Дисертації з теми "Geochemistry"
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1
Spivack, Arthur J. "Boron isotope geochemistry." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/15187.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, and Woods Hole Oceanographic Institution, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN
Vita.
Includes bibliographies.
by Arthur J. Spivack.
Ph.D.
2
Thomas, Jay Bradley. "Melt Inclusion Geochemistry." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11262.
Анотація:
Silicate melt inclusions (MI) are small samples of melt that are trapped during crystal growth at magmatic pressures and temperatures. The MI represent a sample of the melt that was isolated from the magma during host crystal growth. Thus, MI provide a valuable tool for constraining the magmatic history of igneous systems because they provide an unambiguous method to directly determine compositions of melts from which the host crystal grew. As such, coupled petrographic examination and geochemical analyses of MI and host crystals can reveal information about crystal/melt processes in igneous systems that are difficult (or impossible) to assess through conventional methods. Many studies have used MI to monitor large scale petrogenetic processes such as partial melting and fractional crystallization. The research presented below focuses on using MI to constrain processes that operate at the crystal/melt interface because MI are samples of melt that resided adjacent to the host crystal prior to entrapment as an inclusion. Chapter one addresses challenges associated with preparing small crystals containing MI for geochemical analysis. In chapter two trace element analyses of MI and the immediately adjacent host zircon crystals are used to determine zircon/melt partition coefficients. In chapter 3 the significance of boundary layer development adjacent to growing crystals is evaluated by comparing the trace element compositions of MI host crystals that have significantly different trace element mineral/melt partitioning behavior.Ph. D.
3
Heri, Alexandra Regina. "Geochemistry, geochronology and isotope geochemistry of eocene dykes intruding the Ladakh batholith." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B50899624.
Анотація:
Eocene dykes intruding the Ladakh batholith were sampled along the southern margin of the Trans-himalayan plutonic arc in Ladakh, NW-India. Approximately 30 dykes were encountered in the 40 km trail between Leh and Hemis Shugpachan. The dykes in the east of the field are trending E to NE and those in the west trending N to NW, exhibiting sub-parallel orientations within each area. Eighteen dykes were sampled (two of them multiple times) and subjected to petrographic, geochemical and isotopic analyses. They exhibit various degrees of differentiation from basaltic to rhyolitic compositions and are mainly composed of plagioclase, quartz, hornblende (s.l.) and/or biotite and magnetite. Furthermore, dykes in the eastern part of the field area contain quartz xenocrysts resulting from crustal assimilation, while no relict quartz was found in the west. The dykes exhibit alteration phases and features suggesting that they underwent autometamorphism, i.e. hydration reactions due to igneous cooling. Whereas the dykes in the east of the field area record low-T alteration, the mineral parageneses in the west are typical for alteration at elevated temperatures typical for greenschist metamorphic facies. Al-in-hornblende barometry performed on Magnesio-hornblende and Tschermakitic-hornblende phenocrysts of the least altered dyke indicates formation in upper-amphibolite metamorphic facies conditions and pressures of about 6 kbar corresponding to an intrusion depth of approximately 20 km.
Major and trace element analyses and Rb-Sr and Sm-Nd isotope analyses revealed a stunning variability in geochemistry and isotopic composition amongst the coeval dykes. All dykes exhibit LREE enrichment and HREE depletion as well as negative Tb and Nb anomalies characteristic for subduction-related intrusives and extrusives. Their REE patterns support a clear subdivision into chemically distinct groups. The group hypothesis was further tested and found valid using statistical tools designed to assess similarity/dissimilarity amongst individuals of a group with a common ancestor, such as hierarchical cluster analysis and multidimensional scaling. The dykes are cogenetic, but clearly not consanguineous, i.e. have not formed from one, progressively differentiating magma chamber.
The variability observed in Sr-Nd isotopes can be explained by the dykes having undergone differing degrees of crustal assimilation. In particular the dykes in the east containing quartz xenocrysts show negative iiNd) and positive N(Sr) values caused by crustal assimilation, whereas the dykes in the west with no quartz xenocrysts exhibit positive qqNd) and N(Sr) near zero. 39Ar-40Ar dating by incremental heating of several hornblende-bearing dykes revealed crystallization ages between 50 and 54 Ma, whereas two biotite-bearing dykes gave ages of 45 and 37 Ma, likely to be cooling or recrystallisation ages.
The combination of structural field evidence with petrographic, petrologic, geochemical, isotopic and geochronological analyses demonstrates that the dykes, although sharing a common origin, i.e. having formed in the same tectonic setting at roughly the same time, have undergone further geological processes leading to an unexpected diversification of the dykes. These findings provide ample scope for further in-depth and breadth investigations on “late-magmatic dykes” in the future.published_or_final_version
Earth Sciences
Doctoral
Doctor of Philosophy
4
Kiriakoulakis, Konstadinos. "Organic geochemistry of carbonate concretions." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337141.
5
Dredge, Jonathan. "Aerosol contributions to speleothem geochemistry." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5136/.
Анотація:
There is developing interest in cave aerosols due to the increasing awareness of their impacts on the cave environment and speleothems. This study presents the first multidisciplinary investigation into cave aerosols and their contribution to speleothem geochemistry. Modern monitoring of suspended aerosol concentrations, CO2 and temperature in Gough’s Cave, Cheddar Gorge have presented a strong relationship with cave ventilation processes. Temporal variations of aerosol levels have demonstrated the ability of aerosol monitoring to record seasonal ventilation shifts, beyond anthropogenic influences. When used in combination with more established monitoring methods, suspended aerosol monitoring is a beneficial addition to cave environmental studies Theoretical modelling and calculations based on modern aerosol monitoring have established that aerosol contributions are highly variable. Aerosol contributions are of greatest significance under slow growth or hiatus scenarios and high aerosol deposition scenarios. Marine and terrestrial aerosol contributions have been quantified in a flowstone core from New St Michaels Cave, Gibraltar. Additionally, bio-aerosol deposits and bacterial colonisation have been identified as a potential source of trace element bioaccumulation and flowstone coloration in Yarrangobilly Caves, Australia.
6
Wang, David Texan. "The geochemistry of methane isotopologues." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111690.
Анотація:
Thesis: Ph.D. in Geochemistry, Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 123-143).
This thesis documents the origin, distribution, and fate of methane and several of its isotopic forms on Earth. Using observational, experimental, and theoretical approaches, I illustrate how the relative abundances of ¹²CH₄, ¹³CH₄, ¹²CH₃D, and ¹³CH₃D record the formation, transport, and breakdown of methane in selected settings. Chapter 2 reports precise determinations of ¹³CH₃D, a "clumped" isotopologue of methane, in samples collected from various settings representing many of the major sources and reservoirs of methane on Earth. The results show that the information encoded by the abundance of ¹³CH₃D enables differentiation of methane generated by microbial, thermogenic, and abiogenic processes. A strong correlation between clumped- and hydrogen-isotope signatures in microbial methane is identified and quantitatively linked to the availability of H₂ and the reversibility of microbially-mediated methanogenesis in the environment. Determination of ¹³CH₃D in combination with hydrogen-isotope ratios of methane and water provides a sensitive indicator of the extent of C-H bond equilibration, enables fingerprinting of methane-generating mechanisms, and in some cases, supplies direct constraints for locating the waters from which migrated gases were sourced. Chapter 3 applies this concept to constrain the origin of methane in hydrothermal fluids from sediment-poor vent fields hosted in mafic and ultramafic rocks on slow- and ultraslow-spreading mid-ocean ridges. The data support a hypogene model whereby methane forms abiotically within plutonic rocks of the oceanic crust at temperatures above ca. 300 °C during respeciation of magmatic volatiles, and is subsequently extracted during active, convective hydrothermal circulation. Chapter 4 presents the results of culture experiments in which methane is oxidized in the presence of O₂ by the bacterium Methylococcus capsulatus strain Bath. The results show that the clumped isotopologue abundances of partially-oxidized methane can be predicted from knowledge of ¹³C/¹²C and D/H isotope fractionation factors alone.
by David Texan Wang.
Ph.D. in Geochemistry
7
Gurriet, Philippe C. (Philippe Charles). "Geochemistry of Hawaiian dredged lavas." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/54327.
8
Lamadrid, De Aguinaco Hector M. "Geochemistry of fluid-rock processes." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/71350.
Анотація:
When these fluids interact with the surrounding rocks, small aliquots of these fluids are trapped as imperfections in the crystal lattice and fractures of minerals. These microscopic features are called fluid and melt inclusions, and are one of the best tools available to probe, measure and determine the chemical and physical properties of crustal fluids. In the present study we examine new developments into our understanding of fluid-rock interactions using fluid and melt inclusion as tools to provide insights into the evolution of the Earth's crust from the deep continental crust to the surface. Chapter II "Raman spectroscopic characterization of H2O in CO2-rich fluid inclusions in granulite facies metamorphic rocks", is a brief review of the current understanding of granulite rocks and their formation, and a new development into our ability to characterize the composition of the fluids trapped as fluid inclusions in minerals in granulite facies rocks. Chapter III "Reassessment of the Raman CO2 densimeter", details new developments in the use of the Raman spectroscopy to characterize the density of CO2. In this chapter we describe briefly the Raman effect of CO2 and the density dependence of the Fermi diad using different Raman instruments, laser sources and gratings to understand the differences in the published data. Chapter IV "Serpentinization reaction rates measured in olivine micro-batch reactors" describes new insights into the serpentinization process by using olivine micro-reactors. The micro-reactor technique is a new experimental development that allows researchers to monitor the fluid chemistry as well as the mineral composition changes inside synthetic fluid inclusion.Ph. D.
9
Wood, Tamara Michelle. "Numerical modeling of estuarine geochemistry /." Full text open access at:, 1993. http://content.ohsu.edu/u?/etd,240.
10
Curtis, John B. "Evaluation of the hydrocarbon source-rock potential of carbonaceous shales : upper Devonian shales of the Appalachian basin /." Connect to resource, 1989. http://rave.ohiolink.edu/etdc/view.cgi?acc%5Fnum=osu1263906458.
11
Lifton, Nathaniel Aaron 1963. "A new extraction technique and production rate estimate for in situ cosmogenic carbon-14 in quartz." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/289000.
Анотація:
The potential utility of in situ cosmogenic ¹⁴C (in situ ¹⁴C) in surficial process studies is widely recognized, yet a reliable means of isolating it has proved difficult to develop. Here we present a new method for isolating in situ ¹⁴C in quartz that yields more precise estimates of production rates than achieved by previously published extraction techniques. The new technique involves resistance heating of samples, and collection of all evolved carbon as CO₂ between 500°C and 1500°C. Our improved technique holds three distinct advantages over other extraction methods: (1) we can identify and quantitatively eliminate atmospheric/organic ¹⁴C contamination, (2) we can identify the in situ ¹⁴C component unambiguously without assumptions of ¹⁴CO/¹⁴CO₂ production proportions within the rock or equilibria on extraction, and (3) background ¹⁴C levels are consistently low. To develop our new procedures, we identified and sampled wave-cut quartzite benches associated with Lake Bonneville's two highest shorelines, as well as basalts that erupted into the late Pleistocene lake at Tabernacle Hill. Comparison of ¹⁴C thermal release patterns from the shoreline quartzites to well-shielded quartzite samples showed that contaminant ¹⁴C is released at ≤ 500°C, and that ¹⁴C released from 500 to 1500°C is essentially all in situ-produced. Two replicate analyses yield a sampling site production rate of 59.8 ± 4.6 (¹⁴C atoms/g SiO₂)/yr. Uncertainties in altitude and latitude scaling factors yield a 2σ range of sea-level, >60° geomagnetic latitude ¹⁴C production rate estimates consistent with an independent estimate based on an experimental ¹⁴C/¹⁰Be production ratio (Reedy et al., 1994) and ¹⁰Be production rate estimates from similar Lake Bonneville shoreline sites (Gosse and Klein, 1996). Our preferred production rate estimate is thus 18.2 ± 2.0 (¹⁴C atoms/g SiO₂)/yr. This estimate is also consistent with revised in situ ¹⁴C production rate estimates based on our previously published data, but is lower and more precise--indicating that we have successfully reduced contaminant ¹⁴C and other sources of variability in our data. After we have replicated these Lake Bonneville results, our new extraction procedures should bring in situ ¹⁴C into the mainstream of process-oriented cosmogenic nuclide surface studies.
12
Broughton, L. M. "The geochemistry of Westmin Resources Ltd." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/29918.
Анотація:
Westmin Resources Ltd. operate a 3000 tpd copper-lead-zinc mine 93 km by highway south-southwest of Campbell River in Strathcona Provincial Park. The mine began operations in 1966. Tailings were initially discharged directly to the bottom of Buttle Lake; a practice which continued until an on-land tailings disposal facility was commissioned in June 1984.
Testwork has indicated significant acid production potential in the sulphide tailings. Tailings are now deposited by the "subaerial" method; a procedure designed to produce an unsaturated, high density tailings mass with low horizontal and very low vertical permeability. This is a relatively new technique in Western Canada and the Myra Falls facility provided an ideal opportunity to evaluate the effectiveness of subaerial deposition to limit acid generation and contaminant migration.
A number of surveys have been conducted by Environment Canada and Knight and Piesold Ltd. to evaluate the geochemical and geotechnical characteristics of the tailings mass over the deposition history. This report describes a detailed study conducted by Environment Canada and L.M. Broughton in 1989, with reference to the previous study (Broughton and Ferguson, 1989) to evaluate changes over time.
The field sampling component of this study included surface solids sampling of fresh and older tailings, deposited over a seven month time period. Surface water samples were collected. Depth profiles through the newer and old tailings layers in the tailings impoundment and an emergency storage pond were established of the geotechnical and geochemical characteristics through solid sampling over depth, pore water sampling, and laboratory testing including paste analyses, shake flask extraction tests.
Sulphide oxidation was occurring at the surface and over depth in the tailings. Contaminant fronts over the vertical profile of the tailings mass were identified, and the rate of infiltration estimated. Elevated zinc, acidity, sulphate and conductivity levels were detected at depth in the impoundment. The infiltration of alkaline tailings water from freshly placed tailings neutralized low pH fronts and precipitated metals constrained by pH (Cu and Fe) near the interface of fresh and older tailings.
Oxygen and carbon dioxide profiles were developed to determine oxidation rates, oxygen consumption and the ingress of oxygen to the depth in the tailings. Geotechnical characteristics of the tailings mass within the layers sampled were similar to measurements at a conventional saturated tailings impoundment. The placement of a fresh tailings layer did not appear to significantly change the rate of oxidation or contaminant migration through the tailings. Layers of fine silt with high moisture content limited the vertical diffusion of oxygen into the tailings, and the rate of oxidation. Due to operational constraints, there were long periods between tailings deposition which allowed drying and cracking of the subaerial tailings mass, and development of surface oxidation and low pH fronts which have penetrated to depth in the tailings. Vertical cracking of the tailings allowed the ingress of the oxygen to more permeable underlying sand layers promoting oxidation at depth in the tailings.
Relatively simple field and laboratory techniques were developed and applied to evaluate the characteristics and performance of the subaerial tailings mass. Such evaluations should be conducted to determine the nature of the tailings during operation, and for design of alternative closure schemes, but must be carefully designed to recover the essential data within a reasonable time frame and scope of laboratory and field work. The results of investigations of the geochemical nature of the Myra Falls tailings impoundment indicate that acid generation, metal leaching, and contaminant migration are established in the subaerial tailings mass. Closure and reclamation strategies must address limiting the rate and extent of acid generation, and address containment of the contaminated drainage water within the impoundment. All acidic drainage from the Westmin site is collected and treated in a lime neutralization circuit and series of settling ponds, and is sampled and analyzed prior to discharge.Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate
13
Williams, Lynda B. "Boron isotope geochemistry during burial diagenesis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0022/NQ49549.pdf.
14
Huebner, Ralf. "Sediment geochemistry : a case study approach." Thesis, Bournemouth University, 2009. http://eprints.bournemouth.ac.uk/13139/.
Анотація:
The geochemistry of sediments is a very wide field and several important aspects must be taken into account, including, but not limited to, various methodological questions, the analysis of distribution patterns, determination of origins and the assessment of risks. Therefore, this research project adapted a case study approach and analysed several important aspects of contamination in sediments at a time. In case study 1, the distribution of metals in the sediments was analysed in Bigge and Olpe, two small and fast running watercourses in Germany. The metal/metalloid concentrations showed very different distribution patterns. Mobile elements like zinc showed a very homogenous and predictable pattern, while elements with low mobility stick to the sediment and do not migrate much, leading to areas with different concentrations. In addition, it was found that the local monitoring tools in force, which are largely based on analyses of the water, are not sufficient for a reliable assessment of the environmental quality. Case study 2 aimed both to investigate the contamination profile caused by a closed landfill within the Christchurch Harbour nature reserve and the strengths/weaknesses of a partial extraction scheme based on the industrial standardised process DIN 19730. It was found that this procedure can predict the actual migration in the homogenous marshland structure rather well. In the vicinity of a linear channel, however, no correlation between the mobility and dispersion could be detected; the channel acts as an effective drainage system for both the landfill itself and the intertidal marshland in its sphere of influence. Partial extractions are only limited in their ability to predict the migration of contaminants in the ground directly affected by the channel. The main objective of case study 3 was the determination of metal distribution within the Poole Harbour estuary, both in regard to total and mobile metal concentrations. In addition, it was tested if the chosen methodology is an efficient protocol (fast, yet scientifically defendable) for the assessment of the environmental quality of an area of that size. The concentrations and mobilities of all analysed contaminants in Poole Harbour were greatest in the heavily industrialised secondary embayment Holes Bay. Although Wareham Channel typically showed higher concentrations in the total content analyses compared to Southern Bights, the potential risk associated with metals, calculated based on both total concentrations and mobile fractions, was comparable in both areas. In case study 4 a simplified grain-size based normalisation scheme was tested. The efficiency of this approach, together several other normalisation schemes was evaluated in Wareham Channel, located in the west of Poole Harbour. In such fine-grained environments, neither geochemical analyses based on aluminium, nor granulometric normalisation schemes yielded a substantial improvement. Normalisations based on the much simpler iron-ratio reduced the variance considerably. This approach was then applied to the sediments close to a former weapons facility. Case study 5 investigated the interactions between the die-back of the cord grass Spartina anglica in Poole Harbour and the metal contamination in the sediments. Despite having several evolutionary advantages over other plants in this environment, S. anglica is dying back in the estuary since 1925 and the reasons for this process are insufficiently understood. No obvious impact of the metal contamination on S. anglica growth/ die-back could be detected, although the die-back has influenced, in turn, the metal concentrations in the estuary. The overall cadmium concentrations and potential risk of adverse effects have risen since 1925, but in the zones affected by die-back, cadmium stored in the sediment by S. anglica appears to have been washed out rapidly. Existing patches still retain elevated concentrations and are potentially at risk of further cadmium release, especially if sea level rise, caused by climate change, would accelerate the die-back.
15
Baker, Richard Graham Alex. "The geochemistry and cosmochemistry of thallium." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506042.
16
Rice-Birchall, B. "Petrology and geochemistry of basic volcanics." Thesis, Keele University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314570.
17
Woodhouse, Oliver Brian. "Osmium in seawater : analysis and geochemistry." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284676.
18
Hartland, Adam. "Colloidal geochemistry of speleothem-forming groundwaters." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1659/.
Анотація:
Natural aquatic colloids (solids with dimensions between 1 nm and 1 micron) were studied in cave waters that feed secondary carbonates [speleothems]. Results show that during hydrologically quiescent periods, trace metal (Tr) binding (e.g. Cu, Ni, Co) is dominated by humic-like, natural organic matter (NOM), with the smallest NOM-Tr complexes (≤1 to ca. 4 nm diameter) being the least labile at high pH (>pH 10). Partitioning of NOM:Tr between solution and crystal occurs minimally for the strongest complexes, providing a measure of NOM adsorption. Rapid fluxes of coarse (>100 nm) soil organic matter (SOM) and Tr in dripwaters often follow peak infiltration events, the coarse fraction of NOM quenching fluorescence in finer fractions (<100 nm). Termed ‘high-flux’ (HF), this mode of NOM-metal transport contrasts with the humic-like or ‘low-flux’ (LF) mode both hydrologically and chemically, resulting in shifts in trace metal ratios (e.g. Cu:Ni) which are characteristic of changes in the competitive binding of metals for suitable sites in NOM, and diagnostic of qualitative shifts in NOM composition (i.e. relatively more aromatic/hydrophobic). This process becomes manifest in speleothems, resulting in high- and low-flux trace metal end-members and providing information on NOM aromaticity. Changes in HF:LF metal ratios in speleothems are linked to processes in soils which are ultimately mediated by climate (i.e. ambient temperature and infiltrating precipitation); they may provide information on infiltrating precipitation, on the occurrence of surface disturbances (e.g. deforestation) and NOM composition. HF:LF indices complement the existing array of speleothem climate proxies, but each specific system and setting must be understood to ensure their proper interpretation.
19
Gamil, Ali Saif. "Petrology and geochemistry of Shetland granites." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316890.
Анотація:
This study is concerned with the distribution, age, chemistry and geotectonic setting of the 21 granites in Shetland. The granites range in size from a few metres to 8 Km across and in age from Pre-Moine to early Carboniferous. The granites occupy a unique position in being placed approximately half way between Scotland and Norway Caledonides and about 320 Km east of southeast coast of Greenland, if Greenland is restored to its pre-continental Drift position as predicted by the best fit of Greenland and Europe. The Shetland granites have been subdivided into 5 groups according to their location to the east or west of Walls Boundary Fault ( a continuation of Great Glen Fault), mineralogical content and their occurrence in situ as granitic pebbles, as follows; Granites to the east of WBF include (1) hornblende-bearing granites (2) hornblende-free granites and (3) Granitic pebbles a) the Rova Head conglomerate & b) the Funzie conglomerate. Granites to the west of WBF include (4) Ronas Hill granite and its satellites and (5) Sandsting & Bixter granites which are grouped together because of their proximity and because the Bixter granite seems to be the acidic end product of the Sandsting granitoid. A detailed petrological and geochemical study has been made of each group. Samples from each occurrence have been examined for mineralogical content and analysed by a variety of methods for major and trace elements (XRF, INAA, RNAA). This infonnation has been used to derive the mechanisms which may have been responsible for the observed differentiation trends. To the east of the Walls Boundary Fault (WBF) are hornblende-bearing granites, hornblende-free granites and Funzie and Rova Head granitic pebbles. The hornblende-bearing granites are truncated by the WBF and characterized by high Sr and Ba values. The Spiggie granite within this hornblende-bearing group also contains considerable amounts of primary epidote. The hornblende-free granites are a miscellaneous group of granitic rocks ranging between two-mica granites and garnet bearing granites, albite keratophyre and trondhjemite dykes. To the west of WBF are Ronas Hill granophyre and its satellites (with drusy cavities containing crystals of stilpnomelane, quartz and epidote), Sandsting complex and Bixter granites. Major element modelling suggests that a plagioclase, biotite and hornblende fractionation process is appropriate for hornblende-bearing granites and Sandsting granite. Graphical and trace element modelling do not conflict with this too, but rare earth element modelling requires extraction of a quartz-feldspar phase. The classification of Shetland granitoids on the basis of ages and petrology has not been previously attempted. According to the Read classification, the Caledonian hornblende-free granites could be classified as Pretectonic and Syntectonic intrusions equivalent to his older granites. In contrast to the hornblende-bearing granites to the east ofWBF (Graven, Brae complexes and the Spiggie granite), the Graven and Brae appear to belong to the Appinite Suite while the Spiggie granite seems to be a forceful Newer Granite. According to Read the forceful Newer Granites were emplaced just after the Appinite Suite but in Shetland the Graven and Spiggie granites appear to be the same age (400 Ma). The Ronas Hill granite and its satellites, Sandsting and Bixter granites to the west of WBF are Upper Devonian granites and equivalent to the permitted last intrusions of Read, but do not appear to be of the caulderon or ring complex type typical of those in Scotland In terms of ages the hornblende-bearing granites have given K-Ar ages of about 400-430 Ma. The Ronas Hill granite and its satellites, Sandsting complex and Bixter granite give K-Ar ages about 360 Ma. Consideration of typology indicates that the hornblende-bearing granites, Ronas Hill & its satellites, the Sandsting complex and Bixter granite are I-Caledonian type whereas some of the hornblende-free granites are close to S-type. On the De La Roche classification system the Shetland granites are high-K calc-alkaline (except trondhjemite dykes and keratophyre in the hornblende-free granites group) and mostly plotted in the shoshonitic trend The geochemical comparison of the the post Devonian Ronas Hill granite and its satellites on the one hand and the closely associated late Devonian Shetland volcanics on the other, reveals that there is no link between them. A comparison of the Shetland and Scottish granitoids in terms of major, trace and rare earth elements reveals very close similarities between these two Caledonian regions. Both show the same high K-calc-alkaline (peccerillo & Taylor, 1976), the high alumina and alkali (Kuno, 1966) character, also show a general alkali-calcic character (Peacock, 1930) and they also have very good correlation in terms of some trace element variation diagrams such as Sr and Ba
20
Davison, Nigel. "The geochemistry of radioactive waste disposal." Thesis, Aston University, 1987. http://publications.aston.ac.uk/9698/.
Анотація:
The present study attempted to identify the significant parameters which affect radionuclide migration from a low level radioactive waste disposal site located in a clay deposit. From initial sorption studies on smectite minerals, increased Kd with decreasing initial cation concentration was observed, and three sorption mechanisms were identified. The observation of anion dependent sorption was related to the existence of a mechanism in which an anion-cation pair are bound to the clay surface through the anion. The influence of competing cations, typical of inorganic groundwater constituents, depended on: (1) Ni/Co:Mn+(Mn+ = competing cation) ratio, (2) nature of M^n+, (3) total solution ionic strength. The presence of organic material in groundwater is well documented, but its effect on cation sorption has not been established. An initial qualitative investigation involving addition of simple organic ligands to Ni(Co)-hectorite samples demonstrated the formation of metal complexes in the clay interlayers, although some modified behaviour was observed. Further quantitative examination involving likely groundwater organic constituents and more comprehensive physical investigation confirmed this behaviour and enabled separation of the organic compounds used into two classes, according to their effect on cation sorption; (i) acids, (ii) amine compounds. X-ray photoelectron spectroscopy, scanning electron microscopy and Mossbauer spectroscopy were used to investigate the nature of transition metal ions sorbed onto montmorillonite and hectorite. Evidence strongly favoured the sorption of the hexaaquo cation, although a series of sorption sites of slightly different chemical characteristics were responsible for broadened peak widths observed in XPS and Mossbauer investigations. The surface sensitivity of XPS enabled recognition of the two surface sorption sites proposed in earlier sorption studies. Although thermal treatment of Fe^3+/Fe^2+-hectorite samples left iron atoms bonded to the silicate sheet structure, Mossbauer evidence indicated the presence of both ferric and ferrous iron in all samples.
21
Hobson, Andrew James. "Geochemistry of vanadium in hyperalkaline environments." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/20280/.
Анотація:
Hyperalkaline environments associated with leaching of industrial wastes such as steel slags can have a number of deleterious effects on their local environment including rapid carbonate precipitation and mobilisation of potentially toxic trace metals. Steel slag is the primary byproduct of steelmaking and is enriched in trace elements such as Al, Cr and V. V is of particular concern due to its high concentration in steel slag, its potential toxicity and its mobility in high pH leachate as the vanadate oxyanion (VO43-). This study used aerated and air-excluded batch leaching tests, aerated leachate neutralisation tests, field observations, X-ray microanalysis and electron microscopy techniques to investigate the effects of environmental conditions on V mobility, leachate chemistry and secondary phase formation during weathering of steel slags. Scanning electron microscopy/energy- dispersive X-ray spectroscopy (SEM/EDX) identified four principal mineral phases in unweathered slag comprising dicalcium silicate (Ca2SiO4), dicalcium aluminoferrite (Ca2(Al,Fe)2O5), a CaO-rich phase, and a Wüstite-like solid solution ((Fe, Mn, Mg, Ca)O). V was primarily incorporated in the dicalcium aluminoferrite (~1.1 wt%) and dicalcium silicate phases (~0.4 wt%). During leaching, alkalinity was rapidly produced by dissolution of dicalcium silicate and free lime resulting in a high pH (11.5 – 12.5) leachate. Dicalcium silicate dissolution leads to oversaturation with respect to calcium silicate hydrate (Ca-Si-H) phases and their subsequent precipitation. Under aerated conditions, in-gassing of atmospheric CO2 resulted in CaCO3 precipitation which consumed OH- ions and subsequently lowered solution pH to ~8.0. Micro-focus X-ray absorption spectroscopy (µXAS) analysis showed that V was released as V5+ during dicalcium silicate dissolution. V release was significantly higher under aerated conditions than under air-excluded conditions (~850 ppb and 490 ppb respectively in block leaching tests). Aqueous V concentrations were influenced by Ca3(VO4)2 solubility limits which imposed an inverse relationship on Ca and V concentrations. In air-excluded systems, leachate reaches saturation with respect to Ca3(VO4)2 which precipitates thus limiting aqueous V concentrations. Under aerated conditions, precipitation of CaCO3 provided a sink for aqueous Ca. Leachate therefore remained undersaturated with respect to Ca3(VO4)2, allowing higher concentrations of V to accumulate in solution. Leachate neutralisation experiments showed that some V was incorporated into neo-formed CaCO3 at high pH. V removal was enhanced in the presence of goethite (α-FeOOH). Extended X-ray absorption fine structure (EXAFS) analysis showed that vanadate adsorbed to goethite by formation of inner-sphere complexes indicating that Fe (oxy)hydroxides provide an important environmental sink for V in steel slag leachates. This study highlights the importance of leaching environment for V mobility during weathering of steel slags and suggests that prospects for slag reuse and storage may be improved by the formation of a weathered region containing secondary phases including Ca-Si-H and CaCO3. Leachate neutralisation results demonstrate removal mechanisms for aqueous V which will assist with environmental risk assessment and remediation at legacy sites where leachate has been released to the local aquatic environment.
22
Harraway, Trevor John. "Chemical characterisation of landfill leachate and its potential mobility through the Cape Flats sand." Thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/26218.
23
Jindra, Sarah A. "Hydrothermal Atomic Force Microscopy Investigation of Barite Growth: The Role of Spectator Ions in Elementary Step Edge Growth Kinetics and Hillock Morphology." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1503503972572962.
24
Pasilis, Sofie Portia. "Effect of citric acid on uranyl(VI) solution speciation, gas-phase chemistry and surface interactions with alumina." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280730.
Анотація:
Activities related to nuclear weapons production have left a legacy of uranium contamination in the United States. Understanding the chemical interactions that uranium undergoes in the environment is important for prediction of uranium mobility and development of remediation strategies. A detailed spectroscopic examination of the pH-dependent behavior of the UO₂²⁺-citrate system in aqueous solution was completed using Raman, ATR-FTIR, and NMR spectroscopies, combined with ESI-MS. Three structurally-distinct UO₂²⁺-citrate complexes, {(UO₂)₂Cit2}²⁻, {(UO₂)₃Cit₃}³⁻, and (UO₂)₃Cit₂ exist in dynamic equilibrium over a pH range from 2 to 9. ¹⁷O and ¹³C NMR data confirm the previously published structure of {(UO₂)₂Cit₂}²⁻ and indicate that {(UO₂)₃Cit₃}³⁻ is a symmetric, fluxional molecule. The (UO₂)₃Cit₂ complex was found to have a rigid structure and two structural isomers. Chemical interactions of U(VI), citric acid and Al₂O₃ were investigated using ATR-FTIR spectroscopy to examine how complexation of U(VI) by citrate affects adsorption of U(VI) to Al₂O₃. Participation in UO₂²⁺-citrate complexes does not significantly affect the ability of citrate to chemisorb to Al₂O₃. The UO₂²⁺-citrate complexes dissociate upon adsorption, with hydrolysis of UO₂²⁺. Adsorption isotherms developed from ATR-FTIR data indicate enhanced citrate adsorption to Al₂O₃ in the presence of UO₂²⁺ , suggesting that UO₂²⁺ acts as a central link between two citrate ligands, one of which is complexed to Al₂O₃. UO₂²⁺-citrate complexes can physisorb to citrate-saturated Al₂O₃. This study demonstrates how an in-depth infrared spectroscopic analysis of UO₂²⁺-ligand complexes both in solution and adsorbed to oxide surfaces can be used to understand the adsorption mechanisms of these complexes. ESI-MS was investigated for the characterization of U(VI) species in groundwater. Both ion trap and FTICR instruments were used. UO₂²⁺ forms complexes with ligands such as acetate, trifluoroacetate, and nitrate, which readily react with CH₃CN, CH₃OH, and H₂O to form solvated gas-phase species of the form [(UO₂L)Sn]⁺, where L represents the ligand, S represents solvent, and 1 ≤ n ≤ 4. n is directly related to the number of available coordination sites on UO₂²⁺, providing insight into the coordination environment of UO₂²⁺. Solvent exchange and addition reactions readily occur. UO₂²⁺ also forms coordinately saturated negatively-charged complexes with nitrate. UO₂²⁺-carbonate complexes were also investigated.
25
Jung, Daniel Yong Chu. "Ab initio studies in high pressure geochemistry /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17730.
26
Piatak, Nadine. "Geochemistry of Nettle Creek, Champaign County, Ohio /." Connect to resource, 1998. http://hdl.handle.net/1811/28568.
27
Sandison, Carolyn Maree. "The organic geochemistry of marine-influenced coals /." Full text available, 2001. http://adt.curtin.edu.au/theses/available/adt-WCU20030702.111035.
28
Bury, Sarah J. "The geochemistry of North Atlantic ferromanganese encrustacions." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334120.
29
Langford, Emma. "Microbial geochemistry of a lead-zinc mine." Thesis, University of Nottingham, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.594771.
Анотація:
Frongoch is a disused Pb-Zn mine situated approximately 16 km SE of Aberystwyth in central Wales. Despite being disused for over 100 years, the site is leaching heavy metals (Zn and Pb) into the Nant Cwmnewydion and ultimately Ystwyth rivers. The prevalence of heavy metal salts in the River Ystwyth was first reported by Carpenter in 1924 but remains a problem today. In 2002, the Environment Agency released a report ranking Frongoch in the top 50 mine sites impacting surface waters, and in 2010 work commenced to remediate the site. The British Geological Survey (BGS) and Environment Agency have been characterising the geochemistry and hydrology of the site. This study aimed to complement BGS studies by elucidating the total microbial population of tailings, peat and water samples from Frongoch and determining if the microbial population was accelerating leaching of heavy metals from the tailings. Culture dependant and independent methods were used to elucidate the microbial (predominantly Bacterial but also Archaeal and Eukaryotic) populations from a range of samples from Frongoch. However, an emphasis was made on determining the presence of sulphur oxidising bacteria (SOB), as they are known to cause dissolution of Zn and Pb by degradation of sphalerite (Zn5) and galena (PbS). In addition, a microcosm experiment was used to monitor chemical changes over time both in the presence and absence of microorganisms. • A number of known SOB were identified using 165 rDNA PCR DGGE. Subsequent analysis using selective cultures for Suljobacillus and PCR probes specific to Acidithiobacillus errooxidans (a known sulphur- and iron-oxidising species) and the soxB gene of the sulphur oxidase operon ubiquitous to many SOB gave further evidence for the presence of SOB in Frongoch tailings. However, no geochemically significant organisms were detected from water samples. Furthermore, reported microbial communities were diminutive in peat samples when compared to tailings samples with equivalent heavy metal concentrations. During the course of microcosm experiments, dissolution of heavy metals (Zn, Pb and Fe) by a consortium of cultured microorganisms native to Frongoch was detected. However, the pH increased to approximately pH 8.1 over time for all treatments, thus Acid Mine Drainage (AMD) was not generated. In addition, the inclusion of 10 mM ZnS in the growth medium decreased the lag time of the microbial growth curve when compared to cultures from un-spiked growth medium. This means that an increase in ZnS concentration stimulated the growth of microorganisms, suggesting that the culturable microbial population of Frongoch has adapted to use ZnS as a growth substrate .
30
Rock, Gregory John. "The iron geochemistry of mudstones and metapelites." Thesis, University of Newcastle Upon Tyne, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399001.
31
Warren, Edward Arthur. "Geochemistry of authigenic mineral sequences in sandstones." Thesis, University of Sheffield, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267897.
32
Hill, Alan Frederick Mark. "The sulphur geochemistry of Jurassic source rocks." Thesis, University of Aberdeen, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283752.
Анотація:
In immature Jurassic shales of differing depositional environment from Great Britain (Ro<0.5) the C32 hopane and C29 sterane isomerisation provide an accurate indication of relative maturities. For mature Viking Graben samples (Ro>0.7) a reliable indication of relative maturity is gained if Tmax, Ts(Ts+Tm), C29ββ/(ββ+αα) steranes and the Triaromatic Index are considered together. The most reliable parameters for the determination of depositional redox are pristane/phytane and the C35/C34 homohopane ratio, together with the concentrations of V, Cu, Ni and Mo. In the brackish lagoon of the Brora Coal Formation (BCF) low sulphate availability does not appear to have limited the pyritisation of iron relative to the open marine facies of the Brora Argillaceous Formation (BAF). Despite this δ34Spyrite for BCF samples indicates that sulphate reduction took place in a closed system due to the rapid depletion of available sulphate. Only low concentrations of excess H2S were available for incorporation within the organic matter, organic sulphur abundances in the BCF being much lower than for the BAF. In open-marine sequences an increase in TOC is associated with an increase in anoxia, the preservation of hydrogen-rich organic matter and the abundance of organic sulphur. A generally correlated increase in pyrite sulphur suggests both these modes of sulphur are associated with increasing concentrations of diagenetic sulphides (H2S and its partial oxidation products) generated through bacterial sulphate reduction. The greatest abundances of organic sulphur are formed when sulphide concentrations are high whilst sub-oxic surficial sediments are maintained so that polysulphides are generated within the sediment (by partial oxidation of H2S) for rapid sulphur incorporation. Improved preservation of labile organic matter leads to a increase in the abundance of organic compounds (e.g. sterenes and phytol derivatives) in which suitable functionalities exist for sulphur incorporation.
33
James, Doreen Elizabeth. "The geochemistry of feldspar-free volcanic rocks." Thesis, Open University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295080.
34
Maginn, Ellis. "Biomineralisation and geochemistry of hydrothermal vent fauna." Thesis, University of Southampton, 2002. https://eprints.soton.ac.uk/426772/.
Анотація:
Hydrothermal ventfauna, particularly vestimentiferan and polychaete worm tubes, are occasionally preserved in the geological record. The early stages of mineralisation are particularly important in defining whether or not preservation will occur, and they are poorly understood. This dissertation describes 3 separate studies of ventfauna undergoing early mineralisation associated with active seafloor vent systems. Tube samples of the polychaete worm Alvinella pompejana collected from 13°N on the East Pacific Rise were studied to identify the processes occurring during early sulphide mineralisation. Iron sulphide mineralisation is present within the walls of the organic dwelling tube, and is induced by microbialfauna preserved within the tube micro-layers. A laminated tube structure wasformed, comprising alternating layers of tube material and microbially templated iron sulphide-rich interlayers. The iron monosulphides mackinawite and greigite, have been identified as intermediate phases that occur as precursor minerals during theformation ofpyrite. Later marcasite mineralisation is observed toform over some of the pyritised organic layers. Later stagemineralisationprocesses in a selection offossil tube structures recoveredfrom an extinct sulphide mound on the Southern East Pacific Rise were studied. The similarity to existingfaunal assemblages suggests that these structures were also associated with Alvinella sp. polychaete worms. Two generations ofpyrite were identified along with a later stage chalcopyrite phase. Fine scale variability in tube wall geochemistry was demonstrated with electron micro-probe transects across the structures and this is inferred to reflect early mineralisation processes as identified in living polychaete worms. Sulphur isotope analyses of the different sulphide phases gave δ³⁴S values higher than any previously measured for chimney structures on a sediment-free ridge setting (δ³⁴S = 3.8-10.8‰). A two stage model is proposed whereby early pyrite / marcasite laminae originally laid down in association with biogenic tube structures, are replaced by euhedral pyrite, and later stage primary chalcopyrite precipitation. A study ofRidgea piscesae from the Juan de Fuca Ridge demonstrated that silicification processes proceed so rapidly that the vestimentiferan tubes can become mineralised during the worm's life cycle. The organic component of the worm tube is rapidly replaced by amorphous silica which undergoes dewatering toform opal-A. This mineralisation is then overgrown by barite laths, and microbially templated amorphous silica. With time, prograde mineralisation causes the further precipitation and consequent overprinting of the primary mineral suite with iron- and zinc-sulphides. Other observations from samples studied here include micro-tubes (-50 jjm length) associated with adult R. piscesae and a silicified mucus lining to inhabited worm tubes. Associated with the mucus lining is a ligament which runs along the inside of the tube, and is tentatively inferred to be a form of anchor, allowing the worm to rapidly retract into the tube when threatened. Once mineralisation has replaced the organic tube material there is scope for the tube structure to be preserved along with the host sulphide body. Understanding of the mechanisms of early sulphide and silica/barite mineralisation as inferred from detailed observations and measurements of tube worm samples is an important contribution to the growing field of hydrothermal palaeobiology.
35
Ghani, Azman Abdul. "Petrology and geochemistry of Donegal granites Ireland." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243112.
36
Pekka, Larisa. "Geochemistry of the Kola River, northwestern Russia." Licentiate thesis, Luleå tekniska universitet, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25751.
Анотація:
The Kola River in the northern part of the Kola Peninsula, northwestern Russia, flows into the Barents Sea via the Kola Bay. The river is vital for the reproduction of salmon and an important source of drinking water for more than 500,000 people in Murmansk and the surrounding municipalities. To evaluate the environmental status of the Kola River water, extensive sampling of water (the dissolved (ƒ¬0.22 ƒÝm) and suspended (ƒ®0.22 ƒÝm) phases) and aquatic mosses (Fontinalis spp.) was performed on thirteen sites along the Kola River and its tributaries during 2001 and 2002. Major (Ca, K, Mg, Na, S, Si, HCO3 and Cl) and trace (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sr, Ti, and Zn) elements, total and particulate organic carbon (TOC and POC), N and P were analyzed. For aquatic bryophytes, the analyzed metals were Al, As, Ba, Cu, Cd, Co, Fe, Mn, Mo, Pb, Zn and Ni. The levels of major nutrients (P and N), as well of major and trace elements in the Kola River water, with the exception of Na, Cl, Cu, Zn and Ni, were close to natural baseline levels. Comparison with the boreal pristine Kalix River, northern Sweden, shows that, except for Na, Cl, Cu, Zn and Ni, which exceed the concentrations in the Kalix River by as much as 2-3 times, the levels of other major and trace elements are close to or even below the levels in the Kalix River. The water chemistry and the aquatic bryophyte results show a similar picture of pollution status in the Kola River, indicating relatively low contamination in the river. The Kola River shows elevated levels of Cu and Ni both in water and in the aquatic bryophytes compared with the Swedish reference data. Comparison with the unpolluted River Tenojoki, Finland, reveals elevation of Al, Cd, Cu, Co, Ni and Zn concentrations in the aquatic bryophytes in the Kola River. Spatial variations in concentrations of Fe, Al, Co, Pb and Zn in bryophytes show a general trend of increase downstream the watercourse. Aquatic bryophytes and water quality close to the upstream mine areas show elevated concentrations of As, Cu, Mn, Mo and Ni, while values in the middle part of the river are near background levels. The concentrations of As and Cu in the aquatic bryophytes mostly reflect the dissolved phase of the metal in water, while the concentrations of Ba and Co mainly reflect the suspended phase. Fe, Al, Mn, Mo, Ni, Pb and Zn in mosses reflect both the dissolved and the suspended phases of these metals in water. The results demonstrate that pollutants from the two major sources: the open-pit iron mine and ore concentration plant in Olenegorsk in the upper part of the basin and the Varlamov, the Medveziy and the Zemlanoy Creeks, draining the area of large agricultural enterprises in the lower part of the watershed, influence the water quality of the Kola River.Godkänd; 2003; 20070215 (ysko)
37
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.
Анотація:
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 (MgDoctorat en Sciences
info:eu-repo/semantics/nonPublished
38
Williamson, Mark Allen. "Thermodynamic and kinetic studies of sulfur geochemistry." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/38485.
39
Miller, Sarah Jane. "Geochemistry of ferruginous clogging of Karoo wells." Master's thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/4213.
Анотація:
Summary in English.Includes bibliographical references.
The main source of potable water in the Karoo is groundwater and thus any problems resulting from the abstraction of water or from diffifulties in abstractions of water are important. The iron clogging of screens, pumps and filter packs in supply wells is a worldwide problem and the consequences can be severe, leading to costly and harsh rehabilitation measures or even loss of the well. A study was undertaken in order to determine the chemistry and morphology of the precipitates found in relation to the water chemistry, in several wells in the Albertinia-Oudtshoorn-Calitzdorp area of South Africa.
40
Morford, Jennifer Lynn. "The geochemistry of redox-sensitive trace metals /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/8508.
41
Wilson, George B. "Isotope geochemistry and denitrification processes in groundwaters." Thesis, University of Bath, 1986. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370156.
42
Sandison, Carolyn M. "The organic geochemistry of marine-influenced coals." Thesis, Curtin University, 2001. http://hdl.handle.net/20.500.11937/2193.
Анотація:
The importance of organic sulphur fixation in the preservation of organic matter in humic coal-forming environments is demonstrated in this thesis. The transgression of coal depositional systems by marine waters during their deposition and early diagenesis enables the production of reduced inorganic sulphur species by sulphate-reducing bacteria. The presence of these reactive sulphur species, in combination with the altered chemical and microbial regime, influences the preservation and petroleum potential of humic coal.Three lignite samples taken over a two meter depth profile of a core in the Eocene, Heartbreak Ridge lignite deposit, SE Western Australia, were analysed by a suite of geochemical techniques to identify origins and transformation pathways of their organic matter. Rock-Eval, FTIR microscopy, and pyrolysis gas chromatography-mass spectrometry (Py-GCMS) indicate that the composition of the lignite and its extract are typical of immature type III organic matter with a predominance of aromatic and oxygen containing functionalities. Variation in the macromolecular composition of the three lignites are consistent with more pronounced degradation of the organic matter in the lowermost lignite horizon. Nickel boride desulphurisation of polar and asphaltene fractions of the lignites showed the presence of sulphur-bound higher plant triterpenoids, in particular olean-12-ene, n-alkanes of even predominance, C29 steranes and extended 17â(H),21â(H)-hopanes. Deuterium labelling experiments indicated that these components were mostly bound to a single sulphur, at sites about the original functionality in the natural product precursors. The presence of singularly sulphur-bound aromatic ring A degraded and pentacyclic triterpenoids represent the spectrum of aromatic triterpenoid intermediates undergoing diagenesis before sulphur incorporation.Stable carbon isotopic analyses of the free and sulphur-bound aliphatic hydrocarbons confirmed carbon sources from both higher plants and bacteria. Oxygenated lipids consisted of even carbon-numbered n-alkanoic monocarboxylic acids, ù-hydroxy fatty acids and n-alkanols, n-alkan-2-ones, 6,10,14-triinethylpentadecan-2-one, and oxygenated hopanoids and higher plant triterpenoids. BY the onset of sulphurisation in the Heartbreak Ridge lignite, extended hopanoid degradation had come to a hiatus, in marked contrast to the variable alteration of the higher plant triterpenoids. The oxygen-containing lipids of the extracts are implicated as the primary source of the sulphurised hydrocarbons, although not necessarily via direct sulphurisation of their present sent form, but through the formation of more reactive intermediates. These results implicate sulphur fixation as a means by which lipids of similar structures to the natural product precursors are preserved in coal forming environments. That diagenetic alteration of the oxygenated lipids mirrors that of the sulphur-bound hydrocarbons confirms that the onset of marine incursion and the formation of reduced inorganic sulphides does inhibit (and also preserve) the normal biogeochemical transformations of organic matter in coal-forming environments.The technique of reaction gas chromatography-mass spectrometry (R-GCMS) was also applied to the analysis of the polar extracts from a Heartbreak Ridge lignite, together with the polar extracts from the Monterey Formation shale (Naples Beach, USA; Miocene age). Palladium black acting as a catalyst under hydrogen carrier gas in the vaporising injection port of a GCMS, effected gas phase reaction of the volatile constituents in the polar mixtures.The fully active catalyst effected hydrogenation, desulphurisation and decarbonylation/decarboxylation reactions. Polar fractions of the Heartbreak Ridge lignite reacted to produce angiosperm-derived triterpenoids and bacterially-derived hopanoids. The reaction of the Monterey Formation shale polars resulted in the formation of high relative amounts of pristane and phytane with a predominance of the latter, as well. as a suite of steroidal and triterpenoid moieties, typical of marine organic matter. However, R-GCMS provided less detailed information on the exact nature of the functionalised lipids partitioned within the polar fraction than that obtained by more conventional wet chemical analyses.The compositions of 35 marine-influenced, bituminous coals, from the Eocene Brunner Coal Measures of New Zealand were studied to assess the effect of the timing of marine incursion on the molecular characteristics of coals. Based upon their stratigraphic position and their volatile matter and total sulphur contents, coal samples were classified into those where the mire was flooded during or at the end of deposition (Class A/B) and those that experienced postdepositional access of marine water during later diagenetic stages (Class C/D). Rock-Eval pyrolyses showed that sulphur-rich Brunner coals generally display moderate increases in pyrolytic yields with respect to the low-sulphur Brunner coals. Class A-C coals generally release larger quantities of hydrocarbons during Rock-Eval pyrolysis than the Class D coals, suggesting that sulphur fixation can enhance the hydrocarbon potential of buried mires, provided sulphur is introduced early. Variation in Carbon Preference Indices, isoprenoid/alkane ratios, the Methylphenanthrene Index and phenanthrene/anthracene of bitumens and pyrolysates both within different seam profiles and between different sampling localities can be attributed to changes in microbial regime as well as subtle variations in rank.Pristane/phytane, dibenzothiophene/phenanthrene and thiophene ratios are closely related to organic sulphur contents, but are also influenced by these changes in rank and differences in the timing of marine incursion.Organic sulphur contents and biomarker compositions are related through a drillcore profile, which confirms the role of diagenetic sulphur sequestration in preserving specific biomarkers (steranes, higher plant triterpanes, extended hopanes) in coal-forming environments. Biomarker ratios that vary accordingly include the homohopane index, Ts/Tm, C29Ts/norhopane, C30 diahopane/hopane, sterane/hopane ratio, C29 diasterane/sterane, oleanane/hopane, oleanoid triterpane/hopane, and ring A degraded triterpanes/des-E-hopane.Diasterane concentrations were greatest in high sulphur coals. It is suggested that sterenes, generated from sulphur-bound steroids of regular stereochemistry in the subsurface, undergo acid-catalysed rearrangement and hydrogenation to enhance diasterane concentrations. A similar formation mechanism can be invoked for the rearranged hopanes (Ts, C29Ts, C30 diahopane) and oleanoid triterpanes. The timing of sulphur fixation does not appear to have influenced the formation of biomarkers except in one case. The only lipid class that degraded rapidly enough for the precursors required for sulphurisation to be removed prior to saline access is the higher plant triterpenoids. Stable carbon isotopic analysis of the n-alkanes, isoprenoids and hopanoids from the Pike River Outcrop seam section confirms both higher plant and microbial sources. In particular, the carbon isotopic composition of phytane suggests that methanogenic decomposition of the Pike River peat occurred. The isotopic signatures are invariant to changes in the degree or timing (Class A-C only) of sulphur access to this outcrop.This body of work finds that the introduction of marine waters (and the formation of reduced sulphides) in the early stages of mire and peat development preserves the inherited lipid composition of the peat and does not overwhelm this biotic signature during sulphate reduction. As such, the selective preservation of certain biomarkers enables their use as indicators of marine-influence in source rocks. The application of several biomarker ratios to the characterisation of crude oils from the Taranaki Basin of New Zealand provides further evidence for the generation of liquid hydrocarbons from marine-influenced, angiosperm-rich coals.
43
Sandison, Carolyn M. "The organic geochemistry of marine-influenced coals." Curtin University of Technology, School of Applied Chemistry, 2001. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=12911.
Анотація:
The importance of organic sulphur fixation in the preservation of organic matter in humic coal-forming environments is demonstrated in this thesis. The transgression of coal depositional systems by marine waters during their deposition and early diagenesis enables the production of reduced inorganic sulphur species by sulphate-reducing bacteria. The presence of these reactive sulphur species, in combination with the altered chemical and microbial regime, influences the preservation and petroleum potential of humic coal.Three lignite samples taken over a two meter depth profile of a core in the Eocene, Heartbreak Ridge lignite deposit, SE Western Australia, were analysed by a suite of geochemical techniques to identify origins and transformation pathways of their organic matter. Rock-Eval, FTIR microscopy, and pyrolysis gas chromatography-mass spectrometry (Py-GCMS) indicate that the composition of the lignite and its extract are typical of immature type III organic matter with a predominance of aromatic and oxygen containing functionalities. Variation in the macromolecular composition of the three lignites are consistent with more pronounced degradation of the organic matter in the lowermost lignite horizon. Nickel boride desulphurisation of polar and asphaltene fractions of the lignites showed the presence of sulphur-bound higher plant triterpenoids, in particular olean-12-ene, n-alkanes of even predominance, C29 steranes and extended 17â(H),21â(H)-hopanes. Deuterium labelling experiments indicated that these components were mostly bound to a single sulphur, at sites about the original functionality in the natural product precursors. The presence of singularly sulphur-bound aromatic ring A degraded and pentacyclic triterpenoids represent the spectrum of aromatic triterpenoid intermediates undergoing diagenesis before sulphur incorporation.Stable carbon isotopic ++analyses of the free and sulphur-bound aliphatic hydrocarbons confirmed carbon sources from both higher plants and bacteria. Oxygenated lipids consisted of even carbon-numbered n-alkanoic monocarboxylic acids, ù-hydroxy fatty acids and n-alkanols, n-alkan-2-ones, 6,10,14-triinethylpentadecan-2-one, and oxygenated hopanoids and higher plant triterpenoids. BY the onset of sulphurisation in the Heartbreak Ridge lignite, extended hopanoid degradation had come to a hiatus, in marked contrast to the variable alteration of the higher plant triterpenoids. The oxygen-containing lipids of the extracts are implicated as the primary source of the sulphurised hydrocarbons, although not necessarily via direct sulphurisation of their present sent form, but through the formation of more reactive intermediates. These results implicate sulphur fixation as a means by which lipids of similar structures to the natural product precursors are preserved in coal forming environments. That diagenetic alteration of the oxygenated lipids mirrors that of the sulphur-bound hydrocarbons confirms that the onset of marine incursion and the formation of reduced inorganic sulphides does inhibit (and also preserve) the normal biogeochemical transformations of organic matter in coal-forming environments.The technique of reaction gas chromatography-mass spectrometry (R-GCMS) was also applied to the analysis of the polar extracts from a Heartbreak Ridge lignite, together with the polar extracts from the Monterey Formation shale (Naples Beach, USA; Miocene age). Palladium black acting as a catalyst under hydrogen carrier gas in the vaporising injection port of a GCMS, effected gas phase reaction of the volatile constituents in the polar mixtures.The fully active catalyst effected hydrogenation, desulphurisation and decarbonylation/decarboxylation reactions. Polar fractions of the Heartbreak Ridge lignite ++
reacted to produce angiosperm-derived triterpenoids and bacterially-derived hopanoids. The reaction of the Monterey Formation shale polars resulted in the formation of high relative amounts of pristane and phytane with a predominance of the latter, as well. as a suite of steroidal and triterpenoid moieties, typical of marine organic matter. However, R-GCMS provided less detailed information on the exact nature of the functionalised lipids partitioned within the polar fraction than that obtained by more conventional wet chemical analyses.The compositions of 35 marine-influenced, bituminous coals, from the Eocene Brunner Coal Measures of New Zealand were studied to assess the effect of the timing of marine incursion on the molecular characteristics of coals. Based upon their stratigraphic position and their volatile matter and total sulphur contents, coal samples were classified into those where the mire was flooded during or at the end of deposition (Class A/B) and those that experienced postdepositional access of marine water during later diagenetic stages (Class C/D). Rock-Eval pyrolyses showed that sulphur-rich Brunner coals generally display moderate increases in pyrolytic yields with respect to the low-sulphur Brunner coals. Class A-C coals generally release larger quantities of hydrocarbons during Rock-Eval pyrolysis than the Class D coals, suggesting that sulphur fixation can enhance the hydrocarbon potential of buried mires, provided sulphur is introduced early. Variation in Carbon Preference Indices, isoprenoid/alkane ratios, the Methylphenanthrene Index and phenanthrene/anthracene of bitumens and pyrolysates both within different seam profiles and between different sampling localities can be attributed to changes in microbial regime as well as subtle variations in rank.Pristane/phytane, dibenzothiophene/phenanthrene and thiophene ratios are closely related ++
to organic sulphur contents, but are also influenced by these changes in rank and differences in the timing of marine incursion.Organic sulphur contents and biomarker compositions are related through a drillcore profile, which confirms the role of diagenetic sulphur sequestration in preserving specific biomarkers (steranes, higher plant triterpanes, extended hopanes) in coal-forming environments. Biomarker ratios that vary accordingly include the homohopane index, Ts/Tm, C29Ts/norhopane, C30 diahopane/hopane, sterane/hopane ratio, C29 diasterane/sterane, oleanane/hopane, oleanoid triterpane/hopane, and ring A degraded triterpanes/des-E-hopane.Diasterane concentrations were greatest in high sulphur coals. It is suggested that sterenes, generated from sulphur-bound steroids of regular stereochemistry in the subsurface, undergo acid-catalysed rearrangement and hydrogenation to enhance diasterane concentrations. A similar formation mechanism can be invoked for the rearranged hopanes (Ts, C29Ts, C30 diahopane) and oleanoid triterpanes. The timing of sulphur fixation does not appear to have influenced the formation of biomarkers except in one case. The only lipid class that degraded rapidly enough for the precursors required for sulphurisation to be removed prior to saline access is the higher plant triterpenoids. Stable carbon isotopic analysis of the n-alkanes, isoprenoids and hopanoids from the Pike River Outcrop seam section confirms both higher plant and microbial sources. In particular, the carbon isotopic composition of phytane suggests that methanogenic decomposition of the Pike River peat occurred. The isotopic signatures are invariant to changes in the degree or timing (Class A-C only) of sulphur access to this outcrop.This body of work finds that the introduction of marine waters (and the formation of reduced sulphides) in the early stages of mire and peat ++
development preserves the inherited lipid composition of the peat and does not overwhelm this biotic signature during sulphate reduction. As such, the selective preservation of certain biomarkers enables their use as indicators of marine-influence in source rocks. The application of several biomarker ratios to the characterisation of crude oils from the Taranaki Basin of New Zealand provides further evidence for the generation of liquid hydrocarbons from marine-influenced, angiosperm-rich coals.
44
Subroto, Eddy Ariyono. "30-NOR-17 [alpha] (H) - hopanes and their applications in petroleum geochemistry." Thesis, Curtin University, 1990. http://hdl.handle.net/20.500.11937/421.
Анотація:
A suite of samples consisting of twenty-two crude oils and eight sedimentary rocks has been analysed for biological marker compounds by GC-MS. The sedimentary rocks are rich in carbonate minerals and the crude oils were reported to have been derived from carbonate source rocks. These samples are from a variety of geographical origins, geological ages and depositional environments. They consistently contain a homologous series of 30-nor-17 [alpha] (H)-hopanes. Seven homologues (C28 - C34) of the 30-nor-17 [alpha](H)-hopane series have been identified. These compounds appear to be useful biological markers for samples having carbonate associations.A series of 25,30-bisnor-17 [alpha] (H)-hopanes has been observed in a severely biodegraded crude oil of probable carbonate origin. This observation, together with the well-established enrichment of normal hopanes demethylated at position 25 in severely biodegraded crude oils, suggests that the presence of this series of hopanes indicates severe biodegradation of crude oils originating from carbonate-rich source rocks.Another series of hopanes which was previously unreported, the 2-methyl-30-nor-1 [alpha] (H)-hopanes, has also been observed in the carbonate samples. Seven members (C29-C35) of this homologous series have been identified in this study. This series appears to be associated with carbonate rocks deposited under extreme reducing conditions.The biological marker compounds in another sample suite comprising twelve sediments and three crude oils from the North Sumatra Basin, Indonesia, have also been analysed by GC-MS as part of a correlation study. Sediment samples classified as shales, carbonaceous shales and calcareous shales have been shown to contain very different biomarkers. These distinctive biomarkers have enabled the source characteristics of the crude oils to be inferred. Two crude oils have been recognised with similar biomarker characteristics to the shales and one crude oil has the characteristics of the calcareous shale. The distinctive features of the carbonaceous shale were not observed in the crude oils. This study therefore provides an excellent example of how the 30-nor-17 [alpha] (H)-hopane compounds can be useful in oil-source rock correlation studies.
45
Brown, Erik Thorson. "The geochemistry of beryllium isotopes : applications in geochronometry." Thesis, Woods Hole, Mass. : Woods Hole Oceanographic Institution, 1990. http://catalog.hathitrust.org/api/volumes/oclc/23283464.html.
46
Wombacher, Frank. "The stable isotope geochemistry and cosmochemistry of cadmium." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=967287685.
47
Tijhuis, Laurentius. "The Geochemistry of the Topsoil in Oslo, Norway." Doctoral thesis, Norwegian University of Science and Technology, Department of Geology and Mineral Resources Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-164.
Анотація:
In co-operation with the Geological Survey of Norway, 395 samples of topsoil, 44 bedrock samples and 24 samples of sand from sandboxes at kindergartens taken in Oslo, the capital city of Norway, were analysed for a wide range of elements. To get a measure on the bio-availability of arsenic, a five stage sequential extraction procedure was accomplished on a subset of 98 topsoil samples and on all 24 samples of sand from sandboxes. These fractions (i.e. “Exchangeable”, “Carbonate”, “Reducible substrate”, “Organic” and “Residual”) were analysed for arsenic. Bulk concentrations in a representative subset of 10 bedrock samples were determined by XRF analysis.
For the concentrations of the elements As, B, Ba, Cd, Cr, Cu, Hg, Mn, Mo, Ni, P, Pb and Zn in soil, geologic sources are important, but human activity has had a large effect on concentrations in topsoil, especially in the central districts. At least 81% of the samples contain more arsenic than the Norm value for polluted soil used by the Norwegian authorities. For chromium, zinc and lead, the percentages are 65, 74 and 25 respectively. In topsoil, up to 50% of the arsenic is extractable in the exchangeable, the carbonate and the reducible substrate fractions, but only 2% of the samples exceeded the Norm value after the three extraction stages. After four stages of extraction, 69% of the samples exceeded the Norm value.
At 24 kindergartens in the central districts of Oslo, concentrations of As, Cd, Cr, Cu, Ni, Pb and Zn in topsoil samples are higher than in samples of sand from sandpits, but differences in arsenic are low. All topsoil samples and 63% of the sandbox samples exceed the arsenic Norm value for polluted soil used by the Norwegian authorities. Concentrations of at least one of the elements Cr, Cu, Ni, Pb and Zn exceed the Norm value in the topsoil. At two kindergartens all elements, except Cd, exceed the Norm value in the topsoil.
In the samples from the sandboxes, arsenic concentrations in the exchangeable, the carbonate and the reducible substrate fractions, lie at a higher level than in topsoil samples. Leakage of arsenic compounds from impregnated and painted wood have probably caused elevated concentrations of this element in the sand. At two kindergartens the cumulative arsenic content in samples from the sandboxes exceeds the Norm value of 2 mg/kg As for polluted soil already after two fractions (i.e. the “Exchangeable” and the “Carbonate” fraction). After three fractions, the arsenic content in sand at 5 kindergartens exceeds this value. After four fractions this number was still 5. Regarding soil, no kindergartens had a cumulative arsenic content after three stages of the extraction procedure. After four stages 16 kindergartens contained more arsenic than the Norwegian Norm value of 2 mg/kg As.
Bulk concentrations of metals, in the bedrock samples, are generally higher than the acid soluble concentrations. Differences are small for copper and zinc, somewhat higher for lead and nickel and considerably different for chromium. Acid soluble chromium concentrations in soil differ little when compared with acid soluble concentrations in bedrock, but are in general much lower than bulk concentrations in rock. Chromium is probably strongly incorporated in the mineral structure of rock samples and concentrated HNO3 cannot solubilize all chromium molecules. For copper, lead and zinc, the acid soluble concentrations in soil are higher than the bulk concentrations in bedrock. The parent rock material cannot be the only source for these elements in soils and various anthropogenic sources dispersed by air or water probably have major influence.
The enrichment of nickel in topsoil near highways in Oslo might be due to the bitumen content of road dust. The enrichment of chromium and copper might be due to wear and tear of cars and engine parts. There is no enrichment of cadmium and zinc in topsoil near highways. Concentrations of zinc in topsoil in Oslo are generally high, most probably because of industry. The possible addition of zinc from traffic to the topsoil is not observed, in this study.
48
Hales, Philip. "Inorganic geochemistry of tropical lake and swamp sediments." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357524.
49
Sumon, Mahmud Hossain. "Geochemistry of arsenic in Bengal Basin wetland sediments." Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=168311.
Анотація:
Over the last decades, arsenic (As) contamination of soil-plant-water systems has become a major concern for Bangladesh and West Bengal, India. The geochemistry of the sediment depositional environment which subsequently, on sediment burial, give rise to elevated As in Holocene groundwater’s of Southeast Asia, may provide clues to unravelling the mechanistic basis and spatial heterogeneity of this phenomenon. The Sundarbans mangrove ecosystem, Bangladesh, is a modern analogue, and indeed forms a continuum with, the Holocene sediments of concern and thus studying As cycling in surface Sundarbans sediments. Similarly, rice paddy fields in many regions of the Bengal Basin form a continuum with Holocene sediments. Sediment cores were collected from a wide range of locations within the Sundarbans to study surface spatial, as well as down the profile (~1 m), As distribution and it’s association with other geochemical parameters. Pore and surface water, and Diffusive Gradients in Thin films (DGT) were sampled from 4 different interlocked sub-habitats over 0.29 km2: major river bank, main tributary, forest floor and minor tributary. Further experiments were conducted to observe As dynamics in mangrove surface sediments on application of mangrove detritus. Finally 3 interlinked experiments (field manuring, soil batch culture, greenhouse growth trials) were conducted to assess the effect of farm-yard manure (FYM) and rice straw, at a field application rate practised in Bangladesh (5 t/ha), on As mobilization in soil and subsequent assimilation by rice. As concentration in mangrove sediment down the profile was found to be more associated with elevated Fe and Mn than with organic matter (OM), with significant spatial variations among the locations. Sediment particle size was an important factor determining As retention and mobilization, which is also true for deeper Bengal Bay sediments. Proximity to mangrove vegetation and to water bodies was found to have significant effect on As dynamics. Porewaters from coarse textured, low OM riverbank sediment were high in As, but with only a small pool of As for resupply from the solid phase, showing similarities with grey aquifer sediments compared to fine textured and high OM content forest floor sediments. The As column dynamics study showed that As release into porewater was strongly associated with Fe release, indicating the strong association of the 2 elements, with OM playing a major role in their dissolution. The desorption studies also showed OM driving As mobilization within short time. Due to strong redox cycling very little evidence of As methylation was observed in biologically active mangrove porewaters. But we found 10-fold increase in dimethylarsinic acid (DMA) production compared to a non-amended control using the same sediments treated with mangrove detritus in the laboratory. OM amendments lead to considerable mobilization of As into both soil porewaters and standing surface waters in rice paddy. In a greenhouse rice cultivation experiment, flooding initially caused greatly enhanced As mobilization in porewater (< 24 d), but the effects of flooding on As mobilization decreased during later rice growth, particularly at grain fill. However, OM amendment did not cause significant As accumulation in grain and straw compared to control. It was noted in field trials and greenhouse studies that OM fertilization greatly enhanced As mobility to surface waters, which may have major implications for fate of As in paddy agronomic ecosystems.
50
Eady, Angela Elizabeth. "The petrology and geochemistry of the Acheron intrusion." Thesis, University of Canterbury. Geology, 1995. http://hdl.handle.net/10092/6783.
Анотація:
Subalkaline transitional gabbros have intruded the Cretaceous - Paleocene sediments of the Acheron Outlier. The gabbroic magma has differentiated in situ to form a laccolith and sill-like apophysis, as well as having a strong thermal effect on the sediments and especially the coals of the Broken River Formation. This research concentrates on the geochemical characteristics and differentiation processes. Additional research on the thermal alteration of the coals at Acheron has provided data for heating models of the sediments.
Thermal alteration of the sediments is extensive with the thermal aureole of the intrusion affecting the entire thickness of Tertiary sediments exposed at Acheron, increasing coal ranks from regional lignite A to anthracite. Vitrinite reflectance data indicate circulating hydrothermal fluids had a strong control on the degree of heating sediments underwent.
It is suggested that the Acheron magma was modified by flowage differentiation within the conduit prior to emplacement. This created an olivine phenocryst-rich magma and an olivine phenocryst-poor melt. The latter was emplaced into the Tertiary sediments as a thin proto-laccolith which inflated to form the bulk of the Acheron Intrusion prior to the emplacement of the denser and more viscous olivine-rich magma which formed a basal layer within the intrusion and also breached the laccolith margin to form the apophysis. Crystallisation proceeded from the walls, roof and floor by sidewall crystallisation. This produced the five lithotypes recognised within contact gabbro, olivine mela-gabbro, gabbro, monzogabbro and differentiates.
Geochemical analyses of these rocks show differentiation trends consistent with crystal fractionation of a relatively basic melt. Geochemical trends are complicated by the extensive deuteric alteration of the intrusion. Alteration of feldspar by late stagedeuteric fluids has produced secondary analcime and other zeolites, as well as quartz, giving the false impression that the intrusion was originally undersaturated.