bluuebunny/crossref_metadata_2025 huggingface dataset:
The long-term fate of CO
2
in the subsurface: natural analogues for CO
2
storage
Authors: Baines Shelagh J. , Worden Richard H.
Published: April 2008

CO
2
is a common gas in geological systems so that planned storage of CO
2
in the subsurface may do no more than mimic nature. Natural CO
2
has a wide number of sources that can be at least partly identified by carbon stable isotope geochemistry. Three pairs of case studies with different reservoir characteristics and CO
2
contents have been examined to assess the natural impact of adding CO
2
to geological systems. Carbonate minerals partially dissolve when CO
2
is added simply because the CO
2
dissolves in water and forms an acidic solution. Therefore, carbonate minerals in the subsurface are not capable of sequestering secondary CO
2
. The addition of CO
2
to a pure quartz sandstone (or a sandstone in which the supply of reactive aluminosilicate minerals has been exhausted by excess natural CO
2
addition) will have no consequences: the CO
2
will simply saturate the water and then build up as a separate gas phase. The addition of CO
2
to carbonate cemented sandstone without reactive aluminosilicate minerals will induce a degree of carbonate mineral dissolution but no solid phase sequestration of the added CO
2
. When CO
2
is naturally added to sandstones it will induce combined aluminosilicate dissolution and carbonate cementation if the aluminosilicate minerals contain calcium or magnesium (or possibly iron). Examination of a CO
2
-filled porous sandstone with abundant reactive aluminosilicate minerals that received a huge CO
2
charge about 8000 to 100 000 years ago reveals minimal evidence of solid phase sequestration of the added CO
2
. This indicates that either dissolution of reactive aluminosilicates or precipitation of carbonate minerals is relatively slow. It is very likely that the slow dissolution of reactive aluminosilicates is the rate-limiting step.

Solid phase sequestration of CO
2
occurs only when reactive aluminosilicates are present in a rock and when the system has had many tens to hundreds of thousands of years to equilibrate. The two critical aspects of the behaviour of CO
2
when injected into the subsurface are (1) that the rock must contain reactive Ca and Mg aluminosilicates and (2) that reaction to produce carbonate minerals is extremely slow on a human timescale. The reactive minerals include anorthite, zeolite, smectite and other Fe- and Mg-clay minerals. Such minerals are absent from clean sandstones and limestones but are present in ‘dirty’ standstones (lithic arenites which are mineralogically immature) and some mudstones.

The analysis of geological analogues shows that injection of CO
2
into carbonate-bearing rocks that do not contain reactive minerals will induce dissolution of the carbonate, whether it is a matrix cement, rock fragment, fault seal or part of a top-sealing mudstone.
Heat pumps as a tool for energy recovery from mining wastes
Authors: Banks David , Skarphagen H. , Wiltshire R. , Jessop C.
Published: April 2008

Heat pumps extract heat energy from a low-temperature source and transfer it to a higher temperature sink, usually via a closed loop of volatile ‘refrigerant’ fluid in a compression/expansion cycle. They can be efficiently used for space heating (and cooling), extracting heat from seawater, rivers, lakes, groundwater, rocks, sewage, or mine water. Electrical energy powers the heat pump’s compressor. The ratio of total heat output to electrical energy input, called the coefficient of performance, typically ranges from 3.0 to 6.0. The use of mine water for space heating or cooling purposes has been demonstrated to be feasible and economic in applications in Scotland, Canada, Norway, and the USA. Mine water is an attractive energy resource due to: (1) the high water storage and water flux in mine workings, representing a huge renewable enthalpy reservoir; (2) the possibility of re-branding a potentially polluting environmental liability as a ‘green’ energy resource; and (3) the development of many mine sites as commercial/industrial parks with large space heating/cooling requirements. The exothermic nature of the pyrite oxidation reaction (> 1000 kJ/mol) implies added benefits if closed-loop systems can harness the chemical energy released in mine-waste tips. An appreciation of geochemistry also assists in identifying and solving possible problems with precipitation reactions occurring in heat pump systems.
Digital field data acquisition: towards increased quantification of uncertainty during geological mapping
Authors: Jones Richard R. , McCaffrey Kenneth J. W. , Wilson Robert W. , Holdsworth Robert E.
Published: April 2008

Traditional methods of geological mapping were developed within the inherent constraints imposed by paper-based publishing. These methods are still dominant in the earth sciences, despite recent advances in digital technology in a range of fields, including globalpositioning systems, geographical information systems (GIS), 3-D computer visualization, portable computer devices, knowledge engineering and artificial intelligence. Digital geological mapping has the potential to overcome some serious limitations of paper-based maps. Although geological maps are usually highly interpretive, traditional maps show little of the raw field data collected or the reasoning used during interpretation. In geological mapping, interpretation typically relies on the prior experience and prior knowledge of the mapper, but this input is rarely published explicitly with the final printed map. Digital mapping techniques open up new possibilities for publishing maps digitally in a GIS format, together with spatially referenced raw field data, field photographs, explanation of the interpretation process and background information relevant to the map area. Having field data in a digital form allows the use of interpolation methods based on fuzzy logic to quantify some types of uncertainty associated with subsurface interpretation, and the use of this uncertainty to evaluate the validity of competing interpretations.
Flow of partially molten crust and origin of detachments during collapse of the Cordilleran Orogen
Authors: Teyssier C. , Ferré E. C. , Whitney D. L. , Norlander B. , Vanderhaeghe O. , Parkinson D.
Published: April 2008

In metamorphic core complexes two types of detachments develop, coupled by flow of partially molten crust: a channel detachment and a rolling-hinge detachment. The channel detachment, on the hinterland side of the orogen, represents the long-lived interface that separates the partially molten crust flowing in a channel from the rigid upper crustal lid. On the foreland side of the core complex, a rolling-hinge detachment develops. This detachment dips toward the foreland, probably affects the whole crust, and its geometry is governed by strain localization at the critical interface between cold foreland and hot hinterland. Activation of the rolling-hinge detachment drives rapid decompression and melting, leading to the diapiric rise of migmatite domes in the footwall of the detachment. A kinematic hinge (switch in sense of shear) separates the two types of detachments. Structural, metamorphic and geo/thermochronological studies in the Shuswap core complex (North American Cordillera), combined with an anisotropy of magnetic susceptibility study of leucogranites concentrated in the detachments, suggest that this orogen collapsed rapidly through the development of channel and rolling-hinge detachments in the early Eocene. The kinematic hinge is currently located approximately 40 km west of the footwall in which it originated, corresponding to a mean exhumation rate of >5 km Ma−1, which explains the near-isothermal decompression recorded within the migmatite dome.
Nd and Sr isotopic signatures of metasedimentary rocks around the South Pacific margin and implications for their provenance
Authors: Adams C. J. , Pankhurst R. J. , Maas R. , Millar I. L.
Published: April 2008

An Nd-Sr isotope database, includingc.200 new analyses, is presented for Palaeozoic and Mesozoic metasedimentary successions extending through southeastern Australia, New Zealand, West Antarctica and the Antarctic Peninsula to southern South America. Combining with U-Pb detrital zircon age data, this enables characterization of New Zealand terranes, especially within the Eastern Province, where there is a progression from westernmost terranes of both volcanic/volcaniclastic and accretionary origin with primitive sediment sources, to easternmost terranes with mature continental sediment inputs. In southern South America, West Antarctica and the Antarctica Peninsula, similar accretionary complexes have Nd model ages principally reflecting mixing of sedimentary material from multiple sources, both mature and juvenile. A mature Gondwana continental provenance dominates in sedimentary basins inboard of the active margin, especially in the Palaeozoic (Western Province, New Zealand, interior West Antarctica and NW Argentina), and contributes significantly to pre-Mesozoic sedimentary rocks of Patagonia east of the Andes. Along the Gondwanaland margin, Nd systematics for younger (late Palaeozoic to early Mesozoic) accretionary complex metasediments reflect younger source inputs, notably in the Scotia metamorphic complex. Many of the accretionary complex deposits must involve significant crustal reworking. There is no apparent South American equivalent of the primitive provenance of the westernmost accretionary terranes of New Zealand.
Episodicity of Mesozoic terrane accretion along the Pacific margin of Gondwana: implications for superplume-plate interactions
Authors: Vaughan A. P. M. , Livermore R. A.
Published: April 2008

A review of evidence for deformation and terrane accretion on the Late Triassic-Early Jurassic margins of Pangaea and the mid-Cretaceous margins of the palaeo-Pacific ocean shows that deformation was global and synchronous with probable superplume events. Late Triassic-Early Jurassic deformation appears to be concentrated in the period 202–197 Ma and was coeval with eruption of the Central Atlantic Magmatic Province, onset of Pangaea break-up, a period of extended normal magnetic polarity and a major mass extinction event, all possible expressions of a superplume event. Mid-Cretaceous deformation occurred in two brief periods, the first from approximately 116 Ma to 110 Ma in the west palaeo-Pacific and the second from roughly 105 Ma to 99 Ma in the east palaeo-Pacific, with both events possibly represented in northeast Siberia. This deformation was coeval with eruption of major oceanic plateaux, core-complex formation and rifting of New Zealand from Gondwana, the Cretaceous normal polarity epoch, and a major radiation of flowering plants and several animal groups, all linked with the mid-Cretaceous superplume event. A simple unifying mechanism is presented suggesting that large continental or oceanic plates, when impacted by a superplume, tend to break-up/reorganize, associated with gravitational spreading away from a broad, thermally generated topographic high and with a resulting short-lived pulse of plate-marginal deformation and terrane accretion.
The early Palaeozoic Orogen in the Central Andes: a non-collisional orogen comparable to the Cenozoic high plateau?
Authors: Lucassen Friedrich , Franz Gerhard
Published: April 2008

The subduction orogeny of the Central Andes, which created the Cenozoic Altiplano-Puna high plateau, shares many geological features with the early Palaeozoic Orogen at the western margin of South America. The presently available datasets for both orogens are compared. The similarities are a large-scale high temperature metamorphism, which was active in the Palaeozoic Orogen over a geological long period of time in the order of 100 Ma and which is active now in the crust of the Cenozoic plateau. It produced abundant granitoid melts from the crust during the Palaeozoic as well as during the Andean Orogen. The main contribution to granitoid magmatism is recycling of felsic crustal material with only minor additions from the mantle. Transport of deep parts of the crust into the erosion level did not occur in both orogens and, in both orogens, large-scale nappe tectonics typical for collision orogens are absent. Based on the similarities of the two orogens it is argued that the early Palaeozoic Orogen is a non-collisional orogen. Indications for terrane accretion are absent in the development of the high-grade metamorphic and igneous basement. The early Palaeozoic Orogen is an analogue for the presently active continental margin and, thus, allows the extrapolation of features which cannot be observed in the Andean Orogen.
Controls on the heterogeneous distribution of mineral deposits through time
Authors: Groves David I. , Vielreicher Richard M. , Goldfarb Richard J. , Condie Kent C.
Published: April 2008

Mineral deposits exhibit heterogeneous distributions, with each major deposit type showing distinctive, commonly unique, temporal patterns. These reflect a complex interplay between formational and preservational forces that, in turn, largely reflect changes in tectonic processes and environmental conditions in an evolving Earth. The major drivers were the supercontinent cycle and evolution from plume-dominated to modern-style plate tectonics in a cooling Earth. Consequent decrease in the growth rate of continental crust, and change from thick, buoyant sub-continental lithospheric mantle (SCLM) in the Precambrian to thinner, negatively buoyant SCLM in the Phanerozoic, led to progressive decoupling of formational and preservational processes through time. This affected the temporal patterns of deposit types including orogenic gold, porphyry and epithermal deposits, volcanic hosted massive sulphide (VHMS), palaeoplacer Au, iron oxide, copper gold (IOCG), platinum group elements (PGE), diamond and probably massive sulphide SEDEX deposits. Sedimentary mineral deposits mined for redox-sensitive metals show highly anomalous temporal patterns in which specific deposit types are restricted to particular times in Earth history. In particular, palaeoplacer uranium, banded iron formation (BIF) and BIF-associated manganese carbonates that formed in the early Precambrian do not reappear in younger basins. The most obvious driver is progressive oxidation of the atmosphere, with consequent long-term changes in the hydrosphere and biosphere, the latter influencing the temporal distribution and peak development of deposits such as Mississippi Valley types (MVT), hosted in biogenic sedimentary rocks.
Relative oxygenation of the Tithonian — Valanginian Vaca Muerta—Chachao formations of the Mendoza Shelf, Neuquén Basin, Argentina
Authors: Doyle P. , Poiré D. G , Spalletti L. A. , Pirrie D. , Brenchley P. , Matheos S. D.
Published: April 2008

Organic-rich sediments were deposited in the deeper sectors of the Neuquén Basin during the latest Jurassic and the Early Cretaceous. This paper presents the results of a detailed examination of these deposits in the northern-most extension of the basin, in the Mendoza Province, and explores their wider significance for palaeo-oxygenation studies.

The Tithonian—Berriasian Vaca Muerta Formation, the primary source rock for the Neuquén Basin, comprises bituminous shales and interbedded limestones deposited during a major transgression. In the Valanginian, the beginning of a regressive phase enabled the development of shallow-marine carbonates to form the base of the Chachao Formation, which eventually led to extensive biohermal carbonates of the uppermost Chachao Formation. Along the length of the narrow N-S-trending Mendoza Shelf of the Neuquén Basin both units are well exposed, permitting detailed study of the stratigraphy, sedimentology, ichnology and palaeoecology. The analysis of the Tithonian—Valanginian succession in the Salado river valley shows that carbonate production increased up-section. Faunal associations are mostly limited to poorly diverse epibenthos and pseudoplankton in the lower part of the section (Vaca Muerta Formation), with increased diversity in the lower Chachao section, including shallow and deeper infaunal bivalves. A background level of laminated shales to
Chondrites
bioturbation is typical of anoxic—suboxic conditions. Micritic limestones and carbonate sandstones throughout the section commonly show the development of
Thalassinoides suevicus
.

Relative oxygenation curves based on trace fossils and body fossils were developed and compared. There was a primary substrate control on trace fossil diversity and occurrence, with a primary oxygenation signal provided by body fossil evidence. Interpretation of the palaeo-oxygenation on the basis of trace fossil taxa alone, however, would lead to inaccurate results. This study, therefore, demonstrates the importance of integrated trace and body fossil analysis in the fuller understanding of black shales.
Palaeoclimatic implications of Middle Jurassic (Bajocian) coniferous wood from the Neuquén Basin, west-central Argentina
Authors: Morgans-Bell Helen S. , McIlroy Duncan
Published: April 2008

Silicified coniferous wood is commonly found in the Middle Jurassic (Bajocian) Lajas Formation of the Neuquén Basin, west-central Argentina. The wood is preserved in a succession of sandstones, siltstones, mudstones and minor conglomerates that represent deposition as part of tide-dominated deltas and fluvial plains across which large rivers meandered. Most of the wood occurs as dense accumulations in the tidal and fluvial channels. The wood fragments are worn, abraded, and lack both bark and branches, indicating that they were transported prior to deposition. The material is typically 20–30 cm long, with only infrequent examples of larger trunks (
c.
80 cm in diameter, 5–6 m long). No trunks were found with root systems attached, and no stumps were found upright and
in situ
. The fossil wood genus
Araucarioxylon
dominates the assemblage. Growth rings are largely absent from the specimens, although one sample (from Rhea Gorge) displays highly diffuse and irregularly spaced rings, suggesting that it grew in different conditions from the others studied. Large-scale interpretations for southern Gondwana suggest a seasonally dry climate. However, these fossil wood specimens show no evidence of this, indicating that in this area at least the effects of any seasonal component to the climate may have been over-ridden by factors such as a locally plentiful supply of water and/or the possibility that growth was to some extent controlled by the taxonomic affinity of the trees.
Distribution, lithofacies and environmental context of Neogene glacial sequences on James Ross and Vega islands, Antarctic Peninsula
Authors: Hambrey Michael J. , Smellie John L.
Published: April 2008

Considerable controversy exists concerning the stability of the Antarctic Ice Sheet during the Neogene Period. The northern Antarctic Peninsula is in a critical position in this debate as it represents a peripheral area of the ice sheet and is therefore likely to have been sensitive to climatic changes. This paper is concerned with Neogene glacial deposits that occur on James Ross and Vega islands. They occur between a thick volcanic sequence, the James Ross Island Volcanic Group, and Upper Cretaceous sedimentary rocks; they also occur within the volcanic sequence itself. The glacial deposits, where dated, give a series of snapshots of glacial conditions in Neogene time. The deposits are characterized by diamictite and sandy mudstone. Published
87
Sr/
86
Sr ages on shelly fossils in some deposits range from 9.9 to 4.7 Ma, although additional
40
Ar/
39
Ar ages on interbedded volcanic rocks suggest that younger sedimentary deposits are also present. On James Ross Island the basal diamictite is interpreted as glaciomarine sediment that has undergone subaqueous mass movement, and on Vega Island as basal till originating from the west. Provenance studies indicate that the Antarctic Peninsula Ice Sheet expanded sufficiently to deposit these sediments. These diamictites, in places, are overlain by waterlain tuffaceous rocks that include a minor ice-rafted component. Complex deformation of sedimentary and volcanic deposits and contact-metamorphism relationships confirm that volcanism was contemporaneous with glaciation. Later glacial events (within the volcanic sequence) are characterized by glacial erosion of basalt followed by basal till and, possibly, glaciofluvial deposition. The clasts in the latter are almost exclusively local, hence later glaciation was as a small ice cap constructed on the growing volcanic complex of James Ross Island.
Seismic stratigraphy, structure and tectonic evolution of the Levantine Basin, offshore Israel
Authors: Gardosh Michael A. , Druckman Yehezkel
Published: April 2008

Multi-channel seismic reflection data and borehole information were used to study the structure and stratigraphy of the Levantine basin, offshore Israel. A new, 2D seismic survey that covers the southeastern Mediterranean Sea from the Israeli coast to the Eratosthenes Seamount shows the entire Phanerozoic sedimentary fill down to a depth of 14–16 km. The basin-fill is subdivided into six seismo-stratigraphic units interpreted as low-order, major depositional cycles (supersequences A-F). Correlation and mapping of these units allowed an investigation of the geological history of the basin and the analysis of two important tectonic phases: Neotethyan rifting, and Syrian Arc inversion and contraction. The Neotethyan rifting phase is recorded by the strata of supersequences A and B. Faulting took place during the Anisian (Mid-Triassic), continued through the Liassic and ceased during the Mid-Jurassic. The basin opened in a NW-SE direction, between the Eratosthenes Seamount and the Levant margin of the Arabian Massif, at an angle of about 30° to the present-day shoreline. No indications for sea-floor spreading were found in the present study. Late Triassic to Liassic volcanic rocks of assumed intraplate origin accumulated in the northeastern part of the basin. It is hypothesized that the basin originated as an intracontinental rift associated with the nucleation of an oceanic spreading centre, but reached only an early magmatic phase. An inversion and contraction phase, associated with closing of the Neotethyan ocean system, is recorded by supersequences C and D. The contractional structures of the Syrian Arc extend in a wide and elevated fold belt along the eastern edge of the deep-marine basin. These structures were formed by the inversion of pre-existing normal faults. The folding occurred in several pulses starting in the Senonian and ending in the Miocene. The western limit of the main fold belt, located 50–70 km west of the coastline, is defined by a transition in crustal properties. Supersequences E and F record the Late Cenozoic history of the basin. A Messinian, evaporitic basin was limited to the east by the elevated and uplifted Syrian Arc fold belt composed of older, Oligocene to Mid-Miocene strata. During highstand episodes, the Messinian evaporites were deposited on the entire slope and within canyons incised into the shelf. High sedimentation rates of Nilotic and locally derived sediments during the Plio-Pleistocene resulted in the development of extensive submarine deltas and basinward progradation of the Levant shelf break.
Tectonic-sedimentary evolution of the western margin of the Mesozoic Vardar Ocean: evidence from the Pelagonian and Almopias zones, northern Greece
Authors: Sharp Ian R. , Robertson Alastair H. F.
Published: April 2008

The Vardar Zone documents the Mesozoic-Early Cenozoic evolution of several small oceanic basins and a complex history of terrane assembly. Following a Hercynian phase of deformation and granitic intrusion within the Pelagonian Zone to the west, the Vardar Zone rifted in Permian-Triassic time, with the creation of an oceanic basin (Almopias Ocean) during the Late Triassic-Early Jurassic. During the Mid-Jurassic, this ocean subducted northeastwards beneath the Paikon Zone and the Serbo-Macedonian Zone, giving rise to arc volcanism and back-arc rifting. A second ocean basin, the Pindos Ocean, opened to the west of a Pelagonian microcontinent, also during Late Triassic-Early Jurassic time. During the Mid-Late Jurassic, ophiolites were emplaced northeastwards (in present co-ordinates) from the Pindos Ocean onto the Pelagonian microcontinent, forming the Pelagonian ophiolitic mélange within a flexural foredeep. This emplacement is dated at pre-Late Oxfordian-Early Kimmeridgian from the evidence of corals within neritic carbonates that depositionally overlie the emplaced ophiolitic rocks in several areas. Related greenschist- or amphibolite-facies metamorphism is attributed to deep burial following trench-margin collision and the attempted subduction of the Pelagonian continent. An inferred phase of NNW-SSE displacement, also of pre-latest Jurassic age, imparted a regionally persistent stretching lineation and related ductile fabric, apparently related to post-collisional strike-slip. The Pelagonian Zone and its emplaced ophiolitic rocks then underwent extensional exhumation during Late Jurassic-Early Cretaceous time. The western margin of the Vardar Zone experienced extensional (or transtensional) faulting, neritic carbonate and terrigenous clastic deposition, and intermediate-silicic magmatism during Late Jurassic-Early Cretaceous time. Oceanic crust (Meglenitsa Ophiolite) formed further east in the Vardar Zone during Late Jurassic-Early Cretaceous time, possibly above a subduction zone. A near-margin setting is suggested by the presence of a deep-water terrigenous cover, probably derived from the Paikon continental unit to the east. The Vardar Zone as a whole finally closed related to eastward subduction beneath Eurasia, culminating in collision with the Pelagonian microcontinent during latest Cretaceous-Eocene time, as recorded in foreland basin development, HP-LT metamorphism, ophiolite emplacement and large-scale westward thrusting. In contrast to models that suggest closure of the Vardar Ocean in the Mid-Late Jurassic, followed by reopening of a Cretaceous ocean, we believe that the Vardar Ocean remained partly open from Triassic to Late Cretaceous-Early Cenozoic time.
Typical phases of pre-failure damage in granitic rocks under differential compression
Authors: Lei Xinglin
Published: April 2008

The evolution of pre-failure damage in brittle rock samples subjected to differential compression has been investigated by means of acoustic emission (AE) records. The experimental results show that the damaging process is characterized by three typical phases of microcracking activity: primary, secondary, and nucleation. The primary phase reflects the initial activity of pre-existing microcracks, and is characterized by an increase, with increasing stress, both in event rate and
b
value. The secondary phase involves subcritical growth of the microcrack population, revealed by an event rate increase and a dramatic decrease of the
b
value. The nucleation phase corresponds to initiation and accelerated growth of the ultimate macroscopic fracture along one or more incipient fracture planes. During the nucleation phase, the
b
value decreases rapidly to the global minimum value around 0.5. The temporal variation of
b
in every phase clearly correlates with grain size of the test sample, hence indicating that a comparatively larger grain size results in a lower
b
value. In order to investigate the fracture mechanism of each phase, a damage model was tested by employing the constitutive laws of subcritical crack growth of crack populations with a fractal size distribution.
Miocene to present major fault linkages through the Adriatic indenter and the Austroalpine—Penninic collisional wedge (Alps of NE Italy)
Authors: Massironi M. , Zampieri D. , Caporali A.
Published: April 2008

From the Miocene onwards, the Alpine and South Alpine domains have been closely coupled within the framework of fault kinematics and geodynamic processes related to the continuing indentation of the Adria plate against Europe. In this study, the post-Oligocene evolution of a wide sector of the North Adriatic indenter border and nearby areas is re-examined in an extensive regional context by means of structural, geochronological and seismotectonic data. The Adria northern edge roughly corresponds to the Periadriatic lineament which is characterized in the central—eastern Alps by an abrupt change of orientation from east—west to NNE—SSW at the North Giudicarie line. Several strike-slip fault linkages have developed along the northern and southern sections of this major fault since the Miocene. In the Alpine domain, fault connections facilitated tectonic unroofing of the deeper nappes (Penninic units) in the Tauern window and a westward crustal stretching of the upper nappes (Austroalpine units) in the Brenner detachment hanging wall. In the Southern Alps, several fault linkages are observed, which are related to reactivation of inherited faults by the indentation process. These processes began during the early Miocene, were fully developed in the latest Miocene—early Pliocene, and are very probably still continuing. The final result is a complex shear zone of 250 km length, that in the southern part is considered as an incipient divide between the nearly stationary westernmost part of the North Adriatic indenter and the still northward-pushing main body of the Adria plate.
Log-ratios and geochemical discrimination of Scottish Dalradian limestones: a case study
Authors: Thomas C. W. , Aitchison J.
Published: April 2008

Geochemical data are used widely to help correlate lithostratigraphical sequences, particularly where they are unfossiliferous and/or affected by metamorphism and deformation. In this study, geochemical data for variably impure metamorphosed limestones from the Neoproterozoic — Cambrian Dalradian Supergroup of Scotland have been used to aid lithostratigraphical discrimination and correlation in a region where apparently similar sequences crop out in widely separated regions affected by major deformation.

The key problem in the statistical analysis of geochemical data is that the data are constrained to a constant sum and cannot, therefore, be analysed in raw form by conventional statistical techniques. To overcome this problem, the data have been transformed into log-ratios.

Subsequent statistical analysis of the transformed data focuses on determining the simplest sub-composition that effectively discriminates between the limestones. The results show that the Fe
2
O
3
-MgO-CaO subcomposition is sufficient in this regard, with the additional benefit that it reflects the composition of the carbonate component in the limestones. Mann-Whitney tests of the log-ratio Fe
2
O
3
/MgO show that limestones from most different lithostratigraphical levels are statistically different from each other at high levels of significance. The results have clarified interpretations of the lithostratigraphy and subsequent interpretations of the tectonic history of the region.
Ternary sandstone composition and provenance: an evaluation of the ‘Dickinson model’
Authors: Weltje G. J.
Published: April 2008

A popular model proposed by W. R. Dickinson and co-workers in the early 1980s relates the composition of sandstones to the plate-tectonic setting of the sedimentary basins in which they were deposited. The present study is devoted to revision and testing of the ‘Dickinson model’ based on the original data which comprise 11 000 thin sections point-counted by hundreds of different operators over a period of three decades. Statistical analyses based on Aitchison’s additive log-ratio transformation are used to obtain an optimal partitioning of ternary compositional spaces into ‘provenance fields’ and combined with stochastic simulation to assess the success ratio of the optimized ‘Dickinson model’. Results indicate that differences between the grand means of each of the three major provenance associations (continental block, magmatic arc and recycled orogen) are highly significant, whereas overall inferential success ratios range from 64% to 78% in the four ternary systems studied. Current methods of dealing with sands of mixed provenance are unsatisfactory. To improve provenance models, the use of ternary subcompositions should be replaced by analyses of the full six-part (Qm, Qp, P, K, Lv, Ls) composition, and their covariance structure could be employed to ‘unmix’ samples into end-member provenance types.
Two remarkable Permian petrified forests: correlation, comparison and significance
Authors: Rössler Ronny
Published: April 2008

Two outstanding Permian petrified forests, those of Chemnitz, in Germany, and northern Tocantins, in Brazil, contribute to the understanding of the composition, peculiarities and dynamics of Early Permian wetland ecosystems. These assemblages represent seasonally influenced, essentially contemporaneous but quite comparable, tree-fern-dominated plant communities in the Northern and Southern Hemispheres. The Chemnitz fossils are embedded in coarse-grained pyroclastics of the Zeisigwald Tuff Horizon (Leukersdorf Formation, Erzgebirge Basin), whereas those of Tocantins occur in different lithofacies of a cyclic alluvial succession (Pedra de Fogo/Motuca formations, Parnaiba Basin). The outstanding three-dimensional preservation of particularly large fossil remains, made possible by siliceous permineralization, provides the opportunity to study the gross morphology, anatomy and internal organization of plant tissues, as well as taphonomical and ecological aspects of late Palaeozoic plants in a way not allowed by other preservational states. Recent studies of newly collected material permit a re-evaluation of the popular reconstructions of Early Permian floras. Various plant-plant and plant-animal interactions add to our understanding of two diverse lowland ecosystems that, irrespective of their different palaeogeographic position and taphonomic modes, show striking similarities.
ITRAX: description and evaluation of a new multi-function X-ray core scanner
Authors: Croudace Ian W. , Rindby Anders , Rothwell R. Guy
Published: April 2008

A new automated multi-function core scanning instrument, named ITRAX, has been developed that records optical, radiographic and elemental variations from sediment half cores up to 1.8 m long at a resolution as fine as 200 μm. An intense micro-X-ray beam focused through a flat capillary waveguide is used to irradiate samples to enable both X-radiography and X-ray fluorescence (XRF) analysis. Data are acquired incrementally by advancing a split core, via a programmable stepped motor drive, through the flat, rectangular-section X-ray beam. Traditional XRF determination of element composition in sediments provides high-quality data, but it takes a considerable time and normally consumes gram quantities of material that is often only available in limited quantities. The ITRAX core scanner non-destructively collects optical and X-radiographic images, and provides high-resolution elemental profiles that are invaluable for guiding sample selection for further (destructive) detailed sampling. This paper presents a description of the construction, characteristics and capabilities of the ITRAX system. High-resolution ITRAX data obtained from sediment cores are also presented and compared with results from traditional wavelength-dispersive XRF analysis at lower resolution. Finally, some recent technical developments linked to the second-generation ITRAX are presented.
A geochemical application of the ITRAX scanner to a sediment core containing eastern Mediterranean sapropel units
Authors: Thomson J. , Croudace I. W. , Rothwell R. G.
Published: April 2008

The ITRAX micro-X-ray fluoresence (XRF) core scanner has been applied in a sediment geochemistry investigation. The core sections selected contain examples of the organic-rich sedimentary units (sapropels) that form periodically in the eastern Mediterranean basin. Sapropels are visually obvious from their dark coloration, but the ITRAX X-radiograph also reveals physical property changes that result mainly from the high pore-water content of sapropels. A consideration of wavelength-dispersive XRF data from discrete samples of the most recent sapropel (S1) was made along with the set of elements reported by the ITRAX instrument’s energy-dispersive XRF system over core sections containing S1. This allowed selection of a suite of eight inter-element ratios or element integrals through which characteristic features of sapropel development and geochemistry were revealed. While recognizing that the measured XRF element integrals from the ITRAX do not have an exact constant relationship with element concentration over changing sediment types, this combination of ratios provides significant information for geochemical interpretation. These include evidence for: (i) the presence of high C
org
contents in the visual sapropel from Ba/Ti and Br/Cl ratios; (ii) a thinning of the original sapropel thickness by post-depositional oxidation from Mn/Ti and Cu/Ti ratios; (iii) pyrite authigenesis in the residual visual sapropel from Fe/Ti and S/Cl ratios and the As integral; and (iv) aragonite formation in and around the sapropel from the Sr/Ca ratio. These same ratios were then used to interpret ITRAX data from a deeper section of the same core containing the older sapropel S3, where the same characteristics, including the relict post-depositional oxidative thinning of the original unit, could be identified with only minor differences of detail. Directions of supply of Fe, As and Cu into the sapropels could be inferred from profile shapes.
Locking of southward extrusion in favour of rapid crustal-scale buckling of the Greater Himalayan sequence, Nar valley, central Nepal
Authors: Godin L. , Gleeson T. P. , Searle M. P. , Ullrich T. D. , Parrish R. R.
Published: April 2008

The South Tibetan detachment system (STDS) bounds the upper limit of the Greater Himalayan sequence (GHS), which consists of the exhumed middle crust of the Himalaya. In the Annapurna range of central Nepal, the GHS comprises a sequence of amphibolite-grade augen gneisses with a 3.5 km thick leucogranite at the higher structural levels (Manaslu granite). Two major low-angle normal-sense shear zones have been mapped. The Chame detachment has similar grade metamorphic rocks above and below and is interpreted as a ductile shear zone wholly within the GHS. The Phu detachment is a ductile-brittle normal fault which wraps around the top of the Manaslu leucogranite and defines the uppermost, youngest strand of the STDS, placing folded unmetamorphosed Palaeozoic rocks of the Tethyan sedimentary sequence above the GHS. Our data indicate that ductile flow and southward extrusion of the GHS terminated with cessation of movement on the brittle upper strand of the Phu detachment at
c.
19 Ma, which was followed almost immediately by crustal-scale buckling. Argon thermochronology reveals that the bulk of the metamorphic rocks and lower portions of the Tethyan sedimentary sequence in the Nar valley cooled through the hornblende, biotite and muscovite closure temperatures at
c.
16 Ma, suggesting very rapid cooling rates. The thermochronology results indicate that this cooling occurred 2–3 million years earlier than in the frontal part of the extruded GHS. Although the extrusion in the frontal part of the GHS must have locked at the same time as in the Nar valley, the exhumation there was slower, and most probably only assisted by erosion, rather than by rapid folding as is the case in the Nar valley. This buckling indicates a step northward in deformation within the Himalayan belt, which may be a response to a lower deforming taper geometry in the foreland.
Low-dose spironolactone reduces reactive oxygen species generation and improves insulin-stimulated glucose transport in skeletal muscle in the TG(mRen2)27 rat
Authors: Lastra Guido , Whaley-Connell Adam , Manrique Camila , Habibi Javad , Gutweiler Alex A. , Appesh Lama , Hayden Melvin R. , Wei Yongzhong , Ferrario Carlos , Sowers James R.
Published: April 2008

Renin-angiotensin-aldosterone system (RAAS) activation mediates increases in reactive oxygen species (ROS) and impaired insulin signaling. The transgenic Ren2 rat manifests increased tissue renin-angiotensin system activity, elevated serum aldosterone, hypertension, and insulin resistance. To explore the role of aldosterone in the pathogenesis of insulin resistance, we investigated the impact of in vivo treatment with a mineralocorticoid receptor (MR) antagonist on insulin sensitivity in Ren2 and aged-matched Sprague-Dawley (SD) control rats. Both groups (age 6–8 wk) were implanted with subcutaneous time-release pellets containing spironolactone (0.24 mg/day) or placebo over 21 days. Systolic blood pressure (SBP) and intraperitoneal glucose tolerance test were determined. Soleus muscle insulin receptor substrate-1 (IRS-1), tyrosine phosphorylated IRS-1, protein kinase B (Akt) phosphorylation, GLUT4 levels, and insulin-stimulated 2-deoxyglucose uptake were evaluated in relation to NADPH subunit expression/oxidase activity and ROS production (chemiluminescence and 4-hydroxy-2-nonenal immunostaining). Along with increased soleus muscle NADPH oxidase activity and ROS, there was systemic insulin resistance and reduced muscle IRS-1 tyrosine phosphorylation, Akt phosphorylation/activation, and GLUT4 expression in the Ren2 group (each P < 0.05). Despite not decreasing blood pressure, low-dose spironolactone treatment improved soleus muscle insulin signaling parameters and systemic insulin sensitivity in concert with reductions in NADPH oxidase subunit expression/activity and ROS production (each P < 0.05). Our findings suggest that aldosterone contributes to insulin resistance in the transgenic Ren2, in part, by increasing NADPH oxidase activity in skeletal muscle tissue.
Chronic l-arginine administration increases oxidative and nitrosative stress in rat hyperoxaluric kidneys and excessive crystal deposition
Authors: Huang Ho-Shiang , Ma Ming-Chieh , Chen Jun
Published: April 2008

Hyperoxaluric kidneys show an impaired diuretic response to acute infusion of l-arginine. In this study, we examined the chronic effect of l-arginine supplementation on CaOx crystal formation in hyperoxaluric rat kidneys. Eight groups were tested: control (received drinking water), L group (received l-arginine, 0.6%), LN group [received NG-nitro-l-arginine methyl ester (l-NAME, 10 mg/kg)], L + LN group (received l-arginine + l-NAME), HP group [received hydroxyl-l-proline (HP, 5%) mixed with chow to induce hyperoxaluria], L + HP group (received HP + l-arginine), HP + LN group, and L + HP + LN group. The duration was 42 days, and each group had eight animals. Urinary biochemistry and renal CaOx amounts were measured, as well as renal expressions of nitric oxide synthase (NOS) isoforms and NAD(P)H oxidase. The distribution of inducible NOS (iNOS), NAD(P)H oxidase, ED1-positive cells, and nitrotyrosine was examined by immunohistochemical and immunofluorescence studies, whereas superoxide production from the kidneys was examined by fluorescence spectrometric assay. Compared with the HP group, the L + HP group had excessive CaOx crystal accumulation and enhanced endothelial NOS (eNOS), iNOS, and NAD(P)H oxidase protein expression in the kidney. Urinary excretion of nitrotyrosine was markedly increased. Increased superoxide formation in the L + HP kidney was derived from NAD(P)H oxidase and uncoupled eNOS, and increased nitrotyrosine formation might derive from iNOS and ED1-positive cells that gathered around the CaOx crystals. l-NAME cotreatment (L + HP + LN group) reduced renal oxidative nitrosative stress and tubular damage, which were induced by L + HP. The results showed that chronic l-arginine treatment to the hyperoxaluric kidney with massive CaOx crystal deposition may have a toxic effect by enhancing intrarenal oxidative and nitrosative stress.
The in vivo gene expression signature of oxidative stress
Authors: Han Eun-Soo , Muller Florian L. , Pérez Viviana I. , Qi Wenbo , Liang Huiyun , Xi Liang , Fu Chunxiao , Doyle Erin , Hickey Morgen , Cornell John , Epstein Charles J. , Roberts L. Jackson , Van Remmen Holly , Richardson Arlan
Published: April 2008

How higher organisms respond to elevated oxidative stress in vivo is poorly understood. Therefore, we measured oxidative stress parameters and gene expression alterations (Affymetrix arrays) in the liver caused by elevated reactive oxygen species induced in vivo by diquat or by genetic ablation of the major antioxidant enzymes CuZn-superoxide dismutase ( Sod1) and glutathione peroxidase-1 ( Gpx1). Diquat (50 mg/kg) treatment resulted in a significant increase in oxidative damage within 3–6 h in wild-type mice without any lethality. In contrast, treatment of Sod1−/−or Gpx1−/−mice with a similar concentration of diquat resulted in a significant increase in oxidative damage within an hour of treatment and was lethal, i.e., these mice are extremely sensitive to the oxidative stress generated by diquat. The expression response to elevated oxidative stress in vivo does not involve an upregulation of classic antioxidant genes, although long-term oxidative stress in Sod1−/−mice leads to a significant upregulation of thiol antioxidants (e.g., Mt1, Srxn1, Gclc, Txnrd1), which appears to be mediated by the redox-sensitive transcription factor Nrf2. The main finding of our study is that the common response to elevated oxidative stress with diquat treatment in wild-type, Gpx1−/−, and Sod1−/−mice and in untreated Sod1−/−mice is an upregulation of p53 target genes ( p21, Gdf15, Plk3, Atf3, Trp53inp1, Ddit4, Gadd45a, Btg2, Ndrg1). A retrospective comparison with previous studies shows that induction of these p53 target genes is a conserved expression response to oxidative stress, in vivo and in vitro, in different species and different cells/organs.
Thin Metal Film Sensors
Authors: Tellier C. R.
Published: April 2008

During the last decade some progress have been made in the field of sensors using thin film techniques.
In particular thin metal film strain gauges and thin film temperature sensors based on the temperature
dependent resistivity of metal are now commonly used. But changes in other transport parameters with
various measurands are also useful for the design of metal film sensors. Difficulty arises in thin film
techniques when structural defects are frozen in films.

Intensive theoretical investigations are carried out to explain the effect of grain‐boundary and external
surface scatterings on transport parameters. Accordingly the main results are presented to specify the
influence of film structure on the sensor performance. The grain‐boundary effects are discussed
according to applications of metal film sensors. Theoretical predictions are analyzed in terms of
sensitivity, thermal stability and long term behavior. But other problems induced by the presence of grain
boundaries or point defects are also discussed, in particular problems associated with bulk diffusion,
electromigration induced failures or intrinsic stresses.
Voltage Degradation Model of Thin Film Capacitors
Authors: Berlicki T. M.
Published: April 2008

A degradation model of thin film capacitors is presented. This model takes into consideration that:
(a) the damage rate dD/dt is a function of the damage value D, and (b) the critical damage Dc is a
function of working voltage. On the base of this model, the short term breakdown voltage and its
distribution is defined. The experimental data presented conforms with the described model.