bluuebunny/crossref_metadata_2025 huggingface dataset:
Environmental impacts of coal mining and associated wastes: a geochemical perspective
Authors: Younger Paul L.
Published: April 2008

Ever since the commencement of industrial-scale coal mining (in northeast England around 1600), substantial environmental impacts have been recorded as arising from both the mined voids and from the wastes left behind at the surface. In the early days of coal mining, complaints about such impacts were strident, as the newly established industry adversely affected long-established agricultural interests. When the coal trade had come to dominate regional economies in mining districts, its negative impacts came to be accepted as a necessary byproduct of the generation of coal-based wealth. It has only been since large-scale mine closures began to take place in the major coal-mining economies of the developed world during the last few decades that the negative impacts of coal mining have once more been deemed unacceptable. The environmental impacts arising from coal mining activities are fundamentally attributable to the exposure of reduced earth materials (especially coal, pyrite, siderite, and ankerite) to the oxidizing power of the Earth’s atmosphere. The consequences range from the spontaneous combustion of coal to the release of acidic waters from pyrite oxidation. A typology of the known impacts arising from mine voids and wastes in coal mining districts has been developed, which recognizes many subcategories of impacts under five major headings: air pollution, fire hazards, ground deformation, water pollution, and water resource depletion. A robust understanding of geochemical processes is key to understanding how these impacts arise, and to developing sustainable mitigation strategies. The application of the newly developed typology is illustrated using the case of the Shilbottle Coalfield (Northumberland, UK). Although few demonstrable impacts have arisen in the categories of air pollution, fire hazards, or ground deformation, major problems of water pollution have required both preventative and remedial interventions. For the flooded underground voids, these took the form of a pump-and-treat system, whereas emissions of leachates from surface spoil heaps have necessitated the installation of an innovative ‘hybrid’ passive treatment system, comprising a permeable reactive barrier, oxidation ponds, and a wetland. Inverse geochemical modelling has clarified the linkages between the various types of water encountered in the coalfield, providing a baseline geochemical understanding upon which future investigations of remedial system sustainability can be based.
Waste heat problems and solutions in geothermal energy
Authors: Rybach Ladislaus , Kohl Thomas
Published: April 2008

All heat-power conversion systems produce waste heat, which can attain significant portions. This applies to geothermal power generation too; the waste heat fraction depends on the conversion technology. The more of the waste heat that can be utilized for some useful purpose (and consequently requiring less heat to be rejected), the better economy can be achieved, besides benign environmental effects. The best solution to avoid discharge to the atmosphere or to the hydrosphere is cascaded use. This consist of a chain of applications with stepwise decreasing temperatures, for example, from industrial uses through balneology down to fish farming. Constraints given by environmental legislation can lead to beneficiary solutions like in the case of warm tunnel waters in the Swiss Alps: these would need cooling ponds/towers before being permissible for discharge into local rivers. It is described by several specific examples how the tunnel waters can be used instead.
Modelling near- and far-field processes in nuclear waste management
Authors: Bruno J. , Arcos D. , Cera E. , Duro L. , Grivé M.
Published: April 2008

In this chapter we present some of the recent advances concerning process understanding and modelling of radionuclide migration in nuclear waste disposal systems. The present geochemical modelling approaches used to quantify the processes concerning spent fuel dissolution, radionuclide interactions with the canister materials and the bentonite buffer are thoroughly discussed. Finally, some applications to natural analogue studies of spent nuclear fuel disposal, as testing ground for concepts and models developed for waste management systems, are presented.
Mechanisms of uranyl sorption
Authors: Del Nero M. , Froideval A. , Gaillard C. , Mignot G. , Barillon R. , Munier I. , Ozgümüs A.
Published: April 2008

Detailed knowledge of the reactions at the water/colloid/mineral interface is crucial to model accurately actinide behaviour in nature. In this paper, we review current knowledge of the sorption of actinides and of the mechanisms of sorption, with a particular focus on uranyl. Of major interest is the influence of the aqueous uranyl species (e.g., carbonate complexes, polynuclear species, colloids) on the uranyl sorption species. We present extended X-ray absorption fine structure (EXAFS) and X-ray photoelectron spectroscopy (XPS) studies on the coordination of uranyl onto an amorphous Al phase and onto quartz, respectively. Our XPS investigations show that two components having uranyl ions in very distinct coordination environments co-exist on quartz at high uranyl surface coverage, independently of the presence of uranyl carbonate complexes or uranyl colloids in solution. One component corresponds to polynuclear surface species and/or schoepite-like surface precipitates. In the case of similar uranyl concentrations and of high carbonate solution concentrations, polymeric uranyl species are formed on quartz, whereas no such surface species occurs on the Al phase. Uranyl is found on the Al phase as mononuclear uranyl carbonato surface complexes only. These results are of importance because they suggest that mineral surface characteristics strongly control the uranyl surface species in aquifers.
Secondary mineral formation in coal combustion byproduct disposal facilities: implications for trace element sequestration
Authors: Donahoe Rona J.
Published: April 2008

Coal combustion byproducts (CCBs) are high-volume wastes produced by the electrical power industry and typically disposed of in landfills and lagoon impoundments. In the disposal environment, meteoric water or groundwater may percolate through and interact with the ash materials, producing leachate that contains elevated levels of many trace elements. Various geochemical reactions control the release of solutes and the formation of secondary minerals in CCB disposal facilities during weathering. Concern about the potential release of trace elements into the environment has motivated a large number of studies aimed at predicting the maximum concentrations of elements in leachate solutions. Secondary minerals formed during weathering of CCBs have the potential to limit the mobility of trace elements in an ash disposal facility. Geochemical modelling has been used by many investigators to predict the equilibrium concentrations of solutes in CCB leachate solutions and the stable secondary minerals that will form in weathered ash. Unfortunately, basic kinetic, thermodynamic and adsorption data are lacking for many solid phases, particularly those that may contain trace elements. In addition, secondary solid phases are very difficult to identify by direct analytical methods due to their low abundances and/or amorphous character, so it is often not possible to directly determine the identity and compositions of secondary phases in ash disposal environments. Despite these difficulties, numerous secondary solid phases have been directly observed and/or predicted to form via weathering reactions in CCBs. A tabulation of all secondary phases that have formed or have the potential to form in the CCB disposal environment is given, along with the relevant references. The potential for secondary phases to sequester trace elements via precipitation, adsorption and co-precipitation is discussed. Secondary phases with the greatest potential to limit the mobility of trace elements are amorphous Fe-oxyhydroxide and amorphous aluminosilicate phases, which are metastable precursors to Fe-oxide and clay minerals, respectively.
Effects and impact of early-stage anaerobic biodegradation on Kuparuk River Field, Alaska
Authors: Holba Albert G. , Wright Lisa , Levinson Rick , Huizinga Bradley , Scheihing Mark
Published: April 2008

Anaerobic processes have only recently been recognized as an important mechanism in the biodegradation of crude oils. They are normally invoked to explain extensively biodegraded oils with little or no possibility of contact by oxygenated waters from an active aquifer. This work with Kuparuk Field indicates that early stages of anaerobic biodegradation can be subtle and easily missed, yet have economic impact.

Kuparuk River Field, North Slope of Alaska, comprises two reservoir intervals: vertically stratified and imbricated lower shoreface sandstones (A sands), and overlying shallow marine sandstones with complex permeability structure (C sands). The vertical and lateral distribution of viscous oil (less than 20° API) shows a strong relationship to structure and faulting in the Kuparuk Field. Multiple mechanisms for the origin of tars and viscous oils can be proposed, including early aerobic biodegradation, anaerobic biodegradation, inorganic oxidation and gas deasphalting. This geochemical study, integrated with stratigraphic, structural and production data, was undertaken to help understand the origin and distribution of tar and viscous oil in the field.

Obvious depletion of
n
-alkanes and other paraffins, classically regarded as indicative of early biodegradation, is not observed in examined samples. However, Kuparuk viscous oils show slight to extreme selective depletion in long-chain alkyl aromatic (LCAA) hydrocarbon families (e.g. alkylbenzenes and alkyltoluenes). This is interpreted as indicative of an early stage of anaerobic microbial degradation that likely destabilized the oil to promote subsequent precipitation of asphaltenes as tar.

Depletions in LCAAs in core samples in the field are linked to decreased hydrocarbon/nonhydrocarbon ratio and to an increase in the high molecular weight (>C
50+
) components of Rock-Eval 6 pyrolysates. Using a calibration curve constructed from oil Rock-Eval 6 pyrolysis, the API gravity of core oil plus bitumen can be estimated. Tar-plugged formations with depleted LCAAs have estimated API gravities <8°. Portions of the Kuparuk reservoir with higher iron content tend to show greater depletions in LCAA. Anaerobic biodegradation is likely mediated by dissimilatory iron-reducing bacteria. Biodegradation likely destabilizes the oil with respect to asphaltene precipitation such that later arrival of petroleum leads to tar in the reservoir. Increased tar and depleted LCAAS correspond to intervals with lower productivity indices, thus indicating a significant impact on petroleum producibility.
Rates of reservoir fluid mixing: implications for interpretation of fluid data
Authors: Smalley Craig , England William A. , Muggeridge Ann , Abacioglu Yafes , Cawley Stephen
Published: April 2008

This paper highlights the benefits of using knowledge of the rates of fluid mixing in the interpretation of reservoir fluid data. Comparison of the time it would take for a fluid difference to mix with the actual time available for mixing to occur allows two significant advances over a purely statistical analysis of reservoir fluid data: (1) differentiation of a step in fluid properties, indicative of a barrier to fluid communication, from a gradient indicative of incomplete mixing; and (2) quantitative estimation of the
degree
of compartmentalization that can readily be adapted into models for prediction of reservoir production performance.

We review the existing equations that estimate the mixing times for three main types of variation in fluid properties (fluid contacts, fluid density and fluid chemistry). In addition, a new relationship for fluid pressure mixing is presented. In each case the relationships were validated by comparison with numerical simulation. The different fluid mixing processes were compared by applying the equations to a range of simple fluid scenarios in one simple reservoir description. This shows that mixing times for fluid mixing processes are diffusion > fluid density > fluid contacts > fluid pressure. For each scenario, the processes were analysed in terms of the volume of fluid that must move in order to bring the system to equilibrium and the drive for fluid mixing (pressure difference × permeability/viscosity). Perhaps surprisingly, there is an excellent linear relation between fluid mixing times (a) calculated from the mixing equations and (b) estimated from volume/drive. This indicates that fluid volumes and mixing drive are the main controls on fluid mixing times. This can be used to derive simple interpretation guidelines to estimate mixing rates even in the absence of quantitative modelling. A simple field case study demonstrates how this understanding of fluid mixing times can add value to the interpretation of reservoir fluid data.
Development of a compositional kinetic model for hydrocarbon generation and phase equilibria modelling: a case study from Snorre Field, Norwegian North Sea
Authors: Primio Rolando Di , Skeie Jon Erik
Published: April 2008

The possibility to model petroleum composition during hydrocarbon generation as well as the PVT behaviour of the fluids during migration has only recently become available in modern basin modelling software packages. While various compositional kinetic models of petroleum generation have been published in the past few years, none of the studies presented have attempted to match the composition, physical properties and phase state of known petroleum accumulations. Using compositional data from closed-system non-isothermal pyrolysis experiments, we developed a compositional kinetic model of hydrocarbon generation for a marine Type II source rock, which uses 13 components to describe the generated fluid. The data format selected is compatible with the compositional resolution used in reservoir engineering, thus allowing a direct comparison of predicted compositions and phase behaviour with PVT data of natural fluids. Compositional predictions of the model were tuned to a well-documented maturity sequence from the Tampen Spur, Norway, and the calibrated model implemented in a 2D basin modelling study of the Snorre Field, Norway. The results of the modelling led to an excellent correlation between predicted and reported reservoir fluid properties (formation volume factor, GOR and saturation pressure) for the present-day situation. The results indicate that the Snorre reservoir has received a continuous charge since the late Cretaceous-early Tertiary and that it most likely contained a two-phase system prior to the latest Plio-Pleistocene burial and overpressuring event.
A petroleum charge model for the Judy and Joanne Fields, Central North Sea: application to exploration and field development
Authors: Lines Michael D. , Auld Heather A.
Published: April 2008

There is considerable diversity in petroleum type within the Judy and Joanne Fields of the Central Graben. Superficially, the three major reservoir systems can be considered to contain the following fluid types: gas-condensates in the Pre-Cretaceous, undersaturated black oils in the Chalk and gas-condensates in the Palaeocene. Reality is, however, quite different.

This paper presents the results of several geochemical studies undertaken in the area; oil/condensate analyses to identify differences in maturity and source input, a pressure data review, high resolution GC fingerprinting, strontium isotope analyses to investigate reservoir connectivity/compartmentalization, and 2D basin modelling to determine the timing and extent of petroleum expulsion and migration. These components have been synthesized to produce a composite petroleum charge model which adequately explains the differences observed. This, in turn, enables an assessment to be made of the likely impact, if any, on field development. Furthermore, the petroleum charge model can be applied to predict the charge risk, fluid type and likely petroleum-water contacts in untested parts of the field and in the immediate vicinity.

The results of recent development wells are reviewed in the light of the charge model. Subsequent reservoir geochemistry studies have confirmed the validity of the model and highlight additional applications for reservoir management.
Determination of the orientation of magnetic minerals from the anisotropy of magnetic susceptibility
Authors: Jezek J. , Hrouda František
Published: April 2008

The anisotropy of magnetic susceptibility (AMS) of rocks is controlled by preferentially oriented magnetic mineral grains that carry AMS and, therefore, it contains information about both the grain susceptibilities and the grain orientations. Under certain conditions, information about the grain orientations can be deduced from the AMS. For a multigrain system composed of identical grains that are magnetically uniaxial (for the grain principal susceptibilities it holds that
K
1
>
K
2
=
K
3
, or
K
1
=
K
2
>
K
3
), an exact relationship exists between the AMS and the orientation tensor. We investigate the extent to which the theoretical relationships can be used when grains are generally triaxial. The parallelism of the principal directions of the susceptibility tensor and those of the orientation tensor are well preserved in all basic grain configurations. If grain leading axes have polar or girdle distributions and the two other axes have balanced distributions (similar orientation tensors), the parameters of intensity
I
and shape
T
based on the eigenvalues of the orientation tensor are well estimated. For unbalanced distributions, formulas are found for possible errors of
I
and
T
estimates.
A comparison of anisotropy of magnetic remanence methods — a user’s guide for application to palaeomagnetism and magnetic fabric studies
Authors: Potter David K.
Published: April 2008

Anisotropy of magnetic remanence (AMR) is increasingly being applied to palaeomagnetic and structural fabric studies. AMR techniques measure the anisotropy of the remanence carrying particles, and thus are directly relevant to palaeomagnetic studies concerned with computing the direction and intensity of the Earth’s ancient magnetic field from the natural remanent magnetization (NRM) recorded in anisotropic rocks. This paper provides a comparison of several AMR methods, including some of the less well-known techniques, and highlights the relative merits of each. Results from a strongly anisotropic rock and a pottery sherd are presented. The anisotropies of anhysteretic remanent magnetization (AARM) and isothermal remanent magnetization (AIRM) are currently the most commonly applied types of AMR, since they have provided reasonably good analogues of the anisotropy of thermoremanent magnetization (ATRM) acquired in the Earth’s field. They have also helped to correct for inclination shallowing of detrial remanent magnetization (DRM) in sediments. IRM anisotropy is the most rapid AMR technique, and is particularly useful for very low concentrations of remanence carrying particles. The gyroremanences, gyroremanent magnetization (GRM) and rotational remanent magnetization (RRM), are preferentially acquired by stable single-domain (SD) particles, and are thus directly relevant to the particles of major interest in palaeomagnetism. GRM anisotropy is the most sensitive AMR method. It is essentially the remanence equivalent of the anisotropy of magnetic susceptibility (AMS) delineator, since a single application of an alternating field will only produce a GRM in a sample containing an anisotropic distribution of particles. Static ARM methods need to take account of components of GRM that are simultaneously acquired.
Statistical significance of magnetic fabric data in studies of paramagnetic granites
Authors: Pueyo E. L. , Román-Berdiel M. T. , Bouchez J. L. , Casas A. M. , Larrasoaña J. C.
Published: April 2008

The low anisotropies of paramagnetic granites, due to magnetocrystalline anisotropy, require a statistical treatment of the anisotropy of magnetic susceptibility (AMS) data when systematic fabric studies are performed. Absence of statistical information on these data makes evaluation of their quality difficult. The statistical significance of magnetic fabric in granites is evaluated in this paper. Jelinek’s elliptical confidence angles for the three principal susceptibility axes (E
13
, E
12
, E
23
) of a specimen are used as markers of the quality of the AMS data. Comparing these markers at sample-, site- and massif-scale with the mean AMS axes that result from spherical statistical models helps clarify the reliability of the AMS data. This analysis is presented in detail for the plutons of Veiga and Trives (Spain). It is then applied to seven other massifs from the Pyrenees. We propose the following guides: (1) fabrics with E
13
between 10° and 20° tend to isotropy; the directional data and the shape parameter should be considered with great care; (2) lineation is not reliable when E
12
> 25°, i.e. when
K
max
is almost the same as
K
int
; (3) similarly, foliation is considered as not reliable when E
23
> 25°, i.e.
K
min
does not easily differentiate from
K
int
. Errors attached to the mean
K
max
and
K
min
axes should always be produced, thus allowing further interpretation. In Trives and Veiga, ‘perfect’ triaxiality cannot be automatically assumed since foliation and lineation could be defined simultaneously in only 53% of the cases. Finally, a minimum of three cores (9 specimens) per site would considerably increase the proportion of reliable orientation data.
Magnetic fabric constraints on oroclinal bending of the Texas and Coffs Harbour blocks: New England Orogen, eastern Australia
Authors: Aubourg Charles , Klootwijk Chris , Korsch Russell J.
Published: April 2008

We have carried out a magnetic fabric study on deformed, clay-rich rocks from the Carboniferous Texas beds and Coffs Harbour Association in order to test the hypothesis of oroclinal bending of the Texas and Coffs Harbour blocks of the southern New England Orogen, eastern Australia. The magnetic susceptibility is dominated by paramagnetic phyllosilicates, with site-dependent contributions from the ferromagnetic minerals pyrrhotite, magnetite and hematite. Pyrrhotite is ubiquitous in the Texas block and in the central part of the Coffs Harbour block, and may be important as an indicator of the grade of low-temperature metamorphism. The magnetic fabric results, in general, show good agreement with structural observations in the Texas and Coffs Harbour blocks. The magnetic foliation is related to the pervasive cleavage associated with accretionary deformation prior to oroclinal bending. The magnitudes of the anisotropy parameters and the plunge of the magnetic lineation indicate an increase in the intensity of deformation from east of the Coffs Harbour orocline towards the Texas orocline. An imprint from oroclinal deformation is suggested by a significant increase in the anisotropy parameter and by the development of steeply plunging magnetic lineations towards the hinges of the Texas and Coffs Harbour oroclines. The Terrica beds from the Early Permian (Allandale) Terrica inlier in the Texas orocline also show another, pre-tilt induced, tectonic imprint. Remanence data from volcanics in the Alum Rock inlier (293 Ma) and magnetic fabric data from this inlier tentatively constrain the onset of oroclinal bending as prior to extrusion of the Alum Rocks, and the completion of bending as post-Terrica beds deposition and pre-Illawarra Reversal (est. 265 Ma).
Geological prior information and its applications to geoscientific problems
Authors: Wood Rachel , Curtis Andrew
Published: April 2008

Geological information can be used to solve many practical and theoretical problems, both within and outside of the discipline of geology. These include analysis of ground stability, predicting subsurface water or hydrocarbon reserves, assessment of risk due to natural hazards, and many others. In many cases, geological information is provided as an
a priori
component of the solution (i.e. information that existed before the solution was formed and which is incorporated into the solution). Such information is termed ‘geological prior information’.

The key to the successful solution of such problems is to use only
reliable
geological information. In turn this requires that: (1) multiple geological experts are consulted and any conflicting views reconciled, (2) all prior information includes measures of confidence or uncertainty (without which its reliability and worth is unknown), and (3) as much information as possible is quantitative, and qualitative information or assumptions are clearly defined so that uncertainty or risk in the final result can be evaluated. This paper discusses each of these components and proposes a probabilistic framework for the use and understanding of prior information.

We demonstrate the methodology implicit within this framework with an example: this shows how prior information about typical stacking patterns of sedimentary sequences allows aspects of 2-D platform architecture to be derived from 1-D geological data alone, such as that obtained from an outcrop section or vertical well. This example establishes how the extraction of quantitative, multi-dimensional, geological interpretations is possible using lower dimensional data. The final probabilistic description of the multi-dimensional architecture could then be used as prior information sequentially for a subsequent problem using exactly the same method.
Stratal patterns and lithofacies of an intact seismic-scale Carboniferous carbonate platform (Asturias, northwestern Spain): a virtual outcrop model
Authors: Verwer Klaas , Kenter Jeroen A. M. , Maathuis Ben , Della Porta Giovanna
Published: April 2008

Among the more challenging questions in geology are those concerning the anatomy of sedimentary bodies and related stratal surfaces. Though significant progress has been made on the interpretation of depositional environments, little systematic data are available on their dimensions and geometry. With the recent advances in computer power, software development and accuracy of affordable positioning equipment, it has now become possible to extract high-resolution quantitative data on the anatomy of sedimentary bodies. In Asturias, northwestern Spain, aerial photography provides continuous 2-D cross-sections of a seismic-scale, rotated to vertical, carbonate platform margin of the Early Carboniferous. Digital elevation models, orthorectified aerial photographic imagery and ground verification of stratal surfaces generated the elements that are required to reconstruct the true dimensions, angular relationships of bedding planes and the spatial distribution of facies units in this platform margin. Along with biostratigraphy this provides sufficient constraints to estimate rates of progradation, aggradation, growth and removal of sediments in the slope environment. Here we present a methodology to create outcrop models and integrate complementary types of data that provide new insights in sedimentology that were previously unattainable.
Lithospheric structure of the Canadian Shield inferred from inversion of surface-wave dispersion with thermodynamic
a priori
constraints
Authors: Shapiro N. M. , Ritzwoller M. H. , Mareschal J. C. , Jaupart C.
Published: April 2008

We argue for and present a reformulation of the seismic surface-wave inverse problem in terms of a thermal model of the upper mantle and apply the method to estimate lithospheric structure across much of the Canadian Shield. The reformulation is based on a steady-state temperature model, which we show to be justified for the studied region. The inverse problem is cast in terms of three thermal parameters: temperature in the uppermost mantle directly beneath Moho, mantle temperature gradient, and the potential temperature of the sublithospheric convecting mantle. In addition to the steady-state constraint, prior physical information on these model parameters is based on surface heat flow and heat production measurements, the condition that melting temperatures were not reached in the crust in Proterozoic times and other theoretical considerations. We present the results of a Monte Carlo inversion of surface-wave data with this ‘thermal parameterization’ subject to the physical constraints for upper mantle shear velocity and temperature, from which we also estimate lithospheric thickness and mantle heat flux. The Monte Carlo inversion gives an ensemble of models that fit the data, providing estimates of uncertainties in model parameters. We also estimate the effect of uncertainties in the interconversion between temperature and seismic velocity. Variations in lithospheric temperature and shear velocity are not well correlated with geological province or surface tectonic history. Mantle heat flow and lithospheric thickness are anti-correlated and vary across the studied region, from 11 mW/m
2
and nearly 400 km in the northwest to about 24 mW/m
2
and less than 150km in the southeast. The relation between lithospheric thickness and mantle heat flow is consistent with a power law relation similar to that proposed by Jaupart
et al.
(1998), who argued that the lithosphere and asthenosphere beneath the Canadian Shield are in thermal equilibrium and heat flux into the deep lithosphere is governed by small-scale sublithospheric convection.
In situ
seismic investigations of fault zones in the Leventina Gneiss Complex of the Swiss Central Alps
Authors: Ciese R. , Klose C. , Borm G.
Published: April 2008

Underground seismic tomography investigations have been carried out in the Faido access tunnel of the Gotthard Base Tunnel, Switzerland. Velocity measurements were made over a total length of 2651 m of the adit with the tunnel seismic prediction system, ISIS (Integrated Seismic Imaging System). ISIS provides high-resolution seismic imaging, using an array of rock anchors equipped with 3D-geophones.

The first onsets of the compressional and shear waves were used for tomographic inversion. Two-dimensional seismic-velocity models reveal a disturbed zone between 2 and 3 m inward from the tunnel wall, characterized by strong variations from 3500 to 5800 m s
−1
in compressional wave velocity
V
P
, and from 2000 to 3000 m s
−1
in shear-wave velocity
V
S
. High-velocity zones correspond to quartz lenses, and low velocities mainly indicate fractured rock. Beyond the excavation disturbance zone, the variations in seismic velocities are generally smaller. The tomographic image of the rock mass also revealed two major fault zones composed of cataclastic shear planes surrounded by wider fracture zones. These structural characteristics are also useful for the prediction of cataclastic zones at other sites.
Integration of electrical and optical images for structural analysis: a case study from ODP Hole 1105A
Authors: Haggas S. L. , Brewer T. S. , Harvey P. K. , Macleod C. J.
Published: April 2008

A significant problem with basement core data acquired by the Ocean Drilling Program (ODP) is that it is unorientated with respect to grid north and in those cores with < 100% core recovery the data may also be inaccurately located within the borehole. In order for structural data from basement cores to be of any real value, the recovered core must firstly be accurately located and orientated. Here, we develop methods for core reorientation and accurate location within a borehole that integrates wireline borehole electrical images with whole-core digital images. Azimuthal orientation and location of individual core pieces allows for the detailed interpretation of structural data, including fabrics and fractures and reorientation of other spatially anisotropic properties of core, such as palaeomagnetism.

ODP Hole 1105A is one of a pair of holes drilled on the Atlantis Bank in the SW Indian Ocean, which penetrate sections of the lower ocean crust. Hole 1105A was drilled to a depth of 158 metres below sea-floor (mbsf), with core recovery of 83% and the vast majority of the recovered material being represented by gabbroic rocks.

Zones of crystal-plastic deformation occur throughout the core, but overall their frequency increases downhole. In the deformed zones, the gabbros are transformed into equigranular or porphyroclastic gneissose textured rocks, characterized by very prominent planar fabrics. These localized deformation zones relate to the early exhumation history of the lower crust in an environment similar to core-complex formation in continental regions.

Using a combination of digital core and formation microscanner (FMS) images, it is now possible to fully orientate structural features in a borehole and so map the oxide gabbro and crystal-plastic deformation zones in Hole 1105A. From the analysis of the crystal-plastic fabrics, the majority appear to dip southwards, with a few (
c
.5%) dipping to the north. This would suggest that the major exhumation surfaces in this hole are represented by southward-dipping structures, formed at high temperatures during unroofing of the Atlantis Bank.
The interpretation of thermal neutron properties in ocean floor volcanics
Authors: Brewer T. S. , Harvey P. K. , Barr S. R. , Haggas S. L. , Delius H.
Published: April 2008

Using near-complete chemical analyses, computed thermal absorption cross-section values (σ) are calculated for ocean-floor basalts from ODP Holes 896a and 1179D. Comparison with nuclear measurement of σ, demonstrates that this computational method is valid and clarifies the interpretation of σ in ocean-floor basalts. Boron, lithium and the rare-earth elements are important controls on the σ-values, and, of these, the distribution of the rare-earth elements is controlled by primary magmatic processes, whereas the distribution of boron and lithium is strongly influenced by secondary low-temperature alteration processes. Consequently, computed σ-values can be used to discriminate between various basalt types and to identify areas of secondary alteration.

Following calibration of the ‘fresh basalt’ signature, it is possible to interpret log derived neutron absorption measurements of a sample (Σ-values), which, when integrated with other log responses, allow the distribution of alteration within a drilled section to be mapped. Examples from ODP Hole 801C demonstrate the potential of this technique.
Microstructure, filtration, elastic and thermal properties of granite rock samples: implications for HLW disposal
Authors: Petrov V. A. , Poluektov V. V. , Zharikov A. V. , Nasimov R. M. , Diaur N. I. , Terentiev V. A. , Burmistrov A. A. , Petrunin G. I. , Popov V. G. , Sibgatulin V. G. , Lind E. N. , Grafchikov A. A. , Shmonov V. M.
Published: April 2008

This contribution presents preliminary data on the petrographic and mineral—chemical composition of the granitoid and dioritoid core samples of the Itatsky and Kamenny sites in the Nizhnekansky Massif of the Krasnoyarsk Region, in combination with data on structure of their pore space, filtration, elastic, mechanical and thermophysical properties, data necessary to select a site for an underground research laboratory. This laboratory would be a precursor to an underground radioactive waste facility. It was found that the variation of petrophysical properties depends on the degree of metamorphic, hydrothermal—metasomatic and deformational transformations, and differs markedly for two groups of rocks, namely, 1 — granites and granite-gneisses, and 2 — quartz diorites and diorites. Comparative analysis of the data obtained shows that the country rocks of the Kamenny site have a relatively higher degree of heterogeneity in their petrophysical characteristics, than those of the Itatsky site. These results could be applied both to select the preferred site and to make a preliminary estimate of the thermal, hydraulic and mechanical behaviour of country rocks in the vicinity of a prospective underground heat-generating waste repository.
Effect of compositional and structural variations on log responses of igneous and metamorphic rocks. I: mafic rocks
Authors: Bartetzko A. , Delius H. , Pechnig R.
Published: April 2008

Well logging has become a standard method in the oil industry for the investigation of subsurface geology. Accordingly, interpretation techniques have been mainly developed for use in sedimentary rocks, and the log responses of sediments are well known. However, this is not the case for igneous and metamorphic rocks. We present a compilation of log responses for mafic rocks from drill-holes in oceanic and continental basement. The holes cover a variety of mafic rocks: mid-ocean ridge basalt (MORB), gabbro, basalt and andesitic basalt from back-arc basins, flood basalt from large igneous provinces (LIPs), and continental metamorphic rocks. The comparison of log responses shows that rocks from the same geological setting have similar
in situ
physical properties. Differences in physical properties between rocks from different geological settings are mainly related to variations in the structure of the rocks, while variations in composition have only a minor effect on the
in situ
physical properties. In volcanic rocks, variations in fracturing and vesicularity related to cooling of the lava strongly influence log responses. Mafic rocks from continental drill-holes were enriched in radioactive elements during regional metamorphism, resulting in higher values in the total gamma-ray compared to the oceanic rocks.
Investigating glacier-permafrost relationships in high-mountain areas: historical background, selected examples and research needs
Authors: Haeberli Wilfried
Published: April 2008

Investigations on the relationships and interactions between glaciers and permafrost in high-mountain regions have long been neglected. As a consequence, numerous fascinating questions remain open and offer possibilities for highly relevant, innovative and integrative research concerning materials, processes, landforms, environmental aspects and natural hazards. The historical background to this situation is first reviewed, examples are given of some key unanswered questions and two case studies are presented to illustrate the importance of considering the combined effects of glaciers and permafrost, particularly in the context of hazard assessments in high mountains.
Glacier-rock glacier relationships as climatic indicators during the late Quaternary in the Cordillera Ampato, Western Cordillera of southern Peru
Authors: Dornbusch Uwe
Published: April 2008

Mapping of glacial and periglacial features along a 15 km long, north-south trending ridge at the eastern end of the Cordillera Ampato (Fig. 1) has been carried out using aerial photograph interpretation. Over the length of the ridge a distinct change in features from moraines and small rock glaciers in the north to large rock glaciers and a lack of moraines in the south can be observed. It is suggested that this feature change reflects a steep precipitation gradient during the Pleistocene. Comparison with geomorphological mapping — both in the field and from air photographs — in other areas of the Cordillera Ampato and further west shows that this feature change is unique and that its location at the eastern end of the Cordillera is in good agreement with present-day precipitation distribution. This indicates that the general precipitation pattern, and thus the general circulation pattern, during the Pleistocene was very similar to that today.
Kinematics of syneclogite deformation in the Bergen Arcs, Norway: implications for exhumation mechanisms
Authors: Raimbourg Hugues , Jolivet Laurent , Labrousse Loïc , Leroy Yves , Avigad Dov
Published: April 2008

The northwestern part of Holsnøy island, in the Bergen Arcs, Norway, consists of a granulite-facies protolith partially transformed at depth in eclogite (700 °C, > 19 kbars) and amphibolite (650 °C, 8–10 kbars) facies during the Caledonian orogenesis. Eclogitized zones are mainly planar objects (fractures with parallel reaction bands and cm-to-100 m-scale shear zones). Eclogitic zones are distributed in two sets of orientations and the associated deformation can be described as ‘bookshelf tectonics’. The major shear zones strike around N120 and dip to the North, and show consistent top-to-the-NE shear sense throughout the area.

In the large-scale kinematic frame of Caledonian NW-dipping slab, eclogitic shear zones are interpreted as the way to detach crustal units from the subducting slab and to prevent their further sinking. As the retrograde amphibolitic deformation pattern is similar to the eclogitic one, the detached crustal units started their way up along these eclogitic shear zones. Radiometric ages of eclogitic and amphibolitic metamorphism and their comparison with the chronology of Caledonian orogenesis show that the deformation recorded on Holsnøy occurred in a convergent context. The mechanism we propose can thus account for the first steps of exhumation during collision.
Decoupling and its relation to strain partitioning in continental lithosphere: insight from the Periadriatic fault system (European Alps)
Authors: Handy M. R. , Babist J. , Wagner R. , Rosenberg C. , Konrad M.
Published: April 2008

The Periadriatic fault system (PFS) is an array of late orogenic faults (35-15 Ma) in the retro-wedge of the Alpine orogen that accommodated dextral transpression during oblique indentation by the southern Alpine crust. Decoupling along the leading edges of the southern Alpine indenter occurred where inherited lithological and rheological contrasts were accentuated by lateral thermal gradients during emplacement of the warm orogenic retro-wedge next to the cold indenter. In contrast, decoupling within the core and retro-wedge of the orogen occurred in a network of folds and mylonitic faults. In the Eastern Alps, this network comprises conjugate sets of upright, constrictional folds, strike-slip faults and low-angle normal faults that accommodated nearly coaxial NNE-SSW shortening and E-W extensional exhumation of the Tauern thermal dome. The dextral shear component of oblique convergence was taken up by a discrete, brittle fault parallel to the indenter surface. In the Central and Western Alps, a steep mylonitic backthrust, upright folds, and low-angle normal faults effected transpressional exhumation of the Lepontine thermal dome. Mylonitic thrusting and dextral strike-slip shearing along the steep indenter surface are transitional along strike to low-angle normal faults that accommodated extension at the western termination of the PFS. The areal distribution of poles to mylonitic foliation and stretching lineation of these networked structures is related to the local shape and orientation of the southern Alpine indenter surface, supporting the interpretation of this surface as the macroscopic shearing plane for all mylonitic segments of the PFS. We propose that mylonitic faults nucleate as viscous instabilities induced by cooling, or more often, by folding and progressive rotation of pre-existing foliations into orientations that are optimal for simple shearing parallel to the eigenvectors of flow. The mechanical anisotropy of the viscous continental crust makes it a preferred site of decoupling and weakening. Networking of folds and mylonitic fault zones allow the viscous crust to maintain strain compatibility between the stronger brittle crust and upper mantle, while transmitting plate forces through the lithosphere. Decoupling within the continental lithosphere is therefore governed by the symmetry and kinematics of strain partitioning at, and below, the brittle-to-viscous transition.
Late Quaternary shelf-margin wedges and upper slope progradation in the Gulf of Cadiz margin (SW Iberian Peninsula)
Authors: Lobo F. J. , Dias J. M. A. , Hernández-Molina F. J. , González R. , Fernández-Salas L. M. , Díaz Del Río V.
Published: April 2008

The distribution patterns and internal geometries of recent shelf-margin wedges off the Guadiana River, Gulf of Cadiz margin, were studied in order to discern the effects of varying trends of falling sea-level and lowstand on upper slope progradation. A seismic-sequence stratigraphic analysis was conducted, based on the interpretation of a dense grid of high-resolution seismic profiles.

Five major shelf-margin wedges deposited during late Quaternary sea-level fall and lowstand periods were documented. Most of the studied shelf-margin wedges produce upbuilt-outbuilt upper slopes. The analysis of their internal geometries reveals two distinct types of configuration: the four older shelf-margin wedges are mainly composed of forced regressive deposits developed during stepped sea-level falls. The scarceness of lowstand deposits suggests abrupt sea-level fall to rise transitions; and the most recent shelf-margin wedge shows both forced regressive deposits and low-stand deposits significantly preserved. This architecture probably resulted from the occurrence of a long-lived sea-level lowstand after a prolonged period of gentle sea-level fall.

Two types of shelf-margin wedges have been recognized: wedges with elongate parallel depocentres, laterally constant thickness and uniform seaward shelf-break migration, related to linear source supply and high lateral sediment redistribution during gently falling sea level; and wedges with (multi) lobate depocentres with laterally variable thickness, leading to uneven shelf-break migration during periods of faster sea-level fall, due to delta lobe switching and significant shelf valley incision.
Mass transport complexes and tectonic control on confined basin-floor submarine fans, Middle Eocene, south Spanish Pyrenees
Authors: Pickering Kevin T. , Corregidor Jordi
Published: April 2008

The syn-tectonic deep-marine Ainsa fans (Eocene of the Ainsa basin, Spanish Pyrenees) were confined by lateral thrust ramps and influenced by intra-basinal growth anticlines. Mass transport complexes (MTCs) constitute a major component of the stratigraphy and represent an integral part of the evolution and depositional style of the deep-marine clastics. Using an integrated study of outcrop data from sedimentary logs and mapping, with core data from eight wells and micropalaeontological and palynomorph analyses, we demonstrate the lateral step-wise migration of sandy channelized submarine fans, as a foreland-propagating clastic wedge on a time-scale of hundreds of thousands of years. The deep-marine expression of the inferred tectonic pulses began with the large-scale basin-slope collapse as sediment slides and debris flows that formed much of the seafloor topography for each fan and contributed to their lateral confinement. The uppermost slope and any shelf-edge, including the narrow shelf, then collapsed, redepositing unconsolidated sands and gravels into deep water. This is overlain by an interval of mainly channelized and amalgamated sandy deposits, passing up into several tens of metres of less confined, non-amalgamated, medium- and thin-bedded, finer grained sands and marls. These deposits represent the phase of most active fan growth, initially by erosional channel development, sediment bypass and backfill (in several cycles), giving way to non-channelized, finer grained sandy deposition, interpreted as a response to the flushing out of the coarser clastics from the coastal and near coastal fluvial systems. During this latter stage in active fan growth and when sediment accumulation rates probably remained high, the degraded submarine slope was regraded and healed by finer grained depositional events. The high amount of woody material and the high non-marine palynomorph signal in these sandy deposits suggest direct river input as both turbidity currents and hyperpycnal flows for the silty marls. In the upper few metres, a thinning-and-fining-upward sequence shows a return to background marl deposition, representing fan abandonment. Many sequences are overlain by intraformational sediment slides that attest to the increasing seafloor gradients associated with the regrading and healing stage in slope development. These organized, predictable vertical sedimentary sequences provide a testable generic model for submarine fan development where fan growth is strongly influenced by tectonic processes.