geochemical modeling of bacterially induced mineralization of schwertmannite and jarosite in sulfuric acid spring water mineralogy and geochemistry of a sulfuric acid spring water with a ph of 3 37 to 2 89 were investigated to verify the formation processes of iron minerals and the effects of bacteria on their formation to estimate the solubility of schwertmannite experimental dissolution in 10 0 mm h2so4 was conducted and this solubility data was used for geochemical modeling experimental incubation of the spring water containing bacteria was also performed and compared with a simulated abiotic system to evaluate the role of bacteria in the mineral formation the spring water seeps through cracks of hydrothermally altered andesitic rocks containing pyrite and precipitates schwertmannite and jarosite schwertmannite appears as a film like thin layer floating on the water surface and composed of aggregates of spherical particles with diameters of 1 to 5 m jarosite is produced as a precipitate on submerged rock surfaces the precipitate contains well crystallized jarosite spheres 5 to 10 m in diameter some ellipsoidal to rod shaped bacteria covered or decorated by poorly ordered iron minerals are also present in close association with the schwertmannite spheres results of the experimental incubation demonstrate that the oxidation rates of fe2 are 5 3 103 to 7 2 103 times greater than those of the simulated abiotic system suggesting that the formation of the iron minerals is promoted by bacterial oxidation of fe2 the dissolution experiment indicates that the solubility product of the schwertmannite having an average chemical composition of fe8o8 oh 5 9 so4 1 05 is approximately log k s 7 06 0 09 using this data geochemical modeling reveals that the spring water is supersaturated with respect to schwertmannite and also goethite and jarosite but undersaturated with respect to ferrihydrite additionally it is confirmed that the bulk solution chemistry deviates slightly into the stability field of goethite rather than jarosite this suggests that the aquatic environments in contact with the rock surfaces may be more acidic and or enriched in so2 4 relative to the bulk solution which may eventually lead to the formation of jarosite instead of goethite

bryozoan diversity in southern siberia at the devonian carboniferous transition new data confirm a resistivity to two mass extinctions abstract two spectacular mass extinctions namely the kellwasser and the hangenberg events affected the earth s biota during the late devonian early carboniferous diverse assemblages of bryozoans are known from the fasnian tournaisian deposits of southern siberia which includes such regions as the kuznetsk basin the kolyvan tom zone the rudny altay and the gorny altay our new data establish the stratigraphic ranges of 154 species which belong to 56 genera and 21 families these data have been analyzed quantitatively to measure the patterns of diversity dynamics and the changes in the taxonomic diversity structure the species diversity increased at the frasnian famennian transition after a short term but dramatic decrease in the middle famennian the total number of species accelerated in the late famennian and the tournaisian a similar pattern occurred for both genera and families although the radiation at the frasnian famennian transition was not as large and total family diversity decreased slightly in the tournaisian changes in total species diversity differed between orders of bryozoans changes in taxonomic diversity structure were moderately rapid the tournaisian species diversity was governed by the other genera comparing to the early time intervals thus our regional data suggest that bryozoans generally survived both the frasnian famennian and the devonian carboniferous mass extinctions confirming similar conclusions made earlier with global data however a mid famennian regional crisis diversity drop in the evolution of bryozoans is documented within southern siberia bryozoan radiations coincided with pulses of basin deepening that occurred during both mass extinction intervals perhaps explaining why bryozoans were resistant to extinction the mid famennian crisis might have been caused by a rapid regression coupled with basin shallowing

acid drainage reassessment of mining tailings black swan nickel mine kalgoorlie western australia abstract this paper describes the geochemical testing of mine tailings sourced from the black swan ni mine located near kalgoorlie western australia acid base accounting was used to provide an indication of the acid generating capacity of two kinds of mining tailings disseminated ore tailings from the cygnet tailings dam storage facility ctdsf and massive ore tailings from the silver swan tailings dam storage facility sstdsf all of the tailings in sstdsf have acid generating potential which is consistent with previous research reports new findings in this paper reveal that approximately 16 of the tailings in ctdsf have the potential to be acid generating in contrast previous reports state that the disseminated ore tailings are classified as non acid forming most of the potential acid generating tailings in the ctdsf are found in the upper middle sections of the tailings profile but some are located at the bottom of the tailings dam the upper middle section of the tailings is oxidized because these tailings have interacted with atmospheric o 2 and rain and surface water oxidation of the bottom tailings in the ctdsf may be due to infiltration of ground water into hidden fractures under the east bank of ctdsf which caused these tailings to oxidize under closed and reduced conditions the acid drainage in the tailings dam storage facility was observed 3 a after the development of the black swan nickel project this delayed production of acid drainage was likely due to the slow rates of acid neutralization provided by alteration gouge minerals such as mg fe carbonates magnesite siderite series associated with the ni ores the acid drainage leaking from the tailings dams has contaminated neighboring ground water via increased acidity and heavy metals because of the potential acid generation in some of the disseminated ore tailings it is inadvisable to use disseminated ore tailings as cover materials in the storage facility to isolate the underlying potentially acid forming tailings from o 2 and water as proposed by previous research reports

quantitative conodont based approaches for correlation of the late devonian kellwasser anoxic events we present the trends of absolute conodont abundance relative genera abundance and conodont morphometrics across the late devonian kellwasser horizons at three northern gondwanan epicontinental seaway locations at three contrasting depositional settings the kellwasser events are characterized by a decrease in conodont abundance high percentage of the conodont genus icriodus and morphological change of the conodont genus palmatolepis these changes can be identified in sections where the events are expressed as interbedded anoxic and oxic deposits as well as in settings characterized by continuous anoxic sediment accumulation hence these changes are interpreted as global and synchronous and can be thus used for event correlation the paradox of these results is that despite quite similar isotopic signals faunal change during the lower kellwasser event was less than during the upper kellwasser event we interpret that this discrepancy is due to an unconformity including topmost frasnian to earliest famennian at several f f sections which removed the record of peak paleoenvironmental change

examining the ladinian crisis in light of the current knowledge of the triassic biodiversity changes abstract several mass extinctions are known from the history of life but knowledge about minor biotic crises remains incomplete the ladinian is the second stage of the middle triassic epoch available reconstructions of the diversity dynamics of fossil organisms across the entire triassic allow the proposed ladinian biotic crisis to be investigated total biodiversity curves both the conventional curve and that based on sampling standardization fail to identify the crisis but this may be explained by low resolution data or noise in fact the global generic diversity of ammonoids brachiopods and tetrapods declined significantly by 1 1 2 5 times during the ladinian as did the species diversity of conodonts bivalves radiated but their origination rate also decreased during the ladinian land plants were apparently unaffected based on the representative regional record for the northwestern caucasus the number of macroinvertebrate genera dropped by 7 5 times and brachiopods almost totally disappeared foraminifers were also affected significantly thus the proposed biotic crisis appears to have been selective it appears the ladinian biotic crisis was a relatively long term event and its magnitude is comparable to that of other minor mass extinctions e g those of the silurian early jurassic or end cenomanian there are several possible explanations for what caused the ladinian biotic crisis it is possible that global climate cooling was responsible although it is unclear why the palaeobiogeographical differentiation was not favourable for a biotic radiation a eustatic explanation for the drop in diversity is unlikely instead the crisis was mostly likely caused by unstable recovery of the earth s biota after the end permian catastrophe

reconstruction of basal properties in ice sheets using iterative inverse methods inverse problems are used to estimate model parameters from observations many inverse problems are ill posed because they lack stability meaning it is not possible to find solutions that are stable with respect to small changes in input data regularization techniques are necessary to stabilize the problem for nonlinear inverse problems iterative inverse methods can be used as a regularization method these methods start with an initial estimate of the model parameters update the parameters to match observation in an iterative process that adjusts large scale spatial features first and use a stopping criterion to prevent the overfitting of data this criterion determines the smoothness of the solution and thus the degree of regularization here iterative inverse methods are implemented for the specific problem of reconstructing basal stickiness of an ice sheet by using the shallow shelf approximation as a forward model and synthetically derived surface velocities as input data the incomplete gauss newton ign method is introduced and compared to the commonly used steepest descent and nonlinear conjugate gradient methods two different stopping criteria the discrepancy principle and a recent improvement threshold are compared the ign method is favored because it is rapidly converging and it incorporates the discrepancy principle which leads to optimally resolved solutions

diagenetic cycling of arsenic in amazon shelf sediments in order to help elucidate major natural controls on the diagenetic behavior of as vertical profiles of total dissolved and solid phase as were measured in amazon shelf deposits a deltaic region little influenced by human activity arsenic distributions are typically characterized by subsurface porewater maxima and surficial solid phase enrichment maximum porewater as concentrations 2 4 m are an order of magnitude greater than levels reported in most other coastal marine environments and elevated concentrations extend several meters below the sediment surface dissolved as varies inversely with easily leachable as 40 140 nmol g 1 in the solid phase and directly with increases in solid phase fe ii these patterns reflect a strong redox coupling with fe whereby oxidized as is associated with fe oxyhydroxides in surface sediments then subsequently reduced and released upon burial in the extensive suboxic zone upward diffusion and intense physical reworking of sediments presumably releases the dissolved arsenic fraction to the water column or allows for re adsorption in surface sediments arsenic porewater concentrations generally increase away from the river in some cases regular seasonal variations are evident apparently corresponding to nonsteady state ingrowth of diagenetic profiles following extensive sediment reworking during rising river flow the massive cycling of as in amazon shelf sediments is likely due to the combined effects of intense chemical weathering in regions of the drainage basin production of oxides and a turbulent physical regime present on the shelf both of which promote sedimentary cycling of fe and coupled elements during early diagenesis

a continental drift flipbook abstract forty six miniature plate tectonic reconstructions are presented that can be assembled into a flipbook that illustrates the movement of the continents since the late precambrian 750 m yr ago six principal lines of evidence have been used to reconstruct the past positions of the continents 1 linear magnetic anomalies produced by sea floor spreading 2 paleomagnetism 3 hotspot tracks and large igneous provinces 4 the tectonic fabric of the ocean floor mapped by satellite altimetry 5 lithologic indicators of climate e g coals salt deposits tillites and 6 the geologic record of plate tectonic history i discuss the probable uncertainties associated with the plate tectonic reconstructions and give an estimate of the uncertainty in the positions of the continents back through time

late quaternary sedimentary environments and landforms in the ganges delta abstract late quaternary sediments deposited since the lowest stand of sea level during the last glacial maximum in the ganges delta and its surrounding region were classified into five units according to their sedimentary facies these are the lowest unit of sandy gravels the lower unit of sand with a few gravels and the middle upper and uppermost units consisting mainly of sand and silt with occasional peat layers the contact between the lower and middle units is fairly sharp and the upper part of the lower unit is oxidized in some places this suggests a period of subaerial exposure after the deposition of the lower unit during the low stand of sea level about the time of the last glacial maximum rivers in the ganges delta and its surrounding region dissected the surfaces of the region and deposited the lowest unit on the valley floors the lower unit was deposited over the lowest unit during an early stage of the post glacial transgression between ca 12 000 yr bp and 10 000 yr bp the surface of the delta was slightly dissected and the top of the lower unit was weathered and oxidized following this period the middle and upper units of alluvial or deltaic sand and silt with occasional peat were deposited the coastline in the early holocene retreated towards the central part of the present ganges delta in the middle and late holocene the silt and clay with occasional peat layers of the uppermost unit indicate that the lowland gradually became marshy and poorly drained as the rate of transgression became slower

mineralogy and geochemistry of alluvium contaminated by metal mining in the rio tinto area southwest spain the rio tinto in sw spain drains cu and pyrite mines which have been in operation since at least the bronze age extensive metal mining especially from 1873 to 1954 has resulted in contamination of the rio tinto alluvium with as cu pb ag and zn x ray diffraction xrd wavelength dispersive x ray mapping scanning electron microscope petrography and x ray energy dispersive edx analysis has revealed that 4 major groups of contaminant metal and as bearing minerals including sulphides fe as oxides fe oxides hydroxides oxyhydroxides and fe oxyhydroxysulphates occur in the alluvium sulphide minerals including pyrite chalcopyrite arsenopyrite and sphalerite occur in alluvium near the mining areas iron hydroxides and oxyhydroxides such as goethite and possibly ferrihydrite occur in cements in both the mining areas and alluvium downstream and carry minor amounts of as cu and zn iron oxyhydroxysulphates including jarosite plumbojarosite and possibly schwertmannite are the most common minerals in alluvium downstream of the mining areas and are major hosts of cu pb zn and of as next to the fe as minerals this work and other field observations suggest that 1 the extreme acidity and elevated metal concentrations of the river water will probably be maintained for some time due to oxidation of pyrite and other sulphides in the alluvium and mine waste tips and from formation of secondary oxide and oxyhydroxysulphates 2 soluble fe oxyhydroxysulphates such as copiapite which form on the alluvium are a temporary store of contaminant metals but are dissolved during periods of high rainfall or flooding releasing contaminants to the aqueous system 3 relatively insoluble fe oxyhydroxysulphates and hydroxides such as jarosite and goethite may be the major long term store of alluvial contaminant metals and 4 raising river ph will probably cause precipitation of fe oxyhydroxides and oxides hydroxides oxyhydroxides and thus have a positive effect on water quality but this action may destabilise some of these contaminant metal bearing minerals releasing metals back to the aqueous system

reef development at the frasnian famennian mass extinction boundary a newly compiled global reef database indicates that the 5 6 myr long frasnian late devonian metazoan reef episode had relatively lowdiversity compared to middle devonian highs w ith over 200 genera of calcitic rugose and tabulate corals following an initial early rise after late givetian coral and stromatoporoid extinctions reefs expanded for the last time during mid frasnian sealevel highstands but declined markedly in the late frasnian rhenana linguiformis conodont zones belowthe frasnian famennian f f boundary globally metazoan reefs were wiped out by the end frasnian some famennian reefs while partly retaining the structure of the underlying carbonate platform were built by cyanobacterial consortia such as renalcis rothpletzella girvanella and epiphyton during the famennian foraminiferans with calcite walls became abundant for the first time in the phanerozoic adding a newdimension to carbonate platforms colonial rugose corals phaceloid cerioid and thamnasterioid modules were absent in the early post extinction phases up into the mid famennian and very rare and non reefbuilding later but solitary deep water lazarus corals survived locally coral sponge reefs are unknown from the 21 myr long famennian also a time of very lowplatform carbonate production rare small isolated stromatoporoid sponge and lithistid sponge patch reefs returned episodically during the famennian in north america western europe australia and china the aragonitic stromatoporoids became extinct at the end of the famennian during a late devonian tectonically very active collisional caledonian mountain building phase oceanic and atmospheric cooling accompanied by sealevel lowstand systems exposed most carbonate platforms accelerating coastal erosion and karsting this increased the amount of clastics in the shelf slope setting in the last 1 3 myr prior to the f f boundary often burying reefs immediately following there were protracted losses in nearly all major tropical shelf benthic marine invertebrates exceeded only by the end permian extinctions in severity there is no apparent link between black organic rich horizons and reef demise at or close to the f f boundary the f f boundary not also marks the largest change from widespread flooded early and mid paleozoic continental cratons to narrow distal shelves but also spikes the largest known global phanerozoic shift in atmospheric o2 enrichment and co2 drawdown this threshold matched the rise of the first tropical rainforests and expansion of terrestrial biomes on the tropical coastal lowlands formerly occupied by carbonate platforms 6 2002 elsevier science b v all rights reserved

the behavior of trace elements during schwertmannite precipitation and subsequent transformation into goethite and jarosite schwertmannite is a ubiquitous mineral formed from acid rock drainage ard and plays a major role in controlling the water chemistry of many acid streams the formation of schwertmannite was investigated in the acid discharge of the monte romero abandoned mine iberian pyrite belt sw spain schwertmannite precipitated from supersaturated solutions mainly owing to the oxidation of fe ii to fe iii and transformed with time into goethite and jarosite in a few hours schwertmannite precipitation removed more than half of the arsenic load from solution whereas the concentration of divalent trace metals zn cu pb cd ni and co remained almost unchanged in the laboratory natural schwertmannite was kept in contact with its coexisting acid water in a flask with a solid liquid mass ratio of 1 5 for 353 days during this time the ph of the solution dropped from 3 07 to 1 74 and the concentrations of sulfate and fe increased during the first 164 days schwertmannite transformed into goethite plus h3o jarosite but subsequently goethite was the only mineral to form some of the trace elements such as al cu pb and as were depleted in solution during the first stage as schwertmannite transformed into goethite plus h3o jarosite on the contrary the transformation of schwertmannite to goethite with no jarosite during the second stage released al cu and as to the solution despite the variation in their concentrations in solution approximately 80 of the total al and cu inventories and more than 99 as and pb remained in the solid phase throughout the entire aging process

chemical characteristics and acid drainage assessment of mine tailings from akara gold mine in thailand acid mine drainage amd is a great concern in many abandoned mines because of its adverse effect on the environment in mining processes many kinds of wastes are produced these wastes may become eventually sources of environmental degradation the focus of this study is the geochemical characterization of the end processed tailings generated by akara gold mine the biggest gold mine in thailand tailing samples were systematically collected for analyses of chemical and mineralogical compositions as a result their quantitative chemical analyses are slightly different from place to place but mineral components cannot be clearly differentiated for instance it may be assumed that the end processed tailings which were a mixture between high and low grade concentrates would have similar mineral components however the little variation of chemical composition may be caused by the ore refining processes that are somehow varied in proportion to chemical additives alkali cyanide and quick lime in particular in addition clay composition in ore bearing layers may also influence alumina content of tailings accordingly distribution of the tailings is not related to depth and distance of the tailing storage pond because the disposal has sped them over the pond during operation total heavy metals of the tailing samples were analyzed on the basis of the epa 3052 method consequently the most toxic elements e g co cu cd cr pb ni and zn were found falling within the standard of thailand soil quality standards for habitat and agriculture only mn appears to have higher content than the standard in addition leaching tests proved that these tailings contain low metal concentrations as a result at ph 2 mn can leach out exceeding the thailand surface water quality standard for agricultural mn 1 ppm and the thailand industrial effluent standard 5 ppm although leachate at ph 4 and neutral conditions contains lower mn than the industrial effluent standard it still exceeds the surface water quality standard interestingly pb can be leached out exceeding both standards 0 2 ppm for the industrial effluent standard and 0 05 ppm for the surface water quality standard for ni leaching its concentration is lower than the industrial effluent standard at all ph conditions but still exceeds the surface water standard at ph 2 and 4 this information should be taken into consideration for further environmental monitoring acid generating potential of the tailings was estimated using acid base accounting aba and net acid generation nag tests the results of aba and nag tests show that the tailing samples contain a high amount of sulfur however they also contain high acid neutralization capacity consequently these tailings may not have potential to generate acid drainage in the other words they can be classified as a non acid forming naf material however since these tailings contain some heavy metals e g ni mn and pb that are observed in leachates exceeding the standards at low ph the amd conditions may lead to heavy metal release therefore prevention of oxidizing process and dissolution should be considered with great care in addition mn and pb can also be leached at neutral conditions barrier of air and water clay layer for example should be placed over the tailings pound before covering by topsoil for re vegetation growing native grass is recommended for stabilization of the surface and reducing erosion rate monitoring of water quality should also be carried out annually

81kr in the great artesian basin australia a new method for dating very old groundwater abstract the measurement of cosmogenic 81kr t1 2 2 29 0 11 105 yr has been proposed for many years as a reliable tool for groundwater dating in the range from 105 to 106 yr in this paper we report on the first use of 81kr to determine the age of groundwater from four wells in the great artesian basin in australia as the concentration of 81kr in old groundwater is only a few hundred atoms per liter krypton was extracted from large 16 000 l groundwater samples and was analyzed for the isotopic abundance of 81kr by accelerator mass spectrometry ams with a cyclotron 81kr kr isotope ratios of 1 54 0 22 10 13 1 78 0 26 10 13 2 19 0 28 10 13 and 2 63 0 32 10 13 respectively were measured for these samples it is reasonable to assume that krypton dissolved in surface water in contact with the atmosphere has the known atmospheric 81kr kr ratio of 5 20 0 40 10 13 the observed reduction of isotope ratios in the groundwater samples can then be interpreted as being due to radioactive decay since recharge this results in respective groundwater ages of 4 02 0 51 105 yr 3 54 0 50 105 yr 2 87 0 38 105 yr and 2 25 0 42 105 yr the main emphasis of this paper lies on the description of the analytic procedure to extract a reliable 81kr signal from large groundwater samples although the uncertainties are still relatively large primarily due to counting statistics caused by the low cyclotron ams efficiency the new technique enabled for the first time a definite determination of residence times for old groundwater with 81kr it thus confirms the hope that this radionuclide may become a very valuable tool for groundwater dating

mineralogy and geochemistry of tropical rain forest soils ashanti ghana abstract a detailed study of the pedology mineralogy and geochemistry of soils and underlying saprolite has been made in the ashanti area of southwest ghana the soils in the area are kaolinite muscovite ferrasols and vary in thickness from 1 to 10 m depending on saprolite lithology topography and drainage porosity and eh decrease with depth in the soil profile while ph and grain density increased the dominant minerals are kaolinite muscovite goethite and this is reflected in the major element chemistry which is essentially sio 2 al 2 o 3 fe 2 o 3 h 2 o with minor amounts of k 2 o and tio 2 similar geochemical dispersion patterns are present for most elements in the lower or b soil horizons as in the saprolite with a similar correlation between the elements however these patterns are greatly modified in the surface or a soil horizon and the correlation is lost elements such as se mo as cd sb and pb appear to be naturally concentrated by soil processes in the a horizon while other elements such as th y and zr appear concentrated in the b horizon consideration of the trace element distribution patterns indicates that the present weathering profile appears to represent a truncated mature lateritic profile capped by a thin recent organic rich surface soil

the multiple impacts hypothesis for mass extinction a comparison of the late devonian and the late eocene abstract application of the lag time multiple impacts hypothesis poag 1997b palaios 12 582 590 poag et al 2001 columbia univ press to the late devonian leads to the prediction that the frasnian famennian pulsed extinctions were triggered by a rapid drop in global temperature that followed an impact produced anomalous warm interval which interrupted the global cooling trend from the middle devonian greenhouse to the early carboniferous icehouse in actualistic comparison with the late eocene the lag time multiple impacts hypothesis would predict that a frasnian interval of multiple impacts should have occurred between 367 7 and 366 7 ma the fact that three impacts the alamo siljan and flynn creek do occur either within this predicted interval or close to it in time is corroborative evidence that the lag time multiple impacts hypothesis may indeed provide the causal mechanism for the frasnian famennian mass extinction based on the application of the lag time multiple impacts hypothesis to the frasnian famennian mass extinction it is here suggested that future searches for evidence of impact events in the late devonian be concentrated in strata that occur in the frasnian transitans to early hassi zonal interval and not in strata immediately below or above the frasnian famennian boundary

a mineralogical and geochemical study of element mobility in sulfide mine tailings of fe oxide cu au deposits from the punta del cobre belt northern chile two flotation tailings sites ojancos and p cerda from the fe oxide cu au punta del cobre belt south of copiapo atacama desert northern chile are geochemically largely using sequential extractions and mineralogically compared main ore minerals are pyrite magnetite and or hematite and chalcopyrite gangue is dominantly calcite with minor quartz the host silicate assemblage is largely controlled by hydrothermal alteration and consists of variable amounts of the following minerals k feldspar ca amphibole biotite sericite chlorite tourmaline epidote quartz in this study both the ojancos and the p cerda tailings were deposited in valley dam impoundments and when they were filled new tailings were deposited upstream as a result high quantities of seepage migrated downstream into the older tailings impoundment at ojancos the recent upstream tailings have excess of acid potential 7 1 wt calcite and 3 5 wt pyrite whereas the older downstream tailings are characterized by alternations of several meter thick intervals with high neutralizing potential about 40 wt calcite and 2 wt pyrite and intervals with high acid potential about 3 wt calcite and 4 wt pyrite acid mine drainage amd with the precipitation of schwertmannite ph 3 15 and chalcoalumite ph 4 9 flows out at the interface between the uphill and downstream tailings strong downstream element transport is taking place and contributes to the formation of the cementation zone mainly gypsum ferrihydrite and goethite and locally jarosite in the older downstream impoundment the cementation zone ph 4 shows strong enrichment of heavy metals e g up to 6800 ppm cu 680 ppm zn 1100 ppm as mainly adsorbed and as secondary sulfides e g covellite in contrast at the p cerda tailings impoundment carbonates are homogeneously distributed and the overall neutralization potential exceeds the acid potential average of about 10 wt calcite and up to 2 5 wt pyrite the up to 5 m thick oxidation zones paste ph 6 9 8 3 at p cerda are characterized by interlayering of coarser dark gray unoxidized layers with fine grained fe iii hydroxide rich ochre to red brown colored horizons the hyperarid climate dries out first the coarse sulfide rich horizons of the tailings and limits so the oxidation which is restricted to the fine grained due to their higher moisture retention capacity however results indicate that during operation an important element transfer from the younger upstream tailings to the older downstream tailings impoundment took place possibly by sorptive transport at ferric polymers or colloids in the form of neutral mine drainage nmd this would explain the metal enrichments in the cementation zone which are mainly associated to the exchangeable fraction and not as secondary sulfides this results in both cases in ojancos mainly as amd and in p cerda mainly as nmd in fe iii input as ferric cation as ferric polymer or co3 complexes to the downstream impoundment this constitutes a very effective acid potential transfer to the older downstream material because oxidation via input of external fe iii produces 16 mol of protons per mol fes2 i e eight times more than via oxidation with oxygen in addition the created acidity favors dissolution of the abundant fe oxides magnetite and hematite of this ore deposit type providing so additional fe iii for sulfide oxidation

arsenic in the wiśniowka acid mine drainage area south central poland mineralogy hydrogeochemistry remediation abstract this paper summarizes different aspects of arsenic mineralogy and geochemistry in the wi niowka acid mine drainage amd area south central poland the basic source of this metalloid in amd water bodies is micro grained pyrite that forms two different mineralized zones within the upper cambrian rock formation due to specific textural and geochemical characteristics this mineral undergoes rapid oxidation on exposed quarry walls and unvegetated tailings piles thus contributing to elevated arsenic concentrations in acid pit lakes and ponds and locally intermittent pools the latter were highlighted by the highest as levels reaching even 370 mg l of the three amd large reservoirs the podwi niowka eastern lake revealed distinctly raised as concentrations varying from 7 02 to 22 2 mg l another interesting water body is the marczakowe doly acid pond showing diverse seasonal as concentration patterns in colloids and a water column results of geochemical modeling showed that the saturation indices si of hematite and goethite exhibited the highest values range of 6 96 to 12 84 and 2 47 to 5 39 respectively tending to precipitate in all the water bodies examined in addition the positive si values of nanosized e fe2o3 1 64 to 4 13 and schwertmannite 0 90 to 2 10 were found only in the wi niowka duza and marczakowe doly acid waters laboratory experiments revealed that the best chemical and cost effective method out of the limited number of options of arsenic removal from the amd waters examined was the use of high grade powdered limestone fraction 0 0 0 09 mm or more effective although more expensive limewater calcium hydroxide the positive si values of hematite goethite e fe2o3 and schwertmannite of neutralized solutions suggest that these minerals should precipitate due to diverse concentrations in the examined rock series arsenic has been used for fingerprinting hot places within the mining and neighboring areas as well as for predicting the directions and effects of strip mining for quartzites the as signature can also be applied to monitor a detrimental amd impact on local surface and underground waters

calibrating the devonian time scale a synthesis of u pb id tims ages and conodont stratigraphy the recalibrated devonian time scale represents an important improvement of devonian chronology regarding two aspects firstly a data set of 13 biostratigraphically well bracketed u pb id tims zircon and monazite ages constitutes the framework of the scale secondly approximately time linear biostratigraphic scales have been used for the interpolation between the isotopic ages the new construction thus represents a biochronometric time scale which allows the assignment of numeric ages not only to stage boundaries but also to each biozone boundary the method of interpolation applied also enables the projection of the geochronological error onto the time scale according to the newly calibrated scale the devonian lasted 57 4 5 7 ma from 418 1 3 0 to 360 7 2 7 ma this is compared to previously published time scales the longest time span ever calculated for this period the age interpolations for the eight stage boundaries are famennian tournaisian devonian carboniferous 360 7 2 7 ma frasnian famennian 376 1 3 6 ma givetian frasnian 383 7 3 1 ma eifelian givetian 388 1 2 6 ma emsian eifelian 391 9 3 4 ma pragian emsian 409 1 3 8 ma lochkovian pragian 412 3 3 5 ma pridolian lochkovian silurian devonian 418 1 3 0 ma full size table table options view in workspace download as csv the duration of the middle devonian is calibrated here as quite short with 8 2 ma and the emsian and the famennian are the longest stages with interpolated durations of 17 2 and 15 4 ma respectively together all devonian stages contain 57 conodont zones including subzones according to the standard conodont zonation giving a mean duration of about 1 ma in the highly resolved part of the time scale mid eifelian to the devonian carboniferous boundary zonal resolution averages 0 6 ma in contrast the lowest resolution is shown in the early emsian to mid eifelian interval with zonal durations of up to 5 5 ma serotinus zone

spatial variability of arsenic in some iron rich deposits generated by acid mine drainage abstract potential contamination of rivers by trace elements can be controlled among others by the precipitation of oxyhydroxides the streambed of the studied area located in la ch taigneraie district lot river basin france is characterised by iron rich ochreous deposits acidic ph 2 7 4 8 and so 4 mg waters beyond the acid mine drainage the presence of as both in the dissolved fraction and in the deposits is also a problem upstream at the gallery outlet as concentrations are high as max 2 6 mol l and up to 5 wt locally respectively in the dissolved and in the solid fractions downstream as concentrations decrease below 0 1 mol l in the dissolved fraction and to 1327 mg kg in the solid fraction this natural attenuation is related to the as retention within ochreous precipitates amorphous to poorly crystalline fe oxyhydroxides schwertmannite and goethite which have great affinities for this metalloid upstream schwertmannite is dominant while downstream goethite becomes the main mineral the transformation of schwertmannite into goethite is observed in the upstream deposits as schwertmannite is unstable relative to goethite furthermore thermodynamic calculations indicate that the downstream goethite is not able to precipitate in situ according to the water chemistry goethite mainly results from the transformation of schwertmannite and its solid transport downstream moreover as highlighted by leaching experiments carried out on the ochreous precipitates this transformation does not seem to affect the as retention in solids as no release of as was observed in the solution arsenic may either be strongly trapped by co precipitation in the present minerals or it may be quickly released and re adsorbed on the precipitate surface

weathering of bi bearing tennantite abstract the tennantite tetrahedrite solid solution series called fahlore cu ag 6cu4 fe zn cu hg cd 2 sb as bi te 4 s se 13 is widespread in many geological environments since it incorporates heavy metals and toxic elements a better understanding of its weathering behaviour and details of its weathering process is important to evaluate environmental risks emerging mainly from the mobilization of as sb bi and local and global metal fluxes in stream waters and oceans in this study weathering of bi rich members of this mineral group was investigated using microscopy empa sem tem la icp ms raman xrd and mla observations reveal a succession of four distinct stages of weathering during stage 1 irregular tubes within fahlore show an assemblage of nm to m sized romeite group minerals tripuhyite crystalline cu oxides and cu sulfides stage 1 textures and secondary sulfides indicate a low redox potential and a low fluid rock ratio typical of cementation zones mass balance calculations show that during this stage all zn and the majority of as and s are released to the weathering fluids bismuth is immobile in this stage and sb and fe are immobile if bi is sufficiently available from fahlore but both are partly released if the fahlore did not contain sufficient bi during stage 2 amorphous and nano crystalline arsenates replace fahlore as weathering fronts such assemblages indicate a higher redox potential than in stage 1 typical for oxidation zones mass balance calculations reveal that zn sb s and partially cu are lost arsenic and bi are immobile stage 3 occurs only locally dissolving former weathering stages and or precipitating amorphous cu arsenates silicates reflecting processes in micro compartments not characteristic for the general weathering process stage 4 is characterized by the formation of crystalline bi cu ba ca or al bearing arsenates and cu carbonates spatially independent of the precursor fahlore copper and as originate from older weathering assemblages whereas many other elements are derived externally ca ba al this stage reflects the increasing importance of the local host rock and gangue mineralogy as it is typical in near surface environments of oxidation zones or on mine dumps where elements are highly mobile and a high fluid rock ratio prevails gossan mineralization the temporal evolution of fahlore weathering textures reflects the transition from fresh ore to cementation zone oxidation zone and gossan assemblages in one hand specimen thus one fahlore grain can record the uplift and erosion and the increasing fluid rock interaction of a weathered ore deposit with time tube like textures similar to the ones observed in stage 1 have been reported from other weathering environments and from a variety of element oxide arsenide and sulfide phases they also were produced during experimental work in ilmenite this is clear evidence that the diffusive process during the first contact with alteration fluids is a basic physical process and that it is not only valid for fahlore the importance of bi to stabilize sb bearing supergene phases and thereby for the immobilization of toxic sb shown in the present work may stimulate further investigations on the environmental immobilization of toxic elements by companion metals during weathering processes

arsenic and metal mobility from au mine tailings in rodalquilar almeria se spain in the old mining area of rodalquilar mine wastes soil and sediments were characterized and the results revealed high concentration of au ag as bi cu fe mn pb se sb and zn in tailings and sediments the contaminant of greatest environmental concern is as the mean concentration in the tailings was 679 9 and 345 mg kg in the sediments of playazo creek the groundwater samples from the alluvial aquifer showed high concentration of al as cd fe hg mn ni pb se sb and zn and very high concentration of chloride and sulfate which were above the concentration defined in the european standards for drinking water the presence of as in groundwater may be caused by the oxidation of arsenian pyrite the possible as desorption from goethite and ferrihydrite and the jarosite dissolution groundwater concentrations of cd fe mn and possibly cu were associated with low values of eh indicating the possible dissolution of oxy hydroxides of fe and mn the mobility of metals in the column experiments show the release of al fe mn cr cu ni v and zn in significant concentrations but below the detected values in groundwater however as cd sb se pb and au are generally mobilized in concentrations above the detected values in groundwater the possible mass transfer processes that could explain the presence of the contaminants in the aquifer and the leachates was simulated with the phreeqc numerical code and revealed the possible dissolution of the following mineral phases jarosite natrojarosite arsenian pyrite alunite chlorite kaolinite and calcite

the characterization of arsenic in mine waste arsenic is dispersed widely in nature and is the 47th most abundant element among the 88 known natural elements the average crustal abundance is 1 5 ppm with higher concentrations in reduced shales and coals it is concentrated in many metal bearing mineral deposits being a chalcophile element it occurs in many metallic deposits including those of cu ag au zn hg u sn pb mo w ni co and pge arsenic is often more dispersed than ore minerals in those deposits and as such is a useful indicator in geochemical exploration boyle and jonasson 1973 hale 1981 cohen and bowell 2014 consequently elevated concentrations of as are common in mine waste and process waste from metal bearing ores bowell et al 1994 2013 thornton 1994 craw and pacheco 2002 lazareva et al 2002 in particular as is the main element of environmental concern in most hardrock mines in this chapter we outline the principal occurrences of as at mine sites and their environmental significance as an example of the detailed controls on as geochemistry in mine waste we focus on the gold mines in new zealand many mines are significant point sources for as in the environment and some mine sites have high concentrations of as locally often exceeding 1 in ore or waste for almost all of these mines the as is a natural but undesirable component of the ore and therefore the as is discarded with the rest of the mine wastes hence mine wastes especially mine tailings are major repositories of as and have to be managed carefully view this table table 1 major primary mineral hosts for as in mine waste arsenic is an especially common constituent of sulfide bearing mineral deposits where as typically occurs either as separate as minerals table 1 or in solid solution

alteration of as bearing phases in a small watershed located on a high grade arsenic geochemical anomaly french massif central at a watershed scale sediments and soil weathering exerts a control on solid and dissolved transport of trace elements in surface waters and it can be considered as a source of pollution the studied subwatershed 1 5 km sup 2 was located on an as geochemical anomaly the studied soil profile showed a significant decrease of as content from 1500 mg kg sup 1 in the 135 165 cm deepest soil layer to 385 mg kg sup 1 in the upper 0 5 cm soil layer directly in the stream suspended matter and the 63 micro m fraction of bed sediments had as concentrations greater than 400 mg kg sup 1 in all these solid fractions the main representative as bearing phases were determined at two different observation scales bulk analyses using x ray absorption structure spectroscopy xas and microanalyses using scanning electron microscope sem and associated electron probe microanalyses epma as well as micro raman spectroscopy and synchrotron based micro scanning x ray diffraction micro sxrd characterization three main as bearing phases were identified i arsenates mostly pharmacosiderite the most concentrated phases as in both the coherent weathered bedrock and the 135 165 cm soil layer but not observed in the river solid fraction ii fe oxyhydroxides with in situ as content up to 15 4 wt in themore deepest soil layer and iii aluminosilicates the least concentrated as carriers the mineralogical evolution of as bearing phases in the soil profile coupled with the decrease of bulk as content may be related to pedogenesis processes suggesting an evolution of arsenates into as rich fe oxyhydroxides therefore weathering and mineralogical evolution of these as rich phases may release as to surface waters less

formulating an inverse problem to infer the accumulation rate pattern from deep internal layering in an ice sheet using a monte carlo approach using a monte carlo mc method we determine the accumulation rate profile along a flowband the influx of ice into the upstream end of the flowband and the age of an internal layer the data comprise the depth profile of the internal layer a few velocity measurements at the surface and the average accumulation at one location the data in our example were collected at taylor mouth a flank site off taylor dome antarctica we present three alternative formulations of this inverse problem depending on the formulation used this particular inverse problem can have up to four solutions each corresponding to a different spatial accumulation rate pattern this study demonstrates the ability of a mc method to find several solutions to this inverse problem and how to use a metropolis algorithm to determine the probability distribution of each of these different solutions the only disadvantage of the mc method is that it is computationally more expensive than other inverse methods such as the gradient method

geochemistry and stable sulfur and oxygen isotope ratios of the podwiśniowka pit pond water generated by acid mine drainage holy cross mountains south central poland abstract the paper presents the results of a geochemical and isotopic study of acidic pond water in the abandoned podwi niowka quarry poland the scope of investigations also encompassed mineralogical and isotopic studies of pyrite and related supergene minerals compared to similar sites throughout the world the pit pond water examined is characterized by a very low ph averaging 2 64 0 33 and simultaneously very low concentrations of so 4 2 geometric mean of 237 57 mg l 1 fe ii 4 8 3 4 mg l 1 fe iii 10 0 6 2 mg l 1 and other trace elements this acidity has been generated by complex processes of as rich pyrite oxidation combined primarily with hydrolysis precipitation and transformation of fe oxyhydroxysulfates and oxyhydroxides into goethite the specific mineralogy of ore and gangue minerals but especially the lack of acid buffering constituents has additionally contributed to the very low ph and element concentrations of the toxic elements the high content of as 1111 1879 mg kg 1 in the western part of pit pond sediment may be of great concern especially when using lime as a neutralizing agent of the acidic water the 34s of soluble so4 varied from 19 8 to 11 1 and was different from that of efflorescent sulfates 25 7 to 25 4 and host pyrite 25 4 2 5 the comparison of the 18o so 4 2 2 0 1 2 and 18o h2o 6 2 3 5 values indicated that the pyrite underwent bacterially catalyzed oxidation by two natural oxidants primarily by fe3 and to a lesser extent o2

inverse estimation of snow accumulation along a radar transect on nordenskioldbreen svalbard we present an inverse modeling approach to reconstruct annual accumulation patterns from ground penetrating radar gpr data a coupled surface energy balance snow model simulates surface melt and the evolution of subsurface density temperature and water content the inverse problem consists of iteratively calibrating accumulation serving as input for the model by finding a match between modeled and observed radar travel times the inverse method is applied to a 16 km gpr transect on nordenskioldbreen svalbard yielding annual accumulation patterns for 2007 2012 accumulation patterns with a mean of 0 75 meter water equivalent mwe a 1contain substantial spatial variability with a mean annual standard deviation of 0 17 mwe a 1 and show only partial consistency from year to year in contrast to traditional methods accounting for melt water percolation refreezing and runoff facilitates accurate accumulation reconstruction in areas with substantial melt additionally accounting for horizontal density variability along the transect is shown to reduce spatial variability in reconstructed accumulation whereas incorporating irreducible water storage lowers accumulation estimates correlating accumulation to terrain characteristics in the dominant wind direction indicates a strong preference of snow deposition on leeward slopes whereas weaker correlations are found with terrain curvature sensitivity experiments reveal a nonlinear response of the mass balance to accumulation changes the related negative impact of small scale accumulation variability on the mean net mass balance is quantified yielding a negligible impact in the accumulation zone and a negative impact of 0 09 mwe a 1in the ablation area

deposition in the kuznetsk basin siberia insights into the permian triassic transition and the mesozoic evolution of central asia abstract this paper describes the permian mesozoic stratigraphy of the kuznetsk basin southern siberia which is adjacent to the vast and hydrocarbon rich west siberian basin and on the edge of the siberian flood basalts the basin fill is permian to cretaceous in age and is dominated by non marine siliciclastics up to 7 km thick palaeocurrent indicators show dominant flow to the north northeast during the permian to jurassic fourteen lithofacies are grouped in three facies associations fluvial channel belt overbank and floodplain floodplain pond coal bearing permian siliciclastics are interpreted as meandering river deposits in a foreland basin with subsidence generated by thrust sheet loading from at least three basin margins these sediments pass abruptly but conformably upwards into coal barren sandstones and conglomerates and siltstones interpreted as braided river deposits two basalt flows occur within the coal barren succession a recently published precise ar ar age of 250 3 0 7 ma for the lower of these basalts

diversity and richness of the devonian terrestrial plants in the southeastern mountainous altay southern siberia regional versus global patterns abstract devonian deposits of the southeastern mountainous altay a large region in southern siberia contain abundant remains of terrestrial plants a semi quantitative analysis of this regional palaeobotanical record reveals how both the diversity number of taxa and richness number of taxa with an account of their abundances of floristic assemblages changed during the emsian early famennian time interval a total of 60 species representing 42 genera are known from 8 regional assemblages changes in diversity of species and genera occurred simultaneously the number of taxa was high in the early emsian declined in the late emsian rose again in the eifelian middle givetian dropped in the late givetian reached the highest values in the early frasnian and experienced the greatest decline taking place in the late frasnian early famennian the standing diversity number of taxa crossing the time boundaries was maximal in the middle devonian the dynamics of terrestrial plant richness was similar to that of diversity with an exception of middle givetian decline in richness despite growth of diversity the floras were dominated by pteridophytes propteridophytes were less abundant and pinophytes were very rare propteridophyte extinctions were high in the middle givetian concurrent with a brief decline in pteridophytes some regional and global patterns of floral dynamics were similar however propteridophyte decline was not abrupt globally the main abiotic driving factor influencing species richness and diversity appears to have been regional shoreline shifts it does not appear that climate changes was important for regional changes in phytodiversity although both regional and global phytodiversity was at its high during the middle devonian cooling phase a comparison of palaeobotanical data from the southeastern mountainous altay and kazakhstan suggests palaeogeographic proximity and proves an idea of altay mongolian terrane wandered between gondwana kazakhstan and siberia the early emsian and the early frasnian when floras of the study region were diverse and rich are characterized by the very high degree of similarity thus interregional floral exchanges would facilitate plant radiations

arsenic mobility in mildly alkaline drainage from an orogenic lode gold deposit bralorne mine british columbia abstract the historical 1932 1971 bralorne mine produced over 87 million grams of au from an archetypal orogenic lode gold deposit in southwest british columbia high concentrations of as in mine drainage however represent an on going environmental concern prompting a detailed study of effluent chemistry the discharge rate at the mine portal was monitored continuously over a fourteen month period during which effluent samples were collected on a quasi weekly basis water samples were also collected on synoptic surveys of the adit between the portal and the main source of flow in the flooded workings total concentrations of as in the mildly alkaline ph 8 7 portal drainage average 3034 g l whereas at the source they average 5898 g l as emergent waters from the flooded workings flow toward the portal their dissolved oxygen content and ph increase from 0 to 10 mg l and from 7 7 to 9 respectively near the emergence point dissolved fe precipitates rapidly sorbing both as iii and as v with increasing distance from the emergence point dissolved as iii concentrations drop to detection limits through sorption on hydrous ferric oxide and through oxidation to as v concentrations of dissolved as v on the other hand increase and stabilize reflecting lower sorption at higher ph and the lack of available sorbent nonetheless based on synoptic surveys approximately 35 of the source as load is sequestered in the adit resulting in as sediment concentrations averaging 8 5 wt the remaining average as load of 1 34 kg d is discharged from the portal partitioning of as v between dissolved and particulate phases in portal effluent is characterized by a sorption density of 0 37 mol as mol fe 1 and by a distribution coefficient k d of 130 l g hfo the relatively high sorption density may reflect co precipitation of as with fe oxyhydroxides rather than a purely adsorption controlled process results of this study show that the as self mitigating capacity of drainage from orogenic lode gold deposits may be poor in high ph and fe limited settings

architecture and mineral deposit settings of the altaid orogenic collage a revised model abstract the altaids are an orogenic collage of neoproterozoic paleozoic rocks located in the center of eurasia this collage consists of only three oroclinally bent neoproterozoic early paleozoic magmatic arcs kipchak tuva mongol and mugodzhar rudny altai separated by sutures of their former backarc basins which were stitched by new generations of overlapping magmatic arcs in addition the altaids host accreted fragments of the neoproterozoic to early paleozoic oceanic island chains and neoproterozoic to cenozoic plume related magmatic rocks superimposed on the accreted fragments all these assemblages host important many world class late proterozoic to early mesozoic gold copper molybdenum lead zinc nickel and other deposits of various types in the late proterozoic during breakup of the supercontinent rodinia the kipchak and tuva mongol magmatic arcs were rifted off eastern europe siberia and laurentia to produce oceanic backarc basins in the late ordovician the siberian craton began its clockwise rotation with respect to eastern europe and this coincides with the beginning of formation of the mugodzhar rudny altai arc behind the kipchak arc these earlier arcs produced mostly cu pb zn vms deposits although some important intrusion related orogenic au deposits formed during arc arc collision events in the middle cambrian and late ordovician the clockwise rotation of siberia continued through the paleozoic until the early permian producing several episodes of oroclinal bending strike slip duplication and reorganization of the magmatic arcs to produce the overlapping kazakh mongol and zharma saur valerianov beltau kurama arcs that welded the extinct kipchak and tuva mongol arcs this resulted in amalgamation of the western portion of the altaid orogenic collage in the late paleozoic its eastern portion amalgamated only in the early mesozoic and was overlapped by the transbaikal magmatic arc which developed in response to subduction of the oceanic crust of the paleo pacific ocean several world class cu mo porphyry cu pb zn vms and intrusion related au mineral camps which formed in the altaids at this stage coincided with the episodes of plate reorganization and oroclinal bending of magmatic arcs major pb zn and cu sedimentary rock hosted deposits of kazakhstan and central asia formed in backarc rifts which developed on the earlier amalgamated fragments major orogenic gold deposits are intrusion related deposits often occurring within black shale bearing sutured backarc basins with oceanic crust after amalgamation of the western altaids this part of the collage and adjacent cratons were affected by the siberian superplume which ascended at the permian triassic transition this plume related magmatism produced various deposits such as famous ni cu pge deposits of norilsk in the northwest of the siberian craton in the early mesozoic the eastern altaids were oroclinally bent together with the overlapping transbaikal magmatic arc in response to the northward migration and anti clockwise rotation of the north china craton the following collision of the eastern portion of the altaid collage with the siberian craton formed the mongol okhotsk suture zone which still links the accretionary wedges of central mongolia and circum pacific belts in the late mesozoic a system of continent scale conjugate northwest trending and northeast trending strike slip faults developed in response to the southward propagation of the siberian craton with subsequent post mineral offset of some metallogenic belts for as much as 70 400 km possibly in response to spreading in the canadian basin india asia collision rejuvenated some of these faults and generated a system of impact rifts

frasnian famennian mass extinction and cold water oceans suturing of laurussia and africa elimination of easterly tropical currents and consequent equatorial diversion of cold and possibly dysaerobic waters are suggested as prime causes of the frasnian famennian late devonian extinction these are explained by using a new paleogeographic model evidence for stepdown extinctions that took place from givetian through frasnian time is taken particularly from atrypoid brachiopods one of the most abundant representatives of the global tropical shelly marine benthos during the middle and late devonian only 5 of 17 frasnian genera or subgenera of atrypoids are known to be present in late frasnian sediments and possibly only a single genus spinatrypa was present at the frasnian famennian boundary evidence for stepdown extinction from other invertebrate and vertebrate groups in general corroborates that provided by brachiopods

assessing mine drainage ph from the color and spectral reflectance of chemical precipitates the ph of mine impacted waters was estimated from the spectral reflectance of resident sediments composed mostly of chemical precipitates mine drainage sediments were collected from sites in the anthracite region of eastern pennsylvania representing acid to near neutral ph sediments occurring in acidic waters contained primarily schwertmannite and goethite while near neutral waters produced ferrihydrite the minerals comprising the sediments occurring at each ph mode were spectrally separable spectral angle difference mapping was used to correlate sediment color with stream water ph r 2 0 76 band center and band depth analysis of spectral absorption features were also used to discriminate ferrihydrite and goethite and or schwertmannite by analyzing the 4 t1 6 a1 crystal field transition 900 1000 nm the presence of these minerals accurately predicted stream water ph r 2 0 87 and provided a qualitative estimate of dissolved so4 concentrations spectral analysis results were used to analyze airborne digital multispectral video dmsv imagery for several sites in the region the high spatial resolution of the dmsv sensor allowed for precise mapping of the mine drainage sediments the results from this study indicate that airborne and space borne imaging spectrometers may be used to accurately classify streams impacted by acid vs neutral to alkaline mine drainage after appropriate spectral libraries are developed published by elsevier science ltd

a new geochemical classification of sedimentary environments because of the relative constancy of ph in most subaqueous sediments and the general lack of measurability of eh these parameters are not practically useful for classifying sedimentary environments in their place a new classification is offered which derived from studies of modern sediments is based on the presence or absence of dissolved oxygen and dissolved sulfide in the sediments at the time of authigenic mineral formation sedimentary environments are first of all divided into oxic and anoxic depending upon the presence or absence of measurable dissolved oxygen anoxic environments in turn are divided into sulfidic and non sulfidic depending upon the presence of measurable dissolved sulfide anoxic nonsulfidic environments are further divided into postoxic or resulting from oxygen removal without sulfate reduction weakly reducing and methanic or resulting from complete sulfate reduction with consequent methane formation strongly reducing the environments are shown to succeed one another during early diagenesis in the order oxic post oxic sulfidic methanic iron and manganese minerals characteristic and stable in each environment are listed and discussed so that they may be used to distinguish the environments when studying the ancient geological record

diversity dynamics and mass extinctions of the early middle jurassic foraminifers a record from the northwestern caucasus abstract the early middle jurassic foraminiferal assemblages of the northwestern caucasus including a total of 315 species and 68 genera were analysed to establish the principal diversity patterns at substage level of resolution an overall conclusion is that the number of species varied significantly in contrast to the number of genera the most diversified were late sinemurian pliensbachian late toarcian early aalenian and late bajocian assemblages significant diversity drops have been documented in the early toarcian and in the middle aalenian the first of them corresponds to the well known mass extinction which regionally was initiated in the pliensbachian and terminated when rapid late toarcian diversification began the second event could be considered as a regional evidence of a new mass extinction that appeared in the middle aalenian and was most likely associated with the aalenian bajocian regional anoxic event also recorded in the carpathian part of the western tethys the most intense foraminiferal turnovers took place in the toarcian and in the middle aalenian early bajocian the lazarus effect in spite of its high value has not much influenced the estimation of principal diversity trends

mass extinctions and sea level changes abstract review of sea level changes during the big five mass extinctions and several lesser extinction events reveals that the majority coincide with large eustatic inflexions the degree of certainty with which these eustatic oscillations are known varies considerably thus the late ordovician and end cretaceous extinctions are associated with unequivocal major regressions demonstrated from numerous widespread regions in contrast the multiple high frequency sea level changes reported for the frasnian famennian crisis based on the supposed depth preferences of conodont taxa have little support from sequence stratigraphic analyses which reveals the interval to be one of highstand the end permian mass extinction has long been related to a severe first order lowstand of sea level newell n d 1967 revolutions in the history of life geol soc am spec pap 89 63 91 based primarily on the widespread absence of latest permian ammonoid markers but field evidence reveals that the interval coincides with a major transgression newell s hypothesis that marine extinctions are related to shelf habitat loss during severe regression remains tenable for the end guadalupian and end triassic extinction events but not for other crises rapid high amplitude regressive transgressive couplets are the most frequently observed eustatic changes at times of mass extinction with the majority of extinctions occurring during the transgressive pulse when anoxic bottom waters often became extensive the ultimate cause of the sea level changes is generally unclear a glacioeustatic driving mechanism can only be convincingly demonstrated for the end ordovician and end devonian events at other times it is speculated that they may relate to the widespread regional doming and subsequent collapse caused by the impingement of superplumes and ultimate eruption on the base of the lithosphere

selective mineralization of microbes in fe rich precipitates jarosite hydrous ferric oxides from acid hot springs in the waiotapu geothermal area north island new zealand abstract a group of small springs that are informally called orange spring located near hakereteke stream in the northern part of the waiotapu geothermal area feed hot 80 c acidic ph 2 1 2 4 as rich sulfate waters into a discharge channel that is up to 25 cm deep submerged reddish brown precipitates on the channel floor are formed largely of noncrystalline as rich hydrous ferric oxide hfo mainly goethite poorly crystalline lepidocrocite and crystalline jarosite well preserved coccoid and rod shaped microbes are found in the as rich hfo but not in the lepidocrocite or jarosite the jarosite was probably precipitated when the water had a low ph 4 and lower so4 content the fluctuations in the ph and so4 content which led to precipitation of the different mineral phases may reflect mixing of the spring water with stream water that flowed through the channel when hakereteke stream was in flood stage the goethite probably formed when coccoid and rod shaped bacteria acidithiobacillus ferrooxidans mediated rapid oxidization of the fe2 to fe3 that was then immediately coprecipitated with the as such rapid precipitation promoted mineralization of the microbes the lack of mineralized microbes and the lower as in the lepidocrocite and jarosite may reflect precipitation rates that were slower than the decay rates of the microbes or ecological factors that limited their growth

a review of the source behaviour and distribution of arsenic in natural waters the range of as concentrations found in natural waters is large ranging from less than 0 5 g l 1 to more than 5000 g l 1 typical concentrations in freshwater are less than 10 g l 1 and frequently less than 1 g l 1 rarely much higher concentrations are found particularly in groundwater in such areas more than 10 of wells may be affected defined as those exceeding 50 g l 1 and in the worst cases this figure may exceed 90 well known high as groundwater areas have been found in argentina chile mexico china and hungary and more recently in west bengal india bangladesh and vietnam the scale of the problem in terms of population exposed to high as concentrations is greatest in the bengal basin with more than 40 million people drinking water containing excessive as these large scale natural as groundwater problem areas tend to be found in two types of environment firstly inland or closed basins in arid or semi arid areas and secondly strongly reducing aquifers often derived from alluvium both environments tend to contain geologically young sediments and to be in flat low lying areas where groundwater flow is sluggish historically these are poorly flushed aquifers and any as released from the sediments following burial has been able to accumulate in the groundwater arsenic rich groundwaters are also found in geothermal areas and on a more localised scale in areas of mining activity and where oxidation of sulphide minerals has occurred the as content of the aquifer materials in major problem aquifers does not appear to be exceptionally high being normally in the range 1 20 mg kg 1 there appear to be two distinct triggers that can lead to the release of as on a large scale the first is the development of high ph 8 5 conditions in semi arid or arid environments usually as a result of the combined effects of mineral weathering and high evaporation rates this ph change leads either to the desorption of adsorbed as especially as v species and a range of other anion forming elements v b f mo se and u from mineral oxides especially fe oxides or it prevents them from being adsorbed the second trigger is the development of strongly reducing conditions at near neutral ph values leading to the desorption of as from mineral oxides and to the reductive dissolution of fe and mn oxides also leading to as release iron ii and as iii are relatively abundant in these groundwaters and so4 concentrations are small typically 1 mg l 1 or less large concentrations of phosphate bicarbonate silicate and possibly organic matter can enhance the desorption of as because of competition for adsorption sites a characteristic feature of high groundwater as areas is the large degree of spatial variability in as concentrations in the groundwaters this means that it may be difficult or impossible to predict reliably the likely concentration of as in a particular well from the results of neighbouring wells and means that there is little alternative but to analyse each well arsenic affected aquifers are restricted to certain environments and appear to be the exception rather than the rule in most aquifers the majority of wells are likely to be unaffected even when for example they contain high concentrations of dissolved fe

early diagenesis of arsenic in sediments of the kalix river estuary northern sweden solid phase as fe mn s and al and pore water total as fe mn and s have been determined for two cores from the kalix river estuary at the same station the depositional flux of arsenic was measured sediment traps fe iii oxides persist in the anoxic zone of the sediment and act as a carrier for arsenic down to depths of 10 15 cm the release of arsenic into the pore water is controlled by the reduction dissolution of these oxides as a result internal cycling of arsenic i e upward diffusion in pore water re adsorption onto fe iii oxides in the oxidized surface layer and reburial occurs in the uppermost 10 15 cm at the base of the arsenic cycling zone solid phase arsenic maxima 160 170 g g 1 of probable diagenetic origin occur the quantity of arsenic diffusing back towards the oxidized surface layer 2 2 g cm 2 yr 1 as is close to 75 of the quantity of arsenic being deposited due to sedimentation 2 9 g cm 2 yr 1 as however a mass balance for the surface layer indicates that re adsorption of arsenic onto fe iii oxides may effectively prevent diffusion of dissolved arsenic back into the overlying water column it is concluded that the interpretation of sedimentary arsenic profiles may be severely complicated due to post depositional migration of arsenic

hydrogeochemistry of arsenic and other inorganic constituents in groundwaters from la pampa argentina groundwaters from quaternary loess aquifers in northern la pampa province of central argentina have significant quality problems due to high concentrations of potentially harmful elements such as as f no3 n b mo se and u and high salinity the extent of the problems is not well defined but is believed to cover large parts of the argentine chaco pampean plain over an area of perhaps 106 km2 groundwaters from la pampa have a very large range of chemical compositions and spatial variability is considerable over distances of a few km dissolved as spans over 4 orders of magnitude 4 5300 g l 1 and concentrations of f have a range of 0 03 29 mg l 1 b of 0 5 14 mg l l v of 0 02 5 4 mg l 1 no3 n of 0 2 140 mg l 1 mo of 2 7 990 g l 1 and u of 6 2 250 g l 1 of the groundwaters investigated 95 exceed 10 g as l 1 the who guideline value and 73 exceed 50 g as l 1 the argentine national standard in addition 83 exceed the who guideline value for f 1 5 mg l 1 99 for b 0 5 mg l 1 47 for no3 n 11 3 mg l 1 39 for mo 70 g l 1 32 for se 10 g l 1 and 100 for u 2 g l 1 total dissolved solids range between 730 and 11400 mg l 1 the high values resulting mainly from evaporation under ambient semi arid climatic conditions the groundwaters are universally oxidising with high dissolved o2 concentrations groundwater phs are neutral to alkaline 7 0 8 7 arsenic is present in solution predominantly as as v groundwater as correlates positively with ph alkalinity hco3 f and v weaker correlations are also observed with b mo u and be desorption of these elements from metal oxides especially fe and mn oxides under the high ph conditions is considered an important control on their mobilisation mutual competition between these elements for sorption sites on oxide minerals may also have enhanced their mobility weathering of primary silicate minerals and accessory minerals such as apatite in the loess and incorporated volcanic ash may also have contributed a proportion of the dissolved as and other trace elements concentrations of as and other anions and oxyanions appear to be particularly high in groundwaters close to low lying depressions which act as localised groundwater discharge zones concentrations up to 7500 g l 1 were found in saturated zone porewaters extracted from a cored borehole adjacent to one such depression concentrations are also relatively high where groundwater is abstracted from close to the water table presumably because this zone is a location of more active weathering reactions the development of groundwaters with high ph and alkalinity results from silicate and carbonate reactions facilitated by the arid climatic conditions these factors together with the young age of the loess sediments and slow groundwater flow have enabled the accumulation of the high concentrations of as and other elements in solution without significant opportunity for flushing of the aquifer to enable their removal

factors controlling as and u in shallow ground water southern carson desert nevada abstract unusually high as and u concentrations 100 g l are widespread in shallow ground water beneath the southern carson desert the high concentrations which locally exceed 1000 g l are of concern from a human health standpoint because the shallow ground water is used for domestic supply possible affects on wildlife are also of concern because the ground water flows into shallow lakes and marshes within wildlife refuges arsenic and u concentrations in ground water of the southern carson desert appear to be affected by evaporative concentration redox reactions and adsorption the relation of these elements with cl suggest that most of the high concentrations can be attributed to evaporative concentration of carson river water the primary source of recharge some ground water contains higher as and u concentrations that cannot be explained by evaporative concentration alone oxidation reduction reactions involving metal oxides and sedimentary organic matter appear to contribute as u inorganic c fe and mn to the ground water arsenic in fe oxide was confirmed by chemical extraction and is consistent with laboratory adsorption studies uranium in both sedimentary organic c and fe oxide coatings has been confirmed by fission tracks and petrographic examination arsenic concentrations in the ground water and chemical extracts of aquifer sediments are broadly consistent with adsorption as a control on some dissolved as concentrations an apparent loss of as from some ground water as evaporative concentration proceeds is consistent with adsorption as a control on as however evidence for adsorption should be viewed with caution because the adsorption model used values for the adsorbent that have not been shown to be valid for the aquifer sediments throughout the southern carson desert hydrologic and geochemical conditions in the carson desert are similar to other areas with high as and u concentrations in ground water including the salton sea basin and southern san joaquin valley of california hydrologic and geochemical conditions that produced some sandstone type u ore deposits including those in the non marine closed basin sediments of the morrison formation near grants new mexico suggest that the carson desert may be a modern analog for those systems

arsenic in iron cements developed within tailings of a former metalliferous mine enguiales aveyron france abstract arsenopyrite rich waste from a former metalliferous mine were spread out over the sloping side of a deep valley after processing over the past 30 a they have been subjected to rainfall and acid water originating from the abandoned mine galleries this intensive leaching has led to the formation of thin layers of as fe crusts on the tailings surface acting as a cement x ray diffraction and sem coupled with eds determined that jarosite was present in all mineral samples and could contain a small amount of as 5 7 wt in addition empa and raman microspectroscopy characterised the presence of amorphous as v fe hydrates as well as rare arsenate minerals e g scorodite raman microspectroscopy in particular identified a preponderance of goethite or hematite within the mineral framework of the tailings materials that is likely to sorb recalcitrant as species the characterisation of the components of the tailings enable the identification of their evolution shows the progressive decrease of their as content and emphasises the consequences of the temporary trapping of as in the very acidic and oxidising conditions prevailing in such environments resinous amorphous material was identified as the richest in as with as 17 1 wt this material evolved toward more crystallised phases e g goethite jarosite which contained less as 3 2 wt

antimony and arsenic biogeochemistry in the western atlantic ocean the subtropical to equatorial atlantic ocean provides a unique regime in which one can examine the biogeochemical cycles of antimony and arsenic in particular this region is strongly affected by inputs from the amazon river and dust from north africa at the surface and horizontal transport at depth from highlatitude northern e g north atlantic deep water and southern waters e g antarctic bottom and intermediate waters as a part of the 1996 intergovernmental oceanographic commission s contaminant baseline survey data for dissolved as iii v as iii mono and dimethyl arsenic sb iii v sb iii and monomethyl antimony were obtained at six vertical profile stations and 44 sites alongthe 11 000 km transect from montevideo uruguay to bridgetown barbados the arsenic results were similar to those in other oceans with moderate surface depletion deep water enrichment a predominance of arsenate 85 as v and methylated arsenic species and as iii in surface waters that are likely a result of phytoplankton conversions to mitigate arsenate stress toxicity perhaps the most significant discovery in the arsenic results was the extremely low concentrations in the amazon plume as low as 9 8 nmol l that appear to extend for considerable distances offshore in the equatorial region the very low concentration of inorganic arsenic in the amazon river 2 8 nmol l about half those in most rivers is probably the result of intense iron oxyhydroxide scavenging dissolved antimony was also primarily in the pentavalent state 95 antimonate but sb iii and monomethyl antimony were only detected in surface waters and displayed no correlations with biotic tracers such as nutrients and chlorophyll a unlike as iii v s nutrient type vertical profiles sb iii v displayed surface maxima and decreased into the deep waters exhibitingthe behavior of a scavenged element with a strongatmospheric input while surface water sb had a slight correlation with dissolved al it is likely that atmospheric sb is delivered with combustion byproducts and not from mineral aerosols in the amazon plume antimony concentrations dropped substantially and an amazon river sample had a concentration 0 25 nmol l that was less than one fourth those found in other major rivers usingthese river data and estimates of atmospheric fluxes based on

inference of accumulation rate patterns from deep layers in glaciers and ice sheets the spatial pattern of accumulation rate can be inferred from internal layers in glaciers and ice sheets non dimensional analysis determines where finite strain can be neglected shallow layer approximation or approximated with a local one dimensional flow model local layer approxima tion and where gradients in strain rate along particle paths must be included deep layers we develop a general geophysical inverse procedure to infer the spatial pattern of accumulation rate along a steady state flowband using measured topography of the ice sheet surface bed and a deep layer a variety of thermomechanical ice flow models can be used in the forward problem to calculate surface topography and ice velocity which are used to calculate particle paths and internal layer shapes an objective tolerance criterion prevents over fitting the data after making site specific simplifications in the thermomechanical flow algorithm we find the accumulation rate along a flowband through taylor mouth a flank site on taylor dome antarctica using a layer at approximately 100 m depth or 20 of the ice thickness accumulation rate correlates with ice surface curvature at this site gradients along flow paths critically impact inference of both the accumulation pattern and the depth age relation in a 100 m core

the distribution of arsenic iii and arsenic v in geothermal waters examples from the massif central of france the island of dominica in the leeward islands of the caribbean the valles caldera of new mexico u s a and southwest bulgaria abstract data for as iii as v and total as for various types of geothermal spring water are given the different species of as were separated at the time of sampling after filtration acidification and dilution where necessary using an anion exchange method total as as iii and as v were determined by flameless atomic absorption spectrometry the total as content ranges from 5 to 1800 g l 1 samples from dominica show evidence of different sulfur arsenic oxidation kinetics as iii being the major component 85 99 in fluids from deep levels of the geothermal reservoir and also 99 in oxidized waters of the acid sulfate type the bicarbonate spring water of the valles caldera new mexico contains more as iii than as v but there as v is the major component of the acid sulfate springs as iii proves to be the predominant form 60 100 in the warm alkaline waters from southwest bulgaria a selection of co 2 rich spring waters from the central massif france cezallier is analysed two groups are distinguished on the basis of major element chemistry and total as content oxidized forms are mainly encountered in the first group including a well sample containing 0 5 as iii the as iii content of the second group ranges from 10 to 70 these preliminary results indicate that the fluids directly related to hydrothermal systems contain mainly as iii whereas acid sulfate springs have a variable as iii content bicarbonate waters are generally enriched in oxidized as in the absence of springs or sinks within a geothermal region the total as concentration may display conservative properties but both as iii and as v may be reactive during mixing and cooling

assessment of the alteration and acid generating potential of deep boreholes for geological disposal an integrated study including mineralogy geochemistry lead isotopic composition acid base accounting and factor analysis was conducted on the rock core samples from two deep boreholes ah1 and bh3 to assess the alteration and acid generating potential of two representative lithologies of korea granite and geniss for geological disposal the alteration condition represents water circulation features in crystalline basement rocks which is one of the key points to be assessed in repository sites in addition this study proposes that the acid producing potential and acid consuming minerals in the host rock are important for the long term safety of a radioactive waste repository given that sulfide oxidation may occur in artificial fractures created during construction fe3 ions can then react with other sulfide minerals in reducing conditions and release h and so42 which can deteriorate cement based grouting materials used for carven walls as well as the host rock the results of the study show that the composition of pb isotopes is a good indicator of the alteration of rock core samples compared to the chemical index of alteration and loss on ignition the acid potential ratio and net acid production potential indicate that most of the core samples in both boreholes have a high alkali generating potential factor analysis shows that the neutralizing capacity in ah1 is highly correlated with the alteration while the neutralizing capacity in bh3 is correlated with secondary minerals the alteration appears to be related to secondary minerals and the acid producing capacity while the changes in major elements are not related to the pb isotopes in bh3 due to leaching along fractures

large scale reconstruction of accumulation rates in northern greenland from radar data internal layers in polar ice sheets have been mapped in many areas using information from radio echo sounding surveys the layers contain imprints of past accumulation patterns and ice flow and can potentially provide estimates of past accumulation rates in this study average accumulation rates for the past 14 7 ka in north and central greenland are recovered from the mapped depth of one pronounced isochrone using a simple ice flow model accounting for both vertical and horizontal flow combined with formal inversion techniques using this method upstream variations in the accumulation and flow are taken into account when inferring the accumulation rates from the deep layer this resulted in larger spatial variations in the inferred accumulation rates compared to approaches using a one dimensional ice flow model the largest differences were found in areas of significant horizontal flow the inferred accumulation rates agree with holocene estimates from ice cores in the interior of the ice sheet across the central ice divide the inferred accumulation pattern shows a pronounced gradient in accumulation rates similar to the present day pattern suggesting that the large scale pattern in the interior of central northern greenland has been consistent throughout the past 14 7 ka

early diagenetic influences on iron transformations in a freshwater lake sediment abstract iron transformations in a calcium carbonate rich fresh water sediment were studied by analyzing the relevant constituents of both interstitial water and solid matter analysis of interstitial water shows that the observed redox sequence no 3 nh 4 mno 2 mn ii feooh fe ii so 2 4 s ii is roughly in agreement with that predicted by the gibbs free energy for the corresponding reactions in contrast to marine sediments these redox transitions occur in the uppermost sediments i e at depths of 0 4 cm deeper in the sedimentary sequence the depth profile for dissolved iron exhibits a steady non linear increase up to 400 mol dm 3 in this anoxic zone according to thermodynamic predictions iron ii minerals such as iron sulfide siderite and vivianite should precipitate while fe iii oxides should be completely dissolved however microscopic analysis showed that fe iii oxides were present throughout the studied sediment furthermore scanning electron microscope energy dispersive spectroscopy analysis suggests the presence of iron sulfide could be verified but not that of siderite or vivianite these observations indicate kinetic control of iron transformations we have investigated the importance of kinetic control of iron distribution in anoxic sediments using a diagenetic model for dissolved iron ii a rough estimate of time scales for dissolution and precipitation rates was made by imposing limiting boundary conditions using the calculated rate constant we established that more than 1000 years would be required for the complete dissolution of fe iii oxides which is agreement with our observations and experimental data from the literature calculated precipitation rates of fe ii for a given mineral phase such as siderite yield a maximum value of 3 g feco3 g 1 dry sediment yr 1 such low rates would explain the absence of siderite and vivianite finally it can be inferred from the mn t fe t ratio in the sediments that this ratio depends on the redox conditions of the sediment water interface at the time of deposition thus this ratio can be used as paleo redox indicator in lacustrine sediments

holocene accumulation and ice flow near the west antarctic ice sheet divide ice core site the west antarctic ice sheet divide core wdc provided a high resolution climate record from near the ross amundsen divide in central west antarctica in addition radar detected internal layers in the vicinity of the wdc site have been dated directly from the ice core to provide spatial variations in the age structure of the region using these two data sets together we first infer a high resolution holocene accumulation rate history from 9 2 thousand years of the ice core timescale and then confirm that this climate history is consistent with internal layers upstream of the core site even though the wdc was drilled only 24 kilometers from the modern ice divide advection of ice from upstream must be taken into account we evaluate histories of accumulation rate by using a flowband model to generate internal layers that we compare to observed layers results show that the centennially averaged accumulation rate was over 20 percent lower than modern at 9 2 thousand years before present b p increased by 40 percent from 9 2 to 2 3 thousand years b p and decreased by at least 10 percent over the past 2 thousand years b p to the modern values these holocene accumulation rate changes in central west antarctica are larger than changes inferred from east antarctic ice core records despite significant changes in accumulation rate throughout the holocene the regional accumulation pattern has likely remained similar to today and the ice divide position has likely remained on average within 5 kilometers of its modern position continent scale ice sheet models used for reconstructions of west antarctic ice volume should incorporate this accumulation history

the global frasnian famennian kellwasser event during the uppermostp gigas conodont zone p linguiformis zone the stepwise frasnian extinction culminates in the global transgressive regressive frasnian famennian kellwasser event most pelagic organisms of the tropical marine environment are more or less affected by this mass extinction during the early upper devonian extinction rates are clearly related to the deposition of black shales and the storage of a great amount of organic carbon in the shelf sediments contemporaneous positive excursions of the 13c recorded from pelagic limestones of europe and australia prove a worldwide change in the co2 content of the oceans surface water which is in balance with the atmosphere if the climate is controlled by the co2 content of the atmosphere a cyclic operation process might have developed with the succession transgression high organic production deposition of organic carbon lowering of co2 in the atmosphere icehouse effect polar glaciation regression erosion of organic carbon and re supply of co2 to the ocean and atmosphere greenhouse effect deglaciation transgression during the change from a greenhouse to an icehouse effect an overturn of the anoxic oceans probably was one of the causes for the mass killing of low latitude marine organisms

global time scale and regional stratigraphic reference scales of central and west europe east europe tethys south china and north america as used in the devonian carboniferous permian correlation chart 2003 dcp 2003 the boundaries of the devonian carboniferous and permian stages of the global stratigraphic reference scale abbreviated to global stratigraphic scale gss are described in relation to the biostratigraphic and or lithostratigraphic units of the regional stratigraphic reference scales abbreviated to regional stratigraphic scales rss of central and west europe east europe tethys south china eastern tethys and north america in their type regions the boundaries of gss units rarely coincide with those of homonymous rss units moreover the definitions of some rss units have changed several times over the last decades and subsequent misunderstanding of the stratigraphical significance of these changes has often introduced errors into proposed global correlation charts the stratigraphic framework proposed in our global devonian carboniferous permian correlation chart 2003 dcp 2003 devonian carboniferous permian correlation chart 2003 menning m schneider j w alekseev a s amon e o becker g von bitter p h boardman d r bogoslovskaya m braun a brocke r chernykh v chuvashov b i clayton g dusar m davydov v i dybova jachowicz s forke h c gibling m gilmour e h goretzki j grunt t a hance l heckel p h izokh n g jansen u jin y g jones p kading k ch kerp h kiersnowski h klets a klug ch korn d kossovaya o kotlyar g v kozur h w laveine j p martens th nemyrovska t l nigmadganov a l paech h j peryt t m rohn r roscher m rubidge b schiappa t a schindler e skompski s ueno k utting j vdovenko m v villa e voigt s wahlman g p wardlaw b r warrington g weddige k werneburg r weyer d wilde v winkler prins c f work d m 2004 abschlusskolloquium dfg schwerpunktprogramm 1054 evolution des systems erde wahrend des jungeren palaozoikums im spiegel der sedimentgeochemie abstracts univ erlangen germany 2004 p 43 herein abbreviated to dcp 2003 and cited as dcp 2003 in references is an attempt to reduce these errors the dcp 2003 is the stratigraphic base for project 1054 of the deutsche forschungsgemeinschaft dfg the evolution of the late palaeozoic in the light of sedimentary geochemistry this composite time scale has been carefully balanced as far as data allows to remove unnecessary artificial compression and expansion of time intervals biozonations and depositional events the ages selected in dcp 2003 are markedly different to those in the geologic time scale 1989 gts 1989 harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge pp 1 263 and in gradstein and ogg gradstein f m ogg j 1996 a phanerozoic time scale episodes 19 1 2 3 4 insert whereas they are closer to those of the geologic time scale 2004 gts 2004 gradstein f m ogg j g smith a g 2004 a geologic time scale 2004 cambridge univ press cambridge pp 1 589 mostly the ages are rounded to the nearest 0 5 ma in order to avoid estimates of questionable accuracy whereas ages of 0 1 ma in the gts 2004 and their error bars of 0 4 ma to 2 8 ma for the devonian to permian stage boundaries suggest an improved accuracy in contrast in the dcp 2003 questionable ages and positions of stratigraphic boundaries are marked by arrows c 2006 elsevier b v all rights reserved

mineralogical attenuation for metallic remediation in a passive system for mine water treatment passive systems with constructed wetlands have been consistently used to treat mine water from abandoned mines long term and cost effective remediation is a crucial expectation for these water treatment facilities to achieve that a complex chain of physical chemical biological and mineralogical mechanisms for pollutants removal must be designed to simulate natural attenuation processes this paper aims to present geochemical and mineralogical data obtained in a recently constructed passive system from an abandoned mine jales northern portugal it shows the role of different solid materials in the retention of metals and arsenic observed during the start up period of the treatment plant the mineralogical study focused on two types of materials 1 the ochre precipitates formed as waste products from the neutralization process and 2 the fine grained minerals contained in the soil of the wetlands the ochre precipitates demonstrated to be poorly ordered iron rich material which gave rise to hematite upon artificial heating the heating experiments also provided mineralogical evidence for the presence of an associated amorphous arsenic rich compound chemical analysis on the freshly ochre precipitates revealed high concentrations of arsenic 51 867 ppm and metals such as zinc 1 213 ppm and manganese 821 ppm indicating strong enrichment factors relative to the water from which they precipitate mineralogical data obtained in the soil of the wetlands indicate that chlorite illite chlorite vermiculite and mica vermiculite mixed layers vermiculite kaolinite and goethite are concentrated in the fine grained fractions 20 and 2 m the chemical analyses show that high levels of arsenic up to 3 and metals are also retained in these fractions which may be enhanced by the low degree of order of the clay minerals as suggested by an xrd study the obtained results suggest that although the treatment plant has been receiving water only since 2006 future performance will be strongly dependent on these identified mineralogical pollutant hosts

global change in the late devonian modelling the frasnian famennian short term carbon isotope excursions a model of the global biogeochemical cycles coupled to a energy balance climate model the combine model is used to identify the causes of two large n 13 c value excursions across the frasnian famennian f f boundary we test a scenario that links the sea level rise to stratification of the proto tethys ocean through the formation of warm saline deep waters in extended epicontinental seas even though this scenario can produce dysoxia below 100 m depth it fails to increase the global burial flux of organic carbon and thus seawater n 13 c values since stratification of the ocean leads to decreased productivity in surface waters several scenarios postulating a continental origin of the perturbations in the late devonian biogeochemical cycles are then tested we found that weathering of platform carbonates exposed during the early famennian sea level fall can account for a maximum positive shift in n 13 c value of 0 7x at the end of the sea level fall episode another 1 0x increase in n 13 c might originate from rapid spreading of vascular land plants near the f f boundary postulating that higher plants globally increased the weatherability of continental surface and that colonized continental area increased by 30 across the f f boundary finally the n 13 c excursion observed at the base of upper rhenana zone and the rapid increase of the carbon isotope ratios at the f f boundary require an increase of phosphorus delivery to the ocean by 40 coeval with the sea level rises once the calculated n 13 c values are in agreement with the measured data the combine model calculates a decrease in atmospheric pco2 from pre perturbation 2925 ppmv in the lower rhenana conodont zone to 1560 ppmv in the upper triangularis zone this decrease in pco2 is due to the increase in burial of organic matter during the kellwasser events and increased continental weatherability triggered by the spreading of continental vascular plants these changes occur within 4 million years the corresponding global climatic cooling reaches 4 4 c at the pole and 2 1 c at the equator f 2003 elsevier b v all rights reserved

the fate of geothermal arsenic in the madison and missouri rivers montana and wyoming geothermal as from yellowstone national park causes high as concentrations 10 370 g l in the madison and missouri rivers in montana and wyoming arsenic transport is largely conservative in the upper basin as demonstrated by the near equivalence of dissolved and total recoverable as concentrations the constancy of as loads and consistent ratios of concentrations of as to conservative geothermal tracers diurnal cycling of as between aqueous and solid phases in response to ph induced changes in sorption equilibria causes small variations of about 10 20 in dissolved as concentrations hcl extractable as concentrations in river and lake sediment in the upper basin are variable depending on position relative to the as rich headwaters and geochemical and physical processes associated with lakes in the lower missouri river large quantities of suspended sediment from tributaries provide sufficient sorption sites for substantial conversion of as from the aqueous phase to the solid phase

mineralogical and chemical evolution of ochreous precipitates from the libiola fe cu sulfide mine eastern liguria italy abstract the mineralogical and chemical evolution of ochreous precipitates forming from acid mine drainage amd from the abandoned libiola fe cu sulfide mine eastern liguria italy was followed through a multianalytical approach xrd tem xrf icp applied to surface precipitates and associated waters collected from several mine adits the mineralogy of the precipitates changed significantly as a consequence of the variations of the chemical parameters of the circulating solutions mainly ph eh and sulfate concentrations which in turn were mainly controlled by mixing with unpolluted stream and rill waters of the mining area a progressive transition from jarosite to schwertmannite to goethite to ferrihydrite to amorphous dominated precipitates was observed mainly as a consequence of an increase in the ph of the associated solutions this mineralogical evolution agrees well with the aqueous speciation and eh ph stability calculations performed on the waters associated with the different precipitate types furthermore tem analysis indicated that metastable pristine phases schwertmannite tend to transform progressively to well crystallized more stable species here represented by goethite the comparison of the water chemistry and the crystal chemistry of the different precipitates showed a significant decrease in the zn cu ni co contents in waters where the coexisting precipitates were almost exclusively composed of goethite the distribution of v sr as concentrations within the different precipitates showed that the most efficient scavenging phase for these elements was jarosite whereas ferrihydrite efficiently took up pb ions and schwermannite acted as a natural sink for cr the comparative analysis of the precipitates and waters of the libiola mining area indicated that the authigenic fe oxyhydroxides play an important role in controlling the composition of the highly polluted amd waters but this role as cleaning agents was mostly ephemeral minor ph eh oscillations facilitated quick mineralogical transformations via dissolution reprecipitation or solid state transformation which in turn controlled the trace elements that were mobilized or permanently stored within the solid phases

the frasnian famennian biotic crisis how many if any bolide impacts the prime causation of the mid late devonian mass extinction near the frasnian famennian f f boundary remains uncertain nevertheless geochemical evidence has been presented recently as decisive evidence of a giant bolide impact occurring precisely at the f f boundary which promoted the global mortality episode palaeobiological data however imply a gradual global change which is otherwise seen as a record of either multiple extraterrestrial catastrophes or of impact triggered earth bound mechanisms sedimentological mega tsunami physical craters microtektites and geochemical records remain either elusive in many aspects or incompatible with the predicted impact crisis pattern biotic succession across the f f horizon is still poorly known especially in continental domains to evidence a synchronous bedding plane killing event at the close of the crisis instead the commonly documented stepwise loss of biomass and an unproved distinctive dead zone are hard to explain simply as sampling artifacts the assumed mass mortality precisely at the f f boundary may be limited mainly to the pelagic realm the underestimated role of early variscan tectonism and associated volcanic hydrothermal processes resulting in thermal and nutrient pulses as possible prime controls of the f f crisis is suggested as well as resemblances to the superplume conditioned eventful mid cretaceous interval exemplified in the cenomanian turonian mass extinction additional shocks generated by minor cometary strikes are not excluded but may have affected some f f biotas or areas

reactive iron in marine sediments abstract a combined field laboratory study has been undertaken to explore the mineralogy concentrations and reactivity towards sulfide of iron in marine sediments also considered is the importance of bacterial fe liberation in regulating pore water chemistry two contrasting marine environments are included one is the relatively fe poor foam site and the other is the fe rich sediment of the subaqueous mississippi delta results show that oxide minerals are the most important fe phases in early diagenetic pyrite formation however viewed separately lepidocrocite and ferrihydrite are more reactive towards sulfide than goethite and hematite when fe oxides are present in relatively high concentrations dissolved sulfide is nearly absent from sediment pore waters with concomitant high concentrations of dissolved fe even in the presence of active sulfide production by sulfate reduction a combination of experimental results and diagenetic modelling shows that in some sediments pore water fe finds it origin in the bacterial reduction of iron oxides this seems the case even though greater amounts of fe are reduced by reaction of sulfide with iron oxides it appears that distinct microenvironments may exist in marine sediments where in one microenvironment sulfide reacts with fe oxides locally precipitating fe sulfide minerals in another fe reduced and solubilized by microorganisms migrates freely into solution

metal and metalloid leaching from tailings into streamwater and sediments in the old ag pb zn terramonte mine northern portugal tailings deposited over the castanheira a stream which flows through the old ag pb zn terramonte mine area showed a great potential environmental risk due to sulphide weathering facilitated by the tailings water interaction the high concentrations of al fe pb and zn in the tailings are associated with the exchangeable reducible and sulphide fractions and suggest sphalerite and pyrite occurrences oxidation of pyrite is responsible for the low ph values 3 38 4 89 of the tailings the water from the castanheira stream is not suitable for human consumption due to high concentrations of so4 2 mn al cd ni and pb the lowest concentrations of metals and metalloids were detected in downstream stretches of the castanheira however as fe and zn in deeper sediments tend to increase downstream significant concentrations of trivalent forms of arsenic were detected in water samples in downstream stretches of the castanheira some free ions fe2 mn2 and zn2 also predominate and the water is saturated with ferrihydrite goethite hematite lepidocrosite and magnetite

dissolution and pyritization of magnetite in anoxie marine sediments concentrations of magnetite were determined with depth in sediments of varying h2s content taken from long island sound foam nwc and sachem sites and from a site in the rapidly depositing subaqueous portion of the mississippi delta for the three long island sound sites dissolution of magnetite during burial is clearly demonstrated and for all four sites the rate of magnetite dissolution is proportional to the concentration of dissolved pore water sulfide by combining magnetite depth distributions with sedimentation rate data and measurements of dissolved sulfide we find that magnetite dissolution is well described by the following rate law dcmagdt 1 1 10 5c0 5bcmagamag where cmag is the concentration of magnetite grams per gram of sediment cs is the concentration of dissolved sulfide mm and amag is the specific surface area of magnetite in the sediment cm2 per gram of magnetite this equation means that for a typical range of magnetite surface areas and dissolved sulfide concentrations the half life of magnetite in anoxic marine sediments ranges from about 50 to 1000 years sem observations of magnetite grains from the different sediment sites reveal that magnetite dissolution may be accompanied by extensive replacement by pyrite this only occurs if magnetite is in contact with high concentrations of h2s 1 mm for relatively long periods of time several hundred years with low concentrations of h2s 1 mm magnetite dissolution occurs without identifiable pyrite replacement we suggest that this feature of magnetite diagenesis may prove to be a useful paleosulfide indicator

arsenic mobility in two mine tailings drainage systems and its removal from solution by natural geochemical barriers abstract sulfide mineral bearing mill wastes are sources of high concentrations of acid soluble metals and as these are serious problems for ore mining areas such as the kemerovo and cheljabinsk regions in russia this study evaluated the distribution of the mill wastes the mobility of as from the wastes and the potential of natural materials to attenuate as dispersion in the broader environment arsenic contents in wastes of the belovo zn processing kemerovo and the karabash cu smelting plants cheljabinsk are 2 3 orders of magnitude higher than the content of continental crust main mineral forms of as in these wastes are arsenopyrite feass and scorodite feaso 4 2h 2 o high dissolved as concentrations are found in water draining the wastes and in rivers adjacent to the mill sites the water concentrations commonly exceed drinking water standards high as concentrations in bottom sediments of the affected rivers extend a 100 m downstream of the waste drainage input these sediments are also a source of river water contamination experiments were conducted to evaluate the ability of natural water to mobilize as from the wastes the belovo tailings released 86 of their contained as to the infiltrating water whereas the less reactive karabash tailings released only 22 of total as the experimental leachates were used as influent to columns that tested the ability of limestone and natural clay to reduce the concentration of dissolved as and associated metals some dissolved as was precipitated with fe pb and sb initially in the limestone column the decrease in dissolved as is consistent with the accumulation of as in yellow ferriferous sediments in the belovo settling pond in the pond and wetland sediments as mobility is also decreased by the formation of sulfides and arsenides cubanite cufe 2 s 3 klaprothite cu 3 bis 3 rammelsbergite nias 2 maucherite ni 11 as 8 semseyite cu 9 sb 8 s 21 and skutterudite coas 3 were found in the chemically reducing lower sediments of the belovo settling pond

arsenic mobilization in the hyporheic zone of a contaminated stream arsenic behavior was examined in a contaminated stream by sampling the dissolved 0 45 m arsenic and metals in surface water shallow hyporheic zone water and adjacent ground water surface water was oxic and slightly basic and ground water was anoxic and acidic hyporheic zone water had ph values of 6 7 dissolved oxygen concentrations mostly between 0 and 3 mg l 1 and mean concentrations of most metals inbetween surface and ground water sample concentrations however arsenic and iron were enriched in the hyporheic zone most of the hyporheic zone dissolved arsenic was in the form of as iii which is considered to be more toxic to some organisms than as v in the oxic surface water 20 of the total dissolved as was found to occur in its reduced form we hypothesize that upon burial and reduction of fe oxyhydroxides in the streambed sediment bound arsenic is transferred into the dissolved phase as as iii and it is subsequently released into the surface water where it does not immediately reoxidize a continual flux of reduced as to the surface water maintains as iii concentrations above that expected in oxygenated surface waters

jurassic transgressions and regressions in the caucasus northern neotethys ocean and their influences on the marine biodiversity abstract in the jurassic the caucasus presently located in the southwest of russia georgia armenia and azerbaijan was located on the northern active margin of the neotethys ocean facies interpretation in all 62 areas distinguished by differences in facies allows to semi quantitatively evaluate jurassic regional transgressions and regressions for this region major transgressive regressive cycles took place in the hettangian aalenian bajocian bathonian and callovian tithonian each transgression was more extensive than the previous the same cycles are established in the greater caucasus basin deep marine environments were common in the pliensbachian late aalenian and late bathonian whereas they were very restricted in the late jurassic the jurassic transgressions and regressions in the caucasus coincided with the proposed global eustatic changes however some differences were caused by the regional tectonic activity although transgressions and regressions cause some changes in marine biodiversity it seems that only ammonites might have been directly influenced by them diversity of bivalves brachiopods and belemnites was driven by other factors however global changes in marine biodiversity were more closely related to the eustatic fluctuations than it was documented on a regional scale

geochemistry of mine waters draining a low sulfide gold quartz vein deposit bralorne british columbia abstract the bralorne and pioneer mines now inactive produced over 4 million ounces of au from an orogenic lode au deposit located on the eastern edge of the coastal mountains of sw british columbia between 2007 and 2009 drainage from a recently developed exploration adit was investigated in order to better understand and anticipate potential environmental management issues associated with the development of this type of deposit in the future portal discharge rate and specific conductance were monitored continuously over a 14 month period during which 36 water samples were collected additional samples were collected from flooded workings within the adit concentrations of as and sb at the portal range as high as 1738 and 316 g l respectively while those in the mine pool reach 3304 and 349 g l respectively effluent chemistry is mildly alkaline ph 8 7 and is dominated by na ca mg hco3 and so4 geochemical inverse modeling of effluent composition indicates weathering of albite 2515 kg a ferroan dolomite 718 kg a pyrite 456 kg a arsenopyrite 23 kg a and stibnite 2 kg a modeled sulfide reaction coefficients normalized by their corresponding host rock concentrations suggest that oxidation of arsenopyrite is 25 times slower than that of pyrite whereas oxidation of stibnite is 1 5 times faster oxidative dissolution of arsenopyrite and stibnite releases 10 6 kg a of as and 1 1 kg a of sb of which 57 and 46 respectively are sorbed to ferrihydrite and gibbsite on the bed of the shallow channel through which the mine pool drains to the portal although mass balance calculations predict the formation of sufficient ferrihydrite to sorb 100 of the as dissolved in the mine pool this attenuation process was ineffective possibly because the precipitated sorbents settled to the bottom of the water column or because of competition for sorption sites from ca and hco3 the dissolved sb as molar ratio in portal effluent 0 082 is much greater than the sb as ratio of the mineralization 0 002 because of slower arsenopyrite oxidation and somewhat lesser sorption of sb

assessing the acidic potential of waste rock in the akara gold mine thailand acid mine drainage amd is the environmental issue that generates the greatest public concern regarding the mining industry thus characterization of mine waste rock according to acid generation potential is necessary for mining operations to ensure proper waste rock storage and to avoid future adverse environmental effects therefore this study was conducted to estimate the potential of amd generation in the largest operating gold mine in thailand by using acid base accounting and net acid generation tests representative samples of six types of waste rock classified by mining geologists for mineral processing and waste dumping were collected for this study volcanic clastic porphyritic andesite andesite silicified tuff silicified lapilli tuff and sheared tuff under various conditions experimental results indicate that only silicified lapilli tuff and shear tuff are potentially acid forming materials the results indicate that amd generation may possibly occur a long time after mine closure due to the lag time of the dissolution of acid neutralizing sources acidic generation from some waste rocks may occur in the future based on environmental conditions particularly the oxidation of sulphide minerals by the combination of oxygen and water therefore a proper design for waste rock dumping and storage is necessary to reduce the risk of amd generation in future it is advisable to install a surface management system to control the overland flow direction away from the waste dump area and tailing storage facility and to install a second water storage pond next to the main storage pond to store the spilled water during storms and the rainy season a water quality monitoring plan that focuses on disturbed areas such as water storage ponds and mine pits should be put in place

the basal speed of valley glaciers an inverse approach geophysical inverse methods are used to calculate the basal motion of a glacier they are applied to a one dimensional forward model that can be linearized to make the analysis simpler the inverse method finds a solution that fits the data within a given error it selects for smooth solutions to discriminate against unrealistic oscillations the method is applied to a simple model glacier of uniform shape and thickness to test how well a given basal motion field can be reconstructed it shows as expected that optimizing for smoothness lowers maxima and increases minima of the solution a step change in basal velocity is drawn out in the inversion over a distance that is given by the half width of a resolving function this is typically about three times the ice thickness but is also affected by the sampling rate of the data the method is then applied to two glaciers where suitable data are available brown glacier on heard island southern indian ocean and mccall glacier in the brooks range alaska u s a the mccall results agree well with earlier estimates of basal motion