bluuebunny/crossref_metadata_2025_split huggingface dataset:
Integrated hydraulic-hydrogeochemical assessment of flooded deep mine voids by test pumping at the Deerplay (Lancashire) and Frances (Fife) Collieries
Authors: Nuttall C. A. , Adams R. , Younger P. L. 
Published: April 2008

Abstract
To provide the basis for the design of two Coal Authority mine water management schemes, IMC Consulting Engineers (IMC) carried out step-drawdown pumping tests at the Deerplay (Lancashire) and Frances (Fife) abandoned collieries in the summer of 2000. Supplementary hydrochemical investigations were funded by NERC and undertaken by the University of Newcastle and Queen’s University Belfast (QUB).
The results of the step-drawdown tests can only be interpreted by invoking a substantial component of turbulent flow in large open voids. Overall, the Deerplay system behaves in a manner analogous to natural aquifers, lending itself to modelling (using VSS-NET) to obtain effective hydraulic parameters that may be applicable in similar systems of flooded bord-and-pillar workings elsewhere.

The hydrochemical results for both sites showed some similarities, for example there was evidence of depth stratification of water quality in both cases, but also contrasts. For instance, although the total iron in the mine water pumped from the Deerplay Colliery rose gradually to a plateau at around 30 mg 1
−1
, the water remained net-alkaline throughout the test. By contrast, not only did the total iron in the Frances waters rise in abrupt steps to as much as 600 mg 1
−1
, but the water also switched from being net-alkaline at the beginning of the test to become strongly net-acidic by the end.
The structure of the upper mantle beneath southern Africa
Authors: Priestley Keith , McKenzie Dan 
Published: April 2008

Abstract

A large number of velocity models derived from a variety of seismic data and using different seismic techniques have been published for the Archaean and Proterozoic shields. Here, we focus on the structure beneath southern Africa, where velocity models derived from most regional seismic data find the thickness of the seismic lithosphere to be less than 200 km. In contrast, velocity models derived from teleseismic body-wave and long-period surface-wave data determine the seismic lithosphere to be as much as 400 km thick. We believe that this disagreement is due to the ways in which the various datasets average the velocity structure. Our analysis of regional seismograms from propagation paths largely confined to the stable region shows that the average thickness of the seismic lithosphere beneath southern Africa does not exceed 160 km. We compare the vertical S-wave travel time of our velocity model derived from regional seismic data and those models derived from teleseismic data and find no significant difference. We determine the
in situ
velocities and densities from nodules from beneath southern Africa using a recently derived geobarometer and geothermometer; these are in excellent agreement with the velocity found in the high-velocity lid from the analysis of the regional seismic data. The lithospheric model that best fits the nodule data has a mechanical boundary layer thickness of 156 km and a lithosphere thickness of 176 km. However, the shear-wave velocity decrease at the base of the lid does not correspond to a change in mineralogy. Recent experimental studies of the shearwave velocity in olivine as a function of temperature and period of oscillation demonstrate that this decrease can result from grain boundary relaxation at high temperatures at the period of seismic waves. This decrease in velocity occurs where the mantle temperature is closest to the melting temperature.
Formation and early evolution of the atmosphere
Authors: Marty Bernard , Dauphas Nicolas 
Published: April 2008

Abstract

The tectonic activity of the Earth allowed exchange of volatile elements (H, C, N, rare gases) between the surface of the Earth (atmosphere, crust, sediments, oceans) and the mantle. However, some of these elements still present elemental and isotopic heterogeneities that allow us to reconstruct the volatile composition of the terrestrial mantle. The protosolar nebula supplied a significant fraction of helium and neon, which were presumably trapped during the major phase of the Earth’s accretion and were possibly hosted by accreting dust and/or small porous planetesimals. Surprisingly, volatile elements are in chondritic proportion despite their drastic (10
−3
) depletion in the mantle relative to chondrites, in a way that recalls the case of highly siderophile elements. From stable isotope systematics, we find that the contribution of comets to the volatile inventory of the Earth was very limited. The integrated flux of chondritic-like material necessary to provide water, carbon and nitrogen is consistent with that required for the formation of the lunar craters as well as that necessary to account for the inventory of siderophile elements in the mantle. A consequence of this scenario is that the Earth’s surface was oxidized very early. Alternatively, volatile and siderophile elements of the mantle could be the remnant of small patches of chondritic material that did not equilibrate with the core nor drastically degas.
Fermor lecture: The influence of life on the face of the Earth: garnets and moving continents
Authors: Nisbet E. G. 
Published: April 2008

Abstract

The Hadean Earth (before
c.
4 Ga) was abiotic, possibly sterring a bumpy course between brief periods of hot inferno after meteorite impacts, and long episodes of Norse icehell. The earliest Archaean life would probably not have been planet-altering, but restricted to particular habitats. One of the first may have been hot regions around hydrothermal systems where redox contrasts between ocean water and magmatic fluids could be exploited. Molecular evidence suggests that with the evolution of anoxygenic photosynthesis, life became able to occupy wider regions, although focused in the vicinity of hydrothermal systems. Oxygenic photosynthesis by cyanobacteria allowed life fully to occupy the planet, not only forming coastal microbial mats but also possibly inhabiting the broad oceans with abundant photosynthetic bacterial picoplankton, underlain by deeper archaeal picoplankton. In the Belingwe belt, Zimbabwe, textural and isotopic evidence suggests that a complex microbial ecology existed in the late Archaean (2.7 Ga), which was essentially modern in its biochemical abilities and which sequestered into the biosphere the same fraction of primitive carbon emitted from mantle as today. To do this, by the late Archaean the biological productivity must have been significant; not necessarily as large as today, but capable of managing the global carbon budget. When this began is unknown, possibly earlier than 3.5 Ga ago. The controls on the oxidation state of the late Archaean atmosphere—ocean system are not self-evident. Although inorganic controls dominate the long-term balance, short-term biological management of the air may have been crucial. Methane may have played a major role in the pre-metazoan biosphere. The modern atmosphere is a biological construct: oxygen and its reverse, carbon dioxide, are managed by rubisco; nitrogen, its oxides and hydrides mainly by nitrifying and denitrifying bacteria, with a small input from lightning in an oxygen-rich atmosphere; and water (itself the most important greenhouse gas) by its complex interdependence with other greenhouse gases and albedo, including clouds. Earth’s air is highly improbable. In controlling surface temperature a subtle interplay between organic and inorganic controls has operated, perhaps to the extent that it is invalid to ask which was the dominant factor. But there is a reasonable uniformitarian argument that life has constructed the air in the past as now, and that, within the broad constraints of the physical setting, this biologically shaped atmosphere has been the dominant control on the planet’s surface temperature. In turn, the surface temperature has been one of the various controlling factors on the tectonic evolution of the planet. Thus to a significant extent life has helped shape the physical evolution of the planet.
The metamorphic history of the Isua Greenstone Belt, West Greenland
Authors: Rollinson Hugh 
Published: April 2008

Abstract

New geological investigations in the
c.
3.7–3.8 Ga Isua Greenstone Belt in West Greenland have revealed that the belt comprises a number of separate structural domains. Five such domains have been identified on the basis of lithological and structural differences. This study uses the morphology and compositional zoning of garnet porphyroblasts in pelites to investigate the extent to which the various domains within the greenstone belt preserve contrasting deformational and metamorphic histories. Up to three episodes of garnet growth have been identified in a single domain and significant differences in garnet growth history are noted between domains. A distinction is drawn between the relatively simple metamorphic history of a low-strain zone in the NE of the greenstone belt and other domains where more complex histories are preserved. Combining this result with existing geochronology suggests that in the south and west, the greenstone belt was metamorphosed twice, at
c.
3.74 Ga and at
c.
2.8 Ga, whereas in the NE there was a single event at 3.69 Ga. Preliminary garnet-rim thermometry indicates that some rocks experienced an early metamorphism in which temperatures exceeded 610°C. Kyanite is thought to have been in equilibrium with these assemblages, indicating pressures of at least 6 kbar. A later prograde metamorphic event shows a temperature rise from 480 to 550°C. The high pressures indicate a crustal thickness of at least 20 km at 3.7 Ga.
Palaeozoic amalgamation of Central Europe: an introduction and synthesis of new results from recent geological and geophysical investigations
Authors: Winchester J. A. , Pharaoh T. C. , Verniers J. 
Published: April 2008

Abstract

Multidisciplinary studies undertaken within the EU-funded PACE Network have permitted a new 3-D reassessment of the relationships between the principal crustal blocks abutting Baltica along the Trans-European Suture Zone (
TESZ
). The simplest model indicates that accretion was in three stages: end-Cambrian accretion of the Bruno-Silesian, Łysogóry and Małopolska terranes; late Ordovician accretion of Avalonia, and early Carboniferous accretion of the Armorican Terrane Assemblage (
ATA
), which had coalesced during Late Devonian — Early Carboniferous time. All these accreted blocks contain similar Neoproterozoic basement indicating a peri-Gondwanan origin: Palaeozoic plume-influenced metabasite geochemistry in the Bohemian Massif in turn may explain their progressive separation from Gondwana before their accretion to Baltica, although separation of the Bruno-Silesian and related blocks from Baltica during the Cambrian is contentious.

Inherited ages from both the Bruno-Silesian crustal block and Avalonia contain a 1.5 Ga ‘Rondonian’ component arguing for proximity to the Amazonian craton at the end of the Neoproterozoic: such a component is absent from Armorican terranes, which suggests that they have closer affinities with the West African craton.
Models showing the former locations of these terranes and the larger continents from which they rifted, or to which they became attached, must conform to the above constraints, as well as those provided by palaeomagnetic data. Hence, at the end of the Proterozoic and in the early Palaeozoic, these smaller terranes, some of which contain Neoproterozoic ophiolitic marginal basin and magmatic arc remnants, probably occurred within the end-Proterozoic supercontinent as part of a ‘Pacific-type’ margin, which became dismembered and relocated as the supercontinent fragmented.
The
40
Ar/
39
Ar ages from the West Sudetes (NE Bohemian Massif): constraints on the Variscan polyphase tectonothermal development
Authors: Marheine D. , Kachlík V. , Maluski H. , Patočka F. , Żelaźniewicz A. 
Published: April 2008

Abstract

The West Sudetes (NE margin of the Bohemian Massif) consist of a complex mosaic of several tectonometamorphic units juxtaposed during the Variscan orogeny. The polyphase Variscan tectonothermal development of the West Sudetes was determined by
40
Ar/
39
Ar ages of single grains and mineral concentrates. Late Famennian (359 Ma) mica ages from the high-grade Góry Sowie Block suggest continuous uplift after a Late Devonian high temperature-low pressure (HT-LP) event contemporaneous with the end of subduction-related high pressure-low temperature (HP-LT) metamorphism in the East Krkonoše Complex.

Mid-Late Devonian high pressure events in the Krkonoše-Jizera Terrane and Orlica-Śnieżnik Dome are followed by coeval high temperature events between 345 and 335 Ma (Viséan). The latter are interpreted as consequence of uplift, and decompression during overthrusting of both complexes on their forelands. Subsequent small- to large-scale shear movements dated at around 325–320 Ma (early Namurian) affected the Orlica-Śnieżnik Dome, Krkonoše-Jizera Terrane, including the Intra-Sudetic Fault, and also the eastern Lusatian Granitoid Complex. They were accompanied by contemporaneous emplacement of the Krkonoše-Jizera pluton. The upper limit of the tectonometamorphic and magmatic activity is dated at 314–312 Ma (Namurian/Westphalian boundary). The final juxtaposition of the diversified tectonometamorphic units, which constitute the West Sudetes, took place in early Namurian times.
Palaeozoic terrane amalgamation in Central Europe: a REE and Sm-Nd isotope study of the pre-Variscan basement, NE Bohemian Massif
Authors: Crowley Quentin G. , Timmermann Hilke , Noble Stephen R. , Holland J. Grenville 
Published: April 2008

Abstract

The West Sudetes, NE Bohemian Massif, comprises several suspect terranes accreted to the margins of Laurussia during Variscan orogenesis. Whole rock REE and Sm-Nd isotope data for seven separate provinces (Izera, Kaczawa, Rudawy Janowickie and Kłodzko complexes; Fore-Sudetic and Góry Sowie Blocks; Slęża Ophiolite) suggest involvement of a variety of crustal and mantle sources. Felsic metasedimentary rocks (ɛNd(t) = −8.3 to −5.0) have two stage T
DM
ages of 1.9 to 1.5 Ga, whereas acidic metavolcanic rocks and granite gneisses (ɛNd(t) = −5.4 to +0.8) have two stage T
DM
ages of 1.5 to 1.0 Ga. A range of sources is implicated: predominantly Archaean and Palaeoproterozoic sources for the metasedimentary rocks, and Archaean. Palaeoproterozoic and Neoproterozoic to early Palaeozoic sources for the meta-igneous felsic lithologies. LREE depleted tholeiitic metabasites ((Ce/Yb)
N
= 0.8 to 3.4) generally have ɛNd(t) = +4.0 to +9.1, indicating derivation from depleted mantle asthenosphere. LREE enriched meta-alkali basalts ((Ce/Yb)
N
= 4.6 to 10.1) with ɛNd(t) between +3.1 and +7.0 implicate utilization of enriched mantle asthenosphere.

Analogous lithologies from elsewhere in the Sudetes, North Bohemian Massif and the Armorican Terrane Assemblage have similar REE abundances, ɛNd values and T
DM
ages. Complexes previously considered to have had disparate Neoproterozoic to early Palaeozoic histories may be integrated into a unifying geodynamic model of derivation from the North Gondwanan (North African) margin during a widespread episode of continental margin break-up.
The Mariánské-Lázně Complex, NW Bohemian Massif: development and destruction of an early Palaeozoic seaway
Authors: Crowley Quentin G. , Floyd Peter A. , Štědrá Veronika , Winchester John A. , Kachlík Vaclav , Holland J. Grenville 
Published: April 2008

Abstract
The Mariánské-Lázně Complex is a Cambro-Ordovician terrane of oceanic affinity tectonically emplaced between the Saxothuringian Zone and Teplá-Barrandian Unit, NW Czech Republic. It forms a SE-dipping allochthonous body that comprises the largest contiguous exposure of metamorphosed basic and ultrabasic lithologies in the Bohemian Massif. Petrographic evidence indicates that a significant proportion of protoliths underwent eclogite facies metamorphism (570 to 720°C, 1.44 to 2.10 GPa), followed by an increase in temperature (up to around 800°C) and a subsequent widespread retrograde amphibolite facies event (550 to 680 °C, 0.75 to 1.20 GPa). New major and trace element geochemical analyses of metamorphosed basic and ultrabasic lithologies indicate that they exhibit geochemical characteristics attributable to a sea floor origin. The metabasites were generated at a spreading centre that interacted with deep-seated upwelling mantle asthenosphere. Separate, independently fractionating basic melt batches existed: these were derived from depleted and enriched asthenosphere and depleted sub-continental lithosphere sources. Geochemical correlation of the Mariánské-Lázně Complex with other early Palaeozoic metabasic provinces facilitates comparison of metabasic lithologies occurring in tectonically dislocated nappe pile thrust sheets, and allows delineation of important suture zones in the European Variscides.
Coronitic metagabbros of the Mariánské Lázně Complex and Teplá Crystalline Unit: inferences for the tectonometamorphic evolution of the western margin of the Teplá-Barrandian Unit, Bohemian Massif
Authors: Štědrá V. , Kachlík V. , Kryza R. 
Published: April 2008

Abstract
Bodies of coronitic metagabbro occur in the SW Mariánské Lázně Complex (MLC) and the adjacent Teplá Crystalline Unit (TCU) on the western margin of the Teplá-Barrandian Unit (TBU), Bohemian Massif. The characteristic structural, geochemical, petrographic, and metamorphic features of five groups of metagabbros and related rocks are presented, compared with other metabasites of the MLC and Zone of Erbendorff-Vohenstrauss (ZEV), and used to constrain the tectonometamorphic evolution of the western part of the TBU. The metagabbros are considered to be a younger intrusive member of the complicated lower crustal tectonic stack of Upper Proterozoic to Early Palaeozoic age which is formed by the Mariánské Lázně Complex and the Teplá Crystalline Unit together. It is proposed that a significant part of the metamorphic evolution of some parts of these units took place before the emplacement of metagabbros and granitoids at around 496–516 Ma. The sequence of metamorphic events is interpreted to have been as follows. Deep burial of primitive MORB type tholeiitic rocks (a) metamorphosed up to eclogite facies, followed by (b) uplift to lower crustal levels so that the partially exhumed rocks were juxtaposed with other lower/middle crustal rocks. Thermal relaxation (c) followed, with an episode of extension recorded in L-tectonites of amphibolite facies. Once this lithologically variegated stack was welded together, it was intruded by the Upper Cambrian-Lower Ordovician granitoids and gabbros (d). This pre-Variscan metamorphic event may be expressed at the supracrustal level by an unconformity between Upper Cambrian and Lower Ordovician rocks in the Barrandian. The final configuration of the units was established during the Variscan collision of the Teplá Barrandian terrane with Saxothuringia (e) in which the rocks of the MLC and TCU were thrust to the NW over the Saxothuringian para-autochthon. The accompanying metamorphic event reached upper amphibolite facies. The thermally relaxed rocks cooled rapidly, and pre-existing thrust planes were re-activated during the final extensional collapse.
Basement structure in the southern North Sea, offshore Denmark, based on seismic interpretation
Authors: Scheck M. , Thybo H. , Lassen A. , Abramovitz T. , Laigle M. 
Published: April 2008

Abstract
Seismic reflection data from the Danish North Sea are interpreted to map the structure of the Palaeozoic basement in the area of the MONA LISA deep seismic lines. Based on a characteristic near-basement reflection, the upper crystalline crust of Baltica of offshore Denmark is traced to the south into the southern Horn-Graben, and to the west to the eastern shoulder of the Central Graben. A two-way-traveltime map of the near-basement horizon and several interpreted seismic sections reveal that three main tectonic events influenced the topography of the basement: (1) a compressional event which could be Caledonian in age; (2) a Palaeozoic extensional event postdating the compressional deformation and expressed in a system of WSW-ESE to W-E striking Palaeozoic half-grabens; and (3) the Permo-Triassic rifting that led to the formation of NNW-SSE to NNE-SSW trending Mesozoic faults of the Horn Graben and the Central Graben which are oriented sub-perpendicular to the Palaeozoic system. Compressive deformation is localized in a narrow zone around and south of the hitherto interpreted Caledonian Deformation Front and foreland deformation on Baltica is suggested as its origin. The seismic image of the Palaeozoic halfgrabens indicates that the East North Sea High is an inverted Palaeozoic rift which subsequently was cut by younger Late Palaeozoic to Mesozoic rifts of the Horn and Central Grabens. The timing of the first extensional phase remains speculative, but it predates the Rotliegend unconformity. Some of the older Palaeozoic normal faults may have been reactivated as transfer zones between the different graben segments during the Permo-Mesozoic extension.
On the architecture of high-latitude continental margins: the influence of ice-sheet and sea-ice processes in the Polar North Atlantic
Authors: Dowdeswell J. A. , Ó Cofaigh C. , Taylor J. , Kenyon N. H. , Mienert J. , Wilken M. 
Published: April 2008

Abstract
The presence of ice during the Late Cenozoic distinguishes the nature and rates of processes on high-latitude margins from those elsewhere. Ice sheets terminating in marine waters deliver icebergs, meltwater and debris to high-latitude seas. Sea ice influences ocean salinity structure and downslope water and sediment transfer, and also transports fine-grained sediments over long distances. These cryospheric processes have led to the development of a distinctive sedimentary architecture on modern high-latitude continental margins. Large submarine fans made up almost entirely of stacked debris flows are present around the Norwegian-Greenland Sea. Large slides are located in a variety of settings relative to rates of sediment delivery from Quaternary ice-sheet margins, but no large slides have been mapped on the East Greenland margin. However, extensive channel systems and sediment-wave fields are present in the Greenland Basin, probably related to intermittent downslope flow of dense water and turbidity currents. The extensive NE Greenland shelf was not innundated by ice-sheet advance during recent full-glacial conditions, allowing sea-ice and deep-water production during both interglacials and full-glacials. Changes in the nature and rate of sedimentation within the Greenland Basin should provide clues on the rate of dense-water production, with implications for thermohaline circulation in the North Atlantic. Other erosional and depositional features on the Norwegian-Greenland Sea margins include canyons and contourite drifts. High-relief tectonic features influence sediment reworking by turbidity currents at abyssal depths. A simple conceptual model for glacier-influenced marine sedimentation summarizes the role of cryospheric processes in high-latitude margin sedimentary environments.