geochemical and mineralogical impacts of h2so4 on clays between ph 5 0 and 3 0 natural and constructed clay liners are routinely used to contain waste and wastewater the impact of acidic solutions on the geochemistry and mineralogy of clays has been widely investigated in relation to acid mine drainage systems at ph 1 0 the impact of h2so4 leachate characterized by ph 1 0 and potentially negative ph values on the geochemistry and mineralogy of clays is however not clear thus laboratory batch experiments were conducted on three natural clay samples with different mass ratios of smectite illite and kaolinite to investigate the impact of h2so4 on the geochemistry and mineralogy of aluminosilicates from ph 5 0 to 3 0 batch testing was conducted at seven ph treatments 5 0 3 0 1 0 0 0 1 0 2 0 and 3 0 using standardized h2so4 solutions for four exposure periods 14 90 180 and 365 d aqueous geochemical and xrd analyses showed increased dissolution of aluminosilicates with decreasing ph and increasing exposure period that smectite was more susceptible to dissolution than illite and kaolinite precipitation of an amorphous silica phase occurred at ph 0 0 and anhydrite precipitated in ca rich clays at ph 1 0 in addition global dissolution rates were calculated for the clays and showed good agreement to literature smectite illite and kaolinite dissolution rates which suggests global dissolution rates for complex clays could be determined from monomineralic studies a stepwise conceptual model of the impact of h2so4 on aluminosilicate geochemistry and mineralogy between ph 5 0 and 3 0 is proposed

precipitation regime of dronning maud land antarctica derived from antarctic mesoscale prediction system amps archive data 1 the precipitation regime of dronning maud land dml antarctica was studied using antarctic mesoscale prediction system amps archive data precipitation is the most important component of the mass balance of the antarctic ice sheet precipitation studies of dml are particularly important because two deep ice core drilling sites kohnen station and dome fuji are located in this region for the correct interpretation of the ice core properties a thorough understanding of the precipitation regime is necessary we used the high resolution amps archive data for the years 2001 2006 to investigate the temporal and spatial distribution of precipitation the results were compared to a recently published mass balance map derived from glaciological data of western dml the mass balance map and the amps mean annual precipitation field show fairly similar patterns which are mostly related to topography and prevailing wind systems precipitation is found to generally decrease from the coast to the inland plateau along the escarpment between the low altitude coastal areas and the interior plateau local minima and maxima in precipitation correspond to the leeward and windward sides of topographical ridges interannual variability of monthly sums of precipitation is fairly high owing to the influence of cyclone activity on precipitation which affects not only the coastal regions but also the interior of the continent more than previously thought

behavior of gold in the lateritic equatorial environment weathering and surface dispersion of residual gold particles at dondo mobi gabon abstract a supergene gold dispersion halo has developed at dondo mobi southern gabon from the weathering of an auriferous lisvenite under equatorial humid rain forest conditions morphological and chemical studies were performed on gold particles extracted from both fresh and weathered rocks from different parts of the dispersion halo the results demonstrate that the gold particles are residual and are subjected to increasing weathering upward through the profile from the protore to the surface in the central part of the halo and at the surface both laterally upslope and downslope weathering continues downward into the formerly barren saprolites which were derived from proterozoic schist and archean gneiss rim of the halo thus the au content progressively decreases as does the ag content of gold particles with distance from the center of the ore body gold particles subjected to increased weathering are smaller with more rounded shapes and surfaces pitted by dissolution the dispersion pattern is controlled by au dissolution and translocation of residual gold particles these processes involve an autochthonous evolution in the central part of the halo and a para autochthonous evolution at the rim of the halo at dondo mobi chloride and humic substances are the only ligands present in significant concentrations that are capable of complexing au thermodynamic calculations demonstrate that under such acidic conditions ph ranges from 4 to 6 gold stability increases with increasing silver content the dominant au complexes formed have been calculated to be an aurous hydroxichloride complex and an organometallic complex both of which are stable at surficial conditions thus both chemical and translocation processes control the mobility of au and gold particles in equatorial lateritic weathering profiles

dissolved constituents and sr isotopes in river waters from a mountainous island the danshuei drainage system in northern taiwan abstract taiwan is a typical active orogenic belt situated at the collision boundary between the eurasian continental plate and the philippine sea plate dissolved major and trace constituents as well as sr and sr isotopes in river waters collected from the danshuei river basin in northern taiwan have been studied to evaluate chemical weathering processes the results of principal component analysis show that the ion sources in these river waters can be categorized into 3 major components chemical weathering seasalt contribution and local anthropogenic input the chemical weathering is the most dominant factor that contributes about 85 of total variances significantly increased na cl and ca cl as well 87 sr 86 sr were observed in most upper stream samples the na cl and ca cl ratios in the dahan stream however are much higher than the shindien stream even though average rainfall is stronger in the shindien drainage basin chemical evidence from river waters supports less intense weathering in the region selective dissolution of secondary calcites explains the observed high ca cl sr cl and ca na in the dahan stream these results highlight the potential importance of tectonic factors such as uplift and physical erosion in studying chemical weathering in an active orogenic belt the variations of 87 sr 86 sr in the danshuei river are quite large reflecting some strata that released sr most of the upstream waters exhibit more radiogenic 87 sr 86 sr 0 713243 0 714338 due to weathering of ambient low grade metamorphic rocks 0 71678 0 72216 the distributions of cl sr and 87 sr 86 sr in the main stream were affected by somewhat conservative mixing with sources varing between ambient rocks and seasalt in the upper dahan stream heavy 87 sr 86 sr ratios were coincident with large deviations of na cl from the average seawater value as high as 40 the degree of chemical weathering in ambient rocks plays a dominant role in affecting the distribution of sr and 87 sr 86 sr in the danshuei river this isotopic characteristic makes 87 sr 86 sr an invaluable tracer for studying source mixing migration pathways and chemical weathering in an active orogenic belt

the serchio river catchment northern tuscany geochemistry of stream waters and sediments and isotopic composition of dissolved sulfate abstract the serchio river and its tributaries in northern tuscany were investigated for the chemical and isotopic compositions of waters and bed sediments bedrocks are mostly limestone dolomite and siliciclastics thermal spring systems are present in the catchment and the main industrial activity is represented by paper mills main results obtained are 1 major ions in solution appear to be basically controlled by precipitation and lithology as well as subordinately by direct inputs of thermal springs 2 human influence on metals in the waters along the main serchio and lima rivers is indicated at a number of sites by increases in concentration compared to the chemical composition of upstream tributaries 3 s and o isotope compositions delineate two main sources for aqueous so 4 2 that is dissolution of triassic evaporite directly or via thermal springs and oxidation of sulfide dispersed in siliciclastic rocks anthropogenic contributions are probable but they cannot be quantitatively assessed only so 4 2 in the notoriously polluted ozzeri tributary is suspected to be largely anthropogenic and 4 the chemical composition of bed sediments is mainly influenced by lithology apart from a number of technogenic elements in the upper part of the serchio river and in some tributaries contamination possibly occurs at other sites but geochemical indications are weak

tectono metamorphic evolution of syros and sifnos islands cyclades greece abstract miocene exhumation of metamorphic rocks in the aegean sea is partly a consequence of post orogenic extension if the post orogenic mechanism of exhumation is rather well understood the earlier syn orogenic eocene exhumation is still largely enigmatic previous authors have argued in terms of extension or compression new structural and petrological data on sifnos and syros islands show that exhumation of high pressure low temperature hp lt rocks involves crustal scale extensional ductile shear zones during the eocene we observe a continuum of top to the ne and e ductile shear from the eocene in the blueschist facies to the miocene in the greenschist facies this deformation is distributed in the eclogites and blueschists whereas it is rather localised along ductile shear zones in the greenschists eclogites which are preserved only at the top of the structural pile are exhumed with a cold retrograde p t path in the lower part of the structural pile we observe a progressive retrogression of eclogites in blueschist then greenschist facies this lower part of pile is subsequently exhumed with p t paths showing a nearly isothermal decompression before cooling p t t deformation data suggest that the cycladic blueschists are progressively exhumed by a continuum of accretion at the base of the orogenic wedge and by a partly non coaxial extensional deformation above distributed during the syn orogenic stage then localised during the post orogenic stage we then compare the mechanism of syn orogenic exhumation of crete and the cyclades and we discuss a simple geodynamic scenario for the aegean domain and the external hellenides which accounts for 1 the southward migration of the hellenic trench and arc during the cenozoic 2 the p t t deformation data for the cycladic blueschists and the phyllite quartzite nappe and 3 the transition from syn orogenic to post orogenic in the cyclades

forced return flow deep in the subduction channel syros greece we present the results of a detailed structural study in the cycladic blueschist unit at fabrika on syros island greece and discuss their significance for tectonic processes at the subduction int

structure and kinematics of upper cenozoic extensional detachment on naxos and paros cyclades islands greece this paper presents a study of the ductile and brittle deformation on naxos and paros islands cyclades greece previous maps and studies of the two islands have shown that a major low angle fault zone separates surface rocks above the contact from an initially deep seated unit below showing a metamorphic evolution from high to low pressures structural analysis as well as available stratigraphical metamorphic and geochronological data taken together demonstrate that this fault zone is a major normal sense detachment zone dipping to the north rapid denudation of footwall rocks subsequent to high temperature metamorphism at an estimated rate of 1 8 9 5 mm yr attests for tectonic unroofing during regional scale top to the north ductile shearing the change from ductile to brittle behavior of the footwall rocks together with a progressive localization of high strain intensity deformations just below the hangingwall is explained by the progressive cooling of the uprisen footwall of the detachment mio pliocene clastic sediments in the hangingwall represent the infilling of half grabens opened in between major normal faults that are synthetic to the underlying ductile shear zone these sediments are as old as aquitanian 25 ma or younger than the earliest recognized evidence of ductile extension in the footwall this provides a minimum age for the onset of extension in the cyclades which appears significantly older than maximum ages reported up to now 13 5 ma structural data strongly suggest that the detachment fault was initially rather low dipping 35 an evolutionary model is proposed in which migmatite domes in the footwall correspond to the uprise of the lower ductile crust between two separating upper crustal blocks during a process of asymmetric boudinage of the crust this detachment model applies to a previously thickened continental lithosphere which then suffers thermal relaxation and weakening allowing extensional deformation to reach a climax during and subsequent to high temperature metamorphism in the cyclades crustal scale extension started after early cenozoic thrusting while the crust was still thick or less likely before late underthrusting below the present surface

variations of chemical features in a monsoon glacier watershed southeastern tibet plateau the ph ec electric conductivity 18o and major ions in melt water precipitation runoff and groundwater samples which were collected in baishui basin were analyzed based on chemical analysis the characteristic variations are analyzed in this paper the melt water precipitation runoff and groundwater were ca2 mg2 hco3 type with similar ion compositions but showed different ion concentrations normally the content is high in groundwater and runoff water but low in melt water and precipitation from the upper basin glacier downward there was a general increasing trend for the total ion concentrations in basin hco3 and ca2 accounted for more than 80 of total ions in samples indicating that ions mainly came from limestone and water typical of carbonate solution water water rock interaction is the significant contributor to water geochemistry the concentration of inorganic ion in melt water had an obvious diurnal variation with temperature change the 18o values increases with the altitude decrease the similarity of 18o in runoff and groundwater samples was due to their frequent transformation in karst regions

hydrogeochemistry of three watersheds the erlqis zhungarer and yili in northern xinjiang nw china abstract in the arid region of northern xinjiang one of the least studied areas in china three watersheds namely those of the yili zhungarer and erlqis have become the focus of attention due to rapidly increasing human population and water demands the hydrogeochemistry of natural water from the three watersheds was investigated the ionic chemistry of natural waters from these watersheds changes considerably on a regional scale the waters are neutral to alkaline in nature and most of them are soft fresh waters the total dissolved solid tds varies over two orders of magnitude with a mean value of 580 mg l about 1 2 times and 4 6 times those of the huanghe yellow river and the world spatial median respectively but only 40 and 0 8 of those of the tarim and the western alashan watersheds respectively much of the solutes and physicochemical parameters in these waters are under the highest desirable limits of the world health organization who for drinking purpose and a plot of sodium adsorption ratio versus ec shows that most waters are of good water quality for irrigation water rock interaction and saturation index si for selected minerals are evaluated the si of these natural waters is out of equilibrium undersaturated with respect to major carbonates calcite and dolomite and evaporites gypsum and halite the high concentrations of alkali earth metals alkalinity and the high ca mg na k and na cl ratios indicate that the release of major solutes in these waters is controlled largely by dissolution processes of carbonate and partly by silicate weathering while cation exchange reactions soil salt leaching and evaporation processes also play an important role the effects of local pollution are minimal in the montane and piedmont areas of these watersheds but are significant in the oases and central areas of the drainage basins

mechanisms controlling the silicon isotopic compositions of river waters it has been proposed that silicon si isotopes are fractionated during weathering and biological activity leading to heavy dissolved riverine compositions in this study the first seasonal variations of stable isotope compositions of dissolved riverine si are reported and compared with concomitant changes in water chemistry four different rivers in switzerland were sampled between march 2004 and july 2005 the unique high resolution multi collector icp ms nu1700 has been used to provide simultaneous interference free measurements of 28si 29si and 30si abundances with an average limiting precision of 0 04 on 30si this precision facilitates the clarification of small temporal variations in isotope composition the average of all the data for the 40 samples is 30si 0 84 0 19 1 sd despite significant differences in catchment lithologies biomass climate total dissolved solids and weathering fluxes the averaged isotopic composition of dissolved si in each river is strikingly similar with means of 0 70 0 12 for the birs 0 95 0 22 for the saane 0 93 0 12 for the ticino and 0 79 0 19 for the verzasca however the 30si undergoes seasonal variations of up to 0 6 comparisons between 30si and physico chemical parameters such as the concentration of dissolved si and other cations the discharge of the rivers and the resulting weathering fluxes permits an understanding of the processes that control the si budget and the fate of dissolved si within these rivers the main mechanism controlling the si isotope composition of the mountainous verzasca river appears to be a two component mixing between the seepage of soil ground waters with heavier si produced by clay formation and superficial runoff associated with lighter si during high discharge events a biologically mediated fractionation can be excluded in this particular river system the other rivers display increasing complexity with increases in the proportion of forested and cultivated landscapes as well as carbonate rocks in the catchment in these instances it is impossible to resolve the extent of the isotopic fractionation and contributed flux of si contributed by biological processes as opposed to abiotic weathering the presence of seasonal variations in si isotope composition in mountainous rivers provides evidence that extreme changes in climate affect the overall composition of dissolved si delivered to the oceans the oceanic si isotope composition is very sensitive to even small changes in the riverine si isotope composition and this parameter appears to be more critical than plausible changes in the si flux therefore concurrent changes in weathering style may need to be considered when using the si isotopic compositions of diatoms sponges and radiolaria as paleoproductivity proxies

mobility and retention of trace elements in hardpan cemented cassiterite tailings north queensland australia this study reports on the mobility and retention of trace elements in cassiterite tailings at the inactive jumna mill tropical north queensland since the 1980s the uncapped tailings have developed laterally discontinuous fe rich hardpans which are located in the higher parts of gently sloping tailings masses and at the top 50 cm of the tailings piles hardpan cemented tailings comprise thin layers typically 0 2 2 mm thick of hfo hydrous ferric oxides and sulfate efflorescences cementing tailings grains in comparison to the tailings the hardpan cemented tailings contain significantly higher median as ca cd co cu fe in mn mo stotal th u y and zn values partial leaching studies of tailings and pond water analyses indicate that wetting and acidification of fe cemented tailings removes significant proportions of trace elements into pore and surface waters tin shows no mobility due to the presence of weathering resistant cassiterite sno2 and as and pb display limited mobility possibly due to their coprecipitation with jarosite type phases and hfo materials at the top of the tailings profile by contrast the trace elements cd ce cu la ni pb u and zn display the greatest mobility possibly due to their incorporation in soluble sulfate efflorescences and sorption onto mineral and hfo surfaces hence the fe rich hardpans do not protect the sulfidic tailings from further oxidation nor do they cause permanent sequestration of trace elements

a gis based method for evaluating sediment storage and transport in large mining affected river systems currently the evaluation of sediment storage and transport for large river systems with variable flow has proven to be a challenge that often requires complex numerical models to be applied and sometimes costly direct data acquisition to be made the present study proposes a low cost widely available gis based method through which an initial assessment can be made on areas of sediment storage transport and deposition as well as possible environmental risks that the accumulation of contaminated material may pose to riverine communities along the rivers channel the method mainly relies on satellite imagery and elevation data to devise a quick model of the channel the model has been successfully applied to study the bolivian sector of the well known mining contaminated rio pilcomayo the analysis shows that the portion of the channel from villamontes to d orbigny accounts for more than half of the total c 314 km2 sedimentation area of the pilcomayo in bolivia and that the most environmentally problematic area is centreed around puente sucre where agriculture is practiced on the contaminated floodplain combined with supplementary bathymetric data on the depth of the river in various points around the channel the method could offer further insight into the sediment fluxes and transport capacity of the pilcomayo in various sectors and could thus be successfully used to assess other large mining contaminated river channels around the world

role of off shelf to on shelf transitions for east antarctic sea ice dynamics during spring 2003 1 during austral spring 2003 mesoscale sea ice drift and deformation off east antarctica were investigated using in situ data from a nine buoy array upon deployment the array comprised an area of about 4000 km2 with a mean ice concentration of 96 half hourly sea ice velocities were coherent across all buoys at zonal meridional separations of less than 160 km 70 km regional cross spectral correlation was high at synoptic scales and also at semidiurnal periods off the continental shelf atmospheric synoptic scale forcing explained in excess of 85 of the ice drift variability this is significantly more than found in the weddell sea where significant ice drift variability is derived from oceanic forcing peak frequencies of semidiurnal contributions covaried with latitude and are largely associated with the inertial response over the continental shelf coincident diurnal and semidiurnal variances in ice motion arose from tidal forcing net divergence over 37 days resulted in an expansion to 270 of the initial area although regional ice concentration reduced only slightly high frequency processes namely inertial response and to a lesser degree tidal forcing dominated the variability of all deformation parameters in contrast to ice motion low frequency processes played a secondary role in sea ice deformation this high frequency dominance is similar to what has been found in the weddell sea although many observations there were limited to the continental shelf where tidal processes dominate sea ice motion and deformation were not affected by a seasonal transition nor did the regional ice characteristics show any signal of seasonal change instead local ice dynamics were strongly influenced by bathymetrically dependent processes

spatial and temporal analysis of water chemistry records 1958 2000 in the huanghe yellow river basin 1 the chemistry of major dissolved ions ca2 mg2 na k hco3 so42 cl and dissolved silica sio2 in the river water of the huanghe yellow river china was studied from historical records at 100 stations in the drainage basin for the period 1958 2000 not all the parameters were continuously monitored during the entire period this river system 750 000 km2 presents an exceptional temporal and spatial water chemistry variability compared to other major rivers the total dissolved solid tds concentration of the huanghe varied over 2 to 3 orders of magnitude throughout the basin with a median tds concentration of 452 mg l which is about 4 times the world spatial median value wsm in particular the concentrations of na k so42 and cl were 10 20 times higher than in other major world rivers similar to the changjiang yangtze river and many other himalayan rivers the tds at a given station is seasonally variable and inversely related to river runoff with a variation factor less than 2 0 despite a water dilution of fourfold to fivefold in the summer flood season in addition to chemical weathering of sedimentary rocks evaporation and fractional crystallization were found to be the major natural process controlling the major element chemistry of the huanghe owing to the abundance of loess and clastic rocks under arid and semiarid climates a persistent increasing trend from year to year has been observed in the concentrations of tds and all the salts except for hco3 at all main channel stations except for the uppermost lanzhou the rate of increase in the tds concentration was the highest in the middle reaches 10 52 mg l yr 1 at toudaoguai and remained to be unusually high in the lower reaches 5 5 mg l yr 1 at stations luokou and lijin the increasing trend coincided with a significant decrease in water discharge at most of the main channel stations in the past 40 years and is attributed to increasing regulations of reservoirs and intensive water withdrawal for irrigation and diversions as well as many other anthropogenic processes despite the increasing trend in tds concentrations the seaward tds flux to the sea by the huanghe has decreased dramatically from more than 20 109 kg yr in the 1960s to less than 10 109 kg yr at present due to the sharp decrease in water discharge sometimes completely dried up in the lower reaches of the river the significant decreases in sea ward fluxes of water and dissolved salts are expected to have profound physical ecological and socio economic impacts on the lower reaches of the river the coastal areas and the bohai sea

sequential development of interfering metamorphic core complexes numerical experiments and comparison with the cyclades greece the mechanics of metamorphic core complex mcc development and the associated process of lower crustal flow have been the topic of several modelling studies the model setup usually includes a local heterogeneity forcing deformation to localize at a given site enabling only one mcc to develop this paper presents numerical lithospheric scale experiments in whichdeformationis not a priorilocalizedinaspecificplace inordertoexaminewhethermultiple mccs could develop during extension at which conditions and how configurations with either a singlemccorseveralfar distantmccsalignedinthesectionparalleltoextensionare obtainedfor arelativelywiderangeofinitialconditions theonlyfirmrequirementbeingthatthelowercrustand the sub moho mantle both have very low strengths in contrast only a narrow range of conditions leads to the development of closely spaced mccs in this case the mccs interfere with one another the domes are partly superimposed or and share a shear zone in common and develop in sequence this configuration is compared with the cyclades archipelago where closely spaced chains of mccs have been described in the literature a review of available data on the islandsdocumentsa goodagreement with the experiments intermsoffinal depthofthe moho geo metry and kinematic pattern of the mccs and timing of exhumation of the metamorphic rocks based on this agreement we tentatively deduce from the numerical results some of the conditions that prevailed at the initiation of and during post orogenic mcc type extension in the cyclades themostlikely initial thicknessofthecrust is between40 and44 km a thermallithospheric thick ness of only c 60 km is also likely which might be a condition at the onset of extension or may have been obtained during early stages of extension while the lithosphere was warmed up either a backarc subduction setting or a process of mantle delamination may account for this situ ation the numerical results also suggest a boundary velocity of 2 0 2 3 cm a which should basi cally reflect the rate at which the south hellenic subduction zone retreated considering c 500 km as an upper bound for the amount of retreat balanced by aegean extension and assuming that this retreat mostly occurred during mcc type extension in the cyclades we find that the boundary velocity could have been as high as 2 1 cm a if mcc type extension lasted 24 ma starting at c 30 ma and finishing at c 6 ma as suggested by available geochronological data a velocity of 2 1 cm a agrees well with the numerical results

anomalous atmospheric circulation over the weddell sea antarctica during the austral summer of 2001 02 resulting in extreme sea ice conditions during the austral summer of 2001 02 exceptionally heavy sea ice conditions were experienced over the eastern weddell sea satellite microwave imagery showed that large negative positive ice anomalies were present from october 2001 to january 2002 over the north western weddell sea off the coast of dronning maud land these were a result of anomalously high low atmospheric pressure over the south atlantic southern weddell sea and bellingshausen sea which gave strong north to north westerly cyclonic flow over the northern and eastern weddell sea this resulted in convergence of sea ice into the southern weddell sea and inhibited ice advection along the coast of dronning maud land the atmospheric anomalies around the weddell sea were part of an antarctic wide amplification of the mean wavenumber 3 pattern resulting in more intrusions of mid latitude air into the interior of the continent giving rise to near record warm temperatures at several locations

unabated acid mine drainage from cerro rico de potosi bolivia uncommon constituents of concern impact the rio pilcomayo headwaters intensive mining and processing of the polymetallic sulfide ore body of cerro rico de potosi bolivia has occurred since 1545 leading to severe degradation of surface and subsurface waters stream sediments and soils at the headwaters of the economically vital yet highly impacted rio pilcomayo previous studies have documented extremely elevated concentrations of a limited suite of metals in local waterways from acid mine drainage amd terrestrial and in stream tailings and ore processing plant discharges however contamination from a wider variety of ecotoxic metals metalloids was considered likely due to the highly mineralized polymetallic nature of the ore body to screen for this broader range of ecotoxic elements in amd and receiving streams data were gathered during two sampling events timed for the most extreme periods of the dry and wet seasons of one water year concentrations of ag b ba mo sb se sn and v in amd and receiving streams were greater than bolivian discharge limits and receiving water body guidelines as well as international agricultural use standards locally results indicate that contamination from mining cerro rico has a larger scope than previously thought and underscore the importance of remediation globally the results raise the possibility that other mining regions could have unquantified hazards from overlooked ecotoxic elements and that screening for a broader range of contaminants may be warranted

major and trace metal mobility during weathering of mine tailings implications for floodplain soils abstract mine tailings discharged to river systems have the potential to release significant quantities of major and trace metals to waters and soils when weathered to provide data on the mechanisms and magnitudes of short and long term tailings weathering and its influence on floodplain environments three calendar year long column leaching experiments that incorporated tailings from potosi bolivia and soil from unaffected downstream floodplains were carried out these experiments were designed to model 20 cycles of wet and dry season conditions two duplicate columns modeled sub aerial tailings weathering alone a third modeled the effects of long term floodplain tailings contamination and a fourth modeled that of a tailings dam spill on a previously contaminated floodplain as far as was practical local climatic conditions were modeled chemical analysis of the leachate and column solids optical mineralogy xrd sem epma bcr and water soluble chemical extractions and speciation modeling were carried out to determine the processes responsible for the leaching of al ca cu k na mg mn sn sr and ti over the 20 cycles the ph declined to a floor of ca 2 in all columns calcium cu mg mn and na showed significant cumulative losses of up to 100 60 30 95 and 40 respectively compared to those of al k sr sn and ti which were up to 3 1 5 5 1 and 0 05 respectively the high losses are attributed to the dissolution of relatively soluble minerals such as biotite and oxidation of chalcopyrite and cu sulfosalts while low losses are attributed to the presence of sparingly soluble minerals such as svanbergite cassiterite and rutile these results strongly suggest that the release of tailings to floodplains should be limited or prohibited and that all tailings should be removed from floodplains following dam spills

acid neutralization mechanisms and metal release in mine tailings a laboratory column experiment mining and milling of base metal ore deposits can result in the release of metals to the environment when sulfide minerals contained in mine tailings are exposed to oxygen and water they oxidize and dissolve two principal antagonistic geochemical processes affect the migration of dissolved metals in tailings impoundments sulfide oxidation and acid neutralization this study focuses on acid neutralization reactions occurring in the saturated zone of tailings impoundments to simulate conditions prevailing in many tailings impoundments 0 1 mol l sulfuric acid was passed continuously through columns containing fresh unoxidized tailings collected at kidd creek metallurgical site the results of this column experiment represent a detailed temporal observation of ph eh and metal concentrations the results are consistent with previous field observations which suggest that a series of mineral dissolution precipitation reactions control ph and metal mobility typically the series consists of carbonate minerals al and fe iii hydroxides and aluminosilicates in the case of kidd creek tailings the dissolution series consists of ankerite dolomite siderite gibbsite and aluminosilicates in the column experiment three distinct ph plateaus were observed 5 7 4 0 and 1 3 the releases of trace elements such as cd co cr cu li ni pb v and zn were observed to be related to the ph buffering zones high concentrations of zn ni and co were observed at the first ph plateau ph 5 7 whereas cd cr pb as v and al were released as the ph of the pore water decreased to 4 0 or less

the tectonic significance of a porphyroblastic blueschist facies overprint during alpine orogenesis sifnos aegean sea greece the macargon program has been used to model published 40ar39ar apparent age spectra for white micas from the island of sifnos cyclades greece these micas formed during a period of porphyroblastic mineral growth m2 in the epidote blueschist facies at 460 c and 50 c m y and since m2 is followed by d3 we infer that these are the cooling rates during d3 modelling experiments for micas from the greenschist domain gsd structurally underneath the ebd suggest that the gsd cooled rapidly but at 32 ma one tectonic model that might explain the rapidity of cooling rates inferred for the ebd model supposes that ambient temperatures were at 500 c when m2 took place but thereafter the high pressure rocks were thrust to the north and rapidly cooled as the result of their juxtaposition against cooler shallower levels of the crust

potential and limitations of marine and ice core sea ice proxies an example from the indian ocean sector diatom assemblages in marine cores and sea salt deposition fluxes in ice cores have been used as sea ice proxies in the southern hemisphere here a marine and an ice core proxy record for the indian ocean covering the last two glacial cycles are compared in order to illustrate their potential and limitations the marine core was extracted in a location completely ice free under present day conditions and therefore was unable to record changes to the recent sea ice extent similarly no sea ice was recorded at that location during the previous interglacial period during the last glacial period however the site was seasonally covered by sea ice and the diatom assemblages allowed an estimation of average seasonal sea ice presence the ice core data originated from the east antarctic plateau the marine sodium present in the ice core was used as a proxy of the sea ice coverage and on average a larger sea ice surface led to an increased sea salt aerosol flux seen e g at the last glacial inception however the response of the sea salt flux to increasing sea ice extent diminished during peak glacial conditions when only minimal variability was recorded in the ice core record a first order approximation is used to take this non linear response of the ice core sea ice proxy into account based on the ice core proxy record sea ice extent was reduced considerably during the warm episodes of the previous two interglacial periods compared to modern sea ice extent in particular during the peak warmth of the last interglacial the ice core proxy also showed a very strong precessional variability pronounced spectral peak at 23 ka period over the past 240 ka the advantage of combining the two proxy records lies in the complementary nature of their response while the ice core proxy showed limited sensitivity during full glacial conditions the marine proxy recorded the seasonal sea ice coverage once the sea ice retreated south of the location of the marine core the ice core proxy responded to changes in sea ice extent a composite of marine and ice core records may thus provide a data basis for a more detailed reconstruction of sea ice around antarctica over the last few glacial interglacial cycles

mine tailings dams characteristics failure environmental impacts and remediation on a global scale demand for the products of the extractive industries is ever increasing extraction of the targeted resource results in the concurrent production of a significant volume of waste material including tailings which are mixtures of crushed rock and processing fluids from mills washeries or concentrators that remain after the extraction of economic metals minerals mineral fuels or coal the volume of tailings is normally far in excess of the liberated resource and the tailings often contain potentially hazardous contaminants a priority for a reasonable and responsible mining organization must be to proactively isolate the tailings so as to forestall them from entering groundwaters rivers lakes and the wind there is ample evidence that should such tailings enter these environments they may contaminate food chains and drinking water furthermore the tailings undergo physical and chemical change after they have been deposited the chemical changes are most often a function of exposure to atmospheric oxidation and tends to make previously perhaps safely held contaminants mobile and available if the tailings are stored under water contact with the atmosphere is substantially reduced thereby forestalling oxygen mediated chemical change it is therefore accepted practice for tailings to be stored in isolated impoundments under water and behind dams however these dams frequently fail releasing enormous quantities of tailings into river catchments these accidents pose a serious threat to animal and human health and are of concern for extractive industries and the wider community it is therefore of importance to understand the nature of the material held within these dams what best safety practice is for these structures and should the worst happen what adverse effects such accidents might have on the wider environment and how these might be mitigated this paper reviews these factors covering the characteristics types and magnitudes environmental impacts and remediation of mine tailings dam failures

sources of environmental sulfur in the groundwater system southern new zealand abstract sulfide minerals commonly occur in sediments and basement rocks in southern new zealand as authigenic precipitates from groundwater below the oxygenated surface zone there are two principal potential sources for sulfur in the groundwater system weathering of sulfide minerals in the metamorphic basement and rainwater derived marine aerosols we present data for these two key sulfur sources metamorphic sulfide and associated hydrothermal au bearing veins within the otago schist average 34s 1 8 2 4 and an inland saline lake s derived entirely from rainwater 34s 21 4 0 8 we use these two end member 34s values to estimate the contributions of these sources of sulfur in authigenic groundwater sulfide minerals and in waters derived from oxidation of these sulfide minerals across a range of environments we show that authigenic groundwater pyrite along joints in the otago schist is derived primarily from metamorphic basement sulfur in contrast authigenic groundwater pyrite cementing miocene recent aquifers shows a substantial marine aerosol component and represents a distinct hydrogeological system we suggest that marine aerosols represent a significant flux to the terrestrial sulfur cycle that has been present through the groundwater system in otago over the past 20 million years

3d geometrical modelling of post foliation deformations in metamorphic terrains syros cyclades greece superposed to ductile syn metamorphic deformations post foliation deformations affect metamorphic units during their exhumation understanding the role of such deformations in the structuration of metamorphic units is key for understanding the tectonic evolution of convergence zones we characterize post foliations deformations using 3d modelling which is a first order tool to describe complex geological structures but a challenging task where based only on surface data we propose a modelling procedure that combines fast draft models interpolation of orientation data with more complex ones where the structural context is better understood implicit modelling allowing us to build a 3d geometrical model of syros island blueschists cyclades based on field data with our approach the 3d model is able to capture the complex present day geometry of the island mainly controlled by the su perposition of three types of post metamorphic deformations affecting the original metamorphic pile i a top to south ramp flat extensional system that dominates the overall island structure ii large scale folding of the metamorphic units associated with ramp flat extensional system and iii steeply dipping normal faults trending dominantly nnw sse and ew the 3d surfaces produced by this method match outcrop data are geologically consistent and provide reasonable estimates of geological structures in poorly constrained areas

seasonal variations of accumulation and the isotope record in ice cores a study with surface snow samples and firn cores from neumayer station antarctica at the german wintering base neumayer an intensive glacio meteorological program was carried out during the last two decades a complete meteorological data set and data from surface snow samples snow pits firn cores and weekly accumulation measurements from a stake array are available we first investigated the attenuation of the seasonal d18o signal due to water vapour diffusion in the snow pack a comparison of surface snow samples and firn cores of different age shows that only one third of the seasonal d18o signal of the surface snow samples remains in the cores after the first year no further significant change in the amplitude of the seasonal d18o signal is found later changes in the seasonal distribution of accumulation can lead to a bias in ice core properties this is studied on a short time scale using the available high time resolution data of accumulation stable isotope ratios and air temperature mean annual d18o values from firn cores are not well correlated to annual mean air temperatures however the correlation is improved considerably by weighting the annual mean air temperature by accumulation at neumayer mainly the cyclonic activity in late winter early spring determines whether and how the core data are biased

the influence of atmospheric zonal wave three on antarctic sea ice variability 1 the study examines the relationship between atmospheric zonal wave three and antarctic sea ice variability using an index of zonal wave three and sea ice concentration the net sensible heat flux and the surface air temperature are used to explain the apparent atmosphere sea ice interaction the results show that zonal wave three forces an alternating pattern of equatorward colder and poleward warmer flow which influences the temperature difference between the atmosphere and the ocean the net sensible heat flux is positive ocean heat loss is greater and sea ice growth and expansion is greater in regions of colder air the reverse is true in regions of warmer air this influence of zonal wave three on sea ice concentration appears greatest in the southern fall and early winter it is most clearly seen in the ross and weddell seas outflows and off the amery iceshelf

structural and thermochronometric evidence for multi stage exhumation of southern syros cycladic islands greece abstract the attic cycladic metamorphic core complex province was formed during miocene to recent regional back arc extension in response to slab rollback and gravitational collapse the development of several metamorphic core complexes along extensional low angle detachment faults resulted in the exhumation of lower plate rocks and the tectonic denudation of the upper plate that is only sparsely exposed throughout the aegean sea one of these areas is in southern syros where the tectonic configuration includes three tectonometamorphic units separated by two detachment faults the lower plate cycladic blueschist unit underwent late cretaceous eocene hp lt metamorphism and subsequent greenschist facies overprint during oligo miocene times the tectonically overlying greenschist facies upper unit is a tectonic sliver between the cycladic blueschist unit and the structurally highest unit the vari unit which is dominated by quartzofeldspathic gneisses that are affected by four distinct deformation events d1 d4 the late cretaceous upper greenschist facies d1 episode is related to late cretaceous eocene subduction while d2 d4 fabrics were formed in response to late cenozoic extension and exhumation field relations and structural data suggest that the late miocene brittle vari detachment juxtaposes both vari unit and upper unit against the cycladic blueschist unit mylonitic rocks observed at the base of vari unit along the contact with upper unit and zircon and apatite u th he thermochronometry corroborate this scenario with lower plate cycladic blueschist unit rocks recording rapid cooling at 8 10 ma in contrast cooling ages from the vari unit cluster at 13 15 ma indicating rapid exhumation coeval with activity along the livadi detachment on the neighboring island of tinos these data document new evidence that vari unit was affected by a major middle miocene phase of exhumation and an older semi brittle episode both unrelated to late miocene detachment faulting revealing that crustal extension occurred in multiple stages and in a protracted episodic fashion similar to other parts of the cyclades

silicate rock weathering and atmospheric soil co2 uptake in the amazon basin estimated from river water geochemistry seasonal and spatial variations abstract using the data of the camrex project 1982 1984 on the water geochemistry of the amazon river and its main tributaries it was possible to assess the silicate rock weathering processes and the associated consumption of atmospheric soil co2 taking into account seasonal and spatial variations this study confirms the important role of the andes in the fluvial transport of dissolved and particulate material by the amazon and it shows for the first time that the silicate weathering rate and atmospheric soil co2 consumption are higher in the andes than in the rest of the amazon basin the seasonal variations exhibit the significant role of runoff as a major factor controlling silicate weathering processes and show that the chemical erosion rates vary greatly from low discharge to high discharge the average weathering rate estimated for the whole amazon basin 15 m my is comparable to other estimations made for other tropical equatorial environments a comparison between physical and chemical weathering rates of silicate rocks for the amazon basin and for each tributary basin show that in the andes and in the amazon trough the soil thicknesses are decreasing whereas in the shield the soil profiles are deepening

incongruent weathering of cd and zn from mine tailings a column leaching study the weathering of discharged mine tailings can contaminate groundwaters rivers and floodplains with potentially toxic cd and zn depending on tailings mineralogy storage dispersal and climatic conditions the mechanisms of long term tailings weathering and its influence on waste piles and floodplain environments were assessed by a column leaching experiment that incorporated tailings and soil from potosi bolivia and modelled 20 cycles of wet and dry season conditions over three calendar years chemical analysis of the leachate and column solids optical mineralogy xrd sem epma bcr and water soluble chemical extractions and speciation modelling were carried out to determine the processes responsible for the leaching of cd fe s and zn over this period approximately 50 to 95 of the original cd and 50 to 60 of the zn were leached from the columns large amounts of leached cd and zn at the beginning of the experiment are attributed to the dissolution of soluble sulphate minerals present in the original tailings and formed after the first wetting of the columns the zn cd mass ratios of the tailings and soil initially 429 and 400 respectively vary considerably over the course of the experiment low values between 220 and 300 in the early cycles are attributed to preferential weathering of cd rich wurtzite zn fe s and sequestration of zn in preference to cd in secondary fe phases forming in the columns in the middle cycles dissolution of secondary fe oh 3 under low ph 3 conditions and of ferroan cd poor sphalerite zn fe s releases zn and raises the zn cd ratio to 550 600 in the tailings only columns and up to 1500 in the mixed tailings soil columns the very high ratios in the latter are also ascribed to the formation of low molecular weight organic ligands that have high affinity for zn over cd in the later column cycles zn cd ratios return to near initial values due to the weathering of fe poor sphalerite and secondary fe phases and the declining preference of zn over cd in the soil organic acids under the strongly acidic conditions prevailing in the columns the formation and dissolution of secondary soluble sulphate minerals also play a role in cd and zn cycling especially at the beginning of the experiment

interaction between antarctic sea ice and synoptic activity in the circumpolar trough implications for ice core interpretation interactions between antarctic sea ice and synoptic activity in the circumpolar trough have been investigated using meteorological data from european centre for medium range weather forecasts ecmwf interim re analysis and sea ice data from passive microwave measurements total antarctic sea ice extent does not show large interannual variations however large differences are observed on a regional monthly scale depending on prevailing winds and currents and thus on the prevailing synoptic situations the sea ice edge is also a preferred region for cyclogenesis due to the strong meridional temperature gradient high baroclinicity in that area the motivation for this study was to gain a better understanding of the interaction between sea ice extent and the general atmospheric flow particularly the frequency of warm air intrusions into the interior of the antarctic continent since this influences precipitation seasonality and must be taken into account for a correct climatic interpretation of ice cores two case studies of extraordinary sea ice concentration anomalies in relation to the prevailing atmospheric conditions are presented however both strong positive and negative anomalies can be related to warm biases in ice cores indicated by stable isotope ratios especially in connection with the negative phase of the southern annular mode

a climatological analysis of high precipitation events in dronning maud land antarctica and associated large scale atmospheric conditions the link between high precipitation in dronning maud land dml antarctica and the large scale atmospheric circulation is investigated using era interim data for 1979 2009 high precipitation events are analyzed at halvfarryggen situated in the coastal region of dml and at kohnen station located in its interior this study further includes a comprehensive comparison of high precipitation in era interim with precipitation data from the antarctic mesoscale prediction system amps and snow accumulation measurements from automatic weather stations awss with the limitations of such a comparison being discussed the era interim and amps precipitation data agree very well however the correspondence between high precipitation in era interim and high snow accumulation at the awss is relatively weak high precipitation events at both halvfarryggen and kohnen are typically associated with amplified upper level waves this large scale atmospheric flow pattern is preceded by the downstream development of a rossby wave train from the eastern south pacific several days before the precipitation event at the surface a cyclone located over the weddell sea is the main synoptic ingredient for high precipitation both at halvfarryggen and at kohnen a blocking anticyclone downstream is not a requirement for high precipitation per se but a larger share of blocking occurrences during the highest precipitation days in dml suggests that these blocks strengthen the vertically integrated water vapor transport ivt into dml a strong link between high precipitation and the ivt perpendicular to the local orography suggests that ivt could be used as a proxy for high precipitation in particular over dml s interior

aegean paleomagnetic inclination anomalies is there a tectonic explanation abstract more than a decade of paleomagnetic research in the aegean area mainly by french investigators c laj c kissel and their colleagues has provided a valuable data base for the evaluation of cenozoic aegean tectonics systematic rotations are documented and have been interpreted by the original investigators in the light of the evolution of the hellenic arc however less attention has been paid to the significance of the paleomagnetic inclinations which also are anomalous twenty one out of 22 paleomagnetic studies performed to date within the general aegean region have yielded paleolatitudes that are too shallow when compared with reference curves for either africa or eurasia suggesting northward relative transport with respect to both continents sedimentary volcanic and plutonic units are involved ages range from oligocene to pliocene some of these apparent paleolatitude anomalies may merely be the result of inclination flattening in certain kinds of clastic sedimentary rocks however shallow inclinations in igneous rocks cannot be so easily dismissed the explanation for these anomalously shallow inclinations does not appear to lie with the reference curves because several other reference curves calculated in several different ways yield essentially the same result we suggest that the paleomagnetic pattern may reflect real northward displacement of crustal blocks within the aegean region measured with respect to both europe and africa the amount of displacement appears to increase systematically to the west the pattern of local block rotations noticed by earlier investigators argues that the displacement did not involve a single coherent aegean block but rather a collection of smaller blocks moving quasi independently geological consequences of northward relative displacement of the aegean block ought to include mid tertiary and or later compressional structures in the north e g rhodope and extensional structures in the leading edge of the african plate

depositional ages of clastic metasediments from samos and syros greece results of a detrital zircon study siliciclastic metasediments from the islands of samos and syros cycladic blueschist unit greece were studied to determine maximum sedimentation ages four samples from the ampelos unit on samos yielded age distribution spectra that range from 320 ma to 3 2 ga with a dominance of cambrian neoproterozoic zircons 500 1 100 ma the youngest well constrained age groups cluster at 500 550 ma our results allow to link the samos metasediments with occurrences showing similar age distribution patterns elsewhere in the eastern mediterranean region greece turkey libya israel and jordan that record the influx of pan african detritus the lack of post 500 ma zircons in the samos samples is in marked contrast to the data from syros that indicates triassic to cretaceous depositional ages the samples from syros were collected from the matrix of a meta ophiolitic melange that is exposed near the top of the metamorphic succession as well as from outcrops representing the basal part of the underlying marble schist sequence the zircon populations from syros were mainly supplied by mesozoic sources dominated by triassic protolith ages subordinate is the importance of pre triassic zircons but this may reflect bias induced by the research strategy sediment accumulation continued until late cretaceous time but the overall contribution of jurassic to cretaceous detritus is more limited zircon populations are dominated by grains with small degree of rounding suggesting relatively short sediment transportation available observations are in accordance with a model suggesting deposition close to the magmatic source rocks

the impact of tailings dam spills and clean up operations on sediment and water quality in river systems the rios agrio guadiamar aznalcollar spain the aznalcollar tailings dam at boliden apirsa s aznalcollar los frailes ag cu pb zn mine 45 km west of seville spain was breached on 25 april 1998 flooding approximately 4600 hectares of land along the rios agrio and guadiamar with approximately 5 5 million m3 of acidic water and 1 3 106 m3 of heavy metal bearing tailings most of the deposited tailings and approximately 4 7 106 m3 of contaminated soils were removed to the aznalcollar open pit during clean up work undertaken immediately after the spill until january 1999 detailed geomorphological and geochemical surveys of the post clean up channel floodplain and valley floor and sediment and water sampling were carried out in january and may 1999 at 6 reaches representative of the types of river channel and floodplain environments in the rio guadiamar catchment affected by the spill the collected data show that the clean up operations removed enough spill deposited sediment to achieve pre spill metal ag as cd cu pb sb tl zn concentrations in surface sediment these concentrations however are still elevated above pre mining concentrations and emphasise that mining continues to contaminate the agrio guadiamar river system dilution by relatively uncontaminated sediment appears to reduce metal concentrations downstream but increases in metal and as concentrations occur downstream presumably as a result of factors such as sewage and agriculture river water samples collected in may 1999 have significantly greater dissolved concentrations of metals and as than those from january 1999 probably due to greater sulphide oxidation from residual tailings with concomitant release of metals in the warmer early summer months these concentrations are reduced downstream probably by a combination of dilution and removal of metals by mineral precipitation single chemical extractions de ionised water cacl2 0 01 mol l 1 ch3coonh4 1 m ch3coona 1 m and ammonium oxalate 0 2 m on alluvial samples from reaches 1 and 6 the tailings pre spill alluvium and marl have shown that the order of sediment borne contaminant mobility is generally zn cd cu pb as pb and as are relatively immobile except possibly under reducing conditions much of the highly contaminated sediment remaining in the floodplain and channel still contains a large proportion of tailings related sulphide minerals which are potentially reactive and may continue to release contaminants to the agrio guadiamar river system our work emphasises the need for pre mining geomorphological and geochemical data and an assessment of potential contributions of contaminants to river systems from other non mining sources

vertical accumulation of potential toxic elements in a semiarid system that is influenced by an abandoned gold mine abstract the mining zone at el triunfo baja california sur mexico was exploited for gold extraction for 200 years this area includes more than 100 abandoned mining sites these sites contain mine tailings that are highly contaminated with potential toxic elements pte such as as cd pb sb zn and other associated elements over time these wastes have contaminated the sediments in the adjacent fluvial systems our aim was to assess the vertical pte variations in the abandoned mining zone and in the discharge of the main arroyo into a small lagoon at the pacific ocean sediments were collected from the two following locations in the mining zone near the arroyo basin tailings 1 an old alluvial terrace overbank and a test pit tp and 2 two sediment cores locations at the arroyo discharge into a hypersaline small lagoon samples were analyzed by icp ms icp oes and inaa and the methods were validated the overbank was the most contaminated and had as cd pb sb and zn concentrations of 8690 226 84 700 17 400 and 42 600 mg kg 1 respectively which decreased with depth in addition the tp contained elevated as cd pb sb and zn concentrations of 694 18 8 5001 39 2 and 4170 mg kg 1 respectively the sediment cores were less contaminated however the as cd pb sb and zn concentrations were greater than the concentrations that are generally found in the earth s crust the normalized enrichment factors nefs which were calculated from the background concentrations of these elements in the system showed that extremely severe as cd pb sb and zn nef 50 enrichment occurred at the overbank the tp was severe to very severely enriched with as cd pb sb and zn nef 10 50 the sediment cores had a severe enrichment of as pb and zn nef 10 25 their vertical profiles showed that anthropogenic influences occurred in the historic sediment deposition at the overbank and tp and in the sediment cores in addition the as pb and zn concentrations in the sediment cores were related to the deposition of fine sediments and organic carbon

transpression and transtension within different structural levels in the central aegean region in the central aegean region shortening structures within the miocene molasse arc known since long ago nevertheless recently most authors have recognized extensional structures within middle to upper miocene granitoids proposing a basin and range type model for the late cenozoic evolution of the area to resolve this problem structural mapping and mesoscopic analysis of 900 faults sampled from 12 islands have been carried out late orogenic uplift of the central aegean region is the result of a continuous convergence and indentation of the pelagonian plate by the apulian plate that took place throughout the miocene formation of core complexes can be associated with a large oblique upthrusts b steeply dipping strike slip faults and c low angle normal faults the latter are produced by low multidirectional extension which has affected small crustal regions as adjacent areas underwent transpression in the late stages of collision the overthickened crust began to collapse due to transtension which was replaced by extension caused by the roll back of the hellenic subduction zone in the lower pliocene time this extensional regime has lasted until the present day

geochemical compositions of soluble salts in aeolian sands from the taklamakan and badanjilin deserts in northern china and their influencing factors and environmental implications two large sandy seas in northern china the taklamakan and badanjilin deserts were investigated for geochemical variations of soluble salts in aeolian sands the aim was to explore factors influencing the composition and distribution of soluble salts in aeolian sands and their environmental implications the total concentrations of soluble salt in the aeolian sands range between 0 14 and 1 32 with ph ranging between 8 4 and 9 6 indicating a primary degree of salt accumulation and alkaline soil conditions in these regions sodium chloride and bicarbonate are the major salts high inter regional homogenization and small local differences in the chemical compositions and distributional patterns of salt occur in the two deserts the spatial variations in salt content correlate with regional climatic parameters such as precipitation and temperature this suggests that the regional air temperature and moisture conditions of climate have a significant influence on the soluble salts in aeolian sands the domination of sedimentation of soluble salts in aeolian sands deposited via atmospheric processes which is heavily associated with dry deposition is discussed case studies from the two deserts suggest that variations in salt content in sedimentary sequences interlaid by aeolian and lacustrine sediments should be interpreted with care if the aim is to reveal palaeo environmental changes to a certain extent the two deserts as inferred from the carbon bearing salts and the alkalinity of the sandy soils appear to have potential to provide a significant contribution to the global carbon cycle

crustal scale geometry and kinematics of late orogenic extension in the central aegean cyclades and ewia island abstract the aegean continental domain is known to be the site of widespread back arc extension since at least the middle miocene overprinting structures related to the mesozoic cenozoic hellenic orogeny features attributed to early thrusting include the overall ductile deformation within two broad belts that have suffered hp lt metamorphism across the aegean this study summarizes the results of a structural study in the central aegean area cyclades and evvia island examining in particular the relationship between ductile and brittle deformation on a regional scale extension appears to be responsible for most of the ductile deformation within hp rock units that have experienced penetrative greenschist facies and higher grade metamorphic overprinting on each island studied progressive extensional deformation has occurred through the development of a major normal sense detachment zone down to depths of about 18 25 km the geometry of the extensional system on the scale of the central aegean is described taking into account the characteristic features of the regional scale ductile strain field at least two probably three subparallel major north dipping detachment zones are identified trending nw se in the northwestern cyclades and e w in the southeastern cyclades both with initial dips estimated at around 30 45 the present geometry of the extensional system implies that these detachment zones and related metamorphic core complexes interfere with each other two main evolutionary models are considered which can account for such a kinematic link between parallel detachment zones structural data favour the sequential development of synthetic major detachments zones in a direction opposite to the sense of dip of the detachments early oligocene lower miocene detachment type extension in the area studied is related to a late orogenic post thickening back arc setting

geochemistry and geochronology of hp melanges from tinos and andros cycladic blueschist belt greece abstract u pb zircon geochronology sr nd isotope and bulk rock geochemistry have been applied to meta igneous and meta sedimentary rocks from high pressure metamorphic melanges exposed on the cycladic islands of tinos syros and andros ion microprobe shrimp u pb zircon dating of 7 samples representing meta igneous blocks tinos a blackwall zone tinos and chlorite talc schists from block matrix contacts syros and tinos yielded cretaceous ages of c 80 ma many of the criteria commonly used to distinguish between magmatic or metamorphic zircon genesis internal structure th u ratio ree characteristics ti in zircon thermometry enclosed mineral phases do not provide unambiguous constraints for the mode of formation however a magmatic origin for cretaceous zircon of meta gabbros and eclogites is considered likely supporting evidence for a previously suggested metamorphic origin for c 80 ma zircon in eclogite has not been found zircon of the same age occurring in chlorite talc schists is presumably related to non magmatic processes well defined cretaceous age groups clustering at c 79 ma also occur in the detrital zircon populations of 2 quartz mica schists representing the melange matrix on tinos and suggest a much later time for sediment accumulation than previously assumed the importance of c 57 ma zircon ages remains unclear but may record either hp metamorphic processes or a post 57 ma depositional age the youngest age group in a third quartz mica schist from tinos collected outside the main melange occurrences clusters at c 226 238 ma in all clastic metasediments from tinos most data points plot along the concordia between c 300 and 900 ma single data points indicate concordant ages of c 2 5 ga 2 3 ga and 1 ga respectively the youngest 206 pb 238 u age group that has been recognized in a felsic paragneiss from andros indicates an age of 163 1 3 9 ma and mostly represents overgrowths around zircon with ages in the range from 272 to 289 ma single data points of other inherited cores provided 206 pb 238 u ages of c 630 and c 930 ma meta gabbros from tinos show a large compositional variability and were found at 4 locations each with distinct compositional characteristics suggesting different crystallization histories different sources and or significant post magmatic disturbance the geochemistry of melange blocks and the identical u pb zircon ages suggest that the block matrix associations on tinos and syros can be grouped together on a broader regional scale there seem to be similarities between some meta igneous rocks from tinos and evvia field relationships indicate that the melanges occurring in southern andros and northern tinos can be correlated but supporting geochemical and or geochronological evidence for this interpretation could not be established previously published jurassic ages for mafic and felsic melange blocks from andros suggest a genetic relationship to the ophiolite occurrences exposed in the larger balkan region a similar regional correlation is also considered likely for the cretaceous meta gabbros from tinos and syros but cannot be documented with certainty

synchronous variability in the southern hemisphere atmosphere sea ice and ocean resulting from the annular mode zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the southern hemisphere during all seasons this is true not only in observations but also in an unforced 15 000 yr integration of a coarse resolution r15 coupled ocean atmosphere model here it is documented how this mode of atmospheric variability known as the southern annular mode sam generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the sam the positive phase of the sam is associated with an intensification of the surface westerlies over the circumpolar ocean around 608s and a weakening of the surface westerlies farther north this induces ekman drift to the north at all longitudes of the circumpolar ocean and ekman drift to the south at around 308s through mass continuity the ekman drift generates anomalous upwelling along the margins of the antarctic continent and downwelling around 458s the anomalous flow diverging from the antarctic continent also increases the vertical tilt of the isopycnals in the southern ocean so that a more intense circumpolar current is also closely associated with positive sam in addition the anomalous divergent flow advects sea ice farther north resulting in an increase in sea ice coverage finally positive sam drives increases in poleward heat transport at about 308s while decreases occur in the circumpolar region ocean and sea ice anomalies of the opposite sign occur when the sam is negative the ocean and sea ice fluctuations associated with the sam constitute a significant fraction of simulated ocean variability poleward of 308s year round the robustness of the mechanisms relating the sam to oceanic variability suggests that the sam is likely an important source of large scale variability in the real southern hemisphere ocean

climatic and geological factors contributing to the natural water chemistry in an arid environment from watersheds in northern xinjiang china a natural water hydrochemical investigation was carried out on three watersheds in northern xinjiang china to evaluate the climatic geological and anthropogenic influence on aqueous major element chemistry in an arid environment wide spatial variations are observed in the dissolved solids tds and water chemistry the hydrochemistry is typically carbonate and alkaline in nature with ca2 hco3 and so42 dominating the major ion composition four major water types ca hco3 ca nda non dominant anion ca so4 and ndc non dominant cation nda or na nda type are identified in terms of the piper model the water chemistry agrees well with the rock dominance mechanism with a tds value of 80 600 mg l and a na na ca2 ratio of 0 1 0 6 correlation analysis suggests that most of the ions derive from multiple sources stoichiometric analyses indicate that carbonate weathering is the primary source of dissolved ions followed by silicate weathering and evaporite dissolution the effects of local pollution have somewhat greater contribution on the oases and central areas of the zhungarer watershed most parts of the rivers show an increasing trend in the dissolved load toward the lower reaches which is primarily attributed to an evaporation process control along the water course variations in water chemistry show clear correlation with the regional lithological distribution topography and atmospheric precipitation using rainwater as a baseline contributions from atmospheric precipitation and rock weathering to the tributary chemistry are roughly evaluated to be in the range of 2 39 average 13 and 59 98 average 86 respectively implying a high effective control of regional geology on stream chemistry compared with that of atmospheric input c 2012 elsevier b v all rights reserved

rapid extension recorded by cooling age patterns and brittle deformation naxos greece the metamorphic core complex exposed as the island of naxos in the aegean sea records an unusually complete sequence of structures developed as a result of continental extension the structures formed during miocene rise and cooling from ductile upper amphibolite facies and anatectic conditions to brittle near surface conditions beneath the naxos detachment fault top to the north ductile fabrics in the footwall which initially developed during amphibolite facies prograde metamorphism were overprinted by a succession of north directed normal sense lower temperature brittle structures as the footwall was tectonically unloaded and unroofed pseudotachylite and cataclasite formation brittle faulting alteration and erosion of the footwall occurred during continued slip and tectonic denudation neogene conglomerate and megabreccia in part derived from exhumation of this footwall lie structurally above the peripheral naxos fault published k ar and 40ar 39ar ages for hornblende white mica and biotite in the footwall decrease northwestward apparent ages 17 50 ma in the southeast correspond to areas of low metamorphic grade where preextension argon was partially retained published ages 16 10 ma in higher grade rocks of the domal core in the north are cooling ages that for each of the three minerals show a component of younging in the nne direction of extension assuming this is the direction of unroofing we interpret the rate of this younging as the fault slip rate as the footwall rocks moved 20 km ssw relative to their hanging wall along the base of the naxos detachment fault the calculated rates of slip average 5 8 mm yr comparable to maximum rates reported in the basin and range province

magnesium isotope systematics of the lithologically varied moselle river basin france abstract magnesium and strontium isotope signatures were determined during different seasons for the main rivers of the moselle basin northeastern france this small basin is remarkable for its well constrained and varied lithology on a small distance scale and this is reflected in river water sr isotope compositions upstream where the moselle river drains silicate rocks of the vosges mountains waters are characterized by relatively high 87sr 86sr ratios 0 7128 0 7174 in contrast downstream of the city of epinal where the moselle river flows through carbonates and evaporites of the lorraine plateau 87sr 86sr ratios are lower down to 0 70824 magnesium in river waters draining silicates is systematically depleted in heavy isotopes 26mg values range from 1 2 to 0 7 relative to the value presently estimated for the continental crust and a local diorite 0 5 in comparison 26mg values measured in soil samples are higher 0 0 this suggests that mg isotope fractionation occurs during mineral leaching and or formation of secondary clay minerals on the lorraine plateau tributaries draining marls carbonates and evaporites are characterized by low ca mg 1 5 3 2 and low ca sr 80 400 when compared to local carbonate rocks ca mg 29 59 ca sr 370 2200 similar to other rivers draining carbonates the most likely cause of the mg and sr excesses in these rivers is early thermodynamic saturation of groundwater with calcite relative to magnesite and strontianite as groundwater chemistry progressively evolves in the aquifer 26mg of the dissolved phases of tributaries draining mainly carbonates and evaporites are relatively low and constant throughout the year from 1 4 to 1 6 and from 1 2 to 1 4 respectively within the range defined for the underlying rocks downstream of epinal the compositions of the moselle river samples in a 26mg vs 87sr 86sr diagram can be explained by mixing curves between silicate carbonate and evaporite waters with a significant contribution from the vosgian silicate lithologies 70 temporal co variation between 26mg and 87sr 86sr for the moselle river throughout year is also observed and is consistent with a higher contribution from the vosges mountains in winter in terms of runoff and dissolved element flux overall this study shows that mg isotopes measured in waters rocks and soils coupled with other tracers such as sr isotopes could be used to better constrain riverine mg sources particularly if analytical uncertainties in mg isotope measurements can be improved in order to perform more precise quantifications

effectiveness of various cover scenarios on the rate of sulfide oxidation of mine tailings long term environmentally sound disposal of the millions of tons of mining residue is a serious challenge to the international mining industry this paper evaluates through a numerical investigation the potential performance of desulfurized tailings as a cover material for the reduction of acidic drainage from sulfidic tailings this evaluation is facilitated through a comparison of various cover types as decommissioning options the cover types considered consist of a desulfurized tailings material cover exposed to ambient climate conditions a water cover flooded tailings and a combination cover type as part of the evaluation of cover performances the effect of climatic variability on the potential rate of sulfide oxidation in tailings with an open ground surface was also assessed the numerical analysis was conducted using the model pyrox which was modified to allow for variably saturated conditions time varying moisture contents and to account for the temperature dependence of henry s law and gas diffusion in the case study presented here the benign cover material consists of a low sulfide waste stream cassiterite float tails cft a by product of the production of tin concentrate cassiterite sno2 modelling results after a simulation period of 100 years indicate that a water cover alone or an exposed cft cover alone are both less effective options than the combined cover type a water cover alone leads to a reduction of approximately 99 1 in the oxidation rate relative to uncovered tailings while the combined cover type results in the lowest potential extent of sulfide oxidation after mine closure an approximately 99 8 reduction importantly a cft cover exposed to ambient environmental conditions can still substantially reduce the sulfide oxidation rate by approximately 75 82 over a 100 year time period relative to uncovered tailings variability in precipitation and hence percent saturation of the surface layer had less of an effect on the potential sulfide oxidation rate than did the cover type the performance of the exposed cft cover varied by less than 10 within the range of climatic conditions expected at the renison bell mine site in southwest tasmania australia although the modelling results indicate that the combined water and cft cover is the best option this approach achieves only a minor improvement over the water cover alone

uplift and exhumation of high pressure metamorphic terrains the example of the cycladic blueschist belt aegean sea the cycladic blueschists emerged from a depth of more than 50 km during the tertiary these rocks are now covered only by a thin fraction of the synmetamorphic overburden upper plate remnants of the upper plate include low p crystalline rocks and sediments which have been juxtaposed onto the lower plate blueschists in several stages since the early miocene the low angle contacts operated as normal faults which removed the overburden from above the cycladic blueschists detailed investigations on tinos island indicate that the fractured blocks of the upper plate lying above a low angle normal fault did not rotate this shows that the faults initiated as rather gently dipping fractures similar structures were also reported from other blueschist terrains kinematic analysis of such flat lying faults implies that the synmetamorphic overburden should be mostly located several hundred kilometers away from the present exposure of the blueschists considering that the cycladic blueschist belt exposes successively shallower units in the west and that rocks of the upper plate have an anatolian nature we suggest that these blueschists were dragged from beneath turkey we recognize that the blueschist unit has undergone further thrusting in the final stage of the exhumation as have its counterparts elsewhere in the hellenides the emergence of the blueschists in the tertiary was concomitant with continental collision and thrusting in the hellenides the operation of low angle normal faults with large extensional displacements occurred within this context of collision tectonics this extension occurred parallel to the strike of the convergent orogen

geochemistry of the amazon 1 precipitation chemistry and the marine contribution to the dissolved load at the time of peak discharge analyses of precipitation and surface water are used to estimate the fluxes of marine cyclic salts through that part of the amazon river system draining past obidos 80 of the basin at the time of peak discharge in june amazon precipitation chemistry can be devided into two principal components marine and terrestrial the marine component determined from analyses of marine rain consists of na k mg ca and cl in approximately sea salt proportions with s doubly enriched the excess sulfur is probably derived from gas phase inputs the terrestrial component makes an important contribution of k ca s and n much of which can be related to biological emissions the emission of reduced sulfur in the marine and terrestrial environment and nitrogen in the terrestrial environment is responsible for a natural acid rain in the amazon region with a ph from 4 7 to 5 7 this is about one tenth the acidity of polluted urban rain the chloride content of lowland rivers which drain regions lacking significant geologic sources of chloride shows a systematic decrease in chloride with increasing distance from the ocean this trend is used to define the cyclic salt background for amazonian surface waters cyclic salts in general make only a minor contribution relative to terrestrial inputs to the chemistry of amazon basin rivers even those draining intensely weathered terrains an estimated 17 6 cl 6 9 na 1 3 mg 3 6 s 0 4 k and 0 1 ca of the dissolved load at obidos during peak discharge is cyclic

chemical versus mechanical denudation in meta clastic and carbonate bedrock catchments on crete greece and mechanisms for steep and high carbonate topography on crete as is common elsewhere in the mediterranean carbonate massifs form high mountain ranges whereas topography is lower in areas with meta clastic rocks this observation suggests that differences in denudational processes between carbonate rich rocks and quartzofeldspathic units impart a fundamental control on landscape evolution here we present new cosmogenic basin average denudation rate measurements from both 10be and 36cl in meta clastic and carbonate bedrock catchments respectively to assess relationships between denudation rates processes and topographic form we compare total denudation rates to dissolution rates calculated from 49 new and previously published water samples basin average denudation rates of meta clastic and carbonate catchments are similar with mean values of 0 10 mm a and 0 13 mm a respectively the contribution of dissolution to total denudation rate was 10 in the one measured meta clastic catchment and 40 for carbonate catchments 0 05 mm a suggesting the dominance of physical over chemical weathering at the catchment scale in both rock types water mass balance calculations for three carbonate catchments suggests 40 90 of surface runoff is lost to groundwater to explore the impact of dissolution and infiltration to groundwater on relief we develop a numerical model for carbonate denudation we find that dissolution modifies the river profile channel steepness and infiltration changes the fluvial response time to external forcing furthermore we show that infiltration of surface runoff to groundwater in karst regions is an efficient way to steepen topography and generate the dramatic relief in carbonates observed throughout crete and the mediterranean

the north anatolian fault zone distributed neogene deformation in its northward convex part abstract the north anatolian fault zone is composed of two almost rectilinear branches which join in a northward convex bend in this bent zone the pontide anatolide collisional system has been cut across by two transpressional belts of fold and thrust and wrench faults of lower neogene age these structures were reactived during the neotectonic period the time of deposition of the pontus group for both of these deformational events and up to the present the tectonic regime remained generally transpressional with a nw se direction of compression and a ne sw direction of extension it is only recently during the upper pleistocene that the dextral wrench faults became more localized and more straight than previously the complexity of the eastern part of the north anatolian fault zone is better understood if one takes into account the role of inherited miocene pliocene transpressional structures

influence of the southern annular mode on the sea ice ocean system 1 the global sea ice ocean model orca2 lim driven by the ncep ncar national centers for environmental prediction national center for atmospheric research reanalysis daily 2 m air temperatures and 10 m winds and by monthly climatologies for precipitation cloud cover and relative humidity is used to investigate the impact of the southern annular mode sam on the antarctic sea ice ocean system our results suggest that the response of the circumpolar southern ocean consists of an annular and a nonannular component for the sea ice cover the non annular component seems to be the most important the annular component strongly affects the overall patterns of the upper ocean circulation when the sam is in its positive phase a northward surface ekman drift a downwelling at about 45 degreess and an upwelling in the vicinity of the antarctic continent are simulated the non annular component has a significant impact at the regional scale especially in the weddell ross amundsen and bellingshausen seas in those regions the pressure pattern associated with the sam induces meridional winds which advect warmer air in the weddell sea and around the antarctic peninsula and colder air in the amundsen and ross seas this implies a dipole response of sea ice to the sam with on average a decrease in ice area in the weddell sea and around the antarctic peninsula and an increase in the ross and amundsen seas during years with a high sam index the long term trend in the observed sea ice area does not appear to be related to the trend in the sam index

precipitation over the interior east antarctic ice sheet related to midlatitude blocking high activity abstract intermittent atmospheric blocking high activity in the south tasman sea is shown to play a key role in delivering substantial snowfall as far south as at least 75 s on the central east antarctic ice sheet plateau typically cyclones fail to penetrate this far 1000 km inland and accumulation was thought to be dominated by clear sky precipitation in east antarctica the meridional cloud bands delivering the moisture originate from as far north as 35 40 s and appear to preferentially pass over the east antarctic coast in a corridor from 120 to 160 e comparison of surface observations model and satellite data suggests that a few such episodes contribute a significant proportion of the low mean annual accumulation of the central east antarctic ice sheet e g an estimated 44 at dome c over 18 days in december 2001 january 2002 blocking high related incursions also cause abrupt increases in the surface wind speed snow redistribution and air temperature this has implications for th

the geodynamic evolution of the alpine orogen in the cyclades aegean sea greece insights from diverse origins and modes of emplacement of ultramafic rocks

effects of seasonal variability of accumulation on yearly mean δ18o values in antarctic snow the annual mean oxygen isotope content of antarctic snow is strongly influenced by the seasonal variability ofaccumulation since the annual mean 18 o value is frequently used to derive mean annual temperatures from ice cores changes in atmospheric circulation pattern can lead to large errors in the deduced temperature record at the german antarctic wintering base neumayer accumulation measurements have been carried out continuously over the last 16 years weekly readings of accumulation stakes combined with snow pits and shallow firn cores are used to investigate the influence of the seasonal variability of accumulation on the annual mean 18 o values and to estimate the possible error in the determination ofannual mean temperatures from ice cores by using the oxygen isotope record

southern hemisphere synoptic behavior in extreme phases of sam enso sea ice extent and southern australia rainfall abstract the association between southern hemisphere cyclones and anticyclones and the el nino southern oscillation enso southern annular mode sam antarctic sea ice extent sie and rainfall in perth and melbourne is explored those cities are respectively located in the southwestern and southeastern corners of australia where substantial decreasing rainfall trends have been observed over the last decades the need for a more unified understanding of large scale anomalies in storm indicators associated with the climate features itemized above has motivated this study the main aim is to identify cyclone anomalous areas that are potentially important in characterizing continental rainfall anomalies from a hemispheric perspective focusing on midlatitude australia the study covers the satellite era from 1979 to 2003 and was conducted for the southern winter when midlatitude rainfall is predominantly baroclinic the results indicate a well organized hemispheric cyclone pattern associated with en

implications for the interpretation of ice core isotope data from analysis of modelled antarctic precipitation by consideration of model generated atmospheric data dominant anomalies in the synoptic circulation patterns are observed under conditions of high ant arctic precipitation this is associated with strong moisture advection of marine origin examining precipitation at individual locations reveals a strong relationship between local surface temperature and precipitation amount days with 5 mm of precipitation which on average corresponds to about 8 of days over antarctica have surface tem peratures that are around 10 c warmer than the mean this bias suggest that abnormal conditions are captured in the ice core record and that interpretation or reconstruction of palaeotemperatur es will succeed only under the possibly flawed assumption that similar abnormal conditions existed at the time of deposition although isotopic analysis of ant arctic ice cores has been used successfully in palaeoclimate studies a complete under standing of the underlying processes affecting the deposition of the core remains to be found it is reasoned that by obtaining such an understanding it may be possible to recon struct the synoptic conditions under which accumulation occurred

a geologic reconnaissance of the cycladic blueschist belt greece the cycladic blueschist belt consists of two distinctive segments separated by a broad zone of superposed granitic and high temperature metamorphic rocks the northern segment contains early metamorphic fold axes and parallel glaucophane lineations that trend 060 with a progressive increase in metamorphism toward the southeast the southern segment contains similar fold axes and glaucophane lineations that trend 010 with an apparent increase in metamorphism toward the northwest radiometric dating of metamorphic minerals from both segments give apparent ages of about 40 to 80 m y these data suggest the existence of late mesozoic or early cenozoic subduction zones in the aegean region that subsequently collided