bluuebunny/crossref_metadata_2025 huggingface dataset:
Geological controls on coalbed prospectivity in part of the North Staffordshire Coalfield, UK
Authors: MacCarthy F. J. , Tisdale R. M. , Ayers W. B.
Published: September 2007

Westphalian coal seams in the Kinetica/Taurus exploration licence EXL 282, which covers part of the North Staffordshire Coalfield, are estimated to contain over 5.6 × 10
10
m
3
of initial coalbed gas in place. In the evaluation of coalbed gas prospectivity in the licence area, data from the coal and the oil and gas industries were used to map coal occurrence, coal rank, the gas content of coal seams, gas in-place, structure, face cleat and
in situ
stress.

The North Staffordshire Coalfield is structurally and stratigraphically complex. Westphalian strata occur in a SSW plunging synclinorium that is highly segmented by faults with displacements as great as 500 m. These faults may either be barriers or conduits for fluid migration. The maximum
in situ
horizontal compressive stress is generally oriented NNW, subparallel to face cleats and some faults, which may favour openness and transmissivity of those fractures. In the southern part of the licence area, intraformational unconformities occur in the Westphalian. Total coal thickness is greatest (more than 40 m) and coal rank is highest (medium-volatile bituminous) in the northern part of the licence area, coincident with the greatest thickness of Westphalian strata. Predictably then, gas content and initial gas in-place per unit area are greatest in the northern part of the licence area, coincident with the occurrence of thick, high rank coals. In this area, initial gas in-place is estimated to exceed 4.0 × 10
8
m
3
per km
2
in some areas. Although gas resource trends have been identified, production rates of coalbed gas can only be established through well testing.
Cleat mineralization of Upper Permian Baralaba/Rangal Coal Measures, Bowen Basin, Australia
Authors: Faraj Basim S. M. , Fielding Chris R. , Mackinnon Ian D. R.
Published: September 2007

Coals from the Permo-Triassic Bowen Basin have been investigated using a variety of complementary analytical techniques. Face cleat minerals in the studied samples are dominated by authigenic clays, notably pure illite or illite-chlorite mixtures. Butt cleats and joints are dominated by carbonates, mostly calcite with less abundant ferroan calcite, ankerite and siderite. K/Ar ages of cleat-fill illites and one fracture illite-smectite fill indicate three phases of illite formation during the Triassic: (1) an early phase with ages clustered around 244 Ma ago; (2) a second phase about 232 Ma ago; and (3) the latest phase about 219 Ma ago. Thermal modelling of selected boreholes from the study area and other geological data indicate that the first phase of illitization occurred when the coal seams were about 1000 m below the surface and at a temperature of between 70 and 80°C, at a time when the basin was rapidly subsiding. These early illites were stable and retained their 1
M
polytype even after being exposed to temperatures of 150–190°C during maximum burial in the southeastern Bowen Basin. The second phase of illitization (at 232±3) occurred at about the time of maximum burial. The latest phase took place between 223±3 and 212±3 Ma ago and occurred in a wider temperature range (between 170 and 100°C) during a rapid uplift in the Late Triassic. The Bowen Basin area experienced a second cycle of subsidence that commenced in the Early Jurassic with the formation of the Surat Basin, which overlies the Bowen Basin and forms part of the Great Artesian Basin system. Regional uplift and erosion in middle Cretaceous times terminated sediment accumulation in the Surat Basin. During the second cycle of burial widespread carbonate mineralization in butt-cleats and joints took place. Calcite fluid inclusions indicate that calcite was precipitated from meteoric water at about 80°C. The widespread carbonate mineralization in butt cleats and the near-absence of carbonates in the face cleats is here attributed to permeability anisotropy, caused by a change in the direction of lateral compressive stress during Jurassic-Cretaceous times relative to that during the Triassic Hunter-Bowen Orogeny.
Characterization of anthracite
Authors: Davidson M. I. , Bryant R. , Williams D. J. A.
Published: September 2007

Examination of the surface properties of anthracite provides information of assistance in the interpretation of
in situ
behaviour and use of the material as a micronized fuel and as an inexpensive support substrate for growth of micro-organisms. The characteristics of anthracite particles (<10 μm) produced by crushing and grinding larger material (obtained from Cynheidre Colliery, South Wales UK) are reported. Mineral particles, liberated from this anthracite matrix, subsequent to radiofrequency-induced plasma (RFIP) oxidation, were found to constitute 2 wt%, 0.6vol% of that matrix. X-Ray fluorescence analysis and analytical transmission electron microscopy of these particles indicated silicon, aluminium and iron to be the predominant electropositive elements present, with calcium the only other element detected at a level greater than 5wt% of the mineral component. X-Ray diffractometry (XRD) of this component indicated that hematite, pyrite, siderite and a variety of aluminosilicate minerals were present in the original matrix.

Mineral particles liberated by RFIP oxidation of the planar (cut) surface of anthracite were initially captured in plastic replica films and thence transferred to carbon films. Electron microscopic examination of these films indicated that mineral particles present in the anthracite matrix possessed diverse chemistries, were submicron in size and suggested their distribution throughout the carbonaceous matrix to be homogeneous.

Estimates of the surface area of <10μm anthracite particles (107 ± 15 m
2
g
−1
) made using nitrogen adsorption/desorption (BET) analysis, were significantly greater than those predicted for non-porous particles of this size. Equilibration of the surface with nitrogen was reached ≈1.2 × 10
4
s after the imposition of changes in pressure. Hysteresis of the adsorption/desorption isotherms was pronounced, suggesting that the material contained 9%
v/v
pores, of which 75% were estimated to be ≈2 nm diameter.

Potentiometric (aqueous, acid/base, batchwise) titration of the material, at a variety of ionic strengths (
I
), indicated long equilibration times between H
+
/OH
−
and the surface (≈3 × 10
5
s). The dependence of the analytical surface charge density (σ
a
) on pH and
I
were found to be significant though small, with points of zero titration (pH
pzt
) in the range 4 < pH
pzt
< 7 which increased with
I
. at pH < pH < 9, σ
a
was virtually independent of
I
, suggesting a point of zero salt effect to be located in this region or that solute ions were unable to penetrate the surface. The range of σ
a
(based on the surface area determined by BET) was found to be small (−7 < σ
a
< 6 μC cm
−2
) and its nature consistent with that of surfaces of minerals shown and identified by electron microscopy and XRD analysis to be present at low concentration within (and exposed at the surface of) the carbonaceous matrix.
Petrological and spectroscopic structural characteristics of Bohemian and Moravian coals and their possible relation to gas proneness
Authors: Sýkorová I. , Novotná M. , Pavlíková H. , Machovič V.
Published: September 2007

Optical and infra-red microscopy, diffusion reflectance infra-red spectrometry and solid-state nuclear magnetic resonance spectrometry (
13
C CP/MAS NMR) were applied to the determination of the degree of coalification and structural characteristics of lignite and bituminous coal from deposits in the Czech Republic. Structural parameters such as the aliphatic and aromatic contents and carbonyl contents of coal and coal macerals could be valuable tools for determination of gas proneness, e.g. the CH
2
/CH
3
ratio derived from infra-red spectroscopy. Aromaticity,
f
a
, determined by
13
C CP/MAS NMR, is shown to be a valuable parameter reflecting the degree of coalification, particularly for low and middle rank coal, thus supplementing data derived from the vitrinite reflectance
R
o
and (H/C)
at
ratio data. The maceral group of huminite/vitrinite mirrored similar changes with increasing coalification degree as the parent coal. The structure of two macerals of the liptinite group, sporinite and cutinite, was investigated for bituminous coal, and the aromatic and oxygen group contents were higher in cutinite than in sporinite.
Minerals and major elements in density-separated coal fractions from Point of Ayr coal, Wales, UK
Authors: Barraza J. , Gilfillan A. , Cloke M. , Clift D.
Published: September 2007

Density separated coal fractions from 1.30 floats to 1.70 sinks of Point of Ayr coal for the particle sizes −3350+2800, −1000+850, −300+212 and −38+20µm, have been studied for major element and mineral content. Low temperature ash residues were analysed using Fourier transform infra-red and X-ray diffraction spectrometry. Major elements (Al, Ca, Fe, K Mg, Mn, Na and Si) were determined in high-temperature ash residues using atomic absorption spectrometry and atomic emission spectrometry. The minerals identified in the samples were kaolinite, illite, montmorillonite, quartz, dolomite, anhydrite, calcite, gypsum, mica, bassanite and interlayer smectite. The study suggests the origin of the minerals, on the basis of their association with the organic or mineral matter fractions, and indicates that there is a correlation between some major elements and mineral distribution in the coal fractions. It is shown that both the organic affinity of the elements and the abundance of specific minerals are related to the particle size.
Mineralogy, geochemistry and pyrite content of Bulgarian subbituminous coals, Pernik Basin
Authors: Kostova Irena , Petrov Ognyan , Kortenski Jordan
Published: September 2007

The mineralogy and geochemistry of Pernik subbituminous coals (coal bed A) and some genetic peculiarities related to the mineral formation were studied. The mineral matter of the coal consists chiefly of pyrite, kaolinite, siderite, quartz and calcite. Other minerals (dolomite, ankerite, plagioclase and some sulphates) are present in minor amounts, some occurring as accessory single crystals. Pyrite is the main mineral in these coals and exhibits a large array of textures and morphology. Isolated and clustered euhedral, bacterial and inorganic framboidal, cluster-like, homogeneous and microconcretional massive, infilling and replacing anhedral, and cleat-filling and fracture-filling infiltrational pyrite types were observed. Four stages of mineralization were distinguished: pyrite-kaolinite, pyrite, pyrite-siderite and sulphate stages. The amount of pyrite present in two sections of coal bed A was determined by quantitative powder X-ray diffraction analysis. The concentrations of 37 trace elements were determined. As, Cu, Co, Ni, Zn, Pb, V Ti, Mo, Rb, Cr and Mn are typomorphic for this coal. On the basis of their relation to organic or inorganic matter, four groups of trace elements were subdivided; and on the basis of cluster analysis four associations were differentiated.
Subsurface correlation of Carboniferous coal seams and inter-seam sediments using palynology: application to exploration for coalbed methane
Authors: McLean Duncan , Murray Iain
Published: September 2007

Palynology has a long history of application in the hydrocarbon exploration and development industry. Palynological methodologies developed for the study of traditional hydrocarbon reservoirs are directly transferable to exploration for coalbed methane. The principal difference in approach relates to the fact that coal seams usually contain abundant palynomorphs, whereas conventional reservoirs (sandstones and carbonates) do not. Work since the 1930s in the onshore British coalfields and work in the offshore southern North Sea Carboniferous basin illustrate that the high-resolution correlation of coal seams is achievable using palynology. The methods lend themselves to studies of coalbed methane reservoir connectivity and correlation. Other applications, such as the identification of coring points and stratigraphic targets, the monitoring of vertical and horizontal drilling and the study of coal seam maturation by spore colour analyses represent standard palynological applications.
Late Quaternary glacial history and short-term ice-rafted debris fluctuations along the East Greenland continental margin
Authors: Stein Ruediger , Nam Seung-il , Grobe Hannes , Hubberten Hans
Published: September 2007

High-resolution stable oxygen and carbon isotope and sedimentological investigations were carried out on four west-east profiles at the East Greenland continental margin between 68° and 75°N. The sediment cores represent distinct glacial/interglacial palaeoclimatic episodes over the past 190 ka. Based on oxygen isotope stratigraphy and AMS
14
C dating, our data can be well correlated with the global climate record. However, there are some excursions from the global climate curve suggesting a local/regional overprint by meltwater events of the Greenland Ice Sheet, especially at the beginning of isotope stage 3 and during Termination 1. Distinct high-amplitude variations in supply of ice-rafted debris (IRD) indicate repeated advances and retreats of the Greenland Ice Sheet, causing fluctuations in the massive production and transport of icebergs into the Greenland Sea. During the last 190 ka, a number of IRD peaks appear to be correlated with cooling cycles observed in the GRIP Greenland Ice Core. Drastic events in iceberg discharge along the East Greenland continental margin recurred at very short intervals of 1000–3000 years (i.e. much more frequently than the about 10 000 years associated with Heinrich events), suggesting short-term collapses of the Greenland Ice Sheet on these time-scales. These late Weichselian Greenland Ice Sheet oscillations appear to be in phase with those in the Barents Sea area. Maximum flux rates of terrigenous (ice-rafted) material were recorded at the continental slope between about 21 and 16 ka, which may correspond to the maximum (stage 2) extension of glaciers on Greenland. The beginning of Termination I is documented by a distinct shift in the oxygen isotopes and a most prominent decrease in flux of IRD at the continental slope caused by the retreat of continental ice masses.
Late Quaternary sedimentation along a fjord to shelf (trough) transect, East Greenland (
c.
68° N)
Authors: Andrews J. T. , Jennings Anne E. , Cooper T. , Williams Kerstin M. , Mienert J.
Published: September 2007

The East Greenland continental margin between
c.
66 and 68° N consists of a major fjord/trough system that extends from Kangerdlugssuaq Fjord, along Kangerdlugssuaq Trough to Denmark Strait. Measurements of the temperature and salinity of the water column along this transect indicates that ‘warm’ water (0–2°C) underlies the surface Polar Water of the East Greenland Current. A series of short (1–3 m) gravity cores along the fjord/trough transect have sufficient numbers of foraminifera that a suite of AMS
14
C dates has been obtained, including both basal and core-top age estimates. Rates of sediment accumulation vary through space and time; over the last 1 ka estimates vary from
c.
3 to 0.1 m. These dates and measurements of sediment density, together with measurements of the percentages by weight of total organic carbon and biogenic silica, are used to show graphs of fluxes of the organic and inorganic sediment components over the last 1–14 ka. An analysis of the net flux of foraminifera indicates a reduction in numbers during the Younger Dryas chronozone and a general similarity with data from the Renland (East Greenland) ice core data.
Sedimentological examination of the Late Weichselian sea-level history following deglaciation of northern Denmark
Authors: Richardt Niels
Published: September 2007

Modern sedimentological principles are used to examine the Late Weichselian marine history of Vendsyssel, northern Denmark. The purpose is to determine significant sea-level events and to outline a new relative sea-level curve. Five significant events are found: deglaciation, high relative sea level (
c.
60 m above the present sea level), a rapid fall in relative sea level, a marked break in sea-level fall (
c.
20 m above the present sea level) and a renewed fall in relative sea level. The new sedimentologically based sea-level curve is compared with a classical and a revised ecologically based relative sea-level curve. These curves show an initial transgression following deglaciation. The new sedimentologically based curve shows no transgression. It is concluded that this curve is the most reliable. When comparing the new sea-level curve with regional data from Vendsyssel significant differences are found. A time transgressive deglaciation pattern and neotectonic movements might explain these differences. The isostatic position of the study area during the examined time span is sketched. Rapid isostatic uplift commenced as late as
c.
13 300 years
BP
, at least 1300 years after deglaciation of the area.
Deglaciation history and palaeoceanography of the western Spitsbergen margin since the last glacial maximum
Authors: Lloyd J. , Kroon D. , Laban C. , Boulton G.
Published: September 2007

Two high resolution cores from the Spitsbergen margin were studied to increase the understanding of the palaeoceanography and deglaciation of the Spitsbergen continental margin. Planktonic and benthic foraminiferal δ
18
O records along with foraminiferal abundance counts and dropstone analysis were used to interpret the palaeoceanography of the Spitsbergen margin and to link the marine record with deglaciation of the Barents Sea Ice Sheet. High foraminiferal and dropstone abundances during the Late Weichselian glacial maximum show that this period was characterized by seasonally ice-free conditions. The initial deglaciation recognized along the Spitsbergen margin is dated at 14.1 ka
BP
and represents the break up of the Barents Sea Ice Sheet, though some input from the Spitsbergen ice dome is likely. This initial deglaciation was produced by glacio-isostatic relative sea-level rise and/or by increased solar insolation after the minimum of the Late Weichselian. The first unequivocal deglaciation of Spitsbergen ice occurred at 13 ka, whereas the oceanographic regime was still dominated by polar waters. The beginning of the Holocene was heralded by a second deglaciation phase of the Spitsbergen ice mass. The first influx of North Atlantic waters causing rapid iceberg calving and melting was recorded at this time. Dropstone input virtually ended at approximately 9 ka
BP
when most glaciers had retreated beyond their present day positions. A short relatively cool episode produced by the retreat of the North Atlantic waters during the early Holocene was recorded along the Spitsbergen margin.
Late glacial air temperature, oceanographic and ice sheet interactions in the southern Barents Sea region
Authors: Vorren Tore O. , Laberg Jan S.
Published: September 2007

Stratigraphic records from three areas (the Andøya area, the continental slope and the continental shelf of the southern Barents Sea) are used to evaluate the history of the late glacial Barents Sea Ice Sheet and the northern Fennoscandian Ice Sheet. Two late glacial maxima are indicated: one before 22 ka
BP
(LGM I) and the younger after 19 ka
BP
(LGM II). A major deglaciation phase was initiated during a warm spell between 16 and 15 ka
BP
. During a drawdown of marine based ice sheets about 14.5 ka
BP
large parts of the southern Barents Sea Ice Sheet decayed. This deglaciation was retarded between 13.7 and 13 ka
BP
. Most of the eastern and northern Barents Sea was deglaciated during the Bølling-Allerød interstadial complex. During the LGM II there was an ice stream in the Bear Island Trough with an estimated velocity at the front of about 2.5 km/year. An average accumulation rate of 0.3–0.4 m/year is estimated for the drainage area of the Bear Island Trough Ice Stream. A close interrelation exists between summer air temperatures and the waxing and waning phases of the northern Fennoscandian and southern Barents Sea ice sheets. It is suggested that most of the ice sheet decay was due to climatic warming, which caused thinning of the ice sheets, making them susceptible to decoupling from the sea bed and increased calving. The subsequent halts/readvances were due to climatic deteriorations caused by huge inputs of icebergs to the Norwegian Sea which cooled the surface water and in turn promoted sea ice preservation through the summer season and thereby increased the albedo.
Late Weichselian deglaciation of the Barents Sea and low salinity events in the Norwegian Sea
Authors: Punkari Mikko
Published: September 2007

The glacial geomorphology of the northwestern Russian Plain, Pechora lowland, northern Urals and southern Novaya Zemlya was mapped using Landsat satellite imagery. The deglaciation of the ice sheets around the Barents Sea was outlined using geological mapping, published land uplift data and previous observations. The amount of glacial meltwater produced during the deglaciation is compared with other freshwater sources. Freshwater discharges from proglacial lakes are approximated using this ice sheet reconstruction. Variations in precipitation are estimated using ice accumulation rates from an ice core in Greenland.

The ice sheets spreading from the continent and islands surrounding the Barents Sea melted quickly 14-9 ka
BP
. According to glacial flow patterns and the compilation of
14
C dates, the separation of the Scandinavian and Novaya Zemlya ice sheets occurred in the marine zone between the Kanin and Kola Peninsulas at about 13 ka
BP
. The Dvina-Pechora proglacial lake, which had accumulated south of the confluence zone, drained into the Barents Sea, west of the Kanin Peninsula. The size of the lake was about 350 000 km
2
and the volume of water of the order of 10 000 km
3
, equivalent to a 3 cm global sea-level rise.

Low salinity periods at 15-13 ka
BP
have been reported in the North Atlantic and Norwegian Sea. These have been associated either with active glacier calving and melting or with changes in the oceanic circulation system. The rapid decay of the ice sheets at 14-11 ka
BP
yielded meltwater about 600 km
3
/year, but the greatly increased precipitation during the Bölling interstadial at 12.3 ka
BP
became the most important source of freshwater entering the sea. The proposed freshwater pulse from the proglacial lake was a short-lasting event, but it may possibly be recorded in the marine stratigraphy by the oxygen isotope signal preserved in calcite from planktonic foraminifera.
Detailed survey of the western end of the Hurd Deep (English Channel): new facts for a tectonic origin
Authors: Lericolais G. , Guennoc P. , Auffret J.-P. , Bourillet J.-F. , Berne S.
Published: September 2007

During the ‘Sédimanche 2’ survey, a study of the western end of the Hurd Deep was carried out using new high-resolution geophysical techniques. The obtained results, i.e. bathymetry, acoustical imaging and seismic profiling, determine a tectonic control on the first excavation of Hurd Deep, a complex infilling and present-day sediment dynamics.

In size and geometry, the Hurd Deep is a unique feature in the English Channel, terminating abruptly at its western end. It is incised into Jurassic and Late Cretaceous sediments. Except for the trough itself, the sea floor is extensively levelled at a depth between 70 and 90 m.

The Hurd Deep infill, revealed by high-resolution seismic data, is characterized by a set of five main sequences. The thickness of the infill averages 80 m along the axis of the trough and reaches a maximum of 140 m. The side-scan sonar mosaic shows active sediment dynamics characterized by the presence of dunes on the southern part of the present trough.

A Neogene tectonic origin for the Hurd Deep and the interplay of erosion and sedimentation during the last glacial and interglacial periods are presented in terms of geomorphology and sequence stratigraphy.
Evolution of a nearshore and coastal macrotidal sand transport system, Queen Charlotte Islands, Canada
Authors: Barrie J. V. , Conway K. W.
Published: September 2007

An extensive (40 km) coastal plain is prograding on the north coast of the Queen Charlotte Islands off the Pacific margin of Canada while the entire 120 km eastern coast of Graham Island is actively eroding. At the junction of these two systems is Rose Spit, which extends northeastward at a point of sediment transport convergence. Historical bathymetrical data and aerial photographs indicate that a spit platform extends 10 km to the northeast and at least four portions (up to 4 km in length) of the platform bank have become emergent since 1911. The area is seismically active and subject to storm-related sediment transport events superimposed on strong semi-diurnal tidal flows. The rapid emergence of the offshore banks and the net coastal changes are primarily controlled by: (1) convergence of sediment transport between the waters of Hecate Strait to the south and Dixon Entrance to the north, particularly during winter storms; and (2) localized tectonic uplift.

Sediment is transported north from the shallow waters of Hecate Strait by southeasterly winter storms and east, by longshore transport, along the accreting northern coast of the Queen Charlotte Islands to converge at Rose Spit. A ‘hydraulic fence’ has formed resulting in the creation of the elongate spit platform with emergent sand bars, east of the spit. Transpressional folding has occurred in this area east of the Queen Charlotte Fault, which separates the North American and Pacific Plates. This has resulted in localized uplift since Pliocene time, complementing the accretion process.
Geophysics in offshore site investigation: a review of the state of the art
Authors: Davis A. M.
Published: September 2007

Geophysical techniques for seabed and sub-seabed site investigation can be divided into two categories: those providing information on gross structural (geological) and stratigraphical relations, and those producing quantitative data which can be used to predict sediment behaviour under applied loading. The past few years have seen key developments in both fields which have come about through fundamental improvements in data acquisition (technological and procedural), and through an improved understanding of geophysical-geotechnical property relations. For example, high-resolution seismic reflection signatures are now routinely recorded in digital format, and, given the appropriate data quality and processing software, it is now possible to extract geotechnically significant information from the reflection response. Seismic refraction techniques are also beginning to be more widely used to provide quantitative information on the engineering properties of seafloor materials; the seismic shear wave velocity is of particular interest, since it is now being recognized as an indicator of sediment strength and stiffness.

From a review of available data and the results of validation exercises, it would seem that offshore engineering and environmental surveys could reap considerable benefit from these and a range of other related geophysical developments.
Insight into the enigma of Neoproterozoic manganese and iron formations from the perspective of supercontinental break-up and glaciation
Authors: Bühn Bernhard , Stanistreet Ian G.
Published: September 2007

The genesis of manganese and iron formations (MnF and IF) is a closely related process during the Proterozoic, in which oceanic crustal venting provided metal-rich solutions to be deposited on adjacent continental shelves. Their deposition in condensed marine sequences occurred when continental break-up initiated a major transgression and provided favourable conditions for precipitation of chemical sediments from seawater. The Neoproterozoic Rodinian supercontinental break-up shows the relationship between this tectonic process, climate, and MnF/IF genesis. Metallogenesis followed particular rift-drift transitions during supercontinental break-up. MnFs/IFs are often associated with glaciomarine sedimentary rocks. Higher O
2
/CO
2
during continental rifting would, through inducing glacial conditions and withdrawing seawater, increase ocean salinity and thereby allow both deposition of glaciomarine sediments and precipitation of evaporites. Salinities would have been particularly enhanced in the restricted oceanic basins provided by early supercontinental rifting, where atmospheric evaporation would also have played a part. Accumulation of Mn and Fe in the Neoproterozoic may be directly related to a probably glacially derived increased ocean salinity that promoted accumulation and storage of Mn and Fe in ocean water through increased Mn, Fe, and Ba(?) solubility. Very similar processes may have been effective in Palaeoproterozoic times, although then a higher amount of Fe and Mn discharge and different ocean chemistry would have superseded the effect of ocean salinity. Chemical Mn and Fe precipitates related to supercontinental break-up in the Proterozoic as well as the Phanerozoic indicate a similar relationship between tectonics and ore accumulation. The resultant close time and space relationship between potent oceanic source and suitable continental-shelf depositional settings optimised accumulation and preservation of ancient Mn-Fe deposits. This scenario is at variance from present-day environments where source and suitable precipitation areas of long-term preservation potential are mostly widely separated in space.
An EPMA and SEM study of the Mn-oxide mineralization of Kato Nevrokopi, Macedonia, northern Greece: Controls on formation of the Mn
4+
oxides
Authors: Michailidis K. M. , Nicholson K. , Nimfopoulos M. K. , Pattrick R. A. D.
Published: September 2007

EPMA and SEM studies of tunnel-structured todorokite and nsutite and layer-structured chalcophanite and birnessite from the Kato Nevrokopi battery grade Mn-mineralization were performed. The chemistry of todorokite, formed at hypogene and supergene environments in an increasing order of weathering, reflects different pH and oxidation conditions. The data also point to a clear dependence of the development of late stage hypogene and early supergene Mn
4+
-oxide paragenesis on the host rock and protore composition and the mobilities of base metals (mainly Zn), alkalis and alkaline earths (mainly Ca).

The chemistry and development of (large cation-bearing) nsutite as
in situ
oxidations and banded poorly crystalline (with structural defects) aggregates in veins and associated karstic cavities, together with birnessite, indicates the influence of climate, oxidation and water table fluctuations. The data on chalcophanite revealed a deposition, under low
f

O
2

conditions, from acid meteoric fluids produced by weathering of vein sulphides. Birnessite formation reflects a prevalence of higher
f

O
2

in weathered veins and karstic cavities.

The evolution of well developed layer structures through poorly crystalline to amorphous tunnel-structured nsutite is probably controlled by a Zn-saturation of the ore fluids.
Recent manganese oxide deposits in Hokkaido, Japan
Authors: Miura Hiroyuki , Hariya Yu
Published: September 2007

Recent manganese oxide deposits and manganese-bearing hot-spring waters from Hokkaido, Japan have been studied. There are many active hot-springs in the volcanic zones in Japan and stable isotope data (
δ
D) show that the hot-spring water is derived from surface water. Some hot-spring waters precipitate manganese oxides. They are black, soft and muddy. SEM micrographs show a pipe structure coated by manganese oxides which indicates the role of microorganisms in manganese precipitation. X-ray powder diffraction reveals that they consist of todorokite or birnessite. Pyrolusite is not a primary product from hot-spring waters, but a recrystallized product in the post-depositional environment. Manganese oxides alternated with calcareous sinter and are crusty and consist of rancieite. The concentration of heavy metal elements in manganese oxide is controlled by the crystal structure of magnanese oxide minerals present in the deposits and todorokite contains the most heavy metal elements. REE concentration varies widely and the negative Ce anomaly is an indicator of depositional rate.
Geochemistry of manganese oxides: metal adsorption in freshwater and marine environments
Authors: Nicholson Keith , Eley Mark
Published: September 2007

The effect of pH and metal ion concentration on the adsorption of Cu, Co, Cd, Mn, Ni and Zn onto manganese oxides was investigated. The oxides used in the experiments were deposited around individual sand grains in water treatment filter beds in NE Scotland and show reproducible adsorption profiles regardless of location or age. The oxides remained amorphous throughout the four-year study period, and show an inferred pH
ZPC
of 1.5. Metal adsorption increases towards more alkaline pH. The adsorption series Co > Cu > Cd > Zn > Mn > Ni is shown at pH 3 and Cu > Co > Cd > Mn > Zn > Ni at pH 6. Changing the concentration of the metal ions in solution leads to an increase in the mass of metal adsorbed, though the relationship is not linear as the proportion of metal taken up falls as concentration rises. Adsorption from an artificial seawater solution shows a significant reduction in the amount of metal taken up in all cases except Cu which shows an adsorption profile comparable with that in deionized water. The linear Freundlich isotherm accurately and reproducibly models the adsorption profile of all metals at each pH and concentration examined. The data do not, however, replicate the enrichment sequence observed in manganese nodules. The study demonstrates that for the enrichments observed in manganese nodules to be attained, the active oxide surface must be replenished by regular precipitation of fresh oxide material to enable continued adsorption to take place.
The determination of the valency of manganese in mineralogical and environmental samples by X-ray emission spectroscopy
Authors: Gamblin S. D. , Urch D. S.
Published: September 2007

The K
β
X-ray emission spectrum arising from 3
p
→ 1
s
transitions in transition metal ions can be complicated by interaction between unpaired 3
d
electrons and the odd 3
p
electron in the final state. A non-diagram line, K
β′
appears at lower emission energy than the diagram line K
β
1,3
. For lighter transition metals the intensity ratio of K
β′
to K
β
1,3
decreases with the number of unpaired 3
d
electrons. This enables this intensity ratio to be used to determine oxidation state.

This effect is demonstrated for the simple oxides MnO, Mn
2
O
3
and MnO
2
, and for the anion MnO
4
−. Distinct spectra are obtained that can be related to the oxidation state of the manganese. The valency of manganese is then determined in mineral samples and in sand grains coated with manganese encrustations from water purification plants.
One-man-operable probe permeameters
Authors: Prosser D. J. , Hurst A. , Wilson M. R.
Published: September 2007

A steady-state probe permeameter is designed that is robust, insensitive to moisture and can be operated using a low-pressure gas source. Consequently, substantial reduction in weight and bulk are possible and a truly one-man-operable, lightweight (<5 kg) instrument is constructed. Tests on natural samples using a prototype instrument reveal a similar level of precision to other permeameters over a wide range of permeability.
Acoustic wave propagation and permeability in sandstones with systems of aligned cracks
Authors: King M. S. , Shakeel A. , Chaudhry N. A.
Published: September 2007

A polyaxial (true triaxial) stress-loading system has been developed for testing cubic specimens of rock, with the capability of varying each of the principal stresses independently. Facilities are incorporated for measuring all nine components of P and polarized S-wave velocities and attenuation in the principal directions, and for fluid permeability in the 1-direction. Tests have been performed on specimens of five sandstones, in which systems of aligned cracks have been introduced by increasing
σ
1
and
σ
2
together to near failure, while maintaining
σ
3
constant at some low level. Results indicate that there are excellent correlations between permeability in the plane of the aligned cracks as they are closed under hydrostatic stress and both velocities and attenuation of (1) P and S waves propagating in a direction normal to the plane of the cracks, and (2) S waves propagating in the plane of the cracks and polarized normal to the plane.
A simple but powerful model for simulating elastic wave velocities in clastic Silicate rocks
Authors: Xu Shiyu , Doorenbos Just , Raikes Sue , White Roy
Published: September 2007

We describe a practical velocity model for clastic silicate rocks developed from the Kuster and Toksöz, differential effective medium and Gassmann theories. The model divides the total pore space into two parts, one associated with sand grains and the other associated with clays (including bound water). The difference in pore geometry makes the clay fraction more compliant with increasing porosity than the sand fraction. The model accurately simulates the combined effect of lithology, porosity, clay content, water saturation and fluid type on laboratory and logging P- and S-wave velocities. Velocity dispersion is modelled by considering the relaxed and unrelaxed extremes of fluid flow. Of three possible schemes for predicting S-wave logs from other logs, prediction from the P-wave sonic and porosity logs is generally the most accurate; comparisons of blind test predictions and S-wave logs at two Norwegian North Sea wells demonstrate the accuracy and robustness of the method. The predictions were further improved once geological information was provided on the formations encountered in the well. Examples of application to the prediction of velocity dispersion and dry frame moduli, the detection of hydrocarbons from crossplotting the P-wave and S-wave sonic velocities, and sonic log editing confirm the flexibility, accuracy and reliability of the model. The model has proved invaluable in constructing accurate models of the seismic reflection response in the vicinity of wells.
Petrophysical estimation from downhole Mineralogy logs
Authors: Harvey P. K. , Lovell M. A. , Lofts J. C. , Pezard P. A. , Bristow J. F.
Published: September 2007

A number of physical and chemical properties of rocks, many of which are important in petrophysics are simple, usually linear functions, of a rock’s mineralogy. Examples include matrix density, porosity, magnetic susceptibility and cation exchange capacity. Mineralogy logs can be obtained directly from geochemical logs through an inversion process and, in turn, estimates of petrophysical properties such as those noted above can be obtained. The accuracy of such estimates is directly dependent on the quality of both the inversion and the geochemical measurements. Examples from producing oil fields and from deep-sea environments are used to show that accurate estimates of derived parameters can be obtained provided that appropriate inversion procedures are adopted, and that these estimates are generally better than those obtained by conventional log analysis. Logs of some parameters, such as cation exchange capacity, cannot be obtained except through the mineral inversion.
Fractal Geometry, porosity and complex resistivity: from rough pore interfaces to hand specimens
Authors: Da Rocha Brígida Ramati P. , Habashy Tarek M.
Published: September 2007

We propose a new model to interpret the electrical behavior of rocks containing metallic or clay particles. This new model encompasses some of the other commonly used models as special cases.

This model is a generalization of two models, one developed by Dias (Journal of Geophysical Research 77, 4945–4956, 1972) and another by Pelton
et al.
(
Geophysics
Geophysics
, 589–609, 1978). Its circuit analog includes an impedance
K
(
iω
)
−η
which simulates the effects of the fractal rough pore interfaces between the conductive grains (metallic or clay minerals which are blocking the pore paths) and the electrolyte. This generalized Warburg impedance is in series with the resistance of the blocking grains and both are shunted by the double layer capacitance. This combination is in series with the resistance of the electrolyte in the blocked pore passages. The unblocked pore paths are represented by a resistance which corresponds to the normal DC resistivity of the rock. The parallel combination of this resistance with the ‘bulk’ sample capacitance is finally connected in parallel to the rest of the above-mentioned circuit.

The model was tested over a wide range of frequencies against experimental data obtained for amplitude and phase of resistivity or conductivity as well as for the complex dielectric constant. The samples studied are those of sedimentary, metamorphic and igneous rocks.
Feature recognition and the interpretation of images acquired from horizontal wellbores
Authors: Lofts J. C. , Bedford J. , Boulton H. , van Doorn J. A. , Jeffreys P.
Published: September 2007

The acquisition of borehole resistivity and acoustic images has become increasingly common in horizontal wells drilled for hydrocarbons. The appearance, and later interpretation of these images is somewhat different to that of conventional vertical wellbore images. Shallow-dipping bedding planes appear as long drawn-out sinusoids in unrolled workstation images whilst sub-vertical fractures appear as low-amplitude sinusoids, the opposite to what geologists are used to in vertical wells. Due to the sub-parallel orientation of the wellbore with respect to the bedding, such intersections will produce unusual features that can be misleading and difficult to interpret. The mechanics of drilling, and of acquiring image data in a horizontal plane also leads to the creation of certain artefacts or noise in images which must be identified correctly. The most common sedimentary and tectonic features imaged in horizontal wellbores are described and discussed here as a reference for geoscientists.
Approximation via cost sharing
Authors: Gupta Anupam , Kumar Amit , P´al Martin , Roughgarden Tim
Published: September 2007

We present constant-factor approximation algorithms for several widely-studied NP-hard optimization problems in network design, including the multicommodity rent-or-buy, virtual private network design, and single-sink buy-at-bulk problems. Our algorithms are simple and their approximation ratios improve over those previously known, in some cases by orders of magnitude.

We develop a general analysis framework to bound the approximation ratios of our algorithms. This framework is based on a novel connection between random sampling and game-theoretic cost sharing.
When are elections with few candidates hard to manipulate?
Authors: Conitzer Vincent , Sandholm Tuomas , Lang Jérôme
Published: September 2007

In multiagent settings where the agents have different preferences, preference aggregation is a central issue. Voting is a general method for preference aggregation, but seminal results have shown that all general voting protocols are manipulable. One could try to avoid manipulation by using protocols where determining a beneficial manipulation is hard. Especially among computational agents, it is reasonable to measure this hardness by computational complexity. Some earlier work has been done in this area, but it was assumed that the number of voters and candidates is unbounded. Such hardness results lose relevance when the number of candidates is small, because manipulation algorithms that are exponential only in the number of candidates (and only slightly so) might be available. We give such an algorithm for an individual agent to manipulate the Single Transferable Vote (STV) protocol, which has been shown hard to manipulate in the above sense. This motivates the core of this article, which derives hardness results for realistic elections where the number of candidates is a small constant (but the number of voters can be large).

The main manipulation question we study is that of
coalitional
manipulation by
weighted
voters. (We show that for simpler manipulation problems, manipulation cannot be hard with few candidates.) We study both
constructive
manipulation (making a given candidate win) and
destructive
manipulation (making a given candidate not win). We characterize the exact number of candidates for which manipulation becomes hard for the
plurality
,
Borda
,
STV
,
Copeland
,
maximin
,
veto
,
plurality with runoff
,
regular cup
, and
randomized cup
protocols. We also show that hardness of manipulation in this setting implies hardness of manipulation by an individual in unweighted settings when there is uncertainty about the others' votes (but not vice-versa). To our knowledge, these are the first results on the hardness of manipulation when there is uncertainty about the others' votes.
A numerical evaluation of sparse direct solvers for the solution of large sparse symmetric linear systems of equations
Authors: Gould Nicholas I. M. , Scott Jennifer A. , Hu Yifan
Published: September 2007

In recent years a number of solvers for the direct solution of large sparse symmetric linear systems of equations have been developed. These include solvers that are designed for the solution of positive definite systems as well as those that are principally intended for solving indefinite problems. In this study, we use performance profiles as a tool for evaluating and comparing the performance of serial sparse direct solvers on an extensive set of symmetric test problems taken from a range of practical applications.
Exploring many-to-one speech-to-text correlation for web-based language learning
Authors: Chen Herng-Yow , Li Sheng-Wei
Published: September 2007

This article investigates the correlations between multimedia objects (particularly speech and text) involved in language lectures in order to design an effective presentation mechanism for web-based learning. The cross-media correlations are classified into implicit relations (retrieved by computing) and explicit relations (recorded during the preprocessing stage). The implicit temporal correlation between speech and text is primarily to help to negotiate supplementary lecture navigations like tele-pointer movement, lips-sync movement, and content scrolling. We propose a speech-text alignment framework, using an iterative algorithm based on local alignment, to probe many-to-one temporal correlations, and not the one-to-one only. The proposed framework is a more practical method for analyzing general language lectures, and the algorithm's time complexity conforms to the best-possible computation cost,
O(nm)
, without introducing additional computation. In addition, we have shown the feasibility of creating vivid presentations by exploiting implicit relations and artificially simulating some explicit media. To facilitate the navigation of integrated multimedia documents, we develop several visualization techniques for describing media correlations, including guidelines for speech-text correlations, visible-automatic scrolling, and levels of detail of timeline, to provide intuitive and easy-to-use random access mechanisms. We evaluated the performance of the analysis method and human perceptions of the synchronized presentation. The overall performance of the analysis method is that about 99.5% of the words analyzed are of a temporal error within 0.5 sec and the subjective evaluation result shows that the synchronized presentation is highly acceptable to human beings.