The geodynamic evolution of the Southern European Variscides: constraints from the U/Pb geochronology and geochemistry of the lower Palaeozoic magmatic-sedimentary sequences of Sardinia (Italy)

The high-grade metamorphic complex of northern Sardinia consists of a strongly deformed sequence of migmatitic ortho- and paragneisses interlayered with minor amphibolites preserving relic eclogite parageneses. The protolith ages and geochemical characteristics of selected gneiss samples were determined, providing new constraints for reconstructing the Palaeozoic geodynamic evolution of this sector of the Variscan chain. The orthogneisses are metaluminous to peraluminous calcalkaline granitoids with crustal Sr and Nd isotopic signatures. One orthogneiss from the high-grade zone and one metavolcanite from the volcanic belt in southern Sardinia were dated by LAM-ICPMS (and SHRIMP) zircon geochronology. The inferred emplacement ages of the two samples are 469 ± 3.7 and 464 ± 1 Ma, respectively. The analysed paragneisses are mainly metawackes with subordinate metapelites and rare metamarls. Three paragneiss samples were dated: zircon ages scatter between 3 Ga and about 320 Ma, with a first main cluster from 480 to 450 Ma, and a second one from about 650 to 550. Variscan zircon ages are rare and mostly limited to thin rims and overgrowths on older grains. These data indicate that the high-grade complex principally consists of middle Ordovician orthogneisses associated with a thick metasedimentary sequence characterised by a maximum age of deposition between 480 and 450 Ma. The association of nearly coeval felsic-mafic magmatic rocks with immature siliciclastic sedimentary sequences points to a back-arc setting in the north Gondwana margin during the Early Palaeozoic. The Variscan metamorphic evolution recorded by the high-grade gneisses (Ky-bearing felsic gneisses and mafic eclogites) testifies to the transformation of the Late Ordovician–Devonian passive continental margin into an active margin in the Devonian–Early Carboniferous.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

The action of neutral oleic acid in the flotation of hematite

Acidification of solutions of oleate salts forms emulsions of oleic acid. It was found that these emulsions produce a different adsorption behaviour on different size fractions of the same mineral. At low oleate concentrations, for the finer fractions, adsorption at acid pH was higher than chemisorption at pH = 7.5; adsorption was lower for the coarser, flotation-size fractions. Therefore, the conclusions obtained in acid solutions for the adsorption of oleate on fine minerals cannot be applied to flotation-size minerals.At low oleate concentrations there is a good correlation between oleate adsorption and hematite flotation. This does not hold for oleate concentrations > 5· 10^?5M, where there is poor flotability in the acid region, although the adsorption of oleic acid is very high. This is attributed to the disordered character of the layer of cooperatively adsorbed oleic acid.     

Petrophysical and mechanical properties of Euganean trachyte and implications for dimension stone decay and durability performance

Euganean trachyte is a subvolcanic porphyritic rock extracted in northern Italy with an age-old tradition of use as dimension stone, historically linked, in particular, to the fervent building activity brought by the Roman Empire and, later on, the Republic of Venice Serenissima. The results of a comprehensive petrophysical and mechanical characterization of Euganean trachyte from the most representative quarries are discussed here, involving the following properties: density, porosity, water absorption, capillary water uptake, hygroscopic water adsorption, hydric/hygric dilatation, water vapor diffusion, thermal expansion, and resistance to salt attack and abrasion. The different trachyte varieties, although belonging to the same quarry basin, exhibit a relatively wide array of technical performances, which are strongly dependent on pore volume, size, size distribution, shape, and degree of interconnection, controlling modes and rates of water transport and retention. Therefore, indications are provided for evaluating durability performance of the stone, with stress on water-driven weathering. Complementary information is finally given on the possible criteria followed in the antiquity for properly selecting the trachyte quarries to be exploited, and by a comparison with the properties of the most important trachytes extracted in Europe.     

Assessment of toxicological status of a SW Mediterranean segment population of striped dolphin (Stenella coeruleoalba) using skin biopsy

Various studies have revealed high concentrations of contaminants such as organochlorines (OCs) and heavy metals in Mediterranean cetaceans. A geographical trend of contamination (PCBs and DDTs) has been found for striped dolphin (Stenella coeruleoalba). In this study we used a non-lethal approach (skin biopsy) to investigate bioaccumulation of OCs, including polychlorobiphenyls (PCBs), DDTs, polychlorodibenzo-p-dioxins (PCDDs), polychlorodibenzofurans (PCDFs), trace elements (Hg, Cd, Pb) and CYP1A activity (BPMO) in nine striped dolphins sampled in the Aeolian area (Sicily - Italy) in summer 2002. The arithmetic mean value of BPMO activity in this group was 43.46 AUF/g tissue/h. This value is approximately 3 times and 5 times lower, respectively, than the value found in the Ionian and in the Ligurian groups. Skin biopsies of striped dolphins emerged as a suitable material for assessing the toxicological status of the various Mediterranean groups.     

Mixed function oxidase activity and cytochrome P-450 forms in black-headed gulls feeding in different areas

The aim of the present study was to evaluate the mixed function oxidase (MFO) system and the forms of supposed cytochrome P-450 in the liver of black-headed gulls (Larus ridibundus) feeding in a lagoon and on a garbage dump. Tissue levels of polychlorinated biphenyls (PCBs) were also determined. Ethoxyresorufin 10-deethylase (EROD) and aldrin epoxidase activities were higher in the dump gulls than in the lagoon gulls. A marked thickening of the proteins in the cytochrome P-450 area, particularly of P-450c and P-450d, was also found in the dump gulls. No relationship was found between MFO activity and tissue chlorinated hydrocarbon levels.     

Analytical formulation of impulsive collision avoidance dynamics

The paper deals with the problem of impulsive collision avoidance between two colliding objects in three dimensions and assuming elliptical Keplerian orbits. Closed-form analytical expressions are provided that accurately predict the relative dynamics of the two bodies in the encounter b-plane following an impulsive delta-V manoeuvre performed by one object at a given orbit location prior to the impact and with a generic three-dimensional orientation. After verifying the accuracy of the analytical expressions for different orbital eccentricities and encounter geometries the manoeuvre direction that maximises the miss distance is obtained numerically as a function of the arc length separation between the manoeuvre point and the predicted collision point. The provided formulas can be used for high-accuracy instantaneous estimation of the outcome of a generic impulsive collision avoidance manoeuvre and its optimisation.     

Nocturnal Intermittent Coupling Between the Interior of a Pine Forest and the Air Above It

A 1-year set of measurements of CO₂ and energy turbulent fluxes above and within a 25-m pine forest in southern Brazil is analyzed. The study focuses on the coupling state between two levels and its impact on flux determination by the eddy-covariance method. The turbulent series are split in their typical temporal scales using the multiresolution decomposition, a method that allows proper identification of the time scales of the turbulent events. Initially, four case studies are presented: a continually turbulent, a continually calm, a calm then turbulent, and an intermittent night. During transitions from calm to turbulent, large scalar fluxes of opposing signs occur at both levels, suggesting the transference of air accumulated in the canopy during the stagnant period both upwards and downwards. Average fluxes are shown for the entire period as a function of turbulence intensity and a canopy Richardson number, used as an indicator of the canopy coupling state. Above the canopy, CO₂ and sensible heat fluxes decrease in magnitude both at the neutral and at the very stable limit, while below the canopy they increase monotonically with the canopy Richardson number. Latent heat fluxes decrease at both levels as the canopy air becomes more stable. The average temporal scales of the turbulent fluxes at both levels approach each other in neutral conditions, indicating that the levels are coupled in that case. Average CO₂ fluxes during turbulent periods that succeed very calm ones are appreciably larger than the overall average above the canopy and smaller than the average or negative within the canopy, indicating that the transfer of air accumulated during calm portions at later turbulent intervals affects the flux average. The implications of this process for mean flux determination are discussed.     

Keeping the forest for the climate's sake: avoiding deforestation in developing countries under the UNFCCC

Abstract

A process for reducing emissions from deforestation in developing countries has been initiated under the UNFCCC. Efforts to agree on a legally binding instrument to halt deforestation have previously failed in other international fora. The magnitude of the social, economic, technical and political complexities underlying deforestation have led to negotiations being challenging. What policy instruments could provide incentives to reduce deforestation, and how could these instruments be framed, under the UNFCCC? This article analyses the advantages and disadvantages of the available alternatives within and outside of the Kyoto Protocol. Staying within the Kyoto framework means low institutional development costs, established but limited incentives for action, and low flexibility. Alternatives outside the Protocol provide higher institutional development costs, uncertainties with regard to the incentives, but greater flexibility. We argue that a separate protocol may be the most viable option, as it could offer the necessary flexibility and avoid some technical and political pitfalls that would be likely to beset new efforts under the Kyoto Protocol. The article also presents the concept of ‘committed forests’ as a means of defining geographically where the reduction of emissions from deforestation can take place.     

Misattributed tsunami 3: the Mw 7.7 2013.9.24 SE Pakistan earthquake

The M_w 7.7 earthquake that struck SE Pakistan on 24 September 2013 at 11.29.48 UTC was a sinistral strike-slip event on a branch of the Ornach-Nal-Chaman fault system which hereabouts separates the Eurasian Plate from the Indian Plate. Although the focus was at a depth of 15 km and 400 km inland the earthquake was accompanied by the emergence of an island off the Makran coast and the generation of a tsunami with a peak amplitude of 27 cm at Muscat (Oman) and 20 cm at Chah Bahar (Iran). At DART marine buoy 23228 in the Indian Ocean 500 km to the south a series of seismic Rayleigh waves about 4 min after the main shock was followed 54 min later by a tsunami with a peak amplitude of 1 cm. The Rayleigh series is here attributed to seafloor vibration during accelerated subduction of the Arabian Plate beneath the Eurasian Plate, and the tsunami to the development or reactivation of one or more reverse faults on the seaward portion of the Makran imbricate fan. As in the 2010.2.27 M_w 8.8 Maule (Chile), the 2004.12.26 M_w 9.2 Sumatra–Andaman, the 2005.3.28 M_w 8.7 Nias (Indonesia) and the 2011.3.11 M_w 9.0 Tohoku (Japan) earthquakes, the link between tsunami generation and slip on the megathrust is thus very indirect, to the detriment of attempts to mitigate coastal hazards using teleseismic data when nearshore seafloor monitoring would probably prove more effective.     

Relationships between seep-carbonates,mud volcanism and basin geometry in the Late Miocene of the northern Apennines of Italy: the Montardone mélange

The Montardone mélange (Mm) is a chaotic, block-in-matrix unit outcropping in the Montebaranzone syncline in the northern Apennines. The Mm occurs in the uppermost part of the Termina Fm, the Middle–Late Miocene interval of a succession deposited in a wedge-top slope basin (Epiligurian succession). The Mm is closely associated with bodies of authigenic carbonates, characterized by negative values of δ¹³C (from ?18.22 to ?39.05 ‰ PDB) and chemosynthetic benthic fauna (lucinid and vesicomyid bivalves). In this paper, we propose that the Mm is a mud volcano originated by the post-depositional reactivation and rising of a stratigraphically lower mud-rich mass transport body (Canossa–Val Tiepido sedimentary mélange or olistostrome) triggered by fluid overpressure. We base our conclusion on (1) the Mm pierces the entire Termina Fm and older Epiligurian units and represents the direct continuation of the underlying Canossa–Val Tiepido mélange; (2) the geometry and facies distribution of the Montebaranzone sandstone body, which are compatible with a confined basin controlled by the rising of the Mm; (3) the systematic presence of large-scale (lateral extension 300–400 m) seep-carbonates associated with the mélange, suggesting a persistent gas-enriched fluid vent from the ascending overpressured mud; (4) blocks and clasts sourced from the Mm, hosted by the authigenic carbonates, conveyed by ascending mud and gas-enriched fluids. The Mm represents one of the few fossil examples of reactivation of a basin-scale sedimentary mélange (olistostrome); a three-stage model showing mechanisms of Mm raising is proposed.