bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrothermal activity and segmentation in the Magnitogorsk-West Mugodjarian zone on the margins of the Urals palaeo-ocean
Authors: Zaykov V. V. , Maslennikov V. V. , Zaykova E. V. , Herrington R. J.
Published: April 2008

The Magnitogorsk-West Mugodjarian zone is interpreted to have developed as a marginal rift to the main Urals palaeo-ocean. In this zone, seven distinct tectonic segments each with a strike extent between 140 and 220 km have been identified. These segments can be distinguished on the basis of volcanic facies and features of hydrothermal activity. In the three southernmost segments the volcanics comprise basaltic and rhyolite-basalt complexes. The former contain massive sulphides of Cyprus-type and cherty iron-formation whilst the latter contain massive sulphides of ‘Uralian’ type, cherty iron-formation and manganese oxide deposits. In the two central segments rhyolite-basalt complexes are developed associated with giant massive sulphide deposits (Sibay > 100 million tonnes massive sulphides). In the two northernmost segments rhyolite-basalt and andesite-basalt complexes are developed, both associated with cherty iron-formation and manganese oxide deposits. It is proposed that the variations in frequency, size and composition of the metalliferous deposits between the segments are a result of differences in the sequence of Palaeozoic oceanic development. Rifting started during the Eifelian in the south (current position) and in Late Givetian times in the north. This diachronous rifting and tectonic development has influenced the major geological features of the segments.
The hydrothermal imprint on life: did heat-shock proteins, metalloproteins and photosynthesis begin around hydrothermal vents?
Authors: Nisbet E. G. , Fowler C. M. R.
Published: April 2008

Molecular evidence implies that the first living community existed around a hydrothermal system. From this setting, life may have colonized a wide variety of hydrothermal environments. These would have included hydrothermal systems on mid-ocean ridges, around komatiite plume volcanoes, and in a variety of shallow-water settings. Hydrothermal systems on ridge segments may have been crucial in providing habitats to sustain the first communities of life.

The early hydrothermal heritage may now be deeply imprinted in all organic life. Biological processes that use essential metals, especially Fe (typically as 4Fe-4S), Mn, Zn, Cu, Mo, Mg, Se and Ni, may all have hydrothermal descent from reactions that first evolved on a natural hydrothermal metal sulphide substrate, and it is possible that the first supply of P, when life began, was also associated with volcanism. The heat-shock proteins and many important ‘housekeeping’ enzymes of the biosphere, such as urease, hydrogenase, and nitrogenase may all be of hydrothermal origin. Photosynthesis may have originated via infrared phototaxis developed at mid-ocean ridge hydrothermal systems. The modern biosphere may have grown out of bacterial processes originally evolved at mid-ocean ridges.
The thermodynamics of Himalayan orogenesis
Authors: Hodges K. V.
Published: April 2008

Geological and geochemical research in the internal zone of the Himalayan orogen reveal evidence for complex relationships between regional metamorphism, anatexis, thrust faulting and normal faulting in Miocene time. Such interactions share many characteristics with those that define the behaviour of non-equilibrium thermodynamic systems, like chemical oscillators. The internal ordering of such systems arises spontaneously and is maintained by continual exchange of energy with the outside world. Mountain ranges are open thermodynamic systems, equally capable of displaying self-organized behaviour. They accumulate energy through a variety of mechanisms, particularly crustal thickening, but their non-equilibrium structure is maintained through compensating mechanisms of energy dissipation. The simultaneous operation of normal faults and thrust faults in the Himalayan system, ejecting a wedge of middle crust southward from the orogen towards the Indian foreland, was a remarkably efficient method of mass (and therefore energy) dissipation in Miocene time. Research in many branches of science suggests that thermodynamic systems forced far from equilibrium by their boundary conditions may evolve towards establishing the most efficient possible mechanisms for counteracting those conditions. For the Himalaya, one possible explanation for development of a process set characterized by simultaneous normal faulting and thrust faulting, linked through metamorphism and anatexis, is that simple physical erosion alone was inadequate to moderate the extraordinary crustal thickness and topographic gradients that characterized the southern flank of the range in Miocene time. The orogenic system may have adapted to this condition through a new and more efficient mechanism of energy dissipation that required the coordination of a variety of thermal and deformational processes.
Low- to medium-pressure Variscan metamorphism in Galicia (NW Spain): evolution of a kyanite-bearing synform and associated bounding antiformal domains
Authors: Reche J. , Martínez F. J. , Arboleya M. L.
Published: April 2008

Evidence for different substitution relationships between aluminosilicates in two domains east of the Ollo de Sapo gneiss antiform in Galicia (NW Spain) suggests a high dependence of metamorphic evolution on the local tectonic and granitoid intrusion history. The Vivero pelite belt constitutes a pinched synformal domain located between the Ollo de Sapo antiform to the west and the Lugo dome to the east. Within this synform, black, Alrich Silurian pelites contain kyanite that, along with muscovite, formed pseudomorphically after early pre-D
2
andalusite. Syn-D
2
inversion of andalusite to kyanite indicates an evolution from early, low-
P
to medium-
P
regimes. Locally, near the Vivero transtensional fault, which constitutes the E boundary of the synform new, late post-D
2
pleochroic andalusite grew from staurolite and biotite indicating reinstallment of a new low-
P
regime during and after the D
3
deformation phase, which is related to movement along the fault zone. The Ollo de Sapo domain contains only a high
T
-low
P
series of metamorphic assemblages. The peak assemblage within this domain was cordierite-biotite-K-feldspar-andalusite/fibrolite related to emplacement of a pre- to syn-D
2
swarm of sheet-like peraluminous granitoids located mainly in the core of the antiform. Early pre- to syn-D
2
staurolite-biotite ± garnet, and late sillimanite-staurolite-biotite assemblages present on the west side of the Lugo dome testify to an early stage of nearly isothermal decompression followed by decompression with local heating. Stabilization of late andalusite in the Vivero pelite belt and of sillimanite west of the Lugo dome appear almost synchronous and clearly related to a syn-D
3
thermal peak induced by Upper Carboniferous granitoid intrusion along the Vivero transtensional fault separating both domains.
Low-pressure crustal anatexis: the significance of spinel and cordierite from metapelitic assemblages at Nanga Parbat, northern Parkistan
Authors: Whittington Alan , Harris Nigel , Baker Judy
Published: April 2008

Spinel-bearing domains in high-grade metapelitic rocks from Nanga Parbat represent zones of partial melting during biotite breakdown under vapour-undersaturated conditions. Spinel is essentially of the MgAl
2
O
4
-FeAl
2
O
4
solid solution, and is therefore not stabilized by the presence of trace elements such as zinc, but is restricted to a quartz-absent petrogenesis. A new petrogenetic grid for metapelites has been constructed to allow for both vapour-undersaturated and quartz-undersaturated conditions. This grid contains a quartz-absent invariant point in KFASH that predicts quartz-absent melting will occur in biotite-sillimanite assemblages at low pressures.

A
P–T
pseudosection drawn for bulk compositions with intermediate Fe/Mg ratios shows that at low pressures biotite will break down initially in the presence of quartz, to produce cordierite and K-feldspar and melt. At higher temperatures the quartz-absent reaction will be crossed, and biotite will break down to produce spinel in addition to cordierite, K-feldspar and melt. The sequence of assemblages is biotite-cordierite, biotite-cordierite-spinel, and finally cordierite-spinel. This biotite-absent assemblage is not observed, indicating that the quartz-absent reaction did not go to completion. Limits can be placed on the pressures and temperatures at which the biotite breakdown reaction is crossed, from the coexistence of solid phases and granite melt over a range of water activities. For the Nanga Parbat assemblages, pressures and temperatures lay at about 720°C and 5 kbar at water activity, a

H
2
O

≥ 0.6. These conditions are consistent with a rapidly exhuming terrane, as suggested by isotopic constraints and thermal modelling of the region.
Vesiculation processes in silicic magmas
Authors: Navon Oded , Lyakhovsky Vladimir
Published: April 2008

The physics of vesiculation, i.e. the process of bubble formation and evolution, controls the manner of volcanic eruptions. Vesiculation may lead to extreme rates of magma expansion and to explosive eruptions or, at the other extreme, to low rates and calm effusion of lava domes and flows. In this paper, we discuss the theory of the different stages of vesiculation and examine the results of relevant experimental studies. The following stages are discussed: (1) The development of supersaturation of volatiles in melts. Supersaturation may develop due to a decrease in equilibrium solubility following changes in ambient pressure or temperature or due to an increase in the magma volatile content (e.g. in response to crystallization of water-free or waterpoor mineral assemblages). (2) Bubble nucleation. The classical theory of homogeneous nucleation and some modern modifications, heterogeneous nucleation with emphasis on the nucleation of water bubbles in rhyolitic melts and the role of specific crystals as heterogeneous sites. (3) Bubble growth. The effect of diffusion, viscosity, surface tension, ambient pressure and inter-bubble separation on the dynamics of growth. (4) Bubble coalescence. The theory of coalescence of static foams. factors that may effect coalescence in expanding foams and shape relaxation following bubble coalescence.
Observations and models of volcanic eruption columns
Authors: Woods Andrew W.
Published: April 2008

Direct observations, satellite imagery and field studies of air-fall deposits provide a wealth of information about eruption column dynamics. These data have stimulated a wide range of theoretical, experimental and numerical models of eruption columns to expose the fundamental physical controls. These models show that the motion of hot, turbulent, particle-laden eruption columns is sensitive to the eruption velocity and mass flux, as well as the temperature and grain size distribution of the erupting material. In turn, the eruption velocity and mass flux are sensitive to the magma volatile content, the conduit radius and the chamber pressure. The importance of magma-water interactions, the crater geometry, ambient winds and the atmospheric stratification on the motion of the erupted material are also discussed. Predictions of the models are compared and contrasted and possible avenues for future research are suggested.
Pyroclastic density currents
Authors: Druitt T. H.
Published: April 2008

High-speed, gravity-driven flows of hot particles and gas are a common and highly destructive product of explosive volcanism. They range widely in nature from expanded, turbulent suspension currents formed by lateral blasts or by the fountaining of vertical eruption columns, to highly concentrated granular avalanches formed by lava dome col-lapse or as dense underflows beneath suspension currents. The deposits from these flows, here called pyroclastic density currents, range in volume from much less than 1 km
3
to thousands of cubic kilometres, and may extend over 100 km from their source. This chapter reviews the eruption, transport and deposition of pyroclastic density currents from both geological and physical perspectives, focussing on some recent advances.
The great age of some Australian landforms: examples of, and possible explanations for, landscape longevity
Authors: Twidale C. R.
Published: April 2008

According to the major conventional models of landscape evolution there ought to be no land surfaces older than Oligocene, save some that have been exhumed. In reality, substantial areas of the Australian continent (as well as other parts of Gondwana and of Laurasia) are of Mesozoic or greater ages. Surfaces of Late Jurassic or Early Cretaceous ages are especially widespread. Many are of exhumed origin, but several notable features are of epigene-etch type. Their age ranges have been determined stratigraphically. In some instances (e.g. Gawler Ranges, Hamersley Surface, Eastern Uplands), the stratigraphic evidence is incontrovertible. Elsewhere the position and elevation of massifs, such as Arnhem Land, relative to Cretaceous shorelines demonstrate their essential antiquity. The survival of such very old palaeosurfaces is attributed to several factors, but particularly to unequal erosion, reinforcement mechanisms and the prevalence of vertical (epeirogenic or isostatic), rather than orogenic, earth movements.
Tertiary etchsurfaces in the Sudetes Mountains, SW Poland: a contribution to the pre-Quaternary morphology of Central Europe
Authors: Migoń Piotr
Published: April 2008

This paper presents the evidence of the major part played by deep weathering accompanied, or followed, by stripping of a weathering mantle in the formation of Tertiary surfaces in the Sudetes. It also highlights the complicated nature of the topography of surfaces developed upon differentiated bedrock over protracted time-scales. The evidence is gained from the available data about weathering mantles and Tertiary sediments, and from the analysis of pre-Quaternary landforms such as rolling plains, scarps and inselbergs. A classification of the Tertiary surfaces, recognized here as etchsurfaces, is proposed for the Sudetes. The palaeosurfaces in the Sudetes are regarded as a part of an extensive etch surface which dominated the Tertiary landscape of Central and Northern Europe.
The geochemistry and development of lateritized footslope benches: The Kasewe Hills, Sierra Leone
Authors: Bowden D. J.
Published: April 2008

A series of lateritized footslope benches are observed on the isolated hill masses which rise to 500 m above the interior plain of Sierra Leone. Field observations and chemical analyses of samples indicate that each bench has a characteristic geochemistry controlled by its own topography, hydrological environment and leaching history. The benches are related, each inheriting material from above and providing material for the bench below. The material is transported both mechanically and in solution. As a result, the parent material of each bench is not only the bedrock (metamorphosed volcanic and sedimentary rocks of Proterozoic age in the case of the Kasewe Hills), but also material which has undergone various degrees of lateritization. This cratonic region has been subjected to denudational processes since Mesozoic times at least. Denudational processes, especially etchplanation, are long continued, yet weathering, the development of breakaway slopes and subterranean flushing are patently continuing processes: these palaeosurfaces and palaeosoils may, therefore, be ancient in origin but they cannot be considered as being fossilized.
Rheology of planetary lithospheres: a review from impact cratering mechanics
Authors: Thomas P. G. , Allemand P. , Mangold N.
Published: April 2008

Impact craters are the only universal drills to probe planetary lithospheres. The relationship of the lithospheric thickness/crater diameter ratio and the morphology of the outer parts of the crater are controlled by the rheology of the target. These relationships indicate the following: (1) The lithosphere is thicker on silicated bodies than on icy bodies of the same size. (2) The lithosphere is thicker on small planetary bodies than on larger ones. (3) There is a secular lithospheric thickening and a planetary cooling for silicated and icy bodies. (4) Because of the thickness and the continuity of the lithosphere of one-plate planets, local mechanical disturbances may be transmitted over a long distance and may affect the entire planet. (5) Thermal properties of the lithospheres of satellites are incompatible with the chondritic abundance of radioactive nucleids. This indicates that the origin of satellites is more complex than the accretion-collision of chondritic/icy planetesimal swarms. (6) There is no direct relation between plate tectonics and lithospheric thickness. Some planets have (or have had) the same lithospheric thickness as the Earth, but have not developed plate tectonics. This indicates that plate tectonic development is controlled by parameters other than lithospheric thickness.
Tectonics of the southeastern Australian Lachlan Fold Belt: structural and thermal aspects
Authors: Gray David R.
Published: April 2008

The Lachlan Fold Belt of southeastern Australia is a 700 km wide belt of deformed, Palaeozoic deep and shallow marine sedimentary rocks, cherts, and mafic volcanic rocks. Characterized by large areas of chevron-folded turbidite sequences, linked contractional and strike-slip faults, and superposed thrust-belts of different age and vergence, it has large volumes of granite and low pressure/high temperature metamorphic rocks. Surface structural elements suggest that it formed by massive telescoping and strike-slip translation within a continental margin sediment prism along the former margin of Gondwanaland during the mid-Palaeozoic. Migrating, sporadic compressional and extensional events over the 100 Ma deformational history of the belt produced a crustally thickened, high geothermal gradient orogen, involving non-craton directed thrusting in an inferred convergent margin setting. Compressional periods were marked by eastward-migrating deformation zones involving detachment-related folding and reverse faulting in the largely turbidite dominated sequences. High-grade metamorphic rocks are not part of a metamorphic hinterland, but are largely confined to a shear zone-bounded crustal wedge in the central part of the fold-belt. Extension was marked by localized development of rift basins and half grabens accompanied by extensive granitic magmatism and silicic volcanism. Subsequent basin collapse was by reactivation/inversion of the extensional faults and folding of the basinal sequence. Magmatic activity and high temperature/low pressure metamorphism are linked to a convergent margin setting over much of the Middle Palaeozoic, but with major convergence in the Silurian.
The Scandinavian Caledonides and their relationship to the Variscan belt
Authors: Rey P. , Burg J.-P. , Casey M.
Published: April 2008

The main events that mark the contraction and extension histories of the Scandinavian Caledonides and the European Variscides are summarized. It is shown that continental subduction may have developed similarly large and asymmetric thrust systems in both orogens. However, while continent-continent collision developed in the Variscides, extension began in the Scandinavian Caledonides marking the end of continental subduction. This led extensional tectonics to affect two continental crusts with contrasting rheology and therefore led to contrasting extensional modes. We argue that plate divergence, responsible for extension in the Scandinavian Caledonides, was triggered by the Variscan collision between Laurasia and Gondwana. In contrast, horizontal buoyancy forces acting on a thermally softened thickened crust are more likely to have been responsible for extension in the Variscan belt.
Cenozoic evolution of the Central Andes in Bolivia and northern Chile
Authors: Lamb Simon , Hoke Leonore , Kennan Lorcan , Dewey John
Published: April 2008

The Central Andes in Bolivia and northern Chile form part of a wide and obliquely convergent plate-boundary zone where the oceanic Nazca plate is being subducted beneath the continental South American plate. In the latest Cretaceous and Palaeocene, this part of the Central Andes formed a volcanic arc along what is today the forearc region of northern Chile, with a wide zone of subsidence, as much as 400 km wide, at or close to sea level behind the arc. In the Eocene, the central part of the behind-arc basin was inverted to form a zone of uplift (proto-cordillera), about 100 km wide and along what is today the western margin of the Eastern Cordillera of Bolivia. The Altiplano basin and an early foreland basin were initiated at this time, receiving sediment from the Eocene proto-cordillera. Subsequently, the proto-cordillera widened, as the rate of deformation increased and deformation spread westwards into the early Altiplano basin, and also eastwards towards the Brazilian Shield. In the Late Miocene, deformation essentially ceased in the Altiplano and Eastern Cordillera. An intense zone of shortening was initiated in what is today the Subandean Zone on the eastern margin of the Central Andes, deforming the Oligo-Miocene foreland basin. Shortening in the Subandean Zone accommodated both underthrusting of the Brazilian Shield and also bending of the entire mountain belt about a vertical axis. It is suggested that much of the distinctive Cenozoic tectonic evolution of this part of the Andes is related to pre-Andean strength inhomogeneities in the South American lithosphere.
Recent advances in understanding the southern North Sea Basin: a summary
Authors: Glennie K. W.
Published: April 2008

After a short-lived but very successful phase of exploration in the UK North Sea, the need for extreme confidentiality ceased to exist for those fields that had already been discovered, including the gas fields of the southern North Sea; this led to a widespread dissemination of data from 1974 onwards, to the great benefit of the industry as a whole. Early difficulties in producing gas from reservoirs whose permeability had been reduced by the growth of diagenetic illite led to studies in depth- and facies-related diagenesis, which continues today in different parts of the Southern Permian Basin. A change from analogue to digital recording of seismic data coincided with improvements in computer technology, and transformed seismic from a tool with limited depth penetration, which required the skill of a dedicated specialist to interpret, to one that today is used universally by all exploration and production geologists; these advances led, in turn, to much improved stratigraphic and structural resolution.

Recent studies, especially in the former East Germany, have led to a better definition of the Permian. In Central Germany, Lower Rotliegend volcanics are overlain by sedimentary sequences of the Müritz sub-group (Upper Rotliegend 1), which are coeval coveal part of the combined Altmark and Saalian Unconformity. In northern Germany, this major hiatus is overlain by the Havel and Elbe subgroups (Upper Rotliegend 2) which, together with the succeeding Zechstein sequences, were all deposited within the youngest stages of the Permian, covering a probable time span of no more than 16 Ma. Deposition of up to 4000 m or so of Late Permian strata in such a short time indicates structurally controlled subsidence in addition to any of a thermal nature.
Permian (Upper Rotliegend) synsedimentary tectonics, basin development and palaeogeography of the southern North Sea
Authors: George Gareth T. , Berry Jeremy K.
Published: April 2008

Upper Rotliegend sedimentation in the southern North Sea Basin (SNSB) was a response to complex synsedimentary tectonics and cyclical climatic changes. During the early Upper Rotliegend, faulting (?dextral strike-slip) resulted in the formation of a number of isolated sub-basins e.g. the Sole Pit, Silverpit and the Broad Fourteens, which were gradually united as a consequence of the progressive collapse of the Inde-Cleaver Bank High. Basin-margin tectonics controlled the evolution of the basin and the nature and distribution of the various types of alluvial fan and fan delta systems that evolved during pluvial climatic phases. Many of the earlier Upper Rotliegend fans display a systematic lateral displacement along synsedimentary faults. Along the Dowsing Fault Zone, ‘dry-type’ alluvial fans display a progressive northwestward migration with time. Also, fan deltas, sourced from the Texel-Ijsselmeer High, young progressively to the SE along the trend of the main faults. These systematic lateral displacements have been tentatively explained by invoking dextral oblique transfer of the source area relative to the depositional basin, within the context of a strike-slip tectono-sedimentary model. Alternatively, in an extensional model, the distribution pattern could be explained by sourcing the fans from both the footwall scarps and the transfer zones of dip-slip faults. A rapid decline in synsedimentary faulting, and a gradual change to more pluvial climatic conditions, resulted in the development of larger ‘wet type’ fans during the later part of the Upper Rotliegend time interval.
Application of high-frequency cycle analysis in high-resolution sequence stratigraphy
Authors: Yang C. S. , Baumfalk Y. A.
Published: April 2008

High-resolution sequence stratigraphy analysis is based on the integration of third-order sequence analysis and high-frequency (Milankovitch) cyclicity analysis. Sliding window spectral analysis of wireline logs reveals wavelength changes of the high-frequency cycles along the bore hole. The abrupt wavelength change, shown as the break of the sliding window spectrum bands, indicates a stratigraphic discontinuity. The gradual wavelength change, detected by the gradual shift of the spectrum bands, reflects a gradual change in the rate of net sediment accumulation. These cyclicity patterns reflect the thickness variations of preserved depositional cycles, controlled by basin subsidence, eustatic sea-level/base-level fluctuations, and sediment supply. Observations from the subsurface of the southern North Sea indicate that the breaks of spectrum bands as well as the trend of spectrum band shift can be correlated between wells to help detailed sequence correlation. Cyclicity analysis of the synthetic logs generated from a two-dimensional sequence stratigraphic modelling confirms the lateral correlatability of the cyclicity pattern between wells. Integration of cyclicity analysis with traditional methods will help accurate and reliable sequence stratigraphic correlations in various settings, including biostratigraphically barren strata, thick intervals of fine-grained or coarse-grained sediments, and chalk sections. Such correlations are essential for the establishment of a proper geological model in the hydrocarbon exploration, development and production.
The East Irish Sea Basin — from caterpillar to butterfly, a thirty-year metamorphosis
Authors: Colter V. S.
Published: April 2008

In the thirty years since the award of the first licenses, the East Irish Sea Basin has emerged as a significant hydrocarbon province. This paper first lists some of the occasionally almost arbitrary events that led to the first success in the basin, the discovery of the Morecambe Field in 1974. An attempt is made to review progress over those thirty years in certain topics, namely (1) stratigraphy, (2) structure, (3) sedimentology, (4) diagenesis — ‘the Platy Illite problem’ and others, (5) uplift and inversion, (6) hydrocarbon sources and types, (7) East Irish Sea Basin analogues. The paper concludes by summarizing the current state of knowledge.
Stratigraphical relationships and a revised lithostratigraphical nomenclature for the Carboniferous, Permian and Triassic rocks of the offshore East Irish Sea Basin
Authors: Jackson D. I. , Johnson H. , Smith N. J. P.
Published: April 2008

The Lower Permian and Triassic successions of the offshore East Irish Sea Basin are probably the thickest of the United Kingdom Continental Shelf or UK mainland, but currently, no hierarchical lithostratigraphy exists for this offshore area. A summary is presented of the first comprehensive hierarchical lithostratigraphical nomenclature scheme to be established for the Carboniferous, Permian and Triassic rock successions of the offshore East Irish Sea Basin. This scheme, which has been sponsored by interested exploration companies, identifies 25 formal lithostratigraphical divisions following the methodology already established in BGS-UKOOA (British Geological Survey-United Kingdom Offshore Operators’ Association) revisions of North Sea lithostratigraphy.

Sixteen new lithostratigraphical names are introduced (nine in the Mercia Mudstone Group, one in the Sherwood Sandstone Group, three each within the Permian and Carboniferous successions). The lithology, wireline log characteristics and nature of the lower boundary are discussed briefly for each lithostratigraphical unit, together with correlations to the adjacent onshore successions where appropriate. Formal definitions of lithostratigraphic units, including type and reference sections are fully documented elsewhere. The aims of this study are to rationalize the existing terminology and to provide a practical scheme that will have the widest acceptance within the oil industry.
The presence of sulphate-reducing bacteria in live drilling muds, core materials and reservoir formation brine from new oilfields
Authors: Mcgovern-Traa Caroline , Leu Jyh-Yih , Hamilton W. Allan , Spark Iain S. C. , Patey Ian T. M.
Published: April 2008

The sulphate-reducing bacteria (SRB) produce the toxic gas hydrogen sulphide (H
2
S) and cause numerous problems in the oil and gas industry. It has been suggested that these organisms are either introduced to the formation by drilling or water injection or that they may be indigenous. Little is known of the activity and survival mechanisms of the SRB under reservoir conditions. In this study a number of samples from hydrocarbon reservoirs were inoculated into sulphate-rich growth medium to determine the presence and activity of the SRB. The samples studied included freshly drilled core material and live drilling muds. The majority of samples analysed contained SRB which produced H
2
S to varying degrees following different incubation times. Organisms capable of producing H
2
S at temperatures up to 95°C were detected. Often long incubation periods, in excess of 6 months, were necessary before H
2
S was produced. Many of the blank mud samples analysed (e.g. prior to use in the well) were already contaminated with sulphidogenic bacteria. Some of the cultures obtained to date have been studied in reservoir conditions core flood tests. It is hoped that the use of these laboratory tests will highlight any potentially damaging reactions prior to their occurrence in hydrocarbon formations.
Diagenesis of the Sherwood Sandstone Group in the southern East Irish Sea Basin (Blocks 110/13, 110/14 and 110/15): constraints from preliminary isotopic and fluid inclusion studies
Authors: Greenwood P. J. , Habesch S. M.
Published: April 2008

Diagenesis in reservoir sandstones from the southern East Irish Sea Basin has resulted in the precipitation of multiple generations of quartz and carbonate cements. Other cements are volumetrically minor and do not affect sandstone reservoir quality, which overall retains high porosities and permeabilities. Stable isotope data suggest that precipitation of caliche calcite cement during early diagenesis occurred at low temperature (
c.
30°C) from meteoric porewaters (−3‰ SMOW). By contrast δ
34
S data for evaporitic gypsum/anhydrite from the Ormskirk Sandstone Formation and Mercia Mudstone Group suggest that locally, an early marine sulphate source was available following deposition. Late burial anhydrite and barytes cements were derived through dissolution and reprecipitation of the early sulphates, according to stable isotope data. Fluid inclusion data for burial diagenetic cements record elevated temperatures (>100°C) for authigenic quartz, carbonate and sulphate minerals, which precipitated from concentrated brines. Stable isotopes indicate that porewaters enriched in
18
O evolved during burial and late carbonates incorporated increasing quantities of carbon derived from organic maturation at depth. An episode of hydrocarbon migration during burial, predating the influx of hydrocarbons currently found, is preserved as bitumen in the sandstones. Further cementation postdated this episode, including late calcite cements postdating the migration of the current hydrocarbon charge. Petrographic data indicate that the elevated temperatures recorded in burial cements were not achieved entirely through depth of burial but probably reflect periods of elevated heatflow, as a result of the circulation of hot fluids through the reservoir sandstones.
Regional diagenetic controls on reservoir properties in the Millom accumulation: implications for field development
Authors: Cowan Greig , Bradney Joanna
Published: April 2008

The Millom accumulation comprises two dip-closed culminations situated down-flank of the 1 TCF North Morecambe Field. The depositional environments encountered in the Millom area are similar to those in the North Morecambe area and they share a common depositional layering. However, porosity and permeability are low compared to the Morecambe Fields. Although the presence of permeability reducing platy illite throughout the reservoir can explain the reduced permeabilities in the area, it does not account for the reduced porosity. The abundance of mineral cements (quartz and carbonates) increases rapidly away from the crest of the North Morecambe structure, down-dip towards the Millom area. The migration history of fluids outwards from the deeper parts of the basin is preserved by the cement distributions observed in the Morecambe-Millom area. Porosity in North Morecambe is preserved by an early hydrocarbon charge. The Millom structure had not formed during early hydrocarbon migration and was exposed to mineralizing fluids moving from the Keys Basin to the north. Both structures were filled with the present gas charge during late Cretaceous/early Tertiary gas migration. Poor reservoir properties, especially
K
v
, renders Millom unsuitable for development by horizontal wells.
The Lennox oil and gas Field
Authors: Haig D. B. , Pickering S. C. , Probert R.
Published: April 2008

The Lennox oil and gas Field is located in Block 110/15 of the East Irish Sea, approximately 10 km west of Southport, Lancashire. The field was discovered in 1992 with well 110/15-6 drilled by the P791 BHP group. The Lennox structure is a rollover anticline in Permo-Triassic sediments formed in the hanging wall of the Formby Point Fault. The reservoir comprises the Triassic Sherwood Sandstone Group, and is characterized by excellent permeability aeolian and fluvial sandstones. The structure is sealed by the overlying shales and evaporites of the Mercia Mudstone Group. To date four wells have been drilled on the Lennox Field and have delineated a free gas cap in communication with a constant thickness oil rim. The hydrocarbons have been sourced from Namurian Holywell shales and reflect complex migration into the Lennox structure. Reservoir studies indicate likely hydrocarbons-in-place of 463 BCF of gas and 218 MMBO of oil. Development approval for the Lennox Field was granted in 1993 with production due to commence in late 1995 from a series of horizontal oil producers. Gas produced during the early years will be recycled and re-injected into Lennox via a crestal gas well to help maximize the oil production. During the later years, production will switch to sales gas. Lennox will be developed as an integral part of BHP’s Liverpool Bay Development.
The origin of magnetic remanence components of Westphalian C to Stephanian C sediments, West Bohemia: a record of waning Variscan tectonism
Authors: Krs Miroslav , Pešek Jiří , Pruner Petr , Skoček Vladimír , Slepičková Jana
Published: April 2008

Petromagnetic and magnetomineralogical investigations of Westphalian C to Stephanian C rocks from the Central and Western Bohemian Late Palaeozoic Basins were undertaken to determine the origin of magnetic remanence components and of ferrimagnetic minerals — carriers of respective remanence components in a variety of rock types including tuffs, tuffites, siltstones, sandstones, grey and red claystones. Multi-component analysis allowed the separation of remanence components and a selection of petromagnetic and/or magnetomineralogical methods were used to determine the ferrimagnetic minerals. Magnetite was found to be the principal carrier of Variscan remanence components in most non-red-coloured rocks and haematite in red claystones originated during diagenesis in the Carboniferous period. In several samples, haematite, goethite and other Fe-oxides were found to result from recent weathering. In some samples, the Variscan remanence components were separated at relatively low temperatures, from about 150°C onwards. Variscan virtual pole positions have been derived from relatively small sets of samples. Nevertheless, they show that the rocks of the Westphalian C and D ages were more intensively deformed than those of the Stephanian, agreeing with an overall decrease in intensity of deformation in the final stages of the Variscan orogeny.
Turkish lignite deposits
Authors: İnaner H. , Nakoman E.
Published: April 2008

The distribution of lignite deposits in Turkey is such that in general the Eocene lignites are in northern Turkey, Oligocene lignites are in northwestern Turkey, Miocene lignites are in western Turkey, and Pliocene-Pleistocene lignites are in eastern Turkey. Only the Oligocene lignites are paralic deposits, the rest being formed in a limnic environment. Turkey has about 8.4 Gt of lignite reserves of which 3.9 Gt are the exploitable reserves. Most of the known lignite deposits in Turkey are of low calorific value and have high contents of ash, moisture and total sulphur. Almost 80% of the total reserves have calorific values below 2500 kcal kg
−1
. The lignites having low calorific values are generally consumed in power plants. The lignites having relatively high calorific values are exploited for domestic and industrial use in the country. The majority of Turkish lignite deposits are worked in open-pit mines, but there are also some underground operations.
Mössbauer spectroscopic investigation of low rank coal lithotypes
Authors: Kostova Irena , Markova Kalinka , Kuntchev Krasimir
Published: April 2008

Low rank coal lithotypes — xylain, humovitrain, semifusain, fusain and liptain sampled from the Maritsa Iztok coal basin (Bulgaria) have been examined by Mössbauer spectroscopy with no pre-concentration procedures. The results are used to identify three iron species in coal lithotypes and show that covalent iron (Fe
II
) related to pyrite, is the main iron species in xylain, while in humovitrain ferric iron is dominant. The total quantity of iron species in semifusain, fusain and liptain is about the same, but their distribution is different. Ferric iron dominates in all the three lithotypes. Ferrous iron, although present in smaller quantities, has a higher content in fusain than in semifusain. Our results illustrate the type of oxidation processes which formed the coal lithotypes. A transformation of Fe
2+
to Fe
3+
has occurred out as a result of differing oxidation processes. The intensity of that transformation increases during the destructive microbial oxidation and decreases during thermal oxidation and direct oxidation processes. The opposite transformation of ferric to ferrous iron has been achieved during both thermaloxidation and direct oxidation processes.
Aliphatic biological markers in Miocene Maritza-Iztok lignite, Bulgaria
Authors: Stefanova Maya , Magnier Caroline
Published: April 2008

Chromatographic separation and mass spectral studies of bitumens extracted from lithotypes (humovitrain, xylain, liptain and humoclarain) from the Miocene Maritza-Iztok lignite reveal the following: (1) A preponderance of the
α
-phyllocladane skeleton over the pimaranes/abietanes. The variety of tricyclic diterpanes confirms that the generation biota included gymnosperms; (2) The presence of dicotyledonous angiospermaes in the generation biota is indicated by the occurrence of widely distributed des-A-lupane structure; (3) The dominance of terpanes over steranes confirms the prevailing contribution of terrigenous input; (4) The preponderance of C

27
β

hopane and the presence of
ββ
hopanes indicates a low degree of thermal maturation.
Determination of different forms of sulphur in Yugoslav soft brown coals
Authors: Jankes G. , Cvetković O. , Glumičić T.
Published: April 2008

This paper presents the results of determination of different forms of sulphur in two Yugoslav soft brown coals, Kolubara (KOL) and Kostolac (KOST). The forms of sulphur were determined as sulphate, monosulphide, pyrite and organic sulphur containing compounds by step-wise oxidation with perchloric acid. The tests were carried out in an inert atmosphere in Bethge’s apparatus. KOL and Kost were quite different in sulphur content, KOL containing 0.71 wt% of sulphur and KOST 3.11 wt%, as well as in the distribution of each type of sulphur compound. Pyrite was dominant in KOST (1.89 wt%) and organic sulphur in KOL (0.47 wt%). The analytical method applied was simple and good reproductivity of results was shown. It was important that all types of sulphur were determined in a single and small sample, using the same oxidizing agent.
A well logging method for the determination of the sulphur content of coal seams by means of deep gammaspectrometry
Authors: Gregor Vít , Těžký Antonín
Published: April 2008

This contribution describes new spectral logging equipment developed at Geofyzika Brno which is designed to remotely determine the sulphur content in brown coal. The method is based on analyses of the prompt gamma ray spectrum induced in coal seams by a neutron source. Theoretical studies have demonstrated the possibility of using the 5.42 MeV peak of gamma radiation from sulphur. The measured spectrum is analysed in three independent parallel ways. The analyser is calibrated in the range from 0.6% to 10% of sulphur by weight. The lower detection limit is believed to be 0.3–0.5%, and the measurement sensitivity 0.1%.
Conversion of low rank coal into liquid fuels by direct hydrogenation
Authors: Aleksić B. R. , Ercegovac M. D. , Cvetković O. G. , Marković B. Ž. , Glumičić T. L. , Aleksić B. D. , Vitorvić D. K.
Published: April 2008

A study of low-rank coal conversion into liquid products by direct catalytic hydrogenation was undertaken. A soft brown coal from the ‘Tamnava’ field of the Kolubara mines characterized by a huminite reflectance of 0.27 ± 0.03% R
R
, ash content of 10.4 wt% (db), carbon content of 64.0 wt% (daf), and volatiles ca. 50 wt% (db), was submitted to liquefaction in a batch reactor. The effect of reaction parameters on both the yield and nature of liquefaction products was studied for temperatures ranging from 365 to 440°C, and pressure from 13.5 to 16.5 MPa, with process duration from 1 to 8 hours. The total coal conversion was high at all applied reaction conditions (84–93%, daf coal basis), pointing to a high reactivity of this coal. The yield of particular liquid products varied markedly depending on temperature and residence time. The yield of light-oil (
n
-heptane soluble products) increased and that of asphaltenes decreased by increasing the temperature and prolonging the residence time. Changes in petrographic composition of the coal were examined by microscopic analysis. At more severe reaction conditions the content of semicoke and coke increased. With the increase of temperature at mild conditions, the proportions of both the reacted coal and granular residue increased, while the cenospheres and mineral matter decreased. The nature of the changes observed in the organic and mineral components of the coal grains was used to correlate the degree of coal conversion with the experimental conditions.
The use of pulverized lignite/natural gas mixed fuels in the high-temperature process of a cement rotary kiln
Authors: Stanojević M. , Jankes G. , Kuburović M. , Stanojević M. , Blagojević P.
Published: April 2008

This paper presents the results of industrial tests of low grade lignite combustion in the 500 t/day wet-process rotary cement kiln. For the use of pulverized lignite, the following process characteristics are determined: combustion process parameters, flue gas properties, and the influence of coal ash properties on clinker quality. Industrial tests have shown that it is possible to substitute 50–80% of the natural gas with pulverized low-grade lignite, while the output of the kiln, specific heat consumption, and the quality of cement clinker remain unchanged.
Methane emission and its utilization from Ostrava-Karviná Collieries in the Upper Silesian coal basin, Czech Republic
Authors: Takla G. , Vavrušák Z.
Published: April 2008

The Ostrava-Karviná part (OKR) of the Upper Silesian coal basin is the most important hard coal basin in the Czech Republic. This basin extends over an area of 1600 km
2
. The Carboniferous basin fill contains 255 seams with a net coal thickness of 150m. The methane content in the coal is estimated between 4.4 to 20m
3
/t. In the OKR, about 120 million cubic meters per year of methane are produced by gas drainage plants from a number of collieries. The methane is used in local industries. Several measures have been taken to increase the methane extraction in active mines and in areas of closed collieries. Additionally, pilot projects for coalbed methane production have been started in virgin coal bearing areas with no previous coal production. The authors’ company is progressing with such a pilot project, with the first coalbed methane wells completed recently. Results to date are encouraging. All these activities are designed to increase the safety in mines, to reduce methane emission to the atmosphere, and to develop new sources of energy.
Cenozoic plate tectonic reconstructions of SE Asia
Authors: Hall Robert
Published: April 2008

A new plate tectonic model for the Tertiary is proposed, based on the integration of new palaeomagnetic data from east Indonesia recording Philippine Sea plate motion, recent revisions of the history of the South China Sea, and previously available geological and palaeomagnetic data from SE Asia. Early Neogene counter-clockwise rotation of Borneo is interpreted to have closed a proto-South China Sea suggesting a strike-slip boundary in NW Borneo before the Neogene. This rotation suggests that the West Philippine Sea, Celebes Sea and Makassar Strait formed a single basin which opened in the late Paleogene, and widened eastwards. At
c.
25 Ma a major collision, that of Australia with a Philippine Sea plate arc, trapped Indian Ocean lithosphere which later became the Molucca Sea plate. The collision caused clockwise rotation of the Philippine Sea plate, initiated the Sorong Fault system, and then eliminated the Molucca Sea by subduction on its east and west sides. The effects of collision propagated westwards through the region resulting in the initiation of new plate boundaries marked by regional unconformities. The arrival of the Sulawesi ophiolite, which collided with west Sulawesi in the late Oligocene, was the earliest event in collision between Sulawesi and the Bird’s Head microcontinent. Continental crust was thrust beneath Sulawesi in the early Miocene, and the Tukang Besi and Sula platforms were sliced in turn from the microcontinent, transferred to the west-moving Philippine Sea/Molucca Sea plate for a few million years, and finally accreted to Sulawesi. Reconstructing the Molucca Sea and Bird’s Head microcontinent suggests that most of the Banda Sea has a late Neogene extensional origin. Collision between the Philippine arc and the Eurasian continental margin in Taiwan at
c.
5 Ma is the key to present regional tectonics.