cross season relation of the south china sea precipitation variability between winter and summer the present study reveals cross season connections of rainfall variability in the south china sea scs region between winter and summer rainfall anomalies over northern south china sea in boreal summer tend to be preceded by the same sign rainfall anomalies over southern south china sea in boreal winter denoted as in phase relation and succeeded by opposite sign rainfall anomalies over southern south china sea in the following winter denoted as out of phase relation analysis shows that the in phase relation from winter to summer occurs more often in el nino la nina decaying years and the out of phase relation from summer to winter appears more frequently in el nino la nina developing years in the summer during the el nino la nina decaying years cold warm and warm cold sea surface temperature sst anomalies develop in tropical central north pacific and the north indian ocean respectively forming an east west contrast pattern the in phase relation is associated with the influence of anomalous heating cooling over the equatorial central pacific during the mature phase of el nino la nina events that suppresses enhances precipitation over southern south china sea and the impact of the above east west sst anomaly pattern that reduces increases precipitation over northern south china sea during the following summer the impact of the east west contrast sst anomaly pattern is confirmed by numerical experiments with specified sst anomalies in the el nino la nina developing years regional air sea interactions induce cold warm sst anomalies in the equatorial western north pacific the out of phase relation is associated with a rossby wave type response to anomalous heating cooling over the equatorial central pacific during summer and the combined effect of warm cold sst anomalies in the equatorial central pacific and cold warm sst anomalies in the western north pacific during the mature phase of el nino la nina events

rethinking the ancient sulfur cycle the sulfur biogeochemical cycle integrates the metabolic activity of multiple microbial pathways e g sulfate reduction disproportionation and sulfide oxidation along with abiotic reactions and geological processes that cycle sulfur through various reservoirs the sulfur cycle impacts the global carbon cycle and climate primarily through the remineralization of organic carbon over geological timescales cycling of sulfur is closely tied to the redox state of earth s exosphere through the burial of oxidized sulfate and reduced sulfide sulfur species in marine sediments biological sulfur cycling is associated with isotopic fractionations that can be used to trace the fluxes through various metabolic pathways the resulting isotopic data provide insights into sulfur cycling in both modern and ancient environments via isotopic signatures in sedimentary sulfate and sulfide phases here we review the deep time 34s record of marine sulfates and sulfides in light of recent advances in understanding h

production preservation and biological processing of mass independent sulfur isotope fractionation in the archean surface environment mass independent fractionation of sulfur isotopes s mif in archean and paleoproterozoic rocks provides strong evidence for an anoxic atmosphere before 2 400 ma however the origin of this isotopic anomaly remains unclear as does the identity of the molecules that carried it from the atmosphere to earth s surface irrespective of the origin of s mif processes in the biogeochemical sulfur cycle modify the primary signal and strongly influence the s mif preserved and observed in the geological record here a detailed model of the marine sulfur cycle is used to propagate and distribute atmospherically derived s mif from its delivery to the ocean to its preservation in the sediment bulk pyrite in most sediments carries weak s mif because of microbial reduction of most sulfur compounds to form isotopically homogeneous sulfide locally differential incorporation of sulfur compounds into pyrite leads to preservation of s mif which is predicted to be most highly variable in nonmarine and shallow water settings the archean ocean is efficient in diluting primary atmospheric s mif in the marine pools of sulfate and elemental sulfur with inputs from so2 and h2s respectively preservation of s mif with the observed range of magnitudes requires the s mif production mechanism to be moderately fractionating 20 40 constraints from the marine sulfur cycle allow that either elemental sulfur or organosulfur compounds or both carried s mif to the surface with opposite sign to s mif in so2 and h2so4 optimal progress requires observations from nonmarine and shallow water environments and experimental constraints on the reaction of photoexcited so2 with atmospheric hydrocarbons

isotopic evidence for a sizeable seawater sulfate reservoir at 2 1 ga abstract the 2 1 ga tulomozero formation deposited on the fennoscandian shield consists of shallow marine carbonate and siliciclastic rocks dissolution breccias and widespread syndepositional marine evaporites now mostly present as pseudomorphs after ca sulfates this study investigates sulfates hosted in three different proxies to constrain the sulfur isotopic composition of seawater sulfate acknowledging the presence of different types of sulfates carbonate associated sulfate cas breccia associated sulfate bas and sulfate relicts rs in a variety of lithologies of the tulomozero formation a widely used and accepted proxy for the ambient seawater sulfate sulfur isotopic composition is carbonate associated sulfate which was extracted from carbonate samples across the entire tulomozero formation in addition sulfate was extracted from a siliciclastic dissolution breccia which is suggested to have formed after dissolution of sulfate evaporites the sulfate sulfur isotopic composition from both lithologies was measured ex situ 34 s cas 10 9 2 7 34 s bas 9 0 1 1 ubiquitous pseudomorphs after ca sulfates occur in the tulomozero formation and contain m size anhydrite and barite relicts their sulfur isotopic composition was measured in situ by secondary ion mass spectroscopy sims 34 s anhydrite 9 6 1 0 34 s barite 11 0 3 1 sulfur isotope data from carbonate rocks breccias and the sulfate relicts match the existing 34 s record of seawater sulfate during that time and show no distinct stratigraphic variations indicating that the seawater sulfate sulfur isotopic composition remained unaffected from environmental changes during the time of deposition of the tulomozero formation physical evidence for widespread precipitation of sulfate rather than abundant chloride suggests a modern style evaporite sequence with carbonates followed by sulfate and then chlorides however this requires a minimum sulfate concentration of 2 5 mm in the ambient seawater consequently the evidence for persistent evaporitic sulfate deposition in the tulomozero formation implies a substantial seawater sulfate reservoir at 2 1 ga according to the estimated minimum depositional time from the thickness of the carbonate rocks of the formation the residence time of seawater sulfate is expected to have been at least 5 ma the available data support the existence of a sizeable seawater sulfate reservoir in the mid paleoproterozoic ocean in fact more than 10 of the modern sulfate reservoir

multiple sulfur isotope geochemistry of dharwar supergroup southern india late archean record of changing atmospheric chemistry abstract earth s tectonic and climatic systems may have changed fundamentally before the great oxidation event goe at about 2 3 ga sulfur mass independent fractionation s mif has demonstrated that earth s atmosphere was virtually oxygen free before the goe during 3 0 to 2 4 ga the change in 33s and 36s signals may reflect the perturbation of atmospheric chemistry though the mechanisms of the change are uncertain here we reported multiple sulfur isotopic studies of archean volcano sedimentary sequences of the dharwar supergroup distributed in the chitradurga schist belt csb southern india new field mapping and zircon u pb dating allows us to reconstruct detailed lithostratigraphy of the dharwar supergroup the lower unit consists of post 3 0 ga conglomerate stromatolitic carbonate siliciclastics with diamictite chert bif and pillowed basalt in ascending order all of which are older than the 2676 ma dacite dyke that had intruded into the lower unit the upper unit unconformably overlies the pillow basalts at the top of the lower unit and consists of conglomerate sandstone with 2600 ma detrital zircons komatiitic basalt bif and siliciclastic sequence with mafic volcanics sulfur isotope analysis of extracted sulfides shows mif signals s 33 1 with clear s 33 s 36 correlations the lower group of the dharwar supergroup shows a s 36 s 33 slope of 1 48 the middle group shows 1 16 and 1 07 and the upper group shows 0 94 reassessment of all the archean s mif records from sedimentary rocks indicates that the s 36 s 33 slope systematically changed during the archean period the observed trend in the indian section is similar to those of its pilbara kaapvaal equivalents thus it could reflect a global atmospheric signature moreover the isotopic trend seems to correlate with mid archean glaciation thus the s 36 s 33 slope could be a useful tracer for atmospheric chemistry and its link with climate change before the goe

uv induced mass independent sulfur isotope fractionation in stratospheric volcanic sulfate 1 sulfuric acid aerosols produced in the stratosphere following massive volcanic eruptions possess a mass independent sulfur isotopic signature acquired when volcanic so2 experiences uv photooxidation the volcanic data are consistent with laboratory so2 photooxidation experiments using uv light at 248 nm maximum absorption of ozone whereas sulfur isotopic anomalies previously observed in archean samples are consistent with photodissociation at 190 220 nm a mechanism of so2 photooxidation occurring in the early stage of a stratospheric volcanic plume in the range of 220 320 nm weak band absorption of so2 is also proposed since mass independent sulfur isotope anomalies in stratospheric volcanic sulfate appear to depend on the exposure of so2 to uv radiation their measurements might therefore offer the possibility to determine the degree of uv penetration in the ozone absorption window for the present and past atmospheres they can also be used to determine the stratospheric or tropospheric nature of volcanic eruptions preserved in glaciological records offering the possibility to reassess the climatic impact of past volcanic eruptions

sources of sulphur for the proterozoic kiggavik uranium deposit nunavut canada the thelon basin is temporally and spatially related to the athabasca basin in saskatchewan canada which hosts the highest grade unconformity related uranium deposits in the world several uraniu

possible impacts of spring sea surface temperature anomalies over south indian ocean on summer rainfall in guangdong guangxi region of china based on observational and reanalysis data for 1979 2015 the possible impacts of spring sea surface temperature anomalies ssta over the south indian ocean on the inter annual variations of summer rainfall in guangdong and guangxi provinces i e the guangdong guangxi area gg were analysed in this study the physical mechanism behind these impacts was explored two geographic regions over 65 e 95 e 35 s 25 s and 90 e 110 e 20 s 5 s were defined as the western pole region and the eastern pole region respectively for the gg summer precipitation pgg related south indian ocean dipole ssta pattern r siodp the difference between springtime sst anomalies averaged over the western pole region and that averaged over the eastern pole region was defined as the r siodp index the correlation between the spring r siodp index and gg summer precipitation can reach up to 0 52 in the spring of positive r siodp anomaly southerly winds over the western pole of the r siodp weaken whereas the southeast trade winds over the eastern pole strengthen by means of the wind evaporation sst feedback mechanism the enhanced southeast trade winds can weaken the evaporation over the western pole of the r siodp and enhance the evaporation over the eastern pole this results in a sustained positive ssta in the western pole of the r siodp and a sustained negative ssta in the eastern pole whereby the distribution of the sstas maintains until summer the sst dipole abnormally enhances the cross equatorial airflow near 105 e which intensifies the anomalous anti cyclonic circulation over south china sea at 850 hpa and simultaneously results in abnormal enhancement of water vapour transport to gg additionally the sst dipole promotes abnormal divergence in the lower troposphere and abnormal convergence in the upper troposphere over the maritime continent mc region moreover the low level convergence in gg is enhanced which results in abnormal enhancement of ascending motion in the gg that is conducive to positive summer rainfall anomaly in this region in this study the spring r siodp index the sst to the east of australia and to the east of southern africa and the north atlantic oscillation nao index were used to construct a statistical prediction model for the inter annual variability of the gg summer rainfall anomaly this model can well predict the accuracy of the inter annual variation of gg summer rainfall

squid sims is a useful approach to uncover primary signals in the archean sulfur cycle many aspects of earth s early sulfur cycle from the origin of mass anomalous fractionations to the degree of biological participation remain poorly understood in part due to complications from postdepositional diagenetic and metamorphic processes using a combination of scanning high resolution magnetic superconducting quantum interference device squid microscopy and secondary ion mass spectrometry sims of sulfur isotopes 32s 33s and 34s we examined drill core samples from slope and basinal environments adjacent to a major late archean 2 6 2 5 ga marine carbonate platform from south africa coupled with petrography these techniques can untangle the complex history of mineralization in samples containing diverse sulfur bearing phases we focused on pyrite nodules precipitated in shallow sediments these textures record systematic spatial differences in both mass dependent and mass anomalous sulfur isotopic composition over length scales of even a few hundred microns petrography and magnetic imaging demonstrate that mass anomalous fractionations were acquired before burial and compaction but also show evidence of postdepositional alteration 500 million y after deposition using magnetic imaging to screen for primary phases we observed large spatial gradients in 33s 4 in nodules pointing to substantial environmental heterogeneity and dynamic mixing of sulfur pools on geologically rapid timescales in other nodules large systematic radial 34s gradients 20 were observed from low values near their centers increasing to high values near their rims these fractionations support hypotheses that microbial sulfate reduction was an important metabolism in organic rich archean environments even in an archean ocean basin dominated by iron chemistry

a 220 year continuous record of volcanic h2so4 in the antarctic ice sheet continuous h2so4 profiles observed in snow from several antarctic locations reveal four major volcanic events of the past two centuries agung krakatoa tambora and another large scale event not recorded historically acid deposition and interhemispheric distribution mechanisms are quantified and then used to obtain an order of magnitude estimate for the h2so4 emissions from these eruptions

depositional setting of the late archean fe oxide and sulfide bearing chert and graphitic argillite in the shaw dome abitibi greenstone belt canada abstract interbedded chert rich exhalite and graphitic argillite are the only sedimentary rocks deposited in deep water settings during long lived hiatuses in mafic to ultramafic volcanism within the hart area of the shaw dome in the late archean abitibi greenstone belt in canada the fe oxide and sulfide bearing but predominantly cherty exhalite lithological unit in the hart area can be traced laterally to iron formation elsewhere in the shaw dome whole rock as well as fe and s isotope geochemistry suggest that the exhalite unit was formed as a result of direct precipitation from seawater distally from hydrothermal centres fractionation of fe isotopes through the precipitation of iron oxyhydroxides in a neutrally buoyant hydrothermal plume removed the heavier isotopes of fe resulting in the negative 56fe values observed in the exhalite in the hart area archean seawater is generally considered to be anoxic but moderate mn enrichments up to 1 87 wt mno in exhalite along with negative fe isotope values resulting from partial fe ii oxidation suggest the presence of oxygen in the upper part of the water column along the pathway of hydrothermal plumes from their source to the depositional site in the abitibi greenstone belt in contrast the graphitic argillite contains abundant pyrite nodules and bands that exhibit systematic negative fe isotope values but does not show mn enrichment this unit likely formed in a zone of upwelling of nutrient rich waters from deeper parts of the basin resulting in high organic productivity both exhalite and graphitic argillite have negative 33s values suggesting that sulfur was derived from seawater sulfate which is consistent with an anoxic atmosphere with sulfate aerosols produced by photochemical reactions combined our data indicates disequilibrium between anoxic atmosphere and partially oxygenated upper part of the water column during periods of volcanic quiescence in the 2 7 ga abitibi greenstone belt supporting the existence of oxidized oases within the archean ocean

the extreme drought event during winter spring of 2011 in east china combined influences of teleconnection in midhigh latitudes and thermal forcing in maritime continent region abstractthe middle and lower reaches of the yangtze river mlryr in china experienced an extremely severe and persistent drought event from january to may of 2011 using both the observational data and ncep ncar reanalysis features of the drought event and the related circulation anomalies were investigated it is found that the precipitation during the investigated period of 2011 was deficient mostly along the yangtze river the water vapor diverged from mlryr southward into the bay of bengal south china sea and the philippines there were two factors facilitating the drought event one was the quasi stationary rossby wave related teleconnection which propagated eastward at midhigh latitudes from the north atlantic to east asia reinforcing the siberian high and the east asian trough henceforth resulting in the divergence anomalies in mlryr in the lower troposphere this quasi stationary wave train though originating from the north atlantic region was not essentially related to the north atlantic

interdecadal changes in the relationship between southern china winter spring precipitation and enso winter spring precipitation in southern china tends to be higher lower than normal in el nino la nina years during 1953 1973 the relationship between the southern china winter spring precipitation and el nino southern oscillation enso is weakened during 1974 1994 during 1953 1973 above normal southern china rainfall corresponds to warmer sea surface temperature sst in the equatorial central pacific there are two anomalous vertical circulations with ascent over the equatorial central pacific and ascent over southern china and a common branch of descent over the western north pacific that is accompanied by an anomalous lower level anticyclone during 1974 1994 above normal southern china rainfall corresponds to warmer sst in eastern south indian ocean and cooler sst in western south indian ocean two anomalous vertical circulations act to link southern china rainfall and eastern south indian ocean sst anomalies with ascent over eastern south indian ocean and southern china and a common branch of descent over the western north pacific present analysis shows that south indian ocean sst anomalies can contribute to southern china winter spring precipitation variability independently the observed change in the relationship between southern china winter spring rainfall and enso is likely related to the increased sst variability in eastern south indian ocean and the modulation of the pacific decadal oscillation

variations in atmospheric sulphur chemistry on early earth linked to volcanic activity the nature of the atmospheric sulphur cycle on the early earth has been difficult to reconstruct an analysis of sulphur isotopes from 3 2 billion year old volcanic rocks suggests that episodic volcanism released pulses of sulphur dioxide that was then broken down by ultraviolet photodissociation

sequence stratigraphy and plate tectonic significance of the transvaal succession of southern africa and its equivalent in western australia the transvaal succession in the northeastern part of the kaapvaal province of southern africa is the erosional remnant of four 2 7 to 2 1 ga unconformity bounded stratigraphic units or sequences each of which is 102 to 103 m thick and spans 107 to 108 years three of these phanerozoic like cratonic sequences occur in the western part of the kaapvaal province and in the pilbara province of western australia thus the two provinces once were part of the same continent vaalbara the stratigraphically lowest sequence historically assigned to the transvaal succession is part of the ventersdorp supergroup in kaapvaal and the upper part of the fortesque group in pilbara it consists predominantly of arkosic sandstone and basaltic andesite it probably is 2687 2 ma the second sequence contains the quartz arenites dolomites and banded iron formations of the transvaal and griqualand west successions in the kaapvaal and the hamersley group in the pilbara the span of ages 2684 6 to 2432 31 ma lithologies and geographic extent of this sequence imply that the limpopo orogeny which welded the zimbabwe province to vaalbara is 2 47 ga not 2 67 0 05 ga the third sequence the pretoria and postmasburg groups in the kaapvaal and the lower part of the wyloo group in the pilbara probably is the clastic wedge generated by the limpopo orogeny the fourth sequence dominated by the felsites of the rooiberg group is restricted to northeastern kaapvaal sequence stratigraphy lithostratigraphy and lithofacies indicate that the pilbara rifted from the southern edge of western kaapvaal the penge iron formation in northeastern kaapvaal the asbesheuwels iron formation in southwestern kaapvaal and the brockman iron formation in the pilbara are the same formation in which cyclothemic units 0 6 to 15 0 m thick extended 1200 km

sulfur isotope fractionation by broadband uv radiation to optically thin so 2 under reducing atmosphere abstract photochemical mechanisms of sulfur mass independent fractionation s mif are still poorly understood previous laboratory experiments have indicated that the s mif depends largely on the spectrum of the incident light source and the partial pressure of so2 though the basic character of the archean s mif s 36 s 33 1 has never been reproduced we have conducted new photochemical experiments at low pso2 1 10 pa conditions under the presence of co and found a reasonable mechanism to reproduce the 36s 33s slope about 1 as previously suggested ono et al 2013 the low pso2 is key to studying the self shielding effect within a range of realistic atmospheric conditions also reducing conditions are critical for simulating the o2 poor atmosphere whereas photolysis of pure so2 provides excess o atoms that significantly change the overall chemistry our experimental results confirmed that significant s mif s 36 s 33 2 4 can be produced by self shielding in the so2 photolysis band 185 220 nm even if the so2 column density is as low as 1016 molecules cm 2 thus photolysis within a volcanic plume of 0 1 ppm so2 is capable of producing a large s mif signature the isotopic fractionations originating from the different absorption cross sections of so2 isotopologues i e wavelength dependent effect without self shielding are only minor potentially up to 4 for 33s under reducing conditions however another s mif signal with 36s 33s ratio of 0 7 is produced due to collision induced intersystem crossing isc from singlet to triplet states of so2 whitehill et al 2013 and should also be transferred into the final product that is responsible for changing the 36s 33s slope based on a photochemical model of the s o c system with the two s mif yielding reactions the largest s mif observed in the late archean mt mcrae fm s 33 9 4 s 36 7 5 can be reproduced by solar uv irradiation of a so2 column of 6 4 10 16 molecules cm 2 with a sufficiently high concentration of reducing gasses 2 co or ch4 where the isc derived mif contributes 3 through the photoexcitation channel initiated in the 240 340 nm region our work shows that a photochemical model considering the two major s mif yielding reactions so 2 h so o and so 2 1 m so 2 3 m can explain the behavior of the s mif observed in laboratory experiments the combination of the two effects is more important under reducing condition and should be considered to interpret the geological record

a multiple sulfur and organic carbon isotope record from non conglomeratic sedimentary rocks of the mesoarchean witwatersrand supergroup south africa abstract multiple sulfur isotope ratios 36 s 34 s 33 s 32 s and organic carbon isotope ratios 13 c 12 c were measured from 198 non conglomeratic sedimentary samples that were collected from five deep diamond drill cores that cover the majority of the ca 2 96 2 82 ga witwatersrand supergroup 13 c org 34 s py and 33 s py values of the sample set range from 44 3 to 21 9 3 7 to 16 5 and 4 0 to 1 9 respectively these geochemical data vary relative to depositional facies proximal marine distal marine and fluvial dominated and tectonic setting trailing margin and foreland basin in the trailing margin setting of the 2 96 ga hospital hill subgroup the proximal marine depofacies is characterized by relatively high organic carbon contents up to 0 9 wt and 13 c org values around 28 in contrast to the distal marine depofacies that yields low organic carbon contents 0 01 wt and high 13 c org values up to 22 both depofacies yield low sulfur contents 0 02 wt a narrow range of 34 s values 3 2 and positive 33 s values up to 1 9 this data is consistent with photoautotrophic carbon fixation in shallow marine environments and limited organic carbon production preservation in deeper water settings due to longer transport distances and effective biological degradation e g fe reducing microbes positive 33 s values imply that sulfur was largely derived from a photochemical elemental sulfur reservoir in the foreland basin tectonic setting of the 2 94 ga government and 2 92 ga jeppestown subgroups shelf deposits associated with fluvial braidplain depofacies are characterized by 13 c depleted organic carbon 44 to 38 relatively high sulfur contents 0 2 1 3 wt variable 34 s values 3 7 to 16 5 and small negative 33 s values 0 4 these data suggest that the microbial community in the fluvial dominated depofacies may have consisted of photoautotrophs methanogens anaerobic methanotrophs and sulfate reducers sulfate was derived from a variety of sources that include photochemical crustal and marine sulfur reservoirs the occurrence of three regionally persistent diamictite deposits in the government subgroup coincides with the onset of compressional tectonics and development of pyritic shales with highly 13 c depleted organic carbon suggesting that an increase in continental sulfur flux and methane oxidation may have triggered the mesoarchean glaciations drawdown of h 2 and ch 4 however the link between large 33 s anomalies 4 0 to 1 2 and diamictite suggests low levels of atmospheric oxygen and minimal dilution of photochemical signatures

riverine evidence for isotopic mass balance in the earth s early sulfur cycle during a time of negligible atmospheric po2 earth s early sulfur cycle generated a spectacular geological signal seen as the anomalous fractionation of multiple sulfur isotopic ratios the disappearance of this signal from the geologic record has been hypothesized to constrain the timing of atmospheric oxygenation although interpretive challenges exist asymmetry in existing s isotopic data for example suggests that the archaean crust was not mass balanced with the implication that the loss of s isotope anomalies from the geologic record might lag the rise of atmospheric o2 here we present new s isotopic analyses of modern surface and groundwaters that drain archaean terrains in order to independently evaluate archaean s cycle mass balance natural waters contain sulfur derived from the underlying bedrock and thus can be used to ascertain its s isotopic composition at scales larger than typical geological samples allow analyses of 52 water samples from canada and south africa suggest that the archaean crust was mass balanced with an average multiple s isotopic composition equivalent to the bulk earth overall our work supports the hypothesis that the disappearance of multiple s isotope anomalies from the sedimentary record provides a robust proxy for the timing of the first rise in atmospheric o2 the isotopic composition of sulfur minerals formed during the archaean can be reconstructed from dissolved sulfur in rivers draining cratons analyses from canada suggest that the archaean sulfur cycle was in isotopic mass balance

multiple sulfur isotope evidence for surface derived sulfur in the bushveld complex abstract the rustenberg layered suite of the bushveld complex originated in the mantle but is characterized by variably radiogenic strontium neodymium lead and osmium initial isotope ratios and more elevated 18 o values than expected from a partial melt of primitive mantle it is not clear whether bushveld magmas assimilated material from the crust or whether they were instead generated from an eclogitic mantle source that contained crustal material here we report the 33 s of fifteen whole rock and sulfide separate samples from both the main and critical zones of the bushveld including the ug2 chromitite and the merensky reef all samples have positive 33 s values 0 11 0 02 1 and 34 s values 2 2 0 6 1 non zero 33 s is fundamentally a surface process since high temperature processes are not known to produce significant change in 33 s the positive 33 s indicates that the bushveld sulfur contains a sedimentary or surface derived component the homogeneity of 33 s values for this suite of samples contrasts with the heterogeneity displayed by strontium neodymium lead and osmium initial isotope ratios of the bushveld and requires that the sulfur contamination occurred prior to the emplacement of the bushveld in the upper crust possible sources of contamination include lower crust and sub continental lithospheric mantle limited multiple sulfur isotopic measurements of these reservoirs exist more work needs to be done to constrain whether they contain surface derived sulfur with non zero 33 s and if they do whether the concentrations and isotopic compositions of these reservoirs can explain the measured 33 s of the bushveld

origin of two distinct multiple sulfur isotope compositions of pyrite in the 2 5ga klein naute formation griqualand west basin south africa abstract quadruple sulfur isotope ratios 32s 33s 34s 36s were measured by a high precision sf6 method for early diagenetic pyrite in the 2 5 ga upper prieska facies of the griqualand west basin from the agouron drill core gkp01 measured 33s 33s 0 515 34s values range between 2 3 and 8 5 with no apparent meter scale stratigraphic trend for 70 m section it was found that early diagenetic pyrites occur in two texturally and isotopically distinct populations such that bulk rock isotope data would reflect mixing of these two sulfur pools nodular and layered pyrite yield mostly negative down to 2 3 and relatively constant 33s values over a few tens of cm scale disseminated pyrites in contrast yield positive 0 0 8 5 33s values that are heterogeneous in sub cm scales the former pyrite sulfur was likely derived from seawater sulfate through microbial sulfate reduction and the latter preferentially sampled aqueous h2s s0 reservoirs in late archean oceans relatively constant 33s values for layered pyrite suggest archean sulfate reservoirs had residence times of a few million years most data yield a well defined 36s 33s ratios of 0 9 suggesting predominance of a single s mif source reaction four analyses of a two cm length sample 306 5 m yield 36s 33s slope of 1 6 this slope is consistent with the relationship expected for a symmetry breaking isotope effect during the s s2 reaction but deviations from the main archean array i e 36s 33s 0 9 may also result from various combinations of so photolysis and so2 oxidation high spatial resolution high precision sf6 measurements of archean pyrite provide significant new insights into the origin of archean sulfur mass independent fractionation s mif and the late archean sulfur cycle

coupled fe and s isotope variations in pyrite nodules from archean shale ron and sulfur isotope compositions recorded in ancient rocks and minerals such as pyrite fes2 have been widely used as a proxy for early microbial metabolisms and redox evolution of the oceans however most previous studies focused on only one of these isotopic systems herein we illustrate the importance of in situ and coupled study of fe and s isotopes on two pyrite nodules in a c 2 7 ga shale from the bubi greenstone belt zimbabwe fe and s isotope compositions were measured both by bulk sample mass spectrometry techniques and by ion microprobe in situ methods secondary ion mass spectrometry sims spatially resolved analysis across the nodules shows a large range of variations at micrometer scale for both fe and s isotope compositions with 56 fe and 34 s values from 2 1 to 0 7 and from 0 5 to 8 2 respectively and 33 s values from 1 6 to 2 9 the fe and s isotope variations in these nodules cannot be explained by tandem operation of dissimilatory iron reduction dir and bacterial sulfate reduction bsr as was previously proposed but rather they reflect the contributions of different fe and s sources during a complex diagenetic history pyrite formed from two different mineral precursors 1 mackinawite precipitated in the water column and 2 greigite formed in the sediment during early diagenesis the in situ analytical approach reveals a complex history of the pyrite nodule growth and allows us to better constrain environmental conditions during the archean

the cycling and redox state of nitrogen in the archaean ocean organisms that produce oxygen through photosynthesis existed during the late archaean eon about 2 500 million years ago but controversial evidence suggests that they may have evolved several hundred million years earlier oxygen is expected to react with oceanic nitrogen altering its redox state the reaction leaves a signature in the isotopic composition of the nitrogen bound in organic matter here we present a record of the nitrogen isotopic composition of kerogen extracted from minimally altered shales from the campbellrand malmani platform in south africa between the palaeo archaean and about 2 670 million years ago the 15n values of the kerogen rose by about 2 we interpret this increase as an indication of the onset of coupled nitrification and denitrification or anammox reactions in the surface oceans which require the presence of free oxygen a second increase in nitrogen isotopic composition around 2 520 million years ago implies instability of the n cycle with loss of fixed n this evidence for available oxygen in the oceans occurs at least 200 million years before geochemical indications of the presence of significant levels of atmospheric oxygen we suggest that coupled nitrification and denitrification drove the loss of fixed inorganic nitrogen leading to nitrogen limitation and conclude that the low levels of biologically available nitrogen limited the growth of oxygen producing plankton delaying the accumulation of oxygen in the atmosphere the initial production of oxygen in early earth s oceans altered the redox chemistry and cycling of nitrogen a record of nitrogen isotopes from preserved organic matter indicates nitrogen cycling in the presence of free oxygen 2 67 billion years ago about 200 million years before the first geochemical evidence for atmospheric free oxygen

euxinia in the neoarchean the starting point for early oxygenation in a brazilian craton abstract geochemical evidence for local redox transitions is observed 300 ma years prior to the great oxygenation event goe ca 2400 ma and suggests evolving environmental conditions through a continuous sequence where euxinia anoxic and sulfidic preceded the expansion of more oxidizing conditions based on multiproxy data such as iron speciation fepy fehr 0 7 and mo enrichments varying from 3 to 64 we present one of the oldest records of euxinia from the archean pitangui greenstone belt 2700 ma minas gerais brazil the sulfur isotopic composition of sedimentary sulfides indicates early inputs of sulfate from oxidative weathering and an attenuation of sulfur mass independent fractionation that combined with other geochemical signatures fehr fet ce anomalies and rare earth element fractionation is consistent with the expansion of oxygen availability and suggests localized oxic conditions before the goe

comparing orthomagmatic and hydrothermal mineralization models for komatiite hosted nickel deposits in zimbabwe using multiple sulfur iron and nickel isotope data trojan and shangani mines are low grade 0 8 ni komatiite hosted nickel sulfide deposits associated with ca 2 7 ga volcano sedimentary sequences of the zimbabwe craton at both mines nickel sulfide mineralization is present in strongly deformed serpentinite bodies that are enveloped by a complex network of highly sheared silicified and sulfide bearing metasedimentary rocks strong polyphase structural metamorphic metasomatic overprints in both the trojan and shangani deposits make it difficult to ascertain if sulfide mineralization was derived from orthomagmatic or hydrothermal processes or by a combination of both multiple s fe and ni isotope analyses were applied to test these competing models massive ores at shangani mine show mass dependent fractionation of sulfur isotopes consistent with a mantle sulfur source whereas s isotope systematics of net textured ore and disseminated ore in talcose serpentinite indicates mixing of magmatic and sedimentary sulfur sources potentially via post magmatic hydrothermal processes a restricted range of strongly mass independent 33s values in ore samples from trojan mine likely reflects high temperature assimilation of sulfur from supracrustal rocks and later superimposed low temperature hydrothermal remobilization iron isotope values for most ni bearing sulfides show a narrow range suggesting that in contrast to sulfur nearly all of iron was derived from an igneous source negative ni isotope values also agree with derivation of ni from ultramafic melt and a significant high temperature fractionation of ni isotopes fe isotope values of some samples from shangani mine are more fractionated than expected to occur in high temperature magmatic systems further suggesting that hydrothermal processes were involved in either low grade ore formation liberation of ni from olivine by sulfur bearing hydrothermal fluids or remobilization of existing sulfides potentially inducing secondary ni sulfide mineralization

multiple sulphur and iron isotope composition of detrital pyrite in archaean sedimentary rocks a new tool for provenance analysis abstract multiple s 34 s and 33 s and fe 56 fe isotope analyses of rounded pyrite grains from 3 1 to 2 6 ga conglomerates of southern africa indicate their detrital origin which supports anoxic surface conditions in the archaean rounded pyrites from meso to neoarchaean gold and uranium bearing strata of south africa are derived from both crustal and sedimentary sources the latter being characterised by non mass dependent fractionation of s isotopes 33 s as negative as 1 35 and large range of fe isotope values 56 fe between 1 1 and 1 2 most sediment sourced pyrite grains are likely derived from sulphide nodules in marine organic matter rich shales sedimentary exhalites and volcanogenic massive sulphide deposits some sedimentary pyrite grains may have been derived from in situ sulphidised fe oxides prior to their incorporation into the conglomerates as indicated by unusually high positive 56 fe values sedimentary sulphides without significant non mass dependent fractionation of s isotopes were also present in the source of some conglomerates the abundance in these rocks of detrital pyrite unstable in the oxygenated atmosphere may suggest factors other than high p o 2 as the cause for the absence of significant non mass dependent fractionation processes in the 3 2 2 7 ga atmosphere rounded pyrites from the c 2 6 ga conglomerates of the belingwe greenstone belt in zimbabwe have strongly fractionated 34 s 33 s and 56 fe values the source of which can be traced back to black shale hosted massive sulphides in the underlying strata the study demonstrates the utility of combined multiple s and fe isotope analyses for provenance reconstruction of archaean sedimentary successions

subtropical sst dipole events in the southern indian ocean sea surface temperature sst anomalies in the subtropical southern indian ocean show interannual dipole events that are seasonally phase locked to the austral summer a positive phase of the event is characterized by cold sst anomalies in the eastern part i e off australia and warm sst anomalies in the southwestern part south of madagascar such an event is found to produce above normal rainfall over many regions in south central africa the cooling of sst in the eastern part is mainly caused by the enhanced evaporation this is associated with stronger winds along the eastern edge of the subtropical high which is strengthened and shifted slightly to the south during the event on the other hand relative decrease in the seasonal latent heat loss due to reduced evaporation dominates the warming in the southwestern part evolution of such subtropical dipole events shows quite a contrast to that of the tropical dipole events discovered recently in the indian ocean

geochemistry of pyrite from diamictites of the boolgeeda iron formation western australia with implications for the goe and paleoproterozoic ice ages abstract sediments of the ca 2400 ma turee creek group of western australia are coincident with the oxygenation of earth s surface associated with the great oxidation event goe diamictite within the boolgeeda iron formation from the boundary ridge section at the duck creek syncline was previously correlated to the glaciogenic sediments of the meteorite bore member of the turee creek group at the hardey syncline martin 1999 the meteorite bore member is considered correlative and time equivalent with the paleoproterozoic glacial diamictites of the 2 45 2 22 ga huronian supergroup in north america if the diamictite units at boundary ridge correspond to worldwide paleoproterozoic glaciations they should also record the disappearance of mass independently fractionated mif sulfur triple s isotope compositions for pyrites from the boundary ridge sections were measured in situ by a multi collector ion microprobe and yielded both mass dependently fractionated mdf and mif sulfur isotope values 33 s values from 0 44 to 6 27 trace element heterogeneities are indicated by measurements at multiple spatial scales within rounded pyrites in the boundary ridge section consistent with multiple generations of pyrite that incorporated sulfur processed in an anoxic atmosphere a compilation of s isotope data from pyrite in the boundary ridge diamictites analyzed in this study and previous work williford et al 2011 defines multiple 34 s vs 33 s arrays consistent with an origin of detrital pyrite from the underlying hamersley and fortescue groups sulfides in a shale unit from the boundary ridge section plot along the terrestrial fractionation line but still retain positive mif s this and detrital pyrite suggest low atmospheric oxygen immediately before the initiation of paleoproterozoic ice ages this data is inconsistent with a correlation to glacially influenced successions within the north american huronian supergroup in which the mif s signal permanently disappears the diamictites at the duck creek syncline are older than the meteorite bore member because their stratigraphic position is within the boolgeeda iron formation that underlies the turee creek group which is separated from the meteorite bore member by nearly 1000 m of the kungarra shale at the hardey syncline

the enrichment of heavy iron isotopes in authigenic pyrite as a possible indicator of sulfate driven anaerobic oxidation of methane insights from the south china sea abstract sulfate driven anaerobic oxidation of methane so4 aom and organiclastic sulfate reduction osr in marine sediments commonly lead to the precipitation of authigenic pyrite with characteristic sulfur isotopic compositions yet no reports on the iron isotopic composition of so4 aom generated pyrite exist to the best of our knowledge and the processes controlling the distribution of iron isotopes during this biogeochemical process are not understood to investigate the mechanisms involved in iron isotope fractionation during so4 aom we analyzed the isotopic composition of authigenic pyrite from two seafloor sites hs148 and hs217 in the shenhu gas hydrate area south china sea the 56fe values of pyrite were found to vary from 0 349 to 0 267 in core hs148 and from 0 793 to 0 178 in core hs217 relative to average igneous rock with distinct trends towards higher values with increasing burial depth in both cores the 56fe values correlate positively with the extent of pyritization fepy fehr derived from a sequential iron extraction procedure osr was found to drive early diagenetic pyrite formation at shallow depth resulting in relatively 56fe depleted pyrite peaks in the extent of pyritization of 0 45 and 0 47 at ca 6 and 7 m below the sediment surface respectively correlate with high 56fe and high 34s values and are interpreted to reflect periods of enhanced so4 aom in paleo sulfate methane transition zones smtzs the great variability in iron isotopic composition and the observed trends are best explained as a function of the availability of dissolved sulfide reflecting sulfide formation by osr and so4 aom the successive conversion of reactive iron to pyrite via sulfidization apparently resulted in the enrichment of 56fe in the iron reservoir upon the preferential consumption of isotopically light iron leading to the formation of successively 56fe enriched pyrite especially at or in close proximity to the smtz therefore we hypothesize that the combined enrichment of heavy iron isotopes and 34s in authigenic pyrite is a possible tracer of so4 aom in modern and ancient sedimentary sequences

shrimp u pb zircon ages for the palaeoproterozoic kuruman iron formation northern cape province south africa evidence for simultaneous bif deposition on kaapvaal and pilbara cratons abstract stilpnomelane rich tuffaceous mudrocks are an important component of the palaeoproterozoic kuruman and griquatown iron formations in the northern cape province they document volcanic activity during the deposition of these iron formations and the zircon populations that they contain record syn depositional volcanism resedimentation and post depositional isotopic disturbance the trace element signatures of tuffaceous samples suggest that although zircons are felsic volcanogenic in origin mixing of felsic ash with basaltic ash and or muds in the water column was also likely in addition these rocks record minor terrigenous input and some samples indicate mixing with iron rich clays oxides and smectites moreover they reflect a shift from mafic volcanism e g mafic tuffs in the underlying gamohaan formation towards more felsic volcanism that is a trend also recorded for tuffaceous rocks in the brockman iron formation the best estimate of the depositional age for the top of the riries member and hence the kuruman iron formation is 2460 ma where most of the zircon populations were derived from volcanism coeval with bif deposition ages obtained in this study that are older than the 2465 5 ma age for the lower riries member probably represent resedimented pyroclastic deposits i e give eruptive ages from earlier eruptions that contain an unimodal zircon population and as such only provide maximum depositional ages although a compacted sedimentation rate csr for the entire kuruman iron formation is 3 4 m per million years a csr of about 22 m per million years is deduced for the riries member suggesting that there are cryptic gaps within the kuruman stratigraphic record the latter is comparable to the csr of 33 m per million years calculated for hamersley province bifs ages of the tuffaceous horizons in the kuruman iron formation are comparable to those from the brockman iron formation of the hamersley province the 2460 5 ma age for the top of the riries member corresponds to the 2459 3 ma age for the base of the joffre member and the 2463 5 ma whaleback shale member of the brockman iron formation although ca 2468 2478 ma ages reflect detrital or syn depositional zircon populations they are comparable to the 2470 4 ma s13 and the 2479 3 ma s9 macrobands of the dales gorge member brockman iron formation moreover the zircon age spectra and pb loss histories of both the kuruman and brockman iron formation tuffaceous sediments are strikingly similar without doubt the kuruman and brockman iron formations were deposited synchronously whether they were a response to global magmatic events or were deposited in the same basin are questions still being debated

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

chain formation as a mechanism for mass independent fractionation of sulfur isotopes in the archean atmosphere abstract the anomalous abundances of sulfur isotopes in ancient sediments provide the strongest evidence for an anoxic atmosphere prior to 2 45 ga but the mechanism for producing this mass independent fractionation pattern remains in question the prevailing hypothesis has been that it is created by differences in the uv photolysis rates of different so2 isotopologues we investigate here a recently proposed additional source of fractionation during gas phase formation of elemental sulfur s4 and s8 because two minor s isotopes rarely occur in the same chain the longer s4 and s8 chains should be strongly and roughly equally depleted in all minor isotopes this gives rise to negative 33 s values and positive 36 s values in elemental sulfur just the opposite of and much larger than what is predicted from so2 photolysis itself back reactions during chain formation specifically photolysis of s2 and s3 pass sulfur having the opposite fractionation back to atomic s and thence to other sulfur species causing h2s so2 sulfate and short chain elemental sulfur to have positive 33 s and negative 36 s positive 33 s values in elemental sulfur produced in laboratory so2 photolysis experiments could be caused by the initial fractionation during photolysis combined with rapid condensation of short chain sulfur species on the walls of the reaction chamber along with a scarcity of back reactions the simulated fractionations produced by the chain formation mechanism do not directly match fractionations from the rock record the mismatch might be explained if the isotopic signals leaving the atmosphere were significantly modulated by life by uncertainties in the rates of reactions of both major and minor isotopic sulfur species or by the relatively large potential range of atmospheric parameters further work is needed to better constrain these uncertainties but this novel mechanism suggests new avenues to explore in our search for a explanation for the s mif record

new insights into archean sulfur cycle from mass independent sulfur isotope records from the hamersley basin australia we have measured multiple sulfur isotope ratios 34 s 33 s 32 s for sulfide sulfur in shale and carbonate lithofacies from the hamersley basin western australia the v 33 s values v 33 swn 33 s30 515un 34 s shift from 31 9 to 6 9x over a 22 m core section of the lower mount mcrae shale v2 5 ga likewise sulfide sulfur analyses of the jeerinah formation v2 7 ga yield v 33 s values of 30 1 to 8 1x over a 50 m section of core despite wide variations in v 33 s and n 34 s these two shale units yield a similar positive correlation between v 33 s and n 34 s in contrast pyrite sulfur analyses of the carawine dolomite v2 6 ga yield a broad range in n 34 s 3 2 to 16 2x but a relatively small variation and negative values in v 33 s 32 5 to 31 1x the stratigraphic distribution of n 33 s n 34 s and v 33 s in western australia allows us to speculate on the sulfur isotopic composition of archean sulfur reservoirs and to trace pathways in the archean sulfur cycle our data are explained by a combination of massindependent fractionation mif in the atmosphere and biological mass dependent fractionation in the ocean in the archean volcanic sulfur bearing gas species were photolysed by solar ultraviolet uv radiation in an oxygen free atmosphere resulting in mif of sulfur isotopes aerosols of s8 with v 33 ss 0 and sulfuric acid with v 33 s6 0 formed from the products of uv photolysis and carried mass independently fractionated sulfur into the hydrosphere the signatures of atmospheric photolysis were preserved by precipitation of pyrite in sediments pyrite precipitation was mediated by microbial enzymatic catalysis that superimposed mass dependent fractionation on mass independent atmospheric effects multiple sulfur isotope analyses provide new insights into the early evolution of the atmosphere and the evolution and distribution of early sulfur metabolizing organisms a 2003 elsevier science b v all rights reserved

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

zircon ion microprobe studies bearing on the age and evolution of the witwatersrand triad abstract the ventersdorp and witwatersrand supergroups and the dominion group collectively referred to as the witwatersrand triad represent some of the oldest and economically most important volcano sedimentary basins within the kaapvaal craton of southern africa precise age constraints which are vital to models aimed at understanding the formation mineralisation and evolution of these basins have been hampered by analytical and geological problems these problems have been overcome by this ion microprobe study on zircons from volcanic rocks within the three basins felsic and mafic volcanics from the ventersdorp supergroup yield ages of 2709 4 ma and 2714 8 ma respectively constraining the timing of the closure of the witwatersrand basin a maximum age for the witwatersrand basin is indicated by the age of 3074 6 ma for volcanics from the underlying dominion group thus a period of c 350 ma was available for the accumulation of the full witwatersrand basin succession unfortunately dating within the witwatersrand basin itself is not complete and future work could show that extended time breaks may exist within the basin these new data show that previous age determinations on the ventersdorp witwatersrand and dominion basins were inaccurate and that the economically important witwatersrand basin must now be recognised as archaean

multiple sulfur and carbon isotope composition of sediments from the belingwe greenstone belt zimbabwe a biogenic methane regulation on mass independent fractionation of sulfur during the neoarchean abstract to explore the linkage between mass independent sulfur isotope fractionation mif s and 13corg excursions during the neoarchean as well as the contemporary redox state and biogeochemical cycling of carbon and sulfur we report the results of a detailed carbon and multiple sulfur 34s 33s 36s isotopic study of the 2 7 ga manjeri and 2 65 ga cheshire formations of the ngezi group belingwe greenstone belt zimbabwe multiple sulfur isotope data show non zero 33s and 36s values for sediments older than 2 4 ga i e prior to the great oxidation event goe indicating mif s thought to be associated with low atmospheric oxygen concentration however in several 2 7 2 5 ga neoarchean localities small scale variations in mif s signal magnitude seem to correlate with negative excursion in 13corg possibly reflecting a global connection between the relative reaction rate of different mif s source reaction and sulfur exit channels and the biogenic flux of methane into the atmosphere during periods of localized microbiologically mediated shallow surface water oxygenation the manjeri formation black shales studied here display a wide range of 13corg between 35 4 and 16 2 average of 30 3 6 0 1 while the cheshire formation shales have 13corg between 47 7 and 35 1 average 41 3 3 1 the 34s values of sedimentary sulfides from manjeri formation vary between 15 15 and 2 37 average 1 71 4 76 1 showing very small and mostly negative 33s values varying from 0 58 to 0 87 average 0 02 0 43 1 cheshire formation black shale sulfide samples measured in this study have 34s values ranging from 2 11 to 2 39 average 0 25 1 08 1 and near zero and solely positive 33s anomalies between 0 14 and 1 17 average 0 56 0 29 1 moreover 36s 33s in the two formations are comparable with a slope of 1 38 manjeri formation and 1 67 cheshire formation respectively this differs from the archean reference line i e 0 9 the sulfur and carbon isotopic signatures recorded here likely reflect different environmental conditions and or ecosystems within the sampled cheshire and manjeri formations paleofacies the differences in carbon isotopes in different sedimentological facies are interpreted as recording different metabolic pathways including photosynthesis methanogenesis and methanotrophy low 13corg values in the cheshire formation black shales suggest a strong influence of methanotrophy likely preceded by bacterial methanogenesis while the large range of manjeri formation 34s may record bacterial sulfate reduction the c and multiple s isotopic variations recorded here may imply different patterns of c and s fractionation perhaps dependent on variations in the biogenic egress of methane to the atmosphere

identifying global vs basinal controls on paleoproterozoic organic carbon and sulfur isotope records abstract paleoproterozoic sedimentary successions are important archives of the redox evolution of earth s atmosphere and oceans efforts to unravel the dynamics of our planet s early oxygenation from this archive rely on various geochemical proxies including stable carbon and sulfur isotopes however ancient metasedimentary rocks often experienced early and late stage bio geochemical processes making it difficult to discern primary environmental signals from bulk rock 13corg and 34s values such complexity in carbon and sulfur isotope systematics contributes to uncertainty about the redox structure of paleoproterozoic oceans a currently popular idea is that following the great oxidation event global changes led to low oxygen environments and temporally fluctuating ocean redox conditions that lasted until the neoproterozoic the volcano sedimentary rocks of the onega basin have figured prominently in this concept particularly the exceptionally organic rich rocks of the 1 98 ga zaonega formation however a growing body of evidence shows that local depositional processes acted to form the 13corg and pyrite 34s records of the zaonega formation thus calling for careful assessment of the global significance of these isotope records placing new and existing organic carbon and sulfur isotope data from the zaonega formation into the context of basin history and by comparing those results with key paleoproterozoic successions of the francevillian basin gabon the pechenga greenstone belt nw russia and the animikie basin canada we show that the stratigraphic 13corg and pyrite 34s trends can be explained by local perturbations in biogeochemical carbon and sulfur cycling without requiring global drivers despite their temporal disparity we also demonstrate that individual successions share certain geological traits e g magmatic and or tectonic activity hydrocarbon generation basin restriction suggesting that their pyrite 34s and 13corg trends were governed by common underlying mechanisms e g similar basinal evolution and biogeochemical feedbacks and are not necessarily unique to certain time intervals we further show that pyrites in these successions that are most likely to capture ambient seawater sulfate isotopic composition have consistent 34s values of 15 18 which hints at remarkable stability in the marine sulfur cycle over most of the paleoproterozoic era

the unusual summer of 1994 in east asia iod teleconnections 1 an extremely hot and dry summer of 1994 was reported in east asian countries using observational data we have demonstrated that the indian ocean dipole iod is at least one possible cause of the abnormal east asian summer climate an anomalous cyclonic circulation over the western pacific and the southern china weakened the monsoonal northward flow in the lower troposphere an anomalous anticyclonic circulation with the equivalent barotropic structure around japan korea and the northeastern part of china caused the hot and dry summer of 1994 this accumulation of the lower potential vorticity in the far east is related to the wave activity from the mediterranean sahara region the monsoon desert mechanism connects a rossby wave source with the iod induced diabatic heating around the bay of bengal another rossby wave train pattern was generated in the upper troposphere and propagates northeastward from the southern china both the rossby wave patterns influenced the circulation changes over east asia

mass independently fractionated sulfur in archean paleosols a large reservoir of negative δ33s anomaly on the early earth abstract results of multiple sulfur isotope analyses from five archean paleosols show the widespread presence of mass independently fractionated sulfur in the regolith developed on the pre 2 5 ga earth analysis of sulfur from a small set of diamictite samples gave similar results all values of 33 s are negative indicating that the archean surface environments preferentially retained atmospheric s from the so 4 2 pathway which carried a negative 33 s signal whereas a portion of the s from the s 8 pathway with a positive 33 s was transferred to the oceans the soil so 4 2 was then converted to sulfide by bacterial sulfate reduction with terrestrial organic matter in the weathering horizon acting as a reductant some s from the s 8 pathway also included which resulted in a net soil 33 s anomaly from atmospheric s in the range 0 3 to 0 6 similar to values for pyrites from floodplain sediments excess s 8 derived s was carried to the oceans resulting in the negative positive dichotomy between terrestrial and marine systems pyrite that formed in paleosols and pyrite grains that formed in flood plain deposits both carrying the terrestrial 33 s signal were then recycled into detrital pyrite grains now found in sandstones and conglomerates deposited before the rise of atmospheric oxygen therefore the earth s early regolith constituted a reservoir of s with negative 33 s values that could be important for balancing the predominantly positive 33 s signature found in marine sediments

the genesis of solution pipes evidence from the middle late pleistocene bridgewater formation calcarenite southeastern australia abstract solution pipes are abundant in late pleistocene aeolian calcarenites at cape bridgewater in southwestern victoria and were studied using field work morphometric analysis thin sections mineralogical and chemical analyses and osl dating the solution pipes are vertical tubes formed in aeolian limestone with matrix porosity they are typically 0 1 1 m wide and 1 5 m deep with rounded terminations and cemented rims up to 10 cm thick they are overlain by palaeosols and filled mostly with palaeosol material rhizoliths are commonly present in the solution pipe fills and the surrounding calcarenite the solution pipes have formed by focused dissolution of aeolianite relatively quickly after the sand deposition and concurrently filled with soil as they developed they most likely formed beneath trees as a result of focused infiltration due to stemflow or due to fingered flow unstable wetting front that breaks into fingers as it moves downwards solution pipe formation was strongly dependent on climate periods of solution pipe formation followed the deposition of aeolianites at the end of interglacials mis 7 9 and 11 when the dunes were stabilised by vegetation and there was sufficient rainfall for substantial subsoil dissolution the cemented rims formed in the following drier glacial climates solution pipes are most abundant in the youngest aeolianite probably reflecting the wetter climate at the end of mis 7 that allowed a dense forest to cover the dunes from mis 5 to mis 2 no deposition of calcareous sand occurred on cape bridgewater and combined with a very wet interglacial period mis 5e resulted in additional karstification allowing the pipes in the mis 7 aeolianite to extend deeper and drill down into the underlying member a well developed calcrete layer drapes over these solution pipes and probably formed during the dry windy climate of the last glacial maximum

pathways for neoarchean pyrite formation constrained by mass independent sulfur isotopes it is generally thought that the sulfate reduction metabolism is ancient and would have been established well before the neoarchean it is puzzling therefore that the sulfur isotope record of the neoarchean is characterized by a signal of atmospheric mass independent chemistry rather than a strong overprint by sulfate reducers here we present a study of the four sulfur isotopes obtained using secondary ion ms that seeks to reconcile a number of features seen in the neoarchean sulfur isotope record we suggest that neoarchean ocean basins had two coexisting significantly sized sulfur pools and that the pathways forming pyrite precursors played an important role in establishing how the isotopic characteristics of each of these pools was transferred to the sedimentary rock record one of these pools is suggested to be a soluble sulfate pool and the other pool atmospherically derived elemental sulfur is suggested to be largely insoluble and unreactive until it reacts with hydrogen sulfide we suggest that the relative contributions of these pools to the formation of pyrite depend on both the accumulation of the insoluble pool and the rate of sulfide production in the pyrite forming environments we also suggest that the existence of a significant nonsulfate pool of reactive sulfur has masked isotopic evidence for the widespread activity of sulfate reducers in the rock record

multiple oscillations in neoarchaean atmospheric chemistry abstract the great oxidation event goe represents a crucial juncture in earth history signifying the rise in atmospheric oxygen from parts per million to percent levels at 2 45 2 32 billion years ago ga although planetary oxygenation undoubtedly led to the inception of the contemporary earth system the trigger s and mechanism s controlling this chemical reorganisation remain elusive quantitative estimates of the atmosphere s composition in the prelude to the goe are central to understanding this oxygenation event previous analyses of 2 65 2 5 ga sediments from the griqualand basin south africa invoke a tantalising picture of an unusual earth environment alluding to an atmosphere periodically dominated by a layer of organic particles haze formed from methane photolysis however as yet this hypothesis has remained untested here we present four new coupled carbon and quadruple sulphur isotope records from distal time equivalent 2 7 2 5 ga sedimentary successions from south africa and western australia these extended records reveal similar chemostratigraphic trends supporting a dynamic terminal neoarchaean atmosphere oscillating between a hazy state at elevated methane concentrations and a haze free anoxic background state we suggest these atmospheric aberrations were related to heightened biogenic methane fluxes fuelled by enhanced nutrient delivery from climatically or weathering induced feedbacks these data question the canonical view of a simple unidirectional planetary oxygenation and signify that the overture to the goe was governed by complex feedbacks within the earth biosphere system

chronological correlations between the pilbara and kaapvaal cratons abstract the early geological development of the pilbara and kaapvaal cratons has many features in common attempts have been made to correlate geologically similar features of the two cratons and it has been postulated that they originated as contiguous components of a single continent vaalbara during this time the early geological histories of the pilbara and kaapvaal cratons are here compared in detail and the evidence that they were initially contiguous is assessed these comparisons indicate significant differences in the chronologies of magmatic events within the granite greenstone crusts of the pilbara and kaapvaal cratons in addition igneous correlatives emplaced during ca 2985 and 2782 ma magmatic events on the kaapvaal craton have not been identified on the pilbara craton and a well defined 2760 ma magmatic event manifest as widespread emplacement of granitic rocks into the pilbara granite greenstone basement and eruption of flood basalts of the lower part of the fortescue group is absent from the kaapvaal craton furthermore similarities in first and second order transgression regression cycles within the sedimentary supracrustal sequences may be attributable to global sea level fluctuations and thus may be irrevelant to the question of former contiguity however similarities in some aspects of the geological development of the pilbara and kaapvaal cratons imply that there were periods extending for between 60 and 200 ma of the archaean era during which the style of crust formation intensity of volcanism and subaerial erosion and magnitude of sea level fluctuations may have varied on a global scale such similarities include the overall duration of formation of the granite greenstone crusts from ca 3650 to 3100 ma the onset of craton wide erosion in the interval ca 3125 to 3000 ma the major episodes of flood basaltic volcanism between 2760 and 2680 ma the predominance of chemical carbonate and banded iron formation sedimentation between ca 2630 and 2440 ma and the transition to widespread clastic sedimentation within the interval 2440 to 2200 ma

reactions of hydrothermal solutions with organic matter in paleoproterozoic black shales at talvivaara finland evidence from multiple sulfur isotopes abstract stable isotopic studies of archean paleoproterozoic sedimentary rocks older than 2 4 ga have documented large mass anomalous fractionations of sulfur isotopes 33 s 0 0 2 while younger rocks record little to no anomalous fractionation of sulfur isotopes this change from large anomalous fractionations to sulfur isotope values that fall on the terrestrial fractionation line has been proposed to represent the transition from an essentially anoxic archean atmosphere to an oxygenated atmosphere here we present 34 s and 33 s data for 28 core samples from paleoproterozoic 2 1 1 9 ga metamorphosed black shales and associated sulfide ores in eastern finland previous 34 s of studies of the talvivaara and outokumpu deposits of eastern finland focused on single grain analyses of sulfides while this study presents data from sequentially extracted sulfur fractions e g acid soluble sulfides chrome reducible sulfides elemental sulfur the sulfur isotope results range between 16 6 and 11 6 for 34 s 8 6 and 6 0 for 33 s and 1 25 and 0 55 for 33 s the anomalously fractionated samples are not consistent with previous findings that large anomalous fractionations of sulfur isotopes are absent in sedimentary metasedimentary rocks younger than 2 4 ga it is unlikely that talvivaara sulfides are the products of ultraviolet photolysis of volcanic so 2 in an oxygen poor atmosphere alternatively these sulfides could in part be the products of diagenetic reactions between sediments enriched in organic matter c org and hydrothermal solutions rich in sulfate i e thermochemical sulfate reduction laboratory experiments on thermochemical sulfate reduction have shown that mass anomalous fractionations of sulfur isotopes can be recorded in reduced sulfur products from reactions between simple amino acids and sulfate at 150 300 c a thermochemical sulfate reduction pathway for the mass anomalous signatures in talvivaara samples is consistent with previous genetic models proposed for the origin of the sulfur and organic carbon rich black shales now schists associated with the talvivaara and outokumpu ore deposits at talvivaara metalliferous black shales apparently were deposited under an anoxic to sulfidic marine water column the reported multiple sulfur isotopic data are key geological evidence for mass anomalous fractionations of sulfur isotopes during hydrothermal alteration of fine grained organic rich sediments approximately 20 of samples in this study show large offsets in 33 s values between different extracted sulfur fractions from the same sample which can be explained by classical isotope effects associated with the formation of hydrothermal alteration products that predominantly are retained within the precursor fine grained organic rich units

facies relations depositional environments and diagenesis in a major early proterozoic stromatolitic carbonate platform to basinal sequence campbellrand subgroup transvaal supergroup southern africa the campbellrand subgroup and its correlative the malmani subgroup of the transvaal supergroup represent a major 2300 2600 ma old carbonate buildup it is on average between 1500 and 1700 m thick and covers an area of approximately 190 000 km2 on the kaapvaal craton the original depository probably extended across the entire 600 000 km2 surface area of the craton and beyond the buildup consists essentially of two major lithofacies assemblages namely a basinal non stromatolitic laminated carbonate and shale sequence with minor chert iron formation and mafic tuff interbeds off the craton to the west and a shallow water stromatolitic carbonate sequence on the craton proper growth faults along the edge of the craton controlled the platform margin defined by columnar stromatolite oolite and carbonate arenite shoal deposits these are flanked basinward by reef like giant subtidal stromatolitic mounds elongated perpendicular to the platform margin and grading into slope deposits consisting of laminated carbonates with interbeds of chaotic dolomite breccia and conophyton stromatolites platform lagoonal deposits consist of dark grey laminoid fenestrate stratified stromatolites interfingering to the interior of the craton with intertidal to supratidal light grey cherty dolomite units with a variety of structures such as domal and stratified stromatolites laminoid fenestrae tepee structures and flat pebble conglomerates the buildup consisted primarily of limestone which was replaced by early diagenetic dolomite the chemical composition of the dolomite is related to depofacies platform margin and lagoonal dolomites are manganese rich basinal dolomites are iron rich and intertidal to supratidal deposits are virtually free of iron and manganeses indications are that the carbonate buildup developed from an early carbonate ramp stage into a mature rimmed carbonate shelf eventually the carbonate shelf was drowned by a major transgression followed by the deposition of the kuruman iron formation

definition of antarctic oscillation index following walker s work about his thmous three oscillations published during the 1920 30s many papers were written about atmospheric oscillations a iburth atmospheric oscillation in the middle and high southern latitudes was lbund and nanted the grotarctic oscillation ao a refiers to a large scale alternation of atmospheric mass between the mid latitudes and high latitudes surthce pressure in order to understand the spatial structure of sea level pressure variation in detail empirical orthogonal fitnction analysis is applied an objective index of the antarctic oscillation index aoi is defined as the diffierence of zonal mean sea level pressure between 40os and 65os the aoi has the potential tbr clarifying climate regimes in the southern hemisphere similar to how the na and the npo has been used in the northern hemisphere were there other oscillation s besides nao npo and s especially in the southern hemisphere it had been supposed that there might be other atmospheric oscillation s in the high southern latitudes although as early as in the first quarter of this century walker 1928 had stated that just as in the north atlantic there is a pressure opposition between the azores and iceland there is an opposition between the high pressure belt across chile and the argentine on the one hand and the low pressure area of weddell sea and the bellingshausen sea on the other the scarcity of data in the southern hemisphere hindered the search tbr new oscillation s during the last two decades more comprehensive data over the southern hemisphere became available and more analyses were carried out see kidson 1975 rogers and van loon 1982 mo and l 7 ite 1985 2 4o 1986 connolley 1997 gong and wang 1998 a tburth atmospheric oscillation in the middle and high southern latitudes was tbund and nanted as the antarctic oscillation a wang 1992 gong and wang 1998 the term ao relrs to a large scale alternation of atmospheric mass between the mid latitude sur hce pressure

the sign of δ33s is independent of pyrite morphology abstract previous bulk sulphide analyses have suggested a correlation between the morphology of pyrite in archean metasedimentary rocks and the sign of associated 33s however it remains to be determined whether such a correlation exists and what the underlying mechanism is this study measured the multiple sulphur isotopic compositions of pyrite nodules and disseminated pyrite grains from two typical neoarchean shale samples with shrimp si following detailed textural investigations by sodium hypochlorite etching and electron microscopy the roy hill shale sample shows two generations of pyrite in both nodules and disseminated grains reflected by textures the first generation is 33s weakly negative while the second generation is 33s highly positive both generations of pyrite show linear relationships between 34s and 33s although generation two displays wider ranges of 34s and 33s compared with generation one in the 33s 36s diagram generation two plots along the archean reference array ara 36s 33s 1 whereas generation one deviates from the ara in a trend similar to the biological fractionation line 36s 33s 7 the nammuldi shale sample also exhibits two generations of pyrite both of which are 33s and 34s positive albeit of different magnitude for these two shale samples the sign of 33s is not associated with the pyrite morphology a plausible explanation for the morphology specific 33s reported in previous studies could be related to bulk analyses involving pyrite of different generations with opposite 33s furthermore based on the distribution of the earlier nodular and disseminated pyrite in both samples a model involving four stages is proposed for the formation of pyrite nodules studied here 1 formation of pyrite framboids composed of microcrystalline pyrite 2 dissolution of framboidal pyrite and reprecipitation to generate larger single pyrite crystals 3 aggregation of single pyrite crystals into nodules and 4 injection of later hydrothermal fluids

carbonate petrography kerogen distribution and carbon and oxygen isotope variations in an early proterozoic transition from limestone to iron formation deposition transvaal supergroup south africa the transition zone comprises campbellrand microbialaminated replacing cryptalgalaminate limestone and shale with minor dolomite conformably overlain by the kuruman iron formation of which the basal part is characterized by siderite rich microbanded iron formation with minor magnetite and some hematite containing units the iron formation contains subordinate intraclastic and microbialaminated siderite mesobands and was deposited in deeper water than the limestones the sequence is virtually unaltered with diagenetic mineral assemblages reflecting a temperature interval of about 110 degrees to 170 degrees c and pressures of 2 kbars carbonate minerals in the different rock types are represented by primary micritic precipitates now recrystallized to microsparite early precompactional sparry cements and concretions deep burial limpid euhedral sparites and spar cements precipitated from metamorphic fluids in close contact with diabase sills paragenetic pathways of the carbonate minerals are broadly similar in all lithofacies with kerogen intimately associated with them kerogen occurs as pigmentation in carbonate crystals as reworked organic detritus in clastic textured carbonate units and as segregations of kerogen pigment around late diagenetic carbonate crystals locally kerogen may also be replaced by carbonate spar carbon isotope compositions of the carbonate minerals and kerogen are dependent on their mode of occurrence and on the composition of the dominant carbonate species in a specific lithofacies integration of sedimentary petrographic geochemical and isotopic results makes it possible to distinguish between depositional early diagenetic deep burial and metamorphic effects on the isotopic compositions of the carbonate minerals and the kerogen in the sequence major conclusions are that deep burial thermal decarboxylation led to 13c depletion in euhedral ferroan sparites and 13c enrichment in kerogen organic carbon metamorphic sparites are most depleted in 13c carbonates in oxide rich iron formations are more depleted in 13c than those in siderite rich iron formation whereas the kerogens in oxide banded iron formations bif are more enriched this implies that the siderite rich iron formations were not derived from oxide rich iron formation through reduction of ferric iron by organic matter organic matter oxidation by ferric iron did however decrease the abundance of kerogen in oxide rich iron formation and led to the formation of isotopically very light sparry carbonates siderite and calcmicrosparite both represent recrystallized primary micritic precipitates but differ in their 13c composition with the siderites depleted in 13c by 4 6 per mil on average relative to calcmicrosparite this means that the siderites were precipitated from water with dissolved inorganic carbon depleted in 13c by about 9 per mil relative to that from which the limestones precipitated this implies an ocean system stratified with regard to total carbonate with the deeper water from which siderite rich iron formation formed depleted in 13c iron formations were deposited in areas of very low organic matter supply depletion of 13c may therefore derive not from degradation of organic matter but from hydrothermal activity a conclusion which is supported by 18o composition of the carbonate minerals and trace element and rare earth element ree compositions of the iron formations

sulfur sources of sedimentary buckshot pyrite in the auriferous conglomerates of the mesoarchean witwatersrand and ventersdorp supergroups kaapvaal craton south africa large rounded pyrite grains 1 mm commonly referred to as buckshot pyrite grains are a characteristic feature of the auriferous conglomerates reefs in the witwatersrand and ventersdorp supergroups kaapvaal craton south africa detailed petrographic analyses of the reefs indicated that the vast majority of the buckshot pyrite grains are of reworked sedimentary origin i e that the pyrite grains originally formed in the sedimentary environment during sedimentation and diagenesis forty one of these reworked sedimentary pyrite grains from the main vaal basal kalkoenkrans beatrix and ventersdorp contact reefs were analyzed for their multiple sulfur isotope compositions 34s 33s and 36s to determine the source of the pyrite sulfur in addition five epigenetic pyrite samples pyrite formed after sedimentation and lithification from the middelvlei and the ventersdorp contact reefs were measured for comparison the 34s 33s and 36s values of all 41 reworked sedimentary pyrite grains indicate clear signatures of mass dependent and mass independent fractionation and range from 6 8 to 13 8 1 7 to 1 7 and 3 9 to 0 9 respectively in contrast the five epigenetic pyrite samples display a very limited range of 34s 33s and 36s values 0 7 to 4 0 0 3 to 0 0 and 0 3 to 0 1 respectively despite the clear signatures of mass independent sulfur isotope fractionation very few data points plot along the primary archean photochemical array suggesting a weak photolytic control over the data set instead other factors command a greater degree of influence such as pyrite paragenesis the prevailing depositional environment and non photolytic sulfur sources in relation to pyrite paragenesis reworked syngenetic sedimentary pyrite grains pyrite originally precipitated along the sediment water interface are characterized by negative 34s and 33s values suggesting open system conditions with respect to sulfate supply and the presence of microbial sulfate reducers on the contrary most reworked diagenetic sedimentary pyrite grains pyrite originally precipitated below the sediment water interface show positive 34s and negative 33s values suggesting closed system conditions negligible 33s anomalies from epigenetic pyrite suggest that the sulfur was sourced from a mass dependent or isotopically homogenous metamorphic hydrothermal fluid contrasting sulfur isotope compositions were also observed from different depositional environments namely fluvial conglomerates and marine modified fluvial conglomerates the bulk of the pyrite grains from fluvial conglomerates are characterized by a wide range of 34s values 6 2 to 4 8 and small 33s values 0 3 this signature likely represents a crustal sulfate reservoir derived from either volcanic degassing or from weathering of sulfide minerals in the hinterland reworked sedimentary pyrite grains from marine modified fluvial conglomerates share similar isotope compositions but also produce a positive 33s 34s array that overlaps with the composition of archean barite suggesting the introduction of marine sulfur these results demonstrate the presence of multiple sources of sulfur which include atmospheric crustal and marine reservoirs the prevalence of the mass dependent crustal sulfur isotope signature in fluvial conglomerates suggests that sulfate concentrations were probably much higher in terrestrial settings in comparison to marine environments which were sulfate deficient however the optimum conditions for forming terrestrial sedimentary pyrite were probably not during fluvial progradation but rather during the early phases of flooding of low angle unconformities i e during retrogradational fluvial deposition coupled in some cases with marine transgressions immediately following inflection points of maximum rate of relative sea level fall

lithofacies control on multiple sulfur isotope records and neoarchean sulfur cycles abstract triple sulfur isotope ratios 32 s 33 s 34 s were measured for 141 bulk rock samples from two agouron scientific drill cores gkp01 and gkf01 that recovered neoarchean successions of the transvaal supergroup south africa these two deep time cores are correlated to each other with 14 tie lines using volcanic and impact spherule layers in a sequence stratigraphic framework allowing us to evaluate both lithofacies and temporal controls over multiple sulfur isotope systematics the ca 2 5 ga giga annum before present basinal klein naute formation and the ca 2 6 ga peritidal boomplaas and vryburg formations yield an array of data characterized by 33 s 1 4 34 s these linear trends are found in both shallow water and deepwater facies but are characteristic to rocks with high iron content suggesting these may reflect isotopic compositions of aqueous sulfide elemental sulfur reservoirs in the neoarchean oceans data that deviate from this linear array are interpreted as resulting from additional inputs of sulfide from microbial sulfate reduction with or without contribution from sulfur disproportionation sulfate derived sulfur evolved to be either enriched or depleted in 34 s depending on the local depositional environment for example the reivilo formation in core gkf01 is characterized by abundant microbialite textures and shows an isotopic signature of closed system sulfate reduction rapid cementation of these carbonate fabrics may have attenuated the supply of sulfate to pore waters resulting in the progressive 34 s enrichments during bacterial sulfate reduction below the sediment water interface in contrast signatures of open system sulfate reduction are associated with slope facies dominated by granular dolostones preserved in the upper nauga formations in gkf01 and gkp01 the two different sulfur isotope patterns interpreted to reflect closed versus open system sulfate reduction are both found in the lower reivilo formation in both cores this lateral variation of isotope signals documents that observed 34 s shifts can be controlled locally and may not have temporal significance this study demonstrates critical importance of recovering sulfur isotope data from stratigraphically correlated drill cores to evaluate both geographical and temporal shifts of sulfur cycles and their links to the great oxidation event at the end of the archean eon

a review of the application of multiple s isotopes to magmatic ni cu pge deposits and the significance of spatially variable δ33s values the determination of 33 s values in conjunction with 34 s values provides an effective means of evaluating the importance of s derivation from archean country rocks in magmatic ni cu pge ore genesis particularly where 34 s values of potential s source rocks are near 0 and similar to most s of mantle derivation however 33 s values of sulfides in some archean rocks may also be near 0 care should be taken in the evaluation of s derivation from archean rocks based solely on this parameter although anomalous 33 s values are found primarily in archean rocks rare occurrences of nonzero 33 s values have been identified in sulfides from younger rocks and hence knowledge of the multiple s isotope composition of potential contaminants is essential for an accurate assessment of s contamination of mantle derived magmas restricted ranges in 33 s values may be characteristic of particular archean formations and when used in conjunction with mixing calculations may fingerprint a distinct s source rock spatial variability in 33 s values within different types of mineralized systems may be caused by the emplacement of isotopically distinct magma pulses by locally variable mixing proportions and the addition of secondary sulfide to the primary assemblage in the case of conduit type deposits in the midcontinent rift system three component mixing calculations show that both high and low 33 s values in some units that are similar to end member values in the archean country rocks must be a function of assimilation of primarily archean s even though proterozoic carbonaceous sedimentary country rocks contain in excess of 1 wt s and are particularly viable s source rocks

how sulfate driven anaerobic oxidation of methane affects the sulfur isotopic composition of pyrite a sims study from the south china sea abstract sulfate driven anaerobic oxidation of methane so4 aom in marine sediments commonly leads to the precipitation of pyrite it is however frequently challenging to unequivocally unravel the entire history of pyritization because of the common coexistence of so4 aom derived pyrite with pyrite resulting from organiclastic sulfate reduction osr to better understand how so4 aom affects pyritization in methane bearing sediments and how this can be identified we applied secondary ion mass spectroscopy sims to analyze the sulfur isotope composition 34s of authigenic pyrite in addition to sulfur isotope measurements of bulk sulfide and hand picked pyrite aggregates from the two seafloor sites hs148 and hs217 in the shenhu seepage area south china sea authigenic mostly tubular pyrite aggregates from these sites consist of three types of pyrite framboids zoned aggregates with radial overgrowths surrounding a framboidal core and euhedral pyrite crystals framboids with low sims 34s values as low as 41 6 at hs148 and 38 8 at hs217 are dispersed throughout the cores but are especially abundant in the shallow part of the sedimentary column i e above 483 cmbsf in hs148 above 670 cmbsf in hs217 these patterns are interpreted to reflect the dominance of osr during early diagenetic processes in the shallow sediments with increasing depth both 34s values of bulk sulfide minerals and hand picked pyrite aggregates increase sharply at 483 cmbsf in core hs148 and at 700 cmbsf in core hs217 respectively radial pyrite overgrowths and euhedral crystals become abundant at depth typified by high 34s values for hand picked pyrite moreover sims analysis reveals an extreme variability of 34s values for the three pyrite types on a small scale in these zones besides some moderately 34s enriched framboids most of the overgrowths and euhedral crystals display extremely high sims 34s values as high as 114 8 at hs148 and 74 3 at hs217 representing the heaviest stable sulfur isotope composition of pyrite ever reported to the best of our knowledge such an abrupt and extreme increase in 34spyrite values with depth is best explained by an enrichment of 34s in the pool of dissolved sulfide caused by so4 aom in the sulfate methane transition zone smtz the increase in 34s values from framboidal cores to overgrowth layers and euhedral crystals indicates continuous and finally near to complete exhaustion of dissolved sulfate at the smtz following a rayleigh distillation process so4 aom allowed for subsequent growth of later stage pyrite over the initial framboids part of which formed earlier and at shallower depth by osr the combination of a detailed petrographic study of authigenic pyrite with sims analysis of stable sulfur isotopes in organic rich strata proves to be a powerful tool for reconstructing the dynamics of sulfur cycling in modern and potentially ancient sedimentary sequences

summer rainfall variability in low latitude highlands of china and subtropical indian ocean dipole abstractbased on reanalysis and observational datasets this study proposes a reasonable mechanism for summer rainfall variations over the low latitude highlands llh of china in which a subtropical indian ocean dipole siod like pattern is the key external thermal forcing in summers with a positive siod like pattern sea surface temperature sst anomalies may lead to lower tropospheric divergence over the tropical indian ocean and convergence over the subtropical southwestern indian ocean and arabian sea the convergence over the arabian sea can induce easterly anomalies of the divergent wind component off the eastern coast of the bay of bengal bob while the divergence over the tropical indian ocean can change the interhemispheric vertical circulation and produce a descending motion over the same area and cyclonic anomalies in the rotational wind component over the indian peninsula the combined effect of the divergent and rotational wind anomalies and enhanced interhemispheric vertical circulati

atmospheric sulfur rearrangement 2 7 billion years ago evidence for oxygenic photosynthesis mass independently fractionated sulfur isotopes mif s provide strong evidence for an anoxic atmosphere during the archean moreover the temporal evolution of mif s shows increasing magnitudes between 2 7 and 2 5 ga until the start of the great oxidation event g o e at around 2 4 ga the conclusion of a completely anoxic atmosphere up to the g o e is in contrast to recent studies on redox sensitive elements which suggest slightly oxidizing conditions during continental weathering already several hundred million years prior to the g o e in order to investigate this apparent inconsistency we present multiple sulfur isotopes for 2 71 ga pyritic black shales derived from the kidd creek area ontario canada these samples display high positive 33s values up to 3 8 and the typical late archean slope in 36s 33s of 0 9 in contrast the time period before 3 2 2 73 ga is characterized by greatly attenuated mif s magnitudes and a slope in 36s 33s of 1 5 we attribute the increase in 33s magnitude as well as the contemporaneous change in the slope of 36s 33s to changes in the relative reaction rate of different mif s source reactions and changes in atmospheric sulfur exit channels both of these are dependent on atmospheric ch4 co2 and o2 mixing ratios we propose a distinct change in atmospheric composition at 2 7 ga resulting from increased fluxes of oxygen and methane as the best explanation for the observed neoarchean mif s record our data and modeling results suggest that oxygenic photosynthesis was a major contributor to primary productivity 2 7 billion years ago

sedimentation rates basin analysis and regional correlations of three neoarchaean and palaeoproterozoic sub basins of the kaapvaal craton as inferred from precise u pb zircon ages from volcaniclastic sediments abstract calculation of sedimentation rates of neoarchaean and palaeoproterozoic siliciclastic and chemical sediments covering the kaapvaal craton imply sedimentation rates comparable to their modern facies equivalents zircons from tuff beds in carbonate facies of the campbellrand subgroup in the ghaap plateau region of the griqualand west basin transvaal supergroup south africa were dated using the perth consortium sensitive high resolution ion microprobe ii shrimp ii dates of 2588 6 ma and 2549 7 ma for the middle and the upper part of the nauga formation indicate that the decompacted sedimentation rate for the peritidal flat to subtidal below wave base stratifera and clastic carbonate facies southwest of the ghaap plateau at prieska was of up to 10 m ma when not corrected for times of erosion and non deposition dates of 2516 4 ma for the upper gamohaan formation and 2555 19 for the upper monteville formation indicate that some 2000 m of carbonate and subordinate shale sedimentation occurred during 16 ma to 62 ma on the ghaap plateau for these predominantly peritidal stromatolitic carbonates decompacted sedimentation rates were of 40 m ma to over 150 m ma bubnoff units the mixed siliciclastic and carbonate shelf facies of the schmidtsdrif subgroup and monteville formation accumulated with decompacted sedimentation rates of around 20 b for the kuruman banded iron formation a decompacted sedimentation rate of up to 60 b can be calculated thus for the entire examined deep shelf to tidal facies range archaean and phanerozoic chemical and clastic sedimentation rates are comparable four major transgressive phases over the kaapvaal craton followed by shallowing upward sedimentation can be recognized in the prieska and ghaap plateau sub basins in griqualand west and partly also in the transvaal basin and are attributed to second order cycles of crustal evolution first order cycles of duration longer than 50 ma can also be identified the calculated sedimentation rates reflect the rate of subsidence of a rift related basin and can be ascribed to tectonic and thermal subsidence comparison of the calculated sedimentation rates to published data from other archaean and proterozoic basins allows discussion of general precambrian basin development siliciclastic and carbonate sedimentation rates of archaean and palaeoproterozoic basins equivalent to those of younger systems suggest that similar mechanical chemical and biological processes were active in the precambrian as found for the phanerozoic particularly for stromatolitic carbonates matching modern and neoarchaean sedimentation rates are interpreted as a strong hint of a similar evolutionary stage of stromatolite building microbiota the new data also allow for improved regional correlations across the griqualand west basin and with the malmani subgroup carbonates in the transvaal basin the nauga formation carbonates in the southwest of the griqualand west basin are significantly older than the gamohaan formation in the ghaap plateau region of this basin but are in part correlatives of the oaktree formation in the transvaal and of parts of the monteville formation on the ghaap plateau

decoupling of neoarchean sulfur sources recorded in algoma type banded iron formation abstract neoarchean algoma type banded iron formations bifs are widely viewed as direct chemical precipitates from proximal volcanic hydrothermal vents however a systematic multiple sulfur isotope study of oxide facies bif from a type locality in the ca 2 74 ga temagami greenstone belt reveals mainly bacterial turnover of atmospheric elemental sulfur in the host basin rather than deposition of hydrothermally cycled seawater sulfate or sulfur from direct volcanic input trace amounts of chromium reducible sulfur that were extracted for quadruple sulfur isotope 32s 33s 34s 36s analysis record the previously known mass independent fractionation of volcanic so2 in the archean atmosphere s mif and biological sulfur cycling but only minor contributions from juvenile sulfur despite the proximity of volcanic sources we show that the dominant bacterial metabolisms were iron reduction and sulfur disproportionation and not sulfate reduction consistent with limited availability of organic matter and the abundant ferric iron deposited as fe oh 3 that sulfur contained in the bif was not a direct volcanic hydrothermal input as expected changes the view of an important archive of the neoarchean sulfur cycle in which the available sulfur pools were strongly decoupled and only species produced photochemically under anoxic atmospheric conditions were deposited in the bif forming environment

iron and sulfur in the pre biologic ocean tentative geochemical cycles for the pre biologic earth are developed by comparing the relative fluxes of oxygen dissolved iron and sulfide to the atmosphere and ocean the flux of iron is found to exceed both the oxygen and the sulfide fluxes because of the insolubility of iron oxides and sulfides the implication is that dissolved iron was fairly abundant and that oxygen and sulfide were rare in the atmosphere and ocean sulfate produced by the oxidation of volcanogenic sulfur gases was the most abundant sulfur species in the ocean but its concentration was low by modern standards because of the absence of the river borne flux of dissolved sulfate produced by oxidative weathering of the continents these findings are consistent with the geologic record of the isotopic composition of sedimentary sulfates and sulfides except in restricted environments the sulfur metabolism of the earliest organisms probably involved oxidized sulfur species not sulfide

o2 constraints from paleoproterozoic detrital pyrite and uraninite redox sensitive detrital grains such as pyrite and uraninite in sedimentary successions provide one of the most conspicuous geological clues to a different composition of the archean and early paleoproterozoic atmosphere today these minerals are rapidly chemically weathered within short transport distances prior to the rise of oxygen low o2 concentrations allowed their survival in siliciclastic deposits with grain erosion tied only to physical transport processes after the rise of oxygen redox sensitive detrital grains effectively vanish from the sedimentary record to get a better understanding of the timing of this transition we examined sandstones recorded in a scientifi c drill core from the south african 2 415 ga koegas subgroup a mixed siliciclastic and iron formation bearing unit deposited on the western deltaic margin of the kaapvaal craton in early paleoproterozoic time we observed detrital pyrite and uraninite grains throughout all investigated sandstone beds in the section indicating the rise of oxygen is younger than 2 415 ga to better understand how observations of detrital pyrite and uraninite in sedimentary rocks can quantitatively constrain earth surface redox conditions we constructed a model of grain erosion from chemical weathering and physical abrasion to place an upper limit on ancient environmental o2 concentrations even conservative model calculations for deltaic depositional systems with suffi cient transport distances approximately hundreds of kilometers show that redox sensitive detrital grains are remarkably sensitive to environmental o2 concentrations and they constrain the archean and early paleoproterozoic atmosphere to have 3 2 10 5 atm of molecular o2 these levels are lower than previously hypothesized for redox sensitive detrital grains but they are consistent with estimates made from other redox proxy data including the anomalous fractionation of sulfur isotopes the binary loss of detrital pyrite and uraninite from the sedimentary record coincident with the rise of oxygen indicates that atmospheric o2 concentrations rose substantially at this time and were never again suffi ciently low 0 01 atm to enable survival and preservation of these grains in short transport systems

neoarchean carbonate associated sulfate records positive δ s anomalies mass independent fractionation of sulfur isotopes reported as 33s recorded in archean sedimentary rocks helps to constrain the composition of earth s early atmosphere and the timing of the rise of oxygen 2 4 billion years ago although current hypotheses predict uniformly negative 33 s for archean seawater sulfate this remains untested through the vast majority of archean time we applied x ray absorption spectroscopy to investigate the low sulfate content of particularly well preserved neoarchean carbonates and mass spectrometry to measure their 33 s signatures we report unexpected large widespread positive 33 s values from stratigraphic sections capturing over 70 million years and diverse depositional environments combined with the pyrite record these results show that sulfate does not carry the expected negative 33 s from sulfur mass independent fractionation in the neoarchean atmosphere

constraining atmospheric oxygen and seawater sulfate concentrations during paleoproterozoic glaciation in situ sulfur three isotope microanalysis of pyrite from the turee creek group western australia abstract previous efforts to constrain the timing of paleoproterozoic atmospheric oxygenation have documented the disappearance of large mass independent sulfur isotope fractionation and an increase in mass dependent sulfur isotope fractionation associated with multiple glaciations at least one of these glacial events is preserved in diamictites of the 2 4 ga meteorite bore member of the kungarra formation turee creek group western australia outcrop exposures of this unit show the transition from the boolgeeda iron formation of the upper hamersley group into clastic glaciomarine sedimentary rocks of the turee creek group here we report in situ multiple sulfur isotope and elemental abundance measurements of sedimentary pyrite at high spatial resolution as well as the occurrence of detrital pyrite in the meteorite bore member the 15 3 range of 33 s in one sample containing detrital pyrite 3 6 to 11 7 is larger than previously reported worldwide and there is evidence for mass independent sulfur isotope fractionation in authigenic pyrite throughout the section 33 s from 0 8 to 1 0 the 90 range in 34 s observed 45 5 to 46 4 strongly suggests microbial sulfate reduction under non sulfate limiting conditions indicating significant oxidative weathering of sulfides on the continents multiple generations of pyrite are preserved typically represented by primary cores with low 34 s 34 s 4 7 and enrichments in as ni and co the preservation of extremely sharp sulfur isotope gradients 30 p o 2 first became sufficiently high to permit pervasive oxidative weathering of continental sulfides yet remained low enough to permit the production and preservation of mass independent sulfur isotope fractionation

sulfur isotope mass independent fractionation in impact deposits of the 3 2 billion year old mapepe formation barberton greenstone belt south africa abstract theoretical and experimental studies have shown that atmospheric so 2 isotopologue self shielding effects in the 190 220 nm region of the solar spectrum are the likely cause for mass independent fractionation of sulfur isotopes s mif the main products of this photochemical reaction so 3 and s 0 typically define a compositional array of ca 33 s 34 s 0 06 0 14 this is at odds with the generally observed trend in archean sulfides which broadly defines an array of ca 33 s 34 s 0 9 various explanations have been proposed including a diminution of 34 s caused by chemical and biogenic mass dependent fractionation of sulfur isotopes s mdf mixing with photolytic products produced during felsic volcanic events or partial blocking of the low wavelength part of the spectrum due to the presence of reduced atmospheric gases or an organic haze early in earth history large meteorite impacts would have ejected dust and gas clouds into the atmosphere that shielded solar radiation and affected global climate it is thus likely that at certain time intervals of high meteorite flux the atmosphere was significantly perturbed having an effect on atmospheric photochemistry and possibly leaving anomalous sulfur isotopic signatures in the rock record here we describe the sulfur isotopic signatures in sulfides of spherule beds s2 s3 and s4 of the barberton greenstone belt south africa in particular in spherule bed s3 and to a lesser extent s4 a trend of ca 33 s 34 s 0 23 is observed that closely follows the expected trend for so 2 photolysis in the 190 220 nm spectral range this suggests that an impact dust cloud deposited as spherule beds which sampled the higher region of the atmosphere specifically incorporated products of so 2 photolysis in the 190 220 nm range and blocked photochemical reactions at higher wavelengths 250 330 nm band by implication the generally observed archean trend appears to be the result of mixing of different mif s sources arising from a variety of photochemical reactions that took place in the lower part of the atmosphere

potential influence of the november december southern hemisphere annular mode on the east asian winter precipitation a new mechanism as the leading mode of the global atmospheric mass inter annual variability the southern hemisphere annular mode sam may exert potential influences to the northern hemisphere nh climate but the related physical mechanism is not yet clear in this study it is found that the november december nd sam exhibits a significant inverse relationship with the winter precipitation over east asia particularly southern china observational and numerical evidences show that anomalous nd sam is usually associated with a south atlantic pacific dipole sea surface temperature anomaly ssta which persists into ensuring winter the dipole ssta can modulate the variability of the inter tropical convergence zone itcz in pacific subsequently a distinguished atmospheric tele connection pattern is induced and prevails over the nh mid latitude region as a response to the anomalous itcz large areas of high pressure anomalies are triggered at upper troposphere over east asia and centered over southern china which favors less precipitation over east asia particularly southern china and vice versa through such a physical mechanism the notable influence of the nd sam can sustain through the following season and impact on the nh winter climate

a revised classification scheme of pyrite in the witwatersrand basin and application to placer gold deposits abstract pyrite is the most abundant ore mineral in gold bearing quartz pebble conglomerates qpcs of the witwatersrand basin and similar archaean sedimentary units much of the pyrite in archaean conglomerates is detrital in origin implying that it survived weathering transport and reworking under anoxic conditions detrital pyrite is generally found together with authigenic pyrite formed in situ as a result of syn to post depositional processes as pyrite is frequently associated with gold mineralization many authors have developed different pyrite classification schemes in order to better understand the nature and origin of the mineralization although the different classifications cannot always be easily compared as they are largely based on inferred pyrite genesis we propose a revised entirely descriptive classification scheme for detrital and authigenic pyrite in archaean qpcs the scheme was created in order to provide a consistent framework for the petrographic description of pyrite in clastic sedimentary rocks detrital pyrite is subdivided into massive inclusion bearing and coarsely crystalline types authigenic pyrite includes euhedral overgrowth infill aggregate and pseudomorphic types we evaluate the methods used in pyrite classification propose formation pathways for detrital and authigenic pyrites and apply the classification scheme to some well known occurrences of detrital pyrite bearing conglomerates

mystery of the volcanic mass independent sulfur isotope fractionation signature in the antarctic ice core 1 we simulate the record of sulfur mass independent fractionation mif in sulfates found in the antarctic ice cores from the 1991 eruption of mt pinatubo discovery of mif in sulfur isotopes in archean early proterozoic sediments and lack of mif in sulfur in younger rocks placed a strict upper limit on the amount of oxidants and oxygen in the ancient earth s atmosphere prior to 2 3 gyr ago however recent measurements in ice cores suggest that some non zero mif in sulfate can be delivered to antarctica following large volcanic eruptions current photochemical experiments do not identify the specific reaction responsible for sulfur mif production here we show that a time dependent non zero sulfur mif can be delivered to the ground in the present atmosphere if the mif producing process is so3 photolysis fractionation from such photolysis has not been considered before but is consistent with the available experimental data

evidence for free oxygen in the neoarchean ocean based on coupled iron molybdenum isotope fractionation abstract most geochemical proxies and models of atmospheric evolution suggest that the amount of free o2 in earth s atmosphere stayed below 10 5 present atmospheric level pal until the great oxidation event goe that occurred between 2 2 and 2 4 ga at which time free o2 in the atmosphere increased to approximately 10 1 to 10 2 pal although photosynthetically produced o2 oases have been proposed for the photic zone of the oceans prior to the goe it has been difficult to constrain absolute o2 concentrations and fluxes in such paleoenvironments here we constrain free o2 levels in the photic zone of a late archean marine basin by the combined use of fe and mo isotope systematics of ca mg carbonates and shales from the 2 68 to 2 50 ga campbellrand malmani carbonate platform of the kaapvaal craton in south africa correlated fe and mo isotope compositions require a key role for fe oxide precipitation via oxidation of aqueous fe ii by photosynthetically derived o2 followed by sorption of aqueous mo to the newly formed fe oxides a dispersion reaction model illustrates the effects of fe oxide production and mo sorption to fe oxides and suggests that a few to a few tens of m free o2 was available in the photic zone of the late archean marine basin consistent with some previous estimates the coupling of fe and mo isotope systematics provides a unique view into the processes that occurred in the ancient shallow ocean after production of free o2 began but prior to oxygenation of the deep ocean or significant accumulation of free o2 in the atmosphere these results require oxygenic photosynthesis to have evolved by at least 2 7 ga and suggest that the neoarchean ocean may have had a different oxygenation history than that of the atmosphere the data also suggest that the extensive iron formation deposition that occurred during this time was unlikely to have been produced by anoxygenic photosynthetic fe ii oxidation finally these data indicate that the ocean had significant amounts of o2 at least 150 myr prior to previously proposed whiffs of o2 at the archean to proterozoic transition

mass dependent fractionation of quadruple stable sulfur isotope system as a new tracer of sulfur biogeochemical cycles abstract sulfur isotope studies of post archean terrestrial materials have focused on the ratio 34s 32s because additional isotopes 33s and 36s were thought to carry little information beyond the well known mass dependent relationship among multiple isotope ratios we report high precision analyses of 33s and 36s values defined as deviations of 33s and 36s from ideal mass dependent relationships for international reference materials and sedimentary sulfides of phanerozoic age by using a fluorination technique with a dual inlet isotope ratio mass spectrometer measured variations in 33s and 36s are explained as resulting from processes involve branching reactions two or more reservoirs formed or mixing irreversible processes in closed systems rayleigh distillation amplify the isotope effect we outline how this new isotope proxy can be used to gain new insights into fundamental aspects of the sulfur biogeochemical cycle including additional constraints on seawater sulfate budget and processes in sedimentary sulfide formation the isotope systematics discussed here cannot explain the much larger variation of 33s and 36s observed in archean rock records furthermore phanerozoic samples we have studied show a characteristic 33s and 36s relationship that differs from those measured in archean rocks and laboratory photolysis experiments thus high precision analysis of 33s and 36s can be used to distinguish small non zero 33s and 36s produced by mass dependent processes from those produced by mass independent processes in archean rocks and extraterrestrial materials

gold accumulation in the archaean witwatersrand basin south africa evidence from concentrically laminated pyrite abstract concentrically laminated pyrite is a relatively common although volumetrically minor component of auriferous conglomerates in the archaean ca 3 0 2 7 ga witwatersrand basin of south africa this type of pyrite contains high amounts several tens of ppm of au but the origin of the pyrite is debated and the timing of au deposition in these grains is not known in order to constrain the formation of pyrite we have studied concentrically laminated pyrite and other coexisting types of pyrite inclusion rich massive pyrite by analysing the contents and distribution of au and other trace elements by laser ablation icp ms the s and fe isotope composition by sims and the mineral inclusions by scanning electron microscope and laser raman spectroscopy trace element maps indicate that concentrically laminated pyrite is enriched in sb mn au ag tl cu mo mn and contains two types of gold finely dispersed au invisible gold with au ag 0 1 and likely of primary origin and au inclusions with au ag 10 of secondary origin the study of mineral inclusions revealed the presence of muscovite chlorite fine grained carbonaceous matter monazite ti oxides and quartz iron and multiple s isotopes suggest that concentrically laminated pyrite and inclusion rich pyrite were formed from two separate pools of s and fe with different isotope characteristics sulfur was derived from atmospheric s that had undergone mass independent isotope fractionation to form so 4 2 with negative 33 s that constituted concentrically laminated pyrite and elemental s with positive 33 s that formed inclusion rich pyrite iron pools were derived from partial oxidation of fe 2 so that concentrically laminated pyrite formed from a low 56 fe residual fe 2 average 0 2 and inclusion rich pyrite formed from a high 56 fe fe 3 pool average 2 7 biological activity may have been involved in the reduction of so 4 2 causing a wide spread of 34 s values 25 s reducing microorganisms as well as in the partial oxidation of fe 2 anaerobic photosynthetic fe reducers or photosynthetic o 2 producers and in the formation of pyrite from fe 3 dissimilatory fe reducers we propose that concurrent biogenically mediated pyrite formation and au trapping suggest that microbial activity was responsible for the accumulation of au and other trace elements e g sb mn ag tl cu mo mn which are commonly enriched in organic matter rich sediments