The Pontine Islands
The Pontine archipelago consists of several volcanic islands and islets sited at the eastern end of the 41° Parallel line. Ages of exposed products range from about 4.1 Ma to less than 130 ka, and decrease eastward. Calcalkaline rhyolites, peralkaline rhy
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The Pontine Islands
Abstract
The Pontine archipelago consists of several volcanic islands and islets sited at the eastern end of the 41° Parallel line. Ages of exposed products range from about 4.1 Ma to less than 130 ka, and decrease eastward. Calcalkaline rhyolites, peralkaline rhyolites, and trachytes occur in the western islands of Ponza, La Botte, Palmarola and Zannone, where mafic-intermediate calcalkaline to potassic 4.0-3.9 Ma old volcanism has been recently discovered below sea level. A suite of basalt-trachybasalt to phonolite rocks makes up the eastern islands of Ventotene and Santo Stefano. Trachytes and peralkaline rhyolites derived from moderately potassic mafic parents by fractional crystallisation plus crustal assimilation. Calcalkaline rhyolites were formed either by crustal melting or by AFC, starting from mafic-intermediate calcalkaline parents. Basalts and trachybasalts from Ventotene have variable isotopic signatures, which reflect open-system intra-crustal evolution processes and/or source heterogeneity. The mafic rocks from Ventotene have geochemical and isotopic signatures that resemble the moderately potassic rocks from Ernici-Roccamonfina, suggesting similar type of mantle metasomatism and geodynamic significance. The Pontine volcanoes represent the northern termination of a Plio-Pleistocene volcanic alignment that extends from Anchise and the western Aeolian seamounts in the Southern Tyrrhenian Sea to offshore Central Italy. These represent remnant arcs that were constructed across the Tyrrhenian Sea during the eastward migration of the Ionian subduction system. Keywords
Pontine volcanoes Hyaloclastites Calcalkaline rhyolites Peralkaline rocks Potassic rocks Remnant arc 41° parallel line Southern tyrrhenian sea Geodynamics
© Springer International Publishing AG 2017 A. Peccerillo, Cenozoic Volcanism in the Tyrrhenian Sea Region, Advances in Volcanology, DOI 10.1007/978-3-319-42491-0_6
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Introduction
The Pontine archipelago consists of five islands and a number of islets, roughly aligned in a WNW direction, offshore the Campania-Latium coast (Fig. 6.1). The islands are sited on the edge of the continental shelf, about 60–70 km south of the Gulf of Gaeta coast, and are mainly formed of volcanic rocks, except for Zannone and Palmarola, where Paleozoic to Mesozoic metamorphic and sedimentary units, and Upper Pliocene argillaceous marine sediments crop out. Cenozoic limestones have been found by drilling at Ponza (De Rita et al. 1986, 2004; Bellucci et al. 1997, 1999). The Pontine Islands have been previously considered as belonging to the Campania Province (Peccerillo 2005), but they are much older and have distinct petrological-geochemical compositions than the Campania rocks, thus identifying a separate magmatic province. The western islands (Ponza, Palmarola, Zannone and La Botte islet) rise
The Pontine Islands
from the top of a large structural high on the edge of the continental shelf. Volcanism is 4.2–1.0 Ma old, and emplaced an association of m
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