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

controlling mechanisms for molybdenum isotope fractionation in porphyry deposits the qulong example molybdenite bearing porphyry deposits are the predominant supplier of molybdenum to industrialized society and one of the main hosts of mo in the upper continental crust the mo isotope compositions 98 95mo normalized to nist3134 equals 0 of molybdenite show considerable variation 1 62 to 2 27 but the factors controlling this variability remain poorly constrained this information is critical for underpinning genetic models of porphyry deposits understanding elemental cycling and utilizing the 98 95mo of marine sediments as a paleoredox proxy using the well characterized qulong porphyry cu mo deposit tibet as an example here we discuss how rapid cooling facilitated by mixing hot magmatic fluid with cold meteoric water can be a controlling factor on efficient mineralization and then tackle how fluid evolution regulates molybdenum isotope fractionation molybdenites which preferentially partition isotopically light mo rayleigh fractionation precipitated from a single fluid will develop a heavier 98 95mo composition over time and this also creates heterogeneous 98 95mo between molybdenite grains whereas a fluid undergoing multiple episodes of intensive boiling will gradually lose its isotopically heavy mo to the vapor phase molybdenites crystallizing successively from the residual liquid will then have lighter 98 95mo over time however when mineralization efficiency becomes too low a negligible variation in 98 95mo of molybdenite is observed given that the mineralization efficiency i e the amount of mo crystallized as molybdenite from the fluid rarely reaches 100 and molybdenite favors isotopically light mo the presence of a residual fluid with isotopically heavy mo is inevitable this residual fluid may then become trapped in alteration halos hence 98 95mo has the potential to aid in locating the mineralization center e g lighter 98 95mo toward the orebody the residual fluid may also feed surface hydrological systems and eventually impact mo cycling our study highlights that understanding the controls of isotope fractionation is critical to bridge the gap between ore formation and elemental cycling and that other transition metals e g cu fe and zn may follow similar trajectories

re os and pb pb geochronology of the archean salobo iron oxide copper gold deposit carajas mineral province northern brazil rhenium osmium ages were determined for two molybdenite samples and a pb pb age was derived from bornite chalcopyrite magnetite at the salobo iron oxide copper gold deposit to determine the timing of mineralization and its relation to the nearby old salobo granite rhenium osmium dating of molybdenite spatially associated with copper sulfide minerals yields ages with weighted means of 2576 8 and 2562 8 ma removing the error multiplier introduced by the decay constant uncertainty appropriate for comparing ages from the same isotopic system these data convincingly argue for two temporally separated pulses of molybdenite deposition at 2576 1 1 4 ma n 2 and 2561 7 3 1 ma n 3 the 2576 8 ma age coincides with a previously published u pb age of 2573 2 ma for the old salobo granite suggesting that main stage ore formation may have been contemporaneous with granite magmatism the slightly younger 2562 ma age most likely represents new molybdenite precipitation associated with the development or reactivation of local shear zones lead lead stepwise leaching of copper sulfide minerals yields a less precise isochron age of 2579 71 ma and supports an archean age for the salobo ores this is the first documentation of an archean iron oxide copper gold deposit and the re os and pb pb geochronology herein support 2580 2550 ma estimates for basement reactivation and regional granite magmatism associated with the development of brittle ductile shear zones

molybdenite re os and muscovite 40 ar 39 ar dating of quartz vein type w sn polymetallic deposits in northern guangdong south china northern guangdong is an important part of nanling tungsten tin metallogenic belt south china the tungsten mineralization in this area consists of mainly quartz wolframite vein type mineralization with w sn polymetallic deposits mostly distributed at the outer contact zone between concealed late jurassic granitic stocks and cambrian ordovician low metamorphosed sandstones and shales molybdenite re os and muscovite 40ar 39ar isotopic dating of three typical tungsten vein type deposits yaoling meiziwo and jubankeng in northern guangdong show that two episodes of late jurassic w sn polymetallic mineralization occurred in this area an early episode during the late jurassic 158 159 ma represented by the yaoling hongling and meiziwo tungsten deposits and a younger event during the early cretaceous 138 ma represented by the jubankeng deposit analysis of available radiometric ages of several w sn deposits in the nanling region indicate that these deposits formed at several intervals during the mesozoic at 90 100 134 140 144 162 and 210 235 ma and that large scale w sn mineralization in this region occurred mainly between 150 and 160 ma

petrochronology and tims thermal ionization mass spectrometers or tims were developed by the pioneers of mass spectrometry in the mid 20th century and have since been workhorses for generating isotopic data for a wide range of elements later developed mass spectrometric techniques have many advantages over tims including higher spatial resolution with in situ techniques such as secondary ion mass spectrometry sims and laser ablation inductively coupled plasma mass spectrometry la icpms and greater versatility in terms the elements that can be easily and well measured the reason tims persists as an important method for geochronology is that for some key parent daughter systems e g u pb sm nd it can produce isotopic data and resultant dates with 10 100 times higher precision and more quantifiable accuracy than in situ techniques even when sample sizes are very small such as those that might result from single crystals or even small portions of zoned crystals for many questions in the geosciences the highest achievable precision and accuracy are required to resolve the timescales of processes and or correlate events globally as an example modern tims u pb geochronology is capable of producing dates with precision and accuracy better than 0 1 of the age for single crystals with only a few picograms pg of pb therefore it is possible to constrain the durations of single zircon crystal growth in magmatic systems over tens to hundreds of kyr in mesozoic and younger rocks if these dates and rates can be connected with other igneous processes such as magma transfer emplacement and crystallization then it becomes possible to calibrate thermal and mass budgets in magmatic systems and evaluate competing models for pluton assembly and subvolcanic magma storage as another example sm nd geochronology of garnet permits dates with precision better than 1 million years for garnets of any age including multiple concentric growth zones in single crystals such

timing and thermochemical constraints on multi element mineralisation at the nori ra cu mo u prospect great bear magmatic zone northwest territories canada the timing of cu mo u mineralisation at the nori ra prospect in the paleoproterozoic great bear magmatic zone has been investigated using re os molybdenite and 40ar 39ar biotite geochronology the re os molybdenite ages presented are the first robust sulphide mineralisation ages derived from the great bear magmatic zone cu mo u mineralisation is hosted in early to syn deformational hydrothermal veins consisting of quartz and k feldspar or more commonly tourmaline biotite quartz k feldspar with associated wall rock alteration assemblages being predominantly biotite sulphide and oxide minerals consist of chalcopyrite molybdenite and uraninite with lesser pyrite and magnetite elevated light rare earth elements and tungsten concentrations associated with the cu mo u mineralisation have also been reported at the prospect by previous workers molybdenite and uraninite occur intimately in dravitic tourmaline growth zones and at grain margins attesting to their syngenetic nature with respect to hydrothermal veining two molybdenite separates yield re os model ages of 1 874 4 8 7 2 and 1 872 4 8 8 ma 2 with a weighted average model age of 1 873 4 6 1 ma 2 laser step heating of biotite from the marginal alteration of the wall rock adjacent to the veins yields a 40ar 39ar maximum cooling age of 1 875 8 ma mswd 3 8 2 indistinguishable from the re os molybdenite model age and a previously dated syn tectonic aplitic dyke in the region dravitic tourmaline hosts abundant primary liquid vapour solid bearing fluid inclusions analytical results indicate liquid vapour homogenisation at 260 c constraining the minimum temperature of mineralisation the solids which are possibly trapped did not homogenise with the liquid vapour by 400 c salinities in the inclusions are variable raman spectra identify that at least some of the solids are calcite and anhydrite raman spectra also confirm the vapour phases contain some co2 whereas clathrates or ch4 was not observed or detected quartz grains only host secondary fluid inclusions which fluoresce under ultraviolet light indicating trapped hydrocarbons we speculate that these resulted from phanerozoic fluid circulation through the proterozoic basement the collective interpretation of the age hydrothermal character and associated metals high temperature and variable salinity suggests that the nori ra cu mo u mineralisation can be linked with the earliest stages of plutonism in the great bear magmatic zone from a regional perspective the mineralisation may pre date the extensive multi element mineralisation now recognised as part of the iron oxide copper gold iocg spectrum of deposits as iocg provinces generally contain a variety of mineralisation styles we interpret this as the earliest phase of the extensive mineralising system

re os molybdenite age of the cu mo skarn ore deposit at suoerkuduke in east junggar nw china and its geological significance the suoerkuduke cu mo ore is a medium sized skarn deposit in the east junggar orogen of the southern altaids xinjiang northwest china we measured re os isotopes of a molybdenite veinlet from the

subgrain scale decoupling of re and 187os and assessment of laser ablation icp ms spot dating in molybdenite abstract reproducibility of re os molybdenite ages depends on sample size and homogeneity suggesting that re and os are decoupled within individual molybdenite crystals and do not remain spatially linked over time in order to investigate the re os systematics of molybdenite at the subgrain micron scale we report la icp ms re os ages for an archean molybdenite crystal from aittojarvi finland analyzed in situ in a white aplite matrix a related aittojarvi molybdenite a996d in the form of a very fine grained mineral separate is used as one of our in house ntims standards and thus its age of 2760 9 ma is well established measurements of 187 re 187 os 185 re on micron scale spots along 200 m traverses across the crystal yield a wide range of ages demonstrating that in this case microsampling of molybdenite does not produce geologically meaningful ages experimentation with mineral separations and sample size over a 7 yr period predicted that this would be the outcome we suggest that 187 os is more likely to be the mobile species based on its charge and ionic radius and that 187 os becomes decoupled from parent 187 re with time on the micron and larger scale incompatible charge and ionic radius for os ions formed during reduction of molybdenite forming fluids may explain the widely observed absence of common initial os in molybdenite geologically accurate ages for molybdenite can only be obtained for fully homogenized crystals or crystal aggregates so that any post crystallization 187 re 187 os decoupling is overcome a growing number of geologically accurate id ntims 187 re 187 os ages for homogenized molybdenite suggest that postcrystallization mobility of radiogenic 187 os must be limited to within the molybdenite mineral phase we suggest that radiogenic 187 os may be stored in micron scale dislocations kink bands and delamination cracks produced by deformation and that the unusual structure and deformation response of molybdenite results in an increased chemical stability in this mineral migration of 187 os into adjacent silicate phases is highly unlikely but other contacting sulfides may take in os in an example from a proterozoic skarn deposit at pitkaranta western russia we demonstrate minor loss of radiogenic 187 os from molybdenite and a corresponding gain in adjacent chalcopyrite such that the molybdenite age is not perceptibly disturbed whereas the resulting chalcopyrite ages are impossibly old therefore it is unadvisable to perform re os analytical work on any sulfide in contact or intimate association with molybdenite in addition to large errors in the age if the isochron method is employed initial 187 os 188 os ratios could be erroneously high leading to seriously errant genetic interpretations

the influence of oxygen fugacity on tungsten and molybdenum partitioning between silicate melts and ilmenite the partitioning of molybdenum and tungsten between ilmenite ilm and silicic melts has been determined at 800 degrees c 1 kbar of pressure and at two oxygen fugacities at the oxygen fugacity of the graphite methane water buffer d super ilm melt mo 0 42 and d super ilm melt w 0 39 near the nickel nickel oxide buffer d super ilm melt mo 0 22 and d super ilm melt w 0 5 the variations in the partition coefficients with f sub o 2 are significant at the 0 06 and 0 33 levels for molybdenum and tungsten respectively the observed variation with oxygen fugacity is tentatively extrapolated to more complex systems and implies that the oxygen fugacity which prevails during magmatic crystallization may play a role in determining the mo w ratio in porphyry skarn or other hydrothermal mineral deposits examination of the literature on molybdenum and tungsten bearing mineral deposits indicates that systems with high w mo ratios are rather reduced and exhibit high ch 4 co 2 ratios in fluid inclusions low fe super 3 fe super 2 ratios in iron bearing minerals and low oxygen fugacities in associated igneous rocks on the other hand deposits with high mo w ratios are associated with rather oxidized magmatic systems we suggest that f sub o 2 dependent sequestration of molybdenum and tungsten in ferromagnesian phases during plutonic consolidation exerts a control on the relative efficiencies of removal of these metals from magmas into ore forming fluids

geochronology and geochemistry of the max porphyry mo deposit and its relationship to pb zn ag mineralization kootenay arc southeastern british columbia canada the max porphyry mo deposit is located at the northern end of the kootenay arc in southeastern british columbia canada molybdenum mineralization is genetically related to the variably altered trout lake granodiorite stock which has lithogeochemical affinities to the low fluorine calc alkaline granodiorite hosted porphyry mo deposit type three molybdenite samples from early and late mo bearing veins yield re os dates that overlap within analytical error with a weighted average age of 80 3 0 2 ma these dates are in close agreement with two 206pb 238u weighted average zircon ages for phases of the trout lake stock at 80 3 1 6 and 79 2 1 0 ma indicating that crystallization of the stock and hydrothermal molybdenite formation were coeval and likely cogenetic 40ar 39ar plateau ages for primary biotite in igneous dikes secondary biotite in early potassic alteration and muscovite in late phyllic alteration range from 80 to 76 ma the younger 40ar 39ar plateau ages may reflect unusually slow cooling of the magmatic hydrothermal system or a late thermal disturbance pb zn ag vein deposits are common throughout the kootenay arc and several such veins are located within and proximal to the max porphyry mo deposit the presence of rare molybdenite associated with sphalerite and argentiferous galena in some of these pb zn ag veins suggests that they represent a late stage event related to the max magmatic hydrothermal system fluid inclusions in quartz from mo and pb zn ag veins are similar and can be divided into two compositional groups type 1 aqueous liquid rich fluid inclusions and type 2 aqueous carbonic liquid rich fluid inclusions pressure corrected 1 4 1 7 kbar trapping temperatures of typical type 1 inclusions from mo bearing veins range from 430 to 460 c and for pb zn ag veins from 335 to 365 c the ranges of salinity 0 12 wt nacl equiv in fluid inclusions from both vein types are almost identical and type 2 inclusions from both vein types contain similar amounts of co2 avg xco2 0 08 with traces of ch4 the similarity of chemistry in the two vein types suggests a genetic link between porphyry mo mineralization and adjacent pb zn ag deposits however muscovite from the alteration halo around a pb zn ag vein within the max deposit yielded a 40ar 39ar plateau age of 72 2 0 5 ma this date is significantly younger than the 80 ma age of porphyry magmatism and mo mineralization suggesting either that this event is in fact unrelated to porphyry mo mineralization at 80 ma or that the k ar isotope system has been disturbed by a later thermal event

precise zircon u pb and molybdenite re os dating of the shuikoushan granodiorite related pb zn mineralization southern hunan south china abstract the shuikoushan ore district located in southern hunan province south china contains pb zn au mineralization hosted in the devonian to triassic strata and mesozoic granodiorite intrusions ore minerals are mainly pyrite sphalerite galena and minor molybdenite molybdenite usually intergrown with pyrite formed during pb zn hydrothermal mineralization in order to determine the precise age of pb zn mineralization and further understand the relationship between magma emplacement and hydrothermal mineralization in the ore district molybdenite re os dating and zircon sims u pb dating were undertaken the zircon u pb dating reveals that the granodiorite intrusion was emplaced at 158 8 1 8 ma mswd 0 40 re os isotopic age of seven molybdenite samples yields model ages ranging from 157 5 2 5 ma to 161 0 2 4 ma and gives a well defined 187re 187os isochron age of 157 8 1 4 ma 2 mswd 1 3 indicating the timing of pb zn mineralization in the shuikoushan ore district at about 158 ma this date coincides well with the zircon sims u pb age of the granodiorite revealing a genetic association between the pb zn mineralization and the granitic magmatism combined with geochronological data published for other pb zn cu deposits in southern hunan it can be concluded that the granodiorite related pb zn mineralization throughout southern hunan mainly occurred at 160 156 ma rather than 180 170 ma or 170 160 ma as considered previously the pb zn mineralization and major w sn mineralization in southern hunan are coeval and may be related to the same geological event

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

re os geochronology and systematics in molybdenite from the endako porphyry molybdenum deposit british columbia canada precise re os molybdenite ages for the endako porphyry molybdenum deposit and the nithi mountain occurrence british columbia canada yield new information on the timing of molybdenite deposition three episodes of mineralization are indicated 1 154 ma 2 148 to 146 ma and 3 145 ma re os dates agree well with new u pb and 40 ar 39 ar data from granitoids of the nithi phase 155 2 1 5 ma the endako phase 148 4 1 5 ma and a preore dike 147 4 0 6 ma and the casey phase 145 1 0 2 ma plus hydrothermal biotite 144 5 0 75 ma villeneuve et al 2001 the excellent correlation between the re os dates from molybdenite and the ages of granitoids from the area indicates a direct genetic relationship between these plutons and molybdenite mineralization these re os data also provide further insight into the systematics and robustness of re os in molybdenite the endako molybdenum deposit is the product of two episodes of mineralization both associated with moderate salinity 5 15 wt nacl equiv and high temperature 440 c fluids a third low temperature 190 300 c hydrothermal event is associated with eocene faulting selby et al 2000 the clear distinction between two of the re os molybdenite dates in the deposit and the close agreement of these dates to the ages of granitoid intrusions suggest that the re os system in molybdenite is not reset by high temperature 440 c moderate salinity hydrothermal fluids in contrast magmatic biotite in a 147 ma preore dike has a 40 ar 39 ar age of 145 ma identical to the age of the hydrothermal biotite indicating that 440 c fluids reset the ar ar system in biotite hence we interpret that the re os isotope system in molybdenite is resistant to resetting by high temperature fluids 440 c in contrast to the 40 ar 39 ar system in biotite the re os system in molybdenite is also unaffected by postore hydrothermal fluids these data show that molybdenite can provide critical information in understanding sulfide mineral deposition in ore systems which is not recorded by other isotopic systems in alteration minerals

palynological and sedimentological records of holocene human impact from the etang de berre southeastern france pollen and sedimentological analyses of holocene sediments from the etang de berre close to the rhone delta allow human impact on the holocene vegetation and hence on the landscape of the lower r

temporal evolution of mineralization events in the bohemian massif inferred from the re os geochronology of molybdenite molybdenite is a common mineral accompanying sn w au and base metal mineralizations located in different geotectonic units of the bohemian massif but it is also widespread in granitoids and or related quartz veins pegmatites forming disseminated mo mineralization thirty re os ages were obtained for molybdenite samples from the bohemian massif to provide constraints on the timing and duration of mineralization event s within the framework of previously published geochronological data for the host and or associated rocks the obtained data for sn w li deposits in the erzgebirge metallogenetic province indicate the predominance of one and or multiple short time mineralization events taking place between 319 and 323 ma with the exception of the krupka deposit associated with the altenberg teplice caldera where the data may suggest prolonged activity until 315 ma the ages of the pb zn au mo h rky u rakovnika and fe cu as ob i d l mineralizations from the exocontacts of the cista pluton and krkonose jizera plutonic complex respectively provide evidence for synchronous emplacement of the ore and the associated granitic rocks in contrast the padr fe as mo mineralization postdates the age of the associated padr granite disseminated mo mineralization in cadomian and variscan granitoids and or related to quartz veins pegmatites provides re os ages that overlap with the previously published geochronological data for the host rocks suggesting coeval evolution molybdenite samples from the sazava suite granites of the central bohemian plutonic complex cbpc have resolvable younger ages than their host granites but similar to the age of spatially related au mineralization which is associated with the latest evolution of the cbpc

rhenium osmium systematics of the mount isa copper orebody and the eastern creek volcanics queensland australia implications for ore genesis the syn tectonic breccia hosted mount isa cu deposit in northwest queensland is the largest sediment hosted cu deposit in australia whole rock samples of chalcopyrite rich cu ore form an isochron with a re os age of 1 372 41 ma this age is more than 100 ma younger than the previously accepted age of cu ore formation an ar ar mineral age for biotite separated from the host rocks within the alteration envelope to the cu orebody this discrepancy cannot be unequivocally resolved due to a lack of other absolute geochronological constraints for cu mineralisation or the deformation event associated with cu emplacement the 1 372 41 ma date may reflect a the time of cu deposition b the time of a hydrothermal event that reset the re os signature of the cu ore or c mixing of the re os isotope systematics between the host rocks and cu bearing fluids however a range of published ar ar and rb sr dates for potassic alteration associated with cu mineralisation also records an event between 1 350 and 1 400 ma and these are consistent with the 1 372 ma re os age the 1 8 ga eastern creek volcanics are a series of tholeiitic basalts with a primary magmatic cu enrichment which occur adjacent to the mount isa cu deposit the whole rock os isotopic signature of the eastern creek volcanics ranges from mantle like values for the upper pickwick member to more radiogenic crustal values for the lower cromwell member the re os isotope signature of the cu ores overlaps with those calculated for the two volcanic members at 1 372 ma hence the os isotope data are supportive of the concept that the os in the cu ores was sourced from the eastern creek volcanics by inference it is therefore postulated that the eastern creek volcanics are the source of cu in the mount isa deposit as both os and cu are readily transported by oxidised hydrothermal fluids such as those that are thought to have formed the cu orebody the pickwick member yields a re os isochron age of 1 833 51 ma which is within error of previously reported age constraints the initial 187os 188os isotopic ratio of 0 114 0 067 os 0 7 is slightly subchondritic and together with other trace element geochemical constraints is consistent with a subcontinental lithospheric mantle source the pickwick member records a minimum age of ca 1 95 ga for melt depletion in the subcontinental lithospheric mantle beneath the mount isa inlier prior to the extraction of the magmas which formed the eastern creek volcanics this corresponds with the end of subduction related magmatism along the eastern margin of the northern australian craton which included the mount isa inlier

molybdenite re os and u pb zircon dating and genesis of the dayana w mo deposit in eastern ujumchin inner mongolia abstract the dayana w mo deposit in eastern ujumchin of inner mongolia is a quartz vein type deposit in the mid western part of the central asian orogenic belt caob biotite monzogranite quartz porphyry and hornfels host w mo in quartz veins based on spatial relationships molybdenite was deposited first followed by wolframite this contribution presents precise laser ablation inductively coupled plasma mass spectroscopy la icp ms u pb zircon dating and geochemical analysis of the biotite monzogranite the u pb dating shows that the monzogranite is 134 1 ma major and trace element geochemistry shows that the monzogranite is characterized by high sio 2 and k 2 o contents a right inclined shape of the chondrite normalized ree patterns enrichment of large ion lithophile elements liles and depletion of high field strength elements hfses such as nb p ba the monzogranite is high k calc alkaline has a strong negative eu anomaly eu eu 0 04 0 45 low p 2 o 5 content high a cnk of 1 2 enriched in large ion lithophile elements liles such as rb th u nd and hf and notably depleted in ba sr p ti and nb these characteristics define the dayana monzogranite as a highly fractionated peraluminous granite re os isotopic analysis of seven molybdenite samples from the deposit yield an isochron age of 133 3 ma mswd 2 2 which indicates that the monzogranite and ore have the same age within error are probably genetically related and related to a major early cretaceous mineralizing event in china known as the yanshanian

origin of ree mineralization in the bastnas type fe ree cu mo bi au deposits bergslagen sweden the bastnas type deposits with mineral assemblages of fe oxides ca mg silicates rare earth element ree silicates ree fluorocarbonates and cu fe mo bi sulfides are associated with marble horizons in a strongly na k and or mg altered metavolcanic succession over a distance of at least 80 km in a sw ne trending zone in western bergslagen two subtypes occur 1 enriched relative to the other type in light ree lree and fe exemplified by the bastnas and rodbergsgruvan deposits and 2 enriched in heavy ree hree y mg ca and f represented by deposits in the norberg district bastnasite hosts primary fluid h2o co2 inclusions with salinities of 6 29 eq wt cacl2 and with total homogenization temperatures th tot of ca 300 400 c subtype 2 has late stage fluorite with fluid inclusions that show 1 16 eq wt nacl and th tot of ca 90 150 c molybdenite re os ages obtained from three deposits are 1 904 6 1 863 4 and 1 842 4 ma nd isotopic data from five different ree minerals yielded no defined isochron but a range in end 1 88 ga of 0 2 to 1 6 the oxygen isotope values 18osmow of dolomite and calcite from the associated ree mineralized skarn and recrystallized carbonate assemblages lie in the range 6 1 8 6 overlapping with those of the host marbles carbon isotope values 13cpdb show typical magmatic signatures of 6 7 to 4 4 while the host marbles group around ca 2 4 the sulfur isotope 34scdt values of associated sulfides range between 10 8 and 0 2 the combined evidence suggests ree mineralization beginning at 1 9 ga from mainly svecofennian juvenile magmatic 400 c fluids carrying si f cl s co2 and the ree in addition to other metals mineralization occurred through reactions with dolomitic layers in the supracrustal units coevally with regional metasomatic alteration associated with fluid circulation through an extensive active volcano plutonic complex

molybdenite re os and muscovite 40ar 39ar dating of the xihuashan tungsten deposit central nanling district south china abstract the xihuashan tungsten deposit in the central nanling region south china is an important vein type ore deposit hosted in cambrian strata and mesozoic granitic intrusions wolframite and molybdenite are the principal ore minerals the gangue minerals are mainly quartz and muscovite wolframite and molybdenite are products of the first stage hydrothermal activity whereas muscovite formed dominantly at the second stage molybdenite re os and muscovite 40ar 39ar dating have been carried out to investigate the age of mineralization re os isotopic dating for molybdenite associated with wolframite yield a precise well constrained isochron age of 157 8 0 9 ma mswd 1 5 ar ar isotopic analyses of muscovite yield a plateau age of 152 8 1 6 ma in agreement with an inverse isochron age of 152 8 1 6 ma which is 5 mys younger than the re os age the molybdenite re os age is interpreted as the age of tungsten mineralization this age coincides well with the zircon u pb age of the host granitic intrusion reported previously the 5 mys difference between molybdenite re os and muscovite 40ar 39ar ages probably represents the duration of hydrothermal activity the results show that the xihuashan tungsten deposit is one of many important tungsten tin deposits formed during 150 to 160 ma associated with large scale lithospheric extension in south china

a re os isotope study of sedimentary rocks and copper gold ores from the ertsberg district west papua indonesia abstract the ores of the ertsberg district consist of both porphyry stockwork and contact controlled mineralization related to the grasberg and ertsberg intrusion centers high grade copper mineralization with gold occurs in skarns on the periphery of each of the intrusion centers the periphery mineralization includes the kucing liar skarn related ores the massive sulfide lenses on the borders of the grasberg intrusive complex and the giant skarn bodies of the deep and intermediate ore zones together with the ores of the dom complex on the margin of the ertsberg diorite the ertsberg orebody the basis of discovery of the district is a copper gold roof pendant of sedimentary strata in the diorite in order to clarify genetic and geochronologic links between the peripheral sediment hosted ore bodies and the intrusion hosted ore bodies re os isotopes of the ores and subjacent precambrian and phanerozoic crust were analyzed re os geochronology of molybdenites was used to resolve the age relationships of the ore bodies the grasberg and kucing liar molybdenites have older molybdenite mineralization ages of 2 88 0 02 ma and 3 01 0 02 ma respectively whereas the ertsberg molybdenite has a younger age of 2 54 0 02 ma these data agree with ar chronologies of the alteration associated with mineralization pollard and taylor 2000 pollard p j taylor r 2000 geochronology of intrusive rocks and cu au mineralization in the ertsberg district in proceedings of freeport institut teknologi bandung itb geological symposium bandung java pp 17 19 and also indicate that the grasberg and kucing liar molybdenites are closely similar in age and older than the ertsberg intrusive system re os data from pyrite chalcopyrite magnetite gold and the surrounding sedimentary rocks from the district define a mixing relationship between samples from the initial stockwork mineralization and peripheral ores of each intrusion center sulfide and oxide minerals from primary stockwork mineralization are isotopically homogeneous and define trends on isochron diagrams with distinct os initial ratios whereas sulfides and oxides taken from peripheral ores are isotopically heterogeneous and define trends on mixing diagrams one possible end member for the mixing is sedimentary rock surrounding the porphyries the measured os ratios of the sedimentary rocks range from 0 52 to 2 21 and overlap the os initial ratios of the sulfides and oxides sampled from both stockwork and contact mineralization the data suggest a model in which the continental crust supplied some of the os and by inference other metals during magma genesis in the lower crust and the remainder came from sedimentary rocks near the intrusion centers

geochronology geochemistry and sr nd hf s pb isotopes of the early cretaceous taoxihu sn deposit and related granitoids se china abstract the taoxihu deposit eastern guangdong se china is a newly discovered sn polymetallic deposit zircon u pb dating yielded 141 8 1 0 ma for the sn bearing granite porphyry and 145 5 1 6 ma for the biotite granite batholith it intruded the age of the granite porphyry is consistent within error with the molybdenite re os isochron age 139 0 1 1 ma of the sn mineralization indicating a temporal link between the two geochemical data show that the granite porphyry is weakly peraluminous contain high si na and k low fe mg ca and p and relatively high rb sr and low k rb values the rocks are enriched in rb th u k and pb and depleted in ba sr ti and eu resembling highly fractionated i type granites they contain bulk rock initial 87 sr 87 sr of 0 707371 0 707730 and end t of 5 17 to 4 67 and zircon ehf t values from 6 67 to 2 32 with late mesoproterozoic t dm2 ages for both nd and hf isotopes this suggests that the granite porphyry was likely formed by the partial melting of the crustal basement of mesoproterozoic overall residence age with minor mantle input 34 s cdt values of the taoxihu chalcopyrite and pyrite range from 0 1 to 2 1 average 0 9 implying a dominantly magmatic sulfur source the 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb ratios of the taoxihu sulfide ores are 18 497 18 669 15 642 15 673 and 38 764 38 934 respectively indicating a mainly upper continental crustal lead source with minor mantle contribution the highly fractionated and reduced low calculated zircon ce 4 ce 3 and eu n eu n values nature of the ore forming granitic magma may have facilitated the sn enrichment and played a key role in the sn mineralization we propose that the ore forming fluids at taoxihu were of magmatic hydrothermal origin derived from the granite porphyry and that both the granite porphyry and the sn mineralization were likely formed in an extensional setting possibly related to the subduction slab rollback of the paleo pacific plate

a review of molybdenite and fluorite mineralisation in caledonian granite basement western ireland incorporating new field and fluid inclusion studies and re os and u pb geochronology abstract the recent discovery of late magmatic quartz vein hosted molybdenite and exceptional gem quality vein fluorite in the caledonian galway granite complex ggc has prompted a review of these contrasting styles of mineralisation in the late caledonian granite basement connemara western ireland existing published u pb and re os chronometry and fluid inclusion microthermometry are combined with new a geological field observations b u pb zircon and re os molybdenite geochronometry and c fluid inclusion microthermometry to generate a new pressure temperature time model p t t of mineralisation for the ggc re os chronometry molybdenite indicates that granite related molybdenite mineralisation extended from 423 to 380ma overlapping with the ggc emplacement history determined by u pb zircon chronometry the p t t model reflects initial granite emplacement and mo mineralisation at 423ma followed by lower p and t granite emplacement and related quartz vein hosted mo mineralisation at 410ma carna pluton 400ma kilkieran pluton and at 380ma costelloe murvey granite the gem quality fluorite veins in the ggc represent late triassic hydrothermal mineralisation these veins form part of a regional n atlantic european triassic jurassic hydrothermal mineralisation province vein emplacement was triggered by the rifting of the n atlantic facilitating crustal thinning and subsidence of continental crust and initiating hydrothermal activity at the margins of mesozoic basins

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

how accurately can we date the duration of magmatic hydrothermal events in porphyry systems an invited paper determining the absolute duration of magmatic hydrothermal events leading to the formation of porphyry systems i e including porphyry copper skarn and epithermal deposits is one of the key questions in ore geology this is so because the duration of magmatic hydrothermal events in porphyry systems is instrumental to the development of genetic models necessary to explore a category of mineral deposits that provide most of the copper and significant amounts of base and precious metals to our economy the problem of determining the absolute duration of magmatic hydrothermal events in porphyry systems has been addressed through thermal modeling of cooling intrusions and time needed to precipitate specified metal amounts from active hydrothermal systems with known metal concentrations and fluid fluxes both these methods have shown that the likely duration of hydrothermal systems is on the order of a few tens of kilo annum ka isotopic dating in contrast is the only possible way to determine the life span of magmatic hydrothermal events in fossil porphyry systems analytical and methodological developments during the last decade in the fields of the most robust isotopic systems commonly used for absolute dating u pb 40ar 39ar re os allow us to date minerals with internal precisions 0 2 2 for a 10 ma old mineral this corresponds to a 20 ka uncertainty which is marginally sufficient to discriminate the duration of hydrothermal systems at the tens of kilo annum scale however many geochronological studies on fossil porphyry systems have shown that these are most often formed through repeated cycles of several intrusion events which extend the overall life of the porphyry systems to a few 0 x and up to 2 ma in some cases internal precisions of the above mentioned dating methods allow us in theory to comfortably discriminate events at the 0 x scale and the combination of u pb 40ar 39ar and reos geochronology is a tool widely used by ore geologists to bracket the duration of cyclic magmatic hydrothermal events in porphyry systems in this review we discuss some fundamental problems that are systematically overlooked in most geochronological studies trying to bracket the life span of porphyry systems we show that if these problems are not adequately taken into account and tackled the result will be that fundamentally wrong life spans of porphyry systems will be estimated we also provide basic guidelines to follow when trying to resolve the duration of magmatic hydrothermal events in porphyry systems with the highest accuracy and precision currently achievable

neoproterozoic cambrian petroleum system evolution of the micang shan uplift northern sichuan basin china insights from pyrobitumen rhenium osmium geochronology and apatite fission track analysis the neoproterozoic strata of the sichuan basin are a key target for oil and gas to evaluate the hydrocarbon evolution and its relationship with tectonic events in the micang shan uplift northernmost sichuan basin we apply solid bitumen geochemistry bitumen reflectance and fluorescence and re os geochronology the geochemistry of the solid bitumen indicates that it is highly mature pyrobitumen that formed contemporaneously with dry gas generation during oil thermal cracking the pyrobitumen is enriched in both re 106 191 ppb and os 3030 5670 parts per trillion the re os isotope data imply an early jurassic date for pyrobitumen formation which coincides well with age estimates from fluid inclusion data and basin modeling the re os date for pyrobitumen formation coupled with previously presented apatite fission track aft analysis show that exhumation of the neoproterozoic strata occurred during the cretaceous in the micang shan uplift this extensive uplift led to the erosion of any potential gas reservoirs and surface exposure of bitumen bearing neoproterozoic strata in contrast the more southern and central portions of the sichuan basin have experienced less severe exhumation and as a result neoproterozoic sourced gas systems are present this study shows that through the combined application of re os and aft methodologies the timing of gas generation and subsequent erosion of any potential gas reservoirs in the micang shan uplift northern sichuan basin can be quantified moreover the re os and aft data illustrate the potential to constrain the timing of gas generation in petroleum systems worldwide

besshi type vms deposits of the rudny altai central asia for the first time in the rudny altai we propose to distinguish besshi and kuroko type deposits previously considered as members of a single massive sulfide polymetallic group the ores of the two deposit types differ in mineral composition with pyrite pyrrhotite chalcopyrite sphalerite mineralization in the besshi type deposits versus pyrite sphalerite galena chalcopyrite gold mineralization in the kuroko type deposits the besshi type deposits are restricted to the irtysh terrane and associated with deformed and metamorphosed greenschist to mid amphibolite facies mafic siliciclastic rock sequences this contrasts with the well preserved kuroko type deposits hosted in bimodal volcanic sequences in the devonian carboniferous rudny altai magmatic arc our u pb 40ar 39ar and re os isotope dating of sulfides and host rocks of the besshi type deposits suggests that they were probably formed during the early paleozoic in a back arc rift setting they were then metamorphosed during devonian times within the accretionary wedge in front of the rudny altai arc synchronously with formation of the kuroko type deposits

re os and 40ar 39ar ages of porphyry molybdenum deposits in the east greenland volcanic rifted margin precise re os dating of molybdenite from the malmbjerg and flammefjeld rift related porphyry molybdenum deposits indicates that they are among the youngest magmatic events 25 8 0 1 and 39 7 0 2 ma in their respective areas of the east greenland rifted continental margin an 40 ar 39 ar age for biotite from the malmbjerg granite stock 25 7 0 3 ma demonstrates that molybdenite mineralization is essentially concurrent with granite emplacement further the identical ages obtained by argon and re os geochronology suggest that for the youngest events in a region re os and argon based methods produce similar age results whereas this is generally not the case for older ore forming events that have been thermally overprinted in the latter case disturbance of argon systematics produces ages younger than those determined by re os both deposits postdate continental breakup and the associated flood volcanism episode at 56 to 54 ma we suggest that the malmbjerg and flammefjeld molybdenum deposits formed during later periods of lithospheric uplift which at least in the case of malmbjerg may have been related to plate tectonic reorganization of the northeast atlantic ocean basin this uplift may have caused decompression mantle melting and renewed generation of mafic magma that led to crustal anatexis and the establishment of major hydrothermal systems the suggestion that molybdenum mineralization occurred at times of late uplift of a volcanic rifted margin may be useful in prospecting

u pb re os and 40ar 39ar geochronology of porphyry sn cu mo and polymetallic ag pb zn cu vein mineralization at bianjiadayuan inner mongolia northeast china implications for discrete mineralization events

genesis of the zhengguang gold deposit in the duobaoshan ore field heilongjiang province ne china constraints from geology geochronology and s pb isotopic compositions abstract the zhengguang gold deposit in the duobaoshan ore field hosted in volcanic rocks of the middle ordovician duobaoshan formation is one of the largest gold deposits in the northeastern great xing an range of the central asian orogenic belt caob the deposit comprises the no i ii and iii ore zones with a total resource exceeding 35 tonnes of au 100 000 tonnes of zn and 100 tonnes of ag a genetic relationship between gold mineralization and concealed tonalite porphyry is inferred based on the characteristics of cryptoexplosive breccia and hydrothermal alteration indicative of porphyry type and epithermal mineralization zircon la icpms u pb dating reveals that the tonalite porphyry was emplaced at 462 1 1 8 ma middle ordovician the 34 s v cdt values of sulfide minerals range from 3 0 to 1 7 with an average of 2 33 indicating that sulfur was mainly derived from a magmatic source the pb isotopic compositions 206 pb 204 pb ranging from 17 572 to 17 629 207 pb 204 pb from 15 424 to 15 486 and 208 pb 204 pb from 37 206 to 37 418 suggest a major mantle component for pb and by inference for other ore metals therefore we suggest that the ore forming elements in the zhengguang gold deposit may be related to the mantle sourced tonalite porphyry on the basis of the geological characteristics and geochemical signatures documented in this study we conclude that the zhengguang gold deposit was formed in a porphyry to epithermal transitional environment associated with the concealed tonalite porphyry as part of the duobaoshan porphyry epithermal ore system that is related to the subduction of the paleo asian ocean during the ordovician

relationships between porphyry cu mo mineralization in the jinshajiang red river metallogenic belt and tectonic activity constraints from zircon u pb and molybdenite re os geochronology abstract the jinshajiang red river porphyry cu mo metallogenic belt is an important cenozoic porphyry cu mo mineralization concentrating zone in the eastern indo asian collision zone new zircon u pb and molybdenite re os ages and compilation of previously published ages indicate that porphyry cu mo deposits in the belt did not form at the same time i e the porphyry emplacement and relevant cu mo mineralization ages of the ailaoshan red river ore belt in south range from 36 3 ma to 34 6 ma and from 36 0 ma to 33 9 ma respectively which are obviously younger than the porphyry emplacement ages of 43 8 36 9 ma and the relevant cu mo mineralization ages of 41 6 35 8 ma of the yulong ore belt in north tectonic studies indicated that the jinshajiang fault system in north and ailaoshan red river fault system in south of the jinsjiang red river belt had different strike slip patterns and ages the right lateral strike slip motion of the jinshajiang fault system initiated at ca 43 ma with corresponding formation of the yulong porphyry cu mo system whereas the left lateral strike slip motion of the ailaoshan red river fault system initiated at ca 36 ma with corresponding formation of the ailaoshan red river porphyry cu mo system therefore the different ages of porphyry cu mo systems between in north and south of the jinshajiang red river belt indicate that the porphyry cu mo mineralization is closely related to the divergent strike slip movements between the jinshajiang and ailaoshan red river strike slip faulting resulted from the indo asian collision the tanslithospheric jinshajiang red river faulting caused partial melting of the enriched mantle sources of alkali rich porphyries by depressurization or and asthenospheric heating and facilitated the migration of alkali rich magmas and the corresponding formation of alkali rich porphyries and relevant cu mo deposits in the belt

the evolution of aqueous vapor from silicate melts effect on oxygen fugacity abstract the simplest possible aqueous vapor evolved from an iron bearing magma under normal conditions is an h 2 o h 2 mixture hydrogen is produced by the oxidation of fe ii to fe iii by water in the magma yielding an increase in f o 2 equations are derived which model this mass transfer process the resulting differential equation expresses the change in magmatic f o 2 as a function of a change in n 1 h 2 o the vapor evolution progress variable the calculations demonstrate that in this simple scheme very iron poor magmas h 2 o feo are required to produce significant increases in magmatic f o 2 the incremental increase in o 2 during vapor evolution becomes progressively smaller as o 2 increases with this process becoming highly inefficient as the hematite stability field is approached other more complete processes involving meteoric water assimilation of altered rocks and subsolidus processes may produce the observed increase in f o 2 inferred to have occurred in systems of normal iron contents in low iron systems such as the high silica rhyolitic magmas associated with climax type porphyry molybdenum systems high oxygen fugacities may be obtained by this mechanism

an re os date for molybdenite bearing quartz vein mineralization within the kangerlussuaq alkaline complex east greenland implications for the timing of regional metallogenesis the kangerlussuaq alkaline complex east greenland is one of the largest alkaline complexes in the world it is known to host a number of occurrences of base and precious metal mineralization including the flammefjeld porphyry mo deposits and a suite of epithermal style base and precious metal veins in an area around the sondre syenitgletscher here we describe and date a previously unknown occurrence of molybdenite pyrite scheelite bearing quartz veins associated with alkali basalt dikes that intrude the main syenites of the complex the veins appear to be cogenetic with the dikes which crosscut and brecciate granodiorites of the cirque 1320 complex sulfur isotope signatures of molybdenite and pyrite in the veins give a tight range with mean 34 s of 2 2 0 7 consistent with a magmatic s source related to the intrusion of the dikes molybdenite from the veins gave an re os age of 52 74 0 26 ma some 13 m y older than molybdenite at the flammefjeld porphyry deposit thus distinguishing this metallogenic episode as a distinct event temporally unrelated to the known mo mineralization at flammefjeld significantly in terms of the timing of regional metallogenesis and magmatism our date suggests that the age of the kangerlussuaq alkaline complex itself may be slightly older than the 50 ma currently accepted based on 40 ar 39 ar dating from biotites in the main syenites given the common discrepancy in ore systems of 40 ar 39 ar which produce slightly younger dates than those by re os and u pb we suggest the actual age of the kangerlussuaq alkaline complex may be closer to 53 to 52 ma

re os geochronology of quartz enclosed ultrafine molybdenite implications for ore geochronology re os molybdenite geochronology relies on the aliquant analysis taken from a mineral separate although suitable for coarse grained molybdenite samples traditional mineral separation techniques are not ideally suited for samples possessing fine grained molybdenite m and thus hamper the application of re os geochronology for such samples here we demonstrate a room temperature hydrofluoric acid hf chemical separation technique that is capable of isolating ultrafine molybdenite i e m for re os geochronology six re os molybdenite model ages from four molybdenite in house control and nist reference material rm8599 samples exposed to concentrated hf are indistinguishable from the re os molybdenite model ages for aliquants not exposed to hf thus hf exposure at room temperature has no effect on re os molybdenite systematics our hf chemical separation technique was then applied to six ultrafine molybdenite samples from the lupa goldfield southwest tanzania three samples from the kenge deposit provide a weighted average re os molybdenite model age of 1953 5 ma mswd 0 6 n 3 whereas three samples and one repeat analysis from the porcupine deposit provide a weighted average re os molybdenite model age of 1886 5 ma mswd 1 5 n 4 our proposed analytical protocol has allowed us to determine reproducible ages from ultrafine molybdenite samples within the lupa goldfield that were previously unsuitable for molybdenite re os geochronology using conventional mineral separation techniques

genesis of the shangjinshan w mo polymetallic deposit in the eastern jiangnan tungsten belt evidences from geochemistry geochronology and zircon hf isotope analyses abstract the newly discovered shangjinshan w mo polymetallic deposit located at the southern anhui southeast china is a large scale skarn type tungsten polymetallic deposit according to mineral assemblages ore textures structures and superposition relationships of the mineralization three ore types have been recognized veinlet disseminated skarn the primary type quartz vein type and porphyry type the mineralized event of this deposit could be divided into four stages i the prograde skarn stage ii retrograde skarn stage iii quartz sulfide vein stage and iv quartz calcite vein stage the intrusion in the tungsten rich district of the shangjinshan is mainly composed of the granodiorite with zircon u pb ages of 138 4 1 2 ma to 136 7 1 3 ma meanwhile re os isotopic dating of five molybdenite samples yields an isochron age of 141 9 3 1 ma and a weighted average age of 139 3 1 7 ma respectively the ore forming ages are consistent with the rock forming ages within errors indicating that the w mo mineralization is genetically related to the shangjinshan granodiorite the granodiorite is i type granites characterized by metaluminous to slightly peraluminous and high k cal alkaline compositions they are also enriched in large ion lithophile elements liles and light rare earth elements lrees and depleted in high field strength elements hfses and heavy rare earth element hrees with obviously negative eu anomalies eu eu 0 50 0 84 the zircon ehf t values and two stage hf model ages tdm2 fall into the range 6 18 to 2 04 and 1 5 1 3 ga respectively the relatively low rhenium contents in molybdenite and high radioactive pb isotopes of the pyrites from stage ii indicate that the ore forming material was derived from shangjinshan granitic magmatism together with previously published data we propose that the w related granitoids in the jnb were likely generated by partial melting of the shangxi group with some additional mantle materials the granitic magmatism was caused by the asthenosphere upwelling triggered by the roll back of subduced paleo pacific plate during late jurassic to early cretaceous these granitic stocks predominately contributed to the production of skarn alteration and mineralization resulting in the giant tungsten polymetallic district in the jiangnan tungsten belt

reos dating of molybdenites from ore deposits in japan implication for the closure temperature of the reos system for molybdenite and the cooling history of molybdenum ore deposits abstract rhenium and osmium abundances were determined on molybdenites from eighteen ore deposits in japan fifteen vein type a skarn type a greisen type and a pegmatite type deposit re os ages obtained for molybdenites from northeastern central and southwestern japan are 100 130 ma 50 75 ma and ca 10 ma respectively reflecting the ages of regional igneous activities in individual areas for vein type ore deposits re os ages for molybdenites agree with rb sr whole rock ages of host granitoids while they are 3 12 ma older than k ar mineral ages of the host rocks on the other hand re os ages of molybdenites from skarn pegmatite and greisen type ore deposits agree with k ar ages of the host rocks the comparison of re os ages for molybdenites with rb sr and k ar ages of host rocks in vein type deposits suggests that re os closure temperature for vein molybdenite is close to whole rock rb sr closure temperature for host granitic rocks i e roughly estimated to be around 500 c and higher than k ar closure temperature for host granodiorites i e 230 370 c if the thermal history of vein molybdenites is essentially equivalent to that of host rocks one possible explanation for age discrepancies of 3 12 ma between re os ages for molybdenites and k ar ages for the wall rocks observed in vein type molybdenum deposits is that later thermal events after formation of molybdenum ores may reset k ar ages hydrothermal alteration might have occurred in such a temperature condition as to disturb k ar mineral systems in wall rocks and made them younger but not the re os system in molybdenite the other explanation might be that the age discrepancies correspond to a cooling interval from ca 500 to 300 c of host granitoid on the other hand the agreement of re os ages of molybdenites and k ar ages of host rocks in skarn pegmatite and greisen type deposits in this study indicates no later disturbance for k ar system in the wall rock or the rapid cooling of the ore and wall rocks after the formation of molybdenite deposits

further evaluation of the re os geochronometer in organic rich sedimentary rocks a test of hydrocarbon maturation effects in the exshaw formation western canada sedimentary basin abstract re os isotopic analyses of a single organic rich sedimentary rock unit ors of known depositional age and at three levels of regional hydrocarbon maturity show that hydrocarbon maturation does not affect the ability the 187re 187os chronometer to yield a depositional age for such rocks we present re os isotope analyses from the late devonian exshaw formation in the subsurface of the western canada sedimentary basin alberta and obtain a re os isochron age of 358 10 ma 2 model 3 1 666 10 11 a 1 for samples ranging from hydrocarbon immature to overmature this age is within uncertainty of the established absolute age for the exshaw formation hydrocarbon immature and mature plus overmature samples show no significant age differences if regressed individually indicating that hydrocarbon maturation did not greatly disturb the re os isotope system in the exshaw formation as such we propose that the re os geochronometer may be used as a reliable tool for measuring the depositional ages of ors regardless of their level of hydrocarbon maturity we find that minimizing natural variation in the initial 187os 188os ratio is more important than avoiding hydrocarbon maturation in obtaining precise re os ages in particular the exshaw formation appears to contain a nonhydrogenous component of unradiogenic os in addition to the hydrogenous os load a subset of exshaw formation samples with 5 total organic carbon toc which should best reflect the hydrogenous os load alone yields a very well fitted isochron having a depositional age of 358 9 ma 2 1 666 10 11 a 1 with an initial 187os 188os ratio of 0 59 0 05 model 3 mean square of weighted deviates mswd 1 8 the initial 187os 188os ratio of this regression may provide an estimate of the os isotopic composition of local seawater at the time of deposition

re os ages for archean molybdenite and pyrite kuittila kivisuo finland and proterozoic molybdenite kabeliai lithuania testing the chronometer in a metamorphic and metasomatic setting seven 187re 187os ages were determined for molybdenite and pyrite samples from two well dated precambrian intrusions in fennoscandia to examine the sustainability of the re os chronometer in a metamorphic and metasomatic setting using a new 187re decay constant 1 666 10 11y 1 with a much improved uncertainty 0 31 we determined replicate re os ages for molybdenite and pyrite from the kuittila and kivisuo prospects in easternmost finland and for molybdenite from the kabeliai prospect in southernmost lithuania these two localities contain some of the oldest and youngest plutonic activity in fennoscandia and are associated with newly discovered economic au mineralization ilomantsi finland and a cu mo prospect kabeliai lithuania two re os ages for vein hosted kabeliai molybdenite average 1486 5 ma in excellent agreement with a 1505 11 ma u pb zircon age for the hosting kabeliai granite pluton the slightly younger age suggests the introduction of cu mo mineralization by a later phase of the kabeliai magmatic system mean re os ages of 2778 8 ma and 2781 8 ma for kuittila and kivisuo molybdenites respectively are in reasonable agreement with a 2753 5 ma weighted mean u pb zircon age for hosting kuittila tonalite these re os ages agree well with less precise ages of 2789 290 ma for a rb sr whole rock isochron and 2771 75 ma for the average of six sm nd tdm model ages for kuittila tonalite three re os analyses of a single pyrite mineral separate from the same sample of kuittila pluton that yielded a molybdenite separate provide individual model ages of 2710 27 2777 28 and 2830 28 ma re 17 4 12 1 and 8 4 ppb respectively with a mean value of 2770 120 ma in agreement with the kuittila molybdenite age the re and 187os abundances in these three pyrite splits are highly correlated r 0 9994 and provide a 187re 187os isochron age of 2607 47 ma with an intercept of 21 ppt 187os mswd 1 1 it appears that the re os isotopic system in pyrite has been reset on the millimeter scale and that the 21 ppt 187os intercept reflects the in situ decay of 187re during the 160 to 170 m y interval from 2778 ma time of molybdenite pyrite deposition to 2607 ma time of pyrite resetting when the re os data for molybdenites from the nearby kivisuo prospect are plotted together with the kuittila molybdenite and pyrite data a well constrained five point isochron with an age of 2780 8 ma and a 187os intercept 2 4 3 8 ppt of essentially zero results mswd 1 5 we suggest that the pyrite isochron age records a regional metamorphic and or hydrothermal event possibly the time of au mineralization a proposed re os age of 2607 ma for au mineralization is in good agreement with radiometric ages by other methods that address the timing of archean au mineralization in deposits worldwide so called late au model molybdenite in contrast provides a robust re os chronometer retaining its original formation age of 2780 ma despite subsequent metamorphic disturbances in archean and proterozoic time

late holocene east antarctic climate trends from ice core and lake sediment proxies a high resolution record of evaporation for the last 650 years was derived from the diatom salinity signal preserved in a sediment core taken from ace lake vestfold hills 68 28 s 78 11 e antarctica the seasonal oxygen isotope signal preserved in an ice core from law dome 66 44 s 112 50 e antarctica revealed a high resolution summer temperature record for the same time period the two proxies show highly correlated behaviour despite having significantly different climatic response mechanisms and a large geographic separation the correlation observed between proxies based on such differing processes and analytical method ologies provides not only a climate record for the past 650 years that is both robust and regionally representative of coastal east antarctica but also confirmation of the utility of reconstructions using these methods

late archean cu au mo mineralization at gameleira and serra verde carajas mineral province brazil constraints from re os molybdenite ages new re os molybdenite ages provide constraints on the timing of late archean cu au mo mineralization in the northern carajas mineral province molybdenite from the gameleira iron oxide cu au mo deposit yielded an age of 2 614 14 ma this age overlaps within its analytical error with re os ages of molybdenite from the serra verde cu au mo vein deposit 2 609 13 ma and from the nearby small garimpo fernando gold mining operation 2 592 13 and 2 602 13 ma which is probably related to the latter the geochronological data imply that the hydrothermal cu au mo mineralization in these three deposits was epigenetic and coincides with a regional tectonic regime changing from dextral transtension and clastic sedimentation at 2 7 2 6 ga to sinistral transpression and inversion at 2 6 ga previously reported stable isotope and microthermometric data are compatible with a magmatic affiliation of the cu au mo ores at gameleira and serra verde a genetic relationship of mineralization may therefore exist with 2 56 2 76 ga archean alkaline granitoids or with 2 6 2 7 calc alkaline to tholeiitic volcanic arc type magmatism

an early cretaceous carbonate replacement origin for the xinqiao stratabound massive sulfide deposit middle lower yangtze metallogenic belt china stratabound massive sulfide deposits are widespread along the middle lower yangtze metallogenic belt mlymb and serve as an important copper producer in china two contrasting genetic models have been proposed interpreting the stratabound massive sulfide deposits as a carboniferous sedex protore overprinted by cretaceous magmatic hydrothermal system or an early cretaceous carbonate replacement deposit these two contrasting models have been applied to the xinqiao stratabound cu au sulfide deposit which is dominated by massive sulfide ores hosted in marine carbonates of the carboniferous chuanshan and huanglong formations with minor cu au skarn ores localized in the contact zone between the cretaceous diorite jitou stock and the carboniferous carbonate rocks new sims zircon u pb dating suggests that the jitou stock formed at 138 5 1 1 ma 2 mswd 0 6 pyrite re os dating yields an imprecise date of 142 47 ma 2 mswd 7 8 the geochronological data thus constrain the mineralization of the xinqiao deposit at early cretaceous fluid inclusions in prograde skarn diopside have homogenization temperatures of 450 600 c and calculated salinities of 13 58 wt nacl equiv quartz from the stratabound ores and pyrite quartz vein networks beneath the stratabound ores have homogenization temperatures of 290 360 and 200 300 c with calculated salinities of 5 12 and 2 10 wt nacl equiv respectively quartz from the skarn ores and veins beneath the stratabound ores have 18o values of 12 32 0 55 2 sd n 22 and 15 57 1 92 2 sd n 60 respectively corresponding to calculated 18o values of 6 22 1 59 2 and 6 81 2 76 2 for the equilibrated ore forming fluids the fluid inclusion and oxygen isotope data thus support a magmatic hydrothermal origin rather than a sedex system for the stratabound ores with the hydrothermal fluids most likely being derived from the jitou stock or associated concealed intrusion results from this study have broad implications for the genesis and exploration of other stratabound massive sulfide deposits along the mlymb

geology geochemistry and genesis of the longhua low temperature hydrothermal ni co arsenide deposit in sedimentary rocks guangxi south china abstract the longhua ni co deposit hosted in cambrian carbonaceous sandstone and siltstone in south china consists of disseminated niccolite mineralization and high grade ni co arsenides quartz carbonate vein mineralization the disseminated mineralization is characterized by niccolite hosted in the center of quartz fragments and in argillaceous concretions in cambrian banded pisolitic carbonaceous silty mudstone and by parallel niccolite grains in cambrian pisolitic pelite these characteristics indicate that the disseminated niccolite originated through redeposition the ni co vein mineralization forms high grade ores and is composed mainly of ni co arsenides the homogenization temperatures of fluid inclusions in the mineralized vein quartz range from 118 to 219 c with corresponding salinities of 1 2 to 8 8 wt nacl equiv the ore forming fluids yield dv smow and 18oh2o values of 54 to 66 and 3 0 to 7 7 respectively indicating that the source was circulating meteoric water the longhua ni co vein mineralization gives a niccolite re os isochron age of 462 6 8 5 ma mswd 1 03 the geological and geochemical characteristics of the longhua ni co deposit indicate that it formed as follows 1 precambrian quartz niccolite mineralization was eroded and transported to the longhua sediment trap forming low grade disseminated niccolite mineralization or ni co rich source beds during the cambrian 2 high grade ni co arsenide vein mineralization was formed by further enrichment of ni co from the ni rich source beds by circulated meteoric water during the ordovician caledonian orogeny the formation of the longhua low temperature high grade ni co vein ore indicates that ni can be transported in low temperature fluids that are rich in arsenic and hco3 or co32 the longhua ni co deposit might represent a new type of sedimentary hosted low temperature hydrothermal ni deposit

the endako batholith episodic plutonism culminating in formation of the endako porphyry molybdenite deposit north central british columbia the endako batholith is a composite batholith that consists of early foliated hornblende biotite diorites intermediate age unfoliated hornblende biotite diorites and late granodiorites to monzogranites these latter plutons host the endako molybdenite deposit a major porphyry deposit located in the central canadian cordillera extensive k ar dating on the batholith had given relatively reproducible ages centered on 140 ma indicating a short life span for magmatic activity however a combined u pb and 40ar 39ar study has resulted in a substantial reappraisal of the age and time span of intrusive activity and its association with molybdenite mineralization the new data show that the batholith had a protracted emplacement history covering 75 m y with clear evidence for periods of magmatic quiescence the oldest magmatic suite of the endako batholith the stern creek suite is dated at 220 ma and comprises foliated gabbros and diorites mafic to intermediate plutons of the stag lake suite range in age from 180 ma to 161 ma the francois lake suite is divided into two subsuites the glenannan subsuite dated at 157 ma to 155 ma and the 149 to 145 ma endako subsuite that hosts the endako molybdenite deposit 40ar 39ar dating of hydrothermal biotite indicates molybdenite mineralization is genetically associated with terminal stages of magmatic activity biotite within the mine had its 40ar 39ar systematics reset at 145 ma by hydrothermal fluids with temperatures in excess of 300 c this resetting is associated with intrusion of the 145 1 0 2 ma casey phase monzogranite the youngest phase within the endako subsuite a further partial resetting of biotite is interpreted to be coeval with eocene intrusion of the high level miarolitic sam ross creek phase and numerous mafic dikes that cut through the region hydrothermal fluids associated with this latter event were below biotite closure temperature and do not appear to have any relationship to molybdenite mineralization within the endako deposit the new geochronologic data coupled with detailed mapping show a general age progression from mafic plutonism at the margins to a central core of high level granodiorite to monzogranite the data document the existence of a long lived relatively stationary magmatic center pulsed magmatism evident even within individual magmatic suites may play a major role in concentrating and ultimately depositing molybdenite in some porphyry systems at endako molybdenite would have formed within the higher level portions of the batholith a position that would normally have rendered the deposit prone to erosional removal however subsequent eocene extensional block faulting may explain the preservation of this jurassic deposit which is the oldest economic molybdenite deposit in the cordillera of north america

the study of molybdenites through the187re 187os chronometer we determined the re and os concentrations in 11 molybdenites of various ages 30 2700 m y and from various areas no common osmium has been detected and os was found to be purely radiogenic therefore by comparing the concentrations we were able to determine 187 re 187 os ages for most samples these ages are in good agreement with those measured in surrounding rocks and probably correspond to the age of mineralization however two or three re os ages seem unreliable being probably related to some rhenium leaching through later metamorphic and or hydrothermal events this shows that the petrographic characteristics of ores and the type of crystallization of mos 2 are important in choosing samples suitable for dating re and os determinations combined with careful petrographic investigations may give important clues on the genesis and evolution of molybdenum ores

decratonic gold mineralization evidence from the shangzhuang gold deposit eastern north china craton abstract the jiaodong peninsula in the eastern north china craton ncc hosts some of the world class gold deposits among these the shangzhuang gold deposit represents a typical fault zone hosted disseminated and stockwork style gold mineralization the mineralization is characterized by intense hydrothermal alteration halos in the wallrocks with the mineralized veins intruding into altered wallrocks zircon u pb isotope dating constrains the timing of emplacement of the guojialing granodiorite as 130 1 ma five molybdenite samples from the main mineralization stage veins yielded a well fitted isochron age of 126 2 ma mswd 1 3 marking the timing of gold mineralization four types of fluid inclusions are identified at shangzhuang and their petrographic and microthermometric features suggest fluid immiscibility followed by fluid mixing this inference is also supported by oxygen and hydrogen isotopic data of quartz veins from stage iii the measured 18 o values of quartz are 12 3 to 13 7 for stage ii and 11 7 to 12 0 for stage iii with calculated 18 o fluid values for stage ii ranging from 5 9 to 7 3 and for stage iii from 3 4 to 3 7 d values for stage ii and iii quartz range from 65 3 to 75 2 and 70 6 to 74 7 respectively the data suggest that the ore forming fluids were initially derived from magmatic sources followed by mixing with meteoric water sims in situ sulfur isotope analyses of two types of pyrite py i and py ii from different mineralization stages show different sulfur isotope features the 34 s values for py i 10 2 to 11 3 mean 10 8 n 25 are higher than those of the later mostly gold related py ii 4 1 to 6 8 mean 5 4 n 27 the higher 34 s values of py i are correlated to degassing of mantle wedge metasomatized by the slab fluids the relatively lower 34 s values of py ii might suggest increasing of f o2 through fluid mixing between ore forming fluids and meteoric water the temporal spatial and tectonic relations between the giant gold mineralization and destruction of the ncc suggest a genetic linkage the gold mineralization between 126 and 117 ma at jiaodong was probably initiated at the peak of decratonization ca 125 ma of the eastern ncc phanerozoic craton margin orogeny also played a critical role in the generation of the early cretaceous giant gold deposits in the eastern ncc integrated geological characteristics mineralization features metallogenic age sources of ore forming fluids and sulfur and tectonic settings favor a decratonic gold mineralization model for the shangzhuang gold deposit the geodynamic scenario proposed for the early cretaceous giant gold mineralization event in the eastern ncc includes the paleo west pacific plate subduction asthenospheric upwelling multiple subduction collision processes along the margins

geochemical and geochronological constraints on mineralization within the hilltop lewis and bullion mining districts battle mountain eureka trend nevada the hilltop lewis and bullion mining districts located within the northern shoshone range lander county nevada are part of the greater battle mountain eureka trend historic production of mostly ag with au cu pb and zn from all three districts exploited 3 m wide quartz veins hosted mainly within upper plate ordovician devonian siliceous and siliciclastic rocks of the roberts mountains allochthon eocene felsic intrusive rocks located both proximal and distal to the vein deposits were emplaced throughout the northern shoshone range along a west northwest trend molybdenite mineralization is associated with some intrusive rocks and some intrusive rocks host vein type mineralization new and previously published radiometric ages for primary igneous minerals from unaltered rocks within and or proximal to mineralized areas are nearly coincident with published re os ages for several northern shoshone range molybdenite occurrences 40 1 0 6 ma avg supporting a relationship between pluton emplacement and molybdenite mineralization age differences between quartz vein hosted gold base metal mineralization e g 38 3 0 1 ma gray eagle mine bullion district and nearby intrusive rocks e g 39 0 0 1 ma granite mountain imply that vein mineralization probably formed during prolonged hydrothermal activity synchronous with or subsequent to igneous rock emplacement or from heat associated with a second slightly younger phase of intrusive igneous activity primary fluid inclusion salinity 0 6 4 wt nacl equiv and th 115 425 c data from ore bearing vein quartz in conjunction with measured 18ovsmow data 0 97 to 17 3 indicate that vein forming fluids contained variable mixtures of magmatic and meteoric components calculated 18ovsmow values of 16 0 to 13 3 and spanned the epithermal porphyry temperature continuum new and previously published stable isotope c o and s data from vein hosted ore and gangue minerals unaltered and altered siliceous upper plate host rocks and unaltered carbonate lower plate and upper plate rocks indicate mixed and variable sources of vein hosted ore and gangue components and variable interaction between some vein forming fluids and nonsiliceous rock types carbonates bedded barite that underlie the northern shoshone range large vein widths high vein densities and lack of evidence supporting fluid boiling in primary fluid inclusions suggest that vein deposits of the northern shoshone range probably formed at shallow depths 1 km under lithostatic conditions geochronology and stable isotope data support a temporal and genetic link between eocene magmatism quartz vein hosted precious and base metal mineralization and molybdenite porphyry mineralization within the hilltop lewis and bullion mining districts

re os sm nd u pb and stepwise lead leaching isotope systematics in shear zone hosted gold mineralization genetic tracing and age constraints of crustal hydrothermal activity abstract a combined re os sm nd u pb and stepwise pb leaching pbsl isotope study of hydrothermal mo w bearing minerals and base metal sulfides from two adjacent shear zone hosted gold deposits ran kimberley in the harare shamva greenstone belt zimbabwe constrain the timing of the mineralizing events to two periods during an initial late archean event 2 60 ga a first molybdenite scheelite bearing paragenesis was deposited in both shear zone systems followed by a local reactivation of the shear systems during an early proterozoic 1 96 ga tectono thermal overprint during which base metal sulfides and most of the gold was re deposited while pbsl has revealed an open system behavior of the u pb systematics in molybdenite and wolframite from the ran mine initial archean re os ages are still preserved implying that this system in these minerals was more resistant to the overprint a similar retentivity could be shown for the sm nd system in scheelite and powellite associated with the above ore minerals re os isotopic data from the proterozoic mineralization in the kimberley mine point to a recent gain of re most pronouncedly affecting fe rich sulfides such as pyrrhotite a significant re loss in powellitic scheelite an alteration phase of molybdenite bearing scheelite coupled with a marked loss of u in w mo ore minerals complements the observation of a major re uptake in fe sulfides during oxidizing conditions in a weathering environment pyrrhotite under these conditions behaves as an efficient re sink lead isotope signatures from pbsl residues of molybdenite powellite and quartz indicate a continental crustal source and or contamination for the mineralizing fluid by interaction of the fluids with older sedimentary material as represented by the direct host country rocks our investigation reveals the potential of the re os isotopic system applied to crustal hydrothermal ore minerals for genetic tracing and dating purposes the simplified chemical separation of re and os from geological material used in this study together with improvements of chemical yields will enable high precision data to be collected rapidly on crustal material with low os concentrations in the future

introduction to the special issue of canadian journal of earth sciences the nechako natmap project of the central canadian cordillera the canadian cordillera in central british columbia has seen the mesozoic subduction of an oceanic terrane the amalgamation of volcanic arc terranes continued intermittent mesozoic compression and magmatism and tertiary wrenching extension and magmatism except in its northernmost mountain ranges the area is extensively cov ered in glacial drift and thin veneers of tertiary volcanic rocks in 1994 a group of scientists and technologists be lieved they could understand that cover see through it and discover the components of that collision and extensional orogen they would apply modern techniques of isotopic and paleontological geochronology lake sediment till and plant geochemistry detailed gravity magnetic radiometric paleomagnetic and electromagnetic surveys and isotopic and trace element lithochemistry as they conducted extensive bedrock and surficial mapping this special issue summa rizes a cross section of the scientific contributions derived from that mapping conducted under the auspices of the nechako natmap project it demonstrates the absolute necessity of applying modern isotopic and paleontologic geo chronology to understand the phanerozoic geology of the cordillera it emphasizes the necessity of detailed aeromag netic surveys 500 m or less line spacing in looking through covered terranes at anything more than 1 250 000 scale and it shows the immense utility of applying various geochemical techniques to solve geological problems and estab lish baselines for future research and economic development bedrock and surficial mapping in the central cordillera using these and other techniques have established the nature and timing of mesozoic crustal growth tertiary crustal thinning and the associated formation of mineral deposits

dating the giant zhuxi w cu deposit taqian fuchun ore belt in south china using molybdenite re os and muscovite ar ar system abstract the recently discovered zhuxi w cu ore deposit is located within the taqian fuchun ore belt in the southeastern edge of the yangtze block south china its inferred tungsten resources based on new exploration data are more than 280 mt by 2016 at least three paragenetic stages of skarn formation and ore deposition have been recognized prograde skarn stage retrograde stage and hydrothermal sulfide stage secondly greisenization marmorization and hornfels formation are also observed scheelite and chalcopyrite are the dominant metal minerals in the zhuxi deposit and their formation was associated with the emplacement of granite stocks and porphyry dykes intruded into the surrounding carboniferous carbonate sediments huanglong and chuanshan formations and the neoproterozoic slate and phyllites the scheelite was mostly precipitated during the retrograde stage whereas the chalcopyrite was widely precipitated during the hydrothermal sulfide stage a muscovite 40ar 39ar plateau age of about 150 ma is interpreted as the time of tungsten mineralization and molybdenite re os model ages ranging from 145 9 2 0 ma to 148 7 2 2 ma for the subsequent hydrothermal sulfide stage of activity as the time of the copper mineralization our new molybdenite re os and muscovite 40ar 39ar dating results along with previous zircon u pb age data indicate that the hydrothermal activity from the retrograde stage to the last hydrothermal sulfide stage lasted up to 5 myr from 150 6 1 5 to 145 9 1 ma and is approximately coeval or slightly later than the emplacement of the associated granite porphyry and biotite granite the new ages reported here confirm that the zhuxi tungsten deposit represents one of the mesozoic magmatic hydrothermal mineralization events that took place in south china in a setting of lithospheric extension during the late jurassic 160 150 ma it is suggested that mantle material played a role in producing the zhuxi w cu mineralization and associated magmatism

assessment of the 187re decay constant by cross calibration of re os molybdenite and u pb zircon chronometers in magmatic ore systems the past decade has seen renewed interest in 187re 187os geochronology using a variety of matrices including sulfide minerals shales and meteorites the most widely used value of the 187re decay constant 187re is 1 666 0 005 10 11 a 1 0 31 which is based on cross calibration of re os and pb pb chronometers for certain meteorites smoliar m i walker r j and morgan j w 1996 re os isotope constraints on the age of group iia iiia iva and ivb iron meteorites science 271 1099 1102 however other recent studies have yielded alternate values of 187re based upon either direct counting experiments or analysis of meteorites here we provide an independent assessment of 187re using methodology sample materials and preparation of os standard solutions different from those of smoliar et al 1996 combining re os age data for molybdenite formed in magmatic ore deposits with the u pb zircon age of the magmatic rocks a refined 187re value is determined by averaging 11 individual cross calibration experiments spanning ca 2700 ma of earth history using the u decay constants of jaffey jaffey a h flynn k f glendenin l e bentley w c and essling a m 1971 precision measurement of half lives and specific activities of 235u and 238u phys rev 4 1889 1906 a value for 187re of 1 6668 0 0034 10 11 a 1 is determined using the 238u value of jaffey et al 1971 and 235u value of schoene schoene b crowley j l condon d j schmitz m d and bowring s a 2006 reassessing the uranium decay constants for geochronology using id tims u pb data geochim cosmochim acta 70 426 445 a value for 187re of 1 6689 0 0031 10 11 a 1 is determined these values are nominally higher ca 0 1 and ca 0 2 than the value determined by smoliar et al smoliar m i walker r j and morgan j w 1996 re os isotope constraints on the age of group iia iiia iva and ivb iron meteorites science 271 1099 1102 but within calculated uncertainty further refinement of 187re by cross calibrating the molybdenite and u pb zircon chronometers should be possible by utilizing high precision single grain chemical abrasion zircon u pb analyses

constraints of in situ zircon and cassiterite u pb molybdenite re os and muscovite 40ar 39ar ages on multiple generations of granitic magmatism and related w sn mineralization in the wangxianling area nanling range south china abstract the nanling range in south china hosts numerous w sn rare metal deposits associated with several cycles of polygenetic granitic intrusions in the wangxianling area of the middle nanling range igneous intrusions include the wangxianling and hehuaping granite plutons and more than 20 granite porphyry dykes the wangxianling pluton has a central phase of medium grained tourmaline two mica granite and a marginal phase of medium grained tourmaline muscovite granite the pluton hosts several tungsten deposits including shuiyuanshan and yejiwo mineralization type is dominantly scheelite greisen with subordinate scheelite skarn and wolframite quartz veins the hehuaping pluton composed of coarse grained biotite granite and granite porphyry dykes to the east of the wangxianling pluton have an associated hehuaping tin deposit with tin skarn and subordinate porphyry and greisen mineralization in situ zircon and cassiterite u pb dating molybdenite re os and muscovite 40ar 39ar dating techniques are used to refine the age spectra of granitic rocks and w sn mineralization in the wangxianling area granites of the wangxianling pluton have zircon u pb ages of 224 ma tungsten bearing quartz veins from both the shuiyuanshan and yejiwo tungsten deposits have an average molybdenite re os isochron age of 224 ma and muscovite of scheelite greisen from the shuiyuanshan tungsten deposit yields a 40ar 39ar plateau age of 214 ma the two mineralization ages are consistent with the zircon u pb age of the wangxianling pluton indicating a close association between pluton emplacement and w mineralization in the late triassic both the hehuaping pluton and granite porphyry dykes have zircon u pb ages of 156 ma in situ la icp ms u pb dating of cassiterite in both the tin skarn and tin greisen yields an average age of 156 ma showing that the sn mineralization occurred at a similar time to the late jurassic granitic magmatism thus two mineralization events are identified in the wangxianling area and include an earlier w dominant mineralization event and a later sn dominant mineralization event the earlier event is related both spatially and temporally to intrusion of the late triassic s type wangxianling granite pluton whereas the later mineralization is associated both spatially and temporally with intrusion of the late jurassic hehuaping a2 type granite pluton and a2 type granite porphyry dykes

geology mineralization and geochronology of the qianhe gold deposit xiong ershan area southern north china craton the qianhe gold deposit in the xiong ershan area is located along the southern margin of the archean paleoproterozoic north china craton the deposit consists of six orebodies that are hosted in paleoproterozoic andesites to basaltic andesites and structurally controlled by roughly ew trending faults individual orebodies comprise auriferous quartz veins and disseminated au bearing pyrite within hydrothermally altered rocks on both sides of or close to the veins ore related hydrothermal alteration has produced various mixtures of k feldspar quartz sericite chlorite epidote carbonate and sulfides pyrite is the most important ore mineral associated with minor amounts of galena sphalerite and chalcopyrite other trace minerals include molybdenite arsenopyrite scheelite rutile xenotime and parisite gold occurs mostly as native gold and electrum enclosed in pyrite or along microfractures of sulfides and quartz microthermometric measurements of primary inclusions in auriferous quartz suggest that gold and associated minerals were precipitated in the range of 160 305 c from aqueous or carbonic aqueous fluids with salinities of 6 22 wt nacl equiv samples of molybdenite coexisting with au bearing pyrite have re os model ages of 134 135 ma whereas ore related hydrothermal sericite separates yield 40ar 39ar plateau ages between 127 and 124 ma the re os and 40ar 39ar ages are remarkably consistent with zircon u pb ages 134 5 1 5 and 127 2 1 4 ma 1 of the biotite monzogranite from the heyu intrusive complex and granitic dikes in and close to the qianhe gold mine indicating a close temporal and thus possibly genetic relationship between gold mineralization and granitic magmatism in the area fluid inclusion waters extracted from auriferous quartz have d values of 80 to 72 whereas the calculated 18oh2o values range from 3 1 to 3 8 the hydrogen and oxygen isotopes from this study and previous work indicate that ore fluids were likely derived from degassing of magmas with addition of minor amounts of meteoric water gold mineralization at qianhe is temporarily coincident with pervasive bimodal magmatism widespread fault basin formation and well development of metamorphic core complexes in the whole eastern north china craton that have been interpreted as reflecting reactivation of the craton in the late mesozoic after prolonged stabilization since its formation in the late paleoproterozoic it is therefore concluded that the qianhe gold deposit formed as a result of this craton reactivation event

multiple rejuvenation episodes of a silicic magma reservoir at the origin of the large diatreme dome complex and porphyry type mineralization events at cerro de pasco peru abstract the cerro de pasco district in central peru hosts one of the world largest porphyry related epithermal polymetallic deposits the district is centered onto a large diatreme dome complex crosscut by numerous dacite to rhyodacite bodies showing domal structures and quartz monzonite dykes three temporally distinct high temperature porphyry type mineralization events have been recognized pm1 pm2 and pm3 dating of the latter by molybdenite re os and by zircon u pb la icp ms and ca id tims geochronology complements the already available dataset of zircon u pb ages of the subvolcanic and volcanic rocks mostly dacitic in composition occurring in the district and shows the existence of successive short lived episodes 50 at pressures between 0 9 and 3 4 kbar and at temperatures between 680 c and 725 c at such conditions magma is beyond the point of rheological lock up and is not eruptible the emplacement of the mostly dacitic subvolcanic and volcanic rocks has required a series of rejuvenation events of the upper crustal high crystallinity silicic magma reservoir field relationships and geochronology indicate that emplacement of the subvolcanic and volcanic rocks is preceded each time by high temperature 600 c quartz pyrite magnetite chalcopyrite and quartz molybdenite veining forming the three recognized porphyry type mineralization events hydrothermal quartz of these veins host silicate melt inclusions a rare feature in hydrothermal veins their composition determined by la icp ms analysis indicates that the mineralizing fluids potentially sourced from intermediate magma recharges have circulated in a magma reservoir in which the residual interstitial melt was more evolved than the melt trapped as inclusions in the magmatic quartz the combined geochemical and geochronological data obtained show that several episodes of rejuvenation of a highly crystallized upper crustal silicic magma reservoir probably triggered by intermediate magma recharges and by circulation of co2 and s rich fluids exsolved from them are at the origin of the large diatreme dome complex and porphyry type mineralization events at cerro de pasco

timing of skarn deposit formation of the tonglushan ore district southeastern hubei province middle lower yangtze river valley metallogenic belt and its implications abstract the tonglushan ore district in the middle lower yangtze river valley metallogenic belt includes the tonglushan cu fe the jiguanzui au cu and the taohuazui au cu skarn deposits they are characterized by ne striking ore bodies and hosted at the contact of triassic carbonate rocks and late mesozoic granitoid deposits new sensitive high resolution ion microprobe shrimp and laser ablation inductively coupled plasma mass spectrometry la icp ms zircon u pb molybdenite re os and phlogopite 40 ar 39 ar ages indicate that these skarn deposits formed between 140 3 1 1 and 137 3 2 4 ma these dates are identical to the zircon u pb ages for host quartz diorites ranging from 140 2 to 139 1 ma these results confirm that both skarn mineralization and related intrusions were initiated during the early cretaceous the high rhenium contents 261 4 1152 g g of molybdenites indicate that a metasomatic mantle fluid was involved in the ore forming process of these skarn ore systems this conclusion is consistent with previously published constraints from sulfur deuterium and oxygen isotope compositions and the geochemical signatures and sr nd isotopic data of the mineralization hosting intrusions geological and geochronological evidence demonstrates that there were two igneous events in the tonglushan ore district the first resulted in the emplacement of quartz diorite during the early cretaceous 140 2 to 139 1 ma and the second is characterized by the eruption of volcanic rocks during the mid early cretaceous 130 2 to 124 2 ma the former is spatially temporally and genetically associated with skarn gold bearing mineralization 140 3 1 1 to 137 3 2 4 ma the recognition of these two igneous events invalidates previous models that proposed continuous magmatism and associated mineral deposits in the middle lower yangtze river valley metallogenic belt

he ar and s isotopic compositions and origin of giant porphyry mo deposits in the lesser xing an range zhangguangcai range metallogenic belt northeast china abstract the lesser xing an range zhangguangcai range metallogenic belt located at the eastern segment of the central asian metallogenic domain hosts two giant mo porphyry deposits the early jurassic luming deposit and the middle jurassic daheishan deposit in this study the he ar and s isotopic compositions of sulfides from different hydrothermal stages of the daheishan and luming deposits were determined fluid inclusions hosted in pyrites shown that 3he 4he ratios of the luming and daheishan deposit range from 0 02 to 0 32 ra and 0 7 to 2 5 ra respectively 40ar 36ar ratios of the luming and daheishan deposit range from 313 3 to 535 1 and 309 9 to 360 6 respectively he and ar isotopic compositions suggest that the ore forming fluids of the luming deposit are mainly crustal derived fluids with near atmospheric ar and crustal he values mantle derived fluids are a minor component in contrast the ore forming fluids of the daheishan deposit are a mixture between a crust derived fluid and a mantle derived fluid the 34s values of the sulfide samples from the luming deposit 4 98 7 14 and the daheishan deposit 1 83 2 88 indicate that the sulfur in the ore forming fluids was primarily derived from granitic magma the isotopic compositions across the stages within one deposit have no variability the similar he ar and s isotopic compositions of the sulfides from the different mo bearing hydrothermal stages of these two giant mo deposits indicate that the overprinting of the multiple stages of mo bearing hydrothermal fluids may be a key factor in the formation of giant porphyry mo deposits meanwhile the westward subduction of the paleo pacific plate might have played an important role for the formation of the giant mo deposits in the lesser xing an range zhangguangcai range metallogenic belt

rhenium osmium geochronology and oil source correlation of the duvernay petroleum system western canada sedimentary basin implications for the application of the rhenium osmium geochronometer to petroleum systems the re os geochronometer has been applied to many petroleum systems worldwide however it is debated if the re os systematics in petroleum actually record the timing of oil generation here we investigate the re os isotope systematics of the duvernay petroleum system in the western canada sedimentary basin which has been shown to be a relatively simple petroleum system that is associated with oil generated during the late cretaceous early eocene laramide orogeny from a single source the organic geochemistry of the duvernay oils pristane phytane ratios of 1 5 smooth homohopane profile c29 c27 c28 regular sterane distribution and predominance of diasteranes over regular steranes strongly suggests the oil source to be that of type i ii marine organic matter of the upper devonian duvernay formation the asphaltene fraction re os isotope data of the duvernay oil yield an age of 66 31 ma which is in excellent agreement with the timing of the main stage hydrocarbon generation of the duvernay formation based on basin models further the similarity between the 187os 188os compositions of the duvernay formation source rock 0 46 1 48 and the oil 0 55 1 06 at the time of oil generation supports the hypothesis that the 187os 188os composition of an oil is inherited from the source unit at the time of oil generation and therefore shows no or limited influence from interaction with basin fluids this study supports that the re os isotope systematics of an oil can yield the timing of oil generation and be used to trace its source

synvolcanic and younger plutonic rocks from the blake river group implications for regional metallogenesis the blake river group of the abitibi greenstone belt is host to the well known volcanogenic massive sulfide vms deposits of the noranda camp quebec canada in the noranda camp massive sulfide deposits are spatially associated with the coeval flavrian powell intrusive complex which is interpreted to have driven hydrothermal circulation that formed the deposits in the camp in the western blake river group in ontario there are also abundant intrusive rocks yet relatively insignificant accumulations of vms deposits these intrusive rocks are younger 2686 9 1 2 and 2688 5 2 3 ma and are associated with porphyry style cu mo au mineralization with re os molybdenite ages of 2682 4 5 ma the intrusions are also smaller in areal extent and do not have a temporally extended polyphase history like the flavrian powell intrusive complex the intrusions of the western blake river group can also be distinguished by lithogeochemical attributes and a distinct petrological history compared to the flavrian powell intrusive complex they have lower total y yb th hfse and ree with higher zr y la yb sm yb al2o3 yb and la smucn ratios and lower zr nb zr th zr la zr tio2 and nb thucn ratios petrologic modeling is consistent with the western blake river group intrusive rocks being generated as relatively low temperature melts 40 km in the crust where garnet is stable in the residue e g garnet amphibolite residue in contrast modeling of the flavrian powell intrusive complex is consistent with melting at shallower levels in the crust e g 800o to 850oc the occurrence of high temperature magmatism at high levels within this crust that is coeval with volcanic activity explains the occurrence of numerous vms deposits with the flavrian powell intrusive complex as this intrusive complex would have generated abundant heat at high levels in the crust to drive hydrothermal circulation in contrast the intrusions of the western blake river group were generated at depth and at lower temperature increasing the probability of heat loss upon emplacement from depth hence decreasing the probability of hydrothermal circulation at high levels in the crust and likely explaining the paucity of vms mineralization associated with these intrusive rocks the petrological attributes of the flavrian powell intrusive complex and western blake river group may be useful in delineating potentially fertile versus less prospective intrusive complexes in greenfields exploration areas notably the western blake river group intrusions have geochemical features similar to some phanerozoic porphyry cu mo au associated intrusive systems consistent with the observed mineralization and highlighting the potential of porphyry cu mo au systems of late archean age elsewhere in the abitibi

rhenium behavior in molybdenite in hypogene and near surface environments implications for re os geochronometry abstract rhenium is concentrated mainly in molybdenite mos2 and occurs as a major cation in only a few rare minerals this affinity makes molybdenite an ideal mineral for re os geochronometry but research on the behavior of re in molybdenite is limited infrared microscope xrd back scattered electron bse and microprobe techniques have been used in this study to document re behavior in molybdenite affected by hypogene and near surface processes in the hypogene environment both 3r and 2h molybdenite can experience re loss during hydrothermal alteration which also causes increased infrared transparency ir alteration at temperatures as low as 150 c can cause re loss in the presence of advecting fluids and will affect re os dating if it occurs long after primary mineralization re loss in 3r and 2h molybdenite under supergene conditions does not increase ir transparency rhenium is not incorporated into supergene ferrimolybdite but is enriched in k al silicate intergrowths which may be illite these minute intergrowths are present in several samples and would not be detected in a simple optical examination in the supergene environment elemental os is stable whereas re is not rhenium in molybdenite may be removed by supergene fluids after some has decayed to 187os causing erroneously old ages or it may be adsorbed into the illite intergrowths creating ages which are too young in the weathering environment proterozoic molybdenites have altered to re enriched powellite which can be detected using back scattered electron imagery combined microprobe xrd bse and infrared microscopy can be successfully used to detect alteration in molybdenite prior to dating these techniques are non destructive and should be performed before any molybdenite is dated by the re os system

temporal spatial distribution and tectonic setting of porphyry copper deposits in iran constraints from zircon u pb and molybdenite re os geochronology abstract porphyry copper deposits pcds in iran are dominantly distributed in arasbaran nw iran the middle segment of the urumieh dokhtar magmatic arc udma and kerman central se iran with minor occurrences in eastern iran and the makran arc this paper provides a temporal spatial and geodynamic framework of the iranian porphyry cu mo au systems based on geochronologic data obtained from zircon u pb and molybdenite re os dating of host porphyritic rocks and molybdenites in 15 major pcds the dating results define a long metallogenic duration 39 6 ma and suggest a long history of tectonic evolution from the accretionary orogeny related to early cenozoic closure of the neo tethys ocean to subsequent collisional orogeny for the iranian porphyry copper systems the oldest porphyry mineralization occurred in the eastern part of iran after the closure of a branch of the neo tethyan sistan ocean between the lut and afghan blocks in the late eocene 39 37 ma this was followed by mineralization in the kerman porphyry copper belt over a time interval of about 20 m y where two metallogenic epochs have been recognized including late oligocene 29 27 ma and miocene 18 6 ma the bondar e hanza deposit formed in the late oligocene while and the remaining dated deposits belong to miocene epoch according to the deposits characteristics and their ages the miocene epoch can be divided into early middle and late stages the darreh zar bakh khoshk chah firouzeh and sar kuh deposits formed during the early middle miocene the largest porphyry deposits occur in the middle stage during the middle miocene 14 11 ma and include the sar cheshmeh meiduk dar alu and now chun deposits these deposits were formed during crustal thickening uplift and rapid exhumation of the belt the final stage of porphyry mineralization occurred during the late miocene 9 6 ma and formed the iju kerver kuh panj and abdar deposits there were two porphyry mineralization stages in the arasbaran porphyry copper belt in nw iran including an older late oligocene 29 27 ma and a younger early miocene 22 20 ma events the haft cheshmeh deposit belongs to the older stage and the world class sungun and masjed daghi deposits formed during the early miocene in the middle segment of the udma saveh yazd porphyry copper belt pcds formed during middle miocene time 17 15 ma the geochronological results reveal that the porphyry mineralization moved from the northwest to southeast of udma over the time our dating results combined with the possible late eocene oligocene timing for collision between the arabian and iranian plates support a model for iranian pcd formation by partial melting of previously subduction modified lithosphere in a post subduction and post collisional tectonic setting

geological and chronological constraints on the long lived eocene yulong porphyry cu mo deposit eastern tibet implications for the lifespan of giant porphyry cu deposits the yulong porphyry cu mo deposit the third largest porphyry cu deposit in china contains proven reserves of 6 5 million metric tons mt cu and 0 4 mt mo previous radiometric dating studies have provided numerous ages for this deposit but the timing and duration of the process governing the deposition of cu and mo remains not well constrained in this paper we first document multiple stages of mineralization and hydrothermal alteration associated with distinct magmatic pulses at yulong by field and textural relationships and then present high precision molybdenite re os ages of 14 quartz molybdenite chalcopyrite veins representing these stages to precisely constrain the timing and duration of cu mo mineralization the ore hosting yulong composite stock consists of three successive porphyry intrusions 1 monzonitic granite porphyry mgp 2 k feldspar granite porphyry kgp and 3 quartz albite porphyry qap the vein formation cu mo mineralization and ore related alteration are grouped into early transitional and late stages with respect to the intrusive history the first two porphyry intrusions are followed by cyclical sequences of veining that are mainly associated with potassic alteration and have formed 1 me vein ustt 2 ebe t veins 3 a1e t veins 4 a2e bt veins and 5 a3e t veins a2e bt and a3e t veins of the early and transitional stages are dominated by quartz and chalcopyrite pyrite respectively and represent the main cu mo mineralization events more than 80 of cu and mo at yulong were deposited in the early stage with the remainder being formed in the transitional stage the late stage pyrite quartz veins dl which are characterized by sericitic alteration halos postdate the intrusion of qap dikes and have no economic significance molybdenite re os ages of a2e and bt veins indicate that sulfide deposition at yulong was episodic over a prolonged history lasting over 5 13 0 23 m y 1 however the bulk cu mo ores formed in a shorter time interval of 1 36 0 24 m y 1 with most cu precipitated in a more restricted timespan of 0 82 0 24 m y 1 in the early stage these results combined with geochronologic data from porphyry copper deposits elsewhere confirm that multiple magmatic hydrothermal pulses with a lifespan of tens to hundreds of thousands of years are sufficient to form a giant porphyry copper deposit factors such as metal concentration volume and focusing efficiency of ore forming fluids could have played important roles in producing a giant porphyry cu deposit regardless of a short or long lived magmatic hydrothermal system

new u pb and re os age data and the geodynamic setting of the xiaojiayingzi mo fe deposit western liaoning province northeastern china abstract the xiaojiayingzi deposit located in the western liaoning province in northeastern china is a skarn type mo fe deposit with an average mo grade of 0 23 wt the deposit is temporally and spatially associated with fine grained diorite mo fe mineralization is present mainly as veins lenses and layers that are hosted by skarn new shrimp u pb zircon and re os molybdenite age determinations yielded a crystallization age for the diorite of 169 9 1 4 ma and a molybdenite re os isochron age of 165 5 4 6 ma the u pb and re os ages are identical within error the mineralization is therefore considered to be genetically related to diorite emplacement in the middle jurassic a high re content of 21 75 to 163 0 ppm with an average of 64 31 ppm in the molybdenite together with 34 s values between 3 3 and 8 0 of sulfides in the ores indicates that the metal source was a mixed crust mantle system from these geochronological data and previously presented regional geological relationships we propose that diorite emplacement and mo fe mineralization in the xiaojiayingzi mine resulted from an early stage of the subduction of the paleo pacific plate beneath the eurasian block