Water in Mid Ocean Ridge Basalts: Some Like it Hot, Some Like it Cold

The presence in the Earth’s mantle of even small amounts of water and other volatiles has major effects: first, it lowers drastically mantle’s viscosity, thereby facilitating convection and plate tectonics; second, it lowers the melting temperature of the rising mantle affecting the formation of the oceanic crust. H2O concentration in oceanic basalts stays below 0.2 wt% except for basalts sampled near “hot spots” that contain significantly more H2O than normal MORB, implying that their mantle plume sources are unusually H2O-rich. Basalts sampled in the Equatorial Atlantic close to the Romanche transform, a thermal minimum in the Ridge system, have a H2O content that increases as the ridge is cooled approaching the transform offset. These basalts are Na-rich, being generated by low degrees of melting of the mantle, and contain unusually high ratios of light versus heavy rare earth elements implying the presence of garnet in the melting region. H2O enrichment is due not to an unusually H2O-rich mantle source, but to a low extent of melting of the upwelling mantle, confined to a deep wet melting region. Numerical models predict that this wet melting process takes place mostly in the mantle zone of stability of garnet. This prediction is verified by the geochemistry of our basalts showing that garnet must indeed have been present in their mantle source. Thus, oceanic basalts are H2O-rich not only near “hot spots”, but also at “cold spots”

Bio-based furan-polyesters/graphene nanocomposites prepared by in situ polymerization

In situ intercalative polymerization has been investigated as a strategic way to obtain poly(propylene 2,5-furandicarboxylate) (PPF) and poly(hexamethylene 2,5-furandicarboxylate) (PHF) nanocomposites with different graphene types and amounts. Graphene (G) has been dispersed in surfactant stabilized water suspensions. The loading range in composites was 0.25–0.75 wt %. For the highest composition, a different type of graphene (XT500) dispersed in 1,3 propanediol, containing a 6% of oxidized graphene and without surfactant has been also tested. The results showed that the amorphous PPF is able to crystallize during heating scan in DSC and graphene seems to affect such capability: G hinders the polymer chains in reaching an ordered state, showing even more depressed cold crystallization and melting. On the contrary, such hindering effect is absent with XT500, which rather induces the opposite. Concerning the thermal stability, no improvement has been induced by graphene, even if the onset degradation temperatures remain high for all the materials. A moderate enhancement in mechanical properties is observed in PPF composite with XT500, and especially in PHF composite, where a significative increase of 10–20% in storage modulus E’ is maintained in almost all the temperature range. Such an increase is also reflected in a slightly higher heat distortion temperature. These preliminary results can be useful in order to further address the field of application of furan-based polyesters; in particular, they could be promising as packaging materials

Polyvinylamine membranes containing graphene-based nanofillers for carbon capture applications

In the present study, the separation performance of new self-standing polyvinylamine (PVAm) membranes loaded with few-layer graphene (G) and graphene oxide (GO) was evaluated, in view of their use in carbon capture applications. PVAm, provided by BASF as commercial product named Lupamin\u2122, was purified obtaining PVAm films with two degrees of purification: Low Grade (PVAm-LG) and High Grade (PVAm-HG). These two-grade purified PVAm were loaded with 3 wt% of graphene and graphene oxide to improve mechanical stability: indeed, pristine tested materials proved to be brittle when dry, while highly susceptible to swelling in humid conditions. Purification performances were assessed through FTIR-ATR spectroscopy, DSC and TGA analysis, which were carried out to characterize the pristine polymer and its nanocomposites. In addition, the membranes\u2032 fracture surfaces were observed through SEM analysis to evaluate the degree of dispersion. Water sorption and gas permeation tests were performed at 35 \ub0C at different relative humidity (RH), ranging from 50% to 95%. Overall, composite membranes showed improved mechanical stability at high humidity, and higher glass transition temperature (Tg) with respect to neat PVAm. Ideal CO2/N2 selectivity up to 80 was measured, paired with a CO2 permeability of 70 Barrer. The membranes\u2019 increased mechanical stability against swelling, even at high RH, without the need of any crosslinking, represents an interesting result in view of possible further development of new types of facilitated transport composite membranes

Foreland deformational pattern in the Southern Adriatic Sea

Two major deformation belts occur in the portion of the Adriatic Sea offshore the Gargano Promontory. Although these two belts display similar characters on seismic profiles, they are different in other respects. The NE-SWtrending Tremiti Deformation Belt, located north of the Gargano Promontory, originated during the Plio-Quaternary, while the E-W-trending South Gargano Deformation Belt, located south of the Gargano Promontory, formed in a time span that goes from Eocene to early Pliocene. On the ground of structural and stratigrafic evidence these deformation belts are interpreted as originated by tectonic inversion of Mesozoic extensional faults. This inversion tectonics, of Tertiary age, can be related to the evolution of the fold-and-thrust belts that surround the Adriatic Sea. A moderate seismic activity, recorded around the Tremiti Island, and historical seismological data suggest that the whole of study area is, at present, seismically active. Therefore, this portion of the Adriatic block still represents a preferental site of deformation

High H2O content in Pyroxenes of residual mantle Peridotites at a Mid Atlantic ridge segment

Global correlations of mid-ocean-ridges basalt chemistry, axial depth and crustal thickness have been ascribed to mantle temperature variations affecting degree of melting. However, mantle H2O content and elemental composition may also play a role. How H2O is distributed in the oceanic upper mantle remains poorly constrained. We tackled this problem by determining the H2O content of orthopyroxenes (opx) and clinopyroxenes (cpx) of peridotites from a continuous lithospheric section created during 26 Ma at a 11°N Mid-Atlantic Ridge segment, and exposed along the Vema Transform. The H2O content of opx ranges from 119 ppm to 383 ppm; that of cpx from 407 ppm to 1072 ppm. We found anomalous H2O-enriched peridotites with their H2O content not correlating inversely with their degree of melting, although H2O is assumed to be incompatible during melting. Inverse correlation of H2O with Ce, another highly incompatible component, suggests post-melting H2O enrichment. We attribute a major role to post-melting temperature-dependent diffusion of hydrogen occurring above the melting region, where water-rich melt flows faster than residual peridotites through dunitic conduits cross-cutting the uprising mantle. Accordingly, estimates of the H2O content of the MORB mantle source based on H2O in abyssal peridotites can be affected by strong uncertainties

Asymmetries on red giant branch surfaces from CHARA/MIRC optical interferometry

Context. Red giant branch (RGB) stars are very bright objects in galaxies and are often used as standard candles. Interferometry is the ideal tool to characterize the dynamics and morphology of their atmospheres. Aims. We aim at precisely characterising the surface dynamics of a sample of RGB stars. Methods. We obtained interferometric observations for three RGB stars with the MIRC instrument mounted at the CHARA interfer- ometer. We looked for asymmetries on the stellar surfaces using limb-darkening models. Results. We measured the apparent diameters of HD197989 (Epsilon Cyg) = 4.61+-0.02 mas, HD189276 (HR7633) = 2.95+-0.01 mas, and HD161096 (Beta Oph) = 4.43+-0.01 mas. We detected departures from the centrosymmetric case for all three stars with the tendency of a greater effect for lower logg of the sample. We explored the causes of this signal and conclude that a possible explanation to the interferometric signal is the convection-related and/or the magnetic-related surface activity. However, it is necessary to monitor these stars with new observations, possibly coupled with spectroscopy, in order to firmly establish the cause.Comment: Accepted for publication as a Letter in Astronomy and Astrophysics, section 1. Letters to the Editor. The official date of acceptance is 06/03/201

Foreland tectonics in the southern Adriatic Sea

Two major deformation belts occur in the portion of the Adriatic Sea offshore the Gargano Promontory. The NE-SW - trending Tremiti Deformation Belt, located north of the Gargano Promontory, originated during the Plio- Quaternary, while the E-W-trending South Gargano Deformation Belt, located south of the Gargano Promontory, formed in a time span from Eocene to Early Pliocene. These deformation belts may have originated by tectonic inversion of Mesozoic extensional faults. This inversion tectonics, of Tertiary age, can be related to the evolution of the fold-and thrust belts surrounding the Adriatic Sea. The whole of the study area is, at present, seismically active and represents a preferential site of deformation

Intercomparison in the field between the new WISP-3 and other radiometers (TriOS Ramses, ASD FieldSpec, and TACCS)

Optical close-range instruments can be applied to derive water quality parameters for monitoring purposes and for validation of optical satellite data. In situ radiometers are often difficult to deploy, especially from a small boat or a remote location. The water insight spectrometer (WISP-3) is a new hand-held radiometer for monitoring water quality, which automatically performs measurements with three radiometers (L-sky, L-u, E-d) and does not need to be connected with cables and electrical power during measurements. The instrument is described and its performance is assessed by an intercomparison to well-known radiometers, under real fieldwork conditions using a small boat and with sometimes windy and cloudy weather. Root mean squared percentage errors relative to those of the TriOS system were generally between 20% and 30% for remote sensing reflection, which was comparable to those of the other instruments included in this study. From this assessment, it can be stated that for the tested conditions, the WISP-3 can be used to obtain reflection spectra with accuracies in the same range as well-known instruments. When tuned with suitable regional algorithms, it can be used for quick scans for water quality monitoring of Chl, SPM, and aCDOM. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.JRS.6.063615

Tsunami potential source in the eastern Sea of Marmara (NW Turkey), along the North Anatolian Fault system

Based on morphobathymetric and seismic reflection data, we studied a large landslide body from the eastern Sea of Marmara (NW Turkey), along the main strand of the North Anatolian Fault, one of the most seismically active geological structures on Earth. Due to its location and dimensions, the sliding body may cause tsunamis in case of failure possibly induced by an earthquake. This could affect heavily the coasts of the Sea of Marmara and the densely populated Istanbul Metropolitan area, with its exposed cultural heritage assets. After a geological and geometrical description of the landslide, thanks to high-resolution marine geophysical data, we simulated numerically possible effects of its massive mobilization along a basal displacement surface. Results, within significant uncertainties linked to dimensions and kinematics of the sliding mass, suggest generation of tsunamis exceeding 15–20 m along a broad coastal sector of the eastern Sea of Marmara. Although creeping processes or partial collapse of the landslide body could lower the associated tsunami risk, its detection stresses the need for collecting more marine geological/geophysical data in the region to better constrain hazards and feasibility of specific emergency plans