gold in porphyry copper deposits its abundance and fate abstract porphyry copper deposits are among the largest reservoirs of gold in the upper crust and are important potential sources for gold in lower temperature epithermal deposits whether gold remains in porphyry copper deposits is important both to their economic attractiveness and to the distribution of gold in the upper crust cu au atomic ratios of porphyry copper ore deposits form a continuous range from about 5000 to 5 000 000 with a median near 40 000 which separates gold rich and gold poor deposits gold is found in porphyry copper deposits in solid solution in cu fe and cu sulfides and as small grains of native gold usually along boundaries of bornite sims ion probe analyses of ore minerals from the gold rich batu hijau kingking and skouries porphyry copper deposits show that bornite contains about 1 ppm au whereas chalcopyrite contains about an order of magnitude less chalcocite and covellite contain 10 20 ppm au but are not abundant enough to account for a significant part of the gold endowment in many porphyry copper deposits the amount of gold presently in solid solution in cu fe sulfides is not adequate to account for all the gold in porphyry copper deposits and the remainder is present as micron scale grains of native gold experiments in the cu fe s au system show that bornite and chalcopyrite can contain about 1000 ppm gold at typical porphyry copper formation temperatures of 600 700 c and indicate that bornite and chalcopyrite in porphyry copper deposits were saturated with respect to gold at temperatures of only 200 300 c in contrast cu au ratios of bulk ore in porphyry copper deposits would require bornite and chalcopyrite to be saturated with respect to gold at temperatures similar to those at which primary potassic ore and alteration are thought to form this indicates that the maximum gold endowment of porphyry copper deposits is probably fixed by the amount of gold that will go into solid solution in cu fe sulfides when the deposit forms at high temperature and that gold is not commonly added later from other sources although it can be redistributed during cooling or later events the experimental data also suggest that high temperature 600 700 c vapors can extract considerably more gold from porphyry copper systems than can low temperature 300 c alteration comparison to cu au ratios of volcanic emissions suggests further that high temperature processes remove copper relative to gold from porphyry copper systems whereas low temperature processes remove gold preferentially and that this can account for deposits with extremely low and high cu au ratios respectively deposits with cu au ratios between about 20 000 and 100 000 however probably reflect different degrees of removal of gold or copper by immiscible sulfides

effect of degassing on sulfur contents and δ 34 s values in somma vesuvius magmas sulfur contents and 34s values of somma vesuvius magmas are consistent with syneruptive open system degassing at temperatures of 800 850 c for plinian pumices and 1100 1200 c for lavas the extent of degassing appears to be greater in lavas than in pumices the key parameter controlling the 34s 32s ratio of somma vesuvius volcanics is the average magma oxidation state which generally varies from 0 85 to 1 20 nno units for lavas and from 1 20 to 1 40 nno units for pumices consequently s contents and 34s values of magmas constitute a potentially valuable tool in estimating their average redox conditions the results of this study may help in risk mitigation when the vesuvius magmatic system evolves toward eruptive conditions

chloride bearing materials in the southern highlands of mars chlorides commonly precipitate during the evaporation of surface water or groundwater and during volcanic outgassing spectrally distinct surface deposits consistent with chloride bearing materials have been identified and mapped using data from the 2001 mars odyssey thermal emission imaging system these deposits are found throughout regions of low albedo in the southern highlands of mars geomorphologic evidence from orbiting imagery reveals these deposits to be light toned relative to their surroundings and to be polygonally fractured the deposits are small

effects of h2o ph and oxidation state on the stability of fe minerals on mars 1 on mars there is evidence that solutions may have been present on the surface episodically in the past these solutions were derived by weathering minerals such as olivine and sulfides found in mafic ultramafic rocks and possibly sulfates and meteorite fragments upon removal of water and or supersaturation of solutions secondary minerals formed we present a theoretical model for the formation of the solutions and the subsequent precipitation of fe bearing phases the first fe bearing phases to weather via oxidation are sulfides troilite or pyrrhotite which produce secondary fe hydr oxides or fes 2 pyrite or marcasite and fe 2 sulfates such as melanterite melanterite may be replaced by fe sulfates that have decreasing h 2 o 3fe 3 2fe 2 increasing oxidation and increasing bulk oh oh 2so 4 at meridiani planum the presence of jarosite indicates that the solutions were oxidized with ph 4 5 the solutions were likely fe mg ca s04 cl rich and precipitated fe hydr oxides fe phosphates fe sulfates with low oh oh so 4 ca mg sulfates and possible halides along with si rich phases the minerals indicating an acid environment were preserved by either removing components such as salts or water from the system e g in dust storms or episodic aqueous events isolating the mineral surfaces from fluids using disequilibrium processes or a combination at other localities jarosite is below detection limits and schwertmannite may be present if schwertmannite is present the solution had near neutral ph 4 ph 10 and fe hydr oxides would have crystallized rapidly leaving mg na ca s04 cl rich solutions that likely precipitated ca phosphates ca mg na sulfates fe sulfates with moderate high oh oh so 4 halides si rich phases and possibly fe mg ca carbonates

spectral and geological study of the sulfate rich region of west candor chasma mars sulfates have been discovered by the omega spectrometer in different locations of the planet mars they are strongly correlated to light toned layered deposits in the equatorial regions west candor chasma is the canyon with the thickest stack of layers and one with the largest area covered by sulfates a detailed study coupling mineralogy derived from omega spectral data and geology derived from hrsc imager and other datasets leads to some straightforward issues the monohydrated sulfate kieserite is found mainly over heavily eroded scarps of light toned material it likely corresponds to a mineral present in the initial rock formed either during formation and diagenesis of sediments or during hydrothermal alteration at depth because it is typically found on outcrops that are eroded and steep polyhydrated sulfates that match any ca na fe or mg sulfates with more than one water molecule are preferentially present on less eroded and darker outcrops than outcrops of kieserite these variations can be the result of a diversity in the composition and or of the rehydration of kieserite on surfaces with longer exposure the latter possibility of rehydration in the current or recent atmosphere suggests the low surface temperatures preserve sulfates from desiccation and also can rehydrate part of them strong signatures of iron oxides are present on sulfate rich scarps and at the base of layered deposits scarps they are correlated with tes gray hematite signature and might correspond to iron oxides present in the rock as sand size grains or possibly larger concretions that are eroded and transported down by gravity at the base of the scarp pyroxenes are present mainly on sand dunes in the low lying terrains pyroxene is strongly depleted or absent in the layered deposits when mixed with kieserite local observations favor a spatial mixing with dunes over layered deposits sulfates such as those detected in the studied area require the presence of liquid water to form by precipitation either in an intermittent lacustrine environment or by hydrothermal fluid circulation both possibilities require the presence of sulfur rich groundwater to explain fluid circulation the elevation of the uppermost sulfate signatures suggests the presence of aquifers up to 2 5 km above datum only 1 km below the plateau surface

the role of magmatic sulfides and mafic alkaline magmas in the bingham and tintic mining districts utah this paper reports the existence of abundant magmatic sulfides in introduction latite lava vitrophyres and vent facies dikes from the bingham and the eruption of sulfur rich magmas from el chichon tintic districts in central utah these dikes and flows appear to luhr et al 1984 and mt pinatubo westrich gerlach be comagmatic with the ore related monzonite intrusions in addition 1992 in recent years has attracted attention to the limited analytical data suggest that the magmatic sulfides contain most of solubility of sulfur in intermediate magmas and the factors the cu and ag present in the latites magmatic sulfides are preserved potentially responsible for the formation of magmatic only in the least oxidized and least degassed lavas and vitrophyres sulfides and anhydrite however the occurrence of magpetrography of comagmatic dikes and intrusions suggests that matic sulfides in intermediate magmas is not universal resorption and oxidation s degassing of the globules may make many volcanic suites appear to be sulfide unsaturated the metal content available to a magmatic ore fluid minette and inasmuch as magmatic sulfides may sequester chalcophile shoshonite lavas occur in subordinate amounts in the latitic volcanic metals what would their presence signify in magmatic fields associated with latite monzonite intrusions and hydrothermal systems that formed porphyry cu and mesothermal vein ore deposits of the tintic ag pb zn cu au and bingham deposits do they sequester a significant portion of the porphyry cu au mo districts utah the ages chemical and magmatic cu pb zn ag and au thereby restricting modal compositions and field relations of the mafic alkaline lavas metal availability of subsequent ore forming fluids suggest that such magmas mixed and fractionated at shallow crustal we have examined the volcanic rocks from the tintic levels to form the ore related latites and monzonites the unaltered and bingham mining districts fig 1 utah and found mafic alkaline lavas in these districts are some of the most cu rich that almost all of the volcanic units contain magmatic lavas in the great basin province sulfides some quenched dikes and intrusion margins also have preserved magmatic sulfides comparable with those in the volcanic rocks several lines of evidence indicate that the volcanic and intrusive rocks are comagmatic keith et al 1989 1991 waite 1996 the tintic district and east tintic sub district in utah have recorded over

genesis of the au bi cu as cu mo w and base metal au ag mineralization at the mountain freegold yukon canada constraints from ar ar and re os geochronology and pb and stable isotope compositions the genesis of mineralized systems across the mountain freegold area in the dawson range cu au mo belt of the tintina au province was constrained using pb and stable isotope compositions and ar ar and re os geochronology pb isotope compositions of sulfides span a wide compositional range 206pb 204pb 18 669 19 861 208pb 204pb 38 400 39 238 that overlaps the compositions of the spatially associated igneous rocks thus indicating a magmatic origin for pb and probably the other metals sulfur isotopic compositions of sulfide minerals are broadly similar and their 34s vienna canyon diablo troilite v cdt values range from 1 4 to 3 6 consistent with the magmatic range with the exception of stibnite from a au sb quartz vein which has 34s values between 8 1 and 3 1 the 34s values of sulfates coexisting with sulfide are between 11 2 and 14 2 whereas those from the weathering zone range from 3 7 to 4 3 indicating supergene sulfates derived from oxidation of hypogene sulfides the 13c vienna peedee belemnite vpdb values of carbonate range from 4 9 to 1 1 and are higher than magmatic values the 18o v smow values of magmatic quartz phenocrysts and magmatic least altered rocks vary between 6 2 and 10 1 and between 5 0 and 10 1 respectively whereas altered magmatic rocks and hydrothermal minerals quartz and magnetite are relatively 18o depleted 4 2 to 7 9 and 6 3 to 1 5 respectively hydrogen isotope compositions of both least altered and altered igneous rock samples are d depleted from 133 to 161 vienna standard mean ocean water v smow consistent with differential magma degassing and or post crystallization exchange between the rocks and meteoric ground water zircon from a chlorite altered dike has a u pb crystallization age of 108 7 0 4 ma whereas the same sample yielded a whole rock ar ar plateau age of 76 25 0 53 ma likewise molybdenite re os model ages range from 75 8 to 78 2 ma indicating the mineralizing events are genetically related to late cretaceous volcano plutonic intrusions in the area the molybdenite re os ages difference between the nearby nucleus 75 9 0 3 to 76 2 0 3 ma and revenue 77 9 0 3 to 78 2 0 3 ma mineral occurrences suggests an episodic mineralized system with two pulses of hydrothermal fluids separated by at least 2 ma this in combination with geological features suggest the nucleus deposit represents the apical and younger portion of the revenue nucleus magmatic hydrothermal system and may suggest an evolution from the porphyry to the epithermal environments

geochemical behavior of sulfur in granitoids during intrusion of the south mountain batholith nova scotia canada abstract a detailed stable isotope s o and elemental major trace s content study of peraluminous s type granites and granodiorites of the south mountain batholith and the meguma group metasediments into which the batholith was intruded has been conducted on a regional and local scale near mt uniacke sulfur contents of the metasediments range from 5 to 2440 ppm and 34 s ranges from 3 7 to 26 3 sulfur contents of the igneous rocks range from 6 to 570 ppm with the granites 20 ppm having lower sulfur contents than the granodiorites 300 ppm approximately 30 to 60 of the sulfur in the granodiorites is present as pyrrhotite a late phase with most of the remainder being present as sulfur substituted into biotite an early phase 18 oq quartz values of the mt uniacke granodiorites are heavy a 12 2 indicating formation of the magmas by partial melting of sedimentary rocks major element variations suggest that the granites are related to the granodiorites by fractional crystallization of plagioclase quartz and biotite comparison of the sulfur contents of the granodiorites with experimental determinations of sulfur solubility suggest that the distribution coefficient of sulfur d s between the cumulate and the magma during fractional crystallization 4 the regional granodiorites have a relatively restricted range of 34 s values 5 4 to 8 4 while the regional granites have a wide range of 34 s values 1 6 to 15 0 granodiorites at mt uniacke with normal magmatic values 0 76 to 1 42 for 18 o quartz feldspar have 34 s values between 6 6 and 12 3 and show good negative correlations between 34 s and s feo and mgo contents some granodiorites at mt uniacke have anomalously low sulfur contents for their major element composition and 18 o quartz feldspar values 0 45 to 0 67 indicate that these samples have undergone hydrothermal alteration and this alteration event is probably responsible for the low sulfur contents a number of processes have been considered in order to understand the variations of 34 s partial melting of inhomogeneous source rocks may be responsible for some of the regional 34 s variations but this implies that the granites are not genetically related to the granodiorites inhomogeneous source rocks are an unlikely explanation for the systematic variations of 34 s observed over only a few kilometres at mt uniacke rayleigh fractionation accompanying the fractional crystallization of biotite 34 s pyrrhotites silicate s 0 5 to 1 0 can account for only a small component of the observed 34 s variations the assimilation of isotopically variable sulfur derived from the meguma group metasediments during fractional crystallization combined assimilation fractional crystallization or afc provides the best explanation for the 34 s variations transfer of sulfur from the country rock may have been possible by either bulk afc where all of the country rock material is incorporated into the magma or by selective afc where sulfur and other volatile elements only are transferred from the country rock into the magma selective afc could have been effected by a sloping mechanism of intrusion followed by the heating of country rock xenoliths to the point where extensive desulfidation reactions took place with sulfur being transferred from the country rock to the magma by a fluid phase

stockwork tungsten scheelite molybdenum mineralization lake george southwestern new brunswick scheelite molybdenite stockwork mineralization constitutes one component of the lake george polymetallic sb w mo au base metal deposit a complex hydrothermal center of late silurian ca 412 m y age in the fredericton trough of the northern appalachians the stockwork hosted by silurian graywackes in part calcareous is spatially and temporally related to a postkinematic cupola of biotite monzogranite and its formation overlapped in time with the emplacement of monzogranitic porphyry dikes mineralogical and textural evidence indicates that contact metamorphism associated with the cupola had ceased before the initiation of w mo mineralization and that it occurred at pressures of less than 1 75 kb in two stages a peak stage t 600 degrees c evident only in rocks of pelitic composition and a lower temperature reequilibration t 500 degrees c recorded in rocks of both pelitic and marly compositions the w mo deposit comprises three different scheelite and or molybdenite bearing veinlet types type 1 bodies the earliest formed are calc silicate granditic garnet wollastonite clinopyroxene and calcic amphibole quartz veinlets with ubiquitous ca and h metasomatic alteration envelopes mineralogical and fluid inclusion relationships indicate that the fluids ranged in temperature from 550 degrees to 228 degrees c and that temperature decreased away from the cupola the succeeding type 2 veinlets comprise quartz and lesser amounts of perthitic alkali feldspar muscovite calcite scheelite molybdenite and pyrite fluid inclusion evidence shows that mineralization dominantly occurred from 400 degrees to 175 degrees c under a confining pressure of 1 3 kb higher grade scheelite and molybdenite deposition was focused in a lower temperature zone to the north of the cupola in which co 2 effervescence occurred type 3 veinlets the last to form consist of prehnite molybdenite and quartz and represent a volumetrically minor mineralization type in both type 1 and 2 systems scheelite and molybdenite deposition appears to have been controlled by decreasing temperature and increasing ph temperature was a function of distance from the cupola for both veinlet types but the controls on ph were specific to each thus the ph of type 1 fluids was controlled by wall rock interaction h metasomatism whereas that of type 2 fluids was controlled by co 2 effervescence the economic stibnite quartz veins scratch et al 1984 occupy fractures which transect and therefore postdate all stages of w mo mineralization

reply sulphur isotope composition of the brunswick no 12 massive sulphide deposit bathurst mining camp new brunswick implications for ambient environment sulphur source and ore genesis the brunswick no 12 massive sulphide deposit occurs within a middle ordovician bimodal volcanic and sedimentary sequence that is thought to have formed in a continental back arc rift covered with a thick succession of carbonaceous hemipelagic and turbiditic sedimentary rocks the deposit consists of three en echelon lenses that are zoned from vent complex to bedded ore and bedded pyrite facies the bedded ore facies has the lowest average 34s values 14 2 but are only slightly less positive than laminated pyrite in footwall sedimentary rocks 34smean 15 1 34s values for the bedded sulphides show an upward increase from 14 2 in bedded ore to 16 5 in bedded pyrite average 34s values for vent complex 15 8 and underlying stringer sulphides 16 1 are consistently more positive than those for bedded ore in carbonaceous shales and siltstone of the patrick brook formation that underlie the deposit 34s values that range between 13 8 and 25 6 and the similarity of these values to those of the bru

terrane and basement discrimination in northern britain using sulphur isotopes and mineralogy of ore deposits this study of four well characterized and adjacent terranes in northern britain outlines the sulphur isotope variations assesses the overall importance of crustal and mantle sulphur and presents a model that can be applied to terrane distinction throughout the north atlantic caledonides the characteristics of metal components within the mineralization provide additional information that can be related to the nature of underlying basement and events from the onset of sedimentation to the cessation of mineralization within stratigraphically linked packages of rock the delta 34s data show that the dominant crustal units in each terrane whether upper crustal sediments or cratonic basement provide the main alternative sulphur source to the mantle and act also as the main contaminant of subcrustal melts the delta 34s values of granitoid related mineralization are either within the subcrustal melt range of 3 per thousand to 3 per thousand or deviate toward the values of major crustal units in the terrane i e toward 34s depletion in the southern uplands and toward 34s enrichment in the lakesman and grampian terranes more complex mineralization in the northern highland terrane is linked to the presence of thick north atlantic craton beneath upper crustal metasediments across the region the vein systems beyond the influence of magmatic components represent homogenized sulphur metals and fluids from local upper crustal units the sulphur isotope data and style of mineralization for the british terranes are compared with terranes of similar age along strike in eastern canada revealing notable correlations

the position and nature of the gander avalon boundary southern new brunswick based on geochemical and isotopic data from granitoid rocks in southern new brunswick the gander avalon boundary is obscured by boundary parallel faults and various cover sequences siluro devonian granites which intrude unequivocal gander or avalon rocks display exclusively negative 1 9 1 0 and positive 1 9 0 7 end t signatures respectively such contrasting nd isotopic signatures combined with other geochemical differences between plutons are potentially valuable tools for terrane analysis nine small devonian plutons intruding the boundary zone fall into contrasting geochemical groups with la lu n 4 the former are topaz bearing granites while the latter are volcanic arc type granites except for one pluton with an end t signature of 2 0 end t values range from 0 4 to 0 7 spanning the gap between type avalon and type gander plutons these results suggest the plutons sampled either i stratigraphically overlapping or tectonically interleaved gander and avalon basement rocks or ii a distinct basement source beneath the b

controls on palagonitization versus pedogenic weathering of basaltic tephra evidence from the consolidation and geochemistry of the keanakako i ash member kilauea volcano 1 on the summit of kilauea volcano incipient palagonitization and consolidation of vitric tephras from the 90 of the carbon is mantle derived we hypothesize that the palagonitized zones may denote the location of fossil steam vents similar to active vents exposed along circumferential faults on both the north and the south sides of the kilauea caldera elsewhere keanakako i tephras are weathering into pedogenic products that closely reflect modern environmental conditions under acidic soil conditions ph 6 0 tephra is undergoing dissolution with the development of opaline crusts on outcrop faces under more neutral soil ph 6 5 7 8 the pedogenic products reflect the degree of desilication of tephra mitigated by leaching dominantly smectite where mean annual rainfall is 50 cm yr and dominantly kaolinite allophane and or imogolite where rainfall exceeds 250 cm yr

isotopic ratio and concentration of sulfur in the undersaturated alkaline magmas of vulture volcano italy both the 34 value and the total s content of products from vulture volcano italy are mainly controlled by the separation of s gases predominantly so2 from high fo2magmas containing s predominantly as so2 4 the addition of evaporites to such magmas appears to be a relatively uncommon and limited phenomenon the total s content of the most primitive product of vulture volcano 5600 mg kg is very high the high 34s value of 4 indicates an origin through the partial melting of a mantle containing high s enriched in 34s of unknown origin

sulfur diffusion in rhyolite melts diffusion rates for sulfur in rhyolite melt have been measured at temperatures of 800 1100 c water contents of 0 7 3 wt and oxygen fugacities from the quartz fayalite magnetite buffer to air experiments involved dissolution of anhydrite or pyrrhotite into rhyolite melt over time scales of hours to days electron microprobe analysis was used to measure sulfur concentration profiles in the quenched glasses regression of the diffusion data in dry rhyolite melt gives dsulfur 0 05 exp 221 80rt which is one to two orders of magnitude slower than diffusion of other common magmatic volatiles such as h2o co2 and cl diffusion of sulfur in melt with 7 wt dissolved water is 1 5 to 2 orders of magnitude faster than diffusion in the anhydrous melt depending on temperature sulfur is known to dissolve in silicate melts as at least two different species s2 and s6 the proportions of which vary with oxygen fugacity despite this oxygen fugacity does not appear to affect sulfur diffusivity except under extremely oxidizing conditions this result suggests that diffusion of sulfur is controlled by one species over a large range in oxygen fugacity the most likely candidate for the diffusing species is the sulfide ion s2 re equilibration between s2 and s6 in oxidized melts must generally be slow compared to s2 diffusion in order to explain the observed results in a silicic melt undergoing degassing sulfur will tend to be fractionated from other volatile species which diffuse more rapidly this is consistent with analyses of tephra from the 1991 eruption of mount pinatubo philippines and from other high silica volcanic eruptions

metallogeny of tin magmatic differentiation versus geochemical heritage tio 2 sn and rb sr sn variation diagrams for granitic fractionation series from various tin and non tin provinces do not support the concept of geochemical heredity of tin i e the assumption of a primary crustal sn anomaly in tin provinces the controlling factor for the generation of tin granites is a special bulk distribution coefficient of sn probably dependent on the oxygen fugacity of the melt

chemical composition of rock forming minerals in gold related granitoid intrusions southwestern new brunswick canada implications for crystallization conditions volatile exsolution and fluorine chlorine activity chemical composition of rock forming miner als in appalachian siluro devonian granitoid intru sions southwestern new brunswick was systematically determined by electron microprobe the mineral chem ical data together with petrographic examination was used to test magmatic equilibration and to constrain crystallization conditions volatile exsolution and fluo rine chlorine activity of fluids associated with these intrusions mineralogical distinction between late silu rian to early devonian granodioritic to monzogranitic series gms and late devonian granitic series gs rocks is evident although both are subsolvus i type to evolved i type granitoids oxidized to reduced gms rocks consist of quartz plagioclase an 10 k feld spar biotite apatite titanite zircon monazite hornblende pyroxene magnetite ilmenite and sulfide gs rocks comprise quartz k feldspar pla gioclase an 10 mica group minerals zircon mon azite apatite sulfide ilmente magnetite topaz columbite and xenotime inter intrusion and intra intrusion variations in mineral chemistry are in terpreted to reflect petrogenetic processes e g assim ilation and fractional crystallization during granitoid evolution although magmatic equilibration among rock forming minerals are disturbed by subsolidus hy drothermal processes gms rocks appear to have higher magmatic temperatures variable levels of emplacement a range of fo2 i e reduced intrusions 10 16 7 10 13 4 and oxidized intrusions 10 14 0 10 10 5 bars and rela tively low fhf fhcl ratios 10 3 0 10 1 0 in exsolved fluids compared to gs rocks reduced gms intrusions bear higher gold potential and thus may be prospective targets for intrusion related gold systems

radioactive element distribution in the archean granulite terrane of jequie bahia brazil the radioactive element distribution in the archean granulite facies rocks of jequie brazil has been determined the k rb ratios show a large spread with majority of the values falling within the normal field k rb 300 the th u ratios fall into two groups one group with values in the range of 1 7 to 2 6 whereas the other group show th u values greater than 7 7 to 25 these distributions can be explained on the basis of the presence of accessory minerals apatite and zircon the relatively high concentrations of the radioactive and other elements in jequie granulites probably represents the relict primary geochemical character little modified during metamorphism the radiogenic heat production data for the area are calculated and using the measured regional heat flow value from nearby area an estimate of the relative thickness of the continental lithosphere is made using the model developed by oxburgh 1981

sulfur isotopic systematics of granitoids from southwestern new brunswick canada implications for magmatic hydrothermal processes redox conditions and gold mineralization bulk 34srock values sulfur contents and magnetic susceptibility were determined for 12 gold related granitoid intrusions in southwestern new brunswick the canadian appalachians the sulfur isotope compositions of sulfide minerals in some of the granitoid samples were also analyzed this new dataset was used to characterize two distinctive groups of granitoids 1 a late devonian granitic series gs and 2 a late silurian to early devonian granodioritic to monzogranitic series gms the gs rocks have a large range in 34s values of 7 1 to 13 with an average of 2 2 5 0 1 low bulk s contents 33 to 7 710 ppm and low magnetic susceptibility values 10 3 si indicative of oxidized magnetite series granites the exceptions for the gms rocks are the lake george granodiorite and tower hill granite that display reduced characteristics which may have resulted from interaction of the magmas forming these intrusions with graphite or organic carbon bearing sedimentary rocks the bulk 34s values and s contents of the gms rocks are interpreted in terms of selective assimilation fractional crystallization safc processes degassing processes may account for the 34s values and s contents of some gs rocks the characteristics of our sulfur isotope and abundance data suggest that mineralizing components s and au in intrusion related gold systems are dominantly derived from magmatic sources although minor contaminants derived from country rocks are evident in addition the molar sulfate to sulfide ratio in a granitic rock sample can be calculated from the 34srock value of the whole rock sample and the 34ssulfide or 34ssulfate value of sulfide and or sulfate mineral in the sample on the basis of s isotope fractionation and mass balance under the condition of magmatic equilibrium this may be used to predict the speciation of sulfur in granitic rocks which can be a potential exploration tool for intrusion related gold systems

the solubility of sulphur in hydrous rhyolitic melts experiments performed at 2 kbar in the temperature range 800 1000 c with fo2 between nno 2 3 and nno 2 9 where nno is the nickel nickel oxide buffer and varying amounts of sulphur added to hydrous metaluminous rhyolite bulk compositions were used to constrain the solubility of sulphur in rhyolite melts the results show that fs2 exerts a dominant control on the sulphur solubility in hydrous silicate melts and that depending on fo2 a rhyolitic melt can reach sulphur contents close to 1000 ppm at high fs2 at fo2 below nno 1 the addition of iron to a sulphur bearing rhyolite magma produces massive crystallization of pyrrhotite and does not enhance the sulphur solubility of the melt for a given fo2 the melt sulphur content increases with fs2 for fixed fo2 and fs2 temperature exerts a positive control on sulphur solubilities at least for fo2 below nno 1 the mole fraction of dissolved sulphur exhibits essentially linear dependence on fh2s at low fo2 and although the experimental evidence is less clear on fso2 at high fo2 the minimum in sulphur solubility corresponds to the redox range where both fh2s and fso2 are approximately equal a thermodynamic model of sulphur solubility in hydrous rhyolite melts is derived assuming that total dissolved sulphur results from the additive effects of h2s and so2 dissolution reactions the model reproduces well the minimum of sulphur solubility at around nno 1 in addition to the variation of the sulphide to sulphate ratio with fo2 a simple empirical model of sulphur solubility in rhyolitic melts is derived and shows good correspondence between model and observations for high silica rhyolites

paleoclimate of mars as captured by the stratigraphic record in gale crater a kilometers thick sedimentary sequence in gale crater exhibits stratigraphic changes in lithology that are consistent with transitions in aqueous and climatic conditions purported to be global in scale the sequence is divided into two formations where the lower formation exhibits a net transition in mineralogy from clay sulfate to sulfate oxide assemblages and is separated from the overlying upper formation by an erosional unconformity superposition and crater counts suggest strata in the lower formation lie along the noachian hesperian time stratigraphic boundary whereas beds in the upper formation which lack signatures indicative of clay minerals or sulfates are thinner more regularly spaced and clearly younger the observed stratigraphic trends are consistent with the rocks at gale crater recording a global transition from a climate favorable to clay mineral formation to one more favorable to forming sulfates and other salts

morphometric properties of martian volcanoes 1 mars orbiter laser altimeter mola data have been used to construct digital elevation models dem of the martian volcanoes in order to determine height flank slope caldera depth and volumes summit elevations range from 21 1 km to 0 5 km and relief varies from 1 0 km to almost 22 km average flank slopes are in the range of 1 to 10 consistent with basaltic shield volcanism the very low slopes of highland patera are also consistent with pyroclastic volcanism minimum volumes range from 1012 to 1015 m3 estimates of the time required to build these volcanoes on the basis of long term terrestrial eruption rates range from hundreds of thousands to tens of millions of years

magmatic sulfides and au cu ratios in porphyry deposits an experimental study of copper and gold partitioning at 850 c 100 mpa in a haplogranitic melt pyrrhotite intermediate solid solution gold metal assemblage at gas saturation abstract the behavior of copper and gold in the phase assemblage pyrrhotite po intermediate solid solution iss haplogranitic melt gold metal capsule at 850 c 100 mpa and gas saturation ah2o 0 9 has been investigated the results are presented as nernst partition coefficients the partition coefficient dcupo melt 2 6 0 3 103 1 was determined for po and melt in equilibrium with an iss of composition cu 19 1 fe 30 1 s 51 1 2 for gold the partition coefficients are dauiss melt 5 7 2 2 103 1 between iss and melt and daupo melt 140 40 1 between po and melt these imply dauiss po 42 9 1 between iss and po the oxygen fugacity for the experiments log f o 2 13 2 0 3 1 was determined by using the hydrogen sensor technique the sulfur fugacity log f s 2 1 0 0 7 1 was calculated from the composition of po in our experiments melts at iss saturation have cu fe by weight of ca 1 100 the results indicate that crystallization of iss may deplete a melt in gold and crystallization of po may deplete a melt in copper however a melt saturated with iss at a given bulk composition temperature pressure oxygen and sulfur fugacity and feo concentration will have a fixed concentration of cu preventing strong depletion of the melt in cu until iss is fractionated from the melt or changes in environmental conditions destabilize iss a thermodynamic model for the partitioning of cu and au between po and melt in terms of oxygen and sulfur fugacity indicates that dcupo melt and daupo melt may increase greatly with increasing sulfur fugacity and decreasing oxygen fugacity within the po stability field the model also suggests that destabilization of both iss and po relative to magnetite due to changes in oxygen and sulfur fugacities can result in the release of cu and au from the sulfides to the melt

magmatic arc asymmetry and distribution of anomalous plutonic belts in the batholiths of california effects of assimilation crustal thickness and depth of crystallization in order to better understand geologic fac tors controlling pronounced regional variations in whole rock chemistry mineralogy and mineral chemistry in the batholiths of california we calculate the magmatic intensive variables f hf f h 2 o f hf f hcl and f o 2 regional scale west to east increases in f oh in mafic silicates corresponding to the systematic i wc to i mc and i sc progression reflect orders of magnitude increase in f hf f h 2 o attending pluton crystallization low f hf f h 2 o of formation of western i wc types is consistent with their derivation from low fluorine source rocks in subducted oceanic slabs or the upper mantle in contrast higher f hf f h 2 o of crystallization of i mc and i sc types to the east implies the involvement of 1 progressively greater amounts of continental crustal source material such as biotite bearing metamorphic rocks their unweathered sedimentary derivatives retaining f rich mafic minerals or their fusion products and or 2 source materials which become more f rich toward the continental interior the regional distribution of i mc and i sc types suggests that the precambrian craton of western north america or derivative sediments may extend farther north in california and be morphologically more complex than previously thought from seemingly out of place occurrences of i wc plutons on the eastern slopes of the sierra nevada batholith we infer the existence of regions where precambrian basement was thin or absent in mesozoic time which prevented extensive cratonal contamination of subducted slab or upper mantle derived magmas new methods for estimating t f o 2 relations in the magmas demonstrate that i scr granites crystallize at oxygen fugacities as much as five orders of magnitude lower than those of i wc i mc and i sc types under conditions at or below the maximum stability limit of graphite in equilibrium with a c o h s gas phase the local scale formation of i scr granites in plutonic belts within specific wall rock terranes containing highly reducing sediments or metasediments may occur by contamination of i types with graphitic pelite or in some cases by the direct fusion of this reducing pelitic wall rock the spatial distribution of i scr granite provinces therefore is controlled simply by wall rock lithology amphibole geobarometry demonstrates a general west to east decrease in crystallization pressure across the sierra nevada batholith in contrast the peninsular ranges batholith displays a west to east crystallization pressure increase the bulk of the california batholiths crystallized at pressures less than 4 5 kb and depths less than about 15 19 km in the southern sierra nevada batholith the san gabriels and the eastern peninsular ranges however plutons crystallized at pressures exceeding 6 kb at deep crustal levels 23 km reconstruction of the pre erosion top of the batholith shows that in an east west cross section the central sierra nevada batholith was a horizontal tabular body with an aspect ratio of at least five to one

stratigraphy and eruptive history of the late devonian mount pleasant caldera complex canadian appalachians stratigraphic petrographic and geochemical evidence indicate that the volcano sedimentary rocks of the late devonian piskahegan group located in the northern appalachians of southwestern new brunswick represent the eroded remnants of a large epicontinental caldera complex this complex the mount pleasant caldera is one of few recognizable pre cenozoic calderas and is divisible into exocaldera intracaldera and late caldera fill sequences the intracaldera sequence comprises four formations that crop out in a triangular shaped area and includes thick ash flow tuffs thick sedimentary breccias that dip inward and stocks of intermediate to felsic composition that intrude the volcanic pile or are localized along caldera margin faults the exocaldera sequence contains ash flow tuffs mafic lavas alluvial redbeds and porphyritic felsic lavas that comprise five formations the late caldera fill sequence contains rocks that are similar to those of the outflow facies and comprises two formations and two minor intrusive units geochemical and mineralogical data support the stratigraphic subdivision and indicate that the basaltic rocks are mantle derived and have intraplate chemical affinities the andesites were probably derived from basaltic magma by fractional crystallization and assimilation of crustal material the various felsic units are related by episodes of fractional crystallization in a high level zoned magma chamber fractionation was repeatedly interrupted by eruption of material from the roof zone such that seven stages of caldera development have been identified the genesis of the caldera is related to a period of lithospheric thinning that followed the acadian orogeny in the northern appalachians

clay mineral formation and transformation in rocks and soils three mechanisms for clay mineral formation inheritance neoformation and transformation operating in three geological environments weathering sedimentary and diagenetic hydrothermal yield nine possibilities for the origin of clay minerals in nature several of these possibilities are discussed in terms of the rock cycle the mineralogy of clays neoformed in the weathering environment is a function of solution chemistry with the most dilute solutions favouring formation of the least soluble clays after erosion and transportation these clays may be deposited on the ocean floor in a lateral sequence that depends on floccule size clays undergo little reaction in the ocean except for ion exchange and the neoformation of smectite therefore most clays found on the ocean floor are inherited from adjacent continents upon burial and heating however dioctahedral smectite reacts in the diagenetic environment to yield mixed layer illite smectite and finally illite with uplift and weathering the cycle begins again

organic geochemistry and mineralogy i characterisation of organic matter associated with metal deposits abstract as geochemical appraisals of mineral regions of commercial prospectivity evolve the organic matter associated with metal rich ores has attracted greater attention petroleum basin and modern seafloor hydrothermal vent studies have suggested that organic matter can have a significant influence on the behaviour of mineralising fluids there have been many isolated reports of certain organic compositional or morphological e g pyrobitumen features showing an apparent relationships with hydrothermal fluids or minerals raising expectations that organic based parameters might be useful to mineral exploration however the understanding of organic inorganic relationships in earth systems is far from complete for example the detailed mechanics of the interaction of organics with hydrothermal fluids over geological time remain largely undefined organic geochemistry studies have traditionally involved the measurement and interpretation of the hydrocarbon composition of sedimentary rocks here we review the types of aliphatic hydrocarbons aromatic hydrocarbons and metalloporphyrins often detected from organic geochemical investigations in mineral rich regions such molecular data can be particularly diagnostic of biochemical sources and the palaeo environments at the time mineral associated organic matter was deposited sub surface trends of hydrocarbon alteration may also reflect major biogeochemical processes such as thermal maturity and biodegradation organic geochemistry data can also occasionally provide information about the nature e g origin composition temperatures and migration pathways of hydrothermal fluids and can make a contribution to holistic ore genesis models the well preserved organic matter associated with the economic here s your chance pb zn ag mine paleoproterozoic barney creek formation mcarthur basin australia and the transition metal rich early permian kupferschiefer formation germany poland have attracted significant attention a more detailed summary of the organic character of these deposits is provided to highlight the contribution organic geochemistry can make to understanding mineralisation processes most organic geochemical studies of highly mineralised regions however have not adequately addressed the significance of organic matter to mineralisation a slightly different analytical focus than traditionally used for exploration appraisal of petroleum hydrocarbons may be required to properly evaluate the significance of organic species to the mobilisation transport and deposition of ore metals the characterisation and subsequent thermodynamic modeling of organic substances and complexes within metalliferous hydrothermal systems will contribute to a better understanding of the nature and role of organic inorganic fluids or other affiliated organics in ore systems

gold contents of sulfide minerals in granitoids from southwestern new brunswick canada the abundance of gold and selected trace elements in magmatic sulfide and rock forming minerals from silurian devonian granitoids in southwestern new brunswick were quantitatively analyzed by laser ablation inductively coupled plasma mass spectrometry gold is mainly hosted in sulfide minerals i e chalcopyrite pyrrhotite and pyrite in some cases perhaps as submicron inclusions nanonuggets gold is below detection 0 02 ppm in major rock forming minerals i e plagioclase k feldspar biotite hornblende and muscovite and oxides i e magnetite and ilmenite gold distribution coefficients between sulfide and granitoid melt are calculated empirically as d text cpy melt text au 948 pm 269 text d text po melt text au 150 pm 83 text and d text py melt text au 362 pm 96 this result suggests that gold behavior in the granitoid systems is controlled by the conditions of sulfur saturation during magmatic evolution the threshold of physiochemical conditions for sulfur saturation in the melts is a key factor affecting gold activity gold behaves incompatibly prior to the formation of sulfide liquids or minerals but it becomes compatible at their appearance gold would be enriched in sulfur undersaturated granitoid magmas during fractionation partitioning into evolved magmatic fluids and favoring the formation of intrusion related gold deposits however gold becomes depleted in residual melts if these melts become sulfur saturated during differentiation leading to gold precipitation in the early sulfide phases of a granitoid suite late stage cl bearing magmatic hydrothermal fluids with low ph and relatively high oxidation state derived from either progressively cooling magmas at depth or convective circulation of meteoric water buffered by reduced carbon bearing sediments may scavenge gold from early sulfide minerals if a significant amount of gold produced in this manner is concentrated in a suitable geological environment e g shear zones or fracture systems intrusion related gold deposits may also be generated exploration for intrusion related gold systems should focus on the areas around evolved phases of granitoid suites that remained sulfur undersaturated for sulfur saturated granitoid suites the less differentiated phase and associated structures are the most prospective targets

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

emplacement depth and carbon dioxide rich fluid inclusions in intrusion related gold deposits phanerozoic intrusion related gold deposits have many consistent characteristics such as a spatial temporal and geochemical association with moderately reduced predominantly ilmenite series i type intrusions the deposits exhibit a range of characteristics that vary over a wide range of emplacement depths 7 km deposits in shallow crustal settings 5 km have characteristics of mesothermal environments and are hosted by plutons containing sheeted veins greissen and disseminated gold fluid characteristics also vary with depth deposits in shallow environments contain high temperature 350 c immiscible brine 30 wt nacl equiv and low salinity 5 wt nacl equiv vapor that commonly contains carbon dioxide deposits in deeper environments contain abundant low salinity carbon dioxide rich aqueous fluids 10 wt nacl equiv that in some deposits are postdated by moderate to high salinity brines 10 40 wt nacl equiv these contrasting fluid types are interpreted to be magmatic in origin and are the result of the complex interplay between exsolution of different volatiles carbon dioxide water and chlorine from felsic magmas emplaced at different crustal levels experimental studies have shown that carbon dioxide will exsolve from felsic magmas at much higher pressures than water and chlorine due to its lower solubility in the melt thus deposits formed from felsic magmas in deeper environments will contain abundant carbon dioxide rich fluids subsequent fluids released from the magma are likely to be water rich and more saline felsic magmas in shallow environments will contain lower concentrations of carbon dioxide that will partition into the vapor phase during phase separation between brine and vapor

open system degassing of sulfur from krakatau 1883 magma we present the first sulfur and oxygen isotopic data for tephra from the catastrophic 1883 eruption of krakatau sulfur isotopic ratios in unaltered krakatau tephra erupted august 26 27 1883 are markedly enriched in 34s relative to mantle sulfur high 34s values of 6 3 to 16 4 can best be explained by open system or multi stage degassing of so2 from the oxidized rhyodacitic and gray dacitic magmas with 34s enrichment of so2 4 remaining in the melt lower whole rock 34s values of 2 6 and 4 0 in two oxidized gray dacitic samples indicate more primitive subarc mantle sulfur in the 1883 magma chamber initial 34s of the rhyodacitic magma was probably in the 1 5 to 4 0 range and similar to 34s values measured in arc volcanic rocks from the mariana arc

petrologic and sulfur isotopic significance of highly oxidized and sulfur rich magma of mt pinatubo philippines dacitic pumices from pyroclastic flow deposits and air fall tephra of the june 14 15 1991 eruption of mt pinatubo philippines are characteristically rich in sulfur the presence of microphenocrystic anhydrite suggests that sulfur existed mostly as oxidized species in the magma this supposition is corroborated by unusually high sulfur contents up to 0 78 wt as so3 in apatite microphenocrysts and apatite inclusions in other phenocrystic minerals and by the highly oxidized state of the magma near or slightly below the hematite magnetite buffer on the basis of extrapolation from biotite compositions and the two oxide method this highly oxidized state possibly caused the extraordinarily high sulfur content of mt pinatubo dacite through prohibition of sulfide fractionation and because of increasing solubility of sulfur as oxidized species with increasing oxygen fugacity hornblende geobarometry indicates a pressure of 2 kbar for phenocryst formation among the two pumice types cummingtoniterimmed hornblende phenocrysts are typically found in type 1 white and crystal rich pumice whereas rare hypersthene has been observed as discrete microphenocrysts in type 2 tan and crystal poor pumice these observations indicate conditions at least near if not at vapor saturation in type 1 magma and undersaturation in type 2 magma prior to eruption vapor saturated type 1 dacitic magma probably caused the explosive june 14 15 1991 eruption the highly oxidized condition and magmatic water saturation are similar to those of intrusions related to porphyry copper deposits

most mars minerals in a nutshell various alteration phases formed in a single environment in noctis labyrinthus 1 a closed depression in the noctis labyrinthus region of mars at 10 4 s 98 6 w believed to have formed in the late hesperian holds an inner pit partially filled with several hundred meters of stratified material compact reconnaissance imaging spectrometer for mars crism visible near infrared reflectance data reveal signatures of numerous hydrated minerals including halloysite kaolinite fe smectite si oh bearing phases and fe sulfates polyhydrated monohydrated and hydroxylated types including jarosite we use crism data high resolution imagery hirise and hrsc high resolution stereo camera derived elevation to analyze the morphology composition and stratigraphy of these materials we propose an alteration sequence including formation of acid sulfate solutions from groundwater and magmatic sulfur which then locally altered the basaltic bedrock and layered sediments mainly deposited from volcanic tephra forming fe smectite and fe sulfates the mineral variability can mostly be explained by local variations in the ph of the altering fluids with original acidity being buffered by dissolution of primary minerals and by variable fluid input and evaporation and or freezing rates resulting in various water rock ratios this site shows local formation of almost all classes of minerals identified thus far on mars without invoking global conditions processes related to local volcanic activity and associated hydrothermalism were able to produce during an era in which the climate is believed to have been cold a large variety of hydrated minerals this study highlights the importance of the geological setting of hydrated minerals in the understanding of mars geologic and climatic evolution

apatite in igneous systems apatite is a minor but ubiquitous mineral in most igneous rocks although the modal proportion of apatite in common rocks is generally low it can reach high concentrations in enclaves cumulates and other rocks of low abundance i e rocks that constitute a small volume of the crust and mantle e g nelsonites the presence of apatite in most rocks is due not only to its low solubility in naturally occurring melts and aqueous solutions but also to the limited ability of common rock forming minerals to accept the amount of phosphorus that occurs in most rocks into their structure in this paper we will discuss some aspects of the occurrence texture composition physical chemistry and petrogenetic significance of apatite in felsic rocks i e andesite to rhyolite and their plutonic analogs in mafic i e basalts and related rocks and plutonic analogs and ultramafic rocks of the earth s crust and mantle fluorapatite is by far the most common member of apatite family found in igneous rocks however most natural fluorapatite contains some chlorine and hydroxyl as well and these constituents can attain high concentrations in some cases the other halogens bromine and iodine also occur in apatite but their concentrations are much lower than chlorine and fluorine many cations commonly substitute for calcium and phosphorus in apatite however they rarely reach concentrations that warrant the definition of a separate mineral species apatite can be described by the general formula a5 xo4 3z following sommerauer and katz lehnert 1985 the a site accommodates large cations e g ca2 sr2 pb2 ba2 mg2 mn2 fe2 ree3 eu2 cd2 na pan and fleet ch 2 in this volume and comprises two sites that exhibit vii fold

ore forming fluids associated with granite hosted gold mineralization at the sanshandao deposit jiaodong gold province china the sanshandao gold deposit with total resources of more than 60 t of gold is located in the jiaodong gold province the most important gold province of china the deposit is a typical highly fractured and altered disseminated gold system with high grade quartz sulphide vein veinlet stockworks that cut mesozoic granodiorite there are four stages of veins that developed in the following sequence 1 quartz k feldspar sericite 2 quartz pyrite arsenopyrite 3 quartz base metal sulfide and 4 quartz carbonate fluid inclusions in quartz and calcite in vein veinlet stockworks contain c o h fluids of three main types the first type consists of dilute co2 h2o fluids coeval with the early vein stage molar volumes of these co2 h2o fluid inclusions ranging from 50 60 cm3 mol yield estimated minimum trapping pressures of 3 kbar homogenization temperatures obtained mainly from co2 h2o inclusions with lower co2 concentration range from 267 375 c the second inclusion type with a co2 h2o ch4 composition was trapped during the main mineralizing stages these fluids may reflect the co2 h2o fluids that were modified by fluid rock reactions with altered wallrocks isochores for co2 h2o ch4 inclusions with homogenization temperatures ranging from 204 325 c and molar volumes from 55 to 70 cm3 mol provide an estimated minimum trapping pressure of 1 2 kbar the third inclusion type aqueous inclusions trapped in cross cutting microfractures in quartz and randomly in calcite are post mineralization and have homogenization temperatures between 143 228 c and salinities from 0 71 7 86 wt nacl equiv stable isotope data show that the metamorphic fluid contribution is minimal and that ore fluids are of magmatic origin most likely sourced from 120 126 ma mafic to intermediate dikes this is consistent with the carbonic nature of the fluid and the cross cutting nature of those deposits relative to the host mesozoic granitoid

sulfide mineral in intrusive and volcanic rocks of the bingham park city belt utah we report here the results of a reconnaissance study of sulfide inclusions in some intrusive and volcanic rocks from the bingham park city belt in central utah the study was undertaken to determine whether primary sulfides were preserved in these rocks and if so to assess their role in the geochemistry of copper in the magmas numerous samples were studied from the alta clayton peak and flagstaff stocks and a few samples were also studied from the little cottonwood last chance and soldier canyon stocks as well as from the phoenix dike and the keetley volcanics our results show that sulfides are present in unaltered intrusive and volcanic rocks although most of these inclusions lack hematite and pyrite that are typical products of degassing at least some inclusions appear to have been modified possibly by reaction with enclosing iron bearing host minerals measurements of the sizes of inclusions suggest that sulfides contain only 20 to 50 percent of the copper in the rock whereas sulfide selective analyses suggest that all of the copper in the rock is hosted by sulfides despite this uncertainty compositions of sulfides vary systematically from unit to unit the distribution of sulfide inclusions in different minerals suggests that mafic intrusions were saturated with sulfur over a longer period of time during their crystallization history than were felsic intrusions although there are exceptions chalcopyrite is most abundant in intrusions emplaced at deeper levels bornite is found in intrusions emplaced at intermediate levels and pyrrhotite is found in the shallowest intrusions and volcanic rocks finally apparently unaltered samples of the last chance soldiers canyon and phoenix bodies contain talnakhite a copper bearing sulfide mineral that was not observed in the other intrusive rocks in view of the close association of the last chance and phoenix bodies with the bingham porphyry copper deposit this relationship could be of use in evaluation of the mineral potential of felsic intrusive rocks