strengthening of north american dust sources during the late pliocene 2 7 ma here we present orbitally resolved records of terrestrial higher plant leaf wax input to the north atlantic over the last 3 5 ma based on the accumulation of long chain n alkanes and n alkanl 1 ols at iodp site u1313 these lipids are a major component of dust even in remote ocean areas and have a predominantly aeolian origin in distal marine sediments our results demonstrate that around 2 7 million years ago ma coinciding with the intensification of the northern hemisphere glaciation nhg the aeolian input of terrestrial material to the north atlantic increased drastically since then during every glacial the aeolian input of higher plant material was up to 30 times higher than during interglacials the close correspondence between aeolian input to the north atlantic and other dust records indicates a globally uniform response of dust sources to quaternary climate variability although the amplitude of variation differs among areas we argue that the increased aeolian input at site u1313 during glacials is predominantly related to the episodic appearance of continental ice sheets in north america and the associated strengthening of glaciogenic dust sources evolutional spectral analyses of the n alkane records were therefore used to determine the dominant astronomical forcing in north american ice sheet advances these results demonstrate that during the early pleistocene north american ice sheet dynamics responded predominantly to variations in obliquity 41 ka which argues against previous suggestions of precession related variations in northern hemisphere ice sheets during the early pleistocene

constraints on the application of long chain diol proxies in the iberian atlantic margin abstract long chain diols are lipids that have gained interest over the last years due to their high potential to serve as biomarkers and diol indices have been proposed to reconstruct upwelling conditions and sea surface temperature sst however little is known about the sources of the diols and the mechanisms impacting their distribution here we studied the factors controlling diol distributions in the iberian atlantic margin which is characterized by a dynamic continental shelf under the influence of upwelling of nutrient rich cold deep waters and fluvial input we analyzed suspended particulate matter spm of the tagus river marine spm and marine surface sediments along five transects off the iberian margin as well as riverbank sediments and soil from the catchment area of the tagus river relatively high fractional abundances of the c32 1 15 diol normalized with respect to the 1 13 and 1 15 diols were observed in surface sediments in front of major river mouths and this abundance correlated strongly with the bit index a tracer for continental input of organic carbon together with an even higher fractional abundance of the c32 1 15 diol in the tagus river spm and the absence of long chain diols in the watershed riverbank sediments and soils we suggest that this long chain diol is produced in situ in the river further support for this hypothesis comes from the small but distinct stable carbon isotopic difference of 1 3 with the marine c28 1 13 diol the 1 14 diols are relatively abundant in surface sediments directly along the northern part of the coast close to the upwelling zone suggesting that diol indices based on 1 14 diols would work well as upwelling tracers in this region strikingly we observed a significant difference in stable carbon isotopic composition between the mono unsaturated c30 1 1 14 and the saturated c28 1 14 diol 3 8 0 7 suggesting different sources in accordance with their different distributions in addition the long chain diol index ldi a proxy for sea surface temperature was applied to the surface sediments the results correlated well with satellite ssts offshore but revealed a significant discrepancy with satellite derived ssts in front of the tagus and sado rivers this suggests that river outflow might compromise the applicability of this proxy

feldspar saturation state in natural waters the saturation state of feldspar minerals in natural waters ranging from 0 c to over 300 c was studied waters above 200 c have closely approached equilibrium with microcline and low albite this is consistent with the occurrence of these minerals as hydrothermal minerals in active geothermal systems with temperature in excess of some 200 c the na k activity ratio of geothermal waters with temperature as low as 50 c closely approaches that predicted from thermodynamic data for the reaction low albite k microcline na suggesting that na and k ion activities in these geothermal waters are controlled by simultaneous equilibrium with these two feldspars geothermal waters are undersaturated with primary disordered plagioclases and alkali feldspars of compositions typically found in volcanic rocks accordingly these feldspars tend to dissolve in such waters simultaneously with precipitation of ordered alkali feldspars surface and non thermal groundwaters are usually undersaturated with respect to igneous and metamorphic feldspars regardless of composition and al si ordering and tend therefore to dissolve under weathering conditions

the chemistry of geothermal waters in iceland ii mineral equilibria and independent variables controlling water compositions abstract the major element chemistry of icelandic geothermal waters is predictable provided two parameters are known this follows from an attainment of or a close approach to an overall chemical equilibrium in the geothermal systems at temperatures as low as 50 c it is considered that the geothermal system composition temperature and kinetic factors determine which alteration minerals form the system composition is not so much fixed by rock composition as by the rate of leaching of the various constituents from the fresh rock and the composition of inflowing water the water chemistry is determined by the system composition and the external variables acting on the system they include temperature and the mobility of chloride pressure which theoretically should be regarded as an external variable has insignificant effect on water compositions in the range 1 200 bars occurring in the geothermal systems

the use of mixing models and chemical geothermometers for estimating underground temperatures in geothermal systems abstract application of various chemical geothermometers and mixing models indicate underground temperatures of 260 c 280 c and 265 c in the geysir hveravellir and landmannalaugar geothermal fields in iceland respectively mixing of the hot water with cold water occurs in the upflow zones of all these geothermal systems linear relations between chloride boron and 18o constitute the main evidence for mixing which is further substantiated by chloride silica and sulphate relations in the geysir and hveravellir fields a new carbonate silica mixing model is proposed which is useful in distinguishing boiled and non boiled geothermal waters this model can also be used to estimate underground temperatures using data from warm springs this model as well as the chloride enthalpy model and the na li and co2 gas geothermometers invariably yield similar results as the quartz geothermometer sometimes also does by contrast the na k and the na k ca geothermometers yield low values in the case of boiling hot springs largely due to loss of potassium from solution in the upflow the results of these geothermometers are unreliable for mixed waters due to leaching subsequent to mixing

application of the long chain diol index ldi paleothermometer to the early pleistocene mis 96 abstract recently a new organic geochemical paleothermometer based on the relative abundance of long chain alkyl 1 13 and 1 15 diols the so called long chain diol index ldi was proposed because of its novelty the proxy has not been reported for sediments older than 43 ka we therefore determined the ldi for 14 sediment samples from the early pleistocene between 2 49 and 2 41 ma comprising marine isotope stage mis 98 to 95 and converted the values to sea surface temperature sst estimates to test whether the ldi could be applied or not to the early quaternary we show that the long chain diols can be preserved in marine sediments from the early pleistocene although at our study site this is limited to periods of increased biomarker accumulation glacials although the results are based on a limited time interval and number of samples the similarity between ldi based sst and alkenone based sst from the same samples suggests that the ldi proxy may have potential for studies covering the entire quaternary

geothermal surface alteration of basalts krýsuvik iceland alteration mineralogy water chemistry and the effects of acid supply on the alteration process abstract the geothermal surface alteration of basalts and associated water chemistry at kr suvik sw iceland were studied the geothermal area was characterised with zones of intensive surface alteration steam vents mud pots and hot springs the steam heated geothermal surface waters had ph values between 1 69 and 7 67 and total dissolved solid tds concentrations between 154 and 6660 ppm with cl and so 4 concentration decreasing and increasing with decreasing ph respectively alteration mineral assemblages observed were strongly associated with the surface intensity in areas of most intensive activity the basaltic rocks were altered to amorphous silica anatase and pyrite with a crust of native sulphur at the surface with decreased activity kaolinite became important as well as iron oxyhydroxides and oxides on the flanks of the area montmorillonite was the predominant alteration product based on these observations the surface geothermal activity was divided into three groups 1 high activity areas with active steam vents and mud pots and intensive acid leaching 2 medium activity areas where the ground is hot steam vents and mud pots are uncommon and the surface alteration is less intensive and 3 low activity areas on the margins of the surface geothermal activity the primary factors influencing the steam heated acid sulphate alteration of basalts included the redox state oxidation front supply of acids and ph and the extent of reaction the formation of iron and sulphur containing minerals and the respective elemental mobility depended on the redox conditions with pyrite formation under reduced conditions and goethite and or hematite under oxidised conditions at low ph ca mg k and na were mobile and leached out whereas fe ti and al and to a large degree si were retained in the alteration product at higher ph values 5 the mobility of ca mg k and na was reduced due to the formation of clays

the chemistry of trace elements in surface geothermal waters and steam iceland abstract the geochemistry of trace elements in surface geothermal fluids in iceland was studied the sampled fluids included hot springs mud pots steam vents and soil solutions with temperatures ranging from 4 to 100 c ph between 2 01 and 9 10 and total dissolved solids between 86 and 4375 ppm the surface geothermal waters may be categorized into three groups based on their chemical composition namely nacl waters steam heated acid sulfate waters and mixed waters nacl waters with ph 8 are considered to represent aquifer geothermal fluids that have undergone boiling in the upflow they contained only low concentrations of most metals

late pliocene changes in the north atlantic current article i nfo during the late pliocene global climate changed drastically as the northern hemisphere glaciation nhg intensified it remains poorly understood how the north atlantic current nac changed in strength and position during this time interval such changes may alter the amount of northward heat transport and therefore have a large impact on climate in the circum north atlantic region and the growth of northern hemisphere ice sheets using the alkenone biomarker we reconstructed orbitally resolved sea surface temperature sst and productivity records at integrated ocean drilling project iodp expedition 306 site u1313 during the late pliocene and early pleistocene 3 68 2 45 million years ago ma before 3 1 ma ssts in the mid latitude north atlantic were up to 6 c higher than the present and surface water productivity was low indicating that an intense nac transported warm nutrient poor surface waters northwards starting at 3 1 ma surface water characteristics changed drastically as the nhg intensified during glacial periods at the end of the late pliocene and beginning of the pleistocene ssts decreased and surface water productivity in the mid latitude north atlantic increased reflecting a weakened influence of the nac at our site at the same time the increase in surface productivity suggests that the arctic front af reached down into the mid latitudes we propose that during the intensification of the nhg the nac had an almost pure west to east flow direction in glacials and did not penetrate into the higher latitudes the diminished northward heat transport would have led to a cooling of the higher latitudes which may have encouraged the growth of large continental ice sheets in the northern hemisphere

quantifying mixing boiling degassing oxidation and reactivity of thermal waters at vonarskard iceland abstract the chemical composition of geothermal fluids may be altered upon ascent from the reservoir to surface by processes including boiling degassing mixing oxidation and water rock interaction in an attempt to quantify these processes a three step model was developed that includes 1 defining the composition of the end member fluid types present in the system 2 quantifying mixing between the end members using non reactive elemental concentrations and enthalpy and 3 quantifying the changes of reactive elements including degassing oxidation and water rock interaction the model was applied to geothermal water at vonarskard iceland for demonstration having temperatures of 3 98 c ph of 2 15 9 95 and tds of 323 2250 ppm and was thought to be produced from boiled reservoir water condensed steam and non thermal water most geothermal water represented mixture of non thermal water and condensed steam whereas the boiled reservoir water was insignificantly mixed co2 and h2s degassing was found to be quantitative in steam heated water with oxidation of h2s to so4 also occurred in contrast major rock forming elements are enriched in steam heated water relative to their mixing ratios suggesting water rock interaction in the surface zone boiled reservoir water observed in alkaline hot springs have however undergone less geochemical changes upon ascent to surface and within the surface zone

millennial scale climate variability in the subpolar north atlantic ocean during the late pliocene 1 large amplitude millennial scale climate oscillations have been identified in late pleistocene climate archives from around the world these oscillations appear to be of larger amplitude during times of enlarged ice sheets this observation suggests the existence of a relationship between large amplitude millennial variations in climate and extreme glacial conditions and therefore that the emergence of millennial scale climate variability may be linked to the pliocene intensification of northern hemisphere glaciation inhg here we test this hypothesis using new late pliocene high resolution 400 year records of ice rafted debris deposition and stable isotopes in planktic foraminiferal calcite globigerinoides ruber generated from integrated ocean drilling program site u1313 in the subpolar north atlantic a reoccupation of the classic deep sea drilling project site 607 our records span marine oxygen isotope stages mis 103 95 2600 to 2400 ka the first interval during inhg 3 5 to 2 5 ma in which large amplitude glacial interglacial cycles and inferred sea level changes occur our records reveal small amplitude variability at periodicities of 1 8 to 6 2 kyr that prevails regardless of inter glacial state with no significant amplification during the glacials mis 100 98 and 96 these findings imply that the threshold for the amplification of such variability to the proportions seen in the marine archive of the last glacial was not crossed during the late pliocene and in view of all available data likely not until the mid pleistocene transition

late pliocene to early pleistocene changes in the north atlantic current and suborbital scale sea surface temperature variability the strength and latitudinal position of the north atlantic current nac determines the position of the arctic front and heat transport to the high northern latitudes with potentially important consequences for northern hemisphere glaciation a southward shift in the nac and reduced poleward heat transport is hypothesized to have triggered the last major climate transition in earth s history late pliocene intensification of northern hemisphere glaciation inhg in turn inhg is hypothesized to have led to the amplification of climate variability on suborbital time scales to date however only a handful of adequately resolved records are available to test these two hypotheses here we present a new late pliocene to earliest pleistocene record from integrated ocean drilling program site u1313 north atlantic 41 n 2 9 to 2 4 ma we use mg ca derived paleotemperature records in planktic foraminiferal calcite to investigate changes in summer sea surface temperatures sst on orbital and suborbital time scales our results call into question the suggestion that significant weakening and or southward shift of the nac served as a trigger for northern hemisphere cooling and intensified continental ice sheet growth across inhg in contrast to the late pleistocene during inhg we find that the position of the nac and arctic front probably lay well to the north of site u1313 and that the amplitude of suborbital sst variability did not change on glacial interglacial time scales conservative estimates of late pliocene to earliest pleistocene interglacial summer ssts in our record are up to 3 c warmer than present while glacial summer ssts are only 2 c to 3 c cooler in fact our interglacial summer ssts are remarkably similar to those of the mid pliocene our findings indicate that inhg must have involved amplifying feedback mechanisms that are tightly coupled to ice sheet growth but that these processes were insufficiently developed by the late pliocene earliest pleistocene to have triggered large amplitude changes in suborbital climate in the midlatitude north atlantic

source processes of the thermal waters from the phlegraean fields naples italy by means of the study of selected minor and trace elements distribution abstract the geochemical characteristics of hydrothermal waters from the phlegraean fields p f naples italy were analysed for minor and trace elements selectively mobilised in hydrothermal systems such as b f hg as pb and tl the water samples collected from a shallow aquifer likely to be fed by deeper fluids showed various geochemical features resulting from the mixing of three components 1 surface waters of meteoric origin 2 hot deep waters deriving from water rock interaction and including deep waters of marine origin 3 magmatic fluids rising from the local magma chamber lying a few kilometres below the town of pozzuoli this setting although very complex provides a reliable means of studying the distribution of the investigated trace elements in particular within the phlegraean area high contents of b 0 1 48 mg l f 0 5 8 mg l as 16 6050 g l and hg 0 7 232 g l were observed the levels of thallium in the springs close to solfatara about 7 g l were in line with those normally recorded in hydrothermal areas whereas high levels of this element up to 23 3 g l were identified in other wells of the study area lead 1 3 to 29 1 g l appears to be anomalous with respect to its normal content in groundwater about 1 g l owing to the presence of high density brines at depth which enhance the solubility of pb in volcanic rocks under hydrothermal conditions the distribution of the investigated trace elements in the phlegraean fields thermal area is probably related to the different ascent pathways of the fluids clearly apart from the influence exerted by anomalous thermal conditions each element shows a different behaviour depending on its geochemical affinity with mineral phases and as a consequence of the different enthalpy values which determine ion partitioning in gaseous phases based on geochemical evidences and on the distribution of minor and trace elements the source processes of the investigated hydrothermal waters were defined five main groups were identified 1 acid sulphate waters resulting from mixing of meteoric water with magmatic gases mainly h 2 s 2 high sulphate chloride waters from a deep reservoir located in the major upflow zone 3 waters associated with significant degassing of magmatic co 2 4 waters from a deep geothermal neutral chloride reservoir resulting from heating of marine water modified by water rock interaction processes 5 cold waters from the inner area influenced by low temperature water rock interaction processes

boiling and dilution in the shallow portion of the waiotapu geothermal system new zealand abstract the waiotapu geothermal system is the largest in terms of surface extent and heat flow 17 km2 and 600 mw respectively of the 20 major geothermal systems in the taupo volcanic zone new zealand two extinct dacite cones and a rhyolite dome rise about 500 m above the waiotapu valley the majority of thermal features occurs in the valley over a relief of only 100 m and lies within coincident apparent resistivity and 30 m depth thermal anomalies thermal features comprise near neutral ph chloride springs often boiling acid sulfate springs and mud pools and mixed waters the latter including both bicarbonate chloride and acid sulfate chloride springs the majority of the sulfate discharges to the surface in the northern higher altitude area while most chloride that reaches the surface does so in the southern portion of the system comparison of measured and calculated surface chloride flux the latter from measured heat flow and reservoir chloride concentrations indicates that at least half of the deep chloride does not discharge at the surface but flows laterally to the south at shallow depths mixing with groundwater the composition of well discharges indicates a shallow 400 m reservoir of chloride fluid about 1350 mg cl kg at 230 c is diluted by a co2 rich steam heated water nil chloride at about 160 c the latter located on the margins of the system this same dilution trend is apparent from the compositional variation and k na and k mg geothermometry of hot spring waters however there is chemical and stable isotope evidence from hot springs that cold groundwater also acts as a diluent at shallow levels and very near the surface steam heated acid sulfate waters mix with the upflow boiling of the deep chloride fluids prior to dilution results in the stabilization of k feldspar in contrast dilution at shallower depths by the steam heated waters both co2 rich and acid sulfate leads to the water compositions initially shifting to k mica and interstratified clay stability and to kaolinite stability with further dilution and temperature decrease the composition and distribution of these fluids are consistent with alteration mineralogy and zonation observed in drill core although boiling occurs at deeper levels and up to the surface in the upflow zone at waiotapu mixing is also common and is the dominant process on the margin and in the near surface portion of the system boiling of deep chloride fluid is very common in the upper 1 2 km of the upflow zone of most geothermal systems though it may be quenched by mixing with marginal waters either cold groundwater in high relief terrane or steam heated waters in areas of lower relief co2 rich steam heated waters are common on the margins of systems and will generally underlie the near surface acid sulfate steam heated waters interaction with co2 rich waters will form k mica and interstratified clays while acid sulfate waters cause kaolinite and even alunite to form the former assemblage is commonly associated with typical low sulfidation epithermal gold mineralization as wallrock alteration where gold bearing veins comprise adularia and illite in contrast kaolinite is rare and alunite absent from a direct spatial and genetic association with gold mineralization in this environment this implies that mixing of the deep neutral ph chloride fluid with surficial acid sulfate waters does not commonly lead to ore grade gold deposition mixing with and cooling by co2 rich steam heated waters leads to clay stability accounting for the large halos of clay alteration and low grade metal anomalies which often surround veins of high gold grade in contrast mixing with surficial acid sulfate waters is unlikely to cause precious metal mineralization because the chloride fluids have already lost the majority of their gold through deeper boiling and dilution

a diatomaceous origin for long chain diols and mid chain hydroxy methyl alkanoates widely occurring in quaternary marine sediments indicators for high nutrient conditions for the first time a biological source for the long chain alkyl 1 14 diols and 12 hydroxy methyl alkanoates lipids widely occurring in the marine water column and sediments has been identified cultures of proboscia indica and proboscia alata rhizosolenoid diatoms belonging to the widespread diatom genus proboscia contain c28 c28 1 c30 and c30 1 alkyl 1 14 diols and c27 and c29 12 hydroxy methyl alkanoates as major neutral lipids these components form a substantial fraction of lipid fractions from sediment traps or sediments especially in areas with an elevated primary production such as upwelling regions examination of literature data reveals that as much as 20 to 35 of the total lipid flux in the arabian sea is derived from proboscia diatoms during the start of the upwelling season their rapid transfer to the water sediment interface may explain why corresponding 1 14 keto ols inferred oxidation products of diols are hardly formed these interpretations are supported by compound specific carbon isotopic analysis of long chain keto ols and diols in surface sediments of the arabian sea the data indicate that long chain alkyl 1 14 diols and 12 hydroxy methyl alkanoates can be applied as indicators for high nutrient conditions in the photic zone

arsenic and thioarsenic species in the hot springs of the rehai magmatic geothermal system tengchong volcanic region china abstract rehai is the sole geothermal area in mainland china that discharges both acidic and alkaline hot springs with phs ranging from 1 4 to 10 0 the hot springs in rehai are also characterized by a wide range of arsenic concentrations with the highest being 1 35 mg l analysis of the arsenic geochemistry indicates that the alkaline and neutral hot springs in rehai have high arsenic concentrations the alkaline hot springs represent arsenic rich boiled reservoir fluids and the neutral hot springs represent mixtures of these reservoir fluids with non thermal waters and or condensed steam the enrichment of arsenic in the deep reservoir fluids also called primary fluids is primarily attributable to the leaching of reservoir rocks at high temperatures but a possible arsenic contribution from magmatic fluids cannot be ruled out the acidic springs in contrast have much lower arsenic concentrations because they are a mixture of non thermal oxygenated waters and condensed steam both of which are depleted in arsenic in addition to arsenite and arsenate mono di and tri thioarsenates have been detected in the rehai geothermal waters the arsenic speciation in the rehai hot springs is primarily linked to the formation processes of the various secondary fluids at the surface and their sulfide concentrations in addition the speciation is also affected by the ph values and the redox potentials of the waters compared to the springs along secondary e w trending faults the chloride rich springs along the main n s trending faults are generally much less affected by mixing with non thermal waters and or condensed steam they are also more enriched in sulfide and thioarsenates consequently represent a greater proportion of the total arsenic this is the first study to report the thioarsenic geochemistry of hot springs in china

geothermal mineral equilibria the dominant reaction determining the chemistry of fluids in a geothermal system of the new zealand type consists of the conversion of primary plagioclase by co2 to calcite and clays with log pco2 15 26 7850 t 273 2 temperature t in c subsequent reactions involving secondary minerals control relative co2 h2s contents the distribution of mineral phases throughout a geothermal system reflects the stepwise conversion of thermodynamically unstable primary phases through a series of intermediate metastable phases to a thermodynamically stable secondary assemblage the relative stabilities of these phases was evaluated on the basis of their solubilities the least soluble aluminiumsilicate representing the thermodynamically most stable phase under a given set of conditions observed assemblages of secondary minerals in geothermal systems represent indicators allowing mineral fluidinteraction conditions to be evaluated on the basis of multi component mineral stability diagrams

distributional variations in marine crenarchaeotal membrane lipids a new tool for reconstructing ancient sea water temperatures it has recently been shown that membrane lipids of marine crenarchaeota a ubiquitous and abundant component of plankton occur in relatively high concentrations in recent and ancient sediments in this study we investigated the environmental controls on the relative distribution of these lipids in surface sediments we especially focussed on temperature as it is known from the thermophilic genetic relatives of marine crenarchaetoa that the composition of their membrane strongly depends on growth temperature indeed a significant linear correlation r2 0 92 is found between the number of cyclopentane rings in sedimentary membrane lipids derived from marine crenarchaeota and the annual mean sea surface temperatures this suggests that the mechanism of physical adaptation of their membrane compositions to temperature is identical to that of their thermophilic relatives in turn archaeal lipid distributions in sediments may thus allow the reconstruction of sea water temperatures of ancient marine environments

constraining the applicability of organic paleotemperature proxies for the last 90 myrs abstract we evaluated changes in the distributions of long chain alkenones long chain diols and gdgts lipids commonly used for paleothermometry over the last 90 myrs for sediments deposited on the new jersey shelf the bass river site and assessed potential effects of different ancestral producers and diagenesis on their distributions and their impact on the associated temperature proxies as reported before the paleogene distributions of alkenones are generally similar to those in modern haptophytes but unusual alkenone distributions characterized by a dominant di unsaturated c40 alkenone are observed for late cretaceous sediments suggesting different ancestral source organisms for alkenones in this interval the isoprenoid gdgt distributions remained comparable to modern day distributions suggesting that tex86 can be applied up to ca 90 ma the miocene long chain diol distributions are similar to modern day distributions but the older sediments reveal unusual distributions dominated by the c28 1 12 and c26 1 13 diols suggesting different source organisms before 30 ma accordingly the ldi does not match other paleotemperature proxies suggesting its applicability might be compromised for sediments older than the miocene our results indicate that of the three proxies the tex86 seems to be the most applicable for deep time temperature reconstructions

geochemistry of early triassic seawater as indicated by study of the rot halite in the netherlands germany and poland abstract study of three halite sections in the rot basin from the eastern netherlands twente rijn 382 borehole central germany mardorf 6 borehole and western poland o no ig2 borehole shows that the 34 s values in rot sulphates of studied samples 27 14 31 98 are characteristic of marine sulphates of late early triassic these values fit in the rot event shift described in the literature the bromine content in halite is 32 158 ppm in the dutch and polish sections relics of sedimentary structures chevron and hopper are recorded in halite grains these structures contain fluid inclusions that were analysed using the ultramicrochemical method of petrichenko petrichenko o i 1973 metody doslidzhennya vkluchen v mineralakh galogennykh porid kiev naukova dumka 92 pp in the german section no sedimentary halite structures occur because the pressure in the inclusions in recrystallized halite is only slightly greater than atmospheric pressure these inclusions are presumed to be early diagenetic in origin the analysis of individual brine inclusions both in sedimentary and diagenetic forms of halite shows that the rot brines correspond to the na k mg cl so 4 so 4 rich chemical type i e the same type that characterises modern seawater however the rot brines differ from the composition characteristic of modern concentrated seawater by a decrease in the content of sulphate ion and an increase in the content of potassium ion on a janecke diagram the points of the brine composition during deposition of rot halite in poland germany and the netherlands only show a small range this suggests a stable composition of basinal brines during the deposition of the halite at the same time the relative content of sulphate ion in the lower triassic rot basin was slightly lower than that in upper permian evaporite basins but higher than that in lower and middle permian and middle and upper triassic evaporite basins the implication is that the content of sulphate ion in seawater was subject to changes in permian and triassic times

chemical composition of seawater in neoproterozoic results of fluid inclusion study of halite from salt range pakistan and amadeus basin australia abstract data on chemical composition of brines in primary inclusions of marine halites and on mineralogy of marine evaporites and carbonates lead to the conclusion that during the phanerozoic two long term cycles of chemical composition of seawater existed during each of those cycles seawater dominantly a na k mg ca cl ca rich type changed to a na k mg cl so 4 so 4 rich type recrystallised halite from the uppermost neoproterozoic salt range formation ca 545 ma in pakistan contains solitary inclusions indicating so 4 rich brines this supports the concept derived from the study on primary fluid inclusions from the neoproterozoic ara formation of oman so 4 rich seawater existed during latest neoproterozoic time ca 545 ma in contrast samples of recrystallised halite from the bitter springs formation 840 830 ma in australia contain inclusion brines that are entirely ca rich indicating that basin brines and seawater were ca rich during deposition of central australian evaporites these combined data supported by the timing of aragonite and calcite seas suggest that during the proterozoic significant oscillations of the chemical composition of marine brines and seawater occurred which are similar to those known to exist during the phanerozoic it is suggested that ca rich seawater dominated for a substantial period of time more than 200 ma at 650 ma this was replaced by so 4 rich seawater finally returning to ca rich seawater at 530 ma

boiling and fluid mixing in the chlorite zone of the larderello geothermal system abstract the geochemical features of the geothermal fluids produced within the boiling zone in the relatively shallow parts of the larderello geothermal system italy have been documented as a result of deep drilling which provided samples from 1480 to 2500 m depth four wells monteverdi 1 monteverdi 2a sasso 22 and capannoli 2b have been sampled in the intermediate parts of the larderello aquifer located in a metamorphic basement underlying the tertiary nappe complex which constitutes the shallow aquifer at larderello fluid inclusions from recrystallized quartz lenses and quartz veins in samples displaying a predominant quartz chlorite epidote adularia paragenesis have been studied by microthermometry and raman spectroscopy the inclusions are primary and pseudo secondary in origin when formed in authigenic quartz or of secondary origin when located in fluid inclusion planes related to microfracturing of metamorphic quartz lenses several generations of fluids are present and include h 2 o co 2 dominated vapours and liquids and a series of aqueous liquids for the most part of relatively low salinity the t m ice of both early and late inclusions are mostly between 0 0 and 4 5 c indicating that the salinities of the hydrothermal fluid were very low to moderate however rare fluid inclusions with lower t m ice from 4 9 to 25 0 c were also observed these inclusions may record the occasional input of saline fluids which may be derived from the interaction of the hydrothermal waters with the evaporites present in the shallow part of the larderello field at capannoli 2b earliest h 2 o co 2 liquids were trapped under minimal pressures of 610 645 bars which bracket the estimated present day lithostatic pressure 640 bars in all other samples the main stage of quartz chlorite crystallization occurs under boiling conditions attested by the presence of liquid and vapour rich inclusions that in some instances can be texturally interpreted to be coeval their trapping conditions 350 375 c 160 215 bars are higher than the present day temperatures at the same depth later fluid inclusions attest to a significant cooling of the fluids down to temperatures similar to the present day temperatures during this time pressures were close to hydrostatic conditions most fluid inclusions were trapped within the liquid field this indicating that a significant pressure drop has since affected the main aquifers or fractured zones which are at present under vaporstatic conditions

processes controlling the distribution of boron and chlorine in natural waters in iceland abstract the concentrations of b and cl in natural waters in iceland lie in the range 0 001 10 and 1 20 000 ppm respectively lowest concentrations occur in surface and groundwaters in the central highlands highest cl concentrations are found in high temperature waters on the reykjanes peninsula and highest b concentrations in well waters from high temperature geothermal systems in the axial zones of the active volcanic belts the b and cl contents of icelandic basalts are 0 1 6 6 and 75 750 ppm respectively these large variations are considered to result from variable degassing during consolidation as well as concentration variations in the initial magma tholeftes are lowest in both elements av 1 2 ppm b and 170 ppm ci transitional basalts intermediate av 2 1 ppm b and 240 ppm ci and alkali basalts highest av 3 8 ppm b and 340 ppm cl cl b ratios in tholeiites are most often within 25 50 but somewhat lower in alkali basalts most geothermal waters contain b and cl within 0 05 1 and 10 100 ppm respectively these rather low values are attributed to the low content of b and cl in the basaltic rock the b and cl distribution in the icelandic natural waters indicate that these elements act as essentially incompatible their sources of supply include 1 the atmosphere seawater spray and aerosols 2 the rock with which the water interacts 3 seawater groundwater and 4 magma intrusions in surface water and nonthermal groundwater the dominant source of supply of cl is seawater spray and aerosols but the soil and rock contribute often significantly to the b in these waters their cl b ratio is similar to that of seawater 1330 or somewhat lower boron and cl concentrations generally increase with water temperature warm waters cl b ratios intermediate between those of seawater and basalt with increasing temperature this ratio decreases and gradually approaches that of the rock some high temperature geothermal waters have as low cl b ratios as 1 and b concentrations as high as 10 ppm the cause is either b degassing of the magmatic intrusive heat source or phase separation in the producing aquifer some low temperature waters

fluid inclusions in bedded permian halite palo duro basin texas evidence for modification of seawater in evaporite brine pools and subsequent early diagenesis abstract the chemical composition of fluid inclusions trapped within the marine dominated permian evaporite sequence of the palo duro basin texas departs significantly from that expected in the evolution of seawater through evaporative concentration and mineral precipitation the origin of these fluids is evaluated in the context of the sedimentary and diagenetic environments in which the halites evolved the petrography and fabric show that many of the halites escaped advanced recrystallization suggesting that the fluids entrapped in such samples are original brines the seawater derived brine pool and diagenetic brines from which the halites precipitated were modified as a result of fluctuations in water level on an evaporite flat and of a complex hydrological system through which seawate was fed into the basin and refluxed the ionic ratios between ca mg and so4 are influenced by dolomitization and associated reactions of interstitial brines with carbonates adjacent to the halite beds formation and subsequent dissolution of efflorescent evaporite crusts that are not in equilibrium with subaqueously precipitated evaporites shift the ratios of mg na k and cl to br away from the expected path of evaporative seawater concentration syndepositional alteration of clay and feldspar minerals probably also occurred but these effects cannot be evaluated from the present data the variability and complexity of brine evolution within an uncomplicated evaporite setting such as that of the palo duro basin has important implications for interpretation of the origin and history of evaporite influenced brines in other basins laboratory evaporation experiments and analyses of salt pan brines only serve as a basic reference for the evaporation path of seawater they ignore the early diagenetic processes and hence taken alone are inadequate analogs for ancient marine evaporite environments