investigation by multivariate analysis of groundwater composition in a multilayer aquifer system from north africa a multi tracer approach abstract a multi tracer approach has been carried out in the sbeitla multilayer aquifer system central tunisia to investigate the geochemical evolution the origin of groundwaters and their circulation patterns it involves statistical data analysis coupled with the definition of the hydrochemical and isotopic features of the different groundwaters principal components analysis pca of geochemical data used in conjunction with bivariate diagrams of major and trace elements indicate that groundwater mineralization is mainly controlled by water rock interaction and anthropogenic processes in relation to return flow of irrigation waters the pca of isotopic data and bivariate conventional diagrams of stable and radiogenic isotopes i e 18o vs 2h and 18o vs 14c provide valuable information about the origin and the circulation patterns of the different groundwater groups they permit classifying groundwaters into three groups the first group is characterized by low 3h concentrations low 14c activities and depleted stable isotope contents it corresponds to an old end member in relation with palaeoclimatic recharge which occurred during the late pleistocene and the early holocene humid periods the second group is distinguished by high to moderate 3h concentrations high 14c activities and enriched heavy isotope signatures it corresponds to a modern end member originating from a mixture of post nuclear and present day recharge in relation to return flow of irrigation waters the third group is characterized by an average composition of stable and radiogenic isotope signatures it provides evidence for the mixing between the upward moving palaeoclimatic end member and the downward moving present day end member

carbon dioxide generation from coals in taranaki basin new zealand implications for petroleum migration in southeast asian tertiary basins elevated co2 levels in gas accumulations within the onshore area of the taranaki basin can be quantitatively accounted for by decarboxylation of vitrinite rich tertiary coals over the lignite to early high volatile bituminous coal rank range the highest levels are found within sandstone reservoirs vertically adjacent to eocene coal seams that have realized approximately 50 of their co2 generative potential the gas exists as a supercritical fluid under reservoir conditions and appears to be generated in significant amounts comparable to liquid hydrocarbons co2 may aid oil expulsion from coals directly when intense co2 generation coincides with major oil generation or indirectly by creating pressure induced microfractures du ing the relatively rapid generation of large amounts of co2 prior to the main phase of oil generation for these effects to be realized the rate of co2 production relative to removal is considered critical and favorable conditions are probably restricted to basins that have experienced relatively rapid heating in this respect the taranaki basin provides a model for co2 evolution in many southeast asian tertiary basins

nonbiodegraded aromatic condensate associated with volcanic supercritical carbon dioxide otway basin implications for primary migration from terrestrial organic matter abstract liquid co 2 of magmatic origin is produced commercially from a petroleum exploration well caroline 1 in the otway basin south australia the well is located near a 4500 year old maar volcano production of this co 2 rich fluid 98 co 2 1 ch 4 0 5 n 2 from the late cretaceous waarre sandstone is accompanied by a small amount of heavy 15 api gravity low sulphur 0 2 aromatic condensate gasoline range hydrocarbons c 5 c 10 comprise less than 2 of this petroleum however there is no evidence of alteration by water washing or biodegradation whichmight otherwise explain its high specific gravity and unusual aromatic intermediate composition naphthalene and the methylnaphthalenes are the dominant individual components aspects of the condensate s biomarker geochemistry are consistent with its derivation from bacterially reworked terrestrial organic matter deposited in an oxic aquatic environment the methylphenanthrene index of the oil mpi 1 0 59 converts to a calculated vitrinite reflectance of 0 62 mature land plant derived crude oils and condensates usually have a primary paraffinic composition the highly aromatic character of the caroline 1 crude may reflect the involvement of co 2 in its origin in this case supercritical volcanic co 2 appears to have stripped aromatic and less abundant saturated hydrocarbons from marginally mature poor quality type iii iv kerogen in the reservoir rock this enigmatic condensate occurrence highlights the potentially important role played by co 2 in the mobilisation of liquid hydrocarbons from terrestrial organic matter in major petroleum provinces like the cooper basin central australia

geothermometry and circulation depth of groundwater in semnan thermal springs northern iran semnan thermal springs with high tds and moderate temperature are located northwest of semnan the northern part of iran the spatial and temporal variations of physicochemical characteristics of the thermal and cold springs were investigated for the recognition of origin and dominant hydrogeochemical processes results show that the thermal springs have the same origin but due to different ascending flow paths and different conductive cooling mechanism their temperatures vary the chemical composition of thermal waters is controlled by dolomite halite and sulfate minerals dissolution and calcite precipitation and bacterial sulfate reduction the concentration of major and trace elements in the thermal springs does not change in wet and dry seasons notably because they are derived from old groundwater with deep circulation and high temperature seasonal change in the concentration of some trace elements is due to the seasonal variation of ph eh temperature and dilution by shallow waters decreasing so4 and carbonate saturation index and increasing na cl ratios and ca content in the dry season show dilution effect caused by the previous heavy rainfall events the temperature of the heating reservoir based on k mg chalcedony quartz and chemical equilibrium approach was approximately estimated in the range of 60 80 c hydrogeologically a conceptual model was suggested for the thermal springs the general groundwater flow direction is probably from the dolomite lar formation in chenaran anticline toward the adjacent syncline in a confined condition and then a thrust fault acts as a conduit and redirects the thermal water to the emerging springs at the surface

geochemistry of hot springs in the tengchong hydrothermal areas southwestern china abstract as an important volcanic geothermal region in china tengchong belongs to the mediterranean himalayas geothermal belt and is characterized by wide distribution of volcanic rocks fifty eight hydrothermal areas have been identified in tengchong among which the rehai hydrothermal system is the most geothermally active the geothermal waters from rehai are mainly na hco 3 cl and na hco 3 types whereas those from the other hydrothermal areas are mainly na hco 3 na ca hco 3 ca hco 3 ca mg hco 3 mg na ca hco 3 and mg ca hco 3 types both quartz geothermometer and k mg geothermometer indicate that the rehai geothermal field has higher subsurface temperatures than the other hydrothermal areas except for three rehai samples most geothermal water samples collected from tengchong are far from the full equilibrium line in giggenbach s triangular diagram suggesting that the complete chemical re equilibrium has not been achieved as these geothermal waters flow upward from reservoirs towards spring vents and possibly mix with cooler waters statistical analysis shows that cl b li rb and cs are the characteristic constituents of the tengchong geothermal waters and the good linear relations among these elements in the rehai geothermal waters reflect the existence of a deep parent geothermal liquid pgl below rehai an enthalpy chloride diagram of the rehai geothermal waters suggests that the parent geothermal liquid has cl concentration of 291 mg l and enthalpy of 1495 j g the pgl ascends to the surface through different channels and may cool by conduction of heat to reservoir host rocks by boiling or by mixing with cooler shallow groundwaters

volatile organic acids produced during kerogen maturation amounts composition and role in migration of oil abstract maturation dependent generation of organic compounds from north sea source rocks has been investigated by hydrous pyrolysis of powdered source rock samples the generation of water soluble organic acids is emphasised and their composition compared with oil field water samples similar compositions are found matrix adsorption effects are not found to be quantitatively important timing of acid generation relative to oil generation is discussed effects of realistic concentrations of a volatile organic acid in the water phase on interfacial tension is determined and effects on fluid flow of crude oil through water saturated sandstone is investigated using a long core flow rig

hydrogeochemical characterization and conceptual modeling of the edremit geothermal field nw turkey abstract the edremit geothermal field with 42 62 c discharge temperatures is utilized for space heating alternation of permeable and impermeable units created two superimposed aquifers in the area an upper unconfined and a lower confined water samples from 21 hot cold wells were taken in this study 8 of these wells penetrate the deeper confined aquifer while 13 penetrate the shallower unconfined aquifer geochemical analyses revealed that na k so 4 40 c ca hco 3 4 30 40 c waters occur 18 o d compositions point to a meteoric origin for all waters while 14 c analyses suggest longer subsurface residence times for the hot waters compared to the cold warm waters chemical and isotopic compositions indicate that mixing and water rock interaction are the possible subsurface processes when silica and cation geothermometers are evaluated together with fluid mineral equilibria calculations a reservoir temperature range of 92 150 c is evaluated saturation indices do not indicate a serious potential of scaling in the field the hydrogeology of the study area is highly affected by faults infiltrated meteoric water percolates down to 4 5 km depth via deep seated step faults becomes heated and ascends to the surface at the low lands especially through intersection of buried mid graben faults during its ascent geothermal water invades the two superimposed aquifers where mixing between the hot and cold waters takes place

iron biogeochemistry in holocene palaeo and actual salt marshes in coastal areas of the pampean plain argentina in salt marshes the hydrodynamics and the availability of iron organic matter and sulphate influence the formation and or dissolution of iron sulfides and iron oxyhydroxides therefore they constitute key factors affecting the iron biogeochemical processes in these environments the aim of this work is to evaluate the physico chemical and mineralogical variations associated to iron biogeochemistry in palaeo and actual salt marshes in the area of influence of the mar chiquita coastal lagoon pampean plain argentina in soils of exhumed palaeo marshes the iron contents are 56 95 mol g 1 whereas these contents decrease to 36 75 mol g 1 in actual marsh soils the presence of framboidal and poliframboidal pyrites associated with gypsum barite calcite halite and iron oxyhydroxides defines the conditions of the pedosedimentary sequences of the holocene paleomarshes sequences of pyrite formation sulfidization and degradation sulfuricization were observed these processes were evidenced by a sequential extraction reflecting that the largest proportion of iron is in the form of crystalline iron oxides 28 76 and lepidocrocite 6 16 while the proportion associated with ferrihydrite and pyrite is low 0 9 and 1 17 respectively these facts could be partly explained by the complex redox processes characteristic of these environments such as aeration generated by the rhizosphere and intense bioturbation by invertebrates these iron biomineralizations have been useful because they allow paleoenvironmental interpretations and characterization of paleomarshes and environmental inferences related to the management of actual salt marshes

geochemical and isotope characterization of geothermal spring waters in sri lanka evidence for steeper than expected geothermal gradients summary seven geothermal springs from the precambrian high grade metamorphic terrain of sri lanka were investigated to assess their formation processes and to determine reservoir temperatures based on their chemical compositions silica based geothermometric calculations for the marangala and nelumwewa springs showed the highest average reservoir temperatures of 122 c and 121 c respectively samples of low temperature

diagenesis of clay minerals and k bentonites in late permian early triassic sediments of the sichuan basin chaotian section central china abstract detailed clay mineralogical analyses were carried out on late permian early triassic carbonate sediments exposed on the chaotian section sichuan basin central china the clay assemblages are dominantly composed of illite in platform carbonates and clay seams and illite smectite mixed layers i s in tuff layers k bentonites intercalated in the carbonate succession detrital and authigenic volcanogenic clay minerals have been partially replaced through illitisation processes during burial raising questions about diagenetic effects the precise determination of i s occurring in k bentonites shows that the sediments reached a temperature of about 180 c which is consistent with 1 previous estimates based on fluid inclusion homogenisation temperature analysis 2 the burial depth of the sedimentary series deduced from the post palaeozoic geological history of the sichuan basin and 3 the new data t max obtained on organic matter indicating the transition between oil and gas windows the wangpo bed located close to the guadalupian lopingian boundary is interpreted either as a volcanic acidic tuff or as a clastic horizon this controversial origin probably results from mixed volcanogenic and detrital influences the wangpo bed is therefore interpreted as a reworked bentonite as revealed by the occurrence of i s similar to those found in tuff layers together with preserved detrital kaolinite

factors which determine the hydrogeochemical behaviour of karstic springs a case study from the betic cordilleras spain the cabra alcaide karstic massif situated in the south of spain constitutes an important part of the so called natural park of the subbetic sierras this aquifer system is drained by various springs which supply a population of some 100 000 inhabitants the feed areas of these springs show very different characteristics with respect to their geological structure size of the drainage area thickness of the vadose zone elevation and degree of karstification in addition the carbonate rocks lie over a clayey substratum which contains large masses of intercalated evaporites due to these conditions the hydrochemical composition of the springs is relatively variable in this study a hydrogeochemical characterization of the aquifer in both space and time is undertaken and the factors that determine it are discussed to achieve this 19 monthly samples were taken from the 6 most significant springs of the hydrogeological system the commencement of sampling coincided with the transition from a period of several years of severe drought and a very wet two year period which amplified considerably the hydrochemical and hydrodynamic response of the springs to the recharge identification of hydrogeochemical processes was performed by studying hydrographs the temporal evolution of physico chemical parameters ionic ratios mainly mg ca and by means of simple and multivariate statistical analyses the saturation status was established using the wateqf program and the mass transfer was quantified using phreeqc with the exception of the epikarstic subsystem i e the zarza spring the majority of the results indicate that the aquifer exhibits a diffuse flow model in which piston flow phenomena are seen closely linked to the most intense precipitation along the direction of flow hydrochemical trends are seen as the water type changes from ca hco3 to ca mg hco3 at the same time enrichment in some ions derived from the dissolution of evaporitic minerals of the impermeable substratum and dedolomitization processes occur in this way almost 90 of the water samples were oversaturated in calcite the majority of cases being a consequence of the dissolution of the gypsum of the substratum only in the epikarstic springs can it be considered that the oversaturation in calcite is due to loss of co2 from the emerging groundwater it is concluded that hydrodynamic aspects together with hydrogeochemical characteristics need to be taken into account to correctly explain the hydrochemical evolution of the karstic springs moreover the use of both approaches permits a more accurate establishment of the degree of aquifer karstification which in turn needs to be known in order to assess its vulnerability to contamination and to protect recharge zones

speciation and weathering of selenium in upper cretaceous chalk and shale from south dakota and wyoming usa abstract in geologic materials petroleum and the environment selenium occurs in various oxidation states vi iv 0 ii mineralized forms and organo se complexes each of these forms is characterized by specific chemical and biochemical properties that control the element s solubility toxicity and environmental behavior the organic rich chalks and shales of the upper cretaceous niobrara formation and the pierre shale in south dakota and wyoming are bentoniferous stratigraphic intervals characterized by anomalously high concentrations of naturally occurring se numerous environmental problems have been associated with se derived from these geological units including the development of seleniferous soils and vegetation that are toxic to livestock and the contamination of drinking water supplies by se mobilized in groundwater this study describes a sequential extraction protocol followed by speciation treatments and quantitative analysis by hydride generation atomic absorption spectroscopy this protocol was utilized to investigate the geochemical forms and the oxidation states in which se occurs in these geologic units organic se and di selenide minerals are the predominant forms of se present in the chalks shales and bentonites but distinctive variations in these forms were observed between different sample types chalks contain significantly greater proportions of se in the form of di selenide minerals including se associated with pyrite than the shales where base soluble humic organo se complexes are more prevalent a comparison between unweathered samples collected from lithologic drill cores and weathered samples collected from outcrop suggest that the humic organic se compounds in shale are formed during oxidative weathering and that se oxidized by weathering is more likely to be retained by shale than by chalk selenium enrichment in bentonites is inferred to result from secondary processes including the adsorption of se mobilized by groundwater from surrounding organic rich sediments to clay mineral and iron hydroxide surfaces as well as microbial reduction of se within the bentonitic intervals distinct differences are inferred for the biogeochemical pathways that affected sedimentary se sequestration during periods of chalk accumulation compared to shale deposition in the cretaceous seaway mineralogy of sediment and the nature of the organic matter associated with each of these rock types have important implications for the environmental chemistry and release of se to the environment during weathering

multivariate statistical analysis of geochemical data as indicative of the hydrogeochemical evolution of groundwater in a sedimentary rock aquifer system summary the study of groundwater hydrogeochemistry of the paleozoic basses laurentides sedimentary rock aquifer system in quebec produced a large geochemical dataset groundwater samples were collected at 153 sites over a 1500 km2 study area and analyzed for major and minor ions the large number of data can lead to difficulties in the integration interpretation and representation of the results two multivariate statistical methods hierarchical cluster analysis hca and principal components analysis pca were applied to a subgroup of the dataset to evaluate their usefulness to classify the groundwater samples and to identify geochemical processes controlling groundwater geochemistry this subgroup consisted of 144 samples and 14 parameters ca2 mg2 na k hco 3 cl so 4 2 fe2 mn2 br sr2 f ba2 hs seven geochemically distinct clusters c1 c7 resulted from the hca samples from clusters c3 c4 c6 and c7 are mostly located in preferential recharge areas the majority of these samples have ca mg hco3 recharge groundwater c3 c6 c7 and na hco3 evolved groundwater c4 samples from the other three clusters c1 c2 c5 are characteristic of an aquifer system under confined conditions the majority of these samples have na hco3 evolved groundwater c1 c5 and na cl ancient groundwater that exhibits elevated concentrations in br c2 in addition to recognizing the importance of hydrogeological conditions on groundwater geochemistry the distribution of clusters also showed the importance of the geological formations on minor and trace elements such as fe2 mn2 sr2 f and ba2 the first five components of the pca account for 78 3 of the total variance in the dataset component 1 is defined by highly positive loadings in na cl and br and is related to groundwater mixing with champlain sea water and solute diffusion from the marine clay aquitard the high positive loadings in ca2 and mg2 of component 2 suggest the importance of dissolution of carbonate rocks in this aquifer system from their characteristic loadings the first two components are defined as the salinity and hardness components respectively components 3 5 are related to more local and geological effects the integration of the hca and the pca with conventional classification of groundwater types as well as with the hydrogeological and geological contexts allowed the division of the region into four main geochemical areas providing an improved regional picture of the aquifer system dynamics and hydrogeochemical evolution of groundwater the following factors were recognized as influencing the evolution of groundwater identified in every geochemical area 1 geological characteristics including sedimentary rock type and till mineralogy 2 hydrogeological characteristics represented by the level of confinement and the hydraulic gradient and 3 the geological history including the latest glaciation and the champlain sea invasion with its integrated approach this hydrogeochemical study contributes to the characterization and understanding of complex groundwater flow systems and provides an example of the long term geochemical evolution of hydrogeological systems after a major perturbation in this case seawater invasion

variation in pyrolysate composition of sediments from the jurassic walloon coal measures eastern australia as a function of thermal maturation examination of a natural maturity sequence from the jurassic walloon coal measures by quantitative flash pyrolysis gas chromatography py gc and low temperature sealed tube pyrolysis reveals systematic changes in pyrolysate composition in particular gas to oil ratios composition of gas and liquid normal hydrocarbons aromatic and heteroatom content are examined for this immature oil prone rock as it is taken artificially and naturally through the oil window liquid hydrocarbon generation giving a product with a high wax content is shown to occur over a relatively narrow range of maturation significant quantities of gas are generated and the gas to oil ratio remains relatively constant during the main phase of oil generation this reflects a uniform distribution of oil and gas precursors in the original labile kerogen at higher rank where increasing generation from the residual refractory kerogen occurs there is a progressive decrease in the yield of liquid hydrocarbons concomitant with an increase in the gas to oil ratio

fluid geochemistry and geothermometry applications of the kangding high temperature geothermal system in eastern himalayas abstract high temperature geothermal systems hold an enormous capacity for generating geothermal energy the kangding area is a typical high temperature geothermal field in the himalayan geothermal belt hydrogeochemical gas geochemical and isotopic investigations were performed to identify and qualify the main hydrogeochemical processes affecting thermal water composition including mixing and degassing and then to estimate a reliable reservoir temperature nine water samples and four geothermal gas samples were collected and analysed for chemical and isotopic components the results demonstrate the alkaline deep geothermal water is the mixtures of approximately 75 snow melt water and 25 magmatic water it is enriched in na k f li and other trace elements indicating the granite reservoir nature the shallow geothermal water is the mixtures of approximately 30 upward flow of deep geothermal water and 70 meteoric cold water high concentrations of ca mg and hco3 indicate the limestone reservoir nature there is no remarkable oxygen isotope shift in the geothermal water since the rapid circulation is difficult to trigger off strong water rock interaction co2 is the predominant geothermal gas accounting for more than 97 of total gases in volume percentage the concentration of co2 degassing ranged from 0 4 mol l 1 to 0 8 mol l 1 via geothermometrical modelling as a result the geothermal water ph increased from 6 0 to 9 0 and approximately 36 of the total sio2 re precipitate the sources of co2 are the metamorphism of limestone and magmatic degassing based on the composition of carbon isotope the appropriate geothermometers of na k and na li yield reservoir temperature of 280 c the geothermometrical modelling developed to eliminate the effects of co2 degassing yields temperature of 250 c the silica enthalpy mixing model yields temperature of 270 c with no steam separation before mixing

authigenic kaolinite and associated pyrite in chalk of the cretaceous niobrara formation eastern colorado abstract cores from the smoky hill chalk member of the cretaceous niobrara formation have several zones containing authigenic kaolinite as spherical moldic polycrystalline aggregates that occur within single or multichambered foraminiferal tests and are commonly associated with framboidal pyrite such kaolinite is inferred to result from volcanic ash deposited during chalk sedimentation shortly after burial a colloidal aluminous gel or solution formed from the unstable ash and moved into organic rich foraminiferal tests where sulfate reducing bacteria created a favorable microenvironment for the simultaneous crystallization of kaolinite and pyrite

characterization of groundwater quality in kinmen island using multivariate analysis and geochemical modelling kinmen is located in the south west of mainland china and mainly has two islands large kinmen and leiyu residents in kinmen have drunk groundwater over several decades this work characterized the quality of groundwater in kinmen using factor analysis fa cluster analysis ca and geochemical simulation the factor scores were plotted spatially to illustrate the groundwater quality and were used to discuss the grouped relationship using ca salinization redox and organic matter factors are identified from 17 hydrochemical measurements in 18 wells acidic and oxidizing groundwater with nitrate n pollution is distributed mainly in the west of large kinmen saline groundwater is distributed to the north east of large kinmen and in the south of leiyu groundwater with organic matter is present throughout leiyu five groups of the groundwater quality divided by ca can be interpreted according to one to three factors the grouped characteristics of the groundwater quality help the local government and industries to plan the use and protection of groundwater resources furthermore a geochemical simulation was used to demonstrate the formation processes of the acidic and oxidizing groundwater properties in granitic sediments a large amount of the precipitation of the kaolinite and magnetite releases concentrations of hydrogen ion and raises the redox potential in the aquifers copyright 2007 john wiley sons ltd

application of selected geothermometers to exploration of low enthalpy thermal water the sudetic geothermal region in poland the most important intakes of thermal waters within the sudetic geothermal region occur in three separate hydrogeothermal systems 1 l dek 2 duszniki and 3 cieplice all these waters are of meteoric origin and circulate in crystalline rocks to different depths their outflow temperatures are between less than 20 c and to about 87 c to evaluate the geothermal fields in the light of their prospectiveness to further exploration of thermal energy resources we took an effort to apply selected isotopic and chemical geothermometers to assess the maximum possible temperatures which may be found in the reservoirs the only chemical geothermometers which give a reliable range of reservoir temperatures are sio2 chalcedony na ka ca and partly na k ones the oxygen isotopic geothermometer in the so4 h2o system gives a real range of estimated reservoir temperatures only for deeply circulating waters in the cieplice area on the other hand in the case of co2 rich waters in the duszniki area where outflow temperatures do not exceed 30 c application of chemical or isotopic temperature indicators always leads to erroneous results due to the lack of equilibrium in the thermodynamic system of water rock interaction

two way cluster analysis of geochemical data to constrain spring source waters abstract the purpose of the study was to use geochemical characteristics and apparent ages of sampled groundwaters to determine which of the two regionally extensive bedrock aquifers the lower bedrock aquifer or the upper bedrock aquifer is a more likely source of water discharging to springs in the nine springs watershed the use of summary statistics and our knowledge of the regional hydrostratigraphy resulted in the identification of three groups of monitoring points that are representative of groundwaters with distinct geochemical characteristics two way cluster analysis of the geochemical data supports these groupings and further identifies subtle geochemical characteristics of the groups one spring which is representative of smaller springs and seeps found in the watershed belongs to a group that is characterized by variable nitrate and chloride concentrations water discharging from this spring has a groundwater residence time of approximately 8 years based on the tritium helium 3 dating method the water discharging to this small spring is thought to have traveled primarily through the unlithified aquifer as opposed to either of the major bedrock aquifers most of the springs in the watershed belong to a group that is characterized by elevated but consistent nitrate sodium and chloride concentrations in addition cluster analysis revealed that potassium and alkalinity concentrations are somewhat low apparent groundwater ages for this group range from 10 to 15 years the water discharging from the majority of the springs in the watershed is thought to have traveled primarily through the unlithified aquifer and the upper bedrock aquifer before discharging into the former glacial lakebed wetland complex due to the relatively short groundwater residence times spring water quality and flow in the nine springs watershed are likely to be vulnerable to the rapid urban expansion occurring within the watershed

geothermometry applications for the balikesir thermal waters turkey in this study reservoir temperatures of balikesir geothermal waters in northwestern turkey are estimated with various geochemical models the geothermal fluids in the region are represented by na so4 na hco3 and ca hco3 type waters with discharge temperatures up to 98 c it was determined that the solubility of silica in most of the waters is controlled by the chalcedony phase equilibrium states of the balikesir thermal waters studied by means of na k mg ca diagram mineral saturation calculations and activity diagrams in the system composed of na2o cao k2o al2o3 sio2 h2o phases approximate a reservoir temperature of about 120 c most of the waters are found to be equilibrated with calcite chalcedony quartz and muscovite at predicted temperature ranges similar to those calculated from the chemical geothermometers

origin of the cretaceous bridge creek cycles in the western interior united states abstract alternating beds of burrowed limestone and laminated organic carbon rich marlstone in the bridge creek member of the greenhorn formation were deposited during maximum transgression of the cenomanian turonian sea in the western interior of the united states one view of the origin of the bridge creek limestone marlstone rhythms holds that they represent dilution cycles produced by alternating climates within the western interior the marlstones recording wet episodes when high runoff produced a sediment laden brackish lid on the seaway and the limestones recording dry episodes when runoff was low and the water column well mixed a second view holds that the rhythms represent productivity cycles the limestones representing times of high productivity of calcareous planktonic skeletons and the marlstones representing times of low productivity in this view the rhythms were produced by alternations in vertical circulation that characterized much of the world ocean at the time the productivity origin of the rhythms is supported by the presence of abundant calcispheres in the limestone beds the concentration of clay size quartz in many of the limestone beds the comparatively high 18 o and low 13 c in limestone beds the similarity in proportion of clay minerals in marlstone and limestone beds the pelagic depositional rate of the bridge creek member and by the discovery that bridge creek deposition began with a marlstone and not a limestone bed the dilution model is not consistent with these features and it has not been supported by modeling of paleoclimates and lithofacies that were predicted from it nor by macrofaunal distributions within the seaway the dilution model is not consistent with the occurrence of diverse and abundant planktonic foraminifera in both marlstone and limestone beds which indicate that near normal marine salinities prevailed during deposition of both bed by bed analysis of the bridge creek member may provide an analog for events in the tethys that are poorly recorded in deposits from the deep sea itself

substrate control on formation and maturation of glauconites in the middle eocene harudi formation western kutch india formation and maturation of glauconites within the early middle eocene harudi formation built up in a lagoon to shelf transition in western kutch india is addressed taking recourse to a combined sedimentological micropalaeontological and mineralogical investigation the glauconite is authigenic and its occurrence coincides with maximum flooding the glauconite is more matured within the fecal pellets and is less matured within the intra particle pores of bioclasts namely foraminifera ostracoda gastropoda and bryozoa sem eds xrd and geochemical studies clearly document that the infilling within the intra particle pores of bioclasts belong to nascent to slightly evolved glauconite 5 wt k2o while the pellet belongs to slightly evolved to evolved glauconite 5 7 wt k2o based on chemical characteristics and sem investigations the glauconitization process can be best explained by the verdissement theory the glauconite possibly formed as initial authigenic glauconitic smectite precipitates while the pellet matured subsequently by addition of k the process was hindered in case of infillings the maturation process also involved addition of si and release of al with or without release of mg the glauconite maturation was facilitated in case of fecal pellets because of higher porosity inter granular nature of pores and availability of necessary elements in semi confined micro environments in contrast the maturation was aborted at an early stage in case of infillings because of the minute closed nature of the pores and prevalent alkaline conditions not allowing dissolution of calcitic tests a low negative cerium anomaly suggests glauconite formation in sub oxic micro environments created by decay of organic matters within the fecal pellets and bioclasts a clear case of substratum control on glauconitization becomes apparent

hydrochemistry and geothermometry of geothermal water in the central guanzhong basin china a case study in xi an the xi an geothermal field is a typical medium low temperature group of geothermal reservoirs in the guanzhong basin three distinct groundwater systems occur in this field the cold groundwater cg system quaternary cold water reservoir with a depth of less than 300 m the shallow geothermal water sgw system the quaternary zhangjiapo group and lantian bahe group thermal reservoirs with depths ranging between 300 and 2000 m the deep geothermal water dgw system the gaoling group bailuyuan group and proterozoic crystalline rock fissure thermal reservoirs with depths of more than 2000 m the chemical composition of the cg system consists of hco3 ca and hco3 ca mg water types with a low total dissolved solids tds content the chemical composition of the sgw system consists of so4 na and so4 hco3 na water types that have resulted from the partial mixing with water from the cg system through fault structures calculations suggest that about 39 4 42 7 of the water in the sgw system was derived from the cg system the chemical composition of the dgw system consists of so4 na and so4 cl na water types with elevated tds f sio2 and high ion concentrations due to the long residence time of water in this largely closed system the use of geothermometers multiple mineral equilibrium calculations and the silica enthalpy mixing model suggests that temperatures in the sgw and dgw systems lie in the range of 40 85 c and 94 7 135 c respectively the chalcedony geothermometer is considered to provide the most reliable temperature estimates of the shallow reservoir whereas the quartzb maximum steam loss 100 c and na k geothermometers are considered to provide the most reliable estimates for the deep thermal reservoir the results of a q cluster classification of the water agree well with the field classification of the sampled waters and the associations of the principal variables obtained by the r cluster method are consistent with the results obtained by the conventional hydrogeochemical assessment of the samples

compositional modeling of petroleum generation and expulsion trial application to a local mass balance in the smorbukk sor field haltenbanken area norway 1 we present an application of a compositional kinetic model of petroleum generation degradation into gas and residue and simultaneous expulsion petroleum composition is described by four carbon fractions c 1 c 2 c 5 c 6 c 14 c 15 and expulsion is related to a petroleum saturation threshold expulsion is important because rapid expulsion of petroleum from source rocks favors oil whereas late expulsion increases the cracking reactions and favors gas accumulation such a model is tested against field data for the first time by applying it to the smorbukk sor field previously named smorbukk greek beta located in the norwegian sea geometrical and one dimensional thermal reconstructions are performed followed by a computation of a mass balance of expelled and unexpelled products for each source rock throughout the drainage area comparison of the model results is made with rock eval data vitrinite reflectance and actual composition of accumulations lower jurassic coals were the main source expelling gas and oil mainly since 5 ma as the present accumulation accounts for less than 10 of total expelled petroleum major petroleum losses probably occurred through the structural spillpoint this migration scheme is supported by the simila composition of the reservoired petroleum and the petroleum expelled since 0 5 ma although various uncertainties are possible this study shows that our model has the capability to quantify expulsion consistently with the observed amounts of unexpelled petroleum in mature source rocks and with the reported composition of the accumulation