asymmetric mixing transport a horizontal transport mechanism for sinking plankton and sediment in tidal flows a mechanism is described for the net horizontal transport of sinking plankton or sediment by oscillatory tidal flows the mean motion of the plankton or particles is driven by the modulation of vertical mixing between flood and ebb cold water forced over warm water on the flood tide creates enhanced vertical mixing and resuspension of sinking particles higher into the water column on ebb the converse occurs and sinking particles are lower in the water column since friction retards the tidal flow near the bottom this leads to a net horizontal transport toward the less dense water because less dense water tends to be shallower this will tend to move sinking plankton and sediment toward the crest of banks toward the coast and up embayments even in the absence of any mean currents a one dimensional eulerian model of this horizontal transport is developed and is compared to particle motion in a fully nonlinear two dimensional model with an advanced turbulence closure scheme the eulerian model can in most circumstances predict the net horizontal motion of the particles as a function of their sinking speed and observable oceanographic properties the mean horizontal speed of sinking particles is greatest when the sinking speed of the particles is about one seventieth of the tidal velocities or equivalently about one third of the mean turbulent velocity scale u this horizontal transport of plankton and particles requires no behavior more complicated than simple sinking to achieve net horizontal speeds of several kilometers per day for realistic planktonic sinking speeds it is possible that such a mechanism is a factor in larval recruitment and retention in coastal regions for example scallop larvae on georges bank

coesite and pure pyrope in high grade blueschists of the western alps a first record and some consequences a pyrope quartzite originally described by vialon 1966 from the dora maira massif was resampled and reinvestigated garnet up to 25 cm in size phengite kyanite talc and rutile are in textural equilibrium in an undeformed matrix of polygonal quartz the garnet is a pyrope almandine solid solution with 90 to 98 mol mg end member it contains inclusions of coesite which has partially inverted to quartz resulting in a typical radial cracking of the host garnet around the inclusions several lines of evidence show that coesite crystallised under nearly static pressure conditions and that the whole matrix has once been coesite

factors in the preservation of coesite the importance of fluid infiltration the survival of coesite in ultrahigh pressure uhp rocks is most commonly attributed to rapid exhumation continuous cooling during uplift and inclusion in strong phases that can sustain a high internal over pressure during decompression exceptions to all of these criteria exist perhaps less attention has been paid to the role of fluid infiltration in the preservation of coesite we used infrared spectroscopy to measure water contents of coesite and coesite pseudomorphs in a variety of uhp rocks in all cases oh concentrations in coesite are below the detection limit of 100 ppm h2o the silica phases surrounding coesite however show varying amounts of h2o this is most spectacularly observed in pyrope quartzites from the dora maira massif that contain at least three phases of silica replacing coesite also distinguished by varying color of cathodoluminescence cl palisade textured quartz 100 ppm h2o red violet cl mosaic quartz which is actually chalcedony up to 0 4 wt h2o yellow brown cl and a rare highly hydrated silica phase interpreted to be opal 7 wt h2o dark blue cl very similar signatures are observed in a grospydite xenolith from the roberts victor kimberlite the quartz replacing coesite in other uhp samples studied contains on the order of 500 ppm h2o or less and most measurements are under the detection limit of our technique we infer that palisade quartz forms under dry or nearly dry conditions and at high temperatures during dilation of the host phase the formation of hydrous silica phases such as chalcedony and opal however must take place at much lower temperatures after cracking of the host phase which allows external fluids to infiltrate delay of fluid infiltration to low temperatures where kinetics are slow even in the presence of water is the most critical factor in the preservation of coesite

constraints on timing of peak and retrograde metamorphism in the dabie shan ultrahigh pressure metamorphic belt east central china using u th pb dating of zircon and monazite abstract the dabie shan ultrahigh pressure metamorphic uhpm belt occupies the suture between the yangtze and sino korean blocks in east central china the timing of uhpm in the dabie belt is controversial and most recent data come from dating of zircons monazite has recently been recognized as useful for dating of multiple tectonic events due to its preservation of multiple growth zones and monazite growth has been documented to occur during prograde peak and retrograde metamorphism zircons and monazites from uhp mafic rocks from maowu and a uhp jadeite quartzite from shuanghe were imaged in thin sections and in mineral separates and dated using a high resolution ion microprobe maowu mafic rocks are unique in that they contain high light rare earth element concentrations and therefore contain abundant monazite maowu eclogites and garnet pyroxenites contain zircons with mean 206 pb 238 u age of 230 4 ma and monazites from a clinopyroxenite have 208 pb 232 th ages of 209 4 ma multiple lines of evidence suggest that the measured ages represent the timing of new growth and recrystallization and are not cooling ages i e they do not correspond to the cessation of diffusional pb loss as rocks cooled below the closure temperature during exhumation shuanghe jadeite quartzites contain zircons with cores that define a discordia with an upper intercept age 1921 22 ma and lower intercept age of 236 32 ma interpreted to represent the ages of the source rocks and of peak metamorphism respectively zircon rims contain jadeite inclusions that restrict growth to pressures greater than 1 5 gpa their pooled age of 238 3 ma agrees well with the lower intercept defined by cores suggesting that pb loss from cores and growth of new rims occurred during uhpm at 235 240 ma monazite records multiple events during retrograde metamorphism maowu clinopyroxenite and shuanghe jadeite quartzite experienced monazite growth at 209 ma interpreted to reflect regional amphibolite facies overprinting resulting from pervasive retrograde fluid infiltration only the jadeite quartzite records growth at 223 1 ma estimated exhumation rates for maowu are 7 8 km ma

silica precipitates in omphacite from eclogite at alpe arami switzerland evidence of deep subduction observations of oriented sio2 precipitates in omphacite from eclogite with tholeiitic basalt protolith bordering the alpe arami garnet peridotite massif ticino switzerland and petrological studies of the eclogitic mineral assemblages suggest that this rock was subjected to higher pressure metamorphism than previously realized we employed various calibrations of the fe2 mg exchange thermometer and calculations of equilibria with thermodynamic data considering the calcium tschermak s component caal2sio6 of garnet pyroxene pairs from these calculations it is concluded that the eclogitic lenses have recorded at least four stages of mineral growth corresponding to the following stage i prograde c 2 4 gpa 700 c stage iia maximum recorded grade c 7 0 gpa 1100 c stage iib retrograde c 3 7 gpa 900 c stage iii retrograde c 2 1 gpa 750 c because of the preservation of stage i a relatively rapid subduction and exhumation of alpe arami eclogite is suggested the exhumation path of the eclogitic rock is in good agreement with most exhumation paths inferred for the alpe arami garnet lherzolite proposed previously by several authors based upon a variety of different observations although the eclogite and peridotite exhumation paths may diverge at depths greater than 120 km

multiple zircon growth during fast exhumation of diamondiferous deeply subducted continental crust kokchetav massif kazakhstan diamondiferous rocks from the kokchetav massif kazakhstan represent deeply subducted continental crust in order to constrain the age of ultra high pressure uhp metamorphism and subsequent retrogression during exhumation zircons from diamondiferous gneisses and metacarbonates have been investigated by a combined petrological and isotopic study four different zircon domains were distinguished on the basis of transmitted light microscopy cathodoluminescence trace element contents and mineral inclusions mineral inclusions and trace element characteristics of the zircon domains permit us to relate zircon growth to metamorphic conditions domain 1 consists of rounded cores and lacks evidence of uhp metamorphism domain 2 contains diamond coesite omphacite and titanian phengite inclusions providing evidence that it formed at uhp metamorphic conditions p 43 kbar t 950 c domain 3 is characterised by low pressure mineral inclusions such as garnet biotite and plagioclase which are common minerals in the granulite facies overprint of the gneisses p 10 kbar t 800 c this multi stage zircon growth during cooling and exhumation of the diamondiferous rocks can be best explained by zircon growth from zr saturated partial melts present in the gneisses domain 4 forms idiomorphic overgrowths and the rare earth element pattern indicates that it formed without coexisting garnet most probably at amphibolite facies conditions p 5 kbar t 600 c the metamorphic zircon domains were dated by shrimp ion microprobe and yielded ages of 527 5 528 8 and 526 5 ma for domains 2 3 and 4 respectively these indistinguishable ages provide evidence for a fast exhumation beyond the resolution of shrimp dating the mean age of all zircons formed between uhp metamorphic conditions and granulite facies metamorphism is 528 3 ma indicating that decompression took place in less than 6 ma hence the deeply subducted continental crust was exhumed from mantle depth to the base of the crust at rates higher than 1 8 cm year we propose a two stage exhumation model to explain the obtained p t t path fast exhumation on top of the subducted slab from depth 140 to 35 km was driven by buoyancy and facilitated by the presence of partial melts a period of near isobaric cooling was followed by a second decompression event probably related to extension in a late stage of continental collision

large areal extent of ultrahigh pressure metamorphism in the sulu ultrahigh pressure terrane of east china new implications from coesite and omphacite inclusions in zircon of granitic gneiss abstract coesite and omphacite inclusions have been identified for the first time as minute inclusions in zircon from amphibolite facies granitic orthogneiss in the sulu ultrahigh pressure uhp metamorphic terrane of eastern china by raman spectroscopy and microprobe analyses the occurrences of these minerals in the voluminous granitic gneiss of sulu support a regional and pervasive uhp metamorphic event that predated regional amphibolitic retrogression taking into account the widespread discoveries of coesite in other lithologies we thus conclude that a substantial crustal component in the sulu uhp metamorphic terrane appears to have shared a common history of triassic subduction to mantle depths and later exhumation

coesite in clinopyroxene in the caledonides and its implications for geodynamics coesite is reported for the first time from the caledonide orogen it occurs as inclusions in clinopyroxene in the dolomite eclogite at grytting norway and provides valuable new evidence to support the hypothesis of extremely high pressure 30 kbar in certain norwegian eclogites this finding has implications for the geodynamics and kinetics of the concepts of microscale intracrystalline tectonic overpressure and of macroscale local or regional tectonic overpressure and for the hypotheses of subduction and obduction involving a more than 100km vertical component of transport

sm nd and rb sr isotopic chronology and cooling history of ultrahigh pressure metamorphic rocks and their country rocks at shuanghe in the dabie mountains central china abstract ultrahigh pressure metamorphic uhpm rocks at shuanghe area in the dabie mountains occur as a uhpm block within the regional granitic gneiss a sm nd isochron defined by garnet omphacite rutile from coesite bearing eclogite yield an age of 226 3 3 2 ma another sm nd isochron defined by garnet two phengites form uhp gneiss yield a similar age of 226 5 2 3 ma the two consistent sm nd ages defined by three uhpm minerals suggest that nd isotopic equilibrium between uhpm minerals in these rocks during uhp metamorphism has been achieved this may correspond to the age of peak metamorphism with an average metamorphic temperature of 800 c it is demonstrated that the retrograde metamorphism of uhpm rocks occurred in an open chemical system whereas the nd and sr isotopic systematics of uhpm minerals may have remained closed nd and sr isotopic disequilibrium between uhpm minerals and retrograde metamorphic minerals has been observed therefore the tie line of garnet or phengite and whole rock containing retrograde metamorphic minerals gives an old sm nd age and a young rb sr age respectively with no geologic significance however a rb sr ages of 219 0 6 6 ma defined by phengite garnet from a uhpm gneiss indicates that the uhpm rocks at shuanghe cooled down to 500 c at that time it suggests that the uhpm rocks at shuanghe experienced the first rapid cooling during 226 219 ma on the other hand the rb sr ages of 174 7 8 to 169 2 3 3 ma defined by retrograde minerals amphibole or biotite with closure temperature ranging from 450 to 300 c and intensely retrograded metamorphic rocks reflect a second rapid cooling during this time interval this is consistent with the rapid cooling time of 190 170 ma of the orthogneiss in the dabie su lu uhpm belt obtained by ar ar dating method in contrast to uhpm rocks the nd isotopic composition of the garnet in granitic gneiss has been reset during retrograde metamorphism and is in equilibrium with those of retrograde epidote and biotite which yields a sm nd isochron age of 213 5 ma indicating the retrometamorphic time corresponding to amphibolite facies in addition the biotites from the granitic gneiss yield rb sr ages of 171 173 ma similar to those of the uhpm rocks these data suggest that the country rocks granitic gneiss may have a similar cooling history to the uhpm rocks at shuanghe two stages of rapid cooling of uhpm rocks at shuanghe may correspond two stages of fast uplift the initial rapid uplifting and cooling of uhpm rocks during 226 219 ma may be caused by compression tectonics during subducting time of the continental crust whereas the later rapid cooling may reflect the exhumation of the entire subducted continental crust by extension during the early middle jurassic

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

ultrahigh pressure metamorphism and multistage exhumation of eclogite of the luotian dome north dabie complex zone central china evidence from mineral inclusions and decompression textures abstract the studied eclogite is located in the luotian dome in the southwestern part of the north dabie complex zone ndz central china and is a portion of deeply subducted mafic lower continental crust of the south china block petrologic analysis suggests that the eclogite underwent ultrahigh pressure uhp and high pressure eclogite facies metamorphism and subsequent hp granulite facies overprinting and amphibolite facies retrogression during continental subduction and exhumation as a result multiple decompression textures were produced suggesting a multistage exhumation history from eclogite to granulite to amphibolite facies conditions a striking feature of this eclogite is the widespread exsolution of different phases oriented needles of rutile clinopyroxene amphibole apatite in garnet quartz amphibole hypersthene sodic plagioclase in clinopyroxene and pyrrhotite in apatite most importantly we provide for the first time conclusive evidence of quartz pseudomorphs after coesite in garnet and relic coesite confirmed by in situ raman spectroscopy in zircon in addition there are two groups of apatite one is fluor f apatite that occurs as inclusions in garnet or in matrix which is rich in f 3 wt lakes exsolution features and formed at uhp metamorphic conditions the second is associated with the oriented pyrrhotite exsolution and formed during decompression microtextural and petrologic analysis suggests that the eclogites from the southwestern segment of the ndz are similar to eclogites from the northern segment of the ndz e g huangweihe and baizhangyan and underwent uhp metamorphism with a peak pressure 5 7 gpa these results combined with published geochronological data imply that the ndz experienced triassic uhp metamorphism as a coherent unit

tectonics of an ultrahigh pressure metamorphic terrane the dabie shan tongbai shan orogen china ultrahigh pressure metamorphic rocks with coesite and diamond form a tectonic slice over 20 km thick called the eclogite zone within the dabie shan complex in the qinling orogen in central china the orogen separates the sino korean block in the north from the yangtze block in the south the dabie shan complex is a composite terrane made up of eclogite facies and amphibolite facies gneiss slices and represents fragments of the lower continental crust of the yangtze block the dabie shan complex is bounded in the south by a triassic foreland fold thrust belt and in the north by a greenschist facies metaclastic unit the foziling group which probably represents the passive continental apron deposits of the yangtze block farther north is a granulite facies gneiss complex the qinling group which has ultramafic slivers and includes the remnants of an island arc with two bounding suture zones north of the qinling group are early paleozoic active margin deposits of the sino korean block the eclogite zone in the dabie shan complex is sandwiched between amphibolite facies gneiss slices dating by sm nd rb sr and ar ar of two eclogite samples from the eclogite zone gives early to middle triassic ages 236 246 ma the initial end values indicate reworking of a 2 11 and 1 55 ga continental crust a himalayan type tectonic evolution is envisaged for the qinling orogen with the creation of a 100 km thick crustal thrust wedge through continuous underplating during the subduction of the yangtze continental lithosphere exhumation of the ultrahigh pressure metamorphic rocks was chiefly achieved by the southward propagation of the thrust planes thereby isostatically uplifting and eroding the earlier deeply subducted parts of the orogen a total of 680 km of southward thrusting in front of dabie shan is inferred based on the abrupt termination of the tanlu fault normal faulting possibly caused by gravitational collapse probably also had a role in the exhumation process

geochemical and sr nd pb isotopic compositions of cretaceous granitoids constraints on tectonic framework and crustal structure of the dabieshan ultrahigh pressure metamorphic belt china abstract the dabie orogenic belt can be divided into four tectonic and lithological units they are from north to south the north huaiyang nhy unit the northern dabie complex ndc unit the ultrahigh pressure uhp metamorphic unit and high pressure hp metamorphic unit cretaceous granitoids from the four tectonic units irrespective of tectonic unit and lithology show surprisingly similar major and trace element and particularly sr nd pb isotopic compositions indicating a similar crustal source for their magma genesis they have initial 87 sr 86 sr t values of 0 7068 0 7091 and nd depleted mantle model ages of 1 6 2 4 ga and e nd t values at the time of their emplacement 120 ma ranging from 13 to 26 their present day pb isotopic compositions are 206 pb 204 pb 15 62 17 06 207 pb 204 pb 15 21 15 44 and 208 pb 204 pb 36 59 37 81 with comparison to the sr nd pb isotopic compositions of the basement rocks in the dabie orogenic belt the isotopic compositions of the cretaceous granitoids indicate a source that is similar to the northern dabie complex but distinct from the ultrahigh pressure metamorphic unit this strongly suggests that the exposed northern dabie complex extends in the deep crust southward beneath the uhp hp metamorphic units and northward beneath the north huaiyang unit the northern dabie complex is best interpreted as the core of a dome within the dabie orogenic belt the uhp hp metamorphic unit is only a thin skinned slab confined in shallower crustal levels over the northern dabie complex present tectonic framework for the uhp hp terrain was formed by extensional tectonics and post the uhp hp metamorphism the northern dabie complex has an affinity to the yangtze craton the similar source for the cretaceous granitoids also suggests that the suture between the north china and the yangtze cratons is marked by the xiaotian mozitang fault separating the north huaiyang unit and the northern dabie complex rather than the previously thought wuhe shuiko fault which separates the northern dabie complex and the uhp unit

numerical simulations of larval transport into a rip channeled surf zone competent larvae of intertidal invertebrates have to migrate toward shore for settlement however their migration through the surf zone is not understood we investigated larval transport mechanisms at a ripchanneled beach because tracking larvae in the surf zone is infeasible we used a three dimensional biophysical model to simulate the processes the coupled model consists of a physical module for currents and waves and a biological module for adding larval traits and behaviors as well as stokes drift to lagrangian particles model calculations were performed with and without onshore wind forcing without wind wave driven onshore streaming occurs in the bottom boundary layer outside the surf zone with onshore wind onshore currents occur near the surface in the surf zone offshore directed rip currents and compensating onshore directed currents over shoals are formed in both no wind and wind cases in the biological module neutral negative and positive buoyant particles were released offshore additionally particles either sank in the presence of turbulence or not two scenarios achieved successful onshore migration negatively buoyant larvae without wind forcing sink in the turbulent bottom boundary layer and are carried onshore by streaming positively buoyant larvae drift toward shore in wind driven surface currents to the surf zone then sink in the turbulent surf zone and remain near the bottom while transported shoreward in both cases the larval concentration is highest in the rip channel consistent with field data this successful result is only obtained if turbulence dependent sinking behavior and stokes drift are included in the transport of larvae

kinetics of the coesite to quartz transformation abstract the survival of coesite in ultrahigh pressure uhp rocks has important implications for the exhumation of subducted crustal rocks we have conducted experiments to study the mechanism and rate of the coesite quartz transformation using polycrystalline coesite aggregates fabricated by devitrifying silica glass cylinders containing 2850 h 10 6 si at 1000 c and 3 6 gpa for 24 h conditions were adjusted following synthesis to transform the samples at 700 1000 c at pressures 190 410 mpa below the quartz coesite equilibrium boundary reaction proceeds via grain boundary nucleation and interface controlled growth with characteristic reaction textures remarkably similar to those seen in natural uhp rocks we infer that the experimental reaction mechanism is identical to that in nature a prerequisite for reliable extrapolation of the rate data growth rates obtained by direct measurement differ by up to two orders of magnitude from those estimated by fitting a rate equation to the transformation time data fitting the rates to turnbull s equation for growth therefore yields two distinct sets of parameters with similar activation energies 242 or 269 kj mol but significantly different pre exponential constants extrapolation based on either set of growth rates suggests that coesite should not be preserved on geologic time scales if it reaches the quartz stability field at temperatures above 375 400 c the survival of coesite has previously been linked to its inclusion in strong phases such as garnet that can sustain a high internal pressure during decompression other factors that may play a crucial role in preservation are low fluid availability possibly even less than that of our nominally dry experiments and the development of transformation stress which inhibits nucleation and growth these issues are discussed in the context of our experiments as well as recent observations from natural rocks

seascape level variation in turbulence and wave generated hydrodynamic signals experienced by plankton abstract plankton exhibit diverse and dramatic responses to fluid motions and these behaviors are likely critical for survival and fitness fluid motions can be generated by organisms or by physical processes including turbulence and surface gravity waves physical processes vary geographically in their intensity and generate hydrodynamic signals experienced by plankton as fluid forces on their sensory receptors in this synthesis we review how turbulence and waves vary in space the scales and statistics of their motions and the forces exerted on plankton we then quantify the hydrodynamic signals produced by turbulence and waves in four seascape types surf zones inlets and estuaries the continental shelf and the open ocean using published dissipation rates wind and wave data from buoys and observations from two coastal sites in massachusetts usa we relate these geographic patterns in signals to the observed behaviors of example species and to the forces sensed by typical plankters with different receptor types turbulence generated shears are largest in the surf zone inlets and estuaries while wave generated accelerations are larger offshore as a result each seascape exhibits some range of combined shears and accelerations that is distinct these signals generate forces on plankton that vary among habitats and with plankton size and swimming speed spatial patterns in fluid forces create a potential mechanism for dispersing larvae to distinguish habitats by their hydrodynamic signatures however turbulence can be strong in all seascapes and may cause widespread interference in signaling among predators and prey plankton with a single receptor type could identify nearshore habitats while those with multiple receptor types potentially could distinguish inshore vs offshore seascapes or decode signals produced by physical processes and by other organisms

u pb zircon ages constrain the architecture of the ultrahigh pressure qinling dabie orogen china new shrimp and tims zircon ages 40ar 39ar ages and eclogite locations contribute significantly to our understanding of the ultrahigh pressure dabie shan 1 the geographic extent of the yangtze craton that was subducted to ultrahigh pressure extends to the northern edge of the dabie shan 2 the northern half of the dabie shan is a magmatic complex intruded over a 10 myr interval between 137 and 126 ma that accommodated 100 n s stretching of the pre existing collisional architecture 3 granitic orthogneisses and enclosing ultrahigh pressure paragneisses have indistinguishable zircon populations the population of triassic zircon ages ranges from 219 to 245 ma leading us to question the prevailing assumption that 219 ma zircons formed at ultrahigh pressure and to propose instead that they reflect late retrogression at crustal pressures following the bulk of exhumation

a coherent lithostratigraphic unit in the coesite eclogite complex of dabie shan china geologic and petrologic evidence abstract as a contribution to the discussion about the in situ vs exotic origin of the ultrahigh pressure metamorphic uhpm rocks and to the real size of the exhumed tectonic units the wuhe pailou unit wpu in eastern dabie shan was studied the wpu typically consists of two micas epidote gneiss marble with minor eclogite and jadeite bearing granofels with rare garnetite and eclogite nodules these lithologies are enclosed within leucocratic granitic gneiss jadeite bearing granofels is the most peculiar lithology of the wpu being the only felsic rock in dabie shan still preserving extensive relics of the uhpm mineral assemblage the uhp peak assemblage is coesite jadeite garnet epidote phengite kyanite with accessory rutile apatite and zircon all eclogites consist of garnet omphacite quartz coesite rutile or high al titanite phengite clinozoisite kyanite two micas epidote gneiss associated with the jadeite bearing granofels typically consists of epidote muscovite biotite plagioclase k feldspar rare garnet and accessory rutile titanite apatite and zircon locally the wpu paragneiss contains garnet with inclusions of phengite kyanite rutile and amphibole na plagioclase symplectite after omphacite a clockwise p t path was inferred for the wpu which consists of an early prograde part up to coesite eclogite facies conditions p 3 3 gpa and t 720 c an early decompression stage and a late part characterised by a near adiabatic decompression down to medium pressure p 1 1 gpa t 670 c and to low pressure amphibolite facies conditions followed by a final cooling to greenschist facies conditions both field and laboratory data consistently suggest that the wpu characterised by the close association of paragneiss marble eclogite and granofels is a supracrustal metasedimentary sequence which underwent subduction uhpm and exhumation as a coherent tectonic unit therefore within collisional orogens large coherent slices of continental crust may be subducted at depths greater than 100 km

35 ma old ultrahigh pressure metamorphism and evidence for very rapid exhumation in the dora maira massif western alps abstract ion microprobe shrimp data on zircons from various rock types of an ultrahigh pressure uhp metamorphic whiteschist type pyrope quartzite lens of the dora maira massif dmm consistently show domains giving a late eocene age of 35 4 1 0 ma which is taken as the age of uhp metamorphism these domains partially replace the older oscillatory zoning pattern of the zircons formed during primary magmatic crystallization at about 275 ma zircons of a metagranitic country rock next to the uhp metamorphic lens have these primary features best preserved all zircons measured also yield intermediate ages between 275 and 35 ma with a statistical concentration between 260 and 210 ma thus the uniformity of the initial zircon population both in the lens and the country rock evidences a common protolith that is a granite intruded during the late herynian while the intermediate ages are at least partly due to incomplete resetting of the zircons during uhp metamorphism those in the 260 210 ma range may be related to rifting episodes in the permotriassic the mg rich chemistry of the whiteschist lenses is due to local metasomatic alterations of the granite perhaps by fluids derived from evaporitic sediments dating as early as the permotriassic as well the more pervasive resetting of zircon ages during uhp metamorphism in the pyrope quartzite lenses is explained by the ubiquity of fluids and or melts produced during subduction by a series of dehydration reactions that occurred only in the more hydrous mg rich protoliths and not in their drier granitic neighborhood fission track ages determined partly on the same zircon samples yielding 29 9 1 4 ma mark the time when the uhpm unit had reached about 290 c at a shallow location within the crust thus exhumation over a vertical distance of about 120 km must have occurred within about 5 6 ma indicating an average uplift rate of about 20 24 km ma and an average cooling rate of about 85 100 c ma the radiometric data obtained do not lend any support to an eo alpine cretaceous subduction event so that deep subduction and immediately following exhumation all took place during early to mid tertiary time this scenario seems to apply to large portions of the western and central alps as well calling for drastic geodynamic reinterpretations of these parts of the alps

wave induced transport and vertical mixing of pelagic eggs and larvae the transport of pelagic plankton by wind driven ocean currents and surface gravity waves is investigated for the example of northeast arctic cod eggs and larvae on the coast of northern norway previous studies indicate that the wave induced drift i e stokes drift is relevant for the transport of particles in the upper ocean we use an ocean general circulation model together with a numerical wave prediction model and a lagrangian particle tracking model to calculate trajectories of fish eggs and larvae waves are considered not only for particle drift but also for the air sea momentum flux its contribution to the coriolis force and vertical mixing the sample species provides the advantage that many of its physical and behavioral properties are well known e g egg buoyancy allowing investigation of vertical particle displacement by turbulent mixing in response to wind forcing and wave breaking the approach accounting for particle mixing by breaking waves enhances agreement between observed and modeled egg profiles results also show a general shoreward transport of particles by the stokes drift this wave drift exhibits a more constant direction than the eulerian current and hence stabilizes particle diffusion to favor a dominant direction for the case of northeast arctic cod waves concentrated model eggs and larvae on average 1 5 km closer to shore which is 20 of their total distance to the coast this increases the residence time of first feeding larvae close to the spawning areas compared to earlier models

apatite monazite and xenotime in metamorphic rocks this chapter focuses on phosphates that are significant in metamorphic rocks a quick survey of phosphate mineral descriptions at a commercial mineral web site revealed over 500 phosphate mineral names remarkably only three are common in metamorphic rocks apatite monazite and xenotime and this chapter is restricted to discussion of these minerals apatite monazite and to a lesser extent xenotime have enjoyed intensive study during the previous half century following world war ii considerable study was made of minerals that contain fissionable materials and the sometimes large concentrations of u and th in monazite culminated in a number of seminal papers on the occurrence of that mineral e g overstreet 1967 during the 1970s and early 1980s the study of apatite and monazite turned towards their role as a sink for rees and other trace elements in rocks e g watson 1980 watson and capobianco 1981 throughout this period monazite and to some extent xenotime enjoyed attention as a geochronometer e g parrish 1990 and through today this attention has continued to grow accessory minerals such as monazite xenotime and apatite have come to the forefront of research in metamorphic petrology in recent years for two reasons first it has recently been recognized that trace elements in metamorphic rocks and especially trace element zoning in garnet and other major phases contain considerable detailed information about the reaction history a rock has experienced coupled with the fact that diffusion of many trace elements in metamorphic minerals is in general considerably slower than diffusion of major elements in those same minerals the possibility has recently emerged of recovering details of metamorphic petrogenesis that were previously unattainable inasmuch as accessory minerals play a dominant role in the mass budget of many trace elements attention has naturally turned to their paragenesis it has also recently been discovered that

waves cue distinct behaviors and differentiate transport of congeneric snail larvae from sheltered versus wavy habitats marine population dynamics often depend on dispersal of larvae with infinitesimal odds of survival creating selective pressure for larval behaviors that enhance transport to suitable habitats one intriguing possibility is that larvae navigate using physical signals dominating their natal environments we tested whether flow induced larval behaviors vary with adults physical environments using congeneric snail larvae from the wavy continental shelf tritia trivittata and from turbulent inlets tritia obsoleta turbulence and flow rotation vorticity induced both species to swim more energetically and descend more frequently accelerations the strongest signal from waves induced a dramatic response in t trivittata but almost no response in competent t obsoleta early stage t obsoleta did react to accelerations ruling out differences in sensory capacities larvae likely distinguished turbulent vortices from wave oscillations using statocysts statocysts ability to sense acceleration would also enable detection of low frequency sound from wind and waves t trivittata potentially hear and react to waves that provide a clear signal over the continental shelf whereas t obsoleta effectively go deaf to wave motions that are weak in inlets their contrasting responses to waves would cause these larvae to move in opposite directions in the water columns of their respective adult habitats simulations showed that the congeners transport patterns would diverge over the shelf potentially reinforcing the separate biogeographic ranges of these otherwise similar species responses to turbulence could enhance settlement but are unlikely to aid large scale navigation whereas shelf species responses to waves may aid retention over the shelf via stokes drift

present day ultrahigh pressure conditions of coesite inclusions in zircon and garnet evidence from laser raman microspectroscopy coesite the dense high pressure polymorph of quartz occurs as inclusions in mechanically strong minerals in deeply subducted metamorphosed crustal rocks in a number of eurasian collisional orogens it is the primary indicator mineral of ultrahigh pressure p metamorphism whereas some coesite inclusions are untransformed most exhibit partial transformation to palisade quartz and a concomitant increase in volume resulting in rupture and radial fracturing of the host grain coesite can be identified by its diagnostic raman spectrum the strongest band at atmospheric pressure room temperature is at 521 cm 1 laser raman microspectroscopic analyses of coesite inclusions within garnet and zircon in ultrahigh p metamorphic rocks from kazakhstan indonesia and china reveal consistent differences in the raman spectra of 1 partially transformed coesite quartz main raman band at 521 cm 1 and 2 untransformed monomineralic coesite grains main band at 525 526 cm 1 applying the room temperature calibration of pressure dependence of the coesite raman spectrum we conclude that the latter coesite inclusions are subject to a remarkable pressure differential of 19 23 kbar with the host grains and are still undergoing pressure temperature conditions on or close to the quartz coesite equilibrium boundary

petrology of ultrahigh pressure rocks from the southern su lu region eastern china abstract in the su lu ultrahigh p terrane eastern china many coesite bearing eclogite pods and layers within biotite gneiss occur together with interlayered metasediments now represented by garnet quartz jadeite rock and kyanite quartzite in addition to garnet omphacite rutile coesite other peak stage minerals in some eclogites include kyanite phengite epidote zoisite talc nyboite and high al titanite the garnet quartz jadeite rock and kyanite quartzite contain jadeite quartz garnet rutile zoisite apatite and quartz kyanite garnet epidote phengite rutile omphacite assemblages respectively coesite and quartz pseudomorphs after coesite occur as inclusions in garnet omphacite jadeite kyanite and epidote from both eclogites and metasediments study of major elements indicates that the protolith of the garnet quartz jadeite rock and the kyanite quartzite was supracrustal sediments most eclogites have basaltic composition some have experienced variable crustal contamination or metasomatism and others may have had a basaltic tuff or pyroclastic rock protolith the su lu ultrahigh p rocks have been subjected to multi stage recrystallization and exhibit a clockwise p t path inclusion assemblages within garnet record a pre eclogite epidote amphibolite facies metamorphic event ultrahigh p peak metamorphism took place at 700 890 c and p 28 kbar at c 210 230 ma the symplectitic assemblage plagioclase hornblende epidote biotite titanite implies amphibolite facies retrogressive metamorphism during exhumation at c 180 200 ma metasedimentary and metamafic lithologies have similar p t paths several lines of evidence indicate that the supracrustal rocks were subducted to mantle depths and experienced in situ ultrahigh p metamorphism during the triassic collision between the sino korean and yangtze cratons