shelf cross shore flows under storm driven conditions role of stratification shoreline orientation and bathymetry abstractnumerical simulations are used to study the response of long bay south carolina a typical coastal embayment with curved coastline located on the south atlantic bight to realistic climat

time dependent wind driven flow over a shallow midshelf submarine bank 1 during summer 2001 high resolution hydrographic velocity and bio optical surveys were conducted over heceta bank off central oregon north of the bank upwelling over simple bottom topography exhibited a classic response with a midshelf baroclinic coastal jet and upwelled isopycnals the coastal upwelling jet follows the bank topography as it widens offshore before reaching the southern end of the bank where the shelf break turns almost 90 back toward the coast the ensuing adjustment involves the offshelf transport of coastal water and the material it contains the jet meanders anticyclonically in the lee of the bank before resuming its equatorward path seaward of the shelf break a pool of high chlorophyll 15 mg m 3 near surface water is found in the low velocity lee region created by the bank a low temperature high salinity bottom water pool supplied primarily from the south lies over the inshore region of the bank this bottom pool is up to 40 m thick and contains elevated levels of suspended material by creating an east west perturbation in the coastal upwelling front the flow topography interaction introduces an alongshore pressure gradient when southward upwelling favorable winds relax this alongshore pressure gradient can drive flow back to the north this leads to northward flow on the inshore side of the bank ultimately setting up the potential for recirculation around the entire bank complex on a timescale of about 10 days strong northward winds during summer lead to downwelling within 15 km of the coast accompanied by significant 0 2 m s 1 wind driven northward currents

modeling study of variable upwelling circulation in the east china sea response to a coastal promontory abstracta three dimensional high resolution numerical model is used to investigate processes and dynamics of an intensified upwelling that is induced by a coastal promontory over the east china sea ecs shelf the center of the intensified upwelling around the promontory has been constantly observed but so far it has been dynamically unexplained forced by an idealized southeasterly wind stress the model results well capture the observed upwelling at the lee of the coastal promontory the intensified upwelling is formed by a strengthened shoreward transport downstream of the promontory as the upwelling jet veers shoreward the jet is mainly controlled by a cross shore geostrophic balance and is largely modulated by both centrifugal acceleration associated with nonlinear advection and by bottom stress the strengthened shoreward transport is mainly attributed to the cross shore geostrophic current that is induced by a countercurrent negative pressure gradient force pgf and partly attributed to th

kinematics of large syn orogenic intrusions example of the lower proterozoic saraya batholith eastern senegal the large saraya batholith intruded the lower proterozoic sequences of eastern senegal structural analysis indicates that this large granitic batholith corresponds to a composite body consisting of several coalescent plutons and interfering diapirs interpretation of the structural fabric patterns in these plutons and in the host rocks constitutes the basis of a hypothetical model of initiation ascent and emplacement as follows 1 development of a deep n s granitic ridge controled by a major crustal fracture generated by an earlier extensional phase re activated by a strike slip fault which probably would facilitate segregation collection and ascent of magmas 2 intrusion and splitting up of the ridge into several diapirs which ascended simultaneously and separately in a setting of a n s sinistral transcurrent deformation inducing a transverse nw se shortening and forceful emplacement of plutons and 3 final emplacement characterized by interference between regional deformation and pluton ballooning the latter leading to the coalescence of intrusions and to the formation of a larger apparently homogeneous body

coastal wind driven circulation in the vicinity of a bank part ii modeling flow over the heceta bank complex on the oregon coast abstract this study investigates wind driven circulation in the vicinity of the heceta bank complex along the oregon shelf numerical experiments forced with steady winds 0 1 pa are conducted upwelling and downwelling cases are compared the asymmetric bank bathymetry is the only configurational difference from the symmetric bank runs analyzed in part i whitney and allen upwelling favorable winds generate an upwelling front and southward baroclinic jet model results indicate the upwelling jet is centered on the 100 m isobath along the straight shelf the jet follows this isobath offshore around the northern part of the bank but separates from sharply turning isobaths in the southern half and flows over deeper waters the jet turns back toward the coast farther downstream inshore of the main jet currents reverse and flow back onto the bank these reversed currents turn southward again at the bank center and join a secondary southward coastal upwelling jet this secondary coastal jet converges wi

an upwelling case study on florida s west coast using a combination of satellite sea surface temperature imagery in situ currents temperature and sea level data and a numerical circulation model we describe an upwelling event observed along florida s west coast although ubiquitous features of continental shelves descriptions of coastal upwellings or downwellings are generally complicated by the continuum of processes in which they occur for the case study presented the winds were light and the baroclinic background currents were steady for several days prior to the event these conditions allow the evolution of a specific winddriven upwelling event to be viewed as an initial value problem the data and the numerical model analysis show that the route of adjustment by the sea level and currents is a classical ekman geostrophic one sea level drops due to an offshore ekman transport causing a geostrophic alongshore jet and the associated onshore flow within the bottom ekman layer accounts for the appearance of cold water at the surface this surface manifestation occurs as an elongated feature centered about the 25 m isobath that spans roughly half of the florida peninsula from just north of tampa bay to key west the coldest water is observed offshore from tampa bay and we explain this region of locally maximum upwelling on the basis of the coastline and isobath geometries

tourmalines from appalachian caledonian massive sulfide deposits textural chemical and isotopic relationships tourmaline is a common gangue mineral in several strata bound massive sulfide deposits of the appalachian caledonian orogen most of the tourmaline rich deposits occur in dominantly metasedimentary terranes such as bleikvassli norway black hawk maine ore knob north carolina and elizabeth vermont minor amounts of tourmaline are also known in association with volcanic hosted deposits in the appalachians and in the trondheim district of norway the tourmaline forms isolated euhedral crystals or crystal aggregates in massive sulfide and adjacent wall rocks in a few areas it is found in conformable tourmaline rich layers tourmalinites associated minerals may include quartz plagioclase phlogopite and dolomite with pyrrhotite chalcopyrite galena and sphalerite many of the tourmaline crystals are optically zoned in which brown zones concentrically alternate with pale yellow or green zones a few specimens of tourmaline intergrown with massive sulfide e g ore knob display fine delicate growth lamellae similar to those commonly observed in hydrothermal vein sphalerites skarn garnets and sphalerites from the massive sulfide deposits of the kuroko district japan detailed geochemical studies indicate that the tourmalines have characteristic major and trace element compositions electron microprobe analyses show that with rare exception the tourmalines are mg rich dravites avg feo feo mgo 0 21 abrupt transitions between color zones within some tourmaline are accompanied by relative variations in feo feo mgo of as much as 30 percent yellow brown zones are more mg rich than blue or green zones in contrast the fine growth lamellae are not characterized by such variations in chemistry spectrographic analyses of pure mineral separates indicate that the tourmalines also contain high average contents of cr 78 ppm cu 77 ppm pb 114 ppm sr 98 ppm and v 195 ppm while uniformly low in li 7 ppm and mn 382 ppm in all analyzed samples fluorine is much more abundant than chlorine the average f cl ratio is 33 tourmalines from tourmalinites and massive sulfide deposits are typically characterized by heavier delta 18 o values 9 5 15 5ppm and less variable heavier delta d values generally 45 to 60ppm than tourmalines from unmetamorphosed igneous pegmatites the latter typically have delta 18 o 9 5 per mil and delta d or 60 per mil oxygen isotope fractionations between quartz and tourmaline delta 1 27 4 01 do not correlate directly with inferred grade of subsequent metamorphism although in areas of high metamorphic grade the delta values approach those of igneous quartz tourmaline pairs the delta 18 o values of quartz and tourmaline are believed to reflect variation in the oxygen isotope compositions of the host lithologies the similar narrow range in hydrogen isotope composition for tourmaline in all studied deposits is compatible with a modified seawater origin for the tourmaline and sulfide forming fluids the distinctive textural and chemical characteristics of the tourmalines reported here have both exploration and genetic significance though it may have undergone recrystallization and some accompanying chemical and isotopic exchange during regional metamorphism tourmaline in the massive sulfide deposits is an early formed perhaps diagenetic mineral in which fine lameliar zoning may be a preserved premetamorphic feature in any case the tourmalines from the massive sulfide deposits are mg rich dravites with trace element and stable isotope compositions substantially different from those of the fe rich schorls typical of most granitic rocks these geochemical and isotopic signatures are attributed to the original environment of formation of the associated sulfide deposits and suggest that mg rich tourmaline may be a valuable prospecting guide in the search for massive sulfide deposits

dynamics of the summer shelf circulation and transient upwelling off ningaloo reef western australia received 19 july 2012 revised 21 january 2013 accepted 25 january 2013 published 11 march 2013 1 the shelf circulation off ningaloo reef near the north west cape of western australia is driven by complex interactions between the southward flowing leeuwin current and wind driven currents that episodically reverse the coastal flow toward the north the presence of these northward equatorward wind driven currents is thought to make this section of coast one of the few locations along western australia to experience periodic coastal upwelling we used a combination of field observations and numerical modeling to investigate the summer circulation and upwelling dynamics along ningaloo reef we analyzed current and temperature profiles from moorings at four sites across the shelf and used two regional ocean modeling system roms sub models 1 a coarser model of northwestern australia forced by a global ocean model and 2 a nested fine scale model of the ningaloo region this nesting significantly improved model skill as it included the offshore mesoscale dynamics that strongly influenced the shelf circulation off ningaloo the field observations revealed several northward flow reversals accompanied by cooling of the coastal waters adjacent to ningaloo which were associated with strong northward wind events analysis of the coastal heat budget revealed that cooling events were primarily driven by upwelling whereas warming of coastal waters during relaxation events resulted mostly from along shelf advection of warm water from the north due to the combined effects of its relatively steep 1 50 slope shelf and strong summer stratification upwelled water was sourced from the interior of the water column likely influencing the sources and fluxes of nutrients to ningaloo reef

cr bearing tourmaline associated with emerald deposits from swat nw pakistan genesis and its exploration significance carbonate talc altered ultramafic and mafic rocks of the obducted oceanic lithosphere along the main mantle thrust in the swat valley host emerald deposits and are invaded by quartz veins and stockworks both the quartz veins and carbonate talc altered rocks contain discrete grains and clusters of tourmaline crystals which may be associated with emerald and or chromian muscovite tourmalines from the mingora and gujar kili emerald mines and the spin obo kuh area are ni bearing cr rich dravites and oxy dravites that exhibit substantial chemical variability with 2 0 2 5 atoms per formula unit apfu mg relatively low al 4 8 5 8 apfu high cr 0 5 1 8 apfu high cr cr al ratios of 0 08 0 28 significant amounts of ni up to 0 11 apfu and variable calculated w site o 2 0 2 0 8 apfu the mechanisms that appear to control the tourmaline chemistry at these localites are combinations of the dominant substitution al cr with lesser amounts of the mg oh 1 al cr o 2 and al 3 fe 3 substitutions relative to the mingora gujar kili and spin obo kuh areas the charbagh tourmalines are oxy dravites that have comparable mg contents 2 2 2 3 apfu with variable calculated w site o 2 0 6 0 9 apfu but are more fe rich 0 5 apfu and al rich 6 0 6 3 apfu with low cr 0 00 0 01 apfu and ni contents 0 01 0 02 apfu the mechanism that appears to control the variable chemistry of the charbagh tourmalines is primarily mg oh 1 al o 2 the chemical characteristics of tourmalines from the various localities relate most clearly to differences in host rock chemistry tourmalines from the carbonate talc altered ultramafic mafic rocks and the invasive quartz veins have a common hydrothermal origin associated with emplacement and crystallization of younger granitoids furthermore the occurrence of swat emeralds in quartz tourmaline chromian muscovite veins suggests that the tourmaline is cogenetic with emerald formation the quality and quantity of swat emeralds depend on the 1 host rock composition and 2 nature of the hydrothermal fluids large deposits of gem quality emerald occur in carbonate altered ultramafic rocks which also contain cr rich dravites and oxy dravites this suggests that the presence of high cr magnesian tourmalines particularly in magnesite talc altered ultramafic rocks can represent a criterion for further emerald exploration in the lower swat region of pakistan and comparable ultramafic hosted emerald producing regions

the hydraulics of an evolving upwelling jet flowing around a cape upwelling jets flow alongshore in approximate geostrophic balance with the onshore pressure gradient induced by coastal upwelling observations of such jets have shown that they often move offshore downstream of capes leaving a pool of upwelled water inshore comparisons are made between this behavior and the hydraulic transition of a potential vorticity conserving coastal current as it passes a topographic anomaly at which it is exactly critical to long coastal trapped waves an analytic 1 5 layer model of coastal hydraulics with constant potential vorticity in each layer predicts flow fields i e jet separation in critical situations that resemble observations when scales approximate cape blanco on the oregon coast separation occurs at a jet transport of around 0 76 3 106 m3 s21 similar to observed transports time dependent semigeostrophic calculations suggest that during an upwelling season the jet would evolve from a weak flow which was subcritical everywhere and symmetric about the cape to an exactly critical state that made a transition from subcritical to supercritical structure at the head of the cape the predicted flow field at critical transition consists of a narrow upwelling jet upstream of the cape that moves offshore and broadens at the cape this critical state would be accompanied by a downstream jump back to subcritical conditions further upwelling favorable winds would lead to transient waves that propagated upstream and downstream modifying the upstream and downstream conditions and restoring criticality thus the head of the cape exerts hydraulic control on the flow and prevents the jet transport from increasing above its critical level inherent in the hydraulic approach is the assumption that alongshore scales are large for realistic alongshore scales solutions modified by coastline curvature suggest that the convexity of the head of a cape slightly inhibits the transition to a strongly upwelled downstream state by increasing the required critical transport in the presence of topographic features with finite alongshore scale the hydraulic approach can be used to construct a flow field although this flow field has an inherent error arising from the implicit assumptions regarding scales estimation of this error for topography representing cape blanco suggests that in places the cape is rather abrupt for hydraulic theory to be valid

upwelling induced by the frictional stress curl and vertical squeezing of the vortex tube over a submerged valley in the east china sea we conducted a process oriented modeling study to investigate the characteristics and dynamics of the prominent upwelling over a vast submerged valley in the east china sea ecs the valley is inversely funnel shaped with the west bank and the east bank oriented in the north south direction a cross bank upward transport occurred along the west bank it intensified northward and peaked around the head of the valley an along bank southward pressure gradient force pgf formed the cross bank geostrophic transport for the upwelling over the valley the pgf reached its maxima at the head of the valley our momentum and vorticity dynamic analyses revealed that a bottom stress curl mainly contributed the pgf along the west bank at the same time both the bottom stress curl and the nonlinear vorticity advection contributed to the pgf around the head the bottom stress curl was due to the bottom shear vorticity of the coastal current and the curvature vorticity around the head the nonlinear vorticity advection formed because of the vertical squeezing of vortex tube as the current flowed over the valley the nonlinearity mainly affected the pgf around the head whereas the bottom stress curl contributed to the pgf over the entire valley the ratio of the nonlinear to frictional contributions to the pgf increased as the coastal current intensified our study demonstrates that the pgf that drives the upwelling over the valley is the combined result of the nonlinearity due to vertical squeezing of vortex tube and bottom frictional effects

crustal thinning recorded by the shape of the namurian westphalian leucogranite in the variscan belt of the northwest massif central france in the western part of the variscan belt of the french massif central the gueret massif is an extensional allochthon emplaced to the southeast during namurian westphalian time the internal structure of the coeval leucogranites surrounding the western edge of the gueret massif consists of the plateau d9aigurande brame st sylvestre and st goussaud massifs these plutons are asymmetric diapirs rooted in the marche bussiere madeleine and arrenes faults respectively the plutons indicate diverging extravasation from the gueret massif whatever their shapes the plutons have a northwest trending stretching lineation that is also marked in the granite host rocks by retrograde metamorphic minerals the same extension direction is also inferred from namurian westphalian leucogranites and dikes intruding the gueret massif extension related granitoids present typical structural patterns such as asymmetric shapes extravasation from the collapsing area and persistence of a stretching lineation parallel to the regional extension direction these features may be used to diagnose crustal thinning

deformation of the assegaai supracrustals and adjoining granitoids transvaal south africa abstract the structures in archaean quartzites of the assegaai greenstone belt in the transvaal of south africa can be interpreted in terms of three major deformation events earliest d1 involved thrusting along brittle ramp and flat crush zones rising temperatures then led to the mobilization of sio2 and the development of syn d1 stylolites and omnidirectional quartz veins in the quartzites increasingly ductile behaviour results in some of the early d1 crush zones being overprinted by late d1 mylonitic shear zones while eastward verging recumbent folds formed about n s axes in the layered quartzites the assegaai supracrustals were then separated from a contiguous basement of ancient gneiss complex agc by the intrusion of a granitoid sheet about 3 km thick along their sheared subhorizontal contact either late in d1 or in the interval between d1 and d2 the supracrustals were then refolded about steep nne trending axial surfaces by concentric f2 folds on a variety of scales such folds were the second major structures to affect the supracrustals but the first to deform the granitoid sheet the older of two suites of quartzo feldspathic veins in the agc were probably generated penecomtemporaneously with the syn d1 quartz veins in ther assegaai quartzites this interpretation can be tested by removing the intense d2 constriction and 30 volume increase recorded by a later network of syn granitoid quartzofeldspathic veins in the agc from the d1 d2 flattening recorded by the older veins this procedure can be carried out by geometric vector subtraction on a hsu diagram the result reveals that the d1 strains in the assegaai supracrustals and the then contiguous agc were identical penetrative subhorizontal flows prior to the intrusion of the intervening granitoid the last significant strain in the region is represented by a brittle nne trending strike slip fault and locally in the quartzites disharmonic conjugate folds

polyphase wrench tectonics in the southern french massif central kinematic inferences from pre and syntectonic granitoids in the variscan french massif central the south limousin area consists of low to medium grade metamorphic rocks intruded by two granitic bodies the structural and textural analyses of these plutons undertaken in parallel with the structural analysis of their host rocks allow us to characterize and to date different stages in the tectonic evolution of this area this study shows that the south limousin area experienced successivelly two strike slip events along two geographically distinct shear zones from north to south the left lateral estivaux and the right lateral south limousin strike slip faults respectively these ductile faults subdivide the south limousin into three structural units from north to south they are the upper gneiss unit thiviers payzac unit and genis unit the two granitic bodies intrude the thiviers payzac unit only the younger estivaux granite is a syntectonic pluton which emplaced during left lateral wrenching 40ar 39ar dates from biotites indicate an early carboniferous age 346 3 ma the older granite is a pretectonic body it is the ordovician saut du saumon augen orthogneiss in which detailed structural analyses show the polyphase nature of the solid state deformation our microtectonic data indicate that the right lateral motions overprint the left lateral ones and produce apparently symmetrical fabrics

on the spatial structure of coastal circulation off newport oregon during spring and summer 2001 in a region of varying shelf width 1 a time series of hourly surface current maps in the shelf waters off newport oregon was made during april september 2001 using five seasonde hf current mappers during coastal advances in shelf transport coast the surface currents responded rapidly to the changing winds in repeated patterns that were strongly affected by bottom topography an equatorward current jet repeatedly formed in response to upwelling winds its strength but not its trajectory covarying with the meridional wind stress near cape foulweather 44 8 n where the shelf begins to widen the jet rotates weakens and trends offshore to the south first along then across the isobaths below cape foulweather inshore of the jet a lee region of generally weak currents was commonly observed the equatorward jet core was most commonly observed near the 80 m isobath between 45 0 n and 44 4 n but transited offshore between spring and summer over heceta bank at newport 44 6 n it was rarely observed less than 8 km from the coast a second inshore equatorward jet previously unknown was observed repeatedly south of waldport 44 4 n sustained downwelling wind episodes produced poleward currents though less responsively north of cape foulweather strongest poleward flow was generally trapped near the coast surface currents were correlated with the northward wind except regionally far from shore over heceta bank responding within half a day response to the wind varies spatially being intensified in the narrow shelf northern region the equatorward jet persists through periods of zero wind forcing coastal sea level covaries with the meridional wind and the primary mode of ocean current response

are strongly peraluminous magmas derived from pelitic sedimentary sources igneous compositions that require the presence of a phase more aluminous than biotite are here designated as strongly peraluminous ps such compositions are common but subordinate in felsic rocks and exceedingly rare in more mafic rocks the term s type has been applied to many igneous rocks based largely or even solely upon their ps compositions neglecting or placing less emphasis on other criteria for sedimentary parentage in chappell and white s i and s type classification system the s type designation was in fact initially restricted to granites which were thought to have been derived from a chemically mature strongly weathered pelitic shaly source application of chappell s and white s criteria together with others based upon isotopic and phase equilibria considerations leads to the following conclusions about ps igneous rocks worldwide 1 very few ps rocks are derived entirely from pelitic sources 2 a majority are derived largely from intermediate to felsic crustal sources including

stable isotope compositions of tourmalines from granites and related hydrothermal rocks of the karagwe ankolean belt northwest tanzania abstract tourmaline is a ubiquitous mineral in the mid proterozoic peraluminous syn to post tectonic granites and aplites and the related hydrothermal rocks of the karagwe ankolean belt in northwest tanzania electron microprobe analysis indicates that tourmalines from all of the intrusive and hydrothermal lithologies 1 belong to the schorl dravite solid solution series and 2 plot within the field occupied by tourmaline from li poor granitoids on the fe al mg classification diagram oxygen isotope compositions range from 12 2 to 11 6 smow for magmatic tourmalines and from 10 8 to 9 8 for those of hydrothermal origin hydrogen isotope compositions vary from 79 to 65 smow for magmatic tourmalines and from 99 to 84 for hydrothermal tourmalines water contents measured by manometry are constant at 3 0 3 2 wt within the broad grouping there arc systematic variations in both chemical particularly fe tot fe tot mg ratio and isotopic composition that relate to evolving magmatic and hydrothermal conditions igneous differentiation increasing fe tot fe tot mg ratio in magmatic tourmaline has produced trends with higher 18o in quartz lower 18o in tourmaline and larger qtz tour values that reflect a combination of a reduction of crystallization temperature and an increase of fe tot fe tot mg ratio in the residual melt subsequent cooling and interaction of an exsolved b rich magmatic fluid with the pelitic country rocks resulted in the deposition of hydrothermal tourmaline with increasing fe tot fe tot mg ratio ratios and progressively lower 18o and d values

tourmaline occurrences within the penamacor monsanto granitic pluton and host rocks central portugal genetic implications of crystal chemical and isotopic features tourmalinization associated with peraluminous granitic intrusions in metapelitic host rocks has been widely recorded in the iberian peninsula given the importance of tourmaline as a tracer of granite magma evolution and potential indicator of sn w mineralizations in the penamacor monsanto granite pluton central eastern portugal central iberian zone tourmaline occurs 1 as accessory phase in two mica granitic rocks muscovite granites and aplites 2 in quartz mica tourmaline rocks tourmalinites in several exocontact locations and 3 as a rare detrital phase in contact zone hornfels and metapelitic host rocks electron microprobe and stable isotope 18o d 11b data provide clear distinctions between tourmaline populations from these different settings a schorl oxyschorl tourmalines from granitic rocks have variable foititic component x 17 57 and mg mg fe ratios 0 19 0 50 in two mica granitic rocks and 0 05 0 19 in the more differentiated muscovite granite and aplites granitic tourmalines have constant 18o values 12 1 0 1 with wider ranging d 78 2 4 7 and 11b 10 7 to 9 0 values b vein breccia oxyschorl mg mg fe 0 31 0 44 results from late b and fe enriched magma derived fluids and is characterized by 18o 12 4 d 29 5 and 11b 9 3 while replacement tourmalines have more dravitic compositions mg mg fe 0 26 0 64 close to that of detrital tourmaline in the surrounding metapelitic rocks and yield relatively constant 18o values 13 1 13 3 though wider ranging d 58 5 to 36 5 and 11b 10 2 to 8 8 values and c detrital tourmaline in contact rocks and regional host metasediments is mainly dravite mg mg fe 0 35 0 78 and oxydravite mg mg fe 0 51 0 58 respectively boron contents of the granitic rocks are low 650 ppm compared to the minimum b contents normally required for tourmaline saturation in granitic melts implying loss of b and other volatiles to the surrounding host rocks during the late magmatic stages this process was responsible for tourmalinization at the exocontact of the penamacor monsanto pluton either as direct tourmaline precipitation in cavities and fractures crossing the pluton margin vein breccia tourmalinites or as replacement of mafic minerals chlorite or biotite in the host rocks replacement tourmalinites along the exocontact of the granite thermometry based on 18o equilibrium fractionation between tourmaline and fluid indicates that a late b enriched magmatic aqueous fluid av 18o 12 1 at 600 c precipitated the vein breccia tourmaline 18o 12 4 at 500 550 c and later interacted with the cooler surrounding host rocks to produce tourmaline at lower temperatures 400 450 c and an average 18o 13 2 closer to the values for the host rock although b metasomatism associated with some granitic plutons in the iberian peninsula seems to be relatively confined in space extending integrated studies such as this to a larger number of granitic plutons may afford us a better understanding of variscan magmatism and related mineralizations

the relative importance of wind strength and along shelf bathymetric variations on the separation of a coastal upwelling jet abstract a high resolution numerical model with idealized topography is used to investigate the degree to which a coastal upwelling jet separates from the shelf as it flows around a submarine bank depending on the wind strength and the horizontal scale of the bank experiments were run using several wind forcing magnitudes and submarine banks with different geometries so as to explore a wide range of the flow strength as measured by the rossby number ro and the ratio of the squares of the internal rossby radius of deformation and curvature of the topography as denoted by the burger number bu the intensity of the jet separation is strongly dependent on both parameters with maximum separation with increasing ro and bu close to 1 when large amounts of upwelled water are exported toward deeper waters for small bu separation is minimal and independent of ro for high ro the degree of separation decreases at large bu since the bank acts only as a small perturbation to the flow term balances in the a

chemical and stable isotopic b h and o compositions of tourmaline in the maocaoping vein type cu deposit western yunnan china constraints on fluid source and evolution abstract this study determined the chemical and stable isotopic b h and o compositions of three stages of ore related hydrothermal tourmaline in the newly discovered maocaoping vein type cu deposit western yunnan china as well as the chemical and b isotopic compositions of magmatic tourmaline tourmaline g from a neighboring peraluminous granitic intrusion that is contemporaneous with the cu mineralization the objective was to constrain the source and evolution of the co 2 rich ore forming fluid the maocaoping cupriferous veins types v1 and v2 are hosted in mylonitized and metamorphosed jurassic sedimentary rocks early to late stage hydrothermal tourmaline occurs as vein related alteration halos tourmaline a in altered marble or schist as tourmaline v1 in type v1 veins and as tourmaline v2 in type v2 veins tourmaline a v1 and v2 belong to the alkalic group and consist mostly of dravite with 11 b values of 3 9 to 1 1 2 8 to 0 5 and 6 3 to 3 9 respectively tourmaline g belongs to the alkalic group and consists of schorl with 11 b values of 14 7 to 12 2 the similarities in chemical composition between marble and schist hosted tourmalines and between tourmalines in veins and alteration halos indicating their formation at different water rock ratios suggest that the compositions of the hydrothermal tourmaline at maocaoping were controlled mainly by the chemistry of ore fluid rather than that of the host rocks the similarities together with the lack of systematic variations in 11 b values in individual tourmaline grains imply that mixing of multiple fluids cannot be important during the mineralization the positive shift in 11 b values from tourmaline a to tourmaline v1 is interpreted to result from continuous precipitation of tourmaline in a closed fluid system relative to tourmaline a and v1 tourmaline v2 is fe rich al poor and 11 b depleted these differences may be explained by fluid phase separation and subsequent escape of the co 2 rich vapor phase during the formation of type v2 veins consistent with the observations that these veins are extensional contain large amounts of carbonate minerals and include fluid inclusions trapped in the vapor liquid two phase field the earliest tourmaline a records the initial ore fluid chemistry the calculated 11 b 18 o and d values of the initial ore fluid in equilibrium with tourmaline a at mineralization temperatures of 280 to 320 c are 0 3 to 3 0 10 7 to 11 8 and 110 to 84 respectively the 11 b values as well as the chemical compositions of tourmaline a are much different from those of tourmaline g suggesting that the ore fluid at maocaoping was not derived directly from the peraluminous granitic magma the b h o isotopic features as well as enrichment of co 2 in fluid inclusions also suggest the ore fluid cannot solely be derived from basinal fluid or meteoric water the simplest explanation is that the fluid was derived from a metamorphic fluid that had obtained isotopically lighter hydrogen via reaction with organic compounds e g ch 4 h 2 s alternatively the ore fluid sourced from the mixed metamorphic fluid and basinal brine meteoric water or degassed magmatic fluid it implies that the vein cu ore formation in the lanping basin is unlikely as a result of a sole magmatic or basinal fluid activity and it needs the involvement of metamorphic fluid process

modeling bottom mixed layer variability on the mid oregon shelf during summer upwelling abstract results from a model of wind driven circulation are analyzed to study spatial and temporal variability in the bottom mixed layer bml on the mid oregon shelf in summer 2001 the model assimilates acoustic doppler profiler velocities from two cross shore lines of moorings 90 km apart to provide improved accuracy of near bottom velocities and turbulence variables in the area between the mooring lines model results suggest that the response of the bml thickness to upwelling and downwelling favorable winds differs qualitatively between an area of simple bathymetric slope at 45 n and a wider shelf area east of stonewall bank 44 5 n at 45 n the bml grows in response to downwelling favorable conditions in agreement with known theories east of stonewall bank the bml thickness is increased following upwelling events in this area the southward upwelling jet detaches from the coast and flows over a wider part of the oregon shelf creating conditions for ekman pumping near the bottom based on

b and o isotopic compositions of tourmaline constrain late stage magmatic volatile exsolution in tasmanian tin related granite systems the devonian sn mineralized heemskirk and barren pieman heads granites of western tasmania southeast australia contain abundant tourmaline rich features including orbicules patches cavities and veins within their roof zones the delta b 11 and delta o 18 compositions of tourmaline from these texturally different features range from 21 7 to 4 1 parts per thousand average 4 7 4 0 parts per thousand n 127 and from 6 5 to 14 9 parts per thousand average 10 7 1 8 parts per thousand n 38 respectively these data suggest that the tourmaline rich assemblages precipitated mostly from magmatic hydrothermal fluids derived from their host plutons mixed with minor external components sourced from metasedimentary meta ultramafic rocks and or meteoric water the b isotopic values increase sequentially from tourmaline patches to orbicules and or cavities in both granites probably caused by progressive volatile exsolution and systematic fluxing of aqueous boron rich fluids from the s type magmas during emplacement into the shallow crust high degrees of fractional crystallization of the melt may have caused the exsolution of boron rich hypersaline fluids from which the tourmaline orbicules and cavities formed bimodal delta b 11 populations 21 7 to 12 7 parts per thousand and 3 9 to 4 0 parts per thousand imply that the granitic melts were mostly sourced from b 10 rich metapelitic rocks the granites underwent fluid exsolution during the late magmatic stage that contributed to the widespread development of tourmaline rich features and also to the formation of tin deposits associated with the heemskirk granite

modeling upwelling circulation off the oregon coast 1 time dependent three dimensional upwelling circulation on the continental shelf off the oregon coast is studied using a primitive equation numerical model a limited area domain with a high resolution curvilinear grid is utilized the response of the coastal ocean to forcing by observed wind stress and heat flux during the summer 2001 time period of the coastal ocean advances in shelf transport coast field experiment is investigated model results are compared to coast current and hydrographic measurements the shelf velocity and density fields are generally characterized by the presence of a southward alongshore coastal jet with an upwelling density front on the shoreward side of the jet the large variability in shelf topography associated with heceta bank exerts a major influence on the shelf velocity and density fields over the bank the alongshore coastal jet is displaced offshore and colder upwelled water extends farther from the coast northward mean flow and upward motion are found inshore of the jet three dimensional flow structures in response to variable shelf bottom topography are presented and an analysis of time and space dependent alongshore momentum balances is applied to clarify the associated dynamics in general northward pressure gradients set up over the bank during southward upwelling winds accelerate currents on the inshore side of the jet northward when the winds relax analysis of term balances in the depth averaged equation for potential temperature shows that during upwelling across shore advection makes the major contribution to cooling over most of the region except inshore over heceta bank where alongshore advection also plays a significant role

trace element systematics of tourmaline in pegmatitic and hydrothermal systems from the variscan schwarzwald germany the importance of major element composition sector zoning and fluid or melt composition article an extensive data set on the compositional variation of tourmaline from granitic pegmatites from migmatitic gneisses and from various types of hydrothermal veins from the schwarzwald germany is provided the investigated tourmalines are members of the alkali and x vacant groups representing mostly dravite schorl solid solutions with some analyses belonging to the foitite mg foitite series oxygen isotope data on quartz tourmaline pairs indicate formation temperatures between 550 and 350 c for most of the quartz tourmaline veins most of the tourmalines show strong sector zonation fractionating certain major e g na mg minor e g ti ca and trace elements e g sr pb ree among the different crystallographic sectors of the crystals we conclude that comparison of tourmaline compositions for petrogenetic interpretations must be based on the concentrations in the neutral a sector in order to eliminate the effects of intra crystalline fractionation most trace element contents vary over several orders of magnitude with median concentrations generally be tween 0 1 and 10 g g the highest concentrations are found for zn v sr sc sn and li median concentrations of several tens to hundreds of g g whereas very low median concentrations b0 1 g g were found for u th bi tl and cs the concentration of several trace elements e g sr ree co correlates with the major element composition of the tourmaline which implies potential crystal chemical effects on their incorporation conse quently the general assumption that tourmaline is a passive monitor for the chemical compositions of the melts or fluids from which it crystallizes has to be questioned nevertheless our study demonstrates that the trace element composition of tourmaline allows to distinguish between geochemically distinct fluid sources and the trace element composition of tourmaline may therefore be used to unravel the chemical complexity of granite related hydrothermal systems

genesis of the graphite orbicules in the huangyangshan graphite deposit xinjiang china evidence from geochemical isotopic and fluid inclusion data abstract the huangyangshan graphite deposit in the east junggar orogen china contains intriguing graphite orbicules this contribution is designed to present reasonably comprehensive assessment of their origin in this deposit the intrusive orebodies are mechanically juxtaposed against contacts with granitic wall rocks the orbicules are typically concentrically zoned in texture with a notable binary configuration involving a central core and an outer shell the orbicule cores possess mineralogical and compositional variations that are more or less similar to those of the granitic wall rocks the orbicule shells are composed of various ferromagnesian minerals clinopyroxene hornblende in stark contrast to the matrix where hornblende sanidine and albite have higher mg ab and an values respectively the replacement of silicates by graphite and sulfides pyrrhotite chalcopyrite pyrite is common the graphite throughout the matrix and orbicules features a patchy distribution of major elements c and dispersed elements cr ni co s cu zn as pb etc the carbon isotopic compositions of the orbicular ore are 20 9 to 20 5 analogous to those of the surrounding strata i e 25 6 to 19 3 the sulfur isotopic compositions of sulfides in the orbicular ore are 4 8 to 2 6 which differ from those of the surrounding strata i e 16 0 23 0 fluid inclusions principally comprise the volatile component ch4 and solid daughter minerals graphite chalcopyrite with tm 450 c vapor liquid two phase fluid inclusions formed under conditions of th 143 6 367 5 c p 3 194 bar and fo2 52 76 to 31 15 the hydrogen and oxygen isotopic values of the orbicular ore are d 110 3 to 107 0 and 18owater 10 1 11 7 zircons from the orbicular ore have 206pb 238u ages of 304 359 ma with a weighted average of 319 0 6 4 ma overlapping the geochronological age of the granitic host rocks 305 1 321 4 ma the orbicular ore has sio2 concentrations ranging from 53 30 to 72 61 wt falling within the compositional fields of granite quartz monzonite granodiorite diorite and monzodiorite in the tas classification diagram the sr nd and hf isotopic data from the orbicular ore indicate mixing between materials derived from the depleted mantle and materials derived from the crust with a dominant mantle contribution the petrographic geochemical isotopic and fluid inclusion characteristics indicate that the processes of incorporation of h2o and wall rock fragments liquid immiscibility and exsolution of a late magmatic fluid were responsible for orbicule formation in the huangyangshan deposit the following genetic model is proposed 1 in the late carboniferous a new orbicular magma containing organic matter derived ch4 and deep mantle so2 emplaced within the huangyangshan pluton contemporaneously crystal fragments and h2o were incorporated into the orbicular magma from the granitic host rocks 2 h2o saturation was reached in the orbicular magma and fostered segregation of a hydrous ferromagnesian melt orbicules with a silicic residual melt matrix 3 at approximately 630 c 2000 bar and 18 lgfo2 graphite and sulfides formed en masse through deuteric alteration 3ch4 2so2 2 fe2 7 si4o11 2 oh 2 hornblende 3c graphite 2fes pyrrhotite 8sio2 quartz 2 fe3si4o10 oh 2 fe3 oh 6 chlorite following the expulsion of a late magmatic fluid from the ferromagnesian melt

a simple criterion for gyre formation by the surface outflow from a strait with application to the alboran sea a survey of relevant numerical laboratory and observational studies combined with our own laboratory experiments suggests that the surface outflow from a strait generally forms a gyre in the adjacent sea if the exit corner is sharp the gyre grows from an initial separation bubble of radius u f where u is the current speed and f the coriolis frequency the criterion for the maintenance of a coastal jet along a curved coast instead of separation and gyre formation seems to be that the rossby number u frw 1 1 with rw the radius of curvature of the exit corner so that the coriolis force can hold the current to the coast this synthesis disregards factors such as the variation of u across the current but applied to the flow through the strait of gibraltar into the alboran sea suggests that a gyre should always form as the exit corner is sharp we suggest though that the relevant curvature is that where the interface between the two layers intersects the seafloor rather than where the sea surface meets the coast if this is the case supercritical flow or some subcritical flows at the eastern end of the strait should still always lead to gyre formation but the observed replacement of the gyre by a coastal jet along the moroccan coast could be related to subcritical flow that is reduced below its normal value by a barotropic fluctuation or by changes in the interface depth in the mediterranean

phase relations of tourmaline leucogranites and the significance of tourmaline in silicic magmas by means of melting and recrystallization tourmaline seeded experiments phase relations of two natural tourmaline bearing fe rich members of the schorl dravite series leucogranites have been determined between 1 and 3 kbar under h2o saturation with fo2 close to ni nio the presence of tourmaline slightly lowers the solidus temperatures of both samples from 5 to 20 c compared to the corresponding tourmaline free solidus quartz k feldspar and plagioclase phase relations are not significantly dependent on the presence of tourmaline tourmaline is the last major phase to disappear for both samples and a demonstrated liquidus phase exists for one in the recrystallization experiments the compositions of the tourmalines growing from the melt change from more mg rich at high temperatures to more fe rich at lower temperatures the tourmalines are always richer in mg than the melt is but fe and mg are not especially partitioned between crystallizing tourmaline and melt melt compositions do not depart

hydrogen and oxygen isotope variations in the high himalaya peraluminous manaslu leucogranite evidence for heterogeneous sedimentary source abstract the manaslu granite belongs to the high himalaya leucogranitic belt which was produced by melting of the crust during postcollisional thrusting d and 18o values have been determined for whole rock and coexisting minerals from the 8 km thick manaslu massif and its 50 km long dyke sheet its country rocks and the formation 1 f1 paragneisses which are the source of the granite for the granite dmusc range from 70 to 85 and 18o w r from 10 9 to 12 8 h and o isotope fractionations among minerals are consistent with high temperature equilibrium and for oxygen closed system evolution a few samples coming mainly from the dyke swarm have very low d values down to 188 and biotite muscovite h isotope fractionations indicative of disequilibrium the d h ratios of associated magmatic tourmaline are essentially unmodified from the distribution of d values in the granite and its country rocks circulation of very low deuterium meteoric hydrothermal waters was extremely localized because these waters are depleted in deuterium by up to 50 relative to modern meteoric waters the manaslu area was either at an altitude substantially higher than that of today 2500 6000 m for the analyzed samples or a mountain chain once existed to the south the f1 gneisses have 18oquartz between 12 and 14 3 which confirms that the granite was generated from f1 but d values are 20 higher than in the granite such a difference can be a result of degassing of the magma and or introduction of fluid in the melting zone infiltration of low d fluid 90 into the hot but dry f1 probably triggered partial melting these fluids could have come from the dehydration of the midlands sediments which are separated from the overlying f1 by the main central thrust the correlations among 18o 87 sr 86 sr 20 ma and nd values in both f1 and the granite indicate that the variations of these isotopic ratios in the manaslu are inherited from those in f1 at the time of melting in turn these ratios in f1 are related to the proportion of quartz and phyllosilicates for the isotopic ratios of nd and o and to the quantity of radiogenic sr generated within the sediment which is a function of age and rb content amount of phyllosilicate some other himalayan leucogranites require either other crustal source rocks or the 18o and 87 sr 86 sr ratios of f1 vary along the himalaya

on the influence of topography in the induction of coastal upwelling along the chilean coast the contribution of the winds and the topography in the induction of upwelling along the chilean coastal zone is calculated the topographic induced upwelling is estimated taking into account the effect of the meridional changes of the coastline orientation the wind induced upwelling was calculated for the austral summer using nscat scatterometer data resulting a total amount of 2 1 106 m s 1 of water transported offshore for the whole chilean upwelling zone it is shown that the topographic effect dominates the wind induced upwelling in several parts of the chilean coast particularly at 23 s antofagasta 25 5 s 30 s coquimbo 33 s valparaiso and 37 s concepcion antofagasta coquimbo valparaiso and concepcion are well known zones of intense upwelling the results show that the topography plays a key role in the upwelling of the chilean coast specially in its northern part

coastal wind driven circulation in the vicinity of a bank part i modeling flow over idealized symmetric banks abstract this study examines how coastal banks influence wind driven circulation along stratified continental shelves numerical experiments are conducted for idealized symmetric banks the standard bank 200 km long and 50 km wide has dimensions similar to the heceta bank complex along the oregon shelf model runs are forced with 10 days of steady winds 0 1 pa upwelling and downwelling cases are compared the bank introduces significant alongshelf variability in the currents and density fields upwelling favorable winds create an upwelling front and a baroclinic jet flowing opposite coastal trapped wave propagation that bend around the standard bank approximately centered on the 90 m isobath the upwelling jet is strongest over the upstream bank half where it advects a tongue of dense water over the bank there is a current reversal shoreward of the main jet at the bank center upwelling is most intense over the upstream part of the bank while there is reduced upwelling and even downwelling over

chemical and boron isotope variations in tourmalines from an s type granite and its source rocks the erongo granite and tourmalinites in the damara belt namibia tourmaline is widespread in metapelites and pegmatites from the neoproterozoic damara belt which form the basement and potential source rocks of the cretaceous erongo granite this study traces the b isotope variations in tourmalines from the basement from the erongo granite and from its hydrothermal stage tourmalines from the basement are alkali deficient schorl dravites with b isotope ratios typical for continental crust 11b average 8 4 1 4 n 11 one sample at 13 n 2 virtually all tourmaline in the erongo granite occurs in distinctive tourmaline quartz orbicules this main stage tourmaline is alkali deficient schorl 20 30 x site vacancy fe fe mg 0 8 1 with uniform b isotope compositions 11b 8 7 1 5 n 49 that are indistinguishable from the basement average suggesting that boron was derived from anatexis of the local basement rocks with no significant shift in isotopic composition secondary hydrothermal tourmaline in the granite has a bimodal b isotope distribution with one peak at about 9 like the main stage tourmaline and a second at 2 we propose that the tourmaline rich orbicules formed late in the crystallization history from an immiscible na b fe rich hydrous melt the massive precipitation of orbicular tourmaline nearly exhausted the melt in boron and the shift of 11b to 2 in secondary tourmaline can be explained by rayleigh fractionation after about 90 b depletion in the residual fluid

elemental and b o h isotopic compositions of tourmaline and associated minerals in biotite muscovite granite of mashhad ne iran constraints on tourmaline genesis and element partitioning abstract abundant tourmaline occurs in late triassic biotite muscovite granites of mashhad ne iran with several distinct morphologies including tourmaline nodules in granite pegmatitic tourmalines aplitic tourmalines and vein related tourmalines quartz tourmaline vein tourmaline rich vein and radial tourmalines pegmatitic and aplitic tourmalines are compositionally fe rich schorl and the nodule radial and vein tourmalines are mg rich schorl the tourmalines have generally low abundances for most trace elements except for sr ga li be sn pb and some transition elements tourmalines have low ree abundances and are enriched in lree and depleted in hree mostly below detection limits with positive eu anomalies the concentration of several trace elements e g pb be sn ga sr pb and ree correlates well with the major element composition of the tourmalines e g mg mg mg fe vacancy x site vacancy na and na na ca trace element data of coexisting minerals with tourmaline indicate that the oligoclase and albite show the most preference in sr pb and eu and lrees biotite readily incorporates rb ba zn li cs and nb k feldspar has high contents of rb ba sr and pb and garnet incorporates hrees and y during magma differentiation the b o h isotopic compositions for all tourmalines are consistent with an s type granite source that was derived from partial melting of the continental crust the pegmatitic and aplitic tourmalines with fe rich schorl composition indicate magmatic conditions and the radial vein and nodule tourmalines with mg rich schorl composition formed during the transition from magmatic to hydrothermal conditions due to the internal evolution of the granitic magma

vapor phase exsolution as a controlling factor in hydrogen isotope variation in granitic rocks the notch peak granitic stock utah abstract the notch peak granitic stock western utah is comprised of three concentric sequentially intruded rock types from granite at the rim to quartz monzonite i to quartz monzonite ii at the core the 18 o values of whole rocks vary about an average of 9 4 smow irrespective of the rock type and position relative to contact suggesting that the three magmas had the same parent the whole rock d values in the stock range from 100 to 55 d values increase toward the cores of both quartz monzonite i and quartz monzonite ii resulting in concentric contours the d contours of quartz monzonite ii cross cut those of quartz monzonite i suggesting little isotopic interaction between these bodies and the absence of a late pervasive fluid phase there is a positive correlation between d values and water content of the samples where samples from each body define a distinct field the positive correlation is explained by isotopic fractionation attendant on vapor exsolution from the crystallizing magma an observed increase in d with the degree of chloritization a trend opposite to that observed in systems where participation of meteoric water has been demonstrated is the result of subsolidus interaction with the exsolved fluids these results show that large variations in the hydrogen isotope ratios of a granitoid can arise by exsolution of a vapor phase from the melt on crystallization in general magmas with larger modal amount of primary hydrous phases will tend to have higher d values than those with small amounts of hydrous phases furthermore the relatively high d values of chlorites at notch peak confirm the applicability of classical concepts of closed system deuteric alteration to some granitoid bodies thus meteoric water interaction need not be always invoked to explain hydrogen isotope variation and deuteric alteration in granitoids

the paleoproterozoic dorlin gold deposit french guiana genetic constraints of the stable isotope geochemistry abstract this paper reports on oxygen hydrogen carbon and sulphur isotopic compositions of silicates carbonates and sulphides from the dorlin gold deposit in the paleoproterozoic greenstone belt of central french guiana the dorlin orebodies result from the polydeformation of a large tourmalinite bearing stratabound sulphide deposit hosted by volcanic and sedimentary rocks of the paramaca series metamorphosed in the greenschist facies the mineralizing envelope would initially have consisted of an inner zone of tourmaline sulphide bearing ores m2 surrounded by a zone of chlorite sulphide bearing mineralization m1 the stratabound sulphide deposit was locally cut by a muscovite sulphide quartz stockwork m3 the 18 o values of quartz and chlorite from the chlorite sulphide mineralization are 12 2 and about 5 5 smow respectively those of quartz and tourmaline from the tourmaline sulphide mineralization are about 14 and 8 5 smow and those of quartz and muscovite from the discordant stockwork are 12 4 and 6 9 smow d values of the chlorite tourmaline and muscovite are about 45 28 and 38 smow respectively carbonates calcite dolomite ankerite and siderite in the mineralizations have 18 o values between 10 8 and 15 7 relative to smow and 13 c values of 5 2 to 0 8 relative to pdb 34 s values of samples from the three mineralizations range between 0 5 to 2 6 cdt with two exceptions at 2 8 and 2 9 the data support the existence of a zoned hydrothermal system largely controlled by a network of paleofractures and slightly reworked by a late muscovite sulphide quartz stockwork the isotopic geothermometers record temperatures of ore deposition in the range of 200 300 c the d and 18 o values of the chlorites tourmalines and muscovites would indicate a large input of seawater in the dorlin hydrothermal fluids whereas the 18 o and 13 c of the carbonates and 34 s of pyrite provide evidence of a magmatic component resulting probably for a large part from leaching of the volcanic host rocks

finite amplitude evolution of instabilities associated with the coastal upwelling front abstract a primitive equation model is used to study the finite amplitude evolution of instabilities associated with the coastal upwelling front simulations of increasing complexity are examined that represent idealizations of summer conditions off the oregon coast including cases with steady and with time variable wind in a domain with alongshore uniform bathymetry and with time variable wind in a domain with realistic oregon coast bathymetry the numerical results indicate that the fastest growing mode in this system has approximately an 8 10 km alongshore wavelength but that once the disturbances grow to finite amplitude the predominant alongfront scale increases rapidly because of nonlinear effects separation of the total kinetic energy into contributions from the alongshore average flow and perturbation about that average shows that the initial growth of the perturbation kinetic energy is due to potential energy conversion but transfer of energy from the kinetic energy of the alongshore average

topographically induced upwelling off eastern australia abstract a high resolution numerical study of an idealized western boundary current flow over variable topography is presented with application to the east australian current eac the results indicate that alongshelf topographic variations off australia s east coast cause the eac to accelerate over the narrowing continental shelf near cape byron this acceleration is sufficient to hinder the geostrophic adjustment in the bottom boundary layer bbl which would usually cause the eac driven bbl to shut down consequently a region of persistent high bottom stress was established off cape byron which was responsible for driving an upwelling bbl it is shown that the enhanced vertical mixing associated with a low richardson number flow beneath the eac reduced the local stratification consequently the burger number is decreased resulting in a long shutdown timescale of the bbl which enables a nearshore thermal to be established and maintained such fronts are commonly observed in the region as a p

late magmatic immiscibility during batholith formation assessment of b isotopes and trace elements in tourmaline from the land s end granite sw england quartz tourmaline orbicules are unevenly distributed in the roof segment of the land s end granite sw england this study shows that the orbicules formed from an immiscible hydrous borosilicate melt produced during the late stages of crystallization and differentiates tourmaline formed by dominantly magmatic and dominantly hydrothermal processes trace elements and boron isotope fractionation can be tracked in tourmaline and create a timeline for crystallization tourmaline from the granite matrix has higher v cr and mg content and is isotopically heavier than the later crystallizing inner orbicule tourmaline overgrowths of blue tourmaline occurring together with quartz showing hydrothermal cathodoluminescence textures crystallized from an aqueous fluid during the very last crystallization and are significantly higher in sr and sn and isotopically heavier tourmaline associated with sn mineralization is also high in sr and sn but has boron isotopic compositions close to that of the magmatic tourmaline and is not formed by the same fluids responsible for the blue overgrowths the ore forming fluids precipitating tourmaline and cassiterite are likely derived from the same magma source as the granite but exsolved deeper in the magma chamber and at a later stage than orbicule formation tourmaline from massive quartz tourmaline rocks is concentrically zoned with major and trace element compositions indicating crystallization from a similar melt as for the orbicules but shows a more evolved signature

a separating coastal upwelling jet at cape blanco oregon and its connection to the california current system the coastal upwelling region near cape blanco oregon 433n o the west coast of the united states was studied using a towed ctd on seasoar a shipboard acoustic doppler current pro ler adcp satellite sea surface temperature maps and surface drifters during august 1995 the equatorward upwelling jet was inshore of the shelfbreak north of cape blanco meandered gently o shore around the cape and then veered sharply o shore just to the south of the cape analysis of vertical sections of density velocity and spicinessa con rmed the separation of an upwelling jet and front the jet was followed from over the shelfbreak north of the cape to 100 km o shore downstream of the cape the separating jet originates from the coastal upwelling jet leaving the shelf but is augmented by an o shore branching of the poleward undercurrent by combining information from adcp streamfunction maps with analysis of hydrographic data including distributions of the tracer like quantity spicinessa a conceptual model of the three dimensional circulation near the cape emerges a mid shelf upwelling jet encounters a coastal promontory then turns o shore stretching and deepening as it crosses the continental margin the jet then turns back shoreward cyclonically where the deepened equatorward ow encounters the top of the poleward undercurrent owing along the continental slope this causes a portion of the undercurrent to turn o shore to join and strengthen the equatorward transport in the separated jet throughout the separation process the coastal upwelling front and jet are continuous robust features separation of a coastal upwelling jet is an important mechanism for cross shelf transport from the coast to the deep ocean cape blanco appears to be the northernmost point where an equatorward jet regularly separates from the coast to become an oceanic jet and thus serves as the northern boundary of the region where an intense meandering current characteristic of the california current system

a modeling study of the three dimensional continental shelf circulation off oregon part ii dynamical analysis abstract sixty day simulations of the subinertial continental shelf circulation off oregon are performed for a hindcast study of summer 1999 in part i the model results are shown to compare favorably with in situ currents and hydrographic measurements obtained from an array of moored instruments and field surveys and high frequency radar derived surface currents in this paper the modeled three dimensional time varying circulation and dynamical balances are analyzed providing a detailed synoptic description of the continental shelf circulation off oregon for summer 1999 the circulation is clearly wind driven and strongly influenced by alongshore variations in shelf topography in the region of the coast where the alongshore topographic variations are small the upwelling circulation is consistent with standard conceptual models for two dimensional across shore circulation in the regions where the alongshore topographic variations are greater the upwelling circulation is highly three dimensional ov