microbial processes forming daily lamination in a stromatolitic travertine abstract thirty hour continuous observation revealed that cyanobacterial metabolism caused daily lamination of a stromatolitic travertine in the shionoha hot spring sw japan the travertine is mainly composed of dendritic calcite crystals intercalated with bands of micritic particles at sub millimeter intervals cyanobacteria remained in the spaces between the calcite crystals during the daytime rose to the travertine surface to receive illumination as light decreased and formed a biofilm around sunset a micritic band developed on the biofilm where glutinous substances trapped detrital ferrihydrite rich particles transported from upcurrent the trapped particles covered the biofilm and in situ precipitation of calcite crystals became dominant before mid night the depositional model of daily lamination of the shionoha travertine may provide insight into the poorly understood origins and depositional rate of ancient stromatolites

a short term post lomagundi positive c isotope excursion at c 2 03 ga recorded by the wooly dolomite western australia it is generally accepted that carbon isotope variations in seawater were muted between c 2 06 ga after the end of the lomagundi carbon isotope excursion lcie and c 1 3 ga evidence is presented here that c 30 myr after the end of the lcie the biogeochemical cycle of carbon experienced a short term c 2 myr high amplitude up to 8 4 v pdb perturbation recorded in the horseshoe rift basin western australia the basin was initiated at c 2 03 ga with deposition of fluvial and shallow marine sandstones followed by the eruption of flood basalt and culminated with the deposition of platform carbonates and accompanying volcaniclastic and siliciclastic sediments wooly dolomite the horseshoe rift basin during deposition of the wooly dolomite was fault compartmentalized but connected to an ocean six depositional sequences make up the wooly dolomite sequence 1 records establishment of a carbonate platform conformably on basalt and coevally with volcaniclastic sedimentation all other sequences have dominant carbonate platform deposits and are unconformity bounded sequence 3 contains a c 57 m thick section with 13 c enriched carbonates bracketed between carbonates with close to 0 carbon isotope values further high resolution chemostratigraphic studies may reveal a more complex pattern of carbon isotope variations during the boring billion years but without precise geochronology similar short term carbon isotope excursions in carbonate successions could be incorrectly correlated to the lcie supplementary material table 2 including chemical and isotopic data sample locations and their position in figure 8 is available at https doi org 10 6084 m9 figshare c 2868055

upb geochronology of layered mafic intrusions in the eastern baltic shield implications for the timing and duration of paleoproterozoic continental rifting abstract paleoproterozoic layered mafic ultramafic intrusions are widespread in the eastern baltic fennoscandian shield and mark the initial stages of continental rifting and outpouring of voluminous flood basalts u pb zircon baddeleyite ages have been determined for seven layered mafic intrusions and a subvolcanic felsic unit associated with two paleoproterozoic volcanic sedimentary belts the pechenga imandra varzuga belt in the kola peninsula and the sumi sariola belt in karelia the layered intrusions in the sumi sariola belt show an age progression from 2449 0 1 1 ma for the burakovka complex located at the southeastern edge of the belt to 2442 1 1 4 ma and 2441 3 1 2 ma for the lukkulaisvaara and tsipringa intrusions of the olanga complex in northern karelia northeastern part of the belt these age results indicate a total duration of mafic magmatism along the ca 800 km belt in karelia to be less than 10 m y the pechenga imandra varzuga belt kola peninsula contains two distinct age groups of layered mafic intrusions and related rocks the younger of these overlaps with the ages obtained for the olanga intrusions and includes the 2441 0 1 6 ma imandra lopolith and a spatially associated felsic subvolcanic unit dated at 2442 2 1 7 ma the older group of mafic layered intrusions in the kola peninsula includes the 2501 5 1 7 ma pana tundra intrusion the 2504 4 1 5 ma monche pluton and the 2505 1 1 6 ma general skaya mountain intrusion the temporal and spatial distribution of the 2 50 2 44 ga rift related igneous activity in the baltic shield is consistent both with the model of starting mantle plume and with the model of passive rifting controlled by pre existing lithospheric weaknesses

travertine precipitation in the paleoproterozoic kuetsjarvi sedimentary formation pechenga greenstone belt ne fennoscandian shield abstract precambrian travertines tufas and speleothems either formed rarely or they have not been identified in previous studies in the absence of high pco2 soils in paleoproterozoic karst solution and speleothem formation occurred by processes distinct from those commonly found in present day low temperature karst environments however the high pco2 atmosphere could itself have encouraged karst formation the paleoproterozoic kuetsjarvi sedimentary formation of the pechenga greenstone belt nw russia includes abundant terrestrial carbonate precipitates these precipitates were sampled from a drillcore representing a complete section of the ca 120 m thick formation and were investigated for c and o isotopes acid soluble elemental contents and petrography the newly obtained results were used to constrain the origins of the precipitates and to illuminate different terrestrial carbonate types the investigated drillcore includes abundant small scale cavities and veins which are commonly filled with dolomite and quartz dolomite crusts are found both in the cavities and on bedding erosional surfaces dolomite cements coat uneven surfaces and surficial rock fragments the surficial dolomite crusts form distinct and discrete layers whereas the cements do not the cavity and vein fills are likely post depositional in origin whereas the surficial dolomite crusts and dolomite cements are likely syn depositional precipitates the investigated precipitates often show 13c values lower than those reported from their host rocks suggesting the influence of an external carbon source petrographic features and geochemical data suggest dissolution and precipitation of carbonate material originating from deep sourced co2 bearing fluids likely at high earth surface temperatures

extreme 13ccarb enrichment in ca 2 0 ga magnesite stromatolite dolomite red beds association in a global context a case for the world wide signal enhanced by a local environment abstract the palaeoproterozoic positive excursion of 13 c carb is now considered as three positive shifts of 13 c carb separated by returns to 0 which all occurred between 2 40 and 2 06 ma this isotopic event is unique in terms of both duration 300 ma and 13 c enrichment up to 18 the mechanism responsible for one of the most significant carbon isotopic shifts in earth history remains highly debatable to date 13 c of 10 to 15 cannot be balanced by organic carbon burial forg as there is no geological evidence for an enhanced corg accumulation prior to or synchronous with the excursion instead termination of these excursions is followed by formation of a vast reservoir of 13 c depleted organic material 45 at shunga and by one of the earliest known oil generation episodes at 2 0 ga none of the three positive excursions of 13 c carb is followed by a negative isotopic shift significantly below 0 as has always been observed in younger isotopic events reflecting an overturn of a major marine carbon reservoirs this may indicate that forg was constant implying that the mechanism involved in the production of corg was different onset of intensive methane cycling resulting in c change is another possibility the majority of sampled 13 c carb rich localities represents shallow water stromatolitic dolostones red beds and evaporites formed in restricted intracratonic basins and may not reflect global 13 c carb values closely spaced drill core samples n 73 of stromatolitic dolostones from the 1980 27 ma tulomozerskaya formation in the onega palaeobasin russian karelia have been analysed for 13 c carb and 18 o carb in order to demonstrate that different processes were involved in the formation of 13 c carb rich carbonates the 800 m thick magnesite stromatolite dolomite red beds succession formed in a complex combination of environments on the karelian craton peritidal shallow marine low energy protected bights barred basins evaporative ephemeral ponds coastal sabkhas and playa lakes the carbonate rocks exhibit extreme 13 c enrichment with 13 c values ranging from 5 7 to 17 2 vs v pdb mean 9 9 2 3 and 18 o from 18 6 to 26 0 vs v smow mean 22 0 1 6 the tulomozerskaya isotopic excursion is characteristic of the global 2 4 2 06 ga positive shifts of carbonate 13 c 12 c although it reveals the greatest enrichment in 13 c known from this interval an external basin s is considered to have provided an enhanced corg burial and global seawater enrichment in 13 c the global background value for the isotopic shift at tulomozero time ca 2 0 ga is roughly estimated at around 5 an explosion of stromatolite forming microbial communities in shallow water basins evaporative and partly restricted environments high bioproductivity enhanced uptake of 12 c and pene contemporaneous recycling of organic material in cyanobacterial mats with the production and consequent loss of co2 and ch4 are believed to be additional local factors which may have enhanced 13 c from 5 up to 17 such factors should be taken into account when interpreting carbon isotopic data and attempting to discriminate between the local enrichment in 13 c and globally enhanced 13 c values we propose that many previously reported 13 c values from other localities where environmental interpretations are not available or have not been taken into account may not represent the global 13 c values

a preliminary analysis of the formation of travertine and travertine cones in the jifei hot spring yunnan china the jifei hot spring emerges in the form of a spring group in the tibet yunnan geothermal zone southwest of yunnan province china the temperatures of spring waters range from 35 to 81 c and are mainly of hco3 na ca type the total discharge of the hot spring is about 10 l s the spring is characterized by its huge travertine terrace with an area of about 4 000 m2 and as many as 18 travertine cones of different sizes the tallest travertine cone is as high as 7 1 m the travertine formation and evolution can be divided into three periods travertine terrace deposition period travertine cone formation period and death period the hydrochemical characteristics of the jifei hot spring was analyzed and compared with a local non travertine hot spring and six other famous travertine springs the results indicate that the necessary hydrochemical conditions of travertine and travertine cones deposition in the jifei area are 1 high concentration of hco3 and co2 2 about 52 9 deep source co2 with significantly high text p text co 2 value 3 very high milliequivalent percentage of hco3 97 4 with not very high milliequivalent percentage of ca2 24 4 and 4 a large saturation index of calcite and aragonite of the hot water

freshening of the ross sea during the late 20th century ocean measurements in the ross sea over the past four decades one of the longest records near antarctica reveal marked decreases in shelf water salinity and the surface salinity within the ross gyre these changes have been accompanied by atmospheric warming on ross island ocean warming at depths of 300 meters north of the continental shelf a more negative southern oscillation index and thinning of southeast pacific ice shelves the freshening appears to have resulted from a combination of factors including increased precipitation reduced sea ice production and increased melting of the west antarctic ice sheet

cyclicity and paleoenvironmental dynamics rocknest platform northwest canada the superbly exposed rocknest formation northwest territories canada contains 140 to 160 shallowing upward cycles 1 to 15 m thick that contain distinctive marker beds and can be correlated for 200 km parallel to strike and 120 km perpendicular to strike cycles are grouped according to cycle base lithology which reflects paleogeographic position on the platform shale based cycles of the distal inner shelf pass westward into dolosiltite based cycles then into tufa based cycles of the shoal complex and then into grainstone based cycles of the outer shelf cycles are bounded by erosional surfaces that become less pronounced away from the shoal complex cycles formed in response to small asymmetric rapid rise slow fall eustatic oscillations in sea level 10 m during sea level rise rapid transgression and submergence of tidal flats occurred along the eastern margin of the shoal complex followed by eastward expansion of the shoal complex and slow progradation of tidal flats over lagoonal facies during sea level fall a glacio eustatic model for cyclicity accounts for the data favoring asymmetric eustatic sea level oscillations subaerial exposure and vadose diagenesis of platform during sea level falls arrested progradation and incomplete shoaling of many cycles and cycle periods of 20 000 to 100 000 yr 18 000 to 30 000 yr for rocknest inner shelf slopes ranged from 8 cm km average at high sea level stand to 2 cm km average at low sea level stand tidal flat progradation rates were 7 to 9 km 1 000 yr interaction of inner shelf slope sea level fall rate and sedimentation rate generates complete condensed or expanded cycle profiles one dimensional computer modeling reveals that sedimentation rates of shoal complex facies were 250 cm 1 000 yr that lag times in sedimentation following transgression may have ranged from zero on the shoal complex to 2 000 yr on the distal inner shelf and that subtidal sedimentation rates may have ranged from 80 cm 1 000 yr for the proximal inner shelf to 20 cm 1 000 yr for the distal inner shelf

hydrothermalism in the mediterranean sea abstract hydrothermalism in the mediterranean sea results from the collision of the african and european plates with the subduction of the oceanic part of the african plate below europe high heat flows in the resulting volcanic arcs and back arc extensional areas have set up hydrothermal convection systems most of the known hydrothermal sites are in shallow coastal waters

a widespread positive 13ccarbanomaly at around 2 33 2 06 ga on the fennoscandian shield a paradox carbon isotope measurements carried out on 201 carbonate samples from the early proterozoic of the kola peninsula n karelia and norway yield 13c pdb spanning 20 5 to 11 a general 13c secular trend shows that prior to 2 33 ga values are typically normal marine averaging around 3 0 between 2 33 and 2 06 ga in jatulian time there follows a rapid excursion to positive 13c of around 6 post jatulian time is characterized by 13c of sedimentary carbonates fluctuating between 5 and 3 also it is remarkable for the first pronounced development of diagenetic carbonates which have 13c between 14 and 6 the c 6 positive 13c shift with a duration of about 270 myr coincides with a maximum in the diversity and abundance of stromatolites and with widespread development of red beds but does not coincide with the maximum of buried corg mass the fennoscandian shield represents the largest isotoically anomalous carbonate province yet reported and the positive 13c excursion together with a series of major global palaeoenviromental changes seems to be more intense than the precambrian cambrian transition events however it is still not clear what kind of mechanism this phenomenon could be attributed to an increase of the ronov ratio and or broecker ratio and other possible models are discussed as the target for future investigations

degassing of mantle derived co2 and he from springs in the southern colorado plateau region neotectonic connections and implications for groundwater systems groundwaters of the southern colorado plateau arizona transition zone region are a heterogeneous mixture of chemically diverse waters including meteoric epigenic fluids karst aquifer waters and deeply sourced endogenic fluids we investigate the composition of travertine depositing co 2 rich springs to determine the origin transport and mixing of these various components the san francisco mountain recharge area has little surface flow instead waters discharge through major springs hundreds of kilometers away about 70 9340 l s of the total recharge 13 500 l s discharges 100 km to the north in the incised aquifer system at grand canyon most of this water 85 8070 l s emerges through two travertine depositing karst spring systems blue springs 6230 l s and havasu springs 1840 l s about 30 of recharge 4150 l s flows to the south and discharges along nw striking faults in the arizona transition zone forming the base flow for the verde river geochemical data define regional mixing trends between meteoric recharge and different endogenic end members that range from bicarbonate waters to sulfate waters water quality in the region is dictated by the percentage and character of the endogenic inputs that cause a measurable degradation of groundwater quality for water supply sources for the high co 2 include dissolution of limestone and dolostone c carb and external carbon c external c external is computed as the bicarbonate alkalinity dissolved inorganic carbon dic minus the c carb c external dic c carb c external is deconvolved using carbon isotopes into biogenically derived sedimentary carbon c organic and deep co 2 inputs c endogenic measured 13 c values are 17 to 3 versus pee dee belemnite pdb assuming 13 c carb 2 13 c organic 28 and 13 c endogenic 5 water chemistry mixing models indicate that an average of 42 of the total dic comes from dissolution of carbonate rocks 25 from organic carbon including soil respired co 2 and 33 from deep endogenic sources helium isotope values 3 he 4 he in gases dissolved in spring waters in the southern colorado plateau region range from 0 10 to 1 16 r a relative to air indicating that a significant component of the deeply derived fluid is from the mantle mean of 5 asthenospheric or 10 subcontinental lithospheric mantle source measured co 2 3 he ratios of 2 10 9 to 1 4 10 13 are adjusted by removing the proportion of co 2 from c carb and c organic to give values 10 for all but four samples various mixing models using co 2 3 he suggest that the mantle derived components of the co 2 load are highly variable from spring to spring and may make up an average of 10 of the total co 2 load of the regional springs fluid rock interactions involving endogenic fluids are suggested by 87 sr 86 sr 18 o and other tracers the endogenic co 2 component multiplied by discharge for each spring yields an integrated annual flux of deeply derived co 2 to the groundwater system of 1 4 10 9 mol yr this co 2 emission from the colorado plateau region reflects a complex tectonic evolution involving laramide hydration of the lithosphere above the farallon slab addition of fluids from mid tertiary mantle tectonism during slab removal and ongoing fluid movement induced by neotectonic small scale asthenospheric convection

equilibrium vs kinetic fractionation of oxygen isotopes in two low temperature travertine depositing systems with differing hydrodynamic conditions at baishuitai yunnan sw china abstract in order to understand the behavior of oxygen isotopic fractionation and obtain more reliable paleoclimatic data from surficial travertine deposits the hydrochemistry carbonate precipitation rates and the temporal and spatial variations in 18 o values of the modern travertine in two low temperature travertine depositing systems canal and pool with differing hydrodynamic conditions at baishuitai yunnan sw china were investigated during the warm rainy season may 24 to november 2 in 2010 it was found that the oxygen isotopic composition of travertine in the two systems showed distinct controlling mechanisms mainly due to different carbonate precipitation rates and water residence times for the canal system with fast flow large deviations between the calculated and measured temperatures indicated that travertine precipitated out of isotopic equilibrium this was due to rapid carbonate precipitation with intense co 2 degassing 18 o travertine values and water temperature increased downstream 1 and 4 c respectively while 18 o water values remained relatively stable it was shown that the 18 o values of travertine in the canal system recorded the 18 o values of dissolved carbonates hco 3 which also increased along the canal controlled by rayleigh distillation effects in contrast in the pools system with slow flow oxygen isotopic equilibrium between dissolved carbonates hco 3 and h 2 o was achieved and the 18 o travertine values did not display spatial variations calculated water temperatures using the equilibrium fractionation factors of coplen 2007 were identical to the measured ones which indicates that travertine in such pools system is suitable for the reconstruction of paleo precipitating temperatures finally by comparing these two systems we have obtained a simple criterion to determine the suitability of travertine to estimate temperatures the 18 o value of baco 3 precipitated from water samples is compared with the theoretical 18 o value of dissolved carbonate calculated using water temperature and 18 o water to check if the oxygen isotopes of the dissolved carbonate are in equilibrium with the water

large 13c enrichment in primary carbonates from andean altiplano lakes northwest argentina abstract we report here extreme 13 c enrichments up to 13 pdb in primary calcite and aragonite precipitates in saline well oxygenated waters from high altitude lakes in the southern andean altiplano northwestern argentina biological effects as well as variations in carbon source inputs and in the exchange rate with atmospheric co 2 are commonly considered the main controls on the carbon isotope values of authigenic lacustrine carbonate we present sedimentological and geochemical evidence that favors physical processes evaporation effects and co 2 degassing as major controls on 13 c enrichment we propose that large enrichments may result from the non equilibrium gas transfer isotope fractionation during co 2 degassing from thermal springs and evaporation effects in arid environments the dilution effect by large quantities of 14 c free co 2 hinders accurate 14 c chronology of these lake records based on lacustrine organic matter and aquatic plants our results indicate that geothermal and volcanic co 2 sources in lake basins located in volcanic settings and physical fractionation may have a greater significance than commonly accepted to explain lacustrine carbon isotope records

hydrothermal co2 degassing in seismically active zones during the late quaternary natural co2 discharges are abundant in turkey as evident from ongoing deposition of recent terrace mound travertines and emplacement of significant travertine vein and breccia deposits in fractured damage zones of active fault systems we report high precision u series age data for the vein carbonates combined with important field observations and geochemical data to evaluate the travertine veining and co2 degassing history in seismically active areas field evidence suggests that travertine filled veins and associated breccias represent hydrothermal eruption products which probably formed by hydraulic fracturing in response to overpressure of co2 rich fluids stable isotope and ree data support the field observations and indicate that travertine veins formed as thermogene deposits from rapidly ascending co2 rich fluids travertine veins from the kirsehir geothermal field give u series ages in a range from 10 6 0 3 ka to 86 16 1 24 ka with a majority of ages failing between 10 6 0 3 and 11 3 0 2 ka vein samples from the pamukkale geothermal field yield u series ages between 21 1 0 1 ka and 73 6 0 6 ka two major age groups are evident in pamukkale that cluster coherently around 21 ka and 25 ka a large number of travertine veins we dated by high precision u series technique coincide with times of cold dry climate events this is different from surface sinter deposits in geothermal fields which more frequently form during warm and wet periods we propose that a significant reduction in surface discharge of co2 by spring or geothermal waters during dry climate periods may promote oversaturation of co2 in deep reservoirs host rock fracturing in response to seismic shaking and fluid overpressure results in rapid exsolution and expansion of the dissolved gas and may lead to hydrothermal eruptions crown copyright c 2009 published by elsevier b v all rights reserved

high δ13c paleoproterozoic carbonates from the transvaal supergroup south africa marbles from the transvaal supergroup kaapvaal craton south africa record two positive carbon isotope excursions to average 13 c carbonate values of 6 to 8 relative to v pdb separated by carbonates with normal marine 13 c values 0 2 these elevated values have been preserved through metamorphic devolatilization together with an already documented high 13 c excursion in overlying rocks three separate positive carbon isotope excursions occurred on the kaapvaal craton in the interval 2 43 to 1 93 ga it is not yet clear how many of these excursions reflect global rather than local processes

low ph waters discharging from submarine vents at panarea island aeolian islands southern italy after the 2002 gas blast origin of hydrothermal fluids and implications for volcanic surveillance abstract a geochemical survey of thermal waters collected from submarine vents at panarea island aeolian islands southern italy was carried out from december 2002 to march 2007 in order to investigate i the geochemical processes controlling the chemical composition of the hydrothermal fluids and ii the possible relations between the chemical features of the hydrothermal reservoir and the activity of the magmatic system compositional data of the thermal water samples were integrated in a hydrological conceptual model which describes the formation of the vent fluid by mixing of seawater seawater concentrated by boiling and a deep highly saline end member whose composition is regulated by water rock interactions at relatively high temperature and shows clear clues of magmatic related inputs the chemical composition of concentrated seawater was assumed to be represented by that of the water sample having the highest mg content the composition of the deep end member was instead calculated by extrapolation assuming a zero mg end member the na k ca geothermometer when applied to the thermal end member composition indicated an equilibrium temperature of approximately 300 c a temperature in agreement with the results obtained by gas geothermometry

high resolution records of 10be in endogenic travertine from baishuitai china a new proxy record of annual solar activity abstract the accurate reconstruction of past solar activity is a prerequisite for assessing the role of solar forcing on climate variations cosmogenic 10be produced by galactic cosmic rays and stored in natural archives such as ice cores and lake sediments has been shown to be the most reliable as an indicator of past solar activity although reconstructions at a higher annual resolution have remained elusive due to dating imprecision and uncertainties concerning the effect of depositional processes here we employ a methodology that facilitates the annual reconstruction of past cosmic ray and solar activity variations an annual 10be record is assembled from an endogenic travertine in baishuitai china covering the period 2001 2016 ce we demonstrate that the effect of depositional processes when 10be is incorporated into travertine can be accounted for using the associated 9be and potassium k contents and that the resulting corrected 10be content significantly correlates with the modeled global 10be production rates with a time lag of 1 5 2 5 years our results from the baishuitai endogenic travertine suggest that the 10be record in such carbonate sediments has considerable potential as a high resolution proxy for past cosmic ray and solar activity variations

a geochemical evaluation of perennial spring activity and associated mineral precipitates at expedition fjord axel heiberg island canadian high arctic abstract two groups of perennial springs are observed in the canadian high arctic at expedition fjord on axel heiberg island at colour peak and gypsum hill saline discharge 1 3 2 5 molal nacl produces a variety of calcite travertine and gypsum rich precipitates saturation index calculations of the spring waters at colour peak suggest co 2 degassing from the waters causes calcite precipitation gypsum precipitation dominates at gypsum hill where spring waters have lower alkalinity and higher so 4 concentrations mineral accumulations form both channel and rimstone pool morphologies as a result of varying slope conditions at colour peak confined flow in steep slope areas develop massive structures in contrast to more friable porous accumulations in areas where waters fan out on shallower slopes these morphological variations lead to corresponding varying apparent rates of mineral precipitation mineral precipitation at gypsum hill is far less notable as a result of lower discharge rates and annual degradation by icing formation microscopic observations and geochemical analyses of the channel precipitates at colour peak reveal alternating light calcite spar and dark anhedral microcrystalline calcite combined with organic matter and non carbonate minerals laminae rimstone pools forming in lower sections of spring discharge are composed of accumulations of large euhedral calcite crystals interbedded with allochthonous inputs high concentration of dissolved solids is responsible for slow travertine precipitation rates which occurs during winter this precipitation is further retarded during summer months by the introduction of crystal growth inhibitors such as fe 3 and deposition of organic matter and soil sediments

effect of in stream physicochemical processes on the seasonal variations in δ13c and δ18o values in laminated travertine deposits in a mountain stream channel abstract travertines are potential archives of continental paleoclimate records of stable carbon and oxygen isotopic composition 13 c and 18 o in laminated travertine deposits from endogene spring waters show regular cyclic patterns which may be due to seasonal change in climate determinants such as temperature and rainfall in this study 13 c and 18 o measurements of three travertine specimens that grew naturally over the eight years 2004 2011 at upstream middle and downstream sites in a canal at baishuitai sw china are presented they exhibit clear seasonal variations that generally correlate with biannual laminations specifically 13 c and 18 o values show significant positive correlation with each other for the three travertine specimens with the correlation coefficients increasing downstream along the canal to reveal the factors governing the seasonal and spatial variations in 13 c and 18 o values newly formed travertines precipitated on plexiglas substrates are also examined both 13 c and 18 o of the substrate travertines are low in the summer rainy season and high in the winter dry season showing a great consistency with the patterns in the natural travertines spatially isotope values increase downstream in both seasons with higher increase rates in winter that are related to removal of larger fractions of dissolved inorganic carbon dic from the solution and stronger kinetic isotopic fractionation in winter due to in stream physicochemical processes including caco 3 precipitation and the associated degassing of co 2 seasonal changes in 13 c and 18 o in the travertines are amplified by two times between the upstream and downstream sites this is opposite to trends for epigene meteogene tufas whose seasonal changes in stable isotope compositions are reduced downstream we suggest in stream physicochemical processes are a potential reason for underestimation of annual temperature ranges that are inferred from epigene tufa 18 o data

hydrothermal metallogenic processes off the islands of nisiros and kos in the hellenic volcanic arc abstract two submarine hydrothermal fields off nisiros and kos islands in the eastern sector of the hellenic volcanic arc have been investigated using analyses of submarine hydrothermal waters and sediments both the waters and the sediments were found to be enriched in fe mn and zn together with as mo and v in the sediments only resulting from seawater rock interaction processes similar to those described from mid ocean ridge systems differences found between the products of these processes in the two hydrothermal fields studied reflect differences between the rock types being leached the physiographic and geological conditions present including the thickness and composition of the sediment column above the volcanic rocks and the rates of mixing of hydrothermal solutions with normal seawater the geochemical features described support possible sub seafloor formation of metal sulphides at both of the hydrothermal fields studied

the azuaje travertine an example of aragonite deposition in a recent volcanic setting n gran canaria island spain the azuaje travertines in the north of gran canary island crop out in the azuaje gorge which is incised into miocene volcanic breccias of the roque nublo formation this travertine is interesting because of the scarcity of travertines in the canary islands and its close relationship with recent volcanic events part of the travertine overlies a lava flow dated at 2420 40 years bp the travertine is composed mainly of aragonite in both perched systems on the gorge walls and in gorge bottom deposits parallel to the present stream perched systems include deposits from the feeder conduits within the roque nublo formation that spilled out through waterfalls and over barriers the gorge valley bottom system includes barrier and pool deposits the main laminated facies are composed mostly of large fibrous aragonite crystals while there are also common micritic and porous microfabrics shrubs coated grains coated bubbles and rafts are present in many of the deposits detailed study of the microfacies shows the presence of sparsely distributed biogenic features the 13c values are between 4 0 and 11 0 and the 18o values range between 11 0 and 2 0 vpdb these 13c values lie within the range of those of thermogene travertines fed by thermal waters that cooled downstream as indicated by the increase of the carbon and oxygen isotope values in that direction the common occurrence of fibrous radial fabrics is interpreted to be due to disequilibrium conditions during aragonite precipitation disequilibrium was likely caused by rapid co2 degassing of the thermalwaters that led to a rapid increase in the degree of aragonite saturation thus themorphology of the aragonite crystals and the isotopic composition indicate that the formation of the azuaje travertine was mostly due to abiogenic processes induced by rapid degassing of thermalwaters linked to the presence of a recent lava flow within the gorge in short the azuaje travertine shows the important role of volcanic activity in travertine deposition in the facies distribution as well as in the geochemical signatures of the deposits and so can be used as a recent analogue for ancient travertine deposits in volcanic settings

subaerial exposure surfaces in a palaeoproterozoic 13c rich dolostone sequence from the pechenga greenstone belt palaeoenvironmental and isotopic implications for the 2330 2060 ma global isotope excursion of 13c 12c abstract this article reports the discovery of numerous subaerial exposure surfaces which occur in the ca 2200 ma kuetsjarvi sedimentary formation ksf from the pechenga greenstone belt ne fennoscandian shield russia the formation was accumulated within an intraplate rift and is composed of fluviatile deltaic siliciclastic deposits and lacustrine dolostones the dolostones are enriched in 13 c 13 c 6 6 to 7 6 v pdb 18 o 16 7 to 21 5 v smow which is in general assigned to a global perturbation of the carbon cycle the lacustrine dolostone unit contains desiccated and in situ brecciated carbonate beds subaerial erosion and dissolution surfaces epikarst surficial silicification silcretes and hot water spring travertines the dissolution surfaces marked by formation of a few centimetre thick vuggy non laminated dolomicrite capped by silicified nodular zone resemble modern calcretes which formed by capillary rise of surface waters per ascensum calcrete following saturation of the regolith zone under arid or semi arid conditions abundant red iron stained superficial dolocrete implies the existence of an o 2 rich atmosphere rezolith black pebbles alveolar septal structures microcodium and other fabrics associated with plant roots and input of terrestrial organic matter which are typical for post cretaceous pedogenic calcretes have not been identified alfa fabrics can be applied to describe dolocretes though rhombic calcite crystals are lacking neither 13 c depletion nor 13 c enrichment has been documented in the dolocrete which suggests no contribution of co 2 derived from soil or from any other c org rich sources enriched in 12 c and apparent lack of biological uptake of 12 c during formation of the dolocrete both petrographic and carbon isotope data do not support earlier assertions that palaeoproterozoic subaerial surface was colonised by microbial mats a few samples have high 18 o values up to 30 despite diagenetic and metamorphic resetting of the oxygen isotope system suggesting evaporation during formation of the superficial dolocrete such documented episodes of subaerial exposure formation of hot water travertines superficial dolocrete and silcrete suggest that there must have been frequent decoupling between the kuetsjarvi depositional system and the bordering sea this imposes an additional restriction on the use of the isotopic composition of the ksf dolostones for reconstruction of the 13 c carb global secular curve

dissected hydrologic system at the grand canyon interaction between deeply derived fluids and plateau aquifer waters in modern springs and travertine geochemical study of water and gas discharging from the deeply incised aquifer system at the grand canyon arizona provides a paradigm for understanding complex groundwater mixing phenomena and quaternary travertines deposited from cool springs provide a paleohydrologic record of this mixing geochemical data show that springs have marked compositional variability those associated with active travertine accumulations deeply derived endogenic waters are more saline richer in co2 and elevated in 87sr 86sr relative to springs derived dominantly from surface recharge of plateau aquifers epigenic waters endogenic waters and associated travertine are preferentially located along basement penetrating faults we propose a model whereby deeply derived fluids are conveyed upward via both magmatism and seismicity our model is supported by 1 gas analyses from spring waters with high he ar and he n2 and 3he 4he ratios indicating the presence of mantle derived he 2 large volumes of travertine and co2 rich gases in springs recording high co2 fluxes and 3 87sr 86sr in these springs that indicate circulation of waters through precambrian basement geochemical trends are explained by mixing of epigenic waters of the colorado plateau aquifers with different endogenic end member waters in different tectonic subprovinces endogenic waters are volumetrically minor but have significant effects on water chemistry they are an important and largely unrecognized component of the hydrogeochemistry and neotectonics of the southwestern united states

the tectonic development of the hellenic arc and the sea of crete a synthesis abstract we use field analyses together with interpretation of aerial photographs orbital imagery and sea beam data to define more accurately the geometry of fault systems in the hellenic arc the tectonics of the area are dominated by extensional processes related to normal faulting we then use sea beam data previous oceanographic studies and extrapolation of field analyses on surrounding islands to describe the fault pattern of the cretan sea basin which is found consistent with the land fault pattern the mechanisms of the late neogene and quaternary deformation of the central and southern aegean region are analysed in terms of stress trajectories as revealed by field studies of fault populations we then examine the subsidence of the sea of crete in terms of a model of uniform stretching of the lithosphere the opening of the sea of crete was cylindrical and did not result in bending of crete this leads us to modify the southern portion of an earlier kinematic reconstruction of aegea in agreement with recent paleomagnetic results the implications of the opening of the sea of crete on the tectonic evolution of the straits to the west and east of crete are discussed finally the uplift of the outer arc is explained by underplating due to subduction

wet dry seasonal and spatial variations in the δ13c and δ18o values of the modern endogenic travertine at baishuitai yunnan sw china and their paleoclimatic and paleoenvironmental implications abstract seasonal and spatial variations in the 13 c and 18 o values of the modern endogenic thermogene travertine deposited in a calcite depositing canal at baishuitai yunnan sw china were examined to understand their potential for paleoclimatic and paleoenvironmental implications the sampling sites were set in the upstream middle reach and downstream of the canal and the modern endogenic travertine samples were collected semimonthly to measure their 13 c and 18 o values it was found that both 13 c and 18 o values of the endogenic travertine were low in the warm rainy season and high in the cold dry season and correlated with each other the low 18 o values in warm rainy season were mainly related to the higher water temperature and the lower 18 o values of rainwater and the low 13 c values are caused by the dilution effect of overland flow with low 13 c values in the warm rainy season and the reduced co 2 degassing of canal water caused by the dilution effect of the overland flow the linear negative correlation between the travertine 18 o or 13 c values and rainfall amount may be used for paleo rainfall reconstruction if one knows the 18 o or 13 c values of the fossil endogenic travertine at baishuitai though the reconstruction was not straightforward it was also found that there was a progressive downstream increase of the 18 o and 13 c values of the travertine along the canal the former being mainly due to the preferential evaporation of h 2 16 o to the atmosphere and the latter to the preferential release of 12 co 2 to the atmosphere during co 2 degassing however the downstream increase of the travertine 18 o and 13 c values was less intensive in rainy season because of the reduced evaporation and co 2 degassing during the rainy season to conclude the downstream travertine sites could be more favorable for the paleo rainfall reconstruction while the upstream travertine sites are more favorable for the paleo temperature reconstruction so this study demonstrates that endogenic travertine like epigenic meteogene tufa could also be a good candidate for high resolution paleoclimatic and paleoenvironmental reconstruction

thickness and stable isotopic characteristics of modern seasonal climate controlled sub annual travertine laminas in a travertine depositing stream at baishuitai sw china implications for paleoclimate reconstruction a continuous high resolution monthly record of stable isotopes 13c and 18o in a well laminated freshwater travertine deposited at baishuitai sw china from may 1998 to november 2001 was presented the travertine exhibits clear annual bands with coupled brown white color laminations throughout field investigation it was found that the thin 1 5 2 2 mm brown porous lamina was formed in the monsoonal rainy season from april to september whereas the thick 5 8 mm dense white lamina was formed in the dry season from october to march the comparisons of lamina thickness and stable isotope signals in the travertine with the meteorological records allow us to constrain the relevant geochemical processes in the travertine formation under different climate conditions and to relate climate variables to their physicochemical proxies in the travertine record sympathetic variations in lamina thickness 13c and 18o along the sampled profile reflect changes in hydrogeochemistry showing that thin lamina and low 13c and 18o values occur in warm and rainy seasons the decreased amount of calcite precipitation and low 13c values during the warm and rainy seasons is caused by dilution of overland flow after rainfall the low 18o values are believed to be related to the rainfall amount effect in subtropical monsoonal regions this process is thought to be markedly subdued whenever the amount of rainfall is lower than a given threshold accordingly distinct minima in lamina thickness 13c and 18o are interpreted to reflect events with above average rainfall possibly heavy floods and vice versa this study demonstrates the potential of freshwater travertine to provide valuable information on seasonal or even monthly rainfall variations

deep sea and shallow water hydrothermal vent communities two different phenomena hydrothermal vent communities from 76 areas lying at depths from 0 to 4100 m were split into two groups bdeepq and bshallow waterq based on the occurrence of vent obligate restricted to hydrothermal vents taxa of a high rank genus and family the two groups were then compared based on a large set of environmental faunistic and community parameters the degree of obligacy of fauna sharply changes at the depth of approximately 200 m in 21 shallow water areas located at depths b200 m vent obligate taxa are absent or their taxonomic rank does not exceed a species the total number of vent obligate species in shallow water is 8 and their obligacy is uncertain data from 55 areas lying at depths from 200 to 4100 m indicate there are ca 400 obligate species in 47 of these areas obligate vent taxa of the genus or the family rank are present obligate taxa of the genus rank appear at 200 m depth and of the family rank at 386 m the depth ca 200 m corresponds well with differences in community structure and composition and environmental parameters deep sea n200 m hydrothermal communities differ from shallow water ones b200 m in a much higher ratio of vent obligate taxa deep sea vent communities are also distinguished by the lack of diatom and algae bacterial mats phytoplankton lower species richness the development of large sulphide structures higher role of active vents in structuring communities in space replication of a set of dominant taxa in communities within large regions reproduced through the succession at newly formed vent fields more pronounced concentric and vertical zonality higher biomass of macrofauna the important role of symbiotrophic forms dominating the biomass the ratio of species with a bpointq species range endemic to small areas is higher in the deep sea there are no significant differences between the vent and non vent biogeography both in shallow waters and the deep ocean modern deep sea hydrothermal vent communities have a longer evolutionary history than their shallow water counterparts to explain major differences between deep and shallow water hot vent communities evolutionary processes need to be analysed over long geological periods and within global vertical zones it is suggested that the proportion of organic matter derived from chemosynthesis and photosynthesis plays a crucial role in evolution when calculated for global zones this proportion increases with depth to a certain critical level that separates deep and shallow water hot vent communities and fauna vertical zonation in the distribution of obligate taxa in hydrothermal vent communities indicates that this level is reached at approximately 200 m depth

on the lomagundi jatuli carbon isotopic event the evidence from the kalix greenstone belt sweden we report a significant new database on the carbon and oxygen isotopic analyses 233 whole rock and 43 microcored samples obtained from sedimentary dolostones in the kalix greenstone belt from the fennoscandian shield of sweden this characterises the second half of the prominent palaeoproterozoic lomagundi jatuli positive carbon isotope excursion within a 600 m thick succession of alternating volcanic volcaniclastic siliciclastic and dolomitic rocks from greenschist epidote amphibolite metamorphic facies the least altered dolostone samples show a gentle oscillation between 2 and 4 throughout stratigraphy with a second order positive excursion from 4 through 8 and gradually back again to 4 in the c 150 m thick unit in the middle and upper parts of the succession this second order excursion is superimposed on the general relatively rapid 13c decline at the second half of the lomagundi jatuli isotopic event and coincides with the transition from a marine influenced rift to a passive margin setting if the excursion is global it would reveal internal fine structure of the lomagundi jatuli isotopic excursion if not basinal local factors are the main players lithostratigraphic and c isotope correlation between kalix and neighbouring perapohja schist belt successions 40 km apart suggest an incomplete geological record in both successions despite the absence of obvious non depositional unconformities

palaeoproterozoic travertines of volcanic affiliation from a 13c rich rift lake environment abstract the ca 2 2 ga kuetsjarvi sedimentary formation ksf of the pechenga greenstone belt the north east fennoscandian shield contains the oldest travertines so far reported in the literature the travertine hosting succession is composed of flat laminated dolomitic stromatolites micritic and allochemical dolostones all formed in coastal plains of a rift related playa lake system in an arid semiarid climate the travertines are categorised as thermal autochtonous spring travertine crust and spring orifice travertine mounds formed from hot water springs issuing at the playa lakeshore the travertines are represented by crusts and small scale mounds both composed of a series of 1 5 mm thick dark light couplets of fibrous dolomite crystals with compromise boundaries and radiating dolomite crystals travertines are composed of dolomite mg ca 0 42 0 47 exhibiting a general lack of replacement textures travertines exhibit several phases of growth separated by dissolution processes and accompanied by precipitation of sio 2 the upper surface of crusts and mounds are often affected by desiccation joints and covered with thicker sio 2 veneer 18 o 18 6 the host dolostones are characterised by 13 c carb of 6 1 8 8 v pdb and 18 o values ranging from 11 to 19 v smow microcored samples of travertine dolomite exhibit 13 c and 18 o values ranging from 6 1 to 7 7 and from 12 0 to 21 5 respectively the 13 c rich nature of the background stratified dolostones is caused by the 2 4 2 06 ga global shift in 13 c 12 c carbonate carbon associated with enhanced accumulation of c org and perturbation of the global carbon cycle the source of co 2 for the travertines is considered to be of volcanogenic origin with an initial 13 c value of ca 6 0 several processes contributed to carbon and oxygen isotope composition of travertine dolomite i an initial co 2 loss at the spring orifice ii water cooling and rapid co 2 loss during water transit iii persistent evaporation from thermal water ponds pools and iv mixing with co 2 of ambient lake water enriched in 13 c silica is thought to have been dissolved by groundwater from underlying sediments and been transported upwards by a mechanism of capillary rise due to dry climatic condition

processes influencing extreme as enrichment in shallow sea hydrothermal fluids of milos island greece abstract arsenic as is naturally enriched in most terrestrial and marine hydrothermal systems its discharge from shallow sea hydrothermal vents into coastal marine environments can dramatically affect the surrounding ecosystems shallow sea hydrothermal venting of acidic ph 5 hot 40 116 c and highly sulfidic up to 3 1 mm h2s fluids occurs at palaeochori and spathi bays off the southeast coast of milos island greece two distinct types of fluids both extremely as enriched were collected from the submarine vents often within a few meters of each other 1 a high cl fluid enriched in cl by up to 47 relative to seawater depleted in mg and so4 and enriched in major na ca k b sr and br and minor trace elements si li rb ce as fe mn and ba and 2 a low cl fluid depleted in cl by up to 66 relative to seawater also depleted in na mg so4 and br the maximum concentration of as reached 39 m in the high cl fluids and up to 78 m in the low cl fluids this is approximately 3000 times the concentration of as in seawater and far exceeds the concentrations typically found in mid ocean ridge mor and back arc basin bab fluids which are typically we used a combination of elemental analyses and stable and radiogenic isotope data oxygen deuterium and strontium to understand the primary controls on as enrichment those parameters all indicated that the fluids were a mixture of seawater and a hydrothermal fluid originally derived from seawater but altered by water rock interaction subcritical phase separation boiling and vapor brine segregation since as was extremely enriched in both the high cl and the low cl thermal fluids we conclude that this element readily partitions into the vapor phase in the milos hydrothermal system the original source of as is most likely the leaching of the greenschist facies metamorphic basement rocks transpierced by an abundance of secondary quartz and calcite veins rich in pyrite it is possible that these veins were deposited from as rich magmatic fluids similar to some epithermal au deposits a poorly crystalline orpiment precipitates as hydrothermal fluids mix with overlying seawater and removes much of the dissolved as prior to discharge

oxygen isotope fractionation in travertine depositing pools at baishuitai yunnan sw china effects of deposition rates abstract travertine 18o values can be used to reconstruct paleo temperatures if the oxygen isotope fractionation factors between travertine and water are accurately understood for this purpose the 18o values of pool travertine and its parent water and the deposition rates of the calcite were investigated at baishuitai yunnan sw china over the course of the full hydrological year april 23 2006 april 25 2007 the results show that the travertine water isotope fractionation factors are close to the commonly accepted equilibrium line of kim and o neil 1997 this differs from the results obtained by yan et al 2012 who found that the oxygen isotope fractionation factors in the travertine depositing pools were close to the line suggested as equilibrium relationship by coplen 2007 the average calcite deposition rate 2 30 mg cm 2 d 1 in the present study is six times larger than that 0 38 mg cm 2 d 1 in yan et al 2012 if slower calcite precipitation leads to equilibrium oxygen isotopic fractionation then the results of this study support the results of coplen 2007 that indicate that the equilibrium fractionation factor may be greater than the commonly accepted one derived by kim and o neil 1997 the relationship between oxygen isotope fractionation factor and calcite deposition rate in our study also agrees with the results of dietzel et al 2009 who found that the kinetic isotope effect favors preferential incorporation of 16o in solid calcite as the calcite deposition rate increases there was a threshold for calcite precipitation rate control on oxygen isotopic equilibrium in our case of travertine depositing pools when the calcite deposition rate was lower than 0 38 mg cm 2 d 1 oxygen isotopic equilibrium between calcite and water was attained therefore calcite deposition rate is a potentially important consideration when using 18o in natural carbonates as a proxy for terrestrial and ocean temperature

a groundwater conceptual model and karst related carbon sink for a glacierized alpine karst aquifer southwestern china summary in the jade dragon snow mountain jdsm region yunnan province sw china an extensive hydrochemical and stable isotopic study of a glacierized alpine karst aquifer was conducted during the period 2011 2014 the objectives of the study were first to establish a conceptual hydrogeological model of the karst groundwater system second to estimate the proportion of extra glacier melt water infiltrating the karst aquifer that is being induced by the regional climate warming third to calculate the karst related flux of carbon into the karst aquifer knowledge of the local hydrogeological background from previous work was the starting point of the hydrochemical and stable isotopic study some representative spring waters and recharge waters i e glacier melt water and rainwater were investigated both spatially and temporally by hydrochemical and isotopic techniques including analysis of major and some minor ions and o and h stable isotopes a conceptual hydrogeological model of a fracture diffuse flow karst groundwater aquifer was proposed the proportion of glacier melt water infiltrating into the karst aquifer was estimated by using the karst spring as a natural pluviometer and with stable isotope analysis results show that 1 the jdsm karst aquifer is a diffuse flow system 2 it has a number of discharge areas and the jinsha river is the karst drainage base level 3 the proportion of the glacier melt water penetrating the karst aquifer is 29 and 4 the karst related carbon sink is 26 67 3 44 t km 2 a 1 as co 2 which is lower than that in non glacierized karst aquifers but over ten times larger than the carbon sink flux from silicate weathering in non karst areas showing the control of both climate and lithology on the rock weathering related carbon sink and the significance of carbonate weathering in the global carbon cycle

kolosjoki sedimentary formation a record in the aftermath of the paleoproterozoic global positive δ13c excursion in sedimentary carbonates abstract the kolosjoki sedimentary formation of the pechenga greenstone belt north eastern fennoscandia records the aftermath of the paleoproterozoic global positive 13 c excursion in sedimentary carbonates the lomagundi jatuli isotope excursion the goals of this research were to provide detailed new data on the 13 c trend in the kolosjoki sedimentary formation and generate a secular 13 c curve for the time period immediately succeeding the lomagundi jatuli isotope excursion for these purposes sedimentary carbonate samples from two new drillcores representing the kolosjoki sedimentary formation were collected in total 88 whole rock samples and 67 micro drilled subsamples ca 1 3 mg were analyzed for the isotope composition of c and o the whole rock elemental abundances and for the composition of the acid soluble fraction the kolosjoki carbonate rocks are dolostone or calcitic dolostone mg ca 0 50 0 67 with minor limestone mg ca 0 04 0 06 only weak correlation was observed between the mn sr ratios and the 13 c and 18 o values and the carbonate samples have likely retained their near primary 13 c values the sedimentary carbonate rocks show first low 13 c values at 2 to 1 and then a subtle upward increasing 13 c trend from ca 1 to 3 the increasing 13 c trend is interpreted to record a recovery from a 13 c minimum following the lomagundi jatuli isotope excursion

controls on aragonite and calcite precipitation in hot spring travertines at chemurkeu lake bogoria kenya subfossil travertines precipitated around hot spring orifices at chemurkeu on the western shore of lake bogoria kenya are composed of calcite aragonite and minor dolomite aragonite crystal beds which form 5 10 of the travertine by volume are formed of large pseudohexagonal prisms whereas the calcite crystal beds are composed mainly of feather dendrites dolomite is only found between aragonite crystals boundaries between aragonite and calcite crystals commonly display evidence of dissolution but there is no evidence to indicate that calcite formed by inversion of aragonite or that the dolomite replaced the aragonite thus the aragonite calcite and dolomite are each treated as primary precipitates reticulate gelatinous coatings with a high si and mg content cover most external and internal surfaces of the aragonite and calcite crystals the travertines may have formed under more humid conditions than today when the spring waters contained more ca2 the physiochemical conditions at the mo

response of dissolved inorganic carbon dic and δ13cdic to changes in climate and land cover in sw china karst catchments abstract monthly hydrochemical data and 13c of dissolved inorganic carbon dic in karst water samples from september 2007 to october 2012 were obtained to reveal the controlling mechanisms on dic geochemistry and 13cdic under different conditions of climate and land cover in three karst catchments banzhai dengzhanhe and chenqi in guizhou province sw china dic of karst water at the banzhai site comes mainly from carbonate dissolution under open system conditions with soil co2 produced by root respiration and organic carbon decomposition with lowest 13c values under its dense virgin forest coverage weaker carbonate bedrock dissolution due to sparse and thin soil cover results in lower 13cdic pco2 dic and ec and lower cation and anion concentrations at the chenqi site larger soil co2 input from a thick layer of soil results in high pco2 and dic and low ph sic and 13cdic in the karst water at the dengzhanhe site a lesser soil co2 input due to stronger karst rock desertification and strong gypsum dissolution contribute to higher 13cdic high ec and high cation and anion concentrations soil co2 inputs controlled by biological activity and available soil moisture carbonate bedrock dissolution dilution and degassing effects vary seasonally following rainfall and temperature changes consequently there are seasonal cycles in hydrochemistry and 13cdic of the karst water with high pco2 and low ph ec sic and 13cdic values in the warm and rainy seasons and vice versa during the cold and dry seasons a strongly positive shift 3 in 13cdic occurred in the drought year 2011 indicating that 13cdic in groundwater systems can be an effective indicator of environmental and or climate changes

correlating specific conductivity with total hardness in limestone and dolomite karst waters under field conditions modern digital conductivity meters give standardized rapid and reproducible measurements here we investigate the accuracy of their estimates of the composition of karst waters as total hardness th as mg l caco3 for limestone and dolomite these are the fundamental measures of process in carbonate karst geomorphology phreeqc theoretical curves for the dissolution of pure calcite aragonite and dolomite in water at 25 c are compared with water analyses from karst studies worldwide other principal ions encountered are sulphates nitrates and chlorides the snc group from carbonate karsts 2309 spring well and stream samples were divided into uncontaminated snc 20 classes where specific conductivity spc is less than 600 s cm a clear statistical distinction can be drawn between waters having little contamination and substantially contaminated waters with snc 20 as sometimes claimed in manufacturers literature in clean limestone waters th is close to 1 2spc with a standard error of 2 3 mg l the slope of the best fit line for 1949 samples covering all snc classes where spc 600 s cm helps to distinguish polluted waters from clean waters with possible endogenic sources of co2 in the range 250 spc 600 s cm dolomite waters can be readily distinguished from limestone waters copyright 2005 john wiley sons ltd

submarine hydrothermal metallogenesis associated with the collision of two plates the southern aegean sea region abstract the geochemistry of sediments from the southern aegean sea demonstrates that the active tectonics in the hellenic arc trench system favor hydrothermal mineralization processes involving leaching of oceanic crust the distribution and geochemical behavior of mn fe cu zn p and ba indicate a hydrothermal influence i at plate boundaries such as the pliny and strabon trenches ii in fore arc basins such as maleas iraklion and karpathos iii on the island arc all fore arc basins having greater mn enrichments than the trenches are also characterized by higher heat flow values the greatest mn enrichments occur at maleas basin where a mn dispersion halo is recognized this basin is very tectonically active with the largest group of normal faults along the planes of which magmatic material was injected and the highest heat flow values in the sea of crete it also falls in the eastern mediterranean zone of high seismic activity because the fe mn sediments identified in the above geotectonic units are the end members of the hydrothermal fractionation sequence known from areas where leaching of oceanic crust occurs it is suggested that other members of the sequence such as metal sulfides may be found significant geochemical anomalies of pb and zn found in areas of high heat flow and on lines of normal faulting are considered to be traces of the presence of metal sulfides

the greek enigma is development of the aegean orogene dominated by forces related to subduction or obduction abstract numerous papers have been published in the past decade which attribute the neogene geodynamic evolution of the aegean to subduction by the african plate or by a platelet of african affinity new data put these hypotheses in doubt the aegean orogene is characterized by 1 narrow and relatively shallow sediment starved trenches 2 a volcanic arc of widely spaced small volume high k calc alkaline complexes with ages decreasing toward the trenches arc tholeiitic and low k calc alkaline suites are absent 3 a highly seismic upper lithosphere which is separated from a non descript benioff zone by an aseismic wedge of asthenolithic material deformation in the upper lithosphere is dominated by n s extension and that in the benioff zone by ne sw compression and 4 extensive magmatism with shoshonitic and high k calc alkaline affinity in the stretched submerged hinterland hinterland volcanism significantly predated that of the volcanic arc and decreases southwestward towards the later trenches the model proposed for the cenozoic geodynamic evolution of the aegean orogene includes subduction in the late cretaceous eocene strike slip deformation and oblique subduction in the oligocene and obduction as a result of the emplacement of a mantle diapir along the paleosubduction zone in the neogene and quaternary this model supports an earlier observation that obduction caused by mantle diapirism may represent the latest process in the geodynamic evolution of a mediterranean type collision zone

use of uranium thorium dating to determine past 14c reservoir effects in lakes examples from antarctica the chronologies of many lacustrine records suffer from radiocarbon reservoir effects due to the presence of dissolved dead carbon or to slow air water exchange here we use the tims uranium thorium disequilibrium method in conjunction with ams radiocarbon dating to determine the age of lacustrine carbonates and to quantify the past radiocarbon reservoir effect in two antarctic lakes with differing characteristics by correcting a single sample u th age for detrital contamination a 14 c offset of v18 000 yr was obtained for carbonates from the former grounding line of the ross sea ice sheet in glacial lake trowbridge this large reservoir effect is believed to result from the direct input of old co2 from glacial meltwater in the second example an isochron approach on coeval samples formed at the bottom of lake vida now exposed due to lower lake level yielded an age of 9550 340 yr b p and a radiocarbon reservoir age of 3600 yr this offset was probably the result of lack of aeration due to perennial ice cover and or strong density stratification this evidence for long term isolation of the lake bottom indicates another level of hardship for life in the dry valley lacustrine environment an environment studied as an analogue for extreme periods of earth history as well as for exobiological implications the success of the u th technique on these two examples indicates that tims u th dating will be of widespread use in dating the important climate information recorded in the dry valleys both within and beyond the 14 c age range fl 2001 elsevier science b v all rights reserved

uranium series age estimates and paleoclimatic significance of pleistocene tufas from the lahontan basin california and nevada abstract an extended chronology of lahontan basin lake levels based on uranium series age estimates correlates with the global ice volume record lake highstands occur at or shortly after times of maximum ice sheet size moderate size lakes occur when the global ice volume is about 80 of its maximum the data indicate that lake levels rise and fall relative to the proximity of the mean position of the jetstream when the continental ice sheet is above some threshold size or shape it appears that the large scale circulation and climatic conditions are right for producing lakes of moderate to large size within the lahontan basin

two billion year old isotopically heavy carbon evidence from the labrador trough canada forty eight samples of bulk carbonates were studied from the dunphy portage alder uve denault and abner formations and the undivided pistolet subgroup in the labrador trough quebec canada the carbonate units occur as a number of thick beds up to 300 m within 100 600 m thick formations they are interbedded with siliciclastic sediments and are composed of crystalline sparry micritic allochemical and stromatolitic dolostones the carbonate rocks are recrystallized and metamorphosed up to amphibolite grade they are chemically dolostones and include chemical or biochemical laminated and massive dolostones dolorudites dolarenites and dololitites which were deposited in shallow water dunphy denault and abner formations to relatively deep water uve formation marine environments reef facies are present in the denault and abner formations the dunphy portage alder and uve formations deposited between 2 17 and 2 14 ga yield isotopically heavy values of 13c pdb ranging from 5 3 to

wet dry seasonal variations of hydrochemistry and carbonate precipitation rates in a travertine depositing canal at baishuitai yunnan sw china implications for the formation of biannual laminae in travertine and for climatic reconstruction travertine or tufa is a chemical sedimentary deposit that is precipitated from springfed stream water supersaturated with calcite due to co2 degassing liu et al 1995 pentecost 1995 ford and pedley 1996 these deposits have biannual laminations which could provide valuable paleoclimatic and paleoenvironmental information with high resolution liu et al 2006 kano et al 2007 brasier et al 2009 lojen et al 2009

travertine deposits from along the south tibetan fault system near nyalam tibet a newly investigated travertine deposit in southern tibet provides a window into holocene hydrological geomorphic and climatic processes near the boundary of the tibetan plateau and high himalaya travertine deposited as a result of the degassing of co 2 rich groundwater as it emerges on the earth s surface is in many cases formed along the trace of major crustal scale faults in primarily extensional tectonic regimes a travertine platform measuring roughly 1 km by 0 5 km exists near the town of nyalam in southern tibet along a major himalayan down to the n normal fault the south tibetan fault system a wide variety of travertine depositional textures and features are recorded in the platform on a series of terraces active travertine deposition was observed from spring mounds and seeps along the base of the platform at the modern river level palaeotemperatures of spring water calculated from 18 o of the travertine range from 9 to 25 c which closely matches the temperatures recorded from modern springs in the area a complex geomorphological landscape records interaction between growing alluvial fans travertine accumulation and a rapidly down cutting river with associated fluvial terraces river incision was contemporaneous with travertine deposition as indicated by cemented fluvial river gravel layers interbedded with travertine high 87 sr 86 sr ratios in the travertine mean of 0 7168 indicate subsurface fluid interaction with radiogenic crystalline rocks of the underlying greater himalaya uranium series ages of the travertine platform range from 5400 a 950 a to 11 600 a 1000 a and indicate a younging progression from higher terraces near the valley wall to lower terraces at present day river level travertine that overlies a river gravel terrace 18 m above river level formed at 11 600 a this date yields a local incision rate of 1 6 mm a 1 consistent with estimated fluvial incision rates in the high himalaya the range of our u series ages coincides with an interval of higher precipitation associated with greater intensity of the indian monsoon which led to elevated spring discharge and carbonate precipitation in this part of the high himalayas

geochemical evidence for oxygenated bottom waters during deposition of fossiliferous strata of the burgess shale formation abstract deciphering the oxygenation potential of bottom waters during deposition of the fossiliferous strata of the burgess shale is key to understanding the paleoecology of the organisms preserved as fossils and the processes involved in their preservation methods of paleo redox determination that are based upon trace fossils organic carbon content or size analysis of pyrite framboids are problematic when applied to the burgess shale fortunately patterns in redox sensitive trace elements hold great potential for determining paleo redox conditions for these greenschist facies rocks because they are independent of both age and metamorphic grade four burgess shale type bst fossil bearing sections were studied three lie within the burgess shale formation whereas one lies within the slightly younger duchesnay unit of the middle chancellor formation the geochemical proxies of seawater redox conditions that were used are mo u th v cr v v ni ni co and v sc each of these redox sensitive indices suggests that oxygenated conditions prevailed in the overlying seawater during deposition of beds within which bst preservation developed non fossiliferous beds at the base of the mt stephen trilobite beds yield three geochemical indices v v ni v sc ni co that indicate deposition under dysoxic to anoxic conditions thus the only beds to have been deposited under anoxic conditions are barren of fossils of soft bodied taxa further contradicting the notion that bottom water anoxia is a factor in bst preservation the laminated nature of the burgess shale and evidence for subsurface anoxia coupled with evidence for oxygenated bottom waters presence of bacterial mats and surficial trace fossils suggest that the burgess shale was deposited in the exaerobic zone oxic anoxic boundary at the water sediment interface implications of this reinterpretation of the depositional environment of the burgess shale include 1 taphonomic models for bst preservation must account for the presence of oxygen in bottom waters 2 paleoecological interpretations of the burgess shale need to account for a probable autochthonous benthic component in what is a complex assemblage of fossils that includes elements derived from the platform and 3 the possibility of burgess shale communities based upon chemosynthesis and or bacteria grazing must be considered

geothermal mineralization i the mechanism of formation of the beowawe nevada siliceous sinter deposit the siliceous sinter deposit at beowawe nev has a volume of 7 71 x 10 sup 7 m sup 3 and contains 1 28 x 10 sup 11 kg silica this silica precipitated from geothermal solutions that welled up along the malpais fault a graben bounding fault sinter formation involved three steps 1 geothermal solutions saturated with quartz in the reservoir moved to the surface where they cooled and became supersaturated with amorphous silica 2 amorphous silica particles nucleated heterogeneously to produce a colloidal suspension 3 the amorphous silica particles agglomerated and were cemented together by amorphous silica precipitating in the embayments between the particles at least 5 58 x 10 sup 14 kg of geothermal solution must have been produced over time to account for the mass of silica in the beowawe deposit this fluid would have carried at least 4 95 x 10 sup 17 kj of heat to the surface 21 references 6 figures 1 table

the quaternary travertine deposits of europe and asia minor abstract a summary is provided of the published information relating to all aspects of quaternary travertine formation in europe west of the ural mountains the deposits have been divided into two broad groups the meteogene travertines which result primarily from the degassing of soil borne aqueous co 2 and thermogene deposits resulting from the degassing of thermally generated co 2 meteogene deposits are rare above latitude 58 n and in regions where the mean annual air temperature is below 5 c a significant positive correlation exists between mean air temperature and travertine deposit thickness the combined effects of temperature and rainfall are used to provide a zoned map showing the travertine forming potential of limestones within the region information from 14 c dating indicates that deposition reached a maximum in the period 5 10 ka bp and is currently limited by land and water management practices in the populated areas thermogene deposits occur in regions of high co 2 discharge resulting from tectonic activity such as italy and turkey where there is much vulcanism these travertines are frequently more massive and less readily weathered than meteogene deposits fully referenced information is provided for 320 important mostly well studied sites 227 meteogene 93 thermogene of which 156 are currently active

fluvial diffluence episodes reflected in the pleistocene tufa deposits of the river piedra iberian range ne spain abstract the pleistocene deposits of the valley of the river piedra ne spain are represented by thick tufas with small amounts of detrital material the development of these deposits correlates with marine isotopic stages 9 7 6 and 5 the sedimentary scenario in which they formed mostly corresponded to stepped fluvial systems with barrage cascade and associated dammed areas separated by low gradient fluvial stretches mapping and determining the sedimentology and chronology of these deposits distinguished two main episodes of fluvial diffluence that originated as a result of the temporary blockage of the river a consequence of the vertical growth of tufa barrages in the main channel in both episodes water spilt out toward a secondary course from areas upstream of barrages where the water level surpassed the height of the divide between the main and secondary course as a consequence extensive and distinct tufa deposits with very varied facies formed over a gently inclined area toward and indeed within the secondary course the hydrology of this secondary course was episodic fed only by surface water the two diffluence episodes detected occurred during mis 7 and 7 6 and were interrupted by incision events reflected by detrital deposits at the base of each tufa sedimentation stage in the main channel incision which caused the breakage of the barrages allowed water to again flow through the main channel no evidence of diffluence was seen in any younger mis 5 to present day tufa deposits the proposed diffluence model might help explain other carbonate fluvial systems in which 1 tufas appear in areas with no permanent water supply and 2 tufas are absent over extensive areas despite conditions favourable to their formation

first results of study of sulphur rich hydrothermal activity from an island arc environment esmeralda bank in the mariana arc during cruise so 69 of r v sonne active hydrothermal exhalation and deposition along the northern caldera rim of esmeralda bank was observed and sampled esmeralda bank is one of the active submarine volcanoes in the southern seamount province of the mariana island are hydrothermal porous mounds and volcaniclastic breccias cover an area of at least 0 2 km2 on the caldera seafloor and exude vent waters with a minimum temperature of 78 5 c the hydrothermal mounds consist of layers of pyrite marcasite and pure sulphur that are at least 0 8 m thick bottom videos show turbulent gas rich plumes characterized by high methane concentrations of 2 9 104 nl l which are comparable to those found at the hydrothermal site of macdonald seamount in the southwest pacific the deposition of large amount of sulphides is probably related to rock water interaction and degassing from a shallow summit magma chamber in an island arc environment

co2 outgassing and calcite precipitation in falling spring creek virginia u s a abstract chemical and physical observations are presented to explain the evolution of stream water chemistry along the flow path in warm river cave and falling spring creek mixing of two chemically and thermally distinct waters in the cave defines the initial stream water chemistry all along the flow path the observed composition is influenced by outgassing of co2 the water is supersaturated with respect to co2 both in the subsurface and at the surface of the earth but outgassing is greatest in turbulent stretches of the stream above and at the waterfalls the loss of co2 drives the solution to high degrees of supersaturation with respect to calcite physical evidence for calcite precipitation exists in the rimstone dams observed inside the cave and in the travertine deposits above and below the falls along falling spring creek travertine precipitation in the streambed consumes ca2 and hco 3 with most of the precipitation occurring where the stream experiences the most rapid co2 loss the stream water maintains a significant level of supersaturation with respect to calcite over the entire length of the flow path studied

shallow water hydrothermal vent field fluids and communities of the d joao de castro seamount azores d joao de castro seamount has an elevation of 1000 m and is located between the islands of terceira and sao miguel azores on the hyper slow spreading terceira rift the summit of the seamount shoals to 13 m below sea level and has hydrothermal vents at a depth of 20 m this is the first vent system to be described on a hyperslow spreading centre gas discharging from the vents is dominated by co2 90 with lesser h2s h2 and ch4 two distinct vent areas were identified that had different physical and chemical characteristics the white area had vent orifices with white bacterial mats while the yellow area had yellowish coloured vent openings vents in the white area had lower temperatures v43 8c but higher concentrations of h2s ch4 and h2 beggiatoa sp was found in this area the yellow area had vent temperatures up to 63 8c no typical hydrothermal vent fauna was found at these vents the macro species present were similar to those found in coastal and seamount areas of the azorean archipelago there was evidence for the presence of deeper vents on the flanks of the d joao de castro seamount at depths between 150 400 m d 2005 published by elsevier b v

the connection between iron ore formations and mud shrimp colonizations around sunken wood debris and hydrothermal sediments in a lower cretaceous continental rift basin mecsek mts hungary in the early cretaceous the continental rift basin of the mecsek mts hungary was situated on the southern edge of the european plate the opening of the north atlantic ocean created a dilatational regime that expanded to the southern edge of the european plate where several extensional basins and submarine volcanoes were formed during the early cretaceous epoch permanent seaquake activity caused high swell events during which a large amount of terrestrial wood fragments entered into submarine canyons from rivers or suspended woods which had sunk into the deep seafloor these fragments created extended wood fall deposits which contributed large scale flourishing of numerous burrowing thalassinid crustaceans twelve different thalassinid coprolite ichnospecies can be found in the berriasian hauterivian volcano sedimentary formations

hydrochemical and isotope characteristics of spring water and travertine in the baishuitai area sw china and their meaning for paleoenvironmental reconstruction a method of combining hydrochemical data logging and in situ titrating with measurement of stable carbon and oxygen isotopes was used to reveal the hydrochemical and isotopic characteristics in the baishuitai travertine scenic area of sw china it was found that the travertine forming springs have a very high concentration of calcium and bicarbonate and accordingly very high co2 partial pressures which are not likely to be produced by biological activity in soil alone further analysis of the stable carbon isotopes of the springs shows that the high pressure of co2 is mainly related to an endogenic co2 source that means the baishuitai travertine is endogenic in origin this is contrast to the commonly accepted saying that the travertine deposition in this study simply is a product of warm and humid conditions in a karst ecological environment rapid co2 degassing from the water is triggered by the much higher partial pressures in water than that of the surrounding air consequently as the waters flow downstream of the spring the ph increases the waters become supersaturated with respect to calcite and travertine is deposited the preferential release of 12co2 to the atmosphere results in a progressive increase of travertine 13c downstream this is concluded with a preliminary discussion of variation in travertine forming water temperatures according to differences in stable oxygen isotopic compositions of the travertine formed in different epochs at baishuitai it was found that the change in water temperature is as high as 13 c i e from 23 c at about 2500 years b p to 10 c at present this may mainly reflect that the effect of geothermal source on water temperature is decreasing the problems involved in paleoenvironmental reconstruction with endogene travertine are also discussed they are the impacts of dead carbon in radiocarbon dating and the enrichment in 13c of travertine by endogenic co2 and degassing of co2 from water which has to be considered in paleovegetation reconstruction when using 13c data of the endogene carbonate deposits

travertines depositional morphology and the bacterially constructed constituents abstract investigation of travertine accumulations throughout central italy and the west central u s has shown that the carbonate is precipitated in response to both inorganic and organic processes individual deposits range up to 85 m thick and hundreds of square kilometers in areal extent all of the carbonate is low magnesian calcite water chemistry temperature and morphology of the accumulation greatly influence the constituents comprising these deposits harsh environmental situations favor inorganic deposits while increasingly more moderate conditions result in the formation of a greater abundance of organically precipitated material morphological variations of travertine deposits recognized include 1 waterfall or cascade 2 lake fill 3 sloping mound fan or cone 4 terraced ound and 5 fissure ridge gross morphology internal stratification and constituents comprising these deposits vary systematically depending upon the type of accumulation and chemistry of the waters bacterially precipitated calcite forms a large percentage of the carbonate in many travertine accumulations exceeding 90 of the framework grains comprising some of the lake fill deposits bacteria are among the first taxa to inhabit and reproduce in harsh spring environments and produce a variety of fascinating constituents the bacteria are primarily rods generally 0 2 m in diameter and less than 1 0 m in length the rods readily decay resulting in calcite crystals loaded with micropores the basic building block of bacterially constructed travertine is a clump of bacteria averaging 20 m in diameter enclosed in a single crystal of calcite aggregates of these crystals produce a variety of deposits including 1 crudely laminated carbonate mud 2 finely laminat d layers of mud 3 intraclasts 4 foam rock and 5 shrubs the shrubs are most striking commonly forming layers 1 3 cm thick but also producing bacterial pisoids at some locales bacterial stromatolites composed of layers of shrubs alternating with finely laminated layers of bacterial mud comprise essentially the entire deposit the shrub layers are the result of flourishing summer growth of bacteria and furthermore show remarkable daily laminae 0 1 0 5 mm thick the importance of bacteria in the formation of travertine and their universally recognized abundance in modern sediments provides an impetus for a reexamination of the role of bacteria in the origin of other types of ancient deposits

using fossil spring deposits in the death valley region usa to evaluate palaeoflowpaths spring deposits reveal the timing and environment of past groundwater discharge herein however the potential for fossil spring deposits to infer water sources and palaeoflowpaths through trace elements and stable and radiogenic isotopes is examined past discharge 70 to 285 ka in the tecopa basin in the death valley region of southeastern california is represented by tufa deposits including mounds pools cemented ledges and rare calcite feeder veins 18o values indicate that spring discharge was a mixture of far travelled regional water with a significant and perhaps dominant contribution of local recharge on a nearby range front and alluvial pediment rather than simply representing an elevated regional water table 13c values indicate regional water had a high tds whereas solute data imply low overall solute contents consistent with dilution by a large component of local recharge radiogenic isotope data u series 87sr 86sr for tufa indicate that siliciclastic rocks a regional aquitard interacted with discharging water to access this aquitard regional flow was probably partitioned into a permeable north south damage zone of a north south range bounding fault along the foot of the resting spring range which ultimately controlled the location of groundwater discharge existing models for modern discharge in the tecopa basin by contrast call upon westward interbasin flow in carbonate rocks from the spring mountains through the intervening and nearly perpendicular nopah and resting spring ranges understanding the controls on regional groundwater flow is critical in this and other arid regions where water is by definition a scarce resource thus although it is a case study this report highlights a fruitful approach to palaeohydrology that can be widely applied copyright 2007 john wiley sons ltd

calcium isotopic fractionation during travertine deposition under different hydrodynamic conditions examples from baishuitai yunnan sw china abstract revealing the potential of ca isotopes in the research of travertine formation processes is the principal goal of this study to achieve this the hydrochemistry travertine precipitation rates and variations in ca isotopic compositions 44 40 ca of present day endogenic thermogenic travertine in two different hydrodynamic systems canal and pool are studied at baishuitai yunnan sw china in the canal where the travertine precipitation is faster 44 40 ca values of both solution and travertine show a downstream increase with ca isotopic fractionation 44 40 ca caco3 aq equal to 1 6 compared to the canal ca isotopic fractionation between travertine and aqueous ca 2 is smaller 44 40 ca caco3 aq 1 2 in the pools where travertine precipitation rates are lower the spatial variations in 44 40 ca values of solution and travertine are related to the amount of ca removed from the solution when 44 40 ca values of spring water remain stable in addition the results confirm the control of precipitation rates on ca isotopic fractionation between calcite and parent aqueous ca 2 using natural samples the observed negative correlation between 44 40 ca caco3 aq and travertine precipitation rates can be explained by the steady state kinetic surface reaction model proposed by depaolo 2011 with equilibrium and kinetic fractionation factors of eq 1 0000 0 0001 and f 0 9983 0 0002 respectively an important consequence of this study is that ca isotopes in travertine systems are good tools to have access to variations of 44 40 ca aq which are directly linked to the amount of precipitated ca this could then be useful for reconstructing past hydrodynamic conditions when applied to travertine core data

biogenic influences on the geochemistry of certain ferruginous sediments of hydrothermal origin ferruginous sediments formed from hydrothermal brines have been sampled on the island of santorini greece and the reykjanes peninsula iceland special attention was paid to the topmost surface sludge of the santorini sediments this was observed to consist entirely of biogenic fe oxide hydroxide formed on stalks of galionella ferruginea a type of fe oxidizing bacteria deeper down the sediment has been subjected to diagenetic processes and the presence of goethite siderite and pyrite has been verified below the surface sludge of the sediment water interface p was the only other analyzed element which showed substantial enrichment together with fe although on santorini the hydrothermal sediments have in general low values for all trace metals some cu and mn enrichment of ferruginous sediments exists close to the hydrothermal source and increases with sediment depth by contrast in literature fe mn sediments farther away from the hydrothermal source at santorini have been shown to be enriched in a few trace elements with zn tied to the fe phase both the vertical enrichment of cu and mn at the source and the horizontal enrichment of zn with increasing distance from the hydrothermal source are suggested to be uptake effects during the transformation of biogenic fe oxide hydroxide to the crystalline polymorphs a hydrothermal model for the origin of banded fe formations has been suggested recently a major detriment to such a model would be that although fe oxide hydroxide minerals are thought to be among the most important removal mechanisms of many trace metals most fe formations have very low values for transition elements however within a hydrothermal model for the genesis of banded fe formations inorganic precipitation of silica could be combined with biogenic oxidation and precipitation of the fe phase major uptake of trace metals would then be restricted to the transformation stage of the biogenic precipitate to the crystalline polymorphs

geochemical characteristics of greek thermal springs abstract a systematic sampling of all known thermal springs and gas emissions of continental greece has been carried out the main gas and water composition and some trace elements in liquid phase sio 2 h 3 bo 3 nh 4 and li have been determined the chemical composition of most thermal springs analyzed is typical of deep na hco 3 rising hot waters which circulate in co 2 rich silicic formations and which acquire progressively a na cl composition by admixing of colder shallower saline connate waters housed in the rock matrix of marine post orogenic tertiary quaternary sediments on the whole the thermal manifestations of continental greece can be fitted in a tectonic framework where high hydraulic gradients enable waters in hot deep aquifers to reach the surface rapidly along fault systems at the boundary of n s and e w trending tertiary basins equilibration temperatures of 80 120 c in the main storage zone 130 150 c max in the nestos xanthi basin have been assessed for most of the study area high n 2 and low h 2 and h 2 s content in gas emissions associated to water samples are consistent with temperatures assessed by using geothermometers in liquid phase

hydrogeochemistry stable isotope composition and geothermometry of co2 bearing hydrothermal springs from western iran evidence for their origin evolution and spatio temporal variations abstract this study aims to hydrochemically characterise three co2 bearing springs representing distinct hydrofacies in nw gorveh western iran and interpret them in the light of their geological setting the results of laboratory measurements of elemental concentrations stable oxygen carbon and hydrogen isotopes dissolved and particulate organic and inorganic carbon dic doc poc pic and alkalinity are combined with in situ measurements of ph and temperature parameters such as alkalinity dic ca2 and pco2 concentration display strong positively correlated values with systematic decrease from the spring vent in down flow direction for the three spring systems the inverse correlation of ph and 13cdic is caused by co2 degassing the 18o and d values show no significant variation related to minor or no evaporation due to normal ambient temperatures the low concentration of poc pic and doc compared to that of dic and the lack of correlation between them reflect predominant inorganic carbon in these fluids spring i is oversaturated in calcite with additional dissolution of co2 and despite high concentrations of na and cl undersaturated in halite indicating a fluid of geothermal origin and or reflecting steady state dissolution this is related to water rock interaction processes with carbonate and evaporitic rocks that affected the isotopic signature of 18o which is shifted to the right of the global meteoric water line spring i also represents a partially equilibrated and mature deep chloride type water spring ii and iii are less saline and represent a different fluid circulation and or shorter residence time the two latter springs are characterized by peripheral shallow dilute chloride bicarbonate type waters decreasing key parameters especially in spring iii during the winter suggest that superficial mixing with rain and meteoric water results in high temporal variations cation and stable carbon isotope geothermometry applied to the studied springs reveals an average reservoir temperature of 210 110 and 90 c for spring i and ii and iii respectively the geochemical and isotopic data allowed to depict a conceptual model where the hydrothermal reservoir for spring i is residing in carbonate and evaporitic rocks most likely the qom formation situated at a depth of 3 4 km whereas those of spring ii and iii are likely sourced from a shallower depth 1 2 km in correspondence with carbonate and porous and permeable volcanic rocks integration of hydrofacies with conceptual hydrological and geological models forms the base towards a proper understanding of water circulation patterns increasingly important for sustainable water management and geothermal applications

effect of different land use land cover on karst hydrogeochemistry a paired catchment study of chenqi and dengzhanhe puding guizhou sw china summary rainfall spring stage water temperature ph and conductivity in the paired karst spring catchments of chenqi and dengzhanhe which shared the same climatic condition but different land use land cover lulc at puding guizhou province sw china were monitored by two high resolution multi parameter auto recordable instrument of ctdp300 during the hydrological year of september 2007 september 2008 other monthly hydrogeochemical and carbon isotopic 13c variations in the paired karst catchments during the same hydrological year were also investigated a thermodynamic model was used to link the continuous data to monthly hydrogeochemical data allowing the calculation of co2 partial pressure pco2 and calcite saturation index sic on a continuous basis the primary study objective was to understand how the karst processes and karst hydrogeochemistry respond to different lulc which is essential to assessing the karst related carbon cycle marked seasonal and storm scale variations were found for ph conductivity pco2 sic and 13c of the two springs indicating that both springs were dynamic and variable systems however there were differences in the magnitude and direction of the variations of these features between the two springs the higher pco2 and hco 3 concentration and lower ph sic and 13c in chenqi spring than those in dengzhanhe spring tend to be related to the difference in lulc between chenqi and dengzhanhe spring catchments in the chenqi spring catchment there was larger soil cover and the paddy land was located in the discharge area both of which produced and kept more co2 a major driving agent for the karst processes and lower 13c in the soil aquifer system while in the dengzhanhe spring catchment area there was larger bare carbonate rock occurrence and the paddy land was located mainly in the recharge area moreover the ph increased and pco2 decreased generally in chenqi spring after rainfall possibly due to more carbonate dissolution in the larger soil cover rich in limestone fragments in the spring catchment while the ph decreased and pco2 increased generally in dengzhanhe spring after rainfall all these differences show that soil cover and land use pattern played important roles in the karst processes in other words the karst hydrogeochemistry and the karst related carbon cycle could be regulated effectively by different lulc in addition the higher concentrations of ca2 so 4 2 mg2 and conductivity of dengzhanhe spring were due to the dissolution of more gypsum and dolomite minerals in the strata of dengzhanhe spring catchment therefore the karst hydrogeochemical parameters including ph conductivity hco 3 ca2 mg2 so 4 2 pco2 sic and 13cdic could serve as good indicators of different lulc and the other environmental changes

δ13c δ18o and deposition rate of tufa in xiangshui river sw china implications for land cover change caused by climate and human impact during the late holocene

precambrian dolomites petrographic and isotopic evidence that they differ from phanerozoic dolomites dolomites are more common in precambrian than in phanerozoic rocks and from a petrographic isotopic study of the middle to upper proterozoic beck spring dolomite of eastern california it is suggested that precambrian dolomites are different from those of the phanerozoic petrographically all fabric details of precambrian dolomites studied are preserved just as if they were limestones and isotopically they show the same trend as limestones increasingly negative i8 o and to a lesser extent increasingly light i8 c from depositional components through early fibrous dolomite cements to later dolomite spar cements the data suggest that in precambrian time dolomite was the principal carbonate mineral precipitated from seawater and during diagenesis and this implies that precambrian seawater was different from that of the phanerozoic

rapid wastage of alaska glaciers and their contribution to rising sea level we have used airborne laser altimetry to estimate volume changes of 67 glaciers in alaska from the mid 1950s to the mid 1990s the average rate of thickness change of these glaciers was 0 52 m year extrapolation to all glaciers in alaska yields an estimated total annual volume change of 52 15 km 3 year water equivalent equivalent to a rise in sea level sle of 0 14 0 04 mm year repeat measurements of 28 glaciers from the mid 1990s to 2000 2001 suggest an increased average rate of thinning 1 8 m year this leads to an extrapolated annual volume loss from alaska glaciers equal to 96 35 km 3 year or 0 27 0 10 mm year sle during the past decade these recent losses are nearly double the estimated annual loss from the entire greenland ice sheet during the same time period and are much higher than previously published loss estimates for alaska glaciers they form the largest glaciological contribution to rising sea level yet measured

hydrogeochemistry of the middle rio grande aquifer system fluid mixing and salinization of the rio grande due to fault inputs abstract deeply derived fluids influence river and groundwater hydrochemistry at the socorro constriction in the central new mexico rio grande rift new hydrochemical transects in the rio grande rift provide three dimensional perspectives on sources contributing to surface and groundwaters in addition to abrupt salinity increases in the rio grande major and trace ion chemistry 18o d 13c 87sr 86sr 3h and 3he 4he variations in springs and wells across the rift are best explained by mixing of deeply derived endogenic fluids containing both mantle and crustal inputs with shallow groundwater endogenic fluids ascend along rift bounding and intra rift faults and can cause increased salinity accompanied by an increase in metals and overall degradation of water quality our data reinforce models that attribute a downstream increase in salinity to geological not agricultural influences hydrochemical mixing of endogenic waters along faults in shallow aquifers has a major influence on groundwater and surface water quality and variability in arid tectonically active regions with important ramifications for water management

travertine distinctive depositional fabrics of carbonates from thermal spring systems the terrestrial limestones forming at the emergence of thermal springs show a variety of unusual depositional facies the specific lithological and petrological features of these deposits have few counterparts in the marine and continental karst related carbonates but they are typical of the epigean limestone that has been quarried since antiquity in the surroundings of tivoli rome under the name of travertine where it is still forming in hydro geothermal fields linked to extensional tectonics the physicochemical hydrodynamic and geological conditions specific to the tivoli thermal spring system imply hypersaturated alkaline sulphate warm to hot waters upwelling from springs fed through open fractures faults in extensional and or volcanic regimes these features together with the hydrodynamic behaviour of the water flows running from the vents control the petrogenetic features of the travertine a well bedded mostly finely laminated porous but quite compact limestone the results of a detailed comparative petrological analysis carried out on the lithofacies of travertine limestones and of those observed during formation within numerous active thermal spring fields provide the elements required for an exhaustive textural classification of the travertine lithofacies which has not yet been described systematically according to the genetic processes and fabrics the thermal deposits that originate from such hypersaturated alkaline sulphate warm to hot waters can be subdivided into abiotic crystalline crusts microbially mediated crusts microbialites and granular deposits mostly represented by small accumulations of lime mudstone some of the granular deposits and the microbialites are only partially comparable with analogous sediments forming on tidal flats sabkhas or other continental sites however the facies association of crystalline crusts and laminar curled microbialites has no counterpart in the marine realm the widespread presence of thermophile bacteria and sulphobacteria and the general absence of autochthonous eukaryote organisms unable to live in poisonous sulphate waters are also undeniable evidence of their thermal origin