hydrothermal alteration and fluid chemistry of the endako porphyry molybdenum deposit british columbia hydrothermal alteration and fluid chemistry data of the early cretaceous endako porphyry molybdenum deposit british columbia provide new information on the hydrothermal fluids associated with low fluorine molybdenite mineralization molybdenite mineralization and hydrothermal alteration occur as early quartz molydenite stockwork veins with k feldspar bearing selvages and paragenetically later quartz molybdenite ribbon veins with sericite bearing selvages late hydrothermal alteration is associated with the development of kaolinite and postore tertiary age calcite veins fluid inclusions in early formed quartz molybdenite stockwork veins with k feldspar bearing alteration assemblages are dominated by moderate salinity 5 to 15 wt nacl equiv liquid rich type 1 and rare high salinity 30 to 45 wt nacl equiv halite bearing type 3 fluid inclusions type 1 and type 3 fluid inclusions in early veins homogenize between 390 and 430 c and 375 and 420 c respectively secondary fluid inclusions type 2 of low salinity 1 to 5 wt nacl equiv in these early veins are minor and homogenize between 130 and 285 c fluid inclusions in quartz molybdenite ribbon veins with sericite bearing alteration assemblages are dominated by moderate salinity liquid rich type 1 inclusions with minor type 2 fluid inclusions type 1 fluid inclusions of ribbon veins homogenize between 360 and 400 c fluid inclusions in postore calcite veins are of only type 2 fluid inclusions which homogenize at 209 c hydrothermal fluids recorded by type 1 and type 3 fluid inclusions in early veins were trapped under lithostatic to hydrostatic conditions between 0 3 and less than or equal to 2 0 kbar and 360 and 560 c postore fluids recorded by type 2 fluid inclusions were trapped under conditions less than or equal to 0 5 kbar and between 190 and 300 c quartz stockwork and ribbon veins possess 18o values of 8 4 0 2 n 9 and 8 4 0 6 n 13 respectively hydrothermal k feldspar and biotite from k feldspar alteration assemblages possess 18o values of 6 8 0 4 n 7 and 3 5 0 8 n 8 respectively oxygen isotope geothermometry of quartz biotite and quartz k feldspar pairs from k feldspar alteration assemblages yield temperatures between 200 and 490 c which is similar to the trapping temperatures of hydrothermal fluids determined from fluid inclusion studies associated with molybdenite mineralization the development of kaolinite and calcite veins the oxygen isotope temperatures of the quartz biotite and quartz k feldspar pairs suggest that k feldspar and biotite either record the approximate 18o composition of hydrothermal fluids associated with k feldspar alteration or have undergone 18o exchange with late stage hydrothermal fluids hydrogen isotope composition of quartz stockwork and ribbon veins fluid inclusion waters range between 105 and 173 per mil solute chemistry studies of fluid inclusion waters indicate that ore forming fluids from endako have low br cl and br na ratios and high i cl and i br ratios in comparison to porgera epithermal babine lake porphyry cu and st austell capitan pluton vein deposits associated with magmatic processes na k ratios of fluid inclusion waters yield temperatures 308 to 429 c similar to those determined from type 1 and type 3 fluid inclusions and stable isotope thermometry results from fluid inclusion and solute chemistry studies indicate the involvement of hydrothermal fluids exsolved from a crystallizing melt in the formation of the endako molybdenum deposit however oxygen and hydrogen isotope values deviate from the generally accepted magmatic compositions which suggests the early involvement of meteoric water in the ore forming fluids and ore genesis

synthetic fluid inclusions xvii pvtx properties of high salinity h2o nacl solutions 30 wt nacl application to fluid inclusions that homogenize by halite disappearance from porphyry copper and other hydrothermal ore deposits fluid inclusions that homogenize by disappearance of the halite crystal after the vapor bubble has disappeared have been reported from a wide range of ore forming systems while this inclusion type is most commonly observed in porphyry copper and similar magmatichydrothermal ore deposits they have also been reported from iron oxide copper gold iocg mississippi valley type orogenic lode greenstone gold massive sulfide unconformity u and mantotype deposits as well as from non ore associated granitoids and oceanic crust the lack of experimental data to interpret microthermometric data from these inclusions combined with poor petrographic characterization of inclusion origin has led to a wide range of inferred pt trapping conditions for the inclusions the relationship between liquid vapor homogenization temperature thl v halite dissolution temperature tmhalite and pressure has been determined using synthetic h2o nacl fluid inclusions that homogenize by halite disappearance the experimental data cover the range thl v 150 to 500 c and tmhalite 275 to 550 c an empirical equation describing the relationship between pressure thl v and tmhalite has been developed to estimate formation pressures from microthermometric data and is valid from pressures along the liquid vapor halite curve to 300 mpa a detailed literature review reveals that the results of this study cannot be applied retroactively to estimate pressures of previously reported inclusions that homogenize by halite dissolution for several reasons first most workers have not collected and reported the data in a manner that allows one to determine if the inclusions have trapped a single homogeneous phase and have not leaked or changed volume following trapping thus it is not possible to determine if the inclusions show consistent microthermometric behavior within a group of coeval inclusions additionally many published studies provide only summaries of results from numerous samples or present the data graphically precluding application of our results to individual inclusions however based on our review it appears that much of the published data for inclusions that homogenize by halite dissolution represent inclusions that have either trapped a halite crystal along with the liquid or have reequilibrated by necking and or stretching results from this study have been used to estimate minimum formation pressures for inclusions from the ditrau alkaline massif transylvania romania the musoshi stratiform copper deposit zaire the bismark skarn deposit northern mexico the naica chimneymanto deposit mexico the questa porphyry molybdenum deposit new mexico and the bingham canyon porphyry cu mo deposit utah in each case pressures estimated using results from the present study are in good agreement with previous pressure estimates however in some cases estimated pressures both our estimates as well as those of other authors appear to be unreasonably high based on the geologic setting at the time of formation these results highlight the currently limited understanding concerning pressures depths of ore formation

high salinity fluid inclusions in the yinshan polymetallic deposit from the le de metallogenic belt in jiangxi province china their origin and implications for ore genesis a fluid inclusion investigation of the polymetallic mineralization at yinshan from the le de metallogenic belt in jiangxi province of china has been carried out using petrographic and microthermometric techniques the data obtained here indicate that three major types of fluids were involved during the formation of the deposit they are type i vapor rich type ii liquid rich and type iii halite bearing inclusions within the h2o nacl system the high salinity fluids represented by type iii inclusions being unusual to the distal part of an intrusion centered ore forming system such as yinshan have been interpreted as the product of direct exsolution of a crystallizing magma rather than a result of fluid immiscibility from a low salinity fluid evidence used to support such an interpretation includes the mode of homogenization of type iii inclusions exclusively via halite dissolution spatial separation of type i and type iii inclusions on microscopic scale the consistent phase ratios within the inclusions concerned and considerable deviation in homogenization temperature for both type i and type iii inclusions trapping conditions for type i inclusions were estimated to be around 440 degrees c and 260 bars while type iii inclusions were constrained to be trapped at least above 900 bars and 500 degrees c the formation temperatures for type ii inclusions range from 270 to 390 degrees c if a lithostatic pressure of 260 bars is assumed pressure fluctuation determined by this fluid inclusion study coupled with decreases in salinity and temperature as result of the potential fluid mixing are supposed to have played an important role in triggering the precipitation of ore minerals from the hydrothermal solution c 2006 elsevier b v all rights reserved

fluid inclusion characteristics and geological significance of the xi ao copper tin polymetallic deposit in gejiu yunnan province abstract the newly discovered xi ao cu sn polymetallic deposit is located in the inner alteration zone of the laochang kafang granite edge in gejiu yunnan province the mineralization process of this deposit can be divided into four stages cassiterite and chalcopyrite mainly formed at stages ii and iii respectively fluid inclusions at different stages were studied by petrography microthermometry and laser raman spectrometry five fluid inclusion types are observed microthermometry results revealed that the ore forming fluid evolved from high temperature with low to intermediate salinity to low temperature with low salinity at stage i the fluid was under near critical conditions and then separated into coexisting liquid and vapor phases at stage ii finally the fluid was boiling and immiscible at stage iii a meteoric fluid mixing process was also observed at this stage laser raman spectra identified ch4 at the skarn and mineralization stages combined with other geological features the deposit was concluded to have formed under a relatively reduced environment the co2 component abruptly increased at stage iii and probably originated from the exterior fluorine may play an important role in mineralization cassiterite and chalcopyrite were mainly deposited at 340 440 and 300 400 c under pressures of 18 50 and 12 36 mpa respectively boiling and immiscibility are probably the main reason for mineral deposition the deposit of cassiterite and chalcopyrite showed similar salinities but higher temperatures than other mineralization types of deposits in the gejiu area this finding indicated that the study deposit probably represents the high temperature part of the gejiu mineralization system thereby benefiting mineral explorations in the gejiu area

fluid chemistry structural setting and emplacement history of the rosario cu mo porphyry and cu ag au epithermal veins collahuasi district northern chile the rosario cu mo ag deposit is located in the collahuasi district of northern chile it comprises high grade cu ag au epithermal veins superimposed on the core of a porphyry cu mo orebody rosario has mining reserves of 1 094 million metric tons mt at 1 03 percent copper an additional 1 022 mt at 0 93 percent copper occurs in the district at the nearby ujina and quebrada blanca porphyry deposits the rosario reserve contains over 95 percent hypogene ore whereas supergene sulfide ores dominate at ujina and quebrada blanca mineralized veins are hosted within lower permian volcanic and sedimentary rocks lower triassic granodiorite and late eocene porphyritic quartz monzonite the rosario fault system a series of moderate southwest dipping faults has localized high grade cu ag au veins at cerro la grande similar high grade cu ag au veins are hosted in north northeast trending sinistral wrench faults normal movement in the rosario fault system is interpreted to have been synchronous with sinistral strike slip deformation at la grande hydrothermal alteration at rosario is characterized by a k feldspar core focused in the rosario porphyry that grades out to a secondary biotite albite magnetite assemblage paragenetic relationships indicate that magnetite was the earliest formed alteration product but has been replaced by biotite albite vein crosscutting relationships indicate that k feldspar formed during and after biotite albite alteration chalcopyrite and bornite were deposited in quartz veins associated with both k feldspar and biotite albite assemblages the early hydrothermal fluid was a hypersaline brine 40 45 wt nacl that coexisted with vapor between 400 degrees and 600 degrees c weakly mineralized illite chlorite intermediate argillic alteration of the early k and na silicate assemblages was caused by moderate temperature 250 degrees 350 degrees c moderate salinity brines 10 15 wt nacl molybdenite was precipitated in quartz veins that formed between the potassic and intermediate argillic alteration events these fluids were 350 degrees to 400 degrees c with salinities between 10 and 15 wt percent nacl porphyry style ore and alteration minerals were overprinted by structurally controlled quartz alunite pyrite pyrophyllite dickite and muscovite quartz phyllic alteration assemblages the quartz alunite pyrite alteration formed at 300 degrees to 400 degrees c from fluids with a salinity of 10 wt percent nacl the pyrophyllite dickite assemblage formed between 250 degrees and 320 degrees c from dilute 5 wt nacl fluids an upward flared zone of muscovite quartz pyrite altered rocks surrounds the fault controlled domain of advanced argillic alteration thick veins 0 5 2 m wide of fault hosted massive pyrite chalcopyrite and bornite precipitated brines with a salinity of 30 wt percent nacl at temperatures of 250 degrees to 300 degrees c pressure depth estimates indicate that at least 1 km of rock was eroded at rosario between formation of the k na silicate and advanced argillic assemblages this erosion was rapid occurring over a period of 1 8 m y the rosario porphyry intruded immediately after the incaic tectonic phase implying that it was emplaced as the domeyko cordillera underwent gravitational collapse expressed as normal faults in the upper crust gravitational sliding potentially accelerated exhumation and helped to promote telescoping of the high sulfidation environment onto the rosario porphyry the hydrothermal system responsible for porphyry cu mineralization at rosario was partially exhumed prior to the formation of high sulfidation ore and alteration assemblages this implies that emplacement of a second blind intrusion occurred somewhere beneath the rosario and cerro la grande high sulfidation vein systems and is supported by the fault geometry and zoning of precious metals and sulfosalts at the district scale

compositions of biotite amphibole apatite and silicate melt inclusions from the tongchang mine dexing porphyry deposit se china implications for the behavior of halogens in mineralized porphyry systems abstract the dexing deposit located in the circum pacific ore belt is the largest porphyry copper deposit in eastern china it is composed of 3 separate plutons which host three mines tongchang fujiawu and zhushahong mines the porphyritic granodiorite samples studied in this investigation were collected from the tongchang ore forming pluton of this giant deposit this paper presents electron microprobe analyses of biotite apatite amphibole plagioclase potassium feldspar and rehomogenized glassy melt inclusions from the tongchang porphyritic granodiorites petrographic observations of the samples are consistent with portions of the granodioritic magma represented by our samples being overprinted by potassic hydrothermal fluid which variably altered these minerals all of the studied micas are mg rich biotites the biotites are separated into altered magmatic and secondary types based on their petrographic and geochemical characteristics the phlogopite components of the secondary biotites are typically higher than those of the altered magmatic biotites and the x mg values of all biotites correlate negatively with cl contents consistent with the mg cl avoidance principle the x mg values also correlate negatively with k 2 o na 2 o bao feo and tio 2 for both generations of biotites the calculated log f h 2 o f hcl values for 690 k of the coexisting potassic fluids which are determined from the altered magmatic biotite compositions range from 4 43 to 4 67 and are very similar to those of other major porphyry deposits however the log f h 2 o f hf and log f hf f hcl values for the same batch of hydrothermal fluids are significant higher and lower than those of these other porphyry deposits respectively the cl concentrations of amphiboles and melt inclusions range from 0 18 to 0 32 wt and 0 15 to 0 44 wt respectively most apatites trapped in biotite and plagioclase phenocrysts display a bimodal cl distribution 0 19 to 1 35 wt and 1 48 to 3 73 wt similarly the s contents of the apatite also show a distinct bimodal distribution reflecting the effects of variable anhydrite saturation during evolution of the tongchang melt and variable dissolution of anhydrite by saline aqueous fluids the cl contents of the apatites from the tongchang system are typically higher than those of other studied porphyry deposits furthermore the cl contents of the melt inclusions are at or very near the cl saturation levels 0 36 to 0 46 wt at 850 c and 50 mpa and 0 42 to 0 54 wt at 850 c and 200 mpa for these melt compositions at shallow crustal pressures these findings suggest that the area of the granodioritic magma represented by our samples and perhaps the bulk of the tongchang granodioritic magma was rich in cl the melt inclusion compositions are consistent with a high salinity hydrosaline liquid being exsolved directly from the granodioritic melt directly this high salinity hydrosaline liquid was likely very efficient at dissolving transporting and precipitating ore metals in the mineralizing magmatic hydrothermal system

a fluid inclusion and stable isotope study of the pebble porphyry copper gold molybdenum deposit alaska abstract the hydrothermal fluid evolution in the supergiant pebble porphyry cu au mo deposit in southwest alaska has been constrained using fluid inclusion and light stable isotope data the deposit is related to 90 ma granodiorite porphyry intrusions and mineralization occurs primarily in sodic potassic potassic and advanced argillic alteration zones throughout the deposit vein quartz hosts intermediate density fluid inclusion assemblages with an average salinity of 9 5 wt nacl equivalent and homogenization temperatures of 377 to 506 c pressure corrections result in trapping temperatures with a maximum of 610 c this early fluid exsolved from a crystallizing magma at depth and underwent phase separation under varying conditions during cooling and depressurization forming two distinct fluid compositions the two fluids formed two hydrothermal alteration assemblages which have different metal signatures in the hydrothermal core in the eastern part of the system high density quartz veins potassic alteration and the most economically significant mineralization are related to 52 wt nacl equivalent brines that coexist with very low density vapor in the western part of the system peripheral to the hydrothermal core lower quartz vein densities accompanied by sodic potassic alteration and lower grade mineralization are associated with 38 wt nacl equivalent brines and low density vapor sulfide mineralization precipitated late in this early alteration event at temperatures between 375 and 330 c fluids related to sodic potassic alteration minerals have 18 o signatures from 6 0 to 10 5 vsmow and d values from 70 to 41 vsmow which are consistent with a magmatic fluid source fluids related to potassic alteration assemblages have 18 o of 1 7 to 2 3 vsmow and d of 68 to 59 vsmow which suggests that the magmatic fluids evolved to lighter oxygen isotope signatures due to quartz precipitation during alteration lower temperature 280 c sericite and illite alteration followed the high temperature magmatic stage and formed from the rising vapor plume as it mixed with varying amounts of meteoric fluid sericite in quartz sericite pyrite alteration on the periphery of the deposit and illite from areas of illite kaolinite alteration which overprints sodic potassic alteration and forms quartz illite pyrite alteration within the deposit are related to low salinity aqueous fluids that have a significant magmatic component 2 1 to 4 1 18 o and 76 to 67 d illite alteration which overprints both potassic alteration and quartz sericite pyrite alteration formed from fluids with a large meteoric component 9 1 to 4 8 18 o and 101 to 90 d the higher vein density and therefore higher permeability in the core of the deposit facilitated ingress of larger amounts of meteoric fluid compared with the more peripheral region advanced argillic alteration and associated high grade mineralization are related to a second pulse of magmatic fluid which did not intersect the two phase field during cooling and depressurization the fluid contracted to form a 3 wt nacl equivalent aqueous fluid that resulted in a sericite pyrite bornite digenite bearing assemblage with a magmatic signature 4 6 to 6 5 18 o and 108 to 102 d at 340 c cooling and mixing of this fluid with meteoric water resulted in a fluid that formed a pyrophyllite quartz sericite chalcopyrite bearing assemblage 8 9 to 0 6 18 o and 110 to 96 d at 300 c compared to older potassic and sodic potassic alteration the advanced argillic alteration has a highly depleted d signature which is attributed to degassing of a crystallizing intrusive fluid source

geochronology and zircon hf isotope geochemistry of granites in the giant chalukou mo deposit ne china implications for tectonic setting abstract in this contribution the largest porphyry mo deposit in ne china chalukou is selected to provide insights into the tectonic evolution of ne china the deposit was considered to be rift related or climax type porphyry mo deposit developed in an extensional setting while other researchers attributed its formation to the subduction of the paleo pacific ocean in view of different granite petrogenesis between rift type and subduction type porphyry mo deposits geochronological and zircon lu hf isotope studies have been carried out on granitic rocks associated with the chalukou deposit zircon grains from the ore host monzogranite and ore causative granite porphyry yield weighted mean 206pb 238u ages of 166 2 ma and 152 2 ma with molybdenite samples yielding a re os isochron age of 150 2 ma indicating a jurassic age for both granitic intrusion and mo mineralization zircon ehf t values of monzogranite and granite porphyry range from 0 9 to 3 0 and from 1 4 to 0 5 respectively when integrated with published zircon lu hf isotopic data our data suggest that the barren granites both pre and post ore were mainly derived from mantle derived juvenile rocks whereas the syn ore granite requires additional involvement of old continental crust thus a contribution of continental crust to mo mineralization is suggested the petrogenesis and geochemical data reveal that the chalukou deposit is a subduction related porphyry mo deposits and not rift related integrated evidence links its formation to the southeastward subduction of the mongol okhotsk ocean instead of the westward subduction of the paleo pacific ocean

prograde evolution and geothermal affinities of a major porphyry copper deposit the cerro colorado hypogene protore i region northern chile the middle eocene 51 8 0 6 ma hypogene protore underlying the supergene orebody of the cerro colorado porphyry cu mo deposit i region chile exhibits features not commonly documented in such hydrothermal systems early stage alteration of upper cretaceous plagioclase phyric andesite generated a sub horizontal blanket of pervasive extremely fine grained but texture preserving biotite 35 modal albite 40 magnetite 3 alteration 8 km 2 in area but lacking sulfide minerals at least seventy percent of the chalcopyrite pyrite stockwork mineralization was emplaced during the subsequent main stage alteration which comprises with decreasing depth quartz albite sericite chlorite clay smectite quartz sericite clay and andalusite diaspore pyrophyllite assemblages the deposit is apparently unique among documented central andean porphyry systems in the association of the highest grade copper mineralization with intermediate argillic alteration the subsequent transitional stage phyllic i e quartz sericite pyrite tourmaline alteration was associated with the emplacement of molybdenite rich breccia bodies the occurrence of undumortieri tized tourmaline veinlets cutting andalusite diaspore assemblages confirms that much of the advanced argillic alteration took place during the main stage early stage alteration was the product of nonboiling cool trapping temperature ca 380 c low salinity 8 wt nacl equiv fluids which added substantial k na mg fe 2 cl f and water to the host andesite the initial main stage fluids boiling at a paleodepth of ca 2 5 to 3 0 km were up to 160 c hotter 544 c and highly saline 52 wt nacl equiv as these fluids rose they cooled to 320 c were diluted to 37 wt nacl equiv deposited sulfides and leached k na ca mg fe 2 and cl from the host rocks yielding diverse broadly contemporaneous intermediate and advanced argillic alteration facies pressure estimates require that low density 0 3 g cm 3 and thus more acidic fluids were primarily responsible for the formation of the quartz sericite clay and shallow advanced argillic alteration subsequent phyllic alteration was similarly caused by boiling fluids which were hot 486 c and saline 47 wt at depth but cooler 334 c dilute 8 wt and vapor dominated at shallower levels even terminal stage pyrite veins formed at temperatures as high as 450 c albeit from low salinity 8 wt fluids following a major prograde thermal transition from the early to the main stage each sulfide depositing alteration episode at cerro colorado was generated by a pulse of high temperature fluid which cooled and diluted as it rose such changes in fluid characteristics temperature and alteration relationships are well documented in numerous geothermal fields where potassic alteration generally develops at ca 270 to 350 c and are likely to occur at an early stage in any hydrothermal system in which magmatic fluids exsolving at relatively high pressures ascend into the near surface environment the initial alteration at cerro colorado plausibly developed under conditions similar to those in nonexplosive geothermal systems in which hydrothermal fluids cool and disperse laterally at shallow depths extensive zones of biotite rich alteration generally barren and with a hornfelsic appearance occur in many andesite hosted porphyry copper deposits but few data are available elsewhere for mineralogical pressure temperature or metasomatic exchange relationships in such systems cerro colorado may however be representative of a subclass of porphyry copper deposits exhibiting unusually close analogies with geothermal systems

hydrothermal evolution and ore precipitation of the no 2 porphyry cu au deposit in the xiongcun district tibet evidence from cathodoluminescence fluid inclusions and isotopes abstract the no 2 porphyry cu au deposit in the xiongcun district forms part of the gangdese porphyry copper belt of tibet this study clarifies the fluid evolution and ore precipitation mechanisms of the magmatic hydrothermal system that formed the deposit by combining the results of fluid inclusion petrography microthermometry scanning electron microscope cathodoluminescence imaging and stable isotope analyses of multiple quartz dominated veins four distinct sets of quartz dominated veins and eight generations of quartz q1 q8 within the veins were identified namely from early to late early barren quartz veins v1 comprised of equigranular cl bright q1 quartz quartz pyrite chalcopyrite magnetite veins v2 containing early equigranular cl bright q1 quartz and later cl gray or cl dark q2 3 q2 q3 quartz grains intergrown with cu fe sulfides quartz molybdenite pyrite chalcopyrite veins v3 comprised of quartz grains q4 q6 characterized by subhedral comb like textures with well developed oscillatory growth zoning and late quartz veins v4 containing cl gray q7 quartz with euhedral growth zones and later cl dark q8 quartz fluid inclusions in these veins can be classified into six types b40 b40h b80 b15h b15h and b15 the b40 and b40h inclusions b80 inclusions and b15 b15h and b15h inclusions contain vapor bubbles occupying 30 60 vol 70 vol and 5 25 vol respectively in addition b15h b15h and b40h inclusions contain transparent daughter minerals halite and in some cases sylvite raman spectra showed that co2 is only present in b40 and b80 inclusions in the q1 quartz in v1 and v2 veins the dominant type of inclusions is b40 which have homogenization temperatures th of 278 c 389 c peaking at 310 c 330 c and salinities of 2 0 12 8 wt nacl equiv in q2 3 quartz in v2 veins all inclusion types were observed these were trapped at temperatures of approximately 325 c 340 c and had salinities of 1 8 69 7 wt nacl equiv in v3 veins only b15h and b15 inclusions were observed which had th values of 171 c 320 c peaking at 240 c 260 c and 173 c 317 c peaking at 210 c 230 c and salinities of 28 7 33 9 wt nacl equiv and 5 6 23 1 wt nacl equiv respectively in v4 veins only b15 inclusions were observed primary b15 inclusions in v4 veins yielded th values of 166 c 229 c peaking at 170 c 200 c and salinities of 5 1 17 1 wt nacl equiv the 3he 4he and 40ar 36ar ratios of the fluid inclusions exhibited the ranges of 0 08 0 84 ra and 451 3 1567 8 respectively and the 18ofluid and dfluid values varied from 3 2 to 5 8 and 92 8 to 80 3 respectively by integrating all results from the fluid inclusion cathodoluminescence and isotopic analyses we conclude that the initial ore forming fluids of the no 2 deposit were low salinity co2 rich single phase fluids of magmatic origin subsequently fluid immiscibility developed in the initial ore forming fluids generating hypersaline liquid and low salinity vapor phases and leading to the separation of a co2 phase plus chalcopyrite precipitation from the fluids as meteoric water was injected into the hydrothermal system the ore forming fluids gradually evolved to become meteoric water dominated low temperature low salinity and co2 poor in addition fluid cooling due to the meteoric water input resulted in molybdenite precipitation

evidence of fluid inclusions for two stages of fluid boiling in the formation of the giant shapinggou porphyry mo deposit dabie orogen central china abstract the shapinggou porphyry mo deposit one of the largest mo deposits in asia is located in the dabie orogen central china hydrothermal alteration and mineralization at shapinggou can be divided into four stages i e stage 1 ore barren quartz veins with intense silicification followed by stage 2 quartz molybdenite veins associated with potassic alteration stage 3 quartz polymetallic sulfide veins related to phyllic alteration and stage 4 ore barren quartz calcite pyrite veins with weak propylitization hydrothermal quartz mainly contains three types of fluid inclusions namely two phase liquid rich type i two or three phase gas rich co 2 bearing type ii and halite bearing type iii inclusions the last two types of fluid inclusions are absent in stages 1 and 4 type i inclusions in the silicic zone stage 1 display homogenization temperatures of 340 to 550 c with salinities of 7 9 16 9 wt nacl equivalent type ii and coexisting type iii inclusions in the potassic zone stage 2 which hosts the main mo orebodies have homogenization temperatures of 240 440 c and 240 450 c with salinities of 34 1 50 9 and 0 1 7 4 wt nacl equivalent respectively type ii and coexisting type iii inclusions in the phyllic zone stage 3 display homogenization temperatures of 250 345 c and 220 315 c with salinities of 0 2 6 5 and 32 9 39 3 wt nacl equivalent respectively type i inclusions in the propylitization zone stage 4 display homogenization temperatures of 170 to 330 c with salinities lower than 6 5 wt nacl equivalent the abundant co 2 rich and coexisting halite bearing fluid inclusion assemblages in the potassic and phyllic zones highlight the significance of intensive fluid boiling of a nacl co 2 h 2 o system in deep environments up to 2 3 kbar for giant porphyry mo mineralization hydrogen and oxygen isotopic compositions indicate that ore fluids were gradually evolved from magmatic to meteoric in origin sulfur and lead isotopes suggest that the ore forming materials at shapinggou are magmatic in origin re os dating of molybdenite gives a well defined 187 re 187 os isochron with an age of 112 7 1 8 ma suggesting a post collisional setting

porphyry to epithermal transition in the altar cu au mo deposit argentina studied by cathodoluminescence la icp ms and fluid inclusion analysis the middle to late miocene altar porphyry cu au mo deposit located in the andean main cordillera of san juan province argentina is characterized by the superposition of multiple vein generations consisting of both porphyry type and high sulfidation epithermal style alteration and mineralization we constrain the physical and chemical evolution of the hydrothermal fluids that formed this deposit based on description and distribution of vein types scanning electron microscopy cathodoluminescence cl imaging trace elements in quartz veins and fluid inclusion microthermometry quartz cl textures and trace elements chiefly li al ti and ge differentiate among quartz generations precipitated during different mineralization and alteration events early quartz chalcopyrite pyrite veins and quartz molybdenite veins a and b veins show considerable complexity and were commonly reopened and some underwent quartz dissolution early quartz chalcopyrite pyrite veins a veins are dominated by equigranular bright cl quartz with homogeneous texture most of these veins contain higher ti concentrations than any other vein type average 100 ppm and have low to intermediate al concentrations 65 448 ppm quartz molybdenite b veins and chlorite rutile hematite c veins veins contain quartz of intermediate cl intensity that commonly shows growth zones with oscillatory cl intensity quartz from these veins has intermediate ti concentrations 20 ppm and al concentrations similar to those of a veins quartz from later quartz pyrite veins with quartz muscovite tourmaline halos d veins has significantly lower cl intensity low ti 15 ppm and elevated al concentrations up to 1 000 ppm and typically contains euhedral growth zones late veins rich in sulfides and sulfosalts show cl textures typical of epithermal deposits dark cl quartz crustiform banding and euhedral growth zones quartz from these veins typically contains less than 5 ppm ti and al li and ge concentrations are elevated relative to other vein types based on experimentally established relationships between ti concentration in quartz and temperature the decrease in ti content in successively later quartz generations indicates that the temperature of the hydrothermal fluids decreased through time during the evolution of the system vein formation at altar occurred at progressively lower pressure shallower paleodepth and lower temperature under lithostatic pressures the magma supplied low salinity aqueous fluids at depths of 6 to 6 8 km pressures of 1 6 1 8 kbar and temperatures of 670 to 730 c first quartz generation of early quartz chalcopyrite pyrite veins this parental fluid episodically depressurized and cooled at temperatures and pressures below the brine vapor solvus quartz molybdenite veins precipitated from fluids at temperatures of 510 to 540 c and pressures of 800 to 1 000 bars corresponding to depths of 3 to 3 7 km under lithostatic pressures further cooling of hydrothermal fluids to temperatures between 425 and 370 c under hydrostatic pressures of 200 to 350 bars produced pyrite quartz veins and pervasive quartz muscovite tourmaline and illite alteration that overprinted the early hydrothermal assemblages late veins rich in sulfides and sulfosalts that overlapped the deep and intermediate high temperature veins formed from fluids at temperatures of 250 to 280 c and pressures of 20 to 150 bars the epithermal siliceous ledges formed from low temperature fluids 230 c at hydrostatic pressures of 100 bars corresponding to depths of 1 km

alteration and mineralization at the zhibula cu skarn deposit gangdese belt tibet abstract the zhibula cu skarn deposit contains 0 32 mt cu metal with an average grade of 1 64 and is located in the gangdese porphyry copper belt in southern tibet the deposit is a typical metasomatic skarn that is related to the interaction of magmatic hydrothermal fluids and calcareous host rock stratiform skarn orebodies occur at the contact between tuff and marble in the lower jurassic yeba formation alteration zones generally grade from a fresh tuff to a garnet bearing tuff a garnet pyroxene skarn and finally to a wollastonite marble minor endoskarn alteration zonations are also observed in the causative intrusion which grade from a fresh granodiorite to a weakly chlorite altered granodiorite a green diopside bearing granodiorite and to a dark red brown garnet bearing granodiorite prograde minerals which were identified by electron probe microanalysis include andradite grossularite of various colors e g red green and yellow and green diopside retrograde metamorphic minerals overprint the prograde skarn and are mainly composed of epidote quartz and chlorite the ore minerals consist of chalcopyrite and bornite followed by magnetite molybdenite pyrite pyrrhotite galena and sphalerite three types of fluid inclusions are recognized in the zhibula deposit including liquid rich two phase inclusions type l vapor rich two phase inclusions type v and daughter mineral bearing three phase inclusions type s as the skarn formation evolved from prograde stage i to early retrograde stage ii and later retrograde stage iii the ore forming fluids correspondingly evolved from high temperature 405 667 c high salinity up to 44 0 wt nacl equiv and high pressure 500 600 bar to low moderate temperature 194 420 c moderate high salinity 10 1 18 3 and 30 0 44 2 wt nacl equiv and low moderate pressure 250 350 bar isotopic data of 34 s 0 1 to 6 8 estimated 34 s fluids 0 7 d h2o 91 to 159 and 18 o h2o 1 5 to 9 2 suggest that the ore forming fluid and material came from magmatic hydrothermal fluids that were associated with miocene zhibula intrusions fluid immiscibility likely occurred at the stage i and stage ii during the formation of the skarn and mineralization fluid boiling occurred during the stage iii which is the most important cu deposition mechanism for the zhibula deposit

origin and evolution of hydrothermal fluids in the taochong iron deposit middle lower yangtze valley eastern china evidence from microthermometric and stable isotope analyses of fluid inclusions abstract the middle lower yangtze river valley is one of the most important metallogenic belts in china hosting numerous cu fe au mo deposits the taochong deposit is located in the northern part of the fanchang iron ore district of the middle lower yangtze river metallogenic belt the fe orebody is hosted by middle carboniferous to lower permian limestones skarns and fe orebodies occur as tabular bodies along interlayer gliding faults at some distance from the inferred granitic intrusions field evidence and petrographic observations indicate that the three stages of hydrothermal activity the skarn iron oxide main mineralization stage and carbonate stages all contributed to the formation of the taochong iron deposit the skarn stage is characterized by the formation of garnet and pyroxene with high temperature hypersaline hydrothermal fluids with isotopic compositions similar to those of typical magmatic fluids these fluids were probably generated by the separation of brine from a silicate melt instead of the product of aqueous fluid immiscibility the iron oxide stage coincides with the replacement of garnet and pyroxene by actinolite chlorite quartz calcite and hematite the hydrothermal fluids at this stage are represented by saline fluid inclusions that coexist with vapor rich inclusions with anomalously low d values 66 to 94 the decrease in ore fluid 18 o water with time and decreasing depth is consistent with the decreases in fluid salinity and temperature the fluid d values also show a decreasing trend with decreasing depth both fluid inclusion and stable isotopic data suggest that the ore fluid during the main period of mineralization was evolved by the boiling of various mixtures of magmatic brine and meteoric water this process was probably induced by a drop in pressure from lithostatic to hydrostatic the carbonate stage is represented by calcite veins that cut across the skarn and orebody locally producing a dense stockwork this observation indicates the veins formed during the waning stages of hydrothermal activity the fluids from this stage are mainly represented by a variety of low salinity fluid inclusions as well as fewer high salinity inclusions these particular fluids have the lowest 18 o water values 2 2 to 0 4 and a wide of range of d values 40 to 81 which indicate that they were originated from a mixture of residual fluids from the oxide stage various amounts of meteoric water and possibly condensed vapor low temperature boiling probably occurred during this stage we also discuss the reasons behind the anomalously low d values in fluid inclusion water extracted by thermal decrepitation from quartz at high temperatures and suggest that calcite data provide a possible benchmark for adjusting low d values found in quartz intergrown with calcite

geology chronology fluid inclusions and h o s isotopic compositions of the hongyuntan magnetite deposit eastern tianshan nw china abstract the hongyuntan magnetite deposit which is located in the aqishan yamansu belt of eastern tianshan xinjiang is hosted within carboniferous submarine volcanic sedimentary sequences the deposit is characterized by five metallogenic stages stage i garnet diopside stage ii magnetite tremolite chlorite pyrite stage iii magnetite quartz albite actinolite stage iv pyrite quartz epidote and stage v hematite limonite pyrite associated with magnetite formed during the stage ii has a re os isochron age of 324 31 ma four types of fluid inclusions were observed in the mineral assemblages namely two phase liquid and vapor inclusions multi phase daughter mineral bearing inclusions multi phase co2 bearing inclusions and monophase vapor inclusions microthermometry data reveal that the ore forming fluids evolved from high temperature average 532 5 c and high salinity average 26 9 wt nacleqv fluids to moderate low temperature average 203 6 c and low salinity 5 07 wt nacleqv fluids magnetite precipitation may have been greatly assisted by mixing and boiling in stage ii and stage iii respectively the hydrogen and oxygen isotopic values of stage i garnet dv smow 107 9 to 76 7 18ofluid 6 4 10 7 and stage iii quartz dv smow 85 5 to 83 2 18ofluid 3 8 4 7 indicate that the ore forming fluids were dominated by magmatic water whereas fluid mixing occurred during stage ii dv smow 117 3 to 112 6 18ofluid 3 3 5 7 and stage iv dv smow 115 2 to 58 5 18ofluid 1 3 to 4 5 the variable 34s values of pyrite 3 8 to 4 7 and 18omgt values of magnetite 0 6 to 4 1 suggest that they were not sourced from a single reservoir the hongyuntan magnetite deposit is spatially and temporally associated with volcanism and may be genetically related to it the fluid inclusions and isotopic compositions of this deposit indicate that its ore forming fluid was derived from the exsolution of deep seated magmas and that fluid mixing could have effectively triggered the deposition of ore forming materials multiple periods of volcanic activity could have incorporated additional heat and ore metals into the ore forming system based on our data we conclude that the origin of the hongyuntan magnetite deposit is related to the volcanism in the carboniferous period

genesis and evolution of the leimengou porphyry mo deposit in west henan province east qinling dabie belt china constraints from hydrothermal alteration fluid inclusions and stable isotope data abstract the leimengou mo deposit is located in the east qinling dabie metallogenic mo belt located at the southern margin of the north china craton the deposit is hosted within the mesozoic leimengou granite porphyry pluton and at the contact between the granite and late archean gneisses in light of mineral assemblage and crosscutting relationships among veinlets the mineralization and alteration can be classified in four distinct stages 1 a mo barren pre mineralization stage of alteration characterized by massive k feldspar alteration of the granite porphyry 2 a k feldspar quartz vein stage that formed veinlets with minor molybdenite 3 a quartz sulfide veinlet stage which is the main stage of mineralization and 4 post mineralization quartz calcite vein stage stage 1 alteration is associated with fluid inclusions of low medium salinity 2 4 13 1 wt naclequiv that homogenized at medium to high temperatures 238 476 c stage 2 mineralization is associated with fluid inclusions that homogenized at 201 389 c and that have salinities of 2 0 13 6 wt naclequiv fluid inclusions that formed during stage 3 have homogenization temperatures of 205 370 c and corresponding salinities of 1 0 17 6 wt naclequiv to 31 4 40 6 wt naclequiv indicative of fluid immiscibility and mixing of hydrothermal fluids with meteoric water stage 4 h2o nacl fluids were trapped at lower temperatures 148 246 c and have salinities of 1 7 7 9 wt naclequiv stages 1 to 4 have calculated 18ofluid values of 3 6 4 3 2 7 2 8 0 6 2 3 and 3 2 to 3 8 respectively with dfluid values of 72 to 80 83 to 90 68 to 82 and 81 to 90 respectively these results are consistent with the fluid inclusion data outlined above and suggest that early fluids were exsolved from the granitic magma and underwent progressive mixing with meteoric water molybdenum was initially transported from the crystallizing magma in a hot alkaline and oxidized fluid while decreasing temperatures and ph water rock interaction and fluid immiscibility during fluid ascent resulted in its precipitation and deposition

new metallogenic model of telescoped eocene miocene au u epithermal mineral deposit in the placer de guadalupe district chihuahua mexico abstract the chronological repartition of mineral deposits in mexico and the southern usa coincides with the distribution of the three main volcanic pulses of the sierra madre occidental these pulses are eocene to early miocene in age suggesting that a broad migration occurred from northwest to southeast where the last ignimbrite flare up occurred the most fertile event occurred from 36 to 28 ma and produced all of the largest ag au mining districts the placer de guadalupe au u district contain a unique association of metals with high variations in their u au ratios that are not common worldwide the uraninite population dated by wells 1930 yielded an age of ca 36 ma which is comparable to that of the volcanic intrusions and dykes dated in the district yielding ages of ca 36 ma altered uraninite cemented by gold sheets provide an age of 21 ma which is interpreted to be the age of the gold epithermal event studies of fluid inclusions in the quartz and calcite cements formed in the gold event indicate the presence of immiscible magmatic brines and co2 homogenization temperatures by halite melting range from 268 c to 305 c and 266 6 c to 283 c with salinities ranging from 35 9 to 38 9 and 36 0 to 37 5 wt eq nacl in the quartz and calcite stages respectively c o isotopic compositions of u and au calcite cements suggest a trend of low temperature alteration caused by hydrothermal fluids these c o isotopes suggest that during the gold event water rock interaction processes occurred between magmatic fluids and the carbonate host rock ree enrichment in the u calcite cement suggests that la ce enriched carbonatite volcanic formations participated in the mineralizing process the u mineralization event was controlled by 1 a metal and heat source in this case late eocene volcanism and in particular a carbonatite volcanic event 2 an efficient transport mechanism for the large scale input of meteoric water which was channeled heated and u enriched into reactivated crustal eocene faults from a deep u source to a shallow sedimentary chemical trap 3 an effective trap which is represented in this study by the presence of an organic matter rich sedimentary formation the gold mineralization event was characterized by the miocene extensional peak coupled with asthenospheric upwelling which facilitated the melting metamorphism of the lower crust and the expulsion and transport of large amounts of co2 bearing fluids to a shallow crustal level through the reactivated crustal laramide thrust faults the fluids interactions with the entire stratigraphic column from the grenvillian to the late triassic basement favored the leaching of gold and the enrichment of co2 bearing fluids gold deposition appears to be related to boiling but was ultimately favored by water rock interaction with u mineralization and the upper plomosas shale study of the au u placer de guadalupe deposit reveals evidence of a new miocene metallogenic event in central and northern mexico its genetic relationship with the basin and range bnr and rio gande rift rgr in usa and its transition from post orogenic to miocene intraplate extension in mexico provides a new perspective regarding the exploration of miocene gold epithermal deposits in northern mexico and the southern usa

fluid inclusion and stable isotope constraints on the genesis of the world class zhuxi w cu skarn deposit in south china abstract scheelite mineralization accompanied by traces of chalcopyrite occurs in skarn systems in the giant zhuxi deposit in the taqian area northeastern jiangxi province south china three paragenetic stages of skarn with ore deposition have been recognized the prograde skarn retrograde skarn and hydrothermal quartz sulfide stages microthermometer data showed that the prograde skarn were formed at relatively high temperatures 450 500 c and pressures 0 97 1 38 kbars and low oxidation to weak reduction conditions the raman microprobe data demonstrated that the fluid of the stage was h2o nacl kcl cacl2 ch4 c2h4 system the retrograde skarn alteration formed at 1 24 kbars and relatively medium temperatures 280 320 c and the ore forming fluid was h2o nacl kcl cacl2 system during the hydrothermal quartz sulfide stage the fluids were methane bearing aqueous low salinity 0 9 8 0 wt nacleqv and low homogeneous temperature 160 240 c correspondingly the minimum fluid pressures were evaluated between 75 and 252 bars the h and o isotopic values from the prograde and retrograde stages implied that the mineralizing fluids were derived principally from magmatic water the mineralizing fluids in the quartz sulfide hydrothermal stages were mingled with magmatic water with some meteoric water as well as minor contributions of wall rocks the sulfur and lead isotopes indicated that ore forming materials including sulfur lead copper zinc and iron in the zhuxi deposit were derived from local magmatic and sedimentary sources geological fluid inclusion and isotopic data supported that the zhuxi deposit is a typical skarn type w cu deposit related to ilmenite series granitic rocks and formed in a compressional tectonic environment

ore geology and fluid inclusions of the hucunnan deposit tongling eastern china implications for the separation of copper and molybdenum in skarn deposits abstract the hucunnan ore deposit is a representative skarn cu mo deposit in the tongling district an important ore district of the renowned middle lower yangtze river metallogenic belt of china the deposit shows distinct zonation of metals with cu mineralization distributed mainly in the exoskarn zone at shallow depths and mo mineralization occurring chiefly in the endoskarn zone located at deeper depths field evidence and petrographic observations indicate that the ore forming processes can be divided into the skarn quartz molybdenite quartz chalcopyrite and carbonate stages five types of fluid inclusions fis are present in the deposit solid bearing type 1 liquid rich type 2 vapor rich type 3 pure vapor type 4 and co 2 bearing type 5 the skarn stage contains mainly type 1 and 2 but also minor type 3 and 4 fis the fis display homogenization temperatures of 434 570 c and salinities of 2 07 66 0 wt nacl equiv the existence of hematite daughter minerals in the type 1 inclusions together with the presence of magnetite in skarn implies that the skarn stage fluid was oxidizing the skarnization of the granodiorite porphyry is commonly accompanied by potassic alteration suggesting that the fluids were rich in alkali similar to the skarn stage the quartz molybdenite stage contains type 1 and 2 and minor type 3 and 4 fis which yield homogenization temperatures of 280 458 c and salinities of 1 40 54 2 wt nacl equiv the presence of sulfide instead of hematite daughter minerals in the type 1 inclusions in quartz molybdenite veins associated with sericitization indicates that the fluids of the quartz molybdenite stage were more reducing and more acidic than the fluids in the skarn stage the decrease in oxygen fugacity and increase in acidity could have resulted from magnetite crystallization and the consumption of alkali cations and oh respectively during the skarn stage the quartz chalcopyrite stage contains all types of fis which show homogenization temperatures of 203 392 c and salinities of 1 22 46 6 wt nacl equiv observations of hematite bearing type 1 fis in quartz chalcopyrite veins containing anhydrite associated with biotitization suggest that the fluids of the quartz chalcopyrite stage were oxidizing and alkali rich probably on account of the inflow of meteoric water and boiling in an open system in the carbonate stage only type 2 fis are present these fis yield the lowest homogenization temperatures of 156 276 c and the lowest salinities of 1 05 12 3 wt nacl equiv microthermometry and h o isotope data indicate that the ore forming fluids were dominated by magmatic water in the early stages skarn and quartz molybdenite stages and that the magmatic water gradually mixed with circulating meteoric water during the late stages quartz chalcopyrite and carbonate stages the coexistence of saline and vapor rich fis as internal trails or clusters within individual crystals with similar homogenization temperatures but contrasting salinities and homogenization modes to the liquid and vapor respectively in the first three stages strongly suggests that three episodes of fluid boiling occurred in these stages as further supported by the hydrogen isotopic compositions of the fluids which are lower than those of magmatic water based on the above data we conclude that temporal changes in redox conditions acidity and temperature in the mineralizing fluids resulted in the temporal separation of cu and mo by selective sulfide precipitation in the hucunnan skarn deposit the competition among metals e g mo and cu for sulfur in magmatic fluids along with vapor brine immiscibility fluid boiling are major factors that contributed to the spatial separation of cu and mo in the deposit

the origin of ch4 rich fluids in reduced porphyry skarn cu mo au systems abstract although most of the methane on earth is of biogenic origin significant abiogenic methane has been identified in a variety of geological environments moreover the presence of methane has been reported recently in fluid inclusions from a number of reduced porphyry deposits the genesis of this methane however remains poorly understood here we present results of a study of magma exsolved ch4 rich aqueous fluid inclusions in the seleteguole reduced porphyry skarn cu mo au deposit nw china four types of fluid inclusions namely intermediate density two phase aqueous inclusions low density vapor inclusions brine inclusions and aqueous liquid inclusions have been distinguished on the basis of the phases present at room temperature the intermediate density inclusions were trapped as a single phase and contain 3 8 10 4 mol kg ch4 corresponding to an oxygen fugacity between fmq 1 and fmq 0 5 this attests to the remarkably reduced nature of the fluid the 13c value of the ch4 hosted fluid inclusions ranges from 29 4 to 19 1 pdb which distinguishes this methane from biogenic methane indeed the high homogenization temperature of the ch4 rich inclusions 400 c implies that the ch4 was exsolved directly from the magma given the environment in which the magma was likely generated i e at or immediately above a subducting plate we propose that the methane was produced by reactions involving organic matter bearing carbonate rocks in the subduction zone although cu mo and au in most porphyry systems are interpreted to have been transported under oxidizing conditions our results indicate that reduced aqueous liquids and vapors are also capable of transporting appreciable concentrations of these metals

geology fluid inclusions and h o s pb isotopes of the chigou porphyry cu deposit in southern qinling central china implication for ore genesis abstract the chigou porphyry cu deposit is located in eastern segment of the southern qinling metallogenic belt on the southern margin of the central china orogenic belt copper mineralization is associated with quartz diorite quartz diorite porphyry and granite porphyry and occurs as veins veinlets disseminations or veinlet disseminations within host porphyries ore forming process could be divided into three stages stage i quartz k feldspar pyrite chalcopyrite stage ii quartz chlorite chalcopyrite molybdenite and stage iii quartz calcite pyrite four types of fluid inclusions fis were distinguished in quartz bearing veins including vapor rich two phase v type liquid rich two phase l type hypersaline h type and co2 rich c type inclusions the fis were homogenized at temperatures of 330 473 c for stage i 174 345 c for stage ii and 128 272 c for stage iii with corresponding salinities of 3 8 53 6 wt nacl equiv 1 4 15 1 wt nacl equiv and 0 4 7 7 wt nacl equiv respectively hydrogen and oxygen isotope data indicate that the ore forming fluids have a dominant magma signature and were diluted by meteoric water during the late stage chalcopyrite and pyrite from different stages record a narrow range of 34s values from 0 2 to 2 consistent with the sulfur isotopic values of typical magmatic hydrothermal system chalcopyrite has similar 206pb 204pb 207pb 204pb and 208pb 204pb ratios to those of porphyry intrusions all stable and radiogenic isotope results reveal that the ore forming components i e metal and sulfur were sourced from a magmatic reservoir with some crustal materials laser raman micro spectroscopy data and fluid inclusion analytical results suggest that the chigou deposit was formed by an initially high to intermediate temperature high oxygen fugacity fo2 and co2 rich fluid system at an estimated depth of 0 7 2 1 km decreases in temperature and fo2 as well as fluid boiling were critical factors controlling sulfide precipitation at chigou

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

precious metal distribution and fluid inclusion petrography of the elatsite porphyry copper deposit bulgaria the elatsite porphyry copper deposit occurs in an island arc setting hosted by late cretaceous monzonitic monzodioritic porphyry stocks which were emplaced into precambrian cambrian phyllites trace element data of the late cretaceous intrusive rocks suggest that they are i type volcanic arc granitoids two main ore mineral assemblages are distinguished 1 magnetite bornite chalcopyrite and 2 chalcopyrite pyrite the first one is linked to potassic propylitic and the second to phyllic argillic alteration minor ore minerals are hematite molybdenite sphalerite pyrrhotite marcasite hessite and solid solutions of linnaeite siegenite carrollite tetrahedrite tennantite clausthalite galena gold electrum and merenskyite moncheite precious metal contents are relatively high throughout the deposit but au pd and pt are concentrated more strongly in the magnetite bornite chalcopyrite assemblage average grades of au ag pd and pt calculated for the 0 33 cu ore body are 0 96 0 19 0 007 and 0 002 g t respectively analyses of flotation concentrates revealed 25 6 cu and ag au pd and pt contents of 33 0 13 6 0 72 and 0 15 g t respectively the copper mineralisation at elatsite took place at pressures of 120 to 300 bar corresponding to depths of formation of 1 to 3 km under hydrostatic conditions the precious metals were probably transported jointly as chloride complexes in highly saline magmatic hydrothermal solutions the fluids had temperatures of 340 to 700 c and salinities of 28 to 64 nacl and mixed with meteoric water

modification of a palaeoproterozoic porphyry like system integration of structural geochemical petrographic and fluid inclusion data from the aitik cu au ag deposit northern sweden the aitik cu au ag deposit in the gallivare area in northern sweden is sweden s largest sulphide mine with an annual production of 35 mt of ore and the biggest open pit operation in northern europ

timing of the yuchiling giant porphyry mo system and implications for ore genesis the yuchiling mo deposit is a recently discovered giant porphyry system in the east qinling mo belt china its apparent causative intrusion i e the yuchiling granite porphyry is the youngest intrusion phase 4 of the heyu multiphase granite batholith which was emplaced between 143 and 135 ma new robust constraints on the formation of the yuchiling porphyry mo system are provided by combined zircon u pb biotite 40ar 39ar and molybdenite re os dating zircon grains from the mo mineralized granite porphyry yield weighted 206pb 238u age of 134 0 1 4 ma n 19 2 error mswd 0 30 magmatic biotite from the same sample yield a 40ar 39ar plateau age of 135 1 1 4 ma 2 error and an inverse isochron age of 135 6 2 0 ma n 7 2 error mswd 10 8 which are effectively coincident with the zircon u pb age within analytical error three pulses of mineralization can be deduced from the molybdenite re os ages namely 141 137 and 134 ma which agree well with the zircon u pb ages of granitic phases 1 2 and the yuchiling porphyry phase 4 respectively these well constrained temporal correlations indicate that mo mineralization was caused by pulses of granitic magmatism and that the ore forming magmatic hydrothermal activity responsible for the yuchiling porphyry mo system lasted about 8 ma the yuchiling mo deposit represents a unique style of porphyry mo system formed in a post collision setting and associated with f rich high k calc alkaline intrusions which differ from convergent margin associated porphyry mo deposits

copper mineralization around the ahar batholith north of ahar nw iran evidence for fluid evolution and the origin of the skarn ore deposit abstract this investigation presents and interprets fluid inclusion data from different lithological units of the cu skarn deposits at mazraeh north of ahar azarbaijan nw iran the results provide an assessment of the p t conditions and mineral fluid evolution and suggest new exploration parameters five types of inclusions are recognized from quartz and garnet the temperature of homogenization of type i inclusions with daughter minerals halite and sylvite ranges from 312 to 470 c with total salinity of 52 to 63 wt nacl equiv type ii and iii inclusions with halite have homogenization temperatures of 230 to 520 c and salinity of 31 to 50 wt nacl equiv the salinity of types iv and v biphase liquid vapor inclusions based on their final ice melting temperature varies between 10 2 to 20 8 wt nacl equiv t h vs salinity plots of inclusions show that the salinity of the fluids correlates positively with temperature the inclusions formed at low pressure changes in the temperature and salinity of the fluids can be reconstructed from the inclusions highly saline high temperature fluids were most abundant during the main chalcopyrite ore forming phase in the skarn and mineralized quartz veins low salinity aqueous fluids were abundant in barren veins in which there is no evidence for early hot high salinity brine and might have resulted from late stage dilution and mixing of hydrothermal fluids with meteoric water based on petrographic features and fluid inclusion data early stage magnetite deposition is related to boiling of fluid at temperatures of about 500 c at a later stage boiling at temperatures of around 320 to 400 c favored the deposition of sulfides and fe mobility was decreased at these lower temperatures the following inclusion characteristics may be used as exploration parameters in the mazraeh area i presence of high temperature salt bearing inclusions with t h between 300 and 500 c ii high salinity fluid inclusions and iii inclusions showing evidence of boiling of the fluid in addition the presence of magnetite is an important exploration parameter

the evolution of a porphyry cu au deposit based on la icp ms analysis of fluid inclusions bajo de la alumbrera argentina the chemical and physical evolution of magmatic to hydrothermal processes in the porphyry cu au deposit of bajo de la alumbrera northwestern argentina has been reconstructed with a quantitative fluid inclusion study fluid inclusion petrography microthermometry and single inclusion microanalysis by excimer laser ablation inductively coupled plasma mass spectrometry la icp ms are combined to determine the evolution of pressure temperature and ore metal concentrations including cu and au in the fluids complementary hydrogen and oxygen isotope analyses are used to further constrain the water sources in the evolving system the combined data provide a new level of insight into the mechanisms of metal sourcing and ore mineral precipitation in a porphyry style magmatic hydrothermal system based on previously reported observations of the igneous geology alteration geochemistry and veining history of the subvolcanic porphyries at alumbrera the distribution of fluid inclusion types in space and time is documented six major inclusion types are distinguished the highest temperature brine inclusions up to 750 c p 1 kbar are mainly recorded in barren quartz magnetite veins in the core of the alteration system these polyphase brine inclusions halite sylvite multiple opaque and transparent daughter crystals are interpreted as the most primitive magmatic fluid recorded at the level of the deposit they are of moderately high salinity 50 60 wt nacl equiv dominated by nacl kcl and fecl 2 and contain on average 0 33 wt percent cu and 0 55 ppm au upon cooling and decompression these saline liquids exsolve a vapor phase which is preferentially enriched in cu relative to its main salt components but probably plays a minor role in the formation of this particular deposit because of the inferred small mass fraction of vapor cooling and decompression from the highest initial p t conditions down to about 450 c causes magnetite k silicate alteration but no saturation in au or cu sulfides as recorded by continually high ore metal concentrations in the fluid inclusions coprecipitation of cu and au as chalcopyrite and native gold some early bornite occurs over a narrow range of decreasing fluid temperature with cooling from 400 to 305 c the cu concentration in the brine drops by about one order of magnitude to less than 0 07 wt percent without a proportional decrease in major salt components ore mineral precipitation extracts 85 percent of the cu and au from the fluid it is associated with potassic alteration as shown by a concomitant decrease in the k na ratio of the cooling magmatic brine and by an increase in its ba and sr concentrations elements which are probably liberated in the destruction of calcic igneous minerals the fluid chemical data demonstrate that the metal ratios in this and probably many other porphyry style ore deposits are primarily controlled by the magmatic source of the ore brines on the other hand the final hypogene ore grade of the deposit is controlled by the efficiency of ore mineral precipitation at alumbrera metal extraction is governed by the efficiency of cooling a high flux of magmatic fluid within a small rock volume dilution of residual magmatic fluids as recorded by aqueous fluid inclusions of decreasing salinities and temperatures below 295 c follows after the main stage of copper introduction and is associated with feldspar destructive phyllic alteration geometric relationships fluid analyses and stable isotope data together indicate that phyllic alteration results from postmineralization hydrothermal activity involving minor mixing between meteoric water residual brine and a waning input of magmatic vapor

porphyry mo and epithermal au ag pb zn mineralization in the zhilingtou polymetallic deposit south china the zhilingtou polymetallic deposit south china provides an excellent opportunity to investigate the magmatic hydrothermal evolution of the porphyry mo to epithermal au ag pb zn ore spectrum new zircon u pb sphalerite 40ar 39ar and pyrite rb sr ages together with previous molybdenite re os ages indicate that the granitic magmatism and mo au ag pb zn mineralization were coeval and cogenetic in the early cretaceous 113 ma fluid inclusions and h o isotope results have established the evolution from an early high temperature h2o nacl magmatic fluid system mo mineralization to a medium temperature mixed fluid system of magmatic and meteoric water au ag mineralization to a peripheral late stage low temperature h2o nacl meteoric water fluid system epithermal au ag pb zn mineralization moreover the sulfur isotopic compositions 34s 2 1 7 8 of the sulfide minerals confirm a genetic link to the granitic magma lead isotope data from pyrite and the granite rhyolite porphyries are similar indicating that they share a common pb source the geochronological geochemical and isotopic lines of evidences consistently suggest that the porphyry mo and epithermal au ag pb zn mineralization formed in one magmatic hydrothermal system the porphyry epithermal mineralization model for zhilingtou has significant importance for prospecting work in south china where mo and associated pb zn ag resources are abundant

fluid inclusion and h o c isotope geochemistry of the yaochong porphyry mo deposit in dabie shan china a case study of porphyry systems in continental collision orogens the yaochong porphyry mo deposit in xinxian county henan province china is located in the hong an terrane that is the western part of the dabie orogen the dabie orogen is part of a 1 500 km long triassic continental collision belt between the north china block and the south china block four types of vein are present paragenetically from early to late they are as follows stage 1 quartz k feldspar pyrite magnetite vein stage 2 quartz k feldspar molybdenite pyrite vein stage 3 quartz polymetallic sulfides k feldspar vein and stage 4 quartz carbonate fluorite vein four compositional types of fluid inclusion pure co2 co2 bearing aqueous and solid bearing are present in quartz from the first three stages only low salinity aqueous fluid inclusions occur in quartz from the last stage all the estimated salinities are 13 1 wt nacl eq and no halite crystals were identified homogenization temperatures for the fluid inclusions from stages 1 to 4 are in the ranges of 262 501 202 380 168 345 and 128 286 c respectively and estimated depths decrease from 6 9 to 8 9 km through 6 2 7 2 to 4 7 km quartz separates from the veins yielded a 18o value of 7 7 11 2 corresponding to 18oh2o values of 1 3 to 6 9 using temperature estimates from fluid inclusion data dh2o values of fluid inclusion vary from 80 to 55 and 13cco2 from 2 3 to 2 7 suggesting that the ore fluids evolved from magmatic to meteoric sources we conclude that the ore forming fluid system at yaochong was initially high temperature high salinity and co2 rich and then progressively evolved to co2 poor lower salinity and lower temperature by mixing with meteoric water which results in ore precipitation

crystallization and degassing in the basement sill mcmurdo dry valleys antarctica the basement sill is part of the ferrar large igneous province exposed in the mcmurdo dry valleys antarctica the sill is 330 m thick in the bull pass area and 450 m thick in the dais area 12 km to the west and is characterized by phenocryst free lower and upper margins and an orthopyroxene rich central tongue opx 1 5 mm in size halogen variations in apatite from a suite of samples collected along vertical transects through the sill were examined to evaluate the process of crystallization induced degassing i e second boiling and its effects on magma chemistry apatite grains from any given sample are generally unzoned with respect to cl and f concentrations but may vary by 20 30 mol in the halogen site between grains overall average cl f mass ratios increase with height from the lower margin to the center of the sill and then decrease to near zero towards the top margin where the rocks are relatively oxide rich the cl f trend parallels those of bulk mgo and grain size the upper margin contains abundant mafic pegmatoids and the apatite in these segregations has lower cl f ratios compared with that in the host rocks although ree show no measurable difference numerical modeling illustrates that a cooling and crystallizing sill initially develops two separate vapor saturated zones at the lower and upper margins owing to the irreversible heat loss to the cooler country rock vapor separating from the lower zone migrates upward into hotter silicate liquid where it is resorbed thus increasing the cl f mass ratio of the liquid this process leads to saturation and precipitation of apatite from the liquid with a higher cl f ratio than would otherwise occur volatile enrichment can also aid compaction and grain growth in the central part of the sill in contrast the relatively fe rich cl poor nature of the upper zone rocks suggests that these rocks may have crystallized from more evolved degassed silicate liquid possibly compacted out of the underlying crystal mush in addition as vapor sourced from the lower and central parts of the sill ascends into the cooler upper zone of the sill the vapor may be localized along with late interstitial silicate liquid to form pegmatoids at temperatures at which cl is less favored in apatite and can be leached from existing apatite by the ascending vapor the latter causing the observed decrease in the cl f mass ratio of apatite in the evolved pegmatoids

ore genesis and hydrothermal evolution of the baiyinnuo er zinc lead skarn deposit northeast china evidence from isotopes s pb and fluid inclusions the baiyinnuo er zinc lead deposit 32 74 mt at 5 44 zn 2 02 pb and 31 36 g t ag located in the south segment of the great xing an range is the largest zn pb deposit in northern china skarn and orebodies mainly occur between the different units of the huanggangliang formation or within the contact zone between the intrusions and permian marble several phases of igneous rocks exposed within the mining areas and among them the yanshanian plutonic rocks which intruded into limestone of the early permian huanggangliang formation are interpreted to be the source of ore since their pb isotope compositions 206pb 204pb 18 25 18 35 207pb 204pb 15 50 15 56 and 208pb 204pb 38 14 38 32 are highly consistent with the sulfides including sphalerite galena and chalcopyrite 206pb 204pb 18 23 18 37 207pb 204pb 15 47 15 62 and 208pb 204pb 37 93 38 44 sulfur isotope values of the sulfides give a narrow 34s interval of 6 1 to 4 6 mean 5 4 n 15 suggesting the ore forming fluid is of magmatic origin three main paragenetic stages of skarn formation and ore deposition have been recognized based on petrographic observation which are the preore stage garnet clinpyroxene wollastonite magnetite sulfides the synore stage sulfides epidote quartz calcite garnet and the postore stage calcite chlorite quartz fluorite several fluid evolution episodes can be inferred from microthermometric results at the baiyinnuo er zn pb deposit 1 immiscibility preore stage coexistence of halite bearing brine inclusions s1 type 44 wt nacl equiv and vapor rich fluid inclusions v type sharing the same homogenization temperatures 470 c confirms that fluid unmixing occurred under lithostatic pressures of 400 bars 1 5 km and the brine is considered to account for most prograde skarn minerals e g clinopyroxene 2 overpressure trapping preore stage brine inclusions homogenized by halite dissolution s2 type postdated the immiscible assemblages this type of inclusions is characterized by high but variable minimum trapping pressures 150 3 000 bars relative to s1 type inclusions and can be explained as a result of entrapment under overpressuring condition 3 boiling the presence of both vapor and liquid inclusions i e v and l type in the same assemblages within synore stage quartz calcite and sphalerite indicates the occurrence of fluid boiling 350 c at hydrostatic pressures of 150 bars and depth of 1 5 km which resulted in large scale mineralization in the baiyinnuo er zn pb deposit 4 mixing with external fluids fluid inclusions scattered within postore stage calcite or secondary trails in synore stage minerals show low homogenization temperatures 260 c and both decreasing for l type and increasing for cacl2 bearing inclusions i e lc type trends for salinities as homogenization temperatures decrease implying addition of both meteoric water low temperature low salinity and basinal brines low temperature ca rich respectively systematic fluid inclusion studies also indicate that the mineralization related fluid is of magmatic origin prograde minerals formed during the preore stage fluid immiscibility while sulfides deposition occurred during the synore stage fluid boiling mixing with external fluids began as the hydrothermal system cooled to 300 c when the main metal precipitation process had ended

geology mineralization and fluid inclusion characteristics of the lermontovskoe reduced type tungsten cu au bi skarn deposit sikhote alin russia abstract the lermontovskoe deposit 48 kt wo 3 average 2 6 wo 3 0 24 cu 0 23 g t au is situated in a w sn au metallogenic belt that formed in a collisional tectonic environment this tungsten skarn deposit has a w au as bi te sb signature that suggests an affinity with reduced intrusion related au deposits the deposit is associated with an intrusion that is part of the ilmenite series high k peraluminous granitoid granodiorite to granite suite these rocks formed via mantle magma induced melting of crustal sources the deposit comprises reduced type pyroxene dominated prograde and retrograde skarns followed by hydrosilicate amphibole chlorite pyrrhotite scheelite quartz and phyllic muscovite sericite carbonate albite quartz scheelite sulfide with abundant apatite alteration assemblages fluid inclusions from the skarn assemblages indicate high temperature 500 c high pressure 1400 1500 bars and high salinity 53 60 wt nacl equiv magmatic hydrothermal fluids they were post dated by high carbonic methane dominate low salinity fluid at the hydrosilicate alteration stage these fluids boiled at 360 380 c and 1300 1400 bars the subsequent phyllic alteration started again with a high temperature 450 c high pressure 1000 1100 bars and high salinity 42 47 wt nacl equiv fluid with further incursion of high carbonic methane dominated low salinity fluid that boiled at 390 420 c and 1150 1200 bars the latest phyllic alteration included the lower temperature 340 360 c lower pressure 370 400 bars high carbonic methane dominated but with higher co 2 fraction low salinity fluid and then the low temperature 250 300 c h 2 o co 2 ch 4 nacl fluid with both fluids boiled at the deposit level the high salinity aqueous fluids are interpreted to have come from crystallizing granitoid magma whereas the reduced high carbonic fluids probably came from a deeper mafic magma source both of these fluids potentially contributed to the w au as bi te sb metal budget decreasing temperatures coupled with high aca 2 and fluid boiling promoted scheelite deposition at all post skarn hydrothermal stages the deposit is characterized by limited downdip extent of mineralized zones and abundant coarse grained muscovite quartz apatite scheelite aggregates that formed at the phyllic alteration stage together with presence of high temperature high pressure and high salinity fluids directly exsolving from crystallizing magma this suggests a root level of the mineralized magmatic hydrothermal system of reduced w skarn deposits

geology mineralization and fluid inclusion study of the kuru tegerek au cu mo skarn deposit in the middle tien shan kyrgyzstan the kuru tegerek cu au mo deposit is situated in a system of late carboniferous subduction related magmatic arcs of the middle tien shan which together constitute a metallogenic belt of cu au mo w porphyry with local skarns deposits the deposit is related to magnetite series gabbro diorite to tonalite intrusion it contains prograde magnesian and calcic skarns with abundant magnetite associated with gabbro diorite and retrograde skarn with cu mineralization formed after intrusion of tonalite subsequent propylitic alteration introduced abundant chalcopyrite and pyrrhotite and native au culminating in zones overprinting magnetite and garnet skarn later quartz muscovite carbonate veins formed after intrusion of late mafic quartz monzogabbro dikes contain chalcopyrite pyrite arsenopyrite and other sulfides and sulfosalts tellurides and native au the earliest retrograde skarn garnet contains gaseous low salinity 1 7 3 4 wt nacl eq fluid inclusions homogenizing at 460 500 c into vapor indicating that the early fluid released from crystallizing magma was a low density vapor it was followed by more saline 4 0 5 0 wt nacl eq high temperature 400 440 c aqueous fluid as fluid release from the magma progressed boiling of this fluid at temperatures of 420 to 370 c and a pressure of 350 300 bar produced a low salinity 0 6 1 2 wt nacl eq essentially gaseous and high salinity from 39 to 31 wt nacl eq brine with possible metal including cu partitioning into both gaseous and aqueous saline phases boiling was coeval with sulfide deposition in the retrograde skarn the latest episode of the retrograde skarn stage included direct separation of saline 40 42 wt nacl eq fluid from crystallizing magma the separation of saline 40 to 14 wt nacl eq fluids from a crystallizing magmatic melt continued during the propylitic stage when fluid cooling from 370 to 320 c together with decreasing fo2 caused cu and especially au precipitation a new influx of possibly magma derived low salinity 4 5 6 7 wt nacl eq aqueous and then nacl co2 h2o fluids corresponds to the phyllic quartz muscovite carbonate sulfide stage these fluids may have a deeper source associated with the late mafic quartz monzogabbro dikes fluid cooling from 340 to 255 c and boiling of the nacl co2 h2o fluid together with increased fs2 increased the au endowment

fluid and melt inclusion evidence for the origin of idiomorphic quartz crystals in topaz bearing granite from the salmi batholith karelia russia abstract idiomorphic quartz crystals in topaz bearing granite from the salmi batholith contain primary inclusions of silicate melt and abundant mostly secondary aqueous fluid inclusions microthermometric measurements on melt inclusions give estimates for the granite solidus and liquidus of 640 680 c and 770 830 c respectively using published solubility models for h2o in granitic melts and the obtained solidus liquidus temperatures from melt inclusions the initial water concentration of the magma is deduced to have been approximately 3 wt and the minimum pressure about 2 kbar at this initial stage volatile undersaturation conditions of magma were assumed these results indicate that the idiomorphic quartz crystals are magmatic in origin and thus real phenocrysts during subsolidus cooling and fracturing of the granite several generations of aqueous fluid inclusions were trapped into the quartz phenocrysts the h2o inclusions have salinities and densities of 1 41 wt nacl eq and 0 53 1 18 g cm3 respectively

garnets in porphyry skarn systems a la icp ms fluid inclusion and stable isotope study of garnets from the hongniu hongshan copper deposit zhongdian area nw yunnan province china abstract the late cretaceous hongniu hongshan porphyry skarn copper deposit is located in the zhongdian area of northwestern yunnan province china garnets from the deposit have compositions that range from adr14grs86 to almost pure andradite adr98grs2 and display two different styles of zoning the garnets are predominantly of magmatic hydrothermal origin as is evidenced by their 18ofluid 5 4 6 9 and low dfluid 142 to 100 values both of which likely result from late stage magmatic open system degassing three generations of garnet have been identified in this deposit 1 al rich garnets grt i adr22 57grs78 43 are anisotropic have sector dodecahedral twinning are slightly enriched in light rare earth elements lrees compared with the heavy rare earth elements hrees have negative or negligible eu anomalies and contain high concentrations of f fluid inclusions within these al rich garnets generally have salinities of 12 39 wt nacl eq and have liquid vapor homogenization temperatures th of 272 331 c the grt i are most likely associated with low to medium salinity fluids that were generated by the contraction of an ascending vapor phase and that formed during diffusive metasomatism caused by pore fluids equilibrating with the host rocks at low w r water rock ratios these garnets formed as a result of the high f activity of the system which increased the solubility of al within the magmato hydrothermal fluids in the system 2 fe rich garnets adr75 98grs25 2 have trapezohedral faces and are both anisotropic with oscillatory zoning and isotropic these second generation fe rich garnets grt ii have high ree concentrations are lree enriched and hree depleted and generally have positive but variable eu anomalies all of the fe rich garnets contain high salinity fluid inclusions with multiple daughter minerals with salinities of 33 80 wt nacl eq some of them show higher temperatures of halite dissolution 465 591 c than liquid vapor homogenization temperatures 319 473 c and several fe rich garnets contain inclusion groups indicative of boiling the grt ii are associated with high temperature hypersaline fluids that were segregated from magma at a depth of at least 5 6 km and reacted with carbonates at depths shallower than 2 0 km 3 al rich garnet veins adr14 60grs86 40 contain allotriomorphic crystals have lower hfse high field strength element and ree concentrations than the other garnets and have hree enriched and lree depleted patterns with small eu anomalies that are typical of the majority of garnets the grt iii most likely formed from residual metasomatic fluids

a geochemical study of the sweet home mine colorado mineral belt usa hydrothermal fluid evolution above a hypothesized granite cupola deposition of quartz molybdenite pyrite topaz muscovite fluorite and subsequent hubnerite and sulfide fluorite rhodochrosite mineralization at the sweet home mine occurred coeval with the final stage of magmatic activity and ore formation at the nearby world class climax molybdenum deposit about 26 to 25 m y ago the mineralization occurred at depths of about 3 000 m and is related to at least two major fluid systems 1 one dominated by magmatic fluids and 2 another dominated by meteoric water the sulfur isotopic composition of pyrite strontium isotopes and rey distribution in fluorite suggest that the early stage quartz molybdenite pyrite topaz muscovite fluorite mineral assemblage was deposited from magmatic fluids under a fluctuating pressure regime at temperatures of about 400 c as indicated by co2 bearing moderately saline 7 5 12 5 wt nacl equiv fluid inclusions la icpms analyses of fluid inclusions in quartz demonstrate that fluids from the sweet home mine are enriched in incompatible elements but have considerably lower metal contents than those reported from porphyry cu au mo or climax type deposits the ore forming fluid exsolved from a highly differentiated magma possibly related to the deep seated alma batholith or distal porphyry stock s sulfide mineralization marking the periphery of climax type porphyry systems with fluorite and rhodochrosite as gangue minerals was deposited under a hydrostatic pressure regime from low salinity co2 bearing fluids with low metal content at temperatures below 400 c the sulfide mineralization is characterized by mostly negative 34s values for sphalerite galena chalcopyrite and tetrahedrite highly variable 18o values for rhodochrosite and low ree contents in fluorite the pb isotopic composition of galena as well as the highly variable 87sr 86sr ratios of fluorite rhodochrosite and apatite indicates that at least part of the pb and sr originated from a much more radiogenic source than climax type granites it is suggested that the sulfide mineralization at the sweet home mine formed from magmatic fluids that mixed with variable amounts of externally derived fluids the migration of the latter fluids that were major components during late stage mineralization at the sweet home mine was probably driven by a buried magmatic intrusion

incursion of meteoric water triggers molybdenite precipitation in porphyry mo deposits a case study of the chalukou giant mo deposit there has been a long term debate about the timing of the incursion of meteoric water into porphyry systems and whether it plays an important role in ore precipitation to evaluate the role of meteoric water in the mineralization in porphyry mo deposits typical hydrothermal veins of different stages from the chalukou giant porphyry mo deposit are selected for combined scanning electron microscope cathodoluminescence sem cl fluid inclusion microthermometry and high resolution secondary ion mass spectroscopy sims oxygen isotope analyses multiple generations of quartz are identified in almost all of the veins the barren quartz veins and quartz magnetite veins of the early mo mineralization stage are dominated by granular cl bright quartz emq1 which usually shows dissolution and re deposition textures and are overprinted by cl dark quartz emq2 filled healed fractures the molybdenite precipitation in the quartz molybdenite veins of the main mo mineralization stage is synchronous with small volumes 85 of cl bright quartz mmq1 similar to the quartz molybdenite veins the precipitation of pyrite in the quartz pyrite veins during the transitional stage and sphalerite in the quartz sphalerite pyrite veins during the zn pb mineralization stage are also directly associated with cl dark quartz tsq2 zpq2 the sims oxygen isotopic values of emq1 and mmq1 fall into the range of 5 42 9 79 o with calculated equilibrium fluid compositions of 2 07 6 45 0 indicating a magma dominated fluid composition whereas mmq2 tsq2 and zpq2 have very low oxygen isotopic values from 4 68 to 4 29 parts per thousand with corresponding fluid compositions of 13 64 to 5 94 parts per thousand implying that the fluid formed by the mixing of magmatic water and a large proportion of meteoric water the contrasting sem cl features and oxygen isotopic compositions of the two generations of quartz in the quartz molybdenite veins demonstrate that the incursion of meteoric water into the hydrothermal system occurred earlier than the molybdenite precipitation based on these results and the crosscutting relationships and spatial distribution of the veins we reconstructed the quartz evolutionary sequence during the vein development process after the early precipitation of barren quartz the reduction in fluid pressure from lithostatic to hydrostatic conditions allowed the incursion of convecting cool meteoric water into the relatively hot hydrothermal system and the temperature of the evolved mo rich fluid decreased rapidly from 500 degrees c to 400 degrees c leading to concentrated molybdenite precipitation with small volumes of quartz fluid cooling resulting from the incursion of meteoric water may have played a greater role in the metal precipitation in the chalukou mo deposit than wallrock interactions and fluid boiling moreover this process may have also occurred in other porphyry mo deposits

fluid inclusion studies of the chinkuashih high sulfidation gold copper deposits in taiwan epithermal high sulfidation au cu deposits at chinkuashih in northeastern taiwan are found both within pleistocene calc alkaline volcanic rocks and the miocene sedimentary rocks the deposits consist of gold copper veins of the penshan group and breccia pipes of the tushihshan changjen group primary two phase inclusions in hydrothermal quartz and secondary two phase inclusions in hydrothermal quartz as well as igneous quartz phenocrysts probably represent fluids related to mineralization these inclusions have homogenization temperatures generally between 1908c and 2808c and salinities mostly from 0 5 5 0 wt nacl eq in the penshan group microthermometric data indicate that variable amounts of boiling mixing and cooling occurred in the hydrothermal system based on the th of inclusions trapped from boiling fluids and the co contents of the inclusions the hydrostatic pressure is estimated at 6 9 7 9 mpa in the tushihshan 2 changjen group the microthermometry of sulfur gas bearing secondary two phase fluid inclusions from hydrothermal quartz shows bimodal contents for a certain th value perhaps due to the intermittent incursion of brine at depth by phreatic or phreato magmatic explosions the presence of poly phase liquid q vaporq halite sylvite opaques fluid inclusions with high th 3078c 4848c and high salinities 30 51 wt nacl eq in one sample suggests a dense brine of probable magmatic derivation circulated in the chinkuashih system halite bearing inclusions which were homogenized by vapor disappearance coexisting with low salinity vapor rich inclusions in this sample may have been trapped in an immiscibility field at vapor pressures from 7 5 to 21 5 mpa halite bearing inclusions which were homogenized by halite dissolution after the vapor disappearance may have been trapped under even greater pressures fluid inclusion gas in samples were analyzed with a qms the results of bulk analyses indicate that these inclusions contain 99 45 99 67 mol h o 0 27 0 52 mol 2 co 0 015 0 066 mol n 0 0015 0 015 mol ch and small amounts of so in three samples these data suggest that 22 4 2 the inclusion fluids are dominantly meteoric waters that interacted with host rocks and accumulated upward fluxing magmatic volatiles the fluid inclusion data indicate that the hydrothermal fluids related to the ore deposition of the high sulfidation au cu deposits at chinkuashih are characterized by the interaction of magmatic fluids with meteoric water under epithermal conditions q 1999 elsevier science b v all rights reserved

geology mineralization and fluid inclusion characteristics of the kensu w mo skarn and mo w cu au alkalic porphyry deposit tien shan kyrgyzstan the kensu deposit is located within a large metallogenic belt of w mo cu mo w au au and pb zn deposits along the late paleozoic active continental margin of tien shan the deposit is related to a small late carboniferous to early permian multiphase gabbro monzonite syenite granite pluton representing an alkaline potassic shoshonitic suite the igneous rocks are related to a deep rooted magmatic source but the pluton emplacement corresponds to shallow porphyry levels the deposit represents an example of a complex w rich alkalic magmatic hydrothermal system that complements the typical mineral deposits related to shoshonitic igneous suites it contains large bodies of w mo skarn of the oxidized type with abundant andradite garnet scapolite k na feldspars and fe oxides magnetite hematite the skarns are overprinted and surrounded by extensive halos of stockwork disseminated porphyry style mo w mo w cu pb zn and au w mineralization with propylitic chlorite amphibole epidote dominated and phyllic quartz sericite carbonate sulfide alteration assemblages consistent with the oxidized nature of the major mineral assemblages the deposit may represent the oxidized lithophile w mo cu au metallogenic type the hydrothermal stages alternate with magmatic phases and fluid inclusion data show the predominance of high temperature 550 450 c high pressure 1 200 700 bars and high salinity 60 45 wt nacl equiv magmatic hydrothermal fluid at prograde and early retrograde skarn stages with its possible direct exsolution from crystallizing magma the general trend of cooling and dilution was complicated by the influx of higher temperature and higher salinity fluid that correlates to the intrusion of quartz monzonite and the initial stages of its degassing and cooling this more advanced phase of magmatic differentiation likely corresponded to the enrichment of residual melt and related magmatic fluids in w and mo intense fluid boiling and phase separation triggered the deposition of molybdoscheelite in skarns that formed at t 625 500 c and p 510 300 bars and continued to a nonboiling fluid at t 420 370 c and p 1 150 750 bars mineralization in propylitic alteration zones was formed by highly to moderately saline nonboiling fluids late quartz sericite carbonate sulfide stage involved both high to low salinity aqueous fluids and co2 rich fluids under decreasing temperature from 400 c to 200 300 c and varying pressure from 1 200 bars to 750 600 bars

the ridgeway gold copper deposit a high grade alkalic porphyry deposit in the lachlan fold belt new south wales australia ridgeway is a high grade gold copper porphyry deposit 54 mt at 2 5 g t au and 0 77 cu related to an alkalic intrusive complex of monzonitic composition the deposit occurs within the cadia district of new south wales australia which consists of a cluster of four late ordovician gold copper porphyry deposits and two iron copper gold skarn deposits with a combined gold resource in excess of 574 metric tonnes t the deposits lie on a 7 km long northwest oriented corridor of alteration and mineralization transverse to the axis of the postulated volcanic arc alteration and mineralization at ridgeway are zoned around a vertically attenuated intrusive complex of monzodioritic to quartz monzonitic composition distinct styles of veining and alteration are related to different intrusive phases of the monzonite complex with the intensity of alteration and grade of mineralization decreasing from early to late mineral intrusions early mineral intrusions are associated with intense actinolite magnetite biotite calc potassic alteration and up to four stages of high grade quartz magnetite sulfide veining bornite is the most abundant sulfide formed during early stage alteration and correlates well with gold moderate to weak intensity orthoclase biotite plus or minus magnetite potassic alteration accompanies the inter and late mineral intrusions this alteration being associated with chalcopyrite and pyrite rich quartz orthoclase veins propylitic and sodic albite pyrite alteration assemblages are peripheral to and locally overprint the potassic alteration phyllic alteration is restricted to the margins of late stage faults the fluid inclusion assemblage comprises one and two salt bearing brine inclusions in addition to aqueous liquid vapor inclusions of low to moderate salinity no low density vapor rich inclusions are present indicating that the fluids from which the quartz veins precipitated did not enter the liquid vapor field of the h2o nacl system the brine inclusions undergo final homogenization to liquid via halite dissolution this phenomenon in addition to the absence of low density vapor inclusions suggests that the mineralizing fluids at ridgeway were nonboiling hypersaline brines that exsolved directly from the crystallizing magma the presence of mineralized aplitic vein dikes and comb quartz layering are interpreted to indicate that the early and transitional stages of mineralization at ridgeway formed at the transition between magmatic and hydrothermal conditions

geology and hydrothermal evolution of the baituyingzi porphyry mo cu deposit eastern inner mongolia ne china implications for mo and cu precipitation mechanisms in co2 rich fluids abstract the baituyingzi mo cu deposit is a newly identified porphyry deposit located in the southern part of the xilamulun mo metallogenic belt northeast china mo cu mineralization mainly occurs as quartz veinlets and stockwork veinlets in the potassic altered baituyingzi monzogranite porphyry a detailed investigation of fluid inclusions and o h isotopes from hydrothermal veins at baituyingzi allow us to establish the evolving history of the fluid system as well as understand factors controlling cu mo precipitation in co 2 rich fluids six vein types are recognized at baituyingzi which belong to five hydrothermal stages 1 ust quartz vein formed during magmatic hydrothermal transitional stage 2 a 1 vein sulfide barren quartz vein and a 2 vein quartz pyrite chalcopyrite molybdenite vein cu mineralization related to potassic alteration 3 b vein quartz molybdenite chalcopyrite pyrite vein mo mineralization formed during the potassic sericitic transitional stage 4 d vein quartz pyrite molybdenite chalcopyrite vein associated with sericitic alteration and 5 late stage l vein quartz carbonate vein four types of fluid inclusions have been observed in these veins i e liquid rich inclusions l type vapor rich inclusions v type polyphase high salinity inclusions s type and co 2 rich inclusions c type ust quartz veins contain abundant s and co existing v type inclusions accompanied by minor melt inclusions indicating that the parent fluids were likely in the form of bubbly magma 10 wt nacl equiv that was derived from a deep magma chamber a 1 veins are dominated by coexisting s and v type inclusions that homogenized at temperatures ranging from 400 to 548 5 c and pressures between 300 and 750 bar which may represent the result of parent fluid immiscibility vapor brine at depth apart from s and v type inclusions cu bearing a 2 veins are especially rich in isolated l type inclusions homogenized at 347 to 430 c that share the same salinity range as v type inclusions homogenized at 375 to 470 c suggesting that the vapor gradually contracted to a liquid phase at around 350 bar because the system was still in a lithostatic condition revealed by textures of a 2 veins cu precipitation at baituyingzi was thus largely controlled by temperature reduction to below 400 c near the vapor liquid surface in relatively oxidized fluids indicated by the precipitation of abundant hematite c type inclusions homogenize at 275 to 350 c seem to be more widely developed and they commonly co exist with l type inclusions homogenized at 340 to 380 c of similar salinity in b veins implying that they unmixed at temperatures below 350 c and pressures below 200 bar considering that the system had already fluctuated to hydrostatic conditions revealed by clear open space filling textures as well as considering the occurrence of minor feldspar destructive alteration halos in b veins mo precipitation would likely be a result of water co 2 immiscibility at temperatures below 350 c with a sharp pressure reduction to below 200 bar and an increase in fluid acidity d veins contain plentiful l and minor c and s type inclusions that homogenized at lower temperatures 240 to 350 c and pressures 30 to 150 bar the wide feldspar destructive alteration halos indicate that the fluids became progressively more acidic and reacted intensely with wall rocks l veins only contain low temperature 168 to 280 c and low salinity 0 4 to 10 9 wt nacl equiv l type inclusions implying that meteoric water was introduced to the barren magmatic fluids leading to precipitation of a large amount of remnant material 18 o and d isotope ratios in quartz 18 o fluid 3 54 to 7 51 d 107 to 87 also confirm a primary magmatic origin for ore forming fluids in earlier veins except for l veins therefore fluid evolution at baituyingzi was characterized by relatively continuous system scale cooling along an ascent path gradually straddling the vapor brine vapor liquid and water co 2 surface in the vapor dominated h 2 o co 2 nacl fluid system whereas the subtle temporal change in p t redox conditions and acid balance of the evolutionary paths of the magmatic fluid may be responsible for cu and mo separation at the baituyingzi co 2 rich systems additionally water co 2 immiscibility seems to be an additional important mechanism that complicates mo precipitation in co 2 rich systems

magmatic hydrothermal molybdenum isotope fractionation and its relevance to the igneous crustal signature abstract we analysed the mo isotope composition of a comprehensive series of molybdenite samples from the porphyry type questa deposit nm usa as well as one rhyolite and one granite sample directly associated with the mo mineralization the 98mo of the molybdenites ranges between 0 48 and 0 40 with a median at 0 05 the median mo isotope composition increases from early magmatic 0 29 to hydrothermal 0 05 breccia mineralization median bulk breccia 0 17 to late stockwork veining 0 22 moreover variations of up to 0 34 are found between different molybdenite crystals within an individual hand specimen the rhyolite sample with 0 12 g g 1 mo has 98mo 0 57 and is lighter than all molybdenites from the questa deposit interpreted to represent the igneous leftover after aqueous ore fluid exsolution we recognize three mo isotope fractionation processes that occur between about 700 and 350 c affecting the mo isotope composition of magmatic hydrothermal molybdenites 1mo minerals preferentially incorporate light mo isotopes during progressive fractional crystallization in subvolcanic magma reservoirs leaving behind a melt enriched in heavy mo isotopes 2mo magmatic hydrothermal fluids preferentially incorporate heavy mo isotopes upon fluid exsolution 3mo light mo isotopes get preferentially incorporated in molybdenite during crystallization from an aqueous fluid leaving behind a hydrothermal fluid that gets heavier with progressive molybdenite crystallization the sum of all three fractionation processes produces molybdenites that record heavier 98mo compositions than their source magmas this implies that the mean 98mo of molybdenites published so far 0 4 likely represents a maximum value for the mo isotope composition of phanerozoic igneous upper crust

climatic interpretation of a continuous deuterium profile obtained from the vostok ice core antarctica 160 000 years abstract oceanic studies have convincingly demonstrated that there is a link between the pleistocene ice ages and the variations in the elements of the earth s orbit imbrie and others 1984 in contrast the climatic conditions which prevailed over continental areas have been far less well documented and then rarely on a quantitative basis in this context the 2083 m ice core recovered by the soviet antarctic expeditions at vostok east antarctica is of fundamental importance because it covers fully the last glacial interglacial cycle back to the ice age which preceded the last interglacial 160 ka b p potentially it allows access to many climatic and climate related parameters as illustrated by the oxygen 18 data we have recently published lorius and others 1985 from lobe measurements yiou and others 1985 raisbeck and others 1987 from aerosol concentration de angelis and others 1987 and from co 2 measurement barnola and others 1988 this volume our first isotopic data set was largely discontinuous over the last 100 ka only about 7 of the core was analyzed but continuous beyond that time sampling of the ice was completed later in the field and we now have continuous deuterium data for the whole core total ice recovery is about 85 combining the data of the 2083 m core below 138 m and a complementary data set above the core chronology was established using a two dimensional ice flow model and for snow accumulation taking into account change with time lorius and others 1985 there is a general correspondence between this curve and the previously published s 18 0 record lorius and others 1985 however there is obviously far more information in this continuous sd record which we will examine from the deduced temperature record

multiphase magma intrusion ore enhancement and hydrothermal carbonatisation in the siah kamar porphyry mo deposit urumieh dokhtar magmatic zone nw iran abstract the siah kamar mo deposit skmd is located at the northwestern termination of the urumieh dokhtar magmatic zone and it is the only porphyry mo ore reserve in iran the exploration program documented 39 2 mt proved reserves 539 ppm mo and 66 4 mt probable reserves 266 ppm mo in this study field and petrographic investigations integrated with geochemical fluid inclusion and quartz chemistry and geochronological u pb zircon re os molybdenite and rb sr multimineral isochron studies are used to propose a metallogenic model for the mo mineralisation in the skmd the geology of the skmd is characterized by the emplacement of a multiphase oligocene basic intermediate at ca 33 30 ma to acidic 29 28 ma magmatic suite which intruded the eocene volcanic country rocks the alteration zone about 4 3 km in size and with a general nw se trend is centered within the main basic porphyry stock grading from an inner potassic sodic zone to peripheral phyllic propylitic halos the late acidic magmatic products stocks and dykes intruded and post dated the main alteration zone two stage mo mineralisation is recognised including i stage 1 disseminated molybdenite coeval with the formation of potassic sodic alteration and minor microscale fsp bt qz po veinlets and ii stage 2 high grade molybdenite carbonate sericite structurally controlled stockwork veining fluid inclusion systematics combined with titaniq thermometry documents a mineralising fluid system compatible with a transition from high temperature up to ca 600 c magmatic to epithermal 250 c conditions during progressive cooling exhumation and mixing with meteoric sources at shallow crustal conditions ca 7 3 km the re os molybdenite dating constrains the high grade mo ore formation at ca 29 28 ma attesting for the intimate linkage between the main mo mineralisation and the acidic magmatic phase in the area the rb sr geochronology of the potassic sodic alteration zones confirms the two stage magmatic mineralisation scenarios overlapping within errors with the results obtained from the u pb zircon geochronology and constraining the formation of the potassic sodic and phyllic alteration at ca 33 and 28 ma respectively our results document an uncommon scenario of two stage porphyry mo mineralisation associated with intensive late stage carbonate precipitation and achieved during a long lasting and multiphase magmatic pulses of oligocene age we highlight the dominant role of acidic fluid neutralisation for further ore enrichment during polyphase magma intrusion as the dominant factor controlling the mo mineralisation in the skmd comparison at a regional scale indicates that parameters such as longevity of magma supply progressive magma crystallization differentiation and the presence of a possible pre enriched crustal material should be considered responsible for the mo endowment in the udmz

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

the miocene gangdese porphyry copper belt generated during post collisional extension in the tibetan orogen abstract the mid miocene gangdese orogenic belt in southern tibet contains porphyry cu deposits that developed after the indian asian continental collision in the early cenozoic field work confirms that these porphyry cu deposits are temporally and spatially associated with mid miocene monzogranitic and quartz monzonitic stocks which intruded mesozoic cenozoic gangdese granitoid batholiths and surrounding triassic tertiary volcano sedimentary sequences in the lhasa terrane and formed a 50 km wide 400 km long e w belt magmatism occurred during the interval 11 2 to 19 7 ma peaking at 16 ma for the porphyry stocks this is consistent with the age 10 to 18 ma of the east west extension and subsequent ns striking normal fault systems 13 5 ma in the tibetan orogen the stocks typically occur as multiple small diameter intrusions 50 km breakdown of hornblende in the juvenile lower crust source during melting is regarded as fundamental for the formation of the fertile adakite and porphyry cu systems in south tibet the gangdese belt contains four large and three intermediate and small sized porphyry cu mo deposits and shows a continuous spectrum from typical porphyry type cu mo to skarn type zn pb mineralization twenty three samples collected from four deposits yielded a limited range of molybdenite re os isochron ages from 15 2 to 16 0 ma similar to previously reported re os ages 13 8 to 14 9 ma for other porphyry cu mo deposits in the belt suggesting that cu mo mineralization in the belt occurred in a post collisional extension environment the characteristics of porphyry cu mo deposits in the collisional zone are similar in many aspects to those in arc settings i e mineralization style alteration zoning and metal association preliminary fluid inclusion studies indicate that the early hydrothermal fluids are preserved as high temperature 450 c high salinity 40 to 47 wt nacl equiv and high pressure 1100 to 1500 bar fluid inclusions these fluids are interpreted to represent an orthomagmatic fluid that boiled episodically due to fluid overpressuring and hydrofracturing resulting in potassic alteration and precipitation of chalcopyrite molybdenite assemblages on the basis of comparison with porphyry cu deposits in arc settings we proposed that melting of thickened newly formed basaltic crust resulted in generation of cu bearing magmatic systems in the tibetan collision zone and both orogen transverse normal faults and orogen parallel thrust zones during the miocene post collisional extension constrain the temporal and spatial localization of the porphyry cu systems in the collision zone

how precisely can the temperature of a fluid event be constrained using fluid inclusions u s national science foundation ear 1624589 chemical sciences geosciences and biosciences division office of basic energy sciences office of science u s department of energy de fg02 03er15430 bureau of economic geology jackson school of geosciences university of texas austin

direct evolution of brine from a crystallizing silicic melt at the questa new mexico molybdenum deposit molybdenum mineralization in the southwest orebody at the questa deposit is associated with crystallization of aplite porphyry explosive brecciation and exsolution of magmatic hydrothermal fluids quartz k feldspar fluorophlogopite and molybdenite precipitated from exsolving aqueous fluids and cemented aplite porphyry and andesite wall rock clasts forming a magmatic hydrothermal breccia ore fluid inclusions in quartz in the breccia matrix trapped aqueous fluids that transported and precipitated molybdenum two fluid inclusion populations associated with molybdenite mineralization were identified the largest population commonly contains liquid vapor halite sylvite and one or more opaque daughter crystals these inclusions homogenize between 200 degrees and 500 degrees c and have a prominent mode at 360 degrees to 400 degrees c salinities vary from 31 to 57 wt percent nacl equiv low first ice melting temperatures suggest that additional fluid components possibly calcium or magnesium chlorides may be present approximately 80 percent of these inclusions homogenize by halite dissolution phase equilibria constraints require that these inclusions trapped fluids in the vapor absent field the remaining saline inclusions homogenize to liquid at temperatures above halite dissolution temperatures significantly the saline fluid did not coexist with a low density aqueous fluid a second population of inclusions contains fluids with salinities of 2 7 to 25 0 wt percent nacl equiv and homogenizes by vapor bubble disappearance vapor bubble expansion or critical behavior textural relationships and phase behavior during microthermometry indicate that these inclusions constitute a single population which formed as pressure and temperature fluctuated at near critical conditions pressure changes related to brecciation followed by crystallization and system resealing produced the observed fluids saline fluids were trapped as the system sealed following a major brecciation event these high salinity fluids were produced as the melt under pressure that increased from hydrostatic to lithostatic partitioned increasing amounts of chlorine into the exsolving aqueous fluid renewed fracturing and abrupt pressure decrease to hydrostatic conditions reduced the mass of chlorine partitioning to the exsolving fluid lower salinity fluids exsolved at near critical conditions and were trapped by inclusions that homogenize to liquid to vapor or by critical behavior the lack of cogenetic liquid and vapor rich fluid inclusions and phase equilibria constraints indicate that high salinity fluids or 57 wt nacl equiv were generated directly by the crystallizing magma and were not a product of aqueous fluid immiscibility

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

origin of the ore forming fluids of the zefreh porphyry cu mo prospect central iran constraints from fluid inclusions and sulfur isotopes abstract the zefreh porphyry cu mo prospect is located in the central part of the nw trending cenozoic urumieh dokhtar metallogenic belt 75 km ne of isfahan city central iran chalcopyrite and molybdenite mainly occur as disseminated sulfides in the host rocks and to a lesser extent in the surrounding volcanic rocks four types of fluid inclusions were identified in quartz rich veins i e two phase liquid rich two phase vapor rich simple brine and multi phase brine inclusions liquid rich inclusions in ore bearing a type quartz veins homogenized between 350 and 370 c suggesting that fluids trapped in these inclusions were derived from magmatic fluids at high temperatures simple and multi phase brine inclusions exhibited homogenization or partial homogenization over a wide range from 350 to 1209 c the very high homogenization temperatures and the presence of up to six solid phases in multi phase brine inclusions indicate heterogeneous trapping of melt fluid and vapor the zefreh porphyry prospect is thought to have formed from hypersaline liquids and vapors that exsolved from a magmatic intrusion assembled in the shallow crust the 34s values of sulfides from the zefreh porphyry prospect range from 0 8 to 10 7 this indicates that the early ore bearing quartz veins dominated by high 34s pyrites may have interacted with later hydrothermal fluids or alternatively the pyrites are paragenetically late products of propylitic and k feldspar dominated potassic alteration assemblages another plausible explanation for significantly enriched 34s values of sulfides may be mixing of hydrothermal fluids of magmatic origin with the cenozoic seawater 34s 22 it is suggested that the zefreh prospect likely would be a poor target for further exploration

fluid inclusion study of the wunugetu cu mo deposit inner mongolia china hydrothermal alteration and mineralization at the wunugetu porphyry cu mo deposit china include four stages i e the early stage characterized by quartz k feldspar and minor mineralization followed by a molybdenum mineralization stage associated with potassic alteration copper mineralization associated with sericitization and the last pb zn mineralization stage associated with carbonation hydrothermal quartz contains three types of fluid inclusions namely aqueous w type daughter mineral bearing s type and co2 rich c type inclusion with the latter two types absent in the late stage fluid inclusions in the early stage display homogenization temperatures above 510 c with salinities up to 75 8 wt nacl equivalent the presence of s type inclusions containing anhydrite and hematite daughter minerals and c type inclusions indicates an oxidizing co2 bearing environment fluid inclusions in the mo and cu mineralization stages yield homogenization temperatures of 342 508 c and 241 336 c and salinities of 8 6 49 4 and 6 3 35 7 wt nacl equivalent respectively the presence of chalcopyrite instead of hematite and anhydrite daughter minerals in s type inclusions indicates a decreasing of oxygen fugacity in the late stage fluid inclusions yield homogenization temperatures of 115 234 c and salinities lower than 12 4 wt nacl equivalent it is concluded that the early stage fluids were co2 bearing magmatic in origin and characterized by high temperature high salinity and high oxygen fugacity phase separation occurred during the mo and cu mineralization stages resulting in co2 release oxygen fugacity decrease and rapid precipitation of sulfides the late stage fluids were meteoric in origin and characterized by low temperature low salinity and co2 poor

iron skarns of the vegas peladas district mendoza argentina the andean belt southwest of mendoza argentina hosts 23 fe fe cu and cu ag deposits classified variously in the literature as skarn iron oxide copper gold iocg and manto type cu deposits the vegas peladas deposit is one of the best exposed fe skarns with mineral assemblages and hydrothermal features similar to many other calcic fe skarns of the world the plutonic rocks of vegas peladas consist of a series of diorite to granite stocks dikes and sills the major trace and rare earth element geochemistry analyses of these igneous rocks indicate they were derived from subarc mantle sources the vegas peladas deposit formed by the overprinting of two different metamorphic and metasomatic events associated with early diorite and later granite intrusions alteration associated with the early diorite intrusion consists of a metamorphic halo 800 m wide and a zoned calcic skarn with inner garnet ad31 89 py0 2 clinopyroxene magnetite quartz intermediate garnet ad38 51 py1 2 clinopyroxene and distal veins of garnet ad92 100 clinopyroxene hd72 29 jo1 4 the latest alteration consists of widespread albite ab96 98 epidote quartz calcite chlorite pyrite titanite magnetite and hematite are the main iron ore minerals and occur as massive orebodies and veins associated with retrograde epidote and amphibole alteration of the diorite consists of early orthoclase quartz followed by later amphibole quartz magnetite epidote feldspar the granite related skarn overprints the earlier diorite related skarn and consists of garnet clinopyroxene scapolite me28 36 quartz alkali feldspar endoskarn and a zoned exoskarn with proximal garnet clinopyroxene quartz intermediate green garnet ad30 81 py0 1 clinopyroxene di82 93 jo4 2 and distal scapolite me25 36 ferroactinolite pyrite veins based on fluid inclusion stable isotope and ree data the prograde skarn formed at depths of 3 5 km under lithostatic pressure of 1 kbar from high temperature 670 400 c saline and iron rich 50 wt nacl equiv nacl kcl fecl2 magmatic fluids garnet 18oh2o 7 2 8 5 with intermediate oxygen fugacity iron ore and retrograde exoskarn assemblages formed under hydrostatic condition after the fracturing of early skarn fluids in this stage had lower temperature t 550 c and also generated saline 30 3 to 45 3 wt nacl equiv h2o nacl fecl2 vapor fluids by immiscibility that redistributed some of the iron from the previous skarn

metal content and p t evolution of co2 bearing ore forming fluids of the haftcheshmeh cu mo porphyry deposit nw iran abstract the haftcheshmeh cu mo porphyry deposit is located in the nw part of the arasbaran metallogenic magmatic zone nw iran ore mineralisation is generally hosted within the gabbro diorite and granodiorite porphyry stocks presenting various types of hydrothermal quartz veins and veinlets associated with potassic to sericitic alteration stage i corresponds to barren quartz k feldspar biotite anhydrite veins a veins with minor metal sulphides pyrite chalcopyrite surrounded by k feldspar and biotite halos related to potassic alteration stage ii is described with quartz molybdenite chalcopyrite pyrite bornite magnetite hematite biotite veins predominantly occurring in the potassic alteration halos b veins stage iii shows pyrite quartz chalcopyrite molybdenite galena sphalerite associated with sericitic alteration halos d veins the coexistence of halite saturated aqueous rich and low salinity vapour rich fluid inclusions in the h2o nacl co2 system is evidence of fluid boiling in each alteration mineralising stage this process was subsequently followed by meteoric water input diluting the co2 bearing ore forming fluid la icpms data of fluid inclusions associated with the successive stages reveal elevated na k fe mn cu and mo content the metal content of fluid inclusions of stages ii and iii is in large part due to accidentally trapped minerals molybdenite and chalcopyrite started precipitating between stages i and ii from a metal poor fluid the long duration 1 ma of the magmatic hydrothermal activity and associated co2 fluxes and repeated fluid boiling events lead to ore deposition at temperatures of 450 to 250 c and at depths between 3 0 and 1 0 km from near lithostatic to near hydrostatic conditions

partitioning behavior of chlorine and fluorine in the system apatite silicate melt fluid the partitioning behavior of cl among apatite mafic silicate melt and aqueous fluid and of f between apatite and melt have been determined in experiments conducted at 1066 to 1150 c and 199 205 mpa the value of dclapatite melt wt fraction of cl in apatite cl in melt 0 8 for silicate melt containing less than 3 8 wt cl at higher melt cl contents small increases in melt cl concentration are accompanied by large increases in apatite cl concentration forcing dclapatite melt to increase as well melt containing less than 3 8 cl coexists with water rich vapor that containing more cl coexists with saline fluid the salinity of which increases rapidly with small increases in melt cl content analogous to the dependency of apatite composition on melt cl content this behavior is due to the fact that the solubility of cl in silicate melt depends strongly on the composition of the melt particularly its mg ca fe and si contents once the melt becomes saturated in cl additional cl must be accommodated by coexisting fluid apatite or other phases rather than the melt itself because cl solubility depends on composition the cl concentration at which dclapatite melt and dclfluid melt begin to increase also depends on composition the experiments reveal that dfapatite melt 3 4 in contrast to cl the concentration of f in silicate melt is only weakly dependent on composition mainly on melt ca contents so dfapatite melt is constant for a wide range of composition the experimental data demonstrate that the fluids present in the waning stages of the solidification of the stillwater and bushveld complexes were highly saline the cl rich apatite in these bodies crystallized from interstitial melt with high cl f oh ratio the latter was generated by the combined processes of fractional crystallization and dehydration by its reaction with the relatively large mass of initially anhydrous pyroxene through which it percolated

geology mineralization fluid inclusion and stable isotope characteristics of the sinyukhinskoe cu au skarn deposit russian altai sw siberia abstract the sinyukhinskoe deposit 100 t au with average 9 2 g t au is situated in the altaid orogenic system and is part of the regional system of devonian carboniferous cu au to au cu porphyry skarn and other deposits productive plutonic suites were emplaced in a devonian subduction related continental magmatic arc setting with its further evolution toward a late and post collisional environment in the late devonian carboniferous the deposit is related to a magnetite series i type multiphase pluton with the evolution of the intrusive phases from early gabbroic through diorite granodiorite to the late granitic phases the igneous rocks belong to medium k calc alkaline series or are transitional from medium to high k calc alkaline varieties prior to granitic phases this evolution was interrupted by the intrusion of intramineral high k mafic dikes exhibiting a shoshonitic affinity the deposit is characterized by the development of abundant andradite rich garnet and wollastonite in prograde and retrograde skarns locally together with magnetite and bornite the subsequent propylitic epidote chlorite amphibole albite calcite quartz locally with clinozoisite and prehnite alteration assemblages bear more intense cu mineralization chalcopyrite bornite locally tennantite and high fineness 940 910 native gold later phyllic quartz sericite to quartz sericite chlorite alteration assemblages comprise the most intense intermediate fineness 910 880 native gold and cu bornite chalcocite mineralization that is followed by low fineness 820 760 native gold and telluride minerals the retrograde skarn was formed from a high salinity 22 23 wt nacl eq hot 450 50 c high pressure 2 5 0 5 kbar homogenous magmatic hydrothermal fluid under its possible direct separation from crystallizing magma after intrusion of intramineral mafic dikes propylitic alteration assemblages were formed from a moderate salinity 15 18 wt nacl eq homogenous aqueous fluid at the temperatures of 380 400 c this fluid could be supplied by crystallizing magma with its further mixing with heated meteoric waters fluid inclusions in phyllic alteration minerals indicate a new influx of homogenous high salinity 18 wt nacl 22 wt kcl 10 wt cacl2 high pressure 1 3 0 1 kbar aqueous chloride fluid at lower 280 c temperatures elevated bi hg te contents as well as 34s values close to meteorite standard 0 1 5 suggest at least partial fluid sourcing from a mantle derived magma at the phyllic alteration stage

quartz vein emplacement mechanisms at the e26 porphyry cu au deposit new south wales porphyry cu au mo deposits are characterized by numerous fracturing events brittle fracture of mineralized intrusions and the surrounding host rocks is a consequence of hydraulic breakage caused by the interplay of the changing physiochemical properties of magmatic fluids and or the local tectonic regime we have mapped more than 1 400 quartz sulfide vein sets at the ordovician endeavour 26 north e26 deposit central new south wales in order to constrain the processes influencing fracture development around small 200 m porphyritic intrusions veins from intermediate levels in the e26 deposit define complicated patterns within 10 m of the porphyritic intrusions whereas more systematic patterns occur up to 50 m from the intrusive contact the outer parts of the ore deposit are characterized by quartz veins with orientations of 340 and subordinate orthogonal sets of bisecting veins at 240 and 290 the data show a broad range of vein orientations that define a conical distribution around a vertical axis there is a rare subset of near horizontal veins that formed early relative to the main stage of ore bearing vein emplacement many quartz veins exhibit fault displacements at both micro and macroscopic scales and fabrics including serrate fractures slickenlines and asymmetric fiber trails the distribution of veins suggests that the dominant fracture array developed perpendicular to the direction of bulk finite extension but significant vein dilation also occurred in orientations with a component of shear strain we propose a physical model that combines intrusion driven hydraulic fracturing into a preexisting fracture mesh to help explain the observed vein patterns and to better link fracture development and vein emplacement hydraulically driven deformation was important locally at e26 contributing to the formation of the irregular fracture stockwork immediately adjacent to the small intrusive bodies the more predictable vein patterns that occur away from the porphyritic intrusions require part of the hydraulically driven extension to have reactivated the existing fracture mesh parts of this more systematic geometry including the occurrence of flat veins are probably related to the emplacement of larger 10 km diameter magma bodies adjacent to e26 with doming causing the subordinate fracture arrays including the gross conical distribution fluctuating fluid pressures combined with hydraulically driven extension caused dilation of preexisting and synmineralization fractures and superposition of veins with similar orientations vein patterns suggest that the regional stress state that existed prior to or synchronously with porphyry ore deposit formation strongly influenced vein orientation to within tens of meters away from the mineralizing intrusions fractures that localized ore in the e26 porphyry deposit developed in response to the infiltration of fluid batches including magma and magmatic hydrothermal fluids into a regional deformation environment

genesis of the tianbaoshan pb zn cu mo polymetallic deposit in eastern jilin ne china constraints from fluid inclusions and c h o s pb isotope systematics abstract the tianbaoshan pb zn cu mo deposit is located in the eastern part of jilin heilongjiang region ne china which is considered to be the eastern segment of the central asian orogenic belt field and geochronological evidences indicate that this deposit experienced three types of mineralization including hercynian skarn cryptoexplosion breccia pipe and yanshanian quartz vein the early stages of the pb zn cu mineral systems in skarn and cryptoexplosion breccia pipe are characterized by a high temperature high salinity h 2 o co 2 nacl system of hydrothermal fluids that were possibly exsolved from the hercynian wall rock granodiorite these fluids show h o isotopic compositions similar to those of typical magmatic fluids by contrast the low temperature hydrothermal fluids of the later stages are represented by low salinity nacl h 2 o systems with low h o isotopic values the skarn and cryptoexplosive breccia pipe types of pb zn cu mineralization tend to have weakly negative 34 s values of 4 0 to 0 8 mean values of 2 31 and 2 16 respectively indicating that the sulfur was sourced from the hercynian magma therefore the early stage ore forming fluids of the skarn and cryptoexplosive breccia pipe were most likely sourced from high temperature and high salinity fluids closely related to the cooling and fractional crystallization of the hercynian granodiorite while the later stages changed to nacl h 2 o meteoric water influx whereas the ore forming fluids of the quartz vein type of mo mineralization were high temperature high salinity nacl h 2 o systems that differed from those of the skarn and cryptoexplosion breccia pipe but their h o isotopic compositions also indicate a magmatic fluid the weakly enriched 34 s values of molybdenite from the quartz vein type mo mineralization 34 s 0 2 2 8 average of 1 65 are comparable with those of other mesozoic yanshanian mo deposits 34 s 0 4 4 1 with an average of 1 39 3 15 but differ significantly from those of the hercynian pb zn cu skarn and cryptoexplosion breccia pipe this indicates that the sulfur of quartz vein type of mo originated from mesozoic yanshanian magmatism and that the ore forming fluids were derived from yanshanian magmatic rocks rather than being a product of the hercynian activity the 13 c values of the fluid inclusions in quartz from the skarn cryptoexplosion breccia pipe and quartz vein types are in a narrow range of 19 5 to 9 3 similar to those of the shanxiuling group which indicates that the carbon of the three types of mineralization had the same primary origin in the shanxiuling group the lead isotope compositions of ores from the skarn and cryptoexplosion breccia pipe types of mineralization 206 pb 204 pb 18 0725 18 3627 207 pb 204 pb 15 3721 15 5694 and 208 pb 204 pb 37 5542 38 8208 overlap with those of the hercynian granodiorite and shanxiuling group marble suggesting that the lead was probably derived from a mix of two different sources the shanxiuling group and the hercynian granodiorite whereas the lead isotope compositions of ores from the quartz vein type of mo mineralization 206 pb 204 pb 18 3837 18 6949 207 pb 204 pb 15 6824 15 7293 and 208 pb 204 pb 39 1009 39 1889 are significantly higher than those of the shanxiuling group marble and the hercynian granodiorite this indicates that the lead may be a product of yanshanian magmatic activity instead of the nearby hercynian granodiorite

stable isotope and fluid inclusion constraints on the source and evolution of ore fluids in the hongniu hongshan cu skarn deposit yunnan province china the hongniu hongshan cu skarn deposit 77 8 mt at 1 8 cu is located in the central part of the zhongdian porphyry and skarn cu belt in southwestern china skarn and orebodies occur mainly between the different units of the upper triassic qugasi formation or within altered limestone adjacent to late cretaceous intrusions 78 76 ma three main paragenetic stages of skarn formation and ore deposition have been recognized on the basis of petrographic observations 1 pre ore stage hornfels with diopside di87 72hd12 7 small scale endoskarn with reddish grossular adr22 57gr78 43 diopside di83 92hd7 15 vesuvianite and abundant exoskarn with red brown andradite adr75 98gr2 22 sahlite di28 41hd58 71 and wollastonite 2 syn ore stage retrograde minerals sulfides pyrite chalcopyrite pyrrhotite molybdenite galena and sphalerite quartz and calcite and 3 post ore stage calcite veins sulfur isotope values of sulfides are relatively high with an average 34s 4 9 n 40 suggesting that the ore forming fluid was magmatic and that the sulfides precipitated from a relatively reducing ore fluid the coexistence of silicate melt and primary fluid inclusions in quartz phenocrysts of the mineralization related quartz monzonite porphyry indicates the simultaneous entrapment of fluid and melt and records the process of the aqueous fluid exsolving from the crystallizing melt the initial single phase fluid has a salinity of 8 8 to 12 7 wt nacl equiv and homogenization temperatures of 566 to 650 c corresponding to pressures of 680 to 940 bar and lithostatic depth of 2 5 to 3 5 km the primary fluid inclusions in the pre ore stage garnet and pyroxene composed of coeval vapor rich v type and halite bearing s i and s ii types containing sylvite inclusions 32 79 total wt salts share similar homogenization temperatures 450 550 c indicative of the occurrence of fluid unmixing under lithostatic pressures of 550 to 780 bar 2 0 km depth primary fluid inclusions trapped in syn ore quartz calcite and epidote show the common development of s type inclusions 37 3 wt nacl equiv with coexisting v type liquid rich l type and co2 bearing c i type inclusions all of which have homogenization temperatures of 300 to 400 c and trapping pressures of 100 to 400 bar 1 5 km depth brine inclusions homogenized by halite dissolution after vapor disappearance in both the pre and syn ore stages are interpreted to have been trapped under overpressured conditions 1 520 bar oxygen isotope analyses were conducted on garnet wollastonite epidote quartz and calcite the pre ore stage garnet and wollastonite have 18ofluid values of 5 6 to 8 1 whereas the syn ore stage epidote quartz and calcite have more variable 18ofluid values in the range of 3 9 to 17 5 the 18ofluid values of the post ore stage vein calcite 15 2 21 3 are much higher than both the pre and syn ore stages the vapor phase of inclusions contains h2s ch4 and c2h6 in the syn ore stages all these observations reveal that 1 the formation of the cu skarn deposit was dominated by a magmatic hydrothermal system 2 multiple fluid pulses contributed to the formation of the pre and syn ore stage skarn minerals and sulfides and 3 the increase in ph due to the neutralization of the acidic fluid could be the main factor controlling the large scale ore deposition in hongniu hongshan

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

immiscibility between silicate magmas and aqueous fluids a melt inclusion pursuit into the magmatic hydrothermal transition in the omsukchan granite ne russia abstract exsolution unmixing of the volatile element rich phases from cooling and crystallising silicate magmas is critical for element transport from the earth s interior into the atmosphere hydrosphere crustal hydrothermal systems and the formation of orthomagmatic ore deposits unmixing is an inherently fugitive phenomenon and melt inclusions droplets of melt trapped by minerals provide robust evidence of this process in this study melt inclusions in phenocrystic and miarolitic quartz were studied to better understand immiscibility in the final stages of cooling of and volatile exsolution from granitic magmas using the tin bearing omsukchan granite ne russia as an example primary magmatic inclusions in quartz phenocrysts demonstrate the coexistence of silicate melt and magma derived cl rich fluids brine and vapour and emulsions of these during crystallisation of the granite magma microthermometric experiments in conjunction with pixe and other analytical techniques disclose extreme heterogeneity in the composition of the non silicate phases even in fluid globules within the same silicate melt inclusion we suggest that the observed variability is a consequence of strong chemical heterogeneity in the residual silicate melt brine vapour system on a local scale owing to crystallisation immiscibility and failure of individual phases to re equilibrate the possible evolution of non silicate volatile magmatic phases into more typical hydrothermal chloride solutions was examined using inclusions in quartz from associated miarolitic cavities

fluid immiscibility in volcanic environments volatile components enter the atmosphere oceans and other surface waters through pre syn and post eruptive volcanic processes that involve a variety of fluids aluminosilicate poor fluids include aqueous or carbonic to sulfide sulfate chloride fluoride carbonate and phosphate rich compositions in volcanic environments but other more complex combinations of these constituents may be involved giggenbach 1977 roedder 1984 1992 lowenstern 1995 other rare gases and dissolved constituents e g h2 n2 he ar h3bo3 hg ch4 and other hydrocarbon compounds metals and metalloids are also present but in general they are not sufficiently concentrated to form their own phases or control bulk fluid composition and volcanic processes as a result of their diverse compositions volcanic fluids ranging from vapor to liquid exhibit widely different densities and show strong distinctions in heat capacity dielectric behavior viscosity and other chemical and physical characteristics geiger et al 2006a the density of a saline liquid in the system nacl h2o at 50 mpa and 800 c for example is more than 7 times that of the coexisting aqueous vapor e g 0 2 gm cm3 henley and mcnabb 1978 multiple fluids move mix and or unmix in magma chambers and volcanic conduits in the root zone of fumaroles and in the convective hydrothermal systems that are ubiquitous to volcanic environments hydrothermal systems are typically centered on magmatic intrusions and may include crater lakes at the top of eruptive conduits hydrothermal processes involving two or more fluid phases operate through a variety of geologically relevant shallow crustal pressure temperature composition conditions volcanic fluids occur at supersolidus to subsolidus conditions meaning that the dense aluminosilicate melt that is common to volcanism may or may not be present this chapter addresses the evidence for and occurrence of two or more low density aluminosilicate poor fluids

orthomagmatic origin for the ilkwang cu w breccia pipe deposit southeastern kyongsang basin south korea abstract four distinct types of fluid inclusion are associated with brecciation alteration and mineralization in the ilkwang cu w breccia pipe deposit in the southeastern kyongsang basin south korea the earliest fluid inclusions in igneous quartz have salinities of 35 49 wt nacl equiv and homogenize by halite dissolution this fluid exsolved directly from the melt a co2 bearing fluid 2 4 wt nacl equiv was trapped during the initial stages of brecciation and pressure decrease and later brecciation events and continued decreasing pressure in the magma chamber generated low salinity supercritical fluids that boiled to produce brine 40 48 wt nacl equiv and coexisting vapor 2 13 wt nacl equiv at 343 493 c and 120 400 bars the latest fluid 5 24 wt nacl equiv was trapped during the waning stages of hydrothermal activity the oxygen and hydrogen isotopic compositions of the fluid 18 o smow 9 4 4 8 d smow 45 to 49 of quartz and the sulfur isotopic compositions 34 s cdt 0 3 to 0 9 of sulfide minerals cementing the breccia fragments are consistent with a magmatic origin for the hydrothermal fluids fluid inclusion data and stable isotopic compositions suggest that ilkwang cu w mineralization and alteration are products of orthomagmatic hydrothermal processes that were strongly pipe controlled the various types of fluid inclusions in the ilkwang deposit reflect the evolution from a high pressure to a low pressure magmatic system the evolution to a low pressure stage and concomitant aqueous fluid immiscibility in the ilkwang deposit are major factors in the formation of economic mineralization

the donoso copper rich tourmaline bearing breccia pipe in central chile petrologic fluid inclusion and stable isotope evidence for an origin from magmatic fluids the copper rich tourmaline bearing donoso breccia pipe is one among more than 15 different mineralized breccias in the giant 50 million metric tonnes of copper miocene and pliocene rio blanco los bronces copper deposit in the high andes of central chile this breccia pipe bracketed in age between 5 2 and 4 9 ma has dimensions of 500 by 700 m at the current surface 3 670 m above sea level its roots have yet to be encountered and it is 300 m in diameter at the depth of the deepest drill holes the donoso breccia is for the most part monolithic containing clasts of the equigranular quartz monzonite pluton which hosts the pipe it is matrix supported with between 5 and 25 of the total rock volume consisting of breccia matrix minerals which include tourmaline quartz chalcopyrite pyrite specularite and lesser amounts of bornite and anhydrite an open pit mine centered on this breccia pipe has a current production of 50 000 tonnes of ore per day at an average grade of 1 2 copper and copper grade in the breccia matrix is significantly higher measured 18o for tourmaline and quartz from the matrix of the donoso breccia at different levels of the pipe range from 6 9 to 12 0 and measured d in tourmaline ranges from 73 to 95 temperatures of crystallization of these minerals as determined by the highest homogenization temperatures of highly saline fluid inclusions range from 400 to 690 c when corrected for these temperatures the stable isotope data indicate that fluids from which these breccia matrix minerals precipitated were magmatic with 18o between 5 6 to 9 1 and d between 51 to 80 these isotopic data preclude participation of a significant amount of meteoric water in the formation of the donoso breccia they support a model in which brecciation is caused by expansion of magmatic fluids exsolved from a cooling pluton and breccia matrix minerals including copper sulfides precipitated from the same magmatic fluids responsible for brecciation sericitic alteration of clasts in the breccia was also caused by these magmatic fluids different types of fluid inclusions imply that several different magmatic fluids were involved in formation of the donoso breccia these include high temperature highly saline non boiling fluids trapped in inclusions that homogenize by halite dissolution which probably exsolved from a magma cooling under relatively high 1 kbar lithostatic pressure conditions consistent with geologic constraints other high temperature highly saline fluids are trapped in inclusions that homogenize by vapor bubble disappearance and are spatially associated with vapor rich inclusions suggesting either phase separation boiling or simultaneous separation of immiscible brine and vapor from a magma cooling at lower hydrostatic pressure conditions both types of high temperature highly saline fluids circulated intermittently as pressure fluctuated between lithostatic and hydrostatic conditions because of episodes of sealing and rebrecciation

geology mineralization and fluid inclusion characteristics of the kumbel oxidized w cu mo skarn and au w stockwork deposit in kyrgyzstan tien shan the kumbel deposit is located within a metallogenic belt of w mo cu mo au w and au deposits along the late paleozoic active continental margin of tien shan the deposit is related to a late carboniferous multiphase pluton with successive intrusive phases from early olivine monzogabbro through monzonite quartz monzonite to granodiorite and granite with the latest monzogabbro porphyry dikes the deposit represents an example of a complex w cu mo au magmatic hydrothermal system related to magnetite series high k calc alkaline to shoshonitic igneous suite it contains large bodies of w cu mo oxidized prograde and retrograde skarns with abundant andradite garnet magnetite and especially hematite as well as k feldspar molybdoscheelite chalcopyrite and molybdenite with transitions to zones of intense quartz k feldspar with minor andradite and hematite veining the skarns are cut by quartz carbonate adularia sericite veins locally sheeted and stockworks bearing scheelite and minor cu zn pb sulfides as well as au bi te and as mineralization the association of these veins with the oxidized skarns and magnetite series intrusion is consistent with the general oxidized intrusion related w mo cu au type of deposit with an affinity to the alkalic silica saturated cu au mo porphyry deposits the fluid inclusion data show the predominance of magmatic hydrothermal aqueous chloride fluid during the formation of skarns and quartz carbonate scheelite sulfide veins the high fluid pressures 1 750 bars together with their high temperature up to 600 c and high salinity 50 60 wt nacl equiv suggest the formation of skarns and quartz k feldspar andradite hematite veins under conditions typical of magmatic hydrothermal transition depth of 4 5 km of intrusion related mineralized system possibly by exsolution of the fluids from crystallizing magma the auriferous quartz carbonate scheelite sulfide veins formed from high to moderate salinity from 40 to 20 wt nacl equiv and high pressure from 1 200 bars to 850 900 bars aqueous chloride fluids under decreasing temperature from 370 to 120 c the massive deposition of molybdoscheelite in retrograde skarn and scheelite in quartz carbonate scheelite sulfide veins could correspond to enrichment of fluids in ca up to 18 25 wt cacl2 likely from crystallizing magma

fluid inclusion evidence for hydrothermal fluid evolution in the darreh zar porphyry copper deposit iran abstract the darreh zar porphyry copper deposit is associated with a quartz monzonitic granodioritic porphyritic stock hosted by an eocene volcanic sedimentary complex in which magmatic hydrothermal fluids were introduced and formed veins and alteration within the deepest quartz rich and chalcopyrite poor group a veins lvhs2 inclusions trapped high salinity high temperature aqueous fluids exsolved directly from a relatively shallow magma 0 5 kbar these late fluids were enriched in nacl and reached halite saturation as a result of the low pressure of magma crystallization and fluid exsolution these fluids extracted cu from the crystallizing melt and transported it to the hydrothermal system as a result of ascent the temperature and pressure of these fluids decreased from 600 to 415 c and approximately 500 315 bars at these conditions k feldspar and biotite were stabilized type a veins were formed at a depth of 1 2 km under conditions of lithostatic pressure and abrupt cooling upon cooling and decompressing the fluid intersected with the liquid vapor field resulting in separation of immiscible liquid and vapor this stage was recorded by formation of lvhs1 lvhs3 and vl inclusions these immiscible fluids formed chalcopyrite pyrite quartz veins with sericitic alteration envelopes b veins under the lithostatic hydrostatic pressure regime at temperatures between 415 and 355 c at 1 3 km below the paleowater table as the fluids ascended copper contents decreased and these fluids were diluted by mixing with the low salinity external fluid therefore pyrite dominated quartz veins were formed in purely hydrostatic conditions in which pressure decreased from 125 bars to 54 bars and temperature decreased from 355 to 298 c during the magmatic hydrothermal evolution the composition and p t regime changed drastically and caused various types of veins and alterations the abundance of chalcopyrite precipitation in group b veins suggests that boiling and cooling were important factors in copper mineralization in darreh zar

trace element geochemistry of molybdenite from the shapinggou super large porphyry mo deposit china abstract the shapinggou deposit located in the dabie orogenic belt eastern china is one of the largest mo only porphyry deposits in the world alteration types associated with shapinggou include silicic potassic silicic phyllic propylitic and argillic the phyllic alteration can be subdivided into quartz and sericite mainly muscovite phases whereas the argillic alteration is distinguished by poorly crystallized kaolinite kaolinite px muscovite and phengite the ore forming event can be divided into quartz k feldspar quartz molybdenite quartz sericite and quartz fluorite gypsum stages with molybdenite deposited in the first three stages but mainly in the second the molybdenites in shapinggou represent either the 2h1 and or the 2h1 3r polytype and can be subdivided into two groups group one and group two group 1 is associated with stage 1 alteration whereas group 2 is found with stages 2 and 3 there is an increase in the re values from group one to group two with the re contents likely controlled by both the crustal metal source and temperature with decreasing temperature the contents of re and the ratios of mo cu in molybdenites in shapinggou decrease gradually whereas the contents of cu and w sn and the ratios of re cu co ni increase the pb zn values in molybdenite are higher in the porphyry mo deposit associated with pb zn deposits than in porphyry cu mo mo deposits not associated with pb zn deposits the ratios of cl f so2 h2s and h k in the shapinggou fluids increasing over time suggest that the fluids became more oxidised the initial ore forming fluid was 500 c carried ions of mo ca na k cl f s and caused potassic silicic alteration with deposition of only small amounts of molybdenite as the temperature dropped down to 400 c the amounts of mo k cu and cl ions in the fluid decreased leading to silicic sericitic and propylitic alteration and the deposition of the majority of the molybdenite as the temperatures decreased to 300 c the fluid contained ions of ca and f and pb zn was deposited distally around the main mo ore body

multi stage fluid boiling and formation of the giant fujiawu porphyry cu mo deposit in south china abstract the fujiawu cu mo deposit is located in the southeastern part of south china mineralization and alteration at fujiawu include stage 1 barren quartz k feldspar biotite veins and stage 2 quartz molybdenite veins with potassic alteration stage 3 quartz pyrite chalcopyrite veins with phyllic alteration and stage 4 barren quartz pyrite calcite chlorite epidote veins with propylitization two phase liquid rich type i two phase gas rich type ii and halite bearing type iii aqueous inclusions were identified at fujiawu the last two types of fluid inclusions are absent in stages 1 and 4 type i inclusions in stage 1 veins demonstrate homogenization temperatures th of 409 to 556 c with salinities of 7 8 14 4 wt nacl equivalent type iii inclusions that homogenize by vapor bubble disappearance type iii a and coexisting type ii inclusions in stage 2 veins have th of 370 460 c and 374 505 c with salinities of 37 9 52 7 and 3 1 8 2 wt nacl equivalent respectively type iiia inclusions that homogenize by vapor bubble disappearance and coexisting type ii inclusions in stage 3 veins yield th 277 454 c and 323 450 c with salinities of 33 5 49 8 and 1 5 7 9 wt nacl equivalent respectively type i inclusions in stage 4 have th of 146 to 279 c with salinities lower than 4 9 wt nacl equivalent type iii inclusions that homogenize by halite disappearance type iii b in stages 2 and 3 of veins were not formed during fluid boiling processes and could yield extremely high trapping pressures the abundant presence of boiling fluid inclusion assemblages at fujiawu suggests that extensive multi stage boiling events promoted the large scale cu mo mineralization type iiib inclusions cannot be regard as the end member of boiling inclusion assemblages and cannot be used to calculate trapping conditions the estimated trapping pressures estimated by type iiia inclusions are 132 to 284 bars and 44 to 264 bars in stages 2 and 3 respectively re os dating of molybdenite gives a weighted average 187 re 187 os model age of 172 1 ma in response to a localized extensional environment due to a far field stress at the south china plate margin resulting from the initial paleo pacific plate northwestward subduction the high re contents in molybdenite in combination of previously reported high mgo contents of ore related porphyries and regional history indicate that ancient subduction modified lithospheric mantle was crucial for the fujiawu cu mo deposit