Chapter 11 Geology, volcanic history and petrology of Vulcano (central Aeolian archipelago)

Abstract

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 shallowlevel reservoirs. Radiogenic isotope compositions are variable (87Sr/86Sr ¼ 0.70424–0.70587, 143Nd/144Nd ¼ 0.51254–0.51276, 206Pb/204Pb ¼ 19.305–19.759, 207Pb/204Pb ¼ 15.659–15.752, 208Pb/204Pb ¼ 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