linking the basement geology along the africa south america coasts in the south atlantic the work was financially supported by the czech science foundation 15 05988s we thank martin whitehouse and lev ilyinsky for their support while using the nordsim ion probe in stockholm the nordsim facility is jointly funded by denmark finland norway sweden and iceland this is nordsim publication 446 we appreciate the discussions with stano ulrich and pedro oyhantcabal during various stages of this project the paper benefited from the reviews of cees passchier and an anonymous reviewer cees passchier directed us to the work of abraham ortelius mentioned in the introduction and kindly provided the translation from latin

petrogenesis of the early cretaceous adakite like porphyries and associated basaltic andesites in the eastern jiangnan orogen southern china abstract early cretaceous quartz porphyries are associated with mantle derived mafic rocks basaltic andesites in the eastern segment of the neoproterozoic jiangnan orogen southern china zircons from two quartz porphyries yield identical u pb ages at 142 1 ma by the la icp ms method hornblende and augite are the dominant phenocrysts in the basaltic andesites and the groundmass plagioclase has a high anorthite content 80 both of which indicate high h 2 o 6 wt contents in the magma the basaltic andesites have low tio 2 0 68 0 78 wt and nb la 0 23 0 28 nb and ta depletions high initial 87 sr 86 sr ratios 0 710 and unradiogenic nd isotopes e nd t 3 4 to 3 7 implying that they were generated from the partial melting of an isotopically enriched lithospheric mantle source that had been metasomatized by subduction related fluids the quartz porphyries sio 2 65 6 70 5 wt show adakite like geochemical features with high sr y 18 1 53 4 and la yb 18 6 39 4 ratios but low y 9 44 15 2 ppm and yb 0 84 1 43 ppm contents they have low mgo 0 72 1 46 wt ni 1 04 14 7 ppm and cr 2 34 36 7 ppm contents and lower nd isotopic ratios e nd t 6 02 to 7 64 than the basaltic andesites suggesting that they may have been generated from the partial melting of the lower part of a thickened continental crust without interaction with the underlying lithospheric mantle the mafic magmas ascended from the metasomatized and hydrated lithospheric mantle and heated the lower part of thickened continental crust triggering partial melting to form the adakite like porphyries the moderate levels of sr 204 546 ppm and negative eu anomalies eu eu 0 69 0 86 in the porphyries require the presence of minor plagioclase as residual phase in the magma source indicating the continental crust may be not as thick 50 km as previously suggested the new recognition of adakite like porphyries and associated mafic rocks in the eastern jiangnan orogen reveals the significant role of neoproterozoic orogen related crust and oceanic sediments in the formation of mesozoic adakite like rocks of central eastern china

impact of intraseasonal oscillation on the tropical cyclone track in the south china sea this study investigates the impact of the intraseasonal oscillation iso on tropical cyclone tc tracks in the south china sea scs during 1970 2010 about one third of tcs in the scs move eastward while the other two thirds move westward in the tc genesis peak seasons of june october jjaso the westward moving tcs are controlled by the background tc steering flow of easterly and the eastward moving tcs by the tc steering flow induced by the iso the outgoing longwave radiation and wind fields show that the eastward moving tcs were mostly along the main axis of strong tc steering flow anomaly of westerly associated with the iso while the westward moving tcs were only weakly associated with the iso an experiment performed with a simple two level model further confirmed the result the interannual variation of tc tracks in the scs is also discussed it is found that the steering flow anomalies in the scs mostly favor eastward moving tcs in central pacific cp el nino and eastern pacific ep el nino years however the eastward flow anomalies are too weak to have strong influence on the majority of the tcs during la nina years tcs in the scs tend to move westward possibly related to the westward steering flow anomalies

observational evidence for predictions of tropical cyclone propagation relative to environmental steering abstract theories of vortex motion due to the variations of the coriolis parameter and environmental vorticity are compared to observations of tropical cyclone motion relative to computed steering flows using previously published composite data the composite results are manipulated to obtain a vector quantity for the difference between tropical cyclone motion and steering and this vector difference is termed propagation the properties of these propagation vectors within various composite data stratifications provide tentative support for nonlinear numerical results such as i the general magnitude and direction of the induced propagation ii the dependence of such propagation on the outer wind strength of the tropical cyclone and iii the dependence of such propagation on the direction of the environmental vorticity gradient ambiguities in the composite data are discussed with respect to linear and nonlinear theories of tropical cyclone propagation and several new composite data stratific

young eclogite from the greater himalayan sequence arun valley eastern nepal p t t path and tectonic implications abstract garnet geochronology was used to provide the first direct measurement of the timing of eclogitization in the central himalaya lu hf dates from garnet separates in one relict eclogite from the arun river valley in eastern nepal indicate an age of 20 7 0 4 ma significantly younger than ultra high pressure eclogites from the western himalaya reflecting either different origins or substantial time lags in tectonics along strike four proximal garnet amphibolites from structurally lower horizons are 14 15 ma similar to post eclogitization ages published for rocks along strike in southern tibet p t calculations indicate three metamorphic episodes for the eclogite i eclogite facies metamorphism at 670 c and 15 kbar at 23 16 ma ii a peak t granulite event at 780 c and 12 kbar and iii late stage amphibolite facies metamorphism at 675 c and 6 kbar at 14 ma the garnet amphibolites were metamorphosed at 660 c three models are considered to explain the observed p t t evolution the first assumes that the main himalayan thrust basal thrust of the himalayan thrust system cuts deeper at arun than elsewhere while conceptually the simplest this model has difficulty explaining both the granulite facies overprint and the pulse of exhumation between 25 and 14 ma a second model assumes that aborted subduction slab breakoff and ascent of india s leading edge occurred diachronously 50 ma in the western himalaya 25 ma in the central himalaya of nepal and presumably later in the eastern himalaya this model explains the p t t path particularly heating during initial exhumation but implies significant along strike diachroneity which is generally lacking in other features of the himalaya a third model assumes repeated loss of mantle lithosphere first by slab breakoff at 50 ma and again by delamination at 25 ma this model explains the p t t path but requires geographically restricted tectonic behavior at arun the p t t history of the arun eclogites may imply a change in the physical state of the himalayan metamorphic wedge at 16 25 ma ultimately giving rise to the main central thrust by 15 16 ma

sensitivity of typhoon track to asymmetric latent heating rainfall induced by taiwan topography a numerical study of typhoon fanapi 2010 1 typhoon fanapi 2010 traveled westward across the central mountain range of taiwan on 19 september and its rainfall shifted from a symmetric to an asymmetric pattern with convection mostly to the south and southeast meanwhile the storm slowed down from 22 to 14 km h 1 for 12 h upon leaving taiwan and led to heavy rainfall 800 mm and serious flooding over the low lying southwestern plains through simulation and sensitivity tests using the cloud resolving storm simulator at 3 km grid size this study shows that the sudden and temporary speed reduction was caused by the asymmetric latent heating lh not the environmental flow specifically over a 9 h period the model storm moved westward at 16 km h 1 in the control run but increasingly faster and more toward the northwest when the moisture and thus the lh effect and its asymmetry is gradually reduced steering flow analysis and estimation using model results suggest an eastward motion vector of about 8 km h 1 consistent with the observation is produced by the asymmetric lh effect when the effects from the vertical wind shear and beta drift are both taken into account this result is further supported by the diagnosis on storm motion based on potential vorticity tendency although important such feedback to typhoon track from rainfall asymmetry that is induced by the blocking effect of topography have not been reported or studied

microsampling lu hf geochronology on mm sized garnet in eclogites constrains early garnet growth and timing of tectonometamorphism in the north qilian orogenic belt

crustal growth by magmatic overplating in the galapagos the isotopic compositions of xenoliths hosted in lavas from floreana island indicate that they formed from magmas unlike those at present day floreana instead the xenoliths are geochemically more similar to magmas now erupting from sierra negra and cerro azul volcanoes at the leading edge of the galapagos hotspot this is the first evidence for compositional evolution at a galapagos volcano and indicates increasing contributions from an iso topically enriched source with time as the volcano is carried away from the focus of the hot spot clinopyroxenes in many of the xenoliths exhibit positive anomalies of sr and eu which are attributed to the breakdown of plagioclase the growth of clinopyroxene at the expense of plagio clase results from compression as the crust cools compression is caused by growth mostly from above as shallow intrusions and lavas load the middle and upper oceanic crust

geochemistry and detrital zircon u pb and hf isotopes of the paragneiss suite from the quanji massif se tarim craton implications for paleoproterozoic tectonics in nw china abstract the delingha paragneiss suite in the quanji massif southeastern tarim craton is composed of mica schist paragneiss leptynite and quartzite similar to the khondalite suites described from elsewhere in the world the mica schist is rich in al2o3 up to 26 wt and contains graphite and diagnostic minerals including sillimanite and garnet with metamorphism under amphibolite facies to locally granulite facies conditions as manifested by association with amphibolite and granulite the detrital zircon u pb ages and geochemical data indicate that the protolith materials of the delingha paragneiss suite were mainly sourced from 2 20 to 2 45 ga granites felsic volcanic rocks and ttg and were deposited at 2 17 1 92 ga the detrital zircon hf and whole rock nd isotopes document important crustal growth at 2 5 2 7 ga the detrital zircon age spectra the whole rock nd and zircon hf model ages the low maturity of the protolith and short distance transportation suggest that the detritus were derived from the underlying delingha complex and the lower dakendaban sub group the timing of magmatic activities in the source region the depositional age and metamorphic histories of the delingha paragneiss suite are all comparable to those recorded in the khondalite belt along northern margin of the ordos block in the north china craton our study shows that the 2 2 2 45 ga magmatic rocks were generated in arc or active continental margin settings suggesting a prolonged subduction and accretion history prior to final amalgamation 2 5 1 8 ga to form the unified north china craton and the assembly of the tarim craton in nw china

high precision lu and hf isotope analyses of both spiked and unspiked samples a new approach 1 the functional form of instrumentally produced mass fractionation associated with mc icp ms analysis is not accurately known and therefore cannot be fully corrected by traditional approaches of internal normalization using power linear or exponential mass bias laws we present a method for robust correction of instrumentally produced mass fractionation of both spiked and unspiked samples that can be applied to mass analysis of hf as well as nd sr os etc correction of 176hf 177hf for unspiked samples follows a traditional approach of internal normalization using an exponential law followed by normalization to a standard of known composition such as jmc 475 for spiked samples standards are used to characterize a linear instrumental mass bias coefficient the mass bias coefficient is defined by the slope of a tie line between measured and true values of a standard this approximation results in identical precision and accuracy of measurements for spiked and unspiked samples 0 005 2 external reproducibility the effects of the spike on the 176hf 177hf ratio and calculation of the molar spike sample ratio is determined by a closed form solution modified from the double spike approach used for fe isotope analysis by tims johnson and beard 1999 the measured 176lu 175lu ratios are corrected by doping the sample with er and using the 167er 166er ratio to externally normalize the 176lu 175lu ratio using an exponential law finally spike sample equilibration is confirmed for our sample dissolution protocol through analysis of varying physical mixtures of 1 ga garnet and hornblende where all the data lie on a mixing line within error on a 176lu 177hf 176hf 177hf diagram precision of 176lu 177hf ratios is determined to be 0 2 2 for standards and for physical mixtures of garnet and hornblende

decoding whole rock plagioclase zircon and apatite isotopic and geochemical signatures from variably contaminated dioritic magmas zircon and apatite grains from three types of variably contaminated quartz diorite were analyzed in the gesiniec intrusion sw poland the zircon isotopic compositions ehf300 5 5 0 and 18o 5 6 9 3 are consistent with contamination processes zircon is characterized by an increase in u th pb and ree from the least to the most evolved quartz diorite type apatite is characterized by ranges in trace element concentrations and with the progress of contamination its composition evolves from those typical for i type granites toward those typical for s type isotopic and trace element variations in zircon and apatite correlate with sr isotopic composition of plagioclase 87sr 86sr300 0 7069 0 7084 pietranik and waight 2008 however both sr isotopic composition of plagioclase and trace element composition of apatite could be homogenized by late stage resorption leaving zircon as the only record of contamination processes that predate resorption comparison between plagioclase and zircon isotopic composition is consistent with both plagioclase cores and zircons recording similar stages of magma contamination comparison between plagioclase and apatite composition indicates that crystallization of apatite was contemporaneous with crystallization of plagioclase rims the preferred interpretation of isotopic and trace element variations observed in different grains is a two stage contamination by crustally derived magmas early contamination was probably dominated by material typical of the lower crust i e with none or only small amounts of a sedimentary component as indicated by low 18o in zircon 5 6 6 5 in both the least and the most contaminated types later contamination was dominated by crustally derived magmas containing more than 20 of a sedimentary component as the most contaminated sample includes zircon with 18o up to 9 3 partial melts generated from an s type granite source are the most probable contaminant for this second stage contamination as indicated by apatite trace element composition in general isotopic and chemical composition of plagioclase zircon and apatite provides complementary information on magmatic processes but records a longer time span than a single mineral only due to their diachronous crystallization histories

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

crustal evolution of the north qinling terrain of the qinling orogen china evidence from detrital zircon u pb ages and hf isotopic composition abstract the north qinling terrain reveals a different geological history from the north china block to the north and the south qinling micro continental block to the south the timing of events and geochemical features of the north qinling terrain are essential for understanding the evolution of the qinling orogenic belt that joins the north and south china blocks this study presents detrital zircon ages and hf isotopic compositions from the guandaokou group a cover sequence of the north china block and from the kuanping group an upper basement sequence of the north qinling terrain the youngest detrital zircon u pb ages constrain the initiation of sedimentation in the guandaokou group to 1 85 ga and the maximum depositional age of the kuanping group to 640 ma zircon u pb ages and hf data testify to a major phase of magmatism in the north qinling terrain at 1000 900 ma the magmatic rocks were largely produced from reworking of early paleoproterozoic 2 5 2 0 ga crust with minor contribution of late paleoproterozoic 1 7 ga juvenile material this age record differs in time from the two important thermal events of 1 85 ga and 2 5 ga widely manifested in the north china block the north qinling terrain can thus be regarded as a separate micro continent with a pre neoproterozoic evolution different from that of the north china block the final assembly of the north qinling terrain to the north china block took place after about 640 ma

characteristics and timing of the cu mo mineralization in the kighal porphyry stock nw iran implications for the timing of porphyry cu related magmatism in iran and southern armenia abstract the quartz monzonite porphyry stock at kighal in northwestern iran intruded the upper eocene andesite to latite and basalt units and the resulted hydrothermal activities led to the development of hydrothermal alteration zones including potassic phyllic argillic and propylitic coupled with cu mineralization hypogene sulfide mineralization principally occurred within the potassic transitional potassic phyllic and phyllic alteration zones as disseminations stockwork veinlets and open space fillings these hypogene minerals include pyrite chalcopyrite and molybdenite along with lesser amounts of sphalerite and galena at the marginal parts of the porphyry stock by taking into account the development of hydrothermal alteration zones and their spatial distribution stockwork type mineralization of cu mo minerals and even the occurrence of mineralization zoning with cu mo rich ore within the stock and cu pb zn ore in the marginal parts mineralization at kighal in association with the quartz monzonite sub volcanic stock can be regarded as of porphyry copper type however its low cu and mo grade detracts its economic potential zircon u pb geochronology of the porphyry stock yielded early miocene ages of 20 0 0 2 to 18 8 0 2 ma with a weighted mean of 19 24 0 17 ma which correspond to the third porphyry cu metallogenic epoch in nw iran the age data show that it is a little younger than the quartz monzonite porphyry stock in the sungun porphyry copper deposit pcd and the porphyritic granodiorite stock in the niaz prospect while it is almost coeval with the porphyritic granodiorite stock in the haft cheshmeh pcd as well as with the mineralization at the masjed daghi pcd in nw iran the th u ratios of the zircons range between 0 37 and 0 59 corresponding to the values for magmatic zircons the analyzed zircons mainly possess initial ehf t values of 6 7 to 10 0 which suggest a juvenile and homogeneous magmatic source and the predominance of mantle derived magmas with limited crustal assimilation

protracted diagenetic alteration of ree contents in fossil bioapatites direct evidence from lu hf isotope systematics abstract fossil bones and teeth are potentially important repository for geochemical proxy data and a target for radiometric dating the concentration of many trace elements in bones and teeth increases by orders of magnitude after death and it is this diagenetic incorporation that forms the basis for several areas of geochemical study the use of bones and teeth in this context relies on two assumptions first that target metal ions are incorporated rapidly after death reflecting a known environmental signal and second that after early incorporation the bone or tooth remains as an essentially closed system resistant to later diagenetic change a wide literature has developed exploring these assumptions but relatively little direct evidence has been used to assess the long term diagenetic stability of trace elements within bones and teeth in this study we use the lu hf isotope system to show that bones and teeth of cretaceous and triassic age from both terrestrial and marine settings experience continued long term diagenetic change most likely through gradual addition of trace elements modelling suggests that diagenetic addition after initial recrystallisation may account for 50 of the total ree content in the sampled bones the extent depending on initial uptake conditions tooth enamel and enameloid may be more resistant to late diagenetic changes but dentine is probably altered to the same extent as bone these results have significant implications for the use of bones and teeth as hosts of chronological palaeoceanographic palaeoenvironmental and taphonomic information particularly in mesozoic and palaeozoic contexts

petrogenesis of the paleoproterozoic orosirian a type granites of carajas province amazon craton brazil combined in situ hf o isotopes of zircon abstract we present new lu hf and oxygen isotopic analyses and complementary whole rock nd isotopic data for three a type paleoproterozoic suites 1880 ma to 1857 ma serra dos carajas velho guilherme and jamon and related granites of the carajas province eastern amazon craton brazil zircon grains from all the granites have remarkably restricted initial 176hf 177hf and strongly negative ehf t values ranging from 9 to 18 and 18o fairly homogeneous varying from 5 50 to 7 00 small differences were observed internally in the plutons or between them these differences can result for contrasts in the crustal domains of the carajas province that were the source of the granites or of local contamination processes hf model ages indicate paleoarchean sources 3 3 ga to 3 6 ga with a minor contribution from mesoarchean 3 0 ga to 3 2 ga melts for these granites this model ages are older than the exposed archean country rocks of the orosirian granites of the carajas province and more investigation is needed to verify the real existence of that older archean crust on the other hand nd isotope data and geochemical petrological studies indicate that the carajas granites derived from mesoarchean granitoid sources and this hypothesis should be retained the studied samples have hf o isotopic compositions that overlap within error and evidence of contamination crustal assimilation or mixing for a mantle derived magma cannot be seen these plutons crystallized from magmas generated by melting of pre existing igneous rocks with possibly in the velho guilherme suite a minor contribution from a supracrustal metasedimentary component is envisaged the nd hf and o isotope compositions of the paleoproterozoic granites of carajas province clearly attest to an igneous ancient crustal source in the origin of their magmas this anorogenic granites represent a large volume of granitic magmatism generated in the late palaeoproterozoic in the eastern of the amazon craton this work shows the importance of the archean source in the generation of the a type paleoproterozoic granites from carajas province these granites are an example of a type granites derived essentially from crustal sources without significant influence of mantle magmas except as a source of heat

phosphate lu hf geochronology abstract igneous metamorphic and biogenic apatite contains lu and hf in proportions that make this mineral suitable for dating by the 176lu 176hf method we present a new method for separation of lu and hf from apatite that involves a single extraction column step for hf and a second exchange column step for lu this procedure allows rapid sample processing prior to analysis by mc icp ms results from the igneous gardiner skaergaard and khibina intrusions indicate that the closure temperature for the lu hf isotopic system in apatite is relatively high the lu hf isochron age of 60 ma for the skaergaard intrusion east greenland is older than the generally accepted emplacement age but does not appear to be a product of mixing a centimeter sized apatite from the otter lake area grenvillian province yields high and variable 176lu 177hf ratios showing that metamorphic apatite may in some cases allow for mono mineral dating the most important application of the method is undoubtedly its potential use for dating sedimentary formations although we find biogenic apatite in porous matrix highly susceptible to post depositional resetting of the lu hf isotopic system the preservation of a near depositional age for a shark tooth from the impermeable london clay and recent work on crystalline authigenic phosphorites earth planet sci lett 201 2002 203 show the lu hf system to be a promising tool for direct dating of sedimentary formations

zircon petrochronology and 40ar 39ar thermochronology of the adamello intrusive suite n italy monitoring the growth and decay of an incrementally assembled magmatic system the adamello intrusive suite is a composite batholith in northern italy with an estimated 2000 km3 volume assembled incrementally over a time span of 10 to 12 million years the history of crysta

petrogenesis and metallogenic setting of porphyries of the duobuza porphyry cu au deposit central tibet china abstract given that the duobuza deposit was the first porphyry cu au deposit discovered in central tibet the mineralization and mineralized porphyry in this area have been the focus of intensive research yet the overall porphyry sequence associated with the deposit remains poorly understood new geological mapping logging and sampling of an early granodiorite porphyry an inter mineralization porphyry and a late mineralization diorite porphyry were complemented by la icp ms zircon dating whole rock geochemical and sr nd isotopic analyses and in situ hf isotopic analyses for both inter and late mineralization porphyry intrusions all of the porphyry intrusions are high k and calc alkaline and were emplaced at ca 120 ma the geochemistry of these intrusions is indicative of arc magmatism as all three porphyry phases are enriched in light rare earth elements and large ion lithophile elements and depleted in heavy rare earth elements and high field strength elements these similar characteristics of the intrusions when combined with the relatively high 87 sr 86 sr i negative e nd t and positive e hf t values suggest that the magmas that formed the porphyries were derived from a common source region and shared a single magma chamber the magmas were generated by the mixing of upwelling metasomatized mantle wedge derived mafic magmas and magmas generated by partial melting of amphibolite within the lower crust the inter mineralization porphyry has the lowest e nd t and highest 87 sr 86 sr i values suggesting that a large amount of lower crust derived material was incorporated into the melt and that metals such as cu and au from the enriched lower crust were scavenged by the parental magma the relative mafic late mineralization diorite porphyry phase was formed by the residual magma in the magma chamber mixing with upwelling mafic melt derived from metasomatized mantle the magmatic hydrothermal evolution of the magma in the chamber released ore forming fluid that was transported mainly by the inter mineralization porphyry phase during the mineralization stage which ultimately formed the duobuza porphyry cu au deposit these porphyritic intrusions of the duobuza deposit have high mg and low la yb n values and show some high lile hfse ratios indicating the magma source was enriched by interaction with slab derived fluids combined with age constraints on the regional tectonic evolution these dating and geochemical results suggest that the duobuza porphyry cu au deposit formed in a subduction setting during the final stages of the northward subduction of the neo tethyan ocean

mesoarchaean collision of kapisilik terrane 3070ma juvenile arc rocks and 3600ma isukasia terrane continental crust greenland abstract the mesoarchaean kapisilik and eoarchaean isukasia terranes in the nuuk region of southern west greenland were tectonically juxtaposed in the archaean the north of the isukasia terrane is distal from the kapisilik terrane and has only rare growth of 2690 ma metamorphic zircon and no 2980 2950 ma metamorphic zircon the southern part of the isukasia terrane lies between two 2690 ma shear zones and has locally preserved high pressure granulite facies assemblages and widespread growth of 2980 2950 ma metamorphic zircon and also sporadic growth of 2690 ma metamorphic zircon within this southern part of the isukasia terrane there is a folded klippe of mylonitised mesoarchaean detrital meta sedimentary rocks carrying 3600 and 3070 ma detrital zircons mafic and ultramafic rocks with 2970 ma metamorphic zircon overgrowths south of the isukasia terrane is the kapisilik terrane containing 3070 ma arc related volcanic rocks gabbro anorthosites and meta tonalites intruded by 2970 2960 ma granites zircons of an ivis rtoq supracrustal belt 3075 ma intermediate volcanic rock have initial hf values of 2 to 5 thus are juvenile crustal additions 3070 ma tonalites along the northern edge of the kapisilik terrane have whole rock positive initial nd values and thus are also juvenile crustal additions in contrast igneous zircons in 2960 ma granites intruded into juvenile 3075 ma supracrustal rocks of the kapisilik terrane have initial hf values of 5 to 10 and must have involved the partial melting of 3600 ma isukasia terrane rocks the integrated structural and zircon u th pb hf isotopic data show that at 2980 2950 ma the kapisilik terrane juvenile arc components collided with and over rid the isukasia terrane the southern edge of the isukasia terrane came to lie in the deep crust under the ivis rtoq supracrustal belt and melted at 2970 2960 ma to produce granites these granites derived from ancient crust rose into the upper crust where they intruded the overlying allochthonous juvenile 3075 ma ivis rtoq supracrustal belt arc assemblages the southern edge of the isukasia terrane is interpreted as an interior nappe of eoarchaean basement rocks interfolded with a klippe of mesoarchaean metasedimentary and mafic ultramafic rocks both of which are affected by 2980 2950 ma metamorphism the mixed eoarchaean mesoarchaean detrital provenance suggests that the klippe could be dismembered components of an accretionary prism or forearc crust the northern part of the isukasia terrane is interpreted as foreland free of 2980 2950 ma high grade metamorphic overprint this shows that the isukasia terrane is not a coherent block but contains ancient rocks that are parautochthonous or allochthonous to each other with contrasting later metamorphic history at 2690 ma the crustal architecture arisen from mesoarchaean collision between an older continental block and an island arc was reworked along intra crustal shear zones coeval with amphibolite facies metamorphism this reworking followed on from major terrane assembly at 2710 2700 ma in the southern part of the nuuk region when the eoarchaean faeringehavn terrane was juxtaposed with 2840 2825 ma arc rocks thus the 2980 2950 ma assembly of the isukasia and kapisilik terranes is distinct from the later 2710 2700 ma terrane assembly further south in the nuuk region

improvements of precision and accuracy in in situ hf isotope microanalysis of zircon using the laser ablation mc icpms technique abstract we have developed a new analytical technique for precise and accurate in situ hf isotope ratio measurements for zircons by means of laser ablation multiple collector inductively coupled plasma mass spectrometry la mc icpms newly designed sample cell and n 2 mixing technique provided higher elemental sensitivity with smoother signal intensity profiles in order to improve the accuracy of the hf isotope ratio analysis previously reported correction methods for isobaric interferences on 176 hf by 176 yb and 176 lu were rigorously evaluated and we found that the use of independent mass bias factors for hf and yb in the isobaric interference correction resulted in more reliable hf isotopic data in order to test the reliability of the hf isotopic data from 35 m diameter ablation pits that are smaller than the typical size of most zircon grains lu hf isotopes for three zircons harvard 91500 antarctic zircon pma7 and acasta zircon ay199 were measured the present 176 hf 177 hf isotope ratio of 0 282321 46 2 s d and initial 176 hf 177 hf isotope ratio of 0 282315 47 2 s d were obtained for zircon standard 91500 the resulting present 176 hf 177 hf isotope ratio shows an excellent agreement with the previously reported data our in situ isotopic data revealed that the lu hf ratio varied significantly within the 91500 grain 176 lu 177 hf 0 000130 0 000345 suggesting the existence of slight isotopic heterogeneity in present 176 hf 177 hf approximately 15 ppm for antarctic zircon pma7 despite the smaller size of the single grain 50 100 m wide 80 300 m long and the presence of various mineral inclusions resulting analytical precision for the initial 176 hf 177 hf ratio was 128 ppm 0 281208 36 2 s d for acasta zircon ay199 despite the high yb hf 0 05 and lu hf 0 01 isotope ratios with the early archean crystallization age 3 74 ga resulting analytical precision for the initial 176 hf 177 hf ratio was 187 ppm 0 280160 52 2 s d these results demonstrate clearly that in situ hf isotope ratio microanalysis developed here has the potential to become a significant tool for zircon lu hf isotopic study

diagnosing forecast errors in tropical cyclone motion abstractthis paper reports on the development of a diagnostic approach that can be used to examine the sources of numerical model forecast error that contribute to degraded tropical cyclone tc motion forecasts tropical cyclone motion forecasts depend upon skillful prediction of the environment wind field and by extension the synoptic scale weather systems nearby the tc while previous research suggests that the deep layer mean dlm steering flow typically approximates the actual tc motion it is shown that the motion of even mature tcs can depart from the dlm steering flow an optimal environmental steering flow is defined which varies the vertical extent of the steering layer and the radius over which tc vorticity and divergence are removed errors in predicted tc motion are quantified using a diagnostic equation that accounts for not only differences in the synoptic scale flow but also differences in the depth and radius used to define the steering flow differences in the latter two parameters a

post orogenic extension in the eastern part of the jiangnan orogen evidence from ca 800 760ma volcanic rocks we present a systematic geochronological and geochemical study on ca 800 760 ma volcanic rocks in the eastern part of the jiangnan orogen the xucun composite dykes are dated at ca 805 ma the mafic components have oib like trace element patterns and positive anomalies in zr and hf the least contaminated sample has relatively depleted nd isotopic features suggesting the xucun mafic dykes may have been generated from the partial melting of oib like asthenosphere with later crustal contamination the xucun felsic dykes have decoupled nd hf isotopes and the hf isotope compositions of zircons indicate that the dykes may be derived from the partial melting of the early neoproterozoic juvenile crustal materials with minor incorporation of paleoproterozoic crustal components the ca 800 790 ma shangshu volcanics include two compositional series calc alkaline and tholeiitic the shangshu calc alkaline volcanics in the minjiawu area have low abundances of lile hfse and high na2o contents and sr y ratios similar to adakitic rocks the evident arc like geochemical features and radiogenic nd isotopes nd t values of 3 7 to 4 8 suggest that these rocks may have been generated from the partial melting of juvenile lithospheric mantle metasomatized by na rich melts released from the subducted slab the tholeiitic mafic rocks from the shangshu bimodal volcanics represent two different magma sources the partial melting of metasomatized lithospheric mantle led to the formation of arc like basalts with low tio2 contents negative anomalies in zr and hf and high values of mg and nd t 6 2 whereas the partial melting of asthenospheric mantle generated volcanic rocks with high tio2 contents and low positive nd t 1 4 to 2 7 without negative anomalies of nb ta zr and hf the shangshu felsic rocks were formed by the reworking of early neoproterozoic juvenile arc crustal materials the ca 760 ma mafic rocks from the puling bimodal volcanics generally have low tio2 contents 0 9 wt nearly flat ree distributions and arc like trace element patterns they may have been generated from the high degree partial melting of metasomatized lithospheric mantle one sample has a high tio2 content 2 41 wt and high nd t 6 2 with overall oib like trace element patterns implying the local partial melting of asthenospheric mantle the occurrence of significant volumes of bimodal volcanics in the eastern part of the jiangnan orogen suggests an extensional setting in the period ca 800 760 ma the evident partial melting of newly metasomatized lithospheric mantle and subordinate partial melting of asthenosphere suggest that post orogenic extension shortly after the neoproterozoic orogenesis may be a better explanation for the genesis of the mid neoproterozoic magmatic rocks in the eastern part of the jiangnan orogen post orogenic extension may be diachronous along the whole orogenic belt and probably has no direct relationship with the rodinia rifting event a more detailed model is presented to illustrate the evolution of the eastern part of the jiangnan orogen

the role of mantle derived magmas in the isotopic evolution of yellowstone s magmatic system injection of mantle derived magmas into the earth s crust provides the heat necessary to develop and maintain large silicic magmatic systems however the role of mantle derived magmas in controlling the compositional evolution of large silicic systems remains poorly understood here we examine the role of mantle derived magmas in the post caldera magmatic system at yellowstone plateau the youngest magmatism associated with the yellowstone hotspot using microbeam techniques we characterize the age and hf isotope composition of single zircon crystals hosted in rhyolites from the most recent eruptive episode at yellowstone plateau which produced the central plateau member rhyolites we place these zircon data into context by comparing them to new solution hf isotope data for the central plateau member glasses yellowstone basalts and potential local crustal sources zircons in the central plateau member rhyolites record a wide range of hf isotope compositions relative to their host melts and extend from values similar to previously erupted yellowstone rhyolites to values similar to yellowstone basalts most zircons 90 are in isotopic equilibrium with their host melt but a significant proportion show ehf values higher than their host melt thus providing the direct evidence that silicic derivatives of mantle derived basalts have recharged yellowstone s magmatic system mixing models confirm that the isotopic characteristics of the youngest yellowstone rhyolites can be explained by recharge of yellowstone s magma reservoir with silicic derivatives of underplating mantle derived basalts 5 to 10 material added by mass this process helps drive the long term isotopic evolution of yellowstone s magmatic system this article is protected by copyright all rights reserved

timescales and mechanisms of ree and hf uptake in fossil bones abstract rare earth element ree patterns of fossil bones and teeth are widely used as proxies for provenance taphonomy and palaeoenvironment in order to investigate if fossil bones behave as closed systems over geologic time ree profiles were analysed by la icpms along cross sections of 54 bones from various well characterised and well dated settings these include terrestrial and marine diagenetic environments covering early triassic to holocene ages in general all fossil bones exhibit the highest ree concentrations at the outer rim gradually decreasing by up to four orders of magnitude toward the inner bone cortex intra bone ree concentration gradients decrease significantly from quaternary via tertiary to mesozoic specimens suggesting long term ree uptake and open system behaviour of fossil bone this view is further corroborated by 176lu 176hf dating of selected samples all yielding significantly younger ages than the known chronostratigraphic ages hence there is clear evidence for long term open system behaviour of fossil bones with respect to ree which is in marked contrast to currently accepted models suggesting that ree uptake is only early diagenetic although unexpected statistically significant four to seven point isochrons are observed for four fossil dinosaur bone samples and one upper triassic mastodonsaurus tooth with mswds ranging from 0 083 to 4 5 notably mobility of lu alone cannot account for the observed age patterns assuming constant lu uptake rates over time the radiometric ages should only be as low as half of the chronostratigraphic age however a six point isochron defined by subsamples of a single upper triassic mastodonsaurus tooth yields an age of 65 2 1 1 ma mswd 0 68 much younger than half of the stratigraphic age ca 234 ma hence hf must also undergo late diagenetic exchange likely mechanisms to account for the presence of statistically meaningful isochrons as well as for the late diagenetic exchange of both ree and hf are diffusion adsorption and dissolution reprecipitation processes

petrogenesis of paleoproterozoic 2 02 1 96 ga metagranitoids in the southwestern yeongnam massif korean peninsula and their significance for the tectonic history of northeast asia insights from zircon u pb hf isotope and whole rock geochemical compositions abstract the jangsu gokseong area is located in the southwestern part of the yeongnam massif and mainly consists of precambrian metagranitoids metagranite metaleucogranite and metagranodiorite with minor migmatite and marble sensitive high resolution ion microprobe shrimp zircon u pb dating shows that the metagranitoids emplaced during ca 2 02 1 96 ga and metamorphosed at ca 1 89 1 87 ga the metagranitoids show calc alkaline trends enrichment in large lithophile elements and negative nb and ta anomalies with low sr y

the flaw in the crustal zircon archive mixed hf isotope signatures record progressive contamination of late stage liquid in mafic ultramafic layered intrusions

detrital mineral age radiogenic isotopic stratigraphy and tectonic significance of the cuddapah basin india abstract the cuddapah basin is one of a series of proterozoic basins that overlie the cratons of india that due to limited geochronological and provenance constraints have remained subject to speculation as to their time of deposition sediment source locations and tectonic geodynamic significance here we present 21 new stratigraphically constrained u pb detrital zircon samples from all the main depositional units within the cuddapah basin these data are supported by hf isotopic data from 12 of these samples that also encompass the stratigraphic range and detrital muscovite 40ar 39ar data from a sample of the srisailam formation taken together the data demonstrate that the papaghni and lower chitravati groups were sourced from the dharwar craton in what is interpreted to be a rift basin that evolved into a passive margin the nallamalai group is here constrained to be deposited between 1659 22 ma and 1590 ma it was sourced from the coeval krishna orogen to the east and was deposited in its foreland basin nallamalai group detrital zircon u pb and hf isotope values directly overlap with similar data from the ongole domain metasedimentary rocks depositional age constraints on the srisailam formation are permissive with it being coeval with the nallamalai group and it was possibly deposited within the same basin the kurnool group saw a return to dharwar craton derived provenance and is constrained to being neoproterozoic it may represent deposition in a long wavelength basin forelandward of the tonian eastern ghats orogeny detrital zircons from the gandikota formation which is traditionally considered a part of the chitravati group constrain it to being deposited after 1181 29 ma more than 700 ma after the lower chitravati group it is possible that the gandikota formation is correlative with the kurnool group the new data suggest that the nallamalai group correlates temporally and tectonically with the somanpalli group of the pranhita godavari valley basin which is tightly constrained to being deposited at 1620 ma these syn orogenic foreland basin deposits firmly link the se india proterozoic basins to their orogenic hinterland with their discovery filling a missing link in the tectonic development of the region

application of lu hf garnet dating to unravel the relationships between deformation metamorphism and plutonism an example from the prince rupert area british columbia abstract the tectonic history of the prince rupert area is marked by profound crustal thickening from thrusting that produced inverted metamorphic field gradients and transpression in crustal scale shear zones syn tectonic garnet in the prince rupert area has lu hf ages of 102 6 3 7 ma and 108 3 4 1 ma 2 porphyroblast matrix relationships in these samples and samples from the same outcrops indicate syn tectonic garnet growth these relationships imply that the garnet ages directly date the development of the metamorphic foliations a third sample of migmatitic garnet amphibolite from the contact aureole of the 94 90 ma ecstall pluton had complex isotope systematics interpreted to indicate a garnet growth episode 105 ma similar to the ages obtained from the other samples and a growth or equilibration event at 94 ma during pluton emplacement the data show that the older lu hf garnet ages date prograde metamorphism during foliation development and modification during pluton emplacement the ecstall pluton was emplaced 10 to 15 m y after regional metamorphism and thrust stacking in the prince rupert area in order to place our samples in a regional tectonic context we compare our results to patterns of regional deformation metamorphism and plutonism throughout the north american cordillera in the time period between 110 and 85 ma contractional and transpressional deformation occurred throughout much of the north american cordillera at this time from southeastern alaska to the baja peninsula in mexico left lateral transpression dominated the canadian cordillera whereas right lateral transpression affected areas south of the idaho salmon river suture zone including the sierra nevada batholith this reversal in kinematics in the northern and southern cordillera within coeval magmatic belts appears to be a first order feature of the geology of the north american cordillera during the cretaceous

interactions between typhoon megi 2010 and a low frequency monsoon gyre abstractthe arw model is used to investigate the sharp northward turn of super typhoon megi 2010 after it moved westward and crossed the philippines the ncep analyzed fields during this period are separated into a slowly varying background flow component a 10 60 day low frequency component representing the monsoon gyre and a 10 day high pass filtered component representing megi and other synoptic scale motion it appears that the low frequency 10 60 day monsoon gyre interacted with megi and affected its track to investigate the effect of the low frequency mode on megi numerical experiments were designed in the control experiment the total fields of the analysis are retained in the initial and boundary conditions and the model is able to simulate megi s sharp northward turn in the second experiment the 10 60 day monsoon gyre mode is removed from the initial and lateral boundary fields and megi moves westward and slightly northwestward without turning north tracks of the relative positions b

seismic activity along fault branches of the dead sea jordan transform system the carmel tirtza fault system abstract about 550 earthquakes 1 0 m l 5 3 along the carmel tirtza fault a branching fault of the jordandashdead sea transform system recorded by the israel seismograph network isn between 1984 and 1994 were analyzed the seismicity pattern reveals significant activity often confined to known surface traces of active faults or within local grabens earthquake clusters are also observed the seismicity pattern within the mediterranean seems more diffuse possibly due to observational inaccuracies and insufficient knowledge of how the carmel tirtza fault system extends towards the northwest the seismicity along the carmel tirtza fault system since the beginning of this century is characterized by a b value of about 0 9 for 15 events with 3 1 m l 5 3 we found seismic moment estimates m 0 of 0 7 10 14 m 0 10 17 nm and brune stress drop estimates between 0 9 and 16 4 mpa these characteristics are comparable to those for events occurring on the main dead sea jordan transform fault ten individual earthquake focal mechanisms and three joint focal mechanisms for earthquake clusters have been obtained towards the northeastern part of the carmel tirtza fault system a left lateral motion seems to dominate while the seismicity pattern and the focal mechanism solutions near the branching of the carmel tirtza fault and the dead sea jordan rift suggest the present day existence of a complicated tectonic regime stress inversion assuming one stress tensor for the whole region indicates nne ssw extension and wnw ese compression

a routine high precision method for lu hf isotope geochemistry and chronology a method for chemical separation of lu and hf from rock meteorite and mineral samples is described together with a much improved mass spectrometric running technique for hf this allows i geo and cosmochronology using the176lu 176hf decay scheme and ii geochemical studies of planetary processes in the earth and moon chemical yields for the three stage ion exchange column procedure average 90 for hf chemical blanks are 0 2 ng for lu and hf from 1 g of hf a total ion current of 0 5 10 11 ampere can be maintained for 3 5 h yielding 0 01 0 03 precision on the ratio176hf 177hf normalisation to179hf 177hf 0 7325 is used extensive results for the johnson matthey hf standard jmc 475 are presented and this sample is urged as an international mass spectrometric standard suitable aliquots prepared from a single batch of jmc 475 are available from denver lu hf analyses of the standard rocks bcr 1 and jb 1 are given the potential of the lu hf method in isotope geochemistry is assessed

geochemical test for branching decay of 176lu abstract two different groups of values for the 176lu decay constant have been determined by recent high precision experiments the 176lu values of 1 86 1 87 10 11 a 1 were determined by age comparisons using terrestrial minerals of proterozoic and late archean age whereas values of 1 94 10 11 a 1 were determined in age comparison studies of meteorites a possible branched decay of 176lu could be the cause of this discrepancy the decay of 176lu to 176yb was detected in the early studies of radioactivity of 176lu with reported values of in the total 176lu ranging from less than 0 03 to 0 67 if the decay fraction is close to the upper limit of the reported values it can explain the 4 6 difference between the apparent 176lu values to get a reliable estimate for the decay of 176lu we have measured yb isotopic composition in 2 7 ga zircons with lu ybn chondrite normalized ratios of 1 40 and 1 45 in 1 0 ga xenotime with lu ybn 1 23 using yb from the 28 4 ma fish canyon tuff fct zircon and titanite as the modern reference value multiple analyses yielded the following weighted mean values 2 for the 176yb 174yb ratio 0 4022134 0 0000017 for the fct zircon and titanite 0 4022134 0 0000019 for the 1 0 ga xenotime and 0 4022124 0 0000033 for the 2 7 ga zircons these data yield 0 005 0 015 2 and establish an upper limit of 0 9 of total decays for the decay branch branching decay can therefore be eliminated as the cause of the discrepancy in 176lu decay constant estimates we discuss other possible causes of the 176lu terrestrial vs meteorite discrepancy

origin of the granites and related sn and pb zn polymetallic ore deposits in the pengshan district jiangxi province south china constraints from geochronology geochemistry mineral chemistry and sr nd hf pb s isotopes the pengshan sn and pb zn polymetallic deposits are located in the south margin of the jiujiang ruichang jiurui district of the middle lower yangtze river metallogenic belt in south china four large deposits include huangjinwa zengjialong jianfengpo and zhangshiba the former three are sn dominant deposits which occur as stratiform orebodies in the contact zones of the pengshan granites and within the country rock strata whereas zhangshiba consists of stratiform pb zn orebodies within the precambrian metasedimentary strata in this study we present results on zircon u pb ages major and trace elements and mineral chemistry as well as sr nd hf isotope data of the granites pb and s isotopes of both the sn dominant and pb zn dominant deposits and u pb dating of cassiterite from the pengshan district shrimp and la icp ms zircon u pb dating shows that the pengshan granites were emplaced in the early cretaceous 129 128 ma which is in good agreement with the u pb dating 130 128 ma of cassiterite from the jianfengpo sn deposit the pengshan granites consist mainly of weakly peraluminous highly fractionated i type affinity granitic rocks detailed elemental and isotopic data suggest that the granites formed by partial melting of mesoproterozoic metamorphic basement materials with minor input of mantle derived melts the mineral chemistry of biotite demonstrates that the pengshan granitic magma had a low oxygen fugacity thereby precluding the tin dominantly partitioning into the rock forming silicate minerals and favoring accumulation in the exsolved residual liquid during magma crystallization stages sulfur isotopes show a relatively heavy sulfur isotopic composition from 5 8 to 17 6 and no difference for sulfur isotopes between the sn deposits 5 8 13 4 huangjinwa zengjialong jianfengpo and the pb zn deposit mostly 7 1 13 0 except for one 17 6 zhangshiba the sulfur isotope data of pyrite from the host sedimentary rocks show relatively higher 34s values of 22 7 28 7 lead isotopes indicate that the granites have higher 206pb 204pb 207pb 204pb and 208pb 204pb ratios than the host precambrian metasedimentary rocks and the sulfide minerals from the orebodies fall in between them again there is no difference for pb isotopes between the sn deposits huangjinwa zengjialong jianfengpo and the zhangshiba pb zn deposit the coincidence in s and pb isotope compositions for sn and pb zn deposits suggests that similar sources for these mineralization possibly derived from a mixed source of the granitic magmas and the precambrian metasedimentary rocks these data therefore favor of a magmatic hydrothermal origin for both the sn and pb zn polymetallic mineralization in the pengshan district

the growth interval of garnet in the uhp eclogites from the dabie orogen china zircon inclusions extracted from garnet from an ultrahigh pressure eclogite in the eastern part of the dabie orogen were investigated with high spatial resolution u pb geochronology the unzoned zircon rims have garnet and omphacite inclusions and show weak cathodoluminescence low th u ratios 0 02 0 18 flat high rare earth elements patterns and an absence of eu anomalies which suggest metamorphic growth in the presence of garnet and in the absence of feldspar dispersed concordia u pb ages ranging from 205 1 3 3 to 255 3 6 1 ma defined a weighted mean 206 pb 238 u age of 223 8 ma mean square of weighted deviation mswd 38 which is significantly younger than the lu hf garnet whole rock age of 242 2 2 6 ma the u pb age probability distribution indicates two age populations at ca 241 and ca 216 ma the zircon rims with younger ages are distinguished from those with older ages by the occurrence of garnet and omphacite inclusions well preserved prograde major and trace element zoning in garnet and the significant contribution of older garnet cores in bulk isotopic digestion suggest that the lu hf age mostly reflects an early phase of garnet growth likely at amphibolite facies conditions the new lu hf age combined with the u pb ages of the zircon inclusions in garnet suggest that garnet growth was sustained over a time interval of 25 m y

geochemistry zircon u pb ages and hf isotopic compositions of precambrian gneisses in the wonju jechon area of the southern gyeonggi massif implications for the precambrian tectonic evolution of korea and northeast asia abstract understanding the precambrian tectonic evolution of the gyeonggi massif in south korea can provide important insights into the tectonic evolution of korea and northeast asia and the geological relationship between korea and china the wonju jechon area is located in the southeastern part of the gyeonggi massif and is dominated by precambrian gneisses the protoliths of the granitic gneiss and migmatite in this area were emplaced in a collisional and or post collisional tectonic setting at ca 2 5 ga before the intrusion of the protolith of the two mica granitic gneiss in an arc related tectonic setting at 1 94 1 91 ga the intrusion of the two mica granitic gneiss was contemporaneous with the first stage of metamorphism of the granitic gneiss and migmatite in this area the protolith of the porphyritic gneiss then intruded into these granitic gneiss migmatite and two mica granitic gneiss in a post collisional tectonic setting at ca 1 79 ga the final major event recorded by these rocks is the second stage regional metamorphism at ca 285 ma zircons within the precambrian rocks in the wonju jechon area have e hf t values and isotopic model ages t dm2 that provide evidence of two stages of crustal growth at ca 3 3 and 2 7 ga and three periods of crustal reworking at ca 2 5 1 9 and 1 8 ga with generation of the protoliths of the two mica granitic and porphyritic gneisses in this area by the remelting of ancient crustal material the tectonic evolution of the southeastern gyeonggi massif differs from that of the northern gyeonggi and nangrim massifs both of which record continental collision related magmatism and metamorphism at 1 93 1 91 ga post collisional magmatism and metamorphism at ca 1 88 1 85 ga and within plate magmatism at ca 1 84 1 83 ga in comparison the tectonic evolution of the southeastern part of the gyeonggi massif is more similar to that of the northern yangtze block in the south china craton although more research is needed to confirm this relationship

guidelines for reporting zircon hf isotopic data by la mc icpms and potential pitfalls in the interpretation of these data invited technical paper high quality analytical data are essential for the development of sound scientific interpretations to ensure the quality of the data published in chemical geology a new type of contribution has been introduced the invited technical paper when a particular technical issue needing discussion or clarification is identified specialists in the technique will be invited to share their expertise as is true for all articles published in the journal these contributions will be subject to peer review before publication the first topic to be treated concerns in situ hf isotopic measurements in zircon by laser ablation inductively coupled plasma mass spectrometry this is an extremely powerful and promising technique that has been adopted by many laboratories throughout the world however if insufficient care is taken during analysis and data processing inaccurate results can be obtained notably because of the existence of very large isobaric interferences on the isotope of interest to address this issue we have asked christopher fisher jeffery vervoort and john hanchar to provide a set of guidelines that can be adopted to assure that reliable hf isotopic data are obtained by this technique abstract over the past decade the hf isotope composition of zircon as determined in situ by laser ablation multicollector inductively coupled plasma mass spectrometry la mc icpms has been applied increasingly to a wide range of geological problems and has proven to be a valuable analytical tool there has been no uniformity however in the reporting of in situ hf isotopic data and quite often reviewers and readers of papers are not provided with sufficient information to assess data quality the goal of this invited contribution is to provide the non specialist with a brief outline and explanation of what is required for proper presentation and documentation of in situ hf isotopic data from zircon including details of how the challenging large isobaric interference corrections have been made in addition we discuss a number of potential pitfalls vis a vis the assignment of the incorrect age to the measured hf isotope composition non specialists should be aware of these important issues when doing their own analyses and evaluating the analyses done by others

the hf isotope composition of global seawater and the evolution of hf isotopes in the deep pacific ocean from fe mn crusts this paper presents a revised chemical purification method of hf for the measurement of hf isotope ratios of fe mn crusts on a new generation of double focusing multiple collector plasma source mass spectrometer mc icp ms by measuring surface scrapings of hydrogenetic fe mn crusts distributed over the three major ocean basins the present day hf isotope distribution of oceanic deep water is assessed in detail the results show an ehf provinciality correlated with those of other radiogenic isotope tracers such as nd and pb in agreement with previous studies this supports the use of hf isotopes as tracer of element source provenance and water masses fe mn crusts display the same present day hf nd isotope array as given before for mn nodules the smaller isotopic variability of hf compared with nd may either be caused by a more efficient mixing of hf than nd in the ocean due to a longer residence time or may be a consequence of a systematically more radiogenic hf than nd isotope signature delivered to the oceans by weathering of continental crust a hf isotope time series was measured on crust va13 2 to assess the hf isotope compositions of the central pacific deep water over the past 26 ma no consistency is observed between the hf and pb isotope time series in contrast hf and nd isotope time series display similar patterns which are however apparently offset by 2 ma prior to 14 ma differential diffusion of hf and nd does not explain this offset the smaller amplitude in the hf isotope variations compared with the nd isotopes rather argues for more efficient mixing of hf in the ocean we suggest that both isotope systems have responded in a similar way to the processes affecting the dissolved radiogenic isotope composition of pacific deep water during this time interval the parallel increase in ehf and end observed between 14 and 3 ma may probably be attributed to the increased inputs of hf and nd into the central pacific ocean derived from the weathering of the pacific islands arcs over the past 3 ma an increased aeolian continental input derived from asia most likely caused negative shifts in end and ehf recorded by va13 2 the fact that hf and nd isotope compositions plot along the present day array for fe mn crusts and mn nodules over the entire past 26 ma suggests that aeolian supply of hf to the pacific ocean has been a long term important feature

models of tropical cyclone wind distribution and beta effect propagation for application to tropical cyclone track forecasting abstract a model of the tangential wind speed in the outer regions of tropical cyclones is proposed based on approximate conservation of angular momentum the purpose is to derive an operationally useful model of the beta effect propagation bep which barotropic numerical models have shown to be primarily related to the outer wind structure the functional dependence of the predicted bep speeds over a range of latitudes and the radii ro at which the cyclonic winds are reduced to zero is determined from dimensional analysis given the empirical nature of the profile and imprecise estimates of ro only four tropical cyclone sizes or outer wind structures are defined based on the magnitude of the bep speeds and their relative contributions to the total motion a second aspect of bep from the barotropic model integrations is the development of a trailing anticyclone to the southeast of the tropical cyclone as a result of rossby wave dispersion the four tropical cyclone size categories or outer wind structu

on the westward turning of hurricane sandy 2012 effect of atmospheric intraseasonal oscillations abstracthurricane sandy 2012 experienced an unusual westward turning and made landfall in new jersey after its northward movement over the atlantic ocean the landfall caused severe casualties an

tropical cyclone track direction climatology and its intraseasonal variability in the australian region aspects of tropical cyclone tc activity such as the influence of the el nino southern oscillation and the variability of tc genesis location have been examined in numerous previous studies however relatively few studies have examined aspects such as the influence of intraseasonal variability on tc track direction here we focus on a number of knowledge gaps relating to observed tc track directionality and intraseasonal variability in the australian region climatological examinations are presented for tc track directional variability throughout the australian region in contrast to previous studies that have focused on the mean direction of tc movement in this region tc tracks are examined here based on the full spectrum of track directions for a given location or region variability in initial tc track directions is investigated including an examination of the influence of the madden julian oscillation mjo it is demonstrated that there is a considerable degree of seasonal and intraseasonal variation in tc motion in this region these variations result from variations in genesis location throughout the tc season as well as zonal wind anomalies associated with the influence of the mjo on the steering flow winds anomalous westerly steering flow occurs during mjo phase 4 5 and anomalous easterly flow during phase 8 1 in the western basin with resulting changes in the proportion of tc tracks in each direction during these phases of the mjo the results presented here are intended to provide improved seasonal tc activity guidance and enhanced resilience to tc impacts 2016 american geophysical union all rights reserved

observational relationship of climatologic beta drift with large scale environmental flows 1 while many numerical studies suggested that large scale environmental flows significantly affect beta drift this influence was not verified observationally and included in assessing changes of tropical cyclone tc tracks under the background of global warming this study investigates the influence of large scale environmental flow on climatologic beta drift in the northern west pacific using the best track dataset from joint typhoon warming center jtwc and the ncep monthly reanalysis over the period from 1965 to 2007 consistent with most previous numerical studies the meridional shear of zonal wind vertical shear of zonal wind and meridional gradient of relative vorticity which are mainly associated with the zonal environmental wind play an important role in affecting beta drift for the meridional shear of zonal flows the northward beta drift in an anticyclonic shear is faster than that in a cyclonic shear a poleward equatorward gradient of relative vorticity leads to faster slower westward beta drift than in a resting environment tcs tend to move to the left of the vector of vertical wind shear

cluster analysis of typhoon tracks part ii large scale circulation and enso abstract a new probabilistic clustering method based on a regression mixture model is used to describe tropical cyclone tc propagation in the western north pacific wnp seven clusters were obtained and described in part i of this two part study in part ii the present paper the large scale patterns of atmospheric circulation and sea surface temperature associated with each of the clusters are investigated as well as associations with the phase of the el nino southern oscillation enso composite wind field maps over the wnp provide a physically consistent picture of each tc type and of its seasonality anomalous vorticity and outgoing longwave radiation indicate changes in the monsoon trough associated with different types of tc genesis and trajectory the steering winds at 500 hpa are more zonal in the straight moving clusters with larger meridional components in the recurving ones higher values of vertical wind shear in the midlatitudes also accompany the straight moving tracks compared to

147sm 143nd and 176lu 176hf in eucrites and the differentiation of the hed parent body the 147sm 143nd and 176lu 176hf systematics of 21 whole rock eucrites including five cumulates have been investigated by mc icp ms a statistically significant sm nd isochron was obtained on 18 samples with an age of 4464 75 ma mswd 1 26 and an intercept of 0 50680 0 00010 this age clearly is controlled by the cumulate eucrites the 21 basaltic and cumulate eucrites together do not form a statistically significant lu hf isochron basaltic eucrites however form an errorchron with an age of 4604 39 ma mswd 4 52 which becomes an acceptable isochron if the error on the lu hf ratio is doubled with respect to the laboratory estimate the initial 176hf 177hf is 0 27966 0 00002 three of the cumulate eucrites regressed together further yield a statistically significant age of 4470 22 ma indistinguishable from their sm nd age we therefore conclude that cumulate eucrites are 100 myr younger than basaltic eucrites and basaltic eucrites are close in age to the solar system there is no evidence in the present data to support a decay constant of 176lu significantly different from 1 93 10 11 yr 1 sguigna can j phys 60 1982 361 364 the broad range of variation and strong correlation of lu hf and sm nd ratios require that eucrites are partial melts and not residual magmas the relative lu hf and sm nd fractionation is controlled by the plagioclase to mafic mineral ratio in the residue the steep correlation between these two ratios is explained by the enhancement of plagioclase saturation in the low gravity field of the eucrite parent body basaltic eucrites probably formed as large degree melts of a chondritic source the strong lu hf and sm hf fractionation observed in cumulates clearly reflects the presence of residual ilmenite during melting our preferred interpretation is that cumulates were impregnated by small degree melts of ilmenite bearing gabbros since pressure on the eucrite parent body never reaches the garnet stability field this observation questions the ubiquitous presence of residual garnet in the mantle sources of magmas formed on larger planets such as the moon mars and possibly earth

lu hf and sm nd isotopic systematics in chondrites and their constraints on the lu hf properties of the earth sm nd and lu hf isotopic data are presented for 19 chondritic meteorites six carbonaceous chondrites five l chondrites seven h chondrites and a single enstatite chondrite the primary goal of the study is to better define the bulk silicate earth bse reference values for hf isotopes except for one sample with lower sm nd the sm nd data define a cluster around the accepted reference values for chondrites and terrestrial planets giving a mean 147sm 144nd of 0 1960 0 0005 and a mean 143nd 144nd of 0 512631 0 000010 uncertainties are two standard errors it seems appropriate to retain the presently accepted sm nd reference parameters 147sm 144nd 0 1966 and 143nd 144nd 0 512638 when fractionation corrected to 146nd 144nd 0 7219 lu hf isotopic data are not clustered but spread along an approximate 4 5 ga isochron trend with a range of 176lu 177hf from 0 0301 to 0 0354 the data are similar to many of the samples of chondrites presented by bizzarro et al nature 421 2003 931 but lack the range to lower lu hf shown by those authors our chondrite data define a regression line of 4 44 0 34 ga when 1 867 10 11 year 1 is used for the decay constant of 176lu science 293 2001 683 earth planet sci lett 219 2004 311 324 combining our data with the main population of analyses from bizzarro et al nature 421 2003 931 yields 4 51 0 24 ga unless samples of eucrite meteorites and deviating replicates of chondrites with 176lu 177hf less than 0 030 are employed no combination of the main population of chondrite lu hf data yields a regression with sufficiently low error to constrain the decay constant of 176lu sample heterogeneity seems to hinder the acquisition of reproducible lu hf analyses from small manually ground pieces of chondrites and we suggest that analysis of powders prepared from large volumes of meteorite will be needed to adequately characterize the lu hf isotope systematics of chondritic reservoirs and of bse our results for carbonaceous chondrites show higher average 176lu 177hf and 176hf 177hf than ordinary chondrites and the mean of carbonaceous chondrites also coincides with replicate analyses of a powder representing a large volume of meteorite the allende powder from the smithsonian institution use of the carbonaceous chondrite mean for bse lu hf characteristics results in a bse hf nd point that lies well within the array of terrestrial compositions and leads to plausible initial ehf values for precambrian rocks an improved objective resolution of meteorite data and of meteoritic models for the earth needs to occur before bse can be established for lu hf

vortex motion in relation to the absolute vorticity gradient of the vortex environment recent attempts to establish a relationship between tropical cyclone motion and the absolute vorticity gradient of the cyclone environment are reviewed evidence is presented both from analytic and numerical calculations to show that for barotropic vortices there is no unique relationship between vortex motion c and the local absolute vorticity gradient of the imposed environment a our results suggest that it is also unlikely that any similar relationship holds for tropical cyclones it is shown that conventional methods of averaging over an annular region about tropical cyclone centre to determine the absolute vorticity gradient of the cyclone environment may be very sensitive to the size of the region chosen for this reason as well as from theoretical considerations our results would indicate that there are certain intrinsic limitations for tropical cyclone track forecasting arising from statistically derived relationships between c and a

models of garnet differential geochronology abstract rayleigh distillation models are developed to describe theoretical growth zoning of lu hf rb sr sm and nd in typical garnet crystals from metapelites and metabasites effects of diffusion limited transport within the matrix and intracrystalline diffusion are also considered qualitatively theoretical zoning profiles show strong depletions of lu in garnet rims compared to cores but virtually invariant hf rb sr sm and nd profiles generally consistent with natural profiles for lu and hf and previously published models theoretical isochron diagrams for lu hf exhibit distinctive arcuate distributions and high mswds consistent both with himalayan data and with expectations that garnet growth durations exceed chronologic resolution by as much as an order of magnitude predicted isochron diagrams for sm nd and rb sr exhibit vertical arrays for garnet and high mswds that are generally lower than for lu hf in metapelites inherent chronologic resolution for bulk separates is best for lu hf in metapelites and rb sr but analytical considerations favor rb sr or sm nd for chronologic zoning studies diffusion limited transport in the rock matrix strongly influences zoning profiles but does not change the main trends on isochron diagrams intracrystalline diffusion will initially rotate lu hf isochrons to steeper slopes giving older apparent ages the natural himalayan data indicate growth of garnet in one rock from the greater himalayan sequence at 34 ma consistent with previously measured monazite ages from the same rock data from another himalayan rock suggest polymetamorphism that includes a paleozoic component

lu hf isotope systematics of fossil biogenic apatite and their effects on geochronology abstract reliable methods for direct dating of biogenic apatite from pre pleistocene fossils are currently not available and recent attempts using the lu hf decay system yielded highly inaccurate ages for both bones and teeth the geological processes accounting for this poor accuracy of lu hf chronometry are not yet understood here we explore lu hf systematics in fossil bones and teeth in detail by applying five different sample digestion techniques that are tested on bones and composites of bone and sediment our current dataset implies that dissolution methods only slightly affect the resulting lu hf ages while clear differences between the individual digestion techniques became apparent for element concentrations by analysing the insoluble leftovers from incomplete sample dissolution four main reservoirs of hf in fossil bones were identified 1 a radiogenic end member associated with apatite 2 an unradiogenic end member represented by the authigenic minerals or the embedding sediment 3 a highly unradiogenic end member that can be attributed to detrital zircon and 4 a moderately soluble phase probably a zr hf phosphate that yielded very low lu hf but a highly radiogenic hf isotope composition at the same time this zr hf phase must have been precipitated within the fossil bone sample at a late stage of burial history thereby incorporating radiogenic 176 hf released from apatite surfaces over geological timescales a second focus of our study is the effect of different sediment matrices and of crystal size on the preservation of pristine lu hf isotope compositions in bioapatite because near depositional lu hf ages of phosphate fossils have previously been reported for the london clay england and a calcareous marl from tendaguru tanzania we herein investigate specimens fossilised in carbonate matrices calcareous marl from oker germany carbonate concretions from the santana formation brazil carbonate from the eifel germany and argillaceous matrices with low permeability oil shale of messel germany posidonienschiefer of holzmaden germany materials analysed from these localities include bones teeth conodonts as well as coproliths and diagenetic minerals siderite montgomeryite and messelite near depositional lu hf ages were obtained for a bony fish sample notelops brama encapsulated in an early diagenetic carbonate concretion from the early cretaceous santana formation brazil and for conodonts from a middle devonian carbonate from the eifel germany low 176 lu 177 hf ratios in all materials from the middle eocene messel oil shale e g bones fish scales sediment siderite result in poor age precision and an age that is near depositional due to this large analytical error in agreement with previous results all other ages determined here for both bones and teeth are by far younger than respective chronostratigraphic ages a model illustrating the behaviour of lu and hf over time with respect to the fossilisation process is presented which accounts both for the formation of a late diagenetic radiogenic zr hf phase and long term open system behaviour the continuous lu hf element exchange between the fossils and the embedding sediment is probably related to the nm scale crystal size of fossil bones dentine and also of enamel that generate large surface areas facilitating sorption desorption processes and open system behaviour

correlating tephras and cryptotephras using glass compositional analyses and numerical and statistical methods review and evaluation abstract we define tephras and cryptotephras and their components mainly ash sized particles of glass crystals in distal deposits and summarize the basis of tephrochronology as a chronostratigraphic correlational and dating tool for palaeoenvironmental geological and archaeological research we then document and appraise recent advances in analytical methods used to determine the major minor and trace elements of individual glass shards from tephra or cryptotephra deposits to aid their correlation and application protocols developed recently for the electron probe microanalysis of major elements in individual glass shards help to improve data quality and standardize reporting procedures a narrow electron beam diameter 3 5 m can now be used to analyze smaller glass shards than previously attainable reliable analyses of microshards defined here as glass shards in part 2 of the review we describe critically assess and recommend ways in which tephras or cryptotephras can be correlated in conjunction with other information using numerical or statistical analyses of compositional data statistical methods provide a less subjective means of dealing with analytical data pertaining to tephra components usually glass or crystals phenocrysts than heuristic alternatives they enable a better understanding of relationships among the data from multiple viewpoints to be developed and help quantify the degree of uncertainty in establishing correlations in common with other scientific hypothesis testing it is easier to infer using such analysis that two or more tephras are different rather than the same adding stratigraphic chronological spatial or palaeoenvironmental data i e multiple criteria is usually necessary and allows for more robust correlations to be made a two stage approach is useful the first focussed on differences in the mean composition of samples or their range which can be visualised graphically via scatterplot matrices or bivariate plots coupled with the use of statistical tools such as distance measures similarity coefficients hierarchical cluster analysis informed by distance measures or similarity or cophenetic coefficients and principal components analysis pca some statistical methods cluster analysis discriminant analysis are referred to as machine learning in the computing literature the second stage examines sample variance and the degree of compositional similarity so that sample equivalence or otherwise can be established on a statistical basis this stage may involve discriminant function analysis dfa support vector machines svms canonical variates analysis cva and anova or manova or its two sample special case the hotelling two sample t2 test randomization tests can be used where distributional assumptions such as multivariate normality underlying parametric tests are doubtful compositional data may be transformed and scaled before being subjected to multivariate statistical procedures including calculation of distance matrices hierarchical cluster analysis and pca such transformations may make the assumption of multivariate normality more appropriate a sequential procedure using mahalanobis distance and the hotelling two sample t2 test is illustrated using glass major element data from trachytic to phonolitic kenyan tephras all these methods require a broad range of high quality compositional data which can be used to compare unknowns with reference training sets that are sufficiently complete to account for all possible correlatives including tephras with heterogeneous glasses that contain multiple compositional groups currently incomplete databases are tending to limit correlation efficacy the development of an open online global database to facilitate progress towards integrated high quality tephrostratigraphic frameworks for different regions is encouraged

enhanced hydrothermal activity on an ultraslow spreading supersegment with a seismically detected melting anomaly abstract seafloor hydrothermal venting fields occur on all ocean spreading ridges osrs regardless of spreading rates however the distribution of seafloor hydrothermal activity such as frequency and spacing on ultraslow spreading osrs are poorly known chinese dayang cruises from 2015 to 2016 conducted detailed water column surveys for seafloor hydrothermal activity using a towed system with an array of turbidity sensors and a near bottom camera along the ultraslow spreading southwest indian ridge here we report the discovery of multiple hydrothermal plumes overlying segments 28 29 and 30 between the indomed and gallieni fracture zones from these data and earlier explorations in segments 25 27 we identify nine active venting sites the spatial density fs sites 100 km of active sites along the 394 km of ridge axis in our study area is thus 2 8 nearly 3 higher than predicted by the global trend of fs for ultraslow osrs in the interridge database previous studies concluded that an enhanced magma supply to the central indomed gallieni supersegment 11 8 ma is now limited to segment 27 our results indicate that although hydrothermal activity may be most concentrated in segment 27 the discoveries of active venting in segments 25 30 implies the presence of additional magma bodies across a broad extent of the indomed gallieni supersegment

the isotopic composition of yb and the precise and accurate determination of lu concentrations and lu hf ratios by isotope dilution using mc icpms 1 we report yb isotopic data for the purpose of accurately correcting measurements of lu and lu hf ratios during multicollector inductively coupled plasma mass spectrometer mc icpms analysis the yb isotopic ratios agree with recent results of chu et al 2002 and amelin and davis 2004 when corrected for mass fractionation to the same reference values protocols for lu measurement involving simultaneous subtraction of yb interference and application of a fractionation correction based on yb are described it is shown that lu concentrations and lu hf ratios determined by mc icpms using this methodology are more precise and potentially more accurate than results based on analysis of lu by thermal ionization mass spectrometry tims a number of mc icpms lu hf isotopic analyses of standard rocks and other geological samples previously analyzed by tims are presented these document reproducibility of lu hf within 0 2 where most discrepancies can be assigned to the unknown lu mass fractionation during tims analysis

a numerical study on the combined effect of midlatitude and low latitude systems on the abrupt track deflection of typhoon megi 2010 abstractin 2010 supertyphoon megi experienced an abrupt track deflection in the south china sea scs after traversing luzon island to reveal the physical processes responsible for the timing and location of the sudden track deflection the potential vorticity pv diagnosis and numerical simulations with initial strength perturbations are applied to investigate the individual and combined effects of environmental systems on megi s motion based on the steering flow theory results indicate that megi s northward track deflection was mainly determined by the effect of the midlatitude circulation or rather the break of the high pressure belt joined by the continental high ch and the pacific subtropical high sh the retraction of ch played a particularly critical role in the break of the high pressure belt making it the most important feature of the midlatitude circulation to determine megi s deflection in addition a small low latitude anticyclone sa southeast of megi was crucial in affecting the

petrogenesis of granitoids from the lachlan fold belt southeastern australia the role of disequilibrium melting abstract s and i type granites from the lachlan fold belt southeastern australia have been investigated to assess the role of disequilibrium melting in their petrogenesis differences between the median initial ehf compositions of magmatic zircon populations and the host bulk rock ehfblk zrc range from 0 6 to 2 5 e units providing evidence for intra sample and hence inter phase hf isotopic heterogeneity linear variations on harker diagrams and o and hf isotope compositions of magmatic zircon preserved in many i and s type granites are inconsistent with assimilation or simple mixing hypotheses in contrast isotopic disequilibrium between the melt and a restite assemblage can explain the bulk rock versus zircon differences observed in these samples assuming that magmatic zircon records the melt composition differences between the bulk rock ehf and ehf of magmatic zircon ehfblk zrc values measured for i type granites 0 4 2 5 can largely be explained by disequilibrium amphibole dehydration melting of meta igneous protoliths that were either isotopically heterogenous at the time they were formed or perfectly homogeneous before being aged in the crust for 0 4 1 0 billion years prior to partial melting the currowong suite exhibits petrographic features and preserves geochemical and isotopic compositions that do not lend themselves to simple restite model or magma mixing explanations however these observations could be explained by the restite unmixing of magma batches generated from a single source rock if as modelling has suggested separate batches contain different melt compositions by investigating the application of disequilibrium melting to granite genesis this study demonstrates that isotopic heterogeneity at various sampling scales should actually be expected for the production of granites from a single source rather than necessitating the involvement of multiple sources and mixing processes as a result great care should be taken in the interpretation of isotope data from granitic bulk rocks or their zircons

new lu hf and pb pb age constraints on the earliest animal fossils abstract the neoproterozoic doushantuo formation south china preserves a unique assemblage of early multicellular fossils and overlies rocks which are thought to have formed during an ice age of global extent the age of this formation is thus critical for understanding the important biological and climatic events that occurred towards the end of the proterozoic eon until now direct dating of sedimentary formations such as the doushantuo has been difficult and associated with large uncertainties here we show that dating of doushantuo phosphorites by a novel lu hf dating method and conventional pb pb geochronometry independently yield ages of 584 26 ma and 599 3 4 2 ma respectively these ages are in agreement with bio and chemostratigraphical observations and show that the doushantuo animal remains predate diverse ediacaran fossil assemblages making them the oldest unambiguous remains of metazoans currently known furthermore the pb pb age for the post glacial doushantuo rocks suggests that the neoproterozoic glaciation in china might predate glacial rocks in eastern north america commonly associated with the younger marinoan of two major neoproterozoic glaciations the combination of lu hf and pb pb dating shows considerable potential for dating other phosphorite successions and future application of these methods could therefore provide further constraints on proterozoic biological and environmental history

granite related tin metallogenic events and key controlling factors in peninsular malaysia southeast asia new insights from cassiterite u pb dating and zircon geochemistry

upper ocean response to hurricane gilbert the evolving upper ocean response excited by the passage of hurricane gilbert september 14 19 1988 was investigated using current and temperature observations acquired from the deployment of 79 airborne expendable current profilers axcps and 51 airborne expendable bathythermographs from the national oceanic and atmospheric administration wp 3d aircraft in the western gulf of mexico the sea surface temperatures ssts mixed layer depths and bulk richardson numbers were objectively analyzed to examine the spatial variability of the upper ocean response to gilbert net decreases of the ssts of 3o 4oc were observed by the profilers as well as by the airborne infrared thermometer airt along the flight tracks and advanced very high resolution radiometer avhrr imagery the axcps indicated a marked cooling from 29oc to about 25 5oc on september 17 1988 which was about 1 2 inertial periods ip following storm passage this pool of cooler water 3 5 o was located further downstream in the hurricane wake by september 19 2 7 ip following the storm as a result of the near inertial currents in the mixed layer while there was a bias of about 0 6oc and 1 7oc between the in situ and avhrr derived ssts respectively both the avhrr images and the objectively analyzed fields indicated a rightward bias in the upper ocean cooling that extended from the storm track to about 4rmax where rmax the radius of maximum winds is equal to 50 km the larger sst offset of 1 7oc was due to the difference between the time of the avhrr image and the time of the aircraft experiment on september 19 the ssts derived from the avhrr images and the airt also indicated large gradients between the cold wake and the warm eddy in the central gulf of mexico the mixed layer deepened by about 30 35 m on the right side of the track during the storm and 1 2 ip later with little evidence of continued deepening afterward the mixed layer current vectors demonstrate that a strong near inertially rotating current was excited by the passage of gilbert with maxima of about 1 1 4 m s 1 the currents observed during and subsequent to 1 2 ip the storm diverged from the storm track whereas the mixed layer current vectors 2 7 ip after storm passage converged toward the track with relative maxima of 0 8 1 m s 1 this alternating pattern of convergence and divergence of the mixed layer current was associated with the upwelling and downwelling cycles of the baroclinic response considerable current shear existed between the mixed layer and the thermocline currents in the cool wake between the storm track and the 4rmax estimates of the bulk richardson numbers ranged between 0 2 and 1 0 during gilbert and at 1 2 ip which suggests that enhanced current shears were responsible for some of the mixed layer deepening

dissolved hydrogen and methane in the oceanic basaltic biosphere abstract the oceanic basaltic crust is the largest aquifer on earth and has the potential to harbor substantial subsurface microbial ecosystems which hitherto remains largely uncharacterized and is analogous to extraterrestrial subsurface habitats within the sediment buried 3 5 myr old basaltic crust of the eastern juan de fuca ridge flank the circulating basement fluids have moderate temperature 65 c and low to undetectable dissolved oxygen and nitrate concentrations sulfate present in high concentrations is therefore expected to serve as the major electron acceptor in this subsurface environment this study focused on the availability and potential sources of two important electron donors methane ch4 and hydrogen h2 for the subseafloor biosphere high integrity basement fluids were collected via fluid delivery lines associated with integrated ocean drilling program iodp circulation obviation retrofit kits corks that extend from basement depths to outlet ports at the seafloor two new corks installed during iodp 327 in 2010 1362a and 1362b were sampled in 2011 and 2013 the two corks are superior than earlier style corks in that they are equipped with coated casing and polytetrafluoroethylene fluid delivery lines reducing the interaction between casing materials with the environment additional samples were collected from an earlier style cork at borehole 1301a the basement fluids are enriched in h2 0 05 1 8 mol kg suggesting that the ocean basaltic aquifer can support h2 driven metabolism the basement fluids also contain significant amount of ch4 5 32 mol kg revealing ch4 as an available substrate for subseafloor basaltic habitats the 13c values of ch4 from the three boreholes ranged from 22 5 to 58 while the 2h values ranged from 316 to 57 the isotopic compositions of ch4 and the molecular compositions of hydrocarbons suggest that ch4 in the basement fluids is of both biogenic and abiotic origins varying among sites and sampling times the 2h values of ch4 in cork 1301a fluid samples are much more positive than found in all other marine environments investigated to date and are best explained by the partial microbial oxidation of biogenic ch4 in conclusion our study shows that ch4 and h2 are persistently available to fuel the deep biosphere and that ch4 is both produced and potentially consumed by microorganisms in the oceanic basement