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

absolute timing of sulfide and gold mineralization a comparison of re os molybdenite and ar ar mica methods from the tintina gold belt alaska new re os molybdenite dates from two lode gold deposits of the tintina gold belt alaska provide direct timing constraints for sulfide and gold mineralization at fort knox the re os molybdenite date is identical to the u pb zircon age for the host intrusion supporting an intrusive related origin for the deposit however 40ar 39ar dates from hydrothermal and igneous mica are considerably younger at the pogo deposit re os molybdenite dates are also much older than 40ar 39ar dates from hydrothermal mica but dissimilar to the age of local granites these age relationships indicate that the re os molybdenite method records the timing of sulfide and gold mineralization whereas much younger 40ar 39ar dates are affected by post ore thermal events slow cooling and or systemic analytical effects the results of this study complement a growing body of evidence to indicate that the re os chronometer in molybdenite can be an accurate and robust tool for establishing timing relations in ore systems

hydrological changes in western central asia kyrgyzstan during the holocene as inferred from a palaeolimnological study in lake son kul abstract the hydrology of western central asia is highly sensitive to climatic perturbations in order to understand its long term variability and to infer linkages between precipitation and atmospheric and oceanic systems we conducted a thorough sedimentary and geochemical study on a composite core retrieved in lake son kul central kyrgyzstan a multi proxy approach was conducted on lake sediments based on grain size analyses magnetic susceptibility total organic carbon toc total nitrogen tn and carbon and oxygen isotope analyses on bulk and biogenic materials ostracoda and molluscs shells at a resolution equivalent to ca 40 years aiming to characterise the sequence of palaeolimnological changes in son kul as indicated by 18 o record of bulk carbonates mainly consisting of aragonite the holocene hydrological balance was negative during most of time suggesting an excess of evaporation e over precipitation p limnological conditions fluctuated rapidly before 5000 cal yr bp indicating significant changes in regional hydrology and climate in particular the long term negative hydrological balance was impeded by several short stages with marked increase of precipitation lasting several decades to a few centuries e g 8300 8200 6900 6700 6300 6100 5500 5400 5300 5200 and 3100 3000 cal yr bp precipitation changes as inferred from 18 o data are also documented by increased minerogenic detritus and higher toc we propose that the seasonal pattern of precipitation varied transiently in western central asia during the holocene although evaporation changes may also account for the rapid changes observed in 18 o data when the annual water balance was less critical p e the excess of water might be ascribed to increased precipitation during cold seasons mainly because winter precipitation has more negative 18 o than its summer equivalent conversely when the annual water balance is negative p e the moisture was mainly delivered during the warm season as between 5000 and 2000 cal yr bp our results thus imply that moisture sources could have changed as well during the holocene moisture was delivered as today mainly during summer from the extended caspian aral basin and eastern mediterranean although arctic and even north atlantic seas might be important moisture sources when seasonal precipitation was dominated by winter precipitation we hypothesise that warming arctic and north atlantic seas were important for the north hemisphere circulation during the cold season

zircon u pb ages of the metamorphic supracrustal rocks of the xinghuadukou group and granitic complexes in the argun massif of the northern great hinggan range ne china and their tectonic implications abstract the basement of the argun massif in the northern great hinggan range consists of the metamorphic supracrustal rocks of the xinghuadukou group and associated granitic complexes the metamorphic supracrustal rocks were previously interpreted as paleoproterozoic while the granitic complexes were considered mesoproterozoic in age this paper presents new zircon la mc icp ms u pb ages of biotite plagioclase leptynite and biotite schist from the xinghuadukou group in the lulin forest area heilongjiang province zircon shrimp u pb ages of biotite plagioclase gneiss from the xinghuadukou group in lulin forest and quartz diorite and monzogranite from the granitic complexes in mohe county heilongjiang province new geochronological data from the three metasedimentary rock samples of the xinghuadukou group can be preliminarily divided into five groups 1 2017 2765 ma 2 1736 1942 ma 3 1359 1610 ma 4 749 1239 ma and 5 448 716 ma except for the zircons of the 448 716 ma group belonging to a metamorphic origin the other age groups had the youngest age of 749 17 ma indicating that the xinghuadukou group formed during the neoproterozoic era at least

influence of crude oil on the genesis of the lanjiagou porphyry molybdenum deposit western liaoning province china abstract the lanjiagou porphyry molybdenum deposit in western liaoning province china is hosted in fine grained jurassic granites la icp ms zircon u pb analyses indicate that the crystallization of the ore hosting granites took place 185 0 1 8 ma mswd 1 4 molybdenum mineralization in the deposit can be divided into three stages the stockwork quartz vein stage the planar quartz vein stage and the fissure filling quartz vein stage re os isotopic ages for the molybdenite from the stockwork quartz vein type ores yielded an isochron age of 188 8 9 9 ma mswd 3 0 while six samples from the planar quartz vein type ores yielded a similar isochron age of 185 6 1 2 ma mswd 0 5 re os isotopic ages for the molybdenite identical within error to zircon u pb isotopic ages indicate that the molybdenum mineralization is related to the host intrusions apart from primary inorganic fluid inclusions ifis a large number of primary organic fluid inclusions ofis are found in the latter two stages of vein quartz and minors found in the first stage the components and characteristics of ofis in the three stages of vein quartz differ from each other which is also true for the ifis ofis in stockwork vein quartz are characterized by halite bearing inclusions and organic liquids in the inclusions are brown and do not fluoresce under ultraviolet uv light homogenization temperatures t h for the primary ifis coeval with ofis of this stage ranges from 300 c to 450 c while the salinity varies from 10 to 53 wt nacl equiv in planar vein quartz ofis are predominately two phased liquid and gas and salt daughter minerals halite are absent organic liquids are light brown to colorless and show blue fluorescence under uv light the t h range for the ifis of this stage is 250 360 c and the salinity range is 3 17 wt nacl equiv finally ofis in fissure filling vein quartz are marked by liquid gas inclusions organic liquids are generally colorless and show yellow fluorescence under uv light the t h range for the primary ifis is 180 240 c and the salinity range is 4 11 wt nacl equiv organic geochemical analyses indicate that organic matter in the lanjiagou deposit was derived from mature crude oil we suggest that large volumes of crude oil bearing non magmatic fluids were flushed into the lanjiagou porphyry hydrothermal system during all phases of ore formation and likely played important roles in mineralization

ages and geodynamic settings of xilamulun mo cu metallogenic belt in the northern part of the north china craton abstract the xilamulun belt along the northern part of the north china craton is located in eastern segment of the central asian orogenic belt and has great economic potential for mo cu mineralization more than ten medium to large ore deposits have been discovered in this region in the recent years the major types of mineralization type include porphyry chehugou mo cu kulitou mo cu xiaodonggou mo and jiguanshan mo quartz vein nianzigou mo xinjing mo epithermal hongshanzi mo u and alteration assemblage liulingou mo the timing of mineralization was previously thought to be yanshanian 208 290 ma however indosinian 260 208 ma ages for intrusions and mineralization have been recognized in recent years based on geochronologic data and regional geological evidence it is suggested that the mineralization in the xilamulun belt was formed during multiple events the mineralization processes are related to a post collisional extension stage 258 210 ma with the generation of the porphyry molybdenum copper deposit a tectonic stress transformation from ns to ew 185 150 ma that gave rise to vein or porphyry molybdenum deposit and a lithospheric thinning stage 140 110 ma with porphyry molybdenum deposit

re os and u pb geochronology of the clear creek dublin gulch and mactung deposits tombstone gold belt yukon canada absolute timing relationships between plutonism and mineralization new re os molybdenite and u pb zircon dates from deposits of the tombstone gold belt provide direct timing constraints for sulphide mineralization and crystallization of spatially associated plutons at clear creek re os molybdenite dates 93 6 0 3 to 92 4 0 4 ma are in excellent agreement with the host intrusion u pb zircon age 92 3 0 3 ma consequently we propose the nominally younger existing 40 ar 39 ar hydrothermal mica ages 91 7 0 4 and 90 0 0 3 ma for clear creek are a result of slow cooling at dublin gulch the re os molybdenite date 93 2 0 3 ma for a late stage vein is nominally younger than the host intrusion u pb zircon age 94 0 0 3 ma in agreement with the deposits paragenesis the u pb zircon date 92 1 0 2 ma for the mactung pluton which lies adjacent to the w skarn has a younger age than the re os molybdenite dates 97 5 0 5 ma fluid inclusion geochemical data for ore fluid indicate a magmatic origin for the w skarn however the u pb and re os age data suggest that the exposed mactung stock is not the source of ore fluid for the w skarn and that the progenitor pluton for ore fluid is unknown the robust age constraints obtained for mineralization and magmatism in this study are in accord with the hypothesis that these deposits are intrusion related ore systems the results are also in agreement with previous studies demonstrating that the re os molybdenite chronometer can provide accurate and precise dates for the timing of metallic mineralization with rigorous sampling protocol

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

re os and 40ar 39ar ages of the jiguanshan porphyry mo deposit xilamulun metallogenic belt ne china and constraints on mineralization events the large jiguanshan porphyry mo deposit with more than 100 mt of ore and grades ranging from 0 08 to 0 11 is located in the newly identified xilamulun metallogenic belt along the northern margin of the north china craton the mo mineralization is predominantly disseminated in the host granite porphyry but locally occurs as stockworks in lithic tuff and rhyolitic rocks 40ar 39ar dates of samples from groundmass material in the host granite porphyry post ore diabase and quartz porphyry dikes show plateau ages of 155 1 1 9 149 4 0 9 and 147 6 0 9 ma with inverse isochron ages of 156 0 1 8 149 3 1 3 and 148 3 1 2 ma respectively seven samples of disseminated molybdenite yielded a weighted average 187re 187os age of 155 3 0 9 ma whereas six veinlet type molybdenite samples yielded a weighted average 187re 187os age of 153 0 0 9 ma providing direct timing constraints for the mo mineralization at 153 155 ma the regional geological setting together with the emplacement of post ore diabase and quartz porphyry dikes in the jiguanshan deposit are indicative of an extensional regime in late jurassic which was probably linked to lithospheric extension in northeast china

numerical modeling of the global semidiurnal tide in the present day and in the last glacial maximum 1 a hydrodynamic model incorporating a self consistent treatment of ocean self attraction and loading sal and a physically based parameterization of internal tide it drag is used to assess how accurately barotropic tides can be modeled without benefit of data and to explore tidal energetics in the last glacial maximum lgm m2 solutions computed at high resolution with present day bathymetry agree with estimates of elevations from satellite altimetry within 5 cm rms in the open ocean this accuracy and agreement with atlimetric estimates of energy dissipation are achieved only when sal and it drag are included in the model solutions are sensitive to perturbations to bathymetry and inaccuracies in available global databases probably account for much of the remaining error in modeled elevations the 100 m drop in sea level during the lgm results in significant changes in modeled m2 tides with some amplitudes in the north atlantic increasing by factors of 2 or more dissipation is also significantly changed by the drop in sea level if it drag estimated for the modern ocean is assumed dissipation increases by about 50 globally and almost triples in the deep ocean however it drag depends on ocean stratification which is poorly known for the lgm tests with modified it drag suggest that the tendency to a global increase in dissipation is a robust result but details are sensitive to stratification significant uncertainties about paleotides thus remain even in this comparatively simple case where bathymetry is well constrained

evolution of aqueous carbonic fluids during contact metamorphism wall rock alteration and molybdenite deposition at trout lake british columbia the trout lake deposit is associated with a granodiorite tonalite stock that intruded greenschist facies calcareous and pelitic metasedimentary rocks it is typical of the fluorine deficient or granodiorite class of molybdenum deposits the stock is surrounded by a contact metamorphic aureole in which the mineral assemblages record evidence of fluid infiltration at the present erosional surface temperatures were below 400 degrees c and x sub co 2 in the calcareous rocks was 0 01 the confining pressure is estimated to have been 2 kbars contact metamorphism was followed successively by skarn and potassic alteration the latter developed as biotite halos around quartz albite veins in the metasedimentary rocks and as k feldspar halos around quartz veins in the intrusive rocks fluid inclusions in veins formed during potassic alteration are dominantly aqueous and have low to moderate salinities the ensuing quartz feldspar muscovite and muscovite ankerite alteration events were relatively pervasive aqueous carbonic fluid inclusions are commonly observed in quartz feldspar muscovite altered samples and are the dominant fluid inclusion type present in veins associated with muscovite ankerite alteration the aqueous fluid inclusions from all stages of alteration homogenize at temperatures between 170 degrees and 310 degrees c with a peak at 250 degrees c the aqueous carbonic fluid inclusions homogenize to the h 2 o phase between 240 degrees and 340 degrees c oxygen isotope compositions for muscovite quartz pairs yield temperatures of 370 degrees to 400 degrees c for quartz feldspar muscovite and muscovite ankerite alteration this indicates that the fluids were trapped at approximately 1 400 to 1 700 bars i e above the two phase region in the h 2 o co 2 nacl system calculated delta 18 o values for the fluid range from 8 0 to 8 4 per mil and taken in conjunction with pressure and temperature estimates suggest a magmatic and or modified ground water source phase relations of alteration minerals suggest that ph decreased during alteration mineralization is spatially and temporally associated with quartz feldspar muscovite alteration molybdenite is typically intergrown with muscovite that replaced alkali feldspar this textural relationship is interpreted to indicate that molybdenite deposited in response to decreases of temperature and or ph the common occurrence of these intergrowths in other fluorine deficient and enriched deposits suggests that the controls of mineralization for these deposits were similar to those at trout lake

geology re os ages sulfur and lead isotopes of the diyanqinamu porphyry mo deposit inner mongolia ne china the diyanqinamu porphyry mo deposit in the southern greater khingan range of the central asian orogenic belt contains 800 million metric tons mt of ore with an average grade of 0 097 molybdenum the deposit is hosted in late jurassic volcanic rocks of tuff andesite and volcanic breccia multiple stage hydrothermal activities have resulted in propylitic phyllic and argillic alteration in this deposit five stages i v of hydrothermal activity are identified stage i is represented by a mineral assemblage of epidote chlorite and magnetite with some discontinuous barren veinlets of quartz k feldspar fluorite magnetite epidote chlorite stage ii is marked by occurrence of quartz fluorite molybdenite magnetite pyrite sericite siderite veinlets veins with phyllic halos stage iii consists of fluorite siderite quartz molybdenite pyrite ankerite calcite chalcopyrite veins that are commonly related to phyllic alteration and dissemination of fluorite in the altered rocks stage iv has an assemblage of fluorite quartz pyrite ankerite calcite molybdenite chalcopyrite sphalerite galena in coarse veins 10 20 mm wide stage v consists of narrow 5 mm wide veinlets of calcite fluorite pyrite quartz molybdenite mainly occurs in stages ii and iii re os dating results for molybdenite samples from these two stages yielded an isochron age of 156 2 4 2 ma 2 mswd 0 96 n 10 most molybdenite samples have high 34s values 8 4 relative to other sulfide minerals i e galena sphalerite pyrite and chalcopyrite of stages ii to v 34s 2 5 8 3 n 22 molybdenite also has low 207pb 204pb and 208pb 204pb ratios relative to other sulfide minerals although there are minor overlaps in a diagram of 206pb 204pb versus 207pb 204pb these pb isotope data display a positive trend transecting the growth curves of crustal lead which could be invoked by mixing of crustal and mantle sources with distinct pb isotopes in combination with the s isotope data and mineral paragenesis we suggest that magmas were the main source of molybdenum whereas other metals i e pb zn and cu were possibly sourced from the country rocks

geochronology and isotopic geochemistry of the a type granites from the huanggang sn fe deposit southern great hinggan range ne china implication for their origin and tectonic setting abstract the huanggang sn fe deposit inner mongolia is located in southern great hinggan range metallogenic belt la icp ms zircon u pb dating show that the k feldspar granite and granite porphyry in the huanggang mine were formed at 136 7 1 1 ma and 136 8 0 57 ma respectively sr nd pb isotope of the rocks and in situ zircon hf isotopic systematics show that 87 sr 86 sr i values range from 0 70211 to 0 70729 close to the 87 sr 86 sr i of oceanic basalts and lower than those of continental crust the e nd t values and nd model ages t dm vary from 0 8 to 0 9 and 855 to 993 ma respectively the pb isotopic compositions are also variable with 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb values of 18 974 26 107 15 554 15 914 and 38 894 39 890 respectively suggesting that the lead is derived from a mixed source the 176 hf 177 hf values range from 0 282744 to 0 282922 with corresponding e hf t values ranging from 1 9 to 18 3 and two stage hf model ages t dm2 of between 561 and 888 ma the isotope composition shows that huanggang granites were derived from partial melting of juvenile lower crust that originated from depleted mantle perhaps contaminated by small amounts of ancient continental crust younger nd hf isotope model ages imply that an important crustal growth event took place in this area during the neoproterozoic integrating our data with previously published results and the late mesozoic regional tectonic setting we conclude that the huanggang granites were generated in an intraplate tectonic magmatic setting asthenospheric mantle upwelling due to lithospheric delamination and magma underplating caused the partial melting of a mantle wedge metasomatized by the fluids released from subducted oceanic crust or by decompression of depleted mantle this resulted in remelting differentiation and a continued evolution of the mafic juvenile crust producing a large quantity of granitic magma the tectonic setting for these processes may be linked to the nnw subduction of the pacific plate izanagi in the mesozoic which affected most of eastern china

formation of the giant chalukou porphyry mo deposit in northern great xing an range ne china partial melting of the juvenile lower crust in intra plate extensional environment abstract the chalukou porphyry mo deposit 2 46 mt 0 087 mo located in the northern great xing an range ne china is the largest mo deposit discovered in china so far the host rocks consist of aplite porphyry granite porphyry and quartz porphyry and are intruded into lower ordovician intermediate felsic volcanic sedimentary rocks and pre ore monzogranite and are cut by post ore feldspar porphyry diorite porphyry and quartz monzonite porphyry here we present the zircon u pb ages whole rock geochemistry sr nd isotopic and zircon hf isotopic data for the pre ore syn ore and post ore intrusive rocks the chalukou ore forming porphyries intruded during 147 148 ma and have high silica alkali rich metaluminous to slightly peraluminous compositions and are oxidized they are enriched in large ion lithophile elements e g k rb u and th light ree and depleted in high field strength elements e g nb p and ti depletions in eu ba sr nb ta p and ti suggest that they have experienced strong fractional crystallization of plagioclase biotite hornblende and accessory minerals the pre ore monzogranite 172 ma also belongs to the high k calc alkaline series highly fractionated ree patterns la yb n 19 6 21 7 high values of sr y 54 69 and la yb 29 32 are adakite like geochemical features the post ore rocks 141 128 ma have similar geochemical characteristics with ore forming porphyries except that quartz monzonite porphyry shows no ba sr negative anomaly all intrusive rocks have relative low initial 87sr 86sr 0 705413 0 707889 and end t values 1 28 to 0 92 positive ehf t values 2 4 to 10 1 and young two stage nd and hf model ages tdm2 nd 863 977 ma tdm2 hf 552 976 ma these geochemical and isotopic data are interpreted to demonstrate that the ore forming porphyries formed by partial melting of the juvenile lower crust caused by underplating of mafic magmas in an intra plate extensional setting the pre ore monzogranite formed by partial melting of thickened lower crust in a collisional setting caused by closure of mongol okhotsk ocean the post ore feldspar porphyry shares a similar magma source with ore forming porphyry but the quartz monzonite porphyry has a relatively deeper magma source region and has not experienced as much fractional crystallization the transformation from middle jurassic compression to late jurassic extension created favorable conditions for the generation and emplacement of the ore forming magma the juvenile lower crust provided the main source of molybdenum for chalukou deposit enrichment of mo by fractional crystallization played an important role in concentrating mo during formation of the chalukou mo deposit the age 147 ma high fluorine and associated pb zn deposits are all different from other major porphyry mo deposits in ne china chalukou is a new mineral deposit type in the great xing an range

evolution of ore fluids in the donggou giant porphyry mo system east qinling china a new type of porphyry mo deposit evidence from fluid inclusion and h o isotope systematics abstract the donggou mo deposit in the eastern qinling area china is a giant porphyry system discovered based on a targeting concept by using the tectonic model for collisional orogeny metallogeny and fluid flow cmf model mo mineralization is associated with the donggou aluminous a type granite porphyry and was formed during the early cretaceous in a tectonic regime of continental extension the orebodies mainly occur as numerous veinlets in the host rocks hydrothermal ore forming processes include at least three stages characterized by veinlets of 1 quartz k feldspar minor molybdenite 2 quartz molybdenite beryl and 3 quartz carbonate fluorite three types of fluid inclusions fis are distinguished in quartz and beryl in stages 1 and 2 i e aqueous w type carbonic aqueous c type and solid bearing s type with only aqueous fis observed in stage 3 minerals s type fis contain variable daughter minerals including halite chalcopyrite calcite and an unidentified transparent crystal but only halite can dissolve during heating halite bearing s type fis are mainly homogenized by halite dissolution at 182 416 c corresponding to salinities of 30 9 49 2 wt nacl equiv minor halite bearing s type fis are homogenized to liquid at 190 360 c via vapor disappearance with salinities of 29 1 36 2 wt nacl equiv other fis in minerals of stages 1 2 and 3 are homogenized at temperatures of 341 550 c 220 440 c and 125 225 c with salinities of 8 0 18 3 5 3 16 8 and 0 5 7 3 wt nacl equiv respectively the estimated minimum trapping pressures are up to 141 mpa in stage 1 and up to 81 mpa in stage 2 respectively corresponding to an initial mineralization depth of no less than 5 km the quartz in veinlets yields 18 o values of 8 5 10 0 corresponding to 18 o h 2 o values of 2 9 to 5 9 while the d h 2 o values of fluid inclusions range from 59 to 82 these data suggest that the ore fluids forming the donggou deposit changed from high temperature high salinity co 2 rich magmatic to low temperature low salinity and co 2 poor meteoritic fluids via boiling and mixing resembling those of other magmatic hydrothermal systems in qinling orogen and dabie shan this supports the notion that the porphyry systems generated in a post collisional tectonic setting were initially co 2 rich as indicated by abundant c type and co 2 bearing s type fluid inclusions

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

continental island from the upper silurian ludfordian stage of inner mongolia implications for eustasy and paleogeography an unconformity between the silurian xibiehe formation and ordovician igneous rocks marks the perimeter of a small paleoisland near bater obo in north central inner mongolia 180 km northwest of the provincial capital of hohhot the stratigraphic position of the lower part of the xibiehe formation is correlated by means of conodonts with the upper part of the ancoradella ploeckensis zone in the basal ludfordian stage corresponds to mid ludlovian epoch ca 421 ma elongate in plan 610 m 200 m the exhumed diorite core rises 30 m above the lowest elevations of surrounding silurian strata paleoshores along the principal axis of the inlier delineate contrasting facies robust stromatoporoids are in growth position within silty limestones some directly encrusting the unconformity surface of the sheltered southeast margin a basal conglomerate of diorite cobbles and boulders characterizes the high energy northwest margin the depositional constraints and timing of transgressive facies associated with this continental paleoisland have implications for the eustatic and paleogeographic history of the parent sino korean plate burial of the island corresponds to the beginning of a global rise in sea level that peaked in late ludlovian time our interpretation of windward and leeward facies requires an approximate 90 clockwise rotation of the parent plate to accommodate the dominant pattern of low latitude trade winds and storms

a porphyry skarn metallogenic system in the lesser xing an range ne china implications from u pb and re os geochronology and sr nd hf isotopes of the luming mo and xulaojiugou pb zn deposits abstract the luming porphyry mo deposit and the xulaojiugou skarn pb zn deposit are located in the southeast lesser xing an range ne china they are about 15 km apart and are both related to monzogranite mo orebodies in the luming deposit are hosted within the medium to fine grained monzogranite while pb zn orebodies in the xulaojiugou deposit are hosted by the contact zone between the medium grained monzogranite and the marbles of the early cambrian qianshan formation la icp ms zircon u pb dating of the ore related monzogranite in the luming deposit yields crystallization age of 180 7 1 6 ma and the medium grained and porphyritic monzogranites from the xulaojiugou deposit yield crystallization ages of 181 2 1 1 ma and 179 9 1 0 ma respectively analyses of seven molybdenite samples from the luming deposit display re os isochron age of 177 9 2 6 ma these results indicate that the mineralization in the luming and xulaojiugou deposits occurred at about 181 178 ma these two deposits are genetically linked and belong to a porphyry skarn metallogenic system combined with the previously reported geochronological data for ore deposits in adjacent areas we consider that the early jurassic is an important epoch for mo and pb zn mineralization in the lesser xing an range the monzogranites from the luming and xulaojiugou deposits are enriched in and rb th u pb and light rare earth elements lrees and are depleted in ba nb ta p ti and eu they have positive ehf t values of 1 0 4 0 with two stage hf model ages tdm2 of 868 1033 ma whole rock sr and nd isotopes show restricted ranges of initial compositions with 87sr 86sr i between 0 706346 and 0 707384 and end t between 3 5 and 1 8 these data indicate that their primary magmas originated from the partial melting of a depleted lithospheric mantle which had been metasomatized by subducted slab derived fluids melts the early jurassic magmatic metallogenic events in the lesser xing an range are interpreted as a response to the subduction of the paleo pacific plate

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

paleoproterozoic positive δ13ccarb excursion in the northeastern sino korean craton evidence of the lomagundi event abstract the 2 33 2 06 ga positive 13 c carb excursion associated with environmental change and the breakup of the kenorland or superia supercontinent is called the lomagundi or jatulian event or great oxidation event and has been reported in many early precambrian cratons but not yet in the sino korean craton the guanmenshan formation of the liaohe group occurs in the northeastern part of the sino korean craton 13 c carb and 18 o values in 42 samples from this formation range from 3 5 5 9 v pdb and 15 4 24 8 v smow respectively showing a clear positive 13 c carb excursion that characterizes the lomagundi event thirty five of the 42 samples with less hydrothermal alteration have higher 13 c carb and 18 o carb values than the other 7 samples obviously affected by fluid flow confirming that it was fluid flow that reduced the 13 c carb and 18 o carb values this positive 13 c carb excursion places deposition of the guanmenshan formation within the age range of 2 33 2 06 ga

ree geochemistry of carbonates from the guanmenshan formation liaohe group ne sino korean craton implications for seawater compositional change during the great oxidation event abstract the worldwide 2 33 2 06 ga positive 13 c carb excursion has been correlated with the great oxidation event goe and termed as the lomagundi event the 2 3 1 85 ga guanmenshan formation in the liaohe group of the northeastern sino korean craton is characterized by positive 13 c carb excursion and is a potential candidate to evaluate the lomagundi event using rey rare earth element and yttrium ree y chemical fingerprints here we present major and trace element analysis of 42 samples from the guanmenshan formation which are pure marine chemical sediments and use the data to trace the seawater composition during 2 3 1 85 ga 15 least altered dolomicrite samples 600 m strata have ree values of 0 739 4 175 ppm 2 414 1 184 ppm and the y ho ratios of 34 5 56 6 44 1 5 7 they show uniform positive la sn la sn 1 04 0 27 and gd sn gd sn 1 64 0 40 anomalies and notable lree depletions indicated by nd sn yb sn values of 0 24 0 92 average 0 56 0 19 these features are consistent with the geochemistry of well oxygenated shallow ambient seawater and suggest that these samples provide a robust record of the primary rey signature of seawater during the lomagundi event the rey patterns of 15 silicified dolomites marbles locally with veinlets from the pb zn mining camps in the region with average eu cn eu cn 1 56 0 95 are identical to those of high temperature hydrothermal fluids 250 c characterized by a flat pattern and marked positive eu anomalies indicating that these rocks were subjected to metasomatism by hydrothermal fluids the guanmenshan formation shows average ce sn ce sn of 0 93 0 09 and sm cn yb cn of 1 which are higher than those of the archean 2 33 ga chemical sediments generally f o 2 and p co 2 the rey in the dolomicrite were mainly sourced from fluxes of solutes from terrestrial weathering and also from seafloor hydrothermal processes on a subordinate scale the guanmenshan dolomicrites have eu sn eu sn values of 1 34 2 55 i e around 1 53 indicating that they were deposited during 2 33 2 06 ga as the eu sn eu sn 1 53 can be used as a proxy for the 2 33 2 06 ga marine chemical sediments our study shows that the guanmenshan formation was formed at a critical turning point in earth history when the global atmosphere hydrosphere system witnessed a dramatic change from reducing to oxidizing conditions

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

late permian tectonic evolution at the southeastern margin of the songnen zhangguangcai range massif ne china constraints from geochronology and geochemistry of granitoids abstract this paper reports the la icp ms u pb zircon dating and geochemical data for the huangqigou xiaobeihu and lalagou granitic plutons at the southeastern margin of the songnen zhangguangcai range massif which will not only place important constraints on the rock forming ages source characteristics and tectonic setting of these granitic plutons but will also provide insights into understanding the tectonic evolution of the eastern segment of the central asian orogenic belt zircons from three plutons have distinct oscillatory zoning structures in their cathodoluminescene cl images which combined with the th u ratios of 0 28 1 06 indicate their magmatic origins zircon u pb dating results for these granitic plutons indicate that the granitic magmatism occurred mainly in the late permian 256 252 ma the granites have sio2 of 58 0 74 3 na2o of 2 74 3 76 k2o of 2 75 3 95 na2o k2o of 0 77 1 13 mg 100 mg mg fe2 of 21 8 39 9 and a cnk of 0 88 1 08 with ree patterns characterized by lree hree 7 75 12 82 la yb n 7 88 14 9 and eu 0 56 0 87 the trace element spider diagrams indicate that these granites are enriched in large ion lithosphile elements rb ba th u etc and relatively depleted in high field strength elements ti nb ta with sr and pb ranging from 205 to 350 ppm and from 2 02 to 3 60 ppm respectively the in situ hf isotope analysis reveals that ehf t values range from 2 22 to 11 65 and the two stage hf model ages tdm2 range between 641 and 1274 ma these geochemical characteristics indicate that the late permian granitic plutons at the se margin of the songnen zhangguangcai range massif can be assigned to metaluminous and weakly peraluminous high potassium calc alkaline i type granites with low sr and high yb features and that the magmas to have formed these granites were originated from the partial melting of mafic igneous rocks in the lower crust the source rocks are composed mainly of the juvenile crust with small contributions of ancient continental crust considering the existence of coeval mafic intrusive rocks and sedimentary basins we propose that the late permian magmatism in the study area occurred in a post collisional extensional setting following the collision of the xingkai block and the united jiamusi and songnen zhangguangcai range massifs

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

re os sulfide chalcopyrite pyrite and molybdenite systematics and fluid inclusion study of the duobaoshan porphyry cu mo deposit heilongjiang province china abstract the duobaoshan porphyry deposit located in the northwestern part of the lesser hinggan range is one of the biggest porphyry cu mo deposits in the central asian orogenic belt in china the duobaoshan porphyry deposit occurs in granodiorite and volcanic rocks of the middle ordovician duobaoshan formation six types of veins have been identified in three ore forming stages as follows a quartz potassic feldspar vein in the early ore forming stage an early stage quartz molybdenite vein late stage quartz molybdenite and quartz chalcopyrite pyrite veins in the middle ore forming stage and quartz pyrite and calcite quartz veins in the late ore forming stage the following four types of fluid inclusions are distinguished from various quartz veins two phase aqueous pure gas phase co 2 bearing and daughter mineral bearing inclusions the ore forming fluid for the early ore forming stage belongs to the h 2 o co 2 nacl system which is characterized by high temperatures 550 c intermediate salinities 16 2 18 1 wt nacl eqv and high co 2 content the ore forming fluid from the middle ore forming stage evolved to the h 2 o co 2 nacl system which is characterized by intermediate to high temperatures 230 450 c and high low salinities 0 8 to 65 3 wt nacl eqv and is also rich in co 2 and metals the ore forming fluid finally reached cool temperatures 110 200 c low salinities 3 9 8 4 wt nacl eqv and was co 2 poor intensive fluid immiscibility or boiling occurred when the ore forming fluid with temperatures of 230 450 c and pressures of 10 41 mpa ascended to 4 1 km inducing the escape of co 2 depressing the solubility of fluid and depositing abundant metal sulfides the total re and os concentrations of chalcopyrite and pyrite range from 0 15 to 2 95 g g and 0 74 to 15 01 ng g respectively analyses of seven chalcopyrite and pyrite samples yielded isochron ages of 482 486 ma and the model age of one molybdenite sample is 485 6 3 7 ma the mineralization age of the duobaoshan deposit is between 482 and 486 ma and mantle fluid and materials were involved in the mineralization process the duobaoshan deposit is a classic porphyry cu mo deposit that formed in an early palaeozoic island arc tectonic setting

fluid inclusion study of the nannihu giant porphyry mo w deposit henan province china implications for the nature of porphyry ore fluid systems formed in a continental collision setting abstract the nannihu mo w deposit located in the henan province of china is a giant porphyry deposit formed in the qinling orogen during the jurassic continental collision between the north china and yangtze cratons mo w mineralization is associated with the nannihu porphyritic monzogranite occurring as numerous stockwork veinlets in the altered wallrocks and the causative porphyry both the porphyry stock and wallrocks underwent intense hydrothermal alteration ranging outwardly from potassic to phyllic alteration and to carbonation zones with increasing distance from the intrusion the hydrothermal ore forming process can be divided into four stages characterized by veinlets from early to late 1 quartz potassic feldspar molybdenite pyrite 2 quartz molybdenite veins containing minor pyrite and chalcopyrite 3 quartz polymetal sulfide and 4 quartz carbonate fluorite most of the ores are formed during stages 2 and 3 four types of fluid inclusions fis are distinguished in this study based on petrographic and microthermometric criteria i e pure co 2 nacl h 2 o co 2 h 2 o and daughter mineral bearing fluid inclusions all of the four types of fis can be observed in the hydrothermal quartz formed in stages 1 2 and 3 while the stage 4 minerals contain only nacl h 2 o fluid inclusions fluid inclusions of stage 1 are mainly homogenized between 350 and 460 c with salinities ranging from 5 7 to 17 9 wt nacl equiv the stage 2 fis yield homogeneous temperatures of 300 380 c and salinities of 3 5 16 9 wt nacl equiv fis of stage 3 are homogenized between 250 and 370 c with salinities of 1 8 14 3 and 28 6 39 1 wt nacl equiv fis of stage 4 are homogenized at temperatures of 115 to 265 c yielding salinities of 0 5 to 1 2 wt nacl equiv daughter minerals such as halite chalcopyrite and some unknown minerals are frequently present in stage 3 fis which probably represent a reducing and oversaturated fluid system resulting from fluid boiling the daughter mineral bearing fis coexist with vapor and liquid rich nacl h 2 o fis that have contrasting salinities these fis are homogenized in divergent ways at similar temperatures suggesting that fluid boiling took place in stages 2 and 3 the estimated pressures range from 70 to 270 mpa in stage 1 through 30 150 mpa in stage 2 to 30 85 mpa in stage 3 corresponding to a depth of no less than 3 km in other words the ore forming fluids are characterized by high temperature high salinity high f o 2 and high co 2 content and fluid boiling resulted in co 2 release f o 2 decrease and ore mineral precipitation we suggest that the co 2 rich fluid is a distinctive feature of porphyry systems developed in continental collision setting in transitional compressional to extensional regime contrasting to the co 2 poor nacl h 2 o fluids observed in volcanic arcs

the jiguanshan porphyry mo deposit in the xilamulun metallogenic belt northern margin of the north china craton u pb geochronology isotope systematics geochemistry and fluid inclusion studies implications for a genetic model abstract the jiguanshan porphyry mo deposit is located in the southern part of xilamulun metallogenic belt at the northern margin of the north china craton ncc in the jiguanshan mining district two stages of granitoids intrusions have been recognized a pre ore granite porphyry with stockworks and veins of mo mineralization and a granite porphyry with disseminated mo mineralization zircon u pb data and hf isotope analyses show that the dissemination mineralized granite porphyry yielded a weighted mean 206pb 238u age of 156 0 1 3 ma with a crustal ehf t values from 5 6 to 0 2 and that the main group of magmatic zircons from the pre ore granite porphyry have a weighted mean 206pb 238u age of 167 7 1 7 ma with ehf t values from 3 2 to 1 0 combined with groundmass ar ar age data of the granite porphyry and molybdenite re os age it is suggested that the mo mineralization of jiguanshan deposit was formed in the late jurassic 153 155 ma during tectonic and magmatic events that affected northeast china the mo mineralization was a little bit later than the host granite porphyry besides disseminated in the host granite porphyry mo mineralization also presents in middle jurassic pre ore granite porphyry jurassic fine grained diabase triassic quartz porphyry and in rhyolitic volcanic rocks as well as syenite of devonian age the jiguanshan mining district was affected by the tectonic events associated with the paleo asian ocean closure and later by far field tectonism related to subduction of the paleo pacific plate izanagi in the jurassic cretaceous the tectonic and thermal events linked with the latter are commonly referred to as yanshanian tectono thermal event and consists of a series of geodynamic magmatic and ore forming processes which in the mining district area included the intrusion of the pre ore granite porphyry the host granite porphyry mo mineralization and fine grained diabase major and trace element analyses show that the host granite porphyry is characterized by high silica abundances sio2 77 16 to 77 51 high rb sr ratios 13 57 to 14 83 high oxidation fe2o3 feo 34 25 to 62 00 and high alkalies na2o k2o 8 21 to 8 38 petrographic and microthermometry studies of the fluid inclusions from mo mineralized veins characterized by plenty of daughter mineral bearing inclusions showed that the predominant homogenization temperatures range from 250 to 440 c combined with laser raman analysis of the fluid inclusions it is indicated that mo mineralization is related to a high temperature hypersaline and high oxygen fugacity h2o nacl fluid system with high f contents based on geology geochronology isotope systematics geochemistry and fluid inclusion studies as well as regional geology we propose for the first time a genetic model for the jiguanshan porphyry mo deposit during the jurassic geodynamic evolution of northeast china high silicic high oxidized and alkaline rich granitic magma probably derived from partial melting of the lower crust episodically intruded along faults into the country rocks this fluid system fractionating from the highly differentiated granitic magma and bearing mo with minor cu metals migrated upwards and interacted with the older wall rocks and associated fractures in which the ore minerals precipitated resulting in the development of what we refer to as the jiguanshan type porphyry mo deposit

genesis of the 1 76 ga zhaiwa mo cu and its link with the xiong er volcanics in the north china craton implications for accretionary growth along the margin of the columbia supercontinent abstract the east qinling molybdenum belt hosting numerous mesozoic magmatic hydrothermal mo deposits is one of the largest molybdenum provinces in the world the recently discovered zhaiwa mo cu deposit luoning county henan province occurs within the xiong er terrane of the east qinling orogenic belt the mo cu mineralization is associated with widespread stockworks or veinlets occurring within altered amphibolite here we investigate the characteristics of the ore mineralization through systematic fluid inclusion petrography microthermometry and laser raman spectroscopy the typical inclusions in the veins and stockworks are aqueous daughter mineral bearing and a subordinate co2 rich type the homogenization temperatures of the aqueous inclusions in quartz molybdenite veins are up to 370 c which together with some daughter mineral bearing inclusions homogenized by dissolution of halite at 500 c indicates that the ore forming fluids were derived from a hypothermal fluid system the daughter mineral bearing inclusions assign high salinities for the ore forming fluids correlating the ore deposit to a magmatic hydrothermal system we also present h o isotope systematics which support this interpretation the recently reported re os molybdenite age of 1 76 0 03 ga from this deposit is coeval to the xiong er group andesite dominated volcanic sequence 1 8 1 45 ga based on which we propose that the zhaiwa deposit represents the upper domain of a porphyry system developed within a subduction related setting with accretion to the southern margin of the north china craton our study provides new constraints on the outgrowth of the columbia supercontinent during paleoproterozoic

geochronology and geochemistry of middle permian middle triassic intrusive rocks from central eastern jilin province ne china constraints on the tectonic evolution of the eastern segment of the paleo asian ocean abstract to constrain the permian early mesozoic tectonic evolution of the eastern segment of the paleo asian ocean we conducted zircon u pb dating and whole rock geochemical analyses on six middle permian middle triassic intrusive plutons in central eastern jilin province ne china zircons from the six plutons display distinct oscillatory zoning and striped absorption in cathodoluminescence cl images and th u ratios of 0 11 1 41 indicating a magmatic origin zircon u pb dating indicates that the intrusive rocks formed in the middle permian ca 260 ma to middle triassic ca 245 ma in central eastern jilin province the middle permian and middle triassic plutons are composed mainly of strongly deformed monzogranites with affinities to adakitic rocks which are formed from partial melting of thickened mafic lower crust in contrast the late permian the early triassic plutons in central eastern jilin province consist of a bimodal association including gabbros and granitoids and deformed monzonites which typically form in extensional settings these observations along with the results of previous studies on early middle permian granitoids in western jilin province indicate that the eastern segment of the paleo asian ocean underwent the initial closure in central western jilin province during the middle permian and the final closure in eastern jilin province in the middle triassic

geochemical signature of the granitoids in the chalukou giant porphyry mo deposit in the heilongjiang province ne china abstract the chalukou porphyry mo deposit located in the northern great xing an range is the largest mo deposit in the xing an mongolia orogenic belt its ore bodies are mainly hosted in the intermediate felsic complex and jurassic volcanic sedimentary rocks of which late jurassic granite porphyry quartz porphyry and fine grained granite are closely associated with mo mineralization the middle jurassic monzogranite belongs to shoshonite series with sio2 and al2o3 contents of 69 48 to 74 98 and 12 35 to 14 48 respectively the total alkali k2o na2o content ranges from 7 67 to 10 42 with k2o na2o ratios between 1 07 and 2 81 these rocks are strongly enriched in rb and k but are depleted in ta nb p and ti with negative eu anomalies and positive ehf t the late jurassic granite porphyry quartz porphyry and fine grained granite are shoshonite or high k calc alkaline series their sio2 and al2o3 contents range from 73 87 to 78 95 and 10 35 to 13 47 respectively the total alkali k2o na2o contents range from 8 06 to 10 02 with k2o na2o ratios from 1 03 to 8 20 these rocks are strongly enriched in rb k and th but are depleted in p ti ba and sr indicating clear negative eu anomalies and positive ehf t the middle late jurassic granitoids in the chalukou deposit are highly fractionated i type granitoids and derived from juvenile lower crust materials that originated from the neoproterozoic depleted mantle these granitoids formed in the extension tectonic setting of the post collision stage of the mongol okhotsk orogenic belt probably superposed by the back arc extension related to the subduction of the paleo pacific plate

re os isotopic dating of molybdenites in the xiaoliugou w mo deposit in the northern qilian mountains and its geological significance abstract the xiaoliugou is a large scale w mo deposit newly explored in the northern qilian mountains caledonian fold belt northwestern china it is a vein and skarn type deposit genetically associated with the xiaoliugou caledonian granodiorite stock re os isotopic dating for the molybdenite in the deposit yields an isochron age of 462 13 ma 2 and model ages of 436 to 496 ma these results suggest that w mo mineralization occurred before the collision of plates and mineralized substances mainly originated from the crust

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

geodynamic setting of gold deposits in eastern and central trans baikal chita region russia abstract it is proposed that there are three types of gold deposits in eastern and central transbaikalia trans baikal province namely i high sulphide intrusion related deposits with some signs of porphyry deposits ii low sulphide intrusion related deposits and iii low sulphide epithermal au ag deposits most of the gold deposits belong to the first two types and their ages are middle late jurassic deposits of the third type are not numerous and their age is early cretaceous the majority of the gold mineralization is spatially related to the two branches of the mongolia okhotsk suture along which siberia collided at the early middle jurassic boundary with the mongolia north china continent and the onon island arc terrane located between the two continents collision related thrusting folding and magmatism lasted until the latest jurassic when they gave way to post collisional rifting that continued until the end of early cretaceous according to their age relation to magmatism and tectonic framework the intrusion related deposits high and low sulphide were formed in a regional collisional setting extensional environments at that time existed only in local areas in the roofs of great magmatic chambers low sulphide epithermal deposits were formed during early cretaceous post collisional rifting

geology and geochronology of the xilamulun molybdenum metallogenic belt in eastern inner mongolia china the xilamulun molybdenum metallogenic belt located in eastern inner mongolia china has great economic potential as a major producer of molybdenum four major types of mo deposits have been recognized in the xilamulun molybdenum metallogenic belt porphyry quartz vein volcanic hosted and greisen these mesozoic mo deposits are closely related to si and k rich intrusives and are usually hosted by granite plutons or located at the endo or exo contact zones of the granite porphyry shrimp zircon u pb dating gives the emplacement ages of the intrusions related to mo mineralization as 245 1 4 4 152 4 1 6 and 139 1 2 3 ma re os analysis of five molybdenite samples from the chehugou porphyry mo deposit yields an isochron age of 245 5 ma 2 indicating that the mineralization age of the porphyry mo deposit is about 245 ma re os analyses of six molybdenite samples from the nianzigou quartz vein type mo deposit yield an isochron age of 154 3 3 6 ma 2 constraining the mineralization age of the quartz vein mo deposit to 154 ma our results suggest that the mo mineralization in the xilamulun belt formed during at least three stages i e the triassic late jurassic and early cretaceous and is coeval with the granitic magmatism the corresponding geodynamic background covers the syncollision between the north china and siberian plates during the early to middle triassic a compression setting related to the subduction of the paleo pacific plate during the jurassic and lithospheric thinning during the early cretaceous in eastern china

geodynamic settings and tectonic model of skarn gold deposits in china an overview seventy skarn type gold deposits including 1 super large 19 large and 24 medium sized are known from different geotectonic units of china they contain a total resource of approximately 1000 t of gold 625 t in south china and account for 20 of china s gold reserves these skarn deposits are sited in collisional orogenic belts fault controlled magmatic belts and reactivated cratonic margins all of the chinese skarn gold provinces were affected by phanerozoic collisional orogenesis the timing of the metallogenic events and the spatial temporal distribution of the chinese skarn gold deposits indicates that they were formed during ore forming processes linked to the transition from shortening to extension in the geodynamic evolution of a collision orogen and not to subduction systems as is commonly advocated for porphyry copper systems around the pacific rim

mesozoic molybdenum deposits in the east qinling dabie orogenic belt characteristics and tectonic settings abstract the east qinling dabie orogenic belt accommodates the largest mo ore district in the world it contains 8 43 mt of proven mo metal reserves which accounts for 66 of the total proven chinese mo reserves the mo ore district includes 24 deposits and 12 occurrences with four major types of mo mineral systems i e porphyry porphyry skarn skarn and hydrothermal veins the latter can be further subdivided into quartz vein and carbonatite vein types although mo mineralization in the belt began in the paleoproterozoic 1680 24 to 2044 14 ma all economically significant deposits were formed during the mesozoic re os dating of molybdenite has shown that there are three episodes of mo mineralization i e late triassic 233 221 ma late jurassic to early cretaceous 148 138 ma and early to middle cretaceous 131 112 ma late triassic mo deposits developed as molybdenite quartz veins and carbonatite vein types stable isotope systematics c o s and high contents of re and sr indicate that the carbonatite mo veins are mantle derived porphyry and porphyry skarn mo mineral deposits were formed in the late jurassic to early cretaceous and early to middle cretaceous the late jurassic to early cretaceous granite porphyries that are associated with the mo deposits usually occupy less than 1 5 km2 at the surface and are situated in the east qinling area far west of china s continental margin on the other hand the early to middle cretaceous batholiths and granite porphyries with associated mo deposits are located in the dabieshan area and eastern part of the east qinling area the late jurassic to early creataceous granitoids and related mo deposits possibly formed in a back arc extensional setting of the eurasian continental margin which was probably triggered by the oblique subduction of the izanagi plate the early to middle cretaceous batholiths and granite porphyries are linked to the tectonic regime of lithospheric thinning asthenospheric upwelling and partial melting of the crust induced by a change in izanagi plate motion parallel to the continent margin in the east qinling dabie belt there are vein type pb zn ag deposits surrounding porphyry and or porphyry skarn mo w deposits forming well defined ore clusters the same spatial arrangement i e porphyry mo stockworks and outlying pb zn ag ore veins is also observed at the deposit scale thus mo porphyry stockworks and distal polymetallic veins belong to the same ore system and may reflect an outward temperature decrease from the highly fractionated granite plutons both porphyry stockworks and polymetallic veins can be used as vectors for further prospecting

geochronology and geochemistry of the wunugetushan porphyry cu mo deposit in ne china and their geological significance abstract the wunugetushan porphyry cu mo deposit is located in the manzhouli district of ne china on the southern margin of the mesozoic mongol okhotsk orogenic belt concentric rings of hydrothermal alteration and cu mo mineralization surround an early middle jurassic monzogranitic porphyry the cu mo mineralization is clearly related to the quartz potassic and quartz sericite alteration molybdenite re os and groundmass 40 ar 39 ar of the host porphyry dates indicate that the ore formation and porphyry emplacement occurred at 177 6 4 5 ma and 179 0 1 9 ma respectively geochemically the host porphyry of the deposit is characterized by strong lree hree fractionation enrichment in lile ba rb u th and pb and depletion of hfse nb ta ti and hree the sr nd pb isotopic compositions of the porphyry display an varied initial 87 sr 86 sr i ratio a positive e nd t values and high 206 pb 204 pb t 207 pb 204 pb t and 208 pb 204 pb t ratios these data indicate that the magmatic source of the host porphyry comprised two end members lithospheric mantle metasomatized by fluids derived from the subducted slab and continental crust we infer that the primitive magma of the host porphyry was derived from crust mantle transition zone based on regional geology and geochemistry of the host porphyry the wunugetushan deposit is suggested to form in a continental collision environment after closure of the mongol okhotsk ocean

the mo deposits of northeast china a powerful indicator of tectonic settings and associated evolutionary trends abstract northeast ne china lies in the eastern sector of the central asian orogenic belt caob that connects with the circum pacific orogenic belt in the east and accommodates multistage magmatism crustal growth and mineralization in this region 69 mo only or mo dominated and 9 cu mo deposits have been discovered including 65 deposits ranking medium size 10 kt mo metal or larger in tonnage and containing a total resource of 10 5 mt mo metal six giant and seventeen large deposits have total reserves of 6 7 and 3 1 mt mo respectively these deposits occur in the areas surrounding the songliao basin including the northern margin of the north china craton the great hingan range and the ji hei fold belt and have been formed during paleozoic and mesozoic tectono magmatic events all the mo only or mo dominated deposits were formed in the mesozoic postdating the closure of the paleo asia ocean and in a series of pulses around 250 200 ma 200 160 ma 160 130 and

re os ages for molybdenum mineralization in the fengning region of northern hebei province china new constraints on the timing of mineralization and geodynamic setting abstract a recently recognized molybdenum mo metallogenic belt is present within and adjacent to the northern part of the north china craton ncc more than 20 mo deposits are present in the belt including the sadaigoumen and dacaoping porphyry deposits located in the fengning region of the northern part of hebei province the sadaigoumen deposit has a re os molybdenite weighted mean age of 236 5 2 2 ma mswd 1 4 n 6 which is more reliable than existing dates and is interpreted as the precise age for formation of the deposit the dacaoping mo deposit is about 100 million years younger with a re os molybdenite isochron age of 140 1 3 4 ma 2 mswd 0 26 n 5 which is within error of the weighted mean age of 139 4 0 9 ma the ages of the two deposits show that there are at least two episodes of mo porphyry formation in the fengning region in combination with the regional geological evolution of this part of the craton margin we propose that the triassic mo event at sadaigoumen is associated with a collisional event during the closure of the ancient asian ocean whereas the early cretaceous mo event at dacaoping is associated with lithospheric thinning of the ncc

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