Intraplate volcanism in the Danube Basin of NW Hungary: 3D geophysical modelling of the Late Miocene Pásztori volcano

International Journal of Earth Sciences - Three-dimensional geophysical modelling of the early Late Miocene Pásztori volcano (ca. 11–10 Ma) and adjacent area in the Little...     

Enhancing adaptive composite map projections: Wagner transformation between the Lambert azimuthal and the transverse cylindrical equal-area projections

The adaptive composite map projection technique changes the projection to minimize distortion for the geographic area shown on a map. This article improves the transition between the Lambert azimuthal projection and the transverse equal-area cylindrical projection that are used by adaptive composite projections for portrait-format maps. Originally, a transverse Albers conic projection was suggested for transforming between these two projections, resulting in graticules that are not symmetric relative to the central meridian. We propose the alternative transverse Wagner transformation between the two projections and provide equations and parameters for the transition. The suggested technique results in a graticule that is symmetric relative to the central meridian, and a map transformation that is visually continuous with changing map scale.     

Juxtaposition of Barrovian and migmatite domains in the Chinese Altai: a result of crustal thickening followed by doming of partially molten lower crust

Ordovician metasedimentary rocks are the oldest and most extensive sedimentary sequence in the Chinese Altai. They experienced two major episodes of deformation (D1 and D2) resulting in the formation of juxtaposed Barrovian‐type and migmatite domains. D1 is characterized by a penetrative sub‐horizontal fabric (S1), and D2 is marked by upright folds (F2) with NW–SE‐trending axial planes in shallow crustal levels and by sub‐vertical transposition foliations (S2) in the high‐grade cores of large‐scale F2 antiforms. In the Barrovian‐type domain, successive growth of biotite, garnet and staurolite is observed in the S1 fabric. Kyanite included in garnet and plagioclase in the migmatite domain is interpreted to have formed also in S1. In the biotite and garnet zones, the spaced S2 cleavage is marked by biotite and muscovite, and in the staurolite and kyanite zones, the penetrative S2 fabric is characterized by sillimanite, locally with late cordierite. Phase equilibria modelling indicates that the S1 fabric was associated with an increase in pressure and temperature under Barrovian‐type conditions in both domains. The S2 fabric was related to decompression, in which rocks in the biotite and garnet zones well preserve the peak assemblage, and the higher grade rocks in the staurolite and kyanite zones re‐equilibrated to different degrees under high‐temperature/low‐pressure (HT/LP) conditions. The D1 metamorphic history is attributed to the progressive burial related to Early–Middle Palaeozoic crustal thickening and the metamorphism associated with D2 is interpreted to result from exhumation by vertical extrusion. The extrusion of hot rocks was contemporaneous with the formation of gneiss domes accompanied by the intrusion of juvenile magmas at middle crustal levels during the Middle Palaeozoic. Consequently, there is a genetic link between the Barrovian‐type and migmatite domains related to continuous transition of the Barrovian‐type fabric into the HT/LP one during development of domal structures in the southern Altai orogenic belt. This study has a broad impact on the understanding of the thermo‐mechanical behaviour of accretionary orogenic systems worldwide. The lower crustal flow and doming of hot crust, so far reported only in continental collisional settings, seems to be also an integral mechanism responsible for both horizontal and vertical redistribution of accreted material prior to continental collision.     

Using calculated chemical potential relationships to account for replacement of kyanite by symplectite in high pressure granulites

Calculated mineral equilibria are used to account for the formation of sapphirine–plagioclase, spinel–plagioclase and corundum–plagioclase symplectites replacing kyanite in quartz–plagioclase–garnet–kyanite granulite facies gneisses from the Southern Domain of the Athabasca granulite terrane, a segment of the Snowbird tectonic zone in northern Saskatchewan, Canada. Metamorphic conditions of >14 kbar and 800 °C are established for the high pressure, garnet–kyanite assemblage using constraints from P–T pseudosections and Zr‐in‐rutile thermometry. Replacement of kyanite by symplectites reflects the reaction of kyanite with the matrix following near‐isothermal decompression to <10 kbar. The chemical potential gradients developed between the kyanite and the matrix led to diffusion that attempted to flatten the gradients, kyanite persisting as a stable phase while it is consumed by symplectite from its edge. In this local equilibrium model, the mineral and mineral compositional spatial relationships are shown to correspond to paths in μ(Na₂O)–μ(CaO)–μ(K₂O)–μ(FeO)–μ(MgO) in the model chemical system, Na₂O–CaO–K₂O–FeO–MgO–Al₂O₃–SiO₂ (NCKFMAS), with SiO₂ and Al₂O₃ taken to be completely immobile. The values of μ(Na₂O) and μ(CaO) are constrained by fixing P–T conditions and choosing appropriate μ(Na₂O) and μ(CaO) values that correspond to the observed plagioclase compositions. μ(FeO)–μ(MgO) diagrams show the corresponding spatial relationships with kyanite and the symplectite phases. These results demonstrate that the replacement of kyanite by sapphirine–plagioclase and spinel–plagioclase appears to be metastable with respect to replacement by corundum–plagioclase. Replacement by corundum–plagioclase does also occur, apparently overprinting pre‐existing symplectite and also kyanite. Ignoring corundum, the resulting diagrams account for the spatial relationships and compositions observed in the spinel–plagioclase and sapphirine–plagioclase symplectites. They are predicted to occur over both a wide range of P–T conditions (6–11 kbar, 650–850 °C) and plagioclase compositions (X_An = 0.5–0.9). The wide range of P–T conditions that may result in identical spatial and compositional relationships suggests that such reaction textures may be of limited use in accurately quantifying the P–T conditions of retrograde metamorphism.     

The unique environment of the most acidified permanently meromictic lake in the Czech Republic

Changes in the water properties and biological characteristics of the highly acidic Hromnice Lake (Western Bohemia) were investigated. This 110-year-old lake, formed as a consequence of the mining of pyritic shales, is permanently meromictic. Two chemoclines separate an extremely acidic (pH ～ 2.6) mixolimnion from a metal-rich anoxic monimolimnion. The absence of spring mixolimnetic turnover due to ice melting and very slow heat propagation through the chemocline with a 6-month delay were observed. Extreme mixolimnetic oxygen maxima (up to 31 mg l^?1) in phosphorus-rich lake (PO₄^3? up to 1.6 mg l^?1) well correlated with outbursts of phytoplankton. Phytoplankton consist of several acido-tolerant species of the genera Coccomyxa, Lepocinclis, Chlamydomonas and Chromulina. Surface phytoplankton biomass expressed as chlorophyll-a varies from 2 to 140 μg l^?1. Multicellular zooplankton are almost absent with the exception of Cephalodella acidophila, a small rotifer occurring in low numbers. Large red larvae of the midge Chironomus gr. plumosus were found at the bottom close to the shore, with larvulae in the open water. Developmental stages (protonemata) of a moss, resembling filamentous algae, dwell in the otherwise plant-free littoral zone.     

Ordovician and Cretaceous tectonothermal history of the Southern Gemericum Unit from microprobe monazite geochronology (Western Carpathians,Slovakia)

The Southern Gemericum basement in the Inner Western Carpathians experienced a polyphase regional deformation. Differences in the pre-Alpine and Alpine events have been constantly discussed. To address this, monazites from metapelites and acid metavolcanic rocks were dated using the Th–U–Pb electron microprobe method. Three monazite generations, such as Precambrian, Early Paleozoic, and Alpine, have been recognized in the greenschist facies pelites and acid metavolcanic rocks of the Southern Gemericum basement. Both inherited magmatic monazite grains in metavolcanites and rare relics of detrital monazites within the polyphase monazite grains in metapelites yielded the Precambrian age in the time span of 550–660 Ma. They prove the provenance and derivation from deeper crustal Cadomian fragments. High-Y magmatic monazites of Early Paleozoic age (444 ± 13 and 477 ± 7 Ma) have been recorded in the acid metavolcanites and their metavolcaniclastics. These ages roughly fit within the previously published magmatic zircon age determinations (at 494 ± 1.7 and 464 ± 1.7 Ma) that clearly indicate two-phase volcanic activity in the Early Paleozoic Southern Gemericum basin. The Early Paleozoic magmatic monazites were partly overprinted by the low-Y Alpine monazites (133 ± 5 and 184 ± 16 Ma) at their rims. In Al-rich metapelites, the newly formed low-Y monazites of Alpine age commonly occur, reflecting the polystage compression geodynamic evolution with three distinct peaks at 100 ± 8, 133 ± 5, and 190 ± 16 Ma, respectively. No data as the evidence of the pre-Alpine metamorphic events were observed in metapelites. Only some monazites yield the age indications for the Permian extensional thermal re-heating (260–290 Ma). The monazite age data from the Southern Gemericum basement indicate the strong overprinting due to the polyphase Alpine deformation at least in the greenschist facies conditions.     

Analysis of infiltration processes into fractured and swelling soils as triggering factors of landslides

Rainfall infiltration can cause a dramatic decrease of suction in unsaturated soils and, consequently, of shear strength, triggering various instability phenomena, such as the slip of steep surface soil layers. Swelling of cracked soils and capillary barrier effects, induced by fine-grained soils overlying a more permeable material, can also affect water flow through this type of soil systems. In the past, few studies on infiltration and rainfall-induced landslides considered the simultaneous effects of surface cracks, swelling materials, and/or the capillary barrier phenomenon. To this purpose, this paper presents the results obtained by a dual-permeability model, which simulates water flow through a fractured swelling soil overlying a more permeable soil and focusing on the influence of these phenomena on triggering of landslides. Numerical results show that for high-intensity precipitations, flow through fractures quickly reaches significant depths and the capillary barrier is broken, while soil swelling leads to a uniform narrowing of cracks. On the other hand, for low-intensity precipitations, fracture flow and swelling are limited only to the first 30–50 cm of the topsoil, while cracks almost completely closed. Evaluations of the slope stability show that prolonged low-intensity rainfalls might be more dangerous than short high-intensity rains in triggering surface landslides.     

Interactions between European agricultural policy and climate change: a Slovenian case study

This article analyses the interactions between agricultural policy measures in the EU and the factors affecting GHG emissions from agriculture on the one hand, and the adaptation of agriculture to climate change on the other. To this end, the article uses Slovenia as a case study, assessing the extent to which Slovenian agricultural policy is responding to the challenges of climate change. All agricultural policy measures related to the 2007–2013 programming period were analysed according to a new methodological approach that is based on a qualitative (expert evaluation) and a quantitative (budgetary transfers validation) assessment. A panel of experts reached consensus on the key factors through which individual measures affect climate change, in which direction and how significantly. Data on budgetary funds for each measure were used as weights to assess their relative importance. The results show that there are not many measures in (Slovenian) agricultural policy that are directly aimed at reducing GHG emissions from agriculture or at adaptation to climate change. Nevertheless, most affect climate change, and their impact is far from negligible. Current measures have both positive and negative impacts, but overall the positive impacts prevail. Measures that involve many beneficiaries and more budgetary funds had the strongest impact on aggregate assessments. In light of climate change, agricultural policy should pay more attention to measures that are aimed at raising the efficiency of animal production, as it is the principal source of GHG emissions from agriculture.

Policy relevance

Agricultural policy must respond to climate challenges and climate change impact assessment must be included in the process of forming European agricultural policy. Agricultural policy measures that contribute to the reduction of emissions and adaptation, whilst acting in synergy with other environmental, economic and social goals, should be promoted. The approach used in this study combines qualitative and quantitative data, yielding an objective assessment of the climate impact of agricultural policy measures and providing policy makers with a tool for either ex ante or ex post evaluations of climate-relevant policy measures.     

An inelastic stress integration algorithm for a rock mass containing sets of discontinuities

The mechanical behaviour of a rock mass is described in this paper using a method that combines experimental and numerical techniques. A new discontinuity (joint) constitutive model is proposed based on the non-associative yield law. Constitutive relationships for an anisotropic rock mass are determined by introducing an interaction between sets of discontinuities and the monolith in which they occur. The model is based on the concept that deformation of the monolith and its associated sets of discontinuities are coupled. An experimental investigation of the concrete foundations of the Bogovina Dam on the Crni Timok River in Serbia has been used to verify the presented numerical model. The tests included discontinuity and monolith sample investigations and large-scale field tests.