Federico Lucchi

Chapter 13 Eruptive, volcano-tectonic and magmatic history of the Stromboli volcano (north-eastern Aeolian archipelago)

Abstract Stromboli is famous for its persistent volcanic activity consisting of periodic discrete explosions alternating with lava effusion and more violent explosions. This paper presents a detailed reconstruction of the geological history of Stromboli and description of the characteristics and distribution of the volcanic units and structural features. Six main growth stages (Eruptive Epochs 1–6), in addition to the c. 200 ka activity of Strombolicchio, are recognized between c. 85 ka and the present day, displaying a magma composition ranging from calc-alkaline to potassic series which usually varies with changing Eruptive Epochs. The Epochs are subdivided into sequences of eruptions and characterized by dominant central-vent summit activity with episodic phases of flank activity along fissures and eccentric vents. The activity was repeatedly interrupted by erosional and destructive phases driven by recurrent vertical caldera-type (cc1–5) and sector (and flank) collapses (sc1–7) and generally associated with significant quiescences. The different serial character of the Stromboli rocks is associated with largely variable trace element contents and isotope ratios. These petrochemical characteristics together with our new stratigraphy indicate that magmas, generated in a heterogeneous mantle wedge, underwent complex differentiation processes during their ascent. Magmas are characterized by polybaric evolution residing in small magma reservoirs that are alternatively tapped by the different collapses. DVD: The 10 000 scale geological map of Stromboli is included on the DVD in the printed book and can also be accessed online at http://www.geolsoc.org.uk/Memoir37-electronic. Also included is a full geochemical dataset for Stromboli.

Chapter 9 Eruptive history and magmatic evolution of the island of Salina (central Aeolian archipelago)

Abstract Stratigraphic, structural, volcanological and geochemical data allow a detailed reconstruction of the geological history of the island of Salina (central Aeolian sector). Its subaerial volcanism (c. 244 ka to 15.6 ka) developed through six successive Eruptive Epochs interrupted by major quiescence periods, volcano-tectonic collapses and recurrent episodes of marine terrace formation during MIS 7 and MIS 5. Several stratovolcanoes were constructed by strombolian and effusive (Pizzo Capo, Monte Rivi, Monte Fossa delle Felci, Monte dei Porri) to hydromagmatic and subplinian (Monte dei Porri, Pollara) activity, with a general east–west shift of active vents, controlled primarily by the dominant NNW–SSE and minor NE–SW regional tectonic trends, and a progressive chemical differentiation of the erupted products from calc-alkaline basalts to rhyolites. The magma compositions and variations through time are the result of contamination of primary magmas derived from a subduction-modified mantle source with the Calabro–Peloritano lower crust and subsequent differentiation dominated by polybaric fractional crystallization. Magma mixing and mingling processes occurred during individual eruptions. The early basalts were fed from deep reservoirs located near the crust–mantle boundary, whereas the later andesitic to dacitic and, ultimately, rhyolitic magmas originated through combined assimilation and fractional crystallization processes in magma reservoirs at mid- to upper-crustal levels. DVD: The 10 000 scale geological map of Salina is included on the DVD in the printed book and can also be accessed online at http://www.geolsoc.org.uk/Memoir37-electronic. Also included is a full geochemical dataset for Salina.

Chapter 5 Stratigraphic methodology for the geological mapping of volcanic areas: insights from the Aeolian archipelago (southern Italy)

Abstract A stratigraphic approach to geological fieldwork and mapping of the Aeolian archipelago is performed by primarily using unconformity-bounded units (UBUs) in addition to lithosomes and classical lithostratigraphic units, which are the basic mappable units. Lithosomes are largely used to identify the localization of eruptive vents or non-volcanic source areas through time. The UBUs display an encompassing framework of correlation on a scale from local (single islands) to regional (Aeolian archipelago), by placing particular emphasis on the stratigraphic role played by Late Quaternary marine terrace deposits and widespread tephra layers (e.g. Brown Tuffs). By establishing a direct relationship between UBUs and time-stratigraphic units, the volcanic successions are readable in terms of different and successive Eruptive Epochs (separated by prolonged non-volcanic periods), which are characterized by distinctive eruptive vents and eruption types. As such, the UBUs allow the reconstruction of the main steps of geological evolution of a volcano as the result of the interplay between volcanic activity of local and external provenance, sea-level fluctuations and volcano-tectonic or regional fault lineaments.

Long-period seismic events with strikingly regular temporal patterns on Katla volcano's south flank (Iceland)

Katla is a threatening volcano in Iceland, partly covered by the Myrdalsjokull ice cap. The volcano has a large caldera with several active geothermal areas. A peculiar cluster of long-period seism ...

The 2011 unrest at Katla volcano: Characterization and interpretation of the tremor sources

Abstract A 23-hour tremor burst was recorded on July 8–9th 2011 at the Katla subglacial volcano, one of the most active and hazardous volcanoes in Iceland. This was associated with deepening of cauldrons on the ice cap and a glacial flood that caused damage to infrastructure. Increased earthquake activity within the caldera started a few days before and lasted for months afterwards and new seismic activity started on the southern flank. No visible eruption broke the ice and the question arose as to whether this episode relates to a minor subglacial eruption with the tremor being generated by volcanic processes, or by the flood. The tremor signal consisted of bursts with varying amplitude and duration. We have identified and described three different tremor phases, based on amplitude and frequency features. A tremor phase associated with the flood was recorded only at stations closest to the river that flooded, correlating in time with rising water level observed at gauging stations. Using back-projection of double cross-correlations, two other phases have been located near the active ice cauldrons and are interpreted to be caused by volcanic or hydrothermal processes. The greatly increased seismicity and evidence of rapid melting of the glacier may be explained by a minor sub-glacial eruption. A less plausible interpretation is that the tremor was generated by hydrothermal boiling and/or explosions with no magma involved. This may have been induced by pressure drop triggered by the release of water when the glacial flood started. All interpretations require an increase of heat released by the volcano.

Contrasting sediment melt and fluid signatures for magma components in the Aeolian Arc: Implications for numerical modeling of subduction systems

The complex geodynamic evolution of Aeolian Arc in the southern Tyrrhenian Sea resulted in melts with some of the most pronounced along the arc geochemical variation in incompatible trace elements and radiogenic isotopes worldwide, likely reflecting variations in arc magma source components. Here we elucidate the effects of subducted components on magma sources along different sections of the Aeolian Arc by evaluating systematics of elements depleted in the upper mantle but enriched in the subducting slab, focusing on a new set of B, Be, As, and Li measurements. Based on our new results, we suggest that both hydrous fluids and silicate melts were involved in element transport from the subducting slab to the mantle wedge. Hydrous fluids strongly influence the chemical composition of lavas in the central arc (Salina) while a melt component from subducted sediments probably plays a key role in metasomatic reactions in the mantle wedge below the peripheral islands (Stromboli). We also noted similarities in subducting components between the Aeolian Archipelago, the Phlegrean Fields, and other volcanic arcs/arc segments around the world (e.g., Sunda, Cascades, Mexican Volcanic Belt). We suggest that the presence of melt components in all these locations resulted from an increase in the mantle wedge temperature by inflow of hot asthenospheric material from tears/windows in the slab or from around the edges of the sinking slab.

Joint relative location of earthquakes without a pre-defined velocity model: an example from a peculiar seismic cluster on Katla volcano's south-flank (Iceland)

Relative location methods are commonly used to precisely locate earthquake clusters consisting of similar waveforms. Repeating waveforms are often recorded at volcanoes, where, however, the crust s ...