Vittorio Zanon

Bio: Vittorio Zanon is an academic researcher from University of the Azores. The author has contributed to research in topics: Volcano & Magma. The author has an hindex of 19, co-authored 41 publications receiving 930 citations. Previous affiliations of Vittorio Zanon include National Institute of Geophysics and Volcanology & Institut de Physique du Globe de Paris.

The exceptional activity and growth of the Southeast Crater, Mount Etna (Italy), between 1996 and 2001

Abstract: Between 1971 and 2001, the Southeast Crater was the most productive of the four summit craters of Mount Etna, with activity that can be compared, on a global scale, to the opening phases of the Pu‘u ‘Ō‘ō-Kūpaianaha eruption of Kīlauea volcano, Hawai‘i. The period of highest eruptive rate was between 1996 and 2001, when near-continuous activity occurred in five phases. These were characterized by a wide range of eruptive styles and intensities from quiet, non-explosive lava emission to brief, violent lava-fountaining episodes. Much of the cone growth occurred during these fountaining episodes, totaling 105 events. Many showed complex dynamics such as different eruptive styles at multiple vents, and resulted in the growth of minor edifices on the flanks of the Southeast Crater cone. Small pyroclastic flows were produced during some of the eruptive episodes, when oblique tephra jets showered the steep flanks of the cone with hot bombs and scoriae. Fluctuations in the eruptive style and eruption rates were controlled by a complex interplay between changes in the conduit geometry (including the growth of a shallow magma reservoir under the Southeast Crater), magma supply rates, and flank instability. During this period, volume calculations were made with the aid of GIS and image analysis of video footage obtained by a monitoring telecamera. Between 1996 and 2001, the bulk volume of the cone increased by ~36×106 m3, giving a total (1971–2001) volume of ~72×106 m3. At the same time, the cone gained ~105 m in height, reaching an elevation of about 3,300 m. The total DRE volume of the 1996–2001 products was ~90×106m3. This mostly comprised lava flows (72×106 m3) erupted at the summit and onto the flanks of the cone. These values indicate that the productivity of the Southeast Crater increased fourfold during 1996–2001 with respect to the previous 25 years, coinciding with a general increase in the eruptive output rates and eruption intensity at Etna. This phase of intense summit activity has been followed, since the summer of 2001, by a period of increased structural instability of the volcano, marked by a series of important flank eruptions.

Is the ‘Azores Hotspot’ a Wetspot? Insights from the Geochemistry of Fluid and Melt Inclusions in Olivine of Pico Basalts

Abstract: The concept of an 'Azores mantle plume' has been widely debated, and the existence of an Azores hotspot questioned. In an effort to shed new light on this controversy, we present He isotope and major, trace and volatile element compositions for basaltic scoriae from five monogenetic cones emplaced along the fissure zone of Pico Island, the youngest island of the Azores archipelago. The bulk scoriae and lavas are moderately alkaline basalts, and their He isotope ratios, determined on olivine crystals, vary between 10*2 and 11*1 ± 0*1 Ra. In contrast, melt inclusions hosted in olivine (Fo76-83*5) span a large range of compositions (K2O = 0*7-1*7 wt %; Ce = 32-65 ppm; Nb = 21-94 ppm), which extends the compositional field of lavas erupted along the Pico fissure zone. This chemical evolution is predominantly controlled by polybaric fractional crystallization. Most melt inclusions share similar enrichments in large ion lithophile and light rare earth elements, and trace element ratios (La/Sm, La/Yb, Sr/Nd, Ta/Th, Zr/Y) with their bulk-rocks. Only a few of them differ in their lower contents of incompatible elements and La/Sm, Li/Ta and Na/K ratios, a feature that is ascribed to distinct conditions of melting. As a whole, the melt inclusions preserve high and variable volatile contents, and contain up to 1*8-2*0 wt % of H2O and 0*4 wt % of CO2. The total fluid pressures, retrieved from the dissolved CO2 and H2O concentrations, and the PCO2 from fluid inclusions, indicate magma ponding and crystallization at the crust-mantle boundary (ca. 18 km deep). The H2O/Cl and H2O/Ce ratios in the inferred parental undegassed basalts of the Pico fissure zone average 0*036 ± 0*006 and 259 ± 21, respectively. The latter value is significantly higher than that reported for typical mid-ocean ridge basalts from the southern Mid-Atlantic Ridge, but is similar to published ratios for submarine undegassed basalts from the Azores platform. Combining the calculated compositions of Pico primary magmas formed by low degrees of melting with recent geophysical data for the Azores, we propose a model for Azores magma generation involving the decompression melting of a water-enriched mantle domain (H2O = 680-570 ppm) with an estimated temperature excess of ≤120°C with respect to the Mid-Atlantic Ridge.

Magmatic feeding system and crustal magma accumulation beneath Vulcano Island (Italy): Evidence from CO2 fluid inclusions in quartz xenoliths

Abstract: [1] Pure CO2 fluid inclusions are observed in quartz xenoliths from four lava flows in the Island of Vulcano, corresponding to distinct activity stages during the last 120 kyr. Xenoliths, which consist of aggregates of quartz grains, are present in lavas of contrasting composition ranging from basaltic-andesites to rhyolites. Two main generations of CO2 inclusions are observed: early (type I) inclusions were trapped prior to the ascent of the host xenoliths, while type II inclusions were trapped during the ascent into the host magma. Fluid inclusions show a bimodal distribution of homogenisation temperatures, corresponding to two distinct density intervals: 0.89–0.52 g/cm 3 (type I) and 0.42–0.13 g/cm 3 (type II). Type I inclusions indicate pressures of 0.56–0.33 GPa (21– 13 km), relating to the levels of xenolith entrapment in the host lavas. Type II fluid inclusions show considerably lower pressures ranging from 0.14 to 0.03 GPa (5.5–3 km). Present data suggest ponding of mantle-derived magmas in at least two distinct reservoirs, located at lower crustal depths and at shallow levels, respectively. Combined fluid inclusion and petrological data suggest that the deep reservoirs were the sites of extensive fractional crystallization, mixing with source-derived magmas, and various degrees of crustal assimilation. Evolutionary processes also occurred inside shallow magma chambers, in which deep magma mixed with residing melts and rested for short periods of time before being erupted to the surface. INDEX TERMS: 5480 Planetology: Solid Surface Planets: Volcanism (8450); 8414 Volcanology: Eruption mechanisms; 8434 Volcanology: Magma migration;

Depositional processes on oceanic island shelves – Evidence from storm‐generated Neogene deposits from the mid‐North Atlantic

Abstract: Oceanic islands – such as the Azores in the mid-North Atlantic – are periodically exposed to large storms that often remobilize and transport marine sediments along coastlines, and into deeper environments. Such disruptive events create deposits – denominated tempestites – whose characteristics reflect the highly dynamic environment in which they were formed. Tempestites from oceanic islands, however, are seldom described in the literature and little is known about storm-related sediment dynamics affecting oceanic island shelves. Therefore, the geological record of tempestite deposits at oceanic islands can provide invaluable information on the processes of sediment remobilization, transport and deposition taking place on insular shelves during and after major storms. In Santa Maria Island (Azores), a sequence of Neogene tempestite deposits was incorporated in the island edifice by the ongoing volcanic activity (thus preserved) and later exposed through uplift and erosion. Because it was overlain by a contemporary coastal lava delta, the water depth at the time of deposition could be inferred, constituting an excellent case-study to gain insight on the still enigmatic processes of insular shelf deposition. Sedimentological, palaeontological, petrographic and palaeo-water depth information allowed the reconstruction of the depositional environment of these sediments. The sequence typifies the characteristics of a tempestite (or successive tempestites) formed at ca 50 m depth, in a steep, energetic open insular shelf, and with evidence for massive sediment remobilization from the nearshore to the middle or outer shelf. The authors claim that cross-shelf transport induced by storm events is the main process of sediment deposition acting on steep and narrow shelves subjected to high-energetic environments, such as the insular shelves of open-sea volcanic islands.

Simple mixing as the major control of the evolution of volcanic suites in the Equadorian Andes T

Abstract: Examination of an extensive major and trace element database for about 700 whole rocks from the Ecuadorian Andes reveals series of local trends typified by three volcanoes: Iliniza and Pichincha from the Western Cordillera and Tungurahua from the Eastern Cordillera. These local trends are included in a more scattered global trend that reflects typical across-arc chemical variations. The scatter of the global trend is attributed to greater crustal contributions or decreasing melt fractions. Trace element modelling shows that the local trends are consistent with mixing, and not with any fractional crystallization or progressive melting dominated processes. These local trends are extendable to include samples from other Ecuadorian volcanoes, suggesting that mixing processes are dominant throughout the region. Mixing model using trace and major element analyses identifies two end-members: low-silica, basaltic and high-silica, dacitic magmas. It also shows that mixing occurred between magmas after their segregation, rather than earlier mixing between the solid sources prior to melting. As a consequence, there must exist efficient magma-mixing processes that can overcome the obstacles to mixing magmas with contrasting physical properties, and can produce series of hybrid liquids over regional-scale. Model calculations show that estimated silicic end-members are primary magmas and are not co-magmatic derivatives of the corresponding mafic end-members. Lavas of Ecuadorian volcanoes are likely originated from magmas of contrasting origins, such as basaltic magmas generated by fluxed melting of peridotites in the mantle wedge and dacitic, adakite-type magmas originating from the slab or the mafic lower crust.

Basaltic explosive volcanism: Constraints from deposits and models

Abstract: Basaltic pyroclastic volcanism takes place over a range of scales and styles, from weak discrete Strombolian explosions (∼10 2 –10 3 kg s −1 ) to Plinian eruptions of moderate intensity (10 7 –10 8 kg s −1 ). Recent well-documented historical eruptions from Etna, Kīlauea and Stromboli typify this diversity. Etna is Europe's largest and most voluminously productive volcano with an extraordinary level and diversity of Strombolian to subplinian activity since 1990. Kīlauea, the reference volcano for Hawaiian fountaining, has four recent eruptions with high fountaining (>400 m) activity in 1959, 1960, 1969 (–1974) and 1983–1986 (–2008); other summit (1971, 1974, 1982) and flank eruptions have been characterized by low fountaining activity. Stromboli is the type location for mildly explosive Strombolian eruptions, and from 1999 to 2008 these persisted at a rate of ca. 9 per hour, briefly interrupted in 2003 and 2007 by vigorous paroxysmal eruptions. Several properties of basaltic pyroclastic deposits described here, such as bed geometry, grain size, clast morphology and vesicularity, and crystal content are keys to understand the dynamics of the parent eruptions. The lack of clear correlations between eruption rate and style, as well as observed rapid fluctuations in eruptive behavior, point to the likelihood of eruption style being moderated by differences in the fluid dynamics of magma and gas ascent and the mechanism by which the erupting magma fragments. In all cases, the erupting magma consists of a mixture of melt and gaseous bubbles. The depth and rate of degassing, melt rheology, bubble rise and coalescence rates, and extent of syn-eruptive microlite growth define complex feedbacks that permit reversible shifts between fragmentation mechanisms and in eruption style and intensity. However, many basaltic explosive eruptions end after an irreversible shift to open-system outgassing and microlite crystallization in melt within the conduit. Clearer understanding of the factors promoting this diversity of basaltic pyroclastic eruptions is of fundamental importance in order to improve understanding of the range of behaviors of these volcanoes and assess hazards of future explosive events at basaltic volcanoes. The three volcanoes used for this review are the sites of large and growing volcano-tourism operations and there is a public need both for better knowledge of the volcanoes’ behavior and improved forecasting of the likely course of future eruptions.

Ichnology and Sedimentology of Shallow to Marginal Marine Systems

Abstract: Ichnology and Sedimentology of Shallow to Marginal Marine Systems: Ben Nevis & Avalon Reservoirs, Jeanne d’Arc Basin, S. G. Pemberton, M. Spila, A. J. Pulham, T. Saunders, J. A. MacEachern, D. Robbins and I. K. Sinclair, 2001, Geological Association of Canada Short Course Notes, Volume 15, 343 p., ISSN 1189-6094.