silicification and dolomitization of anhydrite nodules in argillaceous terrestrial deposits an example of meteoric dominated diagenesis from the triassic of central spain cauliflower shaped nodules are widespread in a single red mudstone bed in the buntsandstein triassic facies of the iberian range they consist mostly of quartz dolomite and calcite but other minerals such as barite kaolinite and iron oxyhydroxides are also present the nodules are spherical ovoid or elongate in shape and range from 1 to 8 cm across the surface of the nodules is irregular and some show a pedogenic coating of microspar the sedimentological and petrographic data suggest that the initial anhydrite nodules formed through a progressive increase in the porewater concentration of ca2 and so4 2 in a vadose environment occasionally under the influence of pedogenic processes partial replacement of the anhydrite by megaquartz occurred under more dilute conditions in the same type of setting as indicated by the presence of organic filaments on the quartz crystal surfaces in type a nodules the dissolution of the innermost anhydrite was complete and different types of quartz cement filled the porosity fracturing and meteoric cementation by calcite and minor amounts of kaolinite were the latest processes affecting these nodules in type b nodules the dissolution of the anhydrite was incomplete inhibiting quartz cementation and enabling later dolomitization of the anhydrite dolomitization appears to have been driven by sulphate reduction as indicated by the presence of bacterial bodies within the dolomite crystals dedolomitization and precipitation of barite kaolinite and calcite spar cements occurred later under the influence of meteoric solutions the nodules may mark the former locations of the water table and provide evidence for an episode of highly evaporitic conditions throughout wide areas of the basin their occurrence reveals not only a complex diagenetic history but is also indicative of palaeogeographic and palaeoclimatic conditions

rare earths behaviour during the deposition of volcanic sublimates abstract in this study the ree distribution between volcanic fluids and related solids in fumaroles with temperatures ranging from approximately 100 to 421 c was investigated in different geological scenarios the treatment of geochemical ree data was carried out by calculating the ree enrichment factors ef ree relative to the volcanic host rocks in studied sites under the assumption that the ree transport takes place as silicate aerosol in volcanic fluids shale normalised ree concentrations in these fluids have been assessed to investigate whether the ree transport as aqueous complexes in water saturated volcanic gas is reasonable the ree behaviour in alkaline condensates according to the above mentioned treatments of geochemical data is very similar being characterised by positive ce and gd anomalies and significant w type tetrad effects these evidences suggest that the geochemical behaviour of ree in fumarolic fluids is firstly influenced by the sublimate deposition along the fumarolic conduit or around the vents rather than by the transport mechanism of these elements in volcanic fluids the gd enrichment relative to its neighbours eu and tb induces the growth of positive gd anomalies recognised in condensates that in turn results in gd fluxes from the studied fumarolic systems ranging from 0 01 to 0 92 kg y 1 this indication represents a novelty in the well known geochemical gd behaviour where recognised positive gd anomalies have usually been attributed to anthropogenic contamination

an unusual occurrence of surficial anhydrite in a moist temperate zone example from the lockport formation middle silurian of new york abstract gypsum is the most common sulfate mineral that occurs on the earth s surface or in the shallow subsurface whereas anhydrite occurs in relatively deeper subsurface settings anhydrite is described here from the lockport formation middle silurian of new york this occurrence is unusual as the anhydrite is present on the surface in a temperate climatic zone where the regional rainfall averages 80 cm per year the anhydrite is of nodular form and has an incomplete rind composed of megaquartz petrographic characteristics and megafeatures indicate that formation of the nodule followed shortly after dolomitization growth of the nodule probably took place in an open space overall sequence of events is indicated to be dolomitization dissolution of gypsum precipitation of anhydrite partial silicification of the nodule surface

the presence of carbonic dominant volatiles during the crystallization of sulfide bearing mafic pegmatites in the north roby zone lac des iles complex ontario mafic pegmatites in the platinum group element pge mineralized roby zone lac des iles complex northwest ontario canada comprise dikes veins and irregular pods of coarse grained magnesiohornblende pyroxene and labradorite andesine with minor biotite apatite fe ti oxides and intercumulus quartz that grades into massive quartz or graphic quartz base metal sulfide vysotskite pd ni s intergrowth at their cores quartz apatite and magnesiohornblende host primary and secondary assemblages of one or two phase carbonic fluid co 2 up to 10 ch 4 minor h 2 o n 2 inclusions that contain ore metals ni cu pd bi te fe rare trails of late stage high salinity aqueous fluid inclusions are secondary in origin and therefore unrelated to the crystallization of the pegmatites assemblages of primary carbonic fluid inclusions show considerable variation in mode and temperature of homogenization reflecting large fluctuations in confining pressure at the time of quartz crystallization of as much as 1 kbar in single quartz crystals and 2 8 kbars all data independent thermobarometric methods constrain conditions for the following two stages of pegmatite formation and carbonic fluid entrapment 1 the crystallization of magnesiohornblende plagioclase intergrowth at t 650 to 850 c and p 1 to 3 kbars and 2 the crystallization of quartz at t 535 to 650 c and p 0 4 to 3 2 kbars setting the maximum depth of emplacement of the lac des iles complex north roby zone magma at 10 to 12 km the results indicate that aqueous dominant volatile phases were absent during the crystallization of pegmatitic gabbroic rocks at the lac des iles complex and that water poor carbonic fluid entrapment persisted to well below solidus conditions a role played by carbonic fluid as a potential transport medium for ligands involved in the precipitation and remobilization of the pge and base metals is strongly suggested and warrants further investigation

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

gold speciation and transport in geological fluids insights from experiments and physical chemical modelling this contribution provides an overview of available experimental thermodynamic and molecular data on au aqueous speciation solubility and partitioning in major types of geological fluids in the earth s crust from low temperature aqueous solution to supercritical hydrothermal magmatic fluids vapours and silicate melts critical revisions of these data allow generation of a set of thermodynamic properties of the auoh aucl 2 auhs and au hs 2 complexes dominant in aqueous hydrothermal solutions however other complexes involving different sulphur forms chloride and alkali metals may operate in high temperature sulphur rich fluids vapours and melts the large affinity of au for reduced sulphur is responsible for au enrichment in s rich vapours and sulphide melts which are important gold sources for hydrothermal deposits thermo dynamic speciation and partitioning data and their comparison with au and s contents in natural fluid inclusions from magmatic hydrothermal gold deposits provide new constraints on the major physical chemical parameters temperature pressure salinity acidity redox and ubiquitous fluid components sulphur carbon dioxide arsenic affecting au concentration transport precipitation and fractionation from other metals in the crust the availability and speciation of sulphur and their changes with the fluid and melt evolution are the key factors controlling gold behaviour in most geological situations

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

porphyry copper mineralisation in the central srednogorie zone bulgaria the porphyry copper systems in the central part of the srednogorie zone bulgaria are represented by three major deposits elatsite medet and assarel and several smaller deposits and occurrences all of them within the panagyurishte ore district the hydrothermal systems are related to late cretaceous calc alkaline igneous complexes ore mineralisation is developed predominantly in the apical parts of subvolcanic and intrusive bodies as well as within the volcanic and basement metamorphic rocks several of the porphyry systems are spatially associated with shallow level intermediate and high sulphidation volcanic hosted epithermal deposits of economic importance such as the major gold copper mine at chelopech located 10 km from the elatsite porphyry copper deposit mineralisation processes in the porphyry deposits start with intensive hydrothermal alteration of the wall rocks k silicate alteration is characteristic for pre ore hydrothermal activity in all of them and it is located mostly in their central parts propylitic alteration is prominent in the medet and assarel deposits the assarel deposit is located in the central part of a palaeovolcanic structure and shows a large spectrum of pre ore alterations including propylitic sericitic and advanced argillic assemblages the initial stages of the hydrothermal systems are characterised by high temperatures 550 500 c and highly saline 50 20 wt nacl equiv and vapour rich fluids of likely magmatic origin the composition of the fluids gradually changes from h2o nacl fecl2 to h2o nacl kcl and h2o nacl dominated as the fluids cool react with wall rocks and may become diluted with meteoric water fe ti oxide mineral associations were formed early in all deposits later followed in the elatsite deposit by an assemblage of bornite chalcopyrite platinum group element pge phases co ni thiospinels ag and bi tellurides and selenides the main ore stage in all deposits is dominated by chalcopyrite pyrite associated with propylitic alteration at medet k silcate sericite alteration at elatsite and chlorite sericite alteration at assarel specific geochemical features of the ore systems are marked by precipitation of numerous fine grained mineral inclusions in chalcopyrite and pyrite palladoarsenide pd rammelsbergite cu ni sulpharsenides in elatsite co and ni pyrite carrolite vaesite sulvanite and colusite in medet enargite as sulvanite colusite goldfieldite wittichenite calaverite and aikinite in assarel native gold and electrum are observed as small grains except in elatsite where larger aggregates up to several millimetres are found molybdenite is present as small flakes within chalcopyrite or forms felted aggregates within thin quartz veinlets in the elatsite and medet deposits and very rarely at assarel thin veinlets of quartz galena sphalerite are found at the upper parts of the deposits supergene alteration of the primary sulphide minerals is developed in the assarel deposit where a thick blanket of secondary copper mineralisation chalcocite covellite has formed in the other two deposits secondary mineral associations cu and fe oxides and hydroxides are limited to near the surface differences in the deposits studied suggest that elatsite and medet are formed probably at deeper levels of the porphyry systems whereas assarel is developed at rather shallower and lower temperature conditions typical of the apical part of a subvolcanic body intruding its volcanic superstructure

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 miwah high sulphidation epithermal au ag deposit aceh indonesia geology and spatial relationships of gold with associated metals and structures abstract geological mineralogical and whole rock geochemical studies of the plio pleistocene miwah high sulphidation au ag deposit in aceh indonesia revealed evidence of a complex and dynamic interplay between structural development and mineralisation the mineralisation occurs in a zone of predominantly phreatic breccias measuring 1 1 km long by 400 m wide and 200 350 m deep within a fault bounded calc alkaline andesite ridge within this zone low grade disseminated au ag has superimposed narrow high grade au ag zones hydrothermal alteration and mineralisation in three mineralised centres the miwah bluff in the west and the west block m and east block m in the east are controlled by steeply dipping 60 and northerly trending pre to syn mineral feeders this alteration displays an outward sequence of vuggy silica i alunite silica advanced argillic and kaolinite illite argillic a distal chlorite smectite propylitic zone may precede or constitute the end product of the above alteration late silica flooding converted parts of the vuggy silica i and the alunite quartz zone into variably sulphide rich massive silica and vuggy silica ii containing pyrophyllite alunite respectively penecontemporaneous with the massive silicification main stage mineralisation initially deposited intergrowths of pyrite enargite quartz followed by scattered enargite and pyrite and finally rapidly precipitated ag bearing native gold dendrites in vugs with lesser amounts of sulphides the crack seal texture of the host rocks paragenetic variation in precious and base metal mineral species and selective dissolution fracturing and shearing of most of the metallic and gangue minerals are interpreted to reflect transient pulses of fluid flows and mineralisation within zones of structural deformation high grade au zones and associated metals formed clusters along the feeders whereas low grade disseminations of the same metals were spread across the deposit these metals are zoned along the feeders from apical au ag to deep cu as sb te and sn are variably distributed laterally the zonation is from au ag in the feeders through cu as sb bi te and sn and finally to pb or zn in the periphery while these bulk rock metal abundances indicate the efficacy of certain physico chemical conditions of the fluids to accumulate the metals their ratios point to an upward paleo flow path of the fluids along the northerly striking faults and related fractures combining all of the above data we propose that miwah developed in fault fracture networks beneath paleo solfataras in a volcanic crater where the ascending acidic magmatic gas or gas fluids vapours transformed the phreatic breccia host rocks first into vuggy silica and advanced argillic rocks which were subsequently resilicified and mineralised into au and base metal rich massive silica during the depressurisation and condensation of the gas fluid phases mineralisation processes terminated with limited ag enrichment by late stage fluids in the upper segment of the deposit and in deep fractures

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

a review of intermediate sulfidation epithermal deposits and subclassification abstract intermediate sulfidation is veins is one of the subtypes of epithermal deposits formed in subduction related arc settings or post collisional orogenic belts the economic and scientific significance of is deposits has been highlighting importance in ag au pb zn exploration and study of porphyry epithermal systems this epithermal clan of deposits typically have a close relationship with andesitic dacitic volcanic subvolcanic rocks and formed at a depth of 0 3 to as much as 1 km is deposits are typically related to oxidized calcic to calc alkaline magmatism fluid homogenization temperatures and salinities range between 150 and 350 c and 0 and 23 wt nacl equivalent respectively the o and h isotope compositions are consistent with a mixture of magmatic and meteoric water with an increase in meteoric diluent as the hydrothermal system wanes most of the is deposits in the world particularly those in circum pacific metallogenic belts formed during cenozoic time several mesozoic and paleozoic is deposits in the central asian orogenic belt imply great exploration potential for pre cenozoic is deposits in this area the presence of mn carbonate such as rhodochrosite and manganocalcite locally mn silicate e g rhodonite helvite typically in mid to late hydrothermal stages is a common diagnostic feature to discern is from low sulfidation ls deposits in addition the occurrence of intermediate sulfidation state sulfides such as pyrite chalcopyrite sphalerite galena and tetrahedrite tennantite associations are another indicator of the is type light colored fe poor sphalerite is typical of is deposits consistent with relatively oxidized fluids elevated fluid salinity is another characteristic with maximum salinity values of base metal rich is veins usually 5 wt nacl equiv the reported is deposits worldwide show that they develop in compressional volcanic arcs as well as in some extensional settings in this review is deposits are subdivided into nc neutral compressional type is with a low ag au ratio 60 formed in extensional settings such as extensional intra arc post collisional orogenic belts and back arc settings another notable feature of e type is deposits is their large ag endowment compared to nc type is nc type is au ag deposits can be associated with porphyry cu au and or high sulfidation hs au cu deposits and their economic metals are mainly gold and or silver by contrast some e type is deposits can occur on the flanks of porphyry molybdenum deposits e type is veins can also occur together with ls precious metal veins in back arcs or extensional continental margins the most representative examples occurring in mexico the occurrence of the two subtypes of is are largely controlled by the parent magma with parent magma of nc type is primarily derived from depleted mantle or juvenile crust while parent magma of e type is mainly from ancient continental crust the occurrence of is deposits is presumably controlled by tectono magmatic settings and fluid evolution paths neutral to compressive stress regime relatively great depth to an exsolving magma 4 km and low exsolution rate of magmatic fluids plus the presence of syn ore dikes in conjunction with the development of interconnected fracture networks above the porphyry stock could be conducive for the occurrence of is and also hs au veins upon porphyry copper deposits pcds confirmation of sub types and variations of is veins can aid in exploration for spatially and genetic related mineralization types such as porphyry and hs deposits

bulk microanalysis of assemblages of small fluid inclusions by la icp ms methodology and application to orogenic gold systems abstract microanalysis of individual fluid inclusions by laser ablation inductively coupled mass spectrometry la icp ms is a powerful tool for reconstructing the composition of hydrothermal fluids but it demands a sample quality that is unattainable in many cases in orogenic gold deposits the need for direct fluid microanalysis has been present for several decades but due to the high fluid flux and prolonged hydrothermal and tectonic history that typifies these systems most samples do not meet the criteria of fluid inclusion size and distribution that allow la icp ms analysis of individual isolated fluid inclusions to overcome this difficulty a method has been developed and tested whereby areas of quartz densely populated with fluid inclusions e g growth zones secondary planes are analyzed along a single continuous laser ablation profile the generated signals are subsequently converted to time slice datasets and plotted as element ratios in ternary diagrams to reconstruct specific major and trace element ratios the estimated fluid compositions are in good agreement with previous analytical results of the same material microthermometry evaporate mound and conventional la icp ms and are shown to be geologically viable on a boarder scale when compared to literature data from similar ore environments the method has high spatial and chemical resolution which allows the reconstruction of micro scale fluid chemical changes such as significant fluctuation in the relative element concentration e g k rb ba sr and v versus na li and as during crystal growth as observed in one of the test samples the significance of this bulk la protocol is that it allows the quick easy and cost effective microanalysis of samples that are typically inundated with fluid inclusions such as those in orogenic and epithermal systems which would otherwise not be amenable for further quantitative analysis to constrain fluid chemistry

metallogenic efficiency from deposit to region a case study in western zhejiang province southeastern china abstract metallogenic ore efficiency can be defined as the ratio of metal reserves to its total supply and we expanded a typical efficiency calculation model available at the single mineral scale to the regional scale a new cell based model was developed by analogy and by taking some other influences into account i a thicker sedimentary cover ii regional ore and rock controlling structures and their intersections iii the crustal heterogeneity unrelated and related to ores and iv metallic geochemical anomalies finally a regional contour map of weighted efficiency which is essential to metallogenic prediction was obtained it shows that the efficiency anomalies can provide a much better target area for ore positioning than do metallic content anomalies and greater ore efficiency may indicate the likelihood of occurrence of mineral deposits that are larger in size reserves taking northwestern zhejiang province as a case study in which the geochemistry of mesozoic porphyries plausibly show considerable mineralized potential we found that due to the lower magmatic temperature delayed exsolution of the hydrothermal solution and very thick sedimentary cover the cu polymetal ore efficiency associated with granitic plutons in this area is generally low the relatively higher ore productivity efficiency appears mainly in and around small rock bodies rock margins and the contacting zone between different lithologies most ore spots no matter their size fall into areas with nonzero efficiency values there seems to be no interdependence between most ore spots of smaller size and ore efficiency whereas efficiency is essential to regional small and medium scaled metallogensis

hydrothermal venting and mineralization in the crater of kick em jenny submarine volcano grenada lesser antilles kick em jenny is a frequently erupting shallow submarine volcano located 7 5 km off the northern coast of grenada in the lesser antilles subduction zone focused and diffuse hydrothermal venting is taking place mainly within a small 70 110 m depression within the 300 m diameter crater of the volcano at depths of about 265 m much of the crater is blanketed with a layer of fine grained tephra that has undergone hydrothermal alteration clear fluids and gas are being discharged near the center of the depression from mound like vents at a maximum temperature of 180 c the gas consists of 93 96 co2 with trace amounts of methane and hydrogen gas flux measurements of individual bubble streams range from 10 to 100 kg of co2 per day diffuse venting with temperatures 5 35 c above ambient occurs throughout the depression and over large areas of the main crater these zones are colonized by reddish yellow bacteria with the production of fe oxyhydroxides as surface coatings fragile spires up to several meters in height and elongated mounds up to tens of centimeters thick a high resolution photomosaic of the inner crater depression shows fluid flow patterns descending the sides of the depression toward the crater floor we suggest that the negatively buoyant fluid flow is the result of phase separation of hydrothermal fluids at kick em jenny generating a dense saline component that does not rise despite its elevated temperature

investigation of the effect of cl on the transport and sublimation of volatile trace metals in volcanic gases using benchtop fumarole experiments abstract volatile trace metals emitted from volcanoes are frequently complexed with ligands and sublime from gases as halides sulfides sulfates and oxides we investigate the effect of cl as a ligand on the sublimation process by degassing broadly phonolitic composition melts with added trace metals v cu zn as y mo cd sn yb pb and bi and cl in a benchtop fumarole apparatus at 100 kpa sublimates forming from the gas phase at 25 900 c along a silica glass tube suspended above degassed melts are characterized by electron microscopy raman spectroscopy and solution nebulization inductively coupled plasma mass spectrometry sn icp ms silica polymorphs are ubiquitous at all temperatures and halite forms below 600 c szenicsite cu3 moo4 oh 4 and molybdofornacite cupb2 moo4 aso4 oh occur at 500 c the latter phases may have formed from post experiment hydration of original anhydrous molybates or arsenates or alternatively are their cl bearing analogues arsenate and vanadate minerals such as bradaczekite nacu4 aso4 3 and leningradite pbcu3 vo4 2cl2 known in natural fumaroles also occur in the experiments chloride sublimates can host substantial pb tl as cu bi and zn the addition of cl to the melt in the experiments increases the concentration of li rb cs ag cr cu mo and w in the sublimates compared to cl free experiments in cl bearing volcanic gases molybdates and chlorides are the most likely hosts of volatile trace metals and when adhered to ash particles are potential sources of trace metals to the atmosphere and oceans

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

silver base metal epithermal vein and listwanite hosted deposit crnac rogozna mts kosovo part ii a link between magmatic rocks and epithermal mineralization abstract crnac is an intermediate sulfidation pb zn ag epithermal deposit located within the vardar suture zone of the central balkan peninsula the epithermal pb zn ag mineralization consists of i a series of steeply dipping veins hosted within the jurassic amphibolites and ii overlying hydrothermal explosive breccia with angular level iv or rounded fragments of listwanite surface cemented by epithermal mineralization the mineralization is related to the oligocene quartz latite dykes that crosscut the crnac antiform quartz latite rocks predominantly display a shoshonitic character the obtained 40ar 39ar age of fresh quartz latite is 28 9 0 3 ma fine grained sericite from altered quartz latite is dated at 28 6 0 5 ma early alteration related fluid inclusions within quartz latite show coexistence of high density brine and a low density vapor saturated phase that homogenized at 280 405 c phase separation occurs at a paleodepth of 0 6 to 0 9 km epithermal mineralization developed in three stages i early pyrite arsenopyrite pyrrhotite quartz kaolinite ii main sphalerite galena tetrahedrite chalcopyrite and iii late carbonate pyrite arsenopyrite assemblage the onset of mineral deposition within epithermal veins was initiated by boiling of na cl k ca mg fluid at a paleodepth of 0 6 to 0 9 km coexisting vapor and liquid rich inclusions display salinities and trapping temperatures of 4 wt nacl equiv 280 370 c and 2 27 wt nacl equiv 230 375 c respectively boiling continued throughout the deposition of the sphalerite galena tetrahedrite chalcopyrite assemblage late stage carbonate was deposited from diluted non boiling low temperature na ca mg cl co2 fluid 0 2 to 4 8 wt nacl equiv 115 280 c about 100 150 m higher in the system precipitation of listwanite breccia cement began as a result of boiling na cl ca mg k fluid of medium salinities 2 6 to 12 1 wt nacl equiv at temperatures of 245 370 c boiling and dilution of fluids continue throughout the precipitation of the main sphalerite galena tetrahedrite and late mainly carbonate assemblage surface listwanite breccia contain quartz phenocrysts deposited from a homogeneous fluid with a medium salinity 8 10 wt nacl equiv and high temperatures th 295 315 c whereas the early and main stage of a surface listwanite breccia cement precipitated from a boiling fluid of decreasing salinity and temperature aqueous co2 high salinity 16 to 18 wt nacl equiv low temperature 120 c homogeneously trapped fluid that precipitated late stage carbonates is most likely a remnant of boiled off fluid the epithermal assemblage of the surface listwanites precipitated at a paleodepth of 0 4 to 0 6 km the 13c values of the late stage ankerite range from 4 2 to 4 1 whereas 18o range from 9 6 to 17 5 the calculated 18o of fluid that precipitated carbonates within epithermal veins and listwanite breccia cement range from 6 3 to 11 3 indicating a contribution of magmatic water deposition of all mineralization types was initiated by neutralization of primary acidic magmatic fluid by water rock reactions that caused widespread propylitization and sericitization extensive and long lasting boiling combined with dilution by meteoric water increased the ph towards the final stage of hydrothermal activity

fluid density control on vapor liquid partitioning of metals in hydrothermal systems hot aqueous fluids both vapor and saline liquid are primary transporting media for metals in hydrothermal magmatic systems despite the growing geological evidence that the vapor phase formed through boiling of magmatic ore bearing fluids can selectively concentrate and transport metals the physical chemical mechanisms that control the metal vapor liquid fractionation remain poorly understood we performed systematic experiments to investigate the metal vapor liquid partitioning in model water salt gas systems h2o nacl kcl hcl at hydrothermal conditions measurements show that equilibrium vapor liquid fractionation patterns of many metals are directly related to the densities of the coexisting vapor and liquid phases despite differences in the vapor phase chemistry of various metals that form hydroxide chloride or sulfide gaseous molecules of contrasting volatile properties water solute interaction is a key factor that controls the metal transfer by vapor like fluids in earth s crust these findings allow quantitative prediction of the vapor liquid distribution patterns and vapor phase metal transport in a wide range of conditions our density model accounts well for the vapor brine distribution patterns of na si fe zn as sb and ag observed in fluid inclusions from magmatic hydrothermal deposits for au and cu the partitioning in favor of the liquid phase predicted in a sulfur free system contrasts with the copper and gold enrichment observed in natural vapor like inclusions the formation of stable complexes of cu and au with reduced sulfur may allow for their enhanced transport by sulfur enriched magmatic hydrothermal vapors

dating iron skarn mineralization using hydrothermal allanite la u th pb isotopes by laser ablation icp ms abstract trace elements and u th pb isotopes of hydrothermal allanite from the beiminghe iron skarn deposit eastern north china craton were simultaneously analyzed using laser ablation inductively coupled plasma mass spectrometry la icpms to demonstrate the suitability and robustness of the u th pb system in this phase as a geochronometer of ore forming processes allanite grains from the beiminghe deposit typically exhibit optical and chemical zoning and are intergrown or texturally equilibrated with prograde and or retrograde skarn assemblages mainly consisting of tremolite diopside magnetite and garnet in addition they contain abundant aqueous two phase or daughter mineral bearing three phase aqueous fluid inclusions confirming their hydrothermal origin most grains have high la ce ratios 1 19 1 74 and thus are classified as allanite la a notable feature of the hydrothermal allanite la is the lack of common pb with values comparable with those of the zircon standards 91500 and gj 1 used in this study la icpms spot analyses reveal remarkable variation in ca rees rare earth elements fe al and mg within a single grain consistent with the substitution of ree3 mg fe2 for ca al fe3 in the mineral structure traverses of zoned grains show that the rims have th u ratios ranging from 0 73 to 11 55 significantly higher than the core areas 0 07 1 81 fifty nine spot analyses beam size of 32 m or 60 m on 5 allanite la grains yield reproducible 206pb 238u ages of 134 7 to 139 6 ma with a weighted mean 206pb 238u age 206pbexcess corrected 206pb 238u age of 136 1 ma 2 of these 34 analyses on allanite rims have a weighted mean 208pb 232th age of 139 2 ma 2 that is within error of the 206pb 238u age the dating results showed that an increase of beam size from 32 to 60 m significantly reduces the analytical uncertainties 2 petrographic and textural data have demonstrated that the allanite la grains formed during skarn alteration and notably have close paragenetic relationships with retrograde skarn assemblages and iron oxide minerals their u th pb ages therefore are interpreted as the timing of iron skarn mineralization at beiminghe thirteen zircon grains from the ore related diorite intrusion have a weighted mean 206pb 238u age of 136 2 ma 2 consistent with and thus confirming the reliability of the allanite la u th pb ages when interpreted as the formation age of the beiminghe iron deposit our results suggest that hydrothermal allanite with low th and u is a promising u th pb geochronometer and can provide reliable constraints on the timing of hydrothermal mineralization without requiring a matrix matched external standard the present dating results also indicate that the u pb rather than th pb isotope system is preferable for u th pb dating of low th u allanite

decoupled geochemical behavior of as and cu in hydrothermal systems cu rich and as rich growth zones in pyrite provide new insights into the composition of late stage magmatic fluids and their host hydrothermal ore deposits the pyrite is from the pueblo viejo dominican republic and yanacocha peru high sulfidation gold silver deposits which are thought to form from hydrothermal systems that interacted with magmatic vapor plumes electron microprobe analysis secondary ion mass spectrometry and elemental maps show that pyrite the most common sulfide mineral in both deposits contains three different types of growth zones 1 as rich zones that are enriched in au ag sb te and pb 2 cu rich zones with significantly lower concentrations of these elements and 3 barren pyrite zones with no other elements these zones are interpreted to result from mixing between the pyrite forming fluid and vapors that invaded the main hydrothermal system episodically comparison to experimental studies of elemental partitioning and analyses of fumaroles and fluid inclusions from magmatic hydrothermal systems suggests that the as rich vapor formed at high and possibly magmatic temperatures whereas the cu rich vapor formed at lower temperatures possibly during migration of the original magmatic vapor the presence of finely spaced multiple growth zones in pyrite suggests that the composition of at least high sulfidation hydrothermal systems can be affected intermittently and repetitively by vapors probably from underlying magmas

subepithermal au pd mineralization associated with an alkalic porphyry cu au deposit mount milligan quesnel terrane british columbia canada at the mount milligan cu au porphyry deposit quesnel terrane british columbia canada barren and weakly mineralized late stage hydrothermal veins occur in volcanic rocks adjacent to zones of cu au porphyry mineralization and have overprinted the porphyry stage veins the earliest of the late stage hydrothermal veins are barren and consist of quartz pyrite carbonate chlorite tourmaline these veins are similar to transitional to late stage hydrothermal veins in other alkaline porphyry cu au deposits and we consider these to be the equivalent of transitional post porphyry pre epithermal quartz sericite pyrite veins in calc alkaline porphyry environments a later generation of volumetrically minor mineralized veins are composed of pyrite hg and as bearing quartz carbonate chlorite and contain early electrum arsenopyrite tetra hedrite tennantite platinum group element pge tellurides galena sphalerite barite and chalcopyrite as inclusions in pyrite and a later assemblage of electrum pge tellurides arsenides and antimonides galena sphalerite chalcopyrite and various au ag te bi minerals in annealed fractures and open space infillings in quartz and pyrite metal precipitation in these veins was temporally and spatially associated with the deposition and later recrystallization of pyrite primary fluid inclusions in quartz in the barren and weakly mineralized veins are two phase l v homogenize to liquid over a narrow range in t 170 270 c n 96 12 veins and show a wide range in salinity 4 2 wt nacl equiv to 28 7 wt cacl2 equiv when all samples are considered however individual veins show narrow ranges in salinity and homogenization temperature la icp ms analyses indicate that the fluids were highly enriched in as to 2 260 ppm sb to 230 ppm b to 5 400 ppm au 1 2 ppm and pd 0 5 1 ppm but depleted in cu 80 ppm compared to typical porphyry stage fluids metal ratios in the fluids overlap with bulk rock metal ratios in the mineralized veins the inclusions are interpreted to contain a contracted magmatic vapor produced by boiling that lost cu during the formation of porphyry stage veins at depth fluids show decreasing b as sb and increasing sr ca and salinity with time stable c o and h isotope analyses of vein minerals indicate that mixing of this magmatic fluid with meteoric water was not responsible for metal deposition rather metal precipitation was possibly the result of mixing of the magmatic derived fluid with a heated saline groundwater the precious and accessory metal mineralogy of the hydrothermal veins is similar to that found in low to intermediate sulfidation epithermal systems fluid inclusion microthermometry and chlorite thermometry constrain the approximate formation conditions of the veins between 200 and 1 500 bars and 240 and 280 c after the formation of the mineralized veins circulation of low salinity metal depleted fluids occurred these latest stage fluids may have formed by mixing of the saline magmatic fluid groundwater hybrid with meteoric water the results of this study suggest a genetic link between porphyry stage events and the deposition of au and pge in late stage veins in an alkalic igneous environment recognition of hydrothermal processes involving the transport of au pge as sb bi te b rich fluids in the subepithermal regimes implies that low sulfidation epithermal au deposits may have been present in the shallower parts of the magmatic hydrothermal complex and that there is potential for the discovery of pge rich epithermal veins in less deeply exhumed terranes on the other hand the formation of high grade low sulfidation epithermal au pge deposits may be prohibited if porphyry epithermal transitional fluids precipitate ore metals through mixing with groundwater prior to reaching the level where meteoric water mixing and epithermal boiling normally occur

magmatic hydrothermal evolution of highly fractionated granites evidence from the kuiqi miarolite in fujian province se china abstract the kuiqi miarolite a highly evolved alkaline granite pluton is situated in fujian province southeastern china quartz crystals from the kuiqi miarolite contain abundant inclusions which have preserved a complete record of the magmatic hydrothermal evolution five inclusion type were identified i e the melt m type melt fluid ml type daughter mineral bearing s type vapor rich v type and aqueous l type inclusions integrated petrographic microthermometric and laser raman spectroscopy studies demonstrate that the whole magmatic hydrothermal evolution at kuiqi comprises three stages i e the magmatic magmatic hydrothermal and hydrothermal stages the m type inclusions minimal trapping temperatures ca 710 800 c represent the melts entrapped at the magmatic stage of crystallization while the occurrence of euhedral prismatic arfvedsonites in these melt inclusions indicates that the granitic magma was probably volatile rich at the magmatic hydrothermal stage both the ml type inclusions t h ca 500 710 c and coexisting m and v type inclusions reflect the presence of late magmatic fluid circulation and melt volatile immiscibility exhibiting a transition toward the hydrothermal stage at the hydrothermal stage the pressure and temperature 700 485 c drop may have led to oversaturation of the primary saline fluids resulting in the phase separation a highly saline and a volatile rich fluid occurred accompanied by the widespread vapor brine immiscibility the l type inclusions in the miarolitic quartz display bimodal salinity distribution the t h and salinity of the inclusions at the bottom l 1 miarolitic quartz are ca 303 427 c and ca 6 6 17 9 wt nacl equiv respectively while that of the inclusions at the top l 2 are ca 165 232 c and ca 0 2 5 7 wt nacl equiv respectively this indicates a drop of fluid temperature and salinity during the miarolitic cavity formation moreover the low homogenization temperatures and salinities of the l type inclusions suggest an influx of meteoric water during the late hydrothermal evolution stage

the bingham canyon porphyry cu mo au deposit i sequence of intrusions vein formation and sulfide deposition the bingham canyon porphyry copper gold molybdenum deposit is one of the largest and highest grade porphyry orebodies in the world this study focused on the northwest side of the deposit where quartz mon zonite porphyry qmp the first and largest porphyry intrusion hosts the bulk of the high grade copper gold ore 1 0 cu 1 0 ppm au the north northeast trending high grade zone had pre mining dimensions of 1 500 m strike 300 m vertical and 500 m width and contained more than 500 million tonnes mt of ore associated with potassic alteration and abundant quartz veins the lack of superimposed sericitic alteration yielded ideal exposures in which to study the early high temperature stages of ore formation a style of mineralization that in many porphyry deposits represents the major period of copper introduction we mapped multiple porphyry dikes in the sequence 1 qmp 2 latite porphyry lp 3 biotite porphyry bp 4 quartz latite porphyry breccia qlpbx and 5 quartz latite porphyry qlp porphyry dikes faults and quartz veins are steeply dipping and have two dominant orientations north northeast and northwest striking dikes have a north northeast strike but they thicken and develop northwest trending apophyses and host high grade copper gold zones at intersections with northwest faults indicating that magmatic hydrothermal fluids were focused by these structural intersections each porphyry intrusion was accompanied by a similar sequence of veins potassic alteration and sulfides biotite veinlets were followed by fractures with early dark micaceous edm halos of sericite k feldspar biotite andalusite and local corundum containing disseminated bornite chalcopyrite gold edm halos are cut by multiple generations of a quartz veins representing the main cu au ore forming event postdating all intrusions are quartz molybdenite veins followed by quartz sericite pyrite veins cathodoluminescence cl petrography identified distinct a quartz veinlets consisting of dark luminescing quartz filling fractures and dissolution vugs in earlier a quartz veins and adjacent porphyry wall rock these veinlets contain abundant bornite and chalcopyrite and minor k feldspar and are closely linked in time to the introduction of the bulk of the copper and gold although a similar sequence of veins was repeated on emplacement of all porphyry intrusions the vein density and intensity of potassic alteration declined with time the youngest porphyry qlp is mostly weakly mineralized and locally unaltered these observations indicate that magmatic hydrothermal fluids underwent a similar physiochemical evolution during and immediately following emplacement of each of several porphyry dikes the relationship between edm veins and a quartz veins requires that the flux of magmatic fluid from the magma chamber occurred in an episodic manner as opposed to a continuous discharge vein truncation relationships coupled with abrupt changes in copper gold grades sulfide ratios and potassic alteration intensity at porphyry intrusive contacts indicate that the mass of introduced copper and gold decreased significantly during successive porphyry intrusive hydrothermal cycles presumably due to depletion of metals and volatiles in the underlying magma chamber

chert appearance in the cueva bedon carbonate platform upper cretaceous northern spain nodular chert from the cueva bedon carbonate platform late turonian earliest coniacian occurs above the type 1 sequence boundary and in association with a transgressive systems tract deposit it formed by selective replacement of grainstones packstones and thalassinoides burrow fillings other minor types of selective silicification include the replacement of anhydrite nodules forming quartz geodes and the partial or total replacement of oysters and inoceramids the chert nodules consist predominantly of microquartz with volumetrically minor fibrous quartz length fast chalcedony and megaquartz the silica has a mainly biogenic source siliceous sponge spicules and radiolarians lepisphere textures that are indicative of an intermediate opal ct precursor are evident in chert nodules which indicates the chert formed by a maturation process from opala to opal ct to quartz the 18 o values of microquartz suggest a precipitation from marine fluids the fabric of quartz geodes consists of irregular bands of heterometric megaquartz quartzine and lutecite spherulites and a well developed band of petaloidal megaquartz that contains small anhydrite inclusions bivalve shells are replaced mainly by fibrousquartz quartzine lutecite which forms extensive beekite rings the silica source of the replaced fossils is also biogenic but silicification couldhave occurred by direct quartz replacement without an opal ct precursor field and petrographic evidence indicate that silicification was an early diagenetic process that affected both uncompacted and compacted sediments andwas inhibited when the dolomitization began there seems to exist a syncrony in age late turonian earliest coniacian between the nodular chert in the cueva bedon carbonate platform and the bedded and nodular chert ofthe plentzia carbonate turbidites in the deeper basque arc

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

fluid inclusions and hear isotopes in pyrite from the yinjiagou deposit in the southern margin of the north china craton a mantle connection for poly metallic mineralization abstract the yinjiagou poly metallic deposit is located at the southern margin of the north china craton smncc pyrite the most economically important mineral is associated with cu mo au pb zn and ag mineralization two main mineralization stages have been identified and studied a porphyry stage including the quartz molybdenite and quartz sericite pyrite qsp veins and a vein stage including the early and the late economically most important pyrite stages three types of fluid inclusions are distinguished in quartz and pyrite including liquid rich vapor rich biphase lv and halite bearing inclusions the transmitted and infrared microthermometry produced several results 1 each of the three types of fluid inclusions is trapped in the quartz of the porphyry stage with homogenization temperatures of 335 419 c and salinities of 4 7 49 6 wt nacl equiv the coexistence of halite bearing inclusions and low density vapor rich biphase lv inclusions indicates that the fluid was boiling the boiling elevated the fe and s levels in the hyper saline fluid as reflected by the development of pyrite chalcopyrite and s daughter minerals in the halite bearing inclusions 2 the fluid in the early pyrite also displays features characteristic of boiling with homogenization temperatures of 352 400 c and salinities of 3 7 42 4 wt nacl equiv whereas the late pyrite only contains liquid rich biphase lv inclusions with homogenization temperatures of 263 354 c and salinities of 6 0 21 3 wt nacl equiv the relationship between the decreasing salinity and the corresponding decreasing homogenization temperature clearly indicates extensive mixing and dilution 3 finally the infrared calibration indicates that the impact of infrared light intensity on the microthermometric results for the yinjiagou pyrite hosted fluid inclusions is limited the he ar isotopic analysis of the fluid inclusions in the pyrite indicates two different fluid sources that involve abundant mantle input the 3he 4he ratios in the porphyry stage are relatively uniform ranging from 1 39 to 1 78 ra ra 1 39 10 6 for air corresponding to 16 22 mantle 4he contribution this relatively constant range represents the actual helium isotopic composition of the fluids emanating from the cooling intrusions at depth the range of 3he 4he ratios in the vein stage is wide varying from 0 80 to 5 26 ra corresponding to 9 65 mantle 4he the significant variation in the 3he 4he ratios in the vein stage reflects mixing between two fluids these data indicate that there are two different fluid sources and separate evolutionary processes for the porphyry and vein stages and support a multi stage mineralization model the veinlet molybdenite mineralization was induced by the boiling and associated cooling of a magma sourced fluid that emanated from intrusions at depth the qsp veins are likely to be pressure release zones and late fluid flow channels the early pyrite mineralization may be attributed to the influx of a dominantly mantle derived fluid with high 3he 4he ratio 5 26 ra which is most likely related to a later more mafic magmatic event the precipitation of the most economically important pyrite resulted from the mixing and diluting of this mantle derived fluid with a surface derived fluid additionally the high 3he 4he ratios indicate a strongly extensional setting which is most likely related to the late jurassic to early cretaceous lithospheric modification and thinning of the smncc

evolution of fluids in the dasuji porphyry mo deposit on the northern margin of the north china craton constraints from microthermometric and la icp ms analyses of fluid inclusions abstract the newly discovered dasuji mo deposit is located on the northern margin of the north china craton and the mo mineralization is related to triassic granite porphyry and quartz porphyry alteration associated with the deposit includes silicification sericitization chloritization k feldspathization kaolinitization carbonatization and fluoritization the silicification and sericitization phyllic alteration are closely related to the mo mineralization based on mineral assemblages and cross cutting relationships the hydrothermal ore forming process can be divided into four stages stage 1 is characterized by k feldspathization with minor molybdenum mineralization stage 2 is the main stage of molybdenum mineralization stage 3 is involved in lead zinc mineralization and stage 4 is characterized by no mineralization four types of fluid inclusions are recognized liquid rich gas rich co2 h2o and daughter mineral bearing microthermometric data show a decrease in homogenization temperatures and salinities from the early to late stages so that stages 1 4 show homogenization temperatures of 468 375 435 271 318 206 and 222 142 c respectively and the fluids of stages 1 3 and 4 had salinities of 2 57 16 50 along with a few high salinity inclusions 32 04 48 05 0 88 11 19 and 0 88 7 45 wt nacl equiv respectively the salinities of stage 2 fluid inclusions have a bimodal distribution 1 40 17 48 and 29 20 53 25 wt nacl equiv laser ablation inductive coupled plasma mass spectrometer la icp ms analyses show that the fluid compositions are dominated by na k fe and mn in stage 2 fluid inclusions the mo concentrations vary over a range of more than one order of magnitude more than for any other element as a result of fluid rock interactions and molybdenite precipitation cu concentrations remain always relatively high in the fluids during their evolution 26 7092 ppm because there was little chalcopyrite precipitation the stage 3 fluid inclusions are rich in mn pb and zn while ag concentrations increased in stage 3 and 4 fluid due to the addition of meteoric water from the surrounding rock reactions between the wallrock and hydrothermal fluids affected the composition of the hydrothermal fluids sericitic alteration in particular had a great effect on fluid compositions manifesting the variety of the content of sr ba ca pb the ore forming fluids were mainly magmatic hydrothermal fluids that were mixed with meteoric water during stages 3 and 4 fluid immiscibility a rapid decrease in pressure fluid rock reactions and fluid cooling were collectively responsible for the sulfide precipitation in the dasuji deposit

porphyry epithermal transition maricunga belt northern chile the refugio aldebaran and la pepa districts in the maricunga belt of northern chile contain advanced argillic alteration zones that locally host high sulfidation epithermal gold deposits in proximity to porphyry gold copper deposits the spatial association suggests a genetic link mineralized zones are characterized by four main vein types that formed at different times and have specific zonal relationships a veinlets are the earliest and deepest vein type they are restricted to potassic alteration zones in intrusive rocks a veinlets contain variable amounts of quartz magnetite biotite and chalcopyrite and locally have k feldspar halos they have nonmatching irregular vein walls and lack internal symmetry hypersaline liquid rich inclusions coexisting with vapor rich inclusions in a veinlets indicate temperatures as high as nearly 700 c and pressures between 200 and 400 bars assuming a lithostatic load depths of 0 8 to 1 6 km are inferred zones of abundant a veinlets contain mostly 1 ppm gold and 0 1 to 0 4 percent hypogene copper banded quartz veinlets occur mostly above a veinlets and cut a veinlets where they overlap dark gray bands the color resulting from a high density of vapor rich fluid inclusions and micron sized grains of magnetite commonly occur as symmetric pairs near the vein walls vein walls are parallel and slightly wavy vuggy vein centers are common and alteration envelopes are absent data from rare liquid rich inclusions in banded quartz veinlets indicate temperatures 350 c at pressures between 20 and 150 bars assuming a hydrostatic load depths of 0 2 to 1 5 km are inferred zones of abundant banded quartz veinlets generally contain 0 5 to 2 ppm gold and 0 1 percent hypogene copper d veins are pyrite veins with quartz sericite pyrite halos they are widespread and crosscut a veinlets and banded quartz veinlets the brittle nature of d veins and limited fluid inclusion data suggest temperatures 400 c d veins serve as important time lines they are nowhere truncated or crosscut by intrusions a veinlets or banded quartz veinlets quartz alunite replacement veins referred to as ledges in this paper are typical of the high sulfidation epithermal environment they are mostly limited to overlying volcanic rocks they contain local core zones of vuggy residual quartz that can contain enargite or at higher elevations barite of the three districts studied only la pepa has mineable quartz alunite ledges which contain an average gold grade of about 20 ppm a spectrum of porphyry style deposits exists cerro casale at aldebaran shares many characteristics of porphyry copper deposits worldwide whereas verde at refugio is a true porphyry gold deposit potassic alteration zones and a veinlets are strongly developed at cerro casale whereas they are absent at verde banded quartz veinlets predominate at verde whereas they occur only at the upper levels of cerro casale the pancho deposit at refugio and the cavancha deposit at la pepa are telescoped systems in which banded quartz veinlets overprint potassic alteration zones and a veinlets a veinlets and banded quartz veinlets cut and are cut by intrusions indicating multiple cycles of intrusion potassic alteration a veinlets banded quartz veinlets during formation of porphyry style mineralization banded quartz veinlets are thought to have formed by flashing of magmatic fluids during episodic transitions from lithostatic to hydrostatic pressure loss of sulfur to the vapor phase during flashing inhibited formation of copper sulfides in banded quartz veinlets and therefore resulted in high gold copper ratios where rising magmatic vapors condensed into overlying meteoric water along faults barren quartz alunite ledges formed this conclusion is supported by equivalent 40ar 39ar dates on hydrothermal biotite associated with porphyry style ore and alunite from barren ledges at aldebaran 40ar 39ar dates at la pepa indicate alunite formed at least 140 000 years to as long as 900 000 years after hydrothermal biotite within the high sulfidation epithermal environment the development of ore depends on the ability of late moderate salinity magmatic fluids to reach the surface without condensing a brine upon ascent cooling and boiling of the moderate salinity fluid below its critical temperature results in the formation of sericite at depth and alunite near the surface that is essentially synchronous with high sulfidation ore formation the timing of the switch from lithostatic pressures to brittle hydrostatic conditions relative to the life of the hydrothermal system might determine how much porphyry style ore forms relative to high sulfidation epithermal ore

magmatic hydrothermal evolution of the yuanzhuding porphyry cu mo deposit south china insights from mica and quartz geochemistry abstract the yuanzhuding porphyry cu mo deposit located in the southern section of the qinzhou hangzhou belt is characterized by successive generations of quartz bearing veins with complicated crosscutting relationships multiple analytical methods have been applied to different mica types and quartz bearing veins to reveal the evolution history of the yuanzhuding porphyry system four types of micas have been identified in the yuanzhuding porphyry cu mo deposit including magmatic biotite bt i metamorphic biotite bt ii hydrothermal biotite bt iii and hydrothermal sericite ser based on detailed petrological observations all three types of biotite belong to the mg biotite group but can be compositionally distinguished whereas ser lies in the transition zone between li phengite and li muscovite generally decreasing crystallization temperatures with increasing distances from the center of the porphyry have been revealed in bt ii and bt iii based on their compositional variations documenting the outward cooling trends of the yuanzhuding porphyry system early quartz bearing veins with potassic alteration are characterized by granular quartz with homogeneous cl textures in combination with their wavy vein walls which indicate the host rock was ductile during vein formation we infer that they were formed under dominantly lithostatic pressure late quartz bearing veins with sericitic alteration are typically euhedral quartz with growth zones of oscillating cl intensity and they are inferred to be formed under dominantly hydrostatic pressure intersection of fluid inclusion isochores with ti in quartz isopleths revealed that early quartz veins with potassic alteration located close to the ore forming porphyry were formed at up to 575 c late quartz veins with sericitic alteration were formed at 310 c formation depth of the yuanzhuding porphyry deposit is inferred to be 5 3 km hydrogen and oxygen isotopes of bt iii and quartz indicate that the ore forming fluid was mainly magmatic fluid the fluid pressure was high enough to remain stable in single phase through the entire fluid evolution history all fluid inclusions are vapor liquid inclusions the fluid salinity and the cl fugacity remained constantly low which may have limited the efficiency of cu extraction and transportation the hornfels host significant amounts of bt ii and may have served as a reservoir of ferrous iron to reduce the oxidized ore forming fluid and generate reduced sulfur effective metal precipitation occurred in the yuanzhuding porphyry system owing to the coexistence of the generation of reduced s2 and the drop of metal solubility caused by the decrease of fluid temperature

refined insight into 40ar 39ar progressive crushing technique from k cl ar correlations in fluid inclusions abstract hydrothermal fluid activity associated with geological processes can now be dated by 40ar 39ar progressive crushing of minerals thanks to recent advances in high precision mass spectrometry however methods of data analysis and interpretation for these high resolution measurements still need to be refined in this study we report further insights into using k cl ar diagrams as tools for interpreting ages of secondary and primary fluids from 40ar 39ar stepwise crushing experiments three paragenetic mineral pairs of muscovite and wolframites from a southern china tungsten deposit were investigated using the 40ar 39ar technique through laser incremental heating and progressive crushing of single minerals incremental heating analyses of muscovites yielded flat age spectra defining plateau ages of 156 153 ma progressive crushing experiments of wolframites yielded anomalously old apparent ages due to excess 40ar however the apparent ages decline quickly after the initial steps and stabilize to form age plateaus of 156 153 ma without excess 40ar the plateau age steps interpreted as ages of gases derived from primary fluid inclusions pfis yield well defined isochrons with ages ranging from 157 to 153 ma and initial 40ar 36ar values that are indistinguishable from the modern atmospheric value digitally created 2d and 3d diagrams of k cl ar correlations can easily reveal distribution trends and correlation planes from the crushing steps interpretations of these diagrams further reveal the ages of secondary fluid inclusions sfis 87 to 83 ma and primary fluid inclusions pfis 159 to 150 ma raw data from sfis degassed during the initial crushing steps form scatters on inverse isochron plots however 2d and 3d k cl ar diagrams yield sfi ages that agree with 40ar 39ar ages of k feldspar veins cutting the tungsten ore bodies

patterns of silicification in permian pelecypods and brachiopods from wyoming abstract silicified pelecypods and brachiopods are common in the ervay franson and grandeur members of the permian park city formation of central and western wyoming study of hundreds of these fossils has resulted in recognition of five patterns of silicification pattern i is characterized by megaquartz crystals projecting inward from and perpendicular to the skeletal boundary whereas fossils exemplifying pattern ii consist of concentric laminae of chalcedonic quartz in pattern iii an outer lamina of microcrystalline quartz grades abruptly inward to laminated chalcedonic quartz which in turn grades abruptly inward to megaquartz shells demonstrating pattern iv involve megaquartz crystals aligned parallel to the skeletal boundary and lying adjacent to beekite discs pattern v consists of megaquartz crystals aligned parallel to the skeletal boundary in brachiopods these crystals typically exhibit relict skeletal microstruture pelecypod wall layers constructed originally of aragonite are characterized by patterns i ii iii and iv pattern v characterizes all brachiopods and originally calcitic layers of pelecypods patterns i ii iii and iv are interpreted to result from filling of voids created by dissolution of skeletal carbonate pattern v results from concurrent carbonate dissolution and silica precipitation

overprinting mineralization in the paleozoic yandong porphyry copper deposit eastern tianshan nw china evidence from geology fluid inclusions and geochronology abstract the yandong porphyry copper deposit is located in the southern part of the dananhu tousuquan island arc belt in eastern tianshan xinjiang nw china the dananhu tousuquan belt contains a number of large and medium cu deposits among which the yandong deposit 2 0 mt cu 0 67 is the largest the yandong cu deposit is hosted by plagiogranite porphyry and the carboniferous qi eshan group mafic to intermediate calc alkaline volcanic and pyroclastic rocks according to the crosscutting relationships and mineral assemblages the alteration and mineralization processes at yandong comprise three episodes the porphyry mineralization episode including potassic propylitic early phyllic and late phyllic stages the overprinting mineralization episode including main and post mineralization stages and lastly supergene alteration episode fluid inclusions fis in quartz from the potassic early late phyllic and post mineralization stages and anhydrite from the main post mineralization stages include four types 1 vapor liquid two phases w type 2 daughter mineral bearing s type 3 pure liquid pw type and 4 pure vapor pv type the potassic stage contains w s and pv type fis which yielded homogenization temperatures of 304 445 c mainly 340 400 c and salinities of 3 1 16 4 mainly 4 0 10 0 wt nacl eqv at the early phyllic stage three types of fis are identified i e the w s and pv type the s type and w type fis homogenized at 213 441 c mainly 280 300 c and 241 352 c mainly 300 320 c respectively with corresponding salinities of 33 1 52 0 mainly 34 0 40 0 wt nacl eqv and 0 9 15 9 mainly 0 9 4 0 wt nacl eqv respectively the late phyllic stage contains w s and pw type fis which homogenized at 146 248 c mainly 160 180 c with salinities ranging from 3 9 to 18 2 mainly 4 0 8 0 wt nacl eqv mineralization depths calculated from fis are 0 8 1 2 km stage i 0 6 1 8 km stage iiia and 0 4 0 7 km stage iiib fluid boiling and mixing likely occurred during the porphyry mineralization period leading to the precipitation of pyrite and chalcopyrite during the overprinting mineralization the w and pv type fis occur in the main mineralization anhydrite with homogenization temperatures and salinities being 248 421 c mainly 300 340 c and 5 3 13 8 mainly 8 0 10 0 wt nacl eqv respectively the post mineralization quartz and anhydrite homogenized at 105 195 c mainly 120 140 c with salinities of 0 5 13 6 mainly 8 0 10 0 wt nacl eqv the ore forming fluids may have predominantly been entrapped at 0 8 1 6 km stage iv and 0 3 0 6 km stage v the decreasing temperature may have led to the sulfides and sulfate precipitation and enrichment sericite 40 ar 39 ar dating of the altered plagiogranite porphyry yielded a plateau age of 332 8 3 8 ma consistent with the age of the early ore forming plagiogranite porphyry 339 332 ma re os dating of molybdenite coexisting with chalcopyrite anhydrite chlorite calcite assemblage yielded an age of 324 3 2 7 ma weighted mean consistent with the late quartz albite porphyry age zircon u pb 323 6 2 5 ma consequently we propose that at least two mineralization episodes may have occurred at yandong with the second episode contributing to the majority of the cu mo resources such overprinting mineralization style at yandong may represent a good example of the paleozoic cu deposits in the central asian orogenic belt

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

unusual sedimentary geodes filled by gold bearing hematite laths unusual mineralized and silicified carbonate rich geodes were found hosted in lower triassic red mudstones in central spain from their borders to their centres the geodes display a a millimetric carbonate crust b a quartz rim c massive dolomite d gold bearing iron rich infills hematite laths and goethite with up to 7000 ppm of gold and e calcite cements that sometimes seal the central hollow textural evidence indicates that the geodes were originally anhydrite which was subsequently replaced by quartz and dolomite the resultant porosity from this replacement or by later dissolution has been filled by epithermal gold bearing iron oxide hydroxides romanechite and calcite 13c values indicate the participation of meteoric waters in an environment which was characterized by both a sub desert climate and a temperate tropical climate oxygen signatures reflect very variable temperatures for all minerals with the exception of calcite which appears to have precipitated at 38 c iron oxide temperature values can reach up to 85 c epithermal stage the mineralogical assemblages of these unusual geodes denote early diagenetic replacement followed by the epithermal activity this mineralization is linked to the late hercynian calc alkaline volcanism of central spain the hiendelaencina mining district

dedolomitization and other early diagenetic processes in miocene lacustrine deposits ebro basin spain abstract a variety of meteoric diagenetic features reveal the development of a syngenetic karst on lacustrine deposits of the ebro basin diagenetic processes that operated on lacustrine laminated and stromatolitic carbonates include the following 1 a first syndepositional stage with processes such as dolomitization desiccation and related breccia formation and sulphate precipitation either as lenticular gypsum crystals or nodules this stage took place under progressive evaporation due to lake level fall when the previous carbonate deposits became exposed as a supra littoral fringe surrounding saline mud flats of adjacent sulphate depositional environments 2 a second early diagenetic stage in which processes such as sulphate dissolution and collapse brecciation dedolomitization calcite spar cementation and silicification occurred as a result of meteoric water input that caused a progressive rise in lake level light isotopic compositions 13 c and 18 o of diagenetic calcites versus heavier compositions in primary laminated and stromatolitic limestones confirm a meteoric influence the syngenetic karst is best developed at the boundary between two allostratigraphic units and coincided with one of the extensive stages of sulphate deposition at the end of the early miocene the karst facies occurred in an area that was a low relief barrier that separated two sites of sulphate deposition during low lake levels this indicates that the karst development was controlled by topographic changes within the basin and record a shift from arid to wetter climatic conditions as suggested by the overlying freshwater carbonate deposits the presence of diagenetic features such as those described in the central ebro basin affecting saline lacustrine carbonates is relevant because they can be used as indicators of subaerial exposure periods in terrestrial environments and they also reveal important palaeogeographic and palaeoclimatic events of basinal extent

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 and mineralization mechanism of the east kounrad porphyry mo w deposit in the balkhash metallogenic belt central kazakhstan abstract the east kounrad mo w deposit is located in the eastern part of the balkhash metallogenic belt central kazakhstan the intrusion in the east kounrad deposit is a permain complex that includes medium and fine grained granites both the primary magma and hydrothermal fluids of the east kounrad deposit are characterized by high fluorine and high oxygen fugacity which would be important for the formation of high grade large mo deposit four mineralization stages are identified in this study stage i quartz wolframite molybdenite fluorite veins which were associated with intensively greisen alteration were formed from fluids with high temperature 340 460 c high pressure 250 400 bars high low salinity 54 5 wt and 3 4 10 2 wt respectively and high oxygen fugacity with a fluid system of h2o nacl co2 stage ii quartz molybdenite pyrite veins which were accompanied by k feldspars muscovite fluorite alteration were formed from fluids with medium high temperature 260 400 c medium pressure 100 250 bars high low salinity 39 1 58 4 wt and 2 4 11 7 wt respectively and relatively low oxygen fugacity after the main stage of w and mo mineralization stage iii quartz pyrite molybdenite veins associated with quartz sericite alteration were formed from fluids with medium low temperature 160 340 c low pressure less than 100 bars various salinity 4 5 46 2 wt and high oxygen fugacity stage iv quartz polymetallic sulfide veins related to argillic alteration were formed under temperature of 120 220 c and salinity of 1 7 8 1 wt remarkably fluid boiling is the most important precipitation mechanism of molybdenite and wolframite in addition the decreasing oxygen fugacity and temperature also play a vital role in triggering deposition of molybdenite the pb isotopic composition of sulfides shows that the ore forming materials at east kounrad are dominantly derived from the lower crust

genesis of the jinchanggouliang gold deposit chifeng china constraints from fluid inclusions and isotopic geochemistry abstract the jinchanggouliang gold deposit which located south of the hingan mongolian orogenic belt is a large gold deposit in the chifeng chaoyang region field evidence and petrographic observations indicate that the mineralization processes can be divided into three stages including milky or grey quartz stage i quartz pyrite stage ii quartz polymetallic sulfides stage iii five types of fis have been identified in the jinchanggouliang deposit 1 solid bearing inclusions type 1 liquid rich inclusions type 2 vapor rich inclusions type 3 pure vapor inclusions type 4 and co2 h2o inclusions type 5 the first stage contains mainly type 2 but also minor type 3 and 4 fis the fis display homogenization temperatures of 317 384 c and salinities of 4 0 12 5 wt nacl eq the stage ii contains all types of fis mainly type 2 less abundant type 3 and 5 rarely type 1 and 4 which show homogenization temperatures of 288 382 c and salinities of 1 6 41 4 wt nacl eq the types of fis in stage iii are the same as stage ii these fis yield the lowest homogenization temperatures of 245 363 c and salinities of 1 1 36 8 wt nacl eq the ore forming fluids are characterized by moderate high temperature and great fluctuating salinity magmatic hydrothermal fluids the type 2 and 3 fis commonly coexist with simultaneously trapped type 5 fis and the type 2 and 3 fis have similar homogenization temperatures but contrasting homogenization modes to the liquid and vapor respectively in the main mineralization stages which suggests fluid boiling occurred in these two stages combined with the previous h o isotopic data it can be concluded that the ore forming fluids are of granitic magmatic origin the s pb isotopes indicate that the ore materials were mainly derived from deep magma petrographic observations and microthermometric analysis indicating that fluid boiling was the main mineral precipitation mechanism and fluid boiling mainly occurred in the temperature range from 290 c to 370 c in general from the view of fluid inclusions and isotopes geochemistry the jinchanggouliang gold deposit is most probably a magmatic hydrothermal deposit

formation and evolution of multistage ore forming fluids in the miocene bangpu porphyry skarn deposit southern tibet insights from la icp ms trace elements of quartz and fluid inclusions abstract the large bangpu mo cu pb zn deposit is a mo rich 0 089 cu poor 0 32 porphyry skarn deposit located in the northeastern gangdese porphyry copper belt gpcb southern tibet in this study la icp ms data for fluid inclusions and quartz formed during different stages of the mineralization are used to 1 constrain changes in fluid composition during mineralization 2 infer the origin transport pathways and conditions of ore precipitation and 3 explore the influence of magma chamber on fluid exsolution and shallow mineralization the cu content of the vapor rich vl inclusions is higher than that of the halite bearing lvh inclusions while the mo pb and zn contents of the vl and lvh inclusions are similar indicating that mo cu pb and zn had a common source which is inferred to be the intermediate level magma chamber the metal contents of fluid inclusions in the early stage potassic alteration related vein a vein and later stage sericitic alteration related vein b vein are similar but variable implying the intermediate level magma chamber was too small to form a large stable fluid system the enrichment of mo pb and zn in the bangpu deposit relative to other porphyry deposits in the gpcb is related to the participation of ancient crustal material a comparison of our results with those from super large porphyry cu deposits elsewhere indicates that metal rich fluids are not the sole factor to form ore deposits and the variability of metal contents in the early exsolved fluids is a better predictor of mineralization potential than absolute metal concentrations

fluid evolution of the tongkuangyu porphyry copper deposit in the zhongtiaoshan region evidence from fluid inclusions abstract the tongkuangyu porphyry copper deposit is located in the zhongtiaoshan region southern margin of the north china craton more than 2 8 million tons of cu average cu grade 0 68 is hosted in the paleoproterozoic quartz monzonite porphyry 2122 10 ma the ore forming processes of the tongkuangyu porphyry cu deposit are divided into three mineralization stages namely the early main and late mineralization stages the majority of cu ores were formed in the main stage which is characterized by veinlets and disseminated chalcopyrite and minor molybdenite pyrite magnetite and hematite quartz is the major gangue mineral which occurs as veinlets and associates with metallic minerals through systematic petrographic observation the ore bearing quartz veins a type quartz and the quartz hosted in chalcopyrite b type quartz were studied in detail to investigate the fluid evolution of the tongkuangyu porphyry cu deposit four types of fluid inclusions were recognized in the a type quartz which include 1 pure vapor or vapor rich v type inclusions 2 co 2 h 2 o c type inclusions 3 liquid rich l type inclusions and 4 daughter mineral bearing s type inclusions s type inclusions in the main stage a type quartz contain mainly halite and minor sylvite calcite hematite chalcopyrite and anhydrite with homogenization temperatures of 233 450 c v type inclusions coexisting with the s type inclusions homogenize to vapor phase at 282 375 c suggesting that the ore forming fluids may have experienced boiling in the main mineralization stage the late stage s type inclusions have homogenization temperatures of 186 245 c and contain largely halite with minor sylvite fluid inclusions in the b type quartz intergrown with chalcopyrite are closely associated with the ore forming processes the main stage b type quartz contains predominantly s type inclusions with homogenization temperatures of 250 412 c and minor v type inclusions on the other hand the late stage b type quartz contains abundant s type inclusions with homogenization temperatures of 195 230 c and less l type inclusions our results show that the s type inclusions in both the a and b type quartz of the same ore stage have very similar homogenization temperatures therefore fluid boiling may have promoted the cu enrichment in the high salinity fluids and the brine phase is the main metal transport medium in the tongkuangyu porphyry cu deposit the common occurrence of hematite and anhydrite daughter minerals in the s type inclusions further suggests that ferrous ion oxidization may have caused sulfate reduction this process may have played an important role during the cu precipitation event the progressive cooling of fluids and the incorporation of meteoric water in the late mineralization stage possibly resulted in the small scale vein type mineralization

a review and comparison of fracture mineral investigations and their application to radioactive waste disposal abstract a compilation and comparison of fracture mineral studies from the canadian and fennoscandian shields and the french massif central shows many similarities indicating larger external control over fracture mineral deposition with different rock types exerting local controls the sites investigated represent a wide range of geological settings and host rock types ranging from felsic intrusive and extrusives to ultramafic intrusives and volcanics that span an age range from 2 5 to 0 36 ga typical fracture minerals found at canadian shield sites include calcite quartz chlorite and clays and these do not appear to be dependant on age erosional depth or geological environment the fennoscandian shield has a much larger variety of fracture filling minerals with epidote zeolites prehnite fluorite pyrrhotite fe oxides serpentine graphite magnesite and barite in addition to the minerals typically found at canadian shield sites the major control on fracture mineral type is most likely variations in rock type and fluid chemistry and temperature the c and o isotopic range of calcite is very similar among sites late stage hydrothermal calcite with strongly depleted 18o values is common at many sites all of the sites have calcite with 18o isotopic values in the range of 5 to 20 pdb indicative of formation from meteoric water or basinal brines that have undergone varying degrees of water rock interaction one canadian and a few swedish sites have calcite in the shallower portion of the rock that shows isotopic evidence of dissolution and re precipitation in equilibrium with the present day waters there are some striking similarities in fluid inclusion data among sites most sites have an elevated temperature 100 300 c low salinity group of fluid inclusions within the nacl h2o system and a lower temperature 50 150 c higher salinity group of fluid inclusions within the nacl cacl2 h2o system fluid inclusion density plots show some evidence of simple cooling but most sites show two or more fluids were responsible for calcite formation the origin of most of these fluids was magmatic hydrothermal or meteoric water that had undergone varying degrees of water rock interaction but basinal brines and seawater were also possible sources several techniques and methods have been used to further characterize calcites strontium isotopes and rare earth elements can be useful to recognize different families of calcite uranium th dating has found many old calcites beyond the useful range of the technique but also some relatively young calcites that may be related to interglacial periods where fluid inclusion data exists formation temperatures were not consistent with a glacial water origin crush and leach experiments with ion and gas chromatography and thermal ion mass spectrometry have characterized inclusion fluids but special care must be used to ensure only one generation is sampled at a time cathodoluminescence and scanning electron microscopy with energy dispersive spectrometry has been useful in identifying multiple fluid generations within single calcite samples laser ablation and raman spectrometry are additional techniques that are useful in determining individual fluid inclusion chemistry and isotopes

boiling vapour type fluids from the nifonea vent field new hebrides back arc vanuatu sw pacific geochemistry of an early stage post eruptive hydrothermal system in 2013 high temperature vent fluids were sampled in the nifonea vent field this field is located within the caldera of a large shield type volcano of the vate trough a young extensional rift in the new hebrides back arc hydrothermal venting occurs as clear and black smoker fluids with temperatures up to 368 c the hottest temperatures measured so far in the western pacific the physico chemical conditions place the fluids within the two phase field of nacl h2o and venting is dominated by vapour phase fluids with cl concentrations as low as 25 mm the fluid composition which differs between the individual vent sites is interpreted to reflect the specific geochemical fluid signature of a hydrothermal system in its initial post eruptive stage the strong cl depletion is accompanied by low alkali cl ratios compared to more evolved hydrothermal systems and very high fe cl ratios the concentrations of rey 180 nm and as 21 m in the most cl depleted fluid are among the highest reported so far for submarine hydrothermal fluids whereas the inter element rey fractionation is only minor the fluid signature which has been described here for the first time in a back arc setting is controlled by fast fluid passage through basaltic volcanic rocks with extremely high water rock ratios and only limited water rock exchange phase separation and segregation and at least two component fluid mixing metals and metalloids are unexpectedly mobile in the vapour phase fluids and the strong enrichments of fe rey and as highlight the metal transport capacity of low salinity low density vapours at the specific physico chemical conditions at nifonea one possible scenario is that the fluids boiled before the separated vapour phase continued to react with fresh glassy lavas the mobilization of metals is likely to occur by leaching from fresh glass and grain boundaries and is supported by the high water rock ratios the enrichment of b and as is further controlled by their high volatility whereas the strong enrichment of rey is also a consequence of the elevated concentrations in the host rocks however a direct contribution of metals such as as from magmatic degassing cannot be ruled out the different fluid end member composition of individual vent sites could be explained by mixing of vapour phase fluids with another fluid phase of different water rock interaction history

miocene magmatism of sinai related to the opening of the red sea extension associated with the initial early miocene stages of opening of the red sea resulted in intrusion of a widespread system of dikes and smaller bodies primarily along the northeastern margin of the red sea gulf of suez axis dikes some up to more than 800 km in length were emplaced dominantly parallel to the red sea gulf of suez from the sinai peninsula to yemen intrusive rocks are mainly basaltic in composition but minor granophyres are also present in the sinai this magmatic event is about 20 m y old dikes of the southern and southeastern sinai crop out in precambrian terrane in the central and northern sinai they occur in phanerozoic terrane where they may be associated with linear grabens and cryptovolcanic features basaltic dikes of the sinai underwent variable degrees of alteration alteration phases include seriate quartz smectite chlorite and serpentine x ray diffraction and petrographic analysis indicate that in spite of extensive alteration primary minerals still control the major element compositions of the rocks basalts are tholeiitic in composition with sio2 48 5 to 50 and na2o k2o 3 to 3 5 rb and sr concentrations are probably dominated by alteration and by introduction of secondary material primarily carbonate zr tio2 which is relatively unchanged during alteration substantiates that the basaltic rocks are subalkaline initial 87sr 86sr determined after leaching of samples is approximately 0 7043 0 7063 much higher than red sea axial trough basalts 0 703 we infer that these sinai basalts equilibrated at depths of 35 50 km possibly within an enriched mantle whether the main trough of the red sea is underlain by extended and modified continental crust or by oceanic crust is controversial since miocene dikes were intruded along both coasts but primarily the saudi arabian coast of the red sea gulf of suez axis in a zone up to 150 km wide they may also underlie the main trough of the red sea and result at least partially in the discontinuous magnetic and gravity anomalies observed there possibly the abundance of dikes beneath the main trough is much greater than adjacent to the red sea giving rise to properties intermediate between those of continental and oceanic crust downwarping and widespread intrusion of dikes along the red sea 18 26 m y ago probably signified crustal dilation and the initiation of a continental rift because tholeiitic basalts of the sinai are higher in 87sr 86sr than red sea axial trough basalts we infer that the conditions of their origin must also be very different we suggest that the sinai basalts may have been generated within but near the base of subcrustal continental lithosphere perhaps indicating thermal thinning of lithospheric mantle above upwelled asthenosphere associated with continental rifting this inference if correct would indicate that the lithosphere was at least 35 50 km thick during the early miocene phase of rifting but possibly not much thicker since dikes farthest from the red sea are apparently identical in composition to those closest asthenospheric upwarping must have been broad enough that all magmas were derived from approximately the same depth in the yemen ethiopia areas volcanism began earlier about 30 m y ago and was much more voluminous than elsewhere along the red sea gulf of suez axis suggesting the presence of underlying mantle upwelling accompanying rifting of the red sea in spite of differences in age and volume the presence of large volumes of tholeiites among the miocene basalts of the yemen ethiopia areas suggests that the lithosphere was similarly thinned along the entire length of the red sea

an evaluation of synthetic fluid inclusions for the purpose of trapping equilibrated coexisting immiscible fluid phases at magmatic conditions we report data that allow us to evaluate the method of trapping immiscible saline aqueous fluids i e vapor and brine in the nacl kcl hcl fecl2 auhcl2 h2o system as synthetic fluid inclusions in pre fractured quartz cores in order to quantify the concentrations of au fe k and na among coexisting three phase immiscible fluids i e haplogranite melt brine and vapor at magmatic conditions coexisting vapor and brine were trapped experimentally at 800 c and 100 110 mpa as synthetic fluid inclusions in both quartz microfractures and quenched silicate melt i e glass and also sampled indirectly using the recovered quenched aqueous fluid quartz hosted and glass hosted brine inclusions were analyzed by laser ablation inductively coupled plasma mass spectrometry la icpms and instrumental neutron activation analysis inaa respectively quenched aqueous fluid from each experiment containing a quartz core was recovered and analyzed by atomic absorption spectrophotometry aas the composition of aqueous fluids trapped as quartz hosted inclusions glass hosted inclusions and those recovered after quench yield consistent and precise data at the 2 uncertainty level for the elements of interest the overlapping au fe k and na concentrations in aqueous fluids trapped and analyzed via three entirely different instrumental techniques i e la icpms inaa and aas suggest strongly that quartz microfractures heal on a slow enough time scale to permit entrapment of fully equilibrated aqueous fluids at our experimental ptx conditions the data evince clearly that the chemical composition of fluids in quartz microfractures at the time of self healing represents equilibrium conditions hence synthetic fluid inclusions in experiments with low thermal gradients across the charge provide a reasonable estimate of fluid composition at least at the experimental conditions examined in this study

sedimentation in an actively tilting half graben sedimentology and stratigraphy of late tournaisian visean mississippian lower carboniferous carbonate rocks in south county wexford ireland the wexford basin south eastern ireland is a ne sw trending sedimentary basin containing carbonates and evaporites deposited during the late tournaisian and visean two separate depositional areas are defined on the basis of facies and facies associations sediments were deposited in inner ramp lagoonal and peritidal environments near rosslare and in a more open marine shallow to moderately deep water mid to outer ramp environment in the western area around duncormick thick breccia deposits that occur in the wexford basin formed as a result of i fault movement that produced syn sedimentary debris flows in the late chadian breccia type i ii dissolution of anhydrite gypsum and subsequent collapse of sedimentary strata breccia type ii and iii fracturing and brecciation of porous rock caused by the movement of high temperature late diagenetic fluids along fault planes breccia type iii the ne sw facies polarity displayed by both sedimentary successions was the result of nw se extension and the reactivation of the ne sw trending wexford boundary fault during the chadian extension at the se margin of the basin with downthrow to the nnw gave the basin a half graben character thickening of the debris flow deposits to the sw suggests that while the half graben was being tilted it also underwent a ne sw block rotation due to an axial component of that normal fault

porphyry to epithermal transition at the rongna cu au deposit tibet insights from h o isotopes and fluid inclusion analysis abstract the giant rongna cu au deposit is a recently discovered low grade composite porphyry high sulfidation epithermal system in the duolong ore district of central tibet we present fluid inclusion petrography microthermometry stable isotope h o and fluid compositional data la icp ms to constrain the fluid evolution of the rongna deposit hydrothermal quartz and muscovite formed in the porphyry stage yielded fluid values of 8 2 1 0 18oh2o and 75 19 dh2o n 13 pyrophyllite kaolinite and dickite define the isotopic composition of the epithermal fluid 18oh2o 2 2 8 3 dh2o 87 45 this epithermal fluid of lighter oxygen isotope and heavier hydrogen isotope composition still has a magmatic hydrothermal signature and rules out any significant involvement of meteoric water the very high concentration of cu in fluid inclusions from epithermal veins and the common sulfide replacement features suggest that the epithermal mineralization may be partially related with the dissolution and re precipitation of the porphyry stage sulfides combined with fluid inclusion petrography and microthermometric data it is indicated that a single phase fluid exsolved from magma at depth and underwent boiling and cooling forming the porphyry alteration and mineralization with decrease of temperature and pressure the ascending vapor contracted into acid aqueous fluid leaching downward to develop the telescoped high sulfidation epithermal alteration and mineralization

late cretaceous quartz geodes after anhydrite from burgos spain quartz geodes cauliflower like appear in a specific level of the late cretaceous north of burgos due to their anhydrite relicts and spherulitic quartz length slow chalcedony they are considered as pseudomorphs of anhydrite nodules formed during early diagenesis at the same level compact chert nodules sporadically appear presenting a considerable amount of sponge spicules with fibrous texture length fast chalcedony the silicification of the anhydrite nodules took place before total compaction and cementation of the sediment the source of silica is principally biogenic sponge spicules there is no link between the depositional environment and the existence in itself of anhydrite nodules indirectly it is possible to see the effects of an arid climate which have not been recorded in the lithologic column here described modified journal abstract

successive geothermal volcanic hydrothermal and contact metasomatic events in cenozoic volcanic arc basalts south shetland islands antarctica hydrothermal alteration in volcanic arcs occurs in many settings and may involve magmatic marine lacustrine or groundwaters driven by magmatic tectonic or thermal events king george island part of the south shetland island cenozoic volcanic arc contains an 80 km long zone of propylitized volcanic rocks with numerous occurrences of quartz veining silicic sericitic argillic and advanced argillic alteration on barton peninsula a basaltic lava sequence 49 44 ma intruded by a small high level granodiorite pluton 42 ma contains these alteration types previously interpreted as a single porphyry copper system in this study we report three possibly four distinct fossil hydrothermal episodes 1 banded chalcedonic quartz quartz sericite and propylitic alteration occurs along ese faults and as reworked clasts in nearby tuffs drusy quartz calcite veins with silicic sericitic argillic and propylitic wallrocks may represent feeders to the near surface silicification these characteristics and anomalous ag pb sb au plus te se zn as suggest a neutralph geothermal system that was active during volcanism 2 the lavas and banded quartz rocks were brecciated veined and replaced by alunite native sulphur pyrite and pyrophyllite quartz pyrite zunyite diaspore assemblages with anomalous hg se as bi au tl sb cu such advanced argillic alteration is diagnostic of degassing of a felsic magma into shallow 500 m meteoric groundwaters rhyolite tuffs previously not reported on king george island may represent leakage of this magma to the surface 3 subsequent burial to 3 km was followed by emplacement of a granodiorite pluton and formation of a silicic contact metasomatic aureole containing muscovite biotite actinolite magnetite k feldspar and tourmaline disseminated andalusite corundum also formed in areas previously affected by the advanced argillic alteration iron copper sulphide veinlets are locally abundant but a porphyry style geochemical signature is not present early cretaceous ar ar ages near the intrusive contact indicate flow of an excess ar bearing hydrothermal plume up the contact finally isolated areas of propylitic alteration in the lavas nearby may be related either to quartz veins of episode 1 at depth or to 4 continued circulation of heated groundwaters around the cooling pluton

evidence of upgrading of gold tenor in an orogenic quartz carbonate vein system by late magmatic hydrothermal fluids at the madrid deposit hope bay greenstone belt nunavut canada abstract evidence of secondary gold enrichment due to the addition of new gold into an earlier orogenic quartz carbonate vein deposit by magmatic hydrothermal fluids is strongly suggested for the madrid deposit hosted in the hope bay greenstone belt in nunavut canada the conclusion is based on an extensive in situ microanalytical protocol sem confocal raman microspectroscopy microthermometry decrepitate mound analysis la icp ms cathodoluminescence sims not previously applied to gold systems this approach was used to characterize the mineralogy and fluid inclusion systematics associated with the upgrading event mineralization comprised of only ag bearing gold electrum 89 8 at au avg n 8 is present throughout all investigated laminated and brecciated orogenic quartz veins however in high grade vein intersections where gold grades are locally elevated up to 122 g t assemblages containing tennantite tetrahedrite chalcopyrite electrum 80 7 at au avg n 15 ag pb au tellurides occur that are texturally late stage relative to electrum only mineralization subdomains of quartz coeval with this later assemblage are optically and texturally distinct from earlier orogenic quartz this late mineral assemblage is absent in all low grade vein intersections 1 g t au avg examined where only electrum is identified quartz hosted fluid inclusions h2o nacl co2 of intermediate salinity 16 7 1 2 wt nacl equiv n 93 were identified only in the high grade vein samples and are present along healed planes associated with tennantite tetrahedrite chalcopyrite electrum ag pb au telluride assemblages in situ sims 18o analyses of quartz combined with temperature constraints from mineral equilibria show that early orogenic vein quartz and late quartz subdomains associated with gold upgrading precipitated from fluids with similar 18oh2o values of 4 5 12 4 n 10 and 5 5 to 11 8 n 13 respectively isotopic data suggests that meteoric water was a negligible component in fluids responsible for gold precipitation microthermometry and raman spectroscopy show that upgrading fluids were distinct in composition compared to the earlier metamorphic fluids h2o nacl co2 ch4 n2 4 6 1 6 wt nacl equiv n 33 and later canadian shield basement brines h2o nacl 22 4 1 2 wt nacl equiv n 12 which have also been identified in the fluid inclusion record at madrid laser ablation icp ms analyses indicate the gold upgrading fluids are enriched in as sb zn pb and lile cs ba rb sr these data are consistent with late fluids derived from an evolved magmatic hydrothermal system trace element mapping of pyrite coupled with principle component analysis of the data confirms a strong correlation between au and ag te sb bi w as in upgraded veins whereas only au and as strongly correlate in low grade veins the study suggests that gold upgrading either involving newly introduced gold or remobilization of existing gold can be linked to the incursion of a late magmatic hydrothermal fluid that post dated formation of the main orogenic type auriferous quartz vein system the geological setting and mineral chemical features suggest an intrusion related i e porphyry or intermediate sulfidation epithermal mineralization style for the later event this work provides another example of the importance of compositionally distinct cumulative hydrothermal events in the development of high grade gold deposits in orogenic settings

high cu concentrations in vapor type fluid inclusions an artifact abstract studies of natural fluid inclusions have shown that cu commonly occurs at higher concentrations in vapor type inclusions than in coexisting brine inclusions a phenomenon which has been interpreted to arise from copper partitioning into the vapor phase in the first part of this study we attempted to experimentally reproduce this behavior in hydrothermal experiments covering a range of p t conditions 600 800 c 70 130 mpa fluid compositions nacl kcl fecl 2 0 5 6 6 wt s fluid acidities quench fluid ph 0 3 10 and sulfur speciation h 2 s dominated to so 2 dominated however as in several other studies we did not succeed in reproducing conditions under which cu partitions into the vapor phase in view of recent observations that quartz hosted fluid inclusions can diffusively loose or gain cu after entrapment we set out to determine if the evidence from natural fluid inclusions could be compromised for this purpose we synthesized vapor and brine inclusions from cu h 2 o nacl s fluids at 800 c 130 mpa and re equilibrated them in slightly different fluids at 800 c 70 mpa measuring some inclusions by la icp ms after each step vapor inclusions indeed experienced a dramatic increase in cu from 0 3 0 03 to 5 7 3 3 wt while brine inclusions remained largely unmodified leading to a change in the partition coefficient d cu vap brine from a true value i e before re equilibration of 0 4 0 05 to an apparent value of 8 3 4 9 the requirements for substantial diffusional gain of cu in fluid inclusions are a change in the ph of the surrounding fluid from 1 to more neutral and the presence of s in the pre existing fluid inclusions these requirements are also fulfilled in nature cooling magmatic hydrothermal fluids experience a change from acidic to more neutral ph due to buffering along the feldspar mica join and natural vapor inclusions typically contain significant amounts of sulfur a reversal experiment performed on natural quartz hosted fluid inclusions from the erongo granite namibia showed that this process can be reversed with the measured d cu vap brine value of 11 9 3 being modified to 0 06 0 04 thus d cu vap brine values 1 measured on natural fluid inclusions in quartz are likely a secondary feature caused by post entrapment copper diffusion realistic d cu vap brine values in porphyry cu environments are between 0 11 and 0 15 and reconstructed vapor brine mass ratios are in the order of 4 9 this suggests that the main transporting agent of cu at the porphyry level are brines and that models based on copper into the vapor phase are incorrect

early cretaceous bimodal magmatism related epithermal mineralization a case study of the gaosongshan gold deposit in the northern lesser xing an range ne china abstract low sulfidation ls gold mineralization is partially associated with bimodal volcanism in origin sources of ore mineralized fluids and relevant dynamic processes remain poorly understood to better understand these issues a study including deposit geology petrology zircon u pb dating and element and sr nd hf isotope geochemistry of bimodal volcanic rocks at gaosongshan was conducted the bimodal volcanic rocks are composed of andesitic rocks basalt andesite andesite trachyandesite andesitic pyroclastic of the meifeng formation and overlying rhyolite lava of the fuminhe formation cut by equivalent porphyry stocks which contain pyrite bearing granular textured quartz cavity with a sugary appearance with trapped single phase magmatic fluids the andesitic suite formed at approximately 106 108 ma prior to eruption of the younger rhyolitic magmas 105 6 1 7 ma n 13 mswd 1 2 the andesites show calc alkaline affinities which is a subduction related characteristic and show moderate la ybn 7 91 11 36 and weakly negative europium anomalies 0 80 1 02 indicating a source in the asthenospheric mantle with varying contamination by both subduction and continental materials a type rhyolitic rocks are geochemically comparable to the andesitic suite and their higher la ybn 13 01 30 05 and lower eu eu 0 66 0 73 indicate evolved products of andesitic magmas the estimated oxygen fugacity of dry 1 2 water rhyolite lava is fmq 1 87 whereas rhyolite porphyry is more oxidized fmq 0 12 and water rich 2 5 2 8 with probably being water saturated at 2 0 2 4 km depths therefore it is assumed that the essential constraints of bimodal magmatism on epithermal gold mineralization are sequential processes from ascending and gradual differentiation of crustal level mantle derived basaltic magmas to releases of hydrothermal solutions from the silica rich magma reservoir at shallower levels most importantly the oxygen fugacity of and the fluid fluxes from dry rhyolitic melts are critical restricting parameters for the limited reserves at gaosongshan thus this research contributes objective evidence for investigations of deposit genesis and prospecting targets

volatile variations in magmas related to porphyry cu au deposits insights from amphibole geochemistry duolong district central tibet ore forming fluid exsolution in a shallow magma chamber is a critical step in the formation of porphyry cu mo au deposits but one for which direct evidence is rarely found here ci abundance major trace element content and h isotope analysis of amphibole in diorite and barren granodiorite porphyry samples from the duolong porphyry epithermal cu au district are presented in order to reveal processes associated with fluid exsolution and magma evolution low al mg hornblende formed in ore bearing diorite at 750 860 degrees c and similar to 80 200 mpa on primitive mantle normalized diagrams these low al amphibole grains have slightly convex upward ree patterns with distinctly negative eu anomalies and negative anomalies in pb sr eu zr hf and ti anomalies suggesting crystallization from the same arc magma after plagioclase and magnetite crystallization a large variation in estimated melt h2o similar to 6 to 3 wt and ci content 0 09 0 38 wt as well as low 8d values 103 to 113 o indicate that the magma underwent large scale fluid exsolution contributing to the formation of duolong cu au mineralization additionally amphibole from a barren granodiorite porphyry shows two distinct populations distinguished by their a1 content this intrusion has low al amphibole mghornblende which formed at similar conditions to low al amphiboles in the diorite 790 870 degrees c and similar to 100 230 mpa whereas high al amphibole tschermakite formed at similar to 880 970 degrees c and degrees 210 400 mpa some high al amphibole phenocrysts have slightly convex ree patterns with no negative eu anomalies a depletion in nb zr and hf and positive sr ba and pb anomalies likely consistent with amphibole crystallization from more mafic basaltic andesitic melts low al amphibole in the granodiorite porphyry shows different compositional trends compared to those in the diorite suggesting that they crystallized from different magmas considering the evidence for mafic magma replenishment suggested by the positive correlation between al iv and mg values in high al amphibole the low al amphibole in the barren granodiorite porphyry likely crystallized from a new hybrid magma with mafic to intermediate felsic magma compositions meanwhile smaller variations in ci content 0 08 0 24 wt in low al amphibole was dominantly controlled by magma evolution shown by variable mg rather than fluid exsolution thus the low 8d values 102 to 122 o were likely inherited from evolved dioritic magmas that underwent fluid exsolution importantly the ci compositional variation of amphibole has a potential application as a powerful tool to identify ore bearing and barren intrusions within porphyry cu mo au deposits

alunite 40ar 39ar and zircon u pb constraints on the magmatic hydrothermal history of the zijinshan high sulfidation epithermal cu au deposit and the adjacent luoboling porphyry cu mo deposit south china implications for their genetic association

alunite and the role of magmatic fluids in the tambo high sulfidation deposit el indio pascua belt chile the tambo high sulfidation deposit located within the el indio pascua belt in chile produced almost 25 t 0 8 m oz of gold from altered tertiary rhyodacitic volcanic rocks episodic magmatic hydrothermal activity in the district occurred over at least 4 my and is characterized by several stages of acid sulfate alteration including magmatic hydrothermal magmatic steam steam heated and apparent supergene assemblages two stages of aufag mineralization are recognized and are hosted in barite and alunite within hydrothermal breccias and veins isotopic compositions of fluid in alunite show a dominant magmatic signature with only a variable 18 o enriched meteoric water component throughout the entire hydrothermal process alunite 40 ar 39 ar ages constrain the timing of alteration and the duration of the hydrothermal system pre ore alteration occurred at about 10 to 11 ma and was contemporaneous with the volcanism of the tambo formation alunite from this stage of alteration occurs in the matrix of barren breccias and as fine intergrowths of alunite quartzfclays that selectively replaced feldspars and pumice fragments the textural relationships combined with stable isotope systematics suggest a magmatic hydrothermal origin for the alunite with a local magmatic steam overprint early ore stage alunite 8 7f0 2 ma occurs with barite and goldfwalthierite within open spaces of the breccia matrix and has d 34 s values 24 27x typical of magmatic hydrothermal alunite reflecting equilibrium between aqueous h2s and so4 fluid inclusion ratios of h2s so2 approximately 6 are consistent with ratios determined from stable isotope data and indicate reduced fluid conditions during ore deposition vaporphase transport of au and deposition from condensed magmatic vapor rising from the brittle ductile transition is inferred late gold coprecipitated with a third stage of alunite 8 2f0 2 ma that is characterized by nearly uniform chemical compositions and d 34 s values 1x similar to those for associated enargite reflecting disequilibrium between h2s and so4 this third stage of alunite is isotopically and chemically similar to that of post ore coarse banded alunitefhematite quartz veins that crosscut the breccias in the tambo area analyses of fluid inclusion gas from alunite in these veins indicate high so2 and disequilibrium co2 co ch4 h2 species consistent with a magmatic steam origin the gases are also depleted in he and the late goldbearing alunite was probably precipitated from rapidly ascending so2 rich vapors that were flashed from condensed magmatic

the relation between cu au ratio and formation depth of porphyry style cu au mo deposits constraints on gold and copper ore grades in porphyry style cu au mo deposits are re examined with particular emphasis on published fluid pressure and formation depth as indicated by fluid inclusion data and geological reconstruction defining an arbitrary subdivision at a molar cu au ratio of 4 0 104 copper gold deposits have a shallower average depth of formation 2 1 km compared with the average depth of copper molybdenum deposits 3 7 km based on assumed lithostatic fluid pressure from microthermometry the correlation of cu au ratio with depth is primarily influenced by the variations of total au grade despite local mineralogical controls within some ore deposits the overall cu au ratio of the deposits does not show a significant correlation with the predominant type of cu fe sulfide i e chalcopyrite or bornite primary magma source probably contributes to metal endowment on the province scale and in some individual deposits but does not explain the broad correlation of metal ratios with the pressure of ore formation by comparison with published experimental and fluid analytical data the observed correlation of the cu au ratio with fluid pressure can be explained by dominant transport of cu and au in a buoyant s rich vapor coexisting with minor brine in two phase magmatic hydrothermal systems at relatively shallow depth approximately 3 km and greater confining pressure is likely to precipitate copper molybdenum only while sulfur complexed gold remains dissolved in the relatively dense vapor upon cooling this vapor may ultimately contract to a low salinity epithermal liquid which can contribute to the formation of epithermal gold deposits several kilometers above the au poor porphyry cu mo deposit these findings and interpretations imply that petrographic inspection of fluid inclusion density may be used as an exploration indicator low pressure brine vapor systems are favorable for coprecipitation of both metals leading to au rich porphyry copper gold deposits epithermal gold deposits may be associated with such shallow systems but are likely to derive their ore forming components from a deeper source which may include a deeply hidden porphyry copper molybdenum deposit exposed high pressure brine vapor systems or stockwork veins containing a single type of intermediate density inclusions are more likely to be prospective for porphyry copper molybdenum deposits

geological and geochemical studies of the shujiadian porphyry cu deposit anhui province eastern china implications for ore genesis abstract most porphyry deposits in the world occur in magmatic arc settings and are related to subduction of oceanic plates a small proportion of porphyry deposits occur in intracontinental settings however they are still poorly understood shujiadian a newly discovered porphyry cu deposit is located in the middle lower yangtze river valley metallogenic belt and belongs to the intracontinental class the deposit has classic alteration zones defined by a core of potassic alteration and local ca silicate alteration which is overprinted by a feldspar destructive alteration zone and cut by veins containing epidote and chlorite wallrocks of the deposit are unreactive quartz rich sedimentary rocks three main paragenetic stages have been recognized based on petrographic observations silicate stage quartz sulfide stage and sulfide carbonate stage quartz pyrite chalcopyrite molybdenite veins and quartz chalcopyrite pyrite veins of the quartz sulfide stage contribute most of the copper and chalcopyrite chlorite pyrite pyrrhotite quartz illite veins of the sulfide carbonate stage also contribute part of the copper all the mineralized veins are associated with feldspar destructive alteration investigations on the fluid inclusions in shujiadian indicate that the ore forming fluids had four evolutionary episodes immiscibility and overpressure in the silicate stage boiling in the quartz sulfide stage and mixing with meteoric water in the sulfide carbonate stage sulfur and strontium isotope studies suggest that ore metals were mainly derived from magmatic hydrothermal fluids and combined with our study of fluid inclusions we infer that decompression changes in oxygen fugacity and sulfur content were the main factors that caused cu precipitation compared with porphyry deposits in magmatic arc settings there are some differences in the ore bearing rock alteration and the composition of ore forming fluids

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

enhanced vapor phase transport of tin in hydrothermal systems or experimental artifacts comments on the role of vapor in the transportation of tin in hydrothermal systems experimental and case study of the dachang deposit china by zhang et al j volcanol geotherm res 173 2008 313 324

porphyry copper gold mineralization at yulong china promoted by decreasing redox potential during magnetite alteration the yulong porphyry cu au deposit occurs on the eastern margin of the tibetan plateau and is one of the largest porphyry cu au deposits in china containing more than 6 million tons of cu metal similar to other porphyry cu deposits in the world the yulong porphyry is highly oxidized sulfate is the dominant sulfur species in fluid inclusions hosted by magmatic quartz phenocrysts and no sulfide is observed indicating an oxygen fugacity above the sso buffer during magmatic processes the sulfur species changed from sulfate dominant during magmatic processes to sulfide dominant during the main mineralization processes with sulfate and sulfide mineral assemblages observed in fluid inclusions in mineralized quartz veinlets and only sulfides in the orebodies corresponding to a decrease in redox potential from the porphyry to the hydrothermal fluid magnetite crystallization was coincident with the onset of major sulfate reduction indicating that magnetite isolated trivalent iron reducing sulfate and consequently leading to the formation of porphyry cu au mineralization most porphyry cu au ore deposits are spatially associated with and genetically related to oxidized felsic magmas our results indicate that sulfate reduction promoted by magnetite crystallization is essential for the final precipitation of cu au bearing sulfides i e decreasing redox potential of the fluid is the key to and direct cause of ore formation in yulong initial high redox potential is a prerequisite for and may be an indirect indicator of most mineralization of this kind because it enables efficient transportation of cu au redox potential fluctuations can be well preserved in zircon a resistant accessory mineral commonly found in porphyries which might be developed as a handy and reliable exploration tool for porphyry cu deposits associated with magnetite

volatility of se and te during subduction related distillation and the geochemistry of epithermal ores of the western united states subduction partial melting of mantle and magma generation and ultimately magma degassing can lead to the preferential mobilization of volatile elements and compounds research indicates that devolatilization reactions in a subducted slab can cause the overlying mantle to be enriched in volatile ore forming constituents water co2 sulfur metal loid s this process of mantle enrichment plays an important role in subsequent magma generation and initiation of ore genesis furthermore the relative volatility of metal loid s appears to play a role in the ultimate geochemistry of shallow epithermal epizonal hydrothermal ores in the western united states for example there is a general west to east geographic zonation of tertiary ores from se rich to te rich it is proposed that this geographic geochemical zonation is the direct result of the higher geochemical volatility of se as compared to te previously au ag te se hg as sb and tl have been referred to as the epithermal suite of elements it is suggested here that their geochemical cycles are linked by their similar volatile behavior through subduction partial melting in the mantle and subsequent magma degassing processes essentially specific tectonomagmatic events that affected the western united states e g oligocene eocene magmatism in the great basin and southern rocky mountains mid miocene magmatism associated with the inception of the yellowstone hotspot in the pacific northwest were distillation events that drove devolatilization of fertile mantle after the laramide shallow slab event furthermore the metal loid volatility behavior likely occurs in other regions affected by subduction and may play a fundamental role in the metal endowment of these regions

the coupled geochemistry of au and as in pyrite from hydrothermal ore deposits the ubiquity of au bearing arsenian pyrite in hydrothermal ore deposits suggests that the coupled geochemical behaviour of au and as in this sulfide occurs under a wide range of physico chemical conditions despite significant advances in the last 20years fundamental factors controlling au and as ratios in pyrite from ore deposits remain poorly known here we explore these constraints using new and previously published empa la icp ms sims and pixe analyses of as and au in pyrite from carlin type au epithermal au porphyry cu cu au and orogenic au deposits volcanogenic massive sulfide vhms witwatersrand au iron oxide copper gold iocg and coal deposits pyrite included in the data compilation formed under temperatures from 30 to 600 c and in a wide variety of geological environments the pyrite au as data form a wedge shaped zone in compositional space and the fact that most data points plot below the solid solubility limit defined by reich et al 2005 indicate that au1 is the dominant form of au in arsenian pyrite and that au bearing ore fluids that deposit this sulfide are mostly undersaturated with respect to native au the analytical data also show that the solid solubility limit of au in arsenian pyrite defined by an au as ratio of 0 02 is independent of the geochemical environment of pyrite formation and rather depends on the crystal chemical properties of pyrite and post depositional alteration compilation of au as concentrations and formation temperatures for pyrite indicates that au and as solubility in pyrite is retrograde au and as contents decrease as a function of increasing temperature from 200 to 500 c based on these results two major au as trends for au bearing arsenian pyrite from ore deposits are defined one trend is formed by pyrites from carlin type and orogenic au deposits where compositions are largely controlled by fluid rock interactions and or can be highly perturbed by changes in temperature and alteration by hydrothermal fluids the second trend consists of pyrites from porphyry cu and epithermal au deposits which are characterised by compositions that preserve the au as signature of mineralizing magmatic hydrothermal fluids confirming the role of this sulfide in controlling metal ratios in ore systems

condensation behaviour of volatile trace metals in laboratory benchtop fumarole experiments abstract volatile trace metals emitted from volcanoes condense in gas plumes and fumaroles the transient nature of natural eruptions makes it challenging to isolate key variables affecting trace metal condensation in this complex natural system to emulate these conditions in a controlled setting we design a laboratory benchtop fumarole to experimentally measure volatilization and condensation behaviour of volatile trace metals from magma synthetic silicate melt compositions in the na 2 o al 2 o 3 sio 2 and na 2 o fe 2 o 3 sio 2 systems doped with dissolved trace metals v cu zn as y mo cd sn tb pb and bi are degassed in a furnace at 900 c over periods of days to weeks the condensates from the gas phase form on a silica glass tube along a thermal gradient from 725 to 125 c and are examined by electron microscopy and chemical analysis we observe variable crystallinity of condensates as functions of temperature the concentrations of li cu as rb mo ag cd cs w pt tl pb and bi in leachates of the condensates change by orders of magnitude along the glass tube and show maxima at various temperatures between 250 and 600 c a comparison of the experiments with natural examples shows similarities in the condensation pattern for cu as ag and tl the enrichment of certain metals in the experimental gas condensates e g mo is similar to that observed in natural systems but differs greatly for other elements e g bi and cd likely due to lack of cl s or other complexing agents for metals in the experiments our experimental design is a starting point to investigate the role of these and other variables on trace metal condensation behaviour in natural volcanic emissions

trace elements in fluid inclusions of sediment hosted gold deposits indicate a magmatic hydrothermal origin of the carlin ore trend the carlin type deposits in nevada western usa constitute the world9s second largest gold ore province these structurally and stratigraphically controlled sediment hosted ore bodies are characterized by carbonate dissolution attending hydrothermal precipitation of gold rich arsenian pyrite the origin of the mineralizing fluids and the source of the gold remain debated conceptual models favoring either sedimentary metamorphic or magmatic fluid sources are based on isotopic tracers giving ambiguous results here we use the trace element compositions of fluid inclusions to separate geochemical signals of the large scale fluid source from effects of deposit scale fluid interaction with the sedimentary host rocks specifically we compare the ratios of rb k b as sr and ba between clearly magmatic hydrothermal cu au ores at copper canyon in the battle mountain eureka trend with the gold quarry and chukar footwall deposits on the carlin trend that contain high grade gold in similar sedimentary host rocks results indicate that both ore districts can be related to upper crustal hydrous magmatic intrusions but are now exposed at different levels of erosion and formed at different distances from their magmatic fluid source fluid compositions are best explained by separation of a deep magmatic fluid into rb k enriched brine and b as au enriched vapor followed by cooling and contraction of the magmatic vapor phase to an epithermal liquid which reacted with sr ba bearing sedimentary rocks during ascent and eventual precipitation of au rich arsenian pyrite

geology geochronology and geochemistry of the dabate cu mo deposit northern chinese tien shan implications for spatial separation of copper and molybdenum mineralization abstract the dabate deposit is a porphyry cu mo deposit located in the sailimu block northern chinese tien shan the deposit shows a clear separation of cu and mo mineralization with cu mineralization occurring along the edge of the rhyolitic porphyry and mo mineralization in the inner part of the rhyolitic porphyry sm nd isotopic analyses of six fluorite samples from the cu sulfides fluorite veins yield an isochron age of 298 1 5 0 ma and re os isotopic analyses of four molybdenite samples from the molybdenite quartz veins yield an isochron age of 299 6 3 2 ma these geochronological data and accompanying geologic evidence indicate that the cu and mo mineralization belongs to the same hydrothermal system and are closely related to the rhyolitic porphyry which has a youngest zircon 206pb 238u age of 297 3 8 0 ma rare earth element ree and fluid inclusion studies were carried out for fluorite in the cu ores the fluorite related to cu mineralization have high ree 63 4 216 9 ppm and show generally similar ree patterns with the rhyolitic porphyry suggesting that the fluid of cu mineralization is closely related to the rhyolitic porphyry the slight lree depletion and ce depletion of fluorite relative to the rhyolitic porphyry may be due to preferential partitioning of hree into the fluid in neutral to weak alkaline conditions and to mixing with meteoric water which is characterized by ce depletion three types of fluid inclusions were recognized in the fluorite from the cu sulfides fluorite veins liquid vapor lv type co2 bearing c type and solid mineral bearing s type the lv type inclusions have homogenization vapor to liquid temperatures from 175 to 328 c and salinities of 0 4 14 9 wt nacl eqv mode at 0 8 wt nacl eqv and is of h2o nacl composition the c type inclusions have homogenization vapor to liquid temperatures from 206 to 279 c and salinities of 1 6 8 5 wt nacl eqv and is of h2o co2 nacl ch4 composition the s type inclusions have partial homogenization vapor to liquid temperatures of 173 233 c and salinities of 1 2 7 9 wt nacl eqv and is of h2o nacl composition the solid particle in s type inclusions did not change during heating up to 550 c indicating that the solid is not daughter mineral and the s type inclusions are actually the same as the lv type inclusions the lv type inclusions have microthermometric attributes similar to those typically found in the late stages of porphyry deposits whereas the c type inclusions have similar compositions as the inclusions in the mo ores as documented in previous studies at dabate the presence of both lv type and c type inclusions suggests that the cu mineralization may be related to mixing between meteoric water and magmatic fluids as is also indicated by the ree of fluorite comparing with data from mo ores reported in previous studies it is suggested that the mo stage fluids were more reduced and acidic and mo mineralization may be mainly related to fluid pressure decrease and immiscibility whereas the cu stage fluids were more oxidized neutral to weakly alkaline and cu mineralization may be mainly controlled by mixing and cooling the vapor phase produced by fluid immiscibility in the deep area may have carried cu as ag hf co2 and migrated to the outer part of the porphyry precipitated cu sulfides arsenopyrite and fluorite by mixing with meteoric water from the country rocks whereas the liquid phase produced by fluid immiscibility at depth may have carried mo nacl and migrated to the middle west part of the rhyolitic porphyry become immiscible and precipitated molybdenite

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

geochemical properties of rocks and soils in gusev crater mars results of the alpha particle x ray spectrometer from cumberland ridge to home plate 1 geochemical diversity of rocks and soils has been discovered by the alpha particle x ray spectrometer apxs during spirit s journey over husband hill and down into the inner basin from sol 470 to 1368 the apxs continues to operate nominally with no changes in calibration or spectral degradation over the course of the mission germanium has been added to the spirit apxs data set with the confirmation that it occurs at elevated levels in many rocks and soils around home plate twelve new rock classes and two new soil classes have been identified at the spirit landing site since sol 470 on the basis of the diversity in apxs geochemistry the new rock classes are irvine alkaline basalt independence low fe outcrop descartes outcrop similar to independence with higher fe and mn algonquin mafic ultramafic igneous sequence barnhill volcaniclastic sediments enriched in zn cl and ge fuzzy smith high si and ti rock elizabeth mahon high si ni and zn outcrop and rock halley hematite rich outcrop and rock montalva high k hematite rich rock everett high mg magnetite rich rock good question high si low mn rock and torquas high k zn and ni magnetite rich rock new soil classes are gertrude weise very high si soil and eileen dean high mg magnetite rich soil aqueous processes have played a major role in the formation and alteration of rocks and soils on husband hill and in the inner basin

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

first insights on the metallogenic signature of magmatic fluids exsolved from the active magma chamber of vesuvius ad 79 pompei eruption abstract fluid inclusions hosted in sanidine from xenoliths representing the crystallization front of the ad 79 magma chamber of vesuvius offer a rare opportunity to track the composition of magmatic fluids exsolving at the peripheral part of a growing k alkaline magma chamber disrupted by an explosive eruption this work demonstrates that the exsolving magmatic fluids have a complex composition taking in evidence the great capability of metal transport by means of these solutions inclusions are particularly enriched in zn mo w sb bi tl and pb metals display two different positive correlations 1 pb zn tl bi 2 mo w the different trends may reflect the different complexing agent for these elements probably chloride for pb zn tl bi and probably hydroxy for mo w the occurrence of a silicothermal component in these fluids may furthermore favor the metal transport of these solutions this is probably a major previously underestimated process in the enrichment of some metals in magmatic hydrothermal systems this hypothesis may challenge conventional ideas on fluid phase mass transport of components by means of magmatic hydrothermal fluids and should be taken into account in future works on these topics

triggers for the formation of porphyry ore deposits in magmatic arcs porphyry ore deposits supply much of the copper molybdenum gold and silver used by humans a review of the main processes that trigger porphyry ore formation suggests that sulphide saturation of the magmas that supply the metals could be the overriding mechanism that helps control the temporal and spatial distribution of the ore deposits

magmatic to hydrothermal crystallization in the w sn mineralized mole granite nsw australia part i crystallization of zircon and ree phosphates over three million years a geochemical and u pb geochronological study abstract zircon monazite and xenotime crystallized over a temperature interval of several hundred degrees at the magmatic to hydrothermal transition of the sn and w mineralized mole granite magmatic zircon and monazite thought to have crystallized from hydrous silicate melt were dated by conventional u pb techniques at an age of 247 6 0 4 and 247 7 0 5 ma respectively xenotime occurring in hydrothermal quartz is found to be significantly younger at 246 2 0 5 ma and is interpreted to represent hydrothermal growth from associated fluid inclusions it is concluded that it precipitated from a hydrothermal brine 600 c which is below the accepted closure temperature for u pb in this mineral these data are compatible with a two stage crystallization process precipitation of zircon and monazite as magmatic liquidus phases in deep crustal magma followed by complete crystallization and intimately associated sn w mineralization after intrusion of the shallow sill like body of the mole granite later hydrothermal formation of monazite in a biotite fluorite topaz reaction rim around a mineralized vein was dated at 244 4 1 4 ma which distinctly postdates the mole granite and is possibly related to a younger hidden intrusion and its hydrothermal fluid system obtaining precise age data for magmatic and hydrothermal minerals of the mole granite is hampered by uncertainties introduced by different corrections required for multiple highly radiogenic minerals crystallising from evolved hydrous granites including 230 th disequilibrium due to th u fractionation during monazite and possibly xenotime crystallization variable th u ratios of the fluids from which xenotime was precipitating elevated contents of common lead and post crystallization lead loss in zircon enhanced by the fluid saturated environment the data imply that monazite can also survive as a liquidus phase in protracted magmatic systems over periods of 10 6 years the outlined model is in agreement with prominent chemical core rim variation of the zircon

element mobility patterns in magnetite group iocg systems the fab iocg system northwest territories canada this paper documents element mobility patterns from a magnetite group iron oxide copper gold iocg prospect in the northwest territories of canada and explores implications for space time chemical evolution of metasomatic systems hosting iocg deposits the fab system located in the great bear magmatic zone gbmz of the northwest territories canada contains numerous fe cu u showings associated with high temperature ht potassic iron alteration overprinting extensive zones of sodic to ht calcic iron alteration each hydrothermal alteration assemblage is associated with distinct element mobility patterns that record evolving physico chemical properties of the hydrothermal fluids new geochronological data constrain the alteration and iocg mineralization in the fab system to a 3 m y window between 1870 1867 ma which is broadly contemporaneous with extensive high level intrusive activity across the gbmz regional to local scale element mobility patterns characteristic of the sodic and sodic calcic iron alteration type record leaching combined with weak to strong mass losses pure sodic alteration depleted the rocks in ca co cu fe mg th u and v conversely sodic calcic iron alteration records significant depletions of nb ree ta ti th and u these element mobility patterns differ from intense ht calcic iron alteration that is enriched in ca co f fe mg mn ni and v with modest enrichments to locally significant mineralization in th u and ree ht calcic iron alteration is also characterized by substantial mass gains that translate into volume gains in stockwork zones and mass volume gains in zones of intense host rock replacement ht potassic iron alteration is characterized by enrichments in ba k ni u and v along with locally co and cu the temporal and spatial association of the fab system alteration and the emplacement of the porphyritic dacite are indicative of the predominant involvement of magmatic hydrothermal fluids the high f and cl contents of the porphyritic dacite and of the ht calcic iron alteration zones as well as nb ree ta th and ti mobility provide strong evidences of high halogen activities f and cl in the hydrothermal fluids high f and cl activities in the hydrothermal fluid are interpreted to have facilitated the mobilization of normally immobile nb ta ti th or weakly mobile elements as well as some metals e g v ni co the formation of ree fluorocarbonates and calcite in the early and incipient ht calcic iron alteration zones indicates the presence of co2 in the hydrothermal fluids weaker hfse hree and ti mobility during later ht potassic iron alteration is interpreted to reflect decreasing temperatures pressures f activities and increasing fo2 as the fluids evolved and interacted with the host rocks