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

interpretation of slingram conductivity mapping in near surface geophysics using a single parameter fitting with 1d model1 electrical conductivity mapping is a prerequisite tool for hydrogeological or environmental studies its interpretation still remains qualitative but advantages can be expected from a quantitative approach however a full 3d interpretation is too laborious a task in comparison with the limited cost and time which are involved in the majority of such field studies it is then of value to define the situations where lateral variations are sufficiently smooth for a 1d model to describe correctly the underlying features for slingram conductivity measurements criteria allowing an approximate 1d inversion are defined these mainly consist of a limited rate of variation over three times the intercoil spacing in geological contexts where the weathering has generated a conductive intermediate layer between the underlying sound rock and the soil this processing can be applied to determine the thickness of the conductive layer from the apparent resistivity map when the other geoelectrical parameters are known the examples presented illustrate this application

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

layered and laterally constrained 2d inversion of resistivity data in a sedimentary environment quasi layered models often can represent the actual geology more accurately than smooth minimum structure models we present a 2d inversion scheme with lateral constraints and sharp boundaries lci for continuous resistivity data all data and models are inverted as one system producing layered solutions with laterally smooth transitions the models are regularized through lateral constraints that tie interface depths or thicknesses and resistivities of adjacent layers a priori information used to resolve ambiguities and to add for example geological information can be added at any point of the profile and migrates through the lateral constraints to parameters at adjacent sites similarly information from areas with well resolved parameters migrates through the constraints to help resolve areas with poorly constrained parameters the estimated model is complemented by a full sensitivity analysis of the model parameters supporting quantitative evaluation of the inversion result a simple synthetic model proves the need for a quasilayered 2d inversion when compared with a traditional 2d minimum structure inversion a 2d minimum structure inversion produces models with spatially smooth resistivity transitions making identification of layer boundaries difficult a continuous vertical electrical sounding field example from sweden with a depression in the depth to bedrock supports the conclusions drawn from the synthetic example a till layer on top of the bedrock hidden in the traditional inversion result is identified using the 2d lci scheme furthermore the depth to the bedrock surface is easily identified for most of the profile with the 2d lci model which is not the case with the model from the traditional minimumstructure inversion

geology of the east bull lake gabbro anorthosite pluton algoma district ontario the east bull lake pluton a layered gabbro anorthosite intrusion 90 km west of sudbury ontario is in an inward dipping lopolith and is 780 m thick in the centre and elliptical in plan view 13 5 km 3 5 km it intruded archean metavolcanic and metaplutonic rocks of the superior province during the early proterozoic 2480 ma the intrusion consistes of a basal anorthositic unit succeeded by rhythmic layered gabbro troctolite layered gabbro and massive and dendritic gabbro units it is offset by the west northwest striking subvertical folson lake fault south of this fault only anorthosite and massive and dendritic gabbro are exposed north of the fault subsurface lithologies intersected by me boreholes correlate with surface lithologies troctolite the most distinctive marker that can be correlated between boreholes and surface exposures confirms the general attitude and shape of the layers and lopolith chemical composition of the intrusion ranges from high mg tholeiite to calc alkaline high

fractional crystallization of sulfide ore liquids at high temperature tie line compositions of fe ni cu sub 1 x s monosulfide solid solution mss and fe ni cu s liquid in the presence of sulfur vapor have been quenched from temperatures between 1 050 degrees and 1 180 degrees c more than 80 bulk compositions on both sulfur rich and sulfur poor sides of the mss field were investigated by sealed silica tube techniques qualitative observations of wetting behavior suggest increasing mobility in a silicate host rock as sulfide liquids become more cu rich partition coefficients for copper or 0 25 d super mss hq cu are obtained from ni bearing experiments with approximately 2 wt percent cu and no quench phases the equation d super mss hq cu 0 0003 x t degrees c 0 0310 x wt s 0 0069 x wt cu 1 3450 describes partitioning observed in ni free experiments above 1 000 degrees c above 1 000 degrees c the ni distribution coefficient d super mss hq cu decreases with increasing temperature and or sulfur content of the liquid these results yield improved models describing the fractional crystallization of natural sulfide liquids major element fe ni cu s compositions of ores from the sudbury district are shown to be entirely consistent with fractional crystallization at temperatures above 1 000 degrees c with the possible exception of rare samples enriched in both ni and cu sulfide liquids fractionating ni fe rich hanging wall ores at sudbury ontario must have been less cu rich than previously thought at temperatures above 950 degrees c reduced sulfur activity in residual liquids can result in massive late stage bornite rich ores

lithophile elements in huronian low ti continental tholeiites from canada and evolution of the precambrian mantle abstract huronian basalts from central ontario canada dated at about 2450 ma and associated with an early rifting episode are classified as siliceous low ti nb tholeiites they display strong enrichment in large ion lithophile lile and light rare earth lree elements compared to modern oceanic lavas the tectonic setting and geochemistry resemble mesozoic rift related low ti flood basalts including the ferrar group of antarctica and the parana and equivalent etendeka volcanics of south brazil and namibia respectively high lile lree ratios are also similar to subduction related island arc tholeiites and it is suggested that enrichment of the huronian lithospheric mantle source occurred through ancient subduction of crustal material probably during formation and consolidation of the archean continental crust melting models suggest that huronian subcontinental mantle source compositions derived from least contaminated aphyric mafic end members had already undergone a complex evolution including withdrawal of archean basalts and hydrous enrichment in incompatible components despite several subsequent melting episodes and a second probably magmatic enrichment event however many aspects of the huronian source signature were preserved and appeared in later basaltic products of this mantle mass keweenawan volcanics for example dated at about 1100 ma preserve low p zr ti and hree abundances

crystallization of sulfide liquids and the interpretation of ore composition we have been exploring ways to quantitatively assess the extent to which fractionation of sulfide melt has effected variations in composition within magmatic sulfide ore bodies our approach has been to determine by experiment the crystallization paths of sulfide liquids in temperature and composition dimensions in this paper the results of new major element partitioning experiments below 1050 c in the nickel free system are presented and summarized along with new and previous work in the fe ni cu s quaternary the partition coefficients d for cu between monosulfid solid solution mss and sulfide liquid in the ni free system dcu wt cu in mss wt cu in liquid cluster near 0 3 but decrease to nearly 0 1 for cu rich s poor liquids near 1000 c dni also declines with decreasing sulfur content of the liquid but increases with decreasing temperature preliminary data indicate that dni exceeds 1 0 in low ni liquids with greater than 16 wt cu at 1050 c the quality of available data on the

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

metallogeny in response to lithospheric thinning and craton destruction geochemistry and u pb zircon chronology of the yixingzhai gold deposit central north china craton article magmatism and associated metallogeny provide important constraints on geodynamic processes the hengshan terrain of northern taihang mountains located within the central north china craton is well known for several mesozoic gold deposits here we investigate the yixingzhai quartz vein hosted gold deposit associated with the sunzhuang quartz monzodiorite intrusive complex we present u pb data on zircon grains from the monzodiorite which constrain the timing of emplacement of the pluton as ca 134 ma coeval with the formation of yixingzhai quartz vein gold deposit at ca 131 ma the magmatism and metallogenesis during early creta ceous in the hengshan terrain are part of a major regional magmatic and metallogenic event in the taihang mountains and elsewhere in the north china craton at ca 130 ma ago we characterize the zircon grains from the sunzhuang quartz monzodiorite through morphology internal structures and chemistry and also present data from analyses of the chemistry co and ni and s pb d o isotopes of the minerals from the yixingzhai gold deposit and sunzhuang quartz monzodiorite our results reveal a lower crustal signature with mantle input for the source magma of the sunzhuang pluton the magma was enriched in water and alkalis and shows a wide range of crystallization temperature 850 550 c and mainly 650 to 700 c under high oxygen fugacity the ore minerals and the mineralizing fluids in the yixingzhai gold deposit were derived from magma generated in the lower crust with additional input of mantle components our study links the gold metallogenesis with magmatism in the hengshan terrain based on the new results reported in this study and in conjunction with our interpretation of the ultra broadband high precision magnetotelluric sounding profile from the region we suggest that the lithosphere beneath the hengshan terrain was strongly thinned and decoupled between the crust and mantle in the early cretaceous and that the partly destructed lithosphere was largely preserved through the cenozoic to present the metallogenesis in the hengshan terrain was closely related to the lithosphere thinning and crust mantle decoupling in the north china craton

geodynamics of heterogeneous gold mineralization in the north china craton and its relationship to lithospheric destruction abstract the north china craton ncc hosts some of the world class gold deposits on the globe which can be classified into distinct types as the jiaodong type explosive breccia type and skarn type the jiaodong type gold deposits were formed at ca 120 130 ma both in the margins and interior of the ncc two explosive breccia gold deposits formed at ac 180 ma and 120 ma and are located in the southern margin and the interior of the ncc important skarn gold deposits of ca 128 ma formed within the interior of the ncc although the formation and distribution of these gold deposits are temporally and spatially heterogeneous they are commonly related with the lithospheric destruction of the ncc the interplay of several factors such as basement architecture inhomogeneous decratonization crust mantle interaction mantle dynamics magmatic characteristics high heat flow and massive flux of deep derived ore forming fluids operated in generating the gold endowment all the three types of gold systems are closely related with granitoid plutons and different types of dykes the magmas for which were sourced from the lower crust near the moho discontinuity and involved the mixing and mingling of felsic and mafic magmas the ore forming fluids display prominent magmatic signature and were largely derived from deep domains with probable input from the asthenosphere mantle the heterogeneous distribution of the giant gold systems in the ncc was geodynamically controlled by the destruction of the craton the regions at the confluence of two or three precambrian micro continental blocks are generally characterized by thinned lithosphere and high heat flow constituting the potential sites of giant gold deposits the mantle beneath these regions shows em2 characteristics implying the involvement of subducted oceanic components the magmatic intrusions associated with the gold systems crystallized under high oxygen fugacity conditions and were rich in volatiles

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

mineralogical and isotopic studies of base metal sulfides from the jiawula ag pb zn deposit inner mongolia ne china abstract the jiawula ag pb zn deposit is located in the northern part of the da hinggan mountains metallogenic belt in the eastern section of the central asian orogenic belt sphalerite galena pyrite chalcopyrite and arsenopyrite are the major sulfide minerals occurring in this deposit here we report results from electron probe micro analysis epma thermoelectricity and sulfur isotope studies of the constituent silver minerals and sulfide phases of the jiawula deposit petrographic observations and epma study reveal abundant silver mineralization in the ore especially within sphalerite and galena discrete grains of silver minerals including argentite pyrargyrite and canfieldite and isomorphism in silver bearing sulfides are identified silver and tellurium contents in galena are relatively high and show interrelationship significant substitution of s by te in the galena lattice facilitates silver entering the galena structure which might have been promoted by relatively low lg fs2 the thermoelectric coefficient of pyrite shows a marked gradient from n type to p type from pre to post metallogenic stages pyrites in jiawula are enriched in co and as and in the absence of ni displaying features typical of epithermal deposits the isotopic data present a close relationship between the sulfur source and magmatism

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

high temperature brine in chalcopyrite rich quartz vein 40 km southwest of sudbury ontario the lac panache nipissing gabbro intrudes huronian metasediments ca 40 km southwest of the sudbury igneous complex the gabbro contains disseminated sulfides and is in contact with a chalcopyrite rich quartz vein that crystallized from highly saline fluids 46 8 3 equivalent wt nacl at a minimum temperature of 420 27 c chloride and carbonate inclusions in opened fluid inclusion cavities in the vein suggest that the brine contained dissolved metals in addition to nacl such as fe cu mn and co the weakly altered quartz vein postdated regional metamorphism and was probably contemporaneous with the 1 7 ga felsic magmatism and attendant albite alteration in the area cl rich scapolite in the gabbro and highly saline fluid inclusions in the quartz vein suggest the existence of circulating hot brine throughout the tectonic evolution of the region the 2 2 ga old gabbro contains an abundance of cl rich scapolite intergrown with pyrrhotite and chalcopyrite that formed during the early hydrotherma

geochemical and isotopic composition of auriferous pyrite from the yongxin gold deposit central asian orogenic belt implication for ore genesis abstract the yongxin gold deposit is a large fracture controlled ore deposit in the duobaoshan gold copper metallogenic belt within the eastern domain of the central asian orogenic belt caob silicification sericitization and potassic alteration are the main hydrothermal alteration types which display successive zoning surrounding the ore bodies pyrite galena sphalerite and chalcopyrite are the major metallic minerals in the deposit and gold is mainly distributed in pyrite here we investigate the trace element composition and isotope pb and s characteristics of pyrite from this deposit the auriferous pyrite is mainly allotriomorphic and homogeneous in chemistry with a homogenous distribution of as ni mo and fe from the core to rim of grains these features are consistent with the 207pb 206pb 206pb 204pb and 208pb 204pb 206pb 204pb of the grains that suggest a single source with no evidence for involvement of late fluids the 34s values range from 3 5 to 5 4 with an average of 4 48 suggesting a mantle derived magmatic provenance for the sulfur the high co content and co ni ratios low ni and mo ni ratios suggest a mafic ultramafic source for the yongxin gold deposit the co ni as relation indicates a magmatic hydrothermal affinity with a classification as epithermal gold deposit high arsenic and gold contents on the rims of pyrite grains indicate that au and as were simultaneously precipitated in anoxic low temperature and near surface conditions

mineralogical textural sulfur and lead isotope constraints on the origin of ag pb zn mineralization at bianjiadayuan inner mongolia ne china degao zhai jiajun liu nigel j cook xilong wang yongqiang yang anli zhang yingchun jiao

the differential parameter method for multifrequency airborne resistivity mapping helicopter em resistivity mapping began to be accepted as a means of geologic mapping in the late 1970s the data were first displayed as plan maps and images some 10 years later sectional resistivity displays became available using the same pseudolayer half space resistivity algorithm developed by fraser and the new centroid depth algorithm developed by sengpiel known as sengpiel resistivity sections these resistivity depth images proved to be popular for the display of helicopter electromagnetic em data in conductive environments a limitation of the above resistivity and depth algorithms is that the resulting sengpiel section may imply that the depth of exploration of the em system is substantially less than is actually the case for example a target at depth may be expressed in the raw data but its appearance on the sengpiel section may be too shallow which is a problem with the depth algorithm or it may not even appear at all which is a problem with the resistivity algorithm an algorith

geochronological and he ar s isotopic constraints on the origin of the sandaowanzi gold telluride deposit northeastern china abstract northeastern china is characterized by widespread mesozoic volcanic rocks and au cu mo mineral deposits with a total gold reserve of 2000 t amongst those gold deposits the newly discovered sandaowanzi has a total reserve of 25 t of au and an average grade of 15 g t this deposit is important because it is the first reported case of a dominantly au ag telluride deposit containing economically valuable bonanza au and ag telluride ores in the region the sandaowanzi quartz vein system and associated au ag telluride mineralization are mainly hosted by trachyandesites and andesitic breccias native gold is closely associated with abundant tellurides including petzite sylvanite calaverite hessite and altaite twelve pyrite samples from the alteration zone yield a well defined rb sr isochron age of 119 1 3 9 ma which is in agreement with a robust rb sr isochron age of 121 3 2 6 ma derived from 10 auriferous quartz samples the obtained isochron age of 120 ma represents the formation of the sandaowanzi gold telluride epithermal system which is much younger than the host trachyandesite with a zircon u pb age of 312 5 0 5 ma and the spatially associated monzogranite with a zircon u pb age of 182 2 1 1 ma dating results indicate a close relationship between the local au ag te mineralization and a magmatism episode in the early cretaceous noble gas he and ar isotopes obtained from telluride sulfide and quartz and sulfur isotopes determined from sulfides including chalcopyrite sphalerite and pyrite demonstrate clear mixing trends between crustal and mantle derived components confirming a significant contribution of fluid produced from mantle derived magmas into the epithermal system like many mesozoic porphyry cu mo au deposits the coeval epithermal au ag te deposits in the region are genetically related to magmatism triggered by the subduction of the pacific oceanic plate beneath the eurasian continent at the time

mineralogical fluid inclusion and multiple isotope h o s pb constraints on the genesis of the sandaowanzi epithermal au ag te deposit ne china

the geochemistry and petrogenesis of the agnew intrusion canada a product of s undersaturated high al and low ti tholeiitic magmas

mineralogy fluid inclusions and s pb h o isotopes of the erdaokan ag pb zn deposit duobaoshan metallogenic belt ne china implications for ore genesis abstract the recently discovered erdaokan ag pb zn deposit is located in the duobaoshan gold copper metallogenic belt in the eastern part of the central asian orogenic belt the ore bodies occur mainly as veins hosted in the breccia three stages of mineralization including early magnetite quartz pyrite middle silver sulfide bitumen quartz and late carbonate stages were recognized here we report results from electron microprobe analysis epma s pb h o isotopes and fluid inclusions studies to gain insights into the salient characteristics of the ore mineralization and mechanism of silver precipitation the silver occurs mainly as argentite pyrargyrite and invisible silver in the tetrahedrite grains in which ag fe and as isomorphically substituted cu zn and sb respectively the homogenization temperatures of fluid inclusions in the early middle and late stage mineralisation range from 96 to 179 c 78 to 178 c and 98 to 191 c respectively the fluid salinities vary from 0 35 to 5 54 wt nacl equiv the 34s values of the pyrite and galena show a range from 0 97 to 9 31 206pb 204pb vary from 18 0125 to 18 1864 207pb 204pb from 15 561 to 15 081 and 208pb 204pb from 38 0445 to 37 6979 with a mean of 18 0298 15 5125 and 37 7281 respectively the d and 18owater values of the quartz from the ore body range from 119 1 to 109 7 and 4 64 to 1 98 respectively based on these results we argue that the ore forming fluids were derived from a magmatic source with fluid mixing as the dominant mechanism for silver precipitation involving hydrocarbon fluid interaction as inferred from the presence of bitumen in the ore

magma mixing and constitution zone refining in the lac des iles complex ontario genesis of platinum group element mineralization the lac des iles complex is a 2 74 ga old composite intrusion emplaced into a granite and or granite gneiss terrane of the wabigoon subprovince northwestern ontario the complex consists of a gabbroic and ultramafic part the latter has been subdivided into northern and southern intrusive phases both the gabbroic and ultramafic parts contain platinum group element bearing ni cu sulfide mineralization although only the roby zone in the gabbro is of economic importance the southern ultramafic complex consists of a wehrlite to olivine clinopyroxenite core which is surrounded by websterite and gabbronorite cumulates petrographic and geochemical studies suggest that the northern ultramafic complex consists of at least eight cyclic units which ideally are composed of dunite and wehrlite to olivine clinopyroxenite cumulates at the base followed by clinopyroxenite and websterite locally grading into gabbronorite this indicates similar crystallization sequences in both ultramafic centers olivine olivine clinopyroxene clinopyroxene clinopyroxene orthopyroxene or plagioclase in the ultramafic complex platinum group element bearing sulfide mineralization occurs at the top of cyclic units in websterite and orthopyroxenite cumulates sulfide bearing samples up to 1 wt sulfide are enriched in au pd pt and cu relative to ni ir os and ru with pd ir ratios on the order of 250 sulfide immiscibility probably was caused by mixing of fractionated residual melt with more primitive liquid which periodically intruded the magma chamber evidence of mixing is seen in gradational chemical variations across the interface of cyclic units and in the occurrence of inclusions of olivine crystals and crystal aggregates in websterite and gabbronorite cumulates these inclusions are not in equilibrium with their present host rock and presumably formed before mixing in the more primitive magma a mineralized orthopyroxenite cumulate at the top of cyclic unit 2 could not have been produced by the normal crystallization sequence consideration of the phase relationships in the ternary system olivine clinopyroxene plagioclase quartz suggests that these cumulates are the crystallization product of a hybrid magma formed during magma mixing at the interface of cyclic units the gabbroic complex consists mainly of largely altered gabbro and gabbronorite cumulates and is intruded by mafic ultramafic dikes the center of the gabbroic complex contains the economically important roby zone with its platinum group element bearing cu ni sulfide mineralization this is a lithologically and texturally very complex zone in which high grade platinum group element mineralization is associated with pegmatite and mafic ultramaflc dikes the roby zone is characterized by strong enrichments of au pd and pt relative to ir and os and by variable but extremely high pd ir ratios of greater than 10 000 high au pt and pd pt ratios indicate a fractionation of pt from au and pd it is suggested that the high volatile content of the residual magma of the gabbroic complex triggered partial remelting of surrounding gabbro cumulates a process called constitutional zone refining by mcbirney 1987 during the partial melting event compatible elements such as ir and os are buffered by the residual silicate and oxide mineralogy whereas incompatible elements such as au pd and pt as well as volatile components such as h 2 o and h 2 s become highly concentrated in the partial melt phase eventually this newly formed magma may become sulfide saturated either by cooling and fractional crystallization or due to the continuous dissolution of sulfides when the zone of melting proceeds through the gabbro cumulates ratios such as pd ir and pd pt would strongly depend on the degree of remelting and fractional crystallization until the time of sulfide saturation the matrix of the varitextured zone is interpreted as the residuum of this melting process whereas pegmatoids and pegmatites segregationlike gabbro phases and quartz bearing plagioclase and incompatible element rich dikes are regarded as the final crystallization products of the partial melting

using the high mobility of palladium in surface media in exploration for platinum group element deposits evidence from the lac des iles region northwestern ontario platinium group element pge mineralization is commonly accompanied by large amounts of ni fe sulfides which are explored for using a variety of geophysical and geochemical methods appreciation of a new type of pge mineralization is emerging hosted by gabbroic rocks with low concentrations 5 vol of disseminated sulfides the host rocks commonly display textural complexity such as brecciation pods and veins of pegmatite and magma mingling of different lithological units examples include the lac des iles deposit in northwestern ontario the east bull lake suite in eastern ontario and several intrusions in the kola peninsula and northern finland such mineralization does not result in prominent geophysical and geochemical anomalies thus posing a challenge for exploration we initiated a project to develop new geochemical exploration approaches for such pge deposits with low sulfides and selected the lac des iles district northern ontario canada which contains one producing mine and many pd showings mineralization is hosted by gabbroic rocks with low concentrations 5 vol of sulfides enriched elements include pd pt au ni cu and co in separate sulfide rich mineralization base metals can be abundant up to 1 wt percent but pd is insignificant 200 ppb this reduces the relevance of ni cu and co as possible pathfinders for sulfide poor pge mineralization leaving pd pt and au a detailed study in the baker zone at the lac des iles mine and the legris lake property indicates the essentially immobile nature of pt in these surface environments by contrast pd is depleted in b horizon soil suggesting its removal during the conversion of c to b horizon soils the loss of pd in b horizon soil reflects the transport of pd as neutral and anionic complexes probably with oh and possibly with organic ligands which are not adsorbed by fe oxyhydroxides in the soils instead pd migrates in solution to accumulate in humus in swamps and organic rich lake sediments downslope from mineralization the distribution of pd in humus therefore provides a distal indicator of nearby mineralization total digestion of humus using fire assay or aqua regia yielded up to 160 ppb pd whereas a variety of commercially available leaching methods extracted few ppb pd the results indicate that pd is tightly held in organic matter this behavior of pd contrasts with many metallic elements such as cu and ni that are enriched in b horizon soil and may be extracted by a variety of leaching techniques palladium arsenides tellurides antimonides and sulfides are unstable in weathering environments and their dissolution releases pd to surface waters therefore pd can be used to indicate other pge mineralization as it is always abundant among pge where pge mineralization is associated with high concentrations of fe sulfides their oxidation produces acidic waters which further promotes pd dispersion thus the findings of this study are applicable to exploration for both sulfide rich and poor pge mineralization

geochemistry and mineralogy of platinum group element mineralization in the river valley intrusion ontario canada a model for early stage sulfur saturation and multistage emplacement and the implications for contact type ni cu pge sulfide mineralization the river valley intrusion within the 2 48 ga east bull lake intrusive suite in ontario canada is an example of a mafic igneous intrusion with contact type ni cu pge sulfide mineralization along its base whereas many contact type deposits are thought to form from in situ contamination of the magma by the addition of crustal s during emplacement there are some intrusions including the river valley intrusion which appear to have a much more complex history where the timing of s saturation and thus the critical ore genesis processes may have occurred much earlier prior to emplacement the river valley intrusion is made up of a basal 100 m of unlayered inclusion bearing units overlain by layered cumulates the basal units contain autoliths of gabbroic rocks and inclusions of footwall gneiss and amphibolites all within a gabbroic matrix platinum group element rich magmatic sulfide mineralization occurs throughout both the inclusions and the matrix as blebby and disseminated sulfides the matrix and inclusions can be separated into two distinct textural types hydrothermally altered greenschist assemblages and unaltered metamorphic amphibolite assemblages the platinum group mineral pgm assemblages vary only between textural types and not between inclusions and matrix being dominated tellurides in all rock types the hydrothermally altered rocks however have fewer tellurides and an increased amount of sb and as bearing pgm indicative of minor fluid interaction although the pgm have not been mobilized significantly away from the base metal sulfides precious and base metal geochemistry shows all rock types to have an excellent correlation between all the platinum group elements pge indicating the presence of a single well homogenized pge rich sulfide liquid however au and cu appear to be decoupled from the pge at low concentrations although correlate well with each other which is interpreted to be due to minor fluid redistribution and alteration of sulfide bleb margins the overlying layered units above the mineralized units are not pge depleted trace element data including th yb pm and nb th pm ratios demonstrate that all river valley rocks were formed from crustally contaminated magmas following interaction with local country rocks in a deeper subchamber although some samples have s se ratios indicative of crustal s most have s se ratios lower than the mantle range indicative of s loss we propose a multistage model for the formation of the mineralization in the river valley intrusion with a major contamination event at depth with the addition of s from local crustal rocks inducing sulfide saturation sulfide droplets were then enriched in pge within a conduit system with possible further upgrading of sulfide metal tenors and reduction of s se ratios via partial dissolution of sulfide the pge enriched sulfide liquid then settled in a staging chamber and partially crystallized before a major pulse of magma entrained sulfide liquid eroded blocks of precrystallized and mineralized gabbro and footwall rocks and emplaced an inclusion bearing package as the lower 100 m or so of the river valley intrusion later emplacement of main river valley magma was from an s undersaturated pge fertile magma the river valley intrusion is thus an example whereby contact type mineralization is purely a function of the earliest magma intruded containing preformed sulfide mineralization rather than contamination triggering sulfide saturation in situ in such cases processes at depth determine the generation and subsequent tenor of the mineralization in particular dissolution of the sulfide can upgrade metal tenor but subsequently will reduce s se ratios masking the signature of crustal contamination in addition a multistage emplacement such as this will not necessarily preserve the characteristic increase in cu pd ratios in the overlying cumulates that is often used in exploration for pge deposits in mafic intrusions thus a full understanding of all the field geochemical and mineralogical factors is required to construct genetic models for such deposits and especially in the interpretation of s se and cu pd ratios as an indicator of crustal contamination and the presence of pge mineralization

controls on the formation of contact type platinum group element mineralization in the east bull lake intrusion the east bull lake intrusion is the type example of a series of 2 48 to 2 49 ga layered mafic intrusions that developed within the rifted southern margin of the superior craton central ontario the east bull lake intrusion contains contact type pge mineralization e g strata bound pge rich disseminated sulfide mineralization occurring within 200 to 300 m of the contact with footwall and sidewall units although the mineralization locally occurs in massive plagioclase cumulates anorthosite zone most of the sulfides are concentrated within an underlying heterolithic inclusion rich unit inclusion bearing zone that grades into an intrusive breccia disseminated sulfides also occur in fine grained gabbroic veins within brecciated footwall rocks border zone geochemical characteristics of the contact type sulfide mineralization and its host rocks include 1 high average pd abundances throughout the east bull lake intrusion including an average of ca 200 ppb in the lower series 2 low average s contents typically contact type pge mineralization in the east bull lake intrusion reflects flow enhanced gravitational settling of a cu rich sulfide liquid followed by local fractionation of ni rich monosulfide solid solution to produce minor amounts of cu and pt rich residual sulfide liquid most of the observed compositional variation in the sulfides can be modeled using variable silicate liquid sulfide liquid mass ratios field and geochemical observations suggest that the parental magmas to the mineralized parts of the east bull lake intrusion were s saturated and pge rich at the time of their emplacement these fertile parent magmas most likely originated as buoyant feldspathic residual magmas that escaped from a deeper more primitive subchamber although first described from the east bull lake intrusion contact type pge mineralization is now recognized in all of the major east bull lake suite intrusions similar styles of magmatic sulfide mineralization are developed in the contact environments of the bushveld igneous complex platreef deposits and the duluth complex minnesota e g dunka road deposit these contact type deposits are part of the family of basal accumulation magmatic sulfide deposits the economics of low sulfide tenor contact type pge cu ni mineralization such as that developed in the east bull lake intrusion will be most favorable in systems in which 1 the parent magmas possessed high initial pge tenors and reached s saturation prior to emplacement 2 the parent magmas experienced vigorous convection in the early stages of chamber development and 3 segregated sulfide was not diluted by coprecipitating silicate minerals a scenario that is most likely to occur in feldspathic magmas in which plagioclase is the principal high temperature liquidus mineral

roles of xenomelts xenoliths xenocrysts xenovolatiles residues and skarns in the genesis transport and localization of magmatic fe ni cu pge sulfides and chromite abstract most sulfide rich magmatic ni cu pge deposits form in dynamic magmatic systems by partial melting s bearing wall rocks with variable degrees of assimilation of miscible silicate and volatile components and generation of barren to weakly mineralized immiscible fe sulfide xenomelts into which ni cu co pge partition from the magma some exceptionally thick magmatic cr deposits may form by partial melting oxide bearing wall rocks with variable degrees of assimilation of the miscible silicate and volatile components and generation of barren fe ti oxide xenocrysts into which cr mg v ti partition from the magma the products of these processes are variably preserved as skarns residues xenoliths xenocrysts xenomelts and xenovolatiles which play important to critical roles in ore genesis transport localization and or modification incorporation of barren xenoliths autoliths may induce small amounts of sulfide chromite to segregate but incorporation of sulfide xenomelts or oxide xenocrysts with dynamic upgrading of metal tenors pge cu ni co and cr v ti respectively is required to make significant ore deposits silicate xenomelts are only rarely preserved but will be variably depleted in chalcophile and ferrous metals less dense felsic xenoliths may aid upward sulfide transport by increasing the effective viscosity and decreasing the bulk density of the magma denser mafic or metamorphosed xenoliths may also increase the effective viscosity of the magma but may aid downward sulfide transport by increasing the bulk density of the magma sulfide wets olivine so olivine xenocrysts may act as filter beds to collect advected finely dispersed sulfide droplets but other silicates and xenoliths may not be wetted by sulfides xenovolatiles may retard settling of or in some cases float dense sulfide droplets reactions of sulfide melts with felsic country rocks may generate fe rich skarns that may allow sulfide melts to fractionate to more extreme cu ni rich compositions xenoliths xenocrysts xenomelts and xenovolatiles are more likely to be preserved in cooler basaltic magmas than in hotter komatiitic magmas and are more likely to be preserved in less dynamic less turbulent systems domain phases than in more dynamic more turbulent systems domains phases massive to semi massive ni cu pge and cr mineralization and xenoliths are often localized within footwall embayments dilations jogs in dikes throats of magma conduits and the horizontal segments of dike chonolith and dike sill complexes which represent fluid dynamic traps for both ascending and descending sulfides oxides if skarns residues xenoliths xenocrysts xenomelts and or xenovolatiles are present they provide important constraints on ore genesis and they are valuable exploration indicators but they must be included in elemental and isotopic mass balance calculations

geochemical stratigraphy of the huronian continental volcanics at thessalon ontario contributions of two stage crustal fusion the 1500 m thick sequence of huronian continental volcanics at thessalon ontario is subdivided into 4 volcanic cycles each of which includes abundant early mafic end members central intermediate flows and late rhyolite units major and trace element concentrations are dominated by extensive gabbroic fractionation trends that ultimately produced two types of felsic flows 1 rhyolites with high light rare earth element lree and relatively low large ion lithophile element lile concentrations high lree low lile rhyolites and 2 following late separation of ree rich accessory phases rhyolites depleted in lree low lree high lile rhyolites mafic end members of individual volcanic cycle are progressively less siliceous and less enriched in lile and lree with height in the stratigraphic section ti zr ratios gradually rise from 35 in early mafic flows to stabilize at about 85 in late units while average sio2 contents decrease from 56 to about 50 and mg rises from about 48 to 52 nd values are consistently negative indicating variable degrees of pre fractionation crustal contamination of the end member magmas during their uprise through the crust mixing models are consistent with up to 50 contamination by crustal material of tonalitic hornblende gneiss composition a progressive increase in nd from about 5 0 to 0 5 upward in the volcanic succession reflects a decreasing degree of crustal contamination due to development of insulating layers along margins of the feeder system detailed stratigraphic variations suggest that successive magmas batches were intercepted by a progressively fractionating periodically replenished magma source giving rise to open system magmatism despite the prevalence of crustal assimilation in the huronian lavas la sr n ratios are too low in least contaminated end members to be explained by contamination of tholeiitic magmas the late basalts resemble instead modern island are basalts and it is suggested that the subcontinental mantle source was enriched by subduction related processes during crustal formation within individual volcanic cycles gabbroic fractionation trends systematically deviate from calculated factors toward compositions characteristic of hornblende gneiss such relations suggest that further crustal contamination of the magmas occurred simultaneous with crystal fractionation probably within undulating sills at upper crustal levels quantitative analysis suggests assimilation fractional crystallization a fc ratios of about 0 45 as a result of extensive two stage contamination rhyolites from the initial volcanic cycle incorporate a total of over 60 of crust

sulfur saturation and second stage melts application to the bushveld platinum metal deposits a model is presented for the formation of platinum group element ores by precipitation from sulfur deficient platinum group element rich second stage magmas numerous investigations indicate that basaltic magmas originating from undepleted or mildly depleted source regions are sulfur saturated at the time of eruption mantle derived peridotites residual from midocean ridge basalt magma genesis have pd abundances that are uniformly too high for it to have originated solely from silicate melt retained in the source region at the time of segregation they imply the presence of an accessory immiscible sulfide melt to host the platinum group elements the very high sulfide melt silicate melt partition coefficients of the platinum group elements would result in strong fractionation of these metals into the accessory sulfide component during the melting event the extreme platinum group element enrichment of this accessory sulfide component is evidenced by the discovery ofplatinoid minerals in residual mantle nodules containing pd and pt abundances at the low ppb level keays et al 1981 magmas generated by low to moderate degrees of partial melting of undepleted mantle are therefore sulfur saturated at the time of segregation these first stage magmas become impoverished in platinum group elements during the early stages of fractional crystallization because of coprecipitation of an immiscible sulfide phase e g midocean ridge basalt glasses average

genesis of the zhengguang gold deposit in the duobaoshan ore field heilongjiang province ne china constraints from geology geochronology and s pb isotopic compositions abstract the zhengguang gold deposit in the duobaoshan ore field hosted in volcanic rocks of the middle ordovician duobaoshan formation is one of the largest gold deposits in the northeastern great xing an range of the central asian orogenic belt caob the deposit comprises the no i ii and iii ore zones with a total resource exceeding 35 tonnes of au 100 000 tonnes of zn and 100 tonnes of ag a genetic relationship between gold mineralization and concealed tonalite porphyry is inferred based on the characteristics of cryptoexplosive breccia and hydrothermal alteration indicative of porphyry type and epithermal mineralization zircon la icpms u pb dating reveals that the tonalite porphyry was emplaced at 462 1 1 8 ma middle ordovician the 34 s v cdt values of sulfide minerals range from 3 0 to 1 7 with an average of 2 33 indicating that sulfur was mainly derived from a magmatic source the pb isotopic compositions 206 pb 204 pb ranging from 17 572 to 17 629 207 pb 204 pb from 15 424 to 15 486 and 208 pb 204 pb from 37 206 to 37 418 suggest a major mantle component for pb and by inference for other ore metals therefore we suggest that the ore forming elements in the zhengguang gold deposit may be related to the mantle sourced tonalite porphyry on the basis of the geological characteristics and geochemical signatures documented in this study we conclude that the zhengguang gold deposit was formed in a porphyry to epithermal transitional environment associated with the concealed tonalite porphyry as part of the duobaoshan porphyry epithermal ore system that is related to the subduction of the paleo asian ocean during the ordovician

fluid immiscibility in natural processes use and misuse of fluid inclusion data ii interpretation of fluid inclusion data in terms of immiscibility abstract phase equilibrium analysis of the relevant systems together with the application of the principles of chemical equilibrium put severe constraints on the interpretation of fluid inclusion data in terms of immiscibility in part i following from that point the major limits on the accuracy and even the validity of fluid inclusion quantitative data and their interpretation in terms of fluid composition and density are briefly discussed the practical implications of the general constraints temperature pressure topology of the fluid systems are envisaged emphasis is laid on some important consequences such as the use of isochore intercepts and the possible resulting interpretation of fluid mixing rather than unmixing the case of highly saline inclusions the identification and interpretation of heterogeneous trapping the composition and density constraints on coexisting fluids are presented and illustrated by natural examples taking into account all the measurable parameters in fluid inclusions volume temperature and nature of phase transitions more or less complete individual spectroscopic analyses all the available experimental data and all the theoretical constraints may be long and difficult however it is most generally very informative and productive although part of these data is often sufficient to deny unmixing nevertheless a final example on metamorphic fluids demonstrates how such an approach can prove and also characterize a fluid unmixing during a geologic process

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

gold deposits and gold metallogeny of far east russia abstract the russian far east or far east russia fer is host to a huge gold endowment and has produced more than 6500 t of gold since the 1860s much of this gold has come from several mining districts aldan upper amur lower amur okhotsk allakh yun yana kolyma priokhotie omolon and chukotka these districts include several gold deposits mostly of orogenic and epithermal nature as well as large and very large alluvial placer deposits the main gold districts are of late mesozoic age but there are also three districts aldan omolon and southern primorie with pre mesozoic gold ores and three districts kamchatka sakhalin south kurile and lower amur with gold ores of cenozoic age this review paper attempts to marshal on the regional scale all available data aiming to provide a framework for generating and testing new ideas on the gold deposits of fer the focus is on 1 gold metallogeny 2 details of key gold deposits and 3 relationship between gold ore forming processes metamorphic processes and granitoid intrusions in different geodynamic settings the largest gold metallogenic belts in fer were formed in the late mesozoic namely in the late jurassic yana kolyma early cretaceous eastern flank of mongol okhotsk aldan oloy chukotka okhotsk koryak and late cretaceous sikhote alin the mesozoic era was also the time when most of the gold hosting orogens were formed paleozoic mesozoic and cenozoic orogens resulted from the interaction between the pacific oceanic plates with the siberian craton and the north china craton these orogens are products of diverse geodynamic settings and can be divided into four types 1 collisional e g yana kolyma 2 accretionary or uncompleted collisional e g okhotsk koryak or kamchatka 3 combined collisional and transform margin mongol okhotsk and 4 active transform margin sikhote alin the first two types are typical of north east russia whereas the third and fourth types are in the southern part of fer the late cretaceous okhotsk chukotka and east sikhote alin gold provinces are associated with continental margin magmatic arcs and are post accretionary post orogenic comparison of lode gold deposits from different geodynamic settings reveals specific features in metallogeny of the late mesozoic orogens at the southern and eastern margins of the siberian craton yana kolyma collisional orogen okhotsk koryak accretionary orogen and mongol okhotsk transform margin orogen these orogens possess different metal associations the yana kolyma belt contains au sn w and cu pb zn lode deposits the late jurassic transbaikalian sector of the mongol okhotsk orogen contains au mo pb zn sn ta nb w hg sb lode deposits whereas early cretaceous au cu mo hg sb lode deposits are present in the amur sector finally the okhotsk koryak orogen hosts au cu mo cu w bi ag co bi as and be sn li w deposits of early cretaceous age epithermal gold deposits occur in two different geodynamic settings 1 island arcs kamchatka kurile islands and magmatic belts at active continental margins omolon okhotsk chukotka and eastern sikhote alin and 2 rift related magmatism linked with orogenic events and strike slip kinematics such as transform like continental margin settings aldan and upper amur in the mongol okhotsk orogen mineralogic geochemical and isotope systematics indicate a metamorphic magmatic origin of hydrothermal plutonic systems in collisional settings yana kolyma okhotsk koryak and oloy chukotka orogens and active continental margin okhotsk chukotka and east sikhote alin settings with source contributions from the lower crust and mantle the mongol okhotsk and sikhote alin orogens are of transform fault related origin and suggest a source of the ore forming fluids mostly from the mantle

river valley pluton ontario a late archean early proterozoic anorthositic intrusion in the grenville province abstract the river valley pluton is a ca 100 km2 body of anorthositic and gabbroic rocks located about 50 km northeast of sudbury ontario the pluton is situated entirely within the grenville province but its western margin is a series of imbricate thrust faults associated with the grenville front tectonic zone it is dominated by coarse leuconorite and leucogabbro with lesser anorthosite gabbro and rare ultramafics igneous textured rocks are abundant and consist of plagioclase an60 70 charged with fe ti oxide inclusions low ca pyroxene orthopyroxene and or inverted pigeonite and augite the most unfractionated rocks are minor olivine gabbros with fo70 80 a variety of deformed and recrystallized equivalents of the igneous textured rocks is also present and these are composed largely of calcic plagioclase and hornblende ten samples including both igneous and deformed lithologies give a pb pb whole rock isochron of 2560 155ma which is our best estimate of the time of primary crystallization the river valley pluton is thus the oldest anorthositic intrusive yet reported from the grenville province but is more calcic and augitic than typical massifs and lacks their characteristic fe ti oxide ore deposits the river valley body may be more akin to similar gabbro anorthosite bodies situated at the boundary between the archean superior province and huronian supracrustal belt of the southern province west of the grenville front an sm nd isochron from 3 igneous textured leucogabbros and an augite mineral separate gives 2377 68 ma implying slight disturbance of the sm nd whole rock mineral system during later metamorphism the rb sr system has been substantially disturbed giving an age of 2185 105 ma which is similar to internal pb pb isochron ages of 2165 130 ma and 2100 35 ma for two igneous textured rocks it is uncertain whether these ages correspond to a discrete event at this time or represent a partial resetting of the rb sr and pb pb systems from a younger event such as the grenvillian orogeny of ca 1 0 ga none of the isotopic systems we investigated however gives an age near 1 0 ga suggesting that neither the river valley pluton nor the immediately surrounding gneisses were strongly affected by metamorphism associated with the grenvillian orogeny initial isotopic ratios for the river valley pluton correspond to single stage model parameters of 8 06 nd 0 to 3 and isr 0 7015 to 0 7021 collectively these suggest either an enriched mantle source or crustal contamination of a mantle derived magma the crustal component involved must have been older and more radiogenic than the majority of rocks exposed at the surface in the nearby superior province

ore genesis and hydrothermal evolution of the baiyinnuo er zinc lead skarn deposit northeast china evidence from isotopes s pb and fluid inclusions the baiyinnuo er zinc lead deposit 32 74 mt at 5 44 zn 2 02 pb and 31 36 g t ag located in the south segment of the great xing an range is the largest zn pb deposit in northern china skarn and orebodies mainly occur between the different units of the huanggangliang formation or within the contact zone between the intrusions and permian marble several phases of igneous rocks exposed within the mining areas and among them the yanshanian plutonic rocks which intruded into limestone of the early permian huanggangliang formation are interpreted to be the source of ore since their pb isotope compositions 206pb 204pb 18 25 18 35 207pb 204pb 15 50 15 56 and 208pb 204pb 38 14 38 32 are highly consistent with the sulfides including sphalerite galena and chalcopyrite 206pb 204pb 18 23 18 37 207pb 204pb 15 47 15 62 and 208pb 204pb 37 93 38 44 sulfur isotope values of the sulfides give a narrow 34s interval of 6 1 to 4 6 mean 5 4 n 15 suggesting the ore forming fluid is of magmatic origin three main paragenetic stages of skarn formation and ore deposition have been recognized based on petrographic observation which are the preore stage garnet clinpyroxene wollastonite magnetite sulfides the synore stage sulfides epidote quartz calcite garnet and the postore stage calcite chlorite quartz fluorite several fluid evolution episodes can be inferred from microthermometric results at the baiyinnuo er zn pb deposit 1 immiscibility preore stage coexistence of halite bearing brine inclusions s1 type 44 wt nacl equiv and vapor rich fluid inclusions v type sharing the same homogenization temperatures 470 c confirms that fluid unmixing occurred under lithostatic pressures of 400 bars 1 5 km and the brine is considered to account for most prograde skarn minerals e g clinopyroxene 2 overpressure trapping preore stage brine inclusions homogenized by halite dissolution s2 type postdated the immiscible assemblages this type of inclusions is characterized by high but variable minimum trapping pressures 150 3 000 bars relative to s1 type inclusions and can be explained as a result of entrapment under overpressuring condition 3 boiling the presence of both vapor and liquid inclusions i e v and l type in the same assemblages within synore stage quartz calcite and sphalerite indicates the occurrence of fluid boiling 350 c at hydrostatic pressures of 150 bars and depth of 1 5 km which resulted in large scale mineralization in the baiyinnuo er zn pb deposit 4 mixing with external fluids fluid inclusions scattered within postore stage calcite or secondary trails in synore stage minerals show low homogenization temperatures 260 c and both decreasing for l type and increasing for cacl2 bearing inclusions i e lc type trends for salinities as homogenization temperatures decrease implying addition of both meteoric water low temperature low salinity and basinal brines low temperature ca rich respectively systematic fluid inclusion studies also indicate that the mineralization related fluid is of magmatic origin prograde minerals formed during the preore stage fluid immiscibility while sulfides deposition occurred during the synore stage fluid boiling mixing with external fluids began as the hydrothermal system cooled to 300 c when the main metal precipitation process had ended

re os sulfide chalcopyrite pyrite and molybdenite systematics and fluid inclusion study of the duobaoshan porphyry cu mo deposit heilongjiang province china abstract the duobaoshan porphyry deposit located in the northwestern part of the lesser hinggan range is one of the biggest porphyry cu mo deposits in the central asian orogenic belt in china the duobaoshan porphyry deposit occurs in granodiorite and volcanic rocks of the middle ordovician duobaoshan formation six types of veins have been identified in three ore forming stages as follows a quartz potassic feldspar vein in the early ore forming stage an early stage quartz molybdenite vein late stage quartz molybdenite and quartz chalcopyrite pyrite veins in the middle ore forming stage and quartz pyrite and calcite quartz veins in the late ore forming stage the following four types of fluid inclusions are distinguished from various quartz veins two phase aqueous pure gas phase co 2 bearing and daughter mineral bearing inclusions the ore forming fluid for the early ore forming stage belongs to the h 2 o co 2 nacl system which is characterized by high temperatures 550 c intermediate salinities 16 2 18 1 wt nacl eqv and high co 2 content the ore forming fluid from the middle ore forming stage evolved to the h 2 o co 2 nacl system which is characterized by intermediate to high temperatures 230 450 c and high low salinities 0 8 to 65 3 wt nacl eqv and is also rich in co 2 and metals the ore forming fluid finally reached cool temperatures 110 200 c low salinities 3 9 8 4 wt nacl eqv and was co 2 poor intensive fluid immiscibility or boiling occurred when the ore forming fluid with temperatures of 230 450 c and pressures of 10 41 mpa ascended to 4 1 km inducing the escape of co 2 depressing the solubility of fluid and depositing abundant metal sulfides the total re and os concentrations of chalcopyrite and pyrite range from 0 15 to 2 95 g g and 0 74 to 15 01 ng g respectively analyses of seven chalcopyrite and pyrite samples yielded isochron ages of 482 486 ma and the model age of one molybdenite sample is 485 6 3 7 ma the mineralization age of the duobaoshan deposit is between 482 and 486 ma and mantle fluid and materials were involved in the mineralization process the duobaoshan deposit is a classic porphyry cu mo deposit that formed in an early palaeozoic island arc tectonic setting

geology and geochemistry of the east bull lake intrusion district of algoma ontario the east bull lake intrusion is a layered basic lopolith of early aphebian age that intrudes archean basement rocks at the southern margin of the superior province it contains at least two magmatic cycles cumulate olivine plagioclase and clinopyroxene form anorthosite troctolite and olivine gabbro norite in the lower portion of each cycle these rocks are overlain by two pyroxene gabbros norites in which orthopyroxene or pigeonite joins augite and plagioclase as the major cumulate minerals molecular proportion ratio mpr variation diagrams support this interpretation of the petrology of the intrusion and show that the major cumulate rock types represent magmatic liquids formed sequentially by fractionation of the above mentioned cumulate phases small scale phase layering is common in the intrusion size graded layers are absent and cross bedded and igneous lamination features are not common we conclude that this scale of layering formed in a boundary layer along the floor of the intrusion as a

riparian wetlands of the middle reach of the seine river france historical development investigation and present hydrologic functioning a case study along the middle reach of the seine river upstream from paris riparian wetlands that have been functioning for centuries first as a result of a succession of sedimentological hydrological processes and later of continuous management practices where the value of the wetlands has been acknowledged as well as their importance for the ecology here we present the results of a multidisciplinary research programme focused on this system with emphasis on its present hydrological functioning and on the tools used to understand and quantify it the major hydrological and geochemical processes that are active at present are reviewed but past processes are also described as well as the potential long term evolution of the system this study uses several innovative tools to investigate the wetlands and analyse them in space thermographic aerial survey and electromagnetic prospecting resulting in a map of clay layer thickness concerning the wetland hydrology water budgets established at different time scales several years one year a season illustrate the exchanges between the watershed the river and the wetland and water storage in the wetlands during flood events the results show how the upstream reservoirs built during the last 20 years presently control the preservation and functioning of downstream riparian wetlands monitoring and modelling of the hydrological functioning of one wetland site have made it possible to identify and quantify exchanges between the wetland especially in the unsaturated upper layer and its environment in situ measurements of denitrification rates in the wetland were used to make initial estimates of its nitrate elimination capacity

interpretation of shallow electromagnetic instruments resistivity and magnetic susceptibility measurements using rapid 1d 3d inversion we have developed an inversion process of electromagnetic induction emi data based on a two step approach with 1d inversion of the entire studied surface and a fast 3d inversion applied over limited areas this process is similar to that formerly used in resistivity prospection for the study of soil environmental engineering or archaeological explorations low frequency electromagnetic instruments referred to as slingram emi have highly useful specificities they are light are easy to move in the field and can simultaneously measure the ground s electric conductivity and magnetic susceptibility they have thus been used to map these properties over large surface areas within relatively short periods of time and at reasonable expense the possibility of combining several coil geometries has opened up the potential for multidepth techniques and systematic 1d inversion which are found to be sufficiently revealing to allow larger portions of surveyed areas to be analyzed in the targeted areas selected for 3d inversion the geometries of the 3d features and the resistivity and or susceptibility contrasts are determined this step is based on the method of moments where only 3d heterogeneities are meshed and only a small number of major characteristics such as contrast thickness width etc are sought we first applied this process to synthetic data then to data acquired at an experimental test site and finally to field cases the rapid 3d inversion complements the 1d inversion by solving a series of issues correction for the apparent anisotropy generated by the instrument configuration multiarched anomalies precise location of lateral changes and determination of the properties contrasts our inversion results highlighted the importance of the instrument geometry we also have determined that apparent magnetic susceptibility data can be more appropriate for the determination of the volume of man made features and can be highly complementary to conductivity data

joint inversion of em and magnetic data for near surface studies magnetic and electromagnetic measurements are influenced by magnetic susceptibility and thus are widely used in geophysical surveys for archeology or pedology to date the data inversion is performed separately a filtering process incorporating both types of data is presented here after testing the algorithm with synthetic data the algorithm is used in several case studies in archeological prospecting this approach presents two advantages establishing the presence of remanent magnetizations viscous or thermoremanent and achieving more refined depth analysis of the anomaly

isotope geochemistry and geochronology of the niujuan silver deposit northern north china craton implications for magmatism and metallogeny in an extensional tectonic setting the niujuan breccia type silver deposit forms part of the north hebei metallogenic belt along the northern margin of the north china craton the hercynian baiyingou coarse grained granite and the yanshanian er daogou fine grained granite are the major mesozoic intrusions exposed in this region here we investigate the salient characteristics of the mineralization and evaluate its genesis through zircon u pb and fluorite sm nd age data and pb s o h he and ar isotope data the orebodies of the niujuan silver deposit are hosted in breccias which contain angular fragments of the baiyingou and er daogou granitoids the 34s values of pyrite from the silver mineralized veins range from 2 4 to 5 3 the 206pb 204pb 207pb 204pb and 208pb 204pb ratios of the sulfide minerals show ranges of 16 837 16 932 15 420 15 501 and 37 599 37 950 respectively the 3he 4he and 40ar 36ar ratios of the fluids trapped in pyrite are 0 921 4 81ra and 299 34 303 84 respectively the 18o and 18dw values of the ore forming fluids range from 0 6 to 4 15 and from 119 4 to 98 7 respectively our isotopic data suggest that the ore forming fluids were originally derived from the subvolcanic plutons and evolved into a mixture of magmatic and meteoric water during the main hydrothermal stage the ore forming materials were primarily derived from the lower crust with limited incorporation of mantle materials the emplacement time of the er daogou granite is constrained by la icp ms zircon u pb geochronology at 145 5 2 1 ma five fluorite samples from the last hydrothermal stage yielded a sm nd isochron age of 139 2 3 8 ma indicating the upper age limit for the silver mineralization these ages correlate with the formation of the niujuan deposit in an extensional setting associated with the closure of the mongol okhotsk ocean and the subduction of the paleo pacific oceanic plate beneath the north china craton

boiling and dilution in the shallow portion of the waiotapu geothermal system new zealand abstract the waiotapu geothermal system is the largest in terms of surface extent and heat flow 17 km2 and 600 mw respectively of the 20 major geothermal systems in the taupo volcanic zone new zealand two extinct dacite cones and a rhyolite dome rise about 500 m above the waiotapu valley the majority of thermal features occurs in the valley over a relief of only 100 m and lies within coincident apparent resistivity and 30 m depth thermal anomalies thermal features comprise near neutral ph chloride springs often boiling acid sulfate springs and mud pools and mixed waters the latter including both bicarbonate chloride and acid sulfate chloride springs the majority of the sulfate discharges to the surface in the northern higher altitude area while most chloride that reaches the surface does so in the southern portion of the system comparison of measured and calculated surface chloride flux the latter from measured heat flow and reservoir chloride concentrations indicates that at least half of the deep chloride does not discharge at the surface but flows laterally to the south at shallow depths mixing with groundwater the composition of well discharges indicates a shallow 400 m reservoir of chloride fluid about 1350 mg cl kg at 230 c is diluted by a co2 rich steam heated water nil chloride at about 160 c the latter located on the margins of the system this same dilution trend is apparent from the compositional variation and k na and k mg geothermometry of hot spring waters however there is chemical and stable isotope evidence from hot springs that cold groundwater also acts as a diluent at shallow levels and very near the surface steam heated acid sulfate waters mix with the upflow boiling of the deep chloride fluids prior to dilution results in the stabilization of k feldspar in contrast dilution at shallower depths by the steam heated waters both co2 rich and acid sulfate leads to the water compositions initially shifting to k mica and interstratified clay stability and to kaolinite stability with further dilution and temperature decrease the composition and distribution of these fluids are consistent with alteration mineralogy and zonation observed in drill core although boiling occurs at deeper levels and up to the surface in the upflow zone at waiotapu mixing is also common and is the dominant process on the margin and in the near surface portion of the system boiling of deep chloride fluid is very common in the upper 1 2 km of the upflow zone of most geothermal systems though it may be quenched by mixing with marginal waters either cold groundwater in high relief terrane or steam heated waters in areas of lower relief co2 rich steam heated waters are common on the margins of systems and will generally underlie the near surface acid sulfate steam heated waters interaction with co2 rich waters will form k mica and interstratified clays while acid sulfate waters cause kaolinite and even alunite to form the former assemblage is commonly associated with typical low sulfidation epithermal gold mineralization as wallrock alteration where gold bearing veins comprise adularia and illite in contrast kaolinite is rare and alunite absent from a direct spatial and genetic association with gold mineralization in this environment this implies that mixing of the deep neutral ph chloride fluid with surficial acid sulfate waters does not commonly lead to ore grade gold deposition mixing with and cooling by co2 rich steam heated waters leads to clay stability accounting for the large halos of clay alteration and low grade metal anomalies which often surround veins of high gold grade in contrast mixing with surficial acid sulfate waters is unlikely to cause precious metal mineralization because the chloride fluids have already lost the majority of their gold through deeper boiling and dilution

mafic intrusions in the footwall of the sudbury igneous complex origin of the sudbury impact melt sheet and its associated ore deposits abstract the majority of the mafic intrusions and volcanic rocks in the footwall of the sudbury igneous complex sic which is believed to have formed from a melt sheet produced by the impact of a very large bolide belong to one of two large mafic igneous suites viz the 2450 ma east bull lake ebl suite of intrusions or the 2200 ma nipissing diabase suite of intrusions this has been established by u pb la icp ms dating of zircons from the newly recognized frood intrusion which hosts the frood and stobie ore bodies and two of the sudbury gabbro intrusions and comparison of the geochemistry of these intrusions with that of the ebl intrusive suite and the nipissing diabase suite the age of the frood intrusion 2421 32 ma falls within error of other ebl type intrusions whereas the ages of the nairn 2203 11 ma and totten 2168 11 ma intrusions fall within error of published ages for the nipissing diabase moreover the primitive mantle normalized patterns of the petrogenetic trace elements on extended spidergrams of the nairn and totten sudbury gabbros are similar to those of the nipissing diabase as are those of the frood intrusion to other members of the ebl intrusive suite the ni cu pge sulfide deposits at sudbury are associated with the lower contact of the sic where a discontinuous inclusion rich norite contains much of the mineralization at the contact and an inclusion bearing quartz diorite is directly associated with the mineralization of the radial and concentric offset dykes the sublayer rocks and the overlying unit of melanocratic norites provide strong evidence for a relationship between the ore deposits and both inclusions and melts of mafic ultramafic target rocks the most common pre impact mafic ultramafic target rocks are intrusions of the ebl and nipissing diabase suites although there are also archean aged mafic ultramafic enclaves in the gneisses beneath the north range of the sic the totten orebody in the worthington offset and the kelly lake ore body in the copper cliff offset are directly associated with footwall rocks comprising sudbury gabbro and nipissing gabbro respectively whereas the frood stobie offset and the associated frood and stobie ore deposits are sandwiched in a breccia belt containing large rafts of amphibole megacrystic gabbro belonging to the extensively broken up frood intrusion olivine bearing mafic and ultramafic rocks some of which exhibit shock metamorphic features but others do not are common inclusion types and occur in diverse sublayer environments the unshocked melanorite and olivine melanorite inclusions share common geochemical characteristicsde indicating that they were derived from a similar source their geochemistry is also similar to that of the frood intrusion as well as the east bull lake intrusion this indicates that they may have been sourced from east bull lake type intrusions that were incorporated into the melt sheet at the time of melt generation mass balance calculations indicate that the felsic country rocks which account for 77 of the total volume of the sic and contain 18 ppm ni and 21 ppm cu together with the sulfide poor mafic country rocks which account for 23 of the sic and contain 133 ppm ni and 92 ppm cu have too little ni and cu to account for the ni and cu contents of the quartz diorite the composition of which provides an indication of that of the initial melt sheet calculations using the r factor equation of campbell and naldrett 1979 indicate that the magmas that formed the norites and the ore deposits had 137 ppm ni and 121 ppm cu mass balance calculations have been used to determine if the country rocks have sufficient ni and cu in them to generate the ore deposits the weighted median ni content of the sulfide poor

diagenetic and metallogenic ages of duobaoshan porphyry cu mo deposit in heilongjiang province the duobaoshan porphyry cu mo deposit is an important cu deposit in northeast china systematic isotope dating was conducted to determine the metallogenic age of the deposit la icp ms zircon u pb dating indicates that the parent granite porphyry rocks and the host rocks intruded at 474 8 4 7 ma and 478 1 4 1 ma respectively the biotite granodiorite outside the parent granite porphyry was formed at 483 9 4 5 ma meanwhile seven re os isotopic analyses of molybdenite yield a weighted average model age of 475 1 5 1 ma these data show that the ore forming process and the intrusion of the host rocks were completed in the early ordovician according to the ages of mineralization and intrusion of host rocks the sedimentary setting of the duobaoshan formation and the geochemical characteristics of rocks hosting the deposit the authors hold that the porphyry cu mo deposit was formed in an island arc regime related to plate subduction in the early ordovician and that the prospecting direction for such a type of porphyry copper deposits should be in the magma island arc belt distributed in duobaoshan yi ershi area

geochemistry of the j m howland reef of the stillwater complex minneapolis adit area i sulfide chemistry and sulfide olivine equilibrium platinum mineralization in the stillwater complex occurs within a complex sequence of olivine bearing plagioclase rich cumulates about 400 m above the base of the banded zone the reef consists of a 2 m thick layer of disseminated sulfides extending over the entire strike length of the complex in the area of this study the host rock to the reef sulfides shows a lateral transition over a strike length of 700 m from a heterogeneous olivine plagioclase cumulate mixed rock to a plagioclase olivine cumulate containing a high proportion of postcumulus bronzite with olivine preserved only as rare resorbed cores on bronzite grains platinum group elements within the reef correlate strongly with abundances of sulfides which show convincing textural evidence for having originated as immiscible sulfide liquid strong correlations are also observed between all six platinum group elements ni and cu despite the gradation in host rock mineralogy the sulfide fraction of the reef displays a constant bulk composition over 700 m of strike length containing 9 3 percent ni 6 9 percent cu and approximately 0 7 percent total platinum group elements principally pd these platinum group element concentrations are two to three orders of magnitude higher than those found in typical magmatic sulfide deposits and are attributed to equilibration of sulfide liquid with a very large volume of silicate melt olivines from the reef show a range of compositions from fo 71 to fo 85 and from 2 400 to 4 500 ppm ni a positive correlation is observed between nio and feo in olivines from sulfide bearing samples indicating ni fe exchange between olivine and sulfides on a local scale such that ni contents of olivines were buffered by that of the sulfide phase a value of 9 70 or 1 49 is obtained for the ni fe distribution coefficient between sulfide and olivine in agreement with values obtained at magmatic temperatures by boctor 1982 these observations may be interpreted in the framework of the plume model of campbell et al 1983 a pulse of replenishing magma enters the stillwater chamber as a buoyant plume and subsequently spreads to form a layer of hybrid melt sulfide liquation and olivine crystallization occur within the plume and the hybrid layer in response to mixing and subsequent cooling sulfide liquid attains high platinum group element concentrations during turbulent ascent and spreading of the plume crystallization of olivine from the hybrid layer gives rise to olivine sulfide boulders which settle to the floor of the chamber reaction between the boulders and the evolved liquid at the bottom of the chamber causes olivine to become more iron rich subsequent reequilibration between olivine and sulfide grains gives rise to the observed ni fe distribution

up down or sideways emplacement of magmatic fe ni cu pge sulfide melts in large igneous provinces the preferential localization of fe ni cu pge sulfides within the horizontal components of dike sill lava flow complexes in large igneous provinces lips indicates that they were fluid dynamic tra

an evaluation of the solubility of sulfide sulfur in silicate melts from experimental data and natural samples abstract an evaluation of the solubility of sulfur in silicate melts from experimental data obtained under a wide variety of experimental conditions has been undertaken under reducing conditions fo2 below qfm sulfur is present as sulfide ii oxidation state and precipitates as pyrrhotite or an fe s o sulfide phase when the sulfur concentration in the silicate melt is sufficiently high the basic solubility reaction is 1 2 s 2 g o 2 silicate melt 1 2 o 2 g s 2 silicate melt for silicate melts with high feo contents 10 wt feo sulfur dissolves as an fe3so2 or 2feo fes species when saturated with pyrrhotite fes sulfide melt 2feo silicate melt fe 3 so 2 silicate melt log k log x s 21ogx feo 0 8 at 1200 c 1 bar under saturated and unsaturated conditions 1 2 s 2 g 3feo silicate melt fe 3 so 2 silicate melt 1 2 o 2 g log k log x s 1 2 1og o 2 3 log x feo 1 2 log s 2 4 1 at 1200 c 1 bar log k also shows a positive pressure dependence 0 1 per kbar for silicate melts with low feo contents fes sulfide melt o 2 silicate melt feo silicate melt s 2 silicate melt log k log x s log x feo 5 8 9007ndash 1000 c 1 6 kbar for silicate melts with intermediate feo contents 1 10 wt feo the behavior of sulfur is more complex with sulfur probably present as an fes species fes sulfide melt fes silicate melt log k log x s 1 05 3000 t k 850 1200 c 1 bar 2 2 kbar the effects of temperature pressure melt composition and other experimental conditions have been assessed the ability to predict the solubility of sulfur in silicate melts has implications for the formation of ore deposits associated with igneous systems application of the results to natural systems shows that some samples have a concentration of sulfur higher than that which could have been dissolved in the silicate melt indicating that the magma carried excess sulfur and or sulfur has been added after crystallization of the magma

the ordovician igneous rocks with high sr y at the tongshan porphyry copper deposit satellite of the duobaoshan deposit and their metallogenic role abstract a strong link between high sr y arc magmas and porphyry cu mo au deposits has been recognized in recent years the tongshan and duobaoshan deposits are representative large cu mo au deposits in ne china we report la icp ms zircon u pb crystallization age of 471 5 1 3 ma for tongshan ore related granitoid re os isotopic analyses of the two chalcopyrite samples from tongshan deposit show a model age range of 470 2 477 1 ma the duobaoshan and tongshan ore related granitoids show higher sr y and la yb ratios the 34 s values of sulphides from the duobaoshan and tongshan deposits vary from 2 3 to 0 0 belonging to a magmatic hydrothermal system the pb isotopic ratios of the sulphides from the duobaoshan and tongshan deposit range from 17 201 to 18 453 for 206 pb 204 pb 15 445 to 15 551 for 207 pb 204 pb and 36 974 to 37 999 for 208 pb 204 pb indicating the addition of lower crustal material the duobaoshan and tongshan granitoids were formed in a subduction related continental arc setting produced by partial melting of juvenile hydrous basalts underplating the deep continental crust during the ordovician

the east bull lake intrusive suite remnants of a 2 48 ga large igneous and metallogenic province in the sudbury area of the canadian shield the 2 49 to 2 475 ga intrusions of the east bull lake intrusive suite occur in an east northeast trending discontinuous belt along the presently exposed boundary between the archean superior and the proterozoic southern provinces of the canadian shield near sudbury ontario the east bull lake intrusive suite is part of a regional paleoproterozoic magmatic event extending from 2 49 to 2 44 ga which also includes bimodal volcanic rocks felsic plutons and the regionally extensive hearst and matachewan dike swarms this regional magmatic event is thought to be the result of a mantle plume driven intracontinental rifting event that led to the development of a major basin to the south that was subsequently filled by sedimentary rocks of the huronian supergroup the east bull lake intrusive suite appears to have been emplaced along a major axial rift fault related to this rifting event compelling field and geochemical evidence summarized here indicates that the three largest east bull lake suite intrusions the east bull lake agnew lake and river valley intrusions crystallized from similar low ti high al tholeiitic parent magmas that originated in deeper more basic chambers it is proposed that the primary magmas for the east bull lake suite intrusions were second stage melts derived from a sublithospheric depleted mantle source that had been modified by neoarchean subduction and accretion events most of the petrological characteristics of the east bull lake suite intrusions reflect plagioclase dominated fractional crystallization that generated a pronounced fe enrichment trend in the residual magmas orthopyroxene is the high temperature pyroxene and occurs as a cumulus phase through most of the stratigraphy of each intrusion of the suite local olivine rich cumulates present in all of the major east bull lake suite plutons in some instances appear to be comagmatic with associated plagioclase rich cumulates a distinctive marginal facies comprising brecciated and locally thermally recrystallized and or partially melted footwall rocks is a common feature of the east bull lake suite plutons and indicates that a high energy flow regime existed during the initial stages of emplacement this marginal unit typically grades into a heterolithic inclusion rich gabbronorite that contains erratically distributed mafic autoliths and footwall derived xenoliths chemical contamination of the mineralized matrix of these inclusion bearing rocks can be extreme at a local scale the inclusion rich zone is overlain by a thick interval of undifferentiated plagioclase rich cumulates that locally display spectacular glomerocrystic textures rhythmically and irregularly modally layered leucogabbronorite and gabbronorite make up much of the middle parts of the stratigraphy massive to crudely layered ferrogabbro and ferrosyenite only occur in the uppermost part of the agnew lake intrusion varitextured gabbro and pegmatitic gabbro occur as irregular layers and local veins and pods throughout the stratigraphy the east bull lake suite is currently being explored for contact type platinum group element pge cu ni mineralization that has a clear spatial association with orthopyroxene rich cumulates which are otherwise poorly represented in these intrusions disseminated pge and cu rich sulfide mineralization is concentrated within the inclusion bearing zones but extends upward into overlying plagioclase cumulates and appears to have collected along the lower margins of these intrusions through the combined action of vigorous convection of the resident magma and downward percolation of dense mafic residual liquid the resultant narrow zones of sulfide mineralization were thus derived from a much larger volume of parent magma feeder dikes to the mineralized parts of the intrusions appear to have been saturated in sulfide upon emplacement and had relatively high background pge contents compared to those for other known magmatic pge deposits however the economic potential of the contact type mineralization hinges on the efficacy of the physical concentration process which upgraded the metal content and size of the original sulfide particles inside the magma chambers based on the proposed basal accumulation model the best prospective mineralization is most likely to occur in embayments along the sidewall and floor of the intrusions

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

partitioning of palladium iridium platinum and gold between sulfide liquid and basalt melt at 1200 c abstract iron nickel monosulfide and basalt glass containing trace amounts of pge equilibrated at 1200 c and fo 2 10 9 2 close to the wustite magnetite buffer and fs 2 10 0 9 have been analyzed for noble metals by radiochemical and instrumental neutron activation analysis the average contents of pge in coexisting fe ni sulfide and basalt glass respectively are pd 50 ppm and 0 5 ppb ir 50 ppm and 0 5 ppb pt 100 ppm and 10 ppb and au 0 7 ppm and 0 8 ppb the sulfide liquid silicate melt partition coefficients d values for the noble metals are 9 7 10 4 for pd 1 0 7 10 5 for ir 9 6 10 3 for pt and 1 0 9 10 3 for au the noble metals are strongly partitioned into sulfide liquid but the affinity of pd and ir for sulfide liquid is about 50 times greater than that of pt and about 500 times greater than that of au the d values indicate that equilibrium partitioning between immiscible sulfide liquid and basalt magma would result in fractionation of the noble metals which differs significantly from that generally observed in nature

the response of a three dimensional magnetic and conductive body in shallow depth electromagnetic prospecting summary the study of the abilities of an e m apparatus for shallow depth prospecting necessitates that we analyse the experimental data through theoretical modelling a 3 d model for a magnetic and a conductivity contrast is presented here applied to the slingram type sh3 case intercoil spacing equal to 1 5 m and frequency to 8 khz it shows that this apparatus is roughly equivalent to the classical wenner 1 m array and is more sensitive than magnetic prospection to susceptibility changes occurring in the soil above 60 cm depth the 3 d model will also be very valuable for the conception of improvements in the apparatus

rapid 1d 3d inversion of shallow resistivity multipole data examples in archaeological prospection fifteen years ago the introduction of mobile multipole arrays led to substantial improvements in shallow electric prospection because it allowed information related to thevertical distribution of ground resistivity in complement to the horizontal pattern of the detected features to be extracted however to make full use of this wealth of information further progress is needed to extendthequalitativeinterpretationofdatatoamorequantitative evaluation of the explored terrain to that intent we developed a two step process in the first step a 1d electric model is fitted to the data over the full explored area and in the second step using the moment method localized 3d interpretation is applied to limited areas for which the characteristics of a given feature require closer scrutiny after a first test with synthetic data generated using the surface integral 3d modeling method this process was applied to three different archaeological sites and one test site for both handheld pole pole array systems and a multipole continuous electric profiling mechanically pulled system at the test site the characteristics of a known wall were accurately recovered at the duntzenheim site the thickness and width of the archaeological remains determined by 3d interpretation corresponded to the features observedthrough excavation at the other two sites 3d interpretation made it possible to establish that the conductive features extend across the full extent of the superficial resistive second layers