Petrology and geochemistry of Lipari Island (Aeolian archipelago): constraints on magma genesis and evolution

A full set of geochemical and Sr, Nd and Pb isotope data both on bulk-rock and mineral samples is provided for volcanic rocks representative of the whole stratigraphic succession of Lipari Island in the Aeolian archipelago. These data, together with petrographic observations and melt/fluid inclusion investigations from the literature, give outlines on the petrogenesis and evolution of magmas through the magmatic and eruptive history of Lipari. This is the result of nine successive Eruptive Epochs developing between 271 ka and historical times, as derived from recentmost volcanological and stratigraphic studies, combined with available radiometric ages and correlation of tephra layers and marine terrace deposits. These Eruptive Epochs are characterized by distinctive vents partly overlapping in space and time, mostly under control of the main regional tectonic trends (NNW-SSE, N-S and minor E-W). A large variety of lava flows, scoriaceous deposits, lava domes, coulees and pyroclastics are emplaced, ranging in composition through time from calcalkaline (CA) and high-K (HKCA) basaltic andesites to rhyolites. CA and HKCA basaltic andesitic to dacitic magmas were erupted between 271 and 81 ka (Eruptive Epochs 1-6) from volcanic edifices located along the western coast of the island (and subordinately the eastern Monterosa) and the M.Chirica and M.S.Angelo stratocones. These mafic to intermediate magmas mainly evolved through AFC and RAFC processes, involving fractionation of mafic phases, assimilation of wall rocks and mixing with newly injected mafic magmas. Following a 40 ka-long period of volcanic quiescence, the rhyolitic magmas were lately erupted from eruptive vents located in the southern and north-eastern sectors of Lipari between 40 ka and historical times (Eruptive Epochs 7-9). They are suggested to derive from the previous mafic to intermediate melts through AFC processes. During the early phases of rhyolitic magmatism (Eruptive Epochs 7-8), enclaves-rich rocks and banded pumices, ranging in composition from HKCA dacites to low-SiO2 rhyolites were erupted, representing the products of magma mixing between fresh mafic magmas and the fractionated rhyolitic melts. The interaction of mantle-derived magmas with the crust represents an essential process during the whole magmatic hystory of Lipari, and is responsible for the wide range of observed geochemical and isotopic variations. The crustal contribution was particularly important during the intermediate phases of activity of Lipari when the cordierite-bearing lavas were erupted from the M. S.Angelo volcano (Eruptive Epoch 5, 105 ka). These lavas are interpreted as the result of mixing and subsequent hybridization of mantle-derived magmas, akin to the ones characterizing the older phases of activity of Lipari (Eruptive Epochs 1-4), and crustal anatectic melts derived from dehydration-melting reactions of metapelites in the lower crust. A comparison between the adjacent islands of Lipari and Vulcano outlines that their mafic to intermediate magmas seem to be genetically connected and derive from a similar mantle source affected by different degrees of partial melting (and variable extent of crustal assimilation) producing either the CA magmas of Lipari (higher degrees) or the HKCA to SHO magmas of Vulcano (lower degrees). On a regional scale, the most primitive rocks (SiO2<56%, MgO>3.5%) of Lipari, Vulcano, Salina and Filicudi are suggested to derive from a similar MORB-like source, variably metasomatized by aqueous fluids coming from the slab and subordinately by the additions of sediments.

Produzione e circolazione delle anfore greco italiche in area Adriatica

The present study, being part of a wide research program carried by the University of Bologna (Dipartimento di Scienze della Terra e Geo-Ambientali and Dipartimento di Archeologia) together with the Soprintendenze of Emilia-Romagna and Veneto, is aimed at examining the manufacturing and circulation of Greek Italic amphorae in the Adriatic area. This represents an essential step for the historical and archaeological reconstructions and in particular for: - the identification of local manufacturing though the archaeometric comparisons between ceramic samples and raw materials - the reconstruction of the ancient routes connecting different areas of the Roman world The examined archaeologic sites are representative of the main manufacturing areas in the Adriatic region both along the Italian and Albanian coasts: Adria, Cattolica, Rimini, Spina , Suasa and Phoinike. Notably, the Adriatic region not only represents the manufacturing area, but also coincides with the source area where the raw materials were collected. Archaeometric analyses of representative samples from the different areas of interests, were performed adapting the analytical tecniques used in mineralogy, petrography and geochemistry, to the study of ancient archaeological finds. These data were combined with the ones obtained from the analysis of clays, aimed at characterizing the nature of the raw materials. As a whole, an integration of these data with the available archaeologic observations led to significant advances in the scientific knowledge about of the main types of amphoric manufacturing and distribution in the Adriatic region. In particular, a local manufacturing is suggested for all the archaeological finds from Cattolica and for the main part of the archaeological finds from Suasa. Moreover, the occurrence of commercial routes between the sites of Rimini and Suasa and between Adria, Spina and Suasa is evidenced. On the contrary, for the amphorae from Phoinike a provenance from the examined sites is very unlikely.