bismuth selenides from st andreasberg germany an oxidised five element style of mineralisation and its relation to post variscan vein type deposits of central europe carbonate veinlets at roter bar a former underground mine in the polymetallic st andreasberg vein district of the harz mountains germany host selenide minerals that are characterised as bi ag bearing clausthalite pbse tiemannite hgse guanajuatite bi2se3 and a number of selenides of bi zn cu ag and pd an unnamed bi pb ag selenide species with some hg and cu ideally bi4pb3ag2se10 is reported here specular hematite is disseminated within the clausthalite at the marginal zones of which other selenide minerals are located the occurrence of bohdanowiczite agbise2 and umangite cu3se2 constrains the formation temperature to 120 c and the selenide hematite assemblage plus barite in the carbonate gangue identifies highly oxidised conditions selenide assemblages of pb bi ag with and without co and ni occur in many parts of the variscan basement of central europe harz erzgebirge schwarzwald and bohemian massif and represent a high oxidation variety of five element ag as bi co ni veins

the sediment hosted stratiform copper ore system sediment hosted stratiform copper deposits comprise disseminated to veinlet cu and cu fe sulfides in siliciclastic or dolomitic sedimentary rocks sediment hosted stratiform copper deposits are extremely common though economically significant deposits are rare they account for approximately 23 percent of the world s cu production and known reserves in addition to being significant sources of co and ag three sedimentary basins the paleoproterozoic kodaro udokan in siberia the neoproterozoic katangan in central africa and the permian basin of central europe contain supergiant 24 million metric tons mt contained cu deposits sediment hosted stratiform copper deposits are the products of evolving basin scale fluid flow systems that include source s of metal and s source s of metal and s transporting fluids the transport paths of these fluids a thermal and or hydraulic pump to collect and drive the fluids and the chemical and physical processes which result in precipitation of the sulfides metal sources are undoubtedly red bed sedimentary rocks containing fe oxyhydroxides capable of weakly binding metals sulfur may be derived from marine or lacustrine evaporites reduced seawater or hydrogen sulfide bearing petroleum metals appear to have been transported at low to moderate temperatures in moderately to highly saline aqueous fluids with the temperature of the fluid largely dependent on the time of fluid migration in the basin s burial history these basinal fluids were focused to potential metal precipitation sites by thinning of the red bed sequence at basin margins by faults by differentially permeable sedimentary units by paleotopography within the basin or along the margins of salt diapirs fluid movement produced widespread basin scale alteration that has commonly been overlooked but can form an important exploration guide sulfide precipitation occurred due to reduction typically caused by reaction with carbonaceous rocks or petroleum the amount of sulfides present at any deposit may be either metals or sulfide limited or could have been controlled by the amount of available reductant e g petroleum while understanding of sediment hosted stratiform copper ore genesis at the deposit scale is relatively robust there are still significant questions in regards its position in terms of basin evolution a wide variety of basin architectures and processes can lead to the formation of sediment hosted stratiform copper deposits despite general agreement that sulfides postdate sedimentation the absolute age of mineralization in many deposits has been difficult to document and the available evidence suggests that deposits can form throughout a basin s evolution from early diagenesis of ore host sediments to basin inversion and metamorphism supergiant and giant deposits formed in basins which underwent prolonged periods of fluid flow and in which unique conditions allowed for the accumulation of large amounts of metal bearing fluid sufficient reduced s and large amounts of reductants

paleomagnetism of the cu zn pb bearing kupferschiefer black shale upper permian at sangerhausen germany syngenetic diagenetic and epigenetic models have been proposed for the cu zn pb kupferschiefer mineralization at sangerhausen germany paleomagnetic and rock magnetic measurements have been made on 205 specimens from mine workings on the margin of the sangerhausen syncline the mineralization is richest in the 0 5 m thick upper permian 258 2 ma kupferschiefer black marly shale nine sites and dies out over 0 2 m in the underlying weisliegend sandstones three sites and overlying zechstein carbonates two sites except for one site of fault zone gypsum characteristic remanent magnetization directions were isolated for all 14 sites using alternating field and thermal step demagnetization these directions provide a negative fold test indicating that the remanence postdates jurassic fault block tilting rock magnetic measurements show that the kupferschiefer shale marks a redox front between the oxidized weissliegend sandstones and non oxidized zechstein carbonates the 14 site directions give a late jurassic paleopole at 149 3 ma it is significantly different from the paleopole reported by e c jowett and others for primary or early diagenetic rote faule alteration that gives an age of 254 6 ma on the current apparent polar wander path and is associated with kupferschiefer mineralization we suggest that the late jurassic extensional tectonic event that formed the nearby north german basin also reactivated variscan basement faults and extended them up through the overlying strata thereby allowing hydrothermal basement fluids to ascend and epigenetically mineralize the kupferschiefer shale the possibility of a 53 3 ma mineralization age is also considered

limited availability of sulfur promotes copper rich mineralization in hydrothermal pb zn veins a case study from the schwarzwald sw germany abstract mixing of compositionally contrasting fluids is widely accepted as the major ore forming process in unconformity related hydrothermal pb zn fluorite barite veins although the general process is relatively well understood the temporal evolution of such fluid systems which may result in distinct mineralogical changes of the ore and gangue minerals precipitating are insufficiently constrained one specific example is the occurrence of late stage siderite chalcopyrite gersdorffite mineralization in 28 hydrothermal veins of the schwarzwald sw germany post dating the major fluorite barite galena sphalerite phase which is very common in the whole area to investigate the underlying process for this late stage cu ni stage published fluid inclusion data have been complemented by detailed confocal raman micro spectroscopy of fluid inclusions petrographic observations and electron microprobe analyses petrography as well as mineral compositions of sphalerite gersdorffite pyrite arsenopyrite fahlore and galena record a gradual but significant influx of cu and ni into a prevailing pb zn hydrothermal system this influx caused a distinct shift towards lower fo2 and pb zn sb ag s in the hydrothermal system at the transition from the pb zn to the cu ni mineralization stage this transition in mineralogy and the related gradual change of the hydrothermal fluid can be explained by changes in the relative proportion of involved fluid components however the transition to the cu ni mineralization stage by fluid influx is significantly different compared to the common rapid fluid mixing from below which is thought to be responsible for the typical pb zn veins and probably records the gradual transition from long term stable deep fluid reservoirs with constant chemical compositions towards more shallow and perturbed fluid reservoirs during rifting and exhumation

the temperature dependence of hydrogen isotope fractionation between clay minerals and water evidence from a geopressured system abstract d values of water samples from two gulf coast geopressured fields vary linearly with temperature while the d values from the coexisting clays remain constant and are independent of temperature fluid how rates on the order of millimeters per year characteristic of gulf coast geopressured systems provide adequate residence time for hydrogen isotope equilibrium to be achieved between the extant porewaters and clay minerals since equilibrium is achieved these d values are used to calculate the temperature dependence of the hydrogen isotope fractionation factor between illite smectite and water clay waterh between 0 and 150 c 1000 in clay water h 45 3 10 3 t 94 7 this equation predicts values for clay waterh at 96 c which are equal to those predicted by a similar equation derived by yeh 1980 above and below 96 c this new equation predicts values which diverge from those predicted by the equation of yeh 1980 with a difference of 9 at 150 c and 25 at 0 c the possibility is raised that the very slow upward component of flow characteristic of gulf coast geopressured sediments combined with the slow downward subsidence of the clay rich sediments can result in a system which is rock dominated with respect to hydrogen

isotope geochemistry of fluid inclusions in permian halite with implications for the isotopic history of ocean water and the origin of saline formation waters abstract d and 18o values have been determined for fluid inclusions in 45 samples of permian halite the inclusions are enriched in 18o relative to the meteoric water line but are depleted in d relative to ocean water inclusions with the more positive values coincide with the isotopic composition expected for evaporating sea water which follows a hooked trajectory on a d 18o diagram inclusions with more negative values may represent more highly evaporated sea water but probably reflect synsedimentary or diagenetic mixing of meteoric water with evaporite brines the isotope systematics in these inclusions are sufficiently similar to those of a modern evaporite pan to indicate that permian sea water was isotopically similar to modern sea water connate evaporite brines can have negative values because of the probable hooked isotope trajectory of evaporating sea water and or synsedimentary mixing of evaporite brines with meteoric waters subsurface formation waters composed of mixtures of remnant primary evaporite brines and later meteoric waters may be more common than previous isotopic evidence has suggested

the origin of the kupferschiefer type mineralization in the richelsdorf hills germany as deduced from stable isotope and organic geochemical studies abstract the kupferschiefer horizon in the richelsdorf section federal republic of germany acted as a geochemical trap by accumulating metals from ascending brines chemical composition of the extracted bitumens reflects a drastic change in the degree of oxidation of the organic matter towards rote faule this alteration pattern corresponds with regular changes in the isotopic composition of organic carbon and carbonate as well as with the base metal zonation around rote faule the enrichment of the organic material in 13c suggests the preferential release of isotopically light hydrogen equivalents through progressive degradation and oxidation of organic matter the opposite tendency towards lower 13c and 18o values of carbonate minerals provides evidence for isotopic reequilibration between carbonate and isotopically light oxidizing solutions the occurrence of isotopically heavy organic carbon together with low 13c and 18o values of carbonate suggests that 12c rich co2 generated due to oxidation of organic material may have been a source of carbonate the results reveal a post sedimentary formation of high grade mineralization and associated rote faule by ascending oxidizing brines they are in agreement with the results of mineralogical and geochemical studies which provided evidence for metal precipitation from basinal brines enriched in na and sulphate s the organic geochemical and isotopic data suggest that metal precipitation was caused by thermochemical sulphate reduction with organic matter acting as a reducing agent and proton donor

numerical model to determine the composition of h2o nacl cacl2 fluid inclusions based on microthermometric and microanalytical data natural fluids approximated by the h2o nacl cacl2 system are common in a wide range of geologic environments including sedimentary basins associated with hydrocarbon occurrences and mvt deposits submarine hydrothermal systems and other metamorphic magmatic and hydrothermal environments we present a comprehensive numerical model and microsoft excel based computer program to determine the compositions of fluid inclusions in the h2o nacl cacl2 system based on microthermometric and microanalytical data the model consists of six polynomial correlation equations that describe liquid salinity as a function of nacl cacl2 ratio and melting temperature on each of the ice hydrohalite halite antarcticite cacl2 4h2o and cacl2 2h2o vapor saturated liquidus surfaces the cotectic and peritectic boundaries are determined from the intersections of the liquidus surfaces the model is implicitly internally consistent and topologically correct the model expands upon the compositional range of applicability and the data types that can be used for compositional determination it reproduces experimental data for all compositions that lie within the h2o nacl cacl2 4h2o compositional triangle in the h2o nacl cacl2 system and yields accurate reproductions of the h2o nacl and h2o cacl2 binaries furthermore in comparison to previously published models the one presented here eliminates systematic errors wavy isotherms and cotectic and peritectic curves with local bumps

equilibrium oxygen hydrogen and carbon isotope fractionation factors applicable to geologic systems as demonstrated by the chapters in this short course stable isotope techniques are an important tool in almost every branch of the earth sciences central to many of these applications is a quantitative understanding of equilibrium isotope partitioning between substances indeed it was harold urey s 1947 thermodynamically based estimate of the temperature dependence of 18o 16o fractionation between calcium carbonate and water and a recognition of how this information might be used to determine the temperatures of ancient oceans that launched the science of stable isotope geochemistry the approach pioneered by urey has since been used to estimate temperatures for a wide range of geological processes e g emiliani 1955 anderson et al 1971 clayton 1986 valley this volume in addition to their geothermometric applications equilibrium fractionation data are also important in the study of fluid rock interactions including those associated with diagenetic hydrothermal and metamorphic processes baumgartner and valley this volume shanks this volume finally a knowledge of equilibrium fractionation is a necessary first step in evaluating isotopic disequilibrium a widespread phenomenon that is increasingly being used to study temporal relationships in geological systems cole and chakraborty this volume in the fifty four years since the publication of urey s paper equilibrium fractionation data have been reported for many minerals and fluids of geological interest these data were derived from 1 theoretical calculations following the methods developed by urey 1947 and bigeleisen and mayer 1947 2 direct laboratory experiments 3 semi empirical bond strength models and 4 measurement of fractionations in natural samples each of these methods has its advantages and disadvantages however the availability of a variety of methods for calibrating fractionation factors has led to a plethora of calibrations not all of which are in agreement in this chapter we evaluate the major methods for determining fractionation factors

hydrothermal water rock interaction and the redistribution of li b and cl in the taupo volcanic zone new zealand abstract lithium b and cl occur as trace elements in the dominant protoliths rhyolite andesite and greywacke underlying high temperature hydrothermal systems in the taupo volcanic zone tvz the fluid mobility of li decreases substantially at 200 c 20 c with the pervasive deposition of quartz chlorite regardless of protolith and altering fluid compositions boron and cl are more fluid mobile than li at all temperatures with mobility affected by the rock type composition of circulating aqueous solutions and to a limited extent by incorporation of the trace elements in hydrothermal minerals uptake of b by clays decreases its mobility at 320 c occur compared to volcanic rocks the mobility of b and cl in greywackes is very low and thus the b cl signature of greywacke in hydrothermal aqueous solutions of the tvz is overwhelmed by the effects of rhyolite and andesite dissolution temperature dependent transitions from mg fe clays and phyllosilicates to k bearing illitic clays tend to decrease the mg li ratios in aqueous solutions at 200 c

composition and evolution of fluids forming the baiyinnuo er zn pb skarn deposit northeastern china insights from laser ablation icp ms study of fluid inclusions the baiyinnuo er skarn deposit is one of the largest zn pb deposits in northeastern china with 32 74 million metric tons mt resources averaging 5 44 zn 2 02 pb and 31 36 g t ag the deposit formed in three stages the preore stage prograde skarn minerals with minor magnetite the synore stage sulfides and retrograde skarn minerals including calcite and minor quartz and the postore stage late veins composed of calcite quartz fluorite and chlorite cutting the above mineral assemblages in this study we analyzed the composition of single fluid inclusions using laser ablation inductively coupled plasma mass spectrometry la icp ms to 1 determine the composition of the fluids and the evolution through the stages 2 infer the fluid and metal sources and 3 explore the metal deposition mechanisms the preore fluids trapped in pyroxene have higher homogenization temperatures 432 504 c higher salinity 36 5 46 1 wt nacl equiv and higher concentrations of zn 0 9 wt pb 1 4 wt and other elements e g na k li as rb sr cs ba cl and br than synore mineralizing fluids 370 c 10 wt nacl equiv 450 ppm zn and 290 ppm pb the postore fluids show lower temperatures 250 c and a rather dilute composition 4 wt nacl equiv 33 ppm zn and 24 ppm pb geochemically the fluids of all paragenetic stages in baiyinnuo er have magmatic signatures based on the element mass ratios including elevated k na zn na and rb na ratios lower ca k ratios and combined cl br na k ratios which are distinctively different from basinal brines inclusion fluids in preore stage show little variation in composition between 510 and 430 c indicative of a closed cooling system in contrast the major components of the syn and postore fluids including cl na and k decrease and correlate with a drop of homogenization temperatures from 370 to 200 c indicating a dilution by mixing with groundwater the baiyinnuo er mineralizing fluids trapped in sphalerite have higher ca k mass ratios avg 0 78 than other proximal magmatic hydrothermal systems 0 06 0 52 but lower than that of the distal el mochito skarn avg 6 4 probably reflecting a gradually weakened magmatic signal away from the causative intrusions the metal contents in preore fluids are significantly higher than those in synore fluids but no mineralization occurred this confirms that the early fluids were although enriched in metals not responsible for ore precipitation most likely due to their high temperature and high salinities one important factor controlling zn pb mineralization was mixing with groundwater which resulted in temperature decrease and dilution that significantly reduced the metal solubility thereby promoting metal deposition another main driving force was the interaction with carbonate wall rock that buffered the acidity generated during the breakdown of zn and pb cl complexes and the precipitation of sulfides phase separation occurred in both the preore and the early part of the synore stages but no evidence indicated that it caused metal deposition the prograde minerals and retrograde minerals including ore minerals coexisting in the same samples could have been caused by two or more successive pulses of hydrothermal fluids released from residual melts of a progressively downward crystallizing magma each fluid produced a series of proximal high temperature prograde to distal low temperature assemblages with the lower temperature assemblages of later fluids overprinting the higher temperature assemblages at most locations

the role of the kupferschiefer in the formation of hydrothermal base metal mineralization in the spessart ore district germany insight from detailed sulfur isotope studies the spessart district sw germany located at the southwestern margin of the permian kupferschiefer basin in central europe hosts abundant stratabound and structurally controlled base metal mineralization the mineralization styles identified are 1 stratabound cu pb zn ag ores in zechstein sedimentary rocks 2 structurally controlled cu as ag ores in zechstein sedimentary rocks 3 crosscutting co ni bi as and cu fe as veins 4 stratabound metasomatic fe mn carbonate ores in zechstein dolomite 5 barren barite veins and 6 fe mn as veins in permian rhyolites building on previous work that involved mineralogical textural and chemical characterization of the major mineralization types we have performed a comprehensive sulfur isotope study that applied both conventional and novel laser ablation multi collector inductively coupled plasma mass spectrometry techniques the 34s values of sulfide minerals from the different ore types are consistently negative and highly variable in the range between 44 5 and 3 9 whereas the 34s values of barite are all positive in the range between 4 7 and 18 9 remarkably stratabound and structurally controlled mineralization in zechstein sedimentary rocks has the least negative 34s values whereas vein type deposits have consistently more negative 34s values the observed pattern of sulfide 34s values can be best interpreted in terms of fluid mixing at the basement cover interface hydrothermal fluids originating from the crystalline basement migrated upward along subvertical fault zones and were periodically injected into groundwaters that were flowing in the post variscan sedimentary cover these groundwaters had interacted with the zechstein sedimentary rocks resulting in fluids characterized by elevated concentrations of reduced sulfur with negative 34s values and alkaline ph repeated mixing between both chemically contrasting fluids caused rapid and efficient precipitation of sulfide ore minerals in hydrothermal veins with highly variable but distinctly negative 34s values

petrogenesis of the proterozoic athabasca basin northern saskatchewan canada and its relation to diagenesis hydrothermal uranium mineralization and paleohydrogeology abstract in the athabasca basin proterozoic sandstones unconformably overlie archean and aphebian rocks multiple fluid events involving isotopically and chemically distinct fluids which have migrated laterally for considerable distances and along fault zones have produced a paragenetically identifiable assemblage of clay silicate and oxide minerals in the basin and basement rocks altered sandstones and the underlying metasedimentary rocks proximal to fault zones host high grade u ni co unconformity type uranium ore deposits and contain an alteration assemblage of highly crystalline 2m 3t illite 1m kaolinite clinochlore and sudoite hematite dravite and euhedral quartz in the sandstones 18o values of coeval quartz hematite quartz illite quartz dravite illite hematite and kaolinite hematite fluid inclusion temperatures in diagenetic quartz and d values of 1m kaolinite 2m 3t illite dravite and in fluid inclusions in the quartz indicate formation from a basinal fluid that had d values of 60 10 and which underwent salinity temperature and 18o increases from 5 to 34 wt nacl 120 to 240 c and 5 to 3 respectively as a result of increasing burial depth and sustained water rock interactions with the basinal sediments over substantial time periods 18 o 16 o and d h ratios of sudoite and clinochlore in meta sedimentary basement rocks within the alteration haloes indicate formation from a basement derived fluid with 18o and d values of 4 4 and 30 10 respectively that was isotopically distinct from the basinal fluids 18o and d values of late kaolinites in reactivated fault zones indicate formation mainly from low temperature 50 25 c fluids having 18o and d values of 16 and 130 respectively similar to relatively modern meteoric waters in the area some kaolinites have 18o and d values which suggest they formed from meteoric waters at mid latitudes and have experienced varying degrees of oxygen and hydrogen isotope exchange with relatively modern meteoric waters in the re activated faults illite sudoite and dravite have d values that vary by 100 without concurrent changes to their 18o values indicating preferential hydrogen isotope exchange with relatively modern meteoric waters at low temperatures and under conditions of high integrated water rock ratios rb sr isochron and model ages of 1477 57 and 952 ma respectively for the crystalline 2m 3t illites indicate the timing of the high temperature basinal fluid events associated with fluid mixing rb sr and k ar ages on illites with the lowest d values are as young as 300 ma and indicate late stage resetting of their radiogenic isotope systematics as a result of substantial interactions with relatively modern meteoric waters the evolution of sr isotopic compositions of fluids in the basin and basement rocks as reflected by the 87 sr 86 sr ratios of chlorite illite and dravite indicates that mixing of two isotopically distinct fluids in the vicinity of faults was the process by which uranium was precipitated similar to that suggested by oxygen and hydrogen isotope systematics in the clays and silicate minerals nd ratios in the high temperature diagenetic and hydrothermal clay and silicate minerals and the cogenetic uranium ores suggest they all have formed from similar fluids which have interacted substantially with the basin sediments in general the isotopic chemical microthermometric and petrologic data indicate that the athabasca basin has had a protracted fluid history comparable to that documented for more modern sedimentary basins the data clearly show that the major sandstone aquifers have been affected by widespread lateral flow of diagenetic fluids over distances of hundreds of kilometers and also that these fluid migration paths have been modified by cross formational fluid flow near active fault zones

giant uranium deposits formed from exceptionally uranium rich acidic brines the athabasca basin canada is home to some of the world s largest uranium deposits analysis of preserved ore forming fluids and experimental measurement of uranium solubility in analogous solutions show that the giant deposits could have formed relatively rapidly from extremely uranium rich brines under acidic conditions

physical and chemical controls on the composition of waters in sedimentary basins abstract the composition of subsurface waters is determined not only by diagenetic reactions but also by physical processes of fluid convection and hydrodynamic dispersion the south west louisiana gulf coast provides an instructive field example of the net effects of diagenetic reaction and solute transport on pore water compositions in a regional siliciclastic sequence most formation waters here have compositions totally unlike the compositions of the connate meteoric and marine fluids that were buried with their host sediments at the time of deposition dissolved chloride has been generated by the subsurface dissolution of salt domes and has been pervasively transported by fluid flow throughout most of the upper 3 km of the sedimentary section the simultaneous systematic variation in dissolved na k mg ca and alkalinity with chloride in these waters supports the hypothesis that metastable thermodynamic buffering by silicate carbonate mineral assemblages is a first order control on fluid compositions the chemical potential of chloride or alternatively total anionic charge appears to be a master variable which ranks in importance with such other variables as pressure and temperature in driving diagenesis in this region this variable is controlled largely by physical processes of advection and dispersion in the upper 3 km of the section and by dehydration reactions in deeper mudstone dominated sediments where the composition of the fluid is largely rock buffered the ultimate origin of the fluid and its pathway of chemical evolution may be obscured at least in terms of major solute composition non buffered components such as cl and br or isotopic compositions are more likely to retain information on original end member fluid compositions and reaction pathways

quartz content and the quartz to plagioclase ratio determined by x ray diffraction a proxy for ice rafting in the northern north atlantic many paleoceanographic reconstructions of the glacial north atlantic include estimates of iceberg discharge which are based on the variable abundance of ice rafted detritus ird in deep sea sediments ird abundance is most often determined by the mechanical separation and painstaking counting of terrigenous particles larger than a specified threshold grain size typically 150 mum here we present a new proxy for ird based on x ray diffraction xrd analysis of bulk sediments this approach complements results obtained from standard techniques while offering several distinct advantages in addition to the rapid production of objective data xrd measurements on bulk sediments are sensitive to a broader and more characteristic grain size range than counts of individual coarse lithic fragments the technique is demonstrated in a study of 12 sediment cores from the north atlantic bulk quartz content and the quartz to plagioclase ratio exhibit peak to peak correspondence to manual counting results which verifies the identification of large ird influxes the xrd data also reveal variations between the manually identified peaks suggesting increased sensitivity to low level distal or sea ice sources of ird a saw tooth pattern emerges in many ird events which supports a link between ice rafting and atmospheric temperature changes over greenland and providing further evidence of the influence of climate on iceberg discharges c 2003 elsevier b v all rights reserved less

late cretaceous and cenozoic intra plate compressional deformations in the alpine foreland a geodynamic model abstract the mesozoic grabens and wrench induced troughs of western and central europe developed in response to triassic early cretaceous intra plate tensional stresses which affected the arctic north atlantic and the tethys borderlands during the rifting phase preceding the opening of the respective oceans this resulted in the fragmentation of the continental crust of the alpine foreland during the late cretaceous and tertiary alpine orogeny collision related compressive stresses exerted on the foreland induced the reactivation of these fracture systems causing the inversion of mesozoic grabens and the uplifting of major basement blocks at distances up to 1300 km to the north of the present alpine deformation front the structural style of these inverted basins and basement uplifts is indicative of compressional and transpressional deformations the total amount of crustal shortening associated with these deformations is unlikely to exceed a few tens of kilometres these displacements require a coupling between the foreland and the orogen at the alpine a subduction zones and within the foreland a decoupling at intra crustal levels between the crust and mantle and or at deeper lithospheric levels the example of the alpine foreland indicates that compressive stresses inducing major deformations can be transmitted from a collisional plate boundary through continental lithosphere over distances of up to 1300 km circumstantial evidence suggests that collision related compressive stresses not large enough to give rise to significant deformations can be transmitted through continental lithosphere over even greater distances

major to trace element analysis of melt inclusions by laser ablation icp ms methods of quantification current techniques for the quantification of melt inclusion chemistry require that inclusions are compositionally homogeneous and that post entrapment devitrification or crystallization onto the inclusion walls could be reversed by appropriate re melting laser ablation icp ms provides a technique by which single heterogeneous inclusions can be analysed thus avoiding the above prerequisites because host mineral is ablated with the inclusion quantification of the melt composition necessitates deconvolution of the mixed signal by an internal standard this can be obtained in various ways including 1 a fixed pre determined concentration of a given element in the melt 2 whole rock differentiation trends in a given igneous suite 3 a constant measured distribution coefficient between the host and the inclusion melt and 4 determination of the volume ratios between the inclusion and total ablated volume these four approaches were tested on a large set of cogenetic inclusions from a single plagioclase crystal in a rhyodacitic intrusion results suggest that quantification through whole rock differentiation trends is the most widely applicable the most accurate and the least time consuming technique provided that the resulting data are critically interpreted with regard to the underlying assumptions uncertainties on the calculated element concentrations in the inclusions depend on the mass ratio between the melt inclusion and the host for a given ablation they are of the order of 10 if the melt inclusion contributes more than 20 to the bulk analytical signal of a particular element calculated limits of detection for spherical 10 m melt inclusions are of the order of a few ppm for elements strongly enriched in the melt relative to the host crystal concentrations in the melt inclusions can be determined even for elements enriched in the host mineral but in this case uncertainties and calculated limits of detection increase with the concentration in the host the uncertainty on the melt composition from a set of cogenetic inclusions can be commonly decreased by calculating of an uncertainty weighted average of the concentration and their uncertainty

genesis of kupferschiefer cu ag deposits by convective flow of rotliegendes brines during triassic rifting extensive and rich cu ag sulfide mineralization occurs in poland across the contact between the upper permian zechstein restricted marine sequence and the lower permian rotliegende continental volcanic and clastic sequence geologic evidence suggests that the mineralization was formed during late diagenesis when metalliferous brines migrated through the rotliegende leaching metals from the volcanic detritus and up the flanks of basement highs possibly along fracture porosity to the pyritic kupferschiefer and zechstein limestone above thick evaporites in the lower zechstein preclude a vertical flow through model but metal zoning attitudes suggest that the brines overturned where the rotliegende pinched out against the highs and moved laterally along the base of the zechstein toward the basin centers presumably to sink back down into the rotliegende completing a convection cell a middle triassic paleomagnetic age for the metal zoning and kimmerian attitudes of dilatant sulfide veinlets indicate that the mineralizing event coincided with continental rifting associated with the opening of the tethys ocean slow unicellular convection may be commonplace in sandstone basins where small lateral temperature gradients delta t exist but greater velocities are necessary to form large orebodies an anomalous tensional and thermal event such as rifting can increase velocities by increasing permeability slope angle or delta t the paleothermal structure of southwestern poland was determined by modeling the conductive heat flow in 14 one dimensional geologic sections which described the evolution of the basin architecture for 10 m y in the early triassic rifting was simulated by increasing the lower boundary condition from 500 degrees to 1 000 degrees c at 25 km this thermal pulse produced a surprisingly high delta t of 25 degrees c across the lubin ore district solely from differences in thermal conductivities between the basement high 4 2 w m degrees c the sandstone 2 5 w m degrees c and the shale basin center 1 25 w m degrees c unicellular convection patterns would be induced by the lateral boundary conditions of warm basement highs and cold shale centers and by the greater horizontal permeability these cells were 15 to 20 km long 400 m high and subhorizontal a slope angle of 2 degrees and a permeability of 1 d produces a convection velocity of 13 cm yr which with a copper solubility of 1 000 mg kg in 20 to 30 percent ca na cl brines in equilibrium with hematite can form the lubin deposit in less than 6 m y using a fracture permeability of 2 d and a solubility of 300 mg kg the time needed is less than 10 m y the konrad mine can be formed in similar time periods without the continuous recycling of the brine inherent in convective flow 20 times or more the metal solubilities needed to form the lubin deposits by a flow through model would be unreasonably high natural gases likely migrated along with the metalliferous brines and helped convection by creating secondary porosity and increasing the buoyancy of the fluids because the fluids are recirculated and not expelled convection provides a way in which secondary migration of methane and petroleum can occur effectively in solution as well as in separate phases

geochemistry of metal rich brines from central mississippi salt dome basin u s a abstract oil field brines are the most favored ore forming solutions for the sediment hosted mississippi valley type ore deposits detailed inorganic and organic chemical and isotope analyses of water and gas samples from six oil fields in central mississippi one of the very few areas with high metal brines were conducted to study the inorganic and organic complexes responsible for the high concentrations of these metals the samples were obtained from production zones consisting of sandstone and limestone that range in depth from 1900 to 4000 m 70 120 c and in age from late cretaceous to late jurassic results show that the waters are dominantly bittern brines related to the louann salt the brines have extremely high salinities that range from 160 000 to 320 000 mg l total dissolved solids and are na ca cl type waters with very high concentrations of ca up to 48 000 mg l and other alkaline earth metals but with low concentrations of aliphatic acid anions the concentrations of metals in many water samples are very high reaching values of 70 mg l for pb 245 mg l for zn 465 mg l for fe and 210 mg l for mn the samples with high metal contents have extremely low concentrations 2 s samples obtained from the smackover formation limestone have low metal contents that are more typical of oil field waters but have very high concentrations up to 85 mg l of h 2 s computations with the geochemical code solmineq 87 give the following results 1 both pb and zn are present predominantly as aqueous chloride complexes mainly as pbcl 4 2 and zncl 4 2 respectively 2 the concentrations of metals complexed with short chained aliphatic acid anions and reduced s species are minor 3 organic acid anions are important in controlling the concentrations of metals because they affect the ph and buffer capacity of the waters at subsurface conditions and 4 galena and sphalerite solubilities control the concentrations of pb and zn in these waters

water rock interaction processes in the triassic sandstone and the granitic basement of the rhine graben geochemical investigation of a geothermal reservoir saline fluids have been collected in the rhine graben over the last two decades both from the triassic sandstone aquifer and the granitic basement down to a depth of 3500m their salinities and location are compared in order to distinguish the respective influences of temperature and host rock mineralogy in the water rock interaction processes the comparison shows that sulphates in the sedimentary formations were dissolved by the fluids which also led to br enrichment mica dissolution has strongly increased the rb and cs contents which then provide an indication of the degree of water rock interaction the sr isotopic ratios are used to compare the fluids with the granite minerals two relationships are revealed for the fluids in the sandstone and the granite one related to widespread mica dissolution which could have affected both the buntsandstein and the granite and the other to subsequent plagioclase dissolution which is observed only in the granite computations showed that 12 5g of mica and 1 658 of plagioclase per liter of fluid have been dissolved the nature of these two relationships suggests two different evolutions for the fluids and the individualization of the two reservoirs during the graben s history the cation concentrations are mainly controlled by temperature and are independent of the type of host rock equilibrium with the rock mainly caused ca and k concentration variations which has induced clear ca k and ca 18o k 18o correlations geothermometric computations indicate that with increasing depth the cations the silica and the 18o so4 geothermometers evolve towards a value close to 230 c this demonstrates the existence of a hot reservoir in the granite of the graben at a depth estimated at 4 5 5 km

the origin and evolution of base metal mineralising brines and hydrothermal fluids south cornwall uk abstract a fluid inclusion geochemical study has been carried out on quartz from post variscan quartz carbonate base metal sulphide anhydrite fluorite veins hosted by palaeozoic basement porthleven menheniot cornwall and permo triassic sediments western approaches data indicate that the base metal mineralising fluids have a similar bulk chemical composition to the saline fluids found in the permo triassic basinal sequence and support the hypothesis that these basins are the source of the mineralising fluids cl and br systematics suggest that the brines were formed either by the evaporation of seawater or a seawater meteoric water mixture past the point of halite precipitation the major cation composition na ca k mg of the brines is not consistent solely with evaporation processes but may be explained by dolomitisation processes albitisation processes or both which are recognised in the basinal sequences the presence of seawater in the base metal mineralised veins suggests that the first marine incursions late triassic into the region must act as a lower age limit for the mineralisation the halogen chemistry of a second hotter 200 c more dilute 0 5 wt fluid identified in fault hosted e w trending veins in the porthleven area suggests that the chlorinity of these fluids has a magmatic origin circulation of these fluids in post variscan extensional structures was driven by the local high heat producing cornubian batholith the local high heat producing granites provided fracture permeability and a heat source that heated the base metal mineralising fluids as they entered the horst block and the dilute fluids circulating around the granites petrographic evidence suggests that both palaeohydrologic systems were active contemporaneously however each flow system was isolated in differently orientated structures and there is little evidence for fluid mixing

fracturing and fluid flow in a sub decollement sandstone or a leak in the basement crack seal texture within fracture cements in the triassic el alamar formation ne mexico shows that the fractures opened during precipitation of quartz cements later overlapping calcite cements further occluded pore space previous workers defined four systematic fracture sets a oldest to d youngest with relative timing constrained by crosscutting relationships quartz fluid inclusion homogenization temperatures are higher within set b 148 20 c than in set c 105 12 c these data and previous burial history modelling are consistent with set c forming during exhumation fluid inclusions in set c quartz have higher salinity than those in set b 22 9 v 14 2 wt nacl equivalent respectively and set c quartz cement is more enriched in 18 o 20 2 v 18 7 vsmow under most assumptions about the true temperature during fracture opening the burial duration the amount of cement precipitated and fluid flow patterns it appears that the fracture fluid became depleted in 18 o and enriched in 13 c this isotopic evolution combined with increasing salinity suggests that throughout fracture opening there was a gravity driven influx of fluid from upsection jurassic evaporites which form a regional decollement fracture opening amid downward fluid motion suggests that fracturing was driven by external stresses such as tectonic stretching or unloading rather than increases in fluid pressure

hematite breccia hosted iron oxide copper gold deposits require magmatic fluid components exposed to atmospheric oxidation evidence from prominent hill gawler craton south australia

orthogneisses in the spessart crystalline complex north west bavaria silurian granitoid magmatism at an active continental margin the spessart crystalline complex north west bavaria contains two orthogneiss units of granitic to granodioritic composition known as the rotgneiss and haibach gneiss respectively which are structurally conformable with associated metasediments the igneous origin of the rotgneiss is apparent from field and textural evidence whereas strong deformation and recrystallization in the haibach gneiss has obscured most primary textures new geochemical data as well as zircon morphology prove the haibach gneiss to be derived from a granitoid precursor which was chemically similar to the rotgneiss protolith thus suggesting a genetic link between those two rock units both gneiss types have chemical compositions typical of anatectic two mica leucogranites they show characteristics of both i and s type granites rb sr whole rock data on the haibach gneiss provide an isochron age of 407 14 ma ir 0 7077 0 0007 mswd 2 2 which is slightly younger than the published date for the rotgneiss 439 15 ma ir 0 7048 0 0026 mswd 4 9 single zircon dating of six idiomorphic grains using the evaporation method yielded a mean 207pb 206pb age of 410 18 ma for the haibach gneiss and 418 18 ma for the rotgneiss both zircon ages are within analytical error of the rb sr isochron dates and are interpreted to reflect the time of protolith emplacement in silurian times three xenocrystic zircon grains from the rotgneiss yielded 207pb 206pb ages of 2278 12 2490 13 and 2734 10 ma respectively suggesting that late archaean to early proterozoic crust was involved in the generation of the granite from which the rotgneiss is derived although it is assumed that the granitic protoliths of the two gneisses were formed through anatexis of older continental crust the relatively low 87sr 86sr initial ratios of both gneisses may also indicate the admixture of a mantle component the rotgneiss and the haibach gneiss thus document granitic magmatism at an active continental margin during late silurian times

major element compositions of fluid inclusions from hydrothermal vein type deposits record eroded sedimentary units in the schwarzwald district sw germany mixing of sedimentary formation fluids with basement derived brines is an important mechanism for the formation of hydrothermal veins we focus on the sources of the sediment derived fluid component in ore forming processes and present a comprehensive fluid inclusion study on 84 jurassic hydrothermal veins from the schwarzwald mining district sw germany our data derive from about 2300 fluid inclusions and reveal differences in the average fluid composition between the northern central and southern schwarzwald fluids from the northern and southern schwarzwald are characterised by high salinities 18 26 wt nacl cacl2 low ca ca na mole ratios 0 1 0 4 and variable cl br mass ratios 30 1140 in contrast fluids from the central schwarzwald show even higher salinities 23 27 wt nacl cacl2 higher ca ca na mole ratios 0 2 0 9 and less variable cl br mass ratios 40 130 these fluid compositions correlate with the nature and thickness of the now eroded sedimentary cover rocks compared to the northern and the southern schwarzwald where halite precipitation occurred during the middle triassic the sedimentary basin in the central schwarzwald was relatively shallow at this time and no halite was precipitated accordingly cl br ratios of fluids from the central schwarzwald provide no evidence for the reaction of a sedimentary brine with halite whereas those from the northern and southern schwarzwald do instead elevated ca ca na high so4 contents and relatively low cl br imply the presence of a gypsum dissolution brine during vein formation in the central schwarzwald which agrees with the reconstructed regional triassic geology hence the information archived in fluid inclusions from hydrothermal veins in the crystalline basement has the potential for reconstructing sedimentary rocks in the former overburden

fluid and gas migration in the north german basin fluid inclusion and stable isotope constraints fluid inclusions have been studied in minerals infilling fissures quartz calcite fluorite anhydrite hosted by carboniferous and permian strata from wells in the central and eastern part of the north german basin in order to decipher the fluid and gas migration related to basin tectonics the microthermometric data and the results of laser raman spectroscopy reveal compelling evidence for multiple events of fluid migration the fluid systems evolved from a h2o nacl kcl type during early stage of basin subsidence to a h2o nacl cacl2 type during further burial locally fluid inclusions are enriched in k cs li b rb and other cations indicating intensive fluid rock interaction of the saline brines with lower permian volcanic rocks or sediments fluid migration through carboniferous sediments was often accompanied by the migration of gases aqueous fluid inclusions in quartz from fissures in carboniferous sedimentary rocks are commonly associated with co genetically trapped ch4 co2 inclusions p t conditions estimated via isochore construction yield pressure conditions between 620 and 1 650 bar and temperatures between 170 and 300 c during fluid entrapment the migration of ch4 rich gases within the carboniferous rocks can be related to the main stage of basin subsidence and stages of basin uplift a different situation is recorded in fluid inclusions in fissure minerals hosted by permian sandstones and carbonates aqueous fluid inclusions in calcite quartz fluorite and anhydrite are always h2o nacl cacl2 rich and show homogenization temperatures between 120 and 180 c co genetically trapped gas inclusions are generally less frequent when present they show variable n2 ch4 compositions but contain no co2 p t reconstructions indicate low pressure conditions during fluid entrapment always below 500 bar the entrapment of n2 ch4 inclusions seems to be related to phases of tectonic uplift during the upper cretaceous a potential source for nitrogen in the inclusions and reservoirs is corg rich carboniferous shales with high nitrogen content intensive interaction of brines with carboniferous or even older shales is proposed from fluid inclusion data enrichment in li ba pb zn mg and sulfur isotopic compositions of abundant anhydrite from fissures the mainly light 34s values of the fissure anhydrites suggest that sulfate is either derived through oxidation and re deposition of biogenic sulfur or through mixing of so42 rich formation waters with variable amounts of dissolved biogenic sulfide an igneous source for nitrogen seems to be unlikely since these rocks have low total nitrogen content and furthermore even extremely altered volcanic rocks from the study area do not show a decrease in total nitrogen content

cockade breccia product of mineralisation along dilational faults cockade breccias are fault fills in which individual clasts are completely surrounded by concentric layers of cement they occur particularly in low temperature near surface hydrothermal veins at least six mechanisms have been proposed for the formation of cockade breccia like textures but only two repeated rotation accretion and partial metasomatic replacement of clast minerals have been supported by detailed evidence a typical example of cockade breccia from the gower peninsula south wales shows clear evidence for the rotation accretion mechanism in particular overgrown breakage points in cement layers where cockades were previously touching each other and rotated geopetal infills of haematitic sediment based on the available evidence it is proposed that cockade textures result from low rates of cement growth compared to high rates of dilational fault slip seven criteria are given for the correct identification of cockade breccias

inclusions of sedimentary brines in post variscan mineralizations in the federal republic of germany a study by neutron activation analysis abstract the post variscan vein mineralizations in the federal republic of germany are characterized by highly saline fluid inclusions t e t mice 26 to 20 c t h 1 ca 22 000 60 000 mg kg 1 cl 85 000 200 000 mg kg 1 and br 550 2 600 mg kg 1 composition and salinity of the inclusion solutions are similar to brines in deep sedimentary basins it is assumed that formation waters of the na ca cl type migrated out of permo triassic sediment troughs into culmination zones of the variscan orogen where they were heated and caused mineralizations through cooling and mixing with sulfate bicarbonate waters when reascending

sequence stratigraphy of a carbonate evaporite succession zechstein 1 hessian basin germany the evaporitic hessian zechstein basin is a sub basin of the southern zechstein basin situated at its southern margin twelve facies groups were identified in the zechstein limestone and lower werra anhydrite in order to better understand the sequence stratigraphic evolution of this sub basin which contains economically important potassium salts four different paleogeographic depositional areas were recognized based on the regional distribution of facies siliciclastic carbonate carbonate carbonate evaporite and evaporite shallowing upward successions are developed these allow the establishment of parasequences and sequences as well as correlation throughout the hessian basin and into the southern zechstein basin two depositional sequences are distinguished zechstein sequence 1 and zechstein sequence 2 the former comprises the succession from the variscan basement up to the lowermost part of the werra anhydrite including the kupferschiefer as part of the transgressive systems tract the highstand systems tract is defined by the zechstein limestone in which two parasequences are developed in large parts of the hessian basin zechstein sequence 1 is capped by a karstic subaerial exposure surface interpreted as recording a type 1 sequence boundary that formed during a distinct brine level fall low lying central areas central hessian sub basin werra sub basin however were not exposed and show a correlative conformity topography was minimal at the end of sequence 1 widely developed perilittoral sabkha and salina shallowing upward successions indicate a renewed rise of brine level interpreted as a transgressive systems tract because of inflow of preconcentrated brines from the southern zechstein basin to the north this marks the initiation of zechstein sequence 2 which comprises most of the lower werra anhydrite in the central hessian sub basin situated proximal to the brine inflow and on the ridges within the hessian basin physico chemical conditions were well suited for sulphate precipitation to form a thick cyclic succession it consists of four parasequences that completely filled the increased accommodation space in contrast only minor sulphate accumulation occurred in the werra sub basin situated further southwards and distal to the inflow as a result of substantially different sulphate precipitation rates during increased accommodation water depth in the region became more variable the werra sub basin characterized by very low sedimentation rates became increasingly deeper through time trapping dense halite brines and precipitating rock salt deposits werra halite this self organization model for an evaporitic basin in which depositional relief evolves with sedimentation and relief is filled by evaporite thereafter contradicts earlier interpretations that call upon the existence of a tectonic depression in the werra area which controlled sedimentation from the beginning of the zechstein

fluid mixing and recycling during pyrenean thrusting evidence from fluid inclusion halogen ratios abstract syntectonic fluids have been sampled through fluid inclusion microthermometry and crush leach analyses cations and halogens from a 50 km n s transect through the central southern pyrenees the fluid inclusions are contained in syntectonic quartz veins in triassic redbeds cretaceous carbonates and hercynian basement rocks with some calcite and dolomite data from limestones and evaporites in more external parts of the belt the main datasets come from 1 alpine shear zones cutting the neouvielle granodiorite in the hercynian axial zone at the north end of the transect 2 an imbricate zone beneath the alpine gavarnie thrust at the pic de port vieux 3 several localities in the footwall and hangingwall of the gavarnie thrust on the southern margin of the axial zone the inclusion fluids generally decrease in salinity from 27 35 at the northern end of the transect to 7 22 on the southern margin of the axial zone the majority of the inclusions have cl br ratios lower than seawater and are interpreted as relict fluids after seawater evaporation and halite precipitation in the upper trias this interpretation is supported by cl br na systematics which are consistent with a change from halite to halite sylvite precipitation with progressive evaporation fluids in the basement shear zones are interpreted to have essentially the same evaporitic origin as those still contained in sedimentary formations although it is possible that final concentration of brines in the neouvielle massif involved retrograde hydration reactions with removal of water by precipitation of hydrous minerals the fluids are also very similar in salinity and halogen chemistry to those found in veins associated with mesozoic pb zn f deposits which predate the thrusting the lower salinities seen at the southern margin of the axial zone are interpreted to reflect mixing of the brines with a higher level fluid connate or meteoric water circulating within the mesozoic carbonates of the higher thrust sheets at one locality where triassic evaporites are still present high cl br ratios at relatively low salinities are present in inclusions within the underlying triassic redbeds but low cl br ratios at higher salinities are seen lower in the sequence this is consistent with dissolution of halite by a dilute fluid but with limited penetration downwards we suggest that the fluid history of the pyrenees evolved through a series of stages 1 upper triassic evaporite formation with sinking of brines into underlying redbeds and fractured basement rocks 2 circulation of brines with formation of pb zn deposits along faults at some time between the triassic and the upper cretaceous 3 renewed extension with erosion of triassic rocks in many areas and further drawing down of triassic brines into the basement 4 deposition of u cretaceous and palaeocene carbonates containing connate waters of marine origin 5 formation of the pyrenean thrust belt with overpressuring and expulsion of the brines along shear zones and faults 6 creation of topography with a high level circulation system in the mesozoic thrust sheets driven largely by topography at the southern margin of the axial zone there was limited mixing of the deeper overpressured brines with these more dilute hydrostatically pressured fluids an important point is that because of their density hypersaline brines are difficult to expel from the upper crust and may be involved in a succession of alteration and mineralisation events in the same general area over hundreds of millions of years

late quaternary sedimentation in a zone of continental plate convergence the central hellenic trench system abstract the central hellenic trench system south of crete is a tectonically active region forming part of a complex geotectonic regime involving continental plate collision and convergence gravity and piston cores together with seismic reflection profiles provide evidence of significant variations in plio quaternary lithology and sediment geometry that broadly reflect the morphologic diversity of this area and yield data important in the elucidation of analogous ancient sequences gravitite sediments are typically found in the trenches and deep basins while suspensite sediments predominate on highs and in some perched basins in detail the trench floors are characterized by cyclic repetitions of gravitite sediments in high proportions comparable only to submarine fans elsewhere in the mediterranean thick diluted sapropels and hemipelagic calcareous oozes the substantial core to core variations in this and other facies assemblages are attributed to the variety of sub environments present within each depositional province the late quaternary sediment sequences present in cores are well organized and display a cyclic stratigraphy that can be correlated with other eastern mediterranean areas sedimentation rates deduced on the basis of this correlation are noticeably lower than in the western hellenic trench or the nile cone probably because of the reduced supply of fine grained terrigenous material to this area although there is a marked correlation between the late quaternary climatic eustatic oscillations and the sediment types and rates some of the overall variations in lithofacies patterns are best attributed to the tectonic mobility of the area seismic profiles reveal substantial regional variations in the geometry and organization of the plio quaternary sedimentary fill in adjacent sectors of the trenches the thickness of unconsolidated undeformed sediment below the trench floor is also much smaller than that extrapolated from the late quaternary sedimentation rates computed from the cores it is concluded that these variations in geometry and thickness of the sedimentary infill reflect different stages in the process of convergence and plate consumption the differential removal of sediments from adjacent sectors of the trench floor is further interpreted as a discontinuous and diachronous process the geometry thickness and lithofacies represented in the central hellenic trench sequences appear more varied and complex than those reported from modern pacific trenches and it is suggested that the quaternary sediments of this region may furnish more appropriate examples of the deposition associated with alpine type compressional settings than the sedimentary fill of pacific type trenches

an evaporated seawater origin for the ore forming brines in unconformity related uranium deposits athabasca basin canada cl br and δ37cl analysis of fluid inclusions abstract analyses of halogen concentration and stable chlorine isotope composition of fluid inclusions from hydrothermal quartz and carbonate veins spatially and temporally associated with giant unconformity related uranium deposits from the paleoproterozoic athabasca basin canada were performed in order to determine the origin of chloride in the ore forming brines microthermometric analyses show that samples contain variable amounts of a nacl rich brine cl concentration between 120 000 and 180 000 ppm and a cacl2 rich brine cl concentration between 160 000 and 220 000 ppm molar cl br ratios of fluid inclusion leachates range from 100 to 900 with most values between 150 and 350 cl br ratios below 650 seawater value indicate that the high salinities were acquired by evaporation of seawater most 37cl values are between 0 6 and 0 seawater value which is also compatible with a common evaporated seawater origin for both nacl and cacl2 rich brines slight discrepancies between the cl concentration cl br 37cl data and seawater evaporation trends indicate that the evaporated seawater underwent secondary minor modification of its composition by i mixing with a minor amount of halite dissolution brine or re equilibration with halite during burial ii dilution in a maximum of 30 of connate and or formation waters during its migration towards the base of the athabasca sandstones iii leaching of chloride from biotites within basement rocks and iv water loss by hydration reactions in alteration haloes linked to uranium deposition the chloride in uranium ore forming brines of the athabasca basin has an unambiguous dominantly marine origin and has required large scale seawater evaporation and evaporite deposition although the direct evidence for evaporative environments in the athabasca basin are lacking due to the erosion of 80 of the sedimentary pile cl br ratios and 37cl values of brines have behaved conservatively at the basin scale and throughout basin history

chemical evolution of ore forming brines basement leaching metal provenance and the redox link between barren and ore bearing hydrothermal veins a case study from the schwarzwald mining district in sw germany abstract six mineralogically exemplary barren and mineralized hydrothermal veins with pb and zn ores of jurassic cretaceous and cenozoic age in the schwarzwald mining district sw germany were chosen to shed light on the origin of their mineralogical diversity the selection of the veins was guided by the fact that they represent the largest number of veins in the region are very well known mineralogically and geochemically and they provide nice examples of barren and mineralized veins of similar age fluid inclusion data from the individual veins overlap implying their diverse mineralogy is not caused by different fluid compositions participating during fluid mixing la icpms data of single fluid inclusions indicate no systematic variations in major elements but significant changes in fluid mixing ratios which caused variable trace element concentrations of different fluid inclusion assemblages in one sample we suggest that different ore gangue assemblages can be produced by mixing of identical fluid endmembers but variable mixing ratios la icpms analyses of single fluid inclusions in barren and mineralized veins record similar base metal and sulfur concentrations hence sulfide mineralization in the veins appears not to be controlled by metal solubility thermodynamic modeling based on the fluid data indicates that the presence of a reducing phase during fluid mixing is required for sulfide mineralization to precipitate la icpms trace element analyses of feldspars biotites chlorites and clay minerals in granites and paragneisses which are the source of the metal content in the ore forming fluids demonstrate that the dominant provenance for pb zn as sb ba tl mo fe and mn are probably paragneisses while co cu and ni are probably sourced from s type granite a rough quantification indicates that

mixing of sodic and calcic brines and uranium deposition at mcarthur river saskatchewan canada a raman and laser induced breakdown spectroscopic study of fluid inclusions the richest u deposit in saskatchewan canada occurs in the mcarthur river area in the vicinity of the unconformity between the athabasaca sandstones and an archean to lower proterozoic basement paleofluids related to the silicification of the sandstones and the formation of pre and postore cements in breccias were studied using microthermometry raman microspectroscopy and laser induced breakdown spectroscopy libs on individual fluid inclusions a detailed reconstruction of the fluid composition in the system na ca mg cl shows that two types of brines are responsible for the main quartz cements an nacl rich brine 25 wt nacl up to 14 wt cacl 2 and up to 1 wt mgcl 2 which is interpreted as a primary formation water that was expelled from bedded evaporites and a cacl 2 rich brine 5 8 wt nacl 20 wt cacl 2 and up to 11 wt mgcl 2 which is considered to have formed during the interaction between the nacl rich brine and ca rich minerals in the basement and was introduced into the fault system and mixed with the nacl rich brine during the critical stage of u deposition the pressure temperature conditions of formation of the quartz cements are estimated to be 1 200 to1 400 bars and 190 to 235 c for the silicification events during the preore stage and 500 to 900 bars after a pressure decrease from lithostatic conditions and slightly lower temperatures due to the mixing of the nacl rich brine with the cooler approx 140 c cacl 2 rich brine during the main stage of breccia sealing temperature and pressure drops combined with the effects of brine mixing appear to be key factors for the main stages of quartz cementation and u deposition at the mcarthur deposit

orthogneisses of the spessart crystalline complex northwest bavaria indicators of the geotectonic environment the orthogneisses of the spessart crystalline complex are derived from a granitic to granodioritic magma of s type character which must have formed by anatexis of continental crust it intruded into a relatively shallow crustal level 410 420 ma ago at the silurian trace element characteristics are consistent with a post collision geotectonic environment testifying to extensional tectonics at the end of the caledonian era

the evaporation path of seawater and the coprecipitation of br and k with halite brines and salt were sampled at the morton bahamas solar salt production facility on great inagua island in the bahamas the brines were analyzed by ion chromatography to define more precisely than heretofore the evaporation path of seawater to the end of the halite facies at inagua calcium carbonate begins to precipitate at a brine concentration factor of 1 8 times that of seawater gypsum begins to precipitate at a brine concentration of 3 8 times seawater and halite at a concentration factor of 10 6 three of the most concentrated brines from inagua 40 times seawater were evaporated further in the laboratory magnesium sulfate first precipitated at brine concentrations about 70 times those of seawater and potassium bearing phases began to precipitate for these brines at concentrations greater than 90 times those of seawater the distribution of coefficients of br and k between brines and halite were determined by combining analytical data for the inagua brines with measurements of the br and k content of halites from inagua and of halite which had precipitated from inagua brines during storage the observed average value of dbr is 0 032 in good agreement with some of the previous measurements the measured values of dk are highly variable 0 001 to 0 021 dk for halite precipitated early in the halite facies is in the vicinity of 0 015

accurate and precise quantification of major and trace element compositions of calcic sodic fluid inclusions by combined microthermometry and la icpms analysis abstract determination of absolute trace element concentrations in fluid inclusions using laser ablation la icpms requires an internal standard i e the concentration of one element must be independently known from independent observation microthermometric determination of the last melting temperature of ice hydrohalite or halite is routinely used to calculate apparent salinities in wt nacl equivalent using phase relations in the binary h 2 o nacl system to estimate na concentration calculating the concentrations of all other elements requires an empirical correction if additional salt concentrations are of similar magnitude as that of nacl if cacl 2 is the main additional salt component as in many low temperature basin and basement brines absolute na concentrations wt nacl abs can be obtained by observing two melting temperatures hydrohalite and either ice or halite uniquely defining the major element composition of the fluid in the ternary model system h 2 o nacl cacl 2 and allowing na to be used as internal standard for quantifying all minor and trace elements test results for a range of compositions show that calcium concentration can be determined more precisely by microthermometry than by la icpms analysis but that both methods agree within error the combined approach of microthermometry and la icpms analysis described here permits reliable quantification of major ca na as well as trace element concentrations in sodic calcic brine inclusions even in ca rich host minerals such as fluorite or ca bearing carbonates

red bed and basement sourced fluids recorded in hydrothermal mn fe as veins sailauf germany a la icpms fluid inclusion study the hydrothermal mn fe as vein mineralization at sailauf germany hosts a complex sequence of oxide and carbonate minerals that record a protracted fluid history the mineralization is related to a major unconformity that separates permian zechstein sedimentary rocks from underlying variscan crystalline basement the hydrothermal veins contain two principal mineralization stages which are mn oxides associated with calcite and hematite associated with mn calcite the fluid evolution of the hydrothermal system has been reconstructed from fluid inclusion petrography microthermometry and la icpms microanalysis coupled with stable isotope geochemistry of carbonate and oxide minerals the fluid inclusions are high salinity sodic calcic brines and the bulk fluid properties show no major differences between the mn oxide and the hematite stage la icpms analysis of major and trace elements demonstrates that the mineralization formed from chemically distinct fluid pulses characterized by variations in their k li b pb and zn concentrations the fluid that precipitated the mn oxide stage has anomalous pb zn and li b ratios which closely resemble fluids found in fracture fillings in red beds of the permian rotliegend basin by contrast the fluids associated with the hematite stage have pb zn and li b ratios typical of crustal fluids that were derived from interaction with crystalline basement both fluids possess characteristic element ratios including cl br but variable absolute concentrations of most metals this suggests that both fluids were modified by mixing with a common metal depleted brine that had a similar cl br ratio most likely a formation water from the overlying zechstein sedimentary rocks the sailauf mineralization provides insight into the protracted post variscan fluid evolution at the basement cover interface the compositionally anomalous fluid that precipitated the mn oxides is comparable to brines derived from interaction with red beds and likely represents the ore fluid of kupferschiefer type sediment hosted cu deposits conversely the fluid that deposited the hematite mineralization resembles fluids that typically form basement and sediment hosted pb zn deposits

compositional multivariate statistical analysis of thermal groundwater provenance a hydrogeochemical case study from ireland abstract thermal groundwater is currently being exploited for district scale heating in many locations world wide the chemical compositions of these thermal waters reflect the provenance and circulation patterns of the groundwater which are controlled by recharge rock type and geological structure exploring the provenance of these waters using multivariate statistical analysis msa techniques increases our understanding of the hydrothermal circulation systems and provides a reliable tool for assessing these resources hydrochemical data from thermal springs situated in the carboniferous dublin basin in east central ireland were explored using msa including hierarchical cluster analysis hca and principal component analysis pca to investigate the source aquifers of the thermal groundwaters to take into account the compositional nature of the hydrochemical data compositional data analysis coda techniques were used to process the data prior to the msa the results of the msa were examined alongside detailed time lapse temperature measurements from several of the springs and indicate the influence of three important hydrogeological processes on the hydrochemistry of the thermal waters 1 salinity and increased water rock interaction 2 dissolution of carbonates and 3 dissolution of sulfides sulfates and oxides associated with mineral deposits the use of msa within the coda framework identified subtle temporal variations in the hydrochemistry of the thermal springs which could not be identified with more traditional graphing methods or with a standard statistical approach the msa was successful in distinguishing different geological settings and different annual behaviours within the group of springs this study demonstrates the usefulness of the application of msa within the coda framework in order to better understand the underlying controlling processes governing the hydrochemistry of a group of thermal springs in a low enthalpy setting

the mineralogical variability of hydrothermal native element arsenide five element associations and the role of physicochemical and kinetic factors concerning sulfur and arsenic abstract the hydrothermal native element arsenide mineralization comprises ni co and fe arsenides and sulfarsenides which typically form characteristic overgrowth textures on skeletal native silver and or bismuth aggregates native arsenic native antimony antimony arsenic silver alloys and uraninite are present in some of these deposits famous deposits of this type include cobalt ontario bou azzer morocco kongsberg norway jachymov czech republic and schneeberg germany as the physico chemical conditions of formation e g p t fluid composition and the host rocks are variable the only unifying feature for their crystallization is a geologically fast reduction process of a ni co fe as bearing fluid e g by methane graphite or fe2 bearing minerals the present contribution combines a comprehensive literature review with novel calculated stability relations of native elements ag bi as ni co and fe mono di and sulfarsenides and sulfides sulfosalts to understand the details of this formation mechanism and to explain the mineralogical and textural diversity observed in five element assemblages the characteristic sequence of ni co fe diarsenides is ubiquitous and can be explained by continuous reduction of an arsenic and metal bearing aqueous solution this unique succession is largely independent of the metal ratios in the fluid as three orders of magnitude differences between fe co and ni concentrations are needed to change this sequence at neutral ph at more basic conditions the diarsenide sequence changes to co ni fe which has been observed at only two localities valais and pirineos also the prevalence of mono vs diarsenides is mainly ph dependent furthermore differences in reduction agent initial ph fluid rock ratio and the crystallization in contained microenvironments all produce visible differences in mineralogy and or textures that record the details of the formation processes the stability of dissolved sulfide plays a crucial role in five element mineralogy as co and fe arsenides would not form in the presence of appreciable amounts of sulfide the absence of large quantities of sulfide in the arsenide stage can be attributed to a lack of sulfur or a thermodynamic disequilibrium between sulfate and sulfide both cases occur in nature while the fluid prior to reduction must have been oxidized slow reaction kinetics for the sulfate sulfide compared to the arsenite arsenate arsenide conversion favor the formation of arsenides and native metals their formation is hence kinetically controlled which is supported by the commonly skeletal textures sulfarsenides and or sulfides of co ni fe pb and cu appear only late in the five element assemblages when sulfide reduction progresses and the system re attains thermodynamic equilibrium or sufficient influx of sulfide has occurred

genesis of the ores of the zambian copperbelt abstract the theories for the origin of the ores of the copperbelt of zambia and zaire are reviewed following an account of the historical development of ideas from epigenetic through syngenetic to syngenetic diagenetic and ultimately to neohydrothermalist theories models for the genesis of these deposits are critically assessed in the light of the data currently available this examination is conducted with particular regard to the questions of the sources of copper and cobalt the timing of mineralizing events and the physicochemical conditions of metal sulphide precipitation although accepting that the origin of these ores remains controversial it is concluded that the most likely sources of both copper and cobalt are the rocks of the basement complex that metals were probably transported both in surface and ground waters and that the main mineralizing event took place during early diagenesis with sulphide precipitation occurring via bacterial reduction of seawater sulphate the precipitation of sulphides probably occurred at temperatures around 20 60 c and at near neutral ph with minor fluctuations in eh and variations in the solubilities of the metals involved causing mineral zonation the burial and compaction of these sediments probably resulted in the expulsion of metal rich fluids and formation of sulphides in the immediate footwall and hanging wall of the main ore horizon with continued burial resulting in the formation of sulphide bearing pods and veins of lateral secretion origin tectonic deformation and metamorphism in the lufilian orogeny although resulting in a set of cross cutting high temperature mineralized veins appears not to have resulted in significant remobilization of the sulphides

fluid composition and evolution of the langxi ba f deposit yangtze block china new insight from la icp ms study of individual fluid inclusion abstract the langxi vein type ba f deposit located in the southeast of the sichuan basin in the central part of yangtze block south china is hosted by ordovician limestone the paragenesis of the deposit s veins is subdivided into pre syn and post ore stages the syn ore stage includes two fluorite generations with the first fl 1 deposited at 140 to 200 c and the second fl 2 at 140 to 180 c the syn ore barite mineralisation was deposited with the temperature range of 110 160 c and the syn ore calcite records a temperature range of 90 to 140 c these temperature ranges show that the mineralising fluids were low to moderate in temperature and decreased with the initial deposition of fluorite followed by barite and then calcite the types of fluid inclusions in the veins are classified as monophase liquid l type type i biphase liquid vapour l v type type ii and polyphase l v s type type iii brine inclusions the salinity of the mineralising fluid for the three types of inclusions during the deposition of f ba ca is 0 35 21 7 nacl eqv indicating that the ore forming fluid varied greatly during the mineralising process there are no obvious differences in the fluid inclusion density in the different minerals with the average densities being 0 98 g cm3 for fl 1 0 99 g cm3 for fl 2 1 00 g cm3 for barite and 1 01 g cm3 for calcite this shows that the density of the f ba ca mineralising fluid belong to a moderate low density the deposition of the minerals took place with a change from a reducing to an oxidising environment the liquid phase initially included na and cl and evolved containing ca2 so42 k and mg2 la icp ms analyses reveal that the l v type fluid inclusions associated with fl 1 assays 46 600 ppm na 3470 ppm k with a mean na k ratio of 24 28 200 ppm for cl and 1060 ppm br with a mean cl br mass ratio of 27 the second generation fluorite l v type fluid inclusions average around 47 000 ppm na and 12 000 ppm k corresponding to and a na k mass ratio of 7 the halogen content of fl 2 averages 26 200 ppm cl and 950 ppm br corresponding to a cl br mass ratio of 28 these analyses indicate that the mineralising fluid was rich in nacl assuming the fluid inclusions represent samples of the mineralising fluid it is proposed that ba f concentrated in the mineralising fluid were derived from basinal fluids mixed with meteoric water circulating through faults at increased temperature gradients the driving force was late cretaceous tectonic activity related to the subduction of the paleo pacific oceanic plate this model is consistent with the geodynamic setting of other barite fluorite rich districts in the yangtze block of south china

geochemical and isotopic composition of organic matter in the kupferschiefer of the polish zechstein basin relation to maturity and base metal mineralization vs the present depth of the kupferschiefer soluble organic matter som yields and relative proportions of saturated and aromatic hydrocarbons of the som provide evidence for an oxidative alteration of organic matter in highly mineralized kupferschiefer samples near the rote faule zones this is confirmed by differences in the composition of the saturated and aromatic hydrocarbon fractions of the soluble organic matter saturated hydrocarbons from rote faule samples are dominated by short chain n alkanes and higher abundances of pristane and phytane relative to heptadecane n c17 and octadecane n c18 respectively compared with samples more distant to the rote faule zone compositional changes of the aromatic hydrocarbon fractions with decreasing distance to that zone are characterized by the occurrence of polycyclic aromatic hydrocarbons and elevated ratios of phenanthrene to methylphenanthrenes that are attributed to demethylation reactions and resulted in a decrease of the methylphenanthrene index mpi 1 kupferschiefer samples from the barren zone of the polish basin do not show these alteration patterns the observed variations in organic matter composition with burial depth are consistent with changes due to increasing thermal maturation maturity assessment is achieved from mpi 1 and the methyldibenzothiophene ratio mdr from the relationship between the maturity of organic matter in terms of vitrinite reflectance values and depth of the kupferschiefer strata a continuous increase in reflectance of vitrinite is obtained within the polish basin the alteration pattern of organic matter related to base metal mineralization of the kupferschiefer corresponds to changes in the isotopic composition of organic carbon and calcite kerogen within or close to rote faule zone is enriched in 13c caused by the preferential release of isotopically light organic compounds through progressive degradation of organic matter the opposite tendency towards lower 13c and 18o values of calcite provides evidence for isotopic exchange between carbonate and the oxidizing ore bearing solutions and for organic matter remineralization in contrast organic matter and calcite from the kupferschiefer do not show regular trends in 13c with increasing thermal maturation

mass balance evaluation of the late diagenetic hypothesis for kupferschiefer cu mineralization in the lubin basin of southwestern poland ments of the early permian rotliegende sequence fig lb and c the kupferschiefer shale hosts base and precious metal mines that have been important in the development of mining technology and the european mining industry whether the kupferschiefer and adjacent strata were mineralized uring their deposition syngenetic early diagenetic hypothesis or later by brines expelled from the red bed filled basins late diagenetic hypothesis has been a matter of continuing debate see jowett 1991 a data set derived from over 400 cored drill holes