interaction of magmatic fluids and silicate melt residues with saline groundwater in the footwall of the sudbury igneous complex ontario canada new evidence from bulk rock geochemistry fluid inclusions and stable isotopes abstract along the northern margin of the 1 85 ga sudbury igneous complex sic canada a volumetrically minor rock type known as the footwall granophyre fwgp preserves evidence of the interaction of magmatic fluid and groundwater the fwgp comprises veins dikes and irregular bodies of a quartz alkali feldspar plagioclase intergrowth that are most abundant near footwall style cu ni platinum group element mineralization textures and cross cutting relations show that the emplacement of the fwgp created favourable sites for the later deposition of sulfides geochemical and physical evidence show that the fwgp did not form by in situ partial melting of the archean country rocks in the footwall beneath the sic it represents a mobilized injected silicate residue from either the contact between partially melted country rocks and the sic or from the crystallizing sic itself its bulk composition can be modeled as the product of fractional crystallization of a liquid with an initial composition equivalent to granophyric matrix trapped liquid in the lowermost units of the sic norite and sublayer primary fluid saline h 2 o poor and melt silicate h 2 o rich inclusions hosted in quartz from the fwgp have bulk and trace element compositions consistent with those hosted in quartz from the granophyric matrix of the lower units of the sic norite sublayer fluid inclusions contain mixtures of a high salinity 44 70 wt nacl equivalent n 39 na fe rich aqueous magmatic fluid and a lower salinity ca and sr rich groundwater the magmatic end member is thought to be an sic derived volatile phase estimates of the mixing proportions show that primary and secondary inclusions in the fwgp contain 60 100 and 30 80 of the magmatic end member by mass respectively fluids responsible for the remobilization of ore metals represent mixtures containing a much higher proportion of the groundwater end member not less than 70 by mass compared to the fluids trapped in the fwgp at considerable distance 400 m from the sic the chlorine isotope composition of biotite in the fwgp is enriched in 37 cl 37 cl 0 98 to 1 61 scapolite from the high temperature veins and the interstices of rock types in the main mass of the sic shows similar enrichment in 37 cl up to 1 34 whereas biotite from the archean country rocks 37 cl 0 88 to 0 53 and associated groundwater are 37 cl depleted the results of this study lead to two important conclusions concerning genetic and exploration models for the footwall ore zones first magmatic end member fluid introduced into the footwall with the melt from which the fwgp crystallized contained very little cu rarely 100 ppm the main ore metal in the footwall ores this result questions hydrothermal models for footwall ore formation that hypothesize that cu and other ore metals were remobilized from sulfide deposits along the sic contact by magmatic hydrothermal fluids and redeposited in the footwall it is more likely that ore metals were only locally remobilized in the footwall ore zones when metal poor hybrid fluids interacted with pre existing sulfide veins of magmatic origin second inclusions containing the hybrid fluid occur in the fwgp rock type throughout the footwall in both mineralized and unmineralized areas therefore although the fwgp preserves stable cl isotope and fluid inclusion evidence that magmatic fluid was introduced into the footwall detection of this magmatic component alone will not serve as a useful exploration method in contrast mapping the distribution and abundance of fwgp may be ore predictive since fwgp emplacement and its higher abundance in mineralized areas appears to have been a structural and textural prerequisite for footwall ore emplacement

evidence for primary kimberlitic liquids in megacrysts from kimberlites in kentucky u s a inclusions within garnet and diopside megacrysts from kimberlite in eastern kentucky contain ti rich phlogopite serpentine and calcite the garnet inclusions also contain spinel aluminous clinopyroxene and chlorite it is inferred that the inclusions in garnet were once the same as those in diopside but spinel aluminous clinopyroxene and aluminous orthopyroxene now serpentine chlorite formed at the expense of host garnet and included olivine these polymineralic inclusions may represent included liquids of the same composition as the liquid from which the megacrysts crystallized which may be a phlogopite bearing kimberlite unlike the kimberlite host rocks in kentucky

flow transmission along an arid zone anastomosing river cooper creek australia cooper creek is characterized by an exceptionally wide floodplain and a complex system of anastomosing channels which together can accommodate a large range of highly variable flows in consequence flood frequency curves are unusually steep with minimal tributary contribution over the two study lengths currareva nappa merrie 400 km and nappa merrie innamincka 32 km downstream output is largely controlled by upstream input so that similar flow regimes and hydrograph forms can be maintained despite transmission losses and the variable activation of channels input output relationships defined in terms of total flow volume and peak discharge suggest that above a threshold flow of about 25 duration transmission losses exceed 75 on average over the currareva nappa merrie length the large difference in absorption between primary channels on the one hand and subsidiary channels and the floodplain surface on the other means that transmission losses vary non linearly with stage they are relatively low when flow is confined to the primary channels but increase at higher stages as lesser channels and the floodplain are activated early levels do not recur until flows of 0 5 duration are attained when output input ratios increase rapidly with discharge the influences of seasonality and background flow on output discharge are small relative to that of input discharge despite the long river distance peak flows at currareva and nappa merrie are well correlated however over the shorter nappa merrie innamincka length with its more confined system of channels correlations are better and transmission losses less they vary from 60 just above the threshold discharge to lo at flows below 20 duration over this length outflow hydrographs can be effectively estimated by the three parameter muskingum procedure at least on an event by event basis but further application must await additional records to understand fully how the parameters vary in an environment where streamflow is transmitted through a highly variable system of channels

high temperature fluid inclusions and the role of the biotite granodiorite in mineralization at the panguna porphyry copper deposit bougainville papua new guinea

stable chlorine isotopes in the palo duro basin texas evidence for preservation of permian evaporite brines experimental evaporation of seawater yields brines with 37cl from 0 0 initial to 0 9 in the palo duro basin brines with 37cl values overlapping the 0 1 to 0 4 range of halite evaporite can be generated by a set of processes including dissolution of halite in meteoric water such brines occur above and below an evaporite aquitard brines with 37cl values of 0 4 to 1 0 in the evaporite aquitard and in a deep brine aquifer cannot be generated by dissolution of halite considered with br and cl content d and noble gas content the 37cl data indicate that such brines originated as evapoconcentrated seawater high br evaporite brine formed directly from seawater on the eastern side of the basin whereas low br evaporite brines on the western side formed after an influx of meteoric water at the time of evaporite formation there has not been detectable vertical flow of meteoric water across the evaporite aquitard strata beneath the evaporite contain compartments that have been isolated geochemically since the permian

replacement dolomites and ore sulfides as recorders of multiple fluids and fluid sources in the southeast missouri mississippi valley type district halogen 87sr 86sr δ18o δ34s systematics in the bonneterre dolomite replacement dolomites may continue to recrystallize in the presence of subsequent diagenetic and hydrothermal fluids during recrystallization they can change both their solid geochemistry and that of their included fluids by releasing older fluids and entrapping younger fluids thus it may be possible to decipher a complex fluid history by analyzing both the composition of the dolomite 18o 87sr 86sr and its contained fluids cl br as the former reflects temperature and or fluid rock interactions whereas the latter reflects salinity source regions of the last fluid to affect the dolomite applying this approach to the bonneterre dolomite of southeast missouri which hosts the world class viburnum trend mississippi valley type mvt pb zn district reveals the presence of two geochemically distinct types of brines whose influence varied temporally during the bonneterre s history of dolomitization and ore deposition a plot of cl br molar ratios of included fluids versus 87sr 86sr ratios of the enclosing dolomite indicates distinct salinity sources for early halite dissolution and later extreme evaporation of seawater dolomitizing brines comparison with fluids in ore sulfides may permit us to relate replacement dolomites to ore forming events early stage copper and zinc bearing sulfides 34s 0 have fluids with cl br molar ratios 150 1 050 reflecting a similar importance of halite dissolving brine during ore deposition main stage cuboctahedral galena 34s 15 has fluids with cl br molar ratios 100 400 similar to extremely evaporated seawater brines responsible for late replacement dolomites we suggest that resident brines which gained salinity in part through halite dissolution sulfur and metals from local sedimentary and igneous rocks were important for early replacement dolomitization and early stage ore deposition this fluid type was supplanted by later main stage brines that acquired salinity through seawater evaporation and metals in a more distal basinal setting late stage vug filling cubic galena records a renewed importance of the halite dissolving brine as the influence of the more distal basinal brine waned halogen sulfur isotope systematics of sulfides indicate that fluid mixing likely was a dominant ore depositing mechanism during all stages of ore mineralization in the viburnum trend

mesozoic ash flow caldera fragments in southeastern arizona and their relation to porphyry copper deposits jurassic and upper cretaceous volcanic and associated granitic rocks in southeast arizona are remnants of large composite silicic volcanic fields characterized by voluminous ash flow tuffs and associated calderas presence of 10 15 large caldera fragments is inferred primarily from 1 ash flow deposits more than 1 km thick having features of intracaldera ponding 2 exotic block breccias within a tuff matrix interpreted as caldera collapse megabreccias and 3 local granitic intrusions along arcuate structural boundaries of the thick volcanic sequences several porphyry copper deposits are associated with late granitic intrusions within the calderas or along their margins

evaluation of thermobarometers for garnet peridotites the accuracy and precision of a large number of combinations of geothermometers and geo barometers for garnet lherzolites have been evaluated with a suite of well equilibrated xenoliths from kimberlites of northern lesotho accuracy was tested by comparison of p t estimates for a diamond bearing and a graphite bearing xenolith with the experimentally determined diamond graphite univariant curve and by comparison of p t estimates for phlogopite bearing xenoliths to the high temperature stability limit of phlogopite eggler and wendlandt 1979 precision was evaluated by measuring the scatter of p t estimates for each of four xenoliths from a wide range of p and t when many point analyses of the constituent minerals are used for p t estimation a thermobarometer composed of the uncorrected diopside enstatite miscibility gap of lindsley and dixon 1976 combined with the uncorrected isopleths for aluminum in enstatite coexisting with pyrope of macgregor 1974 is most satisfactory correction schemes such as those of wells 1977 and wood 1974 will ultimately provide a better means of p t estimation but at the present stage of development they serve to decrease precision without a demonstrable increase in accuracy thermometers based on fe2 mg exchange reactions are imprecise because of variable and unknown fe2 fe3 in minerals and xenoliths the inflection observed in the northern lesotho paleogeotherm cannot be an artifact of the method of temperature estimation

hydrochemical and isotopic δ18o δ2h 87sr 86sr δ37cl and δ81br evidence for the origin of saline formation water in a gas reservoir abstract the permo triassic kangan gasfield in southern iran is composed of an aquifer the kangan aquifer ka and an overlying gas reservoir it is located in the kangan and dalan formations and consists predominantly of limestone and dolomite the kangan gasfield is exploited from 36 wells at depths from 2300 to 2860 m the quality of the produced formation waters pfw varies from fresh to saline with salinities of up to 60 000 mg l the present study aims to identify the origin of the salinity of the pfws the concentration of major ions li sr and br as well as 18o d 87sr 86sr 37cl and 81br isotope compositions of the ka water and pfw samples a fresh and a brine spring and the persian gulf water were all measured the suite of isotopic 37cl and 81br and hydrochemical data li cl and br concentrations and cf index in this study indicates that the salinity origin of the pfws is evaporated seawater which could be either the ka water or the intergranular saturated brine in the kangan gas reservoir kgr both derived from permo triassic evaporated seawater 18o and 87sr 86sr data exclude the ka water as the source of the saline pfw leaving the intergranular brine of the kgr as the most likely source although further isotopic and geochemical tests are needed to verify this this work also proposes for the first time the use of a li cl versus br cl diagram to distinguish between evaporate formation water water modified by halite dissolution and fresh water it is recommended to apply these comprehensive methods to deep brine aquifers especially related to gasfields

basement controls on sediment hosted zn pb deposits a pb isotope study of carboniferous mineralization in central ireland lead isotope ratios of galenas from carbonate hosted zn pb or ba or cd or ag deposits in central ireland are homogeneous within individual deposits but vary between deposits the variation correlates directly with geographic position defining isoplumbs and not with style of mineralization age of host rock or structural or physico chemical factors the least radiogenic pb occurs in the northwest and the most radiogenic in the southeast this pattern elegantly reflects irish pre caledonian basement geology lewisian gneisses in the northwest and late proterozoic upper crustal rocks in the southeast that the northwestern end member of the irish pb mixing trend is ultimately lewisian is demonstrated by the concordance of the irish pb isotope trend with the trends defined in proterozoic to tertiary rocks and ores of scotland which contain pb of demonstrably lewisian derivation although geologic relations and pb isotope ratios unambiguously implicate basement in the ore forming process we are unable to discriminate between lewisian gneisses themselves and detritus derived from lewisian rocks in the caledonian metamorphic complex as the direct source of pb comparison of the irish deposits with mcarthur river and mississippi valley deposits leads us to conclude that style of mineralization syngenetic syndiagenetic epigenetic is not a fundamental aspect of sediment hosted zn pb deposits but is a reflection of local stress regimes and physico chemical conditions the fundamental link between the types of sediment hosted zn pb deposits may be the onset of a condition such as extension or compression that provides a mechanism for driving fluids in extensional regimes seismic pumping processes may channel fluids toward the surface or into fractures or favorable pore spaces resulting in a wide variety of styles of mineralization the lack of dilatency in sediments in compressional regimes however may inhibit surface exhalation and favors epigenetic styles of mineralization

origin of massive dolostone the upper knox model abstract previous studies of cambro ordovician dolostones from various sites in the u s midcontinent revealed similar textures and geochemistry prompting similar explanations of their origin before these interpretations can be incorporated in a model to explain other massive dolostones they need verification in a contrasting setting the dupont geohydrological survey dghs well continuously cored through the knox group in west central tennessee provides such a contrast this core provides a complete sample of the knox in the setting of a shallowly buried flat lying structurally and stratigraphically simple platform sequence which contrasts with the relatively deeply buried and structurally complex environments that dominate most prior studies light and luminescence petrography xrd sem eds xrf esr and mass spectrometry were used to document the petrology and geochemistry of the upper knox group lower ordovician from 456 m to 1126 m subsea 2018 ft to 4215 ft below the kelly bushing of the dghs well of the 87 samples 81 are dolostone early e 1 dolomite forms a fine to medium crystalline replacive dolostone that lacks luminescence banding its geochemical signature is 13c 2 83 0 76o oo 18o 5 85 2 01o oo stoichiometry 51 6 1 2 mole ca mnpr 79 27 fe 681 237 ppm mn 79 32 ppm and sr 110 63 ppm e 2 dolomite forms a medium to coarse crystalline replacive dolostone that luminescences with a relatively dull core and brighter red rim its geochemical signature is 13c 2 07 0 32o oo 18o 6 96 1 28o oo stoichiometry 51 0 1 3 mole ca mnpr 74 20 fe 880 843 ppm mn 84 52 ppm and sr 79 29 ppm late l 1 dolomite lines vugs and fractures three limestone beds are unaltered remnants of the precursor to e 2 dolomite calcite is present both as relics in dolomite rhombs and as a vug and fracture fill postdating l 1 dolomite three quartz arenite beds and the presence of 1 to 5 well rounded quartz sand grains in many dolostones denote an intermittent clastic source e 1 dolomite began as syndepositional dolomicrite deposited in an upper intertidal to supratidal environment and it was later modified during shallow burial e 2 dolomite formed when subtidal grainstones and packstones were dolomitized during shallow burial l 1 is a late void fill texture and geochemistry of dolostone in the dghs well is similar to that from coeval appalachian ozark and texas oklahoma units numerous vugs fractures and zones of rubble occur throughout the upper knox core suggesting that multiple exposures occurred during its deposition there is no pattern of change with depth for these features or for any other measured or observed parameter we suggest that massive dolostone formation involving dolomite grain growth calcite replacement and dolomite cement took place in association with a succession of exposure related events the large volume of dolomite thus created required a large amount of magnesium so large in fact that a volume of seawater equal to that of the entire modern ocean must have pumped through collective upper knox exposure surfaces

the chloride source for atacamite mineralization at the radomiro tomic porphyry copper deposit northern chile supergene mineralization at the radomiro tomic porphyry copper deposit involves the copper chloride atacamite cu4cl2 oh 6 as the principal ore mineral distributed in a thick oxide zone chloride rich aqueous fluids were introduced during supergene mineralization causing this atypical variation in copper oxide mineralogy the source of this chloride has been investigated using several geochemical techniques including chlorine isotopes and bromide chloride geochemistry these methods have proven to be the most useful in evaluating the potential chloride sources and their likely influence on copper mineralization unmineralized biotite bearing whole rock protore samples from the radomiro tomic deposit have typical igneous values of 2 ppm br and 37cl values of 0 1 to 2 5 per mil in contrast elevated bromine contents 22 180 ppm br and lower 37cl values near 0 0 per mil for the atacamite mineralization at radomiro tomic are clearly indicative of a nonmagmatic origin for the chloride moreover atacamite mineralization at chuquicamata 48 75 ppm br 37cl 0 1 to 0 2 and mina sur 52 48 ppm br 37cl 0 0 0 1 also has elevated bromine contents and lower 37cl values indicating a similar source for the introduction of chloride upper jurassic sediments 22 24 ppm br 37cl 0 8 to 0 5 have geochemical characteristics indicating that they were the source of chloride for the oxide zone atacamite mineralization at radomiro tomic a later mineralization event where chloride was derived from marine evaporites was responsible for the atacamite mineralization in the overlying gravel at radomiro tomic 63 180 ppm br 37cl 0 6 small distal deposits containing atacamite with 20 to 100 ppm br and 37cl values of 0 1 to 3 2 per mil occur to the west and south of radomiro tomic and have geochemical signatures which are indicative of lower jurassic sediment derived chlorine 9 23 ppm br 37cl 0 3 to 2 6 bromide chloride geochemistry of regional atacamite samples is quite variable and therefore argues against a meteoric chloride source which would lead to regionally homogeneous values similarly seawater was ruled out as the primary source of chloride at radomiro tomic due to the distance from the pacific ocean

br cl na systematics in illinois basin fluids constraints on fluid origin and evolution the authors present here bromide chloride and sodium data for fluids from reservoirs of ordovician through pennsylvania age in the illinois basic which suggest that remnant marine fluids contribute significantly to fluid cl budgets cl br and nabr ratios for ordovician through devonian formation fluids are relatively uniform and near those for seawater despite greater than a factor of ten range in cl concentration in contrast fluids from mississippian and pennsylvanian reservoirs separated from older reservoirs by the new albany shale group have more variable fluid cl br and na br ratios most of which are significantly greater then those of seawater the 1 1 stoichiometry of cl and na increases for mississippian and pennsylvanian formation fluids is consistent with halite dissolution nevertheless br systematics and mass balance considerations indicate that he overall cl budget of illinois basin formation fluids appears to be more significantly influenced by the contribution from subaerially evaporated seawater than by halite dissolution

pore water anomalies of submarine gas hydrate zones as tool to assess hydrate abundance and distribution in the subsurface what have we learned in the past decade abstract the most significant new contributions to the study of natural gas hydrates in the past decade have come from findings of the ocean drilling program odp notably legs 112 141 146 and 164 and to a lesser extent legs 131 160 170 and 186 leg 164 in particular was dedicated to gas hydrate drilling in the blake ridge gas hydrate field in the west atlantic in an unprecedented multidisciplinary research effort paull et al 1996 proc ocean drill program initial rep 164 623 pp paull c k matsumoto r wallace p j dillon w p eds 2000a proc ocean drill program sci results 164 ocean drilling program college station tx 459 pp most important for the progress of hydrochemical studies related to gas hydrates has been the growing awareness of the significance of diffusion modulated advective processes shaping the chemical and isotopic pore water profiles in hydrate zones this started with qualitative evidence for advective flow from drilling the hydrate bearing peru and hydrate free barbados active margins continued with the nankai trough accretionary prism the japan trench slope and the cascadia and costa rica active margins and culminated in the quantitative advection diffusion model of egeberg and dickens chem geol 153 1999 53 for the passive margin setting of the blake ridge advective flow regimes are different at active and passive margins as there is a tendency for the flow at active margins to be focussed along landward dipping thrust planes and faults in the wedge of imbricated thrust sheets that finds expression in a step pattern of the pore water profiles for passive margins but also for some active margin sites advection is from sources below the drilled section either through subvertical faults passive margins or from the decollement zone active margins we have learned that the well known coupled pore water anomalies that are ascribed to hydrate dissociation downward chlorinity decrease combined with 18 o increase hesse and harrison 1981 earth planet sci lett 55 1981 453 need not occur together in the presence of hydrates because the isotope effect may be overprinted by the effects of other reactions such as volcanic ash alteration or by the advection of low 18 o fluids however if the anomalies show up hydrates are present almost invariably with the exception of advected low cl high 18 o waters coming to terms with the effects of advection and diffusion has allowed successful modeling of the simpler hydrate affected pore water profiles at passive margins instrumental for modeling are chlorine isotopes which provide an effective tool to assess advection rates the egeberg and dickens model allows estimation of hydrate concentration and distribution in the subsurface because it separates the effects of advection diffusion and hydrate dissociation but critically depends on samples taken under in situ pressure and temperature conditions modeling the more complex pore water profiles of active margins is a challenge for the future compared to geophysical methods to estimate hydrate concentration the geochemical method gives minimum amounts

chlorine isotopic compositions of high temperature hydrothermal vent fluids over ridge axes abstract we present chlorine stable isotope compositions of high temperature hydrothermal vent fluids from two mid oceanic ridges the six hydrothermal fluids come from sites along the slow spreading mid atlantic ridge menez gwen at 37 50 n lucky strike at 37 17 n and rainbow at 36 14 n and the ultrafast spreading east pacific rise from three contiguous segments centered respectively at 17 25 s 18 15 s and 18 26 s these samples exhibit a large range in temperature ph chlorinity and mg content reflecting various geological settings and substrata nature basaltic or ultramafic although showing a large range of chlorinity from 251 to 821 mmol kg the fluids display homogeneous chlorine isotope signatures 37 cl smoc 0 03 0 06 indistinguishable from that of seawater this homogeneity contrasts with the large range of 37 cl previously observed in continental or off axis oceanic fluids this study explores possible processes that may change cl concentration during fluid genesis and discusses their theoretical isotopic effects the 37 cl homogeneity implies that at the p t conditions of the ridge axis the process of phase separation at sub or super critical conditions that explains most of chlorinity variations does not significantly fractionate chlorine isotopes this study shows that the physical and chemical processes that likely alter cl concentrations in ridge axis systems i e transport processes mixing or water rock interaction contribute to minimize the range of 37 cl around the seawater 37 cl value

geochemistry of the fluids related to epigenetic carbonate hosted zn pb deposits in the maestrat basin eastern spain fluid inclusion and isotope cl c o s sr evidence epigenetic zn pb deposits in the maestrat basin eastern spain are hosted by dolostones that replace aptian limestones the deposits have morphologies ranging from mineralized breccias to stratiform massive replacements sphalerite and galena cementing breccias precipitated as well formed crystals whereas the stratiform replacements are characterized by textures such as colloform and skeletal or dendritic growths two mineralized areas are found valdelinares and mas de la mina cedraman the highest ore grades up to 11 zn and largest deposits ca 30 000 t of sulfides occur as stratiform deposits in the valdelinares area resurreccion and restauracion mines in the valdelinares area microthermometry of fluid inclusions reveals that ore stage minerals precipitated by the mixing of two distinct fluids fluid a a high salinity brine with salinity greater than 26 wt percent nacl equiv and temperatures above120oc and fluid b a low salinity fluid with less than 15 wt nacl equiv and temperatures around 40oc fluid a dominated brines are found in mineralized breccias located in the vicinity of major fracture zones whereas more dilute fluids are typical of massive ores in the mas de la mina area the presence of two fluids is less evident although the ranges in both temperature and salinity also point to mixing na k li cl br systematics of the inclusion fluids indicates that fluids a and b were evaporated seawater that did not significantly interact with k and li rich sediments the most diluted mixtures fluid b are characterized by relatively heavy cl 37 cl 1 11 and 1 19 compared to fluid a dominated brines which have 37 cl values close to seawater 0 the sulfur isotope compositions range from 10 5 to 13 4 per mil for sulfides and between 16 and 17 8 per mil for barite such values are consistent with mixing of a metal rich brine with small amounts of 32 s enriched sulfur and a sulfur rich fluid with a 34 s close to the marine sulfate of late cretaceous to early paleocene age the c and o isotope compositions of ore stage calcite 13 c from 0 6 to 7 8 18 o from 17 2 to 20 9 are also explained by the precipitation from different mixtures of fluids a and b from the geochemical data it is inferred that fluid mixing played a key role in the formation of the zn pb deposits in the maestrat basin ore precipitation occurred in places where brines ascending through faults interacted with a dilute sulfur rich fluid deposits with the highest ore grade and size are related to areas where the most extensive mixing occurred

origin and mixing history of brines palo duro basin texas u s a formation waters in the palo duro basin texas u s a fall into four major groups based on integrated chemical and isotopic characteristics 1 interbed brines within the major permian evaporite aquitard these are the most chemically concentrated and18o rich fluids in the basin and are interpreted as evaporatively concentrated sea water which has been hydrologically isolated since the permian 2 brines below the salt on the eastern side of the basin have clbr divalent cation and isotopic systematics indicating a mixture of evaporatively concentrated sea water and meteoric water of d 20 3 brines below the salt on the western side of the basin have chemical and isotopic systematics suggesting a mixture of two pulses of meteoric water one with d 20 and the other with d 55 and 4 waters above the salt have the isotopic composition of meteoric waters diagenetic alteration of the cation chemistry has occurred for brines within and below the salt aquifers below the salt on the eastern side are interpreted as having been charged with dense permian evaporite brines which subsequently mixed in various amounts with a basin wide pulse of triassic meteoric water on the western side the descending triassic meteoric waters became saline by dissolution of halite and are currently mixing with a tertiary pulse of meteoric water initiated by the laramide uplift to the west the hydrochemistry suggests flow on the western side of the basin and static conditions on the eastern side an unrecognized approximately n s permeability restriction or discontinuity in the potentiometric flow surface is inferred for major aquifers in the central area of the basin

constraints of fluid inclusions and c o isotopic compositions on the origin of the dolomites in the xisha islands south china sea abstract the dolomite problem is a key issue in research on carbonate diagenesis and it is still a controversial scientific problem the origin of the neogene dolostones in the xisha islands has remained disputed until now however the geochemical characteristics of dolomite hosted fluid inclusions can potentially provide a relatively direct record of the origin and evolution of their dolomitizing fluid in this article based on the samples selected from the well xike 1 also known as zk 1 and xk 1 reef core of the xisha islands the hydrogen isotopic compositions and gas and liquid compositions of the fluid inclusions hosted in calcite and dolomite were analyzed meanwhile the isotopic compositions of carbon and oxygen in the calcite and dolomite minerals were also tested the origin of the dolomitizing fluid was traced in detail which provided important evidence for establishing the dolomitization model of the primary dolomites in the study area the main gas compositions of the dolomite hosted fluid inclusions are co2 h2o n2 and o2 which are similar to those of the atmosphere indicating that the dolomites in this area experienced a partly oxygenated diagenetic environment from high to low the cation concentrations of the liquid component in the dolomite hosted fluid inclusions are mg2 ca2 na and k whereas their main anion compositions are so42 cl and f which are characterized by high so42 concentrations and low cl br ratios the 13c values pdb of the dolomites range from 1 9 to 3 0 and their 18o values pdb range from 2 1 to 4 7 the calculated z values which can be used to trace the salinity of diagenetic fluid based on the 13c and 18o values of the dolomites range from 133 0 to 135 8 which are higher than that of modern seawater approximately 120 these data indicate that the dolomitizing fluid of the primary dolomites in the xisha islands is the high salinity concentrated seawater derived from a surface environment in addition the model of seepage reflux dolomitization can better interpret the dolomitizing process of the primary dolomites in the xisha islands

chlorine isotopic geochemistry of salt lakes in the qaidam basin china abstract the isotopic compositions of chlorine in salt lake brine coexisting with halite oil field water and river water from the qaidam basin qinghai china have been examined using high precision measurement of chlorine isotopes based on thermal ionization mass spectrometry of the cs 2 cl ion 37 cl values vary from 2 05 to 2 94 with average values of 2 94 for hot spring water 1 35 for river water 0 38 for oil field brine 0 40 for saline water and 0 63 for salt lake brine the preliminary results show isotopic fractionation of chlorine in salt lake brine during salt precipitation the variation of the 37 cl value in these salt lakes is mainly associated with brine evaporation and halite precipitation and with the hydrochemistry of the input water the chlorine isotopic composition may reflect the degree of evaporation of the salt lake brine and may be used to distinguish brines that are in equilibrium with precipitating salts and brines that have dissolved earlier evaporates

source and possible leaching process of ore metals in the uragen sandstone hosted zn pb deposit xinjiang china constraints from lead isotopes and rare earth elements geochemistry abstract the uragen world class zn pb deposit is located in the ulugqat basin in xinjiang china the deposit is characterized by low grade zn pb 3 wt and large tonnage of 4 84 mt metals in the southern ore zone and potentially 10 mt metals for the whole deposit the deposit is mainly hosted in sandstone and conglomerate of the fifth member of the lower cretaceous kezilesu group to provide better constraints on the source of ore metals systematic analyses of the pb isotopes and ree were conducted on sulfides and possible source terranes the sulfides have homogeneous pb isotopic ratios for 206pb 204pb of 18 528 18 690 for 207pb 204pb of 15 545 15 743 and for 208pb 204pb of 38 429 39 082 these ratios are different from those of the upper silurian upper devonian tangaitaer and paleocene aertashi formations the fourth member of the lower cretaceous kezilesu group and the permian granite despite partly overlapping with the values of sulfides the ratios of the proterozoic aksu metamorphic rocks are different in extent and variability however the clastic rocks of the fifth member of the lower cretaceous kezilesu group have almost the same pb isotopic compositions as the sulfides if the preferential leaching of radiogenic pb is taken into account the sulfides in the disseminated ores show lree enriched patterns with high lree hree ratios 3 50 12 06 variable changes of ce anomalies 0 67 1 22 and eu anomalies 0 52 1 33 that are also similar to those of the clastic rocks of the fifth member of the lower cretaceous kezilesu group but are significantly different from those of the basement rocks of the proterozoic aksu group and the evaporite sequences of the paleocene aertashi formation in the ce and eu anomalies petrographic observations indicate that the clastic rocks of the fifth member of the lower cretaceous kezilesu group have undergone sedimentation diagenetic reddening and bleaching reddening is related to the in situ oxidation of mafic minerals such as biotite to produce ferric iron oxide and hydroxide ioh that accompanied the liberation of ore metals from the silicate phase during subsequent crystallization of ioh to hematite preferential adsorption onto hematite could have been the main mechanism for separating zn pb from cu bleaching resulted from the dissolution of ioh during the oil gas infilling stage and based on mass balance calculations substantial amounts of leachable fe zn pb were extracted from the red clastic rocks by the ore forming fluid therefore we propose that the red clastic rocks of the fifth member of the lower cretaceous kezilesu group may be the predominant source of ore metals in the uragen deposit and that the leaching may be possibly related to the bleaching process

strontium isotopic geochemistry of mississippi valley type deposits east tennesse implications for age and source of mineralizing brines strontium isotopic ratios of wall rock ore and gangue minerals from the mascot jefferson city copper ridge and sweetwater mississippi valley type mvt districts and from the lost creek barite deposit in east tennessee were measured in an effort to determine the age of this mineralization and its relation to the tectonic evolution of the appalachian orogen the lower ordovician knox group which hosts the mvt mineralization contains limestones and dolomite karst breccias with 87sr 86sr ratios of 0 70900 to 0 70916 that are similar to those of early ordovician sea water primary diagenetic knox dolomite as well as recrystal line dolomite which formed by later alteration of limestone exhibits 87sr 86sr ratios of 0 70930 to 0 71024 reflecting varying degrees of contamination by solutions with more radiogenic strontium 87sr 86sr isotopic ratios of mineralization in the districts increase in the order lost creek sweetwater copper ridge mascot jefferson city and extend to values significantly higher than those of the enclosing rocks of the three possible source basins for the mvt brines the late proterozoic ocoee cambrian luttrell and ordovician sevier basins the sevier basin appears to be the only one that could have supplied brines of the appropriate composition at geologically reasonable times estimates of the change with time in the isotopic composition of sevier basin brines indicate that the maximum ages of the lost creek sweetwater copper ridge and mascot jefferson city mineralization are 520 460 405 and 395 m y respectively comparison of fluid inclusion temperatures for the sweetwater and mascot jefferson city minerlization with the thermal evolution curve for the sevier basin supports these estimates these ages suggest that the lost creek barite minerlization formed as an exhaltive deposit in the sevier basin and that the sweetwater fluorite barite mineralization formed during the later part of taconic orogeny the copper ridge and mascot jefferson city minerlization could have formed either prior to or during the alleghanian orogeny but prior to deformation of the enclosing rocks depending on the rate of istopic evolution of the sevier basin brines

the carbonate rock hosted epithermal gold deposit of agdarreh takab geothermal field nw iran hydrothermal alteration and mineralisation the disseminated gold deposit of agdarreh 24 5 t at 3 7 g t au is hosted in hydrothermally leached miocene reefal limestone in the takab geothermal field which is part of the cenozoic urumieh dokhtar volcanic arc of nw iran alteration and mineralisation are largely bedding controlled blanket like and include 1 pre ore decalcification 2 first stage silicification associated with pyrite early pyrite with 3 4 wt as late pyrite with 1 3 wt as and sphalerite 3 second stage silicification with precipitation of galena pb sb as sulphides sulphosalts tellurides and native bismuth 4 late stage cinnabar and barite in vugs 5 oxide ore stage and carbonate alteration complex mn fe rich oxyhydroxides arsenates sulphates aps minerals and rutile in residual leached rock and infill of karstic cavities gold occurs invisibly in the jasperoids and is enriched in the mn fe oxyhydroxide surface cap of the jasperoids gold mineralisation is associated with the hydrothermal metal suite of as sb hg te se tl ba zn ag cd bi and pb and is characterised by very low cu contents arsenian pyrite probably carried most of the primary invisible gold native gold occurs in association with the late stage cinnabar and the oxide ore

chlorine stable isotope composition of the oceanic crust implications for earth s distribution of chlorine abstract this first investigation of the cl stable isotope composition of seafloor rocks reveals systematic variations in 37 cl 35 cl of the oceanic crust and its mantle source s relative to seawater chlorine isotopic measurements expressed as 37 cl relative to the seawater 37 cl 35 cl ratio of fresh morb glass hydrothermally produced amphibole containing whole rocks and smectite veins are presented all the samples analyzed are isotopically enriched 0 2 7 5 relative to seawater 0 uptake of cl into amphibole during axial hydrothermal alteration fractionates cl relative to seawater the isotopic compositions of morb glasses are between 0 2 and 7 2 this range appears to be partially due to the assimilation of cl from hydrothermally altered wallrock into morb magmas samples which are unaffected by assimilation have 37 cl between 3 and 7 2 overall the data imply that cl is isotopically fractionated between the surface and mantle reservoirs of earth calculations based on the degree of fractionation suggest that approximately 40 of the cl originally in the degassed mantle now resides on earth s surface

characterizing infiltration and internal drainage of south african dryland soils surface infiltration and internal drainage properties of five soil types from arid drylands of south africa were studied under double ring infiltrometer rainfall simulation plots 1 m2 and instantaneous drainage plots 9 m2 changes in soil water content during 40 minute rainfall simulation for a rainstorm with average intensity of 1 61 mm min 1 and 30 day drainage period were measured at various depths by 1 5 m long capacitance soil water measuring dfm probe different p 0 05 mean surface steady infiltration rate ranged from 0 05 to 4 47 mm min 1 and had a negative power relationship r2 0 65 with horizon clay plus fine silt content power regression r2 86 described rainstorm infiltration and obtained steady rates within an average time of 15 minutes mean total infiltrated soil water content was lowest p 0 05 from surface horizons with either 47 7 clay plus fine silt content or bulk density of 1 91 g cm 3 and exchangeable sodium of not less than 44 mg kg 1 surface horizons with lower surface bulk density and total sand fraction of more than 72 had infiltrated depth and mean total infiltrated soil water content up to 40 cm deeper and 0 55 mm mm 1 greater respectively drainage rate at drained upper limit calculated from the wilcox drainage model r2 0 97 was 0 2 mm day 1 or less were from underlying horizons with either clay plus fine silt of 45 or soft calcium carbonate higher drainage rate with accumulative drainage amount greater than 60 mm were from soil profile horizons with clay plus fine silt content of less than 20 and above unity steady infiltration rates rainstorm infiltration and drainage rates was shown to depend on permeability and coarseness of the respective soil surface and subsurface horizons a phenomenon critical for harnessing rain and flood water to recharge groundwater copyright 2016 john wiley sons ltd

runoff generation from successive simulated rainfalls on a rocky semi arid mediterranean hillslope runoff generation in a mediterranean carbonate rock environment the judaean mountains west bank and israel was studied by a 2 day sprinkling experiment on an 18 x 10 m 2 plot during the first day three spells of 24 1 mm h 1 12 3 mm 27 8 mm h 1 12 3 mm and 14 4 mm h 1 12 5 mm were applied almost saturating the runoff plot on the second day 20 h later two spells of 18 7 mm h 1 34 3 mm and 35 2 mm h 1 25 4 mm followed surface runoff was a combination of infiltration excess runoff from rocky portions of the plot and saturation excess runoff from areas covered by soil soil saturation was accelerated by lateral runoff from adjacent rocky areas once the plot was saturated 80 90 of the applied rainfall became surface runoff significantly different concentrations of chloride sulphate and nitrate ions in the sprinkled water on two successive days served as tracers during the second day a two component hydrograph separation pointed to the importance of shallow reservoirs playing active parts in runoff generation about 14 of the flow collected during the second day originated from water applied during the first day during the second day of sprinkling both water sources obviously mixed in saturated soil reservoirs and contributed in variable percentages to surface flow it is hypothesized that at least during high magnitude rainfall the steep rocky slopes investigated might be regarded as flood generating zones rather than areas of pronounced recharge into the underlying yarkon taninim aquifer

pb isotope evidence for the origin of lead in strata bound pb zn deposits in triassic carbonates of the eastern and southern alps a comparison of ore lead isotope ratios of pb zn deposits hosted in triassic carbonates of the eastern and southern alps with the isotopic composition of trace leads of their host rocks of triassic volcanics and of the underlying clastic sediments shows that these rocks could have supplied only part of the ore lead the isotopic signature of feldspar lead from crystalline basement rocks however reveals that they must have contributed a significant amount of metal to these deposits the presence of barite and of thallium is also indicative that feldspars were the main source of lead arsenic is one of the few important trace elements in these deposits and is known to occur in some areas of lower paleozoic metasediments in unusually high concentrations any model explaining the origin of these deposits must consider the extensive leaching of the basement and to some extent of the overlying clastic sediments as well how the metal bearing solutions entered the lagoonal back reef areas is still open to question as feeder channels have not yet been positively identified the results further demonstrate that the basement also acted as a metal source for galena bearing deposits hosted in permian sediments vein type deposits in permian volcanics and probably the barite fluorite polymetallic deposits along a devonian erosional surface in the carnic alps as well

warm period growth of travertine during the last interglaciation in southern germany abstract late quaternary travertine at two sites near stuttgart formed entirely during interglacial periods the travertine contains structures from growth induced by bacteria and such structures have been dated by 230th u mass spectrometry the resulting ages from both sites imply growth episodes of short duration with growth rates up to 5 mm yr 1 at 99 800 1300 yr b p 2 n 8 and 105 900 1300 yr b p 2 n 7 these episodes were likely part of marine isotope stage mis 5 3 deposition of silt interrupted travertine growth at one of the sites 105 000 yr b p likely correlatives of this silt are the st germain i b stade recorded in the grand pile peat bog and a cold episode 1000 yr long recorded by 18o values in the grip ice core travertine also formed during stage 5 5 115 000 yr and during the early holocene we found no evidence for travertine accumulation in stages 2 3 4 and 5 1 at both sites the sr u ratio and the initial 234u 238u activity ratio resemble those of modern spring water however the sites differ in the chemical composition of spring water and in stratigraphic sequence of travertine accumulation

stable chlorine isotopes in hydrothermal processes abstract values of 37cl can now be routinely measured with an analytical precision of 0 2 as reported herein on fluid inclusion leachates from the elmwood gordonsville mississippi valley type deposit and formation waters from its host formation basin brines from the gulf coast and palo duro basins and fluid inclusion leachates and biotites from the bingham silver bell and panguna porphyry copper deposits isotopic measurements are not affected by reaction yield in the range 85 100 or by generation of free i2 during sample preparation in the elmwood gordonsville deposit five successive paragenetic stages of ore and gangue sphalerite fluorite calcite 2 barite and calcite 3 each yielded multiple 37cl measurements ranges of 37cl vary in alternating fashion between stages with more negative values sphalerite calcites 2 and 3 and those with more positive values fluorite barite an interface between two brine systems with 37 cl and 0 0 appears to have moved back and forth across the zone of mineralization brines from the gulf coast and palo duro basins are apparently bimodal in 37cl with modes near 0 9 and 0 0 consistent with the variation in 37cl observed in fluid inclusion leachates from elmwood gordonsville biotite in the bingham deposit has 37cl values up to 1 7 and chlorine isotopes that are fractionated with respect to salt rich hydrothermal fluid hydrothermal fluids in all three porphyry copper deposits studied have a 37cl range of 0 1 to 0 4 with the one exception of a 0 5 value at bingham loss of low 37 cl chloride in vapor may balance chloride with a net 37 cl 0 in the porphyry deposits

hypogene zn carbonate ores in the angouran deposit nw iran the world class angouran nonsulfide zn pb deposit is one of the major zn producers in iran with resources estimated at about 18 mt at 28 zn mainly in the form of the zn carbonate smithsonite this study aims to characterize these carbonate ores by means of their mineralogy and geochemistry which has also been extended to the host rocks of mineralization and other local carbonate rock types including the prominent travertines in the angouran district as well as to the local spring waters petrographical chemical and stable isotope o h c sr data indicate that the genesis of the zn carbonate ores at angouran is fairly distinct from that of other classical nonsulfide zn deposits that formed entirely by supergene processes mineralization occurred during two successive stages with the zinc being derived from a preexisting sulfide ore body a first main stage of zn carbonates stage i carbonate ore is associated with both preexisting and subordinate newly formed sulfides whereas a second stage is characterized by supergene carbonates zn and minor pb coexisting with oxides and hydroxides stage ii carbonate ore the coprecipitation of smithsonite with galena pyrite and arsenopyrite as well as the absence of fe and mn oxides hydroxides and of any discernible oxidation or dissolution of the sphalerite rich primary sulfide ore shows that the fluids responsible for the main stage i carbonate ores were relatively reduced and close to neutral to slightly basic ph with high fco2 smithsonite 18ovsmow values from stage i carbonate ore range from 18 3 to 23 6 while those of stage ii carbonate ore show a much smaller range between 24 3 and 24 9 the 13c values are fairly constant in smithsonite of stage i carbonate ore 3 2 6 0 but show a considerable spread towards lower 13cvpdb values 4 6 to 11 2 in stage ii carbonate ore this suggests a hypogene formation of stage i carbonate ore at angouran from low temperature hydrothermal fluids probably mobilized during the waning stages of tertiary quaternary volcanic activity in an environment characterized by abundant travertine systems throughout the whole region conversely stage ii carbonate ore is unambiguously related to supergene weathering as evidenced by the absence of sulfides the presence of fe mn oxides and arsenates and by high 18o values found in smithsonite ii the variable but still relatively heavy carbon isotope values of supergene smithsonite ii suggests only a very minor contribution by organic soil carbon as is generally the case in supergene nonsulfide deposits

water soluble chlorides in massive seafloor serpentinites a source of chloride in subduction zones abstract dissolved cation and anion species were measured in the water soluble fraction of massive seafloor serpentinites leached with distilled h 2 o soluble chloride contents ranged from 0 09 to 0 51 wt average 0 26 wt so 4 2 to 0 09 wt mg 2 to 0 16 wt and na to 0 09 wt the concentration of evolved ions was the same in samples equilibrated with water at 25 and 230 c demonstrating that a significant amount of cl present in serpentinites occurs as water soluble salts a nearly equal amount of cl exists in the leached serpentinite likely sited in serpentinite itself the formation of intergranular salts in the serpentinite can be explained by seawater hydrothermal alteration of peridotite hydration reactions and h 2 o incorporation in the serpentine leave the residual fluid with ever increasing salinity and ultimately lead to precipitation of water soluble chlorides chlorine isotope ratios in the water soluble fraction average 1 49 vs standard mean ocean chlorine smoc from a core at the iberian abyssal plain and 0 16 from a much younger core at hess deep the 37 cl value of insoluble cl is 0 33 higher than the soluble fraction the nonzero 37 cl values demonstrate that the cl in the serpentinites is not an artifact of seawater incorporation during drilling the following conclusions are presented 1 serpentinite may be the major conduit for surficial chlorine transfer to mantle depths and an important part of the global chlorine cycle the cl flux in serpentinites into the mantle is larger than all other previously identified fluxes 2 cl is sited in both a water soluble and insoluble component 3 a high salinity fluid plume is evolved during serpentinite dehydration of a subducting slab the high salinity fluid affects metamorphic reactions and melting properties above the slab and can cause intense metasomatism the unusual bulk composition of the whiteschist from dora maira can be explained by channeled passage of a high salinity fluid 4 high salinity fluids reduce the stability field of serpentine causing its dehydration to occur over a broad interval which may partly explain the broad locus of intermediate depth earthquakes

stable and radiogenic isotopes as tracers for the origin mixing and subsurface history of fluids in submarine shallow water hydrothermal systems the shallow water hydrothermal system in tutum bay on the west side of ambitle island papua new guinea provides us with an exceptional opportunity to study isotope systematics in a near shore setting compared to seawater the hydrothermal fluids in tutum bay have lower values for dd d 18 o d 13 c and 87 sr and higher values for 3 h d 34 s so4 and d 18 o so4 the d 18 o and dd records for vents 1 and 4 indicate that fluid compositions remained stable over an extended period interpretation of isotope data clearly demonstrates the predominantly meteoric origin of tutum bay hydrothermal fluids despite their location in a marine environment d 18 o and dd values are identical to mean average annual precipitation in eastern papua new guinea the hypothesis that these fluids are a simple product of mixing between seawater and onshore hydrothermal fluids from the waramung w 1 and kapkai w 2 thermal areas has been rejected because the observed d 37 cl 3 h d 34 s so4 and d 18 o so4 values cannot be explained by a simple mixing model the application of d 18 o so4 and d 13 c thermometers in combination with 3 h values corroborates the three step model of pichler et al pichler t veizer j hall g e m 1999 the chemical composition of shallow water hydrothermal fluids in tutum bay ambitle island papua new guinea and their effect on ambient seawater marine chemistry 64 3 229 252 where 1 phase separation in the deep reservoir beneath ambitle island produces a high temperature vapor that rises upward and subsequently reacts with cooler ground water to form a low ph co2 rich water of approximately 150 160 8c 2 caused by the steep topography this co2 rich fluid moves laterally towards the margin of the hydrothermal system where it mixes with the marginal upflow of the deep reservoir fluid this produces a dilute chloride water of approximately 165 8c and 3 possibly the entrainment of minor amounts of ground or seawater during its final ascent d 2004 elsevier b v all rights reserved

fluid inclusions as microchemical systems evidence and modelling of fluid host interactions in plagioclase dense co2 rich fluid inclusions hosted by plagioclases an45 to an54 of the o v gruber anorthosite body central dronning maud land east antarctica contain varying amounts of small calcite paragonite and pyrophyllite crystals detected by raman microspectroscopy these crystals are reaction products that have formed during cooling of the host and the original co2 rich h2o bearing enclosed fluid variable amounts of these reaction products illustrates that the reaction did not take place uniformly in all fluid inclusions possibly due to differences in kinetics as caused by differences in shape and size or due to compositional variation in the originally trapped fluid the reaction albite 2anorthite 2h2o 2co2 pyrophyllite paragonite 2calcite was thermodynamically modelled with consideration of different original fluid compositions although free h2o is not detectable in most fluid inclusions the occurrence of oh bearing sheet silicates indicates that the original fluid was not pure co2 but contained significant amounts of h2o compared to an actual fluid inclusion it is obvious that volume estimations of solid phases can be used as a starting point to reverse the retrograde reaction and recalculate the compositional and volumetrical properties of the original fluid isochores for an unmodified inclusion can thus be reconstructed leading to a more realistic estimation of p t conditions during earlier metamorphic stages or fluid capturing

rb sr dating of sphalerites from tennessee and the genesis of mississippi valley type ore deposits mississippi valley type mvt ore deposits commonly consist of some combination of lead zinc and iron sulphides accompanied by barite fluorite dolomite and calcite they are thought to form by fluid expulsion from sedimentary successions1 3 but their exact origin has remained controversial because of the scarcity of reliable geochronological data in a recent and widely quoted model the mvt deposits of the central and eastern united states formed as a result of large scale lateral fluid flow driven by the tectonic squeezing of sedimentary successions during the late palaeozoic alleghenian orogeny 330 250 myr 4 here we report the first direct rb sr dating of sphalerites from an mvt deposit and propose this as a useful geochronological technique for sulphide mineralization with poor age control rb sr data for sphalerites from coy mine east tennessee define an isochron age of 377 29 myr ruling out any genetic connection with the alleghenian orogeny instead mvt mineralization in the eastern united states was apparently generated from fluids expelled during thrusting associated with the older acadian orogeny 380 350 myr

tectonics of the zagros orogenic belt of iran new data and interpretations abstract the zagros orogenic belt of iran is the result of the opening and closure of the neo tethys oceanic realm and consists from northeast to southwest of three parallel tectonic subdivisions 1 1 the urumieh dokhtar magmatic assemblage 2 2 the sanandaj sirjan zone and 3 3 the zagros simply folded belt recent detailed and reconnaissance mapping and stratigraphie structural analyses in various parts of the belt indicate that the tectonics of the sanandaj sirjan zone is dominated by either large scale composite duplex structures or low and high angle ne dipping imbricate systems these thrust systems have transported numerous horses and sheets nappes of metamorphosed and non metamorphosed phanerozoic rocks for tens or possibly hundreds of kilometers stratigraphic evidence and synorogenic conglomerates indicate that thrusting was initiated in the late cretaceous and has continued episodically since that time shear sense indicators in various parts of the zone reveal a ne sw direction of transport thrust systems generated in each episode are superimposed upon the previous structures cutting across and displacing them and producing complicated stacks of thrust sheets southwestward transport and stacking of the thrust sheets has resulted in an increase of about 10 15 km in the thickness of the continental crust in the southwestern part of this zone the so called z main zagros thrust which has been traditionally considered as the boundary between the sanandaj sirjan zone and the zagros simply folded belt is by no means a single high angle reverse fault nor is it a narrow zone of crushed rocks but a series of low angle thrusts locally cut by normal faults these thrusts are indistinguishable from those mapped in the sanandaj sirjan zone and are geometrically part of the sanandaj sirjan zone structures there is no single thrust among them that can be singled out and referred to as the main one the boundary of the sanandaj sirjan zone with the urumieh dokhtar magmatic assemblage to the northeast is characterized by a series of structural depressions formed by compression rock sequences including ophiolite complexes exposed along this boundary are strongly dismembered sheared and mylonitized shearing planes and foliations are either subvertical or dipping at high angles to the northeast this zone is suggested to be the suture between the afro arabian and the iranian plates overall the intensity of deformation increases northeastward from the persian gulf mesopotamian basin where strata are undeformed and horizontal through the zagros simply folded belt which is characterized by en echelon doubly plunging flexural slip folds gentle to open in the southwest and close to locally sw overturned in the northeast the intensity of deformation continues to increase further northeastward through the sanandaj sirjan zone where thrust faulting is dominant this pattern suggests that the deformational front has migrated through time from the northeastern part of the sanandaj sirjan zone i e the suture zone to its present position in the central portion of the persian gulf mesopotamian foreland basin

origin of fluids in iron oxide copper gold deposits constraints from δ 37 cl 87 sr 86 sr i and cl br the origin of the hypersaline fluids magmatic or basinal brine associated with iron oxide cu u au ree deposits is controversial we report the first chlorine and strontium isotope data combined with cl br ratios of fluid inclusions from selected iron oxide copper gold iocg deposits candelaria raul condestable sossego a deposit considered to represent a magmatic end member of the iocg class of deposit gameleira and a magnetite apatite deposit el romeral from south america our data indicate mixing of a high 37cl magmatic fluid with near 0 37cl basinal brines in the candelaria raul condestable and sossego iocg deposits and leaching of a few weight percent of evaporites by magmatic hydrothermal fluids at gameleira and el romeral the sr isotopic composition of the inclusion fluids of candelaria raul condestable and el romeral confirms the presence of a non magmatic fluid component in these deposits the heavy chlorine isotope signatures of fluids from the iocg deposits candelaria raul condestable sossego reflecting the magmatic hydrothermal component of these fluids contrast with the near 0 37cl values of porphyry copper fluids known from the literature the heavy chlorine isotope compositions of fluids of the investigated iocg deposits may indicate a prevailing mantle cl component in contrast to porphyry copper fluids an argument also supported by os isotopes or could result from differential cl isotope fractionation processes e g phase separation in fluids of iocg and porphyry cu deposits

polymineralic inclusions in kimberlite hosted megacrysts implications for kimberlite melt evolution abstract megacrysts are large cm to 20 cm in size mantle derived crystals which are commonly entrained by kimberlite magmas comprising of olivine orthopyroxene clinopyroxene phlogopite garnet ilmenite and zircon as common phases numerous studies have shown megacrysts to contain polymineralic inclusions which have been interpreted to represent entrapped kimberlite melt to constrain the origin of these inclusions in megacrysts and their relationship to kimberlite magmatism we present a detailed petrographic and geochemical study of clinopyroxene and olivine megacrysts and their hosted inclusions from the diavik jericho leslie slave craton canada and udachnaya east siberian craton russia kimberlites the studied megacrysts are between 1 and 3 cm in size and representative of both the cr rich and cr poor suites megacrysts contain two types of inclusions i large ii swarms trails of micro melt inclusions mmi textural and geochemical evidence suggests that polymineralic inclusions in megacrysts crystallised from kimberlite melt which infiltrated along fracture vein networks the polymineralic inclusion assemblages resulted from disequilibria reactions between the host megacryst and infiltrating kimberlite melt which was likely enhanced by rapidly changing conditions during magmatic ascent the connectivity of polymineralic inclusions to the kimberlite groundmass via network veins fractures suggests that they are susceptible to infiltrating post emplacement fluids therefore the vast majority of polymineralic inclusions are unlikely to represent pristine entrapped kimberlite melt in contrast mmis are isolated within megacrysts i e not connected to fractures veins and therefore shielded from post magmatic fluids and probably represent entrapped remnants of the variably differentiated kimberlite melt which was more enriched in alkalis cl s co2 than serpentinised polymineralic inclusions and the host rocks exposed at earth s surface as kimberlites

stable chlorine isotopes in arid non marine basins instances and possible fractionation mechanisms abstract stable chlorine isotopes are useful geochemical tracers in processes involving the formation and evolution of evaporitic halite halite and dissolved chloride in groundwater that has interacted with halite in arid non marine basins has a 37 cl range of 0 3 far greater than the range for marine evaporites basins characterized by high positive 1 to 3 near 0 and negative 0 3 to 2 6 are documented halite in weathered crusts of sedimentary rocks has 37 cl values as high as 5 6 salt excluding halophyte plants excrete salt with a 37 cl range of 2 1 to 0 8 differentiated rock chloride sources exist e g in granitoid micas but cannot provide sufficient chloride to account for the observed data single pass application of known fractionating mechanisms equilibrium salt crystal interaction and disequilibrium diffusive transport cannot account for the large ranges of 37 cl cumulative fractionation as a result of multiple wetting drying cycles in vadose playas that produce halite crusts can produce observed positive 37 cl values in hundreds to thousands of cycles diffusive isotope fractionation as a result of multiple wetting drying cycles operating at a spatial scale of 1 10 cm can produce high 37 cl values in residual halite chloride in rainwater is subject to complex fractionation but develops negative 37 cl values in certain situations such may explain halite deposits with bulk negative 37 cl values future field studies will benefit from a better understanding of hydrology and rainwater chemistry and systematic collection of data for both cl and br

deposition and dolomitization of upper knox carbonate sediments copper ridge district east tennessee the upper part of the cambro ordovician knox group in the fault bounded copper ridge zinc district east tennessee consists of interbedded limestones and dolostones with very minor sandy and cherty horizons the nature of allochems suggests that the limestones formed in marine peritidal environments other features such as granular interallochem cements dolomite inclusions in calcite low na content and low sr cr ratio suggest stabilization of the limestones in the presence of fresh water there are two textural varieties of dolostone 1 fine grained and 2 medium to coarser grained fine grained dolostones composed of unzoned 0 02 to 0 05 mm dolomite crystals represent penecontemporaneous dolomitization of calcareous sediments in upper intertidal to supratidal environments evidence for this includes the presence of continuous cryptalgal laminae mud cracks birdseyes and oolitic units the probably former presence of evaporites and the absence of normal marine fauna the oolite units may be analogous to modern shoreline occurrences in laguna madre and baffin bay texas the low na and sr concentrations as well as the nearly stoichiometric ca mg ratio of the fine grained dolostones compared to holocene supratidal dolomites are attributed to the formation or neomorphism of the fine grained dolostones in the presence of fresh water the medium and coarser grained dolostones consist of 0 1 to 0 8 mm dolomite crystals that show textural and compositional zoning these dolostones formed by early diagenetic replacement of limestones due to dilution of marine pore water by fresh water a mixing zone environment of dolomitization is indicated by the following features of the constituent dolomite crystals textural zoning with cloudy centers and clearer rims concentric luminescent zoning increase of fe content toward the rims and low na contents and sr ca ratios untypical of the marine environment the depositional setting within the area of study was a coastal tidal flat environment toward the northwest adjacent to a very shallow marine environment dotted with tidal islands toward the southeast in the rock record the former presence of these islands is indicated by thickening of fine grained dolostones and a corresponding thinning of underlying limestone units

chlorine isotope distribution in formation waters texas and louisiana theoretically the chlorine isotope ratio 37cl 35cl can aid in identifying chloride sources and in distinguishing chloride transport mechanisms among formation waters if ratio differences exist among samples we measured the chlorine ratios of 18 formation water samples from oil fields along the texas louisiana gulf coast representing depths between 2 016 and 4 267 m chloride concentrations of samples ranged from 4 to 94 874 g l the chlorine ratios ranged from 1 24 to 0 58 pmil with respect to standard mean ocean chloride or smoc precision 0 12 pmil and enrichment of 37cl correlates with increasing concentration we also compared the isotope ratios of samples from within the weeks island salt dome with adjacent formation waters in louisiana all ratio measurements on the salt are between 0 1 and 0 3 pmil and for the formation waters are between 0 0 and 0 22 pmil the probability that the salt measurements differ from the waters is 99 we conclude that significant chlorine isotope ratio differences exist among formation waters and between the waters and potential sources in the gulf coast region and that the chlorine ratio will be a valuable tool in interpreting chloride geochemistry in this region

stable isotope geochemistry of carbonate minerals in supergene oxidation zones of zn pb deposits abstract the 18 o 16 o and 13 c 12 c ratios of carbonate minerals formed by supergene oxidation of zn pb deposits and submarine alteration of ancient slags were studied in order to constrain isotope fractionation factors for smithsonite cerussite and phosgenite and to characterize conditions of nonsulfide ore formation we present new isotope data of carbonate hosted ores from the iglesiente district sardinia italy and vila ruiva portugal as well as from the silicate hosted ores of the broken hill district new south wales australia and freihung germany and review previously published isotope data the temperature dependence of oxygen isotope fractionation between pb and zn carbonate minerals and water below 240 c for cerussite and below 100 c for smithsonite and phosgenite can be expressed as 1000ln cerussite water 2 29 10 6 t 2 3 56 1000ln smithsonite water 3 10 10 6 t 2 3 50 1000ln phosgenite water 2 55 10 6 t 2 3 50 with t in kelvin the carbon isotope fractionation between smithsonite phosgenite hydrozincite and calcite is less than about 2 while cerussites are strongly depleted in 13 c by about 10 as compared to the former minerals oxygen isotope variations of individual carbonate minerals within a deposit are relatively small indicating constant formation temperatures and a single meteoric fluid source average formation temperatures of the studied deposits are calculated at 20 5 c using the estimated isotope compositions of local paleometeoric waters we observe a linear relationship between the isotope values of estimated paleometeoric waters and supergene carbonates thus base metal carbonate minerals from supergene deposits may provide paleoclimatic information the carbon isotope values are in most carbonate hosted deposits highly variable more than 10 suggesting at least two isotopically distinct carbon sources the isotopically light component can be related to oxidation of c3 plants soil derived carbon and or microbes that take active part in sulfide oxidation while the isotopically heavy component originates from carbonate carbon from wall rocks and or atmospheric carbon the 13 c enriched component is less dominant in silicate hosted deposits

chlorine isotopes in fluid inclusions determination of the origins of salinity in magmatic fluids abstract thermal ionisation mass spectrometry tims of the cs 2 cl ion has been used to determine the 37 cl value of paleofluids trapped in fluid inclusions modifications to the existing published method have lowered the precision by a factor of 2 0 09 1 thereby allowing real differences to be measured with greater certainty the method has been applied to determine 37 cl of two sets of magmatic fluids trapped in fluid inclusions samples were studied from the capitan pluton in new mexico and the sw england batholith both of which have high temperature fluids whose d and 18 o signatures are distinctly magmatic relative to standard mean ocean chloride smoc the 37 cl values of the capitan samples cluster around 0 whereas those from sw england cluster around 1 8 the br cl ratios of the capitan fluid inclusions are low indicative of halite dissolution and are comparable to local high salinity waters derived from leaching permian evaporites the br cl ratios of the sw england fluid inclusions are much higher and within the range of values normally considered to be magmatic we conclude that the 37 cl value of the capitan magmatic fluids confirms the evidence from br cl ratios that cl was derived from an evaporite source whereas the 37 cl value of the sw england fluids appears to be more representative of a deep magmatic source

age and duration of mississippi valley type ore mineralizing events statistics of a combined paleomagnetic data set from six studies of mississippi valley type deposits and their surrounding host rocks show that the characteristic remanent magnetization of the host rocks predates the magnetization of the mineralization providing a positive contact test confirming that the ore magnetization is primary either multiple fluids or dramatic changes to a single fluid through time are required to account for the separate magnetization ages observed in the host rocks and ores the dispersion of the characteristic remanent magnetization directions provides an estimator for the duration of the mineralizing process suggesting a mineralizing event of about 4 m y duration

thermal comparison of mississippi valley type lead zinc deposits and their host rocks using fluid inclusion and conodont color alteration index data fifteen north american mississippi valley type districts distributed from the arctic archipelago to arkansas and in host rocks ranging in age from late cambrian to early carboniferous were selected for abroad test survey of mississippi valley type district thermal histories for each district in which data were collected histograms of homogenization temperatures for the ore minerals were compared with the temperature range of the corresponding host rocks as indicated by color alteration index cai determinations on conodonts in the host rock carbonates although a special effort was made to collect conodonts from the upper cambrian bonneterre formation host rock to the southeast missouri district all samples were devoid of conodonts thus only 14 districts were used in the final analysis comparison of fluid inclusion homogenization temperatures in main stage ore minerals with color alteration index determined host rock temperatures reveals that a majority of mississippi valley type districts pine point newfoundland zinc mascot jefferson city copper ridge sweetwater central missouri northern arkansas and tri state are representative of group 1 i e they are in thermal equilibrium with their host rocks insofar as could be determined by the color alteration index method ore minerals in group 2 districts upper mississippi valley polaris and central tennessee are significantly hotter than surrounding host rocks and as such define a positive thermal anomaly host rocks to the austinville ivanhoe northern newfoundland and robb lake deposits group 3 revealed the highest color alteration index values of north american mississippi valley type districts with host rock temperatures greatly exceeding ore mineral fluid inclusion temperatures negative thermal anomaly with respect to major tectonic elements of north america group 3 deposits cool ore in hot rocks are positioned within orogenic belts but on the continental side some group 1 deposits ore temperature host rock temperature are well within the continental interior but others are adjacent to orogenic belts on the continental side group 2 deposits hot ore in cool rocks are all within the continental interior current hypotheses regarding the formation of mississippi valley type deposits and simultaneous heating of their host rocks invoke the migration of hot brines set into motion craton ward by the hydraulic gradient produced by orogenic uplift at the craton edge once the ore bearing fluids entered the foreland carbonate platforms they traveled through sedimentary aquifers of the continental interior raising the temperature of the thinly covered carbonate rocks the fluids left as evidence of their passage elevated color alteration index values and group 1 mississippi valley type deposits distributed with decreasing homogenization temperatures away from the orogenic front the correspondence between host rock and ore temperatures suggests that group 1 deposits were deposited essentially within their own aquifers group 2 deposits were formed when the same or genetically similar fluids rose from the regional aquifer s into structurally controlled conduits in the continental interior possibly developed as a result of synorogenic doming and arching this upward channeling of the fluids resulted in rapid and localized fluid flow which precluded or at least inhibited wide spread heating of the host rocks by ore fluids consequently color alteration index values in group 2 districts record only maximum burial depths of the host rocks and bear little relation to temperatures of the ore fluids although the cause of the unusually high color alteration index values 4 5 of group 3 districts is not fully understood it is noted that these districts occur near the extreme outward edge of foreland platforms near or within the leading margins of orogenic belts whether these group 3 host rocks were heated by simple tectonic burial or by passage of heated fluids under shallower conditions is not known

preliminary evidence for fractionation of stable chlorine isotopes in ore forming hydrothermal systems chloride from fluid inclusions in hydrothermal minerals is found to have variable and distinctive delta sup 37 cl values spanning the range 1 1 0 per thousand to 0 8 per thousand in mississippi valley type deposits of tennessee brines of high 0 per thousand and low near 1 per thousand delta sup 37 cl are present high delta sup 37 cl brines may be saline formation waters but low delta sup 37 cl brines remain unexplained in porphyry copper deposits both high delta sup 37 cl 0 8 per thousand 0 3 per thousand and low delta sup 37 cl 1 1 per thousand 0 7 per thousand hypersaline brines of probable magmatic origin occur high salinity magmatic brines with low delta sup 37 cl values contrast isotopically with high delta sup 37 cl less concentrated brines responsible for quartz sericite pyrite assemblages

preferential diffusion of 35cl relative to 37cl in sediments of kau bay halmahera indonesia kau bay a 470 m deep basin is separated from the pacific ocean by a shallow 40 m deep sill during the last glaciation this sill was above sea level and the bay turned into a freshwater lake after glaciation the sea level rose and the bay turned saline again since then chloride from the newly formed saline sediments diffused into the freshwater sediments as the sedimentation rate was constant throughout the holocene it is relatively easy to model the chloride concentration in the sediment pore water the diffusion coefficient of 35cl is slightly higher than the diffusion coefficient of 37cl thus variations in 37cl were expected in the pore water because the pore water history of kau bay is well known it was possible to use 37cl variations to determine the diffusion coefficient ratio d35d37 for the two stable isotopes of chlorine it was found that this ratio is 1 0023 in the pore water from sediments in this bay

a review and comparison of fracture mineral investigations and their application to radioactive waste disposal abstract a compilation and comparison of fracture mineral studies from the canadian and fennoscandian shields and the french massif central shows many similarities indicating larger external control over fracture mineral deposition with different rock types exerting local controls the sites investigated represent a wide range of geological settings and host rock types ranging from felsic intrusive and extrusives to ultramafic intrusives and volcanics that span an age range from 2 5 to 0 36 ga typical fracture minerals found at canadian shield sites include calcite quartz chlorite and clays and these do not appear to be dependant on age erosional depth or geological environment the fennoscandian shield has a much larger variety of fracture filling minerals with epidote zeolites prehnite fluorite pyrrhotite fe oxides serpentine graphite magnesite and barite in addition to the minerals typically found at canadian shield sites the major control on fracture mineral type is most likely variations in rock type and fluid chemistry and temperature the c and o isotopic range of calcite is very similar among sites late stage hydrothermal calcite with strongly depleted 18o values is common at many sites all of the sites have calcite with 18o isotopic values in the range of 5 to 20 pdb indicative of formation from meteoric water or basinal brines that have undergone varying degrees of water rock interaction one canadian and a few swedish sites have calcite in the shallower portion of the rock that shows isotopic evidence of dissolution and re precipitation in equilibrium with the present day waters there are some striking similarities in fluid inclusion data among sites most sites have an elevated temperature 100 300 c low salinity group of fluid inclusions within the nacl h2o system and a lower temperature 50 150 c higher salinity group of fluid inclusions within the nacl cacl2 h2o system fluid inclusion density plots show some evidence of simple cooling but most sites show two or more fluids were responsible for calcite formation the origin of most of these fluids was magmatic hydrothermal or meteoric water that had undergone varying degrees of water rock interaction but basinal brines and seawater were also possible sources several techniques and methods have been used to further characterize calcites strontium isotopes and rare earth elements can be useful to recognize different families of calcite uranium th dating has found many old calcites beyond the useful range of the technique but also some relatively young calcites that may be related to interglacial periods where fluid inclusion data exists formation temperatures were not consistent with a glacial water origin crush and leach experiments with ion and gas chromatography and thermal ion mass spectrometry have characterized inclusion fluids but special care must be used to ensure only one generation is sampled at a time cathodoluminescence and scanning electron microscopy with energy dispersive spectrometry has been useful in identifying multiple fluid generations within single calcite samples laser ablation and raman spectrometry are additional techniques that are useful in determining individual fluid inclusion chemistry and isotopes

geochemistry of the acid kawah putih lake patuha volcano west java indonesia abstract kawah putih is a summit crater of patuha volcano west java indonesia which contains a shallow 300 m wide lake with strongly mineralized acid sulfate chloride water the lake water has a temperature of 26 34 c ph s tot 2500 4600 ppm and cl 5300 12 600 ppm and floating sulfur globules with sulfide inclusions are common sulfur oxyanion concentrations are unusually high with s 4 o 6 2 s 5 o 6 2 s 6 o 6 2 2400 4200 ppm subaerial fumaroles thermodynamic modeling of the lake fluids indicates that the lake water is saturated with silica phases barite pyrite and various pb sb cu as bi bearing sulfides when sulfur saturation is assumed precipitating phases predicted by the model calculations are consistent with the bulk chemistry of the sulfur rich bottom sediments and their identified mineral phases much of the lake water chemistry can be explained by congruent rock dissolution in combination with preferential enrichments from entering fumarolic gases or brines and element removal by precipitating mineral phases as indicated by a comparison of the fluids volcanic rocks and lake bed sediment flank springs on the mountain at different elevations vary in composition and are consistent with local rock dissolution as a dominant factor and ph dependent element mobility discharges of warm sulfate and chloride rich water at the highest elevation and a near neutral spring at lower level may contain a small contribution of crater lake water the acid fluid induced processes at patuha have led to the accumulation of elements that are commonly associated with volcano hosted epithermal ore deposits the dispersal of heavy metals and other potentially toxic elements from the volcano via the local drainage system is a matter of serious environmental concern

s and o isotopic character of dissolved sulphate in the cover rock aquifers of a zechstein salt dome abstract sulfur and o isotope analyses of dissolved so4 were used to constrain a hydrogeological model for the area overlying the gorleben rambow salt structure northern germany samples were collected from 80 wells screened at different depth intervals the study area consists of a set of two vertically stacked aquifer systems generally the isotope data show a good spatial correlation outlining well defined groundwater zones containing so4 of characteristic isotopic composition highly saline waters from deeper parts of the lower aquifer system are characterized by rather constant so4 isotopic compositions which are typical of permian zechstein evaporites 34s 9 6 11 9 18o 9 5 12 1 above this is a transition zone containing ground waters of intermediate salinity and slightly higher isotopic values average 34s 16 6 18o 15 3 the confined groundwater horizon on the top of the lower aquifer system below the low permeable hamburg clays is low in total dissolved solids and is characterized by an extreme 34s enrichment average 34s 39 1 18o 18 4 suggesting that bacterially mediated so4 reduction is a dominant geochemical process in this zone two areas of distinct isotopic composition can be identified in the shallow ground water horizons of the upper hydrogeological system sulfate in groundwaters adjacent to the river elbe and locknitz has a typical meteoric isotopic signature 34s 5 2 18o 8 2 whereas the central part of the area is characterized by more elevated isotopic ratios 34s 12 7 18o 15 6 the two major so4 pools in the area are represented by permian seawater so4 and a so4 of meteoric origin that has been mixed with so4 resulting from the oxidation of pyrite it is suggested that the s isotope compositions observed reflect the nature of the so4 source that have been modified to various extent by bacterial so4 reduction groundwaters with transitional salinity have resulted from mixing between brines and low mineralized waters affected by bacterial so4 reduction

chlorine stable isotope composition of granulites from lofoten norway implications for the cl isotopic composition and for the source of cl enrichment in the lower crust abstract the cl isotopic composition of lower crustal rocks as revealed from granulites from the lofoten islands northern norway centres around the value of standard mean ocean chloride smoc the investigated rocks and mineral separates of cl amphibole and cl biotite have 37 cl values 37 cl 35 cl normalized to smoc of 1 12 to 0 79 with most values concentrated in the range of 0 3 to 0 11 and an average of 0 15 samples from gabbroic and from dry granitic rocks magmatic mangerites and charnockites with highly cl enriched hydrosilicates and from a later amphibolite with low cl amphiboles show no distinct differences in their 37 cl values the results indicate that there was only minor involvement of mantle derived cl in fluid involving processes in the middle and lower crust assuming a 37 cl of 4 7 for the undegassed mantle 1 cl isotopic values of the granulites do not support the influx of significant amounts of mantle derived cl the maximum possible mantle contribution to the sample with the highest 37 cl is about 33 thus the common occurrence of cl enriched minerals in granulite facies terrains is regarded as a product of remobilized crustal cl either during magmatism or during later fluid activity the results support the hypothesis that the crust can be regarded as a reservoir with cl isotopic values very similar to smoc

fluid inclusion evidence for solution mixing sweetwater mississippi valley type district tennessee fluid inclusions in fluorite from the appalachian mississippi valley type fluorite barite deposits of the sweetwater district in east tennessee indicate that the mineralizing solutions were sodium potassium chloride brines with an average temperature of 107 degrees c and an average salinity of about 16 equiv wt percent nacl a strong negative correlation of homogenization and freezing temperatures which was observed for inclusions from the southeast part of the district was interpreted to indicate that two solutions were present during fluorite deposition in this area a warm 160 degrees c less saline 12 solution and a cool 80 degrees c more saline 30 solution a connate source is considered likely for both solutions and the warm less saline solution appears to have come from at or beyond the east edge of the district mixing of these solutions could have caused ore deposition in the southeast belt although cooling probably caused deposition elsewhere in the district published data suggest that two similarly distinct solutions were present in the nearby east tennessee zinc district

fluid inclusion study of the gordonsville zinc deposit central tennessee a complementary paragenetic and fluid inclusion investigation of the carbonate hosted gordonsville zinc deposit was undertaken to trace thermal and chemical evolution of the mineralizing fluid the following paragenetic sequence was established from field and petrographic study white early calcite sphalerite galena fiuorite white to lavender main stage calcite barite clear to amber late stage calcite sphalerite occurs in three textural varieties disseminated yellowish brown massive reddish brown and vug fill dark brown the disseminated sphalerite with somewhat lower fe and cd contents may represent an earlier stage of mineralization but its fluid inclusion characteristics are similar to the other two homogenization and freezing temperatures of two phase liquid vapor inclusions show a pronounced change in the nature of mineralizing fluids between early stage and late stage minerals the early stage minerals early calcite through main stage calcite precipitated from moderately hot 97 degrees 133 degrees c and highly saline na ca mg cl fluids salinity 21 23 equiv wt nacl variations in homogenization temperatures of the early stage minerals probably reflect periodic influx of basinal fluids of similar salinites however the lack of correlation between homogenization and freezing temperatures suggests but does not prove that fluid mixing was not the cause of precipitation of these minerals the fluid inclusion data for sphalerite are consistent with its emplacement from a single solution carrying both zinc and sulfur although the model remains untested without a knowledge of the ph of the gordonsville ore fluid the late stage minerals barite and late stage calcite precipitated from a fluid of some what lower temperature 96 degrees 122 degrees c but markedly lower salinity 7 9 equiv wt nacl suggesting an influx of a more dilute fluid probably heated meteoric water at the end of main stage calcite deposition

hydrothermal fluid origins in mississippi valley type ore districts combined noble gas he ar kr and halogen cl br i analysis of fluid inclusions from the illinois kentucky fluorspar district viburnum trend and tri state districts midcontinent united states samples were selected from three of the classic mississippi valley type districts in the midcontinent area of north america the illinois kentucky fluorspar district belongs to the fluoritic subtype of mississippi valleytype districts and the ozark districts of the viburnum trend and tri state are representative of the pb rich and more typical zn rich subtypes of mississippi valley type mineralization respectively noble gas ar kr and halogen cl br i data have been obtained simultaneously by noble gas mass spectrometry of inclusion fluids released by in vacuo crushing of irradiated fluorite quartz carbonate and sphalerite samples additionally he analyses have been obtained from nonirradiated fluorite from the illinois kentucky fluorspar district fluorite from the illinois kentucky fluorspar district has a maximum 3 he 4 he ratio of 0 35 ra where ra atmospheric 3 he 4 he ratio of 1 4 10 6 higher than values typical of crustal fluids and confirming the presence of a minor mantle component equal to less than 6 percent of the total he in the fluids of the illinois kentucky fluorspar district the br cl mol ratios of all the deposits are with one exception higher than the value of seawater 1 54 10 3 ranging from 1 69 to 3 70 10 3 and indicating acquisition of salinity by the evaporation of seawater beyond the point of halite saturation late quartz from the tri state district contains a very minor component of halite dissolution water and has a br cl mol ratio of 1 46 10 3 the i cl mol ratios are typical of oil field brines and are ubiquitously higher than what is attainable by the evaporation of seawater alone i cl mol ratios are in the range of 6 to 270 10 6 indicating that the fluids have interacted with i rich organic matter present in sedimentary rocks in the ozark districts 40 ar 36 ar ratios vary between 320 and 345 in the tri state and between 350 and 420 in the viburnum trend in the illinois kentucky fluorspar district 40 ar 36 ar ratios reach values of 1 200 the corresponding concentrations of 40 arexcess 40 ar not attributable to radiogenic decay of 40 k or an atmospheric source are similarly elevated in the main stage fluorite mineralization of the illinois kentucky fluorspar district 6 8 18 2 10 4 cm 3 cm 3 h2o relative to the viburnum trend and tri state districts mostly 1 3 3 3 10 4 cm 3 cm 3 h2o and 0 3 1 4 10 4 cm 3 cm 3 h2o respectively together the noble gas and halogen data indicate the existence of three brine provinces 1 a regional tristate brine present throughout the ozark region 2 a viburnum trend brine and 3 an illinois kentucky brine furthermore in the viburnum trend the halogen composition of main stage dolomite is distinct from that of the main stage sphalerite but identical to the regional hydrothermal dolomite seen in the tri state district the data imply that mixing relationships in the viburnum trend are highly complex but are compatible with regional models in which the tri state brine present throughout the ozark region was sourced in the arkoma basin

fluid inclusion evidence for fluid mixing mascot jefferson city zinc district tennessee inverse correlation between homogenization temperature and salinity temperature of formation changes at near constant salinity and low salinity low to moderate temperature inclusion fluids are found in sphalerite formed in limestone an evolved basinal brine component was recognized by its characteristic temperature 100 degrees to 120 degrees c freezing point depression 1 fundamental chemical requirements for formation of pb zn ba f deposits from metal bearing basinal brines modified journal abstract

cl br ratios and stable chlorine isotope analysis of magmatic hydrothermal fluid inclusions from butte montana and bingham canyon utah a bulk geochemical study has been carried out on fluid inclusion leachates extracted from quartz veins from porphyry cu deposits in butte montana usa and bingham canyon utah usa the leachates mostly represent low salinity magmatic hydrothermal fluid inclusions their halogen ratios br cl of fluid inclusion leachates were determined by ion chromatography and 37cl values of the leachates were measured by continuous flow isotope ratio mass spectrometry br cl ratios from early pre main stage and later main stage veins at butte range from 0 60 to 1 88 10 3 m ratios are similar in pre main stage veins with sericite bearing selvages and main stage samples ranging from 0 81 to 1 08 10 3 and from 0 92 to 1 88 10 3 m respectively clustering below seawater 1 54 10 3 m and overlapping mantle values 1 2 10 3 m two samples associated with early pre main stage potassic alteration yield distinctly lower br cl ratios of 0 60 and 0 64 10 3 m butte 37cl values range from 0 8 to 2 3 with no significant difference between pre main stage and main stage samples br cl ratios for quartz veins from bingham canyon range from 0 18 to 3 68 10 3 m br cl ratios from bingham range above and below previously reported for porphyry copper deposits in contrast to butte 37cl values for bingham are lower ranging from 0 9 to 4 1 in the absence of any processes which can significantly fractionate chlorine isotopes at high temperatures we suggest that the porphyry system at bingham and to a lesser extent at butte have inherited negative chlorine isotopic signatures from the subducting slab generated at low temperatures

geochemistry of precambrian carbonates iv early paleoproterozoic 2 25 0 25 ga seawater in an effort to narrow down the first and second order variations in isotopic composition of the early paleoproterozoic 2 25 0 25 ga seawater we report a comprehensive study of mineralogy chemistry and isotopic composition of the malmani dolomite transvaal supergroup south africa duck creek dolomite wyloo group australia and bruce limestone member of the espanola formation huronian supergroup canada based on trace element data their diagenetic rank increases in the order duck creek bruce malmani the interpolation of alteration trends to best values yields an estimate of 0 70550 for 87sr86sr comparable to our previously published value of 0 70496 for 13c the measured range of 0 1 5 pdb is similar to that observed for phanerozoic marine carbonates in contrast the best 18o value for dolostones is 5 pdb depleted in 18o relative to phanerozoic counterparts but comparable to the estimates obtained by similar approach for archean facies the isotope geochemistry and mineralogy of bruce limestone member is consistent with the proposition that the sequence may have been deposited in a lacustrine environment possibly related to the recession of the brace glaciers if such interpretation proves unacceptable from a sedimentological standpoint the origin of the unusual isotopic signatures must be sought despite the above trace element interpretation in as yet unspecified post depositional alteration phenomena in contrast to phanerozoic carbonates the early paleoproterozoic as well as the previously described archean counterparts are enriched in mn and fe

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

isotopic composition of lead in galenas from the viburnum trend missouri the isotopic composition of lead in crystals of galena from the no 28 magmont brushy creek fletcher and ozark mines along the viburnum trend has been determined by ion microprobe variations in the isotopic composition of lead along traverses perpendicular to growth zoning are generally complex patterns of lead isotope variation from the center to the edge of galena crystals can be correlated for distances up to 200 m our lead isotope data together with earlier data for galena from the viburnum trend and the old lead belt lie along a linear band on 207 pb 206 pb 208 pb 206 pb diagrams lead in the paragenetically early octahedral galena is less radiogenic than lead in the paragenetically late cubic galena there is no significant geographic variation in the isotopic composition of the galena leads within the viburnum trend most of the isotopic variations can be explained in terms of the mixing of a normal lead isotope component from oil field brines and a radiogenic lead component derived from the precambrian basement the lead in these brines is derived from a source with a lower time integrated th u value than that of the source of the lead for analyzed oil field brines the isotopic composition of the radiogenic component is most consistent with derivation from a grenvillian 1 0 1 2 b y source the composition of lead in the cubic galenas may also be influenced by the admixture of lead derived from the dissolution of earlier octahedral galena

sphalerite bearing detrital sand bodies in mississippi valley type zinc deposits mascot jefferson city district tennessee implications for the age of mineralization the mississippi valley type sphalerite mineralization in the mascot jefferson city zinc district of east tennessee occurs as open space fillings in breccia bodies within the upper part of the knox group lower ordovician which is truncated by a regional unconformity a lower age limit of mineralization is constrained by the formation of solution collapse breccia bodies which are believed to be related to the post knox unconformity the breccias contain irregularly distributed sand bodies that represent cavities filled with well laminated and size graded sphalerite bearing detrital internal sediments the texture composition and fluid inclusion characteristics of the sphalerite are consistent with its local derivation from the wallrocks as detrital grains the conformability between the laminations in the sediments and the bedding planes of the host carbonate rocks suggests that the sand bodies formed prior to the regional deformation event alleghenian orogeny the stylolitization of carbonate and sphalerite clasts in the internal sediments as well as the deformation of the sphalerite are also consistent with a pre alleghenian age for the emplacement of the main stage sphalerite mineralization in the mascot jefferson city district and by analogy in other lower ordovician hosted mississippi valley type districts of the southern appalachians

lead isotope geochemistry of mississippi valley type deposits of the southern appalachians lead isotope compositions of sphalerite fluorite barite and sparry dolomite in mississippi valley type deposits of the southern appalachians fall into four different isotopic groups most sphalerite forms two small clusters whereas barite fluorite and sparry dolomite compositions are more scattered these lead isotope compositions reflect the distribution of the deposits which are hosted by two main palcoaquifers lower cambrian clastic and carbonate rocks host the austinville zn pb cartersville ba embreeville zn and doughtery zn deposits all of which fall in a cluster of lead isotope compositions near 207 pb 204 pb 15 73 and 206 pb 204 pb 19 45 lower ordovician carbonate rocks of the knox group host the copper ridge zn eve mills zn greeneville fall branch ba f mascot jefferson city zn powell river zn pb russell tazewell ba f and sweetwater ba zn f deposits which have more complex compositions sphalerite from mascot jefferson city eve mills sweetwater and russell tazewell plots in a cluster around 207 pb 204 pb 15 67 and 206 pb 204 pb 19 0 whereas that from copper ridge plots in both clusters fluorite from sweetwater falls on a long array in 207 pb 204 pb 206 pb 204 pb space that has a two stage age of 1 55 to 1 9 ga for t 2 360 ma the previously published 87 sr 86 sr isochron age obtained for the mascot jefferson city district barite and sparry dolomite compositions are relatively similar and have lower 207 pb 204 pb and 208 pb 204 pb ratios than most sphalerite and fluorite the spatial distribution of lead isotope compositions indicates that there were at least two mineralizing solutions represented by the two lead clusters the upper cluster solution dominated the lower ordovician palcoaquifer whereas the lower cluster dominated the lower cambrian palcoaquifer and that the two solutions mixed in most areas except the mascot jefferson city district where zinc mineralization is strongest although the specific sources of these leads cannot be determined from available data on possible source rocks the two lead clusters probably came from relatively young well mixed sedimentary basins and the lead in the fluorite must have come from a source with an unusally high u th ratio such as phosphoritc this study confirms that the isotopic composition of lead in southern appalachian mississippi valley type deposits differs significantly from that found in mid continent deposits

37cl 35cl variations in a diffusion controlled groundwater system abstract groundwaters in the low permeability quaternary glacial deposits of southwestern ontario commonly exhibit increasing cl concentrations with depth because these deposits were formed in a freshwater glacial environment and because cl is not derived from weathering of these deposits previous investigations hypothesized that upward diffusion of saline formation waters from the shallow bedrock caused this cl trend this hypothesis was tested by measuring 37 cl 35 cl ratios in the groundwaters from two typical sites and comparing the results with theoretically derived isotopic distributions produced by diffusion 37cl measurements expressed relative to standard mean ocean chloride smoc ranged from 0 8 to 2 2 and vertical profiles showed a gradual enrichment in 35cl relative to 37cl with increasing distance upward from the bedrock till interface 537cl distributions were simulated with a mathematical solute transport model incorporating the effects of kinetic isotopic partitioning a sensitivity analysis indicated that the model results were affected by the groundwater velocity the isotope enrichment factor and diffusion times agreement between the simulated and observed cl isotope profiles was obtained using a groundwater velocity of 0 an isotopic enrichment factor of 1 0012 and diffusion times ranging from 14 000 to 16 000 years based on these results we conclude that the isotopic enrichment in 35cl was caused by upward diffusion over a period of about 15 000 years this diffusion period is consistent with what is known about the quaternary history of the area

constraints on the sources of ore metals in mississippi valley type deposits in central and east tennessee usa using pb isotopes abstract the mississippi valley type mvt central and east tennessee tn districts contain lead zinc deposits that occur in the early ordovician carbonates of the knox group although both districts share similar host rock have similar temperatures of formation and typically fill open spaces of collapse breccias or replace their host carbonates previous studies may suggest that these ores did not form from the same mineralizing fluids and may have different pb sources nu plasma mc icp ms pb isotopic analyses on sulfides from central and east tn were conducted and the metal sources evaluated pb isotope ratios from the young mine in the east tn district plot within ranges defined by other east tn district samples from previous studies generally pb isotope ratios or ores from the elmwood mine in the central tn district are more radiogenic and plot between samples from the southern appalachians and illinois kentucky districts it appears that the thick black metal rich shales of the appalachian basin have been the source of the pb zn and ore fluids of mvt deposits that formed the east tn deposits when east tn pb data from this study are compared to central tn pb data central tn pb is commonly more radiogenic suggestive of a mineralizing fluid with different compositions lead isotopic signature of central tn ores may imply potential mixing between end member sources originating from the southern appalachians and illinois basins lead isotopes in mvt and carbonate hosted base metal deposits in us south america and europe display two basic types of pb isotopic signatures the classic mvt deposits in the mid continent us se and central missouri illinois kentucky and upper mississippi valley districts have highly radiogenic pb isotopic compositions and they generally display linear pb isotopic arrays in contrast deposits from europe irish type silesian type alpine type and cevennes region the appalachians and andean type deposits have lower pb isotopic values the european deposits except for the irish type have a restricted range of isotopic ratios which suggest a single mineralizing event of relatively short duration it appears that basement rocks or sedimentary rocks derived from the basement contributed pb to many mvt and carbonate hosted base metal deposits worldwide hydrothermal leaching of radiogenic pb from the crystalline basement rocks may have occurred during formation of these ore deposits high 238u 204pb values for several districts also suggest a supracrustal origin of pb

genetic implications of regional and temporal trends in ore fluid geochemistry of mississippi valley type deposits in the ozark region fluids extracted from aqueous fluid inclusions in epigenetic gangue and ore minerals record the migration of huge volumes of highly saline fluids throughout the stratigraphic section of the ozark region the extracted fluids share many similarities regionally but there are significant temporal differences which define two geochemically distinct end member ore forming fluids that we refer to as the viburnum trend main stage or viburnum trend type and the tri state type viburnum trend type fluids are enriched in potassium and are associated only with deposits close to the basal lamotte sandstone the main stage octahedral galena ore of the viburnum trend and much of the old lead belt ore is thought to be derived from this type of ore fluid galena deposited by viburnum trend type fluids contains less radiogenic lead than galena deposited by tri state type fluids sulfides deposited by viburnum trend type fluids also contain isotopically heavier sulfur and significant amounts of copper cobalt nickel and silver tri state type fluids have a low potassium content when compared with viburnum trend type fluids and are characteristic of deposits where ore forming fluids migrated through large volumes of carbonate rock these fluids are thought to have formed the ore deposits of the tri state northern arkansas and central missouri districts the cubic galena stage ore of the viburnum trend and the many trace occurrences of sphalerite throughout the ozark region galena deposited by tri state type fluids has more radiogenic lead and the sulfides have isotopically lighter sulfur than sulfides deposited by viburnum trend type fluids a systematic south to north increase of potassium in the tri state type fluids suggests that they migrated from a southerly source such as the arkoma basin possible explanations for the origins of these two end member fluids include 1 a single parent brine evolved into two distinct fluids due to reactions with geochemically distinct aquifers during migration 2 the two distinct fluids reflect normal fluid evolution within a single source basin of a bittern and of later halite dissolution and 3 the viburnum trend and tri state type brines migrated to southeast missouri from two different source basins our data does not preclude any of these possibilities however the geochemical similarity of the viburnum trend end member fluid to a bittern may be accounted for by water rock modifications of the brine during migration other evidence strongly supports a southerly source for the ore forming brines thus limiting possible sources for the viburnum trend type fluid to the arkoma and or black warrior basins of the ouachita foreland trough viburnum trend type fluid flow was probably funneled northward through basal sandstones within the reelfoot rift and water rock modifications occurring there may have resulted in its unique geochemistry

the origin and evolution of saline formation water lower cretaceous carbonates south central texas u s a abstract land l s and prezbindowski d r 1981 the origin and evolution of saline formation water lower cretaceous carbonates south central texas u s a in w back and r letolle guest editors symposium on geochemistry of groundwater 26th international geological congress j hydrol 54 51ndash 74 systematic chemical variation exists in formation water collected from a dip section through lower cretaceous rocks of south central texas chemical variation can be explained by an interactive water rock diagenetic model the cyclic lower cretaceous shelf carbonates of the edwards group dip into the gulf of mexico coast geosyncline and can be considered to a first approximation as part of a complex aquifer contained by paleozoic basement beneath and by relatively impermeable upper cretaceous clay and chalk above the hydrodynamic character of this carbonate system is strongly controlled by major fault systems major fault systems serve as pathways for vertical movement of basinal brines into the lower cretaceous section formation water movement in this sytem has strong upfault and updip components the parent na ca cl brine originates deep in the gulf of mexico basin at temperatures between 200 and 250 c by the reaction halite detrital plagioclase quartz water albite brine other dissolved components originate by reaction of the fluid with the sedimentary phases k feldspar calcite dolomite anhydrite celestite barite and fluorite significant quantities of pb zn and fe have been mobilized as well as the brine moves updip out of the overpressured deep gulf of mexico basin and encounters limestones of the stuart city reef trend the buried platform margin small amounts of galena precipitate in late fractures continuing to rise upfault and updip the brine becomes progressively diluted on encountering significant quantities of dolomite in the backreef facies the ca rich brine causes dedolomitization although thermochemical consideration suggests that small amounts of several authigenic phases should precipitate most have yet to be found minor amounts of several kinds of calcite spar are present however as the brine evolves by dilution and by cooling no systematic changes in any cation cl ratio occur except for regular updip gain in mg as a result of progressive dedolomitization the formation water highly diluted by meteoric water eventually discharges along faults as hot mineral water

metallogenic provinces and the remobilization process studied by lead isotopes lead zinc ore deposits from the southern massif central france the two main problems of ore genesis are the origin of metals and the process es of emplacement lead isotopes have proven to be a powerful tool for studying these questions we have studied pb zn mineralizations from montagne noire and cevennes southern massif central france by means of lead isotopes this study shows the existence of two populations of ore deposits defined by 17 76 206 pb 204 pb 17 94 and 18 25 206 pb 204 pb 18 63 a general model of lead evolution in these deposits is proposed after evolving in the earth s mantle until approximately 3 b y ago the lead became incorporated into a segment of continental crust then the less radiogenic population of ore deposits was emplaced contemporaneously with the formation of cambrian carbonate host rocks the second population is related to the emplacement of hercynian granitoids or in more general terms to fluid circulations associated with the hercynian orogeny it can also be shown that some of the deposits are remobilized from preexisting ore deposits

lead isotope variations across the central peruvian andes lead isotope values of ore and host rock samples from 18 deposits of nine mining districts in an andean transect between latitudes 9 degrees and 14 degrees s are reported the ore deposits discussed in this paper comprise a relatively narrow age span of about 200 m y upper triassic to early pliocene the lead isotope ratios from different ore deposits correlate closely with their geotectonic settings there is a systematic increase of radiogenic lead isotope ratios from west to east i e from ore deposits located near the coast in the lower cretaceous marginal basin of central peru to ore deposits in the carbonate platform at the margin of the brazilian shield for the coastal deposits ral condestable and los icas the lead may be mantle derived and was supplied via the casma volcanics the more radiogenic lead of the leonila graciela santa cecilia ores may be related to lateral facies variations within the marginal basin it is assumed that here a mantle derived component was mixed with a crustal component the lead isotope ratios from ore deposits in the western cordillera mainly indicate a contribution from the orogen reservoir leaching of the paleozoic basement is probably the main source igneous activity may have facilitated remobilization processes during younger tectonic and magmatic cycles mixing between upper crust and orogen reservoirs with participation of magmatic lead can explain the lead isotope ratios of the ore deposits in the atacocha district the lead isotope signature of the shalipayco ores is interpreted in relation to the permo triassic mitu volcanism leaching of permian rift related volcanics could be responsible for the less radiogenic lead in this deposit the ores of the san vicente deposit are characterized by highly radiogenic values and negative model ages typical of upper crustal leads in cratonic regions the ore lead of san vicente could have been derived by leaching clastic sediments derived from precambrian upper crust brazilian shield

composition of ore fluid inclusions from the viburnum trend southeast missouri district united states implications for transport and precipitation mechanisms fluid inclusions hosted by sphalerite and dolomite cement from the mississippi valley type mvt deposits of the viburnum trend of the southeast missouri district were analyzed by microthermometry and laser ablation inductively coupled plasma mass spectrometry la icp ms to determine the composition of mineralizing fluids and to seek insights into ore forming processes on the whole fluid inclusions from throughout the paragenesis have compositions resembling deep sedimentary brines a population of anomalously pb rich fluid inclusions with concentrations reaching 1 500 ppm was identified in some of the paragenetically early and main stage sphalerite which is interpreted to represent the influx of a pb and possibly overall metal rich fluid into southeast missouri during the time of sulfide mineralization this influx of pb rich fluid appears to have been intermittent as at least one stage of dolomite cement that hosts pb poor fluid inclusions occurs between intervals of sphalerite that host pb rich fluid inclusions if fluid flow into the district was principally from one direction for example from the arkoma basin to the south then the intermittency in high pb concentrations could be explained by compositional changes in the source region or along the flow path alternatively if fluid flow into the district was from two or more directions and fluid arriving from each direction had a different composition then the intermittency in high pb concentrations could be explained by transient variations in the relative flow rates from each direction lead concentrations on the order of thousands of parts per million make it unlikely that the southeast missouri ores were precipitated by any mechanism that involved simultaneous transport of metals and sulfide in the same fluid as the concentrations of sulfide that could coexist with such high concentrations of pb would be too low to allow the ores to be deposited within a geologically reasonable period of time unless the ph was very low or groundwater flow rates were very high thus some type of mixing scenario seems more likely involving either mixing of a metal with a sulfide rich fluid or mixing of a metal and sulfate rich fluid with a reductant present either in the host rock or in another fluid fluid inclusions hosted by sphalerite have k na and ca mg ratios that partly resemble the compositions of both main stage cuboctahedral galena and less abundant late stage cubic galena suggesting that sphalerite was precipitated from a mixture of the fluids that precipitated these two types of galena however the fact that aqueous pb concentration does not correlate with these ratios or other indicators of main stage mineralization such as matrix mn fe co cu ag and cd content in sphalerite suggests that more than two fluids were involved in mixing

stable chlorine isotopes in halite and brine from the gulf coast basin brine genesis and evolution stable chlorine isotope data used in conjunction with other geochemical parameters are useful in determining the origin of solute in formation waters with salinity different from that of seawater jurassic salt in the gulf coast basin has 37cl ranges of 0 5 to 0 3 bedded and 0 0 to 0 5 diapiric the values for bedded salt are consistent with a 37cl value of 0 0 for jurassic seawater chloride as in modern oceans the slightly higher values for diapiric salt are possibly caused by incongruent solution of halite formation waters have a 37cl range of 1 9 to 0 7 waters with 37cl 0 2 low salinity water from geopressured aquifers appears to have resulted from shale dewatering low 37cl values in such water are related to low mcl mna a parameter indicating dewatering but show no general relationship to cl br they are consistent with diffusion of chloride from allochthonous brine diffusion can generate domains of water with negative 37cl on a scale of hundreds of meters in 104 106 years and may also generate positive 37cl chloride in residual source brine

the stable isotope composition of halite and sulfate of hyperarid soils and its relation to aqueous transport halite nacl and gypsum or anhydrite caso4 are water soluble minerals found in soils of the driest regions of earth and only modest attention has been given to the hydrological processes that distribute these salts vertically in soil profiles the two most notable chloride and sulfate rich deserts on earth are the dry valleys of antarctica and the atacama desert of chile while each is hyperarid they possess very different hydrological regimes we first show using previously published s and o isotope data for sulfate minerals that downward migration of water and sulfate is the primary mechanism responsible for depth profiles of sulfate concentration and s and o isotopes in both deserts in contrast we found quite different soluble cl concentration and cl isotope profiles between the two deserts for antarctic soils with an ice layer near the soil surface the cl concentrations increase with decreasing soil depth whereas the ratio of 37 cl 35 cl increases based on previous field observations by others we found that thermally driven upward movement of brine during the winter described by an advection diffusion model qualitatively mimics the observed profiles in contrast in the atacama desert where rare but relatively large rains drive cl downward through the profiles cl concentrations and 37 cl 35 cl ratios increased with depth the depth trends in cl isotopes are more closely explained by a rayleigh like model of downward fluid flow the isotope profiles and our modeling reveal the similarities and differences between these two very arid regions on earth and are relevant for constraining models of fluid flow in arid zone soil and vadose zone hydrology 2012 elsevier ltd all rights reserved

lead isotope geochemistry of mississippi valley type mineralization in the central appalachians lead isotope compositions of sulfide minerals from mississippi valley type deposits in cambrian ordovician and silurian rocks in the central appalachians plot in distinct groups one for each major district data for deposits in the nittany arch and shawangunk districts form circular clusters whereas data for the timberville and friedensville districts form more elongated fields comparison of these data to isotopic compositions of possible source rocks suggests that lead in the nittany arch shawangunk and timberville clusters came largely from paleozoic igneous rocks or sediment derived from these rocks whereas lead in the friedensville deposits came from grenville age basement rocks additional lead from the timberville district appears to have come from triassic diabase suggesting that as least some mineralization there is unusually young these results contrast strongly with those for the southern appalachians where different mississippi valley type districts have similar isotopic compositions over large areas only lead from the ordovician hosted timberville deposits in the central appalachians has an isotopic composition similar to that of any of the southern appalachian deposits and its composition is similar to that of deposits in the lower cambrian paleoaquifer of the southern appalachians rather than the ordovician paleoaquifer these relations indicate that although mississippi valley type brines in the central appalachians participated in significant cross formational flow they were not as regionally extensive as those in the southern appalachians a factor that might account for the relative scarcity of large mississippi valley type deposits in the central appalachians area

the sources and evolution of mineralising fluids in iron oxide copper gold systems norrbotten sweden constraints from br cl ratios and stable cl isotopes of fluid inclusion leachates we have analysed the halogen concentrations and chlorine stable isotope composition of fluid inclusion leachates from three spatially associated fe oxide cu au mineralising systems in norrbotten sweden fluid inclusions in late stage veins in fe oxide apatite deposits contain saline brines and have a wide range of br cl molar ratios from 0 2 to 1 1 10 3 and 37cl values from 3 1 to 1 0 leachates from saline fluid inclusions from the greenstone and porphyry hosted cu au prospects have br cl ratios that range from 0 2 to 0 5 10 3 and 37cl values from 5 6 to 1 3 finally the cu au deposits hosted by the nautanen deformation zone ndz have br cl molar ratios from 0 4 to 1 1 10 3 and 37cl values that range from 2 4 to 0 5 although the bulk of the data fall within 0 0 5 the br cl ratios of leachates are consistent with the derivation of salinity from magmatic sources or from the dissolution of halite most of the isotopic data from the fe oxide apatite and greenstone deposits are consistent with a mantle derived source of the chlorine with the exception of the four samples with the most negative values the origin of the low 37cl values in these samples is unknown but we suggest that there may have been some modification of the cl isotope signature due to fractionation between the mineralising fluids and cl rich silicate assemblages found in the alteration haloes around the deposits if such a process has occurred then a modified crustal source of the chlorine for all the samples cannot be ruled out although the amount of fractionation necessary to generate the low 37cl values would be significantly larger the source of cl in the ndz deposits has a crustal signature which suggests the cl in this system may be derived from meta evaporites or from input from crustal melts such as granitic pegmatites of the lina suite