re os isotopic dating of molybdenite and pyrite in the baishan mo re deposit eastern tianshan nw china and its geological significance the baishan mo re deposit is located in the eastern section of the eastern tianshan orogenic belt nw china the deposit has a grade of 0 06 mo and a high content of rhenium of 1 4 g t rhenium and osmium isotopes in sulfide minerals from the baishan deposit are used to determine the age of mineralization rhenium concentrations in molybdenite samples are between 74 and 250 g g analysis of eight molybdenite samples yields an isochron age of 224 8 4 5 ma 2 pyrite samples have rhenium and osmium concentrations varying in the range 33 4 330 6 ng g and 0 08 0 81 ng g respectively isotope data on seven pyrite samples yield an isochron age of 225 12 ma 2 on the 187re 188os versus 187os 188os plot and an age of 233 14 ma 2 on the 187os versus 187re correlation diagram the ages of molybdenite and pyrite are consistent within the analytical errors combined with field observations the data indicate that mo re mineralization in the baishan deposit is produced by a magmatic hydrothermal event in an intracontinental extensional setting after late paleozoic orogeny the initial 187os 188os ratio of pyrite is 0 3 0 07 the 34s values of molybdenite vary from 0 5 to 3 6 both data indicate that mineralization is derived mainly from a mantle source

sims zircon u pb and molybdenite re os geochronology hf isotope and whole rock geochemistry of the wunugetushan porphyry cu mo deposit and granitoids in ne china and their geological significance abstract the geodynamic setting of magmatic rocks and geodynamic mechanism of cu mo fe sn pb zn ag polymetallic mineralization in northeastern ne china are attracting increasing attention this study explores these issues by providing sims zircon u pb dating whole rock geochemical hf isotopic data of magmatic rocks and molybdenite re os dating exposed in the wunugetushan porphyry cu mo deposit ne china this deposit is located in the western part of the great xing an range on the southeastern margin of the mongol okhotsk orogenic belt molybdenite re os and sims zircon u pb dating of the host monzogranitic porphyry and the wall rock of biotite granite in the wunugetushan porphyry cu mo deposit indicate that the ore formation host porphyry and wall rock emplacement occurred at 180 5 2 0 ma 180 4 1 4 ma and 203 5 1 6 ma respectively and the mineralization of the wunugetushan porphyry cu mo deposit occurred during the same period as that of the host monzogranitic porphyry geochemically the wunugetushan granitoids are characterized by strong lree hree fractionation and pronounced negative nb ta and ti anomalies with slightly negative eu anomalies eu eu 0 71 0 97 of the host monzogranitic porphyry and pronounced negative eu anomalies eu eu 0 29 0 32 of the wall rock of biotite granite in situ hf isotopic analyses of zircons from the host monzogranitic porphyry and the wall rock of biotite granite yielded ehf t values ranging from 0 5 to 8 2 and from 6 9 to 5 9 respectively the geochemical and isotopic data for the wunugetushan granitoids imply that the primary magmas of the host monzogranitic porphyry could have originated by partial melting of a thickened lower crust with input of mantle components while the primary magmas of the wall rock of biotite granite could have been derived by partial melting of a thickened lower crust that mixed with ancient crustal materials based on the regional geological history geochemistry of the wunugetushan granitoids and new isotopic age data we suggest that the formation of the wunugetushan porphyry cu mo deposit was possibly induced in the early jurassic during the period of the southeastward subduction of the mongol okhotsk oceanic plate beneath the erguna massif

fluid inclusions and h o s pb isotope systematics of the baishan porphyry mo deposit in eastern tianshan china abstract the baishan porphyry mo deposit formed in the middle triassic in eastern tianshan xinjiang northwestern china mo mineralization is associated with the baishan monzogranite and granite porphyry stocks mainly presenting as various types of hydrothermal veinlets in alerted wall rocks with potassic phyllic propylitic and fluorite alteration the ore forming process can be divided into four stages stage i k feldspar quartz pyrite veinlets stage ii quartz molybdenite pyrite veinlets stage iii quartz polymetallic sulfide veinlets and stage iv barren quartz calcite veins four types of fluid inclusions fis can be distinguished in the baishan deposit namely liquid rich two phase l type vapor rich two phase v type solid bearing multi phase s type and mono phase vapor m type inclusions but only the stage i quartz contains all types of fis the stages ii and iii quartz have three types of fis with exception of m type in stage iv quartz minerals only the l type inclusions can be observed the fis in quartz of stages i ii iii and iv are mainly homogenized at temperatures of 271 468 c 239 349 c 201 331 c and 134 201 c with salinities of 2 2 11 6 wt nacl equiv 1 1 10 2 wt nacl equiv 0 5 8 9 wt nacl equiv and 0 2 5 7 wt nacl equiv respectively the ore forming fluids of the baishan deposit are characterized by high temperature moderate salinity and relatively reduced condition belonging to a h 2 o nacl ch 4 co 2 system hydrogen and oxygen isotopic compositions of quartz indicate that the ore forming fluids were gradually evolved from magmatic to meteoric in origin sulfur and lead isotopes suggest that the ore forming materials came predominantly from a deep seated magma source from the lower continental crust the mo mineralization in the baishan deposit is estimated to have occurred at a depth of no less than 4 7 km and the decrease in temperature and remarkable transition of the redox condition from alkalinity to acidity of ore forming fluids were critical for the formation of the baishan mo deposit

carbon isotope geochemistry of hydrocarbons in the cerro prieto geothermal field baja california norte mexico hydrocarbon abundances and stable isotopic compositions were measured in wells m5 m26 m35 and m102 which represent a range of depths 1270 2000 m and temperatures 275 330 degrees c in the field in order to simulate the production of the geothermal hydrocarbons gases were collected from the pyrolysis of lignite in the laboratory this lignite was obtained from a well which sampled rock strata which are identical to those occurring in the field but which have experienced much lower subsurface temperatures in both the well and the laboratory observations high temperature environments favored higher relative concentrations of methane ethane and benzene and generally higher delta 13c values in the individual hydrocarbons the best correlation between the laboratory and well data is obtained when laboratory produced gases from experiments conducted at lower 400 degrees c and higher 600 degrees c temperatures are mixed this improved correlation suggests that the wells are sampling hydrocarbons produced from a spectrum of depths and temperatures in the sediments

a review of the western part of the altaids a key to understanding the architecture of accretionary orogens abstract the altaids is one of the largest accretionary collages in the world and the tectonic styles of the accretionary processes have been interpreted in several ways including as an amalgamation of multiple terranes as a result of oroclinal bending of a long single arc or as a caledonian continental collision based on recent tectonostratigraphic analyses together with paleomagnetic data the tectonic styles of the neoproterozoic to paleozoic accretionary processes of the altaids are discussed the western altaids is the main focus of the study which was mainly composed of several independent linear components such as arcs and microcontinents with proterozoic basement and cover rocks various kinds of arcs existed in the paleo asian ocean including a complicated type of arc alaskan type which is a combination of the japan and mariana type intra oceanic arcs and the cordillera type continental arcs these linear components rotated and collided with each other with multiple subduction polarities which could have been an important result of multiple linear element amalgamation and which has contributed greatly to the architecture of the eurasian continent the basic tectonic styles of the altaids can be summarized as arc arc collision oroclinal bending and large scale rotation and multiple subductions with a complicated archipelago paleogeography these basic features of accretionary orogens in general can be attributed to the amalgamation of complicated multiple linear elements some mesozoic to cenozoic accretionary orogens in the world are also characterized by processes of multiple linear element amalgamation more attention should be paid to the multiple linear element amalgamation of ancient accretionary orogens which will shed light on lateral and vertical continental growth

a review of the occurrence form and origin of c bearing species in the khibiny alkaline igneous complex kola peninsula nw russia abstract the khibiny complex hosts a wide variety of carbon bearing species that include both oxidized and reduced varieties oxidised varieties include carbonate minerals especially in the carbonatite complex at the eastern end of the pluton and na carbonate phases reduced varieties include abiogenic hydrocarbon gases particularly methane and ethane dispersed bitumens solid organic substances and graphite the majority of the carbon in the khibiny complex is hosted in either the carbonatite complex or within the so called central arch the central arch is a ring shaped structure which separates khibinites coarse grained eudialite bearing nepheline syenites in the outer part of the complex from lyavochorrites medium grained nepheline syenites and foyaites in the inner part the central arch is petrologically diverse and hosts the major ree enriched apatite nepheline deposits for which the complex is best known it also hosts zones with elevated hydrocarbon dominantly methane gas content and zones of hydrothermally deposited na carbonate mineralisation the hydrocarbon gases are most likely the product of a series of post magmatic abiogenic reactions it is likely that the concentration of apatite nepheline deposits hydrocarbon gases and na carbonate mineralisation is a function of long lived fluid percolation through the central arch fluid migration was facilitated by stress release during cooling and uplift of the khibiny complex as a result carbon with a mantle signature was concentrated into a narrow ring shaped zone

excess methane in continental hydrothermal emissions is abiogenic thermogenic hydrocarbons entirely deriving from the thermal degradation of organic matter usually exhibit methane to ethane plus propane ratios smaller than 100 we present hydrocarbon distribution data of continental hydrothermal gases whose methane has been independently identified to derive from the abiogenic reduction of co2 we find that excess amounts of methane with respect to thermogenic hydrocarbon distributions are characteristic for the investigated gases a similar pattern is observed for well discharges whose temperatures are too high to support any microbially mediated methanogenesis these findings strongly suggest that abiogenic methane production in continental hydrothermal systems is a more widespread process than previously assumed the maximum contribution of such emissions to the modern atmospheric ch4 budget is estimated at 1

medium scale traveling ionospheric disturbances observed with the superdarn hokkaido radar all sky imager and gps network and their relation to concurrent sporadic e irregularities 1 we present midlatitude medium scale traveling ionospheric disturbances mstids observed with a super dual auroral radar network superdarn hf radar at around 10 mhz in hokkaido japan in combination with a 630 nm all sky imager and a gps network geonet that provides total electron content tec data mstids propagating southward from high latitudes are detected at first with the hf radar and then with the imager and geonet we analyze two mstid events one in winter event 1 and the other in summer event 2 to find that mstids appear simultaneously at least at 55 25 n it is shown that nighttime mstids propagate toward the southwest over a horizontal distance of about 4000 km and daytime mstids do so toward the southeast daytime radar echoes are due to ground sea surface gs scatter while nighttime echoes in event 1 return from 15 m scale f region field aligned irregularities fais and those in event 2 are due to gs scatter doppler velocities of the nighttime f region fai echoes in event 1 are negative motion away from the radar within strong echo regions and are positive motion toward the radar within weak echo regions this fact suggests that the strong weak echoes return from suppressed enhanced airglow tec areas in line with previous observations over central japan the nighttime mstids in events 1 and 2 are often accompanied by concurrent coherent echoes from fais in sporadic e es layers the es echo areas in event 2 rather coincide with suppressed airglow tec areas in the f region that are connected with the echo areas along the geomagnetic field indicating the existence of e and f region coupling at night

isotope provinces mechanisms of generation and sources of the continental crust in the central asian mobile belt geological and isotopic evidence abstract the available geological geochronological and isotopic data on the felsic magmatic and related rocks from south siberia transbaikalia and mongolia are summarized to improve our understanding of the mechanisms and processes of the phanerozoic crustal growth in the central asian mobile belt camb the following isotope provinces have been recognised precambrian t dm 3 3 2 9 and 2 5 0 9 ga at the microcontinental blocks caledonian t dm 1 1 0 55 ga hercynian t dm 0 8 0 5 ma and indosinian t dm 0 3 ga that coincide with coeval tectonic zones and formed at 570 475 420 320 and 310 220 ma continental crust of the microcontinents is underlain by or intermixed with juvenile crust as evidenced by its isotopic heterogeneity the continental crust of the caledonian hercynian and indosinian provinces is isotopically homogeneous and was produced from respective juvenile sources with addition of old crustal material in the island arcs or active continental margin environments the crustal growth in the camb had episodic character and important crust forming events took place in the phanerozoic formation of the camb was connected with break up of the rodinia supercontinent in consequence of creation of the south pacific hot superplume intraplate magmatism preceding and accompanying permanently other magmatic activity in the camb was caused by influence of the long term south pacific plume or the asian plume damping since the devonian

a review of the cu ni sulphide deposits in the chinese tianshan and altay orogens xinjiang autonomous region nw china principal characteristics and ore forming processes abstract several cu ni sulphide deposits and occurrences have recently been discovered along parallel deep faults in the chinese tianshan and altay orogenic belts xinjiang province nw china the kalatongke and several other cu ni mineralized intrusions are located along the irtysh fault which separates the altay orogenic belt from the junggar basin the huangshan huangshandong xiangshan tudun erhongwa tula ergen and hongling deposits occur along the kanggurtag suture which separates the jueluotage orogenic belt from the turpan hami tuha basin the baishiquan tianyu and tianxiang deposits are located along the arqikekuduke fault which separates the jueluotage orogenic belt from the central tianshan precambrian terrane the poyi poshi and luodong deposits are located along the baidiwa fault which separates the central tianshan precambrian terrane from the beishan paleozoic rift re os dating of cu ni sulphide ores reveals that these cu ni ore belts formed in a narrow age range of 298 282 ma this age range is about the same as those of associated intrusions and dykes dated by the shrimp zircon u pb method tectonic and geochronological constraints suggest that the amalgamation of continental blocks mainly occurred during the late carboniferous in the central asian orogenic belt large scale hydrothermal and magmatic metallogenesis in the region occurred during post collisional stages of latest carboniferous to early permian age the cu ni sulphide deposits are part of this metallogenic event the cu ni orthomagmatic sulphide deposits in northern xinjiang are represented by 1 net textured type deposits by segregation of a cu ni metal sulphide melt and 2 magma conduit type some mafic ultramafic suites exhibit lithological zoning caused by strong differentiation stratiform orebodies are hosted by ultramafic rocks at the base of the magma chamber good examples are the kalatongke huangshandong and poshi deposits others such as the xiangshan baishiquan tianyu and tula ergen deposits are hosted by magma conduits consisting of peridotite troctolite and pyroxenite these ultramafic rocks either occur within faults or are surrounded by gabbroic and dioritic intrusions these two types of orthomagmatic cu ni sulphide deposits are also distributed along the same ore belts for instance the differentiated sill related huangshandong deposit co exists with the magma conduit type tula ergen deposit in the jueluotage orogenic belt orthomagmatic cu ni sulphide deposits in northern xinjiang formed during post collisional extension and are possibly related to a late carboniferous early permian mantle plume event the mafic ultramafic suites and associated cu ni deposits are commonly accompanied by dyke swarms and are characterized by elongated outcrops occurring along parallel e w trending regional faults these mafic ultramafic suites and accompanying dyke swarms are generally fractionated implying that they were feeders of presently eroded flood basalts

geochronology and fluid inclusion studies of the lailisigaoer and lamasu porphyry skarn cu mo deposits in northwestern tianshan china abstract the lailisigaoer porphyry mo cu and lamasu porphyry skarn cu deposits are located in the northwestern tianshan orogenic belt which is in the northwestern china according to re os analysis of molybdenite the time of mineralization of the lailisigaoer deposit is 377 ma and shrimp zircon u pb analysis dates the ore hosted intrusion of the lamasu deposit to 378 ma five types of fluid inclusions fis have been identified in both deposits h 2 o rich inclusions co 2 bearing inclusions halite bearing inclusions methane rich inclusions and pure co 2 inclusions in the lailisigaoer deposit the early stage fluid of the quartz phenocryst belongs to a nacl h 2 o system with total homogenization temperatures t h ranging from 300 to 395 c with a mean salinity of 9 0 wt nacl in the ore forming stage the fluid develops into a h 2 o nacl co 2 system due to boiling and decarbonation the t h values and salinities cluster between 220 and 370 c and between 0 and 33 0 wt nacl respectively the hydrothermal characteristics of the late quartz calcite stage are similar to those of the meteoric fluid in the lamasu deposit the early stage fluid of the quartz phenocryst belongs to a nacl h 2 o system with t h values ranging from 245 to 459 c and a mean salinity of 6 0 wt nacl in the ore forming stage due to the contact metamorphism between the hydrothermal fluid and wall rock the fluid evolves to a nacl h 2 o ch 4 system the t h values and salinities cluster between 220 and 360 c and between 0 and 17 3 wt nacl respectively the fluid of the late quartz sulfide stage coincides with the meteoric fluid in the mineralizing fluid of the lailisigaoer deposit the captured temperatures and pressures are between 210 and 350 c and between 170 and 600 bars respectively which are consistent with fluctuation between hydrostatic and lithostatic pressure corresponding to the estimated paleodepths of 1 7 2 2 km boiling is the dominant mineralizing mechanism in the lailisigaoer deposit whereas the contact metamorphism between the magmatic hydrothermal fluid and country rocks is the dominant mechanism in the lamasu deposit both deposits are formed in the continental arc setting related to the southward subduction of the north tianshan oceanic slab beneath the yili central tianshan block

neoproterozoic to paleozoic geology of the altai orogen nw china new zircon age data and tectonic evolution abstract we present a synthesis and a new account of the geological and tectonic history of the terranes of the chinese paleozoic altai orogen together with new single zircon ages for granitic and rhyodacitic rocks a central terrane consists of neoproterozoic to silurian amphibolite facies metasedimentary rocks and abundant devonian carboniferous granites the presence of precambrian basement is indicated by sinian fossils our xenocryst ages and published nd mean crustal residence ages of granites felsic arc type lavas on the southern margin of the terrane have a mean 207pb 206pb zircon age of 505 ma reflecting the time of arc volcanism and the presence of xenocysts with ages between 614 and 921 ma suggests derivation by intracrustal melting accordingly we suggest that a cambro ordovician continental magmatic arc was built on the southern margin of the central terrane by northward subduction a low grade ordovician andean type arc with a continental basement is situated above a normal fault on

methane rich fluid evolution of the baogutu porphyry cu mo au deposit xinjiang nw china abstract baogutu is the first porphyry cu mo au deposit discovered in western junggar xinjiang nw china the ore bearing intrusion is a dioritic intrusive complex that includes stage 1 diorites and minor stage 2 diorite porphyries the stage 1 diorites have produced concentric potassic and propylitic alteration zone and overprinted phyllic alteration and host much of the cu mo au mineralization at baogutu the baogutu porphyry cu mo au deposit consists of unusually disseminated and minor vein style mineralization the fluid evolution occurred in stage 1 diorite from late magmatic stage to hydrothermal stage stages 1b and 1c is constructed based on alteration and fluid inclusion analysis by microthermometry raman spectroscopy and quadrupole mass spectrometer five fluid types are distinguished and they are l1 liquid rich 2 phase l2 liquid vapor 2 phase v1 vapor rich 2 phase v2 mono phase vapor and h multi phase solid the dominant inclusions rich in reductive ch4 plus h2o while minor inclusions rich in ch4 and co2 the inclusions in quartz from the late magmatic stage contain the most brine inclusions and less other inclusions with ch4 rich and h2o rich compositions the inclusions in quartz from stage 1b contain all fluid types and have ch4 rich and ch4 h2o compositions with rare co2 the inclusions in quartz from stage 1c are characterized by more vapor inclusions without brine inclusions and a clear co2 concentration in a few assemblages with ch4 co2 composition using microthermometry we estimate fluid trapping conditions at t 400 c and p 1500 to 3100 bar in late magmatic stage t 200 to 400 c and p 50 to 320 bar in disseminated quartz in stage 1b t 180 to 400 c and p 20 to 260 bar in vein quartz in stage 1b and t 170 to 400 c and p 20 to 230 bar in stage 1c such late magmatic conditions are compatible with the fluid evolution as a result of ch4 rich inclusions derived from mantle magma such hydrothermal conditions in stages 1b and 1c with small p t fluctuations are compatible with the dominant disseminated mineralization at baogutu that indicates a weak fracturing the overall fluid path at baogutu is toward lower pressure and small changed temperature with composition transit of fluid from a high halite ch4 rich system to low halite ch4 co2 system it may lead to the formation of this cu mo au deposit

metallogeny during continental outgrowth in the columbia supercontinent isotopic characterization of the zhaiwa mo cu system in the north china craton abstract the eastern qinling molybdenum belt eqmb in central china represents the largest mo province in the world located at the southern margin of the north china craton this mo province is largely associated with mesozoic granitoids here we report re os isochron age of 1761 33 ma 2 mswd 2 9 from molybdenite in the recently discovered zhaiwa porphyry mo cu system within the eqmb this age coincides with the peak eruption period 1 78 1 75 ga of the xiong er group volcanic rocks which unconformably overlie the taihua supergroup and are interpreted to have developed on a continental arc the re concentrations 1 to 43 ppm of the zhaiwa molybdenites are similar to those of typical porphyry cu mo au systems developed on continental arcs the 34 s values of the zhaiwa ores 2 7 7 3 average 5 2 suggest that the sulfur was mainly sourced from a magmatic system the sulfides from the ores yield sr i average of 0 70533 similar to that of the xiong er group 0 70547 albeit higher than that of the kuanping group 0 70334 and lower than the taihua supergroup 0 70763 suggesting a mixed source the average e nd 1 76 ga of the sulfides from the ores 0 9 falls between the averages of the taihua supergroup ca 6 8 and the kuanping group ca 7 4 the pb isotope ratios of the ores are similar to but slightly higher than those of the taihua supergroup reflecting preferential leaching of radiogenic pb from the taihua supergroup by magmatic fluids integrated data and interpretations constrain the zhaiwa mo cu deposit to be a porphyry mineral system developed within a ca 1 76 ga continental arc related to oceanic plate subduction beneath the southern margin of the north china craton a correlation between tectonic settings and metallogenic types clearly indicate that the xiong er group was formed in a volcanic arc confirming paleo mesoproterozoic continental outgrowth along the margins of the columbia supercontinent the isotopic characterization of the zhaiwa deposit provides new insights into the enigma of the widespread distribution of large and super large mo deposits of eqmb along the southern margin of the north china craton

geochronology petrogenesis and tectonic implications of triassic granitoids from beishan nw china abstract five triassic granitic plutons have been identified from the beishan orogen by zircon u pb dating that defines two age groups 240 238 ma and 225 217 ma they belong to the high k calc alkaline and shoshonitic series and have alkalic and alkali calcic characteristics and are weakly peraluminous metaluminous these granitoids are mainly highly fractionated i type granite and a type granite they have high i sr values 0 7049 0 7096 and negative e nd t values of 0 9 to 2 8 with nd model ages of 0 89 1 13 ga suggesting a crustal contribution they also exhibit relatively high zircon e hf t values 1 3 to 6 1 and two stage hf model ages of 1 34 0 87 ga suggesting a mixture of mantle and various amounts of crustal components the mantle component probably originated from underplated magmas produced by partial melting of lithospheric mantle metasomatized by fluids or melts possibly derived from pre existing subducted materials the mid triassic 240 238 ma pluton has relatively high sr y 15 9 41 8 ratios and mgo 1 22 3 77 contents with negligibly to weakly negative eu anomalies eu 0 57 0 80 indicating adakite like features this was likely the result of partial melting of crustal components in response to voluminous underplated mantle derived magmas probably linked to lithospheric delamination and asthenospheric upwelling the late triassic 217 225 ma granitic plutons show strong negative anomalies of eu ba nb ta sr p and ti these were likely the result of fractional crystallization and crustal contamination for the granitic magma emplaced in a post orogenic setting

fluid inclusions and h o s pb isotope systematics of the chalukou giant porphyry mo deposit heilongjiang province china abstract the chalukou giant porphyry mo deposit located in the northern great xing an range is the largest mo deposit in the xing an mongolia orogenic belt this deposit s ore bodies are mainly hosted in an intermediate felsic complex and jurassic volcanic sedimentary rocks of which late jurassic granite porphyry quartz porphyry and fine grained granite are closely associated with the mo mineralization three types of fluid inclusions fis are present in the quartz associated with oxide and sulphide minerals i e liquid rich two phase gas rich two phase and daughter mineral bearing multiphase fis the fis in the quartz phenocrysts of the granite porphyry contain liquid rich two phase gas rich two phase and daughter mineral bearing multiphase fis the homogenization temperatures vary from 230 c to 440 c and 470 c to 510 c and their salinities vary from 0 7 to 53 7 nacl eq and 6 2 to 61 3 nacl eq respectively the fis of k feldspar quartz magnetite veins of the early stage are composed of liquid rich two phase gas rich two phase and daughter mineral bearing multiphase fis with homogenization temperatures and salinities of 320 c to 440 c and 4 2 to 52 3 nacl eq respectively the fis of quartz molybdenite veins and breccia of the middle stage are composed of liquid rich two phase gas rich two phase and daughter mineral bearing multiphase fis with homogenization temperatures and salinities of 260 c to 410 c and 0 4 to 52 3 nacl eq respectively fis of quartz fluorite galena sphalerite veins of the late stage are liquid rich two phase fis with homogenization temperatures and salinities of 170 c to 320 c and 0 5 to 11 1 nacl eq respectively the ore forming fluids of the chalukou deposit are characterised by high temperature high salinity and high oxygen fugacity belonging to an f rich h 2 o nacl co 2 system the 18 o w values vary from 4 5 to 3 2 and the d w values vary from 138 to 122 indicating that the ore forming fluids were a mixture of magmatic and meteoric water the 34 s values range from 1 9 to 3 6 with an average of 1 6 the 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb values of the metallic minerals are in the ranges of 18 269 18 501 15 524 15 567 and 38 079 38 264 respectively both the s and pb isotopic systems indicate that the ore metals and fluids came primarily from a deep seated magma source from the juvenile lower crust the mo mineralization in the chalukou deposit occurred at a depth of 0 5 to 1 3 km and multiple stages of phase separation or immiscibility of ore forming fluid was critical for the formation of the chalukou deposit

epithermal deposits in north xinjiang nw china the north xinjiang region nw china is an important part of the central asia orogenic belt situated at the junction of siberia tarim and kazakhstan plates it is an area characterized by multiple stages of phanerozoic continental growth during which several porphyry and epithermal systems were formed the relationship of these mineral systems to the geodynamic evolution of the region has not yet been well understood in this paper we list the main geological characteristics of 21 significant epithermal precious and base metal deposits in north xinjiang and classify them into high sulfidation and low sulfidation styles with the latter being predominant we have selected seven epithermal deposits representing different styles formed under different tectonic regimes and discuss their geology and geochemistry in some detail the deposit scale geology and geochemistry of epithermal systems in north xinjiang are essentially similar to those in other parts of the world all epithermal deposits in north xinjiang are hosted in volcanic rocks with ages ranging from devonian to triassic with the early carboniferous volcanic sequences being the most important followed by the permian and triassic the devonian early carboniferous host rocks belong to the calc alkaline series that developed in pre collisional arc back arc basin systems whereas the permian triassic host volcanic rocks of shoshonite series formed in post subduction regimes available isotopic ages of these epithermal systems cluster in two periods early carboniferous 320 ma and late carboniferous triassic 320 220 ma reflecting two metallogenic episodes that occurred during subduction related accretion and post subduction collision regimes respectively accordingly three groups of epithermal deposits in north xinjiang can be recognized as 1 pre collisional deposits without or with negligible collisional related modification 2 deposits formed in collision regime and 3 ore systems strongly overprinted by fluid flow in post subduction collision regime

fluid evolution of the yuchiling porphyry mo deposit east qinling china the yuchiling mo deposit east qinling china belongs to a typical porphyry mo system associated with high k calc alkaline intrusions the pure co2 pc co2 bearing c aqueous h2o naci w and

stress changes along the sunda trench following the 26 december 2004 sumatra andaman and 28 march 2005 nias earthquakes 1 the 26 december 2004 mw 9 2 and 28 march 2005 mw 8 7 earthquakes on the sumatra megathrust altered the state of stress over a large region surrounding the earthquakes we evaluate the stress changes associated with coseismic and postseismic deformation following these two large events focusing on postseismic deformation that is driven by viscoelastic relaxation of a low viscosity asthenosphere under coulomb failure stress cfs theory the december 2004 event increased cfs on the future hypocentral zone of the march 2005 event by about 0 25 bar with little or no contribution from viscous relaxation coseismic stresses around the rupture zones of the 1797 and 1833 sunda trench events are negligible but postseismic stress perturbations since december 2004 are predicted to result in cfs increases of 0 1 to 0 2 bar around these rupture zones between 2 and 8 years after the december 2004 event these are considerable stress perturbations given that the 1797 and 1833 rupture zones are likely approaching the end of a complete seismic cycle

characteristics and genesis of kanggur gold deposit in the eastern tianshan mountains nw china evidence from geology isotope distribution and chronology abstract the kanggur gold deposit lies in east tianshan mountains eastern section of central asia orogenic belt the gold mineralization occurs on the northern margin of the aqishan yamansu island arc in the tarim plate it is mainly hosted in lower carboniferous volcanic rocks and controlled by syn tectonic intrusions and the ductile shear zone the host rock is a calc alkaline volcanic rock series consisting of andesite dacite tuff and subvolcanic rocks the gold ore bodies were distributed in transition zone from strong ductile deformation to weak deformation ore controlling structure is ew trending normal brittle ductile shear zone the gold ore bodies are composed of au bearing altered rocks and a few au bearing sulfide quartz veins the mineralization shows vertical zonation in which au was enriched in the upper orebodies au pb zn were enriched in the middle and au cu were enriched in the lower orebodies according to mineral assemblages and alteration intensity hydrothermal alteration could be divided into three zones silicification chloritization pyritization and magnetization zone major ore body pyrite phyllic rock and or sericite alteration zone and sericite chlorite alteration zone five mineralization stages are identified on the basis of mineral assemblage and crosscutting relationship of veins the 34 s values of sulfide in the ores range from 0 9 to 3 3 similar to those of the volcanic and subvolcanic rocks 3 21 1 3 indicating that the sulfur isotope composition is characterized by unfractionated mantle sulfur the lead isotope compositions of ores are between those of the volcanic rocks and subvolcanic rocks the initial 87 sr 86 sr ratios of the ores vary between 0 7077 and 0 7106 similar to those of the host rocks 0 7079 0 7125 according to the sr s and pb isotopic data it is indicated that the ore forming materials were derived from the surrounding volcanic rocks and feature deep source the 18 o values of the ore fluids vary from 3 83 to 1 77 and the d values from 46 to 66 the 18 o vs d and 18 o vs 87 sr 86 sr diagrams indicate that ore fluids were derived from dynamic metamorphic water magmatic water and meteoric water the ore forming ages of kanggur gold deposit are determined by rb sr and sm nd isochron methods the results show that the main ore forming stages of kanggur gold deposit are 290 282 ma secondary mineralization stages are 275 254 ma studies on regional geology ore geology isotope geochemistry and ore forming ages have proved that the kanggur gold deposit was formed in the compression extension transition stage during the latest paleozoic continental collision and is characterized by orogenic gold deposits

multiple mineralization events in the eastern tianshan district nw china isotopic geochronology and geological significance abstract the eastern tianshan district occupies the middle of the central asian orogenic belt and has great economic potential for polymetallic mineralization more than 20 medium to large ore deposits have been discovered in this region since the late 1980s the timing of mineralization was previously thought to be hercynian but mesozoic ages for intrusions and mineralization have been repeatedly reported in recent years based on geochronological data and regional geological evidence it is suggested that the mineralization in the eastern tianshan was formed during multiple events the mineralization processes are related to an subduction island arc stage 360 320 ma with porphyry type and volcano sedimentary copper deposits a collisional accretionary stage 300 280 ma with orogenic type gold deposits a post collisional extension stage 280 245 ma with mafic ultramafic copper nickel and epithermal gold deposits and an intracontinental extensional stage 240 220 ma that gave rise to the jinwuozi gold deposit xiaobaishitou skarn w mo deposit and baishan porphyry mo re deposit

paleozoic multiple accretionary and collisional tectonics of the chinese tianshan orogenic collage abstract subduction related accretion in the junggar balkash and south tianshan oceans paleo asian ocean mainly in the paleozoic gave rise to the present 2400 km long tianshan orogenic collage that extends from the aral sea eastwards through uzbekistan tajikistan kyrgyzstan to xinjiang in china this paper provides an up to date along strike synthesis of this orogenic collage and a new tectonic model to explain its accretionary evolution the northern part of the orogenic collage developed by consumption of the junggar balkash ocean together with paleozoic island arcs northern ili issyk kul and chatkal located in the west which may have amalgamated into a composite arc in the paleozoic in the west and by addition of another two roughly parallel arcs dananhu and central tianshan in the east the western composite arc and the eastern dananhu and central tianshan arcs formed a late paleozoic archipelago with multiple subduction zones the southern part of the orogenic collage developed by the consumption of the south tianshan ocean which gave rise to a continuous accretionary complex kokshaal kumishi which separated the central tianshan in the east and other paleozoic arcs in the west from cratons tarim and karakum to the south cross border correlations of this accretionary complex indicate a general southward and oceanward accretion by northward subduction in the early paleozoic to permian as recorded by successive southward juxtaposition of ophiolites slices of ophiolitic melanges cherts island arcs olistostromes blueschists and turbidites which are mainly paleozoic in age with the youngest main phase being late carboniferous permian the initial docking of the southerly tarim and karakum cratons to this complicated late paleozoic archipelago and accretionary complexes occurred in the late carboniferous early permian in the eastern part of the tianshan and in the late permian in the western part which might have terminated collisional deformation on this suture zone the final stages of closure of the junggar balkash ocean resembled the small ocean basin scenario of the mediterranean sea in the cenozoic in summary the history of the altaids is characterized by complicated multiple accretionary and collisional tectonics

shrimp zircon u pb geochronology geochemistry and h o si s pb isotope systematics of the kanggur gold deposit in eastern tianshan nw china implication for ore genesis abstract the kanggur gold deposit is located in the southern margin of the central asia orogenic belt and in the western segment of the kanggur huangshan ductile shear belt in eastern tianshan northwestern china the orebodies of this deposit are hosted in the lower carboniferous volcanic rocks of the aqishan formation and mainly consist of andesite dacite and pyroclastic rocks the shrimp zircon u pb age data of the andesite indicate that the volcanism in the kanggur area might have occurred at ca 339 ma in the early carboniferous and that the mineralization age of the kanggur gold deposit was later than the age of volcanic rocks in the area geochemically the andesite rocks of the aqishan formation belong to low tholeiite and calc alkaline series and display relative depletions in high field strength elements hfses i e nb ta and ti the 18 o w and d w values vary from 9 1 to 3 8 and 66 0 to 33 9 respectively indicating that the ore forming fluids were mixtures of metamorphic and meteoric waters the 30 si values of 13 quartz samples range from 0 3 to 0 1 with an average of 0 15 and the 34 s values of 18 sulphide samples range from 0 9 to 2 2 with an average of 0 54 the 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb values of 10 sulphide samples range from 18 166 to 18 880 15 553 to 15 635 and 38 050 to 38 813 respectively showing similarities to orogenic pb these values are consistent with those of the andesite from the kanggur area suggesting a common lead source all of the silicon sulphur and lead isotopic systems indicate that the ore forming fluids and materials were mainly derived from the aqishan formation and that the host volcanic rocks of the aqishan formation probably played a significant role in the kanggur gold mineralization integrating the data obtained from studies on geology geochronology petro geochemistry and h o si s pb isotope systematics we suggest that the kanggur gold deposit is an orogenic type deposit formed in eastern tianshan orogenic belt during the permian post collisional tectonism

baogutu an example of reduced porphyry cu deposit in western junggar abstract classic oxidized porphyry copper deposits opcd are characterized by high tonnage and elevated f o 2 and contain highly oxidized minerals including primary anhydrite and hematite in contrast the baogutu deposit contains abundant hypogene pyrrhotite and methane rich fluid inclusions characteristic of lower tonnage reduced porphyry copper deposits rpcd mineral paragenesis and mineral chemistry studies reveal two mineralization periods magmatic and hydrothermal with the hydrothermal period further subdivided into three paragenetic stages including ca na alteration potassic alteration and propylitization locally overlapped by phyllic alteration several independent geothermometers indicate that the temperatures of the magma potassic and propylitization alteration are estimated to be 600 900 c 200 400 c and 200 300 c respectively multiple indicators including mineral assemblages apatite so 3 content whole rock fe 2 o 3 feo ratios and fluid compositions indicate the f o 2 of the magma and hydrothermal fluid to be nno and nno nno 2 respectively hydrothermal fluids associated with primary biotite yield log f h 2 o f hcl fluids values of 4 8 6 2 for diorite and 4 1 4 5 for granodiorite porphyry the log f s2 of the magmatic and potassic alteration are estimated to be 0 7 to 3 0 and 5 5 to 11 0 respectively based on pyrrhotite and sulfide assemblages mineral assemblage and hessite composition suggest the log f te2 of the potassic alteration is 8 5 to 14 5 the low tonnage baogutu deposit displays significantly lower f o 2 than opcds nno 2 and on this basis could be classified as a rpcd other physicochemical conditions including t f s2 log f h2o f hcl fluid do not show obvious differences to those of opcds we deduce that the low f o 2 of baogutu metallogenic granitoids and aqueous fluids likely produced the unusual pyrrhotite arsenopyrite mineral assemblage and the nacl h 2 o ch 4 co 2 ore forming fluids and small tonnage typical of rpcds previous obtained fluid inclusion h o isotope data and sulfide s pb isotope data suggest the methane rich ore forming fluids were derived from deep mantle source with little contamination from sedimentary components however detailed studies are needed to clarify the origin of the ch 4

magmatic arc asymmetry and distribution of anomalous plutonic belts in the batholiths of california effects of assimilation crustal thickness and depth of crystallization in order to better understand geologic fac tors controlling pronounced regional variations in whole rock chemistry mineralogy and mineral chemistry in the batholiths of california we calculate the magmatic intensive variables f hf f h 2 o f hf f hcl and f o 2 regional scale west to east increases in f oh in mafic silicates corresponding to the systematic i wc to i mc and i sc progression reflect orders of magnitude increase in f hf f h 2 o attending pluton crystallization low f hf f h 2 o of formation of western i wc types is consistent with their derivation from low fluorine source rocks in subducted oceanic slabs or the upper mantle in contrast higher f hf f h 2 o of crystallization of i mc and i sc types to the east implies the involvement of 1 progressively greater amounts of continental crustal source material such as biotite bearing metamorphic rocks their unweathered sedimentary derivatives retaining f rich mafic minerals or their fusion products and or 2 source materials which become more f rich toward the continental interior the regional distribution of i mc and i sc types suggests that the precambrian craton of western north america or derivative sediments may extend farther north in california and be morphologically more complex than previously thought from seemingly out of place occurrences of i wc plutons on the eastern slopes of the sierra nevada batholith we infer the existence of regions where precambrian basement was thin or absent in mesozoic time which prevented extensive cratonal contamination of subducted slab or upper mantle derived magmas new methods for estimating t f o 2 relations in the magmas demonstrate that i scr granites crystallize at oxygen fugacities as much as five orders of magnitude lower than those of i wc i mc and i sc types under conditions at or below the maximum stability limit of graphite in equilibrium with a c o h s gas phase the local scale formation of i scr granites in plutonic belts within specific wall rock terranes containing highly reducing sediments or metasediments may occur by contamination of i types with graphitic pelite or in some cases by the direct fusion of this reducing pelitic wall rock the spatial distribution of i scr granite provinces therefore is controlled simply by wall rock lithology amphibole geobarometry demonstrates a general west to east decrease in crystallization pressure across the sierra nevada batholith in contrast the peninsular ranges batholith displays a west to east crystallization pressure increase the bulk of the california batholiths crystallized at pressures less than 4 5 kb and depths less than about 15 19 km in the southern sierra nevada batholith the san gabriels and the eastern peninsular ranges however plutons crystallized at pressures exceeding 6 kb at deep crustal levels 23 km reconstruction of the pre erosion top of the batholith shows that in an east west cross section the central sierra nevada batholith was a horizontal tabular body with an aspect ratio of at least five to one

evidence from fluid inclusions for microbial methanogenesis in the early archaean era methanogenic microbes may be one of the most primitive organisms although it is uncertain when methanogens first appeared on earth during the archaean era before 2 5 gyr ago methanogens may have been important in regulating climate because they could have provided sufficient amounts of the greenhouse gas methane to mitigate a severely frozen condition that could have resulted from lower solar luminosity during these times nevertheless no direct geological evidence has hitherto been available in support of the existence of methanogens in the archaean period although circumstantial evidence is available in the form of approximately 2 8 gyr old carbon isotope depleted kerogen here we report crushing extraction and carbon isotope analysis of methane bearing fluid inclusions in approximately 3 5 gyr old hydrothermal precipitates from pilbara craton australia our results indicate that the extracted fluids contain microbial methane with carbon isotopic compositions of less than 56 per thousand included within original precipitates this provides the oldest evidence of methanogen 3 46 gyr ago pre dating previous geochemical evidence by about 700 million years

reduced porphyry copper gold deposits a new variation on an old theme it is a widely accepted fact that porphyry cu au deposits form from highly oxidized ore fluids despite this assertion several otherwise typical porphyry cu au deposits exhibit clear evidence of having formed from relatively reduced ore fluids these reduced porphyry cu au deposits lack primary hematite magnetite and sulfate minerals i e anhydrite but contain abundant hypogene pyrrhotite commonly have carbonic rich ore fluids with substantial ch 4 and are associated with ilmenite bearing reduced i type granitoids based on a synthesis of theoretical experimental and field data a variation on the classic porphyry cu model is proposed to explain the formation of reduced porphyry cu au deposits and their relatively cu poor but au rich nature the proposed reduced porphyry cu au model does not contradict the current understanding of porphyry cu au formation rather it adds yet another variation on the theme of porphyry cu au genesis