bluuebunny/crossref_metadata_2025 huggingface dataset:
Tectonic control on laccolith emplacement in the northern Apennines fold-thrust belt: the Gavorrano intrusion (southern Tuscany, Italy)
Authors: Mazzarini Francesco , Corti Giacomo , Musumeci Giovanni , Innocenti Fabrizio
Published: April 2008

Mechanical discontinuities within the crust, represented by tectonic structures (faults) or lithological heterogeneities, strongly control the emplacement of magmas as tabular intrusions within the middle-upper crust. The occurrence of mechanical layering is a common feature in fold and thrust belts. In the northern Apenniness, a Cenozoic fold-thrust belt affected in its inner part by Neogene magmatism, the Gavorrano laccolith (southern Tuscany) is a particularly suitable example for studying the relationships between magmatism and tectonic structures. New geological mapping, together with a large amount of subsurface data available from historical mining activity in the area, have allowed the reconstruction of:

1

the original relationships of the intrusion within the nappe pile, and

2

the laccolithic shape of the intrusion.

Using the Gavorrano laccolith as an example, we propose that the emplacement of Neogene intrusions in southern Tuscany was strongly controlled by the occurrence of mechanical discontinuities represented by thrust zones in the nappe pile.
Rate of construction of the Black Mesa bysmalith, Henry Mountains, Utah
Authors: Habert Guillaume , De Saint-Blanquat Michel
Published: April 2008

At shallow-crustal levels, the most efficient process for the accommodation of magma emplacement is roof lifting, which induces an upward vertical displacement of the Earth’s surface. Estimates of the rate and duration of this process have rarely been published. One of the most spectacular places where plutons constructed by such mechanisms are exposed is the Henry Mountains in Utah. In this place, Pollard & Johnson (1973) derive a time of ‘less than several weeks’ for the construction of the Black Mesa bysmalith (BMb), by coupling a mechanical approach with a model for the flow rate of Bingham magma in a tabular conduit with a constant driving pressure at the feeder. The aim of this new study of the BMb is to evaluate the maximum duration of its emplacement and propose a feasible scenario for its construction. Our study of the pluton’s internal structures suggest that the BMb is a multi-pulse pluton. We have constrained the duration of BMb emplacement by simulating the thermal evolution of the growing pluton and its wallrocks for different construction scenarios. We have adjusted the number, the thickness and the frequency of the pulses with our textural ‘time’ constraints, which are the absence of solid-state textures around internal contacts, which implies that a melted zone was maintained in the intrusion during its construction; and the absence of significant contact metamorphism or recrystallization which means that the increase of temperature in the host rock was relatively small, or short-lived, or both. In accordance with the previous estimates of Pollard & Johnson (1973), we propose that the emplacement of the BMb was a very short geological event, with a
maximum
duration in the order of 60 years, implying
minimum
vertical displacement rates of the wallrocks above the pluton of 4 metres per year. Moreover, our simulations indicate that pulses around 20 metres thick rapidly injected approximately every three months are the most consistent with the constraints from field observations.
Rise and fall of a nested Christmas-tree laccolith complex, Elba Island, Italy
Authors: Westerman D. S. , Dini A. , Innocenti F. , Rocchi S.
Published: April 2008

In two separate areas of western and central Elba Island (Italy), Late Miocene granite porphyries are found as shallow-level intrusions inside a stack of nappes rich in physical discontinuities. Detailed mapping of intrusive rocks, along with their relations with country rocks, show that outcrops from western and central Elba Island expose the same rock types, with matching intrusive sequence, petrography and geochemical features. Structural and geological data indicate that these layers were originally part of a single sequence that was split by eastward-directed décollement and tilting. The two juxtaposed portions of the original sequence allow the restoration of a 5-km thick sequence, made up of nine main intrusive layers, building three Christmas-tree laccoliths nested into each other to support a structural dome. During their construction, the role of the neutral buoyancy level was of minor significance with respect to the role played by the relatively thin overburden and/or the large availability of magma traps inside the intruded crustal section. Emplacement of the Monte Capanne pluton into the base of the domal structure likely caused oversteepening and initiated decapitation of the complex, with gravity sliding of the upper half off the top.
Hydrothermal vent complexes associated with sill intrusions in sedimentary basins
Authors: Jamtveit Bjørn , Svensen Henrik , Podladchikov Yuri Y. , Planke Sverre
Published: April 2008

Subvolcanic intrusions in sedimentary basins cause strong thermal perturbations and frequently cause extensive hydrothermal activity. Hydrothermal vent complexes emanating from the tips of transgressive sills are observed in seismic profiles from the Northeast Atlantic margin, and geometrically similar complexes occur in the Stormberg Group within the Late Carboniferous-Middle Jurassic Karoo Basin in South Africa. Distinct features include inward-dipping sedimentary strata surrounding a central vent complex, comprising multiple sandstone dykes, pipes, and hydrothermal breccias. Theoretical arguments reveal that the extent of fluid-pressure build-up depends largely on a single dimensionless number (

Ve

) that reflects the relative rates of heat and fluid transport. For

Ve

>> 1, ‘explosive’ release of fluids from the area near the upper sill surface triggers hydrothermal venting shortly after sill emplacement. In the Karoo Basin, the formation of shallow (< 1 km) sandstone-hosted vents was initially associated with extensive brecciation, followed by emplacement of sandstone dykes and pipes in the central parts of the vent complexes. High fluid fluxes towards the surface were sustained by boiling of aqueous fluids near the sill. Both the sill bodies and the hydrothermal vent complexes represent major perturbations of the permeability structure of the sedimentary basin, and are likely to have long time-scale effects on its hydrogeological evolution.
Irish Lower Carboniferous replacement dolomite: isotopic modelling evidence for a diagenetic origin involving low-temperature modified seawater
Authors: Wright Wayne R. , Somerville I. D. , Gregg J. M. , Shelton K. L. , Johnson A. W.
Published: April 2008

Irish Lower Carboniferous (Dinantian Subsystem) carbonate rocks are extensively replaced by planar dolomite. This dolomitization is unrestricted in lithology replaced, age of host rock and geographical occurrence. This paper presents geochemical (δ
18
O, δ
13
C,
87
Sr/
86
Sr, Sr conc.) modelling evidence, and discussion supporting and extending the theory that replacement planar dolomitization formed in the Waulsortian, and other host rocks under shallow burial conditions via interaction with a low-temperature (
c.
50–70 °C) slightly modified seawater. The probable mechanism for transporting the fluid into the carbonates appears to be a variant of Kohout convection, driven by an elevated geothermal gradient. As seawater was drawn inwards, it encountered the units beneath the Waulsortian and scavenged radiogenic Sr. This warmer fluid then migrated upwards and up-slope into overlying Waulsortian and Supra-Waulsortian platform carbonates still undergoing early diagenesis. Calcium in pore fluids, provided by dissolution-precipitation reactions of calcite, was probably incorporated into the modified, and slightly warmer, seawater resulting in the variability noted in the planar replacement dolomite Sr concentrations. The early low-temperature dolomitization of the carbonate host rocks provided a crucial preparation event by creating/redistributing and preserving porosity and permeability. Younger regionally migrating high-temperature fluids directly related to the Zn-Pb mineralization in Ireland exploited these dolomitzed units as aquifers. The models and methodologies presented for understanding dolomite genesis in the Lower Carboniferous rocks of Ireland can be applied to any dolomitized reservoir.
Origin and petrophysics of dolostone pore space
Authors: Lucia F. Jerry
Published: April 2008

The common claim that dolomitization creates 12% porosity is based on the mole-for-mole replacement equation. However, in the past 50 years, data have been collected demonstrating that dolomitization does not create porosity. Instead, dolostones inherit the porosity and fabric of the precursor limestone, and porosity is reduced by overdolomitization. The porosity of the precursor limestone depends on the diagenetic history up to the time of dolomitization. Data show that: (1) carbonates are born with high porosity and lose porosity gradually over a long period; and (2) mud-dominated fabrics compact more readily than grain-dominated fabrics. The problem of estimating the time of dolomitization is minimized by confining observations to young limestones and associated dolostones. Limited data from Holocene dolomitic sediments suggest no change in porosity with dolomitization. Study of Plio-Pleistocene carbonates in Bonaire, Netherlands Antilles, demonstrates that precursor limestones are more porous than dolostones. Limestones average 25% porosity, whereas dolostones average 11% porosity. Data from the Neogene of the Great Bahama Bank show that dolostones and adjacent limestones both have 40% porosity. Porosity studies of the Jurassic Arab D Formation show that dolostones and associated grain-dominated limestones have similar porosity ranges and that the decrease in porosity with increasing dolomitization results from compaction of the mud-dominated fabrics. These data suggest that porosity in dolostone is not created by a mole-for-mole replacement mechanism. Instead, dolostone porosity is: (1) inherited from the precursor limestone; and (2) occluded by the process of overdolomitization. Palaeozoic dolostones, however, are commonly more porous than juxtaposed limestones. The explanation for this observation is that limestones lose porosity through compaction and cementation, whereas dolostones resist compaction and retain much of their porosity.

Permeability studies have demonstrated that dolomitization of grain-dominated limestones usually does not change porosity-permeability relationships. Instead, precursor limestone fabric controls pore-size distribution. The dolomite crystal size of a muddominated dolostone may, however, be larger than the carbonate mud size, improving the porosity-permeability relationship substantially. Hence, there is a predictable relationship between interparticle (grains or crystals) porosity, permeability, precursor grain size and dolomite crystal size.
Predicting and characterizing fractures in dolostone reservoirs: using the link between diagenesis and fracturing
Authors: Gale Julia F. W. , Laubach Stephen E. , Marrett Randall A. , Olson Jon E. , Holder Jon , Reed Robert M.
Published: April 2008

Fracture geometries and fracture-sealing characteristics in dolostones reflect interactions among mechanical and chemical processes integrated over geological timescales. The mechanics of subcritical fracture growth results in fracture sets having power-law size distributions where the attributes of large, open fractures that affect reservoir flow behaviour can be accurately inferred from observations of cement-sealed microfractures and other microscopic diagenetic features, which are widespread in dolostones. Fracture porosity is governed by the competing rates of fracture opening and cement precipitation during fracture growth and by cements that post-date fracture opening.

Combined analysis of structural and diagenetic features provides the best approach for understanding how fracture systems influence fluid flow. We review previous work and integrate new data on fractures and diagenetic features in cores from the Lower Ordovician Ellenburger and Permian Clear Fork formations in West Texas, and the Lower Ordovician Knox Group in Mississippi, together with outcrop samples of Lower Cretaceous Cupido Formation dolostones from the Sierra Madre Oriental, Mexico, in order to illustrate our approach.
Porosity and permeability in Miocene carbonate platforms of the Marion Plateau, offshore NE Australia: relationships to stratigraphy, facies and dolomitization
Authors: Ehrenberg S. N.
Published: April 2008

Analyses of porosity and permeability are examined from cores drilled in two Miocene carbonate platforms cored by ODP Leg 194, seaward from the Great Barrier Reef, including one site in the Northern Marion Platform (NMP; mostly preserved as limestone) and two sites in the Southern Marion Platform (SMP; mostly dolomitized). The majority of plug samples are from coarse bioclastic facies and their dolomitized equivalents. Dolomitization probably occurred by circulation of normal to slightly modified sea-water. Increasing fabric destruction at greater depth in the SMP may reflect overprinting of multiple dolomitization episodes in older strata, perhaps related to successive cycles of sea-level fluctuation. Both limestones and dolostones show similarly wide variation in porosity and permeability, reflecting extreme metre-scale heterogeneity of lithologies and diagenetic responses. The limestones show poorer porosity-permeability correlation, with generally lower permeability for given porosity compared with the dolostones, but with similar maximum permeabilities. Despite wide textural diversity, the dolostones cluster along a single trend that parallels the ideal relationship described by the Kozeny equation and characteristic of well-sorted sandstones. The low permeability-for-given-porosity of many limestones is explained by the fine grain size of some samples and, in other cases, by isolation of macropores behind mud matrix. Pore systems in the dolostones, however, tend to be dominated by interparticle macroporosiity, consisting of either relict intergranular pores (grainstones with fabric-preserving dolomitization) or intercrystalline pores (fabric-destructive dolostones and packstones with fabric-preserving dolomitization). Although many dolostones have vuggy pore systems, the vugs appear to be effective for fluid flow because they are connected by the enclosing system of interparticle macropores.
Palaeozoic dolomite reservoirs in the Permian Basin, SW USA: stratigraphic distribution, porosity, permeability and production
Authors: Saller Arthur H.
Published: April 2008

Dolomite and dolomite reservoirs are common in Ordovician and middle to upper Permian carbonates in the ‘Permian Basin’ area of the SW United States. Scattered, but significant, dolomite reservoirs also occur in the Silurian and Devonian. In the middle to upper Permian, platform and shelf-top carbonates were dolomitized, while limestones in slope and basinal environments were not. Most dolomitization of Ordovician and Permian carbonates occurred in evaporated seawater shortly after deposition (reflux dolomitization). Most dolomitizing brines apparently formed in tidal flat and restricted lagoonal environments in the platform and shelf interiors, and on depositional highs near shelf and platform margins.

More than 26 billion barrels of oil have been produced from the Permian Basin, with most of that oil coming from Palaeozoic (mainly Permian) dolomites. Permian Basin dolomites have very heterogeneous porosity and permeability on a wide range of scales. Field-scale (km-scale) variations in porosity are commonly related to position in the original dolomitizing system. Porosity generally increases away from the apparent source of the dolomitizing brines because a greater volume of dolomite was precipitated in proximal parts of the dolomitizing system than in the distal parts; hence, porosity is greater in dolomites in the basinward parts of fields.

Most Permian Basin dolomite reservoirs are structural traps with stratigraphic enhancement of closure by loss of porosity and permeability towards the shelf or platform interior. Many traps were formed by compactional drape over the same features that created highs during deposition. Hence, the structurally highest parts of many fields have the poorest porosity and permeability because they coincide with proximal parts of the original dolomitizing system. The most porous, permeable and productive dolomites are on the basinward flanks of structures, and often near the oil-water contact.

Dolomite reservoirs in the Permian Basin are quite variable. Ultimate oil recoveries from these fields range from <1000 barrels to 2 billion barrels, with the largest fields in shallow middle Permian (San Andres/Grayburg) reservoirs. Reservoir depths range from 1500 to more than 14 000 ft (500–4300 m). Average porosities for fields are 1–21%, with porosities generally decreasing with depth. Average permeabilities are 1–1000 mD. Many deeper reservoirs have high permeability related to fractures in karstified Ordovician reservoirs. Recovery efficiencies are 10–65% of the original oil in place, with higher recovery efficiency associated with larger pores and higher permeabilities.
Genesis of some Carboniferous dolomites in the south and east of Ireland
Authors: Mulhall Claire M. , Sevastopulo George D.
Published: April 2008

Dolomitized Tournaisian rocks occur widely in Ireland. They host the major Zn-Pb ore bodies, at Lisheen and Galmoy. Despite significant research and exploration into fluid flow related to both dolomitization and base-metal mineralization, the evolution of the porosity and permeability of the dolomites and precursor limestones remains poorly understood. Study areas, both within and outside the main mineralized zones, have been chosen in an effort to unravel the evolution of the porosity and permeability of the Tournaisian successions. In each area the earliest phase of dolomitization of the limestone lithosome occurred after all of the primary porosity had been occluded. Fluid inclusions from dolomite and authigenic quartz indicate relatively high temperatures (>105 °C) of formation of all phases of dolomite. The fluid-inclusion data demonstrate that there has been no re-equilibration due to later Variscan heating. Laterally restricted bodies of dolomite at Newcastle West and Subulter may have formed under hydrothermal or geothermal conditions. The geometry of the dolomite body at Newcastle West suggests that the dolomitizing fluids moved within a steeply dipping zone. The laterally extensive Regional Dolomite of SE Ireland, examined at Lisheen and in Co. Carlow, is likely to have had a geothermal origin and to have formed at depths of more than 2.5 km. The dolomites are moderately porous with the notable development of vugs; but their permeability is low. The vugs are not related to primary cavities within the limestone.
Nuclear waste forms
Authors: Stefanovsky Sergey V. , Yudintsev Sergey V. , Gieré Reto , Lumpkin Gregory R.
Published: April 2008

This review describes nuclear waste forms for high-level waste (HLW), that is, glasses, ceramics, and glass-ceramics, as well as for low- and intermediate-level waste (LILW), that is, cement, bitumen, glass, glassy slags, and ceramics. Ceramic waste forms have the highest chemical durability and radiation resistance, and are recommended for HLW and actinide (ACT) immobilization. Most radiation-resistant materials are based on phases with a fluorite-related structure (cubic zirconia-based solid solutions, pyrochlore, zirconolite, murataite). Glass is also a suitable matrix for HLW containing fission and corrosion products, and process contaminants such as Na salts. Within the framework of the HLW partitioning concept providing separation of short-lived (Cs, Sr) and long-lived (rare earth element-ACT) fractions, glass may be used for immobilization of the Cs-Sr-bearing fraction, whereas the rare earth-ACT fraction may be incorporated in ceramics. Glass-based materials or clay-based ceramics are the most promising LILW forms, but cement and bitumen may also be applied as matrices for low-level wastes (LLW).
Relevance of analogues for long-term prediction
Authors: Crovisier Jean Louis , Advocat Thierry , Dussossoy Jean Luc
Published: April 2008

The long-term consequences on the environment of materials containing potentially toxic elements must be assessed on the basis of experimental data obtained over short time-scales and from models of the phenomena involved over several tens of thousands of years. Predicting the future is only possible through the study of collection of past events to infer a possible long-term behaviour. However, not everything we would like to predict has already occurred in the past, nor is it necessarily observable under perfectly similar circumstances. Considering natural or artificial analogues permits us to study materials that, even if not homologous, are similar or equivalent to some of the properties of the unknown materials. Examples presented in this paper illustrates the fact that some reactions observed in short-term experiments can be validated over the long term only by examining such natural analogues.
Basaltic dykes in evaporites: a natural analogue
Authors: Steinmann Marc , Stille Peter
Published: April 2008

We present rare earth element (REE) data of basalt and salt samples from central Germany where basaltic dykes of Tertiary age crosscut Upper Permian rock and potash salt. The glassy rims of the dykes can be considered as a natural analogue for the corrosion of nuclear waste glass in a salt repository, whereas the REE data from the salt can serve as an analogue for radionuclide migration in salt next to a leaking nuclear waste repository because the light rare earths (LREE) have a geochemical behavior similar to that of some actinides.

Our basalt data demonstrate mobility and fractionation of the REE during postintrusive circulation of salt brines. The processes controlling this behavior of the REE were dissolution and reprecipitation of phosphate minerals. The salt data show that a small portion of the REE has left the basalt during postintrusive fluid circulation and migrated into the salt where a strong depletion of the LREE can be observed with increasing distance from the basalt contact. This fractionation is most probably due to precipitation of LREE-enriched accessory minerals such as apatite. In analogy to this, a similar behavior might be expected from actinides such as Am and Cm, which would in the case of a leaking salt nuclear waste repository probably be immobilized when phosphate minerals are present in the backfill material.
The chemistry and mineralogy of waste from retorting and combustion of oil shale
Authors: Saether O. M. , Banks D. , Kirso U. , Bityukova L. , Sorlie J. E.
Published: April 2008

Oil shales are comprised of clastic, organic, carbonate and minor sulphide fractions. The relative proportions of these fractions influence the composition and potential environmental impact of wastes produced by mining, combustion, and retorting of these shales. Mining produces spoils and gangues, which may or may not produce acidic leachates, depending on relative proportions of sulphide and carbonate minerals. Combustion of oil shale for power production produces slag and ash, which, when deposited as huge heaps and plateaux, can generate highly alkaline leachates. Power plants also emit acid-producing and greenhouse gases (SO
2
, NO
x
, and CO
2
) and particulate matter. Emitted particulate matter is dominated by basic oxides (e.g., CaO), the fallout of which tends to neutralize any tendency to environmental acidification. Estonian oil shales are highly unfavourable in terms of greenhouse gas emissions: CO
2
is generated both by decomposition of carbonates and oxidation of organic carbon, and 0.029 t/GJ carbon (C) is emitted for an energy yield of only 9 GJ/t shale. Finally, retorting of oil shales produces organically contaminated condensate water and semi-coke solid residue, leachates from which can contain several hundred mg/L phenols.
Injection and trapping of carbon dioxide in deep saline aquifers
Authors: Saylor Beverly Z. , Zerai B.
Published: April 2008

Carbon dioxide (CO
2
) collected from the waste streams of point sources can be injected into deep geologic formations in order to limit the emission of greenhouse gases to the atmosphere. Deep saline aquifers provide the largest potential subsurface storage capacity for injected CO
2
. Once injected, free CO
2
can be retained in deep aquifers for long time periods by slow-moving, downward-directed formation waters. Over time, the injected CO
2
will dissolve in the formation waters and, through reactions with formation minerals, may be converted to carbonate minerals, resulting in permanent sequestration. Factors that influence the mass of CO
2
that can be injected and stored in free or aqueous form, and as mineral phases, are reviewed and applied to estimate storage capacity of the Rose Run Sandstone, a saline aquifer beneath eastern Ohio, USA. It is estimated that 30 years of CO
2
emissions from five of Ohio’s largest coal-fired power plants can be injected into the Rose Run Sandstone and, over time, converted to aqueous and, ultimately, mineral phases.
Geochemical impact of re-injecting geothermal waste waters: example, Larderello, Italy
Authors: Panichi Costanzo
Published: April 2008

The impaccts of re-injection of geothermal waste waters on the physico-chemical characteristics of the fluids of the Larderello vapour-dominated geothermal field in Tuscany (Italy) were monitored using deuterium and oxygen-18 as ‘natural’ tracers. The observed variations were due mainly to mixing between the re-injected and deep components. Large isotopic fractionations occur at depth during the evaporation of the re-injected water in the reservoir and may affect the evaluation of the recovered fluid using a simple mixing model. Stable isotope and gas/steam ratios are closely correlated in the fluid collected from the monitored wells. Maps showing the isotopic distribution of the steam and the distribution of the gas content have been generated for the whole Larderello geothermal field. Evaluation of data collected before and after re-injection reveals a good distinction between natural inflow induced by exploitation, and artificial recharge with waste fluid. Gases other than N
2
in the wells affected by injection are substantially diluted since condensates are formed by evaporation. Isotopic variations of H
2
, CH
4
, and CO
2
have been used to describe the disequilibrium conditions among gas components. This disequilibrium is induced by the settling of a liquid plume at the producing level in the reservoir.
Geophysical and mineralogical impacts of fluid injection in a geothermal system: the Hot Fractured Rock site at Soultz-sous-Forêts, France
Authors: Baldeyrou-Bailly A. , Surma F. , Fritz B.
Published: April 2008

This paper deals with the geothermal system at Soultz-sous-Forêts, an important research site in France of the European Hot Fractured Rock project. A pilot plant is ready for electric energy production of up to 25–30 MW. Several research projects were developed in France, Switzerland, and Germany in order to study various scientific aspects of the geothermal system in parallel with the industrial development. Of primary scientific interest are the geophysical, geological, and geochemical conditions in the geothermal reservoir as well as the predictable consequences of future exploitation on the quality of the reservoir and on induced environmental problems, including: induced seismicity; rock alteration and possible formation of secondary minerals along the water pathways; and evolution of porosity and permeability in the deep aquifers. This paper focuses on two aspects: the geochemical evolution of minerals in the reservoir due to thermal gradients and fluid flow; and the evolution of physical properties of rocks during fluid injection in the wells. The petrophysical study shows that the fluid-rock interactions can be extensive in the reservoir matrix. The experimental study suggests that the fluid-mineral interactions are dynamic and that clay minerals can precipitate.
Phosphate stabilization of municipal solid waste combustion residues: geochemical principles
Authors: Eighmy T. Taylor , Dykstra Eusden J.
Published: April 2008

The use of orthophosphate (PO
4
3
−) as a chemical stabilization agent for municipal solid waste (MSW) combustion residues is widespread in Japan and North America. The application of this technology to MSW ashes generally parallels its use with other metal contaminated wastes (e.g., soils, sediments, smelter dusts, slags, wire chopping wastes, mine tailings), especially Pb-contaminated soils. The technology relies on the fact that PO
4
3
− forms very insoluble and stable minerals for a variety of divalent metal cations (e.g., Pb, Cd, Cu, and Zn). Extensive data from phosphate-treated contaminated soil systems suggest that stabilization involves surface immobilization reactions involving sorption, heterogeneous nucleation and surface precipitation, and/or solution phase precipitation involving homogeneous nucleation and precipitation. A geochemical basis for use of PO
3−
4
in ash systems is presented with a focus on the wide theoretical pH distribution, pH-pE predominance and redox stability of Cd, Cu, Pb, and Zn phosphates within complex bottom ash pore water systems. Stabilization mechanisms in bottom ashes, scrubber residues, and vitrification dusts are similar to those observed in soil systems. Some longer term leaching behaviour of phosphate-stabilized ashes are presented. The roles of Ostwald ripening, solid solutions (e.g., (Pb,Ca)
5
(PO4)
3
OH), and kinetically controlled reaction pathways probably are more important than what is presently envisioned in phosphate-stabilized ash systems.
Development and application of the Nagra/PSI Chemical Thermodynamic Data Base 01/01
Authors: Thoenen Tres , Berner Urs , Curti Enzo , Hummel Wolfgang , Pearson F. J.
Published: April 2008

The Nagra/PSI Chemical Thermodynamic Data Base is a critical selection of thermodynamic data used to support performance assessments for planned radioactive waste repositories in Switzerland. For this purpose, the data base is focused on actinides and fission products, but also includes additional data for major elements occurring in common groundwaters. Recently, a peer-reviewed update was carried out (from data base version 05/92 to 01/01) involving major revisions for most actinides and fission products. Altogether, more than 70% of the data base contents have been revised. Most of the thermodynamic data for U, Np, Pu, Am, and Tc were adopted from the reviews by the NEA TDB project. In contrast, data for Th, Sn, Eu, Pd, Al, as well as the solubility and metal complexation of sulphides and silicates, were extensively reviewed. Less effort was put into the review of data for Zr, Ni, and Se as these elements are currently being reviewed in Phase II of the NEA TDB project. The data for metal complexation with organic ligands from data base version 05/92 were not included in this update. They will be reconsidered in a future update, after completion of the NEA TDB Phase II review of organic ligands. The chemical consistency of the selected data was checked with empirical rules related to the periodic properties of the elements and with correlations based on charge/size relations. As a result of the update, major gaps in the data base could be identified, especially with respect to missing carbonate complexes. In some systems, for example, Th(IV)-H
2
O and U(IV)-H
2
O, conflicting experimental data cannot be described by a unique set of thermodynamic constants and a pragmatic approach closely reproducing measured solubility data was chosen for application to performance assessment. The electronic version of the Nagra/PSI Chemical Thermodynamic Data Base 01/01 and information concerning its full documentation is available on the PSI web site.
Towards a consistent rate law: glass corrosion kinetics near saturation
Authors: Icenhower Jonathan P. , Samson S. , Lüttge A. , McGrail B. P.
Published: April 2008

Although glass corrosion resistance has been tested with laboratory methods for decades, investigators are now just beginning to understand the reaction phenomena at or close to saturation with respect to the rate-limiting phase(s). Near saturation, the phenomena that govern element release rates include alkali-hydrogen (species) exchange, differential reactivity of phase-separated glass, and accelerated corrosion rates due to precipitation of key secondary phases. These phenomena were not anticipated by early models of glass dissolution and are incompletely quantified in current rate representations. This review discusses the two over-arching models for glass reactivity, diffusion and surface reaction control, and demonstrates the importance of glass reactivity in terms of glass composition and micro-heterogeneity of the glass. Our conclusion is that surface reaction control best describes the release of elements to solution, but that models based on current interpretations of transition state theory (TST) must be modified to account for reported anomalies in behaviour near saturation.
Geochemistry of leachates from coal ash
Authors: Spears D. A. , Lee S.
Published: April 2008

The combustion of coal around the world for power generation produces huge volumes of fly ash. In Europe alone this amounted to about 40 Mt in 2000 of which less than 50% was utilized. The waste ends in lagoons, ash mounds, and landfill sites. Coal ashes have high concentrations of many trace elements, some of which are of environmental concern. Although the origin of elements in coals is not considered in this chapter, other aspects of the geochemistry are, and in particular the location of elements within the coal as this influences the behaviour of elements during combustion. During combustion many elements are volatile and are concentrated on the surfaces of the ash particles. Analyses of input coal and combustion residues from Eggborough power station (UK) demonstrate retention of the majority of elements in the solid combustion products, and analyses of size-fractionated fly ash have enabled the percentage surface association to be calculated, which for elements such as As and Mo is considerable. A consideration of the general leaching behaviour leads to the conclusion that it is the surface-associated elements that are most susceptible to leaching in the aqeous environment. The pH is an important control on trace element mobility in water, and in leachates from fly ash ranges from 3.3 to 12.3. High-sulphur coals generate acidic leachates, but not exclusively as the laboratory and field data demonstrate in case studies on UK coals. Batch and column leaching tests on fly ashes are reviewed and data presented for fresh fly ash and weathered fly ashes from two UK mounds dating back 17 and 40 years. The weathered ashes do have lower leachate concentrations than the fresh ash, but in spite of their ages they would not be considered to be inert. The batch leaching tests are of value in simulating high liquid-to-solid ratios encountered in ash lagoons, whereas the column leaching tests relate more closely to ash mounds. Finally, the results of field studies are reviewed and data presented for samples from boreholes in the two ash mounds. Analyses of the ash and extracted porewaters demonstrate depth-related changes due to reaction of the ash with the infiltrating water and whether or not equilibrium was established. Calculations demonstrate that the porewaters achieve saturation with respect to gypsum at depth in the boreholes. Infiltration over the years has led to detectable changes in the concentrations of some of the major elements in the bulk ash, such as Ca, and this enables realistic infiltration rates to be calculated. However, there are not comparable changes in the concentrations of the trace elements in the ash because the rate at which elements are being removed in solution is not sufficiently great.
HCToolkit/EOS interface: an open source, multi-platform phase equilibria framework for exploring phase behaviour of complex mixtures
Authors: Meulbroek Peter , Cathles Larry , Goddard William A.
Published: April 2008

We present a computational framework that can be used to estimate phase equilibria, equation of state properties and composition-dependent viscosity, aimed at the geochemical community for modelling reservoir processes, and at the chemical community to quickly estimate continuum properties of known mixtures. The framework presented is an extensible, component-based set of modules that can be used in calculating phase properties (volumes and densities, compositions and conditions of phase separation, Henry’s Law constants and viscosities) at a wide range of pressures, temperatures and starting compositions. There are two pieces to the model: the HCToolkit (a set of Perl modules that act as computational engines) and the EOSInterface (an ActiveX wrapper for the HCToolkit) which allow the models in the HCToolkit to be usable in Microsoft Office programs. An application hosted in Microsoft Excel is included within the distribution.

The EOS models are adaptable for mixtures of arbitrary complexity, with number and types of components only limited by hardware. Model runs with mixtures of over 100 components have been tested, and are perfectly feasible. Implemented within the software are four equations of state; additional equations of state can easily be added. Also implemented are G
E
models and mixture viscosities. Finally, the EOS models provide liquid-vapour flash calculations, liquid-liquid flash (designed for petroleum-aqueous solutions) and the generation of phase diagrams.
Compositional grading in the oil column: advances from a mass balance and quantitative molecular analysis
Authors: Wavrek David A. , Mosca Fausto
Published: April 2008

The giant oil fields of the Val D’Agri region (Southern Apennines Internal Thrust Zone, Italy) may rank as the largest onshore accumulations in Europe, but these resources pose special technical challenges due to the secondary alteration process identified as compositional grading. This alteration process is attributed to petroleum system elements and processes that lead to the formation of an unstable oil column. These oil columns are studied within a mass balance perspective that allow identification of key molecular fractionations which can be used to properly diagnose this alteration mechanism in other oil accumulations. The molecular signature is defined in the organic sulphur fraction as well as different hydrocarbon classes, and is completely consistent with the engineering criteria for this reservoir process. This discovery is particularly critical to reservoir compartment studies as the failure to recognize this particular signal will invariably lead to the identification of false compartments.
Fluid properties, phase and compartmentalization: Magnolia Field case study, Deepwater Gulf of Mexico, USA
Authors: Weissenburger K. S. , Borbas T.
Published: April 2008

The Magnolia Field in the deepwater northern Gulf of Mexico is a Plio-Pleistocene age mixed phase reservoir whose fluids are not in compositional equilibrium. Fluid heterogeneities have arisen principally due to (1) variations in maturity of the source rock from which the hydrocarbons were derived, (2) the extent to which biogenic methane has been incorporated into the fluids and (3) phase fractionation effects. These influences express themselves both in terms of bulk fluid properties such as gas/liquid ratio, API gravity and saturation pressure and minor compositional attributes such as hydrocarbon gas isotopic composition and gasoline range molecular ratios. Significant compositional variations that cannot be ascribed to gravitational fluid segregation occur within reservoirs that are demonstrably in pressure communication. These variations challenge the notion that hydrocarbon fluid mixing is geologically instantaneous and underscore the importance of testing assumptions regarding compositional equilibria in conjunction with reservoir studies. Although the state of disequilibrium impedes compartmentalization assessments at Magnolia, it provides both opportunities for fluid property and phase predictions and potentially a development setting in which geochemical surveillance techniques may be profitably employed.
High temperature quartz cementation and the timing of hydrocarbon accumulation in the Jurassic Norphlet sandstone, offshore Gulf of Mexico, USA
Authors: Taylor Thomas , Stancliffe Richard , Macaulay Calum , Hathon Lori
Published: April 2008

Jurassic Norphlet Formation sandstone reservoirs in Mobile Bay (offshore Alabama, USA) produce gas from great depths (>6.4 km) and elevated temperatures (>200 °C). Quartz cement is concentrated at the top of these aeolian reservoirs forming a low porosity ‘tight-zone’ of widely variable thickness (3–58 m) above a more porous reservoir section. The extent of the tight-zone is independent of depositional facies and its thickness strongly influences well performance. Intergranular porosity in the Norphlet has been preserved by inhibition of quartz cementation due to the occurrence of robust grain-coating chlorite. Quantitative petrographic data reveal that chlorite grain-coat coverage is less in the tight-zone sands (mean = 92%) than in the reservoir sands (mean = 99%). Burial history and quartz precipitation kinetics modelling indicate that this seemingly minor difference in the completeness of grain coatings is sufficient to produce the observed differences in cementation and porosity. Quartz cementation to form the tight-zone took place under conditions of deep burial and high temperature. It followed in time the onset of pressure solution, emplacement of liquid hydrocarbons, and the precipitation of a solid hydrocarbon film (pyrobitumen) on the walls of the intergranular pores. Fluid inclusion microthermometry data indicate that volumetrically significant quartz cement precipitated at temperatures of 150 °C or greater from highly saline aqueous fluids. Hydrocarbon-bearing inclusions are notably absent in quartz cement of the tight-zone, implying that the pore fluids were predominantly brine during precipitation. Oil and gas associated with pyrobitumen evidently escaped from Norphlet traps prior to tight-zone cementation. Gas presently found in Norphlet reservoirs of Mobile Bay represents a relatively recent accumulation and is not the product of
in situ
thermal cracking of oil.
Distribution anisotropy: the influence of magnetic interactions on the anisotropy of magnetic remanence
Authors: Muxworthy Adrian R. , Williams Wyn
Published: April 2008

The anisotropy of magnetic remanence (AMR) is often used as a tool for examining magnetic anisotropy of rocks. However, the influence of magnetostatic interactions on AMR has not been previously rigorously addressed either theoretically or experimentally, though it is widely thought to be highly significant. Using a three-dimensional micromagnetic algorithm, we have conducted a systematic numerical study of the role of magnetostatic interactions on AMR. We have considered both lineation and foliation, by modelling assemblages of ideal single domain grains and magnetically non-uniform magnetite-like cubic grains. We show that magnetostatic interactions strongly affect the measured AMR signal. It is found that depending on the orientation of the single-grain anisotropy and grain spacing it is possible for the AMR signal from a chain or grid of grains to be either oblate or prolate. For non-uniform grains, the degree of anisotropy generally increases with increasing interactions. In the modelling of AMR anisotropy, saturation isothermal remanence was chosen for numerical tractability. The influence of interactions on other types of more commonly measured AMR, are considered in light of the results in this paper.
Metamorphic control of magnetic susceptibility and magnetic fabrics: a 3-D projection
Authors: Nakamura Norihiro , Borradaile Graham J.
Published: April 2008

Magnetic fabric changes due to progressive metamorphism are poorly understood. Bulk magnetic susceptibility (
κ
) is known to increase with metamorphic grade but anisotropy changes have been neglected. To combine information on anisotropy with bulk susceptibility, we introduce a projection with three axes:
κ
, ellipsoidal eccentricity (

P
j
, the so-called ‘anisotropy degree’, despite the fact that this is quantified

) and ellipsoid symmetry (

T
j

) as independent variables. The projection reveals that metamorphic facies can be discriminated successfully in the 3-D projection, with distinct, significant regression surfaces for crustal metamorphic rocks metamorphosed successively in greenschist, amphibolite, and granulite facies. This emphasizes that bulk magnetic susceptibility (
κ
) and its anisotropies (‘magnetic fabric’) evolve in response to metamorphic process, not just strain. Moreover, post-tectonic granitic plutons, upper mantle harzburgites and serpentinized mantle rocks also have characteristic regression surfaces relating

κ, P
j

and

T
j

in the new projection.
The anisotropy of magnetic susceptibility (AMS) in low-grade, cleaved pelitic rocks: influence of cleavage/bedding angle and type and relative orientation of magnetic carriers
Authors: Debacker Timothy N. , Robion Philippe , Sintubin Manuel
Published: April 2008

Cambrian and Silurian, low-grade, pelitic rocks of the single-phase deformed Brabant Massif consistently have a maximum magnetic susceptibility axis (K1) parallel to the cleavage/bedding intersection. In contrast, the minimum susceptibility axis (K3) either coincides with the bedding pole, with the cleavage pole or occupies an intermediate position. Anisotropy of anhysteretic remanence (AARM) and X-ray pole figure goniometry allow the distinguishing of the orientation distributions of the ferromagnetic and paramagnetic (white mica and chlorite) carriers, respectively. Mismatches between K3 and the poles to the macroscopic fabric elements (i.e. bedding and cleavage) are attributed to different orientations of the different magnetic (
s.l.
) carriers. A strong relationship exists between the cleavage/bedding angle and the shape parameter: low, respectively high angles leading to oblate, respectively prolate susceptibility ellipsoids. However, differences are observed between the Cambrian and Silurian samples in terms of the shape parameter and the behaviour of the degree of anisotropy with changing cleavage/bedding angle. This is tentatively attributed to differences in relative orientation and mineralogy of the magnetic (
s.l.
) carriers. These results demonstrate the influence of the relative orientation of the different carriers on AMS and suggest that, although being a petrofabric tool, AMS cannot be used as a strain gauge in the case of composite magnetic fabrics.