propagation of the great salinity anomaly of the 1990s around the northern north atlantic 1 time series of t and s extending through 2001 are used to describe propagation of the great salinity anomaly of the 1990s gsa 90s comparison of the distance time relations for the gsa 70s 80s and 90s reveals a substantial intensification of the large scale circulation in the northern north atlantic especially in the subarctic gyre between newfoundland and the faroes the advection rate of the gsa 70s 80s and 90s between newfoundland and the faroe shetland channel is conservatively estimated to have been 3 5 10 and 10 cm s respectively the circulation intensification apparently occurred within a decade between the gsa 70s and 80s during the next decade the advection rate increased from 10 to 13 cm s between newfoundland and iceland basin the gsa 90s was advected towards the faroe shetland channel by the northern iceland basin s branch of the north atlantic current whereas the contribution of the southern branch via the rockall trough was minimal

evolution of the arctic ocean salinity 2007 08 contrast between the canadian and the eurasian basins the authors investigate the variability of salinity in the arctic ocean and in the nordic and labrador seas over recent years to see how the freshwater balance in the arctic and the exchanges with the north atlantic havebeenaffectedbytherecentimportantseaicemelting especiallyduringthe2007seaiceextentminimum the global ocean reanalysis and simulations glorys1 global ocean reanalysis based on a global coupled ocean sea ice model with an average of 12 km grid resolution in the arctic ocean is used in this regard althoughno seaicedataandnodataunderseaiceareassimilated simulationoverthe2001 09period is shown to represent fairly well the 2007 sea ice event and the different components accounting for the ocean and sea ice freshwater budget compared to available observations in the reanalysis the 2007 sea ice minimum isdueto anincreaseof thesea iceexportthroughframstrait 25 andan importantseaice meltin the arctic 75 liquid freshwater is accumulated in the beaufort gyre after 2002 in agreement with recent observations and it is shown that this accumulation is due to both the sea ice melt and a spatial redistribution of the freshwater content in the canadian basin in the eurasian basin a very contrasting situation is found with an increase of the salinity the effect of the sea ice melt is counterbalanced by an increase of the atlantic inflow and a modification of the circulation north of fram strait after 2007 the authors suggest that a strong anomaly of the atmospheric conditions was responsible for this change of the circulation

thinning and volume loss of the arctic ocean sea ice cover 2003 2008 1 we present our best estimate of the thickness and volume of the arctic ocean ice cover from 10 ice cloud and land elevation satellite icesat campaigns that span a 5 year period between 2003 and 2008 derived ice drafts are consistently within 0 5 m of those from a submarine cruise in mid november of 2005 and 4 years of ice draft profiles from moorings in the chukchi and beaufort seas along with a more than 42 decrease in multiyear my ice coverage since 2005 there was a remarkable thinning of 0 6 m in my ice thickness over 4 years in contrast the average thickness of the seasonal ice in midwinter 2 m which covered more than two thirds of the arctic ocean in 2007 exhibited a negligible trend average winter sea ice volume over the period weighted by a loss of 3000 km3 between 2007 and 2008 was 14 000 km3 the total my ice volume in the winter has experienced a net loss of 6300 km3 40 in the 4 years since 2005 while the first year ice cover gained volume owing to increased overall area coverage the overall decline in volume and thickness are explained almost entirely by changes in the my ice cover combined with a large decline in my ice coverage over this short record there is a reversal in the volumetric and areal contributions of the two ice types to the total volume and area of the arctic ocean ice cover seasonal ice having surpassed that of my ice in winter area coverage and volume became the dominant ice type it seems that the near zero replenishment of the my ice cover after the summers of 2005 and 2007 an imbalance in the cycle of replenishment and ice export has played a significant role in the loss of arctic sea ice volume over the icesat record

the late archean history of the wyoming province as recorded by granitic magmatism in the wind river range wyoming abstract the wyoming province a small ca 500 000 km 2 archean craton is the most southwestern of the archean provinces in north america it is composed primarily of late archean potassium rich granitic rocks in contrast to many other archean provinces rocks of tonalite trondhjemite affinity are rare over most of the province and are restricted to rocks older than 2 8 ga field petrologic geochemical and isotopic study of the late archean granites exposed in the wind river range have allowed us to identify at least four periods of potassic calc alkalic magmatism at 2 8 2 67 2 63 and 2 55 ga granitic rocks of these ages appear to be widespread across the wyoming province the oldest calc alkalic granites of the wind river range emplaced at ca 2 8 ga appear to be derived predominantly from pre existing crust however nd isotopic data suggest that these granites cannot be the product solely of partial melting of older tonalitic gray gneisses during at least two other periods of plutonism at 2 67 and 2 63 ga generation of the wind river range batholiths involved the incorporation of substantial amounts of isotopically juvenile material either from depleted mantle or young continental crust the information presented below as well as data available from elsewhere in the wyoming province is interpreted to suggest that the wyoming province unlike other archean cratons is not composed of a tectonic amalgamation of smaller exotic terranes although the wyoming province did experience crustal addition in archean time it was not by lateral accretion but by incorporation of mantle derived melts into large granitic batholiths

characterization of natural colloids from a river and spring in a karstic basin colloids are known to transport contaminants over long distances in natural media despite this potentially harmful effect very few studies have been undertaken in subsurface aquifers this paper presents the first results of a study of natural colloids and particles in a karstic aquifer the site was chosen for its coverage by clay layers and peat which deliver various and numerous particle types in water the methodological part describes three methods used for size determination and sample fractionation of surface water and spring water these methods have been adapted for the treatment of multiple samples due to the rapid discharge variation typical of karstic aquifers the analysis of many particle size distributions psd shows that they can be described by a pareto law the variation of the slope of the psd at the spring is mainly dependent on discharge this behavior is interpreted as a washing of the karstic drains during the first phase of high flow events fractionation of the samples allowed application of various characterization techniques to particle size classes x ray diffraction xrd patterns showed that most of the mineral particles originated from quaternary deposits and limestones however the use of scanning electron micrsocopy with energy dispersive spectrometer sem eds detailed the composition of individual particles and revealed particles not found by xrd these techniques also showed the high complexity of the natural particles and the important place of coprecipitation in their formation consequences on the fluxes of particulate matter and its potential role as a carrier of contaminants are discussed

melt segregation and magma interactions during crustal melting breaking out of the matrix abstract differentiation of the continental crust begins with its partial melting the products of crustal melting are silicic hydrous h2o undersaturated granitic liquids that are generated within matrices of residual crystals crustal differentiation requires that felsic magmas form and escape from these solid residua an important question is whether granitic magmas collect into large batches within or near their sources which then give rise to ascent or alternatively bleed out of the sources in smaller streams or pulses we demonstrate that the physical reality is closer to the second alternative and thus question the validity of the concepts of magma segregation and source fertility as they are sometimes visualised granitic plutons contain chemically distinct sub populations formed by source level entrainment of the peritectic assemblages into the melts rapid evacuation at source levels and high ascent rates protect the magmas from wall rock interactions during their tenure at source depths and during their ascent through cool upper crust the existence of different types of granites and hence of clearly defined chemically different magmas within plutons dictates that felsic magmas must separate efficiently from their anatectic sources and must ascend to the sites of their emplacement with minimal chemical interaction with crust through which the magma must move exposed deep crustal sections are typically lithologically diverse with the more fertile rocks commonly forming discrete layers surrounded by rocks with contrasting compositions if the melts were required to segregate and accumulate into large volumes within their hot sources especially by slow gravity driven melt percolation it is very likely that they would be substantially modified by reaction with diverse source rocks thus the processes mooted to occur in melting assimilation storage and homogenisation mash or deep crustal hot dch zones would act to erase original compositional heterogeneities and produce larger batches of more homogeneous magma perhaps carrying evidence of extensive magma mixing from various lines of evidence we conclude that mash and dch zones may not exist and even if they do they cannot form the sources of most granitic magmas the intrinsic heterogeneity in crustal source rocks the likely occurrence of peritectic assemblage entrainment and the inefficiency of magma mixing decree that granitic rocks will retain source inherited chemical and isotopic heterogeneities rapid semi continuous and disequilibrium withdrawal of small magma batches from source rocks means that elements of whole rock trace element chemistry and accessory mineral chemistry will be decoupled from major element variations this also means that a large source with low nominal fertility due to low hydrous mineral content for example could still produce a substantial granitic pluton by additions of individually small increments of magma

what drove the dramatic retreat of arctic sea ice during summer 2007 1 a model study has been conducted of the unprecedented retreat of arctic sea ice in the summer of 2007 it is found that preconditioning anomalous winds and ice albedo feedback are mainly responsible for the retreat arctic sea ice in 2007 was preconditioned to radical changes after years of shrinking and thinning in a warm climate during summer 2007 atmospheric changes strengthened the transpolar drift of sea ice causing more ice to move out of the pacific sector and the central arctic ocean where the reduction in ice thickness due to ice advection is up to 1 5 m more than usual some of the ice exited fram strait and some piled up in part of the canada basin and along the coast of northern greenland leaving behind an unusually large area of thin ice and open water thin ice and open water allow more surface solar heating because of a much reduced surface albedo leading to amplified ice melting the arctic ocean lost additional 10 of its total ice mass in which 70 is due directly to the amplified melting and 30 to the unusual ice advection causing the unprecedented ice retreat arctic sea ice has entered a state of being particularly vulnerable to anomalous atmospheric forcing

extended history of a 3 5 ga trondhjemitic gneiss wyoming province usa evidence from upb systematics in zircon abstract the beartooth bighorn magmatic zone bbmz and the montana metasedimentary province mmp are two major subprovinces of the archean wyoming province in the northwestern beartooth mountains these subprovinces are separated by a structurally lithologically and metamorphically complex assemblage of lithotectonic units that include 1 a strongly deformed complex of trondhjemitic gneiss and interlayered amphibolites and 2 an amphibolite facies mafic unit that occurs in a nappe that structurally overlies the gneiss complex zircons from a trondhjemitic blastomylonite in the gneiss complex yield concordant u pb ages of 3 5 ga establishing it as the oldest rock yet documented in the wyoming province two younger events are also recorded by zircons in this rock 1 an apparently protracted period of high grade metamorphism and or intrusion of additional magmas at 3 25 ga and 2 growth of hydrothermal zircon at 2 55 ga apparently associated with ductile deformation that immediately preceded structural emplacement of the gneiss although this latter event appears confined to areas along the bbmz mmp boundary evidence of 3 25 ga igneous activity is found in the overlying amphibolite 3 24 ga and throughout the mmp these data suggest that this boundary first developed as a major intracratonic zone of displacement at or before 3 25 ga the limited occurrences of 2 8 ga magmatic activity in the mmp suggest that it had a controlling influence on late archean magmatism as well

in suspect terrane provenance of the late archean phantom lake metamorphic suite sierra madre wyoming the 2 68 ga phantom lake metamorphic suite of the sierra madre is a volcanogenic volcaniclastic and siliciclastic sequence that may have been deposited on or near the margin of the wyoming province or alternatively it may represent part of an exotic block accreted onto the southern margin of the wyoming province the metamorphosed supracrustal rocks of the phantom lake metamorphic suite along with quartzofeldspathic gneisses and granitoids of similar age have light rare earth element lree enriched ree patterns with little to no eu anomaly these patterns are comparable to those of modern oceanic arc rocks and sediments both supracrustal and metaigneous rocks have radiogenic initial end from 4 5 to 2 5 and nd crustal residence ages between 2 7 and 3 0 ga it is proposed that these juvenile rocks were part of an intra oceanic arc system formed beyond the influence of detritus from the wyoming province and subsequently were accreted onto the southern wyoming province following intrusion of grani

cretaceous 100 ma high silica granites in the gajin area central tibet petrogenesis and implications for collision between the lhasa and qiangtang terranes abstract high silica granites that occur as isolated plutons are widely distributed in collisional orogenic belts and are considered a hallmark of continental collision processes the late mesozoic collision between the lhasa and qiangtang terranes along the bangong nujiang suture zone was key event in the evolution of the tibetan plateau however the timing of this collision remains debated here we report the ages and geochemical characteristics of granites from the gajin area in the north central lhasa terrane central tibet zircon u pb dating reveals that the gajin granites formed at 100 ma these granites exhibit uniformly high sio2 contents 74 9 78 4 wt are weakly peraluminous compositions and have high k2o moderate na2o and al2o3 and low fe2o3t mgo and cao contents they are characterized by enrichments in rb cs and u and by depletions in zr hf nb and ti these characteristics in combination with high rb sr ratios and pronounced negative eu anomalies indicate that the gajin granites are highly fractionated rocks the granites have enriched whole rock nd end t 4 3 to 2 9 and relatively depleted and slightly variable zircon hf ehf t 1 0 to 5 5 isotope compositions the gajin granites were probably generated by high degrees of crystal fractionations of magma produced by partial melting of mature crustal sources the cretaceous magmatic rocks in the north central lhasa terrane record a magmatic lull between 100 and 85 ma which corresponds to a transition in both geochemical composition e g hf nd isotopes and rock association at 100 ma combining the above characteristics with the development of a regional angular unconformity around the time of the formation of the granites we suggest that the initial continental collision between the lhasa and qiangtang terranes probably occurred between 110 and 90 ma therefore the 100 ma high silica granites in the gajin area were formed during the continuing continental convergence that followed the initial collision between the lhasa and qiangtang terranes the generation of discrete and monotonous high silica granites may constitute evidence for a significant tectonothermal transition in evolution of the continental crust

petrogenesis of late early cretaceous high silica granites from thebangong nujiang suture zone central tibet abstract high silica granites are common in collisional orogenic belts however the petrogenesis of such granites and the geodynamic processes associated with their emplacement are debated in this study we present zircon u pb ages and hf isotopes and whole rock geochemical and sr nd isotopic compositions for biotite granites from the jiang co area in the bangong nujiang suture zone central tibet zircon u pb dating reveals that the jiang co granites were emplaced during the late early cretaceous ca 114 ma these granites are characterized by high and variable sio2 69 7 78 2 wt and k2o 4 7 8 4 wt and low mgo 0 09 1 25 wt and p2o5

on the origins of water masses exported along both sides of greenland a lagrangian model analysis the origin of the water masses exported from the arctic to the north atlantic along both sides of greenland is investigated using an original numerical method a quantitative lagrangian analysis is applied to the monthly climatological 3 d output of a global ocean sea ice high resolution model it allows quantification of the different branches of the export to the north atlantic as well as related timescales and water mass transformations in the model the outflow through davis strait consists in equal parts of pacific and atlantic water whilst the export through fram strait consists almost fully of atlantic water contrary to observations pacific water is transferred quickly o 10 years to the north atlantic through the beaufort gyre where gradual warming and salinification occur atlantic water exiting in the surface layer along both sides of greenland remains about 10 years in the arctic basin and undergoes cooling and significant freshening below the surface water atlantic water exiting through the intermediate and deep layers in fram strait follows different pathways in the arctic with trajectories being subject to topography constraints the travel time depends strongly on the pathway from 1 to 1000 years the intermediate outflow consists mainly of water entering the arctic at fram strait while half the deep outflow is composed of water from the barents sea we find that the barents sea branch which contributes to both the outflows at fram and davis straits is almost fully transformed after a year due to heat exchanges with the very cold atmosphere in the barents sea

archean tectonics of the north snowy block beartooth mountains montana the north snowy block nsb northwestern beartooth mountains montana is composed of seven major lithologic units of archean age 1 mount cowen granitic augen gneiss 2 a paragneiss unit that consists of a variety of quartzofeldspathic gneisses psammitic schists amphibolites and iron formation 3 an augen textured granitic sill 4 the phyllitic davis creek schist 5 a trondhjemitic gneiss amphibolite complex 6 the pine creek nappe complex a regional isoclinal structure with an amphibolite core and symmetrically disposed marble and quartzite and 7 a supracrustal migmatite complex that consists of a quartzite amphibolite unit and a heterogeneous gneiss with lit par lit injections of granitic material into the supracrustal rocks each unit has its own distinct lithologic assemblage metamorphic grade and structural style the contacts between most units are marked by mylonitic rocks which are interpreted as the products of ductile faulting and abrupt changes in metamorphic grade in

the composite archaean grey gneisses petrological significance and evidence for a non unique tectonic setting for archaean crustal growth abstract the geodynamic context of formation of the archaean continental crust is a matter of debate the crust is largely made of grey gneiss complexes a composite rock assemblage dominated by granitoids that are generally regarded as belonging to the ttg tonalite trondhjemite granodiorite series using a large database of published ttg and grey gneiss compositions it is possible to show that the granitoids forming grey gneiss complexes actually belong to at least four main geochemical groups i a potassic component made of granodiorites and formed by melting of existing crustal lithologies and ii three sodic groups ttg proper that comprise low medium and high pressure groups the geochemistry of the low pressure group is consistent with derivation from a plagioclase and garnet amphibolite the medium pressure group was formed in equilibrium with a garnet rich plagioclase poor amphibolite whereas the high pressure group derived from a rutile bearing eclogite as the temperature of melting of metamafic rocks is largely independent from pressure this corresponds to melting along a range of contrasting geothermal gradients in turn reflecting a range of tectonic sites for the formation of the archaean continental crust

salinity trends on the siberian shelves 1 we present an analysis of observed long term 100 year salinity trends on the freshwater dominated siberian continental shelves a multiple regression was performed in the white sea ws the kara sea ks the laptev sea ls and the east siberian sea ess since 1930 the ws has gained freshwater while the ess has lost it consistent with river discharge trends over this period over the past 20 years increases in both river discharge and direct precipitation can explain observed salinity decreases in the ws but not in the ks salinity trends in the ls and ess indicate that ocean circulation plays a dominate role in these areas where in recent years freshwater has been diverted eastward along the coast rather than northward toward the deep ocean

isotopic studies of the late archean plutonic rocks of the wind river range wyoming isotopic studies of the rb sr and u th pb systems in whole rock samples and the u pb systematics for zircons document the existence of two late arehean intrusive events in the wind river range all of the systems examined indicate an age of 2 630 20 m y for the louis lake batholith apparent ages for the bears ears pluton range from 2 504 40 m y to 2 575 50 m y the scatter in apparent ages for the bears ears pluton does not appear to be primarily the result of disturbance by postintrusive events but it may be explained by an isotopically inhomogenous magma at the time of intrusion data for a few samples indicate that the wind river range was affected locally by a postmagmatic hydrothermal event that was approximately tertiary in age this event lowered 18 o values and disturbed parent daughter relationships in most of the isotopic systems investigated but it was recent enough that there is no demonstrable effect in the pb pb system the bears ears pluton has some chemical and petrologic features that are similar to those reported for the granites in the granite mountains to the east these granites are spatially associated with low temperature uranium deposits of tertiary age and have been shown to have lost large amounts of uranium during the early to middle tertiary u pb systematics indicate however that the low to moderate uranium contents and highly variable th u values noted for the bears ears pluton are best interpreted as being primary features if uranium was lost after magma generation the loss most likely occurred at the time of intrusion such a loss could account for uraniferous precambrian pegmatites southwest of the main part of the range the two intrusive units apparently were derived from different protoliths that were formed during early to middle archean initial isotopic ratios and petrochemistry for the louis lake batholith are consistent with an early archean trondhjemitic to tonalitic source the protolith for the bears ears pluton must have been more evolved and somewhat younger inconsistencies as to the degree of evolution of this protolith as inferred from isotopic and trace element data suggest that the protolith may have been subjected to high grade meta morphism that caused loss of rb and u prior to generation of the magma

origin of the charnockites of the louis lake batholith wind river range wyoming the 2 63 ga louis lake batholith a calc alkalic pluton exposed opxand fayalite fay bearing felsic igneous rocks inin wind river range of western wyoming consists of minor diorite clude opdalite opx granodiorite enderbite opx tonalquartz diorite granodiorite and granite at shallow structural levels ite and mangerite opx monzonite le maitre et al the batholith is pyroxene free but at deeper levels all units of the 1989 many of these rock names are not commonly batholith contain pyroxenes on its northern margin the batholith used the term charnockite sensu lato is typically applied was emplaced at p 5 6 kbar t 775 800 c fo2 at to any opx bearing granitoid regardless of its bulk fmq fayalite magnetite quartz 1 5 to fmq 1 8 and composition for example the charnockite suite of south ah2o 0 1 along the southern margin of the batholith the india includes enderbites opdalites and charnockites emplacement pressure was 3 kbar the batholith includes two howie 1955 the nigerian suite includes charnockite compositional series the peraluminous high ree series is rich in and opdalite olarewaju 1987 and that of lofoten is k2o and displays larger feo feo mgo the metaluminous associated with mangerites malm ormaasen 1978 low ree series has less k2o and smaller feo feo mgo because the terms enderbite and opdalite are so rarely in the boulder canyon area most of the rocks belong to the lowused in this paper we use the term charnockite for all ree series the nd pb and sr initial isotopic compositions of opx bearing granitic rocks where it is important to both series vary and do not correlate with sio2 abundance relatively describe a specific rock type we use opx as a varietal constant fe mg ratios over a wide range of sio2 and the large modifer to the rock name e g opx granodiorite instead variation in initial isotopic compositions indicate that the sources of opdalite for the louis lake batholith include older wyoming province crustin the 1980s workers in southern india recognized and mantle derived mafic melts the calc alkalic nature of the areas where biotite bearing granitic gneiss had been boulder canyon charnockites indicates that there is no special cconverted to pyroxene bearing gneiss along fluid pathtype magma instead charnockites will form in any rock type if ways janardhan et al 1982 friend 1985 this led to the water activity is low enough the term charnockitization srikantappa et al 1985 and the concept that charnockite is a metamorphic rather than an igneous rock as a result charnockite has been used incorrectly by some workers as a synonym for

retreat of the cold halocline layer in the arctic ocean we present a comparison of arctic ocean hydrographic data sets from the 1990s with a focus on changes in the upper few hundred meters of the eurasian basin the most recent observations discussed here were collected during the spring 1995 scientific ice expedition scicex 95 the second in a series of scientific cruises to the arctic ocean aboard u s navy nuclear submarines although the 1990s have seen an abundance of synoptic cruises to the arctic this was the only one to take place in winter spring conditions other data considered here were collected during the first scicex cruise in summer 1993 scicex 93 and during an icebreaker cruise to the eurasian basin in summer 1991 oden 91 a new russian american winter climatology is also used as a reference these comparisons reveal that the eurasian basin cold halocline layer has retreated during the 1990s to cover significantly less area than in previous years specifically we find a retreat from the amundsen basin back into the makarov basin the latter is the only region with a true cold halocline layer during scicex 95 changes are also seen in other halocline types and in the atlantic water layer heat content and depth since the cold halocline layer insulates the surface layer and thus the overlying sea ice from the heat contained in the atlantic water layer this should have profound effects on the surface energy and mass balance of sea ice in this region using a simple mixing model we calculate maximum ice ocean heat fluxes of 1 3 w m 2 in the eurasian basin where during scicex 95 the surface layer lay in direct contact with the underlying atlantic water layer the overall cause of water mass changes in the 1990s might have been a shift in the atmospheric wind forcing and resulting sea ice motion during the late 1980s which we speculate influenced the location where fresh shelf waters flow into the deeper basins of the arctic ocean finally we discuss two different mechanisms that have been proposed for cold halocline water formation and we propose a compromise that best fits these data

high silica granites terminal porosity and crystal settling in shallow magma chambers abstract high silica 70 wt sio2 granites hsgs are important carriers of highly incompatible elements thus understanding their origin is relevant to understanding how the composition of the continental crust evolves we examined a large scale geochemical study of plutons in the peninsular ranges batholith in southern california usa to better understand the petrogenetic relationships between hsgs and the batholith using highly incompatible and compatible elements we show that hsgs represent residual liquids within a felsic 69 72 wt sio2 magmatic crystal mush at crystal fractions of 50 60 and residual liquid fractions of 40 50 trace element systematics show that separation of the hsg liquid from the crystal mush is inefficient such that no more than 70 80 of the hsg is fully extracted and the remaining greater than 20 30 remains trapped in cumulate mush we find little evidence of more efficient liquid crystal segregation which suggests that compaction induced segregation may be too slow to be important on a large scale instead the terminal porosity of 20 30 coincides with theoretical maximum packing fraction of unimodal particles settled out of suspension 0 74 which may indicate that crystal settling perhaps in the form of hindered settling drives segregation of viscous silicic melts and crystals unlike compaction settling operates on timescales of 1 10 ky fast enough to generate large volumes of hsg and complementary cumulates with trapped melt before magma chambers freeze many felsic plutons may thus be cumulates but because of trapped melt they are difficult to geochemically distinguish from plutons whose compositions fall along liquid lines of descent the approach here using a combination of highly incompatible and compatible elements provides a way of identifying and quantifying trapped melt fractions finally we show that hsgs appear to form only in the shallow crust

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

the great salinity anomaly in the northern north atlantic 1968 1982 the widespread freshening of the upper 500 800m layer of the northern north atlantic which this paper describes represents one of the most persistent and extreme variations in global ocean climate yet observed in this century though a range of explanations have been advanced to explain this event including in situ changes in the surface moisture flux this paper describes the great salinity anomaly as largely though not entirely an advective event traceable around the atlantic subpolar gyre for over 14 years from its origins north of iceland in the mid to late 1960s until its return to the greenland sea in 1981 1982 the overall propagation speed around this subpolar gyre is estimated at about 3cm s 1 of the total salt deficit associated with the anomaly as it passed south along the labrador coast in 1971 1973 about 72 109 tonnes a deficit equivalent to about two thirds of this figure 47 109 tonnes ultimately passed through the faroe shetland channel to the barents sea arctic ocean and greenland sea during the mid 1970s possible effects on deep water formation and on the representativeness of historical section data are discussed

freshwater fluxes in the east greenland current a decade of observations 1 over a decade of mooring measurements in the western fram strait at 78 50 n shows that the annual mean liquid freshwater flux fwf in the east greenland current is relatively constant at 1274 453 km3 yr 1 40 4 14 4 msv despite the fact that the annual mean total volume transport of the egc has more than doubled since 2001 this is shown to be due to an increase of the transport in the deeper ocean and the fact that the largest fw content is present on the east greenland shelf and not in the core of the egc in order to capture the fwf on the shelf modeling results of naosim are included showing that a mean contribution of fwf on the shelf of at least 807 357 km3 yr 1 25 6 11 3 msv should be added to the fwf obtained for the egc when compared to the extra input of freshwater required to account for the 1960 1990 freshening of the northern north atlantic the observed variations in the 1998 2008 egc liquid freshwater fluxes are small

the origin of extensive neoarchean high silica batholiths and the nature of intrusive complements to silicic ignimbrites insights from the wyoming batholith u s a extensive intrusions composed entirely of biotite granite are common in neoarchean cratons these granites which have high silica and potassium contents are not associated with intermediate and mafic phases one such neoarchean granite batholith herein named the wyoming batholith extends more than 200 km across central wyoming in the granite and the laramie mountains from field characterization petrology geochemistry and nd isotopic data we establish that the magnesian wyoming batholith exhibits continental arc chemical and isotopic signatures it is best interpreted as a large upper crustal silicic batholith that likely formed when the subducting oceanic plate steepened or foundered bringing mantle heat and mass to the base of the crust similar cenozoic settings such as the altiplano puna plateau of the andes and the volcanic provinces of the western united states host large volumes of silicic ignimbrite the magma chambers supplying these eruptions are inferred to be silicic but the structural petrologic and geochemical details are unknown because the batholiths are not exposed we suggest that the wyoming batholith represents an analog for the plutonic complex underlying these ignimbrite systems and provides an opportunity to examine the shallow magma chamber directly our work establishes that aside from more leucocratic margins the sill like magma chamber is petrologically and chemically homogeneous consistent with effective mixing by vertical convection nd isotopic variations across the batholith indicate that horizontal homogenization is incomplete preserving information about the feeder system to the batholith and variations in magma sources the late archean earth may present optimal conditions for the formation of extensive granite batholiths like the wyoming batholith by this time the majority of the planet s continental crust had formed providing the environment in which differentiation distillation and assimilation could occur moreover the neoarchean earth s relatively high radioactive heat production provided the power to drive these processes

timing of plutonism deformation and metamorphism in the yellowknife domain slave province canada u pb zircon titanite and monazite ages for plutonic rocks are used to constrain the timing of post 2660 ma deformational and metamorphic events in the yellowknife domain southern slave province diorite and tonalite plutons of the defeat suite yield ages of 2628 3 and 2624 3 ma older than previous less precise estimates for this suite of ca 2618 2620 ma the defeat suite plutons crosscut and postdate upright f1 folds in turbidites of the ca 2680 2660 ma burwash formation d1 deformation is therefore bracketed between 2660 and 2630 ma the d1 event significantly predates deposition of polymict conglomerates of the jackson lake formation a second folding event f2 represented by northwest to north trending steeply plunging folds of bedding and d1 structures affected the area after intrusion of the hidden lake pluton at 2606 2 ma and synchronously with intrusion of the 2596 2 ma sparrow lake pluton a member of the two mica granite prosperous suite the time of initiation and the duratio

archean geochronological framework of the bighorn mountains wyoming the bighorn mountains of the central wyoming province expose a large tract of archean crust that has been tectonically inactive and at relatively high crustal levels since 2 7 ga seven sensitive high resolution ion microprobe shrimp u pb zircon and titanite age determinations on samples of the main lithologic units provide a geochronological framework for the evolution of this area the oldest precisely dated magmatic event occurred at 2950 5 ma when diorite to granite dykes and sills intruded an older gneiss complex exposed in the central and southern bighorn mountains rocks as old as 3 25 ga may be present in this gneissic basement as indicated by the oldest dates obtained on areas of zircon grains that are interpreted as inherited cores a tonalitic gneiss was intruded into the gneiss complex at 2886 5 ma deformation of the central and southern gneisses preceded the intrusion of the bighorn batholith a tonalitic to granitic intrusion that occupies the northern portion of the uplift this