thresholds of aeolian sand transport establishing suitable values this paper assesses the practical use and applicability of the time fraction equivalence method tfem stout zobeck 1996 of calculating a wind speed threshold for sand grain entrainment in field situations a modification of the original method is used and is applied to 1 hz measurements of wind speed and sand transport on a beach surface calculated grain entrainment thresholds are tested in terms of the percentage of sand transport events that they explain it was found that the calculated thresholds offered a poor representation of the occurrence of saltation activity explaining only about 50 of the measured transport events results are discussed in terms of system response time wind speed measurement height undetected events and sampling period a shear velocity threshold for grain entrainment was also calculated but this also failed to explain a high proportion of the sand transport events the best results 67 91 of transport events explained were found by calculating a threshold based on time averaged 40 s wind velocity measurements the applicability of a single threshold to a natural grain population is discussed a natural surface is likely to possess a range of thresholds varying over short time scales in response to parameters such as grain rearrangement and changes in moisture conditions the results show that calculated thresholds based on 40 s time averaged data consistently explain a high proportion of the recorded sand transport events this is because such a time averaged approach accounts for higher frequency variability inherent in the sand transport system

on the origin of el chichon volcano and subduction of tehuantepec ridge a geodynamical perspective the origin of el chichon volcano is poorly understood and we attempt in this study to demonstrate that the tehuantepec ridge tr a major tectonic discontinuity on the cocos plate plays a key role in determining the location of the volcano by enhancing the slab dehydration budget beneath it using marine magnetic anomalies we show that the upper mantle beneath tr undergoes strong serpentinization carrying significant amounts of water into subduction another key aspect of the magnetic anomaly over southern mexico is a long wavelength 150 km high amplitude 500 nt magnetic anomaly located between the trench and the coast using a 2d joint magnetic gravity forward model constrained by the subduction p t structure slab geometry and seismicity we find a highly magnetic and low density source located at 40 80 km depth that we interpret as a partially serpentinized mantle wedge formed by fluids expelled from the subducting cocos plate using phase diagrams for sediments basalt and peridotite and the thermal structure of the subduction zone beneath el chichon we find that 40 of sediments and basalt dehydrate at depths corresponding with the location of the serpentinized mantle wedge whereas the serpentinized root beneath tr strongly dehydrates 90 at depths of 180 200 km comparable with the slab depths beneath el chichon 200 220 km we conclude that this strong deserpentinization pulse of mantle lithosphere beneath tr at great depths is responsible for the unusual location singularity and probably the geochemically distinct signature adakitic like of el chichon volcano

archean lamprophyre dikes of the superior province canada distribution petrology and geochemical characteristics shoshonitic lamprophyre dikes of late archean age are a volumetrically minor yet widespread component of magmatism in the superior province and preferentially occur along major structures that delineate subprovince boundaries lamprophyre swarms are most prominently developed in fault graben where they are associated with alkali gabbro and trachytes and molasse sediments mineralogically the dikes are characterized by zoned phlogopite or hornblende phenocrysts restriction of feldspar to the groundmass globular segregations of k feldspar and calcite panidiomorphic texture and the sporadic presence of crustal xenoliths compositionally fresh dikes have contents of sio2 47 51 wt tio2 0 55 0 60 and p2o5 0 36 1 58 and k2o na2o ratios 1 5 2 3 and mg numbers 78 80 comparable to phanerozoic shoshonitic lamprophyres unaltered dikes are characterized by extreme enrichments of the lithophile elements k rb ba cs th u and light rare earth elements lree and enhanced abundances of cr 650 920 ppm co 37 42 ni 264 355 and sc 22 28 mid ocean ridge basalt normalized plots display 1 consistent enrichments of k rb and ba relative to sr and lree 2 variable enrichments of rb and ba relative to k and 3 troughs at ta nb and ti compared with fresh rocks altered samples have systematically lower k rb ba and sr contents but similar ree distributions and profiles from th yb and sc ni on normalized diagrams suites of post archean ultramafic lamprophyres in the superior province are enriched in large ion lithophile elements lile lree and compatible elements relative to their archean counterparts and lack troughs at ta nb and ti emplacement of the lamprophyres was diachronous from north 2705 ma to south 2674 ma probably being related to localized extension during the successive accretion of individual subprovinces archean lamprophyre magmas were derived from a depleted mantle source variably enriched in lile and lree by sediments and altered oceanic crust with small variable degrees of crustal contamination whereas the post archean lamprophyres lacked a plate margin setting

aeolian sediment transport on a beach surface moisture wind fetch and mean transport abstract temporal and spatial changes in wind speed wind direction and moisture content are ubiquitous across sandy coastal beaches often these factors interact in unknown ways to create complexity that confounds our ability to model sediment transport at any point across the beach as well as our capacity to predict sediment delivery into the adjacent foredunes this study was designed to measure wind flow and sediment transport over a beach and foredune at greenwich dunes prince edward island national park with the express purpose of addressing these complex interactions detailed measurements are reported for one stormy day october 11 2004 during which meteorological conditions were highly variable wind speed ranged from 4 ms 1 to over 20 ms 1 wind direction was highly oblique varying between 60 and 85 from shore perpendicular and moisture content of the sand surface ranged from a minimum of about 3 by mass to complete saturation depending on precipitation tidal excursion and storm surge that progressively inundated the beach the data indicate that short term variations i e minutes to hours in sediment transport across this beach arise predominantly because of short term changes in wind speed as is expected but also because of variations in wind direction precipitation intensity and tide level even slight increases in wind speed are capable of driving more intense saltation events but this relationship is mediated by other factors on this characteristically narrow beach as the angle of wind approach becomes more oblique the fetch distance increases and allows greater opportunity for the saltation system to evolve toward an equilibrium transport state before reaching the foredunes whether the theoretically predicted maximum rate of transport is ever achieved depends on the character of the sand surface e g grain size slope roughness vegetation moisture content and on various attributes of the wind field e g average wind speed unsteadiness approach angle flow compression boundary layer development moisture content is widely acknowledged as an important factor in controlling release of sediment from the beach surface all other things being equal the rate of sediment transport over a wet surface is lesser than over a dry surface on this beach the moisture effect has two important influences a in a temporal sense the rate of sediment transport typically decreases in association with rainfall and increases when surface drying takes place and b in a spatio temporal sense shoreline excursions associated with nearshore processes such as wave run up storm surge and tidal excursions have the effect of constraining the fetch geometry of the beach i e narrowing the width of the beach because saturated sand surfaces such as found in the swash zone will only reluctantly yield sediments to aeolian entrainment the available beach surface across which aeolian transport can occur becomes narrower as the sea progressively inundates the beach under these constrained conditions the transport system begins to shut down unless wind angle becomes highly oblique thereby increasing fetch distance in this study maximum sediment transport was usually measured on the mid beach rather than the upper beach i e closer to the foredunes this unusual finding is likely because of internal boundary layer development across the beach which yields a decrease in near surface wind speed and hence transport capacity in the landward direction although widely recognized in the fluid mechanics literature this decrease in near surface shear stress as a by product of a developing boundary layer in the downwind direction has not been adequately investigated in the context of coastal aeolian geomorphology

pocho volcanic rocks and the melting of depleted continental lithosphere above a shallowly dipping subduction zone in the central andes the late miocene 7 9 to 4 5 ma pocho volcanic field in argentina occurs 700 km east of the chile trench over the modern shallowly dipping andean wadati benioff zone near 32 s latitude in argentina the field is located in the sierra de cordoba which is the easternmost laramide style block faulted range in the sierras pampeanas pampean ranges the arrival of the shallowly dipping slab initiated both volcanism and the uplift of the sierra de cordoba pocho rocks 52 to 68 sio2 feo mgo 2 2 comprise an older 7 5 0 5 ma high k and a younger 5 3 0 7 ma shoshonitic series mineralogic data and fractionation models show that crystallization occurred under hydrous oxidizing conditions which were most extreme in the high k series an unusual pattern of successively lower ree at higher sio2 concentrations can be modeled by sphene apatite and amphibole removal an arc like trace element signature attributed to an arc component is strongest in the younger shoshonitic series an important depleted lower crustal mantle lithospheric source component in both series is indicated by non radiogenic sr and pb isotopic ratios at nd 0 to 2 low rb sr ratios and low u and th concentrations this depleted signature contrasts with the enriched one in potassic back arc central volcanic zone cvz lavas over the steeper subduction zone to the north and is attributed to several processes in the shallow subduction zone first deep crustal mash processes in the nearly normal thickness crust beneath pocho incorporated depleted proterozoic basement components and not complexly mixed structurally thickened crustal components as in the cvz second the association of pocho volcanism with the arrival of the slab allowed little time for modification of the mantle by subduction components third miocene shallowing of the subduction zone beneath the flat slab required thinning of both the astenosphere and the subcontinental lithosphere thus an important subcrustal component could be from blocks removed from the base of the lithosphere to the west and recycled into the asthenosphere similar magmatic sources would have existed during laramide shallow subduction in western north america

petrology and geochemistry of ultrapotassic rocks from the montefiascone volcanic complex central italy magmatic evolution and petrogenesis abstract the montefiascone volcanic complex belongs to the roman magmatic province of central italy the volcanic activity took place in an extensional post collisional setting during late pleistocene giving rise to lava flows and pyroclastic deposits the extrusive products consist of moderately to strongly undersaturated k rich lavas ranging in composition from trachybasalts through leucite basanites and leucititic tephrites to tephritic leucitites they show the typical geochemical and isotopic characters of the roman potassic magmas i e low tio2 low k2o al2o3 strong enrichment in lile high lile hfse ratios highly radiogenic 87 sr 86 sr ratios 0 71005 0 71112 and unradiogenic 143 nd 144 nd 0 51209 0 51229 corresponding to end 10 7 to 6 8 large chemical variations have been recognized within the montefiascone volcanics resulting both from the occurrence of different primary magmas and shallow level fractionation processes the differentiation mainly took place by means of closed system fractional crystallisation with local influence of crustal assimilation the leucite basanites represent primary mantle magmas which did not yield derivative products whereas the leucititic tephrites tephritic leucitites and trachybasalts comprise highly differentiated rocks strongly depleted in compatible elements and enriched in lile fractional crystallisation dominated respectively by clinopyroxene leucite and clinopyroxene plagioclase yielded the most evolved tephritic leucitites and trachybasalts in contrast assimilation of metamorphic basement rocks characterized by highly radiogenic 87 sr 86 sr is needed to explain the moderate increase of the 87 sr 86 sr ratio within the leucititic tephrites the geochemical and isotopic signatures shown by the montefiascone primary magmas require a clinopyroxene and phlogopite rich mantle source in particular partial melting of a veined lithospheric mantle can account for the occurrence of different primary magmas characterized by relatively constant sr and nd isotopic compositions depleted mantle nd model ages 1 1 1 5 ga suggest that the mantle enrichment may be a very old event unrelated to the subduction that preceded the roman magmatism this hypothesis is further supported by the strong similarity in age and isotopic composition between the montefiascone volcanics and the kamafugitic and carbonatitic rocks of the adjoining ultra alkaline umbria latium district

occurrence of boron rich potassic melts in the vulsini volcanic district italy evidence from melt inclusions abstract boron was analyzed by nuclear microanalysis technique using the 11 b p 8 be reaction in potassic to highly potassic melts mg mg 2 mg 2 fe 2 0 70 trapped as melt inclusions in olivine fo 91 7 90 5 phenocrysts from the vulsini volcanic district northwestern roman province italy these data evidence unusual b concentrations from 60 to 100 ppm up to five times higher than any documented values in primitive subduction related magmas the melt inclusions display variable concentrations in b k sr and f with constant ratios between elements for a single volcanic event that strongly suggest variations of the extents of batch partial melting of a mantle source enriched in b k sr and f conversely b k and b cl ratios in potassic magmas mg 0 70 as exemplified by melt inclusions in olivine fo 90 are variable on the scale of the whole roman province these variations cannot be explained by either fractional crystallization or differing extents of the mantle source melting alone this is also supported by the range in th ta ratios 52 10 of the whole rock samples variability of the b k or b cl ratios cannot be related to a single stage metasomatism event the data indicate the possible occurrence of b rich contaminant and or high inputs of subducted derived components in the mantle wedge beneath the vulsini area within the peculiar geodynamic setting of the northern part of the apenninic arc in addition by determining boron concentrations using nuclear microanalysis involving the 11 b p 8 be nuclear reaction we have illustrated the sensitivity of the nuclear reactions in the analysis of the light elements

effects of time dependent moisture content of surface sediments on aeolian transport rates across a beach wildwood new jersey u s a a one day field investigation on an unvegetated backbeach documents the importance of surface sediment drying to aeolian transport surface sediments were well sorted fine sand moisture content of samples taken in the moist areas on the backbeach varied from 2 9 to 9 2 per cent lack of dry sediment inhibited transport prior to 08 50 by 09 10 conspicuous streamers of dry sand moved across the moist surface barchan shaped bedforms 30 to 40 mm high and composed of dry sand moisture content 0 10 per cent formed where sand streamers converged the surface composed of dry sand increased from 5 per cent of the area of the backbeach at 09 50 to 90 per cent by 12 50 mean wind speeds were beetween 5 6 and 8 6 m s 1 at 6 m above the backbeach corresponding shear velocities were always above the entrainment threshold for dry sand and below the threshold for the moist sand on the backbeach measured rates of sand trapped by vertical cylindrical traps increased during the day relative to calculated rates the measured rate of sand trapped on the moist foreshore was higher than the rate trapped on the backbeach during the same interval indicating that the moist foreshore moisture content 18 per cent was an efficient transport surface for sediment delivered from the dry portion of the beach upwind measured rates of sand trapped show no clear relationship to shear velocities unless time dependent surface moisture content is considered results document conditions that describe transport across moist surfaces in terms of four stages including 1 entrainment of moist sediment from a moist surface 2 in situ drying of surface grains from a moist surface followed by transport across the surface 3 entrainment and transport of dry sediment from bedforms that have accumulated on the moist surface and 4 entrainment of sand from a dry upwind source and transport across a moist downwind surface 1997 john wiley sons ltd

aeolian sediment transport on a beach thresholds intermittency and high frequency variability abstract during a field experiment designed to measure wind flow and sediment transport over the beach and foredune at greenwich dunes prince edward island national park measurements were made on october 11 2004 during a storm with wind speeds ranging from 4 ms 1 to over 20 ms 1 this paper examines thresholds of sand movement intermittency and the relationship between fluctuating winds and transport intensity based on high frequency measurements of wind speed and saltation wind speed was measured at four points across the beach profile using cup anemometers set at a height of 0 6 m the anemometers were co located with saltation probes set at a height of 0 02 m that measure the impacts of saltating sand grains the instruments were sampled at 1 hz during runs of 1 or 2 h over an eight hour period sand transport was highly intermittent early in the day when winds were only slightly above threshold and became more continuous towards the upper beach because of increasing fetch distance and decreasing surface moisture despite more continuous transport and increasing wind speed through the day a zone of highly intermittent transport migrated landward across the beach as water levels rose due to storm surge examination of three thresholds related to measures of wind speed the maximum wind speed without transport u tmax minimum wind speed with transport u tmin and the intermittency threshold u t showed that none provide a consistently robust measure of the threshold although they all provide some insight into conditions controlling entrainment while graphs of instantaneous saltation intensity crudely mimic the pattern of fluctuating wind speed statistical correlations over periods of 2 10 min were generally poor r 2

sediment subduction and the source of potassium in orogenic leucitites leucitites from the italian volcanic province show a marked enrichment of the large ion lithophile elements lile over the high field strength elements hfse indicative of a subduction related origin despite sr and nd isotope ratios similar to those in lamproites trace element variations do not suggest the latter as a source for the k enrichment instead potassium and the other lile and rare earth elements ree are derived from subducted sediments in a multicomponent mixing process that involves both dehydration and partial melting of the subducted material the slightly elevated 18 o and high 87 sr 86 sr values of the primitive italian lavas are shown to be consistent with a three component mixing model which can also explain other unusual geochemical features of the italian lavas stabilization of phlogopite in hybridized mantle above the subduction zone is regarded as an essential aspect of the petrogenesis of the orogenic leucitites

2d magnetotelluric imaging of the anqing guichi ore district yangtze metallogenic belt eastern china an insight into the crustal structure and tectonic units abstract two parallel nw trending magnetotelluric mt profiles were placed perpendicularly to the main structures of the anqing guichi ore district one of the seven ore districts in the middle lower yangtze river metallogenic belt of eastern china in october december 2013 the mt data acquisition was carried out at 117 sites with 0 5 1 km site spacing the mt data has a good quality in the frequency range between 320 and 0 01 hz the dimensionality analysis and 2d resistivity inversion results indicate that 1 the deep of the ore district with three dimensional structural characteristics but two dimensional structural characteristics for shallow 2 there is a clear correlation between resistivity and the main geological units of the ore district as well as correlation with mapped surface faults 3 the gandan deep fault gdf and jiangnan deep fault jnf extend from the surface to 10 km deep with dip of nw45 and dip angles larger than 60 a series of ne trending acidic intrusive rocks were controlled by the gdf

the dynamic effects of moisture on the entrainment and transport of sand by wind abstract there is an increasing awareness of the influence of surface moisture on aeolian entrainment and transport of sediment existing wind tunnel studies have shown the impact of a limited range of moisture contents on entrainment thresholds but similar investigations are lacking in the field the research reported here investigated the influence of changes in surface moisture content on sand entrainment and transport on a meso tidal beach in anglesey north wales high frequency 1 hz wind velocities measured with hot wire anemometers were combined with grain impact data from a sensit monitor and mass flux measurements from a standard sand trap surface and near surface moisture contents were assessed gravimetrically from surface sand scrapes and also directly by using a thetaprobe critical threshold values for entrainment were specified using a modified form of the time fraction equivalence method stout j e zobeck t m 1996a establishing the threshold condition for soil movement in wind eroding fields proceedings of the international conference on air pollution from agricultural operations mwps c 3 kansas city 7 9 february 1996 pp 65 71 results indicate a time dependent change in dominant control of the sand transport system from moisture to wind speed dependent upon the moisture content of the surface sediment this interchange between controlling parameters on both entrainment and transport was very sensitive to prevailing moisture conditions and took place over a period of minutes to hours under conditions experienced in the experiments presented here the critical moisture threshold for sediment entrainment was determined to be between 4 and 6 higher than the 1 4 specified in previous wind tunnel experiments furthermore a moisture content of nearly 2 where moisture was adhered to transported sediment appeared to have little or no impact on the rate of sand flux

geochemical variation with time in the cenozoic high k volcanic rocks of the island of lesbos greece significance for shoshonite petrogenesis shoshonitic and calc alkaline volcanic rocks alternate in the miocene volcanic sequence of the island of lesbos in the eastern aegean sea the sequence and chronology of the lavas is well known which has allowed a study of both spatial and temporal geochemical variation early calc alkaline volcanism 21 5 ma was followed by a hiatus the main shoshonitic phase occurred from 17 to 17 7 ma and was followed by minor late calc alkaline volcanism the earliest shoshonitic lavas skoutaros formation were relatively anhydrous with f as an important volatile phase but later lavas sykaminea formation have abundant phenocrysts of hydrous minerals and show ree patterns indicating amphibole fractionation there is petrographic and mineralogic evidence for magma mixing throughout the volcanic sequence shoshonitic lavas enriched in k nb th and 206pb 204pb interbed with more calc alkaline lavas in both more hydrous and less hydrous stratigraphic units these variations in k nb and th cannot be accounted for by fractionation or crustal assimilation rather they reflect different mantle sources with different pb isotope signatures the k rich source is similar to source mantle for many alkaline ultrapotassic rocks the lower k source resembles normal calc alkaline source mantle both sources are unusually high in 207pb and 208pb suggesting strong th and u enrichment similar to that in roman province and sunda arc rocks the observed volcanic sequence is consistent with partial melting caused by a rising volatile front that initially triggered partial melting at higher levels in the mantle but as volatile content increased allowed partial melting at greater depths in less enriched mantle

detecting impacts of sand grains with a microphone system in field conditions abstract this paper describes the miniphone an instrument to measure aeolian saltation this instrument is a modified electret microphone that detects the impacts of individual grains the unidirectional miniphone is inexpensive approximately us 10 small and poses minimal disruption to the wind field it can be sampled at rates up to 44 100 hz using commonly available sound card technology or it can be interfaced with a data acquisition system data from deployments on beaches on marco island fl usa and near shoalhaven heads nsw australia using sample rates of 44 100 hz and 6000 hz are presented an algorithm for identifying discrete impacts of grains is described the number of saltation impacts was not reduced when sub sampling a record from 44 100 hz to 6000 hz the most immediate use for the miniphone is for short term deployments to detect unsteadiness in the saltation field

post collisional magmatism around northern taiwan and its relation with opening of the okinawa trough being part of an active mountain belt formed by oblique collision of the luzon arc with asia northern taiwan and the offshore islets are marked by a series of latest pliocene quaternary volcanoes whose eruptions have been conventionally ascribed to westward propagation of the ryukyu volcanic arc on the basis of new geochemical data along with supporting geologic and geophysical evidence we propose instead that this young volcanism resulted from post collisional lithospheric extension in the northern taiwan mountain belt and the mantle source regions involved in the melt generation have been significantly modified by the nearby ryukyu subduction related processes magmas thus produced through the northeast to the southwest in the northern taiwan volcanic zone ntvz vary from low k to calc alkaline and then shoshonitic compositions such a spatial geochemical variation characterized by southwestward increase in enrichments of potassium and incompatible trace elements runs subparallel to the southwestern part of the present day ryukyu trench the geochemical variation that can be explained by southwestward decrease in degrees of partial melting of the mantle sources is reconciled with a southwestward weakening extensional regime observed in the ntvz the post collisional extension in northern taiwan furthermore might have played a role in reactivation of the opening in the middle okinawa trough and gave way to its rapid southwestward propagation with associated development of the ryukyu subduction zone west of124oe this nascent subduction in turn resulted in abundant submarine volcanoes which delineate an embryo volcanic front along the southern margin of the trough therefore the southwestern okinawa trough is not a fore arc basin as had been previously alleged but represents an atypical back arc basin which developed broadly synchronously or prior to its arc trench system in this particular collision extension subduction tectonic environment 1999 elsevier science b v all rights reserved

the effect of turbulent flow structures on saltation sand transport in the atmospheric boundary layer the effect of turbulent flow structures on saltation sand transport was studied during two convective storms in niger west africa continuous synchronous measurements of saltation fluxes and turbulent velocity fluctuations were made with a sampling frequency of 1 hz the shear stress production was determined from the vertical and streamwise velocity fluctuations the greatest stress bearing events were classified as turbulent structures with sweep ejection inward interaction and outward interaction described according to the quadrant technique the classified turbulent structures accounted for 63 5 per cent of the average shear stress during the first storm and 56 0 per cent during the second storm the percentage of active time was only 20 6 per cent and 15 8 per cent respectively high saltation fluxes were associated with sweeps and outward interactions these two structures contribute positively sweeps and negatively outward interactions to the shear stress but have in common that the streamwise velocity component is higher than average therefore the horizontal drag force seems primarily responsible for saltation sand transport and not the shear stress this was also reflected by the low correlation coefficients r between shear stress and saltation flux 0 12 and 0 14 respectively while the correlation coefficients between the streamwise velocity component and saltation flux were much higher 0 65 and 0 57 respectively

minette lavas and associated leucitites from the western front of the mexican volcanic belt petrology chemistry and origin during the late pliocene k rich minette and leucitite lavas erupted in the western mexican volcanic belt near the town of los volcanes a region which is located much closer to the middle america trench than the main line of currently active andesite stratovolcanoes during this period the tectonic regime in western mexico was highly complex due to the simultaneous occurrence of active subduction of the young rivera plate and rifting caused by crustal extension most of these basic lavas contain phenocrysts of phlogopite augite and apatite along with microphenocrysts of leucite and fe ti oxide olivine is absent from all but two of the flows one an olivine leucitite and the other a felsic minette the phlogopite phenocrysts and high whole rock fe2o3 feo ratios which are characteristic of this suite record evidence of high magmatic water contents and oxygen fugacities all of these rock types are highly enriched in the large ion lithophile and light rare earth elements with sr 5100 ppm ba 4800 ppm and ce 330 ppm they are also mildly enriched in the high field strength elements e g zr 260 700 ppm and display the strong relative enrichment of the lile over the hfse that is characteristic of magmas erupted in convergent margins consideration of high pressure phase equilibria in the mg2sio4 camgsi2o6 kalsio4 sio2 system shows that the minettes from this region are not related through fractional crystallization to the more mgo rich olivinebearing minettes which have erupted in other parts of the western mexican volcanic belt during the quaternary this conclusion is consistent with both the trace element geochemistry of these lavas and with the results of fractional crystallization models instead the data suggests that these high k magmas were derived from a source region which consists predominantly of phlogopite clinopyroxene and apatite and which has formed through hydrous enrichment of the subarc mantle in response to subduction

a new instantaneous aeolian sand trap design for field use a new aeolian sediment trap is described which can give up to 1 hz measurement frequency in held conditions the trap adopts a circular horizontal trap design with a load cell connection to give continuous unobtrusive trap measurement of sediment flux simultaneous velocity recording is carried out using an anemometer trap construction costs are approximately pound 200 initial results in held conditions using a direct comparison of wind velocity data sampled at an equivalent frequency have given a first order relationship between sediment flux and velocity the trap enables simultaneous sampling of wind velocity and sediment flux at a sufficiently short interval to enable investigation of sediment transport dynamics under a variety of field conditions

origin of sulphur in the quaternary perpotassic melts of italy evidence from hauyne sulphur isotope data abstract hauyne na ca 4 8 alsio 4 6 so 4 s 1 2 is a rare mineral which occurs in ejecta and lavas of perpotassic volcanoes of the roman comagmatic region italy as a high temperature sulphur bearing phase it is a valuable indicator of the sulphur characteristics in the melt therefore sulphur isotope determinations were carried out for the first time on samples from some italian volcanoes on average 34 s values 1 1 to 10 8 are above the normal range 0 to 3 for igneous materials and can be classified into two groups phenocrysts in lavas avg 34 s 4 2 and metasomatic crystals in ejecta avg 34 s 8 3 such data are compatible with the hypothesis that hydrous fluids released from subducted sediments were responsible for the high volatile and lile supply to the mantle region where the magma generating process occurred

wind forces and related saltation transport the effect of several wind characteristics on sand transport was studied in three experiments in north burkina faso west africa the first experiment is used to analyse the relation between wind speed and shear stress fluctuations across height the second experiment is used to study the relation of these wind characteristics with saltation transport for fourteen convective storms registered during the rainy seasons of 2002 and 2003 the effect of sampling time is studied for two of these convective storms the third experiment relates the turbulent structures of four convective storms to saltation transport wind speed measurements were undertaken with two sonic anemometers and sediment transport was measured by two saltiphones the sampling frequency was either 8 or 16 hz the sonic frame of reference was rotated according to a triple rotation horizontal fluctuations showed a fairly good correlation with height because the wind speed at both sensors was affected by the same vortices the correlation coefficients ranged from 0 42 when the distance between the sensors was 1 75 m to 0 92 when the distance was 0 25 m the instantaneous reynolds stress had the weakest correlation correlation coefficient of 0 05 at 1 75 m between the sensors and 0 56 at 0 25 m between the sensors because the momentum at 2 m above the soil surface is transported by different eddies than those close to the ground this also explains the fairly good correlation coefficients between the horizontal components of the wind and saltation compared to the poor correlations between instantaneous reynolds stress and saltation an increase in sampling time did not have much impact on these correlation coefficients up to sampling periods of about 30 s however this sampling interval would be too coarse to describe the vertical wind component adequately the classification of the moments of shear stress into the turbulent structures sweeps ejections inward and outward interactions showed that the mean saltation flux is higher at sweeps and outward interactions than at ejections and inward interactions also saltation occurred more often during sweeps and outward interactions than during ejections and inward interactions

11 11 dune morphology and dynamics this chapter discusses the key types of sand dunes and how they can be classified and assesses the major controls on their development the processes of dune dynamics are reviewed leading to a discussion of the concept of equilibrium in solitary dune form recent advances in modeling are reviewed that show how interactions between dunes may result in equilibrium at the dune field scale rather than at the single dune scale

a shoreline evolution model considering the temporal variability of the beach profile sediment volume sediment gain loss abstract the prediction of shoreline variability along sandy coastlines is a valuable skill for a broad range of coastal engineering applications currently there are multiple proposals in the literature for equilibrium cross shore shoreline evolution models based on a constant equilibrium condition correlated with the shoreline position the aim of this paper is to present an extension of an existing equilibrium shoreline evolution model adding a rate of change component which in turn modifies the relationship between the equilibrium shoreline position and the incident wave energy as a function that advances or retreats over time the proposed model is applied to two study sites on the spanish coast on the one hand one and a half years of shoreline position data obtained from a video camera system at nova icaria beach catalonia are used to evaluate the shoreline evolution during a period of sediment contribution which is attributed to a sand bypass coming from bogatell beach on the other hand 16 years of shoreline position data acquired from beach profile surveys in campo poseidon huelva are used to reproduce the shoreline evolution taking into account the trend of sediment loss due to sediment drift alongshore the results obtained from both study sites using the proposed model show overall good performance the model successfully represents the general shoreline erosion accretion oscillations and the progressive trend of sediment gains or losses through the evolutionary relationship between the equilibrium shoreline position and the incident wave energy

geochemistry mineral chemistry and petrogenesis of a neoproterozoic dyke swarm in the north eastern desert egypt dyke swarms traverse neoproterozoic rocks in the hawashiya region in the extreme northern part of the eastern desert of egypt they are a suite of basaltic andesite and andesite mafic dykes and dacitic and rhyolitic felsic dykes the mafic dyke suite is more abundant in the younger granites 577 6 ma than in the older granitoids 614 ma in which the felsic dykes are the most common the dyke swarms trend predominantly ne sw and the felsic dyke suite is older than the mafic dyke suite both dyke suites are calc alkaline alkaline dykes are rare and are relatively poor in tio 2 and nb but enriched in the incompatible elements and hfse the felsic dyke suite is enriched in ree and is strongly lree fractionated relative to the mafic dyke suite although the hawashiya dykes were emplaced at the end of the neoproterozoic era in an extensional tectonic setting they have geochemical characteristics that are consistent with a subduction related regime these chemical signatures were inherited from the lithospheric rocks that produced their host hawashiya granitoids the felsic dyke suite magma may be derived from crustal rocks essential source component by partial melting the mafic dyke suite magma was generated from a lithospheric mantle and has undergone fractional crystallization of plagioclase amphibole clinopyroxene and magnetite as documented by major and trace elements fractionation modelling

on the controls of oxygen fugacity in the generation and crystallization of peralkaline melts the formation of peralkaline melts is generally recognized to be related to enrichment of the mantle in sodium or potassium during a metasomatic event that predated magma generation the wide range in mineral assemblages mineral compositions and fluid compositions in peralkaline melts are to a large extent a function of the sodium potassium content of these mantle metasomatizing fluids which also governs redox conditions we propose that sodic fluids will reduce the mantle assemblage by depleting ferric iron from garnet to form the aegirine component in pyroxene in contrast potassic fluids would oxidize the mantle assemblage by extracting al2o3 from the garnet to make phlogopite we suggest that during differentiation of peralkaline melts once fe ti oxides have been depleted from the assemblage simple crystallization reactions of common solid phases such as aegirine or arfvedsonite control the oxygen fugacity by equilibria such as

a silurian u pb age for the cape st mary s sills avalon peninsula newfoundland canada implications for silurian orogenesis in the avalon zone mafic sills from cape st mary s on the avalon peninsula of newfoundland give an u pb baddeleyite age of 441 2 ma this age corresponds with the earliest ages recorded for the climactic silurian orogenic event that dominantly affected rocks of the central mobile belt in newfoundland the age is consistent with but in no way necessitates that the avalon and gander zones were juxtaposed during the silurian because sills tend to form in poorly lithified and undeformed sedimentary rocks it is unlikely that cambrian sediments hosting the sills were affected by ordovician orogenic events that strongly affected central newfoundland negative nb and ti anomalies on mid ocean ridge basalt normalized diagrams show that the sill geochemistry is consistent with formation in a transpressional tectonic environment mafic magmas clearly associated with the silurian event share these chemical and tectonic affinities thus both the age and geochemical data are consistent with but do not require a link between the gand

the effect of wind gusts moisture content and fetch length on sand transport on a beach this paper reports on an analysis of instantaneous sediment transport in relation to wind gusts moisture content and fetch length from a field study carried out at skallingen denmark wind speeds were measured with cup anemometers and instantaneous sediment transport with vertical traps coupled to electronic balances moisture content was measured gravimetrically using samples taken along a beach profile at intervals of 1 to 2 h sediment transport and wind speeds were sampled at 1 hz and a 5 s running mean was used to smooth the data from the trap because of limitations of the balance resolution three measures of the threshold of sediment motion the intermittency threshold minimum threshold and maximum threshold were explored using data from five runs carried out on october 26 2000 the intermittency threshold and maximum threshold were largely insensitive to wind speed but varied spatially along the fetch distance the minimum threshold increased significantly with increasing mean wind speed as a result of reduced time for drying of the surface layer examination of time series for instantaneous wind speed and sediment transport for a number of runs on october 26 and november 6 2000 showed close agreement between fluctuations in wind speed and fluctuations in sediment transport cross spectral analysis of instantaneous wind speed and sediment transport for one run on each day where there was continuous transport showed high coherence between the two variables over a range of frequencies from 0 2 hz to 0 01 hz plots of all non zero instantaneous sediment transport values versus wind speed show considerable scatter in general transport rates are highest for traps located further from the upwind non erodible boundary i e along the fetch best fit power relationships show r2 values generally ranging from 0 4 to 0 6 and exponents ranging from 4 5 to 6 94 i e much higher than the traditional value of 3 found in most transport equations traps located close to the upwind boundary had lower r2 values and exponents 2 5

evaluation of saltation flux impact responders safires for measuring instantaneous aeolian sand transport intensity the measurement of aeolian sand transport rates on small scales is of interest to the development and testing of detailed models of sand movement by wind this paper reports on laboratory evaluations and preliminary field tests of a new design of a piezo electric impact responder called a safire capable of measuring saltation impacts at a frequency of 20 hz the advantages of the safire are 1 that it provides high frequency measurements 2 that it presents a minimal obstruction to the wind flow no scour observed in the field and 3 that it is of a relatively low cost laboratory calibrations were performed with a vertical gravity flume generating known sand grain fluxes using both mixed sand and specific size fractions initial tests investigated three fundamental characteristics correspondence between digital and analogue signals generated by the instrument directional response of the probe and linearity of instrument response to mass flux instrument calibration included determination of the momentum threshold required for the sensor to register a grain impact based on this lower limit and the known distribution of grain size and speed at different fall heights a prediction is made as to the sand grain flux the safire ought to measure which is then compared with the signal response the result of this comparison is an assessment of the instrument s efficiency in counting saltating grains these safires were also deployed in the field as part of a larger investigationof spatio temporal transport variability thisexperiment providedthe opportunity to compare the instrument s performancewithtraditional sandtraps andthispaperdevelopsmethodsandassumptionsrequiredtoconvertmeasurements from impact responders to traditional mass transport rates the evaluations indicate that improvements to the instrument production process are required to ensure a standard momentum threshold among individual instruments furthermore the sensor design needs to be reconsidered in order to eliminate the variation in response depending on azimuth direction so that the sensor is uniformly omni directional d 2003 elsevier b v all rights reserved

high mg potassic rocks in the balkan segment of the variscan belt bulgaria implications for the genesis of orogenic lamproite magmas ultrapotassic plutons from several domains of the variscan orogenic belt have been in turn interpreted as syn to post orogenic due to their age spread but assessment of their geodynamic setting and source regions is still open to interpretation in the svoge region bulgaria at the southern margin of the balkan orogen peralkalic plutons are hosted within ordovician pelites the main intrusion with lamproitic affinity which hosts monzodiorite xenoliths and a polyphase syenite suite was emplaced at a shallow level 40 ar 39 ar dating by step heating of amphibole and biotite yielded a early carboniferous intrusion age for the main body 337 4 and 339 1 1 6 ma the lamproite intrusion is silica rich compared with bona fide lamproites and characterized by moderate lile and la n yb n enrichments sr and nd isotopic data initial nd in the range 4 87 to 5 88 suggest an origin in a depleted lithospheric mantle possibly refertilized by eo variscan subduction the high k syn tectonic plutonism in several zones of the variscan orogen bohemian austro alpine vosges french and corsica domains is consistent with a derivation of high k magmatism from partial melting of metasomatized mantle following the subduction along the collision front between gondwana and laurasia

alteration and mineralization zoning in tongshan skarn type copper depositin in guichi anhui province and its genesis the tongshan skarn type copper deposit is located in the anqing guichi ore concentration area along the lower and middle yangtze river reaches iron copper metallogenic belt in the study area skarnization and min eralization occur in the contact zone between carbonate and granodiorite porphyry alteration and mineralization show significant horizontal and vertical zoning characteristics in horizontal zoning the garnet content of skarns near the pluton is high the diopside content of skarns far from the pluton is high and the hedenbergite content of skarns near the marble is also high the limestone far away from the marble experienced strong silicification in vertical zoning hornfels calcareous skarn and magnesian skarn occur in downward succession mineralogical studies show that the skarn zone near the pluton has been relatively strongly oxidized and the garnet in it has relatively high and andradite end member cu is concentrated in such bodies as porphyries with quartz veins skarns a bit far from the pluton and hornfels or marbles while zn is usually abundant in silicified limestones and skarns far from the pluton studies suggest that the alteration and mineralization of the tongshan ore deposit experienced the prograde period and the retrograde period the former period could be divided into the contact metamorphic stage and the prograde metasomatic stage and the latter into the early retrograde stage and the late retrograde stage copper mineralization mainly took place at the early retrograde stage and was further concentrated in quartz veins of the porphyries during the late stage of magmatic evolution

formation and behavior of aeolian streamers received 5 december 2004 revised 31 march 2005 accepted 9 june 2005 published 7 september 2005 1 field experiments were conducted to determine the characteristic spatial and temporal dimensions and behavior of aeolian streamers and to identify the processes responsible for their formation an instrument array that included anemometer towers piezo electric transport sensors safires and hot film probes was deployed to measure streamers and airflow dynamics on both a coastal dune and a desert sand mound in california aeolian transport occurs predominantly in the form of families of intertwining and bifurcating streamers while under intense wind forcing more complex patterns of nested streamers and clouds with embedded streamers develop the streamers display a characteristic width of approximately 0 2 m and an average lateral spacing of about 1 m these dimensions appear to be independent of mean airflow characteristics the observations and measurements of streamers under different environmental conditions suggest that bed surface control in the form of differentiation in moisture content grain size or microtopography is not a necessary condition for the formation of streamers the results show little correlation between possible streamwise vortices or burst sweep events and streamers it is proposed that streamers are generated by near surface gusts that originate from large eddies propagating to the ground from higher regions of the boundary layer these elongated and stretched eddies scrape across the surface and initiate saltation along their path this concept accounts for the characteristic size and spacing of streamers their rapid propagation and the fast response of saltation to wind speed fluctuations

rates of aeolian transport on a beach in a temperate humid climate short term field measurements of aeolian transport using a saltiphone indicate that actual rates of transport deviate considerably from the potential rates predicted by transport equations when examined in detail however potential rates are approached during special conditions mostly when the wind blows offshore parallel or slightly oblique to the beach and relative humidity is below 85 also the potential rates of transport may be approached when wind speeds considerably exceed threshold speed even during showers the main cause of the large deviation of actual from potential rates is in the absence of transport during very wet conditions prolonged rainfall regardless of wind speed and the variation of threshold velocity with time the threshold velocity increases during wet conditions with onshore winds or because of the presence of algae therefore potential transport is defined as the transport optimum to predict the actual rates of transport accurately insight into the variation of the threshold velocity is essential aeolian transport of sand seems to be related to moderate events and not to extreme events conforming to the principle of magnitude and frequency

petrography and chemistry of high mg biotite rich pillow lavas from southwestern panay philippines abstract pillow basalts occurring as lenses within the sewaragan formation of southwestern panay contain phenocrysts of forsteritic olivine diopsidic augite and magnesian chromite set in a glassy mesostasis with abundant spinifex pyroxene acicular biotite and skeletal magnetite plagioclase is absent as a modal phase the lavas are midly undersaturated to saturated with respect to sio 2 with high concentrations of k 2 o mgo nio and cr 2 o 3 and low concentrations of al 2 o 3 and tio 2 present understanding of the tectonics of the central philippines places the sewaragan formation within a forearc region related to mid miocene eastward directed subduction along the northward continuation of the negros trench sio 2 undersaturation and the preponderance of biotite differentiate these lavas from arc tholeiite and boninite the rock is a potassic basalt with unusually high mg and low ti and has many similarities to some komatiitic rocks in view of its distinctive chemistry mineralogy and texture the name panayite is proposed

aeolian beach ridges and their significance for climate and sea level concept and insight from the levant coast east mediterranean abstract relict beach ridges of aeolian origin and associated soils are often used for inferring relative sea level and climate with contrasting results most studies link the aeolian coastal deposits to regressive phases some to high sea level stands and a few to intermediate relative sea level positions we interpret the apparent contradictions as indicating the lack of an over arching concept and the inconsistent usage of sea level related terms in this paper we present an integrated morpho sedimentological concept for a microtidal mid latitudinal coast and review existing data from the levant east mediterranean coast to evaluate the concept and to eliminate nomenclatural confusion a coastal depositional environment in a semi arid environment consists of shallow marine aeolian and alluvial facies which together form an aeolian beach ridge complex as a package of strata which respond simultaneously to sea level change a transgressive complex forms through reworking or overstepping of the coastal foredune and a regressive complex forms by downstepping under transgression the aeolian beach ridge represents the highstand deposit and its adjacent shallow marine sediment is the transgressive deposit under regression the complex represents the falling stage and the associated downdip surface marks the lowstand on the levant coast we find chronologically well constrained offlapping aeolian beach ridges as parts of six downstepping beach ridge complexes formed between 200 ka and 10 ka the complexes represent the falling stage systems tract fsst of a short lived 5th order depositional sequence when the shoreline shifted from a position close to the modern coastline to the shelf or below the shelf edge three of these fssts and their up dip and down dip super bounding surface together form the 4th order 100 ka sequence of the last interglacial glacial cycle the absence of transgressive highstand and lowstand systems tract is explained by the poor preservation potential due to the small sediment budget of the complex the falling stage complex has a high preservation potential because sediment source area increases while the sand drift potential remains above the local threshold on the levant coast sand delivery to the backshore continued during relative sea level falls for distances of up to 10 km between dune and coastline which is unprecedented in most modern analogues the significance of the dune soil succession for climate is limited because the dunes are governed by relative sea level change the vegetation response to changes in precipitation is non linear and the dune dynamics are characterised by low resilience and hysteresis

aeolian transport of sediment on a beach during and after rainfall wildwood nj usa abstract a field investigation was conducted 9 march 1994 on a dissipative beach to compare wind characteristics and aeolian transport during and after a light rain winds blew alongshore during the monitoring period moisture content of surface sediment on the backbeach was above 7 during rain and 4 four hours after rainfall ceased trapping rates measured using a cylindrical vertical trap were 14 1 kg m 1 h 1 during rainfall and 140 2 kg m 1 h 1 for a period beginning 3 h 33 min after rainfall ceased results indicate that light rain resulting in bulk surface moisture values over 7 is not sufficient to eliminate transport but the rate of transport is lower than can occur on the beach three to four hours following rain the amount of sand trapped at wildwood during rainfall is relatively high when compared to many previous studies on beaches in the absence of rain the great length of the beach as a source area combined with parallel or oblique winds are significant in increasing rates of sediment transport

the effect of unsteady winds on sediment transport on the stoss slope of a transverse dune silver peak nv usa rapid 10 s measurements of sediment transport and wind speed on the stoss slope of a transverse dune indicate that the majority of sand transported is associated with fluctuations in wind speed with a periodicity of 5 20 min duration increases in the sediment transport rate towards the dune crest are associated with a small degree of flow acceleration the increase in wind speed is sufficient however to greatly increase values of the intermittency index so that the duration of saltation is extended in crestal regions of the dune the pattern of sediment transport on the stoss slope and therefore the locus of areas of erosion and deposition change with the regional wind speed erosion of the crest occurs during wind speed events just above transport threshold whereas periods of higher magnitude winds result in deposition of sand upwind of the crest thereby increasing dune height although short term temporal and spatial relations between sand transport and wind speed on the stoss slope are well understood it is not clear how these relations affect dune morphology over longer periods of time

the origin of the potassic rock suite from batu tara volcano east sunda arc indonesia abstract atu tara is an active potassic volcano in the eastern sunda arc its leucite bearing rock suite can be subdivided into two groups one less evolved with th 20 ppm 87sr 86sr 18o and trace element systematics in the less evolved group suggests that existence of parental magmas with different mantle origins the mantle below batu tara is most likely heterogeneous and several source components are involved in magma genesis trace element and isotopic compositions of batu tara and adjacent volcanoes are consistent with the involvement of a subducted sedimentary crustal component as well as morb and oib mantle the latter with geochemical characteristics comparable to the mantle underlying muriah java melt extraction from this complex mixture is envisioned as a two stage process partial melts of the crust contaminated morb mantle mix in the mantle wedge with partial melts of oib domains different mixtures of these two melts provide the parental magmas that enter the volcanic plumbing system where crystallization hybridization and refilling processes occur the calcalkaline volcanoes in the arc segment show stronger signatures for a subducted crustal component than batu tara which displays a greater influence from the oib mantle source the potassium enrichment can therefore be attributed to contributions both from the enriched mantle and from subducted crustal material mantle type 18o values of the batu tara magmas indicate that the mantle wedge below potassic orogenic volcanoes is not necessarily strongly enriched in 18o

geochemistry of mafic lavas in the early rio grande rift yarmony mountain colorado u s a abstract mafic lavas high k basalts and shoshonites erupted 21 24 ma ago early miocene near state bridge nw colorado and now exposed on yarmony mountain were related to the initial phase of extension in the northernmost section of the rio grande rift the volcanism was of small volume consisting of eleven flows on yarmony mountain although much more voluminous contemporaneous lavas occur 50 km to the west all eleven flows have been analysed comprehensively for major and trace elements and five of the flows for nd and sr isotopes some samples experienced post eruptive carbonation and leaching of alkali elements the effects of these processes on normative compositions are examined and it is suggested that major element abundances are sufficiently well preserved to be fairly sure that the magmas experienced fractional crystallization at pressures appropriate for the mid lower part of the crust most of the basalts are chemically closely related and have the following characteristics 1 they are depleted in nb and ta relative to lree a feature of volcanic arc magmas 2 they have lower abundances of rb and k and to a lesser extent ba and th for a given lree content than typical magmatic arc magmas and 3 they have nd and sr isotopic ratios similar to both certain low 143 nd 144 nd oceanic basalts notably from the kerguelen area indian ocean and subduction related magmas from mature volcanic arcs notably from the andes south america we argue that the magmas erupted at yarmony mountain were generated by partial melting of asthenospheric mantle which had been modified by subduction of oceanic lithosphere during the cenozoic the relatively low abundances of the alkali elements appears to be a consequence of depletion of these elements in the mantle source by a previous episode of melt extraction before that which generated the yarmony magmas an alternative is that the mantle source was depleted in alkali elements by a dehydration event possibly involving a flow of co2 one of the lavas in the yarmony sequence is elementally and isotopically distinctive having higher k zr ba k 2 o na 2 o la ta and k la and lower 87 sr 86 sr than the rest of the samples it is argued in detail that this is not the result of contamination by any reasonable crustal composition and that this magma contained a component 10 20 of ultrapotassic mafic magma derived by partial melting of subcontinental lithospheric mantle there is no petrographic evidence for mixing and the hybridization probably took place in magma chambers situated in the mid lower crust

petrogenesis geochronology and tectonic significance of granitoids in the tongshan intrusion anhui province middle lower yangtze river valley eastern china abstract the tongshan copper deposit in anhui province is a typical mid sized skarn and porphyry type deposit in the anqing guichi district along the middle lower yangtze river valley eastern china the tongshan intrusion is closely related to this mineralization the intrusion mainly comprises rocks that are quartz diorite porphyry quartz monzonite porphyry and granodiorite porphyry plagioclase in these rocks is mostly andesine an 31 0 42 9 along with minor oligoclase biotite is magnesium rich mg mg fe 0 52 0 67 and aluminum poor al 2 o 3 12 32 14 09 wt and can be classified as magnesio biotite hornblende is tio 2 poor 0 60 and is magnesio hornblende or edenite the shrimp zircon u pb age of the quartz monzonite porphyry is 145 1 1 2 ma which corresponds to the middle yanshanian period whole rock geochemical results show that the rocks are silica rich sio 2 60 23 66 23 wt and alkali rich k 2 o na 2 o 4 97 8 72 wt and low in calcium cao 2 61 5 66 wt trace element results show enrichments in large ion lithophile element e g k rb and ba and depletions in some high field strength elements e g nb ta p and ti the total rare earth element ree content of the rocks is low ree n 10 and small positive eu anomalies average eu 1 16 these mineralogical geochronological and geochemical results show that the intrusion has a mixed crust mantle source the tongshan intrusion was formed by multiple emplacements of crustally contaminated basaltic magma generated by varying degrees of partial melting of enriched lithospheric mantle and lower crust hornblende thermobarometry yielded magmatic crystallization temperatures of 652 788 c and an average crystallization pressure of 1 4 kbar which corresponds to a depth of approx 4 7 km biotite thermobarometry yielded similar temperatures and lower pressures of 735 775 c and 0 6 kbar depth 2 1 km respectively the parental magma had a high oxygen fugacity and was produced in a volcanic arc setting related to subduction of the paleo pacific plate

flow dynamics over a foredune at prince edward island canada time averaged windspeed profiles at eight locations over a relatively high 8 m vegetated topographically simple foredune were measured using cup and ultrasonic anemometry during an onshore wind event in may 2002 the experiment was part of a largerstudyonthesedimentarydynamicsofabeach dunecomplexinthegreenwichdunes princeedwardisland pei canada the foredune is vegetated with ammophila breviligulata and vegetation density ranged from 0 on the foredune ramp to upward of 70 at the dune crest topographic forcing and resulting flow acceleration was observed distinctly in windspeed profiles and linear speedup occurred for all elevations above the vegetation canopy a distinct inflection point is evident in normalized windspeed profiles over the dune indicating a net momentum sink below the vegetation canopy top and systematic speed down within the vegetation was observed up the foredune stoss slope wind speed profile structure was consistent for the range of incident wind speeds measured a comparison of normal and slightly oblique incident winds indicated that for similar approach winds wind speeds are consistently higher during oblique flow conditions the implications for foredune morphodynamics and sedimentation are discussed d 2004 elsevier b v all rights reserved

the effects of surface moisture on aeolian sediment transport threshold and mass flux on a beach this paper presents results from a study designed to explore the effects of beach surface moisture and fetch effects on the threshold of movement intensity of sand transport by wind and mass flux the experiment was carried out over a period of five weeks at greenwich dunes prince edward island canada in may and june 2002 moisture content was measured with a delta t moisture probe over a 50 m by 25 m grid established on the beach measurements of wind speed and direction were made with arrays of cup anemometers and a two dimensional sonic anemometer transport intensity was measured at a height of 2 4 cm above the bed using omnidirectional saltation probes which count the impact of saltating grains on a piezoelectric crystal anemometers and saltation probes were sampled at 1 hz sand transport was measured with vertical integrating sand traps over periods of 10 20 minutes results show that where there is a considerable supply of dry sand the saltation system responds very rapidly 1 2 s to fluctuations in wind speed i e to wind gusts where sand supply from the surface is limited by moisture mean transport rates are much lower and this reflects in both a reduction in the instantaneous transport rate and in a transport system that becomes increasingly intermittent threshold wind speed is significantly correlated with an increase in surface moisture content near the upwind end of the beach fetch but the relationship is not significant at the downwind end where sediment transport is initiated primarily by saltation impact from upwind mass flux increases with increasing fetch length and the relationship is described best by a power function further work is necessary to develop a theoretical function to predict the increase in transport with fetch distance as well as the critical fetch distance copyright 2007 john wiley sons ltd