u pb geochronology isotope systematics and geochemical characteristics of the triassic dasuji porphyry mo deposit inner mongolia north china implications for tectonic evolution and constraints on the origin of ore related granitoids abstract the dasuji porphyry mo deposit is located in the wulanchabu area of inner mongolia within the northern north china craton ncc three phases of mesozoic felsic intrusions have been recognized in the mining area including two pre mineralization intrusions i e a quartz porphyry and a granite porphyry with molybdenite bearing stockworks and veins and an ore related granite porphyry with disseminated and stockwork mo mineralization zircon u pb hf analyses intergrated with the previously reported molybdenite re os isochron ages suggest that the mo mineralization of the dasuji deposit occurred in the late triassic 222 224 ma and that the ore related granitoids were derived from partial melting of old lower crust with a subordinate contribution from mantle materials major and trace element analyses show that the pre ore granite porphyry 227 ma and the ore related granite porphyry 224 ma are both characterized by high silica contents and relatively high levels of oxidation with a high differentiation index di 85 0 98 8 the granitoids belong to the high k calc alkaline series and are highly peraluminous with depletion in ba sr p eu and ti showing similar geochemical characteristics to those of post collision related granitoids in north china based on geological geochronological isotope systematic and geochemical studies integrated with regional geological information we suggest that the dasuji mo deposit was formed in a post collisional setting associated with the transition from regional compression to extension between the ncc and the central asian orogenic belt caob during the late triassic

mechanism of instantaneous coal outbursts thousands of mine workers die every year from mining accidents and instantaneous coal outbursts in underground coal mines are one of the major killers various models for these outbursts have been proposed but the precise mechanism is still unknown we hypothesize that the mechanism of coal outbursts is similar to magma fragmentation during explosive volcanic eruptions i e it is caused by high gas pressure inside coal but low ambient pressure on it breaking coal into pieces and releasing the high pressure gas in a shock wave hence coal outbursts may be regarded as another type of gas driven eruption in addition to explosive volcanic lake and possible ocean eruptions we verify the hypothesis by experiments using a shock tube apparatus knowing the mechanism of coal outbursts is the first step in developing prediction and mitigation measures the new concept of gas driven solid eruption is also important to a better understanding of salt gas outbursts rock gas outbursts and mud volcano eruptions

petrogenesis and metallogenic setting of porphyries of the duobuza porphyry cu au deposit central tibet china abstract given that the duobuza deposit was the first porphyry cu au deposit discovered in central tibet the mineralization and mineralized porphyry in this area have been the focus of intensive research yet the overall porphyry sequence associated with the deposit remains poorly understood new geological mapping logging and sampling of an early granodiorite porphyry an inter mineralization porphyry and a late mineralization diorite porphyry were complemented by la icp ms zircon dating whole rock geochemical and sr nd isotopic analyses and in situ hf isotopic analyses for both inter and late mineralization porphyry intrusions all of the porphyry intrusions are high k and calc alkaline and were emplaced at ca 120 ma the geochemistry of these intrusions is indicative of arc magmatism as all three porphyry phases are enriched in light rare earth elements and large ion lithophile elements and depleted in heavy rare earth elements and high field strength elements these similar characteristics of the intrusions when combined with the relatively high 87 sr 86 sr i negative e nd t and positive e hf t values suggest that the magmas that formed the porphyries were derived from a common source region and shared a single magma chamber the magmas were generated by the mixing of upwelling metasomatized mantle wedge derived mafic magmas and magmas generated by partial melting of amphibolite within the lower crust the inter mineralization porphyry has the lowest e nd t and highest 87 sr 86 sr i values suggesting that a large amount of lower crust derived material was incorporated into the melt and that metals such as cu and au from the enriched lower crust were scavenged by the parental magma the relative mafic late mineralization diorite porphyry phase was formed by the residual magma in the magma chamber mixing with upwelling mafic melt derived from metasomatized mantle the magmatic hydrothermal evolution of the magma in the chamber released ore forming fluid that was transported mainly by the inter mineralization porphyry phase during the mineralization stage which ultimately formed the duobuza porphyry cu au deposit these porphyritic intrusions of the duobuza deposit have high mg and low la yb n values and show some high lile hfse ratios indicating the magma source was enriched by interaction with slab derived fluids combined with age constraints on the regional tectonic evolution these dating and geochemical results suggest that the duobuza porphyry cu au deposit formed in a subduction setting during the final stages of the northward subduction of the neo tethyan ocean

the role of spatial variability in coal seam parameters on gas outburst behaviour during coal mining abstract gas outburst is recognized as a potentially fatal hazard to be managed during the mining of gassy coal seams gas outbursts in australian coal mines have been associated with the presence of geological structures in the coal and surrounding rocks having a range of spatial scales from millimetres to metres the contributing mechanisms are influenced by coal gas reservoir variables including gas composition fluid pressure desorption pressure and rate porosity intrinsic permeability and relative permeability they are also influenced by geomechanical variables such as strength in situ stress and mining induced stress the work described here concerns the influence of variability of permeability and strength on outburst behaviour key coal properties are characterised for a field site in an operational underground coal mine and then used in a series of hypothetical simulations of outburst initiation at the field site an array of horizontal holes was cored in seam well tests for permeability and stress were performed in the holes and recovered core was tested in the laboratory for permeability strength and sorption properties for permeability and strength sufficient numbers of measurements were obtained to describe these properties statistically assuming that the measurements are uncorrelated spatially analysis of the cumulative probability distributions of the field and laboratory permeability data shows a strong size effect that cannot be linearly up scaled using monte carlo techniques these statistical descriptions are used to generate realisations of property values across the model grid used in the simulation analyses the stochastic model approach demonstrates that the variability of the permeability and strength fields can lead to both outburst and non outburst outcomes from the same measured input data depending on the corresponding spatial distribution of permeability and strength at the face these results suggest the potential application of this approach as a tool for outburst risk analysis and assessment

from a long lived upper crustal magma chamber to rapid porphyry copper emplacement reading the geochemistry of zircon crystals at bajo de la alumbrera nw argentina the formation of world class porphyry copper deposits reflect magmatic processes that take place in a deeper and much larger underlying magmatic system which provides the source of porphyry magmas as well as metal and sulphur charged mineralising fluids reading the geochemical record of this large magmatic source region as well as constraining the time scales for creating a much smaller porphyry copper deposit are critical in order to fully understand and quantify the processes that lead to metal concentration within these valuable mineral deposits this study focuses on the bajo de la alumbrera porphyry copper deposit in northwest argentina the deposit is centred on a dacitic porphyry intrusive stock that was mineralised by several pulses of porphyry magma emplacement and hydrothermal fluid injections to constrain the duration of ore formation we dated zircons from four porphyry intrusions including pre syn and post mineralisation porphyries based on intersection relations between successive intrusion and vein generations using high precision ca id tims based on the youngest assemblages of zircon grains which overlap within analytical error all four intrusions were emplaced within 29 ka which places an upper limit on the total duration of hydrothermal mineralisation re os dating of hydrothermal molybdenite fully overlaps with this high precision age bracket however all four porphyries contain zircon antecrysts which record protracted zircon crystallisation during the 200 ka preceding the emplacement of the porphyries zircon trace element variations ti in zircon temperatures and hf isotopic compositions indicate that the four porphyry magmas record a common geochemical and thermal history and that the four intrusions were derived from the same upper crustal magma chamber trace element zoning within single zircon crystals confirms a fractional crystallisation trend dominated by titanite and apatite crystallisation however zircon cathodoluminescence imaging reveals the presence of intermediate low luminescent dark growth zones in many crystals from all intrusions characterised by anomalously high th u and ree concentrations and transient excursions in trace element ratios a return to the same fractionation trend after this excursion excludes external compositional forcing such as magma mixing instead we interpret the dark zones to record zircon crystallisation during a transient event of rapid growth that resulted from mafic magma injection into the base of the magma chamber releasing a co2 rich vapour phase into the dacitic crystal mush we propose that this vapour phase then migrated upwards to the apical part of the magma chamber from where it was expelled together with successive batches of magma to form the porphyry copper deposit within a short time span of less than a few 10 000 years the short duration of host rock emplacement hydrothermal alteration and mineralisation presented in this study provides critical constraints on fluid storage in magma chambers and the genesis of large porphyry copper deposits

potassic ultrapotassic intrusions at the southwestern margin of the yangtze craton southwestern china petrogenesis and implications for the metal and fluid source of non arc porphyry cu mo au deposits abstract magmatic rocks can reveal partial melting processes in the lower crust and mantle therefore the petrogenesis of both ore barren and ore bearing magmatic rocks can provide key insights into the deep geological processes that control porphyry cu mo au deposits pcds here we investigate the petrogenesis of potassic ultrapotassic igneous rocks in the southwestern yangtze craton swyc to constrain their magmatic sources and assess their role in the formation of pcds these igneous rocks can be divided into three suites ore barren granite porphyry lamprophyre and ore bearing quartz monzonite u pb dating of zircons indicates that these potassic ultrapotassic intrusions crystalized simultaneously between 35 4 and 33 6 ma the lamprophyres have low sio2 contents and high mgo and k2o contents exhibiting an ultrapotassic affinity they are depleted in high field strength elements hfses nb ta zr hf and ti and enriched in large ion lithophile elements liles rb k sr and ba the enriched sr nd and hf isotopic compositions of the ore barren lamprophyres suggest that they were derived from low degree partial melting of lithospheric mantle that had been metasomatized by subduction related fluids during the proterozoic the ore barren granite porphyries have high sio2 and k2o contents with high k calc alkaline to shoshonitic characteristics these rocks have low mgo cr ni and co contents all samples exhibit high sr y ratios and highly fractionated rare earth elements rees patterns with weak eu anomalies combined with their low total ree contents 75 81 ppm and ehf t values which are similar to neoproterozoic granulite xenoliths we conclude that the ore barren porphyries are adakites derived from thickened neoproterozoic lower crust the ore bearing intrusions show variable sio2 and high na2o k2o contents plotting in the monzonite to quartz monzonite fields in a sio2 vs na2o k2o diagram these samples have much higher total ree contents 346 671 ppm than the ore barren intrusions the homogeneous sr nd isotopic compositions and linear trends on harker diagrams suggest that the magma that formed the ore bearing rocks underwent fractional crystallization of mainly amphibole and accessory minerals water contents are estimated to have been 9 12 wt at 0 8 gpa on the basis of the retention of plagioclase and low zircon saturation temperatures which suggests that the primitive magmas of the ore bearing intrusions were derived from water fluxed melting rather than dehydration melting the additional water required to promote water fluxed melting was probably derived from underplated poassic ultrapotassic mafic magmas the high total ree contents sr y and la yb n ratios indicate that the primitive magmas of ore bearing intrusions were probably derived from partial melting of potassic ultrapotassic lower crust formed by the underplating of mantle derived potassic ultrapotassic magma these results combined with previous research show that mantle derived potassic ultrapotassic magmas can provide metals and fluids required for the formation of pcds

the effect of titanite crystallisation on eu and ce anomalies in zircon and its implications for the assessment of porphyry cu deposit fertility abstract the redox sensitivity of ce and eu anomalies in zircon has been clearly demonstrated by experimental studies and these may represent an important tool in the exploration for porphyry cu deposits which are thought to be derived from oxidised magmas these deposits are significant because they are the source of much of the world s copper and almost all of the molybdenum and rhenium key elements in many modern technologies however ce and eu anomalies in zircon are also affected by the co crystallisation of ree bearing phases such as titanite here we report the trace element chemistry of zircons from titanite bearing intrusions associated with mineralisation at the world class oyu tolgoi porphyry cu au deposit mongolia based on these data we suggest that neither zircon eu eu nor ce4 ce3 are robust proxies for melt redox conditions because they are both too strongly dependent on melt ree concentrations which are usually poorly constrained and controlled by the crystallisation of titanite and other ree bearing phases in spite of this eu eu can broadly distinguish between fertile and barren systems so may still be an indicator of porphyry magma fertility and a useful tool for exploration

geochemistry and the mineral nutrition of agricultural livestock and wildlife relations between the geochemical nature of soils and their parent materials and the occurrence of nutritional deficiencies and excesses in grazing livestock have been documented since the 1960s and earlier with notable work in australia new zealand united kingdom ireland usa and the soviet union studies at imperial college london into the development of regional geochemical mapping techniques as a means of delineating nutritional problems commenced in the 1960s and have continued to the present research has mainly focussed on deficiencies of cu co and se in cattle and sheep and the role of mo and s in the soil plant system in both clinical and sub clinical hypocuprosis in cattle exposure to heavy metals in particular pb zn cd and the metalloid as have also received attention in areas contaminated by past mining and smelting activities soil and plant factors influencing the dietary supply of both essential trace elements and toxic metals have been studied including their speciation and bioavailability soil ingestion has been recognised as an important exposure pathway of heavy metal contamination to grazing cattle and as an antagonist of cu supply and a source of dietary co in sheep relations between soil geochemistry and the mineral status of wildlife species in particular impala and black rhinoceros have been established in kenya and recent work presented elsewhere in this symposium has concerned the supply of nutrients to the roosevelt sable in kenya the compilation of regional and national multi purpose geochemical atlases based on the systematic sampling of soils or stream sediments is now recognised as a priority in many countries of the developed and developing world this paper explores the opportunities for future research into the application of geochemical maps for the optimisation of land use efficient livestock production and improving conservation of wildlife

control and prevention of gas outbursts in coal mines riosa olloniego coalfield spain abstract underground coal mines have always had to control the presence of different gases in the mining environment among these gases methane is the most important one since it is inherent to coal despite of the technical developments in recent decades methane hazards have not yet been fully avoided this is partly due to the increasing depths of modern mines where methane emissions are higher and also to other mining related circumstances such as the increase in production rates and its consequences difficulties in controlling the increasing methane levels increasing mechanization the use of explosives and not paying close attention to methane control systems the main purposes of this paper are to establish site measurements using some critical parameters that are not part of the standard mining control methods for risk assessment and to analyze the gas behavior of subvertical coal seams in deep mines in order to prevent gas incidents from occurring the ultimate goal is the improvement in mining conditions and therefore in safety conditions for this purpose two different mines were instrumented for mine control and monitoring both mines belong to the riosa olloniego coalfield in the asturias central basin spain and the areas instrumented are mined via subhorizontal sublevels at an actual depth of around 1000 m under the overburden of mount lusorio during this research a property favoring gas outbursts was site measured for the first time in an outburst prone coal 8th coalbed gas pressure and its variations which contributed to complete the data available from previous characterizations and to set some guidelines for assessing the potential outburst prone areas a gas measurement tube set has been designed for measuring gas pressure as well as its variation over time as a result of nearby workings and to calculate permeability the paper establishes the effect of overlapping of works but it also shows the efficacy of two preventive measures to be applied high pressure water infusion and the exploitation of a protective coal seam 7th coalbed that must be mined preferably two complete sublevels before commencing the advance in the outburst prone coalbed both measures constitute an improvement in the mining sequence and therefore in safety and should be completed with a systematic measurement to control the risk gas pressure in the 8th coalbed in the area of influence of other workings to establish the most suitable moment to renew the advance further researches could focus on ascertaining the permeability not only in mined areas but also in areas of the mine that are still not affected by mining work and on tuning more finely the ranges of influence of overstress time and overlap distance of the workings of the 7th coalbed in the 8th coalbed

cospatial eocene and miocene granitoids from the jiru cu deposit in tibet petrogenesis and implications for the formation of collisional and postcollisional porphyry cu systems in continental collision zones abstract jiru is a poorly studied cu deposit located in the west segment of the gangdese porphyry cu belt gpcb 200 km west of lhasa the deposit consists of both collisional and postcollisional stage porphyry type cu systems which are genetically associated with the early eocene granitoid batholith and the miocene jiru porphyry stock respectively in this study we present zircon u pb la icp ms dates and hf isotopes whole rock geochemical and pb isotope geochemical data for the main intrusions in the jiru deposit the early eocene granitoid samples 49 ma are characterized by magmatic arc geochemical features slightly concave ree patterns and well developed negative eu anomalies these geochemical characteristics suggest that the granitoid melts were generated by partial melting of a metasomatized mantle and that the melt had undergone fractional crystallization of amphibole and plagioclase in contrast the miocene porphyry intrusions 16 4 15 5 ma at jiru are characterized by high k contents adakitic affinities e g high sr y and la yb ratios subduction signatures e g enriched cs rb ba and depleted nb ta ti positive zircon ehf t values 1 6 and variable 208pb 204pb ratios 38 5 39 0 similar to other post collisional porphyry intrusions in the gangdese belt based on the above features we propose that the miocene porphyry intrusions at jiru were generated by partial melting of subduction modified lower crust well developed negative eu anomalies and low sr y ratios generally

physicochemical processes in the magma chamber under the black mountain porphyry cu au deposit philippines insights from mineral chemistry and implications for mineralization the black mountain porphyry cu au deposit in the baguio district northern luzon philippines is associated with late miocene to pliocene intrusive rocks that retain primary crystallization signatures providing an excellent natural laboratory to study the details of magma chamber processes each igneous phase contains disequilibrium textures including resorptive textures in plagioclase and distinct core rim textures in amphibole high crystallization temperatures and pressures in felsic 880 c and 2 8 kbar and mafic 1 030 c and 7 7 kbar rocks recorded by amphibole phenocrysts reflect crystallization in the magma chamber amphibole in felsic rocks aged 6 39 0 49 to 2 83 0 23 ma have similar crystallization temperatures and pressures suggesting a long lived and hot felsic magma chamber under the black mountain deposit four independent oxybarometers including amphibole coexisting magnetite ilmenite magmatic anhydrite and zircon consistently show a high oxidation state of nno 1 for the felsic magma and nno 0 7 for the mafic magma element profiles across phenocrystic plagioclase display repeated oscillatory variations of ca fe and sr contents with large anorthite variations and a positive correlation between cao and feo the amphibole is classified as group 1 mg hornblende to tschermakite hornblende in felsic rocks and group 2 mg hastingsite in mafic rocks the group 1 amphiboles show a variety of major and trace element variations from core to rim in disequilibrated grains and transitional compositions to group 2 mg hastingsite both mineral textures and chemistry recorded by phenocrysts of plagioclase and amphibole indicate repeated mafic magma recharge in the felsic magma chamber the common occurrence of rounded or elongated sulfide inclusions in the megacrystic amphibole from the mafic rocks 2 81 0 15 ma suggests a greater enrichment of cu in mafic rocks relative to the ore forming porphyries 2 91 2 83 ma this is also consistent with higher cu contents 3 4 0 9 ppm in the megacrystic amphibole from the mafic rocks relative to amphibole in felsic rocks 1 0 0 2 ppm and may indicate up to 3 4 times higher cu in the mafic magma relative to felsic magma therefore large scale mafic magma recharge particularly at 2 8 ma likely introduced ore forming metals to the long lived felsic magma chamber further contributing to the fertility of the felsic rocks and ultimately to cu au mineralization at the black mountain deposit

the magnetite crisis in the evolution of arc related magmas and the initial concentration of au ag and cu the association of large au cu ag ore deposits with convergent margins is commonly attributed to the higher content of chalcophile elements in the parental magmas generated at subduction zones compared with mid ocean ridges we present new geochemical data for arc like relatively oxidized mantle derived basalt to rhyolite magmas from the pual ridge and vicinity eastern manus basin which show that the initial abundances of base and precious metals in the parental basalts are similar to those of mid ocean ridge basalt morb the contents of au cu and ag are built up in the evolving pual ridge liquids to levels considerably in excess of those in morb because unlike morb they are not saturated in a sulfide phase which is a consequence of their being more oxidized than morb the behaviour of s during the evolution of the pual ridge magmas is obscured by late stage so2 loss during eruption but we show that it may be inferred by using se as a proxy because this element follows s closely during magmatic evolution except it is not lost during low pressure near sea floor degassing the onset of magnetite fractionation at 60 wt sio2 and an mg number of 40 is accompanied by an abrupt decrease in the contents of au cu and ag previously attributed to separation of cu au rich fluid which is also shown by se implying that magnetite fractionation triggers sulfide saturation petrological modelling reveals that the amount of magnetite fractionation involved is sufficient to convert most of the s originally dissolved in the magma as sulfate so42 to sulfide s2 triggering saturation in a cu rich sulfide phase tentatively identified as bornite cu5fes4 this sulfide phase sequesters au and ag elements with the same valence as cu in sulfides but not other potentially chalcophile elements such as ni re and pt which suggests that the phase is crystalline rather than an immiscible sulfide melt the relatively high contents of cu and au characteristic of evolved convergent margin magmas requires no enrichment from subducted material instead the association of major cu au deposits with convergent margin magmatism results specifically from the process of magmatic evolution under oxidizing conditions this same property also leads to early magnetite fractionation triggering the abrupt saturation in the cu rich sulfide hence the easily recognizable trend of magmatic evolution under oxidizing conditions i e the sharp drop in chalcophile element concentrations may be an exploration guide to economic au ag cu provinces or a crucial pre enrichment step in the formation of such deposits the decrease in p2o5 and sr at the same stage in the fractionation sequence 60 wt sio2 indicates that saturation in apatite is concomitant with magnetite sulfide saturation in the eastern manus basin

stream sediment soil and forage chemistry as indicators of cattle mineral status in northeast zimbabwe results of previous studies investigating the use of soil and forage chemistry as indicators of cattle mineral status have been somewhat equivocal possibly due to the limited range of trace element concentrations in the areas investigated this paper describes an investigation of the relationship between trace element concentrations in stream sediments soils forage grass and leaves and cattle blood serum in northeast zimbabwe in order to identify which if any of the sample media provide a reliable guide to cattle mineral status soil forage and cattle serum were collected from an area characterized by a wide range of zn in stream sediments the area was subdivided into three regions of relatively low medium and high zn concentration on the basis of stream sediment data and variations in the chemistry of cattle serum forage soil and stream sediment samples were examined significant correlations exist between element concentrations in stream sediments soils and forage but there are no significant correlations with cattle serum although this lack of direct correlation may in part be due to a range of biological factors it is suggested that high concentrations of fe in soil and forage inhibit i the availability of p to plants and ii the absorption of cu and zn in cattle this may have wide ranging implications due to the predominance of ferrallitic soils in many countries in tropical regions

the ordovician igneous rocks with high sr y at the tongshan porphyry copper deposit satellite of the duobaoshan deposit and their metallogenic role abstract a strong link between high sr y arc magmas and porphyry cu mo au deposits has been recognized in recent years the tongshan and duobaoshan deposits are representative large cu mo au deposits in ne china we report la icp ms zircon u pb crystallization age of 471 5 1 3 ma for tongshan ore related granitoid re os isotopic analyses of the two chalcopyrite samples from tongshan deposit show a model age range of 470 2 477 1 ma the duobaoshan and tongshan ore related granitoids show higher sr y and la yb ratios the 34 s values of sulphides from the duobaoshan and tongshan deposits vary from 2 3 to 0 0 belonging to a magmatic hydrothermal system the pb isotopic ratios of the sulphides from the duobaoshan and tongshan deposit range from 17 201 to 18 453 for 206 pb 204 pb 15 445 to 15 551 for 207 pb 204 pb and 36 974 to 37 999 for 208 pb 204 pb indicating the addition of lower crustal material the duobaoshan and tongshan granitoids were formed in a subduction related continental arc setting produced by partial melting of juvenile hydrous basalts underplating the deep continental crust during the ordovician

recycling of orogenic arc crust triggers porphyry cu mineralization in kerman cenozoic arc rocks southeastern iran pre collisional eocene oligocene arc diorites quartzdiorites granodiorites and volcanic equivalents in the kerman arc segment in central iran lack porphyry cu mineralization and ore deposits whereas collisional middle late miocene adakite like porphyritic granodiorites without volcanic equivalents host some of the world s largest cu ore deposits petrological and structural constraints suggest a direct link between orogenic arc crust evolution and the presence of a fertile metallogenic environment ore hosting kuh panj porphyry intrusions exhibit high sr 400 ppm low y 20 no negative eu anomalies eu eu 1 and relatively non radiogenic sr isotope signatures 87sr 86sr 0 7042 0 7047 relative to eocene oligocene granitoids mainly sr 12 la yb 15 eu eu 1 87sr 86sr 0 7053 0 7068 trace element modeling indicates peridotite melting for the barren eocene oligocene intrusions and a hydrous garnet bearing amphibolite source for middle late miocene ore hosting intrusions the presence of garnet implies collisional arc crustal thickening by shortening and basaltic underplating from about 30 35 to 40 45 km or 12 kbar the changes in residual mineralogy in the source of eocene to miocene rocks in the kerman arc segment reflect probing of a thickening arc crust by recycling melting of the arc crustal keel underplating of cu and sulfur rich melts from fertile peridotite generated a fertile metallogenic reservoir at or near the crust mantle boundary and dehydration melting under oxidizing conditions produced syn and post collisional ore hosting intrusions while the lack of post collisional volcanism prevented the venting of volatiles to the atmosphere from sulfur rich and oxidized adakitic magmas

origin of paleozoic granitoids in the yuhai cu mo deposit eastern tianshan nw china and implications for regional metallogeny abstract the yuhai porphyry cu mo deposit is located at the eastern section of the dananhu tousuquan arc in eastern tianshan nw china cu mo mineralization generally occurs as disseminations and veins in potassic and phyllic alteration zones and is predominantly hosted in the yuhai quartz diorite granodiorite and minor syenogranite intrusions new la icp ms zircon u pb dating indicates that the acidic syenogranite was emplaced at 318 320 ma younger than the intermediate rocks i e quartz diorite and granodiorite with silurian ages the acidic to intermediate intrusions exhibit geochemical affinities with normal arc rocks e g high y and yb contents and low sr y ratios in contrast with the subducted slab derived adakites hosting large porphyry cu deposits e g tuwu yandong in the middle section of the dananhu tousuquan arc the yuhai acidic syenogranite rocks have high sio2 74 90 wt and k2o 3 48 wt relatively low mg and compatible element contents e g cr 0 65 3 37 ppm ni 0 63 1 02 ppm and strong depletions in hfse e g nb ta and ti these geochemical features coupled with isotopic data such as low initial 87sr 86sr 0 7033 positive end t 4 0 to 5 9 and ehf t 11 values young hf model ages and variable 206pb 204pb ratios 18 549 to 19 465 reported in this study suggest that their parental magmas originated from the partial melting of a juvenile lower crust and mixed with some old crustal components beneath the dananhu tousuquan arc in contrast the yuhai intermediate intrusions exhibit relatively low sio2 and k2o contents high mg values 40 56 and a wide range of ehf t values suggesting a source of sub continental lithospheric mantle metasomatized by slab derived fluids and melts zircon trace element and plagioclase compositions of the yuhai granitoids further imply that the silurian intermediate intrusion related magma was moderately oxidized mostly eun eun 0 6 and water rich 9 wt favorable for the copper mineralization whereas the carboniferous syenogranite related magma was weakly oxidized mostly eun eun 0 3 0 6 but also hydrous 6 wt combined with the regional tectono magmatic activities and metallogenic processes we suggest that the yuhai cu mo deposit and associated granitoids were formed in an arc setting and that the magma nature and its source components are the key factors constraining the distribution scale and style of the porphyry copper mineralization in eastern tianshan

sulphide magma as a source of metals in arc related magmatic hydrothermal ore fluids as magma ascends in subduction zones decreasing pressure and temperature cause it to separate into two or more phases in a process known as exsolution hydrothermal ore fluids and metal rich sulphide melts may be products of this exsolution conventionally the ore fluids are thought to acquire their metal content directly from the parent magma however it is probable that the ore fluids and sulphide melts interact after exsolution and therefore possible that the sulphide melts are an important source of metals for the ore fluids here we use petrographic analyses of erupted sulphide melts and compositional analyses of volcanic gases emitted immediately after an eruption at merapi volcano indonesia to show that magmatic hydrothermal fluids can derive their metals from dissolution of sulphide melts we find that the volcanic gases exhibit metal ratios that are comparable to those in the erupted sulphide melts furthermore we show that gases sampled immediately after the eruption have metal concentrations that are orders of magnitude higher than those of gases emitted during periods of quiescence we propose that the metal content of ores forming in volcanic arc environments is established by exsolution accompanying injections of primitive magma immediately before explosive eruptions the metal content of ore deposits formed during subduction zone volcanism was thought to be established when the ore fluid separates from the parent magma analyses of metal concentrations in erupted melts and the volcanic gases emitted after an eruption in indonesia reveal that metals can be added to the ore fluid later during mixing with separated melts

constraints on the origin of adakites and porphyry cu mo mineralization in chongjiang southern gangdese the tibetan plateau chongjiang is a low grade porphyry cu deposit located in the gangdese belt south tibet the petrogenesis and geodynamic settings of the miocene intrusions associated with the deposit remain controversial this study presents new results on in situ zircon hf o isotopic compositions and u pb ages whole rock major and trace elements and sr nd isotopes for the adakitic intrusions from chongjiang deposit the ore bearing biotite monzogranite porphyry has adakitic characteristics with enriched large ion lithophile elements lile and light rare earth elements lree and depleted in high field strength elements hfse p and ti la icp ms zircon u pb dating indicates that the ore bearing and barren adakites were emplaced at 14 9 0 3 ma and 12 9 0 3 ma respectively the porphyry is characterized by relatively high initial sr 87 sr 88 ratios 0 7059 to 0 7066 and negative whole rock epsilon nd t values 3 8 to 2 6 zircon delta 18 0 is slightly higher than mantle values 5 0 to 7 2 parts per thousand with varied epsilon hf t 1 0 to 7 6 most of the in situ zircon hf o isotopic data plot in a binary mixing trend between morb and lower continental crust derived melts these results indicate contributions from mixing of a mantle like source e g slab melts with continental crust interestingly most of the samples plot in the field defined by dabie adakites representing partial melting of the lower continental crust with several samples near in the circum pacific adakite field representing partial melting of subducted oceanic slabs which seemingly indicates that chongjiang adaldtes mostly formed through partial melting of lower continental crust with a small amount derived from oceanic slab melts these may be plausibly explained by plagioclase retention in the thickened tibetan continental crust which lowers sr contents in the magmas during crustal assimilation such a model is supported by other adakite discrimination diagrams which all point towards slab melting crustal contamination can compellingly explain the low grade of the chongjiang deposit considering the temporal spatial distribution of porphyry cu deposits geochemical characteristics and high oxygen fugacity we propose that the subducting ninetyeast ridge probably played a critical role in controlling the formation of miocene adakites and porphyry copper deposits in the eastern gangdese belt c 2017 elsevier b v all rights reserved

an experimental study of the mechanism of coal and gas outbursts in the tectonic regions abstract to reveal the mechanism of coal and gas outbursts in tectonic regions a gas driven multi physics coal and gas outbursts experimental apparatus was developed based on the experimental results the damage characteristics and the mechanism of outbursts of tectonic raw coal under different gas pressures and stress conditions are quantitatively investigated the experimental results show that the damage to coal samples increases with the increase in gas pressure when the gas pressure is 2 0 mpa the damage to the coal sample tends to decrease with increases in the confining and axial stress when the gas pressure exceeds the critical value of 2 2 mpa a strong outburst phenomenon occurs in which the pulverized coal is ejected and the outbursts cavern is blocked however when the gas pressure is 2 4 mpa the coal samples are completely broken down after the tests and the outbursts intensity becomes larger as the axial stress or the confining stress increases in addition the evolution of gas pressure and the degree of fragmentation of coal samples are also discussed quantitatively in the process of coal and gas outbursts the present study of the mechanism of coal and gas outbursts in the tectonic regions is helpful for the assessment and forecasting of potential outbursts

role of continental crust in petrogenesis of orogenic volcanic associations abstract orogenic volcanic rocks form a continuous spectrum between tholeiitic associations of island arcs and calc alkaline associations of continental margins and collision zones although these settings show a wide variation in plate convergence rate depth of scismic zone nature and age of subducted and over riding lithosphere the compositional characteristics of the volcanic association is correlated most strongly with crustal thickness tholeiitic associations dominated by basaltic rocks and with high feott mgo and low k2o for a given sio2 content are restricted to island arcs with crustal thickness less than 20 km more calc alkaline associations dominated by andesitic rocks with lower feot mgo and higher k2o for a given sio2 content occur in areas where crustal thickness exceeds 20 km these suggest that 1 fractional crystallization occurring within the continental crust may be the major mechanism responsible for variations within orogenic volcanic associations and 2 formation of calc alkaline associations may require the presence of continental crust these relationships suggest that calc alkaline magmas may be derived from more tholeiitic magmas by fractional crystallization possibly combined with crustal melting or contamination the extension of these processes might be responsible for formation of silicic ignimbrites occurring in continental areas where the crustal thickness exceeds 30 km in areas of crustal extension

fluid inclusion and stable h o c isotope studies of the giant shuangjianzishan epithermal ag pb zn deposit inner mongolia ne china abstract the shuangjianzishan ag pb zn deposit with a reserve of 145 mt 128 5 g t ag c 18 600 t or 600 moz ag and 2 2 wt pb zn 3 2 mt in the great hinggan range ghr ore district in ne china is the largest known silver deposit in asia the ag pb zn mineralized veins are primarily hosted by a permian slate unit three primary paragenetic stages of early pyrite quartz k feldspar i main ore sulfide sulfosalt quartz calcite sericite chlorite epidote ii and post ore quartz iii have been identified the ore stage ii was the dominant period for silver mineralization with canfieldite ag8sns6 argentite ag2s and freibergite ag cu 12sb4s13 the prevailing silver bearing minerals fluid inclusion microthermometric studies revealed that the ag pb zn vein formation occurred within a temperature range of 250 to 210 c and at a salinity of

an experimental investigation of the influence of water and oxygen fugacity on differentiation of morb at 200 mpa crystallization experiments were performed at 200mpa in the temperature range 1150 950 c at oxygen fugacities corresponding to the quartz fayalite magnetite qfm and mno mn3o4 buffers to assess the role of water and fo2 on phase relations and differentiation trends in mid ocean ridge basalt morb systems starting from a primitive mgo 9 8 wt and an evolved morb mgo 6 49 wt crystallization paths with four different water contents 0 35 4 7 wt h2o have been investigated in primitive morb olivine is the liquidus phase followed by plagioclase clinopyroxene amphibole is present only at water saturated conditions below 1000 c but not all fluid saturated runs contain amphibole magnetite and orthopyroxene are not stable at low fo2 qfm buffer residual liquids obtained at low fo2 show a tholeiitic differentiation trend the crystallization of magnetite at high fo2 mno mn3o4 buffer results in a decrease of melt feo mgo ratio causing a calc alkaline differentiation trend because the magnetite crystallization temperature is nearly independent of the h2o content in contrast to silicate minerals the calc alkaline differentiation trend is more pronounced at high water contents residual melts at 950 c in a primitive morb system have compositions approaching those of oceanic plagiogranites in terms of sio2 and k2o but have ca na ratios and feo contents that are too high compared with the natural rocks implying that fractionation processes are necessary to reach typical compositions of natural oceanic plagiogranites

molybdenum tungsten and manganese partitioning in the system pyrrhotite fe s o melt rhyolite melt impact of sulfide segregation on arc magma evolution abstract experiments were performed to determine the partitioning of molybdenum tungsten and manganese among a rhyolitic melt melt pyrrhotite po and an immiscible fe s o melt fe s o sulfide phases such as these may be isolated from a silicate melt along with other crystallizing phases during the evolution of arc magma and partition coefficients are required to model the effect of this process on molybdenum and tungsten budgets we developed an experimental design to take advantage of properties of the phases under study careful control of temperature allowed pyrrhotite and magnetite to be stable along with an fe s o melt and this phase assemblage allowed the composition of run product pyrrhotite to be used to calculate both fs2 and fo2 for the experiments at run temperature 1042 2 c a rhyolitic melt can be formed at low pressure under nominally dry conditions which removed the need for confining pressure as well as externally imposed fugacities the silica saturated melt allowed the charges to be contained in sealed evacuated silica tubes without danger of reaction and with closed system behavior for molybdenum and tungsten experiments were run for durations up to 2000 min molybdenite mb and wolframite wo were added to the experiments as sources for molybdenum and tungsten respectively manganese was added to the system as both a component of the starting rhyolitic pumice and of mn bearing wolframite oxygen fugacity in these experiments was fixed at the ni nio oxygen fugacity buffer sulfur fugacity was 10 1 bar run products were analyzed by epma and la icp ms analysis of the run products yielded d i a b 1 x standard deviation of the mean d mo fe s o si melt 90 10 d w fe s o si melt 9 3 d mo po si melt 35 3 and d w po si melt 0 0012 0 0006 the partition coefficients for manganese in this system are d mn fe s o si melt 2 9 0 3 and d mn po si melt 1 1 0 1 simple rayleigh fractionation modeling suggests that oxidized felsic melts produced through fractional crystallization may have lost as much as 14 of their initial molybdenum but only 2 of their initial tungsten through the removal of an fe s o melt along with crystalline phases modeling consistent with conditions of oxygen and sulfur fugacity influenced by assimilation of sulfide with low concentrations of molybdenum and tungsten from for example sedimentary rock results in evolved magmas significantly depleted in molybdenum but only moderately depleted in tungsten the molybdenum tungsten ratio can vary by two orders of magnitude these systematics may help to explain some of the variability in metal ratios of intrusion related hydrothermal ore deposits

geochronology and zircon hf isotope geochemistry of granites in the giant chalukou mo deposit ne china implications for tectonic setting abstract in this contribution the largest porphyry mo deposit in ne china chalukou is selected to provide insights into the tectonic evolution of ne china the deposit was considered to be rift related or climax type porphyry mo deposit developed in an extensional setting while other researchers attributed its formation to the subduction of the paleo pacific ocean in view of different granite petrogenesis between rift type and subduction type porphyry mo deposits geochronological and zircon lu hf isotope studies have been carried out on granitic rocks associated with the chalukou deposit zircon grains from the ore host monzogranite and ore causative granite porphyry yield weighted mean 206pb 238u ages of 166 2 ma and 152 2 ma with molybdenite samples yielding a re os isochron age of 150 2 ma indicating a jurassic age for both granitic intrusion and mo mineralization zircon ehf t values of monzogranite and granite porphyry range from 0 9 to 3 0 and from 1 4 to 0 5 respectively when integrated with published zircon lu hf isotopic data our data suggest that the barren granites both pre and post ore were mainly derived from mantle derived juvenile rocks whereas the syn ore granite requires additional involvement of old continental crust thus a contribution of continental crust to mo mineralization is suggested the petrogenesis and geochemical data reveal that the chalukou deposit is a subduction related porphyry mo deposits and not rift related integrated evidence links its formation to the southeastward subduction of the mongol okhotsk ocean instead of the westward subduction of the paleo pacific ocean

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

mesozoic multiple magmatism and porphyry skarn cu polymetallic systems of the yidun terrane eastern tethys implications for subduction and transtension related metallogeny abstract most mineralized porphyries associated with large to giant oxidized porphyry cu deposits show an affinity with relatively high sr y features the mesozoic porphyry skarn cu polymetallic systems of the yidun terrane hosted by the late triassic and late cretaceous intrusions provide chances to investigate the spatial and genetic relationships between subduction and transtension related magmatism and mineralization and determine the petrogenesis and fertility of magmatic rocks zircon u pb ages indicate that the late triassic pre ore quartz diorite porphyries and syn ore quartz monzonite porphyries were emplaced at 225 and 215 ma respectively the late cretaceous syn ore monzogranite porphyries were emplaced at 83 78 ma our new data combined with previously published geochronological data show the spatially overlapping distribution of the multiple mesozoic porphyry systems in the yidun terrane although all the late triassic intrusive rocks share similar geochemical characteristics the pre ore quartz diorite porphyries have normal arc related chemical features with low sr y and la yb n ratios high y and yb abundances while the syn ore quartz monzonite porphyries exhibit high sr y and la yb n ratios low y and yb abundances all samples show similar sr nd hf isotopic compositions 87sr 86sr i 0 7060 0 7117 end t 6 7 to 0 0 zircon ehf t 4 0 to 3 0 suggesting that they were probably derived from partial melting of juvenile lower crust trace element patterns and partial melt modeling indicate that the quartz diorite porphyries were likely formed by partial melting of normal thick lower crust while the causative quartz monzonite porphyries were probably formed by partial melting of eclogitized thickened lower crust we propose that pre ore quartz diorite porphyries were probably generated earlier via the subduction of garze litang oceanic crust and syn ore quartz monzonite porphyries were formed later by partial melting of sulfide enriched thickened juvenile lower crust thus these high sr y quartz monzonite porphyries host several economically important porphyry cu deposits such as pualng xuejiping and songnuo however the late cretaceous syn ore monzogranite porphyries have lower ehf t values 8 4 to 2 9 and end t values 7 5 to 3 8 than the late triassic porphyries indicating that the former mainly originated from ancient crustal materials new dataset and previous studies suggest that the late cretaceous post collisional transtension triggered the asthenospheric upwelling and the underplating of mafic magmas induced the partial melting of garnet bearing amphibolite and thus caused the emplacement of monzogranite porphyries and associated porphyry skarn cu mo deposits

linking mesozoic lode gold deposits to metal fertilized lower continental crust in the north china craton evidence from pb isotope systematics abstract the source s of lode gold deposits formed in precambrian cratons related to accretion collision and cratonic reactivation formerly attributed to either supercrustal volcano sedimentary sequences or deep crustal sub crustal origin remain controversial largely because gold deposits are spatially related to metamorphosed rocks but geochemical data somewhat indicate a poorly understood deep source reconciling such conflicts is important to better understand the main factor controlling the formation of ore deposits and their genetic link with specific tectonic settings giant late mesozoic lode gold provinces in the north china craton ncc were formed ca 1 7 ga later than cratonization metamorphism and contemporaneous with intensively felsic to mafic magmatism related to cratonic reactivation in this study we conduct a comprehensive pb isotope study on major gold deposits from the eastern yanshan belt northern margin of the ncc in order to constrain the source s of gold we attempt to map regional pb isotope variations of lower continental crust lcc and develop a two stage quantitative model punctuated by three prominent geological events at 2 80 ga 1 85 ga and 0 16 ga to reproduce time integrated pb isotopic signatures of deep seated lithospheric reservoirs to make a comparison with pb isotopic signatures of the gold mineralization gold bearing pyrites within different types of host rocks have relatively uniform pb isotopic ratios which are significantly different to high grade metamorphosed host rocks but similar to those of spatially associated late mesozoic granitic rocks our data show that the pb isotopic signatures of gold deposits vary consistently with presumed regional pb isotopes of the lcc during the late mesozoic lead isotopic heterogeneity of the lcc was likely caused by underplating of mafic magmas derived from mantle sources during underplating highly chalcophile elements e g au ag and cu were concentrated at the base of the lcc due to sulfide saturation from mafic magmas integrating petrological geochemical geochronological and considering chalcophile element solubility we propose a new genetic model to describe the formation of late mesozoic gold deposits in the ncc 1 early formation of sulfide bearing cumulates with high au cu ratios during magma differentiation at the base of the lcc 2 subsequent fluid fluxed remelting of these cumulates at the onset of lithospheric extension and release and ascent of ore forming fluids to the site of precipitation considering the metallogenic characteristics of other au ore forming systems we suggest that metal fertilization in deep seated reservoirs and subsequent tectonic decompression are important factors controlling the development of au rich ore deposits worldwide this study demonstrates how pb isotope can be employed to trace source s of gold deposits

controls of variable crustal thicknesses on late triassic mineralization in the yidun arc eastern tibet abstract modern arc related granitic magmas have variable sr y ratios and metal contents depending on the thickness of the arc crust on the global scale however whether this is true of ancient arcs on a regional scale is still unclear the yidun arc is a triassic continental arc in eastern tibet that has magmatic and mineralization characteristics varying between the northern and southern yidun arcs during the triassic several models have been proposed to explain these differences however these models are still controversial to this end we investigated the petrogenesis of the late triassic xiuwacu intrusion which is located between the northern and southern yidun arcs the zircon u pb dating and sr nd hf o isotopes indicate that the late triassic xiuwacu intrusion was emplaced at 215 6 2 2 ma and was predominately derived from partial melting of an enriched metastasized mantle combined with amphibole dominated fractionation and a small amount of crustal assimilation comparing the late triassic xiuwacu intrusion with other volcanic rocks and intrusions in the yidun arc indicates that the late triassic xiuwacu intrusion has a source similar to that of igneous rocks in the southern yidun arc in addition volcanic rocks and porphyries in the southern yidun arc have high dy yb 1 8 2 6 mostly 2 0 and sr y 24 120 ratios lack or have slightly negative eu anomalies and exhibit calc alkaline trends indicating that garnet amphibole and magnetite crystalized from their magma source under high pressure the volcanic rocks in the northern yidun arc have low dy yb 1 3 2 2 mostly

the effect of gas sorption on the strength of coal abstract the sudden violent failure of coal accompanied by the release of large volumes of gas is known as an outburst and represents a major coal mining hazard one parameter affecting coal outbursts is the coal strength provided that the pore fluid is inert the strength will decrease with increasing pore gas pressure in accordance with the law of effective stress however the gases involved in outbursts carbon dioxide and or methane are not inert they sorb onto the coal surfaces reducing the surface energy and thus theoretically at least further reduce the strength of the coal the tensile strength of two coals have been measured in sorbing carbon dioxide and nonsorbing helium atmospheres up to pore gas pressures of 3 5 mpa it has been shown that for these coals gas sorption produces no significant reduction in coal strength at the 95 confidence level hence if these results are representative of all coals it would appear that the strength reduction due to gas sorption is not a factor that need be taken into account in the consideration of coal outbursts

gas driven rapid fracture propagation under unloading conditions in coal and gas outbursts abstract coal and gas outbursts have long posed a serious risk to safe and efficient production in coal mines it is recognised that coal and gas outbursts are triggered by excavation unloading followed by gas driven rapid propagation of a system of pre existing or mining induced fractures gas filled fractures parallel to a working face are likely to experience opening first then expansion and rapid propagation stages under unloading conditions the fracture opening is driven by the effective stress inside the fracture while the fracture expansion and rapid propagation is propelled by the pressure build up of desorbed gas in the vicinity of the fracture based upon this understanding this research aimed to identify the key factors affecting outburst initiation and its temporal evolution during roadway developments specifically the response of pre set fractures in a thin coal seam sandwiched between rock layers to roadway development is simulated using a geomechanical model coupled with fracture mechanics for fracture opening and propagation in addition kinetic gas desorption and its migration into open fractures is considered during simulations outburst is deemed to occur when the fracture length exceeds the dimension of a host element the findings of this research suggest that the simulated coal and gas outburst caused by roadway development may be considered as a dynamic gas desorption driven fracture propagation process the occurrence of coal and gas outbursts is found to be influenced mainly by the coal properties fracture attributes and initial gas pressure and the in situ stress conditions furthermore the model predictions in terms of dome shaped erupted zone and layer by layer coal breakage are consistent with the field reports in addition the model results suggest that delayed occurrence of coal and gas outbursts especially after sudden exposure of a coal seam or after blasting disturbance reported in the literature may be related to the gas desorption behaviour

precursory inflation of shallow magma reservoirs at west sunda volcanoes detected by insar 1 we use 2006 2009 alos interferometric synthetic aperture radar data over the entire west sunda arc indonesia home of 13 of the world s active volcanoes to derive arc wide time dependent ground deformation data we present unambiguous evidence of inflation at six volcanoes three of which erupted after the observation period we show that these volcanoes have shallow magma reservoirs at 1 3 km depth below the average regional elevation a global comparison of reservoir depths at arc volcanoes suggests that volcanoes in extensional and strike slip settings west sunda can develop shallow reservoirs whereas volcanoes in compressional settings may lack them thus magma ascend through the upper crust could be influenced by intra arc tectonic settings

increasing magmatic oxidation state from paleocene to miocene in the eastern gangdese belt tibet implication for collision related porphyry cu mo au mineralization in the gangdese belt of southern tibet paleocene eocene magmas record the final stage of neo tethyan subduction and are associated with few economic porphyry deposits in contrast magmas formed during later stages of the india asia collision in the oligo miocene are associated with several large porphyry cu mo au deposits especially in the eastern part of the belt 89 e 93 e in a previous study we showed that these oligocene miocene magmas were more hydrous than the earlier paleocene eocene magmas in this study we show that the later magmas were also more oxidized paleocene eocene rocks from the eastern gangdese belt are characterized by low zircon ce4 ce3 ratios mostly 50 32 3 141 9 average 74 3 30 1 n 33 and higher f o2 values fmq 0 8 2 9 average 1 8 0 8 n 6 estimated from magnetite ilmenite pairs estimates of magmatic oxidation state from amphibole compositions also show an increase from fmq 1 2 to 2 1 average 1 6 0 2 n 40 in the paleocene eocene to 2 0 to 2 8 average 2 5 0 2 n 58 in the miocene sparse whole rock fe3 fe2 ratios show the same general trend the amphibole results are systematically shifted to higher fmq compared to data from magnetite ilmenite pairs but their trend is internally consistent the higher oxidation states and water contents of miocene igneous rocks from the eastern gangdese belt may explain their unique association with large porphyry deposits in tibet because it has been shown from other studies that the potential for hydrous calc alkaline magmas to transport au is maximized near fmq 1 0 and cu at higher f o2 fmq 1 0 in comparison the somewhat less oxidized and less hydrous paleocene eocene magmas would have been less fertile for the formation of such deposits we suggest that these differences reflect the tectonomagmatic evolution of the cenozoic gangdese collisional orogen from early collision related magmatism in the paleocene eocene to late collisional magmatism in the miocene asthenospheric upwelling following slab breakoff in the miocene caused interaction between mantle derived magmas and previously subduction modified tibetan lithosphere the resultant evolved magmas had high oxidation states and water contents which are favorable properties for the subsequent formation of magmatic hydrothermal porphyry cu mo au deposits

giant ore deposits formed by optimal alignments and combinations of geological processes giant ore deposits are priority targets for mining companies a review of the characteristics of several giant porphyry and epithermal deposits worldwide suggests that they formed from ordinary processes that were fortuitously operating at maximum efficiency

geochronology and petrogenesis of miocene granitic intrusions related to the zhibula cu skarn deposit in the gangdese belt southern tibet abstract the zhibula cu skarn deposit 19 5 mt ore 1 64 near the qulong porphyry cu mo deposit is located in the gangdese porphyry copper belt in southern tibet the deposit is a typical metasomatic skarn that is related to the interaction of magmatic hydrothermal fluids and calcareous host rocks stratiform skarn orebodies are mainly distributed in the contact between tuff and marble in the lower part of the jurassic yeba formation endoskarn zonations for an outward trend are observed in the granodiorite which grade from a fresh granodiorite to a weakly chlorite altered granodiorite a green diopside bearing granodiorite and a dark red brown garnet bearing granodiorite the zhibula granodiorite and monzogranite have similar secondary ion mass spectrometry sims zircon u pb ages of 16 9 0 3 ma and 17 0 0 2 ma respectively they exhibit different fractional crystallization from granodiorite sio 2 64 8 69 3 wt to monzogranite sio 2 72 3 76 8 wt both the granodiorite and monzogranite are characterized by high al 2 o 3 12 6 16 7 wt and k 2 o 1 5 5 5 wt contents high sr y 35 151 and la yb 19 48 ratios and variable mgo 0 16 3 91 and mg 31 61 values they display features of enrichment in large ion lithophile elements liles e g rb ba sr and k depletion in high field strength elements hfses e g nb ta ti and p and moderate negative eu anomalies eu 0 58 0 98 they show restricted in situ zircon hf isotopic compositions 6 7 to 8 8 only one sample is 4 5 and consistent 18 o values 6 0 to 6 6 the geochemical data indicated that the miocene zhibula granitic intrusions formed by the magma that were characterized by high sr y ratios and were derived from the partial melting of the thickened juvenile lower crust which may have been metasomatized by the slab melts during subduction of the neo tethyan oceanic crust and were induced by the convective removal of the thickened lithosphere in addition the zhibula cu skarn deposit and the qulong cu mo deposit form a significant porphyry skarn ore system

the distribution and timing of molybdenite mineralization at the el teniente cu mo porphyry deposit chile this journal is published under the terms of green open access authors may post a copy of the accepted i e post peer review version of their paper https doi org 10 2113 econgeo 110 2 387 in a repository of their choice or to their personal website after the relevant embargo period has passed the embargo period will be 12 months from formal online publication

environmental geochemistry 40years research at imperial college london uk abstract this paper reviews the development of multi purpose geochemical mapping and the progress of research in applied environmental geochemistry and health at imperial college over the past 40 years with funding from the research councils uk government eu industry and ngos research has provided the basis for postgraduate training in areas ranging from the applications of geochemistry to plant agricultural livestock and wildlife nutrition to evaluating contamination from metalliferous mining and smelting understanding the chemical nature of the urban environment and relationships between geochemistry and human health and disease examples include 1 the influence of mo in marine black shales on the cu nutrition of grazing cattle and sheep 2 the importance of soil ingestion on trace element intake and metabolism and metal exposure in farm livestock 3 the impacts of soil contamination from historical metalliferous mining and smelting on agriculture and human exposure to metals including potential health problems from cd at shipham and from as in sw england 4 the growth of urban geochemistry and the importance of pb in the urban environment 5 the health impacts due to hg losses from the informal sector au mining in brazil and 6 health issues relating to f excess and se deficiency in china

zircon compositional evidence for sulfur degassing from ore forming arc magmas porphyry cu mo au and epithermal au ag deposits are major sources of mined metals and are commonly formed by magmatic hydrothermal fluids derived from hydrous magmas in phanerozoic convergent margin settings the igneous rock assemblages associated with porphyry mineral deposits are common in modern convergent margin settings but while many have produced acidic magmatic fluids very few past or present have produced sufficient metal chlorine and sulfur enrichments necessary to engender an ore deposit the reasons for this remain uncertain we report shrimp rg ion microprobe analyses of hafnium titanium and rare earth element ree abundances in zircon a nearly ubiquitous and robust trace mineral in crustal magmas comparison of the compositions of zircons in ore forming and barren granitic plutons indicate that ore forming granites crystallized at relatively low temperature and have relatively small negative europium anomalies mostly eu n eu n 0 4 we interpret these small zircon europium anomalies to indicate oxidizing magmatic conditions and hypothesize that in many cases this reflects oxidation due to so 2 degassing from magmas with a relatively low fe s ratio oxidation of europium and iron in the melt is produced by reduction of magmatic sulfate s 6 to so 2 s 4 upon degassing this interpretation reinforces the important role of oxidized sulfur rich fluids in porphyry and epithermal mineral deposit formation zircon compositions thus may be used to identify ancient magmas that released significant amounts of so 2 rich gases and regional surveys of zircon composition are potentially a valuable tool for mineral exploration

zircon petrochronology reveals the temporal link between porphyry systems and the magmatic evolution of their hidden plutonic roots the eocene coroccohuayco deposit peru abstract we present zircon geochronologic la icpms and id tims trace element and hf isotopic evidence for a complex evolution of the plutonic roots of the eocene coroccohuayco porphyry system southern peru la icpms u pb dating has initially been carried out to optimize grain selection for subsequent high precision id tims dating and to characterize crustal assimilation xenocrystic cores this combined in situ and whole grain u pb dating of the same grains has been further exploited to derive a robust temporal interpretation of the complex magmatic system associated with the coroccohuayco porphyry skarn deposit our data reveal that a heterogeneous gabbrodioritic complex was emplaced at ca 40 4 ma and was followed by a nearly 5 ma long magmatic lull until the emplacement of dacitic porphyry stocks and dykes associated with the mineralizing event at ca 35 6 ma however at the sample scale zircons from the porphyries provide insight into a 2 ma long lived hidden magmatism probably at 4 9 km paleodepth prior to porphyry intrusion and mineralization for which no other evidence can be found on the surface today these dates together with zircon trace element analysis and hf isotopes argue for the development of a long lived magmatic system dominated by amphibole fractionation with an increasing amount of crustal assimilation and the development of a large and sustained thermal anomaly the system was probably rejuvenated at an increasing rate from 37 5 to 35 6 ma with injection of fresh and oxidized magma from the lower crust which caused cannibalism and remelting of proto plutons the porphyry intrusions at coroccohuayco were emplaced at the peak thermal conditions of this upper crustal magma chamber which subsequently cooled and expelled ore fluids zircon xenocrysts and hf isotopes in the porphyritic rocks suggest that this large upper crustal system evolved at stratigraphic levels corresponding to triassic sediments similar to the mitu group that may be present below the district using the zircon ce anomaly as a proxy for oxidation state of the magma through time we show that the high oxidation state of the porphyries is not the result of upper crustal processes but is rather controlled by magmatic processes occurring at deeper levels a comparison of our data with available high precision geochronologic data at other porphyry systems suggests that such deposits may form when injection rate volume and heat of their long lived upper crustal magmatic system reach their peaks these features might be diagnostic of a productive deposit

does subduction polarity control metallogeny the mediterranean case the distribution of ore deposit types in different sectors of the circum mediterranean realm that have been affected by subduction processes since the cretaceous varies in space and time sectors involved in w directed subduction sardinia apennines maghrebides internal betics tyrrhenian western eastern carpathians are dominated by relatively low sulphidation epithermal vms deposits orogens formed by ne directed subduction dinarides hellenides pontides anatolides taurides dhpat were initially dominated by pluton related porphyry skarn high sulphidation epithermal associations these distinct metallogenic styles can be related to the systematic tectono magmatic asymmetry of e ne and w directed subduction systems and are analogous to the relationship observed in circum pacific belts exceptions to this simple pattern occurred in the dhpat in the cenozoic when deposit associations typical of both e directed and w directed systems were formed such exceptions are interpreted to reflect superimposition of contrasting subduction trends and inheritance from earlier metallogenic stages apuseni or the interference of subduction processes with subduction unrelated extension hellenides west anatolia

a new mechanistic model for prediction of instantaneous coal outbursts dedicated to the memory of prof daniel d joseph abstract an instantaneous coal outburst is a sudden and violent simultaneous ejection of large amounts of coal and gas methane carbon dioxide from the working coalface during underground mining the occurrence of such an outburst usually leads to a gas explosion and pollution of the mine despite extensive research efforts in the past 150 years the physical mechanisms causing coal outbursts are still poorly understood here we present a new model combining fracture mechanics gas dynamics and rock mechanics to elucidate the physical mechanisms leading to instantaneous outbursts this model suggests a domino effect that leads to a catastrophic failure of the coal and an instantaneous outburst the model identifies a critical condition for the onset of instantaneous outbursts and it successfully predicts all of the observed phenomena preceding outbursts most of which are explained for the first time the model also predicts a fracture aperture size effect which is confirmed by the existing observation based fracture classification scheme used to assess outburst proneness

skarn metallogeny through zircon record an example from the daye cu au fe mo district eastern china abstract the daye district in eastern china hosts more than 50 fe cu au mo porphyry skarn deposits that are associated with intermediate to felsic rocks of early cretaceous ages the origin of these ore related granitoids has been intensively investigated but the petrogenetic factors controlling variable metal associations e g fe cu mo or cu au fe in different skarn deposits remain not well understood here we present hf isotope and trace element data of zircons from ore related intrusions of four representative skarn deposits i e the lingxiang and chengchao fe skarn the tonglushan cu au fe skarn and the tongshankou cu mo porphyry skarn deposits to better understand controls of the source oxidation state and fractionation degree of the magmas on the polymetallic metallogeny in the daye district zircons from the ore related granodiorite at tongshankou quartz diorite at tonglushan and diorite at lingxiang have comparable ehf t values ranging from 11 3 to 1 1 which are similar to values of the early cretaceous mafic rocks ehf t 11 9 to 1 2 in the daye district and adjacent areas this similarity suggests that these ore related intrusions were largely derived from an enriched lithospheric mantle source in comparison zircons from the ore related diorite and quartz monzonite associated with the chengchao fe skarn have much lower ehf t values 11 6 to 25 3 indicating larger degrees of crustal contribution on average zircons from the cu related intrusions at tongshankou and tonglushan have higher ce ce 1100 method of zhong et al 2019 and ce4 ce3 170 method of ballard et al 2002 ratios which are interpreted reflecting higher oxidation state for the magmas in contrast zircons from fe related intrusions at chengchao and lingxiang have much lower average values of ce ce preliminary results presented here further reveal that zircon eu eu ratio can be a useful discrimination for intrusions associated with the various metal associations in the daye district zircon eu eu of 0 45 broadly separates the fe skarns and cu bearing skarns while eu eu of 0 65 can further distinguish the cu au fe skarn from the cu mo variety this study highlights zircon chemistry as a useful indicator for the nature evolution and metallogeny of the ore related intrusions

insight into zircon ree oxy barometers a lattice strain model perspective abstract zircon rare earth element ree oxy barometers have been widely used to calculate magma oxygen fugacity however sometimes confusing results are obtained such as extremely reduced oxygen fugacity in hadean magmas e g fmq 8 extremely oxidized oxygen fugacity in post hadean magmas e g fmq 10 and contradictory oxygen fugacities recorded in ore related porphyry magmas nno 5 vs nno 1 to address these issues this work reviews the underlying assumption of zircon ree oxy barometers the lattice strain model by introducing a geochemical filter to identify clean inclusion free zircon and a new parameter k to constrain the d zircon whole rock deviation from the lattice strain model we systematically re evaluate the common zircon ree oxy barometers address the issues noted in hadean post hadean and ore related magmas and provide an alternate approach to using zircon ree in studies of magmatic processes

miocene porphyry copper deposits in the eastern tethyan orogenic belt using sr o isotopes and sr y ratios to predict the source of ore related and ore barren magmas abstract there are many miocene collision and subduction related porphyry cu deposits in the eastern tethyan orogenic belt however the petrogenesis of the ore related magmas and the mechanism of metal enrichment remain controversial here we present a geochemical study and comparison of the major miocene ore related porphyries and coeval ore barren magmatic rocks in the urumieh dokhtar magmatic arc in iran and the chagai belt in pakistan and the eastern gangdese belt of the himalaya the results show that ore related porphyries are characterized by relatively depleted mean sr isotopic compositions 0 704217 0 706859 in the urumieh dokhtar magmatic arc 0 705052 0 706588 in the eastern gangdese belt 0 705252 0 706708 in the chagai belt but higher maximum sr y ratios 40 149 in urumieh dokhtar 79 178 in eastern gangdese 52 178 in chagai in contrast the coeval ore barren magmatic rocks yield relatively enriched mean sr isotopic compositions 0 704722 0 707653 in urumieh dokhtar 0 704701 0 707802 in eastern gangdese 0 705982 0 707856 in chagai but lower maximum sr y 2 88 in urumieh dokhtar 61 136 in eastern gangdese and 19 35 in chagai a deep crustal hot zone model provides a robust explanation of these data melts derived from a deeper melt source in juvenile mafic lower crust where mantle derived materials are common have a greater potential to yield a higher tonnage of metallic cu such as the sar cheshmeh deposit in iran which is derived from a deep melt zone and characterized by a low radioactive mean sr isotopic value of 0 704851 but a huge tonnage of metallic cu of 7 2 mt and a high maximum sr y value of 117 representative of a deeper depth of the melt zone whereas the dalli deposit in iran derived from a relatively shallow melt zone has a more radioactive mean sr isotopic value of 0 706859 but a smaller amount of metallic cu of 0 04 mt and a lower maximum sr y ratio of 40 conversely re melting the contact between newly formed and pre existing crust where mantle derived materials are absent will produce ore barren rocks additionally the ore barren rocks with low sr y ratios

the formation mechanism of reduced porphyry mo deposits in the west junggar region xinjiang the suyunhe example abstract some porphyry mo deposits with relatively reduced ore assemblages characterized by high reduced gases e g ch4 and a lack of magnetite and hematite are generally considered as the reduced porphyry mo deposits nevertheless the role of oxygen fugacity fo2 in controlling mo enrichment and precipitation of molybdenite in such reduced porphyry mo deposits is poorly understood the suyunhe reduced porphyry mo deposit with a mo metal reserve of 0 57mt at an average grade of 0 05 0 09 located in the west junggar terrane in xinjiang is associated with early permian granitic rocks which emplaced into the volcano sedimentary sequences of the middle devonian barluk formation in this study we report that the variation of magmatic fo2 the possible mechanism of mo enrichment and the contributions of the reduced gases or matter to molybdenite precipitation results indicate that the primitive magma is still oxidized with fo2 nno ni nio oxygen buffer but it is then reduced due to contamination by the reduced sequences furthermore the decreasing magmatic fo2 does not significantly prevent the enrichment of mo metals during magmatic evolution by contrast the evolved parental magma characterized by highly differentiated and fluorite rich is responsible for improving mo concentration of melts most of reduced gases are derived from decomposition of organic matter occurring in the reduced volcanic sedimentary rocks of barluk formation more importantly these reduced gases e g ch4 play a role in molybdenite precipitation which may effectively improve the efficiency of metal precipitation

characteristics and origins of coal cleat a review abstract cleats are natural opening mode fractures in coal beds they account for most of the permeability and much of the porosity of coalbed gas reservoirs and can have a significant effect on the success of engineering procedures such as cavity stimulations because permeability and stimulation success are commonly limiting factors in gas well performance knowledge of cleat characteristics and origins is essential for successful exploration and production although the coal cleat literature spans at least 160 years mining issues have been the principal focus and quantitative data are almost exclusively limited to orientation and spacing information few data are available on apertures heights lengths connectivity and the relation of cleat formation to diagenesis characteristics that are critical to permeability moreover recent studies of cleat orientation patterns and fracture style suggest that new investigations of even these well studied parameters can yield insight into coal permeability more effective predictions of cleat patterns will come from advances in understanding cleat origins although cleat formation has been speculatively attributed to diagenetic and or tectonic processes a viable mechanical process for creating cleats has yet to be demonstrated progress in this area may come from recent developments in fracture mechanics and in coal geochemistry

airflow disturbance induced by coal mine outburst shock waves a case study of a gas outburst disaster in china abstract we explore the magnitude of airflow disturbance in mine roadways induced by gas outburst shock waves outburst shock wave propagation in the near field of the outburst source is established and simulated in three dimensions using fluent the effects in connected but distal roadways are represented by a simplified one dimensional network model and solved by flowmaster a mesh based parallel code coupling interface mpcci is applied to couple the three dimensional near source model and the one dimensional distal model the coupled model is verified by theoretical analysis and against observations from a coal and gas outburst incident comprising 2887 tonnes of coal that occurred in the jiulishan coal mine china and general characteristics of outburst events explored simulations demonstrate that airflow disturbance induced by outburst shock waves in the coal mine is principally controlled by the shock wave overpressure and fan pressure provided by the main fan of these the shock wave overpressure exerts the dominant impact the larger the shock wave overpressure the more rapid the decrease of airflow in the roadway branches and the larger the ultimate airflow decrease furthermore the arrival time of the minimum air flow rate is delayed when the fan pressure is large the ability to resist airflow disturbance is enhanced and the area subject to countercurrent flow is reduced the initial air flow rate and the restored air flow rate show less correlation with the shock wave overpressures however they are both significantly affected by the pressure of the main fan this work presents a novel approach for the study of airflow disturbance in underground ventilation networks in coal mines caused by coal and gas outbursts and provides guidance for the design of outburst prevention facilities

paleozoic magmatism and porphyry cu mineralization in an evolving tectonic setting in the north qilian orogenic belt nw china abstract the nww striking north qilian orogenic belt records the paleozoic accretion collision processes in nw china and hosts paleozoic cu pb zn mineralization that was temporally and spatially related to the closure of the paleo qilian qinling ocean the wangdian cu deposit is located in the eastern part of the north qilian orogenic belt nw china copper mineralization is spatially associated with an altered early paleozoic porphyritic granodiorite which intruded tonalites and volcaniclastic rocks alteration zones surrounding the mineralization progress outward from a potassic to a feldspar destructive phyllic assemblage mineralization consists mainly of quartz sulfide stockworks and disseminated sulfides with ore minerals chalcopyrite pyrite molybdenite and minor galena and sphalerite gangue minerals include quartz orthoclase biotite sericite and k feldspar zircon la icpms u pb dating of the ore bearing porphyritic granodiorite yielded a mean 206pb 238u age of 444 6 7 8 ma with a group of inherited zircons yielding a mean u pb age of 485 12 ma consistent with the emplacement age 485 3 6 2 ma of the barren precursor tonalite rhenium and osmium analyses of molybdenite grains returned model ages of 442 9 6 8 ma and 443 3 6 2 ma indicating mineralization was coeval with the emplacement of the host porphyritic granodiorite rhenium concentrations in molybdenite 208 9 213 2 ppm suggest a mantle re source the tonalities are medium k calc alkaline they are characterized by enrichment of light rare earth elements lrees and large ion lithophile elements liles depletion of heavy rare earth elements hrees and high field strength elements hfses and minor negative eu anomalies they have ehf t values in the range of 3 6 to 11 1 with two stage hf model ages of 0 67 1 13 ga suggesting that the ca 485 ma barren tonalites were products of arc magmatism incorporating melts from the mantle wedge and the lithosphere in contrast the 40 m y younger ore bearing porphyritic granodiorite is sub alkaline and peraluminous they are enriched in lrees and liles depleted in hfses and show weak negative eu anomalies they display ehf t values of captured or inherited zircons in the range of 8 5 to 10 0 and younger two stage hf model ages of 0 78 ga and 0 86 ga similar to those of ca 485 ma tonalite the ca 445 ma zircons have ehf t values of 2 1 to 9 9 with two stage hf model ages of 0 75 1 27 ga moreover they have relatively high oxygen fugacity than that of the precursor barren tonalite the ca 445 ma magmas at wangdian thus formed in a subduction setting and incorporated melts from the subduction modified lithosphere that had previously been enriched by additions of chalcophile and siderophile element rich materials by the earlier magmatism and metasomatism during the paleo qilian qinling ocean subduction event

petrogenesis of granitoids in the dewulu skarn copper deposit implications for the evolution of the paleotethys ocean and mineralization in western qinling china abstract the tethyan tectonic domain hosts numerous world class mineral deposits among these the dewulu skarn copper deposit in western qinling china belongs to the paleotethys ore belt the skarn and orebodies here occur as stratoids or lenses at the contact between the triassic dewulu intrusive complex and permian marine clastic and carbonates alteration minerals include prograde skarns garnet diopside wollastonite plagioclase hornblende actinolite tremolite epidote chlorite calcite quartz and sericite the main ore types include early disseminated skarn type replacement orebodies and late stage quartz sulfide veins chalcopyrite is the major ore mineral along with pyrite bornite and sphalerite the dewulu intrusive complex comprises quartz diorite quartz diorite porphyry and dioritic mafic microgranular enclaves mme the mmes are spheroidal in shape and have igneous mineral assemblages acicular apatites complex oscillatory zoned plagioclase and quartz megacrysts surrounded by mafic minerals the mmes are metaluminous and calc alkaline to high k calc alkaline and possess relatively high ni cr and mgo contents and mg values they display sub parallel patterns in trace element spider diagrams and rare earth element ree plots they are also characterized by the enrichment of rb u and th depletion of ba sr nb and ta and negative eu anomaly zircon la icp ms u pb dating of the dioritic mme yields an age of 247 0 2 2 ma coeval with the host quartz diorite quartz diorite porphyry and ore related sericite 40ar 39ar plateau ages within analytical uncertainties oxygen fugacity estimated from trace element compositions of zircons from the dioritic mme shows fmq 3 3 the zircons have negative ehf t values in a range of 8 0 to 3 3 corresponding to two stage model ages ranging from 1 48 to 1 78 ga the integrated data from petrology geochronology and bulk geochemistry suggest that the early triassic granitoids associated with cu skarn mineralization at dewulu were products of arc magmatism and involved magma mixing in an active continental margin setting the magma was sourced through partial melting of enriched sub continental lithospheric mantle that had been previously modified by slab derived melt during the continuous northward subduction of the paleotethys oceanic slab

metallogenic potential of porphyries in tulasu basin northwest tianshan insight from magma nature and crustal thickness abstract tulasu basin in northwest tianshan hosts a lot of late paleozoic epithermal deposits such as axi jingxi yelmand and tawuerbieke deposits epithermal deposits are considered as telescoped systems of porphyry deposits however porphyry deposits are not discovered in tulasu basin though granitoid porphyries are widespread in this region tulasu pluton complex as one of the largest intrusions located in northeast part of tulasu basin is composed of the late devonian quartz diorite porphyry and pyroxene diorite porphyry and the late carboniferous granodiorite porphyry and granite porphyry the metallogenic potential of each rock type is evaluated in terms of magma nature and crustal thickness of source the magma nature including magmatic oxygen fugacity and water content is estimated based on trace elements compositions of zircons amphibole hygro barometer and ilmenite magnetite mineral pairs the mean ce4 ce3 ratio magmatic oxygen fugacity and water content of the late devonian quartz diorite porphyry are 291 fmq 1 0 1 8 fmq 0 2 1 5 and 0 9 2 2 wt respectively while those of pyroxene diorite porphyry are 96 fmq 2 6 3 3 and 0 2 1 3 wt the late carboniferous granodiorite porphyry has a mean ce4 ce3 ratio of 138 the crustal thicknesses in the tulasu area are estimated to be 30 35 km at the late devonian and 40 km at the late carboniferous based on whole rock geochemistry of the late devonian dioritic rocks and the late carboniferous granitic rocks considering magmas associated with typical porphyry deposits which have high oxygen fugacity of fmq 1 5 to 3 and water content 4 5 wt and are derived from crustal thickness of 30 km we think both dioritic and granitic rocks of tulasu porphyries have favorable conditions of oxidation state and crustal thickness for porphyry deposit formation however the magmatic water contents of these rocks are relatively low therefore the tulasu porphyries have low potential in forming porphyry cu deposits

origin of miocene cu bearing porphyries in the zhunuo region of the southern lhasa subterrane constraints from geochronology and geochemistry abstract the zhunuo cu bearing porphyries are located in the westernmost part of the miocene gangdese porphyry cu mo au deposit belt zircon u pb dating of the diorite porphyry k feldspar granite porphyry and monzonitic granite porphyry in zhunuo yielded crystallization ages of 12 5 0 4 ma 12 3 0 3 ma and 12 4 0 3 ma respectively the diorite porphyry is characterized by low sio 2 58 61 61 14 wt and th 0 30 0 76 ppm concentrations low th la 0 05 0 1 ratios and high mg 49 values coupled with low 87 sr 86 sr i 0 703777 0 703783 and high e nd t 4 07 to 4 90 values they also have adakite like affinities such as low y 10 5 12 0 ppm and high sr y ratios 61 65 they were probably derived from a thickened juvenile lower continental crust the k feldspar granite porphyry probably originated in the middle upper continental crust because of their high sio 2 73 59 74 98 wt and th 50 1 52 1 ppm concentrations high th la 1 67 2 10 and low sr y 20 2 20 7 ratios and mg 32 38 values combined with high 87 sr 86 sr i 0 710921 0 712008 low e nd t 8 47 to 9 26 isotopic compositions and old nd model ages 1 16 1 25 ga their magmas were most likely partial melts of the preserved ancient crust similar to the central lhasa subterrane the geochemical characteristics and sr nd isotopic compositions of the monzonitic granite porphyry display trends that lie between those of the diorite porphyry and k feldspar granite porphyry and they are therefore likely to be production of hybridization between the above two melts the ore bearing diorite porphyry and monzonitic granite porphyry have higher zircon ce 4 ce 3 ratios than the ore barren k feldspar granite porphyry indicating a higher oxygen fugacity in the ore bearing magmas we suggest that metals were released from the re melting of arc related cumulates which formed during lower crustal growth and thickening this mechanism provides a reasonable explanation for the significant flare up of mineralization during the miocene in the gangdese region the lower continental crust beneath southern lhasa subterrane probably was uniformly juvenile but the region to the west of zhunuo was not mineralized due to input of large ancient crustal materials in the source of these ore barren adakite like rocks

the partitioning of chalcophile elements between sediment melts and fluids at 3 gpa 950 1050 c with implications for slab fluids in subduction zones abstract there is growing evidence for the importance of slab sediment components in transferring trace element signatures to the arc mantle the chalcophile elements are of particular interest due to their differing compatibility in sulfide and sulfate phases the stability of which are dependent on subducted sediment redox many studies have shown that chalcophile elements are compatible in saline fluids at shallow levels of arcs f o 2 conditions where po is present at 1000 c dfluid melt ce 4 0 3 dfluid melt mo 319 43 dfluid melt as 669 134 dfluid melt sb 1437 208 dfluid melt pb 73 4 all errors are 1 and in oxidized conditions where anh is present at 1000 c dfluid melt ce 150 48 dfluid melt mo 3 7 1 9 dfluid melt as 2 5 1 7 dfluid melt sb 12 5 1 dfluid melt pb 3 8 1 8 the contrasting behavior of mo and ce in fluids versus melts is consistent with the notion that elevated mo in lavas from the lesser antilles arc is associated with reduced fluids extracting mo from subducted black shales the mo ce ratio is a promising tool in other arcs to infer the role that fluid may or may not play for chalcophile enrichment in the sub arc mantle unlike melts fluids in equilibrium with reduced po bearing sediments can endow the arc mantle in chalcophile elements without concomitant oxidation

ore genesis and hydrothermal evolution of the baiyinnuo er zinc lead skarn deposit northeast china evidence from isotopes s pb and fluid inclusions the baiyinnuo er zinc lead deposit 32 74 mt at 5 44 zn 2 02 pb and 31 36 g t ag located in the south segment of the great xing an range is the largest zn pb deposit in northern china skarn and orebodies mainly occur between the different units of the huanggangliang formation or within the contact zone between the intrusions and permian marble several phases of igneous rocks exposed within the mining areas and among them the yanshanian plutonic rocks which intruded into limestone of the early permian huanggangliang formation are interpreted to be the source of ore since their pb isotope compositions 206pb 204pb 18 25 18 35 207pb 204pb 15 50 15 56 and 208pb 204pb 38 14 38 32 are highly consistent with the sulfides including sphalerite galena and chalcopyrite 206pb 204pb 18 23 18 37 207pb 204pb 15 47 15 62 and 208pb 204pb 37 93 38 44 sulfur isotope values of the sulfides give a narrow 34s interval of 6 1 to 4 6 mean 5 4 n 15 suggesting the ore forming fluid is of magmatic origin three main paragenetic stages of skarn formation and ore deposition have been recognized based on petrographic observation which are the preore stage garnet clinpyroxene wollastonite magnetite sulfides the synore stage sulfides epidote quartz calcite garnet and the postore stage calcite chlorite quartz fluorite several fluid evolution episodes can be inferred from microthermometric results at the baiyinnuo er zn pb deposit 1 immiscibility preore stage coexistence of halite bearing brine inclusions s1 type 44 wt nacl equiv and vapor rich fluid inclusions v type sharing the same homogenization temperatures 470 c confirms that fluid unmixing occurred under lithostatic pressures of 400 bars 1 5 km and the brine is considered to account for most prograde skarn minerals e g clinopyroxene 2 overpressure trapping preore stage brine inclusions homogenized by halite dissolution s2 type postdated the immiscible assemblages this type of inclusions is characterized by high but variable minimum trapping pressures 150 3 000 bars relative to s1 type inclusions and can be explained as a result of entrapment under overpressuring condition 3 boiling the presence of both vapor and liquid inclusions i e v and l type in the same assemblages within synore stage quartz calcite and sphalerite indicates the occurrence of fluid boiling 350 c at hydrostatic pressures of 150 bars and depth of 1 5 km which resulted in large scale mineralization in the baiyinnuo er zn pb deposit 4 mixing with external fluids fluid inclusions scattered within postore stage calcite or secondary trails in synore stage minerals show low homogenization temperatures 260 c and both decreasing for l type and increasing for cacl2 bearing inclusions i e lc type trends for salinities as homogenization temperatures decrease implying addition of both meteoric water low temperature low salinity and basinal brines low temperature ca rich respectively systematic fluid inclusion studies also indicate that the mineralization related fluid is of magmatic origin prograde minerals formed during the preore stage fluid immiscibility while sulfides deposition occurred during the synore stage fluid boiling mixing with external fluids began as the hydrothermal system cooled to 300 c when the main metal precipitation process had ended

hydrothermal evolution of the el teniente deposit chile porphyry cu mo ore deposition from low salinity magmatic fluids the magmatic hydrothermal evolution of the el teniente porphyry cu mo deposit in the central andes in chile is reconstructed based on field relationships scanning electron microscopy cathodoluminescence petrography and fluid inclusion analysis by microthermometry and laser ablation inductively coupled plasma mass spectrometry la icpms three major stages of cu mo mineralization are observed following the barren hydrothermal stage 1 the stage 2 mineralization is characterized by quartz anhydrite stockwork veins and breccias with chalcopyrite bornite and molybdenite both stages 1 and 2 are associated with pervasive potassic alteration quartz anhydrite veins with chalcopyrite bornite and molybdenite associated with phyllic alteration represent stage 3 mineralization stage 4 mineralization linked to the formation of the large braden diatreme is characterized by breccias and rare veins containing a lower temperature assemblage with tourmaline sericite and lesser tennantite bornite and chalcopyrite with late gypsum in local vugs ten fluid types are distinguished in this study based on petrographic and microthermometric criteria such as phase proportions daughter minerals homogenization behavior and salinity the hydrothermal evolution across the stages of cu deposition is characterized by the contraction of a vapor phase originating by phase separation during stage 2 overall cooling of the system at pressures fluctuating around the two phase fluid surface led to a transition from a two phase fluid state dominated by vapor at 410 c and 300 bars in stage 2 to a single phase low salinity fluid derived from cooling and contraction of magmatic vapor to a liquid which dominates during stage 3 mineralization at 350 c and 200 bars copper mineralization mainly formed from the vapor phase and its low salinity liquid derivatives representing a large volume of fluid with an initially high cu content 1 2 0 4 wt cu copper sulfides precipitated upon cooling between 410 and 320 c indicated by a drop of cu na k mn fe ratios of over four orders of magnitude through the evolution of the deposit from stage 2 to stage 4 the highest mo concentrations occur in residual brines resulting from extreme boiling as indicated by concurrent halite saturation recent geochronology cannell 2005 maksaev et al 2004 suggests a relatively long lived magmatic hydrothermal system at el teniente our fluid chemical data show no evidence for major crystal fractionation in a large fluid generating upper crustal magma chamber because cs na k mn fe is constant from pre ore to all syn ore fluids however the initiation of copper mineralization was associated with a 4 to 10 fold increase in the concentration of cu mo li and fe in the inferred main ore forming input fluid compared with pre ore fluids of intermediate salinity and otherwise very similar major and trace element ratios these data indicate that injection from depth of an exceptionally cu mo li and probably also s rich volatile phase into an already actively evolving upper crustal magmatic hydrothermal system triggered the formation of this unusually large and rich copper deposit

some first order observations on magma transfer from mantle wedge to upper crust at volcanic arcs the viscosity of lavas erupted at volcanic arcs varies over orders of magnitude a comparison of the relative abundance of viscous lava dome eruptions indicates that the average viscosity of arc lavas also varies considerably between arcs it is shown that for continental or transitional arcs with little within arc crustal deformation and without underlying slab windows or tears average lava viscosity is anti correlated with average surface heat flux the latter may be influenced by crustal thickness and crustal magma throughput to constrain the relative contributions of these parameters variations of average lava viscosity with average crustal thickness and plate convergence rate are assessed while crustal thickness appears to have little effect on average lava viscosity a good anticorrelation exists between average lava viscosity and plate convergence rate with the exception of two arcs that show significant intra arc crustal deformation if plate convergence rate is a good proxy of the rate of melt generation within the mantle wedge cf cagnioncle et al 2007 these first order observations indicate that where the rate of mantle melting is high crustal magma throughput is rapid and efficient resulting in low viscosity melts migrating through a hot overriding crust in contrast where the rate of mantle melting is low crustal magma transfer is slow and inefficient resulting in high viscosity melts that may frequently stall within a cool overriding crust prior to eruption uranium series geochemical evidence from dome lavas is presented and lends support to this interpretation finally some explanations are offered for the observed average viscosity variations of arcs with underlying slab windows or tears and or significant intra arc crustal deformation

geochemistry of zircon and apatite from the mo ore forming granites in the dabie mo belt east china implications for petrogenesis and mineralization abstract the dabie molybdenum mo belt in east china is an important mo belt in both china and the world all of the mo deposits in the dabie area are porphyry skarn type the ore related granite samples from the qian echong tangjiaping and doupo mo deposits in the mo belt have been collected for zircon and apatite trace elements analysis additionally the doupo ore related granite has also been chosen for zircon u pb dating la icp ms zircon u pb dating of the ore related granite in the doupo mo deposit yields a crystallization age of 127 1 ma which is consistent with the molybdenite re os age of the deposit the chondrite normalized patterns of all zircons are characterized by positive ce anomalies with variable negative eu anomalies the ore related granites in the qian echong and tangjiaping mo deposits show relatively high magmatic oxygen fugacity fmq 1 5 whereas the doupo ore related granite has a relatively low magmatic oxygen fugacity fmq 0 3 which might have caused it to have relatively small mo reserve compared to the qian echong and tangjiaping deposits all of the apatites from the three mo deposits are characterized by lree enriched and hree depleted chondrite normalized patterns with various degrees of eu depletion and ce enrichment not only redox condition but also other factors could have influenced the eu eu or and ce ce of apatite in this study and the anomalies of eu and ce of apatites from the ore related granites in this study could not be used to evaluate the magma redox states the geochemical characteristics of apatite indicate that the ore forming magmas of the mo deposits in this study are oxidized and metaluminous i or a type magmas during the early cretaceous regional extension and asthenospheric upwelling in the dabie orogen partial melting of the crustal rocks generated oxidized mo bearing magma relatively oxidized condition prevents mo from incorporating into sulfides or silicates in the magma and finally leads to mo precipitation from the ore forming fluids which released from the magma

genesis and tectonic setting of the giant diyanqin amu porphyry mo deposit in great hingan range ne china constraints from u pb and re os geochronology and hf isotopic geochemistry abstract the great hingan range is located in the eastern sector of the central asia orogenic belt and is the second important mo province in china next to the qinling dabie orogenic belt previous studies concluded that all the mo deposits mo only or mo dominated polymetallic in the area were formed in the mesozoic and related either to the syn to post collisional setting following the closure of the paleo asia ocean or to the westward subduction of the pacific plate however the fluids forming the giant diyanqin amu porphyry mo deposit in the area disagree with the features of collision type mo deposits but accord with those of the subduction or continental arc type the mo mineralization is hosted in the late jurassic volcanic rocks and genetically related to the buried porphyritic granite and aplitic granite two porphyritic granite samples yield la icp ms zircon weighted mean 206 pb 238 u ages of 158 7 0 8 ma mswd 0 64 2 and 158 0 0 9 ma mswd 0 38 2 respectively the aplitic granite yields a zircon u pb weighted mean 206 pb 238 u age of 156 9 1 1 ma mswd 0 48 2 slightly younger than the porphyritic granite seven molybdenite samples from the ores yield re os isotope ages of 156 1 2 2 to 158 1 4 3 ma these ages constrain that the diyanqin amu mo system was formed in the period of 159 156 ma the granites at the deposit have high contents of sio 2 k 2 o and al 2 o 3 and low contents of tio 2 mgo and cao showing a peraluminous high k calc alkaline affinity these granites and the host volcanic rocks are characterized by enrichment of k rb u pb th and lree and depletion of nb ta ti and hree with negative eu anomaly which are similar to magmatic rocks in the andean arc zircon grains from the granites show positive e hf t values of 4 2 9 0 with t dm2 hf ages of 0 63 0 94 ga these geochemical data imply that the granites at diyanqin amu are highly fractionated i type formed in a continental arc generated by the southeastward subduction of the mongol okhotsk oceanic plate

geology fluid inclusion and isotope constraints on ore genesis of the post collisional dabu porphyry cu mo deposit southern tibet abstract the dabu cu mo porphyry deposit is situated in the southern part of the lhasa terrane within the post collisional gangdese porphyry copper belt gpcb it is one of several deposits that include the qulong and zhunuo porphyry deposits the processes responsible for ore formation in the dabu deposit can be divided into three stages of veining stage i quartz k feldspar biotite chalcopyrite pyrite stage ii quartz molybdenite pyrite chalcopyrite and stage iii quartz pyrite molybdenite three types of fluid inclusions fis are present liquid rich two phase l type vapor rich two phase v type and solid bearing multi phase s type inclusions the homogenization temperatures for the fis from stages i to iii are in the ranges of 272 475 c 244 486 c and 299 399 c and their salinities vary from 2 1 to 49 1 1 1 to 55 8 and 2 9 to 18 0 wt nacl equiv respectively the coexistence of s type v type and l type fis in quartz of stage i and ii with similar homogenization temperatures but contrasting salinities indicate that fluid boiling is the major factor controlling metal precipitation in the dabu deposit the ore forming fluids of this deposit are characterized by high temperature and high salinity and they belong to a h2o nacl magmatic hydrothermal system the h o s pb isotopic compositions indicate that the ore metals and fluids came primarily from a magmatic source linked to miocene intrusions characterized by high sr y ratios similar to other porphyry deposits in the gpcb the fluids forming the dabu deposit were rich in na and cl derived from metamorphic dehydration of subducted oceanic slab through which nacl brine or seawater had percolated the inheritance of ancient subduction associated arc chemistry without shallow level crustal assimilation and or input of the meteoric water was responsible for the generation of fertile magma as well as co2 poor and halite bearing fis associated with post collisional porphyry deposits the estimated mineralization depths of qulong dabu and zhunuo deposits are 1 6 4 3 km 0 5 3 4 km and 0 2 3 0 km respectively displaying a gradual decrease from eastern to western gangdese deep ore forming processes accounted for the generation of giant sized qulong deposit because the exsolution of aqueous fluids with large fraction of water and chlorine in deep or high pressure systems can extract more copper from melts than those formed in shallow systems however the formation of small sized dabu deposit can be explained by a single magmatic event without additional replenishment of s metal or thermal energy in addition the ore forming conditions of porphyry cu mo deposits in gpcb are comparable to those of porphyry cu au mo deposits formed in oceanic subduction related continental or island arcs but differ from those of porphyry mo deposit formed in the dabie qinling collisional orogens the depth of formation of the mineralization and features of primary magma source are two major controls on the metal types and ore fluid compositions of these porphyry deposits

giant porphyry deposits characteristics distribution and tectonic controls more than half of the 25 largest known porphyry copper deposits defined in terms of contained copper metal formed during three time periods the paleocene to eocene eocene to oligocene and middle miocene to pliocene these giant deposits are clustered within three provinces central chile northern chile and southwest arizona northern mexico other giant deposits occur in montana utah panama peru argentina irian jaya mongolia and iran compressive tectonic environments thickened continental crust and active uplift and erosion were associated with the formation of many of these deposits calc alkalic magmas are most favorable for the formation of giant porphyry copper deposits although several of the largest systems are associated with high k calc alkalic intrusions the 25 largest gold rich porphyry deposits are concentrated in the southwest pacific and south america with other occurrences in eurasia british columbia alaska and new south wales many of the deposits formed in the last 13 m y the largest of the deposits are associated with high k calc alkalic intrusions many calc alkalic porphyritic intrusions have also produced giant gold rich porphyries in the last 20 m y the formation of giant porphyry copper molybdenum and copper gold deposits in the circum pacific region has been closely associated with subduction of aseismic ridges seamount chains and oceanic plateaus beneath oceanic island and continental arcs in several examples these tectonic perturbations have promoted flat slab subduction crustal thickening uplift and erosion and adakitic magmatism coeval with the formation of well endowed porphyry and or epithermal mineral provinces similar tectonic features are inferred to be associated with the giant porphyry copper molybdenum provinces of northern chile eocene oligocene and southwest united states cretaceous paleocene topographic and thermal anomalies on the downgoing slab appear to act as tectonic triggers for porphyry ore formation other factors such as sutures in the overriding plate permeability architecture of the upper crust efficient processes of ore transport and deposition and in some cases formation and preservation of supergene enrichment blankets are also vital for the development of high grade giant ore deposits a low grade geochemical anomaly may be the final product of mineralization if ore forming processes do not operate efficiently even in the most favorable geodynamic settings

tectonic magmatic and metallogenic evolution of the tethyan orogen from subduction to collision abstract this paper reviews the tectonic magmatic and metallogenic history of the tethyan orogen from the carpathians to indochina focus is placed on the formation of porphyry cu mo au deposits as being the most characteristic mineral deposit type formed during both subduction and collisional processes in this region relatively little is known about the history of the paleotethys ocean which opened and closed between gondwana and eurasia in the paleozoic and few ore deposits are preserved from this period the neotethyan ocean opened in the permian early triassic as the cimmerian continental fragments the cores of turkey iran tibet and indochina rifted from the northern gondwana margin and drifted northwards these microcontinents docked with the eurasian margin at various points in the mesozoic and cenozoic and formed a complex archipelago involving several small back arc basins and remnants of the paleotethyan ocean the main neotethyan ocean and these smaller basins were largely eliminated by collision with india and africa arabia in the early eocene and early mid miocene respectively although neotethyan subduction continues beneath the hellenic arc and the makran the majority of porphyry type deposits are found in association with neotethyan subduction mainly in the mesozoic and paleogene and syn to post collisional events in the mid paleogene to neogene they are found throughout the orogen but some sections are particularly well endowed including the carpathians balkans rhodopes eastern turkey lesser caucasus nw iran se iran sw pakistan southern tibet and se tibet indochina other sections that appear barren may reflect deeper levels of erosion young sedimentary cover or lack of exploration although there may also be real reasons for low prospectivity in some areas such as minimal subduction e g the western mediterranean region or lithospheric underthrusting as proposed in western tibet over the last decade improved geochronological constraints on the timing of ore formation and key tectonic events have revealed that many porphyry deposits that were previously assumed to be subduction related are in fact broadly collision related some forming in back arc settings in advance of collision some during collision and others during post collisional processes such as orogenic collapse and or delamination of subcontinental mantle lithosphere while the formation of subduction related porphyries is quite well understood collisional metallogeny is more complex and may involve a number of different processes or sources these include melting of orogenically thickened crust previously subduction modified lithosphere including metasomatized mantle underplated mafic rocks or lower crustal arc plutons and cumulates or upwelling asthenosphere e g in response to delamination slab breakoff back arc extension or orogenic collapse the most fertile sources for syn and post collisional porphyry deposits appear to be subduction modified lithosphere because these hydrated lithologies melt at relatively low temperatures during later tectonomagmatic events and retain the oxidized and relatively metalliferous character of the original arc magmatism unusually metallically enriched lithospheric sources do not seem to be required but the amount of residual sulfide phases in these rocks may control metal ratios e g cu au in subsequent magmatic hydrothermal ore deposits relatively au rich deposits potentially form in these settings as observed in the carpathians e g rosia montan turkey kisladag copler and iran sari gunay dalli although the majority of syn and post collisional porphyries are cu mo rich and resemble normal subduction related deposits e g in the gangdese belt of southern tibet this similarity extends to the associated igneous rocks which being derived from subduction modified sources largely retain the geochemical and isotopic character of those original arc magmas while still retaining a broadly calc alkaline character these rocks may extend to mildly alkaline shoshonitic compositions and may display adakite like trace element signatures high sr y and la yb ratios reflecting melting of deep crustal garnet amphibolitic sources but they are otherwise hard to distinguish from normal subduction related magmas small post collisional mafic alkaline volcanic centers are common throughout the orogen but for the most part appear to be barren however similar rocks in other post subduction settings around the world are associated with important alkalic type porphyry and epithermal au cu deposits and the potential for discovery of such deposits in the tethyan orogen should not be overlooked

high oxidation magmatic evolution in the naruo porphyry cu deposit tibet china abstract the naruo porphyry cu deposit is the third largest deposit discovered in the duolong metallogenic district previous research has focused mainly on the geochemistry of the ore bearing granodiorite porphyry the metallogenesis remains poorly understood in the present work on the basis of outcrops and drilling core geological mapping phases of early mineralization diorite two inter mineralization granodiorite porphyries and late mineralization granodiorite porphyry have been distinguished furthermore the alteration zones were outlined and the vein sequence was identified the diorite and three porphyry phases were subjected to laser ablation inductively coupled plasma mass spectrometry la icp ms zircon u pb dating and in situ hf isotope analyses as well as bulk major element trace element and sr nd isotopic analyses molybdenite re os dating was also conducted the zircon u pb dating results show that the diorite and porphyry intrusions were emplaced at about 120 ma and the molybdenite re os isochron age is 118 8 1 9 ma this indicates that the naruo porphyry cu deposit was formed during a continuous magmatic hydrothermal process all of the diorite and granodiorite porphyry samples showed arc magmatic characteristics moreover the moderate 87 sr 86 sr i ratios and low e nd t and e hf t values of the diorite and porphyry intrusions suggest the source region of the juvenile lower crust the lower 87 sr 86 sr i and 143 nd 144 nd i ratios and higher e nd t values and incompatible element concentrations than those in the granodiorite porphyry samples indicate a two stage magmatic generation process for the intrusions the early mineralization diorite has a high cu concentration implying that the source is enriched in cu however the slightly lower cu content of the late mineralization granodiorite porphyry samples might imply cu release from magmas and deposition within the metallogenic stage the multiple stages of intrusions and subsequent volcanism within the duolong metallogenic district together with high sr y features indicate persistent magmatism during the metallogenic epoch which is necessary for maintaining the activity of magmatic hydrothermal and mineralization processes thus the high cu content in the source region mantle derived melt upwelling and multiple stages of persistent magmatism were favorable for the formation of the naruo porphyry cu deposit the high fe 2 o 3 feo ratios of the diorite and granodiorite porphyry intrusions show very high oxidation features which is coincident with estimated magmatic oxidation state calculated by the zircon trace element compositions the high oxidation facilitates sulfur and chalcophile metals to be scavenged into the magmatic hydrothermal systems which is crucial for the metallogenesis of the naruo porphyry cu deposit

instantaneous outbursts in underground coal mines an overview and association with coal type instantaneous outbursts in underground coal mines have occurred in at least 16 countries involving both methane ch4 and carbon dioxide co2 the precise mechanisms of an instantaneous outburst are still unresolved but must consider the effects of stress gas content and physico mechanical properties of the coal other factors such as mining methods e g development heading into the coal seam and geological features e g coal seam disruptions from faulting can combine to exacerbate the problem prediction techniques continue to be unreliable and unexpected outburst incidents resulting in fatalities are a major concern for underground coal operations gas content thresholds of 9 m 3 t for ch4 and 6 m 3 t for co2 are used in the sydney basin to indicate outburst prone conditions but are reviewed on an individual mine basis and in mixed as situations data on the sorption behaviour of bowen basin coals from australia have provided an explanation for the conflicting results obtained by coal face desorption indices used for outburst proneness assessment a key factor appears to be different desorption rates displayed by banded coals which is supported by both laboratory and mine site investigations dull coal bands with high fusinite and semifusinite contents tend to display rapid desorption from solid coal for a given pressure drop the opposite is true for bright coal bands with high vitrinite contents and dull coal bands with high inertodetrinite contents consequently when face samples of dull fusinite or semifusinite rich coal of small particle size are taken for desorption testing much gas has already escaped and low readings result the converse applies for samples taken from coal bands with high vitrinite and or inertodetrinite contents in terms of outburst potential it is the bright vitrinite rich and the dull inertodetrinite rich sections of a coal seam that appear to be more outburst prone this is due to the ability of the solid coal to retain gas even after pressure reduction creating a gas content gradient across the coal face sufficient to initiate an outburst once the particle size of the coal is reduced rapid gas desorption can then take place c 1998 elsevier science

major and minor structural features of a bedding shear zone along a coal seam and related gas outburst pingdingshan coalfield northern china abstract a fractured coal band traditionally called a soft coal band or structurally referred to as a bedding shear zone within the wu coal seam in the pingdingshan coalfield northern china was structurally studied based on field examination and observations by reflectance microscopy and scanning electron microscopy sem the bedding shear zone is not consistent with a simple bedding fault defined by pioneering geologists but rather a complexly deformed band locally overprinted by ductile shearing fabrics dominant small scale structures within the bedding shear zone are thrusts folds cleavage duplexes and related structures but local refolded folds kink bands and s c band structures also indicate ductile shear deformation typically developed in areas of steep dip such as within the limb of a subordinate fold bed parallel shearing within the coal seam has been considered a serious influence on gas outburst in underground mining production in addition to thickening the seam and reducing the quality of coal locally abnormal thickening of a shear zone and extensive compressive structures where ductile fabrics frequently occur are closely related with the site of an outburst thickening of a shear zone increases the capacity of methane storage and compressive structures within a shear zone may act as a tectonic screen blocking methane migration which can result in a pocket of high methane pressure a potential risk of outburst is indicated as a working face approaches an area of high methane pressure three abnormal phenomena encountered during a mining operation presage methane outburst for seams with a bedding shear zone

large scale porphyry type mineralization in the central asian metallogenic domain a review abstract a series of porphyry type cu mo au deposits including some giant world class deposits such as kounrad aktogai kal makyr oyu tolgoi and chalukou occur in the central asian metallogenic domain camd the outline of the camd almost overlaps with that of the central asian orogenic belt caob which is located between the east europe siberia tarim and north china cratons the camd comprises sparsely exposed tectonic slices of precambrian high grade metamorphic basement rocks that are sandwiched between phanerozoic accretionary complexes and arc rocks according to geological metallogenic geochronological and tectonic setting characteristics the camd comprises three metallogenic provinces 1 the kazakhstan cu au mo 2 the mongolia cu au and 3 the northeast china mo cu metallogenic provinces early paleozoic 490 to 440 ma and late paleozoic 330 to 295 ma large scale porphyry type mineralization in the kazakhstan metallogenic province is intimately associated with the evolution of the central tianshan yili northern tianshan kokchetav chingiz paleozoic arc system which was terminated by the late permian closure of the western segment of the paleo asian ocean in contrast the 370 ma and 240 ma porphyry type mineralization of the mongolia metallogenic province is related to the tuva mongolia arc collage system that was formed during the evolution of the paleo asian ocean in the paleozoic and the mongol okhotsk ocean in the early mesozoic furthermore the northeast china metallogenic province was affected by three distinct geodynamic processes that were associated with the paleo asian mongol okhotsk and paleo pacific oceans during the paleozoic 250 ma the early mesozoic 200 ma and the late mesozoic 200 90 ma respectively except for the early paleozoic cu mineralization at duobaoshan 480 ma and bainaimiao 440 ma the porphyry type mineralization of this metallogenic province is predominantly characterized by widespread mesozoic mo mineralization in general porphyry type deposits of the camd have geological structural metallogenic alteration and fluid characteristics which are consistent either with those related to the oceanic subductional arc settings of the circum pacific metallogenic domain or with those of the continental collisional environment in the tethyan metallogenic domain the involvement of highly oxidized intermediate to felsic magmas is fundamental for the formation of porphyry deposits even though the prevalent mash and slab melting models can be employed to interpret the genesis of some porphyry cu deposits in the camd a here newly suggested model which is based on pre enriched mafic lower crust and the subduction of a relictic mid oceanic ridge is thought to explain the large scale copper mineralization in the balkhash west junggar metallogenic belt of the kazakhstan metallogenic province nevertheless most of the porphyritic suites associated with the mo deposits in the northeast china metallogenic province have relatively depleted mantle like neodymium and hafnium isotopic compositions suggesting that the ore forming granitic magma may have predominantly been derived from juvenile lower crust upwelling of asthenosphere may have triggered the melting of the lower crust during post collisional extension subsequent to the closure of the paleo asian ocean in the triassic the subduction of the paleo pacific ocean in the jurassic and the thinning of the lithosphere caused by rollback of the paleo pacific plate in the cretaceous ancient crustal components were only locally found to have been involved in the magma source of several medium large mo deposits

economic geology copper conundrums the metal content of magmas erupted at subduction zone arcs is thought to be derived from the mantle a correlation between crustal thickness and copper content in arc magmas worldwide however reveals an important role for the crust in the upper plate

relative oxidation states of magmas inferred from ce iv ce iii in zircon application to porphyry copper deposits of northern chile major and trace element compositions of zircons and whole rocks from 14 barren and seven ore bearing calc alkaline intrusions from the chuquicamata el abra porphyry copper belt of northern chile have been measured in situ by excimer laser ablation ela icp ms these data permit the ce iv ce iii ratio within zircon to be calculated using a lattice strain model for mineral melt partitioning of ce iv and ce iii zircon ce iv ce iii and eun eun ratios and by inference magmatic oxidation states generally increase from older mafic to younger felsic units within this sequence porphyry copper mineralization is directly associated only with intrusions with zircon ce iv ce iii 300 and eun eun 0 4 such trends can be understood in terms of interdependent relations between oxygen fugacity sulfur speciation and solubility and chalcophile element partitioning in silicate magmas because zircon occurs in most calc alkaline intrusions and is resistant to subsolidus alteration zircon ce iv ce iii ratios provide a useful tool for evaluating the economic potential of such rocks for magmatic hydrothermal cu au mineralization the approach is general and may provide a means to infer relative oxidation state in a wide range of intermediate to felsic igneous rocks

control of gas emissions in underground coal mines abstract a high level of knowledge is now available in the extremely relevant field of underground gas emissions from coal mines however there are still tasks seeking improved solutions such as prediction of gas emissions choice of the most suitable panel design extension of predrainage systems further optimization of postdrainage systems options for the control of gas emissions during retreat mining operations and prevention of gas outbursts research results on these most important topics are presented and critically evaluated methods to predict gas emissions for disturbed and undisturbed longwall faces are presented prediction of the worked seam gas emission and the gas emission from headings are also mentioned but not examined in detail the ventilation requirements are derived from the prediction results and in combination with gas drainage the best distribution of available air currents is planned the drainage of the gas from the worked coal seam also referred to as predrainage can be performed without application of suction only by over or underworking the seam but in cases where this simple method is not applicable or not effective enough inseam boreholes are needed to which suction is applied for a relatively long time the reason for this is the low permeability of deep coal seams in europe the main influences on the efficiency of the different degasing methods are explained conventional gas drainage employing cross measure boreholes is still capable of improvement in terms of drilling and equipment as well as the geometrical borehole parameters and the operation of the overall system improved control of gas emissions at the return end of retreating faces can be achieved by installation of gas drainage systems based on drainage roadways or with long and large diameter boreholes the back return method can be operated safely only with great difficulty if at all another method is lean gas drainage from the goaf the gas outburst situation in germany is characterized by events predominantly in the form of nonclassical outbursts categorized as sudden liberation of significant quantities of gas recent research results in this field led to a classification of these phenomena into five categories for which suitable early detection and prevention measures are mentioned

spatiotemporal reconstruction of late mesozoic silicic large igneous province and related epithermal mineralization in south china insights from the zhilingtou volcanic intrusive complex silicic large igneous provinces slips generally reflect large scale melting of lower crustal materials and represent significant metal reservoirs the south china block coastal region scb cr slip hosts several large epithermal deposits to better understand these deposits we document the spatio temporal framework of the host slip across the scb cr using zircon u pb dating and geochemical and isotopic analysis we identify four stages of emplacement stage 1 felsophyre ca 149 ma shows a chemical affinity to highly fractionated i type granites stages 2 and 3 of low mg felsic volcanics ca 128 to 111 ma and stage 4 felsite ca 100 ma have higher ehf t and end t values than stage 1 felsophyre suggesting a significant contribution of newly underplated juvenile crust to the magma sources stage 4 diabase ca 101 ma was likely produced by melting of subduction metasomatized asthenospheric mantle together with reliable published data we build a new spatio temporal framework of volcanics and infer that the majority of the scb cr slip was related to the gradual northwestward subduction of the izanagi plate beneath south china in a continental arc setting during ca 170 to 110 ma and minor contribution was from the eastward retreat of the subducting slab in a back arc setting during ca 110 to 90 ma we conclude that the large scale epithermal mineralization was generated by melting of the metal rich thin 30 40 km newly underplated hydrous juvenile crust during the tectonic transition from arc to back arc settings

redox controlled generation of the giant porphyry cu au deposit at pulang southwest china some porphyry cu au deposits with relatively reduced ore assemblages characterized by high hydrothermal pyrrhotite contents and a lack of primary hematite and magnetite are generally considered to be associated with reduced i type granitoids however the role of magmatic oxygen fugacity fo2 in controlling cu au mineralization in such reduced porphyry deposits is poorly understood the giant late triassic ca 216 ma pulang porphyry cu au deposit of southwest china shows typical reduced ore assemblages this study reported the systematical variation of upper crustal magmatic fo2 of pulang deposit based on detailed investigations of mineral crystallization sequences and compositional features of the mineralization related porphyries early p1 and late p2 porphyry results indicate that magma of the mineralization related porphyries experienced complex fo2 fluctuations during its upper crustal evolution the early primary magma had very high initial fo2 with fmq 3 0 at depths of 12 km fmq is the deviation of logfo2 from the fayalite magnetite quartz fmq buffer the fo2 of evolved parental magma subsequently decreased with fmq 1 9 due to injection of relatively reduced dioritic magmas fmq 1 4 to 2 3 from a deeper chamber 17 21 km depth into the primary magma chamber at 10 12 km depth magma mixing had largely ceased at 6 10 km depth the parental magma then ponded within the reduced tumugou formation at a depth of 3 7 km where magmatic fo2 decreased to a moderately oxidized state fmq 1 6 and finally to a moderately reduced state reflected by log fe2o3 feo ratios of 0 5 for p2 porphyry results of this study of magmatic fo2 indicate that porphyry magmas associated with reduced pulang ore assemblages were initially generated as highly oxidized magma which was subsequently reduced through magma mixing and contamination by reduced sedimentary rocks of the tumugou formation the sharp fo2 decrease at very shallow depth prevented the early loss of cu and au because the magma remained oxidized until it was emplaced at 3 7 km depth moderately reduced magmas may thus have a genetic association with porphyry cu au mineralization

contribution of mafic melt to porphyry copper mineralization evidence from mount pinatubo philippines and bingham canyon utah usa mount pinatubo in the philippines known for its cataclysmic eruption in 1991 hosts several porphyry copper deposits and active geothermal systems an underlying mafic melt supplied much of the sulphur for the dacitic magma and its injection into the dacitic magma chamber triggered the eruption the eruption caused purging of the sulphur rich fluid from the dacite to the atmosphere and extensive fracturing similar events took place at bingham canyon utah site of the largest copper and gold deposit in north america at 38 ma the bingham canyon mineralization took place beneath an active stratovolcano and pyroclastic flows contemporaneous with the mineralization show evidence for magma mingling ascent of mafic melt supplied sulphur and chalcophile elements to the felsic magma which consolidated to form the bingham stock and its underlying magma chamber injections of the mafic melt caused periodic eruptions of felsic magma to form the stratovolcano and deposition of sulphide minerals in highly fractured rocks in and around the stock

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

eocene k rich adakitic rocks in the central iran implications for evaluating its cu au mo metallogenic potential abstract the kal e kafi intrusive complex is located in the central iran magmatic zone and includes a series of granitoid rocks ranging in composition from gabbro to granite these granitoids show some affinities with adakites e g high sr y and la yb ratios coupled with low yb and y enrichment in lree and lile with no eu anomalies similar to products from all of which are compatible with derivation from slab melting however relatively their low end t values 0 21 to 2 35 and higher 87 sr 86 sr i 0 7041 0 7044 are inconsistent with an origin by slab melting with these rocks also showing shoshonitic affinities with high k 2 o na 2 o ratios geochemical characteristics indicate that the kal e kafi intrusive complex was probably derived by the partial melting of delaminated lower crust at pressures equivalent to crustal thicknesses of 40 km generated near the boundary between garnet bearing amphibolite or amphibole bearing eclogite melting moreover the kal e kafi adakitic magmas must have interacted with the surrounding metasomatized mantle peridotite during their ascent which elevated not only their mgo cr and ni contents but also the oxygen fugacity o 2 of the magma the high o 2 could have induced oxidation of metallic sulfides in the mantle resulting in the mobilization of chalcophile elements which are required to produce porphyry cu au and mo mineralization

regional metallogeny of mo bearing deposits in northeastern china with new re os dates of porphyry mo deposits in the northern xilamulun district with many new discoveries of giant mo deposits in the past decade northeastern china has become the largest molybdenum mineralization region in china the xilamulun district is in the southern part of northeastern china and contains 25 mo deposits and prospects dominantly of porphyry type these deposits are mostly along the e striking xilamulun fault re os dating of hydrothermal molybdenite from four deposits in the northern xilamulun district revealed mineralization ages of 137 to 129 ma 129 4 3 4 ma for aolunhua 135 3 2 6 ma for shabutai 136 4 0 8 ma for haisugou and 136 1 6 6 ma for banlashan in general agreement with the crystallization ages of their host granitoids the compilation of existing data on mo bearing deposits in northeastern china including the new data of this study shows that mesozoic mo deposits in this region have a wide range of ages from 250 to 90 ma we propose that they are linked to three tectonic magmatic events 1 triassic mo deposits 250 220 ma are mainly distributed along the e trending xilamulun fault and are related to postcollisional crustal extension following the final closure of the paleo asian ocean 2 jurassic mo mineralization 200 140 ma displays a clear younging trend from southeast to northwest coincides with the regional magmatism trend and is interpreted to be related to the northwestward flat slab subduction of the paleo pacific plate beneath the eurasian continent that started in the early jurassic ca 200 ma 3 cretaceous mo mineralization 140 90 ma shows a reversed migration trend from northwest to southeast and can be explained by the coastward migration of slab rollback related to lower crust delamination asthenospheric upwelling and lithospheric thinning in eastern china the spatial temporal distribution of mesozoic mo mineralization is important for regional metallogeny and exploration recently numerous epithermal au cu mo deposits have been recognized in the southeast margin of northeastern china according to this study we predict that hidden porphyry skarn systems could be located beneath these epithermal deposits

tectonic triggers for postsubduction magmatic hydrothermal gold metallogeny in the late cenozoic anatolian metallogenic trend turkey

contrasting ore styles and their role in understanding the evolution of the altaids abstract the altaids is a paleozoic orogenic collage in central asia it occupies 10 of the eurasian continent and it is one of the richest concentrations of mineral deposits in the world comparable to those of the circum pacific and tethyan orogenic belts in particular it contains many types of hydrothermal ore deposits that are sensitive to the nature and origin of their host terranes including porphyry copper gold molybdenum volcanogenic massive sulfide copper lead zinc and orogenic gold deposits which are all diagnostic of convergent continental margins extensional arc related submarine basins and transpressional terrane boundaries within the altaids porphyry copper deposits are mostly concentrated within the kazakhstan and tuva mongolia micro continents where they formed almost continuously from the early ordovician to permian only a few are cambrian and triassic and most are late carboniferous most volcanogenic massive sulfide ore deposits are distributed along the south urals and rudny altai in the western altaids where they formed in a short time window from the early to middle devonian important orogenic gold deposits formed along regional strike slip faults between craton island arc or micro continent boundaries from the neoproterozoic to permian mostly in the early permian in limited key areas volcanogenic massive sulfide deposits formed upon much older 100 ma basement rocks than those of coeval porphyry deposits indicating that the altaids could not have developed from a single arc furthermore the porphyry deposits outline the distribution of several continental fragments the combined area of which is far less than that of the altaids which suggests that extensive new juvenile material has been added into island arc systems which may have been accreted to surrounding continental margins these metallogenic distributions in localized areas were a result of the mechanisms of crustal growth within the overall tectonic evolution of the altaids and they are consistent with the interpretation that the altaids is a multiple subduction accretion collage

the mesozoic caosiyao giant porphyry mo deposit in inner mongolia north china and paleo pacific subduction related magmatism in the northern north china craton abstract the caosiyao giant porphyry mo deposit is located in the wulanchabu area of inner mongolia within the northern north china craton ncc it contains more than 2385 mt of ore with an average grade of 0 075 mo in the caosiyao mining district mo mineralization occurs mainly in a mesozoic granite porphyry as disseminations and stockworks with some mo distributed in archean metamorphic rocks and diabase as stockworks and veins the host granite porphyry is composed of two different phases that can be distinguished based on mineral assemblages and textures one phase contains large and abundant phenocrysts coarse grained while the other phase is characterized by fewer and smaller phenocrysts medium grained zircon u pb hf analyses of the former phase yielded a concordant 206pb 238u age of 149 8 2 4 ma with a 206pb 238u weighted mean age of 149 9 2 4 ma and ehf t values ranging from 12 2 to 18 3 while the latter phase gave a concordant 206pb 238u age of 149 0 2 2 ma with a 206pb 238u weighted mean age of 149 0 2 1 ma and ehf t values ranging from 13 1 to 17 7 five samples of disseminated molybdenite have a 187re 187os isochron age of 149 5 5 3 ma with a weighted average age of 149 0 1 8 ma whereas six veinlet type molybdenite samples have a well constrained 187re 187os isochron age of 146 9 3 1 ma and a weighted average age of 146 5 0 8 ma thus it is suggested that the mo mineralization of the caosiyao deposit occurred during the late jurassic ca 147 149 ma almost coeval with the emplacement of the host granite porphyry ca 149 150 ma the host granite porphyry is characterized by high silica sio2 71 52 74 10 wt relatively high levels of oxidation fe2o3 feo 0 32 0 94 wt and high alkali element concentrations na2o k2o 8 21 8 76 wt the host granite porphyry also shows enrichments in u and k and depletion in ba sr p eu and ti suggesting strong fractional crystallization of plagioclase biotite and accessory minerals these observations together with high sio2 contents and a high differentiation index di 89 04 92 44 indicate a strong differentiation of the granite magma based on geological geochronological isotope systematics and geochemical studies we propose for the first time a genetic model for the caosiyao porphyry mo deposit under a regional extensional setting caused by far field tectonics related to the paleo pacific subduction during the late jurassic a series of geodynamic magmatic and ore forming processes took place including formation of multi directional and multi phase faults emplacement of the granitic host rocks and mo mineralization highly silicic highly oxidized and alkali rich granitic magma derived from partial melting of old lower crust intruded into the country rocks this highly differentiated granitic magma and the exsolved ore forming fluids enriched in mo migrated upward and interacted with the wall rocks eventually ore minerals precipitated in fractures resulting in the extensive deposition of molybdenite

zircon trace elements and magma fertility insights from porphyry skarn mo deposits in ne china it has been widely accepted that magmas genetically linked to porphyry skarn cu mo deposits are commonly oxidized recently using laser ablation inductively coupled plasma mass spectrometry la icp ms techniques zircon ce4 ce3 cen cen eun eun and ce nd ratios and magma fmq values departure from the fayalite magnetite quartz oxygen buffer based on zircon trace element compositions have been used as proxies to quantify magma oxidation state here we present the zircon trace element compositions of 13 mesozoic porphyry skarn mo deposits in ne china of various sizes to examine the relationship between magma mo fertility and magma oxidation state generally the studied deposits with 0 3 mt mo have ce4 ce3 100 cen cen 100 ce nd 10 and eun eun 0 3 whereas those containing 10 mt cu the findings in this study can be used to evaluate an intrusion s potential to produce mo mineralization

copper enrichment in arc magmas controlled by overriding plate thickness the characteristics of magmas typically associated with porphyry copper deposits are thought to be imparted in the mantle statistical assessment of over 40 000 geochemical analyses of magmatic rocks formed in subduction zones worldwide however shows that the characteristics of these magmatic rocks are systematically controlled by the thickness of the arc crust

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

in situ elemental and isotopic compositions of apatite and zircon from the shuikoushan and xihuashan granitic plutons implication for jurassic granitoid related cu pb zn and w mineralization in the nanling range south china abstract the nanling range south china was world famous for hosting abundant granitoid related copper lead zinc cu pb zn polymetallic ore deposits and quartz vein type wolframite w ore deposits both of which have roughly similar formation ages predominately between 150 and 160 ma with a peak of ca 156 ma in this study accessory minerals from typical cu pb zn bearing and w bearing granitic rocks are compared in terms of elemental and isotopic compositions apatite from w bearing granites in the xihuashan pluton has lower end t value 11 9 to 8 6 than that from cu pb zn bearing granitic rocks in shuikoushan with end t value of 8 7 to 4 2 and initial 87sr 86sr ratio of 0 7097 0 7109 zircon grains in xihuashan yielded ehf t value from 14 9 to 11 4 18o value from 8 6 to 10 4 and highly variable and negative 7li value 45 8 to 3 8 whereas those in shuikoushan have relatively higher ehf t value 10 6 to 8 1 lower 18o value 8 4 9 7 and highly variable 7li values from 12 7 to 17 6 in situ hf o li isotopic compositions of zircon and sr nd isotopes of apatite suggesting that the shuikoushan granitic pluton was likely generated from dehydration melting of amphibolite from a metal fertile mafic source in the middle to lower crust whereas the xihuashan granitic pluton could be derived from partial melting of metapelite with minor amphibolite in the middle to upper crust the geochemical records in accessory minerals fingerprint that the shuikoushan granitic magma was characterized by high cl content 0 11 1 44 wt and logfo2 value fmq 1 whereas the xihuashan granitic magma have elevated f 3 51 4 80 wt and li 3 49 42 4 ppm contents with low logfo2 value