Dissertations / Theses on the topic 'Gas geochemistry'
To see the other types of publications on this topic, follow the link: Gas geochemistry.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Gas geochemistry.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Pasilis, Sofie Portia. "Effect of citric acid on uranyl(VI) solution speciation, gas-phase chemistry and surface interactions with alumina." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280730.
Full textAbstract:
Activities related to nuclear weapons production have left a legacy of uranium contamination in the United States. Understanding the chemical interactions that uranium undergoes in the environment is important for prediction of uranium mobility and development of remediation strategies. A detailed spectroscopic examination of the pH-dependent behavior of the UO₂²⁺-citrate system in aqueous solution was completed using Raman, ATR-FTIR, and NMR spectroscopies, combined with ESI-MS. Three structurally-distinct UO₂²⁺-citrate complexes, {(UO₂)₂Cit2}²⁻, {(UO₂)₃Cit₃}³⁻, and (UO₂)₃Cit₂ exist in dynamic equilibrium over a pH range from 2 to 9. ¹⁷O and ¹³C NMR data confirm the previously published structure of {(UO₂)₂Cit₂}²⁻ and indicate that {(UO₂)₃Cit₃}³⁻ is a symmetric, fluxional molecule. The (UO₂)₃Cit₂ complex was found to have a rigid structure and two structural isomers. Chemical interactions of U(VI), citric acid and Al₂O₃ were investigated using ATR-FTIR spectroscopy to examine how complexation of U(VI) by citrate affects adsorption of U(VI) to Al₂O₃. Participation in UO₂²⁺-citrate complexes does not significantly affect the ability of citrate to chemisorb to Al₂O₃. The UO₂²⁺-citrate complexes dissociate upon adsorption, with hydrolysis of UO₂²⁺. Adsorption isotherms developed from ATR-FTIR data indicate enhanced citrate adsorption to Al₂O₃ in the presence of UO₂²⁺ , suggesting that UO₂²⁺ acts as a central link between two citrate ligands, one of which is complexed to Al₂O₃. UO₂²⁺-citrate complexes can physisorb to citrate-saturated Al₂O₃. This study demonstrates how an in-depth infrared spectroscopic analysis of UO₂²⁺-ligand complexes both in solution and adsorbed to oxide surfaces can be used to understand the adsorption mechanisms of these complexes. ESI-MS was investigated for the characterization of U(VI) species in groundwater. Both ion trap and FTICR instruments were used. UO₂²⁺ forms complexes with ligands such as acetate, trifluoroacetate, and nitrate, which readily react with CH₃CN, CH₃OH, and H₂O to form solvated gas-phase species of the form [(UO₂L)Sn]⁺, where L represents the ligand, S represents solvent, and 1 ≤ n ≤ 4. n is directly related to the number of available coordination sites on UO₂²⁺, providing insight into the coordination environment of UO₂²⁺. Solvent exchange and addition reactions readily occur. UO₂²⁺ also forms coordinately saturated negatively-charged complexes with nitrate. UO₂²⁺-carbonate complexes were also investigated.
2
Phillips, William Morton. "Applications of noble gas cosmogenic nuclides to geomorphology." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282369.
Full textAbstract:
The buildup of the cosmogenic nuclides ³He and ²¹Ne in surficial rocks permit exposure ages and erosion rates to be estimated. This dissertation extends the cosmogenic exposure technique to garnets, plagioclase with significant nonspallation ²¹Ne components, and alluvial fill terraces. Garnets from Nanga Parbat, Pakistan have low nucleogenic ³He and moderate radiogenic ⁴He concentrations. ³He exposure ages from garnets in glacial erratics indicate glacial advances at Nanga Parbat at about 16 ka and 55 ka. 3He in alluvial garnets suggests that denudation in small unglaciated basins proceeds 5 to 7 times slower than glacial erosion, and 10 to nearly 100 times slower than regional rock exhumation and surface uplift. Rocks older than several million years possess nucleogenic and mugenic ²¹Ne and ³He components that must be resolved for accurate exposure ages. These nonspallation components in plagioclase and clinopyroxene from the Miocene Columbia River Basalt Group are best isolated with shielded samples. Analyses of ⁴He, U, Th, and Li systematically underpredict the amount of nonspallation ²¹Ne and ³He present in shielded samples, probably because of mugenic production. Step heating experiments suggest that ²¹Ne diffusive loss from plagioclase is possible, but most samples do not exhibit such ²¹Ne loss. The ratio of ²¹Ne in plagioclase and ³He in clinopyroxene is generally constant after correction for the nonspallation component, indicating that little or no ²¹Ne loss has occurred. The last highly erosive floods at Grand Coulee occurred at about 21 ka, early in the cycle of Missoula flooding. Nuclide inheritance must be resolved for accurate exposure ages of stream fill terraces. Depth profiles of cosmogenic ²¹Ne in quartz from terraces on the Pajarito Plateau, northern New Mexico resolve nuclide inheritance. Three patterns of depth profiles are recognized: (1) downward decreasing; (2) downward increasing; and (3) uniform; types 2 and 3 are associated with cumulate deposits and bioturbation, respectively. Inheritance corrected exposure ages for the terraces agree with independent radiocarbon and soil development ages. Denudation rates estimated from the profiles are higher for fill terraces than for straths.
3
Stra̜poć, Dariusz. "Coalbed gas origin and distribution in the southeastern Illinois Basin." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3292447.
Full textAbstract:
Thesis (Ph.D.)--Indiana University, Dept. of Geological Sciences, 2007.Title from dissertation home page (viewed May 29, 2008). Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7193. Advisers: Arndt Scimmelmann; Maria Mastalerz.
4
Hood, Eda Maria. "Characterization of air-sea gas exchange processes and dissolved gas/ice interactions using noble gasses." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/9815.
Full textAbstract:
Thesis (Ph. D.)--Joint Program in Marine Chemistry and Geochemistry, Massachusetts Institute of Technology/Woods Hole Oceanographic Institution, 1998.Includes bibliographical references (p. 251-266).
by Eda Maria Hood.
Ph.D.
5
Moore, Myles Thomas. "An Integrative Geochemical Technique to Determine the Source and Timing of Natural Gas Formation in Gas Hydrates." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1577959057433697.
Full text
6
Hilton, D. R. "A study of hydrothermal systems using rare gas isotopes." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377843.
Full text
7
Mulshaw, Sean Cartwright. "An evaluation of hydrocarbon gas geochemistry as a primary mineral exploration technique." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47582.
Full text
8
Jackson, Richard E. "Geochemistry of coalbed natural gas produced waters in the Powder River Basin, Wyoming." Laramie, Wyo. : University of Wyoming, 2009. http://proquest.umi.com/pqdweb?did=1799840421&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
Full text
9
Moore, Myles Thomas. "Noble Gas and Hydrocarbon Geochemistry of Coalbed Methane Fields from the Illinois Basin." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462561493.
Full text
10
Solano-Acosta, Wilfrido. "Controls on coalbed methane potential and gas sorption characteristics of high-volatile bituminous coals in Indiana." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3277989.
Full textAbstract:
Thesis (Ph.D.)--Indiana University, Dept. of Geological Sciences, 2007.Source: Dissertation Abstracts International, Volume: 68-09, Section: B, page: 5814. Advisers: Arndt Schimmelmann; Maria Mastalerz. Title from dissertation home page (viewed May 9, 2008).
11
Long, David E. "Source rock geochemistry of the southern Tyee Basin, southwest Oregon." PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/4040.
Full textAbstract:
This study examined source rock geochemistry of the southern Tyee Basin. Total organic carbon, rock-eval pyrolysis, vitrinite reflectance, thermal alteration index and visual assessments were performed on splits from cutting samples from five wells and on outcrop samples from four measured sections. Organic matter was found to be dispersed, averaging about 0.5 weight percent. The organic matter is primarily terrestrial in origin, or type I l l , with low potential for gas production and no oil potential. Three coal samples are clearly the richest sources of organic matter examined in this study.
12
Peto, Maria Kocsisne. "Application of noble gas isotopic systems to identify mantle heterogeneities." Thesis, Harvard University, 2014. http://nrs.harvard.edu/urn-3:HUL.InstRepos:13070050.
Full textAbstract:
This study addresses the origin of the combined He-Ne-Ar-Xe noble gas isotopic variation in mantle derived oceanic basalts. High precision heavy noble gas compositions of basalts from the Rochambeau Rift along the Northwestern Lau Basin, the Gakkel Ridge, the Southeast Indian Ridge and the South Atlantic Ridge presented here confirms fundamental differences between the volatile constituents of the depleted mid-ocean ridge basalt (MORB) source and plume sources. We find that the depleted MORB mantle is characterized by systematically lower proportions of Pu-fission derived Xe than the Iceland plume and the Samoan-like plume sampled at the Rochambeau Rift. These two plume sources are associated with low radiogenic \(^{129}Xe/^{130}Xe\) ratios that are not attributable to recycled atmosphere and must sample ancient (4.45 Ga) volatile rich mantle reservoir that experienced a lower degree of mantle processing than the depleted MORB source. I report \(^{128}Xe/^{130}Xe\) ratios in excess with respect to the atmosphere in deeply erupting Gakkel lavas, similar to mantle derived volatiles in natural gas samples. Deconvolution of fission derived xenon isotopes indicate that natural gas samples and the Gakkel MORBs are derived from the same volatile depleted mantle reservoir. The radiogenic He isotopic composition, the low estimated ratio of Pu to U derived xenon isotopes, and the low \(^{129}Xe/^{130}Xe_E\) ratio found in the source of the West Volcanic Zone (WVZ) along the Gakkel Ridge indicates the presence of increased amounts of recycled atmospheric volatiles. I suggest that the low \(^{129}Xe/^{130}Xe\) ratio beneath the WVZ cannot be explained by sampling an ancient (>4.45 Ga) lithospheric mantle component that evolved in isolation from convection throughout Earth's history. Instead, the Xe isotopic composition may be consistent with the presence of subduction derived metasomatizing fluids with atmospheric heavy noble gases trapped in the sub-continental lithospheric mantle sampled along the ridge. Available Ne isotope MORB data and new high precision Ne data presented in this study (including basalts from the East Pacific Rise, the Galapagos Spreading Center, and the Juan de Fuca Ridge) allows me to construct a combined He-Ne isotope distribution and infer first order source mixing systematics in the upper mantle.Earth and Planetary Sciences
13
Wilson, Brien. "Controls on biogenic methane formation in Cherokee basin coalbeds, Kansas." Thesis, Kansas State University, 2015. http://hdl.handle.net/2097/19032.
Full textAbstract:
Master of ScienceGeology
Matthew Kirk
The Cherokee basin in southeastern Kansas is a declining coalbed methane (CBM) field where little is known about how the CBM formed, the extent to which it continues to form, and what factors influence its formation. An understanding of methanogenic processes and geochemistry could lead to potential enhancement of methane formation in the basin. The objectives of this project are to (1) determine the pathway of methane formation and (2) determine whether geochemistry has influenced gas formation. In order to reach the objectives, we analyzed formation water geochemistry, production history, and gas composition and isotopes. Post Rock Energy Corporation gave us access to 16 wells for sampling purposes. We collected gas samples in Isotubes® for compositional and isotopic analyses at a commercial laboratory. We analyzed major ion chemistry from formation water using standard methods. Co-produced water samples we collected are Na-Cl type with total dissolved solids content ranging from 35,367 to 91,565 mg/L. TDS tended to be highest in samples collected from wells with greater total depth. The pH and temperature of sampled water averaged 7.0 and 19°C with an alkalinity ranging from 3.33 to 8.59. Gas dryness and δ¹³C CH[subscript 4] range from 196 to 4531 and -69.95 to -56.5, respectively, which indicate that methane is being produced biologically. Comparing the δ¹³C CH[subscript 4] to the δD CH[subscript 4], which ranges from -228.2 to -217.2, suggest that the primary pathway of methanogenesis is H[subscript 2]/CO[subscript 2] reduction. We calculated Δ (the difference between δ values) in order to correlate isotope data to produced water chemistry. Samples ΔD and Δ¹³C values range from -189.1 to -168.7 and 61.52 to 69.99. Calculated ΔD[subscript CH4-H2O] and Δ¹³C[subscript CO2-CH4] values approach the range for the acetate/methyl pathways as Clˉ concentration increases, potentially indicating a slight shift in methanogenic pathway in deeper, more saline portions of the basin. The culturing results revealed that living methanogens are still able to utilize H[subscript 2], acetate, and methanol present in co-produced formation water from all tested wells.
14
Saquet, Michelle. "Greenhouse gas flux and budget from an experimentally flooded wetland using stable isotopes and geochemistry." Thesis, University of Waterloo, 2003. http://hdl.handle.net/10012/1249.
Full textAbstract:
A boreal forest wetland (L979) was flooded in 1993 at the Experimental Lakes Area, Ontario to imitate a hydroelectric reservoir and to study the effects of flooding on greenhouse gas production and emission. Flooding initially caused CO₂ and CH4 emission rates to increase and changed the wetland from a small, natural carbon sink to a large source of carbon. The increased production of greenhouse gases in the peatland also caused the majority of the peat to float to the surface creating floating peat islands, within 4 years of flooding. The floating peat islands are a larger source than the central pond of CH4 to the atmosphere due to the high water table and small oxidation zone as compared to the earlier undisturbed peatland. The floating peat islands had an average flux of 202 ± 66 mg C-CH4/m²/day comparable to rates measured in 1995. Methane flux rates are spatially and temporally variable ranging from ?117 to 3430 mg C-CH4/m²/day. The variability is partly due to episodic releases of gas bubbles and changes in overlying pressure from the water table. The development of floating peat islands created an underlying water pocket. The water pocket increased water movement between the central pond and the peatland and led to increased peat temperatures and methane oxidation, and removal of debris from the water pocket. DIC, CH4, and O₂ concentrations, and δ13C-DIC, δ13-CH4, and δ18O-O₂ values in the water pocket were similar to values in the central pond. Before flooding, the δ13C-CH4 values from the peatland ranged between ?36 and ?72? indicating that about 65 to 90% of the methane was oxidized before flooding. After flooding, the median δ13C-CH4 value from the floating peat islands was ?52? indicating that about 30% of the methane was oxidized before it was emitted to the atmosphere. Since the floating islands are now vegetated, photosynthesis and transport via plants allow the movement of oxygen into the peat islands Methane oxidation in the central pond was similar in 2001 and 2002. DIC and CH4 isotope mass budgets from June 3 to September 23, 2002 indicate that inputs were smaller than outputs at L979. Calculated net DIC and CH4 production in the central pond was 8490 and 432 kg C, with δ13C-DIC of -18. 5 ? and δ13C-CH4 of -32. 5?. Decomposition of peat was the source of DIC and CH4. O₂ saturation levels indicate that the pond is always undersaturated and that respiration dominates the system; however, the δ18O-O₂ also indicates that photosynthesis is an important process in the central pond of L979. The peat islands contributed about 90% of the total CH4 flux, whereas the open water areas contributed 10%. This indicates that formation of peat islands in a hydroelectric area can significantly affect the greenhouse gas emissions to the atmosphere. The average flux of CH4 from the entire wetland in 2002 was 202 ± 77 mg C-CH4/m²/day, equivalent to 44 ± 17 g C-CH4/m²/year (year = 220 days). This is higher than preflood values of 0. 5 g C-CH4/m²/year in 1992, and the early post-flood value of 8. 9 g C-CH4/m²/year in 1993/1994. The wetland continues to emit methane after ten years of flooding at higher than preflood rates.
15
Blum, Wolfgang. "Direct analysis of free base geoporphyrins and metal geoporphyrin complexes by high temperature glass capillary gas chromatography and capillary supercritical fluid chromatography in combination with mass spectrometry." Thesis, University of Bristol, 1989. http://hdl.handle.net/1983/161a8a1a-ed93-4d53-a565-9c0205f8fd34.
Full text
16
Ilanko, Tehnuka. "Geochemistry of gas emissions from Erebus volcano, Antarctica : an adventure in time, space, and volcanic degassing." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709228.
Full text
17
Mills, Heath Jordan. "Microbial diversity in sediments and gas hydrates associated with cold seeps in the Gulf of Mexico." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-07072004-215909/unrestricted/Mills%5FHeath%5FJ%5F200407%5Fphd.pdf.
Full textAbstract:
Thesis (Ph. D.)--School of Biology, Georgia Institute of Technology, 2005. Directed by Patricia Sobecky.Frank Loeffler, Committee Member ; Roger Wartell, Committee Member ; Joseph Montoya, Committee Member ; Thomas DiChristina, Committee Member ; Patricia Sobecky, Committee Chair. Vita. Includes bibliographical references.
18
Piñero, Melgar Elena. "Sedimentology and geochemistry of gas hydrate rich sediments from the Oregon margin (Ocean Drilling Program Leg 204)." Doctoral thesis, Universitat de Barcelona, 2009. http://hdl.handle.net/10803/1580.
Full textAbstract:
Gas hydrates have been recently recognized as a key factor affecting a number of global processes such as the climatic change, sea floor stability, etc. In this thesis we present the multidisciplinary study of gas hydrate rich sediments recovered during ODP Leg 204. The main objective of this thesis is to study how the textural characteristics of marine sediments can affect the main pathways and intensity of fluid flow and how fluid flow determines the distribution of gas hydrates in the continental margins, as well as the main geochemical processes that occur during early diagenesis.To reach these objectives, a complete sedimentary and geochemical study of 581 sediment samples from southern Hydrate Ridge was carried out. The methods and techniques that were applied include: complete textural analyses, mineralogy, physical properties and geochemistry.
The southern Hydrate Ridge sediments are mainly made up of four lithofacies defined as: hemipelagites, turbidites, ash layers and debrites. Mass‐transport deposits such as turbidites and debrites are more abundant in Lithostratigraphic Unit III and II, as well as in Lithostratigraphic Unit IA in the slope basin of southern Hydrate Ridge. Some increasing trends with depth can be observed in the smectite content in the clay mineral assemblages. These features suggest that the transport in suspension of fine sediments through the California Current was more effective during the Pliocene and early Pleistocene period. Bedload transport of coarse material from local and distal areas was more effective during the middle Pleistocene and Holocene due to the tectonic reactivation of the southern Hydrate Ridge uplift. During the Pleistocene and owing to the pervasive fluctuation of sealevel, gas hydrate dissociation together with the seismic movements in the Oregon margin seems a plausible triggering mechanism for mass‐movements.
The results presented here confirm that the sedimentation patterns in the Hydrate Ridge region are controlled by climate and tectonic parameters such as the regional intensity of the California Current or the local tectonic movements that lead to the uplift of the Ridge. These parameters mainly control the clay mineral distribution as well as the sedimentary facies that were produced.
The sedimentary fabric of gas hydrate‐rich intervals is disturbed during core recovery due to gas hydrate dissociation. The two main disturbance fabrics generated through this process are mousselike and soupy. The gas hydrate‐rich sediments analyzed for this thesis are coarser grained in respect to the hemipelagite sediments. The coarse‐grained layers such as turbidites and ash layers could act as conduits for fluids in the southern Hydrate Ridge region because of their higher porosity and permeability. In this context, methane‐rich fluids migrate through these layers from deep in the sedimentary sequence and into the gas hydrate stability zone. A number of barium fronts have been identified in southern Hydrate Ridge sediments and interstitial waters. Barite fronts were formed as a result of the barite recycling process during early diagenesis, which is controlled by the availability of methane‐rich fluids, in situ decomposition of organic matter and the sulphate gradient. Modelling of these data shows that these processes were active at southern Hydrate Ridge for a period of up to one thousand years.
A number of geochemical and sedimentological processes are proposed in this thesis as plausible mechanisms to allow the survival of the barite fronts during diagenesis. The sedimentary texture plays an important role in controlling the major fluid flow pathways in the continental margins. The temporal evolution of the fluid flow can be studied in a given area through the distribution of the mineral phases that form during early diagenesis, as well as the interstitial water composition.
EXTRACTE DE TESI:
Aquesta tesi integra els resultats de l'anàlisi sedimentológica i geoquímica de sediment marins rics en hidrats de gas, recuperats durant la campanya "Ocean Drilling Program" Leg 204 en el marge d'Oregon (USA). L'objectiu principal d'aquest estudi és conèixer les característiques sedimentàries que afecten el fluxe de fluids i gasos a través del sediment i com els fluids afecten la distribució d'hidrats de gas en aquesta àrea, així com alguns processos geoquímics que operen durant la diagènesi inicial. Els mètodes i tècniques aplicats inclouen l'anàlisi de sedimentològia, mineralogia, susceptibilitat magnètica i geoquímica.
Els sediments de southern Hydrate Ridge estan formats per 4 litofàcies: hemipelagita, turbidita, cendra volcànica i debrita. La sedimentació està controlada per factors climàtics i tectònics com ara la intensitat del corrent oceànic Californià o moviments tectònics locals. Aquests paràmetres exerceixen un control fonamental en la distribució dels minerals d'argila i de les fàcies sedimentàries en el marge continental. La seva evolució des del Pliocè és discutida en aquesta tesi.
Els sediments analitzats rics en hidrats de gas són més grollers que els sediments hemipelàgics. Els sediments més grollers actuen com a conductes preferents per a la circulació de fluids degut a la seva porositat i permeabilitat. En aquest context, fluids rics en metà migren des dels sediments profunds cap a la zona d'estabilitat dels hidrats de gas, on possibiliten la seva formació.
Diversos fronts de barita han estat identificats en els sediments de southern Hydrate Ridge. Es formen com a resultat del reciclatge de barita durant la diagènesi inicial, controlada per la presència de fluids rics en metà, la degradació de matèria orgànica i la presència de sulfat. La modelització de les dades obtinguda mostra que aquest procés va ser actiu durant un període de >1000 anys. En aquesta tesi, es discuteixen els possibles processos geoquímics i sedimentaris que permetrien la supervivència de la barita durant la diagènesis.
La textura sedimentària juga un paper molt important en el flux de fluids als marges continentals. La seva evolució temporal en una àrea determinada pot ser deduïda estudiant les fases minerals que es formen durant la diagènesi.
19
Ricci, Andrea <1989>. "Geochemistry of C-bearing gas compounds in natural fluids under crustal conditions: insights into deep and shallow processes." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/9007/1/ricci_andrea_tesi.pdf.
Full textAbstract:
The PhD research project was aimed to improve the scientific knowledge of the origin and fate of C-bearing gas compounds released from active volcanoes, hydrothermal systems and tectonically active sedimentary basins. The first goal was to investigate the primary source(s) of CH4 and light hydrocarbons in volcanic-hydrothermal gases under crustal conditions. This objective was achieved by comparing the composition of low molecular weight organic fraction (C1-C4) and associated CO2 and H2O in fumarolic gases and geothermal wells from different study areas around the world. We demonstrated that these hydrocarbons derive from biotic sources, i.e., predominantly from the thermal decomposition of organic matter. Meteoric waters and seawater circulating through the crust shuttle organic matter from Earth’s surface into the reservoir rocks. There, high temperature pyrolysis of organic matter and open system degassing generates n-alkanes with isotopic compositions previously classified as being indicative for abiogenesis. These results led us to question the dogma of crustal production of abiotic hydrocarbons and highlighted the potential of n-alkanes to become sensitive indicators of life on habitable (exo)planets. The second goal was to study the secondary processes affecting the composition of CO2, CH4 and light hydrocarbons in natural fluids during their uprising from the deep reservoirs to the surface in different geologic setting, ranging from active volcanoes to sedimentary basins. Under magmatic-hydrothermal conditions, catalytic organic reactions may strongly affect volatile organic compounds, drastically changing alkanes-alkenes-aromatics relative abundances and isotopic composition of C1–C4 hydrocarbons. At peripheral areas of volcanic systems and tectonically active sedimentary basins, composition of CO2 and CH4 in interstitial soil gases and dissolved gases in groundwater are mainly controlled by supergene mechanisms, such as calcite precipitation and microbial-driven processes. These secondary processes likely play a major role in regulating the ultimate release of C-bearing gas compounds into the atmosphere.
20
Whyte, Colin James Stephen. "Evaluating the effects of fluid migration and microbial processes on the noble gas and hydrocarbon geochemistry of shallow groundwater." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1576590616496243.
Full text
21
VENTURA, BORDENCA Claudio. "Noble gas geochemistry in seismic (Umbria, Italy) and volcanic (Grand Comore Island, Indian Ocean) regions: New methodologies and implications." Doctoral thesis, Università degli Studi di Palermo, 2020. http://hdl.handle.net/10447/399971.
Full textAbstract:
The noble gases are among the most powerful geochemical tools in different geological settings. For this reason, they represent one of the most valuable tracers of geochemical processes whose variations can be straightforwardly ascribed to magmatic/crustal dynamics. In this dissertation, noble gas (He, Ne, Ar) geochemistry applied in both seismic and volcanic regions are presented.
The PhD research has firstly been devoted to the test on the field of an auto-sampler for high-frequency collection of the water samples in order to be analysed for their dissolved noble gases. Then, I developed a lab-based methodology for the in-vacuum extraction of noble gases from waters collected in the copper tubes. The auto-sampler, named S.P.A.R.T.A.H. (Syringe Pump Apparatus for the Retrieval and Temporal Analysis of Helium), has been installed for a period of 2 months in a seismically active sector in the Umbria region (central Apennines, Italy), and collected fluids from a natural spring for the entire duration of the deployment with the aim of obtaining short-term noble gas data. The proper functioning and successful operation of the extraction system has been tested and verified in the Noble Gas Laboratory at the Istituto Nazionale di Geofisica e Vulcanologia (INGV) of Palermo.
In second part of the PhD research, I focused my attention on the high-flux CO2–rich gas emissions localized in the central sector of the Apennines. The sampled gases have been analyzed for their chemical and isotopic composition (e.g., noble gases). Then, I developed a background geochemical model of fluid circulation and secondary chemical processes that occur during the transfer of fluid in the shallow crustal layers. Moreover I recognize a progressive northward decrease of the mantle-derived He degassing at regional scale along the Apennines. Furthermore, this study highlighted that the variable compositions of the gas manifestations discharged across the Umbria region can be best interpreted as a result of the combination of two different chemical processes which are not mutually exclusive: 1) a mixing between a magmatic end-member (VCVD) and a shallow-sedimentary sources, and 2) solubility-controlled fractionation mechanisms taking place upon interaction with shallow subsurface waters.
Finally, the project has been also addressed to the investigation of noble gases in fluids of an active volcanic system, Grande Comore Island (Indian Ocean). The noble gases (He, Ne, Ar) from fluid inclusions in peridotite mantle xenoliths coupled to radiogenic components (Sr, Nd, Pb) have been analysed to resolve the mantle source feeding the volcanism. Here I recognized a MORB-type mantle reservoir. In particular, the 3He/4He isotope compositions (up to 7.3Ra) fall in a range that overlaps the MORB mantle signature and the SCLM. The 20Ne/22Ne, 21Ne/22Ne and 40Ar/36Ar isotope ratios plot along a mixing between air and a typical MORB-type reservoir. The Sr-Nd-Pb isotope systematics shows a mixing line between Depleted MORB and Enriched Mantle reservoirs, but for two samples whose higher Sr isotope signatures point towards an EM2 source, showing isotopic similarities with carbonatite rocks from the East African Rift System and central-northern Madagascar alkaline rocks.
22
Osborn, Stephen. "Elemental and Isotope Geochemistry of Appalachian Fluids: Constraints on Basin-Scale Brine Migration, Water-Rock Reactions, Microbial Processes, and Natural Gas Generation." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/194250.
Full textAbstract:
This study utilizes new geochemical analyses of fluids (formation water and gas) collected predominately from Devonian organic-rich shales and reservoir sandstones from the northern Appalachian Basin margin to investigate basin scale hydrologic processes, water-rock reactions, microbial activity, and natural gas generation. Elemental and isotopic composition of co-produced formation waters and natural gas show that the majority of methane in Devonian organic-rich shales and reservoir sandstones is thermogenic in origin with localized accumulations of microbial gas. Microbial methanogenesis appears to be primarily limited by redox buffered conditions favoring microbial sulfate reduction. Thermal maturity (bioavailability) of shale organic matter and the paucity of formation waters may also explain the lack of extensive microbial methane accumulations. Iodine and strontium isotopes, coupled to elemental chemistry demonstrate basin scale fluid flow and clay mineral diagenesis. Evidence for this is based on anomalously high ¹²⁹I/I values sourced from uranium deposits (fissiogenic production of ¹²⁹I) at the structural front of the Appalachian Basin. Radiogenic ⁸⁷Sr/⁸⁶Sr (up to 0.7220), and depleted boron and potassium concentrations support smectite clay diagenesis at temperatures greater than 120 °C. The development of fissiogenic ¹²⁹I as a tracer of basin scale fluid flow is a novel application of iodine isotopes provided that the sources of cosmogenic and anthropogenic ¹²⁹I are reasonably well constrained. The anomalously high ¹²⁹I/I in Appalachian Basin brines may be alternatively explained by microbial fractionation based on a correlation with decreasing δ¹³C-DIC values and decreasing sulfate concentrations in the range of sulfate reduction. These results demonstrate that the microbial fractionation of iodine isotopes may be possible and an important consideration when interpreting ¹²⁹I/I, regardless of the source of ¹²⁹I. Results from this study have important implications for understanding the controls on and origins of natural gas production in sedimentary basins; tectonically and topographically driven basin scale fluid flow, including diagenetically induced waterrock reactions and mineral ore deposition related to orogenesis; and an improvement of the use of iodine isotopes for understanding large scale fluid flow, and possibly its use as a tracer of organic matter diagenesis and the distribution of radionuclides in the environment.
23
Antle, Stacy Wayne. "Indirect Greenhouse Gas Dynamics in Karst Groundwater Systems under Agricultural Land Use." TopSCHOLAR®, 2018. https://digitalcommons.wku.edu/theses/3082.
Full textAbstract:
Greenhouse gases (GHGs) are a major global environmental concern, because their concentrations have continuously increased over the past few centuries, due to global population growth, fossil fuel dependency, and the Industrial Revolution. Since these gases are naturally occurring phenomena, they will never be completely eliminated. Efforts to reduce them span numerous scientific attempts, with minimal improvements in reducing their atmospheric concentrations. In agricultural land practices, greenhouse gases are common byproducts that affect the atmosphere and, potentially, the groundwater where livestock and fertilizers are key contributors. Little is known about the fate of such greenhouse gases in dissolved form, known as indirect greenhouse gases, especially (CH4 and N2O) in karst landscapes. At Crumps Cave, indirect greenhouse gases were analyzed for seasonal changes along with other geochemistry parameters to identify if anthropogenic land use effected greenhouse gases production in the epikarst and bedrock. This study revealed that CO2 flux is mainly controlled by natural vegetation and seasonal influences. In contrast, CH4 is produced and consumed continuously in the epikarst and bedrock, where decay of organic matter is the primary driver for seasonal change and temperature has little effect on methanogens and methanotrophs survival, because of their ability of adaptation to the environment. N2O, via the nitrogen cycle in which nitrification/denitrification occurs, is directly affected by land use during fertilizer
application and crop rotation. Nitrates from the surface provide a nitrogen source for denitrification to occur and produce elevated N2O in the groundwater system, because residence time is decreased and dissolved oxygen is elevated. Indirect greenhouse gases are linked to karst groundwater systems, where they may be transported and stored in karst aquifers under agricultural land use practices through complex interactions of groundwater recharge, microbial activity, and seasonal land use variability.
24
Watkins, Cody S. "Hydrocarbon and CO2 Emissions from Oil and Gas Production Well Pad Soils Comparative to Background Soil Emissions in Eastern Utah." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/5666.
Full textAbstract:
Emissions of methane, non-methane hydrocarbons (NMHC), and carbon dioxide (CO2) at 27 natural gas well pads, 11 non-well locations in oil and gas fields, and 7 hydrocarbon-bearing outcrops in eastern Utah between 2013 and 2016 were measured using a dynamic flux chamber (DFC) in effort to answer the following questions: What effect does the development of oil and gas have on the observed air quality (increased ozone, CO2, volatile organic compounds (VOCs), and/or methane emissions) in northeastern Utah? What percentage of these gases is due to natural background emissions, and what percentage is due to oil and gas development in the region? Methane emissions were the focus of this study, but emissions of other compounds were also measured to better understand the sources and characteristics of emissions. Background methane fluxes were all (mg) meter (m)-2 hour (h)-1. Methane emissions from well pad soils were commonly higher closer to the wellhead, though exceptions existed. Methane fluxes from well pad soils ranged from -5.6 to 70,000 mg m-2h-1. Based on analysis of NMHC emissions data, emissions from 68% of the sampled well pad soils were due to leaks of raw natural gas, whereas the remaining emissions were likely from a combination of raw gas leaks, liquid hydrocarbon spills, and/or methanogenic processes. CO2 emissions were higher than methane emissions 92% of the time at well sites, possibly due to CO2 in natural gas, and/or CO2 emitted from bacterial decomposition of soil organic matter and/or fossil hydrocarbons. Total combustible soil gas concentrations were measured at 21 wells. In summer 2015, soil properties were also analyzed to better understand well leakage. Wells categorized as shut-in had the highest average methane fluxes. Measured methane soil emissions were scaled-up for the entire Uinta Basin to estimate the overall emission from well pad soils, and to compare soil emissions with other natural gas-related sources. Producing and shut-in gas wells were estimated to emit 16.1 ± 4.3 and 8.6 ± 3.2 (90% confidence interval) t y-1 (tonne/year) of methane in the Uinta Basin, respectively, which is
25
Eymold, William Karl. "The Evaluation of Subsurface Fluid Migration using Noble Gas Tracers and Numerical Modeling." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1591894015888803.
Full text
26
Zhang, Qian Verfasser], Ralf [Akademischer Betreuer] [Littke, and Reinhard [Akademischer Betreuer] Sachsenhofer. "Petroleum geochemistry and petrophysics of oil and gas shales from south China and northwest Germany / Qian Zhang ; Ralf Littke, Reinhard Sachsenhofer." Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1231118059/34.
Full text
27
Burdsall, Adam Charles. "Abiotic Reduction of Nitrite and Nitrate by Nanoscale Chemogenic Magnetite: Pathways for Significant Greenhouse Gas Production." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1377455218.
Full text
28
Utting, Nicholas C. "Geochemistry and Noble Gases of Permafrost Groundwater and Ground Ice in Yukon and the Northwest Territories, Canada." Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20541.
Full textAbstract:
In Canada’s western Arctic, perennial discharge from permafrost watersheds is the surface manifestation of active groundwater flow systems, yet understanding the mechanisms of groundwater recharge and flow in periglacial environments remains enigmatic. This thesis addresses questions on how and where groundwater recharge occurs. Watersheds were selected in Yukon (Fishing Branch River at Bear Cave Mountain) and the Northwest Territories at latitudes spanning from continuous to discontinuous permafrost (five tributary rivers to the Mackenzie River from Wrigley to Aklavik). All are characterized by perennial flow with open water in the winter, and discharge from sedimentary formations of karstic carbonates and evaporate rocks. Determinations of groundwater contributions to discharge, mixing, recharge conditions and circulation times were made on the basis of a suite of analytical approaches involving measurements of major dissolved ions, δ18O, δD, δ13CDIC, 3H, noble gases and flow gauging was conducted at some sites.
The application of these tracers show that hydrogeological conditions and flow paths in permafrost terrains are surprisingly similar to those of temperate regions. Groundwater recharge was determined to be a mix of annual precipitation with contributions from snowmelt and precipitation. All systems investigated show that groundwaters have recharged through organic soils with elevated PCO2, which suggests that recharge occurs largely during summer when biological activity is high. Noble gas concentrations show that the recharge temperature was between 0 and 6 °C, which, when considered in the context of discharge temperatures, suggests that there is no significant imbalance of energy flux into the subsurface. Groundwater ages were found using the 3H-3He method and were dependent on flow path. By characterizing groundwater and surface water chemistry, the proportion of groundwater was found in numerous water courses.
The possible impact of ground ice formation and melting on noble gas concentrations in groundwater was considered. To assess this link, a new method to measure the noble gas composition of ground ice bodies was developed. The method can be used to determine the origin of ice, based on changes in noble gas ratios between ice originating from compaction of snow (e.g. glacier ice) vs. ice originating from freezing of water. No significant fractionation of noble gases during groundwater freezing and ground ice formation was identified. Applied to determination of the origin of ground ice bodies, the method was shown to be both diagnostic of ice origin and un-encumbered by reactivity in the subsurface, which compromises the use of the dominant atmospheric gases (O2 and N2).
Résumé
Dans l’Ouest de l'Arctique canadien, la décharge pérenne dans certaines rivières en région de pergélisol est la manifestation en surface d’une circulation d’eau souterraine; cependant la compréhension des mécanismes d’écoulement et de recharge des eaux souterraines en région de pergélisol demeure énigmatique. Cette thèse s’intéresse à la question de savoir comment et où la recharge des eaux souterraines se produit. Des bassins versants ont été choisis au Yukon (Rivière Fishing Branch à Bear Cave Mountain) et dans les Territoire du Nord-Ouest à des latitudes s’étendant du pergélisol discontinu au pergélisol continu (cinq tributaires du Mackenzie entre Wrigley et Aklavik). Toutes ces rivières ont un écoulement d’eau pérenne avec des zones non gelées et une décharge dans des formations sédimentaires de roches carbonatées et d‘évaporites. L’identification des contributions des eaux à la décharge, les mélanges, les conditions de recharge, et les temps de circulation ont été faits à partir d’analyses qui ont inclus les concentrations en éléments majeurs, leur valeur isotopique (δ18O, δD, δ13C, 3H), ainsi que leur teneur en gaz rares. A certain des sites analysés des mesures d’écoulement ont été prises.
L’application de ces traceurs montre que les conditions hydrauliques et le chemin des écoulements en région de pergélisol sont similaires à ceux des régions tempérées. La recharge en eau souterraine a été identifiée comme étant un mélange de précipitations annuelles, avec des contributions de neige et de pluies. Tous les systèmes étudiés montrent que les eaux souterraines se sont rechargées en traversant des sols organiques avec une PCO2 élevée, ce qui suggère que la recharge se produire largement durant l’été quand l’activité biologique est élevée. Cependant, les concentrations en gaz nobles montre que la température de recharge des eaux souterraines était entre 0 et 6 °C ce qui indique qu’il n’y a pas de déséquilibre de flux d’énergie à l’intérieur de la zone proche de la surface. L’âge des eaux a été déterminé par la méthode 3H-3He et cet âge est dépendant du chemin d'écoulement. En caractérisant les paramètres chimiques des eaux de surface et des eaux souterraines, il a été possible de trouver la contribution des eaux souterraines aux eaux surface.
Le possible impact de la formation et de la fonte de la glace souterraine sur les concentrations des gaz nobles a été considéré. Pour déterminer s’il y a un lien entre ceux-ci, une nouvelle méthode pour mesurer la concentration en gaz nobles dans les glaces souterraines a été développée. La méthode peut être utilisée pour déterminer l’origine de la glace; elle est basée sur les changements dans les rapports des gaz nobles entre la glace issue de la compaction de la neige (c’est-à-dire la glace de glacier) par opposition à la glace issue du gel de l’eau. Aucun fractionnement significatif des gaz nobles durant l’engel des eaux souterraines et la formation de glaces souterraines n’a été identifié. Appliquée à l’identification de l’origine des masses de glace enfouies, on a montré que la méthode pouvait permettre d’identifier l’origine des glaces souterraines sans qu’elle soit affectée par des réactions biologiques de sub-surface, lesquelles rendent inutilisables les gaz atmosphériques (O2, and N2).
29
Parai, Rita. "Volatiles in the Earth and Moon: Constraints on planetary formation and evolution." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11652.
Full textAbstract:
The volatile inventories of the Earth and Moon reflect unique histories of volatile acquisition and loss in the early Solar System. The terrestrial volatile inventory was established after the giant impact phase of accretion, and the planet subsequently settled into a regime of long-term volatile exchange between the mantle and surface reservoirs in association with plate tectonics. Therefore, volatiles in the Earth and Moon shed light on a diverse array of processes that shaped planetary bodies in the Solar System as they evolved to their present-day states.Earth and Planetary Sciences
30
Foley, Derek J. "Analysis of the Point Pleasant/Lexington/Trenton Formations: Sulfides, Mineralogy, and Trace Elements as Geochemical Proxies." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461333436.
Full text
31
Taulis, Mauricio. "Groundwater characterisation and disposal modelling for coal seam gas recovery." Thesis, University of Canterbury. Civil Engineering, 2007. http://hdl.handle.net/10092/3104.
Full textAbstract:
Coal Seam Gas (CSG) is a form of natural gas (mainly methane) sorbed in underground coal deposits. Mining this gas involves drilling a well directly into an underground coal seam, and pumping out the water (CSG water) flowing through it. Presently, CSG is under exploration in New Zealand (NZ); however, there is concern about CSG water disposal in NZ mainly because of the controversy that this activity has generated in some basins in the United States (US). The first part of this thesis studies CSG water from a well in Maramarua (NZ) and compares it to water from US basins. The NZ CSG water from this well had high pH (7.8), alkalinity in the order of 360 mg/l as CaCO₃, high sodium (334 mg/l), bicarbonate (435 mg/l), and chloride (146 mg/l). These ions also occur in US CSG waters, and their concentrations follow the same trend - high sodium, bicarbonate, and chloride with low calcium, magnesium, and sulphate concentrations. Prior to this work, little detailed analyses of CSG water quality variability from a well had been carried out. A Factor Analysis of 33 Maramarua samples was conducted and revealed that about one third of the variations were due to sample degassing, which induced calcium carbonate precipitation - this was supported by experimental work (sample sparging) and geochemical modelling (MINTEQA2). This finding is important for CSG water management because, as calcium concentrations decrease, higher SAR values are generated, and this can cause problems if CSG waters are disposed on land. In the second part, this thesis assesses the potential environmental effects of disposing CSG waters in NZ by formulating management options and a simple wastewater treatment system. This was carried out by studying the ecological response (soils, plant, and aquatic life) resulting from CSG water disposal operations in the US, and by applying relevant salinity and sodicity guidelines to the interaction between soils and CSG waters from Maramarua. This work showed that similar problems are likely to occur in NZ if CSG water disposal takes place without proper controls. Such a study has never been carried out in a region before actual CSG development has taken place, so this work shows how to quantify the effects arising from CSG water disposal prior to full scale production. This can be particularly useful for CSG stakeholders wanting to develop this resource in other regions around the world. A simple treatment system using Ngakuru zeolites has proven effective in reducing the SAR of Maramarua CSG water. Laboratory results indicate that these zeolites work by exchanging sodium cations in the water by other cations contained within the zeolite structure but with slow ion exchange kinetics. The calculated sodium absorption capacity for these natural zeolites ranged from 11.3 meq/100g to 16.7 meq/100g (flow-through conditions without previous regeneration). In addition, these experiments showed that the ion exchange process is accompanied by some dissolution (sulphate, boron, TOC, sodium, calcium, magnesium, potassium and reactive silica), but mainly at the beginning of the treatment process. Nevertheless, using this system, 180 grams of zeolite material were used to treat an initial 1.83 litres of Maramarua CSG water thus reducing potential soil infiltration problems to nil. As more CSG water was treated, the zeolites kept reducing SAR values but at a lesser rate until 4.53 litres of CSG water had been treated. A step-by-step methodology to assess treatment design options for these materials has been developed and will aid future researchers and engineers. This thesis presents the first comprehensive study of CSG water management in NZ. It also presents an ion exchange treatment system using natural zeolites already available in NZ. In conclusion, the research finds that, whether through adequate management or active treatment, CSG waters can be safely disposed without creating major environmental problems, and can even be used in beneficial applications.
32
Ross, Daniel John Kerridge. "Investigation into the importance of geochemical and pore structural heterogeneities for shale gas reservoir evaluation." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/359.
Full textAbstract:
An investigation of shale pore structure and compositional/geochemical heterogeneities has been undertaken to elucidate the controls upon gas capacities of potential shale gas reservoirs in northeastern British Columbia, western Canada. Methane sorption isotherms, pore structure and surface area data indicate a complex interrelationship of total organic carbon (TOC) content, mineral matter and thermal maturity affect gas sorption characteristics of Devonian-Mississippian (D-M) and Jurassic strata.
Methane and carbon dioxide sorption capacities of D-M shales increase with TOC content, due to the microporous nature of the organic matter. Clay mineral phases are also capable of sorbing gas to their internal structure; hence D-M shales which are both TOC- and clay-rich have the largest micropore volumes and sorption capacities on a dry basis. Jurassic shales, which are invariably less thermally mature than D-M shales, do not have micropore volumes which correlate with TOC. The covariance of methane sorption capacity with TOC, independent of micropore volume, indicates a solute gas contribution (within matrix bituminite) to the total gas capacity. On a wt% TOC basis, D-M shales sorb more gas than Jurassic shales: a result of thermal-maturation induced, structural transformation of the D-M organic fraction.
Organic-rich D-M strata are considered to be excellent candidates for gas shales in Western Canada. These strata have TOC contents ranging between 1-5.7 wt%, thermal maturities into the dry-gas region, and thicknesses in places of over 1000 m. Total gas capacity estimates range between 60 and 600 bcf/section where a substantial percentage of the gas capacity is free gas, due to high reservoir temperatures and pressures.
Inorganic material influences modal pore size, total porosity and sorption characteristics of D-M shales. Carbonate-rich samples often have lower organic carbon contents (oxic deposition) and porosity, hence potentially lower sorbed and free-gas capacities. Highly mature Devonian shales are both silica and TOC-rich (up to 85% quartz and 5 wt% TOC) and as such, deemed excellent potential shale gas reservoirs because they are both brittle(fracable), and gas-charged. However, quartz-rich Devonian shales display tight-rock characteristics, with poorly developed fabric, small median pore diameters and low permeabilities. Hence potential `frac-zones' will require an increased density of hydraulic fracture networks for optimum gas production.
33
Firesinger, Devon Robert. "Quantity Trumps Quality: Bayesian Statistical Accumulation Modeling Guides Radiocarbon Measurements to Construct a Chronology in Real-time." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6701.
Full textAbstract:
The development of an accurate and precise geochronology is imperative to understanding archives containing information about Earth’s past. Unable to date all intervals of an archive, researchers use methods of interpolation to approximate age between dates. Sections of the radiocarbon calibration curve can induce larger chronological uncertainty independent of instrumental precision, meaning even a precise date may carry inflated error in its calibration to a calendar age. Methods of interpolation range from step-wise linear regression to, most recently, Bayesian statistical models. These employ prior knowledge of accumulation rate to provide a more informed interpolation between neighboring dates. This study uses a Bayesian statistical accumulation model to inform non-sequential dating of a sediment core using a high-throughput gas-accepting accelerator mass spectrometer. Chronological uncertainty was iteratively improved but approached an asymptote due to a blend of calibration uncertainty, instrument error and sampling frequency. This novel method resulted in a superior chronology when compared to a traditional sediment core chronology with fewer, but more precise, dates from the same location. The high-resolution chronology was constructed for a gravity core from the Pigmy Basin with an overall 95% confidence age range of 360 years, unmatched by the previously established chronology of 460 years. This research reveals that a larger number of low-precision dates requires less interpolation, resulting in a more robust chronology than one based on fewer high-precision measurements necessitating a higher degree of age interpolation.
34
Oliveira, Siana Soares de. "Caracterização de reservatórios não convencionais Shale Gas na Formação Barreirinha Bacia do Amazonas." Universidade do Estado do Rio de Janeiro, 2015. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=8731.
Full textAbstract:
Os folhelhos pretos devonianos da Formação Barreirinha caracterizamse pela alta radioatividade na porção basal, grande extensão areal, espessura e profundidade de soterramento variável que vão de exposição na superfície até mais de 3000 m. Eles são as principais rochas geradoras do sistema petrolífero convencional da Bacia do Amazonas, e recentemente foram consideradas como promissores plays de gás não convencional. Folhelhos são geralmente caracterizados por uma matriz fechada, que faz com que sejam relativamente impermeáveis em relação ao fluxo de gás, a menos que ocorram fraturas, e dependendo das suas características geológicas e geoquímicas podem funcionar com um Sistema Petrolífero autossuficiente, atuando tanto como rocha fonte, quanto como reservatório de gás (reservatório Shale Gas). Assim, o gás natural termogênico ou biogênico gerado pode ser armazenado em folhelhos ricos em matéria orgânica na forma livre, adsorvida, ou em estado dissolvido. Em contraste com os sistemas petrolíferos convencionais, reservatórios Shale Gas, possuem mecanismos de aprisionamento e armazenamento únicos, sendo necessária a utilização de técnicas de avaliações específicas. No entanto, folhelhos prolíficos geralmente podem ser reconhecidos a partir de alguns parâmetros básicos: arquitetura geológica e sedimentar, propriedades geoquímicas e petrofísicas e composição mineralógica. Tendo em vista a carência de pesquisas de caráter descritivo, com cunho exploratório dos folhelhos geradores da Formação Barreirinha, esta dissertação tem como objetivo introduzir uma metodologia de identificação de intervalos de folhelho gerador com potencial para reservatório Shale Gas. Começando com uma investigação regional sobre o contexto geológico e sedimentar, seguido de uma avaliação abrangente enfocando as características geoquímicas, petrofísicas e litofácies dos folhelhos a partir da integração de parâmetros obtidos de perfis geofísicos de poço, análises geoquímicas e aplicação dos conceitos de Estratigrafia de Sequencia.The Devonian black shale of Barreirinha formation is characterized by high radioactivity in the basal portion, large areal extension, thickness and depth of burial variable which ranges from exposure to surface to depth greater than 3000 m. This formation contains the main source rocks of conventional petroleum system of the Amazonas Basin, and recently were considered promising unconventional gas plays. Shales are generally characterized by a closed die, which makes them relatively impervious for gas flow unless fracturing occur, and depending on their geological and geochemical characteristics they might behave as a selfcontained Petroleum System, acting as both source rock and as a gas reservoir (Shale gas reservoir). Thus, the thermogenic or biogenic gas generated can be stored in shale rich in organic matter in free form, adsorbed or dissolved state. In contrast to conventional petroleum systems, Shale Gas reservoirs, have trapping mechanisms and unique storage, requiring the use of specific assessment techniques. However, prolific shale can usually be recognized based on some basic parameters: geological and sedimentary architecture, geochemical and petrophysical properties and mineralogical composition. Given the lack of descriptive research, about the exploration potential of the Barreirinha formations shale, this dissertation aims to introduce a methodology of identification of intervals that could be potential shale gas reservoirs. Starting with a regional research about the geological and sedimentary context, followed by a comprehensive review focusing on the geochemical characteristics, petrophysical and lithofacies based on the integration of the parameters obtained by well log, geochemical analysis and application of Sequence Stratigraphy concepts.
35
Butland, Caroline. "Coal seam gas associations in the Huntly, Ohai and Greymouth regions, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2006. http://hdl.handle.net/10092/1304.
Full textAbstract:
Coal seam gas has been recognised as a new, potential energy resource in New Zealand. Exploration and assessment programmes carried out by various companies have evaluated the resource and indicated that this unconventional gas may form a part of New Zealand's future energy supply. This study has delineated some of the controls between coal properties and gas content in coal seams in selected New Zealand locations. Four coal cores, one from Huntly (Eocene), two from Ohai (Cretaceous) and one from Greymouth (Cretaceous), have been sampled and analysed in terms of gas content and coal properties. Methods used include proximate, sulphur and calorifc value analyses; ash constituent determination; rank assessment; macroscopic analysis; mineralogical analysis; maceral analysis; and gas analyses (desorption, adsorption, gas quality and gas isotopes). Coal cores varied in rank from sub-bituminous B-A (Huntly); sub-bituminous C-A (Ohai); and high volatile bituminous A (Greymouth). All locations contained high vitrinite content (~85 %) with overall relatively low mineral matter observed in most samples. Mineral matter consisted of both detrital grains (quartz in matrix material) and infilling pores and fractures (clays in fusinite pores; carbonates in fractures). Average gas contents were 1.6 m3/t in the Huntly core, 4.7 m3/t in the Ohai cores, and 2.35 m3/t in the Greymouth core. The Ohai core contained more gas and was more saturated than the other cores. Carbon isotopes indicated that the Ohai gas composition was more mature, containing heavier 13C isotopes than either the Huntly or Greymouth gas samples. This indicates the gas was derived from a mixed biogenic and thermogenic source. The Huntly and Greymouth gases appear to be derived from a biogenic (by CO2 reduction) source. The ash yield proved to be the dominant control on gas volume in all locations when the ash yield was above 10 %. Below 10 % the amount of gas variation is unrelated to ash yield. Although organic content had some influence on gas volume, associations were basin and /or rank dependant. In the Huntly core total gas content and structured vitrinite increased together. Although this relationship did not appear in the other cores, in the Ohai SC3 core lost gas and fusinite are associated with each other, while desmocollinite (unstructured vitrinite) correlated positively with residual gas in the Greymouth core. Although it is generally accepted that higher rank coals will have higher adsorption capacities, this was not seen in this data set. Although the lowest rank coal (Huntly) contains the lowest adsorption capacity, the highest adsorption capacity was not seen in the highest rank coal (Greymouth), but in the Ohai coal instead. The Ohai core acted like a higher rank coal with respect to the Greymouth coal, in terms of adsorption capacity, isotopic signatures and gas volume. Two hypothesis can be used to explain these results: (1) That a thermogenically derived gas migrated from down-dip of the SC3 and SC1 drill holes and saturated the section. (2) Rank measurements (e.g. proximate analyses) have a fairly wide variance in both the Greymouth and Ohai coal cores, thus it maybe feasible that the Ohai cores may be higher rank coal than the Greymouth coal core. Although the second hypothesis may explain the adsorption capacity, isotopic signatures and the gas volume, when the data is plotted on a Suggate rank curve, the Ohai coal core is clearly lower rank than the Greymouth core. Thus, pending additional data, the first hypothesis is favoured.
36
Chakraborty, Suvankar. "PROVENANCE OF THE NEOPROTEROZOIC OCOEE SUPERGROUP, EASTERN GREAT SMOKY MOUNTAINS." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/76.
Full textAbstract:
The Ocoee Supergroup is a sequence of Neoproterozoic, immature, continental rift facies clastic sediments. Potential source rocks were tested by analyzing modes of detrital framework minerals, detrital mineral chemistry, whole rock geochemistry and detrital zircon U/Pb geochronology by LA-ICP-MS for Ocoee siltstone-sandstone dominated formations. Ocoee units are arkosic to subarkosic siltstones/sandstones, and ternary tectonic discrimination diagrams confirm a continental basement uplift source. Alkali feldspar predominates over plagioclase feldspar. Detrital feldspar compositions of Ocoee sediments as a group are similar to feldspar in local basement granitic rocks except for high-Ca plagioclase grains present locally in basement granitic rocks. The high alkali content of the detrital feldspars in the Ocoee Supergroup is consistent with derivation from an A-type granite source terrane. Normative Q-A-P values, calculated from wholerock chemistry, and trace element diagrams are also supportive of an A-type granite source for these rocks. The siltstones and sandstones of the Snowbird Group contain high abundances of heavy minerals (zircon, titanite, ilmenite, epidote and apatite), which are dispersed among other detrital grains and as concentrations of heavy minerals in discrete laminae. ZTR index and titanite mineral chemistry suggest a granitic source for these sediments. Detrital zircon geochronology in Ocoee sediments indicates a dominantly Grenville (1000 to 1300 Ma) source for these sediments. The youngest zircon age in the basal Ocoee Wading Branch Formation (639±8 Ma) is related to rift magmatism and provides a minimum depositional age for the Ocoee Supergroup.
37
Perlman, Zachary S. "STRATIGRAPHIC, GEOCHEMICAL, AND GEOCHRONOLOGICAL ANALYSIS OF THE WOLFCAMP-D INTERVAL, MIDLAND BASIN, TEXAS." UKnowledge, 2017. http://uknowledge.uky.edu/ees_etds/48.
Full textAbstract:
Subsurface data derived from ~388 ft of drill core from Martin County (TX) were used to understand the depositional setting of the Wolfcamp-D, a petroleum producing interval in the Midland Basin. Elemental geochemistry collected via x-ray fluorescence revealed a highly variable depositional history marked by the deposition of diverse siliciclastic and carbonate lithofacies. Integration of multiple datasets resulted in the interpretation of nine lithofacies, whose deposition appears cyclical. Correlations between molybdenum and total organic carbon indicate slow recharge of bottom waters and anoxic/euxinicconditions within the basin. The presence of phosphatic nodules coinciding with siliceous black mudrocks suggested high levels of primary productivity driven by upwelling. High-frequency sea level variability, driven by far-field glaciation and regional paleoclimate, were key controls on both the chemostratigraphy and lithofacies. Along-strike variability is seen throughout the basin due to paleobathymetry, proximity and connections to paleochannels, and localized structures. Rhenium-osmium (Re/Os) geochronology was conducted on siliceous mudrocks with high total organic carbon. A depositional age of 300 ± 18 Ma was obtained, partially confirming previous correlations to shelf biostratigraphic data. Scatter in the Re/Os data is likely due to mixing in the basin or non-hydrogenous Os incorporated into the analysis due to the method of preparation.
38
Suer, Selin. "Geochemical Monitoring Of The Seismic Activities And Noble Gas Characterization Of The Geothermal Fields Along The Eastern Segment Of The Buyuk Menderes Graben." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611641/index.pdf.
Full textAbstract:
This study aims the real-time monitoring of gases (CO2, N2, O2, H2, H2S, CH4, He, Ar) discharging from natural pools in the Tekke Hamam geothermal field (Denizli) in addition to the geochemical characterization of the field along with the Kizildere geothermal field, both located at the eastern segment of the Büyü
k Menderes Graben. The continuous gas monitoring experiment (November 2007-October 2008) conducted in the Tekke Hamam geothermal field has revealed temporal variations in the gas compositions, gas flow rate and pool temperature. Different variation components, such as daily variation profiles and peak/Multi-day signals, are detected in the monitored data, which are mainly correlated with shallow and deep processes involving mainly meteorological factors and seismicity induced variations, respectively. Particularly, the coupled variations in the gas compositions and flow rate seem to correlate with seismicity induced permeability modifications within the subsurface during the absence of significant meteorological factors, such as high rainfall and varying atmospheric pressure. The noble gas characterization of the fields have revealed both high 3He/4He and 4He/20Ne isotopic ratios, suggesting a mantle contribution of about 18% for Kizildere and 34% for Tekke Hamam, whereas the other noble gases (Ar, Ne, Kr, Xe) are of atmospheric nature. The different mantle contributions observed in both fields can suggest a different mantle-He flux variably contaminated by crustal helium. The chemical (cation-trace element-anion) and stable isotopic (&
#948
18O-&
#948
D) contents of the thermal waters reveal high temperature water-rock interaction accompanied by the effects of deep origined gases (mainly CO2 and H2S) discharging from the fields.
39
Wiersberg, Thomas. "Edelgase als Tracer für Wechselwirkungen von Krusten- und Mantelfluiden mit diamantführenden Gesteinen des östlichen Baltischen Schildes." Phd thesis, Universität Potsdam, 2001. http://opus.kobv.de/ubp/volltexte/2005/27/.
Full textAbstract:
In der vorliegenden Arbeit werden anhand der Edelgaszusammensetzung von Kimberliten und Lamproiten sowie ihrer gesteinsbildenden Minerale die Wechselwirkungen dieser Gesteine mit Fluiden diskutiert. Die untersuchten Proben stammen vom östlichen Baltischen Schild, vom Kola-Kraton (Poria Guba und Kandalaksha) und vom karelischen Kraton (Kostamuksha). Edelgasanalysen nach thermischer oder mechanischer Gasextraktion von 23 Gesamtgesteinsproben und 15 Mineralseparaten ergeben folgendes Bild: Helium- und Neon-Isotopendaten der Fluideinschlüsse von Lamproiten aus Kostamuksha lassen auf den Einfluss einer fluiden Phase krustaler Herkunft schliessen. Diese Wechselwirkungen fanden wahrscheinlich schon während des Magmenaufstiegs statt, denn spätere Einflüsse krustaler Fluide auf die Lamproite und ihr Nebengestein (Quarzit) sind gering, wie anhand der C/36Ar-Zusammensetzung gezeigt wird. Auch sind die mit verschiedenen Datierungsmethoden (Rb-Sr, Sm-Nd, K-Ar) an Mineralseparaten und teilweise an Gesamtgestein ermittelten Alter konsistent und machen eine metamorphe Überprägung unwahrscheinlich. Aufgrund der Verteilung der primordialen Edelgasisotope zwischen Fluideinschlüssen und Gesteinsmatrix ist ein langsamer Magmenaufstieg anzunehmen, was die Möglichkeit der Kontamination mit einem krustalen Fluid während des Magmenaufstiegs erhöht.Die Gasextraktion aus Mineralseparaten erfolgte thermisch, wodurch eine Freisetzung der Gase ausschließlich aus Fluideinschlüssen nicht möglich ist. Hierbei zeigen Amphibol und Klinopyroxen, separiert aus Kostamuksha-Lamproiten, in ihrer Neon-Isotopenzusammensetzung im Vergleich zur krustalen Zusammensetzung (Kennedy et al., 1990) ein leicht erhöhtes Verhältnis von 20Ne/22Ne, was ein Hinweis auf Mantel-Neon sein könnte. Kalifeldspäte, Quarz und Karbonate enthalten dagegen nur Neon krustaler Zusammensetzung. Phlogopite haben sehr kleine Verhältnisse von 20Ne/22Ne und 21Ne/22Ne, zurückzuführen auf in-situ-Produktion von 22Ne in Folge von U- und Th-Zerfallsprozessen.
Wie unterschiedliche thermische Entgasungsmuster für 40Ar und 36Ar zeigen, ist 36Ar in Fluideinschlüssen konzentriert. Das 40Ar/36Ar-Isotopenverhältnis der Fluideinschlüsse von Lamproiten aus Kostamuksha ist antikorreliert mit der durch thermische Extraktion bestimmten Gesamtmenge an 36Ar. Argon aus Fluideinschlüssen setzt sich daher aus zwei Komponenten zusammen: Einer Komponente mit atmosphärischer Argon-Isotopenzusammensetzung und einer krustalen Komponente mit einem Isotopenverhältnis 40Ar/36Ar > 6000. Diffusion von radiogenem 40Ar aus der Kristallmatrix in die Fluideinschlüsse spielt keine wesentliche Rolle.
Kimberlite aus Poria Guba und Kandalaksha zeigen anhand der Helium- und z. T. auch der Neon-Isotopenzusammensetzung eine Mantelkomponente in den Fluideinschlüssen an. Bei einem angenommenen 20Ne/22Ne-Isotopenverhältnis von 12,5 in der Mantelquelle ergibt sich ein 21Ne/22Ne-Isotopenverhältnis von 0,073 ± 0,011 sowie ein 3He/4He-Isotopenverhältnis, welches im Vergleich zum subkontinentalem Mantel (Dunai und Baur, 1995) stärker radiogen geprägt ist. Solche Isotopensignaturen sind mit höheren Konzentrationen an Uran und Thorium in der Mantelquelle der Kimberlite zu erklären.
Rb-Sr- und Sm-Nd-Altersbestimmungen erfolgten von russischer Seite (Belyatskii et al., 1997; Nikitina et al., 1999) und ergeben ein Alter von 1,23 Ga für den Lamproitvulkanismus in Kostamuksha. Eigene K-Ar-Datierungen an Phlogopiten und Kalifeldspäten stimmen mit einem Alter von 1193 ± 20 Ma fast mit den Rb-Sr- und Sm-Nd-Altern überein. Die K-Ar-Datierung an einem Phlogopit aus Poria Guba, separiert aus dem Kimberlit PGK 12a, ergibt ein Alter von 396 Ma, ebenfalls in guter Übereinstimmung mit Rb-Sr-und Sm-Nd-Altern (ca. 400 Ma, Lokhov, pers. Mitteilung). K-Ar-Altersbestimmungen an Gesamtgestein aus Poria Guba erbrachten kein schlüssiges Alter. Die Rb-Sr- und Sm-Nd-Alter des Lamproitmagmatismus in Poria Guba betragen 1,72 Ga (Nikitina et al., 1999).
Vergleiche von gemessenen mit berechneten Edelgaskonzentrationen aus in-situ-Produktion zeigen weiterhin, dass in Abhängigkeit vom Alter der Probe Diffusionsprozesse stattgefunden haben, die zu unterschiedlichen und z. T. erheblichen Verlusten an Helium und Neon führten. Diffusionsverluste an Argon sind dagegen kaum signifikant. Unterschiedliche Diffusionsverluste in Abhängigkeit von Alter und betrachtetem Edelgas zeigen auch die primordialen Edelgase.
In the present thesis, interactions of kimberlites and lamproites as well as their constituent minerals with fluids are discussed based on noble gas compositions. The samples originate from the eastern Baltic Shield, more specifically from the Kola craton (Poria Guba and Kandalaksha) and the Karelia craton (Kostamuksha). Gas was extracted by stepwise heating and crushing from 23 whole rock samples and 15 mineral separates. These two techniques allow differential extraction of gas from fluid inclusions (crushing technique) and from the bulk sample (stepwise heating). The noble gas analyses provide the following information:
Helium and neon isotopic compositions of fluid inclusions in lamproites reveal the presence of a crustal fluid phase. Fluid interaction probably ocurred already during the process of magma ascent. Interaction after lamproite emplacement seems unlikely. The lamproites and their host rock differ in the degree of fluid-rock interaction, as demonstrated by the C/36Ar composition. In addition, various dating methods (Rb-Sr, Sm-Nd, K-Ar) yield almost the same age within analytical error. Thus, a metamorphic overprint can be excluded. The distribution of primordial noble gases between fluid inclusions and crystal lattice suggests a relatively slow magma ascent, making an interaction of the lamproitic magma with crustal fluids even more likely. Since noble gases from mineral separates were extracted only by the stepwise heating method, gases stored in fluid inclusions could not be released separately.
Amphibole and clinopyroxene separates yielded a higher 20Ne/22Ne ratio in comparison to crustal composition (Kennedy et al., 1990). This presumably is an indication of a mantle derived fluid phase. On the other hand, neon isotopic composition of K-feldspar, quartz and carbonate separates are indistinguishable from the crustal composition. In comparison to other mineral separates, phlogopite yields very low ratios of 20Ne/22Ne and 21Ne/22Ne due to in situ production of 22Ne, which is a result of nuclear reactions.
The distinct thermal gas release patterns of 40Ar and 36Ar indicates that 36Ar is concentrated in fluid inclusions. The 40Ar/36Ar isotopic ratio in fluid inclusions shows a negative correlation with the total amount of 36Ar released by thermal extraction. Therefore, argon from fluid inclusions is a simple 2-component mixture of air and a crustal component with an 40Ar/36Ar ratio > 6000. It can be shown that diffusion of 40Ar from the matrix into fluid inclusions is negligible.
In contrast to lamproites, whole rock kimberlite samples from Poria Guba and Kandalaksha show clear evidence in helium and, to a certain extentalso in neon isotope ratios, of interaction with a mantle derived fluid phase. Assuming a 20Ne/22Ne ratio of 12.5 for the mantle endmember, a 21Ne/22 Ne ratio of 0.073 ± 0.011 can be calculated. Likewise, the resulting 3He/4He ratio is more strongly influenced by radiogenic helium in comparison to the mean subcontinental mantle (Dunai und Baur, 1995). Such behaviour reflects higher concentrations of uranium and thorium in the magma source of kimberlites than the subcontinental mantle.
Rb-Sr and Sm-Nd age determinations (Belyatskii et al., 1997; Nikitina et al., 1999) yield 1.23 Ga for the lamproite magmatism in Kostamuksha. K-Ar dating of phlogopite and K-feldspar provides similar ages (1.19 Ga). K-Ar dating of a single phlogopite separate from the Kimberlite sample PGK12a from Poria Guba, yields an age of 396 Ma which corresponds well with Rb-Sr and Sm-Nd ages.
Depending on sample age, distinct and partly extensive diffusive loss of helium and neon has occurred, as shown by comparison of measured and calculated concentrations of in situ produced isotopes. Diffusion loss is negligible for argon. This is also strongly supported by primordial noble gas composition.
40
Stock, Alexander T. Verfasser], Ralf [Akademischer Betreuer] [Littke, and Brian [Akademischer Betreuer] Horsfield. "Unconventional oil and gas potential of the Toarcian Posidonia Shale Formation in the crossjunction of Lower Saxony Basin, Pompeckj Block and Gifhorn Trough, Northern Germany: Implications from Organic Petrography, Geochemistry and 3D Numerical Basin Modelling / Alexander T. Stock ; Ralf Littke, Brian Horsfield." Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1161809066/34.
Full text
41
Williams, Leslie Lavinia. "POST-EMPLACEMENT LEACHING BEHAVIORS OF NANO ZERO VALENT IRON MODIFIED WITH CARBOXYMETHYLCELLULOSE UNDER SIMULATED AQUIFER CONDITIONS." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1389376802.
Full text
42
Levy, David J. "Manganese mineralization hosted by the Rocky Gap Sandstone in Bland County, Virginia." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/104304.
Full text
43
Sando, Brett G. "The geology, petrology and geochemistry of the Tommys Gap area in the Giles Creek Synform, MacDonnell Ranges, South-Eastern Arunta Block, Northern Territory /." Adelaide, 1987. http://web4.library.adelaide.edu.au/theses/09SB/09sbs218.pdf.
Full text
44
Mazot, Agnès. "Activité hydrothermale des volcans Kelud et Papandayan (Indonésie) et évaluation des flux de gaz carbonique." Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210971.
Full textAbstract:
Surface manifestations of hydrothermal fluids such as fumaroles and hot springs provide valuable information about the level of activity of a volcano during quiescent period. Geochemical study of gas and spring waters is useful to elaborate geochemical model for magmatic-hydrothermal system. Furthermore, temporal geochemical monitoring of these fluids with time provides a better understanding in processes occurring inside the volcano and can be useful to detect any changes in the activity of the magmatic-hydrothermal system. This thesis investigates two hydrothermal systems at Kelud and Papandayan volcanoes that are located at Java Island in Indonesia. Kelud is considered as one of the most dangerous volcanoes of Java because of its frequent eruptions. After the last eruption that occurred in 1990, a new lake rapidly filled the crater of Kelud volcano. Water samples collected since 1993 are near neutral Na-K chloride fluids and are typical of aged hydrothermal system where the acidity has been completely neutralized by fluid-rock interaction and where the emission of acid magmatic gases has stopped. Two sudden increases in lake temperature in 1996 and 2001 were accompanied by rapid changes in lake water compositions and suggest the existence of two hydrothermal systems feeding the lake: a shallow hydrothermal system dominated by Ca-Mg sulfate waters and a deepest aquifer with neutral alkali chloride waters. From 2001 to 2005, measurements of CO2 emitted by the surface of the lake were performed by using the accumulation chamber method modified in order to work at the surface of a crater lake. Two statistical methods were used to process data: the graphical statistical and stochastic simulation methods. The results of graphical statistical approach showed that two different degassing processes are acting at the lake surface: one corresponding to CO2 fluxes resulting from rising bubbles and the other corresponding to equilibrium diffusion of dissolved CO2 at the water-air surface. Total CO2 emission rate estimated by stochastic simulation ranges from 105 t/day for 2001 to 32 t/day for 2005. Thermal energy released by the lake was also estimated by using an energy balance model with a new constraint using the CO2 flux. The thermal flux decreased from 200 MW (2001) to 100 MW (2002) and then remained stable. Correlation between the chemical data of waters, the fluxes of CO2 and energy show that a constant decrease in the level of activity of the volcano since 1993 occurred although the lake temperature has been stable since 2003. Since the last magmatic eruption that occurred in 1772, phreatic eruptions occur on Papandayan volcano with the last one in 2002. The volcanic material ejected during this eruption is essentially made of altered rocks from within the hydrothermal system. The interaction of acid waters with the host rocks corresponds to an advanced argilic alteration. The chemical compositions of waters from Papandayan volcano and Kelud lake waters are contrasting. Indeed, the spring waters sampled since 1994 are acid sulfate-chloride waters and acid sulfate waters. The chemical and isotopic analyses of gases and waters suggest a significant magmatic contribution in SO2, HCl and HF to the hydrothermal system. The chemical composition of waters sampled after the 2002 eruption have provided information about origin of this eruption. Decrease in chloride concentration and in delta 34S of dissolved sulfates showed that the magmatic contribution in these fluids are less important and that the waters are likely to be formed by the condensation of steam (H2O, H2S) rising from a boiling aquifer.
Doctorat en sciences, Spécialisation géologie
info:eu-repo/semantics/nonPublished
45
Hodges, Sean Patrick. "Petrogenesis of the phonolitic rocks of the Velay oriental, France." Thesis, University of Oxford, 1991. http://ora.ox.ac.uk/objects/uuid:1d8c0fe8-9f9e-4348-9c4c-21174aa56e70.
Full textAbstract:
The Velay oriental (Massif Central, France) is a basaltic plateau with abundant viscous phonolite extrusions. The plateau lavas grade from alkali basalt to mugearite, but intermediate compositions are volumetrically scarce. Pyroclastics are absent. The most complete plateau sections are in the south, while in the north intermediate lavas appear only as viscous, phenocryst-rich extrusions. The plateau lavas were erupted between 11.7Ma and 7.6Ma, the southern phonolites 8.5Ma- 6.5Ma and new data show that the northern phonolites were erupted between 13.3Ma and 10.5Ma. Basement uplift occurred during the plateau-building stage, due to the emplacement of magma chambers. Intermediate lavas are scarce because they remained in the magma chambers due to their density, whereas phonolite was able to rise hydrostatically. The magma chambers were within 5km of the surface. Phonolites are divided into miaskitic and agpaiitic types on the basis of their chemistry and petrography. They evolved from the basalt by crystal settling in the magma chambers, whereas the aphyric plateau lavas evolved by plating crystals onto their conduit walls as they flowed towards the surface. Sr-isotopes show that the basalt-phonolite series is uncontaminated, whereas the northern intermediate lavas evolved by assimilation-fractional-crystallisation. A suite of cumulate nodules was recovered from a pyroclastic unit, which is probably younger than the Velay Miocene lavas. They are related to the northern intermediate lavas, and belong to the "Group II" class of nodules. Geothermobarometry suggests that both the cumulates and the northern intermediate lavas crystallised at a depth of 15-20km and probably became contaminated due to the smaller temperature difference between the geotherm and granite solidus at that depth. The vast majority of the Velay lavas are identical to alkalic ocean-island lavas, geochemically unaffected by their passage through the lithosphere, but with their relative proportions at the surface controlled by the density contrast between the basalt and basement granite.
46
Nonell, Anthony. "Géochimie élémentaire et isotopique du Zn, du Sr et du Pb dans les gaz volcaniques : méthodologies d'échantillonnage et apports à la compréhension des interactions fluides/solides." Phd thesis, Université Paul Sabatier - Toulouse III, 2005. http://tel.archives-ouvertes.fr/tel-00011689.
Full textAbstract:
Ce manuscrit présente les premiers résultats d'études élémentaires et isotopiques du Zn, du Sr et du Pb, réalisées dans les principaux types d'échantillons liés aux gaz volcaniques (gaz, sublimés, eaux thermales, roches), ainsi que deux nouvelles méthodologies d'échantillonnage des émanations volcaniques. Les variations isotopiques du Zn observées au Merapi suggèrent que les processus de changement de phase (fluides/solides) peuvent provoquer des fractionnements isotopiques significatifs des éléments trace métalliques. L'étude couplée Sr/Pb réalisée à Vulcano indique que les compositions en éléments trace métalliques des fumerolles et des eaux thermales sont influencées par les sources naturelles et anthropiques. Ce travail a aussi permis la mise au point de nouvelles méthodologies d'échantillonnage et d'analyse des gaz et des panaches volcaniques, permettant d'accéder à la composition chimique complète de ces manifestations gazeuses de manière simple et efficace.
47
Dixon, Eleanor Tamiko. "Noble gas geochemistry of Icelandic basalts." Phd thesis, 2000. http://hdl.handle.net/1885/148116.
Full text
48
Chuang, Pei-Chuan, and 莊佩涓. "Gas geochemistry study in gas hydrate potential area offshore SW Taiwan." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/eehyha.
Full textAbstract:
碩士國立臺灣大學
地質科學研究所
94
It has been found that Bottom Simulating Reflections (BSRs) widely distribute in offshore southwestern Taiwan which infer the existence of potential gas hydrates underneath the seafloor sediments. Fluids and gases derived from dissociation of gas hydrates which usually enriched in methane concentrations would affect the compositions of sea water and sediments nearby the venting areas. Hence, methane concentrations of sea waters and sediments become useful proxies for exploration of potential gas hydrates in one area. We systematically collected sea waters and cored sediments for dissolved and pore-space gas analysis through eight cruises: ORI-697, ORI-718, ORII-1207, ORII-1230, ORI-732, Marion Dufresne (MD) cruise, ORI-758 and ORI-765 from 2003 to 2005 in this study. Some unusual high methane concentrations can be found in offshore southwestern Taiwan, e.g., sites G23 of ORI-697, N8 of ORI-718, G96 of ORI-732, MD05-2911(G22), MD05-2912(G24), MD052913(G5A) and MD05-2914(73205) of MD cruise, GH10 and GH16 of ORI-758 cruise, sites A, C, D, and H of ORI-765 cruise. The methane concentrations of cored sediments display an increasing trend with depth. Meanwhile, the water column also showed unusual high dissolve methane concentrations at sites A and H of cruise ORI-765. It indicates that gases are venting actively from seafloor in this region. Compiling the available data, high CH4 concentrations are mainly distributed in active margin SW offshore Taiwan; nevertheless, no abnormally high concentrations were found in passive margin so far. In addition, the profiles of methane and sulfate of cored sediments reveal very shallow depths of sulfate methane interface (SMI) at some sites in this study. The linear sulfate gradients, low total organic carbon (TOC) and high methane concentrations imply that sulfate reduction is mainly driven by the process of anaerobic methane oxidation (AMO) in sediments. Thus, the methane fluxes can be determined through the gradients of sulfate reduction and steady state solutions to diffusion equations and show that the methane fluxes are very high, especially at sites G23 of ORI-697 (4.12×10-2 mmol cm-2yr-1) and N8 of ORI-718 (2.11×10-2 mmol cm-2yr-1) in offshore southwestern Taiwan. It indicates that there is a methane-enriched venting source, which may be the product of dissociation of gas hydrates, in this area. Some selected gas samples from ORI-718 (N6； N8； G22); ORI-732 (G96) and MD cruise have also been analyzed for carbon isotopic compositions. The δ13C data of CH4 gases range from -28.3~ -95.0 o/oo and -11.6 ~ -31.6 o/oo for CO2. The carbon isotopic compositions of methane show that organic gas source is dominated at shallower depth, however, some thermogenic gases might be introduced from deeper source in this region.
49
Gonzalez, Angela M. "Nitrogen-specific gas chromatographic detection by atomic plasma spectral emission. Analytical gas chromatography-mass spectrometry studies of subsurface biomarkers." 1999. https://scholarworks.umass.edu/dissertations/AAI9932315.
Full textAbstract:
Analysis of nitrogen containing compounds by gas chromatography with atomic emission detection has always been problematic. Nitrogen detection has been customarily done using the 174.53 and 174.27 nm atomic lines, with very limited selectivity and sensitivity. Nitrogen can also be detected using the cyanogen (CN) molecular emission bands at 388 nm. It has been reported that a 100-fold improvement in the selectivity using this line can be reached. Therefore, in the present work, the instrument available in the laboratory was modified to allow the use of the 388 nm line for the nitrogen detection. The modification of the instrument involved the use of a mixture of reagent gases that were optimized to produce the best nitrogen emission using the 388 nm line. Figures of merit of the detection using this line, were evaluated and compared with the commonly used nitrogen line (174 nm) and the carbon detection (193 nm). The dependence of the GC-AED response with the molecular structure of the analyte, and its application in the determination of empirical formula was also evaluated, and its application for analysis of petroleum products. The second part of the present work studied the biomarkers in deep subsurface samples and their relationship with the microbial activity. Little is known of microbial community characteristics at depths larger than 50 m below surface, information that is crucial for the clean up of contaminated underground environments. The use of classical approaches to identify microbiota, often results in the characterization of less than 10% of the biota present when analyzing deep subsurface samples, therefore, the analysis of lipid content in the samples have been proposed. Microorganisms use lipids as constituent of their cell walls or as nutritional sources. Monitoring lipids can be used to develop a picture of how, when, where and under which conditions microbes are active in the subsurface. This research was focussed in the biomarker study of a shale and sandstone from Cerro Negro, New Mexico. Biomarkers were determined to study distribution, concentration and availability of resources that support life and microbial activity and their relationship with geochemical parameters.
50
Bhatnagar, Gaurav. "Accumulation of gas hydrates in marine sediments." Thesis, 2008. http://hdl.handle.net/1911/22258.
Full textAbstract:
Generalized numerical models for simulating gas hydrate and free gas accumulation in marine sediments have been developed. These models include several physical processes such as phase equilibrium of gas hydrates, multiphase fluid flow in porous media, biogenic methane production, and sedimentation-compaction of sediments over geologic timescales. Non-dimensionalization of the models lead to the emergence of important dimensionless groups controlling these dynamic systems, such as the Peclet number, Damkohler number, and a sedimentation-compaction group that compares permeability to sedimentation rate. Exploring the entire parameter space of these dimensionless groups helps in delineating different modes of gas hydrate and free gas occurrence, e.g., no hydrate and hydrate with or without underlying free gas. Scaling schemes developed for these systems help in summarizing average gas hydrate saturation for hundreds of simulation results into two simple contour plots. The utility of these contour plots in predicting average hydrate saturation is shown through application to different geologic settings.
The depth to the sulfate-methane transition (SMT) is also developed as an independent proxy for gas hydrate saturation for deep-source systems. It is shown through numerical modeling that scaled depth to the SMT correlates with the average gas hydrate flux through the gas hydrate stability zone (GHSZ). Later, analytical theory is developed for calculating steady-state concentration profiles as well as the complete gas hydrate saturation profile from the SMT depth. Application of this theory to several sites along Cascadia Margin indicates that SMT depth can be used as a fast and inexpensive proxy to get a first-order estimate of gas hydrate saturation, compared to expensive deep-drilling methods.
The effect of overpressure development in low permeability gas hydrate systems is shown to have an important effect on gas hydrate and free gas saturations. Specifically, overpressure development decreases the net amount of gas hydrate and free gas in the system, in addition to extending the base of the hydrate stability zone below the seafloor by a relatively small depth. We also study the role of upward free gas migration in producing long, connected free gas columns beneath the gas hydrate layer. Finally, two-dimensional models are developed to study the effect of heterogeneities on gas hydrate and free gas distribution. Simulation results show that hydrate as well as free gas accumulates in relatively high saturations within these high permeability sediments, such as faults/fracture networks, dipping sand layers, and combinations of both, due to focused fluid flow.