ultra long waves and two dimensional rossby waves abstract the characteristics of planetary wave dispersion in the wintertime troposphere are investigated on the basis of 5 day mean 500 mb height data for 30 winters making use of simple analysis techniques involving lag correlation maps for individual gridpoints and for fourier coefficients of zonal wavenumbers 1 and 2 on 50 n it is shown that the time evolution of the planetary waves is dominated by energy dispersion through longitudinally localized wavetrains with great circle route orientations revealed most clearly by the lag correlation maps for individual gridpoints when the polarity of these localized patterns is such that large anomalies of like opposing sign appear in the atlantic and pacific sectors near 50 n a strong zonal wavenumber 2 1 pattern results these wavenumber 1 and 2 patterns do not retain their identity from one 5 day period to the next as distinctly as the localized wavetrains do the conceptual model of rossby wave propagation along latitude circles still appears to b

precise u pb zircon dating of a post d2 meta dolerite constraints for rapid tectonic development of the southern adelaide fold belt during the cambrian numerous morb like mafic dykes plugs and sills intruded the kanmantoo group and older meta sediments of the southern adelaide fold belt from pre d1 to post d2 during the delamerian orogeny a post d2 meta dolerite yields a precise u pb zircon age of 510 2 ma this age combined with a published shrimp zircon age of 526 4 ma reveals a rapid tectonic evolution of the fold belt during the cambrian events including the thick kanmantoo group9s deposition major mafic magmatism low p high t regional metamorphism and multiple deformations all took place from about 526 to 510 ma this rapid evolution supports the suggestion that the heat source for the metamorphism originated from continental extension associated with mantle upwelling and mafic magmatism

rb sr sm nd and pb isotope systematics of pyrite implications for the age and genesis of lode gold deposits lode gold deposits commonly consist of pyrite and lesser amounts of lead and zinc sulfides accompanied by quartz and calcite their exact origin remains controversial mainly because of the scarcity of reliable geochronological data here we present direct rb sr dating of pyrite from a lode gold deposit and propose the method as a useful geochronological technique for gold mineralization for which age data are poor a positive correlation between present day 87 sr 86 sr and 87 rb 86 sr ratios of pyrite fes 2 subsamples from the linglong gold mine of china corresponds to an age of 122 123 ma which dates the age of gold mineralization the sr nd and pb isotopic compositions of pyrites and the associated rocks suggest that the hydrothermal fluids responsible for the pyrite and gold mineralization were probably derived from a mixed source i e degassing of mafic magmas and meteoric water that had leached the country rocks

influence of the antarctic circumpolar wave on australian precipitation from 1958 to 1997 abstract year to year changes are found in australian precipitation app covarying with those in sea surface temperature sst and troposphere moisture flux mf over the three oceans surrounding australia for 40 yr from 1958 to 1997 australia s wet dry years are associated with warm cool sst anomalies surrounding australia and convergent divergent mf anomalies directly overhead differences in app sst between wet and dry years can reach 0 75 m 1 2 c in northeast australia subtropical indian ocean wet dry years often occur during la nina el nino but significant differences in covarying sst mf and app anomalies from one el nino to the next are found indicating that regional climate changes also influence app covarying sst and mf anomalies on basin space scales and interannual timescales are found to take 2 3 yr to propagate eastward from africa to australia this propagation occurs in association with the antarctic circumpolar wave acw in the southern ocean the north branch of th

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

the effects of enhanced sea ice export from the ross sea on recent cooling and freshening of the southeast pacific abstractthe top 2000 m of the southern ocean has freshened and warmed over recent decades however the high latitude south of 50 s southeast pacific was observed to be cooler and fresher in the

petrogenesis of the late jurassic peraluminous biotite granites and muscovite bearing granites in se china geochronological elemental and sr nd o hf isotopic constraints biotite granites and muscovite bearing granites are dominant rock types of the widespread granites in se china however their petrogenesis has been enigmatic a combined study of zircon u pb dating and lu hf isotopes whole rock element geochemistry and sr nd o isotopes was performed for three late mesozoic granitic plutons xinfengjie jiangbei and dabu in central jiangxi province se china all the plutons are composed of biotite granites and muscovite bearing granites that have been poorly investigated previously the new data not only allow us to assess their sources and magma evolution processes but also helps us to better understand the genetic link to the large scale polymetallic mineralization in se china la icp ms zircon u pb dating shows that three plutons were emplaced in the late jurassic 159 148 ma and that the muscovite bearing granites are almost contemporaneous with the biotite granites the biotite granites have sio2 contents of 70 3 74 4 wt and are weakly to strongly peraluminous with asi from 1 00 to 1 26 and show a general decrease in asi with increasing sio2 they have relatively high zircon saturation temperatures t zr 707 817 c most 745 c and show a general decrease in t zr with increasing sio2 they have high initial 87sr 86sr ratios 0 7136 to 0 7166 and high 18o values 9 1 12 8 most 9 5 and clearly negative e nd t 9 5 to 11 8 and e hf t in situ zircon 13 1 to 13 5 the muscovite bearing granites have high sio2 contents 74 7 78 2 wt they are also weakly to strongly peraluminous with asi of 1 04 1 18 but show a general increase in asi with increasing sio2 they have relatively low t zr 671 764 c most 9 5 and e hf t in situ zircon of 11 3 to 13 1 geochemical data suggest the origin of the biotite granites and muscovite bearing granites as follows partial melting of precambrian metasedimentary rocks mainly two mica schist in the lower crust at temperatures of ca 820 c generated the melts of the less felsic biotite granites such primary crustal melts underwent biotite dominant fractionation crystallization forming the felsic biotite granites progressive plagioclase dominant fractionation crystallization from the evolved biotite granites produced the more felsic muscovite bearing granites thus the biotite granites belong to the s type whereas the muscovite bearing granites are highly fractionated s type granites we further suggest that during the formation of the muscovite bearing granites the fractional crystallization was accompanied by fluid fractionation and most likely the addition of internally derived mineralizing fluids that is why the large scale polymetallic mineralization is closely related to the muscovite bearing granites rather than biotite granites in se china this is important to further understand the source and origin of biotite granites and muscovite bearing granites in se china even worldwide

a paleozoic suture in eastern gondwanaland a new tectonic interpretation of southeastern australia tasmania and north victoria land antarctica is given in which a major n s trending lineament representing a suture zone is recognized separating essentially shallow water shelf and continental deposits of latest cambrian or early ordovician age from deeper water ordovician flysch deposits lateral offset of this lineament which is interpreted as a suture along which thrust telescoping and major strike slip faulting occurred could adequately explain the present distribution of major rock types in the three areas and also removes a number of problems previously encountered in correlation

reestablishing the circumpolar wave in sea ice around antarctica from one winter to the next remarkable correlation exists between warm water poleward winds over the ocean and low sea ice concentrations and extents over the winter sea ice pack around antarctica even to the point of continuing paterns across the ice sea boundary since the wind stress associated with poleward wind is expected to compact the ice during sea ice edge retraction we conclude that the memory of the antarctic circumpolar wave in the sea ice pack is carried from one austral winter to the next by the neighboring water temperatures since the sea ice pack retracts nearly to antarctica in austral summer

sm nd isotopic evidence for the provenance of sediments from the adelaide fold belt and southeastern australia with implications for episodic crustal addition abstract in south australia late proterozoic and cambrian sediments were deposited in basins formed within archaean to early mid proterozoic basement these sequences were subsequently deformed and uplifted by the cambro ordovician delamerian orogeny to form the adelaide fold belt in using the adelaide fold belt to address models for lithospheric evolution it is necessary to understand the mechanisms of basin formation and whether the sequences merely reflect reworking of existing cratonic material or if there were new crustal additions this study presents geochemical and isotopic data on the sediments and basement rocks to complement existing data on the delamerian igneous rocks as a means of investigating these questions the data reveal that the archaean mid proterozoic basement rocks of the gawler craton have nd depleted mantle model ages which average about 2 6 ga and nd values at 800 ma in the range 9 to 24 or at 500 ma from 11 to 28 the late proterozoic adelaidean sediments however have an average model age of 1 9 ga and initial nd values in the range 5 to 11 the sequence can be divided into lowermost rift phase sediments derived from erosion of local gawler craton material and a subsequent widely distributed thermal sag phase sedimentation whose isotopic signature is not compatible with the basement this implies that a more primitive or juvenile source was accessed via broadening of the provenance region the cambrian sediments have slightly older model ages 2 1 ga and lower nd 9 to 13 and can be interpreted as mixtures of basement and reworked adelaidean detritus the early palaeozoic sedimentary sequences of the lachlan fold belt to the east have isotopic compositions very like the south australian late proterozoic and cambrian sequences they have an average model age of 1 85 ma but much higher k 2 o na 2 o this indicates that the widespread flysch of eastern australia is the result of recycling of the late proterozoic and cambrian sediments by erosion of the adelaide fold belt with some modification by the mixture of the cambro ordovician mafic and felsic magmatic rocks in this orogen our data suggest regional intracontinental crustal evolution combined with recycling of older crustal material with new additions from the mantle during orogenesis and to a lesser extent episodes of extension and sedimentation

shrimp u pb geochronological constraints on archean volcanic hosted massive sulfide and lode gold mineralization at mount gibson yilgarn craton western australia the base metal rich mount gibson gold deposits are hosted within the ductile mount gibson shear zone in the retaliation greenstone belt of the murchison province of the archean yilgarn craton the deposits are unique in the context of the yilgarn as they exhibit two main styles of hydrothermal alteration and sulfide mineralization consistent with overprinting of synvolcanic volcanic hosted massive sulfide style mineralization by synorogenic shear hosted lode gold mineralization on the basis of model ages based on sulfide pb isotope ratios these two events are separated by approximately 300 m y subvolcanic intrusive rocks from within the host sequence to mineralization at the orion two and hornet deposits have shrimp ii zircon u pb ages of crystallization of 2929 or 3 and 2934 or 6 ma respectively these ages are within error and provide a minimum age for the host sequence and consequently the volcanic hosted massive sulfide mineralizing event at mount gibson on the basis of geochemical evidence the intrusions are interpreted to have been derived from the same parent magma as the rocks they intrude and consequently ca 2930 ma is probably the approximate age of the host rocks to mineralization the regional granitoid which intrudes the base of the greenstone belt has a crystallization age of 2935 or 3 ma a post tectonic granite porphyry which crops out approximately 25 km north northeast of the mount gibson mine site has a shrimp ii zircon u pb crystallization age of 2623 or 7 ma this granitoid has identical field relationships similar whole rock geochemistry and similar pb isotope ratios to those of an internal granitoid which cuts gold mineralization in the deep south pit and is consequently interpreted to be cogenetic and contemporaneous the 2623 or 7 ma date is therefore interpreted to be a minimum age for synorogenic gold mineralization at mount gibson a morphologically and chemically distinctive population of zircons extracted from the sample of 2934 ma altered felsic schist from the hornet deposit gives a shrimp ii zircon u pb age of 2627 or 13 ma these zircons have characteristics which are consistent with a hydrothermal origin and the age is interpreted to represent the timing of synorogenic gold mineralization at mount gibson the interpreted mineralization age is within error of the inferred age of the postmineralization post tectonic granitoid the age is also within error of the majority of absolute ages for gold mineralization from across the yilgarn craton which generally fall in the range 2630 or 10 ma shrimp zircon u pb geochronology thus provides strong support for the two stage model proposed for mineralization at mount gibson synvolcanic volcanic hosted massive sulfide style mineralization occurred at ca 2930 ma and was overprinted by lode gold mineralization some 300 m y later at ca 2630 ma

oceanic plateaus the fragmentation of continents and mountain building many anomalous rises in today s oceans may be submerged continental fragments detached from previous continents ancient island arcs or basaltic piles formed by hot spots and spreading centers these rises are embedded in their respective moving oceanic plates and are fated to be consumed at active margins where such rises are being consumed at present e g the nazca ridge they cause cessation of volcanism disruption of the downgoing slab and possible shifts in plate boundary configuration many past rises including numerous continental fragments have been recognized within mountain belts as allochthonous terranes they constitute a large portion of the orogenic belts in the north pacific from mexico through western north america alaska east siberia japan and in new zealand the orogenic deformation in these belts is possibly the result of the accretion of the allochthonous terranes many terranes have been accreted with substantial deformation also in the alpine chain well before major continent continent collisions it is suggested therefore that the accretion of fragments may be the common process of the deformation phase of mountain building subduction of normal oceanic crust may be insufficient for deformation whereas full continent continent collision may not be necessary the general validity of this conclusion depends critically on whether allochthonous terranes caused orogenic deformation in the andes or not most of the accreted fragments with continental affinities in the mesozoic cenozoic orogenic belts of the world can be traced back to the breakup of gondwana beginning with a pacifica domain in the permian through a larger india domain in the early mesozoic and continuing through the separation of the somalia plate in the near future the reasons for this 250 million year breakup process are not known but some kind of thermal process possible of mantle wide scale is implied

seismic structure of the southeast australian lithosphere from surface and body wave tomography abstract teleseismic arrival time residuals from the wombat transportable seismic array experiment are inverted to construct a high resolution 3 d p wave velocity model of the upper mantle beneath southeast australia in order to address one of the principal limitations of teleseismic tomography that long wavelength structure is filtered out when data from multiple arrays operating at different times are used an initial model with lower spatial resolution derived from surface tomography is constructed to preserve the broad scale features that would otherwise be lost although the absolute velocities of the final model are not strongly constrained due to the assumption of radial vp vs ratios and differences in regularisation the relative variations appear robust across all scales these reveal a wealth of features that can be related to the geology and tectonic history of the region the most significant being 1 an easterly dipping velocity transition zone which involves a higher velocity delamerian orogen extending beneath the western subprovince of a lower velocity lachlan orogen 2 a distinct region of low velocity in the upper mantle north of melbourne which can be associated with recent quaternary hot spot volcanism 3 a gradual east southeast decrease in velocity towards the coast which is consistent with lithospheric stretching and thinning near a passive margin and 4 a zone of high velocity north of adelaide that may correspond to the presence of the palaeoproterozoic curnamona province at depth these results have important implications for the palaeozoic evolution of the east margin of gondwana the subsequent break up of australia and antarctica and opening of the tasman sea

quasi stationary states in the southern hemisphere abstract pattern correlations between daily anomalies have been used to study the persistence of the southern hemisphere circulations the dataset consists of daily australian analyses of 500 mb heights and sea level pressure for the period from 1972 to 1983 compared to the northern hemisphere the pattern correlations are much lower and more variable in the southern hemisphere the mean one day lag autocorrelation is only 0 57 compared to 0 81 in the northern hemisphere the correlations increase significantly for the filtered anomalies which consist of the planetary wavenumbers from 0 to 4 subjective criteria based on the pattern correlations are used to select quasi stationary events a series of 5 or more daily maps is defined to be quasi stationary if the pattern correlations between all pairs of five consecutive maps in this time series are larger than or equal to 0 5 in winter quasi stationary events can be classified in terms of wavenumbers waves 3 and 4 are by far the dominant waves more

interdecadal changes of surface temperature since the late nineteenth century we present global fields of decadal annual surface temperature anomalies referred to the period 1951 1980 for each decade from 1881 1890 to 1981 1990 and for 1984 1993 in addition we show decadal calendar seasonal anomaly fields for the warm decades 1936 1945 and 1981 1990 the fields are based on sea surface temperature sst and land surface air temperature data the ssts are corrected for the pre world war ii use of uninsulated sea temperature buckets and incorporate adjusted satellite based ssts from 1982 onward our results extend those published in the 1990 intergovernmental panel on climate change scientific assessment and its 1992 supplement we assess the impact of various sources of error in the fields despite poor data coverage initially and around the two world wars the generally cold end of the nineteenth century and start to the twentieth century are confirmed together with the substantial warming between about 1920 and 1940 slight cooling of the northern hemisphere took place between the 1950s and the mid 1970s although slight warming continued south of the equator recent warmth has been most marked over the northern continents in winter and spring but the 1980s were warm almost everywhere apart from greenland the northwestern atlantic and the midlatitude north pacific parts of the middle to high latitude southern ocean may also have been cool in the 1980s but in this area the 1951 1980 climatology is unreliable the impact of the satellite data is reduced because the record of blended satellite and in situ sst is still too short to yield a climatology from which to calculate representative anomalies reflecting climatic change in the southern ocean however we propose a method of using existing satellite data in a step toward this target the maps are condensed into global and hemispheric decadal surface temperature anomalies we show the sensitivity of these estimated anomalies to alternative methods of compositing the spatially incomplete fields running decadal zonal means and annual global and hemispheric time series are also shown finally we discuss some salient features in terms of observed atmospheric circulation changes and of the results of climate model integrations with increasing atmospheric greenhouse gases

influence of basin architecture on the style of inversion and fold thrust belt tectonics the southern adelaide fold thrust belt south australia abstract the southern adelaide fold thrust belt involves neoproterozoic adelaidean strata deposited during protracted rift and sag phases and an overlying cambrian kanmantoo sequence represented by a thick wedge of turbidites rapidly deposited in an eastwards deepening basin deeply incised into the underlying rocks the belt was deformed during the delamerian orogeny developed at the southeastern margin of the australian craton during early palaeozoic nw directed displacement during this shortening event the margin of the kanmantoo basin was reactivated and formed a significant strain guide that controlled key features of the fold thrust belt strain integrated and restored sections reveal contrasting geometric and kinematic styles along the strike of the belt a transpressional zone is developed at the steep basin margin in the south oriented oblique to the structural grain the central parts of the belt are dominated by strong buttressing growth fault reactivation and basement involved footwall shortcut thrusting in the northern part of the belt shortening is accommodated by homogeneous folding above a master de collement these variations in regional structural style and internal strain partitioning reflect significant variations in the original kanmantoo basin margin geometry rheological parameters control the partitioning of strain associated with pervasive fabrics for example cleavage and transposed bedding folding is accompanied by negative line length changes shortening in the northern part of the belt in its thrusted central part pelites commonly show positive line length changes psammites were least affected by line length changes and thus provide key beds for section balancing pervasive strain makes a full restoration of cross sections impossible however incorporating regional strain data assists establishment of balanced and restorable sections which provide a powerful tool in understanding both pre deformational basin geometry and its shortening

tectonic affinity of the mathinna group in the lachlan fold belt abstract pre carboniferous rocks of tasmania comprise two disparate terranes which were brought together during the middle palaeozoic the eastern tasmania terrane consists of middle palaeozoic granitoids and the mathinna group a turbidite succession of ordovician to early devonian age the older part of the adjacent western tasmania terrane the only part of the southern tasmanides with exposed precambrian basement is related to the kanmantoo fold belt and older tectonic provinces located northwest of tasmania the younger part of the western tasmania terrane comprises upper cambrian to lower devonian terrestrial to shallow marine siliciclastics and carbonates a marked contrast to the coeval deep water deposits of the mathinna group the contact between the two terranes is concealed by the tamar valley in northern tasmania the main folds in the eastern tasmania terrane verge to the northeast whereas structures in the adjacent western tasmania terrane indicate tectonic transport to the southwest with the break in structural facing coinciding with the tamar valley reinvestigation of the structure of the westernmost eastern tasmania terrane where there is a large recumbent f1 fold 10 km extent in profile view raises the possibility that a second generation of structures previously regarded as of only local importance could have caused rotation of the upright to steeply west dipping axial surfaces of f1 folds to recumbent attitudes during southwesterly directed thrusting in this interpretation recumbent or near recumbent zones could reflect ramps in a sole thrust and the mid devonian imbricate thrust zone near beaconsfield on the west bank of the tamar river would be either the frontal thrust system or a splay off the sole thrust which continues westward beneath the exposed precambrian badger head block the implications of this new interpretation are that docking of the eastern and western tasmania terranes must have occurred after the ordovician but before the middle devonian during the consolidation phase there were two deformations of the mathinna group the first which occurred in the early devonian prior to emplacement of the st marys porphyrite 388 1 ma produced upright to locally overturned folds verging to the northeast the second which took place during the early middle devonian before deposition of givetian cave deposits resulted in the mathinna group being thrust southwestward this sense of thrusting is opposite to the direction of thrusting at the same time in the melbourne zone of victoria where the fold and thrust belt verges eastward away from the craton a concealed devonian transfer fault zone in bass strait could account for this change of polarity

ordovician contourites in the lachlan fold belt eastern australia abstract the ordovician sequence in the northeastern lachlan fold belt consists of three lithologic units representing an overall fining upward succession from turbidites to black shale the lowest unit dominated by turbidite beds represents a small segment of an extensive ordovician submarine fan sequence that covered much of southeastern australia the overlying unit consists predominantly of ripple bedded sandstone with beds 3 5 cm thick these beds are texturally mature containing heavy minerals mica and silt concentrated on the cross laminae the ripple bedded unit has a mean palaeocurrent trend to 321 which is at 60 to sole marks and almost normal to the trend of ripple cross bedding in the underlying and associated turbidite beds this unit is here interpreted as a sandy contourite sequence that can be attributed to contour currents moving northwards along the eastern margin of gondwana from areas of subpolar downwelling off southern africa and america the two major fining upward successions in the ordovician sequence in southeastern australia may reflect eustatic sea level rises during the middle and late ordovician and thus provide evidence of interglacial periods in the darrawilian and late gisbornian to bolindian the contourites would have accumulated in the latter stages of the glacial periods after sea level had risen sufficiently to cut off major sediment supply to the submarine fan but before the temperature had risen to the extent of preventing deep thermohaline circulation

a modeling study of the relative roles of tropical and extratropical sst anomalies in the variability of the global atmosphere ocean system abstract in three parallel experiments an atmospheric general circulation model has been subjected to observed monthly varying sea surface temperature ssi conditions in each of the following domains near global ocean goga run tropical pacific toga run and midlatitude north pacific moga run four independent realizations were obtained for the model response to the sequence of sst anomalies during the 1946 88 period in each of the above regions the principal modes of coupling between the imposed sst forcing and the simulated northern hemisphere wintertime 5 1 5 mb height field in various experiments have been identified using a singular value decomposition svd procedure the leading svd mode for the goga experiment is qualitatively similar to that based on observational data although the amplitudes of the simulated height anomalies are notably lower than the observed value the sst pattern of this mode resembles that associated with el nino events the accompanying 5 1 5 mb height anomaly i

rb sr dating of differentiated cleavage from the upper adelaidean metasediments at hallett cove southern adelaide fold belt abstract upper adelaidean psammites from the foreland part of the late proterozoic adelaide fold belt at hallett cove have suffered one major deformation which produced upright folds that plunge gently south axial to these folds is a well developed differentiation cleavage inferred to have resulted from constant volume plane strain deformation by solution transfer and now defined by alternating p phyllosilicate rich and q quartz rich domains geochemical analyses show that cleavage development resulted in a 2 4 fold fractionation of rb sr between the p and q domains thus the age of deformation is datable and isotopic analyses show the p and q domains form a 531 32 ma isochron this age is statistically older than the pervasive deformation and metamorphism in the more interior parts of the fold belt inferred from intrusive ages to have occurred at 485 6 ma and thus suggests that deformation either propagated across the fold belt from external to interior zones or that it occurred episodically the age data allow but do not demand that cleavage formation predated the deposition of the overlying cambrian kanmantoo group sediments

characteristic patterns of variability of sea level pressure in the northern hemisphere abstract seasonal and annual mean sea level pressures for the northern hemisphere have been analyzed to determine the dominant modes of interannual and longer period variability using monthly sea level pressure analyses as revised by trenberth and paolino 1980 empirical orthogonal function eof analysis is used to reveal the modes which explain most of the variance for the period 1925 77 in winter kutzbach s 1970 eof 1 for january remains the dominant mode and a closely related pattern dominates all seasons and the annual means although there are differences in detail in each season the dominant mode is basically a high latitude zonal index type pattern with departures in pressure at high latitudes corresponding to anomalies of opposite sign in low latitudes eof 1 is linked to the north atlantic oscillation but the north south fluctuations in mass also occur in the pacific and to a lesser extent elsewhere time series associated with this pattern have highly significant spectral peaks at the

a possible enso signal in the ross sea an examination of the observational record in the ross sea over the period 1982 1994 indicates that there is a statistically significant relationship between the ross sea sea surface temperature sst and the enso signal in the tropical pacific during this period the ross sea ssts lag the enso signal by 2 4 months with the highest correlation coefficient occurring with a lag of 3 months observations of the sea ice concentration during 1982 1994 also indicate a relation between the sea ice concentration in the ross sea and the enso cycle with reduced sea ice concentrations in el nino years

southern hemisphere circulation features associated with el nino southern oscillation events abstract composite seasonal mean and anomaly fields prepared from operational numerical analyses have been used to describe the southern hemisphere sh circulation features associated with el nino southern oscillation enso events the period of analyses available 1972 83 has limited the composites to include only three enso events the reliability and stability of the composites has been tested using multiple permutation methods and by comparison with the results obtained using a longer period 1950 79 of sh rawinsonde station data in the sh winter a weak equivalent barotropic wavetrain pattern of anomalies extends over australia and the south pacific ocean to south america this wavetrain pattern is quite variable in amplitude and location between enso events although it is more stable over the subtropical pacific in the sh summer the circulation anomalies are more zonally symmetric with increased height at low and high latitudes and decreased height in middle latitudes the circulation anoma

the antarctic circumpolar wave its presence and interdecadal changes during the last 142 years abstractthe southern ocean so is the region of the world ocean bordering on antarctica over which significant exchanges between the atmosphere the ocean and the sea ice take place here the strong and nearly unhindered eastward flow of the antarctic circumpolar current plays an important role in mean global climate as it transmits climate anomalies around the hemisphere features of interannual variability have been observed to propagate eastward around the so with the circumpolar flow in the form of a system of coupled anomalies known as the antarctic circumpolar wave acw in the present study the 142 yr series of the twentieth century reanalysis version 2 dataset 850 hpa geopotential height sea level pressure sea surface temperature surface meridional wind and surface air temperature spanning from 1871 to 2012 is used to investigate the presence and variability of acws this examination shows for the first time the presence of the acw before the mid 1950s and interdecadal changes in i

elemental and multiple isotopic evidences of enriched lithospheric mantle origin of the xiadian gold deposit in the jiaodong peninsula east china abstract the jiaodong peninsula is the largest gold concentration district in china and the third largest one in the world it covers no 0 2 of china s total landmass yet accounts for 30 of the total national gold reserves with total proved resources near 5000 t au one wonders where all this gold comes from here we present detailed whole rock element and sr nd pb isotope quartz h o isotope and pyrite he ar isotope geochemical data for the xiadian gold deposit a large jiaojia type gold deposit in the jiaodong district which furnishes new constrains on the sources of ore forming fluids and metals the results indicate that the ore and alterated rock have much higher hree e g yb and y hfse e g nb ta zr and hf and transition elements e g sc ti v cr co and ni than the host granites but similar to the lithospheric mantle derived lamprophyres suggesting an enriched lithospheric mantle origin the h o isotopes dv smow 93 9 to 102 3 18oh2o 0 2 to 1 6 of fluid inclusions in quartzs collected from auriferous pyrite sericite quartz altered rocks are distinctly different from either primary magmatic water and metamorphic water or meteoric water in the jiaodong district but similar to the local enriched mantle derived fluids the he ar isotopes 3he 4 he 0 58 10 6 to 1 90 10 6 0 42 1 36 ra 40ar 36ar 725 1358 of fluid inclusions in pyrites collected from auriferous pyrite sericite quartz altered rocks are also similar to the local enriched mantle derived fluids the ore and alterated rock have distinct nd pb isotopic compositions either from the host linglong granites or from the asthenosphere derived mafic dikes but similar to the lithospheric mantle derived mafic dikes their sr isotopic compositions show a mix trend between the lithospheric mantle derived mafic dikes and neoarchaean basement all the elemental and multiple isotopic features support a metallogenic model that the ore forming fluids and metals were derived from the local previously enriched lithospheric mantle and such deeply sourced fluids may have interacted with neoarchaean basement along their flow path and mixed with a little meteoric water when they arrived high levels in the crust

timing duration and role of magmatism in wide rift systems insights from the jiaodong peninsula china east asia in east asia widespread extensional sedimentary basins together with the close association of metamorphic core complexes and magmatism are prominent features of the large scale wide rift system developed during late mesozoic times this region thus appears as a proper place to study continental extension as well as questions about the link between continental extension and magmatism this paper primarily provides pioneer exhumation time constraints on the linglong mcc jiaodong peninsula including cooling and deformation ages mcc cooling at mid crustal levels occurred at ca 143 ma besides last ductile deformation occurred at ca 134 ma while final exhumation stages under brittle 2 conditions occurred as late as ca 128 ma continuous crustal stretching were then recorded by the emplacement of a synkinematic pluton in the upper crust at ca 128 ma that cooled fast below an intracrustal shear zone crossing the ductile brittle transition at ca 123 ma the ca 120 118 ma age cluster is ascribed to the fast cooling of undeformed plutons marking the end of extension that lasted in the area over a minimum period of ca 30 my combining other mcc exhumation constraints and the onset of subsidence in the sedimentary basins total duration of late mesozoic extension in east asia could be estimated at ca 60 my related with a rather long process for extension from 160 to at least 100 ma east asian continental extension is heterogeneously distributed in space and time as revealed by fundamental differences between two end member classes of migmatite cored mcc already described in other wide rift systems extension seems to have first favoured partial melting which subsequently in turn maintained continental extension

weather regimes in the south american sector and neighbouring oceans during winter we classified 34 years of winter daily 500 hpa geopotential height patterns over the eastern south pacific south america south atlantic region using the k means clustering method we found a significant classification into five weather regimes wrs defined as the most frequent large scale circulation anomalies wr1 trough centred downstream of the drake passage wr2 trough over the sw pacific and ridge downstream wr3 ridge over the se pacific and nw se trough downstream wr4 trough over the se pacific and nw se ridge downstream and wr5 weak ridge to the west of southern south america we also analysed their persistence and temporal evolution including transitions between them and development around onsets and breaks of each regime the preferred transitions wr1 wr3 wr2 wr4 wr1 and also wr1 wr3 wr2 wr1 suggest the progression of a rossby wave like pattern in which each of the regimes resemble the pacific south america modes significant influence of the wrs on local climate over argentina was found the preferred transitions wr1 wr3 and wr3 wr2 induce sustained cold conditions over patagonia and over northern argentina respectively the most significant change in precipitation frequency is found for wr3 with wetter conditions over all the analysed regions finally the interannual to interdecadal significant variations in the occurrence of these regimes were discussed wr1 and wr3 are more frequent and wr2 is less frequent during el nino and wr2 and wr5 are more frequent and wr1 is less frequent during la nina a significant decrease in wr2 and increase of wr4 and wr5 during the 1970s and early 1980s were found

the interannual leading modes of the extratropical variability in the southern hemisphere simulated by the echam 4 atmospheric model an ensemble of twenty three 14 year experiments conducted with the echam 4 gcm has been examined to test the model s capability to simulate the principal modes of interannual variability the integrations were performed under specified monthly sst between 1979 1993 the analysis was focused on the southern hemisphere sh extratropics empirical orthogonal functions analysis eof using seasonal anomaly fields has been performed to isolate the principal modes that dominate the southern extratropical variability at the interannual time scale leading patterns of 500 hpa geopotential height z500 have been compared with those estimated from the ecmwf re analysis dataset the model is able to adequately reproduce the spatial pattern of the annular mode but it represents the temporal variations of the oscillation less satisfactorily the model simulation of the pacific south american psa pattern is better both in the shape of the pattern and in the temporal evolution to verify if the capability of the model to adequately simulate the temporal oscillation of the propagating patterns is related to the increased influence of the tropical external forcing covarying sst atmospheric modes have been identified by singular value decomposition svd in winter july august september jas the tropical sst variability is highly correlated with the enso mode in summer january february march jfm the strength of the teleconnections is related to strong westerly anomalies disrupted by a meridional out of phase relation near to south america the large size of the ensemble was exploited by comparing the time varying model spread and degrees of freedom of the simulated extratropical circulation results show that when the extratropical circulation has a few degrees of freedom the reproducibility is relatively low and the ensemble is governed by a fairly robust zonally symmetric structure of dispersion

dominant propagating signals in sea level anomalies in the southern ocean 1 we examine the time evolution over an 11 yr time series of the dominant modes of variability in sea level anomalies sla from topex poseidon and ers 1 2 in the southern ocean 35 60 s we use hayashi s classical space time spectral analysis and a newly developed method combining a gabor analysis with hayashi s method zonal wavenumbers 3 and 2 emerge unambiguously with null corresponding meridional wavenumber meaning that both associated modes have no meridional propagation their power spectrum density psd is maximum within 50 55 s the 3 0 mode displays a clear westward propagation associated with a 1 04 yr period the 2 0 pair is characterized by a 4 4 yr period and exhibits a clear eastward propagation with a maximal psd just after the 1998 el nino peak zonal wavenumber 2 mode is then probably part of the antarctic circumpolar wave

antarctic pressure and temperature anomalies surrounding the minimum in the southern oscillation index the purpose of our research is to analyze surface pressure and temperature patterns in antarctica for relationships with the el nino southern oscillation enso using monthly anomalies of surface pressure and temperature in antarctica lag correlations are made to the southern oscillation index soi and annual composites are created for years where enso is in a warm phase comparisons are made to annual composites for nonwarm phase years and to six individual enso warm phases occurring between 1957 and 1984 we found a sharp change in the sign of the pressure and temperature anomalies between the year before and the year after the minimum in the soi we hypothesize that the temperature and pressure anomaly patterns are related through a thickness argument to the 500 mbar southern hemispheric flow and the australian branch of the southern oscillation

the antarctic circumpolar wave a combination of two signals abstract a simplified view of the possible mechanisms behind the antarctic circumpolar wave acw interannual variability is provided by a frequency domain decomposition of several observed atmospheric and oceanic variables two significant interannual signals with different temporal and spatial characteristics are identified in the southern ocean and most of the variance of the acw in the interannual band can be accounted for by a linear combination of them the first signal has a period of oscillation of around 3 3 yr and a zonal wavenumber 3 structure across the southern ocean it involves self sustained fluctuations inherent in the southern ocean and driven by coupled air sea interactions in which the atmosphere and the ocean mutually force one another this signal is represented by an atmospheric standing oscillation with centers at fixed locations around antarctica and a propagating oceanic pattern in which the surface antarctic circumpolar current plays an essential role the second signal has a

on the relationship between tropical and north pacific sea surface temperature variations abstract empirical orthogonal function analysis of winter sea surface temperature sst anomalies over the pacific domain 60 n 20 s reveals an el nino southern oscillation enso mode that is linked to the eastern north pacific and a north pacific mode that is linearly independent of enso the north pacific mode exhibits maximum amplitude and variance explained along 40 n west of 170 w ssts in this region have decreased by 1 5 c from 1950 to 1987 the cooling in winter has been associated with a strengthening of the overlying westerly winds

an antarctic circumpolar wave in surface pressure wind temperature and sea ice extent the southern ocean is the only oceanic domain encircling the globe it contains the strong eastward flow of the antarctic circumpolar current and is the unifying link for exchanges of water masses at all depths between the world s major ocean basins1 as these exchanges are an important control on mean global climate the southern ocean is expected to play an important role in transmitting climate anomalies around the globe interannual variability has been often observed at high southern latitudes and observations of sea ice extent suggest that such features propagate eastwards around the southern ocean2 3 here we use data from a variety of observational techniques to identify significant interannual variations in the atmospheric pressure at sea level wind stress sea surface temperature and sea ice extent over the southern ocean these anomalies propagate eastward with the circumpolar flow with a period of 4 5 years and taking 8 10 years to encircle the pole this system of coupled anomalies which we call the antarctic circumpolar wave is likely to play an important role in climate regulation and dynamics both within and beyond the southern ocean

ocean circulation variations associated with the antarctic circumpolar wave altimeter data analysis indicates persistent sea surface height ssh anomalies propagating eastward about the antarctic continent the spatial and temporal characteristics match variations in the atmosphere and sea surface temperature sst that are associated with the antarctic circumpolar wave acw during the observation time period the ssh appears quasiperiodic with a dominant 4 year period and 180 longitude wavelength thus the ssh signature of the acw appears as two anomalies on opposite sides of the antarctic continent propagating eastward at 10 cm s the ssh response to observed wind forcing agrees in terms of amplitude and phase with simple quasigeostrophic dynamics

formation and reactivation of the cambrian kanmantoo trough se australia implications for early palaeozoic tectonics at eastern gondwana s plate margin the kanmantoo group is a thick and largely metamorphosed sedimentary succession that filled an isolated arcuate cambrian basin kanmantoo trough which formed within continental gondwana and now lies on the southern margin of the present australian continent kanmantoo group sediments unconformably overlie neoproterozoic and older cambrian rocks we consider that the geometry of the southern part of this trough was influenced by strike slip movement along an intra continental tear fault to the north the basin changes to a style dominated by orthogonal extension and eventually tapers and dies out normal to the tear fault balanced sections show that the kinematic style and strain distribution developed during early palaeozoic inversion was controlled by the specific architecture of the kanmantoo trough early palaeozoic tear faulting could have linked contrasting subduction polarities along the then contiguous palaeo pacific margin of gondwana the kanmantoo trough is considered to have formed at a passive margin related to east directed subduction in what is now the australian continent in contrast west directed subduction formed an active margin at contiguous parts of current antarctica kanmantoo group sediments were derived from the south by erosion of a grenvillean province mixed with sediments eroded from the emergent active margin of gondwana the inception localization and sedimentation in the kanmantoo trough reflects a complex interaction of tectonic processes along the encroaching ross delamerian orogen

tectonic setting of cambrian rifting volcanism and ophiolite formation in western tasmania abstract in western tasmania small precambrian regions are surrounded by a ramifying system of troughs filled with cambrian sedimentary and volcanic rocks and ophiolite complexes the volcanic associations include a rift related olivine tholeiite association dacite rhyolite and andesite associations and a low ti high mg andesite tholeiite ophiolite association and may have formed during a long lived period of crustal thinning punctuated by episodes of crustal rupturing magmatism and small scale rifting such extensional tectonism could occur in an active continental margin associated with strike slip faulting of regional scale and the volcanic associations may together constitute an igneous assemblage characteristic of magmatism in a transcurrent tectonic regime within an active continental margin undergoing break up the western tasmanian cambrian palaeogeography and volcanism preserve a transitional stage between the late proterozoic kanmantoo regime of sedimentary basins with little volcanism developed at the rifting margin of the proterozoic craton and the tectonic regime of the palaeozoic lachlan fold belt where the cambrian volcanic rocks are dominated by island arc associations and the rift related olivine tholeiite association is absent eastern australian lithosphere may have grown by the insertion of newly formed igneous complexes within the stretched and rifted continental margin as well as by the accretion of terrenes and the addition of packets of subduction complexes which developed off shore

the structure of the upper mantle beneath the delamerian and lachlan orogens from simultaneous inversion of multiple teleseismic datasets abstract distant earthquake data recorded by seven sub arrays of the ongoing wombat rolling seismic array deployment in southeast australia are combined for the first time to constrain 3 d variations in upper mantle p wavespeed via teleseismic tomography the seven arrays comprise a total of 276 short period recorders spaced at intervals of approximately 50 km thus allowing unprecedented resolution of the upper mantle over a large region in the mantle lithosphere immediately below the crust 50 km depth dominant variations in velocity tend to strike east west and share little resemblance to palaeozoic boundaries in the shallow crust inferred from surface geology and potential field data a broad region of elevated wavespeed beneath northern victoria may represent the signature of underplated igneous rocks associated with detachment faulting during the break up of australia and antarctica a distinct low velocity anomaly in southern victoria appears to correlate well with the quaternary newer volcanic provinces towards the base of the mantle lithosphere the dominant structural trend becomes north south and five distinct velocity zones become apparent of particular note is a transition from higher wavespeed in the west to lower wavespeed in the east beneath the stawell zone implying that the proterozoic lithosphere of the delamerian orogen protrudes eastward beneath the western subprovince of the lachlan orogen this transition zone extends northwards from southern victoria into central new south wales the northward limit of the arrays and is one of the dominant features of the model further east there is a transition from lower to higher wavespeeds in the vicinity of the boundary between the western and central subprovinces of the lachlan orogen which has several plausible explanations including the existence of a proterozoic continental fragment beneath the wagga omeo zone the presence of elevated wavespeeds beneath the melbourne zone in victoria although not well constrained due to limited data coverage provides some support to the selwyn block model which proposes a northward extension beneath bass strait of the proterozoic core of tasmania

is climate variability over the north pacific a linear response to enso abstract indices of the dominant spatial patterns of wintertime northern hemisphere 500 mb height and north pacific sea surface temperature are strongly correlated with one another on interannual and interdecadal timescales and both am correlated with indices of the el nin southern oscillation one possible interpretation of these relationships is that the tropical sst anomalies associated with enso force the atmospheric circulation over the north pacific and these atmospheric anomalies in turn give rise to the observed sst anomalies over the extratropical north pacific in this study linear relationships between enso and extratropical variables are examined in two different ways first the component of the observed extratropical variability that is linearly dependent upon enso is removed the dominant spatial patterns in the residual variability of 500 mb height and sst anomalies over the north pacific are shown to be similar to their counterparts in the total fields and remain strongly coupled on

direct dating of fe oxide cu au mineralization by u pb zircon geochronology we present results for direct dating of fe oxide cu au iron oxide copper gold iocg mineralization by u pb zircon geochronology constraining the timing of mineralization has important geodynamic implications for the processes involved in the genesis of these types of deposits and the tectonic evolution of rocks associated with these deposits hydrothermal zircon crystals were separated from four iocg type ore deposits associated with the lyon mountain granite in the adirondack mountains united states zircon grains from these low ti magnetite deposits reveal at least two periods of mineralization one episode ca 1039 ma and a second between ca 1015 and 1000 ma previous age determinations of these deposits were constrained by the age of the altered host granitoids and the assumption that fe mineralization was directly related to pluton emplacement zircon crystals extracted from the ore yield ages that show that ore mineralization was episodic and younger than pluton emplacement

the antarctic circumpolar wave in a coupled ocean atmosphere gcm abstract a phenomenon called the antarctic circumpolar wave acw suggested earlier from fragmentary observational evidence has been simulated realistically in an extended integration of a max planck institute coupled general circulation model the acw both in the observations and in the model constitutes a mode of the coupled ocean atmosphere sea ice system that inhabits the high latitudes of the southern hemisphere it is characterized by anomalies of such climate variables as sea surface temperature sea level pressure meridional wind and sea ice that exhibit intricate and evolving spatial phase relations to each other the simulated acw signal in the ocean propagates eastward over most of the high latitude southern ocean mainly advected along in the antarctic circumpolar current on average it completes a circuit entirely around the southern ocean but is strongly dissipated in the south atlantic and in the southern indian ocean just marginally maintaining statistical significance in these areas

timing of orogenic gold mineralisation in northeastern tasmania implications for the tectonic and metallogenetic evolution of palaeozoic se australia new 40ar 39ar data from sedimentary rock hosted orogenic gold deposits in northeastern tasmania constrain most ore formation to between 395 ma and 385 ma these 385 395 ma ages for the formation of orogenic gold agree well with an inferred early to middle devonian timing for peak deformation and folding across much of northeastern tasmania data from micas within alteration halos in some deposits give dates of 420 430 ma these dates confirm the occurrence of an earlier silurian phase of deformation and suggest that at least some of the mineralisation was possibly generated during this event gold mineralisation hosted by middle devonian post tectonic granites may be genetically related to magmatism following orogeny but these deposits formed virtually synchronously with peak deformation related systems early to middle devonian deformation in northeastern tasmania also reactivated older structures in western tasmania and the formation of quartz vein hosted gold mineralisation there based on geological structural tectonic and metallogenetic similarities northeastern tasmania is interpreted as a lateral equivalent of the turbidite dominated fold thrust belt of the western lachlan orogen however unlike victoria where the sedimentary rock sequence developed on oceanic crust northeastern tasmania was probably underlain by thinned proterozoic crust either as part of a promontory along the gondwana margin or as a microcontinental fragment this may have protected the palaeozoic succession from large scale pre devonian orogeny with collision not beginning until the middle devonian these variations in the structural and tectonic evolution and the timing of deformation and ore formation can explain the difference in contained gold and the distribution and number of major orogenic gold deposits within the palaeozoic of northeastern tasmania

new u pb age constraints for the timing of gold mineralization at the pampalo gold deposit archaean hattu schist belt eastern finland obtained from hydrothermally altered and recrystallised zircon abstract in this paper we present new u pb data on zircon and titanite from the host rocks of the pampalo gold deposit located within the neoarchaean hattu schist belt in eastern finland we also present new u pb data on nearby plutonic rocks plagioclase porphyries at the mine site demonstrate inheritance from 2 82 2 83 ga sources while a suggestive intrusive age is at c 2 76 ga zircon grains extracted from the altered felsic units hosting the gold ore show complex alteration and recrystallisation textures and demonstrate zr mobility this mobility is most probably related to the alteration event although direct link to gold mineralization remains to be shown the preserved or recrystallized parts of the altered zircon grains texturally homogeneous grain aggregates and some overgrowths yield heterogeneous ages which cluster between ca 2 73 and 2 70 ga with a mean age of 2 71 ga this age is considered to place a new constraint on the timing of mobility of au at the pampalo this event postdates the known crustal formation event at 2 76 2 73 ga in the area as recorded by the adjacent plutonic rocks and volcanoclastic rocks within the hattu schist belt the naarva tourmaline granite 10 km nw of pampalo is 2 69 ga and is thus temporally associated with known regional crustal anatexis and metamorphism in the archaean of eastern finland whether this crustal reworking event played a role in the genesis of the gold in eastern finland needs to be further studied

forcing of the antarctic circumpolar wave by el nino southern oscillation teleconnections we address several issues regarding the antarctic circumpolar wave acw these include the extent to which the acw is related to el nino southern oscillation enso cycles and the need to reconcile differences between the observed zonal wavenumber 2 pattern and the wavenumber 3 pattern found in coupled ocean atmosphere models in the present study we revisit the sea surface temperature sst signal of the observed acw we find that the associated sst variations may be decomposed into several empirical orthogonal functions eofs that are linearly independent the first four eofs describe 84 of the total variance on timescales of 3 7 years and superposition of sst signals of the four eofs reproduces sst signals of the observed acw given that eof analysis can only describe standing oscillations we then employ complex eof ceof analysis suitable for studying propagating waves the first two ceofs denoted ceofsst1 and 2 account for 70 of the total variance and the sst variability reconstructed from them again reproduces the observed acw the real part of ceofsst1 44 of the total variance is similar to the first real eof eofsst1 both eofsst1 and ceofsst1 may be identified with enso and have a wavenumber 2 zonal pattern in the southern middle to high latitudes ceofsst1 is the major constituent of the acw in the period of 1981 1997 the associated atmospheric circulation displays a pacific south america psa pattern statistical analyses demonstrate that the psa pattern teleconnected to enso is the major mechanism that forces this principal constituent of the acw ceofsst2 26 of the total variance has a zonal wavenumber 3 pattern in the same latitude band similar to that simulated by several coupled models we suggest that if enso is not adequately resolved in coupled models but structures with zonal wavenumber 3 pattern are then the modeled acw would appear to have a zonal wavenumber 3 pattern

geochronological framework of the xiadian gold deposit in the jiaodong province china implications for the timing of gold mineralization abstract the xiadian gold deposit located in the zhaoyuan laizhou belt of the jiaodong gold province is a typical jiaojia type gold deposit which is characterized by disseminated and stockwork ores enclosed by hydrothermally altered wall rocks the exact age and the genesis of the gold deposit remain controversial here we present precise in situ monazite u pb dating to constrain the age of the gold mineralization which we integrate with published geochronological work on the associated geological events to understand the genesis of the gold deposit the linglong granite represents the earliest magmatic event at xiadian and yielded a zircon la icpms u pb age of 159 5 0 9 ma 2 mswd 0 63 subsequent geologic events were recorded by minor amounts of quartz pyrite molybdenite veins which are dated at 124 8 2 1 ma 2 mswd 0 01 by molybdenite re os dating in a granitic pegmatite the formation of such veins was close to the emplacement of adjacent guojialing granodiorite 130 ma and thus may be considered as a product of post magmatic hydrothermal activity it is proposed that the molybdenum bearing hydrothermal fluids acted as a prelude to gold mineralization and participated in the formation of the latter ore fluids gold mineralization took place at 120 0 1 4 ma 2 mswd 0 59 determined by la icpms u pb dating on hydrothermal monazite from quartz polymetallic sulfide veins prior to and post mineralization voluminous hydrothermally altered porphyritic diorite and fresh quartz diorite porphyry dykes were emplaced which yielded u pb ages of 121 3 1 4 ma 2 mswd 0 28 and 115 8 1 9 ma 2 mswd 0 71 respectively based on these geochronological data we have established a comprehensive geochronologic framework which suggests that the genesis of the xiadian deposit might be related to the craton destruction and lithosphere thinning in the north china craton

ocean sea ice atmosphere oscillations in the southern ocean as simulated by the sintex coupled model this research was supported by the predicate eu project evk2 ct 1999 0020 first author was supported by the prism eu project evr1 ct 2001 40012

thermochronologic constraints on evolution of the linglong metamorphic core complex and implications for gold mineralization a case study from the xiadian gold deposit jiaodong peninsula eastern china abstract the nne trending linglong metamorphic core complex hosts the majority of the gold deposits in the jiaodong peninsula of eastern china many of the deposits are hosted by the 163 155 ma linglong granite in the footwall of the linglong detachment fault argon thermochronology suggests that the granite had cooled to 400 c by 143 1 5 ma possibly as a result of normal movement on the detachment nine zircon fission track zft ages from samples collected along a nw se transect perpendicular to the central part of the linglong detachment fault at the 652 m level in the xiadian deposit constrain the subsequent thermal evolution of linglong metamorphic core complex which overlapped the period of major gold deposition the zft ages vary from 136 9 3 3 ma 1 to 130 1 2 2 ma 1 the unaltered linglong granite in the footwall and amphibolite in the hangingwall have similar ages at 136 9 3 3 ma 1 and 135 0 3 0 ma 1 whereas ages for the disseminated and stockwork style ores appear to be younger at ca 131 130 ma although there is an overlap of ages when considering the 1 precision interestingly zft ages show no marked differences between the hangingwall and footwall of the linglong detachment fault although significant movement along the fault occurred the results are best interpreted to indicate that the linglong granite was emplaced at 160 ma and cooled to 240 50 c at 135 ma as recorded by unaltered rocks in the footwall hydrothermal alteration along the linglong detachment fault led to annealing of zircon fission tracks and the consistent younger ages of 131 ma quartz aggregates associated with gold mineralization show evidence of recrystallization suggesting that the hydrothermal event was initiated at temperatures of at least 300 350 c near the brittle ductile transition but cooled rapidly to zft closure temperatures within a country rock environment that was already relatively cool therefore these zft ages suggest that the timing of mineralization at the xiadian deposit was post 135 ma and likely very close to 131 ma the mineralization and cooling occurred in the footwall of a major detachment fault under an extensional regime possibly related to the progressive slab rollback of the paleo pacific plate and controlled by the linglong metamorphic core complex

low frequency variability of the antarctic circumpolar wave this study evaluates the antarctic circumpolar wave acw variability in the southern ocean using a 27 year series of sea surface temperature sst and sea level pressure slp from a cross covariance analysis we find that the strongest covariation between the extratropical wavenumber 2 in sst and in slp is during the austral summer in the south pacific ocean examination of the time series reveals two timescales of variability a wavenumber 2 structure in sst and slp anomalies correlates well at interannual ia timescales when enso driven teleconnections seem to energize the acw moreover in the 1973 1999 epoch the acw has been modulated by interdecadal id variability possibly related to the southern oscillation

hydrothermal zircon and baddeleyite in val d or archean mesothermal gold deposits characteristics compositions and fluid inclusion properties with implications fortiming of primary gold mineralization zircon and baddeleyite occur within quartz tourmaline veins at four gold deposits in the val d or district of the archean abitibi southern volcanic zone host rocks have experienced intense metasomatic enrichment of zr hf y and rare earth elements the zircons contain primary inclusions of quartz tourmaline pyrite albite k mica scheelite and gold and gold occurs in primary fluid inclusions in zircons magmatic zircons in host rocks do not have this suite of inclusions consequently a wall rock inheritance model for the vein zircons is implausible compositionally the zircons feature pronounced interzone and intergrain variations of hf y yb th and u and sporadic anomalous ce contents of 1100 ppm distinct from magmatic counterparts two principal types of primary fluid inclusion occur in the vein zircons type 1 h2o co2 inclusions have low salinities variable quantities of co2 and homogenization temperatures of 260 380 c and type 2 co2 rich inclusions contain minor h2o and ch4 the vei

southern hemisphere extra tropical forcing a new paradigm for el nino southern oscillation the main goal of this paper is to shed additional light on the reciprocal dynamical linkages between mid latitude southern hemisphere climate and the el nino southern oscillation enso signal while our analysis confirms that enso is a dominant source of interannual variability in the southern hemisphere it is also suggested here that subtropical dipole variability in both the southern indian and atlantic oceans triggered by southern hemisphere mid latitude variability may also provide a controlling influence on enso in the equatorial pacific this subtropical forcing operates through various coupled air sea feedbacks involving the propagation of subtropical sea surface temperature sst anomalies into the deep tropics of the atlantic and indian oceans from boreal winter to boreal spring and a subsequent dynamical atmospheric response to these sst anomalies linking the three tropical basins at the beginning of the boreal spring this atmospheric response is characterized by a significant weakening of the equatorial atlantic and indian inter tropical convergence zone itcz this weakened itcz forces an equatorial cold kelvin wave response in the middle to upper troposphere that extends eastward from the heat sink regions into the western pacific by modulating the vertical temperature gradient and the stability of the atmosphere over the equatorial western pacific ocean this kelvin wave response promotes persistent zonal wind and convective anomalies over the western equatorial pacific which may trigger el nino onset at the end of the boreal winter these different processes explain why south atlantic and indian subtropical dipole time series indices are highly significant precursors of the nino34 sst index several months in advance before the el nino onset in the equatorial pacific this study illustrates that the atmospheric internal variability in the mid latitudes of the southern hemisphere may significantly influence enso variability however this surprising relationship is observed only during recent decades after the so called 1976 1977 climate regime shift suggesting a possible linkage with global warming or decadal fluctuations of the climate system

examples of the horizontal propagation of quasi stationary waves abstract examples of the diagnostic of the horizontal propagation of stationary wave activity proposed by plumb are presented for a simple model of the atmospheric response to thermal forcing in the tropics for the observed southern hemisphere winter mean stationary waves and for several cases of anomalous quasi stationary waves in both the northern and southern hemispheres for the simple model the propagation of wave activity out of the tropics is clear from the observational data the apparent sources of anomalous stationary wave activity are located in the regions of the major middle latitude jets and storm tracks in both hemispheres in most cases the results suggest that midlatitude processes such as instabilities of the jet stream or interaction with transient eddies are the major mechanisms for forcing anomalous stationary waves there are indications that rossby like wave propagation from low latitudes plays a role in forcing anomalous stationary waves associated with southern oscillation ev

craton destruction and related resources craton destruction is a dynamic event that plays an important role in earth s evolution based on comprehensive observations of many studies on the north china craton ncc and correlations with the evolution histories of other cratons around the world craton destruction has be defined as a geological process that results in the total loss of craton stability due to changes in the physical and chemical properties of the involved craton the mechanisms responsible for craton destruction would be as the follows 1 oceanic plate subduction 2 rollback and retreat of a subducting oceanic plate 3 stagnation and dehydration of a subducting plate in the mantle transition zone 4 melting of the mantle above the mantle transition zone caused by dehydration of a stagnant slab 5 non steady flow in the upper mantle induced by melting and or 6 changes in the nature of the lithospheric mantle and consequent craton destruction caused by non steady flow oceanic plate subduction itself does not result in craton destruction for the ncc it is documented that westward subduction of the paleo pacific plate should have initiated at the transition from the middle to late jurassic and resulted in the change of tectonic regime of eastern china we propose that subduction rollback and retreat of oceanic plates and dehydration of stagnant slabs are the main dynamic factors responsible for both craton destruction and concentration of mineral deposits such as gold in the overriding continental plate based on global distribution of gold deposits we suggest that convergent plate margins are the most important setting for large gold concentrations therefore decratonic gold deposits appear to occur preferentially in regions with oceanic subduction and overlying continental lithospheric destruction modification growth

geochronology of the pengjiakuang and rushan gold deposits eastern jiaodong gold province northeastern china implications for regional mineralization and geodynamic setting the jiaodong gold province the largest gold producing district in china is located in the jiaodong peninsula at the eastern margin of the north china craton and bounded by the continental scale tan lu fault 40 kin to the west previous geochronological studies suggest that pervasive gold deposition took place in the western part of the province between 122 and 119 ma here we report high quality ar 40 ar 39 ages of the pengjiakuang and rushan deposits from the eastern part of the jiaodong gold province placing additional chronological constraints on the timing of regional mineralization seven sericite grains extracted from auriferous alteration assemblages at the pengiiakuang deposit yielded well defined plateau ages between 120 9 0 4 and 119 1 0 2 ma 2 sigma three separates of igneous biotite from a sample of the queshan gneissic granite adjacent to the pengjiakuang deposit gave reproducible plateau ages of 124 6 0 6 to 123 9 0 4 ma 2 sigma six sericite separates front two samples in the rushan deposit yielded ar 40 ar 39 plateau ages at 109 3 0 3 to 107 7 0 5 ma 2 sigma whereas biotite from the kunyushan monzogranite that hosts the rushan deposit had plateau ages ranging from 129 0 0 6 to 126 9 0 6 ma 3 separates front one sample the apparent age gap between hydrothermal sericite and magmtic biotite from both deposits together with the similar argon closure temperatures for these mica minerals suggest that gold mineralization had no direct relationship to the granitoid magmatism instead gold deposition coincided with the emplacement of mafic to intermediate dikes widespread in the jiaodong gold province which have been dated at ca 122 to 119 ma and less commonly at 110 to 102 ma the new ar 40 ar 39 ages from the eastern jiaodong peninsula when combined with published data from the western part suggest that gold mineralization was broadly contemporaneous throughout the district the early cretaceous gold mineralization also is widely developed in four other major gold districts along the tan lu fault the temporal and spatial correlation of these gold deposits with mafic to intermediate dikes commonly found in most mineralized areas the presence of well documented metamorphic core complexes and half graben basins along the tan lu fault and voluminous basalts therein suggest that the early cretaceous was an important period of lithospheric extension possibly caused by the late mesozoic lithospheric thinning beneath the eastern block of the north china craton lithospheric thinning and extension could have resulted in abnormally high heat and fluid fluxes necessary for large scaled gold mineralization

atmospheric teleconnections involving the southern ocean 1 i review the characteristic patterns of low frequency interannual and subdecadal variation in atmospheric circulation over the southern hemisphere sh extratropics and their climatic associations e g temperature precipitation winds sea surface temperatures ssts and sea ice conditions for the southern ocean the considerable spatial and temporal limitations of the observational database have strongly conditioned the pace of our understanding of sh teleconnections particularly for the pacific sector where the tropical el nino southern oscillation enso exerts a dominant influence an enso signal appears in the intensity interannual variations of the amundsen sea mean low pressure asl jet streams and long waves these variations comprise the so called pacific south america psa teleconnection patterns of low frequency variability in sh circulation that are mostly extratropical in origin but which can interact with enso are dominated by the zonally symmetric high latitude mode or antarctic oscillation aao the aao involves an alternation of atmospheric mass between middle and high southern latitudes a zonally asymmetric mode of wave number 1 is represented by an oscillation in pressure height between australian and south american sectors depicted by a trans polar circulation index a significant wave number 2 oscillation in the coupled atmosphere ocean ice system or antarctic circumpolar wave acw has a similar periodicity to enso and is strongest in the pacific sw atlantic sectors atmospheric teleconnections involving the southern ocean including those to enso show evidence of recent changes and the climatic implications of these are discussed

tracing magma mixing in granite genesis in situ u pb dating and hf isotope analysis of zircons in situ zircon u pb and hf isotopic data have been determined for mafic microgranular enclaves and host granitoids from the early cretaceous gudaoling batholith in the liaodong peninsula ne china in order to constrain the sources and petrogenesis of granites the zircon u pb age of the enclaves 120 1 ma is identical to that of the host monzogranite 120 1 ma establishing that the mafic and felsic magmas were coeval the hf isotopic composition of the enclaves ehf t 4 5 to 6 2 is distinct from the host monzogranite ehf t 15 1 to 25 4 indicating that both depleted mantle and crustal sources contributed to their origin the depleted mantle component was not previously revealed by geochemical and nd and sr isotopic studies showing that zircon hf isotopic data can be a powerful geochemical tracer with the potential to provide unique petrogenetic information some wall rock contamination is indicated by inherited zircons with considerably older u pb ages and low initial hf isotopic compositions hafnium isotopic variations in early cretaceous zircons rule out simple crystal liquid fractionation or restite unmixing as the major genetic link between enclaves and host rocks instead mixing of mantle derived mafic magmas with crustal derived felsic magmas coupled with assimilation of wall rocks is compatible with the data

on the mechanism of the antarctic circumpolar wave abstract the variability in the subpolar southern hemisphere is studied with a coupled atmosphere ocean sea ice model the ecbilt after having reached an approximate statistical equilibrium in coupled mode without flux corrections a subsequent 1000 yr integration is performed and analyzed a singular value decomposition of austral winter sst anomalies and 800 hpa geopotential height in the antarctic circumpolar current region reveals a mode of covariability that resembles the observed antarctic circumpolar wave subsequent analysis of this mode shows that it is basically an oscillation in the subsurface of the ocean additional experiments suggest that it is generated by the advective resonance mechanism the oscillation is excited by the dominant modes of variability in the atmosphere whereas the timescale is set by the ratio of the horizontal scale of these atmospheric modes and the advection velocity of the mean oceanic currents the atmospheric response mainly consists of a local temperature adjus

a review of the geodynamic setting of large scale late mesozoic gold mineralization in the north china craton an association with lithospheric thinning abstract abundant gold deposits are distributed along the margins of the north china craton ncc occurring throughout the precambrian basement and located in or proximal to mesozoic granitoids these deposits show a consistent spatial temporal association with late jurassic early cretaceous magmatism and are characterized by quartz lode or disseminated styles of mineralization with extensive alteration of wall rock their ages are mainly early cretaceous 130 110 ma and constrain a very short period of metallogenesis sr nd pb isotopic tracers of ores minerals and associated rocks indicate that gold and associated metals mainly were derived from multi sources i e the wall rocks precambrian basement and mesozoic granites and associated mafic rocks previous studies including high surface heat flow uplift and later basin development slow seismic wave speeds in the upper mantle and a change in the character of mantle xenoliths sampled by paleozoic to cenozoic magmas have been used to suggest that ancient cratonic mantle lithosphere was removed from the base of the ncc some time after the ordovician and replaced by younger less refractory lithospheric mantle the geochemistry and isotopic compositions of the mafic rocks associated with gold mineralization 130 110 ma indicate that they were derived from an ancient enriched lithospheric mantle source whereas the mafic dikes and volcanic rocks younger than 110 ma were derived from a relatively depleted mantle source i e asthenospheric mantle according to their age and sources relation to magmatism and geodynamic framework the gold deposits were formed during lithospheric thinning the removal of lithospheric mantle and the upwelling of new asthenospheric mantle induced partial melting and dehydration of the lithospheric mantle and lower crust due to an increase of temperature the fluids derived from the lower crust were mixed with magmatic and meteoric waters and resulted in the deposition of gold and associated metals

interannual enso and interdecadal enso like variability in the southern hemisphere tropospheric circulation abstract recent work has identified variability in the pacific ocean sst with a structure qualitatively similar to enso but at lower frequencies than enso zhang et al have documented the atmospheric circulation anomalies in the tropics and northern hemisphere that are associated with decadal enso like variability and compared these anomalies to those associated with the interannual enso cycle here the authors extend the study of zhang et al to the southern hemisphere using the national centers for environmental prediction national center for atmospheric research reanalysis data for 1958 96 consistent with previous studies the southern hemisphere circulation anomalies associated with enso display a teleconnection pattern from the central tropical pacific into the far southeastern pacific ocean comparatively larger circulation anomalies are found in the southern hemisphere associated with the decadal enso like variability though aloft the structure of the anomalies emphasizes the polar vortex wit

modulation in interannual sea ice patterns in the southern ocean in association with large scale atmospheric mode shift 1 we verified that the synchronous propagations of the spatial patterns of sea ice concentration sic of wave number 2 around the antarctic occurred only for the period 1984 to 1994 an empirical orthogonal function eof analysis of satellite data for 1979 2003 objectively demonstrates that the spatial pattern of sic propagated eastward only in 1984 1994 in other years it did not our results show that interannual variations in sic patterns are associated with differences in the dominant large scale atmospheric patterns in nonpropagating years variance of the tropospheric antarctic oscillation aao predominated however in propagating years the aao variance was subdominant to that of the pacific south american psa teleconnection pattern having a 4 year period such periodic psa enables the sic anomalies to propagate eastward with a periodically reinforced dipole pattern the shift of large scale atmospheric variability is one possible cause of the modulation in the sic pattern the switch of the atmospheric eof leading mode from the psa pattern to the aao in the mid 1990s corresponded to the modulation in the sic pattern and supports the presence of the atmospheric climate shifts

influence of the antarctic circumpolar wave upon new zealand temperature and precipitation during autumn winter abstract autumn winter temperature and precipitation records at 34 stations over new zealand from 1982 to 1995 are found by empirical orthogonal function eof analysis to fluctuate together with 3 6 yr quasi periodicity similar to that associated with the antarctic circumpolar wave acw which propagates slowly eastward past new zealand in its global traverse around the southern ocean by allowing these eof time sequences to represent new zealand temperature and precipitation indices both the positive temperature index related to warm sea surface temperature sst anomalies around new zealand and the positive precipitation index related to warm cool sst anomalies north and east south and west of new zealand are found these warm cool sst anomalies are associated with poleward equatorward meridional surface wind msw anomalies the same as observed in association with the acw when warm cool sst and poleward equatorward msw anomalies are located north south of new zealand then anomalous

the southern ocean as a source region for tropical atlantic variability abstract a coupled model of intermediate complexity is used to examine the effect of the southern ocean on tropical atlantic variability model experiments with positive surface temperature freshwater and wind forcings in the southern ocean show an increased advection of polar water into the atlantic basin resulting in anomalously cold freshwater in the eastern atlantic ocean at 25 s with time these anomalies spread northward and away from the coast into the tropical thermocline the magnitude of the response increases linearly with the strength of the forcing the results of these experiments show that southeastern atlantic ocean temperature and salinity are particularly sensitive to changes in the southern ocean these findings suggest that this link could be the oceanic branch of a mode of variability linking the southern and tropical atlantic oceans a possible mechanism for the as yet unexplained decadal mode of tropical atlantic variability

thermodynamic mechanisms responsible for the tropospheric response to sst anomalies in the antarctic circumpolar wave abstract tropospheric temperature and vorticity budgets for the antarctic circumpolar wave acw are diagnosed utilizing the national centers for environment prediction national center for atmospheric research reanalysis datasets from 1983 to 1992 focusing on the eastern atlantic indian and western and central pacific sectors of the southern ocean where remote forcing from the tropics has been observed to be weak there warm sea surface temperature sst anomalies are found in the acw propagating eastward together with anomalous upward latent heat flux positive precipitation low level convergence upper level divergence midlevel ascent and poleward surface wind diagnosing the anomalous temperature budget finds sst induced latent heat flux instigating anomalous mid to upper level diabatic heating and low level diabatic cooling in the absence of significant eddy heat flux divergence this diabatic heating profile is balanced by a combination of vertical and horizontal heat advection giving rise t

teleconnections in the southern hemisphere abstract teleconnections are calculated from monthly mean anomalies of sea level pressure and 500 mb geopotential height for the southern hemisphere 10 90 s for five month winter and summer seasons the monthly means were calculated from australian analyses for the period from june 1972 to november 1980 zonally averaged anomalies at both sea level and 500 mb display an out of phase relation between low and high latitudes and in midlatitudes are negatively correlated with anomalies in the subtropics and polar regions in winter a striking zonal wavenumber 3 pattern is found over the southern ocean anomalies in 500 mb geopotential heights at 50 s 95 e 58 s 150 w and 38 s 15 w exhibit strong positive correlations while showing weaker negative correlations with heights over antarctica and in low latitudes a similar pattern appears in sea level pressure in summer anomalies in 500 mb geopotential height over the three subtropical continents appear to occur out of phase with anomalies over the su

linking mainland australia and tasmania using ambient seismic noise tomography implications for the tectonic evolution of the east gondwana margin for nearly half a century a number of conflicting tectonic models have been postulated to explain the enigmatic geological relationship between tasmania and victoria with a view to unifying our understanding of the evolution of the eastern margin of gondwana in australia in this study ambient noise data from an array of 24 broadband seismometers is used to produce a high resolution 3 d crustal shear wave velocity model of bass strait the key to understanding the missing link we apply a novel transdimensional and hierarchical bayesian inversion approach to construct group velocity maps in the period range of 2 30 s and subsequently invert group velocity dispersion for 3 d shear wave velocity structure this allows us to image for the first time the entire crust beneath bass strait in high detail and elucidate the geometry and position of key crustal features with corroboration from complementary datasets the three sedimentary basins related to the failed rifting event associated with the australia antarctica breakup in particular bass basin clearly emerge from the tomographic solution model a key feature of the 3 d shear wavespeed model is a distinct mid lower crustal nw se high velocity zone which extends from northwestern tasmania to south central victoria confirming a proterozoic geological connection we also image three north south high velocity belts that appear to span bass strait with some interruption from velocity variations possibly related to more recent tectonic events these belts are consistent with recent gravity and magnetic maps and may indicate the presence of an exotic precambrian terrane the selwyn block the model also images the crustal velocity structure of the southern stawell and bendigo zones and their internal large scale multi layer characters a legacy of their early paleozoic intra oceanic origins another high velocity anomaly imaged in the mid lower crust is an east west lineament beneath the northern part of bass strait which may be an intrusive feature associated with the failed rift

influence of the antarctic circumpolar wave on el nino and its multidecadal changes from 1950 to 2001 1 the slow eastward phase propagation of covarying sea surface temperature sst and sea level pressure slp anomalies in the antarctic circumpolar wave acw persisted in the midlatitude southern ocean from 1950 to 2001 its northern extent reached into the subtropical south indian and south pacific oceans where it influenced the magnitude and phase of el nino in the eastern equatorial pacific ocean this is corroborated by the observation that multidecadal changes in the acw can also explain multidecadal changes in the way el nino evolved over the last half of the twentieth century before 1977 el nino evolved from the slow eastward phase propagation of a coupled sst slp wave across the subtropical south pacific ocean to south america then equatorward along the eastern boundary to the equator during this epoch the acw expanded equatorward into a warmer subtropical south pacific ocean accounting for the subtropical coupled sst slp wave that initiated el nino after 1977 el nino evolved from the slow eastward phase propagation of a coupled sst slp wave across the tropical pacific ocean during this epoch the acw receded from a colder subtropical south pacific ocean but expanded into a warmer subtropical south indian ocean there it spawned a coupled sst slp wave directed equatorward into the warm pool north of australia thereafter propagating eastward into the eastern equatorial pacific ocean to initiate el nino if this pattern of global warming persists into the 21st century then the acw will continue to influence el nino through the south indian ocean

a possible link between the weddell polynya and the southern annular mode abstract shortly after the advent of the first imaging passive microwave sensor on board a research satellite an anomalous climate feature was observed within the weddell sea during the years 1974 1976 a 250 103 km2 area within the seasonal sea ice cover was virtually free of winter sea ice this feature the weddell polynya was created as sea ice formation was inhibited by ocean convection that injected relatively warm deep water into the surface layer though smaller less persistent polynyas associated with topographically induced upwelling at maud rise frequently form in the area there has not been a reoccurrence of the weddell polynya since 1976 archived observations of the surface layer salinity within the weddell gyre suggest that the weddell polynya may have been induced by a prolonged period of negative southern annular mode sam during negative sam the weddell sea experiences colder and drier atmospheric conditions making for a saltier surface layer with reduced pycnocline stability t

la icp ms u pb geochronology trace elemental and lu hf isotopic geochemistry of hydrothermal zircons in the xiadian gold deposit eastern north china craton implications for the timing of gold mineralization and the origin of ore forming fluids abstract the eastern north china craton is characteristic of mesozoic cratonic destruction and largescale gold mineralization previous geochronological studies by 40ar 39ar dating on alteration minerals such as sericite and k feldspar and rb sr and 40ar 39ar dating on quartz and pyrite suggested that the gold mineralization occurred in early cretaceous we have identified hydrothermal zircons from the orebody and alterated rocks in the xiadian gold deposit jiaodong peninsula these zircons contain two phase vapor liquid fluid inclusions or enclose hydrothermal alteration minerals such as sericite they show homogeneous low cl response image and have high u with low th u and also show enriched and flatter normalized lree pattern with high la and low sm la n and ce ce relative to magmatic zircons their petrographical textural and compositional features strongly suggest that they mainly crystallized from the hydrothermal fluids during the pyrite sericite quartz alteration that was closely related to the gold mineralization direct la icp ms u pb dating on such hydrothermal zircons indicates that the gold mineralization in the xiadian deposit mainly occurred during the paleocene and underwent a prolonged metallogenic process 68 7 56 7 ma most likely commenced at the end of cretaceous and lasted at the end of paleocene in situ hf isotopic compositions of the hydrothermal and inherited zircons suggest that the ore forming fluids might have been derived from an enriched lithospheric mantle followed by interacting with archean metamorphic basement during ascent such a gold mineralization event might have been associated with the early cenozoic uppermost lithospheric thinning in eastern north china craton it has important implications for further understanding the geneses and the geodynamics of gold deposits in the whole eastern north china craton

interannual variation of the antarctic ice sheet from a combined analysis of satellite gravimetry and altimetry data assessment of the long term mass balance of the antarctic ice sheet and thus the determination of its contribution to sea level rise requires an understanding of interannual variability and associated causal mechanisms we performed a combined analysis of surface mass and elevation changes using data from the grace and envisat satellite missions respectively using empirical orthogonal functions and singular value decompositions of each data set we find a quasi 4 7 yr periodic signal between 08 2002 and 10 2010 that accounts for 15 30 15 30 of the time variability of the filtered and detrended surface mass and elevation data computation of the density of this variable mass load corresponds to snow or uncompacted firn changes reach maximum amplitude within the first 100 km from the coast where it contributes up to 30 35 of the annual rate of accumulation extending the analysis to 09 2014 using surface mass changes only we have found anomalies with a periodicity of about 4 6 yrs that circle the ais in about 9 10 yrs these properties connect the observed anomalies to the antarctic circumpolar wave acw which is known to affect several key climate variables including precipitation it suggests that variability in the surface mass balance of the antarctic ice sheet may also be modulated by the acw

slow oceanic teleconnections linking the antarctic circumpolar wave with the tropical el nino southern oscillation a case study for the period 1982 1994 shows that a major source for the antarctic circumpolar wave is in the western subtropical south pacific where interannual anomalies in sea surface temperature sst and precipitable water prwat form once established these interannual anomalies in tandem with anomalies in sea level pressure slp move south toward the southern ocean the system then migrates east around the globe through a combination of oceanic advection with the antarctic circumpolar current and ocean atmosphere coupling the coincidence of interannual anomalies in sst slp and prwat indicates the extratropical ocean and atmosphere are tightly linked on these timescales large portions of the interannual sst anomalies branch advectively northward into the south atlantic and indian oceans ultimately reaching the tropics in each basin some 6 8 years after appearing in the low latitude pacific this constitutes a slow oceanic teleconnection that is unique in climate dynamics made possible by the continuity of earth s oceans via the southern ocean in the tropical indian ocean these interannual anomalies move east and arrive at the indo pacific transition in advance of the trans pacific propagation of the respective el nino southern oscillation enso phases the interannual sst and prwat anomalies that appear in the subtropical south pacific are directly linked with the enso cycle on the equator through anomalous vertical convection and a regional overturning cell in the troposphere the same cell that initiates fast planetary waves in the atmosphere that carry enso signals around the southern hemisphere on much shorter timescales

statistics and dynamics of persistent anomalies abstract persistent anomalies with recurrent spatial patterns play an important role in the atmosphere s low frequency variability we establish a connection between statistical and dynamical methods of description and prediction of persistent anomalies this is done by computing and analyzing the empirical orthogonal functions eofs in a simple deterministic model on the one hand and in southern hemisphere geopotential heights on the other the dynamical model is governed by the fully nonlinear equivalent barotropic vorticity equation on the sphere with simplified forcing dissipation and topography model solutions exhibit persistent anomalies identifiable with blocked zonal and wave train anomalies in northern hemisphere atmospheric data flow structures similar to the patterns above occur as high variance eofs of this nonlinear model the southern hemisphere data we analyze consist in gridded daily maps of 500 mb heights from june 1972 to july 1983 two types of persistent anomalies appear in t

the generation of global rotational flow by steady idealized tropical divergence abstract tropical convective heating is balanced on the large scale by the adiabatic cooling of ascent the horizontal divergence of the wind above this heating may be viewed as driving the upper tropospheric rotational wind field a vorticity equation model is used to diagnose this relationship it is shown that because of the advection of vorticity by the divergent component of the flow the rossby wave source can be very different from the simple fd source often used in particular an equatorial region of divergence situated in easterly winds can lead to a rossby wave source in the subtropical westerlies where it is extremely effective this part of the source can be relatively insensitive to the longitudinal position of the equatorial divergence a divergence field which is asymmetric about the equator can lead to a quite symmetric rossby wave source for a steady frictionless flow the rossby wave source averaged over regions within closed streamfunction or absolute vorticity contours is under cert

character distribution and tectonic significance of accretionary terranes in the central alaska range the central part of the alaska range near mount mckinley is composed of nine separate tectonostratigraphic terranes that were accreted in southern alaska during late mesozoic time these terranes now form long linear fault bounded belts that are subparallel to the denali fault on the north but oblique to the fault on the south the postaccretion right lateral offset along the denali fault system is about 200 km from north to south the major terranes are 1 yukon tanana terrane metasedimentary and metavolcanic rocks mostly undated but including rocks of known late paleozoic age polymetamorphosed with terminal events in late mesozoic 2 pingston terrane isoclinally folded upper triassic deep water silty limestone quartzite and carbonaceous slate folded with upper paleozoic phyllite chert tuff and minor limestone 3 mckinley terrane upper paleozoic flysch chert and minor limestone intruded by large gabbro sills and dikes and overlain by thick piles of triassic porphyritic pillow lava the top of the section is thick sequence of upper mesozoic conglomerate flysch chert and phyllite 4 dillinger terrane very thick sequence of strongly folded lower paleozoic micaceous sandstone turbidites graptolitic shale and deep water limestone locally overlain unconformably by jurassic fossiliferous sandstone or triassic pillow basalt 5 windy terrane heterogeneous assemblage of serpentinite basalt tuff and chert ophiolite with paleozoic and mesozoic flysch and blocks of mid paleozoic fossiliferous limestone 6 mystic terrane predominantly upper paleozoic flysch and conglomerate but also includes lower paleozoic graptolitic shale pillow basalt and shallow water limestone and upper paleozoic fossiliferous limestone sandstone chert and undated pillow basalt 7 chulitna terrane upper devonian ophiolite overlain by upper paleozoic chert volcanic conglomerate limestone and flysch capped by lower triassic limestone and upper triassic red beds basalt and interbedded basalt and limestone later mesozoic rocks are sandstone chert and argillite 8 westfork terrane jurassic chert sandstone conglomerate and triassic and jurassic crystal tuff 9 broad pass terrane upper paleozoic chert tuff and argillite with blocks of devonian and older limestone locally associated with serpentinite these diverse terranes of mixed oceanic and continental affinities are now juxtaposed to form a complex sequence of folded and faulted rootless nappes major suture zones between them are occupied by intensely deformed upper mesozoic flysch all of the terranes differ markedly from wrangellia the southermost coherent accreted terrane in alaska paleomagnetic measurements from triassic rocks prove that wrangellia originated near the equator probably in the southern heimsphere paleolatitudes for terranes in the central alaska range are not yet determined but other lines of evidence biogeographic and lithologic suggest large scale northern transport for some terranes

comments on southern mid to high latitude variability a zonal wavenumber 3 pattern and the antarctic circumpolar wave in the csiro coupled model abstract variability in the southern atmospheric circulation at mid to high latitudes with a dominant quasi stationary wavenumber 3 pattern has been reported in many observational studies the variability is barotropic in nature with signals in the middle troposphere as well as at the atmosphere ocean interface moreover there are preferred fixed centers for the strongest anomalies these features are well reproduced by the commonwealth scientific and industrial research organisation coupled model on various timescales on the interannual timescale an index of the modeled wavenumber 3 pattern shows little correlation with the modeled southern oscillation index suggesting that the variability associated with wavenumber 3 anomalies is separate to modeled enso like events however the variation of the pattern index is strikingly similar to and highly correlated with the modeled oceanic variability the associated oceanic anomalies move eastward and are similar to those of the observed antarctic circum

analysis of an interactive instability mechanism for the antarctic circumpolar wave abstract an interactive atmosphere ocean instability mechanism that reproduces some salient properties of the observed antarctic circumpolar wave and also its manifestation in the commonwealth scientific and industrial research organisation csiro mark 2 coupled model is analyzed with a more complete treatment than that studied by others it is suggested that this interaction mechanism is important in maintaining this phenomenon in both the model and the real atmosphere ocean but is not strong enough to initiate it through use of a simple model consisting of a zonally periodic midlatitude beta plane with a uniform mean north south temperature gradient a barotropic atmosphere and a two layer ocean with an inactive lower layer the stability of uniform zonal flow to small perturbations was analyzed the perturbation equations describe the velocity and temperature fields in both the atmospheric and oceanic layers and include the exchange in momentum and heat between them by surface fluxes the interactio

low frequency variability in the southern ocean region in a simplified coupled model 1 patterns of interannual variability of the ocean atmosphere coupled system in the southern hemisphere extratropics are studied with a simple dynamical model in order to determine the basic physical processes of interaction independently of tropical forcing the model used is an atmospheric quasi geostrophic model coupled to a slab oceanic mixed layer which includes mean geostrophic advection by the antarctic circumpolar current acc the ocean atmosphere coupling occurs through surface heat fluxes and ekman current heat advection in a fully coupled simulation the atmospheric part of the model which includes high frequency transient eddies at midlatitudes exhibits a strong southern annular mode sam as the first mode of variability at interannual timescales the sam related wind anomalies induce ekman currents in the mixed layer which produce sea surface temperature anomalies these are then advected along by the acc a forced mechanism where the ocean role is reduced to advect the sea surface temperature sst appears sufficient to reproduce the main features of the variability nevertheless a positive feedback of the ocean was also found it operates through anomalous ekman currents heat advection and contributes to the maintenance of the sst anomaly

u pb dating of hydrothermal zircon from the dongping gold deposit in north china constraints on the mineralization processes abstract the dongping gold deposit is a large deposit with total gold reserves of 100 tons it is located at the northern margin of the north china craton northwestern hebei province china the ore bodies are hosted by the devonian shuiquangou syenite complex and consist mainly of auriferous quartz veins and disseminated ore in the altered and silicified syenite u pb dating of zircon from hornblende syenite on the western margin of the complex yields a crystallization age of 400 3 5 ma mswd 0 018 morphology cathodoluminescence imaging and geochemical classifications of zircon from the first stage of disseminated ore and gray auriferous quartz veins and from later stage low grade quartz veins point to their newly crystallized hydrothermal origin the hydrothermal zircon from the disseminated ore and auriferous gray quartz vein are dated at 389 1 0 ma and 385 5 7 ma respectively which are detectably younger than but close to the crystallization age of the syenite complex and might have been formed by post magmatic hydrothermal processes both types of ore are dominant in the ore deposit and we propose that the pervasive post magmatic hydrothermal alteration is the main ore forming stage hydrothermal zircon from a low grade auriferous quartz vein yields a u pb age of 140 ma interpreted as forming during a younger period of superimposed yanshanian hydrothermal mineralization thus the ore of the dongping gold mine represents a post magmatic devonian hydrothermal ore deposit with jurassic cretaceous hydrothermal overprinting

evidence for the antarctic circumpolar wave in the sub antarctic during the past 50 years sea surface temperatures have been measured at the islands of marion 47 degrees s 38 degrees e from 1949 to 1998 and gough 40 degrees s 10 degrees w from 1956 to 1998 these are some of the longest records of their kind in the sub antarctic evidence for the passage of the antarctic circumpolar wave is apparent at each island presenting one of the most extended documentation of this phenomenon to date the highest negative correlation between the anomalies in each island s sea surface temperature record and the sea ice extent anomalies is observed directly south of each individual island the sea surface temperature anomalies at gough lead those at marion by about one year in average with mean precession periods of 8 6 8 9 and 10 4 years in the 60s 80s and 90s respectively these precession periods can be compared to those observed in the sea ice extent anomalies

a modelling and observational study of the relationship between sea surface temperature in the north west atlantic and the atmospheric general circulation results from four pairs of 50 day wintertime integrations of the meteorological office s 5 level general circulation model with warm and cold sea surface temperature s s t anomalies of about 3 k in the northwest atlantic are described difference fields between the warm and cold integrations are statistically significant at the 1 level with positive geopotential height over the central north atlantic and weaker negative height over europe the storm track over the atlantic is displaced from its normal position results from four further pairs of integrations with halved s s t anomalies are also described the response is approximately linear with systematic differences in 500 mb geopotential height over the atlantic parts of which are just significant at the 10 level with half the full s s t anomaly overall however the model s response is weaker than could be obtained with tropical s s t anomalies of the same magnitude results from the model integrations are compared with results from an observational study of the relationship between wintertime s s t in the north west atlantic and mean sea level pressure and 500mb height two independent 30 year periods were chosen for study thus minimizing the influence of long term trends in s s t over the atlantic and europe the model results compared well with the observations with s s t data lagging the atmosphere by one month the observational study appears to show that the s s t anomalies are initially forced by perturbations in the atmospheric circulation with s s t data leading the atmosphere by one month results show that atmospheric and s s t anomalies are most persistent in the period october to december throughout the winter these lagged relationships are much weaker and not statistically significant diagnostics of e vector divergence from the gcm experiments are used to suggest that anomalous baroclinic wave activity over the atlantic is important as a momentum forcing for the anomalous time mean flow pattern on the other hand the role of thermal forcing provided by anomalous diabatic heating and transient eddy heat flux convergence may be important to substantiate this statement a simple linear steadystate two layer model of the response to extratropical thermal forcing is described with a suitable basic state flow and a mid tropospheric heat source given mainly by the transient eddy heat flux convergence the response is shown to be equivalent barotropic with a downstream ridge and ascent over the thermal source conversely results from an ocean mixed layer model are discussed which suggest that warm s s t anomalies could be maintained by a positive surface pressure perturbation positioned downstream of the anomaly through anomalous northward advection of warm ocean water by ekman drift currents this northward advection would balance the sensible and latent heat loss into the atmosphere over the s s t anomaly hence it is possible that some positive ocean atmosphere feedback may account for the persistence of such atmospheric and oceanic anomalies