far field tectonics associated with a large impact basin applications to caloris on mercury and imbrium on the moon abstract lithospheric readjustments after the formation of a large impact crater have been computed the models predict tectonic perturbations over a major portion of the surface of the planet the weight of the ejecta and the mechanical perturbations in the crater area give rise to membrane stresses if the planetary lithosphere is in compression the direction of maximum compression after the impact is perpendicular to a meridian in a referential where the basin would be at the north pole on mercury the preferential orientation of compressive scarps radial to caloris is explained in this manner for a planet in extension grabens perpendicular and parallel to a meridian can appear successively as the mechanical state of the crater area is modified on the moon this result is consistent with the large scale tectonics associated with imbrium

tin metallogenesis associated with granitoids in the southwestern sanjiang tethyan domain nature deposit types and tectonic setting article i nfo tin mineralization in the southwestern sanjiang tethys sn metallogenic domain extends from the southeast asia tin belt in the south the eastern part of the domain does not contain significant sn deposits whereas the central part of the domain composed of the changning menglian sn belt and related to ca 239 178 ma s type granitoids generated by the collision between tengchong baoshan and simao blocks carries wide spread the hydrothermal vein type mineralization the western part of the domain composed of the tengchong baoshan sn metallogenic belt is related to both 136 113 ma and 89 52 ma s type granitoids the former granitoids resulted from the collision between western burma and tengchong baoshan blocks and generated skarn type tin deposits the younger groups correspond to the india asia continental collision and are associated with the xiaolonghe and lailishan greisen type sn deposits

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

origin of the wangpingxigou pb zn deposit in east qinling orogenic belt china distal response to the giant donggou porphyry mo system abstract the southern margin of the north china craton ncc hosts many world class porphyry mo and vein type pb zn ag deposits forming an important polymetallic metallogenic belt in china even over the world although the mo and pb zn ag mineralization are temporarily and spatially associated with each other their possible genetic links are still unclear to delineate the relationships between the two types of ore mineralization we carried out in situ geochemical and s pb isotopic analyses on sulfides from the two spatially associated deposits i e the wangpingxigou pb zn and donggou porphyry mo deposits in the ore district based on field and microscopic observations on the crosscutting relationships of various veins and paragenetic relationships of various hydrothermal minerals three i iii and four i iv stages of hydrothermal veins have been identified in the wangpingxigou and donggou deposits respectively pyrite grains from stage ii of the wangpingxigou deposit have high co ni ratios mostly 1 and au and as contents similar to those of typical epithermal systems moreover sulfides from this deposit have in situ 206pb 204pb 17 345 17 417 207pb 204pb 15 454 15 514 and 208pb 204pb 38 138 38 364 ratios similar to those of sulfides from the donggou deposit indicating that the two deposits were relevant to a common source the concentrations of many elements i e pb ag sn zn sb mn au and as in pyrite decrease gradually from the stage ii of the wangpingxigou deposit to the stage ii of the donggou deposit consistent with metal zonation typically observed in porphyry related metallogenic systems further considering similar ages of the two deposits we propose that the wangpingxigou pb zn deposit is likely distal to the donggou porphyry mo system the range of 34s values of pyrites 7 63 8 76 from the stage ii in the donggou deposit is similar to those of the ancient strata xiong er group 7 31 8 17 in the ore district indicating that the sulfur in ore forming fluids may be mainly derived from the ancient strata however the 34s values 9 20 9 70 of stage iii sulfides in the donggou deposit are higher than those of stage ii sulfides in the donggou deposit and stage ii sulfides in the wangpingxigou deposit 7 34 9 29 the different sulfur isotopic compositions may be related to varied physicochemical conditions of the ore forming fluids confirmation of a mo pb zn metallogenic system in the region provides important clues on further prospecting of mo and pb zn resources in the southern margin of the north china craton

geochemical compositions of ore related pyrite quartz and fluid inclusions of bangbu gold deposit in the indus yurlung zangbo suture zone tibet abstract the bangbu gold deposit is the largest au deposit and the only deposit in production within an orogenic au belt hosted by the indus yurlung zangbo suture zone in tibet strontium isotopes and in situ trace element data from ore related pyrite quartz and fluid inclusions were used to determine the composition of ore forming fluids the sources of ore components and ore forming processes arsenic se and ge are incorporated into au bearing pyrite by isomorphic substitution for s while co and ni replace fe in the pyrite lattice and au occurs either as lattice bound or in the form of nanoparticles in pyrite the individual fluid inclusions have au contents of 0 59 4 41 ppm with an average of 1 43 ppm single fluid inclusion analyses show a negative correlation between au and cl contents indicating that au did not complex with cl ions and was probably transported as au hs 2 aluminum is positively correlated with li and ge in ore related quartz consistent with a contribution from magmatic hydrothermal fluids the average 87sr 86sr ratio of fluid inclusions in quartz is 0 71577 which indicates a contribution from mantle derived material gold is likely to have been sourced from fluids evolved from mantle derived magma rather than the surrounding rocks

mid silurian back arc spreading at the northeastern margin of gondwana the dapingzhang dacite hosted massive sulfide deposit lancangjiang zone southwestern yunnan china abstract the dapingzhang dacite hosted volcanogenic massive sulfide deposit is located in a late paleozoic collisional zone the sanjiang fold and thrust belt characterized by a collage of gondwana derived terranes at the southern margin of the south china yangtze block this area has experienced repeated paleozoic and mesozoic collisional and extensional events and is overprinted by himalayan strike slip and thrust movements the dapingzhang orebody is strongly sheared into discontinuous ore lenses and blocks and is hosted by a several hundred meter thick volcanic rock sequence of dacite with minor metabasalt spilite rhyolite and chert bulk rock nd isotope data give end 429 ma values of 2 to 5 and indicate a dominantly mantle source or origin from young continental crust tdm 800 1000 ma the dacites have distinctly low abundances of ti nb ta zr th and rees which is typical of subduction related volcanism the base metal mineralization occurs as polymetallic massive sulfide mineralization mainly pyrite sphalerite galena chalcopyrite tetrahedrite tennantite and locally barite and as pyrite chalcopyrite stockworks pervasive hydrothermal alteration is dominantly quartz sericite maximum enrichment in gold bismuth selenium and tellurium is at the interface between the stockwork and massive sulfide mineralization styles deeper parts of the stockwork zone are characterized by elevated molybdenum and rhenium whereas the distal parts to the massive sulfide mineralization have high mercury antimony zinc cadmium arsenic lead and silver the metal association and mineral assemblage are typical of volcanic rock hosted massive sulfides in back arc volcanic settings uranium pb dating on zircon by la icp ms defines an age of 429 3 ma 2 n 19 for the dacite sequence rhenium os isotope data on mo rich bulk ore samples define an isochron of 429 10 ma 2 n 9 mswd 0 21 initial 187os 188os 3 1 1 9 common os is very low and the absolute abundances of 187re and 187os define a model age of 429 4 ma n 9 95 confidence the mid silurian dacite sequence and associated massive sulfide mineralization identify a hitherto unknown early rifting and back arc seafloor spreading event at the northeastern gondwana margin related to the early evolution of the paleotethys ocean

genesis of the datuanshan stratabound skarn cu mo deposit middle lower yangtze valley eastern china constraints from geology re os geochronology mineralogy and sulfur isotopes stratabound deposits are the most abundant and economically significant ore type in the middle lower yangtze river valley one of the most important metallogenic belts in china the datuanshan deposit is one of the largest and most representative stratabound cu mo deposits in the tongling district of the middle lower yangtze river metallogenic belt all the orebodies of the datuanshan deposit occur around mesozoic quartz monzodiorite and are tabular or semi tabular bodies along bedding parallel faults within upper permian to lower triassic strata however discordant and crosscutting relationships e g the host rocks crosscut by skarn and quartz sulfide veins with alteration halos around the veins have also been found especially along the skarn host contact and orebody host contact indicating that skarnitization and mineralization postdated the deposition of the host sediments the skarn consists mainly of prograde garnet and pyroxene and retrograde alteration assemblages of amphibole epidote and chlorite as well as quartz and sulfides electron microprobe analyses show that the garnets and pyroxenes are grossular andradite and hedenbergite diopside series respectively and all samples plot in the field of typical skarn copper deposits worldwide molybdenite samples from stratiform copper ores yield re os model ages of 138 2 139 9 ma with a weighted mean age of 139 2 0 9 ma this is reasonably consistent with the ages of the stratiform mo ores 138 0 140 8 ma and genetically related quartz monzodiorite 135 2 139 3 ma in the datuanshan deposit indicating that the stratiform cu and mo mineralization was contemporaneous with emplacement of the quartz monzodiorite magmas in the early cretaceous fifteen 34s values for sulfides range from 1 8 to 4 7 with a mean of 0 5 indicating that the sulfur was derived mainly from a magmatic source moreover the sulfur isotope values of the ores are consistent with those of mesozoic intermediate acid intrusions but are different from those of sediments in the shizishan orefield based on these lines of evidence we conclude that the datuanshan stratabound cu mo deposit is the result of replacement related to mesozoic magmatic rocks and is not a product of submarine exhalative sedimentary processes

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

cenozoic volcanism and tectonic evolution of the tibetan plateau abstract cenozoic volcanism on the tibetan plateau which shows systematic variations in space and time is the volcanic response to the india asia continental collision the volcanism gradually changed from na rich k rich to potassic ultrapotassic adakitic compositions along with the india asia collision shifting from contact collision i e soft collision or syn collision to all sided collision i e hard collision the sodium rich and potasium rich lavas with ages of 65 40 ma distribute mainly in the lhasa terrane of southern tibet and subordinately in the qiangtang terrane of central tibet the widespread potassic ultrapotassic lavas and subordinate adakites were generated from 45 to 26 ma in the qiangtang terrane of central tibet subsequent post collisional volcanism migrated southwards producing ultrapotassic and adakitic lavas coevally between 26 and 8 ma in the lhasa terrane then potassic and minor adakitic volcanism was renewed to the north and has become extensive and semicontinuous since 20 ma in the western qiangtang and songpan ganze terranes such spatial temporal variations provide important constraints on the geodynamic processes that evolved at depth to form the tibetan plateau these processes involve roll back and break off of the subducted neo tethyan slab followed by removal of the thickened lhasa lithospheric root and consequently northward underthrusting of the indian lithosphere the tibetan plateau is suggested to have risen diachronously from south to north whereas the southern part of the plateau may have been created and maintained since the late oligocene the northern plateau would have not attained its present day elevation and size until the mid miocene when the lower part of the western qiangtang and songpan ganze lithospheres began to founder and detach owing to the persistently northward push of the underthrust indian lithosphere

a hydrothermal origin for the large xinqiao cu s fe deposit eastern china evidence from sulfide geochemistry and sulfur isotopes abstract the xinqiao cu s fe deposit in the tongling ore district middle lower yangtze river valley metallogenic belt mlyb eastern china is located along the northern margin of the yangtze craton the stratiform and skarn type xinqiao mineralization comprises five stages namely the early skarn stage i garnet and diopside late skarn stage ii epidote dominated iron oxides stage iii hematite and magnetite colloform pyrite stage iv and quartz sulfides stage v there are three pyrite types at xinqiao i e colloform py1 stage iv fine grained py2 from py1 recrystallization stage v and coarse grained py3 stage v pyrites scanning electron microscope sem imagery for py1 reveals that they are cubic microcrystalline pyrite aggregates and the eds and xrd data indicate that some py1 contain minor siderite impurities electron microprobe analysis empa and la icp ms geochemical data demonstrate that the three pyrite types have relatively high fe s ratios and distinctly high mn cu and as concentrations compared to py2 and py3 py1 has higher pb bi and ag but lower co ni se cd te and au ratios of fe s 0 837 to 0 906 se te 2 39 to 14 50 and co ni 0 67 to 4 67 of the xinqiao pyrites resemble typical hydrothermal pyrites 34 s cdt of py1 0 6 to 2 7 average 0 58 py2 1 8 to 2 5 average 2 1 and py3 1 9 to 4 4 average 3 5 are close to those of the xinqiao skarn type orebodies 1 3 to 4 1 but distinct from those of the upper carboniferous huanglong formation limestone 9 5 to 15 4 suggesting that the three pyrite types especially py1 were genetically linked to the yanshanian jurassic cretaceous magmatic hydrothermal events with py1 probably reflecting rapid crystallization during fluid mixing we interpret that the xinqiao stratiform mineralization may have been associated with the jitou quartz diorite stock as may be the case also for the skarn type mineralization hosted in the contact between the yanshanian jitou stock and the lower permian qixia formation limestone overall the xinqiao cu s fe mineralization may have been generated by the jurassic cretaceous tectono thermal event in eastern china

the boundary between the simao and yangtze blocks and their locations in gondwana and rodinia constraints from detrital and inherited zircons abstract the simao block which is the northern extension of the indochina block and the yangtze block were amalgamated by the closure of a paleo tethys branch ocean commonly referred to as the ailaoshan ocean the exact location of the suture between these two continental blocks has been contested some researchers believed that it is located within the cenozoic ailaoshan shear zone whereas other researchers thought that it is present 50 km farther to the west the detrital and inherited xenocrystic zircons from paleozoic sedimentary rocks and a triassic granite dyke respectively in the laowangzhai mojiang suspect terrane which occurs between the two suggested locations for the same suture show that neither of these previously suggested locations is accurate the age distribution pattern of detrital and inherited xenocrystic zircons from the laowangzhai mojiang suspect terrane is similar to that of detrital zircons from the simao indochina block but different from that of those from the jianshui area in the western margin of the yangtze block this indicates that the laowangzhai mojiang suspect terrane belongs to the simao indochina block the actual location of the suture between the simao indochina and yangtze blocks is suggested to superimpose the ailaoshan late devonian to early carboniferous ophiolite belt within the suspect terrane the new interpretation is also supported by hf isotopes of detrital zircons from the related continental blocks the age distribution pattern of precambrian detrital zircons from the western part of the yangtze block is different from that of those from australia or tethyan himalaya the northern part of the indian continent indicating that the yangtze block was not an integral part of australia or india in rodinia the age distribution pattern of pre carboniferous detrital zircons from the simao indochina block is remarkably similar to that of those from the tethyan himalaya indicating that the simao indochina block was derived from indian gondwana

three stage formation of greenstone hosted orogenic gold deposits in the val d or mining district abitibi canada evidence from pyrite and tourmaline abstract orogenic gold deposits are the most widespread type of gold deposit worldwide defining important exploration targets in precambrian greenstone belts here we refine the model for orogenic gold formation in the world class val d or mining district quebec canada using geochemical isotopic and mineralogical data from quartz tourmaline carbonate qtc veins from several deposits across the district multi element ag as au b ba co mg mo ni and pb pyrite mapping as well as major trace and rare earth element variations in tourmaline define a three stage paragenesis across several deposits the first reduced phase crystallized the quartz carbonate gold association in the veins the second oxidized phase favored tourmaline and barite crystallization barite was not previously reported from this district the third phase involved a reduced fluid and the crystallization of non auriferous as co ni rich cubic pyrite and tourmaline boron isotope ratios of tourmaline vary from 15 6 to 7 7 which is attributed to the mixing of at least two fluids one related to a deep metamorphic source and the other to shallower possibly relict formation water a systematic regional pattern in b isotope variation is found with lighter values in the volcanic rocks and heavier ones in or close to intrusions which suggests different mixing proportions in the vein field from ne to sw

gold mineralization in as rich mesothermal gold ores of the bogosu prestea mining district of the ashanti gold belt ghana remobilization of invisible gold the bogosu prestea mining district of southwestern ghana is a 33 km section of the early proterozoic ashanti gold belt greenschist facies carbonaceous and carbonate bearing turbidites and greywackes and mafic dikes host numerous economic mesothermal gold deposits structurally higher ores in the bogosu concession have brittle deformation and consist of disseminated sulphide lodes in tectonically disrupted sedimentary rocks and carbonate altered mafic dikes most gold occurs as micrometre size particles in arsenian pyrite and as invisible gold in arsenian pyrite and arsenopyrite the structurally deeper ores of the adjoining prestea concession are associated with brittle ductile deformation and consist of extensive crack seal quartz veins and graphitic shear zones only minor amounts of invisible gold were detected in these deeper lodes gold occurs dominantly as abundant microscopic and larger particles in sulphide arsenide minerals and in gangue the gold distribution patterns revealed by sims microprobe analysis and ion maps emp and colour staining suggest that most of the primary gold in the bogosu prestea system precipitated in solid solution with sulphide arsenide minerals however post depositional concentration and redistribution occurred in increasing degree with 1 increase in metamorphic hydrothermal gradients in the gold system depth 2 decrease in the refractory properties of the host mineral and 3 increase in the amount of post depositional host mineral recrystallization and deformation gold evolved from primary solid solution within sulphide arsenide minerals to colloidal and micrometre size particles concentrated in voids fractures and internal grain boundaries and finally to microscopic and larger particles at sulphide arsenide grain margins and in the gangue assemblage the general conclusions presented here are applicable to as rich gold deposits of all ages worldwide the presence of gold in late fractures is insufficient evidence for late stage introduction of gold in mesothermal gold systems

compositional polarity of triassic granitoids in the qinling orogen china implication for termination of the northernmost paleo tethys abstract the qinling orogen was formed from the closure of the northernmost paleo tethys sea and the tectonic suturing of the yangtze and north china cratons the timing of this collision and the tectonic framework are debated the widely developed triassic granitoids in the western qinling orogen offer a key to understand the tectonic evolution of this region here we compile the geological geochemical and geochronological data of the triassic granitoids from the qingling orogen and conclude that the granitoids north of the mian lue suture were emplaced in an active continental margin related to the northward subduction of the mian lue oceanic plate during 248 200 ma the granitoids can be classified into i and s types with the former constituting the major variety northward from the mian lue fault an s type granite belt appears followed by and locally overlapping with an i type granite belt the i type granite belt can be subdivided into four sub belts from south to north with increasing contents of k2o k2o na2o sio2 th and u and the ratios of k2o na2o rb sr and 87sr 86sr i but decreasing contents of na2o al2o3 mg and ehf t except for the northernmost belt which occurs in the huaxiong block of the north china craton this geochemical polarity of i type granitoids and the zoned distribution of s and i types granitoids cannot be explained through continental collision orogeny including syn to post collision but can be well interpreted by considering the progressive subduction of the northernmost branch of the paleo tethys as represented by the mian lue ocean thus the termination of the northernmost paleo tethys and the onset of the continental collision between the yangtze and the north china plates are considered to have occurred at about 200 ma during the transition from triassic to jurassic our model is also supported by the available data from other studies and provides a revised framework for the timing and tectonics of assembly of the yangtze and the north china cratons

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

molybdenite re os dating and la icp ms trace element study of sulfide minerals from the zijinshan high sulfidation epithermal cu au deposit fujian province china abstract the zijinshan cu au deposit located in fujian province is the largest high sulfidation epithermal hse deposit in southeastern china and is usually regarded as a major part of the porphyry cu system in the zijinshan ore field molybdenite samples collected from the cu mineralization zone yield a first weighted mean re os age of 111 31 0 70 ma which is explained as the time of dickite alunite alteration combining the newly reported muscovite 40ar 39ar and zircon u pb ages 113 ma the mineralization of zijinshan is likely to initiate before ca 110 ma this result is obviously older than the re os age of the adjacent luoboling porphyry cu mo deposit 105 ma pyrite chalcopyrite bornite digenite and covellite collected from the deep potassic middle phyllic and upper epithermal zones are used to conduct la icp ms trace element analysis the spatial zonings of mineralization and alteration and the regular variations of trace elements in sulfides at vertical direction imply a potentially complete transition from porphyry to epithermal mineralization and the deep origin of ore forming fluids mineralogical and trace element characteristics indicate that the chalcopyrite formed in both stages whereas bornite is the product of epithermal mineralization rather than a porphyry stage residue the majority of digenite and covellite has hypogene genesis pyrite and digenite in the epithermal zone are major carriers of primary au au in pyrite is te bi related and exists as solid solutions or different sized telluride and bi sulfosalt inclusions compared to as te and bi played more important roles to scavenge au and ag and achieve the primary au enrichment differently au in digenite is independently locked in digenite lattice bornite and digenite are good carriers of primary ag which mainly exists as solid solutions the high sulfidation state stage is the major period for concentrations of primary au and ag the upward increase of au in primary sulfides of hse cu zone implies that the distribution pattern of upper au enrichment and lower cu enrichment is not only caused by supergene process but is also controlled by hypogene trend based on the mineralization and alteration zonings the spatial variation of trace elements and the presented re os age the ore forming fluids of the zijinshan cu au deposit most likely originate from deep region rather than from the adjacent luoboling porphyry deposit the zijinshan and the luoboling deposits should belong to two independent hydrothermal systems

alteration of eocene lamprophyres in the zhenyuan orogenic gold deposit yunnan province china composition and evolution of ore fluids abstract the zhenyuan orogenic gold deposit 100 t au located in the northern part of the ailaoshan shear zone assz in south china is characterized by extensive alteration and mineralization in a variety of host rocks in the deposit abundant eocene lamprophyres have been infiltrated by ore fluids to produce carbonate veins with zones of disseminated fine grained gold bearing pyrite and arsenopyrite on both margins of the veins primary phlogopite k feldspar and magnetite have been altered to carbonate sericite and fuchsite carbonate minerals and sericite in altered lamprophyre have higher mg contents than in other host rocks reflecting the primitive geochemistry of the lamprophyres since carbonatization is the primary alteration type in the lamprophyres whose main primary components are low ca phlogopite and k feldspar the cao content of the lamprophyres reflects their degree of alteration as alteration increases incompatible element ratios remain essentially constant whereas sr is enriched with ca in addition au with co ni as ag sb and bi are enriched reflecting the addition of these metal elements during alteration of the lamprophyres altered lamprophyres have slightly lower 143nd 144nd t 0 51240 0 51253 and substantially higher 87sr 86sr t 0 70716 0 71234 than unaltered or weakly altered lamprophyres indicative of crustal contamination the auriferous ore forming fluids are thus interpreted to have migrated upwards and interacted with the sedimentary host rocks before altering the lamprophyres lamprophyres commonly show a close spatial and commonly temporal association with orogenic gold deposits worldwide at zhenyuan the lamprophyres shared a common deep source to the auriferous ore fluids but did not themselves contribute to this fluid or its gold content

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

triassic mineralization with cretaceous overprint in the dahu au mo deposit xiaoqinling gold province constraints from shrimp monazite u th pb geochronology abstract the xiaoqinling terrane in central china is the second largest gold producing area in china previous application of age constraints has yielded ages for the gold mineralization ranging from paleoproterozoic through triassic indosinian to jurassic and cretaceous yanshanian shrimp u th pb dating of hydrothermal monazite in a mo mineralized quartz vein from the dahu au mo deposit in the northern xiaoqinling terrane identifies two mineralization episodes hydrothermal monazite intergrown with molybdenite yields an initial precipitation age of 216 5 ma which is identical to but more precise than the molybdenite re os isochron age of 218 41 ma a younger generation of monazite is distinguished by data falling on a mixing array it is inferred that the younger monazite was formed at the expense of the older ones during the yanshanian probably during a single event that occurred at 125 ma combining these results with available geochronological data and geological evidence we conclude that molybdenum mineralization accompanied by monazite deposition took place in the indosinian followed by a yanshanian tectono hydrothermal event that resulted in large scale gold mineralization in the xiaoqinling terrane our observation demonstrates that monazite is sensitive to hydrothermal overprint and thus is useful for dating fluid infiltration event

the geology and mineralogy of the beiya skarn gold deposit in yunnan southwest china the beiya skarn gold deposit is located in the eastern tethyan orogenic belt in western yunnan province china it is one of the largest gold deposits in china with significant amounts of silver and base metals to the end of 2014 the estimated resources are 125 million tonnes mt of ore grading 2 42 g t au 0 48 wt cu 25 5 wt fe 38 85 g t ag 1 24 wt pb and 0 53 wt zn skarn alteration and mineralization are related to shoshonitic quartz monzonite porphyries that were emplaced in triassic carbonates beiya formation re os dating on molybdenite from a skarn orebody indicates an ore forming age of 36 82 0 48 ma which is consistent with previous dating results of the quartz monzonite porphyries at least two paragenetic stages of skarn minerals and associated sulfides were recognized with the early stage typified by garnet pyroxene magnetite and calcite and the late stage characterized by epidote amphibole chlorite quartz and calcite containing up to 70 sulfides pyrite chalcopyrite and minor pyrrhotite the early skarn is dominated by anhydrous minerals which were replaced by hydrous minerals formed during the late stage the garnet in the beiya deposit is andradite rich ad36 97gr3 61 and pyroxene is relatively diopside rich di8 91hd7 89 this mineral assemblage indicates an oxidized skarn system similar to other au cu fe bearing skarn deposits around the world fluid inclusions from pyroxene indicate precipitation from high temperature and high to moderate salinity fluids 420 530 c 11 1 43 3 wt nacl equiv which probably results from boiling of a moderately saline magmatic fluid cooler 180 365 c and moderate to low salinity fluids 1 6 16 5 wt nacl equiv were trapped in garnet and quartz and are interpreted to be responsible for gold deposition chlorite chemistry indicates ore forming temperatures between 300 and 340 c in agreement with fluid inclusion data it appears that gold was transported as chloride complexes under oxidized conditions and was deposited at temperatures of about 300 c when transport of chloride complexes as gold carriers was less efficient

relationship between orogenic gold mineralization and crustal shearing along ailaoshan red river belt southeastern tibetan plateau new constraint from paleomagnetism

geology and pyrite sulfur isotopes of the suoluogou gold deposit implication for crustal continuum model of orogenic gold deposit in northwestern margin of yangtze craton sw china abstract since the crustal continuum model was proposed mainly based on the variation of mineralization and alteration features of hypozonal mesozonal to epizonal deposits genetic relationship between the different types in one ore belt still requires research this issue was addressed by the research on the suoluogou mesozonal orogenic gold deposit and its comparison with the hypozonal orogenic gold deposit in northwestern margin of yangtze craton gold mineralization in suoluogou is controlled by the bends of roughly ew trending brittle fault developed in the late triassic strata and it is associated with quartz sericite chlorite carbonate and sulfide alteration pyrite and arsenopyrite are the predominant sulfide mineral with minor amounts of chalcopyrite sphalerite and galena four paragenetic stages are divided based on crosscutting relationship and mineral assemblage including the pre mineralization stage stage the hydrothermal quartz sulfide stage stage and carbonate quartz sulfide stage stage iii and the post mineralization carbonate pyrite stage stage the 34s values for pyrite in stage vary from 6 01 to 8 59 and those in stage iii are from 0 96 to 4 62 the decrease of 34s value from stage to iii is explained to the result of the isotope fractionation during separation of oxidised sulfur species in the brecciated space the sulfide 34s values in the initial gold mineralization stage of the suoluogou deposit are similar to those of regional hypozonal orogenic deposit with derivation from metasomatized mantle in the craton margin this similarity suggests that the mesozonal and hypozonal gold deposits formed in different depths of a crustal continuum model for the deposits sharing similar subcrustal source

multistage sedimentary and metamorphic origin of pyrite and gold in the giant sukhoi log deposit lena gold province russia gold mineralization at sukhoi log in eastern siberia is hosted in a deformed neoproterozoic organic bearing and pyritic black shale and siltstone sequence that is folded into a tight overturned anticline the deposit contains about 30 million ounces of gold at an average grade of 2 0 g t au and is one of the largest known undeveloped gold resources the high grade gold zone forms a gently dipping tabular body in the core of the anticline the best gold grades occur in narrow bedding parallel pyrite quartz veinlets that have been folded during the main deformation event lower grade gold is associated with disseminated pyrite developed in and around the high grade core of the deposit detailed paragenetic studies of the mineralization and host rocks have defined six stages of pyrite development in the carbonaceous sediments the two earliest forms of pyrite termed py1 and py2 are commonly developed in stratiform layers of micron sized crystals framboids and fine euhedra which are interpreted as synsedimentary to early diagenetic in origin coarser grained bedding parallel aggregates of inclusion rich pyrite termed py3 contain inclusions of arsenopyrite native gold and gold tellurides and are interpreted to form during late diagenesis and earliest deformation coarse euhedral pyrite py4 overgrows the earlier pyrite py1 py2 and py3 and the slaty cleavage developed in the host rocks indicating a syndeformation timing late stage inclusion free pyrite py5 overgrows and replaces earlier sulfides and is considered to be syn to late deformation laser ablation inductively coupled plasma mass spectrometry la icpms analyses of the various pyrite types indicate that the synsedimentary py1 contains the highest levels of invisible gold varying from 0 4 to 12 1 ppm with a mean of 3 22 ppm au and 1 900 ppm as py1 is also enriched in a suite of trace elements mo sb ni co se te ag cu pb zn mn ba cr u v which are similar to those concentrated by organic processes in euxinic sedimentary environments later generations of pyrite from py2 to py5 including pyrite in bedding parallel pyrite quartz veinlets contain progressively lower contents of invisible gold and most other trace elements however this metamorphic and postmetamorphic pyrite contains microinclusions of free gold arsenopyrite pyrrhotite sphalerite and chalcopyrite the paragenetic textural and chemical relationships at sukhoi log suggest that gold was clearly initially introduced prior to cleavage development accompanying sedimentation of the organic rich shales and fixed during diagenesis within the structure of diagenetic arsenian pyrite subsequently accompanying deformation gold was liberated from recrystallized diagenetic pyrite to become concentrated as free gold and gold tellurides within metamorphic pyrite and folded bedding parallel pyrite quartz veinlets two key processes are considered vital to the formation of the sukhoi log deposit original synsedimentary and early diagenetic concentration of gold dissolved within arsenian pyrite in organic rich black shales and metamorphic processes that liberated gold from the early forms of arsenian pyrite to be concentrated as free gold and gold tellurides within late diagenetic and metamorphic pyrite and associated pyrite quartz veinlets in the core of an overturned anticline these ore forming processes are unlikely to be unique to sukhoi log other black shale and turbidite hosted deposits that occur in rifted continental margin environments which have undergone collision and basin inversion may form by similar processes

la icp ms trace element analysis of pyrite from the chang an gold deposit sanjiang region china implication for ore forming process abstract the chang an gold deposit yunnan province is one of five large gold deposits in the ailaoshan gold belt that is the most important ore belt of the sanjiang tethyan metallogenic domain geochemical study of pyrite in the deposit was conducted using laser ablation inductively coupled plasma mass spectroscopy three types of hydrothermal pyrite were identified in the ores and wall rocks i e the coarse euhedral crystals in syenite py1 the coarse grains disseminated in altered sandstones or sandstone ores py2 and the fine grained euhedral pyrite in sandstone ores py3 their trace elements exhibit different concentrations associations and rim core zoning implying different geneses and crystallization processes the cores of py1 were formed by magmatic fluids and have the lowest concentrations of au as cu and zn the cores of py2 were formed by metamorphic fluids and have relatively high au ag ni pb and cu concentrations the py3 grains and the growth rims of py1 and py2 show consistently high contents of au as pb and co suggesting that all of them were rapidly deposited from a mixing fluid system that was probably composed of fluids of metamorphic and magmatic origins this interpretation is supported by the observation that the high grade ores generally contain lots of py2 and py3 hence we consider that the deposit was formed during india asia collision slightly postdate the 33 35 ma tectono magmatism

invisible gold distribution on pyrite and ore forming fluid process of the huangshan orogenic type gold deposit of zhejiang se china implications from mineralogy trace elements impurity and fluid inclusion studies the huangshan orogenic type gold deposit in zhejiang of se china occurred in quartz pyrite veins it is hosted by phyllonite that underwent greenschist facies metamorphism along a large jiangshan shaoxing tectonic belt with a ne sw direction trace elemental characteristics ore forming process and invisible gold on different forms of pyrite and quartz are studied the au associated pyrite can be classified into two categories recrystallized pyrite and euhedral pyrite the precipitation of invisible au on pyrite is mainly derived by co and ni with auhs2 complex in the mineralizing fluids in different events the xps results revealed that valence states of au3 replaced 2fe2 in the pyrite and au0 replaced si4 in the quartz structure the electron paramagnetic resonance and trace elemental results suggested that the element pairs of ge li al in quartz and mn co ni in pyrite have distinct impurities as identified a fluid inclusion study showed that the auriferous quartz is characterized by low saline and co2 rich fluids coexistence of the type i type iii inclusions and same range of homogenization temperature with different mode are evidences of immiscible fluid process the temperature pressure values of ca 250 c 1250 bar and ca 220 c 780 bar for gold precipitation have been calculated by intersection of coexisting fluids during the entrapment the huangshan orogenic type gold deposit may be associated with the wuyi yunkai orogeny during the early paleozoic including an upper mid greenschist facies metamorphism 450 420 ma all the features suggest that the huangshan gold deposit is probably a product linking with the early paleozoic orogeny in south china

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

constraints on depositional conditions and ore fluid source for orogenic gold districts in the west qinling orogen china implications from sulfide assemblages and their trace element geochemistry abstract yangshan mian lue ning and manaoke represent three large orogenic gold districts in the triassic west qinling orogen the third largest gold province in china 1100 t gold resource although their component gold deposits have similar geological characteristics representative deposits from these three gold districts have contrasting ore mineral assemblages and gold speciation suggestive of diversity in gold source and or ore forming depositional conditions or processes decrease in p t conditions of ore formation and metamorphic grades of host rocks in deposits from the mian lue ning through yangshan to manaoke districts is matched by variation in their mineral paragenesis from pyrite chalcopyrite sphalerite galena native gold through pyrite arsenopyrite stibnite to scheelite pyrite arsenopyrite stibnite realgar invisible gold in the deposits of the yangshan and manaoke gold districts contrasts with native gold in the mian lue ning gold district concentrations of ag as au bi cu pb sb tl in hydrothermal pyrite show a gradual systematic increase from mian lue ning through yangshan to manaoke pyrite in the huachanggou gold deposit from the mian lue ning district has high co and low as and au concentrations in contrast with pyrite which is zoned with respect to as and au in gold deposits from the other two districts these variations between gold deposits in the different districts could be due to variable local ore fluid sources derived from the different host rock sequences during metamorphic devolatilization as also allowed by mass balance calculations however previously unmetamorphosed voluminous source rocks that have experienced amphibolite facies metamorphism with liberation of gold and other metals during conversion of gold bearing pyrite into pyrrhotite are limited it appears more likely that an external deeply sourced fluid most logically from devolatilization of the pyrite bearing sediment wedge above the triassic subduction zone associated with the formation of the west qinling orogen was responsible for gold mineralization in this model variation between districts was due to fluid interactions with contrasting host rock sequences under contrasting p t conditions

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

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

gold telluride nanoparticles revealed in arsenic free pyrite pyrite the most abundant sulfide on earth and a common component of gold deposits can be a significant host for refractory gold this is the first documentation of pore attached composite au telluride nanoparticles in arsenic free pyrite trace elements mapping in pyrite from an intrusion hosted au deposit with orogenic overprint dongping china shows trails of tellurides overlapping co ni zonation intragranular microfracturing anomalous anisotropy and high porosity are all features consistent with devolatilization attributable to the orogenic event the pyrite hosted nanoparticles are likely the frozen solid expression of te rich au ag pb bearing vapors discharged at this stage nanoparticle formation as presented here provides the smallest scale tool to fingerprint au trapping during crustal metamorphism

mineralogy and textural relationships among sulphosalts and related minerals in the bleikvassli zn pb cu deposit nordland norway several distinct assemblages of pb sb pb as cu pb sb and cu fe zn sn sulphosalts are identified in sulphide samples from bleikvassli mine norway detailed optical microscopy and electron probe microanalysis have permitted investigation of textural relationships between minerals and compositional variations between different ore types tetrahedrite typically containing 10 16 wt ag rare freibergite containing 25 30 wt ag has also been identified in two samples stannite cu2 fe zn sns4 and meneghinite cupb13sb7s24 are widely distributed as trace constituents throughout massive pyritic and galena rich ores native antimony and pyrargyrite occur in trace amounts in all ore types as the breakdown products of earlier sulphosalts several distinct types of wall rock mineralisation are present at bleikvassli of considerable mineralogical interest are the coarse grained sulphide mobilisates within the wall rock which contain a distinct and characteristic suite of pb as sulphosalts tennantite jordanite pb14as6s23 seligmannite cupbass3 dufrenoysite pb2as2s5 bournonite cupbsbs3 is the only sb bearing sulphosalt recognised in significant amounts within the mobilisates meneghinite and tetrahedrite being conspicuously absent these mobilisates display considerable au enrichment electrum can be confirmed intimately associated with jordanite and tennantite appreciable sb up to 3 wt is contained within galena in the mobilisates in contrast to galena from massive ores which contains only negligible sb contents of ag and bi in galena vary considerably in all ore types but confirm earlier suggestions that galena is a major ag carrier at bleikvassli boulangerite pb5sb4s11 jamesonite fepb4sb6s14 and gudmundite fesbs occur in trace amounts sn sulphosalts are represented by kesterite cu2 zn fe sns4 but commonly zoned with respect to zn fe ratio in the mobilisates rather than by stannite a rare type of mobilisate also in the wall rock in which chalcocite and bornite are the main minerals contains native ag stromeyerite agcus mckinstryite ag cu 2 s ag free tetrahedrite an unnamed cu ag fe sulphide cu3ag2fes4 and native bi myrmekitically intergrown with chalcocite although a comprehensive genetic model for the wall rock mineralisation at bleikvassli is largely impossible given the limitations in the present state of knowledge regarding mechanisms involved in remobilisation processes a multi stage model of remobilisation during regional metamorphism is considered to best explain the observations an interplay of different solid and liquid state remobilisation mechanisms in various combinations is required to account for the macro and microscopic observations remobilisation probably began during the earlier stages of metamorphism with crystallisation and further remobilisation taking place during the entire metamorphic cycle giving rise to the extensive chemical and mineralogical diversity observed today preserved mineral assemblages and their textural relationships reflect a complex sequence of replacement and decomposition reactions taking place during the latest phase of late metamorphic crystallisation and subsequent cooling

metallogenic model of the jinchang au ni deposit in the ailaoshan belt sw china determined on the basis of pyrite trace element contents in situ sulfur isotope composition and pge geochemistry abstract the ailaoshan metallogenic belt in southwestern china contains numerous shear zone related au deposits with au reserves greater than 200 tonnes however the source of ore forming fluids and metals is controversial hampering the construction of genetic models in this study we selected the jinchang au ni deposit in the northern segment of the ailaoshan belt for detailed investigation of pyrite chemistry and in situ sulfur isotope compositions using laser ablation inductively coupled plasma mass spectrometry la icp ms the petrographic and pyrite chemistry analyses revealed four types of hydrothermal pyrite py1 pyrite is euhedral to subhedral and has in situ sulfur isotope 34s values of 5 30 to 6 26 median 2 93 and low concentrations of au ni as sb cu zn pb and ag py1 is interpreted to have formed during the early hydrothermal stage py2 pyrite is subhedral to anhedral and porous with variable size although py2 and py3 show different textural relationships we conclude that both of them formed during the intermediate hydrothermal stage as evidenced by similar sulfur isotope compositions and trace element contents and common intergrowth textures py2 and py3 pyrite have in situ 34s values ranging from 11 6 to 1 29 median 4 45 and relatively elevated concentrations of au ni as sb cu zn pb and ag in py2 and py3 pyrite ni concentrations correlate with co concentration whereas au exhibits moderate positive correlations with ni co and as indicating that au ni and other metals were predominantly sourced from the jinchang ultramafic rocks py4 pyrite is euhedral in shape and has relatively low in situ 34s values of 23 5 to 4 34 median 8 33 the metal concentrations in py4 pyrite are lower than those in py2 and py3 pyrite in general the metal concentrations in the different pyrite populations display systematic changes with low levels in py1 higher levels in py2 andpy3 and low levels again in py4 the average total platinum group element pge concentration of the jinchang ni bearing ultramafic rocks is 26 3 ppb similar to the average value of the primitive mantle of 22 0 ppb the au ni ores from the jinchang deposit have an average pd pt ratio of 5 98 similar to that of hydrothermal ni ores but higher than that of typical magmatic ni ores in contrast the jinchang ultramafic rocks have low pd pt ratios between 0 57 and 1 13 suggesting that the pges in the jinchang intrusion are of magmatic origin similarly the rh ir ratios of au ni ores are consistent with those of hydrothermal ni ores but differ from those of magmatic ni ores the pyrite chemistry in situ sulfur isotope compositions and pge geochemistry suggest that the ore forming fluids and metals associated with the jinchang au ni deposit were dominantly derived from the jinchang ultramafic intrusion mesozoic felsic magmatism or cenozoic regional strike slip activity may have triggered migration of the ore forming fluids leaching of metals from the jinchang intrusion and precipitation of these metals at the boundary between the intrusions and carbonaceous rocks

gold behavior in intermediate sulfidation epithermal systems a case study from the zhengguang gold deposit heilongjiang province ne china abstract the zhengguang gold deposit a typical intermediate sulfidation epithermal deposit is located in the southeastern part of the duobaoshan orefield west of the hegenshan heihe suture zone in the eastern part of the central asian orogenic belt the deposit comprises five ore zones with total au reserves exceeding 35 tonnes with potential additional resources at depth all vein type orebodies are hosted by paleozoic volcanic rocks and comprise multiple vein sets 1 100 cm in thickness although gold generally occurs in native form or as electrum in epithermal deposits like zhengguang both pyrite and sphalerite are known to accommodate modest concentrations of invisible gold this study employs a combination of petrography and sulfide chemistry to determine the role of invisible gold in the zhengguang ores and the mechanisms of gold incorporation into epithermal sulfides three sulfide stages are identified an early quartz pyrite py1a py1b chalcopyrite ccp1 stage a subsequent quartz sphalerite sph2a sph2b pyrite py2a py2b py2c py2d chalcopyrite ccp2a ccp2b galena calcite stage and a late stage containing deformed quartz pyrite py3a py3b sphalerite petrography and sulfide chemistry allow three groups of pyrite au poor au rich and a distinct sb rich group to be distinguished alongside three groups of chalcopyrite bi rich intermediate bi and bi poor and two groups of sphalerite au poor au rich a potential porphyry system is indicated beneath the epithermal system by the appearance of au poor pyrite and bi poor chalcopyrite after precipitation of early au poor sulfides inflow of relatively low temperature epithermal fluids led to alteration and replacement of early porphyry related sulfides and to precipitation of au rich pyrite bi rich and intermediate bi chalcopyrite and sphalerite gold rich pyrite contains up to 140 ppm au interpreted as both as lattice scale substitution au1 and as included particles of native gold au0 epithermal chalcopyrite is an important silver carrier but although au is measurable it is a not a good carrier for gold a strong positive correlation between au and cu in pyrite from the first two stages indicate that gold and other metals were likely sourced from magma derived hydrothermal fluids the deposit was formed in the early paleozoic but some gold ores appear deformed and partially destroyed by a later metamorphic event during which a distinct sb rich pyrite crystallized this study should catalyze exploration in the orefield as it provides further support for an as yet undiscovered porphyry system close to the zhengguang deposit

two episodes of sulfide mineralization at the yuhuang 1 hydrothermal field on the southwest indian ridge insight from zn isotopes abstract the newly discovered yuhuang 1 hydrothermal field yhf on the southwest indian ridge primarily contains two different sulfide distribution areas the southwest sulfide sws and the northeast sulfide nes distribution areas in this study zn isotope compositions and element ratios of zn fe cu and cd in the surface sulfides were analyzed to characterize zn isotopic fractionation ore forming conditions and mineralization processes of the yhf the results indicate that sulfide rich samples in the yhf exhibit intensive zn isotopic fractionation with 66zn values ranging from 0 43 to 1 24 these values are not only larger than those currently reported for seafloor sulfides but are also larger than the values reported for the deposits on land remarkably the obtained 66zn value 0 43 is the lowest one observed in seafloor sulfides 0 26 1 17 currently a study of zn isotope systematics revealed that zn isotope variations of sulfide rich samples in the yhf were controlled by the sphalerite and pyrite content the study also revealed that early minerals are rich in light zn isotopes but later minerals are rich in heavy zn isotopes a comparative study of previous data on zn isotopes shows that zn isotope fractionations in the yhf are likely attributed to rayleigh fractionation caused by mineral precipitation and multiple generations of pyrite further zn cd ratios of sulfide rich samples indicate that the ore forming temperature of the silicified sulfide rich samples in the sws probably formed under lower temperatures as compared with the silicified sulfide rich chimney in the nes furthermore sulfur and zn isotope compositions in the sws are significantly different from those in sulfide rich samples of the nes which suggests pervasively different metallogenic conditions further indicating that they are probably products of separate mineralization episodes

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

superimposed orogenesis and metallogenesis in sanjiang tethys the sanjiang tethyan area experienced the superpoimsed transition from tethyan tectonic evolution in late paleozoic to continental collision orogeny in cenozoic resulting in the accumulation of massive multi stage mineralizations and large amounts of metallic industrial ore deposits the complex metallogenic evolution of this area finds expression in the following aspects large amounts of complex superimposed and reworked ore deposits were developed on the proterozoic substrate of rigid continental segment with special metallic associations of sn cu sn pb zn and fe cu volcanics hosted massive sulfide deposits were developed throughout the evolution of tethyan lithosphere from continental margin rift cu through initial ocean basin cu zn ocean arc cu zn pb and interarcual rift valley or back arc basin pb zn ag to rift basin caused by arc continental collision cu pb zn island type porphyry copper deposits at the tethyan stage were replaced by continental type porphyry copper deposits at the collision orogeny stage metallic ore forming belt and gigantic ore deposits of world class such as the yulong porphyry cu mo metallogenic belt the lanping zn pb cu ag metallogenic belt the ailaoshan au metallogenic belt the chuanxi ree metallogenic belt the tengchong lianghe sn metallogenic belt were generated explosively during the collision orogeny in cenozoic although successful researches on tectonic and metallogenic cheracteristics have been conducted for the sanjiang tethyan metallogenic domain many important scientific problems remain unsolved such as precise time limits and internal connections between tectonic superposition continental accretion and convergence and collision and transformation the control of geological setting over mineralization the constraint of the crust mantle interaction on the formation of ore deposit clusters and the anomalous concentration of large amounts of ore materials space time structure material structure and genetic type of ore deposits of the typical metallogenic system the development mechanism of metallogenic systems and the formation mechanism of large sized ore deposits it is obvious that the solution of these problems will be a great breakthrough in the study of the tectonic evolution and metallogenesis of the sanjiang tethyan metallogenic domain

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

synchronizing holocene lacustrine and marine sediment records using paleomagnetic secular variation high sediment accumulation rates in lacustrine and shallow marine archives around iceland offer the potential to compare high resolution paleoclimatic reconstructions from terrestrial and marine archives however direct comparisons are hampered by difficulties in stratigraphic correlation and in deriving accurate age models for lacustrine archives icelandic paleomagnetic secular variation psv has the potential to synchronize these records here we compare holocene psv from a well dated marine core on the north iceland shelf with psv from two lacustrine archives with comparable sediment accumulation rates hvt03 1a a glacier dominated lake and hak03 1b in a nonglacial catchment geochemically characterized tephra layers combined with unique high amplitude structures in the psv records provide secure tie points every 200 yr once the records are synchronized the chronology from the marine core can be reliably transferred to the two lacustrine records the resultant lacustrine age models reveal large changes in sediment accumulation rate at submillennial scales that escape detection in conventional age models with independent dates every 1 k y sediment accumulation rate changes occur at similar times in both lakes despite very different catchment properties low and regular accumulation rates during the holocene thermal maximum suggest regionally stable vegetated catchments followed by a stepped landscape destabilization during the transition into neoglaciation culminating with maximum sedimentation rates during the little ice age psv allows synchronization between multiple records from nearby marine and lacustrine archives providing improved age models and a means of assessing leads and lags between marine and terrestrial environments

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

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

mantle contributions to crustal thickening during continental collision evidence from cenozoic igneous rocks in southern tibet the tibetan crust is twice as thick as average continental crust crustal compression and shortening as a result of indian asian collision isoftenconsideredtobetheprimarycauseforthecrustalthickening inthispaper weshowthatmagmaticcontributionisalsoimportant we come to this conclusion by documenting the paleogene linzizong volcanic succession lvs its coeval granitoid batholiths and the miocene adakitic rocks along the gangdese magmatic belt in southern tibet it has been widely accepted that the indian asian collision proceeded from a soft phase at 65 70 ma to a hard phase at 45 40 ma followed by continued post collisional convergence to the present in response to the collision and post collision convergence are a series of tectono magmatic events recorded in the gangdese magmaticbelt theseinclude 1 thesyn collisionallvsvolcanism 65 40ma andtheemplacementofsoutherngangdesebatholiths a peakageof 50ma 2 aperiod 40mato25ma thatismagmaticallyquiescent yettectonicallydominatedbyactivecompressionand crustal shortening and 3 the emplacements of post collisional adakitic rocks 25 12 ma potassic ultrapotassic volcanics 25 10 ma and peraluminous muscovite bearing granites between 24 and 18 ma these three major events contribute in different ways to the crustal thickness phase i formation of the lower juvenile crust from 65 ma to 50 ma with crustal thickening largely concentrated at 50 40maviainputofmantle derivedmagmas phaseii crustalthickeningbytectonicshorteningat 40 25ma andphaseiii retaining crustal thickness but thinning of the lithospheric mantle since 25 ma in response to crustal extension and upwelling and lateral flow of asthenosphericmantle weemphasizethatcollision inducedcrustalthickeningtookplacemainlyintheperiodof 50 40maand 25ma i e the period between the late stage of the lvs volcanism and the beginning of the adakitic rock emplacement most of the lvs rocks and the collision related granitoids in southern gangdese have end 0 attesting to the significance of mantle input most likely through remelting of mantle derived basaltic rocks including the subducted neo tethyan ocean crust the petrologic and geochemical characteristics of the miocene potassic adakitic rocks support the idea that the lower portion of the thickened tibetan crust is mafic and is genetically associated with the earlier lvs magmatism we estimate that the mantle material input contributed about 30 of the total thickness of the present day tibetan crust by assuming a pre collision crustal thickness of 35 km then the tectonic contribution would be about 20 km

genesis of the bangbu gold deposit in the southern tibet evidenced from in situ sulfur isotopes and trace element compositions of pyrite abstract the bangbu orogenic gold deposit in the north himalaya of the southern tibet contains more than 40 t au at an average grade of 7 0 g t in this deposits gold bearing quartz veins were controlled by nearly e trending qusong cuogu zhemulang shear zone and occurred within the secondary faults which crosscut late triassic greenschist facies rocks to further understand the sulfur source and ore forming process we have conducted a compressive study of in situ sims sulfur isotopes and la icp ms trace element compositions of two stages of pyrite at bangbu early stage pyrite py1 is coarse grained mostly 0 2 2 mm and euhedral and has gold concentrations of less than 0 3 54 ppm mean of 20 ppm and 34s values of 1 6 5 1 mean of 3 2 late stage pyrite py2 is generally fine grained mostly

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

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

zircon u pb and lu hf isotopic systematics of the daping plutonic rocks implications for the neoproterozoic tectonic evolution of the northeastern margin of the indochina block southwest china abstract the daping neoproterozoic plutonic rocks at the northeastern margin of indochina block in southwest china provide an ideal opportunity for studying the tectonic setting and relationship between the indochina and yangtze blocks la icp ms u pb dating on the zircon cores and rims of a hornblende gabbro yield 206pb 238u weighted means ages of 873 9 1 ma and 769 7 ma respectively and that for cores mantles and rims of a granodiorite yield 206pb 238u weighted means ages of 981 987 ma 829 10 ma and 761 11 ma respectively the zircon cores and mantles are interpreted as inherited from their source region the zircon rims are magmatic their ages represent the emplacement timing the zircon cores and rims from the hornblende gabbro have ehf t values ranging from 5 0 to 5 8 and 0 6 to 6 4 corresponding single stage model ages range from 1626 to 1662 ma and 1094 to 1311 ma respectively for the granodiorite the inherited mantles including cores show two groups 1 ehf t values of 3 3 to 12 3 with single stage hf model ages of 897 to 1235 ma and 2 ehf t values of 1 9 to 7 8 with single stage model ages of 1470 1667 ma the zircon rims are characterized by positive ehf t values 5 4 to 8 2 with single stage model ages ranging from 977 to 1108 ma whole rock geochemical data for the hornblende gabbro such as enrichment of lile and lree negative anomaly of nb and ta and high mg 52 1 65 4 suggest magma generation in a subduction related setting an island arc affinity is strongly supported by the features of high alumina basalt and abundant hornblende in a large hornblende gabbro sill the granodiorites are characterized by high sr contents and sr y ratios strong enrichment of lile and lree and negative anomaly of nb ta p and ti comparable with the features of subduction related plutonic rocks these data show that the hornblende gabbro was generated by the partial melting of a metasomatized mantle wedge peridotite with contribution from aqueous fluids derived from a subducted slab the granodiorite magma is a product of the mixing of mafic magma produced by partial melting of a slab fluid enriched metasomatized mantle wedge peridotite and felsic magma formed by the partial melting of crustal materials the emplacement ages and geochemical features of subduction related daping plutonic rocks are the same as those reported from the western margin of the yangtze block suggesting the presence of an oceanic crust in between with subduction to either side generating island arc magmatism in the neoproterozoic

trace elemental and sulfur lead isotopic variations in metamorphosed volcanogenic massive sulfide vms mineralization systems an example from the keketale pb zn ag deposit nw china abstract the effects of post vms volcanogenic massive sulfide deformation metamorphism on sulfide trace element and sulfur lead isotopic compositions remain unclear the greenschist to lower amphibolite facies metamorphosed keketale vms pb zn ag deposit located in the devonian maizi volcanic sedimentary basin in the chinese altay nw china provides an opportunity to resolve the abovementioned issue two mineralization stages are recognized at keketale including 1 primary banded massive and disseminated ores derived from sea floor hydrothermal mineralization and 2 ore remobilization as represented by intensively deformed ores and quartz polymetallic sulfide ore veins that crosscut the primary ores sulfide trace elements data suggest that stage ii pyrite and pyrrhotite have higher contents of cu zn ag sb and pb whereas contents of these elements are higher in stage i sphalerite and galena than their stage ii counterparts such elemental remobilization was probably caused by the rapid intragrain diffusion and subsequent fluid mediated liberation with trace elements re precipitated as particles within the same grain and nearby minerals respectively the 34scdt values in both stages show a trimodal distribution 25 9 to 22 7 17 0 to 10 6 and 0 6 to 2 1 sulfide mineral pairs formed during primary vms mineralization are not in sulfur isotopic equilibrium and only localized re equilibration occurs during deformation and metamorphism in addition the lead isotopic values of galena from remobilized sulfide veins overlap with those of the stage i galena and pyrite these data indicate that regional deformation and metamorphism of the keketale deposit can be approximated as a closed system in terms of sulfur lead isotopes whilst the presence of the anomalously low 34s values minimum 25 9 and the distinct lead isotopic ratios of sulfides from the calcite quartz veins argue for that in the late part of the metamorphic event some exotic lead and light sulfur were sourced from outside the ore field in situ 34s values of stage i sulfides vary widely 17 0 to 2 1 suggesting that the sulfur was originated from bacterial sulfate reduction bsr of marine sulfates with probably some magmatic input lead isotopes of the sulfides and mineralized meta sedimentary volcanic rocks display a linear distribution between the mantle and upper crust line in the 206pb 204pb vs 207pb 204pb diagram the lead source may be derived from both felsic volcanic rocks and mafic igneous rocks and or magmatic volatiles and the sulfur lead isotopes may result from a shallow level seawater circulating process an additional group of lead isotopic compositions of the meta volcanic rocks show elevated present day 206pb 204pb 207pb 204pb and 208pb 204pb values probably due to decay of th and u carried by deeply penetrative circulation 13 km of co2 f cl rich hydrothermal metamorphic fluids both syn vms shallow seawater and post vms deep metamorphic fluids circulation processes are critical for the metal concentration at keketale

geology c h o s pb isotope systematics and geochronology of the yindongpo gold deposit tongbai mountains central china implication for ore genesis abstract the yindongpo gold deposit is located in the weishancheng au ag dominated polymetallic ore belt in tongbai mountains central china the ore bodies are stratabound within carbonaceous quartz sericite schists of the neoproterozoic waitoushan group the ore forming process can be divided into three stages represented by early barren quartz veins middle polymetallic sulfide veinlets and late quartz carbonate stockworks with most ore minerals such as pyrite galena native gold and electrum being formed in the middle stage the average 18owater values changed from 9 7 in the early stage through 4 9 in the middle stage to 5 9 in the late stage with the d values ranging between 65 and 84 the 13cco2 values of ore fluids are between 3 7 and 6 7 with an average of 1 1 the h o c isotope systematics indicate that the ore fluids forming the yindongpo gold deposit were probably initially sourced from a process of metamorphic devolatilization and with time gradually mixed with meteoric water the 34s values range from 0 3 to 5 2 with peaks ranging from 1 to 4 fourteen sulfide samples yield 206pb 204pb values of 16 990 17 216 207pb 204pb of 15 419 15 612 and208pb 204pb of 38 251 38 861 both s and pb isotope ratios are similar to those of the main lithologies of the waitoushan group but differ from other lithologic units and granitic batholiths in the tongbai area which suggest that the ore metals and fluids originated from the waitoushan group the available k ar and 40ar 39ar ages indicate that the ore forming process mainly took place in the period of 176 140 ma during the transition from collisional compression to extension and after the closure of the oceanic seaway in the qinling orogen the yindongpo gold deposit is interpreted as a stratabound orogenic style gold system formed during the transition phase from collisional compression to extension the ore metals in the waitoushan group were extracted transported and then accumulated in the carbonaceous sericite schist layer the carbonaceous sericite schist layer especially at the junction of collapsed anticline axis and fault structures became the most favorable locus for the ore bodies

the origin and pre cenozoic evolution of the tibetan plateau different hypotheses have been proposed for the origin and pre cenozoic evolution of the tibetan plateau as a result of several collision events between a series of gondwana derived terranes e g qiangtang lhasa and india and asian continent since the early paleozoic this paper reviews and reevaluates these hypotheses in light of new data from tibet including 1 the distribution of major tectonic boundaries and suture zones 2 basement rocks and their sedimentary covers 3 magmatic suites and 4 detrital zircon constraints from paleozoic metasedimentary rocks the western qiangtang amdo and tethyan himalaya terranes have the indian gondwana origin whereas the lhasa terrane shows an australian gondwana affinity the cambrian magmatic record in the lhasa terrane resulted from the subduction of the proto tethyan ocean lithosphere beneath the australian gondwana the newly identified late devonian granitoids in the southern margin of the lhasa terrane may represent an extensional magmatic event associated with its rifting which ultimately resulted in the opening of the songdo tethyan ocean the lhasa northern australia collision at similar to 263 ma was likely responsible for the initiation of a southward dipping subduction of the bangong nujiang tethyan oceanic lithosphere the yarlung zangbo tethyan ocean opened as a back arc basin in the late triassic leading to the separation of the lhasa terrane from northern australia the subsequent northward subduction of the yarlung zangbo tethyan ocean lithosphere beneath the lhasa terrane may have been triggered by the qiangtang lhasa collision in the earliest cretaceous the mafic dike swarms ca 284 ma in the western qiangtang originated from the panjal plume activity that resulted in continental rifting and its separation from the northern indian continent the subsequent collision of the western qiangtang with the eastern qiangtang in the middle triassic was followed by slab breakoff that led to the exhumation of the qiangtang metamorphic rocks this collision may have caused the northward subduction initiation of the bangong nujiang ocean lithosphere beneath the western qiangtang collision related coeval igneous rocks occurring on both sides of the suture zone and the within plate basalt affinity of associated mafic lithologies suggest slab breakoff induced magmatism in a continent continent collision zone this zone may be the site of net continental crust growth as exemplified by the tibetan plateau c 2012 international association for gondwana research published by elsevier b v all rights reserved

ore genesis of the bake gold deposit southeastern guizhou province china constraints from mineralogy in situ trace element and sulfur isotope analysis of pyrite abstract the bake gold deposit is exceptional for its high native gold abundance relative to the other orogenic gold deposits in the southeastern guizhou district the grades of gold can be up to 2 to 3 wt in bonanza ore and native gold preferentially occurs within voids and fractures in pyrite arsenopyrite and quartz gold content can be up to 6 9 ppm in hydrothermal pyrite however the majority of the pyrite analyses have au contents less than 1 ppm mean 0 32 ppm based on la icpms analyses meanwhile empa reveals that arsenopyrite has a maximal au content of up to 0 14 wt but most analyses are below detection limit 0 01 wt moreover native gold grains in cataclastic pyrite and arsenopyrite are commonly high purity with fineness ranging from 949 to 977 given that paragenetically early hydrothermal pyrite and arsenopyrite contain variable but relatively high gold concentrations than later generations of sulfide it is suggested that early invisible gold may have been remobilized to form at least part of the microscopic visible gold post mineralization shear zones which cut the vein bearing anticline may have led to the deformation of the lode quartz vein system on the macro level and microscopically sulfide fragmentation and elemental remobilization although diagenetic pyrite from unaltered host rocks is enriched in invisible gold with mean values at 0 83 ppm evidence supporting the release of au from them is weak corresponding evidence comes from the distinct sulfur isotope signatures in different pyrite generations diagenetic pyrite has 34s values in the narrow range of 9 27 to 10 75 whereas hydrothermal pyrite shows a broad range 6 81 to 17 42 based on la mc icpms analyses the mesoproterozoic lengjiaxi group underlying the xiajiang group is most likely the source region on the basis of geological background and assuming the metamorphic devolatilization model

control of magmatic oxidation state in intracontinental porphyry mineralization a case from cu mo au deposits in the jinshajiang red river metallogenic belt sw china abstract the jinshajiang red river porphyry cu mo au metallogenic belt jrmb is the most important intracontinental porphyry cu mo au mineralizing zone in the sanjiang region southwest china the belt contains a number of giant deposits including yulong 6 50 mt cu and beiya 315 t au in the northern and center parts and several small deposits in the southern part e g tongchang 0 03 mt cu mo chang anchong 0 04 mt cu mo habo 0 57 mt cu mo and chang an 31 t au in order to investigate the mechanisms controlling the variation in size of these deposits the la icp ms zircon u pb dating bulk rock geochemistry and zircon trace element analyses have been performed on the mineralization related porphyries from the tongchang district zircon u pb dating yielded concordant ages of 34 2 0 6 ma tongchang 33 7 0 8 ma chang anchong 35 7 0 5 ma habo and 34 6 1 2 ma chang an these porphyries are peraluminous with relatively high potassium contents k 2 o 4 2 5 7 wt and show shoshonitic affinities bulk rock fe 2 o 3 feo ratios vary from 0 51 to 0 97 typical of moderately oxidized to strongly oxidized magmas zircon ce 4 ce 3 values vary between 25 9 and 371 8 with a mean of 129 3 the log o 2 values vary from 20 7 to 9 6 and plot within the range of fmq fayalite magnetite quartz oxygen buffer to mh magnetite hematite oxygen buffer indicating an oxidizing parental magma the mineralized porphyries from the yulong and beiya deposits which were previous considered to have formed under the same tectonic conditions as those in the tongchang district have higher mean zircon ce 4 ce 3 values of 249 4 and 399 5 suggesting that the oxygen fugacities of the porphyries in the tongchang district is relatively lower this might imply that oxygen fugacity is an important factor that led to the differentiation of deposit size in the jrmb and that larger porphyry deposits are associated with more oxidized magmas

in situ trace element and sulfur isotope of pyrite constrain ore genesis in the shapoling molybdenum deposit east qinling orogen china abstract the early cretaceous ca 128 ma shapoling vein type molybdenum mo mineralization associated with the huashan intrusion is a newly discovered deposit in the xiong ershan district east qinling china where pyrite is a ubiquitous mineral phase here we present results from an integrated study on the texture in situ trace element chemistry from laser ablation inductively coupled plasma mass spectrometry la icp ms and sulfur isotopic composition using secondary ion mass spectrometry sims with a view to understand the geochemical variation genesis of mo mineralization and ore forming process the distinct textural patterns as revealed by petrographic observations suggest three types of pyrites py1 is composed of coarse grained euhedral pyrite in the wall rock and early barren quartz vein at stage i py2 is represented by subhedral anhedral grains coexisting with molybdenite in quartz veins at stage ii and py3 forms irregular interstitial grains in the quartz k feldspar molybdenite dominated veins at stage iii the mo enrichment mainly occurred in py3 with co ni ratios 1 and 34s values mainly

sulfur isotope and trace element compositions of pyrite determined by nanosims and la icp ms new constraints on the genesis of the shuiyindong carlin like gold deposit in sw china the shuiyindong carlin like gold deposit the largest one of this type in china is located in the late paleozoic early mesozoic youjiang basin the pyrites in the studied ore bodies no i to v can be divided into four main types plus several sub types 1 as poor pyrites include py1 py1a and py1b py2 and py3 and 2 as rich pyrite py4 py4a and py4b in situ la icp ms analyses show that the as rich pyrite also contains higher au cu sb and tl than the other pyrite types in situ nanosims analyses show the 34s variation of py1 48 1 67 5 py2 2 4 7 6 py3 9 2 14 2 and py4 3 0 6 6 with the average values of 58 1 5 1 11 4 and 3 1 respectively the large 34s variations of as poor pyrites may reflect a sedimentary source however the narrow ranges of 34s values for the as rich pyrite py4 may not reflect a sedimentary but a magmatic or metamorphic origin a metamorphic sulfur source of py4 is favored due to paucity of coeval magmatism in the region and decreasing variations of 34s values from py1 to py4 integrated transmission electron microscope tem and nanosims element mapping show that the distribution and concentration of au are discordant with as and cu at the submicron scale also implied by the occurrence of some of au as nano submicron particles in py4 overall our new data indicate that the ore fluids were not only enriched in au but also in as cu and s taking an alternative of fluid oxidation probably resulting in the decreasing 34s values of py4 our result of i to v orebodies indicates the mixing between the underlying metamorphic fluid and meteoric water integrated variations in 34s and as au cu correlations across individual pyrite grains infer the physicochemical changes of aqueous and or aqueous carbonic fluids along migration paths