basal platinum group element mineralization in the federov pansky layered mafic intrusion kola peninsula russia the 2501 to 2446 ma federov pansky layered mafic intrusion in the central part of the kola peninsula russia is situated along the northern contact of the early proterozoic imandra varzuga rift and archean granite gneiss the federov pansky intrusion has eight major zones from bottom to top 1 marginal zone mafic schists 50 to 100 m 2 taxitic gabbronorite zone bpca 150 to 300 m 3 norite zone bcpa pbc 200 m 4 main gabbronorite zone pacb 1 000 m 5 lower layered horizon zone bc pc pbac 100 m 6 gabbro zone pacb pbac 1 500 m 7 upper layered horizon zone pocab 250 m 8 upper gabbro zone pacb 400 m the taxitic gabbronorite zone is restricted to the federov and east lastjavr blocks this zone is distinctive due to its pegmatitic taxitic textures and abundant norite xenoliths concentrated near its upper contact with the norite zone chemically the taxitic gabbronorite is more feldspathic and iron enriched than the overlying mgo and cr 2 o 3 rich norite zone and norite xenoliths the zone hosts cu ni pge mineralization with disseminated sulfides which is continuous for over 2 5 km along strike and 150 to 200 m downdip 98 percent of the sulfides consist of varying amounts of pyrrhotite chalcopyrite and pentlandite the mineralization is divided into an upper mineralized section with two higher grade lenses a and b and the restricted lower mineralized section with six narrower lenses the lower mineralized section is less continuous and less uniform in terms of cu ni pge distribution the norite xenoliths and blocks occurring within the taxitic gabbronorite zone are practically barren of sulfide and can dilute higher pge and base metal grades in the gabbronorite matrix average total pge grades in rocks do not exceed a few grams per tonne the mineralization is palladium rich with a pd pt ratio from 4 22 to 4 34 rh and au grades are 0 1 to 0 5 g t os and ir grades are the most common pge bearing minerals are merenskyite moncheite kotulskite sobolevskite and michenerite less common are sperrylite and vysotskite braggite the cu ni pge sulfides are primarily magmatic in origin this is supported by s isotope compositions with a narrow range of 34 s of 0 2 to 1 4 percent and s se ratios of 1 050 to 3 300 a three stage process is postulated for the genesis of the federov mineralization this involves the intrusion of a more fractionated and sulfur saturated gabbronorite magma and its brecciation and mixing with a residual primitive magma forming immiscible sulfides that scavenged cu ni pge the federov resembles other contact type mineralization such as in the portimo intrusion in finland and the lac des iles and east bull lake intrusions in ontario canada

self destructive sulfide segregation systems and the formation of high grade magmatic ore deposits the metal concentrations of sulfide liquids depend upon the mass of silicate magma that they are able to process for metals some high grade magmatic ni cu pge deposits and many magmatic platinum group element pge ni cu deposits demand very high magma sulfide ratios that seem improbable in the light of physical and kinetic constraints recent models for some high grade deposits invoke multistage upgrading processes in which an early formed sulfide liquid reacts with multiple later batches of silicate magma quantitative models of this open system process demonstrate that it is indeed more efficient than a closed system however it is likely that most later magmas in such a system will be sulfur undersaturated and will thus partly redissolve preexisting sulfide liquids further increasing metal concentrations in the remaining sulfide liquids this combined process is termed multistage dissolution upgrading and quantitative models show that it could reduce the mass of silicate magma that must be processed by as much as two orders of magnitude furthermore if sulfide liquids are extensively dissolved during enrichment their base metal concentrations will generally stabilize at a limiting value whereas their pge concentrations will generally increase without limit this divergence could account for unusually high pge concentrations and high pge base metal ratios in many pge dominated deposits the multistage dissolution upgrading model is tested using reasonable degrees of dissolution in the context of natural deposits in the noril sk area and the bushveld intrusion the models reproduce the observed sulfide compositions significantly better than previous models and are also consistent with other aspects of the geology of these deposits thus dynamic sulfide forming magmatic systems may be intrinsically self destructive but this apparently undesirable attribute could play an important role in forming high grade deposits however dissolution could lead to the complete destruction of sulfide liquids and the return of all metals to later magma batches in this case no sulfide deposit would remain but metal depletion signatures indicating sulfide liquid segregation would be preserved in rocks that crystallized from early magmas caution is therefore advised in the use of magmatic depletion signatures to infer overall mineral potential or to estimate the possible sizes of undiscovered magmatic sulfide deposits

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

replacement of base metal sulfides by actinolite epidote calcite and magnetite in the ug2 and merensky reef of the bushveld complex south africa interaction of base metal sulfides pyrrhotite pentlandite and chalcopyrite with aqueous fluids in the ug2 chromitite layer and the merensky reef in the western bushveld complex has produced four common replacements 1 replacement of sulfides and orthopyroxene by actinolite or tremolite 2 replacement of sulfides and plagioclase by epidote 3 replacement of sulfides by calcite and 4 replacement of sulfides by magnetite the first three replacements are directly related to the presence of sulfides in the rocks and occur at the grain scale silicate minerals that are not in direct contact with sulfides are usually not affected the replacement of sulfides by magnetite accompanies regional serpentinization superimposed on the union section platinum group minerals including ru pt and pd sulfides pt and pd tellurides and pd arsenides occur in replacement aureoles around sulfide aggregates as well as within the aggregates suggesting that the platinum group minerals are more resistant to hydrothermal alteration than the associated base metal sulfides redistribution of chalcopyrite at least at the millimeter scale variable losses of s and ni and perhaps decoupling of pt and pd at the centimeter scale took place during secondary hydrothermal alteration these effects should be considered before models of primary mineralization processes can be meaningfully applied

extreme enrichment of se te pge and au in cu sulfide microdroplets evidence from la icp ms analysis of sulfides in the skaergaard intrusion east greenland the platinova reef in the skaergaard intrusion east greenland is an example of a magmatic cu pge au sulfide deposit formed in the latter stages of magmatic differentiation as is characteristic with such deposits it contains a low volume of sulfide displays peak metal offsets and is cu rich but ni poor however even for such deposits the platinova reef contains extremely low volumes of sulfide and the highest pd and au tenor sulfides of any magmatic ore deposit here we present the first la icp ms analyses of sulfide microdroplets from the platinova reef which show that they have the highest se concentrations up to 1200 ppm and lowest s se ratios 190 700 of any known magmatic sulfide deposit and have significant te enrichment in addition where sulfide volume increases there is a change from high pd tenor microdroplets trapped in situ to larger low tenor sulfides the transition between these two sulfide regimes is marked by sharp peaks in au and then te concentration followed by a wider peak in se which gradually decreases with height mineralogical evidence implies that there is no significant post magmatic hydrothermal s loss and that the metal profiles are essentially a function of magmatic processes we propose that to generate these extreme precious and semimetal contents the sulfides must have formed from an anomalously metal rich package of magma possibly formed via the dissolution of a previously pge enriched sulfide other processes such as kinetic diffusion may have also occurred alongside this to produce the ultra high tenors the characteristic metal offset pattern observed is largely controlled by partitioning effects producing offset peaks in the order pt pd au te se cu that are entirely consistent with published d values this study confirms that extreme enrichment in sulfide droplets can occur in closed system layered intrusions in situ but this will characteristically form ore deposits that are so low in sulfide that they do not conform to conventional deposit models for cu ni pge sulfides which require very high r factors and settling of sulfide liquids

mineralogical and isotopic evidence for phenocryst matrix disequilibrium in the garner mountain andesite petrographic trace element and isotopic evidence demonstrates that magma mixing preceded the eruption of the garner mountain andesite the flow contains reversely zoned plagioclase phenocrysts and amphibole pseudomorphs composed of plagioclase clinopyroxene orthopyroxene and opaque oxides partially resorbed quartz grains are also present in contrast to the isotopically uniform matrix plagioclase phenocrysts have 87sr 86sr ratios that correlate negatively with matrix sr and positively with matrix rb abundances these observations demonstrate increasing isotopic disequilibrium between the plagioclase and matrix in the more evolved varieties of the flow

remobilization of andesite magma by intrusion of mafic magma at the soufriere hills volcano montserrat west indies the 1995 1999 eruption of the soufriere hills volcano montintroduction serrat has produced a crystal rich andesite containing quenchthe soufriere hills volcano montserrat located in the textured mafic inclusions which show evidence of having been molten lesser antilles island arc in the west indies began to when incorporated into the host magma individual crystals in the erupt on 18 july 1995 after about 350 years of dormancy andesite record diverse histories amphibole phenocrysts vary from young et al 1998b the eruption was preceded by a pristine and unaltered to strongly oxidized and pseudomorphed by period of seismic swarms which began in january 1992 anhydrous reaction products plagioclase phenocrysts are commonly previous earthquake crises have occurred on montserrat reverse zoned often with dusty sieve textures reverse zoned rims are in 1896 1897 1932 1935 and 1966 1967 powell 1938 also common on orthopyroxene phenocrysts pyroxene geothermometry shepherd et al 1971 initial phreatic and phregives an average temperature of 858 20 c for orthopyroxene atomagmatic activity was followed by extrusion of an phenocryst cores whereas reverse zoned rims record temperatures andesitic lava dome in november 1995 pyroclastic flows from about 880 to 1050 c the heterogeneity in mineral rim generated by gravitational collapse of the unstable dome compositions zoning patterns and textures is interpreted as reflecting have been the dominant form of activity throughout the non uniform reheating and remobilization of the resident magma eruption but periods of explosive activity producing body by intrusion of hotter mafic magma convective remobilization pumice flows and falls have also occurred robertson et results in mixing together of phenocrysts that have experienced al 1998 young et al 1998b dome growth ceased different thermal histories depending on proximity to the intruding suddenly in march 1998 and further activity up to may mafic magma the low temperature and high crystallinity are 1999 has mainly involved gravitational collapses of the interpreted as reflecting the presence of a cool highly crystalline dome and periods of ash venting with some small scale magma body beneath the soufriere hills volcano the petrological vulcanian explosive events observations in combination with data on seismicity extrusion rate the soufriere hills volcano is the only active centre and so2 fluxes indicate that the current eruption was triggered by on montserrat the volcano is a composite of at least recent influx of hot mafic magma five andesitic lava domes flanked by pyroclastic deposits rea 1974 identified four other volcanic centres all

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

the formation of low volume high tenor magmatic pge au sulfide mineralization in closed systems evidence from precious and base metal geochemistry of the platinova reef skaergaard intrusion east greenland the majority of magmatic platinum group element pge deposits in layered mafic ultramafic intrusions are characterized by visible cu ni sulfide mineralization often located in the lower parts of a magmatic stratigraphy that show evidence of multiple magma injections and crustal contamination the platinova reef hosted by the 55 ma skaergaard intrusion east greenland is an example of a rarer type of pge deposit typified by a pd au cu dominant ni pt poor sulfide assemblage present in the upper parts of the host intrusion such deposits are generally considered to form through prolonged fractional crystallization of the magma with magnetite crystallization playing a role in late stage s saturation in the case of the skargaard intrusion the crystallization of the cumulate rocks and the generation of the mineralization hosted within them occurred within a closed system from a single homogenized batch of magma the platinova reef is characterized by offsets in the stratigraphic position of individual metal peaks an anomalously low sulfide content 1 ppm the intermediate zone pd 0 1 1 ppm the au zone au 1 ppm and the upper cu zone cu 200 ppm with precious metals 3 to 10 4 ppm low cu pd ratios and a remarkable upward decrease in pd au ratio from 40 to 1 whereas the sulfides in the cu zone are lower tenor 10 3 ppm pd higher volume and have high cu pd ratios and pd au to explain these features we present a multistage model of preconcentration dissolution upgrading and further metal enrichment this involves initial s saturation of the skaergaard magma at a late stage in the crystallization history the sulfide liquid produced scavenged metals from the entire volume of the chamber as it sank but was then dissolved as it came into contact with hotter fe rich and s undersaturated magma at the bottom of the chamber producing a highly metal rich magma layer at the bottom of the chamber this layer then became s saturated as a result of continued magnetite crystallization with the tiny sufide droplets that segregated into this precious metal enriched magma layer becoming highly enriched in pge themselves these were then trapped in situ by the crystallizing cumulate pile forming the subzone pd zone and intermediate zone sulfides formed in the rest of the chamber which was pge depleted at this stage would have been of low tenor these sulfide droplets grew and settled concentrating any remaining au when they encounter the floor to form the au zone and formed the low tenor sulfides of the cu zone above this we propose that the platinova reef exhibits an unusual example of a style of magmatic precious metal mineralization formed through sulfide dissolution upgrading in the latter stage of crystallization of a closed system the offsets in individual metal peaks mineralization demonstrate the relative partitioning of pd pt au cu into a sulfide liquid from a silicate magma and demonstrates the importance of partitioning behavior in low volume magmatic sulfide melts this feature can lead to the characteristic stratigraphic offsets in peak metal abundances the role of magnetite crystallization appears to be an important control on s saturation in such systems and thus may be an important indicator of the location of mineralized horizons in addition in such deposits indicators of crustal contamination by external s and multiple injections of magma common features of more ni rich pge reefs are less likely to be present

the role of komatiitic and picritic magmatism and s saturation in the formation of ore deposits abstract the introduction of high temperature high magnesium komatiitic and picritic magmas into the earth s upper crust has given rise either directly or indirectly to many of the world s major ore deposits there is a direct association between komatiitic magmatism and kambalda style ni cu pge deposits the link between magma type and mineralization is not as clear cut in the case of the noril sk cu ni pge deposits but nevertheless there is an association between picritic magmatism and ore deposit development komatiitic and or picritic magmatism may also have contributed to the formation of many types of hydrothermal ore deposits recent nd isotope data generated by kent et al 1994 provide strong evidence for the hypothesis proposed by keays in 1983 that the au in archaean au deposits was derived either directly or indirectly from komatiites through the action of metamorphic fluids the importance of komatiitic and picritic magmas in ore forming processes arises from the fact that they are among the few mafic ultramafic magma types that are s undersaturated at the time of magma formation s saturation of magmas leads to marked depletion in the chalcophile metals for example czamanske and moore 1977 estimated that a third of the original cu and ni contents of morb were lost from the magmas due to extraction into magmatic sulphides the depletion in au and the pge is much greater due to their much larger partition coefficients keays and scott 1976 komatiitic and picritic magmas are s undersaturated because they are high temperature magmas produced by large degrees of partial melting of upper mantle sourc regions that were already depleted in s through earlier partial melting events most mafic magmas produced by less than 25 partial melting are s saturated and hence depleted in the ore forming chalcophile elements in contrast komatiitic and picritic magmas have their full complement of chalcophile metals when they do become s saturated they form sulphides that are strongly enriched in ni cu au pge and other strongly chalcophile metals these may accumulate to form ore deposits directly e g magmatic ni cu pge sulphides or be dispersed in komatiitic picritic rocks or their fractionation products making these source rocks for hydrothermal au or vms deposits

textural mineralogical and stable isotope studies of hydrothermal alteration in the main sulfide zone of the great dyke zimbabwe and the precious metals zone of the sonju lake intrusion minnesota usa stratigraphic offsets in the peak concentrations of platinum group elements pge and base metal sulfides in the main sulfide zone of the great dyke and the precious metals zone of the sonju lake intrusion have in part been attributed to the interaction between magmatic pge bearing base metal sulfide assemblages and hydrothermal fluids in this paper we provide mineralogical and textural evidence that indicates alteration of base metal sulfides and mobilization of metals and s during hydrothermal alteration in both mineralized intrusions stable isotopic data suggest that the fluids involved in the alteration were of magmatic origin in the great dyke but that a meteoric water component was involved in the alteration of the sonju lake intrusion the strong spatial association of platinum group minerals principally pt and pd sulfides arsenides and tellurides with base metal sulfide assemblages in the main sulfide zone of the great dyke is consistent with residual enrichment of pt and pd during hydrothermal alteration however such an interpretation is more tenuous for the precious metals zone of the sonju lake intrusion where important pt and pd arsenides and antimonides occur as inclusions within individual plagioclase crystals and within alteration assemblages that are free of base metal sulfides our observations suggest that pt and pd tellurides antimonides and arsenides may form during both magmatic crystallization and subsolidus hydrothermal alteration experimental studies of magmatic crystallization and hydrothermal transport deposition in systems involving arsenides tellurides antimonides and base metal sulfides are needed to better understand the relative importance of magmatic and hydrothermal processes in controlling the distribution of pge in mineralized layered intrusions of this type

precious metals in the jimberlana intrusion western australia implications for the genesis of platiniferous ores in layered intrusions a neutron activation study of the distribution of ir pd and an in the jimberlana intrusion has shown that pd and au partition strongly into the sulfides the pd content of sulfides is governed to a large degree by the r factor a measure of the amount of silicate liquid in equilibrium with the sulfide melt the pd content of the sulfide horizons from the center of the jimberlana intrusion is high but appreciably less than that of the merensky reef and the pt horizon of the stillwater complex the comparatively low pd content of the jimberlana sulfides is believed to be due to the sulfides having reached equilibrium with a smaller volume of silicate liquid than the pt rich sulfides of the bushveld and stillwater complexes at the margin of jimberlana the sulfide content of the rocks may be as high as 10 percent these sulfides have precipitated rapidly resulting in a very low r factor and consequently they have anomalously low precious metal contents variations in the ir content of rocks are independent of the presence of sulfides in the jimberlana intrusion this may have resulted from the f sub o 2 of the magma being less than that of the ir 2 s 3 ir buffer allowing pd but not ir to enter the sulfide melt

genesis of the marathon cu platinum group element deposit port coldwell alkalic complex ontario a midcontinent rift related magmatic sulfide deposit the marathon copper and platinum group element pge deposit is hosted by the two duck lake intrusion located at the eastern margin of the port coldwell alkalic complex northwestern ontario the two duck lake intrusion is subdivided into an upper layered zone and a lower unlayered zone that consists of olivine gabbro and pegmatite with trace amounts of granophyre the sulfides are hosted in the lower zone which is referred to here as two duck lake gabbro petrography mineral chemistry and geochemical data imply that two duck lake gabbro crystallized in situ from a plagioclase crystal mush there is no geochemical evidence for metasomatic alteration of the gabbro the sulfides are disseminated in gabbro and pegmatite and consist of approximately equal proportions of chalcopyrite and pyrrhotite and minor amounts of pentlandite and pyrite samples of two duck lake gabbro exhibit a significant correlation between sulfur and ni ir rh pt pd au and cu further the pd ir and pd ni ratios increase with increasing concentrations of rh pt pd au and cu consequently bulk sulfide compositions are best explained by the separation of a sulfide liquid from a gabbroic magma this origin is contrary to that proposed by previous workers they presented detailed petrographic and mineral chemical data that imply inter action of cl bearing hydrous fluids and sulfides at low temperatures in the light of our study we interpret these observations to indicate that elements migrated over very short distances and that bulk sulfides were not enriched with cu and pge as previously proposed a model for the genesis of the marathon deposit is proposed many characteristics of the marathon deposit bear a striking resemblance to observations reported in disseminated sulfide deposits at the base of the duluth complex minnesota the features include mineral textures abundances and compositions crystallization paths for the host gabbroic bodies silicate sulfide associations trace element trends and chalcophile element fractionation trends the similarities imply that the marathon deposit and deposits in the duluth complex formed by analogous processes

insights into the extreme pge enrichment of the w horizon marathon cu pd deposit coldwell alkaline complex canada platinum group mineralogy compositions and genetic implications the w horizon marathon cu pd deposit in the mesoproterozoic midcontinent rift is one of the highest grade pge repositories in magmatic ore deposits world wide the textural relationships and compositions of diverse platinum group mineral pgm and sulfide assemblages in the extremely enriched ores 100 ppm pd pt au over 2 m of the w horizon have been investigated in mineral concentrates with 10 000 pgm grains and in situ using scanning electron microprobe and microprobe analyses here we show from ore samples with concentrations up to 23 1 pd ppm 8 9 pt ppm 1 4 au ppm and 0 73 rh ppm the diversity of minerals n 52 including several significant unknown minerals and three new mineral species marathonite pd25ge9 mcdonald et al 2016 palladogermanide pd2ge ima 2016 086 mcdonald et al 2017 kravtsovite pdag2s ima no 2016 092 vymazalova et al 2017 the pgm are distributed as pg sulfides 52 vol arsenides 34 vol intermetallics of au ag pd cu and pd ge 10 vol and bismuthides and tellurides 4 vol the discovery of abundant 330 grains large unknown sulfide minerals with rh allows us to present analyses three significant potentially new minerals wuk 1 wuk 2 wuk 3 that are all clearly enriched in rh averaging 4 2 8 5 and 28 21 wt rh respectively several examples of paragenetic sequences and mineral chemical changes for enrichment of cu pd and rh with time are revealed in the pgm and base metal sulfides we suggest this enhanced metal enrichment formed in response to increasing fo2 causing the oxidation of fe2 to fe3 and to a lesser extent s phase relations in the ag pd s rh ni fe s pd ge au pd cu ag pd ag te systems help constrain the crystallization temperatures of the majority of ore minerals in the w horizon at 500 c or moderate to high subsolidus temperatures 400 600 c local transport by aqueous fluids becomes evident as minerals recrystallize down to 300 c the pge enriched w horizon ores exhibit a complex post magmatic history dominated by the effects of oxidation during cooling of a cu pge enriched magma source from a deep reservoir

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

selenium and sulfur concentrations in country rocks from the duluth complex minnesota usa implications for formation of the cu ni pge sulfides various studies suggest that the formation of a magmatic ni cu platinum group element pge sulfide deposit requires addition of s from the country rocks into the magma many sulfide deposits have s se ratios higher than primary magmas which is attributed to the preferential addition of s from the country rocks however this has not been clearly demonstrated because most studies do not determine se in the country rocks partly because although se concentration in igneous rocks can be assessed by most routine analytical techniques their detection limits are too low for measuring with precision the level of se in sedimentary rocks we have determined se abundances using thiol cotton fiber tcf combined with instrumental neutron activation analysis inaa s and delta super 34 s on the magmatic sulfides of the duluth complex and on the host rock sediments of the virginia formation our data show that the pelitic and metapelitic rocks of the virginia formation are characterized by low s se ratios approximately 3 000 close to the mantle values whereas the s rich layer known as the bedded pyrrhotite unit has high s se ratios approximately 20 000 consequently most of the virginia formation sediments and xenoliths are unsuitable as a source of s because they have s se ratios and delta super 34 s values lower than those of the mineralized rocks 10 000 only the bedded pyrrhotite unit which is present at the contact with the intrusion and as partly digested xenoliths within the intrusion has s se ratios and delta super 34 s values higher than those of the magmatic sulfides and could thus be the source of the s furthermore the presence of sulfides in the norites around the xenoliths suggests that the s was released from the xenolith during melting of the xenolith detailed sampling from the xenoliths into the norite shows that the s se ratio and delta super 34 s decrease with distance from the xenolith our results favor a mechanism of crustal s contamination by in situ assimilation of bedded pyrrhotite unit xenoliths

segregation of magmatic fluids and their potential in the mobilization of platinum group elements in the south kawishiwi intrusion duluth complex minnesota evidence from petrography apatite geochemistry and coexisting fluid and melt inclusions abstract pegmatitic and other felsic rock pockets and dike like intrusions are abundant in the south kawishiwi intrusion of the duluth complex including the basal cu ni pge mineralized units these occurrences are found as pockets pods or as veins and contain abundant accessory apatite and quartz quartz hosts primary fluid inclusions as well as silicate melt inclusions combined microthermometry and raman spectroscopy helped to determine the bulk composition of primary fluid inclusions that are co 2 rich 95 mol and contain small amounts of h 2 o 4 5 mol ch 4 0 4 mol and trace n 2 respectively this combined technique also made it possible to measure total homogenization temperatures of the inclusions th tot 225 10 c otherwise not detectable during microthermometry silicate melt inclusions have been quenched to produce homogeneous glasses corresponding to the original melt composition of the entrapped melt is granitoid peraluminous and is very poor in mafic components we interpret the melt as a product of partial melting of the footwall rocks due to the contact effect of the south kawishiwi intrusion the presence of co 2 in the vapor bubbles of the quenched melt inclusions and petrographic evidence suggest that the fluid and melt inclusion assemblages are coeval the composition of the fluid and melt phase implies that the fluid originates from the mafic magma of the south kawishiwi intrusion and the fluid and melt phases coexisted as a heterogeneous melt fluid system until entrapment of the inclusions coexistence of primary fluid and melt inclusions makes it possible to calculate a minimum entrapment pressure 1 7 kbar and thus estimate formation depth 5 8 km for the inclusions chlorine is suggested to behave compatibly in the silicate melt phase in the fluid melt system represented by the inclusions indicated by the high up to 0 3 cl concentrations of the silicate melt and co 2 rich nature of the fluid apatite halogen contents provide further details on the behavior of cl apatite in pegmatitic pockets often has elevated cl concentrations compared to troctolitic rocks suggesting enrichment of cl with progressive crystallization systematic trends of cl loss at some differentiated melt pockets suggest that in some places cl exsolved into a fluid phase and migrated away from its source the segregation of cl from the melt is probably inhibited by the presence of co 2 rich fluids until the last stages of crystallization increasing the potential for the development of late stage saline brines platinum group minerals are often present in microcracks in silicate minerals in late stage differentiated sulfide veinlets and in association with chlorapatite indicating the potential role of cl bearing fluids in the final distribution of pges

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

last glacial pollen climate reconstructions from northland new zealand despite wide ranging interest in the vegetation and climate of northland new zealand during the last glacial cycle the region and timeframe lack quantitative climate reconstructions while land based pollen records have tended to be poorly dated and fragmentary the region is also important for geochronology due to the co occurrence of the rotoehu tephra a widely dispersed isochron near the current limits of radiocarbon dating and extensive subfossil wood remains of agathis australis with strong dendrochronological and dendroclimatological potential we present new pollen records and temperature reconstructions from three sites set in coastal dune belts from western mid northland 35 s all containing rotoehu tephra that collectively span the last 70 ka the phases and amplitude of temperature changes broadly align with those reported from elsewhere in new zealand and with marine isotope climate stratigraphic records including maximum temperature depression of 6 8 c during the last glacial maximum we argue that these climatic patterns are intimately linked to shifts in the southern westerly wind belt the northern margins of which extend to the region today correspondence between the northland temperature shifts and atmospheric co2 supports the model of ocean atmosphere co2 flux modulated by latitudinal migration of the southern westerlies copyright 2017 john wiley sons ltd

a hydrothermal ni as pge geochemical halo around the miitel komatiite hosted nickel sulfide deposit yilgarn craton western australia the remobilization of metals during postdeposition hydrothermal alteration of magmatic sulfide ores has the potential to result in large haloes the recognition of which could potentially enlarge the detectable footprint of this ore type the miitel komatiite hosted nickel sulfide deposit in western australia was used as a case study to investigate the nature and 3 d geometry of the geochemical halo created by the remobilization of base metals gold and platinum group elements pge into the rocks surrounding the mineralization at miitel anomalous metal enrichment is found in the country rocks surrounding the massive sulfides up to 250 m away from the ore this enrichment detected using portable x ray fluorescence pxrf and backed up by laboratory analyses occurs in the mount edwards footwall basalt within decimeters of the contact with the overlying widgiemooltha komatiites it is associated with the presence of nickel arsenides gersdorffite and minor nickeline are concentrated within small quartz and carbonate veinlets and are interpreted to form during the circulation of arsenic rich hydrothermal fluids results of lead fire assay analyses and in situ laser ablation inductively coupled plasma mass spectrometer la icp ms analyses indicate high pge concentrations pd and pt and minor gold associated with the observed nickel and arsenic enrichment results from a larger regional scale study combined with this pge enrichment suggest that the massive nickel sulfides from the miitel ore are the source of the remobilized nickel in the country rocks the presence of pd and pt enriched trace arsenide phases in country rocks and shear zones may be a generally applicable proximity indicator for nickel sulfides in hydrothermally altered terranes

pt and pd mobility in hydrothermal fluids evidence from komatiites and from thermodynamic modelling abstract komatiite host rocks and ores provide a natural laboratory for the study of pt and pd during hydration and carbonation of ultramafic rocks the degree of correlation between pt and pd and of those elements with lithophile elements such as ti in komatiitic rocks and ores is strongly dependent on the magmatic sulfide content of the rock pt and pd are typically very strongly correlated within s poor komatiites and in disseminated ores containing 5 volume or less magmatic sulfides in contrast they are almost completely decoupled in sulfide rich ore samples thermodynamic modelling based on the existing body of published experimental data on pt and pd solubilities suggests that pd and pt can be readily transported as bisulfide complexes in acidic neutral solutions under reduced and moderate oxidation condition at 300 c and chloride complexes are only important under extremely acidic oxidised conditions pd is much more soluble than pt in the case of fluids in sulfide rich environments in equilibrium with the characteristic assemblages found within altered and metamorphosed komatiites solubilities of both elements are much lower in sulfide poor environments especially where ph values are constrained to neutral values by the near ubiquitous presence of carbonate minerals in the alteration assemblage this accounts for the evident near immobility of pt and pd in even the most altered silicate host rocks as compared with their wide dispersion in sulfide rich ores

variable regimes in magma systems documented in plagioclase zoning patterns el misti stratovolcano and andahua monogenetic cones abstract magmas may experience closed or open system evolution during their ascent and evolution in the upper crust chemically closed system processes can involve heat transfer from underplating mafic magmas or decompression due to magma ascent on the other hand newly injected magmas can mix with the residing magma and hybridize plagioclase zonation patterns and electron microprobe major and trace element analysis constrain these contrasting scenarios for andesites from the 80 km3 el misti stratovolcano 5822 m and a field of relatively small monogenetic andahua scoria cones both in southern peru in particular fe concentration in plagioclase reveals valuable information within a magmatic system to explore the dominance of closed vs open system processes large and correlated anorthite fe contrasts at resorption zones identify compositional mixing related to recharge subhorizontal an fe variations record thermal or water induced effects el misti volcano a large but still relatively youthful stratovolcano is dominated during most of its approx 120 ka history by closed system effects during its evolution recharge and mixing mostly occurred cryptically as it is not recorded in drastic compositional changes in magmas or their phenocrysts a small volume erupted at el misti however is affected by strong open system behaviour as reflected in strongly correlated variations in an and fe contents of plagioclase compositions its crystal population is texturally and chemically very similar to lavas of the monogenetic cinder cones of the andahua volcanic field for the el misti magma reservoir resorption events caused by thermal effects or magma ascent are more frequent in comparison to the actual eruption frequencies many cycles of closed system evolution heat transfer and decompression therefore occurred without resulting in an eruption plagioclase zonations from lavas of the monogenetic andahua field indicate that any mafic batch that intruded the much smaller reservoirs immediately triggered an eruption by contrast a large magma system that feeds el misti volcano can easily accommodate a new batch without causing eruption

primary cumulus platinum minerals in the monts de cristal complex gabon magmatic microenvironments inferred from high definition x ray fluorescence microscopy an unusual occurrence of pt enriched pyroxenites in the monts de cristal igneous complex is characterized by unusually high ratios of pt to other platinum group elements pges and very low cu and sulfide contents synchrotron x ray fluorescence microscopy was used to identify over a hundred discrete grains of platinum minerals and relate their occurrence to textural associations in the host heteradcumulate orthopyroxenites element associations backed up by fib sem and pixe probe observations indicate that most of the pt is associated with either as or trace cu ni rich sulfides or both some of the pt as grains can be identified as sperrylite and most are likely to be pt fe alloy the relative abundances and volumes of pt minerals to sulfide minerals are very large compared with typical magmatic sulfides almost all of the grains observed lie at or within a few tens of m of cumulus orthopyroxene grain boundaries and there is no significant difference between the populations of grains located inside or outside plagioclase oikocrysts these oikocrysts are inferred to have crystallized either at the cumulus stage or very shortly thereafter on the basis of their relationship to ti enrichment in the margins of pyroxene grains not enclosed in oikocrysts this relationship precludes a significant role of trapped intercumulus liquid in pt deposition or mobilization and also allows a confident inference that pt rich and pt as enriched phases precipitated directly from the magma at the cumulus stage these observations lead to the conclusion that fractionation of pt from other pges in this magmatic system is a consequence of a solubility limit for solid pt metal and or pt arsenide

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

applications of the combined portable xrf benchtop sem methodology to pge exploration abstract portable xrf pxrf and benchtop scanning electron microscopes equipped with energy dispersive systems bsem eds are two real time analytical techniques that can be combined to collect on site lithogeochemical and mineral chemical results at dramatically reduced cost and time compared to traditional analytical methods the coldwell complex northwestern ontario is used as a case study on how the combination of these techniques can be applied to mineral exploration our results show that whole rock ba v ti cu s determined by pxrf and plagioclase olivine and clinopyroxene compositions measured by bsem eds can be applied to exploration for pge deposits cu s ratios for disseminated sulfides are a proxy for metal tenor which can be applied as a vector towards higher grade mineralization potential magma recharge zones are identified by inspecting down hole variations in plagioclase olivine and clinopyroxene compositions fluctuating down hole variations in these parameters are interpreted to reflect episodic magma recharge whether rocks contain pge mineralization can initially be assessed by documenting the variability of mineral chemistry i e the greater variability of mineral chemistry could be used to vector higher grade pge mineralization particularly if the mineralization is conduit related lastly geochemical mapping of the igneous stratigraphy enables identification of favorable hosts for mineralization down hole whole rock variations in ba and v ti from pxrf and mineral chemical profiles from bsem eds are used to discriminate the mineralized marathon series from the barren layered series throughout the coldwell complex whole rock ba and v ti from pxrf and mineral chemical results from bsem eds could prove useful in other settings of the midcontinent rift e g the duluth complex eagle and eagle east intrusions tamarack intrusive complex and the sonju lake intrusion and elsewhere e g the stillwater complex to identify mineralized host rock types an additional important application is a rapid interpretation of petrogenesis down hole variations in olivine clinopyroxene mg fe exchange coefficients determined by bsem eds analyses show that olivine clinopyroxene pairs in the marathon series units particularly for those within pge mineralized zones have compositions that are closer to chemical equilibrium constant compared to units of the barren layered series highly variable and thus could be a tool for interpreting petrogenetic processes active in the magma chamber or during the mineralization forming event

pgm facies variations for cu pge deposits in the coldwell alkaline complex ontario canada abstract accurate characterization of the platinum group mineral pgm assemblages for cu ni pge deposits are typically constrained by sample size and the difficulty of finding statistically significant numbers of grains which is expected given the low concentrations of platinum group elements 75 m can account for large fractions of total mass despite these limitations an accurate survey of pgm from different deposit types would have significant value towards developing deposit models and respective exploration strategies in this study we present results for a comprehensive evaluation of pgm at four copper pge occurrences hosted within separate but co genetic gabbro or troctolite intrusions in the coldwell alkaline complex and confirm that accurate surveys are possible with sufficient sample material and efficient pgm concentration methods the pgm concentration methods used include 1 hydroseparation of sieved size fractions of pulverized material and 2 panning of grain separates produced by electric pulse disaggregation of drill core specimens a favourable comparison of the results has verified the reliability of each method and added confidence that the pgm assemblages identified at three of the four locations are fully characterized precious metal mineral pmm assemblages are determined for the main zone and w horizon at the marathon deposit and the main zones at each of the geordie lake deposit and area 41 occurrence a total of 10 824 pmm grains pge and au ag and 68 mineral species including 16 unknown minerals were identified of which 768 grains and 31 species occur at the main zone 523 grains and 41 species at area 41 9485 grains and 43 species at w horizon and 56 grains and 12 species at geordie lake the pmm are grouped as follows pd ge pge s as pt fe alloy pd cu pb au pd ni s pd pt sn pt as pd as pd pt sb as pd pt bi te and au ag all of the deposits were found to contain similar proportions of pd pt sb as pd pt bi te and au ag minerals but the w horizon and area 41 are distinguished from the marathon main zone and geordie lake deposits by the presence of minerals in the pge s as pt fe alloy pd cu pb au and pd ge groups taken together the pmm assemblages for deposits in the coldwell exhibit a strong correlation to pge enrichment relative to the range for mantle cu pd values 1000 10 000 and there is no relationship between the abundances of pd pt bi te and pd pt sb as minerals that are commonly associated with hydrous phases and the intensity of hydrothermal alteration thus minerals found only at the w horizon and area 41 where significant pge upgrading has occurred including pt fe alloys rustenburgite marathonite palladogermanide unknown rh ni fe sulfide au pd cu alloy braggite coldwellite laurite zvyagintsevite laflammeite and unknown phases pd 5 as 2 pd 3 as pd 3 as pb bi might be considered as index minerals for pge enriched types of mineralization in the coldwell

nickel copper occurrences in the belleterre angliers belt of the pontiac subprovince and the use of cu pd ratios in interpreting platinum group element distributions within the belleterre angliers greenstone belt of the pontiac subprovince there are a number of ni cu sulfide occurrences associated with synvolcanic gabbros the stratigraphy and geochemistry of the belt suggest that it is a rifted island arc and that the gabbros which contain the ni cu sulfides were derived from the mantle plume that rifted the island arc the conditions under which the sulfides formed may be modeled either by recalculating the sulfide compositions to 100 percent sulfide or by using the cu pd ratios both approaches suggest that most of the sulfide occurrences formed from an enriched morb magma with r factors of 200 to 1 000 one of the occurrences la force is depleted in platinum group elements pge relative to cu and this depletion may be the result of the removal of sulfides from the magma prior to emplacement at this stratigraphic level the advantage of using the cu pd ratio rather than recalculating to 100 percent sulfide is that it is not necessary to have s analyses to model the conditions of formation of the sulfides further the cu pd ratio may be used as a prospecting tool rocks with ratios greater than mantle values formed from magmas depleted in pd possibly due to removal of sulfide from the magma this implies the potential for a pge bearing sulfide deposit at stratigraphically lower levels such an approach has been applied to pge targets in the eastern abitibi subprovince samples from four ni cu occurrences with cu pd ratios close to mantle ratios have the potential to produce pge as a by product samples from seven ni cu sulfide occurrences and the layered intrusions lac dore bell river and cummings complex have cu pd ratios much greater than mantle ratios indicating that these intrusions and sulfides are not good targets for pge at this stratigraphic level although there may be pge rich sulfides present at depth

highly siderophile and strongly chalcophile elements in magmatic ore deposits an ore deposit by definition must be economically viable that is to say it must contain sufficient material at high enough grade to make it possible to mine and process it at a profit bates and jackson 1987 this requires the elements to be collected and concentrated by some phase and for them to be deposited close to the surface of the earth at the oxygen fugacities found in the crust native fe is not normally stable and thus the highly siderophile elements defined as ru rh pd re os ir pt and au cannot behave as siderophile elements except in rare cases such as on disko island klock et al 1986 where the magma is sufficiently reduced for native fe to be present however if mafic magmas become saturated in a base metal sulfide liquid the highly siderophile elements behave as highly chalcophile elements table 1 thus these elements are generally found in association with base metal sulfide minerals which crystallized from a magmatic sulfide liquid namely pyrrhotite pentlandite chalcopyrite cubanite pyrite an exception to this is au although au is strongly chalcophile and is produced as a by product from many platinum group element pge deposits table 2 most primary au deposits consist of native au groves et al 1998 these will not be discussed in this chapter there are many pge deposits i e accumulations of pge minerals and base metal sulfides containing pge bates and jackson 1987 around the world but most of these do not constitute pge ore deposits because they are either too small or their grade is too low or other political or infrastructure factors prevent the economic exploitation of the deposit bates and jackson 1987 for the purpose of this work we have defined pge ore deposits as those which have significant production 2 of the annual world

cu isotope systematics of conduit type cu pge mineralization in the eastern gabbro coldwell complex canada chalcopyrite from the cu pge sulfide deposits in the eastern gabbro coldwell complex canada exhibit a 2 variation in 65cu in the marathon deposit the 65cu of chalcopyrite increases from the lower footwall zone 1 49 to 0 75 to the main zone 1 04 to 0 08 to the upper w horizon 0 35 to 1 07 in the northern deposits chalcopyrite at four dams and sally have 65cu that range from 0 08 to 0 47 and 0 59 to 0 05 respectively notably samples from the marathon deposit with lower chalcopyrite 65cu values tend to have higher s se and cu pd ratios integrated geological and geochemical evidence suggests that secondary hydrothermal alteration and redox processes are unlikely to have been the primary causes of the observed cu isotope variation numerical modeling of 65cu cu pd s se of mineralization in the eastern gabbro illustrates three key aspects of cu isotope behavior in magmatic ni cu pge systems first r factors less than 10 000 can exhibit significant control on the 65cu of sulfides second sulfide liquid silicate melt fractionation factors for cu 65cusul sil greater than 0 5 are applicable to ni cu pge systems third sulfide segregation exhibits no measurable control on the 65cu of sulfides at degrees of fractionation typical of ni cu pge systems 0 3 in the marathon deposit the range of 65cu s se cu pd is attributed to the addition of archean sedimentary cu to a pool of sulfide liquid located at depth followed by progressive dilution of the contaminated 65cu s se signature and decrease in cu pd ratio by influxes of uncontaminated pulses of magma i e increasing r factor some of which had cu isotope compositions heavier than the mantle variably contaminated and enriched with respect to pd sulfides from this pool were entrained by magma pulses and emplaced to form the marathon deposit this contribution demonstrates that cu isotopes can fractionate at high temperatures and when combined with other geochemical proxies can be valuable in characterizing magmatic post magmatic processes in ni cu pge sulfide deposits and for identifying pge rich sulfide deposits

distribution of platinum group elements in magmatic and altered ores in the jinchuan intrusion china an example of selenium remobilization by postmagmatic fluids the division of platinum group elements pge between those hosted in platinum group minerals pgm versus those in solid solution in base metal sulfides bms has been determined for ores from the pge bearing ni cu rich jinchuan intrusion in northwest china all the bms are devoid of pt and ir and magmatic bms are also barren of rh these pge may have been scavenged by arsenic to form pgm during magmatic crystallization of the bms pd os and ru are recorded in bms and pd is predominantly in solid solution in pentlandite unlike the fresh magmatic ores in altered or serpentinized ores pd pgm are present froodite is hosted in magnetite formed during alteration of bms accompanied by sulfur loss and liberation of pd michenerite pd pt bite sperrylite ptas2 and au bearing pgm are located in altered silicates irarsite irass occurs mainly enclosed in bms padmaite pdbise identified at the junctions of magnetite and bms was the last pgm to form and locally partially replaces earlier non se bearing pgm we propose that padmaite formed under oxidizing conditions during late local remobilization of se from the bms se bearing pgm are rare and our review shows they are frequently associated with carbonate suggesting that pd and se can be mobilized great distances in low ph oxidizing fluids and may be precipitated on contact with carbonate s se ratios are used by researchers of magmatic ni cu pge ores to determine sulfur loss assuming se is immobile and representative of magmatic sulfur content this study shows that se as well as s is potentially mobile and this should be considered in the use of s se ratios

a discontinuous ca 80 ka record of late quaternary environmental change from lake omapere northland new zealand we present an integrated record of environmental change from lake omapere northland new zealand based on palaeolimnological analysis of a 7 m long core and eight adjunct cores spanning part of the last 80 calendar cal ka the chronology was developed using tephrochronology palaeomagnetism and radiocarbon dating together with climato and palyno stratigraphy two of 14 tephra layers in the cores provide markers for correlating the record with other new zealand climato stratigraphic sequences deep sea cores and the global marine isotope record pollen diatom palaeomagnetic sedimentologic and pigment analyses show that lake omapere currently 2 m deep has had a discontinuous history occupying a shallow basin perched partly within old basalt lavas the initial alkaline lake formed towards the end of mis 5a at ca 80 cal ka presumably because of blockage of local drainage of a swampy alluvial floodplain inundating peat deposits and forest trees including kauri agathis australis the lake filled rapidly to a level 1 2 m above that at present such filling was probably unrelated to climate but a subsequent phase of variable but generally falling lake levels and increasing dystrophy may have been climatically controlled commencing during mis 4 and culminating in periods early in mis 3 when the lake became swampy or dry conditions of non deposition or non preservation obtained for most of the period after ca 55 cal ka rotoehu ash until formation of the modern lake approximately 600 700 cal years ago or soon after as indicated by the presence of tephra 1 identified in part as kaharoa tephra ad 1314 near the top of the core the modern lake originated possibly through damming of the western outlet as a consequence of accelerated erosion accompanying earliest polynesian deforestation an interpretation supported by maori oral tradition the pollen record indicates that beech nothofagus presumably n truncata was much more common in northland during the last glacial and that for this region the relative abundance of nothofagus vs agathis pollen serves as a better indicator of cooler versus warmer intervals during the quaternary than the ratio of tree to non tree pollen however it seems likely that moisture balance was a more critical factor than temperature in vegetation composition and distribution particularly during the lgm and the long periods of hiatus may also be linked to a drier climate than present correlation coefficients between the pollen curves confirm that several tree species halocarpus bidwillii h biformis and phyllocladus alpinus previously palynologically concealed within generic taxonomic groups occurred about two degrees latitude further north and at a much lower altitude than their current limits during cooler or drier phases of the last glacial a temperature depression in northland of 4 c at various times during the last glacial is inferred from these range expansions nevertheless the persistence of widespread forest cover suggests that the late pleistocene climate of northland was less severe than for most of the rest of new zealand and strengthens the argument for a heightened temperature gradient across northern new zealand during the last glacial

the mineralogy of the voisey s bay ni cu co deposit northern labrador canada influence of oxidation state on textures and mineral compositions the voisey s bay ni cu deposit is one of the most significant discoveries made in canada in the last 30 yr known reserves plus indicated and inferred resources amount to 136 7 106 metric tons t grading 1 59 wt percent ni and 0 85 wt percent cu the deposit can be described in terms of four geologic settings the eastern deeps consisting of massive and disseminated sulfide along the line of intersection of a feeder sheet with the base of a troctolite intrusion the ovoid a 600 m long by 350 m wide 350 by 110 m deep lens of massive sulfide underlain by a feeder sheet the discovery hill zone which comprises a series of swellings containing disseminated and massive sulfides in the troctolite feeder and the reid brook zone which is where the feeder sheet opens out into a deeper level intrusion the principal sulfide minerals are hexagonal pyrrhotite troilite pentlandite chalcopyrite cubanite and magnetite troilite is restricted to the reid brook discovery hill and ovoid zones where it occurs as exsolution lamellae in hexagonal pyrrhotite the texture of pentlandite varies with the presence of troilite in coexisting pyrrhotite where troilite is present pentlandite occurs as equant masses up to several centimeters across where troilite is absent it occurs around pyrrhotite grain margins and as lamellae in a pyrrhotite host the ni content of hexagonal pyrrhotite averages 0 28 wt percent 14 analyses in troilite bearing zones and 0 51 wt percent 8 analyses in troilite absent zones cubanite is restricted to troilite bearing zones the presence of troilite indicates a metal rich high temperature hexagonal monosulfide solid solution from which pentlandite will exsolve at a higher temperature than from a more sulfur rich monosulfide solid solution thus developing as larger masses cubanite can exist with metal rich pyrrhotite but not with sulfur rich pyrrhotite metal rich pyrrhotite indicates an original metal rich sulfide melt which in turn indicates a low oxygen fugacity in the silicate magma with which the sulfides equilibrated this is thought to be due to the presence of graphite in the region where the magma extracted sulfide from surrounding gneisses

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

sulfide oxidation as a process for the formation of copper rich magmatic sulfides typical magmatic sulfides are dominated by pyrrhotite and pentlandite with minor chalcopyrite and the bulk atomic cu fe ratio of these sulfides is typically less than unity however there are rar

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

fractional crystallization induced variations in sulfides from the noril sk talnakh mining district polar siberia russia abstract the distribution of platinum group elements pge within zoned magmatic ore bodies has been extensively studied and appears to be controlled by the partitioning behavior of the pge during fractional crystallization of magmatic sulfide liquids however other chalcophile elements especially tabs te as bi sb and sn have been neglected despite their critical role in forming platinum group minerals pgm tabs are volatile trace elements that are considered to be mobile so investigating their primary distribution may be challenging in magmatic ore bodies that have been somewhat altered magmatic sulfide ore bodies from the noril sk talnakh mining district polar siberia russia offer an exceptional opportunity to investigate the behavior of tabs during fractional crystallization of sulfide liquids and pgm formation as the primary features of the ore bodies have been relatively well preserved in this study new petrographic 2d and 3d and whole rock geochemical data from cu poor to cu rich sulfide ores of the noril sk talnakh mining district are integrated with published data to consider the role of fractional crystallization in generating mineralogical and geochemical variations across the different ore types disseminated to massive despite textural variations in cu rich massive sulfides lenses veins and breccias these sulfides have similar chemical compositions which suggests that cu rich veins and breccias formed from fractionated sulfide liquids that were injected into the surrounding rocks numerical modeling using the median disseminated sulfide composition as the initial sulfide liquid composition and recent dmss liq and diss liq predicts the compositional variations observed in the massive sulfides especially in terms of pt pd and tabs therefore distribution of these elements in the massive sulfides was likely controlled by their partitioning behavior during sulfide liquid fractional crystallization prior to pgm formation our observations indicate that in the cu poor massive sulfides the pgm formed as the result of exsolution from sulfide minerals whereas in the cu rich massive sulfides the pgm formed by crystallization from late stage fractionated sulfide liquids we suggest that the significant amount of sn bearing pgm may be related to crustal contamination from granodiorite whereas as bi te and sb were likely added to the magma along with s from sedimentary rocks large pgm that are scarce and randomly distributed may account for most of the whole rock pt budget based on our results we propose a holistic genetic model for the formation of the magmatic sulfide ore bodies of the noril sk talnakh mining district

new constraints on the origin of the skaergaard intrusion cu pd au mineralization insights from high resolution x ray computed tomography abstract this contribution presents the first detailed three dimensional 3d in situ analysis of samples from the platinova reef using high resolution x ray computed tomography hrxct and 3d image processing and quantification coupled with microscopic and mineralogical investigations our hrxct analyses reveal the complex textural relationships between cu rich sulfides bulk composition close to bornite skaergaardite pdcu au rich phases silicates and fe ti oxides and provide unequivocal textural evidences not observed previously the association in 3d between cu rich sulfide globules pdcu alloy and ilmenite is inconsistent with a hydrothermal origin of the cu pd mineralization in contrast our results combined with phase diagrams strongly support a primary magmatic origin for the cu pd mineralization where cu and pd rich fe poor sulfide liquid represents a cumulus phase that forms by in situ nucleation these sulfide droplets and attached skaergaardite grains were trapped during the formation and crystallization of the fe ti oxides subsequent post cumulus processes led to the partial to total dissolution of the sulfide not entirely enclosed by the fe ti oxides i e not protected from reaction leading to the observed variability in cu and pd composition at the aggregate sulfide pdcu scale and to the occurrence of free pdcu alloys in contrast to the pdcu alloy gold bearing minerals are never observed entirely enclosed within the fe ti oxide two hypotheses can be envisaged for the formation of the gold enriched layer in the upper part of the section gold may have either precipitated from high temperature late magmatic cl rich fluids alternatively gold may have been enriched during fractional crystallization after sulfide had been suppressed from the liquidus after the pd layer crystallized and then deposited along redox barriers

hydrothermal remobilisation around a deformed and remobilised komatiite hosted ni cu pge deposit sarah s find agnew wiluna greenstone belt yilgarn craton western australia the sarah s find nickel deposit located 4 5 km north of the mount keith nickel mine western australia was chosen as a case study to investigate the nature and three dimensional geometry of a geochemical halo created by the hydrothermal remobilisation of base metals and platinum group elements into the country rock surrounding a small massive ni sulphide orebody portable and laboratory based xrf analyses were carried out on samples from a shear zone localised along the basal komatiite dacite contact that hosts the orebody a geochemical halo was identified that extends along the shear zone up to 1780 m away from the massive sulphides parallel to a prominent stretching lineation elevated ni and pd are associated with high as co cu and s palladium and pt concentrations increase with proximity to massive sulphides from 6 to 1190 ppb pd these anomalous concentrations reflect the presence of sulfarsenides and sulphides either physically remobilised and forming veinlets close to the massive sulphides or hydrothermally transported and redeposited within the foliation in situ laser ablation icp ms indicates that pd and pt are hosted within these nickel sulfarsenides this ni co as pd geochemical halo observed around the sarah s find ore body is interpreted as forming syn deformation by the circulation of as rich hydrothermal fluids dissolving base metals pd and pt from the orebody and redepositing them along the sheared footwall contact similar ni co pd pt as geochemical haloes could potentially exist around any magmatic nickel sulphide mineral system that has undergone a phase of arsenic metasomatism and may be a generally applicable proximity indicator for nickel sulphides in hydrothermally altered terranes

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

the lac des iles palladium deposit ontario canada part i the effect of variable alteration on the offset zone the recently discovered offset zone of the mine block intrusion of the lac des iles complex hosts palladium mineralization with unusually high pd pt and pd ir ratios in rocks that range from relatively unaltered norite to amphibolites and chlorite actinolite talc schist quantitative assessment of the effect of progressive alteration using mineral modes was done using total silicate h2o as a monitor of reaction progress moles h2o added to form alteration minerals per 100 g of rock major mineral modal variations define three reaction regions 1 0 00 0 03 characterized by epidote clinozoisite formation and some amphibole 2 0 03 0 23 characterized by formation of chlorite amphibole quartz muscovite sericite and calcite after plagioclase pyroxene and 3 0 23 0 28 characterized by the formation of talc after earlier formed amphibole epidote occurs as an incongruent product from the destruction of plagioclase that is itself lost as the reaction proceeds pyroxene is altered at about twice the rate of plagioclase resulting in pyroxene rich protoliths to be more altered than those relatively enriched in plagioclase major elements variations largely reflect variations in the plagioclase pyroxene ratio of the protolith but compositional trends suggest a loss of na with reaction progress the base metal sulfides chalcopyrite pyrrhotite and pentlandite show decreasing abundance with reaction progress forming pyrite magnetite as an intermediate reaction product that also is lost as the reaction proceeds millerite is overall low but increases slightly a more limited data set on the platinum group minerals suggests that platinum group element pge arsenides increase whereas pge sulfides and pge bi tellurides decrease with reaction progress assuming ore element concentrations in the protolith were constant and similar to relatively fresh norites pd increases modestly by 5 whereas pt decreases by about 65 in the most altered rocks similarly cu au and s decrease by 60 82 and 94 respectively in the most altered rocks the antithetical behavior of pd and the fact that pd enrichment is not seen in altered dikes suggest that the pd originally was enriched in the more melanocratic protoliths that are most extensively altered and that pd also was lost in part these results are consistent with the mineralization having been a high temperature event that predated the amphibolite greenschist alteration

chalcophile element ni cu pge and au variations in the tamarack magmatic sulfide deposit in the midcontinent rift system implications for dynamic ore forming processes the tamarack magmatic sulfide deposit is hosted by the tamarack intrusive complex 1105 6 1 2 ma in the midcontinent rift system the most important sulfide mineralization in the complex occurs in the northern part which consists of two separate intrusive units an early funnel shaped layered peridotite body containing relatively fine grained olivine referred to as the fgo intrusion at the top and a late gabbro troctolite peridotite dike like body containing relatively coarse grained olivine referred to as the cgo intrusion at the bottom disseminated net textured and massive sulfides occur in the base of the fgo intrusion as well as in the upper part of the cgo intrusion the widest part of the cgo intrusion also hosts a large semi massive net textured sulfide ore body locally surrounded by disseminated sulfide mineralization small massive sulfide veins occur in the footwall of the fgo intrusion and in the wall rocks of the cgo dike the sulfide mineralization is predominantly composed of pyrrhotite pentlandite and chalcopyrite plus minor magnetite pyrrhotite containing the highest ni and co contents occurs in the fgo disseminated sulfides and in the cgo semi massive sulfide ores respectively the most important platinum group minerals associated with the base metal sulfides are sperrylite ptas2 sudburyite pdsb and michenerite pdbite nickel shows a strong positive correlation with s in all types of sulfide mineralization and cu shows a strong positive correlation with s in the disseminated sulfide mineralization at a given s content the concentrations of pt pd and au in the cgo disseminated sulfides are significantly higher than those in the fgo disseminated sulfides the semi massive sulfide ores are characterized by significantly higher ipge ir os ru and rh concentrations than most of the massive sulfide ores with few exceptions all of the various textural types of sulfide mineralization collectively show a good positive correlation between pt and pd and between individual ipge at a given pt or pd content however the semi massive sulfide ores have higher ipge contents than the disseminated sulfide samples modeling results show that the variations in pge tenors metals in recalculated 100 sulfide in the tamarack magmatic sulfide deposit are mainly controlled by variable r factors magma sulfide liquid mass ratios during sulfide liquid segregation and subsequent monosulfide solid solution mss fractionation during cooling the initial contents of ir pt and pd in the parental magma estimated from the metal tenors of the disseminated sulfides are 0 2 2 and 1 8 ppb respectively which are 1 5 of the values for the pge undepleted primitive basalts of the midcontinent rift system the variations of pge tenors in the semi massive and massive sulfide ores can be explained by mss fractional crystallization from sulfide liquids extreme variations in the pge contents of the massive sulfides may also in part reflect metal mobility during post crystallization hydrothermal processes the higher pge tenors for the disseminated sulfides in the cgo dike relative to those in the fgo intrusion are consistent with formation in a dynamic conduit where the early sulfide liquids left in the conduit by the fgo magma were subsequently upgraded by the subsequent surge of the cgo magma the relatively low pge tenors for the semi massive and massive sulfides can be explained by lack of such an upgrading process for the sulfide due to their distal locations in a migrating conduit

a vegetation history of the far north of new zealand during the late otira last glaciation abstract during the latter part of the last otira glaciation the forest cover of new zealand was much reduced it has frequently been postulated however that diverse mixed forest communities survived in the far north of north island pollen diagrams and radiocarbon dates from two last glacial and postglacial aranuian sits on the aupouri peninsula in the far north of new zealand are compared with other published palynological and plant macrofossil evidence from the region mixed kauri podocarp angiosperm forest was present at times during the late otiran and aranuian and no evidence was found for substantial loss of forest however radiocarbon samples from one site at least seem to have been contaminated with young carbon this introduces uncertainty into the chronology established at that site possibly nondeposition or erosion has obscured part or all of the late otiran record at all the sites studied so that very much reduced forest cover at that time cannot be ruled out

iridium and palladium as discriminants of volcanic exhalative hydrothermal and magmatic nickel sulfide mineralization neutron activation of pd au and ir in samples from 1 economically significant ni sulfide deposits of western australia 2 the host rocks of these deposits 3 hydrothermal and or metasomatic ni sulfide mainly millerite mineralization in peridotite at nullagine western australia 4 hydrothermal replacement volcanic exhalative ni cu sulfide mineralization at sherlock bay western australia and 5 volcanic exhalative sulfides in inter flow sediments at kambalda are used to show that ir and pd can be used to discriminate between the various origins magmatic volcanic exhalative hydrothermal metasomatic and metamorphic ascribed to ni sulfide deposits all the economically significant ni sulfide deposits in western australia are strongly enriched in the precious metals relative to other crustal rocks and have similar pd ni and ir ni ratios to each other these ratios persist regardless of whether the nickel sulfides occur at the base of volcanic ultramafic piles e g kambalda or as centrally disposed interstitial sulfides in intrusive dunite bodies the strong similarities of the pd ir ratios of the ni sulfide ores and of the spinilex textured komatiites which represent ultramafic liquids from which the ni sulfide liquids were derived together with other features of the precious metal geochemistry of the ores and host rocks of the ni sulfide deposits are used to show that the deposits had magmatic origins in contrast the pd ir and ir ni ratios of the hydrothermal and or metasomatic ni sulfide mineralization at nullagine are distinctly different from those of the major ni deposits the former contains high au moderate but variable pd and exceptionally low ir similarly the volcanic exhalative sulfides at kambalda and sherlock bay contain negligible quantities of pd and ir all the ir in both the interflow sediments and the hydrothermal metasomatic mineralization is contributed by the host rocks and not by the sulfides the western australian data together with precious metal data for other examples of hydrothermal ni cu sulfide mineralization strongly suggest that although ni au and pd may be transported in aqueous solution ir cannot hence the relative abundance of ir can be used as a discriminant of magmatic sulfides

stable isotopic constraints on fluid rock interaction and cu pge s redistribution in the sonju lake intrusion minnesota the sonju lake intrusion part of the 1 1 ga midcontinent rift related beaver bay complex is a 1 200 m thick strongly differentiated layered sequence of mafic cumulates located in northeastern minnesota basal melatroctolite and dunite layers are overlain by troctolite gabbro fe ti oxide rich gabbro apatite diorite and monzodiorite stratigraphic intervals rich in pt pd cu and s occur over 500 m in the fe ti oxide rich gabbro and apatite diorite units peak concentrations show offsets that are similar to those found in other tholeiitic layered intrusions concentrations of pd in excess of 100 ppb are confined to the lowermost 25 m of the interval copper shows a sharp increase to 630 ppm above the pd rich interval sulfur contents are low 375 ppm in the cu rich interval but they increase to values as high as 3 150 ppm above in the apatite diorite disseminated sulfides in the intrusion have 34s values that range from 2 2 to 3 per mil vienna canyon diablo troilite v cdt and suggest that contamination by country rock sulfur was not an important process in the formation of the metal rich interval 18o values of plagioclase from the intrusion range from 5 6 to 12 0 per mil v smow and indicate that a relatively low 18o fluid 18o 3 5 interacted with the rocks of the intrusion at temperatures less than 275 c clinopyroxene and fe ti oxides ilmenite with minor amounts of titanomagnetite show much more restricted ranges in 18o values 4 6 5 7 and 5 5 6 7 per mil respectively and attest to the kinetic control of the oxygen isotope exchange process the externally derived fluid that interacted with rocks now enriched in platinum group elements pge cu and fe sulfide minerals locally liberated sulfur and replaced chalcopyrite and pyrite with goethite in the cu rich zone goethite that replaces chalcopyrite may contain up to 8 5 weight percent cu it is evident that hydrothermal alteration resulted in a decoupling of copper and sulfur with sulfur being transferred out of the cu rich interval interaction between rocks in the pge cu s interval of the sonju lake intrusion and an externally derived fluid at low temperatures modified what appears to have been a primary stratigraphic metal sulfur zonation the effects of hydrothermal alteration on pge and base metal sulfide mobility and redistribution must be understood before models of primary zonation processes can be meaningfully applied

cu ni pge mineralization in the south filson creek area south kawishiwi intrusion duluth complex mineralization styles and magmatic and hydrothermal processes the south filson creek mineralization occurs above the basal units of the south kawishiwi intrusion and represents an uncommon geologic setting of cu ni platinum group element pge mineralization within the duluth complex unlike other mineralization of economic interest in the basal heterogeneous troctolite units along the lower contact it is located at an approximate stratigraphic height of 1 000 m above the contact with the footwall granitoids in the usually unmineralized homogeneous troctolite unit magmatic sulfide mineralization forms disseminated fine grained patches and pockets in an area of approximately km2 of homogeneous troctolitic rocks in the northeastern part of the south kawishiwi intrusion pyrrhotite chalcopyrite pentlandite and cubanite are the main sulfide minerals with subordinate amounts of other copper bearing phases bornite covellite talnakhite cu pd ratios for unaltered mineralization indicate that sulfides were formed from multiple injections of magma that segregated sulfides with different r factors or having different initial compositions variation in the halogen contents of apatite from pegmatoids within troctolitic rocks revealed that a fluid has segregated from the crystallizing melt into which fluid cl and rare earth elements partitioned amphibole chlorite sericite prehnite pumpellyite and carbonate are associated with alteration along brittle structures and isolated patches in the area the hydrothermal fluid rock interaction has affected the composition of primary magmatic sulfide mineralization and is also responsible for mineralization in the anorthositic hanging wall of the south kawishiwi intrusion hydrothermal alteration resulted in a slight pd depletion in magmatic sulfide mineralization which might indicate remobilization of precious metals to an unknown location the hanging wall mineralization is characterized by relative cu enrichment in comparison to the magmatic sulfide mineralization with no pge enrichment partial remobilization of platinum group elements pge has also occurred as a result of a separate alteration event on the evidence that platinum group minerals pgm are also associated with serpentinization of olivine and ca enrichment of plagioclase along grain boundaries with sulfides this alteration was probably effective on a very local scale