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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 15–20m 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.

The Red Sea rift system represents a key case study of the transition from a continental to an oceanic rift. The Red Sea rifting initiated in Late Oligocene to Early Miocene (24–23 Ma) and was accompanied by extensive magmatism throughout the rifted basin, from Afar and Yemen to northern Egypt. Here, we present a petrological and geochemical study of two gabbro bodies and associated basalts from the Tihama Asir igneous complex, which formed at 24–20 Ma within the rifted Arabian-Nubian Shield (ANS). The Tihama Asir is therefore an ideal location to study the initial phase of syn-rift magmatism and its influence on the geodynamic evolution of the Red Sea rift system. The most primitive olivine gabbros present modal, bulk and mineral compositions consistent with formation from Mid-Ocean Ridge Basalt (MORB)-type parental melts, whereas the evolved olivine-free gabbros and oxide-bearing gabbros show saturation of phlogopite and a crystal line of descent diverging from fractional crystallization trends. In detail, whole-rock and mineral compositions in the most evolved lithologies show high Light over Middle Rare Earth Elements (LREE/MREE) ratios (LaN/SmN = 0.89–1.31) and selective enrichments in Sr, K and highly incompatible elements (Rb, Ba, U, Th). We relate these geochemical characteristics to a process of progressive assimilation of host continental crust during the emplacement of the gabbroic plutons. Interestingly, high LREE/MREE ratios (LaN/SmN = 1.45–4.58) and high Rb, Ba, Th and U contents also characterize the basaltic dike swarms associated to the gabbros. Incompatible trace element compositions of these basalts approach those of the melts that formed the most hybridized gabbros. Therefore, we propose that the dike swarms represent melts partially contaminated by assimilation of continental crust material, extracted from the underlying gabbroic crystal mush. Our results suggest that early syn-rift magmatism led to the partial replacement of the thinned continental crust by MORB-type gabbroic bodies, in turn suggesting that oceanic magmatism started prior to continental break-up. Extensive syn-rift magmatism is consistent with the interpretation of the southern Red Sea rift system as a volcanic rifted margin. One possible implication of this study is that extensive but diffuse syn-rift magmatism possibly hampered continental break-up, leading to a protracted rifting stage.

The increasing quality and resolution of marine seismic reflection data, as well as their availability in digital form within large data sets, require the development and testing of new techniques to improve their interpretation. In this work, we present a case study dealing with application of 3D techniques to a set of 2D shallow-water data, where the effect of lateral reflections/diffractions can be neglected. We show how such techniques can be effective in highlighting geological properties/features of the seafloor and sub-seafloor, including reflectivity analysis of prominent horizons, seismic facies classification based on definition of acoustic properties, and compilation of a "flattened" version of seismic sections, by time shifting a particular reflector to a horizontal reference level. This latter technique enables compilations of pseudo-3D grids of seismic volumes, that could be subsequently sampled (time sliced) allowing for compilation of seismic amplitude and reflectivity maps which could be used to infer geological properties and processes.

Oxide gabbros are a minor but diffuse component of the lower oceanic crust. Their presence poses questions on lower crust exhumation processes and magma differentiation at mid ocean ridges because they are systematically associated with shear zones and are hardly explained by classical fractionation and melt migration models. Here, we report on a study of lower-crust gabbros recovered from the Vema Lithospheric Section at 11°N along the Mid Atlantic Ridge, where oxide gabbros are abnormally abundant relative to ridge centred magmatic intrusives and where we found a peculiar lithological occurrence represented by deformed diorites extremely enriched in Fe-Ti-oxides and apatites. Their complex genetic history reveals a hybrid nature consistent with derivation from high pressure injections of Fe-Ti-P saturated nelsonitic melts in a primitive gabbroic groundmass that induced fracturing, de-compaction, mineral resorption and chemical re-equilibration. Melt injections may occur after intense ductile shearing at the edges of the axial magma chamber following lateral differentiation of primitive melts injected at the centre of the ridge axis segment. We propose a regime of lateral, instead of vertical, melt differentiation along the ridge axis and a possible role for melt immiscibility in the formation of Fe-Ti-P melt pockets in oceanic domains.

The heterogeneity of the suboceanic mantle source is usually defined based on MORB lateral geochemical variability. However, tackling short-scale variability is partially hampered by the large extent of mixing occurring during melt extraction and magma chamber processes. We identified a singular region of the Mid Atlantic Ridge at the eastern Romanche Ridge-Transform Intersection (Equatorial Atlantic) characterized by an extreme lateral thermal gradient. Cooling of the upwelling mantle is here induced by heat transfer to a ca. 50 Ma old plate fronting the ridge-transform intersection. Cooling of the plate edge affects the upper mantle for the whole range where melting usually occurs (30-80 km bsl). The resulting ridge axis consequently shows a lateral gradient in magma productivity and composition (Bonatti et al., 2001 and references therein). MORBs erupted at the ridge centre give rise to a "normal" 5 km thick magmatic crust. Moving to the axial tip magmatism diminishes in volume till zero and progressively increases its alkaline character along with the compositional variability revealing the short-scale heterogeneity of the mantle source (Ligi et al., 2005). This thermal and tectonic configuration represents a regional scale natural experiment where to test the effect of varying mantle potential temperature on a given mantle source. Melting a heterogeneous mantle has profound implications on the km-scale heat transfer because of the differential onset of melting of variably fertile lithologies (Brunelli et al., 2018). Here, we will present the results of the upcoming French-Italian SMARTIES expedition, taking place in July-August 2019. We will present a new high-resolution bathymetric coverage of the RTI and peculiar tectonic features where magma is nearly absent accompanied by direct submarine observations and sampling from Nautile dives.

The SPOT Project (potentially triggerable offshore seismicity and tsunamis) is aimed at helping Italian authorities to comply with the application of the Safety of Offshore Oil and Gas Operations European Directive (2013/30/EU) and the ensuing Italian codes. An extensive reconstruction of offshore geological structures is being implemented in order to assess the existence of potentially seismogenic faults in the surroundings of offshore oil and gas platforms, as a propaedeutic step for the assessment of potentially triggered seismicity connected with operations on such platforms. The descriptive parameters of the identified faults will be used to estimate their natural earthquake rates. The impact of these natural earthquakes along the coasts will then be modeled in terms of expected ground shaking and tsunamis. In turn, these models will be used to estimate potential human and economic losses in a multi-hazard approach to risk assessment. Wherever the combined earthquake and tsunami modeling indicates a relevant impact along the coasts, a more detailed analysis will be carried out, also involving the operators of the related platforms, to perform specific models which also take into account production data. The project has been conceived and funded by the Italian Ministry of Economic Development, with the technical support of the National Department of Civil Protection. The involved research institutes are the Institute of Marine Sciences of the National Research Council (ISMAR), the National Institute of Geophysics and Volcanology (INGV), the European Centre for Training and Research in Earthquake Engineering (EUCENTRE), and the Laboratories University Network of Seismic Engineering (ReLUIS).

We have examined the intermediacy of sulfur-centred radical cations in the one-electron oxidation of (anthracen-9-yl)methyl sulfides. Reaction of (anthracen-9-yl)methyl sulfides with ceric ammonium nitrate (CAN) gave predominantly nitration and oxidation products along with products arising through sulfur-centred radical cations in minor amounts. Upon irradiation, (anthracen-9-yl)methyl sulfides underwent efficient intramolecular single electron transfer leading to a variety of products arising through the intermediacy of sulfur-centred radical cations.

New multichannel seismic reflection profiles were acquired to unravel the structure of a portion of the eastern margin of the Tyrrhenian basin. This extensional feature is part of an Oligocene to Present back-arc basin in the hangingwall of the west directed Apennines subduction system. The basin provides excellent conditions to investigate the early stage processes leading to the development of rifted passive margins and to the emplacement of oceanic crust in an oblique setting. The interpreted post-stack-migrated seismic profiles highlight the geometry and kinematics of the Pontine escarpment that connects the Latium-Campania continental margin to the Vavilov basin. The latter is the main feature of the area, related to the early Pliocene extension of the Tyrrhenian Sea. Several morphological variations are pointed out along strike, mirroring different structural settings of the margin itself: a steeper margin to the north corresponds to high-angle possibly transtensional faults, whereas a smooth slope in the southern portion corresponds to several more distributed listric faults. This work contributes to the understanding of the interplay between extensional and transtensional tectonics along the margins of an oblique back-arc basin.

An updated bathy-morphological setting of the aeolian Islands is presented, based on new detailed bathymetric maps of the western, central and eastern sectors of the archipelago. In recent years, the acquisition of multibeam swath bathymetry has greatly expanded knowledge of the submarine portions of the Aeolian volcanic edifices, revealing that their submarine extension is much wider than that of the islands. Indications given by the submarine setting are fundamental for better understanding of the evolution of volcanism and the control exerted by main structural lineaments, as well as to locate large-scale flank instability events and recent submarine eruptive activity. © The Geological Society of London 2013.

SUMMARY We discuss theoretical and computational method on plate-driven mantle flow beneath midocean ridges. We consider a steady-state flow induced by motion of overlying rigid plates in an incompressible viscous mantle beneath a generic ridge-transform-ridge plate boundary. No assumption of orthogonal and symmetric spreading at ridge axis is made. Analytical solutions for viscosity flow in a half-space and in a layered viscosity mantle beneath an infinitesimal thickness lithosphere and beneath plates that thicken with increasing age, are presented. Numerical calculations were carried out using a standard fast Fourier transform algorithm. The difficulty of using standard Fourier methods to predict accurately the mantle flow field in the proximity of the plate boundaries is overcome by applying the Gegenbauer reconstruction post-processing technique to the Fourier pseudo-spectral solutions. Finally, we present some examples of flow computations. We consider, for both models, two different ridge-transformridge geometries consisting of 100 and 1000 km offsets of two ridge segments spreading at 15 mm/yr half rate. We found a significant difference in the flow structure between the two flow models close to ridge axis and ridge-transform intersections. The proposed model and methods are useful for fast mantle flow calculations to investigate melting processes beneath spreading centres, and to predict the relationship between mantle temperature, crustal thickness and geochemistry of the oceanic crust.