paleoceanographic and climatic implications of a new mediterranean outflow branch in the southern gulf of cadiz abstract the presence of contourite drifts in the southern gulf of cadiz goc along the moroccan margin raises questions about the re circulation of mediterranean outflow water mow in the goc and the origin of the currents depositing them here we compare two cores representative of iberian and moroccan contourite drifts covering the last 22 kyr although the whole sequence is contouritic in character it reflects the interaction of distinctive silty contourite facies high flow velocity periods imbedded in muddy contourite facies low flow velocity periods evidence from benthic foraminifera 13c sortable silt grain size oceanographic ctd profiles and numerical simulations indicate the mediterranean water mass as the source of the southern contourite deposits our data therefore suggests an additional branch of upper mow veering southwards off the straits of gibraltar along the moroccan margin during mis marine isotope stage 2 upper mow was a sluggish current while in the holocene upper mow dominated as a fast semi steady flow throughout the deglaciation silty contourites associated with higher flow speeds were deposited in the northern and southern goc during cold events such as heinrich stadial 1 hs1 and the younger dryas forced by global millennial scale climate variability millennial variability also appears to drive the deposition of silty contourites in the holocene we estimated an average duration of 1 ka for the process of depositing a fast contourite unit the case of silty contourite i6 within hs1 allows us to illustrate with extremely high resolution a rapid sequential change in circulation with gradual slow down of dense mediterranean water while surface was freshening hs1 provoking injection of high salinity intermediate waters via contour currents into the goc and hence the north atlantic the subsequent brief collapse of dense water formation in the mediterranean sea triggered a major increase in sea surface temperatures 10 c ka in the goc developing into the next interstadial bolling allerod the impact of mediterranean intermediate waters is manifested here by triggering a substantial rearrangement of intermediate and deep circulation in the north atlantic which would have further impacted the atlantic meridional overturning circulation amoc

tube like schlieren structures in the furstenstein intrusive complex bavarian forest germany evidence for melt segregation and magma flow at intraplutonic contacts abstract tube like schlieren structures occur at the boundary between two units of the furstenstein intrusive complex the tittling and the saldenburg granites we have analysed the magnetic fabrics petrographic variation and geochemistry of key examples of these structures in order to test the hypothesis that they originated as granitic microdiapirs the rims of the schlieren structures have high magnetic susceptibility compared to their interiors and surrounding granite due to the enrichment of biotite opaques the low anisotropy that characterizes the ams fabric is probably caused by magmatic flow hypersolidus microfabrics support this interpretation magnetic fabric orientation within the schlieren structures differs significantly from the ne sw trending magnetic foliation generally observed within the hosting tittling granite a steeply plunging magnetic lineation and a nne ssw girdle distribution of the magnetic foliation poles within the schlieren structures are consistent with the conical geometry of the schlieren structures evolved during the rise of the magma based on geochemistry granite in the schlieren structures is interpreted to be differentiated melt expelled from the tittling granite mush that formed after early crystallization of plagioclase we suggest that the schlieren structures are pockets of residual melt of the tittling granite that were mobilized buoyantly due to a thermal input from the neighbouring saldenburg granite the mafic rims of the schlieren structures formed as a result of early crystallization and subsequent accumulation due of the bagnold effect the results of the magnetic and geochemical investigations allow us to interpret the schlieren structures as diapiric in nature and consequently as within chamber diapirs sensu weinberg et al 2001

incremental growth of an upper crustal a type pluton argentina evidence of a re used magma pathway abstract carboniferous igneous activity in the sierra de velasco nw argentina led to the emplacement of several magmas bodies at shallow levels t 5 8 and ehf t in zircon 2 9 to 4 5 the second group comprises the metaluminous to peraluminous granitic rocks of the youngest units san blas and hualco which were formed by a heterogeneous mixture between mantle and crustal sources end t 0 6 to 4 8 and ehf t in zircon 3 to 6 our results provide a comprehensive view of the evolution of an intrusive complex formed from multiple non consanguineous magma intrusions that utilized the same magmatic plumbing system during downward transfer of host materials as the plutonic system matures the ascent of magmas is governed by the visco elastic flow of host rock that for younger batches include older hot magma mush the latter results in ductile downward flow of older during rise of younger magma such complexes may reflect the plutonic portion of volcanic centers where chemically distinct magmas are erupted

geologic and geophysical investigation of two fine grained granites sierra nevada batholith california evidence for structural controls on emplacement and volcanism the johnson granite porphyry and the silver pass porphyry are two late stage porphyritic intrusions in the cretaceous sierra nevada batholith california both intrusions are characterized by fine grained textures miarolitic cavities pegmatite veins and abundant xenoliths microstructures in the johnson granite porphyry record magmatic flow magnetic fabrics in the johnson granite porphyry determined by anisotropy of magnetic susceptibility show that the poles to magnetic foliations define a nne ssw girdle and magnetic lineations plunge shallowly to moderately to the wnw and ese a gravity survey and three dimensional inversion indicate that the johnson granite porphyry is shallow and tabular extending to 1 5 km depth beneath the southwestern margin a second gravity anomaly was delineated southeast of the johnson granite porphyry suggesting the intrusion continues to depth the silver pass porphyry is deformed by the dextral rosy finch shear zone and records a gradient of high to low temperature solid state fabrics field and magnetic foliations in the silver pass porphyry are subvertical and lineations are shallowly plunging we propose that regional shear zones controlled the emplacement of these intrusions the johnson granite porphyry was emplaced in a three dimensional tension gash associated with the termination of the bench canyon shear zone the rosy finch shear zone facilitated the emplacement of the silver pass porphyry probably as a tension fracture associated with the shear zone the field observations and magnetic fabrics suggest that the johnson granite porphyry may record an extrusive event suggesting that volcanism may be related to deformation along active shear zones

tectonic evolution of the european variscan belt constrained by palaeomagnetic structural and anisotropy of magnetic susceptibility data from the northern vosges magmatic arc eastern france geochronology structural and anisotropy of magnetic susceptibility data from the northern vosges batholith which belongs to the northern vosges mid german crystalline rise arc show contrasting emplacement modes of southern granodiorites and northern granites the ene wsw trending fabrics of granodiorites 346 334 ma are parallel to the metamorphic cleavage affecting the host rocks developed during regional compression the nnw sse trending fabrics of younger granitoids c 330 ma reveal an extensional emplacement mode associated with a normal shear zone separating the two magmatic suites palaeomagnetism shows that the switch from a compressive to an extensional regime coincides with a regional counterclockwise rotation the 330 325 ma extension is further supported by palaeomagnetic and seismic data indicating southeastward tilt of the whole batholith finally the system is rotated clockwise without any structural overprint data from the early carboniferous northern vosges magmatic arc and remote bohemian massif suggest that this evolution is valid for the whole eastern branch of the european variscan belt for which the following model is proposed 1 late devonian early carboniferous east west shortening of the variscides above the rhenohercynian subduction zone 2 axial nnw sse shortening of the assembled variscan orogen associated with 3 internal sinistral rotation of inherited rhenohercynian transform faults and shortening of intervening blocks 4 east west extension and dextral external rotation of blocks between dextrally reactivated transforms supplementary materials analytical procedures for geochronology magnetism anisotropy of magnetic susceptibility and palaeomagnetism are available at www geolsoc org uk sup18635

the gem lake shear zone cretaceous dextral transpression in the northern ritter range pendant eastern sierra nevada california the gem lake shear zone is a northwest striking steeply dipping dextral transpressional shear zone that provides the first direct evidence for dextral deformation in wall rock pendants in the central part of the sierra nevada batholith the gem lake shear zone is a minimum of 30 km in length and extends at least from the north end of the northern ritter range pendant to the southeast edge of the ritter range pendant the amount of displacement on the zone is uncertain but matching fault slivers of pennsylvanian marble in the northern ritter range pendant to similar exposures north of the mount morrison pendant suggests a minimum dextral offset of 20 km the gem lake shear zone was active in early late cretaceous time from before 91 ma the age of the syntectonic granodiorite of kuna crest to at least 80 ma 40ar 39ar age of syndeformational mica from the shear zone in the ritter range pendant deformation in the gem lake shear zone is characterized by combined dextral simple shear and subvertical stretching which are variably partitioned in anastomosing high strain zones in the shear zone at gem lake predominantly dextral deformation is indicated by porphyroclast asymmetries s c fabric and asymmetric crenulations a component of subvertical stretching is indicated by a moderately to steeply plunging stretching lineation in a segment of the shear zone at kuna crest a strongly developed stretching lineation indicates predominantly subvertical stretching with a lesser component of dextral strike slip the gem lake shear zone is considered to be part of a proposed regional system of shear zones in the eastern sierra nevada the sierra crest shear zone system this dextral transpressional system was active prior to and synchronous with intrusion of the late cretaceous sierra nevada batholiths deformation ceased shortly after pluton emplacement the sierra crest shear zone system includes possibly related shear zones as far north as saddlebag lake pendant and at least as far south as oak creek pendant and the owens valley indicating a possible strike length greater than 150 km

observational evidence of salt lens formation in the iberian basin the quasi synoptic picture of the mesoscale eddy field off portugal is presented on the basis of recent hydrographic measurements the dynamic topography and the salinity field at middepths 900 1300 m is shown to be dominated by several isolated meddy structures superimposed on a general east west gradient deduced from the actual dynamical situation there is evidence for meddy generation in this region numerical process studies demonstrate the possibility of vortex formation by baroclinic instability of a northward middepth jet of mediterranean water and by fragmentation of larger scale mediterranean water blobs

characteristics of internal contacts in the tuolumne batholith central sierra nevada california usa implications for episodic emplacement and physical processes in a continental arc magma chamber internal contacts along the eastern margin of the tuolumne batholith central sierra nevada california and structures preserved along these contacts are highly variable the contacts range from relatively sharp to gradational boundaries to sheeted zones to very complex boundaries formed by multiple processes fractional crystallization kilometer scale mixing within broad transition zones voluminous magmatic stoping along sharp contacts and downward return flow and or margin collapse of older magma units were important large scale processes along these contacts during chamber construction in contrast sheeting extensional cracking and diking represent only second order small scale complexities formation of the most complex zones along internal contacts resulted from the interaction of the sequential emplacement of different units with the irregular geometry of these contacts which often resulted from removal of earlier phases by stoping our results indicate that multiple processes are likely during emplacement of large magma bodies within one another and that it is unlikely that evidence for all internal processes during batholith construction are preserved we also argue that fairly large magma chambers existed in this batholith and thus that large accumulations of magma may exist in upper crustal chambers for significant periods of time

significance of composite lineations in the mid to deep crust a case study from the north cascades washington abstract the origin of broadly orogen parallel nw se mineral lineations in cretaceous and paleogene arc plutons and amphibolite facies metamorphic rocks paleodepths of

characteristics of surface signatures of mediterranean water eddies in this work we obtain new results on the manifestation of meddies or of other deep eddies at the sea surface further developing the results by bashmachnikov and carton 2012 the quasi geostrophic equations are used to describe a near axisymmetric vortex in the upper ocean forced at its lower boundary by the isopycnal elevation of a moving meddy the solution thus obtained provides a better approximation of the characteristics of meddy surface signals the results show that in subtropics large meddies with dynamic radius rm 30 km are always seen at the sea surface with aviso altimetry that medium size meddies with rm 20 km may be seen at the sea surface only if they are sufficiently shallow and strong while small meddies with rm 10 km generally cannot be detected with the present accuracy of altimetry data the intensity of meddy surface signals decreases to the south with the decrease of the f n ratio the seasonal variation in intensity of the surface signal for northern meddies 45 n is on the order of 2 3 cm but for subtropical meddies 35 n it can be on the order of 5 10 cm the radii of meddy surface signals range from 1 to 2 times the radii of the corresponding meddies for most of the observed subtropical meddies the upper limit should be used numerical experiments show that surface signals of meddies translated with drift are efficiently dispersed by the radiation of rossby waves at the same time for meddies translated by a background current the surface signal does not show strong dissipation

arms winding around a meddy seen in seismic reflection data close to the morocco coastline the north atlantic temperature and salinity distributions are strongly influenced by the existence of mediterranean eddies meddies which significantly contribute to the transport of the warm and salty mediterranean water along different pathways the most common pathways are observed to be north and west of the canary current however a 2011 seismic reflection cruise conducted by bgr and ifremer near the north western african margin of morocco mirror leg 2 revealed the presence of a meddy south of the azores front and very close to the morocco coastline this unusual location of a strong mediterranean water anomaly is confirmed by other data moreover meddies are long lived structures whose dynamics and dissipation are not yet completely understood recently theoretical studies have revealed critical level baroclinic instabilities of compact lens like vortices this theory supports the slow growth of azimuthal eigenmodes along critical surfaces which leads to the formation of arms winding around the vortex developing sharp internal fronts these structures are very thin and spatially intermittent and are identified for the first time in a seismic dataset this is made possible by the length of seismic sections at high lateral resolution citation menesguen c b l hua x carton f klingelhoefer p schnurle and c reichert 2012 arms winding around a meddy seen in seismic reflection data close to the morocco coastline geophys res lett 39 l05604 doi 10 1029 2011gl050798

multiple magmatic fabrics in the sazava pluton bohemian massif czech republic a result of superposition of wrench dominated regional transpression on final emplacement abstract the sazava pluton 354 ma of the central bohemian plutonic complex was emplaced syntectonically into the upper crustal neo proterozoic and lower paleozoic host rock along the se margin of the tepla barrandian zone bohemian massif czech republic the host rock is characterized by transpressional fabric dominated by steep se nw dipping foliations and subhorizontal ne sw stretching lineations associated with flattening to a plane strain ellipsoid the strain intensity degree of oblateness and temperature conditions of deformation increase in the host rock towards the pluton margin in the pluton quartz microfabric indicates progressive cooling of the syntectonically emplaced magma the ams method revealed multiple magmatic fabrics and lateral variations in the shapes of the ams ellipsoid and the magnetic fabric intensity in the pluton the central part of the pluton yields prolate shapes of the ams ellipsoid and a low degree of anisotropy with preserved steep magnetic lineations whereas along the pluton margins oblate ams ellipsoids are associated with a high degree of anisotropy we interpret the multiple fabrics and the partially decoupled fabric pattern between the host rock and the pluton as being a result of superposition of regional tectonic strain during highly oblique transpression on emplacement related intrusive strain where outer solidified and more rigid edges of the pluton enabled preservation of older steep fabrics in its interior

some remarks on fabric overprints and constrictional ams fabrics in igneous rocks during the ascent emplacement and post emplacement deformation of igneous rocks two or more phases of deformation that overprint each other are often depicted these overprints when magnetic minerals are present are recorded in magnetic fabric in this contribution overprints are studied by means of numerical modeling following several basic scenarios common to igneous rocks biotite and amphibole that occur often together in igneous rocks are considered as carriers of the anisotropy of magnetic susceptibility modeling shows that 1 a constrictional fabric with a low degree of anisotropy as commonly recorded in magmatic rocks may result from a deformation overprint and not necessarily from an extensional transtensional regime and 2 that the constrictional ams fabrics originates from orthogonal superimposition of a deformation event on an ams fabric inherited from earlier magma emplacement history therefore the interpretation of a constrictional fabric must be performed with caution numerical modeling may provide a suitable help in strengthening the interpretation of real magnetic fabric data

stretching lineations in transpressional shear zones an example from the sierra nevada batholith california abstract ductile shear zones and associated stretching lineations are generally considered to be the result of two dimensional simple shear deformations with stretching lineations interpreted to rotate into parallelism with the direction of tectonic transport with increasing deformation however stretching lineations perpendicular to the inferred tectonic transport direction are displayed by some shear zones field studies in the sierra nevada batholith have revealed a single shear zone the rosy finch gem lake shear zone that contains both steeply plunging stretching lineations in older metamorphosed sedimentary and granitic rocks and shallowly plunging stretching lineations in syntectonic granitoids dextral sense of shear indicators are found in all these units and deformation occurred simultaneously along the length of the shear zone theoretical strain modeling indicates that stretching lineations can be either horizontal or vertical within transpressional shear zones to investigate the kinematics of three dimensional deformation we examine the role of stretching lineations which form as a result of finite strain including the possibility of partitioning a component of the strike slip movement onto shear bands comparing the field data with the strain modeling we interpret the along strike variation in lineation behavior within the rosy finch gem lake shear zone to be a result of the differences in finite strain recorded by different units the older units showing steeply plunging lineation have recorded more finite strain across a narrower shear zone than the syntectonic granites which record shallowly plunging lineations we conclude that the orientation of the lineation within transpressional shear zones does not necessarily correlate with the transport direction but may reflect along strike variations in finite strain and or strain partitioning

interpreting magmatic fabric patterns in plutons abstract most plutons have widespread magmatic fabrics the interpretation of which remains controversial we propose a method to constrain likely causes of fabric patterns the application of which indicates the following 1 preserved fabric patterns often form after chamber construction and only rarely provide information about ascent or emplacement 2 fabrics are poor recorders of total strain and are easily reset preserving only the last increment of strain during crystallization 3 in magmatic systems mechanically decoupled from host rocks patterns may result from strain during internally driven flow filter pressing or porous flow in relatively static chambers or by final increments of strain during emplacement 4 with greater emplacement depths fabric patterns increasingly reflect strain caused by regional deformation and 5 given that magmatic fabrics are easily reset and reflect only the last increment of strain of comparatively weak materials they may provide a relatively direct record of paleostress in orogenic belts

merging and migration of two meddies in this study a scenario is developed of two adjacent mediterranean water eddies meddies as they were observed merging and drifting through the iberian basin observations are based on four rafos floats at 850 1050 dbar two hydrographic surveys centered roughly at 38 n 24 w and trajectories of surface drifters drogued at 100 m in april 1991 the meddy a was identified and labeled by surface drifters during the revisit one month later two meddies were encountered b1 and b2 in the vicinity of the former meddy a the coalescence of b1 subsequently identified as a one month older and b2 is inferred from a simple kinematic model describing the observed movement of the rafos floats for up to three months after the second ctd survey the deduced vorticity front radius 15 km within b1 was of insufficient strength to keep the core waters of b1 isolated and prevent the absorption of b1 by b2 the resulting meddy b1 b2 showed a clear near surface dynamical signal its deep root 1800 m could explain the expulsion from the meddy of the remaining rafos float and surface drifter at the time of the meddy s collision with the josephine seamount for the first time a set of lagrangian and hydrographic observations give direct evidence that neighboring meddies can merge as predicted by theoretical considerations

on the southward motion of mediterranean salt lenses abstract a new mechanism is proposed to account for the southward motion of salt lenses in the canary basin it relies on the active mixing that is observed at the periphery of such eddies between the warm salty mediterranean waters of the core and the surrounding fresher and cooler atlantic waters intrusions driven by this thermohaline contrast feed on the eddy potential energy and drain off the eddy volume anomaly submitted to the continuous entrainment of its own fluid by the frontal turbulence the salt lens suffers a velocity divergence at its periphery induced by a geostrophic adjustment process this causes in turn a squashing of the density surfaces and the salt lens must then move southward to conserve its potential vorticity a possibility offered by the spherical nature of the earth it appears that mixing may load to the coherent latitudinal displacement of an ensemble of fluid parcels on a plant while at the same time dissipating the energy of the structure itself

the merger of geophysical vortices at finite rossby and froude number partial support for this research has come from the uk engineering and physical sciences research council grant number ep h001794 1

shear criteria in granite and migmatite deformed in the magmatic and solid states microstructural criteria for the determination of the sense of shear in rocks homogeneously deformed in the partially melted state are similar to those which apply to solid state deformation sense of shear determination is either direct deduced from the sense of rotation of markers or indirect involving the obliquity between the shear and foliation planes or between the successive foliations imprinted at different stages of progressive deformation this study is a by product of the detailed structural and microstructural investigation of a high grade metamorphic rock pile variscan vosges massif france which underwent subhorizontal shearing during partial melting and further solidification depending on the rock chemistry on the position in the pile and the relative timing of progressive deformation layered migmatites and homogeneous granites were variously deformed in the partially melted and solid states the sense of shear obtained from these rock types using the criteria presented here consistently gives a top to sw direction

the development of a single cleavage in an area of repeated folding abstract structural investigations in the variscan fold interference pattern of sw sardinia italy document an intriguing example of the relationship between cleavage folding and finite strain although palaeozoic sediments were affected by two major folding events both under identical low grade metamorphic conditions only a single penetrative cleavage formed which is not unambiguously correlated with either of these events cleavage orientation changes smoothly along sigmoidally curving trajectories throughout the interference pattern thus the same cleavage can be axial planar to either the first or the second phase folds or transect both when curving from one set into the other the singularity of the cleavage is supported by microscopic studies which show no evidence of a pre existing or overprinting tectonic cleavage finite strain determinations and numerous field observations demonstrate that cleavage always parallels the principal plane of finite strain even though local strain varies according to the relative position in the fold interference pattern similar strain patterns were achieved by forward modelling of superposed buckle folds based on our findings we propose i that the finite strain pattern is due to the superposition of the heterogeneous strain fields associated with the individual folding events and ii that cleavage reflects the cumulative deformations that effected the rock this has consequences for the regional interpretation of cleavage in our study area and elsewhere and for the distinction between deformation phases in general

mineral fabrics in high level intrusions recording crustal strain and volcano tectonic interactions the shellenbarger pluton sierra nevada california the minarets caldera is a volcano plutonic complex in the sierra nevada california that exemplifies complex interactions between volcanism and tectonic deformation in continental margin arcs caldera evolution commenced with emplacement of pre collapse rhyolitic ash flow tuff followed by collapse and deposition of volcanic breccia and rhyodacitic ash flow tuff subsequently the volcanic rocks were deformed along the regional bench canyon shear zone the caldera centre was then intruded by the resurgent c 100 ma steep sided shellenbarger granite pluton which steepened the shear zone foliation the pluton was overprinted by syn to post magmatic nne ssw horizontal shortening the same shortening was documented in several other late cretaceous syntectonic plutons in the sierra nevada and interpreted to record dextral transpression during convergence of the farallon and north american plates to explain the unusual tectonic fabric in the shallow level shellenbarger pluton we develop a general model for strain partitioning in syntectonic magma bodies emplaced at various crustal levels we propose that shallow intrusions isolated within stiff crust may tend to accommodate minor pure shear strain whereas simple shear dominates along weak faults and shear zones by contrast a rheological reversal is crossed deeper in the crust and magma bodies become the weakest simple shear dominated parts of the system supplementary material analytical methods and anisotropy of magnetic susceptibility and u th pb isotopic data are available at https doi org 10 6084 m9 figshare c 3582749

a meddy off cape st vincent part i description abstract a meddy an eddy formed from mediterranean source water was surveyed in detail with two types of expendable profilers and a ctd instrument the muddy comprised two distinct vertically aligned tenses with a combined thickness of 650 m both lenses were stratification minima the upper lens was warmer fresher 12 25 c 36 5 psu and more circular the lower lens was cooler more saline 12 1 c 36 65 psu and more elliptical oriented alone a northeast by southwest line the upper lens homogeneous out to a radius of 6 km had a radius of maximum velocity of 9 km its relative vorticity was 0 85 f and its ertel potential vorticity 4 10 12 m s 1 was 17 times below ambient levels due to the combined effects of negative relative vorticity and vortex stretching the meddy contained more kinetic energy than available potential energy energy burger number of 2 5 compared with historical meddies it had a larger burger number and a more negative vorticity rossby number

syn tectonic emplacement of the late mesozoic laojunshan granite pluton in the eastern qinling central china an integrated fabric and geochronologic study abstract the porphyritic monzogranite of laojunshan eastern qinling in central china forms a w e elongated pluton characterized by a varying abundance of cm scale potassium feldspar kfs megacrysts with or without plagioclase mantles mafic microgranular enclaves mmes and associated mafic dykes the measurements of the shape preferred orientation of kfs megacrysts and the tiling of megacrystic pairs throughout the pluton suggest that these megacrysts constitute magmatic foliations subparallel to the pluton s margin possibly resulting from eastward non coaxial magmatic flow felsic mafic magma mixing and mingling were important during magma emplacement as indicated by abundant mmes coeval mafic dykes and disequilibrium textures within kfs megacrysts quantitative analyses of the crystal size distribution and the in situ chemistry of kfs megacrysts revealed that the temperature fluctuation in the deep magma chamber and the resultant textural coarsening are the most likely important mechanisms for the growth of kfs megacrysts the syn tectonic and two main stage emplacement of the pluton in a sinistral transtensional regime is inferred by the mechanical coupling between magmatic submagmatic solid state fabrics in the pluton and wall rock deformations as well as zircon u pb dating results which produce eastward younging emplacement ages spanning from 122 ma to 119 ma combined with other studies our work supports the idea that the qinling dabie orogen was in a sinistral transtensional regime during the early cretaceous which may correspond to the eastward extrusion tectonics in eastern china

a census of meddies in a long term high resolution simulation the output from a high resolution two decade long mediterranean outflow simulation is analysed here to provide a census of mediterranean water eddies aka meddies both anticyclones and cyclones the formation rate of meddies that survive for at least 90 days is of 12 meddies yr 1 of which 12 are cyclones the rate of formation reaches 40 meddies yr 1 30 cyclones when considering all the meddies living over 15 days about 70 of the population is born along the southwestern iberian slope but several robust meddies also originate in points of convergence of the main pathways into the open ocean the longest lived meddies propagate northwestwards but most of the anticyclones veer southwestwards after a while as the meddies drift away from their birthplace their radius tends to increase gradually from 15 to 30 km the thickness depth difference between isopycnals 27 2 and 27 5 of anticyclones born near cape st vincent contracts by approximately 100 m after travelling 1000 km from their source their mean swirl velocities range from about 21 cm s 1 at z 1000 m up to 27 cm s 1 at z 600 m mean salinity and temperature anomalies are significantly lower for cyclones which in general are also more slowly rotating shallower and thinner than anticyclones cyclones are more easily tracked at 600 m depth where longer trajectories are recorded in the vicinity of portimao canyon cyclones outnumber anticyclones while the reverse happens downstream of cape st vincent

surface circulation in the gulf of cadiz model and mean flow structure 1 the mean flow structure of the gulf of cadiz is studied using a numerical model the model consists of a set of one way nested configurations attaining resolutions on the order of 2 6 km in the region of the gulf of cadiz in the large scale configuration the entrainment of the mediterranean water is parameterized implicitly through a nudging term in medium and small scale nested configurations the mediterranean outflow is introduced explicitly the model reproduces all the known features of the azores current and of the circulation inside the gulf of cadiz a realistic mediterranean undercurrent is generated and meddies develop at proper depths on the southwest tip of the iberian slope the hypothesis that the azores current may generate in association with the mediterranean outflow plume theories is confirmed by the model results the time mean flow is dominated by a cyclonic cell generated in the gulf which expands westward and has transports ranging from 4 to 5 sv the connection between the cell and the azores current is analyzed at the scale of the gulf the time mean flow cell is composed by the westward mediterranean undercurrent and by a counterflow running eastward over the outer edge of the mediterranean undercurrent deeper vein as the latter is forced downslope this counterflow feeds the entrainment at the depths of the mediterranean undercurrent and the atlantic inflow at shallower levels coastward and upslope of this recirculation cell a second current running equatorward all the way along the northern part of the gulf is revealed this current is a very robust model result that promotes continuity between the southwestern iberian coast and the strait of gibraltar and helps explain many observations and recurrent sst features of the gulf of cadiz

a census of meddies tracked by floats recent subsurface float measurements in 27 mediterranean water eddies meddies in the atlantic are grouped together to reveal new information about the pathways of these energetic eddies and how they are often modified and possibly destroyed by collisions with seamounts twenty meddies were tracked in the iberian basin west of portugal seven in the canary basin during february 1994 14 meddies were simultaneously observed 11 of them in the iberian basin most 69 of the newly formed meddies in the iberian basin translated southwestward into the vicinity of the horseshoe seamounts and probably collided with them some meddies 31 passed around the northern side of the seamounts and translated southwestward at a typical velocity of 2 0 cm s into the canary basin some meddies observed there were estimated to be up to 5 yr old four meddies in the canary basin collided with the great meteor seamounts and three meddies were inferred to have been destroyed by the collision overall an estimated 90 of meddies collided with major seamounts the mean time from meddy formation to a collision with a major seamount was estimated to be around 1 7 yr combined with the estimated meddy formation rate of 17 meddies yr from previous work this suggests that around 29 meddies co exist in the north atlantic therefore during february 1994 we observed about half of the population of meddies

evidence of magma mixing identified in the early eocene caina pluton from the gangdese batholith southern tibet abstract abundant mafic enclaves are enclosed within the quxu batholith in the eastern gangdese magmatic belt southern tibet this study focuses on the petrogenesis and affinity of these mafic enclaves with their host diorite granodiorite as well as their mechanism of formation and tectonic setting zircon u pb geochronological and hf isotopic results demonstrate that the mafic enclaves and their hosts were emplaced at 50 ma with similar positive zircon ehf t values of 9 12 al in hornblende geobarometry suggests that the mafic enclaves and their hosts intruded at depths of 11 13 km the geochronological and geochemical data point to a magma mixing process resulting in the formation of the host rocks and mafic enclaves our conclusion is further supported by mesoscopic field and microscopic thin section observations consistent with magma mixing we argue that the emplacement of these rocks within the eastern gangdese belt was triggered by slab rollback of the subducted neotethyan oceanic lithosphere during the early phases of the indo asian collision

observations and numerical modelling of the mediterranean outflow splitting and eddy generation during the canigo project the generation of dipolar eddies in the mediterranean water mw layers off south portugal was recorded by subsurface floats from february to november 1998 the role of the bottom topography on the spreading of the mw in the gulf of cadiz and on the generation of these mw eddies was studied in the framework of the medtop project some of the hydrological and velocity observations collected during medtop in 2001 and 2002 also revealed the association of anticyclones meddies and cyclones in the region just south of the portimao canyon the evolution of these structures is studied with subsurface floats deployed in the vortices the splitting of the mw plume in the gulf of cadiz and the generation mechanisms of the mw vortices in the region from portimao canyon to the estremadura promontory are investigated using a bottom following numerical primitive equations model in a regional ocean configuration incorporating the realistic topography of the iberian continental slope the model reproduces the mw division into different cores in the gulf of cadiz as well as the generation of baroclinic dipoles downstream of portimao canyon the role of the bottom topography in the eddy generation process is discussed

mid crustal magmatic sheets in the cascades mountains washington implications for magma ascent abstract diking diapirism ascent along faults and ascent during heterogeneous ductile flow have all been championed as the most important means of magma ascent in the crust we suggest that these mechanisms are end members in a complex spectrum of ascent processes in an attempt to evaluate which combination of ascent processes formed sheet like bodies in the mid crustal 20 25 km entiat pluton washington we examined the tip regions of these sheets the sheets have length width ratios ranging from 6 to 75 with increasing ratios strongly correlated to decreasing sheet tip radii from 850 to 100 m and decreasing ratios of tip diameter sheet width from 0 66 to 0 33 thus these bodies have geometries falling between those of dikes and those associated with elliptical diapirs the sheets are not associated with faults or fracture zones extending from their tips instead sheet walls are oriented parallel to the axial planes of upright syn emplacement folds in sheets with high length width ratios magmatic foliations in sheets are folded or parallel to axial planes of host rock folds with decreasing length width ratios margin parallel foliations in both sheet and host rock are increasingly common our studies indicate that the sheets are emplaced at high angles to 1 not 3 as proposed in elastic dike models and are always associated with complex viscoelastic flow of host rock these observations rule out elastic dike and fault models and instead favor diapiric rise of magma sheets during viscoelastic behavior of host rock

direct observation of deformation processes in crystal mushes isothermal microstructural development in deforming melt bearing crystal mushes is studied using synkinematic microscopy and a polyphase thiocyanate system the aim of the work is to contribute to the basis for understanding the origin of microstructures in rocks which have undergone melt present deformation during high strain rate pure shearing experiments microstructures indicating crystal plasticity and dynamic recrystallization are observed during low strain rate pure shearing experiments a pressure solution like process called contact melting is active resulting in optically strain free crystals crystal boundary sliding is active in both regimes framework scale processes such as filter pressing grain flow and development of a micro shear zone are illustrated some of these processes are cryptic microstructurally and may be difficult or impossible to recognize in rocks the validity of the experimental system as an analog for magmatic systems is discussed we conclude that the experiments can serve as a source of ideas to test against the evidence from rocks but that no direct analogy to the behavior of natural crystal mushes has been or will readily be established

crustal scale en echelon p shear tensional bridges a possible solution to the batholithic room problem the apparent paradox of voluminous granitoid emplacement in an overall compressional magmatic are has been somewhat alleviated by the idea of pluton emplacement in tension cracks and dilational jogs within arc parallel strike slip fault systems as an alternative hypothesis we propose that an en echelon p shear array provides a continuous batholith scale zone of dilation along the trend of active magmatism and that it is favored by transpressional tectonics in the sierra nevada california the late cretaceous granitoids of the cathedral range intrusive epoch are consistent with emplacement into bridges between p shears because 1 they are elongated oblique to the magmatic trend consistent with p shear orientation within a dextral system 2 they were all emplaced within 5 10 m y along a 300 km trend resulting in a displacement rate of 1 cm yr across the arc and 3 syn to late magmatic dextral shear zones bound and crosscut the plutons as in a p shear tensional bridge

meddy trajectories in the canary basin measured during the semaphore experiment 1993 1995 as part of the structures des echanges mer atmosphere proprietes des heterogeneites oceaniques recherche experimentale semaphore experiment four mediterranean water eddies meddies were identified in the canary basin and tracked with freely drifting rafos floats one large and energetic meddy discovered 1700 km west of cape saint vincent portugal set a distance and speed record as it translated another 1700 km southwestward at 3 9 cm s during 1 5 years this meddy traveled 57 of the distance from cape saint vincent toward the spot mcdowell and rossby 1978 found a possible meddy north of the dominican republic two meddies were observed to interact with the azores current as they passed underneath or through it three meddies collided with tall seamounts which seemed to disrupt the normal swirl velocity perhaps fatally in two cases one meddy appeared to bifurcate when it collided with seamounts

magmatic structures in the krkonose jizera plutonic complex bohemian massif evidence for localized multiphase flow and small scale thermal mechanical instabilities in a granitic magma chamber abstract the present paper examines magmatic structures in the jizera and liberec granites of the krkonose jizera plutonic complex bohemian massif the magmatic structures are here interpreted to preserve direct field evidence for highly localized magma flow and other processes in crystal rich mushes and to capture the evolution of physical processes in an ancient granitic magma chamber we propose that after chamber wide mixing and hybridization as suggested by recent petrological studies laminar magma flow became highly localized to weaker channel like domains within the higher strength crystal framework mafic schlieren formed at flow rims and their formation presumably involved gravitational settling and velocity gradient flow sorting coupled with interstitial melt escape local thermal or compositional convection may have resulted in the formation of vertical schlieren tubes and ladder dikes whereas subhorizontal tubes or channels formed during flow driven by lateral gradients in magma pressure after the cessation or deceleration of channel flow gravity driven processes settling of crystals and enclaves gravitational differentiation development of downward dripping instabilities accompanied by compaction filter pressing and melt segregation dominated in the crystal mush within the flow channels subsequently magmatic folds developed in schlieren layers and the magma chamber recorded complex late magmatic strains at high magma crystallinities late stage magma pulsing into localized submagmatic cracks represents the latest events of magmatic history of the chamber prior to its final crystallization we emphasize that the most favorable environments for the formation and preservation of magmatic structures such as those hosted in the jizera and liberec granites are slowly cooling crystal rich mushes therefore where preserved in plutons these structures may lend strong support for a mush model of magmatic systems

four magmatic fabrics in the tuolumne batholith central sierra nevada california usa implications for interpreting fabric patterns in plutons and evolution of magma chambers in the upper crust for the first time four distinct magmatic fabrics are documented in a composite plutonic body the tuolumne batholith central sierra nevada california usa one type of fabric was formed by strain caused by highly localized magma flow type 1 whereas the other three chamber wide fabrics recorded strain increments during boundary processes along batholith margins type 2 superimposed by increments of heterogeneous regional tectonic strain types 3 and 4 our present work indicates that in contrast to studies that consider magmatic fabrics to be simple structures formed by a single process magmatic lineations and foliations in plutons may reflect accumulated finite strain and form as composite structures recording multiple strain increments in relatively static actively deforming and rheologically complex crystal mushes at lower melt percentages we demonstrate that multiple magmatic fabrics in a single batholith may record remarkably different processes and thus preserve a temporal record of strain in the batholith from strain during internal chamber processes to postem placement regional tectonic strain however it may be commonly very problematic to infer the exact nature of flow or even fabric forming process from the preserved rock record our study also exemplifies how examination of magmatic fabric patterns in plutons complemented with geochronology may provide crucial constraints on the interplay among successive magma emplacement fabric preservation temporal evolution of strain fields in a crystallizing magma chamber and the development of crystal mush zones

evolution of landscapes of the moskva river floodplain in the atlantic and subboreal pedological and palynological records abstract floodplain deposits in the valley of the moskva river contain a series of buried soils of the holocene age which can be an important source of paleoecological information these soils were dated as follows soil 1 100 bp soil 2 cal 1200 ad 500 bc soil 3 900 2700 bc and soil 4 3700 6000 bc archeological monuments associated with these soils belong to the neolithic soil 4 early bronze age soil 3 and iron age and middle ages soil 2 buried soils have well developed profiles and diagnostic features dark colored soils of the atlantic period soil 4 in most cases can be attributed to phaeozems pollen analysis shows that these soils were formed under forest steppe communities buried soils of the subatlantic period soil 2 are usually referred to as luvisols unlike them the soils of the subboreal period soil 3 are traced in rare cases and have no clear diagnostic features allowing reconstruction of the paleoenvironment these soils have a light colored humus horizon which does not allow them to be classified as phaeozems however they do not have the bt horizon characteristic of luvisols this paper describes the results of a new comprehensive study of the moskva river floodplain near the zvenigorod biological station zbs of moscow state university the buried soils of the atlantic and subboreal periods were studied by palaeopedological and palynological methods the findings confirmed previously obtained results and indicated that the buried soil 3 at the zbs site could be developed under mixed forests dominated by spruce these results suggest that the landscapes of the lower levels of the valley changed dramatically between 5000 and 4500 cal bp the forest steppe communities were replaced by dense forests due to the early subboreal climate change the paper also examines the specifics of soil and pollen records of the landscape evolution the anthropogenic influence on the floodplain landscapes is also considered

reconstructed mediterranean salt lens trajectories the existence of energetic anticyclonic mid depth vortices of mediterranean water meddies questions the validity of a conventional advective diffusive balance in the eastern atlantic subtropical gyre a mesoscale experiment in the azores madeira region reveals a link of these meddies to large scale subsurface meanders for the first time it is shown that meddies may have strong surface vorticity indicative of a generation process involving the azores current a deep reaching near surface jet

a flower like glomerophyric diorite porphyry from central china constraints on the unusual texture abstract an unusual texture with plagioclase phenocrysts clustered as flower like glomerocrysts has been discovered in the wulong diorite porphyry at the southern margin of north china craton the rock consists mainly of plagioclase and amphibole with the former as dominant phenocryst two groups of the plagioclase phenocrysts have been distinguished flower like glomerocrysts fg type and single isolated phenocrysts sp type chemical compositions of both fg and sp type plagioclases are similar in anorthite contents an35 45 which are slightly higher than the matrix an25 35 calculation of the plagioclase crystallization time based on crystal size distribution csd program shows that the fg type crystals have been formed within a longer timescale 226 2782 years than the sp type crystals 98 1910 years the concave down csds and lack of small crystals for fg type plagioclases suggest that coarsening may have been involved in contrast a concave up csd within the size of 3 10 mm plagioclase indicating that a rejuvenation kinetic process after coarsening a possible formation history for the unusual flower like plagioclase glomerocrysts was proposed as follows 1 initial nucleation and growth of single crystals in a confined environment 2 ascent of early crystals with magma upwelling and radial coarsening at the roof layer of magma chamber 3 remobilization of dense crystal mush and final emplacement at shallow level of crust 4 rapid cooling and extensive nucleation and growth of matrix 5 post magmatic alteration and metamorphism it is likely that the morphologic diversity of plagioclase glomerocrysts are largely influenced by variation of undercooling degrees the second step is the most important for the formation of the flower like glomerophyric texture which requires an environments of relatively low undercooling degree

bursting the bubble of ballooning plutons a return to nested diapirs emplaced by multiple processes a popular model for the emplacement of roughly spherical plutons is that of ballooning or in situ inflation of a magma chamber in a common version of this model magma ascends until loss of heat or buoyancy causes the outermost magma to crystallize and cease ascent while the hotter tail of magma continues to rise and expand the already crystallized outer margin this expansion forms a concentric gneissic to mylonitic foliation and flattening type strain in the outer margin of the pluton by means of subsolidus deformation and pushes aside the surrounding country rock to form a dynamothermal aureole that postdates regional structures our reexamination of three supposedly ballooned plutons ardara ireland cannibal creek australia papoose flat california and evaluation of published descriptions of many others indicate that this model is largely incorrect deflections of country rock structures strains and porphyroblast matrix relationships indicate that only minor to moderate expansion usually 30 or less occurred during emplacement that other emplacement mechanisms must have occurred and that regional deformation continued during and after emplacement internal structures indicate that when magma chamber expansion did occur it did so by flow of magma that magmatic foliations and lineations formed late in the magma chamber evolution that enclave shapes are neither good strain markers nor indicators of the magnitude of expansion and that only minor internal subsolidus deformation results from emplacement this study indicates that many plutons previously interpreted as post tectonic ballooning plutons are better viewed as syntectonic nested diapirs emplaced by a variety of country rock material transfer processes this nested diapir model implies that magma ascent may occur by rise of large magma batches instead of transport in dikes followed by ballooning that magma chamber dynamics differ from that in the ballooning model and that normally zoned plutons may form by intrusion of several pulses of magma rather than by in situ crystal fractionation from a single parent melt

fabric evidence for granodiorite emplacement with extensional shear zones in the variscan gredos massif spanish central system abstract three granitoid bodies in the central part of the gredos massif spanish central system batholith are tabular around 1 km in thickness and intruded into a migmatitic middle crust during the d3 deformation phase of the variscan orogeny petrologically they are composed of bt granodiorite and crd monzogranite and they show varying abundance of large cm scale feldspar megacrysts a detailed study of the shape preferred orientation spo magmatic fabric defined by these megacrysts together with a kinematic analysis of the structures due to interactions between them and the measurement of quartz c axis fabrics in migmatites and granitoids suggests that granitic magma and country rocks were mechanically coupled during deformation the emplacement took place along large scale extensional shear zones active during the first stages of the d3 phase the shape of the spo ellipsoids varies from constrictional at the centre of the granitic bodies to flattening or even oblate at their external contacts with the migmatitic host rocks the favoured interpretation of this spatial fabric variation is the overprinting of the emplacement fabrics by a constrictional tectonic regime associated with the growth of tabular magma chambers along extensional detachments followed by shear zone development commonly at the top of the granitic bodies the entire structure was later folded during the last stages of the d3 phase

fractional crystallization in granites of the sierra nevada how important is it although compositional variation in zoned calc alkalic plutons is often ascribed to crystal fractionation diagnostic large scale field evidence of crystal accumulation in these slowly cooled bodies is generally missing in many plutons however small scale crystal cumulates have been preserved as layered schlieren and in microcosm may allow an assessment of the importance of crystal fractionation in their host pluton9s development small widely separated patches of schlieren in the tuolumne intrusive series yosemite national park california formed as cumulates their darkest layers show high concentrations of magnetite sphene biotite horn blende and zircon and have unusually fractionated major and trace element compositions feo 33 al 2 o 3 in chondrites 750 zr 2000 ppm the layers define smooth trends on major and trace element al 2 o 3 variation diagrams that diverge strongly from patterns for the main sequence rocks of the tuolumne series and granitoids throughout the sierra nevada removal of such cumulates from any main sequence magma would produce al rich evolved rocks not the al poor felsic rocks of the pluton the findings suggest that fractional crystallization did not produce the dominant chemical patterns seen in the tuolumne and similar sierra nevada granites

deciphering magmatic processes in calc alkaline plutons using trace element zoning in hornblende hornblende in the kuna crest lobe kcl of the tuolumne intrusive complex tic and the upper zone of the wooley creek batholith wcb precipitated over a temperature range of 835 to 700 c and thus has the potential to record magmatic processes we measured trace element concentrations in hornblende from the wcb from the kcl of the tic and from one sample from an adjacent interior unit of the tic to compare and contrast magmatic processes in these two mid crustal intrusions in both systems the magmatic amphibole is magnesiohornblende in which ti zr hf nb sr ba and rare earth elements ree typically decrease from crystal interiors to rims an indication of compatible behavior of these elements and the size of the negative eu anomaly decreases in the kuna crest lobe hornblende from individual mapped units differs in trace element abundances and zoning trends some samples contain at least two distinct hornblende populations which is particularly evident in the shapes of ree patterns in contrast compositions of hornblende from all structural levels of the upper wcb and related dacitic roof zone dikes form a single broad array and the ree patterns are essentially indistinguishable regardless of rock type from quartz diorite to granite in the wcb zr hf ratios in hornblende are consistent with crystallization from a melt with chondritic zr hf values in contrast most hornblende in the kcl has zr hf values lower than expected from crystallization from a melt with chondritic values suggesting that zircon fractionation occurred before and during crystallization of the hornblende simple fractional crystallization models indicate that ree high field strength elements sr and ba were compatible in kcl and wcb magmas as hornblende grew these trends require removal of hornblende plagioclase zircon ilmenite biotite the uniform variations of trace element concentrations and patterns in the upper wcb and roof zone dikes indicates crystallization from a large magma body that was compositionally uniform probably stirred by convection caused by influx of mafic magmas at the base of the zone coint et al 2013a 2013b cf burgisser and bergantz 2011 in contrast in the kcl each analyzed sample displays distinct hornblende compositions and zoning patterns some of which are bimodal these features indicate that each analyzed sample represents a distinct magma and that individual magmas were variably modified by fractionation and mixing hornblende trace element contents and zoning patterns prove to be powerful tools for identification of magma batches and for assessing magmatic processes and thereby relating plutonic rocks to hypabyssal and volcanic equivalents

meddy dynamics and interaction with neighboring eddies southwest of portugal observations and modeling 1 during the semane 2000 experiment southwest of portugal two meddies were found in near contact these meddies had hydrological radii of about 20 and 30 km thickness of 900 m maximum temperatures of 12 45 c and 13 45 c and maximum salinities of 36 52 and 36 78 the smaller meddy with more pronounced thermohaline anomalies was clearly double cored at 750 and 1300 m depths while the wider one was more diffuse and more homogeneous the associated geostrophic velocities referenced at 2000 m locally reached 0 5 m s in the smaller meddy and 0 2 m s in the wider one three rafos floats and two deep drogued surface drifters seeded in the two meddies rapidly gathered in the more intense meddy this meddy trajectory revealed by the float motion was first eastward then southward maps of sea level anomaly indicate that this motion did not correspond to the long term evolution of the initial positive sea level anomaly signature of the meddies and that neighboring cyclones must have played a role in the meddy evolution to determine the role of each eddy in the observed evolution several scenarios were studied with a three layer quasi geostrophic numerical model the interaction of two meddies in isolation did not result in the observed meddy trajectories on the long term the interaction of these two meddies with successive neighboring cyclones provided a more realistic trajectory of the meddy containing the floats

real time tracking of a galician meddy we describe the properties and displacement of the northernmost meddy that has ever been studied this meddy was found to the northwest of the iberian peninsula in april 1997 its hydrological properties suggest that it was born offshore galicia the northwestern corner of spain it was tracked in real time for more than one year using recent types of deep drogued buoys and lagrangian floats and remained quasi stationary for an unusually long period of 11 months around 45 n 12 w

a reinterpretation of conjugate folds in the central sierra nevada california conjugate folds and cleavages in the central sierra nevada california are developed in isolated domains along or near ductile shear zones the conjugate folds form by rotation of older jurassic cretaceous fabrics and removal of material along microlithon boundaries and apparently postdate all significant metamorphic events the conjugate structures in this region are thus cretaceous or tertiary maximum shortening directions associated with these folds are in most cases northwest southeast parallel to the present strike of the sierra nevada conjugate folds near briceburg california are unusual in that they are found over a relatively large region are associated with a well developed crenulation cleavage and were formed due to west southwest east northeast shortening shortening in microlithons of as much as 34 is associated with the crenulation cleavage and formed by buckling but with a small component of flattening of an older fabric removal of material and shear along microlithon boundaries caused an unknown amount of additional shortening models based on gravity relaxation elastic recovery and folding of fabrics in shear zones do not fully explain the orientation and style of conjugate structures in the study area instead the conjugate structures reflect cretaceous or tertiary deformation possibly associated with movement along brittle faults in addition shortening directions calculated from incremental strains associated with the conjugate folds near briceburg are in direct conflict with shortening directions based on geometries of experimentally produced conjugate structures indicating that different mechanisms may operate during formation of experimentally and naturally formed conjugate folds

evidence of mediterranean water dipole collision in the gulf of cadiz a collision of mediterranean water dipoles in the gulf of cadiz is studied here using data from the medtop and semane experiments first a mediterranean water eddy meddy was surveyed hydrologically in november 2000 southwest of cape saint vincent then this meddy drifted northeastward from this position accompanied by a cyclone detected only via altimetry thus forming a first dipole in february 2001 a dipole of mediterranean water was measured hydrologically just after its formation near portimao canyon this second dipole drifted southwestward the western and eastern meddies had hydrological radii of about 22 and 25 km respectively with corresponding temperature and salinity maxima of 13 45 c 36 78 and 11 40 c 36 40 rafos float trajectories and satellite altimetry indicate that these two dipoles collided early april 2001 south of cape saint vincent near 35 30 n 10 15 w more precisely the eastern meddy wrapped around the western one this merger resulted in an anticyclone a meddy which drifted southeastward coupled with the eastern cyclone hydrological sections across this final third resulting dipole performed in july 2001 in the southern gulf of cadiz confirm this interaction the thermohaline characteristics of the final meddy can be tracked back to the original structures the subsequent evolution of this dipole was analyzed with rafos float trajectories a numerical simulation of the interaction between the two earlier dipoles is also presented we suggest that these dipole collisions at the mediterranean water level may represent a mechanism of generation of the larger meddies that finally leave the gulf of cadiz

on the time scales of magmatism at island arc volcanoes precise information on timescales and rates of change is fundamental to an understanding of natural processes and the development of quantitative physical models in the earth sciences useries isot

magma flow within the tavares pluton northeastern brazil compositional and thermal convection crystallization coupled with gravity removal of depleted interstitial melt has long been recognized as a mechanism of magma differentiation similarly heat released by synplutonic basaltic magma intrusions has long been recognized as capable of driving convection in granite chambers direct evidence of these processes has seldom been described in granites in the tavares pluton we mapped a number of melt extraction structures from pores of a crystal liquid mush an effectively solid magma where crystals form an interconnected skeleton and a variety of flow structures such as 1 meter scale tear or mushroom shaped blobs representing within chamber diapirs 2 meter scale ellipsoids representing frozen thermal plumes of granite driven by heat released from disrupted diorite intrusions and 3 ladder dikes and snail structures representing cross sections of several superposed cylindrical magma channels possibly feeders of diapirs and plume heads a fundamental feature of the structures in the tavares pluton is that they are well delineated by mafic schlieren developed at active channel margins we postulate a new model for the origin of marginal schlieren which combines shear flow sorting and melt escape from the flowing magma into an effectively solid surrounding mush extraction structures representing melt extraction from mush pores into melt pockets and schlieren representing regions where melt escaped into surrounding mush pores are both favored by magmas that form an interconnected solid framework at low crystal fractions 50 because these mushes are ductile and permeable favorable magmas are those with a high wetting angle between melt and solid 60 and a propitious crystal size and shape distribution we propose a model of compositional and thermal convection that accounts for all described structures

dynamics and evolution of a northern meddy abstract a meddy was discovered in april 1997 off the northwestern corner of spain near 45 n 11 30 w it was tracked during 18 months with lagrangian floats and deep drogued buoys and several cruises were set to collect further hydrological and lowered adcp measurements on it the meddy named ulla was a one core lens with maximum values of temperature and salinity of 11 5 c and 36 17 psu near 1000 m depth yielding anomalies above 2 5 c and 0 5 psu compared to its environment its rotation frequency was close to 1 loop every 5 days the maximum azimuthal velocities of 15 20 cm s 1 were reached near a 15 km radius the meddy had a wide remote influence notably up to the surface and was associated with a total azimuthal volume transport of around 10 sv sv 106 m3 s 1 of which around 2 sv was trapped in the core a widening of the radial structure with decreasing depth was notable in august 1997 meddy ulla was significantly elliptic for most of the time and depending on the periods the main el

an analysis of the evolution of meddies in the north atlantic using floats and multisensor satellite data previous studies focusing on the remote detection of mediterranean eddies meddies have reported that the isopycnal surface changes derived from satellite multisensor measurements at the approximate depth of 400 m can be used to sense the presence of underlying meddies while the isopycnal surface near that depth does indeed reveal the locations of meddies an analysis of isopycnal surface changes in response to the evolution of meddies has yet to be made accordingly this research focuses on analyzing the relationship between isopycnal surface changes and the evolution of meddies the vertical isopycnal surface variability of meddies which is directly related to contributions from rotational velocity interior thermal variation and vertical displacement of meddies is observed and studied using float observations from a mediterranean undercurrent seeding experiment amuse the contributions of each of the three aforementioned parameters are estimated enabling us to understand their relative role in changing the isopycnal surface above meddies furthermore in order to further understand meddies evolution and their associated forcing the dominant frequencies of their horizontal and vertical displacements as well as the sea surface height variability above the meddy are analyzed using the hilbert huang transform finally the horizontal and the vertical eddy viscosity dissipation of meddies is computed and compared with a theoretical model the empirical horizontal and the vertical eddy viscosities are found to be 7 106 cm2 s 1 and 200 cm2 s 1 respectively this study will therefore contribute to understanding how the isopycnal surface is related to the presence of meddies what frequencies dominate its variability and the values of eddy viscosity which can be used for a numerical model

a review of mesoscopic magmatic structures and their potential for evaluating the hypersolidus evolution of intrusive complexes abstract the perception that plutonic bodies are structurally simple is disappearing with the recognition of an array of magmatic structures useful for constraining hypersolidus temporal histories evolving rheologies strain fields flow directions growth and cooling patterns tilting and syn emplacement tectonism these histories provide a powerful means of testing an array of growth emplacement chamber evolution and tectonic models important points include that 1 many structures form in hydrogranular or congested magma slurries during magma mush avalanching local convection and late hypersolidus strain challenging the notion that magmas must have 55 crystals to convect fractionate and form compositional diversity in upper crustal magma chambers 2 magmatic fabrics reflect transient strain in these slurries rather than flow directly the latter must be inferred by linking geometries with temporal and kinematic information 3 caution is needed when using anisotropy of magnetic susceptibility and similar quantitative tools that characterize through a single ellipsoid preferred orientations of mineral grains given the increasing recognition of multiple fabrics in plutons and 4 that future studies are particularly needed in plutons focusing on the distribution and styles of compositionally defined structures magmatic folding shear zones and faults multiple fabrics and of the physical chemical behaviors in hydrogranular slurries

magmatic arc asymmetry and distribution of anomalous plutonic belts in the batholiths of california effects of assimilation crustal thickness and depth of crystallization in order to better understand geologic fac tors controlling pronounced regional variations in whole rock chemistry mineralogy and mineral chemistry in the batholiths of california we calculate the magmatic intensive variables f hf f h 2 o f hf f hcl and f o 2 regional scale west to east increases in f oh in mafic silicates corresponding to the systematic i wc to i mc and i sc progression reflect orders of magnitude increase in f hf f h 2 o attending pluton crystallization low f hf f h 2 o of formation of western i wc types is consistent with their derivation from low fluorine source rocks in subducted oceanic slabs or the upper mantle in contrast higher f hf f h 2 o of crystallization of i mc and i sc types to the east implies the involvement of 1 progressively greater amounts of continental crustal source material such as biotite bearing metamorphic rocks their unweathered sedimentary derivatives retaining f rich mafic minerals or their fusion products and or 2 source materials which become more f rich toward the continental interior the regional distribution of i mc and i sc types suggests that the precambrian craton of western north america or derivative sediments may extend farther north in california and be morphologically more complex than previously thought from seemingly out of place occurrences of i wc plutons on the eastern slopes of the sierra nevada batholith we infer the existence of regions where precambrian basement was thin or absent in mesozoic time which prevented extensive cratonal contamination of subducted slab or upper mantle derived magmas new methods for estimating t f o 2 relations in the magmas demonstrate that i scr granites crystallize at oxygen fugacities as much as five orders of magnitude lower than those of i wc i mc and i sc types under conditions at or below the maximum stability limit of graphite in equilibrium with a c o h s gas phase the local scale formation of i scr granites in plutonic belts within specific wall rock terranes containing highly reducing sediments or metasediments may occur by contamination of i types with graphitic pelite or in some cases by the direct fusion of this reducing pelitic wall rock the spatial distribution of i scr granite provinces therefore is controlled simply by wall rock lithology amphibole geobarometry demonstrates a general west to east decrease in crystallization pressure across the sierra nevada batholith in contrast the peninsular ranges batholith displays a west to east crystallization pressure increase the bulk of the california batholiths crystallized at pressures less than 4 5 kb and depths less than about 15 19 km in the southern sierra nevada batholith the san gabriels and the eastern peninsular ranges however plutons crystallized at pressures exceeding 6 kb at deep crustal levels 23 km reconstruction of the pre erosion top of the batholith shows that in an east west cross section the central sierra nevada batholith was a horizontal tabular body with an aspect ratio of at least five to one

eddy generation in the mediterranean undercurrent abstract in the framework of the european union mast iii project canary islands gibraltar azores observations 24 rafos floats were deployed in the mediterranean water mw undercurrent off south portugal between september 1997 and september 1998 a preliminary analysis of this lagrangian approach complemented with xbt and current meter data show some of the major aspects of the flow associated with the undercurrent as well as associated eddy activity floats that stayed in the undercurrent featured a downstream deceleration and a steering by bottom topography three meddy formations at cape st vincent could be isolated from the float data the dynamical coupling of meddies and cyclones was observed for a considerable period of time the generation of two dipolar structures in the portimao canyon region also was observed with the float data a major bathymetric relief gorringe bank was not only an important constraint to the eddy trajectories and of the flow at the mw levels but also a site for meddy formation

properties and pathways of mediterranean water eddies in the atlantic abstract data from ship vertical casts nodc data set argo profiling floats coriolis data set and rafos type neutral density floats woce data set are used to study characteristics of meddies in the northeast atlantic in total 241 mediterranean water eddies meddies and 236 parts of float trajectories within meddies are selected for detailed analysis the results suggest that the meddy generation rate at the southern and southwestern iberian peninsula portimao canyon cap st vincent estremadura promontory gorringe bank is 3 times that at the northwestern iberian peninsula porto aveiro canyons cape finisterre and galicia bank meddies generated south of estremadura promontory the southern meddies as compared to those generated north of it the northern meddies have smaller radii smaller vertical extension higher aspect ratio higher rossby number and higher stability stronger potential vorticity anomaly these latter properties result from the southern meddies higher relative vorticity and stronger buoyancy frequency anomaly away from the generation regions meddy drift concentrates along four main paths three quasi zonal paths northern central southern and a path following the african coast coastal the quasi zonal paths are aligned to the isolines of the ambient potential vorticity field several cross path exchanges identified in this work are aligned to topographic rises northward translation of the northern meddies within the north atlantic current to the subpolar gyre is detected within the first 600 km from the coast meddy merger is proved to be a common event this explains the observed difference in radii between the newly generated meddies and those away from the iberian margin the decay of the southern meddies proceeds mainly via the loss of their skirts and does not affect meddy cores until the latest stages the decay of the northern meddies goes in parallel with the decay of their cores in average meddy decay is achieved within 1 2 years although may take over 3 years collisions with the mid atlantic ridge and seamounts sensibly decrease meddy lifetimes meddy decay also speeds up when meddies meet the azores current or the north atlantic current a rapid drop in the number of meddies south of the azores current proves that it represents a dynamic barrier for weak meddies

k feldspar megacryst accumulations formed by mechanical instabilities in magma chamber margins asha pluton nw argentina abstract the asha pluton the oldest unit of the san blas intrusive complex early carboniferous exhibits impressive examples of magmatic structures formed by accumulation of k feldspar megacrysts enclaves and schlieren almost all recognized structures are meter scale vertically elongate bodies of variable shapes defined as fingers trails drips and blobs they preferentially developed near the external margin of the asha pluton and generally are superimposed by chamber wide magmatic fabrics they mostly have circular or sub circular transverse sections with an internal fabric defined by margin parallel inward dipping concentric foliation and steeply plunging lineation at upper parts and flat foliation at lower parts the concentration of megacrysts usually grades from upper sections where they appear in a proportion similar to the host granite to highly packed accumulations of k feldspar along with grouped flattened enclaves at lower ends these features suggest an origin by downward localized multiphase magmatic flow narrowing and log jamming and gravitational sinking of grouped crystals and enclaves with compaction and filter pressing as main mechanisms of melt removal crystal size distribution analysis supports field observations arguing for a mechanical origin of accumulations the magmatic structures of the asha pluton represent mechanical instabilities generated by thermal and compositional convection probably owing to cooling and crystallization near the pluton margins during early stages of construction of the intrusive complex

siddies corridor a major east west pathway of long lived surface and subsurface eddies crossing the subtropical south indian ocean south indian ocean eddies siddies originating from a high evaporation region in the eastern indian ocean are investigated by tracking individual eddies from satellite data and co located argo floats a subsurface eddy identification method based on its steric dynamic height anomaly is devised to assign argo profiles to surface eddies surfsiddies or subsurface eddies subsiddies these westward propagating long lived features 3 months prevail over a preferential latitudinal band forming a permanent structure linking the eastern to the western indian ocean that we call the siddies corridor key features have been revealed in the mean thermohaline vertical structure of these eddies anticyclonic siddies are characterized by positive subsurface salinity anomalies with subsiddies not exhibiting negative surface anomalies as opposed to surfsiddies cyclonic subsiddies also occur but their related salinity anomalies are weaker subsiddies exhibit two cores of different temperature polarities in their surface and subsurface levels cyclonic subsiddies have their cores at around 150 200 m depth along the 25 4 25 8 kg m 3 potential density layer with anticyclonic subsiddies having their cores at 250 300 m along the 26 26 4 kg m 3 density layer the siddies corridor acts as a zonal pathway for both eddy types to advect water masses and biogeochemical properties across the basin this study provides a new insight on heat salt fluxes showing that 58 32 of the total heat eddy flux is ascribed to cyclonic anticyclonic subsiddies respectively in the eastern south indian ocean anticyclonic subsiddies have also been found to be the sole high saline water eddy conveyor toward the western indian ocean

magma rheology variations in sheet intrusions of the ardnamurchan central complex scotland inferred from gabbro inclusion characteristics entrainment of xenoliths and their consequent assimilation are key processes in modifying the crystallization kinetics and magma dynamics of conduit systems here an integrated textural and mineral chemical study of the evolution of a suite of gabbroic inclusions within a set of sheet intrusions from the ardnamurchan central complex nw scotland is presented the key findings are as follows 1 the host magma sheets and inclusions are not cognate 2 there are microstructural and mineral chemical similarities between the gabbroic inclusions and the textures and mineralogy of the major hypersthene gabbro on ardnamurchan 3 orientations of magnetic fabrics within the host sheet groundmass and within the gabbroic inclusions are virtually identical field observations suggest that the inclusions were derived from the hypersthene gabbro and were entrained in a few laterally restricted magma segments that subsequently coalesced with inclusion free segments into continuous sheets using stokes law and adaptations thereof we calculate that the magma within the inclusion free segments behaved as a newtonian fluid with a potential settling velocity of50 028 m s in contrast the presence of gabbro inclusions probably modified the magma dynamics to bingham like behaviour we infer that this variation in the magma rheology of separate segments continued after coalescence and internally partitioned the magma sheet preventing lateral mixing and inclusion transport

new observations of meddy movement south of the tejo plateau mediterranean salt lenses meddies are a dominant factor in the salt budget of the atlantic at middepth in spite of their important role their juvenile migration has not yet been directly observed for the first time two rafos float trajectories show strong evidence of a meddy along the iberian continental slope off lisbon over six weeks we obtained drift observations from two levels 629 847 dbar both instruments recorded a series of loops with an azimuthal speed o 30 cm s 1 at a radius of about 25 km relatively high propagation speeds of several centimeters per second indicate the meddy was probably carried along with the undercurrent of mediterranean water the tejo plateau a prominent feature of the continental slope and a natural obstacle for the spreading mediterranean water tongue appears to act as a deflector for advected meddies possibly formed by interaction of the undercurrent with the canyon rich topography farther south

fabric studies within the cascade lake shear zone sierra nevada california abstract the cascade lake shear zone occurs on the eastern margin of the tuolumne intrusive suite sierra nevada batholith california foliation in the zone is nnw trending and subvertical and lineation is moderately south plunging deformation is syn tectonic with emplacement of the cathedral peak granodiorite a deformation gradient exists toward the ne margin of this pluton with higher strains and lower temperatures of deformation found near the contact we compare fabric data collected very densely in this shear zone using several techniques field fabrics 3d orientation of k feldspar megacrysts and ams anisotropy of magnetic susceptibility analysis in general the results from the three different methods are in agreement deformation in this shear zone is part of a larger pattern of deformation within the cathedral peak granodiorite as recorded by ams analysis and dextral shearing associated within the last stage of plutonism within the sierra nevada magmatic arc

large lenses of highly saline mediterranean water isolated compact anticyclonic eddies or salt lenses were found in the canary basin hydrographic surveys of three such lenses show large anomalies of salinity and temperature 0 8 2 5 c they are centered at 1100 m have a vertical extent of up to 900 m and radii of 50 km current meter records indicate anticyclonic velocities up to 29 cm s 1 fine structure with vertical scales of 20 m and less possibly due to intrusive decay appears at the outer edges of the lenses whereas the centers are free of such structure the probability of finding a salt lens at any station in the canary basin is fairly high 0 08

tracking three meddies with sofar floats abstract three meddies were tracked for up to two years in the canary basin using neutrally buoyant sofar floats these meddies have cores of warm salty mediterranean water and are approximately 100 km in diameter 800 m thick and are centered at a depth of 1100 m meddy 1 was tracked for two years 1984 86 with five floats as it drifted 1090 km southward with a mean velocity of 1 8 cm s 1 four shipboard surveys made during these two years revealed the nearly total decay of meddy 1 by gradual mixing processes meddy 2 drifted 530 km southwestward over 8 5 months with a mean velocity of 2 3 cm s 1 until it collided with hyeres seamount near 31 n 29 w the floats trapped in this meddy then stopped looping abruptly implying a major disruption of this meddy meddy 3 drifted 500 km southwestward for a year and a half with a mean translation velocity of 1 1 cm s 1 a comparison of the velocity of meddies to the velocity of nearby floats at 1100 m depth outside of the meddies shows clearly that all three m

bulk arc strain crustal thickening magma emplacement and mass balances in the mesozoic sierra nevada arc quantifying crustal deformation is important for evaluating mass balance material transfer and the interplay between tectonism and magmatism in continental arcs we present a dataset of 650 finite strain analyses compiled from published works and our own studies with associated structural geochronologic and geobarometric information in central and southern sierra nevada california to quantify the arc crust deformation our results show that mesozoic tectonism results in 65 arc perpendicular bulk crust shortening under a more or less plane strain condition mesozoic arc magmatism replaced 80 of this actively deforming arc crust with plutons requiring significantly greater crustal thickening we suggest that by 85 ma the arc crust thickness was 80 km with a 30 km thick arc root resulting in a 5 km elevation most tectonic shortening and magma emplacement must be accommodated by downward displacements of crustal materials into growing crustal roots at the estimated downward transfer rate of 2 13 km myr the downward transfer of crustal materials must occur in active magma channels or in escape channels in between solidified plutons that decrease in size with time and depth resulting in an increase in the intensity of constrictional strain with depth we argue that both tectonism and magmatism control the thickness of the crust and surface elevation with slight modification by surface erosion the downward transported crustal materials initially fertilize the mash zone thus enhancing to the generation of additional magmas as the crustal root grows it may potentially pinch out and cool the mantle wedge and thus cause reduction of arc magmatism

a review of criteria for the identification of magmatic and tectonic foliations in granitoids abstract foliations in granitoids can form by magmatic flow submagmatic flow high temperature solid state deformation and moderate to low temperature solid state deformation a review of previous work suggests that no single criterion can consistently distinguish foliations in granitoids formed by flow during ascent diapiric emplacement and expansion emplacement during regional deformation or regional deformation post dating emplacement however a magmatic origin is favoured for foliations defined by the alignment of igneous commonly euhedral minerals particularly where the foliation is parallel to internal or external pluton contacts foliations formed during expansion or ballooning of diapirs may be strictly magmatic in origin although some studies suggest that solid state deformation also may occur if so we would hope to find evidence of deformation of crystal melt systems and that the solid state deformation occurred at high temperatures the inference of syntectonic foliations is most convincing where magmatic and high temperature solid state foliations are subparallel these foliations are continuous with regionally developed foliations in the wall rocks synkinematic porphyroblasts are present in the wallrocks and igneous minerals have the same age as metamorphic minerals associated with the regional cleavage a strictly tectonic origin for foliations in granitoids is favoured when the foliation is defined by metamorphic minerals no alignment of igneous minerals occurs the foliation is locally at high angles to pluton wallrock contacts and the foliation is continuous with a regionally developed cleavage

the coalescence of two east australian current warm core eddies two warm core eddies coalesced in about 20 days as their centers rotated around a point on the contracting line that joined them in the process of forming the new eddy the subsurface isothermal isohaline signature layer of one eddy was uplifted and somewhat depleted while that of the other was depressed

magmatic erosion of the solidification front during reintrusion the eastern margin of the tuolumne batholith sierra nevada california the tuolumne batholith sierra nevada california consists of several nested granitoid units and is an example of upper crustal normally zoned intrusions the two outermost units of the batholith are separated by a wide gradational contact in what is interpreted to represent a large magma chamber in the potter point area near the eastern margin of the batholith the gradational contact is cross cut by a network of interconnected mafic felsic sheets which grade into zones of magmatic erosion by stoping where the host granodiorite between the sheets was entirely removed and replaced by younger enclave rich quartz diorite we interpret these features to record disruption of a steep solidification front which migrated inwards from the eastern batholith margin and separated the mushy to solidified margin from the remaining active magma chamber when intersecting the gradational contact the solidification front started to break up via a network of tectonically driven fractures accompanied by simultaneous injection of localized magma pulses the solidification front break up is interpreted here as an initial stage of a recycling process whereby older magma mush is disrupted and incorporated into younger magma batches a process we propose to have been widespread along internal contacts in the tuolumne magma chamber

quasi synoptic transport budgets and water mass transformation in the azores gibraltar strait region during summer 2009 abstract we describe the circulation patterns in the azores gibraltar strait region north eastern atlantic during the 2009 caibox cruise on the basis of hydrographic and direct current velocity measurements this study offers new data for a region where importation of central waters subpolar and subtropical modes of eastern north atlantic central water and exports of mediterranean water are strongly related to large scale dynamics in the north atlantic ocean azores current mediterranean water system the description is backed up quantitatively by the results of a box inverse model which was used to obtain absolute water mass transport values consistent with thermal wind equations and with conservation of volume salt and heat the contributions of water masses were determined in an extended optimum multiparameter analysis from a quasi synoptic point of view providing detail in addition to volume salt and heat transport the surface subsurface large scale current system in the region consists of the azores current 13 1 2 5 sverdrup sv 1 sv 10 6 m 3 s 1 the azores counter current 5 2 2 1 sv the portugal current 4 5 1 4 sv and the canary current 7 1 1 1 sv broadly speaking central waters are imported into the caibox region at a rate of 1 6 0 9 sv and mediterranean water is exported at a rate of 1 5 0 4 sv the downwelling of central waters west of gibraltar strait was quantified at 1 1 sv not all this volume participates in mw formation but 0 8 sv of entrained central waters of which 0 5 sv are from central waters of subpolar origin and 0 3 sv from subtropical central waters of the 4 9 sv of subtropical central waters advected by the azores current about 0 7 sv would reach the gulf of cadiz region either to take part in central water entrainment or to flow across the gibraltar strait as part of the atlantic inflow to the mediterranean sea

rejuvenation of the fish canyon magma body a window into the evolution of large volume silicic magma systems voluminous unzoned phenocryst rich pyroclastic deposits considered as erupted batholiths provide a unique opportunity to investigate magmatic processes in silicic magmas the fish canyon tuff a well documented example of these monotonous ignimbrites displays evidence for simultaneous dissolution of feldspars 1 quartz and crystallization of hydrous phases during gradual near isobaric reheating from 720 to 760 8c these observations along with a high crystallinity 45 and near solidus mineral assemblage suggest that the fish canyon magma cooled to a rigid crystal mush before being partly remelted prior to eruption rejuvenation was triggered by intrusion of water rich mafic magmas at the base of the fish canyon mush but the mechanisms of heat transfer remain poorly understood the growth of amphibole during reheating requires addition of mafic components but the absence of any measurable gradients and the paucity of mafic enclaves in the fish canyon magma rule out a reheating event dominated by convective mixing with a mafic magma closed system processes such as heat conduction and convective self mixing could not account for the transport of externally derived mafic components we performed numerical simulations of upward percolation of a hot low density h2o co2 fluid phase gas sparging through a crystalline framework saturated with rhyolitic melt to assess the efficiency of such a process in rejuvenating silicic mushes in open systems sparging by 20 40 km 3 of gas extracted from 3000 km 3 of mafic magma is capable of reheating 7500 km 3 of silicic crystal mush by 40 8c in 150 200 k y moreover the vertical thermal gradient after 150 k y in most of the mush is small 25 8c in the upper 65 gas sparging also produces an increase in the internal pressure of silicic crystal mushes and may lead to the formation of crystal poor rhyolites by expelling interstitial melt however our simulations predict that filter pressing driven by sparging of externally derived gas could not solely account for the generation of the most voluminous rhyolites

the significance of microgranitoid enclave shapes and orientations abstract enclaves are often incorrectly used to measure magmatic strains in plutons we emphasize that microgranitoid enclaves are not like other ellipsoidal markers used to determine strain for the following reasons 1 adjacent enclaves may form at different times and different places and initially have non spherical shapes with axial ratios up to 2 7 2 the final shapes and orientations of enclaves are a complex function of a initial shape and temperature of enclaves b subtle changes in composition melt percents volatiles grain sizes and thus temporally variable viscosity contrasts between the enclave and magma c a competition between strain and interfacial energies and d deformation path which may include internal strain and rigid rotations caused by magma flow during ascent convection expansion chamber boundary processes and tectonism 3 enclaves spend much of their time in magma as relatively rigid objects and thus rigidly rotate and potentially break apart rather than strain at matrix strain rates 4 in some instances enclaves do not record or track finite strain because of the above final enclave populations are heterogeneous and the use of single enclaves or enclave populations as strain markers violates many assumptions needed to complete strain analyses on the other hand a comparison of the preserved characteristics of igneous layering mineral fabrics and carefully evaluated enclave fabrics including internal mineral alignment in enclaves may provide qualitative data on the changing magnitude and kinematics of magmatic strains

lagrangian observations of meddy formation during a mediterranean undercurrent seeding experiment mediterranean eddies meddies play an important role in maintaining the temperature and salinity distributions in the north atlantic but relatively little is known about their early life histories including where how often and by what mechanism they form a major field program called a mediterranean undercurrent seeding experiment has been carried out to directly observe meddy formation and the spreading pathways of mediterranean water into the north atlantic between may 1993 and march 1994 49 rafos floats were deployed sequentially in the mediterranean undercurrent south of portugal and tracked acoustically for up to 11 months the float deployments were accompanied by high resolution xbt sections across the undercurrent nine meddy formation events were observed in the float trajectories six near cape st vincent at the southwestern corner of the iberian peninsula and three near the estremadura promontory along the western portuguese continental slope meddy formation thus occurs where the continental slope turns sharply to the right when facing in the downstream direction of the undercurrent after conditionally sampling the float dataset to identify floats that were well seeded in the undercurrent the authors have estimated a meddy formation rate of 15 20 meddies per year the timescale for meddy formation at cape st vincent was found to be 3 7 days shorter than previous estimates based on the volume of larger meddies meddies were observed to form most frequently when the speed of the mediterranean undercurrent was relatively fast the meddy formation process at cape st vincent resembles the conceptual model of e a d asaro whereby anticyclonically rotating eddies are formed by separation of a frictional boundary layer with negative relative vorticity at a sharp corner comparison of the relative vorticity in the anticyclonic shear zone of the undercurrent and that of the newly formed meddies shows that much of the anticyclonic relative vorticity in meddies can be accounted for by the horizontal shear in the undercurrent this confirms earlier work suggesting that the classical mechanism for the generation of submesoscale coherent vortices by collapse and geostrophic adjustment of a weakly stratified fluid injected into a stratified ocean may not be the principle mechanism at work in the formation of meddies at cape st vincent

rethinking the emplacement and evolution of zoned plutons geochronologic evidence for incremental assembly of the tuolumne intrusive suite california new u pb geochronologic data indicate that the tuolumne intrusive suite california was assembled over a period of at least 10 m y between 95 and 85 ma and that the half dome granodiorite intruded over a period approaching 4 m y simple thermal considerations preclude the possibility that a magma chamber the size of the half dome pluton could have existed as a liquid at shallow crustal depths for that long rather field evidence for sheeting along the margins of the suite the range of ages and the regular decrease of ages toward the center of the suite and within individual plutons suggest incremental assembly geochronologic evidence for incremental assembly is consistent with the failure of geophysical methods to detect large magma chambers with more than 20 melt even in active volcanic areas because it is unlikely that the individual plutons composing the tuolumne ever coexisted as liquid rich magmas the chemical evolution of the suite cannot be the result of simple fractionation and or mixing between exposed units but instead must reflect processes occurring during magma generation

two years in the life of a mediterranean salt lens abstract a lens of mediterranean water meddy was tracked in the eastern north atlantic for two years with sofar floats the meddy was first found between the canary islands and the azores in october 1984 it center moved in an irregular pattern at speeds of a few cm s 1 and translated 1100 km to the south in two years this meddy was surveyed four times by ctd and velocity profilers and once with the microstructure profiler epsonde when observed during the first two surveys the meddy had a core that was stably and smoothly stratified in both salinity and temperature nearly uniform in the horizontal and was saltier than the surrounding ocean by 0 65 psu the meddy was eroded from its edges top and bottom and lost salt and hat with an e folding time of about one year the salinity at the center remained at its original value during the first year and decreased during the second year evidence was seen for mixing by lateral intrusions double diffusion and turbulence the intrusions are thought to