Sm-Nd geochronology of the Erro-Tobbio gabbros (Ligurian Alps, Italy): Insights into the evolution of the Alpine Tethys

摘要: article The Alpine-Apennine ophiolites are considered analogs of the oceanic lithosphere formed at ocean-continent transition zones and very slow spreading centers. They lithospheric remnants Jurassic Piedmont-Ligurian ocean, a branch Mesozoic Tethys separating European Adriatic continental margins. Previous geochronological studies on gabbroic rocks Alpine indicated rather large time span crust formation. In this paper, we present Sm-Nd data well-preserved olivine gabbros intruded in mantle peridotites from Erro-Tobbio ophiolitic unit (Ligurian Alps, Italy). Borghini et al. (2007) documented that these crystallized low-P conditions (b5 kb) primitive N-MORB melts, similar to many ophiolites. Here four plagioclase-clinopyroxene internal isochrons presented, yielding equivalent ages initial eNd values. 177 ± 7 Ma, 179 178 21 Ma 182 19 reflecting weighted mean age 5 with 9.2 0.4 (2SD). Similar only recorded External Liguride Units (Northern Apennines) represent oldest available for Tethys. These Mg-rich can therefore be as representative early (syn-rift) melt intrusions thinned exhumed domains, likely close Adria's margin, hyper-extended Western Iberian Margin. Our new results together previous allow reconstruction spatial distribution over time, evaluation propagation rates paleo-ocean. northward rifting velocity, estimated ~5 cm/year, is presumably higher than lateral rate ~2 cm/year. estimates suggest Red Sea present-day analog evolution ocean. © 2014 Elsevier B.V. All rights reserved.