bluuebunny/crossref_metadata_2025 huggingface dataset:
Acid-gas injection in the Alberta basin, Canada: a CO
2
-storage experience
Authors: Bachu Stefan , Gunter William D.
Published: April 2008

Over the past decade, oil and gas producers in the Alberta basin have been faced with a growing challenge to reduce atmospheric emissions of hydrogen sulphide (H
2
S) that is produced from ‘sour’ hydrocarbon pools. Since surface desulphurization is uneconomic, increasingly operators are turning to acid-gas disposal by injection into deep geological formations. Acid gas, a mixture of hydrogen sulphide and carbon dioxide (H
2
S and CO
2
), is the by-product of ‘sweetening’ sour hydrocarbons. Although the purpose of the acid-gas injection operations is to dispose of H
2
S, significant quantities of CO
2
are also being injected because it is uneconomical to separate the two gases. The acid-gas injection operations in the Alberta basin represent an analogue to geological sequestration of CO
2
. Large-scale injection of CO
2
into depleted oil and gas reservoirs and into deep saline aquifers is one of the most promising methods of geological sequestration of CO
2
, and in this respect it is no different from acid-gas disposal operations. However, before implementation of greenhouse-gas geological sequestration, a series of questions need to be addressed; the most important ones relate to the short- and long-term fate of the injected CO
2
. Thus, the study of the acid-gas injection operations in Alberta provides the opportunity to learn about the safety of these operations and about the fate of the injected gases, and represents a unique opportunity to investigate the feasibility of CO
2
geological sequestration.
Relationship between diatremes, dykes, sills, laccoliths, intrusive-extrusive domes, lava flows, and tephra deposits with unconsolidated water-saturated sediments in the late Variscan intermontane Saar-Nahe Basin, SW Germany
Authors: Lorenz Volker , Haneke Jost
Published: April 2008

The late Varican intermontane Saar-Nahe Basin underwent an intensive episode of synsedimentary intra-basinal magmatism, with magmas ranging from tholeiitic basalts to rhyolites. Volcanism began late in the sedimentary history of the basin, after accumulation of about 5000–5500 m of continental sediments. Basic to silicic maar-diatremes formed mostly on hydraulically active faults or fault intersections. Basic to intermediate sills were emplaced at depths between about 2500 m and almost the original surface. Some sills inflated considerably in thickness. Silicic laccoliths intruded in the same depth range. Ongoing volume inflation of some laccoliths led to huge intrusive-extrusive domes, rock falls and probably block-and-ash flows and even to extensive thick lava extrusions. Some domes are composite or show evidence for magma mingling. In the Baumholder-Idar-Oberstein area, lava flows reach a cumulative thickness of 800–1000 m. Outside this thick lava pile, flows are concentrated in several thinner series. Basic to intermediate lava flows were frequently inflated to a thickness of up to 40 metres and were emplaced like thick flood basalts. Silicic tephra deposits are widespread and mostly phreatomagmatic in origin.

The specific formation of maar-diatremes, sills, laccoliths and most tephra deposits is related to the uppermost 1500 to about 2500 m of the continental sediments of the basin fill. During volcanism and subvolcanism, these sediments were largely unconsolidated and water-saturated, and thus this soft sediment environment influenced very specifically the emplacement of the magmas in the basin. Inflation of laccoliths in this environment caused slumping and washing away of the updomed unconsolidated roof sediments. Consequently, the effective initial overburden decreased with time by this particular process of unroofing, and, upon further inflation, larger inflating intrusive domes became extrusive.
Formation of saucer-shaped sills
Authors: Malthe-Sørenssen A. , Planke S. , Svensen H. , Jamtveit B.
Published: April 2008

We have developed a coupled model for sill emplacement in sedimentary basins. The intruded sedimentary strata are approximated as an elastic material modelled using a discrete element method. A non-viscous fluid is used to approximate the intruding magmatic sill. The model has been used to study quasi-static sill emplacement in simple basin geometries. The simulations show that saucer-shaped sill complexes are formed in the simplest basin configurations defined as having homogeneous infill and initial isotropic stress conditions. Anisotropic stress fields are formed around the sill tips during the emplacement due to uplift of the overburden. The introduction of this stress asymmetry leads to the formation of transgressive sill segments when the length of the horizontal segment exceeds two to three times the overburden thickness. New field and seismic observations corroborate the results obtained from the modelling. Recent fieldwork in undeformed parts of the Karoo Basin, South Africa, shows that saucer-shaped sills are common in the middle and upper parts of the basin. Similar saucer shaped sill complexes are also mapped on new two- and three-dimensional seismic data offshore of Mid-Norway and on the NW Australian shelf, whereas planar and segmented sheet intrusions are more common in structured and deep basin provinces.
Sedimentary dolomite: a reality check
Authors: Wright David T. , Wacey David
Published: April 2008

The failure to precipitate dolomite experimentally at low temperatures or from seawater in which it is both supersaturated and the most thermodynamically favoured carbonate phase, together with its unequal distribution through geological time relative to limestone, are all aspects of the ‘dolomite problem’, a subject of continuing controversy. A plethora of physicochemical models has been invoked to explain sedimentary dolomite formation, none of which satisfactorily addresses the basic problem of how kinetic barriers are overcome. These barriers are related to the disproportionate distribution of the component ions of dolomite, cation hydration and ion complexing in seawater. Competing claims for the effectiveness of sulphate as an inhibitor to dolomite formation further confuse the debate, although there are many reports of modern dolomite associated with bacterial sulphate reduction. The uppermost sediments in some lakes of the Coorong region of South Australia comprise almost 100% dolomite, and afford an ideal opportunity to study this association.

Samples of lake waters taken during late evaporative stages of several shallow hypersaline dolomitic lakes showed high initial sulphate concentrations, high pH and high carbonate alkalinities. Pore waters from unlithified lake sediment cores directly below the lake-water sample sites showed a substantial and progressive decrease in sulphate concentrations with depth, coupled with an exponential increase in carbonate concentrations, through the sulphate-reduction zone. By the end of the evaporative cycle, sulphate was entirely removed. High bacterial counts on cultures from the sediment cores, and sulphur isotope values consistent with ‘bacterial’ fractionation in lake waters, indicate that the chemical changes in ambient water chemistry can be related to active bacterial sulphate reduction. Laboratory experiments using sulphate reducers cultured from the lake sediments and simulating the anoxic microbiogeochemical environment of the lakes, have resulted in the precipitation of dolomite, demonstrating that bacterial sulphate reduction in the Coorong lakes modifies lake-water and pore-water chemistry so that dolomite precipitation is kinetically favoured.

Given the wide spatial and temporal distribution of sulphate-reducing bacteria, and their frequent association, both past and present, with cyanobacteria, it is likely that this process was more widespread in the geological past when dolomite was found in far greater abundance than limestone. Bacterial sulphate reduction may thus have played an important role in dolomite formation throughout the geological record.
Basin fluid flow, base-metal sulphide mineralization and the development of dolomite petroleum reservoirs
Authors: Gregg Jay M.
Published: April 2008

Saline basinal fluids, at temperatures from 60 to 250 °C, have affected almost every sedimentary basin in the world including rocks from Palaeoproterozoic to Cenozoic age. These fluids commonly precipitate base-metal sulphides (pyrite, sphalerite, galena, etc.) and associated minerals (barite, fluorite, calcite, dolomite, etc.) ranging in volume from trace amounts to large economic ore deposits. Such deposits are commonly referred to as Mississippi Valley-type (MVT) after the large Palaeozoic deposits of this kind found in the Mississippi Valley of North America. They are primarily hosted by platform carbonates, typically dolomite, and are usually associated with hydrocarbons.

Dolomites not affected by mineralizing fluids commonly display micron- to decimicron-size planar textures, and have well-developed micro- and mesoporosity networks dominated by intercrystal and vug porosity. However, these and other carbonate rocks affected by basinal fluids may undergo massive geochemical and textural alteration. This occurs even when the affected rocks are distal from the main loci of sulphide mineralization. Alteration includes: dolomitization of limestone; neomorphic recrystallization of existing dolomite; and precipitation at intervals of large volumes of open-space-filling dolomite, calcite and quartz cements alternating with dissolution. Dolomitization of limestone and/or neomorphic recrystallization of dolomite, at elevated temperatures, commonly results in centimicron and larger size crystals, and development of nonplanar textures that increase pore-throat tortuosity. Open-space-filling dolomite, calcite and quartz cementation causes a dramatic reduction of porosity and blockage of pore throats. Periods of carbonate dissolution, proximal to intense sulphide mineralization, result in the development of large-scale macroporosity such as breccias that are commonly superimposed on karst and tectonic fractures.

Exposure to mineralizing basinal fluids substantially alters porosity and permeability distribution, and thus the potential reservoir properties of the dolomite. The resulting reservoir may have little resemblance to its precursor. Understanding the epigenetic history of a dolomite is critical, therefore, as this will ultimately affect its development strategy and production history.
Patterned dolomites: microbial origins and clues to vanished evaporites in the Arab Formation, Upper Jurassic, Arabian Gulf
Authors: Kirkham A.
Published: April 2008

The common occurrence of patterned dolomites in the upper Arab Formation of the Arabian Gulf is highlighted. Their mottled appearance is due to concentrations of microcrystalline iron sulphide. The dolomites are typically devoid of bioclastic debris and are usually interbedded with stromatolites and thin carbonates, both of which commonly contain anhydrite nodules. Previous workers have interpreted the patterned appearance as originating from birds-eye porosity, burrowing activity or plant roots, but their mottled appearance, and possibly also the dolomite, probably originated as a by-product of the activities of sulphate-reducing bacteria in water-logged or subaqueous sediments on the floors of salinas or very highly saline lagoons from which dissolved sulphate and/or gypsum had been removed. This implies that the Arab Formation was originally locally even more gypsiferous than is evident from its existing bedded anhydrites. The related processes of sulphate removal and sulphide formation were penecontemporaneous, as shown by occurrences of the mottled fabrics as intraclasts. Contorted lamination within the patterned dolomites and their frequent involvement with sediment injection structures are evidence of fluidization. Reasons for the contortion and fluidization are considered with respect to compatible Holocene depositional and diagenetic environments. In addition to the comparatively simple depositional models of extensively prograding supratidal sabkhas, which are traditionally applied to facies associations of stromatolites and bedded anhydrites in the Arab Formation, the presence of patterned dolomites demands consideration of less continuous and static facies belts with reduced correlatability that imply higher levels of reservoir heterogeneity.
Contrasting patterns of pore-system modification due to dolomitization and fracturing in Dinantian basin-margin carbonates from the UK
Authors: Bouch Jon E. , Milodowski Antoni E. , Ambrose Keith
Published: April 2008

Two examples of Dinantian basin-margin carbonates from the United Kingdom provide potential analogues for fracture and porosity distributions in hydrocarbon reservoirs in dolostones. In both examples pore systems have been extensively modified by dolomitization, fracturing and related mineralization. However, the detailed processes and the end results show some significant differences, highlighting the importance of developing an understanding of the specific pore-system modifying processes when characterizing and modelling porosity distributions in these settings.

In the first example, predominantly low-porosity and low-permeability limestones in Lower Carboniferous inliers in Leicestershire (Cloud Hill) and south Derbyshire (Ticknall) had their pore systems further degraded by extensive dolomitization. Subsequent fracturing and related mineralization were responsible for significant porosity generation adjacent to fractures.

In contrast, in the Sellafield area (west Cumbria), dolomitization was strongly controlled by fractures that were also mineralized by sulphate-rich brines. In the north of the area fractures were filled with an assemblage of barite-fluorite-hematite-calcite that is resistant to corrosion by low-temperature meteoric groundwater. However, in the south of the area the fractures were cemented by anhydrite, which is readily corroded by saline, but sulphatepoor, groundwater formed by percolating meteoric recharge from the east. Progressive dissolution has been ongoing since Tertiary uplift, and has rejuvenated fracture porosity within the dolomitized limestones.
Geometry and origin of dolomudstone reservoirs: Pekisko Formation (Lower Carboniferous), western Canada
Authors: Hopkins John C.
Published: April 2008

Dolomudstones of the Pekisko Formation in western Canada form small but important oil and gas reservoirs. The reservoirs are irregularly shaped bodies 1 km or so wide and commonly 5–8 m thick. Porosity development within the dolomudstones is a complex function of sedimentation, early facies-selective dolomitization and later telogenetic leaching of calcareous components.

The carbonate sediment precursor of the dolomudstone, interpreted from relict textures preserved in chert nodules, was a microwackestone with abundant silt-sized skeletal fragments. Dolomudstone reservoirs are comprised of dolomudstones, calcareous dolomudstones, and subordinate interbedded dolowackestones and dolograinstones. Some dolomudstone reservoirs are contained entirely within grainstones. Others are capped by tight fenestral lime mudstone that has been dolomitized locally. Dolomitization has been most intense within the centres of these reservoirs, and dolomudstones grade laterally into calcareous dolomudstones.

The association of facies indicates that microwackestones were deposited in subtidal intershoal and lagoonal environments on an inner ramp. Grainstone shoals provided a broad barrier that absorbed wave energy seaward of the lagoon. Fenestral lime mudstones accumulated in peritidal environments in restricted areas of the inner ramp, landward of the lagoon. Dolomitization is interpreted to have been early and selective to the microwackestone facies because it retained permeability or was reactive during early burial. Dolomitizing fluids were most probably derived from overlying formations and made their way downwards through spatially separated conduits. The Pekisko Formation was exposed and sculptured at several Jurassic-Early Cretaceous unconformities. During these times, sandstones and shales were deposited in solution cavities developed within the dolomudstones. Concomitant leaching of calcite increased porosity of the dolomudstone reservoirs.
Reducing the long-term environmental impact of wastes arising from uranium mining
Authors: Hart Kaye
Published: April 2008

Uranium mining and milling produces significant quantities of solid and liquid wastes. Solid wastes include waste rock arising from the mining activity and tailings produced by processing of the ore through the millin circuits. Of these, tailings have the most pronounced impact on the environment as they represent almost the entire mass of material processed in the milling circuits and also contain over 85% of the original radioactivity present in the ore. Modern rehabilitation schemes for tailings impoundments include a number of layers designed to prevent infiltration of water, oxidation of minerals, capillary rise of salts, and release of Rn, thereby minimizing the impact of the disposal of tailings on the environment. Although the effectiveness of these engineered barriers may degrade with time, it is possible, using evidence from natural systems and archaeological constructions, to provide evidence of the long-term isolation of the contaminants contained in the uranium tailings from the environment.
Anthropogenic radionuclide emissions into the environment
Authors: Eikenberg J. , Beer H. , Bajo S.
Published: April 2008

Two sources contribute essentially to the presence of anthropogenic radioisotopes in the environment: (i) release from nuclear materials with a major fraction derived from the nuclear bomb testing period during the period 1950–1963 and (ii) emissions from the nuclear industry, such as waste waters from U-mine tailing or nuclear fuel reprocessing plants. This chapter focuses mainly on the major source responsible for global surface contamination, that is, radioisotope aerosol deposition after release into the atmosphere. The atmospheric emissions were caused mainly via surface atomic bomb tests and reactor accidents, with the Chernobyl reactor catastrophe as the most important contribution. In contrast with most fission products, almost all actinides (which are produced via neutron capture reactions) are rather long lived and can be measured in environmental samples with high precision. Some of the actinides (i.e., U, Pu, Cm) consist of various isotopes (e.g.,
238,239,240,241
Pu) and hence can be used to distinguish between soil contamination from different emission sources. Approaches are therefore presented for calculating the different fractions of contaminants by use of characteristic isotopic signatures.
Atmospheric impact of the fossil fuel cycle
Authors: Golomb D. S. , Fay J. A.
Published: April 2008

Fossil fuels supply about 86% of the global primary energy consumption for transportation, industrial, commercial, and residential uses. While a minor part of fossil fuels is used as a raw material for the chemical industry, the vast majority is combusted providing heat, mechanical, and electric energy for the urban-industrial society. Owing to the combustion of fossil fuels, copious quantities of pollutants are emitted into the air and impact on the local, regional, and global air quality. It is technologically possible to significantly reduce the emissions of most pollutants, albeit at considerable energy and economic penalty. However, the reduction of emissions of carbon dioxide, one of the principal products of fossil fuel combustion, poses technological, economic, societal, and political problems of enormous magnitude. In recent decades it has become evident that rising levels of atmospheric carbon dioxide (and other greenhouse gases) will cause global warming and other climate changes.
Coal combustion wastes: characterization, reuse and disposal
Authors: Glasser F. P.
Published: April 2008

Coal extraction and combustion produce a number of waste streams, some of which can be utilized. Fly ash from the combustion of pulverized coal is characterized; it finds application as a partial replacement for Portland cement in concrete. Relatively few uses exist for other wastes, much of which is stockpiled, stored, or landfilled. These leave a legacy for future generations that must be managed to minimize geochemical impacts on air, soil, and groundwater quality.
The chemistry and mineralogy of coal and coal combustion products
Authors: Tishmack Jody K. , Burns Perre E.
Published: April 2008

The generation of electricity by thermal conversion of coal results in significant volumes of solid waste. Most of these materials are disposed of in surface impoundments near coal-fired power plants or in active coal mines. Disposal rates vary from country to country. In the USA, 60–70 wt% of these materials are disposed. Although these materials rarely meet the definition of hazardous, leachate tests on some coal ash have shown them capable of producing elevated concentrations of some regulated metals. As a result of the well-documented environmental concerns posed by coal combustion, and the disposal of coal combustion products (CCPs), a large body of research has focused on characterizing the mechanisms of mobilization and attenuation of trace elements in coal and its ash. However, groups opposed to coal combustion or unregulated disposal of ash overlook the value of these materials as well-proven replacements for aggregate, cement, or soil in numerous engineering and agricultural applications. An extensive body of knowledge has been gathered describing the variability and versatility of these materials. It has been shown that proper utilization or management of ash requires a good understanding of its chemical, physical, and mineralogical properties. This chapter is intended to provide a broad overview of the chemistry and mineralogy of coal, and the combustion products that are formed when coal is burned.
The beneficiation of coal combustion ash
Authors: Groppo John , Robl Thomas , Hower James C.
Published: April 2008

Pulverized coal combustion ash is an important source of strategic materials in the USA. Bottom ash is used as a source of aggregate for use in concrete and masonry units (blocks). It is processed primarily to improve its grading. A top size is removed and the finest sizes are removed via wet or dry screens. Pyrite and rock may also be present with the ash. These materials can be removed by spiral concentrators and jigs. In some cases high-quality/high-value lightweight aggregates are produced from stored bottom ash. Fly ash is used as a pozzolanic additive to Portland cement concrete. In addition to partially replacing the cement, it contributes substantially to the durability of the concrete. The advent of low-NO
x
burners and selective catalytic reduction (SCR) supported ammonia injection has altered the character of the fly ash, particularly the Class F, low-Ca type, by generally increasing the amount of unburned carbon. This contaminant adsorbs air-entrainment reagents and can decrease the resistance of the concrete to freeze-thaw damage. Over the past decade several technologies and approaches have been developed to remove the carbon from the fly ash, including: air classification; electrostatic separation; and fluidized-bed combustion. Other approaches such as microwave heating also show promise. Froth flotation has been successfully applied to wet ash. The amount of ash that is beneficiated has increased to a current level of about 1 million tons per year in the USA, which is expected to grow in time due to the need for predictable materials with constant characteristics. The primary environmental advantage of ash beneficiation is that it enables the use of combustion ash that would otherwise be disposed as waste. High-quality, consistent products can be generated, thus increasing the usefulness and acceptance of these processed products in both traditional and emerging markets. By doing so, the amount of ash that is utilized will be increased, thus reducing the amount of ash that is disposed, while conserving other resources such as aggregate and sand for other uses not applicable to combustion ash.
Environmental impact of geothermal energy utilization
Authors: Arnórsson Stefán
Published: April 2008

Presently geothermal energy accounts for 0.25% of the annual world-wide energy consumption. Extraction of heat from geothermal reservoirs involves drillings. Exploitation of geothermal resources is generally far less a cause of pollution than fossifuel combustion, making it preferable as a source for power and heat. Geothermal energy exploitation has locally some adverse environmental effects. Possible effects include scenery spoliation, drying out of hot springs, soil erosion, noise pollution, and chemical pollution of the atmosphere and of surface- and groundwaters. Exploitation may enhance seismic activity and cause land subsidence. The development of geothermal fields must sometimes be evaluated against the value of tourism. Various measures have been successfully employed to reduce the adverse environmental effects of geothermal energy utilization. The most important ones are directional drilling and injection of spent geothermal fluid. Future use of geothermal resources should specifically consider further use of geothermal heat pumps, extraction of chemicals from spent geothermal fluids to yield useful byproducts, integrated multiple use of high-temperature systems, and furthering of technology to develop hot-dry-rock systems including those occurring in the roots of active volcanic geothermal systems.
Corrosion and stability of vitrified material derived from municipal solid waste
Authors: Perret D. , Stille P. , Crovisier J.-L. , Shields G. , Mäder U. , Schenk K. , Chardonnens M.
Published: April 2008

Advanced high-temperature technologies for the treatment of municipal solid wastes or residues from conventional incineration can produce vitrified materials with superior physical and chemical characteristics compared to conventional residues (bottom ash, fly ash, filter cake). These materials, which may contain significant metal concentrations, exhibit favourable thermodynamic characteristics and very low contaminant release when subjected to corrosion. Owing to low leachability, these materials could possibly be used as secondary raw materials for civil engineering applications, although the energy demand for their production is high. This chapter presents the physical and chemical characteristics of a range of vitrified materials originating from various high-temperature technologies; their behaviour under highly aggressive conditions of corrosion and their thermodynamic stability are also presented. It is concluded that such high-temperature materials are indeed less likely to be damaging to the environment than conventional residues.
Chemistry and mineralogy of municipal solid waste incinerator bottom ash
Authors: Eggenberger Urs , Schenk Kaarina , Mäder Urs
Published: April 2008

A petrographic study was conducted on a suite of bottom ash samples from 28 municipal solid waste incinerators in Switzerland. Chemical and mineralogical analyses of bottom ash from waste combustors with comparable technology show similar major oxide composition. A significant decrease of SiO
2
was observed in comparison to the chemical composition of bottom ash from 10 years ago. In contrast to major oxide contents, heavy metal concentrations vary significantly in the bottom ash samples, but without any correlation to the type of input waste or plant operating conditions. Similar types and contents of crystalline phases were observed in all samples. The content of newly formed melilite increases with decreasing bulk Si/Ca ratio, indicating that the type of Ca-Mg-Al-silicates crystallizing during incineration and cooling follow petrogenetic rules. A considerable recycling potential for ferrous and non-ferrous metals was identified in the bottom ash. Optimized mechanical metal separation technologies could reduce the waste volume, heavy metal content, H
2
production, and exothermic reactions of the bottom ash in landfills and might be economically viable.
Incinerator waste as secondary raw material: examples of applications in glasses, glass-ceramics and ceramics
Authors: Barbieri Luisa , Lancellotti Isabella
Published: April 2008

The recovery and beneficiation of solid waste residues (bottom and fly ash) produced during incineration of municipal wastes are very important goals from the environmental and economic point of view. Some technologies allow not only to reduce the volume of incinerator waste but also to generate products of economic value by vitrification, devitrification, and ceramic processes. Bottom ash is preferable compared to fly ash as a secondary raw material. Mixed with glass cullet, bottom ash can be easily transformed into homogeneous and inert glasses, which can be transformed into glass fibres or sintered glass-ceramics after controlled thermal treatments. Alternatively, bottom ash can be used to produce tiles, in particular glazed tiles containing vitrified bottom ash in the ceramic body, and possibly bricks. The results presented in this review are promising and in accordance with the waste minimization policy as well as resources conservation.
Environmental impact of energy recovery from waste tyres
Authors: Gieré Reto , LaFree Sara T. , Carleton Loran E. , Tishmack Jody K.
Published: April 2008

Accumulation of millions of worn automotive tyres poses a considerable environmental problem. As an important part of the solid waste stream in today’s society, worn tyres have traditionally been discarded in landfills or stored in stockpiles. Over the past several decades, however, innovative alternatives to disposal have been developed, partly as a result of high tipping fees charged by landfill operators. Because of their high heat content and their low levels of moisture and nitrogen compared to coal, tyres are ideally suited for energy recovery through combustion. Utilization of waste tyres as supplemental or alternate fuel in various industrial combustion facilities, thus, has become one of the most important alternatives to disposal. Combustion processes, however, generate gaseous pollutants and solid waste materials, which must be disposed of or re-used as secondary raw materials. It is therefore important to characterize these combustion products in order to assess the environmental impacts of energy recovery from scrap tyres. Studies have shown that substantial reductions of some environmental pollutants can be achieved by partially replacing conventional fuels with waste tyres. On the other hand, using tyres as fuel may lead to considerable increases in the levels of other pollutants. Most notable among the effects of tyre combustion are, relative to conventional fuels, a pronounced decrease in the emission of nitrogen oxides into the atmosphere, and a generally significant increase in atmospheric zinc emissions as well as in the zinc contents of the solid combustion products. The geochemical effects on solid and gaseous combustion products are more or less pronounced depending on fuel composition, conditions of combustion, type of facility, and effectiveness of air pollution control devices. Thus, the use of tyre fuel has environmental impacts that must be weighed against the benefits of reducing the large volume of waste tyres in the global waste stream.
Colloid influence on the radionuclide migration from a nuclear waste repository
Authors: Geckeis Horst
Published: April 2008

Colloid formation is discussed as a possible pathway for the radionuclide release from a nuclear waste repository. An assessment of the colloid relevance on radionuclide migration requires insight into the possible colloid generation mechanisms, their stability and mobility under given groundwater conditions. In various experiments dedicated to the investigation of nuclear waste form behaviour in contact with groundwater, colloidal species are observed mainly for the tri- and tetravalent actinides even in rather high ionic strength solutions where destabilization of colloids is expected. Experimental evidence of laboratory and field studies suggests colloid instability in saline groundwater with time. Groundwater of low ionic strength and high pH enhances colloid stability, as demonstrated in various laboratory and field experiments. The results of an
in situ
colloid characterization study at the Äspö hard rock laboratory in Sweden are discussed as an example. The mechanism of radionuclide interaction with colloids and notably the reversibility of the radionuclide-colloid binding are other key issues of colloid studies. Kinetic stabilization of the radionuclide binding to colloids may lead to a considerable enhancement of the colloid-mediated radionuclide migration. Substantial kinetic inhibition of actinide dissociation from humic colloids has been established by studying the behaviour of natural humic colloid borne U, Th and rare earth elements. Such behaviour might be explained by the incorporation of these elements into inorganic nanoparticles stabilized by humic coating. Spectroscopic evidence for the occurrence of actinide incorporation into colloidal structures is briefly discussed and the importance of considering the kinetics involved in all kinds of colloidal processes is emphasized. The enhanced migration of tri- and tetravalent actinide ions has been observed recently in various
in situ
dipole tests at the Grimsel hard rock laboratory in Switzerland. Such experimental findings underline the necessity of further studies on the colloid influence on actinide mobility. Moreover, an improved understanding of colloid-rock interaction mechanisms is required, which is essential for the description and prediction of colloid filtration processes.
Hydrological and geochemical factors controlling leachate composition in incinerator ash landfills
Authors: Johnson C. Annette , Abbaspour Karim C.
Published: April 2008

The hydrological and geochemical processes that control leachate composition are discussed for two examples, the first being a landfill containing municipal solid waste incinerator (MSWI) bottom ash, Landfill Lostorf, and the second a lysimeter containing blocks of cement-stabilized MSWI air pollution control (APC) residues. In both examples the leachate consists of a component that takes months to years to pass through the landfill and rainwater that passes through the landfilled material via preferential flow paths. The composition of the leachate is relatively constant and is only diluted with rainwater during rain events. The concentration of major leachate components (Na
+
, K
+
, Cl
−
and OH
−
) is controlled by diffusion processes and by the precipitation of solubility-controlling phases (Ca(II), Al(III), SO
4
2
− and Si(IV)). The observed concentrations of some relatively insoluble heavy metal and metalloid species may be explained by the precipitation of secondary phases. More soluble species may be adsorbed on surfaces of or incorporated in minerals, but the mechanisms remain to be elucidated.
Shaken but not always stirred. Impact of petroleum charge mixing on reservoir geochemistry
Authors: Wilhelms Arnd , Larter Steve
Published: April 2008

Essentially all petroleums are mixtures with different components charged from source rocks at different temperatures. This heterogeneous charge is the basis for compositional differences in reservoirs that are the basic elements of reservoir geochemical approaches. Because many classical petroleum geochemical tracers of source facies and maturity, such as the cyclic biomarker hydrocarbons, show several orders of magnitude variation in concentration in petroleum systems these compounds do not reliably track facies or maturity signals in mixed oil situations. Light hydrocarbon and aromatic hydrocarbon parameters are more reliable in this sense but, as mixtures are the norm, the concept of the maturity of oils needs revising. We suggest an alternative approach is needed which tracks the maturity/petroleum mass fraction relationships for reservoired oils (mass fraction maturity) and allows the bracketing of source kitchen maturity. We strongly advise against using compound ratios in reservoir geochemical studies without having knowledge of the compounds concentration range variations within the petroleum system being studied.
New insights into reservoir filling and mixing processes
Authors: Stainforth John G.
Published: April 2008

A common assumption is that hydrocarbon charge homogenizes with the petroleum already in a trap: thus, compositional gradients reflect only subsequent segregation of the petroleum under the combined influences of gravity, temperature and diffusion. Since such homogenization would entail an unfavourable generation of potential energy, a more plausible hypothesis is that hydrocarbons stack into traps roughly in the density sequences in which they arrive. The commonly accepted model suggests that homogeneous and gravitationally unstable petroleum columns move towards graded equilibrium ones, whereas the hypothesis preferred here implies that they gradually diffuse towards equilibrium from the opposite direction, i.e. poorly mixed initial states.

According to this hypothesis, trends of oil GOR and bubble point (
P
b
) are controlled by either (a) the charge GOR or (b) the evolving PT conditions at the GOC, depending on the gassiness of the charge. By contrast, API gravity trends mainly reflect the integrated maturity histories of source rock kitchens during the trap filling regardless of the charge gassiness. Because trap and kitchen histories are usually (very) different, a wide spectrum of API and GOR (and
P
b
) combinations is possible, from minor API gradients coupled with large GOR gradients and
vice versa
.
An integrated basin modelling study applying asphaltene kinetics from reservoired petroleum in the Snorre Area, northern North Sea
Authors: Skeie Jon Erik , Primio Rolando Di , Karlsen Dag A. , Bjørlykke Knut
Published: April 2008

The evolution of the petroleum systems in the Tampen Spur area, with main focus on the filling directions of the northern part of Snorre field, was addressed through 2D basin modelling (Petromod V. 4.5 and 7.0). The geochemical classification of the petroleum populations in the area represented the framework for considering the different kitchen areas and migration systems. Results from the basin modelling support, in general terms, the previous geochemical classification and petroleum families in the region. However, a separate well-defined main kitchen area for the Snorre Field was deduced opposed to the multiple kitchen areas having contributed to the filling as proposed in the literature. Our conclusions are based on the quantitative evaluation of the different proposed kitchen areas and the timing and extent of petroleum generation.

Modelling of petroleum generation was performed using asphaltene kinetics determined on petroleum asphaltenes from Snorre oils. This approach was chosen in order to avoid problems associated with the kinetic variability encountered in the Draupne formation. The petroleum asphaltene kinetics was used to delineate the extent of the kitchen area, which reached the time/temperature conditions necessary for the generation of the analysed oil phase. The results thus differ from conventional oil window approximations as we utilize kinetic source rock parameters in the migrated oil for tracing out the generative basin.

Three 2D lines crossing the main kitchen areas were modelled in this study. The models were calibrated to data from eight wells, consisting of measured vitrinite reflectance, corrected well temperatures and pore pressure.

Three main kitchen areas were considered; one to the west and northwest of Snorre field, one directly to the north (Møre basin) and one to the east of the field (34/5 kitchen). Modelling suggests that the kitchen area to the west and northwest of Snorre is largely immature and that the volume of potentially generated petroleum is too small to fill the Snorre structure. In the northern kitchen area, the seismic indicated very thin upper Jurassic deposits, which reaches oil window maturities only at a relatively large distance from the structure. The modelling also demonstrated problems related to the filling of the Snorre structure from the Møre Basin. The combined effect of a thin source rock, which implies a regionally large drainage area to fill the structure, and the large distance to the mature kitchen, lead to the conclusion that the Møre Basin did not contribute significant volumes of petroleum to the Snorre field. In contrast, the kitchen area east of Snorre Field (the 34/5 kitchen) proved in the modelling to be mature and volumetrically large enough to account for the entire filling of the Snorre Field.
Problems in interpreting AMS parameters in diamagnetic rocks
Authors: Hrouda František
Published: April 2008

The AMS parameters widely used to characterize the magnetic fabric of rocks (
L, F, P, T
) are not directly applicable to diamagnetic rocks. Namely, there are two principal methods of their definition: (1) from the signed principal susceptibilities or (2) from the absolute values of the principal susceptibilities. The first method results in
L, F
and
P
values less than one in contrast to materials whose susceptibility arises from paramagnetism and/or ferromagnetism
sensu lato
, where they are greater than one by definition. The ratio parameters decrease with increasing intensity of alignment of the magnetic minerals; the calculated shape parameters are, however, correct. The second method gives
L, F
and
P
values greater than one; they increase with increasing preferred orientation, however the ellipsoid shape parameters are inverse. The development of AMS parameters with increasing preferred orientation is modelled mathematically for quartzite/evaporite (para- and/or ferromagnetic AMS superimposed on the isotropic diamagnetic matrix) and for marble/limestone (preferred orientation of calcite in a rock). A rational set of AMS parameters is then recommended.
Anisotropy of magnetic susceptibility of lava flows and dykes: A historical account
Authors: Cañón-Tapia Edgardo
Published: April 2008

The basic assumptions made in the interpretation of the anisotropy of magnetic susceptibility (AMS) of lava flows, dykes and other tabular intrusive rocks have changed with time. This paper presents a historical account of those changes. Because several aspects of the AMS of these types of rocks are still open to debate, the historical perspective helps us to appreciate better the limitations that had to be faced at different times, therefore providing some clues that can be used to solve such controversies. Also, by benefiting from hindsight it is possible to devise alternative approaches that can be employed to interpret the AMS of these types of rocks. Although some adjustments to current models will be made as new results become available, it seems that at present the main commponents of the basic model of AMS in lava flows and tabular intrusive rocks have been finally reached, leaving behind most of the apparent contradictions found in earlier works. This progress is undoubtedly an important advance in our understanding of the nature of AMS in general.
Magmatic flow paths and palaeomagnetism of the Miocene Stoddard Mountain laccolith, Iron Axis region, Southwestern Utah, USA
Authors: Petronis M. S. , Hacker D. B. , Holm D. K. , Geissman J. W. , Harlan S. S.
Published: April 2008

The Stoddard Mountain laccolith is part of a complex of Early Miocene laccoliths intruded along the western edge of the Colorado Plateau in the Iron Axis region of Southwestern Utah. Most Colorado Plateau laccoliths (e.g. Henry and La Sal Mountains) are considered to be fed by a central axial feeder system. However, detailed mapping in the Iron Axis region suggests that the Stoddard Mountain laccolith was fed laterally from the west. Structural and field data suggest the quartz monzonitic magma initially migrated laterally eastward at ∼1 km depth as a sill before spreading laterally north-south where it inflated to ∼1–1.5 km thickness. To test the model of a lateral feeder system, data were collected from 32 palaeomagnetic sites and 76 AMS stations (763 accepted specimens) sampled over the ∼54 km
2
exposed part of the N-S oval-shaped laccolith. The
in situ
AMS fabrics, inferred to correlate with magmatic fabrics, typically show NE trending lineations in the north and S-SE trending lineations in the south part of the intrusion. The palaeomagnetic data are interpreted to indicate a very minimal amount of post-emplacement deformation of the intrusion. The overall lack of westerly-directed and steep magnetic lineations argues against emplacement via a central axial feeder system.
Magma flow inferred from preferred orientations of plagioclase of the Rio Ceará-Mirim dyke swarm (NE Brazil) and its AMS significance
Authors: Archanjo Carlos J. , Launeau Patrick
Published: April 2008

Low-field magnetic and plagioclase fabrics were compared in Mesozoic mafic dykes of the Rio Ceará-Mirim swarm. Coarse titanomagnetites with pervasive ilmenite lamellae constitute the main carrier of the magnetic anisotropy. The hysteresis parameters of the mafic dykes fall in the pseudo-single domain field. The resulting AMS ellipsoid is usually oblate and has a very low anisotropy (<3%). Textures indicate that the oxi-exolution processes and size reduction of the ferrimagnetic domains occurred at subsolidus temperatures on cooling of the dykes. The magmatic fabric was determined by the shape preferred orientation of plagioclase laths. It rarely matches the magnetic fabric. Besides their contrasting shape ellipsoids, prolate and oblate respectively, their corresponding principal directions diverge from each other or exchange their positions depending on the symmetry of the ellipsoids. These discrepancies are attributed principally to small differences in the net shape of Ti-poor magnetite after exsolution of ilmenite and in the inherently oblique fabric of grains with different shapes. These results draw attention to the need to use independent methods to confirm the conclusions about flow fabrics of weakly anisotropic mafic dykes based only in AMS.
Application of magnetic fabrics to the emplacement and tectonic history of Devonian granitoids in central Argentina
Authors: López de Luchi M. G. , Rapalini A. E. , Siegesmund S. , Steenken A.
Published: April 2008

Regional considerations on the tectonic regime during the emplacement of the Early Devonian magmatic units in the Sierra de San Luis are inferred from combined field, petrographic and AMS observations. Devonian granitoids of the Sierra de San Luis, in central Argentina, constitute elliptical composite batholiths and make up the most voluminous magmatism that appears in the Sierra. Detailed fabric studies have been carried out on the La Totora batholith (33°09′S, 65°42′W), which complement previous studies on two of the largest plutons in the Sierra de San Luis: The Renca and Las Chacras-Potrerillos batholiths. The studies comprised systematic field surveys, petrographic observations and anisotropy of magnetic susceptibility (AMS) measurements. Microstructural studies indicate that the batholith rocks are mainly characterized by magmatic microstructures with limited sub-magmatic to high-temperature solid-state deformation. All three batholiths possess concentric foliation patterns. The average magnetic foliation patterns in the studied plutons agree well with the macroscopic fabrics measured in the field indicating that the AMS-data can be used to study the orientation of fabric elements. Bulk susceptibility indicates a predominance of ferromagnetic contributions, although some paramagnetic sub-units are also present. Most foliations and lineations reflect magmatic flow and their attitude is linked to the interference between regional deformation and batholith inflation, i.e. fabrics may be due to regional strain in combination with the internal dynamics of the magma bodies. Rock fabrics are mainly described by oblate magmetic fabric ellipsoids. Magnetic lineations generally show a NNE-SSW trend that is interpreted to be controlled by the opening transtensional pull-apart structures during batholith inflation. It turns out that the Devonian batholiths intruded the basement syn-kinematically with respect to the Achalian deformational cycle.