the 2009 2010 eruption of gaua volcano vanuatu archipelago eruptive dynamics and unsuspected strong halogens source gaua a little known volcano in the northern part of vanuatu archipelago went through a long term eruptive activity between september 2009 and july 2010 the eruption started by a phreatic to phreatomagmatic activity which progressively shifted into a magmatic discharge the first eruptive phase involved the hydrothermal system in place the latter was likely influenced by seawater seepage leading to the formation of anhydrite magma involved hereafter this opening phase is of basaltic andesite and basaltic trachyandesite composition high k calc alkaline series typical of the northern part of the vanuatu archipelago the 2009 2010 activity discharged at least 184 kt of so2 and a significant amount of halogens 72 kt cl and 217 kt f such halogen releases indicate that gaua is a strong source of halogens into the atmosphere high and sustained amount of f discharges are known to induce health issues and should not be ignored on gaua island during this eruption the quiescent and voluminous lake letas was slightly affected by the eruption nevertheless the hydrothermal discharge point into the lake situated on the southeastern part of mt garet appeared to be relatively active at this particular location rock forming elements leached out from volcanic rock by acid fluids released by the new intrusion of magma were discharged along with anions into lake letas this release has triggered localized chemistry changes in the lake we speculate that this discharge has also disturbed the bottom water in a limited perimeter remobilizing reduced fe to the surface and subsequently triggering the change in the water color by fe oxidation

eemian cooling in the norwegian sea and north atlantic ocean preceding continental ice sheet growth changing conditions in the north atlantic region may drive global climate changes1 2 according to previous reconstructions of the last interglacial the eemian north atlantic sea surface tempera tures ssts were similar to present day values3 in the norwegian sea even warmer conditions appeared as a single pulse of short duration4 5 whereas the greenland ice record suggests that the warm interglacial air temperatures were interrupted by several cold periods6 here we use faunal and stable isotope analyses of foraminifera in two sediment cores from the north atlantic ocean and norwegian sea to reconstruct high resolution records of sst and sea surface salinity sss during the eemian interglacial our results which differ significantly from the greenland record6 show a sharp decrease in sst and sss of the norwegian sea associated with a more moderate cooling and freshening of the north atlantic at the middle of isotope substage 5e several millennia before the beginning of continental ice sheet growth changes in the norweg ian sea surface conditions appear to have represented an important climate change affecting global atmospheric and thermohaline circulations

origin of native copper in the parana volcanic province brazil integrating cu stable isotopes in a multi analytical approach different hypotheses exist on the origin of native copper mineralization in the parana volcanic province that invoke magmatic late magmatic or hydrothermal events the average copper content in the host basalts is 200 ppm native copper occurs as dendrites in cooling joints fractures and cavities within amygdaloidal crusts cuprite tenorite chrysocolla malachite and azurite occur in breccias at the top of the lava flows chemical analyses x ray diffraction raman spectrometry electron microprobe analyses la icp ms and cu isotope analyses were used to evaluate the origin of native copper in the volcanic province copper contents in magnetite of the host basalt are close to 1 wt whereas clinopyroxene contains up to 0 04 wt cu cretaceous hydrothermal alteration of magnetite and clinopyroxene released copper to generate hydrothermal copper mineralization the isotopic composition of the native copper in the parana volcanic province varies from 0 9 in the southeastern portion rio grande do sul state to 1 9 in the central portion parana state of the province this study supports a hydrothermal origin followed by supergene enrichment for native copper in the parana volcanic province

erosional and climatic effects on long term chemical weathering rates in granitic landscapes spanning diverse climate regimes abstract we used cosmogenic nuclide and geochemical mass balance methods to measure long term rates of chemical weathering and total denudation in granitic landscapes in diverse climatic regimes our 42 study sites encompass widely varying climatic and erosional regimes with mean annual temperatures ranging from 2 to 25 c average precipitation ranging from 22 to 420 cm year 1 and denudation rates ranging from 23 to 755 t km 2 year 1 long term chemical weathering rates range from 0 to 173 t km 2 year 1 in several cases exceeding the highest granitic weathering rates on record from previous work chemical weathering rates are highest at the sites with rapid denudation rates consistent with strong coupling between rates of chemical weathering and mineral supply from breakdown of rock a simple empirical relationship based on temperature precipitation and long term denudation rates explains 89 95 of the variation in long term weathering rates across our network of sites our analysis shows that for a given precipitation and temperature chemical weathering rates increase proportionally with fresh material supply rates we refer to this as supply limited weathering in which fresh material is chemically depleted to roughly the same degree regardless of its rate of supply from breakdown of rock the temperature sensitivity of chemical weathering rates is two to four times smaller than what one would expect from laboratory measurements of activation energies for feldspar weathering and previous inter comparisons of catchment mass balance data from the field our results suggest that climate change feedbacks between temperature and silicate weathering rates may be weaker than previously thought at least in actively eroding unglaciated terrain similar to our study sites to the extent that chemical weathering rates are supply limited in mountainous landscapes factors that regulate rates of mineral supply from erosion such as tectonic uplift may lead to significant fluctuations in global climate over the long term

recent emerged reef terraces of the yenkahe resurgent block tanna vanuatu implications for volcanic landslide and tsunami hazards emerged reef terraces record the extraordinarily rapid holocene uplift rate of the fault bounded yenkahe resurgent block yrb located within a partially submerged quaternary caldera on tanna island vanuatu southwest pacific the presently active volcano yasur is located at the western end of the yrb episodic uplift of the yrb is probably associated with the movement of magma below the yenkahe area a historically recorded uplift at port resolution bay in a d 1878 raised the shoreline 15 m this a d 1878 event was accompanied by a local earthquake and a tsunami that reached 12 m elevation coral samples from terraces at mean altitudes of 155 m and 15 m above present sea level yield 230 th 234 u dates of a d 1002 pm 10 and a d 1868 pm 4 respectively these ages imply a mean uplift of 156 mm yr for the yrb since a d 1002 until a d 1992 this volcanically related uplift occurs within the context of regional uplift of the southern new hebrides arc the late holocene uplift r

copper isotope fractionation in sedimentary copper mineralization timna valley israel abstract copper isotopes 65 cu 63 cu are potentially powerful new geochemical proxies for oxidation reduction processes and metallic cycling this research presents a cu isotope study of mineralization in historically mined stratiform sediment hosted copper ssc ore deposits of the precambrian and cambrian rocks of the timna valley southern israel these deposits provide a natural laboratory for studying isotopic fractionations between cu sulphides and cu ii minerals copper carbonates hydroxides and silicates formed during sequential cycles of low temperature alteration of igneous copper porphyries marine sedimentary diagenesis and epigenetic mobilization in sandstones isotopic measurements were made using mc icp ms after ion chromatographic separation of the copper from matrix elements in accord with abiogenic experimental studies showing that there should be a negative isotopic fractionation between reduced and oxidized copper minerals 65 cu values of cu sulphides are significantly lower 3 4 to 1 2 than coexisting cu ii carbonates and hydroxides 1 2 to 0 5 cu ii silicates which should only show a very small isotopic fractionation relative to parent cu ii solutions give average 65 cu values of 0 09 0 24 consistent with the fact that the primary source of sedimentary copper was the precambrian igneous rocks isotopic zoning profiles in cu sulphides of the cambrian dolomites suggest they were formed through the interaction of small disconnected cu solution reservoirs with h 2 s formed by bacterial reduction of sulphate containing pore waters mass balance modeling based on the measured cu isotope compositions and experimental fractionation factors shows that the main copper reservoir is the cambrian sandstone shale sequence and that the cu sulphide reservoirs are relatively small thus most of the copper transport occurred in relatively oxidized conditions the calculated reservoir sizes are in agreement with field observations and confirm that copper isotopes are able to trace both the oxidation reduction cycles and mass transfer during sedimentary copper mineralization

new insights on the tectonics along the new hebrides subduction zone based on gps results 1 at the new hebrides nh subduction zone ridges born by the subducting australia plate enter the trench and collide with the overriding margin results from gps surveys conducted on both sides of the trench and new bathymetry maps of the nh archipelago bring new light on the complex tectonics of this area convergence vectors present large variations that are not explained by australia pacific a p poles and that define four segments vectors remain mostly perpendicular to the trench and parallel to the earthquake slip vectors slow convergence i e 30 40 mm yr is found at the central segment facing the d entrecasteaux ridge the southern segment moves faster than a p motion predicts 89 to 124 mm yr relatively to a western north fiji basin wnfb reference the northern and southern segments rotate in opposite directions consistently with the extension observed in the troughs east of both segments both rotations combine in central vanuatu into an eastward translation that bulldozes the central segment into the wnfb at 55 mm yr that model suggests that the motion of the central segment forced by the subduction collision of the d entrecasteaux ridge influences the motion of the adjoining segments the new caledonia archipelago is motionless with respect to the rest of the australia plate despite the incipient interaction between the loyalty ridge and the nh margin southeast of the interaction area convergence is partitioned into a 50 mm yr trench normal component accommodated at the trench and a 90 mm yr trench parallel component close to the a p convergence and presumably accommodated by a transform boundary at the rear of the nh arc

estimation of magma depth for resurgent domes an experimental approach post collapse resurgence is a phenomenon affecting many calderas attributed to a renewed magma rise the process is still poorly understood and the associated source parameters remain poorly constrained a set of experiments has been conducted to gain insight into the structural evolution of caldera resurgent domes a sand plaster mixture was chosen as an analogue for the brittle pile of volcanic rocks and silicone putty simulates the ductile behavior of the intruding magma resurgence is driven by the vertical uplift of the silicone with variable shape and depth similarity conditions are achieved through eight dimensionless numbers which are of the same order of magnitude in both nature and experiments results show that extension due to doming is in many cases accommodated by one axial graben opposite master faults of this graben intersect at depth at the junction with the rising viscous silicone the simplicity of the geometry of the whole analogue system provides equations which allow the estimation of the silicone depth from surface parameters these equations are then used in some field examples to assess the magma depth beneath natural resurgent domes

drivers of explosivity and elevated hazard in basaltic fissure eruptions the 1913 eruption of ambrym volcano vanuatu sw pacific abstract fissure eruptions along linear structures can extend for several tens of kilometres with distinct separate manifestations of volcanism along their length they typically involve low viscosity mafic magmas forming long lava flows and cinder cones eruptions in 1894 and 1913 on ambrym volcano vanuatu showed how these mildly explosive eruptions can rapidly transform into violent explosive events producing significant hazard and widespread volcanic ash clouds during the 1913 episode a fissure began in the central caldera and basaltic magmas broke out in a series of locations down the island s western flank in all sites over 100 m in elevation fissure outbreaks produced vigorous lava fountains and highly fluid lava flows that travelled rapidly to the shoreline when the outbreaks propagated along the island s axis into coastal plain areas a climactic series of explosive eruptions occurred producing a 1 2 km long by 600 m wide maar and tephra ring a further small tuff ring was formed later creating a temporary island 400 m offshore the onshore tephra ring destroyed a hospital and associated buildings its last evacuating occupants were close witnesses to the eruption processes deposits exposed in the lower portion of the tephra ring show that this part of the eruption began with a mild phreatomagmatic explosive eruption from a narrow vent followed by a magmatic scoria producing phase subsequently a complex sequence of highly explosive phreatomagmatic eruptions occurred producing pyroclastic surges along with repeated distinctive breccia horizons rich in coral and lava country rock these features tally with eye witness accounts to indicate that the main eruption phase was produced by a periodically shifting locus of phreatomagmatic fragmentation and eruption along a single e w fissure the glassy and vesicle poor pyroclasts produced during this eruption phase were dominantly fragmented in a brittle manner by magma water interaction low volatile content of the magma upon fragmentation is confirmed by ftir analysis showing

magma dynamics feeding yasur s explosive activity observed using thermal infrared remote sensing 1 a thermal infrared thermometer was used to record the passage of hot gases and fragments across a measurement area located at the exit of one of yasur s active vents recording was completed over 2 h during september 2011 a total of 200 explosive events were recorded we define two types of event low energy events with typical thermal energies of 14 kj and high energy events with typical thermal energies of 97 kj around 180 low energy events were recorded which together released 457 kj of radiant energy in contrast only 20 high energy events were recorded but they released 2042 kj we suggest that low energy events originate from a relatively shallow degassed magma reservoir and are associated with bursting of bubbles formed by bubble coalescence during ascent instead high energy events originate from a relatively deep fresh magma reservoir and are associated with slugs formed by foam collapse

the last interglacial glacial cycle in ne fennoscandia a nearly continuous record from sokli finnish lapland abstract boreholes from the sokli basin in finnish lapland have recovered a unique sequence of diamicts interlayered with fine grained sediments that are rich in fossils the diamicts are interpreted as till beds deposited by the fennoscandian ice sheet the fine grained intercalations seem to represent a series of warm stages that include one interglacial and three interstadials the interglacial is characterized by a mixed taiga pollen assemblage and corresponds to a distinct diatom gyttja bed the interstadials show progressively colder floras from open birch forest to arctic forest limit to shrub tundra their sediments comprise gyttja interlayered with wood and sand interstadial 1 sands grading into sandy gyttja interstadial 2 and sands overlain by laminated silt and clay interstadial 3 the interstadial 2 and 3 deposits are underlain by diamict and are interpreted as deglaciation sequences silts with a tundra pollen assemblage separate the interglacial and interstadial 1 deposits luminescence dating evidence indicates that the interglacial bed most probably represents the nw european mainland eemian interglacial marine isotope stage mis 5e the interstadial 1 2 and 3 deposits are tentatively correlated with the early weichselian brorup and odderade interstadials and an interstadial of middle weichselian age respectively mis 5c 5a and 3 respectively the correlation implies that the easternmost part of the ice divide zone of the fennoscandian continental ice sheet was deglaciated during part of mis 3

ignimbrites of basaltic andesite and andesite compositions from tanna new hebrides arc tanna island is part of a large volcanic complex mainly subsided below sea level on land two series of hydroclastic deposits and ignimbrites overlie the subaerial remains of a basal mainly effusive volcano the older tanna ignimbrite series oti late pliocene or pleistocene in age consists of ash flows and ash and scoria flow deposits associated with fallout tephra layers overlain by indurated pumice flow deposits phreatomagmatic features are a constant characteristic of these tuffs the younger late pleistocene pyroclastics the siwi sequence show basal phreatomagmatic deposits overlain by two successive flow units each comprising a densely welded layer and a nonwelded ash flow deposit whole rock analyses of 17 juvenile clasts from the two sequences vitric blocks from the phreatomagmatic deposits welded blocks scoriaceous bombs and pumices from the ignimbrites show basaltic andesite and andesite compositions sio2 53 60 in addition 296 microprobe analyses of glasses in these clasts show a wide compositional range from 51 to 69 sio2 dominant compositions at 54 56 58 5 and 61 62 sio2 characterize the glass from the oti glass compositions in the lower phreatomagmatic deposits from the siwi sequence also show multimodal distribution with peaks at sio2 55 57 5 61 62 and 64 whereas the upper ignimbrite has a predominant composition at 61 62 sio2 in both cases mineralogical data and crystal fractionation models suggest that these compositions represent the magmatic signature of a voluminous layered chamber the compositional gradient of which is the result of fractional crystallization during two major eruptive stages probably related to two caldera collapses the oti and siwi ignimbrites represent large outpourings from these magmatic reservoirs the successive eruptive dynamics from phreatomagmatic to plinian emphasize the role of water in initiating the eruptions without which the mafic and intermediate magmas probably would not have erupted

copper and zinc isotope systematics of altered oceanic crust at iodp site 1256 in the eastern equatorial pacific this paper presents the first combined cu and zn isotopic study of altered oceanic crust aoc at iodp hole 1256d that penetrates a volcanic section a lava dyke transition zone a sheeted dyke complex and a plutonic complex in the volcanic section all but one rocks have cu and zn isotopic compositions similar to fresh mid ocean ridge basalt morb reflecting restricted seawater circulation and low oxygen fugacity rocks in the transition zone have morb like 65cu and 66zn indicating the dominant influence of basalt derived cu and zn during alteration rocks in the dyke complex have more variable 65cu 0 50 0 90 and 66zn 0 19 0 55 and those in the plutonic complex have 65cu of 0 43 to 0 20 and 66zn of 0 21 to 0 41 the rocks with heavier 66zn and heavier or lighter 65cu relative to morb are characterized by cu zn depletions low li yb 1 0 and low 18o 5 suggesting that hydrothermal extraction during high temperature alteration of oceanic crust can result in significant cu and zn isotope fractionation such large cu and zn isotopic variations are the results of redox transformation of cu as well as cu and zn isotope fractionation between altered basaltic rocks and dissolved cu and zn species in hydrothermal fluids e g cucl3 1 zn hs 42 this work is the first to define the distribution of cu and zn isotopes in an intact oceanic crust with concentration weighted averages of 65cu 0 05 0 03 and 66zn 0 27 0 01 the potential implications of these new observations are discussed

present day temperatures in northern scandinavia during the last glaciation scandinavia is generally considered to have been covered extensively with ice throughout marine isotope stages mis 4 2 between 75 and 10 ka here we present evidence for ice free warm conditions in the central area of the scandinavian glaciations during mis 3 our multiproxy data obtained from a lacustrine sequence in northern fin land reveal not only significant response in the northeastern sector of the scandinavian ice sheet to warming during the early part of mis 3 but also indicate rapid climate warming to present day temperatures in this ice free period new climate model simulations for interstadial conditions in mis 3 confirm the high mean july temperatures northeast of the scandinavian ice sheet in response to the high insolation values and the presence of the ice sheet during mis 3

understanding copper isotope behavior in the high temperature magmatic hydrothermal porphyry environment copper stable isotope geochemistry has the potential to constrain aspects of ore deposit formation once variations in the isotopic data can be related to the physiochemical conditions during metal deposition this study presents cu isotope ratios for samples from the pebble porphyry cu au mo deposit in alaska the 65cu values for hypogene copper sulfides range from 2 09 to 1 11 and show linear correlations with the 18o isotope ratios calculated for the fluid in equilibrium with the hydrothermal alteration minerals in each sample samples with sodic potassic potassic and illite alteration display a negative linear correlation between the cu and o isotope results this suggests that fractionation of cu isotopes between the fluid and precipitating chalcopyrite is positive as the hydrothermal fluid is evolving from magmatic to mixed magmatic meteoric compositions samples with advanced argillic alteration display a weak positive linear correlation between cu and o isotope results consistent with small negative fluid chalcopyrite cu isotope fractionation during fluid evolution the hydrothermal fluids that formed sodic potassic potassic and illite alteration likely transported cu as cuhs0 hydrothermal fluids that resulted in advanced argillic alteration likely transport cu as cucl2 the ph conditions also control cu isotope fractionation consistent with previous experimental work larger fractionation factors were found between fluids and chalcopyrite precipitating under neutral conditions contrasting with small fractionation factors calculated between fluids and chalcopyrite precipitating under acidic conditions therefore this study proposes that hydrothermal fluid compositions and ph conditions are related to cu isotope variations in high temperature magmatic hydrothermal deposits

the roar of yasur handheld audio recorder monitoring of vanuatu volcanic vent activity abstract we describe how near field audio recording using a pocket digital sound recorder can usefully document volcanic activity demonstrating the approach at yasur vanuatu in may 2014 prominent emissions peak at 263 hz interpreted as an organ pipe mode high pass filtering was found to usefully discriminate volcano vent noise from wind noise and autocorrelation of the high pass acoustic power reveals a prominent peak in exhalation intervals of 2 5 4 and 8 s with a number of larger explosive events at 200 s intervals we suggest that this compact and inexpensive audio instrumentation can usefully supplement other field monitoring such as seismic or infrasound a simple estimate of acoustic power interpreted with a dipole jet noise model yielded vent velocities too low to be compatible with pyroclast emission suggesting difficulties with this approach at audio frequencies perhaps due to acoustic absorption by volcanic gases

climatic bisection of the last interglacial warm period in the polar north atlantic new multiproxy marine data of the eemian interglacial mis5e from the norwegian sea manifest a cold event with near glacial surface ocean summer temperatures 3 4 c this mid eemian cooling divided the otherwise relatively warm interglacial climate and was associated with widespread expansions of winter sea ice and polar water masses due to changes in atmospheric circulation and ocean stability while the data also verify a late rather than early last interglacial warm peak which is in general disharmony with northern hemisphere insolation maximum and the regional climatic progression of the early holocene the cold event itself was likely instrumental for delaying the last interglacial climate development in the polar north when compared with regions farther south such a climatic decoupling of the polar region may bear profound implications for the employment of eemian conditions to help evaluate the present and future state of the arctic cryosphere during a warming interglacial

the last termination in the central south atlantic lake sediments and peat deposits from two basins on nightingale island 37 degrees s in the tristan da cunha archipelago south atlantic have been analyzed the studies were focused on the time period 16 2 10 0 cal ka bp determined by 36 c 14 dates from the two sequences a wide variety of proxies were used including pollen and diatom analyzes biogenic silica content c and n analyzes stable isotopes c 13 and n 15 elemental concentrations and magnetic susceptibility measurements to detect environmental changes that can be related to shifts of the circulation belts of the southern ocean in addition climate model simulations were carried out we find that the sediments are underlain by a 2 cal ka bp long hiatus possibly representing a dried out lake bed the climate simulations corroborate that the area might have been exposed to arid conditions as a consequence of the heinrich i event in the north and a southward displacement of the itcz the development on the island after 16 2 cal ka bp is determined by the position of the subtropical front stf and the southern hemisphere westerlies shw the period 16 2 14 75 cal ka bp was characterized by varying influence from shw and with stf situated south of tristan da cunha ending with a humidity peak and cooler conditions the stable conditions 14 7 14 1 cal ka bp with cool and fairly arid conditions imply that stf and shw were both north of the islands during the first part of the antarctic cold reversal the most unstable period 14 1 12 7 cal ka bp indicates incessant latitudinal shifts of the zonal circulation perhaps related to climate variability in the northern hemisphere and bipolar seesaw mechanisms as the strength of the atlantic meridional overturning circulation amoc varied at 12 7 cal ka bp the holocene warming began with a gradually drier and warmer climate as a result of a dampened amoc during the younger dryas cooling in the north with itcz stf and shw being displaced southwards peak warming seems to have occurred in the earliest part of the holocene but this period was also characterized by humidity shifts possibly an effect of retraction and expansion phases of shw during amoc variations in the north c 2015 elsevier ltd all rights reserved less

structure of an active volcano associated with a resurgent block inferred from thermal mapping the yasur yenkahe volcanic complex vanuatu subsurface thermal measurements provide a valuable tool to map hydrothermal fluid release zones in active volcanic areas on the yasur yenkahe volcanic complex tanna island vanuatu archipelago fumaroles and hot springs abound signs of upraising heat fluxes associated to a well developed hydrothermal activity combination of high resolution mapping of ground thermal anomalies with geomorphological analysis allows the characterization of the structural relationships between the active yasur volcano and the yenkahe resurgent block a complex system of heat release and hydrothermal fluid circulation below the yasur yenkahe complex is evidenced circulation though propagating vertically as a whole is funneled by stratification thus the main thermal fluid released is almost exclusively concentrated along structural limits that break the seals induced by the stratified nature of the ground three types of medium high temperature anomalies have been evidenced 1 broad hydrothermalized areas linked with planar stratification that favor lateral spreading 2 linear segments that represent active faults and 3 arcuate segments related to paleo crater rims the limit between the yasur volcano and the yenkahe resurgent block is characterized by an active fault system accommodating both the rapid uplift of the yenkahe block and the overloading induced by the volcano weight in such a setting faults converge below the cone of yasur which acts as a focus for the faults evidence of such structures sometimes hidden in the landscape but detected by thermal measurements is critical for risk assessment of flank landslides

spatial and temporal variability of lake ontogeny in south western greenland abstract holocene palaeolimnological records of diatoms and carotene a proxy for aquatic production from four lakes in the low arctic region of south western greenland were used to investigate the role of climate on lake ontogeny two of the lakes are located in the maritime coastal region near sisimiut and two inland close to the head of kangerlussuaq fjord where there is a more continental climate diatom records from the four lakes at1 at4 ss1381 ss8 had similar long term ontogeny trends independent of climatic setting and the changes are interpreted as responses to first order weathering controls on catchment lake chemistry short term excursions from these broad trends occurred in one coastal site at4 caused by intense erosion of the steep catchment and at inland sites where temporary hydrological closure and lake level decline occurred during the mid holocene 8000 5000 cal a bp algal production as carotene was more closely and consistently correlated with climatic changes it peaked during the mid holocene the warmest period of the holocene at all sites and there were transient increases in production in inland lakes during the medieval climate anomaly and little ice age because of fertilization through increased aeolian dust deposition a synthesis of seven palaeolimnological records from this region identified that only the mid holocene was correlated with diatom stratigraphic zones and there was considerable among site variability in later holocene lake response to climate forcing in this area comparable long term trends in species assemblage turnover dca ca axis 1 scores clearly demonstrate that lakes have predictable ontogeny trends in this region characterised by maximum alkalinity and nutrient availability in the first few millennia followed by progressive oligotrophication and alkalinity loss however individual lake and catchment characteristics lake morphology catchment geomorphology when modified by climatic change vegetation cover erosion weathering rates aeolian dust deposition lake level can diverge from this ontogeny template leading to complex ecological transitions in lakes from this region

patterns in the copper isotope composition of minerals in porphyry copper deposits in southwestern united states cu isotope measurements of minerals from american southwest porphyry cu deposits reveal a positive relationship with the grade of cu and display spatial patterns we measured the cu isotope composition of 87 minerals contained within veins from drill core and hand specimen samples from three deposits the silver bell ray and morenci mines the overall range of cu isotope ratios varies from 13 5 to 8 3 per mil the deposits possess three different cu reservoirs in which each has unique cu isotope signatures where 65cu for leach cap minerals hypogene minerals supergene enrichment minerals the pattern exists in all three deposits and resulted from oxidative weathering of cu at surface and reprecipitation of cu at depth a rayleigh distillation model mimics the cu isotope patterns found in the leach cap and quantifies the degree of leaching a comparison of the isotopic composition of the three reservoirs among the three deposits reveals distinct differences the silver bell mine possesses leach cap minerals that are more depleted in 65cu and enrichment minerals that are more enriched in 65cu than both the morenci and ray mines a possible explanation for the difference among the deposits could indicate that the silver bell deposit experienced a greater degree of leaching than the ray and morenci deposits the comparative analysis of the cu isotope data reveals the exploration potential of using cu isotope fractionation in the supergene environments

copper isotopic zonation in the northparkes porphyry cu au deposit se australia abstract significant systematic cu isotopic variations have been found in the northparkes porphyry cu au deposit nsw australia which is an orthomagmatic porphyry cu deposit copper isotope ratios have been measured in sulfide minerals chalcopyrite and bornite by both solution and laser ablation multi collector inductively coupled plasma mass spectrometry mc icp ms the results from both methods show a variation in 65cu of hypogene sulfide minerals of greater than 1 relative to nist976 significantly the results from four drill holes through two separate ore bodies show strikingly similar patterns of cu isotope variation the patterns are characterized by a sharp down hole decrease from up to 0 8 0 29 0 56 1 n 20 in the low grade peripheral alteration zones phyllic propylitic alteration zone to a low of 0 4 0 25 0 36 1 n 30 at the margins of the most mineralized zones cu grade 1 wt in the high grade cores of the systems the compositions are more consistent at around 0 2 0 19 0 14 1 n 40 the cu isotopic zonation may be explained by isotope fractionation of cu between vapor solution and sulfides at high temperature during boiling and sulfide precipitation processes sulfur isotopes also show an isotopically light shell at the margins of the high grade ore zones but these are displaced from the low 65cu shells such that there is no correlation between the cu and s isotope signatures fe isotope data do not show any discernable variation along the drill core this work demonstrates that cu isotopes show a large response to high temperature porphyry mineralizing processes and that they may act as a vector to buried mineralization

variation of copper isotopes in chalcopyrite from dabu porphyry cu mo deposit in tibet and implications for mineral exploration abstract the study presents copper cu isotope data of mineral separates of chalcopyrite from four drill core samples in the miocene dabu porphyry cu mo deposit formed in a post collisional setting in the gangdese porphyry copper belt southern tibet copper isotope values in hypogene chalcopyrite range from 1 48 to 1 12 displaying a large variation of up to 2 60 which demonstrates cu isotope fractionation at high temperature during hydrothermal evolution the majority of measured chalcopyrite isotopic compositions show a gradual increasing trend from 1 48 to 1 12 with the increase of drilling depth from 130m to 483m as the alteration assemblages change from potassic to phyllic similarly the other 65 cu values 65 cu 65 cu 63 cu sample 65 cu 63 cu standard 1 1000 of the chalcopyrite show a gradual increasing trend from 1 48 to 0 59 with the decrease of drilling depth from 130 m to 57 m as the alteration assemblages change from potassic phyllic through argillic to relatively fresh these observations suggest a genetic link between cu isotope variation and silicate alteration assemblages formed at different temperatures indicative of a rayleigh precipitation process resulting in the large variation of 65 cu values at dabu in general samples closest to the center of hydrothermal system dominated by high temperature potassic alteration are isotopically lighter whereas samples dominated by low temperature phyllic alteration peripheral to the center are isotopically heavier the predicted flow pathways of hydrothermal fluids are from no 0 to no 3 exploration line and the lightest 65 cu values are the most proximal to the hydrothermal source finally we propose that the northwest side of the no 0 exploration line has high potential for hosting undiscovered orebodies the pattern of cu isotope variation in conjunction with the features of silicate alteration in porphyry system can be used to trace the hydrothermal flow direction and to guide mineral exploration

chemical weathering in granitic environments abstract factors controlling chemical weathering in granitic environments are deduced using an extensive database from the literature based on a transition state theory model we evaluated the effects on chemical weathering of runoff temperature and ph the dependence between temperature and runoff and chemical weathering is complicated by other factors such as the presence depth of soil cover soil cover favors chemical weathering when it is thin and rich in weatherable minerals in contrast it reduces chemical weathering when is thick and poor in primary minerals processes that increase the contact time and the surface of the water rock interactions such as physical denudation increase chemical weathering rates in granitic environments the effect of temperature can be quantified assuming an apparent activation energy value of 48 7 kj mol to describe chemical weathering of silica in granitic crystalline environment under high runoff conditions

insights into ore genesis of ni cu pge sulfide deposits of the noril sk province russia evidence from copper and sulfur isotopes abstract combined cu s isotope data for ni cu pge sufides from the economic deposits hosted in the noril sk 1 talnakh and kharaelakh intrusions from the subeconomic deposits in the chernogorsk zub marksheider and vologochan intrusions and from the non economic occurrences in the nizhny talnakh intrusion in the noril sk province russia and the j m reef in the stillwater complex usa are presented for the first time most sulfide samples including the ores from the talnakh intrusion and the stillwater complex have a restricted range of 65 cu values from 1 1 to 0 whereas those from the kharaelakh and noril sk 1 intrusions have more variable 65 cu values of 2 3 to 1 0 samples from the three economic deposits in the noril sk province have distinct mean 65 cu values of 1 56 0 27 for kharaelakh 0 55 0 41 for talnakh and 0 23 0 28 for noril sk 1 consistent with those for carbonaceous chondrite and iron meteorites the variation of 65 cu values is interpreted to represent a primary signature of the ores although a magmatic fractionation of cu isotopes and or assimilation from an external source cannot be ruled out particularly in the case of the kharaelakh ores collectively the eight investigated intrusions have an overall sulfur 34 s range from 0 7 to 13 8 disseminated and massive ores of the same intrusion have similar 34 s values the disseminated and massive ores of the khraelakh intrusion have a mean 34 s value of 12 57 0 54 and 12 76 0 42 respectively which are distinctly different from those of the disseminated 10 97 0 44 and massive ores 10 88 0 77 of the talnakh intrusion the different 34 s values of the intrusions may be attributed to sulfur fractionation in deep seated magma chambers rather than at shallow levels or the present emplacement site the mean 34 s value of the disseminated ores from the subeconomic ni cu pge deposits and non economic occurrences spans over 10 5 averaging 0 39 with a standard deviation of 1 55 for the highly contaminated zub marksheider rocks 6 38 1 89 for nizhny talnakh 6 90 1 17 for vologochan and 10 86 0 43 for chernogorsk samples from the zub marksheider intrusion have mantle like s isotope signatures consistent with a deep seated origin although individual mineralized instrusions have a restricted range the overall trend they define of falling 34 s with rising 65 cu values might be a useful indicator of the economic potential of ni cu pge sulfide deposits

marine evidence for climatic instability during the last interglacial in shelf records from northwest europe data from the greenland ice sheet and continental records from europe have indicated climatic fluctuations during the last interglacial eemian oxygen isotope substage 5e similar fluctuations have not however been documented previously from marine environments here we show the existence of two cold events during substage 5e in two marine benthic foraminiferal shelf records from northwest europe and suggest that these cooling events are a result of fluctuations in the strength of the north atlantic surface water circulation

copper isotopic compositions of the zijinshan high sulfidation epithermal cu au deposit south china implications for deposit origin abstract the zijinshan high sulfidation epithermal cu au deposit is located in the zijinshan ore field of south china comprising porphyry epithermal cu au mo ag ore systems the cu ore body is more than 1000 m thick and is characterized by an assemblage of digenite covellite enargite alunite digenite is the dominant cu bearing mineral which makes this deposit unique although the mechanisms of digenite formation remain controversial to elucidate the genesis of digenite this paper presents the cu isotopic compositions of cu sulfides in the zijinshan high sulfidation cu au deposit the cu isotopic values 65cu relative to nist 976 of all samples range from 2 97 to 0 34 and most values fall in a narrow range from 0 49 to 0 34 which is similar to the cu isotopic signature of typical porphyry systems copper isotope ratios of each mineral decrease with increasing depth a trend that is also typical of porphyry deposits the variation tendency of 65cu values between sulfides is consistent with the sequence of mineral formation these observations suggest that the cu sulfides in the zijinshan cu au deposit have a hypogene origin

was the climate of the eemian stable a quantitative climate reconstruction from seven european pollen records the aim of the present study is to estimate the range of the climatic variability during the eemian interglacial which lasted about 10 000 years marine isotopic stage 5e the modem pollen analogue technique is applied to seven high resolution pollen records from france and poland to infer the annual precipitation and the mean temperature of the coldest month the succession of pollen taxa and the reconstructed climate can be interpreted coherently the warmest winter temperatures are centred in the first three millennia of the eemian interglacial during the mixed oak forest phase with quercus and corylus as dominant trees a rapid shift to cooler winter temperatures of about 6 degrees to 10 degrees c occurred between 4000 and 5000 years after the beginning of the eemian related to the spread of the carpinus forest this shift is more obvious for the reconstructed temperatures than for precipitation and is unique and irreversible for the whole eemian period following this climatic shift of the eemian variations of temperature and precipitation during the fast 5000 years were only slight with an amplitude of about 2 degrees to 4 degrees c and 200 to 400 mm yr the estimated temperature changes were certainly not as strong as those reconstructed for the stage 6 5e termination or the transition 5e 5d this is consistent with the constantly high ratio of tree pollen throughout the eemian indicative of a succession of temperate forest types this gradual transition between different forest landscapes can be related to intrinsic competition between the species rather than to a drastic climatic change c 1998 elsevier science b v all rights reserved

earthquake volcano interaction imaged by coda wave interferometry 1 large earthquakes are often assumed to influence the eruptive activity of volcanoes a major challenge to better understand the causal relationship between these phenomena is to detect and image in detail all induced changes including subtle non eruptive responses we show that coda wave interferometry can be used to image such earthquake induced responses as recorded at yasur volcano vanuatu following a magnitude 7 3 earthquake which occurred 80 km from its summit we use repeating long period events to show that the earthquake caused a sudden seismic velocity drop followed by a slow partial recovery process the spatial distribution of the response amplitude indicates an effect centered on the volcano our result demonstrates that even if no major change in eruptive activity is observed volcanoes will be affected by the propagation of large amplitude seismic waves through their structure suggesting that earthquake volcano interaction is likely a more common phenomenon than previously believed

volcanic craters pit craters and high level magma feeding systems of a mafic island arc volcano ambrym vanuatu south pacific

geochemistry vs seismo tectonics along the volcanic new hebrides central chain southwest pacific abstract compositional variations major and trace element of pleistocene to present rocks along the volcanic new hebrides central chain southwest pacific are presented and discussed using a new set of analyses we focus in particular on the anomalous mg k lile and lree rich and al and si poor character of the basalts from aoba and santa maria volcanoes and to a lesser extent from ambrym volcano all located in the area where the d entrecasteaux zone collides with the arc in addition we note a compositional transition from normal arc basalts to boninite related high mg andesites at the southern termination of the nhcc the peculiar composition of the rocks of the volcanoes facing the d entrecasteaux zone has traditionally been related more or less directly to the collision subduction occurring in this area we present an alternative hypothesis of a strong geochemical anomaly under santa maria and aoba volcanoes unrelated to this collision in this model a westward and upward invasion of dupal type enriched mantle corroborated by the pattern of intermediate seismicity occurs under this part of the arc in strong contrast to the usual pacific type morb mantle source present under all other volcanoes of the nhcc such a dupal type source may explain the anomalous geochemistry of the resulting volcanic products

fluid speciation controls of low temperature copper isotope fractionation applied to the kupferschiefer and timna ore deposits article i nfo mass balance amongreducedandoxidizedsolutionspeciesexertsastrongcontrol ontheisotopiccompositionof sulphide minerals we explore this issue for copper isotopic fractionation in sedimentary copper sulfide deposits through fluid speciation isotopic eh ph calculations based on the thermodynamic stability of copper chloride aqueous solution complexes and experimentally measured copper isotope fractionation factors applying these speciation diagrams to mc icp ms copperisotope data on the kupferschiefer sw partof thelubin sieroszowice copper district and timna s israel sediment hosted stratiform copper deposits ssc identifies differences in ore formation redox conditions timna valley copper sulfides have light cu isotopic compositions of 65 cu 2 04 0 44 2 relatively to srm 976 copper standard which are shown to correspond to eh values of 0 5 to 0 6 v at formation conditions t 40 c ph b6 these eh values indicate precipitation at relatively oxidized conditions where the cu i solution complex cucl3 2 i sb10 of the total solution species in contrast the kupferschiefer cu sulfides analyzed in this work dominantly show significantly higher 65 cu values 0 39 0 36 corresponding to eh values of 0 4 to 0 5 v at formation conditions t 100 c ph 6 3 in these eh conditions most copper in solution occurs as cucl3 2 complexes 80 the above observations are in accord with field relations showing that cu ii minerals dominate the timna system but cu sulfides are the major minerals of the kupferschiefer deposits fluid speciation isotopic calculations show that copper isotopes can be used as effective tracers of redox conditionsandthisapproach can bepotentiallyappliedtovarioushydrothermal oredeposits such as black smokers and volcanic hosted massive sulphide deposits and to other metallic isotope systems however the isotopic fractionation mayalso be strongly influenced by the types ofligand bondingofcopper ions and these effects need to be fully evaluated before the isotope geochemistry of copper ores can be fully understood

current tectonics of the tonga new hebrides region abstract this paper proposes a present day tectonic map of the tonga new hebrides region the result of combining data from bathymetry satellite derived gravity seismicity magnetic measurements and gps observations focal mechanisms and a large amount of bathymetric data collected during the last decade in the lau and north fiji back arc basins indicate a deformation distributed over numerous spreading ridges rather than diffuse and shear dominated as was previously thought the region is also characterised by a large variation of both consumption rate along the arcs and opening rate along the back arc basins spreading centres geometry and rate of spreading in the lau and north fiji back arc basins and segmentation of the tonga and new hebrides arcs are closely related to and significantly influenced by the subduction of aseismic ridges namely the louisville d entrecasteaux and loyalty ridges where subducting aseismic ridges enter the trenches we observe slower convergence arc transverse strike slip faulting thrusting at the rear of arcs and slow or absent back arc spreading rapid subduction correlates with fast back arc opening sometimes parallel spreading ridges in the back arc domain are required to accommodate the fast motion of convergence

major cooling intersecting peak eemian interglacial warmth in northern europe abstract the degree of climate instability on the continent during the warmer than present eemian interglacial around ca 123 kyr ago remains unsolved recently published high resolution proxy data from the north atlantic ocean suggest that the eemian was punctuated by abrupt events with reductions in north atlantic deep water formation accompanied by sea surface temperature cooling here we present multi proxy data at an unprecedented resolution that reveals a major cooling event intersecting peak eemian warmth on the north european continent two independent temperature reconstructions based on terrestrial plants and chironomids indicate a summer cooling of the order of 2 4 c the cooling event started abruptly had a step wise recovery and lasted 500 1000 yr our results demonstrate that the common view of relatively stable interglacial climate conditions on the continent should be revised and that perturbations in the north atlantic oceanic circulation under warmer than present interglacial conditions may also lead to abrupt and dramatic changes on the adjacent continent

new insights from xrf core scanning data into boreal lake ontogeny during the eemian marine isotope stage 5e at sokli northeast finland biological proxies from the sokli eemian marine isotope stage 5e paleolake sequence from northeast finland have previously shown that unlike many postglacial records from boreal sites the lake

cu isotope ratio variations in the dikulushi cu ag deposit drc of primary origin or induced by supergene reworking this study investigates cu isotope ratio variations in the high grade vein type cu ag deposit of dikulushi democratic republic of congo the dikulushi deposit consists of a cu pb zn fe mineralization comprising sphalerite chalcopyrite bornite and chalcocite that precipitated under reducing conditions this mineralization was partly remobilized in more oxidizing conditions into a cu ag mineralization phase which is dominated by ag rich chalcocite the upper part of the deposit is strongly reworked by weathering sulfides from the two types of mineralization and cu carbonates silicates from the weathering zone display significant cu isotope ratio variations chalcopyrite and chalcocite from the cu pb zn fe and cu ag mineralization types are characterized by variable low cu isotope compositions 0 00 to 2 3 65cu the cu isotope composition for some chalcocite from the cu ag mineralization deviates to lower 65cu values relative to that of chalcocite from the cu pb zn fe mineralization this deviation is likely related to remobilization of the cu pb zn fe mineralization in an oxidizing environment the isotopic composition of cu in chalcocite from both mineralization types becomes higher toward the center of the orebody and as a function of depth this variation could be related to physicochemical changes in the precipitation environment as a consequence of interaction of the reduced mineralizing brine with the oxidized host rock or might have been induced by supergene processes afterward the supergene mineralization is composed of malachite azurite and chrysocolla that are enriched in 65cu 1 37 2 65 65cu

eemian and early weichselian temperature and precipitation variability in northern germany abstract dramatic changes in european vegetation occurred during the transition from the eemian interglacial to weichselian glacial climates correlative with major changes in global ice core and marine records quantitative knowledge of climate change is important for understanding of the climate system and for climate modelling for which reconstructions of this transitional period are of special interest however it has been difficult to quantify the climatic changes involved in the eemian to early weichselian transition from terrestrial archives due to the lack of modern vegetation analogues to circumvent this problem we applied a suitable multivariate probabilistic approach to pollen and plant macrofossil assemblages to reconstruct temperature and precipitation for this transition in central europe our reconstructions span the interval from the beginning of the eemian marine isotope stage mis 5e to the odderade interstadial mis 5a they indicate a relatively stable eemian with increasing precipitation reducing the continentality of the climate with time during the transition from the eemian to the herning stadial mean july and january temperatures decreased by 4 c and by as much as 20 c respectively temperatures remained high enough to support forests during the stadials and we infer that the reconstructed decrease of precipitation below 500 mm per year caused the extirpation of forests during these periods thus we conclude that precipitation although difficult to reconstruct is of vital importance for explaining vegetation change during the eemian and eemian early weichselian transition

rapid switches in subpolar north atlantic hydrography and climate during the last interglacial mis 5e plateauing just below early mis 5e values a planktonic d 18 o minimum during the cooling event indicates that marked freshening of the surface waters accompanied the cooling we suggest that switches in the subpolar gyre hydrography occurred during a warmer climate involving regional changes in freshwater fluxes balance and east greenland current influence in the study area the nature of these hydrographic transitions suggests that they are most likely related to large scale circulation dynamics potentially amplified by gis meltwater influences

horizontal and vertical interseismic velocity fields in the vanuatu subduction zone from gps measurements evidence for a central vanuatu locked zone we analyzed interseismic velocity fields along the vanuatu arc subduction zone from more than 45 gps station measurements spanning 15 years convergence with respect to the australian plate ap is normal to the trench with amplitudes that vary greatly from a maximum of 170 mm a a1 at vanikoro to 27 mm a a1 facing the d entrecasteaux ridge der motions expressed relative to the pacific plate pp highlight arc segmentation both the northern and southern segments undergo back arc spreading in a roughly ne sw direction rotating anticlockwise and clockwise respectively while the central block moves eastward at a faster rate with respect to the pp than to the ap more convergence is therefore accommodated at the eastern bound of the arc than at the vanuatu trench a right lateral strike slip movement 26 1 mm a a1 along a zone normal to the trench direction n70 is necessary to accommodate the rate variation between the central and southern parts of the arc horizontal and vertical rates indicate partitioning between malekula southernmost santo and central northern santo blocks simple elastic modeling of the interseismic stage deformation gives locked zone characteristics 25 dip and 50 km width and a 54 mm a a1 long term convergence rate between the ap and the central part of the vanuatu arc from gps horizontal and vertical velocities estimated south of the der the modeling does not fit the observed velocities facing the der probably because it does not account for the inelastic deformation associated with buoyant ridge subduction and back arc thrusting

pyroclast tracking velocimetry illuminates bomb ejection and explosion dynamics at stromboli italy and yasur vanuatu volcanoes a new image processing technique pyroclast tracking velocimetry was used to analyze a set of 30 high speed videos of strombolian explosions from different vents at stromboli italy and yasur vanuatu volcanoes the studied explosions invariably appear to result from the concatenation of up to a hundred individual pyroclast ejection pulses all these pulses share a common evolution over time including 1 a non linear decrease of the pyroclast ejection velocity 2 an increasing spread of ejection angle and 3 an increasing size of the ejected pyroclasts these features reflect the dynamic burst of short lived gas pockets in which the rupture area enlarges while pressure differential decreases we estimated depth of pyroclast release to be approximately 1 and 8 m below the surface at stromboli and yasur respectively in addition explosions featuring more frequent pulses also have higher average ejection velocities and larger total masses of pyroclasts these explosions release a larger overall amount of energy stored in the pressurized gas by a combination of more frequent and stronger ejection pulses in this context the associated kinetic energy per explosion ranging 103 109 j appears to be a good proxy for the explosion magnitude differences in the pulse defining parameters among the different vents suggest that this general process is modulated by geometrical factors in the shallow conduit as well as magma specific rheology indeed the more viscous melt of yasur compared to stromboli is associated with larger vents producing fewer pulses but larger pyroclasts

copper isotopes trace the evolution of skarn ores a case study from the hongshan hongniu cu deposit southwest china abstract transition metal isotopes are sensitive geochemical tracers of ore genesis here we present mc icp ms analytical data of cu isotope compositions from the hongshan hongniu cu deposit in yunnan province the 65 cu values 65 cu 65 cu 63 cu sample 65 cu 63 cu nist976 1 1000 of seven whole rock quartz monzonite porphyries and twenty two chalcopyrite samples from the skarn ore bodies display relatively narrow ranges from 0 15 to 0 38 and from 0 02 to 0 77 respectively the overlap of 65 cu values indicates a genetic relationship between the quartz monzonite porphyry and skarn ore bodies we also evaluate the spatial and temporal variations of cu isotope compositions in the skarn ore bodies by comparison with some well documented porphyry deposits in the world the quartz monzonite porphyry shows compositional zoning with the inner domain enriched in heavy cu isotope and the skarn related to the porphyry depleted in heavy cu isotope the chalcopyrites that formed during the late stage of mineralization tend to be enriched in heavy cu isotope and this feature is analogous to porphyry deposits the 65 cu values of the quartz monzonite porphyry show typical features of hypogene mineralization suggesting a potential scope for deep exploration and development in this deposit

patterns of early lake evolution in boreal landscapes a comparison of stratigraphic inferences with a modern chronosequence in glacier bay alaska the chronosequence approach which infers temporal patterns of environmental change from a spatial array of modem sites has been a major tool for studying successional processes a model of early lake ontogeny in boreal landscapes developed from a chronosequence of lakes in alaska suggests that long term soil development and related hydrological change produce a loss of alkalinity and base cations a decrease in ph an increase in doc and a transient increase followed by a decrease in lakewater nitrogen concentrations over time we compare this model of lake ontogeny with patterns of change reconstructed from diatom assemblages in 10 sediment cores from the same region lakewater ph declined in the majority of lakes but the pattern rate and magnitude of decline varied considerably among sites apparently related to local differences in hydrologic setting inferred trends in nitrogen concentration over time are not spatially uniform and appear to vary because of local differences in vegetation history

atacamite formation by deep saline waters in copper deposits from the atacama desert chile evidence from fluid inclusions groundwater geochemistry tem and 36 cl data the presence of large amounts of atacamite in oxide zones from ore deposits in the atacama desert of northern chile requires saline solutions for its formation and hyperarid climate conditions for its preservation we investigated the nature and origin of atacamite forming solutions by means of coupling groundwater geochemical analyses with fluid inclusion data high resolution mineralogical observations and chlorine 36 36cl data in atacamite from the mantos blancos and spence cu deposits in both deposits the salinities of fluid inclusions in atacamite are comparable to those measured in saline groundwaters sampled from drill holes the average salinity of fluid inclusions in atacamite for the mantos blancos and spence deposits 7 9 and 2 3 wt nacleq respectively are strongly correlated to the salinities at which gypsum supersaturates from groundwaters in both deposits total dissolved solids 5 9 and 1 3 wt nacleq respectively this correlation is confirmed by transmission electron microscopy observations of atacamite bearing samples revealing an intimate association between atacamite and gypsum that can be traced down to the nanometer scale 36cl data in atacamite provide new lines of evidence concerning the origin and age of the saline waters that formed atacamite in various stratabound and porphyry cu deposits from the atacama desert all atacamite samples show very low 36cl to cl ratios 11 10 15 to 28 10 15 at at 1 comparable to previously reported 36cl to cl ratios of deep formation waters and old groundwaters in addition 36cl to cl ratios in atacamite correlate with u and th concentration in the host rocks but are independent from distance to the ocean this trend supports an interpretation of the low 36cl to cl ratios in atacamite as representing subsurface production of fissiogenic 36cl in secular equilibrium with the solutions involved in atacamite formation therefore 36cl in atacamite strongly suggest that the chlorine in saline waters related to atacamite formation is old 1 5 ma but that atacamite formation occurred more recently 1 5 ma than suggested in previous interpretations our data provide new constraints on the origin of atacamite in cu deposits from the atacama desert and support the recent notion that the formation of atacamite in hyperarid climates such as the atacama desert is an ongoing process that has occurred intermittently since the onset of hyperaridity

insights into the evolution of the yenkahe resurgent dome siwi caldera tanna island vanuatu inferred from aerial high resolution photogrammetry the yenkahe dome tanna island vanuatu is one of the most spectacular examples of presently active post caldera resurgence exhibiting a very high uplift rate over the past 1000 years 156 mm year on average although numerous inhabited areas are scattered around the dome the dynamics of this structure and associated hazards remain poorly studied because of its remote location and dense vegetation cover a high resolution photogrammetric campaign was carried out in november 2011 over the dome georeferenced photographs were treated by structure from motion and multiple view stereophotogrammetry methods to produce a 3d digital surface model dsm of the area and its associated orthophotograph this dsm is much more accurate than previously available srtm and aster digital elevation models dems particularly at minimal coastline and maximal altitudes yasur culmination point 390 m while previous mapping relied mostly on low resolution dems and satellite images the high precision of the dsm allows for a detailed structural analysis of the yenkahe dome notably based on the quantification of fault displacements the new structural map inferred from the 3d reconstruction and morphological analysis of the dome reveals a complex pattern of faults and destabilization scars reflecting a succession of constructive and destructive events numerous landslide scars directed toward the sea highlight the probable occurrence of a tsunami event affecting the south eastern coast of tanna simulations of landslide triggered tsunamis show the short time propagation of such a wave 1 2 min which could affect coastal localities even following relatively small destabilized volumes a few million cubic meters

initial stages of weathering and soil formation in the morteratsch proglacial area upper engadine switzerland investigations in alpine soils indicate that mineral weathering is much faster in young soils 1000 yr than in old soils 10 000 yr however little is known about the initial stages of weathering and soil formation i e during the first decades of soil genesis in this study we investigated rock forming minerals weathering at very early stages of soil formation due to the continuous retreat of the morteratsch glacier upper engadine swiss alps the proglacial area offers a full time sequence from 0 to 150 yr old surfaces a low slope and the absence of glacier which might have interrupted soil formation processes contributed to the choice of the morteratsch proglacial valley for this case study the area is well documented regarding vegetation and soils the tectonic unit is the bernina crystalline which is mainly constituted of granitoid rocks consequently the glacial till has an acidic character mineralogical measurements were carried out on the soil fraction 2 mm using xrd and drift for qualitative and quantitative phase analysis in addition chemical analyses of the stream water from the main channel tributaries and of rainwater were performed with a special focus on ca sr and sr isotope ratios 87sr 86sr furthermore the accumulation of organic matter within the time sequence and physical soil properties were measured decreasing grain size with time shows active physical weathering processes soil organic matter has been accumulated during 150 yr at very high rates special emphasis has been given to chemical weathering and to the formation and transformation mechanisms of minerals of special interest were biotite chlorite epidote plagioclase and calcite biotite has been continuously transformed into illite like components within 150 yr the concentration of epidote significantly decreased the high ca sr as well as 87sr 86sr ratios in the stream and spring waters confirmed that ca bearing minerals are weathering and transforming at very high rates in the proglacial area also in cryic ice free environments chemical weathering rates are high leading to the formation and transformation of minerals disseminated calcite in granitoid rocks not confined to sedimentary carbonate rocks also plays a role in subglacial environments it is however not known for how long such an influence is significant and measurable the high ca na and ca sr ratio in the stream and tributary waters showed that calcite contributes to the supply of soluble ca although the ion activity product calculations clearly demonstrated that the waters were undersaturated with respect to this mineral

non residual sr of the sediments in daihai lake as a good indicator of chemical weathering abstract the rb sr ratio of lake sediments has been demonstrated to be a potential indicator of chemical weathering by increasing work however rb and sr in lake sediments are derived from both chemical weathering and physical erosion rb and sr of different forms in lake sediments may record different environmental processes and information in this study the variation patterns of rb and sr of different forms in sediments of daihai lake were investigated the results show that rb and sr of different forms display noticeably different variation patterns due to their different sources and associated environmental processes using the rb sr ratios of bulk lake sediments to reflect chemical weathering is not accurate the non residual sr of the sediments without detrital carbonates representing the sr leached from the catchment can be used as an index of chemical weathering because the weathering of sr minerals is very sensitive to climate change and the non residual sr content of the sediment is determined more by sr2 influx than by the physicochemical conditions of lake water the correspondence between the non residual sr and tic toc in daihai lake also indicates that the non residual sr of the sediments is a good indicator of chemical weathering in the catchment

zinc sulfur and lead isotopic variations in carbonate hosted pb zn sulfide deposits southwest china abstract the sichuan yunnan guizhou pb zn metallogenic province in the western yangtze block southwest china contains more than four hundred pb zn deposits with more than 200 million tons of pb zn ores at mean grades of 5 wt pb and 10 wt zn these deposits are hosted in sinian ediacaran to permian carbonate rocks and are structurally controlled by thrust fault fold structures and are spatially associated with the late permian 260 ma emeishan flood basalts two representative low temperature hydrothermal pb zn sulfide deposits the tianqiao and banbanqiao deposits in the southeastern part of the sichuan yunnan guizhou pb zn metallogenic province are selected for zn s pb isotopic analyses sphalerite from the tianqiao deposit has 66 zn values ranging from 0 26 to 0 58 relative to the jmc 3 0749l zinc isotope standard whereas 66 zn values of sphalerite from the banbanqiao deposit range from 0 07 to 0 71 the zinc isotopic composition of sphalerite from both deposits increase from early to final mineralization stage in addition sphalerite from the center near to bottom part of the no 1 ore body in the tianqiao deposit has lower 66 zn values 0 01 to 0 43 than those 0 11 to 0 57 in the periphery near to top sinian to permian sedimentary rocks and permian emeishan flood basalts the potential zinc metal source rocks have 66 zn values range from 0 24 to 0 17 and from 0 32 to 0 44 respectively the majority of the hydrothermal sphalerite has heavier zinc isotope than the country rocks precluding the mixing of multiple zinc sources as the key factor controlling the spatial and temporal variations of zinc isotope therefore the increased 66 zn values from the early to late stage and from the center to top could be due to kinetic raleigh fractionation sphalerite from the tianqiao and banbanqiao deposits has 34 s values ranging from 10 9 to 14 8 and from 3 9 to 9 0 respectively lower than cambrian to permian marine sulfates 15 to 35 and sulfate bearing evaporates 15 to 28 in the devonian to permian carbonate host rocks sulfur of the pb zn ores from both deposits is interpreted as the result of thermal chemical sulfate reduction of evaporates in the sedimentary rocks most likely the host rocks sphalerite from the tianqiao deposit has pb isotope similar to that of age corrected devonian to permian carbonate host rocks whereas sphalerite from the banbanqiao deposit has pb isotope similar to that of age corrected underlying precambrian basement rocks therefore at least lead in the tianqiao and banbanqiao deposits was mainly originated from the host rocks and the underlying basements respectively zn s pb isotopic studies of sphalerite from both deposits indicate that sources of metals and sulfur in the hydrothermal fluid for the tianqiao deposit are the paleozoic carbonate host rocks whereas for the banbanqiao deposit the sources are the precambrian basements and the paleozoic carbonate host rocks respectively

a structural outline of the yenkahe volcanic resurgent dome tanna island vanuatu arc south pacific abstract a structural study has been conducted on the resurgent yenkahe dome 5 km long by 3 km wide located in the heart of the siwi caldera of tanna island vanuatu arc south pacific this spectacular resurgent dome hosts a small caldera and a very active strombolian cinder cone the yasur volcano in the west and exhibits an intriguing graben in its central part detailed mapping and structural observations make it possible to unravel the volcano tectonic history of the dome it is shown that following the early formation of a resurgent dome in the west a complex collapse caldera plus graben occurred and this was associated with the recent uplift of the eastern part of the present dome eastward migration of the underlying magma related to regional tectonics is proposed to explain this evolution

use of cu isotopes to distinguish primary and secondary cu mineralization in the canariaco norte porphyry copper deposit northern peru a significant proportion of the copper in the canariaco norte porphyry copper deposit in northern peru occurs in chalcocite and covellite rich veins and disseminations that exist from the surface to depths greater than 1 km the overall range of cu isotopic ratios of 42 mineral separates from canariaco varies from 8 42 to 0 61 with near surface chalcocite and fe oxides having isotopically depleted values compared to chalcocite covellite and chalcopyrite from deeper levels the majority 34 of 36 of measured cu sulfides have a typical hypogene copper isotope composition of 65cu 0 18 0 38 with no enriched isotopic signature existing in the canariaco norte sulfide data thus the copper isotope data indicate that most of the chalcocite and covellite formed from high temperature hypogene mineralization processes and that only a minor portion of the deposit is enriched by supergene processes the nonexistence of an enriched 65cu reservoir suggest the presence of an undiscovered lateral exotic cu occurrence that enriched 65cu that remained in solution during weathering regardless of the cause the comparative analysis of the cu isotope dataset reveals that little exploration potential for an extensive supergene enrichment blanket exists because the weathering history at canariaco norte was not conducive to preservation of enriched cu at depth beneath the leach cap

age of supergene oxidation and enrichment in the chilean porphyry copper province twenty five samples of supergene alunite collected from deeply developed supergene profiles in porphyry copper deposits and prospects between latitudes 20 degrees and 27 degrees s in northern chile yield k ar ages ranging from about 34 to 14 ma therefore supergene oxidation and enrichment processes were active from the early oligocene to the middle miocene a minimum of 20 m y supergene activity at individual deposits lasted for at least 0 4 to 6 2 m y the early oligocene supergene activity affected deposits in the paleocene porphyry copper belt whereas early and middle miocene supergene processes are documented in the early cretaceous paleocene and late eocene to early oligocene porphyry copper belts middle miocene oxidation also affected the oldest epithermal gold silver deposits in the maricunga belt farther east supergene activity commenced no less than 11 m y after generation of each porphyry copper deposit because of the time required to unroof the copper bearing parts of the system supergene activity throughout northern chile ceased at approximately 14 ma the geologic features of deposits and prospects and their morphotectonic positions present latitudes and present elevations display no obvious correlations with the supergene chronology exploration for major cumulative enrichment blankets should not be carried out either beneath thick sequences of piedmont gravels or ignimbrites of oligocene through middle miocene age unless their accumulation is demonstrably late in the documented history of supergene activity or in porphyry copper provinces such as those of central chile and northwestern argentina which formed after approximately 14 ma the uplift responsible for efficient cumulative copper enrichment is difficult to correlate convincingly with the brief pulses of compressive tectonism postulated for northern chile and contiguous areas unless their effects were much more prolonged intensifying aridity is confirmed as the likely reason for the cessation of supergene activity in northern chile and tectonic uplift was its most probable cause however more fundamental global controls producing a period of chemical weathering followed by worldwide dessication also may have played a role

mafic pyroclastic flows at santa maria gaua volcano vanuatu the caldera formation problem in mainly mafic island arc volcanoes at santa maria volcano new hebrides island arc extensive ash and scoria flow deposits overlie the mainly effusive pre caldera cone hydromagmatic features characterize these deposits the composition of juvenile clasts ranges from basalt to acid andesite dacite sio2 51 63 6 with a dominant basaltic composition the stratigraphic position of this pyroclastic series and its spatial distribution around a 8 5 km 6 km wide caldera provide evidence of a relationship between this series and the caldera formation in addition these pyroclastic deposits are co genetic to parasitic cones and lava flows developed along faults concentric to the caldera both series result from a compositionally layered magma reservoir the subordinate differentiated magmas being the result of fractional crystallization from the basalts a model of caldera formation which implies a large hydromagmatic eruption at the central vent and minor magma withdrawal by flank eruptions is proposed this model emphasizes the importance of mafic hydroclastic eruptions in the caldera forming event and contradicts a model implying only quiet subsidence a process often proposed for the formation of calderas in island are volcanoes of mainly mafic composition

rare earth element geochemistry of lake baikal sediment its implication for geochemical response to climate change during the last glacial interglacial transition sediments deposited on the bottom of lake baikal have contributed to the understanding of a long term environmental history of continents rare earth elements rees along with major elements and loss on ignition loi of baikal sediments were determined with the aim of evaluating their suitability for a new paleoenvironmental proxy our interest is concentrated on paleoenvironmental change during the last glacial interglacial transition lgit chondrite normalized ree patterns for baikal sediments show a similar variation to those for typical upper continental crustal materials three parameters of la yb n n chondrite normalized value ratio sree tio2 and eu anomaly were used to express detailed characteristics of baikal sediments depth profile of la yb n ratio shows abrupt change whose timing corresponds to the beginning of climatic warming inferred from the profiles of sio2 tio2 and loi in addition la yb n ratio sree tio2 and the degree of eu anomaly correlate with each other this suggests that inflow process of particulate materials into the lake may have changed during the lgit the analytical results of this study lead to the conclusion that ree is a useful paleoenvironmental proxy in the baikal region r 2007 elsevier ltd all rights reserved

spatial distribution of helium isotopes in volcanic gases and thermal waters along the vanuatu new hebrides volcanic arc we report the first helium isotope survey of volcanic gases hot springs and some olivine phenocrysts along the vanuatu island arc from tanna in the south to vanua lava in the north low co2 content and low 3he 4he ratios in thermal fluids of epi 4 0 0 1 ra efate 4 5 0 1 ra and pentecost 5 3 0 5 ra islands coherently indicate reduced mantle gas leakage and crustal contamination by radiogenic helium on these extinct volcanic systems of the former pliocene arc instead presently active vanuatu volcanoes display 3he 4he and c 3he ratios typical of subduction related volcanic arcs 3he 4he ratios range from 6 4 0 5 ra in southernmost tanna and 7 23 0 09 ra in northernmost vanua lava to typical morb values in the central islands of gaua 7 68 0 06 ra ambrym 7 6 0 8 ra and ambae 7 2 ra in groundwaters 7 9 1 4 ra in olivine phenocrysts and 8 0 0 1 ra in summit fumaroles of aoba volcano on ambrym however we discover that hydrothermal manifestations separated by only 10 15 km on both sides of a major e w transverse fault zone crossing the island are fed by two distinct helium sources with different 3he 4he signatures while fluids in southwest ambrym baiap and sesivi areas have typical arc ratios 7 6 0 8 ra fluids on the northwest coast buama bay area display both higher 3he 4he ratios 9 8 0 2 ra in waters to 10 21 0 08 ra in bubbling gases and lower c 3he ratios that evidence a hotspot influence we thus infer that the influx of indian morb mantle beneath the central vanuatu arc from which ambrym magmas originate also involves a 3he rich hotspot component possibly linked to a westward influx of samoan hotspot material or another yet unknown local source this duality in magmatic he source at ambrym fits with the bimodal composition and geochemistry of the erupted basalts implying two distinct magma sources and feeding systems more broadly the wide he isotopic variations detected along the vanuatu arc further verify the complex tectonic and magmatic framework of this intra oceanic island arc

diatom responses to limnological and climatic changes at ribains maar french massif central during the eemian and early wurm abstract high resolution diatom analysis was carried out to assess the limnological and climatic changes that took place at ribains maar french massif central during the late pleistocene 131 105 ka bp with a focus on the eemian interglacial in particular numerical analyses were used to show that most of the variability in the fossil diatom assemblages was due to climate independently from the changes in the lake catchment vegetation as represented by pollen data diatom based quantitative reconstructions of the past limnological conditions as well as a comprehensive literature review on the auto ecological requirements for the principal diatom taxa were used to interpret the record an absolute time scale for the sequence was derived by matching the major pollen shifts with the radiometrically dated changes in oxygen isotopes observed in italian stalagmites this study shows that at ribains maar the transition from the riss saalian glacial to the eemian interglacial was marked by a gradual increase in the contribution of spring blooming diatom species indicating a longer growing season and milder winter spring conditions at that time a short cooling event interrupts this trend and may correspond to a stadial at the start of the eemian a peak in benthic taxa and the suppression of spring blooming flora probably reflects the effects of deglaciation on the catchment during the eemian interglacial itself three main phases were distinguished within the diatom record the first phase 8000 years in duration was dominated by stephanodiscus minutulus which suggests that intense mixing in the water column took place during spring the pollen record was simultaneously dominated by quercus and corylus that typify this phase as the climatic optimum of the eemian the second phase almost equal in duration to the first phase 7000 years is generally dominated by cyclotella taxa and suggests a less productive lake and much reduced period of spring mixing compared with the first phase in the pollen diagram this corresponds to an interval dominated by carpinus picea abies that indicates a cooler and wetter climate the third and last phase of the eemian 2000 year long saw the return to stephanodiscus dominated assemblages indicating a warming that may correspond to the dansgaard oeschger event 25 identified in the greenland ice core record in the early stage of the wurm glacial weichselian assemblages in the melisey i stadial 3000 year long were dominated by either aulacoseira subarctica or asterionella formosa which suggest colder spring conditions than during the late eemian but not as cold as the ones indicated by the pollen record stephanodiscus spp again dominate during the saint germain ia interstadial 5000 year long suggesting a return to the conditions that prevailed before the melisey stadial in agreement with the pollen record the record ends with the montaigu cold event which is characterised by a pinus peak in the pollen record and corresponds to a large abundance of a subarctica in the diatom sequence throughout the eemian the abundance of stephanodiscus spp which is thought to be driven by winter conditions show cyclic fluctuations that most likely match the cooling events identified in a pollen record from germany variation in insolation throughout the eemian may have been the driving factor behind the species succession observed in the diatom sequence while this study demonstrates that diatom analysis of lake sediment can provide very detailed information on long term climate change a review of the few other diatom investigations published on european eemian deposits shows that this technique has been so far seldom used to its full potential in this context in central and southern europe

estimation of the near surface velocity structure of the yasur yenkahe volcanic complex vanuatu small aperture array measurements of seismic noise at seven sites around yasur volcano vanuatu are performed to estimate the vp and vs velocities of the shallow structure the spatial autocorrelation spac and the frequency wavenumber f k methods are used to determine rayleigh phase velocity dispersion curves phase velocities computed with the spac method vary between 580 m s and 960 m s at 1 hz and between 270 m s and 420 m s at 15 hz f k dispersion curves show velocities of 300 340 m s and 800 940 m s at 1 hz and 200 230 m s at 15 hz an inversion technique based on the use of the neighbourhood algorithm has been used to calculate the one dimensional velocity model at each site velocity models reach 200 m deep and mainly contain two layers and a half space for sites close to the siwi caldera rims comparisons with geology and hydrothermal system studies suggest that the two layers highlighted in models may correspond to two large pyroclastic sequences related to caldera collapses based on the flank of an old volcano results obtained for the other three sites located inside the caldera show the influence of the hydrothermal system on p and s wave velocities for these sites fluid circulation inside the volcanic deposits causes lower velocities at depth to obtain a near surface velocity model of the volcanic structure each 1d velocity model is spatially extrapolated according to the surface geology results highlight four distinct areas the siwi caldera edges with high velocities and the resurgent block the ash plain and the yasur edifice with lower velocities at depth

copper isotope systematics of the lucky strike rainbow and logatchev sea floor hydrothermal fields on the mid atlantic ridge in this paper we present the copper isotope signatures of black smoker sulfides massive sulfides and their alteration products and provide new insights into mineralization processes and applications of copper isotope geochemistry to sea floor hydrothermal systems on the mid atlantic ridge the hydrothermal systems studied include the lucky strike field at 37 17 n on a basaltic substrate and the rainbow and logatchev fields situated on ultramafic rock copper isotope variation in the hydrothermal precipitates was examined in conjunction with s isotopes and se and co concentrations the comparison between 65cu and se contents shows that subsurface precipitation of cu rich sulfides does not control significantly the 65cu values of the hydrothermal chimneys it appears that the major cause of copper isotope fractionation in hydrothermal systems up to 3 is the sea floor oxidation of primary copper sulfides enrichment in the heavy copper isotope can be explained by processes occurring at the sea floor such as hydrothermal reworking of previously altered sulfides by high temperature fluid massive sulfides characterized by negative 65cu values have undergone extensive recrystallization in these mineralogical assemblages isotopically heavy copper typical of altered sulfides has been leached and redeposited in the external zones or incorporated in hydrothermal fluids copper isotopes are therefore a promising tool for the study of supergene processes and the recycling of previously oxidized sulfides as well as a means of characterizing the degree of hydrothermal reworking of large sulfide deposits further studies of copper isotope fractionation under controlled laboratory experimental conditions are required to identify copper isotope fractionation during sulfide alteration in particular the possible biological mediation of copper isotope fractionation during sulfide oxidation may be an important direction for further studies

copper isotope characteristics of copper rich minerals from besshi type volcanogenic massive sulfide deposits japan determined using a femtosecond la mc icp ms the copper isotope ratios of chalcopyrite secondary malachite and native copper of metamorphosed besshi type volcanogenic massive sulfide vms deposits from two different mines japan were measured by femtosecond pulsed laser ablation multiple collector inductively coupled plasma mass spectrometry fs la mc icp ms the 65cu where 65cu 65cu 63cu sample 65cu 63cu nist srm976 1 1 000 values of chalcopyrite samples of both mines are relatively narrow 0 34 to 0 29 compared to those of previously reported chalcopyrite from modern submarine hydrothermal deposits at mid oceanic ridge settings 0 98 to 3 14 however the 65cu values of chalcopyrite are slightly different between the two mines this suggests that although metamorphic reequilibration may have reduced the original range of copper isotopes premetamorphic 65cu characteristics of both mines are generally preserved the chalcopyrite samples of one deposit might be significantly affected by dissolution during reworking processes after precipitation on the sea floor secondary malachite 65cu 2 63 2 97 and native copper 65cu 1 43 1 71 have higher 65cu values than chalcopyrite from the same deposit this variation is most reasonably explained in terms of a redox controlled isotope fractionation at low temperature conditions during secondary weathering processes involving the preferential incorporation of 65cu in secondary cu ii solutions it is also suggested that significant negative isotopic fractionations accompanying the reduction of cu ii solutions to native copper cu 0 occurred

origin of sulfur and crustal recycling of copper in polymetallic cu au co bi u ag iron oxide dominated systems of the great bear magmatic zone nwt canada the great bear magmatic zone in northwest canada contains numerous polymetallic mineral occurrences prospects and deposits of the iron oxide copper gold deposit iocg family the mineralization is hosted by the treasure lake group and igneous rocks of the great bear arc and was deposited concomitantly with the arc magmatism ca 1 88 to 1 87 ga in situ 34s n 48 and 65cu n 79 analyses were carried out on ore related sulfides from a number of these systems the 34s values mainly vary between 0 and 5 consistent with derivation of sulfur from the mantle lower 34s values 7 7 to 1 4 from the sue dianne breccia may indicate so2 disproportionation of a magmatic hydrothermal fluid the 65cu values vary between 1 2 and 0 3 and are lower than the igneous 65cu range of values 0 0 0 27 the s and cu isotopic data are decoupled which suggests that cu and possibly some s was dissolved and remobilized from supracrustal rocks during early stages of alteration e g sodic alteration and then precipitated by lower temperature more oxidizing fluids e g ca fe k alteration a limited fluid inclusion dataset and 13c and 18o values are also presented the 18ofluid values are consistent with a magmatic origin or a host rock equilibrated meteoric water source whereas the 13cfluid values support a marine carbonate source combined the s and cu isotopic data indicate that while the emplacement of the great bear magmatic bodies may have driven fluid convection and may be the source of fluids and sulfur metals such as cu could have been recycled from crustal sources

inverting the source mechanism of strombolian explosions at mt yasur vanuatu using a multi parameter dataset abstract the source mechanism of strombolian explosions at mt yasur vanuatu is analyzed using a unique data set which enables us to combine different methodologies the novelty of the approach presented here lies in the combination of seismic acoustic and doppler radar data thus using infrasound and doppler radar observations we are able to provide independent estimates of the volume of the eruptive source in the following we show that a correlation exists between source volume and the maximum particle velocity of the expelled volcanic products in order to determine the source location and the associated mechanism and to compare those two methods we use time reversal imaging and moment tensor inversion while the first method also applies to extended sources the latter might be biased by its intrinsic point source approximation we show that time reversal imaging can deliver an estimate of the source depth without any a priori assumptions even in an unfavorable scenario in terms of topography and receiver setup the inverted source mechanism retrieved from moment tensor inversion is found to be largely isotropic with minor deviatoric components the inverted source location points towards an area to the north west of the active craters indicative of a common feeder system of the activity at mt yasur however it is also evident that to fully locate the source of strombolian activity at yasur location precision must be enhanced

rapid changes in ocean circulation and heat flux in the nordic seas during the last interglacial period the apparent similarity of climate variability in the north atlantic region in the last interglacial period1 5 and the present interglacial holocene has recently been challenged by the rapid oscillations in climate conditions indicated by some marine6 7 and terrestrial climate records8 10 for the last interglacial ocean circulation in the northern north atlantic seems to be intimately coupled to the processes of climate change on various time scales11 12 so that climate variability and the associated mechanisms of change should be well recorded by sediments from these high latitudes previous studies in this region5 13 have indeed indicated an apparently less stable last interglacial climate than at middle latitudes of the north atlantic ocean4 here we present detailed records from marine sediments in the nordic seas of oceanographic conditions during the last interglacial the records show three large sea surface temperature fluctuations a weakening of the east west sea surface temperature gradient with time and changes in deep water properties in contrast similar analyses of a core from the same region indicate that sea surface temperature during the holocene has been relatively stable our data along with those from the labrador sea7 indicate rapid changes in ocean circulation and oceanic heat fluxes at high northern latitudes during the last interglacial which may have been associated with marked temperature changes on adjacent continents

loss of apatite caused irreversible early holocene lake acidification lakes created by retreating ice at the end of the last glaciation underwent rapid acidification during the first few thousand years of their existence a phenomenon attributed in part to progressive leaching of soil bases since it was discovered more than 80 yeas ago though a role for leaching is still acknowledged the most recent studies see this as subordinate to the effects of biological and climatic changes initiated by deglaciation chiefly primary vegetation succession and species immigration until now there has been no quantitative test of the relative importance of these different mechanisms here i use geochemical modelling of runoff acidity to show that the extent and timing of early holocene lake acidification in eight published palaeoecological records can be explained by leaching of the calcium phosphate mineral apatite from the granitic till soils of their catchments at a rate controlled by simple dissolution kinetic factors this shows that a single progressive abiotic process is capabl

copper isotope ratios in magmatic and hydrothermal ore forming environments multi collector inductively coupled plasma mass spectrometry now provides for precise and accurate measurements of cu isotope ratios copper minerals prepared by direct dissolution with and without chromatographic purification yield identical cu isotope ratios within analytic precision of about 0 04x 1r cu isotope ratios have been measured for copper minerals from worldwide magmatic and hydrothermal copper deposits and for several weathered deposits natural variations in d65cu values relative to nbs976 range over 9x chalcopyrite samples from mafic intrusions lie within a narrow range of about 1 5x and most cluster tightly between 0 10xand 0 20x this range lies within the broader black smoker chalcopyrite and iron meteorite ranges and possibly represents a bulk mantle cu isotope ratio most values for hydrothermal native copper from the michigan native copper district also show a narrow range just larger than 0 1xand suggest a common homogeneous source for cu in this large hydrothermal system later copper sulfide and arsenide minerals from this district range to values more than 2x lower than native copper ratios for chalcopyrite and bornite from moderate to high temperature porphyry skarn and replacement deposits as a group and within individual deposits exhibit a broad range of values variations of nearly 1xare observed over distances on the order of 1 m in some cases these variations may result from multiple mineralization events or copper remobilization during retrograde or later hydrothermal activity fractionations between chalcopyrite and bornite where they occur in the same sample or in related samples cluster near 0 4x suggesting equilibrium cu isotope fractionation between them at moderate temperatures in addition weathering of hydrothermal copper minerals produces a wide range of values in secondary copper phases in the supergene environment cuprite typically has higher values than associated native copper therefore redox states appear to exert a significant control over fractionation at low temperatures significant questions remain to be answered before the source of copper in hydrothermal environments can be fully addressed source reservoir cu ratios need to be determined and chemical and physical factors that control cu isotope fractionation must be quantitatively defined d 2003 elsevier b v all rights reserved

first estimate of volcanic so2 budget for vanuatu island arc abstract the spatial and temporal coverage of measurements of volcanic gas emissions remains patchy however over the last decade emissions inventories have improved thanks to new measurements of some of the lesser known volcanic areas we report on one such region the vanuatu island arc in the southwest pacific for which we now have sufficient systematic observations to offer a systematic emissions inventory our new estimate is based on so 2 flux measurements made in the period 2004 2009 with ultraviolet spectroscopy techniques for the following volcanoes yasur lopevi ambrym ambae gaua and vanua lava from south to north these are the first ever measurements for lopevi gaua and vanua lava the results reveal the vanuatu arc as one of earth s prominent sources of volcanic degassing with a characteristic annual emission to the atmosphere of 3 tg of so 2 representing about 20 of hitherto published global estimates our new dataset highlights the sustained prodigious degassing of ambrym volcano whose 5 gg day 1 mean flux of so 2 represents nearly two thirds of the total budget for the vanuatu arc this confirms ambrym as one of the largest volcanic sources worldwide comparable to etna often considered as the most vigorous source of volcanic emission on earth we also report a high degassing for ambae of 2 gg day 1 so 2 representing more than 28 of the vanuatu arc budget thus 90 of the so 2 output from vanuatu is focused in the central part of the arc from ambrym and ambae where magmas originate from enriched indian type mantle and where peculiar tectonic conditions could favor high magma production rates

abrupt change in tropical african climate linked to the bipolar seesaw over the past 55 000 years 1 the tropics play a major role in global climate dynamics and are vulnerable to future climate change we present a record of east african climate since 55 ka preserved in lake malawi sediments that indicates rapid shifts between discrete climate modes related to abrupt warming d o events observed in greenland although the timing of the malawi events cannot be determined exactly our age model implies that they occur prior to their greenland counterparts consistent with southward excursions of the intertropical convergence zone during greenland stadials the magnitude of each of the events recorded in malawi sediments corresponds to the scale of the subsequent greenland warming this suggests that a tropical component of climate sets a template for abrupt high northern latitude climate fluctuations associated with the bipolar seesaw

development of an eemian mis 5e interglacial palaeolake at sokli n finland inferred using multiple proxies a 12 m long lacustrine record from sokli n finland was analyzed for diatoms non pollen palynomorphs macrofossils pollen and geochemistry in order to reconstruct the development of a high latit

characteristics of cu isotopes from chalcopyrite rich black smoker chimneys at brothers volcano kermadec arc and niuatahi volcano lau basin we analysed primary chalcopyrite from modern seafloor black smoker chimneys to investigate high temperature hydrothermal cu isotope fractionation unaffected by metamorphism samples came from nine chimneys collected from brothers volcano kermadec arc and niuatahi volcano lau backarc basin this is the first known study of cu isotopes from submarine intraoceanic arc backarc volcanoes with both volcanoes discharging significant amounts of magmatic volatiles our results n 22 range from 65cu 0 03 to 1 44 0 18 2 sd with the majority of samples between 0 00 and 0 50 we interpret this cluster n 17 of lower 65cu values as representing a mantle source for the chimney cu in agreement with 65cu values for mantle rocks the few higher 65cu values 0 90 occur 1 within the same chimneys as lower values 2 randomly distributed within the chimneys i e near the top and bottom interior and exterior and 3 within chalcopyrite of approximately the same age 1 year this suggests the higher 65cu values are not related to oxidation by mixing with ambient seawater but to isotopic variation within the vent fluids over a relatively short time theoretical studies demonstrate significant isotopic fractionation can occur between aqueous and vapourous complexing species when combined with evidence for periodic release of magmatic volatiles at brothers we believe vapour transport of cu is responsible for the observed isotopic fractionation when compared to global 65cu data for primary chalcopyrite volcanic arc chimneys are most similar to porphyry copper deposits that also form from magmatic hydrothermal processes in convergent tectonic settings

controls on supergene enrichment of porphyry copper deposits in the central andes a review and discussion the central andes host some of the world s largest porphyry copper deposits the economic viability of these deposits is dependent on the size and quality of their supergene enrichment blanket published models that have strongly influenced exploration policy suggest that supergene enrichment ceased at 14 ma due to an increase in aridity here we discuss these models using published geochronological geomorphological and geological data geochronological data indicate that supergene oxidation and enrichment has been active between 17 and 27 s across the forearc of northern chile and southern peru from 44 to 6 ma and on the bolivian altiplano and eastern cordillera of argentina from 11 ma to present there is evidence for cessation at 20 14 and 6 ma however a major problem is that as more geochronological data become available the age ranges and periods of enrichment increase this suggests that the full spectrum of enrichment ages may not have been sampled the relationship between supergene enrichment and the age of regional pediplain surface development is not well constrained only in two areas have surfaces related to enrichment been directly dated southern peru and south of 26 s in chile and suggest formation post 14 ma sedimentological data indicate that a fluctuating arid semi arid climate prevailed across the atacama desert until between 4 and 3 ma climatic conditions that are thought to be favourable for supergene enrichment the balance between uplift erosion burial and sufficient water supply to promote enrichment is complex this suggests that a simple model for controlling supergene enrichment is unlikely to be widely applicable in northern chile general models that involve climatic desiccation at 14 ma related to rainshadow development and or the presence of an ancestral cold upwelling humboldt current are not supported by the available geological evidence the integration of disparate sedimentological geomorphological and supergene age data will be required to fully understand the controls on and distribution of supergene oxidation and enrichment in the central andes

variation in copper isotope ratios and controls on fractionation in hypogene skarn mineralization at coroccohuayco and tintaya peru hypogene chalcopyrite and bornite in copper skarn and related porphyry ore from coroccohuayco and tintaya peru have been analyzed for copper isotope ratios fifty six samples have a range in 65 cu values of 1 29 to 2 98 per mil relative to nist srm 976 using the sample standard bracketing technique to correct for machine drift and machine isotope fractionation effects the range of 65 cu values of vein hosted mineralization at coroccohuayco overlaps with disseminated mineralization in skarn ore but also extends to lower values the overlap of these ranges indicates that different mineralizing events in these deposits cannot be identified solely by their copper isotope compositions geologic and isotopic considerations of the samples analyzed in this investigation indicate that copper mineralization proximal to fluid sources including porphyries and principal fluid pathways tends to be isotopically lighter than more distal samples this suggests that important copper isotope fractionation occurred during mineralization and may have been the result of equilibrium fractionation and or indirect fractionation mechanisms related to the chemical characteristics of the hydrothermal fluid these fractionation mechanisms have produced copper isotope zonation over tens of meters in hypogene ore during the process of ore precipitation at coroccohuayco

high resolution x ray fluorescence core scanning analysis of les echets france sedimentary sequence new insights from chemical proxies the les echets sediment sequence has recently been the subject of a high resolution multi proxy study which revealed shifts in lake productivity linked to greenland stadials and interstadials over the last 40 ka wohlfarth et al 2008 rapid ecosystem response to abrupt climate changes during the last glacial period in western europe 40 16 ka geology 36 407 410 here we present new elemental data for this sequence as acquired using an x ray fluorescence core scanning system which provides in situ high resolution continuous multi element analyses it was found that the strength of associations between the studied elements ti rb k zr si ca sr mn and fe varied over time with changes in lake status which are ultimately driven by changes in climate increases in fine grained detrital input as indicated by ti rb k and zr rb overlap with independently established periods of lower lake productivity and are interpreted to represent more arid conditions several of these arid periods are coincident with low diatom concentrations and the timing of heinrich events h4 h3 and h2 the duration of the environmental impacts linked to the h events varied by proxy with elemental data ti and zr rb estimating shorter events than the diatom data periods of lower detrital input and coarser grain sizes agreed in time with periods of higher lake productivity the elemental data provide new insights into hydrological changes and related sediment processes within the catchment and highlight the need for multi element and multi proxy approaches when reconstructing climate change using lacustrine sediment sequences copyright 2011 john wiley sons ltd

cu isotopes and concentrations during weathering of black shale of the marcellus formation huntingdon county pennsylvania usa abstract the complex weathering processes which govern the production of soil from bedrock have proven difficult to understand for many lithologies weathering of black shale is of particular interest because it releases organic carbon and heavy metals as solutes and therefore impacts the health of terrestrial and aquatic ecosystems to understand black shale weathering a geochemical survey was initiated for soils developed on shales of the marcellus formation at a zero order catchment at a satellite site of the susquehanna shale hills critical zone observatory located in jackson corner pennsylvania this formation is an organic and metal rich carbonaceous shale that underlies much of new york pennsylvania ohio and west virginia in this paper we focus on the effects of weathering on variations of cu isotopes in the shale cu concentration data for soil were normalized using ti concentrations to document the mobility of cu relative to bedrock at both the ridgetop and valley floor depletion profiles for cu are documented in the soils the cu in the soils is depleted in 65 cu average 65 cu 0 5 0 2 compared to the parent material average 65 cu 0 03 0 15 consistent with loss of cu from soils the pore waters contain 10 ppb cu on average and are enriched in the heavy isotope average value 65 cu 1 14 0 44 rayleigh fractionation models using the concentration and isotope data of the soils are consistent with pyrite weathering and loss of cu from the ridgetop but downslope transport and cu re precipitation at the valley floor

eemian lake development hydrology and climate a multi stratigraphic study of the hollerup site in denmark abstract a classic northwest european open section with lacustrine eemian sediments hollerup has been studied with respect to sedimentology geochemistry stable isotopes diatoms and mineral magnetic analyses and correlated by geochemistry and diatoms to a previously pollen analysed section by andersen 1965 this correlation has enabled the section to be related to muller s 1974 tentative eemian absolute chronology and shows that the hollerup eemian sediments appear to cover c 11 000 yr our studies show that the onset of the eemian was characterized by a major lake level rise followed by an almost 3000 yr long period of high but oscillating lake levels it is argued that the latter part of this period of highly maritime climate can be defined as the eemian climatic optimum this period was interrupted by a few hundred years long phase of low lake level coinciding with the immigration of spruce followed by medium high lake levels the next c 3500 yr coinciding with the carpinus pollen zone seem to have been characterized by fairly humid and mild conditions although slightly more arid than during the preceding optimum the carpinus period ended with a more than 1000 yr long gradual lake level fall and this period of lake level change concurring with the transition into the pinus pollen dominated period terminated with an extreme low lake level event this 300 500 yr long arid phase coincides with a distinct peak in pine pollen and was followed by higher but slightly oscillating lake levels in a cooler climate the end of the eemian seems to have been characterised by a gradual cooling until almost pure clastic sedimentation and a marked expansion of herb pollen grains mark the onset of the weichselian based on regional correlations to other european terrestrial and north atlantic marine proxy records we argue that the distinct hydrologic and climatic events displayed in the hollerup record were possibly caused by a combination of sea level changes changes in the hydrologic cycle and changing oceanic circulation patterns the latter two may have been triggered by the opening and closure of the baltic sea white sea connection the initial build up of continental ice sheets and the first major impacts of meltwater induced freshwater in key areas for thermohaline circulation

pleistocene recycling of copper at a porphyry system atacama desert chile cu isotope evidence we present cu isotope data of hypogene and supergene minerals from the late paleocene spence cu mo porphyry in the atacama desert of northern chile chalcopyrite displays a restricted range of 65cu values within the values reported for primary porphyry cu sulfides 0 28 to 0 34 n 6 supergene chalcocite samples show heavier and remarkably homogeneous 65cu values between 3 91 and 3 95 n 6 consistent with previous models of cu leaching and enrichment in porphyry systems secondary cu minerals from the oxide zone show a wider range of composition varying from 1 28 and 1 37 for chrysocolla n 6 to very light cu isotope signatures reported for atacamite between 5 72 to 6 77 n 17 these data suggest redox cycling of cu during supergene enrichment of the spence cu deposit characterized by a first stage of supergene chalcocite formation from acidic isotopically heavy leach fluids of meteoric origin down flowing in a semi arid climate 44 to 15 9 ma reworking of the initial supergene copper assemblage during the pleistocene by rising neutral and chlorine rich deep formation waters under well established hyper arid climate conditions lead to the formation of atacamite with extremely fractionated cu compositions essentially coeval chrysocolla formed by dissolution of atacamite during short episodes of wetter climatic conditions occurring in the latest pleistocene

blast waves from violent explosive activity at yasur volcano vanuatu 1 infrasonic and seismic waveforms were collected during violent strombolian activity at yasur volcano vanuatu averaging 3000 seismic events showed stable waveforms evidencing a low frequency 0 1 0 3 hz signal preceding 5 6 s the explosion infrasonic waveforms were mostly asymmetric with a sharp compressive 5 106 pa onset followed by a small long lasting rarefaction phase regardless of the pressure amplitude the ratio between the positive and negative phases was constant these waveform characteristics closely resembled blast waves infrared imagery showed an apparent cold spherical front 20 m thick which moved between 342 and 405 m s before the explosive hot gas fragments cloud we interpret this cold front as that produced by the vapor condensation induced by the passage of the shock front we suggest that violent strombolian activity at yasur was driven by supersonic dynamics with gas expanding at 1 1 mach number inside the conduit

explosive volcanic activity at mt yasur a characterization of the acoustic events 9 12th july 2011 abstract volcanic processes occur in a wide range of temporal and spatial scales however a key step of magma ascent is recognizable in the dynamics of gas and magma in the shallow plumbing system where volatiles play a fundamental role in controlling the eruptive style with the aim of investigating shallow degassing processes an experimental setup was deployed at mt yasur an active volcano located in tanna island vanuatu arc from 9th to 12th july 2011 the setup comprised high speed and thermal cameras as well as a microphone capable of recording both in the infrasonic and audible range the analysis of acoustic signals validated by observing images from the high speed and thermal cameras has enabled characterizing the explosive activity during the investigated period two types of explosions distinct for spectral features and waveforms were observed i minor events corresponding to small overpressurized bursts occurring almost continuously ii major events characterizing the strombolian activity at mt yasur by investigating variation in the occurrence rate of the minor events we found that on a short timescale the dynamics responsible for the two types of explosions are decoupled these results together with previous literature data bring additional evidence of the existence of distinct sources of degassing finally major events can be distinguished as emergent events i e long lasting signals corresponding to ash rich explosions and impulsive events featuring shorter duration and larger amplitude

strombolian surface activity regimes at yasur volcano vanuatu as observed by doppler radar infrared camera and infrasound abstract in late 2008 we recorded a continuous multi parameter data set including doppler radar infrared and infrasound data at yasur volcano vanuatu our recordings cover a transition in explosive style from ash rich to ash free explosions followed again by a phase of high ash discharge to assess the present paradigm of strombolian behavior in this study we investigate the geophysical signature of these different explosive episodes and compare our results to observations at stromboli volcano italy to this end we characterize yasur s surface activity in terms of material movement temperature and excess pressure the joint temporal trend in these data reveals smooth variations of surface activity and regime like persistence of individual explosion forms over days analysis of all data types shows ash free and ash rich explosive styles similar to those found at stromboli volcano during ash free activity low echo powers high explosion velocities and high temperatures result from the movement of isolated hot ballistic clasts in contrast ash rich episodes exhibit high echo powers low explosion velocities and low temperatures linked to the presence of colder ash rich plumes furthermore ash free explosions cause high excess pressure signals exhibiting high frequencies opposed to low amplitude low frequency signals accompanying ash rich activity to corroborate these findings we compare fifteen representative explosions of each explosive episode explosion onset velocities derived from doppler radar and infrared camera data are in excellent agreement and consistent with overall observations in each regime examination of infrasound recordings likewise confirms our observations although a weak coupling between explosion velocity and excess pressure indicates changes in wave propagation the overall trend in explosion velocity and excess pressure however demonstrates a general correlation between explosive style and explosion intensity and points to stability of the uppermost conduit on timescales shorter than at stromboli volcano