Dissertations / Theses: 'Stable isotopes geochemistry'

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Valdes, Maria. "Geochemistry and Cosmochemistry of Calcium Stable Isotopes." Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/276866.

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Calcium (Ca) is the fifth most abundant element in the rocky planets. As a lithophile, refractory element, Ca does not partition into planetary cores nor is it volatilized during planetary accretion. These characteristics make Ca ideal for investigating the earliest stages of planetary formation and the subsequent chemical evolution of planetary mantles and crusts. This thesis presents observations of and explores the mechanisms involved in high-temperature mass-dependent Ca isotope fractionation in terrestrial, lunar, and meteoritic material. Chapter 1 reports Ca isotope fractionation among a co-genetic suite of samples from the Guelb el Azib ultramafic-mafic-anorthosite complex, which represents the fractional crystallization sequence of a terrestrial igneous magma chamber. The measurements imply that Ca isotope fractionation in an evolving crystallizing magma is mineralogically controlled and that the degree of fractionation can vary according to the Ca composition of the residual magma. Chapter 2 investigates ureilites, a distinctive group of achondritic meteorites, widely regarded to be mantle remnants of a disrupted asteroidal parent body. To date, it is not clear which of their features were inherited from the original chondritic body and which were created during post-accretionary igneous processes such as partial melting. This chapter presents evidence that partial melting on the ureilite parent body is responsible for two such ambiguous characteristics, Ca isotopic and magnesium number (Mg
Doctorat en Sciences
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Gilmour, Iain. "The distribution of carbon stable isotopes within sedimentary organic matter." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373660.

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Morisset, Natalie Carleton University Dissertation Geology. "Stableisotope and radioisotope geochemistry of the Panda Hill carbonatite, Tanzania." Ottawa, 1992.

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Engström, Emma. "Fractionation of the stable silicon isotopes : analytical method developments and selected applications in geochemistry." Licentiate thesis, Luleå tekniska universitet, Geovetenskap och miljöteknik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18719.

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During the last few decades, variations in the 'natural' isotopic abundances of stable elements (termed 'fractionation') have received considerable interest from the scientific community. Though analytical methods and techniques for the measurement of isotopic abundances with adequate figures of merit have been available for light elements (e.g. B, C, N and O) for some time, and the wealth of data produced has secured maturity status for such applications, relatively modest progress in fractionation studies devoted to high-mass elements has been made until recently, mainly because of constraints of the available analytical techniques. The situation has changed drastically with the advent of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), with the number of reports about natural fractionation of Fe, Cu, Zn, Mo, Cd, Sn increasing exponentially during the recent years. In spite of the high Si abundance in nature and the importance of the element in many areas of the Earth sciences (focusing on e.g. weathering, the global Si cycle, paleoclimate studies, paleoceanography, and biological uptake), the available information on Si isotope fractionation remains rather limited due to the laborious and hazardous chemical purification procedures associated with the analyses. The focus of this thesis was the development of analytical methods for the precise and accurate measurements of Si isotope ratios, which is an absolute requirement for meaningful fractionation studies, in various matrices. This work involved detailed studies on sample preparation (including matrix separation) and refining the measurement protocol by using high resolution MC-ICP-MS. In the former stages, quantitative analyte recovery, thorough control of contamination levels and purification efficiency were the major targets, while severe spectral interferences and the need for adequate instrumental mass bias corrections challenged the latter. The performance of the method was tested in the first inter- laboratory performance assessment study of its kind with good results. As limited examples of applications, studies on Si isotope fractionation in aqueous, plant and humus samples were performed utilizing methods developed. The efficient analyte separation, high-resolution capability of the instrument, quantitative Si recovery and accurate mass bias correction using Mg as internal standard, allowed the determination of the Si isotopic composition of natural waters and biological samples with long-term reproducibility, expressed as twice the standard deviation (2σ), equal to or less than 0.10‰ for δ29Si and 0.25‰ for δ30Si. Furthermore, the presence of a challenging spectral interference on 29Si originating from 28SiH+ was revealed during this study, indicating that instrumental resolution in excess of 3500 is required for interference-free Si isotopic analyses. However, despite complete removal of N-, O-, and C-containing interferences appearing on the high-mass side of the Si isotopes, it was found that exact matching of both the acid matrix and the Si concentration are mandatory due to tailing from the abundant 14N16O+ interference on 30Si. This thesis also includes results from the first study of the Si isotopic homogeneity of major biomass components from a defined area in Northern Sweden covered by boreal forest. Since the potential impact of vegetation on the terrestrial biogeochemical cycle has attracted considerable interest, thorough characterization of the Si isotopic composition of the biomass potentially allows the utilization of this isotope system in the assessment of the relative contributions of biogenic and mineral silica in plants, soil solutions and natural waters (including fresh-, brackish- and marine waters). Isotopic analyses of the biological materials yielded a surprisingly homogenous silicon isotopic composition (relative to the NBS28 Si reference material), expressed as δ29Si (2σ), ranging from (- 0.14 ± 0.05)‰ to (0.13 ± 0.04)‰ Furthermore, elemental and isotopic analysis of local airborne particulate matter suggests that vegetation also accumulates silica via incorporation of exogenous Si containing primary and secondary minerals (in addition to root uptake of non-ionic silicic acid), a fact that has been neglected in previously published studies. This strongly indicates that the presence of potential surface contributions must be considered during in situ silicon uptake studies

Godkänd; 2007; 20071011 (ysko)

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Kelly, Jennifer Christine. "The fluid evolution of the Mount Mica and Irish Pit pegmatites, Maine| Evidence from stable isotopes." California State University, Long Beach, 2013.

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Negonga, Lisias. "Geochemistry, stable isotopes and fluid inclusion studies of the Otjikoto gold deposit, Central Namibia." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29190.

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The Otjikoto gold deposit is located within the Damara Orogenic Belt which is part of the system of Pan-African mobile belts. The Damara Belt is a northwest trending orogenic belt which formed through sequences of spreading, rifting, subduction and from continental collision between the Congo, Kalahari and Rio Delta Plata Cratons between 900 Ma and 450 Ma. Mineralisation at Otjikoto is hosted by a group of metamorphic rocks which consist of biotite schists from the Okonguarri Formation, albitites from the Oberwasser member and marble units from the Okawayo member. The gold mineralization occurs in a sheeted vein network system with veins which are positioned parallel towards the foliation of the albitites and hornfels of the Oberwasser Member. The vein types include both quartz and carbonate hosted vein types. The vein mineralogy includes magnetite, pyrite and pyrrhotite which are associated with amphibole, quartz, almandine garnets, and free gold. A fluid inclusion study carried out on the vein quartz showed the co-existence of the aqueous, carbonic and aqueouscarbonic fluid inclusions within the Okonguarri Formation. The aqueous inclusions have moderate to high salinities with salinities ranging from 30.0 to 44.5 wt. % NaCl eq. in aqueous inclusions with halite crystals and from 0.9 to 22.9 wt. % NaCl eq. in inclusions without halite crystals. The total homogenisation temperatures, Th tot (L), ranged from 151 to 488 °C in the aqueous-carbonic inclusions and from 156 to 444 °C in the aqueous inclusions. The melting temperature of CO2 (TmCO2) ranged from -60.3 to -57.5 °C in carbonic inclusions and from - 60.2 to -57.2 °C in aqueous-carbonic inclusions. It is proposed that the aqueous and carbonic inclusions (CO2-CH4) from the Okonguarri Formation are the end members of fluid immiscibility. The presence of CO2 and CH4 is indicated by the low TmCO2 values and may be justified by the decomposition of the carbonaceous metasediments which are found in the stratigraphy at Otjikoto. The δ 18O values range from of 8.35 ‰ to 8.75 ‰ for the magnetite and 17.51 ‰ to 18.47 ‰ for the vein quartz samples. Analysis of the microprobe data on the amphiboles shows that the analysed grains are made up of anthophyllites. Microprobe data of the chlorites showed that the majority of the chlorites are made up of ripidolites. Temperatures of chlorite formation were calculated to be in the range of 221°C to 358 °C by using chlorite geothermometric equations. Major element variation diagrams show a strong negative correlation of TiO2, Al2O3, MgO, Na2O and FeOt vs SiO2. Variation diagrams were also plotted for the trace elements vs Zr. The Sr, Y, La and Ce vs Zr plots show a strong positive correlation.

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Gall, Louise. "Development and application of nickel stable isotopes as a new geochemical tracer." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:ebe3c3e1-0b1b-49ed-b64a-016c8d76f220.

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In this thesis, I have developed a new methodology for the accurate determination of mass-dependent variations in nickel (Ni) isotope compositions. Nickel is initially separated in a three-column ion-exchange procedure, and the purified solutions are analysed by multi-collector inductively coupled plasma mass spectrometry (MCICPMS) using a double-spike technique. Using this methodology, I have measured the first Ni isotope ratios for a wide variety of natural geological samples. Significant Ni isotope variations were observed, with an overall spread in delta 60Ni-values of -0.9 to 2.5 permil. In igneous rocks Ni isotopes appear to be largely homogeneous, with only small variations (0.2 permil) between different rock types. Weathering of silicate rocks does on the other hand appear to cause significant fractionation of Ni isotopes, probably producing an isotopically heavy riverine input to the ocean. A heavy isotope signature is also visible in hydrogenetic ferromanganese crusts, with surface scrapings from globally distributed crusts show an average delta 60Ni-value of 1.65 permil. However, the variation in these samples is over 1.5 permil, likely reflecting local sources or biological processes, or alternatively indicating a heterogeneous Ni isotopic composition of the ocean. Organic-rich sediments also show heavy isotopic compositions, which are possibly transferred to the crude oils originating in these types of sediments. The only significant reservoir of light Ni isotopes found during this project are sulphides from magmatic systems. Overall, this thesis demonstrates the potential of this system as a powerful new tracer for a variety of geochemical processes.

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Brown, Elizabeth Ann. "Taxonomy and Geochemistry of the Globigerinoides ruber-elongatus Plexus, with Paleontological Implications." Scholar Commons, 2011. https://scholarcommons.usf.edu/etd/7479.

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The reliability of foraminifera as stratigraphic index fossils, and as isotopic proxies of marine environments, is based on the assumption that the fossil concepts represent uniform species, responding consistently to their ambient environments. Understanding sources of uncertainty is, therefore, critical. In this dissertation, I explore a potential bias in the application of planktonic foraminifera utilized extensively for Cenozoic paleo-reconstruction and, to a lesser extent, biostratigraphy: the Globigerinoides ruber-elongatus plexus (‘plexus’ meaning a complex network of interconnected members). Taxonomic revisions since 1826 have resulted in the merging of multiple Globigerinoides species names under one general designation (“Globigerinoides ruber”), the implications of which are now under scrutiny. These “morphotypes” of G. ruber have been shown to incorporate stable isotopes and trace elements in seawater dissimilarly, and correspond to multiple genetic species, some of which occupy different environments. Various criteria exist to sub-divide, group, or distinguish members of the Globigerinoides plexus, most notably the recurring use of Globigerinoides elongatus as a less spherical, less symmetrical counterpart to G. ruber. But the efficacy of these various taxonomic criteria has not been tested quantitatively. Most rely on the traits of visually distinctive “end-members,” while specimens in the morphological “transitional zone” are left to an observer’s subjective interpretation. This prevents quantification in census counts, and may lead to erroneous geochemical analyses. Furthermore, molecular clock estimates suggest that the G. elongatus species evolved significantly later than G. ruber, affecting its potential as a biomarker. In this dissertation, I examine the potential of a minimal-criteria system for classifying Globigerinoides-type morphologies using only three conditions: final chamber compression, final chamber asymmetry, and aperture compression. Morphometric analyses on specimens grouped according to this new system allow us to assess to what degree visual classification reflects morphospace discontinuity. Armed with this information, I then explore potential isotopic offsets between members of the Globigerinoides plexus, and its use in reconstructing regional differences in climate or habitat influences in the Gulf of Mexico and Caribbean basins. Finally, having shown that G. ruber and G. elongatus can be reliably visually distinguished, I tracked the species’ fossil presence individually in a deep core from the South China Sea, and confirmed the presence of G. ruber in the South China Sea through the late Miocene, and G. elongatus through the Pleistocene. While it is believed that neither species was traced to its true first occurrence (FO), the relative FO of G. ruber was shown to be 4–5 Ma before G. elongatus

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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.

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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.

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Freimuth, Erika Jacob. "Advancing Leaf Wax Paleohydrology: From Plant Source to Sediment Sink." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535381306803793.

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Engström, Emma. "Fractionation of the stable silicon isotopes studied using MC-ICP-MS : analytical method developments and applications in geochemistry /." Luleå : Department of Chemical Engineering and Geosciences, Division of Geosciences, Luleå University of Technology, 2009. http://pure.ltu.se/ws/fbspretrieve/3522867.

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Diaz, Melisa A. "Geochemistry of soils from the Shackleton Glacier region, Antarctica, and implications for glacial history, salt dynamics, and biogeography." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595542667761355.

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Sutcliffe, Nadine C. "Strontium stable isotope behaviour accompanying melting and magmatism in the Earth-Moon system." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:826ae843-3115-4a3e-975a-f6306f923d4e.

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This thesis concerns the application of a new technique for measuring the stable isotopes of Sr, specifically pertaining to mass dependent fractionation in high temperature processes on the Earth and Moon. Processes such as mantle melting and differentiation on Earth and the formation of the Lunar Magma Ocean are investigated by the application of a double-spike TIMS method to terrestrial and lunar material to obtain high-precision ⁸⁷Sr/⁸⁶Sr, ⁸⁸Sr/⁸⁶Sr and ⁸⁴Sr/⁸⁶Sr data. Measurements of mantle-derived mafic material provide insights into the ⁸⁸Sr/⁸⁶Sr composition of the silicate mantle. Ocean Island Basalts possess restricted δ⁸⁸Sr compositions, whilst Mid-Ocean Ridge Basalts from the Pacific, Atlantic and Indian ridges reveal variations in δ⁸⁸Sr, the majority of which is seen within the FAMOUS section of the Mid-Atlantic Ridge. These variations are attributed partly due to the effects of plagioclase crystallisation and partly due to mantle source heterogeneity. Analyses of mineral separates from three different igneous systems provide an understanding of δ⁸⁸Sr fractionation at a mineral-scale. The possibility of δ⁸⁸Sr fractionation as a result of magmatic differentiation has also been assessed, and found to occur between the basalt and rhyolitic end-members of the Icelandic Hekla suite. Variations in the ⁸⁷Sr/⁸⁶Sr ratios of these rocks are also found, and considered most likely to be due to contamination. Analyses of lunar rocks indicate that the highland suite appears to be relatively uniform in δ⁸⁸Sr, whilst significant fractionation to light δ⁸⁸Sr compositions occurs in the mare basalts. Such variations are thought to be associated with the crystallisation of plagioclase during the differentiation of the lunar magma ocean. Lastly, precise ⁸⁷Rb/⁸⁶Sr and ⁸⁷Sr/⁸⁶Sr data yield a model age for the Moon of 4.523 ± 0.019 Ga.

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Stevenson, Emily Isabel. "Stable strontium isotope fractionation in marine and terrestrial environments." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:a2d97fc7-3e9d-484a-8026-11c118fcc3fd.

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The work reported in this thesis applies a new isotope tracer, stable strontium isotopes (δ^88/86Sr), to address questions concerning changes in global climate that occur in response to continental weathering processes, and to constrain the modern marine geochemical Sr cycle. Stable Sr isotopes are a relatively new geochemical proxy, and as such their behavior needs to be understood in differing forms of marine calcium carbonate, the archives from which records of past stable Sr variability in the oceans can be constructed. Foraminifera, coccoliths and corals (both aragonite and high Mg calcite) acquire δ^88/86Sr values lighter than that of modern day seawater, (approximately 0.11, 0.05, 0.2 and 0.19 ‰ lighter than seawater at ~25°C respectively) providing a measureable offset which can be used to constrain the modern Sr outputs from the ocean and provide a better understanding of the modern Sr cycle. Using foraminifera as a sedimentary archive the first marine δ^88/86Sr record of seawater over the last two glacial cycles has been constructed, and used to investigate changing carbonate input and output over this 145 kyr period. Modelling of the large excursion of δ^88/86Sr to heavier values during Marine Isotope Stage (MIS) 3, reveals that this is more likely to be due to local changes in seawater or post-depositional alteration, rather then whole ocean changes. In the terrestrial environment δδ88/86^Sr has been measured in the dissolved load of rivers from the Himalaya. It is found that, in general, rivers draining carbonate catchments possess lighter isotopic δ^88/86Sr values than those from rivers draining silicates. Covariations of either δ88/86Sr vs. δ30Si or δ^88/86Sr vs. 1/[Sr] can be used to distinguish between rivers draining different catchment areas.

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Faure-Brac, Mathieu. "Effects of thermophysiology on the evolution of Pseudosuchia (Archosauria) : contributions of paleohistology and isotopic geochemistry using phylogenetic comparative methods." Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS233.

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Il est aujourd’hui communément admis que les archosaures sont ancestralement endothermes, soit qu’ils présentent des mécanismes de thermogenèse non frissonnante. Parmi les archosaures, les crocodiliens actuels sont pourtant des ectothermes, mais présentent des caractéristiques anatomiques et moléculaires traditionnellement associées à l’endothermie : un cœur à quatre cavité ; plusieurs acquisitions liées à une respiration efficace, comme un muscle diaphragmatique et un flux d’air unidirectionnel ; la formation de tissus osseux liés à des taux de croissance élevés ; un taux d’évolution mitochondrial important. Des études sur des pseudosuchiens éteints ont conclus que la plupart des espèces du Trias étaient endothermes. La perte de l’endothermie au sein du clade doit cependant toujours être définie. Durant cette thèse, j’ai utilisé la géochimie des isotopes stables et l’ostéohistologie quantitative pour inférer la température corporelle et le taux métabolique au repos, deux proxies de l’endothermie, de plusieurs métasuchiens. J’ai conclus que le clade Metasuchia était ancestralement ectotherme et, à l’aide d’une reconstruction ancestrale des caractères, que l’endothermie a probablement été perdue au nœud Crocodylomorpha. J’en déduit l’hypothèse suivante : l’endothermie des pseudosuchiens était probablement à un stade plus primitif que celle des dinosaures. Contrairement à ces derniers, les pseudosuchiens endothermes n’ont pu survivre à l’extinction de masse de la fin du Trias, ne laissant pour seul survivant que les crocodylomorphes ectothermes
It is today well established that archosaurs are ancestrally endotherms, i.e., they present mechanisms of non shivering thermogenesis. Among archosaurs, extant crocodilians are ectothermic but present particular anatomical and molecular features traditionally associated with endothermy: a fourc hambered heart; several acquisitions linked to an efficient breath such as a diaphragmatic muscle and unidirectional airflow; the deposition of high growth rate bone tissues; a high mitochondrial rate of evolution. Studies on extinct pseudosuchians suggested that most of the Triassic species were endothermic, but the timing of the loss o fendothermy in Pseudosuchia still has to be constrained both temporally and phylogenetically.In this thesis, I use stable isotopic geochemistry and quantitative osteohistology to infer the body temperature and the resting metabolic rate, to proxies to infer endothermy, of several metasuchians. I concluded that metasuchians are primitively ectothermic, and inferred the loss of endothermy at the node Crocodylomorpha using ancestral state reconstruction. I hypothesize pseudosuchian’s endothermy was in a more primitive state than dinosaurs’ and that they were not able to survive the end Triassic mass extinction. The only surviving pseudosuchians were then ectothermic crocodylomorphs, leading to extant species

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Katz, David Allen. "Early and Late Diagenetic Processes of Mississippian Carbonates, Northern U.S. Rockies." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_dissertations/154.

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Integrated sequence stratigraphy and geochemistry has significantly improved our knowledge of the formation and distribution of early and late diagenetic products in North American Mississippian carbonates. Deposition of the Madison Limestone occurred in concert with a major perturbation to the global C-pool, the timing of which was constrained by comparing secular variations in the delta13C values from the Madison Limestone with limited biostratigraphy. These early constraints were then improved by peak matching of 87Sr/86Sr values from this study with European brachiopod 87Sr/86Sr. The secular variations in the delta13C values were then applied as a chronostratigraphic tool to outcrops and subsurface core. As a result, our sequence stratigraphic interpretations and knowledge regarding lateral facies variability in carbonate rocks is significantly improved. Geographic variability in the magnitude of the delta13C values is also documented along the dip-transects which suggests that marine waters experienced increasing restriction in a landward direction. These results show how local changes to the C-pool are controlled by the morphology of the depositional system which can significantly affect the original signal of the global carbon pool. The geographic variability in the delta13C and delta18O values from reservoir quality dolomites along the mid-to-upper Madison ramp suggest they also precipitated from a restricted water mass with increased salinity, temperature and alkalinity which in turn, were responsible for the distribution of massive quantities of strataform dolomite deposited during the continental transgression at the beginning of the Mississippian. Trace element and 87Sr/86Sr values from strataform dolomite suggest initial formation from Mississippian seawater and slight resetting during shallow burial diagenesis. Petrography indicates that the formation of this dolomite ceased in the shallow burial environment, between the Mississippian and Permian. These dolomites are cross-cut by comparatively small volumes of geothermal-hydrothermal dolomite associated with Laramide-age breccias and fractures. Tectonic-hydrothermal activity associated with the Laramide Orogeny was responsible for late stage calcite cemented fractures and breccias which cross-cut all carbonate rocks discussed in this thesis. Radiogenic 87Sr/86Sr, depleted delta18O and enriched delta13C values and the hottest fluid inclusions measured in this study suggest the late stage calcite formed in the hydrothermal environment and under the most open-system and water-dominated conditions. Tectonic-diagenesis is ultimately responsible for establishing vertical barriers in the otherwise porous and permeable strataform dolomites.

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Armytage, Rosalind M. G. "The silicon isotopic composition of inner Solar System materials." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:9034aab2-aadd-4dcb-b3e3-64d4d7c2f029.

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This study uses high precision silicon isotopic measurements to understand events that occurred during the earliest stages of formation of the terrestrial planets. The isotopic compositions of diverse materials such as chondrites, lunar rocks and asteroidal basalts can shed light on the homogeneity of the solar nebula, metal-silicate differentiation on planetary bodies, and terrestrial moon formation. Limited variation in the Si isotopic composition of meteorites is evidence for a relatively homogeneous inner solar system with respect to silicon isotopes. The Si isotopic composition of bulk silicate Earth (BSE) is, however, heavier than meteorites. This points to an event unique to Earth that fractionated Si isotopes, such as core formation at terrestrial conditions. The Δ³⁰Si_{BSE-meteorite} value from this study indicates that the Earth’s core contains 8.7 (+8.1/−6.2) wt% Si. No systematic δ³⁰Si differences were found between any of the lunar lithologies analysed, implying a Si isotopic homogeneity of the sampled lunar source regions. The lunar average, δ³⁰Si = −0.29±0.08permil (2σ_SD), is identical to the recent value of Savage et al. (2010) for BSE of δ³⁰Si = −0.29 ± 0.08permil (2σ_SD). The best explanation of the data is that Si isotopes must have homogenised in the aftermath of the Moon-forming impact with no subsequent fractionation in the proto-lunar disk. The Si isotopic composition of olivine within lunar basalts was found to be the same or heavier than δ³⁰Si(pyroxene). This is not consistent with terrestrial data where δ³⁰Si(pyroxene) is always lighter than δ³⁰Si(olivine). Crystallisation history cannot explain the data, and the slow diffusion rates of Si rule out cooling rates as a cause. Therefore, it appears that inter-mineral fractionation of Si isotopes occurs differently on the Moon. The δ³⁰Si of chondrules picked from Allende spanned a range of ~0.6permil, a factor of two greater than the bulk meteorite range. There is no evidence for the variable δ30Si of the chondrules being the result of post-formation alteration and there is no convincing evidence for precursor heterogeneity being the primary cause. It is likely that Si isotopic composition of chondrules is the result of evaporation and reequilibration with the evaporated phase.

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Rosenberg, Angela D. "Insight from the Depths of the Straits of Florida: Assessing the Utility of Atlantic Deep-water Coral Geochemical Proxy Techniques." Scholarly Repository, 2011. http://scholarlyrepository.miami.edu/oa_theses/244.

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This thesis addresses the utility of deep-water coral geochemistry and its potential to reconstruct oceanographic conditions in the Straits of Florida. Through stable isotope and elemental analyses of the carbonate skeletons and use of available geochemical proxy calibration equations, present and past environmental parameters were determined. Over the last several years, scientific expeditions to the bottom of the Straits of Florida have revealed hundreds of deep-water coral mounds and led to the collection of extensive oceanographic data, sediment samples, and deep-water coral specimens. In 2005-2006, an Autonomous Underwater Vehicle (AUV) was used to map the coral mound fields at five sites with the use of geophysical imaging technology, and the manned Johnson-Sea-Link II submersible was deployed for further exploration and sample collection. The AUV and the submersible CTD also measured numerous environmental parameters, including temperature and salinity. With the goal of reconstructing environmental parameters across the Straits of Florida, Scleractinian and gorgonian deep-water coral specimens were selected from three sites spanning the Straits. Each coral was sampled at the highest resolution possible and analyzed for stable isotopes and elemental concentrations. Resulting geochemical data, specifically d18O, d13C, Sr/Ca, and Mg/Ca, was then used with previously published and newly developed calibration equations to calculate temperature, salinity, and seawater density. Kinetic and vital effects were also examined and taken into account while reconstructing environmental parameters using the coral geochemistry. Additional reconstructions using stable isotopic values from benthic foraminifera corroborated the geochemical reconstructions, and analyses of pteropods and surface sediment samples provided further insight into the oceanographic conditions at the bottom of the Straits of Florida. Results from geochemical reconstructions agreed with in situ data, indicating that slightly warmer bottom temperatures exist on the eastern side of the Straits and salinity variability among the three sites is minimal. This suggests that the deep-water coral skeletons are sensitive recorders of the environmental conditions in which they lived. Ultimately, in situ measurements and reconstructed parameters showed that there is little variability across the bottom of the Straits and that Antarctic Intermediate Water (AAIW) is the only apparent water mass in the area at that depth. Moreover, comparison of the coral habitat from this study with others from around the world demonstrated that certain conditions are required for deep-water coral growth, and that these same parameters are common to deep-water reef systems throughout the globe. Further sampling and geochemical analyses of deep-water corals in the region may be used to gain additional insight into the oceanographic conditions surrounding the coral mounds both presently and in the past. As with other previously studied deep-water coral systems, this highlights the potential for the reconstruction of paleo environmental records from deep-water corals in the Straits of Florida.

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Deegan, Frances M. "Processes of Magma-crust Interaction : Insights from Geochemistry and Experimental Petrology." Doctoral thesis, Uppsala universitet, Berggrundsgeologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-132702.

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This work focuses on crustal interaction in magmatic systems, drawing on experimental petrology and elemental and isotope geochemistry. Various magma-chamber processes such as magma-mixing, fractional crystallisation and magma-crust interaction are explored throughout the papers comprising the thesis. Emphasis is placed on gaining insights into the extent of crustal contamination in ocean island magmas from the Canary Islands and the processes of magma-crust interaction observed both in nature and in experiments. This research underscores that the compositions of ocean island magmas, even primitive types which are classically used as probes of the mantle, are susceptible to modification by crustal contamination. The principal mechanisms of contamination identified from work on both Tenerife and Gran Canaria (Canary Islands) are assimilation and partial melting of the pre-existing island edifice and intercalated sediments by newly arriving magma (i.e. “island recycling”). The information that we can gain from studying solidified magma and entrained crustal xenoliths concerning the rates and mechanisms of crustal assimilation is, however, limited. To address this shortcoming, a series of time-variable crustal carbonate assimilation experiments were carried out at magmatic pressure and temperature using natural materials from Merapi volcano, Indonesia. A temporally constrained reaction series of carbonate assimilation in magma has hence been constructed. The experiments were analysed using in-situ techniques to observe the progressive textural, elemental, and isotopic evolution of magma-carbonate interaction. Crucially, carbonate assimilation was found to liberate voluminous crustally-derived CO2 on a timescale of only seconds to minutes in the experiments. This points to the role of rapid crustal degassing in volcanic volatile budgets, and, pertinently, in magnifying hazardous volcanic behaviour. This thesis, therefore, delivers detailed insights into the processes of magma-crust interaction from experiments and geochemistry. The outcomes confirm that crustal processes are significant factors in both, i) ocean island magma genesis, and ii) magma differentiation towards compositions with greater explosive potential which can, in turn, manifest as hazardous volcanism.
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 707

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20

Frogley, Michael Reginald. "The biostratigraphy, palaeoecology and geochemistry of a long lacustrine sequence from NW Greece." Thesis, University of Cambridge, 1998. https://www.repository.cam.ac.uk/handle/1810/244307.

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Examination of an important new 319m core of lake sediment recovered from Ioannina in NW Greece has attempted to relate changes in the lake to variations in the regional climate of south-central Europe over the last 600,000 years. The site is known to have been extremely sensitive to past climatic change for three reasons: (i) temperate vegetation persisted throughout glacial stages (albeit at low frequencies), so the vegetational response to climatic change would therefore have been almost immediate; (ii) the extreme thickness of the sediments suggests that accumulation rates were high (at times, > 1m per thousand years), which has enabled high-resolution palaeoclimatic reconstructions; and (iii) precipitation of authigenic carbonate has preserved a remarkably sensitive proxy record of productivity variations for most of the lake's history. Well-defined shifts from glacial - interglacial mode have been correlated with vegetational changes identified in a core previously analysed from the same basin (using magnetic susceptibility profiles), enabling tentative correlations to be suggested with other European terrestrial sequences and with the marine oxygen isotope record, back to marine isotope stage 16. Twelve AMS radiocarbon determinations from the upper part of the core, together with the identification of a series of reversed palaeomagnetic events within the Brunhes chron, support the proposed age model for the sequence. The sediments at Ioannina, unlike most of the other long terrestrial European sequences, are calcareous and contain mollusc and ostracod assemblages. Part of this project has involved a comprehensive review of Quaternary and modem aquatic faunas from the lake, as well as the description, illustration and critical assessment of several poorly-known endemic taxa. Faunal assemblage data have been used to provide valuable information concerning the variable response of lake-level to climatic change over time. Convincing new mollusc an evidence indicates low lake-levels at the Last Glacial Maximum, agreeing with regional pollen data, but conflicting with geomorphological evidence derived from Kastritsa, a well-documented nearby Palaeolithic cave site. It is suggested that this discrepancy may be a result of subsequent tectonic uplift of the rockshelter. In addition, stable isotopic analyses of both the ostracods and the bulk carbonate within the sediments have contributed towards deriving a comprehensive palaeoenvironmental history for the site. Although the study analysed physical, biological and geochemical aspects of the entire core, two distinct parts of the record were selected for more detailed investigation. High-resolution analysis over the last interglacial (the Eemian) has revealed evidence for a clear, two-step deglaciation at the beginning of the period, known from elsewhere as the Zeifen-Kattegat Oscillation. Climatic instability has also been detected within the full interglacial. Comparisons are drawn with a range of other Eemian records from across Europe, as well as the Greenland ice cores. High-resolution analysis of the period from the end of the last glacial to the present day has also revealed evidence for climatic instability. A cool and arid oscillation is demonstrated by several climatic proxies that may constitute the first recognition of the Younger Dryas stadial from Greece. A shorter, but more subdued cooling event has also been detected during the first half of the Holocene, which may correspond with a widespread climatic oscillation from high-resolution terrestrial, marine and ice core records that has been dated to between 7,500 and 8,000 years BP.

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21

Brown, Bryce Matthew. "Ancient Maya Agricultural Resources in the Rio Amarillo Valley near Copán, Honduras." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6121.

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The purpose of this study was to use soil physical and chemical analyses to better understand the ancient agricultural landscape around the ancient Maya cities of Rio Amarillo and Piedras Negras, two tributary sites to Copan, Honduras. Our primary objective was to determine whether a mass erosion event around 800 A.D. occurred which could have caused crop failure and famine or if stable soil conditions persisted during the collapse of these city-states. Stable carbon isotope analysis of the humin fraction of the soils showed that much of this valley was used anciently for agriculture, including hillslopes and hilltops; however, there is no evidence of mass erosion in the soil profiles. Soil horizon development and texture is consistent with stable soil conditions in this area. The demise of these city-states was likely caused by a variety of factors including warfare and political unrest, and not solely by environmental degradation as postulated in previous studies of the valley.

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22

Ulmer, Austin Michael. "Indications of Ancient Maya Soil Resource Management in Northern Belize." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5603.

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The objective of this study was to use soil chemical properties, particularly carbon isotopes to describe the agricultural landscape in the Blue Creek region on the Rio Bravo Escarpment in northwestern Belize. The primary question associated with this study focused on the comparative agricultural potential of the soils between the upland karst environment and the lowland coastal plains using the distribution and frequency of ancient Maya maize production. Soil physical features, such as clay concentrations throughout profiles in conjunction with soil chemical properties were used to aid in determining the level of ancient maize production. Isotopic evidence suggests that anciently, lowland soils were used for maize production more so than upland soils. In addition, profiles at Crocodile Lake indicate the potential for transport of soil δ13C signatures as a result of mass movement events.

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Widanagamage, Inoka Hasanthi. "STABLE STRONTIUM ISOTOPE FRACTIONATION IN ABIOTIC AND MICROBIALLY MEDIATED BARITE IN MODERN CONTINENTAL SETTINGS." Kent State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=kent1445344122.

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24

MARCHINA, Chiara. "Geochemical and isotopic investigation on the Po river waters from Monviso sources to its Delta: natural and anthropogenic components." Doctoral thesis, Università degli studi di Ferrara, 2015. http://hdl.handle.net/11392/2389012.

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25

Trevis, Isaac Andrew. "Assessing and Tracking Nitrate Contamination from a Point Source and the Effects on the Groundwater Systems in Mid Canterbury, New Zealand." Thesis, University of Canterbury. Department of Geological Sciences, 2012. http://hdl.handle.net/10092/7603.

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Water is a valuable and crucial resource, the protection of which poses environmental, social and economic challenges. Fundamental to the sustainable use of water is effective management. In the Canterbury region of New Zealand, nitrate contamination has become a resource management issue due to changes in land use and intensification, which have placed pressure on the region’s groundwater and surface water systems. The purpose of this study was to assess and track nitrate concentrations on the Central Canterbury Plains with specific emphasis on a local point source of nitrate, the Ashburton Meat Processors plant. To make this assessment review of historical data was followed by the collection of 131 groundwater and 25 surface water samples to analyse the geochemical properties of the water and the stable isotopic composition of nitrate in the water. It was hypothesised that nitrate concentrations at a regional scale have increased since regular records began and that the stable isotopic composition of different nitrate sources are not discernable. Nitrate concentrations across the Canterbury region were found to have increased, prompting concerns about water quality. Concentrations are elevated above natural background levels across much of the Canterbury Plains and extreme concentrations are associated with local point sources of nitrate. Nitrate concentrations down gradient of the Ashburton Meat Processing plant are shown to have declined approximately 5% per year for the past ten years, which is in contrast to the rest of the region, where average concentrations have nearly doubled in 20 years. The reduction of contamination from the point source is most likely the result of the implementation of better wastewater management practices in the early 21st century. The δ18O and δ15N values of nitrate were found to be relatively homogenous over the Canterbury Plains. Therefore, it is suggested by this study that the dual-isotope approach alone, is not a viable tool for nitrate source identification in the region. The uniform nitrate stable isotopic composition in Canterbury could be attributed to a single, principle source of nitrate, such as clover, that overprints other isotopic compositions of nitrate source, or may also be the result of soil processes and the farming techniques used in the region. This research presents important findings for the future of identifying and managing nitrate sources in the Canterbury region. Better management practices are required for the diffuse source(s) of nitrate contributing to the widespread contamination. Critical thinking and the willingness of stakeholders to engage in the identifying, documenting and solving problems is necessary to ensure the effective management and sustainability of this precious resource.

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Woodruff, Olivia P. "TEMPORAL AND SPATIAL CHARACTERIZATION OF MACONDO 252 SIGNATURES IN GULF OF MEXICO SHELF AND SLOPE SEDIMENTS." UKnowledge, 2014. http://uknowledge.uky.edu/ees_etds/17.

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The long-term fate of hydrocarbons in the Gulf of Mexico (GOMx) following the 2010 Deepwater Horizon oil spill has yet to be fully characterized. Elemental (% C and % N), stable isotopes (δ13Corganic), and polycyclic aromatic hydrocarbon (PAH) molecular signatures were investigated in shelf and slope sediments collected in October 2010 and 2011 to gain insight into processes affecting the distribution and fate of spilled Macondo oil. Particulate organic carbon (POC) ranged between 1.55 and 2.22 wt. % in 2010 and 0.55 and 2.06 % in 2011 while the corresponding δ13Corganic ranges were from -23.37 to -20.77 ‰ (vs. PDB) in 2010, and -22.68 to -20.75 ‰ (vs. PDB) in 2011. Ranges of total polycyclic aromatic hydrocarbon (TPAH) concentrations were from 72.57 to 7,543.53 ng/g in 2010 and 25.55 to 16,582.77 ng/g in 2011. The range of measured values represented significant deviations from previous background measurements. This provided the basis for concluding that the Macondo spill altered the “background” organic carbon and hydrocarbon signature, that Macondo oil has weathered and/or biodegraded in the year following the spill, and that a significant spatial trend of hydrocarbons extended from the Macondo well across the northern GOMx in October 2010 and 2011.

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27

Howell, Brett Andrew. "Spring Responses to Storms and Seasonal Variations in Recharge in the Middle Atlas Region of Morocco." UKnowledge, 2016. http://uknowledge.uky.edu/ees_etds/41.

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Springs in the Middle Atlas Mountains of Morocco are significant sources for public water supply. From March 2014 to May 2015, water temperatures were measured hourly at three springs (Ribaa, Sidi Rached, and Zerouka); water levels were measured hourly at Sidi Rached and Zerouka; and daily turbidity data were obtained from Ribaa. From March 2014 to March 2015, daily water samples were taken at Zerouka for analyses of the stable isotopes deuterium and oxygen-18. Hourly weather data (precipitation and air temperature) were available from March 2014 to May 2015 from Ifrane, near Zerouka. Temperature responses varied between the springs, showing a time-lagged seasonal signal at Sidi Rached, near-constant values at Zerouka, and relatively stable dry-season values followed by flashy wet-season behavior at Ribaa. Stage at Sidi Rached and Zerouka tracked together, with a broad minimum in late summer and responses to individual storms superposed on the signal. Stable isotopes fluctuated daily but were frequently out of phase with each other. Autocorrelation analyses of spring parameters indicate that Sidi Rached and Zerouka have greater inertia than Ribaa. Cross-correlation analyses show characteristic time lags between (1) precipitation and stage, (2) air temperature and water isotopes, and (3) air and water temperatures. However, as shown in previous work, there is a broad range of time lags between precipitation and turbidity. The variety of spring behaviors is consistent with differences in hydraulic connectivity within each spring basin.

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Larsen, Zachary S. "Thin Soils and Sacbes: The Soil Resources of Uci, Yucatan, Mexico." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3505.

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The objective of this study was to use pedological evidence in conjunction with Geographic Information Systems, and soil physical and chemical analyses as means to better understand the agricultural landscape surrounding the ancient Maya city of Uci. Specifically, the query of this thesis is to determine whether there is an association between settlement density and soil resources, and what relationship if any there is between the ancient sacbe of Uci and its surrounding agricultural potential. Stable carbon isotope analysis of the humin fraction of the soil organic matter was conducted on several profiles from karst depressions known as rejolladas near the site center, and from a select number of sufficiently deep profiles along and surrounding the ancient sacbe, and from beneath ancient structures. A strong C isotopic signature of ancient C4 crops was found in a limited number of profiles while a majority of the profiles showed no evidence, or little to inconclusive evidence due to a mixture of C3 and C4 plants in the natural landscape. A majority of the soils surrounding Uci are shallow to extremely shallow and many profiles sampled and studied did not allow for C isotopic analysis. Isotopic evidence along with other soil chemical and physical characteristics suggests that settlement density was linked to soil resources, specifically in the case of the rejolladas proximity to the Uci site center. However, it does not appear that the construction and location of the sacbe was linked to its surrounding soil resources or agricultural potential even though ancient maize crops may have been cultivated sporadically close to the sacbe and nearby structures. The soil resources of Uci are not conducive to the production of large maize crops and the ancient Maya of this area likely utilized maize along with alternative crops, arboriculture, wild game and trade to sustain its population.

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29

Al-Qattan, Nasser M. E. N. A. A. "Interpretation of Oxygen Isotopic Values (d18O) of North American Land Snails." Miami University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=miami1404460805.

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30

Galvão, Paulo Henrique Ferreira. "Modelo hidrogeológico conceitual de Sete Lagoas (MG) e implicações associadas ao desenvolvimento urbano em regiões cársticas." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/44/44138/tde-22092015-151113/.

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Esta pesquisa integrou estudos geológicos, hidrogeológicos, geoquímicos e de isótopos estáveis no município de Sete Lagoas (MG), Brasil, com o objetivo de entender a circulação da água em terreno cárstico e propor alternativas para o seu melhor uso, a fim de se evitar problemas geotécnicos. A área é constituída por calcários neoproterozoicos da Formação Sete Lagoas, onde se desenvolveram condutos cársticos, dando origem ao aquífero homônimo, o qual está coberto por sedimentos cenozoicos inconsolidados e, ocasionalmente, por rochas metasedimentares neoproterozoicas da Formação Serra de Santa Helena. Foi observado que neste aquífero a porosidade primária é muito baixa e a secundária (micro-fraturas) é igualmente reduzida, devido ao preenchimento por calcita. O grande volume de água subterrânea migra através da porosidade terciária caracterizada dominantemente por dois planos de acamamentos carstificados e, em menor grau, por fraturas sub-verticais carstificadas. A recarga, relacionada às chuvas que ocorrem no período de outubro a dezembro, se dá através de sumidouros, entradas de cavernas e onde o calcário está sob os sedimentos cenozoicos. Um detalhado estudo avaliando os efeitos de escala permitiu também o estabelecimento da distribuição das permeabilidades do Aquífero Sete Lagoas. Outros resultados obtidos também estabeleceram que as extrações de águas subterrâneas estão associadas aos eventos geotécnicos cársticos localizados na área urbana do município. A elevada extração das águas subterrâneas faz com que o plano de acamamento carstificado mais raso, em algumas áreas, esteja inteiramente na zona não saturada, provocando os eventos geotécnicos. Um mapa de risco geotécnico identifica, a partir da litologia e do nível de água subterrânea, cinco níveis. Este tipo de mapeamento deveria orientar as extrações e os cuidados na ocupação do terreno urbano em Sete Lagoas, prevenindo ou retardando a ocorrência de novas subsidências ou colapsos.
This research integrated geological, hydrogeological, geochemical, and stable isotope studies conducted in the municipality of Sete Lagoas (MG), Brazil, in order to understand the water circulation in a karst terrain and to propose alternatives for a better water use, aiming to avoid geotechnical problems. The area is constituted by Neoproterozoic limestones from the Sete Lagoas Formation, where karst conduits were developed, giving origin to the homonymous aquifer, which is covered by Cenozoic unconsolidated sediments and, occasionally, by Neoproterozoic metasedimentary rocks from the Serra de Santa Helena Formation. It was observed that in this aquifer the primary porosity is very low and the secondary porosity (micro -fractures) is also reduced, due to the filling by calcite. The great volume of groundwater migrates through the tertiary porosity characterized by two dominant solutionally enlarged bedding planes and, to a lesser extent, by sub-vertical enlarged fractures. The recharge, related to rainfall occurring from October to December, takes place through sinkholes, caves entrances, and where the limestones are under the Cenozoic sediments. A detailed study evaluating the scale effects also allowed the establishment of permeability distributions of the Sete Lagoas Aquifer. Other results obtained also established that the groundwater extractions are associated to karst geotechnical events located in the urbanized area of the municipality. The high groundwater extractions make the shallowest solutionally enlarged bedding plane, in some points, entirely in the unsaturated zone, causing geotechnical events. A geotechnical map identifies five levels of risk, based on the lithology and the groundwater level interaction. This type of mapping should guide the groundwater extractions and caring the urban land occupation in Sete Lagoas, preventing or delaying the occurrence of new subsidences or collapses.

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Pons, Marie-Laure. "La Terre à l'Archéen. Apport des isotopes de métaux de transition (Zn, Fe)." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2011. http://tel.archives-ouvertes.fr/tel-00682665.

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L'Archéen, de 4 à 2,5 Ga, est la période qui a connu les plus grands bouleversements géologiques et biologiques de l'histoire de la Terre : formation des continents, transition d'une tectonique à composante verticale vers une tectonique des plaques horizontale, apparition de la vie, ... Le but de cette thèse est d'étudier les conditions environnementales de la Terre à l'Archéen, par l'analyse des compositions isotopiques de métaux de transition (Fe, Zn) de roches provenant principalement de la province d'Isua au Groenland (3,8 Ga). Après avoir adapté le protocole de séparation du Fe, Cu, Zn à des échantillons riches en Fe, nous avons acquis les données par spectrométrie de masse à source plasma et à multicollection MC-ICPMS. Nous nous sommes d'abord intéressés au processus de serpentinisation de la croûte océanique, réaction produisant à la fois des nutriments pour la vie (CH 4 , H 2 ) et des minéraux catalyseurs (mackinawite) de la formation abiotique d'acides aminés, molécules du vivant. L'affleurement d'Isua comporte une unité ophiolitique présentant les serpentinites les plus anciennes (3.81-3.70 Ga) : leur analyse permet d'appréhender la réaction de serpentinisation à l'Archéen. Les résultats obtenus pour la composition isotopique du zinc dans ces roches et dans des serpentinites modernes ont permis d'établir une correspondance entre le processus de serpentinisation à Isua et la mise en place de volcans de boues de serpentinites à l'aplomb de la fosse des Mariannes. Nous avons ainsi pu identifier Isua comme une zone d'arrière-arc de subduction océanique, lieu d'une serpentinisation produisant des fluides de température variable (100-300°C) et de pH alcalin (9-12). Nous montrons que cette configuration atypique réunissant serpentinisation, fluides alcalins et édifices volcaniques est favorable à l'émergence du vivant. Nous avons ensuite analysé de nombreux échantillons de formations de fer rubané (BIFs), sédiments propres à l'Archéen et au début du Protérozoïque. L'évolution de la composition isotopique du zinc de ces échantillons au cours du temps a permis d'établir une chronologie de l'émersion des continents.Nos résultats sont en faveur d'une émersion débutant il y a 2,9 Ga. Enfin, nos données nous informent sur la colonisation des continents émergés par la vie à 2,6 Ga et sur la pédogenèse de sols archéens comportant un horizon organique.

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32

Rashtchi, Ramina. "Assessing Aquitard Integrity: the Newmarket Till (Southern Ontario)." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40439.

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The Newmarket Till is a regional aquitard in southern Ontario that overlies the Illinoian to Middle Wisconsinan Lower Sediments and is overlain by the Oak Ridges Moraine (ORM). Geological investigations have mapped the distribution of the till and it is understood that erosional channels, subsequently infilled with fluvial material, breach the till and may create enhanced hydraulic connection between overlying and underlying aquifers. However, little is known about the protective capability of the Newmarket Till where it is intact. This study used natural tracers to assess the extent of transport in the aquitard-aquifer system. Stable isotopes of water (δ18O and δ2H) showed a depletion trend versus depth. In the Newmarket Till most of the samples had isotope ratios similar to meteoric water data from the nearest location (Egbert, ON). The depleted values of δ18O in the Thorncliffe Formation suggest a remnant signature of early-Holocene precipitation (-16‰ at the depth of 60 m). Elevated levels of NO3- and Cl- were detected near the surface and because of the low permeability aquitard (Newmarket Till), they could not migrate to depth. Total extractable ammonium concentrations are ranging from 4.09 ppm from near the surface to 60 ppm in the lowest part of the Newmarket and then gradually increase to 514 ppm in the bottom of the Thorncliffe Formation. The combination of high NH4+ values and organic carbon content in the Thorncliffe Formation suggests a natural source from mineralization of organic N. The fractionation which happened between δ15Nsediment and δ15N-NH4 may have three explanations: (1) lighter isotopes diffuse faster than heavier ones, so the higher rate of diffusion can cause fractionation; (2) heavier isotopes partition to exchange sites, causing fractionation along the transport pathway; (3) dissociation of NH4+ to NH3 under anaerobic condition. Positive values for δ13C in groundwater in the Thorncliffe Formation are likely due to i) a contribution of carbonate mineral dissolution, and ii) methanogenesis - the Archea favor the lighter isotope of C (12C). Methanogenesis, therefore, enriches the δ13C-DIC was enriched; however, the δ13C in dissolved organic carbon (DOC) is depleted. These geochemical characteristics demonstrate a long residence time for the porewater in the system and indicate that the Newmarket till inhibits recharge of recent precipitation, thereby providing protection to the underlying aquifers from surface-derived contaminants.

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Guéguen, Bleuenn. "Apport de la géochimie isotopique du Nickel à l'étude des dépôts métallifères océaniques." Thesis, Brest, 2013. http://www.theses.fr/2013BRES0089/document.

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Les explorations scientifiques menées depuis une quarantaine d’années ont permis d'identifier la diversité et la complexité des processus géologiques et géochimiques conduisant à la concentration des métaux dans les grands fonds océaniques. Les dépôts métallifères riches en hydroxydes de Fer et de Manganèse, tels que les encroûtements hydrogénétiques et hydrothermaux et les nodules polymétalliques, présentent des enrichissements variés en éléments d'intérêts économiques tels que le Ni, Cu, Co, Te, Pt et les Terres Rares. Bien que la minéralogie et la géochimie de ces dépôts aient été largement étudiées dans la littérature, les sources de métaux restent encore mal déterminées. Par conséquent, comprendre la géochimie de ces dépôts implique d’une part, de connaître les processus participant à leur genèse, et d’autre part d’avoir de meilleures connaissances sur les sources impliquées (par ex. flux continental et hydrothermal) et leur importance dans les grands cycles biogéochimiques des métaux dans les océans. Afin d’apporter de nouveaux éléments de réponse, notre approche a consisté à utiliser les compositions isotopiques des métaux comme traceurs biogéochimiques. Ce projet est structuré autour de deux hypothèses, (1) le développement et l’utilisation d’un nouveau outil géochimique que sont les isotopes du Ni pour tracer les sources et les processus d’enrichissements en métaux dans les dépôts métallifères océaniques ; (2) la combinaison de plusieurs systèmes isotopiques tels que Fe, Pb, Cu et Zn (et Ni) dans les encroûtements de fer-manganèse comme proxy de la composition isotopique de l’eau de mer profonde. Après avoir développé une méthode d’analyse des isotopes du Ni par MC-ICP-MS et estimé la variabilité isotopique du Ni dans les systèmes naturels par la caractérisation des grands réservoirs terrestres, nous avons évalué expérimentalement le fractionnementisotopique du Ni lors de son adsorption sur les oxyhydroxydes de Fe et Mn comme analogue à ce qui pourrait se produire dans les dépôts de Fe-Mn naturels. Les résultats indiquent que lors de l’adsorption du Ni, la phase solide est enrichie en isotopes légers par rapport à la solution avec des facteurs de fractionnement (Δ60/58Nimin/sol) variant de -1 ‰ pour la birnessite, -0.9 ‰ pour la goethite et -0.4 ‰ pour la ferrihydrite. A partir de ces résultats et d’autres études récentes, nous avons pu appuyer l’hypothèse selon laquelle d’un point de vue global la variabilité isotopique du Ni dans les dépôts métallifères océaniques riches en Fe et Mn s’explique par des processus d’enrichissement et de formation lors de l’incorporation des métaux dans les phases minérales de Fe et Mn plutôt que par des variations des compositions isotopiques des sources. Ainsi les encroûtements hydrogénétiques formés lentement à partir de l’eau de mer ne montrent pas de fractionnement isotopique du Ni, tandis que les dépôts hydrothermaux formés par des processus rapides liés aux apports hydrothermaux montrent des fractionnements du Ni plus importants. Puis, afin d’évaluer la possibilité d’utiliser les signatures isotopiques du Ni comme nouveaux traceurs paléocéanographiques, nous avons mené une étude comparative sur des encroûtements collectés dans le Pacifique Nord (proche de Hawaii) et le Pacifique Sud (proche de Tahiti). Dans ce contexte, les ncroûtements de fer-manganèse formés par précipitation très lente de l’ordre de quelques mm/Ma entre 1500 et 3000 m de profondeur, fournissent un enregistrement de plusieurs millions d’années des métaux dissous dans l’eau de mer. Après avoir réalisé une étude minéralogique et géochimique (éléments majeurs et traces) et calibré les taux de croissance des encroûtements, nous avons mesuré pour la première fois les compositions isotopiques du Ni, Fe, Zn, Cu et Pb sur la même série temporelle
Scientific explorations implemented for around forty years allow to identifying the diversity and the complexity of geological and geochemical processes conducting to metals concentration on the deep seafloor. Fe- and Mn-rich metalliferous deposits such as hydrogenetic and hydrothermal ferromanganese (Fe-Mn) crusts and polymetallic nodules, present various enrichment in elements of economic interests like Ni, Cu, Co, Te, Pt and Rare Earth Elements. Although the mineralogy and geochemistry of these deposits have been largely studied in the literature, metal sources remain poorly determined. Accordingly, understanding the geochemistry of these deposits implies to know which processes are involved in their formation but also to have a better knowledge of the sources (e.g. the continental and hydrothermal fluxes) and their importance in the global oceanic metal biogeochemical cycles. In order to fill this gap, our approach consisted in using metal stable isotope compositions as biogeochemical tracers. This project is organized around two hypotheses, (1) development and utilization of a new geochemical tool, namely Ni isotopes, for tracing metal enrichment sources and processes in oceanic metalliferous deposits; (2) combination of several isotope systematics such as Fe, Pb, Cu, Zn (and Ni) in Fe-Mn crusts as proxies of the deep seawater isotope composition. Upon developing an analytical method for measuring Ni isotopes by MC-ICP-MS and estimating the Ni isotopes variability in natural systems through the characterization of terrestrial reservoirs, we experimentally evaluated Ni isotope fractionation during adsorption on Fe- and Mn-oxyhydroxides since similar processes may potentially occur in natural Fe-Mn deposits. Results indicate that after Ni adsorption, the solid phase is enriched in light Ni isotopes relatively to the solution with fractionation factors (Δ60/58Nimin/sol) varying from -1 ‰ for birnessite, -0.9 ‰ for goethite and -0.4 ‰ for ferrihydrite. These results, and other recent studies, strengthen our hypothesis according to which Ni isotopes variability in Fe- and Mn-rich metalliferous deposits can be explained by enrichment and formation processes during metal incorporation in Fe and Mn mineral phases rather than variations in the isotopic composition of the sources. Thus, hydrogenetic Fe-Mn crusts formed slowly from seawater dissolved metals do not show significant Ni isotope fractionation, whereas hydrothermal deposits formed by relatively rapid processes as a result of hydrothermal inputs exhibit important Ni isotope fractionation

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Leslie, Deborah L. "The Application of Stable Isotopes, δ¹¹B, δ¹⁸O, and δD, in Geochemical and Hydrological Investigations." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1386000037.

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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.

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Wogsland, Brittan Valhalla. "Organomineralization of Microbialites from Storr’s Lake, San Salvador Island, Bahamas: Calcium Stable Isotope Analysis using TIMS and a ⁴²Ca-⁴³Ca double spike." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587723502946554.

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Maslen, Ercin. "Evaluating the source, age, thermal history and palaeoenvironments of deposition of Australian and Western Canadian petroleum systems: compound specific stable isotopes coupled with inorganic trace elements." Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/1098.

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Petroleum geochemistry is an important scientific discipline used in the exploration and production of hydrocarbons. Petroleum geochemistry involves the applications of organic geochemistry to the study of origin, formation, migration, accumulation and alteration of hydrocarbons.Key concepts and applications of petroleum geochemistry include understanding the petroleum systems, biomarkers and stable isotopes for oil‐oil and oil‐source rock correlations and controls on secondary processes (e.g. biodegradation, water‐washing and migration‐contamination) altering the composition and usually the quality of petroleum.In this research, important concepts and novel techniques of petroleum geochemistry have been utilized for characterizing the source rocks, evaluating the thermal history of the source rocks, understanding the age (where possible), establishing the depositional environment and lithology of the source. More specifically, various innovative organic (biomarker and stable isotopes) and inorganic (trace elements) geochemical approaches were undertaken to establish source, age, thermal history and sedimentary depositional environments of petroleum systems in Western Australia and Western Canada petroleum basins.The aim of the study presented in Chapter 2 was to understand the enigmatic occurrence of crocetane (an irregular C20 isoprenoid), that is usuallyfound in sediments associated with gas hydrate settings and used as a molecularindicator for the anaerobic oxidation of methane (AOM), in Devonian sediments and crude oils containing molecular indicators of photic zone euxinia (PZE).This study comprised a detailed molecular and isotopic study of crocetane and Green Sulfur Bacteria (GSB)‐derived carotenoids in Devonian sediments of the Western Canada Sedimentary Basin (WCSB) covering a range of thermal maturities. In addition, a series of oils generated from Devonian source rocks of the basin were analysed for crocetane. Crocetane was found in ten sediments from the WCSB and in seven Devonian WCSB crude oils. Its abundance was found to increase with thermal maturity, whereas the components generated from C40 derived carotenoids of GSB decreased steadily. The preferred proposed natural product precursor for crocetane is thus GSB‐derived carotenoids. This was corroborated by their similar structural features and the δ13C value of combined crocetane and phytane in these samples. Based on the work presented in Chapter 2, it was concluded that crocetane can provide evidence for PZE conditions in highly mature sediments and crude oils of Devonian age.Application of δD values of individual hydrocarbons (isoprenoids and nalkanes) has a great potential to estimate the thermal maturity of sedimentary organic matter. In Chapter 3, to elucidate the effect of thermal history on the δD values of petroleum hydrocarbons, (i) a comprehensive literature review, focussing on variations in δD values of sediment extracts, crude oils (including bulk organic matter and hydrocarbon fractions as well as individual nalkanes and isoprenoids) and kerogen was carried out and (ii) the application of δD values of hydrocarbons as a maturity parameter with new data from Devonian source‐rocks in the WCSB was tested.Previous work has been used to demonstrate systematic variation in D/H of individual compounds in sediments as a function of thermal maturity and our research in Chapter 3 extended the application of D/H of biomarkers to Devonian samples from the Duvernay Formation of the Western Canada Sedimentary Basin (WCSB) which is much older deposits (i.e. Devonian) than previously studied.Based on the work presented in Chapter 3, the n‐alkanes, pristane and phytane from relatively immature sediments have δD values that retain the isotopic signature of their natural product precursors, i.e. biosynthesised lipid components made up of acetyl and isoprene sub‐units, respectively. With increasing maturity, pristane and phytane become more enriched in deuterium (D), while the n‐alkanes generally remain at a constant isotopic composition until an overmature level is reached, at which point there occurs a significant enrichment of D in n‐alkanes. The enrichment of D in pristane and phytane with increasing maturity correlated strongly with changes in traditional maturity parameters including vitrinite reflectance, Tmax, and molecular parameters, providing evidence that D‐enrichment is associated with thermal maturation.The maturity indicator based on compound‐specific δD values has proved useful in cases where traditional biomarker maturity parameters are ineffective, for example at high maturity levels (i.e. % Ro >1.0) or where their associated reactants and products either equilibrate, or are thermally degraded. In addition, such a maturity measurement is applicable to Devonian sediments, where vitrinite reflectance measurements cannot be made because the higher‐plant precursors of vitrinite have not yet evolved.In Chapter 4, an integrated study including organic (stable carbon isotopes of individual hydrocarbons) and inorganic (trace elements) geochemical data, along with statistical analysis (linear discriminant analysis) was carried out for the first time to assess the source and age characteristics of crude oils from Western Australian and Western Canada petroleum basins.A novel rapid, reliable and accurate method of determination of major and trace element contents of crude oils was developed based on Laser Ablation Inductively Coupled Plasma‐Mass Spectrometry (LA‐ICP‐MS). This method has been applied for the first time to a series of petroleum samples for analysis of Fe, Mg, Al, Zn, Cu, Cr, Ni, Co, V, Tm, Mn, Ge, Dy, Si, Pb, B, Sn, Ti, Hg, As, Mo and Se at trace levels, with little or no sample pre‐treatment. δ13C values of individual hydrocarbons were carried out in a systematic manner to compliment the trace element data.The scatter plot of two discriminant functions from the analysis of trace elements (V, Pb, B, Mg, Sn, Ti, Mo and Hg) in crude oils samples confirms the capability for separating samples into their petroleum basins. 91.3% correct classification of the samples analysed was achieved. Analysis using two discriminant functions of combined trace elements (Al, Cr, Ti, Fe, Cu, Si, Tm, Mn, Ge, and Dy) and δ13C of Naphthalene (N), Biphenyl (Bp) resulted in 100% of samples being correctly classified according to their source rock age.In summary, based on the work presented in Chapter 4, the application of linear discriminant analysis and the stable carbon isotope values and trace element concentrations has allowed the classification of crude oils to their geographical (or basinal) sources and age. The use of complimentary inorganic trace element and organic stable isotope techniques for crude oil samples has been demonstrated as a new highly discriminant tool for petroleum exploration.The research presented in Chapter 5 is aimed at establishing the factors controlling the stable carbon isotopic compositions of individual aromatic hydrocarbons analysed by compound specific isotope analysis (CSIA) in crude oils from Western Australian petroleum basins of varying age and facies type but of similar thermal maturity. An evaluation of the data on δ13C of individual aromatic hydrocarbons, like alkylbenzenes, alkylnaphthalenes, alkylphenanthrenes and methylated biphenyls has been carried out to confirm the source and age of these oils and to understand why the Sofer plot is ineffective in establishing source of Western Australian petroleum systems. Previous isotopic work on the oils was mainly based on their bulk δ13C values of saturate and aromatic hydrocarbons. Western Australian oils seemed to follow an erroneous trend regarding their depositional environments (marine vs terrigenous) when they were assessed using only bulk isotopic values.The interpretation of the data presented in Chapter 5 showed that the oils where the δ13C of 1,6‐DMN (dimethylnaphthalene) and 1,2,5‐TMN (trimethylnaphthalene) isomers is most negative are probably derived from a marine source, whereas oils containing 1,6‐DMN and 1,2,5‐TMN with a less negative value are representative of a terrigenous source. The δ13C values falling in between probably have mixed source(s). Less negative δ13C values of 1‐MP and 1,9‐DMP isomers probably reflects the varying inputs of terrigenous organic matter to the source‐rocks of the oils. In addition, plots of P (phenanthrene) /DBT (dibenzothiophene) and Pr (pristane)/Ph (phytane) versus δ13C of DMP (dimethylphenanthrene), 1,6‐DMN, 1,2,5‐TMN, 1‐MP (methylphenanthrene) and 1,9‐MP are constructed to establish the end‐members of terrigenous and marine sourced oils. The ratio of P/DBT and/or the ratio of Pr/Ph and δ13C of aromatic isomers (such as 1,6DMN, 1,2,5‐TMN, 1‐MP and 1,9‐MP) when coupled together, provide a novel and convenient way of establishing crude oil source rock origin and sometimes even lithologies.In summary, oils from terrigenous depositional environments based on their bulk δ13C values were classified as marine based on their δ13C values of individual aromatic compounds. The compound specific isotope data of the aromatic hydrocarbons obtained for the oils may provide opposite conclusions regarding the source of the oils compared to bulk data using the Sofer plot. Thus, great care must be taken when interpreting isotope values of hydrocarbons, particularly those that are only based on bulk parameters.Ultimately, this project has demonstrated that analyses of molecular fossils (biomarkers) and their stable isotopic compositions (δ13C and δD) complemented with trace element data provides an excellent novel tool for better understanding the basic concepts in petroleum basins and for solving a wide range of problems during petroleum exploration.

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Nitzsche, Kai. "Applying isotope geochemistry to identify mechanisms regulating the aquatic-terrestrial carbon and nitrogen dynamics across scales in a moraine landscape." Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2017. http://dx.doi.org/10.18452/17793.

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In dieser Studie wurden stabile Isotopenverhältnisse genutzt um die Mechanismen der aquatisch-terrestrischen C – und N-Dynamiken über verschiedene Skalenebenen hinweg in der Moränenlandschaft von Nordostdeutschland zu identifizieren; einer Landschaft, die stark landwirtschaftlich genutzt wird und in der es eine Vielzahl von kleinen Wasserkörpern (Sölle) gibt. Auf der regionalen Landschaftsskala spiegeln d13C-Isotopenkarten des org. Materials in Oberböden und von Pflanzenblättern eines 38.2 km2 großen Gebietes den Eintrag von org. Material von C3-Pflanzen, deren Wassernutzungseffizienz im org. Material des Bodens eingeprägt wurde, sowie den Eintrag von Mais (C4-Pflanze), wider. Die d15N-Isotopenkarte des org. Materials in Böden weist verschiedene Düngepraktiken hin. Auf der regionalen Sollskala deuten die d13C- und d15N-Isotopenwerte von Oberflächensedimenten von 51 Söllen auf kürzliche Einträge des org. Materials und Bewirtschaftungseffekte im Einzugsgebiet hin. Tiefere Sedimente sind durch die Ablagerung org. Materials von terrestrischen Pflanzen sowie dessen Umsetzungsgrad geprägt in Abhängigkeit von der Wasserführung. Auf der Transekt-Skala, d.h. entlang von Transekten von Erosions- zu Depositionsgebieten im Einzugsgebiet eines Solls, beeinflussen Erosion, Pflanzenproduktion, mikrobielle Umsetzung und Gülledüngung verschiedene Fraktionen des org. Materials. Auf der Aggregat-Skalenebene sind die Art und der Anteil spezifischer organo-mineral Assoziationen entlang des Transekts variabel. Bodenpartikel vom Feld und hereinwachsende Makrophyten sind die Quellen des org. Materials in Sedimenten. Diese Studie hat erfolgreich stabile Isotopenverhältnisse zur Identifikation von Mechanismen der C- und N-Dynamik auf individuellen Skalenebenen angewendet. Kleine Inlandwasserkörper sind Schlüsselelemente für die C- und N-Dynamik in landwirtschaftlich genutzten Moränenlandschaften.
In moraine landscapes, carbon (C) and nitrogen (N) dynamics can vary greatly across landscape structures and soil types especially when small water bodies are interspersed in the landscape. This study used stable isotope ratios to identify the mechanisms regulating the aquatic-terrestrial C and N dynamics across different scales in the young moraine landscape of NE Germany – a landscape intensively used for agriculture and interspersed with countless of small water bodies, the so-called kettle holes. At the regional landscape scale, d13C isoscapes of topsoil bulk soil organic matter (SOM) and plant leaves collected from a 38.2 km2 area revealed long-term inputs OM from C3 crops, which imprinted their water use efficiency status onto the soil, as well as short-term inputs from corn. The d15N SOM isoscape identified fertilization-induced impacts on the N dynamics of agricultural fields and grasslands. At the regional kettle hole scale, d13C and d15N of surface sediments of 51 kettle holes reflected recent OM inputs and management practices in the catchment. Deeper sediments recorded the degree to which the OM has been processed within the kettle hole depending on the water-logging period. At the transect scale, erosion, plant productivity, microbial decomposition and slurry fertilization affected OM fractions in topsoil along transects spanning erosional to depositional areas in the catchment of one arable kettle hole. At the aggregate scale, the pathway and magnitude of OM-mineral associations changed along the transect. OM in sediments was derived from clay- and silt-sized particles from the field, together with emergent macrophyte contributions. By means of stable isotopes techniques, different mechanisms were identified at the individual scales. Consideration of the spatial heterogeneity of all scales is essential to understand landscape C and N dynamics. Small inland water bodies are key constituents of C and N dynamics in moraine agricultural landscapes.

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Lotero, Lozano Laura. "The Role of High-Elevation Headwater Runoff in Streamflow Generation and Water Supply in the Northern Andes, Colombia." Scholar Commons, 2017. https://scholarcommons.usf.edu/etd/7421.

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Water security requires that sufficient quantities of water be available at critical times. This is particularly challenging for high-intensity urban and agricultural settings. In underdeveloped nations, streamflow is commonly the preferred water source, as it is readily available and delivered cost-free to users. Yet, the sources of these critical streamflows are often unknown. This issue is salient in the Northern Andes, where basic knowledge of controlling factors for the quantity, quality, and timing of runoff is lacking. High-elevation headwaters are the primary catchment areas in the Northern Andes, but the extent of water providing to municipalities in the Northern Andes is unknown. In this study, the contribution of water derived from the upper watershed to the streamflow in the Tulúa River which supplies water to 200,000 people in the city of Tulúa was quantified. The river runs 72 km through urban, agricultural, and industrial land use in the Central Cordillera of the Colombian Andes. We collected 32 and 34 water samples in August and November, respectively. The water samples were representative of high-elevation headwaters runoff, shallow groundwater discharge, and streamflow throughout the watershed. Samples were analyzed for dissolved constituents and stable isotopes. The dissolved constituents were used in mass-balance mixing models to identify the source of streamflow in the lower watershed of the Tulúa River, where it the river supports a large municipality. Results indicate that approximately 50% surface runoff largely originates as high-elevation headwater runoff, including high-elevation settings where páramos dominate the land cover. These findings underscore the need for source-water protection efforts in the upper watershed, including the páramos. This project serves as a model for other páramo derived watersheds, where source-water protection is a critical challenge.

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Garbelli, C. "BIOMINERALIZATION AND GLOBAL CHANGES: BRACHIOPOD SHELLS AS ARCHIVES OF THE END PERMIAN EVENTS." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/265524.

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The Permian has been the theatre of major global changes in the Earth’s geodynamics, climate, seawater and atmosphere geochemistry, and thus it represents an interesting case study to understand the response of organisms to environmental changes, a topic which is of increasing interest to the scientific community, who has to face the current global change. In fact, in the Permian the biotic response was dramatic, culminating at the end of the period with the greatest mass extinction of the Phanerozoic. Noteworthy, the end Permian mass extinction coincided with one of the largest known continental eruptions, the Siberian trap basalts, that are considered to have generated more than 100,000 Gt of CO2 as well as CH4, leading to ocean acidification and global warming. Brachiopods, which are low buffered organisms with a heavily calcified shell, can be the perfect candidates to record the trends related to changes in seawater chemistry during this critical interval. The aim of this research is thus to study the biomineralization of brachiopod shells to unravel the patterns of biotic changes caused by the extreme Late Permian events. To reach this goal, I organized my research in three different phases, starting to investigate the main differences in the shell fabric of the brachiopod groups ruling the benthic communities in the Late Permian, that are the classes Rhynchonellata and Strophomenata (phase 1); then comparing the stratigraphic distribution of brachiopod genera during the Late Permian in a paleogeographic perspective (phase 2); finally, analyzing in great details, both qualitatively and quantitatively, the shell fabric of several taxa from Tethyan Permian-Triassic Boundary (PTB) successions, to unravel the biomineralization activity at generic level(phase 3). To develop this research I investigated brachiopods belonging to different paleogeographic localities in the Tethyan realm. The specimens were in part collected by myself during field activity, in part already available from the collections of Dipartimento di Scienze della Terra “A. Desio” and also provided by external partners. The studied brachiopods come from: 1. Nesen Formation, Alborz Mountains, northern Iran; 2. Julfa Formation, Ali Bashi Formation and Boundary Clay, Ali Bashi Mountains, Northwestern Iran; 3. Selong Group, southern Tibet; 4. Gyanyima Formation, southwestern Tibet; 5. Bulla Member, Dolomites, Northern Italy; 6. Gomaniibrik Formation, Hazro, Turkey; 7. Changhsing Limestone and Dalong Formation, South China These data were integrated with the analysis of the available published literature on Upper Permian brachiopods, in particular to develop step 1 and 2. The methods used to develop this research may be grouped in four main categories: 1. Microscopical analysis of the shell structure using SEM (phases 1 and 3) 2. Geochemical analysis of the calcitic shell contents for trace elements (Mg, Sr, Fe, Mn) and stable isotopes (C and O)(phase 1) 3. Image analysis to acquire quantitative parameters of the shell ultrastructure (phase 3) 4. Statistical analysis of the stratigraphic distribution of brachiopod taxa using the logistic regression in order to test association between environmental variable and taxonomic composition (phase 2). Performing phase 1, I discovered important differences in the structural and chemical composition of the shell in the two main Upper Permian brachiopod classes: the Strophomenata and the Rhynchonellata. These taxa bear a different calcitic shell fabric: the former possesses a double or triple layer shell consisting of a primary layer, a secondary layer with cross-bladed laminae and a prismatic tertiary layer; the latter have a shell succession similar to extant ones, which is composed of a primary layer of crystallites, a secondary layer of discrete fibers and, eventually, a tertiary layer of prisms. Their different fabric corresponds to differences in the chemical composition. In particular the Strophomenata, which have a laminar fabric enriched in organic compounds, have higher Sr and Mg contents and a lower δ13C in their shells than co-occurring Rhynchonellata. In phase 2, the logistic regression analysis has shown that important changes in terms of taxonomic composition took place from the Wuchiapingian to the Changhsingian, with the Strophomenata being the dominant group in terms of abundance, but the Rhynchonellata being more prone to high rank diversification. In phase 3, the detailed study of the shell structure at the SEM, has revealed that Upper Permian genera can produce different type of shells, especially regarding the ratio between the organic and inorganic content. In particular, the taxa occurring during the first part of the Late Permian (Wuchiapingian and early Changhsingian) biomineralized thick shells with a relatively high inorganic content. Instead, in the late Changhsingian, brachiopod taxa produced shells with a higher organic content. In addition, the quantitative analysis of the fabric, based on the measured size of its structural units, revealed different trends in the two classes. Rhynchonellata reduced the size of the structural units (fibers) of their shell as approaching the PTB. On the other hand, the Strophomenata show a more complex response, either continuing in their normal biomineralization activity or increasing the size of their structural units (laminae). Through this research, two important conclusions were reached: the first concerns the paleobiological implications of the different biomineralization processes performed by brachiopods, and the second is related to the brachiopod response to the end Permian global environmental changes. It is now clear that the brachiopod classes of Strophomenata and Rhynchonellata have profound differences in terms of the structural and elemental composition of their shell. These differences are likely related to the biomineralization process responsible for the formation of their shell, a collective process where arrays of mantle cells secrete the biocomposite in the Strophomenata, versus a discrete, single cell driven process in the Rhynchonellata . The observed changes in brachiopod shell biomineralization in the latest Permian are compatible with a change in the carbonate saturation state of seawater and thus with ocean acidification, related to Siberian Traps flood basalt volcanism. In fact, a general trend toward production of calcitic shells with higher organic content is recorded up to the PTB in most brachiopod groups. This may have been likely the result of changes in the physical and chemical composition of seawater that produced an increase in the energetic cost for carbonate precipitation in low buffered organisms such as brachiopods.

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Wombacher, Frank. "The stable isotope geochemistry and cosmochemistry of cadmium." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=967287685.

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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.

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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.

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Thomas, Katherine S. S. M. Massachusetts Institute of Technology. "Organic geochemistry and stable isotope constraints on Precambrian biogeochemical processes." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69474.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 91-101).
Details of the biogeochemical cycles and the dominant mechanisms present in Precambrian remain heavily debated topics. The events of the Late Proterozoic onset to glaciations and what types of early life existed in the Archean are two of the many provoking topics within the Precambrian. We set out to improve the understanding of these geologic intervals by examining stable isotopic signatures and molecular fossils (biomarkers) in Late Proterozoic and Mesoarchean ages sedimentary rocks in Northwestern Territories, Canada and Pilbara, Western Australia, respectively. This thesis presents sulfur, carbon, oxygen and nitrogen stable isotopic data along with distribution of steranes and hopanes biomarkers. Geochemical data is analyzed in the context of elucidating the key biological and environmental factors involved in the Mesoarchean marine biosphere and the Late Proterozoic onset of glaciations. Stable isotopic analysis of the Gorge Creek Group in Pilbara, Western Australia reveals organisms capable of microbial sulfur disproportionation were likely the dominant biological players in Mesoarchean deep-ocean sulfur cycling. Biomarker and isotopic proxies of the Coppercap Formation reveal diverse biological activity directly prior to the Sturtian Glaciation with communities of green and purple sulfur bacteria as well as methanotrophs and cyanobacteria. Possible environmental implications of these communities co-existing are explained in context of changes in ocean chemistry and the diversification of eukaryotic life.
by Katherine S. Thomas.
S.M.

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44

Permana, Donaldi Sukma. "Reconstruction of Tropical Pacific Climate Variability from Papua Ice Cores, Indonesia." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449155469.

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45

Khademi-Moghari, Hossein. "Stable isotope geochemistry, mineralogy, and microscopy of gypsiferous soils from central Iran." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23945.pdf.

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46

Dong, Shuofei. "Stable (Cu, Zn) and radiogenic (Pb) isotope geochemistry of airborne particulate matter." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/10746.

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The aim of the thesis was to test the isotope systematics of Cu, Zn and Pb in atmospheric particulate matter and potential source material in order to critically discuss its implications and applications to studies of global biogeochemical cycles and anthropogenic impact. Four specific objectives were addressed: First, we tailored existing analytical methods to enable for the first time accurate and precise Cu and Zn isotope ratio measurements in dust and aerosol samples with low element content. Second, we studied the Pb, Cu and Zn isotope composition in aerosols collected in London to test their potential to trace anthropogenic sources in the urban atmosphere. Third, we characterized the Cu and Zn isotope systematics of major Asian and African dust sources and constrained possible controls and implications on the marine isotope signature. Finally, we investigated the isotope fractionation of Zn during dissolution experiments with acidic solution of natural dust to test the possible effect of atmospheric processing on the isotope signature of deposited Zn. The conclusions from this work are: First, stable isotopes confirm that brake and tyre emissions are the likely dominant sources of Zn and Cu in urban aerosols and that recycled Pb deposited originally from leaded gasoline still contributes significantly to the burden of atmospheric Pb in London. Second, we show that the Cu and Zn isotope signatures vary significantly between the major Asian and African dust sources and we find a significant correlation between Cu isotope ratio and illite content. Mass balance calculation suggest that bulk samples record faithfully the isotope signature of the <4 μm fraction. Third, significant isotope fractionation of Zn is observed during dust dissolution suggesting that the isotope signature of Zn deposited in the surface ocean is not only controlled by source mixing but also by atmospheric processing during long range transportation. The work clearly supports the initial hypothesis that metal isotopes are powerful sources to study global and regional biogeochemical cycles.

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Faure, Kevin. "A stable isotope study of the Kaap Valley Tonalite, Barberton Mountain Land, South Africa." Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/15849.

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Bibliography: pages 100-109.
The Kaap Valley Tonalite (KVT) was a homogenous hornblende+ biotite tonalite that had been subjected to overail propylitic and potassic alteration. Petrographic studies reveal that carbonate alteration and increased proportions of hydrous minerals occur along the KVT and Barberton greenstone belt contact zone, and along major shear zones within the KVT.

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Peel, Kate Elizabeth. "Studies into the Stable Isotope Geochemistry of Copper and Zinc in Aquatic Systems." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503795.

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Hopley, Philip J. "Palaeoenvironmental reconstruction of South African hominin-bearing cave deposits using stable isotope geochemistry." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402265.

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Scott, Gillian Anne. "Contemporary ecology and stable isotope geochemistry of benthic foraminiferids in the Celtic Sea." Thesis, Bangor University, 1998. https://research.bangor.ac.uk/portal/en/theses/contemporary-ecology-and-stable-isotope-geochemistry-of-benthic-foraminiferids-in-the-celtic-sea(ed14ac68-ce51-4156-8420-773fee552fb7).html.

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The primary aim of this thesis was to assess the value of foraminifera in downcore studies of shelfsea stratification using both assemblage and geochemical characteristics. An examination of the modern distribution of foraminifera in the context of stratification in the Celtic Sea and comparison of these distributions with measured environmental variables was undertaken to this end. In addition, several species were examined for their stable oxygen and carbon isotopic composition with reference to the ambient bottom and porewaters. Cruises were run to the Celtic Sea in July, 1995 and July-August, 1996, during which hydrographic data, water and surface sediment samples were collected from 138 stations. Fifty-three samples were subsequently analysed for grainsize, geochernical and foraminiferal properties, while the water samples were analysed for oxygen isotopic composition. A total of six multicores were extracted and sectioned. Each section was analysed for porewater carbon isotopic composition and foraminiferal content. Selected foraminifera from both the surface and subsurface samples were analysed for the oxygen and carbon isotopic composition of their test calcite. Statistical analyses of the foraminiferal data indentifed four distinct assemblages which have potential for palaeostratification studies. The mixed-type assemblage included Cibicides lobatulus, Ammonia beccarfi, Quinqueloculina seminulum, Textularia bockii and Spiroplectammina, wrightfi. The stratifiedtype assemblages included Bulimina marginata, Hyalinea balthica, Nonionella turgida and Adercotryma glomeratum while Stainforthis fusiformis was diagnostic of the front. Bulimina gibba, Elphidium excavatum forma selseyensis and Eggerelloides scabrus defined an eastern asseblage. It is believed that the true controls on these assemblages are oxygen and food supply. Ammonia beccarii precipitated its test in oxygen isotopic equilibrium while Q. seminulum was consistently, negatively offset by approximately 0.5 O/oo. This demonstrates the potential of these species in palaeo-temperature and particularily, palaeo-stratifcation studies. The 'microhabitat effect' was examined for several species of foraminifera but was not observed.

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Dissertations / Theses on the topic 'Stable isotopes geochemistry'

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