bluuebunny/crossref_metadata_2025_split huggingface dataset:
Are laccolith complexes characteristic of transtensional basin systems? Examples from the Permo-Carboniferous of Central Europe
Authors: Breitkreuz Christoph , Mock Alexander 
Published: April 2008

Abstract
By comparing felsic laccolith complexes prominent in the Late Palaeozoic Ilfeld-, Saar-Nahe-, and Saale basins in Germany, a characteristic pattern related to transtensional tectonics is revealed. In contrast to the central magma feeding systems recognized so far for laccolith complexes, individual units of the Late Palaeozoic Central European complexes apparently were fed synchronously by numerous feeder systems arranged laterally in a systematic pattern.
The Ilfeld Basin is a small strike-slip pull-apart basin in the SE of the Hartz Mountains cogenetic with a neighbouring rhomb horst — the Kyffhäuser. The Ilfeld Basin represents a ‘frozen-in’ early stage of laccolith complex evolution, with small isolated intrusions and domes emplaced within a common level at the intersections of intra-basinal Riedel shears. In the Saar-Nahe basin, numerous medium-sized felsic subvolcanic to subaerial complexes emplaced at a common level have been recognized (Donnersberg-type laccolith complex). The magmatic evolution of the Halle Volcanic Complex in the Saale Basin culminated in the more or less synchronous emplacement of voluminous porphyritic laccoliths within different levels of a thick pile of Late Carboniferous sediments (Halle-type laccolith complex). Laccoliths in the Halle area might consist of several laccoliths typical of the Saar-Nahe Basin according to outcrop pattern and host sediment distribution.

The above-mentioned three post-Variscan Central European basins are characterized by a dextral transtensional tectonic regime, leading to a model for laccolith-complex evolution:

1
Initial lithosphere-wide faulting forms pathways for magma ascent.

2
Supracrustal pull-apart leads to the formation of a transtensional basin.

3
Continued transtension gives way to decompressional melting of the mantle lithosphere, especially if fertilized by previous magmatic activity, as in the Variscan orogen. The mantle melts rise into the lower crust to differentiate, mingle or cause anatexis.

4
The melts homogenize and start crystallizing in a mid- to upper-crustal magma chamber tapped during tectonic episodes.

5

The resulting SiO
2
-rich magmas ascend along major transtensional faults into thick sedimentary basin fill.

The amount of transtension and the amount of melt rising from the lithospheric mantle have a major influence on the type and size of the laccolith complex to be formed. Additionally, the presence of a mid- to upper crustal magma chamber is a prerequisite for the formation of the Donnerberg and Halle type laccolith complexes.
Emplacement textures in Late Palaeozoic andesite sills of the Flechtingen-Roßlau Block, north of Magdeburg (Germany)
Authors: Awdankiewicz Marek , Breitkreuz Christoph , Ehling Bodo-Carlo 
Published: April 2008

Abstract

During Late Palaeozoic times, andesite magmas intruded a 100-m thick sequence of Late Carboniferous lacustrine to alluvial siliciclastic rocks, sandwiched between folded Namurian sediments at the base and a thick, partly welded rhyolitic ignimbrite sheet at the top, in the Flechtingen area. An intrusive complex, comprising of two main sills up to 200 m thick and over 20 km in lateral extent, was formed (the Flechtingen Sill Complex, or the ‘lower andesites’, previously interpreted as lava flows). In the supposed feeder area the andesitic magmas locally pierced the ignimbrite seal, forming isolated pipes and domes (the ‘upper andesites’). Thickness variations of the sills suggest ponding of the andesite magma within former depositional troughs and syn-emplacement deformation of the host sequence with the formation of swells, basins and fault-bounded grabens at the top of the sills. Locally, thin ‘failed’ sills are present. In places, sill margins show domains of flattened and aligned vesicles and planar, sharp contacts to the host sediments. However, in many outcrops and drill cores the sill margins consist of variable andesite breccias and peperties. These fragmental rocks reflect auto- to quench-clastic brecciation of chilled andesite magma (
in situ
breccias and perlite), variable magma-sediment interactions and later breciation by hydrothermal fluids.
High-level volcanic-granodioritic intrusions from Zelezniak Hill (Kaczawa Mountains, Sudetes, SW Poland)
Authors: Machowiak Katarzyna , Muszyński Andrzej , Armstrong Richard 
Published: April 2008

Abstract

New petrological and geochemical data on high level (
c.
2 km
2
) silicic lava domes and laccoliths from the Kaczawa Mountains, Sudetes, SW Poland, are presented. The system comprises a carapace facies of exposed ignimbrites and spherlulitic rhyolites. Recovered core (drilled to 55 m) includes volcanic rocks ranging in composition from andesite to rhyodacite, and a plutonic facies of microgranite and granodiorite. Country rocks (greenschist-facies metavolcanogenic rocks) are contact metamorphosed to hornfels and cut by kersantite veins and a pipe breccia of diatremic origin. New
206
Pb-
238
U zircon mineral ages from the volcanic and granitic rocks yield ages of 315 to 316 Ma, making the Zelezniak Hill complex the oldest magmatic rocks so far dated in Avalonia.
Sill complex geometry and internal architecture: a 3D seismic perspective
Authors: Thomson Ken 
Published: April 2008

Abstract
Seismic volume visualization techniques demonstrate that saucer-shaped sill complexes consist of a series of radiating principal flow units rising from an inner saucer and fed by principal magma tubes. Such flow units contain smaller scale secondary flow units, each being fed by a secondary magma tube branching from the principal magma tube. This pattern is repeated down to scales of approximately 100 m with successively smaller flow units being fed from magma tubes repeatedly branching from higher order tubes. The data demonstrates that each sill complex is independently fed from a centrally located point source, that sills grow by climbing from the centre outwards and that peripheral dyking from the upper surface is a common feature. These features suggest a laccolith emplacement style involving peripheral fracturing and dyking during inner saucer growth and thickening.
Experimental constraints on the mechanics of dyke emplacement in partially molten olivines
Authors: Vinciguerra S. , Xiao X. , Evans B. 
Published: April 2008

Abstract

We investigated the mechanics of basalt dyke emplacement during laboratory deformation experiments at up to 300 MPa confining pressure and temperatures up to 1200 °C. Experiments have been conducted on two-phase samples of a basalt (MORB) dyke and a matrix of 90% San Carlos Olivine plus 10% MORB. No migration of MORB is observed when samples have been hot isostatically pressed. Conversely, significant diffusion of basalt into the matrix is found when a deviatoric stress is applied. Creep (80–160 MPa) and strain-rate experiments (from 3 × 10
−4
to 5 × 10
−5
s
−1
) induced melt propagation up to 50% of the initial dyke length/width ratio. The kinematics of deformation are essentially plastic and show a strong dependence on the load applied and the dyke geometry. Local pressure drops, due to dilatancy, are suspected to have enhanced melt migration.
Early dolomitization and fluid migration through the Lower Carboniferous carbonate platform in the SE Irish Midlands: implications for reservoir attributes
Authors: Nagy Zs. R. , Gregg J. M. , Shelton K. L. , Becker S. P. , Somerville I. D. , Johnson A. W. 
Published: April 2008

Abstract
Shallow-marine, Lower Carboniferous carbonate sequences of the SE Irish Midlands, close to the Leinster Massif, are intensely dolomitized. Fine-crystalline (<50 μm), planar-s (subhedral) dolomite is associated with evidence for evaporites, typical of arid peritidal sequences. However, stable isotope data suggest a diagenetic overprint. Volumetrically more important medium-crystalline (50–200 μm), planar-s and minor planar-e (euhedral) dolomites were precipitated from slightly modified Lower Carboniferous seawater. These dolomites replace open-marine intraclastic and bioclastic packstones and grainstones.

Length-slow, fibrous quartz partially replaces crinoids and fills dissolution cavities beneath peritidal strata. Associated dolomites are gradually enriched in
18
O downward through the underlying strata, suggesting vertical brine migration. The widespread occurrence of skeletal material replaced by chalcedony in open-marine wackestones and grainstones further to the west, within the Rathdowney Trend, suggests evaporite cementation in the Zn-Pb mineralized area.

Base-metal mineralization in the fractured Waulsortian ‘reservoir’ is associated with chloride-enriched brines (beyond that expected from seawater evaporation alone). The presence of evaporites in the Leinster Massif area suggests a possible source of the excess chloride. The dolomitizing brine may have contributed to the overall chemistry of the Zn-Pb mineralizing fluid and also to the distribution of porosity within the carbonate platform. An Arundian or younger age is suggested for the mineralization, based on the timing of evaporite cement emplacement, and this is compatible with numerical fluid-flow models of brine movement through the carbonate platform.
Dolomitization of Lower Carboniferous carbonate rocks of the Irish Midlands is comparable to diagenetic histories of several important dolomite petroleum reservoirs. This study provides an example that may be applied to petroleum exploration in similar geological settings.
Environmental impact of the nuclear fuel cycle
Authors: Ewing Rodney C. 
Published: April 2008

Abstract
Nuclear power provides approximately 17% of the world’s electricity, which is equivalent to a reduction in carbon emissions of ∼0.5 Gt of C/year. This is a modest contribution to the reduction of global carbon emissions, ∼6.5 Gt C/year. Most analyses suggest that in order to have a significant and timely impact on carbon emissions, carbonfree sources, such as nuclear power, would have to expand total energy production by a factor of three to ten by 2050. A three-fold increase in nuclear power capacity would result in a projected reduction in carbon emissions of 1 to 2 Gt C/year, depending on the type of carbon-based energy source that is displaced. This paper reviews the impact of an expansion of this scale on the generation of nuclear waste and fissile material that might be diverted to the production of nuclear weapons. There are three types of nuclear fuel cycles that might be utilized for the increased production of energy: open, closed, or a symbiotic combination of different reactor types (such as thermal and fast neutron reactors). Within each cycle, the volume and composition of the nuclear waste and fissile material depend on the type of nuclear fuel, the amount of burn-up, the extent of radionuclide separation during reprocessing, and the types of material used to immobilize different radionuclides. This chapter is a discussion of the relation between the different types of fuel cycles and their environmental impact.
Cement stabilization of heavy-metal-containing wastes
Authors: Johnson C. Annette 
Published: April 2008

Abstract

Cement has found wide usage in the stabilization of heavy-metal-containing wastes as cement minerals can substantially reduce heavy metal solubility as a result of precipitation, adsorption to the surfaces and incorporation. The solubility of some heavy metal cations is limited by the precipitation of hydroxides, while that of some oxyanions is limited by the formation of Ca salts. Only ions that are sufficiently soluble in basic media will be incorporated in or sorbed to hydrated cement minerals to a significant degree. Heavy metal cations may sorb quite strongly to calcium silicate hydrate (C-S-H). The cations diffuse into the C-S-H particles where they are probably sorbed to the silicate chains. Pure phases of oxyanion-substituted ettringite (3CaO·Al
2
O
3
·3(CaSO
4
)·32H
2
O, an AFt phase) and monosulphate (3CaO·Al
2
O
3
·CaSO
4
·12H
2
O, an AFm phase) phases and solid solutions with SO
4
2
− and OH
−
have been synthesized. Some thermodynamic data are available for the pure phases. For most elements an approximate range of solubility has recently become known. However, it is not possible to predict solubility from the available data.
Interpretation of charging phenomena based on reservoir fluid (PVT) data
Authors: Thompson Keith F. M. 
Published: April 2008

Abstract

Molar concentration profiles of reservoir fluids reveal accumulation history and alteration. Slope Factors (SF) define rates of exponential decrease in concentration of light
n
-alkanes (C
3
-
n
C
5
) and liquid pseudo-components (P
10+
) with increasing carbon number. Most petroleum fluids are substantially characterized by SF(C
3
-
n
C
5
) and SF(P
10+
), the former invariably being the greater. Specific paired values of SF(C
3
-
n
C
5
) and SF(P
10+
) are process-diagnostic. In oils, maturation, gas injection, evaporative fractionation and migration depletion involving loss of gas, are recognizable. SF data are interpreted in the light of PVT analyses representing oils (principally from western Canada) and gas-condensates (from numerous basins), also asphaltene pyrolysis experiments and equation of state calculations. Covariant increase of SF(C
3
-
n
C
5
) and SF(P
10+
) during maturation is demonstrated, but correlation is frequently destroyed by modification of the light ends by the admixture of allochthonous gas, increasing only SF(C
3
-
n
C
5
). Secondary gas-enrichment is a requisite process for the generation of gas-condensates by evaporative fractionation. Compositional criteria for the recognition of enrichment are provided for the first time, particularly attainment of a value of SF(C
3
-
n
C
5
) exceeding 1.69 (a tentative limit). Available data indicate that the process has occurred in a large proportion of oil accumulations, ranging from 23% of 30 reservoirs in the Jurassic Smackover Formation in Alabama, to 78% of 36 in the northern North Sea.
An overview of developments related to the characterization and significance of high molecular weight paraffins/hydrocarbons (>C
40
) in crude oils
Authors: Philp R. Paul , Hsieh Michael , Tahira Fazeelat 
Published: April 2008

Abstract

Over the past 10 years, investigations into the characteristics of the high molecular weight hydrocarbon (HMWHC) fraction in crude oils and, to a lesser extent, source rock extracts have continued to reveal novel information concerning the distribution of hydrocarbons >C
40
. The major impetus for this work has come from the fact that HMWHCs can cause significant production problems in certain geographical regions and particularly deepwater frontier areas. Since these HMWHCs appear to be ubiquitous in crude oils, the primary questions that need to be addressed are: what are these compounds, where do they come from, and how do they affect physical properties of oils? Here, we review our work over the past decade and discuss the significance of these results and their potential application to reservoir and production problems involving paraffins and asphaltenes.

It was commonly believed for many years that only oils derived from source rocks containing higher plant source material would have a high paraffin content. However, it is now abundantly clear that oils derived from lacustrine and marine source rocks also contain relatively high concentrations of higher molecular weight hydrocarbons. In addition to developing methods for the qualitative and quantitative separation of HMWHCs from asphaltenes, progress has been made in identifying individual components of the high molecular weight fraction. This fraction is not a simple mixture of
n
-alkanes but a complex mixture of seven or eight homologous hydrocarbon series, each with significantly different physical properties. A knowledge of these structures is important in predicting crude oil properties such as cloud point and pour point. Series identified to date include alkylcyclopentanes, alkylcyclohexanes, alkylbenzenes and various branched hydrocarbons.

In summary, since the 1970s most of the geochemical research emphasis has been placed on compounds below C
40
. Whilst compounds above C
40
may not have the same degree of structural specificity as the traditional biomarkers, the amount of information available from these compounds could be extremely beneficial in the long term, particularly for reservoir characterization and production purposes and other problems involving high molecular weight hydrocarbons.
Application of geochemistry in the evaluation and development of deep Rotliegend dry gas reservoirs, NW Germany
Authors: Mueller Eric , Scholz Torsten 
Published: April 2008

Abstract
The Voelkersen field in northwestern Germany produces thermogenic dry gas from Permian Rotliegend sandstone reservoirs located at depths greater than 4700 m. In addition to this considerable depth Zechstein salt overburden plus the structural complexity and heterogeneity of the reservoirs limit the applicability of conventional methods for definition and characterization of field compartmentalization. The Rotliegend gas is sourced from Westphalian coals of semi-anthracite to anthracite rank with conventional geochemical data suggesting little variation in composition on a field-wide scale. However, detailed analysis of associated condensates and wet-gas hydrocarbons shows considerable differences between compartments and producing horizons, despite the apparent high maturity of the gas. These differences support compartment definition and identification of lateral and horizontal seals. Assuming a quasi-uniform gas composition in communicating reservoirs, variation of carbon and hydrogen isotopic data in particular confirms separation of marginal fault blocks. Additionally, these data also suggest reservoir continuity within a large field compartment and over parts of a major fault system for which the sealing properties so far were previously uncertain.
Evidence of reservoir compartmentalization by calcite cement layers in deepwater sandstones, Bell Canyon Formation, Delaware Basin, Texas
Authors: Dutton Shirley P. , Flanders William A. 
Published: April 2008

Abstract

Sandstones of the Upper Permian Bell Canyon Formation were deposited by turbidity currents in a basin-floor setting. The sandstones were deposited in a channel-levee system that terminated in broad lobes; overbank splays filled topographically low inter-channel areas. Diagenesis and reservoir quality of the sandstones were examined in cores from East Ford field, which is undergoing a CO
2
flood. Porosity and permeability are controlled by calcite cement, mainly concentrated in layers ranging from 5 to 40 cm in thickness. In a new infill well, initial production was of a high gas volume that contained a high concentration of CO
2
from the interval beneath several low-permeability, calcite-cemented layers. The CO
2
was most likely from an injector well and was trapped below the calcite layers. Geophysical log correlations support the interpretation that some calcite layers are laterally continuous over a distance of at least 300 m, causing vertical compartmentalization in the reservoir.
Spatial variations in the composition of formation waters from the central North Sea: implications for fluid flow in the deep high-pressure high-temperature hydrocarbon play
Authors: McCartney R. A. , Winefield P. , Webb P. , Kuhn O. 
Published: April 2008

Abstract

Formation water composition data and formation pressure data from oil, gas and gas condensate fields covering an area of approximately 15000 km
2
in the Central Graben Area of the UK North Sea have been analysed. The purpose was to determine whether large-scale barriers to flow influence the compositional distribution of formation waters and how this aids understanding of overpressure distribution and potential hydrocarbon migration pathways. Analyses (Na, K, Mg, Ca, Sr, Ba and Cl) of water and Elemental Residual Salt Analysis (ERSA) samples from both the water and hydrocarbon legs of wells were analysed statistically to reveal eight different water types in the study area. These were located in distinct geographical areas. Aquifer overpressure from formation pressure data for numerous wells in the area were plotted on large-scale regional maps to reveal the distribution of pressure ‘cell’ or compartments. An integrated interpretation of the location of pressure cells, salinity variations and water types provided information on the current and past fluid flow across the pressure cell boundaries, the operational longevity of these boundaries and the nature of the Mesozoic aquifer. The implications of the work are important for understanding: (a) the usefulness of the new ERSA technique for estimating formation water compositions; (b) the effectiveness of integrating fluid composition and pressure data to understand compartmentalization; (c) fluid flow dynamics in the HPHT sector of the Central North Sea; and (d) likely hydrocarbon migration routes and the character and distribution of overpressured basin compartments.
A mass balance approach for assessing basin-centred gas prospects: integrating reservoir engineering, geochemistry and petrophysics
Authors: Rushing J. A. , Chaouche A. , Newsham K. E. 
Published: April 2008

Abstract
This paper presents a mass balance technique for evaluating the resource-in-place potential of basin-centred gas exploration prospects. As the name implies, the methodology is derived from the conservation of mass principle. Unlike conventional reservoir engineering techniques, the mass balance approach directly integrates dynamic elements of the total petroleum system with all static reservoir engineering, geological and petrophysical data to estimate the resource-in-place. This prospect evaluation technique not only provides an independent estimate of hydrocarbon resource-in-place for comparison with that computed from the conventional reservoir engineering approach, but also gives estimates of hydrocarbons lost from the petroleum system. Accordingly, this technique reduces the inherent uncertainty associated with conventional methods and provides more realistic estimates of resource-in-place.
Anisotropy of magnetic susceptibility of rocks measured in variable weak magnetic fields using the KLY-4S Kappabridge
Authors: Pokorný Jiří , Suza Petr , Hrouda František 
Published: April 2008

Abstract
The theory of the anisotropy of magnetic susceptibility assumes a linear relationship between magnetization and magnetizing field, resulting in field-independent susceptibility. This relationship is valid in diamagnetic and paramagnetic minerals by definition, and also in magnetite in the fields used in common AMS meters. Pyrrhotite, hematite and titanomagnetite may show field variation of susceptibility in the same fields and therefore in principle the linear theory is incorrect for calculating the AMS. Fortunately, the linear theory nevertheless provides accurate determination of the orientations of the principal susceptibilities and of the AMS ellipsoid shape. It gives rise to inaccurate determination of the degree of AMS. Simple techniques are suggested to overcome this problem.