multistage evolution of the neoarchean ca 2 7 ga igarape cinzento gt 46 iron oxide copper gold deposit cinzento shear zone carajas province brazil

reequilibration of fluid inclusions bulk diffusion abstract bulk diffusion of fluid components through quartz which is a nominally anhydrous mineral is one of a series of processes that may alter fluid inclusions in crystals diffusion of water through quartz has been considered an important factor for re equilibration of fluid inclusions however the solubility of water in quartz the nature of the diffusing water related molecules and diffusion coefficients have not been adequately determined to calculate reliable rates of inclusion alteration a new three dimensional mathematical diffusion model is presented to characterize bulk diffusion in quartz with randomly distributed fluid inclusions this model assumes an infinite external fluid source and treats fluid inclusions as instantaneous point sources the computer program reqdif from the software package fluids http fluids unileoben ac at can be used to calculate the effect of diffusion with self defined parameters using a diffusion coefficient of 10 12 m2 s 1 60 the rate of h2o loss or gain of most inclusions is relatively high adapting them within several 10 000 of years to new pore fluid conditions however diffusion according to this model may be restricted and partly inhibited by several important factors such as the low porosity in metamorphic rock and relative low temperatures in sedimentary and diagenetic rocks the imprecision of estimated diffusion coefficients and the undetermined accuracy do not allow reliable diffusion calculations diffusion along micro cracks and dislocations is a more efficient process to transport fluid components through quartz

the influence of the α β phase transition of quartz on fluid inclusions during re equilibration experiments abstract the influence of the quartz phase transition on the properties of fluid inclusions was investigated experimentally the experiments were designed to have no gradients in pressure and fugacity between fluid inclusions and pore fluid deformation due to pressure differences were also excluded in this study h2o rich fluid inclusions with similar densities were synthesized in quartz at approximately 625 c and 280 mpa in the quartz stability field and at approximately 675 c and 320 mpa in the quartz stability field the experimental set up prevented any pressure differences during loading and unloading of the experiments these inclusions were re equilibrated at the same temperature pressure fluid conditions and changes in total homogenization temperature and ice melting temperature were recorded fluid inclusions are sensitive monitors of fluid conditions during entrapment which record minor variation in temperature and pressure and display a corresponding distribution pattern in homogenization temperatures fluid inclusions re equilibrated in the quartz stability field were not affected by changes in density fluid inclusions re equilibrated in the quartz stability field revealed density loss of 0 6 at 320 mpa to 3 0 at 280 mpa which was caused by the quartz phase transition consequently density loss which is probably caused by the formation of micro cracks at the transition from to quartz is more efficient at lower pressures in addition re equilibration experiments were performed with a pure d2o pore fluid to investigate diffusion processes at these experimental conditions diffusion of d2o is more efficient in quartz stability field and may result in near total exchange of the original h2o content within only 19 days fluid inclusions re equilibrated in the quartz stability field contain only half the amount of d2o within the same experimentation run time up to 53 mol d2o

fluids preserved in variably altered graphitic pelitic schists in the dufferin lake zone south central athabasca basin canada implications for graphite loss and uranium deposition the athabasca basin canada contains the highest grade unconformity type uranium deposits in the world underlying the athabasca group sedimentary rocks of the dufferin lake zone are variably graphitic pelitic schists vgps altered to chlorite and hematite red green zone rgz they were locally bleached near the unconformity during paleoweathering and or later fluid interaction overall graphite was lost from the rgz and the bleached zone relative to the original vgps fluid inclusions were examined in different generations of quartz veins using microthermometry and raman spectroscopy to characterize and compare the different fluids that interacted with the rgz and the vgps in the vgps ch4 and n2 rich fluid inclusions which homogenize into the vapor phase between 100 and 74 c and 152 and 125 c respectively and co2 rich fluid inclusions homogenizing either into vapor or liquid between 20 and 28 c are present carbonic fluids could be the result of the breakdown of graphite to ch4 co2 whereas n2 rich fluid is interpreted to be the result of breakdown of feldspars micas to nh4 n2 in the rgz the presence of fluid inclusions with low ice melting temperature 38 to 16 c reflect the presence of cacl2 and fluid inclusions with halite daughter minerals that dissolve between 190 and 240 c indicate the presence of highly saline fluids these fluids are interpreted to be derived from the athabasca basin the circulation of carbonic fluids and brines occurred during two different events related to different p t conditions of trapping the carbonic fluids interacted with basement rocks during retrograde metamorphism of the basement rocks before deposition of the athabasca basin whereas the brines circulated after the deposition of the athabasca basin these latter fluids are similar to brines related to uranium mineralization at mcarthur river and thus in addition to possibly being related to graphite depletion in the rgz they could be linked to uranium mineralization

genetic implications of fluid deposited disordered graphite and methane rich inclusions in the jonnagiri granodiorite hosted gold deposit eastern dharwar craton india abstract laminated quartz veins occurring within sheared granodiorite in the jonnagiri greenstone belt host lode gold mineralization the greenstones were metamorphosed to lower amphibolite facies condition hydrothermal alteration produced inner zone of auriferous laminated quartz vein and contiguous proximal zone within the sheared granodiorite detailed fluid inclusion studies by saravanan et al 2009 reveal presence of three types of fluid inclusions these are type i aqueous gaseous type ii gaseous and type iii low saline aqueous inclusions raman spectroscopic studies performed in this study on type ii inclusions in quartz veins from the inner and proximal zones reveal presence of disordered graphite occurring as thin films within fluid inclusions apart from variable proportions of co 2 ch 4 and h 2 o perple x aided phase diagram computations were carried out in the c o h system at 300 c and 2 kbar to examine the chemical evolution of the c o h fluids the calculated log f o 2 values on the graphite saturation surface range from 35 71 to 32 65 when x o varies from 0 1 to 1 0 however log f o 2 decreases significantly to 49 31 at x o 0 1e 07 that pertains to the stability of almost pure ch 4 nearly similar log f o 2 values were reproduced from the calculations using the coh spread sheet decrease in f o 2 as demonstrated by the occurrence of gaseous fluid inclusions with disordered graphite and varying proportions of co 2 ch 4 in the gaseous part played a dominant role in decreasing gold solubility during fluid rock interaction and precipitating gold at jonnagiri

interpretation of fluid inclusions in quartz deformed by weak ductile shearing reconstruction of differential stress magnitudes and pre deformation fluid properties abstract a well developed theoretical framework is available in which paleofluid properties such as chemical composition and density can be reconstructed from fluid inclusions in minerals that have undergone no ductile deformation the present study extends this framework to encompass fluid inclusions hosted by quartz that has undergone weak ductile deformation following fluid entrapment recent experiments have shown that such deformation causes inclusions to become dismembered into clusters of irregularly shaped relict inclusions surrounded by planar arrays of tiny new formed neonate inclusions comparison of the experimental samples with a naturally sheared quartz vein from grimsel pass aar massif central alps switzerland reveals striking similarities this strong concordance justifies applying the experimentally derived rules of fluid inclusion behaviour to nature thus planar arrays of dismembered inclusions defining cleavage planes in quartz may be taken as diagnostic of small amounts of intracrystalline strain deformed inclusions preserve their pre deformation concentration ratios of gases to electrolytes but their h2o contents typically have changed morphologically intact inclusions in contrast preserve the pre deformation composition and density of their originally trapped fluid the orientation of the maximum principal compressive stress 1 at the time of shear deformation can be derived from the pole to the cleavage plane within which the dismembered inclusions are aligned finally the density of neonate inclusions is commensurate with the pressure value of 1 at the temperature and time of deformation this last rule offers a means to estimate magnitudes of shear stresses from fluid inclusion studies application of this new paleopiezometer approach to the grimsel vein yields a differential stress 1 3 of 300 mpa at 390 30 c during late miocene nnw sse orogenic shortening and regional uplift of the aar massif this differential stress resulted in strain hardening of the quartz at very low total strain 5 while nearby shear zones were accommodating significant displacements further implementation of these experimentally derived rules should provide new insight into processes of fluid rock interaction in the ductile regime within the earth s crust

pressure temperature fluid evolution in eburnean metabasites and metapelites from tamanrasset hoggar algeria abstract tamanrasset central hoggar algeria is part of the 2000 ma eburnean terrane in which spectacular examples of granulite grade metapelites and metabasites occur reactional textures in metabasites supplemented by geothermobarometry fluid inclusions and mineral equilibria indicate a complex metamorphic history characterized by a strong decompression during postpeak uplift peak metamorphic pressure temperature pt conditions of 800 c and 10 kbar respectively were followed by rapidly decreasing pressure to 700 c and 6 kbar at nearly constant temperature during which time the rocks acquired their present mineral assemblages and textures garnet pyroxenites this isothermal decompression path was followed by nearly isobaric cooling throughout this history water activity remained consistently low documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usep

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

fluid record of rock exhumation across the brittle ductile transition during formation of a metamorphic core complex naxos island cyclades greece fluid inclusions trapped in quartz veins hosted by a leucogneiss from the southern part of the naxos metamorphic core complex attic cycladic massif greece were studied to determine the evolution of the fluid record of metamorphic rocks during their exhumation across the ductile brittle transition three sets of quartz veins v m2 v bd v b are distinguished the v m2 and v bd are totally or respectively partially transposed into the foliation of the leucogneiss they formed by hydrofracturing alternating with ductile deformation accommodated by crystal plastic deformation the v b is discordant to the foliation and formed by fracturing during exhumation without subsequent ductile transposition fluids trapped during crystalplastic deformation comprise two very distinct fluid types namely a co2 rich fluid and a high salinity brine that are interpreted to represent immiscible fluids generated from metamorphic reactions and the crystallization of magmas respectively they were initially trapped at approximate to 625 degrees c and 400mpa and then remobilized during subsequent ductile deformation resulting in various degrees of mixing of the two end members with later trapping conditions of approximate to 350 degrees c and 140mpa in contrast brittle microcracks contain aqueous fluids trapped at 250 degrees c and 80mpa all veins display a similar 13c pointing to carbon that was trapped at depth and then preserved in the fluid inclusions throughout the exhumation history in contrast the d signature is marked by a drastic difference between i v m2 and v bd veins that are dominated by carbonic aqueous carbonic and high salinity fluids of metamorphic and magmatic origin characterized by d between 56 parts per thousand and 66 parts per thousand and ii v b veins that are dominated by aqueous fluids of meteoric origin characterized by d between 40 parts per thousand and 46 parts per thousand the retrograde pt pathway implies that the brittle ductile transition separates two structurally chemically and thermally distinct fluid reservoirs namely i the ductile crust into which fluids originating from crystallizing magmas and fluids in equilibrium with metamorphic rocks circulate through a geothermal gradient of 30 degrees c km1 at lithostatic pressure and ii the brittle upper crust through which meteoric fluids percolate through a high geothermal gradient of 55 degrees c km1 at hydrostatic pressure

modification of fluid inclusions in quartz by deviatoric stress iii influence of principal stresses on inclusion density and orientation extraction of useful geochemical petrologic and structural information from deformed fluid inclusions is still a challenge in rocks displaying moderate plastic strain in order to better understand the inclusion modifications induced by deviatoric stresses six deformation experiments were performed with a griggs piston cylinder apparatus natural nacl h2o inclusions in an oriented quartz crystal were subjected to differential stresses of 250 470 mpa at 700 900 c and at 700 1 000 mpa confining pressure independently of the strain rate and of the crystallographic orientation of the quartz the inclusions became dismembered and flattened within a crystallographic cleavage plane subperpendicular to 1 the neonate newly formed inclusions that result from dismemberment have densities that tend towards equilibrium with pfluid 1 at tshearing these results permit ambiguities in earlier deformation experiments on co2 h2o nacl to be resolved the results of the two studies converge indicating that density changes in neonate inclusions are promoted by high differential stresses long periods at high p and high t and fluid compositions that maximize quartz solubility neonates spawned from large precursor inclusions show greater changes in density that those spawned from small precursors these findings support the proposal that deformed fluid inclusions can serve as monitors of both the orientation and magnitude of deviatoric stresses during low strain ductile deformation of quartz bearing rocks

a fluid inclusion and stable isotope study at the loulo mining district mali west africa implications for multifluid sources in the generation of orogenic gold deposits the world class loulo mining district 15 5 moz resource in the birimian terrane of western mali contains a range of mineralogically diverse styles of orogenic gold mineralization the district is distinguished by as rich orebodies as at yalea as well as tourmaline bearing fe rich orebodies as at gara new fluid inclusion and stable isotope data presented here constrain the nature of the hydrothermal fluids responsible for these different types of mineralization and point towards the role of multifluid sources metamorphic and magmatic in the formation of orogenic gold deposits microthermometric and laser raman studies from yalea main and two other similar orebodies loulo 3 and baboto reveal the dominance of coexisting co 2 n 2 ch 4 type 1 and h 2 o nacl type 2 fluid inclusions these inclusions show evidence of fluid unmixing from reduced quartz faylite magnetite qfm buffered low salinity 10 wt nacl equiv co 2 rich h 2 o nacl n 2 ch 4 primary ore fluids the combination of microthermometric data and geothermometry based on ore and alteration assemblages indicate trapping temperatures and pressures of 270 to 340 c at 1 4 to 1 8 kbar the p t x state of the yalea style mineralizing fluids along with the 18 o fluid compositions of 8 8 to 10 7 is consistent with the derivation of auriferous fluids during greenschist facies regional metamorphism of the host terrane similar fluid compositions were previously reported elsewhere in the birimian crust of west africa and in other orogenic gold districts worldwide the precipitation of gold from the h 2 s rich metamorphic fluid is primarily linked to phase separation of the ore fluid which is controlled by p t fluctuations and or fluid rock interaction with carbonaceous host sedimentary rocks confirmed by low 13 c values of 21 7 to 15 8 fluid inclusion investigations from gara and a similar style orebody yalea north indicate the presence of coexisting co 2 n 2 ch 4 type 1 and mixed salinity 5 21 wt nacl equiv co 2 rich h 2 o nacl inclusions type 3 inclusion assemblages also contain common oxidized hematite magnetite hm buffered high temperature 400 c hypersaline 35 50 wt total dissolved solids metalliferous na fe ca cu ni w pb zn multiphase h 2 o rich co 2 nacl fecl 2 inclusions type 4 this inclusion type has not been previously reported in other birimian terranes the composition of the brines along with carbon isotope data 13 c of 14 4 to 4 5 suggests a magmatic input to the gara style hydrothermal system the coexistence in the fluid inclusion assemblages of the magmatic brines with yalea style co 2 rich metamorphic fluids and the positive correlation between salinity and homogenization temperatures suggest mineralization was locally controlled by fluid mixing the interaction of these two chemically contrasting fluids explains the distinctive petrographic characteristics of the gara style orebodies this includes the growth of widespread multi stage fe 3 rich tourmaline b rich granite source and sodic alteration and ore assemblages consisting of abundant nickeloan pyrite ree phosphates ni co pb zn minor trace sulfides and scheelite gold deposition in the gara style hydrothermal system is related to physical and chemical changes of the two fluids during mixing e g decreases in f o2 and t in the brines and retrograde boiling of the co 2 component in the metamorphic fluids a salting out effect

primary carbonate co2 inclusions in sapphirine bearing granulites from central sri lanka high density co2 rich fluid inclusions from a sapphirine bearing granulite hakurutale sri lanka have been studied by microthermometry raman spectrometry and sem analysis based on textural evidence two groups of inclusions can be identified primary negative crystal shaped inclusions group i and pseudo secondary inclusions which experienced a local limited post trapping modification group ii both groups contain magnesite as a daughter mineral occurring in a relatively constant fluid solid inclusion volume ratio volsolid 0 15 total volume co2 densities for group i and ii differ only slightly both groups contain a fluid which was initially trapped at peak metamorphic conditions as a homogeneous co2 mgco3 mixture thermodynamic calculations suggest that such a fluid co2 15 vol mgco3 is stable under granulite facies conditions after trapping magnesite separated upon cooling while the remaining co2 density suffered minor re adjustments a model isochore based on the integration of the magnesite molar volume in the co2 fluid passes about 1 5 2 kbar below peak metamorphic conditions this remaining discrepancy can be explained by the possible role of a small quantity of additional water

geology and geochemistry of gunung subang gold deposit tanggeung cianjur west java indonesia abstract the gunung subang gold deposit is located in the sunda arc volcanic belt in west java indonesia the ore bodies are associated with volcanic rocks from the miocene koleberes and bentang formation to constrain the significance of the ore genesis and mineralization this study was carried out with the aim of examining the deposit using methods such as detailed field observation petrography petrochemistry zircon u pb dating hf isotope fluid inclusion analysis and sulfur and in situ pb isotope analyses the results suggest the following 1 the volcanic rocks in gunung subang belong to the basalt andesite group with 48 66 79 17 average 61 04 sio2 the trace element patterns of the volcanic rocks exhibit relatively low hree content flat hree patterns and weak negative or positive eu anomalies which are similar to those of typical arc magmatic rocks 2 most zircons selected from the volcanic rocks are magmatic and only a few are inherited the magmatic zircons have a weighted mean u pb age of 17 0 0 4 ma and the inherited zircons are from the precambrian dated at 887 2379 ma the magmatic zircons have ehf t values ranging from 1 24 to 13 59 indicating that the magmatism may be contaminated predominantly with juvenile crust but also with a small percentage of ancient crust 3 the sulfur isotopic compositions are fairly uniform and the 34s values of pyrite galena and sphalerite range from 0 53 to 2 97 suggesting a magmatic origin 4 the pb isotopic compositions of pyrite and galena are clustered and some include relatively high amounts of radiogenic lead the mean ratios of 206pb 204pb 207pb 204pb and 208pb 204pb are 18 59 0 007 15 65 0 007 and 38 89 0 017 respectively indicating that the ore forming material is highly related to miocene to pliocene volcanic rocks 5 fluid inclusions in the quartz from the ores are liquid and vapor liquid phases with components of the nacl h2o system with homogenization temperatures of 240 320 c and salinities of 0 2 6 2 wt nacl the coexistence of vapor and liquid rich fluid inclusions suggests that boiling occurred throughout the deposition of the ore 6 the results of electron probe microanalysis epma indicate that pyrite is the major au bearing mineral combined with the observation of scanning electron microscope sem gold is primarily present as au ag telluride minerals and there may also be native gold au0 finally we consider the gunung subang is an epithermal gold deposit related to the mid miocene magmatism

origin and evolution of the um egat and dungash orogenic gold deposits egyptian eastern desert evidence from fluid inclusions in quartz shear zone related mesothermal gold deposits of um egat and dungash in the egyptian eastern desert are hosted by greenschist facies metavolcanic and or metasedimentary rocks of pan african age both deposits comprise boudinaged quartz veins that show evidence of incipient recrystallization and are similar in alteration style structural control and mineralogy the ore mineralogy includes pyrite arsenopyrite pyrrhotite chalcopyrite galena gold occurs both in the veins usually included in arsenopyrite pyrite or pyrrhotite next to fragments of altered country rocks or disseminated in the alteration haloes arsenic in arsenopyrite and aliv in chlorite geothermometers indicate that wall rock alteration and ore mineral precipitation occurred at temperatures between 400 and 250 c fluid inclusions in vein quartz occur in clusters or along trails three types of fluid inclusions were identified based on petrography and laser micro raman spectroscopy 1 two phase carbonic inclusions with co2 ch4 n2 h2o 2 two phase aqueous inclusions and 3 three phase aqueous carbonic inclusions with ch4 final melting of ice tmf for most inclusions occurs at temperatures between 4 and 0 c indicating a low salinity 300 c but cluster into two distinct groups for each type of inclusion inclusions from the same trail or cluster are commonly characterized by different degrees of fill or different th values field petrographic and microthermometric data suggest that low salinity aqueous carbonic fluids interacted with graphite bearing metasedimentary rocks to form ch4 at t 400 c and p 3 kbars these reduced fluids leached gold as they circulated through the metavolcanic rocks carrying it in the form of bisulfide complexes interaction of these aqueous carbonic fluids with the country rocks caused hydrothermal alteration and precipitated gold bearing sulfides in the alteration zones a drop of pressure during the migration of these fluids to shallower depths along the shear zones led to phase separation at t 300 c and p 2 3 kbars quartz crystallizing over a range of lower temperatures and pressures trapped carbonic and aqueous fluids as separate inclusions in clusters along pseudosecondary and secondary trails postdepositional deformation caused decrepitation of some inclusions and the stretching and leakage of others increasing th to 250 c deformation also remobilized the gold depositing it as globules of higher fineness in secondary sites

fluid fluid interactions in magmatic hydrothermal ore formation hydrothermal ore deposits have provided some of the first geological evidence for the interaction of multiple fluids in the earth s interior including fluid mixing as well as fluid phase separation physical evidence comes from veins and breccias documenting the impact of fluids in breaking rocks and creating fracture permeability for ore formation as a result of the fluid expansion that is commonly associated with phase separation between melts and multiple fluids chemical evidence of fluid fluid interaction includes the precipitation of minerals in veins as a result of fluid boiling or mixing between chemically contrasting fluids fluid inclusions record interactions of multiple fluids especially in magmatic hydrothermal ore deposits and associated igneous rocks fig 1 in recent years fluid inclusions have contributed to a more quantitative understanding of the role of fluid fluid interactions since new microanalytical techniques allow determination of element concentrations in all types of fluids from low density vapor through aqueous and hypersaline liquids to hydrous salt melts roedder 1984 samson et al 2003 figure 1 geological evidence for fluid phase separation in ore forming magmatic hydrothermal systems a bonanza grade gold 1 wt that was precipitated together with fine grained pyrite in a fluidized breccia resulting from instantaneous boiling and expansion of magmatic fluids ascending from an underlying andesite porphyry intrusion the breccia consists of adularia sericite altered clasts of sedimentary wall rock s and nodules of originally colloidal pyrite with bright specks of gold p g both cemented by roscoelite r vanadium rich muscovite and late calcite c zone vii ore body porgera papua new guinea ronacher et al 2004 b bladed manganocalcite the characteristic habit of calcite precipitated from aqueous epithermal fluids as a result of the ph change following loss of co2 to a separating vapor phase madan bulgaria kostova et al 2004 c growth band in a euhedral quartz

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

on thermally forced circulations over heated terrain abstracta combination of analytical and numerical models is used to gain insight into the dynamics of thermally forced circulations over diurnally heated terrain solutions are obtained for two layer flows representing the boundary layer and the overlying free troposphere over an isolated mountainlike heat source a scaling based on the linearized boussinesq system of equations is developed to quantify the strength of thermally forced updrafts and to identify three flow regimes each with distinct dynamics and parameter sensitivities this scaling closely matches corresponding numerical simulations in two of these regimes the first characterized by a weakly stable boundary layer and significant background winds and the second by a strongly stable boundary layer in the third regime characterized by weak winds and weak boundary layer stability this scaling is outperformed by a fundamentally different scaling based on thermodynamic heat engines within this regime the inability of wind ventilation or

re equilibration of glass and co2 inclusions in xenolith olivine a tem study co 2 rich fluid inclusions were observed in olivine from mantle xenoliths from the island of tenerife canary islands inclusions that are present in deformed olivine porphyroclasts consist of co 2 fluids minor high alkali silica rich glass ni fe sulfides homogenization temperature distributions reveal that most of the inclusions originally trapped at mantle conditions re equilibrated to lower density values transmission electron microscope tem studies indicate that most fluid inclusions appear as perfectly euhedral negative crystals with variable shape from prismatic to equant size from 2 diffusion consequently they should be taken into account for the correct interpretation of microthermometric results

shock reequilibration of fluid inclusions in coconino sandstone from meteor crater arizona abstract this study examines the effects of natural shock metamorphism on fluid inclusions trapped in porous sedimentary target rocks and compares these results to previous experimental work on single crystal quartz samples of shock metamorphosed coconino sandstone were collected from barringer meteorite crater meteor crater arizona and classified based on their shock features into the six shock stages described by kieffer s w kieffer 1971 shock metamorphism of the coconino sandstone at meteor crater arizona journal of geophysical research 76 5449 5473 the frequency of two phase fluid inclusions decreases dramatically from unshocked samples of coconino sandstone through shock stages 1a 1b and 2 no two phase fluid inclusions were observed in shock stage 3 or 4 samples however the total number of grains containing fluid inclusions remains approximately the same for shock stages 1a 2 suggesting that two phase fluid inclusions reequilibrated during impact to form single phase inclusions in shock stages 3 and 4 the total number of inclusions also decreases indicating that at these higher shock pressures fluid inclusions are destroyed by plastic deformation and phase changes within the host mineral entrained quartz grains within a shock stage 5 sample contain two phase inclusions emphasizing the short duration of melting associated with the impact and the heterogeneous nature of impact processes these results are similar to those observed in single crystal experiments although inclusions survive to slightly higher shock pressures in samples of naturally shocked coconino sandstone results of this study suggest that the rarity of fluid inclusions in meteorites does not preclude the presence of fluids on meteorite parent bodies instead fluid inclusions trapped during alteration events may have been destroyed due to shock processing in addition loss of fluids from inclusion vesicles along fractures and microcracks may lead to shock devolatilization even in unsaturated target rocks

an experimental investigation on fluid transfer mechanisms in ultramafic rocks abstract static annealing and crack cook experiments were performed on wet and dry fabricated san carlos olivine aggregates and a core of balsam gap dunite to investigate fluid infiltration mechanisms for low permeability mantle rocks deionized water 30 40 l was added to cold pressed olivine powders before hot pressing to make wet samples samples hot pressed without added water are dry

fluid inclusion evidence for progressive folding during decompression in metasediments of the voltri group western alps italy abstract quartz veins syntectonic to distinct folding events in metasediments from the voltri group ligurian alps were studied in order to compare fluid and structural evolution studied veins vs1 vs2 vs3 pertain to three distinct generations of folds f 1 f 2 f 3 that formed during the retrograde metamorphic evolution two types of fluids characterize the different generations of veins and are represented essentially by aqueo carbonic mixtures of moderate salinity with decreasing densities 1 01 0 41 g cm 3 the chemical evolution is characterised by a progressive decrease of h 2 o from early fluids associated with opening of vs1 and vs2 xco 2 0 08 to fluids related to vs3 formation xco 2 0 3 the close match between the fluids in vs1 and vs2 suggests that the development of two superimposed systems of folds f 1 and f 2 folds occurs under very similar p t conditions during a progressive and continuous deformational event at glaucophanic and or barroisitic metamorphic grade a different evolution is outlined for the formation of vs3 during low greenschist grade successive isochores allow us to define a retrograde decompression path for the voltri group present results indicate that fluid inclusions are powerful markers to constrain the p t t conditions of different folding events

the effect of dislocation density on the aqueous solubility of quartz and some geologic implications a theoretical approach the internal energy associated with dislocations is calculated in quartz as a function of dislocation density these calculations show that at dislocation densities of 109 1010 1011 and 1012 cm dislocation cm3 the energy stored per mole of quartz is 2 2 19 7 170 and 1426 j respectively the density of free dislocations in natural quartz rarely exceeds 109 line cm cm3 and the resulting increase in free energy is probably too small to affect any geochemical processes significantly this applies to the overwhelming volume of rocks in the earth s crust the density of dislocations in tangles may exceed 1011 line cm 2 which is significant but the volume of quartz containing tangles is a very small fraction of most quartz grains nevertheless where fluid rock ratios are low the aqueous activity of sio2 may be significantly increased by the dissolution of quartz containing dislocation tangles such dissolution could be geologically significant in active greenschist facies fault zones and mylonites where repeated cold working would produce a sustained source and large population of dislocation tangles in such a setting the locally high internal energies of quartz containing dislocation tangles would lead to strain solution the resulting high activity of aqueous silica would enhance the stability of feldspars and would establish chemical potential gradients of sio2 which would drive the diffusive mass transfer of sio2 out of the fault zone

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

post entrapment modification of fluid inclusions due to overpressure evidence from natural samples effects of post entrapment fluid inclusion modification are examined with reference to retrogression related quartz veins from the caledonian ose thrust northern norway the inclusions occur in secondary trails and contain high density hypersaline aqueous fluids on morphological characteristics they are subdivided into type a elongate ellipsoidal and or irregular inclusions and type b more equant regular and or negative crystal form with reference to previous research on post entrapment modification of inclusions in quartz it is proposed that type a inclusions experienced little or no post entrapment modification whereas type b inclusions show features characteristic of post entrapment permanent inelastic stretching and or leakage this produces increased homogenization temperatures th associated with increased inclusion volume and lowering of density whilst maintaining constant salinity the similarity of data for degree of fill and salinity between type a and type b inclusions indicates that type b inclusions have primarily modified by stretch rather than leakage however the spread towards slightly larger volume of vapour in type b inclusions suggests that some leakage has also occurred because stretched and or partially leaked inclusions have increased th isochore projections significantly underestimate trapping pressure pt relative to unmodified inclusions therefore recognition of post entrapment inclusion modification due to overpressure is crucial to avoid misinterpretation of data but has considerable potential for constraining the detail of p t trajectories of individual rocks on this basis rocks from the ose thrust zone north norway are shown to have experienced rapid uplift on a clockwise p t t path during the final stages of caledonian scandian orogenesis

the late alpine evolution of an extensional shear zone naxos greece the mid miocene structural evolution of the metamorphic complex on naxos involved deformation in a kilometre scale low angle ductile shear zone the structures described are consistent with exhumation of the metamorphic complex during crustal extension after and possibly during localized high temperature barrovian style metamorphism non coaxial fabrics developed throughout the structural history indicate that upper levels were transported to the north during ductile extension this shear sense is opposite that inferred previously for the development cordilleran style metamophic core complexes in the cvclades ductile deformation was accompanied during its later stages by e w directed compression

fluid inclusion and stable isotope o h c constraints on the genesis of the pedra branca gold deposit troia massif borborema province ne brazil an example of hypozonal orogenic gold mineralization abstract at the archean paleoproterozoic troia massif ne brazil two major paleoproterozoic greenstone belts are documented algodoes and serra das pipocas they share similar lithostratigraphic characteristics with other 2 2 2 1 ga greenstone belts of the surrounding cratonic domains e g guiana shield and west africa craton gold mineralization in the serra das pipocas greenstone belt is associated with a regional ne trending shear zone in the mineralized area the pedra branca gold deposit the main gold mineralization is found in association with quartz veins calc silicate alteration e g diopside k feldspar amphibole titanite biotite pyrite albite magnetite carbonates and albitization pyrrhotite is commonly found as inclusions in pyrite and late magnetite replaces pyrite suggesting progressive oxidation of the ore forming fluid free milling gold commonly precipitates at the late stages of alteration in close association with magnetite and tellurides the main tellurides found are hessite altaite sylvanite calaverite and tellurobismuthite two fluid inclusion assemblages were identified from mineralized quartz veins assemblage 1 is characterized by pseudo secondary trails that show the coexistence of co2 rich and low salinity 0 8 wt nacl equiv co2 h2o nacl and h2o nacl inclusions suggesting formation during phase separation fluid immiscibility assemblage 2 is represented by late secondary low temperature th

mechanism of mineralization in the changjiang uranium ore field south china evidence from fluid inclusions hydrothermal alteration and h o isotopes abstract the changjiang uranium ore field which contains 10 000 tonnes of recoverable u with a grade of 0 1 0 5 is hosted by triassic two mica and jurassic biotite granites and is one of the most important uranium ore fields in south china the minerals associated with alteration and mineralization can be divided into two stages namely syn ore and post ore the syn ore minerals are primarily quartz pitchblende hematite hydromica chlorite fluorite and pyrite the post ore minerals include quartz calcite fluorite pyrite and hematite the fluid inclusions of the early syn ore stage characteristically contain o 2 and those of the late syn ore and post ore stage contain h 2 and ch 4 the fluid inclusions in quartz of the syn ore stage include h 2 o h 2 o co 2 and co 2 types and they occur in clusters or along trails homogenization temperatures t h for the h 2 o co 2 and two phase h 2 o inclusions range from 106 c to 350 c and cluster in two distinct groups for each type salinities are lower than 10 wt nacl equiv the ore forming fluids underwent co 2 effervescence or phase separation at 250 c under a pressure of 1000 1100 bar the u th values of the altered granites are lowest close to the ore increase outwards but subsequently decrease close to unaltered granites from the unaltered granites to the ore the lowest fe 2 o 3 feo values become lower and the highest values higher the ree patterns of the altered granites and the ores are similar to each other the u contents of the ores show a positive correlation with total ree contents but a negative correlation with lree hree ratios indicating the pitchblende is ree bearing and selectively hree rich the eu values of the ore show a positive correlation with u contents indicating the early syn ore fluids were oxidizing the ce values show a negative correlation indicating the later mineralization environment became reducing the water rock interactions of the early syn ore stage resulted in oxidization of altered granites and reduction of the ore forming fluids and it was this reduction that led to the uranium mineralization during alteration in the early syn ore stage the oxidizing fluids leached uranium from granites close to faults and fe 2 o 3 feo ratios increased in the alteration zones the late syn ore and post ore alteration decreased the fe 2 o 3 feo ratios in the alteration zones the 18 o w smow values of the ore forming fluids range from 1 8 to 5 4 and the d w smow values range from 104 4 to 51 6 suggesting meteoric water the meteoric water underwent at least two stages of water rock interaction the first caused the fluids to become uranium bearing and the second stage which was primarily associated with ore bearing faults led to uranium deposition as pitchblende accompanied by co 2 effervescence

the physical and chemical evolution of fluids in rare element granitic pegmatites associated with the lacorne pluton quebec canada abstract co magmatic rare element be li nb ta granitic pegmatites associated with the lacorne monzogranite pluton of the preissac lacorne batholith quebec range from a least evolved beryl type in the pluton through a transitional beryl spodumene type to a most evolved spodumene type in mafic country rocks they possess internal lithologic fabrics and primary fluid inclusions that provide evidence for saturation of the magma with aqueous fluids immediately after the formation of aplite in the beryl pegmatite and pene contemporaneously with formation of the beryl spodumene and spodumene pegmatites the early fluids are represented by aqueous liquid vapor type 1a and aqueous liquid vapor solid type 2 inclusions in beryl from beryl and beryl spodumene pegmatites and are estimated to have been trapped between 500 and 550 c and at 3 5 kb on the basis of microthermometric measurements analyses of the compositions of the precipitates from decrepitated inclusions and the nature of the solids trapped these fluids are interpreted to have been nacl dominated 16 wt nacl eq and to have contained appreciable fe and dissolved co2 in spodumene pegmatite the equivalent fluid which was trapped at 450 to 500 c contained significant mn li and cs in place of fe consistent with corresponding trends in the chemical evolution of the host rock volatile rich mainly secondary aqueous fluid inclusions type 1b trapped in beryl are interpreted to reflect temporary sharp drops in pressure later in the crystallization history of the beryl bearing pegmatites due to local fluid overpressures that led to brecciation and consequent pressure release these inclusions have high salinity are cacl2 rich and are considered to represent magmatic hydrothermal fluids that acquired their calcium as a result of their interaction with the host lacorne pluton incursion of cacl2 rich fluids into the spodumene pegmatites is interpreted to have occurred earlier in their crystallization history i e upon emplacement of the pegmatites as shown by the fact that a high proportion of primary inclusions in spodumene in these pegmatites contains considerable calcium and calcium contents are generally higher in inclusions in spodumene than in beryl the inclusions in the spodumene pegmatites are thought to have acquired their calcium through interaction of the fluids with the amphibolites metabasalts that host these intrusions the crystallization of the pegmatites terminated with the entrapment of low salinity aqueous carbonic fluids type 3 inclusions in quartz 6 10 wt nacl eq which most likely formed as a result of the unmixing of the magmatic fluid into separate aqueous and carbonic fluids probably at temperatures between 250 and 350 c the results of this study show that aqueous fluid saturation can take place at an early stage of pegmatite emplacement and that magma evolution is matched by changes in the solute chemistry of the exsolving aqueous fluid they also show that evolution to a more volatile rich composition h2o f li may have contributed to the increased mobility of later magma batches thereby helping to explain the regional zonation of the pegmatites from beryl type within the pluton to spodumene type in the adjacent amphibolite

fluid immiscibility and gold deposition in the xincheng deposit jiaodong peninsula china a fluid inclusion study abstract the xincheng gold deposit located in west jiaodong peninsula in southeast north china craton is a representative mesothermal lode deposit hosted in late mesozoic granitoids in jiaodong gold mineralization occurs as disseminated and stockwork style ores within the hydrothermal breccias and cataclastic zones controlled by the jiaojia fault whereas echelon tensile auriferous veins hosted in the ne and nne trending subsidiary faults cutting the granitoids occur subordinately according to crosscutting relationships and mineral paragenesis four paragenetic stages were identified which are pyrite quartz sericite stage 1 quartz pyrite stage 2 quartz polysulfide stage 3 and quartz carbonate stage 4 gold was deposited during the quartz pyrite and quartz polysulfide stages on the basis of microthermometry and raman spectroscopy on fluid inclusions contained within the quartz veins from stages 2 and 3 three types of fluid inclusions were recognized 1 type 1 h 2 o co 2 inclusions that show high temperatures ca 260 c low salinities 2 4 8 9 wt equiv nacl and variable xco 2 0 03 to 0 20 2 type 2 aqueous inclusions with medium temperatures ca 220 c and low to moderate salinities 3 1 13 3 wt equiv nacl 3 type 3 pure co 2 inclusions with a carbonic phase density of 0 712 0 03 g cm 3 types 1 and 2 inclusions appear in the same growth phase of the quartz grains from the breccias and tensile auriferous veins these coexisting inclusions are likely formed by fluid immiscibility due to unmixing from a single homogeneous h 2 o co 2 parent fluid at trapping p t conditions of 221 to 304 c average 261 19 c and 780 to 2080 bar the fluid immiscibility is interpreted to be initiated by fluid pressure decrease at ca 300 c the ore fluid p t x conditions of the xincheng gold deposit are the same as those for mesothermal deposits gold was most probably transported as a au hs 2 complex at xincheng fluid immiscibility over the temperature interval of 221 304 c resulted in significant h 2 s loss from the hydrothermal solution thereby reducing au hs 2 solubility with concomitant deposition of gold the mineralizing process of the granitoid hosted xincheng lode gold deposit is likely related to the fluid immiscibility

aminostratigraphic relations and age of quaternary deposits northern espanola basin new mexico abstract amino acid ratios of gastropods provide a useful basis for correlation and approximate dating of middle to late quaternary fluvial deposits from the northern espanola basin new mexico sparsely fossiliferous slackwater deposits in the rio chama rio grande floodplain were buried episodically by piedmont alluvium during periods of climatic change as the axial river system cut down 120 m during the past 620 000 yr alloisoleucine isoleucine alle ile ratios in the total hydrolysate and free fraction of amino acids in succinea and vallonia are strongly correlated with elevation ratios in succinea range from 0 01 to 0 79 in the total hydrolysate and from 0 00 to 1 15 in the free fraction for deposits that range in age from modern to 620 000 yr old amino acid ratios are tightly clustered for deposits that contain the 620 000 yr old lava creek b tephra layer demonstrating their utility for correlation and providing a calibration point for a local dating curve two 14c ages from younger deposits and limiting ages for erosion surfaces that lie above gastropod bearing units tend to support the validity of much of the curve combining the dating curve with the geologic constraints suggests that aggradation events separated by episodes of net incision occurred at about 620 000 310 000 70 000 170 000 40 000 95 000 15 000 yr ago after 19 000 yr ago and during two minor periods between 80 000 and 25 000 yr ago

hydrothermal alteration and cu ni pge mobilization in the charnockitic rocks of the footwall of the south kawishiwi intrusion duluth complex usa in the neoarchean 2 7 ga contact metamorphosed charnockitic footwall of the mesoproterosoic 1 1 ga south kawishiwi intrusion of the duluth complex the primary metamorphic mineral assemblage and cu ni pge sulfide mineralization is overprinted by an actinolite chlorite cummingtonite prehnite pumpellyite quartz calcite hydrothermal mineral assemblage along 2 3 cm thick veins in calcite hosted by the hydrothermal alteration zones and in a single recrystallized quartz porphyroblast four different fluid inclusion assemblages are documented the composition of these fluid inclusions provide p t conditions of the fluid flow and helps to define the origin of the fluids and evaluate their role in the remobilization and reprecipitation of the primary metamorphic sulfide assemblage pure co2 fluid inclusions were found as early inclusions in recrystallized quartz porphyroblast these inclusions may have been trapped during the recrystallization of the quartz during the contact metamorphism of the footwall charnockite in the footwall of the ski the estimated trapping pressure 1 6 2 0 kbar and temperature 810 920 c conditions correspond to estimates based on felsic veins in the basal zones of the south kawishiwi intrusion fluid inclusion assemblages with co2 h2o nacl and ch4 n2 h2o nacl compositions found in this study along healed microfractures in the recrystallized quartz porphyroblast establish the heterogeneous state of the fluids during entrapment the estimated trapping pressure and temperature conditions 240 650 bar and 120 150 c for co2 h2o nacl inclusions and 315 360 bar and 145 165 c for ch4 n2 h2o nacl inclusions are significantly lower than the p t conditions 700 c and 1 6 2 kbar during the contact metamorphism indicating that this fluid flow might not be related to the cooling of the duluth complex and its contact aureole the presence of chalcopyrite inclusions in these fluid inclusions and in the trails of these fluid inclusion assemblages confirms that at least on local scale these fluids played a role in base metal remobilization no evidences have been observed for pge remobilization and transport in the samples the source of the carbonic phase in the carbonic assemblages co2 ch4 could be the graphite present in the metasedimentary hornfelsed inclusions in the basal zones of the south kawishiwi intrusion the hydrothermal veins in the charnockite can be characterized by an actinolite cummingtonite chlorite prehnite pumpellyite calcite i ii quartz mineral assemblage chlorite thermometry yields temperatures around 276 308 c during the earliest phase of the fluid flow in the late calcite ii phase high salinity 21 6 28 8 nacl cacl2 equiv wt low temperature 90 160 c primary aqueous inclusions were found chalcopyrite sphalerite millerite replacing and intersecting the early hydrothermal phases are associated to the late calcite ii phase the composition of the formational fluids in the canadian shield is comparable with the composition of the studied fluid inclusions this suggests that the composition of the fluids did not change in the past 2 ga and base metal remobilization by formational fluids could have taken place any time after the formation of the south kawishiwi intrusion sulfur isotope studies carried out on the primary metamorphic 34s 7 4 8 9 and the hydrothermal sulfide mineral assemblage 34s 5 5 5 7 proves that during the hydrothermal fluid flow the primary metamorphic ores were remobilized

rheology of a coaxial shear zone in the virginia blue ridge wet quartzite dislocation creep at 250 280 c abstract cambrian quartzite along the western margin of the blue ridge near front royal virginia records significant penetrative strain under subgreenschist facies conditions strain analyses of the quartzite indicate general flattening and octahedral shear strain values up to 1 25 x z up to 5 7 1 samples with x z as low as 1 5 1 have crystallographic preferred orientations that record a dominance of basal slip and patterns consistent with coaxial flattening in most samples quartz has undergone minor amounts of dynamic recrystallization with mean grain sizes 4 5 m locally the quartzite is brittlely deformed and subgrains and recrystallized bulges are present along fractures and extinction bands fluid inclusion planes and fluid inclusions along deformation lamellae are abundant and quartz ftir analyses yield average h 106si values of 1100 3300 indicating fluid flow and high intragranular water content during deformation higher strain samples generally record lower water contents which may indicate that fluids migrated to grain boundaries during deformation dissolution microstructures are rare in high strain samples and we interpret most strain to have been accommodated by dislocation creep thermal modeling of zircon low temperature thermochronology data coupled with quartz c axis opening angle thermometry suggest deformation temperatures were likely 250 280 c these deformation temperatures are lower than what is typically considered the brittle plastic transition in quartz we attribute localization of this high strain zone and dislocation creep at these temperatures to hydrolytic weakening and a relatively low strain rate estimated to be 10 15 s 1

fluid deposited graphitic inclusions in quartz comparison between ktb german continental deep drilling core samples and artificially reequilibrated natural inclusions we used raman microsampling spectroscopy rms to determine the degree of crystallinity of minute 2 15 m graphite inclusions in quartz in two sets of samples experimentally reequilibrated fluid inclusions in a natural quartz grain and biotite bearing paragneisses from the ktb deep drillhole in se germany our sequential reequilibration experiments at 725 c on initially pure co2 inclusions in a quartz wafer and the j krautheim 1993experiments at 900 1100 c on organic compounds heated in gold or platinum capsules suggest that at a given temperature 1 fluid deposited graphite will have a lower crystallinity than metamorphosed organic matter and 2 that the crystallinity of fluid deposited graphite is affected by the composition of the fluid from which it was deposited we determined that the precipitation of more crystalline graphite is favored by lower f h2 higher f o2 and that the crystallinity of graphite is established by the conditions including gas fugacities that pertain as the fluid first reaches graphite saturation graphite inclusions within quartz grains in the ktb rocks show a wide range in crystallinity index reflecting three episodes of carbon entrapment under different metamorphic conditions isolated graphite inclusions have the spectral properties of totally ordered completely crystalline graphite such crystallinity suggests that the graphite was incorporated from the surrounding metasedimentary rocks which underwent metamorphism at upper amphibolite facies conditions much of the fluid deposited graphite in fluid inclusions however shows some spectral disorder the properties of that graphite resemble those of experimental precipitates at temperatures in excess of 700 c and at elevated pressures suggesting that the inclusions represent precipitates from c o h fluids trapped under conditions near those of peak metamorphism at the ktb site in contrast graphite that is intimately associated with chlorite and other presumably low temperature silicates in inclusions is highly disordered and spectrally resembles kerogens this graphite probably was deposited during later greenschist facies retrograde metamorphism at about 400 500 c the degree of crystallinity of fluid deposited graphite is shown to be a much more complex function of temperature than is the crystallinity of metamorphic graphite to some extent experiments can provide temperature calibration of the crystallinity index however the difference in time scales between experimental runs and geologic processes makes it difficult to infer specific temperatures for naturally precipitated graphite

origin and evolution of ore fluid and gold deposition processes at the giant taishang gold deposit jiaodong peninsula eastern china abstract the early cretaceous taishang gold deposit is the largest deposit in the linglong goldfield jiaodong peninsula with a pre mining endowment of 326 t of gold it is hosted in the 165 150 ma linglong biotite granite and controlled by the nee to ne trending potouqing fault near the northern end of the regional zhaoping fault system hydrothermal alteration is well developed in the footwall of the potouqing fault and is characterized by a narrow zone of sericitization followed by a wider zone of silicification and an even wider zone of potassic alteration the main orebodies no i orebody comprise disseminated and stockwork veinlet systems although about 5 of the resources are in larger quartz veins no ii orebody four stages have been identified for both styles of mineralization on the basis of cross cutting relationships and mineralogical and textural characteristics pyrite quartz sericite stage 1 quartz pyrite stage 2 quartz pyrite base metal sulfide stage 3 and quartz carbonate stage 4 gold was mainly deposited in stages 2 and 3 with minor amounts in stage 1 petrographical microthermometric and laser raman spectroscopic studies on fluid inclusion assemblages in quartz and calcite from the four stages reveal three types of primary fluid inclusions type 1 h 2 o rich aqueous carbonic type 2 co 2 rich aqueous carbonic and rare type 3 carbonic inclusions stage 1 quartz primary inclusions are only type 1 inclusions with an estimated composition of 88 h 2 o 10 co 2 4 5 wt nacl equiv and 0 5 ch 4 with trapping at 336 c and 1 7 kbars the gold rich stages 2 and 3 from both orebodies typically contain primary fluid inclusion assemblages with both type 1 and 2 inclusions which show similar phase transition temperatures and were trapped between 246 and 294 c the stage 4 quartz and calcite contain only primary type 1 inclusions which are estimated to have a composition of 93 h 2 o 6 0 co 2 3 6 wt nacl equiv and trace amount of ch 4 and were trapped at temperatures of 236 c the 34 s values of hydrothermal pyrite from the four stages have a narrow range from 4 5 to 8 0 and are within the ranges for whole rock sulfides from the archean jiaodong group and magmatic pyrite from mesozoic granitoid and intermediate basic dikes the 18 o values of hydrothermal quartz range mainly from 10 9 to 12 5 and remain constant for all four stages calculated fluid 18 o values are 1 3 10 0 the d water values calculated from hydrothermal sericite range from 60 to 45 considering the fluid inclusion compositions 18 o and d compositions of ore forming fluids and regional geological events the most likely ultimate potential fluid and metal reservoirs would be the paleo pacific oceanic slab and its overlying sediments which were thrust below the high grade metamorphic rocks of the jiaodong peninsula the initial ore forming fluids were medium high temperature co 2 rich and low salinity h 2 o co 2 nacl ch 4 homogeneous fluids over the duration of the hydrothermal system the fluid remained fairly consistent in p t x although becoming slightly more water rich during final post ore activity fluid immiscibility occurred during stages 2 and 3 ore deposition at pressures that fluctuated strongly from 1700 to 580 bars during hydrofracturing the hs 2 ion was the most probable gold transporting complex at taishang wall rock sulfidation and episodic pressure drops with associated fluid unmixing and other chemical changes were the two main mechanisms of ore deposition

fluid inclusion record of the hypozonal orogenic renco gold deposit zimbabwe during the retrograde p t evolution the hypozonal renco gold deposit in zimbabwe is hosted by a shear zone system cutting granulite facies enderbites the geologic history of the region testifies to a polyphase tectonometamorphic evolution along the exhumation path three major events are notable during which fluid inclusions could have been formed detailed petrographic work and comparison of calculated isochores with the p t evolution allows correlation of inclusion formation with the tectonometamorphic evolution fluid inclusions in the mineralized lithologies of the renco gold mine are dominated by carbonic inclusions of highly variable densities the high density carbonic inclusions are related to the peak of metamorphism their lower density counterparts show a bimodal occurrence some are re equilibrated equivalents of the inclusions trapped at peak metamorphic conditions whereas others clearly post date this event and are related to gold mineralization the latter type of carbonic inclusions occurs in distinct microstructural domains of quartz crystals i e subgrain grain boundaries therefore these inclusions are interpreted to have formed because of selective trapping of co2 from a mixed h2o co2 low salinity ore fluid all the aqueous inclusions observed at renco can be attributed to a late retrograde greenschist facies overprint

timing and mechanism of gold mineralization at the wang ershan gold deposit jiaodong peninsula eastern china abstract the wang ershan gold deposit located in the southern jiaojia goldfield is currently the largest gold deposit hosted within the subsidiary faults in jiaodong peninsula with a gold reserve of 60 t gold at a grade of 4 07 g t au it is hosted in the late jurassic linglong biotite granites and controlled by the second order n to nne trending wang ershan fault and its subsidiary faults which is broadly parallel to the first order jiaojia fault in the goldfield gold mineralization occurs as both disseminated and stockwork style and quartz sulfide vein style ores mainly within altered cataclasites and breccias and sericite quartz and potassic alteration zones respectively mineralization stages can be divided into 1 the pyrite quartz sericite stage 2 the quartz pyrite stage 3 the quartz sulfide stage and 4 the quartz carbonate stage two sericite samples associated with the main ore stage pyrites from pyritic phyllic ores of the deposit with weighted mean plateau 40 ar 39 ar age of 120 7 0 6 ma and 119 2 0 5 ma respectively were selected for 40 ar 39 ar geochronology on the basis of petrography and microthermometry three types of primary fluid inclusions related to the ore forming event were identified type 1 h 2 o co 2 nacl type 2 aqueous and type 3 co 2 fluid inclusions in decreasing abundance stage 1 quartz contains all three primary fluid inclusions while stages 2 and 3 quartz contain both type 1 and 2 inclusions and stage 4 quartz contains only type 2 inclusions the contemporaneous trapping similar salinities and total homogenization temperature ranges and different homogenization phases of type 1 and type 2 inclusions indicate that fluid immiscibility did take place in stages 1 2 and 3 ores with p t conditions of 190 to 85 mpa and 334 to 300 c for stage 1 and 200 to 40 mpa and 288 to 230 c for stages 2 and 3 combined with the h o c s pb isotopic compositions ore forming fluids may have a metamorphic dominant mixed source which could be associated with the dehydration and decarbonisation of a subducting paleo pacific plate and characterized by medium high temperature 285 350 c co 2 bearing 8 mol with minor ch 4 1 4 in carbonic phase and low salinity 3 38 8 45 eq wt nacl during mineralization the fluid finally evolved into a medium low temperature nacl h 2 o system au hs 2 was the most probable gold transporting complex at wang ershan due to the low temperature 157 350 c and near neutral to weakly acidic ore fluids the reaction between gold bearing fluids and iron bearing wall rocks and fluid immiscibility processes caused via fluid pressure cycling during seismic movement along fault zones that host lode gold orebodies which led to breakdown of au hs 2 are interpreted as the two main precipitation mechanisms of gold deposition in general the wang ershan deposit and other deposits in the jiaojia camp have concordant structural system and wall rock alteration assemblages nature of orebodies and gold occurrence conditions as well as the similar geochronology ore forming fluids system and stable isotope compositions thus gold mineralization in the jiaojia goldfield was a large scale unified event with consistent timing origin process and mechanism

modification of fluid inclusions in quartz by deviatoric stress ii experimentally induced changes in inclusion volume and composition fluid inclusions in quartz are known to modify their densities during shear deformation modifications of chemical composition are also suspected however such changes have not been experimentally demonstrated their mechanisms remain unexplained and no criteria are available to assess whether deformed inclusions preserve information on paleofluid properties to address these issues quartz crystals containing natural co2 h2o nacl fluid inclusions have been experimentally subjected to compressive deviatoric stresses of 90 250 mpa at 700 c and 600 mpa confining pressure the resulting microcracking of the inclusions leads to expansion by up to 20 producing low fluid densities that bear no relation to physical conditions outside the sample nevertheless the chemical composition of the precursor inclusions is preserved with time the microcracks heal and form swarms of tiny satellite inclusions with a wide range of densities the highest reflecting the value of the maximum principle stress 1 these new inclusions lose h2o via diffusion thereby passively increasing their salt and gas contents and triggering plastic deformation of the surrounding quartz via h2o weakening using microstructural criteria to identify the characteristic types of modified inclusions both the pre deformation fluid composition and syn deformation maximum stress on the host mineral can be derived from microthermometric analysis and thermodynamic modelling

fluid evolution in the strange lake granitic pluton canada implications for hfse mobilisation abstract strange lake is a mid proterozoic peralkaline granite pluton quebec labrador canada that underwent extreme enrichment in high field strength elements hfse including the rare earth elements ree the hfse mineralisation is confined to highly altered pegmatites and the most altered parts of the granites implying a genetic association between hydrothermal fluids and hfse enrichment this study uses analyses of fluid inclusions to investigate the hydrothermal evolution of the strange lake pluton and the role of hydrothermal processes in concentrating the hfse to potentially exploitable levels five groups of inclusions were distinguished from earliest to latest these groups are primary aqueous inclusions 25 wt nacl eq associated with melt inclusions group 1 primary aqueous inclusions 13 23 wt nacl eq associated with ch 4 inclusions groups 2a and b primary aqueous inclusions 9 wt nacl eq associated with co 2 inclusions group 3 primary aqueous inclusions 9 wt nacl eq which contain no carbonic component group 4 and finally secondary aqueous inclusions 19 wt nacl eq including inclusions that outline mineral pseudomorphs also with no detectable carbonic component group 5 most of the inclusions except those in group 5 have conspicuous implosion haloes evident as numerous tiny voids this indicates that the inclusions re equilibrated most likely during isobaric cooling fluid evolution commenced with the exsolution of a saline aqueous liquid 25 wt nacl eq and an immiscible ch 4 h 2 gas from the pegmatitic melt at temperatures of 450 500 c and a pressure of 1100 bars during isobaric cooling the gas component of the fluid was gradually oxidised evolving from being ch 4 dominant to a ch 4 fluid with a significant proportion of higher order hydrocarbons due to oxidative coupling of methane induced by the consumption of o 2 through the alteration of arfvedsonite to aegirine 325 360 c and finally to a co 2 dominated fluid at 300 c the apparent salinity of the aqueous fluid decreased from 25 to 4 5 wt nacl eq due to fluid rock interaction the latter also caused precipitation of nahcolite as a result of the reaction of newly formed co 2 with sodium from decomposing minerals formation of pseudomorphs after primary na zirconosilicates and na titanosilicates and replacement of primary ree silicates by bastnasite ce owing to this interaction the carbonic component of the fluid was consumed which together with the consumption of h 2 o to form al k and fe phyllosilicates contributed to an increase in the fluid salinity up to 19 wt nacl eq light rare earth elements lree were remobilised over 10s to 100 s of metres by the high temperature high salinity fluid preserved as group 1 and 2a inclusions whereas heavy rare earth elements hree were remobilised on a much smaller scale by a late low temperature high salinity fluid trapped as inclusion group 5 fluid preserved as inclusion group 3 may have been responsible for remobilisation of zr and ti

experimental diffusion of hydrogen into synthetic fluid inclusions in quartz quartz hosted synthetic co2 h2o fluid inclusions behave as open systems with respect to diffusional transfer of hydrogen during laboratory simulated metamorphic re equilibration at 650 750 and 825 c and 1 5 kbar total pressure with fo2 defined by the c ch4 buffer microthermometry and raman spectroscopy show that the initial co2 h2o inclusions become co2 ch4 h2 h2o inclusions after diffusive influx of hydrogen from the reducing confining medium measurable changes are observed in inclusion compositions after only 15 days of re equilibration implying significant hydrogen mobility at still lower temperatures over geological time spans results of synthetic inclusion re equilibrium experiments have profound implications for the interpretation of natural fluid inclusion data failure to account for potential hydrogen migration in inclusions from high temperature geological environments may lead to erroneous estimates of p t and or the compositions of metamorphic fluids

raman spectroscopic characterization of h2o in co2 rich fluid inclusions in granulite facies metamorphic rocks abstract water h2o has been identified during raman analyses at 150 200 c of fluid inclusions from granulites that were previously thought to contain pure co2 at room temperature h2o in a co2 rich fluid inclusion forms an optically unresolvable liquid wetting the inclusion walls during heating the h2o phase evaporates into the co2 phase to produce a homogeneous h2o co2 fluid throughout the inclusion volume and the h2o raman peak at 3640 cm 1 is clearly resolvable at elevated temperatures to test and confirm the method synthetic h2o co2 fi of known composition 87 5 mol and 95 mol co2 were also analyzed previously studied granulite samples from the adirondack mountains usa and from the kerala khondalite belt sittampundi complex and sevitturangampatti india were tested for the presence of h2o in co2 rich fluid inclusions traces of h2o were found in co2 rich fluid inclusions in quartz crystals from the adirondacks and from the kerala khondalite belt h2o was not detected in co2 rich secondary fluid inclusions in garnet from the sittampundi complex and from sevitturangampatti rather hydrogarnet was detected along the walls of inclusions in garnet as evidenced by a peak at 3661 cm 1 the hydrogarnet is interpreted to be a step daughter phase that formed by reaction of the h2o in the fluid inclusion with the garnet host during retrogression these observations confirm the presence of an h2o bearing co2 rich fluid at some time during granulite petrogenesis but do not resolve the question of whether these co2 rich fluids were trapped at peak metamorphic conditions or during retrogression or whether the fluid inclusions have reequilibrated following entrapment

relationship between co2 dominated fluids hydrothermal alterations and gold mineralization in the red lake greenstone belt canada abstract the red lake greenstone belt is one of the foremost au mining camps in canada and hosts the world class campbell red lake au deposit belt scale hydrothermal alteration is characterized by proximal ferroan dolomite zones associated with au mineralization surrounded by distal calcite zones both being accompanied by potassic alterations sericite muscovite and biotite at the campbell red lake and cochenour deposits au mineralization in particular high grade ore is associated with silica and sulfides especially arsenopyrite that replace carbonate quartz veins and the host rocks the prevalence of carbonic fluid inclusions and rare occurrence of aqueous bearing inclusions in carbonate quartz au veins in the campbell red lake deposit and the consistency of homogenization temperatures of carbonic inclusions within individual fluid inclusion assemblages fia have been interpreted to indicate that h2o poor co2 dominated fluids were responsible for the carbonate veining and au mineralization further studies of fluid inclusions in carbonate quartz veins within and outside the deformation zone hosting the campbell red lake deposit the red lake mine trend including the cochenour au deposit the redcon au prospect and outcrops in the distal calcite zone also reveal the dominance of carbonic fluid inclusions in vein minerals these studies indicate that co2 dominated fluids were flowing through fractures during carbonate vein formation and au mineralization both within and outside major structures the carbonic fluid may have been initially undersaturated with water or it may have resulted from phase separation of an h2o co2 nacl fluid in the latter case phase separation modeling indicates that the initial fluid likely had x co 2 values larger than 0 8 calculations based on hydrothermal mineral assemblages indicate x co 2 values in the host rocks from 0 025 to 0 85 reflecting a change from co2 dominated fluids in the fractures veins to h2o dominated fluids in the host rocks away from the fractures the co2 dominated fluids were likely advected from granulite facies in the deeper crust whereas the h2o dominated fluids were derived from the ambient host rocks of amphibole to greenschist facies calculations based on co2 requirements and source constraints indicate that the mineralizing fluids were likely two orders of magnitude more enriched in au than the commonly assumed values of a few g l which may explain why the campbell red lake deposit has a very high grade of au average 21 g t for the whole deposit and 81 g t for the goldcorp high grade zone fluid inclusion data suggest that the carbonate veining and au mineralization likely took place at depths from 7 to 14 km the development of crustiform colloform structures in the carbonate quartz veins which was previously interpreted to indicate relatively shallow environments may alternatively have been related to extremely high fluid pressures and the co2 dominated nature of the fluids which could have enhanced the brittle properties of the rocks due to their high wetting angles

the nature and distribution of fluids during amphibolite facies metamorphism naxos greece on the basis of fluid inclusion evidence pervasive influx of deep seated co2 rich fluids has been invoked to account for mid to upper amphibolite facies m2b metamorphism on the island of naxos cyclades greece in this paper mineral devolatilization and melt equilibria are used to constrain the composition of both syn and post peak m2b fluids in the deepest exposed levels of the metamorphic complex the results indicate that peak m2b fluids were spatially and compositionally heterogeneous throughout the high grade core of the complex whereas post peak m2b fluids were generally water rich the observed heterogeneities in syn m2b fluid composition are inconsistent with pervasive co2 flushing models invoked by previous workers on the basis of fluid inclusion evidence it is likely that few co2 rich fluid inclusions on naxos preserve fluids trapped under peak metamorphic conditions it is suggested that many of these inclusions have behaved as chemically open systems during the intense deformation that accompanied the uplift of the metamorphic complex a similar process may explain the occurrence of some co2 rich fluid inclusions in granulite facies rocks

on the origin of co2 rich fluid inclusions in migmatites nearly pure co2 fluid inclusions are abundant in migmatites although h2o rich fluids are predicted from the phase equilibria processes which may play a role in this observation include 1 the effects of decompression on melt 2 generation of a co2 bearing volatile phase by the reaction graphite quartz biotite plagioclase melt orthopyroxene co2 rich vapour 3 selective leakage of h2o from co2 h2o inclusions when the pressure in the inclusion exceeds the confining pressure during decompression and 4 enrichment of grain boundary vapour in co2 by subsolidus retrograde hydration reactions

transmission electron microscopy applied to fluid inclusion investigations abstract the transmission electron microscope tem allows a detailed characterization of textural and chemical features of fluid inclusions shape inner compositions and inner textures at a resolution higher than that attainable with an optical microscope om tem investigation indicates that most fluid inclusions appear as perfectly euhedral negative crystals with variable shape from prismatic to equant and size typically from a critical feature revealed by tem is that inclusions are often connected to structural defects in particular to dislocation arrays which are undetected by optical microscopy the identification of these hidden nanostructures should be taken into account for the correct petrological interpretation of microthermometric results particularly when controversial data have been obtained in fact these nanostructures may represent a possible path for fluid phase leakage thus modifying the original composition and or density of the inclusions

enrichment of co2 in fluid inclusions in quartz by removal of h2o during crystal plastic deformation abstract ductile strain induced leakage of h 2 o from mixed co 2 h 2 o fluid inclusions in quartz is proposed as a mechanism for producing occurrences of pure co 2 fluid inclusions in metamorphic rocks the h 2 o needed for hydrolytic weakening of quartz under stress may be provided by the h 2 o in fluid inclusions with dislocation creep as dislocations nucleate on the walls of fluid inclusions or intersect them h 2 o can be transported with the dislocations from the inclusion to the grain boundaries the process should continue so long as there is stress on the host quartz and the inclusion contains h 2 o the h 2 o taken to the grain boundaries would due to its wetting properties be wicked out along the grain boundaries if the h 2 o is totally removed from an inclusion by a flux of dislocations through the quartz during the crystal plastic flow then a residual inclusion bearing components other than water should remain a mixed co 2 h 2 o inclusion would as a consequence of the process become a pure co 2 fluid inclusion during dynamic recrystallization the co 2 would collect at grain boundary triple junctions and following grain boundary migration would become incorporated into the recrystallized quartz as fluid inclusions this mechanism of generating pure co 2 inclusions could result in co 2 fluid inclusions having densities appropriate for the pressure temperature conditions during deformation using estimates of temperature of deformation the total confining pressure during deformation could be determined from the density of the co 2 fluid in these inclusions

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

fluids in metamorphic rocks abstract basic principles for the study of fluid inclusions in metamorphic rocks are reviewed and illustrated a major problem relates to the number of inclusions possibly formed on a wide range of p t conditions having also suffered in most cases extensive changes after initial trapping the interpretation of fluid inclusion data can only be done by comparison with independent p t estimates derived from coexisting minerals but this requires a precise knowledge of the chronology of inclusion formation in respect to their mineral host the three essential steps in any fluid inclusion investigation are described observation measurements and interpretation observation with a conventional petrographic microscope leads to the identification and relative chronology of a limited number of fluid types same overall composition eventually changes in fluid density for the chronology the notion of gis group of synchronous inclusions is introduced it should serve as a systematic basis for the rest of the study microthermometry measurements completed by nondestructive analyses mostly micro raman specify the composition and density of the different fluid types the major problem of density variability can be significantly reduced by simple considerations of the shape of density histograms allowing elimination of a great number of inclusions having suffered late perturbations finally the interpretation is based on the comparison between few isochores representative of the whole inclusion population and p t mineral data essential is a clear perception of the relative chronology between the different isochores when this is possible as illustrated by the complicated case of the granulites from central kola peninsula a good interpretation of the fluid inclusion data can be done if not fluid inclusions will not tell much about the metamorphic evolution of the rocks in which they occur

alpine deformation on naxos greece a detailed structural study of naxos attic cycladic massif greece reveals two major deformation events the first one is associated with large scale thrusting and high pressure low temperature metamorphism during an early alpine subduction episode the second event occurred during continental extension and the associated development of localized thermal domes where lower crustal rocks were brought into contact with upper crustal units along a major shallow dipping shear zone we agree with a model of naxos as a cordilleran type metamorphic core complex however our observations show that the sense of shear was upper plate moving north during the second event calling for a reinterpretation of existing tectonic models of the cyclades

metamorphic evolution and fluid composition of garnet clinopyroxene amphibolites from the tatra mountains western carpathians relics suggesting an early high pressure eclogite facies stage have been identified in the garnet and clinopyroxene bearing amphibolites of the tatra mountains in the variscan basement of the western carpathians slovakia in these rocks primary omphacite cpx i has been wholly converted to symplectites of diopside cpx ii and plagioclase apart from minor inclusions in the garnet cores amphibole and plagioclase are secondary minerals formed in the kelyphitic rims between garnet and clinopyroxene several generations of amphibole pargasite hornblende cummingtonite actinolite are evidence of a transformation down to greenschist facies conditions thermobarometric calculations from mineral inclusions in the garnet cores yield 670 700 c and 10 15 kbar recording the initial path from upper amphibolite to eclogite facies conditions the attainment of the eclogite facies stability field is inferred from the composition of a reconstructed omphacite jd36 implying a minimum peak pressure of 15 16 kbar conditions of around 650 c and 8 10 kbar record the post eclogite breakdown and partial re equilibration in the amphibolite facies region the earliest fluid inclusions contain high density nitrogen dominated water absent fluid younger are polyphase brines and two phase h2o n2 ch4 inclusions with signs of heterogeneous entrapment of coexisting gas rich and water rich immiscible phases pure nitrogen 0 5 mol ch4 is considered to have been the major component during the high pressure metamorphism in contrast the later aqueous inclusions are interpreted to represent retrogression related fluids the brines have originated by leaching and re entrapment of saline melt inclusions observed in tonalitic trondhjemitic layers of the amphibolite enclosing the eclogitic relics a similar mechanism is assumed for the origin of the h2o n2 ch4 inclusions these represent relics of the primary eclogite facies related n2 inclusions re equilibrated and re entrapped during retrogression under increasing water activity a possible source of n2 and cl rich fluids was primary amphibole which decomposed during the prograde metamorphism from the amphibolite to the eclogite facies the metamorphic pt path is generally clockwise reflecting a steep increase in pressure and temperature during burial followed by decompression and cooling the retrograded eclogites occur in boudins within an allochthonous unit of an inverted metamorphic sequence their exhumation was facilitated by tectonic transport along a ductile shear zone during the variscan orogeny

micromechanisms of shear zone propagation at the brittle viscous transition our investigation of progressively strained rock samples from the margins of greenschist facies shear zones utilizes a space for time approach to reveal how the mylonitic overprint of metapsammitic and pelitic host rocks at the cap de creus involved brittle fracturing we present a set of microscale observations indicating that microfractures formed immediately prior to or coevally with a fine grained mylonite microfracturing dominated early stages of strain localization on the scale of the shear zones on the microscale centimeter long fractures facilitated strain softening by allowing enhanced fluid access thereby accelerating the dynamic recrystallization of quartz and a metamorphic reaction of biotite as these two processes produce a polyphase matrix of small dislocation poor grains that eventually form an interconnected rheologically weak phase fractures become inactive this represents a strain dependent brittle viscous transition we outline this transition in a conceptual model for the rheological evolution of mid crustal shear zones

fluid inclusions tectonic indicators abstract during the first half of the 20th century fluid inclusions have been studied in ore geology in order to determine the chemistry and physical parameters density of the mineralising fluids apart from a few pioneering works in the middle of the century fluid inclusions were not used as structural markers before the late 1980s during the same time experiments as well as observations of natural samples have shown that the volume shape and density of fluid inclusions may change when submitted to pressure temperature conditions different from their trapping isochores in view of these experiments and based on natural examples from the higher himalaya metamorphic rocks it is evident how fluid inclusions can be used as thermobarometric structural and tectonic markers points of interest for further studies on fluid inclusions in nature and experiments are also stressed

deformation by solution deposition and re equilibration of fluid inclusions in crystals depending on temperature internal pressure and stress abstract changes of shape and density of fluid inclusions in crystals were demonstrated when these crystals were subjected to temperatures and internal pressures greater than those of their growth experimental relations have been established between the rate of length change of the inclusions and the different parameters of the experiment nature of the crystal temperature and internal pressure state of stress on the crystal geometric characters of the inclusion length width orientation of the inclusion with respect to the optical axes of host mineral it is essentially the effect of the variation of surface energy with the curvature around the cavity which causes a mass transfer of the host crystal by diffusion through the fluid under pressure the rate of length change is limited by the rate of dissolution at the median part of elongate inclusions this change of shape and density is known to occur in naturally deformed crystals an example of such a behaviour is given which allowed us to use the inclusions as markers of the conditions of temperature and pressure subsequent to the growth of crystal

fluid inclusion petrography abstract a procedure of fluid inclusion studies is proposed with emphasis on the criteria of selecting fluid inclusions for detailed microthermometry and spectroscopic analysis an overview of descriptive and genetic classifications of fluid inclusions in single crystals and in massive rocks is given with the intention of further differentiating the commonly used terms primary and secondary fluid inclusions some principles of fluid inclusion modification are explained cathodoluminescence cl studies of quartz with the optical high power cl microscope and the electron microprobe provided with a cl detector are an important help in fluid petrography cl textures are subdivided in primary growth textures and a wide variety of secondary microtextures which are in part induced by fluid inclusions the latter is grouped in textures indicative of local lower crystal order increasing defect structures and microtextures indicative of local quartz healing reduction of the defect structures microtextures showing the genetic relationship between fluid inclusions and the host mineral provide information about the possible post entrapment changes of fluid inclusions and therewith testify their geological relevance

development of sigmoidal en echelon microfractures in beryl and the role of strain localization evidenced by fluid inclusions abstract a combined fluid inclusion and microstructural study was carried out in beryl crystals from the san cayetano nb ta bearing pegmatite san luis argentina primary aqueous carbonic fluids t0 were subsequently re trapped during shearing resulting in en echelon microfractures the more brittle behaviour of beryl compared to quartz makes this mineral more suitable for the preservation of fluid inclusions and microstructures the primary inclusions t0 are preserved in strain free domains whereas the pseudo secondary t1 to t3 type inclusions occur in domains showing intracrystalline deformation co2 was relatively immobile or reacted to form carbonate in early t1 type inclusions whereas h2o preferentially migrated along microfractures and was trapped as t2 and t3 type inclusions short intragranular trails of fluid inclusions representing en echelon healed microfractures resulted from progressive strain localization contrary to previous proposals this new model implies the progressive thickness reduction of intracrystalline micro shear zones besides hydrolytic weakening linked to dislocation glide is the most likely mechanism to explain the evolution of fluid inclusions with intracrystalline deformation enhancing anisotropic diffusion this study highlights the potential of combined fluid inclusion and microstructural studies in order to understand the interaction between fluid activity and deformation in this way valuable insights can be provided into the progressive development of overprinted fabrics and low to medium temperature deformation mechanisms of minerals

evolution in h 2 o contents during deformation of polycrystalline quartz an experimental study shear experiments were performed in a griggs type apparatus at 800 c and 1 5 gpa at a strain rate of 2 1 10 5s 1 using different starting materials i powder grain size 6 10 m of dry brazil quartz with 0 15 wt added h2o ii dry brazil quartz porphyroclasts grain size 100 200 m devoid of fluid inclusions embedded in the same fine grained powder and iii wet porphyroclasts grain size 100 200 m containing initially a high density of m scale fluid inclusions embedded in the same powder after hot pressing samples were deformed to large shear strains 3 to 4 5 in order for the microstructures and h2o distribution to approach some state of equilibrium the h2o content and speciation in quartz were analyzed by fourier transform infra red ftir spectroscopy before and after the experiments mechanical peak strength is generally lower in experiments with 100 hydrated matrix intermediate in experiments incorporating wet porphyroclasts with a proportion of 30 or 70 and highest in those with dry porphyroclasts all experiments with porphyroclasts show pronounced strain weakening and the strengths of most samples converge to similar values at large strain wet porphyroclasts are pervasively recrystallized during deformation while dry porphyroclasts recrystallize only at their rims and remain weakly deformed recrystallization of the initially fluid inclusion rich porphyroclasts results in a decrease in inclusion abundance and total h2o content while h2o content of initially dry clasts increases during deformation h2o contents of all high strain samples converge to similar values for matrix and recrystallized grains in samples with wet porphyroclasts shear bands with high porosity and fluid contents develop and they host the precipitation of euhedral quartz crystals surrounded by a free fluid phase these high porosity sites are sinks for collecting h2o in excess of the storage capacity of the grain boundary network of the recrystallized aggregate the h2o storage capacity of the grain boundary network is determined as a h2o boundary film of 0 7 nm thickness

formation of the campbell red lake gold deposit by h 2 o poor co 2 dominated fluids the campbell red lake gold deposit in the red lake greenstone belt with a total of approximately 840 t of gold past production reserves and an average grade of 21 g t au is one of the largest and richest archean gold deposits in canada gold mineralization is mainly associated with silicification and arsenopyrite that replace carbonate veins breccias and wallrock selvages the carbonate veins and breccias which are composed of ankerite quartz and characterized by crustiform cockade textures were formed before and or in the early stage of penetrative ductile deformation whereas silicification arsenopyrite replacement and gold mineralization were coeval with deformation microthermometry and laser raman spectroscopy indicate that fluid inclusions in ankerite and associated quartz q1 and main ore stage quartz q2 are predominantly carbonic composed mainly of co2 with minor ch4 and n2 aqueous and aqueous carbonic inclusions are extremely rare in both ankerite and quartz h2o was not detected by laser raman spectroscopic analyses of individual carbonic inclusions and by gas chromatographic analyses of bulk samples of ankerite and main ore stage quartz q2 fluid inclusions in post mineralization quartz q3 are also mainly carbonic but proportions of aqueous and aqueous carbonic inclusions are present trace amounts of h2s were detected by laser raman spectroscopy in some carbonic inclusions in q2 and q3 and by gas chromatographic analyses of bulk samples of ankerite and q2 3he 4he ratios of bulk fluid inclusions range from 0 008 to 0 016 ra in samples of arsenopyrite and gold homogenization temperatures th co2 of carbonic inclusions are highly variable from 4 1 to 30 4 c mostly to liquid some to vapor but the spreads within individual fluid inclusion assemblages fias are relatively small within 0 5 to 10 3 c carbonic inclusions occur both in fias with narrow th co2 ranges and in those with relatively large th co2 variations the predominance of carbonic fluid inclusions has been previously reported in a few other gold deposits and its significance for gold metallogeny has been debated some authors have proposed that formation of the carbonic fluid inclusions and their predominance is due to post trapping leakage of water from aqueous carbonic inclusions h2o leakage model whereas others have proposed that they reflect preferential trapping of the co2 dominated vapor in an immiscible aqueous carbonic mixture fluid unmixing model or represent an unusually h2o poor co2 dominated fluid single carbonic fluid model based on the fia analysis reported in this study we argue that although post trapping modifications and host mineral deformation may have altered the fluid inclusions in varying degrees these processes were not solely responsible for the formation of the carbonic inclusions the single carbonic fluid model best explains the extreme rarity of aqueous inclusions but lacks the support of experimental data that might indicate the viability of significant transport of silica and gold in a carbonic fluid in contrast the weakness of the unmixing model is that it lacks unequivocal petrographic evidence of phase separation if the unmixing model were to be applied the fluid prior to unmixing would have to be much more enriched in carbonic species and poorer in water than in most orogenic gold deposits in order to explain the predominance of carbonic inclusions the h2o poor co2 dominated fluid may have been the product of high grade metamorphism or early degassing of magmatic intrusions or could have resulted from the accumulation of vapor produced by phase separation external to the site of mineralization

submicron sized fluid inclusions and distribution of hydrous components in jadeite quartz and symplectite forming minerals from uhp jadeite quartzite in the dabie mountains china tem and ftir investigation abstract fluid inclusions and clusters of water molecules at nanometer to submicron scale in size have been investigated using transmission electron microscopy tem and fourier transform infrared spectroscopy ftir in jadeite quartz and symplectite aegirine augite albite taramite and magnetite corona minerals from ultrahigh pressure uhp jadeite quartzite at shuanghe the dabie mountains china fluid inclusions from 0 003 m to 0 78 m in size occur in jadeite and quartz crystals and a small number of fluid inclusions from 0 001 m to 0 25 m have also been detected in symplectite forming minerals most of the fluid inclusions have round or negative crystal morphology and contain aqueous fluids but some contain co 2 rich fluids they are usually connected to dislocations undetectable at an optical scale the dislocations represent favorable paths for fluid leakage accounting for non decrepitation of most fluid inclusions when external pressure decreased at later stages although there was partial decrepitation of some fluid inclusions unconnected to defect microstructures resulting from internal overpressure non decrepitation and partial decrepitation of fluid inclusions resulted in changes of original composition and or density it is clear that identification of hidden re equilibration features has significant implications for the petrological interpretation of post peak metamorphic processes micro ftir results show that all jadeite and quartz samples contain structural water occurring as hydroxyl ions oh and free water h 2 o in the form of clusters of water molecules the h 2 o transformed from oh during exhumation and could have triggered and enhanced early retrograde metamorphism of the host rocks and facilitated plastic deformation of jadeite and quartz grains by dislocation movement and thus the h 2 o released during decompression might represent early stage retrograde metamorphic fluid the nominally anhydrous mineral nam jadeite is able to transport aqueous fluids in concentrations of at least several hundred ppm water along a subduction zone to mantle depths in the form of clusters of water molecules and hydroxyl ions within crystals

dynamics of mineral crystallization from precipitated slab derived fluid phase first in situ synchrotron x ray measurements precipitation of daughter minerals we performed for the first time a single crystal x ray diffraction experiment by synchrotron radiation at diamond light source in combination with electron probe microanalyses this measurement allowed the unique identification of each mineral phase and reciprocal orientations we demonstrated the epitaxial relationship between spinel and garnet and between some hydrous minerals such information is discussed in relation to the physico chemical aspects of nucleation and growth shedding light on the mode of mineral crystallization from a fluid phase trapped at supercritical conditions

mechanical re equilibration of fluid inclusions in san carlos olivine by power law creep fluid inclusions in san carlos olivine stretch via plastic mechanisms when heat treated at 1400 c and 0 1 mpa in controlled f o 2 atmospheres for several days measurable changes in both inclusion dimensions and fluid densities occur densities decrease from 1 0 to 0 7 g cc stretching is fastest along 100 and slower along 001 and 010 the dislocation microstructure around the inclusions suggests that creep mechanisms operate uncertainties in the experimental determinations of stretching rates result from optical resolution limits errors inherent in measuring homogenization temperatures uncertainties in the fluid equation of state and changes in fluid chemistry during the heat treatment inclusion stretching by dislocation creep can be treated using a model developed for hot isostatic pressing in this model we assume spherical symmetry of plastic flow that the material yields by steady state power law creep and that the parameters for the constitutive law and fluid equation of state are known stretching rates are predicted to depend on the difference between the fluid pressure and the external pressure the temperature the constitutive law governing power law creep and geometry predicted stretching rates show fair but not exact agreement with experimentally measured rates the amount of stretching predicted by the model is in rough agreement with estimates based on dislocation microstructures around natural inclusions if xenolith ascent rates are of the order of 1 cm s or faster

synthetic fluid inclusions xv tem investigation of plastic flow associated with reequilibration of fluid inclusions in natural quartz the nature and abundance of dislocations in quartz surrounding fluid inclusions were studied to obtain a better understanding of processes associated with fluid inclusion reequilibration synthetic fluid inclusions containing 10 wt nacl aqueous solution were formed in three samples at 700 c and 5 kbar one of the samples was quenched along an isochore to serve as a reference sample the other two samples were quenched along a p t path that generated internal pressures in excess of the confining pressure the two samples were held at the final reequilibration p t conditions of 625 c and 2 kbar for 30 and 180 days respectively following the experiments microstructures associated with fluid inclusions were examined with the tem quartz in healed fractures in the reference sample that was quenched isochorically shows a moderate dislocation activity quartz adjacent to reequilibrated fluid inclusions in the other two samples however showed a marked increase in dislocation activity compared to the un reequilibrated sample deformation of the inclusion walls occurred anisotropically by expansion of mobile dislocations in their slip systems dislocation expansion was controlled by glide in the rhombohedral planes 1 0 1 1 that was restricted to narrow zones 3 m in the immediate vicinity of the fluid inclusion walls outside of the healed fracture plane these plastic zones were observed after both short term 30 days and long term 180 days experiments and are attributed to hydrolytic weakening of quartz around fluid inclusions owing to diffusion of water into the quartz matrix during the experiment the close spatial association of submicroscopic water bubbles with dislocations and the rarity of water bubbles in the reference sample show clearly that in both the 30 and 180 day experiments reequilibration involves water loss from the fluid inclusions our results indicate that synthetic fluid inclusions in this study recover chemically and volumetrically even at relatively fast experimental loading rates such that internal stresses never reach the point of brittle failure the driving force for fluid inclusion deformation involves two related mechanisms plastic deformation of hydrolytically weakened wet quartz in the healed fracture and water leakage associated with preexisting and strain induced dislocations

the role of subgrain boundaries in partial melting abstract evidence for partial melting along subgrain boundaries in quartz and plagioclase is documented for rocks from the lost creek gneiss of the llano uplift central texas the wet mountains of central colorado and the albany fraser orogen southwestern australia domains of quartz or plagioclase crystals along subgrain boundaries are preferentially involved in partial melting over unstrained domains of these minerals material along subgrain boundaries in quartz and plagioclase has the same morphology as melt pseudomorphs present along grain boundaries and is commonly laterally continuous with this former grain boundary melt indicating the material along subgrain boundaries can also be categorized as a melt pseudomorph subgrain boundaries consist of arrays of dislocations within a crystal lattice and unlike fractures would not act as conduits for melt migration instead the presence of former melt along subgrain boundaries requires that partial melting occurred in these locations because it is kinetically more favorable for melting reactions to occur there preferential melting in high strain locations may be attributed to strain energy which provides a minor energetic contribution to the reaction and leads to preferential melting in locations with weakened bonds and or the presence of small quantities of water associated with dislocations which may enhance diffusion rates or locally lower the temperature needed for partial melting

andalusite bearing veins at vedrette di ries eastern alps italy fluid phase composition based on fluid inclusions andalusite bearing veins formed during contact metamorphism in the aureole of the vedrette di ries tonalite in the veins quartz crystals that are completely armoured by andalusite or that occur in strain shadow areas contain three generations of fluid inclusions low salinity h o co ch mixtures with chj c0 ch 5 0 35 type a low salinity aqueous fluids type b h o free c02 ch fluids with the same carbonic speciation as a type c carbonic types a and c typically have a dark appearance which is attributed to graphite coatings on inclusion walls microstructural analysis of the host quartz and calculated densities indicate that type a inclusions were likely trapped during vein formation these inclusions underwent strain assisted re equilibration during cooling that resulted in density increases without change of composition after the rocks had cooled below about 350 c type c inclusions appear to have formed from one of the immiscible fractions after unmixing of the h20 c02 ch fluid mixtures aqueous type b inclusions apparently trapped between 225 and 350 c could represent an independent fluid or could be the h o rich fraction of unmixed type a fluids taking account of the uncertainties the composition and density of the complex type a inclusion fluids are in good agreement with the properties of primary fluids calculated from the petrological data the fluid inclusion data support the model of vein formation by hydrofracturing as a result of dehydration of graphitic metapelites these new results also demonstrate the importance of considering strain in the interpretation of metamorphic fluid inclusions

strain response and re equilibration of ch4 rich synthetic aqueous fluid inclusions in calcite during pressure drops abstract aqueous fluids in sedimentary basins often contain dissolved methane particularly in petroleum environments pvtx pressure volume temperature composition reconstructions performed using fluid inclusion data are largely based on the assumption that inclusions do not change from the time of trapping until the present many authors however consider that fluid inclusions can re equilibrate particularly in fragile minerals like calcite in order to understand this re equilibration phenomenon in the metamorphic domain previous experiments have been performed under high pt conditions but few have been performed at low to medium pt conditions such as those associated with sedimentary burial diagenesis and no previous studies have examined ch 4 bearing aqueous inclusions in calcite an experimental study of the preservation modification of ch 4 rich synthetic fluid inclusions in calcite during isothermal decompression was conducted an autoclave was used for accurate ptx control allowing equilibrium between liquid and vapour in the ch 4 h 2 o system ptx conditions were maintained at four stages of decreasing pressure with each stage held for 7 days to simulate an isothermal pressure drop in order of decreasing pressure the pressure temperature conditions monitored were 276 10 bar at 180 7 c 176 10 bar at 180 7 c 76 10 bar at 180 7 c and 10 3 bar at 180 15 c at the end of the experiment the calcite was recovered and analyzed by microthermometry and raman microspectroscopy for ptx reconstruction a careful procedure was adopted to limit re equilibration of inclusions during analytical procedures four types of inclusion shapes and four types of strain patterns were differentiated classification of the petrographic strain patterns was carried out these strain patterns were associated with inclusion stretching and or leakage regarding ch 4 t h and p h compared to experimental conditions factors controlling the preservation or acquisition of strain patterns included the initial shape and size of the inclusion and the pressure differential p between the confining pressure p cf and the internal pressure p i within the inclusion most fluid inclusions seemed to be trapped during the first 7 days of the experiment although few 4 of these preserved the initial pt conditions of 276 10 bar whereas 8 preserved the second and third run of pt conditions overall the majority of inclusions 88 did not reflect accurately the ptx trapping conditions a petrographic guide to the inclusions is presented here that allows strain identification for pvt reconstructions re equilibration patterns and evidence for preferential methane leakage from aqueous inclusions in calcite are important findings revealed by this study and may be useful for the reconstruction of post trapping events in investigations of natural samples and in other experiments using synthetic inclusions in calcite

dislocation creep of dry quartz small scale shear zones within the permian truzzo meta granite developed during the alpine orogeny at amphibolite facies conditions in these shear zones magmatic quartz deformed by dislocation creep and recrystallized dynamically by grain boundary migration with minor subgrain rotation recrystallization to a grain size of around 250 750 m consistent with flow at low differential stresses fourier transform infrared ftir spectroscopy reveals very low water contents in the interior of recrystallized grains in the form of discrete oh peaks 20 h 10 6 si and very little broad band absorption 100 h 10 6 si the spectral characteristics are comparable to those of dry brazil quartz in ftir spectra magmatic quartz grains show a broad absorption band related with high water concentrations only in those areas where fluid inclusions are present while other areas are dry drainage of fluid inclusions and synkinematic growth of hydrous minerals indicates that a hydrous fluid has been available during deformation loss of intragranular water during grain boundary migration recrystallization did not result in a microstructure indicative of hardening these ftir measurements provide the first evidence that quartz with extremely low intragranular water contents can deform in nature by dislocation creep at low differential stresses low intragranular water contents in naturally deformed quartz may not be necessarily indicative of a high strength and the results are contrary to implications taken from deformation experiments where very high water contents are required to allow dislocation creep in quartz it is suggested that dislocation creep of quartz in the truzzo meta granite is possible to occur at low differential stresses because sufficient amounts of intergranular water ensure a high recovery rate by grain boundary migration while the absence of significant amounts of intragranular water is not crucial at natural conditions

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

a mechanism for preferential h 2 o leakage from fluid inclusions in quartz based on tem observations preferential leakage of h2o from fluid inclusions containing multiple gas components has been suspected in natural metamorphic rocks and has been demonstrated experimentally for synthetic h2o co2 rich inclusions in natural quartz knowledge of the physical and chemical characteristics of the leakage mechanism which may be very complex increases the value of natural fluid inclusions to metamorphic geology it is proposed that crystal defects play a major role in nondecrepitative preferential h2o leakage through quartz and remain effective during metamorphism inclusions with either an internal overpressure or underpressure produce strain in the adjacent quartz crystal via the nucleation of many dislocations and planar defects like dauphine twin boundaries these defects allow preferential loss of h2o from h2o co2 rich inclusions at supercritical conditions the transport capacity of this leakage mechanism is enhanced by nucleation of small bubbles on defect structures the nucleation of these bubbles seems to be a recovery process in strained crystals solubility gradients of quartz in water in a crystal with internally underpressurized inclusions may result in optical visible implosion halos in a three dimensional spatial arrangement caused by the growth of small bubbles at the expense of the larger original fluid inclusion natural fluid inclusions from naxos greece are always associated with numerous interlinked dislocations these dislocations may have been produced by plastic derormation or by crystal growth related processes e g crack healing the presence of small bubbles on these dislocations indicates that a similar leakage mechanism for h2o must have occurred in these rocks

a comparison of jiaojia and linglong type gold deposit ore forming fluids do they differ abstract the jiaodong peninsula contains the most important concentration of gold deposits in china which can be divided into jiaojia type and linglong type deposits based on mineralization style the former is characterized by disseminated and stockwork style mineralization hosted in first order regional faults with relatively larger tonnages and lower gold grades the latter is characterized by massive auriferous quartz veins commonly hosted in subsidiary second or third order faults with smaller tonnage but higher grade orebodies despite these differences both groups of deposits have the same alteration assemblages mineral paragenesis element concentrations and ore forming ages the mainly jiaojia type luoshan gold deposit and the mainly linglong type fushan gold deposit are characterized by h o s pb isotope data that indicate the ore forming fluids have a dominantly metamorphic source the fluids were derived during the yanshanian orogenic event and were most likely associated with dehydration and decarbonization processes near the top of the subducting paleo pacific plate the linglong type ores have relatively lighter calculated 18 o compositions 3 9 to 2 3 than the jiaojia type ores 0 3 8 0 possibly because of a greater degree of mixing with meteoric water petrographic cathodoluminescence microthermometric and laser raman spectroscopic analyses of fluid inclusion assemblages in quartz from the two types of ores indicate fluids were similar in both cases characterized by medium high homogenization temperatures 211 393 c significant co 2 15 mol minor ch 4 18 in the carbonic phase and low salinity 11 2 wt nacl eq the linglong type ores however have a wider range of co 2 and ch 4 concentration and salinity than the jiaojia type ores fluid immiscibility occurred in main ore stage of both ore types with the trapping conditions of 77 185 mpa and 284 328 c although the unmixing is more intense and widespread in the linglong type ores both fluid wallrock interaction and fluid immiscibility are important gold deposition processes in the two types but immiscibility is more important in the linglong type ores and that has led to the typical higher gold grade in general there is little geochemical differences between the ore forming fluids for jiaojia and linglong type gold deposits both jiaojia and linglong type ores can exist in a single deposit and form in the same metallogenic event the linglong type ores developed as more massive veins because of their location in zones of more extensive extension and they lack significant post ore cataclastic deformation

water in nominally anhydrous minerals implications for partial melting and strain localization in the lower crust low concentrations tens to hundreds of parts per million of water in nominally anhydrous minerals nams of the mantle have been shown to significantly affect the rheology depth of depressurization melting and many other properties of the mantle in this contribution we evaluate the effect of trace concentrations of water in nams on melting of lower continental crust water locked in structural sites and in fluid inclusions in nominally anhydrous minerals in lower crustal granitoids may act as a flux for partial melting of these source rocks water concentrations of 3000 ppm in minerals that make up large volumes of crustal rocks k feldspar plagioclase quartz would lower the dry solidus of granite by 273 c at 1 gpa measurements and maps of water concentration in variably deformed samples of the stevenson granite from northern saskatchewan canada show that during deformation and recrystallization of k feldspar megacrysts water migrated from the interior of megacrysts to finer grained matrix material dark fine grained water richer matrix material consisting of quartz plagioclase alkali feldspar and fine iron oxides are interpreted to be former melt films that resulted at least in part from fluxing by nam derived water deformation may play a role in moving water from nams to phase boundaries where generation of partial melt may lead to further rock weakening and further release of water from nams

solubility of hydroxyl in natural quartz annealed in water at 900 c and 1 5 gpa we have measured the infrared spectra of a natural quartz after annealing it for up to 37 hours in water at 900 1000 c and 1 0 1 5 gpa under chemical conditions buffered through a hydrogen membrane with an assemblage of water nickel metal and nickel oxide from integral absorbances in the 3400 and 2500 cm 1 regions we calculated the concentration of hydrogen and deuterium present in the samples as hydroxyl concentrations reported in this work are calibrated to the deuterium content of a sample annealed 37 hours in d2o18 as determined by nuclear reaction analysis hydrothermal annealing increased the hydroxyl content of natural quartz a 1 from 26 to 75 11 h 106si absorption increased by growth of o h bands it 3318 3483 and 3432 cm 1 associated with a13 samples annealed in d2o18 showed an increase in bands near 2500 cm 1 associated with o d and a13 an o h band in the starting material at 3485 cm 1 associated with li was absent from the spectra of annealed samples fractured samples were characterized by the appearance of a sharp band at 3580 cm 1 and absorption several times larger than unfractured samples microscopic examination of fractured samples showed that they contained water inclusions and healed fractures previous hydroxyl solubility measurements made on fractured samples may be too large due to hydroxyl contamination along fractures at 900 c experiments equilibrated in times consistent with a diffusivity for hydrogen impurity in quartz of 10 7 cm s

experimental formation of pyroxenite veins by reactions between olivine and si al ca na and cl rich fluids at 800 oc and 800 mpa implications for fluid metasomatism in the mantle wedge fluids buffered by a plagioclase matrix are experimentally reacted with olivine megacrysts at 800 oc and 800 mpa piston cylinder press caf2 assembly to form secondary veins of orthopyroxene clinopyroxene in the olivine fluids utilized were varied in both amount 0 2 wt and salinity 0 8 m nacl assuming equilibrium with the plagioclase matrix they are presumed enriched in si al ca na and cl and are thereby similar in composition to slab derived fluids the experiments provide controlled multi component analogs of si metasomatism in the mantle wedge above subduction zones the veins are dominated by orthopyroxene with minor clinopyroxene and form complex interconnected networks along fractures in the olivine the reaction is rate limited by interfacial process of dissolution and precipitation porosity is developed throughout the veins and along sub grain boundaries in the olivine megacrysts these veins strongly resemble the textures observed in secondary metasomatic orthopyroxene veins widely reported in upper mantle xenoliths within arc magmas a review of literature data on natural samples and experiments suggests that orthopyroxene clinopyroxene veins primarily form between 750 950 oc and over a large pressure range from 0 8 3 4 gpa the abundance and composition of these metasomatic veins may vary as a function of pressure variances in the fluid rock partition coefficients and or by modification of the metasomatic fluid during the reaction

textural evolution of synthetic fluid inclusions in quartz during reequilibration with applications to tectonic reconstruction experimental reequilibration of synthetic 10 wt nacl h2o inclusions in natural quartz reveals that reequilibration textures show distinct differences depending upon the p t path followed by the inclusion after formation these differences combined with other geological information may be used to determine whether the sample rock followed a dominantly isothermal or isobaricp t path following entrapment the intensity and style of inclusion reequilibration features is related to the direction and magnitude of the departure of thep t path from the original isochore for the inclusion thus fluid inclusion reequilibration textures not only permit inclusionists to determine whether the rocks followed an isothermal or isobaric retrogradep t path but also the magnitude of departure of this path from one that is isochoric

pvtx characteristics of oil inclusions from asmari formation in kuh e mond heavy oil field in iran incorporating pvt properties and compositional evolution of oil inclusions into reservoir engineering simulator protocols can enhance understanding of oil accumulation reservoir charge history and migration events microthermometry and volumetric analysis have proven to be useful tools in compositional reconstitution and pt studies of oil inclusions and were used to determine composition thermodynamic conditions physical properties and gas to oil ratios of heavy oil samples from asmari carbonate reservoir in kuh e mond heavy oil field in iran pvt properties were predicted using a pvt black oil model and an acceptable agreement was observed between the experiments and the simulations homogenization temperatures were determined using microthermometry techniques in dolomite and calcite cements of the asmari formation as well based on the homogenization temperature data the undersaturated hydrocarbon mixture prior to formation of the gas cap migrated with a higher gas to oil ratio from a source rock according to the oil inclusion data the onset of carbonate cementation occurred at temperatures above 45 c and that cementation was progressive through burial diagenesis pvt black oil simulator results showed that the reservoir pressure and temperature were set at 100 bar and 54 c during the initial stages of oil migration compositional modeling implies that primary and secondary cracking in source rocks were responsible for retention of heavy components and migration of miscible three phase flow during hydrocarbon evolution the pt evolution of the petroleum inclusions indicates changes in thermodynamic properties and mobility due to phenomena such as cracking mixing or and transport at various stages of oil migration