intraplate extension prior to continental extrusion along the ailao shan red river shear zone left lateral movement of the ailao shan red river shear zone lends support to the hypothesis of continental extrusion resulting from the collision of india with asia our new observations from northwestern yunnan china and northwestern vietnam on different sides of the shear zone demonstrate that the sinistral offset was 600 km according to correlations of permian triassic flood basalt successions and late paleogene highly potassic mafic magmas we conclude that the shear was propagating on the south china continental margin and does not correspond to a suture between south china and indochina furthermore the highly potassic magmas were emplaced from ca 40 to 30 ma before the shear movement which was caused by the late oligocene to early miocene ca 27 22 ma extrusion activity this suggests that a late eocene to early oligocene intraplate extension possibly induced by delamination of thickened continental lithosphere took place in northwestern yunnan or eastern tibet as a response to the india asia collision this extension and sea floor spreading of the south china sea that began ca 30 ma could have accounted for the initiation of the ailao shan red river shear zone

origin of the ore forming fluids of the tongchang porphyry cu mo deposit in the jinshajiang red river alkaline igneous belt sw china constraints from he ar and s isotopes abstract the jinshajiang red river alkaline igneous belt with abundant cu mo au mineralization in the eastern indian asian collision zone is an important cenozoic magmatic belt formed under an intra continental strike slip system in southwestern sw china the tongchang deposit is a representative porphyry cu mo deposit in southern segment of the jinshajiang red river alkaline igneous belt with 8621 t cu 1 24 wt and 17 060 t mo 0 218 wt in this study he ar and s isotopic compositions of the tongchang deposit were determined he and ar isotopic compositions suggest that the ore forming fluids with 3he 4he ratios varying from 0 17 to 1 50 ra and 40ar 36ar ratios from 299 1 to 347 3 for the deposit are a mixture between a crust derived fluid masw with near atmospheric ar and crustal he and a mantle derived fluid however the 34s values of the hydrothermal pyrite samples ranging from 1 0 to 1 5 with an average of 1 2 indicate that the sulfur in the ore forming fluids of the tongchang deposit was primarily derived from the magma or indirectly mantle derived without assimilation of crustal sulfur in combination with previously published he and ar isotopic data of the yulong and machangqing deposits in northern and central segments of the jinshajiang red river alkaline igneous belt respectively the ore forming fluids of the yulong and machangqing deposits are obviously richer in 3he and 40ar and poorer in 36ar in comparison with the tongchang deposit implying that more mantle derived fluids were involved in the ore forming fluids of the yulong and machangqing deposits than those for the tongchang deposit this might be one of the most important factors producing larger scales of mineralization in the yulong and machangqing deposits than the tongchang deposit

mantle derived noble gases in ore forming fluids of the granite related yaogangxian tungsten deposit southeastern china more than 90 of the tungsten resources of china are in the nanling region of south china and the yaogangxian vein deposit is the largest tungsten deposit in this region the tungsten deposits have ages of 150 160 ma and are spatially temporally and genetically related to granites which were previously believed to be produced by crustal anatexis this paper provides he and ar isotope data of fluid inclusions in pyrite and arsenopyrite from the yaogangxian w veins 3he 4he ratios range from 0 41 to 3 03 ra where ra is the 3he 4he ratio of air 1 39 10 6 and 40ar 36ar ratios from 328 to 1 191 moreover there are excellent correlations between he and ar isotopic compositions the results suggest that the ore forming fluids are a mixture between a crustal fluid containing atmospheric ar and crustal 4he and a fluid containing mantle components it is likely that the former is a low temperature meteoric fluid and the later is a fluid exsolved from the w associated granitic magma which formed by crustal melting induced by intrusion of a mantle derived magma

different proportion of mantle derived noble gases in the cu fe and fe skarn deposits he ar isotopic constraint in the edong district eastern china abstract cu and fe skarns are two economically important types of skarn deposit worldwide but the critical factors controlling the difference in metal associations remain enigmatic the edong ore district china presents an excellent opportunity to study the differences between cu fe and fe skarn deposits we have measured he ar isotopes trapped in fluid released by crushing pyrite and chalcopyrite from four well known cu fe and fe deposits in the edong district eastern china with the aim of constraining their different fluid source and then discussing the factors controlling their variations between cu fe and fe skarns he ar isotopic compositions are markedly different between the cu fe and fe skarn deposits in the edong district 3he 4he ratios in the cu fe deposits are 0 75 1 87 ra and 40ar 36ar ratios are 300 472 by contrast he ar isotopic compositions in minerals from the fe deposits have lower 3he 4he and 40ar 36ar ratios of 0 08 0 93 ra and 299 361 respectively these results suggest that noble gas of the cu fe and fe skarn deposits in the edong district formed by variable degrees of mixing between a magmatic fluid containing a mantle component and modified air saturated water masw importantly he ar isotope data provide compelling evidence that contrasting fluid sources were involved in the formation of the cu fe and fe deposits i e mineralizing fluids of the cu fe deposits could have a greater contribution from mantle component and little involvement of masw than those of the fe deposits in the edong district this conclusion is consistent with obvious differences in the nature of the intrusions related to mineralization as well as sulfur isotopic compositions of sulfides in the cu fe and fe deposits it is most likely that different proportion of mantle derived noble gases play an essential role in controlling differences between the cu fe and fe skarn deposits

timing of tibetan uplift constrained by analysis of volcanic rocks the tibetan plateau has had a central role in the development of recent models for the mechanics of mountain belts1 2 and cenozoic global climate change3 the present elevation and extensional deformation of the plateau probably result from uplift owing to convective thinning of the underlying lithospheric mantle1 2 an age for the uplift would provide a valuable constraint on these models but because recently proposed indicators of uplift are all climate dependent they are equivocal possibly reflecting global cooling rather than regional uplift4 here we present new geochemical data on post mid miocene lavas from the plateau which show that the lavas were derived from the lithospheric mantle simple thermal arguments indicate that the generation of such magmas also necessitates thinning of the lithospheric mantle thus volcanism is coincident with uplift providing a climate independent means of dating the onset of uplift dating by the laser 40ar 39ar technique places the beginning of this volcanism and therefore the time of uplift of the tibetan plateau at 13 myr ago

he ar and s isotopic constraints on the relationship between a type granites and tin mineralization a case study of tin deposits in the tengchong lianghe tin belt southwest china abstract the tengchong lianghe tin belt in western yunnan province southwest china is the most important tin mineralization belt in the sanjiang tethyan metallogenic domain stmd there are two large tin deposits in this belt the paleogene lailishan and the late cretaceous xiaolonghe deposits the two deposits are spatially and temporally associated with the lailishan and xiaolonghe granitic plutons respectively recent studies suggest that the lailishan and xiaolonghe granitic plutons exhibit most of the mineralogical and geochemical characteristics of a type granites in this study we discuss the he ar and s isotopes of pyrite samples from the two large tin deposits to trace ore forming fluids and elements we also review the relationship between a type granites and tin deposits from a new perspective the 34scdt values of the lailishan tin deposit range from 4 9 to 6 7 with an average value of 5 53 the 34scdt values of the xiaolonghe tin deposit range from 5 0 to 8 1 with an average value of 6 33 these values are slightly higher than those of the granites 0 to 5 7 in the tengchong lianghe area indicating mainly magmatic sources for the sulfur of ore forming fluids with a small amount of s from the wall rocks the lailishan tin deposit has 3he 4he values of 1 57 3 46 ra with an average value of 2 078 ra and 40ar 36ar values of 382 00 622 99 with an average value of 459 67 the xiaolonghe tin deposit has 3he 4he values of 0 53 0 88 ra with an average value of 0 686 ra and 40ar 36ar values of 301 06 348 43 with an average value of 322 04 these values suggest that ore forming fluids of the lailishan and xiaolonghe tin deposits have mixed crustal mantle and a small volume of meteoric water sources in different proportions the mantle 4he values and 3he 4he values of the lailihsan tin deposit 26 44 1 57 3 46 ra are markedly higher than those of the xiaolonghe tin deposit 8 15 0 53 0 88 ra implying increased crust mantle interaction in the paleogene relative to the late cretaceous in western yunnan this interaction may be attributed to the upwelling of the asthenosphere through the break off of the neo tethyan slab during the main collisional period 65 41 ma of india asia

porphyry cu mo au deposits related to melting of thickened mafic lower crust examples from the eastern tethyan metallogenic domain abstract most porphyry cu deposits in the world occur in magmatic arc settings and are formed in association with calc alkaline arc magmas related to subduction of oceanic lithosphere this contribution reviews a number of significant porphyry cu deposits in the eastern tethyan metallogenic domain they widely occur in a variety of non arc settings varying from post late collisional transpressional and extensional environments to intracontinental extensional environments related to orogenic and anorogenic processes their spatial temporal localization is controlled by strike slip faults orogen transverse normal faults lineaments and their intersections in these non arc settings these deposits are dominated by porphyry cu mo deposits with minor porphyry cu au and epithermal au deposits and exhibit a broad similarity with those in magmatic arcs the associated magmas are generally hydrous relatively high fo2 high k calc alkaline and shoshonitic and show geochemical affinity with adakites they are distinguished from arc magmas and or oceanic slab derived adakites by their occurrence as isolated complexes high k2o contents 1 2 8 5 and much wider range of end t values 10 to 3 and positive ehf t values 4 6 to 6 9 these potassic magmas are most likely formed by partial melting of thickened juvenile mafic lower crust or delaminated lower crust but also involving various amounts of asthenospheric mantle components key factors that generate hydrous fertile magmas are most likely crust mantle interaction processes at the base of thickened lower crust in non arc settings rather than oceanic slab dehydration as in arc settings breakdown of amphibole in thickened lower crust e g amphibole eclogite and garnet amphibolite during melting is considered to release fluids into the fertile magmas leading to an elevated oxidation state and higher h2o content necessary for development of porphyry cu mo au systems copper and au in hydrous magmas are likely derived from mantle derived components and or melts which either previously underplated and infiltrated at the base of the thickened lower crust or were input into the primitive magmas by melt mantle interaction in contrast mo and part of the s in the fertile magmas are probably supplied by old crust during melting and subsequent ascent

structural petrological and thermal evolution of a tertiary ductile strike slip shear zone diancang shan yunnan the diancang shan a horst massif within the red river fault zone in yunnan people s republic of china preserves a structural petrological and thermal record of two distinct phases of tectonic activity a left lateral ductile shear that terminated between 20 and 17 ma and a ductile to brittle phase of normal faulting which began at 4 7 ma and remains active mylonitic rocks in the core of the range display an early steep high temperature ht schistosity and a horizontal stretching lineation that are both parallel to the trend of the belt kinematic indicators indicate that shear was left lateral the complex shape of the ht schistosity at the southern termination of the massif likely results from a large scale oblique left lateral c shear plane that dismembered the shear zone and separated the ailao shan and the diancang shan as left lateral deformation terminated thermochronological and thermobarometric results suggest that the gneisses were partially unroofed during this event along the eastern edge of the diancang shan the ht fabrics were overprinted by low temperature structures during activation of east dipping normal faults cooling associated with this normal right lateral faulting along the diancang shan and perhaps activation of the right lateral normal movement on the range front fault farther south along the ailao shan began at 4 7 0 1 ma these results tend to support the view that extrusion of indochina occurred along the left lateral red river shear zone between 35 and 19 17 ma initiation of right lateral normal slip during the late miocene may relate to eastward extensional collapse of the thickened tibetan crust or more probably to initiation of the second phase of extrusion

petrographic and stable isotopic evidences of co2 induced alterations in sandstones in the lishui sag east china sea basin china abstract dawsonite bearing sandstones in the lishui sag east china sea basin china have been investigated as a natural occurrence for co2 induced diagenesis using petrography x ray diffraction and stable isotopes the sandstones are predominantly litharenite with the order of cements growth comprising clay coatings and pyrite siderite pyrite quartz overgrowths ankerite kaolinite and microcrystalline quartz dawsonite and late calcite dawsonite which has recently been considered as trapping mineral after massive co2 charging constituted up to 7 of the whole rock volume occurring as pore filling clusters or replacement of detrital grains stable isotopic data suggest that the co2 in equilibrium with dawsonite and calcite display a mantle magmatic origin and is in close proximity to those of the co2 gas now present in the reservoir indicating the same origin for both the elevated co2 concentrations induced by a mass influx of magmatic co2 into host rock was favourable for dawsonite cementation plagioclase was then considered as the precursor of dawsonite k feldspar could also serve as the aluminum source of dawsonite with an external supply of na in a geochemically open system

the transition from porphyry to epithermal style gold mineralization at ladolam lihir island papua new guinea a reconnaissance study the exceptionally large gold resource at ladolam 1 300 metric tons of gold lihir island resulted from the transition of an early stage low grade porphyry gold system to a low sulfidation epithermal gold event this transition was probably triggered by rapid decompression during the partial slope failure of luise stratovolcano and accompanied by the ingress of seawater the original porphyry stage is indicated by remnant hydrothermal breccia clasts of strongly biotite magnetite altered monzodiorite with disseminated pyrite chalcopyrite and poorly developed pyrite quartz stockwork veins the breccias are overprinted by biotite magnetite alteration and their matrix is strongly mineralized with disseminated auriferous pyrite the breccias are cut by late stage epithermal quartz chalcedony illite adularia pyrite veins and associated illite adularia alteration that locally contain bonanza gold grades of up to 120 g t isotope data suggest a magmatic source of sulfur in the gold bearing fluids at ladolam electronic supplementary material to this paper can be obtained by using the springer link server located at http dx doi org 10 1007 s00126 001 0230 y

sanjiang tethyan metallogenesis in s w china tectonic setting metallogenic epochs and deposit types abstract tectonically the sanjiang tethyan metallogenic domain stmd is located within the eastern himalayan tibetan orogen in the sanjiang tethys southwestern china although this metallogenic domain was initiated in the early palaeozoic extensive metallogenesis occurred in the late palaeozoic late triassic and himalayan tertiary epochs corresponding tectonic settings and environments in the domain are an arc basin system related to the subduction of the palaeo tethyan oceanic slabs a post collision crustal extension setting caused by the lithospheric delamination or slab breakoff underneath the sanjiang tethys during the late triassic large scale strike slip faulting and thrusting systems due to the indo asian continent collision since the palaeocene in this metallogenic domain important gold copper base metals rare metals and tin ore belts incorporating a large number of giant deposits were developed the main types of deposits include 1 porphyry copper deposits controlled by a large scale strike slip fault system 2 vhms deposits mainly occurring in intra arc rift basins and post collision crustal extensional basins 3 shear zone type gold deposits in the ophiolitic melange zone along the thrusting shearing system 4 hydrothermal silver polymetallic deposits in the triassic intra continental rift basins and tertiary strike slip pull apart basins and 5 himalayan granite related greisen type tin and rare metallic deposits within the metallogenic epochs of the late palaeozoic to cenozoic the styles and types of the ore deposits changed from vhms types in the late palaeozoic through exhalative sedimentary type deposits in the late triassic to porphyry type copper deposits shear zone type gold deposits hydrothermal vein type silver polymetallic deposits greisen type tin and rare metal deposits in the cenozoic correspondingly ore forming metals also changed from a pb zn cu ag association through ag cu pb zn fe ag pb and ag au hg associations to ag cu pb zn cu mo au sn and li rb cs nb zr hf y ce sc associations

contribution of mantle components within juvenile lower crust to collisional zone porphyry cu systems in tibet most porphyry cu mo au deposits are found in magmatic arcs worldwide and are associated with hydrous high fo2 calc alkaline magmas derived from a mantle wedge that was metasomatized by the fluids from a subducted oceanic slab recently such deposits have been documented as occurring widely in collisional settings where they are associated with potassic magmas generated during the collisional process but the genesis of the fertile magmas and the mechanism of metallic enrichment remain controversial here we present new geochemical and sr nd hf isotopic data from the post collisional fertile and barren porphyries of the miocene gangdese porphyry belt in the tibetan orogen an orogen formed by the collision of india and asia in the early cenozoic both types of porphyry are characterized by high k2o contents and have geochemical affinities with adakite but the fertile magmas were most likely derived from the melting of a thickened juvenile mafic lower crust formed by the underplating of earlier asthenospheric melts at the base of crust whereas the derivation of the barren magmas involved variable amounts of old lower crust in tibet the melting of sulfide bearing phases in the juvenile mantle components of the tibetan lower crust probably provided cu au and s to the fertile magmas the breakdown of amphibole during melting at the source released the fluids necessary for the formation of the porphyry cu deposits in tibet the thickened crust up to 70 80 km due to collision is thought to be responsible for a decrease in the fo2 of the fertile magmas during their ascent to the upper crust thus preventing the generation of more porphyry cu au and epithermal au deposits in this collisional zone

himalayan cu mo au mineralization in the eastern indo asian collision zone constraints from re os dating of molybdenite we present new re os molybdenite age data on three porphyry cu mo au deposits yulong machangqing and xifanping these deposits are associated with the himalayan adakitic magmatism that occurred in a continental collision environment controlled by large scale cenozoic strike slip faults in the eastern indo asian collision zone three distinct episodes of cu mo au mineralization are recognized at yulong re os isotopic data of four molybdenite samples from sulfide quartz veins in the quartz sericite alteration zone yield an isochron with an age of 40 1 1 8 ma 2 coincident to a zircon sensitive high mass resolution ion microprobe shrimp age of 40 9 0 1 ma for the host monzogranite the molybdenite re os dates together with k ar rb sr u pb and 40ar 39ar dates on the pre and intra ore porphyries suggest that cu mo au mineralization formed during the late stage 40 ma of regional porphyry magmatism but hydrothermal activity probably lasted to at least 36 ma at machangqing molybdenite re os data from the k silicate and quartz sericite alteration zones yield an isochron with an age of 35 8 1 6 ma 2 which is identical to the zircon shrimp and bulk rock rb sr ages 35 36 ma of the host granite but older than bulk rock k ar dates 31 32 ma for associated au bearing quartz syenite with advanced argillic alteration at xifanping five molybdenite samples from the k silicate alteration zone yield the youngest re os isochron age in the area at 32 1 1 6 ma 2 the re os molybdenite dates here are younger than k ar ages 33 5 34 6 for hydrothermal biotite and actinolite there is a positive correlation between the absolute age of the deposits and their cu and au reserves in the eastern indo asian collisional zone episodic stress relaxation probably caused multiple magmatic intrusions which most likely resulted in three episodes of cu mo au mineralization in the eastern indo asian collision zone

new constraints on the structure thermochronology and timing of the ailao shan red river shear zone se asia new structural petrographic and 40ar 39ar data constrain the kinematics of the asrr ailao shan red river shear zone in the xuelong shan xls geochronological data reveal triassic early tertiary and oligo miocene thermal events the latter event 33 26 ma corresponds to cooling during left lateral shear in the fansipan fsp range thrusting of the sapa nappe linked to left lateral deformation and cooling of the fsp granite occurred at 35 ma rapid cooling resumed at 25 29 ma as a result of uplift within the transtensive asrr in the daynuiconvoi dncv foliation trends nw se but is deflected near large scale shear planes stretching lineation is nearly horizontal on steep foliations shear criteria indicate left lateral shear sense zones with flatter foliations show compatible shear senses petrographic data indicate decompression from 6 5 kbar during left lateral shear temperatures 700 c 40ar 39ar data imply rapid cooling from above 350 c to below 150 c between 25 and 22 ma without diachronism along strike along the whole asrr cooling histories show two main episodes 1 rapid cooling from peak metamorphism during left lateral shear 2 rapid cooling from greenschist conditions during right lateral reactivation of the asrr in the nw part of the asrr xls diancang shan we link rapid cooling 1 to local denudations in a transpressive environment in the sw part ailao shan and dncv cooling 1 resulted from regional denudation by zipper like tectonics in a transtensive regime the induced cooling diachronism observed in the ailao shan suggests left lateral rates of 4 to 5 cm yr from 27 ma until 17 ma dncv rocks always stayed in a transtensive regime and do not show cooling diachronism the similarities of deformation kinematics along the asrr and in the south china sea confirms the causal link between continental strike slip faulting and marginal basin opening

helium and argon isotope geochemistry of alkaline intrusion associated gold and copper deposits along the red river jinshajiang fault belt sw china abstract the red river jinshajiang strike slip fault zone on the eastern margin of the tibetan plateau was originally produced by the india eurasia collision 60 70 myr ago numerous post collisional mantle derived alkaline igneous rocks with ages of 40 30 ma have been intruded along this fault zone in recent years several copper and gold deposits associated with the alkaline intrusions of this region were discovered such as the yao an and beiya gold deposits and the yulong and machangqing copper deposits studied in this paper the mineralised intrusions are felsic with sio 2 ranging from 61 4 to 67 7 wt k 2 o na 2 o from 8 1 to 11 5 wt and k 2 o na 2 o 1 the deposits are located at both the exo and endo contact zones of the intrusions the mineral deposits are of hydrothermal origin with the ore forming temperatures mainly in the range 150 450 c this paper presents he and ar isotope analyses of these four deposits the concentrations of 4 he trapped in fluid inclusions of pyrites from the ores are 0 7 54 1 10 6 cm 3 stp g 1 and those of 40 ar are 0 6 7 3 10 6 cm 3 stp g 1 3 he 4 he ratios are 0 3 2 5 ra ra represents the 3 he 4 he ratio of air 1 39 10 6 40 ar 36 ar ratios are 316 1736 and 3 he 36 ar ratios are 0 2 11 2 10 3 generally the 3 he 4 he 40 ar 36 ar and 3 he 36 ar ratios for the gold deposits are higher than those for the copper deposits we suggest that the ore forming fluids of both gold and copper deposits were differentiated from the mantle derived alkaline magmas but were diluted by modified air saturated water masw that experienced intensive interaction with crustal rocks however the magmatic fluids responsible for the gold deposits were less extensively diluted by masw resulting in higher 3 he 4 he 40 ar 36 ar and 3 he 36 ar ratios than the copper deposits

mantle derived helium in two peruvian hydrothermal ore deposits strong differences exist between the helium isotopic compositions of mantle derived magmas1 8 axial vent hotspring fluids9 14 subduction related magmas15 20 and many associated hot springs21 24 and the atmospheric and crustal values fig 1 here we report helium isotope ratios for two late tertiary fossil hydrothermal systems responsible for precious metal base metal and tungsten mineralization and compare them to those of circum pacific hot spring emanations the 3he 4he ratios of inclusion fluids hosted by gangue and sulphide minerals from casapalca and pasto bueno peru all lie between two and three times the atmospheric value indicating the presence of a dilute component of mantle helium consistent with previously reported stable isotope evidence for the presence of magmatic fluids during mineralization25 27 although post trapping modification of the helium isotope composition is possible we suggest that these apparently low values represent the composition of helium inherited from contributing magmas as a tracer of magmatic fluids in hydrothermal systems helium isotopes are decoupled from the factors that govern other stable isotope signatures

single crystal 40ar 39ar dating of pyrite no fool s clock single crystals of dispersed trace pyrite from two igneous rocks were dated by using the 40 ar 39 ar laser probe method and the resulting ages were compared to step heating ages of associated amphibole and phlogopite the isochron ages for 0 1 0 3 mm cubes of pyrite agree well with the respective amphibole ages of these igneous samples preliminary step heating analyses of single pyrite crystals yield internal isochrons with indistinguishable although less precise ages both pyrite and amphibole are significantly older than associated phlogopite in one sample which has undergone postcrystallization alteration these results suggest that pyrite can give reliable and precise 40 ar 39 ar ages even in the presence of subsequent alteration given the ubiquity of pyrite in many geologic environments this technique has great promise for application to the dating of ores sediments and hydrocarbon migration all of which have been very difficult to date directly

helium neon and argon systematics of the european subcontinental mantle implications for its geochemical evolution in this study we present a comprehensive noble gas study of mantle xenoliths from various european cenozoic volcanic provinces the main body of samples is from the massif central france and the eifel germany smaller subsets of samples are from spitsbergen and the graz basin austria in all the helium neon and argon isotopic abundances of a total of forty five mantle xenoliths phenocrysts and xenocrysts were determined the 3he 4he ratios within each volcanic province are very uniform irrespective of the diverse lithologies and p t conditions which are represented by our sample suite mean 3he 4he ratios of the massif central eifel spitsbergen and kapfenstein are 6 53 25 6 03 14 6 65 25 and 6 1 7 1 times the atmospheric ratio ra respectively the strontium and neodymium isotopic composition of some of the cpx separates are highly variable and therefore in contrast to the uniform he signature we thus conclude that he and probably also the other noble gases in the xenoliths are effectively decoupled from the non volatile elements therefore the he signature that is preserved in the xenoliths is actually that of their host magmas published strontium neodymium and lead isotope data of the unevolved host magmas of the xenoliths correlate well with our xenolith he data the position of the fields of the investigated volcanic provinces in hesr hend and hepb variation diagrams depict ternary mixtures between dmm em himu endmembers as the source the host magmas and their volatiles the neon isotopic composition of the gases released from the xenoliths is in most cases atmospheric and probably reflects atmospheric contamination only a few samples reveal indications for morb type ne or evidence of mass fractionation the 40ar 36ar ratios of the xenoliths are mostly radiogenic with the highest ratio being 17 000 however all samples have suffered a certain degree of atmospheric contamination we calculate that the uncontaminated 40ar 36ar ratio of the european subcontinental mantle is 30 000 the4he 40ar ratios have been fractionated since with values around 0 25 they are below both the current production ratio and the morb ratio they cannot be explained by atmospheric contamination as the samples with high 40ar 36ar ratios also have low 4he 40ar ratios helium and ar were probably fractionated during initial closed system degassing of the host magma we calculate the original unfractionated 4he 40ar ratios of the massif central and eifel magma source which are 2 56 18 and 2 71 17 respectively the noble gas systematics are compatible with the notion that addition of crustal material has modified a former morb source signature we use our mean 3he 4 he ratios and reconstructed 4he 40ar ratios to model the time and degree of contamination of a morb like source with crustal material combining our model with evidence from published oxygen strontium neodymium and lead isotope data we judge that the source of the massif central and eifel magmas became enriched in k u and th shortly prior or during the variscan orogeny pre collisional collisional in this case the enrichment in these elements is therefore most probably related to subduction of crustal material in a destructive continental margin setting

insights into the formation of the dasuji porphyry mo deposit north china craton gained from mineral chemistry data abstract the dasuji mo deposit is located within the northern margin of the north china craton based on vein cross cutting relationships mineral assemblages and alteration characteristics the formation of the deposit can be divided into four stages stage 1 consisting of two vein types developed in deep is characterized by k feldspathization with minor molybdenum mineralization stage 2 containing four distinct vein types is the main stage of molybdenum mineralization accompanied by sericitization and silicification stage 3 is involved in lead zinc mineralization associating with carbonatization and fluorination and stage 4 is characterized by no mineralization this paper presents new mineral magnetite rutile molybdenite and pyrite chemistry data that provide new insights into the formation of this deposit the magnetites within veins in the deposit have chemical compositions that are indicative of a magmatic origin suggesting that these magnetites hosted in quartz were captured from syn mineralization granites in the area molybdenite w pb zn and cu concentrations increase with the decreasing temperature of formation suggesting the initiation of w pb zn and cu precipitation at the end of the second stage of mineralization the stage 3 pyrite within the deposit contains the highest concentrations of pb zn and cu consistent with the pb zn cu mineralization that formed during this stage the majority of the f ion deposition occurred at the end of stage 3 and the fluids associated with stage 4 were meteoric water dominated

some metallogenic features of gold and copper deposits related to alkaline rocks and consequences for exploration porphyry copper gold skarn copper gold sediment hosted carlin style gold breccia pipe low sulphidation epithermal gold pluton related mesothermal or orogenic gold vein and volcanogenic massive sulphide deposits associated with alkaline rocks are commonly broadly similar to those hosted by their calc alkaline counterparts in contrast porphyry molybdenum gold deposits are confined to alkaline igneous centres alkaline suites are notably deficient in high sulphidation epithermal gold deposits and even in the advanced argillic lithocaps which host them this is surprising given that the required oxidised sulphur species are seemingly more abundant than in calc alkaline igneous centres highly efficient buffering of acidic fluid by metasomatised alkaline rocks may offer a viable explanation all types of intrusion related zinc deposits also appear to be poorly developed in alkaline provinces the characteristics of several gold and copper deposits associated with alkaline rocks including the giant porgera cripple creek ladolam olympic dam and phalaborwa examples are judged to diverge appreciably from their most closely related deposit types rendering them arguably unique most of these aberrant mineralisation styles may be due to variations in magmatic fluid compositional and liberation characteristics consequent upon the extreme diversity of ore related alkaline magmas most types of gold and copper deposits developed in calc alkaline provinces also constitute exploration targets in and around alkaline igneous centres although porphyry copper gold and low sulphidation epithermal gold deposits are considered to possess the greatest potential perhaps of even greater interest however is the possibility of encountering unconventional giant gold and copper deposits which lack closely analogous examples if already defined aberrant deposits are truly unique then exploration designed specifically to detect additional examples is pointless furthermore exploration for new unique deposits is difficult because their defining geological parameters are unknown alkaline rocks within or behind calc alkaline arcs at convergent plate boundaries probably offer the greatest exploration potential although anorogenic intracontinental extensional settings should not be ignored

mantle derived gaseous components in ore forming fluids of the xiangshan uranium deposit jiangxi province china evidence from he ar and c isotopes abstract the xiangshan u deposit the largest hydrothermal u deposit in china is hosted in late jurassic felsic volcanic rocks although the u mineralization post dates the volcanics by at least 20 ma the mineralization coincides with intrusion of local mantle derived mafic dykes formed during cretaceous crustal extension in south china ore forming fluids are rich in co 2 and u in the fluid is thought to have been dissolved in the form of uo 2 co 3 2 2 and uo 2 co 3 3 4 complexes this paper provides he and ar isotope data of fluid inclusions in pyrites and c isotope data of calcites associated with u mineralization pitchblende in the xiangshan u deposit he isotopic compositions range between 0 1 and 2 0ra where ra is the 3 he 4 he ratio of air 1 39 10 6 and correlates with 40 ar 36 ar although there is potential for significant 3 he production via 6 li n 3 h 3 he reactions in a u deposit due to abundant neutrons nucleogenic production cannot account for either the 3 he concentration in these fluids nor the correlations between he and ar isotopic compositions it is more likely that the high 3 he 4 he ratios represent trapped mantle derived gases a mantle origin for the volatiles of xiangshan is consistent with the 13 c values of calcites which vary from 3 5 to 7 7 overlapping the range of mantle co 2 the he ar and co 2 characteristics of the ore forming fluids responsible for the deposit are consistent with mixing between 3 he and co 2 rich mantle derived fluids and co 2 poor meteoric fluids these fluids were likely produced during cretaceous extension and dyke intrusion which permitted mantle derived co 2 to migrate upward and remobilize u from the acid volcanic source rocks resulting in the formation of the u deposit subsequent decay of u within the fluid inclusions has reduced the 3 he 4 he ratio and variations in u 3 he result in the range in 3 he 4 he observed with u 3 he ratios in the range 5 17 10 3 likely corresponding to u concentrations in the fluids

intraplate tectonics in asia a precise age for large scale miocene movement along the ailao shan red river shear zone china tertiary left lateral movement along the 1000 km long ailao shan red river shear zone appears to have played an important role in absorbing post collisional northward penetration of india into asia crustal strike slip shear along this zone caused the formation of a gneiss belt metamorphosed to amphibolite grade including anatectic melting both metamorphism and melting were induced by ductile deformation yielding the possibility to date the major tectonometamorphic event that shaped the ailao shan red river belt 17 u pb isotope analyses were performed on small size fractions of zircon monazite and xenotime extracted from two different leucogranitic layers the two samples are located about 50 km apart in the central segment of ailao shan in structurally well controlled settings where the melts crystallized within the strongly foliated gneisses during late stages of deformation all mineral u pb analyses had to be corrected for excess or deficit amounts of radiogenic 206 pb originating from initial 230 th disequilibrium in the 238 u decay series in monazite such disequilibrium 206 pb reaches 20 of total radiogenic 206 pb the corrected u pb ages of monazite and xenotime lie between 22 1 and 23 9 ma whereas zircon yields significantly discordant u pb ages between 30 5 and 33 9 ma pointing to precambrian material in the magma source region inherited components could also be detected in monazite the set of u pb data shows that monazite and xenotime formed simultaneously in both localities substantiating an early miocene age of 23 0 0 2ma for late kinematic crystallization of anatectic melts in the metamorphic belt of the ailao shan red river shear zone

n2 ar he compositions in fluid inclusions indicators of fluid source abstract a quadrupole mass spectrometer was used to measure bulk samples of conservative gas species n 2 ar and he in fluid inclusions from a variety of hydrothermal systems analyses of these tracer elements help determine 1 1 if gases extracted by bulk inclusion analyses can provide accurate measurement of n 2 ar he in active and fossil geothermal systems 2 2 if hydrothermal fluids associated with paleogeothermal systems in a continental setting follow n 2 ar he systematics similar to th the western pacific rim active geothermal systems specifically new zealand and 3 3 whether different deposit types systematically vary with regard to n 2 ar he the n 2 ar he ratios of fluid inclusion volatiles released from recently deposited minerals from the valles system are similar to those of present day valles thermal waters those inclusion samples from deep within the valles system below a regional aquitard increase in n 2 compositions for inclusions from the questa and copper flat porphyry deposits are n 2 rich similar to those of arc related volcanic gases whereas those from taylor creek sn deposit appear to be mixtures of magmatic and crustal components n 2 ar he ratios of the precambrian tribag deposit suggest a basalt source but significant levels of self generated he from u and th in the inclusion fluids are also possible inclusions from two epithermal deposits with low salinity inclusions have n 2 ar he ratios trending towards air saturated meteoric waters asw and those inclusions with higher salinities indicate minor to no asw component the n 2 ar he ratios in fresnillo and cochiti inclusions which have magmatic helium isotopic ratios indicate additions of magmatic gases to meteoric fluids inclusions from sediment hosted deposits that contain hydrocarbon bearing brines are he rich as are meteoric waters with a long residence time in the crust at relevant pressure temperature composition conditions henry s law constants of n 2 ar and he are similar and thus the relative amounts of these species trapped under boiling conditions will not vary appreciably from solubility controlled amounts in coexisting liquid furthermore there is no evidence of he loss or gain in inclusions by diffusion process data from the various systems that were examined indicate that fluid inclusion n 2 ar he compositions may be related to magmatic fluid sedimentary brine deep circulating meteoric fluid and shallow circulating meteoric fluid sources which we modified from those proposed by giggenbach 1986 relationships between the n 2 ar he tracer gases and other measurable quantities in fluid inclusions are indicated to be helpful in understanding fluid mixing processes in paleogeothermal systems

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

duration of strike slip movements in large shear zones the red river belt china abstract sixty four size fractions of zircon monazite xenotime and titanite were dated by the u pb method to temporally and spatially constrain left lateral movements in the red river shear zone between the depths of 15 and 20 km the shearing led to the formation of the high grade metamorphic gneisses that form the bulk of the 4200 m high diancang shan and 3100 m high ailao shan mountain ranges the omnipresence of melt layers and pockets in these gneisses shows that temperatures associated with tectonometamorphism lie at and above the solidus of continental crust and deformation patterns are very homogeneous over the entire length of the belt north of the gneisses subvolcanic bodies intrude unmetamorphosed cover rocks in particular eocene red beds along the projected trend of the red river shear zone for a leucogranitic layer in the diancang shan gneisses an age of 24 2 0 2 ma 2 is obtained for monazite and 22 4 0 2 ma is obtained for xenotime whereas zircon formed through two growth stages at 24 23 ma these ages record solidification of the anatectic melts over a period of at least 1 8 0 4 ma during which left lateral shear was continuously active in the ailao shan gneisses zircon and titanite ages are 26 3 0 3 and 26 1 0 2 ma for two monzonitic bodies and 24 1 0 2 and 22 4 0 2 ma for two pegmatitic layers that occur within the monzonitic intrusions these results show that zircon monazite titanite and probably also xenotime are closed systems for u and pb under melting conditions 650 c therefore the ages date mineral formation in the melt rather than cooling below certain closure temperatures a significantly older age of 35 0 0 1 ma is obtained for a monzonitic subvolcanic intrusion north of the diancang shan gneisses because these intrusions follow the trend of the shear zone they most likely represent the surface expression of early activity along that zone indicating that strike slip movement had already occurred in latest eocene time the total set of u pb ages shows that magmatic and metamorphic activity occurred from 35 to 20 ma strengthening the idea that the red river shear zone absorbed most of the intraplate movements required to compensate the opening of the south china sea between 32 and 16 ma the existence of monzonitic syenitic intrusions along the red river zone implies that melting affected source rocks other than the diancang shan and ailao shan gneiss protoliths potential sources to produce such rocks lie in the deep crust possibly including melts from the mantle consequently the red river shear zone must be a deep rooted structure along which melts migrated to the surface moreover the contemporaneity of shear motion and magma generation suggests that melting occurred in direct relation to strike slip activity

abundance and isotopic composition of helium in hydrothermal sulfides from the east pacific rise at 13 n abstract the helium isotopes composition of fluids trapped in hydrothermal sulfides from the east pacific rise 13 n were measured two extraction techniques i e crushing and heating were tested and sulfldes of different mineralogical types were studied the comparison between the two extraction methods suggests that both should give similar results provided the crushing efficiency is sufficiently high sulfides 3 he 4 he ratio for crushed samples are in the range 6 85 8 10 times the atmospheric ratio r a 1 38 10 6 and the measured helium concentration is of the order of 5 5 10 5 cm 3 stp per gram of trapped fluid comparison with the helium isotope composition of the hydrothermal vent fluids themselves shows that the mineral phases formed at the highest temperature i e with less dilution by the ambient seawater retain the helium information most effectively with values almost indistinguishable from the endmember vent fluid

the alkaline porphyry associated yao an gold deposit yunnan china rare earth element and stable isotope evidence for magmatic hydrothermal ore formation the yao an vein type gold deposit is located in the ailaoshan jinshajiang alkaline intrusive belt yunnan province china and is associated both in time and space with 33 5 1 0 ma old alkaline intrusions the gold mineralization is associated with potassic wall rock alteration the ree distribution patterns of secondary k feldspar are generally similar to those of the igneous perthite but with about seven times higher total ree abundances the alteration is ascribed to a high ree magmatic fluid derived from the yao an alkaline intrusive suite the hydrothermal yao an gold deposit formed during two gold bearing stages i e a sulfide pyrite stage and a sulfide oxide stage pyrite specularite the ree abundance of early stage i pyrite is relatively high with strong enrichment in lree la yb n of 40 290 generally positive eu anomalies eu eu 0 86 1 55 and ree patterns very similar to those of secondary feldspar in contrast the later stage ii pyrite has much lower ree concentrations and lower la yb n of 5 5 11 8 eu eu of 0 49 0 76 and flat chondrite normalized spidergram patterns the stage i pyrite has 34s in the range of 2 2 to 3 2 and overlaps with regionally distributed pyrite in least altered syenite porphyry in contrast stage ii pyrite has much higher 34s values between 7 8 and 16 5 carbon isotope data for four samples from stage ii revealed 13c pdb values between 6 and 8 these stable isotope and ree data suggest that magmatic fluids of the alkaline intrusions caused both potassic alteration and stage i sulfide mineralization the system evolved from stage i to stage ii mineralization by influx of meteoric fluids with relatively heavier sulfur although calcite carbon isotope data suggest that the co2 remained dominantly of magmatic origin

fluid inclusion noble gas and halogen evidence on the origin of cu porphyry mineralising fluids the naturally occurring noble gas isotopes 40ar 36ar 84kr and 129xe and halogens cl br i have been determined simultaneously in irradiated quartz vein samples by noble gas mass spectrometry quartz vein samples were collected from the potassic and propylitic alteration zones of six porphyry copper deposits pcd bingham canyon utah and silverbell ray mission pinto valley and globe miami in arizona in addition analyses of 3he 4he have been obtained from sulphide minerals hosted by the quartz veins at silverbell ray pinto valley and globe miami the majority of pcd fluids studied have br cl and i cl ratios that overlap those of fluids included in mantle diamond suggesting that the salinity had a juvenile origin the high i cl 121 10 6 mole m in samples from the propylitic zone of silverbell is attributed to the presence of sedimentary formation water 3he 4he ratios have r ra values in the range 0 3 to 1 72 and provide evidence for the involvement of a crustal component in addition to mantle volatiles 40ar 36ar ratios vary from meteoric values of 317 in the propylitic zone of bingham canyon and 323 in the skarn alteration of mission up to 3225 in the potassic zone of pinto valley fluids in both the potassic and propylitic alteration zones of every deposit are a mixture of a low salinity end member comprising meteoric water and air and a high salinity end member consisting of a mixed mantle and crustal fluid the 40ar cl ratio of fluid inclusions at pinto valley 10 4 m is similar to values obtained previously for mantle fluids the 40ar cl value is two orders of magnitude lower at bingham canyon where a depleted 36ar concentration 0 2 10 6 cm3 g below that of air saturated water asw and a range of highly fractionated noble gas compositions f84kr 13 and f129xe 160 indicate that boiling and pulsed fluid flow have occurred

4he diffusion in 40ar retentive minerals abstract 4he vacuum diffusion experiments were carried out by stepwise degassing minerals normally used in k ar chronometry such as hornblende nepheline and others the study aims at 4he diffusion parameters for uppermost crustal temperatures and thus at he retentivities of the minerals the results indicate long time near quantitative 4he retention in hornblende pyroxene langbeinite and perhaps nepheline for 0 5 mm grains at least at temperatures below about 70 c sanidine and muscovite lose 4he over geologic periods at lower temperatures only the minerals of the first group are possible u th he chronometers or geothermometers provided that other dating problems such as alpha loss and u migration can be settled closure temperatures for rapidly cooling 2 mm hornblende crystals are found to be in the range of 190 to 170 c tentative u he indices indicate that diffusion parameters of the same order of magnitude as determined for the he retentive minerals may be used to select minerals to be further examined for their u th he datability e g ore minerals

carbon helium neon and argon isotopes in a po basin northern italy natural gas field the abundance and isotopic composition of he ne and ar have been determined in 19 gas samples taken from the dosso degli angeli hydrocarbon gas field between 3000 and 3750 m depth in the po basin carbon isotope ratios in these samples vary between 13c ch4 67 5 and 73 4 indicating a predominantly biogenic source for the methane c2 c2h6 c3h8 concentrations increase systematically from 0 04 to 0 17 by volume with depth suggesting that there is a small additional thermogenic or diagenetic hydrocarbon contribution to these gases ch4 36ar ratios in the dosso degli angeli gases are in the range predicted for a groundwater which has derived its rare gas by equilibration with the atmosphere and is ch4 saturated under reservoir conditions there is also up to 10 excess of ch4 which is not associated with the groundwater these results are consistent with 90 of the ch4 in the dosso degli angeli reservoir originating from ch4 saturated groundwater measured 20ne 36ar ratios depart from the predicted ratio in air equilibrated groundwater this fractionation is consistent with water gas phase equilibration under reservoir conditions and is similar to that observed in gas reservoirs in the vienna and pannonian basins austria and hungary respectively the he in the dosso degli angeli gases is almost entirely radiogenic and derived from the crust the concentration of 4he in the reservoir gases requires that he is mostly sourced from outside the reservoir volume radiogenic 4he 40ar ratios input into the reservoir gas must be much higher than averaged crustal production ratios as no shift from the atmospheric 40ar 36ar ratio is observed preferential release of 4he over 40ar from the sites of their production is the preferred explanation this observation contrasts with previous studies from active extensional basins in which radiogenic 4he and 40ar appear to have been stored released and transported at near production ratio on a regional scale the most obvious difference between these studies is the comparatively low thermal gradient of the po basin

zircon ce4 ce3 ratios and ages for yulong ore bearing porphyries in eastern tibet yulong ore bearing porphyries along the northwestern extension of the red river ailao shan fault system in eastern tibet consist of five porphyry deposits containing a total of more than 8 million tons of copper resources u th pb laser inductively coupled plasma mass spectrometry dating of zircon shows that the porphyries were emplaced in early tertiary 41 2 36 9 ma covering a period of 4 3 ma with formation ages decreasing systematically from northwest to southeast the start of porphyry magmatism coincided with the onset of transpressional movement along the red river ailao shan fault system implying a close link between these two events age sequence in intrusions can be plausibly explained by assuming that a region of melting in the lower northwestern plate moved southeasternward along the tuoba mangkang fault relative to the upper plate zircon grains from the yulong ore bearing porphyries have higher ce4 ce3 than those from barren porphyries in the region this suggests that the ore bearing porphyries crystallized from a relatively oxidized magma which has important implications for future ore exploration in the region and other cu deposits in convergent margin environments in general

magnetic susceptibility of the chinese loess palaeosol sequence environmental change and pedogenesis pronounced differences in concentration alignment and grain size distribution of the magnetic minerals have been identified between loess and palaeosol samples from the section at xifeng central chinese loess plateau superparamagnetic magnetite formed in situ plays an important role in controlling magnetic low field susceptibility the variable brown red colouration of the loess palaeosol sequence is due to a significant hematite component produced by pedogenesis the magnetic fabric of the palaeosols is weaker than that of the loesses this is taken as evidence that the formation of ultrafine ferromagnetic minerals by pedogenesis is the most likely explanation for the observed susceptibility enhancement in palaeosols 4 to 10 times higher than in loesses it is argued that variations of frequency dependent susceptibility are sensitive recorders of second order palaeoclimatic variations during glacial periods whereas bulk susceptibility seems to be an appropriate measure of palaeoclimate change during interglacial periods

fluid origin and structural enhancement during mineralization of the jinshan orogenic gold deposit south china the jinshan orogenic gold deposit is a world class deposit hosted by a ductile shear zone caused by a transpressional terrane collision during neoproterozoic time ore bodies at the deposit include laminated quartz veins and disseminated pyrite bearing mylonite most quartz veins in the shear zone with and without gold mineralization were boudinaged during progressive shear deformation with three generations of boudinage structures produced at different stages of progressive deformation observations of ore controlling structures at various scales indicate syn deformational mineralization fluid inclusions from pyrite intergrown with auriferous quartz have 3he 4he ratios of 0 15 0 24 ra and 40ar 36ar ratios 575 3 060 18ofluid values calculated from quartz are 5 5 8 4 and d values of fluid inclusions contained in quartz range between 61 and 75 the 13c values of ankerite range from 5 0 to 4 2 and ankerite 18o values from 4 4 to 8 0 the noble gas and stable isotope data suggest a predominant crustal source of ore fluids with less than 5 mantle component data also show that in situ fluids were generated locally by pervasive pressure solution and that widespread dissolution seams acted as pathways of fluid flow migration and precipitation the in situ fluids and fluids derived from deeper levels of the crust were focused by deformation and deformation structures at various scales through solution dissolution creep crack seal slip and cyclic fault valve mechanisms during progressively localized deformation and gold mineralization

geochemical modelling of co2 water rock interactions in a potential storage formation of the north german sedimentary basin abstract the lower triassic bunter sandstone and lower jurassic rhat formations of the northern germany sedimentary basin constitute feasible reservoirs for the storage of co 2 from combustion of fossil fuels or industrial production processes this study presents analyses of geochemical interactions between co 2 formation fluid and rock of these potential reservoirs using geochemical modelling in order to assess the short and long term impact of co 2 sequestration batch equilibrium modelling was performed first for assessing the consistency of fluid and mineralogy field data and for identifying potential secondary minerals under the influence of injected co 2 inclusion of reaction kinetics in the batch models allowed an observation of reaction paths and to estimate the time frame of geochemical reactions finally one dimensional equilibrium reactive transport modelling was used in order to investigate the direction of reactions under conditions of fluid flow and mass transport and to quantify feedbacks of reactions on transport processes results of the simulations performed show that dawsonite may act as the main co 2 storage mineral in both formations while the carbonates calcite and dolomite dissolve over time also changes in porosity and permeability are significant in the equilibrium reactive transport simulations the time scale of kinetically controlled reactions observed in the kinetic batch modeling however suggests that co 2 mineral trapping in both formations requires very long time frames and hence other mechanisms such as structural or solubility trapping seem to be more relevant within the injection or early post injection phase for the studied formations

petrogenesis and geodynamic setting of granitoids at machangqing cu mo au deposit western yangtze craton southwestern china constraints from zircon u pb and molybdenite re os geochronology lu hf isotopes and geochemistry the machangqing cu mo au deposit is located in the central part of the jinshajiang red river belt in the sanjiang orogen which lies across the qiangtang terrane and western yangtze craton sou

origin of the luping pb deposit in the beiya area yunnan province sw china constraints from geology isotope geochemistry and geochronology abstract the luping pb deposit a newly discovered pb fe au ag zn polymetallic deposit close to the cenozoic beiya porphyry related au fe cu pb zn ag deposit is located in the central sanjiang three rivers jinshajiang lancangjiang and nujiang region western yangtze block in southwestern china ore bodies of the luping deposit are mainly stratiform type host in the middle triassic beiya formation limestone and lower triassic qingtianbao formation sandstone and occur along nnw trending bedding plane faults within axis of beiya qinghe syncline three ore types namely the pb au sulfide fe au and au ores can be discerned regarding their ore metal association with reserves of 2 7 million tonnes mt average grade 3 06 wt pb 0 66 g t au 41 g t ag and 0 82 wt zn 3 mt average grade 30 wt fe 0 96 g t au and 31 g t ag and 0 67 mt average grade 2 16 g t au and 13 g t ag respectively pb au sulfide ores contain mainly galena siderite native gold sphalerite and pyrite with minor chalcopyrite pyrrhotite and arsenopyrite and gangue minerals such as quartz calcite and dolomite sulfide ore textures include mainly brecciated banded and vein and minor massive and disseminated la icp ms zircon u pb dating of alkali rich quartz syenite porphyry from drill holes yielded a late eocene priabonian age 36 2 0 4 ma broadly coeval to the zircon u pb ages ca 38 ma 31 ma of alkaline porphyries and molybdenite re os age 36 9 0 3 ma from the beiya deposit near luping calcite separates have 13cpdb and 18osmow values ranging from 5 8 to 5 1 average 5 6 and 13 2 to 14 7 mean 13 6 respectively suggesting association with the mantle the sulfides have a narrow range of 34scdt values 0 8 2 8 mean 1 8 which is similar to that of mantle derived s 0 3 206pb 204pb 207pb 204pb and 208pb 204pb values of the sulfides range from 18 62 to 18 69 15 66 to 15 70 and 38 92 to 39 08 respectively similar to those of the porphyry whole rock 206pb 204pb 36 ma 18 61 18 71 207pb 204pb 36 ma 15 64 15 77 and 208pb 204pb 36 ma 38 88 39 32 ore deposit geology and c o s pb isotopic data suggest that the sources of metals and ore forming fluids were likely to be derived from the alkali rich porphyries in the beiya area we propose that the luping deposit is best classified as an epithermal pb polymetallic deposit associated with the beiya alkaline porphyries ca 36 ma 31 ma similar to other deposits related to the cenozoic alkaline porphyries in the jinshajiang red river ailaoshan metallogenic belt the luping deposit may have been formed in the india eurasia post collisional setting when partial melting occurred in the triassic stagnant slab that thickened the lower crust and the upper mantle producing the alkaline magmatism and its associated mineralization

helium isotopes as tracers of trapped hydrothermal fluids in ocean floor sulfides helium isotopes have been measured in fluids trapped in minerals from three mid ocean ridge hydrothermal systems at bare rock sites and at the sediment covered site at middle valley northern juan de fuca ridge fluid inclusion 3 he 4 he ratios from the bare rock sites are indistinguishable from those of the vent fluids and are close to the local basalt values values for 34 s of the host sulfide are consistent with variable contributions of seawater sulfate s to the basalt derived s in the hydrothermal fluids this does not affect inclusion hosted 3 he 4 he because of the high he concentration of the hydrothermal fluids relative to seawater fluid inclusion 3 he 4 he ratios from middle valley are a mixture of basalt derived he and radiogenic he acquired from pore fluids in the overlying pleistocene turbidite sediments after seawater basalt interaction the radiogenic he accompanies isotopicalty heavy s demonstrating that he isotopes may be used to distinguish pore fluids from seawater in hydrothermal systems

the pretty hill formation as a natural analogue for co2 storage an investigation of mineralogical and isotopic changes associated with sandstones exposed to low intermediate and high co2 concentrations over geological time abstract the pretty hill formation of the otway basin australia has been studied as a natural analogue for geological storage of anthropogenic co2 in order to examine the effects that co2 concentration and reservoir heterogeneity have on co2 related reactions new petrographic data are presented which validate the use of hylogger as a tool to investigate high resolution vertical changes in reservoir mineralogy the integrated data set confirms earlier interpretations showing that chlorite has been altered to kaolinite and siderite ankerite in reservoir facies exposed to moderate and high co2 concentrations while chlorite remains the dominant clay mineral in all parts of the formation where co2 content is low differences have been observed in the degree of co2 related reaction relative to co2 concentration and reservoir heterogeneity where co2 content is very high c 98 mol and associated with high water saturations both chlorite and detrital feldspars have undergone complete reaction in the reservoir facies resulting in quartzose sandstones with a kaolinite matrix and with siderite as the dominant carbonate precipitate conversely where co2 content is moderate c 29 57 mol and within the gas leg of the reservoir chlorite has undergone significant reaction but much of the original feldspar is preserved suggesting relatively minor reaction carbonate cements from the moderate co2 gas leg comprise calcite siderite and ankerite occurring as cemented zones associated with rock heterogeneities and the present day gas water contact heterogeneities within the gas leg are likely to have associated pore fluid contacts whereby relatively high water saturations will be present in the fine grained baffles and seals the most advanced feldspar reaction occurs locally at the contact between baffles and reservoir rock while reactions have been significantly impeded in the finer grained units due to their low permeabilities stable isotope data presented for carbonate cements analysed from wells with low and moderate co2 levels show no clear distinction relatively early formed calcite has 13c values that require an organic carbon source suggesting precipitation unrelated to the reservoir co2 in the otway basin in contrast diagenetically late calcite and siderite samples display two distinct 13c groups dependent on carbonate type where the calculated fluid carbon isotope compositions are similar to documented magmatic co2 reservoired in the nearby caroline field this suggests that magma derived co2 may have been more prevalent through the pretty hill formation than previously thought although the co2 has not been contained over the long term in the low co2 sites it may have caused the local dissolution of carbonate and laumontite cement and also contributed a source of carbon for late stage calcite cements these studies illustrate the importance of understanding both the reservoir composition and vertical heterogeneity of potential storage systems fluid mineral reactions are likely to be advanced within stacked reservoir facies and impeded within siltstone layers while the distribution of carbonate cement may increase the reservoir heterogeneity by the formation of cemented siltstone sandstone layers thereby creating impermeable barriers or baffles to co2

ree composition of primary and altered feldspar from the mineralized alteration zone of alkaline intrusive rocks western yunnan province china abstract the yao an gold deposit is situated northwest of kunming in yunnan province china is associated spatially with yao an alkaline intrusion the yao an gold mineralization may be divided into two ore stages the stage i sulfide stage fine grained pyrite chalcopyrite galena stringer veins and the stage ii oxide plus sulfide tectonic breccias and banded ore the stage i ores occur in the zones of pervasive potassic alteration the laser ablation icp ms technique was used to analyse ree in primary perthites and altered k feldspars of potassic alteration zone related to mineralization in the yao an gold deposit the primary perthites from yao an syenite porphyry all have similar ree features with light ree enrichment large positive eu anomalies and small but significant negative ce anomalies the ree patterns of altered k feldspars have broadly similar features but compared to the primary perthite have much higher ree concentrations and smaller positive eu anomalies these characteristics show that the hydrothermal fluids responsible for alteration were ree rich due to high levels of complex forming anions but had large negative eu anomalies and other features best ascribed to magmatic crystal fractionation these fluids were derived essentially from the magmatic system

mantle crustal and atmospheric noble gases in ailaoshan gold deposits yunnan province china abstract helium and argon isotopic and elemental compositions of fluids released by crushing pyrite grains are reported from the ailaoshan gold province china the province is a series of gold deposits hosted on a 200 km segment of a major normal fault formed during eocene extension the deposits have been well characterised using conventional geochemical and microthermometric techniques the results of which are consistent with a predominantly high temperature magmatic fluid present in the ore minerals in contrast analyses of noble gases from three gold deposits demonstrate the palaeofluids were a mixture between a mantle derived magmatic fluid and two different low temperature fluids similar to modern groundwaters the specific isotopic and abundance characteristics of helium and argon allow unequivocal identification of both a mantle derived component and a surface derived component to these fluids the magmatic fluid dominates deposits from the northern end of the fault the second groundwater is present only in deposits in the south of the province by assuming fluid inclusion homogenisation temperatures in coexisting quartz are representative of fluid temperature 3he heat ratios can be estimated the 3he heat ratios vary systematically along the fault from 30 10 12 cm3 stp j 1 in the northern deposits to

mantle derived and crustal he and ar in the ore forming fluids of the xihuashan granite associated tungsten ore deposit south china abstract the xihuashan tungsten ore deposit in the central nanling region south china is a vein type hydrothermal deposit associated with the late jurassic granitoids that were previously thought to be the products of crustal anatexis alone in this study we use helium he and argon ar isotopes of fluid inclusions entrapped in pyrite and arsenopyrite to determine the origin of the ore forming fluids the 3he 4he ratios of the crushed fluid inclusions vary from 0 15 to 1 16 ra with a mean of 0 72 ra ra the atmospheric 3he 4he ratio of 1 4 10 6 indicating the presence of mantle derived noble gasses in the fluids the amounts of the mantle derived noble gasses are estimated to be between 2 and 17 the 40ar 36ar ratios of the fluid inclusions vary from 306 to 1023 with an average of 440 these ratios are significantly higher than the average crustal value indicating the presence of air saturated water in the volatiles released from the mineral separates the results from this study indicate that the associated coeval granitoids which is believed to provide the ore forming fluids during magma evolution are not the products of pure crustal melts mantle derived volatiles and heat was also involved in the genesis of the host granite pluton

predictive modeling of co2 sequestration in deep saline sandstone reservoirs impacts of geochemical kinetics abstract one idea for mitigating the increase in fossil fuel generated co 2 in the atmosphere is to inject co 2 into subsurface saline sandstone reservoirs to decide whether to try such sequestration at a globally significant scale will require the ability to predict the fate of injected co 2 thus models are needed to predict the rates and extents of subsurface rock water gas interactions several reactive transport models for co 2 sequestration created in the last decade predicted sequestration in sandstone reservoirs of 17 to 90 kg co 2 m 3 to build confidence in such models a baseline problem including rock water chemistry is proposed as the basis for future modeling so that both the models and the parameterizations can be compared systematically in addition a reactive diffusion model is used to investigate the fate of injected supercritical co 2 fluid in the proposed baseline reservoir brine system in the baseline problem injected co 2 is redistributed from the supercritical sc free phase by dissolution into pore brine and by formation of carbonates in the sandstone the numerical transport model incorporates a full kinetic description of mineral water reactions under the assumption that transport is by diffusion only sensitivity tests were also run to understand which mineral kinetics reactions are important for co 2 trapping the diffusion transport model shows that for the first 20 years 20 a after co 2 diffusion initiates co 2 is mostly consumed by dissolution into the brine to form co 2 aq solubility trapping from 20 to 200 a both solubility and mineral trapping are important as calcite precipitation is driven by dissolution of oligoclase from 200 to 1000 a mineral trapping is the most important sequestration mechanism as smectite dissolves and calcite precipitates beyond 2000 a most trapping is due to formation of aqueous hco 3 ninety seven percent of the maximum co 2 sequestration 34 5 kg co 2 per m 3 of sandstone is attained by 4000 a even though the system does not achieve chemical equilibrium until 25 000 a this maximum represents about 20 co 2 dissolved as co 2 aq 50 dissolved as hco 3 aq and 30 precipitated as calcite the extent of sequestration as hco 3 at equilibrium can be calculated from equilibrium thermodynamics and is roughly equivalent to the amount of na in the initial sandstone in a soluble mineral here oligoclase similarly the extent of trapping in calcite is determined by the amount of ca 2 in the initial oligoclase and smectite sensitivity analyses show that the rate of co 2 sequestration is sensitive to the mineral water reaction kinetic constants between approximately 10 and 4000 a the sensitivity of co 2 sequestration to the rate constants decreases in magnitude respectively from oligoclase to albite to smectite

nature and evolution of fluid inclusions in the cenozoic beiya gold deposit sw china abstract the beiya au deposit in the sanjiang metallogenic belt sw china is a porphyry skarn deposit that formed in an intracontinental setting three stages of hydrothermal veins namely quartz veins stage 1 quartz pyrite veins stage 2 and au rich sulfide quartz veins stage 3 were identified on the basis of field relationship and petrography under scanning electron microscopy cathodoluminescence sem cl intermediate density aqueous fluid inclusions id1 id2 high density brine inclusions b1 b2 and low density vapor inclusions v1 v2 have been identified in both stage 1 and stage 2 veins only liquid rich fluid inclusions l3 were found in stage 3 veins raman spectroscopy revealed that all the inclusions contain abundant co2 h2s was identified in id2 and v2 inclusions salinities and homogenization temperatures of the intermediate density aqueous fluid inclusions id1 id2 high density brine inclusions b1 b2 and low density vapor inclusions v1 v2 are 7 4 1 1 11 9 2 2 33 6 0 5 39 2 1 and 1 6 0 7 5 8 0 8 wt nacl equiv and 400 35 440 37 395 20 414 6 and 386 5 416 4 c respectively salinities and homogenization temperatures of the l3 inclusions range from 4 9 1 6 to 9 8 0 7 wt nacl equiv and from 301 28 to 398 4 c respectively initial intermediate density aqueous fluid inclusions contain 2000 10 000 ppm fe 2000 4000 ppm cu 200 600 ppm zn 200 500 ppm pb 17 89 ppm mo 1 8 ppm ag and 0 9 5 9 ppm au comparable to that of intermediate density inclusions in subduction related porphyry deposits brine inclusions are rich in metals and have 9000 24600 ppm fe 3400 11 000 ppm cu 1200 5200 ppm pb 500 3000 ppm zn hundreds of ppm mo and tens of ppm ag the corresponding vapor inclusions contain lower metal concentrations 400 6000 ppm fe 1700 4700 ppm cu 50 270 ppm pb 100 500 ppm zn and minor mo and ag low to intermediate density fluids are abundant and are inferred to have been the main metal transporting medium a temperature decrease to approximately 350 c during stage 3 triggered metal precipitation

resolving mantle and crustal contributions to ancient hydrothermal fluids hear isotopes in fluid inclusions from dae hwa wmo mineralisation south korea abstract helium and argon isotopes from fluid inclusions in individual colour zones b c d and e of a large scheelite crystal from the 88 ma dae hwa w mo deposit south korea trace the source and history of the ore fluids a gradual decrease of the fluid 3 he 4 he 3 he 36 ar and 40 ar 36 ar from the core to the edge of the scheelite reflects the progressive dilution of a magmatic fluid by meteoric water and is consistent with the previously observed decrease of 18oh2o and fluid inclusion homogenisation temperatures th shelton et al 1987 the covariation of fluid inclusion he ar isotope systematics with 18o and th defines a magmatic component with 3 he 4 he 1 2 10 6 3 he 36 ar 0 01 and 40 ar 36 ar 1000 anomalously high helium and argon isotope ratios in zone d fluids represents undiluted magmatic noble gases this may reflect local variation in the magmatic gas flux or gas loss due to boiling of the hydrothermal fluids prior to mixing with magmatic gas helium and argon isotope systematics constrain mantle and crustal components in the hydrothermal fluids 40 ar 3 he 4 5 104 are close to the mid ocean ridge basalt value implying that 40ar is mantle in origin radiogenic isotope ratios of the mantle endmember 40 ar 4 he 0 69 0 06 are similar to contemporary geothermal fluids the coincidence of mantle derived he and ar in the fluids is strong evidence that mantle melting during late cretaceous subduction triggered the crystal melting responsible for granite formation 40 ar 4 he of the meteoric fluid 0 007 0 001 is far lower than the crystal production ratio 0 2 implying an origin in crust below 200 c

distribution of porphyry deposits in the eurasian continent and their corresponding tectonic settings in the eurasian continent there are three huge metallogenic belts of cu and mo porphyry deposits comprising the paleozoic central asian ore belt in the north the tethyan eurasian ore belt of jurassic to cenozoic age in the southwest and the east margin ore belt of the eurasian continent of jurassic to cretaceous age in the east the latter is considered to be part of the vast circum pacific ore belt some of the main features of the spatial temporal distribution of cu and mo porphyry systems and related geodynamic processes of the three metallogenic belts are described in particular the key role of postsubduction related porphyry ore systems is emphasized comprising collisional and post collisional cu mo porphyry deposits during the geological history of the eurasian continent the recurrent feature of these ore systems and related felsic rocks is their derivation from partial melting of stagnant or residual oceanic slabs and mixing with a variable amount of crustal material during magma ascent to shallower levels 2013 published by elsevier ltd

he pb and s isotopic constraints on the relationship between the a type qitianling granite and the furong tin deposit hunan province china abstract the furong tin deposit located in southern hunan province china is a large newly discovered deposit with an estimated sn reserve of about 700 000 tons the deposit is spatially and temporally associated with the a type qitianling granite the 3he 4he ratios of fluid inclusions trapped in sulfides from the deposit range from 0 13 to 2 95 ra indicating a mixed crust mantle source similar to that of the qitianling granite complex lead isotopes in feldspars of the granite mostly in the range of 206pb 204pb 18 547 19 180 207pb 204pb 15 598 15 825 208pb 204pb 37 912 39 068 and in sulfide minerals 206pb 204pb 18 467 18 836 207pb 204pb 15 503 15 772 208pb 204pb 38 607 39 099 are essentially the same indicating that the lead in both was derived mainly from the upper crust with a small mantle component the sulfur isotopic values of the ore minerals vary widely ranging from 26 1 to 10 4 but are mainly within the range of 0 2 to 10 4 implying that the s in the hydrothermal fluids was derived mainly from magmatic fluids with minor contributions from the mantle sedimentary rocks and biogenic material the he pb and s isotopes all confirm that the ore forming fluids of the furong deposit were magmatic in origin derived from the melts that produced the qitianling a type granite the tin mineralization occurs within or along the margins of the qitianling granite complex and the timing of the mineralization coincides with the intrusive age of the granite the available data suggest that the emplacement of the granites and the mineralization was related to mantle upwelling and extension of the lithosphere in south china during the mesozoic