bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subglacial volcanic features beneath the West Antarctic Ice Sheet interpreted from aeromagnetic and radar ice sounding
Authors: Behrendt John C. , Blankenship D. D. , Morse D. L. , Finn C. A. , Bell R. E. 
Published: September 2007

Abstract

The West Antarctic Ice Sheet (WAIS) flows through the volcanically active, late Cenozoic West Antarctic rift system. Active subglacial volcanism and a vast (> 10
6
km
3
) extent of subglacial volcanic structures have been interpreted from aerogeophysical surveys over central West Antarctica in the past decade, combined with results from 1960s and 1970s aeromagnetic profiles over the WAIS. Modelling of magnetic anomalies constrained by radar ice sounding shows volcanic sources at the base of the ice throughout large areas, whose subglacially erupted hyaloclastite edifices have been eroded by moving ice, as in Iceland. The 1800 m-high divide of the WAIS is underlain by the 400 km-long volcanic Sinuous Ridge, which rises above sea level; most hyaloclastite edifices there have also been glacially removed, indicating migration of the ice divide through time. Northeast of the divide of the WAIS there is a 400-nT positive magnetic anomaly over the shallowest, most rugged bedrock topography (elevation +380m above sea level), probably comprising subaerially erupted flows erupted when the Sinuous Ridge area was deglaciated. Uplift of the Sinuous Ridge may have forced the advance of the WAIS. Other aspects of the subglacial volcanism in Antarctica can be observed in Iceland and have a direct bearing on our understanding of the subglacial conditions of the WAIS and its dynamics.
Spectroscopic and geochemical analyses of ferrihydrite from springs in Iceland and applications to Mars
Authors: Bishop J. L. , Murad E. 
Published: September 2007

Abstract

Ferrihydrite samples were collected from a thermal spring and a cold stream in the Landmannalaugar region of Iceland. Chemical and spectroscopic analyses have been performed on the air-dried and fine-grained fractions of these samples. The ferrihydrite from the cold stream is a pure sample, containing small amounts of Ca, P and Si. The ferrihydrite from the thermal spring is a less pure sample, containing larger amounts of amorphous Si and P with some of the Si incorporated in the ferrihydrite structure. The spectral character of these Icelandic ferrihydrites is compared with those of synthetic ferrihydrites and other iron oxide/oxyhydroxide minerals. Ferrihydrite is characterized by a broad Fe
3+
excitation band near 10 900 cm
−1
(
c.
0.92 μm), a strong Fe-O vibrational feature near 475 cm
−1
(
c.
21 μm), and multiple bands due to H
2
O and OH. Highly pure ferrihydrite has a pair of spectral bands near 1400 and 1500 cm
−1
(
c.
7 μm). Natural ferrihydrites frequently exhibit an extra band near 950–1050 cm
−1
(
c.
10 μm) that is attributed to Si-O bonds. Hydrothermal springs may have been present at one time on Mars in association with volcanic activity. Ferrihydrite formation in such an environment may have contributed to the ferric oxide-rich surface material on Mars.
Distinguishing palagonitized from pedogenically-altered basaltic Hawaiian tephra: mineralogical and geochemical criteria
Authors: Schiffman P. , Southard R. J. , Eberl D. D. , Bishop J. L. 
Published: September 2007

Abstract
Palagonitization is a common, but imperfectly defined process that greatly modifies the physical and chemical properties of glassy basaltic tephra deposited in subaquatic/subglacial environments on Earth and perhaps Mars. It also results in textures and mineralogies that are distinct from other forms of (mainly pedogenic) low temperature alteration. Specifically, the process of palagonitization (1) initially results in the formation of ‘palagonitized glass’, a quasi- or nano-crystalline, rind-like material that contains smectite, as well as lesser amounts of other clays (e.g. serpentine), and (2) eventually results in consolidation of tephra, mediated through the accretion of palagonitized glass and later-formed authigenic cements. Conversely, pedogenic weathering of glassy basaltic tephra is characterized by disaggregation of tephra, and formation of a wide range of pedogenic products, including layer silicates (although not primarily smectite), short-range-order aluminosilicates and oxyhydroxides, whose composition reflects the intensity of the weathering environment. These mineralogical and textural properties can be readily recognized through a variety of techniques including electron microscopy/microprobe analysis, reflectance spectroscopy, X-ray diffraction and soil chemistry. Analyses of samples collected from the summit regions of Kilauea and Mauna Kea volcanoes on the island of Hawaii are presented here in order to illustrate differences between palagonitization and pedogenic weathering of glassy basaltic tephra. In the young Hawaiian tephras studied, palagonitization has occurred in response to hydrothermal activity shortly after deposition. Although some, non-hydrothermally affected tephras may eventually become palagonitized, those that have been strongly desilicated by intense pedogenic weathering will probably never become palagonitized.
Identifying bio-interaction with basaltic glass in oceanic crust and implications for estimating the depth of the oceanic biosphere: A review
Authors: Furnes H. , Thorseth I. H. , Torsvik T. , Muehlenbachs K. , Staudigel H. , Tumyr O. 
Published: September 2007

Abstract

The alteration of basaltic glass in the volcanic part of the oceanic crust is, to a substantial extent, biologically mediated. Evidence of microbial interaction with basaltic glass can be provided by a number of independent observations, such as: (1) Textures at the alteration front, generated by dissolution of the glass and subsequent precipitation. These bio-generated textures can be defined as a granular type (dominant) and a tubular type, and show size and form which are compatible with microbial etching. (2) Filament-like structures, representing organic remains, appear in connection with bio-generated textures. (3) Within areas of the bio-generated textures, particularly at the alteration front, DNA and ribosomal RNA have been demonstrated to be present in relatively young samples. (4) X-ray mapping shows that carbon and nitrogen invariably appear within the bio-generated textures, in young samples most strongly enriched at the alteration front. (5) Carbon isotopes (δ
13
C) in carbonates extracted from the glassy margin of pillows show highly variable values which can be explained in terms of bio-fractionation of the
12
C and
13
C isotopes. Estimates of the proportion of bio-genetic alteration products of basaltic glass, on the basis of textural relationships, suggest that bio-alteration is dominant compared to abiotic alteration in the upper 300 m of the oceanic crust, and declines to become insignificant at a depth of about 500 m.
Thermal expansion and its control on the durability of marbles
Authors: Zeisig Annette , Siegesmund Siegfried , Weiss Thomas 
Published: September 2007

Abstract
Marbles as ornamental stones as well as in their natural environments show complex weathering phenomena. The physical weathering of marbles due to thermal treatment is often discussed as the initial stage of deterioration. Eighteen different well-known marble types were selected to quantify experimentally the effect of heating and cooling within the temperature range of 20°C to 85°C while three different ramps at 40°C, 60°C and 85°C were performed. The marbles differ in composition from calcitic to dolomitic as well as in their fabrics. The average grain size varies from 50 μm up to 3 mm, while the grain boundary geometry differs from a granoblastic foam structure to those with weakly inequigranular-amoeboid structure. The lattice preferred orientations are also highly different in c-axis and a-axis distributions. With respect to the heating and cooling cycles three distinct groups of marbles can be distinguished: Type I is characterized by an isotropic thermal expansion (α) and large isotropic residual strain (permanent length changes); Type II exhibits an anisotopic α and no or small isotropic residual strains; while Type III shows an anisotropic α and anisotropic residual strain. Most samples show deteriorations due to thermal treatment, which cannot be uniformly explained without taking into account the rock fabrics. The magnitude and directional dependence of the thermal expansion is mainly controlled by the lattice and shape preferred orientation. The composition, grain size, grain boundary geometry and pre-existing microcracks modify in a more complex way the progressive loss of cohesion due to dilatancy caused by the anisotropic thermal expansion.
Experimental study on the variation in porosity of marble as a function of temperature
Authors: Malaga-Starzec Katarina , Lindqvist Jan E. , Schouenborg Björn 
Published: September 2007

Abstract
The current condition of many building claddings and historical monuments clearly reveals that they are not immune to weathering action due to daily or seasonal temperature changes. In this study, porosity changes by variation in temperature have been investigated for two marble types: one calcitic and one pure dolomitic. The samples were exposed to ascending temperatures from 40 to 200°C. The results indicate that intergranular decohesion starts between 40 and 50°C. Some significant differences in temperature response for these two marble types could be distinguished. The temperature range 40–60°C is easily reached on building surfaces in most European countries during the summer months. A better understanding of the effect that temperature has on the porosity of marble could be used to develop a methodology for assessing suitable conditioning of marble before testing as well as to suggest appropriate impregnation and/or surface treatments of buildings and outdoor sculptures.
Anisotropic technical properties of building stones and their development due to fabric changes
Authors: Strohmeyer Daniel , Siegesmund Siegfried 
Published: September 2007

Abstract
Technical properties of building stones are of critical importance in applied geosciences such as engineering geology, and also with respect to construction or building physics. Among the many factors which control the technical properties, special importance is given to the rock fabrics influencing the anisotropy of these technical properties. To demonstrate this relationship a sequence of mylonitic rocks, i.e. metagranitoid progressively deformed to mylonite and ultramylonite, was selected. The mineralogical and chemical composition of the protolith and mylonite is nearly identical. All investigated parameters (tensile strength, compressive strength, abrasive strength, magnetic susceptibility and ultrasound wave velocities) are anisotropic and finally controlled by the mineralogical composition and the different fabric elements like microstructural features, the crystallographic and shape preferred orientations and the state of microcracking. The development of the rock fabric with mylonitization, in particular the preferred orientation of mica, seems to be most important for the directional dependence of rock physical properties, at least in mica-rich rocks. However, various sets of microcracks, the degree of grain size reduction, the intensity of the foliation and the compositional layering can significantly modify the results. The interaction of superimposing parameters for different technical properties does not allow any simple cross-correlation.
Impact of endolithic biofilms on carbonate rock surfaces
Authors: Pohl Wolfhart , Schneider Jürgen 
Published: September 2007

Abstract
Almost all natural carbonate rock surfaces as well as carbonate building stones are ubiquitously colonized by micro-organisms such as cyanobacteria, chlorophyceae, fungi and lichens. This colonization occurs endolithically, mostly euendolithically, through active penetration into the rock. Freshly exposed surfaces, such as in glacial forelands of the Dachstein Mountains (Austria) show mature, fully differentiated endolithic colonization after only 15 years of atmospheric exposure. After a time period of 100 to 150 years, coverage of carbonate rock surfaces by endolithic biofilms is almost complete.
Most endolithic biofilms (lichens) show similar internal architecture. Under a residual, protective carbonate rock layer are photobiontic micro-organisms. They occupay a well defined zone between 150 to 300 μm beneath the rock surface. In this zone up to 60% of the rock substrate is replaced by microbial biomass. Within the photobiontic layer a constant recycling of cells takes place, where bacteria act as decomposers. Deeper beneath the substrate develops an initially dense, then progressively thinning hyphal network of the mycobiont (i.e. a fungus).
Significant differences in amounts and distribution of biomass were observed and quantified which are regional and climatic, but also local and surface age-controlled. Temperature, irradiation and water availability are presumed to be the primary factors. Evidence for a biogenic mechanical surface destabilization (grain loss, desquamation, exfoliation) as observed on siliciclastic rocks, was not found on natural carbonate rock surfaces.
The ‘life strategy’ of endolithic biofilms is adapted to conserve their substrates. It commences with quick emplacement within the rock, initially causing some material loss. However, as soon as the endolithic biofilm is established, approaching an equilibrium with the climatic and ecological conditions, it behaves essentially conservatively: it does not continue with growth increments or habitat enlargement.

This adaptation of euendolithic biofilms has a generally
more protective
than destructive impact on their carbonate rock substrates. These observations are important for a better understanding of weathering and deterioration processes, applicable to protection policies and maintenance of cultural monuments.
Biodeterioration of calcareous and granitic building stones in urban environments
Authors: Schiavon Nick 
Published: September 2007

Abstract
Scanning electron microscopy in secondary (SEM) and back-scattered (BSEM) mode associated with energy-dispersive X-ray spectroscopy has been used to investigate decay features associated with biological colonization of calcareous and granitic building stones in monuments and rock outcrops in the UK, Portugal and Spain. In combination with physical decay caused by lichen hyphae penetrating the stone substrate, this study reveals how chemical attack by organic acid exudates derived from metabolic activity of lichens and leading to the crystallization and growth of inorganic salt compounds within the stone microfabric is contributing to the destruction and weakening of the building stone surface. BSEM analysis is particularly useful in showing extensive dissolution and corrosion of mineral surfaces underneath biological patinas. Both Ca-sulphate (gypsum) and Ca-oxalate (weddellite) precipitates are clearly associated with the presence of fungal hyphae and bacterial activity particularly in the case of calcareous building stones; the Ca-oxalates present in the example examined are then the result of biomineralization processes and do not derive from past restoration treatments or from air pollution as suggested by many authors. In urban locations, lichenous cover may facilitate the deposition of particulate airborne pollutants on the stone surface. Biological patinas are by no means forming a protective layer on the biocolonized substrate; as is the case with sulphate or non-sulphate soiling patinas from urban air pollution, they act as localized sites of intense desegregation of the stone underneath. Their promot (but careful) removal and a biocidal treatment of the infested sites in the building is then suggested to avoid permanent loss of detail, particularly harmful in the case of carved surfaces.
Biofilms and their extracellular environment on geomaterials: methods for investigation down to nanometre scale
Authors: Hoppert M. , Berker R. , Flies C. , Kämper M. , Pohl W. , Schneider J. , Ströbel S. 
Published: September 2007

Abstract
On solid surfaces of building material, micro-organisms form a tightly attached layer that may affect the underlying substratum. The biofilm is mainly composed of cells and extracellular polymeric substances (EPS; mostly various polysaccharides). Attachment of the mature biofilm on the substratum is mediated by the EPS. For analysis by transmission electron microscopy, the biofilm structure must be maintained by appropriate methods that stabilize the organisms and especially the EPS. Specially adapted preparation techniques allow detachment of a surface biofilm or dissolution of the substratum without affecting the biofilm structure. The cellular and extracellular structures are retained in such a way that they are detectable by various specific marker systems.
Limestone weathering of historical monuments in Cairo, Egypt
Authors: Fitzner Bernd , Heinrichs Kurt , La Bouchardiere Dennis 
Published: September 2007

Abstract
Since pharaonic times local limestones have been used in Cairo for monument construction. Weathering damage on many historical stone monuments in Cairo is alarming. Studies on properties and weathering behaviour of the limestones were carried out by means of laboratory tests and in situ investigation of many historical monuments. The laboratory studies reveal considerable petrographical variations for the Middle Eocene limestones. The limestone weathering was assessed with respect to weathering forms, weathering products and weathering profiles. A classification scheme of weathering forms and their intensities was tailored to optimal applicability for all Cairo historical monuments constructed from limestones. Monument mapping has been applied for the detailed registration of weathering forms and as a basis for the quantitative rating of stone damage by means of damage categories and damage indices. For the historical monuments in the centre of Cairo the combined evaluation of weathering forms, weathering products and weathering profiles shows clear correlations between the development of weathering damage and salt loading of the limestones as a consequence of air pollution and rising humidity. They demonstrate the need and urgency for monument preservation measures.
Characterizing the construction materials of a historic building and evaluating possible preservation treatments for restoration purposes
Authors: Alvarez de Buergo Ballester M. , Fort González R. 
Published: September 2007

Abstract
The palace of Nuevo Baztán is a state-designated historic monument in central Spain built in the early eighteenth century. The main building material used in its facades is limestone. The aim of this investigation was to characterize the limestone, defining deterioration mechanisms contributing to the decay of the stone facades and testing a series of potential preservation treatments. The limestone is a biosparite; two microfacies were identified according to microscopic differences (limestones A and B) with distinct petrophysical characteristics mainly due to their different pore systems. Primary deterioration mechanisms were identified as those related to cycles of thermal and hygric stress, biodeterioration and those associated with structural movements. Main decay forms in the surface of the stone are erosion with material loss, spalling and flaking, chromatic alteration, fissures and biodeterioration. Conservation products prossessing water-repellent properties were therefore considered. From an initial selection of ten products, two siloxane-based products were ultimately determined to be the most effective on the basis of chromatic variables, water vapour permeability, water-stone contact angle, scanning electron microscope observations and durability (artificial ageing tests). Both products reduce water absorption rates and are expected to slow the rate of limestone decay. This study also demonstrates the value of advance testing of potential treatment methods before application in the field.
Investigations into provenance and properties of ancient building sandstones of the Zittau/Görlitz region (Upper Lusatia, Eastern Saxony, Germany)
Authors: Michalski Steffen , Götze Jens , Siedel Heiner , Magnus Michael , Heimann Robert B. 
Published: September 2007

Abstract
Mineralogical and technical properties were investigated of building sandstones from ancient monuments of the Zittau/Görlitz region (Germany) as well as material from potential source quarries. The complex study included macroscopic rock description and detailed investigations by polarizing microscopy (phase composition, texture, grain size distribution), cathodoluminescence (quartz types, feldspar and kaolinite content), scanning electron microscopy (accessories, pore cement, diagenetic grain surface features) as well as the analysis of open macroporosity (total water uptake) and the pore size distribution function (Hg porosimetry). For the first time, mineralogical and technical data were obtained for building sandstones of the Zittau region. The results not only confirmed earlier conjectures concerning different source areas for the ancient building sandstones of the Zittau and Görlitz area but also allowed the unequivocal assignment of historically used material to specific sandstone occurrences. The data obtained provide a comprehensive basis for the interpretation of weathering damage suffered by the historical monuments and give useful hints for their successful conservation and reconstruction.
Constraints on the structural development of Afar imposed by the kinematics of the major surrounding plates
Authors: Garfunkel Z. , Beyth M. 
Published: September 2007

Abstract
The development of the Afar rift-rift-rift triple junction is analysed from the view-point of the Nubia, Arabia and Somali plate kinematics. A variety of constraints allow definition of a range of kinematic models that approximate well to the plate motions with a resolution of a couple to tens of kilometres. Rigid plate kinematics probably cannot resolve smaller motions. The size and location of the new area that opened between the major plates is inferred from plate kinematics and this provides a framework in which to assess the structural development that accommodates plate separation.
The development of the Afar region was complicated by the presence of microplates — the Danakil and Aisha blocks — which results in a complex plate boundary geometry. This led to local deformation that does not directly reflect the divergence of the major plates, e.g. rotations of microplates and of minor blocks about vertical axes and strike-slip faulting. The opening of new area was accommodated by various crustal growth and accretion mechanisms, e.g. building of thick new igneous crust, normal seafloor spreading, and/or crustal stretching. Thus, plate motions by themselves do not determine the development of the plate boundaries, as this is strongly influenced by other factors such as lateral variations of the rates of magma supply (e.g. away from, and over, the Afar plume).

The plate boundaries changed — e.g. the Gulf of Aden spreading centre propagated westward
c.
2 Ma ago and normal seafloor spreading began along portions of the Red Sea axis since
c.
5 Ma ago — while there were no resolvable changes in the plate motions. Such changes therefore signify a reorganization of the way in which plate divergence and addition of new area is accommodated: diffuse extension may give way to separation along a narrow spreading centre, or new plate boundaries may form at the expense of other boundaries that became inactive.