fluid inclusion characteristics and geological significance of the dajinshan w sn polymetallic deposit in yunfu guangdong province abstract the dajinshan tungsten tin polymetallic deposit is a quartz vein type ore deposit located in western guangdong province the ore bodies show a fairly simple shape and mainly occur as tungsten tin polymetallic bearing sulfide quartz veins including quartz vein quartz greisens and sulfide quartz veins and their distribution is spatially related to dajinshan granitoids the formation of the deposit experienced three stages a wolframite molybdenite quartz stage a wolframite cassiterite sulfide quartz stage and a fluorite calcite carbonate stage based on detailed petrographic observations we conducted microthermometric and raman microspectroscopic studies of fluid inclusions formed at different ore forming stages in the dajinshan tungsten tin polymetallic deposit identifying four dominant types of fluid inclusions aqueous two phase inclusions co2 bearing inclusions solid or daughter mineral bearing inclusions and gas rich inclusions the gas compositions of ore forming fluids in the dajinshan tungsten tin polymetallic deposit are mostly co2 ch4 and h2o the hydrogen oxygen and sulfur isotopic data imply that the ore forming fluids in the dajinshan tungsten tin polymetallic deposit were mainly derived from magmatic fluids mixed with meteoric water in the ore formation process these results indicate that the fluid mixing and boiling led to the decomposition of the metal complex in ore forming fluids and ore deposition

genesis of the fuxing porphyry cu deposit in eastern tianshan china evidence from fluid inclusions and c h o s pb isotope systematics abstract the fuxing porphyry cu deposit is a recently discovered deposit in eastern tianshan xinjiang northwestern china the cu mineralization is associated with the fuxing plagiogranite porphyry and monzogranite mainly presenting as various types of hydrothermal veins or veinlets in alerted wall rocks with potassic chlorite phyllic and propylitic alteration developed the ore forming process can be divided into four stages stage i barren quartz veins stage ii quartz chalcopyrite pyrite veins stage iii quartz polymetallic sulfide veins and stage iv quartz calcite veins four types of fluid inclusions fis can be distinguished in the fuxing deposit including hypersline h type vapor rich two phase v type liquid rich two phase l type and trace amounts of pure vapor inclusions p type but only the stage i quartz contains all types of fis the stages ii and iii quartz have two types of fis with exception of h and p types in stage iv quartz minerals only the l type inclusions can be observed the fis in quartz of stages i ii iii and iv are mainly homogenized at temperatures of 357 518 c 255 393 c 234 322 c and 145 240 c with salinities of 1 9 11 6 wt nacl equiv 1 6 9 6 wt nacl equiv 1 4 7 7 wt nacl equiv and 0 9 3 7 wt nacl equiv respectively the ore forming fluids of the fuxing deposit are characterized by high temperature moderate salinity and relatively oxidized condition carbon hydrogen and oxygen isotopic compositions of quartz indicate that the ore forming fluids were gradually evolved from magmatic to meteoric in origin sulfur and lead isotopes suggest that the ore forming materials were derived from a deep seated magma source the cu mineralization in the fuxing deposit occurred at a depth of 1 km and the changes of oxygen fugacity decompression boiling and local mixing with meteoric water were most likely critical for the formation of the fuxing cu deposit

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

fluid inclusion characteristics and molybdenite re os geochronology of the qulong porphyry copper molybdenum deposit tibet the qulong porphyry copper and molybdenum deposit is located at the southwest margin of the lhasa terrane and in the eastern region of the gangdese magmatic belt it represents china s largest porphyry copper system with 2200 million tonnes of ore comprising 0 5 cu and 0 03 mo the mineralization is associated with miocene granodiorite monzogranite and quartz diorite units which intruded into jurassic volcanic units in a post collisional indian asian tectonic setting field observations and core logging demonstrate the alteration and mineralization at qulong are akin to typical porphyry copper systems in subduction settings which comprise similar magmatic hydrothermal potassic propylitic and phyllic alteration assemblages molybdenite re os geochronology confirms the relative timeframe defined by field observations and core logging and indicates that the bulk copper and molybdenum at qulong were deposited within 350 000 years between 16 10 0 06 0 08 without and with decay constant uncertainty and 15 88 0 06 0 08 ma this duration for mineralization is in direct contrast to a long lived intrusive episode associated with mineralization based on previous zircon u pb data our fluid inclusion study indicates that the ore forming fluid was oxidized and contained na k ca fe cu mo cl and s the magmatic hydrothermal transition occurred at 425 c under lithostatic pressure while potassic propylitic and phyllic alteration occurred at hydrostatic pressure with temperature progressively decreasing from 425 to 280 c the fluid inclusion data presented here suggests that there has been 2 3 km of erosion at qulong after its formation and this erosion may be related to regional uplift of the lhasa terrane

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

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

a review of the geological characteristics and geodynamic setting of late paleozoic porphyry copper deposits in the junggar region xinjiang uygur autonomous region northwest china abstract in this review we describe the geological characteristics of porphyry copper deposits in junggar region xinjiang and place these into their metallogenic tectonic context these porphyry copper deposits are mainly found in four metallogenic belts 1 a late silurian to early devonian cu mo metallogenic belt in the qiongheba area 2 the late devonian kalaxiange er cu metallogenic belt 3 the early carboniferous xilekuduke suoerkuduke porphyry skarn cu mo metallogenic belt and 4 the late carboniferous baogutu porphyry cu metallogenic belt the ages of mineralization can be divided into three broad intervals

copper deposition during quartz dissolution by cooling magmatic hydrothermal fluids the bingham porphyry abstract scanning electron microscope cathodoluminescence imaging is used to map successive generations of fluid inclusions in texturally complex quartz veinlets representing the main stage of ore metal introduction into the porphyry cu au mo deposit at bingham utah following conventional fluid inclusion microthermometry laser ablation inductively coupled plasma mass spectrometry la icpms is applied to quantify copper and other major and trace element concentrations in the evolving fluid with the aim of identifying the ore forming processes textures visible in cathodoluminescence consistently show that the bulk of vein quartz q1 characterized by bright luminescence crystallized early in the vein history cu fe sulfides are precipitated later in these veins in a microfracture network finally filled with a second generation of dull luminescing q2 quartz mapping of brine and vapor inclusion assemblages in these successive quartz generations in combination with la icpms microanalysis shows that the fluids trapped before and after cu fe sulfide precipitation are very similar with respect to their major and minor element composition except for copper copper concentrations in inclusions associated with ore formation drop by two orders of magnitude in a tight pressure temperature interval between 21 and 14 mpa and 425 350 c several hundred degrees below the temperature of fluid exsolution from the magma copper deposition occurs within a limited p t region in which sulfide solubility shows strong normal temperature dependence while quartz solubility is retrograde this permits copper sulfide deposition while secondary vein permeability is generated by quartz dissolution the brittle to ductile transition of the quartz feldspar rich host rocks occurs in the same temperature range which further enhances vein reactivation and promotes cooling and expansion of fluids ascending across the transition from lithostatic to hydrostatic conditions

geology and alteration geochemistry of the porphyry cu au deposit at bajo de la alumbrera argentina this paper describes the igneous geology alteration mineralogy and geochemistry as well as the ore mineralization history of bajo de la alumbrera a world class porphyry copper gold deposit in northwestern argentina the deposit occurs in the k rich calc alkaline farallon negro volcanic complex located 200 km east of the main andean porphyry copper belt of chile the deposit consists of a composite stock of dacitic porphyry intrusions and extends into the surrounding andesitic volcanic rocks two of the earliest intrusions now occupying the center of the intrusive complex show intense hydrothermal alteration and mineralization these two porphyries host the highest ore grades and were subsequently intruded by several weakly mineralized or barren porphyries intense quartz magnetite k feldspar alteration pervades the first mineralized porphyry whereas similar but lower intensity alteration affected the second laterally this alteration grades into potassic alteration secondary k feldspar and biotite which affects all porphyries except the latest dikes andesitic wall rocks within a hundred meters of the intrusions are dominated by dark hydrothermal biotite an outer halo of propylitic alteration epidote chlorite albite calcite extends up to 1 km into the andesites feldspar destructive alteration sericite pyrite clay minerals gypsum overprints the potassic and propylitic alteration in the volcanic rocks and all porphyries the alteration is locally controlled by faults and late fractures and developed most pervasively upon the outer part of the potassic zone and toward the transition to propylitic alteration in the upper part of the deposit mass balance calculations show small positive changes in net volume for the potassic alteration and minor volume decreases for the chlorite epidote and feldspar destructive alteration the intensely quartz magnetite veined sample of quartz magnetite alteration indicates a total volume increase of 350 percent copper and gold are intimately associated at all scales they occur as composite gold sulfide grains chalcopyrite rarely bornite show a close correlation of ore grades in sample assays and have a closely overlapping distribution on the mine scale a well developed ore shell coincides with potassic alteration and partly with the distribution of intense quartz magnetite veins even though the bulk of the ore minerals now occupy texturally late positions in vugs and fractures a barren zone with intense quartz magnetite potassic alteration and veins but little or no sulfides is interpreted as the focus of upflow of high temperature ore fluids prior to ore mineral saturation and coprecipitation of copper sulfides and gold in the ore shell

evidence for magmatic hydrothermal fluids and ore forming processes in epithermal and porphyry deposits of the baguio district philippines the baguio district contains a diverse array of epithermal porphyry and skarn deposits together with a large broadly strata bound advanced argillic lithocap magmatism mineralization and alteration occurred in response to subduction of the south china sea plate and the scarborough ridge beneath northern luzon over the past 3 m y rapid uplift and exhumation resulted in epithermal veins overprinting several porphyry cu au deposits most of the epithermal au ag deposits of the baguio district including antamok and acupan the two largest au deposits are intermediate sulfidation state quartz carbonate adularia illite base metal sulfide veins that contain electrum and minor au ag tellurides in contrast high sulfidation mineralization at kelly includes enargite tennantite electrum and precious metal tellurides and is associated with advanced argillic alteration although the mineralizing fluids that formed the porphyry and epithermal deposits had distinct temperatures and salinities stable and radiogenic data provide evidence for direct magmatic contributions into each deposit type the epithermal mineralizing fluids were dilute generally 600 c hypersaline brines 30 to 70 wt nacl equiv and low density vapor sulfur isotope compositions of sulfides in the porphyry skarn and intermediate sulfidation epithermal veins of the southern and central baguio district are mostly between 1 and 6 per mil consistent with a predominance of h2s in the mineralizing fluids i e reducing conditions in contrast sulfides from the high sulfidation porphyry and intermediate sulfidation deposits located adjacent to the baguio lithocap mostly have negative sulfur isotope values 6 9 to 0 8 consistent with oxidizing so42 predominant mineralizing fluids intermediate sulfidation epithermal veins at acupan have crosscut a well mineralized porphyry cu au stock work at ampucao the two deposits cannot be distinguished on the basis of radiometric age determinations ampucao 0 51 0 26 ma acupan 0 65 0 07 ma and are interpreted to be cogenetic with telescoping of the two environments caused by the rapid uplift and exhumation associated with ridge subduction measured 34ssulfide 1 1 to 6 6 34ssulfate 10 4 to 31 8 values and initial strontium ratios of anhydrite 0 70378 0 70385 are consistent with identical and predominantly magmatic sources of these components for the ampucao porphyry and acupan epithermal veins helium isotopes provide further evidence of mantle derived components in the epithermal veins r ra values of 6 0 and 6 7 oxygen deuterium and carbon isotopes provide evidence for predominantly magmatic water at ampucao and for hybrid magmatic meteoric waters at acupan that precipitated precious metals due to boiling the proportion of magmatic water relative to meteoric water and precious metal grades both decreased with time during epithermal vein formation at acupan the common observation of cross cutting relationships between porphyry and epithermal veins observed throughout the baguio district imply that the evolution of porphyry style to intermediate sulfidation style mineralization was a common phenomenon in this region and contributed significantly to its rich metal endowment

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

p t x conditions origin and evolution of cu bearing fluids of the shear zone hosted huogeqi cu pb zn fe deposit northern china abstract huogeqi is a shear zone hosted epigenetic deposit within the greenschist amphibolite facies of the mesoproterozoic langshan group in the langshan district on the northern margin of the north china craton ncc copper mineralization in the huogeqi deposit was formed in two stages a main stage controlled by the shear zone and characterized by brittle ductile ore forming structures and a lower greenschist facies mineral assemblage and a late stage characterized by open space filling textures and low temperature minerals based on microthermometric and raman microprobe analysis the main stage cu bearing fluid was mesothermal low salinity and h 2 o ch 4 dominant and was generated by an interaction between a deep crustal metamorphic fluid and graphite bearing host rocks this interaction resulted in a more ch 4 rich fluid which was more amenable to be immiscible we showed that immiscibility of the h 2 o ch 4 fluid occurred due to temperature decrease prior to the main stage cu mineralization cu was finally precipitated from the resultant h 2 o rich aqueous fluid main stage cu mineralization temperature was obtained using various methods 310 370 c by intersection of isochors of coexistent ch 4 and aqueous inclusions 364 41 c on average by pressure correction of the homogenization temperatures of aqueous inclusions and 362 26 c using the chlorite geothermometer pressure during cu deposition fluctuated between lithostatic and hydrostatic at depths of ca 10 12 km but it seemingly had no effect on the mineralization process the late stage cu bearing fluid was a low temperature low salinity h 2 o of meteoric origin

genesis of the wurinitu w mo deposit inner mongolia northeast china constraints from geology fluid inclusions and isotope systematics abstract the wurinitu w mo deposit is located in the erlian east ujimqin metallogenic belt in the great xing an range ne china tungsten and molybdenum mineralization generally occurs as veins in quartz hosted by the middle to lower ordovician wall rocks or as disseminations in the early cretaceous monzogranite intrusions fluid inclusion studies and multiple isotope analyses provide systematic evidence to determine the evolution of the hydrothermal fluids the source of metals and fluids as well as mineral precipitation mechanisms which are significant for the magmatic hydrothermal system but are poorly understood three types of fluid inclusion assemblages fias including l liquid rich two phase fias v vapor rich two phase fias and l v liquid vapor two phase fias have been identified in quartz veins from the w mineralization i mo mineralization ii and quartz carbonate iii stages at wurinitu the ore forming fluids evolved from a high to moderate temperature and moderate to low salinity h2o nacl co2 system in the w and mo mineralization stages to a low temperature and low salinity h2o nacl system in the quartz carbonate stage they were trapped at temperatures of 365 c 266 c and 198 c the results of hydrogen and oxygen isotope analyses 18oh2o 4 0 to 7 7 dh2o 116 to 92 indicate that the stage i fluids dominantly originated from magmatic water and the stages ii and iii show addition of meteoric water sulfur 34svcdt 1 9 4 0 and lead isotope values 206pb 204pb 18 099 18 728 207pb 204pb 15 527 15 616 and 208pb 204pb 38 019 38 465 suggest that the ore metals in the hydrothermal fluids were derived from the granitic magma all these observations reveal that 1 the wurinitu w mo deposit is a magmatic hydrothermal ore system 2 w and mo mineralization occurred under lithostatic pressure of 203 294 bars and hydrostatic pressure of 102 bars respectively and 3 fluid boiling and mixing with meteoric water might be the key factors controlling the large scale ore deposition at wurinitu

magma mixing origin for the aolunhua porphyry related to mo cu mineralization eastern central asian orogenic belt abstract many cu mo au deposits are considered to be related to adakitic porphyries formed in non arc settings e g in collisional orogenic zones and intra plate environments but their genesis is still under discussion the aolunhua porphyry complex and its related mo cu deposit from the eastern central asian orogenic belt caob provide important insights into this issue the porphyries are characterized by high sr 496 705 ppm and sr y and la yb ratios similar to those of typical adakitic rocks and low i sr ratios 0 7049 0 7052 and positive e nd t 0 5 to 1 4 and e hf t 3 5 to 9 8 values these features along with the occurrence of mafic microgranular enclaves mmes compositional and textural disequilibrium of plagioclase phenocrysts and relatively high mg values 45 52 indicate that they were derived from mixing of felsic magma from partial melting of a juvenile arc type lower crust and mafic magma from a lithospheric mantle previously metasomatized by subduction zone fluids melts high sr y and la yb ratios are indicative of contribution from enriched mantle derived materials with high liles e g sr la which were strengthened by subsequent fractionation of ferromagnesian phases such as pyroxene and hornblende mmes hosted by the ore bearing porphyry have zircon u pb ages of ca 132 ma similar to those of the host rocks the enclaves have elevated mg 56 63 liles e g sr 660 891 ppm lree la n 68 150 la sm n 3 0 4 0 la yb n 12 0 19 6 and ratios of radiogenic isotopes of nd and hf e nd 0 7 to 1 6 e hf 3 3 to 10 9 suggesting that their parental magmas were derived from the metasomatized mantle source the mo cu mineralization was probably related to the high water content high oxygen and sulfur fugacity of hybrid magma formation of the adakitic porphyries and related mo cu deposits of the eastern caob could be related to the early cretaceous lithospheric extension caused by the subduction of the paleo pacific plate and its induced reactivation of juvenile arc type lower crust

ore forming conditions and genesis of the huogeqi cu pb zn fe deposit in the northern margin of the north china craton evidence from ore petrologic characteristics abstract the huogeqi cu pb zn fe deposit is located in the langshan district in the western segment of the northern margin of the north china craton the deposit is hosted by upper greenschist lower amphibolite facies 550 650 c rocks of the langshan group most orebodies are hosted in a shear zone that developed in parallel with the sedimentary bedding of the langshan group fe was precipitated coeval with the deposition of the host rocks i e a syngenetic origin whereas cu pb and zn were precipitated in hydrothermal systems postdating formation of the host rocks i e an epigenetic origin the hydrothermal mineralization process can be subdivided into two stages 1 a main stage with predominant cu pb zn mineralization stage where ore forming structures are characterized by brittle ductile and brittle shear deformation the main stage sulfide veins cut the mylonite fabrics of the host rocks mineral paragenesis and compositions indicate that main stage cu mineralization took place at 330 440 c and 3 4 3 9 kbar this pressure temperature p t condition is consistent with that of the brittle ductile transition zone but lower than that of the peak metamorphism of the host rocks compared with cu mineralization the main stage pb zn mineralization took place at relatively lower temperature and pressure the syngenetically formed fe orebodies and iron formations in the huogeqi deposit were favorable sites for epigenetic cu precipitation the h 2 s rich cu fluids would have reacted with fe in the host rocks when flowing through fe orebodies and iron formations such a reaction would have led to a reduction in h 2 s of the ore forming fluids and consequently cu precipitation 2 the late stage cu mineralization is of less economic importance characterized by open space filling textures and a low temperature mineral assemblage that constrains the ore forming temperature as lower than 330 c this late stage mineralization took place in an epithermal like hydrothermal system at a shallower crustal depth

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

rare earth elements yttrium and pb isotope ratios in thermal spring and well waters of west anatolia turkey a hydrochemical study of their origin abstract rare earth elements ree yttrium major elements and pb isotope ratios were determined in thermal well and spring waters and rocks of the buyuk menderes and gediz grabens turkey which includes the geothermal fields of kizildere salavatli germencik kula and salihli together with the results of short and long time leaching of local rocks ree and y and pb isotope ratios indicate that the palaeozoic mica schists dominantly control the ree and y signatures of the deep seated na hco 3 waters marbles may also be involved but their low ree contribution is overridden by the much higher ree and y abundances in the mica schists palaeozoic gneisses can be excluded as source rocks by both pb isotope ratios and ree leaching behaviour the deep seated waters either ascend rapidly in production wells and precipitate carbonate silica scales at temperatures of about 200 c or these waters ascend slowly to springs become enriched in ca 2 cl and so 4 2 and discharge with temperatures up to 100 c as fumaroles or hot springs some of these spring waters precipitate large amounts of travertine upon exsolution of co 2 in contrast the thermal ca hco 3 type of water from pamukkale has its source in the regional pliocene limestones

origin of the jiaodong type xinli gold deposit jiaodong peninsula china constraints from fluid inclusion and c d o s sr isotope compositions abstract the xinli gold deposit within the sanshandao cangshang gold belt in the jiaodong gold province is a typical jiaojia type ore deposit with high grade quartz sulfide vein veinlet stockworks that cut mesozoic granodiorite four ore stages are distinguished in the following sequences i quartz k feldspar sericite pyrite ii quartz pyrite iii quartz polymetallic sulfide and iv quartz calcite pyrite fluid inclusions in quartz and calcite in the ores contain c o h fluids dominantly of six types with varied liquid vapor ratio ore fluid in the main ore stage is characterized by medium low temperature low salinity reducing condition and nacl h 2 o co 2 ch 4 in composition the 18 o water smow of quartz in ore stages ii and iii range from 2 82 to 5 34 and the d smow are between 69 6 and 88 3 both suggest that the ore fluid was dominantly magmatic water the 13 c pdb of the calcite are from 6 4 to 2 4 indicating mantle contribution to the ore fluid the pyrite 34 s cdt from four ore stages are basically similar varying from 9 42 to 11 62 which implies significant involvement of crustal materials the initial 87 sr 86 sr ratios in the calcite ranging from 0 710657 to 0 711542 also denote a crustal contribution the fluid composition and systematic h o c s sr isotopic data are explained by a model of slab subduction induced gold mineralization in the model the ore fluid and metals were considered to associate with the dehydration and desulfidation of the subducting paleo pacific slab and the subsequent devolatilization of enriched mantle wedge the h 2 o in the fluid might have been released from the devolatilization of enriched mantle wedge the co 2 could be from mantle wedge or subcontinental lithospheric mantle and the sulfur and strontium would be initially released from the subducted seafloor sediments this process was further supported by the geochemical features of intermediate basic dykes contemporaneous to the gold ore deposits the deposit features and ore forming process of the xinli gold deposit hardly concur those of the orogenic gold deposit and the pluton related gold deposit the study supports the argument of that the gold deposits in the jiaodong belong to a unique gold type related to a complex slab subduction related process the geodynamic engine of the jiaodong type gold deposit is specific i e the slab subduction coupling with the consequent lithospheric thinning and structure adjustment

the crustal accretion history and tectonic evolution of the ne china segment of the central asian orogenic belt abstract the basement rocks in parts of ne china constitute a khondalitic sequence of sillimanite and garnet bearing gneisses hornblende plagioclase gneiss and various felsic paragneisses zircon u pb dating of garnet sillimanite gneiss samples from the erguna xing an jiamusi and khanka blocks indicates that high grade metamorphism occurred at 500 ma evidence from detrital zircons in paleozoic sediments from the songliao block also indicates the former presence of a 500 ma component this uniformity of u pb ages across all crustal blocks in ne china establishes a 1300 km long late pan african khondalite belt which we have named the ne china khondalite belt this indicates the blocks of ne china were amalgamated prior to 500 ma contrary to current belief one scenario is that this amalgamated terrane had a tectonic affinity to the siberia craton once forming part of the late pan african 500 ma sayang baikal orogenic belt extensively developed around the southern margin of the siberia craton this belt was the result of collision between currently unidentified terranes with the southeastern angara anabar province at about 500 ma where the rocks were deformed and metamorphosed to granulite facies it appears likely that at sometime after 450 ma the combined ne china blocks rifted away from siberia and moved southward to form what is now ne china the combined block collided with the north china craton along the solonker xar moron changchun suture zone at 230 ma rather than in the end permian as previously thought local rifting at the eastern extremity of the developing central asian orogenic belt caob resulted in the splitting away of the jiamusi khanka bureya blocks however this was only transient and sometime between 210 and 180 ma these were re united with the caob by the onset of pacific plate subduction which has dominated the tectonic evolution of the region since that time

tethys tectonic evolution and its bearing on the distribution of important mineral deposits in the sanjiang region sw china abstract the sanjiang region in se tibet plateau and nw yunnan is known to have formed by amalgamation of gondwana derived continental blocks and arc terranes as a result of oceanic subduction followed by continental collision from paleozoic to mesozoic in this paper we provide a synthesis of tectonic evolution magmatism and metallogeny in the region based on data from literatures early paleozoic ophiolites 473 439 ma in the changning menglian belt indicate the existence of a proto tethys ocean in this region two episodes of subduction related magmatism in the early paleozoic one occurred in the baoshan and tengchong blocks at 502 455 ma and the other occurred in the simao block at 421 401 ma are regarded as evidence for two different events of subduction of the proto tethys ocean at different locations the proto tethys was succeeded in early devonian by the paleo tethys which comprised the main ocean and three branches ailaoshan jinshajiang and garze litang the changning menglian main ocean existed from middle devonian to middle triassic the remnants of the oceanic crust are preserved in a few places in the longmu tso shuanghu suture as well as in the changning menglian ophiolite belt the eastward subduction of the main oceanic plate from early permian to early triassic formed a prominent arc terrane stretching 1500 km from yunnan to eastern tibet from the waning stage of subduction to post subduction numerous s type granite plutons with ages varying between 230 and 219 ma such as the lincang batholith in yunnan were emplaced at or close to the suture this event produced several hydrothermal w sn deposits in the region the tectonic evolution and associated magmatism of the jinshajiang and ailaoshan branch oceans are generally comparable to those of the main ocean however the branch oceans were subducted westward instead the garze litang branch ocean also underwent westward subduction from middle devonian to late triassic arc related high sr y porphyry intrusions and associated porphyry skarn cu mo au deposits are common in the jinshajiang ailaoshan region especially in the yidun arc which formed prior to jurassic the vms deposits in the sanjiang region formed in diverse tectonic settings including middle silurian back arc basins carboniferous oceanic islands paleozoic subduction zones and triassic post subduction rifting environments the mesozoic and early cenozoic evolution of the baoshan and tengchong blocks was largely influenced by eastward oceanic subduction of the meso and neo tethys from late permian to middle cretaceous and from late cretaceous to 50 ma respectively abundant early cretaceous granitoids and associated skarn type pb zn and sn fe deposits in the baoshan and tengchong blocks were produced in the background of the shan boundary oceanic slab subduction to the west and the break off of the nujiang bitu oceanic slab to the north the subduction of the neo tethys oceanic plate beneath the tengchong block from late cretaceous to paleogene formed abundant s type granitoids and many skarn type and greisen type sn w deposits granitoids formed at 105 to 81 ma and contemporaneous hydrothermal w mo ag and au deposits which temporally coincided with the subduction of the neo tethys are common in the yidun arc terrane

late jurassic early cretaceous closure of the mongol okhotsk ocean demonstrated by new mesozoic palaeomagnetic results from the trans baikal area se siberia summary we present new palaeomagnetic results from the transba ikal area se siberia from the mongol okhotsk suture zone the boundary between the amuria and siberia blocks in order to better constrain the time of closure of the mongol okhotsk ocean in the mesozoic we col lected 532 rock samples at 68 sites in six localities of basalts trachy basalts and andesites from both sides of the mongol okhotsk suture at unda river j 3 51 7 n 117 4 e kremljevka peak k1 51 8 n 117 5 e and torey lakes k 1 50 1 n 115 9 e on the southern side of the suture and at monostoy river j 1 51 1 n 106 8 e ingoda river k 1 51 2 n 112 2 e and bichura town k 1 50 6 n 107 6 e on the northern side progressive thermal demagnetization enabled us to resolve low ltc and high htc temperature components of magnetization at most sites jurassic palaeopoles computed from the htcs show a large discrepancy with respect to the apparent polar wander path of eurasia which we interpret in terms of 1700 2700 km of post late jurassic northward movement of amuria with respect to siberia although ge ological data suggest a middle jurassic closure of the mongol okhotsk ocean in the west trans baikal region our data give evidence of a large remaining palaeolatitude difference between the amuria and siberia blocks in contrast early cretaceous sites cluster remarkably well along a small circle which is centred on the average site location this implies the absence of post early cretaceous northward motion of amuria relative to siberia and demonstrates the pre early cretaceous closure of the mongol okhotsk ocean finally we interpret the very large tectonic rotations about local vertical axes evidenced by the small circle distribution of poles as arising both from collision processes and from left lateral shear movement along the suture zone due to the eastward extrusion of amuria under the effect of the collision of india into asia

origin of the wunugetushan porphyry cu mo deposit inner mongolia ne china constraints from geology geochronology geochemistry and isotopic compositions abstract the wunugetushan porphyry cu mo deposit is located in the southeastern margin of the mongol okhotsk orogenic belt and in the northwestern segment of the great xing an range ne china the orebodies of this deposit are mainly hosted in the monzogranitic porphyry stock and in contact with the granitic porphyry dyke and biotite granite batholith the shrimp zircon u pb dating of the granitic porphyry dyke yielded ages of 201 4 3 1 ma 2 mswd 1 5 these results indicate that the magmatism in the wunugetushan area might have occurred at ca 201 ma in the early jurassic and that the mineralization age ca 181 ma of this deposit is later than the age of intrusive granitic porphyry in the area geochemically the wunugetushan granitoids belong to high k calc alkaline and shoshonitic series enriched in k rb nd and pb and depleted in sr nb ti and p with negative eu anomalies in situ hf isotopic analyses of zircons using la mc icp ms indicate that the ehf t values for zircons from a granitic porphyry sample vary from 2 4 to 11 8 and that the corresponding crustal model ages tdmc vary from 483 to 1088 ma the least altered monzogranitic porphyry granitic porphyry and biotite granite yielded relatively uniform end t values from 1 0 to 0 6 and low 87sr 86sr i ratios ranging from 0 704387 to 0 708385 the geochemical and sr nd hf isotopic data for the granitoids indicate that the source magma for these rocks could be derived from a juvenile lower crust the 34s values of sulfides show a narrow range 0 76 to 3 20 similar to those of magmatic sulfur further implying a lower crust origin based on the results of this study and the regional geodynamic evolution it is proposed that the formation of the wunugetushan deposit and associated granitoids should be linked to the southeastward subduction of the mongol okhotsk oceanic plate beneath the erguna massif during the early jurassic and that the monzogranitic porphyry intrusions in wunugetushan area probably provided important ore metals responsible for the large scale cu mo mineralization

characteristics and genesis of mineral deposits in east ujimqin banner western segment of the great xing an mountains ne china abstract the east ujimqin banner located in the western segment of the great xing an mountains ne china has undergone a long and multi stage tectonic evolution which has resulted in significant fe ag pb zn au cu mo deposits there are two main types of mineralization vein and skarn types the jilinbaolige and aerhada vein deposits and the chagan obo and chaobuleng skarn type deposits are four typical deposits in this area the vein deposits mainly occur as veins with hydrothermal alteration in fractures within pre mineralization clastic rocks and felsic volcanic rocks the skarn type deposits always show a temporal and spatial relationship with mesozoic granite intruded into paleozoic limestone the sulfur isotope data from the sulfides in these four deposits have a very narrow range 1 to 8 suggesting that most were derived from magma the 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb ratios range from 17 949 to 18 529 15 370 to 15 691 and 37 653 to 38 460 respectively indicating that the metals derive mainly from the mantle source in the diagrams 207 pb 204 pb vs 206 pb 204 pb and 208 pb 204 pb vs 206 pb 204 pb the points of lead isotope of the sulfide ores are very near or coincide to the k feldspar indicating that the ore forming materials sources have the genetic relationship it seems that there are four key factors controlling the mineralization styles in this district the tectonic setting magmatic activity wall rocks and structures the superposition of multi stage tectonism from a mesozoic extensional setting on a paleozoic subduction setting provided a remobilization and enrichment mechanism for the ore forming elements the magmatic activities were sources of metals and fluids and drove them to the mineralization sites the wall rocks are key factors for mineralization styles when metal bearing fluid flows into clastic rocks and felsic volcanic rocks the mineralization is mainly vein type and mineralization in limestone is mainly skarn type ne and nw trending extensional faults may have provided the channels for the movement of metal bearing fluids and depositional space for metals

the genesis of the ores and intrusions at the yuhai cu mo deposit in eastern tianshan nw china constraints from geology geochronology geochemistry and hf isotope systematics abstract the yuhai porphyry cu mo deposit is located in the eastern tianshan orogenic belt of the southern central asian orogen belt being an economically important porphyry cu deposit in nw china the deposit comprises sixteen buried orebodies that are predominantly associated with dioritic and granodioritic intrusions and are structurally controlled by roughly ne trending faults la icp ms zircon u pb dating yielded crystallization ages of 441 6 2 5 ma mswd 0 03 n 24 for diorite and 430 4 2 9 ma mswd 0 04 n 19 and 430 3 2 6 ma mswd 0 09 n 24 for granodiorite in situ zircon hf isotope data on a diorite sample show e hf t values from 8 7 to 18 6 and two granodiorite samples exhibit similar e hf t values from 12 6 to 19 6 and 12 6 to 18 9 respectively the dioritic and granodioritic intrusions belong to a low k tholeiite series and are relatively enriched in large ion lithophile elements k ba pb and sr and are depleted in high field strength elements th nb ta and ti moreover these intrusions have high sio 2 al 2 o 3 and mgo contents low na 2 o p 2 o 5 and tio 2 contents low nb ta ratios and slightly positive eu anomalies re os dating of molybdenite intergrowth with chalcopyrite yielded a well constrained 187 re 187 os isochron age of 351 7 2 9 ma mswd 1 5 with a weighted average age of 355 7 2 4 ma mswd 0 69 ma indicating that the yuhai cu mo deposit is younger than the intrusion of the diorite and granodiorite combined with the regional geological history and above mentioned data we suggest that the yuhai intrusions were most likely derived from the partial melting of mantle components that were previously metasomatized by slab melts formed by the northward subduction of the ancient tianshan ocean plate beneath the dananhu tousuquan island arc during the silurian to carboniferous under the subduction related tectonic setting the metasomatized mantle magma was emplaced into the shallow crust and induced the formation of the early carboniferous yuhai cu mo deposit and the hydrothermal fluids of enriched sulfides probably played an important role in the cu mo mineralization

fluid inclusions in sedimentary and diagenetic systems abstract some of the major problems in sedimentary geology can be solved by using fluid inclusions in sedimentary and diagenetic minerals important fluids in the sedimentary realm include atmospheric gases fresh water of meteoric origin lake water seawater mixed water evaporated water formation waters deep in basins oil and natural gas preserving a record of the distribution and composition of these fluids from the past should contribute significantly to studies of paleoclimate and global change research is essential for improving understanding of diagenetic systems and provides useful information in petroleum geology applications of fluid inclusions to sedimentary systems are not without their complexities some fluid inclusions exposed to natural conditions of increasing temperature may be altered by thermal reequilibration which results in stretching or leakage and refilling of some fluid inclusions similarly overheating in the laboratory can also cause reequilibration of fluid inclusions so fluid inclusions from the sedimentary realm must be handled carefully and protected from overheating natural overheating of fluid inclusions must be evaluated through analysis of the most finely discriminated events of fluid inclusion entrapment fluid inclusion assemblages fia consistency in homogenization temperatures within a fluid inclusion assemblage consisting of variably sized and shaped inclusions is the hallmark of a data set that has not been altered through thermal reequilibration in contrast fluid inclusion assemblages yielding variable data may have been altered through thermal reequilibration if a fluid inclusion assemblage has not been altered by thermal reequilibration its fluid inclusions may be useful as geothermometers for low and high temperature systems or useful as geobarometers applicable throughout the sedimentary realm if a fluid inclusion assemblage has been altered partially by thermal reequilibration techniques for distinguishing between altered and unaltered fluid inclusions may be applied in studies of global change fluid inclusions can be used as sensitive indicators of paleotemperature of surface environments fluid inclusions also preserve microsamples of ancient seawater and atmosphere the analysis of which could figure prominently into discussions of past changes in chemistry of the atmosphere and oceans in petroleum geology fluid inclusions have proven to be useful indicators of migration pathways of hydrocarbons they can delineate the evolution of the chemistry of hydrocarbons and they remain important in understanding the thermal history of basins and relating fluid migration events to evolution of reservoir systems in studies of diagenesis fluid inclusions can be the most definitive record most diagenetic systems are closely linked to temperature and salinity of the fluid thus fluid inclusions are sensitive indicators of diagenetic environments

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

geological and isotopic evidence for magmatic hydrothermal origin of the ag pb zn deposits in the lengshuikeng district east central china the lengshuikeng ore district in east central china has an ore reserve of 43 mt with an average grade of 204 53 g t ag and 4 63 pb zn based on contrasting geological characteristics the mineralization in the lengshuikeng ore district can be divided into porphyry hosted and stratabound types the porphyry hosted mineralization is distributed in and around the lengshuikeng granite porphyry and shows a distinct alteration zoning including minor chloritization and sericitization in the proximal zone sericitization silicification and carbonatization in the peripheral zone and sericitization and carbonatization in the distal zone the stratabound mineralization occurs in volcano sedimentary rocks at 100 400 m depth without obvious zoning of alterations and ore minerals porphyry hosted and stratabound mineralization are both characterized by early stage pyrite chalcopyrite sphalerite middle stage acanthite native silver galena sphalerite and late stage pyrite quartz calcite the 34s values of pyrite sphalerite and galena in the ores range from 3 8 to 6 9 with an average of 2 0 the c o isotope values of siderite calcite and dolomite range from 7 2 to 1 5 with an average of 4 4 v pdb and from 10 9 to 19 5 with an average of 14 8 v smow respectively hydrogen oxygen and carbon isotopes indicate that the hydrothermal fluids were derived mainly from meteoric water with addition of minor amounts of magmatic water geochronology employing la icp ms analyses of zircons from a quartz syenite porphyry yielded a weighted mean 206pb 238u age of 136 3 0 8 ma considered as the emplacement age of the porphyry rb sr dating of sphalerite from the main ore stage yielded an age of 126 9 7 1 ma marking the time of mineralization the lengshuikeng mineralization classifies as an epithermal ag pb zn deposit

metallogenic province derived from mantle sources nd sr s and pb isotope evidence from the central asian orogenic belt abstract the central asian orogenic belt caob is one of the most important regions for cu au and polymetallic and rare metallic li be nb ta mineralization over the world most of the ore deposits in the caob are closely associated with granitoids available sr nd s and pb isotopic data indicate that the metallogenic epoch and sources of the mineral deposits in the caob are consistent with that of the regional granites available data suggest that mantle sources could have played an important role in the paleozoic to mesozoic mineralization in the caob

macflincor and its application to fluids in archean lode gold deposits abstract macflincor was developed to process laboratory data gathered on fluid inclusions and to calculate isochores for geologically important fluids composed of h2o c02 ch4 nacl and n2 within the program interactive diagrams are available to describe those chemical systems which cannot be adequately constrained numerically the user can choose from various published equations of state describing fluid behavior and can easily compare the results obtained by using different equations the program once the basic fluid parameters have been established allows the data to be used to determine the p t trapping conditions to evaluate possible pressure corrections and to compare different depths of formation based on the pressure calculations and given geothermal gradients for illustrative purposes macflincor has been utilized here to constrain different physical chemical parameters of fluid inclusions trapped in ore related quartz veins and breccias of archean lode gold deposits in western australia inferred pressures from individual deposits show a wide range of values which may be due to post entrapment modifications and or observational uncertainties including estimation of liquid vapor ratios

spatial temporal relationships of mesozoic volcanic rocks in ne china constraints on tectonic overprinting and transformations between multiple tectonic regimes abstract la icp ms zircon u pb ages and geochemical data are presented for the mesozoic volcanic rocks in northeast china with the aim of determining the tectonic settings of the volcanism and constraining the timing of the overprinting and transformations between the paleo asian ocean mongol okhotsk and circum pacific tectonic regimes the new ages together with other available age data from the literature indicate that mesozoic volcanism in ne china can be subdivided into six episodes late triassic 228 201 ma early middle jurassic 190 173 ma middle late jurassic 166 155 ma early early cretaceous 145 138 ma late early cretaceous 133 106 ma and late cretaceous 97 88 ma the late triassic volcanic rocks occur in the lesser xing an zhangguangcai ranges where the volcanic rocks are bimodal and in the eastern heilongjiang jilin provinces where the volcanics are a type rhyolites implying that they formed in an extensional environment after the final closure of the paleo asian ocean the early middle jurassic 190 173 ma volcanic rocks both in the erguna massif and the eastern heilongjiang jilin provinces belong chemically to the calc alkaline series implying an active continental margin setting the volcanics in the erguna massif are related to the subduction of the mongol okhotsk oceanic plate beneath the massif and those in the eastern jilin heilongjiang provinces are related to the subduction of the paleo pacific plate beneath the eurasian continent the coeval bimodal volcanic rocks in the lesser xing an zhangguangcai ranges were probably formed under an extensional environment similar to a backarc setting of double direction subduction volcanic rocks of middle late jurassic 155 166 ma and early early cretaceous 145 138 ma age only occur in the great xing an range and the northern hebei and western liaoning provinces limited to the west of the songliao basin and they belong chemically to high k calc alkaline series and a type rhyolites respectively combined with the regional unconformity and thrust structures in the northern hebei and western liaoning provinces we conclude that these volcanics formed during a collapse or delamination of a thickened continental crust related to the evolution of the mongol okhotsk suture belt the late early cretaceous volcanic rocks widely distributed in ne china belong chemically to a low to medium k calc alkaline series in the eastern heilongjiang jilin provinces i e the eurasian continental margin and to a bimodal volcanic rock association within both the songliao basin and the great xing an range the volcanics in the eastern heilongjiang jilin provinces formed in an active continental margin setting related to the subduction of the paleo pacific plate beneath the eurasian continent and the bimodal volcanics formed under an extensional environment related either to a backarc setting or to delamination of a thickened crust or both late cretaceous volcanics limited to the eastern heilongjiang jilin provinces and the eastern north china craton ncc consist of calc alkaline rocks in the eastern heilongjiang jilin provinces and alkaline basalts in the eastern ncc suggesting that the former originated during subduction of the paleo pacific plate beneath the eurasian continent whereas the latter formed in an extensional environment similar to a backarc setting taking all this into account we conclude that 1 the transformation from the paleo asian ocean regime to the circum pacific tectonic regime happened during the late triassic to early jurassic 2 the effect of the mongol okhotsk suture belt on ne china was mainly in the early jurassic middle late jurassic and early early cretaceous and 3 the late early cretaceous and late cretaceous volcanics can be attributed to the subduction of the paleo pacific plate beneath the eurasian continent

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

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

geologic and geochemical insights into the formation of the taiyangshan porphyry copper molybdenum deposit western qinling orogenic belt china abstract taiyangshan is a poorly studied copper molybdenum deposit located in the triassic western qinling collisional belt of northwest china the intrusions exposed in the vicinity of the taiyangshan deposit record episodic magmatism over 20 30 million years pre mineralization quartz diorite porphyries which host some of the deposit were emplaced at 226 6 6 2 ma syn collisional monzonite and quartz monzonite porphyries which also host mineralization were emplaced at 218 0 6 1 ma and 215 0 5 8 ma respectively mineralization occurred during the transition from a syn collisional to a post collisional setting at ca 208 ma a barren post mineralization granite porphyry marked the end of post collisional magmatism at 200 7 5 1 ma the ore bearing monzonite and quartz monzonite porphyries have a e hf t range from 2 0 to 12 5 which is much more variable than that of the slightly older quartz diorite porphyries with t dm2 of 1 15 1 23 ga corresponding to the positive e hf t values and t dm1 of 0 62 0 90 ga corresponding to the negative e hf t values molybdenite in the taiyangshan deposit with 27 70 to 38 43 ppm re suggests metal sourced from a mantle crust mixture or from mafic and ultramafic rocks in the lower crust the 34 s values obtained for pyrite chalcopyrite and molybdenite from the deposit range from 1 3 to 4 0 0 2 to 1 1 and 5 3 to 5 9 respectively suggesting a magmatic source for the sulfur calculated 18 o fluid values for magmatic k feldspar from porphyries 13 3 hydrothermal k feldspar from stockwork veins related to potassic alteration 11 6 and hydrothermal sericite from quartz pyrite veins 8 6 to 10 6 indicate the taiyangshan deposit formed dominantly from magmatic water hydrogen isotope values for hydrothermal sericite ranging from 85 to 50 may indicate that magma degassing progressively depleted residual liquid in deuterium during the life of the magmatic hydrothermal system alternatively d variability may have been caused by a minor amount of mixing with meteoric waters we propose that the ore related magma was derived from partial melting of the ancient mesoproterozoic to neoproterozoic middle to lower continental crust this crust was likely metasomatized during earlier subduction and the crustal magmas may have been contaminated with lithospheric mantle derived magma triggered by mash e g melting assimilation storage and homogenization processes during collisional orogeny in addition a significant proportion of the metals and sulfur supplied from mafic magma were simultaneously incorporated into the resultant hybrid magmas

pseudo 3d imaging of a low slip rate active normal fault using shallow geophysical methods the geleen fault in the belgian maas river valley in a detailed site survey for paleoseismic trenching we applied shallow geophysical prospecting techniques including ground penetrating radar gpr electric resistivity tomography ert and resistivity mapping to identify locate and visualize in 3d the geleen fault an active normal fault bordering the roer valley graben in northeast belgium because of a low slip rate the geomorphic expression of this fault is very faint in the relatively young deposits of the maas river valley ert profiles show the fault as a broad near vertical anomaly characterized by sharp lateral resistivity contrasts with an associated vertical offset of sediment layers we observed offsets of 15 m and 5 m for the base and top respectively of a middle late pleistocene fluvial gravel layer shallow ert and gpr profiles indicate that younger sediments are also affected by faulting but the amount and sense of offset appear to be conflicting ert profiles show a near surface high resistivity layer with an apparent rever

separation of molybdenum and copper in porphyry deposits the roles of sulfur redox and ph in ore mineral deposition at bingham canyon the giant bingham canyon porphyry cu mo au deposit utah is associated with eocene subvolcanic intrusions it shows a distinct metal zonation above a barren core with dominantly shallow cu au mineralization cu stage following the early quartz monzonite porphyry qmp intrusion and spatially deeper mo mineralization mo stage occurring in a separate vein set exclusively after a late quartz latite porphyry qlp intrusion that truncates earlier cu au veins to understand this metal separation and the geochemical process of molybdenite mineralization we investigated fluid inclusions by microthermometry raman spectroscopy and laser ablation inductively couple plasma mass spectrometry la icp ms microanalysis in low and high grade quartz veins of both mineralization stages in deep low grade quartz veins interpreted to represent the root zone of the cu stage we found high concentrations of cu s and mo in the fluid inclusions whereas in low grade mo stage veins we found lower cu but similar concentrations of s and mo compared to the inferred input fluids to the cu stage sulfur and copper concentrations were similar in intermediate density type fluid inclusions in deep low grade cu stage samples whereas intermediate density type inclusions in low grade mo stage veins have s contents that exceed their cu contents in high grade mo stage vein we found large variations of mo concentrations in coexisting brine and vapor inclusions compared to the p t conditions of the cu precipitation stage 90 260 bars and 320 430 c the mo precipitating fluids were trapped at higher pressures and temperatures of 140 to 710 bars and 360 to 580 c mass balance calculation based on the compositions of intermediate density inclusions and brine vapor assemblages interpreted to be derived by phase separation during decompression of the ascending single phase intermediate density fluid indicate that the mass of vapor phase exceeded that of brine by about 9 1 in both mineralization stages combining this mass balance with the analyzed vapor brine partitioning data indicates that more than 70 of mo and s by mass in the deposit were deposited from the vapor phase earlier cu au deposition was similarly dominated by vapor but recently published data about postentrapment cu diffusion in and out of fluid inclusions cast doubt on previous quantifications suggesting that almost none of the copper was deposited by brine mo is less likely to be modified by selective diffusion and high mo contents max 0 0054 mo na in intermediate density 380 g g mo in brine in the hydrothermal fluids were maintained from the early cu stage to the late mo stage this indicates that mo concentration was not the decisive factor for separate precipitation of late mo ore at bingham canyon instead the metal separation may be explained by a reduction in redox potential and an increase in acidity in the evolving source region of the fluids i e a large subvolcanic magma reservoir this is indicated by the stoichiometry of chalcopyrite and molybdenite precipitation reactions a tentative difference in the fe mn ratio in fluids of both veining stages incipient muscovite alteration along high temperature molybdenite veins and an increasing tendency for mo to fractionate from brine to vapor we suggest that the early cu stage fluids were slightly more oxidized and neutral allowing cu fe sulfides to saturate first while molybdenite saturation was suppressed and mo was lost from the early ore stage by contrast during the later mo stage the fluids were more reduced and acidic thereby allowing selective saturation of molybdenite as the first precipitating sulfide in the cooling and expanding two phase fluid consistent with textural observations this interpretation may imply more generally that small differences in redox potential and acid base balance of the magmatic source of porphyry mineralizing systems may be decisive in the temporal and spatial separation of the two metals