interaction of magmatic fluids and silicate melt residues with saline groundwater in the footwall of the sudbury igneous complex ontario canada new evidence from bulk rock geochemistry fluid inclusions and stable isotopes abstract along the northern margin of the 1 85 ga sudbury igneous complex sic canada a volumetrically minor rock type known as the footwall granophyre fwgp preserves evidence of the interaction of magmatic fluid and groundwater the fwgp comprises veins dikes and irregular bodies of a quartz alkali feldspar plagioclase intergrowth that are most abundant near footwall style cu ni platinum group element mineralization textures and cross cutting relations show that the emplacement of the fwgp created favourable sites for the later deposition of sulfides geochemical and physical evidence show that the fwgp did not form by in situ partial melting of the archean country rocks in the footwall beneath the sic it represents a mobilized injected silicate residue from either the contact between partially melted country rocks and the sic or from the crystallizing sic itself its bulk composition can be modeled as the product of fractional crystallization of a liquid with an initial composition equivalent to granophyric matrix trapped liquid in the lowermost units of the sic norite and sublayer primary fluid saline h 2 o poor and melt silicate h 2 o rich inclusions hosted in quartz from the fwgp have bulk and trace element compositions consistent with those hosted in quartz from the granophyric matrix of the lower units of the sic norite sublayer fluid inclusions contain mixtures of a high salinity 44 70 wt nacl equivalent n 39 na fe rich aqueous magmatic fluid and a lower salinity ca and sr rich groundwater the magmatic end member is thought to be an sic derived volatile phase estimates of the mixing proportions show that primary and secondary inclusions in the fwgp contain 60 100 and 30 80 of the magmatic end member by mass respectively fluids responsible for the remobilization of ore metals represent mixtures containing a much higher proportion of the groundwater end member not less than 70 by mass compared to the fluids trapped in the fwgp at considerable distance 400 m from the sic the chlorine isotope composition of biotite in the fwgp is enriched in 37 cl 37 cl 0 98 to 1 61 scapolite from the high temperature veins and the interstices of rock types in the main mass of the sic shows similar enrichment in 37 cl up to 1 34 whereas biotite from the archean country rocks 37 cl 0 88 to 0 53 and associated groundwater are 37 cl depleted the results of this study lead to two important conclusions concerning genetic and exploration models for the footwall ore zones first magmatic end member fluid introduced into the footwall with the melt from which the fwgp crystallized contained very little cu rarely 100 ppm the main ore metal in the footwall ores this result questions hydrothermal models for footwall ore formation that hypothesize that cu and other ore metals were remobilized from sulfide deposits along the sic contact by magmatic hydrothermal fluids and redeposited in the footwall it is more likely that ore metals were only locally remobilized in the footwall ore zones when metal poor hybrid fluids interacted with pre existing sulfide veins of magmatic origin second inclusions containing the hybrid fluid occur in the fwgp rock type throughout the footwall in both mineralized and unmineralized areas therefore although the fwgp preserves stable cl isotope and fluid inclusion evidence that magmatic fluid was introduced into the footwall detection of this magmatic component alone will not serve as a useful exploration method in contrast mapping the distribution and abundance of fwgp may be ore predictive since fwgp emplacement and its higher abundance in mineralized areas appears to have been a structural and textural prerequisite for footwall ore emplacement

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

fractional crystallization of anhydrous sulfide liquid in the system fe ni cu s with application to magmatic sulfide deposits abstract phase relations for coexisting monosulfide solid solution fe ni 1 xs mss and sulfide liquid have been determined in the fe rich portion of the anhydrous quaternary system fe ni cu s at 52 5 and 50 0 at s 850 1050 c and low pressure equations for the complex dependence of the mss solidus sulfide liquidus and distribution coefficients for exchange of ni cu and fe cu on temperature s content and proportion of metals have been derived by multiple regression analysis these equations may be used for geothermometry of pristine magmatic sulfides and prediction of liquid evolution paths but a limiting factor is uncertainty in the precise bulk composition of natural assemblages and particularly of s content intermediate solid solution cu fe s1 x iss is stable up to 900 950 c in ni poor compositions and a large field of a new ternary fe cu ni s solid solution intermediate between iss and mss exists at and below 850 c disseminated sulfides in komatiites are markedly depleted in cu relative to an origin by sulfide liquid immiscibility the compositions of magmatic sulfide ores from sudbury canada and the insizwa complex transkei are not consistent with derivation of the associated late cu rich ores by fractional crystallization of sulfide magma although the cu rich ores of the noril sk talnakh district russia could have evolved through a complex sequence of fractional crystallization events

lower timberline in central colorado during the past 15 000 yr a 15 000 yr paleoenvironmental record at the elevation of lower timberline in central colorado suggests two major paleoclimatic changes during that interval 1 at 10 000 yr b p from cool moist conditions to warm moist conditions and 2 at 4 000 yr b p to warm dry conditions this sequence can be interpreted as a shift from precipitation predominantly originating from pacific winter storms before 10 000 yr b p to a predominantly monsoonal type regime lasting until 4 000 yr b p to the present pattern contemporaneity of higher upper timberline and lower lower timberline during the 10 000 to 4 000 yr b p interval is not contradictory but a result of changes in those circulation patterns

compositional variations of olivine from the jinchuan ni cu sulfide deposit western china implications for ore genesis the jinchuan ni cu sulfide deposit is hosted by an elongated olivine rich ultramafic body that is divided by subvertical strike slip faults into three segments central eastern and western the central segment is characterized by concentric enrichments of cumulus olivine crystals and interstitial sulfides pyrrhotite pentlandite chalcopyrite intergrowth whereas the eastern and western segments are characterized by an increase of sulfides toward the lower contacts in all segments sulfides are concentrated at the expense of intercumulus silicates olivine re crystallization is found to be associated with actinolite alteration in some samples the compositional variations of primary olivine from the sulfide poor samples can be explained by a small degree of olivine crystallization 50 modal and sulfide averaging 5 wt in the rocks are consistent with the interpretation that the jinchuan deposit was formed by olivine and sulfide laden magma successively ascending through a conduit to a higher now eroded level sulfide enrichment toward the center in the central segment and toward the lower contact in the eastern and western segments may have in part resulted from flow differentiation and gravitational settling during magma ascent respectively

footwall type cu ni pge mineralization in the broken hammer area wisner township north range sudbury structure footwall type cu ni pge platinum group element deposits are a major focus of recent exploration in the sudbury mining camp owing to their higher cu and precious metal contents compared to orebodies situated along the lower contact of the sudbury igneous complex the most important footwall type orebodies occur in the onaping levack area of the north range but economic deposits are found along the east range of the structure as well recently promising occurrences were also discovered in wisner township of the north range in this paper we report results from two main footwall type cu ni pge occurrences the broken hammer zone and the south zone of wisner township both discoveries are situated in intensely brecciated zones of the footwall sudbury breccia 1 300 and 500 m respectively north of the present sudbury igneous complex footwall contact the mineralization consists of 1 massive sulfide veins 2 disseminated replacement sulfides and 3 silicate quartz dominated veins although massive sulfide veins account for the major part of the resource sulfide poor disseminations may have similarly high precious metal contents ore assemblages are dominated by chalcopyrite millerite magnetite and or pyrite quartz and hydrous silicates these are accompanied by platinum group minerals pgm and other trace minerals which commonly occur as composite grains within sulfides and hydrous silicates these include minerals typical of footwall type deposits e g merenskyite michenerite hessite but also minerals found only in a few sudbury deposits e g clausthalite sopcheite naumannite bohdanowiczite an unnamed cupdbis 3 mineral is one of the most abundant pgm at broken hammer and might be a pd equivalent of muckeite cunibis 3 statistical investigation of metal distribution patterns using grab sample and drilling data sets from both localities indicate important differences between the two occurrences and the various mineralization styles e g increasing cu cu ni and decreasing pt pt pd ratio with increasing sulfide content metal concentrations recalculated to 100 sulfides decrease by up to two orders of magnitude for all metals from the disseminated to the massive sulfides fluid inclusion studies revealed three fluid generations which are very similar to those described from well known footwall type deposits of the onaping levack area primary polyphase fluid inclusions in cu ni pge bearing assemblages represent a highly saline 30 40 wt nacl equiv magmatic hydrothermal system with a high temperature min 450 500 c and a lower temperature min 300 350 c stage a later low temperature ca rich fluid min 100 200 c is most probably part of a post sudbury igneous complex regional fluid flow in which temperature was controlled by the geothermal gradient and not related to ore forming processes the fluid inclusion data indicate that mobilization of highly saline and relatively high temperature 400 500 c sudbury igneous complex related magmatic hydrothermal fluids similar to those described from the onaping levack embayment also occurred in the wisner footwall although our studies do not rule out the possibility of an initial magmatic sulfide melt emplacement they prove that magmatic hydrothermal fluids played a significant role in the transport and deposition of metals

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

preliminary evaluation of trace hydrocarbon speciation and abundance as an exploration tool for footwall style sulfide ores associated with the sudbury igneous complex ontario canada deposits of cu ni platinum group elements pge rich sulfides occur along the north range footwall of the sudbury igneous complex ontario canada the deposits have been modified chemically mineralogically and texturally by multiple syn to postmagmatic hydrothermal events and are hosted mainly within sudbury breccia a contact metamorphosed and hydrothermally altered impact breccia the composition of c1 to c6 unsaturated and saturated hydrocarbons in bulk fluid inclusion volatiles in the matrix of the sudbury breccia was investigated using in line rock crushing gas chromatography gc in order to compare the hydrocarbon composition of this rock type in breccia zones containing economic footwall sulfide deposits at the morrison deposit levack mine north range sudbury ontario with barren breccia zones trace hydrocarbons possibly abiogenic in origin occur throughout the sudbury igneous complex footwall and country rocks investigated however there are differences in the composition and abundance of bulk hydrocarbons released from mineralized and barren sudbury breccia when fluid inclusions are opened volatiles released from samples of sudbury breccia from sulfide mineralized and sulfide barren environments showed the following 1 higher average abundances of light saturated hydrocarbons c1 c4 and an approximately 2 higher total abundance of hydrocarbons mol g of rock basis associated with samples from the mineralized study area and 2 comparable average unsaturated hydrocarbon abundances in both settings but a larger range in unsaturated hydrocarbon abundances in the mineralized study area differences in bulk hydrocarbon abundance and composition reflect differences in the abundance and hydrocarbon content of fluid inclusions trapped in the barren and mineralized sudbury breccia zones in addition the compositional modification of circulating fluids by processes and conditions unique to the mineralized sudbury breccia environment may have occurred prior to inclusion entrapment e g modification by mineral catalysts differences in temperature and oxygen fugacity preliminary spatial analysis of the hydrocarbon distribution within and surrounding the morrison deposit shows that the total hydrocarbon abundance in the sudbury breccia does not change with orebody proximity within a single host breccia zone however volatiles trapped in the sudbury breccia matrix near the top of the footwall deposit where it is physically connected to contact style ni cu pge ores have elevated unsaturated hydrocarbon abundances e g propene compared to other parts of the same breccia zone distal to this zone of physical connection samples of the pge enriched sudbury breccia and mineralized veins containing alteration assemblages characteristic of the footwall ore styles have higher unsaturated hydrocarbon abundances and unsaturated saturated ratios compared to sudbury breccia and vein samples that are pge poor localized enrichments in unsaturated hydrocarbons in sudbury breccia zones may be the result of specific ore minerals and metal complexes involving the pge and group viii metals that acted as catalytic agents modifying the composition of initially light saturated hydrocarbon species prior to entrapment in fluid inclusions to apply the analysis of hydrocarbon compositions in trapped fluid inclusions to discriminating mineralized from barren zones of sudbury breccia samples from targeted areas were compared to samples of barren sudbury breccia background although a large data set is presented here to establish these compositional fields analysis of smaller sample subsets from each environment yields a statistically significant separation between the two environments total hydrocarbon abundance c3 c1 ratios and unsaturated saturated hydrocarbon ratios are useful indicators of sulfide ore proximity and may help delineate regions enriched in pge

ni cu pge magmatic sulfide deposits in the yangliuping area permian emeishan igneous province sw china the ni cu pge sulfide deposits in the yangliuping area sw china are hosted in mafic ultramafic sills the four mineralized sills are located in the yangliuping tectonic dome and intrude devonian carbonaceous marble graphitic schist the sills are 200 300 m thick and 1 000 2 000 m in strike length and now consist chiefly of serpentinite talc schist tremolite schist and meta gabbro disseminated ni cu sulfide mineralisation occurs in the serpentinite in the lower parts of the sills massive sulfide mineralisation is located in the base of the sills and in the footwall along fractures beneath the mineralized serpentinite although the sulfide ores have been modified by hydrothermal activity there are relict cumulate textures in the disseminated sulfides indicating a magmatic origin for the ores the yangliuping intrusions and the dashibao formation have similar primitive mantle normalized trace element and platinum group element pge patterns indicating that they are derived from a common parental magma type the positive correlation between cu concentrations and cu zr ratios of the dashibao formation basalts indicates that the chalcophile elements were removed before eruption we propose that fractional crystallization of the yangliuping magma accompanied by the introduction of s and co2 from the wall rocks caused the magma to become s saturated leading to the segregation of magmatic sulfides that became enriched in ni cu pge the sills acted as conduits for the overlying dashibao formation basalts with the sulfide liquid along with early crystallizing olivine and pyroxene segregating from the magma as it passed through the conduits prior to eruption

textural morphological and compositional varieties of modern arc sulfides a case study of the tolbachik volcano kamchatka abstract magma unmixing into separate sulfide and silicate melts is a key process in the formation of magmatic sulfide ore deposits sulfide inclusions in olivine preserve the original chemical composition of the segregated sulfide melt whereas the phase compositions of the solidified sulfide droplets and their textures record the final stages of sulfide evolution sulfide globules hosted in olivine phenocrysts of magnesian basalts from the tolbachik volcano kamchatka display a variety of textures ranging from homogeneous to fine grained to coarse grained and lamellar porous textures and textures associated with the oxidation and dissolution of sulfides were identified as separate categories the outer surfaces of sulfides vary significantly in shape which includes normal spherical or elliptical globules gravitationally layered inclusions thin sulfide foils and concave deformed sulfides in contact with fluid bubbles the estimated cooling rate of olivine phenocrysts responsible for observed crystallization textures varies by five orders of magnitude the fe ni cu ratio also exerts an influence on the resulting texture whereas the size of the globules does not have any significant effect the morphology and textural patterns of individual grains indicates that fine grained textures resulted from the rapid breakdown of a homogeneous solid phase which the sulfide melt solidified into during extremely rapid quenching the presence of large or abundant small pores in sulfides along with channels at the globule periphery indicates the separation of an appreciable amount of dissolved fluid from the sulfide melt during crystallization sulfides in the form of thin foils and planar swarms in healed cracks indicate cyclic pressure changes in the olivine environment which resulted in phenocrysts rupturing and healing the sulfide mineralogy is represented by high temperature sulfides mss monosulfide solid solution and iss intermediate solid solution as well as pyrrhotite pentlandite chalcopyrite cubanite bornite magnetite assemblages which formed at lower temperatures

reply to the comment by c li and s j barnes on fractional crystallization of anhydrous sulfide liquid in the system fenicus with application to magmatic sulfide deposits

the significance of partial melting processes in hydrothermal low sulfide cu ni pge mineralization within the footwall of the sudbury igneous complex ontario canada we present new results and review existing data highlighting different aspects of the genetic relationship between partial melting and hydrothermal mineralizing processes in the contact aureole of the sudbury igneous complex at the basal contact of the igneous complex in the footwall breccia crystallized partial melt pods and veins referred to as footwall granophyres are abundant and intrude all rock types including the breccia matrix as well as massive ni cu sulfide ore the final crystallization of these melts was accompanied by the segregation of high salinity fluids dominantly in the temperature range of 450 to 550 c as revealed by ti inquartz thermometry and studies on primary fluid inclusions in mineralized parts of the footwall breccia there is clear evidence that interaction of partial melts exsolved fluids and preexisting magmatic sulfides occurred in the deeper footwall of the sudbury igneous complex similar footwall granophyres occur as networks of veins intruding impact brecciated sudbury breccia country rocks and have an intimate spatial association with hydrothermal low sulfide assemblages highly enriched in pt pd and au with a unique assemblage of pgm including malyshevite and lisiguangite it is suggested that partial melting processes were widespread in the contact and proximal footwall environment of the igneous complex and they were important in providing high salinity magmatic fluids to a hydrothermal system responsible for redistribution of base and precious metals we describe observations which may evidence the migration of partial melts from the contact into the deeper footwall furthermore we suggest a cogenetic model for the precipitation of sulfide hydrous silicate assemblages in close spatial association to footwall granophyres we emphasize that the use of footwall granophyres in mineral exploration for cu ni pge ores in the footwall of the sudbury igneous complex is clearly justified mapping of footwall granophyre vein networks highlights areas that were proximal to the contact environment and point out structural pathways that may have been used by syn or postgenetic mineralizing fluids in a given area widespread partial melting appears to have occurred in the footwall of other large mafic ultramafic complexes such as bushveld and duluth and similar genetic relationships of partial melting and ore forming hydrothermal processes may have possibly existed also in these systems

sr nd os s isotope and pge geochemistry of the xiarihamu magmatic sulfide deposit in the qinghai tibet plateau china the newly discovered xiarihamu ni cu deposit is located in the eastern kunlun orogenic belt in the northern part of the qinghai tibet plateau western china it is the largest magmatic ni cu sulfide deposit found thus far in an arc setting worldwide and ranks second in china in terms of total ni resources fe ni cu sulfide mineralization occurs in a small ultramafic body that is part of a larger mafic ultramafic complex formed by protracted silurian early devonian basaltic magmatism the mineralized ultramafic body is composed predominantly of lherzolite and olivine websterite with minor dunite websterite and orthopyroxenite here we report new pge platinum group element data and the results of a new integrated sr nd os s isotope study the initial concentrations of rh and pd in the parental magma are estimated to be 0 014 ppb and 0 24 ppb respectively which are more than one order of magnitude lower than those in undepleted mantle derived magmas such as many continental picrites the observed pge depletions in the xiarihamu parental magma are attributed to sulfide retention in the source mantle because the degree of partial melting required to generate the xiarihamu primary magma was not high enough for a magma of that composition to dissolve all sulfides in the source the 87sr 86sr i ratios and end t of the xiarihamu host rocks range from 0 7062 to 0 7105 and from 1 97 to 5 74 respectively indicating 5 30 wt crustal contamination in the xiarihamu magma these data also reveal that the source mantle for the xiarihamu magma is isotopically sr nd more enriched than that for the average cenozoic arc basalt the os t and 34s values of sulfide ores from the xiarihamu deposit range from 78 to 1393 and from 2 to 6 respectively these values clearly indicate addition of crustal os and s to the xiarihamu parental magma metal tenors such as ni and rh are inversely correlated with os t and 34s values this indicates that mixing between different pulses of magma with different isotope compositions took place during magma emplacement at xiarihamu and that external s played a critical role in the formation of the xiarihamu magmatic ni cu sulfide deposit

copper solubility in a basaltic melt and sulfide liquid silicate melt partition coefficients of cu and fe the solubility of copper in a sulfur saturated basaltic melt has been determined at 1245 c as a function of fo2 and fs2 copper solubilities at log fo2 values between 8 and 11 fall into two distinct populations as a function of fs2 at log fs2 values 1 65 sulfide liquid that coexists with the basaltic glass quenches to sulfur poor bornite solid solution at log fs2 values in excess of 1 65 the sulfide liquid quenches to a complex intergrowth of sulfur rich bornite and intermediate solid solution copper solubilities in the low fs2 population range from 594 to 1550 ppm whereas those in the high fs2 population range from 80 to 768 ppm sulfide liquid silicate liquid partition coefficients d for cu and fe range from 480 to 1303 and 0 7 to 13 6 respectively metal sulfur complexing in the silicate liquid is shown to be insignificant relative to metal oxide complexing for fe but permissible for cu at high fs2 values on log dfe sulfide silicate and log dcu sulfide silicate vs log fs2 log fo2 diagrams both fs2 populations show distinct but parallel trends the observation of two d values for any fs2 fo2 ratio indicates nonideal mixing of species involved in the exchange reaction the two distinct trends observed for both cu and fe are thought to be due to variations in activity coefficient ratios e g feo fes and cuo0 5 cus0 5 results of the experiments suggest that accurate assessments of fs2 fo2 ratios are required for the successful numerical modeling of processes such as the partial melting of sulfide bearing mantle and the crystallization of sulfide bearing magmas as well as the interpretation of sulfide mineralogical zoning in addition the experiments provide evidence for oxide or oxy sulfide complexing for cu in silicate magmas and suggest that the introduction of externally derived sulfur to mafic magma may be an important process for the formation of cu rich disseminated magmatic sulfide ore deposits

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

multi stage hydrothermal processes involved in low sulfide cu ni pge mineralization in the footwall of the sudbury igneous complex canada amy lake pge zone east range the amy lake pge zone is a low sulfide type cu ni pge mineralization in the east range footwall of the 1 85 ga sudbury igneous complex occurring in a 100 m wide sudbury breccia belt that coincides with an impact related major fracture zone bay fault zone detailed hydrothermal alteration mapping fluid inclusion trace element and stable isotope studies revealed a complex alteration and mineralization history in a multi source multi stage sudbury related hydrothermal system the two major stages of syn sudbury hydrothermal activity are characterized by similarly high salinity high temperature fluids that are 1 locally derived from footwall granophyre bodies and typified with high ni cu and pge s ratios and high ree contents magmatic hydrothermal stage and 2 a more voluminous cu ni pge rich fluid flux probably originated from the sudbury igneous complex footwall contact hydrothermal stage the second hydrothermal flux was introduced by brittle fractures in the area and resulted in a complex zonation of alteration assemblages and mineralization governed by local footwall composition the sudbury related hydrothermal event was overprinted by shear related epidote veining and calcite chlorite replacement both regionally present in the sudbury structure based on analogies the most important factors involved in the formation of hydrothermal low sulfide mineralization are proposed to be 1 accumulation of pge enriched fluids 2 large scale brittle structures as conduits to these fluids and 3 adequate host rock composition as a chemical trap resulting in sulfide and pgm precipitation in environments meeting these criteria hydrothermal pge mineralization is known to have formed not only in the sudbury footwall but also from mafic ultramafic intrusions associated with primary magmatic pge from several locations around the world

quantifying the effect of solid phase composition and structure on solid liquid partitioning of siderophile and chalcophile elements in the iron sulfur system we report experimentally determined partition coefficients between solid and liquid phases for bulk compositions on either side of the fe fes eutectic for a suite of siderophile chalcophile and lithophile elements experiments were performed at conditions of 1 5 and 2 gpa in pressure p 1323 k in temperature t and virtually identical eutectic sulfide liquid compositions in equilibrium with either solid face centered cubic fe or solid fes this enabled isolation of the effect of solid phase composition and structure from pressure temperature melt composition effects solid phase liquid metal partition coefficients d values for ge re ni co cr mn v sn pb re and w differ significantly if partitioning occurs between identical metallic liquids but different solid phases whereas zn cu and mo are virtually unaffected for all elements except ge and sn measured solid fe liquid sulfide partition coefficients at 1 5 and 2 gpa are inconsistent with model predictions based on atmospheric pressure experiments indicating that such models may not be appropriate for modeling core crystallization processes at non ambient pressure the framework of a lattice strain based model of solid liquid metal partitioning stewart et al 2009 enables us to quantify the effect of the solid phase changing the solid phase from fe to fes leads to systematic increases in r0 from 1 54 to 1 65 a and apparent young s modulus e from 112 to 178 gpa these systematic changes can be used to predict element partitioning in eutectic solid fes bearing systems from measurements in eutectic solid fe bearing systems although changing the solid phase from face centered cubic fe to fes is an end member example our data suggest that changes with pressure in the structure e g to hexagonally close packed at high pressure and composition e g to higher s content at high pressure of solid iron could affect the partitioning of elements between fe and liquid metal during the solidification of planetary cores

late stage sulfide liquid mobility in the main mass of the sudbury igneous complex examples from the victor deep mccreedy east and trillabelle deposits massive sulfide in the contact sublayer in three different deposits of the sudbury igneous complex is overlain by substantial thicknesses of norite hosted disseminated sulfide mineralization with anomalous compositions in the trill embayment the levack trough mccreedy east and the victor nickel rim embayment victor deep disseminated sulfides are present at concentrations of 1 to 5 percent over a vertical thickness locally exceeding 100 m within the main mass i e texturally homogeneous inclusion free norites above massive contact ores of the sublayer where primary textures are preserved they show that sulfide liquid remained present as an interstitial liquid during the entire crystallization history of the enclosing silicate cumulate rocks the disseminated sulfides show remarkably constant compositions over a large stratigraphic interval they cannot have formed due to fractional segregation of sulfide liquid from the main mass magma accompanying the deposition of the enclosing silicate cumulus phases because this would lead to extreme depletion in all platimun group elements within a stratigraphic interval much shorter than the hundreds of meters in which their compositions are observed to remain approximately constant geochemical modeling of sulfide liquation and fractional crystallization shows that the massive sulfides are cumulates rich in monosulfide solid solution mss the overlying disseminated sulfides represent mss left behind by an upward migrating fractionated sulfide liquid residual to the formation of the massive cumulates at the base these results show that cu rich sulfide liquids are capable of migrating distances greater than 100 m through almost completely solidified cumulate rocks at volume fractions of sulfide as low as one percent the presence of a halo of disseminated sulfide mineralization with a distinctly fractionated geochemical character up to several hundred meters wide above zones of massive sulfide mineralization could be used to detect deeply buried massive sulfide orebodies at sudbury and elsewhere

siderophile and chalcophile elemental constraints on the origin of the jinchuan ni cu pge sulfide deposit nw china abstract the jinchuan deposit nw china is one of the world s most important ni cu pge sulfide deposits related to a magma conduit system and is hosted in an ultramafic intrusion the intrusion is composed of lherzolite and dunite with the two largest sulfide ore bodies named as ore body 1 and 2 in its middle portion the sulfide ores may be disseminated net textured or massive the disseminated and net textured sulfide ores are characterized by variable but generally low pge concentrations 10 3200 ppb pt 240 9800 ppb pd 17 800 ppb ir 25 1500 ppb ru and 15 400 ppb rh in 100 sulfides the massive sulfide ores are extremely low in pt 4 to 4 5 10 5 the low pge contents suggest that the sulfide ores formed from the silicate magmas that had already experienced prior sulfide separation our calculations indicate that if the first stage basaltic magmas had contained 6 3 ppb pt 6 2 ppb pd and 0 1 ppb ir 0 008 sulfide removal would result in pge depletion in the residual magma with 0 57 ppb pt 0 25 ppb pd and 0 009 ppb ir the jinchuan sulfides were formed by a second stage of sulfide segregation from a pge depleted magma under silicate sulfide liquid ratios r factor ranging from 10 3 to 10 4 in a deep seated staging chamber the massive sulfide ores and some of the net textured sulfide ores exhibit strong negative pt anomalies that cannot be explained by sulfide segregation under variable r factors instead the sulfide melts that formed the massive ores were segregated from magmas experienced prior fractionation of pt fe alloy alternatively the pt may have been selectively leached by hydrothermal fluids during remobilization of the sulfide melts that produced the massive sulfides which occur in cross cutting veins we propose that the jinchuan intrusion and ore bodies were formed by injections of sulfide free and sulfide bearing olivine mushes from a deep seated staging chamber

190pt 186os and 187re 187os systematics of the sudbury igneous complex ontario abstract we measured by negative thermal ionization mass spectrometry ntims re os and 186 os 188 os and 187 os 188 os in 26 samples of 18 ni cu sulfide ores from the falconbridge mccreedy west and strathcona mines at sudbury ontario at mccreedy west and falconbridge the isochron re os ages are 1835 70 ma and 1827 340 ma and the initial 187 os 188 os ratios 0 514 0 019 and 0 550 0 024 respectively the ages agree with the canonical value of 1850 1 ma for the sudbury igneous complex sic for hangingwall and deep zone ores at strathcona the age of 1780 7 ma may reflect resetting by dyke activity the high initial 187 os 188 os of 0 934 0 005 in these ores is distinct from those at mccreedy west and falconbridge strathcona deep copper zone ores have highly radiogenic os giving a mean model age of 1883 54 ma that is similar to ages at mccreedy west and falconbridge but distinct from other strathcona sulfides initial 186 os 188 os in two strathcona ores with low 190 pt 188 os average 0 119 826 0 000 009 n 3 and 0 119 827 0 000 004 n 3 respectively with a grand mean of 0 119 827 0 000 003 this ratio may be slightly lower than the chondritic value at that time similar ores at falconbridge and mccreedy west show more scatter averaging 0 119 855 0 000 008 n 6 and 0 119 867 0 000 020 n 3 respectively these values are substantially suprachondritic the re os isotope systematics of sudbury ores are clearly of crustal origin and may be derived from a binary mixture of superior province and huronian metasedimentary rocks with strathcona falconbridge and mccreedy west ores containing respectively 55 16 and 12 of os from superior sediments the suprachondritic 186 os 188 os at mccreedy west and falconbridge may be due to admixture of archean or paleozoic mafic rocks with 190 pt 188 os 0 1 no trace of the asteroid that produced the sudbury structure has been reported at the whistle mine s poor olivine melanorite inclusions with high ni and os and low 187 os 188 os may contain the signature of a magmatically fractionated asteroidal core contributing 1 to 2 5 metal the s poor melanorite ni and os data are equally well explained by admixture of 40 mantle peridotite however

platinum group minerals from the jinbaoshan pd pt deposit sw china evidence for magmatic origin and hydrothermal alteration the jinbaoshan pt pd deposit in yunnan sw china is hosted in a wehrlite body which is a member of the permian 260 ma emeishan large igneous province elip the deposit is reported to contain one million tonnes of pt pd ore grading 0 21 ni and 0 16 cu with 3 0 g t pd pt platinum group minerals pgm mostly are 10 m in diameter and are commonly te sn and as bearing including moncheite ptte2 atokite pd3sn kotulskite pdte sperrylite ptas2 irarsite irass cooperite pts sudburyite pdsb and pt fe alloy primary rock forming minerals are olivine and clinopyroxene with clinopyroxene forming anhedral poikilitic crystals surrounding olivine primary chromite occurs either as euhedral grains enclosed within olivine or as an interstitial phase to the olivine however the intrusion has undergone extensive hydrothermal alteration most olivine grains have been altered to serpentine and interstitial clinopyroxene is often altered to actinolite tremolite and locally biotite interstitial chromite grains are either partially or totally replaced by secondary magnetite base metal sulfides bms such as pentlandite and chalcopyrite are usually interstitial to the altered olivine pgm are located with the bms and are therefore also interstitial to the serpentinized olivine grains occurring within altered interstitial clinopyroxene and chromite or along the edges of these minerals which predominantly altered to actinolite tremolite serpentine and magnetite hydrothermal fluids were responsible for the release of the platinum group elements pge from the bms to precipitate the pgm at low temperature during pervasive alteration a sequence of alteration of the pgm has been recognized initially moncheite and atokite have been corroded and recrystallized during the formation of actinolite tremolite and then cooperite and moncheite were altered to pt fe alloy where they are in contact with serpentine sudburyite occurs in veins indicating late pd mobility however textural evidence shows that the pgm are still in close proximity to the bms they occur in pge rich layers located at specific igneous horizons in the intrusion suggesting that pge were originally magmatic concentrations that within a pge rich horizon crystallized with bms late in the olivine clinopyroxene crystallization sequence and have not been significantly transported during serpentinization and alteration

geochronological and geochemical constraints on sulfide mineralization in the qingmingshan mafic intrusion in the western part of the proterozoic jiangnan orogenic belt along the southern margin of the yangtze craton abstract the qingmingshan magmatic fe ni cu sulfide deposit is located in the southern margin of the yangtze craton in the western part of the proterozoic jiangnan orogenic belt sulfide mineralization occurs as disseminated zones in a dike like mafic body intruding early neoproterozoic meta sedimentary rocks the host intrusion can be further divided into an upper gabbronorite unit a middle dolerite unit and a lower gabbronorite unit each unit contains at least one disseminated sulfide zone sulfide mineral assemblages are composed of pyrrhotite pentlandite and chalcopyrite zircon u pb dating yields a crystallization age of 847 8 3 8 ma 2 for the intrusion the host rocks are characterized by enrichment in light rare earth elements ree relative to heavy ree and show pronounced negative nb ta anomalies similar to the characteristics of arc mafic igneous rocks worldwide mixing calculations indicate that the variations of th yb n and th nb n in the intrusion are consistent with between 10 and 20 wt crustal contamination of the parental magma the sulfide separates are characterized by elevated 34s values from 1 5 to 3 5 with a peak at 2 6 and by os values from 2 to 89 indicating addition of crustal sulfur and os to the parental magma the trace element data and s os isotopes support the premise that sulfide saturation in the qingmingshan magma was triggered by crustal contamination variations of pge tenors in different sulfide zones can be explained by variable r factors from 300 to 1000 during sulfide segregation from the magma mass balance calculations indicate that the parental magma was severely depleted in pge which could be a primary signature of arc basaltic magma formed by low degrees of partial melting or due to previous sulfide segregation at depth the lithological and mineralization zonation across the dike like qingmingshan mafic intrusion indicates that at least three separate pulses of sulfide charged magma were involved in the formation of the qingmingshan magmatic sulfide deposit the qingmingshan mafic intrusion is interpreted to be a part of a sub arc magma plumbing system coeval ultramafic intrusions formed from more primitive magma in the region are good exploration targets for magmatic sulfide deposits with higher ni cu ratios than the qingmingshan deposit

komatiites and nickel sulfide ores of the black swan area yilgarn craton western australia 4 platinum group element distribution in the ores and genetic implications the black swan komatiite sequence in the eastern goldfields province of the archaean yilgarn craton in western australia is a body of dominantly olivine rich cumulates with lesser volumes of spinifex textured rocks interpreted as a section through an extensive komatiite lava flow field the sequence hosts a number of nickel sulfide orebodies including the silver swan massive shoot and the cygnet and black swan disseminated orebodies the massive sulfide orebodies of the black swan succession are pervasively depleted in all platinum group elements pges particularly pt and pd despite very high ni contents this depletion cannot be explained by r factor variations which would also require relatively low ni tenors the pge depletion could be explained in part if the ores are enriched in a monosulfide solid solution mss cumulate component but requires some additional fractional segregation of sulfide melt upstream from the site of deposition the silver swan orebody shows a remarkably consistent vertical zonation in pge contents particularly in ir ru rh os which increase systematically from very low levels at the stratigraphic base of the sulfide body to maxima corresponding roughly with the top of a lower layer of the orebody rich in silicate inclusions platinum shows the opposite trend but is somewhat modified by remobilisation during talc carbonate alteration a similar pattern is also observed in the adjacent white swan orebody this zonation is interpreted and modelled as the result of fractional crystallisation of mss from the molten sulfide pool the strong ipge depletion towards the base of the orebody may be a consequence of sulfide liquid crystallisation in an inverted thermal gradient between a thin rapidly cooling upper rind of komatiite lava and a hot substrate

the trace metal content of amphibole as a proximity indicator for cu ni pge mineralization in the footwall of the sudbury igneous complex ontario canada alteration veins containing cl poor actinolite and actinolitic hornblende are a common feature throughout the archean aged gneisses and granitoids along the northern margin of the sudbury igneous complex ontario canada crosscutting relations and structural measurements show that the veins postdate the sudbury impact event but predate the emplacement of footwall style cu ni pge platinum group element sulfide ores the veins are four to five times more abundant in brecciated mineralized outcrop than in unbrecciated barren outcrop analyses of vein hosted amphibole by electron microprobe emp and laser ablation icp ms la icp ms show elevated concentrations of ni up to 100 times background increasing from 100 ppm to 1 0 wt cu up to 4 times background and sn up to 2 5 times background in proximity to sulfide veins copper and sn contents in amphibole are only anomalous within 10 to 20 m of mineralization and require quantification by la icp ms however anomalous ni concentrations in vein hosted amphibole may be detected with a high level of confidence solely by emp up to 700 m from mineralization in rocks that contain no visible sulfides in hand sample or thin section and show no bulk rock ni or cu anomalies the relationship between the ni content in amphibole in ppm and mineralization proximity distance d in meters is given by the following equation batchmode documentclass fleqn 10pt legalpaper article usepackage amssymb usepackage amsfonts usepackage amsmath pagestyle empty begin document ni amp 5100 d 0 45 end document the data indicate wide scale ni mobility in hydrothermal solutions in the sudbury footwall the formation of ni rich amphibole in the fracture networks by either the growth of primary ni rich amphibole or metasomatic ni enrichment of preexisting ni poor amphibole was associated with circulation of a sodium and halogen rich fluid between 390o and 550oc nickel may have been released into the footwall environment by extensive hydrothermal alteration of ni rich contact style sulfide ores that lie in the hanging wall of the cu rich footwall style ores in the footwall rocks pre existing fracture networks now amphibole bearing veins acted as common structural pathways first for the circulation of early ni rich fluids associated with leaching in the contact region and the onset of footwall mineralization and second for the emplacement of cu rich footwall style sulfide veins other metal concentrations in amphibole pb zn co show no relationship to mineralization proximity these metals may have been derived locally from country rocks during alteration reactions that promoted amphibole growth in the fractures identification of fracture hosted amphibole with anomalous ni contents in thin section or ni cu sn anomalous amphibole grains liberated from surface weathered rocks hosting sulfide veins may serve as useful proximity indicators for hidden footwall style sulfide deposits at sudbury

heterogeneity of s isotope compositions recorded in the sudbury igneous complex canada significance to formation of ni cu sulfide ores and the host rocks sulfur isotope ratios of sulfide ores and their host rocks and the overlying main mass sequence of norites quartz gabbros and granophyres from the sudbury igneous complex have been analyzed to establish the extent of isotopic heterogeneity of the complex and the impact melt sheet from which it was produced noritic rocks located above the sublayer in the lower portion of the main mass of the sudbury igneous complex are characterized by uniform sulfur isotope ratios with 34s values of 2 59 0 48 rocks from the granophyric portion of the main mass are characterized by elevated and variable 34s values from 4 4 to 14 1 the more 34s enriched s in the granophyre was produced by secondary sulfide precipitation related to hydrothermal alteration systems developed in the upper altered granophyric part of the main mass as it cooled footwall and contact style mineralization from the sublayer show variable 34s values from 0 2 to 4 3 south range mineralization is characterized by low ratios from 0 2 to 2 5 north and northeast range mineralization exhibits locally elevated but variable 34s values for example mineralization from whistle mine varies from 3 1 to 4 3 whereas mineralization from victor varies between 2 4 and 2 9 there is typically only a small difference in s isotope ratio of contact and proximal footwall mineralization country rocks in the area of the sudbury igneous complex are also characterized by a wide range in 34s values and the sulfur isotope homogeneity of the noritic rocks can be explained by mixing of sulfur from several potential sources however the variability present between deposits at the lower contact of the complex requires that country rocks of locally variable sulfur isotope composition interacted with magma at the base of the cooling melt sheet there is no evidence that deposit size correlates with 34s value variations between deposits may involve local s isotope exchange reactions between the country rock and the melt sheet as the melt digested the footwall this study illustrates the application of s isotope data in constraining the scale of convective mixing and contamination in the largest known terrestrial melt sheet

variation in trace element content of magnetite crystallized from a fractionating sulfide liquid sudbury canada implications for provenance discrimination abstract laser ablation icp ms analysis has been applied to many accessory minerals in order to understand better the process by which the rock formed and for provenance discrimination we have determined trace element concentrations of fe oxides in massive sulfides that form ni cu pge deposits at the base of the sudbury igneous complex in canada the samples represent the crystallization products of fractionating sulfide liquids and consist of early forming fe rich monosulfide solution mss cumulates and residual cu rich intermediate solid solution iss this study shows that fe oxide geochemistry is a sensitive petrogenetic indicator for the degree of fractionation of the sulfide liquid and provides an insight into the partitioning of elements between sulfide and fe oxide phases in addition it is useful in determining the provenance of detrital fe oxide in a sulfide melt all lithophile elements cr ti v al mn sc nb ga ge ta hf w and zr are compatible into fe oxide the concentrations of these elements are highest in the early forming fe oxide titanomagnetite which crystallized with fe rich mss upon the continual crystallization of fe oxide from the sulfide liquid the lithophile elements gradually decrease so that late forming fe oxide magnetite which crystallized from the residual cu rich liquid is depleted in these elements this behavior is in contrast with fe oxides that crystallized from a fractionating silicate melt whereby the concentration of incompatible elements such as ti increases rather than decreases the behavior of the chalcophile elements in magnetite is largely controlled by the crystallization of the sulfide minerals with only ni co zn mo sn and pb present above detection limit in magnetite nickel mo and co are compatible in fe rich mss and thus the co crystallizing fe oxide is depleted in these elements in contrast magnetite that crystallized later from the fractionated liquid with cu rich iss is enriched in ni mo and co because fe rich mss is absent the concentrations of sn and pb which are incompatible with fe rich mss are highest in magnetite that formed from the fractionated cu rich liquid at subsolidus temperatures ilmenite exsolved from titanomagnetite whereas al spinel exsolved from the cores of some magnetite locally redistributing the trace elements however during laser ablation icp ms analysis of these fe oxides both the magnetite and its exsolution products are ablated so that the analysis represents the original magmatic composition of the fe oxide that crystallized from the sulfide melt

comment on fractional crystallization of anhydrous sulfide liquid in the system fenicus with application to magmatic sulfide deposits by m e fleet and y pan

geochronological and geochemical study of the baixintan magmatic ni cu sulphide deposit new implications for the exploration potential in the western part of the east tianshan nickel belt nw china abstract several newly discovered magmatic ni cu sulphide deposits are located in the east tianshan nickel belt in the southern part of the central asian orogenic belt in nw china the baixintan magmatic sulphide deposit is one of these new discoveries the host mafic ultramafic intrusion of the baixintan deposit is composed of plagioclase bearing lherzolite pl bearing olivine websterite olivine norite and gabbro zircon crystals from olivine norite yielded a u pb age of 286 0 1 6 ma similar to the ages of other magmatic ni cu sulphide ore deposits in this belt disseminated sulphide mineralization is present in olivine bearing rocks the fo and ni contents of olivine crystals from the sulphide barren samples vary from 81 7 to 85 6 mol and from 956 to 2837 ppm respectively exhibiting a positive fo ni correlation that is consistent with the fractional crystallization of olivine plus removal of small amounts of immiscible sulphide liquid the baixintan mafic ultramafic rocks are characterized by light ree enrichment pronounced negative nb ta anomalies low initial 87sr 86sr ratios from 0 7035 to 0 7039 positive end chur 286 ma values from 6 0 to 7 4 and zircon ehf chur 286 ma values from 11 6 to 15 8 these data indicate that the parental magmas were derived from a depleted mantle source with moderate degrees of contamination by the upper crust the variations in pge tenor in the baixintan deposit which are characterized by positive correlations between ipge and ppge can be explained by variable r factors r 400 3000 mass balance calculations indicate that the parental magma was severely depleted in pge which could be likely due to prior sulphide segregation at depth or sulphide retention in the mantle during partial melting both fractional crystallization and crustal contamination may have played a role in triggering second stage sulphide saturation in the baixintan magma the similarities in ages lithological controls and bulk sulphide composition between the baixintan deposit and other known magmatic ni cu sulphide ore deposits in the east tianshan nickel belt encourage further exploration in the baixintan mafic ultramafic intrusion as well as expansion of the on going regional ni exploration program

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

hydrous sulfide melting experimental evidence for the solubility of h2oin sulfide melts the effect of h 2 o on sulfide melting temperatures has been investigated in the fes pbs zns system at 1 5 gpa revealing that the addition of h 2 o results in a 35 c drop in melting temperature from 900 to 865 c in addition to the melting point depression the solubility of h 2 o is confirmed by the presence of vesicles in the quenched melt no oxide phases were present in any of the run products ruling out oxidation as a cause of the melting point depression confirmation of the solubility of h 2 o in sulfide melts is consistent with the recent suggestion by mungall and brenan 2003 of a magmatic origin for halogen rich alteration associated with magmatic sulfide ore deposits as the hydrous component of the alteration may similarly originate in the fractionating sulfide melt anatectic sulfide melts could be expected to contain more h 2 o than magmatic sulfide melts owing to the lack of a parental silicate melt that buffers the h 2 o content of magmatic sulfide melts fluids expelled from the cooling anatectic melts such as that present during granulite facies metamorphism of sulfide deposits at broken hill australia may have been responsible for associated retrograde hydrothermal alteration

interfacial tension between magmatic sulfide and silicate liquids constraints on kinetics of sulfide liquation and sulfide migration through silicate rocks we have measured the interfacial tension sf between sulfide and silicate melts over the temperature range from 1250 to 1325 c by in situ measurement of the shapes of sessile drops of sulfide immersed in silicate melt sitting upon level alumina substrates the silicate melt was an alkali free synthetic basaltic liquid the sulfide melts were synthetic mixtures of fe cu ni s or fe s o the interfacial tension ranges from about 500 mj m 2 for sulfide of fes composition to approximately 600 mj m 2 for sulfide containing 16 wt cu or 6 5 wt ni and up to 650 mj m 2 for fe s o liquid containing 4 wt o contact angles vary from 150 to 180 showing that sulfide liquid does not wet oxide minerals in silicate magmas the density of sulfide melt does not depend strongly on cu or ni content remaining between 4 0 and 4 5 g cm 3 over the range of cu and ni contents expected in sulfide magmas but increases substantially to about 5 5 g cm 3 in fe s o melts containing 4 wt o our results can be combined with conventional concepts of nucleation theory to indicate that when silicate magmas exist at small degrees of supersaturation sulfide drops may nucleate rarely and at widely spaced intervals leading to kinetic control of the compositions of the resulting droplets in light of our results we use simple scaling arguments to argue that sulfide magmas are not capable of migrating through partially molten silicate rocks by capillary forces alone but may be forced through narrow grain boundaries or grain edges only by the flow of the enclosing silicate melt during melt extraction by compaction of partially molten mantle peridotite it is highly unlikely that silicate flow rates could be sufficiently rapid to permit the entrainment of droplets of sulfide liquid at temperatures below the solidus of enclosing silicate rocks sulfide melt will be free to travel along fractures or grain boundaries the mobility of sulfide melts through completely solidified silicate rocks may account for the widespread observation that late stage highly fractionated sulfide liquids have escaped from cooling bodies of massive sulfide to form veins and disseminations of cu rich sulfide minerals in their silicate host rocks

geology petrography geochemistry and genesis of sulfide rich pods in the lac des iles palladium deposits western ontario canada the lac des iles pd deposits are known for their pd rich sulfide poor mineralization however previously undocumented sulfide rich pods also occur within the intrusion that hosts the deposits given the complex magmatic and hydrothermal history of the mineralization at lac des iles the sulfide rich pods could have crystallized from magmatic sulfide liquids or precipitated from hydrothermal fluids sulfide rich pods occur throughout the stratigraphy in all rock types and along comagmatic shear zones and contain net textured to massive sulfides they can be divided into four main groups based on the variation in mineral assemblages 1 pyrrhotite pentlandite pyrite chalcopyrite magnetite ilmenite 2 chalcopyrite pyrrhotite pentlandite pyrite magnetite ilmenite 3 pyrite pentlandite chalcopyrite pyrrhotite magnetite ilmenite and 4 magnetite ilmenite pyrrhotite pentlandite pyrite chalcopyrite whole rock metal contents and s isotopic compositions do not change with the amount of pyrite present except for slight enrichments in as and bi the presence of an essentially magmatic sulfide mineral assemblage pyrrhotite pentlandite chalcopyrite with pentlandite exsolution flames in pyrrhotite in some pods suggests that the pods crystallized from magmatic sulfide liquids the very low cu contents of the pods suggests that they are mainly cumulates of monosulfide solid solution mss we propose a model whereby sulfide liquids were concentrated into dilation zones prior to crystallizing cumulus mss intermediate solid solution crystallized from the fractionated liquids at the edges of some pods leaving residual liquids enriched in pt pd au as bi sb and te these residual liquids are no longer associated with the pods during subsequent alteration pyrite replaced mss pyrrhotite but this did not affect the platinum group element contents of the pods