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Coexisting calc-alkaline and ultrapotassic magmatism at Monte Ernici, Mid Latina Valley (Latium, central Italy)
No full textNew major and trace element data, and Sr-Nd-Pb-O isotopic ratios for volcanic mafic rocks outcropping at Monti Ernici in the Mid Latina Valley (southern Latium) are reported, with the aim of investigating the nature and evolution of Plio-Quaternary K-rich volcanism in Central Italy. Petrographical and geochemical studies allow us to identify mafic rocks ranging from ultrapotassic (HKS) to shoshonitic (SHO), and calc-alkaline (CA), these last ones being identified for the first time. The CA rocks exhibit the most primitive signatures for Sr, Nd, and Pb isotopes (87Sr/ 86Sr = 0.706326-0.706654; 143Nd/I44Nd = 0.512388-0.512361; 206Pb/204Pb = 18.944-18.940). The δ180 values are variable (δ18Ocpx from +5.75 to +7.08 ‰ and , δ180ol, from +5.50 to +6.23‰), suggesting interaction with carbonate wall rocks. Radiogenic isotope ratios and incompatible elements distribution have several characteristic in common with equivalent rocks from Pontine Islands (Ventotene), Campania and Aeolian arc volcanoes. Conversely, the HKS rocks closely resemble the ultrapotassic rocks from the Roman Province (87Sr/86Sr = 0.709679-0.711102; δ 18Ocpx from +6.27 to +7.08 ‰). The high ratios of LILE (Large Ion Lithophile Elements: Rb, Cs, Th, U, K, LREE) and HFSE (High Field Strength Elements: Ta, Nb, Zr, Hf, Ti), and radiogenic isotope compositions of CA to HKS rocks indicate that all suites contain subduction-related components, and suggest a N-MORB-type mantle source variably contaminated by hydrous fluids and/or melts released by undergoing slabs, possibly during two distinct stages of metasomatism. The coexistence of ultra-alkaline and sub-alkaline orogenic magmatism, combined with tectonic, geophysical and geological evidence, support the possibility that the mantle beneath central-southern Italy (Ernici-Roccamonfina Province) was vertically zoned and produced different magma suites during time. © 2007 E. Schweizerbart'sche Verlagsbuchhandlung
The Aeolian volcanism District: volcanism and magmatism.
No full textThe Aeolian Volcanic District is a geologically complex region characterised by a wide spectrum of volcanism and compositionally
variable magmatism younger than 1-1.3 Ma. Submarine and subaerial volcanic activities formed seven large strato-volcanoes, that upraise
from ~1500-2000 m b.s.l., and several seamounts. The Aeolian volcanism is the result of the long interplaying among collision,
subduction and extension processes occurred in the Mediterranean area affected by multiple geodynamic processes. Geophysical, seismological
and geochemical data allow recognition of three main sectors, each characterized by remarkably similar structural, volcanological
and compositional features. The eastern sector (including Stromboli-Panarea) is characterised by a prevailing nne-ssw to
ne-sw striking fault system, deep seismicity and magmas with variable affinity, from CA to KS, generally outpured through low-intensity
eruptions. The central sector (including Lipari, Vulcano and the younger part of Salina) is strongly affected by the presence of
the nnw-sse oriented strike-slip lithospheric fault system known as ‘Tindari-Letojanni’. Eruptive activity in the central sector shows
the wider spectrum of magma compositions in the archipelago – ranging from basalts to rhyolites, with CA, HKCA, SHO and KS
affinity – and the eruptions with the highest intensity and magnitude. The western sector (including the older part of Salina, Filicudi
and Alicudi) is characterized by a main wnw-ese striking fault system that conditioned the development of both subaerial and submarine
volcanoes, basically characterized by CA to HKCA mafic and intermediate magmas of subduction origin. Going from east to
west, a general increase of crust thickness (from ~17 km below Stromboli up to ~25 km below the western sector) and magma composition
variations (with a general decrease of Sr-isotopes and an increase of Nd-, Pb-isotope and LILE/HFSE ratios) are observed.
Overall, trace elements and radiogenic isotopes signatures variations along the avd indicate modifications in the nature and intensity
of metasomatic processes occurred in the Aeolian mantle.
The eruptive history of each island is reconstructed by giving special emphasis to the chronostratigraphic role played by fossil marine
conglomerates intercalated to volcanic products. Older and more primitive CA basalt to basalt-andesite volcanic products related
to strombolian and effusive volcanic activity were emplaced on Salina and Filicudi in a poorly constrained time span started around
430-400 ka. After an apparently long period of quiescence, volcanic activity started again between ~220 and 124 ka on Filicudi, Salina,
Lipari and Panarea, with the emplacement of CA basalt-andesite to andesite and dacite volcanics related to mainly strombolian and
effusive activity, with a minor role for explosive hydromagmatic eruptions. Between ~124 and 80 ka, HKCA andesitic and subordinate
dacitic volcanic products related to both explosive (mainly hydromagmatic) and effusive volcanic activity were emplaced on Lipari,
and Alicudi, whereas on Vulcano and Stromboli SHO products were erupted together with minor HKCA lavas. Starting from ~80 ka,
more evolved CA and HKCA andesitic to daci-trachytic -up to rhyolitic products were mainly erupted on Lipari and Salina and to a
lesser extent on Panarea, Alicudi and Filicudi. Most of these magmas were produced by effusive activity (mainly dome-forming) and
associated high-energy explosive eruptions. In the last 25 ka ca., a growing and intensification of the volcanism in the central sector –
probably associated to increased activity of the Tindari-Letojanni fault system – occurred; whereas volcanism ceased in the western
sector and was regular and almost continuous in the eastern one through Stromboli. At present time Vulcano, Stromboli and submarine
area of Panarea show active volcanic phoenomena
Geologia - Inquadramento Geologico e Storia Eruttiva
No full textIn the framework of the Aeolian Volcanic District evolution, the chapter provides the reconstruction of the Vulcano Island history through the subdivision in eight Eruptive Epochs.Published33-473.5. Geologia e storia dei vulcani ed evoluzione dei magmiope
Modeling the magma plumbing system of Vulcano (Aeolian Islands, Italy) by integrated fluid inclusion geo-barometry, petrology and geophysics
No full textAn integrated petrological, geophysical, and fluid-inclusion model is presented for the internal structure of the active Vulcano Island, Southern Tyrrhenian Sea. The present
structure of the magma storage system in the crust consists of two major deep accumulation zones located at 17–21 km and 8–13 km depth, plus a minor one at 1–5 km depth, beneath Fossa Cone. The deepest magma accumulation zone contains mafic melts and is
located at the transition between the upper mantle and a granulitic lower crust. This reservoir has been active since the onset of the exposed volcanism, and has undergone
continuous fractional crystallization, crustal assimilation, and mixing with primary melts from the mantle. Slightly differentiated magmas from the deep reservoir feed a shallower accumulation zone in the middle and upper crust, or erupt directly to the surface through lateral vents. Deep melts probably enter the shallowest reservoir shortly before magma outbreak at the surface, and may represent the trigger of eruptions. According to our model, magmatic eruptions at Vulcano are related to deep magma dynamics, whereas most of the changes in the geochemical and geophysical parameters observed at the active cone in the last century could be due to shallow depth modification of rock permeability, possibly as a result of cone gravitative instability and/or tectonic events. Implications for strategies of volcano monitoring and for forecasting eruptions are briefly discussed
Geologia - Inquadramento Geologico e Storia Eruttiva
No full textIn the framework of the Aeolian Volcanic District evolution, the chapter provides the reconstruction of the Vulcano Island history through the subdivision in eight Eruptive Epochs.Published33-473.5. Geologia e storia dei vulcani ed evoluzione dei magmiope
Volcanological and petrological evolution of Vulcano island (Aeolian Arc, southern Thyrrhenian sea)
No full textRelative roles of rifting tectonics and magma ascent processes: Inferences from geophysical, structural, volcanological, and geochemical data for the Neapolitan volcanic region (southern Italy)
No full textThe Neapolitan volcanic region is located within the graben structure of the Campanian Plain (CP), which developed between the western sector of the Appenine Chain and the eastern margin of the Tyrrhenian Sea. Two volcanic areas, spaced less than 10 km apart, are situated within the CP: the Somma - Vesuvius Volcano (SVV) and the Phlegraean Volcanic District (PVD). SVV is a typical stratovolcano, whereas PVD, including Campi Flegrei, Procida, and Ischia, is composed mostly of monogenetic centers. This contrast is due to different magma supply systems: a widespread fissure-type system beneath the PVD and a central-type magma supply system for the SVV. Volcanological, geophysical, and geochemical data show that magma viscosity, magma supply rate, and depth of magma storage are comparable at PVD and SVV, whereas different structural arrangements characterize the two areas. On the basis of geophysical data and magma geochemistry, an oblique-extensional tectonic regime is proposed within the PVD, whereas in the SVV area a compressive stress regime dominates over extension. Geophysical data suggest that the area with the maximum deformation rate extends between the EW-running 41st parallel and the NE-running Magnaghi-Sebeto fault systems. The PVD extensional area is a consequence of the Tyrrhenian Sea opening and is decoupled from the surrounding areas (Roccamonfina and Somma-Vesuvius) which are still dominated by Adriatic slab dynamics. Spatially, we argue that the contribution of the asthenospheric wedge become much less important from W-NW to E-SE in the CP. The development of the two styles of volcanism in the CP reflects the different tectonic regimes acting in the area. Copyright 2005 by the American Geophysical Union
Evidence for different magma evolution processes in the El Tatio volcanic region (22°.16 to 22°30 S, Central Volcanic Zone, Andes).
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