New insights into geological setting of the summit area of mount Etna volcano (Italy) inferred from 2D gravity data modelling

Gravimetric observations were carried out in 2015, to image the uppermost portion of the volcanic plumbing system of Mt. Etna (Italy). Gravity measurements were performed using two relative gravimeters, along a profile that crosses the summit craters area (elevations between 2,820 and 3,280 m a.s.l.). Accurate positioning of the gravity observation points was determined through GPS measurements. After applying elevation and terrain corrections, the reduced gravity data were used to build a 2D density model of the uppermost part of the volcano edifice. This model was constrained using to-date knowledge of the structural setting of the area and the available volcanological data. We highlighted the presence of low-density material below the summit craters, down to the depth of about 2.1 km, interpreted as highly altered, fumarolized and structurally weakened material. It is also likely that the close presence of the conduits feeding the summit craters of the volcano contributes to the gravity low in the SW half of the measurement profile. Conversely, the gravity low observed at the northern edge of the profile could reflect the high concentration of faults and eruptive fissures in the Pizzi Deneri area, in correspondence of the Ellittico caldera rim

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

Three-dimensional geophysical modelling of the early Late Miocene Pásztori volcano (ca. 11–10 Ma) and adjacent area in the Little Hungarian Plain Volcanic Field of the Danube Basin was carried out to get an insight into the most prominent intra-crustal structures here. We have used gridded gravity and magnetic data, interpreted seismic reflection sections and borehole data combined with re-evaluated geological constraints. Based on petrological analysis of core samples from available six exploration boreholes, the volcanic rocks consist of a series of alkaline trachytic and trachyandesitic volcanoclastic and effusive rocks. The measured magnetic susceptibilities of these samples are generally very low suggesting a deeper magnetic source. The age of the modelled Pásztori volcano, buried beneath a 2 km-thick Late Miocene-to-Quaternary sedimentary sequence, is 10.4 +/− 0.3 Ma belonging to the dominantly normal C5 chron. Our model includes crustal domains with different effective induced magnetizations and densities: uppermost 0.3–1.8 km thick layer of volcanoclastics underlain by a trachytic-trachyandesitic coherent and volcanoclastic rock units of a maximum 2 km thickness, with a top situated at minimal depth of 2.3 km, and a deeper magmatic pluton in a depth range of 5–15 km. The 3D model of the Danube Basin is consistent with observed high ΔZ magnetic anomalies above the volcano, while the observed Bouguer gravity anomalies correlate better with the crystalline basement depth. Our analysis contributes to deeper understanding of the crustal architecture and the evolution of the basin accompanied by alkaline intraplate volcanism

A review of geophysical studies of the lithosphere in the Carpathian–Pannonian region

International audienceHere, we revisit the most prominent features of the complete Bouguer anomaly map and their interpretation, along with the current knowledge of the lithospheric thickness in the Carpathian–Pannonian region. The stripped gravity map, i.e., the sediment-stripped complete Bouguer anomaly map, was used to interpret the most prominent highs and lows of the gravity field. The complete Bouguer anomaly data were used in structural density modelling and integrated geophysical modelling to determine or revise the previously known sources of the most pronounced gravity features of the region. The Carpathian gravity low was divided into three sub-lows: the Western, Eastern, and Southern. The Western Carpathian gravity low consists of the clearly distinguishable External and Internal lows, which are due to different causes. The source of the External Western Carpathian gravity low reflects the low-density sediments of the External Western Carpathians (2.49–2.59 g cm–3) and the Foredeep (~2.43 g cm–3), while the Internal Western Carpathian gravity low is explained by the upper crustal deficit mass, which is formed by the rocks of the Alpine Tatric and Veporic units. These tectonic units are built mainly from granites and crystalline schists, of which the average density (~2.70 g cm–3) is lower than the average density of the lower crust of the Internal Western Carpathians (~2.90 g cm–3). The main sources of the Eastern and Southern Carpathian gravity lows are the gravity effects of the crustal roots created by continental collision, the Foredeep, and the surface sediments of the External Carpathians. The Pannonian gravity high is caused by the expressive Moho elevation (24–26 km). Since the Pannonian Basin upper mantle, which is built by high-density peridotites or dunites, is located several kilometres closer to the surface, this rock material represents a great excess mass (high-density anomalous bodies). Based on the calculated stripped gravity map, several local gravity highs (˃ +50 mGal) have been recognised, and they are all located in the Danube Basin, the Transcarpathian Basin, the Békés Basin, as well as the Makó trough. Their sources are high-density crustal bodies (Eo-Alpine metamorphic complexes), whose apical parts reach depths of only 7 to 12 km. Finally, the expressive different depths of the lithosphere-asthenosphere boundary in the Western and Eastern Carpathians were explained by the different Neo-Alpine development of both orogens. The mantle lithospheric root (~240 km) in the Eastern Carpathians is results from the sinking of the upper part of the broken slab during the frontal continental collision. On the contrary, no thickening of the mantle lithosphere was observed in the junction zone of the Western Carpathians and the Bohemian Massif. The typical thickness of the continental lithosphere (~100 km) in this zone was explained by the oblique continental collision. The Pannonian Basin system is characterised by one of the thinnest continental crusts (~25 km) and lithospheres (~75 km) in the world

3D density modelling of Gemeric granites of the Western Carpathians

The position of the Gemeric Superunit within the Western Carpathians is unique due to the occurrence of the Lower Palaeozoic basement rocks together with the autochthonous Upper Palaeozoic cover. The Gemeric granites play one of the most important roles in the framework of the tectonic evolution of this mountain range. They can be observed in several small intrusions outcropping in the western and south-eastern parts of the Gemeric Superunit. Moreover, these granites are particularly interesting in terms of their mineralogy, petrology and ages. The comprehensive geological and geophysical research of the Gemeric granites can help us to better understand structures and tectonic evolution of the Western Carpathians. Therefore, a new and original 3D density model of the Gemeric granites was created by using the interactive geophysical program IGMAS. The results show clearly that the Gemeric granites represent the most significant upper crustal anomalous low-density body in the structure of the Gemeric Superunit. Their average thickness varies in the range of 5–8 km. The upper boundary of the Gemeric granites is much more rugged in comparison with the lower boundary. There are areas, where the granite body outcrops and/or is very close to the surface and places in which its upper boundary is deeper (on average 1 km in the north and 4–5 km in the south). While the depth of the lower boundary varies from 5–7 km in the north to 9–10 km in the south. The northern boundary of the Gemeric granites along the tectonic contact with the Rakovec and Klátov Groups (North Gemeric Units) was interpreted as very steep (almost vertical). The results of the 3D modelling show that the whole structure of the Gemeric Unit, not only the Gemeric granite itself, has an Alpine north-vergent nappe structure. Also, the model suggests that the Silicicum–Turnaicum and Meliaticum nappe units have been overthrusted onto the Golčatov Group