geothermal energy and ore forming potential of 600 c mid ocean ridge hydrothermal fluids the 4500 m deep iceland deep drilling project iddp borehole iddp 2 in iceland penetrated the root of an active seawater recharged hydrothermal system below the mid atlantic ridge as direct sampling of pristine free fluid was impossible we used fluid inclusions to constrain the in situ conditions and fluid composition at the bottom of the hydrothermal convection cell the fluid temperature is 600 c and its pressure is near hydrostatic 45 mpa the fluid exists as two separate phases an h2o rich vapor with an enthalpy of 59 4 kj mol and an fe k rich brine containing 2000 g g cu 3 5 g g ag 1 4 g g u and 0 14 g g au occasionally the fluid inclusions coexist with rhyolite melt inclusions these findings indicate that the borehole intersected high energy steam which is valuable for energy production and discovered a potentially ore forming brine we suggest that similar fluids circulate deep beneath mid ocean ridges worldwide and form volcanogenic massive sulfide cu zn au ag ore deposits

recent developments in element concentration and isotope ratio analysis of individual fluid inclusions by laser ablation single and multiple collector icp ms abstract laser ablation inductively coupled plasma mass spectrometry la icp ms has become a most powerful technique for the elemental analysis of individual polyphase inclusions completely enclosed in minerals be they solid or a solid liquid gas mixture at the time of measurement simultaneous accurate quantification of major to ultra trace element concentrations from li to u by well controlled ablation of the entire fluid or melt inclusion content and successful use of largely matrix independent external calibration protocols are unique features of this method this contribution reviews fluid inclusion fundamentals relevant for their bulk analysis by la icp ms and discusses key aspects of the analytical protocol emphasis is on figures of merit precision accuracy obtained from the analysis of individual inclusions and fluid inclusion assemblages and procedures and technical developments to improving data quality are elaborated a new equation for the calculation of detection limits for la icp ms analysis is presented which closely follows iupac conventions applications are reviewed with emphasis on the use of synthetic fluid inclusions in constraining metal solubility and distribution between co existing phases new data for natural bismuth fluid inclusions document the seamless transition to melt inclusion analysis by la icp ms thus highlighting the fact that the procedures presented here are generally applicable to the analysis of inclusions in complex host minerals isotope ratio analysis of individual fluid inclusions by multicollector icp ms mc icp ms is a recent development that requires fast transient signals to be accurately recorded by instrumentation designed for high precision static measurements of long lasting stable ion beams we address the general principles based on pb isotopes and review a first application to the bingham canyon porphyry cu au mo deposit a pilot study using about 50 synthetic fluid inclusions containing srm 987 sr and variable nacl ca and rb concentrations demonstrates that accurate 87 sr 86 sr isotope ratios can be obtained on an individual rb poor fluid inclusion at absolute 2 precisions of 0 0003 to 0 002 a residual trend in 87 sr 86 sr as a function of the rb sr abundance ratio in the fluid inclusions suggests that interference correction of 87 rb on mass 87 assuming identical mass bias coefficients for the two elements may be inaccurate however the offset can be accurately corrected for by regressing the data to zero 87 rb the versatility and detection power of la icp ms makes this technique the method of choice for solute abundance and isotope ratio analysis of individual fluid inclusions significant future progress can be achieved by improvements in ion production transmission and data recording efficiency and by further improving control on inclusion ablation by pulsed laser beams data quantification strategies may also have to be further refined to keep pace with instrumental progress and innovation

synthetic fluid inclusions in natural quartz iii determination of phase equilibrium properties in the system h2o nacl to 1000 c and 1500 bars phase equilibria in the system h2o nacl have been determined to 1000 c and 1500 bars using synthetic fluid inclusions formed by healing fractures in inclusion free brazilian quartz in the presence of the two coexisting immiscible h2o nacl fluids at various temperatures and pressures petrographic and microthermometric analyses indicate that the inclusions trapped one or the other of the two fluids present or mixtures of the two salinities of the two coexisting phases were obtained from heating and freezing studies on those inclusions which trapped only a single homogeneous fluid phase results of the present study are consistent with previously published data on the h2o nacl system at lower temperatures and pressures and indicate that the two phase field extends well into the p t range of most shallow magmatic hydrothermal activity as a consequence chloride brines exsolved from many epizonal plutons during the process of second boiling should immediately separate into a high salinity liquid phase and a lower salinity vapor phase and produce coexisting halite bearing and vapor rich fluid inclusions this observation is consistent with results of numerous fluid inclusion studies of ore deposits associated with shallow intrusions particularly the porphyry copper deposits in which halite bearing and coexisting vapor rich inclusions are commonly associated with the earliest stages of magmatic hydrothermal activity

δ15n of n2 in air trapped in polar ice a tracer of gas transport in the firn and a possible constraint on ice age gas age differences with respect to gas transport the fim near the surface of an ice sheet can be divided into three zones the uppermost is a convective zone located just below the surface of the ice sheet in which the air is rapidly flushed by convective exchange with the overlying atmosphere below the convective zone there is a diffusive air column in which diffusion is rapid but there is no convection between the bottom of the diffusive air column and the bubble close off region there may be a nondiffusive zone in which diffusion is so slow that negligible gas transport occurs the diffusive air column is characterized by progressive enrichment with depth of 15n in n2 and heavy isotopes of gases in general as predicted using the barometric equation in this paper we present data on the 15n of n2 in recently trapped air samples from 12 ice cores along with numerous downcore samples from byrd vostok and dome c bubble close off depths for these cores calculated from a densification model ranged from 51 to 114 meters below the surface mbs we used these data and the barometric equation to calculate the thickness of the diffusive air column and found that it comprised 46 to 93 of the total firn thickness at our study sites paleo close off depths calculated from the densification model for glacial sections of byrd vostok and dome c are 15 25 m deeper than close off depths today diffusive column heights calculated from 15n varied in a more complex manner the diffusive column height at byrd appears to have decreased from 74 m during the last glacial period to 50 m during the holocene at vostok and dome c the diffusive column height calculated from 15n increase from about 65 m during the last glacial period to about 80 m in the holocene we use records of surface temperature and co2 at byrd and vostok along with their respective chronologies to constrain the ice age gas age difference age throughout the section of the vostok ice core corresponding to the last glacial termination in principle age values calculated from these data can be used to discriminate whether gas in the fim mixes to the bubble close off depth or to a depth equivalent to the diffusive column height in practice however uncertainties in the chronology of byrd and vostok are too great to allow us to distinguish between these two possibilities one can only say that at the time of the last termination age for vostok was between 3 and 10 5 kyr previous estimates fall within this range

calibrating the ice core paleothermometer using seasonality high resolution oxygen isotope measurements on the dome summit south dss ice core from law dome antarctica provide a seasonal profile that is sufficiently stable and undistorted by biases in accumulation to permit comparison with measured temperature seasonality this comparison yields an isotope temperature relation with a gradient d dt of 0 44 0 02 c and provides a new method for exploring the isotope temperature relationship at high accumulation sites if applied to the observed isotope record from the dss core which extends through the last glacial and beyond this calibration suggests that at its coldest the last glaciation was 13 c colder than present at this site after correcting for elevation change this finding compares with a temperature difference of 8 c computed by using the local spatially derived calibration

electrical resistivity sounding of the east antarctic ice sheet electrical resistivity soundings using a schlumberger array have been carried out at dome c east antarctica 74 39 s 124 10 e elevation 3400 m to sound the entire 3500 m depth of the ice sheet changes in density and temperature are largely separated in the ice at dome c so activation energies for both firn and ice could be determined we find an activation energy of 0 25 ev in both solid ice and firn between 15 c and 58 c a common value of the activation energy points to a single transport regime in which the charge carriers and conduction paths are the same in firn and ice to evaluate the variation of resistivity with density we have considered five dielectric mixture models that fit the available data on the high frequency dielectric constant of firn only looyenga s equation fits the field data for dc resistivity in the upper 900 m of the ice sheet where impurity concentrations are known from core samples we find no correlation between resistivities and the concentrations of salts or acids instead we find it likely that resistivities are correlated with the crystal size hence with the holocene wisconsin boundary in the ice column a pronounced increase in resistivity to a value comparable with that in temperate glacier ice occurs deep within the ice sheet we attribute this to a large increase in the size and irregularity of the ice crystals which destroys the continuity of the impurity shells surrounding the ice crystals that we believe supply the conduction paths shabtaie and bentley 1994a high resistivity does not imply removal of the impurities from the system moderate concentrations of impurities can be accommodated by locating them in disconnected domains

middle and low latitude ionosphere response to 2015 st patrick s day geomagnetic storm this paper presents a study of the st patrick s day storm of 2015 with its ionospheric response at middle and low latitudes the effects of the storm in each longitudinal sector asian african american and pacific are characterized using global and regional electron content at the beginning of the storm one or two ionospheric positive storm effects are observed depending on the longitudinal zones after the main phase of the storm a strong decrease in ionization is observed at all longitudes lasting several days the american region exhibits the most remarkable increase in vertical total electron content vtec while in the asian sector the largest decrease in vtec is observed at low latitudes using spectral analysis we were able to separate the effects of the prompt penetration of the magnetospheric convection electric field ppef and of the disturbance dynamo electric field ddef on the basis of ground magnetic data concerning the ppef earth s magnetic field oscillations occur simultaneously in the asian african and american sectors during southward magnetization of the b z component of the interplanetary magnetic field concerning the ddef diurnal magnetic oscillations in the horizontal component h of the earth s magnetic field exhibit a behavior that is opposed to the regular one these diurnal oscillations are recognized to last several days in all longitudinal sectors the observational data obtained by all sensors used in the present paper can be interpreted on the basis of existing theoretical models

changing brine inputs into hydrothermal fluids southern cleft segment juan de fuca ridge author s wheat cg zierenberg ra paduan jb caress dw clague da chadwick ww abstract 2020 the authors in 2016 temperature recorders were recovered temperatures were measured and fluid samples were collected from vent 1 a high temperature 338 c hydrothermal discharge site on the southern cleft segment of the juan de fuca ridge coupled with previous sampling efforts this collection represents a 32 year record of discharge from a single chimney structure the longest record to date remarkably the fluid has remained brine dominated for more than three decades this brine formed during phase separation and segregation prior to initial observations in 1984 although the chloride concentration of the discharging fluid has decreased with time the fluid temperature has remained nearly constant for at least 3 3 years and probably for 15 or even 22 years compositions of the discharging fluids are consistent with inputs from a deep sourced brine which was last equilibrated at g400 c at a depth consistent with the base of the sheeted dikes and the brittle ductile transition this brine mixed diffusion or dispersion with a likely non phase separated hydrothermal fluid prior to discharge a survey of hydrothermal endmember fluids with chlorinities in excess of 700 mmol kg shows with the exception of fe a single trend between major ion concentrations and chlorinity even though data are from a range of crustal compositions spreading rates and water and magma depths calculated deep sourced brines from hydrothermal fluid data are similar to data based on fluid inclusions and estimates of brine assimilation in magmas a better understanding of brines is required given their potential duration of discharge and capacity for mobilizing metals

features of meteorological events preserved in a high resolution law dome east antarctica snow pit snow pitandshallow firn corerecordsofoxygenisotoperatios d 18 o and traceionspeciesweregeneratedatahigh accumulationsiteonlaw dome eastantarctica concordancebetweenaccumulationeventsidentifiedin recordsupto 7 7kmapartconfirms that the observed glaciochemical variations are the result of regional rather than local sur face effects this allows calibration of the snow pit records with measured meteorological parameters netaccumulationperiodsthatcomprisethesnow pitrecordareidentifiedusing hourly snow accumulation measurements from a co located automatic weather station aws particular focus isgiventothreenetaccumulationperiods preservedduringaustral summer 1999 2000 that correspond to the top 0 5m of the snow pit local meteorological conditions recorded during the summer accumulation periods by the aws are combined with regional and synoptic scale meteorology derived from casey station 110km away and advancedvery high resolution radiometer satellite imagery to identify potential source regions forchemical signals preserved in summer snowat law dome

gold enrichment in active geothermal systems by accumulating colloidal suspensions the origins of high grade hydrothermal ore deposits are debated but active geothermal systems provide important clues to their formation the highest concentrations of gold are found in geothermal systems with direct links to island arc magmatism yet similar concentrations have also been found in the absence of any input from arc magmas for example in the reykjanes geothermal field iceland here we analyse brine samples taken from deep wells at reykjanes and find that gold concentrations in the reservoir zone have increased over the past seven years from an average of 3 ppb to 14 ppb the metal concentrations greatly exceed the maximum solubility of gold in the reservoir under saturated conditions and are now nearly two orders of magnitude higher than in mid ocean ridge black smoker fluids the direct analogues of reykjanes deep liquids we suggest that ongoing extraction of brine the resulting pressure drop and increased boiling have caused gold to drop out of solution and become trapped in the reservoir as a colloidal suspension this process may explain how the stock of metal in the reservoirs of fossil geothermal systems could have increased over time and thus become available for the formation of gold rich ore deposits

heterogeneous melt and hypersaline liquid inclusions in shallow porphyry type mineralization as markers of the magmatic hydrothermal transition cerro de pasco district peru recently identified occurrences of porphyry style mineralization evidence the link of the world s second largest known epithermal base metal cerro de pasco deposit peru to a porphyry system emplaced at depth they consist of i quartz monzonite dykes and ii the south western part of the large diatreme dome complex adjacent to the main ore bodies of cerro de pasco and iii stockwork of banded quartz magnetite chalcopyrite pyrite porphyry type veinlets crosscutting trachyte porphyritic intrusion cropping out at surface in the central part of the diatreme dome complex the latter porphyry type mineralization observed at the same erosion level as the main epithermal base metal carbonate replacement ore bodies is the subject of this work geological constraints indicate a shallow emplacement level depth 1 km p 270 bar implying rather unusual low pressure and high temperature environment for the formation of porphyry style mineralization the banded porphyry type veinlets record a multiphase history of formation with two successive high temperature n600 c stages followed by a lower temperature b350 c stage more than 90 of the quartz in veinlets precipitates during the first two high temperature stages stage 1 is characterized by the entrapment in hydrothermal quartz of inclusions containing variable proportions of both silicate melt and metal rich hypersaline n90 wt nacl eq liquid hereafter referred to as heterogeneous silicate melt inclusions hsmis the latter are rarely described in porphyry type mineralization we suggest that during stage 1 the inclusions result from heterogeneous entrapment of an evolved hydrous rhyolitic melt mixed with a hypersaline fluid phase at low pressure 270 bar and high temperature n600 c the stage 2 is marked by the entrapment of metaland sulfur rich hypersaline liquid inclusions with salinity around 70 wt nacl eq originated from the adiabatic ascent of magmatic hypersaline fluids transferred fromdeeper parts of the system the lower temperature stage 3 is characterized by an important temperature drop from n600 c to b350 c as revealed bymicrothermometry of aqueous two phase liquid vapor l v inclusions quartz textures revealed by sem cl imaging allowascribing the sulfide precipitation to the low temperaturemineralization stage 3 in situ sims 18o 16o isotope analyses of quartz across the veinlets are indicative of a magmatic signature of the fluids during the first two stages while quartz from stage 3 has oxygen isotopic compositions suggestive of minor contribution of meteoric waters to a predominantly magmatic aqueous fluid 10 vol of meteoric input which probably triggered cu fe sulfide precipitation in the stockwork high metal and sulfur contents of hsmis and hypersaline liquid inclusions determined by la icp ms are interpreted to represent the fluid composition prior to the main sulfide precipitation event the similar pb zn ratio of the bulk ore extracted from the epithermal ore bodies at cerro de pasco and the hsmis and hypersaline liquid inclusions suggest a common source of the fluids associated with the different mineralization styles at cerro de pasco

ice flow at the dome c ice divide based on a deep temperature profile we calculate the temperature distribution with depth at the dome c ice divide east antarctica for a number of vertical strain rate functions assuming two dimensional flow to solve the heat equation we use the dome c oxygen isotope profile and radar data to specify the surface and basal boundary conditions respectively two different sets of simple monotonie polynomials are used as strain rate test functions for a net surface warming of about 9 c through the wisconsinan holocene climatic transition we find that the best agreement to the measured 800 m dome c temperature profile results from a vertical strain rate of the form 1 z h p with h the ice thickness and p 2 5 using dated horizons in the oxygen isotope profile obtained by cross correlation with a marine sediment core we find virtually no change in accumulation rate at dome c since the end of the wisconsinan glacial

planetary magnetic signature of the storm wind disturbance dynamo currents ddyn 1 during magnetic storms joule heating and ion drag in auroral zones strongly influence the circulation of thermospheric neutral winds joule heating produces equatorward neutral winds at f region heights with return flow at e region altitudes around the equator the so called hadley cell the modified thermospheric circulation produces upwelling of molecule enriched air at high latitudes and global changes in the atmospheric composition the equatorward neutral winds extending from the auroral zone to mid and low latitudes through the coriolis force create westward storm wind which drives an equatorward dynamo current in this paper we detect for the first time in the three longitude sectors the planetary magnetic signature ddyn of ionospheric disturbance dynamo with its main features 1 the decrease of the equatorial electrojet due to a westward electric current flow opposite to the regular eastward current flow and 2 the equatorward ionospheric disturbance dynamo currents at midlatitudes

diatom evidence for late holocene climatic events in granite harbor antarctica downcore diatom data from a deep basin in granite harbor antarctica provide new high resolution information concerning changes in oceanographic and depositional processes that have occurred during approximately the last 1250 years the influence of global scale climatic change during the time of the medieval warm period and possibly the little ice age is revealed by long term changes in floral assemblages as recorded by changes in the relative concentration of nitzschia cylindrus the diatom data suggest that granite harbor experienced less annual ice and pack ice cover during both these periods possibly because of higher temperatures during the medieval warm period and stronger offshore winds during the little ice age the sedimentary record reveals several distinct short lived events in which nearly monospecific blooms of corethron criophilum and chaetoceros spp occurred possibly the result of strong stabilization of the upper water column and were most likely a response to regional rather than global conditions although short lived these events may play a significant role in the delivery of organic carbon and biogenic silica to the seafloor

decadal timescale links between antarctic peninsula ice core oxygen 18 deuterium and temperature the antarctic peninsula region has exprienced a long term warming trend over the twentieth century with the 1971 90 mean at faraday being 1 9 c warmer than the mean over 1903 41 based on expedition reports for the period prior to 1900 there is conflicting evidence from different data sources an initial interpretation of isotopic data from ice cores suggests that the nineteenth century was warmer than the twentieth century in contrast snow accumulation rate data for the nineteenth century from the same ice cores suggest lower temperatures here we investigate these facts by studying the links between atmospheric temperature over the antarctic peninsula circulation parameters and isotopic data over the period of instrumental records we show that the relationships between these variables are complex and highly spatially variable in particular the correlations between temperature and 18o and d are generally of the order r 0 5 or less on timescales of one to five years conflicts between evidenc

wally was right predictive ability of the north atlantic conveyor belt hypothesis for abrupt climate change linked abrupt changes of north atlantic deep water formation north atlantic sea ice extent and widespread climate occurred repeatedly during the last ice age cycle and beyond in response to changing freshwater fluxes and perhaps other causes this paradigm developed and championed especially by w s broecker has repeatedly proven to be successfully predictive as well as explanatory with high confidence much work remains to fully understand what happened and to assess possible implications for the future but the foundations for this work are remarkably solid

distribution patterns of the elements in the ocean a synthesis the observed partition patterns of elements between a marine solid phase e g pelagic clays deep sea manganese nodules seamount manganese crusts and plankton and seawater can be to the first approximation explained by the james and healy adsorption model except for ce co mn pb and tl which are concentrated in the solid phase through oxidative uptake processes in other words the composition of seawater is mainly controlled by the compositions of source materials i e the crustal igneous rocks and primary magmatic volatiles and the physicochemical principles regulating the adsorption processes of various chemical species in seawater onto oceanic pelagic clays

the iceland deep drilling project at reykjanes drilling into the root zone of a black smoker analog the aim of the iceland deep drilling project is to drill into supercritical geothermal systems and examine their economic potential the exploratory well iddp 2 was drilled in the reykjanes geothermal field in sw iceland on the landward extension of the mid atlantic ridge the reykjanes geothermal field produces from a 300 c reservoir at 1 to 2 5 km depth and is unusual because it is recharged by seawater the well was cased to 3000 m depth and then angled towards the main up flow zone of the system to a total slant depth of 4659 m 4500 m vertical depth based on alteration mineral assemblages joint inversion of wireline logging and rate of heating measurements the bottom hole temperature is estimated to be about 535 c the major problem encountered during drilling was the total loss of circulation below 3 km depth and continuing to the final depth drilling continued without recovering drill cuttings consequently spot coring provided the only deep rock samples from the well these cores are characteristic of a basaltic sheeted dike complex with hydrothermal alteration mineral assemblages that range from greenschist to amphibolite facies hornblende hornfels and pyroxene hornfels allowing the opportunity to investigate water rock interaction in the active roots of an analog of a submarine hydrothermal system as they have not yet been sampled the composition of the deep fluids at reykjanes is unknown at present cold water is currently being injected with the aim of enhancing permeability at depth before allowing the well to heat up prior to flow tests planned for early 2019 the well has at least two fluid feed zones a dominant one at 3 4 km depth and a second smaller one at 4 5 km extensive geophysical surveys of the reykjanes peninsula completed recently allow correlation of geophysical signals with rocks properties and in situ conditions in the subsurface earthquake activity monitored with a local seismic network during drilling the iddp 2 drilling detected abundant small earthquakes ml 2 within the depth range of 3 5 km a zone at 3 5 km depth below the producing geothermal field that was generally aseismic prior to drilling but became seismically active during the drilling the drilling of the iddp 2 has achieved number of scientific and engineering firsts it is the deepest and hottest drill hole so far sited on an active mid ocean spreading center it penetrated an active supercritical hydrothermal environment at depths analogous to those postulated as the high temperature reaction zones feeding black smoker systems

non climate influences on stable isotopes at taylor mouth antarctica the late holocene trends in 18 o differ significantly in two ice cores 30 km apart from the area of taylor dome antarctica it is unlikely that the trend in the core from taylor mouth the flank site is due to a standard 18 o surface temperature relationship assuming that the taylor dome near summit core records local climate variations common to both cores we assess two leading possible causes for the observed differences 1 relative to taylor dome taylor mouth may collect snow from more sources with distinct isotopic compositions 2 vapor motion during prolonged near surface exposure may cause post depositional isotope enrichment at taylor mouth where the accumulation rate is low our model of firn pore space vapor and sublimating ice grains suggests that post depositional processes can modify 18 o values by several o isotopic samples from areas with significantly different accumulation rates near taylor mouth could differentiate between possibilities 1 and 2

signature of the coronal hole near the north crest equatorial anomaly over egypt during the strong geomagnetic storm 5 april 2010 in this paper we study the ionospheric magnetic disturbance during a strong magnetic storm on 5 april 2010 associated to a coronal hole the earth was under the influence of a high speed solar wind stream during four days and imf was southward during a very long period the variation of the disturbed magnetic observations and gps tec are compared with the variation of quiet days during the same month in order to obtain the characteristics of gps tec and magnetic disturbances due to the coronal hole effect we use multi instruments as scinda gps station at helwan egypt 29 86 n 31 32 e and asw magdas station at aswan egypt 23 59 n 32 51 e in the equatorial region at the beginning of the storm our data highlights the effect of the prompt penetration of the magnetosphere electric field which strongly increases the tec during the recovery phase of the storm we observe on tec and magnetic data the signature of the ionospheric disturbance dynamo due to wind produced by joule heating in the auroral zone it is the first time that we observe an anti sq circulation on magnetic data during four consecutive days associated to the high speed solar wind streams

a 400 years isotope record of the antarctic peninsula climate a 400 year deuterium record has been obtained from a 154 3 m ice core drilled on dalinger dome james ross island antarctic peninsula based on a comparison between the isotope profile and the temperature data over the recent period aristarain et al 1986 an interpretation is proposed in terms of temperature changes the warmest part of this proxy record occurs around 1850 with as a salient feature a temperature decline of 2 c from that time up until present conditions this feature at odds with the long timescale warming trend recorded for both hemispheres over the same period likely reflects a regional characteristic related to the lack of a high latitude low latitude link in southern hemisphere circulation patterns

longitudinal responses of the equatorial low latitude ionosphere over the oceanic regions to geomagnetic storms of may and september 2017 this study presents the longitudinal dependence of responses of the equatorial low latitude ionosphere over the oceanic regions to geomagnetic storms of 28th may and 8th september 2017 we investigated the interplanetary origins of the storms total electron content tec data were obtained from global navigation satellite system stations located around the oceanic areas in the equatorial low latitude regions the rate of change of tec index roti was used as a proxy for ionospheric irregularities over the study locations further variations of the horizontal component of the earth s magnetic fields obtained from ground based magnetometers were studied we used ionospheric disturbance currents polar cap and auroral electrojet indices to monitor the storm time electric fields the may 2017 storm was driven by sheath and magnetic cloud fields while the september 2017 storm was driven by sheath fields we observed a comparative dominance of tec intensities over the oceans than over the landlocked areas empirically our results validated a theoretical suggestion of the existence of a dynamic ocean ionosphere coupling made by godin et al 2015 prompt penetration electric fields ppef was observed to be a key factor that controls tec responses to storms ppefs caused tec enhancements mainly over the pacific ocean longitudes during the may 2017 storm and enhanced tec over the atlantic ocean and the pacific oceans longitudes during the september 2017 storm these ppefs triggered irregularities over the pacific

significance of high temperature fluids and melts in the grasberg porphyry copper gold deposit abstract a study of quartz sulfide veins from the grasberg cu au deposit has shown that the quartz crystals initially grew from the walls of the veins into open fractures cathodoluminescence cl imaging shows concentric growth zones in the larger crystals and changes in the orientation of the growth zones with occasional truncation of the zoning towards the centre of veins the crystals become smaller and irregularly shaped but exhibit cl banding parallel to vein walls which is normally associated with crack seal processes the vein quartz contains silicate and sulfide rich melt inclusions virtually water free salt melt inclusions and coexisting hypersaline and vapour rich inclusions late stage secondary aqueous inclusions are also present in some veins most fluid inclusions homogenised at temperatures below 620 c however hypersaline b2 inclusions had a very complex behaviour and exhibited partial homogenisation to salt melt and clear immiscible fluid at temperatures ranging from 820 c to 1300 c these inclusions contain the highest cu concentrations up to 6 3 wt suggesting they play a role in metal transport the contemporaneous trapping of the k feldspar rich melt inclusions hypersaline and vapour rich inclusions suggests a common source for these fluids and a process involving heterogeneous entrapment of immiscible silicate melt hypersaline fluid and vapour as previously proposed for other porphyry copper deposits furthermore the grasberg deposit is estimated to have formed at pressures below 400 bar which may explain the presence of salt melt inclusions as the vapour halite field of the h2o nacl system is dominant below 800 c at these pressures the unrealistically high temperatures reported herein may have resulted from entrapment of either immiscible silicate melt hypersaline fluid and vapour or cumulates of an evolving silicate melt saturated in k spar brine and vapour although these temperatures may not be directly useful these inclusions give important clues to metal enrichment processes these melt and fluid inclusions record cycles of transitory high temperature 700 c hydrofracturing melt and fluid release and vein formation in a cooler 500 600 c background host rock thermal regime high sulfur and cu contents of sulfide melt and hypersaline b2 inclusions are interpreted to be the fluid composition before the main sulfide precipitation event and therefore may be used as tracers of the magmatic body from which they exsolved at depth

magnetic signature of the ionospheric disturbance dynamo at equatorial latitudes ddyn 1 during magnetic storms wind disturbances produced by auroral phenomena can affect the whole thermospheric circulation and associated ionospheric dynamo currents for many hours after the end of the storms in this paper we define criteria to select a new simple type of ionospheric disturbance dynamo events that allow a simple interpretation over all longitude sectors these events exhibit a weak auroral activity during at least 24 ut hours on the day after the storm we analyze the magnetic disturbances ddyn observed at equatorial latitudes in the three longitude sectors of such selected events it is found for all the cases that the amplitude of the h component of the earth s magnetic field is reduced on the day after storm at equatorial latitudes in agreement with the ionospheric disturbance dynamo model blanc and richmond 1980 the observation of h component decrease on the day after storm is longitudinally asymmetric the observed signature of the ionospheric disturbance dynamo process in a specific longitude sector is strongly dependent on the magnitude the start time and the duration of the storm

fe zn cu pb mineralization in the salton sea geothermal system imperial valley california the salton sea geothermal system is an area of active metamorphism in a plio pleistocene deltaic sedimentary sequence within it hypersaline brines containing up to 250 000 ppm total dissolved solids and temperatures up to 365 degrees c are causing incipient sulfide and oxide mineralization we have made a detailed analysis of ore mineralization in two boreholes drilled to depths of up to 2 500 m in this system major ore minerals observed are in order of decreasing abundance pyrite hematite sphalerite chalcopyrite pyrrhotite marcasite and galena the associated nonore minerals are mainly calcite quartz epidote anhydrite adularia and chlorite ore mineralization can be divided into three main types diagenetic sulfide mineralization occurring at depths less than 760 m and temperatures less than 250 degrees c consists of fine grained stratiform iron sulfides occurring as cement in sandstone and as disseminations and bands in shale metamorphic sulfide mineralization occurring at depths greater than 760 m and temperatures greater than 250 degrees c includes the progressive development of porphyroblastic pyrite with increasing depth and temperature its replacement by other fe cu zn pb sulfides at depths greater than 1 220 m and its decomposition into skeletal aggregates at depths greater than 1 525 m concurrent with hornfelsic recrystallization of the host sediments vein and related pore filling ore mineralization is of two contrasting types hematite silicate sulfide or sulfate and sulfide carbonate or silicate the first type occurs in open porous veins in single vertical zones at least 220 m thick in each borehole the second type occurs in veins that are generally sealed and occur in relatively thin scattered vertical intervals in both boreholes thermodynamic analysis indicates that the modern reservoir brines are near equilibrium with the hematite silicate sulfide or sulfate vein assemblage at 300 degrees c with ph 5 4 and log a sub o 2 30 reactions between hematite pyrite and iron bearing silicates chlorite epidote probably control the redox state of the present brines calculated metal chloride complex solubilities for fe zn pb and cu agree well with brine analyses hematite pyrite and chalcopyrite are supersaturated galena and sphalerite are undersaturated in the modern brines the phase relations of the presently sealed sulfide carbonate or silicate veins require that earlier fluids if formed at the same temperature and ph had to be more reduced and sulfur rich than the present slightly oxidized sulfur poor brines contrasting fluid redox states may be caused by a late lateral or fault controlled influx of more oxidized surficial waters lack of acid alteration implies boiling has not occurred to produce the oxidized fluids early formed diagenetic iron sulfides are commonly replaced by later cu pb zn sulfides and iron oxides and enveloped and resorbed by veins acting as nuclei and sources of s and fe for later mineralization precipitation probably occurs when seismic or hydraulic fracturing allows the metal rich sulfur poor brines to interact with earlier pyrite sulfur in the host rocks thus the geothermal system as presently explored is best classified as an incipient stratabound sulfide deposit that is being overprinted by hydrothermal and metamorphic processes

static electrical conductivity as an indicator of the sulfate content of polar ice cores past atmospheric sulfate content is probably recorded in polar snow and ice a simple method based on electrical conductivity measurements on ice cores has been proposed recently to easily detect atmospheric sulfate changes caused by violent volcanic eruptions in the past we show that this method is particularly useful when used in central polar areas but that its application must be done carefully when analyzing coastal or bedrock ices for which aging effects are able to seriously disturb their electrical properties

evidence for an early holocene climatic optimum in the antarctic deep ice core record in the interpretation of the antarctic deep ice core data little attention has been given to the holocene part of the records as far as translation of the stable isotope content in terms of temperature is concerned this can be understood because expected temperature changes may be obscured by isotopic noise of various origins and because no 14c dating has yet been available for this type of sequence in this article we focus on the dome c and vostok cores and on a new 850 m long ice core drilled out at komsomolskaia by the soviet antarctic expeditions these three sites are located in east antarctica on the antarctic plateau in a region essentially undisturbed by ice flow conditions so that their detailed intercomparison may allow us to identify the climatically significant isotopic signal our results compare well with the proximal records of southern hemisphere high latitudes and support the existence of a warmer climatic optimum between 10 and 6 ka y bp maximum temperatures are reached just at the end of the last deglaciation which confirms previous observations at high latitudes in contrast with later dates for the atlantic and hypsithermal optima in europe and north america

magmatic salt melt and vapor extreme fluids forming porphyry gold deposits in shallow subvolcanic settings the recently discovered biely vrch deposit in the western carpathian magmatic arc is the most extreme example of a porphyry gold deposit being practically free of copper molybdenum or any other sulfide minerals microanalytical data on fluid inclusions in quartz veinlets including a characteristic type of banded veinlets show that this deposit formed from nearly anhydrous fe k na cl salt melts containing 10 ppm au coexisting with hydrous vapor of very low density this exceptional fluid evolution required an fe rich dioritic source magma that was emplaced at shallow subvolcanic depth 3 5 km directly exsolving a hypersaline liquid and magmatic vapor at high temperature 850 c during ascent to the level of the porphyry intrusion 0 5 1 km fluid expansion at high temperature but low pressure led to halite precipitation and further water loss to the vapor generating an increasingly fe k rich salt melt that transported high concentrations of au but negligible cu into the fractured porphyry stock the low sulfur fugacity resulting from fluid expansion suppressed precipitation of sulfide explaining the gold only enrichment in this globally recurring but rare type of gold ore

eight centuries of volcanic signal and climate change at talos dome east antarctica 1 during the 1996 programma nazionale di ricerche in antartide international trans antarctic scientific expedition traverse two firn cores were retrieved from the talos dome area east antarctica at elevations of 2316 m td 89 m long and 2246 m st556 19 m long cores were dated by using seasonal variations in non sea salt nss so42 concentrations coupled with the recognition of tritium marker level 1965 1966 and nss so42 spikes due to the most important volcanic events in the past pinatubo 1991 agung 1963 krakatoa 1883 tambora 1815 kuwae 1452 unknown 1259 the number of annual layers recognized in the td and st556 cores was 779 and 97 respectively the d record obtained from the td core has been compared with other east antarctic isotope ice core records dome c epica south pole taylor dome these records suggest cooler climate conditions between the middle of 16th and the beginning of 19th centuries which might be related to the little ice age lia cold period because of the high degree of geographical variability the strongest lia cooling was not temporally synchronous over east antarctica and the analyzed records do not provide a coherent picture for east antarctica the accumulation rate record presented for the td core shows a decrease during part of the lia followed by an increment of about 11 in accumulation during the 20th century at the st556 site the accumulation rate observed during the 20th century was quite stable

little ice age neoglacial paleoenvironmental conditions at siple station antarctica the 550 year records of 18 o and dust concentrations from siple station antarctica suggest warmer and less dusty atmospheric conditions from 1600 to 1830 a d which encompasses much of the northern hemisphere little ice age lia dust and 18 o data from south pole station indicate that the opposite conditions e g cooler and more dusty were prevalent there during the lia meteorological data from 1945 85 show that the lia temperature opposition between amundsen scott and siple inferred from 18 o is consistent with the present spatial distribution of surface temperature there is some observational evidence suggesting that under present conditions stronger zonal westerlies produce a temperature pattern similar to that of the lia these regional differences demonstrate that a suite of spatially distributed high resolution ice core records will be necessary to characterize the lia in antarctica

synthetic fluid inclusions xx critical ptx properties of h2o fecl2 fluids abstract iron chloride is a common and abundant component in hydrothermal fluids in many geologic environments yet the thermodynamic and ptx properties of fecl2 bearing aqueous fluids are poorly known in this study we have used the synthetic fluid inclusion technique to characterize the ptx conditions along the critical curve of the system h2o fecl2 for a given temperature or salinity the critical pressure in the h2o fecl2 system is lower than that in the h2o nacl system in contrast the critical curves of aqueous solutions of other divalent cation chlorides such as mgcl2 and cacl2 are at higher pressure than that of nacl solutions of equivalent temperature or salinity the results of this study provide the first quantitative constraints on the ptx extent of liquid vapor immiscibility for fecl2 rich fluids owing to the low pressure along the critical curve compared to other common aqueous chloride systems immiscibility of fecl2 rich fluids appears to be limited to relatively low pressures or relatively shallow levels in the crust compared to other saline hydrothermal fluids