HR: 1340h
AN: V13D-1589    [Abstracts]
TI: Nd-Sr-Pb Isotopic Link Between Panarea And Sardinia Predating The Opening Of The Tyrrhenian Sea
AU: * Raia, F
EM: raia@sci.ccny.cuny.edu
AF: City College of New York and CUNY Graduate Center, MR106, 138th and Convent Avenue, New York, NY 10031, United States
AU: Ayuso, R A
EM: rayuso@usgs.gov
AF: U.S. Geological Survey, 953 National Center, Reston, VA 20192, United States
AU: De Vivo, B
EM: bdevivo@unina.it
AF: Universita di Napoli Federico II, Via Mezzocannone 8, Naples, 80134, Italy
AU: Somma, R
AF: INGV, Osservatorio Vesuviano, Via Diocleziano 328, Naples, 80124, Italy
AB: Plio-Quaternary Tyrrhenian magmatism in the Italian peninsula and Aeolian volcanic rocks is characterized by systematic trends in Sr-Nd-Pb isotopic space, implicating different mantle end-member source contributions [1 and reference therein]. The isotopic trends also support the notion of mantle–crust interaction during magma genesis. New isotopic data on lava and tephra from Panarea island represent its entire eruptive history, and together with the GEOROC database, allow for a regional evaluation of the isotopic trends in the Tyrrhenian region. Panarea rocks vary from andesite to rhyolite, show a systematic depletion of CaO, FeOT, MnO, MgO, TiO2 wt.% and enrichment in alkalis consistent with crystal fractionation. Most Sr-Nd-Pb isotopic compositions (86Sr/87Sr:0.70464-0.70604; 143Nd/144Nd:0.512473-0.512578; 206Pb/204Pb:19.162-19.241; 207Pb/204Pb:15.628-15.709; 208Pb/204Pb:39.270-39.016) fall midway between the compositions of the calc- alkaline western sector and Stromboli and Campanian volcanic rocks (located in the Aeolian eastern sector and Southern Italian Peninsula respectively). Notably, some rocks in Panarea display comparable Pb-Sr isotope compositions but much lower Nd-isotope ratios (143Nd/144Nd:0.512235-0.512415) than previously found in the Aeolian archipelago. Nd and Sr isotopic compositions plot close to the fields of the northern and central Plio- Quaternary volcanic rocks (e.g.Mt Arci) and Oligo-Miocene rocks (143Nd/144Nd:0.51218-0.51270) from Sardinia and trend toward a mantle end-member (EM1). This newly observed isotopic similarity between Panarea and Sardinia could represent an ancient source link predating the opening of the Tyrrhenian Sea that can be explained by 1) delamination of the Sardinian lower crust during Hercynian continental collision, or 2) modification of the lithospheric mantle during Oligo-Miocene arc-type volcanism, coeval back arc extension, and counter- clockwise rotation of the Corsica-Sardinia block. [1] Peccerillo, A. Plio-Quaternary Volcanism in Italy (2005) Springer, 365p.
DE: 1040 Radiogenic isotope geochemistry
DE: 3640 Igneous petrology
DE: 8400 VOLCANOLOGY
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting