Abstract. Petrological and geochemical data are reported for volcanic rocks from Vulcano island. The subaerial volcanism (120 ka to present) built up a NW-SE elongated composite structure, affected by two intersecting multistage calderas. Volcanics older than 20 ka consist mostly of high-K calc-alkaline (HKCA) to shoshonitic (SHO) mafic rocks. These magmas interacted significantly with the continental crust, which generated variable Sr isotopic ratios (0.70412-0.70520). However, a major role was also played by input of parental liquids into the magma chamber, which prevented further evolution of the magmas. HKCA, SHO, and potassic (
Vulcano is an active NW–SE-elongated composite volcano located in the central Aeolian archipelago. Based on available radiometric ages and tephrochronology, the exposed volcanism started at c. 127 ka and spread through eight Eruptive Epochs separated by volcano-tectonic events and major quiescent stages. Various eruptive centres and two intersecting multi-stage calderas resulted from such evolution. Vulcano geological history displays several changes of eruption magnitude, eruption styles and composition of magmas through time. Vulcano rocks range from basalt to rhyolite and show variable alkali contents, roughly increasing during time. Magmas with low to intermediate SiO2 contents and high-K to shoshonite affinity prevail in the early Epochs 1–5 (c. 127–28 ka), whereas intermediate to high-SiO2 shoshonite and potassic alkaline products dominate the last three Epochs (<30 ka). This sharp increase in silicic products is related to the shallowing of the plumbing system and resulting major role of the differentiation processes in shallow-level reservoirs. Radiogenic isotope compositions are variable (87Sr/86Sr=0.70424–0.70587, 143Nd/144Nd=0.51254–0.51276, 206Pb/204Pb=19.305–19.759, 207Pb/204Pb=15.659–15.752, 208Pb/204Pb=39.208–39.559) as a result of both source heterogeneities and shallow-level interaction of magmas with continental crust. The compositional variations of mafic magmatism with time suggest that the source zone changed from a metasomatized, fertile, ocean island basalt- (OIB-) like mantle to a metasomatized depleted lithospheric mantle.DVD:The 10 000 scale geological map of Vulcano 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 data set for Vulcano.
[1] The Aeolian volcanoes are located between the Southern Tyrrhenian Sea back arc and the Calabrian Arc forearc region. Structural, geochemical and seismological data indicate that the early phases of volcanic activity (1.3 Myr) developed in the western sector along WNW-ESE tear faults controlling the southeastward migration of the forearc -back arc system. This magmatism ceased when delamination processes affected the Calabrian Arc. At 0.8 Myr, the volcanism migrated southeastward and concentrated on the ''new'' formed NNW-SSE tear faults related to the postsubduction extensional strain. The compressive strain deduced by focal mechanism of earthquakes in the western sector explains the volcanism ending. The still active volcanism in the central and eastern sectors develops on a NNW-SSE striking lithospheric discontinuity that crosses the ring-shaped volcanic belt. Moho upwelling occurs in the area of active volcanism. Fault-slip data and focal mechanisms from M > 5 earthquakes indicate that the NNW-SSE discontinuity moves in response to an oblique (strikeslip/normal) stress related to a WNW-ESE extension. This direction of extension is consistent with that of the forearc region, where thrust-type events are lacking and the last compressive phases occurred during Pliocene. The later phases of the Aeolian volcanism are related to the melting of shallower source(s) consistent with a continental rift magmatism. The Aeolian Islands represent a postcollisional, rift-type volcanism emplaced in an older collision zone.
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.
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