deciphering the hydrothermal evolution of a vms system by la icp ms using trace elements in pyrite an example from the bracemac mcleod deposits abitibi canada and implications for exploration textural and chemical characterization of pyrite was used to reconstruct the hydrothermal evolution of the bracemac mcleod archean volcanogenic massive sulfide vms deposits 6 mt in the matagami district abitibi canada the mineralization hosted in a bimodal volcanic sequence is divided into a 1 zn rich zone concordant to the key tuffite a marker horizon at the district scale 2 a cu rich zone which locally crosscuts the stratigraphic pile and 3 some localized magnetite rich zones replacing sphalerite and pyrite detailed petrographic and laser ablation inductively coupled plasma mass spectrometry la icp ms studies of whole pyrite grains including inclusions and zonation from the key tuffite and from the different ore zones of the deposits has revealed five pyrite types nodular pyrites i in the key tuffite and subidiomorphic pyrites from the low temperature 250 c zn rich zone ii have the same chemical signature suggesting that both precipitated under similar physicochemical conditions a wide range of trace elements cu zn ag sn sb te au pb bi tl are present in both but compared to the other types of pyrite they are significantly enriched in sb and tl subidiomorphic pyrites from the copper rich zone iii have a different signature enriched only in se co in pb and bi these pyrites commonly overgrow the nodular pyrites and are related to later higher temperature fluids 300 c pyrite preserved during a later magnetite replacement 350 c stage iv also are enriched in se but are depleted in all other elements a similar signature is found in idiomorphic metamorphic pyrite v which occurs at the district scale during high temperature recrystallization of pyrite iv and v only the contents of ni co as and se are mostly preserved whereas other base metals are expelled from the pyrite structure consequently only ni co as se sb and tl were useful to reconstruct the hydrothermal evolution of the vms system and used to build a suite of discrimination diagrams specifically the ratio se tl can discriminate pyrites from mineralized zn rich zone se tl 10 000 the innovative approach of this study based on la icp ms acquisition of the chemistry of entire pyrite grains makes our results directly applicable for exploration consequently pyrite concentrate samples analyzed for as tl and se by more classical mass spectrometric techniques have the potential to be used for vectoring to ore by using the proposed discrimination diagrams

constraints on the energy and chemical balances of the modern tag and ancient cyprus seafloor sulfide deposits the size chemical composition energy flux and fluid composition of the tag hydrothermal sulfide deposit at the mid atlantic ridge and the size chemical composition and reaction zone characteristics of the skouriotissa volcanogenic massive sulfide deposit of the troodos ophiolite in cyprus are used to examine the energy requirements and chemical balances associated with the generation of a large volcanogenic massive sulfide deposit we conclude that formation of large sulfide deposits from oceanic hydrothermal systems is a geologically rapid process and occurs on timescales of hundreds of years with episodes of activity as short as a few tens of years separated by thousands of years of inactivity about 2 1019 j of energy supplied at high temperature is required to form a deposit the size of the tag mound metals up to 4 times the mass of any element present in the sulfide deposit are leached out of relatively small reaction zones most likely at the base of the sheeted dikes chemical balance can be struck for all elements except sulfur with a reaction zone 1 2 km3 in volume from which a small proportion of iron and large proportions of copper zinc and manganese are removed a sulfur balance requires that a significant fraction of sulfur be derived from reduction of seawater sulfate as suggested by stable isotope analyses we argue that the principal source of energy that drives hydrothermal circulation is latent heat of crystallization of magma close to the top of the plutonic section furthermore we speculate that activity of the tag hydrothermal system is related to periods of more rapid magma supply from the mantle at magma supply rates similar to those observed in volcanoes in hawaii and iceland

evaluating isotopic equilibrium among sulfide mineral pairs in archean ore deposits case study from the kidd creek vms deposit ontario canada recent developments in the measurement of 34s and 33s in sulfide minerals provide a new framework to evaluate isotopic equilibrium among sulfide minerals and a new tool to investigate mineralizing processes or sources of sulfur in ore forming systems isotopic equilibrium requires that values of 34s and 33s are highly correlated between mineral pairs and that deviations quantified as 33s from a reference mass dependent fractionation are the same for both minerals within experimental error in this contribution we apply this framework for the first time to natural samples and evaluate isotopic equilibrium among sulfide minerals from the archean kidd creek volcanogenic massive sulfide deposit in ontario canada two of eight sulfide mineral pairs showed clear isotopic disequilibrium in agreement with interpreted paragenetic relationships six other pairs have isotopic compositions that are consistent with equilibrium we discuss the implications of these results for the interpretation of mineral paragenesis and sulfur isotope geothermometry at kidd creek this technique offers new possibilities for evaluating sulfur isotope systematics in archean 2 45 ga ore deposits in which the range of 34s values is small but non zero values of 33s are common

petrology geochemistry and stable isotope studies of the miocene igneous rocks and related sulphide mineralisation of oued amizour ne algeria abstract the oued amizour granitoids of north africa were studied in order to assess the role of magma processes in the formation of the large zn deposit in the region access to material from a 800 m drillhole cutting the entire igneous succession greatly facilitated the investigation the rocks reveal from the top to the bottom two distinct lithologies volcanic mainly pyroclastic rocks and sub volcanic microgranitic plutonic granodioritic rocks both lithologies were subject to hydrothermal alteration the boundary between the two lithologies is marked by a massive 10 m thick anhydrite layer the geochemistry of these rocks shows that they are intermediate to felsic in composition and exhibit high k to shoshonitic calc alkaline features with i type signature the negative eu sr and nb anomalies and the high lile and lree enrichment observed in the whole igneous suite indicate that the various volcanic and plutonic rocks are genetically related the granitoids are considered to have formed under post collisional geotectonic regime during the miocene similar to those described in the alpine belt of northern africa the main sulphide mineralisation is dominated by sphalerite with rare marcasite melnikovite galena and minor but ubiquitous pyrite the sphalerite ore body of about 20 30 m thick is hosted by hydrothermally altered andesite breccias and volcanic tuff between the anhydrite layer at the base and the volcanic pile at the top replacement colloform and open space filling are the main ore texture patterns which indicate hydrothermal processes throughout successive percolation phases 34s of sulphides sphalerite pyrite and chalcopyrite vary between 7 2 and 4 5 n 22 mean 1 3 suggesting that magmatic fluids have played a major role in the formation of the oued amizour zn deposit however 34s of sulphates anhydrite and gypsum which are isotopically heavier ranging between 13 2 and 20 6 n 10 mean 16 3 likely reflect mixing between miocene seawater sulphate and magmatic sulphur fluid inclusion microthermometric measurements on anhydrite and gangue calcite yield a mean temperature of 200 c and salinity between 22 3 and 26 6 eq nacl calcite 18ov smow varies between 11 2 and 20 2 n 12 mean 16 7 and 13cv pdb varies between 3 7 and 11 0 mean 7 8 these results confirm the magmatic origin of the mineralising fluids with a marked contribution of seawater for precipitation of the oued amizour zn mineralisation low 13cv pdb could however be attributed to the contribution of carbon from unconsolidated mudstones and or magmatic carbon the observed data on the oued amizour zn deposit show that the mineralisation is part of vhms group with a kuroko type signature

morphological instabilities in pattern formation by precipitation and crystallization processes morphological instabilities in periodic patterns occurring both in precipitation and crystallization processes liesegang rings and crystal zoning are investigated and compared with similar patterns in geological samples zebra rocks and mud bands in snow sediments in classical liesegang systems undisturbed parallel or concentric precipitation bands are emanated from even or concentric diffusion sources in homogeneous diffusion matrices of gelatine or other gels in the case of superposing diffusion sources sources with undulatory curvatures or local diffusion barriers there may occur several types of instabilities within the sequence of regular patterns a gaps within the bands forming radial alleys free of precipitate b transition from broken bands to speckled patterns and c apparent branching of bands linked together by so called anastomoses calculations with a competitive particle growth cpg model show that lateral instabilities in liesegang bands gaps and radial alleys of gaps are the result of ostwald ripening effects taking place after precipitation apparent branching of bands or formation of anastomoses can be simulated with a prenucleation model according to ostwald s supersaturation theory similar irregularities can be observed in zebra rocks e g banded siderite whose bandings are commonly explained by sequential sedimentation processes a very different mechanism is assumed to be responsible for the origin of mud bands in snow sediments an initially homogeneous distribution of intrinsic mud in snow sediments can be arranged into parallel bands according to a crystal zoning mechanism which is based on repeated thawing and freezing of the snow sediment due to the daily alternation of sun and darkness

the multiple sulfur isotope architecture of the golden mile and mount charlotte deposits western australia the golden mile and mount charlotte deposits in the kalgoorlie terrane western australia display three main mineralization styles fimiston comprised of interconnected shear zones associated with ankerite pyrite hematite magnetite gold telluride alteration oroya made up of breccia bodies with v muscovite ankerite pyrite pyrrhotite gold telluride alteration and mount charlotte which consists of vein arrays with symmetrical ankerite sericite albite pyrite pyrrhotite gold alteration pyrite is in equilibrium with gold in all three mineralization styles and has been selected as a proxy to record the sulfur source of the mineralizing fluids as well as the nature of the hydrothermal processes the 34s 33s and 36s analyses on pyrite grains from the different mineralization styles including oxidized and reduced sulfide oxide assemblages reveal 1 a large variation in 34s from 12 6 to 23 5 and 2 a previously unrecognized occurrence of anomalous 33s and 36s signatures from 1 0 to 1 1 and from 2 3 to 0 9 respectively it is argued that the mineralizing fluids that formed the golden mile and mount charlotte deposits record mixing among three components mantle sulfur oxidized seawater sulfur e g so4 and reduced elemental sulfur e g s8 petrographic evidence in conjunction with 33s and 36s data suggest that mif s was acquired during the deposition of shales and basalts present in the kalgoorlie terrane and later mixed with mantle derived sulfur during the mineralization events the negative 34s values that predominate in fimiston style mineralization are consistent with a prevalence of oxidized fluids during the ore forming process as reflected by the presence of hematite pyrite magnetite gold assemblages conversely the positive 34s values that dominate in the mt charlotte and oroya mineralization styles reflect a reducing environment as reflected by the presence of pyrite pyrrhotite gold assemblages

in situ multiple sulfur isotope analysis by sims of pyrite chalcopyrite pyrrhotite and pentlandite to refine magmatic ore genetic models with growing interest in the application of in situ multiple sulfur isotope analysis to a variety of mineral systems we report here the development of a suite of sulfur isotope standards for distribution relevant to magmatic magmatic hydrothermal and hydrothermal ore systems these materials include sierra pyrite fes2 nifty b chalcopyrite cufes2 alexo pyrrhotite fe 1 x s and vmso pentlandite fe ni 9s8 that have been chemically characterized by electron microprobe analysis isotopically characterized for 33s 34s and 36s by fluorination gas source mass spectrometry and tested for homogeneity at the micro scale by secondary ion mass spectrometry beam sample interaction as a function of crystallographic orientation is determined to have no effect on 34s and 33s isotopic measurements of pentlandite these new findings provided the basis for a case study on the genesis of the long victor nickel sulfide deposit located in the world class kambalda nickel camp in the southern kalgoorlie terrane of western australia results demonstrate that precise multiple sulfur isotope analyses from magmatic pentlandite pyrrhotite and chalcopyrite can better constrain genetic models related to ore forming processes data indicate that pentlandite pyrrhotite and chalcopyrite are in isotopic equilibrium and display similar 33s values 0 2 this isotopic equilibrium unequivocally fingerprints the isotopic signature of the magmatic assemblage the three sulfide phases show slightly variable 34s values 34schalcopyrite 2 9 0 3 34spentlandite 3 1 0 2 and 34spyrrhotite 3 9 0 5 which are indicative of natural fractionation careful in situ multiple sulfur isotope analysis of multiple sulfide phases is able to capture the subtle isotopic variability of the magmatic sulfide assemblage which may help resolve the nature of the ore forming process hence this sims based approach discriminates the magmatic sulfur isotope signature from that recorded in metamorphic and alteration related sulfides which may not be resolved during bulk rock fluorination analysis the results indicate that unlike the giant dunite hosted komatiite systems that thermo mechanically assimilated volcanogenic massive sulfides proximal to vents and display negative 33s values the kambalda ores formed in relatively distal environments assimilating abyssal sulfidic shales

multiple dolomitization events along the pozalagua fault pozalagua quarry basque cantabrian basin northern spain the pozalagua quarry in the basque cantabrian basin of northern spain exposes a unique set of fault associated dolomites that can be studied on a decametre scale the dolomites developed along the pozalagua fault system in slope deposited limestones of albian age following marine phreatic diagenesis the limestones were subject to meteoric karst formation the resulting cavities were filled either by angular limestone fragments in a black clay rich matrix or by cave floor pond now dolomitized sediments the subsequent diagenetic history reflects repeated periods of fracturing fluid expulsion dissolution and cementation contrasting fluid pulses resulted in the formation of a network of hydrothermal karst and the subsequent development of coarse crystalline calcite cement zebra dolomite recrystallized coarse crystalline dolomite elongated blue grey coarse crystalline dolomite cement in the open fault and finally coarse crystalline saddle dolomite decimetre size reworked host rock fragments present in the latter two dolomite phases probably reflect roof collapse fragments of a cave system that developed along the pozalagua fault system however there are also metre scale host rock fragments that apparently float in the coarse crystalline saddle dolomites implying that either fragment assimilation was a widespread process or violent expulsion of fluids occurred along the pozalagua fault system the presence of pre dolomite and post dolomite stylolites parallel to bedding supports a linkage between the diagenetic events and the late albian tectonism that affected the region

a comparison of the horne volcanogenic massive sulfide deposit and intracauldron deposits of the mine sequence noranda quebec most of the massive sulfide deposits of the rouyn noranda area are associated with rhyolite and andesite flows of the mine sequence and occur within the noranda cauldron a volcanic subsidence structure related to partial evacuation of an underlying magma chamber the flavrian pluton the horne massive sulfide orebodies lie within a sequence of rhyolitic breccias located just south of the inferred margin of the subsidence structure and are separated from the mine sequence by the horne creek fault traditionally the horne deposits and the intracauldron deposits have been interpreted to occur within the same stratigraphic interval even though they share some characteristics such as mineral zoning patterns alteration assemblages and an association with synvolcanic faults the two deposit groups are clearly distinguishable intracauldron massive sulfide deposits are small 5 mt cu zn rich concordant mounds associated with interflow horizons and are closely linked to vent zones where synvolcanic faulting provided hydrothermal fluids with cross stratal structural permeability the three major sulfide deposits at the horne mine are much larger 20 150 mt and formed in a fault bounded sediment filled graben on the flank of a rhyolitic vent complex the orebodies are au cu rich but zn poor and have bowl shaped morphologies which resulted from extensive subsea floor sulfide precipitation whereas the intracauldron sulfide deposits lie within a bimodal flow dominated succession consisting mainly of andesite basalt and high silica rhyolite with volumetrically insignificant pyroclastic rocks the horne orebodies occur in felsic fragmental rocks and rhyolite flows which are part of a stratigraphic sequence which contains virtually no mafic volcanic rocks also compared to all intracauldron rhyolites the horne rhyolites show a fundamental depletion in incompatible trace elements such as the high field strength and rare earth elements which implies that the horne rhyolites may have followed a different magmatic evolutionary path such differences in deposit characteristics their paleoenvironments of formation and the physical volcanology and geochemistry of their host volcanic successions suggest that contrary to previous interpretations the massive sulfide deposits of the intracauldron mine sequence and those of the horne sequence may have formed at different stages in the evolution of the noranda cauldron

microchemical and sulfur isotope constraints on the magmatic and hydrothermal evolution of the black swan succession western australia the black swan succession consists of an archean bimodal dacite komatiite association largely dominated by ultramafic cumulates hosting a number of massive and disseminated magmatic sulfide orebodies although it was affected by multiple alteration events the low degree of penetrative deformation allowed the preservation of magmatic textures and stratigraphic relationships in this context we apply a combined multiple sulfur isotope and microchemical approach to unravel the potential of sulfides to simultaneously retain information about their magmatic and hydrothermal history negative 33s signatures in both massive 0 56 and disseminated 0 66 sulfide orebodies reflect the assimilation of photochemically derived sulfur into the komatiite magma which attained sulfide liquid supersaturation through the assimilation of crustal material analogous to the intercalated breccia dacite hosting colloform sulfides 33s 0 91 the slightly different 33s signatures between disseminated and massive orebodies reflect the assimilation of different proportions of crustally derived sulfur and imply that the respective sulfide liquids segregated from distinct komatiite magma pulses subsequent alteration episodes imparted to the black swan succession a concentric zonation consisting of a serpentinite core and talc carbonate margins the black swan disseminated orebody extends through both alteration styles without major variations in the dominant millerite pyrite sulfide assemblage pyrite in both serpentinite and talc carbonate samples exhibits a consistent trace element signature suggesting a relative immobile behavior of ni and co during the percolation of the talc carbonate fluids conversely variable 34s signatures between the two alteration styles reflect mobilization of sulfur during talc carbonate alteration whereas the 2 range of 34s values in serpentinites can be attributed to moderate equilibrium fractionation processes the 10 range of 34s values in talc carbonate rocks suggests that highly oxidizing fluids promoted the mobilization of sulfur as so42 which decreased the 34s of the disseminated sulfides furthermore sulfur isotope and microchemical signatures of euhedral pyrite from intercalated dacitic breccia indicate that this pyrite generation was deposited from a late hydrothermal event which is characterized by variable and least negative 33s signatures between 0 20 and 0 48 relative to all sulfide orebodies these features suggest that the late fluids developed in a heterogeneous hydrothermal system with a minor component of sulfur recycled from the sulfide orebodies

sulfur isotope and trace element data from ore sulfides in the noranda district abitibi canada implications for volcanogenic massive sulfide deposit genesis we examine models for volcanogenic massive sulfide vms mineralization in the 2 7 ga noranda camp abitibi subprovince superior province canada using a combination of multiple sulfur isotope and trace element data from ore sulfide minerals the noranda camp is a well preserved vms deposit rich area that is thought to represent a collapsed volcanic caldera due to its economic value the camp has been studied extensively providing a robust geological framework within which to assess the new data presented in this study we explore previously proposed controls on mineralization within the noranda camp and in particular the exceptional au rich horne and quemont deposits we present multiple sulfur isotope and trace element compositional data for sulfide separates representing 25 different vms deposits and showings within the noranda camp multiple sulfur isotope data for this study have 34sv cdt values of between 1 9 and 2 5 and 33sv cdt values of between 0 59 and 0 03 we interpret the negative 33s values to be due to a contribution of sulfur that originated as seawater sulfate to form the ore sulfides of the noranda camp vms deposits the contribution of seawater sulfate increased with the collapse and subsequent evolution of the noranda caldera an inference supported by select trace and major element analyses in particular higher concentrations of se occur in samples with 33s values closer to 0 as well as lower fe zn ratios in sphalerite suggesting lower pressures and temperatures of formation we also report a relationship between average au grade and 33s values within au rich vms deposits of the noranda camp whereby higher gold grades are associated with near zero 33s values from this we infer a dominance of igneous sulfur in the gold rich deposits either leached from the volcanic pile and or directly degassed from an associated intrusion

intense fracturing and fracture sealing induced by mineral growth in porous rocks article i nfo mineral precipitation in the pores of a rock may exert a force which is called crystallization pressure this process has been studied experimentally and results bring a new look on the way fractures may develop and seal in natural systems cylindrical core samples of porous limestone and sandstone were left for several weeks in contact with an aqueous solution saturated with sodium chloride at 30 or 45 c under axial normal stress in the range 0 02 0 26 mpa the fluid was allowed to rise in the core samples by capillary forces up to a controlled height where evaporation and precipitation occurred the uniaxial deformation of the samples was measured using high resolution displacement sensors the samples were characterized using computed x ray tomography allowing therefore imaging in 3d the intensity and localization of the damage two kinds of damage could be observed firstly small rock fragments were peeled from the sample surface secondly

composite synvolcanic intrusions associated with precambrian vms related hydrothermal systems large subvolcanic intrusions are recognized within most precambrian vms camps of these 80 are quartz diorite tonalite trondhjemite composite intrusions the vms camps spatially associated with composite intrusions account for 90 of the aggregate sulfide tonnage of all the precambrian intrusion related vms camps these low alumina low k and high na composite intrusions contain early phases of quartz diorite and tonalite followed by more voluminous trondhjemite they have a high proportion of high silica 74 sio2 trondhjemite which is compositionally similar to the vms hosting rhyolites within the volcanic host rock successions the quartz diorite and possibly tonalite phases follow tholeiitic fractionation trends whereas the trondhjemites fall within the composition field for primitive crustal melts these transitional m i type primitive intrusive suites are associated with extensional regimes within oceanic arc environments subvolcanic composite intrusions related to the archean sturgeon lake and noranda and paleoproterozoic snow lake vms camps range in volume from 300 to 1 000 km3 three have a sill morphology with strike lengths between 15 and 22 km and an average thickness between 1 500 and 2 000 m the fourth has a gross stock like shape the vms deposits are principally restricted to the volcanic strata above the strike length of the intrusions as are areally extensive thin exhalite units the composite intrusions contain numerous internal phases which are commonly clustered within certain parts of the composite intrusion these clusters underlie eruptive centers surrounded by areas of hydrothermal alteration and which contain most of the vms deposits early quartz diorite and tonalite phases appear to have intruded in rapid succession evidence includes gradational contacts magma mixing and disequilibrium textures they appear to have been emplaced as sill dike swarms these early phases are present as pendants and xenoliths within later trondhjemite phases the trondhjemite phases contain numerous internal contacts indicating emplacement as composite sills common structural features of the composite intrusions include early xenolith phases abundant small comagmatic dikes fractures and veins and in places columnar jointing internal phases may differ greatly in texture from fine to coarse grained aphyric and granophyric through seriate to porphyritic mineralogical and isotopic evidence indicates that early phases of each composite intrusion are affected by pervasive to fracture controlled high temperature 350 450 c alteration reflecting seawater rock interaction trondhjemite phases contain hydrothermal magmatic alteration assemblages within miarolitic cavities hydrothermal breccias and veins this hydrothermal magmatic alteration may in part be inherited from previously altered wall rocks two of the four intrusions are host to cu mo rich intrusive breccias and porphyry type mineralization which formed as much as 14 ma after the main subvolcanic magmatic activity the recognition of these precambrian subvolcanic composite intrusions is important for greenfields vms exploration as they define the location of thermal corridors within extensional oceanic arc regimes which have the greatest potential for significant vms mineralization the vms mineralization may occur for 2 000 m above the intrusions in some cases vms mineralization has been truncated or enveloped by late trondhjemite phases of the composite intrusions evidence that much of the trondhjemitic magmatism postdates the principal vms activity is a critical factor when developing heat and fluid flow models for these subseafloor magmatic hydrothermal systems

origin of dinantian zebra dolomites south of the brabant wales massif belgium zebra dolomites characterized by a repetition of dark grey a and light b coloured dolomite sheets building up abbabba sequences occur in dinantian strata from deep boreholes 2000 m south of the brabant wales massif in belgium these zebra dolomite sequences are several tens of metres thick the dark grey dolomite sheets a consist of non planar crystals 80 150 m in diameter these crystals display a mottled red orange luminescence and are interpreted to be replacive in origin the white dolomite sheets b consist of coarse crystalline nonplanar b1 dolomite which evolves outwards into transparent saddle shaped b2 dolomite the b1 dolomites possess a mottled red orange luminescence similar to the a dolomites while the saddle shaped b2 rims display red to dark brown luminescent zones the b1 dolomites are possibly partly replacive and partly cavity filling their b2 rims display criteria typical for a cement origin locally cavities exist between two succeeding white dolomite sheets these cavities make up 5 of the zebra rocks and are locally filled by saddle shaped ankerite and or xenomorphic ferroan calcite geochemical and fluid inclusion data th 120 c indicate a burial diagenetic origin for these zebra dolomites the a and b1 dolomites are characterized by similar geochemical compositions and fluid inclusion data pointing toward a related origin to explain the development of the zebra textures suprahydrostatic pressures in conjunction with late variscan tectonic compression are invoked a model involving dolomitizing fluids expelled during the variscan orogeny is proposed an overpressured system is also invoked to explain the important porosity development the creation of centimetre scale subvertical displacements of the zebra pattern and the microfractures affecting the b1 b2 dolomite crystals

atmospheric sulfur in the orogenic gold deposits of the archean yilgarn craton australia the origin of sulfur and gold in archean orogenic gold systems should provide significant insights into the dynamics of fluid movement in the crust of the early earth but is poorly constrained and highly debated our natural laboratory to address this knowledge gap is the metal endowed yilgarn craton western australia where we measured the multiple sulfur isotope signatures of representative sulfide bearing auriferous samples from 24 archean orogenic gold deposits varying in size and geological setting utilizing chemically conservative mass independent fractionated sulfur mif s isotope signatures we fingerprinted a major source of sulfur in these deposits contrary to previous studies our data show that they display mif s isotope anomalies with 33 s values ranging from 1 18 to 2 04 most of the studied deposits show a sulfur signature that is consistent with a crustally derived source unlike smaller deposits which may form with sulfur derived from a single sedimentary sulfur source therefore providing a coherent archean atmospheric signal in their 33 s 36 s slope 0 9 1 5 the formation of giant deposits may require sourcing from a wider range of sulfur reservoirs and using different processes as reflected in their apparently random 33 s 36 s slopes

oxygen and sulfur isotopic composition of volcanic sulfate aerosol at the point of emission volcanic sulfate aerosol is emitted from the vents of many active volcanoes but its origin has not yet been explained we report the first measurements of the isotopic compositions of near vent volcanic aerosol sulfate and use the combined sulfur and oxygen isotope systematics of the aerosol and magma at masaya volcano nicaragua to draw preliminary conclusions about the production mechanism of near source volcanic sulfate the sulfate aerosol does not display a significant mass independent oxygen or sulfur isotopic signature which suggests that primary volcanic aerosol does not contribute to the larger mass independent anomalies found in some ambient atmospheric aerosols and as preserved in ice cores the oxygen isotope composition of the sulfate appeared to become heavier on the particle filters with increasing amount of sample collected and suggests that the 18o value of the sulfate aerosol is 8 the sulfur isotopic composition of the sulfate did not vary with sample loading on the filters and had a mean 34s value of 7 7 0 8 similar to that of the magma 6 6 0 2 the low 17o value the 18o value of the magma 6 6 0 3 and the high 18o value of atmospheric oxygen 23 5 suggest that known atmospheric oxidation pathways at ambient temperatures are not the major routes of production for this sulfate instead the isotopic systematics of aerosol and magma are consistent with sulfate production either by high temperature equilibration of the magmatic gas mixture with small amounts of atmospheric oxygen or by direct emission of so4 2 from the magma

zebra dolomitization as a result of focused fluid flow in the rocky mountains fold and thrust belt canada discordant zebra dolomite bodies occur locally in the middle cambrian cathedral and eldon formations of the main ranges of the canadian rocky mountains fold and thrust belt they are characterized by alternating dark grey a and white b bands forming an abba diagenetic cyclicity these bands developed parallel to both bedding and cleavage dark grey a bands consist of fine 300 m non planar crystalline impure dolomite the white b bands are composed of coarse up to several millimetres milky white pure saddle dolomites b1 which are often covered by pore lining zoned dolomite b2 the b phases often possess a saddle shaped morphology in contrast to the replacement origin of the a dolomite the zoned b2 dolomite rims are interpreted as a cement formed in open cavities the b1 dolomite is interpreted as the result of recrystallization with diagenetic leaching of non carbonate components all the zebra dolomites studied are nearly stoichiometric and are characterized by enriched na and depleted sr concentrations fe and mn concentrations in these dolomites differ depending on the sample locality fluid inclusion data indicate that the dolomites formed from relatively hot th 130 200 c saline 20 23 wt cacl2 eq fluids a diagenetic high temperature origin is also supported by depleted 18o values 20 to 14 vpdb a contribution of 87sr enriched fluids is reflected in the 87sr 86sr values 0 7091 0 7123 zebra dolomite development is explained by focused fluid flow which exploited areas of structural weaknesses e g basin platform rim areas faults etc expulsion of hot basinal brines in a tectonically active regime generated overpressures which explains the development of secondary porosity during zebra dolomitization as well as the intra zebra fracturing at decimetre to micrometre scale

the significance of diagenetic crystallization rhythmites at the nanisivik pb zn ag deposit baffin island canada rhythmically banded ore textures at the nanisivik pb zn ag deposit are identical to those commonly referred to as diagenetic crystallization rhythmites or dcrs the presence of such textures in a demonstrably epigenetic orebody indicates that their formation is not necessarily indicative of early diagenetic sulfide mineralization although the development of such textures may occur in near surface and or early diagenetic environments their presence alone is not a compelling constraint on the timing of ore formation

caldera forming processes and the origin of submarine volcanogenic massive sulfide deposits certain volcanogenic massive sulfide vms ore deposits form in submarine calderas this association is well known but the link between caldera formation and the origins of the deposits remains poorly understood here we show that the size and location of a vms deposit within a submarine caldera may be determined by how and when the caldera formed these spatial temporal conditions control development of the hydrothermal system associated with the vms deposit we propose that caldera opening along outward dipping faults promotes magma degassing seawater influx and high temperature leaching resulting in a metal rich hydrothermal fluid these outward dipping faults are considered to provide critical pathways for ore forming fluids responsible for some caldera hosted vms deposits and may also be fundamentally important for the formation of many other caldera hosted ore deposit types

diagenetic replacement controlled by force of crystallization many diagenetic replacements in sedimentary rocks occur along thin solution films between the authigenic and host phases rather than conventionally invoking bulk pore water undersaturation for host phase dissolution we propose that many diagenetic replacements occur by a force of crystallization controlled replacement mechanism whereby nonhydrostatic stresses resulting from authigenic crystal growth are principally responsible for host phase dissolution this model explains diagenetic features such as the restriction of host phase dissolution to authigenic host crystal contacts and euhedral authigenic crystal faces in planar contact with unreplaced host phases as well as the relative replacement tendencies of some common authigenic minerals

genesis of the mississippi valley type zn pb deposit of san vicente central peru geologic and isotopic sr o c s pb evidence the san vicente zn pb ore deposit is situated 300 km east of lima in central peru within the upper triassic lower jurassic carbonate platform pucara group at the western margin of the brazilian shield production during the last 20 years and present reserves exceed 12 million tons of ore assaying about 12 percent zn and 1 percent pb sphalerite and galena the only ore minerals occur as lens shaped bodies generally parallel to the bedding within the 1 400 m thick pucara sequence three ore bearing dolomite units occur the ore lenses are bound to dolomitized tidal flat and lagoon facies with cryptalgal lamination and evaporite molds and to adjacent oolithic grainstones of barrier facies strontium carbon oxygen and sulfur isotope geochemistry was carried out on consecutive crystallization generations the results obtained display systematic trends the 87 sr 86 sr ratios range between 0 7077 and 0 7084 the first generations display values very similar to those of upper triassic lower jurassic ocean water later generations are slightly enriched in radiogenic strontium the degree of enrichment in radiogenic strontium is low compared to other mississippi valley type deposits the delta 18 o values range between 6 and 10 per mil pdb and the delta 13 c values between 2 and 1 per mil pdb the late crystallization generations are enriched in the light isotopes of oxygen and carbon compared to the first generations the sulfur isotope ratios of sphalerite are relatively homogeneous ranging between 9 9 and 13 0 per mil a trend to lighter sulfur isotope ratios with advancing diagenetic stage can also be recognized the san vicente lead zinc deposit formed during burial diagenesis the temperatures indicated by sulfur isotope geothermometry 75 degrees 92 degrees c would be consistent with temperatures reached at a burial depth of about 2 to 3 km this might have been reached by the end of the jurassic a model based on abiogenic reduction of sulfates at or near the ore site and the introduction of a zinc and lead bearing basinal brine characterized by strontium isotope ratios slightly higher than contemporaneous seawater and highly radiogenic lead is favored the association of the orebodies with peritidal facies with abundant sulfate molds is important evidence favoring the existence of two separate reservoirs for sulfur and metals leaching of detrital material derived from precambrian upper crust from the brazilian shield would explain both strontium and lead isotope ratios

internal zonation in a carbonate hosted zn pb ag deposit nanisivik baffin island canada zn pb ag ores at nanisivik northwest baffin island are hosted by upper proterozoic laminated dolostone of the society cliffs formation sulfide orebodies containing pyrite sphalerite galena sparry dolomite and pyrite pseudomorphous after marcasite are characterized by well banded ore textures considered to have resulted from the progressive replacement of carbonate wall rock textural and mineralogical variations enable the main orebody to be divided into three vertical and four horizontal ore zones the upper lens of the main orebody may be further subdivided into six texturally distinct laterally extensive mine units in the eastern upper lens where textural variations are best developed fluid inclusions indicate that most ore mineralization took place over the temperature range of 165 degrees to 210 degrees c and involved a brine containing 20 to 38 wt percent nacl equiv the sulfur isotope compositions of main and late stage pyrite crystals range from delta 34 s 27 4 to 28 0 per mil iron contents of sphalerite vary from 14 to 0 mole percent fes corresponding to well developed color zoning and constrain the oxygen activity of the ore fluid to 10 super 46 to 10 super 41 at 200 degrees c during sphalerite precipitation interbanded primary marcasite and sparry dolomite gangue indicates that the ore fluid fluctuated around ph 5 ore formation is modeled based on processes involving in situ reduction of sulfate by hydrocarbons and minor h 2 s encountered at the site of ore deposition the location and configuration of the orebodies was probably controlled in part by the former position of a horizontal fluid interface banding is likely the result of repetitive sulfate reduction metal precipitation wall rock dissolution and dolomite recrystallization in response to the pulsatory influx of ore fluid textural and mineralogic variations probably resulted from slight variations in the availability of reduced sulfur

australian volcanic hosted massive sulfide deposits features styles and genetic models the cambro ordovician period has yielded the major development of volcanic hosted massive sulfide vhms deposits in australia resulting in about 12 million metric tons of contained metal copper lead and zinc concentrated in the mount read volcanics tasmania and the mount windsor volcanics queensland the archean 4 million metric tons of metal and the silurian 3 5 million metric tons of metal constitute the next important episodes while the devonian and permian have produced isolated deposits the deposits range from cu type to zn cu type to zn pb cu type the zn cu type deposits are restricted to the archean and silurian whereas the cu type and zn pb cu type occur sporadically throughout the time span from early archean to permian in general terms the major vhms bearing districts are calc alkaline in character and display a thick basal pile of rhyolitic volcanics 1 3 km thick including lavas epiclastics and subvolcanic intrusions which is overlain by a polymodal sequence containing various proportions of rhyolite dacite andesite basalt and sediments the major deposits are commonly located at the top contact of the rhyolite pile or within the lower part of the overlying polymodal sequence there is a wide range in variability of styles of australian vhms deposits including mounds pipes sheets layered deposits stacked deposits stockwork and disseminated deposits distal reworked deposits and cyclic layered deposits although these various styles show a range of features there is a consistent theme across the spectrum of metal zonation alteration mineralogy alteration chemistry sulfur isotopes macrotextures microtextures and host volcanic relationships which strongly suggests that they all belong to the one genetic group of ore deposit the classic mound style deposits such as hellyer have a series of key features subsets of which are represented in the other deposit styles the mound deposits are considered to form from deposition of metal sulfides on the sea floor immediately around the hydrothermal vent growth of the mound occurs by upward replacement of sulfide assemblages stable at higher fluid temperatures leading to zone refining and lead zinc silver gold enrichment in the outer and upper parts of the mound departure from the classic mound style of deposit is related principally to three key factors the chemistry of the ore fluid salinity temperature f02 and ah2s the nature permeability and chemistry of the volcanic pile and the sea hoor environment sea hoor topography and seawater depth these factors control the aspect ratio of the deposit the extent of stringer zone development the degree of subsea floor replacement mineralization the nature and spatial development of footwall alteration and the development and style of related distal mineralization sulfur isotope studies of australian vhms deposits indicate that reduced seawater sulfate is a major source of sulfur in the deposit whereas lead and strontium isotope results are compatible with the metals being derived by seawater convection and leaching from the volcanic pile and basement rocks this conclusion is supported by the application of various leaching models which demonstrate the availability of an adequate source of both base and precious metals in the footwall volcanic sequences the input of metals directly from volcanic magma chambers is not precluded by the available data and one likely scenario involves the contribution of gold and copper from a magmatic vapor plume rising to mix with convective seawater fluids which contribute lead zinc silver and gold leached from the footwall volcanics and basement rocks the relative importance of the magmatic input compared with the seawater convective input may help to explain the spectrum of deposit styles arid their spatial relationship to volcanic centers or adjacent sedimentary basins

multiple sulfur isotopes and the evolution of earth s surface sulfur cycle abstract the distribution of sulfur isotopes in geological materials reveals information about earth history and biogeochemical processes research during the last several decades has used sulfur isotope geochemistry as a tool to better understand microbial processes harrison and thode 1958 kaplan 1975 monster et al 1979 peck 1959 peck 1962 rees 1973 and sediment diagenesis berner 1969 berner 1982 canfield et al 1993b earth historians also realized this potential as there exists a rich record of environmental change within the sedimentary records canfield and teske 1996 claypool et al 1980 goodwin et al 1976 habicht et al 2002 kah et al 2004 monster et al 1979 shen et al 2001 strauss 1993 thode and goodwin 1983 these applications have championed the use of the two most abundant sulfur isotopes 32s and 34s and provide a rich introduction to what the sulfur isotope record has to offer see canfield 2004 canfield and raiswell 1999 within the last decade this information has been supplemented by new data derived from the less abundant isotopes 33s and 36s the measurement of all four stable sulfur isotopes multiple sulfur isotope geochemistry has expanded our understanding of biological evolution and activity atmospheric chemistry and transport crustal recycling and many more fields related to earth surface processes see farquhar and wing 2003 here i present a review of recent works in multiple sulfur isotope geochemistry with a focus on results that inform our understanding of biogeochemical processes and earth surface evolution

crystal growth diagrams as an aid to interpreting the fabrics of calcite aggregates abstract the morphological and optical properties of crystal aggregates which develop by nucleated growth from a plane substrate are modelled by crystal growth diagrams such diagrams show that fabric maturation occurs through three growth stages 1 isolated 2 competitive and 3 parallel diagrams are presented which are constructed using calcite rhombohedra of equant 1011 obtuse 0112 and acute 4041 form the acute form develops in the most mature parallel growth stage length fast columnar crystals this graphical model is matched by a natural calcite cemented neptunian dyke the obtuse form develops in the most mature parallel growth stage approximately length slow bladed crystals this graphical model is matched by a natural calcite cemented dilational vein diagrams are presented which show seeded in contrast to nucleated growth seeding produces overgrowths which are divisible into an early epitaxial stage of rapid growth and a later idiomorphic stage the volume of epitaxial growth depends on surface area shape and lattice perfection of the seed and on the crystal habit of the overgrowth the overriding importance of echinoderm skeletal elements in stimulating epitaxial growth in limestones is related to their large size relative to other seeds and to their lattice properties polycrystalline seeds with parallel c axis orientation develop overgrowth aggregates which omit the competitive stage because the crystals are constrained to develop normally to seed surfaces even when these are not the directions of most rapid growth growth from polycrystalline seeds with random c axis orientation produce crystal aggregates similar to those developed by nucleation from a passive substrate crystal growth diagrams are presented to show the effect of a change in crystal habit during continuous growth the acute to obtuse change examined results in the crystal s greatest growth vector s being reorientated which in turn causes a new episode of fabric maturation this graphical model is matched by a calcite cement from a south wales grainstone t shaped crystals growth hiatuses on some crystal surfaces and enfacial junctions are created in both model and natural example the use of crystal fabrics in the diagnosis of cement the correlation between crystal fabric and saturation state and the standard of crystallographic observation in studies of calcite cement are criticized the match between accurately drawn crystal growth diagrams and natural crystal aggregates is excellent these diagrams are an underused aid in the stereological assessment of crystal aggregates and reveal features that are not intuitively obvious

geochemical characteristics of pyrite in the dabaozhuang deposit in the middle lower yangtze river metallogenic belt eastern china abstract dabaozhuang is a pyrite deposit in the luzong volcanic basin eastern china and has similar exhalation sedimentary features to volcanic massive sulfide deposits vms which commonly form in seawater to better understand the ore forming process of this special type of deposit we employed shrimp si and la icp ms to measure sulfur isotope and trace element compositions of anhydrite and four types of pyrite from the dabaozhuang deposit shrimp in situ sulfur isotope analysis indicates a narrow range in 34s of anhydrite 21 0 21 7 and variable ranges for pyrite 9 9 10 7 for pyrite vein in the deep py i 9 2 to 2 0 for cyclic annular and oval shaped pyrite in massive ore py ii 3 1 5 3 for massive or disseminated pyrite in the footwall tuff and hematite py iii and 29 7 to 30 4 for euhedral and coarse pyrite in the carbonate cement py iv 33s and 36s in four types of pyrite have no abnormal values indicating that sulfur isotope fractionation is mainly controlled by thermochemical sulfate reduction tsr the higher 34s values in type i pyrite and anhydrite indicate a mixing process of magmatic fluid and evaporates at depth py ii and iv have negative 34s data indicating the formation temperature of pyrite decreases because of the mixing of lake water 34s values in py iii are close to magmatic sulfur which shows the igneous sulfur tuff is an important sulfur source for the disseminated mineralization cobalt and ni content also show that the formation temperature of py i is highest and py iv is lowest this research indicates that the vms like deposits could be formed in continental volcanic lakes and are genetically related to so42 rich ioa iron oxide apatite deposits

the cryogenian balcanoona reef complexes of the northern flinders ranges implications for neoproterozoic ocean chemistry abstract the cryogenian balcanoona reef complexes of south australia consist of several dolomite platforms with well defined backreef reef margin and slope basinal facies the mature platforms have prograded large distances into the basin 15 km and have high relief margins over 1 km of relief at the platform margin backreef facies are dominantly ooidal peloidal grainstones with abundant tepees and marine cemented sheet cavities the reef margin facies consists of upper stromatolitic boundstones and where present deeper water non stromatolitic chambered and clotted boundstones the deepwater chambered and clotted boundstones grew on near vertical escarpments below 150 m paleo water depths and consist of a complex array of marine cemented cavernous and calcimicrobial material the strongly prograding platforms range from accretionary low angle stromatolitic boundstone margins through to more mature escarpment margins the mature escarpment margins 200 m high escarpment are characterized by the development of both stromatolitic and non stromatolitic boundstones the slope basin facies of the mature escarpment margins consists of coarse debris deposits talus debrites and allochthonous blocks proximal to the platforms and calcareous dolomitic mudrocks distal to the platforms the development of an accretionary escarpment margin together with the large proportion of deepwater boundstone suggests that these cryogenian reefs were fundamentally different from phanerozoic reefal systems the enormous volume of deepwater boundstone in these reefs may be due to a severely anoxic water column that prevailed during this period of the cryogenian anoxia led to greater degrees of carbonate saturation at depth that enabled the development of deepwater boundstones with escarpment margins a community of anoxic adapted non photosynthetic organisms that were perhaps similar in their ecology to phanerozoic coelobiontic reefal communities may have constructed the enigmatic deepwater boundstone just prior to the final termination of the reef the system was subject to large scale erosion and margin collapse producing a major regional unconformity following this the reefs briefly re grew before final and complete cessation of the reef complexes the large scale margin collapse event may have been triggered by sea level fluctuation and or changes in ocean chemistry associated with late cryogenian oxygenation

multiple dolomitization episodes in deep water limestones of the triassic lagonegro basin southern italy from early reflux to tectonically driven fluid flow abstract massive dolomitization does not commonly occur in deep water carbonates however this regional study on outcrops and subsurface samples of triassic lagonegro basinal carbonates from the southern apennines fold and thrust belt italy shows that the evolution of the lagonegro basin was punctuated by two events of massive dolomitization these processes resulted in two distinct dolomite types displaying different petrographic and geochemical features a medium crystalline and fabric preservative dolomite in the northern area molise campagna and san fele mount pierno contrasts with a medium to coarse crystalline and fabric destructive dolomite in the southern area from pignola to the high val d agri geochemical data increase in 18o with respect to typical late triassic seawater values high sr and low mn and fe content sr isotopes consistent with late triassic seawater indicate that the dolomite in the northern area is the result of an early replacement caused by a marine and possibly oxidizing fluid during shallow burial dolomitizing fluids likely were expelled through reflux from the norian apenninic carbonate platform towards the proximal lagonegro basin this reflux was promoted by the norian peculiar paleoceanographic and climatic conditions in the tethyan region and affected only the proximal basinal facies dolomites in the southern area display a decrease in 18o compared to late triassic seawater values and show lower sr higher mn and fe contents and higher sr isotope ratios compared to the early dolomites of the northern area fluid inclusion microthermometry reveals homogenization temperatures between 70 and 120 c and salinities of 1 9 to 6 4 wt nacl eq for saddle dolomites these geochemical signatures indicate that the southern area was affected by late diagenetic burial dolomitization interpreted to be the result of large scale tectonically driven fluid flow during the second compressional phase characterizing the southern apennines fold and thrust belt emplacement the dolomite distribution across the lagonegro basin northern and southern is possibly controlled by the paleogeographic distribution of the facies proximal vs distal as well as by their proximity to thrust faults the lagonegro case study demonstrates that basinal successions may undergo multiple dolomitization episodes in a manner similar to carbonate platform successions from early shallow to deep burial diagenesis one of the relevant implications is that in areas of restricted oceanographic circulation during periods of aridity reflux dolomitization may extend beyond the platform margin into deep water carbonates having the potential to alter their reservoir quality

evolution of the south central segment of the archean abitibi belt quebec part ii tectonic evolution and geomechanical model in this paper we describe the relations between the paleogeographic and tectonic evolution of the southwestern part of the archean abitibi and bellecombe belts volcanism in the abitibi belt created a very thick anisotropic plate composed of competent volcanic rocks and broken by the duparquet destor break the depocenters of the upper division of diverse volcanic rocks subsided about 10 km relative to their surroundings and some central volcanic complexes within this division were consolidated by synvolcanic plutons and their thermal metamorphic aureole the cadillac break a normal fault separated the abitibi and bellecombe belts the latter consisted of comparatively incompetent sedimentary rocks on top of a basement composed of ultramafic mafic flows north south compression of the volcanic terrain during the kenoran orogeny produced a set of flexure folds f1 that curve around the consolidated cores of central volcanic complexes generally in an easterly direction synclinoria nucleated at the dee

mineral growth in rocks kinetic rheological models of replacement vein formation and syntectonic crystallization abstract we model three cases of coupling between mineral growth kinetics and mechanical response of the rock i dispersed spherical crystals growing by replacement in a hydrostatically stressed elastic rock ii growth of veins or vein networks accommodated by viscous relaxation of surrounding rock and iii syntectonic crystallization in a rock undergoing bulk pure shear such models for the microscopic environment of mineral growth together with additional assumptions or knowledge about rheological behavior and aggregate geometry provide refined estimates of the behavior of a macroscopic volume element which could be combined with geochemical reaction transport models crucial in the models are the various consequences pressure solution creep fracturing of the local stress that is necessarily generated by mineral growth in rocks other than in pores in the first model the dispersed spherical crystals of mineral a are assumed to grow within a spherical volume of rock consisting of mineral b the mineralized zone mz itself embedded in elastic rock the macroscopic stress in the mz and the far field stress in the surrounding rock are uniform and hydrostatic mineral growth of the a crystals is driven by supersaturation with respect to mineral a is accommodated by replacement of b grains and leads to an expansion of the mz described by an infinitesimal strain the radial growth rate of a spherical crystal of mineral a with replacement of mineral b is da dt k a r tln a k b v 0 b k b v 0 b k a v 0 a where ka and kb are kinetic constants r is the gas constant t the temperature in kelvin and v0a and v0b are specific volumes reference saturation states of mineral a a 1 and host mineral b b 1 are specified at the far field hydrostatic stress 0 the microscopic environment of each crystal of a is modeled by a representative volume element rve consisting of a sphere of mineral a embedded in a spherical shell of mineral b in each rve stress is neither uniform nor hydrostatic the model links the local microscopic stress with the macroscopic stress in the mz and surrounding rock the second model refers to veins that make room for themselves by growing not to veins that form by cementation of previously opened or opening cracks if the growth of mineral a as propagating veins or as an interconnected vein network takes place by deformation and expansion of the mz with the deformation itself driven by the stress arising from the supersaturation driven growth the surrounding rock undergoes deformation and is treated as viscous the rate of growth in vein width w is dw dt 2 k a rtln a sv 0 a 1 m where m 16 kav0ac2 3b3 is the medium viscosity c is the vein radius and each vein is treated as centered in a spherical rve of radius b s is an effective tensile stress required for vein propagation for a vein network in which veins surround equant polyhedra of rock of radius b we set c b and drop the term in s for simplicity veins may also widen by replacement the ratio of vein widening by expansion to that by replacement is dw dt expansion dw dt replacement 3 b 16 3 b 16 k a v 0 a k b v 0 b k b v 0 b k a v 0 a both mechanisms of accommodation contribute equally when 3b 16kbv0b at higher viscosity replacement is dominant the incipient growth of a cylindrical crystal with circular cross section in a medium deforming in pure shear simulates syntectonic crystallization both dissolution and deformation of the host accommodate growth in the model the crystal tends to grow faster in the direction of maximum rate of extension in this direction the host mineral may either dissolve to accommodate growth or precipitate to form a pressure shadow accommodation by host dissolution is greatest in the direction of maximum rate of shortening

crystallization pressure versus crack seal as the mechanism for banded veins banded fibrous veins are often pointed to as evidence for episodic crack opening driven by oscillations in fluid pressure or bulk strain advances in understanding the geochemistry of precipitation data on veins and experiments suggest that pressure due to growing crystals may be an alternate explanation for many observations on these types of veins we propose that some veins originate at sites of precipitation and then propagate due to the pressure exerted by the crystal growth as materials precipitate the vein walls are pushed apart the resulting veins have shapes typical for mode i cracks except that mechanically crystallization pressure replaces the role of internal fluid pressure in their propagation a nonzero remote differential stress serves to align veins mechanical and geochemical considerations suggest that this process will be most important in fine grained rocks such as greenschist grade pelites where diffusion from sites of dissolution rather than advection is the dominant mass transport process veins may owe their orientation to tectonism but their initiation and growth are due to processes that supersaturate the pore fluid veins formed by this mechanism involve cracking to the extent that precipitation forces an original flaw to extend during precipitation cyclic quartz mica bands may indicate geochemical self organization at the vein wall driven by pressure solution enhanced supersaturation in the pore fluid and nonlinear precipitation kinetics at the vein wall

effects of temperature sulfur and oxygen fugacity on the composition of sphalerite from submarine hydrothermal vents experimental studies have shown that temperature pressure sulfur fugacity fs2 and oxygen fugacity fo2 influence the fe content of sphalerite we present compositional in situ data on sphalerite from submarine volcanic hosted massive sulfide vhms ores of hydrothermal vents from different plate tectonic settings and with variable host rock compositions sphalerite from sediment hosted vents has systematically higher s contents and fe zn ratios than those of the sediment starved vents reflecting an influence of fs2 and fo2 on fe partitioning between fluid and sphalerite the fe zn ratios of sphalerite from sediment starved vent systems apparently increase systematically with the fluid temperatures of the corresponding vents we conclude that the composition of sphalerite can be used to 1 distinguish between sediment hosted and sediment starved hydrothermal processes and 2 estimate minimum fluid temperatures of sphalerite precipitation from inactive sediment starved hydrothermal vent sites and fossil vhms deposits

siliciclastic grain breakage and displacement due to carbonate crystal growth an example from the lueders formation permian of north central texas u s a the lueders formation mid permian in baylor county texas is an intercalated suite of fluvial siliciclastic shallow marine siliciclastic and shallow marine carbonate strata there are at least two generations of carbonate cements probably originally composed of calcite in the fluvial sandstones where fractured grains are observed these cements represent the initial stages of caliche formation cementation is envisioned as a two step process in the first step calcite cements form from supersaturated fluids in a freshwater vadose environment as a meniscus cement at grain contacts areas of cement formation are restricted to these sites because fluid distribution is restricted to these sites stresses generated by the growth of cements at grain contacts are transmitted through and concentrated at quartz quartz grain point contacts until the stress is sufficient to fracture quartz grains even though the ultimate strength of calcite is less than that of quartz per unit area this process occurs too rapidly to be accommodated by pressure solution in the second phase of cementation cement nucleation is no longer restricted by vadose conditions in this phase calcite growth can no longer result in quartz grain breakage rather the quartz grains are dispersed in poikilotopic calcite cement

biogenic and thermogenic sulfate reduction in the sullivan pb zn ag deposit british columbia canada evidence from micro isotopic analysis of carbonate and sulfide in bedded ores abstract the layered clastic hosted sedex type proterozoic ca 1475 ma sullivan pb zn ag deposit was metamorphosed by several episodes of metamorphic recrystallization that have extensively modified or erased primary grain to grain textural relationships yet genetically significant variations of sulfur and carbon isotope ratios have been preserved at the millimeter and greater scale whereas sulfur isotope fractionations on a grain to grain scale cannot distinguish between likely formation temperatures and post peak metamorphic cooling the preserved fine scale and deposit scale stratigraphic variations of 34 s and 13 c bear on the origin and formational history of this deposit high spatial resolution documentation of accurate grain to grain and stratigraphic sulfur isotope variations in selected portions of bedded ore from the sullivan deposit was made possible by use of a cold stage during in situ laser assisted isotopic analysis pyrrhotite formed from biogenic sulfate reduction in the water column can be distinguished from sulfides e g sphalerite with higher 34 s values that formed in response to hydrothermal fluids in a brine pool isotopic analysis of carbonates in the presence of abundant sulfides was facilitated by development of a gas chromatographic carbonate extraction system with a high efficiency cryogenic trap calcite present in interlayered massive sulfide and siliciclastic layers in the bedded ore zone in trace amounts to a few weight percent records a carbon isotopic stratigraphy that suggests variable thermogenic sulfate reduction stratigraphic curves illustrating the variation in carbon and sulfur isotopes from the base of the main band to above the hu bands mine stratigraphic names in the bedded ore zone are similar in shape values of 13 c decrease abruptly at the base of the main band decrease slightly to the c band then increase to pre ore values the values of 34 s decrease from the base of the main band to the c band and then increase to pre ore values this similarity suggests some linkage between carbon and sulfur isotopic systematics and a sulfur budget dominated in the early stages of massive sulfide precipitation by hydrothermal processes involving thermogenic sulfate reduction giving way to bacteriogenic sulfate reduction in a closed then finally open marine basin

mineral deposits of canada a synthesis of major deposit types district metallogeny the evolution of geological provinces and exploration methods wayne d goodfellow editor 1 068 pp geological association of canada mineral deposits division special publication no 5 2007 hardcover isbn 13 978 1 897095 24 9 price members cdn 60 00 non members cdn 80 00 following in the footsteps of other landmark reviews of major ore producing countries such as australia hughes 1990 solomon and groves 1994 and south africa anhaeusser and maske 1986 this substantial 1 000 pages monograph is a great achievement that should be in every geologic research library in the world in many ways it sets a new standard most notably in that all figures and photographs are in color and that the entire volume is available in electronic form both as an included dvd and mostly on the gac website it is common in such compendia to have a spectacular cover photo or frontispiece to catch the reader s attention and this book does not disappoint the frontispiece photo is of a 61 8 kg sample from the dome mine timmins ontario and is stated to contain 20 wt percent gold at today s prices the gold alone would be worth 1 5 million dollars

investigating sulfur pathways through the lithosphere by tracing mass independent fractionation of sulfur to the lady bountiful orogenic gold deposit yilgarn craton abstract as sulfur is the primary complexing ligand for gold transport in aqueous fluids recent work has demonstrated that the archean systems can preserve mass independent fractionation of sulfur mif s to yield near zero values 33s1 0 0 5 in such cases interpretation of the geological significance of such isotopic signatures may be compromised as it is known that mass dependent fractionation of sulfur mdf s can yield small 33s values herein as 33sb often owing to geobiological reactions involving sulfur in this study we reassess the range of possible values of 33sb from the traditionally accepted value of 0 0 2 to demonstrate that this range is not constant but rather directly linked to the degree of 34s fractionation we present a multiple sulfur isotope dataset from the neoarchean lady bountiful orogenic gold deposit from the yilgarn craton western australia this deposit contains pyrite with an isotopic composition of 34s 2 1 0 8 and 33s 0 14 0 06 2sd on the mean the analysis of these results as well as of a data compilation from other 2 65 ga orogenic gold deposits of the yilgarn craton indicates that 33s1 values are too large to be the result of purely mdf s processes in addition when compared to a compilation of 3400 33s0 measurements of archean sedimentary rocks which shows highly variable positive and negative signals the remarkably constant positive mif s1 signature of gold deposits from the yilgarn craton with 33s1 values between 0 and 0 6 is evidence that the source of the auriferous fluids equilibrated at depth by mixing with a non mif s0 bearing sulfur reservoir by enhancing the application of mif s1 33s1 as a powerful and indelible tracer to understand the source and emplacement pathways of gold bearing fluids through the lithosphere the outcomes from this study demonstrate the recorded 33s1 signature in the auriferous fluids reflects the presence of sulfur that was at least partially sourced from an archean sediment reservoir

zebra textures in carbonate rocks fractures produced by the force of crystallization during mineral replacement abstract zebra textures are enigmatic banded fabrics that occur in many carbonate hosted ore deposits dolomite hydrocarbon reservoirs and carbonate successions globally they consist of a variety of minerals and are characterised by parallel light and dark bands that occur at a millimetre to centimetre scale based on petrological evidence there is general consensus that the dark bands formed by replacement of the carbonate host rock historically more contention surrounds the origin of the light bands but the dominant view is that these are mineral filled cavities which is supported by overwhelming textural evidence overall the feature common to all versions of zebra textures is mineral replacement of the original carbonate host we suggest that mineral replacement and the force of crystallization in association with open space generation is a viable mechanism for the development of zebra cavity systems dissolution and open space generation in either evaporites or carbonates adjacent to the site of replacement reactions is necessary to remove the confining pressure from the rock and to allow the development of fractures the pressure of the growing replacement crystals within the carbonate pervasively splits the carbonate apart producing thin strips of carbonate surrounded by open space the fractures may then be subject to dissolution and are later filled by cements very regular stratabound zebra textures as found in ore deposits like cadjebut australia and san vicente peru may be related to stratabound dissolution of evaporites or carbonates whereas irregularly distributed zebra textures are more likely to be associated with irregular carbonate dissolution

quadruple sulfur isotope analysis of ca 3 5 ga dresser formation new evidence for microbial sulfate reduction in the early archean abstract multiple sulfur isotope system is a powerful new tracer for atmospheric volcanic and biological influences on sulfur cycles in the anoxic early earth here we report high precision quadruple sulfur isotope analyses 32s 33s 34s 36s of barite pyrite in barite and sulfides in related hydrothermal and igneous rocks occurring in the ca 3 5 ga dresser formation western australia our results indicate that observed isotopic variations are mainly controlled by mixing of mass dependently md and non mass dependently fractionated non md sulfur reservoirs based on the quadruple sulfur isotope systematics 34s 33s 36s for these minerals four end member sulfur reservoirs have been recognized 1 non md sulfate 34s 5 2 33s 3 1 2 md sulfate 34s 10 3 3 non md sulfur 34s 6 33s 4 and 4 igneous md sulfur 34s 33s 0 the first and third components show a clear non md signatures thus probably represent sulfate and sulfur aerosol inputs the md sulfate component 2 is enriched in 34s 10 3 and may have originated from microbial and or abiotic disproportionation of volcanic s or so2 our results reconfirm that the dresser barites contain small amounts of pyrite depleted in 34s by 15 22 relative to the host barite these barite pyrite pairs exhibit a mass dependent relationship of 33s 34s with slope less than 0 512 which is consistent with that expected for microbial sulfate reduction and is significantly different from that of equilibrium fractionation 0 515 the barite pyrite pairs also show up to 1 difference in 36s values and steep 36s 33s slopes which deviate from the main archean array 36s 33s 0 9 and are comparable to isotope effects exhibited by sulfate reducing microbes 36s 33s 5 to 11 these new lines of evidence support the existence of sulfate reducers at ca 3 5 ga whereas microbial sulfur disproportionation may have been more limited than recently suggested

a review of the origin and setting of tepees and their associated fabrics carbonate hardgrounds often occur at the surface of shallow subtidal to supratidal lacustrine and subaerial carbonate shelf sediments these are commonly disrupted and brecciated when the surface area of these crusts increases in the subtidal environment megapolygons form when cementation of the matrix causes the surface area of the hardgrounds to expand similar megapolygons form in the supratidal lacustrine and subaerial settings when repeated incremental fracturing and fracture fill by sediment and or cement also causes the area of the hardgrounds to expand the arched up antiform margins of expansion megapolygons are known as tepees the types of tepees found in the geological record include 1 submarine tepees which form in shallow carbonate saturated waters where fractured and bedded marine grainstones are bound by isopachous marine phreatic acicular and micritic cements the surfaces of these brecciated crusts have undergone diagenesis and are bored unlike tepees listed below they contain no vadose pisolites or gravity cements 2 peritidal and lacustrine tepees are formed of crusts characterized by fenestral pisolitic and laminar algal fabrics this similarity in fabric makes these tepees of different origins difficult to separate peritidal tepees occur where the marine phreatic lens is close to the sediment surface and the climate is tropical they are associated with fractured and bedded tidal flat carbonates their fracture fills contain geopetal asymmetric travertines of marine vadose origin and or marine phreatic travertines and or terra rossa sediments the senile form of these peritidal tepees are cut by labyrinthic dissolution cavities filled by the same material lacustrine tepees form in the margins of shallow salinas where periodic groundwater resurgence is common they include groundwater tepees which form over evaporitic boxwork carbonates and extrusion tepees which also form where periodic groundwater resurgence occurs at the margins of shallow salinas but the dominant sediment type is carbonate mud these latter tepee crusts are coated and crosscut by laminated micrite the laminae extend from the fractures downward into the underlying dolomitic micrite below the crust both peritidal and lacustrine tepees form where crusts experience alternating phreatic and vadose conditions in time intervals of days to years cement morphologies reflect this and the crusts often contain gravitational meniscus vadose cements as well as phreatic isopachous cement rinds 3 caliche tepees which are developed within soil profiles in a continental setting they are formed by laminar crusts which contain pisolites and fractures filled by micritic laminae microspar spar and terra rossa most of the cements are gravitational and or meniscoid in ancient carbonates when their cementation and diagenetic fabric can be interpreted tepee structures can be used as environmental indicators they can also be used to trace the evolution of the depositional and hydrological setting

the fluid evolution of the nimbus ag zn au deposit an interplay between mantle plume and microbial activity abstract the nimbus ag zn au volcanic hosted massive sulfide vhms deposit represents an exceptional orebody in the yilgarn craton of western australia it is located in a zone of juvenile crust running n s through the eastern goldfields superterrane however unlike most other vhms occurrences associated with the 2690 2680 ma rift sequence teutonic bore jaguar bentley erayinia it is hosted by the ca 2705 ma plume related stratigraphy which is more typically associated with komatiite hosted nickel sulfide mineralization the nimbus deposit displays hybrid vhms epithermal characteristics resulting from low temperature and shallow water conditions which developed a quartz carbonate sericite dominated alteration assemblage in the dacite host rocks sulfide mineralization comprises pyrite sphalerite galena arsenopyrite ag sb pb bi sulfosalts and rare chalcopyrite in this study we applied a combination of in situ analytical techniques to monitor the evolving sulfur isotope signature of the mineralizing fluids and propose that the nimbus vhms deposit developed as a result of a bimodal fluid history in the first stage the hydrothermal system powered by plume related magmatism deposited a series of barren pyrite lenses with colloform textures their variable but consistently negative mass independent sulfur isotope fractionation signature 33s 0 81 reflects the interaction between mantle derived magmatic fluids and archean seawater the ubiquitous presence of carbon rich porous textures and the remnants of carbonaceous nests in colloform pyrite also indicate a significant contribution of microbial sulfate reducers during the incipient stages of sulfide precipitation the gradual formation of colloform lenses eventually sealed the hydrothermal system establishing a physical barrier that limited the interaction with seawater this process promoted the onset of higher temperature and pressure conditions required to form the high grade zn ag mineralization sourcing sulfur and fluids largely from a magmatic reservoir 33s 0 09 whereas the identification of a predominantly magmatic sulfur source is supported by sulfur isotope signatures the recognition of a magmatic origin of the fluid may only be inferred indirectly it is consistent with the observed quartz sericite alteration style and the proposed mechanism of sulfide deposition via decompression which does not require any interaction with seawater the trace element distribution of the ore related sulfides also supports a closed hydrothermal system developed through multiple fluid pulses indeed this ore forming scenario is commonly favored by high confining pressures which at nimbus were established following the deposition of the colloform pyrite lenses that progressively sealed the hydrothermal system creating the favorable conditions for mineralization

mass independent isotope effects in archean 2 5 to 3 8 ga sedimentary sulfides determined by ion microprobe analysis we report sulfur isotope anomalies with 33 s the deviation from a mass dependent fractionation line for the three isotope system 34 s 32 s vs 33 s 32 s ranging up to 2 within individual archean sedimentary sulfides from a variety of localities our measurements which are made in situ by multicollector secondary ion mass spectrometry unequivocally corroborate prior bulk measurements of mass independent fractionations mif in sulfur and provide additional evidence for an anoxic atmosphere on the earth before 2 ga this technique also offers new opportunities for exploring ancient sulfur metabolisms preserved in the rock record the presence of mif sulfur in sulfides from a 3 8 ga fe rich quartzite from akilia island west greenland is consistent with a marine sedimentary origin for this rock copyright 2003 elsevier science ltd

evaluating the role of microbial sulfate reduction in the early archean using quadruple isotope systematics abstract microscopic pyrites with low 34 s 32 s ratios in 3 47 gyr old sedimentary barites from north pole australia have been interpreted as evidence for microbial sulfate reduction and or sulfur disproportionation in the early archean we show that these microscopic sulfides have similar to slightly less negative 33 s and slightly more negative 36 s values compared to the enclosing sulfate crystals this finding is consistent with a primary mass independent signature overprinted by biological sulfate reduction as calibrated by previous experimental laboratory culture studies however it is inconsistent with an overprint by abiological sulfate reduction or sulfur disproportionation as predicted by isotope exchange theory and laboratory culture studies thus our multiple sulfur isotope measurements support the contention that sulfate reducing microbes had evolved by 3 47 billion years ago

ore textures within the u lens of the navan zn pb deposit ireland recent exploration in the vicinity of the giant 90 mt navan orebody has resulted in the discovery of ore grade mineralisation to the southwest of the deposit much of which occurs within the upper pale beds a horizon that is only weakly mineralised above the main orebody within this new u lens mineralisation preferentially occurs within bioclastic carbonate grainstones and calcareous quartz sandstones and is dominated by sulphide replacement of the carbonate component of the host sequence much of the replacive mineralisation is spatially associated with hydrothermal cavities which are filled by a variable mixture of brecciated replacement sulphide minerals space filling sulphide and gangue cements and internal sediments mineralisation also occurs within veins and dissolution seams and as disseminated sulphide minerals massive mineralisation is typically a complex chaotic combination of replacement cavity and fracture filling sulphides fluid inclusion analyses of ore stage saddle dolomite indicate temperatures at the time of sulphide precipitation of 90 150 c with a maximum of 175 c these temperatures are lower than those typically proposed for irish type deposits

extreme sulfur isotope fractionation in the late devonian dry creek volcanogenic massive sulfide deposit central alaska abstract the dry creek zn pb cu ag au volcanogenic massive sulfide vms deposit in east central alaska occurs in a late devonian sequence of peralkaline rhyolite tuff minor graphitic argillite and local peralkaline quartz porphyry rhyolite intrusions principal mineralized facies are semi massive and massive sulfide in variably silicified and graphitic rhyolite tuff massive sulfide in graphitic argillite disseminated sulfides in graphitic and non graphitic rhyolite tuff and vein hosted sulfides in a subvolcanic peralkaline quartz porphyry intrusion in situ analysis of the sulfur isotope composition of sulfide minerals from all facies of the deposit shows a total range in 34s values from 48 0 to 23 1 this remarkable 71 1 variation is more than twice the largest range known for sulfides in nearly all individual vms deposits both modern and ancient which typically is high precision ca id tims u pb geochronology of zircons from a synvolcanic peralkaline quartz porphyry intrusion yields a weighted mean 206pb 238u date of 363 02 0 43 ma 2 total uncertainty this date indicates that the formation of graphitic and sulfidic sediments at dry creek and contemporaneous vms mineralization occurred at least 3 6 m y before and hence are unrelated to widespread black shale deposition during the hangenberg event at ca 359 ma

origin and reservoir characteristics of upper ordovician trenton black river hydrothermal dolomite reservoirs in new york in the past decade more than 20 new natural gas fields have been discovered in laterally discontinuous dolomites of the upper ordovician black river group in south central new york the dolomites form around basement rooted wrench faults that are detectable on seismic data most fields occur in and around elongate fault bounded structural lows interpreted to be negative flower structures away from these faults the formation is composed of impermeable limestone and forms the lateral seal for the reservoirs in most cases the faults die out within the overlying trenton limestone and utica shale most porosity occurs in saddle dolomite coated vugs breccias and fractured zones matrix porosity is uncommon in the black river cores described for this study the patchy distribution around basement rooted faults and geochemical and fluid inclusion analyses supports a fault related hydrothermal origin for the saddle and matrix dolomites this play went for many years without detection because of its unconventional structural setting i e structural lows versus highs using the appropriate integrated structural stratigraphic diagenetic model more hydrothermal dolomite natural gas reservoirs are likely to be discovered in the black river of new york and in carbonates around the world

three dimensional visualization of the archean horne and quemont au bearing volcanogenic massive sulfide hydrothermal systems blake river group quebec the hydrothermal system architecture related to the formation of the contemporaneous au bearing horne and quemont volcanogenic massive sulfide vms deposits was visualized by employing kriging methods to map whole rock oxygen isotope compositions zones of silica addition and loss and water contents in two and three dimension zones of alteration were mapped in three dimensions in the vicinity of the steeply dipping horne deposit to depths of as much as 2 km in all nearly 300 samples were analyzed for oxygen isotopes and supplemented by previously published whole rock analyses contents of sio2 h2o mgo al2o3 and s from chemical analyses of nearly 5 000 samples within the two and three dimensional study regions were used separately and in combination with the oxygen isotope data for modeling and hydrothermal mapping purposes the horne and quemont deposits formed within a similar time frame but in different magmatic hydrothermal systems distinguished by their mapped hydrothermal architecture the quemont deposit appears to be centered on the powell pluton which intruded late into an apparent volcanic filled rift graben structure although structural complexities are apparent we infer mineralizing high temperature upflow in the footwall of the quemont deposit to have emanated from a reaction zone above the powell pluton and its precursors beneath a zone of extensive silicification faulting on the andesite fault and horne creek faults plus erosion has removed evidence of the upflow zone in the hydrothermal system of the horne deposit areas of silicification correspond in general with isotopic evidence of lower temperature alteration such alteration east of the quemont deposit signaled the waning of hydrothermal activity the suggested cooling for the most part promoted the precipitation of silica in the case of the horne deposit mixing of metalliferous hydrothermal fluid with cold seawater in the permeable footwall rocks in an apparently relatively stratigraphically stable and long lived hydrothermal system evidently led to marked footwall silicification the silicified footwall may have contributed to an increased efficiency of sulfide precipitation in the horne deposit continued intrusion and some post vms hydrothermal activity is recorded in the hanging wall section to the horne deposit our data suggest that deposition of the 10 million ounces moz of au within the horne deposit was syngenetic and not the product of subsequent hydrothermal activity

dimensions texture distribution and geochemical heterogeneities of fracture related dolomite geobodies hosted in ediacaran limestones northern oman predicting spatial distribution dimension and geometry of diagenetic geobodies as well as heterogeneities within these bodies is challenging in subsurface applications and can impact the results of reservoir modeling in this outcrop based study we generated a data set of the dimensions of fracture related dolomite geobodies hosted in ediacaran khufai formation limestones of the oman mountains that are up to several hundreds of meters long and a few tens of meters wide the dolomite formed under burial conditions by fluids that interacted with siliciclastic layers as demonstrated by the enriched fe up to 4 4 and mn up to 0 8 contents and signatures dolomitization probably occurred during the hercynian orogeny or pre permian because dolomitization predates some folding and pre permian rocks have seen intense deformation related to the carboniferous hercynian orogeny moreover dolomitization occurred between the onset and termination of bedding parallel stylolitization and thus most likely before deep burial related to the alpine orogeny hence dolomitization most likely occurred before deep burial related to the alpine orogeny and during or following the intense deformation related to the carboniferous hercynian orogeny had affected pre permian rocks the clumped isotope signature yields a temperature of approximately 260 c 500 f interpreted as the apparent equilibrium temperature obtained during uplift after deepest burial during the late cretaceous lateral transects across the dolomite bodies show that zebra dolomite textures are common throughout the body and that vugs are more common at the rim than the center of the bodies moreover a weak geochemical trend exists with more depleted fe and mn concentrations in the core than at the rim of the dolomite bodies these results show that minor heterogeneities exist within the dolomite bodies investigated these data contrast with previous studies in which more significant variation is reported in width of the dolomitization halo and texture for larger dolomite bodies that formed in host rocks more permeable than the examples from the oman mountains

evidence of local sourcing of sulfur and gold in an archaean sediment hosted gold deposit abstract determining the source of sulfur in an ore deposit is key to understanding the nature of the ore forming processes the neoarchaean paulsens sediment hosted gold deposit 1 moz 7 6 g t located in the pilbara craton of western australia exhibits many of the characteristics of phanerozoic shale hosted gold deposits e g huijiabao trend northern carlin trend and sukhoi log in that 1 black shales are the dominant host rock 2 gold is hosted in pyrite as both free gold and dissolved gold in the lattice of the pyrite and 3 multiple generations of pyrite have formed due to a variety of geological processes in this contribution we utilised secondary ion mass spectrometer sims to measure the in situ quadrupole 32 s 33 s 34 s and 36 s sulfur isotope compositions of the different generations of pyrite our results indicate that the both diagenetic and hydrothermal pyrite generations display similar and anomalous 33 s signatures up to 0 4 further the 33 s 36 s arrays in the hydrothermal pyrite generations lie on a slope which is similar to that of the diagenetic pyrite these data support the hypothesis that the sulfur in the ore zones came from the host hardey formation black shales we also performed trace element analyses of syn sedimentary and early diagenetic pyrite from the hardey formaiton using nano secondary ion mass spectrometry nanosims electron probe microanalysis epma and laser ablation inductively coupled plasma mass spectrometry la icpms all of which show that the syn sedimentary and early diagenetic pyrite contain high concentrations of many trace elements as ni co cu ag se te bi including up to 1 5 ppm au these metals contents are also abundant in the several generations of mineralised hydrothermal pyrite and form clear patterns of growth associated with couple dissolution reprecipitation reactions these findings clearly indicate that the fluid that transported the au must have also been enriched in the base and precious metals that are contained in the early syn diagenesis pyrite data from this study clearly support the hypothesis that in some sediment hosted gold systems all the sulfur and gold required to form the deposit are sourced from the local sedimentary package by using the presence of anomalous mass independent sulfur isotope signatures as chemically conservative and indelible tracers it is possible to fingerprint the source of sulfur in a wide range of mineral systems thus enhancing predictive exploration strategies at the regional to camp scales

multiple sulfur isotopes and the evolution of the atmosphere interest in multiple sulfur isotope analyses has been fueled by recent reports of mass independent sulfur isotope signatures in the geologic record a non zero multiple isotopic signature of sulfur 33s and 36s is produced primarily through photochemical reactions and it is an almost perfect tracer of the source of sulfur once the signature is passed on to a given sulfur reservoir it will be preserved unless there is addition of sulfur with a different 33s or 36s in the geological record this signature has been used to study the evolution of the earth s atmosphere and to trace movement of sulfur through geological systems early in earth s history recently small but significant mass independent signatures have been reported for some younger samples raising the possibility of additional applications of multiple isotope studies the purpose of this review is to introduce and discuss the implications of multiple isotope studies and to focus attention on these anomalous but not uncommon isotopic signatures

zebra and boxwork fabrics in hydrothermal dolomites of northern canada indicators for dilational fracturing dissolution or in situ replacement zebra and boxwork fabrics in manetoe and presqu ile hydrothermal dolomites provide critical data for discrimination between hypotheses for their origin in a unique occurrence sets of weakly imbricated decimetre sized curvilinear lenticles of white dolospar are developed within sub metre sized tongues of greyish white dolomitized crinoidal packstone and grainstone this nascent zebra fabric has developed along wavy to nodular intra bed sedimentary partings primary bedding can be traced through dolomitized masses containing these fabrics into the surrounding undolomitized limestone all zebra and boxwork fabrics are confined within single beds consistent with an early burial time of origin no change in bed thickness occurs across zebra or boxwork fabrics within beds this indicates a dissolutional rather than a dilational origin for the creation of pore space partly cemented with white dolospar the dolomitized groundmass displays an abruptly gradational or sharp transition to centripetal saddle dolomite cement which partially to nearly completely occludes vugs circulation of geothermally heated hypersaline devonian elk point basinal sea water brines led to dissolution and replacive dolomitization of limestone adjacent to vugs and near contemporaneous precipitation of white dolospar within dissolutional vugs consistent with geochemical simulations the presence of downward extending galleries of white dolospar cemented solution collapse breccia provides further support for an interpretation of regional thermally driven convection of hydrothermal evaporative sea water brines across a broad area of northern canada the absence of gases under pressure in vacuoles within fluid inclusions from manetoe and presqu ile dolospars is also more consistent with a dissolutional and contemporaneous dolomitization origin for these fabrics rather than an origin involving dilational fracturing for space creation and dolospar precipitation the ubiquitous presence of zebra and boxwork fabrics in hydrothermal dolomite reservoirs indicates that they are not confined fault zones and instead occur wherever precursor limestones had relatively greater porosity and permeability prior to dolomitization

massive hydrothermal dolomites in the southwestern cantabrian zone spain and their relation to the late variscan evolution abstract large scale massive burial dolomitization affected upper carboniferous carbonates of the southwestern variscan cantabrian zone spain replacive and void filling dolomites formed and were post dated by calcite cementation the process of dolomitization was due to the circulation of hypersaline and hydrothermal marine derived brines controlled by rock anisotropies the dolomites probably formed in early permian time during post thrusting orocline formation in an extensional setting lithospheric delamination induced increased heat flow and allowed thermal convection of the fluids the dolomites from the cantabrian zone are excellently exposed and represent an interesting outcrop analogue for hydrocarbon reservoirs elsewhere in comparable geotectonic settings of the european variscan orogen large masses of similar dolomites could have formed if mg rich brines were available

synvolcanic and younger plutonic rocks from the blake river group implications for regional metallogenesis the blake river group of the abitibi greenstone belt is host to the well known volcanogenic massive sulfide vms deposits of the noranda camp quebec canada in the noranda camp massive sulfide deposits are spatially associated with the coeval flavrian powell intrusive complex which is interpreted to have driven hydrothermal circulation that formed the deposits in the camp in the western blake river group in ontario there are also abundant intrusive rocks yet relatively insignificant accumulations of vms deposits these intrusive rocks are younger 2686 9 1 2 and 2688 5 2 3 ma and are associated with porphyry style cu mo au mineralization with re os molybdenite ages of 2682 4 5 ma the intrusions are also smaller in areal extent and do not have a temporally extended polyphase history like the flavrian powell intrusive complex the intrusions of the western blake river group can also be distinguished by lithogeochemical attributes and a distinct petrological history compared to the flavrian powell intrusive complex they have lower total y yb th hfse and ree with higher zr y la yb sm yb al2o3 yb and la smucn ratios and lower zr nb zr th zr la zr tio2 and nb thucn ratios petrologic modeling is consistent with the western blake river group intrusive rocks being generated as relatively low temperature melts 40 km in the crust where garnet is stable in the residue e g garnet amphibolite residue in contrast modeling of the flavrian powell intrusive complex is consistent with melting at shallower levels in the crust e g 800o to 850oc the occurrence of high temperature magmatism at high levels within this crust that is coeval with volcanic activity explains the occurrence of numerous vms deposits with the flavrian powell intrusive complex as this intrusive complex would have generated abundant heat at high levels in the crust to drive hydrothermal circulation in contrast the intrusions of the western blake river group were generated at depth and at lower temperature increasing the probability of heat loss upon emplacement from depth hence decreasing the probability of hydrothermal circulation at high levels in the crust and likely explaining the paucity of vms mineralization associated with these intrusive rocks the petrological attributes of the flavrian powell intrusive complex and western blake river group may be useful in delineating potentially fertile versus less prospective intrusive complexes in greenfields exploration areas notably the western blake river group intrusions have geochemical features similar to some phanerozoic porphyry cu mo au associated intrusive systems consistent with the observed mineralization and highlighting the potential of porphyry cu mo au systems of late archean age elsewhere in the abitibi

multiple sulfur isotope analyses support a magmatic model for the volcanogenic massive sulfide deposits of the teutonic bore volcanic complex yilgarn craton western australia we report sensitive high mass resolution ion microprobe stable isotopes shrimp si multiple sulfur isotope analyses 32s 33s 34s to constrain the sources of sulfur in three archean vms deposits teutonic bore bentley and jaguar from the teutonic bore volcanic complex of the yilgarn craton western australia together with sedimentary pyrites from associated black shales and interpillow pyrites the pyrites from vms mineralization are dominated by mantle sulfur but include a small amount of slightly negative mass independent fractionation mif anomalies whereas sulfur from the pyrites in the sedimentary rocks has pronounced positive mif with 33s values that lie between 0 19 and 6 20 with one outlier at 1 62 the wall rocks to the mineralization include sedimentary rocks that have contributed no detectable positive mif sulfur to the vms deposits which is difficult to reconcile with the leaching model for the formation of these deposits the sulfur isotope data are best explained by mixing between sulfur derived from a magmatic hydrothermal fluid and seawater sulfur as represented by the interpillow pyrites the massive sulfide lens pyrites have a weighted mean 33s value of 0 27 0 05 mswd 1 6 nearly identical with 0 31 0 08 mswd 2 4 for pyrites from the stringer zone which requires mixing to have occurred below the sea floor we employed a two component mixing model to estimate the contribution of seawater sulfur to the total sulfur budget of the two teutonic bore volcanic complex vms deposits the results are 15 to 18 for both teutonic bore and bentley much higher than the 3 obtained by jamieson et al 2013 for the giant kidd creek deposit similar calculations carried out for other neoarchean vms deposits give value between 2 and 30 which are similar to modern hydrothermal vms deposits we suggest that multiple sulfur isotope analyses may be used to predict the size of archean vms deposits and to provide a vector to ore deposit but further studies are needed to test these suggestions

evaporites in situ sulfur source for rhythmically banded ore in the cadjebut mississippi valley type zn pb deposit western australia the cadjebut orebody northern western australia is a mississippi valley type deposit with reserves of 3 5 million metric tons of 17 percent combined zn pb mineralization is hosted by carbonate evaporite units in the givetian lower dolomite sequence of the pillara limestone platform and occurs as two types 1 an early zn rich stratiform rhythmically banded ore and 2 a later crosscutting breccia fill pb rich ore the rhythmically banded ore comprises 0 1 to 1 0 m thick layers of repetitive 5 to 15 mm thick bands of sphalerite galena fe sulfide and calcite three generations of sphalerite are developed symmetrically about a dark brown hydrocarbon bearing lamination of sucrose dolomite detrital quartz and feldspar galena is associated with the second generation colloform sphalerite and marcasite occurs as a post main ore mineral phase late stage blocky calcite fills open cavities evidence for precursor evaporitic laminites as the host rock to the rhythmically banded ore includes 1 preservation of rhythmically banded primary evaporites in stratigraphically equivalent units to the lower dolomite near cadjebut 2 the ubiquitous occurrence of ore calcite pseudomorphous after primary lenticular laths rosettes and mosaic mesh textures in ore equivalent horizons both inside and outside the orebody 3 antiformal tepee structures within the banded ore 4 enterolithic structures in unmineralized and mineralized ore equivalent horizons 5 solution breccias in the rhythmically banded ore horizons and 6 homogeneous heavy sulfur isotope signatures of the banded ore sulfides with values just below those of lower dolomite evaporites and mid devonian seawater mineralization at cadjebut occurred during burial of the reefal platform in the mid late carboniferous during platform burial the conversion of gypsum to anhydrite is interpreted to have resulted in volume loss and creation of an anastomosing network of microgeode like cavities along stylolitized cyanobacteria mat laminations these open cavities provided the passageway for the introduction of early zn saturated hydrocarbon bearing solutions focused along regional and local faults to the evaporites the hydrocarbons introduced with the ore fluids acted as a catalyst for sulfate reduction of the host evaporites resulting in the precipitation of base metal sulfides and concomitant enlargement of the geode cavities the formation of the banded ore is fabric mimicking such that primary sedimentary structures remained intact during the process despite the fact that it did not involve replacement sensu stricto the presence of evaporites constrains the chemical model for cadjebut mineralization in that only a single fluid mechanism is required for base metal transport and precipitation in situ reduction of oxidized sulfur species acquired at the site of ore deposition is implied sulfur isotope values yield disequilibrium yet rather homogeneous values that range from 4 5 to 0 5 per mil less than the interpreted source lower dolomite evaporites the data are consistent with reduction of the host sulfates by thermochemical sulfate reduction the direct correlation between evaporite host rocks and base metal mineralization at cadjebut is considered an important relationship not only for genetic models for this style of mineralization in northern australia and elsewhere but also for mississippi valley type exploration models in general

genetic and exploration significance of the zinc ratio 100 zn zn pb in massive sulfide systems comparison of the 100 zn zn pb ratio zinc ratio of various styles of mineralization in the mount read volcanics of tasmania indicates that volcanogenic massive sulfide deposits have a restricted range of mean values 60 77 and low standard deviations less than 15 whereas other mineralization styles have a broader but lower range of mean values 39 61 and higher standard deviations greater than 26 thermochemical calculations on lead and zinc transport in saturated ore solutions show that the solution zinc ratio is controlled only by temperature and salinity and is independent of ph f sub o 2 and activity of dissolved sulfur zinc ratios calculated for saturated ore solutions at conditions typical of the deposition of sphalerite and galena in massive sulfide deposits 250 degrees 150 degrees c and 0 5 1 5 m nacl are very similar to those observed in polymetallic massive sulfide deposits in particular those of the rosebery hercules and hellyer deposits in western tasmania this similarity along with the shape of the pb vs zn plots suggests that zinc and lead as chloride complexes were saturated in the metal deficient m sub sigma metal m sub h 2 s hydrothermal fluid that formed the rosebery and hellyer ores variations in the zinc ratio between individual massive sulfide deposits in the mount read volcanics indicate that lead zinc saturation of the ore solution rather than lead zinc content in the footwall volcanic source rocks was the major control on the zinc ratio of the deposits however this is probably not the case for the pb poor cu zn type massive sulfides e g cyprus deposits canadian archean deposits and present day black smokers where low concentrations of lead in the basalt dominated source rocks result in complete undersaturation of lead in the hydrothermal solutions the low mean values and high standard deviations of cambrian vein deposits in the mount read volcanics and in ordovician and devonian deposits of the dundas trough may be explained by a lack of zinc lead saturation in the relevant hydrothermal fluids the characteristic zinc ratio of volcanogenic massive sulfide style mineralization can be used to distinguish these deposits from other mineralization types in the mount read volcanics effective use of this simple technique requires a reasonable number of anomalous samples minimum 15 and an unoxidized sample medium drill core samples are preferable in combination with geology and lead isotope studies the zinc ratio provides an excellent early screening of prospects

palynological assessment of organic tissues and metallic minerals in the jerritt canyon gold deposit nevada u s a abstract organic tissues and metallic minerals were studied in acid residues and thin section of the jerritt canyon bell mine gold deposit the purpose was to compare gold bearing and gold free rocks characterize their differences and assess a possible relationship between the invisible gold and the organic tissues in these early paleozoic carbonaceous limestones dolomites and claystones the most visually abundant acid resistant component in the sooty unoxidized gold bearing rocks is a black rectangular carbon bearing mineraloid in x ray diffraction it is poorly crystalline in nuclear magnetic resonance it is a highly aromatized structure the increase in gold content that accompanies the increase in content of this protographite suggests that it may be the major gold bearing compound less abundant among the acid resistant residues are uncarbonized organic tissues that are typical of marine settings the tissues not in the vicinity of silicified veins are medium to dark brown the dominant tissues are the amorphous remains of algae and their zooplankton predators these uncarbonized indigenous tissues indicate that temperatures were lower than those determined by geochemical and fluid inclusion methods the presence of different kinds of carbon bearing compounds could account for the discrepancy between the palynological and geochemical data the uncarbonized organic tissues comprise such a small percentage of these rocks that they could be easily missed by bulk analytical methods the presence of uncarbonized tissues helps to constrain the duration of the high heat flow that is shown by the fluid inclusion data the presence of mixed signals suggests that the protographite may be the product of chemical rather than thermal reactions

structurally controlled hydrothermal dolomite reservoir facies an overview structurally controlled hydrothermal dolomite htd reservoir facies and associated productive leached limestones are major hydrocarbon producers in north america and are receiving increased exploration attention globally they include multiple trends in the ordovician locally silurian and devonian of the michigan appalachian and other basins of eastern canada and the united states and in the devonian and mississippian of the western canada sedimentary basin they also occur in jurassic hosts along rifted atlantic margins in the jurassic cretaceous of the arabian gulf region and elsewhere hydrothermal dolomitization is defined as dolomitization occurring under burial conditions commonly at shallow depths by fluids typically very saline with temperature and pressure t and p higher than the ambient t and p of the host formation the latter commonly is limestone proof of a hydrothermal origin for htd reservoir facies requires integration of burial thermal history plots fluid inclusion temperature data and constraints on timing of emplacement hydrothermal dolomite reservoir facies are part of a spectrum of hydrothermal mineral deposits that include sedimentary exhalative lead zinc ore bodies and htd hosted mississippi valley type sulfide deposits all three hydrothermal deposits show a strong structural control by extensional and or strike slip wrench faults with fluid flow typically focused at transtensional and dilational structural sites and in the hanging wall transtensional sags above negative flower structures on wrench faults are favored drilling sites for htd reservoir facies saddle dolomite in both replacive and void filling modes is characteristic of htd facies for many reservoirs matrix replacive dolomite and saddle dolomite appear to have formed near contemporaneously and from the same fluid and temperature conditions the original host facies exerts a major influence on the lateral extent of dolomitization resultant textures pore type and pore volume breccias zebra fabrics shear microfractures and other rock characteristics record short term shear stress and pore fluid pressure transients particularly proximal to active faults high temperature hydrothermal pulses may alter kerogen in host limestones a process designated forced maturation basement highs underlying sandstone and or carbonate aquifers probably overpressured and overlying and internal shale seals and aquitards also may constrain or influence htd emplacement although many questions and uncertainties remain particularly in terms of mg and brine source and mass balance recognition and active exploration of the htd play continues to expand increasing use of three dimensional seismic imagery and seismic anomaly mapping combined with horizontal drilling oblique to linear trends defined by structural sags helps to reduce risk