Bearing capacity of spatially random rock masses obeying Hoek–Brown failure criterion

This paper presents a probabilistic analysis to compute the probability density function of the bearing capacity of a strip footing resting on a spatially varying rock mass. The rock is assumed to follow the generalised Hoek–Brown failure criterion. The uniaxial compressive strength of the intact rock (σc) was considered as a random field and the geological strength index was modelled as a random variable. The uncertainty propagation methodology employed in the analysis is the sparse polynomial chaos expansion. A global sensitivity analysis based on Sobol indices was performed. Some numerical results were presented and discussed.     

Partial melting of the Indarch (EH4) meteorite: A textural,chemical, and phase relations view of melting and melt migration

Abstract— To test whether aubrites can be formed by melting of enstatite chondrites and to understand igneous processes at very low O fugacities, we have conducted partial melting experiments on the Indarch (EH4) chondrite at 1000–1500 °C. Silicate melting begins at 1000 °C, and Indarch is completely melted by 1500 °C. The metal-sulfide component melts completely at 1000 °C. Substantial melt migration occurs at 1300–1400 °C, and metal migrates out of the silicate charge at 1450 °C and ～50% silicate partial melting. As a group, our experiments contain three immiscible metallic melts (Si-, P-, and C-rich), two immiscible sulfide melts (Fe- and FeMgMnCa-rich), and silicate melt. Our partial melting experiments on the Indarch (EH4) enstatite chondrite suggest that igneous processes at low fO₂ exhibit several unique features. The complete melting of sulfides at 1000 °C suggests that aubritic sulfides are not relics. Aubritic oldhamite may have crystallized from Ca and S complexed in the silicate melt. Significant metal-sulfide melt migration might occur at relatively low degrees of silicate partial melting. Substantial elemental exchange occurred between different melts (e.g., S between sulfide and silicate, Si between silicate and metal), a feature not observed during experiments at higher fO₂. This exchange may help explain the formation of aubrites from known enstatite chondrites.     

Isotopic composition of dissolved inorganic carbon in subsurface sediments of gas hydrate-bearing mud volcanoes, Lake Baikal: implications for methane and carbonate origin

We report on the isotopic composition of dissolved inorganic carbon (DIC) in pore-water samples recovered by gravity coring from near-bottom sediments at gas hydrate-bearing mud volcanoes/gas flares (Malenky, Peschanka, Peschanka 2, Goloustnoe, and Irkutsk) in the Southern Basin of Lake Baikal. The δ¹³C values of DIC become heavier with increasing subbottom depth, and vary between ?9.5 and +21.4‰ PDB. Enrichment of DIC in ¹³C indicates active methane generation in anaerobic environments near the lake bottom. These data confirm our previous assumption that crystallization of carbonates (siderites) in subsurface sediments is a result of methane generation. Types of methanogenesis (microbial methyl-type fermentation versus CO₂-reduction) were revealed by determining the offset of δ¹³C between dissolved CH₄ and CO₂, and also by using δ¹³C and δD values of dissolved methane present in the pore waters. Results show that both mechanisms are most likely responsible for methane generation at the investigated locations.     

The Late Triassic microvertebrate fauna of Tytherington,UK

The Late Triassic fissure fills from the region of Bristol, SW England and S Wales, preserve unique assemblages of small vertebrates derived from an archipelago of palaeo-islands that document aspects of a critical transition in the history of terrestrial ecosystems. Tytherington Quarry, in south Gloucestershire, is the site of several fossiliferous fissures, all dated as Rhaetian (terminal Triassic), and source of abundant remains of the ‘Bristol dinosaur’, Thecodontosaurus antiquus. In addition, the fissure sediments have yielded previously unreported microvertebrate assemblages, including over 400 jaw remains from three genera of sphenodontians and 100 archosaur teeth assigned to 15 morphotypes. The land fauna is dominated by sphenodontians, with Diphydontosaurus by far the most common form, followed by Clevosaurus, then the sauropodomorph dinosaur Thecodontosaurus, and then the sphenodontian Planocephalosaurus. There are, in addition, rare remains of contemporaneous bony fishes, as well as fossils apparently reworked from the Carboniferous limestones, namely conodonts, holocephalian (chimaeroid) teeth, and a shark tooth. Many typical latest Triassic animals, such as temnospondyls, phytosaurs, aetosaurs, rauisuchians, plateosaurids and dicynodonts are not represented at Tytherington, perhaps because these generally larger animals did not live on the palaeo-island, or because their carcasses could not fit into the fissures. The absence of tritylodonts and early mammals is, however, less easy to explain on the basis of size, although it is known that these forms were abundant here by the Early Jurassic.     

Hydrogeological properties of a complex Dinaric karst catchment: Miljacka Spring case study

Miljacka is a karst spring situated in Dalmatia, Croatia. The interpretation of the Miljacka Spring catchment area boundary has repeatedly changed in the past, and the main conclusions of previous studies were that the spring, which is located in the Krka River canyon, receives all of its water from another karst river, Zrmanja. Here, we review a new hypothesis that the Miljacka Spring receives some of its water from the Krka River. It was not possible to verify the hypothesis by solely studying the geological composition, structural–tectonic relations and tracer test results. Therefore, a hydrochemical study was performed to confirm the hypothesis. By studying the geological composition, it was found that part of the catchment area of the Krka River is built of evaporites (gypsum and anhydrite), which are different in their mineral composition than carbonates, the usual rock mass of the Dinaric karst. The hydrochemical model was made using the NETPATH-WIN and PHREEQC software packages. The mixing model results confirmed the hypothesis that the Miljacka Spring waters come from both the Zrmanja (including smaller proportion of precipitation infiltrated directly in the karst aquifer) and Krka rivers. This case study shows the great importance of the application of hydrochemical investigations in karst hydrogeology, where research is often difficult due to the complexity of the groundwater system.     

Geochemical survey of Slovenian bottled waters

The geochemistry of the major components and trace elements in Slovenian bottled water available on the market in 2004 and 2008 was studied. The waters were predominantly from the Radenska and Rogaška Slatina mineral water source region. In this paper, a comparison of two data sets from two time periods was performed based on the Kolmogorov–Smirnov independent two-sample test. The bottled waters in the data sets were in agreement with drinking water and mineral water standards. Discrepancies were only present for B and Ni in highly mineralised waters. Analyses of the labels on the bottle packaging showed that the analytical results were in general agreement with the values reported on the labels. At the same time, the values reported on the labels by the producers showed that the chemical compositions of products available on the market for longer time periods vary. Slovenian bottled waters are predominantly controlled by a CaCO₃–CO₂–H₂O system where Na, Cl⁻ and SO₄²⁻ are present as the major components, in different combinations.     

Biomarkers in environmental and human health risk assessment

Marine pollution is a major threat to human and environmental health. Given the complexity of function of marine and coastal ecosystems, it is unlikely that a balanced view of the nature and extent of risk will easily be achieved if human and environmental risk assessments continue to be conducted in isolation. Here, the integration of assessment protocols is advocated as a holistic means of improving risk management. Biomarkers can provide the common conceptual framework and measurable endpoints necessary for successful integration. Examples are given of the ways in which suites of biomarkers encompassing molecular change, cellular pathology and physiological impairment can be developed and adapted for human and ecological scenarios. By placing a greater emphasis on the health status of impacted biota, it is more likely that risk assessment will develop the efficiency, reliability and predictive power to adapt to the unforeseen environmental threats that are an inevitable consequence of human development and global change.     

U-Pb ID-TIMS age of the Tiksheozero carbonatite: expression of 2.0 Ga alkaline magmatism in Karelia, Russia

The Tiksheozero carbonatite in northern Russian Karelia is a transitional type between alkaline ultramafic — carbonatitic and alkaline gabbroic suites. The complex is dominated by pyroxenite with a variety of subordinate mafic and ultramafic phases and nepheline syenite. Carbonatite occurs in a main central body and in veins. In this study we have obtained a reliable age for the complex by single grain ID-TIMS U-Pb analyses of zircon and baddeleyite. The age of 1999 ± 5 Ma is important because it places the emplacement of the alkaline complexes in the context of craton-wide extension and break-up events which preceded the initiation of a major Paleoproterozoic orogenic cycle. The Paleoproterozoic age also emphasizes the fact that not all members of the Kola alkaline province are of Paleozoic age.