共查询到20条相似文献，搜索用时 906 毫秒
1.
Abundant natural gas inclusions were found in calcite veins filled in fractures of Central Fault Belt across the centre of Ordos Basin. Time of the calcite veins and characteristics of natural gas fluid inclusion were investigated by means of dating of thermolum luminescence (TL) and analyzing stable isotope of fluid inclusion. Results show that natural gas inclusion formed at 130–140°C with salinity of 5.5 wt%–6.0 wt% NaCl. It indicates that natural gas inclusion is a kind of thermal hydrocarbon fluid formed within the basin. Method of opening inclusion by heating was used to analyze composition of fluid inclusion online, of which the maximal hydrocarbon gas content of fluid inclusion contained in veins is 2.4219 m3/t rock and the maximal C1/ΣC i ratio is 91%. Laser Raman spectroscopy (LRS) was used to analyze chemistry of individual fluid inclusion in which the maximal hydrocarbon gas content is 91.6% compared with little inorganic composition. Isotope analysis results of calcite veins show that they were deposited in fresh water, in which the δ 13CPDB of calcite veins is from −5.75‰ to 15.23‰ and δ 18OSMOW of calcite veins is from 21.33‰ to 21.67‰. Isotope results show that δ 13C1 PDB of natural gas fluid inclusion is from −21.36‰ to −29.06‰ and δDSMOW of that is from −70.89‰ to −111.03‰. It indicates that the gas of fluid inclusion formed from coal source rocks and it is the same as that of natural gas of Mizhi gas reservoir. Results of TL dating show that time of calcite vein is (32.4±3.42)×104 a, which is thought to be formation time of gas inclusion. It indicated that natural gas inclusion contained in calcite veins recorded natural gas leakage from Mizhi gas reservoir through the Central Fault Belt due to Himalayan tectonic movement.
相似文献2.
Stable isotope data on humid tropical hydrology are scarce and, at present, no such data exist for Borneo. Delta18O, δ2H and δ13C were analysed on 22 water samples from different parts of the Sungai (river) Niah basin (rain, cave drip, rainforest pool, tributary stream, river, estuary, sea) in north‐central Sarawak, Malaysian Borneo. This was done to improve understanding of the modern stable isotope systematics of the Sungai Niah basin, essential for the palaeoenvironmental interpretation of the Late Quaternary stable isotope proxies preserved in the Great Cave of Niah. The Niah hydrology data are put into a regional context using the meteoric water line for Southeast Asia, as derived from International Atomic Energy Agency/World Meteorological Organization isotopes in precipitation network data. Although the Niah hydrological data‐set is relatively small, spatial isotopic variability was found for the different subenvironments of the Sungai Niah basin. A progressive enrichment occurs towards the South China Sea (δ18O ?4·6‰; δ2H ?29·3‰; δ13C ?4·8‰) from the tributary stream (δ18O ?8·4‰; δ2H ?54·7‰; δ13C ?14·5‰) to up‐river (δ18O c. ?8‰; δ2H c. ?51‰; δ13C c. ?12‰) and down‐river values (δ18O c. ?7·5‰; δ2H c. ?45‰; δ13C c. ?11‰). This is thought to reflect differential evaporation and mixing of different components of the water cycle and a combination of depleted biogenic δ13C (plant respiration and decay) with enriched δ13C values (due to photosynthesis, atmospheric exchange, mixing with limestone and marine waters) downstream. Cave drip waters are relatively enriched in δ13C as compared to the surface waters. This may indicate rapid degassing of the cave drips as they enter the cave atmosphere. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
3.
Hironobu Harada Tatsuki Tsujimori Keitaro Kunugiza Katsuyuki Yamashita Shogo Aoki Kazumasa Aoki Hideko Takayanagi Yasufumi Iryu 《Island Arc》2021,30(1):e12389
Marble has a great potential to understand a history of various geological events occurring during tectonic processes. In order to decode metamorphic–metasomatic records on C–O isotope compositions of marble at mid-crustal conditions, we conducted a C–O–Sr isotope study on upper amphibolite-facies marbles and a carbonate–silicate rock from the Hida Belt, which was once a part of the crustal basement of the East Asian continental margin. Carbon and oxygen isotope analyses of calcite from marbles (Kamioka area) and a carbonate–silicate rock (Wadagawa area) show a large variation of δ13C [VPDB] and δ18O [VSMOW] values (from −4.4 to +4.2 ‰ and +1.6 to +20.8 ‰, respectively). The low δ13C values of calcites from the carbonate–silicate rock (from −4.4 to −2.9 ‰) can be explained by decarbonation (CO2 releasing) reactions; carbon–oxygen isotope modeling suggests that a decrease of δ13C strongly depends on the amount of silicate reacting with carbonates. The occurrence of metamorphic clinopyroxene in marbles indicates that all samples have been affected by decarbonation reactions. All δ18O values of calcites are remarkably lower than the marine-carbonate values. The large δ18O variation can be explained by the isotope exchange via interactions between marble, external fluids, and/or silicates. Remarkably low δ18O values of marbles that are lower than mantle value (~+5 ‰) suggest the interaction with meteoric water at a later stage. Sr isotope ratios (87Sr/86Sr = 0.707255–0.708220) might be close to their protolith values. One zircon associated with wollastonite in a marble thin-section yields a U–Pb age of 222 ± 3 Ma, which represents the timing of the recrystallization of marble, triggered by H2O-rich fluid infiltration at a relatively high-temperature condition. Our isotope study implies that the upper amphibolite-facies condition, like the Hida Belt, might be appropriate to cause decarbonation reactions which can modify original isotope compositions of marble if carbonates react with silicates. 相似文献
4.
Abstract Isotopic analyses of organic carbon from the mid-Cretaceous sequence in Hokkaido, Japan, revealed a 2‰ positive excursion of δ13C values at the biostratigraphically defined Cenomanian/Turonian (C/T) boundary recognized in the Yezo Group. The planktonic foraminiferal Whiteinella archaeocretacea Zone, which is known to bracket the Cenomanian/Turonian boundary elsewhere in the world, was recognized in the Oyubari area of central Hokkaido based on the distribution of commonly occurring planktonic foraminifera. In the Tappu area of northwestern Hokkaido, where diagnostic planktonic foraminifera are rare but calcareous nannoplankton occur commonly, the interval coeval with the W. archaeocretacea Zone can also be established by recognizing the conjoined last appearance levels of Corollithion kennedyi and Axopodorhabdus albianus, both calcareous nannoplankton species. Carbon isotope profiles exhibit a similar pattern with comparable peaks and troughs occurring in the same stratigraphic position in the sequences. A prominent, positive 2‰ shift of δ13C values, here called ‘δ13C spike’ occurs in the middle of the W. archaeocretacea Zone in the Oyubari area and just above the conjoined last appearances of the two above-mentioned nannoplankton taxa in the Tappu area. The Cenomanian/Turonian boundary can be drawn just above the peak position of the spike in both sections. The Rock Eval analyses and biomarker analyses of organic carbon indicate that organic carbon subjected to our isotope analyses is of terrestrial origin. Therefore, the observed 2%o shift should reflect changes in the isotopic composition of the atmospheric CO2. A unique layer composed predominantly of sand-grain sized spumellarian Radiolaria is present immediately above the δ13C spike both in the Oyubari and Tappu areas, suggesting an increasing availability of both nutrients and silica in surface waters. 相似文献
5.
Multiple sulfur isotopes(32S, 33 S, 34 S, 36S) and oxygen isotopes(16O, 18O) in Beijing aerosols were measured with MAT-253 isotope mass spectrometer. The δ34S values of Beijing aerosol samples range from 1.68‰ to 12.57‰ with an average value of 5.86‰, indicating that the major sulfur source is from direct emission during coal combustion. The δ18O values vary from 5.29‰ to 9.02‰ with an average value of 5.17‰, revealing that the sulfate in Beijing aerosols is mainly composed of the secondary sulfate. The main heterogeneous oxidation of SO2 in atmosphere is related to H2O2 in July and August, whereas H2O2 oxidation and Fe3+ catalytic oxidation with SO2 exist simultaneously in September and October. Remarkable sulfur isotope mass-independent fractionation effect is found in Beijing aerosols, which is commonly attributed to the photochemical oxidation of SO2 in the stratosphere. In addition, thermochemical reactions of sulfur-bearing compounds might be also a source of sulfur isotope anomalies based on the correlation between ?33S and CAPE. 相似文献
6.
Periodic summer hypoxia occurring in the Northern Gulf of Mexico has been attributed to large nutrient inputs, especially nitrate‐nitrogen, from the Mississippi–Atchafalaya River system. The 2008 Gulf Hypoxia Action Plan calls for river corridor wetland restoration to reduce nitrate loads, but it is largely unknown how effective riverine wetland systems in the lower Mississippi River are for nitrate removal. We carried out an intensive isotope study to address this question by comparing nitrate isotopic signatures of the well‐channelized Mississippi River with those of the Atchafalaya River, which has extensive floodplains and backwater swamps. We investigated changes in δ15NNO3 and δ18ONO3 for water samples collected biweekly to monthly over a 2‐year period at the Atchafalaya River outlets (Morgan City and Wax Lake) and on the Mississippi River at Baton Rouge. In addition, in situ water quality parameters including temperature, dissolved oxygen and pH were recorded for each sampling date. Waters from both rivers showed moderately high nitrate concentration (>1 mg l?1) and undetectable (< 0.01 mg l?1) nitrite throughout the study period. The Mississippi River had slightly, but significantly higher (p=0.01) mean nitrate concentrations (1.5 mg l?1) and higher δ15NNO3 (7.7‰) than the Atchafalaya (1.1 mg l?1, 7.0‰); while no difference in δ18ONO3 (4.6‰) was found between the rivers. Flux‐weighted mean isotope values were overall lower than mean values for both the Mississippi and Atchafalaya Rivers, with a greater difference between the two rivers (7.4‰ versus 6.5‰, respectively). River flooding and hurricane storm surge also appeared to affect nitrate isotopic values. The lack of large difference in isotopic values between the Atchafalaya and Mississippi Rivers suggests that the majority of nitrate is transported through the Atchafalaya River with relatively little processing, and that riverine floodplains and wetlands are not effective sinks for nitrate, as previously assumed, because of insufficient residence time and well‐oxygenated river waters. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
7.
The pre‐Cenozoic history of the South China Sea (SCS) region is the object of continued debate. To trace the evolution of the SCS, a better understanding of the petrogenesis and tectonic affiliation of the granitic rocks that comprise the microblocks within the region is necessary. In this study, we analyzed the whole‐rock oxygen and lead isotope ratios of granitic samples dredged from two locations in the Nansha microblock, one of the microblocks in the SCS. Oxygen isotope data combined with previously published Sr isotope data show that group I rocks (δ18O = 6.00–7.20‰; average = 6.64‰) originated from a mantle source contaminated by material and/or fluid input from a Mesozoic subduction zone in the southeastern side of the microblock. Group II rocks (δ18O = 6.86‰–9.13‰; average = 7.75‰) also came from the same source, but they were additionally affected by crustal contamination. The Nansha microblock has high radiogenic lead ratios (206Pb/204Pbi = 18.602–18.756, 207Pb/204Pbi = 15.660–15.713, 208Pb/204Pbi = 38.693–38.893), which indicate that the Nansha microblock is tectonically affiliated with the Nanling–Hainan or South China block. This notion is consistent with the results of a previous Nd isotope study. As a whole, results of our study suggest that some of the other microblocks dispersed in the SCS are also possible fragments of South China block, and thus further studies are needed to better constrain the pre‐Cenozoic evolutionary history of the SCS region. 相似文献
8.
E. G. Kalacheva Yu. A. Taran T. A. Kotenko S. Inguaggiato E. V. Voloshina 《Journal of Volcanology and Seismology》2017,11(5):335-352
This paper reports a detailed geochemical study of thermal occurrences as observed in the edifice and on the flanks of Mendeleev Volcano, Kunashir Island in August and September 2015. We showed that three main types of thermal water are discharged there (neutral chloride sodium, acid chloride sulfate, and acid sulfate types); these waters exhibit a zonality that is typical of volcano-hydrothermal island arc systems. Spontaneous and solfataric gases have relatively low 3He/4He ratios, ranging between 5.4Ra and 5.6Ra, and δ13C-CO2 between –4.8‰ and –3.1‰, and contain a light isotope of carbon in methane (δ13C ≈ –40‰). Gas and isotope geothermometers yield relatively low temperatures around 200°C. The isotope compositions in all types of water are similar to that of local meteoric water. The distribution of microcomponents varies among different types. The isotope composition of dissolved Sr varies considerably, from 0.7034 as observed in Kunashir rocks on an average to 0.7052 in coastal springs, which may have resulted from admixtures of seawater. The total hydrothermal transport rates of magmatic Cl and SO4, as observed for Mendeleev Volcano, are 7.8 t/d and 11.6 t/d, respectively. The natural outward transport of heat by the volcano’s hydrothermal system is estimated as 21 MW. 相似文献
9.
Stefan Terzer-Wassmuth Leonard I. Wassenaar Jeffrey M. Welker Luis J. Araguás-Araguás 《水文研究》2021,35(6):e14254
Patterns of δ18O and δ2H in Earth's precipitation provide essential scientific data for use in hydrological, climatological, ecological and forensic research. Insufficient global spatial data coverage promulgated the use of gridded datasets employing geostatistical techniques (isoscapes) for spatiotemporally coherent isotope predictions. Cluster-based isoscape regionalization combines the advantages of local or regional prediction calibrations into a global framework. Here we present a revision of a Regionalized Cluster-Based Water Isotope Prediction model (RCWIP2) incorporating new isotope data having extensive spatial coverage and a wider array of predictor variables combined with high-resolution gridded climatic data. We introduced coupling of δ18O and δ2H (e.g., d-excess constrained) in the model predictions to prevent runaway isoscapes when each isotope is modelled separately and cross-checked observed versus modelled d-excess values. We improved model error quantification by adopting full uncertainty propagation in all calculations. RCWIP2 improved the RMSE over previous isoscape models by ca. 0.3 ‰ for δ18O and 2.5 ‰ for δ2H with an uncertainty <1.0 ‰ for δ18O and < 8 ‰ for δ2H for most regions of the world. The determination of the relative importance of each predictor variable in each ecoclimatic zone is a new approach to identify previously unrecognized climatic drivers on mean annual precipitation δ18O and δ2H. The improved RCWIP2 isoscape grids and maps (season, monthly, annual, regional) are available for download at https://isotopehydrologynetwork.iaea.org . 相似文献
10.
Abundant natural gas inclusions were found in calcite veins filled in fractures of Central Fault Belt across the centre of Ordos Basin. Time of the calcite veins and characteristics of natural gas fluid inclusion were investigated by means of dating of thermolum luminescence (TL) and analyzing stable isotope of fluid inclusion. Results show that natural gas inclusion formed at 130–140°C with salinity of 5.5 wt%–6.0 wt% NaCl. It indicates that natural gas inclusion is a kind of thermal hydrocarbon fluid formed within the basin. Method of opening inclusion by heating was used to analyze composition of fluid inclusion online, of which the maximal hydrocarbon gas content of fluid inclusion contained in veins is 2.4219 m3/t rock and the maximal C1/ΣC i ratio is 91%. Laser Raman spectroscopy (LRS) was used to analyze chemistry of individual fluid inclusion in which the maximal hydrocarbon gas content is 91.6% compared with little inorganic composition. Isotope analysis results of calcite veins show that they were deposited in fresh water, in which the δ 13CPDB of calcite veins is from ?5.75‰ to 15.23‰ and δ 18OSMOW of calcite veins is from 21.33‰ to 21.67‰. Isotope results show that δ 13C1 PDB of natural gas fluid inclusion is from ?21.36‰ to ?29.06‰ and δDSMOW of that is from ?70.89‰ to ?111.03‰. It indicates that the gas of fluid inclusion formed from coal source rocks and it is the same as that of natural gas of Mizhi gas reservoir. Results of TL dating show that time of calcite vein is (32.4±3.42)×104 a, which is thought to be formation time of gas inclusion. It indicated that natural gas inclusion contained in calcite veins recorded natural gas leakage from Mizhi gas reservoir through the Central Fault Belt due to Himalayan tectonic movement. 相似文献
11.
Calculated univariant equilibria and oxygen isotope compositions of silicates and carbonates support the proposal that the “Mottled Zone Event” is a low-pressure (1–25 atm), high-temperature (200° < T < 1300°C) metamorphism of calcareous siliceous sediments in which the thermal energy is provided by combustion of organic matter. δ18O of silicates decreases systematically with increasing metamorphic grade from averages of 18.1‰ in protolith shales, to 16.6‰ in grossular-diopside-zeolite rocks, 15.6‰ in wollastonite and anorthite-diopside-gehlenite-grossular fels, 14.1‰ in spurrite-brownmillerite marbles and 11.7‰ in the highest-grade larnite-gehlenite-brownmillerite assemblages. Decarbonation is the principal mechanism influencing the oxygen isotope compositions. The progressive decrease of δ18O in silicates can be modelled as a Rayleigh distillation of CO2 approximately 16‰ enriched in 18O relative to whole rock assemblages i.e., of initial isotopic composition 8.5‰ heavier than the parent carbonates. The mineral assemblage of one sample with an unusual granoblastic texture is in apparent isotopic equilibrium at a temperature of 540°C. 相似文献
12.
LIU SiBing HUANG SiJing SHEN ZhongMin Lü ZhengXiang SONG RongCai 《中国科学:地球科学(英文版)》2014,57(5):1077-1092
Carbonate cement is the most abundant cement type in the Fourth Member of the Xujiahe Formation in the Xiaoquan-Fenggu area of the West Sichuan Depression. Here we use a systematic analysis of carbonate cement petrology, mineralogy, carbon and oxygen isotope ratios and enclosure homogenization temperatures to study the precipitation mechanism, pore fluid evolution, and distribution of different types of carbonate cement in reservoir sand in the study area. Crystalline calcite has relatively heavy carbon and oxygen isotope ratios(δ13C = 2.14‰, δ18O = -5.77‰), and was precipitated early. It was precipitated directly from supersaturated alkaline fluid under normal temperature and pressure conditions. At the time of precipitation, the fluid oxygen isotope ratio was very light, mainly showing the characteristics of a mixed meteoric water-seawater fluid(δ18O = -3‰), which shows that the fluid during precipitation was influenced by both meteoric water and seawater. The calcite cement that fills in the secondary pores has relatively lighter carbon and oxygen isotope ratios(δ13C = -2.36‰, δ18O = -15.68‰). This cement was precipitated late, mainly during the Middle and Late Jurassic. An important material source for this carbonate cement was the feldspar corrosion process that involved organic matter. The Ca2+, Fe3+ and Mg2+ ions released by the clay mineral transformation process were also important source materials. Because of water-rock interactions during the burial process, the oxygen isotope ratio of the fluid significantly increased during precipitation, by about 3‰. The dolomite cements in calcarenaceous sandstone that was precipitated during the Middle Jurassic have heavier carbon and oxygen isotope ratios, which are similar to those of carbonate debris in the sandstone(δ13C = 1.93‰, δ18O = -6.11‰), demonstrating that the two are from the same source that had a heavier oxygen isotope ratio(δ18O of about 2.2‰). The differences in fluid oxygen isotope ratios during cement precipitation reflect the influences of different water-rock interaction systems or different water-rock interaction strengths. This is the main reason why the sandstone containing many rigid particles(lithic quartz sandstone) has a relatively negative carbon isotope ratio and why the precipitation fluid in calcarenaceous sandstone has a relatively heavier oxygen isotope ratio. 相似文献
13.
Spatial and temporal variations of pCO2, dissolved inorganic carbon and stable isotopes along a temperate karstic watercourse 
下载免费PDF全文
下载免费PDF全文 Robert van Geldern Peter Schulte Michael Mader Alfons Baier Johannes A. C. Barth 《水文研究》2015,29(15):3423-3440
This study investigated CO2 degassing and related carbon isotope fractionation effects in the Wiesent River that drains a catchment in the karst terrain of the Franconian Alb, Southern Germany. The river was investigated by physico‐chemical and stable isotope analyses of water and dissolved inorganic carbon during all seasons along 65‐km long downstream transects between source and mouth. Calculated pCO2 values at the source were 21 400 ± 2400 µatm. The pCO2 rapidly decreased in the river water and dropped to an average of 1240 ± 330 µatm near the mouth. About 90% of this decrease occurred within the first 6 km of the river. The river was supersaturated with respect to CO2 over its entire course and must have acted as a continuous year‐round CO2 source to the atmosphere. The average CO2 flux from the karst river was estimated with 450 mmol m?2 day?1 with higher fluxes up to 5680 mmol m?2 day?1 at the source. At the source, δ13CDIC values showed no seasonal variations with an average of ?14.2 ± 0.2‰. This indicated that groundwater retained high pCO2 mainly from soil CO2. The contribution of soil CO2 to dissolved inorganic carbon was estimated at 65% to 72%. The downstream CO2 loss caused a positive shift in δ13CDIC values of 2‰ between source and mouth because of the preferential loss of the 12C isotope during degassing. Considering the findings of this study and the fact that carbonate lithology covers a significant part of the earth's surface, CO2 evasion from karst regions might contribute notably to the annual carbon dioxide release from global freshwater systems. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
14.
Svetlana S. Kostrova Hanno Meyer Francisco Fernandoy Martin Werner Pavel E. Tarasov 《水文研究》2020,34(1):51-67
The paper presents oxygen and hydrogen isotopes of 284 precipitation event samples systematically collected in Irkutsk, in the Baikal region (southeast Siberia), between June 2011 and April 2017. This is the first high-resolution dataset of stable isotopes of precipitation from this poorly studied region of continental Asia, which has a high potential for isotope-based palaeoclimate research. The dataset revealed distinct seasonal variations: relatively high δ18O (up to −4‰) and δD (up to −40‰) values characterize summer air masses, and lighter isotope composition (−41‰ for δ18O and −322‰ for δD) is characteristic of winter precipitation. Our results show that air temperature mainly affects the isotope composition of precipitation, and no significant correlations were obtained for precipitation amount and relative humidity. A new temperature dependence was established for weighted mean monthly precipitation: +0.50‰/°C (r2 = 0.83; p <.01; n = 55) for δ18O and +3.8‰/°C (r2 = 0.83, p < 0.01; n = 55) for δD. Secondary fractionation processes (e.g., contribution of recycled moisture) were identified mainly in summer from low d excess. Backward trajectories assessed with the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model indicate that precipitation with the lowest mean δ18O and δD values reaches Irkutsk in winter related to moisture transport from the Arctic. Precipitation originating from the west/southwest with the heaviest mean isotope composition reaches Irkutsk in summer, thus representing moisture transport across Eurasia. Generally, moisture transport from the west, that is, the Atlantic Ocean predominates throughout the year. A comparison of our new isotope dataset with simulation results using the European Centre/Hamburg version 5 (ECHAM5)-wiso climate model reveals a good agreement of variations in δ18O (r2 = 0.87; p <.01; n = 55) and air temperature (r2 = 0.99; p <.01; n = 71). However, the ECHAM5-wiso model fails to capture observed variations in d excess (r2 = 0.14; p < 0.01; n = 55). This disagreement can be partly explained by a model deficit of capturing regional hydrological processes associated with secondary moisture supply in summer. 相似文献
15.
The direct H2Oliquid–H2Ovapour equilibration method utilizing laser spectroscopy (DVE-LS) is a way to measure soil pore water stable isotopes. Various equilibration times and calibration methods have been used in DVE-LS. Yet little is known about their effects on the accuracy of the obtained isotope values. The objective of this study was to evaluate how equilibration time and calibration methods affect the accuracy of DVE-LS. We did both spiking and field soil experiments. For the spiking experiment, we applied DVE-LS to four soils of different textures, each of which was subjected to five water contents and six equilibration times. For the field soil experiment, we applied three calibration methods for DVE-LS to two field soil profiles, and the results were compared with cryogenic vacuum distillation (CVD)-LS. Results showed that DVE-LS demonstrated higher δ2H and δ18O as equilibration time increased, but 12 to 24 hr could be used as optimal equilibration time. For field soil samples, DVE-LS with liquid waters as standards led to significantly higher δ2H and δ18O than CVD-LS, with root mean square error (RMSE) of 8.06‰ for δ2H and 0.98‰ for δ18O. Calibration with soil texture reduced RMSE to 3.53‰ and 0.72‰ for δ2H and δ18O, respectively. Further, calibration with both soil texture and water content decreased RMSE to 3.10‰ for δ2H and 0.73‰ for δ18O. Our findings conclude that the calibration method applied may affect the measured soil water isotope values from DVE-LS. 相似文献
16.
Compound‐Specific Isotope Analyses to Assess TCE Biodegradation in a Fractured Dolomitic Aquifer 下载免费PDF全文
下载免费PDF全文 The potential for trichloroethene (TCE) biodegradation in a fractured dolomite aquifer at a former chemical disposal site in Smithville, Ontario, Canada, is assessed using chemical analysis and TCE and cis‐DCE compound‐specific isotope analysis of carbon and chlorine collected over a 16‐month period. Groundwater redox conditions change from suboxic to much more reducing environments within and around the plume, indicating that oxidation of organic contaminants and degradation products is occurring at the study site. TCE and cis‐DCE were observed in 13 of 14 wells sampled. VC, ethene, and/or ethane were also observed in ten wells, indicating that partial/full dechlorination has occurred. Chlorine isotopic values (δ37Cl) range between 1.39 to 4.69‰ SMOC for TCE, and 3.57 to 13.86‰ SMOC for cis‐DCE. Carbon isotopic values range between ?28.9 and ?20.7‰ VPDB for TCE, and ?26.5 and ?11.8‰ VPDB for cis‐DCE. In most wells, isotopic values remained steady over the 15‐month study. Isotopic enrichment from TCE to cis‐DCE varied between 0 and 13‰ for carbon and 1 and 4‰ for chlorine. Calculated chlorine‐carbon isotopic enrichment ratios (?Cl/?C) were 0.18 for TCE and 0.69 for cis‐DCE. Combined, isotopic and chemical data indicate very little dechlorination is occurring near the source zone, but suggest bacterially mediated degradation is occurring closer to the edges of the plume. 相似文献
17.
18.
Flooding associated with tropical storms can cause extreme perturbations in riverine and coastal ecosystems. Measuring isotope variability of tropical storm events can help investigate the impacts of flooding. We measured the water isotope composition (δD and δ18O) of rain and associated floodwater collected during two storms and subsequent major and minor flooding events in the subtropical coast of eastern Australia. Compared with baseline regional rainfall isotope values of ?15.0 ± 1.9‰ for δD and ?3.3 ± 0.2‰ for δ18O, floodwater had lower values with ?33.8 ± 2.5‰ δD and ?5.1 ± 0.4‰ δ18O for the major flood and ?29.4 ± 1.0‰ δD and ?4.6 ± 0.1‰ δ18O for the minor flood. The low isotope composition of the floodwater was associated with the transport of large quantities of suspended sediments, with sediment loads 30 to 70 times larger than during base flow conditions. Floods carried up to 35% of the annual phosphorus and up to 208% of the currently calculated average annual nitrogen load of the Brisbane River. The dramatic changes caused by a rapid increase in discharge from 2 to 2015 m3 s?1 over 2 days in the major flood would have major consequences in riverine and coastal ecosystems of the region. These changes could potentially be traced using the isotope composition of the floodwaters. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
19.
《Earth and Planetary Science Letters》2007,253(1-2):96-111
The Ca isotope compositions of 37 late Mesozoic skeletal carbonates, belemnites and brachiopods, from the Tethyan realm were analyzed by thermal (TIMS) and plasma (MC-ICP-MS) ionization mass spectrometry. A poor correlation between δ44/40Ca and δ18O values of belemnites suggests only a weak temperature dependency for the Ca isotope composition of belemnites, likely less than 0.02‰/°C. The δ44/40Ca record of belemnites was therefore used to reconstruct the Ca isotope composition of paleo-seawater (δ44/40CaSW), based on an experimentally determined fractionation factor between seawater Ca and belemnite calcite (αCC–SW) of ∼ 0.9986. The inferred δ44/40CaSW record, with an average stratigraphic resolution of 1 Ma, shows systematic temporal variation of ∼ 0.5‰ with the Middle/Late Jurassic (∼ 154 Ma) minimum of ∼ 1.4‰ and a subsequent general increase to the Early Cretaceous (∼ 124 Ma) maximum of ∼ 1.9‰. The global nature of the δ44/40CaSW record is supported by identical Ca isotope compositions of coeval (Kimmeridgian) belemnites collected from two distinct paleogeographic regions, the southern (New Zealand) and northern (Germany) margin of the Tethys Ocean. The observed late Mesozoic δ44/40CaSW record was simulated using a simple Ca isotope mass balance model, and the results indicate that the variation in δ44/40CaSW record can be explained by changes in oceanic input fluxes of Ca that were independent of the carbonate ion fluxes, such as the hydrothermal Ca flux or the release of Ca to the oceans via dolomitization of marine carbonates. 相似文献
20.
The Tieluping silver deposit, located in the NE-trending faults within the metamorphic basement of the Xiong'er Mountain, is a typical altered fracture type deposit. Its ore-forming process includes three stages with temperatures concentrated at 373°C, 223°C and 165°C respectively. With δD=90‰,\(\delta ^{13} C_{CO_2 } \)=2.0‰ and δ{si18}O=8094‰, the early stage fluid was generated from reworking and metamorphism of the carbonate rich formation; the late one, with δD=−70‰,\(\delta ^{13} C_{CO_2 } \)=-1.2‰, δ18O=1.89‰, was meteoric hydrothermal solution; and the middle. δD=−109‰,\(\delta ^{13} C_{CO_2 } \)=0.1‰, δ18O=1.79‰, might be a hybrid mixed by reworking-metamorphic fluid and meteoric hydrothermal solution. Crystallized rapidly in the condition of fluid-boiling and fluid-mixing, the middle stage minerals have far more fluid inclusions with higher content of ions, higher ratios of H2O/CO2 and KN/MC. Consequently, they have much more ore elements such as gold compared with those of the early and late stages. It was the northward intracontinental subduction along the Machaoying fault during the Mesozoic collision between the South China and North China paleocontinents that intrigued large-scale fluidization and magmatism and led to the appearance of more than 10 large and medium hydrothermal deposits, including the Tieluping silver deposit. The study on ore-forming fluidization of the Tieluping silver deposit proves the CPMF model.
相似文献