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

gravity and potential changes due to shear and tensile faults in a half space analytic expressions derived from a simplified model are invaluable because they often provide deep insight into geophysical phenomena such is the case with potential and gravity changes here we present expressions of potential and gravity changes caused by faulting on a finite rectangular plane buried in a homogeneous half space the expressions can be used to evaluate coseismic changes in surface gravity and geoid height observed gravimetric data combined with our formulae thus provide constraints on the fault geometry and magnitudes of dislocation

high spatial resolution u pb geochronology and pb isotope geochemistry of magnetite apatite ore from the pea ridge iron oxide apatite deposit st francois mountains southeast missouri usa the pea ridge iron oxide apatite ioa deposit is one of the major rhyolite hosted magnetite deposits of the st francois mountains terrane which is located within the mesoproterozoic 1 5 1 3 ga granite rhyolite province in the u s midcontinent precise and accurate determination of the timing and duration of oreforming processes in this deposit is crucial for understanding its origin and placing it within a deposit scale and regional geologic context apatite and monazite well established u pb mineral geochronometers are abundant in the pea ridge orebody however the potential presence of multiple generations of dateable minerals processes of dissolution reprecipitation and occurrence of micrometer sized intergrowths and inclusions complicate measurements and interpretations of the geochronological results here we employ a combination of several techniques including id tims and high spatial resolution geochronology of apatite and monazite using la sc icpms and shrimp and pb isotope geochemistry of pyrite and magnetite to obtain the first direct age constraints on the formation and alteration history of the pea ridge ioa deposit the oldest apatite tims 207 pb 206 pb dates are 1471 1 and 1468 1 ma slightly younger than but within error of the 1474 to 1473 ma u pb zircon ages of the host rhyolites dating of apatite and monazite inclusions within apatite provides evidence for at least one younger metasomatic event at 1 44 ga and possibly multiple superimposed metasomatic events between 1 47 and 1 44 ga lead isotop analyses of pyrite show extremely radiogenic 206 pb 204 pb ratios up to 80 unsupported by in situ u decay this excess radiogenic pb in pyrite may have been derived from the spatially associated apatite as apatite recrystallized several tens of million years after its formation the low initial 206 pb 204 pb ratio of 16 5 and 207 pb 204 pb ratio of 15 4 for individual magnetite grains indicate closed u pb system behavior in this mineral and are consistent with derivation of the pb from a mantle like source

crustal dilatation observed by grace after the 2004 sumatra andaman earthquake we report the detection of an earthquake by a space based measurement the gravity recovery and climate experiment grace satellites observed a 15 microgalileo gravity change induced by the great december 2004 sumatra andaman earthquake coseismic deformation produces sudden changes in the gravity field by vertical displacement of earth s layered density structure and by changing the densities of the crust and mantle grace s sensitivity to the long spatial wavelength of gravity changes resulted in roughly equal contributions of vertical displacement and dilatation effects in the gravity measurements the grace observations provide evidence of crustal dilatation resulting from an undersea earthquake

lead and sulfur isotope microstratigraphy in galena crystals from mississippi valley type deposits the development of an analytical procedure for lead and sulfur isotope analysis by secondary ion microprobe mass spectrometry allowed us to provide in situ isotopic microanalyses of galena crystals we performed analyses across the growth zones of two crystals of galena from mississippi valley type ore deposits with a spatial resolution of 50 mu m and a spacing of 250 mu m these analyses show frequent variations for both lead and sulfur isotope compositions which occurred during the time of the crystal growth we can demonstrate that for both elements these variations involved changes in the sources of the brines which formed the ore deposits the comparison of lead and sulfur isotope behavior suggests that for the picher deposit lead and sulfur originated from common sources whereas for the buick mine deposit lead and sulfur had separate sources the two galenas exhibit rapid and frequent changes in isotopic composition this suggests numerous and discontinuous inputs of lead and sulfur to the ore deposits this model agrees well with a physical model for mississippi valley type deposits proposed by cathles and smith 1983 the isotopically different sources were probably different sedimentary layers and perhaps basement rocks in the same basin whose formation waters were channeled in preferred water conduits to the ore deposit location during the subsidence of the basin allowing mixing between the different sources to occur during the brines travel

strontium isotopic constraints on the origin of ore forming fluids of the viburnum trend southeast missouri abstract we have measured 87 sr 86 sr and rb and sr concentrations in several minerals primarily sulfides spanning the paragenesis of hydrothermal mineralization in the viburnum trend in southeast missouri separate measurements were made for fluid inclusions opened by crushing or thermal decrepitation and for the solids for comparison measurements were also made on samples of probable local aquifers the bonneterre formation and the lamotte sandstone for some of the samples concentrations of k ca cl na and mg are also reported in several cases 87 sr 86 sr ratios are different higher in the solids than in the fluid inclusions we have investigated the possibility that either type of sample gives spurious results e g that the fluid inclusions are secondary or contaminated by host dolomite or that sr in the solids reflects a detrital rather than an authigenic source consideration of mass balance overall solute chemistry and examination of non sulfide dissolution residue however suggests that both types of sample reflect primary fluid sr composition we thus adopt the working hypothesis that sr isotopic composition in fluids at the time of hydrothermal mineralization was highly variable the observed results for the viburnum trend do not conform well to expected trends for mississippi valley type mvt mineralization based primarily on analyses of gangue carbonates barite and fluorite fluid inclusion sr in some of the viburnum trend samples is more radiogenic than in the host dolomite but only moderately so in other samples notably main stage octahedral galena fluid inclusion sr composition is within the range observed for the host dolomite in contrast sr in some of the sulfides is very radiogenic much more so than previously reported for mvt minerals and is very radiogenic early in the paragenesis pyrite chalcopyrite sphalerite less radiogenic during main stage ore deposition and again more radiogenic in later paragenetic stages

origins of nd sr pb isotopic variations in single scheelite grains from archaean gold deposits western australia accessory gangue scheelite cawo4 from the archaean mt charlotte lode au deposit can be divided into two types with different rare earth element ree signatures in some scheelite grains specific ree signatures are reflected by different cathodoluminescence colours which can be used to map their often complex oscillatory intergrowths domains with specific ree contents from two grains were sampled for sm nd rb sr and pb isotopic analyses using a micro drilling technique type i scheelite is strongly enriched in middle ree mree and eu anomalies are either absent or slightly positive four fragments collected from type i regions of two crystals have initial 87sr 86sr and end values ranging from 0 70141 to 0 70163 and 2 5 to 3 5 respectively and pb isotope ratios reflecting the composition of greenstone sequence this may indicate that nd and pb have their source either locally or regionally in the greenstones basic greenstone lithologies have 87sr 86sr 0 7015 and the radiogenic sr signatures indicate that part of the sr originated from felsic lithologies located either within or beneath the host greenstone pile alternatively the sr signature may have evolved from preferential leaching of a rb rich mineral during hydrothermal alteration of the greenstone the ree patterns of type ii scheelite are either flat or mree depleted and have strong positive eu anomalies three fragments collected from type ii regions of the same two crystals have initial 87sr 86sr ratios and end values between 0 70130 and 0 70146 and 1 1 to 2 6 respectively and pb isotope signatures that are once again similar to that of the greenstone this implies that 87sr 86sr ratios in type ii fluids were closer to those of the host dolerite 0 7008 0 7013 due to more extensive fluid interaction with the dolerite a positive correlation between na and ree suggests that ree3 are accommodated by the coupled substitution ree3 na 2 ca2 into both type i and type ii scheelite this is consistent with a fractional crystallisation model to explain the change in ree patterns from type i to type ii but not with a model involving different coupled substitutions and fluids from different origins we propose that the complex ree and isotopic signatures of scheelite at mt charlotte are related to small m to medium km scale processes involving mixing between fresh batches of hydrothermal fluid with fluids that had already been involved in extensive wall rock alteration the very high end values measured in some scheelites have been previously used to link gold mineralisation with komatiites containing unusually high sm nd ratios however tiny 20 m grains of secondary hydroxyl bastnasite were found within micro fractures of one scheelite grain containing an extremely high end signature the hydroxyl bastnasite probably formed during recent ree redistribution within the scheelite as a result of meteoric fluid circulation the scale of this cryptic low temperature alteration is sufficient to explain the anomalously high endi values observed in scheelite from western australia

archaeological reconstruction of medieval lead production implications for ancient metal provenance studies and paleopollution tracing by pb isotopes abstract the identification of metal provenance is often based on chemical and pb isotope analyses of materials from the operating chain mainly ores and metallic artefacts such analyses however have their limits some studies are unable to trace metallic artefacts or ingots to their ore sources even in well constrained archaeological contexts possible reasons for this difficulty are to be found among a variety of limiting factors i problems of ore signatures ii mixing of different ores alloys iii the use of additives during the metallurgical process iv metal recycling and v possible pb isotopic fractionation during metal production this paper focuses on the issue of pb isotope fractionation during smelting to address the issue of metal provenance through an experimental reconstruction of argentiferous pb production in the medieval period an attempt was made to better understand and interpret the pb isotopic composition of ore smelting products it is shown that the measured differences outside the total external uncertainties of 0 005 2 sd for 206 pb 204 pb ratios in pb signatures measured between ores slag and smoke are not due to pb mass fractionation processes but to 1 ore heterogeneity 206 pb 204 pb slag ores 0 066 and 2 the use of additives during the metallurgical process 206 pb 204 pb slag ores 0 083 even if these differences are due to causes 1 and or 2 smoke from the ore reduction appears to reflect the ore mining area without a significant disturbance of its pb signature for all the isotopic ratios 206 pb 204 pb smokes ores 0 026 thus because the isotopic heterogeneity of the mining district and additives is averaged in slags slag appears as the most relevant product to identify ancient metal provenance whereas aiming at identifying a given mine seems beyond the possibilities provided by the method searching for the mining district through analysis of the smelting workshop materials should provide a more appropriate approach in cases where no archaeological evidence of ancient mining is available furthermore smoke pb isotopic composition does not seem to be significantly affected by the metallurgical process paleopollution recorded in peat deposits could help to detect ancient mining production and workshops integrated collaboration between mining archaeologists and geochemists appears crucial to achieve this goal

ion microprobe analysis of oxygen isotope ratios in granulite facies magnetites diffusive exchange as a guide to cooling history ion microprobe analysis of magnetites from the adirondack mountains ny yields oxygen isotope ratios with spatial resolution of 2 8 m and precision in the range of 1 1 sigma these analyses represent 11 orders of magnitude reduction in sample size compared to conventional analyses on this material and they are the first report of routinely reproducible precision in the 1 per mil range for analysis of 18o at this scale high precision micro analyses of this sort will permit wide ranging new applications in stable isotope geochemistry the analyzed magnetites form nearly spherical grains in a calcite matrix with diopside and monticellite textures are characteristic of granulite facies marbles and show no evidence for retrograde recrystallization of magnetite magnetites are near to fe3o4 in composition and optically and chemically homogeneous a combination of ion probe plus conventional brf5 analysis shows that individual grains are homogeneous with 18o 8 9 1 smow from the core to near the rim of 0 1 1 2 mm diameter grains depth profiling into crystal growth faces of magnetites shows that rims are 9 depleted in 18o these low 18o values increase in smooth gradients across the outer 10 m of magnetite rims in contact with calcite these are the sharpest intracrystalline gradients measured to date in geological materials this discovery is confirmed by bulk analysis of 150 350 m diameter magnetites which average 1 2 lower in 18o than coarse magnetites due to low 18o rims conventional analysis of coexisting calcite yields 18o 18 19 suggesting that bulk 18o cc mt 9 3 and yielding an apparent equilibration temperature of 525 c over 200 c below the temperature of regional metamorphism consideration of experimental diffusion data and grain size distribution for magnetite and calcite suggests two contrasting cooling histories the data for oxygen in calcite under hydrothermal conditions at high p h2o indicates that diffusion is faster in magnetite and modelling of the low 18o rims on magnetite would suggest that the adirondacks experienced slow cooling after grenville metamorphism followed by a brief period of rapid cooling possibly related to uplift conversely the data for calcite at low p h2o show slower oxygen diffusion than in magnetite modelling based on these data is consistent with geochronology that shows slow cooling through the blocking temperature of both minerals suggesting that the low 18o rims form by exchange with late low temperature fluids similar to those that infiltrated the rock to serpentinize monticellite and which infiltrated adjacent anorthosite to form late calcite veinlets in either case the ion microprobe results indicate that two distinct events are recorded in the post metamorphic exchange history of these magnetites recognition of these events is only possible through microanalysis and has important implications for geothermometry

sims measurements of δ34s in sulfide minerals from adjacent vein and stratabound ores abstract the effects of sample matrix and secondary ion energy on the instrumental fractionation of sulfur isotopes have been studied for troilite pyrite and galena using the cameca ims 3f ion microprobe an analytical procedure is described for the measurement of 34 s on negatively charged sulfur ions from pyrite and galena with a reproducibility better than 1 5 sulfur isotope ratios were measured in pyrite and galena from adjacent stratabound manto orebodies and crosscutting veins in the hualgayoc district of northern peru isotopic compositions 34 s cdt of sulfur in pyrite and galena from vein and manto deposits have a total range from 20 to 10 sulfur in manto galenas has a wide range of isotopic compositions and is usually isotopically heavier than pyrite when both minerals have been analyzed in the same sample isotopic disequilibrium between pyrite and galena suggests precipitation from separate fluids consistent with textural evidence that galena is paragenetically later than pyrite and often replaces it formation of ore minerals in the veins appears to have overlapped temporally with the later stages of manto mineralization and continued after manto formation ceased sulfur isotope values in pyrite and galena from veins are lower by about 5 on average than the same sulfides in the mantos and 34 s values of vein galenas decrease over the course of vein formation this shift of 34 s toward lower values with time may be the result of increased mixing with sulfur from diagenetic sulfides or a decrease in the 34 s value of aqueous sulfide due to oxidation of the ore fluid in the later stages of deposition the latter hypothesis is favored because the lead isotopic compositions of the same vein minerals do not indicate an influx of sediment derived lead and because of the appearance of barite in the final stages of several vein deposits the majority of pyrite and galena analyses from vein and manto ores are compatible with precipitation from ore fluids having 34 s of aqueous sulfur of 0 5 this result indicates that the associated igneous rocks may have been the source of sulfur in the ore minerals as well as of lead low values of 34 s in manto galena may be accounted for by incorporation of sulfur derived from diagenetic iron sulfides

sulfur isotope evidence for penetration of mvt fluids into igneous basement rocks southeast missouri usa previous studies of galena and sphalerite from paleozoic mvt deposits in the viburnum trend southeast missouri documented large variations in 34s values throughout the ore forming event the present study of cu fe sulfides reveals a similar 34s variation that reflects two end member sulfur reservoirs whose relative importance varied both temporally and spatially more 34s enriched sulfides 34s approaching 25 indicate introduction of sulfur from basinal sedimentary sources whereas more 32s enriched sulfides 34s 600 m vertically through underlying precambrian igneous rocks such basement involvement has been suggested for other carbonate hosted base metal districts e g irish base metal deposits and should be considered an integral part of the ore forming process in southeast missouri

pb isotope evidence for the role of mesozoic basins in the genesis of mississippi valley type mineralization in somerset uk the mendip bristol veinfield is one of a number of british mississippi valley type deposits the genesis of which has never been fully explained the mendip bristol pb zn ba vein mineralization is hosted in carboniferous permo triassic and jurassic sediments the metal sources involved during mineralization were investigated using pb isotope analysis of vein galenas 206 pb 206 pb values range from 18 311 to 18 594 207 pb 204 pb values from 15 601 to 15 688 and 208 pb 204 pb values from 38 257 to 38 565 the data show three isotopically different mineralizing fluids which it is suggested reflect fluid expulsion from adjacent mesozoic sedimentary basins as a result of overpressuring due to rapid subsidence in the triassic jurassic

limist on the metal content of fluid inclusions in gangue minerals from the viburnum trend southeast missouri determined by laser ablation icp ms the hydrothermal fluids that deposited the ores of the viburnum trend of the southeast missouri district have long been recognized to be sedimentary basinal brines the major element composition of these brines has been well characterized however there have been no attempts to measure their metal content which is only loosely constrained by theoretical solubility relations the present study is an effort to assess the metal content of these mineralizing brines by analyzing fluid inclusions from gangue minerals in the viburnum trend using laser ablation inductively coupled plasma mass spectrometry la icp ms and microthermometry by focusing on gangue minerals instead of metal sulfide minerals interferences from the mineral matrix are avoided a high priority was to determine whether brines of anomalously high metal content were circulating through southeast missouri during the time of mississippi valley type mineralization fluid inclusions in dolomite quartz and calcite gangue from throughout the viburnum trend and representative of the entire paragenesis were analyzed none of the inclusions contained measurable quantities of pb zn or cu and only a few contained measurable quantities of ba which ranged from about 100 to 500 ppm where detection limits were not exceeded they indicated maximum possible concentrations of the element in the fluid inclusion maximum possible concentrations varied from inclusion to inclusion and were controlled by the mass of analyte within the fluid volume the larger or more saline the inclusion the lower the detection limit these results showed that the fluid that deposited quartz calcite and most of the dolomite gangue in the viburnum trend is unlikely to have had order of magnitude concentrations of pb and zn higher than 102 ppm or order of magnitude concentrations of cu higher than 101 ppm concentrations of pb and zn during deposition of stage 3 dolomite could not have been higher than 103 ppm and concentrations of cu could not have been higher than 102 ppm these upper limits on possible metal concentrations with the principal exception of those in stage 3 dolomite fluid inclusions are of magnitude similar to the highest measured concentrations of pb zn cu and ba found in typical sedimentary brines thus the brines responsible for depositing gangue minerals in the viburnum trend are unlikely to have had higher ore metal concentrations than typical basinal brines the lack of temporal overlap between gangue and metal sulfide deposition and the higher k na and lower ca mg ratios in fluid inclusions in the gangue minerals compared with fluid inclusions in the metal sulfides leaves open the possibility that the metal content of the fluid that deposited the sulfides was different from that responsible for depositing gangue however the data show that fluid entering the southeast missouri district was not pervasively metal rich throughout time and that if metal enriched fluid ever entered the district it did so at discrete intervals

development of in situ sulfur four isotope analysis with multiple faraday cup detectors by sims and application to pyrite grains in a paleoproterozoic glaciogenic sandstone abstract an in situ sulfur four isotope analysis technique with multiple faraday cup detectors by ion microprobe was developed and applied to detrital pyrite grains in 2 4 ga glaciogenic sandstone from the meteorite bore member of the turee creek group western australia data are standardized with the uwpy 1 pyrite standard 34s 16 04 0 18 33s 0 003 0 009 and 36s 0 21 0 24 2 sd whose sulfur four isotopes were newly determined by gas source mass spectrometry typical reproducibility at two standard deviations 2 sd of spot to spot analyses of standard uwpy 1 pyrite with a primary beam size of 20 m were 0 23 0 05 and 0 86 for 34s 33s and 36s respectively the measured 36s 32s ratio 1 6641 27 is approximately 19 lower than the published ratio for vcdt and we propose a revision of the 36s abundance in vcdt pyrite grains in 2 4 ga glaciogenic sandstone have wide ranging sulfur isotope ratios 32 7 to 13 5 for 34s 3 03 to 11 66 for 33s and 9 7 to 4 6 for 36s respectively some pyrite grains are zoned in 34s values within a grain sulfur isotope ratios of most pyrite grains are distributed along a line with slope 0 9 for 33s vs 36s suggesting that pyrite grains mostly derived from a limited range of source rocks and near surface sulfur reservoirs one pyrite aggregate has a distinct texture from other pyrite grains in the same sandstone and yields a significant mass independent deficit in 36s with a small excess in 33s 36s 33s 4 this is used to suggest that this grain authigenically formed by biological activity during or after sedimentation this work demonstrates that the use of multiple faraday cup detectors provides improved accuracy and precision for in situ sulfur four isotope analysis with secondary ion mass spectrometry

u redox fronts and kaolinisation in basement hosted unconformity related u ores of the athabasca basin canada late u remobilisation by meteoric fluids proterozoic basement hosted unconformity related uranium deposits of the athabasca basin saskatchewan canada were affected by significant uranium redistribution along oxidation reduction redox fronts related to cold and late meteoric fluid infiltration these redox fronts exhibit the same mineralogical and geochemical features as the well studied uranium roll front deposits in siliclastic rocks the primary hydrothermal uranium mineralisation 1 6 1 3 ga of basement hosted deposits is strongly reworked to new disseminated ores comprising three distinctly coloured zones a white green zone corresponding to the previous clay rich alteration halo contemporaneous with hydrothermal ores a uranium front corresponding to the uranium deposition zone of the redox front brownish zone rich in goethite and a hematite rich red zone marking the front progression the three zones directly reflect the mineralogical zonation related to uranium oxides pitchblende sulphides iron minerals hematite and goethite and alumino phosphate sulphate aps minerals the zoning can be explained by processes of dissolution precipitation along a redox interface and was produced by the infiltration of cold 50 c meteoric fluids to the hydrothermally altered areas u fe ca pb s ree v y w mo and se were the main mobile elements in this process and their distribution within the three zones was for most of them directly dependent on their redox potential the elements concentrated in the redox fronts were sourced by the alteration of previously crystallised hydrothermal minerals such as uranium oxides and light rare earth element lree rich aps the uranium oxides from the redox front are characterised by lree enriched patterns which differ from those of unconformity related ores and clearly demonstrate their distinct conditions of formation uranium redox front formation is thought to be linked to fluid circulation episodes initiated during the 400 300 ma period during uplift and erosion of the athabasca basin when it was near the equator and to have been still active during the last million years a major kaolinisation event was caused by changes in the fluid circulation regime reworking the primary uranium redox fronts and causing the redistribution of elements originally concentrated in the uranium enriched meteoric related redox fronts

contribution of satellite gravimetry to understanding seismic source processes of the 2011 tohoku oki earthquake 1 the 2011 great tohoku oki earthquake apart from shaking the ground perturbed the motions of satellites orbiting some hundreds km away above the ground such as grace due to coseismic change in the gravity field significant changes in inter satellite distance were observed after the earthquake these unconventional satellite measurements were inverted to examine the earthquake source processes from a radically different perspective that complements the analyses of seismic and geodetic ground recordings we found the average slip located up dip of the hypocenter but within the lower crust as characterized by a limited range of bulk and shear moduli the grace data constrained a group of earthquake source parameters that yield increasing dip 7 16 2 and simultaneously decreasing moment magnitude 9 17 9 02 0 04 with increasing source depth 15 24 km the grace solution includes the cumulative moment released over a month and demonstrates a unique view of the long wavelength gravimetric response to all mass redistribution processes associated with the dynamic rupture and short term postseismic mechanisms to improve our understanding of the physics of megathrusts

basinal brines at the origin of the imiter ag hg deposit anti atlas morocco evidence from la icp ms data on fluid inclusions halogen signatures and stable isotopes h c o the imiter ag hg deposit is located in the precambrian volcano sedimentary formations of the saghro inlier eastern part of the anti atlas mountains morocco the orebodies consist of northeast southwest to east west veins and lenses hosted by cryogenian black shales and gray wackes and neoproterozoic conglomerates and are controlled by an east west fault network the so called imiter fault mineralogical and paleo fluid geochemistry investigations microthermometry raman spectroscopy la icp ms on individual inclusions bulk crush leach analyses and stable isotope data o h show that the main ag ore stage is related to circulation of deep basinal sedimentary brines na k mg salinity 16 7 to 26 wt nacl equiv molar cl br 330 18 o 2 15 2 35 smow and d 53 8 to 65 5 smow at temperatures of about 180 to 220 c and hydrostatic pressures the main driving mechanism for silver ore deposition is the dilution of ore bearing brines by a low salinity meteoric fluid containing a low density volatile component n 2 ch 4 co 2 t h 180 to 220 c 18 o 1 4 smow and d of about 28 2 smow silver content of the brines ranges from 2 to 30 mmol kg solution up to 3 200 ppm ag avg ag concentration about 900 ppm whereas the maximum ag content found in dilute waters is about 0 4 mmol kg solution 40 ppm the ore forming model proposed for the imiter deposit is 1 ag extraction from the basement by the penetration of deep basinal brines and 2 deposition in a structural trap through fluid mixing with recharge fluids this model is comparable to that described worldwide for the origin of pb zn f ba and u deposits near unconformities between basement and sedimentary basins similarities among the major ag deposits from the anti atlas imiter zgounder bou azzer strongly suggest that they resulted from a unique event likely related to the opening of the atlantic ocean the silver ores are superimposed on the same lineament as a preexisting uneconomic pan african co ni as system linked to magmatic intrusions but ag ores have no genetic relationship with them

comment on georgiev et al structure and u pb zircon geochronology of an alpine nappe stack telescoped by extensional detachment faulting kulidzhik area eastern rhodopes bulgaria in this discussion we evaluate the field chemical sedimentary structural and metamorphic data related to the kulidzhik area tectonic proposal

high resolution historical records from pettaquamscutt river basin sediments 2 pb isotopes reveal a potential new stratigraphic marker a high resolution record of pb deposition in rhode island over the past 250 yr was constructed using a sediment core from the anoxic pettaquamscutt river basin the sedimentary pb concentration record shows the well described maximum associated with leaded gasoline usage in the united states diminished pb variability during recorded periods of local industrial activity 1735 to 1847 supports the greater importance of regional atmospheric lead transport vs local inputs the pb isotopic composition at this site shows a clear maximum in anthropogenic 206 pb 207 pb in the mid 1800s similar peaks have also been observed in sediments from chesapeake bay and the great lakes suggesting a common source possible causes for this event include mining and smelting of pb ores in the upper mississippi valley district which accounted for almost all pb production in the united states in that period the timing of this event can provide an important stratigraphic marker for sediments deposited in the past 200 yr in the northeastern united states the downcore profile of anthropogenic 206 pb 207 pb provides a classic example of how changes in the mixture of ores for production of tetraethyl lead caused a regional scale shift in the sedimentary record and suggests that coal could have played a secondary role in pb emissions after 1920 copyright 2005 elsevier ltd

stable lead isotopes contaminant metals and radionuclides in upper hudson river sediment cores implications for improved time stratigraphy and transport processes radionuclide stable lead isotope and trace metal analyses on fine grained sediment cores collected along a 24 mile reach of the upper hudson river were used to establish temporal trends of contaminant loadings to establish stable lead isotopes as an additional stratigraphic tool and as tracers for resolving particle transport fluxes over periods of decades very large contaminant inputs of cd sb pb and cr were evident in the sediment record one potential large source for these metals was from a pigment manufacturing facility in glens falls ny the total range in stable lead isotope ratios observed in well dated cores from about 15 miles downstream of the potential metal inputs was large e g maximum difference in 206 pb 207 pb is 10 and characterized by four major shifts occurring in the 1950s 1960s 1970s and 1980s the temporal trend in 206 pb 207 pb has been used to establish precise dating of a sediment core from 24 miles further downstream the large magnitude and abrupt shifts in stable lead isotope ratios preserved in upper hudson sediment cores provide a way to significantly improve dating models based only on radionuclide analyses cadmium lead and antimony were identified as quite sensitive tracers of upper hudson sediments due to the magnitude of contamination and the lack of significant additional downstream sources of these contaminant metals metal measurements in a pair of sediment cores located 24 miles apart were used to constrain relative fluxes of sediment entering the river between the two coring locations with sediment sections deposited between the early 1960s and the late 1970s in these two cores suggesting that 3 4 times more sediment entered the river between the two coring sites than was transported from upstream these dilution factors agree very well with estimates based on suspended sediment measurements during a flood event in april 1994 and with estimates based on mechanistic model of suspended sediment transport between 1977 and 1992 d 2003 elsevier science b v all rights reserved

stable isotope and fluid inclusion studies of early zn cu ni co rich ores lower ore zone of brushy creek mine viburnum trend mvt district missouri u s a products of multiple sulfur sources and metal specific fluids abstract mississippi valley type mvt deposits of the viburnum trend are typically lead dominant and occur in the upper portion of the cambrian bonneterre dolomite unusual zinc and copper rich ores with notable enrichments in ni co and ag have been discovered within the lower bonneterre dolomite more than 30 m below the district s main ore bearing horizon these ores appear to be localized along fault fracture zones within the lamotte sandstone which promoted extreme dissolution of the base of the overlying bonneterre dolomite and resulted in pronounced vertical zoning of early ni co cu zn and pb ores above the sandstone dolomite contact stable isotope and fluid inclusion studies were undertaken to assess whether the deep ores resulted from a single fluid reservoir that evolved from cu ni co rich to zn rich to pb rich or are instead products of distinct fluids unrelated to the stratigraphically higher main pb rich ores of the district sphalerite hosted fluid inclusions from the lower orebody appear to be geochemically distinct from those that formed the upper orebodies they record the highest k na and mg na ratios in the southeast missouri mvt district suggesting dominance of siliceous lithologies arkose and or felsic igneous rocks over limestones along their ore fluid pathways paragenetic trends indicate that distinct fluid compositions are associated with specific generations of sphalerite which likely reflects the presence of multiple fluids the 34s values of ore minerals early pyrite and chalcopyrite 7 to 5 early sphalerite 6 to 15 main sphalerite 7 to 17 v cdt indicate deposition from fluids that utilized isotopically distinct sulfide reservoirs low 34s sulfur sources for early ores likely included sulfide in local brines within the lamotte sandstone and diagenetic sulfide minerals within the basal units of the bonneterre dolomite a trend of increasing 34s values of ore sulfides from 5 toward 17 with vertical distance above the lamotte sandstone bonneterre dolomite contact indicates that as the deep ore fluid system worked its way upward it breached less permeable units in the lower bonneterre dolomite allowing incorporation of high 34s sulfide from brines present higher in the stratigraphic section a concomitant up section pattern of decreasing 18o values of dolomite cement and recrystallized remnant host rock from 3 toward 9 v pdb is also consistent with a localized deep mineralizing fluid system which interacted progressively with the stratigraphically higher regional scale pb rich fluid system the episodic nature of metal sulfide deposition in the lower ore zone points to a system in which fluid mixing would have been highly variable both temporally and spatially reaction path models require mixing of multiple ore metal specific and sulfide bearing fluids in order to form the orebody the sequence and concentrations of metal sulfides are inconsistent with ore formation from a single evolving metal bearing fluid this study indicates that faults localized early metal and sulfide bearing fluids facilitating mixing of fluids that resulted in the accumulation of high grade ores near the bonneterre dolomite lamotte sandstone contact recognition of fault fracture patterns beneath more typical pb rich orebodies in the viburnum trend may be a viable exploration strategy for similar zn cu co ni rich deposits

pb isotope evidence on the origin of the west shropsh orefield england pb isotope data on ore galenas from the west shropshire orefield show a significant spread of 20 pb 204 pb values with minor variation in 207pb 204 pb and 208pb 204 pb ratios these indicate that lead was derived from multiple sources some of them uranium enriched and incompletely mixed prior to ore deposition four possible mineralizing agents are considered circulating sea water metamorphic waters basinal brines and convecting formation waters pb isotope data exclude a circulating sea water origin for the mineralization and best support a convecting formation water mineralizing agent a model involving a single fluid tapping multiple lead sources is proposed to explain the observed pb isotope variation

metallogenesis of the abitibi greenstone belt of canada a contribution from the analysis of trace lead in sulfide minerals pb isotopic compositions are reported for 12 ore localities within the late archean abitibi greenstone belt the studied samples carry massive or disseminated sulfides hosted in a variety of materials including mafic ultramafic igneous rocks felsic lavas porphyries and sedimentary iron formations repeated leaching experiments on these sulfides frequently revealed the presence of a radiogenic pb component which is attributed to in situ decay of u and th the leaching experiments make it possible in some cases to separate the radiogenic pb from the initial pb included in the minerals six pb pb isochrons formed by the analyses on leachates and residues show little evidence of secondary perturbations and yield ages that are within error similar to those determined for the supracrustal assemblage this implies that the ores were concentrated synchronously with the main phases of magmatic activity close to 2 7 ga the initial isotopic compositions of the sulfide specimens point to the existence of two different sources of metals i juvenile mantle derived igneous rocks and ii older recycled supracrustal series ore formation frequently involves mixing of metals from these two sources in variable proportions the initial isotopic composition of these two reservoirs is best evaluated by examining the composition of sulfides associated with komatiitic lava flows and with sedimentary iron formations respectively la composition isotopique du plomb a ctc dctermin6e pour 12 indices mctallifkres situcs dans la ceinture mctavolcanique de i abitibi les cchantillons ctudics ctaient porteurs de sulfures massifs ou disscminks dans diffkrents types de matkriaux cornme des roches ignces ultramafiques des laves felsiques des porphyres et des formations de fer sdimentaires l extraction du plomb contenu dans ces sulfures par des attaques mcnagces et rkpktitives met en kvidence la prksence de plomb radiogcnique provenant de la dkroissance radioactive in situ d uranium et de thorium la pratique des attaques mcnagces permet dans un certain nombre de cas de scparer le plomb radiogknique du plomb initial des mincraux six isochrones pb pb ont ctc ainsi obtenues celles ci montrent peu d kvidence d ouverture du systkme u pb et livrent des bges qui sont aux erreurs prks semblables 2 ceux obtenus dans leur encaissant ceci montre que la formation des concentrations mctallifkres est voisine de 2 7 ga et synchrone des principales phases d activitk magmatique les compositions isotopiques initiales obtenues sur ces cchantillons mettent en cvidence l existence de deux sources pour les mctaux i des roches ignces juvcniles directement dcrivces du manteau et ii des roches issues du recyclage d une crotite continentale plus bgce la plupart des minkralisations sulfurces resultent d un mclange de mctaux issus de ces deux sources la composition isotopique de ces deux rcservoirs est bien dcfinie par l analyse de sulfures assocics d une part aux cpanchements komatiitiques et d autre part aux formations de fer sdimentaires

sulfur isotope variability in biogenic pyrite reflections of heterogeneous bacterial colonization the top 20 cm of sediments at active cold seeps in monterey bay coastal california contain framboidal pyrite that occurs as infillings and pseudomorphs of the chambers of the tests of foraminifera and rarely as irregularly shaped grains sulfur isotope compositions obtained with the ion microprobe show depletions in 34 s d 34 s 52 41 to 25 cdt and large variations both within and among these pyrite grains intergranular differences in d 34 s values in the same sediment are as large as 35 and intragranular zoning reaches 15 zoning is regular in some grains with systematic isotope changes from core to rim or from one foraminiferal chamber to another but irregular in others the regular zoning is consistent with an increase in 34 s through time backscattered electron imaging reveals three types of pyrite isolated framboids in a porous aggregation pf pyrite agglomerated framboids with cementing interstitial pyrite f 1i pyrite and recrystallized pyrite with isolated relicts of framboids rf pyrite in individual grains rf pyrite cores grade into f1i pyrite toward grain rims and f1i pyrite grades into pf pyrite at the grain edges these textures are consistent with a paragenetic sequence whereby framboids first agglomerate pf pyrite then cement f1i pyrite and finally recrystallize rf pyrite the d 34 s values of rf pyrite are generally lower than that of f1i pyrite if the paragenetic sequence is correct then this trend parallels the regular core rim isotopic zoning observed in some grains the implied increase in d 34 s with time is consistent with rayleigh fractionation of sulfur in a closed system bacteria are intimately involved in the production of pyrite from our samples and heterogeneous colonization by bacteria provides a simple explanation for the sulfur isotope heterogeneity among and within grains the foraminifera provide open space for colonization and local nutrients for bacterial growth whereas the cell walls of the bacteria may provide a local nucleation site for sulfides if so then initial colonization is reflected in lower d 34 s values whereas later bacterial emigration to other foraminifera chambers is indicated by higher d 34 s values

regional gravity decrease after the 2010 maule chile earthquake indicates large scale mass redistribution 1 we report small but detectable changes in the grace satellites relative trajectory after the m8 8 maule chile earthquake on 27 february 2010 that can be used to delineate the shift in the gravity field a gravity anomaly of 5 gal with a spatial scale of 500 km was found east of the epicenter after the earthquake based on coseismic models the long wavelength negative gravity change is primarily the result of crustal dilatation as well as surface subsidence in the onland region the offshore positive gravity anomaly predicted from finite fault coseismic models is considerably smaller because the gravity changes due to surface uplift and interior deformation are opposite in polarity our study suggests a role for large scale gravity observations in deciphering changes of the earth s interior during great earthquakes by filling in the seldom observed long wavelength spectrum of earthquake deformations as a complement to surface geodetic measurements and seismic data

micro analysis of sulfur isotope ratios and zonation by laser microprobe the university of wisconsin laser microprobe mass spectrometer system combines high spatial resolution with precise accurate and rapid analysis of sulfur isotope ratios spot sizes of 100 200 m are routine and much higher spatial resolution may be possible analytical precision ranges from 1 0 15 pyrite pyrrhotite sphalerite to 1 0 43 galena chalcopyrite comparison of laser microprobe and conventional combustion analyses indicates that laser 34s values are approximately equal to or lower than combustion values for these minerals and an empirical correction of 0 1 sphalerite to 1 4 pyrrhotite is required variations in 18o of so2 laser power density and burn duration affect the magnitude of this correction thus consistent technique is critical natural samples were analyzed by laser microprobe to evaluate the extent of sulfur isotope ratio zonation coexisting sulfide mineral pairs from the rua cove mine alaska show that isotopic equilibrium exists in the stockwork feeder zone while disequilibrium characterizes coexisting pairs from the overlying more rapidly cooled massive sulfide blanket conventional sulfur isotope extraction data on these samples are not valid due to the fine grained intergrown nature of the sulfide phases which precludes satisfactory mineral separation isotopically homogeneous sphalerite and pyrite crystals were found in samples from the amphibolite facies balmat mine while isotopically heterogeneous pyrite crystals were found in a sample from the upper greenschist facies sullivan mine sulfur isotope zonation up to 2 9 in 200 m was found in banded sphalerite blacksmoker chimney material from the bayda mine oman retrograde sulfides from the marcy anorthosite massif vary by 4 2 over 1 cm and finely disseminated sulfides from an amphibolite granulite facies transition zone sample southern india are in disequilibrium across the 25 cm facies transition these results show that sulfur isotope homogeneity may be attained in the cores of annealed high grade metamorphic minerals while lower temperature retrograde or hydrothermally deposited minerals are often isotopically zoned due to temporal variations in fluid chemistry and temperature

displacement above the hypocenter of the 2011 tohoku oki earthquake the moment magnitude m w 9 0 2011 tohoku oki mega thrust earthquake occurred off the coast of northeastern japan combining global positioning system gps and acoustic data we detected very large sea floor movements associated with this event directly above the focal region an area with more than 20 meters of horizontal displacement that is four times larger than those detected on land stretches several tens of kilometers long along the trench the largest amount reaches about 24 meters toward east southeast just above the hypocenter furthermore nearly 3 meters of vertical uplift occurred contrary to observed terrestrial subsidence

geochemistry of mississippi valley type mineralizing fluids of the ozark plateau a regional synthesis the compositions of fluid inclusions hosted in ore and gangue minerals from mississippi valley type mvt pb zn ba deposits of the ozark plateau region were measured to develop a regional hydro geochemical conceptual model for ore emplacement this model may explain the diverse compositions of fluids involved in mineral precipitation the ore precipitation mechanism and the temporal change in composition of fluids invading the ore districts the conceptual model additionally provides evidence for what factors may have controlled deposit size stratigraphic location and zn pb ratio high pb concentrations up to 1 0009s of ppm were identified in sphalerite hosted fluid inclusions from all of the region9s districts if these high pb concentrations were transported in the same fluid with sulfide then total sulfur concentration in the fluid must have been low mass balance calculations demonstrate that the arkoma basin a presumed source basin for the mineralizing fluids is too small to have contained enough fluid to precipitate the observed masses of sulfur in the larger mvt districts given the low sulfide concentrations that could coexist in the fluid with such high concentrations of pb high methane concentrations in sphalerite hosted fluid inclusions from all of the region9s districts in dolomite hosted fluid inclusions from the tri state and northern arkansas districts and quartz hosted fluid inclusions from the northern arkansas district suggest that the prevailing redox conditions during mvt mineralization were reducing making it unlikely that sulfate was transported in large concentrations in the fluids during sphalerite precipitation assuming saturation with respect to carbon dioxide measured methane concentrations in sphalerite hosted fluid inclusions would have required oxygen fugacity to have been at least two log units below the sulfate predominance field boundary fluid inclusion methane concentrations can also be used to estimate minimum burial depths of mineralization of about 0 08 to 1 2 km available evidence indicates that sulfide mineral precipitation in the ozark plateau mvt districts most likely occurred primarily as a result of the introduction of sulfide into a pb and zn rich ore fluid in the two larger mvt districts sulfide may have been supplied by local organic and sulfur rich carbonate facies an apparent mixing line between high ca na ratio and low ca na ratio fluids hosted predominantly in main stage sulfide minerals and paragenetically late minerals respectively indicates the ore fluid was relatively ca enriched the lack of continuity in high pb concentrations in fluid inclusions in sulfide and nonsulfide minerals from across the mineral parageneses suggests that the ore fluids entered the districts intermittently and or had variable metal contents over time

grace gravity data help constraining seismic models of the 2004 sumatran earthquake 1 the analysis of gravity recovery and climate experiment grace level 2 data time series from the center for space research csr and geoforschungszentrum gfz allows us to extract a new estimate of the co seismic gravity signal due to the 2004 sumatran earthquake owing to compressible self gravitating earth models including sea level feedback in a new self consistent way and designed to compute gravitational perturbations due to volume changes separately we are able to prove that the asymmetry in the co seismic gravity pattern in which the north eastern negative anomaly is twice as large as the south western positive anomaly is not due to the previously overestimated dilatation in the crust the overestimate was due to a large dilatation localized at the fault discontinuity the gravitational effect of which is compensated by an opposite contribution from topography due to the uplifted crust after this localized dilatation is removed we instead predict compression in the footwall and dilatation in the hanging wall the overall anomaly is then mainly due to the additional gravitational effects of the ocean after water is displaced away from the uplifted crust as first indicated by de linage et al 2009 we also detail the differences between compressible and incompressible material properties by focusing on the most robust estimates from grace data consisting of the peak to peak gravity anomaly and an asymmetry coefficient that is given by the ratio of the negative gravity anomaly over the positive anomaly we show that they are quite sensitive to seismic source depths and dip angles this allows us to exploit space gravity data for the first time to help constraining centroid momentum tensor cmt source analyses of the 2004 sumatran earthquake and to conclude that the seismic moment has been released mainly in the lower crust rather than the lithospheric mantle thus grace data and cmt source analyses as well as geodetic slip distributions aided by gps complement each other for a robust inference of the seismic source of large earthquakes particular care is devoted to the spatial filtering of the gravity anomalies estimated both from observations and models to make their comparison significant

implications of postseismic gravity change following the great 2004 sumatra andaman earthquake from the regional harmonic analysis of grace intersatellite tracking data 1 we report gravity recovery and climate experiment grace satellite observations of coseismic displacements and postseismic transients from the great sumatra andaman islands thrust event mw 9 2 earthquake in december 2004 instead of using global spherical harmonic solutions of monthly gravity fields we estimated the gravity changes directly using intersatellite range rate data with regionally concentrated spherical slepian basis functions every 15 day interval we found significant step like coseismic and exponential like postseismic behavior in the time series of estimated coefficients from may 2003 to april 2007 for the spherical slepian functions after deriving coseismic slip estimates from seismic and geodetic data that spanned different time intervals we estimated and evaluated postseismic relaxation mechanisms with alternate asthenosphere viscosity models the large spatial coverage and uniform accuracy of our grace solution enabled us to clearly delineate a postseismic transient signal in the first 2 years of postearthquake grace data our preferred interpretation of the long wavelength components of the postseismic gravity change is biviscous viscoelastic flow we estimated a transient viscosity of 5 1017 pa s and a steady state viscosity of 5 1018 1019 pa s additional years of the grace observations should provide improved steady state viscosity estimates in contrast to our interpretation of coseismic gravity change the prominent postearthquake positive gravity change around the nicobar islands is accounted for by seafloor uplift with less postseismic perturbation in intrinsic density in the region surrounding the earthquake

stable isotope thermometry at high temperatures determination of accurate temperatures for geological events has been the grail of stable isotope geochemistry since the seminal 1947 paper by urey in theory this should be simple calibrated mineral pairs are common analysis is rapid and there is no significant pressure correction however in spite of widespread application the promise of reliable thermometry has been elusive stable isotope temperatures in metamorphic and igneous rocks are often controversial is the fractionation between two phases a thermometer speedometer rate dependant hygrometer p h2o dependant or chimera a number of factors have contributed to this uncertainty including incomplete and sometimes conflicting calibration of isotope fractionation factors limited understanding of the kinetics of mineral exchange and the lack of microanalytical techniques this situation has improved dramatically over the past decade permitting reliable and detailed thermal histories to be inferred in a landmark paper bottinga and javoy 1975 empirically calibrated the oxygen isotope fractionation factors among ten rock forming minerals at t 500 c their compilation shows that 84 of analyzed samples contain at least three minerals meeting a concordance test for equilibrium they concluded the great majority of igneous and metamorphic rocks has conserved a state of oxygen isotope exchange equilibrium if correct this bodes well for thermometry however this conclusion was contested by deines 1977 who critically examined the existing data and concluded that less than half of the rocks analyzed to date would yield concordant 18o derived temperatures while seeming irreconcilable both conclusions are based on fact all rocks contain some degree of disequilibrium but many also preserve a thermometric record it is the purpose of this review to discuss the new strategies for reliable isotope thermometry and to explore disequilibrium processes so they may be recognized and properly interpreted the organization of this paper will be to discuss the assumptions

insights into ore genesis of the jinding zn pb deposit yunnan province china evidence from zn and in situ s isotopes abstract the jinding zn pb deposit located in the mesozoic cenozoic lanping basin of southwest china has ore reserves of 220 mt with an average grade of 6 1 zn and 1 3 pb the mineralization is hosted by sandstone in the early cretaceous jingxing formation and limestone breccia in the paleocene yunlong formation mineralization in both types of host rocks is characterized by a paragenetic sequence beginning with marcasite sphalerite stage 1 followed by pyrite marcasite sphalerite galena stage 2 and then galena sphalerite pyrite sulfate carbonate stage 3 pyrite from these stages have different 33 s compositions with pyrite from stage 1 averaging 9 6 stage 2 averaging 8 9 and stage 3 averaging 0 3 sphalerite hosted by the sandstone has similar 66 zn values ranging from 0 10 to 0 30 in all stages of the mineralization but sphalerite samples from the limestone breccia hosted ore show variable 66 zn values between 0 03 and 0 20 our data on sphalerite precipitated during the earlier stages of mineralization has a constant 66 zn value and cogenetic pyrite displays a very light sulfur isotope signature which we believe to reflect a sulfur source that formed during bacterial sulfate reduction bsr the stage 3 sphalerite and pyrite precipitated from a late influx of metal rich basinal brine which had a relatively constant variable 66 zn isotopic composition due to open system isotope fractionation and a near zero 33 s composition due to the influence of abiotic thermochemical sulfate reduction from observed sulfates in the host rock