ore metal redistribution by hydrocarbon brine and hydrocarbon halide melt phases north range footwall of the sudbury igneous complex ontario canada we report methane dominant hydrocarbon fluid inclusions ch4 c2h6 c2h2 c3h8 coexisting with primary brine inclusions and secondary halide melt solid nacl inclusions in au pt rich quartz sulfide epidote alteration veins associated with the footwall style cu pge platinum group element au deposits at the fraser mine north range of the sudbury igneous complex evidence for coentrapment of immiscible hydrocarbon brine and hydrocarbon halide melt mixtures is demonstrated a primary ch4 brine assemblage was trapped during quartz growth at relatively low t min ttrapping 145 315 c and p max ptrapping 500 bar prior to the crystallization of sulfide minerals in the veins secondary inclusions contain solid halite and a mixture of ch4 c2h6 c2h2 and c3h8 and were trapped at a minimum t of 710 c the halite inclusions may represent halide melt that exsolved from crystallizing sulfide ores that texturally postdate by replacement early alteration quartz hosting the primary lower t brine ch4 assemblage laser ablation icp ms analyses show that the brine hydrocarbon and halide melt inclusions contain significant concentrations of cu 0 1 1 wt range au bi ag and pt all 0 1 10 ppm range cu pt and cu au ratios in the inclusions are significantly up to 4 log units lower than in the host alteration veins and adjacent massive sulfide ore veins suggesting either 1 early cu loss from the volatiles by chalcopyrite precipitation or 2 enhanced au and pt solubilities relative to cu at the temperatures of entrapment concentration ratios between coexisting brine and ch4 inclusions c rm elem rm brine c rm elem rm ch 4 are lower for cu au bi and ag than for other elements na ca fe mn zn pb indicating that during interaction with the brine the hydrocarbon phase was enriched in ore metals the high concentrations of ore metals in hydrocarbon brine and halide melt phases confirm that both aqueous and non aqueous volatiles were carriers of precious metals in the sudbury environment over a wide range of temperatures volatile evolution and magmatic sulfide differentiation were clearly part of a single continuous process in the sudbury footwall the exsolution of h2o poor volatiles from fractionated sulfide liquid may have been a principal mechanism controlling the final distribution of pge and au in the footwall ore systems the study reports the first measurements of precious metal concentrations in fluid inclusions from a magmatic ni cu pge environment the sudbury district

changes in sulfides and platinum group minerals with the degree of alteration in the roby twilight and high grade zones of the lac des iles complex ontario canada the lac des iles complex hosts pd deposits with unusually high pd pt and pd ir ratios these high ratios have been attributed to the introduction of pd by late magmatic hydrothermal fluids the presence of hydrous silicates and low temperature sulfide mineral assemblages has been advanced as evidence for fluid overprint this idea has been investigated by documenting the change in silicate sulfide and platinum group mineralogy and texture in samples from the deposit ranging from fresh gabbronorite to extensively altered chlorite actinolite schist in addition whole rock analysis combined with laser ablation analysis of the sulfides was used to determine which phase controlled each of the pge in fresh gabbronorite the sulfide assemblage is igneous pyrrhotite pentlandite chalcopyrite and pd is present mainly in pentlandite and kotulskite pdte inclusions associated with the sulfide minerals all other pge except pt are present in solid solution in pyrrhotite and pentlandite platinum is present as sperrylite ptas2 and montcheite ptte2 inclusions associated with the sulfide minerals these observations suggest that the pge in the fresh gabbronorite were all collected by magmatic sulfide liquid in the chlorite actinolite schist the sulfide assemblage is a low temperature assemblage consisting of chalcopyrite pyrite millerite a minor amount of palladium is present in millerite but most is present as bismuth rich kotulskite and pd arsenides both of which are associated with hydrous silicate all other pge except pt are hosted by pyrite a minor amount of pt is present in pyrite but most is found as sperrylite and montcheite associated with hydrous silicate minerals the pyrite could have formed by fe loss from pyrrhotite resulting in the pyrite inheriting os ir ru and rh and fe loss from pentlandite to form millerite resulting in the millerite inheriting some pd the pge concentrations of the whole rock show there is no direct correlation between the sulfide assemblage the degree of alteration of the silicate minerals and ore grade thus although fluids have clearly altered the sulfide silicate and platinum group mineralogy and their textures it is not clear that these fluids have changed the pge content of the rocks

chalcophile and platinum group element pge concentrations in the sulfide minerals from the mccreedy east deposit sudbury canada and the origin of pge in pyrite magmatic sulfide deposits consist of pyrrhotite pentlandite chalcopyrite pyrite and platinum group minerals pgm understanding the distribution of the chalcophile and platinum group element pge concentrations among the base metal sulfide phases and pgm is important both for the petrogenetic models of the ores and for the efficient extraction of the pge typically pyrrhotite and pentlandite host much of the pge except pt which forms pt minerals chalcopyrite does not host pge and the role of pyrite has not been closely investigated the ni cu pge ores from the south range of sudbury are unusual in that sulfarsenide pgm rather than pyrrhotite and pentlandite are the main carrier of pge probably as the result of arsenic contribution to the sulfide liquid by the as bearing metasedimentary footwall rocks in comparison the north range deposits of sudbury such as the mccreedy east deposit have as poor granites in the footwall and the ores commonly contain pyrite our results show that in the pyrrhotite rich ores of the mccreedy east deposit os ir ru rh ipge and re are concentrated in pyrrhotite pentlandite and surprisingly in pyrite this indicates that sulfarsenides which are not present in the ores were not important in concentrating pge in the north range of sudbury palladium is present in pentlandite and together with pt form pgm such as ptpd tebi 2 platinum is also found in pyrite two generations of pyrite are present one pyrite is primary and locally exsolved from monosulfide solid solution mss in small amounts 2 wt together with pyrrhotite and pentlandite this pyrite is unexpectedly enriched in ipge as pt and the concentrations of these elements are oscillatory zoned the other pyrite is secondary and formed by alteration of the mss cumulates by late magmatic hydrothermal fluids this pyrite is unzoned and has inherited the low concentrations of ipge and re from the pyrrhotite and pentlandite that it has replaced

quantitative mass balance of platinum group elements in the kelly lake ni cu pge deposit copper cliff offset sudbury a mineralogical mass balance has been calculated for the fraction of platinum group elements pge incorporated as solid solution in sulfides and sulfarsenides and the fraction that occurs as major constituents in platinum group minerals pgm in the kelly lake ni cu pge sulfide deposit in the copper cliff offset sudbury low levels of pge in sulfides were determined quantitatively for the first time in sudbury ores by laser ablation microprobe inductively coupled plasma mass spectrometry lam icp ms providing significantly more accurate data on the inventory and mineralogical distribution of the pge than in previous studies the majority of the pt 98 rh 97 and ir 86 91 and lesser but still large fractions of pd 77 87 and ru 67 71 occur as discrete pgm with the remainder occurring in decreasing abundance in solid solution in gersdorffite 1 700 ppm pge pentlandite 1 35 ppm chalcopyrite 0 5 ppm and pyrrhotite 0 3 ppm although the pge are present in low concentrations in sulfides the abundances of these phases can be high enough to constitute a significant fraction of the total pge in particular significant proportions of the pd 14 23 and ru 30 in the kelly lake samples are hosted by sulfides and sulfarsenides this has important implications for the genesis of the pge for the redistribution of the pge during cooling and hydrothermal alteration and for metal recovery during ore beneficiation

partition coefficients for ni cu pd pt rh and ir between monosulfide solid solution and sulfide liquid and the formation of compositionally zoned ni cu sulfide bodies by fractional crystallization of sulfide liquid many nickel copper sulfide orebodies contain cu and fe rich portions the fe rich ore is generally richer in os ir ru and rh and poorer in pt pd and au than the cu rich ore in komatiite hosted ores ni tends to be concentrated in the cu rich ore whereas in tholeiitic ores it tends to be concentrated in the fe rich ore the origin of this zonation could be due to crystal fractionation of fe rich monosulfide solid solution from a sulfide liquid the crystal fractionation would produce an fe rich cumulate enriched in os ir ru and rh and a fractionated liquid enriched in cu pt pd and au this model can be tested for zoned orebodies by applying experimentally determined partition coefficients for the metals into monosulfide solid solution we have compared our experimental results with those of other workers to show that the partition coefficients are strongly influenced by the sulfur content of the system there is a positive correlation between the partition coefficients and sulfur content of th

platinum group minerals in the limoeiro ni cu pge sulfide deposit brazil the effect of magmatic and upper amphibolite to granulite metamorphic processes on pgm formation the limoeiro ni cu platinum group elements pge deposit is a recent discovery associated with an igneous tubular conduit system in northeastern brazil representative ores from the deposit have been used for platinum group minerals pgm identification and for pge in base metal sulfides bms quantification ninety eighty percent of the pgm in the massive sulfide ores is homogeneous pt ni bi bearing merenskyite pdte2 enclosed primarily by pyrrhotite suggesting that it is formed by exsolution from monosulfide solid solution mss merenskyite gradually but systematically becomes poorer in pt and ni with increasing fractionation which is interpreted to reflect a transition to a more evolved sulfide liquid that segregated in the eastern parts of the intrusion in massive sulfide ores merenskyite forms unusually large up to 5000 m2 euhedral grains commonly in contact with spherical silicate inclusions bms hosts 12 16 of the pd with the remainder hosted by pgm which is interpreted to indicate that merenskyite recrystallized from a pge bearing bismuthotelluride metamorphic melt formed during high grade metamorphism sperrylite ptas2 is the second most abundant pgm 18 of pgm in disseminated ore and in contrast to merenskyite occurs mainly as very small median of 25 m2 inclusions in high temperature silicates and oxides interpreted to have crystallized at high temperatures directly from sulfide blebs that formed and were transported within the limoeiro magma conduit

emplacement of metabreccia along the whistle offset dike sudbury implications for post impact modification of the sudbury impact structure the whistle offset dike is a radial dike linked to the ca 1850 ma sudbury igneous complex sic in sudbury ontario it is linked through the funnel shaped whistle embayment which formed as a depression along the floor of a superheated impact melt sheet represented by the present day sic the dike consists of metabreccia quartz diorite and inclusion bearing quartz diorite emplaced in older archean gneisses and intrusions metabreccia has a fine grained igneous textured matrix surrounding archean basement clasts it overlaps in major element compositions mgo cao sio 2 with the two quartz diorites the three have similar chondrite normalized rare earth element patterns characterized by pronounced negative slopes i e la yb n 17 29 and a weak negative eu anomaly this suggests that they originated from the same source melts metabreccia has higher high field strength element hfse ratios i e gd yb ce yb zr y and lower model initial 207 pb 204 pb isotopic ratios than the two quartz diorites suggesting that it assimilated more archean rocks with higher hfse ratios and lower 207 pb 204 pb ratios it formed as sic melts mixed with melted basement rocks at the sic basement contact this produced a strongly contaminated inclusion bearing melt which drained downward into an offset structure or fault entrained more fragments plucked from the walls of the fault and crystallized as metabreccia less contaminated quartz diorite was then emplaced in the still viscous metabreccia during reactivation of the fault caused by isostatic readjustment of the gravitationally unstable crater more melting assimilation of clasts and mixing of sic melts at the sic basement contact produced inclusion bearing quartz dioritic melts that were emplaced last along the whistle offset fault

on the mechanisms for low sulfide high platinum group element and high sulfide low platinum group element mineralization in the eastern gabbro coldwell complex canada evidence from textural associations s se values and platinum group element concentrations of base metal sulfides

precious metals in magmatic fe ni cu sulfides from the potosi chromitite deposit eastern cuba abstract the moa baracoa ophiolite in eastern cuba is one of the few known ophiolites that display sulfide mineralization attributable to a magmatic origin in association with podiform chromite ores hosted in the mantle crust transition these sulfide ores chiefly consist of fe ni cu sulfides namely pyrrhotite pentlandite chalcopyrite and cubanite partly altered to valleriite the sulfide mineralization is located along the contact between the podiform like chromite ores and intruding pegmatitic gabroic dykes the detailed mineralogical study of the sulfide mineralization coupled with the first ever laser ablation icp ms analysis reveals that this sulfide mineralization show contents of the precious metals os ir ru pt re au ag and other semi metals co ni cu se te bi pb as sb comparable to those sulfides from the magmatic sulfide deposits associated with mafic complexes hosted in the continental crust the results obtained from this study confirm that fe ni cu sulfides at potosi are magmatic in origin and very likely derived from the solidification of droplets of sulfide melt segregated by immiscibility from the intruding mafic melts once they interacted with the pre existing chromitite at the mantle crust transition zone of the ophiolite the immiscibility of sulfide melt was achieved as a result of a progressive increase of fs2 very likely triggered by a set of circumstances including the progressive fractionation of the intruding mafic melt leading to increase of asio2 and accumulation of volatiles as well as the crystallization of oxides two main generations of pentlandite were observed one generation is primary in origin and it was locally exsolved along with pyrrhotite from monosulfide solid solution mss during low temperature cooling the second type of pentlandite resulted from the reaction of mss with coexisting droplets of cu and ni rich sulfide melt la icp ms analysis reveals that most precious metals ru os ir re au ag were concentrated along with the base metal sulfides bms although their distribution among the different bms pyrrhotite pentlandite chalcopyrite and cubanite does not strictly follow the expected distribution according to the known melt solid and solid solid partition coefficients unlike the other analyzed pges pt was not preferentially concentrated in bms but as discrete micrometer sized sperrylite grains the crystallization of sperrylite took place before and contemporaneous to sulfide segregation and pt as nanoparticles probably played an important role in the pt uptake as nucleation seeds for the formation of micron sized sperrylite grains these observations highlight the open system nature of the ore forming system as well as the important role of arsenic in concentrating pge in high temperature silicate and sulfide melts

a laser ablation inductively coupled plasma mass spectrometry study of the distribution of chalcophile elements among sulfide phases in sedimentary and magmatic rocks of the duluth complex minnesota usa abstract nickel copper sulfide deposits occur in the basal unit of the partridge river intrusion duluth complex minnesota usa many lines of evidence suggest that these sulfides are formed after assimilation of the proterozoic s rich black shales known as the bedded pyrrhotite unit in addition to s black shales are enriched in te as bi sb and sn tabs and the basaltic magma of the intrusion is contaminated by the partial melt of the black shales the tabs are chalcophile and together with the platinum group elements ni and cu partitioned into the magmatic sulfide liquid that segregated from the duluth magma the tabs are important for the formation of platinum group minerals pgm thus their role during crystallization of the base metal sulfide minerals could affect the distribution of the pge however the concentrations of tabs in magmatic ni cu pge deposits and their distribution among base metal sulfide minerals are poorly documented in order to investigate whether the base metal sulfide minerals host tabs in magmatic ni cu pge deposits a petrographic and laser ablation inductively coupled plasma mass spectrometry la icp ms study has been carried out on base metal sulfide and silicate phases of the partridge river intrusion duluth complex petrographic observations showed that the proportions of the base metal sulfide minerals vary with rock type the sulfide assemblage of the least metamorphosed bedded pyrrhotite unit from outside the contact metamorphic aureole consists of pyrite with minor pyrrhotite plus chalcopyrite 95 with small amount of chalcopyrite our la icp ms study shows that sulfides of the bedded pyrrhotite unit are rich in tabs consistent with these s rich black shales being the source of tabs that contaminated the mafic magma most of the tabs are associated with sulfides and platinum group minerals in the rocks of the bedded pyrrhotite unit from the contact aureole the bedded pyrrhotite unit xenoliths and the mafic rocks of the duluth complex in addition to these phases the laser maps show that silicate phases i e orthopyroxene and plagioclase contain sn and pb respectively in contrast in the least metamorphosed samples of the bedded pyrrhotite unit from outside the contact aureole although the pyrite contains some tabs mass balance calculations indicates that most the tabs are contained in other phases in these rocks galena hosts significant amounts of te bi sb sn and ag and few very small grains of sb rich phases were also observed the host phases for as were not established but possibly organic compounds may have contributed

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

platinum group element gold silver and base metal distribution in compositionally zoned sulfide droplets from the medvezky creek mine noril sk russia concentrations of ag au cd co re zn and platinum group elements pge have been determined in sulfide minerals from zoned sulfide droplets of the noril sk 1 medvezky creek mine the aims of the study were to establish whether these elements are located in the major sulfide minerals pentlandite pyrrhotite chalcopyrite and cubanite to establish whether the elements show a preference for a particular sulfide mineral and to investigate the model which suggests that the zonation in the droplets is caused by the crystal fractionation of monosulfide solid solution mss nickel cu ag re os ir ru rh and pd were found to be largely located in the major sulfide minerals in contrast less than 25 of the au cd pt and zn in the rock was found to be present in these sulfides osmium ir ru rh and re were found to be concentrated in pyrrhotite and pentlandite palladium and co was found to be concentrated in pentlandite silver cd and zn concentrations are highest in chalcopyrite and cubanite gold and platinum showed no preference for any of the major sulfide minerals the enrichment of os ir ru rh and re in pyrrhotite and pentlandite exsolution products of mss and the low levels of these elements in the cubanite and chalcopyrite exsolution products of intermediate solid solution iss support the mss crystal fractionation model because os ir ru rh and re are compatible with mss the enrichment of ag cd and zn in chalcopyrite and cubanite also supports the mss fractionation model these minerals are derived from the fractionated liquid and these elements are incompatible with mss and thus should be enriched in the fractionated liquid gold and pt do not partition into either iss or mss and become sufficiently enriched in the final fractionated liquid to crystallize among the iss and mss grains as tellurides bismithides and alloys during pentlandite exsolution pd appears to have diffused from the cu rich portion of the droplet into pentlandite

platinum palladium gold copper rich stringers at the strathcona mine sudbury their enrichment by fractionation of a sulfide liquid recent study of the platinum group elements pge in the strathcona ni cu sulfide deposit has shown that their distribution is zoned pt pd au and cu increase progressively from the hanging wall ore zone through the main zone into the deep ore zone rh ru ir and os show a reverse trend naldrett et al 1982 the copper and deep copper zones at strathcona are the farthest away from contact with the sudbury igneous complex and consist of veins of massive sulfides up to 6 m in width which narrow down to thin veins

the formation of pt ir alloys and cu pd rich sulfide melts by partial desulfurization of fe ni cu sulfides results of experiments and implications for natural systems abstract we propose a model of high temperature formation of platinum group element pge alloys from base metal sulfides subjected to decreasing sulfur fugacity f s 2 for this purpose we experimentally investigated the effect of partial desulfurization of monosulfide solid solution mss with variable ni and cu contents on the distribution behaviour of pt ir and pd at 1000 c we partially removed sulfur from the pge bearing mss using the tube in tube technique and pyrrhotite as an f s 2 buffer we found that mss undergoing s loss can produce 1 pt and ir exsolution from the mss matrix in the form of pge bearing alloys 2 partial melting of the cu ni bearing mss to form fe rich mss cu ni pd rich sulfide liquid and fe ir pt alloy both of these processes are geologically important the partial melting of the s depleted sulfides could explain the presence of two types of sulfides found in the mantle mss dominated sulfides and s poor sulfides consisting mainly of pentlandite and chalcopyrite we also suggest that the cu ni pd rich liquid formed by partial melting of the sulfides could migrate away from the mss and fe ir pt alloys thus spatially decoupling ir pt and cu pd as observed in reefs and mantle nodules in addition the formation of pge alloys in response to the desulfurization processes potentially could occur 1 after pressure falls during transport of the basalt magma with entrained sulfide droplets 2 after sulfur removal by s undersaturated melts or fluids from pge enriched sulfide proto ore 3 after degassing of the sulfide droplets occurring in a sub volcanic chamber and 4 as a result of sulfide interaction with chromite

applying a three dimensional velocity model waveform cross correlation and cluster analysis to locate southern california seismicity from 1981 to 2005 we compute high precision earthquake locations using southern california pick and waveform data from 1981 to 2005 our latest results are significantly improved compared to our previous catalog by the following 1 we locate events with respect to a new crustal p and s velocity model using three dimensional ray tracing 2 we examine six more years of waveform data and compute cross correlation results for many more pairs than our last analysis and 3 we compute locations within similar event clusters using a new method that applies a robust fitting method to obtain the best locations satisfying all the differential time constraints from the waveform cross correlation these results build on the relocated catalogs of hauksson and shearer 2005 and shearer et al 2005 and provide additional insight regarding the fine scale fault structure in southern california and the relationship between the san andreas fault saf and nearby seismicity in particular we present results for two regions in which the seismicity near the southern saf seems to align on dipping faults

shear zone controlled post magmatic ore formation in the huangshandong ni cu sulfide deposit nw china abstract the huangshandong ni cu sulfide deposit located in the kangguer jing erquan ductile shear zone belongs to the jueluotage island arc belt in eastern tianshan of the central asian orogenic belt the huangshandong mafic ultramafic pluton which has a fusiform shape is believed to have intruded strongly foliated late carboniferous volcanic rocks during the development of the regional ductile shear zone some orebodies in the deposit show intense ductile deformation among them the no 17 orebody is entirely controlled and hosted by the ductile shear zone host rocks and ores from this orebody show intense deformation and alteration and could be called ore mylonites furthermore numerous anastomosing veinlets can be observed in copper rich carbonate sulfide veins in the ductile shear zone geological field investigation and ore petrography studies indicate that sulfide ores at huangshandong are composed of three types undeformed magmatic ores deformed magmatic ores and hydrothermal overprinted ores magmatic ores with net fabrics remain unaltered and undeformed and sulfide minerals in them show only brittle fractures silicate and sulfide minerals in deformed magmatic ores are characterized by intense deformation fabrics examples for such fabrics are kink bands wavy extinction of uralite domino structure of phlogopite and elongated grains of pyrrhotite and pentlandite hydrothermal overprinted ores are characterized by strong deformation flattened grains and recrystallization of pyrrhotite moreover annealing of pyrrhotite is frequently observed pyrrhotite pentlandite and chalcopyrite in hydrothermal overprinted ores have high ni and co concentrations in pyrrhotite a higher ni concentration in pentlandite and high ag and cd concentrations respectively we attribute ni and co in fluid overprinted ores mainly to the alteration of olivine and the dissolution of primary chalcopyrite is the likely source of copper in chalcopyrite rich hydrothermal overprinted ores during the intruding and cooling of the huangshandong pluton intense regional ductile shearing caused the ductile deformation of sulfide ores in the deposit and subsequently ore mylonites were formed gangue minerals in the deformed orebodies were crushed to fine grained minerals and altered to serpentine chlorite and uralite during these processes fluid and ore elements were released and reacted with deformed rocks and ores forming anastomosing veinlets on hydrothermal overprinted ores

compositional variations within and between five sudbury ore deposits recent work on the platinum group element pge content in ni sulfide ores has shown that those associated with komatiite magmas generally have low pt pd ru ir os ratios 13 the levack west and little stobie 1 and 2 deposits conform with this generalization having ratios of 18 6 19 2 and 13 2 respectively hoffman et al 1979 pt and pd are present in roughly equal proportions in these deposits ranging between 1 000 and 3 000 ppm in massive sulfides new data from the strathcona deposit indicate values of close to 400 ppm for both pt and pd approximately one third of the levels at the nearby levack west deposit both strathcona and levack west are strongly zoned with respect to platinum group elements au and base metals cu ni zn pt pd and au increase away from the irruptive hanging wall into the footwall and co rh ru ir and os increase in the reverse direction at strathcona this zoning results in a decrease of the pt pd ru ir os ratio from 132 in the footwall to 2 2 in the hanging wall ore relevant phase equilibria data indicate that cu ni zn pt and pd are likely to become enriched in the residual liquid of a fractionating sulfide melt whereas co rh and ru will concentrate in the early crystallizing monosulfide solid solution the correspondence between the experimental data and natural observations is strong evidence that the zoning is the consequence of the fractionation of a sulfide melt with the residual liquid being expelled progressively into the footwall average data obtained for the falconbridge depost resemble those of the hanging wall at strathcona both in the low pt pd ru ir os ratio of 2 3 and in a low cu ni ratio suggesting that the ore sampled represents an early crystallizing fraction and that a late crystallizing pt rich fraction equivalent to the footwall ore at strathcona and amounting to perhaps twice the present volume of ore was not included in the sampling and may well not be within the present orebody the deposit is located largely within a vertical fault zone it is possible that the sulfide melt was introduced up the fault crystallizing as it moved upward and that the pt rich portion crystallized farthest up the fault and has been removed by erosion however sampling over a 1 600 m vertical interval of the ore zone has failed to reveal any progressive variation in the pt pd ru ir os ratio within the fault zone an alternative and preferred hypothesis is that the deposit was originally zoned as at strathcona with the pt rich portion forming away from the irruptive within the footwall this portion may have been faulted off leaving the early crystallizing portion behind to become remobilized into the fault zone if true the present location of the pt rich portion is intriguing in addition to having lower concentrations of platinum group elements than levack west the strathcona deposit also has lower concentrations of ni and cu these compositional differences can be modeled in terms of a larger amount of sulfide equilibrating with a given amount of the host silicate magma at the former deposit than at the latter sequences of similar magmatic events coupled with a proposed fractionation of olivine can account for many of the compositional variations between different sudbury deposits

relationship between microstructures and grain scale trace element distribution in komatiite hosted magmatic sulphide ores komatiite hosted nickel sulphides from the yilgarn craton australia consist of two main sulphide phases pyrrhotite fe7s8 and pentlandite fe ni 9s8 two minor sulphide phases chalcopyrite cufes2 and pyrite fes2 and trace arsenides samples of massive sulphides from three deposits with diverse deformation and metamorphic histories the silver swan perseverance and flying fox deposits have been studied by electron backscatter diffraction and laser ablation inductively coupled plasma mass spectrometry and nano scale secondary ion mass spectrometry these ore bodies were selected to investigate the relationship between microstructures and mineral trace element chemistry in three dominant sulphide species in each deposit in all three samples pyrrhotite preserves a strong evidence of crystal plasticity relative to both pentlandite and pyrite the trace element composition of pyrrhotite shows significant variation in specific elements pb bi and ag this variation correlates spatially with intragrain pyrrhotite microstructures such as low angle and twin boundaries minor signatures of crystal plasticity in pyrite and pentlandite occur in the form of rare low angle boundaries pentlandite and mild lattice misorientation pyrite trace element compositions of pentlandite and pyrite show no correlation with microstructures variations in pyrrhotite are interpreted as a result of intragrain diffusion during the syn and post deformation history of the deposit intragrain diffusion can occur either due to bulk diffusion dislocation impurity pair diffusion or by pipe diffusion i e along fast diffusion pathways at high and low angle and twin boundaries this contribution examines three different diffusion models and suggests that dislocation impurity pair diffusion and pipe diffusion are the most likely processes behind increased trace element concentration along the microstructures in pyrrhotite the same phenomenon is observed in samples from three different deposits that experienced widely different metamorphic conditions implying that the final disposition of these elements reflects a post peak metamorphic stage of the geological history of all three deposits

geochemistry and mineralogy of pd in the magnetitite layer within the upper gabbro of the mesoarchean nuasahi massif orissa india palladium concentrations of 1 3 ppm with an average pt pd ratio of 0 15 have been located for the first time in a magnetitite layer in the nuasahi massif in orissa india this layer occurs at a high stratigraphic level in the complex and is nearly 4 km long and 5 12 m thick the sections of the pd rich zone identified to date extend over a distance of 1 km at the southern end of the layer several phases of mineralization are evident the first primary assemblage of platinum group minerals pgm contains pd sulfides vysotskite pd pb alloys zvyagintsevite and a pd in alloy a mineral probably new to mineralogy these pgm are confined to central magnetite grains in the magnetitites the magnetite grains with exsolved fine laths of ilmenite at centers are referred to as central magnetite grains these central magnetite grains are commonly surrounded by blebs of ilmenite and magnetite that contain the majority of the pgm these are dominated by pd antimonides variably altered to pd oxides and other pgm including ptas2 sperrylite rus2 laurite and irrhass irarsite hollingwothite many of these pgm also occur in the interstitial silicates with rare occurrences in the central magnetite grains we propose that the platinum group elements pge crystallized during a minor sulfide saturation event that occurred as the magnetitites crystallized this event produced the minor cu sulfides in these magnetitites later introduction of antimony and arsenic during the alteration event that produced the blebby ilmenite and magnetite led to the more primary pgm being succeeded by the main pgm assemblage dominated by pd antimonides these are associated with secondary cu minerals and sperrylite subsequent oxidation during weathering in the hot wet indian climate produced the pd oxides the nuasahi massif is a sill like archean layered ultramafic mafic intrusion genetically linked to high mg siliceous basalt or boninites and is characterized by unusually thick layers of chromitite pge are concentrated in these chromitites and in the base metal sulfide bearing breccias in the overlying gabbro the pd in the magnetitites described here indicates the presence of a third level where pge are concentrated and a magma that crystallized to produce pge concentrations at three stratigraphic levels in the massif this indicates that similar thin sill like intrusions hosting unusually thick chromitites may also have pge concentrations at a number of stratigraphic levels

geology of the giant sudbury polymetallic mining camp ontario canada a new 1 100 000 scale compilation bedrock geology map provided with this issue presents a geologic synthesis of canada s most prolific mining camp the world class sudbury structure with total past production and current reserves of over 1 7 billion tonnes of ni cu co pt pd au ag ore lydon 2007 the polymetallic ore is hosted within one of earth s largest preserved impact craters the new map of the ni cu pge sudbury district after ames et al 2005 is included in a pocket at the back of this issue map 1 and is linked to mineral deposit commodity and geochronology data in tables 1 and 2 of this paper view this table table 1 list of mineral deposits and occurrences of the sudbury map area map 1 view this table table 2 u pb isotope data across the map area since 1891 six compilation maps of the geology of sudbury have been published bell 1891 collins 1937 cooke 1946 card 1969 dressler 1984 ames et al 2005 fig 1 some of the ni cu pge mines have operated for over a century whereas new ore deposits discovered as recently as 2004 are already in production or are in the process of being developed i e advanced prospects in the last 15 years sudbury has been the training ground for 60 postgraduate geoscience students in north america fig 1 from 1903 to 1990 only 23 graduate theses were completed on sudbury related topics eight of them in the 1970s after the discovery of shatter cones dietz 1964 fig 1 number of graduate theses of north american geoscientists trained on sudbury geology per decade showing the minor peak in training after the discovery of shatter cones and the recent education boom with over 50 geoscience graduate theses completed since 1990 the dashed lines represent the regional geologic maps of the sudbury area

br cl ratios and o h c and b isotopic constraints on the origin of saline waters from eastern canada saline groundwaters were recovered from undisturbed restigouche deposit and active brunswick 12 mine zn pb volcanogenic massive sulfide deposits in the bathurst mining camp bmc northern new brunswick canada these groundwaters along with fresh to brackish meteoric ground and surface waters from the bmc have been analyzed to determine their major trace element and stable isotopic o h c and b compositions saline groundwaters total dissolved solids 22 45 g l are characterized by relatively high na ca ratios compared to brines from the canadian shield and low na clmolar and d 11 b isotopic compositions 2 5 to 11 1 compared to seawater although saline waters from the canadian shield commonly have oxygen and hydrogen isotopic compositions that plot to the left of the global meteoric water line those from the bmc fall close to the water line fracture and vein carbonate minerals at the restigouche deposit have restricted carbon isotopic compositions of around 5 to 6 the carbon isotopic compositions of the saline waters at the restigouche deposit 12 d 13 cdic are the result of fractionation of dissolved inorganic carbon by methanogenesis we suggest that unlike previous models for shield brines the composition of saline waters in the bmc is best explained by prolonged water rock reaction with no requirement of precursor seawater we suggest that elevated br cl ratios of saline waters compared to seawater may be explained by differential uptake of br and cl during groundwater evolution through water rock reaction 2007 elsevier ltd all rights reserved

laser ablation icp ms study of platinum group elements in sulphides from the platreef at turfspruit northern limb of the bushveld complex south africa the platreef unit of the northern bushveld complex comprises a diverse package of pyroxenites peridotites and mafic lithologies with associated ni cu platinum group element pge mineralisation base metal sulphides bms are generally more abundant in the platreef than in other bushveld pge deposits such as the merensky reef and the ug2 chromitite but the platreef though thicker has lower overall pge grades despite a commonly held belief that pges are closely associated with sulphide mineralisation a detailed study by laser ablation icp ms la icp ms on a core through the platreef at turfspruit suggests that this is not strictly the case while a significant proportion of the pd os and ir were found to be hosted by bms pt irrespective of its whole rock concentration was not only at the top of the platreef is pt directly associated with sulphide minerals where pt pd sb te bi bearing inclusions were detected in the chalcopyrite portions of large composite sulphides in contrast pd os and ir occur in solid solution and as discrete inclusions within the bms throughout the core for os and ir this is usually in the form of os ir alloys whereas pd forms a range of pd te bi sb phases scanning electron microscope observations on samples from the top of the core revealed the presence of 0 2 mm long ptpd 2 sb te bi 2 michenerite maslovite laths within the chalcopyrite portions of large composite sulphides additional pt bearing minerals including sperrylite and geversite and a number of pd te bi sb minerals were observed in or close to the alteration rims of these sulphides this textural association was observed throughout the core similar platinum group minerals pgms were observed within the felsic assemblages composed of quartz plagioclase alkali feldspar and clinopyroxene produced by late stage felsic melts that permeated the platreef many of these pgms occur a significant distance away from any sulphide minerals we believe these features can all be linked to the introduction of as sb te and bi into the magmatic system through assimilation of sedimentary footwall rocks and xenoliths where the degree of contamination was high all of the pt and some of the pd formed as and sb bearing pgm that were expelled to the edges of the sulphide droplets many of these were redistributed where they came into contact with late stage felsic melts where no felsic melt interactions occurred the expelled pt and pd arsenides and antimonides remained along the margins of the sulphides at the top of the platreef where the effects of contamination were relatively low some of the pt remained within the sulphide liquids on cooling this formed the micro inclusions and blade like laths of pt pd sb bi te in the chalcopyrite

the distribution of platinum group elements pge and other chalcophile elements among sulfides from the creighton ni cu pge sulfide deposit sudbury canada and the origin of palladium in pentlandite concentrations of platinum group elements pge ag as au bi cd co mo pb re sb se sn te and zn have been determined in base metal sulfide bms minerals from the western branch 402 trough orebodies of the creighton ni cu pge sulfide deposit sudbury canada the sulfide assemblage is dominated by pyrrhotite with minor pentlandite chalcopyrite and pyrite and they represent monosulfide solid solution mss cumulates the aim of this study was to establish the distribution of the pge among the bms and platinum group minerals pgm in order to understand better the petrogenesis of the deposit mass balance calculations show that the bms host all of the co and se a significant proportion 40 90 of os pd ru cd sn and zn but very little 35 of the ag au bi ir mo pb pt rh re sb and te osmium and ru are concentrated in equal proportions in pyrrhotite pentlandite and pyrite cobalt and pd 1 ppm are concentrated in pentlandite silver cd sn zn and in rare cases au and te are concentrated in chalcopyrite selenium is present in equal proportions in all three bms iridium rh and pt are present in euhedrally zoned pge sulfarsenides which comprise irarsite irass hollingworthite rhass pge ni rich cobaltite coass and subordinate sperrylite ptas2 all of which are hosted predominantly in pyrrhotite and pentlandite silver au bi mo pb re sb and te are found predominantly in discrete accessory minerals such as electrum au ag alloy hessite ag2te michenerite pdbite and rhenium sulfides the enrichment of os ru ni and co in pyrrhotite pentlandite and pyrite and ag au cd sn te and zn in chalcopyrite can be explained by fractional crystallization of mss from a sulfide liquid followed by exsolution of the sulfides the early crystallization of the pge sulfarsenides from the sulfide melt depleted the mss in ir and rh the bulk of pd in pentlandite cannot be explained by sulfide fractionation alone because pd should have partitioned into the residual cu rich liquid and be in chalcopyrite or in pgm around chalcopyrite the variation of pd among different pentlandite textures provides evidence that pd diffuses into pentlandite during its exsolution from mss the source of pd was from the small quantity of pd that partitioned originally into the mss and a larger quantity of pd in the nearby cu rich portion intermediate solid solution and or pd bearing pgm the source of pd became depleted during the diffusion process thus later forming pentlandite rims of coarse granular veinlets and exsolution flames contains less pd than early forming pentlandite cores of coarse granular

textural and compositional evidence for the formation of pentlandite via peritectic reaction implications for the distribution of highly siderophile elements the distribution of highly siderophile elements is used in the study of a wide variety of geological topics from planet formation and evolution to the formation of ore deposits under mantle and crustal conditions these elements behave as highly chalcophile elements and pentlandite pn is an important host for most of these elements therefore understanding how pn forms is important to understanding the processes that control these elements the classic model for the formation of pn is that below 650 c the high temperature sulfides monosulfide solid solution mss and intermediate solid solution iss are no longer stable and exsolve into pyrrhotite po pn and chalcopyrite ccp however pn has been shown to be the main host of pd in many ore deposits and given that pd is incompatible with both mss and iss this observation is inconsistent with the exsolution model furthermore experimental work has shown that pn can form by peritectic reaction between mss and fractionated sulfide liquid to date this type of pn has not been reported in natural samples in our study of chalcophile element concentrations in pn from iconic magmatic ni cu platinum group element deposits we observed three textures of pn contact pn in between po and ccp granular pn included within ccp or po and flame pn included within po the contact pn shows zonation in mo rh ru re os and ir with these elements being enriched toward the po contact and depleted toward the ccp contact in some cases pd displays a zonation antithetical to that of these elements in this contribution we propose that the contact pn formed via the peritectic reaction described above and inherited mo ru rh re os and ir from the mss whereas pd was contributed from the fractionated sulfide liquid we expect that this type of pn should be present wherever mss and fractionated sulfide liquid remained in contact

evidence for as contamination and the partitioning of pd into pentlandite and co platinum group elements into pyrite in the fazenda mirabela intrusion brazil the fazenda mirabela intrusion in brazil hosts two zones of mineralization the santa rita ni cu sulfide ore zone occurring predominantly in an orthopyroxenite layer and an underlying basal platinum group element pge anomaly hosted in s poor dunite we show that in the northern and southern marginal zones of the intrusion pt pd ni cu fe bi te 2 minerals are accompanied by as bearing platinum group minerals pgm sperrylite ptas2 and irarsite rhirpt ass these as bearing pgm are extremely rare in the central zone of the intrusion suggesting that as has been introduced into the margins of the intrusion from the country rocks via crustal assimilation or synmagmatic hydrothermal processes other pgm and precious metal minerals pmm including hessite ag2te pd ag tellurides electrum and native au are observed in the santa rita ore zone and do not show any lateral variation in the semimetal and s poor dunite hosting the basal pge anomaly pge are predominantly retained in the base metal sulfides and only minor pge alloys are present in this s poor dunite pt au and semimetals partitioned into a fractionated cu rich liquid which formed during the crystallization of monosulfide solid solution mss and was largely removed by high temperature magmatic fluids palladium was not affected by this process and significant concentrations of pd are identified in pentlandite suggesting that pd preferentially partitioned into mss as it crystallized and subsequently pentlandite as it exsolved pyrite in the santa rita ore zone is co rich and contains higher concentrations of ipge os ir ru and rh than pyrrhotite and pentlandite suggesting that pyrite has not replaced and inherited the pge concentrations of these sulfides the pd poor nature of pyrite also indicates that it has not replaced pd rich pentlandite it is proposed that the ipge and co preferentially partitioned into pyrite as it exsolved from mss

platinum group elements in sulphide minerals platinum group minerals and whole rocks of the merensky reef bushveld complex south africa implications for the formation of the reef the concentrations of platinum group elements pge co re au and ag have been determined in the base metal sulphide bms of a section of the merensky reef in addition we performed detailed image analysis of the platinum group minerals pgm the aims of the study were to establish 1 whether the bms are the principal host of these elements 2 whether individual elements preferentially partition into a specific bms 3 whether the concentration of the elements varies with stratigraphy or lithology 4 what is the proportion of pge hosted by pgm 5 whether the pgm and the pge found in bms could account for the complete pge budget of the whole rocks in all lithologies most of the pge 65 up to 85 are hosted by pgm essentially pt fe alloy pt pd sulphide pt pd bismuthotelluride lesser amounts of pge occur in solid solution within the bms in most cases the pgm occur at the contact between the bms and silicates or oxides or are included within the bms pentlandite is the principal bms host of all of the pge except pt and contains up to 600 ppm combined pge it is preferentially enriched in pd rh and co pyrrhotite contains rh os ir and ru but excludes both pt and pd chalcopyrite contains very little of the pge but does concentrate ag and cd platinum and au do not partition into any of the bms instead they occur in the form of pgm and electrum in the chromitite layers the whole rock concentrations of all the pge except pd are enriched by a factor of five relative to s ni cu and au this enrichment could be attributed to bms in these layers being richer in pge than the bms in the silicate layers however the pge content in the bms varies only slightly as a function of the stratigraphy the bms in the chromitites contain twice as much pge as the bms in the silicate rocks but this is not sufficient to explain the strong enrichment of pge in the chromitites in the light of our results we propose that the collection of the pge occurred in two steps in the chromitites some pgm formed before sulphide saturation during chromitite layer formation the remaining pge were collected by an immiscible sulphide liquid that percolated downward until it encountered the chromitite layers in the silicate rocks pge were collected by only the sulphide liquid

noble metal enrichment processes in the merensky reef bushveld complex we have analysed sulphides silicates and chromites of the merensky introduction reef for platinum group elements pges re and au using laser the enrichment of noble metals in layered gabbroic ablation inductively coupled plasma mass spectrometry and synthetic intrusions to form stratiform merensky type ore horizons pyrrhotite standards annealed with known quantities of noble metals is an extremely efficient yet poorly understood process os ir and ru reside in solid solution in pyrrhotite and pentlandite metal enrichment must be related to the formation of rh and part of the reef s pd in pentlandite whereas pt au re magmatic layering as the ore horizons form an integral and some pd form discrete phases olivine and chromite often part of the magmatic stratigraphies of their host insuspected to carry os ir and ru are pge free all phases analysed trusions metal concentration is also related to the prescontain noble metals as discrete micro inclusions with diameters ence of magmatic sulphides because the noble metals are either dissolved in base metal sulphides or occur as typically 100 nm inclusions in sulphides commonly have the discrete noble mineral phases intergrown with sulphides element combinations os ir pt and pt pd au inclusions in vermaak hendriks 1976 ballhaus ryan 1995 olivine and chromite are dominated by pt au pd few inclusion ballhaus ulmer 1995 spectra can be related to discrete noble metal phases and few there is considerable controversy as to where the inclusions have formed by sub solidus exsolution rather some metals came from and how metal enrichment worked pge inclusions notably those in olivine and chromite are earlyfor a stratiform platinum group element pge deposit magmatic nuggets trapped when their host phases crystallized we inside the magmatic stratigraphy of a layered intrusion suggest that the silicate melt layer that preceded the merensky reef there are two possibilities either the metals were derived was pge oversaturated at early cumulus times experiments from the melt column above the ore horizon or they came combined with available sulphide silicate partition coefficients sugfrom the magma equivalent to the cumulate package gest that a silicate melt in equilibrium with a sulphide melt underlying the ore owing to the large density contrast containing the pge spectrum of the merensky ore would indeed be between silicate and sulphide melt a popular view is that oversaturated with respect to the least soluble noble metals sulphide the metals were enriched by gravitational settling of melt apparently played little role in enriching the noble metals in sulphide melt i e out of the magma column above the the merensky reef rather its role was to immobilize a pre existing ore campbell et al 1983 barnes naldrett 1985 in situ stratiform pge anomaly in the liquid stratified magma naldrett et al 1987 on the other hand it is well chamber established that gravitational crystal settling plays little role in producing magmatic layering and magmatic stratigraphies mcbirney noyes 1979 morse 1986 campbell 1987 and this cannot remain without consequence for stratiform noble metal deposits a third alternative is noble metal enrichment by late

distribution of chalcophile and platinum group elements among pyrrhotite pentlandite chalcopyrite and cubanite from the noril sk talnakh ores implications for the formation of platinum group minerals in most magmatic sulfide deposits platinum group elements pge are found both within the structure of the base metal sulfides bms pyrrhotite po pentlandite pn chalcopyrite ccp and cubanite cbn and as platinum group minerals pgm tellurium as bi sb and sn tabs are essential elements in many of these pgm the potential role of tabs in collecting pge and thus forming a pge deposit has not been closely investigated we have determined the concentrations of a full suite of chalcophile elements in po pn ccp and cbn using laser ablation inductively coupled plasma mass spectrometry on samples from the noril sk talnakh ni deposits in these deposits the po rich ore is thought to represent monosulfide solid solution mss cumulate of the initial sulfide liquid and the ccp rich ore a mixture of the fractionated sulfide liquid and intermediate solid solution iss the bms from the po rich ore contain lower concentrations of tabs pd pt and au and higher concentrations of mo ru rh re os and ir than bms from the ccp rich ores this observation is consistent with experimental results which show that tabs pd pt and au are incompatible with mss whereas the other elements are compatible in mss counter intuitively in the po rich ore the bulk of the pd and tabs is hosted by bms this is because during crystallization although only a small amount of the incompatible elements partitioned into the bms the fractionated liquid has migrated away thus the po rich ores represent mss adcumulates therefore as the po rich ores contain very little trapped liquid fraction the bms host the bulk of pd and tabs in contrast in the ccp rich ore the bulk of au pd pt and tabs is present as pgm or electrum grains this is because more trapped liquid is present and as tabs au pd and pt are not compatible with iss they concentrated into the very last sulfide liquid and crystallized as intergrowths of pd pt tabs pgm the tabs then do not appear to collect pd pt and au but rather all elements are concentrated in the most fractionated sulfide liquid by crystal fractionation

distribution of platinum group elements in the platreef at overysel northern bushveld complex a combined pgm and la icp ms study detailed mineralogical and laser ablation inductively coupled plasma mass spectrometry studies have revealed the physical manifestation of the platinum group elements pge within the platreef at overysel northern bushveld complex south africa the pge in the platreef were originally concentrated in an immiscible sulfide liquid along with semi metals such as bi and te as the sulfide liquid began to crystallize virtually all the os ir ru and rh partitioned into monosulfide solid solution mss which on further cooling exsolved to form pyrrhotite and pentlandite with os ir and ru remaining in solid solution in both phases with rh prefentially partitioning into pentlandite platinum some pd and au were concentrated in the residual sulfide liquid after mss crystallization and were then concentrated in an immiscible late stage melt along with semi metals which was expelled to the grain boundaries during crystallization of intermediate solid solution iss to form pt and pd tellurides and electrum around the margins of the sulfide grains tiny droplets of this melt trapped in the crystallizing mss and iss cooled to form pt bi te microinclusions in all sulfide phases whilst the excess pd was accommodated in solid solution in pentlandite minor redistribution and recrystallization by hydrothermal fluids occurred around xenoliths and at the very base of the mineralized zone within the footwall however the overall lack of secondary alteration coupled with the volatile poor nature of the gneissic footwall have allowed the preservation of what may be the most primary style of platreef mineralization the lack of pgm inclusions within early liquidus phases suggests very early sulfur saturation in the platreef lending support to theories involving s saturation occurring prior to intrusion of the platreef possibly within a staging chamber

mineralogy of ni cu platinum group element sulfide ore in the 800 and 810 orebodies copper cliff south mine and p t x conditions during the formation of platinum group minerals the 800 and 810 orebodies are two major deposits in the copper cliff south mine located at opposite contacts between the quartz diorite of the copper cliff offset dike and metapelite of the mckim formation the copper cliff south mine is one of the richest cu ni platinum group elements pge deposits in the copper cliff offset dike the ore is composed of variable proportions of pyrrhotite chalcopyrite and pentlandite and occurs as massive sulfides semimassive sulfides with inclusions of quartz diorite and wall rocks net textured sulfides disseminated sulfides and veins sphalerite and magnetite are also present in minor amounts the primary magmatic minerals in the quartz diorite are plagioclase quartz amphibole and biotite the most common platinum group mineral pgm in the copper cliff south mine is sperrylite ptas 2 it occurs in every textural type of ore typically enclosed by chalcopyrite pyrrhotite pentlandite cobaltite and hydrous silicates such as chlorite amphibole and epidote sperrylite may be homogeneous zoned with sb rich cores and sb poor rims associated with hollingworthite rhass and cobaltite or it may contain inclusions the pd bearing minerals are froodite pdbi 2 and michenerite pdbite which are most commonly enclosed by silicates chlorite biotite quartz or chalcopyrite hollingworthite invariably occurs in the center of zoned cobaltite in veins or in disseminated sulfides argentian gold au 0 56 ag 0 44 occurs as small grains in chalcopyrite and in a veinlet with parkerite ni 2 bi 3 s 2 the most abundant ag mineral is hessite ag 2 te which is present in almost every sample with galena gersdorffite and locally pgm volynskite agbite 2 occurs as a zoned grain with tsumoite bite in the center the most common trace minerals spatially and genetically associated with pgm are tsumoite galena gersdorffite cobaltite hessite melonite and native te the copper cliff south mine area was affected by more than one hydrothermal event deformation and metamorphism all of which affected the primary igneous textures and mineralogy of the rocks the first hydrothermal event was responsible for the extensive remobilization of metals including some pge this is revealed by the presence of pgm in large veins in quartz diorite and metapelite and by chlorite amphibole epidote biotite and quartz that often enclose pgm the temperature at the time of this event was estimated in samples containing garnet and biotite in equilibrium to be 327 to 540 c pressure estimated using amphibole chemistry may have been as high as 3 to 4 kbars the fluid responsible for the transport of metals was very rich in cl and oxidizing the fluid composition temperature and or pressure changed with time suggested by the presence of zoned minerals including sperrylite gersdorffite and cobaltite based on the textural relationships sperrylite precipitated before tellurides and galena and after or at the same time as michenerite a second hydrothermal event produced calcite bearing veinlets that cut larger veins

petrology and crystallization history of multiphase sulfide droplets in a mafic dike from uruguay implications for the origin of cu ni pge sulfide deposits sulfide blebs in a mafic dike belonging to the uruguayan dike swarm replicate at a small scale many features observed in larger platinum group element enriched nickel copper sulfide deposits such as in sudbury and noril sk these blebs formed by the crystallization of droplets of immiscible sulfide liquid form 1 cm sized ovoid geopetal structures with pyrrhotite and pentlandite at the base chalcopyrite and cubanite at the top and titaniferous magnetite at the margins magnetite crystallized first followed by nickel and iron rich monosulfide solid solution which sank to the bottom of the droplets and from which pyrrhotite and pentlandite subsequently exsolved the remaining copper rich liquid in the upper part of the droplets crystallized to form an intermediate solid solution from which chalcopyrite and cubanite subsequently exsolved the final extremely evolved cu fe s rich pd sn pb mo ag bi te and sb bearing liquid crystallized as 10 to 20 sized veinlets filling fractures in the magnetite and adjacent silicate minerals the veinlets crossing the magnetite often terminate in 100 m sized subrounded globules at the contact of the magnetite and the surrounding silicate minerals indicating a direction of veinlet filling away from the center of the blebs textural evidence in the blebs illustrates that as crystallization proceeded and the immiscible sulfide liquid droplets within the dike sank a distance of less than 1 mm relative to the adjacent silicate onto already partially crystallized silicate minerals the sulfide liquid surrounded and resorbed the already solid magnetite grains at the top of the blebs magnetite grains were isolated above the sulfide liquid and partially surrounded by quartz plagioclase and amphibole an assemblage representing a late stage magma that had been drawn into the space created above the droplets as they sank and which is more evolved than that of the surrounding host dike the location of the blebs within the dike isolated from influences external to the dike indicates both that the fracture filling by evolved immiscible cu rich sulfide liquid is related to crystallization processes rather than later tectonic events and that the bismuth tellurium and antimony have a late magmatic origin associated with crystallization of the immiscible sulfide liquid

sulphide mineral evolution and metal mobility during alteration of the oceanic crust insights from odp hole 1256d fluxes of metals during the hydrothermal alteration of the oceanic crust have far reaching effects including buffering of the compositions of the ocean and lithosphere supporting microbial life an