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Faulting migration and localization at fast extension rates during rifting of the Tyrrhenian Basin have lead to break up and mantle exhumation

AuthorsRanero, César R. CSIC ORCID; Sallarès, Valentí CSIC ORCID ; Vendrell, M. G. CSIC; Prada, Manel CSIC ORCID ; Grevemeyer, Ingo; Zitellini, Nevio
Issue Date9-Dec-2013
CitationAGU Fall Meeting: T12B-06 (2013)
AbstractThe Tyrrhenian basin has been formed by extension of continental lithosphere driven by roll back of the Ionian slab across the mantle during the last ~12 Ma. Rifting opened from west to east, achieving increasing stretching factors from north to south. Extension is currently not active but coincided wide-angle seismic (WAS) and multichannel reflection seismic (MCS) transects of the structure attained at different stretching (beta) factors provide information of the formation processes. The seismic information is analyzed in a 3D context with the integration of multibeam bathymetry that covers the entire basin. Analysis of the WAS data has provided a characterization of the type of crust and its lateral distribution. The northernmost region stopped rifting at beta factors about 1.8. Increasing extension towards the south continues until full crustal separation. Break up was followed by formation of ocean crust. Faulting activity migrated and localized in a different region of the rift system causing a second episode of continental break that in this case was followed by extensive mantle exhumation. The final structure displays two conjugate continental margins separated by an intervening region of ocean crust that laterally abruptly changes to exhumed mantle. Analysis of the MCS images indicates the tectonics processes involved during rifting and also the timing and rates of extension. Seismic stratigraphy calibrated with drill holes indicates that the north to south changes in structure are related mainly to changes in extension rates rather than on large changes in the age of rifting. In addition, the seismic stratigraphy indicates that the change from oceanic back arc spreading to mantle exhumation occurred at fast opening rates, comparable to those of fast spreading centers. Extensive mantle exhumation was followed by an episode of localized basaltic magmatism that stopped possibly coeval with the end of the extension processes in the region. The lateral distribution of rock types, and fast extension rates leading mantle exhumation challenge current conceptual models of continental rifting. We speculate that the spatially abrupt changes in structure, and anomalously fast mantle exhumation followed by basaltic volcanism are related to the three-dimensional structure of the overriding plate. We speculate that the evolution of tectonic and magmatic processes may have been controlled changes in subduction-system dynamics combined with lateral heterogeneities in the thermal and chemical structure of the mantle, and re-fertilization processes related to the slab fluids
DescriptionAmerican Geophysical Union (AGU) Fall Meeting, 9-13 December 2013, San Francisco
Publisher version (URL)http://fallmeeting.agu.org/2013/
Appears in Collections:(ICM) Comunicaciones congresos
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