cation ratios of fluid inclusions in a gold quartz vein at brusson val d ayas northwestern italian alps comparison of bulk crush leach results with sims analyses of individual inclusions abstract this study tests the widely made assumption that with favourable fluid inclusion samples bulk crush leach analyses accurately reflect the electrolyte compositions of individual fluid inclusions secondary ion mass spectrometric sims analyses of individual inclusions calibrated by synthetic fluid inclusion standards are compared to crush leach analyses of the same natural quartz sample quartz from the bechaz mesothermal au vein at brusson northwestern italian alps is dominated by fluid inclusions of uniform low salinity low x co 2 composition these inclusions represent the liquid phase of an originally immiscible hydrothermal system whereas much rarer high x co 2 inclusions of even lower salinity represent the conjugate vapour phase sims analyses of the low x co 2 inclusions yield mean molar k n 0 050 and ca na 0 016 these results are identical well within experimental uncertainty to replicate crush leach analyses made in two different laboratories the excellent agreement between the sims and crush leach results confirms the accuracy of both analytical methods despite the low salinity of the bechaz fluid inclusions and the rare muscovite and dolomite impurities in the host quartz the crush leach analyses are both highly precise and accurate furthermore the agreement between methods demonstrates that sims analyses of natural multi component fluid inclusions may be reliably calibrated by synthetic inclusions with simple compositions a sims analysis of a high x co 2 vapour inclusion yields k na and ca na ratios that are not significantly different from those of the coexisting low x co 2 inclusions this suggests that under the p t conditions of immiscibility in the bechaz vein 230 c and 600 bar liquid vapour fractionation of k and ca relative to na was only very slight

the effect of crystal melt partitioning on the budgets of cu au and ag we have performed five separate sets of experiments to elucidate the effects of magnetite ulvospinel magnetite solid solution and pyrrhotite crystallization on the budgets of au cu and ag at magmatic conditions the experiments were done in both hydrous and anhydrous assemblages at temperatures between 800 and 1050 c pressures from ambient to 140 mpa log f o2 from nno 0 25 to nno and log f s2 from 1 5 to 3 0 nernst type partition coefficients 1 at 800 c in a water saturated assemblage are d agmt melt 2 10 4 2 10 9 d cumt melt 0 82 0 69 d cuusp melt 26 17 d auusp melt 50 31 d cupo melt 174 25 nernst type partition coefficients 1 at 1050 c in an anhydrous assemblage are d cupo melt 200 d agpo melt 58 8 d aupo melt 120 50 the calculated values for d auusp melt and d cuusp melt indicate that the addition of ti to magnetite increases significantly the au and cu scavenging potential of ulvospinel relative to end member magnetite partition coefficients for cu and au between pyrrhotite and melt indicate that a temperature change from 1050 to 800 c in an anhydrous and hydrous assemblage respectively results in no observable change in cu partitioning the calculated partition coefficients are used to model the effect of crystal fractionation on the concentrations of ag cu and au model results suggest that the co crystallization of magnetite and pyrrhotite sequester no more than 2 ag 7 cu and 37 au from the melt over the first 25 solidification if the melt reaches volatile saturation after 25 crystallization the presence of end member magnetite and pyrrhotite do not appear to inhibit the cu au and ag ore potential of the magma ulvospinel magnetite however may reduce the au concentration in the melt by approximately one third relative to its initial value that decreases the overall au available to partition into the volatile phase

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

sequence stratigraphy of source rocks applied to the study of the kim meridgian tithonian in the north west european shelf dorset uk yorkshire uk and boulonnais france abstract in dorset and yorkshire england the sedimentation of kimmeridgianfrithonian age mutabilis to pallasioides zones shows ordered organic sequences the distribution of the organic matter content per cent total organic carbon petroleum potential hydrogen indices is not random but occurs as widespread primary organic rich cycles nested within each other these organic rich cycles with thicknesses of about 0 5 m show regular variations in organic carbon contents reaching a maximum value midway through the cycle they formed in response to widespread phenomena and can be correlated over long distances the cycles were deposited in marine environments mainly below the storm wave base they show little sedimentological evidence of sea level fluctuation either transgression or regression in the boulonnais france a more proximal setting the comparable strata show a greater lithological contrast and depositional environments corresponding to bathymetric changes are more easily determined a comparison of the distribution of organic matter through the sequence dated by ammonites in the three areas studied shows a good correlation between the distal dorset and yorkshire and the proximal boulonnais areas the main result of the biostratigraphic revision in the boulonnais france concerns the argiles de ch tillon which can be subdivided into two members these belong to the autissiodorensis zone autissiodorensis subzone and the gigas elegans zone respectively thus the kim meridgian tithonian boundary is located within this formation transgression does not appear to be the main factor determining the accumulation of autochthonous organic matter type ii not every major transgressive facies change seen in the kimmeridgian tithonian of the boulonnais is characterized by an enrichment in organic matter in the basinal area good source rocks with high petroleum potentials result from a conjunction between the physiography the transgression and the climate this last causes the variations in primary productivity which produce the organic rich cycles transgressions act mostly to reveal the climatic variations they are a necessary condition for the accumulation of the autochthonous organic matter but they are not sufficient by themselves as demonstrated by the transgressions in the autissiodorensis and elegans zones in the first instance the strata are depleted in organic matter in both the distal and proximal areas in the second instance type ii organic matter accumulated in both distal and proximal environments the vertical fluctuations in the total organic carbon contents the types of organic matter and the petroleum potentials of the organic rich cycles determine the oil potentials of transgressive sequences in sedimentary basins

variations in os isotope ratios of pyrrhotite as a result of water rock and magma rock interaction constraints from virginia formation duluth complex contact zones abstract os isotope ratios in pyrrhotite bearing pelitic rocks of the 1 85 ga virginia formation are variable with perturbations linked to the emplacement of the 1 1 ga duluth complex pyrrhotite in footwall rocks of the contact aureole show evidence for a mixing event at 1 1 ga involving a low 187 os 188 os fluid however because rocks with perturbed pyrrhotite os isotope ratios occur 1 km or more from the duluth complex the fluid is unlikely to have been of magmatic origin fluid inclusions in layer parallel quartz veins provide evidence of the involvement of a boiling fluid at temperatures between 300 and 400 c analyses of fluid inclusions via la icp ms show that the fluids contain up to 1 7 wt na 1 1 wt k 4330 ppm fe 2275 ppm zn and 415 ppm mg the veins also contain pyrite or pyrrhotite plus minor amounts of chalcopyrite bornite pentlandite and sphalerite the re os isotopic ratios of pyrite from the veins indicate that they crystallized from low 187 os 188 os fluids 18 o values of vein quartz range from 7 7 to 9 5 consistent with an origin involving fluid with a relatively low 18 o value between 2 and 5 meteoric water with such a low 18 o value could have interacted with the igneous rocks of the complex and would have acquired os with a low 187 os 188 os ratio strongly serpentinized olivine rich rocks of the complex are commonly characterized by such low 18 o values and we propose that the fluid involved in serpentinization was also responsible for the perturbation of the os isotopic system recorded by pyrrhotite in the virginia formation two important observations are that only pyrrhotite bearing assemblages in the contact aureole show isotopic perturbation and that intervals showing os exchange are spatially restricted and not uniformly distributed os exchange and mixing has occurred only where temperatures were sufficient to convert pyrite to pyrrhotite and where time integrated water rock ratios in the aureole were high enough to provide a supply of os troctolitic and gabbroic rocks of the partridge river intrusion duluth complex are characterized by os isotope ratios that are indicative of variable degrees of crustal contamination os values of 0 543 xenoliths of carbonaceous and sulfidic pelitic rocks of the virginia formation found in the igneous rocks provide evidence that os was released by organic matter and pyrite in the sedimentary rocks and assimilated by mantle derived magma however residual pyrrhotite produced as a result of pyrite breakdown in the xenoliths is characterized by 187 os 188 os ratios that are much lower than anticipated and similar to those of pyrrhotite in the contact aureole the os exchange and addition shown by pyrrhotite in the xenoliths highlight an unusual cycle of re os liberation during devolatilization kerogen maturation and pyrite to pyrrhotite conversion processes that contribute to magma contamination followed by os uptake by pyrrhotite during back reaction involving magma and or fluid characterized by a relatively low 187 os 188 os ratio the extreme os uptake recorded by pyrrhotite in the xenoliths as well as the lesser degree of uptake recorded by pyrrhotite in the contact aureole is in line with the high os diffusivity in pyrrhotite experimentally determined by brenan et al 2000 our data confirm that os isotope ratios in pyrrhotite bearing rocks may be readily perturbed for this reason caution should be exercised in the interpretation of os isotope ratios in rocks where pyrrhotite may be the primary host of os

ore metal redistribution by hydrocarbon brine and hydrocarbon halide melt phases north range footwall of the sudbury igneous complex ontario canada we report methane dominant hydrocarbon fluid inclusions ch4 c2h6 c2h2 c3h8 coexisting with primary brine inclusions and secondary halide melt solid nacl inclusions in au pt rich quartz sulfide epidote alteration veins associated with the footwall style cu pge platinum group element au deposits at the fraser mine north range of the sudbury igneous complex evidence for coentrapment of immiscible hydrocarbon brine and hydrocarbon halide melt mixtures is demonstrated a primary ch4 brine assemblage was trapped during quartz growth at relatively low t min ttrapping 145 315 c and p max ptrapping 500 bar prior to the crystallization of sulfide minerals in the veins secondary inclusions contain solid halite and a mixture of ch4 c2h6 c2h2 and c3h8 and were trapped at a minimum t of 710 c the halite inclusions may represent halide melt that exsolved from crystallizing sulfide ores that texturally postdate by replacement early alteration quartz hosting the primary lower t brine ch4 assemblage laser ablation icp ms analyses show that the brine hydrocarbon and halide melt inclusions contain significant concentrations of cu 0 1 1 wt range au bi ag and pt all 0 1 10 ppm range cu pt and cu au ratios in the inclusions are significantly up to 4 log units lower than in the host alteration veins and adjacent massive sulfide ore veins suggesting either 1 early cu loss from the volatiles by chalcopyrite precipitation or 2 enhanced au and pt solubilities relative to cu at the temperatures of entrapment concentration ratios between coexisting brine and ch4 inclusions c rm elem rm brine c rm elem rm ch 4 are lower for cu au bi and ag than for other elements na ca fe mn zn pb indicating that during interaction with the brine the hydrocarbon phase was enriched in ore metals the high concentrations of ore metals in hydrocarbon brine and halide melt phases confirm that both aqueous and non aqueous volatiles were carriers of precious metals in the sudbury environment over a wide range of temperatures volatile evolution and magmatic sulfide differentiation were clearly part of a single continuous process in the sudbury footwall the exsolution of h2o poor volatiles from fractionated sulfide liquid may have been a principal mechanism controlling the final distribution of pge and au in the footwall ore systems the study reports the first measurements of precious metal concentrations in fluid inclusions from a magmatic ni cu pge environment the sudbury district

the nature of mineralizing fluids of the kipushi zn cu deposit katanga democratic repubic of congo quantitative fluid inclusion analysis using laser ablation icp ms and bulk crush leach methods fluid inclusions from the epigenetic zn cu deposit of kipushi central african copper belt katanga democratic republic of congo have been subjected to an integrated microthermometric bulk crush leach and laser ablation inductively coupled plasma mass spectrometric la icp ms study to elucidate the physicochemical conditions of ore formation and the origin of the mineralizing fluids the kipushi deposit is hosted in carbonates and partly in siliciclastic rocks that have undergone regional low grade greenschist facies metamorphism and which were strongly deformed during the lufilian orogeny main deformation phase 550 ma investigation of host rock gangue and ore samples enabled reconstruction of the paragenesis of ore deposition the main zn cu ge pb sulfide mineralization was accompanied by three generations of hydrothermal dolomite and a generation of coarse grained quartz primary and pseudosecondary fluid inclusions in these minerals contain predominantly halite saturated aqueous brines 30 43 wt nacl equiv with locally unidentified trapped solids these inclusions mostly decrepitate upon heating before total homogenization which could suggest that they also trapped excess carbonic vapor they show petrographic and microthermometric evidence for postentrapment reequilibration prohibiting their use as accurate geothermometers and geobarometers previous studies on chlorite and sphalerite geothermometry framed the formation temperature of the kipushi cu zn deposit between 290 to 380 c younger fluids are present as secondary inclusions in the gangue minerals and as primary fluid inclusions in sphalerite from a minor secondary mineralization phase these two phase aqueous inclusions have a slightly lower salinity 23 31 wt nacl equiv and have homogenization temperatures ranging from 170 to 80 c in successive fluid inclusion assemblages sporadically some mixed aqueous carbonic and gaseous co2 ch4 inclusions are present but their genetic position is un clear and they are insignificant with regard to the mineralization process as a whole crush leach bulk analysis of the fluid inclusions show that the mineralizing fluids had a molar cl br ratio close to or somewhat higher than the seawater value which rules out a major contribution from bittern brines and suggests that the fluids gained their salinity primarily by the dissolution of evaporites younger fluids that circulated through the deposit after the main phase of ore formation have cl br and na br signatures indicative of a greater involvement of halite dissolution brines values much higher than that of seawater la icp ms analyses of the mineralizing fluids reveal that they have molar li na ca na mg na mn na and sr na in the range of natural high salinity fluids in metamorphic environments worldwide however they have relatively high molar fe na zn na pb na and especially very high ba na ratios their molar k na is also somewhat higher than for other low grade metamorphic fluids but is nevertheless in agreement with the values predicted by the k na geothermometer at the conditions of ore formation this suggests that the major element composition of the fluids was buffered by fluid mineral equilibria their relatively high metal contents ba zn fe and pb suggest that they interacted with and leached these elements from felsic basement rocks at higher temperatures whatever the origin of the fluids their salinity and the metals their uniformly high ba and ore metal content together with the absence of barite and the occurrence of ba silicates at kipushi indicates that sulfide mineralization occurred when the metal bearing fluids encountered a reducing h2s rich reservoir the ubiquitous presence of preexisting metamorphosed carbonic material shungite in the sulfides and host rock and a sulfur isotope signature of the ores in agreement with thermogenic sulfate reduction suggests that this condition was likely created due to the high initial reduced carbon content of the host rocks at kipushi which seems to be exceptional in the copper belt therefore we postulate that a critical factor in the formation of major vein type zn cu mineralization was the presence of a hydrocarbon rich facies of the lower nguba carbonates at kipushi

physicochemical evolution of a porphyry breccia system a laser ablation icp ms study of fluid inclusions in the mount leyshon au deposit queensland australia the evolution of magmatism brecciation alteration and mineralization is described for the mount leyshon intrusive complex queensland australia using p t v x analysis and major to trace element analysis of single fluid inclusions using laser ablation icp ms the 290 ma mount leyshon intrusive complex is a subvolcanic porphyry breccia system mined for 97 metric tons t au 70 mt at 1 4 g t au between 1986 and 2000 the mount leyshon intrusive complex is characterized by several generations of genetically related breccias and magmatic intrusions both alteration and mineralization can be traced to specific intrusive events the earliest phase of brecciation was followed by widespread biotite magnetite alteration stage 1 fluid inclusions associated with stage 1 were trapped at 350 c and 145 bars and were anomalously k and fe rich this stage was followed by the emplacement of rhyolite to dacite stocks and coeval breccia pipes stage 2 fluids exsolved from these magmas simultaneously exsolved na k fe mn rich brine 60 wt nacl equiv and dilute vapor at 500 bars 2 km paleodepth and 600 c pressures likely oscillated between lithostatic and sublithostatic conditions in response to the transient rupture and sealing of intrusions and wall rocks hydrothermal fluids infiltrating breccia pore space produced base metal mineralization stage 3 stage 3 fluid inclusions contain 2 to 10 wt percent nacl equiv and were trapped at 300 to 400 c below 500 bars stage 3 fluids were depleted in k fe and mn and enriched in ca sr and ba relative to stage 2 brines this trend is consistent with the transition from potassic alteration in stage 2 to feldspar destructive phyllic alteration in stage 3 cu zn and pb were conservative elements above 350 c and precipitated nonselectively as sulfides below 350 c in a bulk ratio very similar to that measured in fluid inclusions subsequent emplacement of andesite to rhyodacite dikes stage 4 was marked by au and additional base metal sulfide mineralization in veins and breccia cavities stage 4 fluids are chemically similar to stage 3 but contain several mol percent co2 perhaps suggesting a more mafic co2 charged magma source relative to earlier intrusive pulses in addition to fluid cooling the destabilization of au bisulfide complexes attending phase separation of h2o co2 nacl fluids below 400 c and 400 bars was the likely cause for au precipitation mount leyshon appears to indicate that co2 can play a crucial role in the transport of gold bearing solutions from a magmatic source at depth into much shallower hydrothermal environments

lead isotope compositions of late cretaceous and early tertiary igneous rocks and sulfide minerals in arizona implications for the sources of plutons and metals in porphyry copper deposits porphyry copper deposits in arizona are genetically associated with late cretaceous and early tertiary igneous complexes that consist of older intermediate volcanic rocks and younger intermediate to felsic intrusions the igneous complexes and their associated porphyry copper deposits were emplaced into an early proterozoic basement characterized by different rocks geologic histories and isotopic compositions lead isotope compositions of the proterozoic basement rocks define from northwest to southeast the mojave central arizona and southeastern arizona provinces porphyry copper deposits are present in each pb isotope province lead isotope compositions of late cretaceous and early tertiary plutons together with those of sulfide minerals in porphyry copper deposits and of proterozoic country rocks place important constraints on genesis of the magmatic suites and the porphyry copper deposits themselves the range of age corrected pb isotope compositions of plutons in 12 late cretaceous and early tertiary igneous complexes is 206 pb 204 pb 17 34 to 22 66 207 pb 204 pb 15 43 to 15 96 and 208 pb 204 pb 37 19 to 40 33 these pb isotope compositions and calculated model th u are similar to those of the proterozoic rocks in which the plutons were emplaced thereby indicating that pb in the younger rocks and ore deposits was inherited from the basement rocks and their sources no pb isotope differences distinguish late cretaceous and early tertiary igneous complexes that contain large economic porphyry copper deposits from less rich or smaller deposits that have not been considered economic for mining lead isotope compositions of late cretaceous and early tertiary plutons and sulfide minerals from 30 metallic mineral districts furthermore require that the southeastern arizona pb province be divided into two subprovinces the northern subprovince has generally lower 206 pb 204 pb and higher model th u and the southern subprovince has higher 206 pb 204 pb and lower model th u these pb isotope differences are inferred to result from differences in their respective post 1 7 ga magmatic histories throughout arizona pb isotope compositions of late cretaceous and early tertiary plutons and associated sulfide minerals are distinct from those of jurassic plutons and also middle tertiary igneous rocks and sulfide minerals these differences most likely reflect changes in tectonic setting and magmatic sources within late cretaceous and early tertiary igneous complexes that host economic porphyry copper deposits there is commonly a decrease in pb isotope composition from older to younger plutons this decrease in pb isotope values with time suggests an increasing involvement of crust with lower u pb than average crust in the source s of late cretaceous and early tertiary magmas lead isotope compositions of the youngest porphyries in the igneous complexes are similar to those in most sulfide minerals within the associated porphyry copper deposit this pb isotope similarity argues for a genetic link between them however not all pb in the sulfide minerals in porphyry copper deposits is magmatically derived some sulfide minerals particularly those that are late stage or distal to the main orebody or in proterozoic or paleozoic rocks have elevated pb isotope compositions displaced toward the gross average pb isotope composition of the local country rocks the more radiogenic isotopic compositions argue for a contribution of pb from those rocks at the site of ore deposition combining the pb isotope data with available geochemical isotopic and petrologic data suggests derivation of the young porphyry copper related plutons most of their pb and other metals from a hybridized lower continental crustal source because of the likely involvement of subduction related mantle derived basaltic magma in the hybridized lower crustal source an indiscernible mantle contribution is probable in the porphyry magmas clearly in addition pb was contributed from the local country rocks this is most evident in sulfide minerals in veins that are late stage hosted in proterozoic gneiss and or peripheral to the porphyry copper deposit

synthetic fluid inclusions vii re equilibration of fluid inclusions in quartz during laboratory simulated metamorphic burial and uplift p t conditions inferred from fluid inclusions in metamorphic rocks often disagree with the values predicted from mineral equilibria calculations these observations suggest that inclusions formed during early stages of regional metamorphism continue to re equilibrate during burial and subsequent uplift in response to differential pressure p t conditions accompanying burial and uplift were experimentally simulated by initially forming pure h2o inclusions in quartz at elevated temperatures and pressures and then re equilibrating the inclusions in the presence of a 20 wt nacl solution such that final confining pressures ranged from 5 kbar above to 4 kbar below the initial internal pressure of the inclusions at the temperature of re equilibration in all samples re equilibrated at confining pressures below the internal pressure some inclusions were formed that had compositions of 20 wt nacl and densities in accord with the final p t conditions additionally some inclusions were observed to contain fluids of intermediate salinities between 0 and 20 wt nacl densities of these inclusions were also consistent with formation at the re equilibration p t conditions the remainder of the fluid inclusions observed in these samples contained pure h2o and their homogenization temperatures corresponded to densities intermediate between the initial and final p t conditions in short term experiments 7 days where the initial internal overpressure exceeded 1 kbar no inclusions were found that contained the original density and none were found to have totally re equilibrated instead most h2o inclusions re equilibrated until their internal pressures were between 750 and 1500 bars above the confining pressure regardless of the initial pressure differential in a long term experiment 52 days inclusions re equilibrated at a lower confining pressure than the initial internal pressure displayed homogenization temperatures corresponding to a range in final internal pressures between 0 kbar i e total re equilibration and 1 2 kbar above the confining pressure in experiments where the confining pressure during re equilibration exceeded the initial internal pressure densities of pure h2o inclusions increased to values intermediate between the initial and final p t conditions additionally these inclusions were generally surrounded by a three dimensional halo of smaller inclusions also of intermediate density resulting in a texture similar to that previously ascribed to decrepitation from internal overpressure in extreme cases where confining pressures were 4 5 kbar above the initial pressure the parent inclusion almost completely closed leaving only the three dimensional array of small 5 m inclusions the outline of which may be several times the volume of the original inclusion groups of such inclusions closely resemble textures commonly observed in medium to high grade metamorphic rocks inclusions containing 10 and 42 wt nacl solutions trapped at 600 c and 3 kbar were re equilibrated at 600 c and 1 kbar for 5 days in dry argon to evaluate the importance of h2o diffusion as a mechanism of lowering the inclusion bulk density salinities of re equilibrated inclusions obtained from freezing point depressions and halite dissolution temperatures indicate that original compositions were preserved density changes similar to those previously described were noted in these experiments in inclusions showing no visible microfractures therefore density variations observed in inclusions in this study re equilibrated under rapid deformation conditions are considered to result from a change in the inclusion volume without significant loss of contents by diffusion or leakage

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

evolution from magmatic to hydrothermal activity beneath the cerro escorial volcano nw argentina as sampled by erupted quartz and brines abstract large quartz pebbles erupted with the escorial ignimbrite provide insight into the late magmatic evolution of the shallow cooling magmatic hydrothermal system below the cerro escorial volcano of the southern central volcanic zone in the argentine andes the ignimbrite is of relatively small volume crystal rich dacitic in composition and not particularly water rich as amphibole is absent eruption temperature was estimated to be close to 850 c the quartz pebbles provide insight into the magmatic hydrothermal transition beneath the volcano based on textures trace element composition analyzed by laser ablation inductively coupled plasma mass spectrometry and inclusion content the pebbles can be separated into pegmatite like megacrysts and lower temperature epithermal microcrystalline quartz both types are distinct from magmatic phenocrysts present in porphyritic clasts ejected by the ignimbrite the megacrysts show a wide range of trace element concentrations with elevated al concentrations and al ti and ge ti ratios compared to quartz phenocrysts although some contamination by submicroscopic inclusions and cooling to near solidus temperatures may perturb the signal in some cases the range of trace element concentrations in quartz crystals from this system may reflect a change in crystallization conditions from initial precipitation from typical evolved silicate melt to fast growth from residual melt and or fluid in pegmatitic pockets or coarse grained hydrothermal veins at locally variable precipitation conditions abundant primary and secondary silicate melt inclusions and a variety of secondary fluid inclusions are present within the megacrysts in particular brine inclusions are densely packed with salt crystals sometimes anhydrite and or a silicate crystal but no visible liquid at room temperature and co existing vapor inclusions are of very low density heating experiments of brine inclusions reveal last salt and vapor bubble dissolution temperatures around 600 700 c but an immiscible silicate melt surrounding the homogenized salt globule remains even at unreasonably high temperature the co existence of silicate melt and fluid inclusions reinforces the magmatic nature of the fluids while boiling trails of brine with cu concentrations of several percent and vapor point to relatively low pressures

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

the composition of hypersaline iron rich granitic fluids based on laser icp and synchrotron xrf microprobe analysis of individual fluid inclusions in topaz mole granite eastern australia abstract high temperature 550 c hypersaline 50 wt salts fluid inclusions representative of the earliest hydrothermal fluids associated with the sn w cu pb zn mineralised mole granite of eastern australia are well developed in topaz from the fielders hill locality methods based on inductively coupled plasma emission spectroscopy following laser ablation and on synchrotron x ray fluorescence microanalysis are described and applied to the semiquantitative point analysis of these inclusions crushleach analysis provides further information as well as highlighting the importance of point methods when several generations of inclusions are present the laser icp results confirm the dominance of fe k and na in these early high temperature fluids the mean fe k na atomic ratios 0 95 0 79 1 00 are entirely in agreement with published experimental data on the composition of chloride brines in equilibrium with synthetic granite at magmatic temperatures and support the view that these fluids are direct products from a cooling granite magma a number of trace and minor elements have also been detected in the inclusions these include ca mg li b be ba sr and several of the ore metals order of magnitude estimates of the ore metal contents of these fluids based on combined xrf microprobe and laser icp analysis are in the percent range for fe mn and zn in the range from several hundred to several thousand ppm in the case of sn cu and pb and less than 600 ppm for mo and w these results have important implications for ore genesis in granitic environments and point to the very high ore carrying potential of high temperature hypersaline chloride rich brines exsolved from cooling granite magmas

novel 3d sequence stratigraphic numerical model for syn rift basins analysing architectural responses to eustasy sedimentation and tectonics syn rift clastic sedimentary systems preserve a complicated stratigraphic architecture that records the interplay of tectonics eustatic sea level and storage and routing of sediments previous conceptual models describe and explain changes in depositional stacking patterns along a fault segment however stacking patterns and the nature of key stratigraphic surfaces is challenging to predict accurately with conventional sequence stratigraphic models that do not consider the three dimensional interplay of subsidence sedimentation and eustasy we present a novel geometric 3d sequence stratigraphic model syn strat which applies temporally and spatially variable fault scale tectonic constraints to stratigraphic forward modelling as well as allowing flexibility in the other controls in time and space syn strat generates a 3d graphical surface that represents accommodation although the model has the capacity to model footwall variation here we present model results from the hangingwall of a normal fault with temporal and spatial dip and strike predictions made of stacking patterns and systems tracts for a given set of controls sensitivity tests are tied to the depositional architecture of field based examples from the loreto basin gulf of california and alkyonides basin gulf of corinth here the relative influence of major sedimentary controls different subsidence histories varying sedimentation distribution including along strike variation in stacking patterns are assessed and demonstrate the potential of syn strat for reducing subsurface uncertainties by resolving multiple scenarios in addition the model demonstrates the nature of diachroneity of key stratigraphic surfaces that can arise in syn rift settings which could be represented by a bypass surface sequence boundary or reservoir seal maximum flooding surface in the rock record enabling a quantitative assessment of these surfaces is critical for prospect analysis in hangingwall half graben fills where these surfaces are heavily relied upon for well correlations that are used for hydrocarbon volume and production rate predictions

the partitioning behavior of silver in a vapor brine rhyolite melt assemblage abstract the partitioning of silver in a sulfur free rhyolite melt vapor brine assemblage has been quantified at 800 c pressures of 100 and 140 mpa and f o 2 nno nickel nickel oxide silver solubility 2 in rhyolite increases 5 fold from 105 21 to 675 98 g g as pressure increases from 100 to 140 mpa nernst type partition coefficients d ag i j 2 describing the mass transfer of silver at 100 mpa between vapor and melt brine and melt and vapor and brine are 32 30 1151 238 and 0 026 0 004 respectively at 140 mpa values for d ag i j 2 for vapor and melt brine and melt and vapor and brine are 32 10 413 172 and 0 06 0 03 respectively apparent equilibrium constant values 2 describing the exchange of silver and sodium between vapor and melt k ag na v m at 100 and 140 mpa are 105 68 and 14 6 the average values 2 for silver and sodium exchange between brine and melt k ag na b m at 100 and 140 mpa are 313 288 and 65 12 these data indicate that the mass transfer of silver from rhyolite melt to an exsolved volatile phase s is enhanced at 100 mpa relative to 140 mpa suggesting that decompression increases the silver ore generative potential of an evolving silicate magma model calculations using the new data suggest that the evolution of low density aqueous fluid i e vapor may be responsible for the the silver tonnage of many porphyry type and perhaps epithermal type ore deposits for example halter et al halter w e pettke t and heinrich c a 2002 the origin of cu au ratios in porphyry type ore deposits science 296 1842 1844 used detailed silicate and sulfide melt inclusion and vapor and brine fluid inclusions analyses to estimate a melt volume on the order of 15 km3 to satisfy the copper budget at the bajo de la alumbrera copper gold silver ore deposit using their melt volume estimate with the data presented here model calculations for a 15 km3 felsic melt saturated with pyrrhotite and magnetite suggest that a low salinity magmatic vapor may scavenge on the order of 7 1012 g of silver from the melt this quantity of silver exceeds the discovered 2 109 g of ag at alumbrera calculated tonnages for numerous other deposits yield similar results the excess silver in the vapor remaining after porphyry formation is then available to precipitate at lower ptconditions in the stratigraphically higher epithermal environment these data suggest that silver and perhaps other ore metals in the porphyry epithermal continuum may be derived solely from the time integrated flux of dominantly low salinity vapor exsolved from a series of sequential magma batches

composition and evolution of fluids forming the baiyinnuo er zn pb skarn deposit northeastern china insights from laser ablation icp ms study of fluid inclusions the baiyinnuo er skarn deposit is one of the largest zn pb deposits in northeastern china with 32 74 million metric tons mt resources averaging 5 44 zn 2 02 pb and 31 36 g t ag the deposit formed in three stages the preore stage prograde skarn minerals with minor magnetite the synore stage sulfides and retrograde skarn minerals including calcite and minor quartz and the postore stage late veins composed of calcite quartz fluorite and chlorite cutting the above mineral assemblages in this study we analyzed the composition of single fluid inclusions using laser ablation inductively coupled plasma mass spectrometry la icp ms to 1 determine the composition of the fluids and the evolution through the stages 2 infer the fluid and metal sources and 3 explore the metal deposition mechanisms the preore fluids trapped in pyroxene have higher homogenization temperatures 432 504 c higher salinity 36 5 46 1 wt nacl equiv and higher concentrations of zn 0 9 wt pb 1 4 wt and other elements e g na k li as rb sr cs ba cl and br than synore mineralizing fluids 370 c 10 wt nacl equiv 450 ppm zn and 290 ppm pb the postore fluids show lower temperatures 250 c and a rather dilute composition 4 wt nacl equiv 33 ppm zn and 24 ppm pb geochemically the fluids of all paragenetic stages in baiyinnuo er have magmatic signatures based on the element mass ratios including elevated k na zn na and rb na ratios lower ca k ratios and combined cl br na k ratios which are distinctively different from basinal brines inclusion fluids in preore stage show little variation in composition between 510 and 430 c indicative of a closed cooling system in contrast the major components of the syn and postore fluids including cl na and k decrease and correlate with a drop of homogenization temperatures from 370 to 200 c indicating a dilution by mixing with groundwater the baiyinnuo er mineralizing fluids trapped in sphalerite have higher ca k mass ratios avg 0 78 than other proximal magmatic hydrothermal systems 0 06 0 52 but lower than that of the distal el mochito skarn avg 6 4 probably reflecting a gradually weakened magmatic signal away from the causative intrusions the metal contents in preore fluids are significantly higher than those in synore fluids but no mineralization occurred this confirms that the early fluids were although enriched in metals not responsible for ore precipitation most likely due to their high temperature and high salinities one important factor controlling zn pb mineralization was mixing with groundwater which resulted in temperature decrease and dilution that significantly reduced the metal solubility thereby promoting metal deposition another main driving force was the interaction with carbonate wall rock that buffered the acidity generated during the breakdown of zn and pb cl complexes and the precipitation of sulfides phase separation occurred in both the preore and the early part of the synore stages but no evidence indicated that it caused metal deposition the prograde minerals and retrograde minerals including ore minerals coexisting in the same samples could have been caused by two or more successive pulses of hydrothermal fluids released from residual melts of a progressively downward crystallizing magma each fluid produced a series of proximal high temperature prograde to distal low temperature assemblages with the lower temperature assemblages of later fluids overprinting the higher temperature assemblages at most locations

copper deposition during quartz dissolution by cooling magmatic hydrothermal fluids the bingham porphyry abstract scanning electron microscope cathodoluminescence imaging is used to map successive generations of fluid inclusions in texturally complex quartz veinlets representing the main stage of ore metal introduction into the porphyry cu au mo deposit at bingham utah following conventional fluid inclusion microthermometry laser ablation inductively coupled plasma mass spectrometry la icpms is applied to quantify copper and other major and trace element concentrations in the evolving fluid with the aim of identifying the ore forming processes textures visible in cathodoluminescence consistently show that the bulk of vein quartz q1 characterized by bright luminescence crystallized early in the vein history cu fe sulfides are precipitated later in these veins in a microfracture network finally filled with a second generation of dull luminescing q2 quartz mapping of brine and vapor inclusion assemblages in these successive quartz generations in combination with la icpms microanalysis shows that the fluids trapped before and after cu fe sulfide precipitation are very similar with respect to their major and minor element composition except for copper copper concentrations in inclusions associated with ore formation drop by two orders of magnitude in a tight pressure temperature interval between 21 and 14 mpa and 425 350 c several hundred degrees below the temperature of fluid exsolution from the magma copper deposition occurs within a limited p t region in which sulfide solubility shows strong normal temperature dependence while quartz solubility is retrograde this permits copper sulfide deposition while secondary vein permeability is generated by quartz dissolution the brittle to ductile transition of the quartz feldspar rich host rocks occurs in the same temperature range which further enhances vein reactivation and promotes cooling and expansion of fluids ascending across the transition from lithostatic to hydrostatic conditions

sediment hosted gold deposits in guizhou china products of wall rock sulfidation by deep crustal fluids sediment hosted gold deposits in guizhou china are hosted in late paleozoic and early mesozoic sedimentary rocks along the southwest margin of the precambrian yangtze craton they have characteristics similar to carlin type gold deposits in nevada and are notably enriched in as sb hg and tl the shuiyindong and yata deposits consist of disseminated strata bound sulfides in permian bioclastic limestone and fault controlled mineralization in middle triassic calcareous clastic rocks respectively mineralization in both deposits consists of barren milky quartz veins disseminated gold bearing arsenian pyrite and arsenopyrite stibnite realgar and orpiment the barren milky quartz veins occur in the ore controlling structures with an envelope of gold mineralization in the host rock consisting of disseminated gold bearing arsenian pyrite and arsenopyrite and replacement style quartz veinlets later drusy quartz stibnite realgar and orpiment fill fractures and vugs on the periphery of gold mineralization petrography microthermometry laser raman spectroscopy and laser ablation inductively coupled plasma mass spectrometric la icp ms analyses of fluid inclusions are used to characterize the chemical evolution of ore fluids at shuiyindong and yata early barren milky quartz veins trapped aqueous fluid with moderate salinity 6 0 wt nacl equiv and minor co2 2 4 mol at a temperature of 230 30 c this fluid contains measurable b na k cs sr as sb and au 3 8 0 5 5 7 2 3 g g determined by la icp ms and is interpreted to approximate the mineralizing fluid responsible for precipitation of early barren quartz veins low salinity 0 9 2 3 wt nacl equiv co2 bearing 6 3 8 4 mol aqueous fluids are recorded in replacement style quartz veinlets they formed gold bearing arsenian pyrite and arsenopyrite and quartz veinlets at a temperature of 210 20 c and pressures of 450 to 1 150 bars corresponding to depths between 1 7 and 4 3 km under lithostatic conditions fluid inclusions in late stibnite orpiment realgar quartz veins contain high co2 58 64 mol and n2 19 2 23 7 mol with trace ch4 up to 1 6 mol the increasing content of co2 and decrease in the concentrations of au and as in aqueous carbonic inclusions are interpreted to result from carbonate dissolution at the level of the deposits during gold mineralization covariance of au as sb and sr concentrations in the fluids is interpreted to reflect deposition of as and sb sulfides and gold concurrent with carbonate crystallization iron is below detection limit 400 g g in all fluid inclusion types suggesting that the ore fluids were fe poor but possibly sulfur rich possibly explaining their exceptionally high gold contents iron in sulfide minerals was probably derived from dissolution of ferroan minerals in the host rocks sulfidized by h2s rich fluids to precipitate arsenian pyrite arsenopyrite and gold pressure fluctuation induced by faulting resulted in local fluid immiscibility and led to late deposition of realgar orpiment stibnite and calcite hydrogen and oxygen isotope compositions of ore fluids d h2o 35 to 68 18o h2o 4 16 5 indicate a metamorphic origin possibly related to crustal thickening and prograde metamorphism during the late yanshanian orogeny

physical chemical properties and metal budget of au transporting hydrothermal fluids in orogenic deposits we use a set of analytical techniques for fluid inclusion analysis to determine the bulk properties of the ore fluids from five orogenic gold deposits the most common ore fluid is a low salinity 0 4 6 5 wt nacl twoto three phase aqueous carbonic fluid its th total range is 200 400 8c and total homogenization occurs by bubble or liquid disappearance a less common aqueous fluid of similar bulk salinity and t h total is also documented microchemical data show that the ore fluid in the five deposits is chemically uniform and made of na subordinate k and b and minor to trace amounts of cu as li sr rb ba cs sb and au range 0 5 5 mg g thermodynamic modelling carried out for one of the studied deposits indicates that the ore fluid was in equilibrium with vein minerals at the time of gold deposition and that its vapour phase was distinctly enriched in au b as and sb the proposed mechanism of gold precipitation is a combination of fluid decompression and boiling combining these results with 3d geometrical reconstructions of one of the studied deposits sigma we estimate that a minimum ore fluid volume of c 0 1 1 0 km is sufficient to generate a world class orogenic deposit orogenic deposits provide about a third of the global gold production goldfarb et al 2001 frimmel 2008 these deposits are formed within active continental margins in orogenic belts where major tectonic boundaries juxtapose metamorphosed volcanic plutonic and sedimentary terranes the ore bodies consist of au mineralized vein networks filled with quartz carbonates and other silicates that in places crosscut the stacked terranes of the continental margins the veins are dilated portions of vertically extensive brittle ductile to ductile fracture networks that form due to the advection of aqueous hydrothermal fluids within the continental crust ridley et al 1996 groves et al 2003 these ore fluids are generated in still undefined source regions deep in the crust and transported to shallower levels 3 15 km depth through the vein networks along which they deposit gold a number of studies kerrich et al 2000 ridley diamond 2000 groves et al 2003 showed that although these networks do not occur systematically in all orogens they have a set of important geological features in common which include 1 formation during accretionary orogenic events 2 occurrence relatively close to regional tectonic lineaments especially along lower order splays of these structures 3 spatial association with granitoid intrusions 4 occurrence within some metamorphic belts with gold precipitation being synto postmetamorphic in age 5 relatively low sulphide abundance within the veins 6 carbonate sericitealbite sulphide hydrothermal alteration of host rocks postdating metamorphism 7 poorly developed mineral and metal zoning within the ore bodies and 8 genesis from low to moderate salinity ore fluids over a large temperature range 250 700 8c but mostly within 300 350 8c these common traits occur systematically in deposits from different terrains having distinct ages suggesting that a common geological process and au transporting fluid are responsible for their formation here we present a database of fluid inclusion properties from five typical orogenic deposits which show most of the geological characteristics listed above the database was constructed with the aim of determining as accurately as possible the properties of the au transporting fluid in this geological environment in particular laser ablation inductively coupled plasma mass spectrometry la icp ms of single fluid inclusions paragenetically coeval with vein gold provides the concentration of a suite of metals including au in this fluid this dataset when combined with 3d geometrical reconstructions of one of these deposits offers new constraints on the volume of the ore from garofalo p s ridley j r eds gold transporting hydrothermal fluids in the earth s crust geological society london special publications 402 http dx doi org 10 1144 sp402 8 the geological society of london 2014 publishing disclaimer www geolsoc org uk pub ethics by guest on april 3 2014 http sp lyellcollection org downloaded from

fluid fractionation of tungsten during granite pegmatite differentiation and the metal source of peribatholitic w quartz veins evidence from the karagwe ankole belt rwanda abstract the identification of a magmatic source for granite associated rare metal w nb ta and sn mineralisation in metasediment hosted quartz veins is often obscured by intense fluid rock interactions which metamorphically overprinted most source signatures in the vein system in order to address this recurrent metal sourcing problem we have studied the metasediment hosted tungsten bearing quartz veins of the nyakabingo deposit of the karagwe ankole belt in central rwanda the vein system 992 2 ma is spatiotemporal related to the well characterised b rich f poor g4 leucogranite pegmatite suite 986 10 ma to 975 8 ma of the gatumba gitarama area which culminated in nb ta sn mineralisation muscovite in the nyakabingo veins is significantly enriched in granitophile elements rb cs w and sn and show alkali metal signatures equivalent to muscovite of less differentiated pegmatite zones of the gatumba gitarama area pegmatitic muscovite records a decrease in w content with increasing differentiation proxies rb and cs in contrast to the continuous enrichment of other high field strength elements nb and ta and sn this is an indication of a selective redistribution for w by fluid exsolution and fluid fractionation primary fluid inclusions in tourmaline of these less differentiated pegmatites demonstrate the presence of medium to low saline h 2 o nacl kcl mgcl 2 complex salt e g rb cs fluids which started to exsolve at the g4 granite pegmatite transition stage laser ablation inductively coupled plasma mass spectrometry shows significant tungsten enrichment in these fluid phases 5 500 ppm fractional crystallisation has been identified previously as the driving mechanism for the transition from g4 granites less differentiated biotite biotite muscovite towards muscovite pegmatites and eventually columbite tantalite mineralised pegmatites the general absence of tungsten mineralisation in this magmatic suite including the most differentiated columbite tantalite mineralised pegmatites of the gatumba gitarama area emphasises the efficiency of fluid saturation to extract crystal melt incompatible tungsten from the differentiating melt phase fluid melt crystal partitioning calculations support the concept of a magmatic hydrothermal fluid source for tungsten and constrain the range of permissible crystal melt and fluid melt partition coefficients together with realistic values for water solubility in the parental g4 granitic melt consequently we propose that for highly differentiated b rich f poor granite systems fluid saturation started prior to or at the granite pegmatite transition stage resulting in apical to peribatholitic tungsten veins systems that are paragenetically older than the final pegmatite stage

the bingham canyon porphyry cu mo au deposit iii zoned copper gold ore deposition by magmatic vapor expansion fluid inclusion microthermometry and laser ablation icpms microanalysis are combined with geological and textural observations to reconstruct the spatial and temporal evolution of magmatic fluids that formed the subvolcanic porphyry cu au mo ore deposit at bingham canyon utah the bingham canyon orebody is exposed over 1 6 km vertically and has the shape of an inverted cup with distinct metal zoning fluid inclusions in the barren but highly veined and potassically altered deep center of the system have intermediate density 0 6 g cm 3 and a salinity of 7 wt percent nacl equiv they have subequal concentrations of na k fe and cu and contain minor co2 the intermediate density fluids were trapped as a single phase mostly at 500 c and 800 bars the au cu rich center near the top of the orebody contains low density vapor inclusions 0 2 g cm 3 coexisting with brine inclusions containing 45 wt percent nacl equiv the vertical transition of different inclusion types indicates phase separation of the single phase input fluid upon volume expansion associated with a pressure drop to 200 100 bars mass balance calculation based on all analyzed inclusion components indicates that the mass of the vapor phase exceeded that of the brine by 9 1 the vapor contained cu as its dominant cation 1 5 wt and contributed about 95 percent of the total amount of copper transported to the base of the orebody bornite chalcopyrite and native gold were precipitated in a narrow temperature interval from 430 to 350 c into secondary pore space created by local redissolution of vein quartz as a result of retrograde quartz solubility in the vapor dominated fluid system intermediate density fluid inclusions in the deepest parts of the peripheral copper ore zone have identical density and composition including similar gold contents as those in the deep center microthermometry and statistical estimation of phase proportions in the inclusions show that the vapor in the peripheral cu rich but au poor ore zone remained denser and the separating brine was less saline 36 wt nacl equiv compared to vapor and brine in the central au cu ore zone this indicates that the peripheral fluids experienced a lower degree of phase separation due to slightly higher fluid pressure at equivalent temperature compared to more strongly expanding fluids in the center of the system the systematic zoning of au cu within the ore shell despite compositionally similar input fluids is interpreted to have resulted from slightly different pressure temperature density evolution paths of magmatic fluids copper was selectively precipitated in the peripheral ore zone in contrast to complete coprecipitation of au and cu in the central upflow zone of the vapor plume the formation of particularly rich cu au ore in the center of the upward expanding fluid plume is consistent with published experimental data showing that the solubility of metals in hydrous vapor decreases sharply with falling pressure due to destabilization of the hydration shell around metal complexes in expanding vapor this interpretation supports the classic vapor plume model for porphyry copper ore formation but additionally emphasizes the role of sulfur bearing complexes as a key chemical control on magmatic hydrothermal metal transport and the deposition of cu and au in porphyry ores our interpretation of selective cu au precipitation as a function of vapor density can explain the more general observation that most gold rich porphyry copper deposits are formed in shallow sub volcanic environments whereas deeper seated porphyry cu mo deposits are generally gold poor

anisotropy of magnetic susceptibility in alkali feldspar and plagioclase feldspars are the most abundant rock forming minerals in the earth s crust but their magnetic properties have not been rigorously studied this work focuses on the intrinsic magnetic anisotropy of 31 feldspar samples with various chemical compositions because feldspar is often twinned or shows exsolution textures measurements were performed on twinned and exsolved samples as well as single crystals the anisotropy is controlled by the diamagnetic susceptibility and displays a consistent orientation of principal susceptibility axes the most negative or minimum susceptibility is parallel to 010 and the maximum least negative is close to the crystallographic 001 axis however the magnetic anisotropy is weak when compared to other rock forming minerals 1 53 10 9 m3 kg 1 at maximum therefore lower abundance minerals such as augite hornblende or biotite often dominate the bulk paramagnetic anisotropy of a rock ferromagnetic anisotropy is not significant in most samples in the few samples that do show ferromagnetic anisotropy the principal susceptibility directions of the ferromagnetic subfabric do not display a systematic orientation with respect to the feldspar lattice these results suggest that palaeointensity estimates of the geomagnetic field made on single crystals of feldspar will not be affected by a systematic orientation of the ferromagnetic inclusions within the feldspar lattice

internal and external fluid sources for eclogite facies veins in the monviso meta ophiolite western alps implications for fluid flow in subduction zones to contribute to our understanding of the mechanisms and pathways of fluid movement through deeply subducted crust we investigate high pressure veins cutting eclogite facies 2 0g pa and 6008c metagabbros of the monviso ophiolite italian western alps the veins consist mainly of omphacite with minor garnet rutile talc and accessory zircon most of the vein minerals have major and trace element compositions that are comparable with the host rock minerals and vein and host rock zircons have similar hf isotopic compositions these observations support the conclusions of previous studies that these veins largely formed from a locally sourced hydrous fluid during prograde or peak metamorphism however the bulk rock cr and ni contents of the veins are significantly higher than those of the surrounding host eclogites we also document distinct cr rich up to weight per cent levels zones in omphacite garnet and rutile in some vein samples vein garnet and talc also have relatively high mgo and ni contents x ray maps of vein garnet and rutile grains reveal complex internal zoning features which are largely defined by micrometre scale variations in cr content some grains have concentric and oscillatory zoning in cr whereas others feature a chaotic fracture like pattern these cr rich zones are associated with high concentrations of ni b as sb nb zr and high ratios of light rare earth elements lree to middle ree mree compared with low cr vein and host rock minerals petrological and mass balance constraints verify that the cr rich zones in the veins were not derived from internally sourced fluids but represent precipitates from an external fluid the external source that is consistent with the distinctive trace element characteristics of the vein components is antigorite serpentinite which forms the structural basement of the high pressure metagabbros we propose at least two separate growth mechanisms for the monviso veins most vein infillings were formed during progressive prograde metamorphism from locally derived fluid influx of the serpentinitederived or other external fluid was transient and episodic and was probably achieved via brittle fractures which preferentially formed along the pre existing vein structures the dehydration of serpentinite at high pressures in subduction zones may provide crucial volatiles and trace elements for arc magmas our results indicate that the movement of these fluids through subducted oceanic crust is likely to be highly channeled and transient so the progressive development of vein systems in mafic rocks may also be crucial for forming channelways for long distance fluid flow at depth in subduction zones

tracking meteoric infiltration into a magmatic hydrothermal system a cathodoluminescence oxygen isotope and trace element study of quartz from mt leyshon australia the oxygen isotope and trace element composition of hydrothermal quartz has been integrated with scanning electron microscope cathodoluminescence sem cl images and fluid inclusion properties to track fluid sources and hydrothermal processes in the mt leyshon an deposit australia oxygen isotope and trace element data were collected on parallel traverses across the same quartz sections using secondary isotope mass spectrometry sims and laser ablation inductively coupled plasma mass spectrometry la icp ms respectively with sem cl images obtained before analysis for petrographic context over the 280 to 650 degrees c quartz precipitation range suggested by fluid inclusion microthermometry delta o 18 quartz varies from 0 0 to 14 4 o corresponding to a wide range of equilibrium delta o 18 fluid values from 6 1 to 10 2 o vs v smow the delta o 18 quartz signature varies systematically among distinct sem cl quartz generations both within and between samples and can be correlated with variations in temperature and fluid composition but is independent of intra generational oscillatory zoning in contrast al and li concentrations correlate broadly with cl intensity in oscillatory quartz whereas their concentration is unpredictable in sealed fractures and overgrowths concentrations of b mg na p cl k ti mn fe ge and sn are independent of al li and oscillatory cl features but ti correlates with quartz precipitation temperature although no systematic correlation between delta o 18 quartz and trace element concentrations was found complementary patterns exist in narrow overgrowths of low delta o 18 quartz similar to 0 o and high al g 10 000 ppma these quartz zones likely formed during the incursion of o 18 depleted meteoric water into the magmatically dominated mt leyshon hydrothermal system we interpret the highest al concentrations as the result of high quartz precipitation rates triggered by depressurisation of the hydrothermal cell the decoupling of oxygen isotope and trace element patterns in quartz leads to the suggestion that 1 under most circumstances temperature and fluid chemistry dominate delta o 18 quartz and 2 the trace element record and in particular al and li is influenced by the superimposed effects of quartz precipitation rate c 2007 elsevier b v all rights reserved

mobility and h2o loss from fluid inclusions in natural quartz crystals petrographic observations on quartz crystals from the mole granite australia and other localities shed new light on the mechanisms of post entrapment modification of fluid inclusions these modifications include migration away from pseudosecondary trails changes in fluid salinity and density shape distortion and the formation of sweat haloes around strongly deformed inclusions increases in fluid salinity which usually are associated with inclusion migration indicate water losses of up to 50 however la icp ms analysis of unmobilized and mobilized inclusions of the same trail reveals basically unchanged ratios of major and trace element cations with the exception of li which seems to be incorporated into the crystal lattice during migration despite the fact that all these modifications are closely related to deformation processes they occur not only in mechanically deformed quartz but also in free standing crystals in the latter samples stress has been generated internally as a result of brazil twinned growth and compositional zonation these observations and their interpretation leads to a list of practical criteria that should help in differentiating between reliable and suspect fluid inclusions in other samples

thermal regime reconstruction and fluid inclusion la icp ms analysis on intermediate sulfidation epithermal pb zn veins implications for porphyry cu deposits exploration in the xianhualing district anhui china abstract the xianhualing district at jinzhai in the northern dabie orogen china is a significant area for pb zn cu au polymetallic exploration the main rocks in the area are mica quartz schist of the neoproterozoic foziling group and magmatic rocks which are controlled by two sets of faults striking nne and nw recent drilling has revealed that the orebody occurs mainly in mica quartz schist in the form of breccia and veinlets major ore minerals include pyrite sphalerite galena chalcopyrite magnetite gold silver and silver sulfosalts with alteration assemblages of predominantly quartz sericite calcite and chlorite three types of fluid inclusions occur in quartz sulfide vein samples collected from eight drill holes two phase liquid rich inclusions type i two phase vapor rich inclusions type and halite bearing inclusions type iii microthermometric studies of type i and fluid inclusions indicate homogenization temperatures of 161 378 c and salinities of 0 5 7 8 wt nacl equivalent fluid inclusion microthermometric data and mineralization and alteration characteristics indicate an intermediate sulfidation epithermal environment current exploration is focused on the location of potential deep porphyry mineralization associated with epithermal mineralization in this study 28 drill core samples from different levels were selected for fluid inclusion microthermometry to elucidate fluid evolution pathways and hence to determine the likelihood of porphyry bodies the consistent fluid inclusion petrography distribution patterns and fluid evolution trends indicate that the deeper part of the dongchong area may have been the regional thermal center of fluid flow the estimated mineralization depths of type iii fluid inclusions are in the range 0 4 1 5 km indicating a relatively shallow formation fluid chemical compositions obtained from single inclusion laser ablation inductively coupled plasma mass spectrometry la icp ms analyses support the occurrence of a single magmatic hydrothermal fluid source which has a degree of mixing with meteoric water and a small amount of basinal brines during the migration path and the fluid evolution pattern agrees well with the fluid inclusion mapping result quartz vein hosted fluid inclusions contain significant amounts of pb zn and cu indicating good exploration prospects for porphyry cu mineralization at depth

a systematic evaluation of the zr in rutile thermometer in ultra high temperature uht rocks the zr in rutile geothermometer is potentially a widely applicable tool to estimate peak metamorphic temperatures in rocks from diverse geological settings in order to evaluate its usefulness and reliability to record and preserve high temperatures in granulite facies rocks rutile from uht rocks was investigated to assess different mechanisms of zr re distribution following cooling from high temperature granulite facies paragneisses from the lowermost part of the ivrea zone italy incorporated as thin sheets into the extensive basaltic body of the mafic complex were selected for this study the results show that zr in rutile thermometry if properly applied is well suited to identify and study uht terranes as it preserves a record of temperatures up to 1190 c although the thermometer is susceptible to partial post peak metamorphic resetting by zr diffusion texturally homogeneous rutile grains preserve zr concentrations corresponding to temperatures of prograde rutile growth diverse rutile textures and relationships between some rutile host grains and included or adjacent zr bearing phases bear testimony to varying mechanisms of partial redistribution and resetting of zr in rutile during cooling and link zr in rutile temperatures to different steps of the metamorphic evolution rutile grains that equilibrated their zr concentrations at temperatures above 1070 c i e 1 1 wt zr could not retain all zr in the rutile structure during cooling and exsolved baddeleyite zro2 by subsequent reaction of baddeleyite exsolution lamellae with sio2 zircon needles formed before the system finally closed at 650 700 c without significant net loss of zr from the whole host rutile grain by reintegration of zircon exsolution needles peak metamorphic temperatures of up to 1190 c are derived for the studied rocks which demonstrates the suitability of this solution thermometer to record uht conditions and also confirms the extraordinary geological setting of the lowermost part of the ivrea zone

synthetic fluid inclusions in natural quartz i compositional types synthesized and applications to experimental geochemistry synthetic fluid inclusions having a wide range of geologically applicable compositions in the c o h s na k ca cl cu fe system have been formed by healing fractures in inclusion free natural quartz and by precipitating new quartz overgrowths on an original seed crystal inclusion types synthesized include 1 1 liquid rich pure h2o inclusions of primary and secondary origin 2 2 pure h2o inclusions with the critical density 3 3 liquid rich inclusions containing undersaturated aqueous solutions of nacl or kcl or cacl2 or mixtures of the three salts 4 4 h2o nacl inclusions containing halite daughter minerals 5 5 h2o nacl kcl inclusions containing halite and sylvite daughter minerals 6 6 h2o co2 inclusions of various compositions containing liquid h2o and either co2 vapor or co2 liquid or both at 25 c 7 7 h2o co2 nacl inclusions containing an aqueous phase liquid and vapor co2 and halite at 25 c 8 8 c o h inclusions containing liquid h2o a co2 ch4 liquid phase and graphite daughter minerals at 25 c 9 9 h2o nacl inclusions that contain a chalcopyrite daughter mineral and 10 10 inclusions representing trapping of the coexisting immiscible fluids in the h2o nacl h2o co2 nacl and na c o h systems the inclusions exhibit uniform phase ratios at room temperature and the temperatures of various phase changes within individual inclusions agree with those predicted from experimental and theoretical data indicating that the inclusion fluid has the same composition and density as the parent solution these miniature autoclaves thus may be used to study various problems related to fluid inclusion research to calibrate analytical equipment used to study natural inclusions and to study phase equilibria solubility and pvt relations of a variety of chemical systems

composition and evolution of ore fluids in a magmatic hydrothermal skarn deposit the chemistry of brine vapor and low salinity fluid inclusions measured by proton induced x ray emission from the bismark skarn deposit mexico is consistent with an evolving magmatic hydrothermal system with no evidence for external fluid inputs the results support a model that invokes early phase separation of magmatic fluids into brine and vapor two phase field at high temperature and lithostatic pressure followed by the entrapment of a low salinity magmatic fluid one phase field at lower temperature and hydrostatic pressure the early brine and vapor inclusions contain high pb and zn concentrations and low cu however the vapor contains significantly more cu than the brine and was likely transported as a sulfur complex the fluid phase changes observed and behavior of cu are comparable to those of porphyry cu systems the later low salinity fluid at bismark represents a distinct pulse of magmatic fluid with a high k ca ratio in which base metals including cu were transported by chloride complexes paragenetic relationships and variations in the relative concentrations of cu pb and zn suggest that this fluid was primarily responsible for ore deposition the relative cu pb and zn concentrations in fluid inclusions at bismark are consistent with those measured from base metal ores in high temperature carbonate replacement deposits throughout mexico and suggest that the bulk metal budget of these deposits is primarily controlled by magmatic hydrothermal fluids deficient in cu

major to trace element analysis of melt inclusions by laser ablation icp ms methods of quantification current techniques for the quantification of melt inclusion chemistry require that inclusions are compositionally homogeneous and that post entrapment devitrification or crystallization onto the inclusion walls could be reversed by appropriate re melting laser ablation icp ms provides a technique by which single heterogeneous inclusions can be analysed thus avoiding the above prerequisites because host mineral is ablated with the inclusion quantification of the melt composition necessitates deconvolution of the mixed signal by an internal standard this can be obtained in various ways including 1 a fixed pre determined concentration of a given element in the melt 2 whole rock differentiation trends in a given igneous suite 3 a constant measured distribution coefficient between the host and the inclusion melt and 4 determination of the volume ratios between the inclusion and total ablated volume these four approaches were tested on a large set of cogenetic inclusions from a single plagioclase crystal in a rhyodacitic intrusion results suggest that quantification through whole rock differentiation trends is the most widely applicable the most accurate and the least time consuming technique provided that the resulting data are critically interpreted with regard to the underlying assumptions uncertainties on the calculated element concentrations in the inclusions depend on the mass ratio between the melt inclusion and the host for a given ablation they are of the order of 10 if the melt inclusion contributes more than 20 to the bulk analytical signal of a particular element calculated limits of detection for spherical 10 m melt inclusions are of the order of a few ppm for elements strongly enriched in the melt relative to the host crystal concentrations in the melt inclusions can be determined even for elements enriched in the host mineral but in this case uncertainties and calculated limits of detection increase with the concentration in the host the uncertainty on the melt composition from a set of cogenetic inclusions can be commonly decreased by calculating of an uncertainty weighted average of the concentration and their uncertainty

mesozoic fluorite veins in ne spain record regional base metal rich brine circulation through basin and basement during extensional events abstract basinal brines are commonly involved in the formation of hydrothermal base metal ore deposits in sedimentary basins although in many instances the source of metals is often thought to be the underlying basement rocks the evidence of brine infiltration through the basement is sometimes directly found in vein systems in fracture zones crosscutting the basement that is the case of the fluorite barite base metal veins found throughout the hercynian basement of europe north africa and the appalachians a geochemical study of brines trapped in these veins can reveal their origin and evolution but also their mineralizing potential and coupled with the timing of fluid circulation can give clues to elucidate the role of these or similar brines in the genesis of base metal mineralizations together with their possible links to tectonic events the sm nd dating of fluorite samples from one of these veins in ne spain the rigros fluorite vein has yielded an age of 137 25 ma 2 mswd 0 40 the vein formation took place during the late jurassic early cretaceous rifting event in the western european basins which is related to the opening of the atlantic inclusion fluids in samples from rigros and another vein system from the same region the berta fluorite vein have been studied with microthermometry crush leach and la icp ms the brines trapped in the two studied vein systems are na ca cl k mg brines with homogenization temperatures 120 c and salinities up to 25 equiv mass nacl the source of this salinity is related to evaporated seawater at least in the halite precipitation field and to the leaching of mesozoic halite and gypsum sequences by seawater and or meteoric water the basinal brines later evolved through water rock interaction with the crystalline basement resulting in some sodium loss and potassium calcium strontium the latter inferred from isotope data and barium enrichment the analyzed brines have concentrations of zn between 3 and 790 ppm of pb between 3 and 995 ppm and of fe between 27 and 2639 ppm which are similar to those reported in comparable hydrothermal veins and mississippi valley type deposits but higher than in most present day sedimentary brines despite the fact they were able to transport large amounts of metals no significant precipitation of sulfides occurred in the veins and consequently the mineralizing potential of these brines was still preserved after fluorite vein formation

the geochemistry of apatite from the los colorados iron oxide apatite deposit chile implications for ore genesis apatite grains from the los colorados iron oxide apatite ioa deposit the largest ioa deposit in the chilean iron belt cib exhibit significant intracrystalline spatial variability with respect to the concentrations of f cl and oh and trace elements statistical interrogation of the compositional data indicates that individual apatite grains contain spatially discrete f rich and cl rich domains the chemical composition of the f rich domains is consistent with apatite growth from silicate melts whereas the chemical composition of the cl rich domains is consistent with apatite growth from a magmatic hydrothermal fluid that cooled as it percolated outward from the los colorados fault the structural control for emplacement of the ore body into the surrounding brecciated diorite and andesite host rocks apatite in the deposit is intimately intergrown with magnetite and actinolite for which trace element fe h and o stable isotope data indicate a combined magmatic magmatic hydrothermal genesis for the deposit the compositional data for apatite are consistent with a genetic model wherein f rich apatite cores crystallized with magnetite from silicate melt followed by exsolution of a magmatic hydrothermal fluid during decompression of the parent magma experimental studies demonstrate that magmatic hydrothermal volatile phase bubbles preferentially nucleate and grow on the surfaces of apatite and magnetite microlites during decompression of a magma body continued degassing of the melt results in the volatile phase sweeping up apatite and magnetite microlites and forming a magnetite apatite fluid suspension that is buoyant in the magma chamber and ascends from the source magma along faults during regional extension halite saturated fluid inclusions in magnetite which is paragenetically equivalent to apatite at los colorados indicate that the magmatic hydrothermal fluid was a brine which allows this fluid to efficiently scavenge cl p rare earth elements and other fluid compatible elements from the silicate melt during ascent the xcl xf ratio of apatite increases as it grows from the evolving cl rich magmatic hydrothermal fluid during decompression and cooling

metal fractionation between magmatic brine and vapor determined by microanalysis of fluid inclusions the major and trace element compositions of individual fluid inclusions from a range of magmatic hydrothermal ore deposits were analyzed by laser ablation inductively coupled plasma mass spectrometry to explore the behavior of ore forming components during fluid phase separation boiling in high temperature saline fluid systems data from 13 samples showing unambiguous evidence for coeval trapping of a liquid brine and a coexisting vapor phase identify two groups of elements with drastically different geochemical behavior na k fe mn zn rb cs ag sn pb and tl preferentially partition into the brine probably as cl complexes whereas cu as au probably as hs complexes and b selectively partition into the vapor fluid phase separation is probably a major previously underestimated process in the chemical differentiation that contributes to the extreme range of selective element enrichments in magmatic hydrothermal systems from deep plutons through porphyry style and greisen deposits to epithermal mineralization and volcanic fumaroles

fluid evolution in zoned cordilleran polymetallic veins insights from microthermometry and la icp ms of fluid inclusions abstract fluid inclusion analysis through the paragenetic sequence of one symmetrically zoned vein sample is used to reconstruct the p t x fluid evolution of a porphyry intrusion related cordilleran polymetallic vein from morococha central peru results record an evolution from initial deep seated precipitation of quartz pyrite and base metal sulphides to final near surface deposition of carbonates demonstrating progressive mineralisation during uplift and erosion this is the first detailed study addressing meso to epithermal zn pb ag cu rich ore in a magmatic hydrothermal system by combination of fluid inclusion microthermometry with laser ablation inductively coupled plasma mass spectrometry la icp ms quantifying metal as well as sulphur concentrations in the evolving hydrothermal fluid scanning electron microscopy cathodoluminescence sem cl imaging of quartz and detailed transmitted and reflected light petrography provide textural evidence that early moderately saline 4 5 wt nacl eq and co 2 bearing fluids with homogenisation temperatures of 340 380 c precipitate cu bearing minerals in this open hydrothermal system the fluids record decreasing salinities co 2 contents and temperatures while zn pb and ag sulphides precipitate fluids related to early precipitation in the vein have metal contents of several 1000 g g s and fe over 1000 g g cu 100 g g pb 10 g g ag and several 100 g g zn sulphur concentrations in the fluid are sufficiently high to precipitate all metals in solution as sulphides the latest generation of fluid inclusions associated with abundant carbonate precipitation in the centre of the vein has homogenisation temperatures ranging from 260 to 220 c low metal concentrations and no measurable co 2 during vein formation cooling and several kilometres of erosion resulted in telescoping of consecutively precipitated mineral assemblages the deep input fluid dominating in the early vein stage is interpreted to be of magmatic origin most likely a single phase magmatic fluid of intermediate salinity and density it cooled to an aqueous liquid separated minor co 2 rich vapour and was eventually diluted by meteoric water in the late stages of vein formation when the progressively eroded land surface was only several hundred meters above the vein location

brine rock interaction in the athabasca basement mcarthur river u deposit canada consequences for fluid chemistry and uranium uptake terra nova 22 303 308 2010 abstract the nature of uranium source rocks transport conditions and deposition processes are still highly controversial for world class unconformity related u deposits this article presents the first detailed chemistry of brines associated with the giant mcarthur river u deposit canada la icp ms analysis of individual fluid inclusions suggests mixing between a na ca mg k sr ba brine and a ca mg na k sr ba brine the brines share a common origin evaporated seawater and show evidence for contrasting interaction with basement rocks the na rich brine lost mg and k in alteration haloes around u ores while the ca rich brine results from na ca exchange and sr ba gain u concentrations 0 3 530 g g 1 are anomalously high compared with usual basinal fluids this indicating that u uptake occurred within basement rocks the two brine end members have mixed within the main u deposit area which could be one of the major driving forces for u deposition

modeling of gold scavenging by bismuth melts coexisting with hydrothermal fluids the effect of gold scavenging by bismuth melts is investigated using equilibrium thermodynamic modeling of an aqueous solution mineral melt system the calculations for the au bi na cl s h o system performed at temperatures between 300 and 450 c demonstrate that au concentrations in the melt are several orders of magnitude higher than in the coexisting fluid indicating the possible formation of economic gold deposits from undersaturated aqueous fluids in which mineralization would not be expected in the absence of a bismuth melt the model applies to any deposit where a bi melt is stable and coexists with a hydrothermal fluid examples of such deposits are known from skarn intrusion related orogenic and volcanogenic massive sulfide vms gold systems in sulfur poor systems the partitioning curves presented here can be used directly to correlate the gold concentration in the fluid and the au grade in the ore e g escanaba trough vms deposit these results also illustrate important principles generally applicable to understanding magmatic hydrothermal and metamorphic deposits that may have contained significant volumes of more complex polymetallic melts

fluid evolution in a volcanic hosted epithermal carbonate base metal gold vein system alto de la blenda farallon negro argentina alto de la blenda is a 6 6 ma intermediate sulphidation epithermal vein system in the farallon negro volcanic complex which also hosts the 7 1 ma porphyry cu au deposit of bajo de la alumbrera the epithermal vein system is characterised by a large extent and continuity 2 km 400 m open to depth 6 m maximum width and an average gold grade of 8 g t the vein is best developed within an intrusion of a fine grained equigranular monzonite interpreted as the central conduit of a stratovolcano whose extrusive activity ended prior to porphyry cu au emplacement at bajo de la alumbrera which is in turn cut by minor epithermal veins the alto de la blenda vein consists predominantly of variably mn rich carbonates and quartz with a few percent of pyrite sphalerite galena and other sulphide and sulphosalt minerals four phases of vein opening hydrothermal mineralisation and repeated brecciation can be correlated between different vein segments stages 2 and 3 contain the greatest fraction of sulphide and gold they are separated by the emplacement of a polymictic breccia containing clasts of quartz feldspar porphyry as well as basement rocks fluid inclusions in quartz related to stages 2 to 4 are liquid rich with 2 4 wt nacl eq they homogenise between 160 and 300 c with very consistent values within each assemblage vapour inclusions are practically absent in the epithermal vein quartz fragments in the polymictic breccia contain inclusions of intermediate to vapour like density and similar low salinity 3 wt nacl eq besides rare brine inclusions containing halite laser ablation inductively coupled plasma mass spectrometry la icp ms analyses of epithermal inclusions indicate high concentrations of k fe as sb cs and pb that significantly vary within and through subsequent vein stages careful consideration of detection limits for individual inclusions shows high gold concentrations of 0 5 to 3 ppm dissolved in the ore fluid which contains variably high sulphur concentrations in excess over fe and other chalcophile metals compositional variations are interpreted to reflect cooling and contraction of lower density magmatic fluids at depth like those preserved in porphyry clasts that were mechanically transported up by the polymictic breccia ore mineral precipitation from the magmatic fluid occurred by further cooling and possibly minor mixing with surface derived water leading to sulphide saturation de sulphidation of the magmatic fluid and consequent gold precipitation the absence of flash boiling and or reduction by carbonaceous host rocks has led to relatively modest but constant gold grades in the carbonate base metal gold veins of alto de la blenda

isotope systematics in vein gold from brusson val d ayas nw italy 1 pb pb evidence for a piemonte metaophiolite au source the monte rosa gold district nw italian alps comprises hundreds of late alpine epigenetic gold bearing quartz veins we report a lead isotope study on an important one of these veins fenilia brusson val d ayas which reveals a complex isotope geochemistry of petrographically cogenetic vein minerals petrographic observations allow to distinguish a quartz dominated main stage and a quartz poor final stage mineral assemblage most of the free gold crystallized in the beginning of the final stage whereas sulphides were deposited during its waning three distinct lead isotope fields result for the paragenetic sequence of vein minerals the variable lead isotope signature 15 517 15 706 as well as from the uniform radiogenic lead 15 649 207pb 204pb 15 691 characteristic of the waning final stage we favour a model where the deeply circulating final stage fluid the ultimate source of which remains obscure acquired lead and thus possibly its gold in piemonte metaophiolitic rocks beneath the monte rosa nappe during ascent the primitive gold bearing fluid was variably contaminated by an evolved crustal lead 15 706 207pb 204pb 15 743 compatible with derivation from monte rosa nappe rocks during deposition of final stage minerals the pb isotope composition of the fluid changed to a constant signature becoming again dominated by a radiogenic lead source thus within an assemblage defined as cogenetic on petrographic grounds the pb isotopic signature is not necessarily uniform and source modelling based on lead isotopes of associated minerals may be inappropriate it remains open at present whether the inferred piemonte metaophiolite gold source is confined to the fenilia vein in val d ayas only or whether it might be more widespread in the monte rosa gold district

fluid and gas migration in the north german basin fluid inclusion and stable isotope constraints fluid inclusions have been studied in minerals infilling fissures quartz calcite fluorite anhydrite hosted by carboniferous and permian strata from wells in the central and eastern part of the north german basin in order to decipher the fluid and gas migration related to basin tectonics the microthermometric data and the results of laser raman spectroscopy reveal compelling evidence for multiple events of fluid migration the fluid systems evolved from a h2o nacl kcl type during early stage of basin subsidence to a h2o nacl cacl2 type during further burial locally fluid inclusions are enriched in k cs li b rb and other cations indicating intensive fluid rock interaction of the saline brines with lower permian volcanic rocks or sediments fluid migration through carboniferous sediments was often accompanied by the migration of gases aqueous fluid inclusions in quartz from fissures in carboniferous sedimentary rocks are commonly associated with co genetically trapped ch4 co2 inclusions p t conditions estimated via isochore construction yield pressure conditions between 620 and 1 650 bar and temperatures between 170 and 300 c during fluid entrapment the migration of ch4 rich gases within the carboniferous rocks can be related to the main stage of basin subsidence and stages of basin uplift a different situation is recorded in fluid inclusions in fissure minerals hosted by permian sandstones and carbonates aqueous fluid inclusions in calcite quartz fluorite and anhydrite are always h2o nacl cacl2 rich and show homogenization temperatures between 120 and 180 c co genetically trapped gas inclusions are generally less frequent when present they show variable n2 ch4 compositions but contain no co2 p t reconstructions indicate low pressure conditions during fluid entrapment always below 500 bar the entrapment of n2 ch4 inclusions seems to be related to phases of tectonic uplift during the upper cretaceous a potential source for nitrogen in the inclusions and reservoirs is corg rich carboniferous shales with high nitrogen content intensive interaction of brines with carboniferous or even older shales is proposed from fluid inclusion data enrichment in li ba pb zn mg and sulfur isotopic compositions of abundant anhydrite from fissures the mainly light 34s values of the fissure anhydrites suggest that sulfate is either derived through oxidation and re deposition of biogenic sulfur or through mixing of so42 rich formation waters with variable amounts of dissolved biogenic sulfide an igneous source for nitrogen seems to be unlikely since these rocks have low total nitrogen content and furthermore even extremely altered volcanic rocks from the study area do not show a decrease in total nitrogen content

hydrothermal evolution of the el teniente deposit chile porphyry cu mo ore deposition from low salinity magmatic fluids the magmatic hydrothermal evolution of the el teniente porphyry cu mo deposit in the central andes in chile is reconstructed based on field relationships scanning electron microscopy cathodoluminescence petrography and fluid inclusion analysis by microthermometry and laser ablation inductively coupled plasma mass spectrometry la icpms three major stages of cu mo mineralization are observed following the barren hydrothermal stage 1 the stage 2 mineralization is characterized by quartz anhydrite stockwork veins and breccias with chalcopyrite bornite and molybdenite both stages 1 and 2 are associated with pervasive potassic alteration quartz anhydrite veins with chalcopyrite bornite and molybdenite associated with phyllic alteration represent stage 3 mineralization stage 4 mineralization linked to the formation of the large braden diatreme is characterized by breccias and rare veins containing a lower temperature assemblage with tourmaline sericite and lesser tennantite bornite and chalcopyrite with late gypsum in local vugs ten fluid types are distinguished in this study based on petrographic and microthermometric criteria such as phase proportions daughter minerals homogenization behavior and salinity the hydrothermal evolution across the stages of cu deposition is characterized by the contraction of a vapor phase originating by phase separation during stage 2 overall cooling of the system at pressures fluctuating around the two phase fluid surface led to a transition from a two phase fluid state dominated by vapor at 410 c and 300 bars in stage 2 to a single phase low salinity fluid derived from cooling and contraction of magmatic vapor to a liquid which dominates during stage 3 mineralization at 350 c and 200 bars copper mineralization mainly formed from the vapor phase and its low salinity liquid derivatives representing a large volume of fluid with an initially high cu content 1 2 0 4 wt cu copper sulfides precipitated upon cooling between 410 and 320 c indicated by a drop of cu na k mn fe ratios of over four orders of magnitude through the evolution of the deposit from stage 2 to stage 4 the highest mo concentrations occur in residual brines resulting from extreme boiling as indicated by concurrent halite saturation recent geochronology cannell 2005 maksaev et al 2004 suggests a relatively long lived magmatic hydrothermal system at el teniente our fluid chemical data show no evidence for major crystal fractionation in a large fluid generating upper crustal magma chamber because cs na k mn fe is constant from pre ore to all syn ore fluids however the initiation of copper mineralization was associated with a 4 to 10 fold increase in the concentration of cu mo li and fe in the inferred main ore forming input fluid compared with pre ore fluids of intermediate salinity and otherwise very similar major and trace element ratios these data indicate that injection from depth of an exceptionally cu mo li and probably also s rich volatile phase into an already actively evolving upper crustal magmatic hydrothermal system triggered the formation of this unusually large and rich copper deposit

experimental study of the behavior of copper and zinc in a boiling hydrothermal system vapor liquid partitioning coefficients for cu and zn in aqueous fluid were determined under boiling conditions at 500 650 c and 35 100 mpa in sulfur bearing and sulfur free systems a synthetic fluid inclusion technique was used to sample the experimental system of coexisting vapor rich and liquid rich fluid inclusions the cu and zn concentrations in individual fluid inclusions were then analyzed by synchrotron radiation x ray fluorescence the vapor liquid distribution constant of cu k d m cu vapor m cu liquid where m denotes the molality of metal is found to be strongly dependent on the sulfur content in the experimental solutions in sulfur bearing systems cu preferentially partitions into the vapor phase whereas zn preferentially fractionates into the hypersaline liquid the k d values for cu and zn obtained in this study correspond well with those obtained from natural fluid inclusions in hydrothermal ore deposits the results suggest that differential volatility of metals is an important factor affecting the enrichment of certain metals in different hydrothermal ore deposits

mixing of magmatic hydrothermal and metamorphic fluids and the origin of peribatholitic sn vein type deposits in rwanda abstract the fluid sources of granite related sn quartz vein deposits are commonly obscured by fluid mixing or fluid rock interactions as a result fluid inclusions minerals and isotopes in these veins indicate an intermediate composition between magmatic and metamorphic but the degree of mixing between these endmembers is currently unquantified this study presents a novel quantitative approach to assess the degree of mixing between magmatic hydrothermal and external metamorphic fluids in the formation of peribatholitic sn quartz veins in particular fluid mixing in the sn mineralized rwamagana musha ntunga pegmatite quartz vein field in east rwanda has been evaluated by the following four methods quartz stable isotopes muscovite geochemistry fluid inclusion microthermometry and la icp ms and geochemical modelling the quartz stable isotope data 18o 13 1 to 15 8 v smow d 27 6 to 59 7 v smow cannot uniquely differentiate between a metamorphic fluid origin or an initial magmatic hydrothermal fluid origin with subsequent metamorphic fluid mixing or host rock interaction however granitophile element concentrations in magmatic muscovite from pegmatites and hydrothermal muscovite from associated sn quartz veins are equally high indicating a close genetic link rb 530 8740 ppm li 110 1990 ppm sn 87 810 ppm cs 62 420 ppm primary h2o co2 n2 nacl medium saline magmatic fluid inclusions in quartz of pegmatites 12 7 wt nacleq and h2o co2 n2 nacl low saline fluid inclusions in barren metamorphic quartz veins 4 9 wt nacleq were analyzed by la icp ms these results show an enrichment in li rb sn and cs for the magmatic fluid while the metamorphic fluid is characterized by low granitophile element concentrations and high sr and ba contents the expected rb cs and rb sn signature of the sn quartz vein muscovite was modelled using the measured fluid endmember compositions confirming mixing between magmatic and metamorphic fluids in the formation of the veins the quantification suggests that the hydrothermal sn quartz vein fluid contains 5 80 of an external metamorphic fluid component

alkali metals control the release of gold from volatile rich magmas magmatic hydrothermal ore deposits are a major resource of gold volatiles exsolving from magmas rising through the earth s crust are the key agent for enrichment of gold in these deposits we report the first experimental determination of gold solubilities in the magmatic volatile phases at conditions typical of most magmas associated with gold deposits t 1000 degrees c p 150 mpa we show that gold hydrosulfide complexes supersede gold chloride complexes and more importantly that the stability of gold hydrosulfide complexes is greatly increased by the presence of minute concentrations of kc or nacl 0 1 0 5 mol kg h2o the amplifying effect of alkali chlorides on the solubility of gold in h2s bearing volatiles may explain the preferential association of many giant hydrothermal gold deposits with high potassium alkaline mafic to intermediate igneous rocks which exsolve volatiles that simultaneously contain both h2s and alkali chlorides in significant concentrations c 2010 elsevier b v all rights reserved

causes for large scale metal zonation around mineralized plutons fluid inclusion la icp ms evidence from the mole granite australia detailed reconstruction of the fluid evolution in several ore deposits associated with the sn w and base metal mineralized mole granite shows that multiple factors contributed to the zonal metal distribution around this intrusion information about the mechanism of ore formation was obtained from field relationships detailed petrographic studies and laser ablation inductively coupled plasma mass spectrometry la icp ms microanalysis of single fluid inclusions premineralization fluid inclusions in sn deposits are characterized by high sn w ratios whereas early fluid inclusions from w deposits contain higher w concentrations and comparatively low sn w ratios this indicates that the metal ratio in these deposits already was predefined by the composition of the magmatic input fluid however in both types of deposits the input fluid actually contained much higher concentrations of base metals pb zn cu etc than sn and w demonstrating that metal precipitation was highly selective the metal zonation around the mole granite therefore reflects both a compositional variation of the source fluid as well as sequential metal precipitation from it an additional process contributing to metal fractionation occurred by phase separation of the hydrothermal fluid into saline brine and low density vapor whereby cu b li as s ag la preferentially partitioned into the vapor phase analyses on six assemblages of unambiguously coexisting vapor and brine inclusions allowed direct determination of vapor brine distribution coefficients for 24 elements

the fate of b cl and li in the subducted oceanic mantle and in the antigorite breakdown fluids we present an inventory of b cl and li concentrations in a key minerals from a set of ultramafic samples featuring the main evolutionary stages encountered by the subducted oceanic mantle and in b fluid inclusions produced during high pressure breakdown of antigorite serpentinite samples correspond to i nonsubducted serpentinites northern apennine and alpine ophiolites ii high pressure olivine bearing antigorite serpentinites western alps and betic cordillera iii high pressure olivine orthopyroxene rocks recording the subduction breakdown of antigorite serpentinites betic cordillera two main dehydration episodes are recorded by the sample suite partial serpentinite dewatering during formation of metamorphic olivine followed by full breakdown of antigorite serpentine to olivine orthopyroxene fluid ion probe and laser ablation icp ms la icp ms analyses of cl b and li in the rock forming minerals indicate that the hydrous mantle is an important carrier of light elements the estimated bulk rock b and cl concentrations progressively decrease from oceanic serpentinites 46 7 ppm b and 729 ppm cl to antigorite serpentinites 20 ppm b and 221 ppm cl to olivine orthopyroxene rocks 9 4 ppm b and 45 ppm cl this suggests release of oceanic cl and b in subduction fluids apparently without inputs from external sources lithium is less abundant in oceanic serpentinites 1 3 ppm and the initial concentrations are still preserved in high pressure antigorite serpentinites higher li contents in olivine ti clinohumite of the olivine orthopyroxene rocks 4 9 ppm bulk rock li as well as in the coexisting fluid inclusions suggest that their budget may not be uniquely related to recycling of oceanic li but may require input from external sources laser ablation icp ms analyses of fluid inclusions in the olivine orthopyroxene rocks enabled an estimate of the li and b concentrations in the antigorite breakdown fluid the inclusion compositions were quantified using a range of salinity values 0 4 2 wt naclequiv as internal standards yielding maximum average fluid rockdb 5 and fluid rockdli 3 5 we also performed model calculations to estimate the b and cl loss during the two dehydration episodes of serpentinite subduction the first event is characterized by high fluid rock partition coefficients for cl 100 and b 60 and by formation of a fluid with salinity of 4 8 wt naclequiv the antigorite breakdown produces less saline fluids 0 4 2 wt naclequiv and is characterized by lower partition coefficients for cl 25 60 and b 12 30 our calculations indicate that the salinity of the subduction fluids decreases with increasing depths fluid rockdb fluid rockdcl 1 0 5 indicates that cl preferentially partitions into the evolved fluids relative to b and that the b cl of fluids progressively increases with increasing depths and temperatures despite light element release in fluids appreciable b cl and li are still retained in chlorite olivine and ti clinohumite beyond the antigorite stability field this permits a bulk storage of about 10 ppm b 45 ppm cl and 5 ppm li i e concentrations much higher than in mantle reservoirs chlorite is the cl repository and its stability controls the cl and h2o budget beyond the antigorite stability b and li are bound in olivine and clinohumite the subducted oceanic mantle thus retains light elements beyond the depths of arc magma sources potentially introducing anomalies in the upper mantle

episodic hydrothermal alteration recorded by microscale oxygen isotope analysis of white mica in the larderello travale geothermal field italy abstract microscale oxygen isotope analysis 18o 16o of minerals can identify distinct events of fluid rock interaction this method is however still limited to a few major and accessory minerals of which most are anhydrous minerals we present the systematic study of oxygen isotope distribution in white mica by secondary ion mass spectrometry sims texturally and chemically distinct white mica populations in granitic and contact metamorphic rocks from the larderello travale geothermal field ltgf italy record stages of magmatic crystallization metamorphic hydrothermal replacement and fluid rock interaction the large range in intra and inter grain white mica 18o values between 1 and 14 reflects varying protoliths and degrees of fluid mineral interaction at variable temperatures 180 450 c present day temperatures p d t this variability reflects the large scale circulation of both 1 magmatic syn intrusive to early contact metamorphic hydrothermal fluids with high 18o values and 2 meteoric fluids with 18o values of 7 during a post intrusive late hydrothermal stage metasedimentary rocks from the upper reservoir contain distinct white mica populations occurring in close proximity m scale including detrital grains 18o 12 14 high na low mg partially altered white mica 18o 8 9 and late hydrothermal white mica 1 6 low na mid mg the late hydrothermal white mica has similar 18o values to other secondary minerals and is in equilibrium with meteoric dominated fluids with a 18o of 6 to 0 5 which circulated in the late hydrothermal stage downhole towards the lower reservoir white mica from two contact metamorphic micaschist samples shows either 1 homogeneous 18o values of ca 9 likely due to recrystallization in the contact metamorphic hydrothermal stage t ca 600 c or 2 a large spread in 18o from 2 to 12 within and across grains of variable texture and chemistry in the host rock and a cross cutting quartz white mica vein ca 300 c present day temperature hereafter p d t this contrasting 18o signature of white mica is also recorded in granite cored at up to 4 6 km depth the carboli granite contains white mica with a homogeneous magmatic 18o of 10 0 6 whereas older granite samples from radicondoli have magmatic to hydrothermal white micas that vary in 18o from 4 to 10 a pronounced intra grain 18o variability of up to 6 occurs in white mica domains with higher fe mg ti halos around inclusions of chloritized biotite as a result of interaction with dominantly meteoric fluids that infiltrated to depths of at least 4 6 km in the porto azzurro granite on elba italy altered white mica has 18o values of 2 6 down from 10 in unaltered grains the distribution of oxygen isotope ratios in white mica is thus firstly a result of pervasive versus selective fluid alteration at depth sample and grain scale secondly the actual preservation of these m scale variabilities indicates that volume diffusion is not detectable at microscale at p d t at or below 350 c where most of the heterogeneous white mica is found selective sample and grain scale fluid penetration occurs episodically and anisotropically on micro and megascale along faults fractures and cleavages producing lower 18o white mica at various times in zones of higher secondary permeability and active hydrothermal fluid circulation

the role of sulfur in the formation of magmatic hydrothermal copper gold deposits abstract essential resources of many rare metals including copper zinc molybdenum silver and gold occur in natural sulfide mineral deposits understanding the origin of these metal resources has been limited by a lack of data about the geochemistry of sulfur the most important and abundant element of ore deposits we report the first directly measured sulfur concentrations in high temperature fluids together with their ore metal contents using a new method for sulfur quantification in fluid inclusions by laser ablation inductively coupled plasma mass spectrometry la icp ms co genetic brine and vapor inclusions from magmatic hydrothermal ore deposits and granitic intrusions show an excess of sulfur over ore metals as required for efficient ore mineral precipitation the results demonstrate that s cu and au are highly enriched in vapor like magmatic fluids implying that such low salinity fluids are the key agent for the formation of porphyry copper and epithermal gold deposits

volatile exsolution at the dinkidi cu au porphyry deposit philippines a melt inclusion record of the initial ore forming process immiscible phases derived from degassing silicate magmas are considered to be precursors of metal bearing hydrothermal fluids in porphyry deposits the development of melt inclusion techniques provides a window into this critical period of porphyry formation when the cooling decompression and crystallization of silicate melts result in the formation of immiscible phases the record of magmatic to hydrothermal evolution is presented using inclusions in clinopyroxene phenocrysts from the syenitic balut dike one of the host rock lithologies for mineralization at the dinkidi cu au porphyry deposit philippines primary inclusions include silicate glass multiphase aggregates comprising salts silicates sulfates carbonates sulfides and oxides and highly saline aqueous fluids various analyses including in situ laser ablation inductively coupled plasma mass spectrometry of the multiphase inclusions determined elevated concentrations of cl s as tl k na and a number of metals including those that form ore grade deposits e g cu and those that do not e g mo pb zn and w at the dinkidi porphyry deposit silicate melt and multiphase salt rich inclusions in clinopyroxene are interpreted as having originally formed as immiscible phases at magmatic temperatures

morphological ripening of fluid inclusions and coupled zone refining in quartz crystals revealed by cathodoluminescence imaging implications for cl petrography fluid inclusion analysis and trace element geothermometry cathodoluminescence cl studies have previously shown that some secondary fluid inclusions in luminescent quartz are surrounded by dark non luminescent patches resulting from fracture sealing by late trace element poor quartz this finding has led to the tacit generalization that all dark cl patches indicate influx of low temperature late stage fluids in this study we have examined natural and synthetic hydrothermal quartz crystals using cl imaging supplemented by in situ elemental analysis the results lead us to propose that all natural liquid water bearing inclusions in quartz whether trapped on former crystal growth surfaces i e of primary origin or in healed fractures i e of pseudosecondary or secondary origin are surrounded by three dimensional non luminescent patches cross cutting relations show that the patches form after entrapment of the fluid inclusions and therefore they are not diagnostic of the timing of fluid entrapment instead the dark patches reveal the mechanism by which fluid inclusions spontaneously approach morphological equilibrium and purify their host quartz over geological time fluid inclusions that contain solvent water perpetually dissolve and reprecipitate their walls gradually adopting low energy euhedral and equant shapes defects in the host quartz constitute solubility gradients that drive physical migration of the inclusions over distances of tens of m commonly up to several mm rarely inclusions thus sequester from their walls any trace elements e g li al na ti present in excess of equilibrium concentrations thereby chemically purifying their host crystals in a process analogous to industrial zone refining non luminescent patches of quartz are left in their wake fluid inclusions that contain no liquid water as solvent e g inclusions of low density h2o vapor or other non aqueous volatiles do not undergo this process and therefore do not migrate do not modify their shapes with time and are not associated with dark cl zone refined patches this new understanding has implications for the interpretation of solids within fluid inclusions e g ti and al minerals and for the elemental analysis of hydrothermal and metamorphic quartz and its fluid inclusions by microbeam methods such as la icpms and sims as ti is a common trace element in quartz its sequestration by fluid inclusions and its depletion in zone refined patches impacts on applications of the ti in quartz geothermometer

relationships between sem cathodoluminescence response and trace element composition of hydrothermal vein quartz laser ablation icp ms data of hydrothermal vein quartz with zonation in scanning electron microscope cathodoluminescence reveal two groups of trace elements one that co varies in concentration with luminosity and another that remains uniform throughout bright luminosity correlates with a high total abundance of trace elements in early quartz including al up to 410 g g ti up to 240 g g k up to 330 g g li up to 8 g g na up to 36 g g and fe up to 20 g g up to 20 times lower concentrations of these elements are associated with dark luminosity in late quartz concentrations of p 21 g g ga 0 3 g g ge 1 3 g g sn 1 5 g g cu 0 3 g g and ag 0 1 g g demonstrate no relationship with luminosity charge balance cannot be achieved for bright luminescent quartz unless the presence of up to 6 g g h not analyzed by la icpms or interstitial al3 is invoked interestingly the inferred 6 g g h remains constant for quartz containing more than 10 mol total trace elements and might represent the solubility of h in hydrothermal quartz at temperatures between 450 and 700 c la icpms results indicate that the fluid chemistry determines the quartz trace element pattern which may serve as a monitor for the chemical environment from which quartz crystallized ratios of na al and ti al are uniform whereas k al evolves toward lower values with decreasing luminosity combined evidence including quartz vein textures silica solubility data and estimates of the temperature of quartz growth suggest that early quartz crystallized fast but late quartz grew more slowly at 350 to 425 c it is speculated that the higher the quartz growth rate is the more trace elements are incorporated into quartz besides the temperature dependence known from the literature clearly growth rate temperature and fluid chemistry are important parameters affecting luminosity however their relative importance may vary from case to case

a method to synthesize large fluid inclusions in quartz at controlled times and under unfavorable growth conditions a new synthesis technique allows large fluid inclusions to be produced at conditions under which one normally would obtain only small inclusions with the additional advantage that the timing of fluid entrapment can be controlled in the first step primary fluid inclusions are grown at p t conditions under which it is relatively easy to produce large inclusions in the second step which can be performed either during the same experiment or during a separate experiment after a desired time of pre equilibration some of the primary inclusions produced during the first step are re opened by in situ fracturing causing partial replacement of the inclusion content the sample is then left at high pressure and temperature until the cracks leading to the re opened inclusions are healed to test the method and quantify the efficiency of fluid replacement in the re opened inclusions we produced primary inclusions at 700 c 200 mpa and re opened them during a second experiment in the presence of a compositionally different fluid at 500 c 70 mpa laser ablation icp ms la icp ms analyses of eight primary and 11 refilled inclusions demonstrate that in the latter more than 97 of the original fluid was replaced by new fluid thus the refilled inclusions are representative of the surrounding fluid at the time of in situ fracturing

composition of ore fluid inclusions from the viburnum trend southeast missouri district united states implications for transport and precipitation mechanisms fluid inclusions hosted by sphalerite and dolomite cement from the mississippi valley type mvt deposits of the viburnum trend of the southeast missouri district were analyzed by microthermometry and laser ablation inductively coupled plasma mass spectrometry la icp ms to determine the composition of mineralizing fluids and to seek insights into ore forming processes on the whole fluid inclusions from throughout the paragenesis have compositions resembling deep sedimentary brines a population of anomalously pb rich fluid inclusions with concentrations reaching 1 500 ppm was identified in some of the paragenetically early and main stage sphalerite which is interpreted to represent the influx of a pb and possibly overall metal rich fluid into southeast missouri during the time of sulfide mineralization this influx of pb rich fluid appears to have been intermittent as at least one stage of dolomite cement that hosts pb poor fluid inclusions occurs between intervals of sphalerite that host pb rich fluid inclusions if fluid flow into the district was principally from one direction for example from the arkoma basin to the south then the intermittency in high pb concentrations could be explained by compositional changes in the source region or along the flow path alternatively if fluid flow into the district was from two or more directions and fluid arriving from each direction had a different composition then the intermittency in high pb concentrations could be explained by transient variations in the relative flow rates from each direction lead concentrations on the order of thousands of parts per million make it unlikely that the southeast missouri ores were precipitated by any mechanism that involved simultaneous transport of metals and sulfide in the same fluid as the concentrations of sulfide that could coexist with such high concentrations of pb would be too low to allow the ores to be deposited within a geologically reasonable period of time unless the ph was very low or groundwater flow rates were very high thus some type of mixing scenario seems more likely involving either mixing of a metal with a sulfide rich fluid or mixing of a metal and sulfate rich fluid with a reductant present either in the host rock or in another fluid fluid inclusions hosted by sphalerite have k na and ca mg ratios that partly resemble the compositions of both main stage cuboctahedral galena and less abundant late stage cubic galena suggesting that sphalerite was precipitated from a mixture of the fluids that precipitated these two types of galena however the fact that aqueous pb concentration does not correlate with these ratios or other indicators of main stage mineralization such as matrix mn fe co cu ag and cd content in sphalerite suggests that more than two fluids were involved in mixing

cl br of scapolite as a fluid tracer in the earth s crust insights into fluid sources in the mary kathleen fold belt mt isa inlier australia a combination of analytical methods including trace element analysis of br in scapolite by la icp ms was employed to unravel the fluid rock interaction history of the mary kathleen fold belt of northern australia halogen ratios in the metamorphic and hydrothermally derived scapolite from a range of rock types record interaction between the host rocks and magmatic hydrothermal fluids derived from granite plutons and regional metamorphism the results show that halite dissolution supplied at best only minor chlorine to fluids in the fold belt chlorine bromine ratios in metamorphic scapolite indicate that fluids were dominantly derived from basinal brines formed from sub aerial evaporation of seawater beyond the point of halite saturation this bittern fluid infiltrated the under lying sedimentary sequences prior to regional metamorphism zoned scapolite in a major late meta morphic mineralized shear zone records three discrete pulses of magmatic and metamorphic fluid and it is suggested that fluid mixing may have assisted mineralization along and around this shear zone as a crucial prerequisite for halogen fluid tracer studies using scapolite we find in our samples that cl and br do not fractionate when incorporated in scapolite furthermore unaltered rims of heavily retrogressed scapolite show indistinguishable cl br signatures compared with fresh grains from the same sample indicating retrograde metamorphism did not significantly affect cl and br signatures in scapolite group minerals

constraints on fluid evolution during metamorphism from u th pb systematics in alpine hydrothermal monazite abstract the timing and duration of hydrothermal activity during orogenesis are difficult to constrain because such systems are open and multistage using mm sized monazite crystals from two alpine clefts from the central alps switzerland we demonstrate that combined u th pb isotopic systematics of hydrothermal monazite can constrain both timing and fluid evolution during crystallization our data highlight four major characteristics of the cleft monazites i extreme th u ratios ii significant common pb in the u system up to 39 206 pb iii excess 206 pb up to 54 and iv precise and reliable th pb ages comparison of our results with literature data indicates that th u in monazite is a remarkable discriminant of geological conditions capable of distinguishing metasedimentary magmatic and hydrothermal origin hydrothermal monazite crystals are characterized by th u ratios up to 629 among the highest values ever reported extreme th u ratios in monazite enhance incorporation of 230 th a short lived intermediate product in the 238 u 206 pb decay chain generating 206 pb excess which if not accounted for results in 206 pb 238 u ages that are too old for example in the samples investigated here by as much as 300 for the two zoned monazite crystals studied in detail 208 pb 232 th ages are reliable for the different compositional domains visible in back scattered electron bse images 232 th 208 pb ages for the older domains 15 2 0 3 ma and 14 1 0 3 ma respectively are consistent with the structural relationships of the hydrothermal veins indicating early retrograde genesis the youngest rim age at 13 5 0 4 ma for the blauberg crystal marks termination of monazite precipitation the resolvable age difference is interpreted to reflect pulsed monazite growth over an extended period of hydrothermal activity in both crystals the outer rims have the highest 206 pb excess confirming a two stage crystallization two scenarios are envisaged to account for the 206 pb excess evolution in the first increasing 206 pb excess is caused by a modification of the th u fractionation between monazite and fluid due to an evolution of the fluid towards more oxidizing conditions that favor partitioning of hexavalent u into the fluid alternatively it is possible that 230 th increased with time in the fluid in this second case monazite growth would have occurred in a closed system from a fluid that was initially in disequilibrium with the 238 u 206 pb decay chain and progressively equilibrated t

advances in lithium analysis in solids by means of laser induced breakdown spectroscopy an exploratory study lithium is an important geochemical tracer for fluids or solids however because the electron microprobe cannot detect li variations of li abundance at the micrometric scale are most often estimated from bulk analyses in this study the li intense emission line at 670 706 nm in optical emission spectroscopy was used to perfect the analysis of li at the micrometric scale by means of laser induced breakdown spectroscopy libs to estimate lithium content for different geological materials libs calibration of the emission line at 670 706 nm was achieved by use of synthetic glasses and natural minerals the detection limit for this method is 5 ppm li three applications to geological materials show the potential of libs for lithium determination namely for li bearing minerals melt inclusions quartz and associated fluid inclusions for spodumene and petalite from granite pegmatite dikes portugal the li2o concentrations are 7 6 1 6 wt and 6 3 1 3 wt respectively by use of libs these values agree with ion microprobe analyses bulk analyses or both for eucryptite crystals the li concentrations are scattered because grain size is smaller than the libs spatial resolution 6 to 8 m lithium concentrations of melt inclusions from the streltsovka u deposit siberia are in the range of 2 to 6 2 wt li2o for li rich daughter minerals lithium estimations on silicate glasses display values between 90 and 400 ppm lithium was also analyzed as a trace element in quartz transverse profiles were performed in hydrothermal barren quartz veins from the spanish central system sierra de guadarrama the highest li concentrations 250 to 370 ppm were found in specific growth bands in conjunction with the observed variation in optical cathodoluminescence intensity considering the fluid inclusion analysis the source of fluid responsible to the li enrichment in quartz is probably high salinity fluids derived from sedimentary basins

improved time control on cretaceous coastal deposits new results from sr isotope measurements using laser ablation sr isotope measurements of unaltered oyster shell calcite using laser ablation multi collector icpms techniques represent a powerful tool capable of establishing a chronostratigraphic framework for fossil near shore deposits this approach is tested on two shoal water successions from the portuguese algarve and lusitanian basins covering late barremian to albian strata 87 sr 86 sr values derived from low mg calcite of oyster shells fluctuate between 0 70717 0 00001 and 0 70746 0 00002 absolute values as well as stratigraphic trends match well with the global open marine seawater signal the new sr isotope results in combination with existing bio and chemostratigraphic records allow for identification of an early aptian biocalcification crisis at both studied localities and show that this event has severely affected coastal environments along the evolving atlantic siliciclastic intervals in the algarve section are interpreted as near shore equivalents of enhanced detrital shedding into shelf and deep sea environments as a consequence of increased chemical weathering rates during humid climate episodes

synthetic fluid inclusions in natural quartz ii application to pvt studies synthetic fluid inclusions have been used to determine volumetric properties of h2o and a 20 wt kcl solution from 300 700 c and 1 3 kb comparison of results obtained for h2o with previously published data indicates that the synthetic fluid inclusion technique provides pvt data that are within a few percent of those obtained from conventional pvt studies this technique thus provides a fast relatively simple means of determining pvt properties of many fluids of geologic interest

platinum solubility and partitioning in a felsic melt vapor brine assemblage abstract the solubility and partitioning of pt in a s free vapor brine rhyolite melt pt metal assemblage has been quantified at 800 c f o 2 nno and pressures of 100 and 140 mpa vapor and brine were sampled at run conditions by trapping these phases as glass hosted fluid inclusions as the melt cooled through the glass transition temperature the vapor and brine were in equilibrium with the melt at the time of trapping and thus represent fluids which were sampled at the termination of each experimental run the microthermometrically determined salinities of vapor and brine are 2 and 63 wt nacl eq and 9 and 43 wt nacl eq at 100 and 140 mpa respectively platinum solubilities in vapor brine and glass i e quenched melt were quantified by using laser ablation inductively coupled plasma mass spectrometry la icp ms equilibrium is discussed with reference to the major and trace element concentrations of glass hosted fluid inclusions as well as the silicate melt over run times that varied from 110 to 377 h at 140 mpa and 159 to 564 h at 100 mpa platinum solubility values 1 in h2o saturated felsic melt are 0 28 0 13 g g and 0 38 0 06 g g at 140 and 100 mpa respectively platinum solubility values 1 x at 140 and 100 mpa respectively in aqueous vapor are 0 91 0 29 g g and 0 37 0 17 g g and in are brine 16 10 g g and 3 3 1 0 g g the measured solubility data were used to calculate nernst type partition coefficients for pt between vapor melt brine melt and vapor brine the partition coefficient values 1 x for vapor melt brine melt and vapor brine at 140 mpa are 2 9 1 0 67 27 and 0 13 0 05 and at 100 mpa are 1 0 0 2 6 8 2 4 and 0 15 0 05 the partitioning data were used to model the pt scavenging capacity of vapor and brine during the crystallization driven degassing i e second boiling of a felsic silicate melt over a depth range i e 3 6 km consistent with the evolution of magmatic hydrothermal ore deposits model calculations suggest that aqueous vapor and brine can scavenge sufficient quantities of pt and by analogy other platinum group elements pge to produce economically important pge rich magmatic hydrothermal ore deposits in earth s upper continental crust

fluid evolution in the w cu zn pb san cristobal vein peru fluid inclusion and stable isotope evidence abstract the zn pb ag cu san cristobal district is located 100 km east of lima in the western cordillera of peru it is centred around the chumpe intrusion and is composed of vein and carbonate replacement ore types the main san cristobal vein presents a paragenesis that can be divided into three stages a an early wolframite quartz pyrite stage b a quartz base metal stage and c a late quartz carbonate barite stage fluid inclusions in quartz from the tungsten stage are biphase lv at room temperature and homogenise to the liquid phase between 146 and 257 c their salinities range between 2 1 and 5 1 wt nacl equiv rare inclusions contain an additional crystal of halite and have salinities of 46 54 wt nacl equiv data of the first two stages show a decrease in homogenisation temperatures concomitant with a salinity decline fluid inclusions in quartz from the late stage homogenise at higher temperatures between 252 and 323 c with salinities ranging between 4 6 and 6 7 wt nacl equiv hydrogen and oxygen isotope data indicate a two stage evolution isotopic compositions of the fluid associated with the first two stages define a trend with constant 18 o values and decreasing d values 18 o 3 2 to 5 0 v smow and d 60 to 112 v smow which is interpreted as mixing of a dominantly magmatic component with minor meteoric water that had equilibrated with the host rocks this interpretation is supported by sulphur and lead isotopic data from previous studies by contrast the quartz carbonate barite stage bears isotopic characteristics defining a trend with a coupled decrease of 18 o and d 18 o 8 1 to 2 5 v smow and d 57 to 91 v smow and is explained by addition of meteoric water to the system and subsequent mixing with a less important magmatic component different fluid origins are confirmed by laser ablation icp ms analyses of the triphase lvh and biphase lv primary inclusions the concentrations of the major ore elements i e w cu zn and pb decrease throughout the paragenesis w and to a lesser extent cu show significant variations associated with a steep decrease in their concentration the decreasing concentrations can be explained by mineral deposition and dilution by the meteoric fluid differences in the rate of decrease indicate selective precipitation of w fluid inclusions of the quartz carbonate stages show an abrupt increase in ba and sr concentrations this is interpreted to reflect a higher volume of host rock silicate alteration probably due to the increasing size of the fluid flow cell and is explained by the input of a third fluid of unknown origin la icp ms analyses show that the fluids were already depleted in w and cu before reaching the emplacement of carbonate replacement ore type whereas zn and pb were still present in considerable amounts this is again due to selective precipitation and is consistent with the interpretation that the economically interesting metals were dominantly introduced by magmatic fluids

fluid inclusion evidence for p v t x evolution of hydrothermal solutions in late alpine gold quartz veins at brusson val d ayas northwest italian alps

fluid composition and evolution of the langxi ba f deposit yangtze block china new insight from la icp ms study of individual fluid inclusion abstract the langxi vein type ba f deposit located in the southeast of the sichuan basin in the central part of yangtze block south china is hosted by ordovician limestone the paragenesis of the deposit s veins is subdivided into pre syn and post ore stages the syn ore stage includes two fluorite generations with the first fl 1 deposited at 140 to 200 c and the second fl 2 at 140 to 180 c the syn ore barite mineralisation was deposited with the temperature range of 110 160 c and the syn ore calcite records a temperature range of 90 to 140 c these temperature ranges show that the mineralising fluids were low to moderate in temperature and decreased with the initial deposition of fluorite followed by barite and then calcite the types of fluid inclusions in the veins are classified as monophase liquid l type type i biphase liquid vapour l v type type ii and polyphase l v s type type iii brine inclusions the salinity of the mineralising fluid for the three types of inclusions during the deposition of f ba ca is 0 35 21 7 nacl eqv indicating that the ore forming fluid varied greatly during the mineralising process there are no obvious differences in the fluid inclusion density in the different minerals with the average densities being 0 98 g cm3 for fl 1 0 99 g cm3 for fl 2 1 00 g cm3 for barite and 1 01 g cm3 for calcite this shows that the density of the f ba ca mineralising fluid belong to a moderate low density the deposition of the minerals took place with a change from a reducing to an oxidising environment the liquid phase initially included na and cl and evolved containing ca2 so42 k and mg2 la icp ms analyses reveal that the l v type fluid inclusions associated with fl 1 assays 46 600 ppm na 3470 ppm k with a mean na k ratio of 24 28 200 ppm for cl and 1060 ppm br with a mean cl br mass ratio of 27 the second generation fluorite l v type fluid inclusions average around 47 000 ppm na and 12 000 ppm k corresponding to and a na k mass ratio of 7 the halogen content of fl 2 averages 26 200 ppm cl and 950 ppm br corresponding to a cl br mass ratio of 28 these analyses indicate that the mineralising fluid was rich in nacl assuming the fluid inclusions represent samples of the mineralising fluid it is proposed that ba f concentrated in the mineralising fluid were derived from basinal fluids mixed with meteoric water circulating through faults at increased temperature gradients the driving force was late cretaceous tectonic activity related to the subduction of the paleo pacific oceanic plate this model is consistent with the geodynamic setting of other barite fluorite rich districts in the yangtze block of south china

direct analysis of ore precipitating fluids combined ir microscopy and la icp ms study of fluid inclusions in opaque ore minerals laser ablation inductively coupled plasma mass spectrometry la icp ms in combination with near infrared microscopy of fluid inclusions hosted by ore minerals that are opaque to visible light can provide the composition of ore precipitating fluids we applied the two techniques to well constrained fluid inclusion assemblages hosted by pyrite enargite and quartz to trace the source and evolution of the fluids in high sulfidation epithermal veins overprinting a porphyry copper deposit at rosia poieni romania despite some analytical limitations caused by the sulfide host minerals the data demonstrate that fluids trapped in apparently cogenetic quartz and ore minerals are chemically different systematic changes in major and trace element ratios between liquid vapor vapor rich and brine fluid inclusion assemblages in the three minerals record an evolving fluid source at the porphyry to epithermal transition regarding their cs na k ratios most of epithermal quartz hosted fluid inclusion assemblages form a well defined cluster which coincides with the narrow range of the porphyry stage fluids trapped in early quartz of the porphyry stockwork veins their cu na k ratios are 10 to 100 times lower compared to the pyrite hosted inclusions and correspond to the lowest cu na k ratios recorded for the porphyry stage fluids by contrast pyrite hosted vapor rich fluid inclusions have the highest cu na k similar to the highest cu na k ratios measured in the porphyry stage fluid inclusions the results led to the conclusion that the gangue and ore minerals in the high sulfidation epithermal veins at rosia poieni formed by successive pulses of chemically distinct hydrothermal fluids that were successively exsolved from residual melt batches of a progressively crystallizing magma at greater depth these results are consistent with detailed textural observations but petrography alone could not have led to this unambiguous conclusion

rapid quench hydrothermal experiments at mantle pressures and temperatures new experimental methods for the encapsulation extraction and analysis of large volumes of aqueous fluids enable studies of mineral solubilities and dissolution kinetics with the piston cylinder apparatus quench rates and volumes of experimental fluids with these methods are comparable with those used in modern hydrothermal experiments employing cold seal vessels analyses of fluid compositions are reproducible and consistent with independent results the techniques permit experimental investigations that will better characterize fluid rock interaction in such environments as subducting slabs the mantle wedge barrovian metamorphic belts and middle to lower crustal granulites