response of southern ocean ventilation to changes in midlatitude westerly winds abstractchanges in ventilation of the southern hemisphere oceans in response to changes in midlatitude westerly winds are examined by analyzing the ideal age tracer from global eddy permitting ocea

p t t paths of collisional orogens pressure temperature time p t t paths summarize the changes in pressure and temperature imposed on a metamorphic rock during orogenesis they provide a convenient framework for the interpretation of complex metamorphic histories and also offer insight into the thermal and tectonic factors controlling metamorphism in collisional orogens p t t data are acquired through a combination of textural observations thermobarometry and thermochronometry and assembled into a p t t path using geological constraints one dimensional p t t models assuming instantaneous deformation and thermal relaxation by conduction are flexible and useful for testing tectonic models particularly where geochronological constraints are available two dimensional models allow more sophisticated deformation geometries and allow the effects of advection to be incorporated analysis of collisional orogens in terms of critical wedge theory can yield p t t paths that reflect coupling between thickening uplift exhumation erosion and convergence where rates of erosion approach rates of tectonic uplift as is currently happening in the southern alps of new zealand high grade metamorphic rocks can be exhumed rapidly from considerable depth alternatively rapid exhumation may reflect gravity driven extension in an over steepened or thermally weakened orogen

southern ocean isopycnal mixing and ventilation changes driven by winds observed and predicted changes in the strength of the westerly winds blowing over the southern ocean have motivated a number of studies on the response of the antarctic circumpolar current and southern ocean meridional overturning circulation moc to wind perturbations and led to the hypothesis of the eddy compensation regime wherein the moc becomes insensitive to wind changes in addition to the moc tracer transport also depends on mixing processes here we show in a high resolution process model that isopycnal mixing by mesoscale eddies is strongly dependent on the wind strength this dependence can be explained by mixing length theory and is driven by increases in eddy kinetic energy the mixing length does not change strongly in our simulation simulation of a passive ventilation tracer analogous to cfcs or anthropogenic co2 demonstrates that variations in tracer uptake across experiments are dominated by changes in isopycnal mixing rather than changes in the moc we argue that to properly understand tracer uptake under different wind forcing scenarios the sensitivity of isopycnal mixing to winds must be accounted for

low frequency whale and seismic airgun sounds recorded in the mid atlantic ocean beginning in february 1999 an array of six autonomous hydrophones was moored near the mid atlantic ridge 35 n 15 n 50 w 33 w two years of data were reviewed for whale vocalizations by visually examining spectrograms four distinct sounds were detected that are believed to be of biological origin 1 a two part low frequency moan at roughly 18 hz lasting 25 s which has previously been attributed to blue whales balaenoptera musculus 2 series of short pulses approximately 18 s apart centered at 22 hz which are likely produced by fin whales b physalus 3 series of short pulsive sounds at 30 hz and above and approximately 1 s apart that resemble sounds attributed to minke whales b acutorostrata and 4 downswept pulsive sounds above 30 hz that are likely from baleen whales vocalizations were detected most often in the winter and blue and fin whale sounds were detected most often on the northern hydrophones sounds from seismic airguns were recorded frequently particularly during

synchronous peak barrovian metamorphism driven by syn orogenic magmatism and fluid flow in southern connecticut usa recent work in barrovian metamorphic terranes has found that rocks experience peak metamorphic temperatures across several grades at similar times this result is inconsistent with most geodynamic models of crustal over thickening and conductive heating wherein rocks which reach different metamorphic grades generally reach peak temperatures at different times instead the presence of additional sources of heat and or focusing mechanisms for heat transport such as magmatic intrusions and or advection by metamorphic fluids may have contributed to the contemporaneous development of several different metamorphic zones here we test the hypothesis of temporally focussed heating for the wepawaug schist a barrovian terrane in connecticut usa using sm nd ages of prograde garnet growth and u pb zircon crystallization ages of associated igneous rocks peak temperature in the biotite garnet zone was dated via sm nd on garnet at 378 9 1 6 ma 2r whereas peak temperature in the highest grade staurolite kyanite zone was dated via sm nd on garnet rims at 379 9 6 8 ma 2r these garnet ages suggest that peak metamorphism was pene contemporaneous within error across these metamorphic grades ion microprobe u pb ages for zircon from igneous rocks hosted by the metapelites also indicate a period of syn metamorphic peak igneous activity at 380 6 4 7 ma 2r indistinguishable from the peak ages recorded by garnet a 388 6 2 1 ma 2r garnet core age from the staurolite kyanite zone indicates an earlier episode of growth coincident with ages from texturally early zircon and a previously published monazite age along the prograde regional metamorphic t t path the timing of peak metamorphism and igneous activity as well as the occurrence of extensive syn metamorphic quartz vein systems and pegmatites best supports the hypothesis that advective heating driven by magmas and fluids focussed major mineral growth into two distinct episodes the first at c 389 ma and the second corresponding to the regionally synchronous peak metamorphism at c 380 ma

where and how long ago was water in the western north atlantic ventilated maximum entropy inversions of bottle data from woce line a20 1 a maximum entropy me method is used to deconvolve tracer data for the joint distribution of locations and times since last ventilation the deconvolutions utilize world ocean circulation experiment line a20 repeat hydrography for cfc 11 potential temperature salinity oxygen and phosphate as well as global ocean data analysis project glodap radiocarbon data combined with surface boundary conditions derived from the atmospheric history of cfc 11 and the world ocean atlas 2005 and glodap databases because of the limited number of available tracers the deconvolutions are highly underdetermined leading to large entropic uncertainties which are quantified using the information entropy of relative to a prior distribution additional uncertainties resulting from data sparsity are estimated using a monte carlo approach and found to be of secondary importance the me deconvolutions objectively identify key water mass formation regions and quantify the local fraction of water of age or older last ventilated in each region ideal mean age and radiocarbon age are also estimated but found to have large entropic uncertainties that can be attributed to uncertainties in the partitioning of a given water parcel according to where it was last ventilated labrador irminger seawater l water is determined to be mostly less than 40 a old in the vicinity of the deep western boundary current dwbc at the northern end of a20 but several decades older where the dwbc recrosses the section further south pointing to the importance of mixing via a multitude of eddy diffusive paths overflow water lies primarily below l water with young waters 40 a at middepth in the northern part of a20 and waters as old as 600 a below 3500 m

estimating changes in ocean ventilation from early 1990s cfc 12 and late 2000s sf6 measurements transient tracer measurements can constrain the rates and pathways of ocean ventilation and act as proxies for biogeochemically relevant gases such as co2 and oxygen various techniques have deduced changes in ocean ventilation over decadal timescales using transient tracer measurements made on repeat sections but these require a priori assumptions about mixing in the ocean interior here we introduce a simple direct observational method that takes advantage of the similar atmospheric increase rates of chlorofluorocarbon 12 and sulfur hexafluoride but with a time lag offset of 1415 years such repeat measurements can be directly compared without prior assumptions about mixing a difference larger than similar to 2 years between modern sulfur hexafluoride and historical chlorofluorocarbon 12 tracer ages implies a change in ventilation although lack of difference does not necessarily imply no change several tracer data sets are presented which suggest changes in ventilation in the south pacific and north atlantic oceans

paleoatmospheric consequences of co2 released during early cenozoic regional metamorphism in the tethyan orogen the eocene was the warmest epoch of the cenozoic with published estimates of eocene atmospheric co2 content ranging from two to six times the current value calculations of co2 consumption by silicate weathering show that co2 fluxes to the atmosphere of ca 1018 myr could account for inferred paleocene eocene atmospheric co2 contents and the resulting greenhouse effect would have contributed to eocene warmth extensive portions of the tethyan orogen underwent regional metamorphism culminating in the eocene prograde metamorphism may have been contemporaneous with the late paleocene global warming we calculated the amount of metamorphic co2 produced at depth in the himalayan orogen with data on the timing of the india asia collison duration of prograde regional metamorphism and proportions and bulk compositions of metamorphic co2 source rocks if co2 was generated at a constant rate over a 10 myr period of prograde metamorphism in the himalayan orogen we estimate that ca 1018 1019 moles myr of metamorphic co2 were produced at depth significant expulsion of metamorphic co2 to the atmosphere may have occurred by focused fluid flow along shear zones such as the extensive main central thrust in the himalayan orogen an additional ca 1018 myr could have been contributed by eocene regional metamorphism in the mediterranean tethys i e from the alps to turkey the extensive metamorphism associated with the india asia collision and the closing of tethys may have contributed to co2 greenhouse warming in the early to mid cenozoic

sounds source levels and associated behavior of humpback whales southeast alaska humpback whales in southeast alaskan waters produced five categories of sounds moans grunts pulse trains blowhole associated sounds and surface impacts frequencies hz of moans and grunts were 20 1900 major energy in low frequency pulse trains was in a band of 25 80 hz with pulse duration of 300 400 ms blowhole associated sounds recorded as transiting whales encountered one another were of two types shrieks 555 2000 hz and trumpetlike horn blasts with fundamental at 414 hz median pulses and spread spectrum noise were associated with gas bubble formation and explosive bursts respectively in connection with spiral feeding maneuvers surface impacts resulted from fluke or flipper slaps in sequences of 3 21 sounds source levels ranged from 162 low frequency pulse trains to 192 db surface impacts re 1 pa 1 m songs commonly heard on winter breeding grounds were absent from our recordings feeding and perhaps certain other whale activities can be monitored based on sound production

antarctic bottom water warming and freshening contributions to sea level rise ocean freshwater budgets and global heat gain abstractfreshening and warming of antarctic bottom water aabw between the 1980s and 2000s are quantified assessing the relative contributions of water mass changes and isotherm heave the analysis uses highly accurate full depth ship based conductivity temperature depth measurements taken along repeated oceanographic sections around the southern ocean fresher varieties of aabw are present within the south pacific and south indian oceans in the 2000s compared to the 1990s with the strongest freshening in the newest waters adjacent to the antarctic continental slope and rise indicating a recent shift in the salinity of aabw produced in this region bottom waters in the weddell sea exhibit significantly less water mass freshening than those in the other two southern basins however a decrease in the volume of the coldest deepest waters is observed throughout the entire southern ocean this isotherm heave causes a salinification and warming on isobaths from the bottom up to the shallow potential tem

cooling history of nested plutons from the variscan tichka plutonic complex morocco four imbricated mafic to felsic plutons of variscan age from morocco have been investigated for their cooling history and geochemical interactions with surrounding continental rocks oxygen isotope compositions of whole rocks and minerals have been used to model the cooling rates of these kilometer sized intrusions by combining both the knowledge of oxygen self diffusion data of rock forming minerals and the determination by ir spectroscopy of the water content of quartz the cooling times are estimated ranging from 10 to 5 10 years in agreement with the shallow emplacement 4 6 km depth of these intrusions into the continental crust such fast cooling rates could explain why after assimilation of the various country rocks heterogeneities of both neodymium and strontium isotope ratios were still preserved a progressive o increase from the mafic to felsic terms of the plutonic suite which does not excess 1 to 1 5 could be explained by the assimilation of metamorphosed pelitic and volcanic rocks that constitute the basement of the tichka plutonic complex

fluid rock interactions during ultra high pressure metamorphism dabie shan china oxygen isotope analyses of garnet separates and whole rock samples of gneiss and marble hosted eclogites from the ultra high pressure uhp dabie shan terrain fall in the range 6 76 to 10 76 comparison of the isotopic compositions of the eclogites with those of their host rocks leads to the following conclusions 1 the basaltic protolith of the eclogites had isotopic compositions in the range 2 15 to 4 99 it is proposed that this is the result of contamination of the parent basaltic magma with hydrothermally altered18o depleted source materials 2 18o enriched eclogite compositions resulted from local scale 3 m interaction between this basaltic eclogite protolith and fluids produced by decarbonation of impure marble lithologies during uhp metamorphism 3 18o depleted eclogite and gneiss compositions resulted from regional scale meteoric hydrothermal alteration of the basalts and their host rocks prior to uhp metamorphism epidote separates and whole rocks from the cores and rims of mineralogically zoned eclogite boudins within amphibolite grade biotite gneisses show no distinct isotopic differences this suggests that the preferential recrystallisation of the gneisses and the associated amphibolite grade overprint of the rims of eclogite bodies could not have resulted from regional scale infiltration of significant volumes of fluid during the exhumation of the dabie shan terrain

characteristics and mode of emplacement of gneiss domes and plutonic domes in central eastern pyrenees abstract gneiss domes and plutonic granitoid domes make up almost 50 of the pre hercynian terrains in the central and eastern pyrenees from a structural study of the shape and internal structure of the domes and of their relationships with the enclosing rocks it can be shown that both types of domes were emplaced diapirically during the major regional deformation phase and the peak of regional metamorphism the study also shows that the internal structure the overall shape and general behaviour relative to the host rocks are similar for plutonic domes and for gneiss domes this appears to be in good agreement with h ramberg s 1967 gravity deformation and the earth s crust academic press london 1970 model studies in relation to intrusion of plutonic bodies in mechanisms of igneous intrusion edited by newall g rast n geol j spec issue 2 261 286 model studies showing that dome or mushroom like structures similar to those observed develop when there is a small viscosity ratio between the rising body and its enclosing medium this implies a high crystal content for the granitoid magma this crystal content has been estimated by i calculating the viscosity and density in natural conditions from petrological data for the magma considered as a suspension using the model and program of j p carron et al 1978 bull soc geol fr 20 739 744 ii using the recent results of experimental deformation of partially melted granites of i van der molen m s paterson 1979 contr miner petrol 70 299 318 and ii comparing the preceding results with the data obtained by deformation experiments on rocks similar to those enclosing the domes the minimum crystal content for the development of a dome like structure has been thus estimated to about 70 i e a value very close to that estimated by van der molen paterson 1979 to be the critical value separating the granular framework flow from suspension like behaviour the effect of small variations in the viscosity of the rising body are then simulated by centrifuge experiments these small variations appear to exert a strong control on the shape and rate of rise of the domes they are thought to be sufficient to account for the variations in shape and structure and the level of emplacement of the different types of gneissic and plutonic domes finally more complex experiments with models built in order to simulate as closely as possible the natural structural evolution of the region as deduced from petrological and structural data are reported their implications for the regional interpretation of the relationships between gneissic and plutonic domes is then discussed

petrogenesis of ca 1 95 ga meta leucogranites from the jining complex in the khondalite belt north china craton water fluxed melting of metasedimentary rocks abstract anatexis occurs in response to changing p t fluid conditions during orogenesis is thus crucial for understanding the tectonic evolution of orogenic belts here we report an integrated petrological geochemical whole rock oxygen isotopic and zircon u pb hf o isotopic study of meta leucogranites from the jining complex north china craton to unravel its petrogenesis and constrain the tectonic evolution of the paleoproterozoic khondalite belt the meta leucogranites are weakly peraluminous with homogeneous minimum melt compositions and are characterized by low rb contents and rb sr ratios high ba and sr contents and sr y ratios and moderately fractionated ree patterns without obvious eu anomalies these trace element characteristics differ from that of leucogranites derived from fluid absent melting considering their low whole rock zr saturation temperatures 746 780 c and comparable compositions with experimentally generated melts produced by water fluxed melting we infer that the meta leucogranites are low temperature granites and were generated by water fluxed melting of metasedimentary rocks at 6 8 kbar sims zircon u pb analyses suggest that the meta leucogranites were emplaced at 1 95 ga or slightly earlier and were subsequently metamorphosed and cut by a pegmatite dike at 1 92 ga the abundant inherited zircons yield nearly concordant 207 pb 206 pb ages ranging from 2 24 to 1 98 ga which are consistent with the detrital zircon age spectra of the metasedimentary rocks from the khondalite belt the hf isotopic compositions of inherited and magmatic zircons e hf t 0 2 to 7 7 closely overlap with the time evolved e hf range of detrital zircons from metasediments in the khondalite belt different types of zircons inherited magmatic and metamorphic zircons have similar 18 o values of 7 2 9 2 which is lower than that of metamorphic zircons 10 0 13 6 from surrounding metasediments thus we propose that the meta leucogranites were formed by water fluxed melting of metasedimentary rocks from the khondalite belt at 1 95 ga during the prograde upper amphibolite facies metamorphism

decadal changes in southern ocean ventilation inferred from deconvolutions of repeat hydrographies changes in southern ocean ventilation imprint on dissolved gases nutrients radiocarbon temperature and salinity we deconvolve tracer measurements for the distribution g of times and locations of last ventilation using a maximum entropy approach decadal changes of gare quantified by deconvolving hydrographies measured during the early 1990s and again some 15 years later our analysis reveals coherent changes across the 5 meridional sections analyzed the fraction of water younger than 30 years decreased by 20 decade south of 40 s in circumpolar deep water cdw and increased by 10 decade north of 40 s in subantarctic mode water samw ventilation locations shifted with more water south of 40 s being ventilated north of the subantarctic front these ventilation changes impacted cfc uptake with concentrations south of 40 s less than and north of 40 s higher than expected for steady flow the inferred changes imply increased samw formation and cdw upwelling consistent with strengthened westerly winds

regional metamorphism of the vassalboro formation south central maine usa a case study of the role of fluid in metamorphic petrogenesis progressively metamorphosed carbonate rocks of the vassalboro formation serve a natural laboratory for the investigation of fluid rock interactions during metamorphism an integrated study of their whole rock chemistry mineralogy mineral chemistry and mineral abundances has led to the following results a prograde mineral reactions involved hydrolysis as well as dehydration and decarbonation the hydrolysis reactions have resulted in an almost quantitative extraction of k and na from high grade metacarbonates b prograde mineral reactions buffered the x co 2 of coexisting metamorphic fluid during almost all of the rocks metamorphic history c the carbonate rocks were infiltrated by large volumes of h 2 o rich fluid while the buffering reactions progressed during the metamorphic event some high grade metacarbonates were infiltrated by at least 3 rock volumes of fluid combined buffering and infiltration appears to be a general metamorphic phenomenon in carbonate bearing rocks to depths of 30 km in the crust d there is an excellent positive correlation between the heat budget of individual metacarbonate rock samples and calculated fluid rock ratios convective heat transfer by metamorphic fluids is therefore likely to be an important item in the heat budget of metamorphic terrains consideration of these results leads to a model of regional metamorphism which involves infiltration of rock by large volumes of acid h 2 o rich fluid large scale acid infiltration metasomatism in this model the infiltrating fluid exerts enormous control over the mineralogical evolution of the carbonate rocks during the metamorphic event it drives mineral reactions it changes whole rock chemistry and it supplies heat

water fluxed melting of the continental crust a review abstract water fluxed melting also known as fluid or water present melting is a fundamental process in the differentiation of continents but its importance has been underestimated in the past 20 years during which research efforts focused mostly on dehydration melting reactions involving hydrate phases in the absence of a separate aqueous phase the presence of a free aqueous phase in anatectic terranes influences all major physical and chemical aspects of the melting process from melt volumes viscosity and ability to segregate from rock pores to melt chemical and isotopic composition a review of the literature shows that melting due to the fluxing of aqueous fluids is a widespread process that can take place in diverse tectonic environments active tectono magmatic processes create conditions for the release of aqueous fluids and deformation driven transient high permeability channels capable of fluxing high temperature regions of the crust where they trigger voluminous melting water fluxed melting can be either congruent in regions at the water saturated solidus or incongruent at suprasolidus p t conditions incongruent melting reactions can give rise to peritectic hornblende or to nominally anhydrous minerals such as garnet sillimanite or orthopyroxene in this case the presence of an aqueous phase is indicated by a mismatch between the large melt fraction generated and the much smaller fractions predicted in its absence the relatively small volumes of aqueous fluids compared to that of rocks imply that melting reactions are generally rock buffered fluids tend to move upwards and down temperature however there are cases in which pressure gradients drive fluids up temperature potentially fluxing suprasolidus terranes crustal regions at conditions equivalent to the water saturated solidus represent a natural impediment to the up temperature migration of aqueous fluids because they are consumed in melting reactions in this case continued migration into supra solidus terranes take place through the migration of water rich melts thus melts become the transport agent of water into supra solidus terranes and responsible for water fluxed melting other processes such as the relatively rapid fluid migration through fractures also allow regional aqueous fluids to by pass the water saturated solidus fluid trap and trigger melting above solidus conditions when aqueous fluids or hydrous melts flux rocks at supra solidus conditions they equilibrate with the surroundings through further melting decreasing water activity and giving rise to undersaturated melts it is in these conditions that hornblende or anhydrous peritectic phases are stabilized unlike dehydration melting the melt fraction generated in this case is not limited by the water contained in hydrous minerals but by the volume of water added to the system unlike melting at the water saturated solidus these melts are capable of rising without freezing and do give rise to upper crustal granitic bodies

ion microprobe survey of the grain scale oxygen isotope geochemistry of minerals in metamorphic rocks abstract the oxygen isotope compositions of calcite diopside dolomite forsterite garnet k feldspar kyanite plagioclase quartz and wollastonite were analyzed in suites of contact and regional metamorphic rocks using an ion microprobe spatial resolution was 10 m precision measured as the standard deviation of working standards averaged over the entire project was 0 13 0 18 for three carbonate standards and 0 11 0 12 for two silicate standards a total of 1176 analyses excluding standards were made of 73 minerals in 23 samples both intercrystalline and intracrystalline variability in 18 o is greater in contact than in regional metamorphic rocks of 27 minerals analyzed in contact metamorphosed rocks 70 exhibit statistically significant grain to grain variability in 18 o over areas 1 41 cm 2 with the largest range in silicates and carbonates in a single sample of 7 4 forsterite and 10 6 dolomite of 88 grains analyzed in two or more places in contact metamorphosed rocks 32 exhibit statistically significant intracrystalline variability in 18 o with the largest range in a single silicate and carbonate grain of 3 1 forsterite and 10 1 dolomite in contrast 44 of 45 minerals in regional metamorphic rocks exhibit significant grain to grain variability in 18 o over areas 1 17 cm 2 with the largest range in silicates and carbonates in a single sample of only 1 1 plagioclase and 0 9 calcite only 6 of 144 grains analyzed in two or more places in regional metamorphic rocks exhibit significant intracrystalline variability in 18 o with the largest range in a single silicate and carbonate grain of only 1 5 diopside and 0 7 calcite the difference in intercrystalline and intracrystalline variability in 18 o between contact and region metamorphic rocks is explained by the longer duration and slower reaction rates of regional metamorphism rather than to differences in temperature there is no significant difference in intercrystalline and intracrystalline variability in 18 o in regional metamorphic rocks among samples from the biotite garnet and kyanite zones calcite inclusions in forsterite and calcite and quartz inclusions in garnet either have 18 o that is statistically indistinguishable from 18 o of the same mineral occurring as nearby matrix grains or have statistically significant lower 18 o no reversed isotope fractionations were measured between coexisting mineral pairs minerals in individual samples however exhibit a wide range in the degree to which they attained and preserve oxygen isotope fractionations consistent with metamorphic temperatures recorded by mineral equilibria processes that account for grain scale departures from isotope exchange equilibrium include a overstepping of prograde mineral reactions b growth zoning in low diffusivity minerals c interaction of rocks with fluids at the peak of metamorphism and or during cooling d retrograde mineral reactions and e closed system isotope exchange between coexisting minerals during cooling this study provides new information about 1 the degree to which a variety of textural changes experienced by rocks during metamorphism are associated with changes in 18 o 2 oxygen isotope homogenization at the outcrop scale among contrasting lithologies 3 changes in 18 o with increasing grade of regional metamorphism and 4 time scales of metamorphic process

structural controls on syntectonic metasomatic tremolite and tremolite plagioclase pods in the molanite valley mt isa australia abstract in the molanite valley west of mt isa tremolite bearing metasomatic pods showing sharp contacts with enclosing rocks occur over a strike length of 7 4 km in the biotite zone bortala formation in relatively low strain rocks of the western part of the valley plagioclase tremolite pods have replaced psammite or mica schist surrounding the terminations of buck quartz veins whereas in intensively sheared rocks to the east pods of medium to coarse grained massive tremolite commonly containing greater than 95 tremolite have replaced marble quartzite and psammite talc chlorite schists formed by dissolution of carbonates during shearing of marble are associated with some of the massive tremolite pods the direct relationship between structural domains and metasomatism suggests that migration of externally derived fluids was controlled by fractures and the shear zone the fluids having migrated along fractures interacted with wall rocks to produce plagioclase tremolite pods in the shear zone buck quartz veins some tremolite bearing show no obvious geometric relationship to massive tremolite pods it is postulated that the metasomatic fluids fluxed through shear domains and penetrated progressive shortening domains to replace the host rocks and form the massive tremolite pods both styles of metasomatic rocks developed from late s 2 to early s 3 during a progressive e w shortening event which corresponds to the regional metamorphism the metasomatic rocks represent only a small part of widespread metasomatism across the mt isa inlier

antarctic ocean and sea ice response to ozone depletion a two time scale problem theresponseofthesouthernoceantoarepeatingseasonalcycleofozonelossisstudiedintwocoupledclimate models and is found to comprise both fast and slow processes the fast response is similar to the interannual signature of the southern annular mode sam on sea surface temperature sst onto which the ozone hole forcing projects in the summer it comprises enhanced northward ekman drift inducing negative summertime sst anomalies around antarctica earlier sea ice freeze up the following winter and northward expansion of the sea ice edge year round the enhanced northward ekman drift however results in upwelling of warm waters from below the mixed layer in the region of seasonal sea ice with sustained bursts of westerly winds induced by ozone hole depletion this warming from below eventually dominates over the cooling from anomalous ekman drift the resulting slow time scale response years to decades leads to warming of ssts around antarctica and ultimately a reduction in sea ice cover year round this two time scale behavior rapid cooling followed by slow but persistent warming is found in the two coupled models analyzed one with an idealized geometry and the other with a complex global climate model with realistic geometry processes that control the time scale of the transition from cooling to warming and their uncertainties are described finally the implications of these results are discussed for rationalizing previous studies of the effect of the ozone hole on sst and sea ice extent

pressure temperature and metamorphic zonation studies of pelitic schists in the merrimack synclinorium south central new hampshire metamorphic isograds in pelitic rocks in nine 15 quadrangles in south central new hampshire are divisible into the upper 5 of tracy s 1975 high grade zones 2 the staurolite sillimanite zone 3 the sillimanite zone 4 the sillimanite alkali feldsparmuscovite zone 5 the sillimanite alkali feldspar zone 6 and the sillimanite alkali feldspar cordierite zone these zones replace the single alkali feldspar sillimanite zone originally mapped by thompson and norton 1968 biotite garnet geothermometry and plagioclase composition studies confirm the zonal pattern deduced from the mineralogical relations three stages of acadian metamorphism are recognized an early m 1 andalusite metamorphism is evidenced by sillimanite pseudomorphs after andalusite and flecky gneisses occurring near the contacts of the devonian kinsman series plutons this early metamorphism has been strongly overprinted bv m 2 metamorphism which locally attained cordierite alkali feldspar grade and produced the dominant isograd pattern m 2 metamorphism cross cuts devonian kinsman and spaulding series plutons in this region m 3 locally retrograded the m 2 terrane and produced a lower temperature decussate muscovite

recycling processes in granite granodiorite complex genesis the querigut case studied by ndsr isotope systematics abstract using the isotopic rb sr and sm nd petrogenetic tracers we have studied the calc alkaline plutonic complex of querigut pyrenees france which is famous for its acid to mafic rock association and is a typical post tectonic hercynian granitoid its age of 280 m y is already known 2 23 24 and our purpose is to examine the relationship between its different petrographic units and the problem of their source composition the sm nd isotopic results rule out any genetic process involving a unique homogeneous source and imply the presence of old recycled continental materials in contrast the rb sr isotope system seems to have been homogenized by hot fluids maybe post magmatic this is also true for pb isotopes as shown previously by michard vitrac et al 18 on the basis of the isotopic results and the major element data a model of combined fractional crystallization assimilation of country rocks is proposed for the basic part of the complex in contrast acid parts are mainly the result of the continental anatexis this study also constrains the basement s age 1200 1900 m y of the area and suggests a scheme for the gological history of the eastern pyrenees

transient response of the southern ocean to changing ozone regional responses and physical mechanisms abstractthe impact of changing ozone on the climate of the southern ocean is evaluated using an ensemble of coupled climate model simulations by imposing a step change from 1860 to 2000 conditions response functions associated with this change are estimated the physical processes that drive this response are different across time periods and locations as is the sign of the response itself initial cooling in the pacific sector is driven not only by the increased winds pushing cold water northward but also by the southward shift of storms associated with the jet stream this shift drives both an increase in cloudiness resulting in less absorption of solar radiation and an increase in net freshwater flux to the ocean resulting in a decrease in surface salinity that cuts off mixing of warm water from below a subsurface increase in temperature associated with this reduction in mixing then upwells along the antarctic coast producing a subsequent warming similar changes in convective activity occur

isotopic disequilibrium in migmatitic hornfels of the gennargentu igneous complex sardinia italy records the formation of low 87sr 86sr melts from a mica rich source isotopic disequilibrium is increasingly recognized as a common feature of magmatic systems but the details of the mechanism s underpinning the development of isotopic disequilibrium during partial melting processes are not fully understood partial melting of mica rich lithologies may be predicted to generate melts enriched in radiogenic sr compared to the bulk protolith compositions due to the typically high rb sr ratio coupled with low melting temperature of mica in crustal rocks here we report a puzzling case study where the sr isotope composition of the melt fraction leucosome of partially molten metapelites migmatites is instead less radiogenic than the restitic component melanosome the examined migmatites fringe 50 m wide zone a low pressure 200 mpa high temperature 1050 c quartz dioritic intrusion which was emplaced in the gennargentu igneous complex sardinia italy at 306 26 ma bulk rock rb sr dating the migmatites derive from anatexis of the muscovite rich metapelitic wall rocks they include a quartzo feldspathic leucosome and a melanosome containing cordierite k feldspar plagioclase biotite fe ti oxide minerals and both corundum and hercynite the leucosome has a less radiogenic sr and more radiogenic nd isotope composition than the melanosome 87sr 86sr 306 ma 0 71068 and 0 71536 end 306 ma 6 4 and 9 2 respectively with bulk migmatite samples having intermediate compositions the significantly lower content of mica in the migmatites compared to the protolith indicates that muscovite and to a lesser extent biotite largely contributed to melt formation however the leucosome volume 50 estimated through mass balance calculations is considerably higher than the amount of melt 10 vol generally produced by mica dehydration melting in the crust suggesting that partial melting was enhanced by an external hydrous fluid the o isotope composition of the migmatites is lower than the typical metapelite values 10 but overlaps with the 18o range of the quartz diorites 8 8 9 9 suggesting that such a hydrous fluid was released from the quartz dioritic intrusion we put forward a model whereby the anatexis temperature conditions t 800 c favored the preservation of isotopic disequilibrium of micas and plagioclase in the protolith in this context the leucosome formed by the preferential melting of less radiogenic plagioclase rather than more radiogenic micas the melt was then efficiently separated from the melanosome containing restitic biotite and peritectic k feldspar and magnetite derived from mica breakdown during the anatectic process the quartz diorite provided not only the heat budget but also the fluid amount responsible for i the hydration of the pelitic country rock ii the increase of melt fraction and iii the higher mobility of anatectic magma

evolution of structurally contrasting anatectic migmatites in the 3 kbar ballachulish aureole scotland anatectic migmatites of contrasting structural style are found adjacent to the contacts of the ballachulish igneous complex argyllshire scotland on the east flank evidence for migmatization is largely restricted to the local development of millimetre centimetre scale kfs qtz rich leucocratic segregations which accompany fragmentation of brittle hornfels layers and ductile deformation of mm cm scale semipelitic layers large volumes of semipelitic rock rich in feldspar and quartz on the east flank show no migmatitic features and bedding is usually preserved undisturbed right up to the contact on the west flank in contrast similar semipelitic rocks show widespread migmatitic features and disruption of layering is substantial and widespread over a 400 m wide zone within the west flank migmatites 1 100 cm scale rigid bedding fragments schollen may be suspended and disoriented in a semipelitic matrix that underwent ductile deformation the p t conditions on both flanks are in the same range 3 kbar and 650 700 c the contrast in gross structural style is believed to result from differences in the volumes of melt produced and differences in the proportion of rock in which the critical melt fraction of the rocks was exceeded on the east flank only on a mm cm scale was enough melt locally accumulated to cause disruption of some layers and segregation of melt on the west flank melting proceeded substantially in a broad tract of semipelitic rocks resulting in larger scale contrasts in rheology that led to the present chaotic structures in this zone because migmatization occurred at a pressure too low for muscovite dehydration melting and at temperatures too low for substantial biotite dehydration melting the different amounts of melting on the east and west flanks most probably resulted from the introduction of differing amounts of externally derived water on the east flank and throughout most of the aureole the absence of melting even in quartzofeldspathic protoliths indicates that there was no substantial movement of fluid towards or away from the igneous complex during migmatization the contrasting situation on the west flank may have resulted from devolatilization of underlying quartz diorite magma 690 710 c which released heat and fluids into the overlying quartz and feldspar rich semipelites solidus temperature 650 680 c

carbon isotopic thermometry calibrated by dolomite calcite solvus temperatures abstract the temperature dependence of carbon isotopic fractionations between calcite and graphite and between dolomite and graphite are calibrated by the calcite dolomite solvus geothermometry using marbles collected from the contact metamorphic aureole in the kasuga area central japan the carbon isotopic fractionations 13ccc gr and 13cdo gr systematically decrease with increasing metamorphic temperature the concordant relationships between the fractionations and solvus temperatures are approximately linear with t 2 over the temperature range 400 to 680 c 13ccc gr 5 6 106 t 2 k 2 4 13cdo gr 5 9 106 t 2 k 1 9 these systematic relationships between fractionation and temperature suggest that carbon isotopic equilibria between carbonates and graphite were attained in many cases the equation for the calcite graphite system has a slope steeper than bottinga s 1969 results it is however in good agreement with that of valley and o neil 1981 in the temperature range from 600 to 800 c because of the relatively high sensitivity to temperature these isotopic geothermometers are useful for determining the temperatures in moderate to high grade metamorphosed carbonate rocks

synchronous variability in the southern hemisphere atmosphere sea ice and ocean resulting from the annular mode zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the southern hemisphere during all seasons this is true not only in observations but also in an unforced 15 000 yr integration of a coarse resolution r15 coupled ocean atmosphere model here it is documented how this mode of atmospheric variability known as the southern annular mode sam generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the sam the positive phase of the sam is associated with an intensification of the surface westerlies over the circumpolar ocean around 608s and a weakening of the surface westerlies farther north this induces ekman drift to the north at all longitudes of the circumpolar ocean and ekman drift to the south at around 308s through mass continuity the ekman drift generates anomalous upwelling along the margins of the antarctic continent and downwelling around 458s the anomalous flow diverging from the antarctic continent also increases the vertical tilt of the isopycnals in the southern ocean so that a more intense circumpolar current is also closely associated with positive sam in addition the anomalous divergent flow advects sea ice farther north resulting in an increase in sea ice coverage finally positive sam drives increases in poleward heat transport at about 308s while decreases occur in the circumpolar region ocean and sea ice anomalies of the opposite sign occur when the sam is negative the ocean and sea ice fluctuations associated with the sam constitute a significant fraction of simulated ocean variability poleward of 308s year round the robustness of the mechanisms relating the sam to oceanic variability suggests that the sam is likely an important source of large scale variability in the real southern hemisphere ocean

stable isotope geochemistry and formation mechanisms of quartz veins extreme paleoaltitudes of the central alps in the neogene quartzveins ranging in size from less than 50 cm length and 5 cm width to greater than 10 m in length and 5 m in width are found throughout the central swiss alps in some cases the veins are completely filled with milky quartz while in others sometimes spectacular void filling quartz crystals are found the style of vein filling and size is controlled by host rock composition and deformation history temperatures of vein formation estimated using stable isotope thermometry and mineral equilibria cover a range of 450 c down to 150 c vein formation started at 18 to 20 ma and continued for over 10 my the oxygen isotope values of quartz veins range from 10 to 20 permil and in almost all cases are equal to those of the hosting lithology the strongly rock buffered veins imply a low fluid rock ratio and minimal fluid flow in order to explain massive nearly monomineralic quartz formation without exceptionally large fluid fluxes a mechanism of differential pressure and silica diffusion combined with pressure solution is proposed for early vein formation fluid inclusions and hydrous minerals in late formed veins have extremely low d values consistent with meteoric water infiltration the change from rock buffered static fluid to infiltration from above can be explained in terms of changes in the large scale deformation style occurring between 20 and 15 ma the rapid cooling of the central alps identified in previous studies may be explained in part by infiltration of cold meteoric waters along fracture systems down to depths of 10 km or more an average water flux of 0 15 cm3 cm 2yr 1 entering the rock and reemerging heated by 40 c is sufficient to cool rock at 10 km depth by 100 c in 5 million years the very negative d values of

on the occurrence and wider implications of anomalously low δd fluids in quartz veins south cornwall england a chemical and hydrogen isotopic study has been carried out on quartz hosted fluid inclusions from three different quartz carbonate sulphide sulphate veins from southwest england two fluid types have been identified in these veins by fluid inclusion microthermometry 1 a low temperature 80 150 c saline 20 27 wt nacl cacl2 equiv nacl cacl2 brine and 2 a moderate temperature 200 c low salinity 0 5 wt nacl equiv fluid d values for the brines range from 39 to 103 and values for the dilute fluids are in the range 46 to 79 both fluid types have at least some values of d which are defined as anomalous i e cannot be directly related to either a low d source fluid or to modification of a source fluid by common physicochemical processes such as evaporation or boiling examination of these data in the given geological context suggest the anomalously low values are unlikely to be attributable to analytical artifacts or post entrapment changes of the fluid inclusions similarly fluid interaction with a suitable mineral or organic phase cannot adequately explain the data we conclude that an as yet unidentified process is responsible for producing low d fluids in southwest england and that this may be a common phenomenon in low temperature basinal environments

petrogenetic and tectonic significance of young leucogranites from the northwestern himalaya pakistan in the himalaya of northwestern pakistan small discordant bodies of leucogranite intrude metamorphosed basement of the indian crust as the first step in assessing the tectonic significance of these granites we have used the shrimp ion microprobe to obtain u pb dates on zircon zircons of igneous appearance are scarce in the leucogranites and with one exception are associated with xenocrystic components which occur as discrete grains and as cores rimmed by young zircon zircons of igneous appearance are high in u 5000 to 40 000 ppm low in th u 0 01 to 0 05 and frequently colored a distinct blue xenocrystic components give a range of proterozoic ages consistent with ages previously reported for indian crust in sharp contrast zircons of igneous appearance yield clusters of concordant tertiary ages two leucogranite dikes from southern localities yield rather old emplacement ages of about 35 ma swat and about 50 ma naran together with previously determined 40ar 39ar and fission track cooling ages these ages document immediate and rapid metamorphism and denudation following eocene collision three leucogranite dikes from northern localities within the nanga parbat haramosh massif are very young having emplacement ages of about 2 3 ma 5 ma and 7 ma the formation and emplacement of these leucogranites during the rapid late tertiary denudation of the nanga parbat region suggests to us that decompression melting may be a viable mechanism for leucogranite genesis

genesis and mobility of the h2o co2 fluid phase during regional greenschist and epidote amphibolite facies metamorphism a petrological and stable isotope study in the scottish dalradian during high pressure low temperature greenschist and epidote amphibolite facies metamorphism in dalradian rocks of the sw scottish highlands mineral assemblages in metabasites and calcareous metasediments were dominantly controlled by infiltration of hydrous fluids consequently mineral assemblages capable of buffering the fluid phase composition were rare equilibrium prograde h 2 o co 2 fluids usually contained less or much less than about 1 2 mol co 2 three fluid infiltration events are recognized during prograde greenschist facies metamorphism metabasic sills were infiltrated by large volumes of co 2 bearing hydrous fluid carbon isotope studies indicate that the co 2 was locally derived by widespread oxidation of graphite or other organic carbon in adjacent metasediments this may have occurred under approximately lower greenschist facies conditions as a result of mixing of fluids of varying f o 2 initiated by thermal expansion of water during heating decompression and consequent hydraulic fracturing in the epidote amphibole facies garnet zone dehydration reactions in metabasites generated large quantities of water which removed carbonate from metabasites on a regional scale and infiltrated calcareous metasediments to produce assemblages containing grossular diopside k feldspar amphibole clinozoisite and sphene a late retrograde infiltration of co 2 bearing hydrous fluid under lower greenschist facies conditions generated assemblages containing k feldspar chlorite rutile dolomite in calcareous rocks and albite prophyroblast schists in zones of intense secondary deformation large scale infiltration of fluid into greenschist facies metadolerite sills was intimately related to and possibly controlled by penetrative deformation and in the absence of a penetrative deformation grain boundary diffusion by itself was an ineffectual mechanism of fluid transport

localization of marine mammals near hawaii using an acoustic propagation model humpback whale songs were recorded on six widely spaced receivers of the pacific missile range facility pmrf hydrophone network near hawaii during march of 2001 these recordings were used to test a new approach to localizing the whales that exploits the time difference of arrival time lag of their calls as measured between receiver pairs in the pmrf network the usual technique for estimating source position uses the intersection of hyperbolic curves of constant time lag but a drawback of this approach is its assumption of a constant wave speed and straight line propagation to associate acoustic travel time with range in contrast to hyperbolic fixing the algorithm described here uses an acoustic propagation model to account for waveguide and multipath effects when estimating travel time from hypothesized source positions a comparison between predicted and measured time lags forms an ambiguity surface or visual representation of the most probable whale position in a horizontal plane around the array this is an important benefit because it allows for automated peak extraction to provide a location estimate examples of whale localizations using real and simulated data in algorithms of increasing complexity are provided

common humpback whale megaptera novaeangliae sound types for passive acoustic monitoring humpback whales megaptera novaeangliae are one of several baleen whale species in the northwest atlantic that coexist with vessel traffic and anthropogenic noise passive acoustic monitoring strategies can be used in conservation management but the first step toward understanding the acoustic behavior of a species is a good description of its acoustic repertoire digital acoustic tags dtags were placed on humpback whales in the stellwagen bank national marine sanctuary to record and describe the non song sounds being produced in conjunction with foraging activities peak frequencies of sounds were generally less than 1 khz but ranged as high as 6 khz and sounds were generally less than 1 s in duration cluster analysis distilled the dataset into eight groups of sounds with similar acoustic properties the two most stereotyped and distinctive types wops and grunts were also identified aurally as candidates for use in passive acoustic monitoring this identification of two of the most common sound types will be useful for moving forward conservation efforts on this northwest atlantic feeding ground

the thermal effects of pervasive and channelized fluid flow in the deep crust heat advection by upward migrating fluids in one possible mechanism for elevating temperatures within the earth s crust models are presented that compare the thermal impact of a pervasive upward flux of fluids to that of the same flux focused into vertical parallel planar channels in channelized flow the average temperature across channels is lower than that of pervasive flow at comparable times in the systems evolutions as the channel spacing decreases the evolution through time and steady state approach that of pervasive flow with pervasive flow representing the limiting case of zero spacing when channel spacings are small relative to the length of the vertical flow path lateral temperature gradients around channels will be very shallow for any geologically reasonable flux when small fluxes such as may be generated from pelites undergoing progressive metamorphism are focused into very widely spaced channels the resultant temperature increase around channels may be discernable with geothermo

mantle derived volatiles in continental crust the massif central of france co2 rich gases and groundwaters from springs and boreholes originating within the basement of the massif central have variable3he 4he ratios with correspondingr ra values ranging from 0 8 to 5 5 and 0 3 to 2 8 respectively indicating the presence of a significant component of mantle helium molar concentrations of rare gases in the co2 rich gases are approximately 5 orders of magnitude greater than in the waters and suggest that a near surface henry s law fractionation has occurred between exsolving co2 and water 13c values of the co2 rich gases are in the range 4 2 to 6 1 i e in that range normally attributed to mantle carbon but which could also represent an average crustal composition and therefore do not discriminate between mantle and crustal sources c 3he ratios show 4 orders of magnitude variation from 1 4 1012 to 5 108 and compared to a mantlec 3he ratio of 109 indicate that either a complex fractionation has occurred between mantle helium and mantle co2 or more likely that mantle rare gases have been diluted by large quantities of co2 with an average crustal carbon isotope composition the regional distribution of3he and c does not show any obvious relationship to age or proximity of volcanic centres or major faults suggesting that mantle derived c and he components decoupled from their silicate melt sources at some depth the results from this area of active fluid circulation suggest that c isotope data derived from metamorphic terrains should be interpreted with great caution but that input of some mantle derived carbon is expected to accompany crustal extension

natural and experimental fluorine substitution in biotite implications for fluid rock thermochronometry and application to the serido belt northeastern brazil abstract we modeled non steady state fluid assisted diffusion in a sheet plane infinite cylinder and finite thin cylinder using analytical solutions of the diffusion equation and the experimental diffusivity of f in biotite diffusion experiments on natural biotite in the presence of hydrofluoric acid at 0 4 gpa and 650 700 and 750 c produced diffusive influx perpendicular to the c axis epma mapping and profiling allow us to define the following arrhenius expression of f diffusion in biotite d 7 04 m 2 s 10 4 exp 221 kj mol rt 1 the results yield the discrimination of a high t homogenization domain where cooling paths continuously reequilibrate f in biotite an intermediate t zonation domain where cooling paths record f in biotite diffusion profiles and a low t closure domain where f in biotite remains unchanged the zonation domain significantly expands with increasing cooling rates and decreasing diffusion time we systematically analyzed f in biotite with electron microprobe in samples collected along representative cross sections within the serido belt northeastern brazil its metasedimentary units reached upper amphibolite grade metamorphic conditions with constant f in biotite f 0 33 wt in grains from mica schist and paragneiss the ti in biotite geothermometer yielded nearly constant temperatures around 623 c the f in biotite regional background values remain unchanged at the contact with the major ediacaran f rich acari pluton it indicates the absence of magmatic fluid influx into the host rocks and is evidence for a fluid absent nature of melts by contrast the f in biotite of the metric mica schist enclaves within dykes and sills of cambrian pegmatitic granites was reequilibrated by interaction with exsolved fluids the ti in biotite geothermometer indicates temperatures around 642 c and our model suggests 100 kyr as a minimal duration for fluid rock interaction the preservation of intra grain f in biotite homogeneity requires fluid flux cessation before cooling or fluid present cooling rates below 100 c myr 1 higher cooling rates would generate f in biotite intra grain zonation at the contact with the pegmatitic granites the metasedimentary rocks show meter scale f in biotite gradients due to thermal profiles setting the fluid fh2o fhf gradient the preservation of such gradients is related to a relatively fast fluid flux episode compared to the overall duration of the elevated thermal profile the absence of intra grain zonation indicates that f in biotite re equilibration was fast relative to that of the fluid flux duration we found intra grain f in biotite zonation within an orthogneiss sample from the paleoproterozoic caico complex basement nearby the metasedimentary belt and intruded plutons the fit of the natural profile by modeled profiles for cooling rates below 10 c myr 1 obtained from available serido belt u pb and 40ar 39ar ages indicates that the orthogneiss cooled from 475 c it suggests the existence of a thermal gradient as the inner part of the belt cooled from 623 c

geologic implications of the oxygen isotope profile of the toa baja drill hole puerto rico the whole rock o isotopic compositions of volcanic and volcaniclastic samples from the toa baja drill hole demonstrate that low temperature 200 c processes have strongly enriched the island arc materials in 18o subsequent to eruption processes such as subaerial weathering alteration during transport and deposition in volcaniclastic aprons submarine weathering burial diagenesis and prograde regional metamorphism through the beginning of the prehnite pumpellyite facies have raised average whole rock 18o values by 4 for basalt and andesite lava flows and by 8 for volcaniclastic sandstones these o isotopic disturbances were probably caused by oxygen exchange with regionally circulating seawater under rather high water rock conditions the processes associated with ageing of volcanic and volcaniclastic materials in the oceanic environment are probably more important to the global budgets of the oxygen isotopes than has been assumed in the past integration of these results into global models for the oxygen isotopes awaits analysis of more varied oceanic terranes to determine the generality of the o isotopic conclusions preferred here and to more carefully evaluate the relative sizes of volcanic volcaniclastic and oceanic oxygen reservoirs and their variabilities in time

heat capacities and entropies of andalusite and sillimanite the influence of fibrolitization on the phase diagram of the al 2 sio 5 polymorphs

stable isotope geochemistry of hercynian granitoid rocks from the sarrabus massif southeastern sardinia italy abstract measurements have been made of the oxygen and hydrogen isotopic compositions of 37 samples of granitoid rocks from the sarrabus massif in several cases mineral separates have also been analyzed the 18 o values of whole rocks range from 7 0 to 10 5 and are independent of petrologic type o and sr isotopic ratios indicate that parental magmas were formed by partial melting of material which was dominantly of lower crustal origin retrograde effects are evident in the quartz biotite fractionations of which values are too large for equilibrium fractionations at igneous temperatures the d values of whole rocks range from 87 to 40 and are consistent with the conclusions reached upon the basis of the oxygen isotopic compositions the geographic distribution pattern of both 18 o and d values allows the contouring of an area in the central western part of the massif which is characterized by relatively lower 18 o and higher d content this area was affected by a strong tectonism and mineralized with fluorite by hydrothermal fluids

contrasting serpentinization processes in the eastern central alps stable isotope compositions have been determined for serpentinites from between davos arosa platta nappe switzerland and the valmalenco italy d and 18o values 120 to 60 and 6 10 respectively in the arosa platta nappe indicate that serpentinization took place on the continent at relatively low temperatures in the presence of limited amounts of metamorphic fluids that contained a component of meteoric water one sample of chrysotile has a 18o value of 13 providing evidence of high w r ratios and low formation temperature of lizardite chrysotile in this area in contrast relatively high d values 42 to 34 and low 18o values 4 4 7 4 for serpentine in the eastern part of the valmalenco suggest a serpentinization process that took place at moderate temperatures in fluids that were dominated by ocean water the antigorite in the valmalenco is the first reported example of continental antigorite with an ocean water signature an amphibole sample from a metasomatically overprinted contact zone to metasediments d 36 indicates that the metasomatic event also took place in the presence of ocean water lower d values 93 to 60 of serpentines in the western part of the valmalenco suggest a different alteration history possibly influenced by fluids associated with contact metamorphism low water rock ratios during regional metamorphism and metasomatism have to be assumed for both regions

how much deep water is formed in the southern ocean three tracers are used to place constraints on the production rate of ventilated deep water in the southern ocean the distribution of the water mass tracer po4 phosphate star in the deep sea suggests that the amount of ventilated deep water produced in the southern ocean is equal to or greater than the outflow of north atlantic deep water from the atlantic radiocarbon distributions yield an export flux of water from the north atlantic which has averaged about 15 sv over the last several hundred years cfc inventories are used as a direct indicator of the current production rate of ventilated deep water in the southern ocean although coverage is as yet sparse it appears that the cfc inventory is not inconsistent with the deep water production rate required by the distributions of po4 and radiocarbon it has been widely accepted that the major part of the deep water production in the southern ocean takes place in the weddell sea however our estimate of the southern ocean ventilated deep water flux is in conflict with previous estimates of the flux of ventilated deep water from the weddell sea which lie in the range 1 5 sv possible reasons for this difference are discussed

the relative permeabilities of quartzites and schists during active metamorphism at mid crustal levels the hot spot near bristol new hampshire was an area of high fluid flow during metamorphism in order to determine the mechanisms of fluid flow through the area we made a detailed study of the 18o values of quartz from an outcrop of interlayered quartzites and schists results indicate that the permeability of the quartzite was very low in comparison to that of the schist the 18qtz values from schist layers are remarkably homogenous 15 5 15 8 in contrast to the 18qtz values of schist units outside of the hot spot which vary widely quartz veins that cut the quartzites and pinch out in the schists have the same 18o values 15 7 as quartz from the schists in the quartzites 18qtz values immediately adjacent to the veins and schists are similar to those in the veins and schists but decrease by 1 permil in the centers of the layer we interpret these results to indicate that fluid flow in the hot spot was mainly through the schists and fractures in the quartzites the oxygen isotope exchange fronts in the quartzites prove that there was some flow from the the schists and the fractures into the quartzites comparisons of the shapes of these exchange fronts with exchange fronts predicted by two different models of fluid flow in rocks indicate that fluid transport in the quartzite was predominantly by advection and that the kinetic rates of isotope exchange were fast relative to the advective velocity of the fluid infiltrating the system considering the slow rate of oxygen isotope exchange between quartz and a fluid this implies that fluid flow from the schist and vein fracture into the quartzite was extremely limited

acoustic properties of humpback whale songs a vertical array of five hydrophones was used to measure the acoustic field in the vertical plane of singing humpback whales once a singer was located two swimmers with snorkel gear were deployed to determine the orientation of the whale and position the boat so that the array could be deployed in front of the whale at a minimum standoff distance of at least 10m the spacing of the hydrophones was 7m with the deepest hydrophone deployed at a depth of 35m an eight channel tascam recorder with a bandwidth of 24khz was used to record the hydrophone signals the location distance and depth of the singer was determined by computing the time of arrival differences between the hydrophone signals the maximum source level varied between individual units in a song with values between 151 and 173db re 1 pa one of the purposes of this study was to estimate potential sound exposure of nearby conspecifics the acoustic field determined by considering the relative intensity of higher frequency harmonics in the s

sound source localization technique using a seismic streamer and its extension for whale localization during seismic surveys marine seismic surveys are under increasing scrutiny because of concern that they may disturb or otherwise harm marine mammals and impede their communications most of the energy from seismic surveys is low frequency so concerns are particularly focused on baleen whales extensive mitigation efforts accompany seismic surveys including visual and acoustic monitoring but the possibility remains that not all animals in an area can be observed and located one potential way to improve mitigation efforts is to utilize the seismic hydrophone streamer to detect and locate calling baleen whales this study describes a method to localize low frequency sound sources with data recoded by a streamer beamforming is used to estimate the angle of arriving energy relative to sub arrays of the streamer which constrains the horizontal propagation velocity to each sub array for a given trial location a grid search method is then used to minimize the time residual for relative arrival times along the streamer estimated by cross correlation results from both simulation and experiment are shown and data from the marine mammal observers and the passive acoustic monitoring conducted simultaneously with the seismic survey are used to verify the analysis

the acadian thermal history of the merrimack synclinorium in new hampshire the acadian structural history of the merrimack synclinorium involves a phase of nappe emplacement and thrusting at 400 m y b p followed by a second thickening event before 370 m y b p at the end of this phase the present erosion surface was buried at pressures of 6 to 8 kbar and subsequently experienced peak metamorphic temperatures in the range of 500 c to 650 c the thermal history of the acadian metamor phism of the merrimack synclinorium is examined in a well studied area of central new hampshire to determine the conditions required for the high grade metamorphism of the region constraints are provided by metamorphic pressure estimates by information on the erosional history and by present day heat flow determinations in the synclinorium one dimensional heat transfer calculations show that the high grade metamorphism could readily have been produced during thermal relaxation of the thickened continental crust under conditions of normal continental heat flow these conditions also permit the me

pressure temperature time paths of regional metamorphism i heat transfer during the evolution of regions of thickened continental crust the development of regional metamorphism in areas of thickened continental crust is investigated in terms of the major controls on regional scale thermal regimes these are the total radiogenic heat supply within the thickened crust the supply of heat from the mantle the thermal conductivity of the medium and the length and time scales of erosion of the continental crust the orogenic episode is regarded as consisting of a relatively rapid phase of crustal thickening during which little temperature change occurs in individual rocks followed by a lengthier phase of erosion at the end of which the crust is at its original thickness the principal features of pressure temperature time ptt paths followed by rocks in this environment are a period of thermal relaxation during which the temperature rises towards the higher geotherm that would be supported by the thickened crust followed by a period of cooling as the rock approaches the cold land surface the temperature increase that occurs is governed by the degree of thickening of the crust its conductivity and the time that elapses before the rock is exhumed sufficiently to be affected by the proximity of the cold upper boundary for much of the parameter range considered the heating phase encompasses a considerable portion of the exhumation decompression part of the ptt path in addition to the detailed calculation of ptt paths we present an idealized model of the thickening and exhumation process which may be used to make simple calculations of the amount of heating to be expected during a given thickening and exhumation episode and of the depth at which a rock will start to cool on its ascent path an important feature of these ptt paths is that most of them lie within 50 c of the maximum temperature attained for one third or more of the total duration of their burial and uplift and for a geologically plausible range of erosion rates the rocks do not begin to cool until they have completed 20 to 40 per cent of the total uplift they experience considerable melting of the continental crust is a likely consequence of thickening of crust with an average continental geotherm a companion paper discusses these results in the context of attempts to use metamorphic petrology data to give information on tectonic processes 1984 oxford university press

chemistry source and behavior of fluids involved in alpine thrusting of the central pyrenees quartz veins occupying extensional fractures that formed relatively late in the alpine thrusting history of the pyrenees contain abundant inclusions of hypersaline brines small amounts of bitumen also occur a range of brine compositions is apparent from the freezing behavior of fluid inclusions from different samples with large variations in na ca ratio but many individual samples contain only one brine composition all brine types display a bimodal distribution of homogenization temperature which is interpreted as the result of fluctuation in fluid pressure from a maximum value equal to lithostatic at 5 7 km depth and around 270 c to a value up to 700 bars lower this is ascribed to dilatancy pumping chemical analyses of brines leached from two samples yields balanced analyses for 14 elements both analyses appear to represent sedimentary formation waters and are closely analogous to oil field brines a basement origin is precluded by the presence of bitumens and the low k ca ratios differences between the analyses probably reflect different source bed mineralogy including the presence or absence of dolomite but triassic red beds are likely to be a major source the occurrence of these brines in the fault planes provides constraints on both the sources and movement of the fluids involved in thrusting significant infiltration of either surface waters or metamorphic water of dehydration can be ruled out because of the high salinities typically 20 25 wt dissolved salts hence although permeability was locally high due to fracturing around the faults fluids were pumped into these fractures from sedimentary formations adjacent to the fault individual fluid pathways were short lived relative to the duration of the deformation event so that different fluids were pumped into the faults at different times in response to local fault propagation

stable isotopic evidence for large scale seawater infiltration in a regional metamorphic terrane the trois seigneurs massif pyrenees france oxygen isotopic analyses of 95 metamorphic and igneous rocks and minerals from a hercynian metamorphic sequence in the trois seigneurs massif pyrenees france indicate that all lithologies at higher metamorphic grades than the andalusite in isograd have relatively homogeneous 18o values the extent of homogenization is shown by the similarity of 18o values in metacarbonates metapelites and granitic rocks 11 to 13 and by the narrow range of oxygen isotopic composition shown by quartz from these lithologies these values contrast with the 18o values of metapelites of lower metamorphic grade 18o about 15 homogenization was caused by a pervasive influx of hydrous fluid mass balance calculations imply that the fluid influx was so large that its source was probably high level groundwaters or connate formation water hydrogen isotopic analyses of muscovite from various lithologies are uniform and exceptionally heavy at d 25 to 30 suggesting a seawater origin many lines of petrological evidence from the area independently suggest that metamorphism and anatexis of pelitic metasediment occurred at depths of 6 12 km in the presence of this water rich fluid the composition of which was externally buffered deep penetration of surface waters in such environments has been hitherto unrecognized and may be a key factor in promoting major anatexis of the continental crust at shallow depth three types of granitoid are exposed in the area the leucogranites and the biotite granite quartz diorite are both mainly derived from fusion of local paleozoic pelitic metasediment because all these rocks have similar whole rock 18o values 11 to 13 the post metamorphic biotite granodiorite has a distinctly different 18o 9 5 to 10 0 and was probably derived from a deeper level in the crust rare mafic xenoliths within the deeper parts of the biotite granite quartz diorite also have different 18o 8 0 to 8 5 and possibly represent input of mantle derived magma which may have provided a heat source for the metamorphism