mineralogy and geochemistry of gold bearing arsenian pyrite from the shuiyindong carlin type gold deposit guizhou china implications for gold depositional processes arsenian pyrite in the shuiyindong carlin type gold deposit in guizhou china is the major host for gold with 300 to 4 000 ppm au and 0 65 to 14 1 wt as electron miroprobe data show a negative correlation of as and s in arsenian pyrite which is consistent with the substitution of as for s in the pyrite structure the relatively homogeneous distribution of gold in arsenian pyrite and a positive correlation of as and au with au as ratios below the solubility limit of gold in arsenian pyrite suggest that invisible gold is likely present as au1 in a structurally bound au complex in arsenian pyrite geochemical modeling using the laser ablation inductively coupled plasma mass spectrometry la icp ms analysis of fluid inclusions for the major ore forming stage shows that the dominant au species were au hs 2 77 and auhs aq 0 23 gold hydroxyl and gold chloride complexes were negligible the ore fluid was undersaturated with respect to native au with a saturation index of 3 8 the predominant as species was h3aso30 aq pyrite in the shuiyindong deposit shows chemical zonation with rims richer in as and au than cores reflecting the chemical evolution of the ore bearing fluids the early ore fluids had relatively high activities of as and au to deposit unzoned and zoned arsenian pyrite that host most gold in the deposit the ore fluids then became depleted in au and as and formed as poor pyrite overgrowth rims on gold bearing arsenian pyrite arsenopyrite overgrowth aggregates on arsenian pyrite indicate a late fluid with relatively high activity of as the lack of evidence of boiling and the low iron content of fluid inclusions in quartz suggest that iron in arsenian pyrite was most likely derived from dissolution of ferroan minerals in the host rocks with sulfidation of the dissolved iron by h2s rich ore fluids being the most important mechanism of gold deposition in the shuiyindong carlin type deposit

precious and base metal geochemistry and mineralogy of the grasvally norite pyroxenite anorthosite gnpa member northern bushveld complex south africa implications for a multistage emplacement the grasvally norite pyroxenite anorthosite gnpa member within the northern limb of the bushveld complex is a mineralized layered package of mafic cumulates developed to the south of the town of mokopane at a similar stratigraphic position to the platreef the concentration of platinum group elements pge in base metal sulfides bms has been determined by laser ablation inductively coupled plasma mass spectrometry these data coupled with whole rock pge concentrations and a detailed account of the platinum group mineralogy pgm provide an insight into the distribution of pge and chalcophile elements within the gnpa member during both primary magmatic and secondary hydrothermal alteration processes within the most unaltered sulfides containing pyrrhotite pentlandite and chalcopyrite only the majority of ipge rh and some pd occur in solid solution within pyrrhotite and pentlandite with an associated pt as and pd bi te dominated pgm assemblage these observations in conjunction with the presence of good correlations between all bulk pge and base metals throughout the gnpa member indicate the presence and subsequent fractionation of a single pge rich sulfide liquid which has not been significantly altered in places the primary sulfides have been replaced to varying degrees by a low temperature assemblage of pyrite millerite and chalcopyrite these sulfides are associated with a pgm assemblage characterized by the presence of pd antimonides and pd arsenides which are indicative of hydrothermal assemblages the presence of appreciable quantities of ipge pd and rh within pyrite and to a lesser extent millerite suggests these phases directly inherited pge contents from the pyrrhotite and pentlandite that they replaced the replacement of both the sulfides and pgm occurred in situ thus preserving the originally strong spatial association between pgm and bms but altering the mineralogy precious metal geochemistry indicates that fluid redistribution of pge is minimal with only pd au and cu being partially remobilized and decoupled from bms this is also indicated by the lower concentrations of pd evident in both pyrite and millerite compared with the pentlandite being replaced the observations that the gnpa member was mineralized prior to intrusion of the main zone and that there was no local footwall control over the development of sulfide mineralization are inconsistent with genetic models involving the in situ development of a sulfide liquid through either depletion of an overlying magma column or in situ contamination of crustal s we therefore believe that our observations are more compatible with a multistage emplacement model where preformed pge rich sulfides were emplaced into the gnpa member such a model explains the development and distribution of a single sulfide liquid throughout the entire 400 800 m thick succession it is therefore envisaged that the gnpa member formed in a similar manner to its nearest analogue the platreef notable differences however in pge tenors indicate that the ore forming process may have differed slightly within the staging chambers that supplied the platreef and gnpa member

a review of te and se systematics in hydrothermal pyrite from precious metal deposits insights into ore forming processes abstract pyrite is one of the most common minerals in many precious and base metal hydrothermal ore deposits and is an important host to a range of trace elements including au and co and the semi metals as se sb te and bi as such in many hydrothermal ore deposits where pyrite is the dominant sulphide phase it can represent a major repository for these elements furthermore the concentrations and ratios of au as and co in pyrite have been used to infer key ore forming processes however the mechanisms controlling the distribution of te and se in pyrite are less well understood here we compare the te and se contents of pyrite from a global dataset of carlin type orogenic au and porphyry epithermal deposits to investigate 1 the potential of pyrite to be a major repository for these elements and 2 whether te and se provide insights into key ore forming processes pyrite from carlin type low sulphidation and alkaline igneous rock hosted epithermal systems is enriched in te and se compared to pyrite from high sulphidation epithermal and porphyry cu deposits orogenic au pyrite is characterised by intermediate te and se contents there is an upper solubility limit for te as a function of as in pyrite similar to that established for au by reich et al 2005 and this can be used to identify te present as telluride inclusions which are common in some epithermal porphyry and orogenic au deposits physicochemical fluid parameters such as ph redox and temperature as well as crystal chemistry control the incorporation and concentration of se and te in pyrite neutral to alkaline fluids have the ability to effectively mobilise and transport te fluid boiling in porphyry epithermal systems as well as wall rock sulphidation and oxidation in carlin type and orogenic au deposits can effectively precipitate te in association with pyrite and au in contrast se concentrations in pyrite apparently vary systematically in response to changes in fluid temperature irrespective of ph and f o 2 hence we propose that the se contents of pyrite may be used as a new geo thermometer for hydrothermal ore deposits furthermore the comparison of bulk ore and pyrite chemistry indicates that pyrite represents the major host for te and se in carlin type and some epithermal systems and thus pyrite can be considered to be of economic interest as a potential source for these elements

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

trace element systematics of pyrite from submarine hydrothermal vents abstract submarine hydrothermal sulfide ores occur at mid ocean ridges intra oceanic arcs and in back arc basins associated with host rocks of highly variable composition pyrite is the dominant sulfide mineral in most samples presented within this study and thus the trace element composition of pyrite may reflect the different metal sources and precipitation processes here we report on a systematic study of minor and trace element contents in pyrite from active and inactive submarine hydrothermal vent fields at different plate tectonic settings including the indian and mid atlantic ridges the tonga kermadec intra oceanic arc the lau back arc and the central okinawa trough our results show that the trace element contents of pyrite from different locations vary significantly but for most elements without any systematic correlation to the concentration in the magmatic host rocks only as appears to be depleted in pyrite from ultramafic hosted vent systems that are affected by serpentinization these as depleted pyrites preferentially host au 0 micro or nano particles bismuth is enriched in pyrite from hydrothermal systems that contain a sedimentary component and micro inclusions of sphalerite are either due to fluid sediment interaction or phase separated fluid venting pyrites from individual locations have highly variable concentrations of elements like au co cu se mo ag and sb that are most likely related to fluid evolution and changes in fluid composition sub seafloor hydrothermal fluid seawater mixing influences the distribution of au co cu se and mo in pyrite elements like au ag sb and pb often have a characteristic affinity to as while cd correlates closely with zn a magmatic volatile contribution to the hine hina hydrothermal system may result in the precipitation of cu enriched pyrite our results show that the concentrations of most trace metals in pyrite are a function of the physicochemical parameters of the fluid phase rather than a reflection of the magmatic host rock composition

trace element systematics and ore forming processes in mafic vms deposits evidence from the troodos ophiolite cyprus abstract the volcanogenic massive sulfide vms deposits in the troodos ophiolite cyprus are ancient analogues for modern day seafloor massive sulfide mineralisation formed in a supra subduction zone environment in this study we present the first detailed in situ study of trace elements in sulfides from twenty vms deposits hosted in the troodos ophiolite to better understand factors that influence the distribution enrichment and incorporation of trace elements in different sulfide minerals on a mineral scale trace elements exhibit systematic variations between pyrite chalcopyrite and sphalerite pyrite preferentially incorporates as sb au and te whilst chalcopyrite is enriched in co and se sphalerite is trace element poor with the exception of ag and cd selenium averages 278 ppm n 150 in chalcopyrite but only 42 ppm n 1322 in pyrite bismuth and te in pyrite show a weak positive correlation r2 0 35 in some vms deposits possibly linked with the occurrence of bi telluride inclusions trace element concentrations also vary between colloform and euhedral pyrite with an enrichment of au as sb cu and zn in colloform compared to euhedral pyrite time resolved laser ablation profiles reveal that the trace element distribution on a mineral scale is not uniform and varies with crystallographic effects fluctuating physicochemical fluid conditions such as temperature ph fs2 fo2 and ligand availability during sulfide precipitation incorporation mechanisms in sulfides differ between elements in pyrite ag as se and pb are hosted in solid solution or as nanoscale inclusions whilst au sb and te may form micro scale inclusions on a regional scale 20 km the distribution of trace elements exhibits systematic variations between three major structural domains namely the solea mitsero and larnaca grabens the vms deposits of the magmatic tectonic solea graben are enriched in se co te au and cu relative to mitsero which is a purely extensional feature therefore we hypothesise that a variable magmatic volatile influx related to a magma volume b migration of the magmatic hydrothermal crack front and associated brine liberation or c a variation in protolith metal concentration are responsible for regional scale variations in vms geochemistry this is suggested to be intrinsically linked to the spreading architecture of troodos

fractionation of sulfur isotopes and selenium between coexisting sulfide minerals from the besshi deposit central shikoku japan fractionation of sulfur isotopes and selenium was measured between coexisting pyrite and chalcopyrite and between coexisting pyrrhotite and chalcopyrite from the besshi deposit of kieslager type central shikoku japan in all the pyrite chalcopyrite pairs studied 34s is enriched in pyrite relative to chalcopyrite while selenium is enriched conversely in chalcopyrite relative to pyrite the mean 34spy cp value is 0 53 0 36 per mil and the mean value of the distribution coefficient of selenium dcp py is 2 58 0 64 in all the pyrrhotite chalcopyrite pairs studied the two minerals are very close to each other both in sulfur isotope and se s ratios the mean 34spo cp value is 0 08 0 16 per mil and the mean dcp po value is 0 99 0 05 the results have been discussed in comparison with similar data obtained for the hitachi deposits of kieslager type japan yamamoto et al 1983

systematic variations of trace element and sulfur isotope compositions in pyrite with stratigraphic depth in the skouriotissa volcanic hosted massive sulfide deposit troodos ophiolite cyprus the troodos ophiolite represents one of the best preserved fossil analogs of modern oceanic crust and includes numerous volcanic hosted massive sulfide deposits the skouriotissa deposit can be separated into a stockwork ore zone and an overlying massive sulfide lens that is covered by metalliferous sediments representing the former sulfide seawater interface pyrite is the dominant sulfide mineral within these ores the trace element composition of pyrite varies systematically with stratigraphic depth down to 150 mbsf probably reflecting fluid temperature variations and effects of phase separation co ni se te bi and cu metal remobilization due to hydrothermal zone refining zn sb and pb and fluid seawater mixing at the seafloor mo represent further important processes controlling the pyrite chemistry massive sulfide hosted sphalerite and euhedral pyrite probably formed from hot fluids 400 c while the occurrence of colloform pyrite indicates lower precipitation temperatures 400 c similar 18o quartz fluid equilibration temperatures 400 c in the stockwork zone suggest that the skouriotissa fluids did not cool significantly during the final 150 m of fluid ascent to the seafloor the 34s composition of deep stockwork pyrite 1 4 suggests that an isotopically light magmatic volatile phase 0 was added to the hydrothermal system of skouriotissa during further fluid ascent about 38 of cretaceous seawater 34s 18 19 was added leading to the precipitation of stockwork pyrite with positive 34s values 6 1 in addition the chemical and textural similarities between skouriotissa and modern seafloor vent systems and massive sulfide deposits suggest that the skouriotissa hydrothermal system has a modern analog

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

pyrite zoning as a record of mineralization in the ventersdorp contact reef witwatersrand basin south africa the archean metasedimentary succession of the witwatersrand basin south africa hosts the largest au deposit in the world gold mineralization is mostly concentrated in conglomerate horizons or reefs and is tightly associated with pyrite trace element zoning of pyrite from the ventersdorp contact reef studied by x ray elemental as ni co and pb maps electron microprobe analysis and laser ablation inductively coupled plasma mass spectrometry indicates successive stages of pyrite formation each characterized by different textures and trace element composition as 2 2 wt ni 1 37 wt co 1 98 wt four generations have been distinguished generation 1 is detrital and includes compact nonporous porous and laminated pyrite generations 2 to 4 are postsedimentary authigenic generation 4 pyrite formed at near peak metamorphic conditions t 270 350 c chlorite geothermometry porous and concentrically laminated pyrite grains generation 1 are particularly enriched in au average 6 4 ppm maximum 70 ppm in addition to sb tl pb mn mo cu and ag in comparison with compact pyrite types of all generations in these grains au occurring as invisible gold and other trace elements might be finely dispersed with the phyllosilicates filling the pyrite pores trace element composition of porous and concentrically laminated pyrite is reminiscent of pyrite known to form in suboxic to anoxic environments black shales the presence of au in detrital pyrite indicates an early introduction of au in the ventersdorp contact reef gold is also present as secondary inclusions of electrum associated with the last pyrite generation generation 4 together with sphalerite chalcopyrite galena and pyrrhotite

sediment hosted gold deposits in guizhou china products of wall rock sulfidation by deep crustal fluids sediment hosted gold deposits in guizhou china are hosted in late paleozoic and early mesozoic sedimentary rocks along the southwest margin of the precambrian yangtze craton they have characteristics similar to carlin type gold deposits in nevada and are notably enriched in as sb hg and tl the shuiyindong and yata deposits consist of disseminated strata bound sulfides in permian bioclastic limestone and fault controlled mineralization in middle triassic calcareous clastic rocks respectively mineralization in both deposits consists of barren milky quartz veins disseminated gold bearing arsenian pyrite and arsenopyrite stibnite realgar and orpiment the barren milky quartz veins occur in the ore controlling structures with an envelope of gold mineralization in the host rock consisting of disseminated gold bearing arsenian pyrite and arsenopyrite and replacement style quartz veinlets later drusy quartz stibnite realgar and orpiment fill fractures and vugs on the periphery of gold mineralization petrography microthermometry laser raman spectroscopy and laser ablation inductively coupled plasma mass spectrometric la icp ms analyses of fluid inclusions are used to characterize the chemical evolution of ore fluids at shuiyindong and yata early barren milky quartz veins trapped aqueous fluid with moderate salinity 6 0 wt nacl equiv and minor co2 2 4 mol at a temperature of 230 30 c this fluid contains measurable b na k cs sr as sb and au 3 8 0 5 5 7 2 3 g g determined by la icp ms and is interpreted to approximate the mineralizing fluid responsible for precipitation of early barren quartz veins low salinity 0 9 2 3 wt nacl equiv co2 bearing 6 3 8 4 mol aqueous fluids are recorded in replacement style quartz veinlets they formed gold bearing arsenian pyrite and arsenopyrite and quartz veinlets at a temperature of 210 20 c and pressures of 450 to 1 150 bars corresponding to depths between 1 7 and 4 3 km under lithostatic conditions fluid inclusions in late stibnite orpiment realgar quartz veins contain high co2 58 64 mol and n2 19 2 23 7 mol with trace ch4 up to 1 6 mol the increasing content of co2 and decrease in the concentrations of au and as in aqueous carbonic inclusions are interpreted to result from carbonate dissolution at the level of the deposits during gold mineralization covariance of au as sb and sr concentrations in the fluids is interpreted to reflect deposition of as and sb sulfides and gold concurrent with carbonate crystallization iron is below detection limit 400 g g in all fluid inclusion types suggesting that the ore fluids were fe poor but possibly sulfur rich possibly explaining their exceptionally high gold contents iron in sulfide minerals was probably derived from dissolution of ferroan minerals in the host rocks sulfidized by h2s rich fluids to precipitate arsenian pyrite arsenopyrite and gold pressure fluctuation induced by faulting resulted in local fluid immiscibility and led to late deposition of realgar orpiment stibnite and calcite hydrogen and oxygen isotope compositions of ore fluids d h2o 35 to 68 18o h2o 4 16 5 indicate a metamorphic origin possibly related to crustal thickening and prograde metamorphism during the late yanshanian orogeny

decoupled geochemical behavior of as and cu in hydrothermal systems cu rich and as rich growth zones in pyrite provide new insights into the composition of late stage magmatic fluids and their host hydrothermal ore deposits the pyrite is from the pueblo viejo dominican republic and yanacocha peru high sulfidation gold silver deposits which are thought to form from hydrothermal systems that interacted with magmatic vapor plumes electron microprobe analysis secondary ion mass spectrometry and elemental maps show that pyrite the most common sulfide mineral in both deposits contains three different types of growth zones 1 as rich zones that are enriched in au ag sb te and pb 2 cu rich zones with significantly lower concentrations of these elements and 3 barren pyrite zones with no other elements these zones are interpreted to result from mixing between the pyrite forming fluid and vapors that invaded the main hydrothermal system episodically comparison to experimental studies of elemental partitioning and analyses of fumaroles and fluid inclusions from magmatic hydrothermal systems suggests that the as rich vapor formed at high and possibly magmatic temperatures whereas the cu rich vapor formed at lower temperatures possibly during migration of the original magmatic vapor the presence of finely spaced multiple growth zones in pyrite suggests that the composition of at least high sulfidation hydrothermal systems can be affected intermittently and repetitively by vapors probably from underlying magmas

la icpms and epma studies of pyrite arsenopyrite and loellingite from the bhukia jagpura gold prospect southern rajasthan india implications for ore genesis and gold remobilization abstract the bhukia jagpura gold prospect is hosted by a paleoproterozoic metasedimentary rock sequence that constitutes the lowermost part of the aravalli supergroup lying in close proximity to the basement cover contact a combined ore petrographic la icpms and epma studies of iron sulfides and sulfarsenides from the prospect has revealed four varieties of pyrite and two varieties of arsenopyrite with different trace element compositions the data indicates a sedimentary diagenetic origin for the earliest pyrites py i and ii which are devoid of any gold in contrast to hydrothermal py iii and iv with a minor but significant content of invisible gold 0 3 1 6 ppm associated loellingite 35 51 ppm and arsenopyrite aspy i 0 28 10 ppm contain the maximum concentration of invisible gold while it is substantially lower in aspy ii 0 06 1 5 ppm the compositions of the gold bearing pyrites low ni co ratios arsenopyrites and loellingite rich in co and the presence of au bi te mineral phases within arsenopyrite support a magmatic hydrothermal model for the origin of gold sulfide mineralization which appears to have taken place during the peak of regional metamorphism or at an earlier stage the different stages of deformation and metamorphism released and remobilized gold in invisible and discrete forms from the sulfarsenides during prograde metamorphism of aspy i gold was partially incorporated and relatively enriched within the structure of loellingite later during retrograde metamorphism gold was exsolved as visible grains at the interface of loellingite and aspy ii and or within loellingite

carlin type gold mineralization at saint andre de ristigouche gaspe peninsula quebec canadian appalachians the gaspe peninsula in the canadian appalachians hosts a variety of mineral occurrences that are spatially associated with the grand pabos and restigouche faults among these occurrences the saint andre de ristigouche gold sar au showing has peculiar features comparable with carlin type gold deposits at the regional district and prospect scales the most striking ones are 1 the calcareous nature of the host rocks 2 the au as sb hg metallic signature with absence of base metals and ag 3 the association with a crustal scale fault zone 4 the hydrothermal alteration characterized by silicification calcite and quartz veinlets at the margin of the au bearing zones and the occurrence of kaolinite in large halos of argillic alteration 5 numerous felsic dikes 6 the occurrence of au in as rich pyrite forming overgrowths on premineralization as free pyrite and in arsenopyrite 7 hydrothermal fluids equilibrated with host rocks at high temperature 200 which cooled to precipitate arsenopyrite and then mixed with evolved meteoric water to precipitate stibnite in veins although the sar au showing is relatively small analogies with carlin type mineralization encourage exploration in the gaspe peninsula and in similar settings elsewhere in the appalachians

selenium and tellurium resources in kisgruva proterozoic volcanogenic massive sulphide deposit norway abstract the former mining site at kisgruva near kongsberg norway is primarily composed of worked sulphide ore deposits of hydrothermal origin which occur within precambrian metamorphic basement though the original targets at the kisgruva mine site were extraction of copper cu sulphur s and iron fe the sulphide ore also contains exceptionally high concentrations of selenium se and tellurium te hosted within selenides clausthalite and minor naumannite and tellurides hessite and minor altaite and tellurobismuthite both se and te are also present within the sulphide ore in pyrite and chalcopyrite which contain exceptionally high concentrations of up to 688 ppm se and 81 ppm te additionally oxidative weathering of the exposed bedrock has resulted in the accumulation of hyper enriched unconsolidated weathered crust deposits at surface se up to 1590 ppm te up to 63 ppm containing selenite seo32 and tellurite teo32 ions concentrations of se and te are subsequently higher in the weathering products than in the sulphide ore due to fixation on to organic matter 0 4 in weathered ore crusts jarosite formed from oxidation of sulphides from the primary ore ferric oxide and hydroxide phases goethite and haematite increasing demand for se and te to use in green technologies has led to the reassessment of these orebodies and their associated weathered ore crust deposits though these elements are currently considered mining contaminants this and similar sites may be of future economic importance particularly as demand for se and te continues to rise

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

the ratio of tellurium and selenium in geological material as a possible paleo redox proxy abstract only few data for both tellurium and selenium in different geological materials including international reference materials have been available so far in this study the te se ratio has been investigated in more detail to provide a better understanding of the correlation of these two elements in the geological environment nine international reference materials irms and 79 different geological samples spanning a wide range of formation times and conditions from the paleoproterozoic to present were analyzed with quadrupole dynamic reaction cell drc icp ms these samples include basalts shales river and beach sediments loess dolomites a recent cold water coral precambrian manganese and iron formations and cenozoic marine ferromanganese nodules and crusts a wide range of concentrations between 0 01 and 1 5 g g for se and 0 01 and 90 g g for te was measured and the most interesting feature was found to be the te se ratio in the different geological matrices while most rock and sediment samples fall within the range of te se ratios typical of the average earth s crust a significant enrichment of te over se is evident for modern marine mn fe oxide precipitates with the most pronounced te enrichment found for hydrogenetic ferromanganese crusts which form under fully oxidizing conditions the apparent positive trend of the degree of te se fractionation with the redox potential of the formation environment suggests that the te se ratio may represent a potential paleo proxy for redox environments

visible gold in arsenian pyrite at the shuiyindong carlin type gold deposit guizhou china implications for the environment and processes of ore formation abstract carlin type gold deposits are best known for the scarcity of visible gold in their ores it has long been recognized that the majority of gold is invisible such that it cannot be resolved by conventional microscopy and resides in arsenian pyrite shuiyindong differs in that sub m to m sized native gold is present in arsenian pyrite veinlets and disseminations it is also the largest 55 tonnes and highest grade 7 to 18 ppm stratabound carlin type gold deposit in guizhou china and has produced 5 tonnes of gold from sulfide refractory ores extracted by underground mining methods in this study an electron microprobe analyzer empa was used to map the spatial distribution of invisible gold and sub m to m size visible gold particles in arsenian pyrite in high grade ore samples from the shuiyindong the samples studied are hosted in permian bioclastic ferroan limestone of the longtan formation and exhibit evidence of decarbonation silicification and sulfidation arsenian pyrite with detectable au 400 to 3800 ppm is disseminated in altered limestone and was deposited in two stages separated by an episode of corrosion in a veinlet the results show that there are two populations of native gold in arsenian pyrite one is comprised of sub m size gold particles 0 1 to 0 2 m that are occasionally present in the gold bearing arsenian pyrite disseminated in the host rocks this arsenian pyrite is interpreted to have been formed by sulfidation of ferroan calcite and dolomite another is comprised of coarser 1 to 6 m native gold grains present in the arsenian pyrite veinlet either on the first stage where it has been corroded or on the second stage the lack of fluid inclusion or other evidence of boiling and the low iron content of fluid inclusions in quartz suggest the veinlet formed by sulfidation of another fluid containing fe the fe bearing fluid may be a depleted ore fluid that gained fe by dissolution of ferroan limestone after h 2 s had been consumed the association of the largest visible gold grains with an episode of corrosion suggests that fluids episodically became undersaturated with arsenian pyrite while remaining saturated with gold e g ph decrease or an increase in the oxidation state this may have resulted from incursion of relatively acidic or oxidized fluids that were able to dissolve arsenian pyrite and remain saturated with gold in this case sulfidation of iron from the host rock was the most important depositional mechanism for au bearing arsenian pyrite with or without grains of native gold

distribution mineralogy and geochemistry of selenium in felsic volcanic hosted massive sulfide deposits of the finlayson lake district yukon territory canada three significant base metal deposits were recently discovered in the finlayson lake district yukon territory canada however widely varying selenium contents e g 1 100 ppm avg se at wolverine 200 ppm avg se at kudz ze kayah and 7 ppm avg se at gp4f have hindered their rapid exploitation observations and data from the deposits in the finlayson lake district show a strong positive correlation between high temperature 300 c copper rich sulfide assemblages at the base of volcanic hosted massive sulfide vhms and the selenium content of all sulfide minerals thermodynamic calculations for selenide and sulfide minerals indicate significantly higher temperatures of formation and lower solubilities of selenide versus sulfide minerals which is consistent with petrographic observations and can explain the distribution of selenium in zone refined vhms and volcanic sediment hosted massive sulfide deposits volumetric mass balance calculations indicate that some selenium could be sourced from contemporaneous volatile degassing of seo 4 its rapid reduction to h 2 se and subsequent entrainment into hydrothermal ore fluid however estimates for the kudz ze kayah and wolverine deposits suggest an additional large se reservoir volumetric mass balance estimates indicate that contemporaneous volcanic rocks and black shales are likely selenium reservoirs for the kudz ze kayah and wolverine deposits respectively

characterization of organic matter and its implications for pyrite hosted refractory gold mineralization along the south purulia shear zone eastern india abstract refractory gold bearing sulphide mineralization is spatially associated with the carbonaceous matter rich meta sedimentary rocks of the proterozoic south purulia shear zone spsz the carbon rich layers occurring as black continuous laminae are the metamorphosed derivatives of carbonaceous matter which were originally present in the sedimentary rocks and bear the characteristics of initial sedimentary environment of the refractory gold bearing formations of spsz the carbonaceous laminae aligned along the bedding foliation planes got remobilized into the sulfide bearing quartz carbonate veins during the metamorphic and deformational events the typical disordered bands as well as graphitic band in the raman spectra indicate that the carbonaceous matter is partially graphitized from the precursor carbon rich layers the light and homogeneous carbon isotopic values 13c 26 7 to 28 2 of the graphitized carbon suggests its origin due to the evolution from an organic precursor the 13c values fall within the range typical for organic carbon deposited during the paleo to meso proterozoic period the organic matter is considered to have played an essential role in buffering the oxygen fugacity of the initial sedimentary basin the dissolved sulfate ions in seawater were reduced resulting in sulfidation and adsorption of au in sedimentary pyrites to form refractory gold later during the deformational stages the hydrothermal fluids interacted with the graphitized matter which provided suitable redox conditions for the precipitation of auriferous sulfides such as pyrite pyrrhotite chalcopyrite and arsenopyrite within the quartz carbonate veins

native antimony in the baogutu gold deposit west junggar nw china its occurrence and origin abstract the baogutu gold deposit west junggar xinjiang nw china is composed of quartz sulfide veins and their stockworks and is hosted within an early carboniferous volcanic sedimentary sequence three ore forming paragenetic stages can be identified coarse grained quartz sulfide vein stage i gold bearing fine grained quartz sulfide vein stage ii and native antimony bearing calcite sulfide veinlets stage iii the estimated formation temperatures approximately 360 to 220 c f s 2 7 to 15 log units and f o 2 26 to 43 log units decrease from stage i through stage ii to stage iii the nature of the hydrothermal fluid changed from weakly acidic ph 5 to 6 at stage i to alkaline ph 7 at stage iii two different occurrences of native antimony could be identified one coexists with chalcopyrite and pyrrhotite whereas the other occurs as isolate grains within calcite veins native antimony up to 100 m in size contains minor amounts of as 2 0 to 2 7 wt empirical formula sb 0 95 0 96 as 0 03 0 04 decrease of temperature and f o 2 at high ph and low f s 2 conditions favored co precipitation of native antimony ullmannite assemblages and the decomposition of tetrahedrite native antimony crystallized later than the native gold suggesting fractionation between au and sb during the hydrothermal evolution of the deposit

lead isotope systematics and pyrite trace element geochemistry of two granitoid associated mesothermal gold deposits in the southeastern lachlan fold belt

trace element concentrations in porphyry copper deposits from metaliferi mountains romania a reconnaissance study there are fifteen miocene intrusions with porphyry copper mineralization in the metaliferi mountains romania most are associated with epithermal au ag te bi se ge vein systems the investigation of fifty samples from six deposits rosia poieni bucium tarni a colnic rovina valea morii and bolcana indicated bulk rock mean values of 0 16 0 88 ppm au 1000 ppm in bornite in the porphyry type mineralization galena forms microinclusions in pyrite chalcopyrite and bornite and contains up to 3750 ppm ag 17 380 ppm se 1570 ppm ge and 780 ppm te galena and pyrite from the epithermal mineralization in the m gura bolcana troi a system contain concentrations of ag and se ten times lower than in the same minerals from the porphyry copper mineralization the present data show that te is a significant trace element in the potassic zone of the investigated porphyry systems the data also shows that this does not correlate with the presence or absence of ophiolitic basement or with variation in the chemistry of the host intrusions tellurium enrichment in porphyry type deposits of the metaliferi mountains supports their genetic relationship with the spatially associated epithermal systems

nanoscale liquid inclusions of as fe s in arsenian pyrite a new mode of arsenic incorporation into arsenian pyrite has been discovered electron microprobe analyses and elemental maps of arsenian pyrite from pueblo viejo dominican republic show that its chemical composition varies from fe0 998as0 003 1 001s2 to fe0 963as0 050cu0 003ag0 001 1 017s2 and that arsenic is inversely correlated with fe high resolution transmission electron microscopy hrtem images show that some arsenic in this pyrite is present as nanoscale inclusions of amorphous as fe s in a matrix of arsenian pyrite the amorphous inclusions display negative facets with a cubic or rectangular morphology typical of negative inclusions of pyrite and arsenopyrite or marcarsite respectively and they are oriented parallel to the lattice fringes 100 of the arsenian pyrite matrix elemental maps collected by high angle annular dark field scanning transmission electron microscopy haadf stem show that the inclusions have a higher content of arsenic than the surrounding pyrite and tem edx analyses indicate approximate atomic proportions of 62 at s 28 at fe and 10 at as for the inclusions which are near the minimum melting temperature in the as fe s ternary these observations suggest that the inclusions were trapped as liquids during growth of the surrounding arsenian pyrite although not a new mineral this constitutes a third form for arsenian pyrite which has previously been shown to contain arsenic as either as1 or as3

a proposed new type of arsenian pyrite composition nanostructure and geological significance this report describes a new form of arsenian pyrite called as3 pyrite in which as substitutes for fe fe as s2 in contrast to the more common form of arsenian pyrite as1 pyrite in which as1 substitutes for s fe as s 2 as3 pyrite has been observed as colloformic overgrowths on as free pyrite in a hydrothermal gold deposit at yanacocha peru xps analyses of the as3 pyrite confirm that as is present largely as as3 empa analyses show that as3 pyrite incorporates up to 3 05 at of as and 0 53 at 0 1 at 0 27 at 0 22 at 0 08 at and 0 04 at of pb au cu zn ni and co respectively incorporation of as3 in the pyrite could be written like as3 y au 1 y 2 fe2 where au and vacancy help to maintain the excess charge hrtem observations reveal a sharp boundary between as free pyrite and the first overgrowth of as3 pyrite 20 40 nm thick and co linear lattice fringes indicating epitaxial growth of as3 pyrite on as free pyrite overgrowths of as3 pyrite onto as free pyrite can be divided into three groups on the basis of crystal size 8 20 nm 100 300 nm and 400 900 nm and the smaller the crystal size the higher the concentration of toxic arsenic and trace metals the yanacocha deposit in which as3 pyrite was found formed under relatively oxidizing conditions in which the dominant form of dissolved as in the stability field of pyrite is as3 in contrast reducing conditions are typical of most environments that host as1 pyrite as3 pyrite will likely be found in other oxidizing hydrothermal and diagenetic environments including high sulfidation epithermal deposits and shallow groundwater systems where probably kinetically controlled formation of nanoscale crystals such as observed here would be a major control on incorporation and release of as3 and toxic heavy metals in oxidizing natural systems

gold deposits of the northern margin of the north china craton multiple late paleozoic mesozoic mineralizing events the northern margin of the north china craton is well endowed with lode gold deposits hosting a resource of approximately 900 tonnes t of gold the 1 500 km long region is characterized by east trending blocks of metamorphosed archean and proterozoic strata that were episodically uplifted during variscan indosinian and yanshanian deformational and magmatic events at least 12 gold deposits from the daqinshan yan liao includes the zhangjiakou yanshan and chifeng gold districts and changbaishan gold provinces contain resources of 20 100 t au each most deposits are hosted in uplifted blocks of precambrian metamorphic rocks although felsic paleozoic and mesozoic plutons are typically proximal and host 30 of the deposits the lodes are characterized by sulfide poor quartz veins in brittle structures with low base metal values and high au ag ratios although phyllic alteration is most common intensive alkali feldspar metasomatism characterizes the wulashan dongping and zhongshangou deposits but is apparently coeval with variscan alkalic magmatism only at wulashan stepwise 40ar 39ar geochronology on 16 samples from gangue and alteration phases combined with unpublished shrimp u pb dates on associated granitoids suggest that gold mineralizing events occurred during variscan indosinian and yanshanian orogenies at circa 350 250 200 180 150 and 129 ma however widespread permo triassic 250 ma and early jurassic 180 ma thermal events caused variable resetting of most of the white mica and k feldspar argon spectra as well as previously reported k ar determinations compiled and new stable isotope and fluid inclusion data show that most 18o values for ore stage veins range from 8 to 14 indicating a fluid in equilibrium with the precambrian metamorphic basement rocks d values from fluid inclusions range widely from 64 to 154 which is indicative of a local meteoric component in some veins and highly variable 34s data 7 to 17 even within individual deposits indicate various local country rock sources for sulfur fluid inclusions from all districts show variable homogenization temperatures between 240 and 400 c and are consistently characterized by low salinity h2o co2 ch4 n2 solutions although the data are largely consistent with that from orogenic gold veins intrusion related veins and epithermal veins are also recognized the multiple episodes of mineralization are coincident with episodic tectonic reactivations and associated magmatism along the northern margin of the north china craton electronic supplementary material to this paper can be obtained by using the springer link server located at http dx doi org 10 1007 s00126 001 0239 2

detecting magmatic derived fluids using pyrite chemistry example of the chibougamau area abitibi subprovince quebec abstract magmatic fluids are an important carrier of precious and base metals in many mineralized systems porphyry deposits intrusion related gold systems irgs volcanogenic massive sulfides vms recognizing magmatic inputs is essential for understanding metallogenic processes and for developing accurate exploration models and the importance of fluids exsolved from magmas remains a source of much debate for some contexts such as irgs and orogenic gold deposits this study aims to identify magmatic fluids in the chibougamau area northeastern corner of the neoarchean abitibi subprovince canada using pyrite chemistry this is achieved by comparing the chemistry of pyrites recovered from the cu au magmatic hydrothermal porphyry systems of the chibougamau area to background compositions i e the chemistry of pyrites from weakly mineralized rocks from the same area analyses of quantitative laser ablation inductively coupled plasma mass spectrometry la icp ms are processed in three distinct manners to better evaluate the trace elements controlled by silicates oxides sulfides and sulfosalt inclusions and the trace elements that are structurally bound to pyrite detailed investigation of the trace element content of pyrite indicates that most elements are controlled by silicate inclusions some reflect the composition of the host rock others correlate with the mineralizing style and only te and bi are discriminant of the porphyry systems of the chibougamau area tellurium is structurally bound to pyrite or forms telluride nanoparticles in the study area while the distribution of bi is controlled by galena and chalcopyrite inclusions and pyrite chemistry is interpreted using absolute te values and bi ratios bi pb and bi cu this study provides insight into the cu au magmatic hydrothermal systems of the chibougamau area it also has implications for the way pyrite chemistry can be used to probe for magmatic fluids in other mineralized contexts

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

origin of high grade gold ore source of ore fluid components and genesis of the meikle and neighboring carlin type deposits northern carlin trend nevada the meikle mine exploits one of the world s highest grade carlin type gold deposits with reserves of ca 220 t gold at an average grade of 24 7 g t locally gold grades exceed 400 g t several geologic events converged at meikle to create these spectacular gold grades prior to mineralization a devonian hydrothermal system altered the bootstrap limestone to fe rich dolomite subsequently the rocks were brecciated by faulting and late jurassic intrusive activity the resulting permeability focused flow of late eocene carlin type ore fluids and allowed them to react with the fe rich dolomite fluid inclusion data and mineral assemblages indicate that these fluids were hot ca 220 c of moderate salinity 2 s rich gold rich pyrite formed by dissolution of dolomite and sulfidation of its contained fe where dissolution and replacement were complete ore stage pyrite and other insoluble minerals were all that remained locally these minerals accumulated as internal sediments in dissolution cavities to form ore with gold grades 400 g t petrographic observations geochemical data and stable isotope results from the meikle mine and other deposits at the goldstrike mine place important constraints on genetic models for meikle and other carlin type gold deposits on the northern carlin trend the ore fluids were meteoric water d 135 18 o 5 that interacted with sedimentary rocks at a water rock ratio of ca 1 and temperatures of ca 220 c the absence of significant silicification suggests that there was little cooling of the ore fluids during mineralization these two observations strongly suggest that ore fluids were not derived from deep sources but instead flowed parallel to isotherms the gold was transported by h 2 s 34 s 9 which was derived from paleozoic sedimentary rocks the presence of auriferous sedimentary exhalative mineralization in the local stratigraphic sequence raises the possibility that preexisting concentrations of gold contributed to the carlin type deposits taken together our observations suggest that meteoric water evolved to become an ore fluid by shallow circulation through previously gold and sulfur enriched rocks carlin type gold deposits formed where these fluids encountered permeable reactive fe rich rocks

bimodal distribution of gold in pyrite and arsenopyrite examples from the archean boorara and bardoc shear systems yilgarn craton western australia this study investigates the microstructures geochemistry and hydrothermal evolution of gold bearing pyrite and arsenopyrite from six orogenic gold deposits in the archean eastern goldfields province western australia scanning electron microscope sem electron microprobe emp and laser ablation inductively coupled plasma mass spectroscopy la icp ms analyses show that the gold bearing minerals possess a number of similar textural features including the occurrence of invisible gold within initial phases of growth and later stage visible gold associated with alteration rims the alteration rims are characterized by a higher than average atomic mass mainly owing to arsenic enrichment and are preferentially located along fractures and grain boundaries in the pyrite and arsenopyrite these observations suggest that visible gold formation is associated with hydrothermal alteration of preexisting pyrite and arsenopyrite textural observations and la icp ms data suggest that some invisible gold was remobilized from early formed pyrite and arsenopyrite to form visible gold during development of these alteration rims gold may also have been added by hydrothermal fluids during a later stage of mineralization in situ geochemistry and phase relationships of alteration rims are used to further constrain the hydrothermal process responsible for formation of alteration rims and visible gold in fractures based on sulfide stability relations our data indicate that development of arsenopyrite alteration rims associated with late stage visible gold formation was related to an increase in temperature maximum increase from 310 to 415 c and up to of sic orders of magnitude increase in sulfur fugacity whereas changes in oxygen fugacity were less important la icp ms analyses show that the relative and absolute variations in selected trace element au ag sb bi ba te pb co and mo concentrations can also be used to distinguish between unaltered and altered pyrite and arsenopyrite in general trace elements within pyrite and arsenopyrite have a relatively uniform distribution whereas later stage alteration rims have more variable trace element distributions although the observed textures are typical of prograde metamorphic coronae we suggest that they are the consequence of variations in fluid conditions and chemistry and that mineralization occurred in response to syn and or postpeak metamorphic fluid infiltration

mineralogy and sulfur isotope characteristics of metalliferous sediments from the tangyin hydrothermal field in the southern okinawa trough abstract we present and compare mineralogy and sulfur isotopic composition data of two surface metalliferous sediment samples tvg11 2 and rov11 r2 from the newly discovered tangyin hydrothermal field in the southern okinawa trough s ot and one surface metalliferous sediment sample 2 t4 from the iheya north knoll hydrothermal field in the middle okinawa trough m ot the purpose of this study is to better understand the hydrothermal ore forming environment and material source in the s ot samples tvg11 2 and rov11 r2 were derived from different types of chimneys sample tvg11 2 was derived from a black chimney which experienced formation process from high temperature to low temperature with large gradients and fluctuations rov11 r2 was directly derived from a low temperature white chimney or low temperature diffuse flow the sulfur isotopic compositions of sulfides and native sulfur in the s ot are significantly lower than the sulfur isotopic compositions of pyrite and native sulfur in the m ot indicating there is another source with a lower sulfur isotopic composition the low forming temperature and similar basement rocks of rhyolite in iheya north knoll and dacite in tangyin exclude phase separation and basement rock differences as the main reasons for low sulfur isotopic compositions in tvg11 2 and rov11 r2 the occurrence of different bacterial communities between s ot and m ot may affect the sulfur isotopic compositions but the influencing mechanism is still unclear the addition of magmatic h2s may be the most possible reason for lower sulfur isotopic compositions in the tangyin hydrothermal field

evolution of hydrothermal fluids in the ashanti gold belt ghana stable isotope geochemistry of carbonates graphite and quartz the oxygen and carbon isotope systematics of ankerite siderite calcite quartz and graphite from the bogosu and prestea mining districts of the ashanti gold belt ghana are used to speculate on the processes leading to hydrothermal alteration and gold deposition the geologic environment of this turbidite and graywacke hosted gold system was a sediment dominated accretionary complex the gold ores are localized within the ashanti structural belt which we suggest became a conduit for deep seated fluids during uplift and dilatancy ankerite and siderite in mineralized sedimentary rocks are broadly similar in oxygen and carbon isotope compositions to corresponding minerals in the metasedimentary country rocks evidence of alteration that preceded gold mineralization is best preserved in spatially associated altered mafic dikes the compositions of fluids responsible for the gold mineralization and associated alteration have been reconstructed using temperatures from carbonate mineral geothermometry alteration of country rocks occurred under rock dominant greenschist facies conditions the isotopic composition of the least altered mafic dikes was influenced by interaction with fluids generated from birimian greenschist facies metasedimentary rocks later extensive carbonate alteration of mafic dikes adjacent to the structural conduit occurred during slow upward migration of fluids lateral diffusion of hydrogen into the structural conduit permitted partial conversion of co 2 to methane resulting in 13 c enrichment of both the residual co 2 and the deposited carbonate minerals rapid even explosive expulsion of deep seated fluids and co 2 h 2 o phase separation occurred episodically throughout the evolution of the hydrothermal system this caused precipitation of sulfides arsenides and gold at relatively high crustal levels and low ambient pressure and temperature during mineralization fluid ascent was too rapid for isotopic and chemical reequilibration between the deep seated ore fluid and adjacent country rocks the ore fluid had chemical and isotopic compositions consistent with deep seated metamorphic fluids that were subsequently modified by preferential partitioning of 18 o and 13 c into a gas phase the composition of the deep seated metamorphic fluid determined using chemical equilibria co 2 h 2 o rich 7 25 mole co 2 is in approximate agreement with that required to produce the isotopic depletion of the residual fluid via phase separation

a carbonaceous sedimentary source rock model for carlin type and orogenic gold deposits this paper presents evidence and arguments that carbonaceous sedimentary rocks were a source for au and as in sediment hosted orogenic and carlin type gold deposits and develops a corresponding genetic model in this two stage basin scale model gold and arsenic are introduced early into black shale and turbidite basins during sedimentation and diagenesis stage 1 and concentrated to ore grades by later hydrothermal structural or magmatic processes stage 2 in reduced continental margin basin settings organic matter sedimented under anoxic to euxinic conditions immobilizes and concentrates gold arsenic and a range of trace elements particularly v ni se ag zn mo cu u present in marine bottom waters into fine grained black mudstone and siltstone of slope and basin facies during early diagenesis gold and certain other trace elements ni se te ag mo cu pge are preferentially partitioned into arsenian pyrite that grows in the muds these processes produce regionally extensive black shale and turbidite sequences enriched in syngenetic gold and arsenic commonly from 5 to 100 ppb au and 10 to 200 ppm as rare organic and sulfide rich metalliferous black shales may contain up to 1 to 2 ppm au and over 1 000 ppm as present as refractory gold in arsenian pyrite and nanoparticles of free gold during late diagenesis and early metamorphism stage 2 the diagenetic arsenian pyrite is recrystallized to form coarser grained pyrite generations and the organic matter is cooked to bitumen under higher grade metamorphism lower greenschist facies and above arsenian pyrite in carbonaceous shales is converted to pyrrhotite these processes release gold arsenic sulfur and other elements sb te cu zn mo bi tl and pb from the source rocks to become concentrated by hydrothermal processes locally to produce gold ores in structural sites such as fold hinge zones shear or breccia zones within or above the black shale sequence la icp ms analyses of diagenetic pyrite in carbonaceous sediments both associated and not associated with gold deposits suggests that invisible gold contents of greater than 250 ppb in diagenetic pyrite are indicative of carbonaceous shale source rocks with the potential to produce economic gold deposits application of this sedimentary source rock model enables a systematic exploration approach for sediment hosted gold deposits based on the distribution composition and structure of carbonaceous shale sequences and their contained diagenetic pyrite

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

major and trace element and multiple sulfur isotope composition of sulfides from the paleoproterozoic surda copper deposit singhbhum shear zone india implications for the mineralization processes abstract the present study combines major and trace element composition and sulfur s isotope data of pyrite and chalcopyrite from the surda copper sulfide deposit in the singhbhum shear zone the most important copper and uranium producing belt singhbhum cu u belt in india three textural and compositional types of both pyrite and chalcopyrite were distinguished unzoned to partially zoned pyrite ia with high co up to 54900 ppm and low ni content is earliest followed by oscillatory zoned pyrite ib with high as up to 25600 ppm and co up to 46800 ppm both occurring in pyrite i chalcopyrite i pyrrhotite magnetite apatite vein cobaltite type substitution fe1 xcox s1 xasx 2 is suggested for pyrite ib gold occurs in pyrite i as minor invisible gold and as electrum inclusions it also occurs along with cu mn ni hg ag pb sb zn ce y u and th in micro fractures that transgress the primary zoning pattern defined by as co and ni in pyrite ib the early inclusion rich chalcopyrite generation chalcopyrite i contains high concentration of zn and se and minor to trace amounts of co ni hg pb sb te and bi appeared in between pyrite i and ii low co high ni up to 37700 ppm content pyrite ii and inclusion free chalcopyrite ii enriched in co ni hg bi mn ag sb v and pb are cogenetic and occurring in pyrite ii pyrrhotite pentlandite chalcopyrite ii violarite vein low co and ni containing pyrite iii chalcopyrite iii occur mainly as disseminated grains the relative timing of formation of pyrite ii chalcopyrite ii with pyrite iii chalcopyrite iii remains uncertain pyrite chalcopyrite textures indicate that all pyrite chalcopyrite formed at some time prior to the end of deformation and metamorphism both in situ and mineral separates of all pyrite types and associated chalcopyrite yield a narrow range of positive 34s values between 3 8 and 6 9 suggesting sulfur being derived from a similar source consistent positive 34s values and other circumstantial evidence indicate that most sulfur was derived from seawater sulfate or modified seawater brine evaporite 33s values revealed mass dependent fractionation mdf signature it is proposed that incorporation of mdf sulfur of the mineralization event in paleoproterozoic singhbhum cu u belt took place after the great oxidation event the high se concentrations 260 400 ppm and se s ratios for both pyrite i and ii from surda deposit 4 4 5 7 10 4 suggest a low temperature of the cu rich ores 250 350 c and precipitation from a metalliferous fluid with a high se s ratio 10 4 to 10 3 consistent with igneous input of these elements

an extensive survey of dayside diffuse aurora based on optical observations at yellow river station by using 7 years optical auroral observations obtained at yellow river station magnetic latitude 76 24 n at ny alesund svalbard we performed the first extensive survey for the dayside diffuse auroras ddas and acquired observational results as follows 1 the ddas can be classified into two broad categories i e unstructured and structured ddas the unstructured ddas are mainly distributed in morning and afternoon but the structured ddas predominantly occurred around the magnetic local noon mln 2 the unstructured ddas observed in morning and afternoon present obviously different properties the afternoon ones are much stable and seldom show pulsating property 3 the ddas are more easily observed under geomagnetically quiet times 4 the structured ddas mainly show patchy stripy and irregular forms and are often pulsating and drifting the drifting directions are mostly westward with speed 5 km s but there are cases showing eastward or poleward drifting 5 the stripy ddas are exclusively observed near the mln and most importantly their alignments are confirmed to be consistent with the direction of ionospheric convection near the mln 6 a new auroral form called throat aurora is found to be developed from the stripy ddas based on the observational results and previous studies we proposed our explanations to the ddas we suggest that the unstructured ddas observed in the morning are extensions of the nightside diffuse aurora to the dayside but that observed in the afternoon are predominantly caused by proton precipitations the structured ddas occurred near the mln are caused by interactions of cold plasma structures which are supposed to be originated from the ionospheric outflows or plasmaspheric drainage plumes with hot electrons from the plasma sheet we suppose that the cold plasma structures for producing the patchy ddas are in lumpy and are more likely from the plasmaspheric drainage plumes the cold plasma structure for producing the stripy ddas should be in wedge like and is generated by conveying the cold plasmas from lower l shell toward higher l shell with magnetospheric convection and that for producing the irregular ddas is resulted from deforming the wedge like structure by disturbance the throat aurora is supposed to be projection of a newly opened flux of reconnection in addition we also found that structured ddas correspond to structured electron precipitations in the ionosphere which implies that the cold plasma structures in the magnetosphere are magnetically mapped to the ionosphere and act as a duct for producing the structured ddas we argue that we have presented some new observational results about dda in this paper which will be useful for fully understanding the ddas

uncloaking invisible gold use of nanosims to evaluate gold trace elements and sulfur isotopes in pyrite from carlin type gold deposits one hundred nm resolution secondary ionizing mass spectrometry nanosims was used to determine the distribution of au cu as sb and s and stable isotopes of s 34s 32s in gold bearing pyrite from two refractory carlin type gold deposits west banshee northern carlin trend and turquoise ridge getchell trend located in northern nevada nanosims maps reveal that gold occurs in two discrete episodes in each deposit elevated gold concentrations correlate with elevated concentrations of as sb cu te and lower 34s 32s ratios compared to periods when gold was not deposited precipitation of elevated gold and trace elements at west banshee was followed by precipitation of pyrite with lower gold concentrations whereas at turquoise ridge precipitation of trace element rich pyrite was followed by precipitation of late ore stage minerals these nanosims results are consistent with formation of the deposits by the episodic incursion of gold rich fluids into hydrothermal systems otherwise dominated by gold poor fluids such gold rich fluid pulses may be related to incursions of magmatic fluid which have been shown to have high concentrations of gold arsenic and copper in porphyry and high sulfidation epithermal systems

fluid inclusion and noble gas studies of the dongping gold deposit hebei province china a mantle connection for mineralization the dongping gold deposit 100 t au occurs about 200 km inboard of the northern margin of the north china craton the deposit is mainly hosted by syenite of a middle paleozoic alkalic intrusive complex that was emplaced into late archean basement rocks both groups of rocks are intruded by late jurassic to early cretaceous crustal melt granite dikes and stocks some within a few kilometers of the deposit the gold ores were deposited during this latter magmatic period at about 150 ma a time that was characterized by widespread regional north south compression that formed the east west trending yanshan deformational belt the ores include both the telluride mineral bearing low sulfide quartz veins and the highly k feldspar altered syenite with most of the resource concentrated in two orebodies 1 and 70 fluid inclusion microthermometry indicates heterogeneous trapping of low salinity e g 5 7 wt nacl equiv fluids that varied from a few to 60 mole percent nonaqueous volatile species laser raman spectroscopy confirms that the vapor phase in these inclusions is dominated by co2 but may be comprised of as much as 9 mole percent h2s and 20 mole percent n2 methane concentrations in the vapor phase are consistently 1 mole percent the variable phase ratios are consistent with fluid immiscibility during ore formation fluid inclusion trapping conditions are estimated to be 250 to 375 c and 0 6 to 1 0 kbar helium isotope studies of fluid inclusions in ore stage pyrites indicate 3he 4he ratios of 2 1 to 5 2 ra ra 1 4 10 6 for air for orebody 1 and 0 3 to 0 8 ra for orebody 70 the former data suggest that at least 26 to 65 percent mantle helium occurs in the fluids that deposited the veins in orebody 1 the lower values for orebody 70 which is characterized by a more disseminated style of gold mineralization are interpreted to reflect an increased interaction of ore fluids with surrounding crustal rocks which may have contributed additional 4he to the fluids a mantle source for at least some of the components of the gold forming fluid is consistent with upwelling of hot asthenosphere and erosion of as much as 100 to 150 km of cool archean lithosphere beneath the craton during this time the dongping deposit is located along the 100 km wide north south gravity lineament which marks the western border of the thinned crust as both regional metamorphism of mesoproterozoic and younger cover rocks and widespread granite magmatism also occurred at ca 150 ma it is unclear as to whether one or both of these also contributed fluid and or metals to the hydrothermal system importantly these new data suggest that economically significant gold deposits of similar mineral style and fluid composition which are scattered along the margins of the craton may all be products of a fluid originally partly sourced within the mantle

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

a fluid inclusion study of au bearing quartz vein systems in the central and north deborah deposits of the bendigo gold field central victoria australia the central and north deborah gold deposits with a production of about 7 tons au are located in one of 15 domes in the bendigo gold field central victoria australia an important mesothermal lode gold province the gold bearing quartz vein systems are hosted predominantly by reverse faults in lower ordovician turbidites which underwent lower greenschist facies metamorphism in the central and north deborah mines there are six stages of quartz veins that developed in the following sequence 1 laminated veins with a metal association of au as sb pb zn ni 2 spurs au 3 massive barren veins main dilation stage 4 brecciated veins with au as 5 quartz ankerite veinlets and 6 late pure quartz or calcite veinlets of the three mineralized vein stages 1 2 and 4 only the first one predated or was coeval with the main deformation event whereas stages 2 and 4 postdated the main deformation the vein structures indicate that vein development was controlled by repeated fluctuations of fluid pressure inducing hydraulic fracturing fluid inclusions in vein quartz contain c o h fluids of variable compositions three main types of fluid inclusions are recognized at room temperature type i two phase primary ch4 v h2o l fluid inclusions type ii two or three phase primary pseudosecondary co2 v or l ch4 v or l h2o l fluid inclusions including iia ch4 co2 h2o and iib co2 h2o fluid inclusions and type iii h2o v h2o l fluid inclusions type iii fluid inclusions are further divided into three groups iiia primary pseudosecondary vapor rich iiib primary pseudosecondary liquid rich and iiic secondary liquid rich data from fluid inclusion distribution microthermometry and raman spectroscopy indicate that fluids associated with au mineralized quartz veins stages 1 2 and 4 have moderate salinity ranging from 0 to 12 wt percent nacl equiv modeled salinities around 7 8 wt nacl equiv these veins formatted at temperatures from 325 to 375 c and pressures of 200 to 300 mpa with emplacement depths of about 8 to 12 km fluids associated with barren quartz veins stages 3 5 and 6 have a low salinity of about 0 to 3 wt percent nacl equiv modeled salinities about 2 3 wt nacl equiv and lower temperatures there is evidence of fluid immiscibility in all vein stages and mixing between fluids of the same souce but differing fo2 may also have influenced gold deposition cox et al 1995 hydrothermal ore forming fluids responsible for gold mineralization are in the ch2 co2 h2o nacl system whereas those of massive barren veins stage 3 and veinlets stages 5 and 6 are in the co2 h2o nacl and h2o nacl systems respectively the carbonic phases of type i and ii fluid inclusions range from pure ch4 through mixed ch4 and co2 to pure co2 gold ore forming fluids were weakly acidic with f o2 estimated to have been 10 25 to 10 37 bars and generally above the co2 ch4 and below the so2 h2s buffer boundaries throughout gold mineralization the relatively reduced mineralizing fluids are similar to those of other turbidite hosted lode gold deposits and counterparts in volcanic plutonic terranes

pyrite as a record of hydrothermal fluid evolution in a porphyry copper system a sims empa trace element study porphyry copper deposits are currently the world s largest source of copper and molybdenum and are also among the largest reservoirs of gold in the upper crust despite the fact that pyrite is a ubiquitous mineral phase in these deposits and secondary cu enrichment processes are commonly controlled by the abundance of this sulfide the major and trace element chemistry of pyrite from porphyry systems remains unconstrained in this study we report the first comprehensive trace element database of pyrite from the dexing deposit china s largest porphyry cu deposit by combining high spatial resolution and x ray mapping capabilities of electron microprobe analysis empa with low detection limits and depth profiling capabilities of secondary ion mass spectrometry sims in a suite of samples from the dexing deposit we show that the concentrations of precious metals e g au ag metalloids e g as sb se te and heavy metals e g cu co ni zn hg in pyrite from porphyry systems are more significant than previously thought among the elements analyzed cu as au and ni are the most abundant with concentrations that vary from sub ppm levels to a few wt i e 6 wt cu 3 wt as 0 25 wt au and 0 2 wt ni detailed wavelength dispersive spectrometry wds x ray maps and sims depth vs isotope concentration profiles reveal that pyrite from the dexing deposit is characterized by complex chemical zoning where the studied elements occur in different mineralogical forms while as occurs as a structurally bound element in pyrite cu and au can occur as both solid solution and micro to nano sized particles of chalcopyrite and native au or au tellurides respectively indicating that pyrite can control metal speciation and partitioning during porphyry cu mineralization the well developed oscillatory zoning detected in pyrite where cu rich as depleted growth zones alternate with cu depleted as rich layers indicates that cu is geochemically decoupled from as suggesting that this selective partitioning of metals into pyrite is most likely the result of changes in hydrothermal fluid composition

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

sulfur isotope and trace element systematics of zoned pyrite crystals from the el indio au cu ag deposit chile we present a comparative study between early massive pyrite preceding cu ag sulfosalt mineralization in high temperature feeder zones early pyrite and late pyrite that formed during silicic alteration associated with au deposition late pyrite at the el indio high sulfidation au ag cu deposit chile we use coupled in situ sulfur isotope and trace element analyses to chronologically assess geochemical variations across growth zones in these pyrite crystals early pyrite that formed in high temperature feeder zones shows intricate oscillatory zonation of cu with individual laminae containing up to 1 15 wt cu and trace co as bi ni zn se ag sb te au pb and bi late pyrite formed after cu ag sulfosalt mineralization it contains up to 1 14 wt as with trace cu zn pb v mn co ni ge se ag sb te pb and bi as well as colloform cu rich growth bands containing vugs toward the outer edges of some crystals plotting the trace element data in chronological order i e from core to rim revealed that co and ni were the only elements to consistently co vary across growth zones other trace elements were coupled in specific growth zones but did not consistently co vary across any individual crystal the 34s of early pyrite crystals in high temperature feeder zones range from 3 19 to 1 88 0 5 consistent with sublimation directly from a high temperature magmatic vapor phase late pyrite crystals are distinctly more enriched in 34s than early pyrite 34s 0 05 4 77 0 5 as a consequence of deposition from a liquid phase at lower temperatures it is unclear whether the late pyrite was deposited from a small volume of liquid condensate or a larger volume of hydrothermal fluid both types of pyrite exhibit intracrystalline 34s variation with a range of up to 3 31 recorded in an early pyrite crystal and up to 4 48 in a late pyrite crystal variations in 34spyrite at el indio did not correspond with changes in trace element geochemistry the lack of correlation between trace elements and 34s as well as the abundance of microscale mineral inclusions and vugs in el indio pyrite indicate that the trace element content of pyrite at el indio is largely controlled by nanoscale syn depositional mineral inclusions co and ni were the only elements partitioned within the crystal structure of pyrite cu rich oscillatory zones in early pyrite likely formed by nanoscale inclusions of cu rich sulfosalts or chalcopyrite evidence of deposition from a fluid cyclically saturated in ore metals this process may be restricted to polymetallic high sulfidation like deposits

the lepanto cu au deposit philippines a fossil hyperacidic volcanic lake complex abstract hyperacidic lakes and associated solfatara in active volcanoes are the expression of magmatic gas expansion from source to surface here we show for the first time that the vein system that comprises the 2 ma high sulfidation lepanto copper gold deposit in the mankayan district philippines was associated with a contemporary hyperacidic volcanic lake complex possibly the first such lake recognized in the geological record a 15 20 difference in sulfur isotopic composition between barite and sulfides and sulfosalts in the vent fumarole encrustations supports the interpretation that so 2 rich volcanic gas vented into the base of the lake and marginal to it and ties the mineralization directly to magmatic gas expansion fracture propagation and mineralization that occurred through a series of decompression steps within the feeder fracture network these data confirm that crater lake environments such as kawah ijen java indonesia provide modern day analogs of the lepanto and other high sulfidation cu au depositing environments we also provide extensive analysis of sulfosalt sulfide reactions during vein formation within the hyperacidic lake complex pyrite silica deposited first at high temperature followed by enargite that preserves the vapor solid diffusion of for example antimony tin and tellurium into the vapor from the crystallizing solid subsolidus intra crystalline diffusion continued as temperature declined pyrite and enargite are replaced by fe tennantite in the lodes which initially has low sb sb as atomic ratios around 13 5 close to the ideal tennantite formula but evolves to higher ratios as crystallization proceeds fumarole encrustation clasts and sulfosalts in the lake sediment are more highly evolved with a larger range of trace element substitutions including antimony substitution of especially zn te ag and sn into tennantite records metal and semi metal fractionation between the expanding magmatic gas and deposited sulfide sublimates provides a rare insight into the fate of metals and semi metals in the shallower parts of fracture arrays that feed modern hyperacidic lakes these data support a growing understanding of the formation of high sulfidation gold deposits as the consequence of single phase expansion of gas from magmatic gas reservoirs beneath the surface of active volcanoes without the intervention of a later aqueous fluid including groundwater aggressive sulfide sulfosalt reactions including pitting and the almost complete dissolution of earlier minerals are persistent characteristics of the vein assemblages and precious metals typically occur late in pits or along brittle fractures these characteristics support a hypothesis of mineral deposition at temperatures of the order of 600 c in contrast to available fluid inclusion data from enargite that record temperatures following phase transitions in the sulfosalt during the retrograde devolution of the deposit in the presence of groundwater

timing of gold and arsenic sulfide mineral deposition at the getchell carlin type gold deposit north central nevada pregold mineralization at the getchell carlin type gold deposit includes quartz and base metal vein mineralization associated with intrusion of a cretaceous granodiorite stock the veins contain minor pyrite and trace chalcopyrite arsenopyrite galena and sphalerite the pyrite is moderately coarse and in thin section has high relief is well polished and is fractured and locally cemented by the gold ore assemblage white micas are associated with veins near the granodiorite intrusion gold was not observed or detected by fire assay analyses of samples or electron microprobe analyses of pyrites microprobe analyses show that pregold pyrites have near stoichiometric compositions variable low arsenic is present in pyrite in samples overprinted by gold mineralization secondary ion mass spectrometry sims analyses detected trace gold in the coarse near stoichiometric pyrite in overprinted samples the pregold vein assemblage was fractured and cemented by gold ore stage mineralization the gold ore stage assemblage consists of gold and arsenic enriched pyrite and marcasite encompassed by jasperoid and drusy quartz and local late fluorite orpiment and galkhaite the consistent spatial association of jasperoid and ore pyrite reflects their near contemporaneous formation the ore pyrite occurs as either fine irregularly shaped grains or rims on earlier gold free pyrite in thin section the pyrite is visibly distinct and has a low polishing relief and a poor polish sims and electron microprobe analyses show that ore pyrites commonly contain 8 to 11 wt percent arsenic and as much as 2 400 ppm gold near the end of the ore stage fluorite orpiment and galkhaite precipitated locally in open space created by faulting or limestone dissolution late ore stage mineralization consists dominantly of open space filling realgar and calcite with minor quartz stibnite and framboidal pyrite realgar conforms to euhedral crystal faces of ore stage quartz fluorite and galkhaite calcite filled most remaining open space and conforms to euhedral crystal faces of quartz fluorite and realgar significant textural observations argue against an earlier interpretation that the gold mineralization and arsenic minerals formed as two discrete events separated by 40 m y in a few areas where calcite and realgar are in contact with ore stage quartz containing gold bearing pyrite realgar and calcite enclose gold bearing pyrite grains massive realgar and calcite distal from these contacts do not contain the gold bearing pyrite the presence of ore pyrite in realgar calcite and jasperoid requires close timing of these minerals and shows that there is no major time break separating ore stage and late ore stage mineral deposition textures indicate instead that the ore stage and late ore stage formed as part of a single evolving hydrothermal system the consistent successive overgrowth of younger minerals on perfectly preserved euhedral faces of older minerals supports the continuous evolution of the gold ore stage into the late ore stage these results are consistent with fluid inclusions that indicate that paragenetically successive minerals precipitated from an aqueous ore fluid with consistent salinity and gas contents but at declining temperatures results show that within error the 34 39 and 42 ma ages determined for fluorite and galkhaite at getchell and adularia at the nearby twin creeks mine respectively most closely approximate the timing of gold deposition at getchell

the coupled geochemistry of au and as in pyrite from hydrothermal ore deposits the ubiquity of au bearing arsenian pyrite in hydrothermal ore deposits suggests that the coupled geochemical behaviour of au and as in this sulfide occurs under a wide range of physico chemical conditions despite significant advances in the last 20years fundamental factors controlling au and as ratios in pyrite from ore deposits remain poorly known here we explore these constraints using new and previously published empa la icp ms sims and pixe analyses of as and au in pyrite from carlin type au epithermal au porphyry cu cu au and orogenic au deposits volcanogenic massive sulfide vhms witwatersrand au iron oxide copper gold iocg and coal deposits pyrite included in the data compilation formed under temperatures from 30 to 600 c and in a wide variety of geological environments the pyrite au as data form a wedge shaped zone in compositional space and the fact that most data points plot below the solid solubility limit defined by reich et al 2005 indicate that au1 is the dominant form of au in arsenian pyrite and that au bearing ore fluids that deposit this sulfide are mostly undersaturated with respect to native au the analytical data also show that the solid solubility limit of au in arsenian pyrite defined by an au as ratio of 0 02 is independent of the geochemical environment of pyrite formation and rather depends on the crystal chemical properties of pyrite and post depositional alteration compilation of au as concentrations and formation temperatures for pyrite indicates that au and as solubility in pyrite is retrograde au and as contents decrease as a function of increasing temperature from 200 to 500 c based on these results two major au as trends for au bearing arsenian pyrite from ore deposits are defined one trend is formed by pyrites from carlin type and orogenic au deposits where compositions are largely controlled by fluid rock interactions and or can be highly perturbed by changes in temperature and alteration by hydrothermal fluids the second trend consists of pyrites from porphyry cu and epithermal au deposits which are characterised by compositions that preserve the au as signature of mineralizing magmatic hydrothermal fluids confirming the role of this sulfide in controlling metal ratios in ore systems

evolution of the monte negro acid sulfate au ag deposit pueblo viejo dominican republic important factors in grade development this study was undertaken to determine the geologic factors that were important in making pueblo viejo which contains over 600 000 kg of gold in relatively high grade ore one of the few acid sulfate deposits to be mined economically on a large scale orebodies at pueblo viejo including monte negro the focus of this study are found around a maar diatreme complex that formed in the upper part of the lower cretaceous los ranchos formation ore is hosted by spilite spilite derived conglomerate and intramaar carbonaceous sandstone and mudstone regional seawater alteration of these rocks was overprinted by two stages of advanced argillic alteration both of which are associated with precious metals stage i produced deep alunite quartz pyrite and overlying kaolinite quartz pyrite assemblages and deposited gold in association with disseminated pyrite in wall rock stage ii which overprinted stage i produced deep pyrophyllite or diaspore and an overlying recrystallized silica cap pyrite or sphalerite or enargite veins that probably formed in response to hydrofracturing of the silica cap contain gold grades of as much as 100 ppm vein density and assay data show that approximately 60 percent of the gold at monte negro is in disseminated stage i ore with the remainder in stage ii veins phase equilibria and sulfur isotope thermometry show that stage i alteration took place below 260 degrees c at ph values between 2 and 3 stage ii pyrophyllite or diaspore formation occurred above 285 degrees c from a fluid with an initial ph of 1 to 1 5 while the silica caps formed below 220 degrees c geologic constraints indicate that stage i wall rock gold at monte negro was deposited by sulfidation of fe rich wall rock whereas stage ii vein hosted gold could have formed by cooling boiling or mixing with overlying ground water use of the programs solveq and chiller to evaluate the relative efficiencies of these ore forming processes confirms that sulfidation was capable of depositing disseminated stage i gold whereas stage ii vein gold was probably deposited by boiling related to pressure release during hydrofracturing and subsequent mixing with ground water these observations indicate that development of grade and tonnage at pueblo viejo was greatly facilitated by 1 the porous permeable maar diatreme complex which hosted large shallow hydrothermal cells and probably served as a conduit for rising magmatic gases 2 the presence of iron rich wall rock which caused early deposition of background disseminated gold by sulfidation and 3 later hydrothermal activity which formed impermeable silica caps that hydrofractured to create the high grade vein overprint remobilization of stage i background gold into stage ii veins might also have been an important factor in upgrading the deposits exploration for similar deposits should focus on areas of explosive volcanism in andesitic island arc terranes

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

pyrite physical and chemical textures pyrite may crystallize initially in forms as diverse as framboids or cubes depending upon the temperatures and pressures fluid rich diagenesis or low grade metamorphism clearly results in thorough recrystallization and the common formation of cubes once these have formed the pyrite becomes much more refractory and retains many characteristics even in deposits which have undergone penetrative deformation this is in strong contrast to the behavior of most of the accompanying sulfides which often undergo ductile deformation solid state or chemical remobilization and annealing pyrite deforms sparingly until there is brittle failure however there may be significant pyrite corrosion and regrowth during metamorphism as the result of sulfur exchange with other minerals especially pyrrhotite pyrite fabrics may also be significantly modified by pressure solution or coble creep optical microscopic examination and electron microprobe chemical mapping of pyrites from a variety of mineral deposits including several high grade metamorphic ones reveals that the pyrites frequently contain both physical and chemical textures that may be interpreted in terms of the depositional and the post depositional history of the deposits inclusions of sulfides or other minerals reveal information on the timing of the crystallization or recrystallization of the pyrite chemical mapping of elements such as ni co and as reveals information on the relative time of transport of these elements in the ore fluids

hydrothermal alteration and ore forming fluids associated with gold tellurium mineralization in the dongping gold deposit china abstract the dongping gold deposit hosted in syenites is one of the largest hydrothermal gold deposits in china and composed of ore veins in the upper parts and altered zones in the lower parts of the ore bodies pervasive potassic alteration and silicification overprint the wall rocks of the ore deposit the alteration minerals include orthoclase microcline perthite quartz sericite epidote calcite hematite and pyrite with the quartz pyrite and hematite assemblages closely associated with gold mineralization the phases of hydrothermal alteration include i potassic alteration ii potassic alteration silicification iii silicification epidotization hematitization iv silicification sericitization pyritization and v carbonation mass balance calculations in potassic altered and silicified rocks reveal the gain of k2o na2o sio2 hfses and transition elements tes and the loss of rees most major elements were affected by intense mineral reactions and the ree patterns of the ore are consistent with those of the syenites gold silver and tellurium show positive correlation and close association with silicification fluid inclusion homogenization temperatures in quartz veins range from 154 c to 382 c peak at 275 c 325 c with salinities of 4 9 wt nacl equiv at temperatures of 325 c the fluid is estimated to have ph 3 70 5 86 log fo2 32 4 to 28 1 with au and te transported as au hs 2 and te22 complexes the ore forming fluids evolved from high ph and fo2 at moderate temperatures into moderate low ph low fo2 and low temperature conditions the fineness of the precipitated native gold and the contents of the oxide minerals e g magnetite and hematite decreased followed by precipitation of au and ag bearing tellurides the hydrothermal system was derived from an alkaline magma and the deposit is defined as an alkaline rock hosted hydrothermal gold deposit

gold distribution and source of the j4 gold bearing breccia pipe in the qiyugou district north china craton constraints from ore mineralogy and in situ analysis of trace elements and s pb isotopes abstract the qiyugou district is one of the most important gold deposit distribution areas in the xiong ershan region north china craton these deposits are hosted in archean taihua supergroup rocks as gold bearing breccia pipes here we report a detailed in situ analysis of trace elements and s pb isotopes in sulfides from different ore stages in combination with electron probe microanalysis of ore minerals from the gold bearing j4 breccia pipe in the qiyugou district to unravel the gold distribution and their textural relationships to pyrite the metal sources and s pb isotopic composition variations during the ore forming processes the qiyugou breccia pipes hosted gold ore over 70 t au average grade of 2 5 g t that formed in four mineralization stages i e an early k feldspar biotite magnetite quartz pyrite py 1 stage i that can be further divided into two substages namely the ia k feldspar biotite magnetite stage and the ib quartz pyrite stage a gold pyrite py 2 quartz stage ii a gold quartz polymetallic sulfide py 3 stage iii and a late quartz carbonate stage iv the visible native gold and electrum grains occur as small inclusions and disseminations in the fractures within py 2 and py 3 tellurides and bi pb minerals are widespread in the stage ii stockworks and veins as is intergrowth with visible native gold and py 2 in situ la icp ms trace element analysis reveals the presence of invisible gold hosted in three types of pyrite with extremely low au content py 1 0 05 ppm py 2 0 03 ppm py 3 0 02 ppm concentrations of te bi and pb in pyrite are high and correlate well with au concentrations but as content is low therefore the te bi and pb played a significant role in gold mineralization in as deficient ore fluids in the j4 gold bearing breccia pipe from the qiyugou district high precision in situ laser ablation multiple collector inductively coupled mass spectrometry la mc icp ms lead isotope analyses indicate that the sulfides have 206pb 204pb 207pb 204pb and 208pb 204pb ratios from 17 250 to 17 629 from 15 401 to 15 621 and from 37 649 to 38 290 respectively which are similar to the granite porphyry in the district and indicative of their similar lead sources high precision in situ la mc icp ms sulfur isotope analyses of pyrite show a large 34s variation e g from 18 1 to 11 1 per mil for py 1 from 12 2 to 6 6 per mil for py 2 and from 4 9 to 1 6 per mil for py 3 with a remarkable increasing trend from stage i stage iito stage iii this trend may record a decreasing oxygen fugacity of the ore forming fluids during mineralization

direct analysis of ore precipitating fluids combined ir microscopy and la icp ms study of fluid inclusions in opaque ore minerals laser ablation inductively coupled plasma mass spectrometry la icp ms in combination with near infrared microscopy of fluid inclusions hosted by ore minerals that are opaque to visible light can provide the composition of ore precipitating fluids we applied the two techniques to well constrained fluid inclusion assemblages hosted by pyrite enargite and quartz to trace the source and evolution of the fluids in high sulfidation epithermal veins overprinting a porphyry copper deposit at rosia poieni romania despite some analytical limitations caused by the sulfide host minerals the data demonstrate that fluids trapped in apparently cogenetic quartz and ore minerals are chemically different systematic changes in major and trace element ratios between liquid vapor vapor rich and brine fluid inclusion assemblages in the three minerals record an evolving fluid source at the porphyry to epithermal transition regarding their cs na k ratios most of epithermal quartz hosted fluid inclusion assemblages form a well defined cluster which coincides with the narrow range of the porphyry stage fluids trapped in early quartz of the porphyry stockwork veins their cu na k ratios are 10 to 100 times lower compared to the pyrite hosted inclusions and correspond to the lowest cu na k ratios recorded for the porphyry stage fluids by contrast pyrite hosted vapor rich fluid inclusions have the highest cu na k similar to the highest cu na k ratios measured in the porphyry stage fluid inclusions the results led to the conclusion that the gangue and ore minerals in the high sulfidation epithermal veins at rosia poieni formed by successive pulses of chemically distinct hydrothermal fluids that were successively exsolved from residual melt batches of a progressively crystallizing magma at greater depth these results are consistent with detailed textural observations but petrography alone could not have led to this unambiguous conclusion

copper arsenic decoupling in an active geothermal system a link between pyrite and fluid composition abstract over the past few decades several studies have reported that pyrite hosts appreciable amounts of trace elements which commonly occur forming complex zoning patterns within a single mineral grain these chemical zonations in pyrite have been recognized in a variety of hydrothermal ore deposit types e g porphyry cu mo au epithermal au deposits iron oxide copper gold carlin type and archean lode au deposits among others showing in some cases marked oscillatory alternation of metals and metalloids in pyrite growth zones e g of cu rich as au ag depleted zones and as au ag rich cu depleted zones this decoupled geochemical behavior of cu and as has been interpreted as a result of chemical changes in ore forming fluids although direct evidence connecting fluctuations in hydrothermal fluid composition with metal partitioning into pyrite growth zones is still lacking in this study we report a comprehensive trace element database of pyrite from the tolhuaca geothermal system tgs in southern chile a young and active hydrothermal system where fewer pyrite growth rims and mineralization events are present and the reservoir fluid i e ore forming fluid is accessible we combined the high spatial resolution and x ray mapping capabilities of electron microprobe analysis empa with low detection limits and depth profiling capacity of secondary ion mass spectrometry sims in a suite of pyrite samples retrieved from a 1 km drill hole that crosses the argillic 20 450 m and propylitic 650 1000 m alteration zones of the geothermal system we show that the concentrations of precious metals e g au ag metalloids e g as sb se te and base and heavy metals e g cu co ni pb in pyrite at the tgs are significant among the elements analyzed as and cu are the most abundant with concentrations that vary from sub ppm levels to a few wt i e up to 5 wt as 1 5 wt cu detailed wavelength dispersive spectrometry wds x ray maps and sims depth vs isotope concentration profiles reveal that pyrites from the tgs are characterized by chemical zoning where the studied elements occur in different mineralogical forms arsenic and co occur as structurally bound elements in pyrite cu and au in pyrite can occur as both solid solution and submicron sized particles of chalcopyrite and native au or au tellurides respectively pyrites from the deeper propylitic zone do not show significant zonation and high cu co as concentrations correlate with each other in contrast well developed zonations were detected in pyrite from the shallow argillic alteration zone where cu co rich as depleted cores alternate with cu co depleted as rich rims these microanalytical data were contrasted with chemical data of fluid inclusions in quartz and calcite veins high cu as ratios and borehole fluid low cu as ratios reported at the tgs showing a clear correspondence between cu and as concentrations in pyrite forming fluids and chemical zonation in pyrite these observations provide direct evidence supporting the selective partitioning of metals into pyrite as a result of changes in ore forming fluid composition most likely due to separation of a single phase fluid into a low density vapor and a denser brine capable of fractionating cu and as