prolonged magmatism juvenile nature and tectonic evolution of the chinese altai nw china evidence from zircon u pb and hf isotopic study of paleozoic granitoids abstract paleozoic granitoid magmatism played an important role in the tectonic evolution of the chinese altai and zircon u pb and hf isotopic compositions have been determined for samples from eleven granitic plutons batholiths the jiadengyu gneissic granitic pluton yielded a zircon u pb age of 479 ma and thus it does not represent precambrian basement as suggested previously our results and published data demonstrate that voluminous granitoids were continuously emplaced over more than 30 area of the chinese altai during the period from 447 ma to 368 ma with a climax at ca 400 ma ages for zircon overgrowth rims demonstrate additional thermal events at ca 360 and 280 ma respectively positive e hf t values 0 to 9 of normal magmatic zircons suggest that the granitoid magmas were derived from juvenile sources xenocrystic zircon cores are 543 421 ma old and also give positive e hf t values 2 5 to 12 suggesting their origin as early crystallized minerals in the magma chambers or as inherited cores from newly accreted meterials the strong magmatism at ca 400 ma significantly changed the hf isotopic composition of the magma source by substantial input of juvenile material in a relatively short period geophysical geological and geochemical data support that ridge subduction was a possible mechanism for the strong magmatism ca 400 ma and the above mentioned change of hf isotopic composition in the magma source

depleted mantle source for the ulungur river a type granites from north xinjiang china geochemistry and nd sr isotopic evidence and implications for phanerozoic crustal growth abstract the ulungur river granites from north xinjiang china display two petrological trends 1 a peralkaline trend composed of alkali amphibole and alkali pyroxene bearing granites and dykes and 2 an aluminous trend represented by alkali granites monzogranites and aluminous granite dykes within the peralkaline granites rb sr whole rock isochron dating yielded an age of 300 ma for the emplacement of the peralkaline granites and 270 ma for the aluminous granites the ulungur river granites share all the geochemical features common to a type granites of the world the ulungur river granites are post orogenic and emplaced in a post collisional extensional environment the peralkaline and aluminous rocks have indistinguishable nd isotopic compositions they have unusually positive and relatively uniform nd t values ranging from 5 1 to 6 7 for the peralkaline rocks at 300 ma and from 5 5 to 5 9 for the aluminous rocks at 270 ma the initial 87sr 86sr ratios cannot be determined precisely by the whole rock isochron technique mainly because most samples are highly radiogenic and have high rb sr ratios in addition the large variation in sr isotopic compositions can partly be explained by crustal contamination during magma differentiation the nd isotopic data clearly indicate that both the peralkaline and aluminous rocks were derived from a long lived depleted mantle reservoir the formation of the ulungur river a type granites is hypothesized as follows 1 a depleted mantle was first metasomatised then subjected to partial melting leading to the generation of basic magmas now represented by the kalatongke mafic ultramafic complex in the ulungur river area 2 the basic magmas have undergone high degrees of fractional crystallisation with separation of biotite hornblende plagioclase potassium feldspar and other accessory phases such as apatite and ilmenite with the residual magmas forming the peralkaline granites during the magmatic differentiation the liquids were probably contaminated by crustal materials as evidenced by nb depletion and nd sr isotopic systematics on the other hand the formation of aluminous granites involved a replenishment of new mantle derived magmas into the differentiating magma chamber and followed by fractional crystallisation with retention of hydrous phases hornblende and biotite the petrological evolution of the ulungur river granites is thus from peralkaline to calc alkaline and not from calc alkaline to peralkaline as more often observed elsewhere the ulungur river granites in common with the voluminous granitoids occurring in the central asian orogenic belt represent a significant juvenile addition of the continental crust in the phanerozoic

seismic structure and rheology of the crust under mainland china abstract the crust and upper mantle in mainland china were relatively densely probed with wide angle seismic profiling since 1958 and the data have provided constraints on the amalgamation and lithosphere deformation of the continent based on the collection and digitization of crustal p wave velocity models along related wide angle seismic profiles we construct several crustal transects across major tectonic units in mainland china in our study we analyzed the seismic activity and seismic energy releases during 1970 and 2010 along them we present seismogenic layer distribution and calculate the yield stress envelopes of the lithosphere along the transects yielding a better understanding of the lithosphere rheology strength beneath mainland china our results demonstrate that the crustal thicknesses of different tectonic provinces are distinctively different in mainland china the average crustal thickness is greater than 65 km beneath the tibetan plateau about 35 km beneath south china and about 36 38 km beneath north china and northeastern china for the basins the thickness is 55 km beneath qaidam 50 km beneath tarim 40 km beneath sichuan and 35 km beneath songliao our study also shows that the average seismic p wave velocity is usually slower than the global average equivalent with a more felsic composition of crust beneath the four tectonic blocks of mainland china resulting from the complex process of lithospheric evolution during triassic and cenozoic continent continent and mesozoic ocean continent collisions we identify characteristically different patterns of seismic activity distribution in different tectonic blocks with bi or even tri peak distribution of seismic concentration in south tibet which may suggest that crustal architecture and composition exert important control role in lithosphere deformation the calculated yield stress envelopes of lithosphere in mainland china can be divided into three groups the results indicate that the lithosphere rheology structure can be described by jelly sandwich model in eastern china and creme brulee models with weak and strong lower crust corresponding to lithosphere beneath the western china and kunlun orogenic belts respectively the spatial distribution of lithospheric rheology structure may provide important constraints on understanding of intra or inter plate deformation mechanism and more studies are needed to further understand the tectonic process es accompanying different lithosphere rheology structures

contrasting styles of mineralization in the chinese altai and east junggar nw china implications for the accretionary history of the southern altaids abstract the chinese altai east junggar collage in the southern altaids hosts three metallogenic belts which are from north to south 1 a volcanogenic massive sulphide vms cu pb zn belt 2 a belt of shear zone related gold deposits 3 a porphyry cu au mo belt the vms deposits formed in two pulses c 405 ma and c 375 ma in the chinese altai arc the porphyry deposits developed in three pulses in the east junggar arc the first two synchronous with the vms mineralization and the third at c 330 ma the shear zone related gold deposits developed in the late carboniferous to permian at the contact between the chinese altai and east junggar arcs time space distributions of diverse ore deposits across the altai east junggar collage indicate that the collage developed from two independent arcs the chinese altai and the east junggar the vms and porphyry deposits developed in the chinese altai and east junggar arcs respectively the chinese altai arc is interpreted to be a japanese type arc and the east junggar arc a mariana type arc during the latest palaeozoic the two arcs were juxtaposed by the erqis fault when many shear zone related lode gold deposits were emplaced these metallogenic distributions were a likely response to spatially localized mechanisms of crust growth and to the tectonic evolution of the altai east junggar collage and they are consistent with interpretation of the altaids as a multiple subduction accretion collage

zircon u pb and hf isotopic study of gneissic rocks from the chinese altai progressive accretionary history in the early to middle palaeozoic abstract gneissic rocks in the chinese altai mountains have been interpreted as either paleozoic metasedimentary rocks or precambrian basement this study reports geochemical and geochronological data for banded paragneisses and associated gneissic granitoids collected along a ne sw traverse in the northwestern chinese altai petrological and geochemical data suggest that the protoliths of the banded gneisses were possibly immature sediments with significant volcanic input and that the gneissic granitoids were derived from i type granites formed in a subduction environment three types of morphological features can be recognized in zircons from the banded gneisses and are interpreted to correlate with different sources zircons from five samples of banded paragneiss cluster predominantly between 466 and 528 ma some give neoproterozoic ages and a few yield discordant paleoproterozoic to archean ages zircon hf isotopic compositions indicate that both juvenile mantle and crust materials were involved in the generation of the source rocks from which these zircons were derived in contrast zircons occur ubiquitously as elongated euhedral prismatic crystals in the four samples of the gneissic granitoids and define single populations for each sample with mean ages between 380 and 453 ma the general absence of precambrian inheritance and positive zircon hf values for these granitoids suggest insignificant crustal contribution to the generation of the precursor magmas our data can be interpreted in terms of a progressive accretionary history in early to middle palaeozoic times and the chinese altai may possibly represent a magmatic arc built on a continental margin dominated by neoproterozoic rocks

a synthesis of zircon u pb ages and hf isotopic compositions of granitoids from southwest mongolia implications for crustal nature and tectonic evolution of the altai superterrane abstract granitoid magmatism is extensively developed in the altai superterrane but the timing of magmatic events is not so well determined in this study twelve granitoid intrusions from southwest mongolia were dated by the zircon u pb method and analyzed for zircon hf isotopic compositions the new age data indicated three phases of magmatic emplacement middle paleozoic 398 350 ma late paleozoic 317 289 ma and triassic ca 244 211 ma the first phase magmatism is mainly composed of hornblende bearing i type granitoids formed during a long lasting subduction process in the early to middle paleozoic the second phase magmatism was manifested by a few small intrusions primarily distributed along the erqis fault zone and probably formed in a transitional tectonic regime from subduction to post tectonic setting in the late paleozoic the third phase magmatism was represented by post tectonic granitoids emplaced in an intraplate extensional setting model ages that were calculated using the composition of new continental crust are predominantly neoproterozoic to early paleozoic indicating that the protoliths of granitoids were likely dominated by paleozoic juvenile crust with minor neoproterozoic materials the altai superterrane was a huge paleozoic tectonic collage produced by amalgamation of subduction accretion complexes in the margin of the siberian continent and the tuva mongol microcontinent

petrogenesis and magmatic hydrothermal evolution time limitation of kelumute no 112 pegmatite in altay northwestern china evidence from zircon upb and hf isotopes abstract granitic pegmatites and associated rare metal deposits unique features in the altay orogen are located in a key tectonic position of the southern central asian orogenic belt caob and document the tectonic evolution of the paleo asian ocean the kelumute no 112 pegmatite which intruded into the jideke two mica granites hosts abundant rare metal e g li be nb ta ore deposits and ranks only second to the koktokay no 3 pegmatite in both size and reserves to explore the evolution time limitation of magmatic magmatic hydrothermal and hydrothermal stages in the pegmatite magma system the tectonic setting and the genetic relationship between pegmatites and granites this study presents zircon u pb and hf isotopic compositions of the kelumute no 112 pegmatite and the wall rocks two mica granite and biotite granite as determined by la icpms and la mc icpms the weighted mean 206 pb 238 u ages of the internal textural zones of the pegmatite including zones i ii iii v and vi are 238 3 2 0 ma 233 5 3 7 ma 188 3 1 7 ma 218 8 1 9 ma and 210 7 1 6 ma respectively wall rocks of two mica granite and biotite granite are dated at 445 6 4 3 ma and 455 6 5 4 ma respectively zircons from the kelumute no 112 pegmatite have lower positive e hf t values 0 03 to 2 35 with t dm model ages of 1112 1225 ma wall rocks show similar zircon e hf t values 1 41 to 4 13 and t dm model ages 1172 to 1515 ma however three xenocrystic zircons from the granites are characterized by larger negative ehf t values 5 85 to 9 83 and older t dm model ages 1839 to 2090 ma thus the following conclusions can be drawn 1 the kelumute no 112 pegmatite and its wall rocks jideke two mica granite and biotite granite have no genetic relationship as indicated by the large gaps between their formation ages however they did originate from a common source composed of ancient crust and mantle derived materials under two different tectonic settings 2 the magmatic magmatic hydrothermal transition and hydrothermal stages of the no 112 pegmatite magma lasted for 5 ma 23 ma and 22 ma respectively and 3 the no 112 pegmatite magma was most likely formed in a post collision tectonic setting indicating that block amalgamation and collisional orogeny of the caob continued into the triassic

reassessment of continental growth during the accretionary history of the central asian orogenic belt we argue that the production of mantle derived or juvenile continental crust during the accretionary history of the central asian orogenic belt caob has been grossly overestimated this is because previous assessments only considered the palaeozoic evolution of the belt whereas its accretionary history already began in the latest mesoproterozoic furthermore much of the juvenile growth in central asia occurred in late permian and mesozoic times after completion of caob evolution and perhaps related to major plume activity we demonstrate from zircon ages and nd hf isotopic systematics from selected terranes within the caob that many neoproterozoic to palaeozoic granitoids in the accreted terranes of the belt are derived from melting of heterogeneous precambrian crust or through mixing of old continental crust with juvenile or short lived material most likely in continental arc settings at the same time juvenile growth in the caob occurred during the latest neoproterozoic to palaeozoic in oceanic island arc settings and during accretion of oceanic island arc and precambrian terranes however taking together our data do not support unusually high crust production rates during evolution of the caob significant variations in zircon ehf values at a given magmatic age suggest that granitoid magmas were assembled from small batches of melt that seem to mirror the isotopic characteristics of compositionally and chronologically heterogeneous crustal sources we reiterate that the chemical characteristics of crustally derived granitoids are inherited from their source s and cannot be used to reconstruct tectonic settings and thus many tectonic models solely based on chemical data may need re evaluation crustal evolution in the caob involved both juvenile material and abundant reworking of older crust with varying proportions throughout its accretionary history and we see many similarities with the evolution of the sw pacific and the tasmanides of eastern australia

modeling the northern adriatic double gyre response to intense bora wind a revisit 1 a combination of recent intensive observations and simulations with two numerical models is used to revisit the issue of the northern adriatic response to strong bora episodes new observed and simulated data reinforce the view that an episode of strong bora wind provokes a double gyre cyclonic trieste and anticyclonic rovinj response north of the po delta pula line during an intense bora episode both measured and modeled statistics picture a downwind highly polarized and almost depth independent flow within the trieste gyre nw arm its ne arm maintains a sharp polarization and strong depth dependence while exhibiting lower speeds with models in good accord with observations the current statistics for rovinj gyre provide lower maximum and average speed values and less polarized but still rather depth independent flow while exhibiting clockwise rotation the north arm of the senj gyre positioned south of the po delta pula line enjoys more lateral freedom and exhibits less rectilinear flow our review reinforces the notion that modeling studies based on ecmwf wind forcing fail to properly take into account the orographic control of the dinaric alps and to produce correct bora induced gyral pattern the coamps model successfully simulated the onset duration and decay of the wind peaks but exhibited a tendency to overpredict the strength of the bora wind our simulations have identified the shallow nw coastal strip as an important source of colder water observed in a sequence of remotely sensed sst fields derived from avhrr data

origin of permian gabbroic intrusions in the southern margin of the altai orogenic belt a possible link to the permian tarim mantle plume abstract zircon u pb dating and hf isotopic compositions whole rock and mineral geochemistry as well as field and petrographic observations are reported for the permian gabbroic intrusions in the southern margin of the altai orogenic belt similar zircon ages 280 ma of these intrusions to that of the permian tarim mantle plume suggest a possible link to the tarim plume olivine grains from the intrusions have fo contents ranging from 69 to 81 and nio from 0 05 to 0 21 wt indicating the crystallization from evolved mafic magmas clinopyroxene grains from the intrusions have 0 3 to 1 5 wt tio 2 and display a rift to arc like affinity the intrusions are tholeiitic and have slightly lree depleted to lree enriched chondrite normalized rare earth element ree patterns zircons from the intrusions have e hf t values higher than 8 0 whereas the whole rock e nd t values range from 2 7 to 7 0 rocks from the intrusions have nb la of 0 2 to 0 8 consistent with the derivation from a depleted sub lithospheric mantle with variable degrees of crustal contamination the presence of primary hornblende and or biotite in the rocks indicates metasomatism by slab derived fluids melts in the mantle source we propose that upwelling of asthenospheric mantle in the permian tarim mantle plume along the irtish suture zone resulted in partial melting of the sub continental lithospheric mantle based on a comparison between the ni cu sulfide bearing kalatongke complex and un mineralized intrusions we suggest that ni cu sulfide mineralized intrusions in the altai orogenic belt are characterized by the enrichments of lrees and liles and by the presence of primary water bearing minerals

geostrophic circulation patterns in the northeastern adriatic sea and the effects of air sea coupling may september 2003 1 ctd data were collected weekly during 20 cruises from may to september 2003 over a 19 station grid in a coastal region of the northeastern adriatic sea as part of the adriatic sea integrated coastal areas and river basin management system pilot project adricosm relative geostrophic velocities indicated fine scale circulation patterns in the area consisting of two pronounced circulation cells of cyclonic and anticyclonic character and that were present in the area for most of the investigated period these motions were induced primarily by spatial variations in the temperature field and may be strengthened during episodes of very strong northeasterly bora wind when the investigated region is not heated cooled uniformly

geochemistry and nd isotopic composition of the early paleozoic flysch sequence in the chinese altai central asia evidence for a northward derived mafic source and insight into nd model ages in accretionary orogen abstract although nd isotopic composition of sedimentary rocks is considered as a useful tool to trace the provenance their nd model age tdm is usually misused to discuss the timing of crustal formation in accretionary orogen in the central asian orogenic belt an early paleozoic flysch sequence extensively occurs in the chinese altai and adjacent western mongolian terranes sedimentary rocks in the northwestern chinese altai were collected from the flysch sequence for geochemical and nd isotopic studies although these rocks show different geochemical characteristics e g arenaceous and argillaceous they all have relatively low cia chemical index of alteration values 49 75 indicating a relatively weak weathering source or the absence of compositionally mature alumina rich minerals produced by chemical weathering processes their relatively high icv index of compositional variability values 0 95 1 35 reveal an immature source and indicate that these rocks were probably deposited in an active tectonic setting the sedimentary rocks from the flysch sequence have high mgo sc co and low y nb which suggest significant addition of mafic rocks into the source modeling based on nb cr and zr mgo contents displays nearly 20 to 50 addition of mafic materials in combination with the age and distribution of mafic rocks in the chinese altai and adjacent terranes a northward derived mafic source is recommended for the sedimentary sequence although the sedimentary rocks have nd model ages tdm 1 44 1 57 ga older than devonian granites tdm 1 6 1 1 ga young detrital zircons from the sediments and inherited zircons from the granites 450 500 ma suggest a mixed source consisting of both old crust components and juvenile or less evolved crustal components this reveals that nd model ages tdm of metasedimentary rocks and igneous rocks can hardly provide close constrains on the timing of crustal formation in accretionary orogen with the progresses in adjacent western mongolian terranes a tectonic scenario dominated by subduction accretionary process is suggested to interpret the formation of the early paleozoic flysch sequence in the chinese altai and adjacent terranes

isotope provinces mechanisms of generation and sources of the continental crust in the central asian mobile belt geological and isotopic evidence abstract the available geological geochronological and isotopic data on the felsic magmatic and related rocks from south siberia transbaikalia and mongolia are summarized to improve our understanding of the mechanisms and processes of the phanerozoic crustal growth in the central asian mobile belt camb the following isotope provinces have been recognised precambrian t dm 3 3 2 9 and 2 5 0 9 ga at the microcontinental blocks caledonian t dm 1 1 0 55 ga hercynian t dm 0 8 0 5 ma and indosinian t dm 0 3 ga that coincide with coeval tectonic zones and formed at 570 475 420 320 and 310 220 ma continental crust of the microcontinents is underlain by or intermixed with juvenile crust as evidenced by its isotopic heterogeneity the continental crust of the caledonian hercynian and indosinian provinces is isotopically homogeneous and was produced from respective juvenile sources with addition of old crustal material in the island arcs or active continental margin environments the crustal growth in the camb had episodic character and important crust forming events took place in the phanerozoic formation of the camb was connected with break up of the rodinia supercontinent in consequence of creation of the south pacific hot superplume intraplate magmatism preceding and accompanying permanently other magmatic activity in the camb was caused by influence of the long term south pacific plume or the asian plume damping since the devonian

zircon u pb geochronology and hf isotopic composition of granitiods in russian altai mountain central asian orogenic belt the central asian orogenic belt caob consists of many tectonic terranes with distinct origin and complicated evolutionary history understanding of individual block is crucial for the reconstruction of the geodynamic history of the gigantic accetionary collage this study presents zircon u pb ages and hf isotopes for the granitoid rocks in the russian altai mountain range including gorny altai altai mongolian terrane and ctus suture zone between them in order to clarify the timing of granitic magmatism source nature continental crustal growth and tectonic evolution our dating results suggest that granitic magmatism of the russian altai mountain range occurred in three major episodes including 445 429 ma 410 360 ma and 241 ma zircons from these granitoids yield comparable positive ehf t values and neoproterozoic crustal model ages which favor the interpretation that the juvenile crustal materials produced in the early stage of the caob were probably dominant sources for the paleozoic magmatism in the region the inference is also supported by widespread occurrence of short lived juvenile materials including ophiolites seamount relics and arc assemblages in the northern caob consequently the paleozoic massive granitic rocks maybe do not represent continental crustal growth at the time when they were emplaced but rather record reworking of relatively juvenile proterozoic crustal rocks although mantle derived mafic magma was possibly involved to serve as heat engine during granitic magma generation the early triassic granitic intrusion may be a product in an intra plate environment as the case of same type rocks in the adjacent areas the positive ehf t values 1 81 7 47 and corresponding hf model ages 0 80 1 16 ga together with evidence of petrology are consistent with the interpretation that the magma source of the triassic granitic intrusion was derived from enriched mantle and melted under an usually high temperature condition likely due to basaltic magma that underplated the lower crust our data combined with evidence of the regional geology enable us to conclude that the gorny altai and altai mongolian terranes possibly have similar tectonic natures but represent two separate accretionary systems before devonian collision the accretion and amalgamation processes resulted in the paleozoic granitoid magmatism and caused the two terranes to merge as a composite tectonic domain at the siberian continental margin

post accretionary permian granitoids in the chinese altai orogen geochronology petrogenesis and tectonic implications the altai orogen is an important constituent of the central asian orogenic belt caob the main orogenic processes occurred mainly in the early to middle paleozoic and involved a series of northward subduction and terrane accretion however termination of the accretionary and post accretionary processes remains poorly defined the chinese altai is located in the southern part of this orogeny which is widely intruded by permian granitic plutons these plutons are approximately circular in shape free of deformation and generally cutting pre permian structures suggesting a post tectonic formation we report the results of geochronological and geochemical data from five specific granitic plutons buerjin xibodu daqiaonan aweitan and adenbluk which all yielded magmatic zircon u pb ages of about 270 ma these plutons are composed of high k calc alkaline rocks including k feldspar megaphyric granite biotite granite and monzogranite that have metaluminous to weakly lree enriched coupled with negative eu anomalies significant negative anomalies of ba sr p and ti are also observed in the primitive mantle normalized diagram they have positive whole rock end t 1 3 to 7 2 and zircon ehf t values 5 6 to 12 9 yielding sm nd model ages of 0 9 ga therefore these granitoids are proposed to have been generated by differentiation of mantle derived magmas with variable crustal contamination in view of the field occurrence structural analysis regional tectonics and geochemical characteristics these permian plutons are concluded to be post accretionary or post collisional asthenospheric upwelling after the collision and amalgamation of the altai and junggar blocks could have caused the mantle derived magmas that evolved to form the granitoids we note that permian intrusions are not only widespread but also voluminous in the caob they mostly are post collisional products and some of them might have been related to the large igneous province activity in the tarim block

ocean bottom deformation due to present day mass redistribution and its impact on sea level observations present day mass redistribution increases the total ocean mass and on average causes the ocean bottom to subside elastically therefore barystatic sea level rise is larger than the resulting global mean geocentric sea level rise observed by satellite altimetry and gps corrected tide gauges we use realistic estimates of mass redistribution from ice mass loss and land water storage to quantify the resulting ocean bottom deformation and its e ect on global and regional ocean volume change estimates over 1993 2014 the resulting globally averaged geocentric sea level change is 8 percent smaller than the barystatic contribution over the altimetry domain the di erence is about 5 percent and due to this e ect barystatic sea level rise will be underestimated by more than 0 1 mm y over 1993 2014 regional di erences are of ten larger up to 1 mm y over the arctic ocean and 0 4 mm y in the south paci c ocean bottom deformation should be considered when regional sea level changes are observed in a geocentric reference frame

neoproterozoic to paleozoic geology of the altai orogen nw china new zircon age data and tectonic evolution abstract we present a synthesis and a new account of the geological and tectonic history of the terranes of the chinese paleozoic altai orogen together with new single zircon ages for granitic and rhyodacitic rocks a central terrane consists of neoproterozoic to silurian amphibolite facies metasedimentary rocks and abundant devonian carboniferous granites the presence of precambrian basement is indicated by sinian fossils our xenocryst ages and published nd mean crustal residence ages of granites felsic arc type lavas on the southern margin of the terrane have a mean 207pb 206pb zircon age of 505 ma reflecting the time of arc volcanism and the presence of xenocysts with ages between 614 and 921 ma suggests derivation by intracrustal melting accordingly we suggest that a cambro ordovician continental magmatic arc was built on the southern margin of the central terrane by northward subduction a low grade ordovician andean type arc with a continental basement is situated above a normal fault on

an analysis of dense water production on the north adriatic shelf abstract the aim of this paper is to investigate the mechanism of dense water formation in the northern shelf region of the adriatic sea and its spreading towards the middle and south adriatic the analyses encompass temperature salinity sigma t and dissolved oxygen data collected during 1951 1989 interval in the deep trench located in the middle of the adriatic hydrographic sections as well as current and temperature time series collected in the north and middle adriatic were analysed too the data outline linear trends of salinity by 0 0036 0 0017 year 1 and of dissolved oxygen content by 0 022 0 008 ml l 1 year 1 whereas temperature data reveal three periods having different attributes strong fluctuations 1951 1962 higher 1966 1980 and lower 1981 1989 temperature values two types of north adriatic dense water naddw formation result from the analysis the first with rather low temperatures high rates of surface buoyancy losses e g 1956 1981 1984 and the second with high salinity large inflow of levantine intermediate water liw e g 1955 1968 after formation on the shelf naddw can bifurcate and goes close to the western main branch and or eastern secondary branch flanks by correlating hydrological data collected at the bottom of the trench with the north adriatic surface buoyancy fluxes and the po river discharges main naddw current velocity is calculated to be higher than 8 cm s 1 therefore reaching the jabuka pit about 1 month after generation whereas the secondary branch arrives there about 1 month later naddw current lasted for about 2 months spring 1984 preconditionings favourable for the naddw formation are achieved too by correlating both surface buoyancy fluxes and the po river discharges with temperature data measured at the bottom of the jabuka pit

late paleozoic magmatic record of east junggar nw china and its significance implication from zircon u pb dating and hf isotope abstract late paleozoic magmatic rocks including basic dykes basaltic andesite rhyolite keratophyre and syenite porphyry with minor tuff are widespread in the western margin of the east junggar terrane in situ zircon u pb dating and hf isotope analyses were carried out for these magmatic rocks from the baijiangou and zhangpenggou localities of east junggar integrating with geochemical data to investigate their tectonic evolution as well as crustal accretionary process of this region in the late paleozoic inherited zircons from basic dykes range in age from 435 ma to 300 ma the zhangpenggou rhyolite and keratophyre have typical arc like geochemical signatures and were formed in the early carboniferous 332 ma and 336 ma respectively suggesting they are products of subduction related magmatism the baijiangou rhyolites were formed in the late carboniferous 315 ma and 323 ma and their formation ages are similar to those of the syenite porphyries 307 ma and 312 ma the hf model ages and the formation ages of zircons from these magmatic rocks are alike with positive e hf t values vary from 0 7 to 16 6 implying that voluminous growth of juvenile crust happened in the east junggar terrane during the late paleozoic the absence of precambrian inherited zircons in basic dykes indicates the lack of precambrian basement beneath the east junggar terrane taking geochronological studies on regional ophiolites into account the east junggar terrane is considered as a devonian carboniferous oceanic island arc which has been continuously accreted to the southern active margin of the siberian craton since the early carboniferous

late devonian early permian a type granites in the southern altay range northwest china petrogenesis and implications for tectonic setting of a 2 type granites abstract the altay range is an important part of the central asian orogenic belt caob that contains a type granites that have been attributed to a post collisional setting during the late carboniferous permian however our new la icp ms zircon u pb age data demonstrates that there were two episodes of a type granite magmatism in the southern altay range a late carboniferous to early permian 308 291 ma suite does occur in the vicinity of qiakuerte but a distinct late devonian 382 367 ma suite is present in the kouan area the early kouan a type granites are mainly composed of alkali feldspar granites which are approximately synchronous with adakites boninites high ti basalts picrites ophiolitic rocks and high temperature low pressure metamorphic rocks whereas the late qiakuerte a type granites mainly consist of arfvedsonite and aegirine bearing granites which are approximately coeval with some mafic ultramafic rocks in the southern altay range a type granites are commonly classified as a1 and a2 sub types which are considered to be generated in anorogenic rift or plume related or post collisional settings respectively both suites of the southern altay range are geochemically similar to typical a2 type granites e g high k2o na2o feo mgo and ga al and y nb values and low cao ba sr and eu contents the kouan a type granites have relatively low la yb n 2 7 5 9 high end t 6 7 to 7 7 and nb la 0 59 1 67 and variable ehf t 5 0 to 14 1 values whereas the qiakuerte a type granites have comparatively high la yb n 4 2 9 2 low end t 5 3 to 6 0 and nb la 0 33 0 74 and variable ehf t 10 0 to 18 7 values the early kouan a type granites may have been generated by partial melting of a mafic source containing more depleted mantle derived components than the late qiakuerte a type granites we suggest that the late carboniferous to early permian qiakuerte granites were formed in a post collisional extensional setting as is typical of a2 type granites however the late devonian kouan a type granites were more plausibly generated in an extensional setting as a result of slab window caused by a ridge subduction in this case the upwelling of asthenosphere through the slab window provided the source of parental magmas or the heat for the generation of devonian magmas therefore our results suggest that a2 type granites can also form in a ridge subduction related extensional setting

geochemical and isotopic studies of the sedimentary and granitic rocks of the altai orogen of northwest china and their tectonic implications the altai orogen northwest china represents the southwestern margin of the central asian orogenic belt geochemical and nd sr isotope analyses were carried out on the palaeozoic sedimentary and granitic rocks in order to trace their sources and to evaluate the pattern of continental growth of the orogen nd isotopic data for both the granites and sediments suggest a significant proportion of middle proterozoic crust beneath the altai orogen however addition of juvenile material arc back arc oceanic crust during palaeozoic times is also significant trace elements and isotopic data of sediments suggest their sources were immature they represent mixtures between a palaeozoic juvenile component and an evolved continental crust the early palaeozoic sediments show e nd t 3 4 to 5 0 t dm 1 5 1 8 ga and i sr 0 710 0 712 they represent a passive margin setting with a predominance of evolved crustal material in the source the devonian sequences however might have been deposited in a back arc basin setting produced by subduction of the junggar oceanic crust along the irtysh fault a significant addition of arc material into the sedimentary basin is responsible for the highly variable e nd values 6 to 0 and i sr 0 711 0 706 the carboniferous rocks were also deposited in a back arc basin setting but with predominantly arc material in the source as suggested by an abrupt increase in e nd t 6 to 3 and decrease in i sr 0 7045 0 7051 voluminous syn orogenic granitoids have e nd t 2 1 to 4 3 i sr 0 705 0 714 and t dm 0 7 1 6 ga they were not derived by melting of local metasedimentary rocks as suggested by previous workers but by melting of a more juvenile source at depth post orogenic granites have higher e nd t 4 4 than the syn orogenic granitoids indicating their derivation from a deeper crustal level where juvenile crust may predominate

february 2003 marine atmospheric conditions and the bora over the northern adriatic 1 a winter oceanographic field experiment provided an opportunity to examine the atmospheric marine conditions over the northern adriatic mean february winds are from a northeasterly direction over most of the adriatic and a more northerly direction along the western coast wind speeds are fastest in jets over the ne coast during bora events and weakest in the mid northwestern adriatic diurnal air temperature cycles are smallest on the ne coast and largest in the midwestern adriatic the maximum sea air difference is 10 c on the eastern coast and near zero on the midwestern adriatic boras are northeasterly from wind events that sweep off croatia and slovenia bringing slightly colder and drier air over the northern adriatic the main bora season is december to march winter 2002 2003 was normal for bora events synoptic scale temporal variations are correlated over the northern adriatic fastest bora winds and highest wind stress over the northern adriatic is concentrated in four topographically controlled jets the strongest is the senj jet while the trieste jet extends across the entire northern adriatic between each two jets is a weak wind zone the greatest mean net heat loss is in bora jets in the ne adriatic where it was 438 w m 2 and is weakest in the midwestern northern adriatic where it was near zero wind stress is concentrated over the ne half of adriatic in four bora jets while wind stress is weak in the nw adriatic there is significant variation in wind stress mean and standard deviation structure over the northern adriatic with each bora event

devonian alaskan type ultramafic mafic intrusions and silicic igneous rocks along the southern altai orogen implications on the phanerozoic continental growth of the altai orogen of the central asian orogenic belt abstract in this contribution we have carried out an integrated study of the petrography geochronology geochemistry and mineral chemistry for the devonian alaskan type ultramafic mafic complexes and granitoids widely distributed along the southern altai orogen in order to provide a better understanding of the continental growth process and the regional tectonic evolution la icpms zircon u pb dating of three mafic samples one acidic volcanic rock sample and one granitic sample yielded the concordia ages of ca 400 ma olivine chemical compositions indicate these mafic intrusions crystallized from evolved mafic magmas and compositions of the clinopyroxene and hornblende show typical arc affinities whole rock compositions reveal their tholeiitic signature with enriched lrees and liles and intensive depleted hfses nb ta zr and hf leading to low hfse lree ratios nb la 0 1 0 4 isotopically these mafic intrusions have positive zircon e hf t 7 6 to 14 3 mostly 10 and positive whole rock e nd t 0 8 to 5 3 values which suggest that their parental magmas were derived from a time integrated depleted mantle source these features together with the presence of primary water bearing minerals biotite and or hornblende suggest that their primitive magmas were derived from a time integrated depleted lithosphere mantle which were metasomatized by fluids released from subduction slab these findings in combination with coeval voluminous granitoids and arc signature volcanic rocks indicate that the underplating of mafic magmas at the continental arc root leads to the partial melting of the continental crust it is inferred that mafic magmatic underplating in the altai orogenic belt significantly contributed to the phanerozoic vertical continental crust growth in the altai orogen

general circulation of the northern adriatic sea results of long term measurements abstract residual sea currents of the northern adriatic were analysed in the sense of the general global circulation over a period of 42 months in one main and two control stations at the end of the summer season and the beginning of autumn in the so called inversion period residual surface 6 m sea currents at the main station showed characteristic seasonal behaviour a change of direction from the north nw n ne to the south east se the sequence with se directions lasted about 1 5 months after that directions changed again to the nw or n the direction of bottom residual currents 37 m in this inversion period had the same pattern as the surface ones this behaviour of the currents can be associated with the change of the cyclonic gyre into the anticyclonic in all other periods at the main station the surface residual sea currents have predominant north directions bottom residual currents mainly followed the pattern of surface currents for all stations and periods except during the periods from january to june 1990 and 1992 when they were of opposite direction at station b

junggar basin northwest china trapped late paleozoic ocean abstract the junggar basin originated during the late paleozoic as either a remnant lower to mid paleozoic ocean basin or a mid carboniferous back arc intra or inter arc basin bounded by emergent volcanic arcs south of the siberian craton the retreating junggar sea left behind a regressive sedimentary section comprising at least 3 4 km of marine volcaniclastics in the southern junggar area sandstones deposited in the junggar basin since the devonian are exclusively volcaniclastic demonstrating that precambrian basement rocks have never been exposed in the basin and supporting the hypothesis that the junggar is underlain by oceanic crustal materials the mid carboniferous junggar ocean may have been a remnant ocean basin of early to mid paleozoic age or alternatively may have been an extending intra or inter arc basin formed behind an emergent volcanic arc in the northern turpan region subsequent strike slip deformation and the general sparsity of geologic and geophysical data from the junggar area make it difficult to distinguish between these models late early permian through triassic sediments of the junggar basin are exclusively non marine deposited in a flexurally subsiding foreland basin during initial uplift of the ancestral tian shan mountains the sedimentary section deposited during the late permian early triassic appears to be inconsistent with a proposed rifting episode during this period

time variable gravity from space and present day mass redistribution in theearth system abstract since 2002 the us german grace gravity recovery and climate experiment mission has been providing a precise survey of earth s time variable gravity field with unprecedented temporal and spatial sampling grace time variable gravity fields provide a means of measuring temporal and spatial variations of mass redistribution within the earth system the grace mission has launched a new era in studying a series of geophysical problems ranging from deep earth structure to tracking mass redistribution on and near the surface of the earth grace has greatly improved understanding of mass redistribution in various compartments of the climate system atmosphere oceans terrestrial water and cryosphere in this review we use examples to show how grace has fundamentally enriched a number of fields including but not limited to the global water cycle and land hydrology mass balance of polar ice sheets and mountain glaciers ocean mass and global sea level change and solid earth geophysics

geochronology petrogenesis and tectonic significance of peraluminous granites from the chinese altai nw china abstract the paleozoic granites in the chinese altai are important for the study of tectonic evolution and crustal growth in the central asian orogenic belt caob four representative peraluminous granitic intrusions were selected for systematic studies of zircon u pb and hf isotopic compositions and whole rock geochemical and nd sr isotopic analyses these rocks have high asi alumina saturation index al 2 o 3 cao na 2 o k 2 o 1 01 1 46 molecular ratios with 0 6 5 6 wt of normative corundum and are characterized by moderately negative eu anomalies eu eu 0 38 0 98 and strong depletion in ba nb and sr elements our data suggest that these intrusions were emplaced from 419 to 393 ma consistent with a period of intensive magmatic activities and high temperature metamorphism in the chinese altai while in situ zircon hf isotopic analyses for these granites give predominantly positive e hf t values 0 8 to 12 8 a few inherited zircons yield negative e hf t values from 12 5 to 1 53 the u pb age and hf isotopic data of these inherited zircons are similar to that of the widespread metasediments in addition the peraluminous granitic rocks have near zero or negative e nd t values 3 3 to 0 5 and relatively high initial 87 sr 86 sr ratios 0 7079 0 7266 distinct from those of the i type granites in the study region but similar to the early paleozoic habahe sediments these isotopic compositions suggest that the newly accreted metasediments of habahe group may be the major source rock of the peraluminous granites the geochemical compositions indicate that their precursor magmas were derived from a relatively shallow crustal level p 5 kbar and zircon saturation temperatures suggest that these granitic intrusions were emplaced at 672 861 c the peraluminous granitic magmas were generated by dehydration melting of newly accreted materials which were possibly brought to at least middle crustal depth by subduction related processes in an active margin and were subsequently molten by strikingly high ambient temperature probably caused by upwelling of the hot asthenosphere associated with ridge subduction in the paleozoic

contrasting deep crustal compositions between the altai and east junggar orogens sw central asian orogenic belt evidence from zircon hf isotopic mapping abstract there are long standing uncertainties over the deep crustal composition and basement nature of the chinese altai and junggar orogens of the southwestern central asian orogenic belt caob zircon lu hf isotopic tracer techniques applied to granitoids are helpful in distinguishing old from young deep crustal compositions this study aims to characterize the basement nature ancient juvenile of the chinese altai and east junggar orogens using hf isotopic mapping of granitoids 510 200 ma zircon hf isotopic data 18 new and 79 published samples indicate that the study area can be divided into six hf isotopic provinces on the basis of tdmc ages province i 1 4 ga ii 1 4 1 2 ga iii 1 2 1 0 ga iv 1 0 0 8 ga v 0 8 0 6 ga and vi 0 6 0 4 ga provinces i ii and iii occur mainly in the central units 2 and 3 and southern unit 4 altai orogen and have slightly positive zircon ehf t values of 0 5 to 9 1 with slightly old tdmc ages of 1 53 0 81 ga provinces iv and v are mainly distributed in the northern unit 1 and southernmost unit 5 altai orogen with zircon ehf t values of 7 5 to 11 1 and young tdmc ages of 0 84 0 60 ga in contrast province vi east junggar orogen has zircon ehf t values of 11 6 to 14 9 with much younger tdmc ages of 0 59 0 35 ga except for the small taheir area with a negative ehf t value of 2 5 and an older tdmc age of 2 5 ga there is a sharp contrast between the deep crustal compositions of the altai and junggar orogens which are ancient in central altai and relatively juvenile in east junggar this confirms that significant neoproterozoic phanerozoic continental crustal growth occurred in the southern altai and junggar orogens with juvenile crust occupying 78 of the study area and that the caob is a site of significant phanerozoic continental growth the distribution of juvenile and ancient crust in the altai and east junggar orogens provides new evidence for the tectonic division of the two orogens by the erqis fault zone and explains the heterogeneity of crustal growth in the southwestern caob

early permian post collisional high k granitoids from liuyuan area in southern beishan orogen nw china petrogenesis and tectonic implications abstract early permian magmatism is one of the most important tectonothermal events in the central asian orogenic belt caob early permian granitic magmatism has been recognized from southern beishan nw china and they were emplaced between 275 ma and 279 ma according to la icpms zircon u pb dating they are mainly metaluminous i type and belong to the high k calc alkaline and shoshonitic series the granitoids have calc alkalic and alkali calcic features their sri values range from 0 7028 to 0 7047 end t values from 2 5 to 1 2 with nd model ages tdm of 1 06 1 25 ga suggesting a mixed magma source of juvenile material with old continental crust furthermore some granitoids have weak heterogeneous zircon ehf t values 1 7 to 9 6 and hf model ages tdm2 0 84 1 57 ga that are also indicative of juvenile components with a small involvement of old continental crust based on geochemical and isotopic features these high k granitoids were derived from melting of heterogeneous crustal sources or through mixing of old continental crust with juvenile components and minor afc assimilation and fractional crystallization the juvenile components probably originated from underplated basaltic magmas in response to asthenospheric upwelling these early permian high k calc alkaline granitoids in the southern beishan orogen were probably emplaced in a post collisional extensional setting and suggest vertical continental crustal growth in the southern caob which is the same or similar to most granitoids in caob this study provides new evidence for determining the post accretionary evolution of the southern caob

nd sr isotopic mapping of the chinese altai and implications for continental growth in the central asian orogenic belt article i nfo the chinese altai orogen is a typical domain of the central asian orogenic belt and in previous syntheses was divided into six tectonic units or terranes in this paper 41 new and 36 published whole rock nd and sr isotopic data for granitoid intrusions and mafic dykes within units 2 and 3 of the central altai and units 4 to 6 of the southern altai were used for isotopic mapping the age of the samples used is known from u pb zircon dating end t values range from 4 to 2 in the central altai units 2 and 3 and from 1 4 to 6 in the southern altai units 4 and 5 and up to 8 4 in unit 6 correspondingly nd model ages tdm decrease from 1 6 1 1 ga in the central altai to 1 0 0 5 ga in the southern altai except for a continental fragment in unit 4 isr is elevated in the central units decreasing to b0 705 in the southern units 5 and 6 these results demonstrate that the central altai contains widespread old crustal components in its basement whereas the southern altai comprises a higher proportion of juvenile crust when integrated with published u pb zircon ages our data show that new crust grew southwards in the chinese altai in addition our data suggest that units 2 and 3 are a single tectonic unit whereas the southern altai unit 4 which previously was regarded as a single young accretionary terrane should be subdivided into two units a younger arc and an older continental fragment the granitoids in the chinese altai can be divided into syn and post non orogenic groups the syn orogenic granitoids have ca 50 80 mantle derived component whereas the post non orogenic granitoids contain ca 70 90 the generation of syn and post non orogenic granitoids represents horizontal lateral and vertical crustal growth which contributed ca 18 28 and 7 8 respectively to the area of the chinese altai this work shows that isotopic mapping is an effective approach to elucidate terrane composition in the central asian orogenic belt and thereby better constrain palaeozoic crustal growth

paleozoic multiple accretionary and collisional tectonics of the chinese tianshan orogenic collage abstract subduction related accretion in the junggar balkash and south tianshan oceans paleo asian ocean mainly in the paleozoic gave rise to the present 2400 km long tianshan orogenic collage that extends from the aral sea eastwards through uzbekistan tajikistan kyrgyzstan to xinjiang in china this paper provides an up to date along strike synthesis of this orogenic collage and a new tectonic model to explain its accretionary evolution the northern part of the orogenic collage developed by consumption of the junggar balkash ocean together with paleozoic island arcs northern ili issyk kul and chatkal located in the west which may have amalgamated into a composite arc in the paleozoic in the west and by addition of another two roughly parallel arcs dananhu and central tianshan in the east the western composite arc and the eastern dananhu and central tianshan arcs formed a late paleozoic archipelago with multiple subduction zones the southern part of the orogenic collage developed by the consumption of the south tianshan ocean which gave rise to a continuous accretionary complex kokshaal kumishi which separated the central tianshan in the east and other paleozoic arcs in the west from cratons tarim and karakum to the south cross border correlations of this accretionary complex indicate a general southward and oceanward accretion by northward subduction in the early paleozoic to permian as recorded by successive southward juxtaposition of ophiolites slices of ophiolitic melanges cherts island arcs olistostromes blueschists and turbidites which are mainly paleozoic in age with the youngest main phase being late carboniferous permian the initial docking of the southerly tarim and karakum cratons to this complicated late paleozoic archipelago and accretionary complexes occurred in the late carboniferous early permian in the eastern part of the tianshan and in the late permian in the western part which might have terminated collisional deformation on this suture zone the final stages of closure of the junggar balkash ocean resembled the small ocean basin scenario of the mediterranean sea in the cenozoic in summary the history of the altaids is characterized by complicated multiple accretionary and collisional tectonics

closure of the budget of global sea level rise over the grace era the importance and magnitudes of the required corrections for global glacial isostatic adjustment abstract the budget of global sea level rise includes contributions from several distinct factors including thermosteric effects the wasting of small ice sheets and glaciers and the loss of mass by the great polar ice sheets and by the continents due to desiccation since the former contribution may be estimated on the basis of both hydrographic survey data and more recently using argo float data the second may be estimated on the basis of mass balance measurements on existing ice fields and the latter on the basis of modern grace based time dependent gravity field measurements the inputs to the globally averaged rate of sea level rise may be directly constrained since grace also provides a measurement of the rate at which mass is being added to the oceans we are now in a position to ask whether this rate of mass addition to the oceans matches the rate at which mass is being removed from the continents as demonstrated herein the mass component of the budget of global sea level is closed within the observational errors when the mass derived contribution is added to the thermosteric contribution it is furthermore shown that the inference of the net rate of global sea level rise by the altimetric satellites topex poseidon and jason 1 is also reconcilable over the grace era it is noted those individual terms in the budget especially the contribution from small ice sheets and glaciers remains insufficiently accurate it is demonstrated that the lingering influence of the late quaternary ice age upon sea level is profound and that closure of the budget requires an accurate model of its impact

ocean mass from grace and glacial isostatic adjustment 1 we examine geoid rates and ocean mass corrections from two published global glacial isostatic adjustment gia models both of which have been used in previous studies to estimate ocean mass trends from gravity recovery and climate experiment grace satellite gravity data these two models are different implementations of the same ice loading history and use similar mantle viscosity profiles the model results are compared with each other and with geoid rates determined from grace during august 2002 to november 2009 when averaged over the global ocean the two models have rates that differ by nearly 1 mm yr 1 of ocean mass with the first model giving a correction closer to 2 mm yr 1 and the second closer to 1 mm yr 1 by comparing the two models we have discovered that 50 of the difference is caused by a global land ocean mean in the first model while it is appropriate to include this mean when subtracting gia effects from measurements of sea level change measured by tide gauges or satellite altimetry the mean should not be included when subtracting gia effects from ocean mass variations derived from satellite gravity data when this mean is removed the ocean mass corrections from the two models still disagree by 0 4 mm yr 1 we trace the residual difference to the fact that the first model also has large trends over the ocean related to large rates in its predicted degree 2 order 1 geoid coefficients such oceanic trends are not observed by grace nor are they predicted by the second model and they are shown to be inconsistent with the polar wander rates predicted by the first model itself if these two problems are corrected we find that the two model predictions agree at the 3 level on the basis of this analysis we conclude that the ocean mass correction for grace is closer to 1 mm yr 1 than 2 mm yr 1 although significant uncertainties remain

unraveling the early middle paleozoic paleogeography of kazakhstan on the basis of ordovician and devonian paleomagnetic results abstract it is a common concept that different tectonic units in the western part of the central asian orogenic belt were united into the landmass of the kazakhstania continent in the paleozoic but many important details of its history remain enigmatic and controversial recently published paleomagnetic data from this region demonstrate that the 2000 km long horseshoe shaped devonian volcanic belt was created by oroclinal bending of an originally rectilinear active margin of kazakhstania still the silurian and devonian paleomagnetic results which this interpretation is based upon are limited and unevenly spread along the belt and additional middle paleozoic data are highly desirable accordingly we studied three mid paleozoic objects from different segments of this volcanic belt two of the three new objects yielded paleomagnetic directions that fit perfectly into the oroclinal scenario whereas the third one provided no interpretable data the earlier history of kazakhstania however remains misty we obtained three new ordovician results in north central kazakhstan and found similar inclinations but widely dissimilar declinations previously published data show a large scatter of ordovician declinations in south kazakhstan and kyrgyzstan as well we analyzed all seven middle late ordovician paleolatitudes and came to the conclusion that a nearly e w trending active margin of the kazakhstania landmass had existed at low 10 s latitudes at that time we hypothesize that this margin of the kazakhstania landmass collided with another island arc called baydaulet akbastau and with the aktau junggar microcontinent by the ordovician silurian boundary as a result of this collision subduction ceased and regional deformation magmatism and rotations of crustal fragments took place in most of kazakhstania in silurian time kazakhstania moved northward crossing the equator and rotating clockwise by 45 this changed the orientation of the kazakhstania to nw se and thereby established the rectilinear predecessor of the modern curved devonian volcanic belt

accretionary orogenesis of the chinese altai insights from paleozoic granitoids zircon u pb dating and whole rock major oxide trace element and nd sr isotope compositions have been determined for four representative granitic intrusions in the sw chinese altai in order to understand the orogenesis and history of crustal growth in the central asian orogenic belt caob the ashile and halatas bodiesare relatively small intrusions formed in the late carboniferous 318 6ma andpermian 267 4ma respectively thelargertarlang tb andkeketuohaibatholiths kb havemagmaticagesof 359 to 412 ma the granitoids consist chiefly of tonalite granodiorite and granite and are metaluminous to weakly peraluminous in composition asi 0 8 1 1 the ashile pluton is characterized by relatively high mgo 2 73 3 54 wt and sr 395 456 ppm contents with low k2o na2o ratios 0 31 0 42 and mantle like nd sr isotopic compositions endt 2 85 to 3 26 initial 87 sr 86 sr 0 7047 0 7051 it probably formed by fractional crystallization of a mantle derived magma with limited assimilation of oldcrustalmaterial theotherintrusionshavenear zeroornegative endtvalues 0 67to 4 41 andhighersrisotopiccompositions initial 87 sr 86 sr 0 7067 0 7092 indicating a mixture of juvenile and old components in their genesis these intrusions are characterized by relatively low k rb cs contents and low rb sr ratios mostly b0 6 and generally exhibit moderate to high heavy rare earth element hree concentrations ybn 8 26 and weak hree fractionation dy ybnb1 5 with or without negative europium anomalies eu eu 0 5 1 0 these characteristics are consistent with an origin by dehydration melting of a hornblendebearing mid crustal source above the garnet stability field dominated by mafic to intermediate rocks this suggests that the deep crust of the chinese altai may contain a considerable proportion of juvenile material mantle derived magmatism probably in an active extensional continental margin setting played an important role in the formation of the chinese altai acting not only as a heat sourceforcrustalmeltingbutasasourceofjuvenilecomponents therelativelysmallvolumesanddistinctgeochemicalcompositions of the ashile and halatas plutons may imply a substantial change in the geodynamic setting in the late paleozoic 2007 elsevier b v all rights reserved

episodic growth of the gondwana supercontinent from hafnium and oxygen isotopes in zircon it is thought that continental crust existed as early as 150 million years after planetary accretion but assessing the rates and processes of subsequent crustal growth requires linking the apparently contradictory information from the igneous and sedimentary rock records for example the striking global peaks in juvenile igneous activity 2 7 1 9 and 1 2 gyr ago imply rapid crustal generation in response to the emplacement of mantle super plumes rather than by the continuous process of subduction yet uncertainties persist over whether these age peaks are artefacts of selective preservation and over how to reconcile episodic crust formation with the smooth crustal evolution curves inferred from neodymium isotope variations of sedimentary rocks detrital zircons encapsulate a more representative record of igneous events than the exposed geology and their hafnium isotope ratios reflect the time since the source of the parental magmas separated from the mantle these model ages are only meaningful if the host magma lacked a mixed or sedimentary source component but the latter can be diagnosed by oxygen isotopes which are strongly fractionated by rock hydrosphere interactions here we report the first study that integrates hafnium and oxygen isotopes all measured in situ on the same precisely dated detrital zircon grains the data reveal that crust generation in part of gondwana was limited to major pulses at 1 9 and 3 3 gyr ago and that the zircons crystallized during repeated reworking of crust formed at these times the implication is that the mechanisms of crust formation differed from those of crustal differentiation in ancient orogenic belts

resonant coupling of a traveling air pressure disturbance with the east adriatic coastal waters 1 exceptional sea level oscillations and strong current reversals observed in the east adriatic on 27 june 2003 are analyzed using available meteorological and tide gauge measurements and numerical model results it is shown that the variability in the atmosphere sea system was characterized by high frequencies 0 01 0 1 min 1 and sea level and current amplitudes surpassing 1 m and 1 m s 1 respectively the event was related to the occurrence of a gravity disturbance in the atmosphere above the adriatic the disturbance traveled toward the east southeast at a speed of 22 m s 1 and was resonantly coupled with a wave in the sea 50 m deep the resulting forced wave was further amplified when entering funnel shaped bays opened to it there are indications that the forcing disturbance and its counterpart in the sea excited normal modes of the bays and harbors in the area moreover nonlinear steepening of the forced wave seemingly occurred resulting in the formation of high frequency wave trains this process along with the generation of coastal seiches could explain the observed and modeled differences between the spectra of coastal variability and the spectrum of forcing wave

summer breakout of trapped bottom dense water from the northern adriatic 1 the paper deals with an intriguing dense water breakout episode in mid august 2004 which has been observed in the bottom layers of the oil rig located in the middle of the northern adriatic various data temperature series and vertical t s profiles currents meteorological measurements and satellite images have been analyzed in order to understand conditions which preceded were active and followed the breakout episode a stationary bottom pool of dense water generated during the previous winter has been suspected to be a source of the dense water observed during the breakout with a permanent position established by a stationary northern adriatic cyclonic anticyclonic gyre system the breakout lasted for 3 days advecting the bottom waters more than 2 c colder than residing waters at the oil rig site the main result of modeling experiments concerns the generative force for the observed breakout which was found to be a mesoscale storm that occurred over the open north adriatic on 8 august 2004 the storm has been reproduced by the coupled ocean atmosphere mesoscale prediction system coamps atmospheric model which was then used to force the princeton ocean model pom at the surface results of simulations reveal the capability of the storm to break the thermohaline fronts through the wind induced baroclinic transport and downwelling at the exposed shorelines this is the first study in the adriatic which evaluates the impact of mesoscale summer storm to the sea driving bottom layer circulation through the convergence divergence dynamics in addition to the direct impact on the sea surface through the wind stress forcing

genesis of post collisional granitoids and basement nature of the junggar terrane nw china nd sr isotope and trace element evidence the post collisional magmatism of the junggar terrane is characterized by intrusion of large amounts of granitoids and minor basic ultrabasic rocks the granitoids comprise two magmatic suites calc alkaline and alkaline which were emplaced contemporaneously at about 294 ma the calc alkaline rocks are typically sodium rich na2o k2o 1 1 3 5 and metaluminous a nk 1 0 a cnk 0 78 1 04 they show mildly fractionated ree patterns la yb n 15 and spidergrams with strong depletion of nb ti and to a lesser extent sr the alkaline granites have high contents of sio2 75 78 alkalis nb hree y sn f and high feo mgo ratios and huge sr and eu depletion in the spidergrams moreover they display characteristic tetrad ree patterns and non charac trace element behaviour the two rock suites have similar initial nd and sr isotopic compositions with end t in the range 5 2 to 7 1 and isr mostly in the range 0 7031 0 7041 this points to a predominance of juvenile components in their sources the calc alkaline rocks are most probably derived by dehydration melting of a basic lower crust leaving behind a granulite residue the process was probably triggered by underplating of mantle derived basic magmas in an extensional regime the alkaline granites are considered to have formed by differentiation of the calc alkaline granitoids our study argues for a juvenile continental crust for the basement of the junggar terrane which is likely dominated by early paleozoic oceanic crust and arc complex that were deeply buried during the late paleozoic subduction and accretion

evolution source and tectonic significance of early mesozoic granitoid magmatism in the central asian orogenic belt central segment abstract numerous early mesozoic granitoids have been recognized from the central segment of the central asian orogenic belt caob they can be broadly classified into two groups according to zircon u pb ages an early stage group covering the time span from early to middle triassic 250 230 ma and a late stage group emplaced during late triassic to early jurassic ca 230 190 ma early stage 250 230 ma granitoids are mainly distributed in the western central mongolia erguna belt cmeb the western altai belt ab the south mongolia xing an belt smxb and the beishan inner mongolia jilin belt bijb they consist mainly of quartz diorites granodiorites and monzogranites mostly of i type with minor mafic intrusions with some of them showing adakite like signatures and some with s type features late stage 230 190 ma granitoids mainly occur in the north mongolia transbaikalia belt nmtb the eastern cmeb erguna massif and the eastern altai belt ab they are predominately syenogranites monzogranites and syenites associated with many alkaline granites and mafic intrusions and are a type and transitional i a type or highly fractionated i type granites whole rock sr nd and zircon hf isotopic data have been compiled for regional isotopic mapping the end t values show large variations from 7 0 to 7 4 and nd model ages tdm from 0 46 ga to 1 43 ga as well as the initial sr isotopic ratios sri from 0 7023 to 0 7174 the zircon ehf t values vary from 4 6 to 15 3 and give two stage hf model ages tdm2 from 0 30 ga to 2 09 ga the extremely large variations of whole rock sr nd and zircon hf isotopes demonstrate strong isotopic heterogeneity of the source regions that are mainly dominated by juvenile components with significant old crustal participation furthermore the late stage granitoids in the nmtb the cmeb and the ab generally have more negative end t values and more variable zircon ehf t values than those of the early stage granitoids in the same belt implying an increasing crustal signature from early to late stage in the assumed heterogeneous source regions within the same belt which probably results from melting of shallower crust in parallel with a shift to more alkaline chemistry of the late granitoid magmas by contrast most late stage granitoids in the smxb and the bijb have more positive end t values and homogeneous zircon ehf t values than those of the early stage granitoids in the same belt indicating more juvenile contribution to the source of the these granitoids the generation of the early mesozoic granitoid magmas in the nmtb and the cmeb was dominated by the ongoing closure of the mongol okhotsk ocean and some was probably related to a mantle plume process they were possibly derived from subducted materials melting or juvenile components with some probable contributions from ancient continental crust early mesozoic granitoid magmas in the smxb the ab and the bijb were generated in a post non orogenic setting after the closure of the paleo asian ocean and were the results of partial melting of crustal components in response to underplating of mantle derived magmas most likely linked to lithospheric thickening and delamination and asthenospheric upwelling early mesozoic granitoid magmatism provides critical information on mesozoic post accretionary tectonic evolution of the paleo asian ocean and transitional tectonic regimes from early mesozoic subduction to late mesozoic closure of the mongol okhotsk ocean as well as post accretionary continental growth

contribution of ice sheet and mountain glacier melt to recent sea level rise altimeter data suggest that sea level rose by about 2 4 mm per year from 2005 to 2011 but estimates of the relative contributions of ocean warming and increased ocean mass are equivocal an analysis of ocean temperature and satellite gravity data suggests that the delivery of meltwater from ice sheets and mountain glaciers contributed 75 of the observed sea level rise

carboniferous mantle derived felsic intrusion in the chinese altai nw china implications for geodynamic change of the accretionary orogenic belt abstract this paper reports whole rock sr nd and zircon u pb and hf isotopic compositions as well as major and trace element data for the granodiorites and their mafic microgranular enclaves mmes in the tuokesalei area northwestern chinese altai the granodiorites are characterized by peraluminous compositions a cnk 1 01 1 45 with relatively high sio 2 64 4 to 70 9 wt and low mgo 0 75 to 1 97 wt contents these rocks possess low total rare earth element ree contents 67 187 ppm with weakly negative eu anomalies and mantle like whole rock nd sr isotopic compositions e nd t 2 5 to 4 5 87 sr 86 sr i 0 7038 to 0 7048 and zircon e hf t values 5 93 to 12 9 the mmes contain abundant magmatic amphiboles and needle like apatites have low sio 2 51 7 to 54 3 wt and high mgo 2 86 to 3 75 wt and ree contents 162 298 ppm and are characterized by moderately negative eu anomalies eu eu 0 40 0 60 and slightly depleted to enriched lree la nd n 0 74 1 41 and flat hree gd yb n 1 16 1 39 patterns the mmes have whole rock nd sr isotopic compositions e nd t 2 6 to 2 7 87 sr 86 sr i 0 7034 0 7050 similar to those of the host granodiorites their similarities in crystallization age mineral assemblage and isotopic composition document that the mmes may represent an early crystallized phase which was broken into pieces and brought to the shallow level during the host magma ascent and emplacement their precursor magmas were probably derived from an oceanic lithospheric mantle which was characterized by pronounced nd ta depletions mineral compositions of mmes suggest that amphibole was a major early fractional mineral which effectively differentiated the mantle derived basaltic liquids to silica rich melts zircon u pb dating yielded an age of 313 5 ma for the host granodiorites and 313 13 ma for their mmes the geochemical data of this study records an important episode of magmatism in an environment transitional from a subduction related regime to a post tectonic extension results of this study suggest that the accretionary orogenic process did not completely terminate until the late carboniferous to permian in this region

the adriatic sea general circulation part ii baroclinic circulation structure abstract in the second part of the paper dedicated to the adriatic sea general circulation the horizontal structure of the hydrographic parameters and dissolved oxygen fields is described on a seasonal timescale maps of temperature and salinity climatological fields reveal the enhanced seasonal variability of the adriatic sea which at the surface is associated with the major dilution effects of river runoff the density and derived dynamic height fields show for the first time the baroclinic geostrophic structure of the general circulation winter is dominated by compensation effects between temperature and salinity fronts along the western coastline the resulting baroclinic circulation is weak and suggests the presence of barotropic current components not accessible by the dataset spring and summer seasons have the smallest spatial scales in the temperature and salinity fields and stronger subbasin scale gyres and current systems which have been classified in a schematic representation of the circu