GNGTS 2017 - 36° Convegno Nazionale

602 GNGTS 2017 S essione 3.1 basalt breccia (Kasten and Mascle, 1990). This finding was initially interpreted as a refractory sliver of arc/subduction-related upper mantle (Bonatti et al. , 1980). However, MEDOC Vp models support that sampled peridotite is not a local anomaly within a basaltic crust, but it rather represents the groundtruthing of the exhumed mantle in the Vavilov and Magnaghi Basins. A second WAS campaign carried out in the Southeast Tyrrhenian on August 2015 during CHIANTI cruise has found that mantle exhumation may have also occurred in the Marsili Basin. The WAS data are now being modeled but preliminary analysis show that: 1) apparent velocities are very similar to those obtained in Magnaghi-Vavilov Basins, and 2) there is no evidence of PmPs, strongly suggesting that the basement nature is actually the same (i.e. serpentinized peridotite). Previousmodels for the formation of theTyrrhenian basin assume that the continental thinning of the margin by rifting occurs prior to sea floor spreading, within the Northern Tyrrhenian and along the Sardinia Basin-Cornaglia Terrace on the western side of the Tyrrhenian, and along the Campania Terrace on its eastern side. The MEDOC WAS data suggest instead that the basement of Cornaglia and Campania Terraces are anomalous, being characterized by lower crustal velocities that range between 6.5-7.5 km/s. This is ~10% higher than the velocity of typical continental crust suggesting that the continental crust is heavily intruded by magmatism, or that magmatic accretion pre-dates messinian deposition. This sequence of events differs from conventional models of rifting, mantle exhumation at COT, and seafloor spreading. References Bonatti E., Seyler M., Channell J., Girardeau J., Mascle G.; 1990: Peridotites drilled from the Tyrrhenian Sea, ODP Leg 107, Peridotites drilled from the Tyrrhenian Sea . ODP Leg 107 , pp. 37-47. Colantoni P., Fabbri A., Gallignani P., Sartori R., Rehault J.P.; 1981: Carta Litologica e Stratigrafica dei Mari Italiani, scala 1/1.500.000 . Litografia Artistica Cartografica, Firenze, Italy. Dietrich V., Emmermann R., Keller J., Puchelt H.; 1977:, Tholeitic basalts from the Tyrrhenian sea floor . Earth Planet. Sci. Let., 36 , 285-296. Diviacco P., Wardell N., Forlin E., Sauli, C., Burca, M., Busato, A. Centonze, J., Pelos, C.; 2015: “Data rescue to extend the value of vintage seismic data: The OGS-SNAP experience” . GeoResJ 6 , 44–52, DOI 10.1016/ j.grj.2015.01.006 Duschenes J., Sinha M.C., Louden K.E.; 1986: A seismic refraction experiment in the Tyrrhenian Sea . Geophys. J. R. Astron. Soc. 85 , 139–160. Fabbri A., Curzi P.V.; ����� � 1979: T he Messinian of the Tyrrhenian Sea: seismic evidence and dynamic implications . Giornale di Geologia 43 (2), 215-248. Faccena C., Becker T.W., Lucente F.P., Jolivet L., Rossetti F.; 2001: History of subduction and back-arc extension in the Central Mediterranean . Gophys. J. Int., 145 , 809-820. Funiciello R., Parrotto M., Praturlon A.; 1981: Carta tettonica D’Italia . �������� ����������� ������������ Progetto finalizzato Geodinamica, pubblicazione n. 269 Kastens K., Mascle J.; 1990: The geological evolution of the Tyrrhenian Sea: an introduction to the scientific results of ODP LEG 107 . In Kastens, K.A., Mascle, J., et al. (Eds.), Proceedings of the Ocean Drilling Program, Scientific Results 107 , pp. 3-26, doi:10.2973/odp.proc.sr.107.187.1990 Lustrino M., Duggen S., Rosenberg C.L.; 2011: The Central-Western Mediterranean: Anomalous igneous activity in an anomalous collision tectonic setting . Earth-Science Reviews, 104 , 1-40, doi:10.1016/j.earscirev.2010.08.002 Mauffret A., Contrucci I., Brunet C.; 1999: Structural evolution of the Northern Tyrrhenian Sea from new seismic data. Marine and Petroleum Geology, 16 (5), 381-407. Moeller S., Grevemeyer I., Ranero C.R., Berndt C., Klaeschen D., Sallarès V., Zitellini N., de Franco R.; 2013: Rifted structure in the northern Tyrrhenian Sea Basin: results from a combined wide-angle and multichannel seismic study . Geochem. Geophy. Geosy., doi:10.1002/ggge.20180 Moeller S., Grevemeyer I., Ranero C. R., Berndt C., Klaeschen D., Sallarès V., Zitellini N., and de Franco R.; 2014: Crustal thinning in the northern Tyrrhenian Rift: Insights from multichannel and wide-angle seismic data across the basin ., J. Geophys. Res. Solid Earth, 119 , 1655–1677, doi:10.1002/2013JB010431. Prada M., Sallarès V., Ranero C.R., Vendrell M.G., Grevemeyer I., Zitellini N., and de Franco R.; 2014: Seismic structure of the Central Tyrrhenian Basin: Geophysical constraints on the nature of the main crustal Domains . J. Geophys. Res. Solid Earth, 119 , doi:10.1002/2013JB010527. Prada M., Sallarès V., Ranero C.R., Vendrell M.G., Grevemeyer I., Zitellini N., and de Franco R. ;2015: The complex 3-D transition from continental crust to back-arc magmatism and exhumed mantle in the Central Tyrrhenian Basin . Geoph. J. Int., 203 (1), 63-78, doi:10.1093/gji/ggv271