation throughout the intrusion and resulting in limited internal geochemical fractionation increased abundance of minerals bearing highly incompatible elements e g columbite group minerals and cassiterite and network modifiers e g phosphates in albitite indicates it is a fractionation product from pegmatite crystallisation enrichment in incompatible elements b li rb cs and f in spodumene pegmatite exocontacts in different country rock types suggests unmixing of a hydrous fluid from the residual melt after the crystallisation of main pegmatitic assemblages and that the h2o rich component was mobilised into country rocks

anti clockwise hysteresis in suspended sediment concentration during individual storms holbeck catchment yorkshire england abstract analysis of the flow sediment hysteresis shape may assist in determining the sediment source area in a small basin a clockwise hysteresis occurs when sediment is derived from the bed and banks of the channel or areas adjacent to the channel whereas an anti clockwise hysteresis occurs when the upper part of the slopes is the sediment source area

mixed layer instabilities and restratification abstract the restratification of the oceanic surface mixed layer that results from lateral gradients in the surface density field is studied the lateral gradients are shown to be unstable to ageostrophic baroclinic instabilities and slump from the horizontal to the vertical these instabilities which are referred to as mixed layer instabilities mlis differ from instabilities in the ocean interior because of the weak surface stratification spatial scales are o 1 10 km and growth time scales are on the order of a day linear stability analysis and fully nonlinear simulations are used to study mlis and their impact on mixed layer restratification the main result is that mlis are a leading order process in the ml heat budget acting to constantly restratify the surface ocean climate and regional ocean models do not resolve the scales associated with mlis and are likely to underestimate the rate of ml restratification and consequently suffer from a bias in sea surface temperatures and ml depths in a

character and dynamics of the red sea and persian gulf outflows historical hydrographic data and a numerical plume model are used to investigate the initial transformation dynamics and spreading pathways of red sea and persian gulf outflow waters where they enter the indian ocean the annual mean transport of these outflows is relatively small 0 4 sv but they have a major impact on the hydrographic properties of the indian ocean at the thermocline level because of their high salinity they are different from other outflows in that they flow over very shallow sills depth 200 m into a highly stratified upper ocean environment and they are located at relatively low latitudes 12 n and 26 n furthermore the red sea outflow exhibits strong seasonal variability in transport the four main results of this study are as follows first on the basis of observed temperature salinity t s characteristics of the outflow source and product waters we estimate that the red sea and persian gulf outflows are diluted by factors of 2 5 and 4 respectively as they descend from sill depth to their depth of neutral buoyancy the high dilution factor for the persian gulf outflow results from the combined effects of large initial density difference between the outflow source water and oceanic water and low outflow transport second the combination of low latitude and low outflow transport and associated low outflow thickness results in ekman numbers for both outflows that are o 1 this indicates that they should be thought of as frictional density currents modified by rotation rather than geostrophic density currents modified by friction third different mixing histories along the two channels that direct red sea outflow water into the open ocean result in product waters with significantly different densities which probably contributes to the multilayered structure of the red sea product waters in both outflows seasonal variations in source water and oceanic properties have some effect on the t s of the product waters but they have only a minor impact on equilibrium depth fourth product waters from both outflows are advected away from the sill region in narrow boundary currents at least during part of the year at other times the product water appears more in isolated patches

mesoscale eddies in the gulf of aden and their impact on the spreading of red sea outflow water abstract the gulf of aden goa in the northwestern indian ocean is the receiving basin for red sea outflow water rsow one of the world s few high salinity dense overflows but relatively little is known about spreading pathways and transformation of rsow through the gulf here we combine historical data satellite altimetry new synoptic hydrographic surveys and the first in situ direct observations of subsurface currents in the goa to identify the most important processes in the spreading of rsow the new in situ data sets were collected in 2001 2003 as part of the red sea outflow experiment redsox and consist of two ctd ladcp surveys and 49 one year trajectories from acoustically tracked floats released at the depth of rsow the results indicate that the prominent positive and negative sea level anomalies frequently observed in the goa with satellite altimetry are associated with anticyclonic and cyclonic eddies that often reach to at least 1000 m depth i e through the depth range of equilibrated rsow the eddies dominate rsow spreading pathways and help to rapidly mix the outflow water with the background eddies in the central and eastern gulf are basin scale 250 km diameter and have maximum azimuthal speeds of about 30 cm s at the rsow level in the western gulf smaller eddies not detectable with satellite altimetry appear to form as the larger westward propagating eddies impale themselves on the high ridges flanking the tadjura rift both the hydrographic and lagrangian observations show that eddies originating outside the gulf often transport a core of much cooler fresher water from the arabian sea all the way to the western end of the goa where the highest salinity outflow water is found this generates large vertical and horizontal gradients of temperature and salinity setting up favorable conditions for salt fingering and diffusive convection both of these mixing processes were observed to be active in the gulf two new annually appearing anticyclonic eddies are added to the previously identified gulf of aden eddy gae prasad and ikeda 2001 and somali current ring scr fratantoni et al 2006 these are the summer eddy se and the lee eddy le both of which form at the beginning of the summer monsoon when strong southwest winds blowing through socotra passage effectively split the gae into two smaller eddies the se strengthens as it propagates westward deeper in the goa while the lee eddy remains stationary in the lee of socotra island both eddies are strengthened or sustained by ekman convergence associated with negative wind stress curl patches caused by wind jets through or around high orography the annual cycle in the appearance propagation and demise of these new eddies and those described in earlier work is documented to provide a comprehensive view of the most energetic circulation features in the goa the observations contain little evidence of features that have been shown previously to be important in the spreading of mediterranean outflow water mow in the north atlantic namely a wall bounded subsurface jet the mediterranean undercurrent and submesoscale coherent lenses containing a core of mow meddies this is attributed to the fact that the rsow enters the open ocean on a western boundary high background eddy kinetic energy typical of western boundary regimes will tend to shear apart submesoscale eddies and boundary undercurrents even if a submesoscale lens of rsow did form in the goa westward self propagation would transport the eddy and its cargo of outflow water back toward rather than away from its source

an index to distinguish surface and subsurface intensified vortices from surface observations in this study the authors first show that it is difficult to reconstruct the vertical structure of vortices using only surface observations in particular they show that the recent surface quasigeostrophy sqg and interior and surface quasigeostrophy isqg methods systematically lead to surface intensified vortices and those subsurface intensified vortices are thus not correctly modeled the authors then investigate the possibility of distinguishing between surface and subsurface intensified eddies from surface data only using the sea surface height and the sea surface temperature available from satellite observations a simple index based on the ratio of the sea surface temperature anomaly and the sea level anomaly is proposed while the index is expected to give perfect results for isolated vortices the authors show that in a complex environment errors can be expected in particular when strong currents exist in the vicinity of the vortex the validity of the index is then analyzed using results from a realistic regional circulation model of the peru chile upwelling system where both surface and subsurface eddies coexist the authors find that errors are mostly associated with double core eddies aligned surface and subsurface cores and that the index can be useful to determine the nature of mesoscale eddies surface or subsurface intensified from surface satellite observations however the errors reach 24 and some possible improvements of the index calculations are discussed

submesoscale vortical wakes in the lee of topography abstractan idealized framework of steady barotropic flow past an isolated seamount in a background of constant stratification with frequency n and rotation with coriolis parameter f is used to

piston cylinder calibration at 400 to 500 mpa a comparison of using water solubility in albite melt and nacl melting a crushable alumina pyrex nacl solid media assembly for the piston cylinder apparatus was calibrated by nacl melting at 500 mpa 920 c and used to assess a new calibration technique based upon the solubility of water in albite melt at 400 to 500 mpa 800 and 1200 c use of the difference from 100 technique to measure water solubility with the electron microprobe produces a calibration accuracy of 25 mpa both calibration techniques agree and demonstrate that the real pressure is 50 mpa greater than the nominal pressure the water solubility in albite calibration is advantageous because it can be used to demonstrate that pressure temperature and time have no effect on the pressure calibration additionally a single capsule containing albite water can act as an in situ pressure monitor in solid media assemblies containing other experiments these calibrations demonstrate that the piston cylinder apparatus can be used reliably at middle to upper crustal conditions for long duration experiments

global observations of large oceanic eddies 1 ten years of sea surface height ssh fields constructed from the merged topex poseidon t p and ers 1 2 altimeter datasets are analyzed to investigate mesoscale variability in the global ocean the higher resolution of the merged dataset reveals that more than 50 of the variability over much of the world ocean is accounted for by eddies with amplitudes of 5 25 cm and diameters of 100 200 km these eddies propagate nearly due west at approximately the phase speed of nondispersive baroclinic rossby waves with preferences for slight poleward and equatorward deflection of cyclonic and anticyclonic eddies respectively the vast majority of the eddies are found to be nonlinear

testing munk s hypothesis for submesoscale eddy generation using observations in the north atlantic a high resolution satellite image that reveals a train of coherent submesoscale 6 km vortices along the edge of an ocean front is examined in concert with hydrographic measurements in an effort to understand formation mechanisms of the submesoscale eddies the infrared satellite image consists of ocean surface temperatures at inline image m resolution over the midlatitude north atlantic 48 69 n 16 19 w concomitant altimetric observations coupled with regular spacing of the eddies suggest the eddies result from mesoscale stirring filamentation and subsequent frontal instability while horizontal shear or barotropic instability bti is one mechanism for generating such eddies munk s hypothesis we conclude from linear theory coupled with the in situ data that mixed layer or submesoscale baroclinic instability bci is a more plausible explanation for the observed submesoscale vortices here we assume that the frontal disturbance remains in its linear growth stage and is accurately described by linear dynamics this result likely has greater applicability to the open ocean i e regions where the gradient rossby number is reduced relative to its value along coasts and within strong current systems given that such waters comprise an appreciable percentage of the ocean surface and that energy and buoyancy fluxes differ under bti and bci this result has wider implications for open ocean energy buoyancy budgets and parameterizations within ocean general circulation models in summary this work provides rare observational evidence of submesoscale eddy generation by bci in the open ocean

spodumene pegmatites from the pusila pluton in the higher himalaya south tibet lithium mineralization in a highly fractionated leucogranite batholith abstract the himalayan leucogranite belt is evaluated as a prospect for rare metal mineralization the pusila pluton is located 44 km northwest of mount everest and consists of two mica granite muscovite granite albite granite and pegmatites numerous pegmatite dikes have intruded the higher himalayan crystalline sequence and the granites oligocene pegmatites in the chomogu and cuore areas which we constrain to have formed at ca 25 23 ma were investigated in this study because they are strongly enriched in li up to 8460 ppm and contain abundant spodumene petalite lithium was progressively enriched from the two mica granite to the muscovite granite and finally li mineralization occurred in the highly fractionated pegmatites the chomogu no 1 pegmatite is a well zoned dike that hosts beryl columbite cassiterite and li minerals which are concentrated in the inner parts of the dike scanning electron microscopy and cathodoluminescence images reveal two stages of li mineralization primary spodumene spd 1 crystallized in the magmatic stage whereas secondary spodumene spd 2 and petalite formed later in the hydrothermal stage the pusila pluton is thus an important site of li mineralization in the himalayan leucogranite belt

compact intrathermocline eddies in the sargasso sea we report observations of isolated lenses of constant temperature water embedded in the permanent thermocline in the sargasso sea these features are observed to have vertical extents of 220 m horizontal dimensions of 65 km and residence depths near 700 m a dynamic model is constructed which permits a balance among the pressure gradient coriolis and cyclostrophic forces and maintains the lens against gravitational collapse a result is that anticyclonic rim velocities approaching 20 cm s 1 are permitted and that these eddies have finite radii of the order of 50 km at which their thicknesses fall to zero

seasonal spreading of the persian gulf water mass in the arabian sea the characteristics of the subsurface salinity maximum associated with the persian gulf water mass pgw are used to quantify the spreading and mixing of pgw in the thermocline of the arabian sea based on a bimonthly climatology of temperature and salinity examination of the seasonal cycles of heat and freshwater fluxes in the persian gulf region indicates that pgw forms as a result of elevated evaporative cooling in conjunction with reduced insolation during winter maps are presented of the distributions of depth salinity and geostrophic flow on 26 5 which nearly coincides with the core of the pgw after intense mixing in the strait of hormuz the property fields suggest that warm 17 c and high salinity 36 2 psu pgw enters the arabian sea to form a subsurface salinity extremum between 200 and 300 m we have found variability in the distribution of pgw in the arabian sea associated with monsoonal changes in the arabian sea circulation during the winter monsoon there is southward spreading of pgw along the western boundary during summer it is not present lateral mixing with low salinity water from the bay of bengal in the region south of 10 n and along the west coast of india during winter accounts for changes in the characteristics of pgw along these paths associated with the findlater jet during summer the entire thermohaline structure is vertically displaced along the coasts of somalia and arabia ekman convergence in the central arabian sea accounts for deepening of the pgw either lateral or vertical mixing would cause changes in pgw properties in these regions during this time pgw spreads predominantly southward along the central arabian sea as indicated by a tongue of high salinity

isotope fractionation by chemical diffusion between molten basalt and rhyolite abstract experimental diffusion couples were used to study chemical diffusion between molten rhyolite and basalt with special emphasis on the associated fractionation of calcium and lithium isotopes diffusion couples were made by juxtaposing firmly packed powders of a natural basalt suny morb and a natural rhyolite lake county obsidian and then annealing them in a piston cylinder apparatus for times ranging from 0 1 to 15 7 h temperatures of 1350 1450 c and pressures of 1 2 1 3 gpa profiles of the major elements and many trace elements were measured on the recovered quenched glasses the diffusivities of all elements except lithium were found to be remarkably similar while the diffusivity of lithium was two to three orders of magnitude larger than that of any of the other elements measured chemical diffusion of calcium from molten basalt into rhyolite was driven by a concentration ratio of 18 and produced a fractionation of 44ca from 40ca of about 6 because of the relatively low concentration of lithium in the natural starting materials a small amount of spodumene lialsi2o6 was added to the basalt in order to increase the concentration difference between basalt and rhyolite which was expected to increase the magnitude of diffusive isotopic fractionation of lithium the concentration ratio between li doped basalt and natural rhyolite was 15 and the resulting diffusion of lithium into the rhyolite fractionated 7li from 6li by about 40 we anticipate that several other major rock forming elements such as magnesium iron and potassium will also exhibit similarly larger isotopic fractionation whenever they diffuse between natural melts with sufficiently large differences in the abundance of these elements

the suspended sediment dynamics in the inner mongolia reaches of the upper yellow river article i nfo suspended sediment dynamics are still imperfectly understood especially in the upper yellow river where few studies on this issue have been conducted this study analyzed the variability in suspended sediment concentration at different temporal scales within flood monthly seasonal and annual using a dataset up to 49 years long 1954 2002 at toudaoguai station this paper provided insight into the characteristics of suspended sediment transport in the ningxia inner mongolia reaches of the upper yellow river the results show that in a single flood event changes in ssc are not simultaneous with changes in discharge resulting in counterclockwise hysteretic loops clockwise loops or figure eight loops the c q loops and sediment rating curves for different seasons had different characters the diversiform c q loops in the inner mongolia reaches of the upper yellow river may be mainly caused by the sediment inputs from tributaries the differ ent propagation velocity of sediment and water discharge spatial and temporal storage depletion processes of available sediment at annual scale the variations of annual mean discharge and ssc displayed a similar gradually deceasing trend and the relation between water discharge and ssc during 1954 2002 could be de scribed by a cubic polynomial function since the joint operation of liujiaxia and longyangxia reservoirs after 1986 the transport capacity of the upper yellow river has been much reduced

crustal melts below 400 c we propose that the internally zoned li bearing tin mountain pegmatite in the harney peak granite pegmatite system of the black hills south dakota crystallized from fluid rich compositionally complex melts at 400 350 c the low crystallization temperatures resulted from the combined fluxing effects of li b p h 2 o and carbonate anions the presence of hydrous silicate melts at temperatures of 350 c is revealed by microthermometric data on primary fluid inclusions cogenetic with crystallized melt inclusions mineral assemblages of the crystallized melt inclusions and chemistry of bulk fluid leachates indicate that the melts and fluids contained significant amounts of li and na as carbonates and or borates that acted as powerful fluxes the low temperatures give a new perspective on the stability of silicate melts in the crust

geomorphic and sedimentological controls on the effectiveness of an extreme flood the 1993 flood on the upper mississippi river was a rare large magnitude hydrological event field and aerial survey analyses and landsat 5 thematic mapper data were used to appraise the thickness of overbank deposits on leveed and unleveed reaches results indicate that minimal 5 mm overbank sedimentation occurred except in the immediate vicinity of a levee break unleveed sections also lacked overbank sedimentation little geomorphological or sedimentological evidence of this extreme event is likely to be preserved this raises questions about the completeness of the stratigraphic record in situations where wide floodplains with cohesive soils provide effective resistance and dissipate energy so that erosion is minimized and or sediment supply is limited by event timing or sequencing a large flood may leave little or no substantive evidence of its occurrence

lithium isotope fractionation during fluid exsolution implications for li mineralization of the bailongshan pegmatites in the west kunlun nw tibet abstract granitic pegmatites are considered significant host rocks for the rare metal deposits however the enrichment mechanisms for the rare metal elements e g li be nb and ta remain debated here we report the whole rock and mineral e g muscovite and spodumene major trace elements and li isotopic compositions of the bailongshan granitic pegmatites in the west kunlun nw tibet to address this issue the bailongshan pegmatites hosting a super large li rb polymetallic deposit are composed of li poor and li rich pegmatites the li poor pegmatites display high 7li values in the whole rock 2 30 4 94 and muscovite 2 22 7 55 in contrast the li rich pegmatites show low 7li values in the whole rock 1 89 to 0 35 muscovite 3 39 to 4 49 and spodumene 2 83 to 1 87 these results together with the variations of the elements suggest that the li poor and li rich pegmatites were produced by the melt fluid separation during the late stage of granitic magma evolution this means that the li poor pegmatites were formed in a h2o poor silicate rich melt system while the li rich pegmatites were generated in a h2o rich silicate poor melt supercritical fluid system the melt fluid separation can lead to significant li isotope fractionation with 7li enriched in the strongly bonded residual silicate melt and 6li preferring to weaker hydrated bonds in the fluid alternatively the li rich pegmatites enriched in 6li could have been induced by preferential accumulation of the faster diffusing 6li in the supercritical or near critical fluid the li rich pegmatites experienced extensive crystal fluid interaction in a relatively closed magmatic hydrothermal system which resulted in the leaching and reprecipitation of ore forming elements but produced restricted li isotope fractionation the exsolved supercritical fluid is more enriched in alkali fluxing components li rb cs p and f by the continuous interaction with the residual silicate melt therefore the supercritical fluid exsolution plays an important role in the li isotope fractionation and rare metal mineralization

frequency analysis of annual maximum suspended sediment concentrations in abiod wadi biskra algeria sediment transport processes in the mediterranean semi arid areas have interested a great number of hydrologists and statisticians frequency analysis fa procedures are commonly applied for several hydrological events such as floods and droughts however in general fa is not widely applied to treat suspended sediment concentration ssc especially in semi arid regions in the present study an fa was performed on ssc data from 1979 to 1991 observed upstream from the foum el gherza dam which is located at biskra in the south east of algeria this dam is problematic in terms of silting therefore this study is mainly motivated by providing an fa model and risk evaluation in order to assist dam managers to better evaluate the potential of silting resulting from ssc transport to the reservoir probability distributions commonly used in hydrology were tested to ssc data recorded at the m chounech station on abiod wadi located upstream the dam all the fa steps were considered including classical techniques e g goodness of fit tests statistical criteria as well as recently developed tools tail distribution classification their application led to the selection of the lognormal distribution ln2 to fit the considered data and hence an accurate risk assessment could be obtained because of the presence of a slight trend non stationary models are also considered in the present study copyright 2013 john wiley sons ltd

nucleation and growth of bubbles on plagioclase crystals during experimental decompression degassing of andesitic melts abstract the nucleation growth and attachment detachment of gas bubbles on crystals in silicate melts is one of the key drivers of volcanic eruptions and can greatly influence their explosivity formerly oxides were considered the best candidates for heterogeneous bubble nucleation but recent studies showed that silicate crystals can also be bubble nucleation sites at 1 atmosphere atm this study examines whether bubbles can nucleate on plagioclase crystal surfaces during decompression which is a more common natural situation than 1 atm degassing experimental samples were synthesised from andesitic rock powder h2o and plagioclase seed crystals and melted and decompressed in a piston cylinder apparatus the products were imaged with 3d x ray computed tomography due to partial melting the plagioclase crystals developed sieve rims and rough crystal melt interfaces all plagioclase crystals in all samples were covered with bubbles bubble size distribution comparisons between bubbles in contact with plagioclase and bubbles in the melt show that bubbles belong to two populations generated by two different events one of which is heterogeneous nucleation on plagioclase crystal surfaces and the other is homogeneous nucleation within the melt the latter potentially accompanied by heterogeneous nucleation on oxide microlite surfaces the calculated attachment force between the bubbles and the plagioclase surface is stronger than the detachment force hence such bubbles would remain attached during crystal movements in our experiments the net buoyancy of the bubble crystal aggregates indicates that they could sink in an andesitic melt our findings highlight the need to reconsider the role of plagioclase crystals in magmatic degassing and shows interesting possibilities for magma mixing triggered degassing

submesoscale coherent vortices in the gulf stream seismic images and glider sections of the gulf stream front along the u s eastern seaboard capture deep lens shaped submesoscale features these features have radii of 5 20 km thicknesses of 150 300 m and are located at depths greater than 500 m these are typical signatures of anticyclonic submesoscale coherent vortices a submesoscale resolving realistic simulation which reproduces submesoscale coherent vortices with the same characteristics is used to analyze their generation mechanism submesoscale coherent vortices are primarily generated where the gulf stream meets the charleston bump a deep topographic feature due to the frictional effects and intense mixing in the wake of the topography these submesoscale coherent vortices can transport waters from the charleston bump s thick bottom mixed layer over long distances and spread them within the subtropical gyre their net effect on heat and salt distribution remains to be quantified plain language summary the interior of the ocean is populated by small scale coherent vortices which redistribute water properties on the scale of basins these structures are very difficult to observe they have no surface signature and small dimensions on the order of 1 50 km such that they are missed by satellites and sampled only by chance furthermore climate scale ocean models do not resolve these type of motions and do not take into account their impacts for the large scale transport and distribution of heat nutrients and other materials understanding and parameterizing these phenomena within models is critical for a better prediction of climate here we present new observations of submesoscale coherent vortices from seismic images and glider sections in the region of the gulf stream we use a numerical model at very high resolution to reproduce vortices with the same characteristics and to analyze their generation mechanism these vortices are generated where the gulf stream interacts with a deep topographic feature called the charleston bump due to frictional effects and intense mixing in the wake of the topography these vortices transport waters from the charleston bump s thick bottom mixed layer and act to spread them all around the subtropical gyre

generation of submesoscale vortices a new mechanism small scale intense vortices composed of water with anomalous values of quasi conservative tracers have been observed in many oceans they are particularly numerous in the beaufort gyre of the arctic ocean possible mechanisms responsible for the generation of these features are examined conservation of temperature salinity and nutrients requires that beaufort sea vortices be created from water that flows into the arctic ocean from the pacific ocean across the broad shallow chukchi sea much of this water passes through barrow canyon near point barrow alaska observations in the canyon show the generation of vortices of approximately the same size as those observed in the beaufort sea barrow canyon is therefore a likely site for the generation of beaufort sea vortices most observed beaufort sea vortices have a central potential vorticity near zero because of a relative vorticity close to their chukchi sea source water is typically stratified with little relative vorticity so that its potential vorticity is nonzero a key step in the generation of the vortices is therefore the reduction of the potential vorticity of chukchi sea water to nearly zero it is proposed that this occurs through the action of frictional torques occurring as the chukchi sea water flows through barrow canyon rather than througji the action of vertical mixing because this flow is driven by a downstream pressure gradient it is concentrated on the right hand wall of the canyon by the coriolis force the frictional torques thus preferentially reduce the potential vorticity of the fluid anticyclonic vortices are therefore preferentially generated it is suggested that a similar scenario may play a role in the generation of submesoscale vortices containing water from the mediterranean and labrador seas

seasonal controls on sediment delivery in a small coastal plain watershed north carolina usa field measurements of drainage ditch sedimentation and suspended sediment transport were used to construct a simple sediment budget and relate seasonal variations in vegetation and the hydrological characteristics of storms to sediment dynamics in a small agricultural watershed in north carolina results indicate that seasonal variations in crop coverage and vegetation in drainage ditches influence sediment delivery following the harvesting of crops and mowing of drainage ditches in late autumn conditions are favorable to soil erosion and sediment transport through early spring storms need not be very intense or produce large rainfall totals to transport significant sediment loads the maturation of field crops and ditch vegetation in spring produces conditions less conducive to both soil erosion and sediment transport intense summer thunderstorms however are capable of mobilizing and transporting significant amounts of sediment the computed sediment yield of 0 1 mg ha yr probably represents a low estimate that nevertheless is an order of magnitude less than measured ditch storage and more than two orders of magnitude less than regional estimates of soil loss on coastal plain croplands the results show that headwater ditches may be decoupled from slopes so that much of the eroded soil is stored within small watersheds rather than being transported out of the basin

vapor undersaturated experiments with macusani glass h 2 o at 200 mpa and the internal differentiation of granitic pegmatites vapor undersaturated fractional crystallization experiments with macusani glass macusanite a peraluminous rhyolite obsidian at 200 mpa yield mineralogical fabrics and zonation and melt fractionation trends that closely resemble those found in zoned granitic pegmatites and other granitoids of comparable composition typically peraluminous li be ta rich deposits the zonation from the edge of charges inward is characterized by 1 fine grained sodic feldspar quartz border zones 2 a fringe of very coarse grained graphic quartz feldspar intergrowths that flair radially toward melt and terminate with nearly monophase k feldspar 3 cores of very coarse grained nearly monominerallic quartz or virgilite lialsi5o12 mica and 4 late stage fine grained albite mica intergrowths that are deposited from alkaline na rich interstitial melt at vapor saturation similar experimental products have been observed in compositionally simpler less evolved systems liquid lines of descent from initially h2o undersaturated runs are marked by a decrease in sio2 and increases in na k b p f h2o and a variety of trace lithophile cations these trends are believed to be governed by three factors 1 disequilibrium growth of feldspars quartz via metastable supersaturation 2 fractionation of melt toward sio2 depleted na rich compositions due to increases in b p and f and 3 changes in nucleation and growth rates mostly as a function of the h2o content of melt x w m in contrast experiments that are cooled below the liquidus from the field of melt aqueous vapor london et al 1988 fail to replicate pegmatitic characteristics in most respects on the basis of these and other experiments we suggest that the formation of pegmatite fabrics stems primarily from fractional crystallization in volatile rich melts and that enrichments in normally trace lithophile elements result from melt differentiation trends toward increasingly alkaline silica depleted compositions although vapor saturation at near solidus and subsolidus conditions may promote extensive recrystallization an aqueous vapor phase does not appear to be necessary for the generation of most of the salient characteristics of pegmatites