major types and time space distribution of mesozoic ore deposits in south china and their geodynamic settings the ore deposits of the mesozoic age in south china can be divided into three groups each with different metal associations and spatial distributions and each related to major magmatic events the first event occurred in the late triassic 230 210 ma the second in the mid late jurassic 170 150 ma and the third in the early mid cretaceous 120 80 ma the late triassic magmatic event and associated mineralization is characterized by peraluminous granite related w sn nb ta mineral deposits the triassic ore deposits are considerably disturbed or overprinted by the later jurassic and cretaceous tectono thermal episodes the mid late jurassic magmatic and mineralization events consist of 170 160 ma porphyry skarn cu and pb zn ag vein deposits associated with i type granites and 160 150 ma metaluminous granite related polymetallic w sn deposits the late jurassic metaluminous granite related w sn deposits occur in a ne trending cluster in the interior of south china such as in the nanling area in the early mid cretaceous from about 120 to 80 ma but peaking at 100 90 ma subvolcanic related fe deposits developed and i type calc alkaline granitic intrusions formed porphyry cu mo and porphyry epithermal cu au ag mineral systems whereas s type peraluminous and or metaluminous granitic intrusions formed polymetallic sn deposits these cretaceous mineral deposits cluster in distinct areas and are controlled by pull apart basins along the south china continental margin based on mineral assemblage age and space time distribution of these mineral systems integrated with regional geological data and field observations we suggest that the three magmatic mineralization episodes are the result of distinct geodynamic regimes the triassic peraluminous granites and associated w sn nb ta mineralization formed during post collisional processes involving the south china block the north china craton and the indo china block mostly along the dabie sulu and songma sutures jurassic events were initially related to the shallow oblique subduction of the izanagi plate beneath the eurasian continent at about 175 ma but i type granitoids with porphyry cu and vein type pb zn ag deposits only began to form as a result of the breakup of the subducted plate at 170 160 ma along the nne trending qinzhou hangzhou belt also referred to as qin hang or shi hang belt which is the neoproterozoic suture that amalgamates the yangtze craton and cathaysia block a large subduction slab window is assumed to have formed in the nanling and adjacent areas in the interior of south china triggering the uprise of asthenospheric mantle into the upper crust and leading to the emplacement of metaluminous granitic magma and associated polymetallic w sn mineralization a relatively tectonically quiet period followed between 150 and 135 ma in south china from 135 ma onward the angle of convergence of the izanagi plate changed from oblique to parallel to the coastline resulting in continental extensional tectonics and reactivation of regional scale ne trending faults such as the tan lu fault this widespread extension also promoted the development of ne trending pull apart basins and metamorphic core complexes accompanied by volcanism and the formation of epithermal cu au deposits granite related polymetallic sn w deposits and hydrothermal u deposits between 120 and 80 ma with a peak activity at 100 90 ma

textural control on gold distribution in as free pyrite from the dongping huangtuliang and hougou gold deposits north china craton hebei province china article i nfo pyrite from the dongping huangtuliang and hougou gold deposits hebei province china was investigated using a combination of ore microscopy including back scattered imaging and in situ laser ablation inductively coupled plasma mass spectroscopy la icp ms a range of elements including au te ag pb bi cu co ni and as was analyzed with the aim to constrain the textural controls and influence of superimposed deformation on the distribution of invisible gold in as free pyrite thedatasetshowsexcellentcorrespondence betweenmeasuredhighgoldvaluesandthreekeytexturalcriteria i areasofclusteredtellurideinclusions especiallyindongping ii microshearingandfracturing brecciation dongping and huangtuliang and iii pyrite recrystallization huangtuliang invisible gold is only at trace levels in the hougou and gold bearing telluride minerals are not observed this is considered to result from larger scale remobilization of gold during advanced brecciation and recrystallization of pyrite pyrite grains containing clustered inclusions have by far the highest gold concentrations up to 1 wt with consistent values of thousands of ppm au interpretation of textures and la icp ms data infers that in these areas the distribution of telluride inclusions extends pervasively from micron to nanoscale i e as fields of nanoparticles local employment of coupled dissolution reprecipitation reaction between pyrite and fluids driving the k metasomatic alteration dated at 150 ma is invoked to explain such patterns syn deformational grain scale mobilization of gold and other elements took place leading to a portion of the gold being recrystallized within fractures and microshears the deformational event leads to gold enrichment in the huangtuliang pyrite where brittle fracturing brecciation has been followed by a resorption and recrystallization in the latter case foam textured pyrites again without as can contain up to hundreds of ppm gold theinterpreted sequenceof pyritepost depositional eventsis inaccordancewith the protracted magmaticevolution of the area starting with variscan alkaline intrusions 390 ma and reactivated during the yanshanian orogeny 150 ma thestudyshows i thatas freepyritecanreadilycontainsignificantamountsofinvisiblegold bothasnanoparticles

40 ar 39 ar isotopic dating of tin mineralization in furong deposit of hunan province and its geological significance the newly discovered furong ore deposit located in the southern part of the qitianling pluton emplaced at 151 162 ma in southern hunan is a superlarge tin deposit it consists of bailashui anyuan taoxiwo sanmenkou and maziping heishanli ore districts and its ore veins occur in qitianling pluton and the inner or outer contact zone between the granite pluton and the late palaeozoic sedimentary rocks in this study ar ar isotope dating of muscovite hornblende and phlogopite was carried out in order to constrain the tin mineralization timing of the furong deposit the plateau ages of three phlogopite samples from the bailashui ore district are 150 6 1 0 ma 157 3 1 0 ma and 154 7 1 1 ma respectively and the plateau age of hydrothermal hornblende from the same mining district is 156 9 1 1 ma the plateau ages of two muscovite samples from the taoxiwo ore district are 159 9 0 5 ma and 154 8 0 6 ma respectively these age data are coincident with the intrusion time of the qitianling granite 151 162 ma and also in accordance with the ages of other nonferrous metal deposits such as the shizhuyuan w sn mo bi f deposit the xintianling w deposit the yaogangxian w deposit and the huangshaping pb zn polymetallic deposit in this area the large scale mineralization in southern hunan is probably ascribed to the mesozoic lithospheric extension in south china

a new distinct mechanism of river bank erosion in a forested catchment abstract it has been thought that the two main processes responsible for river bank retreat are the removal of particles or layers of material by flow erosion or sloughing and collapse by slumping a third process involving the development of a subsurface cavity after washout of gravels which is succeeded by slow subsidence of a segment of the former channel bank has been identified at a site in the new forest southern england the process was monitored over a 9 month period and was observed to be assisted by the hydrological effects of a dam of coarse woody debris across the channel as these dams occur frequently the process is likely to have occurred elsewhere along channels in forested areas

progressive 18o depletion during co2 separation from a carbon dioxide rich hydrothermal fluid evidence from the grey river tungsten deposit newfoundland oxygen isotope data for the grey river tungsten prospect newfoundland canada indicate a progressive depletion in 18ofluid during mineralization early veins with pegmatitic affinities were deposited at 470 c and pressures greater than 1 kbar 100 mpa from a fluid with a 18o composition of 7 4 presumed to be of magmatic origin successive vein deposition at progressively lower temperatures and pressures culminated in the precipitation of wolframite bearing veins at a temperature of 300 c and pressures of 150 320 bar 15 32 mpa from a low salinity fluid with a 18o composition in the range 3 2 1 6 low values of 18o and dfluid are recorded in many vein tungsten deposits and are normally interpreted as reflecting mixing of isotopically light meteoric fluids or formation brines with magmatic fluids however fluid inclusion evidence for the grey river mineralization indicates that a 40 mol co2 loss occurred by immiscibility and retrograde boiling of the hydrothermal fluid between 420 and 3

double vein ore bearing vs ore free structures in the xitian ore field south china implications for fluid evolution and mineral exploration abstract two types of spatially and temporally associated hydrothermal veins ore bearing and ore free occur as double vein structures in the xitian ore field south china here we investigated the genetic relationship material provenance fluid properties and prospecting significance of the co developed veins in the granite related fault controlled vein type xiangdong w goudanlan w chaling pb zn and xinggao fluorite deposits of the xitian ore field focusing on two common minerals quartz and zircon petrographic cl microthermometric and h o isotopic analyses of stage i and stage ii quartz in both the ore bearing and ore free veins of these deposits document two episodes of hydrothermal activity the first episode involved a high temperature up to 370 high salinity up to 28 nacl equiv high 18o 2 1 to 7 2 and high 2h 82 to 54 mean 68 n 13 fluid that corresponds to the main magmatic hydrothermal stage of the deposits and the second episode involved a low temperature down to 90 low salinity down to 1 nacl equiv low 18o 8 8 to 5 3 and low 2h 83 to 60 mean 73 n 6 fluid that represents an accessary mineralization stage variations in fluid inclusion types and compositions indicate that the processes of fluid mixing boiling cooling and degassing played important roles in mineralization and that magmatic fluid became less important than meteoric water along during the formation of ore free veins la icpms u pb dating reveals totally different age populations for these veins zircons from the ore bearing quartz veins yield older and more variable ages pre devonian 400 ma n 68 that are similar to that of the local basement sedimentary rocks whereas zircons from the ore free quartz veins yield younger and less variable ages triassic 250 200 ma n 31 and jurassic 170 140 ma n 13 that are identical to those of the host granite zircons in addition the ore free veins show lower temperatures salinities and total rees as recorded by quartz but greater alteration as reflected by cl and trace element features of hydrothermally altered zircons and wider vein size than the ore bearing veins we propose a mineral water separation model to explain the formation of the double vein structures in this model ore bearing veins and ore free veins formed in succession during faulting events ore bearing veins formed first in the smaller fractures and were the dominant sites of mineralization whereas the ore free veins served as dissipating passageways for residual water and silica in larger fractures we suggest that the mineral water separation model has good application prospects in mineral exploration and that zircons can be applied as an indicative mineral to differentiate the mineralization potential of different types of quartz veins

characterization of organic matter in late cretaceous black shales of the eastern alps kainach gosau group austria abstract bituminous marls occur at the base of the late cretaceous kainach gosau basin eastern alps they interfinger with local coaly layers and are overlain by a turbiditic sequence forty outcrop samples with different lithologies were studied by rock eval pyrolysis seven bituminous marls one coaly sample two siltstones from the turbiditic sequence and solid bitumen from the paleozoic basement have been characterized in detail by organic geochemical and petrographic techniques the organic matter from bituminous marls can be subdivided into allochthonous terrigenous material mainly recycled vitrinite which is present in all samples in similar amounts and autochthonous hydrogen rich organic matter alginite liptodetrinite which is most probably of lacustrine origin organic richness varies from 0 4 to 2 3 toc the amount of the autochthonous organic matter is controlled primarily by different oxygen concentrations sedimentological lack of bioturbation and geochemical data e g pristane phytane ratios homohopane indices c 30 c 29 ts ratios distribution of phenol and alkylphenols in the pyrolyzate suggest that the water column above the sediment surface was suboxic to dysoxic but probably not anoxic high energy events were responsible for short periods with enriched oxygen in the water column the organic matter in the resulting sediments is of a residual type drift wood was transported from the nearby shore into the lake paleontological evidence proves a temporary marine influence vitrinite reflectance and tmax indicate maturation levels ranging from the beginning to the peak stage of oil generation despite the fact that some hydrocarbons have already been generated hi values of kerogens of bituminous marls reach 605 mg hc g toc most analysed bituminous marls produce a high wax paraffinic oil during maturation and are good sources for oil pyrolysis gas chromatography and biomarker data indicate that changing wax contents of oils generated from bituminous marls might be a function of different oxygen concentrations in the water column coaly samples have a very good gas potential

stockwork tungsten scheelite molybdenum mineralization lake george southwestern new brunswick scheelite molybdenite stockwork mineralization constitutes one component of the lake george polymetallic sb w mo au base metal deposit a complex hydrothermal center of late silurian ca 412 m y age in the fredericton trough of the northern appalachians the stockwork hosted by silurian graywackes in part calcareous is spatially and temporally related to a postkinematic cupola of biotite monzogranite and its formation overlapped in time with the emplacement of monzogranitic porphyry dikes mineralogical and textural evidence indicates that contact metamorphism associated with the cupola had ceased before the initiation of w mo mineralization and that it occurred at pressures of less than 1 75 kb in two stages a peak stage t 600 degrees c evident only in rocks of pelitic composition and a lower temperature reequilibration t 500 degrees c recorded in rocks of both pelitic and marly compositions the w mo deposit comprises three different scheelite and or molybdenite bearing veinlet types type 1 bodies the earliest formed are calc silicate granditic garnet wollastonite clinopyroxene and calcic amphibole quartz veinlets with ubiquitous ca and h metasomatic alteration envelopes mineralogical and fluid inclusion relationships indicate that the fluids ranged in temperature from 550 degrees to 228 degrees c and that temperature decreased away from the cupola the succeeding type 2 veinlets comprise quartz and lesser amounts of perthitic alkali feldspar muscovite calcite scheelite molybdenite and pyrite fluid inclusion evidence shows that mineralization dominantly occurred from 400 degrees to 175 degrees c under a confining pressure of 1 3 kb higher grade scheelite and molybdenite deposition was focused in a lower temperature zone to the north of the cupola in which co 2 effervescence occurred type 3 veinlets the last to form consist of prehnite molybdenite and quartz and represent a volumetrically minor mineralization type in both type 1 and 2 systems scheelite and molybdenite deposition appears to have been controlled by decreasing temperature and increasing ph temperature was a function of distance from the cupola for both veinlet types but the controls on ph were specific to each thus the ph of type 1 fluids was controlled by wall rock interaction h metasomatism whereas that of type 2 fluids was controlled by co 2 effervescence the economic stibnite quartz veins scratch et al 1984 occupy fractures which transect and therefore postdate all stages of w mo mineralization

fluid inclusion study of the ballinglen w sn sulphide mineralization se ireland scheelite mineralized microtonalite sheets occur on the se margin of the end caledonian leinster granite in se ireland scheelite polymetallic sulphides and minor cassiterite occur in veins in the microtonalites disseminated throughout the greisened microtonalite sheets and in the adjacent wallrocks two major mineralized vein types occur in the microtonalite sheets 1 scheelite arsenopyrite pyrrhotite occur in quartz fluorite veins generally without a muscovite selvage 2 sphalerite chalcopyrite pyrite galena cassiterite stannite occur in quartz fluorite veins with a coarse muscovite selvage and are often intergrown with the muscovite quartz hosted fluid inclusions were examined from representative samples of both vein types using petrographic microthermometric and laser raman spectroscopic techniques three distinct types of fluid inclusions have been recognized primary vapour rich type 1 inclusions in quartz from the scheelite mineralized veins are of h2o co2 ch4 n2 h2s nacl composition and formed between 360 530 c primary and secondary liquid rich type 2 fluid inclusions in the base metal sulphide mineralized veins are of h2o ch4 n2 h2s nacl composition and formed between 340 480 c they also occur as pseudosecondary and secondary inclusions in scheelite mineralized veins late dilute low temperature h2o nacl kcl fluid inclusions may be related to late caledonian convection of meteoric waters around the cooling leinster granite batholith

in situ la icp ms trace element analyses of scheelite and wolframite constraints on the genesis of veinlet disseminated and vein type tungsten deposits south china abstract veinlet disseminated and vein type tungsten deposits are important tungsten resources in south china and show remarkable diversity in dominant tungsten minerals to better understand their genesis scheelite from the shimensi veinlet disseminated deposit and wolframite from the xihuashan and piaotang vein type deposits were selected to conduct in situ laser ablation inductively coupled plasma mass spectrometry trace element analyses the shimensi tungsten mineralization occurs in intensively altered granitic rocks and is characterized by scheelite two generations of scheelite in a single grain can be identified by cathodoluminescence cl imaging the early scheelite dark domains in cl images is characterized by nearly flat chondrite normalized ree ree n patterns with significantly negative eu anomalies whereas the late one bright domains in cl images shows light rare earth element lree enriched ree n patterns and obviously positive eu anomalies the former has higher ree na nb and ta and lower sr contents than the latter the xihuashan and piaotang wolframite quartz veins are developed in greisenized granite type i and metasedimentary rocks type ii both types of wolframite show lree depleted patterns but type i exhibits strongly negative eu anomalies and type ii positive eu anomalies type i contains higher ree nb and ta concentrations and lower feo mno ratios than type ii variations of eu anomalies and trace element compositions in both scheelite and wolframite can be used to decipher the origin and processes of tungsten mineralization both the early scheelite and wolframite type i display significantly negative eu anomalies and have high ree nb and ta contents suggesting that the initial ore forming fluids were of magmatic origin precipitation of tungsten minerals and alteration would effectively modify the composition of ore forming fluids deposition of the early tungsten minerals would lower ree nb and ta in the mineralizing fluids leading to depletion of these elements in the late ones although both the type i and ii wolframite have different ree contents and eu anomalies they show similar left dipped ree n patterns implying that compositional variation of fluids is likely driven by crystallization of wolframite during the processes of fluid evolution in contrast the elevated lree hree heavy rare earth element ratios eu eu n eu n values and sr abundances in the late scheelite are possibly caused by the decomposition of plagioclase and k feldspar alteration plays an important role in the formation of veinlet disseminated scheelite deposits it can be concluded that vein type wolframite mineralization is mainly formed by filling and that veinlet disseminated scheelite mineralization is associated with metasomatism

re os isotopic chronology of molybdenites in huangshaping lead zinc deposit southeast hunan and its geological implications the huangshaping lead zinc polymetallic deposit in southeast hunan is genetically related to the intrusion of huangshaping granitic rocks and occur in the contact zone between the granodioritic porphyry and the limestone of lower carboniferous shidengzi formation as well as in the neighboring bedding plane fault zone previously the metallogenic epoch of the deposit was indirectly deduced by the ages of such nearby granitic rocks as granite porphyry and quartz porphyry or altered minerals based on the re os isochron method of molybdenites this paper measured directly the ore forming age from skarn ore in the huangshaping deposit and got a re os age of 153 8 4 8 ma which is in accordance with the previous k ar age of 153 157 ma obtained from phlogopite in the ore bearing skarn of the deposit combined with related rare earth element and trace element geochemistry of huangshaping granites and ore bearing skarn it is concluded in this paper that the age of 154 ma should represent the metallogenic epoch of the deposit and that there existed a close relationship between the ore forming process of the deposit and the granite porphyry which were both formed during the peak stage of early yanshanian large scale rock forming and ore forming activities in south china

roles of carbonate co2 in the formation of quartz vein wolframite deposits insight from the crystallization experiments of huebnerite in alkali carbonate aqueous solutions in a hydrothermal diamond anvil cell abstract quartz vein type wolframite deposits are a primary type of tungsten deposits traditionally f and cl were considered as important agents in tungsten transportation during ore formation process however ore forming fluids enriched in co2 were commonly observed in natural fluid inclusions associated with quartz vein type wolframite deposits indicating that carbonate or co2 could be important for their formation in this paper we report experiments of the dissolution and crystallization of huebnerite in the mnwo4 li2co3 or na2co3 h2o system using a hydrothermal diamond anvil cell hdac the results showed that mnwo4 dissolved in alkali carbonate aqueous solutions and in some cases in associated carbonate melts during heating and subsequently huebnerite crystallized into needle and column shaped crystals during cooling in situ raman spectra obtained during heating of the experimental charge in the sample chamber of the hdac showed that wo42 was the only tungsten bearing ion detected in the carbonate melt or aqueous solution the dissolution of mnwo4 mainly attributed to the alkaline environment in the alkali carbonate aqueous solution furthermore the weak alkali condition in the carbonate solutions enhanced the crystallization of huebnerite when the temperature and pressure were decreased the experimental results indicate that although the crystallization temperature pressure conditions of huebnerite vary in a wide range conditions lower than approximately 200 mpa and 450 c are not favorable for huebnerite crystallization our experimental results also suggest that the alkali carbonate aqueous solution could serve as a medium for the transport of tungsten in the ore forming process

isotopic geochemistry zircon u pb ages and hf isotopes of a type granites from the xitian w sn deposit se china constraints on petrogenesis and tectonic significance abstract zircon u pb geochronological geochemical and petrological analyses have been carried out on the xitian granite emplaced in the middle part of shi hang zone which is closely related to the economically important xitian tungsten tin deposit in hunan province southeast china la icp ms zircon u pb dating of two representative samples yielded weighted means 206 pb 238 u age of 151 7 1 2 ma and 151 8 1 4 ma these granites are comprised mainly of k feldspar quartz plagioclase fe rich biotite and minor fluorite and are characterized by enrichments in rb th rees total ree 159 351 ppm and hfses e g zr and y but depletions in ba sr p eu and ti they are metaluminous to weakly peraluminous and show a clear a type granite geochemical signature with high sio 2 73 44 78 45 wt total alkalis na 2 o k 2 o 2 89 8 98 wt fe 2 o 3 mgo ratios and low p 2 o 5 cao mgo and tio 2 contents in situ zircon hf isotope analysis suggests their e hf t values ranging from 7 43 to 14 69 sr nd isotope data show their e nd t values in the range of 9 2 to 7 3 with corresponding t dm2 ages of 1 72 1 56 ga these characteristics indicate that the xitian granite originated from partial melting of metamorphic basement rocks with a certain amount of mantle derived materials combined with previous geochemical and isotopic data it is derived that mantle crust interaction was gradually enhanced from the early to late stages of magmatism the ore forming materials and fluids of the xitian w sn deposit are mainly produced by the early yanshanian granitic magmatism which is also responsible for the late jurassic ca 152 ma a type granitic rocks that host the w sn polymetallic deposits distributed along the shi hang zone implying a significant mesozoic extensional event in southeast china likely caused by the subduction of the paleo pacific plate

regional and local variations in the composition of the wolframite series from sw japan and possible factors controlling compositional variations the regional and local variations in the composition of the wolframite series associated with the ilmeniteseries and magnetite series granitoids in the inner zone of sw japan were investigated using x ray diffraction and microprobe analyses it is concluded that the variation in mn fe ratios in the source materials granitic magmas in most cases is the dominant factor controlling the regional variation in the wolframite compositions while as exemplified by the kaneuchi mine kyoto prefecture the wallrock chemistry and ph of ore fluids are responsible for the local variation within a single vein system within a fresh euhedral crystal from the mine only slight compositional variation of less than 3 mole mnwo4 is found in the form of oscillatory zoning this study combined with the fluid inclusion research indicates that the wolframite compositions mn fe ratios cannot be used as a geothermometer

geological characteristics and re_os dating of molybdenites in hehuaping tin polymetallic deposit southern hunan province the hehuaping tin polymetallic deposit a large tin ore field newly discovered in southern hunan consists of skarn and cassiterite sulfide ores at present the controlled reserves amount to about 110 700 tons of tin 10 000 tons of bismuth 50 000 tons of lead and 10 000 tons of zinc with the advance of the exploration work four ore bodies have been explored which are located in the southeast portion of wangxianling indosinian gra nite pluton and hosted in granite granite porphyry and devonian limestone and sandstone respectively re os dating of molybdenites yields model ages between 223 3 2 9 and 225 2 2 7 ma and an isochron age of 224 0 1 9 ma for the skarn ore related to wangxianling granite indicating that w sn mineralization in southern hunan also took place in indosinian period the zircon shrimp u pb dating of the late granite porphyry is 142 3 ma the granite porphyry has been partly mineralized and altered and contains tin ore bodies all this implies that there existed late mineralization of yanshanian period in hehuaping area the early mineralization is supposed to correspond to underplating of the basic magma

geology and genesis of the hehuaping magnesian skarn type cassiterite sulfide deposit hunan province southern china abstract magnesian skarn type tin deposits are relatively rare in the world the hehuaping cassiterite sulfide deposit in southern china having a total reserve of approximately 130 000 t of tin 50 000 t of lead and 10 000 t of zinc is identified as such type the deposit is related to the late jurassic 157 ma hehuaping medium to coarse grained biotite granite that intruded the middle devonian qiziqiao dolomite formation and the tiaomajian sandstone formation four paragenetic stages of skarn and ore formation have been recognized i prograde stage ii retrograde stage iii cassiterite sulfide stage and iv carbonate stage alteration zoning between fresh granite and unaltered country rocks can be identified the skarn are typified by mg mineral assemblages of forsterite spinel diopside tremolite serpentine talc and phlogopite the geochemistry of various skarn minerals shows a gradually decrease of mg end member and correspondingly an increase of fe and especially mn end members along the process of skarn alteration tin mineralization developed during the late retrograde stage resulted in cassiterite magnetite diopside skarn however the deposition of cassiterite occurred predominantly as cassiterite sulfide veins along fractures and interlayer fracture zones during stage iii the petrogeochemistry of hehuaping granite as well as s and pb isotopic analyses suggest that the ore forming elements have a magmatic source originated from the upper crust the h o isotopic and fluid inclusion analyses indicate that high temperature ore forming fluids in early anhydrous skarn stage stage i are also magmatic origin in comparison the retrograde fluids are characterized by relatively low salinity 2 to 10 wt nacl equiv and low temperature 220 to 300 c suggesting a mixed origin of meteoric waters with magmatic fluids the major ore forming stage iii fluids are characterized by lower temperature 170 to 240 c and salinity 1 to 6 wt nacl equiv indicating fluid mixing could be an efficient tin mineralizing mechanism meteoric waters are dominant in stage iv resulting in a further lowering of temperature 130 to 200 c and salinity 0 4 to 1 wt nacl equiv

a precise u pb age on cassiterite from the xianghualing tin polymetallic deposit hunan south china we report the first precise u pb isotope data on cassiterite from the large xianghualing tin polymetallic deposit in the central nanling district south china the results show that four separates from sample xf 51 have a relatively narrow range of 206pb 238u apparent ages varying from 152 to 157 ma and the three 206pb 238u apparent ages yield a weighted average value of 156 4 ma mswd 0 32 separates from two other cassiterite samples do not have sufficient radiogenic pb to generate a reliable 206pb 238u age seven separates from the above three cassiterite samples define a well constrained 238u 206pb isochron corresponding to an age of 157 6 ma mswd 34 a comparison of the u pb cassiterite ages with published ar ar dates on muscovite from this deposit and k ar age data on biotite from the pluton genetically related to the tin mineralization in this area demonstrates that the u pb isotope system of cassiterite is a potential geochronometer combined with the ar ar dates of muscovite from this deposit we can constrain the absolute age of tin polymetallic mineralization in xianghualing at 154 157 ma the dates obtained in this study consistent with the published geochronological results from other important deposits in this region reveal that the large scale tungsten tin mineralization in the central nanling region was predominantly emplaced during 150 161 ma

mesozoic metallogeny in east china and corresponding geodynamic settings an introduction to the special issue abstract the giant east china mesozoic metallogenic province hosts some of the world s largest resources of tungsten tin molybdenum antimony and bismuth ores of gold silver mercury lead zinc copper uranium and iron are also of major importance the province and its constituent metallogenic belts or regions south china middle lower yangtze river valley east qinling dabie interior of north china craton yan liao and north east china are the products of several pulses of igneous activity and mineralisation between 240 and 80 ma each successive stage has produced a distinctive suite of deposits that can be readily related to the geodynamic evolution of the region during the mesozoic this geodynamic evolution is linked to a complex series of tectonic events involving far field subduction plate collisions crustal thickening post collision collapse and rifting

granite pegmatite connection and mineralization age of the giant renli tanb deposit in south china constraints from u th pb geochronology of coltan monazite and zircon abstract the recently discovered renli ta nb deposit in northeastern hunan province is the largest known pegmatite ta nb deposit in south china previous research has shown that biotite monzogranite is locally spatially associated with the pegmatites and could be the parental granite of the nb ta mineralization in this study we determine that muscovite monzogranite also has a close spatial relationship with the nb ta pegmatites we present new u th pb ages for coltan monazite and zircon that constrain the timing of nb ta mineralization and related magmatism laser ablation inductively coupled plasma mass spectrometry la icp ms u pb dating of coltan from the nb ta pegmatite yielded a weighted mean 206pb 238u age of 140 2 2 3 ma zircon grains from the biotite monzogranite and muscovite monzogranite yielded weighted mean 206pb 238u ages of 154 1 2 5 ma and 141 0 2 4 ma respectively and monazite grains from the muscovite monzogranite yielded a weighted mean th pb age of 140 7 2 2 ma rare earth element contents of the coltan suggest that the nb ta mineralization is related to highly evolved granite the muscovite monzogranite shows highly evolved features with higher contents of sio2 and al2o3 and lower contents of fe2o3t k2o tio2 cao mgo and p2o5 than the biotite monzogranite the obtained ages and the close spatial relationship between the pegmatite type mineralization and the muscovite monzogranite together with the major and trace element compositions indicate that the nb ta mineralization is genetically related to the early cretaceous muscovite monzogranite rather than the late jurassic biotite monzogranite muscovite monzogranite that formed during the early cretaceous should be considered a target for nb ta exploration in south china

hydrothermal alteration veining and fluid inclusion characteristics of the kalzas wolframite deposit yukon kalzas is a sheeted vein and stockwork wolframite deposit crosscutting continental margin sedimentary rocks of the proterozoic windermere supergroup in central yukon mineralization is synchronous with cretaceous post tectonic granites of the selwyn plutonic suite parallel sets of planar quartz veins contain coarse euhedral wolframite and are generally oriented perpendicular to southeast plunging fold axes widespread alteration of the host rocks and intense stockwork veining surround the veins alteration and mineralization show a distinct concentric zonation across a 2 5 km long southeast trending oval the core zone is characterized by orthoclase contained within quartz tourmaline wolframite veins minor phases include apatite molybdenite bismuthinite pyrite chalcopyrite and pyrrhotite host rocks are prevasively tourmalinized and sericitized hydrothermal alteration here at the core of the system overprints early biotitization of the host rocks the biotitization appears to have been the result

geochronology hf isotopic compositions and geochemical characteristics of xitian a type granite and its geological significance zircon la mc icp ms u pb analysis was carried out for the xitian granite in east hunan province two samples from the first period of medium fine grained porphyritic biotite monzonitic granite show ages of 220 9 0 6 ma and 220 7 0 7 ma respectively the age of the second period of medium fine grained two mica monzonitic granite is 154 4 0 7 ma granites of both periods are high potassium rich in alkali and weakly peraluminous their compositions are characterized by high ree rich u and th depleted hfse such as ti p and lile such as ba sr and high 104 ga al these characteristics indicate that they are a type granites the indosinian granite is rich in lree with rather weak eu negative anomaly the yanshanian granite shows no obvious fractionation between lree and hree with significant eu negative anomaly hf isotopic analysis indicates that the two periods of granite have low ehf t 4 91 11 04 and the two stage hf model ages of the depleted mantle are concentrated in 1 6 1 8 ga in accordance with characteristics of the old metamorphic basement of cathaysian block therefore the xitian granite is a product from partial melting of proterozoic crust materials of cathaysian block under the extensional setting the confirmation of xitian a type granite has important significance for understanding the tectonic background of the east part of hunan province during indosinian and yanshanian movements it also provides more evidence that there is w sn mineralization related to a type granite during indosinian period in south china

in situ elemental and boron isotopic variations of tourmaline from the maogongdong deposit in the dahutang w cu ore field of northern jiangxi province south china insights into magmatic hydrothermal evolution abstract in this paper we present a systematic investigation of in situ major trace elements and boron isotopic variations of tourmaline from the maogongdong deposit in the dahutang w cu ore field of northern jiangxi province south china which demonstrates both the magmatic and hydrothermal origin for the formation of the tourmalines the tourmaline occurs mainly in granites pegmatites and quartz veins five types of tourmaline are identified 1 disseminated tourmaline in the pegmatites tur p type 2 isolated and disseminated tourmaline clots in the granites tur r1 type 3 typical anhedral quartz tourmaline nodulars in the granites tur r2 type 4 tourmaline clots in quartz tungsten sulfide veins tur q1 type 5 euhedral needle columnar tourmaline crystals in quartz or quartz sulfide veins tur q2 type these tourmalines mostly fall into the alkali group representing schorl dravite solid solution series petrography and chemical discrimination diagrams suggest that the tur p tur r1 and tur r2 are of magmatic origin and the tur q1 and tur q2 are of hydrothermal origin hydrothermal tourmalines have higher mg mg fe ratios higher li be sn rb co sr v pb zn ni contents and lower na na ca ratios lower nb ta contents than the magmatic tourmalines the tur p show negative eu anomalies and their ree patterns are equivalent to the muscovite granite the eu anomalies in tur r1 and tur r2 change from negative to positive compared with magmatic tourmalines tur q1 and tur q2 exhibit more pronounced positive eu anomalies and a majority of the tur q1 and tur q2 have higher ree contents tourmalines from the maogongdong deposit have a b isotopic composition range from 17 9 to 12 3 the average 11b values of the tur p tur r1 and tur r2 are 13 8 14 8 and 14 5 respectively tourmalines in early hydrothermal veins have similar 11b values average 14 6 while the tourmalines in later hydrothermal veins have slightly lower 11b values average 16 5 boron isotopic variations of tourmaline are controlled by temperature rayleigh fractionation and external fluid

fluid inclusion studies of longshang tin polymetallic deposit in xitian ore field eastern hunan province the longshang ore deposit is a large size tin polymetallic deposit in the xitian ore field eastern hunan province fluid inclusions in fluorite and quartz from the skarn and fracture zone altered rocks of the longshang tin polymetallic deposit were studied by such means as petrography microthermometry and laser raman spectrometer analysis the results show that fluid inclusions are composed of nacl h2o type fluid inclusions type a co2 rich two phase inclusions type b and co2 bearing three phase inclusions type c type a comprises single phase liquid inclusions a1 and two phase liquid vapor inclusions a2 type b includes co2 rich two phase inclusions and type c consists of co2 bearing three phase inclusions which have been homogenized into lh2o c1 and co2 bearing three phase inclusions which have been homogenized into vco2 c2 the homogenization temperatures of the three ore forming stages are 290 380 for stage i 210 240 for stage ii and 90 190 for stage iii at the early stage of the ore forming process stage i fluid inclusions of co2 nacl h2o and nacl h2o cacl2 types which had close homogenization temperatures were associated with each other and the main ore forming fluids were co2 and nacl h2o with small amounts of h2s and ch4 at the late stages of the ore forming process stage ii iii the main ore forming fluid was nacl h2o according to characteristics of the fluid inclusions high 3he 4he ratios and the existence of lots of mafic microgranular inclusions the authors consider that the ore forming materials of the longshang tin polymetallic deposit were derived from multiple sources the ore forming fluids were mixed with mantle crust and atmospheric water under the control of igneous and surrounding rocks the mantle ore forming fluids played a key role in mineralization at the early stage of the ore forming process

metamorphosed pb zn ag ores of the keketale vms deposit nw china evidence from ore textures fluid inclusions geochronology and pyrite compositions abstract the keketale pb zn deposit is located in the devonian volcanic sedimentary maizi basin of the altay orogenic belt the mineralization at keketale is hosted in marbles and deformed volcanic tuffs and biotite garnet chlorite schists folded into a series of overturned synclines formed in multiple deformation events keketale contains economic amounts of pb 0 89 mt 1 51 wt zn 1 94 mt 3 16 wt and ag 650 t 40 g t detailed petrographic studies have defined two main generations of sulfide development the banded pyrite of the early stage a is commonly stratiform with minor galena sphalerite and chalcopyrite stage b is characterized by a large amount of polymetallic sulfides including pyrrhotite chalcopyrite sphalerite and galena with minor pyrite hosted in quartz veins three types of fluid inclusions fis including mixed carbonic aqueous c type pure carbonic pc type and aqueous w type have been recognized in quartz of stage b the c type fis have homogenization temperatures of 150 326 c and salinities of 0 2 16 6 wt nacl equivalent the pc type fis are dominated by co2 with minor ch4 and n2 and have initial ice melting temperatures of 57 5 to 56 7 c co2 homogenization temperatures of 11 14 1 c the w type primary fis were completely homogenized at temperatures of 124 359 c with salinities of 5 0 14 6 wt nacl equivalent such co2 rich fluid inclusions are consistent with those discovered in orogenic type deposits in the altay area and elsewhere muscovite separates from the polymetallic quartz veinlets of stage b yield a well defined 40ar 39ar isotopic plateau age of 259 33 2 56 ma with an isochron age of 259 62 2 65 ma this age is coeval with the closure of the paleo asia ocean and reactivation of the ertix fault system la icp ms analyses of two generations of pyrite indicate that the banded pyrite of stage a is relatively depleted in metallic elements and contains low contents of cu 0 39 ppm ag 0 20 ppm au below the detection limits pb 17 43 ppm and zn 14 38 ppm whereas the pyrite in quartz polymetallic sulfide veinlets of the stage b is relatively rich in metallic elements e g cu 2 56 ppm ag 3 07 ppm au 0 01 ppm pb 1047 ppm and zn 1136 ppm the trace amounts of cu pb zn au and ag are interpreted to have been initially locked in the lattice of type a pyrite and then liberated and precipitated as micromineral inclusions with type b pyrite during subsequent metamorphism and deformation two key factors are considered vital to the formation of economic ores of the keketale pb zn deposit namely the original devonian banded pyrite formed in a vms system and subsequent permian deformation and metamorphic processes that liberated cu pb zn au and ag from the lattice of type a pyrite to form galena sphalerite and chalcopyrite with minor muscovite in quartz veinlets the model provides a new interpretation of vms pb zn deposit occurring in back arc basin environments followed by collision and new insights into the unique regional fe cu pb zn au mineralization in the altay orogenic belt

fluid evolution and mineralization in a subvolcanic granite stock the mount pleasant w mo sn deposits new brunswick canada in the fire tower zone at mount pleasant new brunswick porphyry style w mo stage i and stanniferous polymetallic vein and replacement stage ii mineralization is hosted principally by a complex hydrothermal breccia pipe which overlies a subvolcanic fine grained granite stock wolframite and molybdenite of stage i occur in quartz or topaz and or fluorite veinlets and breccia matrices and as disseminations in altered wall rocks quartz and topaz with lesser green biotite chlorite and k feldspar are the main alteration minerals sericite occurs as a late alteration product in the main ore zone stage ii comprises mineralogically complex sn bearing sulfide vein and replacement bodies that contain abundant fluorite and chlorite the stage ii mineralization has been superimposed on stage i and is spatially related to later dikes of granite porphyry quartz fluorite and topaz contain three types of fluid inclusions type 1 are low salinity mostly 10 equiv wt nacl cacl 2 liquid vapor inclusions which homogenize to liquid type 2 are vapor rich inclusions that homogenize to vapor and type 3 are high salinity 30 60 equiv wt nacl liquid vapor solid inclusions most of which homogenize to the liquid phase by solid generally halite disappearance all three inclusion types are found in minerals from stage i whereas only type 1 is found in minerals from stage ii crystallization of the fine grained granite resulted in the generation of a subcritical mixture of orthomagmatic low salinity vapors and high salinity liquids the increase in volume associated with the separation of these fluids caused overpressuring in the apical portions of the fine grained granite magma which resulted in failure of the overlying sequence and in the formation of the breccia pipe the resultant decrease in pressure caused adiabatic cooling of the fluid and explains some of the observed salinity variations a consideration of phase equilibria in aqueous salt systems indicates that the high salinity liquids must have cooled approximately isobarically to produce the observed fluid inclusions this cooling is thought to have been achieved through mixing with ground waters the high salinity fluids were responsible for the precipitation of the bulk of the stage i quartz and associated wolframite and molybdenite and for silica topaz and biotite alteration the later intrusion of the granite porphyry and or porphyritic granite provided a second generation of subcritical orthomagmatic fluids which may have been responsible for tin greisen mineralization located at depth in the porphyritic granite after each of these orthomagmatic events low to moderate salinity ground waters dominated the system in both cases these late fluids deposited fluorite and sulfides and caused chloritic alteration in the latter event they formed the stage ii sn bearing polymetallic zones

multiple fluids involved in granite related w sn deposits from the world class jiangxi province china abstract this paper aims at providing new insights into w sn ore forming processes within one of the largest granitic provinces in the world nanling range south china which was emplaced during the jurassic cretaceous period the origin composition and pressure temperature conditions of fluids involved in the w sn ore forming processes have been investigated by microthermometry raman spectroscopy la icpms hydrogen isotope analyses of fluid inclusions and oxygen isotope analyses of minerals from the maoping and piaotang w sn deposits for each deposit pre quartz syn wolframite and cassiterite and post ore quartz topaz and fluorite minerals were studied in both deposits the vast majority of fluid inclusions are aqueous with salinities between 0 0 and 12 6 wt equiv nacl and homogenization temperatures between 136 and 349 c a minor proportion 5 of inclusions observed in the ore stage quartz from maoping have aquo carbonic compositions for both deposits four compositional groups are defined early quartz fluid inclusions are characterized by salinities between 0 4 and 9 0 wt equiv nacl trapping temperatures between 150 and 350 c and pressures between 20 and 150 mpa la icpms analyses of these fluid inclusions reveal a wide range of na k and li concentrations as well as relatively low metal contents w at piaotang fluid inclusions in wolframite as well as in post ore quartz and fluorite have salinities of 5 6 to 12 6 wt eq nacl trapping temperatures between 150 and 400 c and pressures of 20 to 150 mpa la icpms analyses of these fluid inclusions reveal similar compositions to early quartz fluid inclusions values of 18o in wolframite and quartz crystals range from 0 8 to 5 2 vsmow while the d values of fluid inclusions range from 66 to 62 vsmow collectively the data suggest the involvement of four aqueous fluid end members mixed episodically in the mineralization process a a low salinity low temperature metal poor low 18o low d fluid derived from meteoric water b a high salinity high temperature metal poor high 18o low d fluid derived from a differentiated peraluminous granitic magma c a high salinity high temperature metal rich lower d magmatic fluid derived from a more differentiated peraluminous granitic magma and d a high salinity high temperature metal rich high 18o low d magmatic fluid this study shows that multiple fluids with distinct magmatic and meteoric origins were involved in the formation of these w sn deposits and that the dilution of metal bearing magmatic fluids by meteoric fluids was probably the main driver for ore deposition the common fluid history of the two deposits studied as well as similarities with other deposits in the jiangxi province points toward common ore forming processes at the regional scale

fault fluid evolution in the xitian w sn ore field south china constraints from scheelite texture and composition abstract understanding fault fluid evolutionary processes is crucial for understanding the genesis of vein type deposits scheelite and quartz are common hydrothermal minerals in w sn ore field faults in the xitan ore field nanling range south china scheelite textural and compositional features were studied and two types of scheelite were identified type i represented by scheelite in the xihu fault is intergrown with quartz has oscillatory zonation variable zonation band width and is homogeneous light grey color in cathodoluminescence images and type ii represented by scheelite in the goudalan fault is intergrown with quartz that shows multi stage growth has oscillatory zonation and each zonation band is the same width scheelite grains of both types have homogeneous major element distribution e g w and ca however trace element contents e g mg nb are slightly variable and rare earth element ree and y contents gradually decrease by an order of magnitude from the core to the rim in both types of scheelite from core to rim the chondrite normalized ree patterns of type i scheelite change from flat curves with no or slightly positive eu anomalies to intense concave shapes with intense positive eu anomalies the middle rees gradually become depleted indicating the mree fractionation associated with early scheelite precipitation in a relatively closed fault fluid system in contrast the chondrite normalized ree patterns of type ii scheelite grains are similar all showing weak mree depletion from the core to rim implying recurrent fluid pulses in an open fault fluid system the ree patterns in the cores of the type i scheelite are similar to those of the scheelite from jurassic granites related to the w sn mineralization suggesting that the initial ore forming fluids were exsolved from the jurassic magma the ree patterns in the rims of type ii scheelite are consistent with those of scheelite from the goudalan w deposit suggesting that the fault fluid system experienced a similar evolution to the ore forming fluid system combining the results of this work with previous quartz h o isotopic and fluid inclusion studies it can be concluded that fluid mixing occurred in both the fault fluid system and the ore forming fluid system triggering large scale w precipitation

trace and minor elements in sphalerite from base metal deposits in south china a la icpms study laser ablation icp mass spectroscopy has been used to investigate the geochemistry of sphalerite in a range of nine zn pb deposits in south china the deposits which are of different ages and belong to different metallogenic provinces have been assigned to the following genetic types skarn hetaoping luziyuan syngenetic massive sulphide dabaoshan laochang and bainiuchang and mississippi valley type huize mengxing niujiaotang based on the features of the ore even though their origin is heavily debated based on other criteria the giant jinding deposit is considered separately sphalerite from each genetic class of deposit shows a distinct chemical signature sphalerite from the skarn deposits is characterised by elevated lattice bound concentrations of co and mn the distal character of these skarn systems is reflected by the low in content of sphalerite the three syngenetic massive sulphide deposits feature sphalerite strongly enriched in in sn and ga whereas the deposits of mvt type are typically enriched in ge cd tl and as these divergent characters are reflected in absolute element abundances as well as in element ratios time resolved depth profiles for sphalerite from the chinese deposits confirm the presence of elements such as co in ge ga and cd in solid solution but the dataset expands the understanding of sphalerite mineral chemistry by also indicating that other elements whose ability to enter the crystal structure of sphalerite has been previously debated ag sn tl sb may also be in solid solution sphalerite is a refractory mineral and trace element analysis of sphalerite shows promise as a tracer of ore genesis even in overprinted ores systematic work on larger sample suites may help define the geochemical signature of different metallogenic epochs in regions as geologically complex as south china and help resolve the mechanism by which many of the debated ore deposits were formed

the molybdenite re os isotope chronology in situ scheelite and wolframite trace elements and sr isotope characteristics of the chuankou tungsten ore field south china abstract the chuankou tungsten ore field situated in the central area of the qing hang ancient suture zone in south china is characterized by predominantly quartz vein type tungsten mineralization that formed near the contact between the chuankou granite and slightly metamorphosed silt bearing sericite slate based on field work cathodoluminescence molybdenite re os dating and in situ laser ablation inductively coupled plasma mass spectrometry la icp ms analysis the chuankou tungsten ore was formed at 230 6 2 9 ma to 229 4 2 6 ma in a typical indosinian metallogenic event in addition three distinct generations of scheelite and two types of wolframite can be clearly distinguished type 1 wolframite has a semiautomorphic grain or brecciated vein structure with a high heavy rare earth element hree content and an obvious negative eu anomaly type 2 wolframite grains are strongly altered as residual pseudomorphic structures by ore forming fluids and have relatively low ree contents sch 1 scheelite is present in the interior of the type 2 wolframite grains the sch 1 scheelite grains have an elevated ree content and low 87sr 86sr ratios with a strongly negative eu anomaly which suggests an inheritance signal of the host rocks comparatively sch 2 and the altered sch 1 scheelite have characteristic extremely low ree contents and remarkably strong positive eu anomalies these scheelites also have increased 87sr 86sr ratios and low 88sr signals sch 3 is idiomorphic with perfect oscillating zoning the ree content of sch 3 which typically has the lowest 87sr 86sr ratios is higher than those in sch 1 and sch 2 and the extremely high 88sr signals indicate a distinct thermal fluid event that was directly derived from the host rock the correlations between the ree and nb of scheelite imply a type b substitution of sch 1 and sch 2 but a type c substitution for sch 3 the correlation of eun and eun shows an eu3 substitution process for stages sch 1 and sch 2 and an eu2 substitution process for stage sch 3 thus we confirm that ore bearing hydrothermal rocks must undergo early stage metasomatism and filling middle stage fluid mixing between wall rocks and magmatic hydrothermal activity and refilling of late stage magmatic hydrothermal activity during the metallogenic process during the indosinian period the mineralization stages of polymetallic deposits in the indosinian were composed of stage 1 240 to 220 ma and stage 2 220 to 200 ma the chuankou tungsten ore field can be considered as the typical representation of the stage 1 metallogenic event in south china this ore field is derived from remelting of the ancient basement and was reduced by regional extension under the dominant compression regime in the south china block

ore forming mechanism of quartz vein type w sn deposits of the xitian district in se china implications from the trace element analysis of wolframite and investigation of fluid inclusions abstract the xitian w sn district is located in eastern hunan province of se china and comprises the heshuxia goudalan and longshang w sn deposits our study on the occurrence mineral assemblage and geochemistry of the orebodies shows that quartz vein orebodies are dominant mode of mineralization and can be divided into three stages stage i quartz molybdenite wolframite i stage ii quartz wolframite ii polymetallic sulfides and stage iii quartz pyrite fluorite the elements nb ta sc sn zn cr v mo cu and zr are abundant in both wolframite i and wolframite ii wolframite i contains higher concentrations of nb 1408 9245 ppm ta 241 2407 ppm and sc 123 521 ppm than wolframite ii nb 144 1080 ppm ta 3 76 315 ppm and sc 1 86 11 44 ppm these results indicate that wolframite i was formed closer to the host rock and at a greater ore forming depth than wolframite ii the total ree concentrations of wolframite i and ii range from 34 96 to 133 36 ppm and 21 30 to 43 73 ppm respectively both wolframite i and wolframite ii have low lree concentrations 0 00 0 05 and 0 08 8 18 ppm respectively and high hree concentrations 34 96 133 31 and 21 23 41 87 ppm respectively the enrichment of hrees in wolframite may be due to the fact that the sizes of the hrees3 0 94 1 02 a in combination with nb5 or ta5 0 72 a are closer to that of w6 0 68 a in combination with ca2 1 08 a or mg2 0 80 a than that of the lrees3 1 03 1 13 a making the coupled substitution easier a study of fluid inclusions in the coexisting gangue minerals shows that the homogenization temperatures of the fluid inclusions decrease from stage i to stage iii stage i 187 382 c average 275 c stage ii 122 278 c average 175 c stage iii 92 172 c average 139 c whereas the salinities of the fluid inclusions increase from stages i to ii and decrease from stages ii to iii stage i 1 8 18 2 wt nacleqv average 10 3 wt nacleqv stage ii 7 3 24 4 wt nacleqv average 14 9 wt nacleqv stage iii 0 2 5 3 wt nacleqv average 1 5 wt nacleqv raman spectroscopy reveals that the fluid inclusions mainly contain h2o co2 is minor and h2s ch4 and n2 are rare we conclude that the formation of wolframite was driven by post magmatic thermodynamic processes the ore forming fluid flowed through a multi fractured low pressure zone in the fault system in the district and a temperature pressure decrease led to fluid immiscibility characterized by co2 escaping in a low ph and high eh environment in stage i crust mantle mixed fluid and meteoric water mixing in stage ii and natural cooling of the fluid system in stage iii

tracing metal sources in peribatholitic hydrothermal w deposits based on the chemical composition of wolframite the example of the variscan french massif central abstract we present a complete dataset for major minor and trace elements in wolframite fe mn wo4 based on the example of several peribatholitic hydrothermal w deposits located in the variscan french massif central fmc the wolframite samples were characterized down to the micrometer scale by combining scanning electron microscopy observations and in situ chemical analysis by electron probe microanalyzer and laser ablation inductively coupled plasma mass spectrometry most samples are fe dominated wolframites and are characterized by variable fe fe mn values for the studied deposits from 0 36 to 0 86 without significant alteration features wolframites present intracrystalline variations for concentrations of several minor and trace elements principally for nb ta and sn which reflect growth zoning the minor and trace element compositions of the different wolframite samples show at first order similar enrichments in ta nb sn zn and in as well as depletions in lree li th ti zr hf pb v co and mg compared to the upper continental crust second order compositional variations are observed between the studied deposits which can be separated in four main regional geochemical groups this work highlights that the chemical composition of wolframite is controlled by both the crystallochemical parameters and the composition of the primary hydrothermal fluid the regional variations observed in the geochemical signatures of wolframite reflect local variations in the composition of the hydrothermal fluid i e variable metal sources therefore this suggests that the minor and trace element contents in wolframite likely represent direct markers of the source of the hydrothermal fluid and ultimately of the metals the comparison between the trace element compositions of wolframite with the compositions of regional granitic rocks and worldwide shales suggests that evolved peraluminous granites represent the main source of metals in peribatholitic hydrothermal w deposits from the fmc whereas metasedimentary rocks have a limited to no influence on the metal budget

zircons reveal multi stage genesis of the xiangdong dengfuxian tungsten deposit south china abstract as a typical tungsten deposit of the xitian ore field nanling range south china the xiangdong deposit is a quartz vein type w deposit related to a triassic jurassic granitic complex with total ore reserves of 7 mt wo3 30 kt in this study zircon cl and bse imaging la mc icp ms u pb dating trace element and hf isotopic analyses were carried out on the fluid altered granites and related w ores in the xiangdong deposits aiming to reveal the genesis of the deposit zircon u pb dating yielded three age clusters pre triassic 250 ma n 19 triassic 227 214 ma or 220 ma n 111 and jurassic 159 149 ma or 150 ma n 27 zircon morphology and geochemistry suggest that triassic granites and jurassic quartz veins experienced stronger influences from high temperature hydrothermal fluids than other geological bodies in the deposit high contents of p y pb and u are found in triassic granite zircons whereas high concentrations of nb and ta occur in jurassic quartz vein zircons indicating different hydrothermal fluid systems during the triassic and jurassic the triassic and jurassic zircons yield high y ho ratios up to 35 representing fractionated non chondritic compositions which are indicative of a late stage residual melt that co existed with f rich fluids decreases in zircon ce ce and eu eu ratios from the triassic to the jurassic suggest a decline in fo2 that is likely to have facilitated large scale jurassic w mineralization high 176yb 177hf and 176lu 177hf ratios in the hydrothermally altered jurassic zircons indicate intense fluid exsolution from the source magma whereas the more variable 176hf 177hf ratios and hf model ages of the triassic zircons suggest multiple fluid sources and more complex alteration processes a new ore genesis model is proposed for the xiangdong w deposit initial enrichment of ore materials during the late triassic followed by large scale tungsten precipitation during the late jurassic the triassic granite provided the initial w source whereas granite derived fluids successively formed magma differentiated ore veins and infilling metasomatic ore veins during the jurassic

fluid regime and ore formation in the tungsten yttrium deposits of kyzyltau mongolian altai evidence for fluid variability in tungsten tin ore systems abstract the kyzyltau ore field is located in the northern part of the mongolian altai mountains w y be mo mineralization occurs in veins and stockworks in granites felsic volcanics basaltic flows and conglomerates the main ore minerals in the veins are wolframite fluorite beryl and minor molybdenite inclusions in hydrothermal quartz fluorite and beryl from veins as well as in magmatic quartz in vein hosting granites of the ulaan uul buraat uul and tsunkheg deposits were investigated using microthermometry and laser raman spectroscopy pseudosecondary primary inclusions in the kyzyltau ore veins are predominantly liquid rich aqueous inclusions containing variable amounts of co 2 as the main gas component and showing n 2 ch 4 ratios 1 secondary inclusions contain no or only trace concentrations of gases as indicated by clathrate melting the t h values of pseudosecondary primary inclusions in veins are between 180 and 433 c fluid inclusion data indicate that phase separation processes leading to fluid immiscibility occurred in vuggy quartz ii and green fluorite ii in the ulaan uul and buraat uul ore veins phase separation pressures of 100 350 bars were estimated fluorite i from the kyzyltau ore field shows a strong enrichment of hree and a strong negative eu anomaly common for rare metal bearing ore systems fluorite ii from buraat uul and tsunkheg is characterized by a change in the incorporation of rare earth elements ree with decreasing hree contents and a decreasing eu anomaly the ree distribution patterns in fluorite ii from ulaan uul remained unchanged compared with fluorite i despite a strong increase in the total ree content a review of the literature shows that from high temperature fe rich k dominated brines cassiterite ores can precipitate in quartz veins together with fe chlorite and fe tourmaline bolivian type if phase separation of a gas rich low salinity and fe rich fluid occurs cassiterite wolframite ores may be deposited cornwall devon type the deposits of kyzyltau are characterized by low fe alteration assemblages a predominance of sodium over potassium high contents of ree and y and a lack of extended tin mineralization despite the tin potential of the ore systems fluid inclusion data as well as geochemical and geological indications suggest formation of the tungsten deposits near the tops of li f rich sub volcanic intrusions we interpret the ph of the mineralizing fluid to be the main factor controlling wolframite precipitation in the kyzyltau ore field fluid wall rock interactions a lowering of the temperature and unmixing processes in the ore fluid generated contributions to neutralization and buffering of the acid co 2 bearing fluid into a ph range where tungstates were precipitated it can be inferred that formation of tungsten ores without precipitation of extended tin mineralization is possible in deposits characterized by high potential tin and tungsten according to this inference tin mineralization may be found in a more favourable setting in the vicinity of the kyzyltau deposits

invisible gold in arsenian pyrite and arsenopyrite from a multistage archaean gold deposit sunrise dam eastern goldfields province western australia the sunrise dam gold mine 11 1 moz au is the largest deposit in the archaean laverton greenstone belt eastern goldfields province yilgarn craton western australia the deposit is characterized by multiple events of fluid flow leading to repeated alteration and mineralization next to a major crustal scale structure the au content of arsenian pyrite and arsenopyrite from four mineralizing stages d1 d3 d4a and d4b and from different structural and lithostratigraphic environments was measured using in situ laser ablation inductively coupled plasma mass spectrometry pyrite contains up to 3 067 ppm au n 224 whereas arsenopyrite contains up to 5 767 ppm n 19 gold in arsenopyrite d4a stage was coprecipitated and remained as invisible gold nanoparticles and or lattice bound during subsequent deformation events in contrast gold in pyrite is present not only as invisible gold but also as micrometer size inclusions of native gold electrum and au ag tellurides pristine d1 and d3 arsenian pyrite contains relatively low au concentrations 26 ppm the highest au concentrations occur in d4a arsenian rich pyrite that has recrystallized from d3 pyrite textures show that this recrystallization proceeded via a coupled dissolution reprecipitation process and this process may have contributed to upgrading au grades during d4a in contrast au in d4b pyrite shows grain scale redistribution of invisible gold resulting in the formation of micrometer scale inclusions of au minerals the speciation of au at sunrise dam and the exceptional size of the deposit at province scale result from multiple fluid flow and multiple au precipitating mechanisms within a single plumbing system

evolution and paragenetic context of low δd hydrothermal fluids from the panasqueira w sn deposit portugal new evidence from microthermometric stable isotope noble gas and halogen analyses of primary fluid inclusions abstract the evolution paragenetic context and origin of remarkably low d hydrothermal fluids from the hercynian panasqueira w sn cu ag deposit have been investigated through a combined microthermometric stable isotope halogen and noble gas fluid inclusion study large variations in d between 60 and 134 have been observed in primary fluid inclusions from growth zones in a quartz crystal pa66 paragenetically constrained to the main sulfide stage mss of ore formation the same fluids exhibited relatively constant fluid inclusion homogenisation temperatures 254 to 260 c salinities 7 4 to 8 7 wt nacl equivalent and calculated fluid 18o 3 8 to 4 4 all the fluids exhibited 40ar excesses mean molar br cl and i cl ratios varied from 2 3 10 3 4 2 10 3 and 8 10 4 10 10 4 respectively with the more br rich fluids being associated with the more deuterium depleted fluids the low palaeolatitude of panasqueira throughout the main stages of ore formation and the overwhelming predominance of meteoric fluids in the main late and post ore mineralising fluids with d of 40 to 65 lends little support for any models involving low d palaeometeoric water the limited range of 40ar cl ratios 1 1 10 5 1 6 10 5 also precludes boiling during the mss or mixing of meteoric water with highly fractionated deuterium depleted magmatic waters as viable mechanisms for producing the low d fluids the high br cl and i cl of the mss fluids indicate significant fluid interactions with organic rich sediments or metasediments in particular regionally abundant carboniferous coals or coaly sediments that are inferred to be depleted in deuterium by around 85 compared to palaeometeoric water the large range of d observed in the mss fluids may be explained by isotopic exchange of palaeometeoric water with these coals at varying water rock wt wt ratios between 0 02 and 0 002 with fluid oxygen isotopic compositions controlled by exchange with the beira schists such a model is consistent with the requirements that any satisfactory model must take into account viz i the relative constancy of temperature salinity 40ar and fluid 18o during excursions to low d ii the high i cl and br cl ratios observed and iii the coincidence of these low d fluids with the onset of precipitation of polymetallic sulfides and phosphates under reducing conditions the model indicates that meta sedimentary sources of ore forming components became increasingly important during the evolution of the panasqueira sn w deposit and accounts in part for the observed progression from oxide dominated to base metal sulfide dominated parageneses

precise molybdenite re os and mica ar ar dating of the mesozoic yaogangxian tungsten deposit central nanling district south china the yaogangxian deposit in the central nanling region south china consists of vein type ore bodies hosted in cambrian to jurassic strata and mesozoic granitic intrusions wolframite and molybdenite are the dominant ore minerals intergrown with gangue minerals of quartz feldspar phlogopite and muscovite we have carried out molybdenite re os and phlogopite and muscovite 40ar 39ar dating to better understand the timing and genesis of mineralization re os dating of eight molybdenite samples yielded model ages ranging from 152 0 3 5 to 161 1 4 5 ma with an average of 156 0 ma the re os analyses give a well defined 187re 187os isochron with an age of 154 9 2 6 ma mswd 2 4 hydrothermal phlogopite and muscovite display extremely flat 40ar 39ar age spectra phlogopite yields a 40ar 39ar plateau age of 153 0 1 1 ma whereas muscovite yields a plateau age of 155 1 1 1 ma both 40ar 39ar ages are in good agreement with the re os ages placing the timing of tungsten mineralization at about 154 ma this age is consistent with the field relationships our new data when combined with published geochronological results from other major deposits in this region suggest that large scale w sn mineralization occurred throughout the central nanling region in the late jurassic

zircon u pb molybdenite re os and muscovite ar ar isotopic dating of the xitian w sn polymetallic deposit eastern hunan province south china and its geological significance the xitian tungsten tin w sn polymetallic deposit located in eastern hunan province south china is a recently explored region containing one of the largest w sn deposits in the nanling w sn metallogenic province the mineral zones in this deposit comprise skarn greisen structurally altered rock and quartz vein types the deposit is mainly hosted by devonian dolomitic limestone at the contact with the xitian granite complex the xitian granite complex consists of indosinian late triassic 230 215 ma and yanshanian late jurassic early cretaceous 165 141 ma granites zircons from two samples of the xitian granite dated using laser ablation inductively coupled mass spectrometer la icpms u pb analysis yielded two ages of 225 6 1 3 ma and 151 8 1 4 ma representing the emplacement ages of two episodic intrusions of the xitian granite complex molybdenites separated from ore bearing quartz veins yielded a re os isochron age of 149 7 0 9 ma in excellent agreement with a weighted mean age of 150 3 0 5 ma two samples of muscovites from ore bearing greisens yielded 40ar 39ar plateau ages of 149 5 1 5 ma and 149 4 1 5 ma respectively these isotopic ages obtained from hydrothermal minerals are slightly younger than the zircon u pb age of 151 8 1 4 ma of the yanshanian granite in the xitian area indicating that the w sn mineralization is genetically related to the late jurassic magmatism the xitian deposit is a good example of the early yanshanian regional w sn ore forming event 160 150 ma in the nanling region the relatively high re contents 8 7 to 44 0 ppm average of 30 5 ppm in molybdenites suggest a mixture of mantle and crustal sources in the genesis of the ore forming fluids and melts based upon previous geochemical studies of early yanshanian granite and regional geology we argue that the xitian w sn polymetallic deposit can be attributed to back arc lithosphere extension in the region which was probably triggered by the break off of the flat slab of the palae pacific plate beneath the lithosphere

origin and evolution of w mo producing fluids in a granitic hydrothermal system geochemical studies of quartz vein deposits around the susan granite hwanggangri district republic of korea the hwanggangri mineralized district is located approximately 130 km southeast of seoul within the paleozoic ogcheon belt of south korea the jungbo suri and deogman mines in the district occur around the late cretaceous whole rock k ar age 89 0 or 2 0 ma susan granite and are located on w mo bearing quartz veins these veins fill fractures in the granite and its host rocks which comprise early paleozoic limestone rich sedimentary rocks the k ar date of vein muscovite 88 58 or 1 95 ma is very similar to that of the susan granite 89 04 or 1 95 ma indicating that w mo mineralization was associated with intrusion of the granite molybdenite and wolframite rich deposits occur within or near 285 degrees c from h 2 o co 2 fluids with salinities of 0 4 to 9 7 wt percent nacl equiv probably in response to ph increase due to boiling including co 2 unmixing of the hydrothermal fluid at pressures between 150 and 220 bars following w mo deposition the high temperature fluids gave way to progressively cooler more dilute fluids associated with scheelite base metal sulfide deposition 200 degrees 320 degrees c 0 7 7 2 wt nacl equiv and carbonate fluorite deposition 105 degrees 225 degrees c 0 0 3 2 wt nacl equiv these trends are interpreted as the result of progressive mixing of magmatic fluids with cooler more dilute meteoric waters there is a systematic decrease in the measured and calculated isotopic compositions of hydrothermal waters with increasing paragenetic time and decreasing temperature stage i delta 18 o water 8 0 to 1 5 per mil and delta d water 56 to 74 per mil stage ii delta 18 o water 1 9 to 5 6 per mil and delta d water 88 to 95 per mil stage iii delta 18 o water 0 9 to 3 0 per mil and delta d water 93 to 97 per mil the trend reflects the progressive increase of meteoric water involvement in the mineralizing system during the cooling history of the susan granite stock molybdenum and tungsten were partitioned preferentially into a coexisting magmatic hydrothermal fluid delta 18 o 8ppm delta d 56 to 72ppm sulfur isotope analyses of hydrothermal sulfide minerals suggest an igneous source of sulfur with a delta 34 s sub sigma s value near 4 per mil following deposition of molybdenite and wolframite from magmatic fluids wolframite was dissolved or replaced by scheelite in the outer and or shallower portions of the hydrothermal system this remobilization of tungsten and later redeposition as scheelite at temperatures of 200 degrees 280 degrees c from fluids with delta 18 o 1 2ppm accompanied mixing with low temperature meteoric fluids increasing involvement of progressively larger volumes of meteoric water resulted in successive deposition of base metal sulfides fluorite and carbonates

zircon u pb geochronology and hf isotopic compositions of ore related granites from huangshaping polymetallic deposit of hunan province u pb radioactive age and hf isotope composition were systematically determined by means of la mc icp ms for zircons from granophyre granite porphyry and quartz porphyry in the huangshaping polymetallic deposit of hunan province which is distributed in the west of the qianlishan qitianling ore forming belt and in the north of the nanling mountains granite belt la icp ms analysis shows that the crystallization ages of ore related porphyries are 150 1 0 4 ma 150 2 0 4 ma and 155 3 0 7 ma respectively suggesting a middle yanshanian emplacement the in situ hf isotope analysis reveals that these ore related porphyries were derived from the mixed sources of the lower crust and the mantle based on this study in combination with the tectonic background the authors hold that the formation process of huangshaping ore related porphyries might have been related to some mantle materials and formed under an extensional regime which had to do with middle late jurassic farallon izanagi triple ridge subduction and transform faults subduction

gold and trace element zonation in pyrite using a laser imaging technique implications for the timing of gold in orogenic and carlin style sediment hosted deposits laser ablation icp ms imaging of gold and other trace elements in pyrite from four different sedimenthosted gold arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit an early synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace elements in particular as ni pb zn ag mo te v and se and a later hydrothermal stage where gold forms as either free gold grains in cracks in overgrowth metamorphic and or hydrothermal pyrite or as narrow goldarsenic rims on the outermost parts of the overgrowth hydrothermal pyrite compared to the diagenetic pyrites the hydrothermal pyrites are commonly depleted in ni v zn pb and ag with cyclic zones of co ni and as concentration the outermost hydrothermal pyrite rims are either as au rich as in moderate to highgrade deposits such as carlin and bendigo or co ni rich and as au poor as in moderate to low grade deposits such as sukhoi log and spanish mountain the early enrichment of gold in arsenic bearing syngenetic to diagenetic pyrite within black shale facies of sedimentary basins is proposed as a critical requirement for the later development of carlin style and orogenic gold deposits in sedimentary environments the best grade sediment hosted deposits appear to have the gold climax event toward the final stages of deformation related hydrothermal pyrite growth and fluid flow

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

petrogenesis and tectonic setting of the early mesozoic xitian granitic pluton in the middle qin hang belt south china constraints from zircon u pb ages and bulk rock trace element and sr nd pb isotopic compositions abstract the xitian pluton in southeast hunan province is one of the early mesozoic indosinian granitic plutons in the south china block it is composed of biotite adamellite with k feldspar megacrysts biotite adamellite and biotite granite that have u pb zircon ages of 229 9 1 4 ma 223 6 1 3 ma and 224 0 1 4 ma respectively the indosinian granitoids in the xitian pluton belong to s type granites with highly radiogenic initial 87sr 86sr ratios 0 71397 0 71910 negative end t values ranging from 10 1 to 9 4 and old nd model ages 1858 1764 ma they are enriched in radiogenic pb isotopes with 206pb 204pb t ranging from 18 130 to 18 903 207pb 204pb t from 15 652 to 15 722 and 208pb 204pb t from 38 436 to 39 037 respectively these features indicate that the granitoidswithin the xitian pluton were formed from magmas generated by remelting of metapelite and metapsammite of the paleoproterozoic metamorphic basement at temperatures of ca 800 c with low oxygen fugacity the sr nd isotopic compositions of the rocks from xitian pluton indicate that the granitic magmas were mixed with less than 10 mantle derived magmas we suggest that the xitian pluton was emplaced in an extensional tectonic setting related to release of compressional stresses within the thickened crust during the early mesozoic

pyrite and pyrrhotite textures and composition in sediments laminated quartz veins and reefs at bendigo gold mine australia insights for ore genesis the various types textures and compositional zoning of pyrite in the gold bearing saddle reefs quartz veins and surrounding sedimentary rocks provide new information on the potential source and timing of gold and arsenic and related fluid processes responsible for mineralization at bendigo nodular diagenetic pyrite in the black shale tops to sandstone turbidites is enriched in invisible gold and arsenic with mean values of 0 61 ppm au 1 300 ppm as and au ag 1 based on la icpms analyses other elements enriched in the diagenetic pyrite within the organic rich shales are mn zn mo cu v ba ag cd tl co ni bi pb and te in contrast euhedral and growth zoned hydrothermal pyrite in the turbidites and bedding parallel laminated quartz veins contains lower contents of most trace elements but has higher contents of invisible au and as especially on the outermost rim of the pyrite the gold rich pyrite rims generally become thicker a few to hundreds of microns in proximity to the gold bearing saddle reefs pyrite in the reef commonly has the highest levels of invisible au and as and the lowest levels of other trace elements it is characterized by au ag 1 and au pb 0 01 in the deepest stratigraphic levels below known productive gold reefs diagenetic pyrite in the most carbonaceous shales has been replaced by pyrrhotite during metamorphism la icpms analyses reveal that the disseminated pyrrhotite contains similar levels of ni and co to the diagenetic pyrite but is strongly depleted in as and au the spatial relationships between organic rich shales folded bedding parallel laminated quartz veins and gold arsenic bearing saddle reefs combined with the consistent trends in the trace element composition of pyrite hosted by these three geological elements is interpreted to indicate that the black shales were an initial source of au and as and the laminated quartz veins acted as the initial pathways for hydrothermal fluid flow carrying au and as from the source shales to the saddle reefs maximum gold and arsenic input into the reefs principally as free gold plus arsenopyrite occurred late during deformation toward the end of the hydrothermal cycle and is expressed by the au as rich rims to hydrothermal pyrite in the sedimentary host rocks laminated quartz veins and reefs this corresponds with final fold lockup and the development of through going fault arrays linking adjacent anticlines the source of au and as for this final and most economically important fluid flow event is considered to be from carbonaceous shales deeper in the basin where original gold bearing diagenetic arsenian pyrite reacts with organic matter and is converted to pyrrhotite with release of au as and s to the metamorphic fluid

the p v t x f o2 evolution of h2o co2 ch4 bearing fluid in a wolframite vein reconstruction from fluid inclusion studies aqueous carbonaceous and later pure aqueous fluid inclusions in quartz from a ferberite fe 95mn 05 wo4 vein within the low grade metamorphic aureole of the borne granite french massif central have been studied by microthermometry and raman spectrometry the bulk v x properties of the aqueous carbonaceous inclusions have been derived using the equation of state of heyenet al 1982 for the low temperature co2 ch4 system a p t path has been proposed for their trapping using the equations of state of jacobs and kerrick 1981a for the h2o co2 ch4 system two main episodes were reconstructed for the history of the aqueous carbonaceous fluid 1 primary h2o co2 ch4 vapourrich inclusions in quartz indicated the early circulation of a low density fluid 65 mole h2o 34 mole co2 1 mole ch4 and traces of n2 d 0 35 gcm 3 at around 550 50 c and 700 100 bar fluid cooled approximately isobarically to 450 400 c and was progressively diluted by h2o with a concomitant increase in density the fo2 of the h2oco2 ch4 fluid estimated from the equilibrium co2 2h2o ch4 2o2 first ranged from 10 22 to 10 27 bar close to the q f m buffer within analytical errors these values were consistent with the presence of graphite in equilibrium with the fluid 2 a drop in pco2 and therefore a drop in fo2 was recorded by the secondary liquid rich inclusions in quartz the inclusions formed at and below 400 c were composed of h2o and ch4 only and fo2 at that stage was below that fixed by the graphite fluid equilibrium this second episode in the fluid rock system could be explained by the drop of temperature below the blocking temperature of the graphite fluid equilibrium according to this interpretation the blocking of the graphite fluid equilibrium occurred at t 370 c and probably at 400 c on account of the pressure correction mass spectrometric data show that ferberite contains h2o co2 and ch4 in fluid inclusions which lie in the gap of the v x properties of the aqueouscarbonaceous fluid in quartz deposition of ferberite probably occurred at around 400 c the previously inferred blocking temperature resulting from either the drop in pco2 the drop fo2 and or the related ph increase it is concluded that the existence of a blocking temperature for the graphite fluid chemical equilibrium may be a critical factor for maintaining a stable fluid pressure gradient in geothermal systems occurring under greenschist facies conditions in graphite bearing rocks

la icp ms trace element analysis of pyrite from the xiaoqinling gold district china implications for ore genesis abstract the xiaoqinling district the second largest gold producing district in china is located on the southern margin of the north china craton it consists of three ore belts namely the northern ore belt the middle ore belt and the southern ore belt pyrite from the dahu gold deposit in the northern ore belt and wenyu and yinxin gold deposits in the southern ore belt were investigated using a combination of ore microscopy and in situ laser ablation inductively coupled plasma mass spectrometry la icp ms a range of trace elements was analyzed including au te ag pb bi cu co ni zn mo hg as and si the results show that there are no systematic differences between the trace element compositions of pyrite in the three deposits from different ore belts in general au concentrations in pyrite are low from 2 rich ore fluids spatial association with large scale compressional structures of the qinling orogen 18 o and d data suggestive of mixing between metamorphic and meteoric waters 34 s and pb isotopic data that point to a mixed crustal mantle source all point to typical orogenic type gold deposits high ni concentrations up to 8425 ppm of pyrite possibly linked to deep seated mafic ultramafic metamorphic rocks provide further evidence on the orogenic gold deposit affinity but against the model of a granitic derivation of the mineralizing fluid as previously suggested by some workers generally low au concentration in pyrite is also consistent with those from worldwide orogenic gold deposits therefore the gold mineralization in the xiaoqinling district is described as orogenic type and is probably related to indosinian collision between the north china craton and the yangtze craton

in situ raman spectroscopic investigation of the hydrothermal speciation of tungsten implications for the ore forming process abstract knowledge on hydrothermal tungsten w species is vital towards a better understanding of tungsten transport and mineralization mechanisms in this study in situ raman spectra of a 0 005 0 1 mol kg m k2wo4 solution containing co2 hcl and nahco3 were collected at 50 400 c and 20 60 mpa the spectra for the symmetric stretching vibration mode of the w o bond v1 w o were analyzed to investigate the hydrothermal tungstate species results showed that carbonate bicarbonate do not associate with tungstate to form carbonic tungstate species nevertheless the presence of co2 can increase the fluid acidity which favors the formation of polymeric tungstate species at o modes of these species are centered at 930 cm 1 and 950 cm 1 based on the above observations we simulated the mineralization process in the context of fluid rock interactions using tungstate and alkali tungstate ion pairs as the only aqueous w species the thermodynamic simulations showed that a the timing of mineralization mainly depends on the w concentration in the initial mineralizing fluid and the availability of ca2 fe2 and mn2 with higher w concentrations generally favoring higher temperature mineralization b highly w enriched fluid is not essential for w mineralization while extremely low contents of fe mn and ca in the magma are useful to maintain the mobility of aqueous w until favorable host rocks are encountered and c a hydrogen reservoir effect was identified for dissolved co2 the presence of co2 can promote the extraction of fe ii from the pelitic host rocks thereby facilitating a high grade vein type w mineralization at o modes are centered at 965 995 cm 1 are important hydrothermal w species along with monomeric tungstates therefore polymeric tungstate species should be considered in future thermodynamic modeling of w transport and mineralization at

fluid evolution in the w cu zn pb san cristobal vein peru fluid inclusion and stable isotope evidence abstract the zn pb ag cu san cristobal district is located 100 km east of lima in the western cordillera of peru it is centred around the chumpe intrusion and is composed of vein and carbonate replacement ore types the main san cristobal vein presents a paragenesis that can be divided into three stages a an early wolframite quartz pyrite stage b a quartz base metal stage and c a late quartz carbonate barite stage fluid inclusions in quartz from the tungsten stage are biphase lv at room temperature and homogenise to the liquid phase between 146 and 257 c their salinities range between 2 1 and 5 1 wt nacl equiv rare inclusions contain an additional crystal of halite and have salinities of 46 54 wt nacl equiv data of the first two stages show a decrease in homogenisation temperatures concomitant with a salinity decline fluid inclusions in quartz from the late stage homogenise at higher temperatures between 252 and 323 c with salinities ranging between 4 6 and 6 7 wt nacl equiv hydrogen and oxygen isotope data indicate a two stage evolution isotopic compositions of the fluid associated with the first two stages define a trend with constant 18 o values and decreasing d values 18 o 3 2 to 5 0 v smow and d 60 to 112 v smow which is interpreted as mixing of a dominantly magmatic component with minor meteoric water that had equilibrated with the host rocks this interpretation is supported by sulphur and lead isotopic data from previous studies by contrast the quartz carbonate barite stage bears isotopic characteristics defining a trend with a coupled decrease of 18 o and d 18 o 8 1 to 2 5 v smow and d 57 to 91 v smow and is explained by addition of meteoric water to the system and subsequent mixing with a less important magmatic component different fluid origins are confirmed by laser ablation icp ms analyses of the triphase lvh and biphase lv primary inclusions the concentrations of the major ore elements i e w cu zn and pb decrease throughout the paragenesis w and to a lesser extent cu show significant variations associated with a steep decrease in their concentration the decreasing concentrations can be explained by mineral deposition and dilution by the meteoric fluid differences in the rate of decrease indicate selective precipitation of w fluid inclusions of the quartz carbonate stages show an abrupt increase in ba and sr concentrations this is interpreted to reflect a higher volume of host rock silicate alteration probably due to the increasing size of the fluid flow cell and is explained by the input of a third fluid of unknown origin la icp ms analyses show that the fluids were already depleted in w and cu before reaching the emplacement of carbonate replacement ore type whereas zn and pb were still present in considerable amounts this is again due to selective precipitation and is consistent with the interpretation that the economically interesting metals were dominantly introduced by magmatic fluids

direct dating of hydrothermal tungsten mineralization using in situ wolframite u pb chronology by laser ablation icp ms abstract the wolframite series may contain relatively high u and low common pb contents and thus has been used for direct u pb dating of hydrothermal w mineralization in this paper we present in situ laser ablation inductively coupled plasma mass spectrometry la icpms analysis of u pb isotopes and trace elements of wolframite crystals from the giant yaogangxian and piaotang w deposits in the extensive nanling metallogenic belt south china the objective of this work is to directly constrain the timing of hydrothermal w mineralization in these two deposits wolframite crystals from both deposits show textural evidence for two generations early wolframite wol 1 has higher fe and lower mn contents relative to those in the late wolframite wol 2 uranium is correlated positively with nb5 tetravalent ti sn zr hf and trivalent sc v y rees cations in all wolframite samples suggesting that the incorporation of u into wolframite is controlled by the coupled substitution mechanisms the early and late wolframite domains from the yaogangxian deposit yielded u pb ages of 159 1 2 0 ma 2 mswd 0 7 and 153 7 0 7 ma 2 mswd 0 5 respectively similarly two wolframite generations from the piaotang deposits yielded u pb ages of 159 5 1 3 ma 2 mswd 0 3 and 152 1 0 9 ma 2 mswd 0 5 the obtained u pb ages confirm two successive episodes of hydrothermal w mineralization at 159 ma and 153 ma in the yaogangxian and piaotang deposits this study demonstrates the potential of u pb dating of wolframite by la icpms and highlights its importance for directly dating hydrothermal ore forming processes

distal relationship of the taihexian pb zn au deposit to the dengfuxian magmatic hydrothermal system south china constraints from mineralogy fluid inclusion h o pb and in situ s isotopes abstract the taihexian pb zn au vein style deposit is located in the well preserved dengfuxian magmatic hydrothermal w sn ore field south china the deposit can be divided into three mineralization stages i pyrite arsenopyrite chalcopyrite gold tourmaline quartz stage ii pyrite arsenopyrite chalcopyrite sphalerite galena quartz stage and iii pyrite galena sphalerite quartz calcite fluorite stage liquid rich nacl aqueous inclusions vapor rich nacl aqueous inclusions co2 rich inclusions and three phase co2 h2o inclusions occur in quartz and calcite of the ore veins at taihexian the ore veins of the three stages formed at around 310 c 210 c and 170 c respectively precipitated from h2o nacl co2 ch4 fluids with salinities averaging around 5 wt nacl eq the ore forming mechanisms include fluid immiscibility a potential trigger for metal precipitation from hydrothermal fluids during stage i fluid mixing during stage ii and cooling during stage iii oxygen 18ofluid 1 5 6 9 and hydrogen dfluid 61 to 53 isotopes suggest that the ore forming fluids originated from a mixture of magmatic water with ground water and or meteoric water sulfur isotopes 34s 7 8 3 1 suggest a magmatic origin for sulfur in stages i and ii and then possibly mixing with sulfur from sedimentary rocks in stage iii lead isotopes 206pb 204pb 18 05 18 65 207pb 204pb 15 53 15 75 208pb 204pb 37 91 38 88 indicate that ore metals originated mainly from the upper crust with minor mantle contributions comparing arsenopyrite sulfur isotope and fluid inclusion geothermometers it is estimated that the ore formation pressure was about 58 120 mpa corresponding to a depth of approximately 2 2 4 5 km taihexian appears to form part of a regional magmatic hydrothermal system centered on the dengfuxian pluton