Syngenetic, thin graphite-rich horizons in lower crustal rocks from the Serre San Bruno, Calabria (Italy), and implications for the nature of high-conducting deep crustal layers

In order to better understand the nature of deep crustal high electrical conductivity, we studied the electrical properties of a tilted section of a former lower continental crust exposed in the Calabrian arc of the Alpine-Apennine mountain system. Geoelectric field measurements and impedance measurements on rock samples showed that these high-grade metamorphic rocks are generally highly resistive as expected for crystalline, electrolytically conducting rocks of low porosity. This holds for graphite-free metabasites as well as for metapelites which generally contain accessory, up to 3% biogenic graphite in the form of isolated grains. Clearly as an exception, a group of thin stratiform black horizons with thicknesses of 1-15 cm within the metapelitic series was detected by means of self-potential (SP) measurements. Rock samples from these horizons exhibit high, quasi-metallic bulk conductivities of up to 50 S/m (0.02 Ωm) in agreeement with up to 20% syngenetic graphite, forming a network of interconnected streaks or crack fillings. The high amount of carbon most probably originates from organic matter of C_org-rich black shales. Relative enrichment of the low mobility graphitic matter compared to the carbon content of the assumed protoliths may have been due to pressure solution and partial melting during prograde metamorphism, without major contribution of a fluid phase, resulting in isolated graphite flakes. Although enriched, graphite in this form has little effect on electrical conductivity. For the Calabrian black horizons, microscopic analyses make conceivable that, in a further decisive step, isolated graphite grains were mechanically smeared to continuous pathways during uplift by shearing, producing hereby the observed graphitic network which is needed to generate high conductivity. As C_org-rich black shales are common members of sedimentary sequences throughout the earth’s history, good conductors of this type may be expected in the continental crust at any depth depending on tectonic and metamorphic history, with the exception of magmatic protoliths. Regarding the extremely high conductivity of the meta-black shale samples containing syngenetic sheared graphite, a total thickness of a few meters of such rocks is sufficient to explain magnetotelluric high conductivity anomalies in the deep crust.     

Untersuchung von drei Grundwasserwerken auf Vorkommen von Acanthamoeben,Naeglerien und anderen freilebenden Amöben

Prevalence of Acanthamoebae, Naegleriae and Other Free-living Amoebae in the Course of Water Treatment in Three Well Waterworks Numerous species of free-living amoebae and other protozoa had been observed in the raw water of three representative waterworks with enriched well water. They were eliminated most effectively during the water treatment procedure. Acanthamoebae and Naegleriae including thermophilic strains of these genera could not be identified in any of the clear water samples. Acanthamoebae and Vannellae isolated from different samples exhibited repeatedly intracellular infections with bacteria of the genus Cytophaga. Their role as possible hosts of different pathogenic and non pathogenic bacteria like Legionella sp., Listeria sp., and Pseudomonas sp. is confirmed by this observation. As known from earlier findings in connection with the Acanthamoeba-Legionella model, it can be assumed, that bacteria multiplying in trophozoites or being enclosed in cysts are protected against high concentrations of chlorine and other biocides.     

The metamorphic complex of Beloretzk, SW Urals, Russia — a terrane with a polyphase Meso- to Neoproterozoic thermo-dynamic evolution

An integrated geological study of the tectono-metamorphic evolution of the metamorphic complex of Beloretzk (MCB) which is part of the eastern Bashkirian mega-anticlinorium (BMA), SW Urals, Russia shows that the main lithological units are Neoproterozoic (Riphean and Vendian age) siliciclastic to carbonate successions. Granitic, syenitic and mafic intrusions together with subaerial equivalents comprise the Neo- and Mesoproterozoic magmatic rocks. The metamorphic grade ranges from diagenetic and very low grade in the western BMA to high-grade in the MCB. The N–S trending Zuratkul fault marks the change in metamorphic grade and structural evolution between the central and eastern BMA. Structural data, Pb/Pb-single zircon ages, ⁴⁰Ar/³⁹Ar cooling ages and the provenance signature of Riphean and Vendian siliciclastic rocks in the western BMA give evidence of Mesoproterozoic (Grenvillian) rifting, deformation and eclogite-facies metamorphism in the MCB and a Neoproterozoic (Cadomian) orogenic event in the SW Urals. Three pre-Ordovician deformation phases can be identified in the MCB. The first SSE-vergent, isoclinal folding phase (D₁) is younger than the intrusion of mafic dykes (Pb/Pb-single zircon: 1350 Ma) and older than the eclogite-facies metamorphism. High P/low T eclogite-facies metamorphism is bracketed by D₁ and the intrusion of the Achmerovo granite (Pb/Pb-single zircon: ≤970 Ma). An extensional, sinistral, top-down-to-NW directed shearing (D₂) is correlated with the first exhumation of the MCB. E-vergent folding and thrusting (D₃) occurred at retrograde greenschist-facies metamorphic conditions. The tremolite ⁴⁰Ar/³⁹Ar cooling age (718±5 Ma) of amphibolitic eclogite and muscovite ⁴⁰Ar/³⁹Ar cooling ages (about 550 Ma) of mica schists indicate that a maximum temperature of 500±50 °C was not reached during the Neoproterozoic orogeny. The style and timing of the Neoproterozoic orogeny show similarities to the Cadomian-aged Timan Range NW of the Polar Urals. Geochronological and thermochronological data together with the abrupt change in structural style and metamorphism east of the Zuratkul fault, suggest that the MCB is exotic with respect to the SE-margin of the East European Platform. Thus, the MCB is named the ‘Beloretzk Terrane’. Recognition of the ‘Beloretzk Terrane’ and the Neoproterozoic orogeny at the eastern margin of Baltica has important implications for Neoproterozoic plate reconstruction and suggests that the eastern margin of Baltica might have lain close to the Avalonian–Cadomian belt.     

Shapes of the saturnian icy satellites and their significance

The sizes and shapes of six icy saturnian satellites have been measured from Cassini Imaging Science Subsystem (ISS) data, employing limb coordinates and stereogrammetric control points. Mimas, Enceladus, Tethys, Dione and Rhea are well described by triaxial ellipsoids; Iapetus is best represented by an oblate spheroid. All satellites appear to have approached relaxed, equilibrium shapes at some point in their evolution, but all support at least 300 m of global-wavelength topography. The shape of Enceladus is most consistent with a homogeneous interior. If Enceladus is differentiated, its shape and apparent relaxation require either lateral inhomogeneities in an icy mantle and/or an irregularly shaped core. Iapetus supports a fossil bulge of over 30 km, and provides a benchmark for impact modification of shapes after global relaxation. Satellites such as Mimas that have smoother limbs than Iapetus, and are expected to have higher impact rates, must have relaxed after the shape of Iapetus was frozen.     

Space use by Rhabdosargus holubi in a southern African estuary,with emphasis on fish movements and ecosystem connectivity

Twenty-one juvenile Cape stumpnose Rhabdosargus holubi (140–190 mm fork length) were tagged with internal acoustic transmitters in the lower, middle and upper reaches of the Kowie Estuary, South Africa. The movements of each fish were continually monitored from October 2014 to February 2015 using 22 stationary data-logging acoustic receivers situated at approximately equidistant intervals along the length of the estuary (21 km). Juvenile R. holubi spent the greatest proportion of time within the estuarine environment (83%), with the sea (16%) and riverine (1%) environments used to a much lesser extent. Within the estuarine environment, tagged individuals showed high levels of residency and fidelity to their capture and release sites; however, the degree of residency was dependent on the position of the release site, with batches in the upper and lower reaches exhibiting different space-use patterns. When larger juvenile R. holubi migrated back to the sea for the next phase of their life cycle, they generally did not return to the estuarine environment, thus indicating a permanent ontogenetic shift in habitat use with the onset of sexual maturity. This contribution to our understanding of the ecology of a ubiquitous estuarine fish further highlights the importance of estuarine habitats as nursery areas that require effective management.