formation age and metamorphic history of the nuvvuagittuq greenstone belt abstract the nuvvuagittuq greenstone belt ngb in northern quebec canada is dominated by mafic and ultramafic rocks metamorphosed to at least upper amphibolite facies rare felsic intrusive rocks provide zircon ages of up to 3 8 ga david et al 2009 cates and mojzsis 2007 establishing the minimum formation age of the ngb as eoarchean primary u rich minerals that may provide reliable formation ages for the dominant mafic lithology called the ujaraaluk unit have yet to be found metamorphic zircons rutiles and monazites are present in the unit and give variably discordant results with 207pb 206pb ages ranging from 2 8 ga to 2 5 ga the younger ages overlap 2686 4 ma zircon ages for intruding pegmatites david et al 2009 and sm nd ages for garnet formation in the ujaraaluk rocks suggesting this era as the time of peak metamorphism and metasomatism in the ngb coeval with regional metamorphism of the superior craton sm nd data for ujaraaluk whole rocks scatter about a sm nd vs 143nd 144nd correlation mswd 134 whose slope would correspond to 3 6 0 2 ga if interpreted as an isochron this isochron is seen to consist of a series of younger 3 2 2 5 ga slopes for the different geochemical groups within the ujaraaluk emanating from a baseline distribution older than 4 ga the 146sm 142nd chronometer is less affected by metamorphism at 2 7 ga because of 146sm extinction prior to 4 ga expansion of the 142nd dataset for the ujaraaluk and associated ultramafic rocks continues to show a good correlation between sm nd ratio and 142nd 144nd that corresponds to an age of 4388 15 17 ma the dataset now includes samples with superchondritic sm nd ratios that extend the correlation to 142nd excesses of up to 8 ppm compared to the terrestrial standard with a total range in 142nd 144nd of 26 ppm the upper sm nd ratio end of the ujaraaluk correlation is defined by rocks that are interpreted to be cumulates to compositionally related extrusive rocks indicating that this crystal fractionation had to occur while 146sm decay was active i e well before 4 ga intruding gabbros give 143nd and 142nd isochron ages of respectively 4115 100 ma and 4313 41 69 ma also supporting an hadean age for the gabbros and providing a minimum age for the intruded ujaraaluk unit 3 6 ga tonalites surrounding the ngb 3 8 ga trondhjemitic intrusive veins and a 2 7 ga pegmatite show a deficit in 142nd compared to the terrestrial standard these felsic rocks plot to the low sm nd ratio side of the ujaraaluk isochron and do not show a correlation between their sm nd and 142nd 144nd ratios which can be explained if they are melts of ancient lree enriched mafic rocks such as the ujaraaluk with the melting occurring after 146sm was extinct a subset of least disturbed ujaraaluk samples has coherent isotopic compositions for both short lived and long lived nd isotopic systems giving 143nd and 142nd isochron ages overlapping within error of 4321 160 ma mswd 6 3 and 4406 14 17 ma mswd 1 0 respectively this age represents our best age estimate for the ujaraaluk unit the ngb thus preserves over 1 6 billion years of early earth history including an expanse of mafic crust formed in the hadean

about the role of westerly wind events in the possible development of an el nino in 2014 similarities between early 1997 and 2014 has prompted climate scientists to wonder if an el nino matching the 1997 el nino of the century could develop in 2014 until april 2014 the equatorial pacific exhibited positive heat content anomalies along with an eastward warm pool displacement similar to those found during the onset of strong el nino events yet in july 2014 the warm pool had retreated back to its climatological positions and equatorial temperature anomalies were much weaker than in mid 1997 dedicated oceanic simulations reveal that these weak interannual anomalies can be attributed to differences in westerly wind event wwe sequences in contrast with 1997 the lack of wwes from april to june significantly limited the growth of eastern pacific anomalies and the eastward warm pool displacement in 2014 with the absence of additional wwe activity prospects for a mature el nino in late 2014 are fading

westerly wind events in the tropical pacific 1986 95 abstract based on examination of 10 yr of 10 m winds and wind anomalies from european centre for medium range weather forecasts ecwmf analysis definitions for westerly wind events wwes of eight different types are proposed the authors construct a composite for each type of event show that a simple propagating gaussian model satisfactorily describes the evolution of zonal wind anomaly for each type of event and determine the scales of each composite event by fitting the model to each composite the authors discuss the wwes that occurred during the tropical oceans global atmosphere coupled ocean atmosphere response experiment toga coare intensive observing period iop and show the extent to which these composite events are able to reproduce the major westerly wind features of the iop the frequency of occurrence of each type of wwe for each year of this record and by calendar month are described the authors find several types of events are negatively correlated with the annual mean troup souther

using physical volcanology chemical stratigraphy and pyrite geochemistry for volcanogenic massive sulfide exploration an example from the blake river group abitibi greenstone belt an innovative approach to enhance volcanogenic massive sulfide vms exploration in regions outside of mining camps is to first use physical volcanology with litho and chemostratigraphy to establish the location of effusive centers in the volcanic units and use pyrite geochemistry in sulfide bearing stratified intervals with whole rock geochemistry in the underlying volcanic units to identify hydrothermal upflow zones this methodology is illustrated by this study in the archean blake river group within the abitibi greenstone belt of quebec and ontario the blake river group contains numerous vms deposits yet large segments remain underexplored including the hebecourt formation which contains four tholeiitic units that range from basalt to rhyolite in composition effusive centers are located for three felsic units and subunits 1 low ti porphyritic subunit of the main rhyolite 2 high ti aphyric subunit of the main rhyolite and 3 the upper rhyolite and for a basaltic andesite unit stringer and disseminated zn cu mineralization occurs within the flank breccia of the low ti rhyolite dome an inferred vent area for an overlying basaltic andesitic unit has also been identified in this area illustrating the coincidence of hydrothermal upflow zones with volcanic vents la icp ms analysis of pyrite grains from several sulfide bearing stratified intervals indicates two broad areas of higher cu zn au and ag contents the eastern region corresponds to known volcanic vents and mineralization the western region also indicates upflow of cu bearing hydrothermal fluids and corresponds to a possible effusive center for the high ti subunit the western region does not contain known mineralization at lower stratigraphic positions but it has not been thoroughly explored

hydrothermal germanium over the southern east pacific rise germanium enrichment in the oceanic water column above the southern axis of the east pacific rise results from hydrothermal solutions emanating from hot springs along the rise crest this plume signature provides a new oceanic tracer of reactions between seawater and sea floor basalts during hydrothermal alteration in contrast to the sharp plumes of 3he and manganese the germanium plume is broad and diffuse suggesting the existence of pervasive venting of low temperature solutions off the ridge axis

diagenetic fractionation of ge and si in reducing sediments the missing ge sink and a possible mechanism to cause glacial interglacial variations in oceanic ge si the average ge si ratio in the ocean is determined by the budgets for each of these elements previous budget formulations have assumed that the only important sink for both elements is burial as opal based on studies of the si cycle and the close oceanic coupling observed between inorganic ge and si distributions however these budgets implied two paradoxes 1 hydrothermal flow through ocean ridges is smaller than predicted by other tracers and 2 the lower ge si ratio of opal deposited during glacial times compared to that deposited during interglacial times required enhanced weathering during cooler drier climates both paradoxes could be resolved if a significant sedimentary sink for ge other than opal burial could be identified and the objective of this study was to search for one two pore water profiles collected in equatorial pacific sediments show that ge and si behave similarly in the upper 10 cm of sediment indicating no evidence for a significant non opal sink for ge in oxic sediments by contrast profiles in several cores from the california margin demonstrate that in reducing sediments ge diagenesis is poorly coupled to si diagenesis significant ge removal is evident both downcore and sometimes in the near surface benthic flux chamber measurements at three continental slope stations all with an oxic layer less than 1 cm thick and large iron gradients in near surface pore waters showed that 55 9 of the ge released by opal dissolution is sequestered however at two locations with anoxic sediments but little pore water fe 2 in the upper 2 cm flux measurements indicated little fractionation from the oceanic ratio during diagenesis implicating the importance of iron for fractionating ge from si during diagenesis if the ge sequestration observed in the iron rich ca margin sediments is typical of all slope sediments using a depth range of 200 1000 m then the ge sink is sufficient to bring the hydrothermal budget based on ge into concurrence with that based on other tracers the temporal variation in oceanic ge si could be explained if ge and si inputs remain constant and the effective diagenetic fractionation of ge increases by a factor of 2 3 during glacial times increased fractionation would require that glacial periods are characterized by increased opal dissolution in iron rich reducing sediments this could be caused by 1 thinning of the oxygenated sediment layer in response to decreased bottom water oxygen concentrations or increased rain of organics to the sea floor 2 increased rain of iron rich detrital sediments in areas receiving high opal rain 3 increased rain of opal to sediments in margin areas if the oceanic ge si ratio reflects increased rain of diatom opal or organic carbon in margin areas during glacial periods it may indicate an increase in the efficiency of the biological pump for co2 during glacial times

germanium geochemistry in the southern california borderlands abstract concentrations of ge oh 4 denoted as ge i or inorganic germanium and si oh 4 were measured in water column and pore water samples from san pedro and san nicolas basins in the southern california borderlands there is a characteristic linear relationship between ge i and si in the water column which implies that the distributions of germanium and silica are controlled by similar processes in contrast the pore water chemistry of germanium appears to differ from that of silica particularly in the reducing organic rich sediments of san pedro basin silica concentrations in san pedro basin pore water asymptotically increase to 480 m at 35 40 cm depth ge i concentrations in the topmost 2 cm of pore water from san pedro basin are an order of magnitude greater than bottom water concentrations below 2 cm ge i concentrations decrease exponentially with a half distance of about 8 cm cycling of ferric oxyhydroxides at a redox boundary is the most likely cause of the ge i enrichment in san pedro basin pore water while authigenic pyrite formation with the concomitant inclusion of germanium is a probable but undocumented cause of the downcore decrease in ge i pore water ge i and silica concentrations in sediments of san nicolas basin are generally greater than bottom water concentrations but vary irregularly with depth probably due to irrigation

germanium isotopic variations in igneous rocks and marine sediments a new technique for the precise and accurate determination of ge stable isotope compositions has been developed and applied to silicate rocks and biogenic opal the analyses were performed using a continuous flow hydride generation system coupled to a mc icpms samples have been purified through anion and cation exchange resins to separate ge from matrix elements and eliminate potential isobaric interferences variations of 74ge 70ge ratios are expressed as 74ge values relative to our internal standard and the long term external reproducibility of the data is better than 0 2 for sample size as low as 15 ng of ge data are presented for igneous and sedimentary rocks and the overall variation is 2 4 in 74ge representing 12 times the uncertainty of the measurements and demonstrating that the terrestrial isotopic composition of ge is not unique co variations of 74ge 70ge 73ge 70ge and 72ge 70ge ratios follow a mass dependent behaviour and imply natural isotopic fractionation of ge by physicochemical processes the range of 74ge in igneous rocks is only 0 25 without systematic differences among continental crust oceanic crust or mantle material on this basis a bulk silicate earth reservoir with a 74ge of 1 3 0 2 can be defined in contrast modern biogenic opal such as marine sponges and authigenic glauconite displayed higher 74ge values between 2 0 and 3 0 this suggests that biogenic opal may be significantly enriched in light isotopes with respect to seawater and places a lower bound on the 74ge of the seawater to 3 0 this suggests that seawater is isotopically heavy relative to bulk silicate earth and that biogenic opal may be significantly fractionated with respect to seawater deep sea sediments are within the range of the bulk silicate earth while mesozoic deep sea cherts opal and quartz have 74ge values ranging from 0 7 to 2 0 the variable values of the cherts cannot be explained by binary mixing between a biogenic component and a detrital component and are suggestive of enrichment in the light isotope of diagenetic quartz further work is now required to determine ge isotope fractionation by siliceous organisms and to investigate the effect of diagenetic processes during chert lithification

advances in marine chemistry 1979 1982 these four years saw advances in many areas further developments in sampling and analytical techniques have opened new avenues of exploration for trace elements and particulate matter the impact of the geosecs expedition was further felt in the field of marine chemistry as the results were still being published a major field effort occurred as a follow on to the geosecs work tto and intensive sampling was performed in the newly discovered submarine hydrothermal vent fields an important and unresolved controversy has arisen regarding the ability to measure preformed co2 in the seawater system in many respects the field of marine chemistry appears to be gaining a momentum spurred by both improvements in analytic techniques and an increasing social and economic relevance

hydrothermal origin of syndepositional chert bands and nodules in the mesoproterozoic wumishan formation implications for the evolution of mesoproterozoic cratonic basin north china abstract abundant chert bands and nodules are discovered throughout the mesoproterozoic wumishan formation 1 5 ga in the north china block the middle part of the wumishan formation consists of cyclic deposition of calcareous shale massive microbial dolostone thrombolites and stromatolites and laminated dolostone chert bands occur most abundantly in the laminated dolostone although they are also found with lower abundance in other lithologies chert bands are normally parallel to the bedding plane and show soft deformation structures suggesting early silicification at or near the water sediment interface the wumishan chert is composed of two types of silica fabric the microcrystalline and cryptocrystalline quartz that derives from the replacement of host dolomitic rock and the mosaic chalcedonic quartz representing typical void filling precipitation we measured the germanium silica ratios ge si and the ree compositions of the chert bands nodules collected from a 60 m interval in the middle part of the wumishan formation in the mopanyu section ge si ratios of the buck samples measured by icp ms range from 13 6 to 35 6 mol mol additional la icp ms analyses allow the measurements of individual silica fabric providing more detailed information about the geochemistry of chert nodules and bands ge si ratios of the replacive chert vary between 10 and 20 mol mol while the mosaic chalcedonic quartz has wider range of variation 1 1 93 2 mol mol these values are 1 order of magnitude higher than the modern seawater value 0 72 mol mol but is within the range of hydrothermal fluids 3 4 51 3 mol mol average 13 mol mol n 101 suggesting hydrothermal fluid as an important si source this conclusion is consistent with the positive eu anomaly in the ree pattern a mass balance calculation indicates that hydrothermal fluid would account for 10 15 20 25 40 55 and 75 of si for the fluid temperature of 100 c 150 c 200 c and 250 c respectively although large igneous provinces are not discovered in the north china block during the deposition of the wumishan formation the studied wumishan cherts have significant contribution from hydrothermal fluid which might be related to the early rifting activities in the north china block before the breakup of supercontinent nuna

the nature of the stochastic wind forcing of enso abstractel nino southern oscillation enso is commonly viewed as a low frequency tropical mode of coupled atmosphere ocean variability energized by stochastic wind forcing despite many studies h

transfer of germanium to marine sediments insights from its accumulation in radiolarites and authigenic capture under reducing conditions some examples through geological ages in the geosphere germanium ge has a chemical behavior close to that of silicon si and ge commonly substitutes for si in small proportions in silicates studying the evolution of the respective proportions of ge and si through time allows us to better constrain the global si cycle the marine inventory of ge present as dissolved germanic acid is facing two main sinks known through the study of present sediments 1 incorporation into diatom frustules and transfer to sediments by these shuttles 2 capture of ge released to pore water through frustule dissolution by authigenic mineral phases forming within reducing sediments our goals are to determine whether such a bio induced transfer of ge is also achieved by radiolarian and whether ge could be trapped directly from seawater into authigenic phases with no intervention of opal secreting organisms shuttles to this end we studied two paleozoic radiolarite formations and geological formations dated of devonian jurassic and cretaceous deposited under more or less drastic redox conditions our results show that the ge si values observed for these radiolarites are close to slightly above those measured from modern diatoms and sponges in addition our results confirm what is observed with some present day reducing sediments the ancient sediments that underwent reducing depositional conditions are authigenically enriched in ge furthermore it is probable that at least a part of the authigenic ge came directly from seawater the recurrence and extent through time and space of anoxic conditions affecting sea bottoms have been quite important through the geological times consequently the capture of ge by reducing sediments must have impacted ge distribution and in turn the evolution of the seawater ge si ratio

a review of the superior province of the canadian shield a product of archean accretion abstract the superior province consists of northern and southern high grade gneiss subprovinces and a central region of alternating granite greenstone and metasedimentary belts subprovinces are commonly fault bounded and display contrasting lithological assemblages metamorphic and structural styles geophysical characteristics and ages they are comparable to phanerozoic suspect terranes the middle and late archean rocks of the superior province are of mantle and juvenile crustal origin with little evidence of inheritance of components older than ca 3 1 ga high grade gneiss subprovinces are mainly deeper level equivalents of the supracrustal rich belts but one minnesota river valley is part of an older ca 3 6 ga terrane that was juxtaposed late in the tectonic history granite greenstone terranes are characterized by low grade volcano sedimentary sequences tholeiitic komatiitic submarine lava plain tholeiitic calc alkalic submarine to subaerial central complexes early platform type quartz arenite stromatolitic carbonate late timiskaming type shoshonitic alkalic volcanic fluvial sediment that range in age from ca 3 0 ga to 2 7 ga the volcanics represent oceanic island arc and continental arc volcanism the quartz arenite carbonate sequences deposition on relatively stable early formed ca 3 0 ga crust and the timiskaming type sequences deposition in pull apart basins developed along strike slip faults late archean ca 2 75 2 70 ga greenstone sequences occur throughout the superior province middle archean ca 3 0 2 8 ga sequences are common in northern and central superior province rare or absent in the south volcanism was accompanied by mafic to trondhjemitic plutonism the metasedimentary belts consist of variably metamorphosed volcanogenic turbidites with detrital zircons ranging in age from ca 3 0 ga to 2 7 ga the metasediments were deposited after major volcanism and probably represent accretionary prisms late archean orogenesis accompanied and followed by calc alkalic plutonism youngs southward from about 2 73 2 72 ga to 2 70 2 68 ga it involved large scale north south compression and dextral transpression and displays thin to thick skinned transitions the contemporaneity of events along the lengths of the belts and their southward younging coupled with the evidence of major compression are consistent with subduction driven oblique accretion of oceanic and continental volcanic arcs accretionary sedimentary wedges older microcontinental fragments etc in a convergent margin setting analogous to parts of the pacific rim differences eg abundance of komatiites and tonalitic plutonic suites are attributable to a hotter archean mantle

on the physical interpretation of the lead relation between warm water volume and the el nino southern oscillation the warm water volume wwv a proxy for the equatorial pacific heat content is the most widely used oceanic precursor of the el nino southern oscillation enso the standard interpretation of this lead relation in the context of the recharge oscillator theory is that anomalous easterlies during e g la nina favour a slow recharge of the equatorial band that will later favour a transition to el nino here we demonstrate that wwv only works as the best enso predictor during boreal spring i e during enso onset in both observations and cmip5 models at longer lead times the heat content in the western pacific wwvw is the best enso predictor as initially formulated in the recharge oscillator theory using idealised and realistic experiments with a linear continuously stratified ocean model and a comprehensive wave decomposition method we demonstrate that spring wwv mostly reflects the fast kelvin wave response to wind anomalies early in the year rather than the longer term influence of winds during the previous year wwv is hence not an adequate index of the slow recharge invoked in the recharge oscillator the wwvw evolution before spring is dominated by forced rossby waves with a smaller contribution from the western boundary reflection wwvw can be approximated from the integral of equatorial wind stress over the previous 10 months thus involving a longer term time scale than wwv main time scale 3 months we hence recommend using wwvw rather than wwv as an index for the slow recharge before the spring predictability barrier

equatorial pacific easterly wind surges and the onset of la nina events abstractthe processes responsible for the onset of la nina events have not received the same attention as those responsible for the onset of el nino events for which westerly wind events wwes in the tropical pacific have been identified as important contributors results here show that synoptic scale surface easterly wind surges ewss play an important role in the onset of la nina events akin to the role of wwes in the onset of el nino events it is found that ewss are a substantial component of zonal wind stress variance along the equatorial pacific using reanalysis wind stress fields validated against buoy measurements 340 ews events are identified between 1986 and 2012 their distributions in space time and el nino southern oscillation enso state are described about 150 ewss occur during enso neutral conditions during the months associated with la nina initiation and growth april december composites of changes in sea surface temperature anomaly ssta following these 150 events show s

subduction influence of philippine sea plate on the mantle beneath northern kyushu sw japan an examination of boron contents in basaltic rocks abstract northern kyushu characterized by the subduction of two oceanic slabs a hot shikoku basin and a cold philippine sea plate beneath the eurasian plate forms a complex portion of southwestern japan arc in order to evaluate the effect of slab derived fluids from these two contrasting oceanic plates we determined the boron b contents in basaltic rocks from ten volcanoes and three old volcanic fields which erupted since 11 ma since b is distinctly concentrated into slab derived fluids among the earth s materials we attempted to estimate the influences of subduction on the sub arc mantle composition from the interpretation of the b data in basaltic rocks old 11 6 ma basaltic rocks contain low ratios of b sm 0 5 1 3 b zr 0 02 0 05 and b nb 0 2 0 5 suggesting little influence of subduction similarly backarc basaltic rocks occurring throughout the observed period show little influence of subduction in contrast volcanic products from young aso volcano located at the volcanic front show a strong influence of subduction as indicated by the high b sm 1 6 4 3 b zr 0 07 0 16 and b nb 1 4 3 7 ratios after 6 ma the volcanic arc segment containing aso volcano is associated with the subduction of the cold philippine sea plate hence a b rich fluid was probably added to the sub arc mantle however yufu tsurumi and kuju volcanoes which are located at the same volcanic front show small b sm 0 9 1 9 b zr 0 04 0 07 and b nb 0 5 0 9 ratios this implies that the subduction of the hot shikoku basin released fluids from the slab at shallow depths therefore it is depleted of b and other subduction components by the time it reaches the volcanic front

magmatic affinity of modern and ancient subalkaline volcanic rocks determined from trace element discriminant diagrams when dealing with ancient subalkaline volcanic rocks the alkali total iron magnesium afm diagram is of limited use in assigning a tholeiitic versus calc alkaline affinity because these eleme

westerly wind bursts and their relationship with intraseasonal variations and enso part ii energetics over the western and central pacific abstract the mechanism of synoptic scale eddy development in the generation of westerly wind bursts wwbs over the western central pacific and their relationship with the el nino southern oscillation enso and the madden julian oscillation mjo were examined in the wwb occurrences barotropic structures of equatorial eddy westerlies with cyclonic disturbances were found from the surface to the upper troposphere the dominant contributions to substantial eddy kinetic energy eke were the barotropic energy conversion kmke in the lower and middle tropospheres and the conversion from eddy available potential energy peke in the upper troposphere low frequency environmental westerlies centered near the equator preceded strong zonal convergence and meridional shear resulting in the substantial kmke the activation of synoptic convection also contributed to an increase in eke through peke these energies were redistributed to the lower equatorial troposphere through energy flux convergence gke the

diagenetic ge si fractionation in continental margin environments further evidence for a nonopal ge sink we present data for dissolved germanic and silicic acids from several settings sediment pore water profiles collected from the peru chile continental margin fluxes measured with in situ benthic flux chambers and shipboard whole core incubations and water column profiles from the california continental margin collectively these data show that ge and si are fractionated in these continental margin sedimentary environments during diagenesis with 50 of the ge released by opal dissolution being sequestered within the sediments the areal extent of this diagenetic fractionation covers station depths from 100 m to 1000 m sediments from these sites typically have high pore water fe2 present in the upper 2 cm at sites with low fe2 concentrations in the upper pore waters the ge si benthic regeneration ratio indicates little or no fractionation during diatom dissolution consistent with the sedimentary fractionation water column dissolved ge si ratios along the continental margin are on average lower 0 66 mol mol than the global average ratio 0 72 mol mol mortlock and froelich 1996 this lower average ratio is driven by two distinct ge si data trends having similar slopes but different intercepts data from the upper 150 m has a ge si slope of 0 74 0 04 mol mol 2 and an intercept of 0 5 0 4 whereas below 550 m the slope is 0 70 0 06 mol mol but the intercept is 5 0 8 0 assuming that the sediments sampled here are representative of all reducing marine environments an assumption requiring further testing our calculations indicate that sequestration of ge into a nonopal phase throughout the global ocean in the depth range 0 2 1 km is sufficient to balance the ge budget thus we tentatively conclude that sequestering of ge in reducing continental margin sediments is the missing ge sink

trace element geochemistry and petrogenesis of felsic volcanic rocks associated with volcanogenic massive cu zn pb sulfide deposits volcanogenic massive cu zn pb sulfide vms deposits occur primarily in subaqueous rift related environments e g oceanic fore arc arc back arc continental margin or continental are hosted primarily by bimodal mafic felsic volcanic successions and are typically associated with felsic volcanic rocks with specific geochemical characteristics fi alkalic dacites and rhyodacites despite being abundant in the rock record are typically barren some fii calc alkalic rhyodacites and rhyolites host vms deposits but most are barren fiii tholeiitic and fiv depleted rhyolites and high silica rhyolites are much less abundant in the rock record but commonly host vms deposits regardless of age and fiii rhyolites appear to host the largest deposits most petrogenetic models proposed for the formation of fii and fiii fiv felsic volcanic rocks link felsic magma genesis to fractionation processes in high level magma chambers now represented by associated subvolcanic intrusions where the magma is also interpreted to have supplied the heat and or metals required to generate and sustain the vms forming convective hydrothermal system however the relatively constant compositions of fii and fiii fiv felsic volcanic rocks within individual areas the high eruptive temperatures at or above liquidus of fiii rhyolites and the bimodality of vms hosting volcanic successions indicate that fractional crystallization within subvolcanic intrusions could not have generated or significantly modified the compositions of fii and fiii fiv magmas this coupled with detailed geological geochemical and geochronological studies indicates that many of these subvolcanic intrusions were emplaced in multiple phases and that the later most voluminous phases often cut ore associated hydrothermally altered rocks a reassessment of the physical conditions responsible for producing the geochemistry of ore associated fii and fiii fiv felsic volcanic rocks and a review of the compositions of felsic volcanic rocks associated with vms deposits that range in age from mesoarchean to cenozoic provide important constraints on models for vms associated felsic volcanic rocks and their relationship to mineralization the compositions of felsic volcanic rocks may be explained by low to moderate degrees of partial melting of mafic sources at a range of depths within rift environments where the mineralogy and composition of the source regions modes and degrees of partial melting pressure and temperature of melting and to a lesser extent subsequent fractionation processes account for the compositional variations from fi through fii to fiii fiv long lived enhanced heat flow and structural permeability of rift environments that allows partial melting to form some fii rhyolites at midcrustal levels 10 15 km and fiii fiv rhyolites at shallow crustal levels 10 km both within the zone of brittle fracture permeability are essential to sustain the high temperature convective hydrothermal systems that are required to form large vms deposits and camps rift environments contain long lived thermal magmatic and structural corridors that focus magma ascent heat flow high temperature convective hydrothermal systems and emplacement of subvolcanic intrusions that are favorable environments for the formation of vms deposits and fii and fiii fiv felsic volcanic rocks

contemporaneously erupted tholeiitic and calc alkaline magmas in the archean colomb chaboullie greenstone belt james bay quebec petrologic implications abstract archean greenstone terranes are key to understanding the geological processes active during early earth history these areas are also of economic interest due to their association with volcanogenic massive sulphide vms deposits and several other types of mineral deposits the archean colomb chaboullie greenstone belt is located between the nemiscau and opatica subprovinces of the superior province quebec canada this belt comprises three submarine volcanic units pillowed to massive basaltic lavas variably porphyritic massive to pillowed intermediate lavas intrusions and intermediate to felsic volcaniclastic rocks the calc alkaline intermediate lavas and volcaniclastic assemblages are intercalated with the tholeiitic to transitional basaltic lavas this implies that these volcanic rocks were contemporaneously formed within a limited geographical area the major element trends of the basalts are explained by crystal fractionation while the trace elements are influenced by independently occurring minor degrees of crustal contamination the major and trace element geochemistry of the calc alkaline rocks share many geochemical characteristics with pre existing crustal contaminants we therefore propose that the intermediate and felsic assemblages were produced via crustal contamination and mixing processes within a pre existing magma chamber the basalts spent less time in the crust and had a more direct passage to the surface massive to semi massive au ag cu showings along with associated paleo hydrothermal manifestations are dominantly associated with the basaltic lavas and show evidence of a syn volcanic origin chemo stratigraphy in conjunction with detailed mapping of the gold bearing lac marcaut vms showing allows a basalt basalt contact to be identified which may be favourable for exploration elsewhere in the colomb chaboullie belt

observations of warm water volume changes in the equatorial pacific and their relationship to el nino and la nina abstract this paper describes observed changes in surface winds sea surface temperature sst and the volume of water warmer than 20 c wwv in the equatorial pacific ocean for the period 1980 99 the purpose is to test recent hypotheses about the relationship between variations in wwv and the el nino southern oscillation enso cycle the results confirm inferences based on theory models and previous empirical analyses using proxy data namely sea level that enso involves a recharge and discharge of wwv along the equator and that the cyclic nature of enso results from a disequilibrium between zonal winds and zonal mean thermocline depth the authors also find that the magnitude of enso sst anomalies is directly related to the magnitude of zonal mean wwv anomalies furthermore for a given change in equatorial wwv the corresponding warm el nino sst anomalies are larger than the corresponding cold la nina anomalies this asymmetry between the warm and cold phases of the enso cycle implies differences

twentieth century simulation of the southern hemisphere climate in coupled models part ii sea ice conditions and variability we examine the representation of the mean state and interannual variability of antarctic sea ice in six simulations of the twentieth century from coupled models participating in the intergovernmental panel on climate change fourth assessment report the simulations exhibit a largely seasonal southern hemisphere ice cover as observed there is a considerable scatter in the monthly simulated climatological ice extent among different models but no consistent bias when compared to observations the scatter in maximum winter ice extent among different models is correlated to the strength of the climatological zonal winds suggesting that wind forced ice transport is responsible for much of this scatter observations show that the leading mode of southern hemisphere ice variability exhibits a dipole structure with anomalies of one sign in the atlantic sector associated with anomalies of the opposite sign in the pacific sector the observed ice anomalies also exhibit eastward propagation with the antarctic circumpolar current as part of the documented antarctic circumpolar wave phenomenon many of the models do simulate dipole like behavior in sea ice anomalies as the leading mode of ice variability but there is a large discrepancy in the eastward propagation of these anomalies among the different models consistent with observations the simulated antarctic dipole like variations in the ice cover are led by sea level pressure anomalies in the amundsen bellingshausen sea these are associated to different degrees in different models with both the southern annular mode and the el nino southern oscillation enso there are indications that the magnitude of the influence of enso on the southern hemisphere ice cover is related to the strength of enso events simulated by the different models

germanium incorporation into sponge spicules development of a proxy for reconstructing inorganic germanium and silicon concentrations in seawater abstract measurements of germanium ge in deep sea sponge skeletons are presented for sponges collected by dredge and for spicules isolated from a range of deep sea sediment cores germanium to silicon si ratios ge si sp for sponge silica ranged between 0 075 and 0 380 mol mol which are much lower than the present day seawater ge si ratio of 0 7 mol mol a plot of ge si sp versus estimated seawater ge and si concentration produced a linear relationship with the ge content of spicules increasing with seawater ge concentration plots of ge si sp versus depth for both dredged sponges and sediment bound spicules produced oceanic profiles similar to those of dissolved ge and si concentration to explain the fractionation seen in the sponge ge si sp data two models are presented the first model used to interpret the data assumes that sponges only respond to the ge content of the ambient seawater implying that ge incorporation into sponge silica is independent of the seawater ge si ratio up to a si concentration of about 100 mol l this model is consistent with the 68 ge uptake results of davie et al e i davie t l simpson r garonne experimental germanium incorporation into siliceous sponge spicules biol cell 48 1983 191 202 for cultured spicules their results showed that the incorporation of ge in sponge silica is only dependent on the ge concentration of the water in which a sponge is growing the second model used to explain the data assumes that ge si sp fractionation results from subtle differences in the uptake kinetics of ge and si while the assumptions used by each model to describe the data are different it is possible to use sponge ge si sp data to reconstruct palaeo ge concentrations using model i and to reconstruct palaeo si concentrations using both models palaeo si concentrations estimated using both models are in good agreement

germanium silicon fractionation during biogenic opal formation model results and empirical data show that germanium is fractionated from silica during biogenic opal formation in a two box model of the ocean particulate ge si can vary between the average ocean ge si and the average ocean ratio times the ge fractionation coefficient the two box model requires a ge fractionation coefficient near 0 48 to reproduce si and ge concentrations similar to the ocean analysis of paired water and opal samples yields a ge fractionation coefficient of 0 51 as a consequence of this fractionation the ge si of opal can be an upwelling indicator small shifts of opal ge si in adjacent centimeter scale lighter and darker layers in the miocene monterey formation are consistent with other sedimentologic indicators of productivity and upwelling variations opal ge si are lower in lighter layers and are consistent with interpretations that the lighter layers were formed by increased productivity in overlying waters

giant granulite terranes of northeastern superior province the ashuanipi complex and minto block the ashuanipi complex and minto block of the superior province are large regions that have been classified as high grade gneiss terranes on the basis of the presence of orthopyroxene bearing units like the granite greenstone and metasedimentary subprovinces of the southern superior province the two terranes consist predominantly of intrusive rocks but are distinguished by their primary magmatic orthopyroxene both high grade and gneiss are misnomers because granulite facies gneisses are only sparingly present and the regions consist dominantly of massive unmetamorphosed plutonic rock the ashuanipi complex consists of a deformed metamorphosed package of metasedimentary rocks and primitive early tonalite cut by widespread orthopyroxene garnet granodiorite diatexite as well as plutons of tonalite granite and syenite based on its lithological and chronological similarity and on strike position the complex appears to be the continuation of metasedimentary subprovinces such as the quetico its evolution involved deposition of immature greywacke in an accretionary prism early arc tonalitic magmatism and deformation followed by widespread intracrustal magmatism in the period 2700 2670 ma both metamorphic and igneous rocks record equilibration under granulite facies conditions 700 835 c 0 35 0 65 gpa a 0 3 and indicate exposure levels of 20 km the minto block at the latitude of leaf river consists of several north northwest trending domains of similar scale and diversity to the east trending subprovinces of the southern superior province the central goudalie domain is dominantly amphibolite facies tonalitic rocks including some with ages 3 ga with small belts of volcanic and sedimentary origin lake minto domain contains poorly preserved supracrustal remnants in a plutonic complex comprising hornblende granodiorite clinopyroxene orthopyroxene granodiorite orthopyroxene biotite diatexite and granite the hornblende granodiorite suite constitutes most of the utsalik and tikkerutuk domains and is thought to represent continental arc magmatism on the basis of their distinct aeromagnetic and lithological character two additional domains are evident north of the leaf river area the inukjuak domain in the west and the douglas harbour domain in the east the northerly grain of the minto block appears to have been established in situ with respect to the easterly belts of the southern superior province i e no large scale block rotation during the same interval of time 3 0 2 7 ga modification of the tectonic framework for the superior province is required to explain minto arc magmatism in the interval 2730 2690 ma ago a continental magmatic arc built the berens river and bienville subprovinces and minto block on the southern and eastern edges respectively of a northern protocratonic foundation in the same period primitive volcanic arcs and accretionary prisms developed outboard on oceanic crust and were accreted to form a southern tectonic regime

tropical pacific sea surface temperature anomalies el nino and equatorial westerly wind events abstract the authors examine global statistical relationships between westerly wind events wwes and sea surface temperature anomaly ssta variability using a compositing technique for the period 1986 98 the authors describe the extent to which equatorial wwes are associated with central and eastern equatorial pacific waveguide warming and with local ssta changes under the wwe their goal is to quantify the extent to which equatorial wwes are fundamental to the onset and maintenance of warm el nino southern oscillation conditions in order to understand the effect of wwes on ssta evolution they begin by examining how ssta changes in the absence of equatorial wwes they find that ssta tends toward mean climate values in the absence of equatorial wwes whether the eastern equatorial pacific has close to normal ssta or warmer than normal ssta the two equatorial wwe types whose main surface wind anomalies are west of the date line are associated with weak local surface cooling the equatorial wwe type t

the geochemistry of inorganic germanium in natural waters we present the initial results from a survey of the distribution of dissolved inorganic germanium in rivers in the oceans and in hydrothermal vents and plumes in the ocean germanium cycling mimics that of silica since siliceous organisms incorporate ge as a trace constituent in biogenic opal the vertical and horizontal distributions of ge concentrations in seawater are thus identical to those of silica ge si 0 7 10 6 and reflect uptake into and dissolution from the frustules of siliceous organisms germanium enters the ocean via dissolution of continental and seafloor silicates the naturally weathered flux from continents to oceans carries a dissolved ge si atom ratio in rivers of about 0 7 10 6 which reflects the ratio in average continental granites rivers draining industrial regions with significant coal combustion are contaminated with ge leached from fly ash particles resulting in ge si ratios up to tenfold above the naturally weathered background the flux to the oceans via high temperature alteration of seafloor basalts hot springs produces a ge anomaly in hydrothermal plumes over the east pacific rise crest 20 s combining the observed ge and 3he anomalies in plumes with 3he si observations in hot springs suggests that the ge si hydrothermal flux to the oceans is about 4 10 6 near the ratio for average oceanic basalts 2 6 10 6 vent effluents from the galapagos hot springs measured directly display ge si ratios of 16 10 6 suggesting that the ratio is variable between vent fields metalliferous sediments accumulating on the epr crest 17 s are enriched in germanium suggesting that a fraction of the hydrothermal germanium source on the rise crest is scavenged into these rapidly accumulating iron and manganese hydroxyoxide phases

role of high and low frequency winds and wave reflection in the onset growth and termination of the 1997 1998 el nino the present study aims at studying the role played by high frequency wind variability wave reflection and easterly wind anomalies in the western pacific in the onset growth and termination phases of the 1997 1998 el nino using the trident intermediate coupled model and observations while the anomalous strength of the trade winds in 1996 favored the initiation of a warm event in 1997 via western pacific boundary rossby wave reflection the actual timing of the onset and the amplitude of the event resulted from the large march 1997 wind event once initiated high frequency westerly winds strongly contributed to the rapid growth of the warm event and to the displacement of the eastern edge of the warm pool moreover both easterly and westerly high frequency wind variability in 1997 1998 contributed to the amplitude of the event set the evolution of the warm event and potentially influenced the equatorial pacific conditions at least one year after the el nino event in addition eastern boundary reflection also significantly contributed to the amplitude and duration of the warm event whereas its termination was a combination of various factors reflection of upwelling rossby waves at the western boundary and large easterly wind anomalies observed in the western pacific from november 1997 to early 1998 these factors were sufficient to terminate the event and to switch temperature anomalies from warm to cold to conclude understanding the coupling between the high and low frequency wind variability i e studying enso as a multi scale phenomenon will certainly lead to a better comprehension of the diversity of its behavior and potentially to an improvement of its predictability

early diagenesis of germanium in sediments of the antarctic south atlantic in search of the missing ge sink pore water and solid phase geochemistry profiles were obtained from several cores between 41 degree s and 53 degree s in the atlantic sector of the southern ocean pore water nitrate manganese and iron profiles delineate standard redox zones in these sediments and help characterize those with classic vs burn down behaviors pore water si and ge profiles demonstrate that ge released during opal dissolution is removed pervasively throughout the uppermost interval of silicate release and also downwards into the suboxic zone by as yet unidentified precipitation mechanisms these results indicate that early diagenesis of ge is uncoupled from that of opal solid phase extractions fe mn u mo ge cu ni co v and cd in a few cores suggest that anthigenic ge removal in the suboxic zone is not associated with peaks in authigenic mn cycling mno sub 2 and related metals but rather with processes deeper in the sediments perhaps fe or u diagenesis below the interval of ge removal pre water ge increases linearly with depth by over two orders of magnitude indicating a deep below recovery source of large magnitude the fraction of opal derived ge precipitated authigenically in these sediments ranges from approximately 1 to 96 and correlates strongly with the detrital fraction asmore well as the detrital to opal ratio both of which generally decrease from north to south the ge sink observed in these sediments would need to be globally representative to account for the entire missing ge sink in today s oceanic ge balance which seems unlikely benthic fluxes of ge and si estimated from these pore water profiles and from measurements in three benthic flux chamber experiments at high carbon rain continental margin sites demonstrate that the ge si rate released from the seafloor in locations with high benthic silicate and carbon fluxes is congruent with holocene opal dissolution ge si approximately 0 7 x 10 sup minus 6 in contrast ge si flux ratios in areas with low silicate fluxes are ge depleted ge si 0 5 x 10 sup minus 6 the authors speculate that glacial interglacial changes in oceanic ge si as recorded in diatoms may be due in part to variations in this authigenic ge sink perhaps related to shifts in siliceous productivity from open ocean antarctic siliceous oozes during interglacials to areas of higher detrital input sub antarctic continental margins and possibly also to generally more reducing conditions in sediments during glacials less

paleozoic and mesozoic silica rich seawater evidence from hematitic chert jasper deposits laterally extensive beds of highly siliceous hematitic chert jasper are associated with many volcanogenic massive sulfide vms deposits of late cambrian to early cretaceous age yet are unknown in analogous younger including modern settings textural studies suggest that vms related jaspers in the ordovician lokken ophiolite of norway were originally deposited as si and fe rich gels that precipitated from hydrothermal plumes as colloidal silica and iron oxyhydroxide particles rare earth element patterns and ge si ratios of the jaspers reflect precipitation from plumes having seawater dilution factors of 10 3 to 10 4 similar to modern examples we propose that silica in the ancient jaspers is not derived from submarine hydrothermal fluids as suggested by previous workers but instead was deposited from silica rich seawater flocculation and precipitation of the silica were triggered inorganically by the bridging effect of positively charged iron oxyhydroxides in the hydrothermal plume a model involving amorphous silica opal a precursors to the jaspers suggests that silica contents of cambrian early cretaceous oceans were at least 110 mg l sio 2 compared to values of 40 60 mg l sio 2 estimated in other studies the evolution of ancient silica rich to modern fe rich precipitates in submarine hydrothermal plumes reflects a changeover from silica saturated to silica depleted seawater through phanerozoic time due mainly to ocean wide emergence of diatoms in the cretaceous

conditions and timing of metamorphism in the southern abitibi greenstone belt quebec regional metamorphism ranging in grade from the subgreenschist facies to the greenschist amphibolite facies transition affects all archean supracrustal rocks 2677 ma in the rouyn noranda area contact metamorphic minerals associated with the posttectonic preissac lacorne batholith 2643 ma show no evidence of a regional retrograde event accordingly the age of regional metamorphism can be bracketed between 2677 and 2643 ma three reaction isograds were mapped in subgreenschist facies metabasites dividing the low grade rocks into three metamorphic zones the pumpellyite actinolite zone the prehnite pumpellyite zone and the prehnite epidote zone in addition the pumpellyite actinolite epidote quartz bathograd corresponding to a pressure of approximately 200 mpa occurs on both sides of the porcupine destor fault low pressure regional metamorphism is also indicated both by the occurrence of an actinolite oligoclase zone and the persistence of pre regional metamorphic andalusite the coincidence

beryllium in the water column of the central north pacific the existence of the cosmogenic radioisotope of beryllium 10be t1 2 1 5 myr was first confirmed1 2 almost 25 yr ago subsequently merrill et al 3 worked out the sedimentary geochemistry of the stable isotope of the element 9be the geochronological potential of 10 be could not be exploited however because of its extremely low abundance global average production rate 1 08 atoms cm 2 min 1 4 and the difficulties associated with the analysis of the stable species 9be particularly in natural waters this situation is changing dramatically with the application of accelerator techniques to the detection of the radioisotope5 it thus becomes important to obtain a detailed understanding of the geochemistry of 9be since the potential use of the stable isotope for normalization purposes would significantly enhance the usefulness of the radioactive species in dating studies we report here the first detailed profile for 9be in the oceanic water column

germanium geochemistry and mineralogy abstract germanium is enriched in the following geologic environments 1 1 iron meteorites and terrestrial iron nickel 2 2 sulfide ore deposits particularly those hosted by sedimentary rocks 3 3 iron oxide deposits 4 4 oxidized zones of ge bearing sulfide deposits 5 5 pegmatites greisens and skarns and 6 6 coal and lignitized wood in silicate melts ge is highly siderophile in the presence of native iron nickel otherwise it is highly lithophile among silicate minerals ge is concentrated in those having less polymerized silicate tetrahedra such as olivine and topaz in deposits formed from hydrothermal solutions ge tends to be enriched mostly in either sulfides or in fluorine bearing phases it is thus concentrated both in some hydrothermal sulfide deposits and in pegmatites greisens and skarns in sulfide deposits that formed from solutions having low to moderate sulfur activity ge is concentrated in sphalerite in amounts up to 3000 ppm sulfide deposits that formed from solutions having higher sulfur activity allowed ge to either form its own sulfides particularly with cu or to substitute for as sn or other metals in sulfosalts the ge in hydrothermal fluids probably derives from enrichment during the fractional crystallization of igneous fluids or is due to the incorporation of ge from the country rocks particularly from those containing organic material germanium bonds to lignin derivative organic compounds that are found in peat and lignite accounting for its common concentration in coals and related organic material germanium is precipitated from water together with iron hydroxide accounting for its concentration in some sedimentary and supergene iron oxide deposits it also is able to substitute for fe in magnetite in a variety of geologic environments in the oxidized zone of ge bearing sulfide deposits ge is concentrated in oxides hydroxides and hydroxy sulfates sometimes forming its own minerals it is particularly enriched in some iron and manganese bearing oxides and hydroxides including goethite up to 5300 ppm and hematite up to 7000 ppm

germanium silica ratios in diagenetic chert nodules from the ediacaran doushantuo formation south china abstract germanium silica ge si ratios of dolostone and mudstone hosted chert nodules from the ediacaran 635 542 ma doushantuo formation in the yangtze gorges area south china are reported these chert nodules typically have a calcite rim a pyrite rim and a silica core the latter sometimes containing disseminated pyrite the silica core was precipitated by early diagenetic replacement of carbonate and silty muddy sediments two types of chert nodules are identified based on their mineralogy and geochemistry type 1 chert nodules are poor in disseminated pyrite in the silica core they also have low al and show a strong positive correlation between al contents and ge si with a near zero or negative intercept in contrast type 2 chert nodules contain abundant disseminated pyrite in the silica core and show a weakly positive correlation between ge si ratios and al contents with a large positive intercept on the ge si axis the ge si of doushantuo nodules are greater than those of cretaceous deep sea cherts suggesting that the ge si ratio of ediacaran seawater porewater was greater than the cretaceous due to the more effective discrimination against ge by inorganic opal precipitation relative to biogenic opal precipitation the positive correlation between ge si and al can be interpreted using a mixing model with a pure chert characterized by a low ge si ratio and an al rich endmember characterized by a high ge si ratio the latter is most likely represented by a clay component but the model based estimate of the ge si ratio inferred for the al rich clay endmember is much higher than that of phanerozoic clay minerals these high ge si ratios for the clay endmember may be related to the generally high ge si ratio of ediacaran seawater but could also be related to clay organic matter interactions organic matter absorbed to clays could provide an additional source of ge because certain organic molecules are known to have a high affinity for ge due to their strong metal ion chelating properties the high ge si ratio of the al rich endmember in type 1 chert nodules suggests that ge in porewaters from which these cherts precipitated may have been dominated by ge organic complexes the low ge si ratio inferred for the al rich endmember in type 2 chert nodules is therefore taken to indicate that ge was released from organic matter perhaps due to anaerobic degradation of organic matter accompanied by the formation of pyrite and was redistributed between clay organic endmembers and pure chert resulting in a non zero intercept in the ge si vs al 2 o 3 plots these observations suggest that a strong terrestrial influence in a restricted sedimentary basin or a high content of dissolved organic carbon in ediacaran seawater and porewater may have contributed to the dominance of ge organic complexes in the doushantuo basin in the yangtze gorges area

influence of westerly wind events stochasticity on el nino amplitude the case of 2014 vs 2015 the weak el nino of 2014 was preceded by anomalously high equatorial pacific warm water volume wwv and strong westerly wind events wwes which typically lead to record breaking el nino like in 1997 and 2015 here we use the cnrm cm5 coupled model to investigate the causes for the stalled el nino in 2014 and the necessary conditions for extreme el ninos this model is ideally suited to study this problem because it simulates all the processes thought to be critical for the onset and development of el nino it captures el nino preconditioning by wwv the wwes characteristics and their deterministic behaviour in response to warm pool displacements our main finding is that despite their deterministic control wwes display a sufficiently strong stochastic component to explain the distinct evolutions of el nino in 2014 and 2015 a 100 member ensemble simulation initialized with early spring equatorial conditions analogous to those observed in 2014 and 2015 demonstrates that early year elevated wwv and strong wwes preclude the occurrence of a la nina but lead to el ninos that span the weak with few wwes to extreme with many wwes range sensitivity experiments confirm that numerous strong wwes shift the el nino distribution toward larger amplitudes with a particular emphasis on summer fall wwes occurrence which result in a five fold increase of the odds for an extreme el nino a long simulation further demonstrates that sustained wwes throughout the year and anomalously high wwv are necessary conditions for extreme el nino to develop in contrast we find no systematic influence of easterly wind events ewes on the el nino amplitude in our model our results demonstrate that the weak amplitude of el nino in 2014 can be explained by wwes stochastic variations without invoking ewes or remote influences from outside the tropical pacific and therefore its peak amplitude was inherently unpredictable at long lead time

u pb geochronology of the opatica tonalite gneiss belt and its relationship to the abitibi greenstone belt superior province quebec u pb ages for zircon monazite and titanite from samples collected from two transects across the opatica tonalite gneiss belt in the superior province of quebec indicate that the belt contains rocks that are significantly older than those in the adjacent low grade northern abitibi belt tonalite and tonalite gneiss which make up most of the belt formed over an interval of 100 ma from pre 2800 to 2702 ma five samples have ages of ca 2807 13 2773 23 and 2702 3 ma zircon growth at 2718 2721 ma in the two oldest samples may record an early period of high grade metamorphism in the belt hornblende diorite monzodiorite and tonalite plutons were intruded at 2693 2696 ma particularly along the southern boundary with the abitibi belt these include the canet pluton at ma the lac ouescapis pluton at 2693 2 ma and the barlow pluton at 2696 3 ma pink granite plutons and dykes are the youngest intrusive rocks in the belt three samples have yielded zircon ages of 2690 2 and 2686 4 ma

inorganic germanium and silica in the indian ocean biological fractionation during ge si opal formation hydrographic profiles of inorganic germanium and silica in the western indian ocean confirm the silicalike behavior of inorganic germanium in seawater combining all existing oceanic data indian atlantic pacific bering sea and antarctic these new data provide an improved oceanic ge to si relationship ge pm 0 699 0 004 si m 3 6 0 4 simple box models of the ocean demonstrate that the positive ge intercept in this relationship results from biological fractionation of the ge si ratio siliceous organisms discriminate against germanium during production of biogenic opal this result is confirmed by ge si opal analyses of diatoms and radiolaria separated from siliceous oozes of holocene core tops a rapid rise in diatom ge si opal recorded in an antarctic piston core over the interval from the last glacial 18 thousand years before present to the holocene present suggests that biosiliceous productivity was lower and preformed silica concentrations were higher in southern ocean surface waters during glacial times

germanium silicon as a flow path tracer application to the rio icacos watershed 1 we use dissolved silicon together with its geochemical twin germanium for the first time as a hydrologic tracer to study water delivery to the stream during storm events in the rio icacos watershed puerto rico ge and si were measured on base flow stormflow springwater and soil water samples compositions of all of these waters appear to reflect varying contributions from three components which we attribute to solutes released from bedrock weathering groundwater from short term soil water interaction quick soil water and longer term soil water interaction matrix soil water base flow stream waters have high si and moderate ge ge si ratio 0 29 mol mol consistent with a predominantly bedrock weathering source as indicated by their similarity with water sampled from springs emerging from the saprolite bedrock boundary on a hillslope landslide scar during storm events there is a shift toward more dilute compositions but higher ge si ratios similar to those measured on water samples from temporary depression storage and overland flow quick soil water geochemical mass balance shows that 80 90 of the stream chemistry can be explained by mixing groundwater with this quick soil water composition which we infer to reflect new water traveling as shallow throughflow stream water 18o values decrease to more negative values typical of precipitation supporting rapid delivery of rainwater to the stream channel during stormflow the third component with a ge rich composition characteristic of soil matrix water sampled by tension lysimeters is required to explain higher stream water ge si ratios measured during hydrograph recession we infer from this an additional slower and less dominant pathway for delivery of soil water to the stream channel

silicon isotopes record dissolution and re precipitation of pedogenic clay minerals in a podzolic soil chronosequence by providing the largest part of the reactive surface area of soils secondary minerals play a major role in terrestrial biogeochemical processes the understanding of the mechanisms governing neo trans formation of pedogenic clay minerals in soils is therefore of the utmost importance to learn how soils evolve and impact the chemistry of elements in terrestrial environments soil forming processes governing the evolution of secondary aluminosilicates in podzols are however still not fully understood the evolution of silicon si isotope signature in the clay fraction of a podzolic soil chronosequence can provide new insight into these processes enabling to trace the source of si in secondary aluminosilicates during podzol forming processes characterized by the mobilization transport and precipitation of carbon metals and si the si isotope compositions in the clay fraction comprised of primary and secondary minerals document an increasing light 28 si enrichment and depletion with soil age respectively in illuvial b horizons and eluvial e horizon the mass balance approach demonstrates that secondary minerals in the topsoil eluvial e horizons are isotopically heavier with 30 si values increasing from 0 39 to 0 64 in c a 200years while secondary minerals in the illuvial bhs horizon are isotopically lighter 30 si 2 31 compared to the original unweathered secondary minerals in bc horizon 30 si 1 40 the evolution of si isotope signatures is explained by the dissolution of pedogenic clay minerals in the topsoil which is a source of light 28 si for the re precipitation of new clay minerals in the subsoil this provides consistent evidence that in strong weathering environment such as encountered in podzols si released from secondary minerals is partially used to form tertiary clay minerals over very short time scales ca 300years our dataset demonstrates the usefulness to measure si isotope signatures in the clay fraction to discern clay mineral changes e g neoformation versus solid state transformation during soil evolution this offers new opportunity to better understand clay mineral genesis under environmental changes and the short term impact of the dissolution and re precipitation of pedogenic clay minerals on soil fertility soil carbon budget and elemental cycles in soil plant systems 2014 elsevier b v

the marine geochemistry of germanium ekasilicon the geochemical behavior of dissolved germanium in rivers estuaries and the oceans is similar to that of silicon it is chemically weathered from continental rocks and transported by rivers to the oceans where it is taken up by siliceous organisms and deposited in biogenic opal the ratio of germanium to silicon buried in siliceous oozes must reflect the oceanic input ratios from rivers crustal weathering and sea floor vents mid ocean ridge hydrothermal weathering the opal germanium silicon ratio may thus monitor relative variations in these weathering processes and provide information about the geochemical history of seawater

the role of lateral ocean physics in the upper ocean thermal balance of a coupled ocean atmosphere gcm the sensitivity of the upper ocean thermal balance of an ocean atmosphere coupled gcm to lateral ocean physics is assessed three 40 year simulations are performed using horizontal mixing isopycnal mixing and isopycnal mixing plus eddy induced advection the thermal adjustment of the coupled system is quite different between the simulations confirming the major role of ocean mixing on the heat balance of climate the initial adjustment phase of the upper ocean sst is used to diagnose the physical mechanisms involved in each parametrisation when the lateral ocean physics is modified significant changes of sst are seen mainly in the southern ocean a heat budget of the annual mixed layer defined as the bowl shows that these changes are due to a modified heat transfer between the bowl and the ocean interior this modified heat intake of the ocean interior is directly due to the modified lateral ocean physics in isopycnal diffusion this heat exchange especially marked at mid latitudes is both due to an increased effective surface of diffusion and to the sign of the isopycnal gradients of temperature at the base of the bowl as this gradient is proportional to the isopycnal gradient of salinity this confirms the strong role of salinity in the thermal balance of the coupled system the eddy induced advection also leads to increased exchanges between the bowl and the ocean interior this is both due to the shape of the bowl and again to the existence of a salinity structure the lateral ocean physics is shown to be a significant contributor to the exchanges between the diabatic and the adiabatic parts of the ocean

modulation of westerly wind bursts by sea surface temperature a semistochastic feedback for enso abstract westerly wind bursts wwbs in the equatorial pacific are known to play a significant role in the development of el nino events they have typically been treated as a purely stochastic external forcing of enso recent observations however show that wwb characteristics depend upon the large scale sst field the consequences of such a wwb modulation by sst are examined using an ocean general circulation model coupled to a statistical atmosphere model i e a hybrid coupled model an explicit wwb component is added to the model with guidance from a 23 yr observational record the wwb parameterization scheme is constructed such that the likelihood of wwb occurrence increases as the western pacific warm pool extends a semistochastic formulation which has both deterministic and stochastic elements the location of the wwbs is parameterized to migrate with the edge of the warm pool it is found that modulation of wwbs by sst strongly affects the characteristics of enso in particular coupled fe

the march 1997 westerly wind event and the onset of the 1997 98 el nino understanding the role of the atmospheric response in a previous study the effect of the march 1997 westerly wind event wwe on the evolution of the tropical pacific ocean was studied using an ocean general circulation model gcm the response was characterized by i a cooling of the far western pacific 0 88c ii a rapid eastward displacement of the warm pool 2000 km in a month and iii a weak warming of the central eastern pacific along the path of the oceanic kelvin wave excited by the wwe 0 58c in this study the atmospheric response to these aspects of the sea surface temperature sst response are investigated using an atmospheric gcm forced with the sst anomalies from the ocean only experiments the results have demonstrated that the three aspects of the sst anomaly field generated by the wwe

the geochemistry of germanium in deep sea cherts nineteen chert samples from a continuous core of the dsdp leg 17 hole 167 were analysed for ge in addition we analysed five samples from other cores the ages range between late jurassic and late eocene the concentration of ge changes with age from 0 87 ppm in the oldest samples to 0 23 ppm in the youngest equivalent to a gesi decrease from 0 72 10 6 to 0 19 10 6 the decrease in gesi is well correlated with the 87sr86sr ratio in sea water of the relevant age the interpretation of this trend may reflect a different levels of gesi in sea water as a result of a different ratio between hydrothermal and riverine input b a diagenetic trend in siliceous sediments c recording by radiolaria a transition between a radiolaria dominated ocean with relatively high gesi ratios in sea water and diatom domination or d a combination of the above

effects of westerly wind bursts on el nino a new perspective daily observations from 1971 to 2010 reveal that every el nino during this period was accompanied by congregated westerly wind bursts suggesting a close relationship of these bursts with both cold tongue and warm pool el nino events with the addition of burst like multiplicative noise to an intermediate ocean atmosphere coupled model it is shown that westerly wind bursts by generating eastward equatorial surface currents and downwelling kelvin waves could be responsible for the existence of the warm pool el nino and for the irregularity and extremes of the cold tongue el nino whether these bursts give rise to one type of el nino or the other depends on the timing of their occurrence relative to the phase of the recharge discharge cycle of the equatorial upper ocean heat content

enso asymmetry in cmip5 models abstractthe el nino la nina asymmetry is evaluated in 14 coupled models from phase 5 of the coupled model intercomparison project cmip5 the results show that an underestimate of enso asymmetry a common problem noted in cmip3 models remains a common problem in cmip5 coupled models the weaker enso asymmetry in the models primarily results from a weaker sst warm anomaly over the eastern pacific and a westward shift of the center of the anomaly in contrast sst anomalies for the la nina phase are close to observations corresponding atmospheric model intercomparison project amip runs are analyzed to understand the causes of the underestimate of enso asymmetry in coupled models the analysis reveals that during the warm phase precipitation anomalies are weaker over the eastern pacific and westerly wind anomalies are confined more to the west in most models the time mean zonal winds are stronger over the equatorial central and eastern pacific for most models wind forced ocean gcm experiments suggest

the isotope composition of inorganic germanium in seawater and deep sea sponges abstract although dissolved concentrations of germanium ge and silicon si in modern seawater are tightly correlated uncertainties still exist in the modern marine ge cycle germanium stable isotope systematics in marine systems should provide additional constraints on marine ge sources and sinks however the low concentration of ge in seawater presents an analytical challenge for isotopic measurement here we present a new method of pre concentration of inorganic ge from seawater which was applied to measure three ge isotope profiles in the southern ocean and deep seawater from the atlantic and pacific oceans germanium isotopic measurements were performed on ge amounts as low as 2 6 ng using a double spike approach and a hydride generation system coupled to a mc icp ms germanium was co precipitated with iron hydroxide and then purified through anion exchange chromatography results for the deep i e 1000 m depth pacific ocean off hawaii nearby loihi seamount and the deep atlantic off bermuda bats station showed nearly identical 74 70ge values at 3 19 0 31 2sd n 9 and 2 93 0 10 2sd n 2 respectively vertical distributions of ge concentration and isotope composition in the deep southern ocean for water depth 1300 m yielded an average 74 70ge 3 13 0 25 2sd n 14 and ge si 0 80 0 09 mol mol 2sd n 12 significant variations in 74 70ge from 2 62 to 3 71 were measured in the first 1000 m in one station of the southern ocean near sars seamount in the drake passage with the heaviest values measured in surface waters isotope fractionation by diatoms during opal biomineralization may explain the enrichment in heavy isotopes for both ge and si in surface seawater however examination of both oceanographic parameters and 74 70ge values suggest also that water mass mixing and potential contribution of shelf derived ge also could contribute to the variations combining these results with new ge isotope data for deep sea sponges sampled nearby allowed us to determine a ge isotope fractionation factor of 0 87 0 37 2sd n 12 during ge uptake by sponges although ge has long been considered as a geochemical twin of si this work underpins fundamental differences in their isotopic behaviors both during biomineralization processes and in their oceanic distributions this suggests that combined with si isotopes ge isotopes hold significant promise as a complementary proxy for delineating biological versus source effects in the evolution of the marine silicon cycle through time

the potential role of ridge flank hydrothermal systems on oceanic germanium and silicon balances abstract sediment pore water samples and warm spring fluids from three ridge flank hydrothermal systems 40 75 c were analyzed for ge si and mg to quantify the contribution of these systems to oceanic ge and si balances these warm hydrothermal fluids have elevated concentrations of ge and si relative to bottom seawater indicating that these systems are net sources of ge and si to the oceans end member ge si molar ratios range from 12 to 34 mol mol which is similar to but elevated relative to the average ratio from high temperature 350 c midocean ridge hydrothermal systems the source for this ge and si is suggested to be a combination of seawater reaction with basalt and diffusive exchange with overlying basal pore waters which are in pseudo equilibrium with amorphous silica because the ge si molar ratio in both basalt and sediment is much less than those measured in the dissolved phase a net preferential removal of si relative to ge must occur within basaltic basement as suggested for high temperature hydrothermal systems we suggest that this removal mechanism is likely a consequence of quartz precipitation and the formation of secondary clays i e smectite we estimate that ridge flank hydrothermal systems likely provide 10 of the ge and si fluxes to the oceans

triggering of el nino by westerly wind events in a coupled general circulation model two ten members ensemble experiments using a coupled ocean atmosphere general circulation model are performed to study the dynamical response to a strong westerly wind event wwe when the tropical pacific has initial conditions favourable to the development of a warm event in the reference ensemble cref no wind perturbation is introduced whereas a strong westerly wind event anomaly is introduced in boreal winter over the western pacific in the perturbed ensemble cwwe our results demonstrate that an intense wwe is capable of establishing the conditions under which a strong el nino event can occur first it generates a strong downwelling kelvin wave that generates a positive sea surface temperature sst anomaly in the central eastern pacific amplified through a coupled ocean atmosphere interaction this anomaly can be as large as 2 5 c 60 days after the wwe secondly this wwe also initiates an eastward displacement of the warm pool that promotes the occurrence of subsequent wwes in the following months these events reinforce the initial warming through the generation of additional kelvin waves and generate intense surface jets at the eastern edge of the warm pool that act to further shift warm waters eastward the use of a ten members ensemble however reveals substantial differences in the coupled response to a wwe whereas four members of cwwe ensemble develop into intense el nino warming as described above four others display a moderate warming and two remains in neutral conditions this diversity between the members appears to be due to the internal atmospheric variability during and following the inserted wwe in the four moderate warm cases the warm pool is initially shifted eastward following the inserted wwe but the subsequent weak wwe activity when compared to the strong warming cases prevents to further shift the warm pool eastwards the seasonal strengthening of trade winds in june july can therefore act to shift warm waters back into the western pacific reducing the central eastern pacific warming this strong sensitivity of the coupled response to wwes may therefore limit the predictability of el nino events as the high frequency wind variability over the warm pool region remains largely unpredictable even at short time lead

the extreme el nino of 2015 2016 the role of westerly and easterly wind bursts and preconditioning by the failed 2014 event at the beginning of 2015 as one year earlier in 2014 the scientific community anticipated that el nino conditions could develop in the tropical pacific by year end such projections were related to the occurrence of westerly wind bursts during winter spring of each year that generated strong downwelling kelvin waves indicative of an emerging el nino however the event s progression quickly stalled in 2014 but actively continued in 2015 leading to an extreme warm event comparable to 1997 or 1982 here we compare climate evolution during these two years using satellite observations and numerical simulations we show that during 2014 el nino development was interrupted mid year by an exceptionally strong easterly wind burst whereas during the second year it continued through the summer further we show that the failed 2014 event created favorable conditions for el nino development during the next year as it kept ocean heat content recharged and the western pacific warm pool extended eastward subsequently the winter spring westerly wind bursts in 2015 were followed by a series of state dependent westerly bursts as part of a strong positive bjerknes feedback analogue simulations with a coupled gcm wherein we superimpose the observed sequences of westerly and easterly wind bursts support these conclusions stressing the role of the failed 2014 event in preconditioning the ocean atmosphere system for the development of an extreme el nino in our simulations the probability of an extreme event following early year westerly wind bursts increases from 14 to nearly 60 due to this preconditioning thus the interplay between westerly and easterly wind bursts shapes el nino development and diversity

depositional gaps in abitibi greenstone belt stratigraphy a key to exploration for syngenetic mineralization models of greenstone belt development are crucial for exploration allochthonous models predict belts to be a collage of unrelated fragments whereas autochthonous models allow for prediction of syngenetic mineral deposits within specific stratigraphic intervals superior province greenstone belts consist of mainly volcanic units unconformably overlain by largely sedimentary timiskaming style assemblages and field and geochronological data indicate that the abitibi greenstone belt developed autochthonously we describe major revisions to stratigraphy of the abitibi greenstone belt and the implications of an autochthonous development of the volcanic stratigraphy for exploration for syngenetic mineralization the abitibi greenstone belt is subdivided into seven discrete volcanic stratigraphic episodes on the basis of groupings of numerous u pb zircon ages of pre 2750 2750 to 2735 2734 to 2724 2723 to 2720 2719 to 2711 2710 to 2704 and 2704 to 2695 ma we present revised lithotectonic and or stratigraphic nomenclature using these time intervals including 1 isotopic inheritance in younger episodes which indicates that the older episodes 2750 2735 and 2734 2724 ma had greater extent than is presently seen 2 dikes feeding younger volcanic episodes 2706 ma cutting older volcanic units 2734 2724 ma and 3 2710 to 2704 ma mafic to ultramafic sills intruding the 2719 to 2711 ma episode changes to the nomenclature include the identification of pre 2750 ma volcanic episode supracrustal fragments in the northern and southern abitibi greenstone belt and subdivision of the 2719 to 2711 ma 2710 to 2704 ma and 2704 to 2695 ma episodes into lower and upper parts we present the results of this lithostratigraphic subdivision as the first geochronologically constrained stratigraphic and or lithotectonic map of the abitibi greenstone belt many of the volcanic episodes are intercalated with and capped by a relatively thin sedimentary interface zone dominated by chemical sedimentary rocks stratigraphic and geochronological analysis of these zones indicates discontinuous deposition with localized gaps of 2 to 27 m y between volcanic episodes the zones consist of up to 200 m of iron formation chert breccia heterolithic debris flows of volcanic provenance sandstone and or argillite and conglomerate modeling of the time required for deposition of the volcanic units based on rates of magma production in modern arc and plume environments is on the order of 103 to 104 years whereas the time interval between basalt rhyolite cycles is 106 years the sedimentary interface zones are therefore interpreted as condensed sections zones with very low rates of sedimentation in a basinal setting or zones with negligible rates of sedimentation marked by silicification of existing rock types the sedimentary interface zones are therefore considered submarine correlative conformities disconformities or unconformities separating the equivalent of group level stratigraphic and lithotectonic units the unconformity bounded stratigraphic model provides a new regional to deposit scale interpretive model for use in exploration for syngenetic mineralization

westerly wind bursts enso s tail rather than the dog westerly wind bursts wwbs in the equatorial pacific occur during the development of most el nino events and are believed to be a major factor in enso s dynamics because of their short time scale wwbs are normally considered part of a stochastic forcing of enso completely external to the interannual enso variability recent observational studies however suggest that the occurrence and characteristics of wwbs may depend to some extent on the state of enso components implying that wwbs which force enso are modulated by enso itself satellite and in situ observations are used here to show that wwbs are significantly more likely to occur when the warm pool is extended eastward based on these observations wwbs are added to an intermediate complexity coupled ocean atmosphere enso model the representation of wwbs is idealized such that their occurrence is modulated by the warm pool extent the resulting model run is compared with a run in which the wwbs are stochastically applied the modulation of wwbs by enso results in an enhancement of the slow frequency component of the wwbs this causes the amplitude of enso events forced by modulated wwbs to be twice as large as the amplitude of enso events forced by stochastic wwbs with the same amplitude and average frequency based on this result it is suggested that the modulation of wwbs by the equatorial pacific sst is a critical element of enso s dynamics and that wwbs should not be regarded as purely stochastic forcing in the paradigm proposed here wwbs are still an important aspect of enso s dynamics but they are treated as being partially stochastic and partially affected by the large scale enso dynamics rather than being completely external to enso it is further shown that wwb modulation by the large scale equatorial sst field is roughly equivalent to an increase in the ocean atmosphere coupling strength making the coupled equatorial pacific effectively self sustained

structure of the high grade opatica belt and adjacent low grade abitibi subprovince canada an archaean mountain front plutonic gneisses in the archaean opatica belt in canada record crustal scale wsw vergent i e longitudinal high temperature d1 ductile shearing similar structures occur in adjacent greenstone belts but only in narrow amphibolite facies zones near the base metavolcanics in the greenschist facies portions do not record penetrative d1 structures the greenstone belts are interpreted as allochthonous on the gneisses they form the uppermost d1 thrust sheets sse vergent i e approximately transverse d2 thrusting imbricated the opatica belt and formed a large antiform either a culmination or an antiformal stack in the southern opatica the imbricated opatica belt wedged under the northern part of the abitibi subprovince and created a tight syncline with nnw vergent d2 thrusts interpreted as backthrusts on its northern limb the opatica belt abitibi subprovince contact therefore resembles some phanerozic mountain fronts further southwards propagating imbrication of the crust beneath the abitibi subprovince created a s vergent foreland fold and thrust belt in the overlying greenstones high grade opatica gneisses and adjacent low grade abitibi greenstones contain complementary structural patterns and may therefore represent the internal and foreland parts of an archaean mountain belt similar in many respects to phanerozoic examples

geochemical behavior of inorganic germanium in an unperturbed estuary abstract eleven monthly estuarine profiles of dissolved inorganic germanium gei and silica si in a natural pristine river bay system demonstrate that ge removal and input parallel the seasonal silica cycle reflecting ge uptake by and dissolution from diatoms the ge si atom ratio of the river is 0 6 0 15 10 6 which is near the average value for continental granites and for uncontaminated remote natural rivers 0 7 0 3 10 6 the ge si ratio escaping this estuary to the ocean is 0 8 10 6 reflecting some estuarine enhancement of the fluvial ge flux probably due to release of gei from fluvial particulates nevertheless the post estuarine ge si ratio is not significantly different from the continental crustal ratio but is very different from the ratio in sea floor hot springs and mid ocean ridge hydrothermal plumes 4 2 10 6 and in oceanic basalts 2 6 10 6 thus natural estuarine processes do not obscure the contrasting ge si signatures entering the ocean from dissolution of continental and sea floor silicates

pacific meridional mode and el nino southern oscillation 1 we present intriguing evidence that the majority of el nino events over the past four decades are preceded by a distinctive sea surface warming and southwesterly wind anomaly in the vicinity of the intertropical convergence zone itcz during the boreal spring this phenomenon known as the meridional mode mm is shown to be intrinsic to the thermodynamic coupling between the atmosphere and ocean the mm effectively acts as a conduit through which the extratropical atmosphere influences enso modeling results further suggest that the mm plays a vital role in the seasonal phase locking behavior of enso the findings provide a new perspective for understanding the important role of thermodynamic ocean atmosphere feedback in enso and may have profound implications for enso prediction particularly the unresolved issue of the spring predictability barrier citation chang p l zhang r saravanan d j vimont j c h chiang l ji h seidel and m k tippett 2007 pacific meridional mode and el nino southern oscillation geophys res lett 34 l16608 doi 10 1029 2007gl030302

late cenozoic ge si record of marine biogenic opal implications for variations of riverine fluxes to the ocean we have determined germanium silicon ratios in purified diatoms and radiolarians from siliceous sediments in holocene core tops one late pleistocene piston core and four high latitude southern ocean deep sea drilling project dsdp sites ranging in age from holocene to oligocene high latitude holocene diatoms in the 10 to 38 m size fraction ge si opal 0 693 0 039 10 6 faithfully record the present oceanic ratio ge si seawater 0 699 0 004 10 6 this confirms that diatoms from siliceous oozes are monitors of seawater ge si and may record past changes in rates of delivery of weathering products to the sea from continental and seafloor weathering large diatoms and radiolarians display ratios much lower than ge si seawater suggesting that ge si opal to some extent displays the effects of biological fractionation from 0 to 2 5 m y b p ge si opal in diatoms from dsdp sites ranges from about 0 54 to 0 70 10 6 similar to the range observed in one late pleistocene piston core over the last 25 kyr from 2 5 to 6 m y b p the ratio is more variable while prior to 10 m y b p ratios are clearly higher averaging about 0 9 10 6 in the early to middle miocene low values of the ratio are consistent with global weathering regimes dominated by river silica input to the sea while higher ratios suggest periods of enhanced hydrothermal input or reduced fluvial contribution nevertheless an oceanic one box model with variable river and hydrothermal inputs and biogenic opal output cannot adequately account for the magnitude or the timing of changes observed in the record suggesting the existence of other sources sinks for inorganic germanium and or silicon to or from the sea

coupled ge si and ge isotope ratios as geochemical tracers of seafloor hydrothermal systems case studies at loihi seamount and east pacific rise 9 50 n germanium ge and silicon si exhibit similar geochemical behavior in marine environments but are variably enriched in seafloor hydrothermal fluids relative to seawater in this study ge isotope and ge si ratio systematics were investigated in low temperature hydrothermal vents from loihi seamount pacific ocean 18 54 n 155 15 w and results were compared to high temperature vents from the east pacific rise epr at 9 50 n loihi offers the opportunity to understand contrasting ge and si behavior in low temperature seafloor hydrothermal systems characterized by abundant fe oxyhydroxide deposition at the seafloor the results show that both ge si and 74 70ge in hydrothermal fluids are fractionated relative to the basaltic host rocks the enrichment in ge vs si relative to fresh basalts together with ge isotope fractionation 74 70gefluid basalt up to 1 15 at epr 9 50 n and 1 64 at loihi are best explained by the precipitation of minerals e g quartz and fe sulfides during higher temperature seawater rock reactions in the subsurface the study of fe rich hydrothermal deposits at loihi largely composed of fe oxyhydroxides shows that ge isotopes are also fractionated upon mineral precipitation at the seafloor we obtained an average ge isotope fractionation factor between fe oxyhydroxide ferrihydrite and dissolved ge in the fluid of 2 0 0 6 2sd and a maximum value of 3 6 0 6 2sd which is consistent with recent theoretical and experimental studies the study of a hydrothermal chimney at bio 9 vent at epr 9 50 n also demonstrates that ge isotopes are fractionated by approximately 5 6 0 6 2sd during precipitation of metal sulfides under hydrothermal conditions using combined ge si and estimated ge isotope signatures of ge sinks and sources in seawater we propose a preliminary oceanic budget of ge which reveals that an important sink referred as the missing ge sink may correspond to ge sequestration into authigenic fe oxyhydroxides in marine sediments this study shows that combining ge si and 74 70ge systematics provides a useful tool to trace hydrothermal ge and si sources in marine environments and to understand formation processes of seafloor hydrothermal deposits

role of non linear oceanic processes in the response to westerly wind events new implications for the 1997 el nino onset in march 1997 a strong westerly wind event wwe occurred in the western equatorial pacific prior to the 1997 1998 el nino event it produced downwelling kelvin waves that interacted non linearly with the surface temperature salinity and zonal current fronts located at the eastern edge of the warm fresh pool eewp this non linear interaction locally increased zonal currents by a factor of three compared to a theoretical linear response and advected the eewp at an unexpected rate 1m s to which the ocean atmosphere coupled system may have been responding rapidly to trigger el nino conditions

comparison of eruptive and intrusive samples from unzen volcano japan effects of contrasting pressure temperature time paths abstract core samples from the conduit of unzen volcano obtained only 9 years after cessation of the 1991 1995 eruption exhibit important differences in physical characteristics and mineralogy and subtle differences in bulk chemistry from erupted samples these differences in the conduit samples reflect emplacement under a confining pressure where about half of the original magmatic water was retained in the melt phase maintenance at hypersolidus temperature for some unknown but significant time span and subsequent subsolidus hydrothermal alteration in contrast magma that extruded as lava underwent decompression to 1 atm with nearly complete loss of magmatic water and cooling at a sufficiently rapid rate to produce glass the resulting hypabyssal texture of the conduit samples while clearly distinct from eruptive rocks is also distinct from plutonic suites given the already low temperature of the conduit less than 200 c nakada s uto k yoshimoto m eichelberger j c shimizu h 2005 scientific results of conduit drilling in the unzen scientific drilling project usdp sci drill 1 18 22 when it was sampled by drilling this texture must have developed within a decade and perhaps within a much shorter time after emplacement the fact that all trace element concentrations of the conduit and the last emplaced lava of the spine 1300 m above it are identical to within analytical uncertainty provides strong evidence that both were produced during the same eruption sequence changes in conduit magma that occurred between emplacement and cooling to the solidus were collapse of vesicles from less than or equal to the equilibrium value of about 50 vol to about 0 1 vol continued resorption of quartz and reaction of biotite phenocrysts due to heating of magma prior to ascent by intruding mafic magma breakdown of hornblende and micro crystallization of rhyolitic melt to feldspar and quartz subsolidus changes were deposition of calcite and pyrite growth of sericite in anorthite rich zones of plagioclase and development of montmorillonite as an alteration product significant changes in bulk composition were depletion of mg fe and na and enrichment in c and s these changes were due mainly to the breakdown of hornblende and plagioclase and addition of carbonate and pyrite respectively the identical concentrations of rees in the conduit and surface lava are consistent with low water to rock ratios during alteration this suggests to us that despite convective hydrothermal removal of heat from the conduit chemical open system effects were limited to early loss of magmatic water and later addition of magmatic co2 and so2 and or h2s streaming up the conduit from deeper levels